Analysis of real-time head accelerations in collegiate football players.

PubMed

Duma, Stefan M; Manoogian, Sarah J; Bussone, William R; Brolinson, P Gunnar; Goforth, Mike W; Donnenwerth, Jesse J; Greenwald, Richard M; Chu, Jeffrey J; Crisco, Joseph J

2005-01-01

To measure and analyze head accelerations during American collegiate football practices and games. A newly developed in-helmet 6-accelerometer system that transmits data via radio frequency to a sideline receiver and laptop computer system was implemented. From the data transfer of these accelerometer traces, the sideline staff has real-time data including the head acceleration, the head injury criteria value, the severity index value, and the impact location. Data are presented for instrumented players for the entire 2003 football season, including practices and games. American collegiate football. Thirty-eight players from Virginia Tech's varsity football team. Accelerations and pathomechanics of head impacts. : A total of 3312 impacts were recorded over 35 practices and 10 games for 38 players. The average peak head acceleration, Gadd Severity Index, and Head Injury Criteria were 32 g +/- 25 g, 36 g +/- 91 g, and 26 g +/- 64 g, respectively. One concussive event was observed with a peak acceleration of 81 g, a 267 Gadd Severity Index, and 200 Head Injury Criteria. Because the concussion was not reported until the day after of the event, a retrospective diagnosis based on his history and clinical evaluation suggested a mild concussion. The primary finding of this study is that the helmet-mounted accelerometer system proved effective at collecting thousands of head impact events and providing contemporaneous head impact parameters that can be integrated with existing clinical evaluation techniques.

Analysis of WBV on standing and seated passengers during off-peak operation in KL monorail

NASA Astrophysics Data System (ADS)

Hasnan, K.; Bakhsh, Q.; Ahmed, A.; Ali, D.; Jamali, A. R.

2018-03-01

In this study, the Whole-Body Vibration (WBV) was analyzed on the standing and seated passenger during off-peak operating hours when train was on the track. The experiments were conducted on two car train at one constant location (bogie-1, which is near to driver’s cabin) during downward direction from KL sentral station towards Titiwangsa station. The aim of this study was to analyze that, in which posture of passenger’s exposures the maximum level of WBV. Since, one passenger was performed the whole journey in standing posture whereas, the other passenger was in seated posture. The result obtained from experiments for the RMS accelerations (Arms), maximum acceleration (Amax) and minimum acceleration (Amin) during the trip. As per standard ISO 2631-1, the daily vibration exposure (A8), Vibration Dose value (VDV) and Crest Factor (CF) of this trip for both standing and sitting orientations were calculated. Results shows that the seated passenger was exposed to longer periods of continuous vibration as compared to the standing passenger. Whereas, the Vibration Dose value (VDV) value was greater than the action value as per ISO 2631-1 and within the limit values. The study concluded that whole body vibration transmitted towards both passengers either standing or seated during their journey. But in overall results comparison of both orientations, the seated passengers gained higher vibration than the standing one.

Preliminary recognition of whole body vibration risk in private farmers' working environment.

PubMed

Solecki, Leszek

2007-01-01

The objective of the study was the preliminary recognition of whole body mechanical vibration risk among farmers in the rural work environment. The study covered 15 farms using cultivated land of the size of over 10 ha, carrying out mixed production (plant-animal), equipped with agricultural tractors, and a basic set of tractor-mounted agricultural machinery, with a partial contribution of self-propelled agricultural machines. The scope of the study covered the measurements of effective vibration RMS acceleration (equivalent, maximum, minimum, peak) frequency corrected on the seats of agricultural vehicles in the three spatial directions of vibration (X, Y, Z). These measurements were realized while performing various field and transport work activities during the period of the whole year. A analysis of the peak, maximum and minimum vibration accelerations confirms that in the agricultural occupational environment there occurs a considerable variation of the vibration values registered. This is also evidenced by high values of the Crest Factor, sometimes exceeding a score of 10. Analysis of the registered equivalent values of vibration acceleration (frequency corrected) from the hygienic aspect showed that vibration occurring on the seats may create risk for farmers' health while performing such work activities as: tending and raking of hay, fertilizers spreading, soil aggregation, grass mowing and cultivation. Analysis of the spatial distribution of the measured, frequency corrected vibration accelerations indicates that considerably the highest acceleration values occur in the vertical plane (direction-Z). Literature data clearly confirm an unfavourable effect of whole body vibration present in agricultural vehicles on discomfort and the occurrence of back pain in the operators, especially in the low back region (lumbar spine), as well as degenerative changes in the spine.

VLF Wave Local Acceleration & ULF Wave Radial Diffusion: The Importance of K-Dependent PSD Analysis for Diagnosing the cause of Radiation Belt Acceleration.

NASA Astrophysics Data System (ADS)

Ozeke, L.; Mann, I. R.; Claudepierre, S. G.; Morley, S.; Henderson, M. G.; Baker, D. N.; Kletzing, C.; Spence, H. E.

2017-12-01

We present results showing the temporal evolution of electron Phase Space Density (PSD) in the outer radiation belt during the most intense geomagnetic storm of the last decade which occurred on March 17th 2015. Based on observations of growing local PSD peaks at fixed first and second adiabatic invariants of M=1000 MeV/G and K=0.18 G1/2Re respectively, previous studies argued that the outer radiation belt flux enhancement that occurred during this storm resulted from local acceleration driven by VLF waves. Here we show that the vast majority of the outer radiation belt consisted of electrons with much lower K-values than 0.18 G1/2Re, and that at these lower K-values there is no clear evidence of growing local PSD peaks consistent with that expected from local acceleration. Contrary to prior studies we show that the outer radiation belt flux enhancement is consistent with inward radial diffusion driven by ULF waves and present evidence that the growing local PSD peaks at K=0.18 G1/2Re and M=1000 MeV/G result from pitch-angle scattering of lower-K electrons to K=0.18 G1/2Re. In addition, we also show that the observed outer radiation belt flux enhancement during this geomagnetic storm can be reproduced using a radial diffusion model driven by measured ULF waves without including any local acceleration. These results highlight the importance of careful analysis of the electron PSD profiles as a function of L* over a range of fixed first, M and second K, adiabatic invariants to correctly determine the mechanism responsible for the electron flux enhancements observed in the outer radiation belt.

Assessment of head injury risk associated with feet-first free falls in 12-month-old children using an anthropomorphic test device.

PubMed

Thompson, Angela K; Bertocci, Gina; Pierce, Mary Clyde

2009-04-01

Short distance falls are a common false history provided in cases of child abuse. Falls are also a common occurrence in ambulating young children. The purpose of this study was to determine the risk of head injury in short distance feet-first free falls for a 12-month-old child. Feet-first free falls were simulated using an anthropomorphic test device. Three fall heights and five surfaces were tested to determine whether changing fall environment characteristics leads to differences in head injury risk outcomes. Linear head accelerations were measured and angular head accelerations in the anterior-posterior direction were determined. Head injury criteria values and impact durations were also determined for each fall. The mean peak linear head acceleration across all trials was 52.2g. HIC15 values were all below the injury assessment reference value. The mean peak angular head acceleration across all trials was 4,246 rad/s2. Impact durations ranged from 12.1 milliseconds to 27.8 milliseconds. In general, head accelerations were greater and impact durations were lower for surfaces with lower coefficients of restitution (a measure of resiliency). In falls onto wood and linoleum over concrete, the ground-based fall was associated with greater accelerations than the two higher fall heights. Results show that fall dynamics play an important role in head injury outcome measures. Different fall heights and impact surfaces led to differences in head injury risk, but the risk of severe head injury across all tested scenarios was low for a 12-month-old child in feet-first free falls.

Magnitude of Head Impact Exposures in Individual Collegiate Football Players

PubMed Central

Wilcox, Bethany J.; Machan, Jason T.; McAllister, Thomas W.; Duhaime, Ann-Christine; Duma, Stefan M.; Rowson, Steven; Beckwith, Jonathan G.; Chu, Jeffrey J.; Greenwald, Richard M.

2013-01-01

The purpose of this study was to quantify the severity of head impacts sustained by individual collegiate football players and to investigate differences between impacts sustained during practice and game sessions, as well as by player position and impact location. Head impacts (N = 184,358) were analyzed for 254 collegiate players at three collegiate institutions. In practice, the 50th and 95th percentile values for individual players were 20.0 g and 49.5 g for peak linear acceleration, 1187 rad/s2 and 3147 rad/s2 for peak rotational acceleration, and 13.4 and 29.9 for HITsp, respectively. Only the 95th percentile HITsp increased significantly in games compared with practices (8.4%, p= .0002). Player position and impact location were the largest factors associated with differences in head impacts. Running backs consistently sustained the greatest impact magnitudes. Peak linear accelerations were greatest for impacts to the top of the helmet, whereas rotational accelerations were greatest for impacts to the front and back. The findings of this study provide essential data for future investigations that aim to establish the correlations between head impact exposure, acute brain injury, and long-term cognitive deficits. PMID:21911854

Experimental characterization of a coaxial plasma accelerator for a colliding plasma experiment

NASA Astrophysics Data System (ADS)

Wiechula, J.; Hock, C.; Iberler, M.; Manegold, T.; Schönlein, A.; Jacoby, J.

2015-04-01

We report experimental results of a single coaxial plasma accelerator in preparation for a colliding plasma experiment. The utilized device consisted of a coaxial pair of electrodes, accelerating the plasma due to J ×B forces. A pulse forming network, composed of three capacitors connected in parallel, with a total capacitance of 27 μF was set up. A thyratron allowed to switch the maximum applied voltage of 9 kV. Under these conditions, the pulsed currents reached peak values of about 103 kA. The measurements were performed in a small vacuum chamber with a neutral-gas prefill at gas pressures between 10 Pa and 14 000 Pa. A gas mixture of ArH2 with 2.8% H2 served as the discharge medium. H2 was chosen in order to observe the broadening of the Hβ emission line and thus estimate the electron density. The electron density for a single plasma accelerator reached peak values on the order of 1016 cm-3 . Electrical parameters, inter alia inductance and resistance, were determined for the LCR circuit during the plasma acceleration as well as in a short circuit case. Depending on the applied voltage, the inductance and resistance reached values ranging from 194 nH to 216 nH and 13 mΩ to 23 mΩ, respectively. Furthermore, the plasma velocity was measured using a fast CCD camera. Plasma velocities of 2 km/s up to 17 km/s were observed, the magnitude being highly correlated with gas pressure and applied voltage.

Preliminary analysis of strong-motion recordings from the 28 September 2004 Parkfield, California earthquake

USGS Publications Warehouse

Shakal, A.; Graizer, V.; Huang, M.; Borcherdt, R.; Haddadi, H.; Lin, K.-W.; Stephens, C.; Roffers, P.

2005-01-01

The Parkfield 2004 earthquake yielded the most extensive set of strong-motion data in the near-source region of a magnitude 6 earthquake yet obtained. The recordings of acceleration and volumetric strain provide an unprecedented document of the near-source seismic radiation for a moderate earthquake. The spatial density of the measurements alon g the fault zone and in the linear arrays perpendicular to the fault is expected to provide an exceptional opportunity to develop improved models of the rupture process. The closely spaced measurements should help infer the temporal and spatial distribution of the rupture process at much higher resolution than previously possible. Preliminary analyses of the peak a cceleration data presented herein shows that the motions vary significantly along the rupture zone, from 0.13 g to more than 2.5 g, with a map of the values showing that the larger values are concentrated in three areas. Particle motions at the near-fault stations are consistent with bilateral rupture. Fault-normal pulses similar to those observed in recent strike-slip earthquakes are apparent at several of the stations. The attenuation of peak ground acceleration with distance is more rapid than that indicated by some standard relationships but adequately fits others. Evidence for directivity in the peak acceleration data is not strong. Several stations very near, or over, the rupturing fault recorded relatively low accelerations. These recordings may provide a quantitative basis to understand observations of low near-fault shaking damage that has been reported in other large strike-slip earthquak.

Beyond Bernoulli

PubMed Central

Donati, Fabrizio; Myerson, Saul; Bissell, Malenka M.; Smith, Nicolas P.; Neubauer, Stefan; Monaghan, Mark J.; Nordsletten, David A.

2017-01-01

Background— Transvalvular peak pressure drops are routinely assessed noninvasively by echocardiography using the Bernoulli principle. However, the Bernoulli principle relies on several approximations that may not be appropriate, including that the majority of the pressure drop is because of the spatial acceleration of the blood flow, and the ejection jet is a single streamline (single peak velocity value). Methods and Results— We assessed the accuracy of the Bernoulli principle to estimate the peak pressure drop at the aortic valve using 3-dimensional cardiovascular magnetic resonance flow data in 32 subjects. Reference pressure drops were computed from the flow field, accounting for the principles of physics (ie, the Navier–Stokes equations). Analysis of the pressure components confirmed that the spatial acceleration of the blood jet through the valve is most significant (accounting for 99% of the total drop in stenotic subjects). However, the Bernoulli formulation demonstrated a consistent overestimation of the transvalvular pressure (average of 54%, range 5%–136%) resulting from the use of a single peak velocity value, which neglects the velocity distribution across the aortic valve plane. This assumption was a source of uncontrolled variability. Conclusions— The application of the Bernoulli formulation results in a clinically significant overestimation of peak pressure drops because of approximation of blood flow as a single streamline. A corrected formulation that accounts for the cross-sectional profile of the blood flow is proposed and adapted to both cardiovascular magnetic resonance and echocardiographic data. PMID:28093412

C-5A Cargo Deck Low-Frequency Vibration Environment

DTIC Science & Technology

1975-02-01

SAMPLE VIBRATION CALCULATIONS 13 1. Normal Distribution 13 2. Binomial Distribution 15 IV CONCLUSIONS 17 -! V REFERENCES 18 t: FEiCENDIJJ PAGS 2LANKNOT...Calculation for Binomial Distribution 108 (Vertical Acceleration, Right Rear Cargo Deck) xi I. INTRODUCTION The availability of large transport...the end of taxi. These peaks could then be used directly to compile the probability of occurrence of specific values of acceleration using the binomial

Shrinking of core neoclassical tearing mode magnetic islands due to edge localized modes and the role of ion-scale turbulence in island recovery in DIII-D

NASA Astrophysics Data System (ADS)

Bardóczi, L.; Rhodes, T. L.; Carter, T. A.; La Haye, R. J.; Bañón Navarro, A.; McKee, G. R.

2017-06-01

Experimental signature of long-wavelength turbulence accelerating the recovery of Neoclassical Tearing Mode (NTM) magnetic islands after they have been transiently reduced in size due to interaction with Edge Localized Modes (ELMs) is reported for the first time. This work shows that perturbations associated with ELMs result in peaking of the electron temperature (Te) in the O-point region of saturated core m/n = 2/1 islands (m/n being the poloidal/toroidal mode numbers). In synchronization with this Te peak, the island width shrinks by as much as 30% suggesting a key role of the Te peak in NTM stability due to modified pressure gradient (∇p) and perturbed bootstrap current (δjBS) at the O-point. Next, this Te peak relaxes via anomalous transport (i.e., the diffusivity is 2 orders of magnitude larger than the neoclassical value) and the island recovers. Long-wavelength turbulent density fluctuations ( n ˜ ) are reduced at the O-point of flat islands but these fluctuations are increased when Te is peaked which offers an explanation for the observed anomalous transport that is responsible for the relaxation of the Te peak. Linear gyrokinetic simulations indicate that n ˜ inside the peaked island is dominantly driven by the Ion Temperature Gradient instability. These measurements suggest that n ˜ accelerates NTM recovery after an ELM crash via accelerating the relaxation of ∇p at the O-point. These observations are qualitatively replicated by coupled predator-prey equations and modified Rutherford equation. In this simple model, turbulence accelerates NTM recovery via relaxing ∇p and therefore restoring δjBS at the O-point. The key physics of the relationship between the Te peak and NTM stability has potentially far-reaching consequences, such as NTM control via pellet injection in high-β tokamak plasmas.

Shrinking of core neoclassical tearing mode magnetic islands due to edge localized modes and the role of ion-scale turbulence in island recovery in DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bardóczi, Laszlo; Rhodes, Terry L.; Carter, Troy A.

Experimental signature of long-wavelength turbulence accelerating the recovery of Neoclassical Tearing Mode (NTM) magnetic islands after they have been transiently reduced in size due to inter- action with Edge Localized Modes (ELMs) is reported for the first time. This work shows that per- turbations associated with ELMs result in peaking of the electron temperature (Te) in the O-point region of saturated core m/n 1/4 2/1 islands (m/n being the poloidal/toroidal mode numbers). In syn- chronization with this Te peak, the island width shrinks by as much as 30% suggesting a key role of the Te peak in NTM stability duemore » to modified pressure gradient (rp) and perturbed bootstrap cur- rent (djBS) at the O-point. Next, this Te peak relaxes via anomalous transport (i.e., the diffusivity is 2 orders of magnitude larger than the neoclassical value) and the island recovers. Long-wavelength turbulent density fluctuations (n~) are reduced at the O-point of flat islands but these fluctuations are increased when Te is peaked which offers an explanation for the observed anomalous transport that is responsible for the relaxation of the Te peak. Linear gyrokinetic simulations indicate that n~ inside the peaked island is dominantly driven by the Ion Temperature Gradient instability. These measure- ments suggest that n~ accelerates NTM recovery after an ELM crash via accelerating the relaxation of rp at the O-point. These observations are qualitatively replicated by coupled predator-prey equations and modified Rutherford equation. In this simple model, turbulence accelerates NTM recovery via relaxing rp and therefore restoring djBS at the O-point. The key physics of the rela- tionship between the Te peak and NTM stability has potentially far-reaching consequences, such as NTM control via pellet injection in high-b tokamak plasmas.« less

Shrinking of core neoclassical tearing mode magnetic islands due to edge localized modes and the role of ion-scale turbulence in island recovery in DIII-D

DOE PAGES

Bardóczi, Laszlo; Rhodes, Terry L.; Carter, Troy A.; ...

2017-06-08

Experimental signature of long-wavelength turbulence accelerating the recovery of Neoclassical Tearing Mode (NTM) magnetic islands after they have been transiently reduced in size due to inter- action with Edge Localized Modes (ELMs) is reported for the first time. This work shows that per- turbations associated with ELMs result in peaking of the electron temperature (Te) in the O-point region of saturated core m/n 1/4 2/1 islands (m/n being the poloidal/toroidal mode numbers). In syn- chronization with this Te peak, the island width shrinks by as much as 30% suggesting a key role of the Te peak in NTM stability duemore » to modified pressure gradient (rp) and perturbed bootstrap cur- rent (djBS) at the O-point. Next, this Te peak relaxes via anomalous transport (i.e., the diffusivity is 2 orders of magnitude larger than the neoclassical value) and the island recovers. Long-wavelength turbulent density fluctuations (n~) are reduced at the O-point of flat islands but these fluctuations are increased when Te is peaked which offers an explanation for the observed anomalous transport that is responsible for the relaxation of the Te peak. Linear gyrokinetic simulations indicate that n~ inside the peaked island is dominantly driven by the Ion Temperature Gradient instability. These measure- ments suggest that n~ accelerates NTM recovery after an ELM crash via accelerating the relaxation of rp at the O-point. These observations are qualitatively replicated by coupled predator-prey equations and modified Rutherford equation. In this simple model, turbulence accelerates NTM recovery via relaxing rp and therefore restoring djBS at the O-point. The key physics of the rela- tionship between the Te peak and NTM stability has potentially far-reaching consequences, such as NTM control via pellet injection in high-b tokamak plasmas.« less

Velocity spectrum for the Iranian plateau

NASA Astrophysics Data System (ADS)

Bastami, Morteza; Soghrat, M. R.

2018-01-01

Peak ground acceleration (PGA) and spectral acceleration values have been proposed in most building codes/guidelines, unlike spectral velocity (SV) and peak ground velocity (PGV). Recent studies have demonstrated the importance of spectral velocity and peak ground velocity in the design of long period structures (e.g., pipelines, tunnels, tanks, and high-rise buildings) and evaluation of seismic vulnerability in underground structures. The current study was undertaken to develop a velocity spectrum and for estimation of PGV. In order to determine these parameters, 398 three-component accelerograms recorded by the Building and Housing Research Center (BHRC) were used. The moment magnitude (Mw) in the selected database was 4.1 to 7.3, and the events occurred after 1977. In the database, the average shear-wave velocity at 0 to 30 m in depth (Vs30) was available for only 217 records; thus, the site class for the remaining was estimated using empirical methods. Because of the importance of the velocity spectrum at low frequencies, the signal-to-noise ratio of 2 was chosen for determination of the low and high frequency to include a wider range of frequency content. This value can produce conservative results. After estimation of the shape of the velocity design spectrum, the PGV was also estimated for the region under study by finding the correlation between PGV and spectral acceleration at the period of 1 s.

Research on Shock Responses of Three Types of Honeycomb Cores

NASA Astrophysics Data System (ADS)

Peng, Fei; Yang, Zhiguang; Jiang, Liangliang; Ren, Yanting

2018-03-01

The shock responses of three kinds of honeycomb cores have been investigated and analyzed based on explicit dynamics analysis. According to the real geometric configuration and the current main manufacturing methods of aluminum alloy honeycomb cores, the finite element models of honeycomb cores with three different cellular configurations (conventional hexagon honeycomb core, rectangle honeycomb core and auxetic honeycomb core with negative Poisson’s ratio) have been established through FEM parametric modeling method based on Python and Abaqus. In order to highlight the impact response characteristics of the above three honeycomb cores, a 5 mm thick panel with the same mass and material was taken as contrast. The analysis results showed that the peak values of longitudinal acceleration history curves of the three honeycomb cores were lower than those of the aluminum alloy panel in all three reference points under the loading of a longitudinal pulse pressure load with the peak value of 1 MPa and the pulse width of 1 μs. It could be concluded that due to the complex reflection and diffraction of stress wave induced by shock in honeycomb structures, the impact energy was redistributed which led to a decrease in the peak values of the longitudinal acceleration at the measuring points of honeycomb cores relative to the panel.

Response measurements for two building structures excited by noise from a large horizontal axis wind turbine generator

NASA Technical Reports Server (NTRS)

Hubbard, H. H.; Shepherd, K. P.

1984-01-01

Window and wall acceleration measurements and interior noise measurements ere made for two different building structures during excitation by noise from the WTS-4 horizontal axis wind turbine generator operating in a normal power generation mode. With turbine noise input pulses resulted in acceleration pulses for the wall and window elements of the two tests buildings. Response spectra suggest that natural vibration modes of the structures are excited. Responses of a house trailer were substantially greater than those for a building of sturdier construction. Peak acceleration values correlate well with similar data for houses excited by flyover noise from commercial and military airplanes and helicopters, and sonic booms from supersonic aircraft. Interior noise spectra have peaks at frequencies corresponding to structural vibration modes and room standing waves; and the levels for particular frequencies and locations can be higher than the outside levels.

Human occupants in low-speed frontal sled tests: effects of pre-impact bracing on chest compression, reaction forces, and subject acceleration.

PubMed

Kemper, Andrew R; Beeman, Stephanie M; Madigan, Michael L; Duma, Stefan M

2014-01-01

The purpose of this study was to investigate the effects of pre-impact bracing on the chest compression, reaction forces, and accelerations experienced by human occupants during low-speed frontal sled tests. A total of twenty low-speed frontal sled tests, ten low severity (∼2.5g, Δv=5 kph) and ten medium severity (∼5g, Δv=10 kph), were performed on five 50th-percentile male human volunteers. Each volunteer was exposed to two impulses at each severity, one relaxed and the other braced prior to the impulse. A 59-channel chestband, aligned at the nipple line, was used to quantify the chest contour and anterior-posterior sternum deflection. Three-axis accelerometer cubes were attached to the sternum, 7th cervical vertebra, and sacrum of each subject. In addition, three linear accelerometers and a three-axis angular rate sensor were mounted to a metal mouthpiece worn by each subject. Seatbelt tension load cells were attached to the retractor, shoulder, and lap portions of the standard three-point driver-side seatbelt. In addition, multi-axis load cells were mounted to each interface between the subject and the test buck to quantify reaction forces. For relaxed tests, the higher test severity resulted in significantly larger peak values for all resultant accelerations, all belt forces, and three resultant reaction forces (right foot, seatpan, and seatback). For braced tests, the higher test severity resulted in significantly larger peak values for all resultant accelerations, and two resultant reaction forces (right foot and seatpan). Bracing did not have a significant effect on the occupant accelerations during the low severity tests, but did result in a significant decrease in peak resultant sacrum linear acceleration during the medium severity tests. Bracing was also found to significantly reduce peak shoulder and retractor belt forces for both test severities, and peak lap belt force for the medium test severity. In contrast, bracing resulted in a significant increase in the peak resultant reaction force for the right foot and steering column at both test severities. Chest compression due to belt loading was observed for all relaxed subjects at both test severities, and was found to increase significantly with increasing severity. Conversely, chest compression due to belt loading was essentially eliminated during the braced tests for all but one subject, who sustained minor chest compression due to belt loading during the medium severity braced test. Overall, the data from this study illustrate that muscle activation has a significant effect on the biomechanical response of human occupants in low-speed frontal impacts.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Capacio, B.R.; Harris, L.W.; Anderson, D.R.

The accelerating rotarod was used to assess motor performance decrement in rats after administration of candidate anticonvulsant compounds (acetazolamide, amitriptyline, chlordiazepoxide, diazepan, diazepam-lysine, lorazepam, loprazolam, midazolam, phenobarbital and scopolamine) against nerve agent poisoning. AH compounds were tested as the commercially available injectable preparation except for diazepam-lysine and loprazolam, which are not FDA approved. A peak effect time, as well as a dose to decrease performance time by 50% from control (PDD50), was determined. The calculated PDD50 (micrometer ol/kg) values and peak effect tunes were midazolam, 1.16 at 15 min; loprazolam, 1.17 at 15 min; diazepam-lysine, 4.17 at 30 min; lorazepwn,more » 4.98 at 15 min; diazepam, 5.27 at 15 min; phenobarbital, 101.49 at 45 min; chlordiazepoxide, 159.21 at 30 min; scopolamine, amitriptyline and acetazolamide did not demonstrate a performance decrement at any of the doses tested. The PDD50 values were compared with doses which have been utilized against nerve agent-induced convulsions or published ED50 values from standard anticonvulsant screening tests (maximal electroshock MES and subcutaneous pentylenetetrazol (scMET)). I serve agents, anticonvulsants, diazepam, accelerating rotarod, motor performance.« less

RF pulse compression for future linear colliders

NASA Astrophysics Data System (ADS)

Wilson, Perry B.

1995-07-01

Future (nonsuperconducting) linear colliders will require very high values of peak rf power per meter of accelerating structure. The role of rf pulse compression in producing this power is examined within the context of overall rf system design for three future colliders at energies of 1.0-1.5 TeV, 5 TeV, and 25 TeV. In order to keep the average AC input power and the length of the accelerator within reasonable limits, a collider in the 1.0-1.5 TeV energy range will probably be built at an x-band rf frequency, and will require a peak power on the order of 150-200 MW per meter of accelerating structure. A 5 TeV collider at 34 GHz with a reasonable length (35 km) and AC input power (225 MW) would require about 550 MW per meter of structure. Two-beam accelerators can achieve peak powers of this order by applying dc pulse compression techniques (induction linac modules) to produce the drive beam. Klystron-driven colliders achieve high peak power by a combination of dc pulse compression (modulators) and rf pulse compression, with about the same overall rf system efficiency (30-40%) as a two-beam collider. A high gain (6.8) three-stage binary pulse compression system with high efficiency (80%) is described, which (compared to a SLED-II system) can be used to reduce the klystron peak power by about a factor of two, or alternatively, to cut the number of klystrons in half for a 1.0-1.5 TeV x-band collider. For a 5 TeV klystron-driven collider, a high gain, high efficiency rf pulse compression system is essential.

Assessing women's lacrosse head impacts using finite element modelling.

PubMed

Clark, J Michio; Hoshizaki, T Blaine; Gilchrist, Michael D

2018-04-01

Recently studies have assessed the ability of helmets to reduce peak linear and rotational acceleration for women's lacrosse head impacts. However, such measures have had low correlation with injury. Maximum principal strain interprets loading curves which provide better injury prediction than peak linear and rotational acceleration, especially in compliant situations which create low magnitude accelerations but long impact durations. The purpose of this study was to assess head and helmet impacts in women's lacrosse using finite element modelling. Linear and rotational acceleration loading curves from women's lacrosse impacts to a helmeted and an unhelmeted Hybrid III headform were input into the University College Dublin Brain Trauma Model. The finite element model was used to calculate maximum principal strain in the cerebrum. The results demonstrated for unhelmeted impacts, falls and ball impacts produce higher maximum principal strain values than stick and shoulder collisions. The strain values for falls and ball impacts were found to be within the range of concussion and traumatic brain injury. The results also showed that men's lacrosse helmets reduced maximum principal strain for follow-through slashing, falls and ball impacts. These findings are novel and demonstrate that for high risk events, maximum principal strain can be reduced by implementing the use of helmets if the rules of the sport do not effectively manage such situations. Copyright © 2018 Elsevier Ltd. All rights reserved.

An extended stochastic method for seismic hazard estimation

NASA Astrophysics Data System (ADS)

Abd el-aal, A. K.; El-Eraki, M. A.; Mostafa, S. I.

2015-12-01

In this contribution, we developed an extended stochastic technique for seismic hazard assessment purposes. This technique depends on the hypothesis of stochastic technique of Boore (2003) "Simulation of ground motion using the stochastic method. Appl. Geophy. 160:635-676". The essential characteristics of extended stochastic technique are to obtain and simulate ground motion in order to minimize future earthquake consequences. The first step of this technique is defining the seismic sources which mostly affect the study area. Then, the maximum expected magnitude is defined for each of these seismic sources. It is followed by estimating the ground motion using an empirical attenuation relationship. Finally, the site amplification is implemented in calculating the peak ground acceleration (PGA) at each site of interest. We tested and applied this developed technique at Cairo, Suez, Port Said, Ismailia, Zagazig and Damietta cities to predict the ground motion. Also, it is applied at Cairo, Zagazig and Damietta cities to estimate the maximum peak ground acceleration at actual soil conditions. In addition, 0.5, 1, 5, 10 and 20 % damping median response spectra are estimated using the extended stochastic simulation technique. The calculated highest acceleration values at bedrock conditions are found at Suez city with a value of 44 cm s-2. However, these acceleration values decrease towards the north of the study area to reach 14.1 cm s-2 at Damietta city. This comes in agreement with the results of previous studies of seismic hazards in northern Egypt and is found to be comparable. This work can be used for seismic risk mitigation and earthquake engineering purposes.

Equations for estimating horizontal response spectra and peak acceleration from western North American earthquakes: A summary of recent work

USGS Publications Warehouse

Boore, D.M.; Joyner, W.B.; Fumal, T.E.

1997-01-01

In this paper we summarize our recently-published work on estimating horizontal response spectra and peak acceleration for shallow earthquakes in western North America. Although none of the sets of coefficients given here for the equations are new, for the convenience of the reader and in keeping with the style of this special issue, we provide tables for estimating random horizontal-component peak acceleration and 5 percent damped pseudo-acceleration response spectra in terms of the natural, rather than common, logarithm of the ground-motion parameter. The equations give ground motion in terms of moment magnitude, distance, and site conditions for strike-slip, reverse-slip, or unspecified faulting mechanisms. Site conditions are represented by the shear velocity averaged over the upper 30 m, and recommended values of average shear velocity are given for typical rock and soil sites and for site categories used in the National Earthquake Hazards Reduction Program's recommended seismic code provisions. In addition, we stipulate more restrictive ranges of magnitude and distance for the use of our equations than in our previous publications. Finally, we provide tables of input parameters that include a few corrections to site classifications and earthquake magnitude (the corrections made a small enough difference in the ground-motion predictions that we chose not to change the coefficients of the prediction equations).

[Effect of vibrational factors on the evaluation of whole-body vibrational intensity].

PubMed

Suzuki, H

1997-12-01

The aim of this study is to obtain basic data useful to evaluate the riding comfort of railway vehicles. The apparatus used in the present experiment made it possible to simulate various vibrations of railway vehicles. Twenty-two adult subjects participated in this experiment. They were exposed to lateral vibration with varying peak and root mean square (rms) accelerations and frequencies. The types and ranges of vibrations used in this experiment approximated to the typical vibrations of railway vehicles. The subjects were asked to rate the intensity of each vibration given to them successively, using the 7-step rating scale. Results indicated that both peak and rms accelerations significantly affected for the evaluation, although the effect of frequency was not significant. As for interactions, it was found that there were significant interacting effects between frequency and peak acceleration, between frequency and rms acceleration, and between peak and rms accelerations. It was also found that the relationship between the rms acceleration and the evaluated score changed with varying peak accelerations.

Prediction of peak response values of structures with and without TMD subjected to random pedestrian flows

NASA Astrophysics Data System (ADS)

Lievens, Klaus; Van Nimmen, Katrien; Lombaert, Geert; De Roeck, Guido; Van den Broeck, Peter

2016-09-01

In civil engineering and architecture, the availability of high strength materials and advanced calculation techniques enables the construction of slender footbridges, generally highly sensitive to human-induced excitation. Due to the inherent random character of the human-induced walking load, variability on the pedestrian characteristics must be considered in the response simulation. To assess the vibration serviceability of the footbridge, the statistics of the stochastic dynamic response are evaluated by considering the instantaneous peak responses in a time range. Therefore, a large number of time windows are needed to calculate the mean value and standard deviation of the instantaneous peak values. An alternative method to evaluate the statistics is based on the standard deviation of the response and a characteristic frequency as proposed in wind engineering applications. In this paper, the accuracy of this method is evaluated for human-induced vibrations. The methods are first compared for a group of pedestrians crossing a lightly damped footbridge. Small differences of the instantaneous peak value were found by the method using second order statistics. Afterwards, a TMD tuned to reduce the peak acceleration to a comfort value, was added to the structure. The comparison between both methods in made and the accuracy is verified. It is found that the TMD parameters are tuned sufficiently and good agreements between the two methods are found for the estimation of the instantaneous peak response for a strongly damped structure.

Predicting Arrival Of Protons Emitted In Solar Flares

NASA Technical Reports Server (NTRS)

Spagnuolo, John N., Jr.; Schwuttke, Ursula M.; Han, Cecilia S.; Hervias, Felipe

1996-01-01

Visual Utility for Localization of Corona Accelerated Nuclei (VULCAN) computer program provides both advance warnings and insight for post-event analyses of effects of solar flares. Using measurements of peak fluxes, times of detection, flare location, solar wind velocities, and x-ray emissions from Sun, as electronically sent by NOAA (National Oceanographic and Atmospheric Administration), VULCAN predicts resulting intensities of proton fluxes at various user-chosen points (spacecraft or planets) of solar system. Also predicts times of onset of fluxes of protons and peak values of fluxes.

Liquefaction at Oceano, California, during the 2003 San Simeon earthquake

USGS Publications Warehouse

Holzer, T.L.; Noce, T.E.; Bennett, M.J.; Tinsley, J. C.; Rosenberg, L.I.

2005-01-01

The 2003 M 6.5 San Simeon, California, earthquake caused liquefaction-induced lateral spreading at Oceano at an unexpectedly large distance from the seismogenic rupture. We conclude that the liquefaction was caused by ground motion that was enhanced by both rupture directivity in the mainshock and local site amplification by unconsolidated fine-grained deposits. Liquefaction occurred in sandy artificial fill and undisturbed eolian sand and fluvial deposits. The largest and most damaging lateral spread was caused by liquefaction of artificial fill; the head of this lateral spread coincided with the boundary between the artificial fill and undisturbed eolian sand deposits. Values of the liquefaction potential index, in general, were greater than 5 at liquefaction sites, the threshold value that has been proposed for liquefaction hazard mapping. Although the mainshock ground motion at Oceano was not recorded, peak ground acceleration was estimated to range from 0.25 and 0.28g on the basis of the liquefaction potential index and aftershock recordings. The estimates fall within the range of peak ground acceleration values associated with the modified Mercalli intensity = VII reported at the U.S. Geological Survey (USGS) "Did You Feel It?" web site.

Scaled accelerographs for design of structures in Quetta, Baluchistan, Pakistan

NASA Astrophysics Data System (ADS)

Bhatti, Abdul Qadir

2016-12-01

Structural design for seismic excitation is usually based on peak values of forces and deformations over the duration of earthquake. In determining these peak values dynamic analysis is done which requires either response history analysis (RHA), also called time history analysis, or response spectrum analysis (RSA), both of which depend upon ground motion severity. In the past, PGA has been used to describe ground motion severity, because seismic force on a rigid body is proportional to the ground acceleration. However, it has been pointed out that single highest peak on accelerograms is a very unreliable description of the accelerograms as a whole. In this study, we are considering 0.2- and 1-s spectral acceleration. Seismic loading has been defined in terms of design spectrum and time history which will lead us to two methods of dynamic analysis. Design spectrum for Quetta will be constructed incorporating the parameters of ASCE 7-05/IBC 2006/2009, which is being used by modern codes and regulation of the world like IBC 2006/2009, ASCE 7-05, ATC-40, FEMA-356 and others. A suite of time history representing design earthquake will also be prepared, this will be a helpful tool to carryout time history dynamic analysis of structures in Quetta.

Some Key Features of the Strong-Motion Data from the M 6.0 Parkfield, California, Earthquake of 28 September 2004

USGS Publications Warehouse

Shakal, A.; Haddadi, H.; Graizer, V.; Lin, K.; Huang, M.

2006-01-01

The 2004 Parkfield, California, earthquake was recorded by an extensive set of strong-motion instruments well positioned to record details of the motion in the near-fault region, where there has previously been very little recorded data. The strong-motion measurements obtained are highly varied, with significant variations occurring over only a few kilometers. The peak accelerations in the near fault region range from 0.13g to over 1.8g (one of the highest acceleration recorded to date, exceeding the capacity of the recording instrument The largest accelerations occurred near the northwest end of the inferred rupture zone. These motions are consistent with directivity for a fault rupturing from the hypocenter near Gold Hill toward the northwest. However, accelerations up to 0.8g were also observed in the opposite direction, at the south end of the Cholame Valley near Highway 41, consistent with bilateral rupture, with rupture southeast of the hypocenter. Several stations near and over the rupturing fault recorded relatively weak motions, consistent with seemingly paradoxical observations of low shaking damage near strike-slip faults. This event had more ground-motion observations within 10 km of the fault than many other earthquakes combined. At moderate distances peak horizontal ground acceleration (PGA) values dropped off more rapidly with distance than standard relationships. At close-in distance the wide variation of PGA suggests a distance-dependent sigma may be important to consider. The near-fault ground-motion variation is greater than that assumed in ShakeMap interpolations, based on the existing set of observed data. Higher density of stations near faults may be the only means in the near future to reduce uncertainty in the interpolations. Outside of the near-fault zone the variance is closer to that assumed. This set of data provides the first case where near-fault radiation has been observed at an adequate number of stations around the fault to allow detailed study of the fault-normal and fault-parallel motion and the near-field S-wave radiation. The fault-normal motions are significant, but they are not large at the central part of the fault, away from the ends. The fault-normal and fault-parallel motions drop off quite rapidly with distance from the fault. Analysis of directivity indicates increased values of peak velocity in the rupture direction. No such dependence is observed in the peak acceleration, except for stations close to the strike of the fault near and beyond the ends of the faulting.

Peak impact accelerations during track and treadmill running.

PubMed

Bigelow, Erin M R; Elvin, Niell G; Elvin, Alex A; Arnoczky, Steven P

2013-10-01

To determine whether peak vertical and horizontal impact accelerations were different while running on a track or on a treadmill, 12 healthy subjects (average age 32.8 ± 9.8 y), were fitted with a novel, wireless accelerometer capable of recording triaxial acceleration over time. The accelerometer was attached to a custom-made acrylic plate and secured at the level of the L5 vertebra via a tight fitting triathlon belt. Each subject ran 4 miles on a synthetic, indoor track at a self-selected pace and accelerations were recorded on three perpendicular axes. Seven days later, the subjects ran 4 miles on a treadmill set at the individual runner's average pace on the track and the peak vertical and horizontal impact magnitudes between the track and treadmill were compared. There was no difference (P = .52) in the average peak vertical impact accelerations between the track and treadmill over the 4 mile run. However, peak horizontal impact accelerations were greater (P = .0012) on the track when compared with the treadmill. This study demonstrated the feasibility for long-term impact accelerations monitoring using a novel wireless accelerometer.

Theoretical z -pinch scaling relations for thermonuclear-fusion experiments.

PubMed

Stygar, W A; Cuneo, M E; Vesey, R A; Ives, H C; Mazarakis, M G; Chandler, G A; Fehl, D L; Leeper, R J; Matzen, M K; McDaniel, D H; McGurn, J S; McKenney, J L; Muron, D J; Olson, C L; Porter, J L; Ramirez, J J; Seamen, J F; Speas, C S; Spielman, R B; Struve, K W; Torres, J A; Waisman, E M; Wagoner, T C; Gilliland, T L

2005-08-01

We have developed wire-array z -pinch scaling relations for plasma-physics and inertial-confinement-fusion (ICF) experiments. The relations can be applied to the design of z -pinch accelerators for high-fusion-yield (approximately 0.4 GJ/shot) and inertial-fusion-energy (approximately 3 GJ/shot) research. We find that (delta(a)/delta(RT)) proportional (m/l)1/4 (Rgamma)(-1/2), where delta(a) is the imploding-sheath thickness of a wire-ablation-dominated pinch, delta(RT) is the sheath thickness of a Rayleigh-Taylor-dominated pinch, m is the total wire-array mass, l is the axial length of the array, R is the initial array radius, and gamma is a dimensionless functional of the shape of the current pulse that drives the pinch implosion. When the product Rgamma is held constant the sheath thickness is, at sufficiently large values of m/l, determined primarily by wire ablation. For an ablation-dominated pinch, we estimate that the peak radiated x-ray power P(r) proportional (I/tau(i))(3/2)Rlphigamma, where I is the peak pinch current, tau(i) is the pinch implosion time, and phi is a dimensionless functional of the current-pulse shape. This scaling relation is consistent with experiment when 13 MA < or = I < or = 20 MA, 93 ns < or = tau(i) < or = 169 ns, 10 mm < or = R < or = 20 mm, 10 mm < or = l < or = 20 mm, and 2.0 mg/cm < or = m/l < or = 7.3 mg/cm. Assuming an ablation-dominated pinch and that Rlphigamma is held constant, we find that the x-ray-power efficiency eta(x) congruent to P(r)/P(a) of a coupled pinch-accelerator system is proportional to (tau(i)P(r)(7/9 ))(-1), where P(a) is the peak accelerator power. The pinch current and accelerator power required to achieve a given value of P(r) are proportional to tau(i), and the requisite accelerator energy E(a) is proportional to tau2(i). These results suggest that the performance of an ablation-dominated pinch, and the efficiency of a coupled pinch-accelerator system, can be improved substantially by decreasing the implosion time tau(i). For an accelerator coupled to a double-pinch-driven hohlraum that drives the implosion of an ICF fuel capsule, we find that the accelerator power and energy required to achieve high-yield fusion scale as tau(i)0.36 and tau(i)1.36, respectively. Thus the accelerator requirements decrease as the implosion time is decreased. However, the x-ray-power and thermonuclear-yield efficiencies of such a coupled system increase with tau(i). We also find that increasing the anode-cathode gap of the pinch from 2 to 4 mm increases the requisite values of P(a) and E(a) by as much as a factor of 2.

The Auroral Field-aligned Acceleration - Cluster Results

NASA Astrophysics Data System (ADS)

Vaivads, A.; Cluster Auroral Team

The four Cluster satellites cross the auroral field lines at altitudes well above most of acceleration region. Thus, the orbit is appropriate for studies of the generator side of this region. We consider the energy transport towards the acceleration region and different mechanisms for generating the potential drop. Using data from Cluster we can also for the first time study the dynamics of the generator on a minute scale. We present data from a few auroral field crossings where Cluster are in conjunction with DMSP satellites. We use electric and magnetic field data to estimate electrostatic po- tential along the satellite orbit, Poynting flux as well as the presence of plasma waves. These we can compare with data from particle and wave instruments on Cluster and on low latitude satellites to try to make a consistent picture of the acceleration region formation in these cases. Preliminary results show close agreement both between in- tegrated potential values at Cluster and electron peak energies at DMSP as well as close agreement between the integrated Poynting flux values at Cluster and the elec- tron energy flux at DMSP. At the end we draw a parallels between auroral electron acceleration and electron acceleration at the magnetopause.

Cardiopulmonary Responses to Supine Cycling during Short-Arm Centrifugation

NASA Technical Reports Server (NTRS)

Vener, J. M.; Simonson, S. R.; Stocks, J.; Evettes, S.; Bailey, K.; Biagini, H.; Jackson, C. G. R.; Greenleaf, J. E.; Dalton, Bonnie P. (Technical Monitor)

2001-01-01

The purpose of this study was to investigate cardiopulmonary responses to supine cycling with concomitant +G(sub z) acceleration using the NASA/Ames Human Powered Short-Arm Centrifuge (HPC). Subjects were eight consenting males (32+/-5 yrs, 178+/-5 cm, 86.1+/- 6.2 kg). All subjects completed two maximal exercise tests on the HPC (with and without acceleration) within a three-day period. A two tailed t-test with statistical significance set at p less than or equal to 0.05 was used to compare treatments. Peak acceleration was 3.4+/-0.1 G(sub z), (head to foot acceleration). Peak oxygen uptake (VO2(sub peak) was not different between treatment groups (3.1+/-0.1 Lmin(exp -1) vs. 3.2+/-0.1 Lmin(exp -1) for stationary and acceleration trials, respectively). Peak HR and pulmonary minute ventilation (V(sub E(sub BTPS))) were significantly elevated (p less than or equal to 0.05) for the acceleration trial (182+/-3 BPM (Beats per Minute); 132.0+/-9.0 Lmin(exp -1)) when compared to the stationary trial (175+/-3 BPM; 115.5+/-8.5 Lmin(exp -1)). Ventilatory threshold expressed as a percent of VO2(sub peak) was not different for acceleration and stationary trials (72+/-2% vs. 68+/-2% respectively). Results suggest that 3.4 G(sub z) acceleration does not alter VO2(sub peak) response to supine cycling. However, peak HR and V(sub E(sub BTPS)) response may be increased while ventilatory threshold response expressed as a function of percent VO2(sub peak) is relatively unaffected. Thus, traditional exercise prescription based on VO2 response would be appropriate for this mode of exercise. Prescriptions based on HR response may require modification.

Optimality and oscillations near the edge of stability in the dynamics of autonomous vehicle platoons

NASA Astrophysics Data System (ADS)

Davis, L. C.

2013-09-01

A model that includes the mechanical response of a vehicle to a demanded change in acceleration is analyzed to determine the string stability of a platoon of autonomous vehicles. The response is characterized by a first-order time constant τ and an explicit delay td. The minimum value of the acceleration feedback control gain is found from calculations of the velocity of vehicles following a lead vehicle that decelerates sharply from high speed to low speed. Larger values of ξ (in the stable range) give larger values of deceleration for vehicles in the platoon. Optimal operation is attained close to the minimum value of ξ for stability. Small oscillations are found after the main peak in deceleration for ξ in the stable region but near the transition to instability. A theory for predicting the frequency and amplitude of the oscillations is presented.

Altered auditory function in rats exposed to hypergravic fields

NASA Technical Reports Server (NTRS)

Jones, T. A.; Hoffman, L.; Horowitz, J. M.

1982-01-01

The effect of an orthodynamic hypergravic field of 6 G on the brainstem auditory projections was studied in rats. The brain temperature and EEG activity were recorded in the rats during 6 G orthodynamic acceleration and auditory brainstem responses were used to monitor auditory function. Results show that all animals exhibited auditory brainstem responses which indicated impaired conduction and transmission of brainstem auditory signals during the exposure to the 6 G acceleration field. Significant increases in central conduction time were observed for peaks 3N, 4P, 4N, and 5P (N = negative, P = positive), while the absolute latency values for these same peaks were also significantly increased. It is concluded that these results, along with those for fields below 4 G (Jones and Horowitz, 1981), indicate that impaired function proceeds in a rostro-caudal progression as field strength is increased.

Pulsed electromagnetic acceleration

NASA Technical Reports Server (NTRS)

Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

1973-01-01

Direct measurements of the power deposited in the anode of a multimegawatt MPD accelerator using thermocouples attached to a thin shell anode reveal a dramatic decrease in the fractional anode power from 50% at 200 KW input power to less than 10% at 20 MW power. The corresponding local power flux peak at a value of 10,000 W/sq cm at the lip of the anode exhaust orifice, a distribution traced to a corresponding peak in the local current density at the anode. A comparison of voltage-current characteristics and spectral photographs of the MPD discharge using quartz, boron nitride and plexiglas insulators with various mass injection configurations led to the identification of different voltage modes and regions of ablation free operation. The technique of piezoelectric impact pressure measurement in the MPD exhaust flow was refined to account for the effects due to probe yaw angle.

Pulsed power accelerator for material physics experiments

DOE PAGES

Reisman, D.  B.; Stoltzfus, B.  S.; Stygar, W.  A.; ...

2015-09-01

We have developed the design of Thor: a pulsed power accelerator that delivers a precisely shaped current pulse with a peak value as high as 7 MA to a strip-line load. The peak magnetic pressure achieved within a 1-cm-wide load is as high as 100 GPa. Thor is powered by as many as 288 decoupled and transit-time isolated bricks. Each brick consists of a single switch and two capacitors connected electrically in series. The bricks can be individually triggered to achieve a high degree of current pulse tailoring. Because the accelerator is impedance matched throughout, capacitor energy is delivered tomore » the strip-line load with an efficiency as high as 50%. We used an iterative finite element method (FEM), circuit, and magnetohydrodynamic simulations to develop an optimized accelerator design. When powered by 96 bricks, Thor delivers as much as 4.1 MA to a load, and achieves peak magnetic pressures as high as 65 GPa. When powered by 288 bricks, Thor delivers as much as 6.9 MA to a load, and achieves magnetic pressures as high as 170 GPa. We have developed an algebraic calculational procedure that uses the single brick basis function to determine the brick-triggering sequence necessary to generate a highly tailored current pulse time history for shockless loading of samples. Thor will drive a wide variety of magnetically driven shockless ramp compression, shockless flyer plate, shock-ramp, equation of state, material strength, phase transition, and other advanced material physics experiments.« less

Controlling laser driven protons acceleration using a deformable mirror at a high repetition rate

NASA Astrophysics Data System (ADS)

Noaman-ul-Haq, M.; Sokollik, T.; Ahmed, H.; Braenzel, J.; Ehrentraut, L.; Mirzaie, M.; Yu, L.-L.; Sheng, Z. M.; Chen, L. M.; Schnürer, M.; Zhang, J.

2018-03-01

We present results from a proof-of-principle experiment to optimize laser driven protons acceleration by directly feeding back its spectral information to a deformable mirror (DM) controlled by evolutionary algorithms (EAs). By irradiating a stable high-repetition rate tape driven target with ultra-intense pulses of intensities ∼1020 W/ cm2, we optimize the maximum energy of the accelerated protons with a stability of less than ∼5% fluctuations near optimum value. Moreover, due to spatio-temporal development of the sheath field, modulations in the spectrum are also observed. Particularly, a prominent narrow peak is observed with a spread of ∼15% (FWHM) at low energy part of the spectrum. These results are helpful to develop high repetition rate optimization techniques required for laser-driven ion accelerators.

Emittance of positron beams produced in intense laser plasma interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Hui; Hazi, A.; Link, A.

2013-01-15

The first measurement of the emittance of intense laser-produced positron beams has been made. The emittance values were derived through measurements of positron beam divergence and source size for different peak positron energies under various laser conditions. For one of these laser conditions, we used a one dimensional pepper-pot technique to refine the emittance value. The laser-produced positrons have a geometric emittance between 100 and 500 mm{center_dot}mrad, comparable to the positron sources used at existing accelerators. With 10{sup 10}-10{sup 12} positrons per bunch, this low emittance beam, which is quasi-monoenergetic in the energy range of 5-20 MeV, may be usefulmore » as an alternative positron source for future accelerators.« less

Simulation of double stage hall thruster with double-peaked magnetic field

NASA Astrophysics Data System (ADS)

Ding, Yongjie; Li, Peng; Sun, Hezhi; Wei, Liqiu; Xu, Yu; Peng, Wuji; Su, Hongbo; Li, Hong; Yu, Daren

2017-07-01

This study adopts double permanent magnetic rings and four permanent magnetic rings to form two symmetrical magnetic peaks and two asymmetrical magnetic peaks in the channel of a Hall thruster, and uses a 2D-3V PIC-MCC model to analyze the influence of magnetic strength on the discharge characteristic and performance of Hall thrusters with an intermediate electrode and double-peaked magnetic field. As opposed to the two symmetrical magnetic peaks formed by double permanent magnetic rings, increasing the magnetic peak value deep within the channel can cause propellant ionization to occur; with the increase in the magnetic peak deep in the channel, the propellant utilization, thrust, and anode efficiency of the thruster are significantly improved. Double-peaked magnetic field can realize separate control of ionization and acceleration in a Hall thruster, and provide technical means for further improving thruster performance. Contribution to the Topical Issue "Physics of Ion Beam Sources", edited by Holger Kersten and Horst Neumann.

Ground-motion parameters of the southwestern Indiana earthquake of 18 June 2002 and the disparity between the observed and predicted values

USGS Publications Warehouse

Street, R.; Wiegand, J.; Woolery, E.W.; Hart, P.

2005-01-01

The M 4.5 southwestern Indiana earthquake of 18 June 2002 triggered 46 blast monitors in Indiana, Illinois, and Kentucky. The resulting free-field particle velocity records, along with similar data from previous earthquakes in the study area, provide a clear standard for judging the reliability of current maps for predicting ground motions greater than 2 Hz in southwestern Indiana and southeastern Illinois. Peak horizontal accelerations and velocities, and 5% damped pseudo-accelerations for the earthquake, generally exceeded ground motions predicted for the top of the bedrock by factors of 2 or more, even after soil amplifications were taken into consideration. It is suggested, but not proven, that the low shear-wave velocity and weathered bedrock in the area are also amplifying the higher-frequency ground motions that have been repeatedly recorded by the blast monitors in the study area. It is also shown that there is a good correlation between the peak ground motions and 5% pseudo-accelerations recorded for the event, and the Modified Mercalli intensities interpreted for the event by the U.S. Geological Survey.

Injury Prevention in Aircraft Crashes: Investigative Techniques and Applications (la Prevention des lesions lors des accidents d’ avions: les techniques d’investigation et leurs applications)

DTIC Science & Technology

1998-02-01

provide the aircrew and passengers with a level of protection commensurate with the risk of operating aircraft in the military and civilian...the time taken to reach peak acceleration and upon the peak acceleration level attained. Long duration acceleration, which can be experienced in...acceleration depends principally on the plateau level of the acceleration imposed on the body, as the response to long duration acceleration is due

Pics d'accélération du mouvement sismique observés lors du séisme de Chichi à Taiwan : application à l'estimation de l'aléa sismiqueAnalysis of peak ground accelerations during the Chichi earthquake, Taiwan: application to seismic hazard evaluation

NASA Astrophysics Data System (ADS)

Chang, Tsui-Yu; Cotton, Fabrice; Angelier, Jacques; Shin, Tzay-Chyn

2001-07-01

Attenuation laws are widely used in order to estimate the peak ground acceleration that may occur at a given locality during an earthquake, for hazard evaluation purposes. However, these simplified laws should be regarded acceptable only in the first approximation, because numerous significant parameters at the local and regional scales are often ignored. We examined the relationship between distance and peak acceleration based on examples from the dense accelerometric network of Taiwan, specifically for the Chichi destructive earthquake. We thus observed significant discrepancies between the predicted and observed accelerations, resulting from (1) near-field saturation, (2) amplification in sedimentary basins, and (3) hanging wall effect. We mapped the residual accelerations (difference between observed and predicted peak ground accelerations). This highlights the role of the regional structure, independently revealed by the geological analysis, as a significant factor that controls the transmission of the seismic accelerations.

Biomechanical changes in the head associated with penetrating injuries of the maxilla and mandible: an experimental investigation.

PubMed

Tan, Yinghui; Zhou, Shuxia; Jiang, Hetian

2002-05-01

In this experiment, we studied the craniocerebral injury that occurs due to the transmission of forces when maxillofacial gunshot wounds are sustained by the facial bones and cranium. Forty fresh pigs' heads were wounded by one of the following methods: steel spheres weighing 1.03 g at an impact velocity of 1,400 m/s, steel spheres weighing 1.03 g at an impact velocity of 800 m/s, M193 military bullets, or M56 military bullets. Pressure waves in the brain, acceleration of the head, and stress changes in the facial bones and cranium at the moment of the impact were recorded by pressure and acceleration transducers and strain gauges and were statistically compared. Some obvious differences between the mechanical values obtained from high-and low-velocity missile wounds were found. A negative relationship between the peak value of the pressure wave in the brain and the distance from the point of impact to the transducer was obtained. The acceleration of the head in the direction of the ballistic path was the strongest in absolute value. There were differences in the stress values between the mandible and the temporal bone. Acceleration of the head, pressure wave changes in the brain, and injury from bony stress conduction all play important roles in associated craniocerebral damage after maxillofacial firearm wounds. Copyright 2002 American Association of Oral and Maxillofacial Surgeons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, John

This project aims to understand the characteristics of the free-field strong-motion records that have yielded the 100 largest peak accelerations and the 100 largest peak velocities recorded to date. The peak is defined as the maximum magnitude of the acceleration or velocity vector during the strong shaking. This compilation includes 35 records with peak acceleration greater than gravity, and 41 records with peak velocities greater than 100 cm/s. The results represent an estimated 150,000 instrument-years of strong-motion recordings. The mean horizontal acceleration or velocity, as used for the NGA ground motion models, is typically 0.76 times the magnitude of thismore » vector peak. Accelerations in the top 100 come from earthquakes as small as magnitude 5, while velocities in the top 100 all come from earthquakes with magnitude 6 or larger. Records are dominated by crustal earthquakes with thrust, oblique-thrust, or strike-slip mechanisms. Normal faulting mechanisms in crustal earthquakes constitute under 5% of the records in the databases searched, and an even smaller percentage of the exceptional records. All NEHRP site categories have contributed exceptional records, in proportions similar to the extent that they are represented in the larger database.« less

Landing Characteristics of a Reentry Capsule with a Torus-Shaped Air Bag for Load Alleviation

NASA Technical Reports Server (NTRS)

McGehee, John R.; Hathaway, Melvin E.

1960-01-01

An experimental investigation has been made to determine the landing characteristics of a conical-shaped reentry capsule by using torus-shaped air bags for impact-load alleviation. An impact bag was attached below the large end of the capsule to absorb initial impact loads and a second bag was attached around the canister to absorb loads resulting from impact on the canister when the capsule overturned. A 1/6-scale dynamic model of the configuration was tested for nominal flight paths of 60 deg. and 90 deg. (vertical), a range of contact attitudes from -25 deg. to 30 deg., and a vertical contact velocity of 12.25 feet per second. Accelerations were measured along the X-axis (roll) and Z-axis (yaw) by accelerometers rigidly installed at the center of gravity of the model. Actual flight path, contact attitudes, and motions were determined from high-speed motion pictures. Landings were made on concrete and on water. The peak accelerations along the X-axis for landings on concrete were in the order of 3Og for a 0 deg. contact attitude. A horizontal velocity of 7 feet per second, corresponding to a flight path of 60 deg., had very little effect upon the peak accelerations obtained for landings on concrete. For contact attitudes of -25 deg. and 30 deg. the peak accelerations along the Z-axis were about +/- l5g, respectively. The peak accelerations measured for the water landings were about one-third lower than the peak accelerations measured for the landings on concrete. Assuming a rigid body, computations were made by using Newton's second law of motion and the force-stroke characteristics of the air bag to determine accelerations for a flight path of 90 deg. (vertical) and a contact attitude of 0 deg. The computed and experimental peak accelerations and strokes at peak acceleration were in good agreement for the model. The special scaling appears to be applicable for predicting full-scale time and stroke at peak acceleration for a landing on concrete from a 90 deg. flight path at a 0 deg. It appears that the full-scale approximately the same as those obtained from the model for the range of attitudes and flight paths investigated.

Precise measurement of energy of the first excited state of 115Sn (Eexc ≃ 497.3 keV)

NASA Astrophysics Data System (ADS)

Zheltonozhsky, V. A.; Savrasov, A. M.; Strilchuk, N. V.; Tretyak, V. I.

2018-01-01

Single beta decay of 115In to the first excited level of 115Sn (E\\text{exc}≃ 497.3 \\text{keV} ) is known as β-decay with the lowest Qβ value. To determine the Qβ precisely, one has to measure very accurately the E\\text{exc} value. A sample of tin enriched in 115Sn to 50.7% was irradiated by a proton beam at the U-120 accelerator of INR, Kyiv. The 115Sb radioactive isotope, created in the 115Sn(p,n)115Sb reaction, decays with T1/2 = 32 \\text{min} to 115Sn populating the 497 keV level with ≃ 96{%} probability. The total statistics of ˜105 counts collected in the 497 keV peak in a series of measurements, the exact description of the peak shape and the precisely known calibration points around the 497 keV peak allowed to obtain the value E\\text{exc}= 497.342(3) \\text{keV} , which is the most precise to-date. This leads to the following Qβ\\ast value for the decay 115In → 115Sn*: Qβ\\ast= 147 +/- 10 \\text{eV} .

Tibial Acceleration and Spatiotemporal Mechanics in Distance Runners During Reduced-Body-Weight Conditions.

PubMed

Moran, Matthew F; Rickert, Brendan J; Greer, Beau K

2017-05-01

Treadmills that unload runners via a differential air-pressure (DAP) bladder (eg, AlterG Anti-Gravity Treadmill) are commonly used to reduce effective body weight (BW) in a clinical setting. However, the relationship between the level of unloading and tibial stress is currently unknown. To determine the relationship between tibial impact acceleration and level of BW unloading during running. Cross-sectional. University motion-analysis laboratory. 15 distance runners (9 male, 6 female; 20.4 ± 2.4 y, 60.1 ± 12.6 kg). Peak tibial acceleration and peak-to-peak tibial acceleration were measured via a uniaxial accelerometer attached to the tibia during a 37-min continuous treadmill run that simulated reduced-BW conditions via a DAP bladder. The trial began with a 10-min run at 100% BW followed by nine 3-min stages where BW was systematically reduced from 95% to 60% in 5% increments. There was no significant relationship between level of BW and either peak tibial acceleration or peak-to-peak tibial acceleration (P > .05). Both heart rate and step rate were significantly reduced with each 5% reduction in BW level (P < .01). Although ground-reaction forces are reduced when running in reduced-BW conditions on a DAP treadmill, tibial shock magnitudes are unchanged as an alteration in spatiotemporal running mechanics (eg, reduced step rate) and may nullify the unloading effect.

Three-dimensional evaluation of postural stability in Parkinson's disease with mobile technology.

PubMed

Ozinga, Sarah J; Koop, Mandy Miller; Linder, Susan M; Machado, Andre G; Dey, Tanujit; Alberts, Jay L

2017-01-01

Postural instability is a hallmark of Parkinson's disease. Objective metrics to characterize postural stability are necessary for the development of treatment algorithms to aid in the clinical setting. The aim of this project was to validate a mobile device platform and resultant three-dimensional balance metric that characterizes postural stability. A mobile Application was developed, in which biomechanical data from inertial sensors within a mobile device were processed to characterize movement of center of mass in the medial-lateral, anterior-posterior and trunk rotation directions. Twenty-seven individuals with Parkinson's disease and 27 age-matched controls completed various balance tasks. A postural stability metric quantifying the amplitude (peak-to-peak) of sway acceleration in each movement direction was compared between groups. The peak-to-peak value in each direction for each individual with Parkinson's disease across all trials was expressed as a normalized value of the control data to identify individuals with severe postural instability, termed Cleveland Clinic-Postural Stability Index. In all conditions, the balance metric for peak-to-peak was significantly greater in Parkinson's disease compared to controls (p < 0.01 for all tests). The balance metric, in conjunction with mobile device sensors, provides a rapid and systematic metric for quantifying postural stability in Parkinson's disease.

Lower Arm Muscle Activation during Indirect-Localized Vibration: The Influence of Skill Levels When Applying Different Acceleration Loads.

PubMed

Padulo, Johnny; Di Giminiani, Riccardo; Dello Iacono, Antonio; Zagatto, Alessandro M; Migliaccio, Gian M; Grgantov, Zoran; Ardigò, Luca P

2016-01-01

We investigated the electromyographic response to synchronous indirect-localized vibration interventions in international and national table tennis players. Twenty-six male table tennis players, in a standing position, underwent firstly an upper arms maximal voluntary contraction and thereafter two different 30-s vibration interventions in random order: high acceleration load (peak acceleration = 12.8 g, frequency = 40 Hz; peak-to-peak displacement = 4.0 mm), and low acceleration load (peak acceleration = 7.2 g, frequency = 30 Hz, peak-to-peak displacement = 4.0 mm). Surface electromyography root mean square from brachioradialis, extensor digitorum, flexor carpi radialis, and flexor digitorum superficialis recorded during the two vibration interventions was normalized to the maximal voluntary contraction recording. Normalized surface electromyography root mean square was higher in international table tennis players with respect to national ones in all the interactions between muscles and vibration conditions (P < 0.05), with the exception of flexor carpi radialis (at low acceleration load, P > 0.05). The difference in normalized surface electromyography root mean square between international table tennis players and national ones increased in all the muscles with high acceleration load (P < 0.05), with the exception of flexor digitorum superficialis (P > 0.05). The muscle activation during indirect-localized vibration seems to be both skill level and muscle dependent. These results can optimize the training intervention in table tennis players when applying indirect-localized vibration to lower arm muscles. Future investigations should discriminate between middle- and long-term adaptations in response to specific vibration loads.

Lower Arm Muscle Activation during Indirect-Localized Vibration: The Influence of Skill Levels When Applying Different Acceleration Loads

PubMed Central

Padulo, Johnny; Di Giminiani, Riccardo; Dello Iacono, Antonio; Zagatto, Alessandro M.; Migliaccio, Gian M.; Grgantov, Zoran; Ardigò, Luca P.

2016-01-01

We investigated the electromyographic response to synchronous indirect-localized vibration interventions in international and national table tennis players. Twenty-six male table tennis players, in a standing position, underwent firstly an upper arms maximal voluntary contraction and thereafter two different 30-s vibration interventions in random order: high acceleration load (peak acceleration = 12.8 g, frequency = 40 Hz; peak-to-peak displacement = 4.0 mm), and low acceleration load (peak acceleration = 7.2 g, frequency = 30 Hz, peak-to-peak displacement = 4.0 mm). Surface electromyography root mean square from brachioradialis, extensor digitorum, flexor carpi radialis, and flexor digitorum superficialis recorded during the two vibration interventions was normalized to the maximal voluntary contraction recording. Normalized surface electromyography root mean square was higher in international table tennis players with respect to national ones in all the interactions between muscles and vibration conditions (P < 0.05), with the exception of flexor carpi radialis (at low acceleration load, P > 0.05). The difference in normalized surface electromyography root mean square between international table tennis players and national ones increased in all the muscles with high acceleration load (P < 0.05), with the exception of flexor digitorum superficialis (P > 0.05). The muscle activation during indirect-localized vibration seems to be both skill level and muscle dependent. These results can optimize the training intervention in table tennis players when applying indirect-localized vibration to lower arm muscles. Future investigations should discriminate between middle- and long-term adaptations in response to specific vibration loads. PMID:27378948

On baseline corrections and uncertainty in response spectrafor baseline variations commonly encountered in digital accelerograph records

USGS Publications Warehouse

Akkar, Sinan; Boore, David M.

2009-01-01

Most digital accelerograph recordings are plagued by long-period drifts, best seen in the velocity and displacement time series obtained from integration of the acceleration time series. These drifts often result in velocity values that are nonzero near the end of the record. This is clearly unphysical and can lead to inaccurate estimates of peak ground displacement and long-period spectral response. The source of the long-period noise seems to be variations in the acceleration baseline in many cases. These variations could be due to true ground motion (tilting and rotation, as well as local permanent ground deformation), instrumental effects, or analog-to-digital conversion. Very often the trends in velocity are well approximated by a linear trend after the strong shaking subsides. The linearity of the trend in velocity implies that no variations in the baseline could have occurred after the onset of linearity in the velocity time series. This observation, combined with the lack of any trends in the pre-event motion, allows us to compute the time interval in which any baseline variations could occur. We then use several models of the variations in a Monte Carlo procedure to derive a suite of baseline-corrected accelerations for each noise model using records from the 1999 Chi-Chi earthquake and several earthquakes in Turkey. Comparisons of the mean values of the peak ground displacements, spectral displacements, and residual displacements computed from these corrected accelerations for the different noise models can be used as a guide to the accuracy of the baseline corrections. For many of the records considered here the mean values are similar for each noise model, giving confidence in the estimation of the mean values. The dispersion of the ground-motion measures increases with period and is noise-model dependent. The dispersion of inelastic spectra is greater than the elastic spectra at short periods but approaches that of the elastic spectra at longer periods. The elastic spectra from the most basic processing, in which only the pre-event mean is removed from the acceleration time series, do not diverge from the baseline-corrected spectra until periods of 10-20 sec or more for the records studied here, implying that for many engineering purposes elastic spectra can be used from records with no baseline correction or filtering.

Performances of the Alpha-X RF gun on the PHIL accelerator at LAL

NASA Astrophysics Data System (ADS)

Vinatier, T.; Bruni, C.; Roux, R.; Brossard, J.; Chancé, S.; Cayla, J. N.; Chaumat, V.; Xu, G.; Monard, H.

2015-10-01

The Alpha-X RF-gun was designed to produce an ultra-short (<100 fs rms), 100 pC and 6.3 MeV electron beam with a normalized rms transverse emittance of 1π mm mrad for a gun peak accelerating field of 100 MV/m. Such beams will be required by the Alpha-X project, which aims to study a laser-driven plasma accelerator with a short wavelength accelerating medium. It has been demonstrated on PHIL (Photo-Injector at LAL) that the coaxial RF coupling, chosen to preserve the gun field cylindrical symmetry, is perfectly understood and allows reaching the required peak accelerating field of 100 MV/m giving beam energy of 6.3 MeV. Moreover, a quite low beam rms relative energy spread of 0.15% at 3.8 MeV has been measured, completely agreeing with simulations. Dark current, quantum efficiencies and dephasing curves measurements have also been performed. They all show high values of the field enhancement factor β, which can be explained by the preparation of the photocathodes. Finally, measurements on the transverse phase-space have been carried out, with some limitations given by the difficult modelization of one of the PHIL solenoid magnets and by the enlargement of the beam transverse dimensions due to the use of YAG screens. These measurements give a normalized rms transverse emittance around 5π mm mrad, which does not fulfill the requirement for the Alpha-X project.

Injury Risk Functions in Frontal Impacts Using Data from Crash Pulse Recorders

PubMed Central

Stigson, Helena; Kullgren, Anders; Rosén, Erik

2012-01-01

Knowledge of how crash severity influences injury risk in car crashes is essential in order to create a safe road transport system. Analyses of real-world crashes increase the ability to obtain such knowledge. The aim of this study was to present injury risk functions based on real-world frontal crashes where crash severity was measured with on-board crash pulse recorders. Results from 489 frontal car crashes (26 models of four car makes) with recorded acceleration-time history were analysed. Injury risk functions for restrained front seat occupants were generated for maximum AIS value of two or greater (MAIS2+) using multiple logistic regression. Analytical as well as empirical injury risk was plotted for several crash severity parameters; change of velocity, mean acceleration and peak acceleration. In addition to crash severity, the influence of occupant age and gender was investigated. A strong dependence between injury risk and crash severity was found. The risk curves reflect that small changes in crash severity may have a considerable influence on the risk of injury. Mean acceleration, followed by change of velocity, was found to be the single variable that best explained the risk of being injured (MAIS2+) in a crash. Furthermore, all three crash severity parameters were found to predict injury better than age and gender. However, age was an important factor. The very best model describing MAIS2+ injury risk included delta V supplemented by an interaction term of peak acceleration and age. PMID:23169136

Influence of Spatial Variation in Ground Motion Peak Acceleration on Local Site Effects Estimation at Bucovina Seismic Array (BURAR) Romania

NASA Astrophysics Data System (ADS)

Ghica, D. V.; Radulian, M.; Popa, M.; Grecu, B.

2006-05-01

Basically, array processing techniques require a high signal coherency across the seismic site; therefore the local crustal velocities below the station, signal amplitude differences between array elements and local noise conditions, resulting in local site effects will affect calculation of phase arrival times, propagation velocities and ground motion amplitudes. In general, array techniques assume a homogenous structure for all sites, and a simple relief correction is taking in account for the data analysis. To increase the results accuracy, individual element corrections must be applied, based on the biases factors systematically observed. This study aims at identifying the anomalous amplitude variations recorded at the Bucovina Seismic Array (BURAR) and at explaining their influence on site effects estimation. Maximum amplitudes for the teleseismic and regional phases in four narrow frequency bands (0.25-0.5Hz; 0.5-1Hz; 1-2Hz; 1.5-3Hz) are measured. Spatial distribution of ground motion peak acceleration in BURAR site, for each band, is plotted; a different behavior was observed at frequencies below 2Hz. The most important aspect observed is the largest amplitude exhibited by BUR07 across the whole array at high frequencies (an amplification factor of about two). This can be explained by the different geology at BUR07 site (mica schist outcrops), comparing with the rest of elements (green schist outcrops). At the lowest frequencies (0.25-0.5Hz), BUR09 peak amplitudes dominate the other sites. Considering BUR07 as reference site, peak acceleration ratios were investigated. The largest scattering of these ratios appears at the highest frequencies (1.5-3Hz), when the weight of over unit values is about 90 %. No azimuth and distance dependence was found for these effects, suggesting the absence of the dipping layer structures. Although an increase of the ratio values is noticed for epicentral distance between 8000 and 10000 km, for frequencies over 1 Hz. The results of this study are essential to further develop the calibration technique for seismic monitoring with BURAR array, in order to improve the detection and single-array location capabilities of the system.

Hoof accelerations and ground reaction forces of Thoroughbred racehorses measured on dirt, synthetic, and turf track surfaces.

PubMed

Setterbo, Jacob J; Garcia, Tanya C; Campbell, Ian P; Reese, Jennifer L; Morgan, Jessica M; Kim, Sun Y; Hubbard, Mont; Stover, Susan M

2009-10-01

To compare hoof acceleration and ground reaction force (GRF) data among dirt, synthetic, and turf surfaces in Thoroughbred racehorses. 3 healthy Thoroughbred racehorses. Forelimb hoof accelerations and GRFs were measured with an accelerometer and a dynamometric horseshoe during trot and canter on dirt, synthetic, and turf track surfaces at a racecourse. Maxima, minima, temporal components, and a measure of vibration were extracted from the data. Acceleration and GRF variables were compared statistically among surfaces. The synthetic surface often had the lowest peak accelerations, mean vibration, and peak GRFs. Peak acceleration during hoof landing was significantly smaller for the synthetic surface (mean + or - SE, 28.5g + or - 2.9g) than for the turf surface (42.9g + or - 3.8g). Hoof vibrations during hoof landing for the synthetic surface were < 70% of those for the dirt and turf surfaces. Peak GRF for the synthetic surface (11.5 + or - 0.4 N/kg) was 83% and 71% of those for the dirt (13.8 + or - 0.3 N/kg) and turf surfaces (16.1 + or - 0.7 N/kg), respectively. The relatively low hoof accelerations, vibrations, and peak GRFs associated with the synthetic surface evaluated in the present study indicated that synthetic surfaces have potential for injury reduction in Thoroughbred racehorses. However, because of the unique material properties and different nature of individual dirt, synthetic, and turf racetrack surfaces, extending the results of this study to encompass all track surfaces should be done with caution.

A High Peak Current Source for the CEBAF Injector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yunn, Byung; Sinclair, Charles; Krafft, Geoffrey

1992-07-01

The CEBAF accelerator can drive high power IR and UV FELs, if a high peak current source is added to the existing front end. We present a design for a high peak current injector which is compatible with simultaneous operation of the accelerator for cw nulear physics (NP) beam. The high peak current injector provides 60 A peak current in 2 psec long bunches carrying 120 pC charge at 7.485 MHz. At 10 MeV that beam is combined with 5 MeV NP beam (0.13pC, 2 psec long bunches at 1497 MHz) in an energy combination chicane for simultaneous acceleration inmore » the injector linac. The modifications to the low-energy NP transport are described. Results of optical and beam dynamics calculations for both high peak current and NP beams in combined operation are presented.« less

Collimated electron beam accelerated at 12 kV from a Penning discharge.

PubMed

Toader, D; Oane, M; Ticoş, C M

2015-01-01

A pulsed electron beam accelerated at 12 kV with a duration of 40 μs per pulse is obtained from a Penning discharge with a hollow anode and two cathodes. The electrons are extracted through a hole in one of the cathodes and focused by a pair of coils. The electron beam has a diameter of a few mm in the cross section, while the beam current reaches peak values of 400 mA, depending on the magnetic field inside the focussing coils. This relatively inexpensive and compact device is suitable for the irradiation of small material samples placed in high vacuum.

Particle Acceleration by Cme-driven Shock Waves

NASA Technical Reports Server (NTRS)

Reames, Donald V.

1999-01-01

In the largest solar energetic particle (SEP) events, acceleration occurs at shock waves driven out from the Sun by coronal mass ejections (CMEs). Peak particle intensities are a strong function of CME speed, although the intensities, spectra, and angular distributions of particles escaping the shock are highly modified by scattering on Alfven waves produced by the streaming particles themselves. Element abundances vary in complex ways because ions with different values of Q/A resonate with different parts of the wave spectrum, which varies with space and time. Just recently, we have begun to model these systematic variations theoretically and to explore other consequences of proton-generated waves.

Wave-function-renormalization effects in resonantly enhanced tunneling

NASA Astrophysics Data System (ADS)

Lörch, N.; Pepe, F. V.; Lignier, H.; Ciampini, D.; Mannella, R.; Morsch, O.; Arimondo, E.; Facchi, P.; Florio, G.; Pascazio, S.; Wimberger, S.

2012-05-01

We study the time evolution of ultracold atoms in an accelerated optical lattice. For a Bose-Einstein condensate with a narrow quasimomentum distribution in a shallow optical lattice the decay of the survival probability in the ground band has a steplike structure. In this regime we establish a connection between the wave-function-renormalization parameter Z introduced by P. Facchi, H. Nakazato, and S. Pascazio [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.86.2699 86, 2699 (2001)] to characterize nonexponential decay and the phenomenon of resonantly enhanced tunneling, where the decay rate is peaked for particular values of the lattice depth and the accelerating force.

MO-F-16A-02: Simulation of a Medical Linear Accelerator for Teaching Purposes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlone, M; Lamey, M; Anderson, R

Purpose: Detailed functioning of linear accelerator physics is well known. Less well developed is the basic understanding of how the adjustment of the linear accelerator's electrical components affects the resulting radiation beam. Other than the text by Karzmark, there is very little literature devoted to the practical understanding of linear accelerator functionality targeted at the radiotherapy clinic level. The purpose of this work is to describe a simulation environment for medical linear accelerators with the purpose of teaching linear accelerator physics. Methods: Varian type lineacs were simulated. Klystron saturation and peak output were modelled analytically. The energy gain of anmore » electron beam was modelled using load line expressions. The bending magnet was assumed to be a perfect solenoid whose pass through energy varied linearly with solenoid current. The dose rate calculated at depth in water was assumed to be a simple function of the target's beam current. The flattening filter was modelled as an attenuator with conical shape, and the time-averaged dose rate at a depth in water was determined by calculating kerma. Results: Fifteen analytical models were combined into a single model called SIMAC. Performance was verified systematically by adjusting typical linac control parameters. Increasing klystron pulse voltage increased dose rate to a peak, which then decreased as the beam energy was further increased due to the fixed pass through energy of the bending magnet. Increasing accelerator beam current leads to a higher dose per pulse. However, the energy of the electron beam decreases due to beam loading and so the dose rate eventually maximizes and the decreases as beam current was further increased. Conclusion: SIMAC can realistically simulate the functionality of a linear accelerator. It is expected to have value as a teaching tool for both medical physicists and linear accelerator service personnel.« less

Review of Seismic Hazard Issues Associated with Auburn Dam Project, Sierra Nevada Foothills, California

USGS Publications Warehouse

Schwartz, D.P.; Joyner, W.B.; Stein, R.S.; Brown, R.D.; McGarr, A.F.; Hickman, S.H.; Bakun, W.H.

1996-01-01

Summary -- The U.S. Geological Survey was requested by the U.S. Department of the Interior to review the design values and the issue of reservoir-induced seismicity for a concrete gravity dam near the site of the previously-proposed Auburn Dam in the western foothills of the Sierra Nevada, central California. The dam is being planned as a flood-control-only dam with the possibility of conversion to a permanent water-storage facility. As a basis for planning studies the U.S. Army Corps of Engineers is using the same design values approved by the Secretary of the Interior in 1979 for the original Auburn Dam. These values were a maximum displacement of 9 inches on a fault intersecting the dam foundation, a maximum earthquake at the site of magnitude 6.5, a peak horizontal acceleration of 0.64 g, and a peak vertical acceleration of 0.39 g. In light of geological and seismological investigations conducted in the western Sierran foothills since 1979 and advances in the understanding of how earthquakes are caused and how faults behave, we have developed the following conclusions and recommendations: Maximum Displacement. Neither the pre-1979 nor the recent observations of faults in the Sierran foothills precisely define the maximum displacement per event on a fault intersecting the dam foundation. Available field data and our current understanding of surface faulting indicate a range of values for the maximum displacement. This may require the consideration of a design value larger than 9 inches. We recommend reevaluation of the design displacement using current seismic hazard methods that incorporate uncertainty into the estimate of this design value. Maximum Earthquake Magnitude. There are no data to indicate that a significant change is necessary in the use of an M 6.5 maximum earthquake to estimate design ground motions at the dam site. However, there is a basis for estimating a range of maximum magnitudes using recent field information and new statistical fault relations. We recommend reevaluating the maximum earthquake magnitude using current seismic hazard methodology. Design Ground Motions. A large number of strong-motion records have been acquired and significant advances in understanding of ground motion have been achieved since the original evaluations. The design value for peak horizontal acceleration (0.64 g) is larger than the median of one recent study and smaller than the median value of another. The value for peak vertical acceleration (0.39 g) is somewhat smaller than median values of two recent studies. We recommend a reevaluation of the design ground motions that takes into account new ground motion data with particular attention to rock sites at small source distances. Reservoir-Induced Seismicity. The potential for reservoir-induced seismicity must be considered for the Auburn Darn project. A reservoir-induced earthquake is not expected to be larger than the maximum naturally occurring earthquake. However, the probability of an earthquake may be enhanced by reservoir impoundment. A flood-control-only project may involve a lower probability of significant induced seismicity than a multipurpose water-storage dam. There is a need to better understand and quantify the likelihood of this hazard. A methodology should be developed to quantify the potential for reservoir induced seismicity using seismicity data from the Sierran foothills, new worldwide observations of induced and triggered seismicity, and current understanding of the earthquake process. Reevaluation of Design Parameters. The reevaluation of the maximum displacement, maximum magnitude earthquake, and design ground motions can be made using available field observations from the Sierran foothills, updated statistical relations for faulting and ground motions, and current computational seismic hazard methodologies that incorporate uncertainty into the analysis. The reevaluation does not require significant new geological field studies.

Measuring saccade peak velocity using a low-frequency sampling rate of 50 Hz.

PubMed

Wierts, Roel; Janssen, Maurice J A; Kingma, Herman

2008-12-01

During the last decades, small head-mounted video eye trackers have been developed in order to record eye movements. Real-time systems-with a low sampling frequency of 50/60 Hz-are used for clinical vestibular practice, but are generally considered not to be suited for measuring fast eye movements. In this paper, it is shown that saccadic eye movements, having an amplitude of at least 5 degrees, can, in good approximation, be considered to be bandwidth limited up to a frequency of 25-30 Hz. Using the Nyquist theorem to reconstruct saccadic eye movement signals at higher temporal resolutions, it is shown that accurate values for saccade peak velocities, recorded at 50 Hz, can be obtained, but saccade peak accelerations and decelerations cannot. In conclusion, video eye trackers sampling at 50/60 Hz are appropriate for detecting the clinical relevant saccade peak velocities in contrast to what has been stated up till now.

Seismic hazard assessment for Guam and the Northern Mariana Islands

USGS Publications Warehouse

Mueller, Charles S.; Haller, Kathleen M.; Luco, Nicholas; Petersen, Mark D.; Frankel, Arthur D.

2012-01-01

We present the results of a new probabilistic seismic hazard assessment for Guam and the Northern Mariana Islands. The Mariana island arc has formed in response to northwestward subduction of the Pacific plate beneath the Philippine Sea plate, and this process controls seismic activity in the region. Historical seismicity, the Mariana megathrust, and two crustal faults on Guam were modeled as seismic sources, and ground motions were estimated by using published relations for a firm-rock site condition. Maps of peak ground acceleration, 0.2-second spectral acceleration for 5 percent critical damping, and 1.0-second spectral acceleration for 5 percent critical damping were computed for exceedance probabilities of 2 percent and 10 percent in 50 years. For 2 percent probability of exceedance in 50 years, probabilistic peak ground acceleration is 0.94 gravitational acceleration at Guam and 0.57 gravitational acceleration at Saipan, 0.2-second spectral acceleration is 2.86 gravitational acceleration at Guam and 1.75 gravitational acceleration at Saipan, and 1.0-second spectral acceleration is 0.61 gravitational acceleration at Guam and 0.37 gravitational acceleration at Saipan. For 10 percent probability of exceedance in 50 years, probabilistic peak ground acceleration is 0.49 gravitational acceleration at Guam and 0.29 gravitational acceleration at Saipan, 0.2-second spectral acceleration is 1.43 gravitational acceleration at Guam and 0.83 gravitational acceleration at Saipan, and 1.0-second spectral acceleration is 0.30 gravitational acceleration at Guam and 0.18 gravitational acceleration at Saipan. The dominant hazard source at the islands is upper Benioff-zone seismicity (depth 40–160 kilometers). The large probabilistic ground motions reflect the strong concentrations of this activity below the arc, especially near Guam.

Seismic design parameters - A user guide

USGS Publications Warehouse

Leyendecker, E.V.; Frankel, A.D.; Rukstales, K.S.

2001-01-01

The 1997 NEHRP Recommended Provisions for Seismic Regulations for New Buildings (1997 NEHRP Provisions) introduced seismic design procedure that is based on the explicit use of spectral response acceleration rather than the traditional peak ground acceleration and/or peak ground velocity or zone factors. The spectral response accelerations are obtained from spectral response acceleration maps accompanying the report. Maps are available for the United States and a number of U.S. territories. Since 1997 additional codes and standards have also adopted seismic design approaches based on the same procedure used in the NEHRP Provisions and the accompanying maps. The design documents using the 1997 NEHRP Provisions procedure may be divided into three categories -(1) Design of New Construction, (2) Design and Evaluation of Existing Construction, and (3) Design of Residential Construction. A CD-ROM has been prepared for use in conjunction with the design documents in each of these three categories. The spectral accelerations obtained using the software on the CD are the same as those that would be obtained by using the maps accompanying the design documents. The software has been prepared to operate on a personal computer using a Windows (Microsoft Corporation) operating environment and a point and click type of interface. The user can obtain the spectral acceleration values that would be obtained by use of the maps accompanying the design documents, include site factors appropriate for the Site Class provided by the user, calculate a response spectrum that includes the site factor, and plot a response spectrum. Sites may be located by providing the latitude-longitude or zip code for all areas covered by the maps. All of the maps used in the various documents are also included on the CDROM

Testing the hypothesis of accelerated cerebral white matter aging in schizophrenia and major depression.

PubMed

Kochunov, Peter; Glahn, David C; Rowland, Laura M; Olvera, Rene L; Winkler, Anderson; Yang, Yi-Hong; Sampath, Hemalatha; Carpenter, Will T; Duggirala, Ravindranath; Curran, Joanne; Blangero, John; Hong, L Elliot

2013-03-01

Elevated rate of aging-related biological and functional decline, termed "accelerated aging," is reported in patients with schizophrenia (SCZ) and major depressive disorder (MDD). We used diffusion tensor imaging derived fractional anisotropy (FA) as a biomarker of aging-related decline in white matter (WM) integrity to test the hypotheses of accelerated aging in SCZ and MDD. The SCZ cohort comprised 58 SCZ patients and 60 controls (aged 20-60 years). The MDD cohort comprised 136 MDD patients and 351 controls (aged 20-79 years). The main outcome measures were the diagnosis-by-age interaction on whole-brain-averaged WM FA values and FA values from 12 major WM tracts. Diagnosis-by-age interaction for the whole-brain average FA was significant for the SCZ (p = .04) but not the MDD (p = .80) cohort. Diagnosis-by-age interaction was nominally significant (p<.05) for five WM tracts for SCZ and for none of the tracts in the MDD cohort. Tract-specific heterochronicity of the onset of age-related decline in SCZ demonstrated strong negative correlations with the age-of-peak myelination and the rates of age-related decline obtained from normative sample (r =-.61 and-.80, p<.05, respectively). No such trends existed for MDD cohort. Cerebral WM showed accelerated aging in SCZ but not in MDD, suggesting some difference in the pathophysiology underlying their WM aging changes. Tract-specific heterochronicity of WM development modulated presentation of accelerated aging in SCZ: WM tracts that matured later in life appeared more sensitive to the pathophysiology of SCZ and demonstrated more susceptibility to disorder-related accelerated decline in FA values with age. This trend was not observed in MDD cohort. Copyright © 2013 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

Testing the hypothesis of accelerated cerebral white matter aging in schizophrenia and major depression

PubMed Central

Kochunov, P.; Glahn, D.C.; Rowland, L.M.; Olvera, R.L.; Winkler, A; Yang, Y.H.; Sampath, H.; Carpenter, W.T.; Dugarrila, R.; Curran, J.; Blangero, J.; Hong, L.E.

2012-01-01

Introduction Elevated rate of aging-related biological and functional decline, termed accelerated aging, is reported in patients with schizophrenia (SCZ) and major depressive disorder (MDD). We used diffusion tensor imaging (DTI) derived fractional anisotropy (FA) as biomarkers of aging-related decline in white matter (WM) integrity to test the hypotheses of accelerated aging in SCZ and MDD. Methods The SCZ cohort was composed of 58/60 SCZ patients/controls (age=20–60years). MDD cohort was composed of 136/351 MDD patients/controls (age=20–79years). Main outcome measures were the diagnosis-by-age interaction on whole-brain-averaged WM FA values and FA values from twelve major WM tracts. Results Diagnosis-by-age interaction for the whole-brain average FA was significant for the SCZ (p=0.04) but not in MDD cohort (p=0.80). Diagnosis-by-age interaction was nominally significant (p<0.05) for five WM tracts for SCZ and for none of the tracts in the MDD cohort. Tract-specific heterochronicity of the onset of age-related decline in SCZ demonstrated strong negative correlations with the age-of- peak myelination and the rates of age-related decline obtained from normative sample (r=−0.61 and −0.80, p<0.05, respectively). No such trends existed for MDD cohort. Conclusion Cerebral WM showed accelerated aging in SCZ but not in MDD, suggesting some difference in the pathophysiology underlying their WM aging changes. Tract-specific heterochronicity of WM development modulated presentation of accelerated aging in SCZ: white matter tracts that matured later in life appeared more sensitive to the pathophysiology of SCZ and demonstrated more susceptibility to disorder-related accelerated decline in FA values with age. This trend was not observed in MDD cohort. PMID:23200529

The structural response of a rail accelerator

NASA Technical Reports Server (NTRS)

Wang, S. Y.

1983-01-01

The transient response of a 0.4 by 0.6 cm rectangular bore rail accelerator was analyzed by a three dimensional finite element code. The copper rail deflected to a peak value of 0.08 mm in compression and then oscillated at an amplitude of 0.02 mm. Simultaneously the insulating side wall of glass fabric base, epoxy resin laminate (G-1o) was compressed to a peak value of 0.13 mm and rebounded to a steady state in extension. Projectile pinch or blowby due to the rail extension or compression, respectively, can be identified by examining the time history of the rail displacement. The effect of blowby was most significant at the side wall characterized by mm size displacement in compression. Dynamic stress calculations indicate that the G-10 supporting material behind the rail is subjected to over 21 MPa at which the G-10 could fail if the laminate was not carefully oriented. Results for a polycarbonate resin (Lexan) side wall show much larger displacements and stresses than for G-10. The tradeoff between the transparency of Lexan and the mechanical strength of G-10 for sidewall material is obvious. Displacement calculations from the modal method are smaller than the results from the direct integration method by almost an order of magnitude, because the high frequency effect is neglected.

Multimegawatt cyclotron autoresonance accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirshfield, J.L.; LaPointe, M.A.; Ganguly, A.K.

1996-05-01

Means are discussed for generation of high-quality multimegawatt gyrating electron beams using rf gyroresonant acceleration. TE{sub 111}-mode cylindrical cavities in a uniform axial magnetic field have been employed for beam acceleration since 1968; such beams have more recently been employed for generation of radiation at harmonics of the gyration frequency. Use of a TE{sub 11}-mode waveguide for acceleration, rather than a cavity, is discussed. It is shown that the applied magnetic field and group velocity axial tapers allow resonance to be maintained along a waveguide, but that this is impractical in a cavity. In consequence, a waveguide cyclotron autoresonance acceleratormore » (CARA) can operate with near-100{percent} efficiency in power transfer from rf source to beam, while cavity accelerators will, in practice, have efficiency values limited to about 40{percent}. CARA experiments are described in which an injected beam of up to 25 A, 95 kV has had up to 7.2 MW of rf power added, with efficiencies of up to 96{percent}. Such levels of efficiency are higher than observed previously in any fast-wave interaction, and are competitive with efficiency values in industrial linear accelerators. Scaling arguments suggest that good quality gyrating megavolt beams with peak and average powers of 100 MW and 100 kW can be produced using an advanced CARA, with applications in the generation of high-power microwaves and for possible remediation of flue gas pollutants. {copyright} {ital 1996 American Institute of Physics.}« less

Physical and physiological demands in women pole dance: a single case study.

PubMed

Ruscello, Bruno; Iannelli, Sara; Partipilo, Filippo; Esposito, Mario; Pantanella, Laura; Dring, Mary B; D'Ottavio, Stefano

2017-04-01

to investigate the physical and physiological demands of a pole dancer's performance studied during a simulated competition, lasting 3 min 30 sec. one single woman pole dancer, (age: 22 years; height: 1.56m; body weight: 52kg; BMI: 21.4kg·m-2; estimated HRmax:192.6 bpm) participated in the study. Physical data pertaining to accelerations and rotational values were collected by the means of a tri-axial accelerometer device integrating three gyroscopes. A complete video footage was recorded using four video cameras, using different sampling rates. Blood Pressure, Heart Rates, Breathing Rates, Blood Lactate concentrations were recorded during the performance. Accelerations (positive and negative), along the vertical axis reached 2G and rotational movements around the pole, reached 400°/s. Blood Pressure values ranged from 120/75 before and to 145/58 mmHg at the end of performance, respectively. Heart Rates reached a peak value of 96% of the Maximal Estimated Heart Rate (HRmax) and a mean %HRmax of 92.85 ± 3.15% during the simulated competition. Breathing Rate reached a peak value of 37 bpm and a mean value during competition of 31.87±3.42 bpm. Blood Lactate concentration ranged from 10.2 to 10.7 mmol/L measured at 1 min and 5 min after the completion of the competition, respectively. The results of this case study confirm that the Pole Dance is a performing art requiring heavy physiological and physical demands on the performers. Specific training routines should be designed in order to cope efficiently with this physical activity, taking into account the performance model we provided with this study.

Foot strike pattern differently affects the axial and transverse components of shock acceleration and attenuation in downhill trail running.

PubMed

Giandolini, Marlene; Horvais, Nicolas; Rossi, Jérémy; Millet, Guillaume Y; Samozino, Pierre; Morin, Jean-Benoît

2016-06-14

Trail runners are exposed to a high number of shocks, including high-intensity shocks on downhill sections leading to greater risk of osseous overuse injury. The type of foot strike pattern (FSP) is known to influence impact severity and lower-limb kinematics. Our purpose was to investigate the influence of FSP on axial and transverse components of shock acceleration and attenuation during an intense downhill trail run (DTR). Twenty-three trail runners performed a 6.5-km DTR (1264m of negative elevation change) as fast as possible. Four tri-axial accelerometers were attached to the heel, metatarsals, tibia and sacrum. Accelerations were continuously recorded at 1344Hz and analyzed over six sections (~400 steps per subject). Heel and metatarsal accelerations were used to identify the FSP. Axial, transverse and resultant peak accelerations, median frequencies and shock attenuation within the impact-related frequency range (12-20Hz) were assessed between tibia and sacrum. Multiple linear regressions showed that anterior (i.e. forefoot) FSPs were associated with higher peak axial acceleration and median frequency at the tibia, lower transverse median frequencies at the tibia and sacrum, and lower transverse peak acceleration at the sacrum. For resultant acceleration, higher tibial median frequency but lower sacral peak acceleration were reported with forefoot striking. FSP therefore differently affects the components of impact shock acceleration. Although a forefoot strike reduces impact severity and impact frequency content along the transverse axis, a rearfoot strike decreases them in the axial direction. Globally, the attenuation of axial and resultant impact-related vibrations was improved using anterior FSPs. Copyright © 2016 Elsevier Ltd. All rights reserved.

Martial arts striking hand peak acceleration, accuracy and consistency.

PubMed

Neto, Osmar Pinto; Marzullo, Ana Carolina De Miranda; Bolander, Richard P; Bir, Cynthia A

2013-01-01

The goal of this paper was to investigate the possible trade-off between peak hand acceleration and accuracy and consistency of hand strikes performed by martial artists of different training experiences. Ten male martial artists with training experience ranging from one to nine years volunteered to participate in the experiment. Each participant performed 12 maximum effort goal-directed strikes. Hand acceleration during the strikes was obtained using a tri-axial accelerometer block. A pressure sensor matrix was used to determine the accuracy and consistency of the strikes. Accuracy was estimated by the radial distance between the centroid of each subject's 12 strikes and the target, whereas consistency was estimated by the square root of the 12 strikes mean squared distance from their centroid. We found that training experience was significantly correlated to hand peak acceleration prior to impact (r(2)=0.456, p =0.032) and accuracy (r(2)=0. 621, p=0.012). These correlations suggest that more experienced participants exhibited higher hand peak accelerations and at the same time were more accurate. Training experience, however, was not correlated to consistency (r(2)=0.085, p=0.413). Overall, our results suggest that martial arts training may lead practitioners to achieve higher striking hand accelerations with better accuracy and no change in striking consistency.

Peaks in Phase Space Density: A Survey of the Van Allen Probes Era

NASA Astrophysics Data System (ADS)

Boyd, A. J.; Turner, D. L.; Reeves, G. D.; Spence, H. E.

2017-12-01

One of the challenges of radiation belt studies is the differentiation between acceleration mechanisms, particularly local acceleration and radial diffusion. This is often done through careful examination of phase space density profiles in terms of adiabatic coordinates. In particular, local acceleration processes produce growing peaks in phase space density. Many previous studies have shown clear observations of these features for individual events. However, it remains unclear how often and where these growing peaks are observed over a long time period. With the availability of several years of high quality observations from multiple spacecraft, we now have an opportunity to quantify phase space density profiles not only for multiple events, but also across a wide range of energies. In this study, we examine phase space density from more than four years of data from the Van Allen Probes and THEMIS to determine the statistical properties of the observed peaks in phase space density. First, we determine how often growing peaks are observed. Second, we examine where the peaks are located in terms of the adiabatic invariants mu, K and L* and how these locations relate to geomagnetic indices, solar wind conditions and the plasmapause location. Third, we explore how these peaks evolve in time. Together, these results will reveal the relative importance of different acceleration processes and how these affect the various electron populations within the radiation belt.

Crew Exploration Vehicle (CEV) (Orion) Occupant Protection. [Appendices Part 2

NASA Technical Reports Server (NTRS)

Currie-Gregg, Nancy J.; Gernhardt, Michael L.; Lawrence, Charles; Somers, Jeffrey T.

2016-01-01

The purpose of this study was to determine the similarity between the response of the THUMS model and the Hybrid III Anthropometric Test Device (ATD) given existing Wright-Patterson (WP) sled tests. There were four tests selected for this comparison with frontal, spinal, rear, and lateral loading. The THUMS was placed in a sled configuration that replicated the WP configuration and the recorded seat acceleration for each test was applied to model seat. Once the modeling simulations were complete, they were compared to the WP results using two methods. The first was a visual inspection of the sled test videos compared to the THUMS d3plot files. This comparison resulted in an assessment of the overall kinematics of the two results. The other comparison was a comparison of the plotted data recorded for both tests. The metrics selected for comparison were seat acceleration, belt forces, head acceleration and chest acceleration. These metrics were recorded in all WP tests and were outputs of the THUMS model. Once the comparison of the THUMS to the WP tests was complete, the THUMS model output was also examined for possible injuries in these scenarios. These outputs included metrics for injury risk to the head, neck, thorax, lumbar spine and lower extremities. The metrics to evaluate head response were peak head acceleration, HIC15, and HIC36. For the neck, N (sub ij) was calculated. The thorax response was evaluated with peak chest acceleration, the Combined Thoracic Index (CTI), sternal deflection, chest deflection, and chest acceleration- 3 ms clip. The lumbar spine response was evaluated with lumbar spine force. Finally the lower extremity response was evaluated by femur and tibia force. The results of the simulation comparisons indicate the THUMS model had a similar response to the Hybrid III dummy given the same input. The primary difference seen between the two was a more flexible response of the THUMS compared to the Hybrid III. This flexibility was most pronounced in the neck flexion, shoulder deflection and chest deflection. Due to the flexibility of the THUMS, the resulting head and chest accelerations tended to lag the Hybrid III acceleration trace and have a lower peak value. The results of the injury metric comparison identified possible injury trends between simulations. Risk of head injury was highest for the lateral simulations. The risk of chest injury was highest for the rear impact. However, neck injury risk was approximately the same for all simulations. The injury metric value for lumbar spine force was highest for the spinal impact. The leg forces were highest for the rear and lateral impacts. The results of this comparison indicate the THUMS model performs in a similar manner as the Hybrid III ATD. The differences in the responses of model and the ATD are primarily due to the flexibility of the THUMS. This flexibility of the THUMS would be a more human like response. Based on the similarity between the two models, the THUMS should be used in further testing to assess risk of injury to the occupant.

Strong ground motion from the November 12, 2017, M 7.3 Kermanshah earthquake in western Iran

NASA Astrophysics Data System (ADS)

Babaie Mahani, Alireza; Kazemian, Javad

2018-05-01

In this paper, we analyzed the strong ground motion from the November 12, 2017, Kermanshah earthquake in western Iran with moment magnitude (M) of 7.3. Nonlinear and linear amplification of ground motion amplitudes were observed at stations with soft soil condition at hypocentral distances below and above 100 km, respectively. Observation of large ground motion amplitudes dominated with long-period pulses on the strike-normal component of the velocity time series suggests a right-lateral component of movement and propagation of rupture towards southeast. Comparison of the horizontal peak ground acceleration (PGA) from the M 7.3 earthquake with global PGA values showed a similar decay in ground motion amplitudes, although it seems that PGA from the M 7.3 Kermanshah earthquake is higher than global values for NEHRP site class B. We also found that the bracketed duration (D b) was higher in the velocity domain than in the acceleration domain for the same modified Mercalli intensity (MMI) threshold. For example, D b reached 30 s at the maximum PGA while it was 50 s at the maximum peak ground velocity above the threshold of MMI = 5. Although the standard design spectrum from Iranian Code of Practice for Seismic Resistant Design of Buildings (standard No. 2800) seems to include appropriate values for the design of structures with fundamental period of 1 s and higher, it is underestimated for near-field ground motions at lower periods.

Biomechanical tolerance of whole lumbar spines in straightened posture subjected to axial acceleration.

PubMed

Stemper, Brian D; Chirvi, Sajal; Doan, Ninh; Baisden, Jamie L; Maiman, Dennis J; Curry, William H; Yoganandan, Narayan; Pintar, Frank A; Paskoff, Glenn; Shender, Barry S

2018-06-01

Quantification of biomechanical tolerance is necessary for injury prediction and protection of vehicular occupants. This study experimentally quantified lumbar spine axial tolerance during accelerative environments simulating a variety of military and civilian scenarios. Intact human lumbar spines (T12-L5) were dynamically loaded using a custom-built drop tower. Twenty-three specimens were tested at sub-failure and failure levels consisting of peak axial forces between 2.6 and 7.9 kN and corresponding peak accelerations between 7 and 57 g. Military aircraft ejection and helicopter crashes fall within these high axial acceleration ranges. Testing was stopped following injury detection. Both peak force and acceleration were significant (p < 0.0001) injury predictors. Injury probability curves using parametric survival analysis were created for peak acceleration and peak force. Fifty-percent probability of injury (95%CI) for force and acceleration were 4.5 (3.9-5.2 kN), and 16 (13-19 g). A majority of injuries affected the L1 spinal level. Peak axial forces and accelerations were greater for specimens that sustained multiple injuries or injuries at L2-L5 spinal levels. In general, force-based tolerance was consistent with previous shorter-segment lumbar spine testing (3-5 vertebrae), although studies incorporating isolated vertebral bodies reported higher tolerance attributable to a different injury mechanism involving structural failure of the cortical shell. This study identified novel outcomes with regard to injury patterns, wherein more violent exposures produced more injuries in the caudal lumbar spine. This caudal migration was likely attributable to increased injury tolerance at lower lumbar spinal levels and a faster inertial mass recruitment process for high rate load application. Published 2017. This article is a U.S. Government work and is in the public domain in the USA. J Orthop Res 36:1747-1756, 2018. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Foul tip impact attenuation of baseball catcher masks using head impact metrics

PubMed Central

White, Terrance R.; Cutcliffe, Hattie C.; Shridharani, Jay K.; Wood, Garrett W.; Bass, Cameron R.

2018-01-01

Currently, no scientific consensus exists on the relative safety of catcher mask styles and materials. Due to differences in mass and material properties, the style and material of a catcher mask influences the impact metrics observed during simulated foul ball impacts. The catcher surrogate was a Hybrid III head and neck equipped with a six degree of freedom sensor package to obtain linear accelerations and angular rates. Four mask styles were impacted using an air cannon for six 30 m/s and six 35 m/s impacts to the nasion. To quantify impact severity, the metrics peak linear acceleration, peak angular acceleration, Head Injury Criterion, Head Impact Power, and Gadd Severity Index were used. An Analysis of Covariance and a Tukey’s HSD Test were conducted to compare the least squares mean between masks for each head injury metric. For each injury metric a P-Value less than 0.05 was found indicating a significant difference in mask performance. Tukey’s HSD test found for each metric, the traditional style titanium mask fell in the lowest performance category while the hockey style mask was in the highest performance category. Limitations of this study prevented a direct correlation from mask testing performance to mild traumatic brain injury. PMID:29856814

Accelerating Improvements in the Energy Efficiency of Room Air Conditioners (RACs) in India: Potential, Cost-Benefit, and Policies (Interim Assessment)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abhyankar, Nikit; Shah, Nihar; Park, Won Young

Falling AC prices, increasing incomes, increasing urbanization, and high cooling requirements due to hot climate are all driving increasing uptake of Room Air Conditioners (RACs) in the Indian market. Air conditioning already comprises 40-60% of summer peak load in large metropolitan Indian cities such as Delhi and is likely to contribute 150 GW to the peak demand in 2030. Standards and labeling policies have contributed to improving the efficiency of RACs in India by about 2.5% in the last 10 years (2.5% per year) while inflation adjusted RAC prices have continued to decline. In this paper, we assess the technicalmore » feasibility, cost-benefit, and required policy enhancements by further accelerating the efficiency improvement of RACs in India. We find that there are examples of significantly more accelerated improvements such as those in Japan and Korea where AC efficiency improved by more than 7% per year resulting in almost a doubling of energy efficiency in 7 to 10 years while inflation adjusted AC prices continued to decline. We find that the most efficient RAC sold on the Indian market is almost twice as efficient as the typical AC sold on the market and hence see no technology constraints in a similar acceleration of improvement of efficiency. If starting 2018, AC efficiency improves at a rate of 6% instead of 3%, 40-60 GW of peak load (equivalent to connected load of 5-6 billion LED bulbs), and over 75 TWh/yr (equivalent to 60 million consumers consuming 100 kWh/month) will be saved by 2030; total peak load reduction would be as high as 50 GW. The net present value (NPV) of the consumer benefit between 2018-2030 will range from Rs 18,000 Cr in the most conservative case (in which prices don’t continue to decline and increase based estimates of today’s cost of efficiency improvement) to 140,000 Cr in a more realistic case (in which prices are not affected by accelerated efficiency improvement as shown by historical experience). This benefit is achievable by ratcheting up the 1 star level for fixed and inverter ACs to the level of today’s five star rating for inverter ACs by 2022. Bulk procurement (similar to the Domestic Efficient Lighting Program) and incentive programs can complement the accelerated ratcheting up of star levels. Similar programs can also be implemented for other types of ACs.« less

A comparison of the capacity of ice hockey goaltender masks for the protection from puck impacts.

PubMed

Nur, Sarah; Kendall, Marshall; Clark, J Michio; Hoshizaki, T Blaine

2015-01-01

Goaltenders in ice hockey are the only players that are on the ice for the entire game. Their position exposes them to impacts from collisions with other players, falls to the ice, and puck impacts. In competitive ice hockey leagues, head injuries resulting from puck impacts have been reported with some cases resulting in ending the player's career. Considerable research has been conducted to assess the performance of hockey helmets; however, few have assessed the performance of goaltenders' masks. The purpose of this study was to compare the capacity of four goaltenders' masks for the protection from puck impact as measured by head acceleration and peak force. A Hybrid III headform was fitted with four different goaltender masks and impacted with a hockey puck in three locations at 25 m/s. The masks were found to vary in the level of protection they offered as the mask with the thickest liner resulted in lower forces than the thinnest mask for side impacts; however, the thinnest mask resulted in the lowest force for front impacts. Despite performance differences at specific locations, no one mask proved to be superior as peak acceleration and peak force values did not exceed the thresholds necessary for concussion.

Impact data from a transport aircraft during a controlled impact demonstration

NASA Technical Reports Server (NTRS)

Fasanella, E. L.; Alfaro-Bou, E.; Hayduk, R. J.

1986-01-01

On December 1, 1984, the FAA and NASA conducted a remotely piloted air-to-ground crash test of a Boeing 720 transport aircraft instrumented to measure crash loads of the structure and the anthropomorphic dummy passengers. Over 330 time histories of accelerations and loads collected during the Full-Scale Transport Controlled Impact Demonstration (CID) for the 1-sec period after initial impact are presented. Although a symmetric 1 deg. nose-up attitude with a 17 ft/sec sink rate was planned, the plane was yawed and rolled 13 deg. at initial (left-wing) impact. The first fuselage impact occurred near the nose wheel well with the nose pitched down 2.5 deg. Peak normal (vertical) floor accelerations were highest in the cockpit and forward cabin near the nose wheel well and were approximately 14G. The remaining cabin floor received normal acceleration peaks of 7G or less. The peak longitudinal floor accelerations showed a similar distribution, with the highest (7G) in the cockpit and forward cabin, decreasing to 4G or less toward the rear. Peak transverse floor accelerations ranged from about 5G in the cockpit to 1G in the aft fuselage.

Effects of haloperidol on Kv4.3 potassium channels.

PubMed

Lee, Hong Joon; Sung, Ki-Wug; Hahn, Sang June

2014-10-05

Haloperidol is commonly used in clinical practice to treat acute and chronic psychosis, but it also has been associated with adverse cardiovascular events. We investigated the effects of haloperidol on Kv4.3 currents stably expressed in CHO cells using a whole-cell patch-clamp technique. Haloperidol did not significantly inhibit the peak amplitude of Kv4.3, but accelerated the decay rate of inactivation of Kv4.3 in a concentration-dependent manner. Thus, the effects of haloperidol on Kv4.3 were estimated from the integral of the Kv4.3 currents during the depolarization pulse. The Kv4.3 was decreased by haloperidol in a concentration-dependent manner with an IC50 value of 3.6 μM. Haloperidol accelerated the decay rate of Kv4.3 inactivation and activation kinetics in a concentration-dependent manner, thereby decreasing the time-to-peak. Haloperidol shifted the voltage dependence of the steady-state activation and inactivation of Kv4.3 in a hyperpolarizing direction. Haloperidol also caused an acceleration of the closed-state inactivation of Kv4.3. Haloperidol produced a use-dependent block of Kv4.3, which was accompanied by a slowing of recovery from the inactivation of Kv4.3. These results suggest that haloperidol blocks Kv4.3 by both interacting with the open state of Kv4.3 channels during depolarization and accelerating the closed-state inactivation at subthreshold membrane potentials. Copyright © 2014 Elsevier B.V. All rights reserved.

Preliminary map of peak horizontal ground acceleration for the Hanshin-Awaji earthquake of January 17, 1995, Japan - Description of Mapped Data Sets

USGS Publications Warehouse

Borcherdt, R.D.; Mark, R.K.

1995-01-01

The Hanshin-Awaji earthquake (also known as the Hyogo-ken Nanbu and the Great Hanshin earthquake) provided an unprecedented set of measurements of strong ground shaking. The measurements constitute the most comprehensive set of strong- motion recordings yet obtained for sites underlain by soft soil deposits of Holocene age within a few kilometers of the crustal rupture zone. The recordings, obtained on or near many important structures, provide an important new empirical data set for evaluating input ground motion levels and site amplification factors for codes and site-specific design procedures world wide. This report describes the data used to prepare a preliminary map summarizing the strong motion data in relation to seismicity and underlying geology (Wentworth, Borcherdt, and Mark., 1995; Figure 1, hereafter referred to as Figure 1/I). The map shows station locations, peak acceleration values, and generalized acceleration contours superimposed on pertinent seismicity and the geologic map of Japan. The map (Figure 1/I) indicates a zone of high acceleration with ground motions throughout the zone greater than 400 gal and locally greater than 800 gal. This zone encompasses the area of most intense damage mapped as JMA intensity level 7, which extends through Kobe City. The zone of most intense damage is parallel, but displaced slightly from the surface projection of the crustal rupture zone implied by aftershock locations. The zone is underlain by soft-soil deposits of Holocene age.

Fokker-Planck-Based Acceleration for SN Equations with Highly Forward Peaked Scattering in Slab Geometry

NASA Astrophysics Data System (ADS)

Patel, Japan

Short mean free paths are characteristic of charged particles. High energy charged particles often have highly forward peaked scattering cross sections. Transport problems involving such charged particles are also highly optically thick. When problems simultaneously have forward peaked scattering and high optical thickness, their solution, using standard iterative methods, becomes very inefficient. In this dissertation, we explore Fokker-Planck-based acceleration for solving such problems.

Testing relativistic electron acceleration mechanisms

NASA Astrophysics Data System (ADS)

Green, Janet Carol

2002-09-01

This dissertation tests models of relativistic electron acceleration in the earth's outer radiation belt. The models fall into two categories: external and internal. External acceleration models transport and accelerate electrons from a source region in the outer magnetosphere to the inner magnetosphere. Internal acceleration models accelerate a population of electrons already present in the inner magnetosphere. In this dissertation, we test one specific external acceleration mechanism, perform a general test that differentiates between internal and external acceleration models, and test one promising internal acceleration model. We test the models using Polar-HIST data that we transform into electron phase space density (PSD) as a function of adiabatic invariants. We test the ultra low frequency (ULF) wave enhanced radial diffusion external acceleration mechanism by looking for a causal relationship between increased wave power and increased electron PSD at three L* values. One event with increased wave power at two L* values and no subsequent PSD increase does not support the model suggesting that ULF wave power alone is not sufficient to cause an electron response. Excessive loss of electrons and the duration of wave power do not explain the lack of a PSD enhancement at low L*. We differentiate between internal and external acceleration mechanisms by examining the radial profile of electron PSD. We observe PSD profiles that depend on local time. Nightside profiles are highly dependent on the magnetic field model used to calculate PSD as a function of adiabatic invariants and are not reliable. Dayside PSD profiles are more robust and consistent with internal acceleration of electrons. We test one internal acceleration model, the whistler/electromagnetic ion cyclotron wave model, by comparing observed pitch angle distributions to those predicted by the model using a superposed epoch analysis. The observations show pitch angle distributions corresponding to electrons with energy >=4.0 MeV becoming more peaked at 90° during the storm recovery phase. The observation is consistent with but does not confirm the model. Our tests indicate that relativistic electrons are accelerated by an internal source acceleration mechanism but we do not identify a unique mechanism.

A NEW GUI FOR GLOBAL ORBIT CORRECTION AT THE ALS USING MATLAB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pachikara, J.; Portmann, G.

2007-01-01

Orbit correction is a vital procedure at particle accelerators around the world. The orbit correction routine currently used at the Advanced Light Source (ALS) is a bit cumbersome and a new Graphical User Interface (GUI) has been developed using MATLAB. The correction algorithm uses a singular value decomposition method for calculating the required corrector magnet changes for correcting the orbit. The application has been successfully tested at the ALS. The GUI display provided important information regarding the orbit including the orbit errors before and after correction, the amount of corrector magnet strength change, and the standard deviation of the orbitmore » error with respect to the number of singular values used. The use of more singular values resulted in better correction of the orbit error but at the expense of enormous corrector magnet strength changes. The results showed an inverse relationship between the peak-to-peak values of the orbit error and the number of singular values used. The GUI interface helps the ALS physicists and operators understand the specifi c behavior of the orbit. The application is convenient to use and is a substantial improvement over the previous orbit correction routine in terms of user friendliness and compactness.« less

Player Monitoring in Indoor Team Sports: Concurrent Validity of Inertial Measurement Units to Quantify Average and Peak Acceleration Values

PubMed Central

Roell, Mareike; Roecker, Kai; Gehring, Dominic; Mahler, Hubert; Gollhofer, Albert

2018-01-01

The increasing interest in assessing physical demands in team sports has led to the development of multiple sports related monitoring systems. Due to technical limitations, these systems primarily could be applied to outdoor sports, whereas an equivalent indoor locomotion analysis is not established yet. Technological development of inertial measurement units (IMU) broadens the possibilities for player monitoring and enables the quantification of locomotor movements in indoor environments. The aim of the current study was to validate an IMU measuring by determining average and peak human acceleration under indoor conditions in team sport specific movements. Data of a single wearable tracking device including an IMU (Optimeye S5, Catapult Sports, Melbourne, Australia) were compared to the results of a 3D motion analysis (MA) system (Vicon Motion Systems, Oxford, UK) during selected standardized movement simulations in an indoor laboratory (n = 56). A low-pass filtering method for gravity correction (LF) and two sensor fusion algorithms for orientation estimation [Complementary Filter (CF), Kalman-Filter (KF)] were implemented and compared with MA system data. Significant differences (p < 0.05) were found between LF and MA data but not between sensor fusion algorithms and MA. Higher precision and lower relative errors were found for CF (RMSE = 0.05; CV = 2.6%) and KF (RMSE = 0.15; CV = 3.8%) both compared to the LF method (RMSE = 1.14; CV = 47.6%) regarding the magnitude of the resulting vector and strongly emphasize the implementation of orientation estimation to accurately describe human acceleration. Comparing both sensor fusion algorithms, CF revealed slightly lower errors than KF and additionally provided valuable information about positive and negative acceleration values in all three movement planes with moderate to good validity (CV = 3.9 – 17.8%). Compared to x- and y-axis superior results were found for the z-axis. These findings demonstrate that IMU-based wearable tracking devices can successfully be applied for athlete monitoring in indoor team sports and provide potential to accurately quantify accelerations and decelerations in all three orthogonal axes with acceptable validity. An increase in accuracy taking magnetometers in account should be specifically pursued by future research. PMID:29535641

Discrete Element Method Simulation of a Boulder Extraction From an Asteroid

NASA Technical Reports Server (NTRS)

Kulchitsky, Anton K.; Johnson, Jerome B.; Reeves, David M.; Wilkinson, Allen

2014-01-01

The force required to pull 7t and 40t polyhedral boulders from the surface of an asteroid is simulated using the discrete element method considering the effects of microgravity, regolith cohesion and boulder acceleration. The connection between particle surface energy and regolith cohesion is estimated by simulating a cohesion sample tearing test. An optimal constant acceleration is found where the peak net force from inertia and cohesion is a minimum. Peak pulling forces can be further reduced by using linear and quadratic acceleration functions with up to a 40% reduction in force for quadratic acceleration.

Calculating the radiation characteristics of accelerated electrons in laser-plasma interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, X. F.; Graduate School of Engineering, Utsunomiya University, 7-1-2 Yohtoh, Utsunomiya 321-8585; Yu, Q.

2016-03-15

In this paper, we studied the characteristics of radiation emitted by electrons accelerated in a laser–plasma interaction by using the Lienard–Wiechert field. In the interaction of a laser pulse with a underdense plasma, electrons are accelerated by two mechanisms: direct laser acceleration (DLA) and laser wakefield acceleration (LWFA). At the beginning of the process, the DLA electrons emit most of the radiation, and the DLA electrons emit a much higher peak photon energy than the LWFA electrons. As the laser–plasma interaction progresses, the LWFA electrons become the major radiation emitter; however, even at this stage, the contribution from DLA electronsmore » is significant, especially to the peak photon energy.« less

Effect of 3 Weeks Use of Compression Garments on Stride and Impact Shock during a Fatiguing Run.

PubMed

Lucas-Cuevas, A G; Priego-Quesada, J I; Aparicio, I; Giménez, J V; Llana-Belloch, S; Pérez-Soriano, P

2015-10-01

Excessive and prolonged exposure to impact acceleration during running is associated with increased injury rate. Acute use of compressive garments has been speculated to improve attenuation. However, it is unknown how longer interventions of compressive garments influence attenuation in running. 40 runners trained with compressive and placebo stockings for 3 weeks. Perception of comfort, stride parameters (rate, length) and impact acceleration (head and tibial peak acceleration, magnitude, acceleration rate and attenuation) were measured every 5 min during a fatigue run (30 min at 80% of the individual's maximal aerobic speed). Compressive stockings reduced tibial peak acceleration and magnitude compared to placebo stockings at every minute (p<0.05) except for the initial measurement (p>0.05). Moreover, compressive stockings led to a lower rate of increase in tibial peak acceleration (14%, p<0.005) and magnitude (16%, p<0.001) as a result of the development of fatigue compared to placebo stockings (24% and 26% increase, p=0.014 and p=0.003, respectively). Similar perception of comfort was reported for both garments. Training with compressive stockings for 3 weeks reduced impact acceleration and the rate of increase in acceleration compared to placebo stockings. These findings suggest that compressive stockings may play a protective role by reducing impact accelerations during running. © Georg Thieme Verlag KG Stuttgart · New York.

Physiological correlates of skating performance in women's and men's ice hockey.

PubMed

Gilenstam, Kajsa M; Thorsen, Kim; Henriksson-Larsén, Karin B

2011-08-01

The purpose of the current investigation was to identify relationships between physiological off-ice tests and on-ice performance in female and male ice hockey players on a comparable competitive level. Eleven women, 24 ± 3.0 years, and 10 male ice hockey players, 23 ± 2.4 years, were tested for background variables: height, body weight (BW), ice hockey history, and lean body mass (LBM) and peak torque (PT) of the thigh muscles, VO2peak and aerobic performance (Onset of Blood Lactate Accumulation [OBLA], respiratory exchange ratio [RER1]) during an incremental bicycle ergometer test. Four different on-ice tests were used to measure ice skating performance. For women, skating time was positively correlated (p < 0.05) to BW and negatively correlated to LBM%, PT/BW, OBLA, RER 1, and VO2peak (ml O2·kg(-1) BW(-1)·min(-1)) in the Speed test. Acceleration test was positively correlated to BW and negatively correlated to OBLA and RER 1. For men, correlation analysis revealed only 1 significant correlation where skating time was positively correlated to VO2peak (L O2·min(-1)) in the Acceleration test. The male group had significantly higher physiological test values in all variables (absolute and relative to BW) but not in relation to LBM. Selected off-ice tests predict skating performance for women but not for men. The group of women was significantly smaller and had a lower physiological performance than the group of men and were slower in the on-ice performance tests. However, gender differences in off-ice variables were reduced or disappeared when values were related to LBM, indicating a similar capacity of producing strength and aerobic power in female and male hockey players. Skating performance in female hockey players may be improved by increasing thigh muscle strength, oxygen uptake, and relative muscle mass.

The Potential Effect of Sea Level Rise on Coastal Property Values

NASA Astrophysics Data System (ADS)

O'Donnell, J.

2015-12-01

It is well established that one consequence of increasing global sea level is that the frequency of flooding at low-lying coastal sites will increase. We review recent evidence that the effects coastal geometry will create substantial spatial variations in the changes in flooding frequency with scales of order 100km. Using a simple model of the evolution of coastal property values we demonstrate that a consequence of sea level rise is that the appreciation of coastal properties will peak, and then decline relative to higher properties. The time when the value reach a maximum is shown to depend upon the demand for the coastal property, and the local rate of change of flooding frequency due to sea level rise. The simple model is then extended to include, in an elementary manner, the effects on the value of adjacent but higher properties. We show that the effect of increased flooding frequency of the lower properties leads to an accelerated appreciation of the value of upland properties and an accelerated decline in the value of the coastal properties. We then provide some example calculations for selected sites. We conclude with a discussion of comparisons of the prediction of the analyses to recent data, and then comments on the impact of sea level rise on tax base of coastal communities.

Evaluation of selected sidewalk pavement surfaces for vibration experienced by users of manual and powered wheelchairs.

PubMed

Cooper, Rory A; Wolf, Erik; Fitzgerald, Shirley G; Kellerher, Annmarie; Ammer, William; Boninger, Michael L; Cooper, Rosemarie

2004-01-01

Obstacles such as bumps, curb descents, and uneven driving surfaces cause vibrations that affect the wheelchair, and in turn, the wheelchair user. Chronic exposure can cause low-back pain, disk degeneration, and other harmful effects. Little research has been conducted to assess the vibrations experienced by wheelchair users. The purpose of this study was to conduct an evaluation of the vibration exposure during electric-powered wheelchair driving and mechanical energy requirements for manual wheelchair propulsion over selected sidewalk surfaces. The goal was to determine the criteria for a wheelchair-pedestrian access route that does not require excessive propulsive work or expose wheelchair users to potentially harmful vibrations. Ten unimpaired individuals participated in this study. Six sidewalk surfaces were tested. Measured variables included power of the acceleration per octave, mechanical work to propel over surfaces, peak acceleration, and frequency at which peak acceleration occurs. For both the manual and electric-powered wheelchair, at 1 m/s, significant differences were found in peak accelerations between the seat and footrest (P < 0.0001) and between the sidewalk surfaces (P = 0.004). The greatest risk for injury caused by shock and vibration exposure occurs at frequencies near the natural frequency of seated humans (4-15 Hz). The values for work required to propel over the surfaces tested were not statistically significantly different. Besides appearance and construction, the only distinguishing characteristic was surface roughness caused by the joints. When treating the poured concrete sidewalk as the standard, surfaces 2, 3, 5, and 6 compared most favorably in terms of vibration exposure, whereas surface 4 produced mixed results. Surfaces 2, 3, 5, and 6 yielded results that were similar to the poured concrete sidewalk and could be considered acceptable for wheelchair users. In conclusion, surfaces other than the traditional poured concrete can be used for pedestrian access routes without adding vibration exposure or reducing propulsion efficiency.

Scaling magnetized liner inertial fusion on Z and future pulsed-power accelerators

DOE PAGES

Slutz, Stephen A.; Stygar, William A.; Gomez, Matthew R.; ...

2016-02-04

In this study, the MagLIF (Magnetized Liner Inertial Fusion) concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)] has demonstrated fusion–relevant plasma conditions [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] on the Z accelerator with a peak drive current of about 18 MA. We present 2D numerical simulations of the scaling of MagLIF on Z as a function of drive current, preheat energy, and applied magnetic field. The results indicate that deuterium-tritium (DT) fusion yields greater than 100 kJ could be possible on Z when all of these parameters are at the optimum values:more » i.e., peak current = 25 MA, deposited preheat energy = 5 kJ, and B z = 30 T. Much higher yields have been predicted [S. A. Slutz and R. A. Vesey, Phys. Rev. Lett. 108, 025003 (2012)] for MagLIF driven with larger peak currents. Two high performance pulsed-power accelerators (Z300 and Z800) based on linear-transformer-driver technology have been designed [W. A. Stygar et al., Phys. Rev. ST Accel. Beams 18, 110401 (2015)]. The Z300 design would provide 48 MA to a MagLIF load, while Z800 would provide 65 MA. Parameterized Thevenin-equivalent circuits were used to drive a series of 1D and 2D numerical MagLIF simulations with currents ranging from what Z can deliver now to what could be achieved by these conceptual future pulsed-power accelerators. 2D simulations of simple MagLIF targets containing just gaseous DT have yields of 18 MJ for Z300 and 440 MJ for Z800. The 2D simulated yield for Z800 is increased to 7 GJ by adding a layer of frozen DT ice to the inside of the liner.« less

Scaling magnetized liner inertial fusion on Z and future pulsed-power accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slutz, Stephen A.; Stygar, William A.; Gomez, Matthew R.

In this study, the MagLIF (Magnetized Liner Inertial Fusion) concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)] has demonstrated fusion–relevant plasma conditions [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] on the Z accelerator with a peak drive current of about 18 MA. We present 2D numerical simulations of the scaling of MagLIF on Z as a function of drive current, preheat energy, and applied magnetic field. The results indicate that deuterium-tritium (DT) fusion yields greater than 100 kJ could be possible on Z when all of these parameters are at the optimum values:more » i.e., peak current = 25 MA, deposited preheat energy = 5 kJ, and B z = 30 T. Much higher yields have been predicted [S. A. Slutz and R. A. Vesey, Phys. Rev. Lett. 108, 025003 (2012)] for MagLIF driven with larger peak currents. Two high performance pulsed-power accelerators (Z300 and Z800) based on linear-transformer-driver technology have been designed [W. A. Stygar et al., Phys. Rev. ST Accel. Beams 18, 110401 (2015)]. The Z300 design would provide 48 MA to a MagLIF load, while Z800 would provide 65 MA. Parameterized Thevenin-equivalent circuits were used to drive a series of 1D and 2D numerical MagLIF simulations with currents ranging from what Z can deliver now to what could be achieved by these conceptual future pulsed-power accelerators. 2D simulations of simple MagLIF targets containing just gaseous DT have yields of 18 MJ for Z300 and 440 MJ for Z800. The 2D simulated yield for Z800 is increased to 7 GJ by adding a layer of frozen DT ice to the inside of the liner.« less

Scaling magnetized liner inertial fusion on Z and future pulsed-power accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slutz, S. A.; Stygar, W. A.; Gomez, M. R.

The MagLIF (Magnetized Liner Inertial Fusion) concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)] has demonstrated fusion–relevant plasma conditions [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] on the Z accelerator with a peak drive current of about 18 MA. We present 2D numerical simulations of the scaling of MagLIF on Z as a function of drive current, preheat energy, and applied magnetic field. The results indicate that deuterium-tritium (DT) fusion yields greater than 100 kJ could be possible on Z when all of these parameters are at the optimum values: i.e., peak current = 25 MA, deposited preheatmore » energy = 5 kJ, and B{sub z} = 30 T. Much higher yields have been predicted [S. A. Slutz and R. A. Vesey, Phys. Rev. Lett. 108, 025003 (2012)] for MagLIF driven with larger peak currents. Two high performance pulsed-power accelerators (Z300 and Z800) based on linear-transformer-driver technology have been designed [W. A. Stygar et al., Phys. Rev. ST Accel. Beams 18, 110401 (2015)]. The Z300 design would provide 48 MA to a MagLIF load, while Z800 would provide 65 MA. Parameterized Thevenin-equivalent circuits were used to drive a series of 1D and 2D numerical MagLIF simulations with currents ranging from what Z can deliver now to what could be achieved by these conceptual future pulsed-power accelerators. 2D simulations of simple MagLIF targets containing just gaseous DT have yields of 18 MJ for Z300 and 440 MJ for Z800. The 2D simulated yield for Z800 is increased to 7 GJ by adding a layer of frozen DT ice to the inside of the liner.« less

Superconducting radio-frequency cavities made from medium and low-purity niobium ingots

DOE PAGES

Ciovati, Gianluigi; Dhakal, Pashupati; Myneni, Ganapati R.

2016-04-07

Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q 0-values. In this contribution we present the results from cryogenic RF tests of 1.3–1.5 GHz single-cell cavities made of ingot Nbmore » of medium (RRR = 100–150) and low (RRR = 60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with an average Q 0-value of 2 × 10 10 at 2 K after standard processing treatments. As a result, the performances of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.« less

Characterization of Vertical Impact Device Acceleration Pulses Using Parametric Assessment: Phase 3 Wiaman Seat

DTIC Science & Technology

2016-07-01

711 HPW/RHCPT) and their in-house technical support contractor , Infoscitex, conducted a series of tests to identify the performance capabilities of...Cell Seat Configuration Drop Ht . (in) Mean Peak Acceleration (G) Mean Velocity Change (ft/s) SH1 WS1 20 80.08 ± 3.71 13.54 ± 0.49 SH2...6. Test Matrix for VID Response with WS2 Test Cell Seat (Felt) Configuration Drop Ht . (in) Mean Peak Acceleration (G

The Fatigue Approach to Vibration and Health: is it a Practical and Viable way of Predicting the Effects on People?

NASA Astrophysics Data System (ADS)

Sandover, J.

1998-08-01

The fatigue approach assumes that the vertebral end-plates are the weak link in the spine subjected to shock and vibration, and fail as a result of material fatigue. The theory assumes that end-plate damage leads to degeneration and pain in the lumbar spine. There is evidence for both the damage predicted and the fatigue mode of failure so that the approach may provide a basis for predictive methods for use in epidemiology and standards. An available data set from a variety of heavy vehicles in practical situations was used for predictions of spinal stress and fatigue life. Although there was some disparity between the predictive methods used, the more developed methods indicated fatigue lives that appeared reasonable, taking into account the vehicles tested and our knowledge of spinal degeneration. It is argued that the modelling and fatigue approaches combined offer a basis for estimating the effects of vibration and shock on health. Although the human variables are such that the approach, as yet, only offers rough estimates, it offers a good basis for understanding. The approach indicates that peak values are important and large peaks dominate risk. The method indicates that long term r.m.s. methods probably underestimate the risk of injury. The BS 6841Wband ISO 2631Wkweightings have shortcomings when used where peak values are important. A simple model may be more appropriate. The principle can be applied to continuous vibration as well as high acceleration events so that one method can be applied universally to continuous vibrations, high acceleration events and mixtures of these. An endurance limit can be hypothesised and, if this limit is sufficiently high, then the need for many measurements can be reduced.

Ultrasonic and optical evaluation of surgical implant materials and devices. A durability study of pericardial bioprostheses

NASA Technical Reports Server (NTRS)

Schuster, P. R.

1984-01-01

Laser Doppler Anemometry (LDA) and accelerated fatigue testing were used in an attempt to assess the durability of two cardiac value bioprostheses. The LDA system was used to monitor the function of the cardiac valves over time. This was done through flow characterization in an aortic flow chamber, designed to closely simulate in vivo conditions, both in the near vicinity (sinuses of valsalva region) and also somewhat downstream (aortic region) from the values. The accelerated fatigue tester was operated by opening and closing the valves at a rate of 1300 R.P.M., about 18 x the normal rate. The results from the two test valves indicate a definite change in the flow characteristics downstream from the valve after certain accelerated test intervals. The high velocity cross-sectional flow area seems to increase over time in use, causing a decrease in the peak velocity. The tissue became more flaccid in certain areas, and tears were apparent at about 9.4 million cycles for the Ionescu-Shiley valve and at 24 million cycles for the Carpentier-Edwards valve. The use of Doppler ultrasound as a technique for monitoring the function of bioprostheses over time in vivo is also discussed.

How Well Does the Latest Anthropomorphic Test Device Mimic Human Impact Responses?

NASA Technical Reports Server (NTRS)

Newby, N.; Somers, J. T.; Caldwell, E.; Gernhardt, M.

2014-01-01

One of the goals of the NASA Occupant Protection Group is to understand the human tolerance to dynamic loading. This knowledge has to come through indirect approaches such as existing human response databases, anthropometric test devices (ATD), animal testing, post-mortem human subjects, and models. This study investigated the biofidelity of the National Highway Traffic Safety Administration's ATD named the THOR (test device for human occupant restraint). If THOR responds comparably to humans, then it could potentially be used as a human surrogate to help validate space vehicle requirements for occupant protection. The THOR responses to frontal and spinal impacts (ranging from 8 to 12 G with rise times of 40, 70, and 100 ms) were measured and compared to human volunteer responses (95 trials in frontal and 58 in spinal) previously collected by the U. S. Air Force on the same horizontal impact accelerator. The impact acceleration profiles tested are within the expected range of multi-purpose crew vehicle (MPCV) landing dynamics. A correlation score was calculated for each THOR to human comparison using CORA (CORrelation and Analysis) software. A two-parameter beta distribution model fit was obtained for each dependent variable using maximum likelihood estimation. For frontal impacts, the THOR head x-acceleration peak response correlated with the human response at 8 and 10-G 100 ms but not 10-G 70 ms. The phase lagged the human response. Head z-acceleration was not correlated. Chest x-acceleration was in phase, had a higher peak response, and was well correlated with lighter subjects (Cora = 0.8 for 46 kg vs. Cora = 0.4 for 126 kg). Head x-displacement had a leading phase. Several subjects responded with the same peak displacement but the mean of the group was lower. The shoulder x-displacement was in phase but had higher peaks than the human response. For spinal impacts, the THOR head x-acceleration was not well correlated. Head and chest z-acceleration was in phase but had a higher peak response. Chest z-acceleration was highly correlated with heavier subjects at lower G pulses (Cora = 0.86 for 125 kg at 8 G). The human response was variable in shoulder z-displacement but the THOR was in phase and was comparable to the mean peak response. Head xand z-displacement was in phase but had higher peaks. Seat pan forces were well correlated, were in phase, but had a larger peak response than most subjects. The THOR does not respond to frontal and spinal impacts exactly the same way that a human does. Some responses are well matched and others are not. Understanding the strengths and weaknesses of this ATD is an important first step in determining its usefulness in occupant protection at NASA

An analytical reconstruction model of the spread-out Bragg peak using laser-accelerated proton beams.

PubMed

Tao, Li; Zhu, Kun; Zhu, Jungao; Xu, Xiaohan; Lin, Chen; Ma, Wenjun; Lu, Haiyang; Zhao, Yanying; Lu, Yuanrong; Chen, Jia-Er; Yan, Xueqing

2017-07-07

With the development of laser technology, laser-driven proton acceleration provides a new method for proton tumor therapy. However, it has not been applied in practice because of the wide and decreasing energy spectrum of laser-accelerated proton beams. In this paper, we propose an analytical model to reconstruct the spread-out Bragg peak (SOBP) using laser-accelerated proton beams. Firstly, we present a modified weighting formula for protons of different energies. Secondly, a theoretical model for the reconstruction of SOBPs with laser-accelerated proton beams has been built. It can quickly calculate the number of laser shots needed for each energy interval of the laser-accelerated protons. Finally, we show the 2D reconstruction results of SOBPs for laser-accelerated proton beams and the ideal situation. The final results show that our analytical model can give an SOBP reconstruction scheme that can be used for actual tumor therapy.

Radiation skyshine from a 6 MeV medical accelerator.

PubMed

Gossman, Michael S; McGinley, Patton H; Rising, Mary B; Pahikkala, A Jussi

2010-05-06

This study assesses the dose level from skyshine produced by a 6 MeV medical accelerator. The analysis of data collected on skyshine yields professional guidance for future investigators as they attempt to quantify and qualify radiation protection concerns in shielding therapy vaults. Survey measurements using various field sizes and at varying distances from a primary barrier have enabled us to identify unique skyshine behavior in comparison to other energies already seen in literature. In order to correctly quantify such measurements outside a shielded barrier, one must take into consideration the fact that a skyshine maximum may not be observed at the same distance for all field sizes. A physical attribute of the skyshine scatter component was shown to increase to a maximum value at 4.6 m from the barrier for the largest field size used. We recommend that the largest field sizes be used in the field for the determination of skyshine effect and that the peak value be further analyzed specifically when considering shielding designs.

Influence of 10 % Cold Rolling Reduction on Ageing Behaviour of Hot Rolled Al-Cu-Si-Mn-Mg Alloy

NASA Astrophysics Data System (ADS)

Ghosh, S. K.

2014-10-01

In the current study, the effect of 10 % cold rolling on the different ageing phenomena of Al-Cu-Si-Mn-Mg alloy was investigated. Both hot rolled and cold rolled alloys were subjected to both natural and artificial ageing processes. Hardness was measured to understand the change in the mechanical property of the alloy before and after rolling and also during ageing processes. From microscopy, it was evident that the cold rolling and subsequent ageing provided the alloy with a structure in which CuAl2 precipitates were uniformly distributed. The alloy exhibited the peak hardness value of 92 VHN after 2 days of natural ageing, whereas the cold deformed (10 %) alloy exhibited the higher peak hardness value of 139 VHN after 3 days of natural ageing. Peak hardness of the alloy reached 94 VHN, when hot rolled alloy was subjected to ageing at 250 °C for 1 h, whereas 10 % cold rolling followed by ageing (100 °C, 15 min) demonstrated accelerated and elevated hardening. The ageing behaviours thus obtained permit the alloy to provide a range of desirable combinations of strength and ductility for high strength weight saving applications.

An algorithm developed in Matlab for the automatic selection of cut-off frequencies, in the correction of strong motion data

NASA Astrophysics Data System (ADS)

Sakkas, Georgios; Sakellariou, Nikolaos

2018-05-01

Strong motion recordings are the key in many earthquake engineering applications and are also fundamental for seismic design. The present study focuses on the automated correction of accelerograms, analog and digital. The main feature of the proposed algorithm is the automatic selection for the cut-off frequencies based on a minimum spectral value in a predefined frequency bandwidth, instead of the typical signal-to-noise approach. The algorithm follows the basic steps of the correction procedure (instrument correction, baseline correction and appropriate filtering). Besides the corrected time histories, Peak Ground Acceleration, Peak Ground Velocity, Peak Ground Displacement values and the corrected Fourier Spectra are also calculated as well as the response spectra. The algorithm is written in Matlab environment, is fast enough and can be used for batch processing or in real-time applications. In addition, the possibility to also perform a signal-to-noise ratio is added as well as to perform causal or acausal filtering. The algorithm has been tested in six significant earthquakes (Kozani-Grevena 1995, Aigio 1995, Athens 1999, Lefkada 2003 and Kefalonia 2014) of the Greek territory with analog and digital accelerograms.

Measurement of heat load density profile on acceleration grid in MeV-class negative ion accelerator.

PubMed

Hiratsuka, Junichi; Hanada, Masaya; Kojima, Atsushi; Umeda, Naotaka; Kashiwagi, Mieko; Miyamoto, Kenji; Yoshida, Masafumi; Nishikiori, Ryo; Ichikawa, Masahiro; Watanabe, Kazuhiro; Tobari, Hiroyuki

2016-02-01

To understand the physics of the negative ion extraction/acceleration, the heat load density profile on the acceleration grid has been firstly measured in the ITER prototype accelerator where the negative ions are accelerated to 1 MeV with five acceleration stages. In order to clarify the profile, the peripheries around the apertures on the acceleration grid were separated into thermally insulated 34 blocks with thermocouples. The spatial resolution is as low as 3 mm and small enough to measure the tail of the beam profile with a beam diameter of ∼16 mm. It was found that there were two peaks of heat load density around the aperture. These two peaks were also clarified to be caused by the intercepted negative ions and secondary electrons from detailed investigation by changing the beam optics and gas density profile. This is the first experimental result, which is useful to understand the trajectories of these particles.

RF conditioning and beam experiments on 400 keV RFQ accelerator at BARC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, Shrikrishna; Rao, S.V.L.S.; Kumar, Rajesh, E-mail: sgupta@barc.gov.in

2014-07-01

A 400 keV Radio-frequency quadrupole accelerator (RFQ) has been designed, developed and tested at BARC. This will be used as a neutron generator (via D-T reaction). The RFQ operates at a resonant frequency of 350 MHz and needs an RF power of ∼ 60 kW to accelerate the deuteron beam to 400 keV within a length of 1.03 m. Though the RFQ is designed for deuteron beam, it was tested by accelerating both the proton and deuteron beams to their designed values of 200 and 400 keV respectively. The proton and deuteron beam experiments required peak RF power of approx.more » 15 kW and 60 kW respectively at 350 MHz. The RF power from the tetrode amplifier and coaxial transmission lines is coupled to the cavity by a coaxial loop coupler. As the coupler and cavity operated at vacuum of better than 2e-6 torr, extensive RF conditioning of the cavity and coupler was performed to reach at the desired power levels. (author)« less

Experiment on the concrete slab for floor vibration evaluation of deteriorated building

NASA Astrophysics Data System (ADS)

Hong, S. U.; Na, J. H.; Kim, S. H.; Lee, Y. T.

2014-08-01

Damages from noise and vibration are increasing every year, and most of which are noises between floors in deteriorated building caused by floor impact sound. In this study, the floor vibration of the deteriorated buildings constructed with the concrete slabs of thickness no more than 150 mm was evaluated by the vibration impact sound. This highly reliable study was conducted to assess floor vibration according with the serviceability evaluation standard of Reiher / Meister and Koch and vibration evaluation standard of ISO and AIJ. Designed pressure for the concrete slab sample of floor vibration assessment was 24MPa, and the sample was manufactured pursuant to KS F 2865 and JIS A 1440-2 with size of 3200 mm × 3200 mm × 140 mm. Tests were conducted twice with accelerometers, and Fast Fourier Transform was performed for comparative analysis by the vibration assessment criteria. The peak displacement from Test 1 was in the range of 0.00869 - 0.02540 mm; the value of peak frequency ranged from 18 to 27 Hz, and the average value was 22Hz. The peak acceleration value from Test 2 was in the range of 0.47 - 1.07 % g; the value of peak frequency was 18.5 - 22.57 Hz, and the average was 21Hz. The vibration was apparently recognizable in most cases according to the Reiher/Meister standard. In case of Koch graph for the damage assessment of the structure, the vibration was at the medium level and causes no damage to the building structure. The measured vibration results did not exceed the damage limit or serviceability limit of building according to the vibration assessment criteria of ISO and residential assessment guidelines provided by Architectural Institute of Japan (AIJ).

The effect of motorcycle helmet fit on estimating head impact kinematics from residual liner crush.

PubMed

Bonin, Stephanie J; Gardiner, John C; Onar-Thomas, Arzu; Asfour, Shihab S; Siegmund, Gunter P

2017-09-01

Proper helmet fit is important for optimizing head protection during an impact, yet many motorcyclists wear helmets that do not properly fit their heads. The goals of this study are i) to quantify how a mismatch in headform size and motorcycle helmet size affects headform peak acceleration and head injury criteria (HIC), and ii) to determine if peak acceleration, HIC, and impact speed can be estimated from the foam liner's maximum residual crush depth or residual crush volume. Shorty-style helmets (4 sizes of a single model) were tested on instrumented headforms (4 sizes) during linear impacts between 2.0 and 10.5m/s to the forehead region. Helmets were CT scanned to quantify residual crush depth and volume. Separate linear regression models were used to quantify how the response variables (peak acceleration (g), HIC, and impact speed (m/s)) were related to the predictor variables (maximum crush depth (mm), crush volume (cm 3 ), and the difference in circumference between the helmet and headform (cm)). Overall, we found that increasingly oversized helmets reduced peak headform acceleration and HIC for a given impact speed for maximum residual crush depths less than 7.9mm and residual crush volume less than 40cm 3 . Below these levels of residual crush, we found that peak headform acceleration, HIC, and impact speed can be estimated from a helmet's residual crush. Above these crush thresholds, large variations in headform kinematics are present, possibly related to densification of the foam liner during the impact. Copyright © 2017 Elsevier Ltd. All rights reserved.

Analysis on the time and frequency domains of the acceleration in front crawl stroke.

PubMed

Gil, Joaquín Madera; Moreno, Luis-Millán González; Mahiques, Juan Benavent; Muñoz, Víctor Tella

2012-05-01

The swimming involves accelerations and decelerations in the swimmer's body. Thus, the main objective of this study is to make a temporal and frequency analysis of the acceleration in front crawl swimming, regarding the gender and the performance. The sample was composed by 31 male swimmers (15 of high-level and 16 of low-level) and 20 female swimmers (11 of high-level and 9 of low-level). The acceleration was registered from the third complete cycle during eight seconds in a 25 meters maximum velocity test. A position transducer (200Hz) was used to collect the data, and it was synchronized to an aquatic camera (25Hz). The acceleration in the temporal (root mean square, minimum and maximum of the acceleration) and frequency (power peak, power peak frequency and spectral area) domains was calculated with Fourier analysis, as well as the velocity and the spectrums distribution in function to present one or more main peaks (type 1 and type 2). A one-way ANOVA was used to establish differences between gender and performance. Results show differences between genders in all the temporal domain variables (p<0.05) and only the Spectral Area (SA) in the frequency domain (p<0.05). Between gender and performance, only the Root Mean Square (RMS) showed differences in the performance of the male swimmers (p<0.05) and in the higher level swimmers, the Maximum (Max) and the Power Peak (PP) of the acceleration showed differences between both genders (p<0.05). These results confirms the importance of knowing the RMS to determine the efficiency of the swimmers regarding gender and performance level.

An insight on correlations between kinematic rupture parameters from dynamic ruptures on rough faults

NASA Astrophysics Data System (ADS)

Thingbijam, Kiran Kumar; Galis, Martin; Vyas, Jagdish; Mai, P. Martin

2017-04-01

We examine the spatial interdependence between kinematic parameters of earthquake rupture, which include slip, rise-time (total duration of slip), acceleration time (time-to-peak slip velocity), peak slip velocity, and rupture velocity. These parameters were inferred from dynamic rupture models obtained by simulating spontaneous rupture on faults with varying degree of surface-roughness. We observe that the correlations between these parameters are better described by non-linear correlations (that is, on logarithm-logarithm scale) than by linear correlations. Slip and rise-time are positively correlated while these two parameters do not correlate with acceleration time, peak slip velocity, and rupture velocity. On the other hand, peak slip velocity correlates positively with rupture velocity but negatively with acceleration time. Acceleration time correlates negatively with rupture velocity. However, the observed correlations could be due to weak heterogeneity of the slip distributions given by the dynamic models. Therefore, the observed correlations may apply only to those parts of rupture plane with weak slip heterogeneity if earthquake-rupture associate highly heterogeneous slip distributions. Our findings will help to improve pseudo-dynamic rupture generators for efficient broadband ground-motion simulations for seismic hazard studies.

How Well Does the Latest Anthropomorphic Test Device Mimic Human Impact Responses?

NASA Technical Reports Server (NTRS)

Newby, Nate; Somers, Jeff; Caldewll, Erin; Gernhardt, Michael

2014-01-01

One of the goals of the NASA Occupant Protection Group is to understand the human tolerance to dynamic loading. This knowledge has to come through indirect approaches such as existing human response databases, anthropometric test devices (ATD), animal testing, post-­-mortem human subjects, and models. This study investigated the biofidelity of the National Highway Traffic Safety Administration's ATD named the THOR (test device for human occupant restraint). If THOR responds comparably to humans, then it could potentially be used as a human surrogate to help validate space vehicle requirements for occupant protection. The THOR responses to frontal and spinal impacts (ranging from 8 to 12 G with rise times of 40, 70, and 100 ms) were measured and compared to human volunteer responses (95 trials in frontal and 58 in spinal) previously collected by the U. S. Air Force on the same horizontal impact accelerator. The impact acceleration profiles tested are within the expected range of multi-­-purpose crew vehicle (MPCV) landing dynamics. A correlation score was calculated for each THOR to human comparison using CORA (CORrelation and Analysis) software. A two-­-parameter beta distribution model fit was obtained for each dependent variable using maximum likelihood estimation. For frontal impacts, the THOR head x-­-acceleration peak response correlated with the human response at 8 and 10-­-G 100 ms but not 10-­-G 70 ms. The phase lagged the human response. Head z-­-acceleration was not correlated. Chest x-­-acceleration was in phase, had a higher peak response, and was well correlated with lighter subjects (Cora = 0.8 for 46 kg vs. Cora = 0.4 for 126 kg). Head x-­-displacement had a leading phase. Several subjects responded with the same peak displacement but the mean of the group was lower. The shoulder x-­-displacement was in phase but had higher peaks than the human response. For spinal impacts, the THOR head x-­-acceleration was not well correlated. Head and chest z-­-acceleration was in phase but had a higher peak response. Chest z-­-acceleration was highly correlated with heavier subjects at lower G pulses (Cora = 0.86 for 125 kg at 8 G). The human response was variable in shoulder z-­-displacement but the THOR was in phase and was comparable to the mean peak response. Head x-­- and z-­-displacement was in phase but had higher peaks. Seat pan forces were well correlated, were in phase, but had a larger peak response than most subjects. The THOR does not respond to frontal and spinal impacts exactly the same way that a human does. Some responses are well matched and others are not. Understanding the strengths and weaknesses of this ATD is an important first step in determining its usefulness in occupant protection at NASA

Effects of different computer typing speeds on acceleration and peak contact pressure of the fingertips during computer typing.

PubMed

Yoo, Won-Gyu

2015-01-01

[Purpose] This study showed the effects of different computer typing speeds on acceleration and peak contact pressure of the fingertips during computer typing. [Subjects] Twenty-one male computer workers voluntarily consented to participate in this study. They consisted of 7 workers who could type 200-300 characteristics/minute, 7 workers who could type 300-400 characteristics/minute, and 7 workers who could type 400-500 chracteristics/minute. [Methods] This study was used to measure the acceleration and peak contact pressure of the fingertips for different typing speed groups using an accelerometer and CONFORMat system. [Results] The fingertip contact pressure was increased in the high typing speed group compared with the low and medium typing speed groups. The fingertip acceleration was increased in the high typing speed group compared with the low and medium typing speed groups. [Conclusion] The results of the present study indicate that a fast typing speed cause continuous pressure stress to be applied to the fingers, thereby creating pain in the fingers.

Compressibility effects on rotor forces in the leakage path between a shrouded pump impeller and its housing

NASA Technical Reports Server (NTRS)

Cao, Nhai The

1993-01-01

A modified approach to Childs' previous work on fluid-structure interaction forces in the leakage path between an impeller shroud and its housing is presented in this paper. Three governing equations consisting of continuity, path-momentum, and circumferential-momentum equations were developed to describe the leakage path inside a pump impeller. Radial displacement perturbations were used to solve for radial and circumferential force coefficients. In addition, impeller-discharge pressure disturbances were used to obtain pressure oscillation responses due to precessing impeller pressure wave pattern. Childs' model was modified from an incompressible model to a compressible barotropic-fluid model (the density of the working fluid is a function of the pressure and a constant temperature only). Results obtained from this model yielded interaction forces for radial and circumferential force coefficients. Radial and circumferential forces define reaction forces within the impeller leakage path. An acoustic model for the same leakage path was also developed. The convective, Coriolis, and centrifugal acceleration terms are removed from the compressible model to obtain the acoustics model. A solution due to impeller discharge pressure disturbances model was also developed for the compressible and acoustics models. The results from these modifications are used to determine what effects additional perturbation terms in the compressible model have on the acoustic model. The results show that the additional fluid mechanics terms in the compressible model cause resonances (peaks) in the force coefficient response curves. However, these peaks only occurred at high values of inlet circumferential velocity ratios greater than 0.7. The peak pressure oscillation was shown to occur at the wearing ring seal. Introduction of impeller discharge disturbances with n = 11 diametral nodes showed that maximum peak pressure oscillations occurred at nondimensional precession frequencies of f = 6.4 and f = 7.8 for this particular pump. Bolleter's results suggest that for peak pressure oscillations to occur at the wearing ring seal, the nondimensional excitation frequency should be on the order of f = 2.182 for n = 11. The resonances found in this research do not match the excitation frequencies predicted by Bolleter. At the predicted peak excitation frequencies given by Bolleter, the compressible model shows an attenuation of the pressure oscillations at the seal exit. The compressibility of the fluid does not have a significant influence on the model at low values of nondimensional excitation frequency. At high values of nondimensional frequency, the effects of compressibility become more significant. For the acoustic analysis, the convective, Coriolis, and centrifugal acceleration terms do affect the results to a limited extent for precession excitation and to a large extent for a pressure excitation when the fluid operates at relatively high Mach numbers.

Stochastic shock response spectrum decomposition method based on probabilistic definitions of temporal peak acceleration, spectral energy, and phase lag distributions of mechanical impact pyrotechnic shock test data

NASA Astrophysics Data System (ADS)

Hwang, James Ho-Jin; Duran, Adam

2016-08-01

Most of the times pyrotechnic shock design and test requirements for space systems are provided in Shock Response Spectrum (SRS) without the input time history. Since the SRS does not describe the input or the environment, a decomposition method is used to obtain the source time history. The main objective of this paper is to develop a decomposition method producing input time histories that can satisfy the SRS requirement based on the pyrotechnic shock test data measured from a mechanical impact test apparatus. At the heart of this decomposition method is the statistical representation of the pyrotechnic shock test data measured from the MIT Lincoln Laboratory (LL) designed Universal Pyrotechnic Shock Simulator (UPSS). Each pyrotechnic shock test data measured at the interface of a test unit has been analyzed to produce the temporal peak acceleration, Root Mean Square (RMS) acceleration, and the phase lag at each band center frequency. Maximum SRS of each filtered time history has been calculated to produce a relationship between the input and the response. Two new definitions are proposed as a result. The Peak Ratio (PR) is defined as the ratio between the maximum SRS and the temporal peak acceleration at each band center frequency. The ratio between the maximum SRS and the RMS acceleration is defined as the Energy Ratio (ER) at each band center frequency. Phase lag is estimated based on the time delay between the temporal peak acceleration at each band center frequency and the peak acceleration at the lowest band center frequency. This stochastic process has been applied to more than one hundred pyrotechnic shock test data to produce probabilistic definitions of the PR, ER, and the phase lag. The SRS is decomposed at each band center frequency using damped sinusoids with the PR and the decays obtained by matching the ER of the damped sinusoids to the ER of the test data. The final step in this stochastic SRS decomposition process is the Monte Carlo (MC) simulation. The MC simulation identifies combinations of the PR and decays that can meet the SRS requirement at each band center frequency. Decomposed input time histories are produced by summing the converged damped sinusoids with the MC simulation of the phase lag distribution.

32-channel 3 Tesla receive-only phased-array head coil with soccer-ball element geometry.

PubMed

Wiggins, G C; Triantafyllou, C; Potthast, A; Reykowski, A; Nittka, M; Wald, L L

2006-07-01

A 32-channel 3T receive-only phased-array head coil was developed for human brain imaging. The helmet-shaped array was designed to closely fit the head with individual overlapping circular elements arranged in patterns of hexagonal and pentagonal symmetry similar to that of a soccer ball. The signal-to-noise ratio (SNR) and noise amplification (g-factor) in accelerated imaging applications were quantitatively evaluated in phantom and human images and compared with commercially available head coils. The 32-channel coil showed SNR gains of up to 3.5-fold in the cortex and 1.4-fold in the corpus callosum compared to a (larger) commercial eight-channel head coil. The experimentally measured g-factor performance of the helmet array showed significant improvement compared to the eight-channel array (peak g-factor 59% and 26% of the eight-channel values for four- and fivefold acceleration). The performance of the arrays is demonstrated in high-resolution and highly accelerated brain images. Copyright (c) 2006 Wiley-Liss, Inc.

Imprint of Rupture Directivity From Ground Motions of the 24 August 2016 Mw6.2 Central Italy Earthquake

NASA Astrophysics Data System (ADS)

Ren, Yefei; Wang, Hongwei; Wen, Ruizhi

2017-12-01

An Mw6.2 earthquake occurred in Central Italy on 24 August 2016. The objective of this study was to reveal the imprint of rupture directivity using the strong motion recordings. The strong motion stations were separated into two groups: southeast (SE) and northwest (NW). The effects of rupture directivity on the peak ground acceleration (PGA), peak ground velocity (PGV), and pseudo spectral acceleration (PSA) were investigated. The observed values of these parameters were compared with predicted values derived from ground motion prediction equations. The results showed that the residuals between the observed and predicted PGAs, PGVs, and PSAs at periods of T < 1 s were correlated significantly with azimuth angle and generally larger in the NW sector, reflecting that the observed PGAs, PGVs, and short-period PSAs in the NW sector were generally larger than observed in the SE sector. These phenomena are accordant with the theoretical law that the rupture directivity causes higher amplitudes in the forward direction compared with the backward direction. Finally, selected source rupture parameters were inverted using PGAs and PGVs. This revealed that the rupture was predominantly unilateral rupture, the major rupture was likely at an azimuth of 360°, and the length of the major rupture was proportional to 70%-100% of the total ruptured fault, confirming that rupture directivity caused the differences in the ground motions observed in the SE and NW sectors.

Effect of long-duration spaceflight on postural control during self-generated perturbations

NASA Technical Reports Server (NTRS)

Layne, C. S.; Mulavara, A. P.; McDonald, P. V.; Pruett, C. J.; Kozlovskaya, I. B.; Bloomberg, J. J.

2001-01-01

This report is the first systematic evaluation of the effects of prolonged weightlessness on the bipedal postural control processes during self-generated perturbations produced by voluntary upper limb movements. Spaceflight impacts humans in a variety of ways, one of which is compromised postflight postural control. We examined the neuromuscular activation characteristics and center of pressure (COP) motion associated with arm movement of eight subjects who experienced long-duration spaceflight (3--6 mo) aboard the Mir space station. Surface electromyography, arm acceleration, and COP motion were collected while astronauts performed rapid unilateral shoulder flexions before and after spaceflight. Subjects generally displayed compromised postural control after flight, as evidenced by modified COP peak-to-peak anterior-posterior and mediolateral excursion, and pathlength relative to preflight values. These changes were associated with disrupted neuromuscular activation characteristics, particularly after the completion of arm acceleration (i.e., when subjects were attempting to maintain upright posture in response to self-generated perturbations). These findings suggest that, although the subjects were able to assemble coordination modes that enabled them to generate rapid arm movements, the subtle control necessary to maintain bipedal equilibrium evident in their preflight performance is compromised after long-duration spaceflight.

Effect of Long-Duration Spaceflight on Postural Control During Self-Generated Perturbations

NASA Technical Reports Server (NTRS)

Layne, Charles S.; Mulavera, Ajitkumar P.; McDonald, P. Vernon; Pruett, Casey J.; Kozlovskaya, Innessa B.; Bloomberg, Jacob J.

2001-01-01

This report is the first systematic evaluation of the effects of prolonged weightlessness on the bipedal postural control processes during self-generated perturbations produced by voluntary upper limb movements. Spaceflight impacts humans in a variety of ways, one of which is compromised postflight postural control. We examined the neuromuscular activation characteristics and center of pressure motion (COP) associated with arm movement of eight subjects who experienced long duration spaceflight (3-6 months) aboard the Mir space station. Surface electromyography (EMG), arm acceleration, and COP motion were collected while astronauts performed rapid unilateral shoulder flexions prior to and after spaceflight. Subjects displayed compromised postural control after flight as evidenced by modified peak-to-peak COP anterior-posterior and medio-lateral motion and COP pathlength relative to preflight values. These changes were associated with disrupted neuromuscular activation characteristics, particularly after the completion of arm acceleration (i.e. when subjects were attempting to maintain their upright posture). These findings suggest that although the subjects were able to assemble coordination modes that enabled them to generate rapid arm movements, the subtle control necessary to maintain bipedal equilibrium evident in their preflight performance is compromised after long duration spaceflight.

Head impact exposure sustained by football players on days of diagnosed concussion.

PubMed

Beckwith, Jonathan G; Greenwald, Richard M; Chu, Jeffrey J; Crisco, Joseph J; Rowson, Steven; Duma, Stefan M; Broglio, Steven P; McAllister, Thomas W; Guskiewicz, Kevin M; Mihalik, Jason P; Anderson, Scott; Schnebel, Brock; Brolinson, P Gunnar; Collins, Michael W

2013-04-01

This study compares the frequency and severity of head impacts sustained by football players on days with and without diagnosed concussion and to identify the sensitivity and specificity of single-impact severity measures to diagnosed injury. One thousand two hundred eight players from eight collegiate football teams and six high school football teams wore instrumented helmets to measure head impacts during all team sessions, of which 95 players were diagnosed with concussion. Eight players sustained two injuries and one sustained three, providing 105 injury cases. Measures of head kinematics (peak linear and rotational acceleration, Gadd severity index, head injury criteria (HIC15), and change in head velocity (Δv)) and the number of head impacts sustained by individual players were compared between days with and without diagnosed concussion. Receiver operating characteristic curves were generated to evaluate the sensitivity and specificity of each kinematic measure to diagnosed concussion using only those impacts that directly preceded diagnosis. Players sustained a higher frequency of impacts and impacts with more severe kinematic properties on days of diagnosed concussion than on days without diagnosed concussion. Forty-five injury cases were immediately diagnosed after head impact. For these cases, peak linear acceleration and HIC15 were most sensitive to immediately diagnosed concussion (area under the curve = 0.983). Peak rotational acceleration was less sensitive to diagnosed injury than all other kinematic measures (P = 0.01), which are derived from linear acceleration (peak linear, HIC15, Gadd severity index, and Δv). Players sustained more impacts and impacts of higher severity on days of diagnosed concussion than on days without diagnosed concussion. In addition, of historical measures of impact severity, those associated with peak linear acceleration are the best predictors of immediately diagnosed concussion.

Head Impact Exposure Sustained by Football Players on Days of Diagnosed Concussion

PubMed Central

Beckwith, Jonathan G.; Greenwald, Richard M.; Chu, Jeffrey J.; Crisco, Joseph J.; Rowson, Steven; Duma, Stefan M.; Broglio, Steven P.; McAllister, Thomas W.; Guskiewicz, Kevin M.; Mihalik, Jason P.; Anderson, Scott; Schnebel, Brock; Brolinson, P. Gunnar; Collins, Michael W.

2012-01-01

Purpose This study compares the frequency and severity of head impacts sustained by football players on days with and without diagnosed concussion and to identify the sensitivity and specificity of single impact severity measures to diagnosed injury. Methods 1,208 players from eight collegiate and six high school football teams wore instrumented helmets to measure head impacts during all team sessions, of which 95 players were diagnosed with concussion. Eight players sustained two injuries and one three, providing 105 injury cases. Measures of head kinematics (peak linear and rotational acceleration, Gadd Severity Index (GSI), Head Injury Criteria (HIC15), change in head velocity (Δv)) and the number of head impacts sustained by individual players were compared between days with and without diagnosed concussion. Receiver operator characteristic curves were generated to evaluate the sensitivity and specificity of each kinematic measure to diagnosed concussion using only those impacts that directly preceded diagnosis. Results Players sustained a higher frequency of impacts and impacts with more severe kinematic properties on days of diagnosed concussion than on days without diagnosed concussion. Forty-five injury cases were immediately diagnosed following head impact. For these cases, peak linear acceleration and HIC15 were most sensitive to immediately diagnosed concussion (AUC = 0.983). Peak rotational acceleration was less sensitive to diagnosed injury than all other kinematic measures (p = 0.01) which are derived from linear acceleration (peak linear, HIC15, GSI, and Δv). Conclusions Players sustain more impacts and impacts of higher severity on days of diagnosed concussion than on days without diagnosed concussion. Additionally, of historical measures of impact severity, those associated with peak linear acceleration are the best predictors of immediately diagnosed concussion. PMID:23135363

Estimates of Tibial Shock Magnitude in Men and Women at the Start and End of a Military Drill Training Program.

PubMed

Rice, Hannah M; Saunders, Samantha C; McGuire, Stephen J; O'Leary, Thomas J; Izard, Rachel M

2018-03-26

Foot drill is a key component of military training and is characterized by frequent heel stamping, likely resulting in high tibial shock magnitudes. Higher tibial shock during running has previously been associated with risk of lower limb stress fractures, which are prevalent among military populations. Quantification of tibial shock during drill training is, therefore, warranted. This study aimed to provide estimates of tibial shock during military drill in British Army Basic training. The study also aimed to compare values between men and women, and to identify any differences between the first and final sessions of training. Tibial accelerometers were secured on the right medial, distal shank of 10 British Army recruits (n = 5 men; n = 5 women) throughout a scheduled drill training session in week 1 and week 12 of basic military training. Peak positive accelerations, the average magnitude above given thresholds, and the rate at which each threshold was exceeded were quantified. Mean (SD) peak positive acceleration was 20.8 (2.2) g across all sessions, which is considerably higher than values typically observed during high impact physical activity. Magnitudes of tibial shock were higher in men than women, and higher in week 12 compared with week 1 of training. This study provides the first estimates of tibial shock magnitude during military drill training in the field. The high values suggest that military drill is a demanding activity and this should be considered when developing and evaluating military training programs. Further exploration is required to understand the response of the lower limb to military drill training and the etiology of these responses in the development of lower limb stress fractures.

The September 19, 1985 Michoacan Earthquake: Aftershock acceleration data recorded by a temporary installation of strong motion instruments

NASA Astrophysics Data System (ADS)

Munguía, Luis; Simila, Gerry W.; McNally, Karen C.; Thompson, Howard

1986-06-01

We describe acceleration signals recorded for nine aftershocks of the September 19, 1985 Michoacan earthquake. To obtain this data set, three A-700 Teledyne-Geotech digital strong-motion instruments were operated temporarily at two sites on the José María Morelos (La Villita) Dam, and at a site located at about 12 km to the west of the town of Zihuatanejo. Peak horizontal accelerations of 0.005 g to 0.031 g were recorded at epicentral distances between 10 and 75 km, for earthquakes with magnitude (mb) between 4.5 and 5.3. It was observed that the peak accelerations recorded at a site on the embankment of the dam (near the crest ) are approximately three times those recorded on the abutment bedrock portion of the dam. Although these sites were spatially separated by no more than 300 m, differences among their records are also significant. Waveforms recorded at the embankment site look more complex than those from the abutment site. This fact, as well as the higher peak accelerations on the embankment, provides evidence of a strong influence of the structure of the dam on the ground motion at the embankment site.

Footwear affects the behavior of low back muscles when jogging.

PubMed

Ogon, M; Aleksiev, A R; Spratt, K F; Pope, M H; Saltzman, C L

2001-08-01

Use of modified shoes and insole materials has been widely advocated to treat low back symptoms from running impacts, although considerable uncertainty remains regarding the effects of these devices on the rate of shock transmission to the spine. This study investigated the effects of shoes and insole materials on a) the rate of shock transmission to the spine, b) the temporal response of spinal musculature to impact loading, and c) the time interval between peak lumbar acceleration and peak lumbar muscle response. It was hypothesised that shoes and inserts a) decrease the rate of shock transmission, b) decrease the low back muscle response time, and c) shorten the time interval between peak lumbar acceleration and peak lumbar muscle response. Twelve healthy subjects were tested while jogging barefoot (unshod) or wearing identical athletic shoes (shod). Either no material, semi-rigid (34 Shore A), or soft (9.5 Shore A) insole material covered the force plate in the barefoot conditions and was placed as insole when running shod. Ground reaction forces, acceleration at the third lumbar level, and erector spinae myoelectric activity were recorded simultaneously. The rate of shock transmission to the spine was greater (p < 0.0003) unshod (acceleration rate: Means +/- SD 127.35 +/- 87.23 g/s) than shod (49.84 +/- 33.98 g/s). The temporal response of spinal musculature following heel strike was significantly shorter (p < 0.023) unshod (0.038 +/- 0.021 s) than shod (0.047 +/- 0.036 s). The latency between acceleration peak (maximal external force) and muscle response peak (maximal internal force) was significantly (p < 0.021) longer unshod (0.0137 +/- 0.022s) than shod (0.004 +/- 0.040 s). These results suggest that one of the benefits of running shoes and insoles is improved temporal synchronization between potentially destabilizing external forces and stabilizing internal forces around the lumbar spine.

Earthquake Macro-zonation Based Peak Ground Acceleration, Modified Mercalli Intensity, And Type of Rocks around Matano Fault

NASA Astrophysics Data System (ADS)

Karnaen, Muh; Suriamihardja, D. A.; Maulana, A.; Jaya, A.

2018-03-01

This study aims to determine earthquake vulnerable zones. We conducted research on earthquake macro-zonation based on PGA, Modified Mercalli Intensity (MMI), and type of rocks around Matano Fault in the area of 1.60 S to 2.990 S and 120.50 E to 122.470 E. We have acquired Maximum PGA and Modified Mercalli Intensity (MMI) for each observation point on the ground from the four major earthquake events. The empirical model is used due to lack of acceleration data recorded. We tried some empirical methods, but the McGuire method is found to be acceptable for this area. The result gives the maximum variation of PGA which is ranged between 18.40 - 363.54 gals. While the variation of MMI using empirical Wald attenuation gives values ranging from 2.9 - 7.7 MMI. The most vulnerable zone is located around Sorowako city with PGA value of 326.55 gals and MMI value of 7.5 MMI. This area is between ultra-basic rock and metamorphic rock formation. The vulnerable zone is near largest earthquake 6.2 M on 15-02-2011.

Observation of High Transformer Ratio of Shaped Bunch Generated by an Emittance-Exchange Beam Line.

PubMed

Gao, Q; Ha, G; Jing, C; Antipov, S P; Power, J G; Conde, M; Gai, W; Chen, H; Shi, J; Wisniewski, E E; Doran, D S; Liu, W; Whiteford, C E; Zholents, A; Piot, P; Baturin, S S

2018-03-16

Collinear wakefield acceleration has been long established as a method capable of generating ultrahigh acceleration gradients. Because of the success on this front, recently, more efforts have shifted towards developing methods to raise the transformer ratio (TR). This figure of merit is defined as the ratio of the peak acceleration field behind the drive bunch to the peak deceleration field inside the drive bunch. TR is always less than 2 for temporally symmetric drive bunch distributions and therefore recent efforts have focused on generating asymmetric distributions to overcome this limitation. In this Letter, we report on using the emittance-exchange method to generate a shaped drive bunch to experimentally demonstrate a TR≈5 in a dielectric wakefield accelerator.

A semi-empirical analysis of strong-motion peaks in terms of seismic source, propagation path, and local site conditions

NASA Astrophysics Data System (ADS)

Kamiyama, M.; Orourke, M. J.; Flores-Berrones, R.

1992-09-01

A new type of semi-empirical expression for scaling strong-motion peaks in terms of seismic source, propagation path, and local site conditions is derived. Peak acceleration, peak velocity, and peak displacement are analyzed in a similar fashion because they are interrelated. However, emphasis is placed on the peak velocity which is a key ground motion parameter for lifeline earthquake engineering studies. With the help of seismic source theories, the semi-empirical model is derived using strong motions obtained in Japan. In the derivation, statistical considerations are used in the selection of the model itself and the model parameters. Earthquake magnitude M and hypocentral distance r are selected as independent variables and the dummy variables are introduced to identify the amplification factor due to individual local site conditions. The resulting semi-empirical expressions for the peak acceleration, velocity, and displacement are then compared with strong-motion data observed during three earthquakes in the U.S. and Mexico.

Electron acceleration in downward auroral field-aligned currents

NASA Astrophysics Data System (ADS)

Cran-McGreehin, Alexandra P.; Wright, Andrew N.

2005-10-01

The auroral downward field-aligned current is mainly carried by electrons accelerated up from the ionosphere into the magnetosphere along magnetic field lines. Current densities are typically of the order of a few μ Am-2, and the associated electrons are accelerated to energies of several hundred eV up to a few keV. This downward current has been modeled by Temerin and Carlson (1998) using an electron fluid. This paper extends that model by describing the electron populations via distribution functions and modeling all of the F region. We assume a given ion density profile, and invoke quasi-neutrality to solve for the potential along the field line. Several important locations and quantities emerge from this model: the ionospheric trapping point, below which the ionospheric population is trapped by an ambipolar electric field; the location of maximum E∥, of the order of a few mVm-1, which lies earthward of the B/n peak; the acceleration region, located around the B/n peak, which normally extends between altitudes of 500 and 3000 km; and the total potential increase along the field line, of the order of a few hundred V up to several kV. The B/n peak is found to be the central factor determining the altitude and magnitude of the accelerating potential required. Indeed, the total potential drop is found to depend solely on the equilibrium properties in the immediate vicinity of the B/n peak.

Ion velocity distributions in dipolarization events: Distributions in the central plasma sheet

NASA Astrophysics Data System (ADS)

Birn, J.; Runov, A.; Zhou, X.-Z.

2017-08-01

Using combined MHD/test particle simulations, we further explore characteristic ion velocity distributions in the central plasma sheet (CPS) in relation to dipolarization events. Distributions in the CPS within the dipolarized flux bundle (DFB) that follows the passage of a dipolarization front typically show two opposing low subthermal-energy beams with a ring-like component perpendicular to the magnetic field at about twice the thermal energy. The dominance of the perpendicular anisotropy and a field-aligned peak at lower energy agree qualitatively with ion distribution functions derived from "Time History of Events and Macroscale Interactions during Substorms" observations. At locations somewhat off the equatorial plane the field-aligned peaks are shifted by a field-aligned component of the bulk flow, such that one peak becomes centered near zero net velocity, which makes it less likely to be observed. The origins of the field-aligned peaks are low-energy lobe (or near plasma sheet boundary layer) regions, while the ring distribution originates mostly from thermal plasma sheet particles on extended field lines. The acceleration mechanisms are also quite different: the beam ions are accelerated first by the E × B drift motion of the DFB and then by a slingshot effect of the earthward convecting DFB (akin to first-order Fermi, type B, acceleration), which causes an increase in field-aligned speed. In contrast, the ring particles are accelerated by successive, betatron-like acceleration after entering the high electric field region of an earthward propagating DFB.

Peake in Columbus with sensor

NASA Image and Video Library

2016-01-26

ISS046e024411 (01/26/2016) --- European Space Agency (ESA) astronaut Timothy Peake prepares to install a space acceleration measurement system sensor inside the European Columbus module aboard the International Space Station. The device is used in an ongoing study of the small forces (vibrations and accelerations) on the International Space Station resulting from the operation of hardware, crew activities, dockings and maneuvering. Results generalize the types of vibrations affecting vibration-sensitive experiments.

Is midsole thickness a key parameter for the running pattern?

PubMed

Chambon, Nicolas; Delattre, Nicolas; Guéguen, Nils; Berton, Eric; Rao, Guillaume

2014-01-01

Many studies have highlighted differences in foot strike pattern comparing habitually shod runners who ran barefoot and with running shoes. Barefoot running results in a flatter foot landing and in a decreased vertical ground reaction force compared to shod running. The aim of this study was to investigate one possible parameter influencing running pattern: the midsole thickness. Fifteen participants ran overground at 3.3 ms(-1) barefoot and with five shoes of different midsole thickness (0 mm, 2 mm, 4 mm, 8 mm, 16 mm) with no difference of height between rearfoot and forefoot. Impact magnitude was evaluated using transient peak of vertical ground reaction force, loading rate, tibial acceleration peak and rate. Hip, knee and ankle flexion angles were computed at touch-down and during stance phase (range of motion and maximum values). External net joint moments and stiffness for hip, knee and ankle joints were also observed as well as global leg stiffness. No significant effect of midsole thickness was observed on ground reaction force and tibial acceleration. However, the contact time increased with midsole thickness. Barefoot running compared to shod running induced ankle in plantar flexion at touch-down, higher ankle dorsiflexion and lower knee flexion during stance phase. These adjustments are suspected to explain the absence of difference on ground reaction force and tibial acceleration. This study showed that the presence of very thin footwear upper and sole was sufficient to significantly influence the running pattern. Copyright © 2014 Elsevier B.V. All rights reserved.

A link between occupant and vehicle accelerations during common driving tasks.

PubMed

Mathias, Anne C; Shibata, Peggy A; Sprague, James K

2014-01-01

When evaluating occupant motions during driving tasks, it is desirable to have a well-established correlation between vehicle and occupant accelerations. Therefore, this study demonstrated a methodology to quantify accelerations experienced by the driver of a passenger vehicle and compare them to associated vehicle motions. Acceleration levels were measured at the seat and the driver’s head, cervical spine, and lumbar spine during six non-collision driving tasks. Tasks included mounting a 127 mm (5 in) -high curb, crossing railroad tracks, driving on a rough road, braking heavily from 13.4 m/s (30 mph), having a 89 mm (3.5 in)-diameter roller sequentially pass under two tires, and dropping one tire from a 171-mm (6.75 in) height. The driver experienced peak resultant accelerations of similar magnitudes across all trials. Peak body accelerations were less than 1.2 g, including 0.82 g lumbar acceleration during heavy braking and 0.88 g head acceleration during the curb mount. These preliminary measurements are comparable to or lower than accelerations experienced during non-driving activities such as sitting quickly. This study contributes to the scientific understanding of accelerations experienced by vehicle occupants and demonstrates the potential to relate vehicle and occupant accelerations during common driving activities that do not involve collisions.

Quantifying Diastolic Function: From E-Waves as Triangles to Physiologic Contours via the 'Geometric Method'.

PubMed

Golman, Mikhail; Padovano, William; Shmuylovich, Leonid; Kovács, Sándor J

2018-03-01

Conventional echocardiographic diastolic function (DF) assessment approximates transmitral flow velocity contours (Doppler E-waves) as triangles, with peak (E peak ), acceleration time (AT), and deceleration time (DT) as indexes. These metrics have limited value because they are unable to characterize the underlying physiology. The parametrized diastolic filling (PDF) formalism provides a physiologic, kinematic mechanism based characterization of DF by extracting chamber stiffness (k), relaxation (c), and load (x o ) from E-wave contours. We derive the mathematical relationship between the PDF parameters and E peak , AT, DT and thereby introduce the geometric method (GM) that computes the PDF parameters using E peak , AT, and DT as input. Numerical experiments validated GM by analysis of 208 E-waves from 31 datasets spanning the full range of clinical diastolic function. GM yielded indistinguishable average parameter values per subject vs. the gold-standard PDF method (k: R 2  = 0.94, c: R 2  = 0.95, x o : R 2  = 0.95, p < 0.01 all parameters). Additionally, inter-rater reliability for GM-determined parameters was excellent (k: ICC = 0.956 c: ICC = 0.944, x o : ICC = 0.993). Results indicate that E-wave symmetry (AT/DT) may comprise a new index of DF. By employing indexes (E peak , AT, DT) that are already in standard clinical use the GM capitalizes on the power of the PDF method to quantify DF in terms of physiologic chamber properties.

Two Distinct Types of CME-flare Relationships Based on SOHO and STEREO Observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, Soojeong; Moon, Yong-Jae; Kim, Rok-Soon

In this paper, we present two distinct types of coronal mass ejection (CME)-flare relationships according to their observing time differences using 107 events from 2010 to 2013. The observing time difference, Δ T , is defined as flare peak time minus CME first appearance time at Solar Terrestrial Relations Observatory ( STEREO ) COR1 field of view. There are 41 events for group A (Δ T < 0) and 66 events for group B (Δ T ≥ 0). We compare CME 3D parameters (speed and kinetic energy) based on multi-spacecraft data ( SOlar and Heliospheric Observatory ( SOHO ) andmore » STEREO A and B ) and their associated flare properties (peak flux, fluence, and duration). Our main results are as follows. First, there are better relationships between CME and flare parameters for group B than that of group A. In particular, CME 3D kinetic energy for group B is well correlated with flare fluence with the correlation coefficient of 0.67, which is much stronger than that (cc = 0.31) of group A. Second, the events belonging to group A have short flare durations of less than 1 hr (mean = 21 minutes), while the events for group B have longer durations up to 4 hr (mean = 81 minutes). Third, the mean value of height at peak speed for group B is 4.05 Rs, which is noticeably higher than that of group A (1.89 Rs). This is well correlated with the CME acceleration duration (cc = 0.75). A higher height at peak speed and a longer acceleration duration of CME for group B could be explained by the fact that magnetic reconnections for group B continuously occur for a longer time than those for group A.« less

The sensitivity of human mesenchymal stem cells to vibration and cold storage conditions representative of cold transportation

PubMed Central

Nikolaev, N. I.; Liu, Y.; Hussein, H.; Williams, D. J.

2012-01-01

In the current study, the mechanical and hypothermic damage induced by vibration and cold storage on human mesenchymal stem cells (hMSCs) stored at 2–8°C was quantified by measuring the total cell number and cell viability after exposure to vibration at 50 Hz (peak acceleration 140 m s−2 and peak displacement 1.4 mm), 25 Hz (peak acceleration 140 m s−2, peak displacement 5.7 mm), 10 Hz (peak acceleration 20 m s−2, peak displacement 5.1 mm) and cold storage for several durations. To quantify the viability of the cells, in addition to the trypan blue exclusion method, the combination of annexin V-FITC and propidium iodide was applied to understand the mode of cell death. Cell granularity and a panel of cell surface markers for stemness, including CD29, CD44, CD105 and CD166, were also evaluated for each condition. It was found that hMSCs were sensitive to vibration at 25 Hz, with moderate effects at 50 Hz and no effects at 10 Hz. Vibration at 25 Hz also increased CD29 and CD44 expression. The study further showed that cold storage alone caused a decrease in cell viability, especially after 48 h, and also increased CD29 and CD44 and attenuated CD105 expressions. Cell death would most likely be the consequence of membrane rupture, owing to necrosis induced by cold storage. The sensitivity of cells to different vibrations within the mechanical system is due to a combined effect of displacement and acceleration, and hMSCs with a longer cold storage duration were more susceptible to vibration damage, indicating a coupling between the effects of vibration and cold storage. PMID:22628214

Reconstruction of the Mars Science Laboratory Parachute Performance and Comparison to the Descent Simulation

NASA Technical Reports Server (NTRS)

Cruz, Juan R.; Way, David W.; Shidner, Jeremy D.; Davis, Jody L.; Adams, Douglas S.; Kipp, Devin M.

2013-01-01

The Mars Science Laboratory used a single mortar-deployed disk-gap-band parachute of 21.35 m nominal diameter to assist in the landing of the Curiosity rover on the surface of Mars. The parachute system s performance on Mars has been reconstructed using data from the on-board inertial measurement unit, atmospheric models, and terrestrial measurements of the parachute system. In addition, the parachute performance results were compared against the end-to-end entry, descent, and landing (EDL) simulation created to design, develop, and operate the EDL system. Mortar performance was nominal. The time from mortar fire to suspension lines stretch (deployment) was 1.135 s, and the time from suspension lines stretch to first peak force (inflation) was 0.635 s. These times were slightly shorter than those used in the simulation. The reconstructed aerodynamic portion of the first peak force was 153.8 kN; the median value for this parameter from an 8,000-trial Monte Carlo simulation yielded a value of 175.4 kN - 14% higher than the reconstructed value. Aeroshell dynamics during the parachute phase of EDL were evaluated by examining the aeroshell rotation rate and rotational acceleration. The peak values of these parameters were 69.4 deg/s and 625 deg/sq s, respectively, which were well within the acceptable range. The EDL simulation was successful in predicting the aeroshell dynamics within reasonable bounds. The average total parachute force coefficient for Mach numbers below 0.6 was 0.624, which is close to the pre-flight model nominal drag coefficient of 0.615.

9 GeV energy gain in a beam-driven plasma wakefield accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Litos, M.; Adli, E.; Allen, J. M.

2016-02-15

An electron beam has gained a maximum energy of 9 GeV per particle in a 1.3 m-long electron beam-driven plasma wakefield accelerator. The amount of charge accelerated in the spectral peak was 28.3 pC, and the root-mean-square energy spread was 5.0%. The mean accelerated charge and energy gain per particle of the 215 shot data set was 115 pC and 5.3 GeV, respectively, corresponding to an acceleration gradient of 4.0 GeV m -1 at the spectral peak. Moreover, the mean energy spread of the data set was 5.1%. Our results are consistent with the extrapolation of the previously reported energymore » gain results using a shorter, 36 cm-long plasma source to within 10%, evincing a non-evolving wake structure that can propagate distances of over a meter in length. Wake-loading effects were evident in the data through strong dependencies observed between various spectral properties and the amount of accelerated charge.« less

Two-color ionization injection using a plasma beatwave accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroeder, C. B.; Benedetti, C.; Esarey, E.

Two-color laser ionization injection is a method to generate ultra-low emittance (sub-100 nm transverse normalized emittance) beams in a laser-driven plasma accelerator. A plasma beatwave accelerator is proposed to drive the plasma wave for ionization injection, where the beating of the lasers effectively produces a train of long-wavelength pulses. The plasma beatwave accelerator excites a large amplitude plasma wave with low peak laser electric fields, leaving atomically-bound electrons with low ionization potential. A short-wavelength, low-amplitude ionization injection laser pulse (with a small ponderomotive force and large peak electric field) is used to ionize the remaining bound electrons at a wakemore » phase suitable for trapping, generating an ultra-low emittance electron beam that is accelerated in the plasma wave. Using a plasma beatwave accelerator for wakefield excitation, compared to short-pulse wakefield excitation, allows for a lower amplitude injection laser pulse and, hence, a lower emittance beam may be generated.« less

Two-color ionization injection using a plasma beatwave accelerator

DOE PAGES

Schroeder, C. B.; Benedetti, C.; Esarey, E.; ...

2018-01-10

Two-color laser ionization injection is a method to generate ultra-low emittance (sub-100 nm transverse normalized emittance) beams in a laser-driven plasma accelerator. A plasma beatwave accelerator is proposed to drive the plasma wave for ionization injection, where the beating of the lasers effectively produces a train of long-wavelength pulses. The plasma beatwave accelerator excites a large amplitude plasma wave with low peak laser electric fields, leaving atomically-bound electrons with low ionization potential. A short-wavelength, low-amplitude ionization injection laser pulse (with a small ponderomotive force and large peak electric field) is used to ionize the remaining bound electrons at a wakemore » phase suitable for trapping, generating an ultra-low emittance electron beam that is accelerated in the plasma wave. Using a plasma beatwave accelerator for wakefield excitation, compared to short-pulse wakefield excitation, allows for a lower amplitude injection laser pulse and, hence, a lower emittance beam may be generated.« less

A Low Cost VLSI Architecture for Spike Sorting Based on Feature Extraction with Peak Search.

PubMed

Chang, Yuan-Jyun; Hwang, Wen-Jyi; Chen, Chih-Chang

2016-12-07

The goal of this paper is to present a novel VLSI architecture for spike sorting with high classification accuracy, low area costs and low power consumption. A novel feature extraction algorithm with low computational complexities is proposed for the design of the architecture. In the feature extraction algorithm, a spike is separated into two portions based on its peak value. The area of each portion is then used as a feature. The algorithm is simple to implement and less susceptible to noise interference. Based on the algorithm, a novel architecture capable of identifying peak values and computing spike areas concurrently is proposed. To further accelerate the computation, a spike can be divided into a number of segments for the local feature computation. The local features are subsequently merged with the global ones by a simple hardware circuit. The architecture can also be easily operated in conjunction with the circuits for commonly-used spike detection algorithms, such as the Non-linear Energy Operator (NEO). The architecture has been implemented by an Application-Specific Integrated Circuit (ASIC) with 90-nm technology. Comparisons to the existing works show that the proposed architecture is well suited for real-time multi-channel spike detection and feature extraction requiring low hardware area costs, low power consumption and high classification accuracy.

Dynamic control of ocular disaccommodation: First and second-order dynamics

PubMed Central

Bharadwaj, Shrikant R.; Schor, Clifton M.

2006-01-01

Velocity and acceleration characteristics provide valuable information about dynamic control of accommodation. We investigated velocity and acceleration of disaccommodation (near-far focusing) from three starting positions. Peak velocity and peak acceleration of disaccommodation increased with the proximity of starting position however for a given starting position they were invariant of response magnitude. These results suggest that all disaccommodation responses are initiated towards a constant primary destination and are switched mid-flight to attain the desired final position. Large discrepancies between the primary destination and desired final position appear to produce overshoots and oscillations of small responses from proximal starting positions. PMID:16045960

Generation and characterization of electron bunches with ramped current profiles in a dual-frequency superconducting linear accelerator.

PubMed

Piot, P; Behrens, C; Gerth, C; Dohlus, M; Lemery, F; Mihalcea, D; Stoltz, P; Vogt, M

2012-01-20

We report on the successful experimental generation of electron bunches with ramped current profiles. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a superconducing radio frequency linear accelerator operating at two frequencies and a current-enhancing dispersive section. The produced ~700-MeV bunches have peak currents of the order of a kilo-Ampère. Data taken for various accelerator settings demonstrate the versatility of the method and, in particular, its ability to produce current profiles that have a quasilinear dependency on the longitudinal (temporal) coordinate. The measured bunch parameters are shown, via numerical simulations, to produce gigavolt-per-meter peak accelerating electric fields with transformer ratios larger than 2 in dielectric-lined waveguides. © 2012 American Physical Society

Intermittent Lagrangian velocities and accelerations in three-dimensional porous medium flow.

PubMed

Holzner, M; Morales, V L; Willmann, M; Dentz, M

2015-07-01

Intermittency of Lagrangian velocity and acceleration is a key to understanding transport in complex systems ranging from fluid turbulence to flow in porous media. High-resolution optical particle tracking in a three-dimensional (3D) porous medium provides detailed 3D information on Lagrangian velocities and accelerations. We find sharp transitions close to pore throats, and low flow variability in the pore bodies, which gives rise to stretched exponential Lagrangian velocity and acceleration distributions characterized by a sharp peak at low velocity, superlinear evolution of particle dispersion, and double-peak behavior in the propagators. The velocity distribution is quantified in terms of pore geometry and flow connectivity, which forms the basis for a continuous-time random-walk model that sheds light on the observed Lagrangian flow and transport behaviors.

A physically-based method for predicting peak discharge of floods caused by failure of natural and constructed earthen dams

USGS Publications Warehouse

Walder, J.S.; O'Connor, J. E.; Costa, J.E.; ,

1997-01-01

We analyse a simple, physically-based model of breach formation in natural and constructed earthen dams to elucidate the principal factors controlling the flood hydrograph at the breach. Formation of the breach, which is assumed trapezoidal in cross-section, is parameterized by the mean rate of downcutting, k, the value of which is constrained by observations. A dimensionless formulation of the model leads to the prediction that the breach hydrograph depends upon lake shape, the ratio r of breach width to depth, the side slope ?? of the breach, and the parameter ?? = (V.D3)(k/???gD), where V = lake volume, D = lake depth, and g is the acceleration due to gravity. Calculations show that peak discharge Qp depends weakly on lake shape r and ??, but strongly on ??, which is the product of a dimensionless lake volume and a dimensionless erosion rate. Qp(??) takes asymptotically distinct forms depending on whether < ??? 1 or < ??? 1. Theoretical predictions agree well with data from dam failures for which k could be reasonably estimated. The analysis provides a rapid and in many cases graphical way to estimate plausible values of Qp at the breach.We analyze a simple, physically-based model of breach formation in natural and constructed earthen dams to elucidate the principal factors controlling the flood hydrograph at the breach. Formation of the breach, which is assumed trapezoidal in cross-section, is parameterized by the mean rate of downcutting, k, the value of which is constrained by observations. A dimensionless formulation of the model leads to the prediction that the breach hydrograph depends upon lake shape, the ratio r of breach width to depth, the side slope ?? of the breach, and the parameter ?? = (V/D3)(k/???gD), where V = lake volume, D = lake depth, and g is the acceleration due to gravity. Calculations show that peak discharge Qp depends weakly on lake shape r and ??, but strongly on ??, which is the product of a dimensionless lake volume and a dimensionless erosion rate. Qp(??) takes asymptotically distinct forms depending on whether ?????1 or ?????1. Theoretical predictions agree well with data from dam failures for which k could be reasonably estimated. The analysis provides a rapid and in many cases graphical way to estimate plausible values of Qp at the breach.

K-t GRAPPA-accelerated 4D flow MRI of liver hemodynamics: influence of different acceleration factors on qualitative and quantitative assessment of blood flow.

PubMed

Stankovic, Zoran; Fink, Jury; Collins, Jeremy D; Semaan, Edouard; Russe, Maximilian F; Carr, James C; Markl, Michael; Langer, Mathias; Jung, Bernd

2015-04-01

We sought to evaluate the feasibility of k-t parallel imaging for accelerated 4D flow MRI in the hepatic vascular system by investigating the impact of different acceleration factors. k-t GRAPPA accelerated 4D flow MRI of the liver vasculature was evaluated in 16 healthy volunteers at 3T with acceleration factors R = 3, R = 5, and R = 8 (2.0 × 2.5 × 2.4 mm(3), TR = 82 ms), and R = 5 (TR = 41 ms); GRAPPA R = 2 was used as the reference standard. Qualitative flow analysis included grading of 3D streamlines and time-resolved particle traces. Quantitative evaluation assessed velocities, net flow, and wall shear stress (WSS). Significant scan time savings were realized for all acceleration factors compared to standard GRAPPA R = 2 (21-71 %) (p < 0.001). Quantification of velocities and net flow offered similar results between k-t GRAPPA R = 3 and R = 5 compared to standard GRAPPA R = 2. Significantly increased leakage artifacts and noise were seen between standard GRAPPA R = 2 and k-t GRAPPA R = 8 (p < 0.001) with significant underestimation of peak velocities and WSS of up to 31 % in the hepatic arterial system (p <0.05). WSS was significantly underestimated up to 13 % in all vessels of the portal venous system for k-t GRAPPA R = 5, while significantly higher values were observed for the same acceleration with higher temporal resolution in two veins (p < 0.05). k-t acceleration of 4D flow MRI is feasible for liver hemodynamic assessment with acceleration factors R = 3 and R = 5 resulting in a scan time reduction of at least 40 % with similar quantitation of liver hemodynamics compared with GRAPPA R = 2.

An improved oxygen diffusion model to explain the effect of low-temperature baking on high field losses in niobium superconducting cavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ciovati, Gianluigi

Radio-frequency (RF) superconducting cavities made of high purity niobium are widely used to accelerate charged particle beams in particle accelerators. The major limitation to achieve RF field values approaching the theoretical limit for niobium is represented by ''anomalous'' losses which degrade the quality factor of the cavities starting at peak surface magnetic fields of about 100 mT, in absence of field emission. These high field losses are often referred to as ''Q-drop''. It has been observed that the Q-drop is drastically reduced by baking the cavities at 120 C for about 48 h under ultrahigh vacuum. An improved oxygen diffusionmore » model for the niobium-oxide system is proposed to explain the benefit of the low-temperature baking on the Q-drop in niobium superconducting rf cavities. The model shows that baking at 120 C for 48 h allows oxygen to diffuse away from the surface, and therefore increasing the lower critical field towards the value for pure niobium.« less

GLAST answers about high-energy peaked BL Lacs: double-humped {gamma}-ray peak and extreme accelerators?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costamante, L.; Aharonian, F.; Khangulyan, D.

2007-07-12

An often overlooked fact is that the MeV-GeV emission from High-energy peaked BL Lacs (HBL) is basically unknown: there are only 3 objects of this type among all EGRET identified blazars with measured spectra. GLAST will be able to measure the spectrum for many of them, in particular TeV-blazars, and surprises are expected. GLAST will tell if the {gamma}-ray peak in some HBL is actually a ''double peak'', as suggested by the comparison of EGRET and HESS data in PKS 2155-304, We also remind and argue that a new class of BL Lacs could exist, where particles are shock-accelerated nearmore » the maximum possible rate, characterized by the synchrotron emission peaking in the GLAST band (100 MeV - few GeV). Such objects could easily have escaped detection or identification so far, and could now be unveiled by GLAST.« less

Spatiotemporal processing of linear acceleration: primary afferent and central vestibular neuron responses

NASA Technical Reports Server (NTRS)

Angelaki, D. E.; Dickman, J. D.

2000-01-01

Spatiotemporal convergence and two-dimensional (2-D) neural tuning have been proposed as a major neural mechanism in the signal processing of linear acceleration. To examine this hypothesis, we studied the firing properties of primary otolith afferents and central otolith neurons that respond exclusively to horizontal linear accelerations of the head (0.16-10 Hz) in alert rhesus monkeys. Unlike primary afferents, the majority of central otolith neurons exhibited 2-D spatial tuning to linear acceleration. As a result, central otolith dynamics vary as a function of movement direction. During movement along the maximum sensitivity direction, the dynamics of all central otolith neurons differed significantly from those observed for the primary afferent population. Specifically at low frequencies (

Thermal Fatigue Evaluation of Pb-Free Solder Joints: Results, Lessons Learned, and Future Trends

NASA Astrophysics Data System (ADS)

Coyle, Richard J.; Sweatman, Keith; Arfaei, Babak

2015-09-01

Thermal fatigue is a major source of failure of solder joints in surface mount electronic components and it is critically important in high reliability applications such as telecommunication, military, and aeronautics. The electronic packaging industry has seen an increase in the number of Pb-free solder alloy choices beyond the common near-eutectic Sn-Ag-Cu alloys first established as replacements for eutectic SnPb. This paper discusses the results from Pb-free solder joint reliability programs sponsored by two industry consortia. The characteristic life in accelerated thermal cycling is reported for 12 different Pb-free solder alloys and a SnPb control in 9 different accelerated thermal cycling test profiles in terms of the effects of component type, accelerated thermal cycling profile and dwell time. Microstructural analysis on assembled and failed samples was performed to investigate the effect of initial microstructure and its evolution during accelerated thermal cycling test. A significant finding from the study is that the beneficial effect of Ag on accelerated thermal cycling reliability (measured by characteristic lifetime) diminishes as the severity of the accelerated thermal cycling, defined by greater ΔT, higher peak temperature, and longer dwell time increases. The results also indicate that all the Pb-free solders are more reliable in accelerated thermal cycling than the SnPb alloy they have replaced. Suggestions are made for future work, particularly with respect to the continued evolution of alloy development for emerging application requirements and the value of using advanced analytical methods to provide a better understanding of the effect of microstructure and its evolution on accelerated thermal cycling performance.

Development of new S-band SLED for PAL-XFEL Linac

NASA Astrophysics Data System (ADS)

Joo, Youngdo; Park, Yongjung; Heo, Hoon; Heo, Jinyul; Park, Sung-Soo; Kim, Sang-Hee; Kim, Kwang-Hoon; Kang, Heung-Sik; Lee, Heung-Soo; Noh, Sungju; Oh, Kyoungmin

2017-01-01

In order to achieve beam acceleration to the beam energy of 10 GeV at the end of its 716 m-long linear accelerator (Linac), the Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) is going to operate the Stanford Linear Accelerator Energy Doubler (SLED) at the maximum klystron output peak power of 80 MW, with a pulse length of 4 μs, and at a repetition rate of 60 Hz. The original SLED that had been used in Pohang Light Source-II (PLS-II) can no longer sustain such a high-power operation because excessive radiation caused by RF breakdown has been frequently detected even at the lower klystron peak power during the PLS-II operation. Therefore, a new SLED is designed by modifying both the 3-dB power hybrid and the waveguide-cavity coupling structure of the original SLED where the excessive radiation has been mainly detected. The finite-difference time-domain (FDTD) simulation in the CST Microwave Studio shows that the new SLED has a peak electric field and a surface current lower than those of the original SLED at the same level of the RF input peak power, which would secure stable high-power operation. All of the 42 SLEDs in the PAL-XFEL Linac are newly fabricated and installed. During the RF conditioning of the PAL-XFEL Linac, no significant vacuum and radiation issue was found in the new SLEDs. Finally, the accelerated electron beam energy of 10 GeV obtained at the end of the PAL-XFEL Linac verified that the RF performance of the new SLED is stable.

The adequate stimulus for mammalian linear vestibular evoked potentials (VsEPs)

PubMed Central

Jones, Timothy A.; Jones, Sherri M.; Vijayakumar, Sarath; Brugeaud, Aurore; Bothwell, Marcella; Chabbert, Christian

2013-01-01

Short latency linear vestibular sensory evoked potentials (VsEPs) provide a means to objectively and directly assess the function of gravity receptors in mammals and birds. The importance of this functional measure is illustrated by its use in studies of the genetic basis of vestibular function and disease. Head motion is the stimulus for the VsEP. In the bird, it has been established that neurons mediating the linear VsEP respond collectively to the rate of change in linear acceleration during head movement (i.e. jerk) rather than peak acceleration. The kinematic element of motion responsible for triggering mammalian VsEPs has not been characterized in detail. Here we tested the hypothesis that jerk is the kinematic component of head motion responsible for VsEP characteristics. VsEP amplitudes and latencies changed systematically when peak acceleration level was held constant and jerk level was varied from ~0.9 to 4.6 g/ms. In contrast, responses remained relatively constant when kinematic jerk was held constant and peak acceleration was varied from ~0.9 to 5.5g in mice and ~0.44 to 2.75g in rats. Thus the mammalian VsEP depends on jerk levels and not peak acceleration. We conclude that kinematic jerk is the adequate stimulus for the mammalian VsEP. This sheds light on the behavior of neurons generating the response. The results also provide the basis for standardizing the reporting of stimulus levels, which is key to ensuring that response characteristics reported in the literature by many laboratories can be effectively compared and interpreted. PMID:21664446

The adequate stimulus for avian short latency vestibular responses to linear translation

NASA Technical Reports Server (NTRS)

Jones, T. A.; Jones, S. M.; Colbert, S.

1998-01-01

Transient linear acceleration stimuli have been shown to elicit eighth nerve vestibular compound action potentials in birds and mammals. The present study was undertaken to better define the nature of the adequate stimulus for neurons generating the response in the chicken (Gallus domesticus). In particular, the study evaluated the question of whether the neurons studied are most sensitive to the maximum level of linear acceleration achieved or to the rate of change in acceleration (da/dt, or jerk). To do this, vestibular response thresholds were measured as a function of stimulus onset slope. Traditional computer signal averaging was used to record responses to pulsed linear acceleration stimuli. Stimulus onset slope was systematically varied. Acceleration thresholds decreased with increasing stimulus onset slope (decreasing stimulus rise time). When stimuli were expressed in units of jerk (g/ms), thresholds were virtually constant for all stimulus rise times. Moreover, stimuli having identical jerk magnitudes but widely varying peak acceleration levels produced virtually identical responses. Vestibular response thresholds, latencies and amplitudes appear to be determined strictly by stimulus jerk magnitudes. Stimulus attributes such as peak acceleration or rise time alone do not provide sufficient information to predict response parameter quantities. Indeed, the major response parameters were shown to be virtually independent of peak acceleration levels or rise time when these stimulus features were isolated and considered separately. It is concluded that the neurons generating short latency vestibular evoked potentials do so as "jerk encoders" in the chicken. Primary afferents classified as "irregular", and which traditionally fall into the broad category of "dynamic" or "phasic" neurons, would seem to be the most likely candidates for the neural generators of short latency vestibular compound action potentials.

Tests of a Lightweight 200 kW MHD Channel and Diffuser.

DTIC Science & Technology

1980-03-01

used for measuring differential electrode voltages. The difference electrode voltage was determined by subtracting voltages that were picked up in...transients, instantaneous accelerations as high as 75 g were recorded. The acceleration peaks during steady-state firing were normally in the 15 g...normally in the range of 0.01 g2/Hz except for narrow peaks at 2-3 kHz which reach 0.05 - 0.1 g /Hz. The highest spectrum measured was accelerometer

Peak horizontal acceleration and velocity from strong-motion records including records from the 1979 imperial valley, California, earthquake

USGS Publications Warehouse

Joyner, William B.; Boore, David M.

1981-01-01

We have taken advantage of the recent increase in strong-motion data at close distances to derive new attenuation relations for peak horizontal acceleration and velocity. This new analysis uses a magnitude-independent shape, based on geometrical spreading and anelastic attenuation, for the attenuation curve. An innovation in technique is introduced that decouples the determination of the distance dependence of the data from the magnitude dependence.

Estimated cause of extreme acceleration records at the KiK-net IWTH25 station during the 2008 Iwate-Miyagi Nairiku earthquake, Japan

NASA Astrophysics Data System (ADS)

Ohmachi, Tatsuo; Inoue, Shusaku; Mizuno, Ken-Ichi; Yamada, Masato

During the 2008 Iwate-Miyagi Nairiku earthquake in Japan (MJ =7.2), extremely high accelerations were recorded at the KiK-net IWTH25 (Ichinoseki-nishi) station. The peak acceleration in the vertical component of the surface record was about 4 g where g is acceleration due to gravity, and the upward acceleration in the surface record was much larger than the downward acceleration. Some researchers have suggested that the ground surface was tossed into the air like a body on a trampoline. However, additional features found in the surface record suggest rocking motion accompanied with downward impact of the station with the ground. For example, there are many vertical peaks that can be found to occur at the same time as the horizontal peaks. After obtaining information about the station, in-situ investigations, shake-table experiments, and numerical simulations were conducted to determine the fundamental characteristics of the rocking motion and to reproduce the acceleration time histories of the surface record by using the bore-hole record at a depth of 260 m as the input motion. Prior to the numerical simulation, the wave velocities of subsurface layers were evaluated from Fourier spectra of both records, which showed that the velocities were reduced considerably during the main shock. A 2-D FEM code capable of handling separation and impact between the elements was used for the numerical simulation. Simulation results are shown in Figs. 17 and 18 indicating the impact between the IWTH25 station and the ground at around 4 sec when the acceleration in the vertical direction was about 4 g. Three kinds of acceleration time histories are shown with fairly good agreement between the simulated and observed time histories, suggesting the influence of the station is included in the record. It is also indicated that the vertical acceleration at the free surface without the influence of the IWTH25 station is about 1.6 g.

Response of Olive View Hospital to Northridge and Whittier earthquakes

USGS Publications Warehouse

Celebi, M.

1997-01-01

The purpose of this paper is to study the response of the conventionally designed new Olive View Medical Center (OVMC) building at 16 km from the epicenter of the January 17, 1994 Northridge, California earthquake (Ms = 6.8). OVMC is on an alluvial deposit. The building was subjected to design level peak accelerations during the earthquake and suffered only limited structural and nonstructural damage. The recorded motions at different levels of the OVMC building as well as its associated free-field sites are analyzed using spectral analyses and system identification techniques. The new OVMC building was conservatively designed in 1976 with very high lateral load resisting capability - particularly as a reaction to the detrimental fate of the original Olive View Hospital that was heavily damaged during the 1971 San Fernando earthquake. The original hospital building was later razed. The replacement structure, the new cross-shaped OVMC building, experienced peak acceleration of 2.31g at the roof while its peak ground floor acceleration was 0.82g. The free-field peak acceleration was 0.91g. The lateral load resisting system of the OVMC building consists of concrete shear walls in the lower two stories and steel shear walls at the perimeter of the upper four stories. Spectral analysis shows that this stiff structure was not affected by the long duration pulses of the motions recorded at this site.

Tracking Second Thoughts: Continuous and Discrete Revision Processes during Visual Lexical Decision

PubMed Central

Barca, Laura; Pezzulo, Giovanni

2015-01-01

We studied the dynamics of lexical decisions by asking participants to categorize lexical and nonlexical stimuli and recording their mouse movements toward response buttons during the choice. In a previous report we revealed greater trajectory curvature and attraction to competitors for Low Frequency words and Pseudowords. This analysis did not clarify whether the trajectory curvature in the two conditions was due to a continuous dynamic competition between the response alternatives or if a discrete revision process (a "change of mind") took place during the choice from an initially selected response to the opposite one. To disentangle these two possibilities, here we analyse the velocity and acceleration profiles of mouse movements during the choice. Pseudowords' peak movement velocity occurred with 100ms delay with respect to words and Letters Strings. Acceleration profile for High and Low Frequency words and Letters Strings exhibited a butterfly plot with one acceleration peak at 400ms and one deceleration peak at 650ms. Differently, Pseudowords' acceleration profile had double positive peaks (at 400 and 600ms) followed by movement deceleration, in correspondence with changes in the decision from lexical to nonlexical response buttons. These results speak to different online processes during the categorization of Low Frequency words and Pseudowords, with a continuous competition process for the former and a discrete revision process for the latter. PMID:25699992

RoboPol: the optical polarization of gamma-ray-loud and gamma-ray-quiet blazars

NASA Astrophysics Data System (ADS)

Angelakis, E.; Hovatta, T.; Blinov, D.; Pavlidou, V.; Kiehlmann, S.; Myserlis, I.; Böttcher, M.; Mao, P.; Panopoulou, G. V.; Liodakis, I.; King, O. G.; Baloković, M.; Kus, A.; Kylafis, N.; Mahabal, A.; Marecki, A.; Paleologou, E.; Papadakis, I.; Papamastorakis, I.; Pazderski, E.; Pearson, T. J.; Prabhudesai, S.; Ramaprakash, A. N.; Readhead, A. C. S.; Reig, P.; Tassis, K.; Urry, M.; Zensus, J. A.

2016-12-01

We present average R-band optopolarimetric data, as well as variability parameters, from the first and second RoboPol observing season. We investigate whether gamma-ray-loud and gamma-ray-quiet blazars exhibit systematic differences in their optical polarization properties. We find that gamma-ray-loud blazars have a systematically higher polarization fraction (0.092) than gamma-ray-quiet blazars (0.031), with the hypothesis of the two samples being drawn from the same distribution of polarization fractions being rejected at the 3σ level. We have not found any evidence that this discrepancy is related to differences in the redshift distribution, rest-frame R-band luminosity density, or the source classification. The median polarization fraction versus synchrotron-peak-frequency plot shows an envelope implying that high-synchrotron-peaked sources have a smaller range of median polarization fractions concentrated around lower values. Our gamma-ray-quiet sources show similar median polarization fractions although they are all low-synchrotron-peaked. We also find that the randomness of the polarization angle depends on the synchrotron peak frequency. For high-synchrotron-peaked sources, it tends to concentrate around preferred directions while for low-synchrotron-peaked sources, it is more variable and less likely to have a preferred direction. We propose a scenario which mediates efficient particle acceleration in shocks and increases the helical B-field component immediately downstream of the shock.

IMU: inertial sensing of vertical CoM movement.

PubMed

Esser, Patrick; Dawes, Helen; Collett, Johnny; Howells, Ken

2009-07-22

The purpose of this study was to use a quaternion rotation matrix in combination with an integration approach to transform translatory accelerations of the centre of mass (CoM) from an inertial measurement unit (IMU) during walking, from the object system onto the global frame. Second, this paper utilises double integration to determine the relative change in position of the CoM from the vertical acceleration data. Five participants were tested in which an IMU, consisting of accelerometers, gyroscopes and magnetometers was attached on the lower spine estimated centre of mass. Participants were asked to walk three times through a calibrated volume at their self-selected walking speed. Synchronized data were collected by an IMU and an optical motion capture system (OMCS); both measured at 100 Hz. Accelerations of the IMU were transposed onto the global frame using a quaternion rotation matrix. Translatory acceleration, speed and relative change in position from the IMU were compared with the derived data from the OMCS. Peak acceleration in vertical axis showed no significant difference (p> or =0.05). Difference between peak and trough speed showed significant difference (p<0.05) but relative peak-trough position between the IMU and OMCS did not show any significant difference (p> or =0.05). These results indicate that quaternions, in combination with Simpsons rule integration, can be used in transforming translatory acceleration from the object frame to the global frame and therefore obtain relative change in position, thus offering a solution for using accelerometers in accurate global frame kinematic gait analyses.

Identifying head-trunk and lower limb contributions to gaze stabilization during locomotion

NASA Technical Reports Server (NTRS)

Mulavara, Ajitkumar P.; Bloomberg, Jacob J.

2002-01-01

The goal of the present study was to determine how the multiple, interdependent full-body sensorimotor subsystems respond to a change in gaze stabilization task constraints during locomotion. Nine subjects performed two gaze stabilization tasks while walking at 6.4 km/hr on a motorized treadmill: 1) focusing on a central point target; 2) reading numeral characters; both presented at 2 m in front at the level of their eyes. While subjects performed the tasks we measured: temporal parameters of gait, full body sagittal plane segmental kinematics of the head, trunk, thigh, tibia and foot, accelerations along the vertical axis at the head and the tibia, and the vertical forces acting on the support surface. We tested the hypothesis that with the increased demands placed on visual acuity during the number recognition task, subjects would modify full-body segmental kinematics in order to reduce perturbations to the head in order to successfully perform the task. We found that while reading numeral characters as compared to the central point target: 1) compensatory head pitch movement was on average 22% greater despite the fact that the trunk pitch and trunk vertical translation movement control were not significantly changed; 2) coordination patterns between head and trunk as reflected by the peak cross correlation between the head pitch and trunk pitch motion as well as the peak cross correlation between the head pitch and vertical trunk translation motion were not significantly changed; 3) knee joint total movement was on average 11% greater during the period from the heel strike event to the peak knee flexion event in stance phase of the gait cycle; 4) peak acceleration measured at the head was significantly reduced by an average of 13% in four of the six subjects. This was so even when the peak acceleration at the tibia and the transmission of the shock wave at heel strike (measured by the peak acceleration ratio of the head/tibia and the time lag between the tibial and head peak accelerations) remained unchanged. Taken together these results provide further evidence that the full body contributes to gaze stabilization during locomotion, and that its different functional elements can be modified online to contribute to gaze stabilization for different visual task constraints.

The Roles of Flares and Shocks in determining SEP Abundances

NASA Technical Reports Server (NTRS)

Cane, H. V.; Mewaldt, R. A.; Cohen, C. M. S.; vonRosenvinge, T. T.

2007-01-01

We examine solar energetic particle (SEP) event-averaged abundances of Fe relative to O and intensity versus time profiles at energies above 25 MeV/nucleon using the SIS instrument on ACE. These data are compared with solar wind conditions during each event and with estimates of the strength of the associated shock based on average travel times to 1 AU. We find that the majority of events with an Fe to 0 abundance ratio greater than two times the average 5-12 MeV/nuc value for large SEP events (0.134) occur in the western hemisphere. Furthermore, in most of these Fe-rich events the profiles peak within 12 hours of the associated flare, suggesting that some of the observed interplanetary particles are accelerated in these flares. The vast majority of events with Fe/O below 0.134 are influenced by interplanetary shock acceleration. We suggest that variations in elemental composition in SEP events mainly arise from the combination of flare particles and shock acceleration of these particles and/or the ambient medium.

Ultrahigh 6D-brightness electron beams for the light sources of the next generation

NASA Astrophysics Data System (ADS)

Habib, Fahim; Manahan, Grace G.; Scherkl, Paul; Heinemann, Thomas; Sheng, Z. M.; Bruhwiler, D. L.; Cary, J. R.; Rosenzweig, J. B.; Hidding, Bernhard

2017-10-01

The plasma photocathode mechanism (aka Trojan Horse) enables a path towards electron beams with nm-level normalized emittance and kA range peak currents, hence ultrahigh 5D-brightness. This ultrahigh 5D-brightness beams hold great prospects to realize laboratory scale free-electron-lasers. However, the GV/m-accelerating gradient in plasma accelerators leads to substantial energy chirp and spread. The large energy spread is a major show-stopper towards key application such as the free-electron-laser. Here we present a novel method for energy chirp compensation which takes advantage of tailored beam loading due to a second ``escort'' bunch released via plasma photocathode. The escort bunch reverses the accelerating field locally at the trapping position of the ultrahigh 5D-brightness beam. This induces a counter-clockwise rotation within the longitudinal phase space and allows to compensate the chirp completely. Analytical scaling predicts energy spread values below 0.01 percentage level. Ultrahigh 5D-brightness combined with minimized energy spread opens a path towards witness beams with unprecedented ultrahigh 6D-brightness.

Seismic hazard analysis with PSHA method in four cities in Java.

NASA Astrophysics Data System (ADS)

Elistyawati, Y.; Palupi, I. R.; Suharsono

2016-11-01

In this study the tectonic earthquakes was observed through the peak ground acceleration through the PSHA method by dividing the area of the earthquake source. This study applied the earthquake data from 1965 - 2015 that has been analyzed the completeness of the data, location research was the entire Java with stressed in four large cities prone to earthquakes. The results were found to be a hazard map with a return period of 500 years, 2500 years return period, and the hazard curve were four major cities (Jakarta, Bandung, Yogyakarta, and the city of Banyuwangi). Results Java PGA hazard map 500 years had a peak ground acceleration within 0 g ≥ 0.5 g, while the return period of 2500 years had a value of 0 to ≥ 0.8 g. While, the PGA hazard curves on the city's most influential source of the earthquake was from sources such as fault Cimandiri backgroud, for the city of Bandung earthquake sources that influence the seismic source fault dent background form. In other side, the city of Yogyakarta earthquake hazard curve of the most influential was the source of the earthquake background of the Opak fault, and the most influential hazard curve of Banyuwangi earthquake was the source of Java and Sumba megatruts earthquake.

Predicting Dynamic Postural Instability Using Center of Mass Time-to-Contact Information

PubMed Central

Hasson, Christopher J.; Van Emmerik, Richard E.A.; Caldwell, Graham E.

2008-01-01

Our purpose was to determine whether spatiotemporal measures of center of mass motion relative to the base of support boundary could predict stepping strategies after upper-body postural perturbations in humans. We expected that inclusion of center of mass acceleration in such time-to-contact (TtC) calculations would give better predictions and more advanced warning of perturbation severity. TtC measures were compared with traditional postural variables, which don’t consider support boundaries, and with an inverted pendulum model of dynamic stability developed by Hof et al. (2005). A pendulum was used to deliver sequentially increasing perturbations to 10 young adults, who were strapped to a wooden backboard that constrained motion to sagittal plane rotation about the ankle joint. Subjects were instructed to resist the perturbations, stepping only if necessary to prevent a fall. Peak center of mass and center of pressure velocity and acceleration demonstrated linear increases with postural challenge. In contrast, boundary relevant minimum TtC values decreased nonlinearly with postural challenge, enabling prediction of stepping responses using quadratic equations. When TtC calculations incorporated center of mass acceleration, the quadratic fits were better and gave more accurate predictions of the TtC values that would trigger stepping responses. In addition, TtC minima occurred earlier with acceleration inclusion, giving more advanced warning of perturbation severity. Our results were in agreement with TtC predictions based on Hof’s model, and suggest that TtC may function as a control parameter, influencing the postural control system’s decision to transition from a stationary base of support to a stepping strategy. PMID:18556003

Angular Impact Mitigation System for Bicycle Helmets to Reduce Head Acceleration and Risk of Traumatic Brain Injury

PubMed Central

Hansen, Kirk; Dau, Nathan; Feist, Florian; Deck, Caroline; Willinger, Rémy; Madey, Steven M.; Bottlang, Michael

2013-01-01

Angular acceleration of the head is a known cause of traumatic brain injury (TBI), but contemporary bicycle helmets lack dedicated mechanisms to mitigate angular acceleration. A novel Angular Impact Mitigation (AIM) system for bicycle helmets has been developed that employs an elastically suspended aluminum honeycomb liner to absorb linear acceleration in normal impacts as well as angular acceleration in oblique impacts. This study tested bicycle helmets with and without AIM technology to comparatively assess impact mitigation. Normal impact tests were performed to measure linear head acceleration. Oblique impact tests were performed to measure angular head acceleration and neck loading. Furthermore, acceleration histories of oblique impacts were analyzed in a computational head model to predict the resulting risk of TBI in the form of concussion and diffuse axonal injury (DAI). Compared to standard helmets, AIM helmets resulted in a 14% reduction in peak linear acceleration (p < 0.001), a 34% reduction in peak angular acceleration (p < 0.001), and a 22% to 32% reduction in neck loading (p < 0.001). Computational results predicted that AIM helmets reduced the risk of concussion and DAI by 27% and 44%, respectively. In conclusion, these results demonstrated that AIM technology could effectively improve impact mitigation compared to a contemporary expanded polystyrene-based bicycle helmet, and may enhance prevention of bicycle-related TBI. Further research is required. PMID:23770518

Regional patterns of earthquake-triggered landslides and their relation to ground motion

NASA Astrophysics Data System (ADS)

Meunier, Patrick; Hovius, Niels; Haines, A. John

2007-10-01

We have documented patterns of landsliding associated with large earthquakes on three thrust faults: the Northridge earthquake in California, Chi-Chi earthquake in Taiwan, and two earthquakes on the Ramu-Markham fault bounding the Finisterre Mountains of Papua New Guinea. In each case, landslide densities are shown to be greatest in the area of strongest ground acceleration and to decay with distance from the epicenter. In California and Taiwan, the density of co-seismic landslides is linearly and highly correlated with both the vertical and horizontal components of measured peak ground acceleration. Based on this observation, we derive an expression for the spatial variation of landslide density analogous with regional seismic attenuation laws. In its general form, this expression applies to our three examples, and we determine best fit values for individual cases. Our findings open a window on the construction of shake maps from geomorphic observations for earthquakes in non-instrumented regions.

Determination of crash test pulses and their application to aircraft seat analysis

NASA Technical Reports Server (NTRS)

Alfaro-Bou, E.; Williams, M. S.; Fasanella, E. L.

1981-01-01

Deceleration time histories (crash pulses) from a series of twelve light aircraft crash tests conducted at NASA Langley Research Center (LaRC) were analyzed to provide data for seat and airframe design for crashworthiness. Two vertical drop tests at 12.8 m/s (42 ft/s) and 36 G peak deceleration (simulating one of the vertical light aircraft crash pulses) were made using an energy absorbing light aircraft seat prototype. Vertical pelvis acceleration measured in a 50 percentile dummy in the energy absorbing seat were found to be 45% lower than those obtained from the same dummy in a typical light aircraft seat. A hybrid mathematical seat-occupant model was developed using the DYCAST nonlinear finite element computer code and was used to analyze a vertical drop test of the energy absorbing seat. Seat and occupant accelerations predicted by the DYCAST model compared quite favorably with experimental values.

Lateral thrust of anterior cruciate ligament-insufficient knees and posterior cruciate ligament-insufficient knees.

PubMed

Yoshimura, Ichiro; Naito, Masatoshi; Zhang, Jingfan

2002-01-01

Leaving anterior cruciate ligament (ACL) insufficiency and posterior cruciate ligament (PCL) insufficiency untreated frequently leads to osteoarthritis (OA). The purpose of this study was to evaluate dynamically the lateral thrust of ACL-insufficient knees and PCL-insufficient knees, and from the findings investigate the relationship between cruciate ligament insufficiency and OA occurrence. An acceleration sensor was attached to the affected and control anterior tibial tubercles, acting in medial-lateral and perpendicular directions. The lateral thrust immediately after heel strike was measured continuously by a telemeter under stabilised walking conditions. When compared to the contralateral healthy knee, the peak value of lateral acceleration immediately after heel strike was significantly larger in the ACL-insufficient knee; and lateral thrust was increased, but not significantly, in the PCL-insufficient knee. Given that lateral thrust of the knee during walking increases due to ACL or PCL injury, it may be a principal contributor to OA progression.

Tree-stem diameter fluctuates with the lunar tides and perhaps with geomagnetic activity.

PubMed

Barlow, Peter W; Mikulecký, Miroslav; Střeštík, Jaroslav

2010-11-01

Our initial objective has been to examine the suggestion of Zürcher et al. (Nature 392:665–666, 1998) that the naturally occurring variations in stem diameter of two experimental trees of Picea alba were related to near simultaneous variations in the lunisolar tidal acceleration. The relationship was positive: Lunar peaks were roughly synchronous with stem diameter peaks. To extend the investigation of this putative relationship, additional data on stem diameter variations from six other tree species were gathered from published literature. Sixteen sets of data were analysed retrospectively using graphical representations as well as cosinor analysis, statistical cross-correlation and cross-spectral analysis, together with estimated values of the lunisolar tidal acceleration corresponding to the sites, dates and times of collection of the biological data. Positive relationships were revealed between the daily variations of stem diameter and the variations of the lunisolar tidal acceleration. Although this relationship could be mediated by a 24.8-h lunar rhythm, the presence of a solar rhythm of 24.0 h could not be ruled out. Studies of transpiration in two of the observed trees indicated that although this variable was not linked to stem diameter variation, it might also be subject to lunisolar gravitational regulation. In three cases, the geomagnetic Thule index showed a weak but reciprocal relationship with stem diameter variation, as well as a positive relationship with the lunisolar tidal force. In conclusion, it seems that lunar gravity alone could influence stem diameter variation and that, under certain circumstances, additional regulation may come from the geomagnetic flux.

Superconducting traveling wave accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farkas, Z.D.

1984-11-01

This note considers the applicability of superconductivity to traveling wave accelerators. Unlike CW operation of a superconducting standing wave or circulating wave accelerator section, which requires improvement factors (superconductor conductivity divided by copper conductivity) of about 10/sup 6/ in order to be of practical use, a SUperconducting TRaveling wave Accelerator, SUTRA, operating in the pulsed mode requires improvement factors as low as about 10/sup 3/, which are attainable with niobium or lead at 4.2K, the temperature of liquid helium at atmospheric pressure. Changing from a copper traveling wave accelerator to SUTRA achieves the following. (1) For a given gradient SUTRAmore » reduces the peak and average power requirements typically by a factor of 2. (2) SUTRA reduces the peak power still further because it enables us to increase the filling time and thus trade pulse width for gradient. (3) SUTRA makes possible a reasonably long section at higher frequencies. (4) SUTRA makes possible recirculation without additional rf average power. 8 references, 6 figures, 1 table.« less

Relationship between SEP Peak intensity and CME Acceleration, Speed and Width

NASA Astrophysics Data System (ADS)

Xie, H.; St Cyr, O. C.; Makela, P. A.; Gopalswamy, N.

2017-12-01

We study the large solar energetic particle (SEP) events that were detected by GOES in the >10 MeV energy channel during December 2006 to January 2016. Data used in this study includes the Solar Electron Proton Telescope (SEPT) and High Energy Telescopes (HET) on STEREO A and B, the Electron, Proton, and Alpha Monitor (EPAM) on ACE, and the Energetic and Relativistic Nuclei and Electron instrument (ERNE) on SOHO. By choosing the smallest connection angles between SEP solar locations and magnetic foot-points of each spacecraft, we divide SEP events as SOHO SEPs or STEREO SEPs. We then compute the SEP peak intensity I0 at the center of the Gausssian using the Gausssian expression from Richardson et al. (2014) and study the relationship between SEP electron and proton peak intensity and CME acceleration, speed and width. By using I0 derived from multi-spacecraft observations we found that the correlations between SEP peak intensity and CME acceleration and speed improved. We also found that this correlation can be further improved by taking into account the effects of CME width and its solar source latitude. The implication for the SEP forecast of our obtained results will be discussed.

Simulation study of the sub-terawatt laser wakefield acceleration operated in self-modulated regime

NASA Astrophysics Data System (ADS)

Hsieh, C.-Y.; Lin, M.-W.; Chen, S.-H.

2018-02-01

Laser wakefield acceleration (LWFA) can be accomplished by introducing a sub-terawatt (TW) laser pulse into a thin, high-density gas target. In this way, the self-focusing effect and the self-modulation that happened on the laser pulse produce a greatly enhanced laser peak intensity that can drive a nonlinear plasma wave to accelerate electrons. A particle-in-cell model is developed to study sub-TW LWFA when a 0.6-TW laser pulse interacts with a dense hydrogen plasma. Gas targets having a Gaussian density profile or a flat-top distribution are defined for investigating the properties of sub-TW LWFA when conducting with a gas jet or a gas cell. In addition to using 800-nm laser pulses, simulations are performed with 1030-nm laser pulses, as they represent a viable approach to realize the sub-TW LWFA driven by high-frequency, diode-pumped laser systems. The peak density which allows the laser peak power PL˜2 Pc r of self-focusing critical power is favourable for conducting sub-TW LWFA. Otherwise, an excessively high peak density can induce an undesired filament effect which rapidly disintegrates the laser field envelope and violates the process of plasma wave excitation. The plateau region of a flat-top density distribution allows the self-focusing and the self-modulation of the laser pulse to develop, from which well-established plasma bubbles can be produced to accelerate electrons. The process of electron injection is complicated in such high-density plasma conditions; however, increasing the length of the plateau region represents a straightforward method to realize the injection and acceleration of electrons within the first bubble, such that an improved LWFA performance can be accomplished.

B-value and slip rate sensitivity analysis for PGA value in Lembang fault and Cimandiri fault area

NASA Astrophysics Data System (ADS)

Pratama, Cecep; Ito, Takeo; Meilano, Irwan; Nugraha, Andri Dian

2017-07-01

We examine slip rate and b-value contribution of Peak Ground Acceleration (PGA), in probabilistic seismic hazard maps (10% probability of exceedence in 50 years or 500 years return period). Hazard curve of PGA have been investigated for Sukabumi and Bandung using a PSHA (Probabilistic Seismic Hazard Analysis). We observe that the most influence in the hazard estimate is crustal fault. Monte Carlo approach has been developed to assess the sensitivity. Uncertainty and coefficient of variation from slip rate and b-value in Lembang and Cimandiri Fault area have been calculated. We observe that seismic hazard estimates are sensitive to fault slip rate and b-value with uncertainty result are 0.25 g dan 0.1-0.2 g, respectively. For specific site, we found seismic hazard estimate are 0.49 + 0.13 g with COV 27% and 0.39 + 0.05 g with COV 13% for Sukabumi and Bandung, respectively.

Accelerated time-resolved three-dimensional MR velocity mapping of blood flow patterns in the aorta using SENSE and k-t BLAST.

PubMed

Stadlbauer, Andreas; van der Riet, Wilma; Crelier, Gerard; Salomonowitz, Erich

2010-07-01

To assess the feasibility and potential limitations of the acceleration techniques SENSE and k-t BLAST for time-resolved three-dimensional (3D) velocity mapping of aortic blood flow. Furthermore, to quantify differences in peak velocity versus heart phase curves. Time-resolved 3D blood flow patterns were investigated in eleven volunteers and two patients suffering from aortic diseases with accelerated PC-MR sequences either in combination with SENSE (R=2) or k-t BLAST (6-fold). Both sequences showed similar data acquisition times and hence acceleration efficiency. Flow-field streamlines were calculated and visualized using the GTFlow software tool in order to reconstruct 3D aortic blood flow patterns. Differences between the peak velocities from single-slice PC-MRI experiments using SENSE 2 and k-t BLAST 6 were calculated for the whole cardiac cycle and averaged for all volunteers. Reconstruction of 3D flow patterns in volunteers revealed attenuations in blood flow dynamics for k-t BLAST 6 compared to SENSE 2 in terms of 3D streamlines showing fewer and less distinct vortices and reduction in peak velocity, which is caused by temporal blurring. Solely by time-resolved 3D MR velocity mapping in combination with SENSE detected pathologic blood flow patterns in patients with aortic diseases. For volunteers, we found a broadening and flattering of the peak velocity versus heart phase diagram between the two acceleration techniques, which is an evidence for the temporal blurring of the k-t BLAST approach. We demonstrated the feasibility of SENSE and detected potential limitations of k-t BLAST when used for time-resolved 3D velocity mapping. The effects of higher k-t BLAST acceleration factors have to be considered for application in 3D velocity mapping. Copyright 2009 Elsevier Ireland Ltd. All rights reserved.

High Peak Power Test and Evaluation of S-band Waveguide Switches

NASA Astrophysics Data System (ADS)

Nassiri, A.; Grelick, A.; Kustom, R. L.; White, M.

1997-05-01

The injector and source of particles for the Advanced Photon Source is a 2856-MHz S-band electron-positron linear accelerator (linac) which produces electrons with energies up to 650 MeV or positrons with energies up to 450 MeV. To improve the linac rf system availability, an additional modulator-klystron subsystem is being constructed to provide a switchable hot spare unit for each of the five exsisting S-band transmitters. The switching of the transmitters will require the use of SF6-pressurized S-band waveguide switches at a peak operating power of 35 MW. Such rf switches have been successfully operated at other accelerator facilities but at lower peak powers. A test stand has been set up at the Stanford Linear Accelerator Center (SLAC) Klystron Factory to conduct tests comparing the power handling characteristics of two WR-284 and one WR-340 switches. Test results are presented and their implications for the design of the switching system are discussed.

Seismic hazard study for selected sites in New Mexico and Nevada

NASA Astrophysics Data System (ADS)

Johnston, J. C.

1983-12-01

Seismic hazard evaluations were conducted for specific sites in New Mexico and Nevada. For New Mexico, a model of seismicity was developed from historical accounts of medium to large shocks and the current microactivity record from local networks. Ninety percent confidence levels at Albuquerque and Roswell were computed to be 56 gals for a 10-year period and 77 gals for a 20-year period. Values of ground motion for Clovis were below these values. Peak velocity and displacement were also computed for each site. Deterministic spectra based on the estimated maximum credible earthquake for the zones which the sites occupy were also computed. For the sites in Nevada, the regionalizations used in Battis (1982) for the uniform seismicity model were slightly modified. For 10- and 20-year time periods, peak acceleration values for Indian Springs were computed to be 94 gals and 123 gals and for Hawthorne 206 gals and 268 gals. Deterministic spectra were also computed. The input parameters were well determined for the analysis for the Nevada sites because of the abundance of data. The values computed for New Mexico, however, are likely upper limits. As more data are collected from the area of the Rio Grande rift zone, the pattern of seismicity will become better understood. At this time a more detailed, and thus more accurate, model may emerge.

The Sidebar Computer Program, a seismic-shaking intensity meter: users' manual and software description

USGS Publications Warehouse

Evans, John R.

2003-01-01

The SideBar computer program provides a visual display of seismic shaking intensity as recorded at one specific seismograph. This software allows a user to tap into the seismic data recorded on that specific seismograph and to display the overall level of shaking at the single location where that seismograph resides (usually the same place the user is). From this shaking level, SideBar also estimates the potential for damage nearby. SideBar cannot tell you the “Richter magnitude” of the earthquake (see box), only how hard the ground shook locally and this estimate of how much damage is likely in the neighborhood. This combination of local effects is called the “seismic intensity”. SideBar runs on a standard desktop or laptop PC, and is intended for the media, schools, emergency responders, and any other group hosting a seismograph and who want to know immediately after an earthquake the levels of shaking measured by that instrument. These local values can be used to inform the public and help initiate appropriate local emergency response activities in the minutes between the earthquake and availability of the broader coverage provided by the USGS over the Web, notably by ShakeMap. For example, for instruments installed in schools, the level of shaking and likely damage at the school could immediately be Web broadcast and parents could quickly determine the likely safety of their children—their biggest postearthquake concern. Also, in the event of a Web outage, SideBar may be a continuing primary source of local emergency response information for some additional minutes. Specifically, SideBar interprets the peak level of acceleration (that is, the force of shaking, as a percentage of the force of gravity) as well as the peak velocity, or highest speed, at which the ground moves. Using these two basic measurements, SideBar computes what is called Instrumental Intensity—a close approximation of the Modified Mercalli Intensity scale, or “MMI” (using the Wald et al., 1999a, relationships between acceleration, velocity, and shaking intensity). Intensity is a measure of local shaking strength and the potential for damage—of how bad the earthquake effects were locally. The intensity level is what SideBar displays most prominently on the PC monitor. Intensity is shown as a large, colored bar that gets taller and changes color up a rainbow from blues toward reds as the shaking level increases. As opposed to earthquake magnitudes, which are reported as decimal values (like “7.6”), intensity is traditionally given as a Roman numeral, with “I” to “X+” assigned to levels of potential damage and perceived shaking strength. For good measure, SideBar shows the actual values of the force of shaking (peak ground acceleration as a percentage of gravity) and the speed of ground motion (peak ground velocity in inches per second, by default, or in centimeters per second, if you wish), both these values as decimal numbers. SideBar also remembers the most recent earthquakes (for up to one week), and can store as many of these previous earthquakes as the user allows (and as the user’s PC has room for)—typically thousands. SideBar also remembers forever the three largest earthquakes it has seen and all earthquakes over intensity IV so that one never loses particularly important events.

A comparative study of different PGA attenuation and error models: Case of 1999 Chi-Chi earthquake

NASA Astrophysics Data System (ADS)

Mebarki, Ahmed

2009-03-01

In order to evaluate the horizontal peak ground acceleration (HPGA) during earthquakes, the author studies the respective efficiency of two existing attenuation models [Mébarki, A., 2003a, Risques sismiques: aléas, vulnérabilité et aide à la décision par cartes SIG. Proceedings of International Conference on "Risks, Vulnerability and Reliability in Construction. Towards a reduction of disasters". ISBN: 9961-891-01-5, pp. 82-97. Algiers, October 11-12, Mébarki, A., 2003b. Proposal of a parametric attenuation model and comparison with some worldwide earthquakes. VII o Congreso Venezolano de Sismologia y Ingenieria Sísmica, Barquisimeto, Venezuela. November 12-13, (CD-ROM), Mébarki A., 2004. Modèle d'atténuation sismique: prédiction probabiliste des pics d'accélération, RFGC — Revue Française de Génie Civil, Hermès Ed., 8 (9-10), 1071-1086]. A comparative study of their performances is done in the case of 1999 Chi-Chi earthquake (Taiwan). The reported PGA (Peak Ground Accelerations) values correspond to hypocentral distances ranging from 15 up to 180 km with observed acceleration peaks ranging from (0.04 g) up to (1.16 g). The author considers two kinds of probabilistic distributions for the error model in order to describe the uncertainty and the variability that affect the values of the PGA: a Gamma distribution and a Log-normal distribution. The adopted error models assume that the variability of the PGA is such that its coefficient of variation is equal to 55% [Mébarki, A., 2003a. Risques sismiques: aléas, vulnérabilité et aide à la décision par cartes SIG. Proceedings of International Conference on "Risks, Vulnerability and Reliability in Construction. Towards a reduction of disasters". ISBN: 9961-891-01-5, pp. 82-97. Algiers, October 11-12, Mébarki, A., 2003b. Proposal of a parametric attenuation model and comparison with some worldwide earthquakes. VII o Congreso Venezolano de Sismologia y Ingenieria Sísmica, Barquisimeto, Venezuela. November 12-13, (CD-ROM), Mébarki, A., 2004. Modèle d'atténuation sismique: prédiction probabiliste des pics d'accélération, RFGC — Revue Française de Génie Civil, Hermès Ed., 8 (9-10), 1071-1086]. The obtained results show that both attenuation models provide adequate values of the PGA when a Gamma distribution is adopted for the error model. The attenuation models efficiency decreases slightly when a Log-normal distribution is adopted for the error model.

Accelerated deforestation in the humid tropics from the 1990s to the 2000s

NASA Astrophysics Data System (ADS)

Kim, Do-Hyung; Sexton, Joseph O.; Townshend, John R.

2015-05-01

Using a consistent, 20 year series of high- (30 m) resolution, satellite-based maps of forest cover, we estimate forest area and its changes from 1990 to 2010 in 34 tropical countries that account for the majority of the global area of humid tropical forests. Our estimates indicate a 62% acceleration in net deforestation in the humid tropics from the 1990s to the 2000s, contradicting a 25% reduction reported by the United Nations Food and Agriculture Organization Forest Resource Assessment. Net loss of forest cover peaked from 2000 to 2005. Gross gains accelerated slowly and uniformly between 1990-2000, 2000-2005, and 2005-2010. However, the gains were overwhelmed by gross losses, which peaked from 2000 to 2005 and decelerated afterward. The acceleration of humid tropical deforestation we report contradicts the assertion that losses decelerated from the 1990s to the 2000s.

Effects of Anisometropic Amblyopia on Visuomotor Behavior, Part 2: Visually Guided Reaching

PubMed Central

Niechwiej-Szwedo, Ewa; Goltz, Herbert C.; Chandrakumar, Manokaraananthan; Hirji, Zahra; Crawford, J. Douglas; Wong, Agnes M. F.

2016-01-01

Purpose The effects of impaired spatiotemporal vision in amblyopia on visuomotor skills have rarely been explored in detail. The goal of this study was to examine the influences of amblyopia on visually guided reaching. Methods Fourteen patients with anisometropic amblyopia and 14 control subjects were recruited. Participants executed reach-to-touch movements toward targets presented randomly 5° or 10° to the left or right of central fixation in three viewing conditions: binocular, monocular amblyopic eye, and monocular fellow eye viewing (left and right monocular viewing for control subjects). Visual feedback of the target was removed on 50% of the trials at the initiation of reaching. Results Reaching accuracy was comparable between patients and control subjects during all three viewing conditions. Patients’ reaching responses were slightly less precise during amblyopic eye viewing, but their precision was normal during binocular or fellow eye viewing. Reaching reaction time was not affected by amblyopia. The duration of the acceleration phase was longer in patients than in control subjects under all viewing conditions, whereas the duration of the deceleration phase was unaffected. Peak acceleration and peak velocity were also reduced in patients. Conclusions Amblyopia affects both the programming and the execution of visually guided reaching. The increased duration of the acceleration phase, as well as the reduced peak acceleration and peak velocity, might reflect a strategy or adaptation of feedforward/feedback control of the visuomotor system to compensate for degraded spatiotemporal vision in amblyopia, allowing patients to optimize their reaching performance. PMID:21051723

Induction linear accelerators

NASA Astrophysics Data System (ADS)

Birx, Daniel

1992-03-01

Among the family of particle accelerators, the Induction Linear Accelerator is the best suited for the acceleration of high current electron beams. Because the electromagnetic radiation used to accelerate the electron beam is not stored in the cavities but is supplied by transmission lines during the beam pulse it is possible to utilize very low Q (typically<10) structures and very large beam pipes. This combination increases the beam breakup limited maximum currents to of order kiloamperes. The micropulse lengths of these machines are measured in 10's of nanoseconds and duty factors as high as 10-4 have been achieved. Until recently the major problem with these machines has been associated with the pulse power drive. Beam currents of kiloamperes and accelerating potentials of megavolts require peak power drives of gigawatts since no energy is stored in the structure. The marriage of liner accelerator technology and nonlinear magnetic compressors has produced some unique capabilities. It now appears possible to produce electron beams with average currents measured in amperes, peak currents in kiloamperes and gradients exceeding 1 MeV/meter, with power efficiencies approaching 50%. The nonlinear magnetic compression technology has replaced the spark gap drivers used on earlier accelerators with state-of-the-art all-solid-state SCR commutated compression chains. The reliability of these machines is now approaching 1010 shot MTBF. In the following paper we will briefly review the historical development of induction linear accelerators and then discuss the design considerations.

Acoustic emission energy b-value for local damage evaluation in reinforced concrete structures subjected to seismic loadings

NASA Astrophysics Data System (ADS)

Sagasta, Francisco; Zitto, Miguel E.; Piotrkowski, Rosa; Benavent-Climent, Amadeo; Suarez, Elisabet; Gallego, Antolino

2018-03-01

A modification of the original b-value (Gutenberg-Richter parameter) is proposed to evaluate local damage of reinforced concrete structures subjected to dynamical loads via the acoustic emission (AE) method. The modification, shortly called energy b-value, is based on the use of the true energy of the AE signals instead of its peak amplitude, traditionally used for the calculation of b-value. The proposal is physically supported by the strong correlation between the plastic strain energy dissipated by the specimen and the true energy of the AE signals released during its deformation and cracking process, previously demonstrated by the authors in several publications. AE data analysis consisted in the use of guard sensors and the Continuous Wavelet Transform in order to separate primary and secondary emissions as much as possible according to particular frequency bands. The approach has been experimentally applied to the AE signals coming from a scaled reinforced concrete frame structure, which was subjected to sequential seismic loads of incremental acceleration peak by means of a 3 × 3 m2 shaking table. For this specimen two beam-column connections-one exterior and one interior-were instrumented with wide band low frequency sensors properly attached on the structure. Evolution of the energy b-value along the loading process accompanies the evolution of the severe damage at the critical regions of the structure (beam-column connections), thus making promising its use for structural health monitoring purposes.

Analytical study of seismic effects of a solar receiver mounted on concrete towers with different fundamental periods

NASA Astrophysics Data System (ADS)

Deng, Lin

2016-05-01

This paper examines the seismic effects experienced by a solar receiver mounted on concrete towers with different fundamental periods. Ten concrete towers are modeled with the empty solar receiver structure and loaded solar receiver structure to examine the tower seismic effects on the solar receiver. The fundamental periods of the towers range from 0.22 seconds to 4.58 seconds, with heights ranging from 40.5 meters to 200 meters. Thirty earthquake ground motion records are used to investigate the responses of each of the combined receiver-on-tower models as well as the receiver-on-ground models by the STAAD Pro software using time history analyses. The earthquake ground motion records are chosen based on the ratio of the peak ground acceleration to the peak ground velocity, ranging from 0.29 g/m/s to 4.88 g/m/s. For each of the combined models, the base shear at the interface between the receiver and the concrete tower is compared with the base shear of the receiver-on-ground model, and the ratio of the two base shears represents the structure amplification factor. It is found that the peak mean plus one standard deviation value of the structure amplification factor matches well with equation 13.3-1 in ASCE 7-10 for the empty solar receiver structure. However, when the solar receiver structure is loaded with dead loads, the peak value is greatly suppressed, and using equation 13.3-1 in ASCE 7-10 will be overly conservative.

Stress Analysis of Transcatheter Aortic Valve Leaflets Under Dynamic Loading: Effect of Reduced Tissue Thickness.

PubMed

Abbasi, Mostafa; Azadani, Ali N

2017-07-01

In order to accommodate transcatheter valves to miniaturized catheters, the leaflet thickness must be reduced to a value which is typically less than that of surgical bioprostheses. The study aim was to use finite-element simulations to determine the impact of the thickness reduction on stress and strain distribution. A 23 mm transcatheter aortic valve (TAV) was modelled based on the Edwards SAPIEN XT (Edwards Lifesciences, Irvine, CA, USA). Finite-element (FE) analysis was performed using the ABAQUS/Explicit solver. An ensemble-averaged transvalvular pressure waveform measured from in-vitro tests conducted in a pulse duplicator was applied to the leaflets. Through a parametric study, uniform TAV leaflet thickness was reduced from 0.5 to 0.18 mm. By reducing leaflet thickness, significantly higher stress values were found in the leaflet's fixed edge during systole, and in the commissures during diastole. Through dynamic FE simulations, the highest stress values were found during systole in the leaflet fixed edge. In contrast, at the peak of diastole high-stress regions were mainly observed in the commissures. The peak stress was increased by 178% and 507% within the leaflets after reducing the thickness of 0.5 mm to 0.18 mm at the peak of systole and diastole, respectively. The study results indicated that, the smaller the leaflet thickness, the higher the maximum principal stress. Increased mechanical stress on TAV leaflets may lead to accelerated tissue degeneration. By using a thinner leaflet, TAV durability may not atch with that of surgical bioprostheses.

Kilometric shock-associated events and microwave bursts

NASA Technical Reports Server (NTRS)

Kundu, M. R.; Macdowall, R. J.; Stone, R. G.

1990-01-01

The peak times of impulsive microwaves bursts are compared with those of shock-associated (SA) kilometric radio events. The first peaks in these two frequency regimes are usually well-correlated in time, but the last peaks of the SA events observed at 1 MHz occur an average of 20 min after the last impulsive microwave peaks. In some cases, the SA events overlap in time with the post-burst increases of microwave bursts; sometimes there is general correspondence in their intensity time profiles. These observations suggest that the earlier components of the SA events are usually caused by electrons accelerated in or near the microwave source region. The possibility that the later components of some SA events could be associated with nonthermal electrons responsible for microwave post-burst increases, although they have traditionally been attributed to electrons accelerated at type II burst producing shocks in the upper corona is discussed.

Self-accelerating parabolic beams in quadratic nonlinear media

NASA Astrophysics Data System (ADS)

Dolev, Ido; Libster, Ana; Arie, Ady

2012-09-01

We present experimental observation of self-accelerating parabolic beams in quadratic nonlinear media. We show that the intensity peaks of the first and second harmonics are asynchronous with respect to one another in the two transverse coordinates. In addition, the two coupled harmonics have the same acceleration within and after the nonlinear medium. We also study the evolution of second harmonic accelerating beams inside the quadratic media and their correlation with theoretical beams.

Evaluation of Biomechanical Changes in Myopia Patients with Unsatisfactory Corneas After Femto Second-Laser In Situ Keratomileusis (FS-LASIK) Concurrent with Accelerated Corneal Collagen Cross-Linking Using Corvis-ST: Two-Year Follow-Up Results.

PubMed

Xu, Weiwei; Tao, Ye; Wang, Liqiang; Huang, Yifei

2017-07-27

BACKGROUND Some myopia patients with unsatisfactory corneas consider corneal refractive surgery for different reasons. Accelerated corneal collagen crosslinking (ACXL) is an effective method to enhance the resistance of the cornea. The present investigation was designed to evaluate the changes of biomechanical properties in patients with myopia and thin corneas after femtosecond-laser in situ keratomileusis (FS-LASIK) concurrent with ACXL. MATERIAL AND METHODS A prospective study was designed. A total of 22 eyes of 11 myopia astigmatism patients with unsatisfactory corneas were enrolled. The patients were assigned to femtosecond-laser in situ keratomileusis concurrent with accelerated corneal collagen crosslinking (FS-LASIK-ACXL). The follow-up duration was 24 months. Manifest refraction, uncorrected (UDVA), and corrected distance visual acuity (CDVA), ultra-high-speed camera (Corvis-ST), corneal topography, anterior segment OCT (AS-OCT), Pentacam, and endothelial cell density (ECD) were examined before and after the operation. The corneal biomechanical and refractive data was analyzed using SAS9.3. Data were analyzed through normal distribution test and variance of analysis. The difference was considered as statistically significant when p<0.05. RESULTS The steep K (Ks) values, flat K (Kf) values, average keratometry values (Avek) values, and central corneal thickness (CCT) declined significantly after FS-LASIK-ACXL operation. The values of first applanation length (A1L), the second applanation length (A2L), the first applanation velocity (A1V), the second applanation velocity (A2V), deformation amplitude (DA), highest concavity peak distance (PD), and radius of curvature at the time of highest concavity (HCR) did not show significant difference after the operation. CONCLUSIONS FS-LASIK-ACXL is an effective and safe surgery for improving visual acuity for myopic patients with thin corneas, and it does not increase the risk of iatrogenic keratectasia.

Strong nonlinear dependence of the spectral amplification factors of deep Vrancea earthquakes magnitude

NASA Astrophysics Data System (ADS)

Marmureanu, Gheorghe; Ortanza Cioflan, Carmen; Marmureanu, Alexandru

2010-05-01

Nonlinear effects in ground motion during large earthquakes have long been a controversial issue between seismologists and geotechnical engineers. Aki wrote in 1993:"Nonlinear amplification at sediments sites appears to be more pervasive than seismologists used to think…Any attempt at seismic zonation must take into account the local site condition and this nonlinear amplification( Local site effects on weak and strong ground motion, Tectonophysics,218,93-111). In other words, the seismological detection of the nonlinear site effects requires a simultaneous understanding of the effects of earthquake source, propagation path and local geological site conditions. The difficulty for seismologists in demonstrating the nonlinear site effects has been due to the effect being overshadowed by the overall patterns of shock generation and path propagation. The researchers from National Institute for Earth Physics ,in order to make quantitative evidence of large nonlinear effects, introduced the spectral amplification factor (SAF) as ratio between maximum spectral absolute acceleration (Sa), relative velocity (Sv) , relative displacement (Sd) from response spectra for a fraction of critical damping at fundamental period and peak values of acceleration(a-max),velocity (v-max) and displacement (d-max),respectively, from processed strong motion record and pointed out that there is a strong nonlinear dependence on earthquake magnitude and site conditions.The spectral amplification factors(SAF) are finally computed for absolute accelerations at 5% fraction of critical damping (β=5%) in five seismic stations: Bucharest-INCERC(soft soils, quaternary layers with a total thickness of 800 m);Bucharest-Magurele (dense sand and loess on 350m); Cernavoda Nuclear Power Plant site (marl, loess, limestone on 270 m) Bacau(gravel and loess on 20m) and Iassy (loess, sand, clay, gravel on 60 m) for last strong and deep Vrancea earthquakes: March 4,1977 (MGR =7.2 and h=95 km);August 30,1986(MGR =7.0 and h=130 km);May 30,1990 (MGR =6.7 and h=90 km) and May 31,1990 (MGR =6.1 and h=87 km). With a view to understand the characteristics of nonlinear soil behavior and the nonlinearity in the seismology and the influence to hazard and risk assessment ,this study examined the ways that nonlinearity would expected to appear on strong motion records made on Romania territory during to last Vrancea earthquake. The effect on nonlinearity is very large. For example, if we maintain the same amplification factor (SAF=5.8942) as for relatively strong earthquake on May 31,1990 with magnitude Ms =6,1 then at Bacau seismic station for earthquake on May 30,1990 (MGR =6.7) the peak acceleration has to be a*max =0.154g( +14.16%) and the actual recorded was only, a max =0.135g. Also, for Vrancea earthquake on August 30,1986, the peak acceleration has to be a*max=0.107g (+45,57%), instead of real value of 0.0736 g recorded at Bacau seismic station. More, the spectral amplification factors(SAF) are function of earthquake magnitude and there is a strong nonlinear dependence of the SAF of earthquake magnitude. The median values of SAF of the last strong Vrancea earthquakes for damping 5% are: 4.16; 3.63 and 3.26 corresponding to May 31,1990 Vrancea earthquake (Ms=6.1),May 30,1990 Vrancea earthquake(Ms=6.7),respectively, August 30,1986 Vrancea one(Ms=7.0). At the same seismic station, for example at Bacau, for 5% damping, SAF for accelerations is 5.22 for May 31,1990 earthquake (Ms =6.1);4.32 for May 30,1990 earthquake (Ms =6.7) and 3,94 for August 30,1986 one (Ms=7.0) etc. Finally, it will be made a comment in connection to U.S. Atomic Energy Commission-Regulatory Guide 1.60 on "Design Response Spectra for seismic design of nuclear power plants " to see spectral amplification factors for deep Vrancea earthquakes are larger and different.

Burst mode FEL with the ETA-III induction linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lasnier, C.J.; Allen, S.L.; Felker, B.

1993-05-13

Pulses of 140 GHz microwaves have been produced at a 2 kHz rate using the ETA-III induction linac and IMP wiggler. The accelerator was run in bursts of up to 50 pulses at 6 MeV and greater than 2 kA peak current. A feedback timing control system was used to synchronize acceleration voltage pulses with the electron beam, resulting in sufficient reduction of the corkscrew and energy sweep for efficient FEL operation. Peak microwave power for short bursts was in the range 0.5--1.1 GW, which is comparable to the single-pulse peak power of 0.75--2 GW. FEL bursts of more thanmore » 25 pulses were obtained.« less

Near Fault Strong Ground Motion Records in the Kathmandu Valley during the 2015 Gorkha Nepal Earthquake

NASA Astrophysics Data System (ADS)

Takai, N.; Shigefuji, M.; Rajaure, S.; Bijukchhen, S.; Ichiyanagi, M.; Dhital, M. R.; Sasatani, T.

2015-12-01

Kathmandu is the capital of Nepal and is located in the Kathmandu Valley, which is formed by soft lake sediments of Plio-Pleistocene origin. Large earthquakes in the past have caused significant damage as the seismic waves were amplified in the soft sediments. To understand the site effect of the valley structure, we installed continuous recording accelerometers in four different parts of the valley. Four stations were installed along a west-to-east profile of the valley at KTP (Kirtipur; hill top), TVU (Kirtipur; hill side), PTN (Patan) and THM (Thimi). On 25 April 2015, a large interplate earthquake Mw 7.8 occurred in the Himalayan Range of Nepal. The focal area estimated was about 200 km long and 150 km wide, with a large slip area under the Kathmandu Valley where our strong motion observation stations were installed. The strong ground motions were observed during this large damaging earthquake. The maximum horizontal peak ground acceleration at the rock site was 271 cm s-2, and the maximum horizontal peak ground velocity at the sediment sites reached 112 cm s-1. We compared these values with the empirical attenuation formula for strong ground motions. We found the peak accelerations were smaller and the peak velocities were approximately the same as the predicted values. The rock site KTP motions are less affected by site amplification and were analysed further. The horizontal components were rotated to the fault normal (N205E) and fault parallel (N115E) directions using the USGS fault model. The velocity waveforms at KTP showed about 5 s triangular pulses on the N205E and the up-down components; however the N115E component was not a triangular pulse but one cycle sinusoidal wave. The velocity waveforms at KTP were integrated to derive the displacement waveforms. The derived displacements at KTP are characterized by a monotonic step on the N205E normal and up-down components. The displacement waveforms of KTP show permanent displacements of 130 cm in the fault normal direction and 60 cm in the upward direction; the vector sum of these is 143 cm. Inside the Kathmandu Valley, 147 cm deformation and the same moving direction as the USGS fault normal direction were reported using with GPS data. Our results derived from the KTP records are consistent with these observations.

Safety and severity of accelerations delivered from whole body vibration exercise devices to standing adults.

PubMed

Muir, Jesse; Kiel, Douglas P; Rubin, Clinton T

2013-11-01

Whole body vibration devices are used as a means to augment training, and their potential to treat a range of musculoskeletal diseases and injuries is now being considered. The goal of this work is to determine the degree to which acceleration delivered by whole body vibration devices at the plantar surfaces of a standing human is transmitted through the axial and appendicular skeleton, and how this mechanical challenge corresponds to the safety threshold limit values established by the International Standards Organization ISO-2631. Non-blinded laboratory assessment of a range of whole body vibration devices as it pertains to acceleration transmission to healthy volunteers. Using skin and bite-bar mounted accelerometers, transmissibility to the tibia and cranium was determined in six healthy adults standing on a programmable whole body vibration device as a function of frequency and intensity. Measures of transmissibility were then made from three distinct types of whole body vibration platforms, which delivered a 50-fold range of peak-to-peak acceleration intensities (0.3-15.1 gp-p; where 1g is Earth's gravitational field). For a given frequency, transmissibility was independent of intensity when below 1g. Transmissibility declined non-linearly with increasing frequency. Depending on the whole body vibration device, vibration ranged from levels considered safe by ISO-2631 for up to 8h each day (0.3 gp-p @ 30 Hz), to levels that were seven times higher than what is considered a safe threshold for even 1 min of exposure each day (15.1 gp-p @ 30 Hz). Transmissibility to the cranium was markedly attenuated by the degree of flexion in the knees. Vibration can have adverse effects on a number of physiologic systems. This work indicates that readily accessible whole body vibration devices markedly exceed ISO guidelines for safety, and extreme caution must be practiced when considering their use. Copyright © 2013 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Error compensation of IQ modulator using two-dimensional DFT

NASA Astrophysics Data System (ADS)

Ohshima, Takashi; Maesaka, Hirokazu; Matsubara, Shinichi; Otake, Yuji

2016-06-01

It is important to precisely set and keep the phase and amplitude of an rf signal in the accelerating cavity of modern accelerators, such as an X-ray Free Electron Laser (XFEL) linac. In these accelerators an acceleration rf signal is generated or detected by an In-phase and Quadrature (IQ) modulator, or a demodulator. If there are any deviations of the phase and the amplitude from the ideal values, crosstalk between the phase and the amplitude of the output signal of the IQ modulator or the demodulator arises. This causes instability of the feedback controls that simultaneously stabilize both the rf phase and the amplitude. To compensate for such deviations, we developed a novel compensation method using a two-dimensional Discrete Fourier Transform (DFT). Because the observed deviations of the phase and amplitude of an IQ modulator involve sinusoidal and polynomial behaviors on the phase angle and the amplitude of the rf vector, respectively, the DFT calculation with these basis functions makes a good approximation with a small number of compensation coefficients. Also, we can suppress high-frequency noise components arising when we measure the deviation data. These characteristics have advantages compared to a Look Up Table (LUT) compensation method. The LUT method usually demands many compensation elements, such as about 300, that are not easy to treat. We applied the DFT compensation method to the output rf signal of a C-band IQ modulator at SACLA, which is an XFEL facility in Japan. The amplitude deviation of the IQ modulator after the DFT compensation was reduced from 15.0% at the peak to less than 0.2% at the peak for an amplitude control range of from 0.1 V to 0.9 V (1.0 V full scale) and for a phase control range from 0 degree to 360 degrees. The number of compensation coefficients is 60, which is smaller than that of the LUT method, and is easy to treat and maintain.

Vestibular Response to Electrical Stimulation of the Otolith Organs. Implications in the Development of A Vestibular Implant for the Improvement of the Sensation of Gravitoinertial Accelerations.

PubMed

Ramos de Miguel, Angel; Falcon Gonzalez, Juan Carlos; Ramos Macias, Angel

2017-08-01

Electrical stimulation of the utricular and saccular portions of the vestibular nerve improves stability in patients suffering from vestibular dysfunction. The main objective of this study was to evaluate a new technique, vestibular response telemetry (VRT), for measuring the electrically evoked vestibular compound action potential (saccular and utricular) after stimulating the otolith organ (saccular and utricular) in adults. This study used evidence that the otolith organ can be electrically stimulated in order to develop a new vestibular implant design to improve the sensation of gravitoinertial acceleration. Four adult patients were evaluated by using a variety of measurement procedures with novel VRT software. VRT values were obtained by stimulating with three full-band Nucleus CI24RE (ST) electrodes. Specific stimuli were used. Simultaneously, electrical ocular vestibular evoked myogenic potentials (eoVEMPs) were recorded in the contralateral side. Electrically evoked compound action potentials were obtained in 10 of the 12 electrodes tested, and eoVEMPs were recorded when VRT was present. In addition to the validation of this technique, a set of default clinical test parameters was established. The VRT response morphology consisted of a biphasic waveform with an initial negative peak (N1) followed by a positive peak (P1), and latencies were typically 400 μs for N1 and 800 μs for P1. The consequences for the development of a vestibular implant for the improvement of gravitoinertial acceleration sensation are also presented. The VRT measurement technique has been shown to be a useful tool to record neural response on the otolith organ, and thus it is a convenient tool to evaluate whether the implanted electrodes provide a neural response or not. This can be used for the early development of vestibular implants to improve gravitoinertial acceleration sensation.

Homogenization of Vehicle Fleet Frontal Crash Pulses from 2000–2010

PubMed Central

Locey, Caitlin M.; Garcia-Espana, J. Felipe; Toh, Akira; Belwadi, Aditya; Arbogast, Kristy B.; Maltese, Matthew R.

2012-01-01

Full-scale vehicle crash tests are performed globally to assess vehicle structure and restraint system performance. The crash pulse, captured by accelerometers mounted within the occupant compartment, measures the motion of the vehicle during the impact event. From an occupant’s perspective, the crash pulse is the inertial event to which the vehicle’s restraint systems must respond in order to mitigate the forces and accelerations that act on a passenger, and thus reduce injury risk. The objective of this study was to quantify the characteristics of crash pulses for different vehicle types in the contemporary North American fleet, and delineate current trends in crash pulse evolution. NHTSA and Transport Canada crash test databases were queried for full-frontal rigid barrier crash tests of passenger vehicles model year 2000–2010 with impact angle equaling zero degrees. Acceleration-time histories were analyzed for all accelerometers attached to the vehicle structure within the occupant compartment. Custom software calculated the following crash pulse characteristics (CPCs): peak deceleration, time of peak deceleration, onset rate, pulse duration, and change in velocity. Vehicle body types were classified by adapting the Highway Loss Data Institute (HLDI) methodology, and vehicles were assigned a generation start year in place of model year in order to more accurately represent structural change over time. 1094 vehicle crash tests with 2795 individual occupant compartment-mounted accelerometers were analyzed. We found greater peak decelerations and and shorter pulse durations across multiple vehicle types in newer model years as compared to older. For midsize passenger cars, large passenger cars, and large SUVs in 56 km/h rigid barrier tests, maximum deceleration increased by 0.40, 0.96, and 1.57 g/year respectively, and pulse duration decreased by 0.74, 1.87, and 2.51 ms/year. We also found that the crash pulse characteristics are becoming more homogeneous in the modern vehicle fleet; the range of peak deceleration values for all vehicle classes decreased from 17.1 g in 1997–1999 generation start years to 10.7 g in 2009–2010 generation years, and the pulse duration range decreased from 39.5 ms to 13.4 ms for the same generation year groupings. This latter finding suggests that the designs of restraint systems may become more universally applicable across vehicle body types, since the occupant compartment accelerations are not as divergent for newer vehicles. PMID:23169139

Generation of anomalously energetic suprathermal electrons by an electron beam interacting with a nonuniform plasma

NASA Astrophysics Data System (ADS)

Sydorenko, Dmytro

2015-11-01

Electrons emitted by electrodes surrounding or immersed in the plasma are accelerated by the sheath electric field and become electron beams penetrating the plasma. In plasma applications where controlling the electron velocity distribution function (EVDF) is crucial, these beams are an important factor capable of modifying the EVDF and affecting the discharge properties. Recently, it was reported that an EVDF measured in a dc-rf discharge with 800 V dc voltage has not only a peak of 800 eV electrons emitted from the dc-biased electrode, but also a peak of suprathermal electrons with energy up to several hundred eV. Initial explanation of the suprathermal peak suggested that the fast long plasma waves excited by the beam decay parametrically into ion acoustic waves and short plasma waves with much lower phase velocity which accelerate bulk electrons to suprathermal energies. Particle-in-cell simulation of a dc beam-plasma system, however, reveals that the short waves appear not due to the parametric instability, but due to the plasma nonuniformity. Moreover, the acceleration may occur in two stages. Plasma waves excited by the beam in the middle of the system propagate towards the anode and enter the density gradient area where their wavelength and phase speed rapidly decrease. Acceleration of thermal electrons by these waves is the first stage. Some of the accelerated electrons reflect from the anode sheath, travel through the plasma, reflect near the cathode, and enter the accelerating area again but with the energy higher than before. The acceleration that occurs now is the second stage. The energy of a particle after the second acceleration exceeds the initial thermal energy by an order of magnitude. This two-stage mechanism plays a role in explaining previous observations of energetic suprathermal electrons in similar discharges. The study is performed in collaboration with I. D. Kaganovich (PPPL), P. L. G. Ventzek and L. Chen (Tokyo Electron America).

Radiation skyshine from a 6 MeV medical accelerator

PubMed Central

McGinley, Patton H.; Rising, Mary B.; Pahikkala, A. Jussi

2010-01-01

This study assesses the dose level from skyshine produced by a 6 MeV medical accelerator. The analysis of data collected on skyshine yields professional guidance for future investigators as they attempt to quantify and qualify radiation protection concerns in shielding therapy vaults. Survey measurements using various field sizes and at varying distances from a primary barrier have enabled us to identify unique skyshine behavior in comparison to other energies already seen in literature. In order to correctly quantify such measurements outside a shielded barrier, one must take into consideration the fact that a skyshine maximum may not be observed at the same distance for all field sizes. A physical attribute of the skyshine scatter component was shown to increase to a maximum value at 4.6 m from the barrier for the largest field size used. We recommend that the largest field sizes be used in the field for the determination of skyshine effect and that the peak value be further analyzed specifically when considering shielding designs. PACS numbers: 87.52.‐g, 87.52.Df, 87.52.Tr, 87.53.‐j, 87.53.Bn, 87.53.Dq, 87.66.‐a, 89., 89.60.+x

Strong ground motion in the Kathmandu Valley during the 2015 Gorkha, Nepal, earthquake

NASA Astrophysics Data System (ADS)

Takai, Nobuo; Shigefuji, Michiko; Rajaure, Sudhir; Bijukchhen, Subeg; Ichiyanagi, Masayoshi; Dhital, Megh Raj; Sasatani, Tsutomu

2016-01-01

On 25 April 2015, a large earthquake of Mw 7.8 occurred along the Main Himalayan Thrust fault in central Nepal. It was caused by a collision of the Indian Plate beneath the Eurasian Plate. The epicenter was near the Gorkha region, 80 km northwest of Kathmandu, and the rupture propagated toward east from the epicentral region passing through the sediment-filled Kathmandu Valley. This event resulted in over 8000 fatalities, mostly in Kathmandu and the adjacent districts. We succeeded in observing strong ground motions at our four observation sites (one rock site and three sedimentary sites) in the Kathmandu Valley during this devastating earthquake. While the observed peak ground acceleration values were smaller than the predicted ones that were derived from the use of a ground motion prediction equation, the observed peak ground velocity values were slightly larger than the predicted ones. The ground velocities observed at the rock site (KTP) showed a simple velocity pulse, resulting in monotonic-step displacements associated with the permanent tectonic offset. The vertical ground velocities observed at the sedimentary sites had the same pulse motions that were observed at the rock site. In contrast, the horizontal ground velocities as well as accelerations observed at three sedimentary sites showed long duration with conspicuous long-period oscillations, due to the valley response. The horizontal valley response was characterized by large amplification (about 10) and prolonged oscillations. However, the predominant period and envelope shape of their oscillations differed from site to site, indicating a complicated basin structure. Finally, on the basis of the velocity response spectra, we show that the horizontal long-period oscillations on the sedimentary sites had enough destructive power to damage high-rise buildings with natural periods of 3 to 5 s.

Within-Event and Between-Events Ground Motion Variability from Earthquake Rupture Scenarios

NASA Astrophysics Data System (ADS)

Crempien, Jorge G. F.; Archuleta, Ralph J.

2017-09-01

Measurement of ground motion variability is essential to estimate seismic hazard. Over-estimation of variability can lead to extremely high annual hazard estimates of ground motion exceedance. We explore different parameters that affect the variability of ground motion such as the spatial correlations of kinematic rupture parameters on a finite fault and the corner frequency of the moment-rate spectra. To quantify the variability of ground motion, we simulate kinematic rupture scenarios on several vertical strike-slip faults and compute ground motion using the representation theorem. In particular, for the entire suite of rupture scenarios, we quantify the within-event and the between-events ground motion variability of peak ground acceleration (PGA) and response spectra at several periods, at 40 stations—all approximately at an equal distance of 20 and 50 km from the fault. Both within-event and between-events ground motion variability increase when the slip correlation length on the fault increases. The probability density functions of ground motion tend to truncate at a finite value when the correlation length of slip decreases on the fault, therefore, we do not observe any long-tail distribution of peak ground acceleration when performing several rupture simulations for small correlation lengths. Finally, for a correlation length of 6 km, the within-event and between-events PGA log-normal standard deviations are 0.58 and 0.19, respectively, values slightly smaller than those reported by Boore et al. (Earthq Spectra, 30(3):1057-1085, 2014). The between-events standard deviation is consistently smaller than the within-event for all correlations lengths, a feature that agrees with recent ground motion prediction equations.

Generation of quasi-monoenergetic heavy ion beams via staged shock wave acceleration driven by intense laser pulses in near-critical plasmas

NASA Astrophysics Data System (ADS)

Zhang, W. L.; Qiao, B.; Shen, X. F.; You, W. Y.; Huang, T. W.; Yan, X. Q.; Wu, S. Z.; Zhou, C. T.; He, X. T.

2016-09-01

Laser-driven ion acceleration potentially offers a compact, cost-effective alternative to conventional accelerators for scientific, technological, and health-care applications. A novel scheme for heavy ion acceleration in near-critical plasmas via staged shock waves driven by intense laser pulses is proposed, where, in front of the heavy ion target, a light ion layer is used for launching a high-speed electrostatic shock wave. This shock is enhanced at the interface before it is transmitted into the heavy ion plasmas. Monoenergetic heavy ion beam with much higher energy can be generated by the transmitted shock, comparing to the shock wave acceleration in pure heavy ion target. Two-dimensional particle-in-cell simulations show that quasi-monoenergetic {{{C}}}6+ ion beams with peak energy 168 MeV and considerable particle number 2.1 × {10}11 are obtained by laser pulses at intensity of 1.66 × {10}20 {{W}} {{cm}}-2 in such staged shock wave acceleration scheme. Similarly a high-quality {{Al}}10+ ion beam with a well-defined peak with energy 250 MeV and spread δ E/{E}0=30 % can also be obtained in this scheme.

Analysis of head impacts during sub-elite hurling practice sessions.

PubMed

O'Sullivan, D; Roe, M; Blake, C

2018-06-01

The reported incidence of head and neck injuries in hurling is 0.12 per 1000 hours, but no previous research has quantified head impact characteristics in this sport. Here, a wireless accelerometer and gyroscope captured head impacts, in 20 senior club level hurling players. Peak linear and rotational acceleration and impact location were recorded during three hurling training sessions, each player participating once. A mean of 27.9 impacts (linear acceleration >10g) per player, per session were recorded; 1314 impacts during a total exposure time of 247 minutes. Only 2.6% impacts had peak linear acceleration of >70g and 6.2% had peak rotational acceleration >7900 rad/s 2 . There were significant differences in the number and magnitude of impacts, quantified by the accelerometer, between three training sessions of differing intensity (ŋ2 0.03-0.09, p < 0.001). This study represents a first step in quantifying head impacts during hurling, demonstrating the feasibility of this technology in the field. The sensors were able to discriminate between sessions of varying intensity. These data can be used to develop athlete monitoring protocols and may be useful in developing innovative helmet-testing standards for hurling. The potential for this technology to provide feedback has clinical utility for team medical personnel.

Horizontal vestibuloocular reflex evoked by high-acceleration rotations in the squirrel monkey. IV. Responses after spectacle-induced adaptation

NASA Technical Reports Server (NTRS)

Clendaniel, R. A.; Lasker, D. M.; Minor, L. B.; Shelhamer, M. J. (Principal Investigator)

2001-01-01

The horizontal angular vestibuloocular reflex (VOR) evoked by sinusoidal rotations from 0.5 to 15 Hz and acceleration steps up to 3,000 degrees /s(2) to 150 degrees /s was studied in six squirrel monkeys following adaptation with x2.2 magnifying and x0.45 minimizing spectacles. For sinusoidal rotations with peak velocities of 20 degrees /s, there were significant changes in gain at all frequencies; however, the greatest gain changes occurred at the lower frequencies. The frequency- and velocity-dependent gain enhancement seen in normal monkeys was accentuated following adaptation to magnifying spectacles and diminished with adaptation to minimizing spectacles. A differential increase in gain for the steps of acceleration was noted after adaptation to the magnifying spectacles. The gain during the acceleration portion, G(A), of a step of acceleration (3,000 degrees /s(2) to 150 degrees /s) increased from preadaptation values of 1.05 +/- 0.08 to 1.96 +/- 0.16, while the gain during the velocity plateau, G(V), only increased from 0.93 +/- 0.04 to 1.36 +/- 0.08. Polynomial fits to the trajectory of the response during the acceleration step revealed a greater increase in the cubic than the linear term following adaptation with the magnifying lenses. Following adaptation to the minimizing lenses, the value of G(A) decreased to 0.61 +/- 0.08, and the value of G(V) decreased to 0.59 +/- 0.09 for the 3,000 degrees /s(2) steps of acceleration. Polynomial fits to the trajectory of the response during the acceleration step revealed that there was a significantly greater reduction in the cubic term than in the linear term following adaptation with the minimizing lenses. These findings indicate that there is greater modification of the nonlinear as compared with the linear component of the VOR with spectacle-induced adaptation. In addition, the latency to the onset of the adapted response varied with the dynamics of the stimulus. The findings were modeled with a bilateral model of the VOR containing linear and nonlinear pathways that describe the normal behavior and adaptive processes. Adaptation for the linear pathway is described by a transfer function that shows the dependence of adaptation on the frequency of the head movement. The adaptive process for the nonlinear pathway is a gain enhancement element that provides for the accentuated gain with rising head velocity and the increased cubic component of the responses to steps of acceleration. While this model is substantially different from earlier models of VOR adaptation, it accounts for the data in the present experiments and also predicts the findings observed in the earlier studies.

Rail accelerators for space transportation: An experimental investigation

NASA Technical Reports Server (NTRS)

Zana, L. M.; Kerslake, W. R.; Sturman, J. L.

1986-01-01

An experimental program was conducted at the Lewis Research Center with the objective of investigating the technical feasibility of rail accelerators for propulsion applications. Single-stage, plasma driven rail accelerators of small (4 by 6 mm) and medium (12.5 by 12.5 mm) bores were tested at peak accelerating currents of 50 to 450 kA. Streak-camera photography was used to provide a qualitative description of plasma armature acceleration. The effects of plasma blowby and varying bore pressure on the behavior of plasma armatures were studied.

Momentary discomfort caused by vibration of railway vehicle.

PubMed

Suzuki, H

1998-04-01

When trains pass level crossings or turnouts, they are momentarily subject to relatively strong vibrations. In railway engineering, evaluation of the riding comfort under such occasional vibrations is called the momentary evaluation, which is distinguished from the long-term evaluation. In order to identify the effective vibrational characteristics on the momentary evaluation now controversial in Japan, an experiment was performed with a riding comfort simulator. Twenty adult subjects were exposed to lateral vibration with varying peak acceleration and crest factor. Referring to the vibrations of real trains, the peak acceleration in the range of 0.35-2.00 m/s2 were varied in steps of 0.35 m/s2 and the crest factors in the range of 1.5-5.0 were varied in steps of 0.5. The frequency was set constant at 2 Hz. The task was to rate the degree of discomfort under each vibration which was given them successively. Results indicate that changes in the peak acceleration are most effective, and application of the crest factor in parallel improves the correlation with the perceived discomfort. Whether subjects can perceive changes in the peak or not affects the evaluation. Weights of vibrational characteristics that make a cue to the evaluation by subjects differ from person to person.

Role of vision in aperture closure control during reach-to-grasp movements.

PubMed

Rand, Miya K; Lemay, Martin; Squire, Linda M; Shimansky, Yury P; Stelmach, George E

2007-08-01

We have previously shown that the distance from the hand to the target at which finger closure is initiated during the reach (aperture closure distance) depends on the amplitude of peak aperture, as well as hand velocity and acceleration. This dependence suggests the existence of a control law according to which a decision to initiate finger closure during the reach is made when the hand distance to target crosses a threshold that is a function of the above movement-related parameters. The present study examined whether the control law is affected by manipulating the visibility of the hand and the target. Young adults made reach-to-grasp movements to a dowel under conditions in which the target or the hand or both were either visible or not visible. Reaching for and grasping a target when the hand and/or target were not visible significantly increased transport time and widened peak aperture. Aperture closure distance was significantly lengthened and wrist peak velocity was decreased only when the target was not visible. Further analysis showed that the control law was significantly different between the visibility-related conditions. When either the hand or target was not visible, the aperture closure distance systematically increased compared to its value for the same amplitude of peak aperture, hand velocity, and acceleration under full visibility. This implies an increase in the distance-related safety margin for grasping when the hand or target is not visible. It has been also found that the same control law can be applied to all conditions, if variables describing hand and target visibility were included in the control law model, as the parameters of the task-related environmental context, in addition to the above movement-related parameters. This suggests that that the CNS utilizes those variables for controlling grasp initiation based on a general control law.

Role of vision in aperture closure control during reach-to-grasp movements

PubMed Central

Rand, Miya K.; Lemay, Martin; Squire, Linda M.; Shimansky, Yury P.; Stelmach, George E.

2007-01-01

We have previously shown that the distance from the hand to the target at which finger closure is initiated during the reach (aperture closure distance) depends on the amplitude of peak aperture, as well as hand velocity and acceleration. This dependence suggests the existence of a control law according to which a decision to initiate finger closure during the reach is made when the hand distance to target crosses a threshold that is a function of the above movement-related parameters. The present study examined whether the control law is affected by manipulating the visibility of the hand and the target. Young adults made reach-to-grasp movements to a dowel under conditions in which the target or the hand or both were either visible or not visible. Reaching for and grasping a target when the hand and/or target were not visible significantly increased transport time and widened peak aperture. Aperture closure distance was significantly lengthened and wrist peak velocity was decreased only when the target was not visible. Further analysis showed that the control law was significantly different between the visibility-related conditions. When either the hand or target was not visible, the aperture closure distance systematically increased compared to its value for the same amplitude of peak aperture, hand velocity, and acceleration under full visibility. This implies an increase in the distance-related safety margin for grasping when the hand or target is not visible. It has been also found that the same control law can be applied to all conditions, if variables describing hand and target visibility were included in the control law model, as the parameters of the task-related environmental context, in addition to the above movement-related parameters. This suggests that that the CNS utilizes those variables for controlling grasp initiation based on a general control law. PMID:17476491

Application of Single Voxel 1H Magnetic Resonance Spectroscopy in Hepatic Benign and Malignant Lesions.

PubMed

Yang, Zifeng; Sun, Shiqiang; Chen, Yuanli; Li, Rui

2016-12-19

BACKGROUND To quantify the metabolite changes in hepatic tumors by single-voxel 1H magnetic resonance spectroscopy (MRS) at 3.0 T and explore the application value of 1HMRS in the diagnosis of hepatic benign and malignant lesions. MATERIAL AND METHODS A total of 45 patients (55 lesions) diagnosed with hepatic lesions by ultrasound and/or computer topography (CT) from November 2006 to March 2007 were included in this study. All patients underwent 3D-dynamic enhanced scan with liver acquisition with acceleration volume acquisition (LAVA) sequence and single-voxel 1HMRS imaging with PRESS (point-resolved spectroscopy) sequence. The metabolite concentrations such as choline (Cho) and lipids (Lip) were measured. RESULTS There was significant difference regarding the occurrence rate of the obvious elevated Cho peaks between benign and malignant tumors (7/27 vs. 21/28, p=0.000). There was statistical significant differences regarding the Cho/Lip ratios in hepatic benign (0.0686±0.0283, 95% CI: 0.0134-0.1245) and malignant (0.1266 ±0.1124, 95% CI: 0.0937-0.2203) lesions (p<0.05). When compared with the pathological results, the sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy were 85.7% (24/28), 92.6% (25/27), 92.3% (24/26), 86.2% (25/29), and 89.1% (49/55) respectively for the MRI assessment, and 92.6% (26/28), 88.9% (24/27), 89.7 (26/29), 92.3 (24/26), and 90.9% (50/55) respectively for 1HMRS combined with MRI assessment. CONCLUSIONS Single Cho peaks or Lip peaks cannot be used for the diagnosis of hepatic benign and malignant lesions. Combined use of 1HMRS and MRI can greatly improve the application value of MRI assessment in the diagnosis of hepatic benign and malignant lesions with a higher sensitivity, negative predictive value, and overall accuracy.

A physically-based method for predicting peak discharge of floods caused by failure of natural and constructed earthen dams

USGS Publications Warehouse

Walder, J.S.

1997-01-01

We analyse a simple, physically-based model of breach formation in natural and constructed earthen dams to elucidate the principal factors controlling the flood hydrograph at the breach. Formation of the breach, which is assumed trapezoidal in cross-section, is parameterized by the mean rate of downcutting, k, the value of which is constrained by observations. A dimensionless formulation of the model leads to the prediction that the breach hydrograph depends upon lake shape, the ratio r of breach width to depth, the side slope ?? of the breach, and the parameter ?? = (V/ D3)(k/???gD), where V = lake volume, D = lake depth, and g is the acceleration due to gravity. Calculations show that peak discharge Qp depends weakly on lake shape r and ??, but strongly on ??, which is the product of a dimensionless lake volume and a dimensionless erosion rate. Qp(??) takes asymptotically distinct forms depending on whether ?? > 1. Theoretical predictions agree well with data from dam failures for which k could be reasonably estimated. The analysis provides a rapid and in many cases graphical way to estimate plausible values of Qp at the breach.

On the early stages of wind wave under non-stationary wind conditions.

NASA Astrophysics Data System (ADS)

Robles-Diaz, Lucia; Ocampo-Torres, Francisco J.; Branger, Hubert

2017-04-01

Most efforts in the study of the generation and evolution of wind waves have been conducted under constant wind. The balance of the transfer of different properties has been studied mainly for situations where the wave has already reached the equilibrium with the constant wind conditions. The purpose of these experiments is to study the early stages of the generation of waves under non-stationary wind conditions and to determine a balance in the exchange at the air-water interface for non-equilibrium wind conditions. A total of 16 experiments with a characteristic acceleration and deceleration rate of wind speed were conducted in a large wind-wave facility of Institut Pythéas (Marseille-France). The wave tank is 40 m long, 2.7 m wide and 1 m deep. The air section is 50 m long, 3 m wide and 1.8 m height. The momentum fluxes were estimated from hot wire anemometry at station 7. Also, the free surface displacement was measured along the channel tank at 11 stations where resistance wires were installed, except at stations 1, 2, and 7 where capacitance wires were installed. The sampling frequency for wind velocity and surface displacement measurements was 256 Hz. During experiments the wind intensity was abruptly increased with a constant acceleration rate over time, reaching a constant maximum intensity of 13 m/s. This constant velocity remains some time until the intensity is again reduced suddenly. We observed that wind drag coefficient values are higher for the experiments that present the lower acceleration rate; some field data from previous studies is presented for reference (Large and Pond 1981; Ocampo-Torres et al. 2011; Smith 1980; Yelland and Taylor 1996). The empirical grow curves show that in the experiments with lower acceleration, the wave field is more developed, showing higher dimensional energy and lower dimensional peak frequency. In the evolution of the spectral wave energy, there is first high frequency energy saturation, followed by a downshift of the wave-spectral peak frequency. Under the same wind speed, these two processes are more developed when the acceleration is low. Therefore, the acceleration rate has a direct impact in controlling how the energy and momentum transfer take place from the wind to the wave field. This work represents a contribution of RugDiSMar Project (CONACYT 155793), and of project CONACYT CB-2015-01 255377.

Generation and Characterization of Electron Bunches with Ramped Current Profiles in a Dual-Frequency Superconducting Linear Accelerator

DOE PAGES

Piot, P.; Behrens, C.; Gerth, C.; ...

2011-09-07

We report on the successful experimental generation of electron bunches with ramped current profiles. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a superconducing radiofrequency linear accelerator operating at two frequencies and a current-enhancing dispersive section. The produced {approx} 700-MeV bunches have peak currents of the order of a kilo-Ampere. Data taken for various accelerator settings demonstrate the versatility of the method and in particular its ability to produce current profiles that have a quasi-linear dependency on the longitudinal (temporal) coordinate. The measured bunch parameters are shown, via numerical simulations, to produce gigavolt-per-meter peak acceleratingmore » electric fields with transformer ratios larger than 2 in dielectric-lined waveguides.« less

Proton beam spatial distribution and Bragg peak imaging by photoluminescence of color centers in lithium fluoride crystals at the TOP-IMPLART linear accelerator

NASA Astrophysics Data System (ADS)

Piccinini, M.; Ronsivalle, C.; Ampollini, A.; Bazzano, G.; Picardi, L.; Nenzi, P.; Trinca, E.; Vadrucci, M.; Bonfigli, F.; Nichelatti, E.; Vincenti, M. A.; Montereali, R. M.

2017-11-01

Solid-state radiation detectors based on the photoluminescence of stable point defects in lithium fluoride crystals have been used for advanced diagnostics during the commissioning of the segment up to 27 MeV of the TOP-IMPLART proton linear accelerator for proton therapy applications, under development at ENEA C.R. Frascati, Italy. The LiF detectors high intrinsic spatial resolution and wide dynamic range allow obtaining two-dimensional images of the beam transverse intensity distribution and also identifying the Bragg peak position with micrometric precision by using a conventional optical fluorescence microscope. Results of the proton beam characterization, among which, the estimation of beam energy components and dynamics, are reported and discussed for different operating conditions of the accelerator.

Kinetic Sprint Asymmetries on a non-motorised Treadmill in Rugby Union Athletes.

PubMed

Brown, Scott R; Cross, Matt R; Girard, Olivier; Brocherie, Franck; Samozino, Pierre; Morin, Jean-Benoît

2017-11-01

The purpose of this study was to present a potential link between sprint kinetic (vertical [F V ] and horizontal force [F H ]) asymmetries and athletic performance during acceleration and maximal velocity (v max ) sprinting. Thirty un-injured male rugby athletes performed 8-s sprints on a non-motorised treadmill. Kinetic data were divided into 'strong' and 'weak' legs based on individually averaged peak values observed during sprinting and were analysed to evaluate asymmetry. Large differences were found between the strong and weak legs in F H during acceleration (4.3 vs. 3.5 N·kg -1 ) and v max (3.7 vs. 2.8 N·kg -1 ) sprinting (both ES=1.2), but not in F V (21.8 vs. 20.8 N·kg -1 , ES=- 0.6 for acceleration; 23.9 vs. 22.8 N·kg -1 , ES=- 0.5 for v max , respectively). Group mean asymmetry was lower in F V compared to F H during acceleration (1.6 vs. 6.8%) and v max (1.6 vs. 8.2%). The range of asymmetry was much lower in F V (0.03-4.3%) compared to F H (0.2-28%). In un-injured rugby athletes, the magnitude and range of asymmetry scores in F H , occurring during acceleration and v max phases, where much greater than those found in F V . These findings highlight the potential for some un-injured athletes to possess kinetic asymmetries known as crucial components for acceleration performance in sprinting. © Georg Thieme Verlag KG Stuttgart · New York.

Review: Progress in rotational ground-motion observations from explosions and local earthquakes in Taiwan

USGS Publications Warehouse

Lee, William H K.; Huang, Bor-Shouh; Langston, Charles A.; Lin, Chin-Jen; Liu, Chun-Chi; Shin, Tzay-Chyn; Teng, Ta-Liang; Wu, Chien-Fu

2009-01-01

Rotational motions generated by large earthquakes in the far field have been successfully measured, and observations agree well with the classical elasticity theory. However, recent rotational measurements in the near field of earthquakes in Japan and in Taiwan indicate that rotational ground motions are 10 to 100 times larger than expected from the classical elasticity theory. The near-field strong-motion records of the 1999 Mw 7.6 Chi-Chi, Taiwan, earthquake suggest that the ground motions along the 100 km rupture are complex. Some rather arbitrary baseline corrections are necessary in order to obtain reasonable displacement values from double integration of the acceleration data. Because rotational motions can contaminate acceleration observations due to the induced perturbation of the Earth’s gravitational field, we started a modest program to observe rotational ground motions in Taiwan.Three papers have reported the rotational observations in Taiwan: (1) at the HGSD station (Liu et al., 2009), (2) at the N3 site from two TAiwan Integrated GEodynamics Research (TAIGER) explosions (Lin et al., 2009), and (3) at the Taiwan campus of the National Chung-Cheng University (NCCU) (Wu et al., 2009). In addition, Langston et al. (2009) reported the results of analyzing the TAIGER explosion data. As noted by several authors before, we found a linear relationship between peak rotational rate (PRR in mrad/sec) and peak ground acceleration (PGA in m/sec2) from local earthquakes in Taiwan, PRR=0.002+1.301 PGA, with a correlation coefficient of 0.988.

Probabilistic Seismic Hazard Assessment for Himalayan-Tibetan Region from Historical and Instrumental Earthquake Catalogs

NASA Astrophysics Data System (ADS)

Rahman, M. Moklesur; Bai, Ling; Khan, Nangyal Ghani; Li, Guohui

2018-02-01

The Himalayan-Tibetan region has a long history of devastating earthquakes with wide-spread casualties and socio-economic damages. Here, we conduct the probabilistic seismic hazard analysis by incorporating the incomplete historical earthquake records along with the instrumental earthquake catalogs for the Himalayan-Tibetan region. Historical earthquake records back to more than 1000 years ago and an updated, homogenized and declustered instrumental earthquake catalog since 1906 are utilized. The essential seismicity parameters, namely, the mean seismicity rate γ, the Gutenberg-Richter b value, and the maximum expected magnitude M max are estimated using the maximum likelihood algorithm assuming the incompleteness of the catalog. To compute the hazard value, three seismogenic source models (smoothed gridded, linear, and areal sources) and two sets of ground motion prediction equations are combined by means of a logic tree on accounting the epistemic uncertainties. The peak ground acceleration (PGA) and spectral acceleration (SA) at 0.2 and 1.0 s are predicted for 2 and 10% probabilities of exceedance over 50 years assuming bedrock condition. The resulting PGA and SA maps show a significant spatio-temporal variation in the hazard values. In general, hazard value is found to be much higher than the previous studies for regions, where great earthquakes have actually occurred. The use of the historical and instrumental earthquake catalogs in combination of multiple seismogenic source models provides better seismic hazard constraints for the Himalayan-Tibetan region.

Sustained Accelerated Idioventricular Rhythm in a Centrifuge-Simulated Suborbital Spaceflight.

PubMed

Suresh, Rahul; Blue, Rebecca S; Mathers, Charles; Castleberry, Tarah L; Vanderploeg, James M

2017-08-01

Hypergravitational exposures during human centrifugation are known to provoke dysrhythmias, including sinus dysrhythmias/tachycardias, premature atrial/ventricular contractions, and even atrial fibrillations or flutter patterns. However, events are generally short-lived and resolve rapidly after cessation of acceleration. This case report describes a prolonged ectopic ventricular rhythm in response to high G exposure. A previously healthy 30-yr-old man voluntarily participated in centrifuge trials as a part of a larger study, experiencing a total of 7 centrifuge runs over 48 h. Day 1 consisted of two +Gz runs (peak +3.5 Gz, run 2) and two +Gx runs (peak +6.0 Gx, run 4). Day 2 consisted of three runs approximating suborbital spaceflight profiles (combined +Gx and +Gz). Hemodynamic data collected included blood pressure, heart rate, and continuous three-lead electrocardiogram. Following the final acceleration exposure of the last Day 2 run (peak +4.5 Gx and +4.0 Gz combined, resultant +6.0 G), during a period of idle resting centrifuge activity (resultant vector +1.4 G), the subject demonstrated a marked change in his three-lead electrocardiogram from normal sinus rhythm to a wide-complex ectopic ventricular rhythm at a rate of 91-95 bpm, consistent with an accelerated idioventricular rhythm (AIVR). This rhythm was sustained for 2 m, 24 s before reversion to normal sinus. The subject reported no adverse symptoms during this time. While prolonged, the dysrhythmia was asymptomatic and self-limited. AIVR is likely a physiological response to acceleration and can be managed conservatively. Vigilance is needed to ensure that AIVR is correctly distinguished from other, malignant rhythms to avoid inappropriate treatment and negative operational impacts.Suresh R, Blue RS, Mathers C, Castleberry TL, Vanderploeg JM. Sustained accelerated idioventricular rhythm in a centrifuge-simulated suborbital spaceflight. Aerosp Med Hum Perform. 2017; 88(8):789-793.

Gender differences in head-neck segment dynamic stabilization during head acceleration.

PubMed

Tierney, Ryan T; Sitler, Michael R; Swanik, C Buz; Swanik, Kathleen A; Higgins, Michael; Torg, Joseph

2005-02-01

Recent epidemiological research has revealed that gender differences exist in concussion incidence but no study has investigated why females may be at greater risk of concussion. Our purpose was to determine whether gender differences existed in head-neck segment kinematic and neuromuscular control variables responses to an external force application with and without neck muscle preactivation. Forty (20 females and 20 males) physically active volunteers participated in the study. The independent variables were gender, force application (known vs unknown), and force direction (forced flexion vs forced extension). The dependent variables were kinematic and EMG variables, head-neck segment stiffness, and head-neck segment flexor and extensor isometric strength. Statistical analyses consisted of multiple multivariate and univariate analyses of variance, follow-up univariate analyses of variance, and t-tests (P < or = 0.05). Gender differences existed in head-neck segment dynamic stabilization during head angular acceleration. Females exhibited significantly greater head-neck segment peak angular acceleration (50%) and displacement (39%) than males despite initiating muscle activity significantly earlier (SCM only) and using a greater percentage of their maximum head-neck segment muscle activity (79% peak activity and 117% muscle activity area). The head-neck segment angular acceleration differences may be because females exhibited significantly less isometric strength (49%), neck girth (30%), and head mass (43%), resulting in lower levels of head-neck segment stiffness (29%). For our subject demographic, the results revealed gender differences in head-neck segment dynamic stabilization during head acceleration in response to an external force application. Females exhibited significantly greater head-neck segment peak angular acceleration and displacement than males despite initiating muscle activity earlier (SCM only) and using a greater percentage of their maximum head-neck segment muscle activity.

Seismic hazard assessment in the megacity of Blida (Algeria) and its surrounding regions using parametric-historic procedure

NASA Astrophysics Data System (ADS)

Bellalem, Fouzi; Talbi, Abdelhak; Djellit, Hamou; Ymmel, Hayet; Mobarki, Mourad

2018-03-01

The region of Blida is characterized by a relatively high seismic activity, pointed especially during the past two centuries. Indeed, it experienced a significant number of destructive earthquakes such as the earthquakes of March 2, 1825 and January 2, 1867, with intensity of X and IX, respectively. This study aims to investigate potential seismic hazard in Blida city and its surrounding regions. For this purpose, a typical seismic catalog was compiled using historical macroseismic events that occurred over a period of a few hundred years, and the recent instrumental seismicity dating back to 1900. The parametric-historic procedure introduced by Kijko and Graham (1998, 1999) was applied to assess seismic hazard in the study region. It is adapted to deal with incomplete catalogs and does not use any subjective delineation of active seismic zones. Because of the lack of recorded strong motion data, three ground prediction models have been considered, as they seem the most adapted to the seismicity of the study region. Results are presented as peak ground acceleration (PGA) seismic hazard maps, showing expected peak accelerations with 10% probability of exceedance in 50-year period. As the most significant result, hot spot regions with high PGA values are mapped. For example, a PGA of 0.44 g has been found in a small geographical area centered on Blida city.

Probabilistic seismic hazard assessment for the two layer fault system of Antalya (SW Turkey) area

NASA Astrophysics Data System (ADS)

Dipova, Nihat; Cangir, Bülent

2017-09-01

Southwest Turkey, along Mediterranean coast, is prone to large earthquakes resulting from subduction of the African plate under the Eurasian plate and shallow crustal faults. Maximum observed magnitude of subduction earthquakes is Mw = 6.5 whereas that of crustal earthquakes is Mw = 6.6. Crustal earthquakes are sourced from faults which are related with Isparta Angle and Cyprus Arc tectonic structures. The primary goal of this study is to assess seismic hazard for Antalya area (SW Turkey) using a probabilistic approach. A new earthquake catalog for Antalya area, with unified moment magnitude scale, was prepared in the scope of the study. Seismicity of the area has been evaluated by the Gutenberg-Richter recurrence relationship. For hazard computation, CRISIS2007 software was used following the standard Cornell-McGuire methodology. Attenuation model developed by Youngs et al. Seismol Res Lett 68(1):58-73, (1997) was used for deep subduction earthquakes and Chiou and Youngs Earthq Spectra 24(1):173-215, (2008) model was used for shallow crustal earthquakes. A seismic hazard map was developed for peak ground acceleration and for rock ground with a hazard level of a 10% probability of exceedance in 50 years. Results of the study show that peak ground acceleration values on bedrock change between 0.215 and 0.23 g in the center of Antalya.

Photo-triggering and secondary electron produced ionization in electric discharge ArF* excimer lasers

NASA Astrophysics Data System (ADS)

Xiong, Zhongmin; Kushner, Mark J.

2011-10-01

Electric discharge excimer lasers are sustained in multi-atmosphere attaching gas mixtures that are typically preionized to enable a reproducible, uniform glow, which maximizes optical quality and gain. This preionization is often accomplished using UV light produced by a corona discharge within the plasma cavity. To quantify the relationship between corona discharge properties and those of the laser discharge, the triggering of electron avalanche by preionizing UV light in an electric discharge-pumped ArF* excimer laser was numerically investigated using a two-dimensional model. The preionizing UV fluxes were generated by a corona-bar discharge driven by the same voltage pulse as the main discharge sustained in a multi-atmospheric Ne/Ar/Xe/F2 gas mixture. The resulting peak photo-electron density in the inter-electrode spacing is around 108 cm-3, and its distribution is biased toward the UV source. The preionization density increases with increasing dielectric constant and capacitance of the corona bar. The symmetry and uniformity of the discharge are, however, improved significantly once the main avalanche develops. In addition to bulk electron impact ionization, the ionization generated by sheath accelerated secondary electrons was found to be important in sustaining the discharge current at experimentally observed values. At peak current, the magnitude of the ionization by sheath accelerated electrons is comparable to that from bulk electron impact in the vicinity of the cathode.

Probabilistic seismic hazard assessment of southern part of Ghana

NASA Astrophysics Data System (ADS)

Ahulu, Sylvanus T.; Danuor, Sylvester Kojo; Asiedu, Daniel K.

2018-05-01

This paper presents a seismic hazard map for the southern part of Ghana prepared using the probabilistic approach, and seismic hazard assessment results for six cities. The seismic hazard map was prepared for 10% probability of exceedance for peak ground acceleration in 50 years. The input parameters used for the computations of hazard were obtained using data from a catalogue that was compiled and homogenised to moment magnitude (Mw). The catalogue covered a period of over a century (1615-2009). The hazard assessment is based on the Poisson model for earthquake occurrence, and hence, dependent events were identified and removed from the catalogue. The following attenuation relations were adopted and used in this study—Allen (for south and eastern Australia), Silva et al. (for Central and eastern North America), Campbell and Bozorgnia (for worldwide active-shallow-crust regions) and Chiou and Youngs (for worldwide active-shallow-crust regions). Logic-tree formalism was used to account for possible uncertainties associated with the attenuation relationships. OpenQuake software package was used for the hazard calculation. The highest level of seismic hazard is found in the Accra and Tema seismic zones, with estimated peak ground acceleration close to 0.2 g. The level of the seismic hazard in the southern part of Ghana diminishes with distance away from the Accra/Tema region to a value of 0.05 g at a distance of about 140 km.

Turbulence Hazard Metric Based on Peak Accelerations for Jetliner Passengers

NASA Technical Reports Server (NTRS)

Stewart, Eric C.

2005-01-01

Calculations are made of the approximate hazard due to peak normal accelerations of an airplane flying through a simulated vertical wind field associated with a convective frontal system. The calculations are based on a hazard metric developed from a systematic application of a generic math model to 1-cosine discrete gusts of various amplitudes and gust lengths. The math model simulates the three degree-of- freedom longitudinal rigid body motion to vertical gusts and includes (1) fuselage flexibility, (2) the lag in the downwash from the wing to the tail, (3) gradual lift effects, (4) a simplified autopilot, and (5) motion of an unrestrained passenger in the rear cabin. Airplane and passenger response contours are calculated for a matrix of gust amplitudes and gust lengths. The airplane response contours are used to develop an approximate hazard metric of peak normal accelerations as a function of gust amplitude and gust length. The hazard metric is then applied to a two-dimensional simulated vertical wind field of a convective frontal system. The variations of the hazard metric with gust length and airplane heading are demonstrated.

Optimal trajectories for an aerospace plane. Part 2: Data, tables, and graphs

NASA Technical Reports Server (NTRS)

Miele, Angelo; Lee, W. Y.; Wu, G. D.

1990-01-01

Data, tables, and graphs relative to the optimal trajectories for an aerospace plane are presented. A single-stage-to-orbit (SSTO) configuration is considered, and the transition from low supersonic speeds to orbital speeds is studied for a single aerodynamic model (GHAME) and three engine models. Four optimization problems are solved using the sequential gradient-restoration algorithm for optimal control problems: (1) minimization of the weight of fuel consumed; (2) minimization of the peak dynamic pressure; (3) minimization of the peak heating rate; and (4) minimization of the peak tangential acceleration. The above optimization studies are carried out for different combinations of constraints, specifically: initial path inclination that is either free or given; dynamic pressure that is either free or bounded; and tangential acceleration that is either free or bounded.

Pharmacology of saccadic eye movements in man. 1. Effects of the benzodiazepine receptor ligands midazolam and flumazenil.

PubMed

Ball, D M; Glue, P; Wilson, S; Nutt, D J

1991-01-01

A paradigm for assessing benzodiazepine receptor sensitivity was developed using intravenous midazolam in normal volunteers. After administration of incremental doses of midazolam, alterations in saccadic eye movement parameters and psychological self ratings were assessed. Significant changes included dose-dependent slowing of peak velocity, peak acceleration, peak deceleration, reduced saccade acceleration/deceleration ratio and saccade accuracy, and increased sedation self-ratings. Changes in saccade variables and sedation ratings were significantly correlated, and also correlated with plasma midazolam concentrations. No significant changes were seen in saccade latency or anxiety self-ratings. Pharmacological specificity of these changes was demonstrated by their reversal with the benzodiazepine antagonist flumazenil. This challenge paradigm appears to be a sensitive means of assessing benzodiazepine receptor function in man.

Comparing Newmark

NASA Astrophysics Data System (ADS)

Rodríguez-Peces, M. J.; García-Mayordomo, J.; Azañón-Hernández, J. M.; Jabaloy-Sánchez, A.

2009-04-01

The Lorca Basin (Eastern Betic Cordillera, SE Spain) is one of the most seismically active regions of Spain. In this area there are well known cases of earthquake-induced slope instabilities associated to specific earthquakes (e.g., Bullas 2002, La Paca 2005). Furthermore, this area is characterized by moderate magnitude seismicity which mainly produces rock-falls and avalanches. In this work we present the results of our research at regional and site scales. For the regional scale, we have used a geographic information system (GIS) to develop an implementation of the Newmark's sliding rigid block method. We have particularly proposed a new variation of Newmark's method to consider soil and topographic amplification effects. Subsequently, we produced "Newmark displacement" maps for both probabilistic and deterministic seismic scenarios in the Lorca Basin. Probabilistic seismic scenarios consider three hazard maps in terms of peak ground acceleration (PGA) on rock corresponding to the 475-, 975- and 2475-year return periods (exceedance probability of 10, 5 and 2% in 50 years, respectively) in the Murcia Region. Deterministic seismic scenarios consider the occurrence of the most probable earthquake for a 475-year return period (Mw=5.0) at every location, or either a complete rupture of Lorca-Totana (Mw=6.7) or Puerto Lumbreras-Lorca (Mw=6.8) segments of Alhama de Murcia Fault. The Newmark displacement maps allowed us to identify areas with the highest potential seismic hazard, and also locate areas for future particular studies. We have found that rock-falls produced during the last earthquakes in Lorca Basin (e.g., Bullas 2002, La Paca 2005) match very well with areas with values of Newmark displacement lower than 2 cm in all the seismic scenarios considered. Therefore, it seems that low values of Newmark displacements are very likely associated with rock-falls. To support this hypothesis we have applied the Newmark method at a site scale. To do this, we have selected La Paca rock-fall which was generated during La Paca 2005 earthquake (mbLg=4.7, IEMS=VI-VII). We have used a terrestrial laser scanner in order to obtain a high resolution digital elevation model of La Paca rock-fall area. Moreover, we have performed a back-analysis based on field data to estimate the static safety factor previous to the earthquake and the critical acceleration. Furthermore, we have selected a representative strong ground motion record for La Paca earthquake from international databases. The critical acceleration and the peak ground acceleration values obtained from the strong ground motion record allowed us to estimate the actual soil and topographic amplification effects. Finally, we have calculated analytically the real Newmark displacement at La Paca rock-fall and we have compared this displacement with our GIS estimation in order to improve the calibration of Newmark's method at the regional scale.

Accelerated ions and self-excited Alfvén waves at the Earth's bow shock

NASA Astrophysics Data System (ADS)

Berezhko, E. G.; Taneev, S. N.; Trattner, K. J.

2011-07-01

The diffuse energetic ion event and related Alfvén waves upstream of the Earth's bow shock, measured by AMPTE/IRM satellite on 29 September 1984, 06:42-07:22 UT, was studied using a self-consistent quasi-linear theory of ion diffusive shock acceleration and associated Alfvén wave generation. The wave energy density satisfies a wave kinetic equation, and the ion distribution function satisfies the diffusive transport equation. These coupled equations are solved numerically, and calculated ion and wave spectra are compared with observations. It is shown that calculated steady state ion and Alfvén wave spectra are established during the time period of about 1000 s. Alfvén waves excited by accelerated ions are confined within the frequency range (10-2 to 1) Hz, and their spectral peak with the wave amplitude δB ≈ B comparable to the interplanetary magnetic field value B corresponds to the frequency 2 × 10-2 Hz. The high-frequency part of the wave spectrum undergoes absorption by thermal protons. It is shown that the observed ion spectra and the associated Alfvén wave spectra are consistent with the theoretical prediction.

Prediction of spectral acceleration response ordinates based on PGA attenuation

USGS Publications Warehouse

Graizer, V.; Kalkan, E.

2009-01-01

Developed herein is a new peak ground acceleration (PGA)-based predictive model for 5% damped pseudospectral acceleration (SA) ordinates of free-field horizontal component of ground motion from shallow-crustal earthquakes. The predictive model of ground motion spectral shape (i.e., normalized spectrum) is generated as a continuous function of few parameters. The proposed model eliminates the classical exhausted matrix of estimator coefficients, and provides significant ease in its implementation. It is structured on the Next Generation Attenuation (NGA) database with a number of additions from recent Californian events including 2003 San Simeon and 2004 Parkfield earthquakes. A unique feature of the model is its new functional form explicitly integrating PGA as a scaling factor. The spectral shape model is parameterized within an approximation function using moment magnitude, closest distance to the fault (fault distance) and VS30 (average shear-wave velocity in the upper 30 m) as independent variables. Mean values of its estimator coefficients were computed by fitting an approximation function to spectral shape of each record using robust nonlinear optimization. Proposed spectral shape model is independent of the PGA attenuation, allowing utilization of various PGA attenuation relations to estimate the response spectrum of earthquake recordings.

Experimental investigation of shock wave diffraction over a single- or double-sphere model

NASA Astrophysics Data System (ADS)

Zhang, L. T.; Wang, T. H.; Hao, L. N.; Huang, B. Q.; Chen, W. J.; Shi, H. H.

2017-01-01

In this study, the unsteady drag produced by the interaction of a shock wave with a single- and a double-sphere model is measured using imbedded accelerometers. The shock wave is generated in a horizontal circular shock tube with an inner diameter of 200 mm. The effect of the shock Mach number and the dimensionless distance between spheres is investigated. The time-history of the drag coefficient is obtained based on Fast Fourier Transformation (FFT) band-block filtering and polynomial fitting of the measured acceleration. The measured peak values of the drag coefficient, with the associated uncertainty, are reported.

NOx profile around a signalized intersection of busy roadway

NASA Astrophysics Data System (ADS)

Kim, Kyung Hwan; Lee, Seung-Bok; Woo, Sung Ho; Bae, Gwi-Nam

2014-11-01

The NOx pollution profile around a signalized intersection of a busy roadway was investigated to understand the effect of traffic control on urban air pollution. Traffic flow patterns were classified into three categories of quasi-cruising, a combination of deceleration and acceleration, and a combination of deceleration, idling, and acceleration. The spatial distribution of air pollution levels around an intersection could be represented as a quasi-normal distribution, whose peak height was aggravated by increased emissions due to transient driving patterns. The peak concentration of NOx around the signalized intersection for the deceleration, idling, and acceleration category was five times higher than that for the quasi-cruising category. Severe levels of NOx pollution tailed off approximately 400 m from the center of the intersection. Approximately 200-1000 ppb of additional NOx was observed when traffic was decelerating, idling, and accelerating within the intersection zone, resulting in high exposure levels for pedestrians around the intersection. We propose a fluctuating horizontal distribution of motor vehicle-induced air pollutants as a function of time.

Dual Ion Species Plasma Expansion from Isotopically Layered Cryogenic Targets

NASA Astrophysics Data System (ADS)

Scott, G. G.; Carroll, D. C.; Astbury, S.; Clarke, R. J.; Hernandez-Gomez, C.; King, M.; Alejo, A.; Arteaga, I. Y.; Dance, R. J.; Higginson, A.; Hook, S.; Liao, G.; Liu, H.; Mirfayzi, S. R.; Rusby, D. R.; Selwood, M. P.; Spindloe, C.; Tolley, M. K.; Wagner, F.; Zemaityte, E.; Borghesi, M.; Kar, S.; Li, Y.; Roth, M.; McKenna, P.; Neely, D.

2018-05-01

A dual ion species plasma expansion scheme from a novel target structure is introduced, in which a nanometer-thick layer of pure deuterium exists as a buffer species at the target-vacuum interface of a hydrogen plasma. Modeling shows that by controlling the deuterium layer thickness, a composite H+/D+ ion beam can be produced by target normal sheath acceleration (TNSA), with an adjustable ratio of ion densities, as high energy proton acceleration is suppressed by the acceleration of a spectrally peaked deuteron beam. Particle in cell modeling shows that a (4.3 ±0.7 ) MeV per nucleon deuteron beam is accelerated, in a directional cone of half angle 9°. Experimentally, this was investigated using state of the art cryogenic targetry and a spectrally peaked deuteron beam of (3.4 ±0.7 ) MeV per nucleon was measured in a cone of half angle 7°-9°, while maintaining a significant TNSA proton component.

Interior noise and vibration measurements on operational military helicopters and comparisons with various ride quality criteria

NASA Technical Reports Server (NTRS)

Clevenson, S. A.; Leatherwood, J. D.; Hollenbaugh, D. D.

1983-01-01

The results of physical measurements of the interior noise and vibration obtained within eight operational military helicopters are presented. The data were extensively analyzed and are presented in the following forms: noise and vibration spectra, overall root-mean-square acceleration levels in three linear axes, peak accelerations at dominant blade passage frequencies, acceleration exceedance data, and overall and ""A'' weighted sound pressure levels. Peak acceleration levels were compared to the ISO 1-hr reduced comfort and fatigue decreased proficiency boundaries and the NASA discomfort criteria. The ""A'' weighted noise levels were compared to the NASA annoyance criteria, and the overall noise spectra were compared to MIL-STD-1294 (""Acoustical Noise Limits in Helicopters''). Specific vibration components at blade passage frequencies for several aircraft exceeded both the ISO reduced comfort boundary and the NASA passenger discomfort criteria. The ""A'' weighted noise levels, corrected for SPH-4 helmet attenuation characteristics, exceeded the NASA annoyance threshold for several aircraft.

Short-Term Adaptive Modification of Dynamic Ocular Accommodation

PubMed Central

Bharadwaj, Shrikant R.; Vedamurthy, Indu; Schor, Clifton M.

2009-01-01

Purpose Indirect observations suggest that the neural control of accommodation may undergo adaptive recalibration in response to age-related biomechanical changes in the accommodative system. However, there has been no direct demonstration of such an adaptive capability. This investigation was conducted to demonstrate short-term adaptation of accommodative step response dynamics to optically induced changes in neuromuscular demands. Methods Repetitive changes in accommodative effort were induced in 15 subjects (18–34 years) with a double-step adaptation paradigm wherein an initial 2-D step change in blur was followed 350 ms later by either a 2-D step increase in blur (increasing-step paradigm) or a 1.75-D step decrease in blur (decreasing-step paradigm). Peak velocity, peak acceleration, and latency of 2-D single-step test responses were assessed before and after 1.5 hours of training with these paradigms. Results Peak velocity and peak acceleration of 2-D step responses increased after adaptation to the increasing-step paradigm (9/12 subjects), and they decreased after adaptation to the decreasing-step paradigm (4/9 subjects). Adaptive changes in peak velocity and peak acceleration generalized to responses that were smaller (1 D) and larger (3 D) than the 2-D adaptation stimulus. The magnitude of adaptation correlated poorly with the subject's age, but it was significantly negatively correlated with the preadaptation dynamics. Response latency decreased after adaptation, irrespective of the direction of adaptation. Conclusions Short-term adaptive changes in accommodative step response dynamics could be induced, at least in some of our subjects between 18 and 34 years, with a directional bias toward increasing rather than decreasing the dynamics. PMID:19255153

A proposal for antiparallel acceleration of positrons using CEBAF

NASA Astrophysics Data System (ADS)

Tiefenback, M.; Wojtsekhowski, B.

2018-05-01

We present a scheme for positron beam acceleration in CEBAF antiparallel to the normal electron path, requiring no change in polarity of the magnet systems. This feature is essential to the principal benefit: enabling extremely simple configuration changes between conventional (clockwise) e- acceleration and counter clockwise e+ acceleration. Additionally, it appears possible to configure the accelerating cavity phases to support concurrent acceleration of the electron and positron beams. The last mode also may enable use of the higher peak current electron beam for system diagnostics. The inherent penalty of the concurrent mode in acceleration efficiency and increased energy spread may render this a commissioning-only diagnostic option, but the possibility appears worthy of consideration.

Acceleration of domain wall movement by photoirradiation in perovskite-type cobaltite

NASA Astrophysics Data System (ADS)

Okimoto, Y.; Kurashima, M.; Seko, K.; Ishikawa, T.; Onda, K.; Koshihara, S.; Kyomen, T.; Itoh, M.

2011-04-01

Femtosecond reflection spectroscopy was performed on a perovskite-type cobalt oxide, namely, Pr0.5Ca0.5CoO3, that undergoes a photoinduced spin-state transition. After photoirradiation at 30 K, the time profile of the reflectance change shows a broad peak reflecting the propagation of the photodomain (about 60 Co sites per one photon). Analysis of the peak position indicates the sudden increase of the velocity of the propagation with increasing the excitation intensity. Such acceleration with increase in fluence originates from an abrupt sound velocity change driven by a cooperative photoinduced structural transition.

Numerical investigation of particle-blast interaction during explosive dispersal of liquids and granular materials

NASA Astrophysics Data System (ADS)

Pontalier, Q.; Lhoumeau, M.; Milne, A. M.; Longbottom, A. W.; Frost, D. L.

2018-05-01

Experiments show that when a high-explosive charge with embedded particles or a charge surrounded by a layer of liquid or granular material is detonated, the flow generated is perturbed by the motion of the particles and the blast wave profile differs from that of an ideal Friedlander form. Initially, the blast wave overpressure is reduced due to the energy dissipation resulting from compaction, fragmentation, and heating of the particle bed, and acceleration of the material. However, as the blast wave propagates, particle-flow interactions collectively serve to reduce the rate of decay of the peak blast wave overpressure. Computations carried out with a multiphase hydrocode reproduce the general trends observed experimentally and highlight the transition between the particle acceleration/deceleration phases, which is not accessible experimentally, since the particles are obscured by the detonation products. The dependence of the particle-blast interaction and the blast mitigation effectiveness on the mitigant to explosive mass ratio, the particle size, and the initial solid volume fraction is investigated systematically. The reduction in peak blast overpressure is, as in experiments, primarily dependent on the mass ratio of material to explosive, with the particle size, density, and initial porosity of the particle bed playing secondary roles. In the near field, the blast overpressure decreases sharply with distance as the particles are accelerated by the flow. When the particles decelerate due to drag, energy is returned to the flow and the peak blast overpressure recovers and reaches values similar to that of a bare explosive charge for low mass ratios. Time-distance trajectory plots of the particle and blast wave motion with the pressure field superimposed, illustrate the weak pressure waves generated by the motion of the particle layer which travel upstream and perturb the blast wave motion. Computation of the particle and gas momentum flux in the multiphase flow generated during explosive particle dispersal indicates that the particle momentum flux is the dominant term in the near field. Both the gas and particle loading must be taken into account when determining the damage to nearby structures following the detonation of a high-explosive charge surrounded by a material layer.

Numerical investigation of particle-blast interaction during explosive dispersal of liquids and granular materials

NASA Astrophysics Data System (ADS)

Pontalier, Q.; Lhoumeau, M.; Milne, A. M.; Longbottom, A. W.; Frost, D. L.

2018-04-01

Experiments show that when a high-explosive charge with embedded particles or a charge surrounded by a layer of liquid or granular material is detonated, the flow generated is perturbed by the motion of the particles and the blast wave profile differs from that of an ideal Friedlander form. Initially, the blast wave overpressure is reduced due to the energy dissipation resulting from compaction, fragmentation, and heating of the particle bed, and acceleration of the material. However, as the blast wave propagates, particle-flow interactions collectively serve to reduce the rate of decay of the peak blast wave overpressure. Computations carried out with a multiphase hydrocode reproduce the general trends observed experimentally and highlight the transition between the particle acceleration/deceleration phases, which is not accessible experimentally, since the particles are obscured by the detonation products. The dependence of the particle-blast interaction and the blast mitigation effectiveness on the mitigant to explosive mass ratio, the particle size, and the initial solid volume fraction is investigated systematically. The reduction in peak blast overpressure is, as in experiments, primarily dependent on the mass ratio of material to explosive, with the particle size, density, and initial porosity of the particle bed playing secondary roles. In the near field, the blast overpressure decreases sharply with distance as the particles are accelerated by the flow. When the particles decelerate due to drag, energy is returned to the flow and the peak blast overpressure recovers and reaches values similar to that of a bare explosive charge for low mass ratios. Time-distance trajectory plots of the particle and blast wave motion with the pressure field superimposed, illustrate the weak pressure waves generated by the motion of the particle layer which travel upstream and perturb the blast wave motion. Computation of the particle and gas momentum flux in the multiphase flow generated during explosive particle dispersal indicates that the particle momentum flux is the dominant term in the near field. Both the gas and particle loading must be taken into account when determining the damage to nearby structures following the detonation of a high-explosive charge surrounded by a material layer.

Identifying Head-Trunk and Lower Limb Contributions to Gaze Stabilization During Locomotion

NASA Technical Reports Server (NTRS)

Mulavara, Ajitkumar P.; Bloomberg, Jacob J.

2003-01-01

The goal of the present study was to determine how the multiple, interdependent full-body sensorimotor subsystems respond to a change in gaze stabilization task constraints during locomotion. Nine subjects performed two gaze stabilization tasks while walking at 6.4 km/hr on a motorized treadmill: 1) focusing on a central point target; 2) reading numeral characters; both presented at 2m in front at the level of their eyes. While subjects performed the tasks we measured: temporal parameters of gait, full body sagittal plane segmental kinematics of the head, trunk, thigh, shank and foot, accelerations along the vertical axis at the head and the shank, and the vertical forces acting on the support surface. We tested the hypothesis that with the increased demands placed on visual acuity during the number recognition task, subjects would modify full-body segmental kinematics in order to reduce perturbations to the head in order to successfully perform the task. We found that while reading numeral characters as - compared to the central point target: 1) compensatory head pitch movement was on average 22% greater despite the fact that the trunk pitch and trunk vertical translation movement control were not significantly changed; 2) coordination patterns between head and trunk as reflected by the peak cross correlation between the head pitch and trunk pitch motion as well as the peak cross correlation between the head pitch and vertical trunk translation motion were not significantly changed; 3) knee joint total movement was on average 11% greater during the period from the heel strike event to the peak knee flexion event in stance phase of the gait cycle; 4) peak acceleration measured at the head was significantly reduced by an average of 13% in four of the six subjects. This was so even when the peak acceleration at the shank and the transmissibility of the shock wave at heel strike (measured by the peak acceleration ratio of the head/shank) remained unchanged. Taken together these results provide further evidence that the full body contributes to gaze stabilization during locomotion, and that its different functional elements can be modified online to contribute to gaze stabilization for different visual task constraints.

Spectral analysis of femoral artery blood flow waveforms of conscious domestic cats.

PubMed

dos Reis, Gisele F M; Nogueira, Rodrigo B; Silva, Adriana C; Oberlender, Guilherme; Muzzi, Ruthnéa A L; Mantovani, Matheus M

2014-12-01

The qualitative and quantitative aspects of femoral artery blood flow waveform spectra were evaluated in 15 male and 15 female Persian and mixed breed domestic cats (Felis catus), which were healthy and not sedated, using duplex Doppler ultrasonography (DDU). Spectral Doppler demonstrated a biphasic characteristic in 16 (53.34%) of the animals evaluated, and a triphasic characteristic in the 14 (46.66%) remaining animals. The systolic blood pressure and heart rate values were within the normal range for the species. The quantitative parameters evaluated, based on the spectral Doppler, were as follows: systolic velocity peak (SVP), recent diastolic velocity peak (RDVP), end diastolic velocity peak (EDVP), mean velocity (MV), integral velocity time (ITV), artery diameter (AD), femoral flow volume (FFV), pulsatility index (PI), resistive index (RI), systolic peak acceleration time (AT) and deceleration time (DT). The respective mean values were: 36.41 ± 7.33 cm/s, 4.69 ± 0.90 cm/s, 10.74 ± 2.74 cm/s, 23.06 ± 4.86 cm/s, 3.91 ± 1.05 cm, 0.17 ± 0.04 cm, 0.11 ± 0.08 cm(3), 3.85 ± 0.19, 1.40 ± 0.20, 39.84 ± 7.38 ms, and 114.0 ± 22.15 ms. No significant differences were found between males and females. The analyses carried out on the femoral artery flow spectrum obtained by DDU showed that it is easy to use and highly tolerated in non-sedated, healthy cats. It appears that DDU may be a useful diagnostic technique, but further studies are needed to evaluate how it compares with invasive telemetric methodology or high-definition oscillometric waveform analytic techniques. © ISFM and AAFP 2014.

CONSTRAINTS ON THE SYNCHROTRON EMISSION MECHANISM IN GAMMA-RAY BURSTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beniamini, Paz; Piran, Tsvi, E-mail: paz.beniamini@mail.huji.ac.il, E-mail: tsvi.piran@mail.huji.ac.il

2013-05-20

We reexamine the general synchrotron model for gamma-ray bursts' (GRBs') prompt emission and determine the regime in the parameter phase space in which it is viable. We characterize a typical GRB pulse in terms of its peak energy, peak flux, and duration and use the latest Fermi observations to constrain the high-energy part of the spectrum. We solve for the intrinsic parameters at the emission region and find the possible parameter phase space for synchrotron emission. Our approach is general and it does not depend on a specific energy dissipation mechanism. Reasonable synchrotron solutions are found with energy ratios ofmore » 10{sup -4} < {epsilon}{sub B}/{epsilon}{sub e} < 10, bulk Lorentz factor values of 300 < {Gamma} < 3000, typical electrons' Lorentz factor values of 3 Multiplication-Sign 10{sup 3} < {gamma}{sub e} < 10{sup 5}, and emission radii of the order 10{sup 15} cm < R < 10{sup 17} cm. Most remarkable among those are the rather large values of the emission radius and the electron's Lorentz factor. We find that soft (with peak energy less than 100 keV) but luminous (isotropic luminosity of 1.5 Multiplication-Sign 10{sup 53}) pulses are inefficient. This may explain the lack of strong soft bursts. In cases when most of the energy is carried out by the kinetic energy of the flow, such as in the internal shocks, the synchrotron solution requires that only a small fraction of the electrons are accelerated to relativistic velocities by the shocks. We show that future observations of very high energy photons from GRBs by CTA could possibly determine all parameters of the synchrotron model or rule it out altogether.« less

Electrostatic acceleration of helicon plasma using a cusped magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harada, S.; Mitsubishi Heavy Industry ltd., 16-5 Konan 2-chome, Minato-ku, Tokyo 108-8215; Baba, T.

2014-11-10

The electrostatic acceleration of helicon plasma is investigated using an electrostatic potential exerted between the ring anode at the helicon source exit and an off-axis hollow cathode in the downstream region. In the downstream region, the magnetic field for the helicon source, which is generated by a solenoid coil, is modified using permanent magnets and a yoke, forming an almost magnetic field-free region surrounded by an annular cusp field. Using a retarding potential analyzer, two primary ion energy peaks, where the lower peak corresponds to the space potential and the higher one to the ion beam, are detected in themore » field-free region. Using argon as the working gas with a helicon power of 1.5 kW and a mass flow rate of 0.21 mg/s, the ion beam energy is on the order of the applied acceleration voltage. In particular, with an acceleration voltage lower than 150 V, the ion beam energy even exceeds the applied acceleration voltage by an amount on the order of the electron thermal energy at the exit of the helicon plasma source. The ion beam energy profile strongly depends on the helicon power and the applied acceleration voltage. Since by this method the whole working gas from the helicon plasma source can, in principle, be accelerated, this device can be applied as a noble electrostatic thruster for space propulsion.« less

Electrostatic acceleration of helicon plasma using a cusped magnetic field

NASA Astrophysics Data System (ADS)

Harada, S.; Baba, T.; Uchigashima, A.; Yokota, S.; Iwakawa, A.; Sasoh, A.; Yamazaki, T.; Shimizu, H.

2014-11-01

The electrostatic acceleration of helicon plasma is investigated using an electrostatic potential exerted between the ring anode at the helicon source exit and an off-axis hollow cathode in the downstream region. In the downstream region, the magnetic field for the helicon source, which is generated by a solenoid coil, is modified using permanent magnets and a yoke, forming an almost magnetic field-free region surrounded by an annular cusp field. Using a retarding potential analyzer, two primary ion energy peaks, where the lower peak corresponds to the space potential and the higher one to the ion beam, are detected in the field-free region. Using argon as the working gas with a helicon power of 1.5 kW and a mass flow rate of 0.21 mg/s, the ion beam energy is on the order of the applied acceleration voltage. In particular, with an acceleration voltage lower than 150 V, the ion beam energy even exceeds the applied acceleration voltage by an amount on the order of the electron thermal energy at the exit of the helicon plasma source. The ion beam energy profile strongly depends on the helicon power and the applied acceleration voltage. Since by this method the whole working gas from the helicon plasma source can, in principle, be accelerated, this device can be applied as a noble electrostatic thruster for space propulsion.

Stochastic finite-fault simulation of ground motion from the August 11, 2012, M w 6.4 Ahar earthquake, northwestern Iran

NASA Astrophysics Data System (ADS)

Heidari, Reza

2016-04-01

In this study, the 11 August 2012 M w 6.4 Ahar earthquake is investigated using the ground motion simulation based on the stochastic finite-fault model. The earthquake occurred in northwestern Iran and causing extensive damage in the city of Ahar and surrounding areas. A network consisting of 58 acceleration stations recorded the earthquake within 8-217 km of the epicenter. Strong ground motion records from six significant well-recorded stations close to the epicenter have been simulated. These stations are installed in areas which experienced significant structural damage and humanity loss during the earthquake. The simulation is carried out using the dynamic corner frequency model of rupture propagation by extended fault simulation program (EXSIM). For this purpose, the propagation features of shear-wave including {Q}_s value, kappa value {k}_0 , and soil amplification coefficients at each site are required. The kappa values are obtained from the slope of smoothed amplitude of Fourier spectra of acceleration at higher frequencies. The determined kappa values for vertical and horizontal components are 0.02 and 0.05 s, respectively. Furthermore, an anelastic attenuation parameter is derived from energy decay of a seismic wave by using continuous wavelet transform (CWT) for each station. The average frequency-dependent relation estimated for the region is Q=(122± 38){f}^{(1.40± 0.16)}. Moreover, the horizontal to vertical spectral ratio H/V is applied to estimate the site effects at stations. Spectral analysis of the data indicates that the best match between the observed and simulated spectra occurs for an average stress drop of 70 bars. Finally, the simulated and observed results are compared with pseudo acceleration spectra and peak ground motions. The comparison of time series spectra shows good agreement between the observed and the simulated waveforms at frequencies of engineering interest.

rf breakdown tests of mm-wave metallic accelerating structures

DOE PAGES

Dal Forno, Massimo; Dolgashev, Valery; Bowden, Gordon; ...

2016-01-06

In this study, we explore the physics and frequency-scaling of vacuum rf breakdowns at sub-THz frequencies. We present the experimental results of rf tests performed in metallic mm-wave accelerating structures. These experiments were carried out at the facility for advanced accelerator experimental tests (FACET) at the SLAC National Accelerator Laboratory. The rf fields were excited by the FACET ultrarelativistic electron beam. We compared the performances of metal structures made with copper and stainless steel. The rf frequency of the fundamental accelerating mode, propagating in the structures at the speed of light, varies from 115 to 140 GHz. The traveling wavemore » structures are 0.1 m long and composed of 125 coupled cavities each. We determined the peak electric field and pulse length where the structures were not damaged by rf breakdowns. We calculated the electric and magnetic field correlated with the rf breakdowns using the FACET bunch parameters. The wakefields were calculated by a frequency domain method using periodic eigensolutions. Such a method takes into account wall losses and is applicable to a large variety of geometries. The maximum achieved accelerating gradient is 0.3 GV/m with a peak surface electric field of 1.5 GV/m and a pulse length of about 2.4 ns.« less

Combining Diffusive Shock Acceleration with Acceleration by Contracting and Reconnecting Small-scale Flux Ropes at Heliospheric Shocks

NASA Astrophysics Data System (ADS)

le Roux, J. A.; Zank, G. P.; Webb, G. M.; Khabarova, O. V.

2016-08-01

Computational and observational evidence is accruing that heliospheric shocks, as emitters of vorticity, can produce downstream magnetic flux ropes and filaments. This led Zank et al. to investigate a new paradigm whereby energetic particle acceleration near shocks is a combination of diffusive shock acceleration (DSA) with downstream acceleration by many small-scale contracting and reconnecting (merging) flux ropes. Using a model where flux-rope acceleration involves a first-order Fermi mechanism due to the mean compression of numerous contracting flux ropes, Zank et al. provide theoretical support for observations that power-law spectra of energetic particles downstream of heliospheric shocks can be harder than predicted by DSA theory and that energetic particle intensities should peak behind shocks instead of at shocks as predicted by DSA theory. In this paper, a more extended formalism of kinetic transport theory developed by le Roux et al. is used to further explore this paradigm. We describe how second-order Fermi acceleration, related to the variance in the electromagnetic fields produced by downstream small-scale flux-rope dynamics, modifies the standard DSA model. The results show that (I) this approach can qualitatively reproduce observations of particle intensities peaking behind the shock, thus providing further support for the new paradigm, and (II) stochastic acceleration by compressible flux ropes tends to be more efficient than incompressible flux ropes behind shocks in modifying the DSA spectrum of energetic particles.

COMBINING DIFFUSIVE SHOCK ACCELERATION WITH ACCELERATION BY CONTRACTING AND RECONNECTING SMALL-SCALE FLUX ROPES AT HELIOSPHERIC SHOCKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Roux, J. A.; Zank, G. P.; Webb, G. M.

2016-08-10

Computational and observational evidence is accruing that heliospheric shocks, as emitters of vorticity, can produce downstream magnetic flux ropes and filaments. This led Zank et al. to investigate a new paradigm whereby energetic particle acceleration near shocks is a combination of diffusive shock acceleration (DSA) with downstream acceleration by many small-scale contracting and reconnecting (merging) flux ropes. Using a model where flux-rope acceleration involves a first-order Fermi mechanism due to the mean compression of numerous contracting flux ropes, Zank et al. provide theoretical support for observations that power-law spectra of energetic particles downstream of heliospheric shocks can be harder thanmore » predicted by DSA theory and that energetic particle intensities should peak behind shocks instead of at shocks as predicted by DSA theory. In this paper, a more extended formalism of kinetic transport theory developed by le Roux et al. is used to further explore this paradigm. We describe how second-order Fermi acceleration, related to the variance in the electromagnetic fields produced by downstream small-scale flux-rope dynamics, modifies the standard DSA model. The results show that (i) this approach can qualitatively reproduce observations of particle intensities peaking behind the shock, thus providing further support for the new paradigm, and (ii) stochastic acceleration by compressible flux ropes tends to be more efficient than incompressible flux ropes behind shocks in modifying the DSA spectrum of energetic particles.« less

Artificial stimulation of auroral electron acceleration by intense field aligned currents

NASA Technical Reports Server (NTRS)

Holmgren, G.; Bostrom, R.; Kelley, M. C.; Kintner, P. M.; Lundin, R.; Bering, E. A.; Sheldon, W. R.; Fahleson, U. V.

1979-01-01

A cesium-doped high explosion was detonated at 165 km altitude in the auroral ionosphere during quiet conditions. An Alfven wave pulse with a 200-mV/m electric field was observed, with the peak occurring 135 ms after the explosion at a distance of about 1 km. The count rate of fixed energy 2-keV electron detectors abruptly increased at 140 ms, peaked at 415 ms, and indicated a downward field-aligned beam of accelerated electrons. An anomalously high-field aligned beam of backscattered electrons was also detected. The acceleration is interpreted as due to production of an electrostatic shock or double layer between 300 and 800 km altitude. The structure was probably formed by an instability of the intense field-aligned currents in the Alfven wave launched by the charge-separation electric field due to the explosion.

Numerical modeling of laser-driven ion acceleration from near-critical gas targets

NASA Astrophysics Data System (ADS)

Tatomirescu, Dragos; Vizman, Daniel; d’Humières, Emmanuel

2018-06-01

In the past two decades, laser-accelerated ion sources and their applications have been intensely researched. Recently, it has been shown through experiments that proton beams with characteristics comparable to those obtained with solid targets can be obtained from gaseous targets. By means of particle-in-cell simulations, this paper studies in detail the effects of a near-critical density gradient on ion and electron acceleration after the interaction with ultra high intensity lasers. We can observe that the peak density of the gas jet has a significant influence on the spectrum features. As the gas jet density increases, so does the peak energy of the central quasi-monoenergetic ion bunch due to the increase in laser absorption while at the same time having a broadening effect on the electron angular distribution.

Evaluation of Horizontal Seismic Hazard of Shahrekord, Iran

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amiri, G. Ghodrati; Dehkordi, M. Raeisi; Amrei, S. A. Razavian

2008-07-08

This paper presents probabilistic horizontal seismic hazard assessment of Shahrekord, Iran. It displays the probabilistic estimate of Peak Ground Horizontal Acceleration (PGHA) for the return period of 75, 225, 475 and 2475 years. The output of the probabilistic seismic hazard analysis is based on peak ground acceleration (PGA), which is the most common criterion in designing of buildings. A catalogue of seismic events that includes both historical and instrumental events was developed and covers the period from 840 to 2007. The seismic sources that affect the hazard in Shahrekord were identified within the radius of 150 km and the recurrencemore » relationships of these sources were generated. Finally four maps have been prepared to indicate the earthquake hazard of Shahrekord in the form of iso-acceleration contour lines for different hazard levels by using SEISRISK III software.« less

The effects of temperature and aeration on the corrosion of A508III low alloy steel in boric acid solutions at 25-95 °C

NASA Astrophysics Data System (ADS)

Xiao, Qian; Lu, Zhanpeng; Chen, Junjie; Yao, Meiyi; Chen, Zhen; Ejaz, Ahsan

2016-11-01

The effects of temperature, solution composition and dissolved oxygen on the corrosion rate and electrochemical behavior of an A508III low alloy steel in boric acid solution with lithium hydroxide at 25-95 °C are investigated. In aerated solutions, increasing the boric acid concentration increases the corrosion rate and the anodic current density. The corrosion rate in deaerated solutions increases with increasing temperature. A corrosion rate peak value is found at approximately 75 °C in aerated solutions. Increasing temperature increases the oxygen diffusion coefficient, decreases the dissolved oxygen concentration, accelerates the hydrogen evolution reaction, and accelerates both the active dissolution and the film forming reactions. Increasing dissolved oxygen concentration does not significantly affect the corrosion rate at 50 and 60 °C, increases the corrosion rate at 70 and 80 °C, and decreases the corrosion rate at 87.5 and 95 °C in a high concentration boric acid solution with lithium hydroxide.

Time-dependent Electron Acceleration in Blazar Transients: X-Ray Time Lags and Spectral Formation

NASA Astrophysics Data System (ADS)

Lewis, Tiffany R.; Becker, Peter A.; Finke, Justin D.

2016-06-01

Electromagnetic radiation from blazar jets often displays strong variability, extending from radio to γ-ray frequencies. In a few cases, this variability has been characterized using Fourier time lags, such as those detected in the X-rays from Mrk 421 using BeppoSAX. The lack of a theoretical framework to interpret the data has motivated us to develop a new model for the formation of the X-ray spectrum and the time lags in blazar jets based on a transport equation including terms describing stochastic Fermi acceleration, synchrotron losses, shock acceleration, adiabatic expansion, and spatial diffusion. We derive the exact solution for the Fourier transform of the electron distribution and use it to compute the Fourier transform of the synchrotron radiation spectrum and the associated X-ray time lags. The same theoretical framework is also used to compute the peak flare X-ray spectrum, assuming that a steady-state electron distribution is achieved during the peak of the flare. The model parameters are constrained by comparing the theoretical predictions with the observational data for Mrk 421. The resulting integrated model yields, for the first time, a complete first-principles physical explanation for both the formation of the observed time lags and the shape of the peak flare X-ray spectrum. It also yields direct estimates of the strength of the shock and the stochastic magnetohydrodynamical wave acceleration components in the Mrk 421 jet.

Evaluation of the antibacterial activity of a cationic polymer in aqueous solution with a convenient electrochemical method.

PubMed

Wang, Yihong; Guo, Qing; Wang, Huafu; Qian, Kun; Tian, Liang; Yao, Chen; Song, Wei; Shu, Weixia; Chen, Ping; Qi, Jinxu

2017-02-01

Quaternized chitosan is a cationic biopolymer with good antibacterial activity, biocompatibility, and biodegradability, and it has been widely applied in many fields. We have developed a convenient method to evaluate the antibacterial activity of hydroxypropyltrimethylammonium chloride chitosan (HACC) with a nonionic surfactant poloxamer in aqueous solution by monitoring the change of the oxidation peak current in cyclic voltammetry. Increasing values of the oxidation peak current were positively correlated with the antibacterial activity of HACC-poloxamer solutions. Optical microscope images, the zeta potential, and fluorescence spectroscopy showed that the aggregation state of HACC-poloxamer was related to the ratio of the two polymers and also to the antibacterial activity and oxidation peak current. At an HACC-to-poloxamer ratio of 1:0.75, the maximum surface charge density and the smooth edge of HACC-poloxamer aggregates can accelerate diffusion in aqueous solution. It is expected that this convenient method can be applied for a quick evaluation of the antibacterial activity of cationic biopolymers in aqueous solution. Graphical Abstract The cyclic voltammograms of MB in HACC/poloxamer solution, and the antibacterial efficiency against S. aureus after incubated with HACC (a) and 1/0.75 of HACC/poloxamer (b).

Lumbar spinal loads and muscle activity during a golf swing.

PubMed

Lim, Young-Tae; Chow, John W; Chae, Woen-Sik

2012-06-01

This study estimated the lumbar spinal loads at the L4-L5 level and evaluated electromyographic (EMG) activity of right and left rectus abdominis, external and internal obliques, erector spinae, and latissimus dorsi muscles during a golf swing. Four super VHS camcorders and two force plates were used to obtain three-dimensional (3D) kinematics and kinetics of golf swings performed by five male collegiate golfers. Average EMG levels for different phases of golf swing were determined. An EMG-assisted optimization model was applied to compute the contact forces acting on the L4-L5. The results revealed a mean peak compressive load of over six times the body weight (BW) during the downswing and mean peak anterior and medial shear loads approaching 1.6 and 0.6 BW during the follow-through phases. The peak compressive load estimated in this study was high, but less than the corresponding value (over 8 BW) reported by a previous study. Average EMG levels of different muscles were the highest in the acceleration and follow-through phases, suggesting a likely link between co-contractions of paraspinal muscles and lumbar spinal loads.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dal Forno, Massimo; Dolgashev, Valery; Bowden, Gordon

This study explores the physics of vacuum rf breakdowns in subterahertz high-gradient traveling-wave accelerating structures. We present the experimental results of rf tests of 200 GHz metallic accelerating structures, made of copper and copper-silver. These experiments were carried out at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory. The rf fields were excited by the FACET ultrarelativistic electron beam. The traveling-wave structure is an open geometry, 10 cm long, composed of two halves separated by a gap. The rf frequency of the fundamental accelerating mode depends on the gap size and can be changedmore » from 160 to 235 GHz. When the beam travels off axis, a deflecting field is induced in addition to the longitudinal field. We measure the deflecting forces by observing the displacement of the electron bunch and use this measurement to verify the expected accelerating gradient. Furthermore, we present the first quantitative measurement of rf breakdown rates in 200 GHz metallic accelerating structures. The breakdown rate of the copper structure is 10 –2 per pulse, with a peak surface electric field of 500 MV/m and a rf pulse length of 0.3 ns, which at a relatively large gap of 1.5 mm, or one wavelength, corresponds to an accelerating gradient of 56 MV/m. For the same breakdown rate, the copper-silver structure has a peak electric field of 320 MV/m at a pulse length of 0.5 ns. For a gap of 1.1 mm, or 0.74 wavelengths, this corresponds to an accelerating gradient of 50 MV/m.« less

Observations of a Radio-Quiet Solar Preflare

NASA Astrophysics Data System (ADS)

Benz, Arnold O.; Battaglia, Marina; Güdel, Manuel

2017-10-01

The preflare phase of the flare SOL2011-08-09T03:52 is unique in its long duration, in that it was covered by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Nobeyama Radioheliograph, and because it showed three well-developed soft X-ray (SXR) peaks. No hard X-rays (HXR) are observed in the preflare phase. Here we report that no associated radio emission at 17 GHz was found either, despite the higher sensitivity of the radio instrument. The ratio between the SXR peaks and the upper limit of the radio peaks is higher by more than one order of magnitude than the ratio in regular flares. The result suggests that the ratio between acceleration and heating in the preflare phase was different than in regular flares. Acceleration to relativistic energies, if any, occurred with lower efficiency.

Validity of an ultra-wideband local positioning system to measure locomotion in indoor sports.

PubMed

Serpiello, F R; Hopkins, W G; Barnes, S; Tavrou, J; Duthie, G M; Aughey, R J; Ball, K

2018-08-01

The validity of an Ultra-wideband (UWB) positioning system was investigated during linear and change-of-direction (COD) running drills. Six recreationally-active men performed ten repetitions of four activities (walking, jogging, maximal acceleration, and 45º COD) on an indoor court. Activities were repeated twice, in the centre of the court and on the side. Participants wore a receiver tag (Clearsky T6, Catapult Sports) and two reflective markers placed on the tag to allow for comparisons with the criterion system (Vicon). Distance, mean and peak velocity, acceleration, and deceleration were assessed. Validity was assessed via percentage least-square means difference (Clearsky-Vicon) with 90% confidence interval and magnitude-based inference; typical error was expressed as within-subject standard deviation. The mean differences for distance, mean/peak speed, and mean/peak accelerations in the linear drills were in the range of 0.2-12%, with typical errors between 1.2 and 9.3%. Mean and peak deceleration had larger differences and errors between systems. In the COD drill, moderate-to-large differences were detected for the activity performed in the centre of the court, increasing to large/very large on the side. When filtered and smoothed following a similar process, the UWB-based positioning system had acceptable validity, compared to Vicon, to assess movements representative of indoor sports.

AN ACCELERATION MECHANISM FOR NEUTRON PRODUCTION IN Z-PINCH DISCHARGES,

DTIC Science & Technology

A model has been developed for the acceleration of deuterons in the tightly compressed column of a z-pinch discharge, in particular that of a plasma ... focus discharge. It was assumed that an annular current distribution undergoes a rapidly contracting transition to an axially peaked distribution, and

Detection of novel visible-light region absorbance peaks in the urine after alkalization in patients with alkaptonuria.

PubMed

Tokuhara, Yasunori; Shukuya, Kenichi; Tanaka, Masami; Mouri, Mariko; Ohkawa, Ryunosuke; Fujishiro, Midori; Takahashi, Tomoo; Okubo, Shigeo; Yokota, Hiromitsu; Kurano, Makoto; Ikeda, Hitoshi; Yamaguchi, Seiji; Inagaki, Shinobu; Ishige-Wada, Mika; Usui, Hiromi; Yatomi, Yutaka; Shimosawa, Tatsuo

2014-01-01

Alkaptonuria, caused by a deficiency of homogentisate 1,2-dioxygenase, results in the accumulation of homogentisic acid (2,5-dihydroxyphenylacetic acid, HGA) in the urine. Alkaptonuria is suspected when the urine changes color after it is left to stand at room temperature for several hours to days; oxidation of homogentisic acid to benzoquinone acetic acid underlies this color change, which is accelerated by the addition of alkali. In an attempt to develop a facile screening test for alkaptonuria, we added alkali to urine samples obtained from patients with alkaptonuria and measured the absorbance spectra in the visible light region. We evaluated the characteristics of the absorption spectra of urine samples obtained from patients with alkaptonuria (n = 2) and compared them with those of urine specimens obtained from healthy volunteers (n = 5) and patients with phenylketonuria (n = 3), and also of synthetic homogentisic acid solution after alkalization. Alkalization of the urine samples and HGA solution was carried out by the addition of NaOH, KOH or NH4OH. The sample solutions were incubated at room temperature for 1 min, followed by measurement of the absorption spectra. Addition of alkali to alkaptonuric urine yielded characteristic absorption peaks at 406 nm and 430 nm; an identical result was obtained from HGA solution after alkalization. The absorbance values at both 406 nm and 430 nm increased in a time-dependent manner. In addition, the absorbance values at these peaks were greater in strongly alkaline samples (NaOH- KOH-added) as compared with those in weakly alkaline samples (NH4OH-added). In addition, the peaks disappeared following the addition of ascorbic acid to the samples. We found two characteristic peaks at 406 nm and 430 nm in both alkaptonuric urine and HGA solution after alkalization. This new quick and easy method may pave the way for the development of an easy method for the diagnosis of alkaptonuria.

Detection of Novel Visible-Light Region Absorbance Peaks in the Urine after Alkalization in Patients with Alkaptonuria

PubMed Central

Tokuhara, Yasunori; Shukuya, Kenichi; Tanaka, Masami; Mouri, Mariko; Ohkawa, Ryunosuke; Fujishiro, Midori; Takahashi, Tomoo; Okubo, Shigeo; Yokota, Hiromitsu; Kurano, Makoto; Ikeda, Hitoshi; Yamaguchi, Seiji; Inagaki, Shinobu; Ishige-Wada, Mika; Usui, Hiromi; Yatomi, Yutaka; Shimosawa, Tatsuo

2014-01-01

Background Alkaptonuria, caused by a deficiency of homogentisate 1,2-dioxygenase, results in the accumulation of homogentisic acid (2,5-dihydroxyphenylacetic acid, HGA) in the urine. Alkaptonuria is suspected when the urine changes color after it is left to stand at room temperature for several hours to days; oxidation of homogentisic acid to benzoquinone acetic acid underlies this color change, which is accelerated by the addition of alkali. In an attempt to develop a facile screening test for alkaptonuria, we added alkali to urine samples obtained from patients with alkaptonuria and measured the absorbance spectra in the visible light region. Methods We evaluated the characteristics of the absorption spectra of urine samples obtained from patients with alkaptonuria (n = 2) and compared them with those of urine specimens obtained from healthy volunteers (n = 5) and patients with phenylketonuria (n = 3), and also of synthetic homogentisic acid solution after alkalization. Alkalization of the urine samples and HGA solution was carried out by the addition of NaOH, KOH or NH4OH. The sample solutions were incubated at room temperature for 1 min, followed by measurement of the absorption spectra. Results Addition of alkali to alkaptonuric urine yielded characteristic absorption peaks at 406 nm and 430 nm; an identical result was obtained from HGA solution after alkalization. The absorbance values at both 406 nm and 430 nm increased in a time-dependent manner. In addition, the absorbance values at these peaks were greater in strongly alkaline samples (NaOH- KOH-added) as compared with those in weakly alkaline samples (NH4OH-added). In addition, the peaks disappeared following the addition of ascorbic acid to the samples. Conclusions We found two characteristic peaks at 406 nm and 430 nm in both alkaptonuric urine and HGA solution after alkalization. This new quick and easy method may pave the way for the development of an easy method for the diagnosis of alkaptonuria. PMID:24466168

Modular compact solid-state modulators for particle accelerators

NASA Astrophysics Data System (ADS)

Zavadtsev, A. A.; Zavadtsev, D. A.; Churanov, D. V.

2017-12-01

The building of the radio frequency (RF) particle accelerator needs high-voltage pulsed modulator as a power supply for klystron or magnetron to feed the RF accelerating system. The development of a number of solid-state modulators for use in linear accelerators has allowed to develop a series of modular IGBT based compact solid-state modulators with different parameters. This series covers a wide range of needs in accelerator technology to feed a wide range of loads from the low power magnetrons to powerful klystrons. Each modulator of the series is built on base of a number of unified solid-state modules connected to the pulse transformer, and covers a wide range of modulators: voltage up to 250 kV, a peak current up to 250 A, average power up to 100 kW and the pulse duration up to 20 μsec. The parameters of the block with an overall dimensions 880×540×250 mm are: voltage 12 kV, peak current 1600 A, pulse duration 20 μsec, average power 10 kW with air-cooling and 40 kW with liquidcooling. These parameters do not represent a physical limit, and modulators to parameters outside these ranges can be created on request.

rf breakdown measurements in electron beam driven 200 GHz copper and copper-silver accelerating structures

DOE PAGES

Dal Forno, Massimo; Dolgashev, Valery; Bowden, Gordon; ...

2016-11-30

This study explores the physics of vacuum rf breakdowns in subterahertz high-gradient traveling-wave accelerating structures. We present the experimental results of rf tests of 200 GHz metallic accelerating structures, made of copper and copper-silver. These experiments were carried out at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory. The rf fields were excited by the FACET ultrarelativistic electron beam. The traveling-wave structure is an open geometry, 10 cm long, composed of two halves separated by a gap. The rf frequency of the fundamental accelerating mode depends on the gap size and can be changedmore » from 160 to 235 GHz. When the beam travels off axis, a deflecting field is induced in addition to the longitudinal field. We measure the deflecting forces by observing the displacement of the electron bunch and use this measurement to verify the expected accelerating gradient. Furthermore, we present the first quantitative measurement of rf breakdown rates in 200 GHz metallic accelerating structures. The breakdown rate of the copper structure is 10 –2 per pulse, with a peak surface electric field of 500 MV/m and a rf pulse length of 0.3 ns, which at a relatively large gap of 1.5 mm, or one wavelength, corresponds to an accelerating gradient of 56 MV/m. For the same breakdown rate, the copper-silver structure has a peak electric field of 320 MV/m at a pulse length of 0.5 ns. For a gap of 1.1 mm, or 0.74 wavelengths, this corresponds to an accelerating gradient of 50 MV/m.« less

A proposal for antiparallel acceleration of positrons using CEBAF

DOE PAGES

Tiefenback, M.; Wojtsekhowski, B.

2018-05-01

Here, we present a scheme for positron beam acceleration in CEBAF antiparallel to the normal electron path, requiring no change in polarity of the magnet systems. This feature is essential to the principal benefit: enabling extremely simple configuration changes between conventional (clockwise) e - acceleration and counter clockwise e + acceleration. Additionally, it appears possible to configure the accelerating cavity phases to support concurrent acceleration of the electron and positron beams. The last mode also may enable use of the higher peak current electron beam for system diagnostics. The inherent penalty of the concurrent mode in acceleration efficiency and increasedmore » energy spread may render this a commissioning-only diagnostic option, but the possibility appears worthy of consideration.« less

A proposal for antiparallel acceleration of positrons using CEBAF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tiefenback, M.; Wojtsekhowski, B.

Here, we present a scheme for positron beam acceleration in CEBAF antiparallel to the normal electron path, requiring no change in polarity of the magnet systems. This feature is essential to the principal benefit: enabling extremely simple configuration changes between conventional (clockwise) e - acceleration and counter clockwise e + acceleration. Additionally, it appears possible to configure the accelerating cavity phases to support concurrent acceleration of the electron and positron beams. The last mode also may enable use of the higher peak current electron beam for system diagnostics. The inherent penalty of the concurrent mode in acceleration efficiency and increasedmore » energy spread may render this a commissioning-only diagnostic option, but the possibility appears worthy of consideration.« less

Rapid acceleration leads to rapid weakening in earthquake-like laboratory experiments

NASA Astrophysics Data System (ADS)

Chang, J. C.; Lockner, D. A.; Reches, Z.

2012-12-01

We simulated the slip of a fault-patch during a large earthquake by rapidly loading an experimental, ring-shaped fault with energy stored in a spinning flywheel. The flywheel abruptly delivers a finite amount of energy by spinning the fault-patch that spontaneously dissipates the energy without operator intervention. We conducted 42 experiments on Sierra White granite (SWG) samples, and 24 experiments on Kasota dolomite (KD) samples. Each experiment starts by spinning a 225 kg disk-shaped flywheel to a prescribed angular velocity. We refer to this experiment as an "earthquake-like slip-event" (ELSE). The strength-evolution in ELSE experiments is similar to the strength-evolution proposed for earthquake models and observed in stick-slip experiments. Further, we found that ELSE experiments are similar to earthquakes in at least three ways: (1) slip driven by the release of a finite amount of stored energy; (2) pattern of fault strength evolution; and (3) seismically observed values, such as average slip, peak-velocity and rise-time. By assuming that the measured slip, D, in ELSE experiments is equivalent to the average slip during an earthquake, we found that ELSE experiments (D = 0.003-4.6 m) correspond to earthquakes in moment-magnitude range of Mw = 4-8. In ELSE experiments, the critical-slip-distance, dc, has mean values of 2.7 cm and 1.2 cm for SWG and KD, that are much shorter than the 1-10 m in steady-state classical experiments in rotary shear systems. We attribute these dc values, to ELSE loading in which the fault-patch is abruptly loaded by impact with a spinning flywheel. Under this loading, the friction-velocity relations are strikingly different from those under steady-state loading on the same rock samples with the same shear system (Reches and Lockner, Nature, 2010). We further note that the slip acceleration in ELSE evolves systematically with fault strength and wear-rate, and that the dynamic weakening is restricted to the period of intense acceleration (up to 25 m/s2 during ~0.1 s). Thus, the weakening distance, dc, is reached within the initial acceleration spike. These observations are not unique, and similar weakening-acceleration associations were reported in stick-slip, rotary shear, and impact shear experiments. These studies greatly differ from each other in slip distance, normal stress, acceleration, and slip-velocities with the outstanding commonality of abrupt loading and intense acceleration. We propose that impact loading induces extremely high strain-rates that significantly increase rock brittleness, fracture tendency, and fragmentation. We envision that these processes intensify fault wear as manifested in ELSE experiments by extremely high initial wear-rates. This intense, early wear generates a layer of fine-grain gouge that reduces the fault strength by powder-lubrication. Our analysis indicates that rapid acceleration associated with earthquake rupture accelerates fault weakening and shortens the weakening-distance.

Active Control of F/A-18 Vertical Tail Buffeting using Piezoelectric Actuators

NASA Technical Reports Server (NTRS)

Sheta, Essam F.; Moses, Robert W.; Huttsell, Lawerence J.; Harrand, Vincent J.

2003-01-01

Vertical tail buffeting is a serious multidisciplinary problem that limits the performance of twin-tail fighter aircraft. The buffet problem occurs at high angles of attack when the vortical flow breaks down ahead of the vertical tails resulting in unsteady and unbalanced pressure loads on the vertical tails. This paper describes a multidisciplinary computational investigation for buffet load alleviation of full F/A-18 aircraft using distributed piezoelectric actuators. The inboard and outboard surfaces of the vertical tail are equipped with piezoelectric actuators to control the buffet responses in the first bending and torsion modes. The electrodynamics of the smart structure are expressed with a three-dimensional finite element model. A single-input-single-output controller is designed to drive the active piezoelectric actuators. High-fidelity multidisciplinary analysis modules for the fluid dynamics, structure dynamics, electrodynamics of the piezoelectric actuators, fluid-structure interfacing, and grid motion are integrated into a multidisciplinary computing environment that controls the temporal synchronization of the analysis modules. Peak values of the power spectral density of tail tip acceleration are reduced by as much as 22% in the first bending mode and by as much as 82% in the first torsion mode. RMS values of tip acceleration are reduced by as much as 12%.

Potential clinical impact of laser-accelerated beams in cancer ion therapy

NASA Astrophysics Data System (ADS)

Obcemea, Ceferino

2016-09-01

In this article, I present three advantages of plasma-accelerated ion beams for cancer therapy. I discuss how: 1. low-emittance and well-collimated beams are advantageous in proximal normal tissue-sparing; 2. highly-peaked quasi-monoenergetic beams are ideal for fast energy selection and switching in Pencil Beam Scanning (PBS) as a treatment delivery; 3. high fluence and ultra-short pulse delivery produce collective excitations in the medium and enhance the stopping power. This in turn produces denser ionization track signatures (spurs, blobs, etc.) in target tumors, higher linear energy transfer, higher Bragg peak, and higher radiobiological effectiveness at the micro-level.

Point-source stochastic-method simulations of ground motions for the PEER NGA-East Project

USGS Publications Warehouse

Boore, David

2015-01-01

Ground-motions for the PEER NGA-East project were simulated using a point-source stochastic method. The simulated motions are provided for distances between of 0 and 1200 km, M from 4 to 8, and 25 ground-motion intensity measures: peak ground velocity (PGV), peak ground acceleration (PGA), and 5%-damped pseudoabsolute response spectral acceleration (PSA) for 23 periods ranging from 0.01 s to 10.0 s. Tables of motions are provided for each of six attenuation models. The attenuation-model-dependent stress parameters used in the stochastic-method simulations were derived from inversion of PSA data from eight earthquakes in eastern North America.

Mass sensitivity studies for an inductively driven railgun

NASA Astrophysics Data System (ADS)

Scanlon, J. J., III; Young, A. F.

1991-01-01

Those areas which result in substantial system mass reductions for an HPG (homopolar generator) driven EML (electromagnetic launcher) are identified. Sensitivity studies are performed by varying launch mass, peak acceleration, launcher efficiency, inductance gradient, injection velocity, barrel mass per unit length, fuel tankage and pump estimates, and component energy and power densities. Two major contributors to the system mass are the allowed number of shots per barrel versus the number required for the mission, and the barrel length. The effects of component performance parameters, such as friction coefficient, injection velocity, ablation coefficient, rail resistivity, armature voltage, peak acceleration, and inductance gradient on these two areas, are addressed.

Laron syndrome. First report from Greece.

PubMed

Galli-Tsinopoulou, Assimina; Nousia-Arvanitakis, Sanda; Tsinopoulos, Ioannis; Bechlivanides, Christos; Shevah, Orit; Laron, Zvi

2003-01-01

Laron-type dwarfism is an autosomal recessive disorder caused by deletions or mutations of the growth hormone receptor gene. It is characterized by high circulating levels of growth hormone (GH) and low levels of insulin-like growth factor I (IGF-I). Patients are refractory to both endogenous and exogenous GH, and present severe growth retardation and obesity. Therapy with recombinant human insulin-like growth factor-I (rhIGF-I) accelerates linear growth. We describe a 2-year old girl with Laron syndrome, who presented with postnatal growth failure and hypoglycaemic seizures. Her evaluation disclosed high GH values during a glucagon test (peak GH value 170 ng/ml) and very low IGF I value (0.1 ng/ml) with no rise following GH administration. The growth velocity improved considerably with the administration of IGF I. Molecular analysis showed a heterozygous mutation on exon 4 of the GH receptor gene, inherited from the mother, a rather puzzling finding considering the clinical findings in mother and infant. This case constitutes the first report of Laron syndrome from Greece.

Subcutaneous gonadotropin-releasing hormone agonist (triptorelin) test for diagnosing precocious puberty.

PubMed

Poomthavorn, Preamrudee; Khlairit, Patcharin; Mahachoklertwattana, Pat

2009-01-01

A test involving 100 microg of intravenous gonadotropin-releasing hormone (GnRH) is a gold standard for confirming the diagnosis of central precocious puberty (CPP). However, intravenous GnRH for testing is commercially limited. To develop subcutaneous GnRH agonist (GnRH-A) testing and define a peak luteinizing hormone (LH) cutoff value in diagnosing CPP. A retrospective study of 101 girls with sexual precocity was undertaken. All girls underwent 100 microg subcutaneous GnRH-A (triptorelin) testing. Blood samples before and 30, 60, 90 and 120 min after GnRH-A injection were analyzed for LH and follicle-stimulating hormone levels. Criteria for diagnosing CPP include accelerated height, advanced bone age and pubertal-sized uterus and ovaries. Fifty-five girls were documented as having CPP. The remaining 46 girls were diagnosed with premature thelarche (PT). Peak LH concentration in the CPP group was significantly greater than that of the PT group with a median (range) of 10.0 IU/l (2.93-65.39) and 3.04 IU/l (0.19-8.82), respectively. Peak LH was achieved within 60 min following GnRH-A injection. Peak LH of 6 IU/l provided the most appropriate cutoff level in diagnosing CPP with a sensitivity of 89.1% and a specificity of 91.3%. Subcutaneous GnRH-A can be used as an alternative to confirm the diagnosis of CPP. Copyright 2009 S. Karger AG, Basel.

Plasma Wake-field Acceleration in the Blow-out Regime

NASA Astrophysics Data System (ADS)

Barov, Nikolai; Rosenzweig, James

1999-11-01

Recent experiments at Argonne National Laboratory, investigating the blow-out regime of the plasma wake-field accelerator, are discussed. These experiments achieved stable underdense (beam denser than the ambient plasma density) beam transport, and measured average acceleration of 25 MV/m, corresponding to peak wave fields of over 60 MVm. A comparison of the results to simulation is given, and the physics of the system is discussed. Potential for improvements in performance and achieved acceleration gradient, as well as accelerated beam quality are examined within the context of the next generation of experiments at the Fermilab Test Facility. The status of these experiments will be given.

Characterization of Vertical Impact Device Acceleration Pulses Using Parametric Assessment: Phase II Accelerated Free-Fall

DTIC Science & Technology

2016-04-30

support contractor , Infoscitex, conducted a series of tests to identify the performance capabilities of the Vertical Impact Device (VID). The VID is a...C. Table 3. AFD Evaluation with Red IMPAC Programmer: Data Summary Showing Means and Standard Deviations Test Cell Drop Ht . (in) Mean Peak

The light ion pulsed power induction accelerator for ETF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mazarakis, M.G.; Olson, R.E.; Olson, C.L.

1994-12-31

Our Engineering Test Facility (ETF) driver concept is based on HERMES III and RHEPP technologies. Actually, it is a scaled-down version of the LMF design incorporating repetition rate capabilities of up to 10 Hz CW. The preconceptual design presented here provides 200-TW peak power to the ETF target during 10 ns, equal to 2-MJ total ion beam energy. Linear inductive voltage addition driving a self-magnetically insulated transmission line (MITL) is utilized to generate the 36-MV peak voltage needed for lithium ion beams. The {approximately} 3-MA ion current is achieved by utilizing many accelerating modules in parallel. Since the current permore » module is relatively modest ({approximately}300 kA), two-stage or one-stage extraction diodes can be utilized for the generation of singly charged lithium ions. The accelerating modules are arranged symmetrically around the fusion chamber in order to provide uniform irradiation onto the ETF target. In addition, the modules are fired in a programmed sequence in order to generate the optimum power pulse shape onto the target. This design utilizes RHEPP accelerator modules as the principal power source.« less

Studies on the S-band bunching system with the Hybrid Bunching-accelerating Structure

NASA Astrophysics Data System (ADS)

Pei, Shi-Lun; Gao, Bin

2018-04-01

Generally, a standard bunching system is composed of a standing-wave (SW) pre-buncher (PB), a traveling-wave (TW) buncher (B) and a standard accelerating structure. In the industrial area, the bunching system is usually simplified by eliminating the PB and integrating the B and the standard accelerating structure together to form a β-varied accelerating structure. The beam capturing efficiency for this kind of simplified system is often worse than that for the standard one. The hybrid buncher (HB) has been proved to be a successful attempt to reduce the cost but preserve the beam quality as much as possible. Here we propose to exclusively simplify the standard bunching system by integrating the PB, the B and the standard accelerating structure together to form a Hybrid Bunching-accelerating Structure (HBaS). Compared to the standard bunching system, the one based on the HBaS is more compact, and the cost is lowered to the largest extent. With almost the same beam transportation efficiency (∼70%) from the electron gun to the linac exit, the peak-to-peak (p-to-p) beam energy spread and the 1 σ emittance of the linac with the HBaS are ∼20% and ∼60% bigger than those of the linac based on the split PB/B/standard accelerating structure system. Nonetheless, the proposed HBaS can be widely applied in the industrial linacs to greatly increase the beam capturing efficiency without fairly increasing the construction cost.

Analysis of the ability of catcher's masks to attenuate head accelerations on impact with a baseball.

PubMed

Shain, Kellen S; Madigan, Michael L; Rowson, Steven; Bisplinghoff, Jill; Duma, Stefan M

2010-11-01

The goals of this study were to measure the ability of catcher's masks to attenuate head accelerations on impact with a baseball and to compare these head accelerations to established injury thresholds for mild traumatic brain injury. Testing involved using a pneumatic cannon to shoot baseballs at an instrumented Hybrid III headform (a 50th percentile male head and neck) with and without a catcher's mask on the head. The ball speed was controlled from approximately 26.8 to 35.8 m/s (60-80 mph), and the regulation National Collegiate Athletic Association baseballs were used. Research laboratory. None. Catcher's masks and impact velocity. The linear and angular head accelerations of the Hybrid III headform. Peak linear resultant acceleration was 140 to 180 g without a mask and 16 to 30 g with a mask over the range of ball's speed investigated. Peak angular resultant acceleration was 19 500 to 25 700 rad/s without a mask and 2250 to 3230 rad/s with a mask. The Head Injury Criterion was 93 to 181 without a mask and 3 to 13 with a mask, and the Severity Index was 110 to 210 without a mask and 3 to 15 with a mask. Catcher's masks reduced head acceleration metrics by approximately 85%. Head acceleration metrics with a catcher's mask were significantly lower than contemporary injury thresholds, yet reports in the mass media clearly indicate that baseball impacts to the mask still occasionally result in mild traumatic brain injuries. Further research is needed to address this apparent contradiction.

Comparative studies of perceived vibration strength for commercial mobile phones.

PubMed

Lee, Heow Pueh; Lim, Siak Piang

2014-05-01

A mobile phone, also known as cell phone or hand phone, is among the most popular electrical devices used by people all over the world. The present study examines the vibration perception of mobile phones by co-relating the relevant design parameters such as excitation frequency, and size and mass of mobile phones to the vibration perception survey by volunteers. Five popular commercially available mobile phone models were tested. The main findings for the perception surveys were that higher vibration frequency and amplitude of the peak acceleration would result in stronger vibration perception of the mobile phones. A larger contact surface area with the palms and figures, higher peak acceleration and the associated larger peak inertia force may be the main factors for the relatively higher vibration perception. The future design for the vibration alert of the mobile phones is likely to follow this trend. Copyright © 2013 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Towards Coupling of Macroseismic Intensity with Structural Damage Indicators

NASA Astrophysics Data System (ADS)

Kouteva, Mihaela; Boshnakov, Krasimir

2016-04-01

Knowledge on basic data of ground motion acceleration time histories during earthquakes is essential to understanding the earthquake resistant behaviour of structures. Peak and integral ground motion parameters such as peak ground motion values (acceleration, velocity and displacement), measures of the frequency content of ground motion, duration of strong shaking and various intensity measures play important roles in seismic evaluation of existing facilities and design of new systems. Macroseismic intensity is an earthquake measure related to seismic hazard and seismic risk description. Having detailed ideas on the correlations between the earthquake damage potential and macroseismic intensity is an important issue in engineering seismology and earthquake engineering. Reliable earthquake hazard estimation is the major prerequisite to successful disaster risk management. The usage of advanced earthquake engineering approaches for structural response modelling is essential for reliable evaluation of the accumulated damages in the existing buildings and structures due to the history of seismic actions, occurred during their lifetime. Full nonlinear analysis taking into account single event or series of earthquakes and the large set of elaborated damage indices are suitable contemporary tools to cope with this responsible task. This paper presents some results on the correlation between observational damage states, ground motion parameters and selected analytical damage indices. Damage indices are computed on the base of nonlinear time history analysis of test reinforced structure, characterising the building stock of the Mediterranean region designed according the earthquake resistant requirements in mid XX-th century.

Peak power in the hexagonal barbell jump squat and its relationship to jump performance and acceleration in elite rugby union players.

PubMed

Turner, Thomas S; Tobin, Daniel P; Delahunt, Eamonn

2015-05-01

Recent research suggests that jump squats with a loaded hexagonal barbell are superior for peak power production to comparable loads in a traditional barbell loaded jump squat. The aim of this study was to investigate the relationship between relative peak power output during performance of the hexagonal barbell jump squat (HBJS), countermovement jump (CMJ) height, and linear acceleration speed in rugby union players. Seventeen professional rugby union players performed 10- and 20-m sprints, followed by a set of 3 unloaded CMJs and a set of 3 HBJS at a previously determined optimal load corresponding with peak power output. The relationship between HBJS relative peak power output, 10- and 20-m sprint time, and CMJ height was investigated using correlation analysis. The contribution of HBJS relative peak power output and CMJ height to 10- and 20-m sprint time was investigated using standard multiple regression. Strong, significant, inverse correlations were observed between HBJS relative peak power output, 10-m sprint time (r = -0.70, p < 0.01), and 20-m sprint time (r = -0.75, p < 0.01). A strong, significant, positive correlation was observed between HBJS relative peak power output and CMJ height (r = 0.80, p < 0.01). Together, HBJS relative peak power output and CMJ height explained 46% of the variance in 10-m sprint time while explaining 59% of the variance in 20-m sprint time. The findings of the current study demonstrate a significant relationship between relative peak power in the HBJS and athletic performance as quantified by CMJ height and 10- and 20-m sprint time.

Lateralized Motor Control Processes Determine Asymmetry of Interlimb Transfer

PubMed Central

Sainburg, Robert L.; Schaefer, Sydney Y.; Yadav, Vivek

2016-01-01

This experiment tested the hypothesis that interlimb transfer of motor performance depends on recruitment of motor control processes that are specialized to the hemisphere contralateral to the arm that is initially trained. Right-handed participants performed a single-joint task, in which reaches were targeted to 4 different distances. While the speed and accuracy was similar for both hands, the underlying control mechanisms used to vary movement speed with distance were systematically different between the arms: The amplitude of the initial acceleration profiles scaled greater with movement speed for the right-dominant arm, while the duration of the initial acceleration profile scaled greater with movement speed for the left-non-dominant arm. These two processes were previously shown to be differentially disrupted by left and right hemisphere damage, respectively. We now hypothesize that task practice with the right arm might reinforce left-hemisphere mechanisms that vary acceleration amplitude with distance, while practice with the left arm might reinforce right-hemisphere mechanisms that vary acceleration duration with distance. We thus predict that following right arm practice, the left arm should show increased contributions of acceleration amplitude to peak velocities, and following left arm practice, the right arm should show increased contributions of acceleration duration to peak velocities. Our findings support these predictions, indicating that asymmetry in interlimb transfer of motor performance, at least in the task used here, depends on recruitment of lateralized motor control processes. PMID:27491479

Simulation of strong ground motion parameters of the 1 June 2013 Gulf of Suez earthquake, Egypt

NASA Astrophysics Data System (ADS)

Toni, Mostafa

2017-06-01

This article aims to simulate the ground motion parameters of the moderate magnitude (ML 5.1) June 1, 2013 Gulf of Suez earthquake, which represents the largest instrumental earthquake to be recorded in the middle part of the Gulf of Suez up to now. This event was felt in all cities located on both sides of the Gulf of Suez, with minor damage to property near the epicenter; however, no casualties were observed. The stochastic technique with the site-dependent spectral model is used to simulate the strong ground motion parameters of this earthquake in the cities located at the western side of the Gulf of Suez and north Red Sea namely: Suez, Ain Sokhna, Zafarana, Ras Gharib, and Hurghada. The presence of many tourist resorts and the increase in land use planning in the considered cities represent the motivation of the current study. The simulated parameters comprise the Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), and Peak Ground Displacement (PGD), in addition to Pseudo Spectral Acceleration (PSA). The model developed for ground motion simulation is validated by using the recordings of three accelerographs installed around the epicenter of the investigated earthquake. Depending on the site effect that has been determined in the investigated areas by using geotechnical data (e.g., shear wave velocities and microtremor recordings), the investigated areas are classified into two zones (A and B). Zone A is characterized by higher site amplification than Zone B. The ground motion parameters are simulated at each zone in the considered areas. The results reveal that the highest values of PGA, PGV, and PGD are observed at Ras Gharib city (epicentral distance ∼ 11 km) as 67 cm/s2, 2.53 cm/s, and 0.45 cm respectively for Zone A, and as 26.5 cm/s2, 1.0 cm/s, and 0.2 cm respectively for Zone B, while the lowest values of PGA, PGV, and PGD are observed at Suez city (epicentral distance ∼ 190 km) as 3.0 cm/s2, 0.2 cm/s, and 0.05 cm/s respectively for Zone A, and as 1.3 cm/s2, 0.1 cm/s, and 0.024 cm respectively for Zone B. Also the highest PSA values are observed in Ras Gharib city as 200 cm/s2 and 78 cm/s2 for Zone A and Zone B respectively, while the lowest PSA values are observed in Suez city as 7 cm/s2 and 3 cm/s2 for Zone A and Zone B respectively. These results show a good agreement with the earthquake magnitude, epicentral distances, and site characterizations as well.

TIME-DEPENDENT ELECTRON ACCELERATION IN BLAZAR TRANSIENTS: X-RAY TIME LAGS AND SPECTRAL FORMATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, Tiffany R.; Becker, Peter A.; Finke, Justin D., E-mail: pbecker@gmu.edu, E-mail: tlewis13@gmu.edu, E-mail: justin.finke@nrl.navy.mil

2016-06-20

Electromagnetic radiation from blazar jets often displays strong variability, extending from radio to γ -ray frequencies. In a few cases, this variability has been characterized using Fourier time lags, such as those detected in the X-rays from Mrk 421 using Beppo SAX. The lack of a theoretical framework to interpret the data has motivated us to develop a new model for the formation of the X-ray spectrum and the time lags in blazar jets based on a transport equation including terms describing stochastic Fermi acceleration, synchrotron losses, shock acceleration, adiabatic expansion, and spatial diffusion. We derive the exact solution formore » the Fourier transform of the electron distribution and use it to compute the Fourier transform of the synchrotron radiation spectrum and the associated X-ray time lags. The same theoretical framework is also used to compute the peak flare X-ray spectrum, assuming that a steady-state electron distribution is achieved during the peak of the flare. The model parameters are constrained by comparing the theoretical predictions with the observational data for Mrk 421. The resulting integrated model yields, for the first time, a complete first-principles physical explanation for both the formation of the observed time lags and the shape of the peak flare X-ray spectrum. It also yields direct estimates of the strength of the shock and the stochastic magnetohydrodynamical wave acceleration components in the Mrk 421 jet.« less

Skeletal site-specific effects of whole body vibration in mature rats: from deleterious to beneficial frequency-dependent effects.

PubMed

Pasqualini, Marion; Lavet, Cédric; Elbadaoui, Mohamed; Vanden-Bossche, Arnaud; Laroche, Norbert; Gnyubkin, Vasily; Vico, Laurence

2013-07-01

Whole body vibration (WBV) is receiving increasing interest as an anti-osteoporotic prevention strategy. In this context, selective effects of different frequency and acceleration magnitude modalities on musculoskeletal responses need to be better defined. Our aim was to investigate the bone effects of different vibration frequencies at constant g level. Vertical WBV was delivered at 0.7 g (peak acceleration) and 8, 52 or 90 Hz sinusoidal vibration to mature male rats 10 min daily for 5 days/week for 4 weeks. Peak accelerations measured by skin or bone-mounted accelerometers at L2 vertebral and tibia crest levels revealed similar values between adjacent skin and bone sites. Local accelerations were greater at 8 Hz compared with 52 and 90 Hz and were greater in vertebra than tibia for all the frequencies tested. At 52 Hz, bone responses were mainly seen in L2 vertebral body and were characterized by trabecular reorganization and stimulated mineral apposition rate (MAR) without any bone volume alteration. At 90 Hz, axial and appendicular skeletons were affected as were the cortical and trabecular compartments. Cortical thickness increased in femur diaphysis (17%) along with decreased porosity; trabecular bone volume increased at distal femur metaphysis (23%) and even more at L2 vertebral body (32%), along with decreased SMI and increased trabecular connectivity. Trabecular thickness increased at the tibia proximal metaphysis. Bone cellular activities indicated a greater bone formation rate, which was more pronounced at vertebra (300%) than at long bone (33%). Active bone resorption surfaces were unaffected. At 8 Hz, however, hyperosteoidosis with reduced MAR along with increased resorption surfaces occurred in the tibia; hyperosteoidosis and trend towards decreased MAR was also seen in L2 vertebra. Trabecular bone mineral density was decreased at femur and tibia. Thus the most favorable regimen is 90 Hz, while deleterious effects were seen at 8 Hz. We concluded that the skeleton is frequency-scalable, thus highlighting the importance of WBV regimen conditions and suggesting that cautions are required for frequencies less than 10 Hz, at least in rats. Copyright © 2013 Elsevier Inc. All rights reserved.

Equivalent peak resolution: characterization of the extent of separation for two components based on their relative peak overlap.

PubMed

Dvořák, Martin; Svobodová, Jana; Dubský, Pavel; Riesová, Martina; Vigh, Gyula; Gaš, Bohuslav

2015-03-01

Although the classical formula of peak resolution was derived to characterize the extent of separation only for Gaussian peaks of equal areas, it is often used even when the peaks follow non-Gaussian distributions and/or have unequal areas. This practice can result in misleading information about the extent of separation in terms of the severity of peak overlap. We propose here the use of the equivalent peak resolution value, a term based on relative peak overlap, to characterize the extent of separation that had been achieved. The definition of equivalent peak resolution is not constrained either by the form(s) of the concentration distribution function(s) of the peaks (Gaussian or non-Gaussian) or the relative area of the peaks. The equivalent peak resolution value and the classically defined peak resolution value are numerically identical when the separated peaks are Gaussian and have identical areas and SDs. Using our new freeware program, Resolution Analyzer, one can calculate both the classically defined and the equivalent peak resolution values. With the help of this tool, we demonstrate here that the classical peak resolution values mischaracterize the extent of peak overlap even when the peaks are Gaussian but have different areas. We show that under ideal conditions of the separation process, the relative peak overlap value is easily accessible by fitting the overall peak profile as the sum of two Gaussian functions. The applicability of the new approach is demonstrated on real separations. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The laser accelerator-another unicorn in the garden

NASA Astrophysics Data System (ADS)

Hand, L. N.

1981-07-01

Some proposed techniques for using laser beams to accelerate charged particles was reviewed. Two specific ideas for grating type accelerating structures are discussed. Speculations are presented about how a successful laser accelerator could be used in a multipass collider; a type of machine which would have characteristics intermediate between those of synchrotrons and linear (single pass) colliders. No definite conclusions about practical structures for laser accelerators are reached, but it is suggested that a serious effort be made to design a small prototype machine. Achieving a reasonable luminosity demands that the accelerator either be a cw machine or that laser peak power requirements to be much higher than those presently available. Use of superconducting gratings requires a wavelength in the sub-millimeter range.

Studies on motion sickness caused by high curve speed railway vehicles. Evaluation of the swing and its effects on passengers and conductors.

PubMed

Ueno, M; Ogawa, T; Nakagiri, S; Arisawa, T; Mino, Y; Oyama, K; Kodera, R; Taniguchi, T; Kanazawa, S; Ohta, T

1986-07-01

The high curve speed railway vehicles (HCSRVs) of the Japanese National Railway have been operating since 1973 with the aim of increasing speed on ordinary routes with many curve track sections. Although the aim of increased speed has been attained, it has been pointed out that the swing of HCSRVs is stronger than that of ordinary-type trains and it may increase motion sickness among the passengers and conductors. In this study, the authors examined motion sickness symptoms among 119 passengers and 100 conductors of both trains with a self-administered questionnaire, and evaluated the vibration acceleration on the floor by using the 1/3 Octave Band Analyzer and the Fast Fourier Transform method (FFT). The results can be summarized as follows: There were more passengers and conductors suffering from motion sickness riding on HCSRVs than those on the control trains. HCSRVs had the peak values of vibration acceleration within the range of 0.5 Hz and 1 Hz at horizontal, although the control train showed them above 1.0 Hz. These results suggest that the high rates of subjective complaints of passengers and conductors riding on HCSRVs were affected by vibration acceleration of frequency lower than 1 Hz.

Efficient Optical Energy Harvesting in Self-Accelerating Beams

PubMed Central

Bongiovanni, Domenico; Hu, Yi; Wetzel, Benjamin; Robles, Raul A.; Mendoza González, Gregorio; Marti-Panameño, Erwin A.; Chen, Zhigang; Morandotti, Roberto

2015-01-01

We report the experimental observation of energetically confined self-accelerating optical beams propagating along various convex trajectories. We show that, under an appropriate transverse compression of their spatial spectra, these self-accelerating beams can exhibit a dramatic enhancement of their peak intensity and a significant decrease of their transverse expansion, yet retaining both the expected acceleration profile and the intrinsic self-healing properties. We found our experimental results to be in excellent agreement with the numerical simulations. We expect further applications in such contexts where power budget and optimal spatial confinement can be important limiting factors. PMID:26299360

[AUTONOMIC CONTROL OF HEART RATE, BLOOD LACTATE AND ACCELERATION DURING COMBAT SIMULATION IN TAEKWONDO ELITE ATHLETES].

PubMed

Cerda-Kohler, Hugo; Aguayo Fuentealba, Juan Carlos; Francino Barrera, Giovanni; Guajardo-Sandoval, Adrián; Jorquera Aguilera, Carlos; Báez-San Martín, Eduardo

2015-09-01

the aim of the study was to measure the heart rate recovery, blood lactate and movement acceleration during simulated taekwondo competition. twelve male subjects who belong to the national team, with at least five years of experience participated in this research. They performed a simulated combat to evaluate the following variables: (i) Blood lactate after one minute recovery between each round, (ii) Heart rate recovery (HRR) at thirty and sixty seconds in each minute rest between rounds, (iii) Peak acceleration (ACCp) in each round performed. The significance level was set at p < 005. the results showed no significant differences between winners and losers in the HRR at both, thirty and sixty seconds (p > 0.05), blood lactate (p > 0.05), peak acceleration (p > 0.05) and the average acceleration of combat (p = 0.18). There was no correlation between delta lactate and ACCp (r = 0.01; p = 0.93), delta lactate and HRR (r = -0.23; p = 0.18), and ACCp and HRR (r = 0.003; p = 0.98). these data suggest that studied variables would not be decisive in the simulated combat outcomes. Other factors such as technical-tactical or psychological variables could have a significant impact on athletic performance. Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.

k-t accelerated aortic 4D flow MRI in under two minutes: Feasibility and impact of resolution, k-space sampling patterns, and respiratory navigator gating on hemodynamic measurements.

PubMed

Bollache, Emilie; Barker, Alex J; Dolan, Ryan Scott; Carr, James C; van Ooij, Pim; Ahmadian, Rouzbeh; Powell, Alex; Collins, Jeremy D; Geiger, Julia; Markl, Michael

2018-01-01

To assess the performance of highly accelerated free-breathing aortic four-dimensional (4D) flow MRI acquired in under 2 minutes compared to conventional respiratory gated 4D flow. Eight k-t accelerated nongated 4D flow MRI (parallel MRI with extended and averaged generalized autocalibrating partially parallel acquisition kernels [PEAK GRAPPA], R = 5, TRes = 67.2 ms) using four k y -k z Cartesian sampling patterns (linear, center-out, out-center-out, random) and two spatial resolutions (SRes1 = 3.5 × 2.3 × 2.6 mm 3 , SRes2 = 4.5 × 2.3 × 2.6 mm 3 ) were compared in vitro (aortic coarctation flow phantom) and in 10 healthy volunteers, to conventional 4D flow (16 mm-navigator acceptance window; R = 2; TRes = 39.2 ms; SRes = 3.2 × 2.3 × 2.4 mm 3 ). The best k-t accelerated approach was further assessed in 10 patients with aortic disease. The k-t accelerated in vitro aortic peak flow (Qmax), net flow (Qnet), and peak velocity (Vmax) were lower than conventional 4D flow indices by ≤4.7%, ≤ 11%, and ≤22%, respectively. In vivo k-t accelerated acquisitions were significantly shorter but showed a trend to lower image quality compared to conventional 4D flow. Hemodynamic indices for linear and out-center-out k-space samplings were in agreement with conventional 4D flow (Qmax ≤ 13%, Qnet ≤ 13%, Vmax ≤ 17%, P > 0.05). Aortic 4D flow MRI in under 2 minutes is feasible with moderate underestimation of flow indices. Differences in k-space sampling patterns suggest an opportunity to mitigate image artifacts by an optimal trade-off between scan time, acceleration, and k-space sampling. Magn Reson Med 79:195-207, 2018. © 2018 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Non-Maximal Tripartite Entanglement Degradation of Dirac and Scalar Fields in Non-Inertial Frames

NASA Astrophysics Data System (ADS)

Salman, Khan; Niaz, Ali Khan; M. K., Khan

2014-03-01

The π-tangle is used to study the behavior of entanglement of a nonmaximal tripartite state of both Dirac and scalar fields in accelerated frame. For Dirac fields, the degree of degradation with acceleration of both one-tangle of accelerated observer and π-tangle, for the same initial entanglement, is different by just interchanging the values of probability amplitudes. A fraction of both one-tangles and the π-tangle always survives for any choice of acceleration and the degree of initial entanglement. For scalar field, the one-tangle of accelerated observer depends on the choice of values of probability amplitudes and it vanishes in the range of infinite acceleration, whereas for π-tangle this is not always true. The dependence of π-tangle on probability amplitudes varies with acceleration. In the lower range of acceleration, its behavior changes by switching between the values of probability amplitudes and for larger values of acceleration this dependence on probability amplitudes vanishes. Interestingly, unlike bipartite entanglement, the degradation of π-tangle against acceleration in the case of scalar fields is slower than for Dirac fields.

Dynamics of book sales: endogenous versus exogenous shocks in complex networks.

PubMed

Deschâtres, F; Sornette, D

2005-07-01

We present an extensive study of the foreshock and aftershock signatures accompanying peaks of book sales. The time series of book sales are derived from the ranking system of Amazon.com. We present two independent ways of classifying peaks, one based on the acceleration pattern of sales and the other based on the exponent of the relaxation. They are found to be consistent and reveal the coexistence of two types of sales peaks: exogenous peaks occur abruptly and are followed by a power law relaxation, while endogenous sale peaks occur after a progressively accelerating power law growth followed by an approximately symmetrical power law relaxation which is slower than for exogenous peaks. We develop a simple epidemic model of buyers connected within a network of acquaintances which propagates rumors and opinions on books. The comparison between the predictions of the model and the empirical data confirms the validity of the model and suggests in addition that social networks have evolved to converge very close to criticality (here in the sense of critical branching processes of opinion spreading). We test in detail the evidence for a power law distribution of book sales and confirm a previous indirect study suggesting that the fraction of books (density distribution) P (S) of sales S is a power law P(S) approximately 1/ S(1+mu) with mu approximately equal to 2 .

Dynamics of book sales: Endogenous versus exogenous shocks in complex networks

NASA Astrophysics Data System (ADS)

Deschâtres, F.; Sornette, D.

2005-07-01

We present an extensive study of the foreshock and aftershock signatures accompanying peaks of book sales. The time series of book sales are derived from the ranking system of Amazon.com. We present two independent ways of classifying peaks, one based on the acceleration pattern of sales and the other based on the exponent of the relaxation. They are found to be consistent and reveal the coexistence of two types of sales peaks: exogenous peaks occur abruptly and are followed by a power law relaxation, while endogenous sale peaks occur after a progressively accelerating power law growth followed by an approximately symmetrical power law relaxation which is slower than for exogenous peaks. We develop a simple epidemic model of buyers connected within a network of acquaintances which propagates rumors and opinions on books. The comparison between the predictions of the model and the empirical data confirms the validity of the model and suggests in addition that social networks have evolved to converge very close to criticality (here in the sense of critical branching processes of opinion spreading). We test in detail the evidence for a power law distribution of book sales and confirm a previous indirect study suggesting that the fraction of books (density distribution) P(S) of sales S is a power law P(S)˜1/S1+μ with μ≈2 .

High peak current acceleration of narrow divergence ions beams with the BELLA-PW laser

NASA Astrophysics Data System (ADS)

Steinke, Sven; Ji, Qing; Treffert, Franziska; Bulanov, Stepan; Bin, Jianhui; Nakamura, Kei; Gonsalves, Anthony; Toth, Csaba; Park, Jaehong; Roth, Markus; Esarey, Eric; Schenkel, Thomas; Leemans, Wim

2017-10-01

We present a parameter study of ion acceleration driven by the BELLA-PW laser. The laser repetition rate of 1Hz allowed for scanning the laser pulse duration, relative focus location and target thickness for the first time at laser peak powers of above 1 petawatt. Further, the long focal length geometry of the experiment (f\\65) and hence, large focus size provided ion beams of reduced divergence and unprecedented charge density. This work was supported by Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and Laboratory Directed Research and Development (LDRD) funding from Lawrence Berkeley National Laboratory.

First results with the novel petawatt laser acceleration facility in Dresden

NASA Astrophysics Data System (ADS)

Schramm, U.; Bussmann, M.; Irman, A.; Siebold, M.; Zeil, K.; Albach, D.; Bernert, C.; Bock, S.; Brack, F.; Branco, J.; Couperus, JP; Cowan, TE; Debus, A.; Eisenmann, C.; Garten, M.; Gebhardt, R.; Grams, S.; Helbig, U.; Huebl, A.; Kluge, T.; Köhler, A.; Krämer, JM; Kraft, S.; Kroll, F.; Kuntzsch, M.; Lehnert, U.; Loeser, M.; Metzkes, J.; Michel, P.; Obst, L.; Pausch, R.; Rehwald, M.; Sauerbrey, R.; Schlenvoigt, HP; Steiniger, K.; Zarini, O.

2017-07-01

We report on first commissioning results of the DRACO Petawatt ultra-short pulse laser system implemented at the ELBE center for high power radiation sources of Helmholtz-Zentrum Dresden-Rossendorf. Key parameters of the laser system essential for efficient and reproducible performance of plasma accelerators are presented and discussed with the demonstration of 40 MeV proton acceleration under TNSA conditions as well as peaked electron spectra with unprecedented bunch charge in the 0.5 nC range.

Method and apparatus for analog pulse pile-up rejection

DOEpatents

De Geronimo, Gianluigi

2013-12-31

A method and apparatus for pulse pile-up rejection are disclosed. The apparatus comprises a delay value application constituent configured to receive a threshold-crossing time value, and provide an adjustable value according to a delay value and the threshold-crossing time value; and a comparison constituent configured to receive a peak-occurrence time value and the adjustable value, compare the peak-occurrence time value with the adjustable value, indicate pulse acceptance if the peak-occurrence time value is less than or equal to the adjustable value, and indicate pulse rejection if the peak-occurrence time value is greater than the adjustable value.

Method and apparatus for analog pulse pile-up rejection

DOEpatents

De Geronimo, Gianluigi

2014-11-18

A method and apparatus for pulse pile-up rejection are disclosed. The apparatus comprises a delay value application constituent configured to receive a threshold-crossing time value, and provide an adjustable value according to a delay value and the threshold-crossing time value; and a comparison constituent configured to receive a peak-occurrence time value and the adjustable value, compare the peak-occurrence time value with the adjustable value, indicate pulse acceptance if the peak-occurrence time value is less than or equal to the adjustable value, and indicate pulse rejection if the peak-occurrence time value is greater than the adjustable value.

Probabilistic seismic hazard maps for Sinai Peninsula, Egypt

NASA Astrophysics Data System (ADS)

Deif, A.; Abou Elenean, K.; El Hadidy, M.; Tealeb, A.; Mohamed, A.

2009-09-01

Sinai experienced the largest Egyptian earthquake with moment magnitude (Mw) 7.2 in 1995 in the Gulf of Aqaba, 350 km from Cairo. It is characterized by the presence of many tourist projects in addition to different natural resources. The aim of the current study is to present, for the first time, the probabilistic spectral hazard maps for Sinai. Revised earthquake catalogues for Sinai and its surroundings, from 112 BC to 2006 AD with magnitude equal or greater than 3.0, are used to calculate seismic hazard in the region of interest between 27°N and 31.5°N and 32°E and 36°E. We declustered these catalogues to include only independent events. The catalogues were tested for the completeness of different magnitude ranges. 28 seismic source zones are used to define the seismicity. The recurrence rates and the maximum earthquakes across these zones were also determined from these modified catalogues. Strong ground motion relations for rock are used to produce 5% damped spectral acceleration values for four different periods (0.2, 0.5, 1.0 and 2.0 s) to define the uniform response spectra at each site (grid of 0.2° × 0.2° all over the area). Maps showing spectral acceleration values at 0.2, 0.5, 1.0 and 2.0 s periods as well as peak ground acceleration (PGA) for the return period of 475 years (equivalent to 90% probability on non-exceedence in 50 years) are presented. In addition, Uniform Hazard Spectra (UHS) at 25 different periods for the four main cities (Hurghda, Sharm El-Sheikh, Nuweibaa and Suez) are graphed. The highest hazard is found in the Gulf of Aqaba with maximum spectral accelerations 356 cm s-2 at a period of 0.22 s for a return period of 475 years.

Analysis of the ground motions from the MW 7.8 Gorkha and MW 7.3 Dolakha earthquakes in Nepal in 2015

NASA Astrophysics Data System (ADS)

Martin, S. S.; Hough, S. E.; Gahalaut, V. K.; Joshi, A.; Landes, M.; Bossu, R.

2016-12-01

While the 25 April 2015 MW7.8 Gorkha, Nepal, earthquake took a heavy toll in Nepal, damage and fatalities were lower than expected. There is thus an urgent need to understand ground motions from the mainshock and largest aftershock. We collected 3,831 accounts of macroseismic effects that include sufficient information to assign intensities. To assess intensities reliably, we apply EMS guidelines with an appreciation for issues associated with macroseismic effects of earthquakes in the Indian subcontinent. We as also analyze 21 available strong motion recordings. Available data are consistent with the peak ground acceleration (PGA) versus intensity relationship of Worden et al. (2012). We use this relationship to estimate peak ground acceleration (PGAEMS) from all intensities. For nearest-fault distances (RRUP<200km), PGAEMS is consistent with the Atkinson and Boore (2003) (AB03) subduction zone ground motion prediction equation (GMPE); at greater distances, instrumental PGA values are consistent with AB03, while PGAEMS is systematically higher. We use PGAEMS values within 200 km to investigate the variability of ground motions using the AB03 GMPE as a baseline. Across the near-field region, PGAEMS is higher by a factor of 2.0-2.5 towards the northern edge of the rupture compared to the near-field region nearer to the southern, up-dip edge of the rupture. Inferred de-amplification in the deepest part of the Kathmandu valley supports the conclusion that former lake-bed sediments experienced a pervasive non-linear response during the mainshock (Dixit et al., 2015). Ground motions were amplified in the southern Gangetic basin, but were relatively low in the northern basin. The overall distribution of ground motions and damage during the Gorkha earthquake thus reflects a combination of complex source, path, and site effects. We also analyze ground motions for the 12 May 2015 Dolakha aftershock, which we conclude was likely a high stress-drop event.

Accurate Measurement of Velocity and Acceleration of Seismic Vibrations near Nuclear Power Plants

NASA Astrophysics Data System (ADS)

Arif, Syed Javed; Imdadullah; Asghar, Mohammad Syed Jamil

In spite of all prerequisite geological study based precautions, the sites of nuclear power plants are also susceptible to seismic vibrations and their consequent effects. The effect of the ongoing nuclear tragedy in Japan caused by an earthquake and its consequent tsunami on March 11, 2011 is currently beyond contemplations. It has led to a rethinking on nuclear power stations by various governments around the world. Therefore, the prediction of location and time of large earthquakes has regained a great importance. The earth crust is made up of several wide, thin and rigid plates like blocks which are in constant motion with respect to each other. A series of vibrations on the earth surface are produced by the generation of elastic seismic waves due to sudden rupture within the plates during the release of accumulated strain energy. The range of frequency of seismic vibrations is from 0 to 10 Hz. However, there appears a large variation in magnitude, velocity and acceleration of these vibrations. The response of existing or conventional methods of measurement of seismic vibrations is very slow, which is of the order of tens of seconds. A systematic and high resolution measurement of velocity and acceleration of these vibrations are useful to interpret the pattern of waves and their anomalies more accurately, which are useful for the prediction of an earthquake. In the proposed work, a fast rotating magnetic field (RMF) is used to measure the velocity and acceleration of seismic vibrations in the millisecond range. The broad spectrum of pulses within one second range, measured by proposed method, gives all possible values of instantaneous velocity and instantaneous acceleration of the seismic vibrations. The spectrum of pulses in millisecond range becomes available which is useful to measure the pattern of fore shocks to predict the time and location of large earthquakes more accurately. Moreover, instead of average, the peak values of these quantities are helpful in proper design of earthquake resistant nuclear power plants, buildings and structures. The proposed measurement scheme is successfully tested with a microprocessor based rocking vibration arrangement and the overall performance is recorded at dynamic conditions.

Galaxy Formation Efficiency and the Multiverse Explanation of the Cosmological Constant with EAGLE Simulations

NASA Astrophysics Data System (ADS)

Barnes, Luke A.; Elahi, Pascal J.; Salcido, Jaime; Bower, Richard G.; Lewis, Geraint F.; Theuns, Tom; Schaller, Matthieu; Crain, Robert A.; Schaye, Joop

2018-04-01

Models of the very early universe, including inflationary models, are argued to produce varying universe domains with different values of fundamental constants and cosmic parameters. Using the cosmological hydrodynamical simulation code from the EAGLE collaboration, we investigate the effect of the cosmological constant on the formation of galaxies and stars. We simulate universes with values of the cosmological constant ranging from Λ = 0 to Λ0 × 300, where Λ0 is the value of the cosmological constant in our Universe. Because the global star formation rate in our Universe peaks at t = 3.5 Gyr, before the onset of accelerating expansion, increases in Λ of even an order of magnitude have only a small effect on the star formation history and efficiency of the universe. We use our simulations to predict the observed value of the cosmological constant, given a measure of the multiverse. Whether the cosmological constant is successfully predicted depends crucially on the measure. The impact of the cosmological constant on the formation of structure in the universe does not seem to be a sharp enough function of Λ to explain its observed value alone.

Galaxy formation efficiency and the multiverse explanation of the cosmological constant with EAGLE simulations

NASA Astrophysics Data System (ADS)

Barnes, Luke A.; Elahi, Pascal J.; Salcido, Jaime; Bower, Richard G.; Lewis, Geraint F.; Theuns, Tom; Schaller, Matthieu; Crain, Robert A.; Schaye, Joop

2018-07-01

Models of the very early Universe, including inflationary models, are argued to produce varying universe domains with different values of fundamental constants and cosmic parameters. Using the cosmological hydrodynamical simulation code from the EAGLE collaboration, we investigate the effect of the cosmological constant on the formation of galaxies and stars. We simulate universes with values of the cosmological constant ranging from Λ = 0 to Λ0 × 300, where Λ0 is the value of the cosmological constant in our Universe. Because the global star formation rate in our Universe peaks at t = 3.5 Gyr, before the onset of accelerating expansion, increases in Λ of even an order of magnitude have only a small effect on the star formation history and efficiency of the universe. We use our simulations to predict the observed value of the cosmological constant, given a measure of the multiverse. Whether the cosmological constant is successfully predicted depends crucially on the measure. The impact of the cosmological constant on the formation of structure in the universe does not seem to be a sharp enough function of Λ to explain its observed value alone.

Synchronous acceleration with tapered dielectric-lined waveguides

NASA Astrophysics Data System (ADS)

Lemery, F.; Floettmann, K.; Piot, P.; Kärtner, F. X.; Aßmann, R.

2018-05-01

We present a general concept to accelerate nonrelativistic charged particles. Our concept employs an adiabatically-tapered dielectric-lined waveguide which supports accelerating phase velocities for synchronous acceleration. We propose an ansatz for the transient field equations, show it satisfies Maxwell's equations under an adiabatic approximation and find excellent agreement with a finite-difference time-domain computer simulation. The fields were implemented into the particle-tracking program astra and we present beam dynamics results for an accelerating field with a 1-mm-wavelength and peak electric field of 100 MV /m . Numerical simulations indicate that a ˜200 -keV electron beam can be accelerated to an energy of ˜10 MeV over ˜10 cm with parameters of interest to a wide range of applications including, e.g., future advanced accelerators, and ultra-fast electron diffraction.

Potential applications of the dielectric wakefield accelerators in the SINBAD facility at DESY

NASA Astrophysics Data System (ADS)

Nie, Y. C.; Assmann, R.; Dorda, U.; Marchetti, B.; Weikum, M.; Zhu, J.; Hüning, M.

2016-09-01

Short, high-brightness relativistic electron bunches can drive ultra-high wakefields in the dielectric wakefield accelerators (DWFAs). This effect can be used to generate high power THz coherent Cherenkov radiation, accelerate a witness bunch with gradient two or three orders of magnitude larger than that in the conventional RF linear accelerators, introduce energy modulation within the driving bunch itself, etc. The paper studies potential applications of the DWFAs in the SINBAD facility at DESY. The simulations show that the ultra-short relativistic bunches from the SINBAD injector ARES can excite accelerating wakefields with peak amplitudes as high as GV/m at THz frequencies in proper DWFA structures. In addition, it illustrates that the DWFA structure can serve as a dechirper to compensate the correlated energy spread of the bunches accelerated by the laser plasma wakefield accelerator.

A nonlinear stretching based electromagnetic energy harvester on FR4 for wideband operation

NASA Astrophysics Data System (ADS)

Mallick, Dhiman; Amann, Andreas; Roy, Saibal

2015-01-01

We report a nonlinear stretching-based electromagnetic energy harvester using FR4 as a vibrating spring material due to its low Young’s modulus. We show analytically that the nonlinearity is caused by the stretching, in addition to the bending, of the specially designed spring arms; this gives rise to a wider half-power bandwidth of 10 Hz at 1 g acceleration, which is almost 5 times higher than that of a comparable linear counterpart. The output spectra show the first reported experimental evidence of a symmetry broken nonlinear secondary peak in a single potential well system at frequencies close to the nonlinear jump frequency, which may appear to be due to the dynamic symmetry breaking of the oscillator or to the inherent asymmetry of the built prototype. The presence of this secondary peak is useful in generating a significant amount of power compared to the symmetric states, producing ˜3 times more power at the secondary peak than the nearby symmetric states. 110% of the peak power obtained for 0.5 g acceleration is achieved at the secondary peak during the frequency up-sweep. The experimental results are compared with a deterministic numerical model based on the Duffing oscillator, and we include a qualitative discussion on the influence of noise in an experimental energy harvesting system.

Vertical drop test of a transport fuselage section located aft of the wing

NASA Technical Reports Server (NTRS)

Fasanella, E. L.; Alfaro-Bou, E.

1986-01-01

A 12-foot long Boeing 707 aft fuselage section with a tapering cross section was drop tested at the NASA Langley Research Center to measure structural, seat, and occupant response to vertical crash laods and to provide data for nonlinear finite element modeling. This was the final test in a series of three different transport fuselage sections tested under identical conditions. The test parameters at impact were: 20 ft/s velocity, and zero pitch, roll, and yaw. In addition, the test was an operational shock test of the data acquisition system used for the Controlled Impact Demonstration (CID) of a remotely piloted Boeing 720 that was crash tested at NASA Ames Dryden Flight Research Facility on December 1, 1984. Post-test measurements of the crush showed that the front of the section (with larger diameter) crushed vertically approximately 14 inches while the rear crushed 18 inches. Analysis of the data traces indicate the maximum peak normal (vertical) accelerations at the bottom of the frames were approximately 109 G at body station 1040 and 64 G at body station 1120. The peak floor acceleration varied from 14 G near the wall to 25 G near the center where high frequency oscillations of the floor were evident. The peak anthropomorphic dummy pelvis normal (vertical) acceleration was 19 G's.

A Study of the Response of the Human Cadaver Head to Impact

PubMed Central

Hardy, Warren N.; Mason, Matthew J.; Foster, Craig D.; Shah, Chirag S.; Kopacz, James M.; Yang, King H.; King, Albert I.; Bishop, Jennifer; Bey, Michael; Anderst, William; Tashman, Scott

2008-01-01

High-speed biplane x-ray and neutral density targets were used to examine brain displacement and deformation during impact. Relative motion, maximum principal strain, maximum shear strain, and intracranial pressure were measured in thirty-five impacts using eight human cadaver head and neck specimens. The effect of a helmet was evaluated. During impact, local brain tissue tends to keep its position and shape with respect to the inertial frame, resulting in relative motion between the brain and skull and deformation of the brain. The local brain motions tend to follow looping patterns. Similar patterns are observed for impact in different planes, with some degree of posterior-anterior and right-left symmetry. Peak coup pressure and pressure rate increase with increasing linear acceleration, but coup pressure pulse duration decreases. Peak average maximum principal strain and maximum shear are on the order of 0.09 for CFC 60 Hz data for these tests. Peak average maximum principal strain and maximum shear increase with increasing linear acceleration, coup pressure, and coup pressure rate. Linear and angular acceleration of the head are reduced with use of a helmet, but strain increases. These results can be used for the validation of finite element models of the human head. PMID:18278591

Racquet string tension directly affects force experienced at the elbow: implications for the development of lateral epicondylitis in tennis players

PubMed Central

Mohandhas, Badri R; Makaram, Navnit; Drew, Tim S; Wang, Weijie; Arnold, Graham P

2016-01-01

Background Lateral epicondylitis (LE) occurs in almost half of all tennis players. Racket-string tension is considered to be an important factor influencing the development of LE. No literature yet exists that substantiates how string-tension affects force transmission to the elbow, as implicated in LE development. We establish a quantitative relationship between string-tension and elbow loading, analyzing tennis strokes using rackets with varying string-tensions. Methods Twenty recreational tennis players simulated backhand tennis strokes using three rackets strung at tensions of 200 N, 222 N and 245 N. Accelerometers recorded accelerations at the elbow, wrist and racket handle. Average peak acceleration was determined to correlate string-tension with elbow loading. Results Statistically significant differences (p < 0.05) were observed when average peak acceleration at the elbow at 200 N string-tension (acceleration of 5.58 m/s2) was compared with that at 222 N tension (acceleration of 6.83 m/s2) and 245 N tension (acceleration of 7.45 m/s2). The 200 N racket induced the least acceleration at the elbow. Conclusions Although parameters determining force transmission to the elbow during a tennis stroke are complex, the present study was able to control these parameters, isolating the effect of string-tension. Lower string-tensions transmit less force to the elbow in backhand strokes. Reducing string-tension should be considered favourably with respect to reducing the risk of developing LE. PMID:27583017

The LeRC rail accelerators: Test designs and diagnostic techniques

NASA Technical Reports Server (NTRS)

Zana, L. M.; Kerslake, W. R.; Sturman, J. C.; Wang, S. Y.; Terdan, F. F.

1983-01-01

The feasibility of using rail accelerators for various in-space and to-space propulsion applications was investigated. A 1 meter, 24 sq mm bore accelerator was designed with the goal of demonstrating projectile velocities of 15 km/sec using a peak current of 200 kA. A second rail accelerator, 1 meter long with a 156.25 sq mm bore, was designed with clear polycarbonate sidewalls to permit visual observation of the plasma arc. A study of available diagnostic techniques and their application to the rail accelerator is presented. Specific topics of discussion include the use of interferometry and spectroscopy to examine the plasma armature as well as the use of optical sensors to measure rail displacement during acceleration. Standard diagnostics such as current and voltage measurements are also discussed.

A test of various site-effect parameterizations in probabilistic seismic hazard analyses of southern California

USGS Publications Warehouse

Field, E.H.; Petersen, M.D.

2000-01-01

We evaluate the implications of several attenuation relationships, including three customized for southern California, in terms of accounting for site effects in probabilistic seismic hazard studies. The analysis is carried out at 43 sites along a profile spanning the Los Angeles basin with respect to peak acceleration, and 0.3-, 1.0-, and 3.0-sec response spectral acceleration values that have a 10% chance of being exceeded in 50 years. The variability among currently viable attenuation relationships (espistemic uncertainty) is an approximate factor of 2. Biases between several commonly used attenuation relationships and southern California strong-motion data imply hazard differences that exceed 10%. However, correcting each relationship for the southern California bias does not necessarily bring hazard estimates into better agreement. A detailed subclassification of site types (beyond rock versus soil) is found to be both justified by data and to make important distinctions in terms of hazard levels. A basin depth effect is also shown to be important, implying a difference of up to a factor of 2 in ground motion between the deepest and shallowest parts of the Los Angeles basin. In fact, for peak acceleration, the basin-depth effect is even more influential than the surface site condition. Questions remain, however, whether basin depth is a proxy for some other site attribute such as distance from the basin edge. The reduction in prediction error (sigma) produced by applying detailed site and/or basin-depth corrections does not have an important influence on the hazard. In fact, the sigma reduction is less than epistemic uncertainties on sigma itself. Due to data limitations, it is impossible to determine which attenuation relationship is best. However, our results do indicate which site conditions seem most influential. This information should prove useful to those developing or updating attenuation relationships and to those attempting to make more refined estimates of hazard in the near future.

Strong correlation between stress drop and peak ground acceleration for recent M1–4 earthquakes in the San Francisco Bay Area

DOE PAGES

Trugman, Daniel Taylor; Shearer, Peter M.

2018-03-06

Theoretical and observational studies suggest that between-event variability in the median ground motions of larger ( M≥5 ) earthquakes is controlled primarily by the dynamic properties of the earthquake source, such as Brune-type stress drop. Analogous results remain equivocal for smaller events due to the lack of comprehensive and overlapping ground-motion and source-parameter datasets in this regime. Here in this paper, we investigate the relationship between peak ground acceleration (PGA) and dynamic stress drop for a new dataset of 5297 earthquakes that occurred in the San Francisco Bay area from 2002 through 2016. For each event, we measure PGA onmore » horizontal-component channels of stations within 100 km and estimate stress drop from P-wave spectra recorded on vertical-component channels of the same stations. We then develop a nonparametric ground-motion prediction equation (GMPE) applicable for the moderate (M 1–4) earthquakes in our study region, using a mixed-effects generalization of the Random Forest algorithm. We use the Random Forest GMPE to model the joint influence of magnitude, distance, and near-site effects on observed PGA. We observe a strong correlation between dynamic stress drop and the residual PGA of each event, with the events with higher-than-expected PGA associated with higher values of stress drop. The strength of this correlation increases as a function of magnitude but remains significant even for smaller magnitude events with corner frequencies that approach the observable bandwidth of the acceleration records. Mainshock events are characterized by systematically higher stress drop and PGA than aftershocks of equivalent magnitude. Coherent local variations in the distribution of dynamic stress drop provide observational constraints to support the future development of nonergodic GMPEs that account for variations in median stress drop at different source locations.« less

Strong correlation between stress drop and peak ground acceleration for recent M1–4 earthquakes in the San Francisco Bay Area

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trugman, Daniel Taylor; Shearer, Peter M.

Theoretical and observational studies suggest that between-event variability in the median ground motions of larger ( M≥5 ) earthquakes is controlled primarily by the dynamic properties of the earthquake source, such as Brune-type stress drop. Analogous results remain equivocal for smaller events due to the lack of comprehensive and overlapping ground-motion and source-parameter datasets in this regime. Here in this paper, we investigate the relationship between peak ground acceleration (PGA) and dynamic stress drop for a new dataset of 5297 earthquakes that occurred in the San Francisco Bay area from 2002 through 2016. For each event, we measure PGA onmore » horizontal-component channels of stations within 100 km and estimate stress drop from P-wave spectra recorded on vertical-component channels of the same stations. We then develop a nonparametric ground-motion prediction equation (GMPE) applicable for the moderate (M 1–4) earthquakes in our study region, using a mixed-effects generalization of the Random Forest algorithm. We use the Random Forest GMPE to model the joint influence of magnitude, distance, and near-site effects on observed PGA. We observe a strong correlation between dynamic stress drop and the residual PGA of each event, with the events with higher-than-expected PGA associated with higher values of stress drop. The strength of this correlation increases as a function of magnitude but remains significant even for smaller magnitude events with corner frequencies that approach the observable bandwidth of the acceleration records. Mainshock events are characterized by systematically higher stress drop and PGA than aftershocks of equivalent magnitude. Coherent local variations in the distribution of dynamic stress drop provide observational constraints to support the future development of nonergodic GMPEs that account for variations in median stress drop at different source locations.« less

Analysis of Movement Acceleration of Down's Syndrome Teenagers Playing Computer Games.

PubMed

Carrogi-Vianna, Daniela; Lopes, Paulo Batista; Cymrot, Raquel; Hengles Almeida, Jefferson Jesus; Yazaki, Marcos Lomonaco; Blascovi-Assis, Silvana Maria

2017-12-01

This study aimed to evaluate movement acceleration characteristics in adolescents with Down syndrome (DS) and typical development (TD), while playing bowling and golf videogames on the Nintendo ® Wii™. The sample comprised 21 adolescents diagnosed with DS and 33 with TD of both sexes, between 10 and 14 years of age. The arm swing accelerations of the dominant upper limb were collected as measures during the bowling and the golf games. The first valid measurement, verified by the software readings, recorded at the start of each of the games, was used in the analysis. In the bowling game, the groups presented significant statistical differences, with the maximum (M) peaks of acceleration for the Male Control Group (MCG) (M = 70.37) and Female Control Group (FCG) (M = 70.51) when compared with Male Down Syndrome Group (MDSG) (M = 45.33) and Female Down Syndrome Group (FDSG) (M = 37.24). In the golf game the groups also presented significant statistical differences, the only difference being that the maximum peaks of acceleration for both male groups were superior compared with the female groups, MCG (M = 74.80) and FCG (M = 56.80), as well as in MDSG (M = 45.12) and in FDSG (M = 30.52). It was possible to use accelerometry to evaluate the movement acceleration characteristics of teenagers diagnosed with DS during virtual bowling and golf games played on the Nintendo Wii console.

Ground Motion Prediction Models for Caucasus Region

NASA Astrophysics Data System (ADS)

Jorjiashvili, Nato; Godoladze, Tea; Tvaradze, Nino; Tumanova, Nino

2016-04-01

Ground motion prediction models (GMPMs) relate ground motion intensity measures to variables describing earthquake source, path, and site effects. Estimation of expected ground motion is a fundamental earthquake hazard assessment. The most commonly used parameter for attenuation relation is peak ground acceleration or spectral acceleration because this parameter gives useful information for Seismic Hazard Assessment. Since 2003 development of Georgian Digital Seismic Network has started. In this study new GMP models are obtained based on new data from Georgian seismic network and also from neighboring countries. Estimation of models is obtained by classical, statistical way, regression analysis. In this study site ground conditions are additionally considered because the same earthquake recorded at the same distance may cause different damage according to ground conditions. Empirical ground-motion prediction models (GMPMs) require adjustment to make them appropriate for site-specific scenarios. However, the process of making such adjustments remains a challenge. This work presents a holistic framework for the development of a peak ground acceleration (PGA) or spectral acceleration (SA) GMPE that is easily adjustable to different seismological conditions and does not suffer from the practical problems associated with adjustments in the response spectral domain.

Rotational motions from the 2016, Central Italy seismic sequence, as observed by an underground ring laser gyroscope

NASA Astrophysics Data System (ADS)

Simonelli, A.; Igel, H.; Wassermann, J.; Belfi, J.; Di Virgilio, A.; Beverini, N.; De Luca, G.; Saccorotti, G.

2018-05-01

We present the analysis of rotational and translational ground motions from earthquakes recorded during October/November, 2016, in association with the Central Italy seismic-sequence. We use co-located measurements of the vertical ground rotation rate from a large ring laser gyroscope (RLG), and the three components of ground velocity from a broadband seismometer. Both instruments are positioned in a deep underground environment, within the Gran Sasso National Laboratories (LNGS) of the Istituto Nazionale di Fisica Nucleare (INFN). We collected dozens of events spanning the 3.5-5.9 Magnitude range, and epicentral distances between 30 km and 70 km. This data set constitutes an unprecedented observation of the vertical rotational motions associated with an intense seismic sequence at local distance. Under the plane wave approximation we process the data set in order to get an experimental estimation of the events back azimuth. Peak values of rotation rate (PRR) and horizontal acceleration (PGA) are markedly correlated, according to a scaling constant which is consistent with previous measurements from different earthquake sequences. We used a prediction model in use for Italy to calculate the expected PGA at the recording site, obtaining consequently predictions for PRR. Within the modeling uncertainties, predicted rotations are consistent with the observed ones, suggesting the possibility of establishing specific attenuation models for ground rotations, like the scaling of peak velocity and peak acceleration in empirical ground-motion prediction relationships. In a second step, after identifying the direction of the incoming wave-field, we extract phase velocity data using the spectral ratio of the translational and rotational components.. This analysis is performed over time windows associated with the P-coda, S-coda and Lg phase. Results are consistent with independent estimates of shear-wave velocities in the shallow crust of the Central Apennines.

The influence of headform orientation and flooring systems on impact dynamics during simulated fall-related head impacts.

PubMed

Wright, Alexander D; Laing, Andrew C

2012-10-01

Novel compliant flooring systems are a promising approach for reducing fall-related injuries in seniors, as they may provide up to 50% attenuation in peak force during simulated hip impacts while eliciting only minimal influences on balance. This study aimed to determine the protective capacity of novel compliant floors during simulated 'high severity' head impacts compared to common flooring systems. A headform was impacted onto a common Commercial-Carpet at 1.5, 2.5, and 3.5 m/s in front, back, and side orientations using a mechanical drop tower. Peak impact force applied to the headform (F(max)), peak linear acceleration of the headform (g(max)) and Head Injury Criterion (HIC) were determined. For the 3.5 m/s trials, backwards-oriented impacts were associated with the highest F(max) and HIC values (p<0.001); accordingly, this head orientation was used to complete additional trials on three common floors (Resilient Rubber, Residential-Loop Carpet, Berber Carpet) and six novel compliant floors at each impact velocity. ANOVAs indicated that flooring type was associated with all parameters at each impact velocity (p<0.001). Compared to impacts on the Commercial Carpet, Dunnett's post hoc indicated all variables were smaller (25-80%) for the novel compliant floors (p<0.001), but larger for Resilient Rubber (31-159%, p<0.01). This study demonstrates that during 'high severity' simulated impacts, novel compliant floors can substantially reduce the forces and accelerations applied to a headform compared to common floors including carpet and resilient rubber. In combination with reports of minimal balance impairments, these findings support the promise of novel compliant floors as a biomechanically effective strategy for reducing fall-related injuries including traumatic brain injuries and skull fractures. Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

Energy Evolution Mechanism and Confining Pressure Effect of Granite under Triaxial Loading-Unloading Cycles

NASA Astrophysics Data System (ADS)

Wang, Hao; Miao, Sheng-jun

2018-05-01

Rock mass undergoes some deformational failure under the action of external loads, a process known to be associated with energy dissipation and release. A triaxial loading-unloading cycle test was conducted on granite in order to investigate the energy evolution pattern of rock mass under the action of external loads. The study results demonstrated: (1) The stress peaks increased by 50% and 22% respectively and the pre-peak weakening became more apparent in the ascending process of the confining pressure from 10MPa to 30MPa; the area enclosed by the hysteresis loop corresponding to 30MPa diminished by nearly 60% than that corresponding to 10MPa, indicating a higher confining pressure prohibits rock mass from plastic deformation and shifts strain toward elastic deformation. (2) In the vicinity of the strength limit, the slope of dissipation energy increased to 1.6 from the original 0.7 and the dissipation energy grew at an accelerating rate, demonstrating stronger propagation and convergence of internal cracks. (3) At a pressure of 70% of the stress peak, the elastic energy of the granite accounted for 88% of its peak value, suggesting the rock mechanical energy from the outside mostly changes into the elastic energy inside the rock, with little energy loss.(4) Prior to test specimen failure, the axial bearing capacity dropped with a decreasing confining pressure in an essentially linear way, and the existence of confirming pressure played a role in stabilizing the axial bearing capacity.

Development of Maximum Considered Earthquake Ground Motion Maps

USGS Publications Warehouse

Leyendecker, E.V.; Hunt, R.J.; Frankel, A.D.; Rukstales, K.S.

2000-01-01

The 1997 NEHRP Recommended Provisions for Seismic Regulations for New Buildings use a design procedure that is based on spectral response acceleration rather than the traditional peak ground acceleration, peak ground velocity, or zone factors. The spectral response accelerations are obtained from maps prepared following the recommendations of the Building Seismic Safety Council's (BSSC) Seismic Design Procedures Group (SDPG). The SDPG-recommended maps, the Maximum Considered Earthquake (MCE) Ground Motion Maps, are based on the U.S. Geological Survey (USGS) probabilistic hazard maps with additional modifications incorporating deterministic ground motions in selected areas and the application of engineering judgement. The MCE ground motion maps included with the 1997 NEHRP Provisions also serve as the basis for the ground motion maps used in the seismic design portions of the 2000 International Building Code and the 2000 International Residential Code. Additionally the design maps prepared for the 1997 NEHRP Provisions, combined with selected USGS probabilistic maps, are used with the 1997 NEHRP Guidelines for the Seismic Rehabilitation of Buildings.

Strong ground motion of the 2016 Kumamoto earthquake

NASA Astrophysics Data System (ADS)

Aoi, S.; Kunugi, T.; Suzuki, W.; Kubo, H.; Morikawa, N.; Fujiwara, H.

2016-12-01

The 2016 Kumamoto earthquake that is composed of Mw 6.1 and Mw 7.1 earthquakes respectively occurred in the Kumamoto region at 21:26 on April 14 and 28 hours later at 1:25 on April 16, 2016 (JST). These earthquakes are considered to rupture mainly the Hinagu fault zone for the Mw 6.1 event and the Futagawa fault zone for the Mw 7.1 event, respectively, where the Headquarter for Earthquake Research Promotion performed the long-term evaluation as well as seismic hazard assessment prior to the 2016 Kumamoto earthquake. Strong shakings with seismic intensity 7 in the JMA scale were observed at four times in total: Mashiki town for the Mw 6.1 and Mw 7.1 events, Nishihara village for the Mw 7.1 event, and NIED/KiK-net Mashiki (KMMH16) for the Mw 7.1 event. KiK-net Mashiki (KMMH16) recorded peak ground acceleration more than 1000 cm/s/s, and Nishihara village recorded peak ground velocity more than 250 cm/s. Ground motions were observed wider area for the Mw 7.1 event than the Mw 6.1 event. Peak ground accelerations and peak ground velocities of K-NET/KiK-net stations are consistent with the ground motion prediction equations by Si and Midorikawa (1999). Peak ground velocities at longer distance than 200 km attenuate slowly, which can be attributed to the large Love wave with a dominant period around 10 seconds. 5%-damped pseudo spectral velocity of the Mashiki town shows a peak at period of 1-2 s that exceeds ground motion response of JR Takatori of the 1995 Kobe earthquake and the Kawaguchi town of the 2004 Chuetsu earthquake. 5%-damped pseudo spectral velocity of the Nishihara village shows 350 cm/s peak at period of 3-4 s that is similar to the several stations in Kathmandu basin by Takai et al. (2016) during the 2015 Gorkha earthquake in Nepal. Ground motions at several stations in Oita exceed the ground motion prediction equations due to an earthquake induced by the Mw 7.1 event. Peak ground accelerations of K-NET Yufuin (OIT009) records 90 cm/s/s for the Mw 7.1 event and 723 cm/s/s for the near-by induced event.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hand, L.N.

Some proposed techniques for using laser beams to accelerate charged particles are reviewed. Two specific ideas for 'grating-type' accelerating structures are discussed. Speculations are presented about how a successful laser accelerator could be used in a 'multi-pass collider', a type of machine which would have characteristics intermediate between those of synchrotrons and linear (single-pass) colliders. No definite conclusions about practical structures for laser accelerators are reached, but it is suggested that a serious effort be made to design a small prototype machine. Achieving a reasonable luminosity demands that the accelerator either be a cw machine or that laser peak powermore » requirements be much higher than those presently available. Use of superconducting gratings requires a wavelength in the sub-millimeter range.« less

Evaluation of New Actuators in a Buffet Loads Environment

NASA Technical Reports Server (NTRS)

Moses, Robert W.; Wieseman, Carol D.; Bent, Aaron A.; Pizzochero, Alessandro E.

2001-01-01

Ongoing research in buffet loads alleviation has provided an application for recently developed piezoelectric actuators capable of higher force output than previously existing actuators could provide and that can be embedded within the vehicle s structure. These new actuators, having interdigitated electrodes, promise increased performance over previous piezoelectric actuators that were tested on the fin of an F/A-18 aircraft. Two new actuators being considered by the United States Air Force to reduce buffet loads on high performance aircraft were embedded into the fins of an F/A-18 wind-tunnel model and tested in the Transonic Dynamics Tunnel at the NASA Langley Research Center. The purpose of this test program, called ENABLE (Evaluation of New Actuators in a Buffet Loads Environment), was to examine the performance of the new actuators in alleviating fin buffeting, leading to a systems -level study of a fin buffet loads alleviation system architecture being considered by the USAF, Boeing, and NASA for implementation on high performance aircraft. During this windtunnel test, the two actuators performed superbly in alleviating fin buffeting. Peak values of the power spectral density functions for tip acceleration were reduced by as much as 85%. RMS values of tip acceleration were reduced by as much as 40% while using less than 50% of the actuators capacity. Details of the wind-tunnel model and results of the wind-tunnel test are provided herein.

Effects of acceleration rate on Rayleigh-Taylor instability in elastic-plastic materials

NASA Astrophysics Data System (ADS)

Banerjee, Arindam; Polavarapu, Rinosh

2016-11-01

The effect of acceleration rate in the elastic-plastic transition stage of Rayleigh-Taylor instability in an accelerated non-Newtonian material is investigated experimentally using a rotating wheel experiment. A non-Newtonian material (mayonnaise) was accelerated at different rates by varying the angular acceleration of a rotating wheel and growth patterns of single mode perturbations with different combinations of amplitude and wavelength were analyzed. Experiments were run at two different acceleration rates to compare with experiments presented in prior years at APS DFD meetings and the peak amplitude responses are captured using a high-speed camera. Similar to the instability acceleration, the elastic-plastic transition acceleration is found to be increasing with increase in acceleration rate for a given amplitude and wavelength. The experimental results will be compared to various analytical strength models and prior experimental studies using Newtonian fluids. Authors acknowledge funding support from Los Alamos National Lab subcontract(370333) and DOE-SSAA Grant (DE-NA0001975).

Spot size measurement of a flash-radiography source using the pinhole imaging method

NASA Astrophysics Data System (ADS)

Wang, Yi; Li, Qin; Chen, Nan; Cheng, Jin-Ming; Xie, Yu-Tong; Liu, Yun-Long; Long, Quan-Hong

2016-07-01

The spot size of the X-ray source is a key parameter of a flash-radiography facility, and is usually quoted as an evaluation of the resolving power. The pinhole imaging technique is applied to measure the spot size of the Dragon-I linear induction accelerator, by which a two-dimensional spatial distribution of the source spot is obtained. Experimental measurements are performed to measure the spot image when the transportation and focusing of the electron beam are tuned by adjusting the currents of solenoids in the downstream section. The spot size of full-width at half maximum and that defined from the spatial frequency at half peak value of the modulation transfer function are calculated and discussed.

Tuner control system of Spoke012 SRF cavity for C-ADS injector I

NASA Astrophysics Data System (ADS)

Liu, Na; Sun, Yi; Wang, Guang-Wei; Mi, Zheng-Hui; Lin, Hai-Ying; Wang, Qun-Yao; Liu, Rong; Ma, Xin-Peng

2016-09-01

A new tuner control system for spoke superconducting radio frequency (SRF) cavities has been developed and applied to cryomodule I of the C-ADS injector I at the Institute of High Energy Physics, Chinese Academy of Sciences. We have successfully implemented the tuner controller based on Programmable Logic Controller (PLC) for the first time and achieved a cavity tuning phase error of ±0.7° (about ±4 Hz peak to peak) in the presence of electromechanical coupled resonance. This paper presents preliminary experimental results based on the PLC tuner controller under proton beam commissioning. Supported by Proton linac accelerator I of China Accelerator Driven sub-critical System (Y12C32W129)

Use of the CEBAF Accelerator for IR and UV Free Electron Lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yunn, Byung; Sinclair, Charles; Leemann, Christoph

1992-08-01

The CEBAF superconducting linac is capable of accelerating electron beams suitable for driving high-power free-electron lasers. The 45 MeV injector linac with a 6 cm period wiggler can produce kilowatt output powers of infrared light (3.6-17 micrometer), while the 400 MeV north linac can produce ultraviolet light (~200 nm) at similar powers. The FELs require the addition of a high-peak intensity electron source (~ 60 A peak current) and extraction beam lines to wigglers with appropriate electron and photon optics. FEL operation is compatible with simultaneous baseline CEBAF nuclear physics operation. A design for a CEBAF-based FEL facility has beenmore » developed. The current status of the FEL project is reported.« less

An Adiabatic Phase-Matching Accelerator

DOE PAGES

Lemery, Francois; Floettmann, Klaus; Piot, Philippe; ...

2018-05-25

We present a general concept to accelerate non-relativistic charged particles. Our concept employs an adiabatically-tapered dielectric-lined waveguide which supports accelerating phase velocities for synchronous acceleration. We propose an ansatz for the transient field equations, show it satisfies Maxwell's equations under an adiabatic approximation and find excellent agreement with a finite-difference time-domain computer simulation. The fields were implemented into the particle-tracking program {\\sc astra} and we present beam dynamics results for an accelerating field with a 1-mm-wavelength and peak electric field of 100~MV/m. The numerical simulations indicate that amore » $$\\sim 200$$-keV electron beam can be accelerated to an energy of $$\\sim10$$~MeV over $$\\sim 10$$~cm. The novel scheme is also found to form electron beams with parameters of interest to a wide range of applications including, e.g., future advanced accelerators, and ultra-fast electron diffraction.« less

Synchronous acceleration with tapered dielectric-lined waveguides

DOE PAGES

Lemery, Francois; Floettmann, Klaus; Piot, Philippe; ...

2018-05-25

Here, we present a general concept to accelerate non-relativistic charged particles. Our concept employs an adiabatically-tapered dielectric-lined waveguide which supports accelerating phase velocities for synchronous acceleration. We propose an ansatz for the transient field equations, show it satisfies Maxwell's equations under an adiabatic approximation and find excellent agreement with a finite-difference time-domain computer simulation. The fields were implemented into the particle-tracking program {\\sc astra} and we present beam dynamics results for an accelerating field with a 1-mm-wavelength and peak electric field of 100~MV/m. The numerical simulations indicate that amore » $$\\sim 200$$-keV electron beam can be accelerated to an energy of $$\\sim10$$~MeV over $$\\sim 10$$~cm. The novel scheme is also found to form electron beams with parameters of interest to a wide range of applications including, e.g., future advanced accelerators, and ultra-fast electron diffraction.« less

Guided post-acceleration of laser-driven ions by a miniature modular structure

PubMed Central

Kar, Satyabrata; Ahmed, Hamad; Prasad, Rajendra; Cerchez, Mirela; Brauckmann, Stephanie; Aurand, Bastian; Cantono, Giada; Hadjisolomou, Prokopis; Lewis, Ciaran L. S.; Macchi, Andrea; Nersisyan, Gagik; Robinson, Alexander P. L.; Schroer, Anna M.; Swantusch, Marco; Zepf, Matt; Willi, Oswald; Borghesi, Marco

2016-01-01

All-optical approaches to particle acceleration are currently attracting a significant research effort internationally. Although characterized by exceptional transverse and longitudinal emittance, laser-driven ion beams currently have limitations in terms of peak ion energy, bandwidth of the energy spectrum and beam divergence. Here we introduce the concept of a versatile, miniature linear accelerating module, which, by employing laser-excited electromagnetic pulses directed along a helical path surrounding the laser-accelerated ion beams, addresses these shortcomings simultaneously. In a proof-of-principle experiment on a university-scale system, we demonstrate post-acceleration of laser-driven protons from a flat foil at a rate of 0.5 GeV m−1, already beyond what can be sustained by conventional accelerator technologies, with dynamic beam collimation and energy selection. These results open up new opportunities for the development of extremely compact and cost-effective ion accelerators for both established and innovative applications. PMID:27089200

An Adiabatic Phase-Matching Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemery, Francois; Floettmann, Klaus; Piot, Philippe

2017-12-22

We present a general concept to accelerate non-relativistic charged particles. Our concept employs an adiabatically-tapered dielectric-lined waveguide which supports accelerating phase velocities for synchronous acceleration. We propose an ansatz for the transient field equations, show it satisfies Maxwell's equations under an adiabatic approximation and find excellent agreement with a finite-difference time-domain computer simulation. The fields were implemented into the particle-tracking program {\\sc astra} and we present beam dynamics results for an accelerating field with a 1-mm-wavelength and peak electric field of 100~MV/m. The numerical simulations indicate that amore » $$\\sim 200$$-keV electron beam can be accelerated to an energy of $$\\sim10$$~MeV over $$\\sim 10$$~cm. The novel scheme is also found to form electron beams with parameters of interest to a wide range of applications including, e.g., future advanced accelerators, and ultra-fast electron diffraction.« less

Experiment on interface separation detection of concrete-filled steel tubular arch bridge using accelerometer array

NASA Astrophysics Data System (ADS)

Pan, Shengshan; Zhao, Xuefeng; Zhao, Hailiang; Mao, Jian

2015-04-01

Based on the vibration testing principle, and taking the local vibration of steel tube at the interface separation area as the study object, a real-time monitoring and the damage detection method of the interface separation of concrete-filled steel tube by accelerometer array through quantitative transient self-excitation is proposed. The accelerometers are arranged on the steel tube area with or without void respectively, and the signals of accelerometers are collected at the same time and compared under different transient excitation points. The results show that compared with the signal of compact area, the peak value of accelerometer signal at void area increases and attenuation speed slows down obviously, and the spectrum peaks of the void area are much more and disordered and the amplitude increases obviously. whether the input point of transient excitation is on void area or not is irrelevant with qualitative identification results. So the qualitative identification of the interface separation of concrete-filled steel tube based on the signal of acceleration transducer is feasible and valid.

Improving maximum power point tracking of partially shaded photovoltaic system by using IPSO-BELBIC

NASA Astrophysics Data System (ADS)

Al-Alim El-Garhy, M. Abd; Mubarak, R. I.; El-Bably, M.

2017-08-01

Solar photovoltaic (PV) arrays in remote applications are often related to the rapid changes in the partial shading pattern. Rapid changes of the partial shading pattern make the tracking of maximum power point (MPP) of the global peak through the local ones too difficult. An essential need to make a fast and efficient algorithm to detect the peaks values which always vary as the sun irradiance changes. This paper presents two algorithms based on the improved particle swarm optimization technique one of them with PID controller (IPSO-PID), and the other one with Brain Emotional Learning Based Intelligent Controller (IPSO-BELBIC). These techniques improve the maximum power point (MPP) tracking capabilities for photovoltaic (PV) system under partial shading circumstances. The main aim of these improved algorithms is to accelerate the velocity of IPSO to reach to (MPP) and increase its efficiency. These algorithms also improve the tracking time under complex irradiance conditions. Based on these conditions, the tracking time of these presented techniques improves to 2 msec, with an efficiency of 100%.

Yielding of tantalum at strain rates up to 10{sup 9 }s{sup −1}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crowhurst, Jonathan C., E-mail: crowhurst1@llnl.gov; Armstrong, Michael R., E-mail: armstrong30@llnl.gov; Gates, Sean D.

2016-08-29

We have used a 45 μJ laser pulse to accelerate the free surface of fine-grained tantalum films up to peak velocities of ∼1.2 km s{sup −1}. The films had thicknesses of ∼1–2 μm and in-plane grain widths of ∼75–150 nm. Using ultrafast interferometry, we have measured the time history of the velocity of the surface at different spatial positions across the accelerated region. The initial part of the histories (assumed to correspond to the “elastic precursor” observed previously) exhibited measured strain rates of ∼0.6 to ∼3.2 × 10{sup 9 }s{sup −1} and stresses of ∼4 to ∼22 GPa. Importantly, we find that elastic amplitudes exhibit littlemore » variation with strain rate for a constant peak surface velocity, even though, via covariation of the strain rate with peak surface velocity, they vary with strain rate. Furthermore, by comparison with data obtained at lower strain rates, we find that amplitudes are much better predicted by peak velocities rather than by either strain rate or sample thickness.« less

The effects of exogenous hormones on rooting process and the activities of key enzymes of Malus hupehensis stem cuttings.

PubMed

Zhang, Wangxiang; Fan, Junjun; Tan, Qianqian; Zhao, Mingming; Zhou, Ting; Cao, Fuliang

2017-01-01

Malus hupehensis is an excellent Malus rootstock species, known for its strong adverse-resistance and apomixes. In the present study, stem cuttings of M. hupehensis were treated with three types of exogenous hormones, including indole acetic acid (IAA), naphthalene acetic acid (NAA), or green growth regulator (GGR). The effects and mechanisms of exogenous hormone treatment and antioxidant enzyme activity on adventitious root formation were investigated. The results showed that the apparent morphology of the adventitious root had four stages, including root pre-emergence stage (S0), early stage of root formation (S1), massive root formation stage (S2), and later stage of root formation (S3). The suitable concentrations of the three exogenous hormones, IAA, NAA and GGR, were 100 mg·L-1, 300 mg·L-1, and 300 mg·L-1, respectively. They shortened the rooting time by 25-47.4% and increased the rooting percentages of cuttings by 0.9-1.3 times, compared with that in the control. The dispersion in S0 stage was 3.6 times of that in the S1 stage after exogenous hormone application. The earlier the third critical point (P3) appeared, the shorter the rooting time and the greater the rooting percentage of the cuttings. During rhizogenesis, the activities of three antioxidant enzymes (POD, SOD, and PPO) showed an A-shaped trend. However, peak values of enzyme activity appeared at different points, which were 9 d before the P3, P3, and the fourth critical point (P4), respectively. Exogenous hormone treatment reduced the time to reach the peak value by 18 days, although the peak values of the enzymatic activities did not significantly changed. Our results suggested that exogenous hormone treatment mainly acted during the root pre-emergence stage, accelerated the synthesis of antioxidant enzymes, reduced the rooting time, and consequently promoted root formation. The three kinds of antioxidant enzymes acted on different stages of rooting.

Two-dimensional angular energy spectrum of electrons accelerated by the ultra-short relativistic laser pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borovskiy, A. V.; Galkin, A. L.; Department of Physics of MBF, Pirogov Russian National Research Medical University, 1 Ostrovitianov Street, Moscow 117997

The new method of calculating energy spectra of accelerated electrons, based on the parameterization by their initial coordinates, is proposed. The energy spectra of electrons accelerated by Gaussian ultra-short relativistic laser pulse at a selected angle to the axis of the optical system focusing the laser pulse in a low density gas are theoretically calculated. The two-peak structure of the electron energy spectrum is obtained. Discussed are the reasons for its appearance as well as an applicability of other models of the laser field.

A Consistent Wave Impact Load Model for Studying Structure, Equipment Ruggedness, Shock Isolation Seats, and Human Comfort in Small High Speed Craft

DTIC Science & Technology

2016-11-01

acceleration at a cross-section was used as a measure of the wave impact load in units of g. Later developments included publication of the envelope...Republic, 4 – 7 October 2004. PICKFORD, E.V., MAHONE, R.R., WOLK, H.L. (1975). Slam/Shock Isolation Pedestal, United States Patent Number, 3,912,248, 14...accelerations. The rigid body peak acceleration is a measure of the impact load in units of g. In the following plots the data corresponds to head-sea

Effects of Variable Resistance Using Chains on Bench Throw Performance in Trained Rugby Players.

PubMed

Godwin, Mark S; Fernandes, John F T; Twist, Craig

2018-04-01

Godwin, MS, Fernandes, JFT, and Twist, C. Effects of variable resistance using chains on bench throw performance in trained rugby players. J Strength Cond Res 32(4): 950-954, 2018-This study sought to determine the effects of variable resistance using chain resistance on bench throw performance. Eight male rugby union players (19.4 ± 2.3 years, 88.8 ± 6.0 kg, 1RM 105.6 ± 17.0 kg) were recruited from a national league team. In a randomized crossover design, participant's performed 3 bench throws at 45% one repetition maximum (1RM) at a constant load (no chains) or a variable load (30% 1RM constant load and 15% 1RM variable load; chains) with 7 days between conditions. For each repetition, the peak and mean velocity, peak power, peak acceleration, and time to peak velocity were recorded. Differences in peak and mean power were very likely trivial and unclear between the chain and no chain conditions, respectively. Possibly greater peak and likely greater mean bar velocity were accompanied by likely to most likely greater bar velocity between 50 and 400 ms from initiation of bench press in the chain condition compared with the no chain condition. Accordingly, bar acceleration was very likely greater in the chain condition compared with the no chain condition. In conclusion, these results show that the inclusion of chain resistance can acutely enhance several variables in the bench press throw and gives support to this type of training.

Monitoring of degradation of porous silicon photonic crystals using digital photography

PubMed Central

2014-01-01

We report the monitoring of porous silicon (pSi) degradation in aqueous solutions using a consumer-grade digital camera. To facilitate optical monitoring, the pSi samples were prepared as one-dimensional photonic crystals (rugate filters) by electrochemical etching of highly doped p-type Si wafers using a periodic etch waveform. Two pSi formulations, representing chemistries relevant for self-reporting drug delivery applications, were tested: freshly etched pSi (fpSi) and fpSi coated with the biodegradable polymer chitosan (pSi-ch). Accelerated degradation of the samples in an ethanol-containing pH 10 aqueous basic buffer was monitored in situ by digital imaging with a consumer-grade digital camera with simultaneous optical reflectance spectrophotometric point measurements. As the nanostructured porous silicon matrix dissolved, a hypsochromic shift in the wavelength of the rugate reflectance peak resulted in visible color changes from red to green. While the H coordinate in the hue, saturation, and value (HSV) color space calculated using the as-acquired photographs was a good monitor of degradation at short times (t < 100 min), it was not a useful monitor of sample degradation at longer times since it was influenced by reflections of the broad spectral output of the lamp as well as from the narrow rugate reflectance band. A monotonic relationship was observed between the wavelength of the rugate reflectance peak and an H parameter value calculated from the average red-green-blue (RGB) values of each image by first independently normalizing each channel (R, G, and B) using their maximum and minimum value over the time course of the degradation process. Spectrophotometric measurements and digital image analysis using this H parameter gave consistent relative stabilities of the samples as fpSi > pSi-ch. PMID:25242902

Transthoracic Coronary Flow Data at Rest Predict High-Risk Stress Tests.

PubMed

Zagatina, Angela; Zhuravskaya, Nadezhda; Vareldzhyan, Yuliya; Kamenskikh, Maxim; Shmatov, Dmitry; Benacka, Jozef; Kucera, Martin; Kruzliak, Peter

2018-06-01

Background Several recent studies have reported the opportunity to diagnose significant narrowing of the coronary arteries without stress testing using local flow acceleration. Purpose To define how often patients with increased coronary flow velocities at rest (≥ 0.70 m/s) have a positive exercise echocardiography test. Material and Methods A total of 150 patients scheduled for exercise echocardiography were studied using transthoracic Doppler echocardiography in order to assess coronary artery flow velocity before exercise. Pulsed wave Doppler registered blood flow velocity placed on the color signal. The maximal diastolic velocity of coronary flow was measured. Results Of participants, 16% had a velocity of more than 0.70 m/s in the left main/proximal left anterior/proximal left circumflex arteries (LM/pLAD). A significant correlation was observed between the value of the maximal velocity in LM/pLAD and the ejection fraction at the peak of exercise ( r ≈ -0.39, P < 0.0001); between the value of the maximal velocity in LM/pLAD and index of wall motion abnormalities (IWMA) at the peak of exercise ( r ≈ 0.44, P < 0.0001); and between the value of the maximal velocity in LM/pLAD and dIWMA ( r ≈ 0.41, P < 0.0001). Afterwards, severe ischemia in stress echocardiography tests was observed in this group. The average IWMA of these tests was found to be 2.3. Sixty-two angiograms were available for comparison with Doppler data. Conclusion There is a significant correlation between the value of the maximal velocity in LM/pLAD/pLCx at rest and the severity of wall motion abnormalities during exercise tests.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hogan, Mark

Plasma wakefield acceleration has the potential to dramatically shrink the size and cost of particle accelerators. Research at the SLAC National Accelerator Laboratory has demonstrated that plasmas can provide 1,000 times the acceleration in a given distance compared with current technologies. Developing revolutionary and more efficient acceleration techniques that allow for an affordable high-energy collider is the focus of FACET, a National User Facility at SLAC. The existing FACET National User Facility uses part of SLAC’s two-mile-long linear accelerator to generate high-density beams of electrons and positrons. FACET-II is a new test facility to develop advanced acceleration and coherent radiationmore » techniques with high-energy electron and positron beams. It is the only facility in the world with high energy positron beams. FACET-II provides a major upgrade over current FACET capabilities and the breadth of the potential research program makes it truly unique. It will synergistically pursue accelerator science that is vital to the future of both advanced acceleration techniques for High Energy Physics, ultra-high brightness beams for Basic Energy Science, and novel radiation sources for a wide variety of applications. The design parameters for FACET-II are set by the requirements of the plasma wakefield experimental program. To drive the plasma wakefield requires a high peak current, in excess of 10kA. To reach this peak current, the electron and positron design bunch size is 10μ by 10μ transversely with a bunch length of 10μ. This is more than 200 times better than what has been achieved at the existing FACET. The beam energy is 10 GeV, set by the Linac length available and the repetition rate is up to 30 Hz. The FACET-II project is scheduled to be constructed in three major stages. Components of the project discussed in detail include the following: electron injector, bunch compressors and linac, the positron system, the Sector 20 sailboat and W chicanes, and experimental area and infrastructure.« less

Generation and application of ultrashort coherent mid-infrared electromagnetic radiation

NASA Astrophysics Data System (ADS)

Wandel, Scott

Particle accelerators are useful instruments that help address critical issues for the future development of nuclear energy. Current state-of-the-art accelerators based on conventional radio-frequency (rf) cavities are too large and expensive for widespread commercial use, and alternative designs must be considered for supplying relativistic beams to small-scale applications, including medical imaging, secu- rity screening, and scientific research in a university-scale laboratory. Laser-driven acceleration using micro-fabricated dielectric photonic structures is an attractive approach because such photonic microstructures can support accelerating fields that are 10 to 100 times higher than that of rf cavity-based accelerators. Dielectric laser accelerators (DLAs) use commercial lasers as a driving source, which are smaller and less expensive than the klystrons used to drive current rf-based accelerators. Despite the apparent need for compact and economical laser sources for laser-driven acceleration, the availability of suitable high-peak-power lasers that cover a broad spectral range is currently limited. To address the needs of several innovative acceleration mechanisms like DLA, it is proposed to develop a coherent source of mid-infrared (IR) electromagnetic radiation that can be implemented as a driving source of laser accelerators. The use of ultrashort mid-IR high peak power laser systems in various laser-driven acceleration schemes has shown the potential to greatly reduce the optical pump intensities needed to realize high acceleration gradients. The optical intensity needed to achieve a given ponderomotive potential is 25 times less when using a 5-mum mid-IR laser as compared to using a 1-mum near-IR solid-state laser. In addition, dielectric structure breakdown caused by multiphoton ionization can be avoided by using longer-wavelength driving lasers. Current mid-IR laser sources do not produce sufficiently short pulse durations, broad spectral bandwidths, or high energies as required by certain accelerator applications. The use of a high-peak-power mid-IR laser system in DLA could enable tabletop accelerators on the MeV to GeV scale for security scanners, medical therapy devices, and compact x-ray light sources. This dissertation reports on the design and construction of a simple and robust, short-pulse parametric source operating at a center wavelength of 5 mum. The design and construction of a high-energy, short-pulse 2-mum parametric source is also presented, which serves as a surrogate pumping source for the 5-mum source. An elegant method for mid-IR pulse characterization is demonstrated, which makes use of ubiquitous silicon photodetectors, traditionally reserved for the characterization of near-IR radiation. In addition, a dual-chirped parametric amplification technique is extended into the mid-IR spectral region, producing a bandwidth-tunable mid-IR source in a simple design without sacrificing conversion efficiency. The design and development of a compact single-shot mid-IR prism spectrometer is also reported, and its implementation in a number of condensed matter studies at the Linac Coherent Light Source (LCLS) at the Stanford Linear Accelerator Center is discussed. Rapid tuning and optimization of a high-energy parametric laser system using the mid-IR spectrometer is demonstrated, which significantly enhances the capabilities of performing optical measurements on superconducting materials using the LCLS instrument. All of the laser sources and optical technologies presented in this dissertation were developed using relatively simple designs to provide compact and cost-e ective systems to address some of the challenges facing accelerator and IR spectroscopy technologies. (Abstract shortened by ProQuest.).

Optimization of seismic isolation systems via harmony search

NASA Astrophysics Data System (ADS)

Melih Nigdeli, Sinan; Bekdaş, Gebrail; Alhan, Cenk

2014-11-01

In this article, the optimization of isolation system parameters via the harmony search (HS) optimization method is proposed for seismically isolated buildings subjected to both near-fault and far-fault earthquakes. To obtain optimum values of isolation system parameters, an optimization program was developed in Matlab/Simulink employing the HS algorithm. The objective was to obtain a set of isolation system parameters within a defined range that minimizes the acceleration response of a seismically isolated structure subjected to various earthquakes without exceeding a peak isolation system displacement limit. Several cases were investigated for different isolation system damping ratios and peak displacement limitations of seismic isolation devices. Time history analyses were repeated for the neighbouring parameters of optimum values and the results proved that the parameters determined via HS were true optima. The performance of the optimum isolation system was tested under a second set of earthquakes that was different from the first set used in the optimization process. The proposed optimization approach is applicable to linear isolation systems. Isolation systems composed of isolation elements that are inherently nonlinear are the subject of a future study. Investigation of the optimum isolation system parameters has been considered in parametric studies. However, obtaining the best performance of a seismic isolation system requires a true optimization by taking the possibility of both near-fault and far-fault earthquakes into account. HS optimization is proposed here as a viable solution to this problem.

Blast-Induced Acceleration in a Shock Tube: Distinguishing Primary and Tertiary Blast Injury

DTIC Science & Technology

2015-10-01

these well-defined exposure conditions, anesthetized rats are used to simultaneously record intracranial pressure (ICP), intravascular pressure , and...blast flow conditions (e.g. peak static and total pressure , positive phase duration, and impulse) and acceleration and displacement of a wide range of...resultant pressure responses in varied compartments in concert with the neuropathological, neurochemical, and neurobehavioral consequences of exposures

The magnitude of translational and rotational head accelerations experienced by riders during downhill mountain biking.

PubMed

Hurst, Howard T; Atkins, Stephen; Dickinson, Ben D

2018-03-21

To determine the magnitude of translational and rotational head accelerations during downhill mountain biking. Observational study. Sixteen male downhill cyclists (age 26.4±8.4years; stature 179.4±7.2cm; mass 75.3±5.9kg) were monitored during two rounds of the British Downhill Series. Riders performed two runs on each course wearing a triaxial accelerometer behind the right ear. The means of the two runs for each course were used to determine differences between courses for mean and maximum peak translational (g) and rotational accelerations (rad/s 2 ) and impact duration for each course. Significant differences (p<0.05) were revealed for the mean number of impacts (>10g), FW=12.5±7.6, RYF=42.8±27.4 (t (22.96) =-4.70; p<0.001; 95% CI=17.00 to 43.64); maximum peak rotational acceleration, FW=6805.4±3073.8rad/s 2 , RYF=9799.9±3381.7rad/s 2 (t (32) =-2.636; p=0.01; 95% CI=680.31 to 5308.38); mean acceleration duration FW=4.7±1.2ms, RYF=6.5±1.4ms (t (32) =-4.05; p<0.001; 95% CI=0.91 to 2.76) and maximum acceleration duration, FW=11.6±4.5ms, RYF=21.2±9.1 (t (29.51) =-4.06; p=0.001; 95% CI=4.21 to 14.94). No other significant differences were found. Findings indicate that downhill riders may be at risk of sustaining traumatic brain injuries and course design influences the number and magnitude of accelerations. Copyright © 2018 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Instrumental intensity distribution for the Hector Mine, California, and the Chi-Chi, Taiwan, earthquakes: Comparison of two methods

USGS Publications Warehouse

Sokolov, V.; Wald, D.J.

2002-01-01

We compare two methods of seismic-intensity estimation from ground-motion records for the two recent strong earthquakes: the 1999 (M 7.1) Hector Mine, California, and the 1999 (M 7.6) Chi-Chi, Taiwan. The first technique utilizes the peak ground acceleration (PGA) and velocity (PGV), and it is used for rapid generation of the instrumental intensity map in California. The other method is based on the revised relationships between intensity and Fourier amplitude spectrum (FAS). The results of using the methods are compared with independently observed data and between the estimations from the records. For the case of the Hector Mine earthquake, the calculated intensities in general agree with the observed values. For the case of the Chi-Chi earthquake, the areas of maximum calculated intensity correspond to the areas of the greatest damage and highest number of fatalities. However, the FAS method producees higher-intensity values than those of the peak amplitude method. The specific features of ground-motion excitation during the large, shallow, thrust earthquake may be considered a reason for the discrepancy. The use of PGA and PGV is simple; however, the use of FAS provides a natural consideration of site amplification by means of generalized or site-specific spectral ratios. Because the calculation of seismic-intensity maps requires rapid processing of data from a large network, it is very practical to generate a "first-order" map from the recorded peak motions. Then, a "second-order" map may be compiled using an amplitude-spectra method on the basis of available records and numerical modeling of the site-dependent spectra for the regions of sparse station spacing.

NCAP test improvements with pretensioners and load limiters.

PubMed

Walz, Marie

2004-03-01

New Car Assessment Program (NCAP) test scores, measured by the United States Department of Transportation's (USDOT) National Highway Traffic Safety Administration (NHTSA), were analyzed in order to assess the benefits of equipping safety belt systems with pretensioners and load limiters. Safety belt pretensioners retract the safety belt almost instantly in a crash to remove excess slack. They tie the occupant to the vehicle's deceleration early during the crash, reducing the peak load experienced by the occupant. Load limiters and other energy management systems allow safety belts to yield in a crash, preventing the shoulder belt from directing too much energy on the chest of the occupant. In NCAP tests, vehicles are crashed into a fixed barrier at 35 mph. During the test, instruments measure the accelerations of the head and chest, as well as the force on the legs of anthropomorphic dummies secured in the vehicle by safety belts. NCAP data from model year 1998 through 2001 cars and light trucks were examined. The combination of pretensioners and load limiters is estimated to reduce Head Injury Criterion (HIC) by 232, chest acceleration by an average of 6.6 g's, and chest deflection (displacement) by 10.6 mm, for drivers and right front passengers. The unit used to measure chest acceleration (g) is defined as a unit of force equal to the force exerted by gravity. All of these reductions are statistically significant. When looked at individually, pretensioners are more effective in reducing HIC scores for both drivers and right front passengers, as well as chest acceleration and chest deflection scores for drivers. Load limiters show greater reductions in chest acceleration and chest deflection scores for right front passengers. By contrast, in make-models for which neither load limiters nor pretensioners have been added, there is little change during 1998 to 2001 in HIC, chest acceleration, or chest deflection values in NCAP tests.

Proof-of-principle demonstration of Nb3Sn superconducting radiofrequency cavities for high Q0 applications

NASA Astrophysics Data System (ADS)

Posen, S.; Liepe, M.; Hall, D. L.

2015-02-01

Many future particle accelerators require hundreds of superconducting radiofrequency (SRF) cavities operating with high duty factor. The large dynamic heat load of the cavities causes the cryogenic plant to make up a significant part of the overall cost of the facility. This contribution can be reduced by replacing standard niobium cavities with ones coated with a low-dissipation superconductor such as Nb3Sn. In this paper, we present results for single cell cavities coated with Nb3Sn at Cornell. Five coatings were carried out, showing that at 4.2 K, high Q0 out to medium fields was reproducible, resulting in an average quench field of 14 MV/m and an average 4.2 K Q0 at quench of 8 × 109. In each case, the peak surface magnetic field at quench was well above Hc1, showing that it is not a limiting field in these cavities. The coating with the best performance had a quench field of 17 MV/m, exceeding gradient requirements for state-of-the-art high duty factor SRF accelerators. It is also shown that—taking into account the thermodynamic efficiency of the cryogenic plant—the 4.2 K Q0 values obtained meet the AC power consumption requirements of state-of-the-art high duty factor accelerators, making this a proof-of-principle demonstration for Nb3Sn cavities in future applications.

Intense laser pulse propagation in capillary discharge plasma channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hubbard, R. F.; Moore, C. I.; Sprangle, P.

Optical guiding of intense laser pulses is required for plasma-based accelerator concepts such as the laser wakefield accelerator. Reported experiments have successfully transported intense laser pulses in the hollow plasma column produced by a capillary discharge. The hollow plasma has an index of refraction which peaks on-axis, thus providing optical guiding which overcomes beam expansion due to diffraction. In more recent experiments at Hebrew University, 800 nm wavelength, 0.1 mJ, 100 fs pulses have been guided in {approx}300 micron radius capillaries over distances as long as 6.6 cm. Simulations of these experiments using a 2-D nonlinear laser propagation model producemore » the expected optical guiding, with the laser pulse radius r{sub L} exhibiting oscillations about the equilibrium value predicted by an analytical envelope equation model. The oscillations are damped at the front of the pulse and grow in amplitude in the back of the pulse. This growth and damping is attributed to finite pulse length effects. Simulations also show that further ionization of the discharge plasma by the laser pulse may hollow the laser pulse and introduce modulations in the spot size. This ionization-defocusing effect is expected to be significant at the high intensities required for accelerator application. Capillary discharge experiments at much higher intensities are in progress on the Naval Research Laboratory T{sup 3} laser, and preliminary results are reported.« less

Neck injury criteria formulation and injury risk curves for the ejection environment: a pilot study.

PubMed

Parr, Jeffrey C; Miller, Michael E; Pellettiere, Joseph A; Erich, Roger A

2013-12-01

Helmet mounted displays provide increased pilot capability, but can also increase the risk of injury during ejection. The National Highway Transportation Safety Administration's (NHTSA's) neck injury criteria (Nij) metric is evaluated for understanding the impact of helmet mass on the risk of injury and modified risk curves are developed which are compatible with the needs of the aviation community. Existent human subject data collected under various accelerative and head loading conditions were applied to understand the sensitivity of the Nij construct to changes in acceleration and helmet mass, as well as its stability with respect to gender, body mass, neck circumference, and sitting height. A portion of this data was combined with data from an earlier postmortem human subject study to create pilot study modified risk curves. These curves were compared and contrasted with the NHTSA risk curves. A statistically significant difference in the peak mean Nij was observed when seat acceleration increased by 2 G, but not when helmet mass was varied from 1.6 kg to 2 kg at a constant seat acceleration of 8 G. Although NHTSA risk curves predict a 13% risk of AIS 2+ injury for the 8-G, 2-kg helmet condition mean Nij of 0.138, no AIS 2+ injuries were observed. Modified risk curves were produced which predict a 0.91% risk of AIS 2+ injury under these conditions. The Nij was shown to be sensitive to changes in acceleration and generally robust to anthropometric differences between individuals. Modified risk curves are proposed which improve risk prediction at lower Nij values.

Mechanisms Underlying Isovolumic Contraction and Ejection Peaks in Seismocardiogram Morphology

PubMed Central

Gurev, Viatcheslav; Tavakolian, Kouhyar; Constantino, Jason; Kaminska, Bozena; Blaber, Andrew P.; Trayanova, Natalia A.

2012-01-01

A three-dimensional (3D) finite element electromechanical model of the heart is employed in simulations of seismocardiograms (SCGs). To simulate SCGs, a previously developed 3D model of ventricular contraction is extended by adding the mechanical interaction of the heart with the chest and internal organs. The proposed model reproduces the major peaks of seismocardiographic signals during the phases of the cardiac cycle. Results indicate that SCGs record the pressure of the heart acting on the ribs. In addition, the model reveals that the rotation of the rib with respect to the heart has a minor effect on seismocardiographic signal morphology during the respiratory cycle. SCGs are obtained from 24 human volunteers and their morphology is analyzed. Experimental results demonstrate that the peak of the maximum acceleration of blood in the aorta occurs at the same time as the global minimum of the SCG. It is confirmed that the first SCG peak after the electrocardiogram R-wave corresponds to aortic valve opening, as determined from the impedance cardiogram (p = 0.92). The simulation results reveal that the SCG peaks corresponding to aortic valve opening and the maximum acceleration of blood in the aorta result from ventricular contraction in the longitudinal direction of the ventricles and a decrease in the dimensions of the ventricles due to the ejection of blood, respectively. PMID:23105942

Intelligent peak deconvolution through in-depth study of the data matrix from liquid chromatography coupled with a photo-diode array detector applied to pharmaceutical analysis.

PubMed

Arase, Shuntaro; Horie, Kanta; Kato, Takashi; Noda, Akira; Mito, Yasuhiro; Takahashi, Masatoshi; Yanagisawa, Toshinobu

2016-10-21

Multivariate curve resolution-alternating least squares (MCR-ALS) method was investigated for its potential to accelerate pharmaceutical research and development. The fast and efficient separation of complex mixtures consisting of multiple components, including impurities as well as major drug substances, remains a challenging application for liquid chromatography in the field of pharmaceutical analysis. In this paper we suggest an integrated analysis algorithm functioning on a matrix of data generated from HPLC coupled with photo-diode array detector (HPLC-PDA) and consisting of the mathematical program for the developed multivariate curve resolution method using an expectation maximization (EM) algorithm with a bidirectional exponentially modified Gaussian (BEMG) model function as a constraint for chromatograms and numerous PDA spectra aligned with time axis. The algorithm provided less than ±1.0% error between true and separated peak area values at resolution (R s ) of 0.6 using simulation data for a three-component mixture with an elution order of a/b/c with similarity (a/b)=0.8410, (b/c)=0.9123 and (a/c)=0.9809 of spectra at peak apex. This software concept provides fast and robust separation analysis even when method development efforts fail to achieve complete separation of the target peaks. Additionally, this approach is potentially applicable to peak deconvolution, allowing quantitative analysis of co-eluted compounds having exactly the same molecular weight. This is complementary to the use of LC-MS to perform quantitative analysis on co-eluted compounds using selected ions to differentiate the proportion of response attributable to each compound. Copyright © 2016 Elsevier B.V. All rights reserved.

ANTICIPATORY POSTURAL ADJUSTMENTS PRIOR TO STEP INITIATION ARE HYPOMETRIC IN UNTREATED PARKINSON'S DISEASE: AN ACCELEROMETER-BASED APPROACH

PubMed Central

Mancini, Martina; Zampieri, Cris; Carlson-Kuhta, Patricia; Chiari, Lorenzo; Horak, Fay B.

2010-01-01

Background and purpose Anticipatory postural adjustments (APAs), prior to step initiation, are bradykinetic in advanced Parkinson's disease (PD) and may be one of the factors associated with ‘start hesitation’. However, little is known about APAs in the early stage of PD. In this study, we determined whether body-worn accelerometers could be used to characterize step initiation deficits in subjects with early-to-moderate, untreated PD. Methods Eleven PD and 12 healthy control subjects were asked to take two steps. Postural adjustments were compared from center of pressure (COP) and from acceleration of the trunk at the center of mass level (L5). Results Our findings show that APAs measured from the peak COP displacement towards the swing leg and the peak trunk acceleration towards the stance leg were smaller in untreated PD compared to control subjects. The magnitude of APAs measured from peak COP displacements and accelerations were correlated. Conclusion These results suggest that quantitative analysis of step initiation from one accelerometer on the trunk could provide useful information for the characterization of patients in early stages of PD, when clinical evidence of start hesitation may not be detectable. Ambulatory monitoring of step initiation is also promising for monitoring patient progression in the home environment, and eventually providing feedback for preventing freezing of gait episodes. PMID:19473350

Flow and turbulence structure in a hypertidal estuary with the world's biggest tidal bore

NASA Astrophysics Data System (ADS)

Tu, Junbiao; Fan, Daidu

2017-04-01

Turbulent and flow structure associated with breaking tidal bores are deliberately investigated on the basis of field measurements. High-resolution velocity and hydrographic data are collected in the middle Qiantang Estuary by a vertical array of acoustic Doppler velocimeters and optical backscatter sensors, collaborated with a bottom-mounted acoustic Doppler current profiler. Besides obvious variations in diurnal and spring-neap tidal cycles, the estuarine dynamics is featured by extreme asymmetry in flood and ebb tides. The flood tide is abnormally accelerated to generate tidal bores at the first 10 min or more, with breaking or undular configurations at the front. The occurrence of peak flow velocity, turbulent kinetic energy (TKE), and TKE dissipation rate (ɛ) is definitely associated with breaking bores, with their values several times to 2 orders of magnitude larger than the corresponding secondary peak values during the maximum ebb flows. Flow and turbulence dynamics are significantly affected by the tidal-bore Froude number. A sandwich ɛ structure is clear exhibited with the maximum value at the surface, secondary maximum near the bed, and the minimum at the intermediate. Dual TKE sources are indicated by an approximate local balance between shear production and dissipation near the bottom, and a top-down TKE dissipation using the modified Froude scaling in the vertical water column. The highly elevated dissipation by breaking bores is comparable to that by intense breaking waves in the surf zone, and the former potentially penetrates the entire water column to produce extreme sediment-resuspension events in combination with intense bottom shear stress.

Improving particle beam acceleration in plasmas

NASA Astrophysics Data System (ADS)

C. de Sousa, M.; L. Caldas, I.

2018-04-01

The dynamics of wave-particle interactions in magnetized plasmas restricts the wave amplitude to moderate values for particle beam acceleration from rest energy. We analyze how a perturbing invariant robust barrier modifies the phase space of the system and enlarges the wave amplitude interval for particle acceleration. For low values of the wave amplitude, the acceleration becomes effective for particles with initial energy close to the rest energy. For higher values of the wave amplitude, the robust barrier controls chaos in the system and restores the acceleration process. We also determine the best position for the perturbing barrier in phase space in order to increase the final energy of the particles.

Note: A kinematic shaker system for high amplitude, low frequency vibration testing

NASA Astrophysics Data System (ADS)

Swaminathan, Anand; Poese, Matthew E.; Smith, Robert W. M.; Garrett, Steven L.

2015-11-01

This note describes a shaker system capable of high peak-velocity, large amplitude, low frequency, near-sinusoidal excitation that has been constructed and employed in experiments on the inhibition of Rayleigh-Bénard convection using acceleration modulation. The production of high peak-velocity vibration is of interest in parametric excitation problems of this type and reaches beyond the capabilities of standard electromagnetic shakers. The shaker system described employs a kinematic linkage to two counter-rotating flywheels, driven by a variable-speed electrical motor, producing peak-to-peak displacements of 15.24 cm to a platform mounted on two guide rails. In operation, this shaker has been demonstrated to produce peak speeds of up to 3.7 m/s without failure.

Muscle fatigue effects can be anticipated to reproduce a movement kinematics learned without fatigue.

PubMed

Monjo, Florian; Forestier, Nicolas

2016-12-17

Muscle fatigue modifies the gain between motor command magnitude and the mechanical muscular response. In other words, post-fatigue, central drives to the muscles must increase to maintain a particular submaximum mechanical output. In this study, we tested the hypothesis that this modified gain can be predicted by the central nervous system (CNS) during discrete ballistic movements. In two separate experiments, subjects were required to perform shoulder flexions in standing and sitting positions at submaximum target peak accelerations. They were assisted with visual feedback informing them on their performance after each trial. Shoulder flexions were performed before and after fatiguing protocols of the focal muscles. Acceleration signals, focal and postural muscle electromyograms (EMGs) were recorded. The results demonstrated that participants were able to reach with precision the target acceleration during the first movements post-fatigue at the cost of significant increase in focal motor command magnitude. Decreased variance of peak accelerations associated with increased focal command variability was observed post-fatigue. During the standing experiment, postural muscle EMGs revealed that anticipatory postural adjustments (APAs) scaled to focal movement acceleration post-fatigue. All these results support that fatigue effects are taken into account during movement planning. Indeed, given that no feedback could enable participants to adjust acceleration during movement, this capacity to anticipate fatigue effects is the exclusive result of feedforward processes. To account for this prediction capacity, we discuss the role of fatigue-related modifications in sensory inputs from the working muscles. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

Measurement of Impact Acceleration: Mouthpiece Accelerometer Versus Helmet Accelerometer

PubMed Central

Higgins, Michael; Halstead, P. David; Snyder-Mackler, Lynn; Barlow, David

2007-01-01

Context: Instrumented helmets have been used to estimate impact acceleration imparted to the head during helmet impacts. These instrumented helmets may not accurately measure the actual amount of acceleration experienced by the head due to factors such as helmet-to-head fit. Objective: To determine if an accelerometer attached to a mouthpiece (MP) provides a more accurate representation of headform center of gravity (HFCOG) acceleration during impact than does an accelerometer attached to a helmet fitted on the headform. Design: Single-factor research design in which the independent variable was accelerometer position (HFCOG, helmet, MP) and the dependent variables were g and Severity Index (SI). Setting: Independent impact research laboratory. Intervention(s): The helmeted headform was dropped (n = 168) using a National Operating Committee on Standards for Athletic Equipment (NOCSAE) drop system from the standard heights and impact sites according to NOCSAE test standards. Peak g and SI were measured for each accelerometer position during impact. Main Outcome Measures: Upon impact, the peak g and SI were recorded for each accelerometer location. Results: Strong relationships were noted for HFCOG and MP measures, and significant differences were seen between HFCOG and helmet g measures and HFCOG and helmet SI measures. No statistically significant differences were noted between HFCOG and MP g and SI measures. Regression analyses showed a significant relationship between HFCOG and MP measures but not between HFCOG and helmet measures. Conclusions: Upon impact, MP acceleration (g) and SI measurements were closely related to and more accurate in measuring HFCOG g and SI than helmet measurements. The MP accelerometer is a valid method for measuring head acceleration. PMID:17597937

Heavy ion acceleration in the radiation pressure acceleration and breakout afterburner regimes

NASA Astrophysics Data System (ADS)

Petrov, G. M.; McGuffey, C.; Thomas, A. G. R.; Krushelnick, K.; Beg, F. N.

2017-07-01

We present a theoretical study of heavy ion acceleration from ultrathin (20 nm) gold foil irradiated by high-intensity sub-picosecond lasers. Using two-dimensional particle-in-cell simulations, three laser systems are modeled that cover the range between femtosecond and picosecond pulses. By varying the laser pulse duration we observe a transition from radiation pressure acceleration (RPA) to the relativistic induced transparency (RIT) regime for heavy ions akin to light ions. The underlying physics of beam formation and acceleration is similar for light and heavy ions, however, nuances of the acceleration process make the heavy ions more challenging. A more detailed study involving variation of peak laser intensity I 0 and pulse duration τFWHM revealed that the transition point from RPA to RIT regime depends on the peak laser intensity on target and occurs for pulse duration {τ }{{F}{{W}}{{H}}{{M}}}{{R}{{P}}{{A}}\\to {{R}}{{I}}{{T}}}[{{f}}{{s}}]\\cong 210/\\sqrt{{I}0[{{W}} {{{cm}}}-2]/{10}21}. The most abundant gold ion and charge-to-mass ratio are Au51+ and q/M ≈ 1/4, respectively, half that of light ions. For ultrathin foils, on the order of one skin depth, we established a linear scaling of the maximum energy per nucleon (E/M)max with (q/M)max, which is more favorable than the quadratic one found previously. The numerical simulations predict heavy ion beams with very attractive properties for applications: high directionality (<10° half-angle), high fluxes (>1011 ions sr-1) and energy (>20 MeV/nucleon) from laser systems delivering >20 J of energy on target.

High-frequency ground motion amplification during the 2011 Tohoku earthquake explained by soil dilatancy

NASA Astrophysics Data System (ADS)

Roten, D.; Fäh, D.; Bonilla, L. F.

2013-05-01

Ground motions of the 2011 Tohoku earthquake recorded at Onahama port (Iwaki, Fukushima prefecture) rank among the highest accelerations ever observed, with the peak amplitude of the 3-D acceleration vector approaching 2g. The response of the site was distinctively non-linear, as indicated by the presence of horizontal acceleration spikes which have been linked to cyclic mobility during similar observations. Compared to records of weak ground motions, the response of the site during the Mw 9.1 earthquake was characterized by increased amplification at frequencies above 10 Hz and in peak ground acceleration. This behaviour contrasts with the more common non-linear response encountered at non-liquefiable sites, which results in deamplification at higher frequencies. We simulate propagation of SH waves through the dense sand deposit using a non-linear finite difference code that is capable of modelling the development of excess pore water pressure. Dynamic soil parameters are calibrated using a direct search method that minimizes the difference between observed and simulated acceleration envelopes and response spectra. The finite difference simulations yield surface acceleration time-series that are consistent with the observations in shape and amplitude, pointing towards soil dilatancy as a likely explanation for the high-frequency pulses recorded at Onahama port. The simulations also suggest that the occurrence of high-frequency spikes coincided with a rapid increase in pore water pressure in the upper part of the sand deposit between 145 and 170 s. This sudden increase is possibly linked to a burst of high-frequency energy from a large slip patch below the Iwaki region.

Quasi-monoenergetic proton acceleration from cryogenic hydrogen microjet by ultrashort ultraintense laser pulses

NASA Astrophysics Data System (ADS)

Sharma, A.; Tibai, Z.; Hebling, J.; Fülöp, J. A.

2018-03-01

Laser-driven proton acceleration from a micron-sized cryogenic hydrogen microjet target is investigated using multi-dimensional particle-in-cell simulations. With few-cycle (20-fs) ultraintense (2-PW) laser pulses, high-energy quasi-monoenergetic proton acceleration is predicted in a new regime. A collisionless shock-wave acceleration mechanism influenced by Weibel instability results in a maximum proton energy as high as 160 MeV and a quasi-monoenergetic peak at 80 MeV for 1022 W/cm2 laser intensity with controlled prepulses. A self-generated strong quasi-static magnetic field is also observed in the plasma, which modifies the spatial distribution of the proton beam.

THREE-DIMENSIONAL NON-VACUUM PULSAR OUTER-GAP MODEL: LOCALIZED ACCELERATION ELECTRIC FIELD IN THE HIGHER ALTITUDES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirotani, Kouichi

2015-01-10

We investigate the particle accelerator that arises in a rotating neutron-star magnetosphere. Simultaneously solving the Poisson equation for the electro-static potential, the Boltzmann equations for relativistic electrons and positrons, and the radiative transfer equation, we demonstrate that the electric field is substantially screened along the magnetic field lines by pairs that are created and separated within the accelerator. As a result, the magnetic-field-aligned electric field is localized in higher altitudes near the light cylinder and efficiently accelerates the positrons created in the lower altitudes outward but does not accelerate the electrons inward. The resulting photon flux becomes predominantly outward, leadingmore » to typical double-peak light curves, which are commonly observed from many high-energy pulsars.« less

The impact performance of headguards for combat sports.

PubMed

McIntosh, Andrew S; Patton, Declan A

2015-09-01

To assess the impact energy attenuation performance of a range of headguards for combat sports. Seven headguards worn during combat sport training or competition, including two Association Internationale de Boxe Amateur (AIBA)-approved boxing models, were tested using drop tests. An International Organization for Standardization (ISO) rigid headform was used with a 5.6 kg drop assembly mass. Tests were conducted against a flat rigid anvil both with and without a boxing glove section. The centre forehead and lateral headguard areas were tested. Peak headform acceleration was measured. Tests from a selection of drop heights and repeated tests on the same headguard were conducted. Headguard performance varied by test condition. For the 0.4 m rigid anvil tests, the best model headguard was the thickest producing an average peak headform acceleration over 5 tests of 48 g compared with 456 g for the worst model. The mean peak acceleration for the 0.4, 0.5 and 0.6 frontal and lateral rigid anvil impact tests was between 32% and 40% lower for the Top Ten boxing model compared with the Adidas boxing model. The headguard performance deterioration observed with repeat impact against the flat anvil was reduced for impacts against the glove section. The overall reduction in acceleration for the combination of glove and headguard in comparison to the headguard condition was in the range of 72-93% for 0.6 and 0.8 m drop tests. The impact tests show the benefits of performance testing in identifying differences between headguard models. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Effect of injection-gas concentration on the electron beam quality from a laser-plasma accelerator

NASA Astrophysics Data System (ADS)

Mirzaie, Mohammad; Zhang, Guobo; Li, Song; Gao, Kai; Li, Guangyu; Ain, Quratul; Hafz, Nasr A. M.

2018-04-01

By using 25-45 TW ultra-short (30 fs) laser pulses, we report on the effect of the injection gas concentration on the quality of electron beams generated by a laser-driven plasma wakefield acceleration employing the ionization-injection. For a plasma formed from helium-nitrogen gas mixture and depending on the concentration of the nitrogen gas, we could distinguish a clear trend for the quality of the generated electron beams in terms of their peak energy, energy-spread, divergence angle, and beam charge. The results clearly showed that the lower the nitrogen concentration, the better the quality (higher peak energy, smaller energy spread, and smaller emittance) of the generated electron beams. The results are in reasonable agreement with two-dimensional particle-in-cell simulations.

Active head rotations and eye-head coordination

NASA Technical Reports Server (NTRS)

Zangemeister, W. H.; Stark, L.

1981-01-01

It is pointed out that head movements play an important role in gaze. The interaction between eye and head movements involves both their shared role in directing gaze and the compensatory vestibular ocular reflex. The dynamics of head trajectories are discussed, taking into account the use of parameterization to obtain the peak velocity, peak accelerations, the times of these extrema, and the duration of the movement. Attention is given to the main sequence, neck muscle EMG and details of the head-movement trajectory, types of head model accelerations, the latency of eye and head movement in coordinated gaze, gaze latency as a function of various factors, and coordinated gaze types. Clinical examples of gaze-plane analysis are considered along with the instantaneous change of compensatory eye movement (CEM) gain, and aspects of variability.

PULSAR OUTER-GAP ELECTRODYNAMICS: HARDENING OF SPECTRAL SHAPE IN THE TRAILING PEAK IN THE GAMMA-RAY LIGHT CURVE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirotani, Kouichi, E-mail: hirotani@tiara.sinica.edu.tw

2011-06-01

The spectral characteristics of the pulsed gamma-ray emission from outer-magnetospheric particle accelerators are investigated. Either positrons or electrons are accelerated outward by the magnetic-field-aligned electric field to emit gamma rays via the curvature process. Since the particles move along relatively straight paths in the trailing side of a rotating magnetosphere, they attain higher Lorentz factors to emit more energetic gamma rays than those in the leading side. It is first demonstrated that the cutoff energy of the curvature radiation evolves with the rotation phase owing to the variation of the curvature radii of the particle paths and maximizes at amore » slightly later phase of the trailing peak in the gamma-ray light curve.« less

Ocular motor responses to abrupt interaural head translation in normal humans

NASA Technical Reports Server (NTRS)

Ramat, Stefano; Zee, David S.; Shelhamer, M. J. (Principal Investigator)

2003-01-01

We characterized the interaural translational vestibulo-ocular reflex (tVOR) in 6 normal humans to brief (approximately 200 ms), high-acceleration (0.4-1.4g) stimuli, while they fixed targets at 15 or 30 cm. The latency was 19 +/- 5 ms at 15-cm and 20 +/- 12 ms at 30-cm viewing. The gain was quantified using the ratio of actual to ideal behavior. The median position gain (at time of peak head velocity) was 0.38 and 0.37, and the median velocity gain, 0.52 and 0.62, at 15- and 30-cm viewing, respectively. These results suggest the tVOR scales proportionally at these viewing distances. Likewise, at both viewing distances, peak eye velocity scaled linearly with peak head velocity and gain was independent of peak head acceleration. A saccade commonly occurred in the compensatory direction, with a greater latency (165 vs. 145 ms) and lesser amplitude (1.8 vs. 3.2 deg) at 30- than 15-cm viewing. Even with saccades, the overall gain at the end of head movement was still considerably undercompensatory (medians 0.68 and 0.77 at 15- and 30-cm viewing). Monocular viewing was also assessed at 15-cm viewing. In 4 of 6 subjects, gains were the same as during binocular viewing and scaled closely with vergence angle. In sum the low tVOR gain and scaling of the response with viewing distance and head velocity extend previous results to higher acceleration stimuli. tVOR latency (approximately 20 ms) was lower than previously reported. Saccades are an integral part of the tVOR, and also scale with viewing distance.

Convergence of linear acceleration and yaw rotation signals on non-eye movement neurons in the vestibular nucleus of macaques.

PubMed

Newlands, Shawn D; Abbatematteo, Ben; Wei, Min; Carney, Laurel H; Luan, Hongge

2018-01-01

Roughly half of all vestibular nucleus neurons without eye movement sensitivity respond to both angular rotation and linear acceleration. Linear acceleration signals arise from otolith organs, and rotation signals arise from semicircular canals. In the vestibular nerve, these signals are carried by different afferents. Vestibular nucleus neurons represent the first point of convergence for these distinct sensory signals. This study systematically evaluated how rotational and translational signals interact in single neurons in the vestibular nuclei: multisensory integration at the first opportunity for convergence between these two independent vestibular sensory signals. Single-unit recordings were made from the vestibular nuclei of awake macaques during yaw rotation, translation in the horizontal plane, and combinations of rotation and translation at different frequencies. The overall response magnitude of the combined translation and rotation was generally less than the sum of the magnitudes in responses to the stimuli applied independently. However, we found that under conditions in which the peaks of the rotational and translational responses were coincident these signals were approximately additive. With presentation of rotation and translation at different frequencies, rotation was attenuated more than translation, regardless of which was at a higher frequency. These data suggest a nonlinear interaction between these two sensory modalities in the vestibular nuclei, in which coincident peak responses are proportionally stronger than other, off-peak interactions. These results are similar to those reported for other forms of multisensory integration, such as audio-visual integration in the superior colliculus. NEW & NOTEWORTHY This is the first study to systematically explore the interaction of rotational and translational signals in the vestibular nuclei through independent manipulation. The results of this study demonstrate nonlinear integration leading to maximum response amplitude when the timing and direction of peak rotational and translational responses are coincident.

Atypical soil hardening during the Tohoku earthquake of March 11, 2011 ( M w = 9.0)

NASA Astrophysics Data System (ADS)

Pavlenko, O. V.

2017-10-01

Based on the records of KiK-net vertical arrays, models of soil behavior down to depths of 100-200 m in the near-fault zones during the Tohoku earthquake are examined. In contrast to the regular pattern observed during strong earthquakes, soft soils have not broadly demonstrated nonlinear behavior, or a reduction (with the onset of strong motions) and recovery (after strong motions finished) of the shear modulus in soil layers. At the stations where anomalously high peak ground accelerations were recorded (PGA > 1g), the values of the shear modulus in soil layers increased with the onset of strong motions and reached a maximum when motions were the most intensive, which indicated hardening of soils. Soil behavior was close to linear, here. The values of the shear moduli decrease along with a decrease in intensity of strong ground motions, and at soft soil stations, this was accompanied by a stepwise decrease in the frequency of motion.

Seismic Hazard Assessment for the Baku City and Absheron Peninsula, Azerbaijan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Babayev, Gulam R.

2006-03-23

This paper deals with the seismic hazard assessment for Baku and the Absheron peninsula. The assessment is based on the information on the features of earthquake ground motion excitation, seismic wave propagation (attenuation), and site effect. I analyze active faults, seismicity, soil and rock properties, geological cross-sections, the borehole data of measured shear-wave velocity, lithology, amplification factor of each geological unit, geomorphology, topography, and basic rock and surface ground motions. To estimate peak ground acceleration (PGA) at the surface, PGA at the basic rock is multiplied by the amplification parameter of each surface layers. Quaternary soft deposits, representing a highmore » risk due to increasing PGA values at surface, are studied in detail. For a near-zone target earthquake PGA values are compared to intensity at MSK-64 scale for the Absheron peninsula. The amplification factor for the Baku city is assessed and provides estimations for a level of a seismic motion and seismic intensity of the studied area.« less

Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

NASA Astrophysics Data System (ADS)

Gessner, Spencer; Adli, Erik; Allen, James M.; An, Weiming; Clarke, Christine I.; Clayton, Chris E.; Corde, Sebastien; Delahaye, J. P.; Frederico, Joel; Green, Selina Z.; Hast, Carsten; Hogan, Mark J.; Joshi, Chan; Lindstrøm, Carl A.; Lipkowitz, Nate; Litos, Michael; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; O'Shea, Brendan; Vafaei-Najafabadi, Navid; Walz, Dieter; Yakimenko, Vitaly; Yocky, Gerald

2016-06-01

Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. Here we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel is created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m-1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.

Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

PubMed Central

Gessner, Spencer; Adli, Erik; Allen, James M.; An, Weiming; Clarke, Christine I.; Clayton, Chris E.; Corde, Sebastien; Delahaye, J. P.; Frederico, Joel; Green, Selina Z.; Hast, Carsten; Hogan, Mark J.; Joshi, Chan; Lindstrøm, Carl A.; Lipkowitz, Nate; Litos, Michael; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; O'Shea, Brendan; Vafaei-Najafabadi, Navid; Walz, Dieter; Yakimenko, Vitaly; Yocky, Gerald

2016-01-01

Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. Here we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel is created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m−1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations. PMID:27250570

Sprint Acceleration Mechanics: The Major Role of Hamstrings in Horizontal Force Production

PubMed Central

Morin, Jean-Benoît; Gimenez, Philippe; Edouard, Pascal; Arnal, Pierrick; Jiménez-Reyes, Pedro; Samozino, Pierre; Brughelli, Matt; Mendiguchia, Jurdan

2015-01-01

Recent literature supports the importance of horizontal ground reaction force (GRF) production for sprint acceleration performance. Modeling and clinical studies have shown that the hip extensors are very likely contributors to sprint acceleration performance. We experimentally tested the role of the hip extensors in horizontal GRF production during short, maximal, treadmill sprint accelerations. Torque capabilities of the knee and hip extensors and flexors were assessed using an isokinetic dynamometer in 14 males familiar with sprint running. Then, during 6-s sprints on an instrumented motorized treadmill, horizontal and vertical GRF were synchronized with electromyographic (EMG) activity of the vastus lateralis, rectus femoris, biceps femoris, and gluteus maximus averaged over the first half of support, entire support, entire swing and end-of-swing phases. No significant correlations were found between isokinetic or EMG variables and horizontal GRF. Multiple linear regression analysis showed a significant relationship (P = 0.024) between horizontal GRF and the combination of biceps femoris EMG activity during the end of the swing and the knee flexors eccentric peak torque. In conclusion, subjects who produced the greatest amount of horizontal force were both able to highly activate their hamstring muscles just before ground contact and present high eccentric hamstring peak torque capability. PMID:26733889

Impact Accelerations of Barefoot and Shod Running.

PubMed

Thompson, M; Seegmiller, J; McGowan, C P

2016-05-01

During the ground contact phase of running, the body's mass is rapidly decelerated resulting in forces that propagate through the musculoskeletal system. The repetitive attenuation of these impact forces is thought to contribute to overuse injuries. Modern running shoes are designed to reduce impact forces, with the goal to minimize running related overuse injuries. Additionally, the fore/mid foot strike pattern that is adopted by most individuals when running barefoot may reduce impact force transmission. The aim of the present study was to compare the effects of the barefoot running form (fore/mid foot strike & decreased stride length) and running shoes on running kinetics and impact accelerations. 10 healthy, physically active, heel strike runners ran in 3 conditions: shod, barefoot and barefoot while heel striking, during which 3-dimensional motion analysis, ground reaction force and accelerometer data were collected. Shod running was associated with increased ground reaction force and impact peak magnitudes, but decreased impact accelerations, suggesting that the midsole of running shoes helps to attenuate impact forces. Barefoot running exhibited a similar decrease in impact accelerations, as well as decreased impact peak magnitude, which appears to be due to a decrease in stride length and/or a more plantarflexed position at ground contact. © Georg Thieme Verlag KG Stuttgart · New York.

Orion Landing Simulation Eight Soil Model Comparison

NASA Technical Reports Server (NTRS)

Mark, Stephen D.

2009-01-01

LS-DYNA finite element simulations of a rigid Orion Crew Module (CM) were used to investigate the CM impact behavior on eight different soil models. Ten different landing conditions, characterized by the combination of CM vertical and horizontal velocity, hang angle, and roll angle were simulated on the eight different soils. The CM center of gravity accelerations, pitch angle, kinetic energy, and soil contact forces were the outputs of interest. The simulation results are presented, with comparisons of the CM behavior on the different soils. The soils analyzed in this study can be roughly categorized as soft, medium, or hard, according to the CM accelerations that occur when landing on them. The soft group is comprised of the Carson Sink Wet soil and the Kennedy Space Center (KSC) Low Density Dry Sand. The medium group includes Carson Sink Dry, the KSC High Density In-Situ Moisture Sand and High Density Flooded Sand, and Cuddeback B. The hard soils are Cuddeback A and the Gantry Unwashed Sand. The softer soils were found to produce lower peak accelerations, have more stable pitch behavior, and to be less sensitive to the landing conditions. This investigation found that the Cuddeback A soil produced the highest peak accelerations and worst stability conditions, and that the best landing performance was achieved on the KSC Low Density Dry Sand.

Occupant responses in conventional and ABTS seats in high-speed rear sled tests.

PubMed

Viano, David C; Parenteau, Chantal S; Burnett, Roger; Prasad, Priya

2018-01-02

This study compared biomechanical responses of a normally seated Hybrid III dummy on conventional and all belts to seat (ABTS) seats in 40.2 km/h (25 mph) rear sled tests. It determined the difference in performance with modern (≥2000 MY) seats compared to older (<2000 MY) seats and ABTS seats. The seats were fixed in a sled buck subjected to a 40.2 km/h (25 mph) rear sled test. The pulse was a 15 g double-peak acceleration with 150 ms duration. The 50th percentile Hybrid III was lap-shoulder belted in the FMVSS 208 design position. The testing included 11 <2000 MY, 8 ≥2000 MY, and 7 ABTS seats. The dummy was fully instrumented, including head accelerations, upper and lower neck 6-axis load cells, chest acceleration, thoracic and lumbar spine load cells, and pelvis accelerations. The peak responses were normalized by injury assessment reference values (IARVs) to assess injury risks. Statistical analysis was conducted using Student's t test. High-speed video documented occupant kinematics. Biomechanical responses were lower with modern (≥2000 MY) seats than older (<2000 MY) designs. The lower neck extension moment was 32.5 ± 9.7% of IARV in modern seats compared to 62.8 ± 31.6% in older seats (P =.01). Overall, there was a 34% reduction in the comparable biomechanical responses with modern seats. Biomechanical responses were lower with modern seats than ABTS seats. The lower neck extension moment was 41.4 ± 7.8% with all MY ABTS seats compared to 32.5 ± 9.7% in modern seats (P =.07). Overall, the ABTS seats had 13% higher biomechanical responses than the modern seats. Modern (≥2000 MY) design seats have lower biomechanical responses in 40.2 km/h rear sled tests than older (<2000 MY) designs and ABTS designs. The improved performance is consistent with an increase in seat strength combined with improved occupant kinematics through pocketing of the occupant into the seatback, higher and more forward head restraint, and other design changes. The methods and data presented here provide a basis for standardized testing of seats. However, a complete understanding of seat safety requires consideration of out-of-position (OOP) occupants in high-speed impacts and consideration of the much more common, low-speed rear impacts.

Comparison of the peak resolution and the stationary phase retention between the satellite and the planetary motions using the coil satellite centrifuge with counter-current chromatographic separation of 4-methylumbelliferyl sugar derivatives.

PubMed

Shinomiya, Kazufusa; Zaima, Kazumasa; Harada, Yukina; Yasue, Miho; Harikai, Naoki; Tokura, Koji; Ito, Yoichiro

2017-01-20

Coil satellite centrifuge (CSC) produces the complex satellite motion consisting of the triplicate rotation of the coiled column around three axes including the sun axis (the angular velocity, ω 1 ), the planet axis (ω 2 ) and the satellite axis (the central axis of the column) (ω 3 ) according to the following formula: ω 1 =ω 2 +ω 3 . Improved peak resolution in the separation of 4-methylumbelliferyl sugar derivatives was achieved using the conventional multilayer coiled columns with ethyl acetate/1-butanol/water (3: 2: 5, v/v) for the lower mobile phase at the combination of the rotation speeds (ω 1 , ω 2 , ω 3 )=(300, 150, 150rpm), and (1:4:5, v/v) for the upper mobile phase at (300:100:200rpm). The effect of the satellite motion on the peak resolution and the stationary phase retention was evaluated by each CSC separation with the different rotation speeds of ω 2 and ω 3 under the constant revolution speed at ω 1 =300rpm. With the lower mobile phase, almost constant peak resolution and stationary phase retention were yielded regardless of the change of ω 2 and ω 3 , while with the upper mobile phase these two values were sensitively varied according to the different combination of ω 2 and ω 3 . For example, when ω 2 =147 or 200rpm is used, no stationary phase was retained in the coiled column while ω 2 =150rpm could retain enough volume of stationary phase for separation. On the other hand, the combined rotation speeds at (ω 1 , ω 2 , ω 3 )=(300, 300, 0rpm) or (300, 0, 300rpm) produced insufficient peak resolution regardless of the choice of the mobile phase apparently due to the lack of rotation speed except at (300, 0, 300rpm) with the upper mobile phase. At lower rotation speed of ω 1 =300rpm, better peak resolution and stationary phase retention were obtained by the satellite motion (ω 3 ) than by the planetary motion (ω 2 ), or ω 3 >ω 2 . The effect of the hydrophobicity of the two-phase solvent systems on the stationary phase retention was further examined using the n-hexane/ethyl acetate/1-butanol/methanol/water system at different volume ratios. In the satellite motion at (ω 1 , ω 2 , ω 3 )=(300, 150, 150rpm), almost constant stationary phase retention was obtained with the lower mobile phase regardless of the hydrophobicity of the solvent system whereas the stationary phase retention varied according to the volume ratio of the two-phase solvent system for the upper mobile phase. However, stable stationary phase retention was observed with either phase used as the mobile phase. In order to analyze the acceleration acting on the coiled column, an acceleration sensor was set on the column holder by displacing the multilayer column. The combination of the rotation speeds at (300, 100, 200rpm) showed double loops in the acceleration track, whereas (300, 150, 150rpm) showed a single loop, and all other combinations showed, complex tracks. The overall results indicate that the satellite motion is seriously affected by the combination of rotation speeds and the hydrophobicity of the two-phase solvent system when the upper phase was used as the mobile phase for separation. Copyright © 2016 Elsevier B.V. All rights reserved.

Comparison of the peak resolution and the stationary phase retention between the satellite and the planetary motions using the coil satellite centrifuge with counter-current chromatographic separation of 4-methylumbelliferyl sugar derivatives

PubMed Central

Shinomiya, Kazufusa; Zaima, Kazumasa; Harada, Yukina; Yasue, Miho; Harikai, Naoki; Tokura, Koji; Ito, Yoichiro

2016-01-01

Coil satellite centrifuge (CSC) produces the complex satellite motion consisting of the triplicate rotation of the coiled column around three axes including the sun axis (the angular velocity, ω1), the planet axis (ω2) and the satellite axis (the central axis of the column) (ω3) according to the following formula: ω1 = ω2 + ω3. Improved peak resolution in the separation of 4-methylumbelliferyl sugar derivatives was achieved using the conventional multilayer coiled columns with ethyl acetate/1-butanol/water (3 : 2 : 5, v/v) for the lower mobile phase at the combination of the rotation speeds (ω1, ω2, ω3) = (300, 150, 150 rpm), and (1 : 4 : 5, v/v) for the upper mobile phase at (300 : 100 : 200 rpm). The effect of the satellite motion on the peak resolution and the stationary phase retention was evaluated by each CSC separation with the different rotation speeds of ω2 and ω3 under the constant revolution speed at ω1 = 300 rpm. With the lower mobile phase, almost constant peak resolution and stationary phase retention were yielded regardless of the change of ω2 and ω3, while with the upper mobile phase these two values were sensitively varied according to the different combination of ω2 and ω3. For example, when ω2 = 147 or 200 rpm is used, no stationary phase was retained in the coiled column while ω2 = 150 rpm could retain enough volume of stationary phase for separation. On the other hand, the combined rotation speeds at (ω1, ω2, ω3) = (300, 300, 0 rpm) or (300, 0, 300 rpm) produced insufficient peak resolution regardless of the choice of the mobile phase apparently due to the lack of rotation speed except at (300, 0, 300 rpm) with the upper mobile phase. At lower rotation speed of ω1 = 300 rpm, better peak resolution and stationary phase retention were obtained by the satellite motion (ω3) than by the planetary motion (ω2), or ω3 > ω2. The effect of the hydrophobicity of the two-phase solvent systems on the stationary phase retention was further examined using the n-hexane/ethyl acetate/1-butanol/methanol/water system at different volume ratios. In the satellite motion at (ω1, ω2, ω3) = (300, 150, 150 rpm), almost constant stationary phase retention was obtained with the lower mobile phase regardless of the hydrophobicity of the solvent system whereas the stationary phase retention varied according to the volume ratio of the two-phase solvent system for the upper mobile phase. However, stable stationary phase retention was observed with either phase used as the mobile phase. In order to analyze the acceleration acting on the coiled column, an acceleration sensor was set on the column holder by displacing the multilayer column. The combination of the rotation speeds at (300, 100, 200 rpm) showed double loops in the acceleration track, whereas (300, 150, 150 rpm) showed a single loop, and all other combinations showed, complex tracks. The overall results indicate that the satellite motion is seriously affected by the combination of rotation speeds and the hydrophobicity of the two-phase solvent system when the upper phase was used as the mobile phase for separation. PMID:28040269

Direct acceleration in intense laser fields used for bunch amplification of relativistic electrons

NASA Astrophysics Data System (ADS)

Braenzel, J.; Andreev, A. A.; Ehrentraut, L.; Schnürer, M.

2017-05-01

A method, how electrons can be directly accelerated in intense laser fields, is investigated experimentally and discussed with numerical and analytical simulation. When ultrathin foil targets are exposed with peak laser intensities of 1x1020 W/cm2 , slow electrons ( keV kinetic energy), that are emitted from the ultrathin foil target along laser propagation direction, are post-accelerated in the transmitted laser field. They received significant higher kinetic energies (MeV), when this interaction was limited in duration and an enhanced number of fast electrons were detected. The decoupling of the light field from the electron interaction we realized with a second separator foil, blocking the transmitted laser light at a particular distance and allowing the fast electrons to pass. Variation of the propagation distance in the laser field results in different energy gains for the electrons. This finding is explained with electron acceleration in the electromagnetic field of a light pulse and confirms a concept being discussed for some time. In the experiments the effect manifests in an electron number amplification of about 3 times around a peak at 1 MeV electron energy. Measurements confirmed that the overall number in the whole bunch is enhanced to about 109 electrons covering kinetic energies between 0.5 to 5 MeV. The method holds promise for ultrashort electron bunch generation at MeV energies for direct application, e.g. ultra-fast electron diffraction, or for injection into post accelerator stages for different purposes.

A dynamic model of the radiation-belt electron phase-space density based on POLAR/HIST measurements

NASA Astrophysics Data System (ADS)

Vassiliadis, D.; Green, J. C.

2007-12-01

The response of the energetic-electron phase-space density (PSD) in the radiation belts is subject to a delicate combination of acceleration and loss processes which are strongly determined by the magnetospheric configuration and field disturbance level. We quantify the response of the density to stormtime fields as observed by the HIST detector on board POLAR. Several distinct modes are identified, characterized by peak second- and third- adiabatic invariants and peak delay time. The modes represent quasiadiabatic transport due to ring current activity; high L* (~6), day-long acceleration linked to ULF wave-particle interaction; and low-L* (~3), minute- to hour-long acceleration interpreted to be due to transient inductive fields or VLF wave-particle interaction. The net transport due to these responses is not always or everywhere diffusive, therefore we quantify the degree of departure from diffusive transport for specific storm intervals and radial ranges. Taken together the response modes comprise a dynamic, nonlinear model which allows us to better understand the historic variability of the high-energy tail of the electron distribution in the inner magnetosphere.

Experiments and PIC simulations on liquid crystal plasma mirrors for pulse contrast enhancement

NASA Astrophysics Data System (ADS)

Cochran, G. E.; Poole, P. L.; Krygier, A.; Foster, P. S.; Scott, G. G.; Wilson, L. A.; Bailey, J.; Bourgeois, N.; Hernandez-Gomez, C.; Heery, R.; Purcell, J.; Neely, D.; Rajeev, P. P.; Freeman, R. R.; Schumacher, D. W.

2016-10-01

High pulse contrast is crucial for performing many experiments on high intensity lasers in order to minimize modification of the target surface by pre-pulse. This is often achieved through the use of solid dielectric plasma mirrors which can limit laser shot rates. Liquid crystal films, originally developed as variable thickness ion acceleration targets, have been demonstrated as effective plasma mirrors for pulse cleaning, reaching peak reflectivities over 70%. These films were used as plasma mirrors in an ion acceleration experiment on the Scarlet laser and the resultant increase in peak proton energy and change in acceleration direction will be discussed. Also presented here are novel 2D3V, LSP particle-in-cell simulations of dielectric plasma mirror operation. By including multiphoton ionization and dimensionality corrections, an excellent match to experiment is obtained over 4 decades in intensity. Analysis of pulse shortening and plasma critical surface behavior in these simulations will be discussed. Formation of thin films at 1.5 Hz will also be presented. Performed with support from the DARPA PULSE program through AMRDEC, from NNSA, and from OSC.

Chromospheric evaporation flows and density changes deduced from Hinode/EIS during an M1.6 flare

NASA Astrophysics Data System (ADS)

Gömöry, P.; Veronig, A. M.; Su, Y.; Temmer, M.; Thalmann, J. K.

2016-04-01

Aims: We study the response of the solar atmosphere during a GOES M1.6 flare using spectroscopic and imaging observations. In particular, we examine the evolution of the mass flows and electron density together with the energy input derived from hard X-ray (HXR) in the context of chromospheric evaporation. Methods: We analyzed high-cadence sit-and-stare observations acquired with the Hinode/EIS spectrometer in the Fe xiii 202.044 Å (log T = 6.2) and Fe xvi 262.980 Å (log T = 6.4) spectral lines to derive temporal variations of the line intensity, Doppler shifts, and electron density during the flare. We combined these data with HXR measurements acquired with RHESSI to derive the energy input to the lower atmosphere by flare-accelerated electrons. Results: During the flare impulsive phase, we observe no significant flows in the cooler Fe xiii line but strong upflows, up to 80-150 km s-1, in the hotter Fe xvi line. The largest Doppler shifts observed in the Fe xvi line were co-temporal with the sharp intensity peak. The electron density obtained from a Fe xiii line pair ratio exhibited fast increase (within two minutes) from the pre-flare level of 5.01 × 109 cm-3 to 3.16 × 1010 cm-3 during the flare peak. The nonthermal energy flux density deposited from the coronal acceleration site to the lower atmospheric layers during the flare peak was found to be 1.34 × 1010 erg s-1 cm-2 for a low-energy cut-off that was estimated to be 16 keV. During the decline flare phase, we found a secondary intensity and density peak of lower amplitude that was preceded by upflows of ~15 km s-1 that were detected in both lines. The flare was also accompanied by a filament eruption that was partly captured by the EIS observations. We derived Doppler velocities of 250-300 km s-1 for the upflowing filament material. Conclusions: The spectroscopic results for the flare peak are consistent with the scenario of explosive chromospheric evaporation, although a comparatively low value of the nonthermal energy flux density was determined for this phase of the flare. This outcome is discussed in the context of recent hydrodynamic simulations. It provides observational evidence that the response of the atmospheric plasma strongly depends on the properties of the electron beams responsible for the heating, in particular the steepness of the energy distribution. The secondary peak of line intensity and electron density detected during the decline phase is interpreted as a signature of flare loops being filled by expanding hot material that is due to chromospheric evaporation. A movie is available at http://www.aanda.org

Characterizing cerebral and locomotor muscle oxygenation to incremental ramp exercise in healthy children: relationship with pulmonary gas exchange.

PubMed

Vandekerckhove, Kristof; Coomans, Ilse; Moerman, Annelies; De Wolf, Daniel; Boone, Jan

2016-12-01

To characterize the oxygenation responses at cerebral and locomotor muscle level to incremental exercise in children and to assess the interrelationship with the pulmonary gas exchange responses. Eighteen children (9 boys, 9 girls) (mean age 10.9 ± 1.0 years) performed incremental cycle ramp exercise to exhaustion. The concentration of cerebral and muscle oxygenated (O 2 Hb) and deoxygenated (HHb) hemoglobin (by means of near-infrared spectroscopy) and pulmonary gas exchange was recorded. Cerebral and muscle O 2 Hb and HHb values were expressed as functions of oxygen uptake (VO 2 ) and breakpoints were detected by means of double linear model analysis. The respiratory compensation point (RCP) was determined. The breakpoints in cerebral and muscle O 2 Hb and HHb were compared and correlated to RCP. The subjects reached peak power output of 105 ± 18 W and VO 2peak of 43.5 ± 7.0 ml min -1  kg -1 . Cerebral O 2 Hb increased to an intensity of 89.4 ± 5.5 %VO 2peak , where a breakpoint occurred at which cerebral O 2 Hb started to decrease. Cerebral HHb increased slightly to 88.1 ± 4.8 %VO 2peak , at which the increase was accelerated. Muscle HHb increased to 90.5 ± 4.8 %VO 2peak where a leveling-off occurred. RCP occurred at 89.3 ± 4.3 %VO 2peak . The breakpoints and RCP did not differ significantly (P = 0.13) and were strongly correlated (r > 0.70, P < 0.05). There were no differences between boys and girls (P = 0.43) and there was no significant correlation with VO 2peak (P > 0.05). It was shown that cerebral and muscle oxygenation responses undergo significant changes as work rate increases and show breakpoints in the ongoing response at high intensity (85-95 %VO 2peak ). These breakpoints are strongly interrelated and associated with changes in pulmonary gas exchange.

Application of Gumbel I and Monte Carlo methods to assess seismic hazard in and around Pakistan

NASA Astrophysics Data System (ADS)

Rehman, Khaista; Burton, Paul W.; Weatherill, Graeme A.

2018-05-01

A proper assessment of seismic hazard is of considerable importance in order to achieve suitable building construction criteria. This paper presents probabilistic seismic hazard assessment in and around Pakistan (23° N-39° N; 59° E-80° E) in terms of peak ground acceleration (PGA). Ground motion is calculated in terms of PGA for a return period of 475 years using a seismogenic-free zone method of Gumbel's first asymptotic distribution of extreme values and Monte Carlo simulation. Appropriate attenuation relations of universal and local types have been used in this study. The results show that for many parts of Pakistan, the expected seismic hazard is relatively comparable with the level specified in the existing PGA maps.

Bubbling in vibrated granular films.

PubMed

Zamankhan, Piroz

2011-02-01

With the help of experiments, computer simulations, and a theoretical investigation, a general model is developed of the flow dynamics of dense granular media immersed in air in an intermediate regime where both collisional and frictional interactions may affect the flow behavior. The model is tested using the example of a system in which bubbles and solid structures are produced in granular films shaken vertically. Both experiments and large-scale, three-dimensional simulations of this system are performed. The experimental results are compared with the results of the simulation to verify the validity of the model. The data indicate evidence of formation of bubbles when peak acceleration relative to gravity exceeds a critical value Γ(b). The air-grain interfaces of bubblelike structures are found to exhibit fractal structure with dimension D=1.7±0.05.

Quasi-monoenergetic laser-plasma acceleration of electrons to 2 GeV

PubMed Central

Wang, Xiaoming; Zgadzaj, Rafal; Fazel, Neil; Li, Zhengyan; Yi, S. A.; Zhang, Xi; Henderson, Watson; Chang, Y.-Y.; Korzekwa, R.; Tsai, H.-E.; Pai, C.-H.; Quevedo, H.; Dyer, G.; Gaul, E.; Martinez, M.; Bernstein, A. C.; Borger, T.; Spinks, M.; Donovan, M.; Khudik, V.; Shvets, G.; Ditmire, T.; Downer, M. C.

2013-01-01

Laser-plasma accelerators of only a centimetre’s length have produced nearly monoenergetic electron bunches with energy as high as 1 GeV. Scaling these compact accelerators to multi-gigaelectronvolt energy would open the prospect of building X-ray free-electron lasers and linear colliders hundreds of times smaller than conventional facilities, but the 1 GeV barrier has so far proven insurmountable. Here, by applying new petawatt laser technology, we produce electron bunches with a spectrum prominently peaked at 2 GeV with only a few per cent energy spread and unprecedented sub-milliradian divergence. Petawatt pulses inject ambient plasma electrons into the laser-driven accelerator at much lower density than was previously possible, thereby overcoming the principal physical barriers to multi-gigaelectronvolt acceleration: dephasing between laser-driven wake and accelerating electrons and laser pulse erosion. Simulations indicate that with improvements in the laser-pulse focus quality, acceleration to nearly 10 GeV should be possible with the available pulse energy. PMID:23756359

Trirotron: triode rotating beam radio frequency amplifier

DOEpatents

Lebacqz, Jean V.

1980-01-01

High efficiency amplification of radio frequencies to very high power levels including: establishing a cylindrical cloud of electrons; establishing an electrical field surrounding and coaxial with the electron cloud to bias the electrons to remain in the cloud; establishing a rotating electrical field that surrounds and is coaxial with the steady field, the circular path of the rotating field being one wavelength long, whereby the peak of one phase of the rotating field is used to accelerate electrons in a beam through the bias field in synchronism with the peak of the rotating field so that there is a beam of electrons continuously extracted from the cloud and rotating with the peak; establishing a steady electrical field that surrounds and is coaxial with the rotating field for high-energy radial acceleration of the rotating beam of electrons; and resonating the rotating beam of electrons within a space surrounding the second field, the space being selected to have a phase velocity equal to that of the rotating field to thereby produce a high-power output at the frequency of the rotating field.

Development and testing of a pulsed helium ion source for probing materials and warm dense matter studies

NASA Astrophysics Data System (ADS)

Ji, Q.; Seidl, P. A.; Waldron, W. L.; Takakuwa, J. H.; Friedman, A.; Grote, D. P.; Persaud, A.; Barnard, J. J.; Schenkel, T.

2016-02-01

The neutralized drift compression experiment was designed and commissioned as a pulsed, linear induction accelerator to drive thin targets to warm dense matter (WDM) states with peak temperatures of ˜1 eV using intense, short pulses (˜1 ns) of 1.2 MeV lithium ions. At that kinetic energy, heating a thin target foil near the Bragg peak energy using He+ ions leads to more uniform energy deposition of the target material than Li+ ions. Experiments show that a higher current density of helium ions can be delivered from a plasma source compared to Li+ ions from a hot plate type ion source. He+ beam pulses as high as 200 mA at the peak and 4 μs long were measured from a multi-aperture 7-cm-diameter emission area. Within ±5% variation, the uniform beam area is approximately 6 cm across. The accelerated and compressed pulsed ion beams can be used for materials studies and isochoric heating of target materials for high energy density physics experiments and WDM studies.

Development and testing of a pulsed helium ion source for probing materials and warm dense matter studies.

PubMed

Ji, Q; Seidl, P A; Waldron, W L; Takakuwa, J H; Friedman, A; Grote, D P; Persaud, A; Barnard, J J; Schenkel, T

2016-02-01

The neutralized drift compression experiment was designed and commissioned as a pulsed, linear induction accelerator to drive thin targets to warm dense matter (WDM) states with peak temperatures of ∼1 eV using intense, short pulses (∼1 ns) of 1.2 MeV lithium ions. At that kinetic energy, heating a thin target foil near the Bragg peak energy using He(+) ions leads to more uniform energy deposition of the target material than Li(+) ions. Experiments show that a higher current density of helium ions can be delivered from a plasma source compared to Li(+) ions from a hot plate type ion source. He(+) beam pulses as high as 200 mA at the peak and 4 μs long were measured from a multi-aperture 7-cm-diameter emission area. Within ±5% variation, the uniform beam area is approximately 6 cm across. The accelerated and compressed pulsed ion beams can be used for materials studies and isochoric heating of target materials for high energy density physics experiments and WDM studies.

Development and testing of a pulsed helium ion source for probing materials and warm dense matter studies

DOE PAGES

Ji, Q.; Seidl, P. A.; Waldron, W. L.; ...

2015-11-12

In this paper, the neutralized drift compression experiment was designed and commissioned as a pulsed, linear induction accelerator to drive thin targets to warm dense matter (WDM) states with peak temperatures of ~1 eV using intense, short pulses (~1 ns) of 1.2 MeV lithium ions. At that kinetic energy, heating a thin target foil near the Bragg peak energy using He + ions leads to more uniform energy deposition of the target material than Li + ions. Experiments show that a higher current density of helium ions can be delivered from a plasma source compared to Li + ions frommore » a hot plate type ion source. He + beam pulses as high as 200 mA at the peak and 4 μs long were measured from a multi-aperture 7-cm-diameter emission area. Within ±5% variation, the uniform beam area is approximately 6 cm across. Finally, the accelerated and compressed pulsed ion beams can be used for materials studies and isochoric heating of target materials for high energy density physics experiments and WDM studies.« less

Osteoclastogenesis in Local Alveolar Bone in Early Decortication-Facilitated Orthodontic Tooth Movement

PubMed Central

Liu, Chang; Jiang, Yu-Xi; Qu, Hong; Li, Cui-Ying; Jiang, Jiu-Hui

2016-01-01

Objective In the current study, we aimed to investigate the effects of alveolar decortication on local bone remodeling, and to explore the possible mechanism by which decortication facilitates tooth movement. Materials and Methods Forty rabbits were included in the experiment. The left mandible was subjected to decortication-facilitated orthodontics, and the right mandible underwent traditional orthodontics as a control. The animals were sacrificed on the days 1, 3, 5, 7 and 14, after undergoing orthodontic procedures. Tooth movement was measured by Micro-CT, and the local periodontal tissues were investigated using H&E, Masson's trichrome and tartrate-resistant acid phosphatase (TRAP) staining. The mRNA levels of genes related to bone remodeling in the alveolar bone were analyzed using real-time PCR. Result On days 3, 5, 7 and 14, tooth movement was statistically accelerated by decortication (P < 0.05) and was accompanied by increased hyperemia. Despite the lack of new bone formation in both groups, more osteoclasts were noted in the decorticated group, with two peak counts (P < 0.05). The first peak count was consistent with the maximum values of ctsk and TRAP expression, and the second peak counts accompanied the maximum nfatc1 and jdp2 expression. The increased fra2 expression and the ratio of rankl/opg also accompanied the second peak counts. Conclusions Following alveolar decortication, osteoclastogenesis was initially induced to a greater degree than the new bone formation which was thought to have caused a regional acceleratory phenomenon (RAP). The amount of steoclastogenesis in the decorticated alveolar bone was found to have two peaks, perhaps due to attenuated local resistance. The first peak count in osteoclasts may have been due to previously existing osteoclast precursors, whereas the second may represent the differentiation of peripheral blood mononuclear cells which came from circulation as the result of hyperemia. PMID:27096621

Relativistic Electron Acceleration with Ultrashort Mid-IR Laser Pulses

NASA Astrophysics Data System (ADS)

Feder, Linus; Woodbury, Daniel; Shumakova, Valentina; Gollner, Claudia; Miao, Bo; Schwartz, Robert; Pugžlys, Audrius; Baltuška, Andrius; Milchberg, Howard

2017-10-01

We report the first results of laser plasma wakefield acceleration driven by ultrashort mid-infrared laser pulses (λ = 3.9 μm , pulsewidth 100 fs, energy <20 mJ, peak power <1 TW), which enables near- and above-critical density interactions with moderate-density gas jets. We present thresholds for electron acceleration based on critical parameters for relativistic self-focusing and target width, as well as trends in the accelerated beam profiles, charge and energy spectra which are supported by 3D particle-in-cell simulations. These results extend earlier work with sub-TW self-modulated laser wakefield acceleration using near IR drivers to the Mid-IR, and enable us to capture time-resolved images of relativistic self-focusing of the laser pulse. This work supported by DOE (DESC0010706TDD, DESC0015516); AFOSR(FA95501310044, FA95501610121); NSF(PHY1535519); DHS.

Commonly used reference values underestimate oxygen uptake in healthy, 50-year-old Swedish women.

PubMed

Genberg, M; Andrén, B; Lind, L; Hedenström, H; Malinovschi, A

2018-01-01

Cardiopulmonary exercise testing (CPET) is the gold standard among clinical exercise tests. It combines a conventional stress test with measurement of oxygen uptake (V O 2 ) and CO 2 production. No validated Swedish reference values exist, and reference values in women are generally understudied. Moreover, the importance of achieved respiratory exchange ratio (RER) and the significance of breathing reserve (BR) at peak exercise in healthy individuals are poorly understood. We compared V O 2 at maximal load (peakV O 2 ) and anaerobic threshold (V O 2@ AT ) in healthy Swedish individuals with commonly used reference values, taking gender into account. Further, we analysed maximal workload and peakV O 2 with regard to peak RER and BR. In all, 181 healthy, 50-year-old individuals (91 women) performed CPET. PeakV O 2 was best predicted using Jones et al. (100·5%), while SHIP reference values underestimated peakV O 2 most: 112·5%. Furthermore, underestimation of peakV O 2 in women was found for all studied reference values (P<0·001) and was largest for SHIP: women had 128% of predicted peakV O 2 , while men had 104%. PeakV O 2 was similar in subjects with peak RER of 1-1·1 and RER > 1·1 (2 328·7 versus 2 176·7 ml min -1 , P = 0·11). Lower BR (≤30%) related to significantly higher peakV O 2 (P<0·001). In conclusion, peakV O 2 was best predicted by Jones. All studied reference values underestimated oxygen uptake in women. No evidence for demanding RER > 1·1 in healthy individuals was found. A lowered BR is probably a normal response to higher workloads in healthy individuals. © 2016 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

Slot-coupled CW standing wave accelerating cavity

DOEpatents

Wang, Shaoheng; Rimmer, Robert; Wang, Haipeng

2017-05-16

A slot-coupled CW standing wave multi-cell accelerating cavity. To achieve high efficiency graded beta acceleration, each cell in the multi-cell cavity may include different cell lengths. Alternatively, to achieve high efficiency with acceleration for particles with beta equal to 1, each cell in the multi-cell cavity may include the same cell design. Coupling between the cells is achieved with a plurality of axially aligned kidney-shaped slots on the wall between cells. The slot-coupling method makes the design very compact. The shape of the cell, including the slots and the cone, are optimized to maximize the power efficiency and minimize the peak power density on the surface. The slots are non-resonant, thereby enabling shorter slots and less power loss.

BESTIA - the next generation ultra-fast CO 2 laser for advanced accelerator research

DOE PAGES

Pogorelsky, Igor V.; Babzien, Markus; Ben-Zvi, Ilan; ...

2015-12-02

Over the last two decades, BNL’s ATF has pioneered the use of high-peak power CO 2 lasers for research in advanced accelerators and radiation sources. In addition, our recent developments in ion acceleration, Compton scattering, and IFELs have further underscored the benefits from expanding the landscape of strong-field laser interactions deeper into the mid-infrared (MIR) range of wavelengths. This extension validates our ongoing efforts in advancing CO 2 laser technology, which we report here. Our next-generation, multi-terawatt, femtosecond CO 2 laser will open new opportunities for studying ultra-relativistic laser interactions with plasma in the MIR spectral domain, including new regimesmore » in the particle acceleration of ions and electrons.« less

Low Emittance, High Brilliance Relativistic Electron Beams from a Laser-Plasma Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brunetti, E.; Shanks, R. P.; Manahan, G. G.

2010-11-19

Progress in laser wakefield accelerators indicates their suitability as a driver of compact free-electron lasers (FELs). High brightness is defined by the normalized transverse emittance, which should be less than 1{pi} mm mrad for an x-ray FEL. We report high-resolution measurements of the emittance of 125 MeV, monoenergetic beams from a wakefield accelerator. An emittance as low as 1.1{+-}0.1{pi} mm mrad is measured using a pepper-pot mask. This sets an upper limit on the emittance, which is comparable with conventional linear accelerators. A peak transverse brightness of 5x10{sup 15} A m{sup -1} rad{sup -1} makes it suitable for compact XUVmore » FELs.« less

Adjusting central and eastern North America ground‐motion intensity measures between sites with different reference‐rock site conditions

USGS Publications Warehouse

Boore, David; Campbell, Kenneth W.

2017-01-01

Adjustment factors are provided for converting ground‐motion intensity measures between central and eastern North America (CENA) sites with different reference‐rock site conditions (VS30=760, 2000, and 3000  m/s) for moment magnitudes ranging from 2 to 8, rupture distances ranging from 2 to 1200 km, Fourier amplitude spectra (FAS) for frequencies ranging from 0.01 to 100 Hz, response spectra for periods ranging from 0.01 to 10.0 s, peak ground acceleration, and peak ground velocity. The adjustment factors are given for a wide range of the site diminution parameters (κ0) for sites with VS30=760  m/s and for a κ0 of 0.006 s for two harder rock sites. Fourteen CENA velocity profiles with VS30 values within a factor of 1.1 of 760  m/s were used to derive average FAS amplification factors as a function of frequency, which were then used in simulations of peak ground‐motion parameters and response spectra to derive the adjustment factors. The amplification function differs from that used in western North America (e.g., Campbell and Boore, 2016) in having a peak near 9 Hz, due to the resonance of motions in the relatively thin low‐velocity material over hard rock that characterizes many CENA sites with VS30 near 760  m/s. We call these B/C sites, because this velocity marks the boundary between National Earthquake Hazards Reduction Program site classes B and C (Building Seismic Safety Council, 2004). The adjustments for short‐period motions are sensitive to the value of κ0, but there are very few if any determinations of κ0 for CENA B/C sites. For this reason, we determined κ0 from multiple recordings at Pinyon Flat Observatory (PFO), California, which has a velocity‐depth profile similar to those of CENA B/C sites. The PFO and other results from the literature suggest that appropriate values of κ0 for CENA B/C sites are expected to lie between 0.01 and 0.03 s.

Adjusting central and eastern North America ground-motion intensity measures between sites with different reference-rock site conditions

USGS Publications Warehouse

Boore, David; Campbell, Kenneth W.

2017-01-01

Adjustment factors are provided for converting ground‐motion intensity measures between central and eastern North America (CENA) sites with different reference‐rock site conditions (VS30=760, 2000, and 3000  m/s) for moment magnitudes ranging from 2 to 8, rupture distances ranging from 2 to 1200 km, Fourier amplitude spectra (FAS) for frequencies ranging from 0.01 to 100 Hz, response spectra for periods ranging from 0.01 to 10.0 s, peak ground acceleration, and peak ground velocity. The adjustment factors are given for a wide range of the site diminution parameters (κ0) for sites with VS30=760  m/s and for a κ0 of 0.006 s for two harder rock sites. Fourteen CENA velocity profiles with VS30 values within a factor of 1.1 of 760  m/s were used to derive average FAS amplification factors as a function of frequency, which were then used in simulations of peak ground‐motion parameters and response spectra to derive the adjustment factors. The amplification function differs from that used in western North America (e.g., Campbell and Boore, 2016) in having a peak near 9 Hz, due to the resonance of motions in the relatively thin low‐velocity material over hard rock that characterizes many CENA sites with VS30 near 760  m/s. We call these B/C sites, because this velocity marks the boundary between National Earthquake Hazards Reduction Program site classes B and C (Building Seismic Safety Council, 2004). The adjustments for short‐period motions are sensitive to the value of κ0, but there are very few if any determinations of κ0 for CENA B/C sites. For this reason, we determined κ0from multiple recordings at Pinyon Flat Observatory (PFO), California, which has a velocity‐depth profile similar to those of CENA B/C sites. The PFO and other results from the literature suggest that appropriate values of κ0 for CENA B/C sites are expected to lie between 0.01 and 0.03 s.

An Active Smart Material Control System for F/A-18 Buffet Alleviation

NASA Technical Reports Server (NTRS)

Sheta, Essam F.; Moses, Robert W.; Huttsell, Lawrence J.; Harrand, Vincent J.

2003-01-01

The vertical tail buffet problem of fighter aircraft occurs at high angles of attack when the vortical flow breaks down ahead of the vertical tails resulting in unsteady and unbalanced pressure loads on the vertical tails. The buffet loads imposed upon the vertical tails resulted in a premature fatigue failure of the tails, and consequently limits the performance and super maneuverability of twin-tail fighter aircraft. An active smart material control system using distributed piezoelectric actuators has been developed for buffet alleviation and is presented. The inboard and outboard surfaces of the vertical tail are equipped with piezoelectric actuators to control the buffet responses in the first bending and torsion modes. The electrodynamics of the piezoelectric actuators are expressed with a three-dimensional finite-element model. A single-input-single-output controller is designed to drive the active piezoelectric actuators. High-fidelity multidisciplinary analysis modules for the fluid dynamics, structure dynamics, electrodynamics of the piezoelectric actuators, control law, fluid structure interfacing, and grid motion are integrated into a multidisciplinary computing environment that controls the temporal synchronization of the analysis modules. At 30 degree angle of attack, RMS values of tip acceleration are reduced by as much as 12%. The peak values of the power spectral density of tail-tip acceleration are reduced by as much as 22% in the first bending mode and by as much as 82% in the first torsion mode. The actively controlled piezoelectric actuators were also effective in adding damping at wide range of angles of attack.

Balance Performance During Perturbed Standing Is Not Associated With Muscle Strength and Power in Young Adults.

PubMed

Zemková, Erika; Jeleň, Michal; Kováčiková, Zuzana; Miklovič, Peter; Svoboda, Zdeněk; Janura, Miroslav

2017-01-01

The authors investigate the ways in which varied postural responses to translating platform perturbations are associated with the variables of strength and power. Twenty-four physically active and 27 sedentary young adults were exposed to a set of postural perturbations at varied velocities (10 and 20 cm/s) and the respective accelerations (6.4 and 6.9 m/s 2 ), constant distance (6 cm), and 4 directions of platform motion (forward, backward, left-lateral, and right-lateral). They also performed maximum voluntary isometric contraction (MVC) and chair rising/chair jumping tests. The analysis of variance revealed significant interaction effect for peak center of pressure displacement, direction by velocity: F 3,129 = 24.43, p = .002; and direction by acceleration: F 3,129 = 34.18, p = .001. There were no significant correlations between peak center of pressure displacements and peak force and peak rate of force development measured during MVC in either standing (r = .27-57) or sitting positions (r = .12-51) and peak power during chair jumping (r = .47-.59) in all participants. As such, only a small proportion of variance was explained (9-39%, 3-23%, and 23-41%, respectively). In conclusion, interaction effects indicate that the composition of stimuli strongly influences compensatory responses and this effect is more pronounced in sedentary than in physically active young adults. Nevertheless, the dynamic balance is not associated with muscle strength and power in either group.

Electron Transport and Ion Acceleration in a Low-power Cylindrical Hall Thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

A. Smirnov; Y. Raitses; N.J. Fisch

2004-06-24

Conventional annular Hall thrusters become inefficient when scaled to low power. Cylindrical Hall thrusters, which have lower surface-to-volume ratio, are therefore more promising for scaling down. They presently exhibit performance comparable with conventional annular Hall thrusters. Electron cross-field transport in a 2.6 cm miniaturized cylindrical Hall thruster (100 W power level) has been studied through the analysis of experimental data and Monte Carlo simulations of electron dynamics in the thruster channel. The numerical model takes into account elastic and inelastic electron collisions with atoms, electron-wall collisions, including secondary electron emission, and Bohm diffusion. We show that in order to explainmore » the observed discharge current, the electron anomalous collision frequency {nu}{sub B} has to be on the order of the Bohm value, {nu}{sub B} {approx} {omega}{sub c}/16. The contribution of electron-wall collisions to cross-field transport is found to be insignificant. The plasma density peak observed at the axis of the 2.6 cm cylindrical Hall thruster is likely to be due to the convergent flux of ions, which are born in the annular part of the channel and accelerated towards the thruster axis.« less

The effects of bed rest on crew performance during simulated shuttle reentry. Volume 1: Study overview and physiological results

NASA Technical Reports Server (NTRS)

Chambers, A.; Vykukal, H. C.

1974-01-01

A centrifuge study was carried out to measure physiological stress and control task performance during simulated space shuttle orbiter reentry. Jet pilots were tested with, and without, anti-g-suit protection. The pilots were exposed to simulated space shuttle reentry acceleration profiles before, and after, ten days of complete bed rest, which produced physiological deconditioning similar to that resulting from prolonged exposure to orbital zero g. Pilot performance in selected control tasks was determined during simulated reentry, and before and after each simulation. Physiological stress during reentry was determined by monitoring heart rate, blood pressure, and respiration rate. Study results indicate: (1) heart rate increased during the simulated reentry when no g protection was given, and remained at or below pre-bed rest values when g-suits were used; (2) pilots preferred the use of g-suits to muscular contraction for control of vision tunneling and grayout during reentry; (3) prolonged bed rest did not alter blood pressure or respiration rate during reentry, but the peak reentry acceleration level did; and (4) pilot performance was not affected by prolonged bed rest or simulated reentry.

Numerical simulations of the occupant head response in an infantry vehicle under blunt impact and blast loading conditions.

PubMed

Sevagan, Gopinath; Zhu, Feng; Jiang, Binhui; Yang, King H

2013-07-01

This article presents the results of a finite element simulation on the occupant head response in an infantry vehicle under two separated loading conditions: (1) blunt impact and (2) blast loading conditions. A Hybrid-III dummy body integrated with a previously validated human head model was used as the surrogate. The biomechanical response of the head was studied in terms of head acceleration due to the impact by a projectile on the vehicle and intracranial pressure caused by blast wave. A series of parametric studies were conducted on the numerical model to analyze the effect of some key parameters, such as seat configuration, impact velocity, and boundary conditions. The simulation results indicate that a properly designed seat and internal surface of the infantry vehicle can play a vital role in reducing the risk of head injury in the current scenarios. Comparison of the kinematic responses under the blunt impact and blast loading conditions reveals that under the current loading conditions, the acceleration pulse in the blast scenario has much higher peak values and frequency than blunt impact case, which may reflect different head response characteristics.

Observation of Quasichanneling Oscillations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wistisen, T. N.; Mikkelsen, R. E.; Uggerhoj, U. I.

2017-07-13

Here, we report on the first experimental observations of quasichanneling oscillations, recently seen in simulations and described theoretically. Although above-barrier particles penetrating a single crystal are generally seen as behaving almost as in an amorphous substance, distinct oscillation peaks nevertheless appear for particles in that category. The quasichanneling oscillations were observed at SLAC National Accelerator Laboratory by aiming 20.35 GeV positrons and electrons at a thin silicon crystal bent to a radius of R = 0.15 m, exploiting the quasimosaic effect. For electrons, two relatively faint quasichanneling peaks were observed, while for positrons, seven quasichanneling peaks were clearly identified.

Observation of Quasichanneling Oscillations

NASA Astrophysics Data System (ADS)

Wistisen, T. N.; Mikkelsen, R. E.; Uggerhøj, U. I.; Wienands, U.; Markiewicz, T. W.; Gessner, S.; Hogan, M. J.; Noble, R. J.; Holtzapple, R.; Tucker, S.; Guidi, V.; Mazzolari, A.; Bagli, E.; Bandiera, L.; Sytov, A.; SLAC E-212 Collaboration

2017-07-01

We report on the first experimental observations of quasichanneling oscillations, recently seen in simulations and described theoretically. Although above-barrier particles penetrating a single crystal are generally seen as behaving almost as in an amorphous substance, distinct oscillation peaks nevertheless appear for particles in that category. The quasichanneling oscillations were observed at SLAC National Accelerator Laboratory by aiming 20.35 GeV positrons and electrons at a thin silicon crystal bent to a radius of R =0.15 m , exploiting the quasimosaic effect. For electrons, two relatively faint quasichanneling peaks were observed, while for positrons, seven quasichanneling peaks were clearly identified.

Effect of Footwear Modifications on Oscillations at the Achilles Tendon during Running on a Treadmill and Over Ground: A Cross-Sectional Study.

PubMed

Meinert, Ilka; Brown, Niklas; Alt, Wilfried

2016-01-01

Achilles tendon injuries are known to commonly occur in runners. During running repeated impacts are transferred in axial direction along the lower leg, therefore possibly affecting the oscillation behavior of the Achilles tendon. The purpose of the present study was to explore the effects of different footwear modifications and different ground conditions (over ground versus treadmill) on oscillations at the Achilles tendon. Oscillations were measured in 20 male runners using two tri-axial accelerometers. Participants ran in three different shoe types on a treadmill and over ground. Data analysis was limited to stance phase and performed in time and frequency space. Statistical comparison was conducted between oscillations in vertical and horizontal direction, between running shoes and between ground conditions (treadmill versus over ground running). Differences in the oscillation behavior could be detected between measurement directions with peak accelerations in the vertical being lower than those in the horizontal direction, p < 0.01. Peak accelerations occurred earlier at the distal accelerometer than at the proximal one, p < 0.01. Average normalized power differed between running shoes (p < 0.01) with harder damping material resulting in higher power values. Little to no power attenuation was found between the two accelerometers. Oscillation behavior of the Achilles tendon is not influenced by ground condition. Differences in shoe configurations may lead to variations in running technique and impact forces and therefore result in alterations of the vibration behavior at the Achilles tendon. The absence of power attenuation may have been caused by either a short distance between the two accelerometers or high stiffness of the tendon. High stiffness of the tendon will lead to complete transmission of the signal along the Achilles tendon and therefore no attenuation occurs.

Effect of Footwear Modifications on Oscillations at the Achilles Tendon during Running on a Treadmill and Over Ground: A Cross-Sectional Study

PubMed Central

Meinert, Ilka; Brown, Niklas; Alt, Wilfried

2016-01-01

Background Achilles tendon injuries are known to commonly occur in runners. During running repeated impacts are transferred in axial direction along the lower leg, therefore possibly affecting the oscillation behavior of the Achilles tendon. The purpose of the present study was to explore the effects of different footwear modifications and different ground conditions (over ground versus treadmill) on oscillations at the Achilles tendon. Methods Oscillations were measured in 20 male runners using two tri-axial accelerometers. Participants ran in three different shoe types on a treadmill and over ground. Data analysis was limited to stance phase and performed in time and frequency space. Statistical comparison was conducted between oscillations in vertical and horizontal direction, between running shoes and between ground conditions (treadmill versus over ground running). Results Differences in the oscillation behavior could be detected between measurement directions with peak accelerations in the vertical being lower than those in the horizontal direction, p < 0.01. Peak accelerations occurred earlier at the distal accelerometer than at the proximal one, p < 0.01. Average normalized power differed between running shoes (p < 0.01) with harder damping material resulting in higher power values. Little to no power attenuation was found between the two accelerometers. Oscillation behavior of the Achilles tendon is not influenced by ground condition. Conclusion Differences in shoe configurations may lead to variations in running technique and impact forces and therefore result in alterations of the vibration behavior at the Achilles tendon. The absence of power attenuation may have been caused by either a short distance between the two accelerometers or high stiffness of the tendon. High stiffness of the tendon will lead to complete transmission of the signal along the Achilles tendon and therefore no attenuation occurs. PMID:27010929

Diastolic time – frequency relation in the stress echo lab: filling timing and flow at different heart rates

PubMed Central

Bombardini, Tonino; Gemignani, Vincenzo; Bianchini, Elisabetta; Venneri, Lucia; Petersen, Christina; Pasanisi, Emilio; Pratali, Lorenza; Alonso-Rodriguez, David; Pianelli, Mascia; Faita, Francesco; Giannoni, Massimo; Arpesella, Giorgio; Picano, Eugenio

2008-01-01

A cutaneous force-frequency relation recording system based on first heart sound amplitude vibrations has been recently validated. Second heart sound can be simultaneously recorded in order to quantify both systole and diastole duration. Aims 1- To assess the feasibility and extra-value of operator-independent, force sensor-based, diastolic time recording during stress. Methods We enrolled 161 patients referred for stress echocardiography (exercise 115, dipyridamole 40, pacing 6 patients). The sensor was fastened in the precordial region by a standard ECG electrode. The acceleration signal was converted into digital and recorded together with ECG signal. Both systolic and diastolic times were acquired continuously during stress and were displayed by plotting times vs. heart rate. Diastolic filling rate was calculated as echo-measured mitral filling volume/sensor-monitored diastolic time. Results Diastolic time decreased during stress more markedly than systolic time. At peak stress 62 of the 161 pts showed reversal of the systolic/diastolic ratio with the duration of systole longer than diastole. In the exercise group, at 100 bpm HR, systolic/diastolic time ratio was lower in the 17 controls (0.74 ± 0.12) than in patients (0.86 ± 0.10, p < 0.05 vs. controls). Diastolic filling rate increased from 101 ± 36 (rest) to 219 ± 92 ml/m2* s-1 at peak stress (p < 0.5 vs. rest). Conclusion Cardiological systolic and diastolic duration can be monitored during stress by using an acceleration force sensor. Simultaneous calculation of stroke volume allows monitoring diastolic filling rate. Stress-induced "systolic-diastolic mismatch" can be easily quantified and is associated to several cardiac diseases, possibly expanding the spectrum of information obtainable during stress. PMID:18426559

Large-Grain Superconducting Gun Cavity Testing Program Phase One Closing Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hammons, L.; Bellavia, S.; Belomestnykh, S.

2013-10-31

This report details the experimental configuration and RF testing results for the first phase of a large-grained niobium electron gun cavity testing program being conducted in the Small Vertical Testing Facility in the Collider-Accelerator Department. This testing is meant to explore multi-pacting in the cavity and shed light on the behavior of a counterpart cavity of identical geometry installed in the Energy Recovery LINAC being constructed in the Collider-Accelerator Department at Brookhaven National Laboratory. This test found that the Q of the large-grained cavity at 4 K reached ~6.5 × 10 8 and at 2 K reached a value ofmore » ~6 × 10 9. Both of these values are about a factor of 10 lower than would be expected for this type of cavity given the calculated surface resistance and the estimated geometry factor for this half-cell cavity. In addition, the cavity reached a peak voltage of 0.6 MV before there was sig-nificant decline in the Q value and a substantial increase in field emission. This relatively low volt-age, coupled with the low Q and considerable field emission suggest contamination of the cavity interior, possibly during experimental assembly. The results may also suggest that additional chemical etching of the interior surface of the cavity may be beneficial. Throughout the course of testing, various challenges arose including slow helium transfer to the cryostat and cable difficulties. These difficulties and others were eventually resolved, and the re-port discusses the operating experience of the experiment thus far and the plans for future work aimed at exploring the nature of multipacting with a copper cathode inserted into the cavity.« less

Intense terahertz pulses from SLAC electron beams using coherent transition radiation.

PubMed

Wu, Ziran; Fisher, Alan S; Goodfellow, John; Fuchs, Matthias; Daranciang, Dan; Hogan, Mark; Loos, Henrik; Lindenberg, Aaron

2013-02-01

SLAC has two electron accelerators, the Linac Coherent Light Source (LCLS) and the Facility for Advanced Accelerator Experimental Tests (FACET), providing high-charge, high-peak-current, femtosecond electron bunches. These characteristics are ideal for generating intense broadband terahertz (THz) pulses via coherent transition radiation. For LCLS and FACET respectively, the THz pulse duration is typically 20 and 80 fs RMS and can be tuned via the electron bunch duration; emission spectra span 3-30 THz and 0.5 THz-5 THz; and the energy in a quasi-half-cycle THz pulse is 0.2 and 0.6 mJ. The peak electric field at a THz focus has reached 4.4 GV/m (0.44 V/Å) at LCLS. This paper presents measurements of the terahertz pulses and preliminary observations of nonlinear materials response.

Role of the calcaneal heel pad and polymeric shock absorbers in attenuation of heel strike impact.

PubMed

Noe, D A; Voto, S J; Hoffmann, M S; Askew, M J; Gradisar, I A

1993-01-01

The capacity of the calcaneal heel pad, with and without augmentation by a polymeric shock absorbing material (Sorbothane 0050), to attenuate heel strike impulses has been studied using five fresh human cadaveric lower leg specimens. The specimens, instrumented with an accelerometer, were suspended and impacted with a hammer; a steel rod was similarly suspended and impacted. The calcaneal heel pad attenuated the peak accelerations by 80%. Attenuations of up to 93% were achieved by the shock absorbing material when tested against the steel rod; however, when tested in series with the calcaneal heel pad, the reduction in peak acceleration due to the shock absorbing material dropped to 18%. Any evaluation of the effectiveness of shock absorbing shoe materials must take into account their mechanical interaction with the body.

Peak oxygen uptake in Paralympic sitting sports: A systematic literature review, meta- and pooled-data analysis.

PubMed

Baumgart, Julia Kathrin; Brurok, Berit; Sandbakk, Øyvind

2018-01-01

Peak oxygen uptake (VO2peak) in Paralympic sitting sports athletes represents their maximal ability to deliver energy aerobically in an upper-body mode, with values being influenced by sex, disability-related physiological limitations, sport-specific demands, training status and how they are tested. To identify VO2peak values in Paralympic sitting sports, examine between-sports differences and within-sports variations in VO2peak and determine the influence of sex, age, body-mass, disability and test-mode on VO2peak. Systematic literature review and meta-analysis. PubMed, CINAHL, SPORTDiscusTM and EMBASE were systematically searched in October 2016 using relevant medical subject headings, keywords and a Boolean. Studies that assessed VO2peak values in sitting sports athletes with a disability in a laboratory setting were included. Data was extracted and pooled in the different sports disciplines, weighted by the Dersimonian and Laird random effects approach. Quality of the included studies was assessed with a modified version of the Downs and Black checklist by two independent reviewers. Meta-regression and pooled-data multiple regression analyses were performed to assess the influence of sex, age, body-mass, disability, test mode and study quality on VO2peak. Of 6542 retrieved articles, 57 studies reporting VO2peak values in 14 different sitting sports were included in this review. VO2peak values from 771 athletes were used in the data analysis, of which 30% participated in wheelchair basketball, 27% in wheelchair racing, 15% in wheelchair rugby and the remaining 28% in the 11 other disciplines. Fifty-six percent of the athletes had a spinal cord injury and 87% were men. Sports-discipline-averaged VO2peak values ranged from 2.9 L∙min-1 and 45.6 mL∙kg-1∙min-1 in Nordic sit skiing to 1.4 L∙min-1 and 17.3 mL∙kg-1∙min-1 in shooting and 1.3 L∙min-1 and 18.9 mL∙kg-1∙min-1 in wheelchair rugby. Large within-sports variation was found in sports with few included studies and corresponding low sample sizes. The meta-regression and pooled-data multiple regression analyses showed that being a man, having an amputation, not being tetraplegic, testing in a wheelchair ergometer and treadmill mode, were found to be favorable for high absolute and body-mass normalized VO2peak values. Furthermore, high body mass was favourable for high absolute VO2peak values and low body mass for high body-mass normalized VO2peak values. The highest VO2peak values were found in Nordic sit skiing, an endurance sport with continuously high physical efforts, and the lowest values in shooting, a sport with low levels of displacement, and in wheelchair rugby where mainly athletes with tetraplegia compete. However, VO2peak values need to be interpreted carefully in sports-disciplines with few included studies and large within-sports variation. Future studies should include detailed information on training status, sex, age, test mode, as well as the type and extent of disability in order to more precisely evaluate the effect of these factors on VO2peak.

Peak oxygen uptake in Paralympic sitting sports: A systematic literature review, meta- and pooled-data analysis

PubMed Central

Brurok, Berit; Sandbakk, Øyvind

2018-01-01

Background Peak oxygen uptake (VO2peak) in Paralympic sitting sports athletes represents their maximal ability to deliver energy aerobically in an upper-body mode, with values being influenced by sex, disability-related physiological limitations, sport-specific demands, training status and how they are tested. Objectives To identify VO2peak values in Paralympic sitting sports, examine between-sports differences and within-sports variations in VO2peak and determine the influence of sex, age, body-mass, disability and test-mode on VO2peak. Design Systematic literature review and meta-analysis. Data sources PubMed, CINAHL, SPORTDiscusTM and EMBASE were systematically searched in October 2016 using relevant medical subject headings, keywords and a Boolean. Eligibility criteria Studies that assessed VO2peak values in sitting sports athletes with a disability in a laboratory setting were included. Data synthesis Data was extracted and pooled in the different sports disciplines, weighted by the Dersimonian and Laird random effects approach. Quality of the included studies was assessed with a modified version of the Downs and Black checklist by two independent reviewers. Meta-regression and pooled-data multiple regression analyses were performed to assess the influence of sex, age, body-mass, disability, test mode and study quality on VO2peak. Results Of 6542 retrieved articles, 57 studies reporting VO2peak values in 14 different sitting sports were included in this review. VO2peak values from 771 athletes were used in the data analysis, of which 30% participated in wheelchair basketball, 27% in wheelchair racing, 15% in wheelchair rugby and the remaining 28% in the 11 other disciplines. Fifty-six percent of the athletes had a spinal cord injury and 87% were men. Sports-discipline-averaged VO2peak values ranged from 2.9 L∙min-1 and 45.6 mL∙kg-1∙min-1 in Nordic sit skiing to 1.4 L∙min-1 and 17.3 mL∙kg-1∙min-1 in shooting and 1.3 L∙min-1 and 18.9 mL∙kg-1∙min-1 in wheelchair rugby. Large within-sports variation was found in sports with few included studies and corresponding low sample sizes. The meta-regression and pooled-data multiple regression analyses showed that being a man, having an amputation, not being tetraplegic, testing in a wheelchair ergometer and treadmill mode, were found to be favorable for high absolute and body-mass normalized VO2peak values. Furthermore, high body mass was favourable for high absolute VO2peak values and low body mass for high body-mass normalized VO2peak values. Conclusion The highest VO2peak values were found in Nordic sit skiing, an endurance sport with continuously high physical efforts, and the lowest values in shooting, a sport with low levels of displacement, and in wheelchair rugby where mainly athletes with tetraplegia compete. However, VO2peak values need to be interpreted carefully in sports-disciplines with few included studies and large within-sports variation. Future studies should include detailed information on training status, sex, age, test mode, as well as the type and extent of disability in order to more precisely evaluate the effect of these factors on VO2peak. PMID:29474386

Review of laser-driven ion sources and their applications.

PubMed

Daido, Hiroyuki; Nishiuchi, Mamiko; Pirozhkov, Alexander S

2012-05-01

For many years, laser-driven ion acceleration, mainly proton acceleration, has been proposed and a number of proof-of-principle experiments have been carried out with lasers whose pulse duration was in the nanosecond range. In the 1990s, ion acceleration in a relativistic plasma was demonstrated with ultra-short pulse lasers based on the chirped pulse amplification technique which can provide not only picosecond or femtosecond laser pulse duration, but simultaneously ultra-high peak power of terawatt to petawatt levels. Starting from the year 2000, several groups demonstrated low transverse emittance, tens of MeV proton beams with a conversion efficiency of up to several percent. The laser-accelerated particle beams have a duration of the order of a few picoseconds at the source, an ultra-high peak current and a broad energy spectrum, which make them suitable for many, including several unique, applications. This paper reviews, firstly, the historical background including the early laser-matter interaction studies on energetic ion acceleration relevant to inertial confinement fusion. Secondly, we describe several implemented and proposed mechanisms of proton and/or ion acceleration driven by ultra-short high-intensity lasers. We pay special attention to relatively simple models of several acceleration regimes. The models connect the laser, plasma and proton/ion beam parameters, predicting important features, such as energy spectral shape, optimum conditions and scalings under these conditions for maximum ion energy, conversion efficiency, etc. The models also suggest possible ways to manipulate the proton/ion beams by tailoring the target and irradiation conditions. Thirdly, we review experimental results on proton/ion acceleration, starting with the description of driving lasers. We list experimental results and show general trends of parameter dependences and compare them with the theoretical predictions and simulations. The fourth topic includes a review of scientific, industrial and medical applications of laser-driven proton or ion sources, some of which have already been established, while the others are yet to be demonstrated. In most applications, the laser-driven ion sources are complementary to the conventional accelerators, exhibiting significantly different properties. Finally, we summarize the paper.

Determination of the measurement threshold in gamma-ray spectrometry.

PubMed

Korun, M; Vodenik, B; Zorko, B

2017-03-01

In gamma-ray spectrometry the measurement threshold describes the lover boundary of the interval of peak areas originating in the response of the spectrometer to gamma-rays from the sample measured. In this sense it presents a generalization of the net indication corresponding to the decision threshold, which is the measurement threshold at the quantity value zero for a predetermined probability for making errors of the first kind. Measurement thresholds were determined for peaks appearing in the spectra of radon daughters 214 Pb and 214 Bi by measuring the spectrum 35 times under repeatable conditions. For the calculation of the measurement threshold the probability for detection of the peaks and the mean relative uncertainty of the peak area were used. The relative measurement thresholds, the ratios between the measurement threshold and the mean peak area uncertainty, were determined for 54 peaks where the probability for detection varied between some percent and about 95% and the relative peak area uncertainty between 30% and 80%. The relative measurement thresholds vary considerably from peak to peak, although the nominal value of the sensitivity parameter defining the sensitivity for locating peaks was equal for all peaks. At the value of the sensitivity parameter used, the peak analysis does not locate peaks corresponding to the decision threshold with the probability in excess of 50%. This implies that peaks in the spectrum may not be located, although the true value of the measurand exceeds the decision threshold. Copyright © 2017 Elsevier Ltd. All rights reserved.

Conceptual design of a 15-TW pulsed-power accelerator for high-energy-density–physics experiments

DOE PAGES

Spielman, R. B.; Froula, D. H.; Brent, G.; ...

2017-06-21

We have developed a conceptual design of a 15-TW pulsed-power accelerator based on the linear-transformer-driver (LTD) architecture described by Stygar [W. A. Stygar et al., Phys. Rev. ST Accel. Beams 18, 110401 (2015)]. The driver will allow multiple, high-energy-density experiments per day in a university environment and, at the same time, will enable both fundamental and integrated experiments that are scalable to larger facilities. In this design, many individual energy storage units (bricks), each composed of two capacitors and one switch, directly drive the target load without additional pulse compression. Ten LTD modules in parallel drive the load. Each modulemore » consists of 16 LTD cavities connected in series, where each cavity is powered by 22 bricks connected in parallel. This design stores up to 2.75 MJ and delivers up to 15 TW in 100 ns to the constant-impedance, water-insulated radial transmission lines. The transmission lines in turn deliver a peak current as high as 12.5 MA to the physics load. To maximize its experimental value and flexibility, the accelerator is coupled to a modern, multibeam laser facility (four beams with up to 5 kJ in 10 ns and one beam with up to 2.6 kJ in 100 ps or less) that can provide auxiliary heating of the physics load. The lasers also enable advanced diagnostic techniques such as x-ray Thomson scattering and multiframe and three-dimensional radiography. In conclusion, the coupled accelerator-laser facility will be the first of its kind and be capable of conducting unprecedented high-energy-density-physics experiments.« less

Conceptual design of a 15-TW pulsed-power accelerator for high-energy-density–physics experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spielman, R. B.; Froula, D. H.; Brent, G.

We have developed a conceptual design of a 15-TW pulsed-power accelerator based on the linear-transformer-driver (LTD) architecture described by Stygar [W. A. Stygar et al., Phys. Rev. ST Accel. Beams 18, 110401 (2015)]. The driver will allow multiple, high-energy-density experiments per day in a university environment and, at the same time, will enable both fundamental and integrated experiments that are scalable to larger facilities. In this design, many individual energy storage units (bricks), each composed of two capacitors and one switch, directly drive the target load without additional pulse compression. Ten LTD modules in parallel drive the load. Each modulemore » consists of 16 LTD cavities connected in series, where each cavity is powered by 22 bricks connected in parallel. This design stores up to 2.75 MJ and delivers up to 15 TW in 100 ns to the constant-impedance, water-insulated radial transmission lines. The transmission lines in turn deliver a peak current as high as 12.5 MA to the physics load. To maximize its experimental value and flexibility, the accelerator is coupled to a modern, multibeam laser facility (four beams with up to 5 kJ in 10 ns and one beam with up to 2.6 kJ in 100 ps or less) that can provide auxiliary heating of the physics load. The lasers also enable advanced diagnostic techniques such as x-ray Thomson scattering and multiframe and three-dimensional radiography. In conclusion, the coupled accelerator-laser facility will be the first of its kind and be capable of conducting unprecedented high-energy-density-physics experiments.« less

Acceleration and Orientation Jumping Performance Differences Among Elite Professional Male Handball Players With or Without Previous ACL Reconstruction: An Inertial Sensor Unit-Based Study.

PubMed

Setuain, Igor; González-Izal, Miriam; Alfaro, Jesús; Gorostiaga, Esteban; Izquierdo, Mikel

2015-12-01

Handball is one of the most challenging sports for the knee joint. Persistent biomechanical and jumping capacity alterations can be observed in athletes with an anterior cruciate ligament (ACL) injury. Commonly identified jumping biomechanical alterations have been described by the use of laboratory technologies. However, portable and easy-to-handle technologies that enable an evaluation of jumping biomechanics at the training field are lacking. To analyze unilateral/bilateral acceleration and orientation jumping performance differences among elite male handball athletes with or without previous ACL reconstruction via a single inertial sensor unit device. Case control descriptive study. At the athletes' usual training court. Twenty-two elite male (6 ACL-reconstructed and 16 uninjured control players) handball players were evaluated. The participants performed a vertical jump test battery that included a 50-cm vertical bilateral drop jump, a 20-cm vertical unilateral drop jump, and vertical unilateral countermovement jump maneuvers. Peak 3-dimensional (X, Y, Z) acceleration (m·s(-2)), jump phase duration and 3-dimensional orientation values (°) were obtained from the inertial sensor unit device. Two-tailed t-tests and a one-way analysis of variance were performed to compare means. The P value cut-off for significance was set at P < .05. The ACL-reconstructed male athletes did not show any significant (P < .05) residual jumping biomechanical deficits regarding the measured variables compared with players who had not suffered this knee injury. A dominance effect was observed among non-ACL reconstructed controls but not among their ACL-reconstructed counterparts (P < .05). Elite male handball athletes with previous ACL reconstruction demonstrated a jumping biomechanical profile similar to control players, including similar jumping performance values in both bilateral and unilateral jumping maneuvers, several years after ACL reconstruction. These findings are in agreement with previous research showing full functional restoration of abilities in top-level male athletes after ACL reconstruction, rehabilitation and subsequent return to sports at the previous level. Copyright © 2015 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

Small female head and neck interaction with a deploying side airbag.

PubMed

Duma, Stefan M; Crandall, Jeff R; Rudd, Rodney W; Kent, Richard W

2003-09-01

This paper presents dummy and cadaver experiments designed to investigate the injury potential of an out-of-position small female head and neck from a deploying side airbag. Seat-mounted, thoracic-type, side airbags were selected for this study to represent those currently available on selected luxury automobiles. A computer simulation program was used to identify the worst case loading position for the small female head and neck. Once the initial position was identified, experiments were performed with the Hybrid III 5th percentile dummy and three small female cadavers, using three different inflators. Peak head center of gravity (CG) accelerations for the dummy ranged from 71x g to 154 x g, and were greater than cadaver values, which ranged from 68 x g to 103 x g. Peak neck tension as measured at the upper load cell of the dummy increased with inflator aggressivity from 992 to 1670N. A conservative modification of the US National Highway Traffic Safety Administration's (NHTSA's) N(ij) proposed neck injury criteria, which combines neck tension and bending, was used. All values were well below the 1.0 injury threshold for the dummy and suggested a very low possibility of neck injury. In agreement with this prediction, no injuries were observed. Even in a worst case position, small females are at low risk of head or neck injuries under loading from these thoracic-type airbags; however, injury risk increases with increasing inflator aggressivity.

LET and ion-species dependence for mutation induction and mutation spectrum on hprt locus in normal human fibroblasts.

PubMed

Tsuruoka, Chizuru; Suzuki, Masao; Fujitaka, Kazunobu

2004-11-01

We have been studying LET and ion species dependence of RBE in mutation frequency and mutation spectrum of deletion pattern of exons in hprt locus. Normal human skin fibroblasts were irradiated with heavy-ion beams, such as carbon- (290 MeV/u and 135 MeV/u), neon- (230 MeV/u and 400 MeV/u), silicon- (490 MeV/u) and iron- (500 MeV/u) ion beams, generated by Heavy Ion Medical Accelerator in Chiba (HIMAC) at national Institute of Radiological Sciences (NIRS). Mutation induction in hprt locus was detected to measure 6-thioguanine resistant colonies and deletion spectrum of exons was analyzed by multiplex PCR. The LET-RBE curves of mutation induction for carbon- and neon-ion beams showed a peak around 75 keV/micrometers and 155 keV/micrometers, respectively. On the other hand, there observed no clear peak for silicon-ion beams. The deletion spectrum of exons was different in induced mutants among different ion species. These results suggested that quantitative and qualitative difference in mutation occurred when using different ion species even if similar LET values.

Plasma block acceleration based upon the interaction between double targets and an ultra-intense linearly polarized laser pulse

NASA Astrophysics Data System (ADS)

Xu, Yanxia; Wang, Jiaxiang; Hora, Heinrich; Qi, Xin; Xing, Yifan; Yang, Lei; Zhu, Wenjun

2018-04-01

A new scheme of plasma block acceleration based upon the interaction between double targets and an ultra-intense linearly polarized laser pulse with intensity I ˜ 1022 W/cm2 is investigated via two-dimensional particle-in-cell simulations. The targets are composed of a pre-target of low-density aluminium plasma and an overdense main-target of hydrogen plasma. Through intensive parameter optimization, we have observed highly efficient plasma block accelerations with a monochromatic proton beam peaked at GeVs. The underlying mechanism is attributed to the enhancement of the charge separation field due to the properly selected pre-target.

Gamma-Ray Emission in Dissipative Pulsar Magnetospheres: from Theory to Fermi Observations

NASA Technical Reports Server (NTRS)

Kalapotharakos, Konstantinos; Harding, Alice K.; Kazanas, Demosthenes

2014-01-01

We compute the patterns of gamma-ray emission due to curvature radiation in dissipative pulsar magnetospheres. Our ultimate goal is to construct macrophysical models that are able to reproduce the observed gamma-ray light curve phenomenology recently published in the Second Fermi Pulsar Catalog. We apply specific forms of Ohm's law on the open field lines using a broad range for the macroscopic conductivity values that result in solutions ranging, from near-vacuum to near-force-free. Using these solutions, we generate model gamma-ray light curves by calculating realistic trajectories and Lorentz factors of radiating particles under the influence of both the accelerating electric fields and curvature radiation reaction. We further constrain our models using the observed dependence of the phase lags between the radio and gamma-ray emission on the gamma-ray peak separation. We perform a statistical comparison of our model radio-lag versus peak-separation diagram and the one obtained for the Fermi standard pulsars. We find that for models of uniform conductivity over the entire open magnetic field line region, agreement with observations favors higher values of this parameter. We find, however, significant improvement in fitting the data with models that employ a hybrid form of conductivity, specifically, infinite conductivity interior to the light cylinder and high but finite conductivity on the outside. In these models the gamma-ray emission is produced in regions near the equatorial current sheet but modulated by the local physical properties. These models have radio lags near the observed values and statistically best reproduce the observed light curve phenomenology. Additionally, they also produce GeV photon cut-off energies.

Intense laser pulse propagation in capillary discharge plasma channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hubbard, R.F.; Moore, C.I.; Sprangle, P.

Optical guiding of intense laser pulses is required for plasma-based accelerator concepts such as the laser wakefield accelerator. Reported experiments have successfully transported intense laser pulses in the hollow plasma column produced by a capillary discharge. The hollow plasma has an index of refraction which peaks on-axis, thus providing optical guiding which overcomes beam expansion due to diffraction. In more recent experiments at Hebrew University, 800 nm wavelength, 0.1 mJ, 100 fs pulses have been guided in {approximately}300 micron radius capillaries over distances as long as 6.6 cm. Simulations of these experiments using a 2-D nonlinear laser propagation model producemore » the expected optical guiding, with the laser pulse radius r{sub L} exhibiting oscillations about the equilibrium value predicted by an analytical envelope equation model. The oscillations are damped at the front of the pulse and grow in amplitude in the back of the pulse. This growth and damping is attributed to finite pulse length effects. Simulations also show that further ionization of the discharge plasma by the laser pulse may hollow the laser pulse and introduce modulations in the spot size. This ionization-defocusing effect is expected to be significant at the high intensities required for accelerator application. Capillary discharge experiments at much higher intensities are in progress on the Naval Research Laboratory T{sup 3} laser, and preliminary results are reported. {copyright} {ital 1999 American Institute of Physics.}« less

Up-to-date Probabilistic Earthquake Hazard Maps for Egypt

NASA Astrophysics Data System (ADS)

Gaber, Hanan; El-Hadidy, Mahmoud; Badawy, Ahmed

2018-04-01

An up-to-date earthquake hazard analysis has been performed in Egypt using a probabilistic seismic hazard approach. Through the current study, we use a complete and homogenous earthquake catalog covering the time period between 2200 BC and 2015 AD. Three seismotectonic models representing the seismic activity in and around Egypt are used. A logic-tree framework is applied to allow for the epistemic uncertainty in the declustering parameters, minimum magnitude, seismotectonic setting and ground-motion prediction equations. The hazard analysis is performed for a grid of 0.5° × 0.5° in terms of types of rock site for the peak ground acceleration (PGA) and spectral acceleration at 0.2-, 0.5-, 1.0- and 2.0-s periods. The hazard is estimated for three return periods (72, 475 and 2475 years) corresponding to 50, 10 and 2% probability of exceedance in 50 years. The uniform hazard spectra for the cities of Cairo, Alexandria, Aswan and Nuwbia are constructed. The hazard maps show that the highest ground acceleration values are expected in the northeastern part of Egypt around the Gulf of Aqaba (PGA up to 0.4 g for return period 475 years) and in south Egypt around the city of Aswan (PGA up to 0.2 g for return period 475 years). The Western Desert of Egypt is characterized by the lowest level of hazard (PGA lower than 0.1 g for return period 475 years).

Proof-of-principle demonstration of Nb 3Sn superconducting radiofrequency cavities for high Q 0 applications

DOE PAGES

Posen, S.; Liepe, M.; Hall, D. L.

2015-02-23

Many future particle accelerators require hundreds of superconducting radiofrequency (SRF) cavities operating with high duty factor. The large dynamic heat load of the cavities causes the cryogenic plant to make up a significant part of the overall cost of the facility. Our contribution can be reduced by replacing standard niobium cavities with ones coated with a low-dissipation superconductor such as Nb 3Sn. Here, we present results for single cell cavities coated with Nb 3Sn at Cornell. Five coatings were carried out, showing that at 4.2 K, high Q 0 out to medium fields was reproducible, resulting in an average quenchmore » field of 14 MV/m and an average 4.2 K Q 0 at quench of 8 x 10 9 . In each case, the peak surface magnetic field at quench was well above H c1, showing that it is not a limiting field in these cavities. Furthermore, the coating with the best performance had a quench field of 17 MV/m, exceeding gradient requirements for state-of-the-art high duty factor SRF accelerators. It is also shown that—taking into account the thermodynamic efficiency of the cryogenic plant—the 4.2 K Q 0 values obtained meet the AC power consumption requirements of state-of-the-art high duty factor accelerators, making this a proof-of-principle demonstration for Nb 3Sn cavities in future applications.« less

Dopamine controls the neural dynamics of memory signals and retrieval accuracy.

PubMed

Apitz, Thore; Bunzeck, Nico

2013-11-01

The human brain is capable of differentiating between new and already stored information rapidly to allow optimal behavior and decision-making. Although the neural mechanisms of novelty discrimination were often described as temporally constant (ie, with specific latencies), recent electrophysiological studies have demonstrated that the onset of neural novelty signals (ie, differences in event-related responses to new and old items) can be accelerated by reward motivation. While the precise physiological mechanisms underlying this acceleration remain unclear, the involvement of the neurotransmitter dopamine in both novelty and reward processing suggests that enhanced dopamine levels in the context of reward prospect may have a role. To investigate this hypothesis, we used magnetoencephalography (MEG) in combination with an old/new recognition memory task in which correct discrimination between old and new items was rewarded. Importantly, before the task, human subjects received either 150 mg of the dopamine precursor levodopa or placebo. For the placebo group, old/new signals peaked at ∼100 ms after stimulus onset over left temporal/occipital sensors. In contrast, after levodopa administration earliest old/new effects only emerged after ∼400 ms and retrieval accuracy was reduced as expressed in lower d' values. As such, our results point towards a previously unreported role of dopamine in controlling the chronometry of neural processes underlying the distinction between old and new information. They also suggest that this relationship follows a nonlinear function whereby slightly enhanced dopamine levels accelerate neural/cognitive processes and excessive dopamine levels impair them.

Role of awareness in head-neck acceleration in low velocity rear-end impacts.

PubMed

Kumar, S; Narayan, Y; Amell, T

2000-03-01

Fourteen normal healthy seated and restrained young adults were delivered rear-end impacts of four intensities of acceleration. The chair was delivered a regulated and controlled pneumatic blow using a 30 cm cylinder to cause an acceleration of 0.5, 0.9, 1.1 and 1.4g. The accelerated chair was stopped suddenly by impacting the stopper at the other end of the 2 m long friction reduced track. In one set of trials, subjects were informed about the impending impact and in the other they were blindfolded and provided with loud auditory input to eliminate cues of the impact. The accelerations of the chair, shoulder and head of the participating subjects were measured triaxially and compared between levels of acceleration and expectation. The multiple analyses of variance revealed that the peak acceleration was significantly affected by the gender (P < 0.01), intensity of impact (P < 0.001), and expectation (P < 0.0001). The accelerations were significantly different in different axes (P < 0.001). A significant two-way interaction between acceleration and expectation (P < 0.03), and expectation and axes of acceleration (P < 0.02) would imply that awareness of the impending impact serves to significantly reduce the level of accelerations of head and neck.

Distinguishing spinocerebellar ataxia with pure cerebellar manifestation from multiple system atrophy (MSA-C) through saccade profiles.

PubMed

Terao, Yasuo; Fukuda, Hideki; Tokushige, Shin-Ichi; Inomata-Terada, Satomi; Yugeta, Akihiro; Hamada, Masashi; Ugawa, Yoshikazu

2017-01-01

Patients with spinocerebellar ataxia with pure cerebellar presentation (SCD) and multiple system atrophy (MSA-C) show similar symptoms at early stages, although cerebellofugal pathology predominates in SCD, and cerebellopetal pathology in MSA-C. We studied whether saccade velocity profiles, which reflect the accelerating and braking functions of the cerebellum, can differentiate these two disorders. We recorded visually guided (VGS) and memory guided saccades (MGS) in 29 MSA-C patients, 12 SCD patients, and 92 age-matched normal subjects, and compared their amplitude, peak velocity and duration (accelerating and decelerating phases). Hypometria predominated in VGS and MGS of MSA-C, whereas hypometria was less marked in SCD, with hypermetria frequently noted in MGS. Peak velocity was reduced, and deteriorated with advancing disease both in SCD and MSA-C groups at smaller target eccentricities. The deceleration phase was prolonged in SCD compared to MSA-C and normal groups at larger target eccentricities, which deteriorated with advancing disease. Saccades in MSA-C were characterized by a more prominent acceleration deficit and those in SCD by a more prominent braking defect, possibly caused by the cerebellopetal and cerebellofugal pathologies, respectively. Saccade profiles provide important information regarding the accelerating and braking signals of the cerebellum in spinocerebellar ataxia. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Parameter study for child injury mitigation in near-side impacts through FE simulations.

PubMed

Andersson, Marianne; Pipkorn, Bengt; Lövsund, Per

2012-01-01

The objective of this study is to investigate the effects of crash-related car parameters on head and chest injury measures for 3- and 12-year-old children in near-side impacts. The evaluation was made using a model of a complete passenger car that was impacted laterally by a barrier. The car model was validated in 2 crash conditions: the Insurance Institute for Highway Safety (IIHS) and the US New Car Assessment Program (NCAP) side impact tests. The Small Side Impact Dummy (SID-IIs) and the human body model 3 (HBM3) (Total HUman Model for Safety [THUMS] 3-year-old) finite element models were used for the parametric investigation (HBM3 on a booster). The car parameters were as follows: vehicle mass, side impact structure stiffness, a head air bag, a thorax-pelvis air bag, and a seat belt with pretensioner. The studied dependent variables were as follows: resultant head linear acceleration, resultant head rotational acceleration, chest viscous criterion, rib deflection, and relative velocity at head impact. The chest measurements were only considered for the SID-IIs. The head air bag had the greatest effect on the head measurements for both of the occupant models. On average, it reduced the peak head linear acceleration by 54 g for the HBM3 and 78 g for the SID-IIs. The seat belt had the second greatest effect on the head measurements; the peak head linear accelerations were reduced on average by 39 g (HBM3) and 44 g (SID-IIs). The high stiffness side structure increased the SID-IIs' head acceleration, whereas it had marginal effect on the HBM3. The vehicle mass had a marginal effect on SID-IIs' head accelerations, whereas the lower vehicle mass caused 18 g higher head acceleration for HBM3 and the greatest rotational acceleration. The thorax-pelvis air bag, vehicle mass, and seat belt pretensioner affected the chest measurements the most. The presence of a thorax-pelvis air bag, high vehicle mass, and a seat belt pretensioner all reduced the chest viscous criterion (VC) and peak rib deflection in the SID-IIs. The head and thorax-pelvis air bags have the potential to reduce injury measurements for both the SID-IIs and the HBM3, provided that the air bag properties are designed to consider these occupant sizes also. The seat belt pretensioner is also effective, provided that the lateral translation of the torso is managed by other features. The importance of lateral movement management is greater the smaller the occupant is. Light vehicles require interior restraint systems of higher performance than heavy vehicles do to achieve the same level of injury measures for a given side structure. Copyright © 2012 Taylor & Francis Group, LLC

Achieving Stable Radiation Pressure Acceleration of Heavy Ions via Successive Electron Replenishment from Ionization of a High-Z Material Coating

NASA Astrophysics Data System (ADS)

Shen, X. F.; Qiao, B.; Zhang, H.; Kar, S.; Zhou, C. T.; Chang, H. X.; Borghesi, M.; He, X. T.

2017-05-01

A method to achieve stable radiation pressure acceleration (RPA) of heavy ions from laser-irradiated ultrathin foils is proposed, where a high-Z material coating in front is used. The coated high-Z material, acting as a moving electron repository, continuously replenishes the accelerating heavy ion foil with comoving electrons in the light-sail acceleration stage due to its successive ionization under laser fields with Gaussian temporal profile. As a result, the detrimental effects such as foil deformation and electron loss induced by the Rayleigh-Taylor-like and other instabilities in RPA are significantly offset and suppressed so that stable acceleration of heavy ions are maintained. Particle-in-cell simulations show that a monoenergetic Al13 + beam with peak energy 3.8 GeV and particle number 1 010 (charge >20 nC ) can be obtained at intensity 1 022 W /cm2 .

Electron injection and acceleration in the plasma bubble regime driven by an ultraintense laser pulse combined with using dense-plasma wall and block

NASA Astrophysics Data System (ADS)

Zhao, Xue-Yan; Xie, Bai-Song; Wu, Hai-Cheng; Zhang, Shan; Hong, Xue-Ren; Aimidula, Aimierding

2012-03-01

An optimizing and alternative scheme for electron injection and acceleration in the wake bubble driven by an ultraintense laser pulse is presented. In this scheme, the dense-plasma wall with an inner diameter matching the expected bubble size is placed along laser propagation direction. Meanwhile, a dense-plasma block dense-plasma is adhered inward transversely at some certain position of the wall. Particle-in-cell simulations are performed, which demonstrate that the block plays an important role in the first electron injection and acceleration. The result shows that a collimated electron bunch with a total number of about 4.04×108μm-1 can be generated and accelerated stably to 1.61 GeV peak energy with 2.6% energy spread. The block contributes about 50% to the accelerated electron injection bunch by tracing and sorting statistically the source.

High energy protons generation by two sequential laser pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xiaofeng; Shen, Baifei, E-mail: bfshen@mail.shcnc.ac.cn, E-mail: zhxm@siom.ac.cn; Zhang, Xiaomei, E-mail: bfshen@mail.shcnc.ac.cn, E-mail: zhxm@siom.ac.cn

2015-04-15

The sequential proton acceleration by two laser pulses of relativistic intensity is proposed to produce high energy protons. In the scheme, a relativistic super-Gaussian (SG) laser pulse followed by a Laguerre-Gaussian (LG) pulse irradiates dense plasma attached by underdense plasma. A proton beam is produced from the target and accelerated in the radiation pressure regime by the short SG pulse and then trapped and re-accelerated in a special bubble driven by the LG pulse in the underdense plasma. The advantages of radiation pressure acceleration and LG transverse structure are combined to achieve the effective trapping and acceleration of protons. Inmore » a two-dimensional particle-in-cell simulation, protons of 6.7 GeV are obtained from a 2 × 10{sup 22 }W/cm{sup 2} SG laser pulse and a LG pulse at a lower peak intensity.« less

Tunnel flexibility effect on the ground surface acceleration response

NASA Astrophysics Data System (ADS)

Baziar, Mohammad Hassan; Moghadam, Masoud Rabeti; Choo, Yun Wook; Kim, Dong-Soo

2016-09-01

Flexibility of underground structures relative to the surrounding medium, referred to as the flexibility ratio, is an important factor that influences their dynamic interaction. This study investigates the flexibility effect of a box-shaped subway tunnel, resting directly on bedrock, on the ground surface acceleration response using a numerical model verified against dynamic centrifuge test results. A comparison of the ground surface acceleration response for tunnel models with different flexibility ratios revealed that the tunnels with different flexibility ratios influence the acceleration response at the ground surface in different ways. Tunnels with lower flexibility ratios have higher acceleration responses at short periods, whereas tunnels with higher flexibility ratios have higher acceleration responses at longer periods. The effect of the flexibility ratio on ground surface acceleration is more prominent in the high range of frequencies. Furthermore, as the flexibility ratio of the tunnel system increases, the acceleration response moves away from the free field response and shifts towards the longer periods. Therefore, the flexibility ratio of the underground tunnels influences the peak ground acceleration (PGA) at the ground surface, and may need to be considered in the seismic zonation of urban areas.

Ground motion values for use in the seismic design of the Trans-Alaska Pipeline system

USGS Publications Warehouse

Page, Robert A.; Boore, D.M.; Joyner, W.B.; Coulter, H.W.

1972-01-01

The proposed trans-Alaska oil pipeline, which would traverse the state north to south from Prudhoe Bay on the Arctic coast to Valdez on Prince William Sound, will be subject to serious earthquake hazards over much of its length. To be acceptable from an environmental standpoint, the pipeline system is to be designed to minimize the potential of oil leakage resulting from seismic shaking, faulting, and seismically induced ground deformation. The design of the pipeline system must accommodate the effects of earthquakes with magnitudes ranging from 5.5 to 8.5 as specified in the 'Stipulations for Proposed Trans-Alaskan Pipeline System.' This report characterizes ground motions for the specified earthquakes in terms of peak levels of ground acceleration, velocity, and displacement and of duration of shaking. Published strong motion data from the Western United States are critically reviewed to determine the intensity and duration of shaking within several kilometers of the slipped fault. For magnitudes 5 and 6, for which sufficient near-fault records are available, the adopted ground motion values are based on data. For larger earthquakes the values are based on extrapolations from the data for smaller shocks, guided by simplified theoretical models of the faulting process.

Diffusive Shock Acceleration and Reconnection Acceleration Processes

NASA Astrophysics Data System (ADS)

Zank, G. P.; Hunana, P.; Mostafavi, P.; Le Roux, J. A.; Li, Gang; Webb, G. M.; Khabarova, O.; Cummings, A.; Stone, E.; Decker, R.

2015-12-01

Shock waves, as shown by simulations and observations, can generate high levels of downstream vortical turbulence, including magnetic islands. We consider a combination of diffusive shock acceleration (DSA) and downstream magnetic-island-reconnection-related processes as an energization mechanism for charged particles. Observations of electron and ion distributions downstream of interplanetary shocks and the heliospheric termination shock (HTS) are frequently inconsistent with the predictions of classical DSA. We utilize a recently developed transport theory for charged particles propagating diffusively in a turbulent region filled with contracting and reconnecting plasmoids and small-scale current sheets. Particle energization associated with the anti-reconnection electric field, a consequence of magnetic island merging, and magnetic island contraction, are considered. For the former only, we find that (i) the spectrum is a hard power law in particle speed, and (ii) the downstream solution is constant. For downstream plasmoid contraction only, (i) the accelerated spectrum is a hard power law in particle speed; (ii) the particle intensity for a given energy peaks downstream of the shock, and the distance to the peak location increases with increasing particle energy, and (iii) the particle intensity amplification for a particular particle energy, f(x,c/{c}0)/f(0,c/{c}0), is not 1, as predicted by DSA, but increases with increasing particle energy. The general solution combines both the reconnection-induced electric field and plasmoid contraction. The observed energetic particle intensity profile observed by Voyager 2 downstream of the HTS appears to support a particle acceleration mechanism that combines both DSA and magnetic-island-reconnection-related processes.

Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

DOE PAGES

Gessner, Spencer; Adli, Erik; Allen, James M.; ...

2016-06-02

Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. In this study, we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel ismore » created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m -1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.« less

Radiobiological effectiveness of laser accelerated electrons in comparison to electron beams from a conventional linear accelerator.

PubMed

Laschinsky, Lydia; Baumann, Michael; Beyreuther, Elke; Enghardt, Wolfgang; Kaluza, Malte; Karsch, Leonhard; Lessmann, Elisabeth; Naumburger, Doreen; Nicolai, Maria; Richter, Christian; Sauerbrey, Roland; Schlenvoigt, Hans-Peter; Pawelke, Jörg

2012-01-01

The notable progress in laser particle acceleration technology promises potential medical application in cancer therapy through compact and cost effective laser devices that are suitable for already existing clinics. Previously, consequences on the radiobiological response by laser driven particle beams characterised by an ultra high peak dose rate have to be investigated. Therefore, tumour and non-malignant cells were irradiated with pulsed laser accelerated electrons at the JETI facility for the comparison with continuous electrons of a conventional therapy LINAC. Dose response curves were measured for the biological endpoints clonogenic survival and residual DNA double strand breaks. The overall results show no significant differences in radiobiological response for in vitro cell experiments between laser accelerated pulsed and clinical used electron beams. These first systematic in vitro cell response studies with precise dosimetry to laser driven electron beams represent a first step toward the long term aim of the application of laser accelerated particles in radiotherapy.

The beat in laser-accelerated ion beams

NASA Astrophysics Data System (ADS)

Schnürer, M.; Andreev, A. A.; Abicht, F.; Bränzel, J.; Koschitzki, Ch.; Platonov, K. Yu.; Priebe, G.; Sandner, W.

2013-10-01

Regular modulation in the ion velocity distribution becomes detectable if intense femtosecond laser pulses with very high temporal contrast are used for target normal sheath acceleration of ions. Analytical and numerical analysis of the experimental observation associates the modulation with the half-cycle of the driving laser field period. In processes like ion acceleration, the collective and laser-frequency determined electron dynamics creates strong fields in plasma to accelerate the ions. Even the oscillatory motion of electrons and its influence on the acceleration field can dominate over smoothing effects in plasma if a high temporal contrast of the driving laser pulse is given. Acceleration parameters can be directly concluded out of the experimentally observed modulation period in ion velocity spectra. The appearance of the phenomenon at a temporal contrast of ten orders between the intensity of the pulse peak and the spontaneous amplified emission background as well as remaining intensity wings at picosecond time-scale might trigger further parameter studies with even higher contrast.

Body acceleration distribution and O2 uptake in humans during running and jumping

NASA Technical Reports Server (NTRS)

Bhattacharya, A.; Mccutcheon, E. P.; Shvartz, E.; Greenleaf, J. E.

1980-01-01

The distribution of body acceleration and associated oxygen uptake and heart rate responses are investigated in treadmill running and trampoline jumping. Accelerations in the +Gz direction were measured at the lateral ankle, lumbosacral region and forehead of eight young men during level treadmill walking and running at four speeds and trampoline jumping at four heights, together with corresponding oxygen uptake and heart rate. With increasing treadmill speed, peak acceleration at the ankle is found always to exceed that at the back and forehead, and acceleration profiles with higher frequency components than those observed during jumping are observed. Acceleration levels are found to be more uniformly distributed with increasing height in jumping, although comparable oxygen uptake and heat rates are obtained. Results indicate that the magnitude of the biomechanical stimuli is greater in trampoline jumping than in running, which finding could be of use in the design of procedures to avert deconditioning in persons exposed to weightlessness.

Neutron Source from Laser Plasma Acceleration

NASA Astrophysics Data System (ADS)

Jiao, Xuejing; Shaw, Joseph; McCary, Eddie; Downer, Mike; Hegelich, Bjorn

2016-10-01

Laser driven electron beams and ion beams were utilized to produce neutron sources via different mechanism. On the Texas Petawatt laser, deuterized plastic, gold and DLC foil targets of varying thickness were shot with 150 J , 150 fs laser pulses at a peak intensity of 2 ×1021W /cm2 . Ions were accelerated by either target normal sheath acceleration or Breakout Afterburner acceleration. Neutrons were produced via the 9Be(d,n) and 9Be(p,n) reactions when accelerated ions impinged on a Beryllium converter as well as by deuteron breakup reactions. We observed 2 ×1010 neutron per shot in average, corresponding to 5 ×1018n /s . The efficiencies for different targets are comparable. In another experiment, 38fs , 0.3 J UT3 laser pulse interacted with mixed gas target. Electrons with energy 40MeV were produced via laser wakefield acceleration. Neutron flux of 2 ×106 per shot was generated through bremsstrahlung and subsequent photoneutron reactions on a Copper converter.

Earthquake ground motion simulation at Zoser pyramid using the stochastic method: A step toward the preservation of an ancient Egyptian heritage

NASA Astrophysics Data System (ADS)

Khalil, Amin E.; Abdel Hafiez, H. E.; Girgis, Milad; Taha, M. A.

2017-06-01

Strong ground shaking during earthquakes can greatly affect the ancient monuments and subsequently demolish the human heritage. On October 12th 1992, a moderate earthquake (Ms = 5.8) shocked the greater Cairo area causing widespread damages. Unfortunately, the focus of that earthquake is located about 14 km to the south of Zoser pyramid. After the earthquake, the Egyptian Supreme council of antiquities issued an alarm that Zoser pyramid is partially collapsed and international and national efforts are exerted to restore this important human heritage that was built about 4000 years ago. Engineering and geophysical work is thus needed for the restoration process. The definition of the strong motion parameters is one of the required studies since seismically active zone is recorded in its near vicinity. The present study adopted the stochastic method to determine the peak ground motion (acceleration, velocity and displacement) for the three largest earthquakes recorded in the Egypt's seismological history. These earthquakes are Shedwan earthquake with magnitude Ms = 6.9, Aqaba earthquake with magnitude Mw = 7.2 and Cairo (Dahshour earthquake) with magnitude Ms = 5.8. The former two major earthquakes took place few hundred kilometers away. It is logic to have the predominant effects from the epicentral location of the Cairo earthquake; however, the authors wanted to test also the long period effects of the large distance earthquakes expected from the other two earthquakes under consideration. In addition, the dynamic site response was studied using the Horizontal to vertical spectral ratio (HVSR) technique. HVSR can provide information about the fundamental frequency successfully; however, the amplification estimation is not accepted. The result represented as either peak ground motion parameters or response spectra indicates that the effects from Cairo earthquake epicenter are the largest for all periods considered in the present study. The level of strong motion as indicated by peak ground acceleration reaches the value of 250 gals which is considerably high. At the end, it is worth to mention that the information resulted from the present work may be useful for the planned restoration decision of the Zoser pyramid site.

Primary and submovement control of aiming in C6 tetraplegics following posterior deltoid transfer

PubMed Central

2014-01-01

Background Upper limb motor control in fast, goal-directed aiming is altered in tetraplegics following posterior-deltoid musculotendinous transfer. Specifically, movements have similar end-point accuracy but longer duration and lower peak velocity than those of age-matched, neurotypical controls. Here, we examine in detail the interplay between primary movement and submovement phases in five C6 tetraplegic and five control participants. Methods Aiming movements were performed in two directions (20 cm away or toward), with or without vision. Trials that contained a submovement phase (i.e., discontinuity in velocity, acceleration or jerk) were identified. Discrete kinematic variables were then extracted on the primary and submovements phases. Results The presence of submovements did not differ between the tetraplegic (68%) and control (57%) groups, and almost all submovements resulted from acceleration and jerk discontinuities. Tetraplegics tended to make a smaller amplitude primary movement, which had lower peak velocity and greater spatial variability at peak velocity. This was followed by a larger amplitude and longer duration secondary submovement. Peak velocity of primary movement was not related to submovement incidence. Together, the primary and submovement phases of both groups were equally effective in reducing end-point error. Conclusions C6 tetraplegic participants exhibit some subtle differences in measures of motor behaviour compared to control participants, but importantly feedforward and feedback processes work effectively in combination to achieve accurate goal-directed aiming. PMID:25055852

High-efficiency acceleration in the laser wakefield by a linearly increasing plasma density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Kegong; Wu, Yuchi; Zhu, Bin

The acceleration length and the peak energy of the electron beam are limited by the dephasing effect in the laser wakefield acceleration with uniform plasma density. Based on 2D-3V particle in cell simulations, the effects of a linearly increasing plasma density on the electron acceleration are investigated broadly. Comparing with the uniform plasma density, because of the prolongation of the acceleration length and the gradually increasing accelerating field due to the increasing plasma density, the electron beam energy is twice higher in moderate nonlinear wakefield regime. Because of the lower plasma density, the linearly increasing plasma density can also avoidmore » the dark current caused by additional injection. At the optimal acceleration length, the electron energy can be increased from 350 MeV (uniform) to 760 MeV (linearly increasing) with the energy spread of 1.8%, the beam duration is 5 fs and the beam waist is 1.25 μm. This linearly increasing plasma density distribution can be achieved by a capillary with special gas-filled structure, and is much more suitable for experiment.« less

Macroseismic Intensity and Instrumental Ground Motion Parameter Correlations for Central Mexico

NASA Astrophysics Data System (ADS)

Sandoval Gómez, H.; Ramirez Guzman, L.; Espindola, V.

2012-12-01

We present instrumental intensity prediction equations for earthquakes in Central Mexico based on the correlation of observed Instrumental Ground-Motion Parameters (IGMP) and Modified Mercalli Intensity (MMI) scale reports. The goal of this study is to provide a model that can be used by the near real-time earthquake response system operated by the Institutes of Engineering and Geophysics at the National Autonomous University of Mexico (UNAM), which delivers estimates of key information associated with the societal impact due to earthquakes not available in the immediate aftermath of the event. Correlations of MMI and IGMP have been derived in other countries with different tectonic settings and built environments, but this is the first study devoted to the development of equations for the central region of Mexico. The IGMP are obtained from records of several stations for earthquakes with Mw 5.0-8.0 from the seismic networks operated by UNAM and other institutions in Mexico. The MMI observations were primarily obtained from the Did You Feel It (DYFI) report service of the U.S. Geological Survey and re-interpreted MMI reports from UNAM earthquake bulletin archives. For each instrumental observation we assigned a mean MMI intensity based on the proximity of the site where reported value are available, constrained by geological conditions and a visual inspection to guarantee that the intensity would be within one unit of the assigned value; following the procedure by Atkinson and Kaka (2006). We derived correlations for peak ground velocity (pgv) and acceleration, and three spectral acceleration periods (T=1, 2 and 3 s). In addition, we analyzed the Mw and distance dependence. We concluded that pgv and the spectral accelerations are the most useful IGMP predictors for MMI in the region of interest and the correlations differ significantly from those obtained in regions with other tectonic settings and infrastructure vulnerabilities (e.g. Wald et al, 1999; Atkinson and Kaka, 2006, Cramer and Dangkua, 2011).

Out-of-field doses and neutron dose equivalents for electron beams from modern Varian and Elekta linear accelerators.

PubMed

Cardenas, Carlos E; Nitsch, Paige L; Kudchadker, Rajat J; Howell, Rebecca M; Kry, Stephen F

2016-07-08

Out-of-field doses from radiotherapy can cause harmful side effects or eventually lead to secondary cancers. Scattered doses outside the applicator field, neutron source strength values, and neutron dose equivalents have not been broadly investigated for high-energy electron beams. To better understand the extent of these exposures, we measured out-of-field dose characteristics of electron applicators for high-energy electron beams on two Varian 21iXs, a Varian TrueBeam, and an Elekta Versa HD operating at various energy levels. Out-of-field dose profiles and percent depth-dose curves were measured in a Wellhofer water phantom using a Farmer ion chamber. Neutron dose was assessed using a combination of moderator buckets and gold activation foils placed on the treatment couch at various locations in the patient plane on both the Varian 21iX and Elekta Versa HD linear accelerators. Our findings showed that out-of-field electron doses were highest for the highest electron energies. These doses typically decreased with increasing distance from the field edge but showed substantial increases over some distance ranges. The Elekta linear accelerator had higher electron out-of-field doses than the Varian units examined, and the Elekta dose profiles exhibited a second dose peak about 20 to 30 cm from central-axis, which was found to be higher than typical out-of-field doses from photon beams. Electron doses decreased sharply with depth before becoming nearly constant; the dose was found to decrease to a depth of approximately E(MeV)/4 in cm. With respect to neutron dosimetry, Q values and neutron dose equivalents increased with electron beam energy. Neutron contamination from electron beams was found to be much lower than that from photon beams. Even though the neutron dose equivalent for electron beams represented a small portion of neutron doses observed under photon beams, neutron doses from electron beams may need to be considered for special cases.

The effects of exogenous hormones on rooting process and the activities of key enzymes of Malus hupehensis stem cuttings

PubMed Central

Tan, Qianqian; Zhao, Mingming; Zhou, Ting; Cao, Fuliang

2017-01-01

Malus hupehensis is an excellent Malus rootstock species, known for its strong adverse-resistance and apomixes. In the present study, stem cuttings of M. hupehensis were treated with three types of exogenous hormones, including indole acetic acid (IAA), naphthalene acetic acid (NAA), or green growth regulator (GGR). The effects and mechanisms of exogenous hormone treatment and antioxidant enzyme activity on adventitious root formation were investigated. The results showed that the apparent morphology of the adventitious root had four stages, including root pre-emergence stage (S0), early stage of root formation (S1), massive root formation stage (S2), and later stage of root formation (S3). The suitable concentrations of the three exogenous hormones, IAA, NAA and GGR, were 100 mg·L-1, 300 mg·L-1, and 300 mg·L-1, respectively. They shortened the rooting time by 25–47.4% and increased the rooting percentages of cuttings by 0.9–1.3 times, compared with that in the control. The dispersion in S0 stage was 3.6 times of that in the S1 stage after exogenous hormone application. The earlier the third critical point (P3) appeared, the shorter the rooting time and the greater the rooting percentage of the cuttings. During rhizogenesis, the activities of three antioxidant enzymes (POD, SOD, and PPO) showed an A-shaped trend. However, peak values of enzyme activity appeared at different points, which were 9 d before the P3, P3, and the fourth critical point (P4), respectively. Exogenous hormone treatment reduced the time to reach the peak value by 18 days, although the peak values of the enzymatic activities did not significantly changed. Our results suggested that exogenous hormone treatment mainly acted during the root pre-emergence stage, accelerated the synthesis of antioxidant enzymes, reduced the rooting time, and consequently promoted root formation. The three kinds of antioxidant enzymes acted on different stages of rooting. PMID:28231330

Material Model Evaluation of a Composite Honeycomb Energy Absorber

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Annett, Martin S.; Fasanella, Edwin L.; Polanco, Michael A.

2012-01-01

A study was conducted to evaluate four different material models in predicting the dynamic crushing response of solid-element-based models of a composite honeycomb energy absorber, designated the Deployable Energy Absorber (DEA). Dynamic crush tests of three DEA components were simulated using the nonlinear, explicit transient dynamic code, LS-DYNA . In addition, a full-scale crash test of an MD-500 helicopter, retrofitted with DEA blocks, was simulated. The four material models used to represent the DEA included: *MAT_CRUSHABLE_FOAM (Mat 63), *MAT_HONEYCOMB (Mat 26), *MAT_SIMPLIFIED_RUBBER/FOAM (Mat 181), and *MAT_TRANSVERSELY_ANISOTROPIC_CRUSHABLE_FOAM (Mat 142). Test-analysis calibration metrics included simple percentage error comparisons of initial peak acceleration, sustained crush stress, and peak compaction acceleration of the DEA components. In addition, the Roadside Safety Verification and Validation Program (RSVVP) was used to assess similarities and differences between the experimental and analytical curves for the full-scale crash test.

Strong-motion observations of the M 7.8 Gorkha, Nepal, earthquake sequence and development of the N-shake strong-motion network

USGS Publications Warehouse

Dixit, Amod; Ringler, Adam; Sumy, Danielle F.; Cochran, Elizabeth S.; Hough, Susan E.; Martin, Stacey; Gibbons, Steven; Luetgert, James H.; Galetzka, John; Shrestha, Surya; Rajaure, Sudhir; McNamara, Daniel E.

2015-01-01

We present and describe strong-motion data observations from the 2015 M 7.8 Gorkha, Nepal, earthquake sequence collected using existing and new Quake-Catcher Network (QCN) and U.S. Geological Survey NetQuakes sensors located in the Kathmandu Valley. A comparison of QCN data with waveforms recorded by a conventional strong-motion (NetQuakes) instrument validates the QCN data. We present preliminary analysis of spectral accelerations, and peak ground acceleration and velocity for earthquakes up to M 7.3 from the QCN stations, as well as preliminary analysis of the mainshock recording from the NetQuakes station. We show that mainshock peak accelerations were lower than expected and conclude the Kathmandu Valley experienced a pervasively nonlinear response during the mainshock. Phase picks from the QCN and NetQuakes data are also used to improve aftershock locations. This study confirms the utility of QCN instruments to contribute to ground-motion investigations and aftershock response in regions where conventional instrumentation and open-access seismic data are limited. Initial pilot installations of QCN instruments in 2014 are now being expanded to create the Nepal–Shaking Hazard Assessment for Kathmandu and its Environment (N-SHAKE) network.

Enhanced laser radiation pressure acceleration of protons with a gold cone-capillary

NASA Astrophysics Data System (ADS)

Lv, Chong; Xie, Bai-Song; Wan, Feng; Hou, Ya-Juan; Jia, Mo-Ran; Sang, Hai-Bo; Hong, Xue-Ren; Liu, Shi-Bing

2017-03-01

A scheme with a gold cone-capillary is proposed to improve the protons acceleration, and involved problems are investigated by using the two-dimensional particle-in-cell simulations. It is demonstrated that the cone-capillary can efficiently guide and collimate the protons to a longer distance and result in a better beam quality with a dense density ≥ 10 n c , monoenergetic peak energy E k ˜ 1.51 GeV , spatial emittance ˜ 0.0088 mm mrad with divergence angle θ ˜ 1.0 ° and diameter ˜ 0.5 μ m . The enhancement is mainly attributed to the focusing effect by the transverse electric field generated by the cone as well as the capillary, which can prevent greatly the protons from expanding in the transverse direction. Comparable to without the capillary, the protons energy spectra have a stable monoenergetic peak and divergence angle nearby 1.0 ° in longer time. Besides, the efficiency of acceleration depending on the capillary length is explored, and the optimal capillary length is also achieved. Such a target may be beneficial to many applications such as ion fast ignition in inertial fusion, proton therapy and so on.

Traveling-wave induction launchers

NASA Technical Reports Server (NTRS)

Elliott, David G.

1989-01-01

An analysis of traveling-wave induction launchers shows that induction is a feasible method of producing armature current and that efficient accelerators can be built without sliding contacts or arcs. In a traveling-wave induction launcher the armature current is induced by a slip speed between the armature and a traveling magnetic field. At 9 m/s slip speed a 9 kg projectile with an aluminum armature weighing 25 percent of the total mass can be accelerated to 3000 m/s in a 5 m-long barrel with a total ohmic loss in the barrel coils and armature of 4 percent of the launch kinetic energy and with an average armature temperature rise of 220 deg C, but a peak excitation frequency of 8600 Hz is required. With a 2 kg launch mass the ohmic loss is 7 percent. A launcher system optimized for rotating generators would have a peak frequency of 4850 Hz; with an aluminum armature weighing 33 percent of the launch mass and a slip speed of 30 m/s the total ohmic loss in the generators, cables, and accelerator would be 43 percent of the launch kinetic energy, and the average armature temperature rise would be 510 deg C.

Generation of narrow energy spread ion beams via collisionless shock waves using ultra-intense 1 um wavelength laser systems

NASA Astrophysics Data System (ADS)

Albert, Felicie; Pak, A.; Kerr, S.; Lemos, N.; Link, A.; Patel, P.; Pollock, B. B.; Haberberger, D.; Froula, D.; Gauthier, M.; Glenzer, S. H.; Longman, A.; Manzoor, L.; Fedosejevs, R.; Tochitsky, S.; Joshi, C.; Fiuza, F.

2017-10-01

In this work, we report on electrostatic collisionless shock wave acceleration experiments that produced proton beams with peak energies between 10-17.5 MeV, with narrow energy spreads between Δ E / E of 10-20%, and with a total number of protons in these peaks of 1e7-1e8. These beams of ions were created by driving an electrostatic collisionless shock wave in a tailored near critical density plasma target using the ultra-intense ps duration Titan laser that operates at a wavelength of 1 um. The near critical density target was produced through the ablation of an initially 0.5 um thick Mylar foil with a separate low intensity laser. A narrow energy spread distribution of carbon / oxygen ions with a similar velocity to the accelerated proton distribution, consistent with the reflection and acceleration of ions from an electrostatic field, was also observed. This work was supported by Lawrence Livermore National Laboratory's Laboratory Directed Research and Development program under project 15-LW-095, and the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA2734.

A Characterization of the Radiation from a Rod-Pinch Diode

NASA Astrophysics Data System (ADS)

Swanekamp, Stephen B.; Allen, Raymond J.; Hinshelwood, David D.; Mosher, David; Schumer, Joseph W.

2002-12-01

Coupled PIC-Monte-Carlo simulations of the electron-flow and radiation production in a rod-pinch diode show that multiple scatterings in the rod produce incident electron energies that ranging from zero to slightly higher than the applied voltage. It is speculated that those electrons that gain energy do so by remaining in phase with a rapidly varying electric field near the tip of the rod. The simulations also show that multiple passes in the rod produce a wide spread in incident electron angles. For diode voltages of V=2 MV, the angular distribution of electrons incident on the rod is broad and peaked near 90° to the axis of the rod with a larger fraction of electrons striking the rod at angles less than 90°. The electron angular distribution for V=4 MV is narrower and peaked at 105° with a larger fraction of electrons incident on the rod with angles greater than 90°. The photon distributions are peaked along the direction of the high-energy electrons. For V=2 MV the dose filtered through 21/4-cm thick Plexiglas is peaked at 90° and is 1.8 times higher than the forward-directed [0°] dose. For V=4 MV the dose filtered through 21/4-cm thick Plexiglas is peaked at 120° and is 2.3 times higher than the forward-directed dose. Similar angular variation of the dose has been observed on the 4-MV Asterix accelerator [2] and on 1-2 MV accelerators at the Atomic Weapons Establishment [8].

Assessment of the Accuracy of Certain Reduced Order Models used in the Prediction of Occupant Injury during Under-Body Blast Events

DTIC Science & Technology

2014-04-15

the floor on which the platform is dropped upon. Alternatively, a base excitation can be provided to the sliding platform in the upward vertical...7ms clips of chest resultant acceleration, (7) 7ms clip of pelvic vertical acceleration, (8,9) Peak and 30ms clips of lumbar spine compression, and...10) Pelvic vertical Dynamic Response Index (DRI)[12]. The sample size for each of the three seating variants consisted of 230 MADYMO

One-Dimensional Analysis of Hall Thruster Operating Modes

DTIC Science & Technology

2001-08-01

Hall thruster structure with no screens or other control surfaces makes it difficult to understand the interrelationships which, in the end, localize and shape the various plasma regions existing in the accelerating channel. Since the radial magnetic field is usually shaped with a peak near the channel exit, the plasma structure has often been explained as simply a reflection of the magnetic field distribution. However, this is inadequate to explain the plasma dynamics inside the accelerating channel. We develop a macroscopic model gathering reliability and clarity.

[Diagnostic value of baseline serum luteinizing hormone level for central precocious puberty in girls].

PubMed

Ou-Yang, Li-Xue; Yang, Fan

2017-07-01

To evaluate the diagnostic value of baseline serum luteinizing hormone (LH) level for central precocious puberty (CPP) in girls. A total of 279 girls with precocious puberty were subjected to assessment of growth and development, bone age determination, baseline LH test, and follicle-stimulating hormone (FSH) test, gonadotropin-releasing hormone stimulation test, and other related examinations. Of the 279 patients, 175 were diagnosed with CPP and 104 with premature thelarche (PT). The receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of baseline LH and FSH levels and their peak levels for CPP, and the correlation between the baseline LH level and the peak LH level was analyzed. The CPP group had significantly higher bone age, baseline LH and FSH levels, peak LH and FSH levels, and ratio of peak LH level to peak FSH level than the PT group (P<0.01). The ROC curve proved that baseline LH level and peak LH level had good diagnostic values for CPP. Among the three bone age subgroups in the CPP group (7.0-9.0 years, 9.0-11.0 years, and >11.0 years), baseline LH level showed the best diagnostic value in the >11.0 years subgroup, with the largest area under the ROC curve. At a baseline LH level of 0.45 IU/L, the Youden index reached the peak value, and the sensitivity and specificity were 66.7% and 80% respectively, for the diagnosis of CPP. At a peak LH level of 9.935 IU/L, the Youden index reached the peak value, and the sensitivity and specificity were 74.8% and 100% respectively, for the diagnosis of CPP. The baseline LH level was positively correlated with the peak LH level (r=0.440, P<0.01). Baseline LH level can be used as an primary screening index for the diagnosis of CPP. It has a certain diagnostic value for CPP at different bone ages, and may be used as a monitoring index during the treatment and follow-uP.

Integrated passive/active vibration absorber for multi-story buildings

NASA Technical Reports Server (NTRS)

Lee-Glauser, Gina J.; Ahmadi, Goodarz; Horta, Lucas G.

1995-01-01

Passive isolator, active vibration absorber, and an integrated passive/active (hybrid) control are studied for their effectiveness in reducing structural vibration under seismic excitations. For the passive isolator, a laminated rubber bearing base isolator which has been studied and used extensively by researchers and seismic designers is considered. An active vibration absorber concept, which can provide guaranteed closed-loop stability with minimum knowledge of the controlled system, is used to reduce the passive isolator displacement and to suppress the top floor vibration. A three-story building model is used for the numerical simulation. The performance of an active vibration absorber and a hybrid vibration controller in reducing peak structural responses is compared with the passively isolated structural response and with absence of vibration control systems under the N00W component of El Centro 1940 and N90W component of the Mexico City earthquake excitation records. The results show that the integrated passive/active vibration control system is most effective in suppressing the peak structural acceleration for the El Centro 1940 earthquake when compared with the passive or active vibration absorber alone. The active vibration absorber, however, is the only system that suppresses the peak acceleration of the structure for the Mexico City 1985 earthquake.

On the Health Risk of the Lumbar Spine due to Whole-Body VIBRATION—THEORETICAL Approach, Experimental Data and Evaluation of Whole-Body Vibration

NASA Astrophysics Data System (ADS)

Seidel, H.; Blüthner, R.; Hinz, B.; Schust, M.

1998-08-01

The guidance on the effects of vibration on health in standards for whole-body vibration (WBV) does not provide quantitative relationships between WBV and health risk. The paper aims at the elucidation of exposure-response relationships. An analysis of published data on the static and dynamic strength of vertebrae and bone, loaded with various frequencies under different conditions, provided the basis for a theoretical approach to evaluate repetitive loads on the lumbar spine (“internal loads”). The approach enabled the calculation of “equivalent”—with respect to cumulative fatigue failure—combinations of amplitudes and numbers of internal cyclic stress. In order to discover the relation between external peak accelerations at the seat and internal peak loads, biodynamic data of experiments (36 subjects, three somatotypes, two different postures—relaxed and bent forward; random WBV,aw, r.m.s. 1·4 ms-2, containing high transients) were used as input to a biomechanical model. Internal pressure changes were calculated using individual areas of vertebral endplates. The assessment of WBV was based on the quantitative relations between peak accelerations at the seat and pressures predicted for the disk L5/S1. For identical exposures clearly higher rates of pressure rise in the bent forward compared to the relaxed posture were predicted. The risk assessment for internal forces considered the combined internal static and dynamic loads, in relation to the predicted individual strength, and Miner's hypothesis. For exposure durations between 1 min and 8 h, energy equivalent vibration magnitudes (formula B.1, ISO 2631-1, 1997) and equivalent vibration magnitudes according to formula B.2 (time dependence over-energetic) were compared with equivalent combinations of upward peak accelerations and exposure durations according to predicted cumulative fatigue failures of lumbar vertebrae. Formula B.1 seems to underestimate the health risk caused by high magnitudes, formula B.2 is recommended for the evaluation of such conditions.

Neck muscle load distribution in lateral, frontal, and rear-end impacts: a three-dimensional finite element analysis.

PubMed

Hedenstierna, Sofia; Halldin, Peter; Siegmund, Gunter P

2009-11-15

A finite element (FE) model of the human neck was used to study the distribution of neck muscle loads during multidirectional impacts. The computed load distributions were compared to experimental electromyography (EMG) recordings. To quantify passive muscle loads in nonactive cervical muscles during impacts of varying direction and energy, using a three-dimensional (3D) continuum FE muscle model. Experimental and numerical studies have confirmed the importance of muscles in the impact response of the neck. Although EMG has been used to measure the relative activity levels in neck muscles during impact tests, this technique has not been able to measure all neck muscles and cannot directly quantify the force distribution between the muscles. A numerical model can give additional insight into muscle loading during impact. An FE model with solid element musculature was used to simulate frontal, lateral, and rear-end vehicle impacts at 4 peak accelerations. The peak cross-sectional forces, internal energies, and effective strains were calculated for each muscle and impact configuration. The computed load distribution was compared with experimental EMG data. The load distribution in the cervical muscles varied with load direction. Peak sectional forces, internal energies, and strains increased in most muscles with increasing impact acceleration. The dominant muscles identified by the model for each direction were splenius capitis, levator scapulae, and sternocleidomastoid in lateral impacts, splenius capitis, and trapezoid in frontal impacts, and sternocleidomastoid, rectus capitis posterior minor, and hyoids in rear-end impacts. This corresponded with the most active muscles identified by EMG recordings, although within these muscles the distribution of forces and EMG levels were not the same. The passive muscle forces, strains, and energies computed using a continuum FE model of the cervical musculature distinguished between impact directions and peak accelerations, and on the basis of prior studies, isolated the most important muscles for each direction.

Efficient injection of radiation-pressure-accelerated sub-relativistic protons into laser wakefield acceleration based on 10 PW lasers

NASA Astrophysics Data System (ADS)

Liu, M.; Weng, S. M.; Wang, H. C.; Chen, M.; Zhao, Q.; Sheng, Z. M.; He, M. Q.; Li, Y. T.; Zhang, J.

2018-06-01

We propose a hybrid laser-driven ion acceleration scheme using a combination target of a solid foil and a density-tailored background plasma. In the first stage, a sub-relativistic proton beam can be generated by radiation pressure acceleration in intense laser interaction with the solid foil. In the second stage, this sub-relativistic proton beam is further accelerated by the laser wakefield driven by the same laser pulse in a near-critical-density background plasma with decreasing density profile. The propagating velocity of the laser front and the phase velocity of the excited wakefield wave are effectively lowered at the beginning of the second stage. By decreasing the background plasma density gradually from near critical density along the laser propagation direction, the wake travels faster and faster, while it accelerates the protons. Consequently, the dephasing between the protons and the wake is postponed and an efficient wakefield proton acceleration is achieved. This hybrid laser-driven proton acceleration scheme can be realized by using ultrashort laser pulses at the peak power of 10 PW for the generation of multi-GeV proton beams.

Explanation of the variance in quality of life and activity capacity of patients with heart failure by laboratory data.

PubMed

Athanasopoulos, Leonidas V; Dritsas, Athanasios; Doll, Helen A; Cokkinos, Dennis V

2010-08-01

This study was conducted to explain the variance in quality of life (QoL) and activity capacity of patients with congestive heart failure from pathophysiological changes as estimated by laboratory data. Peak oxygen consumption (peak VO2) and ventilation (VE)/carbon dioxide output (VCO2) slope derived from cardiopulmonary exercise testing, plasma N-terminal prohormone of B-type natriuretic peptide (NT-proBNP), and echocardiographic markers [left atrium (LA), left ventricular ejection fraction (LVEF)] were measured in 62 patients with congestive heart failure, who also completed the Minnesota Living with Heart Failure Questionnaire and the Specific Activity Questionnaire. All regression models were adjusted for age and sex. On linear regression analysis, peak VO2 with P value less than 0.001, VE/VCO2 slope with P value less than 0.01, LVEF with P value less than 0.001, LA with P=0.001, and logNT-proBNP with P value less than 0.01 were found to be associated with QoL. On stepwise multiple linear regression, peak VO2 and LVEF continued to be predictive, accounting for 40% of the variability in Minnesota Living with Heart Failure Questionnaire score. On linear regression analysis, peak VO2 with P value less than 0.001, VE/VCO2 slope with P value less than 0.001, LVEF with P value less than 0.05, LA with P value less than 0.001, and logNT-proBNP with P value less than 0.001 were found to be associated with activity capacity. On stepwise multiple linear regression, peak VO2 and LA continued to be predictive, accounting for 53% of the variability in Specific Activity Questionnaire score. Peak VO2 is independently associated both with QoL and activity capacity. In addition to peak VO2, LVEF is independently associated with QoL, and LA with activity capacity.

Reliability and validity of gait analysis by android-based smartphone.

PubMed

Nishiguchi, Shu; Yamada, Minoru; Nagai, Koutatsu; Mori, Shuhei; Kajiwara, Yuu; Sonoda, Takuya; Yoshimura, Kazuya; Yoshitomi, Hiroyuki; Ito, Hiromu; Okamoto, Kazuya; Ito, Tatsuaki; Muto, Shinyo; Ishihara, Tatsuya; Aoyama, Tomoki

2012-05-01

Smartphones are very common devices in daily life that have a built-in tri-axial accelerometer. Similar to previously developed accelerometers, smartphones can be used to assess gait patterns. However, few gait analyses have been performed using smartphones, and their reliability and validity have not been evaluated yet. The purpose of this study was to evaluate the reliability and validity of a smartphone accelerometer. Thirty healthy young adults participated in this study. They walked 20 m at their preferred speeds, and their trunk accelerations were measured using a smartphone and a tri-axial accelerometer that was secured over the L3 spinous process. We developed a gait analysis application and installed it in the smartphone to measure the acceleration. After signal processing, we calculated the gait parameters of each measurement terminal: peak frequency (PF), root mean square (RMS), autocorrelation peak (AC), and coefficient of variance (CV) of the acceleration peak intervals. Remarkable consistency was observed in the test-retest reliability of all the gait parameter results obtained by the smartphone (p<0.001). All the gait parameter results obtained by the smartphone showed statistically significant and considerable correlations with the same parameter results obtained by the tri-axial accelerometer (PF r=0.99, RMS r=0.89, AC r=0.85, CV r=0.82; p<0.01). Our study indicates that the smartphone with gait analysis application used in this study has the capacity to quantify gait parameters with a degree of accuracy that is comparable to that of the tri-axial accelerometer.

Measurement of inflight shell areal density near peak velocity using a self backlighting technique

NASA Astrophysics Data System (ADS)

Pickworth, L. A.; Hammel, B. A.; Smalyuk, V. A.; MacPhee, A. G.; Scott, H. A.; Robey, H. F.; Landen, O. L.; Barrios, M. A.; Regan, S. P.; Schneider, M. B.; Hoppe, M., Jr.; Kohut, T.; Holunga, D.; Walters, C.; Haid, B.; Dayton, M.

2016-05-01

The growth of perturbations in inertial confinement fusion (ICF) capsules can lead to significant variation of inflight shell areal density (ρR), ultimately resulting in poor compression and ablator material mixing into the hotspot. As the capsule is accelerated inward, the perturbation growth results from the initial shock-transit through the shell and then amplification by Rayleigh-Taylor as the shell accelerates inwards. Measurements of ρR perturbations near peak implosion velocity (PV) are essential to our understanding of ICF implosions because they reflect the integrity of the capsule, after the inward acceleration growth is complete, of the actual shell perturbations including native capsule surface roughness and “isolated defects”. Quantitative measurements of shell-ρR perturbations in capsules near PV are challenging, requiring a new method with which to radiograph the shell. An innovative method, utilized in this paper, is to use the self-emission from the hotspot to “self- backlight” the shell inflight. However, with nominal capsule fills there is insufficient self-emission for this method until the capsule nears peak compression (PC). We produce a sufficiently bright continuum self-emission backlighter through the addition of a high-Z gas (∼ 1% Ar) to the capsule fill. This provides a significant (∼10x) increase in emission at hυ∼8 keV over nominal fills. “Self backlit” radiographs are obtained for times when the shock is rebounding from the capsule center, expanding out to meet the incoming shell, providing a means to sample the capsule optical density though only one side, as it converges through PV.

Internal combustion engine cylinder-to-cylinder balancing with balanced air-fuel ratios

DOEpatents

Harris, Ralph E.; Bourn, Gary D.; Smalley, Anthony J.

2006-01-03

A method of balancing combustion among cylinders of an internal combustion engine. For each cylinder, a normalized peak firing pressure is calculated as the ratio of its peak firing pressure to its combustion pressure. Each cylinder's normalized peak firing pressure is compared to a target value for normalized peak firing pressure. The fuel flow is adjusted to any cylinder whose normalized peak firing pressure is not substantially equal to the target value.

Increasing the Life of a Xenon-Ion Spacecraft Thruster

NASA Technical Reports Server (NTRS)

Goebel, Dan; Polk, James; Sengupta, Anita; Wirz, Richard

2007-01-01

A short document summarizes the redesign of a xenon-ion spacecraft thruster to increase its operational lifetime beyond a limit heretofore imposed by nonuniform ion-impact erosion of an accelerator electrode grid. A peak in the ion current density on the centerline of the thruster causes increased erosion in the center of the grid. The ion-current density in the NSTAR thruster that was the subject of this investigation was characterized by peak-to-average ratio of 2:1 and a peak-to-edge ratio of greater than 10:1. The redesign was directed toward distributing the same beam current more evenly over the entire grid andinvolved several modifications of the magnetic- field topography in the thruster to obtain more nearly uniform ionization. The net result of the redesign was to reduce the peak ion current density by nearly a factor of two, thereby halving the peak erosion rate and doubling the life of the thruster.

Preliminary evaluation of magnitude and frequency of floods in selected small drainage basins in Ohio

USGS Publications Warehouse

Kolva, J.R.

1985-01-01

A previous study of flood magitudes and frequencies in Ohio concluded that existing regionalized flood equations may not be adequate for estimating peak flows in small basins that are heavily forested, surface mined, or located in northwestern Ohio. In order to provide a large data base for improving estimation of flood peaks in these basins, 30 crest-stage gages were installed in 1977, in cooperation with the Ohio Department of Transportation, to provide a 10-year record of flood data The study area consists of two distinct parts: Northwestern Ohio, which contains 8 sites, and southern and eastern Ohio, which contains 22 sites in small forested or surface-mined drainage basins. Basin characteristics were determined for all 30 sites for 1978 conditions. Annual peaks were recorded or estimated for all 30 sites for water years 1978-82; an additional year of peak discharges was available at four sites. The 2-year (Q2) and 5-year (Q5) flood peaks were determined from these annual peaks.Q2 and Q5 values also were calculated using published regionalized regression equations for Ohio. The ratios of the observed to predicted 2-year (R2) and 5-year (R5) values were then calculated. This study found that observed flood peaks aree lower than estimated peaks by a significant amount in surface-mined basins. The average ratios of observed to predicted R2 values are 0.51 for basins with more than 40 percent surface-minded land, and 0.68 for sites with any surface-mined land. The average R5 value is 0.55 for sites with more than 40 percent surface-minded land, and 0.61 for sites with any surface-mined land. Estimated flood peaks from forested basins agree with the observed values fairly well. R2 values average 0.87 for sites with 20 percent or more forested land, but no surface-mined land, and R5 values average 0.96. If all sites with more than 20 percent forested land and some surface-mined land are considered, R2 the values average 0.86, and the R5 values average 0.82.

Counting missing values in a metabolite-intensity data set for measuring the analytical performance of a metabolomics platform.

PubMed

Huan, Tao; Li, Liang

2015-01-20

Metabolomics requires quantitative comparison of individual metabolites present in an entire sample set. Unfortunately, missing intensity values in one or more samples are very common. Because missing values can have a profound influence on metabolomic results, the extent of missing values found in a metabolomic data set should be treated as an important parameter for measuring the analytical performance of a technique. In this work, we report a study on the scope of missing values and a robust method of filling the missing values in a chemical isotope labeling (CIL) LC-MS metabolomics platform. Unlike conventional LC-MS, CIL LC-MS quantifies the concentration differences of individual metabolites in two comparative samples based on the mass spectral peak intensity ratio of a peak pair from a mixture of differentially labeled samples. We show that this peak-pair feature can be explored as a unique means of extracting metabolite intensity information from raw mass spectra. In our approach, a peak-pair peaking algorithm, IsoMS, is initially used to process the LC-MS data set to generate a CSV file or table that contains metabolite ID and peak ratio information (i.e., metabolite-intensity table). A zero-fill program, freely available from MyCompoundID.org , is developed to automatically find a missing value in the CSV file and go back to the raw LC-MS data to find the peak pair and, then, calculate the intensity ratio and enter the ratio value into the table. Most of the missing values are found to be low abundance peak pairs. We demonstrate the performance of this method in analyzing an experimental and technical replicate data set of human urine metabolome. Furthermore, we propose a standardized approach of counting missing values in a replicate data set as a way of gauging the extent of missing values in a metabolomics platform. Finally, we illustrate that applying the zero-fill program, in conjunction with dansylation CIL LC-MS, can lead to a marked improvement in finding significant metabolites that differentiate bladder cancer patients and their controls in a metabolomics study of 109 subjects.

SENSITIVITY OF STRUCTURAL RESPONSE TO GROUND MOTION SOURCE AND SITE PARAMETERS.

USGS Publications Warehouse

Safak, Erdal; Brebbia, C.A.; Cakmak, A.S.; Abdel Ghaffar, A.M.

1985-01-01

Designing structures to withstand earthquakes requires an accurate estimation of the expected ground motion. While engineers use the peak ground acceleration (PGA) to model the strong ground motion, seismologists use physical characteristics of the source and the rupture mechanism, such as fault length, stress drop, shear wave velocity, seismic moment, distance, and attenuation. This study presents a method for calculating response spectra from seismological models using random vibration theory. It then investigates the effect of various source and site parameters on peak response. Calculations are based on a nonstationary stochastic ground motion model, which can incorporate all the parameters both in frequency and time domains. The estimation of the peak response accounts for the effects of the non-stationarity, bandwidth and peak correlations of the response.

Fabrication and Characterization of Woodpile Structures for Direct Laser Acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGuinness, C.; Colby, E.; England, R.J.

2010-08-26

An eight and nine layer three dimensional photonic crystal with a defect designed specifically for accelerator applications has been fabricated. The structures were fabricated using a combination of nanofabrication techniques, including low pressure chemical vapor deposition, optical lithography, and chemical mechanical polishing. Limits imposed by the optical lithography set the minimum feature size to 400 nm, corresponding to a structure with a bandgap centered at 4.26 {micro}m. Reflection spectroscopy reveal a peak in reflectivity about the predicted region, and good agreement with simulation is shown. The eight and nine layer structures will be aligned and bonded together to form themore » complete seventeen layer woodpile accelerator structure.« less

Model uncertainties of the 2002 update of California seismic hazard maps

USGS Publications Warehouse

Cao, T.; Petersen, M.D.; Frankel, A.D.

2005-01-01

In this article we present and explore the source and ground-motion model uncertainty and parametric sensitivity for the 2002 update of the California probabilistic seismic hazard maps. Our approach is to implement a Monte Carlo simulation that allows for independent sampling from fault to fault in each simulation. The source-distance dependent characteristics of the uncertainty maps of seismic hazard are explained by the fundamental uncertainty patterns from four basic test cases, in which the uncertainties from one-fault and two-fault systems are studied in detail. The California coefficient of variation (COV, ratio of the standard deviation to the mean) map for peak ground acceleration (10% of exceedance in 50 years) shows lower values (0.1-0.15) along the San Andreas fault system and other class A faults than along class B faults (0.2-0.3). High COV values (0.4-0.6) are found around the Garlock, Anacapa-Dume, and Palos Verdes faults in southern California and around the Maacama fault and Cascadia subduction zone in northern California.

Polarization transfer in the H2(e→,e'p→)n reaction up to Q2=1.61(GeV/c)2

NASA Astrophysics Data System (ADS)

Hu, B.; Jones, M. K.; Ulmer, P. E.; Arenhövel, H.; Baker, O. K.; Bertozzi, W.; Brash, E. J.; Calarco, J.; Chen, J.-P.; Chudakov, E.; Cochran, A.; Dumalski, S.; Ent, R.; M. Finn, J.; Garibaldi, F.; Gilad, S.; Gilman, R.; Glashausser, C.; Gomez, J.; Gorbenko, V.; Hansen, J.-O.; Hovebo, J.; Jager, C. W. De; Jeschonnek, S.; Jiang, X.; Keppel, C.; Klein, A.; Kozlov, A.; Kuhn, S.; Kumbartzki, G.; Kuss, M.; Lerose, J. J.; Liang, M.; Liyanage, N.; Lolos, G. J.; Markowitz, P. E. C.; Meekins, D.; Michaels, R.; Mitchell, J.; Papandreou, Z.; Perdrisat, C. F.; Punjabi, V.; Roche, R.; Rowntree, D.; Saha, A.; Strauch, S.; Todor, L.; Urciuoli, G.; Weinstein, L. B.; Wijesooriya, K.; Wojtsekhowski, B. B.; Woo, R.

2006-06-01

The recoil proton polarization was measured in the H2(e→,e'p→)n reaction in Hall A of the Thomas Jefferson National Accelerator Facility. The electron kinematics were centered on the quasielastic peak (xBj≈1) and included three values of the squared four-momentum transfer, Q2=0.43,1.00 and 1.61 (GeV/c)2. For Q2=0.43 and 1.61 (GeV/c)2, the missing momentum, pm, was centered at zero, whereas for Q2=1.00(GeV/c)2 two values of pm were chosen: 0 and 174MeV/c. At low pm, the Q2 dependence of the longitudinal polarization, Pz', is not well described by a state-of-the-art calculation. Further, at higher pm, a 3.5σ discrepancy was observed in the transverse polarization, Px'. Understanding the origin of these discrepancies is important to confidently extract the neutron electric form factor from the analogous H2(e→,e'n→)p experiment.

Experimental and analytical studies on multiple tuned mass dampers for seismic protection of porcelain electrical equipment

NASA Astrophysics Data System (ADS)

Bai, Wen; Dai, Junwu; Zhou, Huimeng; Yang, Yongqiang; Ning, Xiaoqing

2017-10-01

Porcelain electrical equipment (PEE), such as current transformers, is critical to power supply systems, but its seismic performance during past earthquakes has not been satisfactory. This paper studies the seismic performance of two typical types of PEE and proposes a damping method for PEE based on multiple tuned mass dampers (MTMD). An MTMD damping device involving three mass units, named a triple tuned mass damper (TTMD), is designed and manufactured. Through shake table tests and finite element analysis, the dynamic characteristics of the PEE are studied and the effectiveness of the MTMD damping method is verified. The adverse influence of MTMD redundant mass to damping efficiency is studied and relevant equations are derived. MTMD robustness is verified through adjusting TTMD control frequencies. The damping effectiveness of TTMD, when the peak ground acceleration far exceeds the design value, is studied. Both shake table tests and finite element analysis indicate that MTMD is effective and robust in attenuating PEE seismic responses. TTMD remains effective when the PGA far exceeds the design value and when control deviations are considered.

Analysis of strong ground motions and site effects at Kantipath, Kathmandu, from 2015 Mw 7.8 Gorkha, Nepal, earthquake and its aftershocks

NASA Astrophysics Data System (ADS)

Dhakal, Yadab P.; Kubo, Hisahiko; Suzuki, Wataru; Kunugi, Takashi; Aoi, Shin; Fujiwara, Hiroyuki

2016-04-01

Strong ground motions from the 2015 Mw 7.8 Gorkha, Nepal, earthquake and its eight aftershocks recorded by a strong-motion seismograph at Kantipath (KATNP), Kathmandu, were analyzed to assess the ground-motion characteristics and site effects at this location. Remarkably large elastic pseudo-velocity responses exceeding 300 cm/s at 5 % critical damping were calculated for the horizontal components of the mainshock recordings at peak periods of 4-5 s. Conversely, the short-period ground motions of the mainshock were relatively weak despite the proximity of the site to the source fault. The horizontal components of all large-magnitude (Mw ≥ 6.3) aftershock recordings showed peak pseudo-velocity responses at periods of 3-4 s. Ground-motion prediction equations (GMPEs) describing the Nepal Himalaya region have not yet been developed. A comparison of the observational data with GMPEs for Japan showed that with the exception of the peak ground acceleration (PGA) of the mainshock, the observed PGAs and peak ground velocities at the KATNP site are generally well described by the GMPEs for crustal and plate interface events. A comparison of the horizontal-to-vertical ( H/ V) spectral ratios for the S-waves of the mainshock and aftershock recordings suggested that the KATNP site experienced a considerable nonlinear site response, which resulted in the reduced amplitudes of short-period ground motions. The GMPEs were found to underestimate the response values at the peak periods (approximately 4-5 s) of the large-magnitude events. The deep subsurface velocity model of the Kathmandu basin has not been well investigated. Therefore, a one-dimensional velocity model was constructed for the deep sediments beneath the recording station based on an analysis of the H/ V spectral ratios for S-wave coda from aftershock recordings, and it was revealed that the basin sediments strongly amplified the long-period components of the ground motions of the mainshock and large-magnitude aftershocks.

SPE-5 Ground-Motion Prediction at Far-Field Geophone and Accelerometer Array Sites and SPE-5 Moment and Corner-Frequency Prediction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Xiaoning; Patton, Howard John; Chen, Ting

2016-03-25

This report offers predictions for the SPE-5 ground-motion and accelerometer array sites. These predictions pertain to the waveform and spectral amplitude at certain geophone sites using Denny&Johnson source model and a source model derived from SPE data; waveform, peak velocity and peak acceleration at accelerometer sites using the SPE source model and the finite-difference simulation with LLNL 3D velocity model; and the SPE-5 moment and corner frequency.

Step Detection Robust against the Dynamics of Smartphones

PubMed Central

Lee, Hwan-hee; Choi, Suji; Lee, Myeong-jin

2015-01-01

A novel algorithm is proposed for robust step detection irrespective of step mode and device pose in smartphone usage environments. The dynamics of smartphones are decoupled into a peak-valley relationship with adaptive magnitude and temporal thresholds. For extracted peaks and valleys in the magnitude of acceleration, a step is defined as consisting of a peak and its adjacent valley. Adaptive magnitude thresholds consisting of step average and step deviation are applied to suppress pseudo peaks or valleys that mostly occur during the transition among step modes or device poses. Adaptive temporal thresholds are applied to time intervals between peaks or valleys to consider the time-varying pace of human walking or running for the correct selection of peaks or valleys. From the experimental results, it can be seen that the proposed step detection algorithm shows more than 98.6% average accuracy for any combination of step mode and device pose and outperforms state-of-the-art algorithms. PMID:26516857

Detailed Experimental Study of Ion Acceleration by Interaction of an Ultra-Short Intense Laser with an Underdense Plasma

PubMed Central

Kahaly, S.; Sylla, F.; Lifschitz, A.; Flacco, A.; Veltcheva, M.; Malka, V.

2016-01-01

Ion acceleration from intense (Iλ2 > 1018 Wcm−2 μm2) laser-plasma interaction is experimentally studied within a wide range of He gas densities. Focusing an ultrashort pulse (duration  ion plasma period) on a newly designed submillimetric gas jet system, enabled us to inhibit total evacuation of electrons from the central propagation channel reducing the radial ion acceleration associated with ponderomotive Coulomb explosion, a mechanism predominant in the long pulse scenario. New ion acceleration mechanism have been unveiled in this regime leading to non-Maxwellian quasi monoenergetic features in the ion energy spectra. The emitted nonthermal ion bunches show a new scaling of the ion peak energy with plasma density. The scaling identified in this new regime differs from previously reported studies. PMID:27531755

Ontogeny of vestibular compound action potentials in the domestic chicken

NASA Technical Reports Server (NTRS)

Jones, S. M.; Jones, T. A.

2000-01-01

Compound action potentials of the vestibular nerve were measured from the surface of the scalp in 148 chickens (Gallus domesticus). Ages ranged from incubation day 18 (E18) to 22 days posthatch (P22). Responses were elicited using linear acceleration cranial pulses. Response thresholds decreased at an average rate of -0.45 dB/day. The decrease was best fit by an exponential model with half-maturity time constant of 5.1 days and asymptote of approximately -25.9 dB re:1.0 g/ms. Mean threshold approached within 3 dB of the asymptote by ages P6-P9. Similarly, response latencies decreased exponentially to within 3% of mature values at ages beyond P9. The half-maturity time constant for peripheral response peak latencies P1, N1, and P2 was comparable to thresholds and ranged from approximately 4.6 to 6.2 days, whereas central peaks (N2, P3, and N3) ranged from 2.9 to 3.4 days. Latency-intensity slopes for P1, N1, and P2 tended to decrease with age, reaching mature values within approximately 100 hours of hatching. Amplitudes increased as a function of age with average growth rates for response peaks ranging from 0.04 to 0.09 microV/day. There was no obvious asymptote to the growth of amplitudes over the ages studied. Amplitude-intensity slopes also increased modestly with age. The results show that gravity receptors are responsive to transient cranial stimuli as early as E19 in the chicken embryo. The functional response of gravity receptors continues to develop for many days after all major morphological structures are in place. Distinct maturational processes can be identified in central and peripheral neural relays. Functional improvements during maturation may result from refinements in the receptor epithelia, improvements in central and peripheral synaptic transmission, increased neural myelination, as well as changes in the mechanical coupling between the cranium and receptor organ.

SU-F-T-146: Comparing Monte Carlo Simulations with Commissioning Beam Data for Mevion S250 Proton Therapy System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prusator, M; Jin, H; Ahmad, S

2016-06-15

Purpose: To evaluate the Monte Carlo simulated beam data with the measured commissioning data for the Mevion S250 proton therapy system. Method: The Mevion S250 proton therapy system utilizes a passive double scattering technique with a unique gantry mounted superconducting accelerator and offers effective proton therapy in a compact design concept. The field shaping system (FSS) includes first scattering foil, range modulator wheel (RMW), second scattering foil and post absorber and offers two field sizes and a total of 24 treatment options from proton range of 5 cm to 32 cm. The treatment nozzle was modeled in detail using TOPASmore » (TOolkit for PArticle Simulation) Monte Carlo code. The timing feathers of the moving modulator wheels were also implemented to generate the Spread Out Bragg Peak (SOBP). The simulation results including pristine Bragg Peak, SOBP and dose profiles were compared with the data measured during beam commissioning. Results: The comparison between the measured data and the simulation data show excellent agreement. For pristine proton Bragg Peaks, the simulated proton range (depth of distal 90%) values agreed well with the measured range values within 1 mm accuracy. The differences of the distal falloffs (depth from distal 80% to 20%) were also found to be less than 1 mm between the simulations and measurements. For the SOBP, the widths of modulation (depth of proximal 95% to distal 90%) were also found to agree with the measurement within 1 mm. The flatness of the simulated and measured lateral profiles was found to be 0.6 % and 1.1 %, respectively. Conclusion: The agreement between simulations and measurements demonstrate that TOPAS could be used as a viable platform to proton therapy applications. The matched simulation results offer a great tool and open opportunity for variety of applications.« less

Ontogeny of Vestibular Compound Action Potentials in the Domestic Chicken

PubMed Central

M. Jones, Sherri

2000-01-01

Compound action potentials of the vestibular nerve were measured from the surface of the scalp in 148 chickens (Gallus domesticus). Ages ranged from incubation day 18 (E18) to 22 days posthatch (P22). Responses were elicited using linear acceleration cranial pulses. Response thresholds decreased at an average rate of –0.45 dB/day. The decrease was best fit by an exponential model with half-maturity time constant of 5.1 days and asymptote of approximately –25.9 dB re:1.0 g/ms. Mean threshold approached within 3 dB of the asymptote by ages P6–P9. Similarly, response latencies decreased exponentially to within 3% of mature values at ages beyond P9. The half-maturity time constant for peripheral response peak latencies P1, N1, and P2 was comparable to thresholds and ranged from approximately 4.6 to 6.2 days, whereas central peaks (N2, P3, and N3) ranged from 2.9 to 3.4 days. Latency-intensity slopes for P1, N1, and P2 tended to decrease with age, reaching mature values within approximately 100 hours of hatching. Amplitudes increased as a function of age with average growth rates for response peaks ranging from 0.04 to 0.09 μV/day. There was no obvious asymptote to the growth of amplitudes over the ages studied. Amplitude-intensity slopes also increased modestly with age. The results show that gravity receptors are responsive to transient cranial stimuli as early as E19 in the chicken embryo. The functional response of gravity receptors continues to develop for many days after all major morphological structures are in place. Distinct maturational processes can be identified in central and peripheral neural relays. Functional improvements during maturation may result from refinements in the receptor epithelia, improvements in central and peripheral synaptic transmission, increased neural myelination, as well as changes in the mechanical coupling between the cranium and receptor organ. PMID:11545229

How to use your peak flow meter

MedlinePlus

Peak flow meter - how to use; Asthma - peak flow meter; Reactive airway disease - peak flow meter; Bronchial asthma - peak flow meter ... your airways are narrowed and blocked due to asthma, your peak flow values drop. You can check ...

Probabilistic seismic hazard analysis (PSHA) for Ethiopia and the neighboring region

NASA Astrophysics Data System (ADS)

Ayele, Atalay

2017-10-01

Seismic hazard calculation is carried out for the Horn of Africa region (0°-20° N and 30°-50°E) based on the probabilistic seismic hazard analysis (PSHA) method. The earthquakes catalogue data obtained from different sources were compiled, homogenized to Mw magnitude scale and declustered to remove the dependent events as required by Poisson earthquake source model. The seismotectonic map of the study area that avails from recent studies is used for area sources zonation. For assessing the seismic hazard, the study area was divided into small grids of size 0.5° × 0.5°, and the hazard parameters were calculated at the center of each of these grid cells by considering contributions from all seismic sources. Peak Ground Acceleration (PGA) corresponding to 10% and 2% probability of exceedance in 50 years were calculated for all the grid points using generic rock site with Vs = 760 m/s. Obtained values vary from 0.0 to 0.18 g and 0.0-0.35 g for 475 and 2475 return periods, respectively. The corresponding contour maps showing the spatial variation of PGA values for the two return periods are presented here. Uniform hazard response spectrum (UHRS) for 10% and 2% probability of exceedance in 50 years and hazard curves for PGA and 0.2 s spectral acceleration (Sa) all at rock site are developed for the city of Addis Ababa. The hazard map of this study corresponding to the 475 return periods has already been used to update and produce the 3rd generation building code of Ethiopia.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartolac, S; Letourneau, D; University of Toronto, Toronto, Ontario

Purpose: Application of process control theory in quality assurance programs promises to allow earlier identification of problems and potentially better quality in delivery than traditional paradigms based primarily on tolerances and action levels. The purpose of this project was to characterize underlying seasonal variations in linear accelerator output that can be used to improve performance or trigger preemptive maintenance. Methods: Review of runtime plots of daily (6 MV) output data acquired using in house ion chamber based devices over three years and for fifteen linear accelerators of varying make and model were evaluated. Shifts in output due to known interventionsmore » with the machines were subtracted from the data to model an uncorrected scenario for each linear accelerator. Observable linear trends were also removed from the data prior to evaluation of periodic variations. Results: Runtime plots of output revealed sinusoidal, seasonal variations that were consistent across all units, irrespective of manufacturer, model or age of machine. The average amplitude of the variation was on the order of 1%. Peak and minimum variations were found to correspond to early April and September, respectively. Approximately 48% of output adjustments made over the period examined were potentially avoidable if baseline levels had corresponded to the mean output, rather than to points near a peak or valley. Linear trends were observed for three of the fifteen units, with annual increases in output ranging from 2–3%. Conclusion: Characterization of cyclical seasonal trends allows for better separation of potentially innate accelerator behaviour from other behaviours (e.g. linear trends) that may be better described as true out of control states (i.e. non-stochastic deviations from otherwise expected behavior) and could indicate service requirements. Results also pointed to an optimal setpoint for accelerators such that output of machines is maintained within set tolerances and interventions are required less frequently.« less

Comparison of measured with calculated dose distribution from a 120-MeV electron beam from a laser-plasma accelerator.

PubMed

Lundh, O; Rechatin, C; Faure, J; Ben-Ismaïl, A; Lim, J; De Wagter, C; De Neve, W; Malka, V

2012-06-01

To evaluate the dose distribution of a 120-MeV laser-plasma accelerated electron beam which may be of potential interest for high-energy electron radiation therapy. In the interaction between an intense laser pulse and a helium gas jet, a well collimated electron beam with very high energy is produced. A secondary laser beam is used to optically control and to tune the electron beam energy and charge. The potential use of this beam for radiation treatment is evaluated experimentally by measurements of dose deposition in a polystyrene phantom. The results are compared to Monte Carlo simulations using the geant4 code. It has been shown that the laser-plasma accelerated electron beam can deliver a peak dose of more than 1 Gy at the entrance of the phantom in a single laser shot by direct irradiation, without the use of intermediate magnetic transport or focusing. The dose distribution is peaked on axis, with narrow lateral penumbra. Monte Carlo simulations of electron beam propagation and dose deposition indicate that the propagation of the intense electron beam (with large self-fields) can be described by standard models that exclude collective effects in the response of the material. The measurements show that the high-energy electron beams produced by an optically injected laser-plasma accelerator can deliver high enough dose at penetration depths of interest for electron beam radiotherapy of deep-seated tumors. Many engineering issues must be resolved before laser-accelerated electrons can be used for cancer therapy, but they also represent exciting challenges for future research. © 2012 American Association of Physicists in Medicine.

Simultaneous Multislice Echo Planar Imaging With Blipped Controlled Aliasing in Parallel Imaging Results in Higher Acceleration: A Promising Technique for Accelerated Diffusion Tensor Imaging of Skeletal Muscle.

PubMed

Filli, Lukas; Piccirelli, Marco; Kenkel, David; Guggenberger, Roman; Andreisek, Gustav; Beck, Thomas; Runge, Val M; Boss, Andreas

2015-07-01

The aim of this study was to investigate the feasibility of accelerated diffusion tensor imaging (DTI) of skeletal muscle using echo planar imaging (EPI) applying simultaneous multislice excitation with a blipped controlled aliasing in parallel imaging results in higher acceleration unaliasing technique. After federal ethics board approval, the lower leg muscles of 8 healthy volunteers (mean [SD] age, 29.4 [2.9] years) were examined in a clinical 3-T magnetic resonance scanner using a 15-channel knee coil. The EPI was performed at a b value of 500 s/mm2 without slice acceleration (conventional DTI) as well as with 2-fold and 3-fold acceleration. Fractional anisotropy (FA) and mean diffusivity (MD) were measured in all 3 acquisitions. Fiber tracking performance was compared between the acquisitions regarding the number of tracks, average track length, and anatomical precision using multivariate analysis of variance and Mann-Whitney U tests. Acquisition time was 7:24 minutes for conventional DTI, 3:53 minutes for 2-fold acceleration, and 2:38 minutes for 3-fold acceleration. Overall FA and MD values ranged from 0.220 to 0.378 and 1.595 to 1.829 mm2/s, respectively. Two-fold acceleration yielded similar FA and MD values (P ≥ 0.901) and similar fiber tracking performance compared with conventional DTI. Three-fold acceleration resulted in comparable MD (P = 0.199) but higher FA values (P = 0.006) and significantly impaired fiber tracking in the soleus and tibialis anterior muscles (number of tracks, P < 0.001; anatomical precision, P ≤ 0.005). Simultaneous multislice EPI with blipped controlled aliasing in parallel imaging results in higher acceleration can remarkably reduce acquisition time in DTI of skeletal muscle with similar image quality and quantification accuracy of diffusion parameters. This may increase the clinical applicability of muscle anisotropy measurements.

Centrifuge-Simulated Suborbital Spaceflight in a Subject with Cardiac Malformation.

PubMed

Blue, Rebecca S; Blacher, Eric; Castleberry, Tarah L; Vanderploeg, James M

2015-11-01

Commercial spaceflight participants (SFPs) will introduce new medical challenges to the aerospace community, with unique medical conditions never before exposed to the space environment. This is a case report regarding the response of a subject with multiple cardiac malformations, including aortic insufficiency, pulmonary atresia, pulmonary valve replacement, ventricular septal defect (post-repair), and pulmonary artery stenosis (post-dilation), to centrifuge acceleration simulating suborbital flight. A 23-yr-old man with a history of multiple congenital cardiac malformations underwent seven centrifuge runs over 2 d. Day 1 consisted of two +G(z) runs (peak = +3.5 G(z), run 2) and two +G(x) runs (peak = +6.0 G(x), run 4). Day 2 consisted of three runs approximating suborbital spaceflight profiles (combined +G(x) and +G(z)). Data collected included blood pressure, electrocardiogram, pulse oximetry, neurovestibular exams, and post-run questionnaires regarding motion sickness, disorientation, greyout, and other symptoms. Despite the subject's significant medical history, he tolerated the acceleration profiles well and demonstrated no significant abnormal physiological responses. Potential risks to SFPs with aortic insufficiency, artificial heart valves, or valvular insufficiency include lower +G(z) tolerance, earlier symptom onset, and ineffective mitigation strategies such as anti-G straining maneuvers. There are no prior studies of prolonged accelerations approximating spaceflight in such individuals. This case demonstrates tolerance of acceleration profiles in an otherwise young and healthy individual with significant cardiac malformations, suggesting that such conditions may not necessarily preclude participation in commercial spaceflight.

Global Energetics of Several Large Solar Eruptive Events

NASA Technical Reports Server (NTRS)

Emslie, A. G.; Dennis, B. R.; Shih, A. Y.; Chamberlin, P. C.; Mewaldt, R. A.; Share, G. H.; Vourlidas, A.; Welsch, B. T.

2012-01-01

We have evaluated the energetics of 38 solar eruptive events observed by a variety of spacecraft instruments between February 2002 and December 2006, as accurately as the observations allow. The measured energetic components include: (1) the radiated energy in the GOES 1 { 8 A band; (2) the total energy radiated from the soft X-ray (SXR) emitting plasma; (3) the peak energy in the SXR-emitting plasma; (4) the bolometric radiated energy over the full duration of the event; (5) the energy in are-accelerated electrons above 20 keV and in ions above 1 MeV; (6) the kinetic and potential energies of the coronal mass ejection (CME); (7) the energy in solar energetic particles (SEPs); and (8) the amount of free (nonpotential) magnetic energy estimated to be available in the pertinent active region. Major conclusions include: (1) the energy radiated by the SXR-emitting plasma exceeds, by about half an order of magnitude, the peak energy content of the thermal plasma that produces this radiation; (2) the energy content in are-accelerated electrons and ions is sufficient to supply the bolometric energy radiated across all wavelengths throughout the event; (3) the energy contents of are-accelerated electrons and ions are comparable; (4) the energy in SEPs is typically a few percent of the CME kinetic energy (measured in the rest frame of the solar wind); and (5) the available magnetic energy is sufficient to power the CME, the are-accelerated particles, and the hot thermal plasma.

The Effect of the Ionosphere on Radiowave Signals and Systems Performance Based on Ionospheric Effects Symposium Held on 1-3 May 1990

DTIC Science & Technology

1990-05-03

winter and a minimum in summer ; in contrast, at sunspot maximum the seasonal peaks tend to occur around the equinoxes and the minima in summer . ’riis is...more clearly seen in Figures 4(b) ahnd 4(c). Note that around sunspot maximum the summer noon value may be less than the summer midnight value. (3) The...seasonal variation of the midnight values show summer peaks and winter minima with high values near the peaks of the sunspot cycles and low values

Ground vibration investigation at highway construction sites : final report.

DOT National Transportation Integrated Search

1975-06-01

The purpose of this study was to measure vibration magnitudes on construction projects in terms of particle velocity rather than particle displacement or acceleration. Peak particle velocity was chosen as the best means of measurement after the U.S. ...

Spectral investigation of somatotropin for different pH values

NASA Astrophysics Data System (ADS)

Otero de Joshi, Virginia; Gil, Herminia; Contreras, Silvia; Joshi, Narahari V.; Hernandez, Luis

1996-04-01

Spectral investigations of absorbance in deep ultra-violet region (from 200 nm to 350 nm) of (STM) was carried out for different pH values. On the high energy side the peak is located at 195 nm which is generally attributed to peptide bonds. This peak, as expected, does not show any shift with pH value (4.3 to 10.8). A rather broad peak is spread in the region from 200 nm to 240 nm which could be the superposition of the peaks corresponding to the absorption due to (alpha) helix and (beta) structure. This peak shows a red shift as pH value increases. The same hormone was glycated by a conventional method and the process was estimated with the absorption spectra. The results are discussed in the light of nonenzymatic glycation. It was found that glycation mucus somatotropin resistant towards the denaturation process.

Plasma vasopressin and renin activity in women exposed to bed rest and +G/z/ acceleration

NASA Technical Reports Server (NTRS)

Keil, L. C.; Ellis, S.

1976-01-01

To study the effect of prolonged recumbency on plasma vasopressin and renin activity, eight women were subjected to 17 days of absolute bed rest. The tolerance to +3G vertical acceleration of the subjects was tested before and after 14 days of bed rest. From day 2 and through day 17 of bed rest, plasma arginine vasopressin (AVP) levels were reduced 33%. Plasma renin activity (PRA) increased 91% above ambulatory control values from days 10 through 15 of bed rest. When compared to precentrifuge values, exposure to vertical acceleration prior to bed rest provoked a 20-fold rise in mean plasma AVP but resulted in only a slight increase in PRA. After bed rest, acceleration increased plasma AVP 7-fold; however, the magnitude of this increase was less than the post +3G acceleration value obtained prior to bed rest. After bed rest, no significant rise was noted in PRA following +3G acceleration. This study demonstrates that prolonged bed rest leads to a significant rise in the PRA of female subjects, while exposure to positive vertical acceleration provokes a marked rise in plasma AVP.