On the electrostatic deceleration of argon atoms in high Rydberg states by time-dependent inhomogeneous electric fields

NASA Astrophysics Data System (ADS)

Vliegen, E.; Merkt, F.

2005-06-01

Argon atoms in a pulsed supersonic expansion are prepared in selected Stark components of Rydberg states with effective principal quantum number in the range n* = 15-25. When traversing regions of inhomogeneous electric fields, these atoms get accelerated or decelerated depending on whether the Stark states are low- or high-field seeking states. Using a compact electrode design, which enables the application of highly inhomogeneous and time-dependent electric fields, the Rydberg atoms experience kinetic energy changes of up to 1.2 × 10-21 J (i.e. 60 cm-1 in spectroscopic units) in a single acceleration/deceleration stage of 3 mm length. The resulting differences in the velocities of the low- and high-field seeking states are large enough that the corresponding distributions of times of flight to the Rydberg particle detector are fully separated. As a result, efficient spectral searches of the Rydberg states best suited for acceleration/deceleration experiments are possible. Numerical simulations of the particle trajectories are used to analyse the time-of-flight distributions and to optimize the time dependence of the inhomogeneous electric fields. The decay of the Rydberg states by fluorescence, collisions and transitions induced by black-body radiation takes place on a timescale long enough not to interfere significantly with the deceleration during the first ~5 µs.

Free electron laser using Rf coupled accelerating and decelerating structures

DOEpatents

Brau, Charles A.; Swenson, Donald A.; Boyd, Jr., Thomas J.

1984-01-01

A free electron laser and free electron laser amplifier using beam transport devices for guiding an electron beam to a wiggler of a free electron laser and returning the electron beam to decelerating cavities disposed adjacent to the accelerating cavities of the free electron laser. Rf energy is generated from the energy depleted electron beam after it emerges from the wiggler by means of the decelerating cavities which are closely coupled to the accelerating cavities, or by means of a second bore within a single set of cavities. Rf energy generated from the decelerated electron beam is used to supplement energy provided by an external source, such as a klystron, to thereby enhance overall efficiency of the system.

Stereoscopic camera and viewing systems with undistorted depth presentation and reduced or eliminated erroneous acceleration and deceleration perceptions, or with perceptions produced or enhanced for special effects

NASA Technical Reports Server (NTRS)

Diner, Daniel B. (Inventor)

1991-01-01

Methods for providing stereoscopic image presentation and stereoscopic configurations using stereoscopic viewing systems having converged or parallel cameras may be set up to reduce or eliminate erroneously perceived accelerations and decelerations by proper selection of parameters, such as an image magnification factor, q, and intercamera distance, 2w. For converged cameras, q is selected to be equal to Ve - qwl = 0, where V is the camera distance, e is half the interocular distance of an observer, w is half the intercamera distance, and l is the actual distance from the first nodal point of each camera to the convergence point, and for parallel cameras, q is selected to be equal to e/w. While converged cameras cannot be set up to provide fully undistorted three-dimensional views, they can be set up to provide a linear relationship between real and apparent depth and thus minimize erroneously perceived accelerations and decelerations for three sagittal planes, x = -w, x = 0, and x = +w which are indicated to the observer. Parallel cameras can be set up to provide fully undistorted three-dimensional views by controlling the location of the observer and by magnification and shifting of left and right images. In addition, the teachings of this disclosure can be used to provide methods of stereoscopic image presentation and stereoscopic camera configurations to produce a nonlinear relation between perceived and real depth, and erroneously produce or enhance perceived accelerations and decelerations in order to provide special effects for entertainment, training, or educational purposes.

Effects of drop acceleration and deceleration on particle capture in a cross-flow gravity tower at intermediate drop Reynolds numbers.

PubMed

Kumar, Anoop; Gupta, S K; Kale, S R

2007-04-01

Cross-flow gravity towers are particle scrubbing devices in which water is sprayed from the top into particle-laden flow moving horizontally. Models for predicting particle capture assume drops traveling at terminal velocity and potential flow (ReD > 1000) around it, however, Reynolds numbers in the intermediate range of 1 to 1000 are common in gravity towers. Drops are usually injected at velocities greater than their terminal velocities (as in nozzles) or from near rest (perforated tray) and they accelerate/decelerate to their terminal velocity in the tower. Also, the effects of intermediate drop Reynolds number on capture efficiency have been simulated for (a) drops at their terminal velocity and (b) drops accelerating/decelerating to their terminal velocity. Tower efficiency based on potential flow about the drop is 40%-50% greater than for 200 mm drops traveling at their terminal velocity. The corresponding values for 500 mm drops are about 10%-20%. The drop injection velocity is important operating parameter. Increase in tower efficiency by about 40% for particles smaller than 5 mm is observed for increase in injection velocity from 0 to 20 m/s for 200 and 500mm drops.

Tunable inertia of chiral magnetic domain walls

PubMed Central

Torrejon, Jacob; Martinez, Eduardo; Hayashi, Masamitsu

2016-01-01

The time it takes to accelerate an object from zero to a given velocity depends on the applied force and the environment. If the force ceases, it takes exactly the same time to completely decelerate. A magnetic domain wall is a topological object that has been observed to follow this behaviour. Here we show that acceleration and deceleration times of chiral Neel walls driven by current are different in a system with low damping and moderate Dzyaloshinskii–Moriya exchange constant. The time needed to accelerate a domain wall with current via the spin Hall torque is much faster than the time it needs to decelerate once the current is turned off. The deceleration time is defined by the Dzyaloshinskii–Moriya exchange constant whereas the acceleration time depends on the spin Hall torque, enabling tunable inertia of chiral domain walls. Such unique feature of chiral domain walls can be utilized to move and position domain walls with lower current, key to the development of storage class memory devices. PMID:27882932

Task-control of arousal and the effects of repeated unidirectional angular acceleration on human vestibular responses.

DOT National Transportation Integrated Search

1963-11-01

Subjects were exposed to a 10-day habituation series of 200 CW accelerations in total darkness while performing attention-demanding tasks. Decelerations were sub-threshold. Preliminary and post-tests indicated that slow-phase nystagmus and duration o...

Kinetics of the Shanghai Maglev: Kinematical Analysis of a Real "Textbook" Case of Linear Motion

NASA Astrophysics Data System (ADS)

Hsu, Tung

2014-10-01

A vehicle starts from rest at constant acceleration, then cruises at constant speed for a time. Next, it decelerates at a constant rate.… This and similar statements are common in elementary physics courses. Students are asked to graph the motion of the vehicle or find the velocity, acceleration, and distance traveled by the vehicle from a given graph.1 However, a "constant acceleration-constant velocity-constant deceleration" motion, which gives us an ideal trapezoidal shape in the velocity-time graph, is not common in everyday life. Driving a car or riding a bicycle for a short distance can be much more complicated. Therefore, it is interesting to take a look at a real case of "constant acceleration-constant velocity-constant deceleration" motion.

Effect of Peripheral μ-, δ-, and κ-Opioid Ligands on the Development of Tolerance to Ethanol-Induced Analgesia.

PubMed

Sudakov, S K; Alekseeva, E V; Nazarova, G A

2017-06-01

We studied the rate of development of tolerance to the ethanol-induced analgesia under the effect of μ-, δ-, and κ-opioid agonists and antagonists not crossing the blood-brain barrier and rapidly inactivated by gastric and duodenal proteolytic enzymes. Activation of gastric κ-opioid receptors eliminated the analgesic effect of ethanol and accelerated the development of tolerance to ethanol-induced analgesia. In contrast, activation of gastric μ-opioid receptors decelerated the development of this tolerance. Activation of gastric δ-opioid receptors produced no effect on examined tolerance. μ-Opioid receptor antagonist decelerated and δ-opioid receptor antagonist accelerated the development of tolerance to ethanol-induced analgesia. Thus, the state of gastric opioid receptors affects the manifestation of ethanol-induced analgesia and the development of tolerance to this effect.

A bridge between unified cosmic history by f( R)-gravity and BIonic system

NASA Astrophysics Data System (ADS)

Sepehri, Alireza; Capozziello, Salvatore; Setare, Mohammad Reza

2016-04-01

Recently, the cosmological deceleration-acceleration transition redshift in f( R) gravity has been considered in order to address consistently the problem of cosmic evolution. It is possible to show that the deceleration parameter changes sign at a given redshift according to observational data. Furthermore, a f( R) gravity cosmological model can be constructed in brane-antibrane system starting from the very early universe and accounting for the cosmological redshift at all phases of cosmic history, from inflation to late time acceleration. Here we propose a f( R) model where transition redshifts correspond to inflation-deceleration and deceleration-late time acceleration transitions starting froma BIon system. At the point where the universe was born, due to the transition of k black fundamental strings to the BIon configuration, the redshift is approximately infinity and decreases with reducing temperature (z˜ T2). The BIon is a configuration in flat space of a universe-brane and a parallel anti-universe-brane connected by a wormhole. This wormhole is a channel for flowing energy from extra dimensions into our universe, occurring at inflation and decreasing with redshift as z˜ T^{4+1/7}. Dynamics consists with the fact that the wormhole misses its energy and vanishes as soon as inflation ends and deceleration begins. Approaching two universe branes together, a tachyon is originated, it grows up and causes the formation of a wormhole. We show that, in the framework of f( R) gravity, the cosmological redshift depends on the tachyonic potential and has a significant decrease at deceleration-late time acceleration transition point (z˜ T^{2/3}). As soon as today acceleration approaches, the redshift tends to zero and the cosmological model reduces to the standard Λ CDM cosmology.

Anticipating the effects of visual gravity during simulated self-motion: estimates of time-to-passage along vertical and horizontal paths.

PubMed

Indovina, Iole; Maffei, Vincenzo; Lacquaniti, Francesco

2013-09-01

By simulating self-motion on a virtual rollercoaster, we investigated whether acceleration cued by the optic flow affected the estimate of time-to-passage (TTP) to a target. In particular, we studied the role of a visual acceleration (1 g = 9.8 m/s(2)) simulating the effects of gravity in the scene, by manipulating motion law (accelerated or decelerated at 1 g, constant speed) and motion orientation (vertical, horizontal). Thus, 1-g-accelerated motion in the downward direction or decelerated motion in the upward direction was congruent with the effects of visual gravity. We found that acceleration (positive or negative) is taken into account but is overestimated in module in the calculation of TTP, independently of orientation. In addition, participants signaled TTP earlier when the rollercoaster accelerated downward at 1 g (as during free fall), with respect to when the same acceleration occurred along the horizontal orientation. This time shift indicates an influence of the orientation relative to visual gravity on response timing that could be attributed to the anticipation of the effects of visual gravity on self-motion along the vertical, but not the horizontal orientation. Finally, precision in TTP estimates was higher during vertical fall than when traveling at constant speed along the vertical orientation, consistent with a higher noise in TTP estimates when the motion violates gravity constraints.

Compact two-beam push-pull free electron laser

DOEpatents

Hutton, Andrew [Yorktown, VA

2009-03-03

An ultra-compact free electron laser comprising a pair of opposed superconducting cavities that produce identical electron beams moving in opposite directions such that each set of superconducting cavities accelerates one electron beam and decelerates the other electron beam. Such an arrangement, allows the energy used to accelerate one beam to be recovered and used again to accelerate the second beam, thus, each electron beam is decelerated by a different structure than that which accelerated it so that energy exchange rather than recovery is achieved resulting in a more compact and highly efficient apparatus.

40 CFR Appendix I to Subpart B of... - Appendix I to Subpart B of Part 205

Code of Federal Regulations, 2011 CFR

2011-07-01

...: Acceleration Test: Deceleration Test: Acceleration Test Run No. 1 2 3 4 5 dBA Left Right Highest RPM attained in End Zone Calculated Sound Pressure dBA Deceleration Test with Exhaust Brake Applied dBA Left Right Calculated Sound Pressure dBA TEST Personnel: (Name) Recorded By: Date:......... (Signature) Supervisor...

40 CFR Appendix I to Subpart B of... - Appendix I to Subpart B of Part 205

Code of Federal Regulations, 2010 CFR

2010-07-01

...: Acceleration Test: Deceleration Test: Acceleration Test Run No. 1 2 3 4 5 dBA Left Right Highest RPM attained in End Zone Calculated Sound Pressure dBA Deceleration Test with Exhaust Brake Applied dBA Left Right Calculated Sound Pressure dBA TEST Personnel: (Name) Recorded By: Date:......... (Signature) Supervisor...

Reaction time to changes in the tempo of acoustic pulse trains.

NASA Technical Reports Server (NTRS)

Smith, R. P.; Warm, J. S.; Westendorf, D. H.

1973-01-01

Investigation of the ability of human observers to detect accelerations and decelerations in the rate of presentation of pulsed stimuli, i.e., changes in the tempo of acoustic pulse trains. Response times to accelerations in tempo were faster than to decelerations. Overall speed of response was inversely related to the pulse repetition rate.

The effect of viscosity on steady transonic flow with a nodal solution topology

NASA Technical Reports Server (NTRS)

Owocki, Stanley P.; Zank, Gary P.

1991-01-01

The effect of viscosity on a steady, transonic flow for which the inviscid limit has a nodal solution topology near the critical point is investigated. For the accelerating case, viscous solutions tend to repel each other, so that a very delicate choice of initial conditions is required to prevent them from diverging. Only the two critical solutions extend to arbitrarily large distances into both the subsonic and supersonic flows. For the decelerating case, the solutions tend to attract, and so an entire two-parameter family of solutions now extends over large distances. The general effect of viscosity on the solution degeneracy of a nodal topology is thus to reduce or limit it for the accelerating case and to enhance it for the decelerating case. The astrophysical implications of these findings are addressed.

Automated Fetal Heart Rate Analysis in Labor: Decelerations and Overshoots

NASA Astrophysics Data System (ADS)

Georgieva, A. E.; Payne, S. J.; Moulden, M.; Redman, C. W. G.

2010-10-01

Electronic fetal heart rate (FHR) recording is a standard way of monitoring fetal health in labor. Decelerations and accelerations usually indicate fetal distress and normality respectively. But one type of acceleration may differ, namely an overshoot that may atypically reflect fetal stress. Here we describe a new method for detecting decelerations, accelerations and overshoots as part of a novel system for computerized FHR analysis (OxSyS). There was poor agreement between clinicians when identifying these FHR features visually, which precluded setting a gold standard of interpretation. We therefore introduced `modified' Sensitivity (SE°) and `modified' Positive Predictive Value (PPV°) as appropriate performance measures with which the algorithm was optimized. The relation between overshoots and fetal compromise in labor was studied in 15 cases and 15 controls. Overshoots showed promise as an indicator of fetal compromise. Unlike ordinary accelerations, overshoots cannot be considered to be reassuring features of fetal health.

Braking and Propulsive Impulses Increase with Speed during Accelerated and Decelerated Walking

PubMed Central

Peterson, Carrie L.; Kautz, Steven A.; Neptune, Richard R.

2011-01-01

The ability to accelerate and decelerate is important for daily activities and likely more demanding than maintaining a steady-state walking speed. Walking speed is modulated by anterior-posterior (AP) ground reaction force (GRF) impulses. The purpose of this study was to investigate AP impulses across a wide range of speeds during accelerated and decelerated walking. Kinematic and GRF data were collected from ten healthy subjects walking on an instrumented treadmill. Subjects completed trials at steady-state speeds and at four rates of acceleration and deceleration across a speed range of 0 to 1.8 m/s. Mixed regression models were generated to predict AP impulses, step length and frequency from speed, and joint moment impulses from AP impulses during non-steady-state walking. Braking and propulsive impulses were positively related to speed. The braking impulse had a greater relationship with speed than the propulsive impulse, suggesting that subjects modulate the braking impulse more than the propulsive impulse to change speed. Hip and knee extensor, and ankle plantarflexor moment impulses were positively related to the braking impulse, and knee flexor and ankle plantarflexor moment impulses were positively related to the propulsive impulse. Step length and frequency increased with speed and were near the subjects’ preferred combination at steady-state speeds, at which metabolic cost is minimized in nondisabled walking. Thus, these variables may be modulated to minimize metabolic cost while accelerating and decelerating. The outcomes of this work provide the foundation to investigate motor coordination in pathological subjects in response to the increased task demands of non-steady-state walking. PMID:21356590

Compliance control for a hydraulic bouncing system.

PubMed

Chen, Guangrong; Wang, Junzheng; Wang, Shoukun; Zhao, Jiangbo; Shen, Wei

2018-05-17

This paper is to reduce the contact impact, control the leg stiffness and bouncing height. Firstly, the combining position/force active compliance control was involved in the deceleration phase to decrease the impact force and improve the leg compliance capacity. Then a reasonable velocity control of cylinder was addressed to control the bouncing height to the given value in the acceleration phase. Due to the model uncertainties and disturbances in the deceleration and acceleration phase, a near inverse like controller with a proportional and differential control (PD) was added into the velocity control of acceleration phase to compensate the bouncing height control error. Finally, the effectiveness of proposed controller was validated by experiments. Experimental results showed the impact force could be reduced effectively and a significant bouncing height control performance could be achieved. The influences of initial energy, preload of spring and velocity of cylinder on the bouncing height were addressed as well. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

GDP-GTP exchange processes of G{alpha}i1 protein are accelerated/decelerated depending on the type and the concentration of added detergents.

PubMed

Kubota, Makoto; Tanaka, Takeshi; Kohno, Toshiyuki; Wakamatsu, Kaori

2009-12-01

Although detergents have been widely used in G-protein studies to increase solubility and stability of the protein, we noticed that detergents modulate the nucleotide-binding properties of G-proteins. Hence, we analysed the effects of detergents on guanine nucleotide exchange reactions of Galpha(i1). Lubrol PX, a non-ionic detergent, which has been widely used in nucleotide dissociation/binding assays, was found to accelerate both GDP dissociation and GTPgammaS binding from/to Galpha in parallel at above its critical micelle concentration (cmc). Sodium cholate, an anionic detergent, which have been used to extract G-proteins from animal tissues, decelerated and accelerated GDP dissociation below and above its cmc, respectively. Surprisingly, micellar cholate decelerated GTPgammaS binding, and the binding rate constant was decreased by three orders of magnitude in the presence of 2% cholate. These results demonstrate that the guanine nucleotide exchange reactions of Galpha(i1) are drastically modulated by detergents differently depending on the type and the state (monomeric or micellar) of the detergents and that dissociation of GDP from Galpha(i1) does not necessarily lead to immediate binding of GTP to Galpha(i1) in some cases. These effects of detergents on G-proteins must be taken into account in G-protein experiments.

Accelerated and decelerated expansion in a causal dissipative cosmology

NASA Astrophysics Data System (ADS)

Cruz, Miguel; Cruz, Norman; Lepe, Samuel

2017-12-01

In this work we explore a new cosmological solution for an universe filled with one dissipative fluid, described by a barotropic equation of state (EoS) p =ω ρ , in the framework of the full Israel-Stewart theory. The form of the bulk viscosity has been assumed of the form ξ =ξ0ρ1 /2. The relaxation time is taken to be a function of the EoS, the bulk viscosity and the speed of bulk viscous perturbations, cb. The solution presents an initial singularity, where the curvature scalar diverges as the scale factor goes to zero. Depending on the values for ω , ξ0, cb accelerated and decelerated cosmic expansion can be obtained. In the case of accelerated expansion, the viscosity drives the effective EoS to be of quintessence type, for the single fluid with positive pressure. Nevertheless, we show that only the solution with decelerated expansion satisfies the thermodynamics conditions d S /d t >0 (growth of the entropy) and d2S /d t2<0 (convexity condition). We show that an exact stiff matter EoS is not allowed in the framework of the full causal thermodynamic approach; and in the case of a EoS very close to the stiff matter regime, we found that dissipative effects becomes negligible so the entropy remains constant. Finally, we show numerically that the solution is stable under small perturbations.

Beam dynamic simulation and optimization of the CLIC positron source and the capture linac

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

Bayar, C., E-mail: cafer.bayar@cern.ch; CERN, Geneva; Doebert, S., E-mail: Steffen.Doebert@cern.ch

2016-03-25

The CLIC Positron Source is based on the hybrid target composed of a crystal and an amorphous target. Simulations have been performed from the exit of the amorphous target to the end of pre-injector linac which captures and accelerates the positrons to an energy of 200 MeV. Simulations are performed by the particle tracking code PARMELA. The magnetic field of the AMD is represented in PARMELA by simple coils. Two modes are applied in this study. The first one is accelerating mode based on acceleration after the AMD. The second one is decelerating mode based on deceleration in the first acceleratingmore » structure. It is shown that the decelerating mode gives a higher yield for the e{sup +} beam in the end of the Pre-Injector Linac.« less

Correlation of prefrontal cortical activation with changing vehicle speeds in actual driving: a vector-based functional near-infrared spectroscopy study

PubMed Central

Yoshino, Kayoko; Oka, Noriyuki; Yamamoto, Kouji; Takahashi, Hideki; Kato, Toshinori

2013-01-01

Traffic accidents occur more frequently during deceleration than during acceleration. However, little is known about the relationship between brain activation and vehicle acceleration because it has been difficult to measure the brain activation of drivers while they drive. In this study, we measured brain activation during actual driving using vector-based functional near-infrared spectroscopy. Subjects decelerated from 100 to 50 km/h (speed reduction task) and accelerated from 50 to 100 km/h (speed increase task) while driving on an expressway, in the daytime and at night. We examined correlations between average vehicle acceleration in each task and five hemodynamic indices: changes in oxygenated hemoglobin (ΔoxyHb), deoxygenated hemoglobin (ΔdeoxyHb), cerebral blood volume (ΔCBV), and cerebral oxygen exchange (ΔCOE); and the phase angle k (degrees) derived from the other hemoglobin (Hb) indices. ΔoxyHb and ΔCBV reflect changes in cerebral blood flow, whereas ΔdeoxyHb, ΔCOE, and k are related to variations in cerebral oxygen metabolism. Most of the resulting correlations with specific brain sites, for all the indices, appeared during deceleration rather than during acceleration. Faster deceleration resulted in greater increases in ΔdeoxyHb, ΔCOE, and k in the prefrontal cortex (r < −0.5, p < 0.01), in particular, in the frontal eye field, and at night, it also resulted in greater decreases in ΔoxyHb and ΔCBV in the prefrontal cortex and in the parietal lobe (r > 0.4, p < 0.01), suggesting oxygen metabolism associated with transient ischemic changes. Our results suggest that vehicle deceleration requires more brain activation, focused in the prefrontal cortex, than does acceleration. From the standpoint of the indices used, we found that simultaneous analysis of multiple hemodynamic indices was able to detect not only the blood flow components of hemodynamic responses, but also more localized frontal lobe activation involving oxygen metabolism. PMID:24399953

Unsteady forces on a spherical particle accelerating or decelerating in an initially stagnant fluid

NASA Astrophysics Data System (ADS)

Keshav, Yashas Mudlapur Phaneesh

Flows with particles play an important role in a number of engineering applications. These include trajectories of droplets in sprays in fuel-injected-reciprocating-piston and gas-turbine engines, erosion of materials due to particle impact on a surface, and deposition of materials on surfaces by impinging droplets or particles that could solidify or bond on impact. For these applications, it is important to understand the forces that act on the particles so that their trajectories could be predicted. Considerable work has been done on understanding the forces acting on spherical particles, where the Reynolds numbers (Rep) based on the particle diameter and the relative speed between the particle and the fluid is less than unity. When Rep is larger than unity and when the particle is accelerating or decelerating, the added-mass effect and the Basset forces are not well understood. In this study, time-accurate numerical simulations were performed to study laminar incompressible flow induced by a single non-rotating rigid spherical particle that is accelerated or decelerated at a constant rate in an initially stagnant fluid, where the unsteady flow about the spherical particle is resolved. The Rep studied range from 0.01 to 100, and the acceleration number (Ac), where A c is the square of the relative velocity between the particle and the fluid divided by the acceleration times the particle diameter studied was in the range 2.13x-7 < |Ac |< 21337. Results obtained show the added mass effect for Rep up to 100 has the same functional form as those based on potential theory where the Rep is infinite and creeping flow where Rep is less than unity. The Basset force, however, differs considerably from those under creeping flow conditions and depends on Rep and the acceleration number (Ac). A model was developed to provide the magnitude of the added-mass effect and the Basset force in the range of Rep and Ac studied. Results obtained also show the effect of unsteadiness to become negligible when Ac reaches 80.

Low External Workloads Are Related to Higher Injury Risk in Professional Male Basketball Games.

PubMed

Caparrós, Toni; Casals, Martí; Solana, Álvaro; Peña, Javier

2018-06-01

The primary purpose of this study was to identify potential risk factors for sports injuries in professional basketball. An observational retrospective cohort study involving a male professional basketball team, using game tracking data was conducted during three consecutive seasons. Thirty-three professional basketball players took part in this study. A total of 29 time-loss injuries were recorded during regular season games, accounting for 244 total missed games with a mean of 16.26 ± 15.21 per player and season. The tracking data included the following variables: minutes played, physiological load, physiological intensity, mechanical load, mechanical intensity, distance covered, walking maximal speed, maximal speed, sprinting maximal speed, maximal speed, average offensive speed, average defensive speed, level one acceleration, level two acceleration, level three acceleration, level four acceleration, level one deceleration, level two deceleration, level three deceleration, level four deceleration, player efficiency rating and usage percentage. The influence of demographic characteristics, tracking data and performance factors on the risk of injury was investigated using multivariate analysis with their incidence rate ratios (IRRs). Athletes with less or equal than 3 decelerations per game (IRR, 4.36; 95% CI, 1.78-10.6) and those running less or equal than 1.3 miles per game (lower workload) (IRR, 6.42 ; 95% CI, 2.52-16.3) had a higher risk of injury during games (p < 0.01 in both cases). Therefore, unloaded players have a higher risk of injury. Adequate management of training loads might be a relevant factor to reduce the likelihood of injury according to individual profiles.

Vestibular-ocular accommodation reflex in man

NASA Technical Reports Server (NTRS)

Clark, B.; Randle, R. J.; Stewart, J. D.

1975-01-01

Stimulation of the vestibular system by angular acceleration produces widespread sensory and motor effects. The present paper studies a motor effect which has not been reported in the literature, i.e., the influence of rotary acceleration of the body on ocular accommodation. The accommodation of 10 young men was recorded before and after a high-level deceleration to zero velocity following 30 sec of rotating. Accommodation was recorded continuously on an infrared optometer for 110 sec under two conditions: while the subjects observed a target set at the far point, and while they viewed the same target through a 0.3-mm pinhole. Stimulation by high-level rotary deceleration produced positive accommodation or a pseudomyopia under both conditions, but the positive accommodation was substantially greater and lasted much longer during fixation through the pinhole. It is hypothesized that this increase in accommodation is a result of a vestibular-ocular accommodation reflex.

Vestibular-ocular accommodation reflex in man.

PubMed

Clark, B R; Randle, R J; Stewart, J D

1975-11-01

Stimulation of the vestibular system by angular acceleration produces widespread sensory and motor effects. The present study was designed to study a motor effect which has not been reported in the literature, i.e., the influence of rotary acceleration of the body on ocular accommodation. The accommodation of 10 young men was recorded before and after a high-level deceleration to zero velocity following 30 s of rotation. Accommodation was recorded continuously on an infrared optometer for 110 s under two conditions; while the subjects observed a target set at the far point, and while they viewed the same target through a 0.3-mm pinhole. Stimulation by high-level rotary deceleration produced positive accommodation or a pseudomyopia under both conditions, but the positive accommodation was substantially greater and lasted much longer during fixation through the pinhole. It is hypothesized that this increase in accommodation is a result of a vestibular-ocular accommodation reflex.

Anticipating the effects of gravity when intercepting moving objects: differentiating up and down based on nonvisual cues.

PubMed

Senot, Patrice; Zago, Myrka; Lacquaniti, Francesco; McIntyre, Joseph

2005-12-01

Intercepting an object requires a precise estimate of its time of arrival at the interception point (time to contact or "TTC"). It has been proposed that knowledge about gravitational acceleration can be combined with first-order, visual-field information to provide a better estimate of TTC when catching falling objects. In this experiment, we investigated the relative role of visual and nonvisual information on motor-response timing in an interceptive task. Subjects were immersed in a stereoscopic virtual environment and asked to intercept with a virtual racket a ball falling from above or rising from below. The ball moved with different initial velocities and could accelerate, decelerate, or move at a constant speed. Depending on the direction of motion, the acceleration or deceleration of the ball could therefore be congruent or not with the acceleration that would be expected due to the force of gravity acting on the ball. Although the best success rate was observed for balls moving at a constant velocity, we systematically found a cross-effect of ball direction and acceleration on success rate and response timing. Racket motion was triggered on average 25 ms earlier when the ball fell from above than when it rose from below, whatever the ball's true acceleration. As visual-flow information was the same in both cases, this shift indicates an influence of the ball's direction relative to gravity on response timing, consistent with the anticipation of the effects of gravity on the flight of the ball.

Study on the influence of three-grid assembly thermal deformation on breakdown times and an ion extraction process

NASA Astrophysics Data System (ADS)

Mingming, SUN; Yanhui, JIA; Yongjie, HUANG; Juntai, YANG; Xiaodong, WEN; Meng, WANG

2018-04-01

In order to study the influence of three-grid assembly thermal deformation caused by heat accumulation on breakdown times and an ion extraction process, a hot gap test and a breakdown time test are carried out to obtain thermal deformation of the grids when the thruster is in 5 kW operation mode. Meanwhile, the fluid simulation method and particle-in-cell-Monte Carlo collision (PIC-MCC) method are adopted to simulate the ion extraction process according to the previous test results. The numerical calculation results are verified by the ion thruster performance test. The results show that after about 1.2 h operation, the hot gap between the screen grid and the accelerator grid reduce to 0.25–0.3 mm, while the hot gap between the accelerator grid and the decelerator grid increase from 1 mm to about 1.4 mm when the grids reach thermal equilibrium, and the hot gap is almost unchanged. In addition, the breakdown times experiment shows that 0.26 mm is the minimal safe hot gap for the grid assembly as the breakdown times improves significantly when the gap is smaller than this value. Fluid simulation results show that the plasma density of the screen grid is in the range 6 × 1017–6 × 1018 m13 and displays a parabolic characteristic, while the electron temperature gradually increases along the axial direction. The PIC-MCC results show that the current falling of an ion beam through a single aperture is significant. Meanwhile, the intercepted current of the accelerator grid and the decelerator grid both increase with the change in the hot gap. The ion beam current has optimal perveance status without thermal deformation, and the intercepted current of the accelerator grid and the decelerator grid are 3.65 mA and 6.26 mA, respectively. Furthermore, under the effect of thermal deformation, the ion beam current has over-perveance status, and the intercepted current of the accelerator grid and the decelerator grid are 10.46 mA and 18.24 mA, respectively. Performance test results indicate that the breakdown times increase obviously. The intercepted current of the accelerator grid and the decelerator grid increases to 13 mA and 16.5 mA, respectively, due to the change in the hot gap after 1.5 h operation. The numerical calculation results are well consistent with performance test results, and the error comes mainly from the test uncertainty of the hot gap.

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.

Decelerations of Parachute Opening Shock in Skydivers.

PubMed

Gladh, Kristofer; Lo Martire, Riccardo; Äng, Björn O; Lindholm, Peter; Nilsson, Jenny; Westman, Anton

2017-02-01

High prevalence of neck pain among skydivers is related to parachute opening shock (POS) exposure, but few investigations of POS deceleration have been made. Existing data incorporate equipment movements, limiting its representability of skydiver deceleration. This study aims to describe POS decelerations and compare human- with equipment-attached data. Wearing two triaxial accelerometers placed on the skydiver (neck-sensor) and equipment (rig-sensor), 20 participants made 2 skydives each. Due to technical issues, data from 35 skydives made by 19 participants were collected. Missing data were replaced using data substitution techniques. Acceleration axes were defined as posterior to anterior (+ax), lateral right (+ay), and caudal to cranial (+az). Deceleration magnitude [amax (G)] and jerks (G · s-1) during POS were analyzed. Two distinct phases related to skydiver positioning and acceleration direction were observed: 1) the x-phase (characterized by -ax, rotating the skydiver); and 2) the z-phase (characterized by +az, skydiver vertically oriented). Compared to the rig-sensor, the neck-sensor yielded lower amax (3.16 G vs. 6.96 G) and jerk (56.3 G · s-1 vs. 149.0 G · s-1) during the x-phase, and lower jerk (27.7 G · s-1 vs. 54.5 G · s-1) during the z-phase. The identified phases during POS should be considered in future neck pain preventive strategies. Accelerometer data differed, suggesting human-placed accelerometry to be more valid for measuring human acceleration.Gladh K, Lo Martire R, Äng BO, Lindholm P, Nilsson J, Westman A. Decelerations of parachute opening shock in skydivers. Aerosp Med Hum Perform. 2017; 88(2):121-127.

Low External Workloads Are Related to Higher Injury Risk in Professional Male Basketball Games

PubMed Central

Caparrós, Toni; Casals, Martí; Solana, Álvaro; Peña, Javier

2018-01-01

The primary purpose of this study was to identify potential risk factors for sports injuries in professional basketball. An observational retrospective cohort study involving a male professional basketball team, using game tracking data was conducted during three consecutive seasons. Thirty-three professional basketball players took part in this study. A total of 29 time-loss injuries were recorded during regular season games, accounting for 244 total missed games with a mean of 16.26 ± 15.21 per player and season. The tracking data included the following variables: minutes played, physiological load, physiological intensity, mechanical load, mechanical intensity, distance covered, walking maximal speed, maximal speed, sprinting maximal speed, maximal speed, average offensive speed, average defensive speed, level one acceleration, level two acceleration, level three acceleration, level four acceleration, level one deceleration, level two deceleration, level three deceleration, level four deceleration, player efficiency rating and usage percentage. The influence of demographic characteristics, tracking data and performance factors on the risk of injury was investigated using multivariate analysis with their incidence rate ratios (IRRs). Athletes with less or equal than 3 decelerations per game (IRR, 4.36; 95% CI, 1.78-10.6) and those running less or equal than 1.3 miles per game (lower workload) (IRR, 6.42 ; 95% CI, 2.52-16.3) had a higher risk of injury during games (p < 0.01 in both cases). Therefore, unloaded players have a higher risk of injury. Adequate management of training loads might be a relevant factor to reduce the likelihood of injury according to individual profiles. Key points The number of decelerations and the total distance can be considered risk factors for injuries in professional basketball players. Unloaded players have greater risk of injury compared to players with higher accumulated external workload. Workload management should be considered a major factor in injury prevention programs. PMID:29769830

Study of the key factors affecting the triple grid lifetime of the LIPS-300 ion thruster

NASA Astrophysics Data System (ADS)

Mingming, SUN; Liang, WANG; Juntai, YANG; Xiaodong, WEN; Yongjie, HUANG; Meng, WANG

2018-04-01

In order to ascertain the key factors affecting the lifetime of the triple grids in the LIPS-300 ion thruster, the thermal deformation, upstream ion density and component lifetime of the grids are simulated with finite element analysis, fluid simulation and charged-particle tracing simulation methods on the basis of a 1500 h short lifetime test. The key factor affecting the lifetime of the triple grids in the LIPS-300 ion thruster is obtained and analyzed through the test results. The results show that ion sputtering erosion of the grids in 5 kW operation mode is greater than in the case of 3 kW. In 5 kW mode, the decelerator grid shows the most serious corrosion, the accelerator grid shows moderate corrosion, and the screen grid shows the least amount of corrosion. With the serious corrosion of the grids in 5 kW operation mode, the intercept current of the acceleration and deceleration grids increases substantially. Meanwhile, the cold gap between the accelerator grid and the screen grid decreases from 1 mm to 0.7 mm, while the cold gap between the accelerator grid and the decelerator grid increases from 1 mm to 1.25 mm after 1500 h of thruster operation. At equilibrium temperature with 5 kW power, the finite element method (FEM) simulation results show that the hot gap between the screen grid and the accelerator grid reduces to 0.2 mm. Accordingly, the hot gap between the accelerator grid and the decelerator grid increases to 1.5 mm. According to the fluid method, the plasma density simulated in most regions of the discharge chamber is 1 × 1018‑8 × 1018 m‑3. The upstream plasma density of the screen grid is in the range 6 × 1017‑6 × 1018 m‑3 and displays a parabolic characteristic. The charged particle tracing simulation method results show that the ion beam current without the thermal deformation of triple grids has optimal perveance status. The ion sputtering rates of the accelerator grid hole and the decelerator hole are 5.5 × 10‑14 kg s‑1 and 4.28 × 10‑14 kg s‑1, respectively, while after the thermal deformation of the triple grids, the ion beam current has over-perveance status. The ion sputtering rates of the accelerator grid hole and the decelerator hole are 1.41 × 10‑13 kg s‑1 and 4.1 × 10‑13 kg s‑1, respectively. The anode current is a key factor for the triple grid lifetime in situations where the structural strength of the grids does not change with temperature variation. The average sputtering rates of the accelerator grid and the decelerator grid, which were measured during the 1500 h lifetime test in 5 kW operating conditions, are 2.2 × 10‑13 kg s‑1 and 7.3 × 10‑13 kg s‑1, respectively. These results are in accordance with the simulation, and the error comes mainly from the calculation distribution of the upstream plasma density of the grids.

Influence of carbon monoxide poisoning on the fetal heart monitor tracing: a report of 3 cases.

PubMed

Towers, Craig V; Corcoran, Vincent A

2009-03-01

The diagnosis of carbon monoxide poisoning in the third trimester of pregnancy requires an index of suspicion, and the appearance of the fetal heart monitor tracing may help in this regard. Three cases of third-trimester acute carbon monoxide poisoning occurred. In each pregnancy, the fetal heart monitor tracing on admission was correlated with the maternal carboxyhemoglobin level, and how the pattern changed following the institution of therapy was analyzed. In all 3 cases, the initial fetal heart rate pattern demonstrated decreased variability with an elevated baseline and an absence of accelerations and decelerations. Within 45-90 minutes of treatment onset, the baseline fetal heart rate dropped by 20-40 beats per minute, the variability became moderate, and accelerations occurred. Absent accelerations with minimal variability, if caused by uteroplacental insufficiency, are usually preceded by recurrent decelerations. Absent accelerations with minimal variability in the absence of recurrent decelerations may suggest another cause, of which carbon monoxide intoxication can be added to the differential, especially since this disorder often has nonspecific clinical symptoms.

Does attention speed up processing? Decreases and increases of processing rates in visual prior entry.

PubMed

Tünnermann, Jan; Petersen, Anders; Scharlau, Ingrid

2015-03-02

Selective visual attention improves performance in many tasks. Among others, it leads to "prior entry"--earlier perception of an attended compared to an unattended stimulus. Whether this phenomenon is purely based on an increase of the processing rate of the attended stimulus or if a decrease in the processing rate of the unattended stimulus also contributes to the effect is, up to now, unanswered. Here we describe a novel approach to this question based on Bundesen's Theory of Visual Attention, which we use to overcome the limitations of earlier prior-entry assessment with temporal order judgments (TOJs) that only allow relative statements regarding the processing speed of attended and unattended stimuli. Prevalent models of prior entry in TOJs either indirectly predict a pure acceleration or cannot model the difference between acceleration and deceleration. In a paradigm that combines a letter-identification task with TOJs, we show that indeed acceleration of the attended and deceleration of the unattended stimuli conjointly cause prior entry. © 2015 ARVO.

Impact accelerations

NASA Technical Reports Server (NTRS)

Vongierke, H. E.; Brinkley, J. W.

1975-01-01

The degree to which impact acceleration is an important factor in space flight environments depends primarily upon the technology of capsule landing deceleration and the weight permissible for the associated hardware: parachutes or deceleration rockets, inflatable air bags, or other impact attenuation systems. The problem most specific to space medicine is the potential change of impact tolerance due to reduced bone mass and muscle strength caused by prolonged weightlessness and physical inactivity. Impact hazards, tolerance limits, and human impact tolerance related to space missions are described.

Landing Characteristics in Waves of Three Dynamic Models of Flying Boats

NASA Technical Reports Server (NTRS)

Benson, James M.; Havens, Robert F.; Woodward, David R.

1947-01-01

Powered models of three different flying boats were landed in oncoming wave of various heights and lengths. The resulting motions and acceleration were recorded to survey the effects of varying the trim at landing, the deceleration after landing, and the size of the waves. One of the models had an unusually long afterbody. The data for landing with normal rates of deceleration indicated that the most severe motions and accelerations were likely to occur at some period of the landing run subsequent to the initial impact. Landings made at abnormally low trims led to unusually severe bounces during the runout. The least severe landing occurred after a small lending when the model was rapidly decelerated at about 0.4 g in a simulation of the proposed use of braking devices. The severity of the landings increased with wave height and was at a maximum when the wave length was of the order of from one and one-half to twice the over-all length of the model. The models with afterbodies of moderate length frequently bounced clear of the water into a stalled attitude at speeds below flying speed. The model with the long afterbody had less tendency to bounce from the waves and consequently showed less severe accelerations during the landing run than the models with moderate lengths of afterbody.

The effect of the acceleration/deceleration trauma in angioid streaks: A pathogenic hypothesis.

PubMed

Fajardo Sánchez, J; Chau Ramos, C E; Mazagatos Used, P J; Aparicio Hernandez-Lastras, M J

2016-09-01

A 59-year-old male with acceleration/deceleration cranial trauma (ADT), caused by a car accident. After one month, he presented with loss of visual acuity in the right eye. A fluorescein angiography test was performed and it detected centrifugal hyperfluorescent lines from the optic nerve head, a characteristic compatible with the diagnosis of angioid streaks. The loss of visual acuity was demonstrated by the discovery of a juxtafoveal choroidal neovascular membrane (CNV). ADT can cause hyper-extension of the eyeball in its equator line, producing the rupture of fragile structures such as the Bruch membrane (MB) in patients with angioid streaks and the subsequent formation of CNV. Copyright © 2016 Sociedad Española de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.

Phasic heart rate responses and cardiac cycle time in auditory choice reaction time.

PubMed

van der Molen, M W; Somsen, R J; Orlebeke, J F

1983-01-01

This study investigated the cardiovascular-behavioral interaction under short and long stimulus interval conditions. In addition, the cardiovascular-behavioral interaction was studied as affected by cardiac cycle duration. Fourteen subjects performed a choice reaction time (RT) task employing a mixed speed-accuracy tradeoff design in which reactions were paced to coincide with a signal that occurs randomly at either 200 or 500 msec after the reaction stimulus. The preparatory interval between a warning stimulus and a lead-reaction stimulus complex was also varied (2 vs. 4.5 sec). Anticipatory deceleration occurred within the 4.5 sec interval but not in the 2 sec interval. The depth of anticipatory deceleration did not discriminate between fast and slow reactions; but an earlier shift from deceleration to acceleration was associated with fast reactions. The effect of stimulus timing relative to the R-wave of the electrocardiogram was also analysed. Meaningful stimuli tended to produce cardiac slowing as previously described in the literature. Early occurring stimuli prolong the cycle of their occurrence more than late occurring stimuli. The later prolong the subsequent cycle. Cardiac cycle time effects were absent for unattended stimuli. The results of anticipatory deceleration suggested that the depth of deceleration was regulated by time-uncertainty and speed-accuracy criterion.

An Anaylsis of Control Requirements and Control Parameters for Direct-Coupled Turbojet Engines

NASA Technical Reports Server (NTRS)

Novik, David; Otto, Edward W.

1947-01-01

Requirements of an automatic engine control, as affected by engine characteristics, have been analyzed for a direct-coupled turbojet engine. Control parameters for various conditions of engine operation are discussed. A hypothetical engine control is presented to illustrate the use of these parameters. An adjustable speed governor was found to offer a desirable method of over-all engine control. The selection of a minimum value of fuel flow was found to offer a means of preventing unstable burner operation during steady-state operation. Until satisfactory high-temperature-measuring devices are developed, air-fuel ratio is considered to be a satisfactory acceleration-control parameter for the attainment of the maximum acceleration rates consistent with safe turbine temperatures. No danger of unstable burner operation exists during acceleration if a temperature-limiting acceleration control is assumed to be effective. Deceleration was found to be accompanied by the possibility of burner blow-out even if a minimum fuel-flow control that prevents burner blow-out during steady-state operation is assumed to be effective. Burner blow-out during deceleration may be eliminated by varying the value of minimum fuel flow as a function of compressor-discharge pressure, but in no case should the fuel flow be allowed to fall below the value required for steady-state burner operation.

Deceleration efficiencies of shrub windbreaks in a wind tunnel

NASA Astrophysics Data System (ADS)

Wu, Xiaoxu; Zou, Xueyong; Zhou, Na; Zhang, Chunlai; Shi, Sha

2015-03-01

Artemisia and Salix are dominant shrub species for windbreaks in arid areas of China, and they show similar features to shrubs in other arid areas of the world. We compared the mean velocity fields and shelter effects of two shrub windbreaks with different layouts. For a single plant of Artemisia, the higher the free airflow velocity is, the more the wind velocity around two sides of the plant increases. The velocity gradient around a single plant of Salix is smaller than that around an Artemisia plant due to the difference in the plant shapes. Seven new velocity zones in the horizontal direction appear when airflow passes through an Artemisia windbreak, including four deceleration zones and three acceleration zones. The mean velocity field that is affected by a Salix windbreak can be divided into a deceleration zone in the front, an acceleration zone above, a vortex zone behind and a restoration zone downwind of the vortex zone. Shelter effects of the shrub windbreaks vary with the wind velocity and are influenced by the construct of the windbreaks. Shrub windbreaks that have a complex construction have better shelter effects than simple ones. The shelter effects of plant windbreaks are also influenced by the growth features of the plants. Considering the plant characteristics and the shelter effects of Salix and Artemisia windbreaks, it is optimal to plant these two windbreaks together in a sand-control system. This research is intended to be useful for sand movement control in arid areas.

Effects of morphine and naloxone on feline colonic transit

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

Krevsky, B.; Libster, B.; Maurer, A.H.

1989-01-01

The effects of endogenous and exogenous opioid substances on feline colonic transit were evaluated using colonic transit scintigraphy. Naloxone accelerated emptying of the cecum and ascending colon, and filling of the transverse colon. Endogenous opioid peptides thus appear to play a significant role in the regulation of colonic transit. At a moderate dose of morphine cecum and ascending colon transit was accelerated, while at a larger dose morphine had no effect. Since naloxone, a relatively nonspecific opioid antagonist, and morphine, a principally mu opioid receptor agonist, both accelerate proximal colonic transit, a decelerating role for at least one of themore » other opioid receptors is inferred.« less

Optimization of vehicle deceleration to reduce occupant injury risks in frontal impact.

PubMed

Mizuno, Koji; Itakura, Takuya; Hirabayashi, Satoko; Tanaka, Eiichi; Ito, Daisuke

2014-01-01

In vehicle frontal impacts, vehicle acceleration has a large effect on occupant loadings and injury risks. In this research, an optimal vehicle crash pulse was determined systematically to reduce injury measures of rear seat occupants by using mathematical simulations. The vehicle crash pulse was optimized based on a vehicle deceleration-deformation diagram under the conditions that the initial velocity and the maximum vehicle deformation were constant. Initially, a spring-mass model was used to understand the fundamental parameters for optimization. In order to investigate the optimization under a more realistic situation, the vehicle crash pulse was also optimized using a multibody model of a Hybrid III dummy seated in the rear seat for the objective functions of chest acceleration and chest deflection. A sled test using a Hybrid III dummy was carried out to confirm the simulation results. Finally, the optimal crash pulses determined from the multibody simulation were applied to a human finite element (FE) model. The optimized crash pulse to minimize the occupant deceleration had a concave shape: a high deceleration in the initial phase, low in the middle phase, and high again in the final phase. This crash pulse shape depended on the occupant restraint stiffness. The optimized crash pulse determined from the multibody simulation was comparable to that from the spring-mass model. From the sled test, it was demonstrated that the optimized crash pulse was effective for the reduction of chest acceleration. The crash pulse was also optimized for the objective function of chest deflection. The optimized crash pulse in the final phase was lower than that obtained for the minimization of chest acceleration. In the FE analysis of the human FE model, the optimized pulse for the objective function of the Hybrid III chest deflection was effective in reducing rib fracture risks. The optimized crash pulse has a concave shape and is dependent on the occupant restraint stiffness and maximum vehicle deformation. The shapes of the optimized crash pulse in the final phase were different for the objective functions of chest acceleration and chest deflection due to the inertial forces of the head and upper extremities. From the human FE model analysis it was found that the optimized crash pulse for the Hybrid III chest deflection can substantially reduce the risk of rib cage fractures. Supplemental materials are available for this article. Go to the publisher's online edition of Traffic Injury Prevention to view the supplemental file.

Inhomogeneities in dusty universe — a possible alternative to dark energy?

NASA Astrophysics Data System (ADS)

Chatterjee, S.

2011-03-01

There have been of late renewed debates on the role of inhomogeneities to explain the observed late acceleration of the universe. We have looked into the problem analytically with the help of the well known spherically symmetric but inhomogeneous Lemaitre-Tolman-Bondi(LTB) model generalised to higher dimensions. It is observed that in contrast to the claim made by Kolb et al. the presence of inhomogeneities as well as extra dimensions can not reverse the signature of the deceleration parameter if the matter field obeys the energy conditions. The well known Raychaudhuri equation also points to the same result. Without solving the field equations explicitly it can, however, be shown that although the total deceleration is positive everywhere nevertheless it does not exclude the possibility of having radial acceleration, even in the pure dust universe, if the angular scale factor is decelerating fast enough and vice versa. Moreover it is found that introduction of extra dimensions can not reverse the scenario. To the contrary it actually helps the decelerating process.

Conceptual design of an intense positron source based on an LIA

NASA Astrophysics Data System (ADS)

Long, Ji-Dong; Yang, Zhen; Dong, Pan; Shi, Jin-Shui

2012-04-01

Accelerator based positron sources are widely used due to their high intensity. Most of these accelerators are RF accelerators. An LIA (linear induction accelerator) is a kind of high current pulsed accelerator used for radiography. A conceptual design of an intense pulsed positron source based on an LIA is presented in the paper. One advantage of an LIA is its pulsed power being higher than conventional accelerators, which means a higher amount of primary electrons for positron generations per pulse. Another advantage of an LIA is that it is very suitable to decelerate the positron bunch generated by bremsstrahlung pair process due to its ability to adjustably shape the voltage pulse. By implementing LIA cavities to decelerate the positron bunch before it is moderated, the positron yield could be greatly increased. These features may make the LIA based positron source become a high intensity pulsed positron source.

Periodic components of hand acceleration/deceleration impulses during telemanipulation

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

Draper, J.V.; Handel, S.

1994-01-01

Responsiveness is the ability of a telemanipulator to recreate user trajectories and impedance in time and space. For trajectory production, a key determinant of responsiveness is the ability of the system to accept user inputs, which are forces on the master handle generated by user hand acceleration/deceleration (a/d) impulses, and translate them into slave arm acceleration/deceleration. This paper presents observations of master controller a/d impulses during completion of a simple target acquisition task. Power spectral density functions (PSDF`s) calculated from hand controller a/d impulses were used to assess impulse waveform. The relative contributions of frequency intervals ranging up to 25more » Hz for three spatially different versions of the task were used to determine which frequencies were most important. The highest relative power was observed in frequencies between 1 Hz and 6 Hz. The key frequencies related to task difficulty were in the range from 2 Hz to 8 Hz. the results provide clues to the source of the performance inhibition.« less

Mechanisms of force and power production in unsteady ricochetal brachiation.

PubMed

Usherwood, James R; Larson, Susan G; Bertram, John E A

2003-04-01

Brachiators travel by swinging beneath handholds, and it is not obvious how these animals manage to accelerate and decelerate in a horizontal direction, especially when moving rapidly. Most previous analyses focused on brachiation in highly constrained laboratory conditions that induced steady-state locomotion. Emerging understanding of brachiation suggests that much of gibbon locomotory behavior and morphology must be considered within the context of the complexities of the natural environment: the forest canopy is three-dimensional, with high variation in handhold availability and properties. The goal of this paper is to quantify the active mechanisms by which gibbons can dynamically control their velocity. Force production and kinematics were analyzed from a white-handed gibbon Hylabates lar during ricochetal brachiation. Both the mechanisms of force production and power input may be inferred for accelerating and decelerating brachiation by combining force data with kinematics. Examples of steady-state, accelerating, and decelerating ricochetal brachiation are highlighted. Gibbons are able to produce net horizontal impulses by releasing early (resulting in a loss of potential energy, but an accelerating horizontal impulse) or delaying release (associated with an increase in potential energy, and a decelerating horizontal impulse). Torque about the shoulder, leg-lifting (or dropping), and elbow flexing (or straightening) are discussed as potential mechanisms for controlling energy within the brachiating system. Of these possibilities, leg-lifting and arm-flexing were observed as mechanisms of adding mechanical energy. Net energy loss, and substantial torques about the shoulder, were not observed. Copyright 2003 Wiley-Liss, Inc.

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

Sairam, T., E-mail: sairamtvv@gmail.com; Bhatt, Pragya; Safvan, C. P.

A deceleration lens coupled to one of the beam lines of the electron cyclotron resonance based low energy beam facility at Inter University Accelerator Centre is reported. This system is capable of delivering low energy (2.5 eV/q–1 keV/q) highly charged ion beams. The presence of plasma potential hinders the measurements of low energies (<50 eV), therefore, plasma potential measurements have been undertaken using a retarding plate analyzer in unison with the deceleration assembly. The distributions of the ion energies have been obtained and the effect of different source parameters on these distributions is studied.

Updates to Blast Injury Criteria Models for Nuclear Casualty Estimation

DTIC Science & Technology

2015-12-01

the likelihood of blast-related injury use a two-step process. First, the maximum velocity obtained by the human body or secondary missile is determined...the human body . Secondary injuries are caused by missiles that are accelerated by the blast wave. Tertiary injuries are caused by the acceleration of...the human body and the ensuing deceleration. In this work, we focus on secondary and tertiary injuries. Because of the dramatic effects experienced

A novel facility for reduced-gravity testing: A setup for studying low-velocity collisions into granular surfaces

NASA Astrophysics Data System (ADS)

Sunday, C.; Murdoch, N.; Cherrier, O.; Morales Serrano, S.; Valeria Nardi, C.; Janin, T.; Avila Martinez, I.; Gourinat, Y.; Mimoun, D.

2016-08-01

This work presents an experimental design for studying low-velocity collisions into granular surfaces in low-gravity. In the experiment apparatus, reduced-gravity is simulated by releasing a free-falling projectile into a surface container with a downward acceleration less than that of Earth's gravity. The acceleration of the surface is controlled through the use of an Atwood machine, or a system of pulleys and counterweights. The starting height of the surface container and the initial separation distance between the projectile and surface are variable and chosen to accommodate collision velocities up to 20 cm/s and effective accelerations of ˜0.1 to 1.0 m/s2. Accelerometers, placed on the surface container and inside the projectile, provide acceleration data, while high-speed cameras capture the collision and act as secondary data sources. The experiment is built into an existing 5.5 m drop tower frame and requires the custom design of all components, including the projectile, surface sample container, release mechanism, and deceleration system. Data from calibration tests verify the efficiency of the experiment's deceleration system and provide a quantitative understanding of the performance of the Atwood system.

A novel facility for reduced-gravity testing: A setup for studying low-velocity collisions into granular surfaces.

PubMed

Sunday, C; Murdoch, N; Cherrier, O; Morales Serrano, S; Valeria Nardi, C; Janin, T; Avila Martinez, I; Gourinat, Y; Mimoun, D

2016-08-01

This work presents an experimental design for studying low-velocity collisions into granular surfaces in low-gravity. In the experiment apparatus, reduced-gravity is simulated by releasing a free-falling projectile into a surface container with a downward acceleration less than that of Earth's gravity. The acceleration of the surface is controlled through the use of an Atwood machine, or a system of pulleys and counterweights. The starting height of the surface container and the initial separation distance between the projectile and surface are variable and chosen to accommodate collision velocities up to 20 cm/s and effective accelerations of ∼0.1 to 1.0 m/s(2). Accelerometers, placed on the surface container and inside the projectile, provide acceleration data, while high-speed cameras capture the collision and act as secondary data sources. The experiment is built into an existing 5.5 m drop tower frame and requires the custom design of all components, including the projectile, surface sample container, release mechanism, and deceleration system. Data from calibration tests verify the efficiency of the experiment's deceleration system and provide a quantitative understanding of the performance of the Atwood system.

Flow acceleration structure of Aurelia aurita: implications on propulsion

NASA Astrophysics Data System (ADS)

Kim, Jin-Tae; Piper, Matthew; Chamorro, Leonardo P.

2017-11-01

The jetting and paddling mechanisms used by Aurelia aurita jellyfish allows for one of the most efficient propulsion among other metazoans. Characterization of the induced flow acceleration is critical to uncover distinctive patterns. We found four acceleration structures using 3D measurements of body and flow dynamics in Lagrangian frame of reference. Two intense structures occur near the bell margin and are generated by paddling; the other two around the center of the jellyfish and half magnitude are a result of jetting. Their interaction leads to the maximum flow velocity in the middle of the relaxation, where relatively straight flow trajectories occur. The jellyfish achieves an efficient relaxation by generating flow deceleration with minor body deceleration.

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

Glascoe, E A; Zaug, J M; Burnham, A K

The effect of pressure on the thermal decomposition rate of the energetic material HMX was studied. HMX was precompressed in a diamond anvil cell (DAC) and heated at various rates. The parent species population was monitored as a function of time and temperature using Fourier transform infrared (FTIR) spectroscopy. Decomposition rates were determined by fitting the fraction reacted to the extended-Prout-Tompkins nucleation-growth model and the Friedman isoconversional method. The results of these experiments and analysis indicate that pressure accelerates the decomposition at low to moderate pressures (i.e. between ambient pressure and 1 GPa) and decelerates the decomposition at higher pressures.more » The decomposition acceleration is attributed to pressure enhanced autocatalysis whereas the deceleration at high pressures is attributed pressure inhibiting bond homolysis step(s), which would result in an increase in volume. These results indicate that both {beta} and {delta} phase HMX are sensitive to pressure in the thermally induced decomposition kinetics.« less

Nonlinear dynamics of autonomous vehicles with limits on acceleration

NASA Astrophysics Data System (ADS)

Davis, L. C.

2014-07-01

The stability of autonomous vehicle platoons with limits on acceleration and deceleration is determined. If the leading-vehicle acceleration remains within the limits, all vehicles in the platoon remain within the limits when the relative-velocity feedback coefficient is equal to the headway time constant [k=1/h]. Furthermore, if the sensitivity α>1/h, no collisions occur. String stability for small perturbations is assumed and the initial condition is taken as the equilibrium state. Other values of k and α that give stability with no collisions are found from simulations. For vehicles with non-negligible mechanical response, simulations indicate that the acceleration-feedback-control gain might have to be dynamically adjusted to obtain optimal performance as the response time changes with engine speed. Stability is demonstrated for some perturbations that cause initial acceleration or deceleration greater than the limits, yet do not cause collisions.

On Electron Hole Evolution in Inhomogeneous Plasmas

NASA Astrophysics Data System (ADS)

Kuzichev, I.; Vasko, I.; Agapitov, O. V.; Mozer, F.; Artemyev, A.

2017-12-01

Electron holes (EHs) are the stationary localized non-linear structures in phase space existing due to an electron population trapped within EH electrostatic potential. EHs were found to be a common phenomenon in the Earth's magnetosphere. Such structures were observed in reconnecting current sheets, injection fronts in the outer radiation belt, and in many other situations. EHs usually propagate along magnetic field lines with velocities about electron thermal velocity, are localized on the scale of about 4-10 Debye lengths, and have the field amplitude up to hundreds of mV/m. Generation of these structures, evolution, and their role in relaxation of instabilities and energy dissipation, particle energization, supporting large-scale potential drops is under active investigation. In this report, we present the results of 1.5D gyrokinetic Vlasov-Maxwell simulations of the EH evolution in plasmas with inhomogeneous magnetic field and inhomogeneous density. Our calculations show that the inhomogeneity has a critical effect on the EH dynamics. EHs propagating into stronger (weaker) magnetic field are decelerated (accelerated) with deceleration (acceleration) rate dependent on the magnetic field gradient. During the deceleration of EH, the potential drop (weak double layer) along EH is generated. Such a potential drop might be experimentally observable even for single EH in the reconnecting current sheets. The same holds for the propagation in the plasma with inhomogeneous density. For some parameters of the system, the deceleration results in the turning of the hole. The interesting feature of this process is that the turning point depends only on the EH parameters, being independent of the average inhomogeneity scale. Our calculations also demonstrate the significant difference between "quasi-particle" concept and real evolution of the hole. Indeed, the EH is accelerated (decelerated) faster than it follows from a quasi-particle energy conservation law. It indicates that the efficient energy exchange between the EH and resonant untrapped electrons takes place. We expect that the revealed features will be helpful for interpreting spacecraft observations and results of advanced particle simulations. I.K. was supported by RFBR 16-32-00721. I.V., O.A., and F. M. by JHU/APL contract 922613 (RBSPEFW).

A scheme for reducing deceleration-phase Rayleigh-Taylor growth in inertial confinement fusion implosions

NASA Astrophysics Data System (ADS)

Wang, L. F.; Ye, W. H.; Wu, J. F.; Liu, Jie; Zhang, W. Y.; He, X. T.

2016-05-01

It is demonstrated that the growth of acceleration-phase instabilities in inertial confinement fusion implosions can be controlled, especially in the high-foot implosions [O. A. Hurricane et al., Phys. Plasmas 21, 056314 (2014)] on the National Ignition Facility. However, the excessive growth of the deceleration-phase instabilities can still destroy the hot spot ignition. A scheme is proposed to retard the deceleration-phase Rayleigh-Taylor instability growth by shock collision near the waist of the inner shell surface. Two-dimensional radiation hydrodynamic simulations confirm the improved deceleration-phase hot spot stability properties without sacrificing the fuel compression.

A scheme for reducing deceleration-phase Rayleigh–Taylor growth in inertial confinement fusion implosions

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

Wang, L. F., E-mail: wang-lifeng@iapcm.ac.cn; Ye, W. H.; Liu, Jie

It is demonstrated that the growth of acceleration-phase instabilities in inertial confinement fusion implosions can be controlled, especially in the high-foot implosions [O. A. Hurricane et al., Phys. Plasmas 21, 056314 (2014)] on the National Ignition Facility. However, the excessive growth of the deceleration-phase instabilities can still destroy the hot spot ignition. A scheme is proposed to retard the deceleration-phase Rayleigh–Taylor instability growth by shock collision near the waist of the inner shell surface. Two-dimensional radiation hydrodynamic simulations confirm the improved deceleration-phase hot spot stability properties without sacrificing the fuel compression.

The crystal acceleration effect for cold neutrons

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

Braginetz, Yu. P., E-mail: aiver@pnpi.spb.ru; Berdnikov, Ya. A.; Fedorov, V. V., E-mail: vfedorov@pnpi.spb.ru

A new mechanism of neutron acceleration is discussed and studied experimentally in detail for cold neutrons passing through the accelerated perfect crystal with the energies close to the Bragg one. The effect arises due to the following reason. The crystal refraction index (neutron-crystal interaction potential) for neutron in the vicinity of the Bragg resonance sharply depends on the parameter of deviation from the exact Bragg condition, i.e. on the crystal-neutron relative velocity. Therefore the neutrons enter into accelerated crystal with one neutron-crystal interaction potential and exit with the other. Neutron kinetic energy cannot vary inside the crystal due to itsmore » homogeneity. So after passage through such a crystal neutrons will be accelerated or decelerated because of the different energy change at the entrance and exit crystal boundaries.« less

A cell-based study on pedestrian acceleration and overtaking in a transfer station corridor

NASA Astrophysics Data System (ADS)

Ji, Xiangfeng; Zhou, Xuemei; Ran, Bin

2013-04-01

Pedestrian speed in a transfer station corridor is faster than usual and sometimes running can be found among some of them. In this paper, pedestrians are divided into two categories. The first one is aggressive, and the other is conservative. Aggressive pedestrians weaving their way through crowd in the corridor are the study object of this paper. During recent decades, much attention has been paid to the pedestrians' behavior, such as overtaking (also deceleration) and collision avoidance, and that continues in this paper. After sufficiently analyzing the characteristics of pedestrian flow in transfer station corridor, a cell-based model is presented in this paper, including the acceleration (also deceleration) and overtaking analysis. Acceleration (also deceleration) in a corridor is fixed according to Newton's Law and then speed calculated with a kinematic formula is discretized into cells based on the fuzzy logic. After the speed is updated, overtaking is analyzed based on updated speed and force explicitly, compared to rule-based models, which herein we call implicit ones. During the analysis of overtaking, a threshold value to determine the overtaking direction is introduced. Actually, model in this paper is a two-step one. The first step is to update speed, which is the cells the pedestrian can move in one time interval and the other is to analyze the overtaking. Finally, a comparison between the rule-based cellular automata, the model in this paper and data in HCM 2000 is made to demonstrate our model can be used to achieve reasonable simulation of acceleration (also deceleration) and overtaking among pedestrians.

Ultrasound and polar homogeneous reactions.

PubMed

Tuulmets, A

1997-04-01

The effect of ultrasound on the rates of homogeneous heterolytic reactions not switched to a free radical pathway can be explained by the perturbation of the molecular organization of or the solvation in the reacting system. A quantitative analysis of the sonochemical acceleration on the basis of the microreactor concept was carried out. It was found that (1) the Diels-Alder reaction cannot be accelerated by ultrasound except when SET or free radical processes are promoted, (2) the rectified diffusion during cavitation cannot be responsible for the acceleration of reactions, and (3) the sonochemical acceleration of polar homogeneous reactions takes place in the bulk reaction medium. This implies the presence of a 'sound-field' sonochemistry besides the 'hot-spot' sonochemistry. The occurrence of a sonochemical deceleration effect can be predicted.

Canine fetal heart rate: do accelerations or decelerations predict the parturition day in bitches?

PubMed

Gil, E M U; Garcia, D A A; Giannico, A T; Froes, T R

2014-10-15

Ultrasonography is a safe and efficient technique for monitoring fetal development and viability. One of the most important and widely used parameters to verify fetal viability is the fetal heart rate (HR). In human medicine, the fetal HR normally oscillates during labor in transient accelerations and decelerations associated with uterine contractions. The present study investigated whether these variations also occur in canine fetuses and its relationship to parturition. A cohort study was conducted in 15 pregnant bitches undergoing two-dimensional high-resolution ultrasonographic examination during the 8th and 9th week of gestation. Fetal HR was assessed in M-mode for 5 minutes in each fetus in all bitches. In addition, the bitches were monitored for clinical signs of imminent parturition. Associations between the HR, antepartum time, and delivery characteristics were evaluated with a Poisson regression model. Fetal HR acceleration and deceleration occurred in canine fetuses and predicted the optimal time of parturition. These findings can help veterinarians and sonographers better understand this phenomenon in canine fetuses. Copyright © 2014 Elsevier Inc. All rights reserved.

Clinical course of untreated tonic-clonic seizures in childhood: prospective, hospital based study.

PubMed Central

van Donselaar, C. A.; Brouwer, O. F.; Geerts, A. T.; Arts, W. F.; Stroink, H.; Peters, A. C.

1997-01-01

OBJECTIVE: To assess decleration and acceleration in the disease process in the initial phase of epilepsy in children with new onset tonic-clonic seizures. STUDY DESIGN: Hospital based follow up study. SETTING: Two university hospitals, a general hospital, and a children's hospital in the Netherlands. PATIENTS: 204 children aged 1 month to 16 years with idiopathic or remote symptomatic, newly diagnosed, tonic-clonic seizures, of whom 123 were enrolled at time of their first ever seizure; all children were followed until the start of drug treatment (78 children), the occurrence of the fourth untreated seizure (41 children), or the end of the follow up period of two years (85 untreated children). MAIN OUTCOME MEASURES: Analysis of disease pattern from first ever seizure. The pattern was categorised as decelerating if the child became free of seizures despite treatment being withheld. In cases with four seizures, the pattern was categorised as decelerating if successive intervals increased or as accelerating if intervals decreased. Patterns in the remaining children were classified as uncertain. RESULTS: A decelerating pattern was found in 83 of 85 children who became free of seizures without treatment. Three of the 41 children with four or more untreated seizures showed a decelerating pattern and eight an accelerating pattern. In 110 children the disease process could not be classified, mostly because drug treatment was started after the first, second, or third seizure. The proportion of children with a decelerating pattern (42%, 95% confidence interval 35% to 49%) may be a minimum estimate because of the large number of patients with an uncertain disease pattern. CONCLUSIONS: Though untreated epilepsy is commonly considered to be a progressive disorder with decreasing intervals between seizures, a large proportion of children with newly diagnosed, unprovoked tonic-clonic seizures have a decelerating disease process. The fear that tonic-clonic seizures commonly evolve into a progressive disease should not be used as an argument in favour of early drug treatment in children with epilepsy. PMID:9040384

Detection of linear ego-acceleration from optic flow.

PubMed

Festl, Freya; Recktenwald, Fabian; Yuan, Chunrong; Mallot, Hanspeter A

2012-07-20

Human observers are able to estimate various ego-motion parameters from optic flow, including rotation, translational heading, time-to-collision (TTC), time-to-passage (TTP), etc. The perception of linear ego-acceleration or deceleration, i.e., changes of translational velocity, is less well understood. While time-to-passage experiments indicate that ego-acceleration is neglected, subjects are able to keep their (perceived) speed constant under changing conditions, indicating that some sense of ego-acceleration or velocity change must be present. In this paper, we analyze the relation of ego-acceleration estimates and geometrical parameters of the environment using simulated flights through cylindrical and conic (narrowing or widening) corridors. Theoretical analysis shows that a logarithmic ego-acceleration parameter, called the acceleration rate ρ, can be calculated from retinal acceleration measurements. This parameter is independent of the geometrical layout of the scene; if veridical ego-motion is known at some instant in time, acceleration rate allows updating of ego-motion without further depth-velocity calibration. Results indicate, however, that subjects systematically confuse ego-acceleration with corridor narrowing and ego-deceleration with corridor widening, while veridically judging ego-acceleration in straight corridors. We conclude that judgments of ego-acceleration are based on first-order retinal flow and do not make use of acceleration rate or retinal acceleration.

Transition from AdS universe to DS universe in the BPP model

NASA Astrophysics Data System (ADS)

Kim, Wontae; Yoon, Myungseok

2007-04-01

It can be shown that in the BPP model the smooth phase transition from the asymptotically decelerated AdS universe to the asymptotically accelerated DS universe is possible by solving the modified semiclassical equations of motion. This transition comes from noncommutative Poisson algebra, which gives the constant curvature scalars asymptotically. The decelerated expansion of the early universe is due to the negative energy density with the negative pressure induced by quantum back reaction, and the accelerated late-time universe comes from the positive energy and the negative pressure which behave like dark energy source in recent cosmological models.

Speed control with end cushion for high speed air cylinder

DOEpatents

Stevens, Wayne W.; Solbrig, Charles W.

1991-01-01

A high speed air cylinder in which the longitudinal movement of the piston within the air cylinder tube is controlled by pressurizing the air cylinder tube on the accelerating side of the piston and releasing pressure at a controlled rate on the decelerating side of the piston. The invention also includes a method for determining the pressure required on both the accelerating and decelerating sides of the piston to move the piston with a given load through a predetermined distance at the desired velocity, bringing the piston to rest safely without piston bounce at the end of its complete stroke.

Interobserver agreement in CTG interpretation using the 2015 FIGO guidelines for intrapartum fetal monitoring.

PubMed

Rei, Mariana; Tavares, Sara; Pinto, Pedro; Machado, Ana P; Monteiro, Sofia; Costa, Antónia; Costa-Santos, Cristina; Bernardes, João; Ayres-De-Campos, Diogo

2016-10-01

Visual analysis of cardiotocographic (CTG) tracings has been shown to be prone to poor intra- and interobserver agreement when several interpretation guidelines are used, and this may have an important impact on the technology's performance. The aim of this study was to evaluate agreement in CTG interpretation using the new 2015 FIGO guidelines on intrapartum fetal monitoring. A pre-existing database of intrapartum CTG tracings was used to sequentially select 151 cases acquired with a fetal electrode, with duration exceeding 60minutes, and signal loss less than 15%. These tracings were presented to six clinicians, three with more than 5 years' experience in the labor ward, and three with 5 or less years' experience. Observers were asked to evaluate tracings independently, to assess basic CTG features: baseline, variability, accelerations, decelerations, sinusoidal pattern, tachysystole, and to classify each tracing as normal, suspicious or pathologic, according to the 2015 FIGO guidelines on intrapartum fetal monitoring. Agreement between observers was evaluated using the proportions of agreement (Pa), with 95% confidence intervals (95%CI). A good interobserver agreement was found in the evaluation of most CTG features, but not bradycardia, reduced variability, saltatory pattern, absence of accelerations and absence of decelerations. For baseline classification Pa was 0.85 [0.82-0.90], for variability 0.82 [0.78-0.85], for accelerations 0.72 [0.68-0.75], for tachysystole 0.77 [0.74-0.81], for decelerations 0.92 [0.90-0.95], for variable decelerations 0.62 [0.58-0.65], for late decelerations 0.63 [0.59-0.66], for repetitive decelerations 0.73 [0.69-0.78], and for prolonged decelerations 0.81 [0.77-0.85]. For overall CTG classification, Pa were 0.60 [0.56-0.64], for classification as normal 0.67 [0.61-0.72], for suspicious 0.54 [0.48-0.60] and for pathologic 0.59 [0.51-0.66]. No differences in agreement according to the level of expertise were observed, except in the identification of accelerations, where it was better in the more experienced group. A good interobserver agreement was found in evaluation of most CTG features and in overall tracing classification. Results were better than those reported in previous studies evaluating agreement in overall tracing classification. Observer experience did not appear to play a role in agreement. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

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.

Viscous cosmology in new holographic dark energy model and the cosmic acceleration

NASA Astrophysics Data System (ADS)

Singh, C. P.; Srivastava, Milan

2018-03-01

In this work, we study a flat Friedmann-Robertson-Walker universe filled with dark matter and viscous new holographic dark energy. We present four possible solutions of the model depending on the choice of the viscous term. We obtain the evolution of the cosmological quantities such as scale factor, deceleration parameter and transition redshift to observe the effect of viscosity in the evolution. We also emphasis upon the two independent geometrical diagnostics for our model, namely the statefinder and the Om diagnostics. In the first case we study new holographic dark energy model without viscous and obtain power-law expansion of the universe which gives constant deceleration parameter and statefinder parameters. In the limit of the parameter, the model approaches to Λ CDM model. In new holographic dark energy model with viscous, the bulk viscous coefficient is assumed as ζ =ζ 0+ζ 1H, where ζ 0 and ζ 1 are constants, and H is the Hubble parameter. In this model, we obtain all possible solutions with viscous term and analyze the expansion history of the universe. We draw the evolution graphs of the scale factor and deceleration parameter. It is observed that the universe transits from deceleration to acceleration for small values of ζ in late time. However, it accelerates very fast from the beginning for large values of ζ . By illustrating the evolutionary trajectories in r-s and r-q planes, we find that our model behaves as an quintessence like for small values of viscous coefficient and a Chaplygin gas like for large values of bulk viscous coefficient at early stage. However, model has close resemblance to that of the Λ CDM cosmology in late time. The Om has positive and negative curvatures for phantom and quintessence models, respectively depending on ζ . Our study shows that the bulk viscosity plays very important role in the expansion history of the universe.

Holographic dark energy and late cosmic acceleration

NASA Astrophysics Data System (ADS)

Pavón, Diego

2007-06-01

It has been persuasively argued that the number of effective degrees of freedom of a macroscopic system is proportional to its area rather than to its volume. This entails interesting consequences for cosmology. Here we present a model based on this 'holographic principle' that accounts for the present stage of accelerated expansion of the Universe and significantly alleviates the coincidence problem also for non-spatially flat cosmologies. Likewise, we comment on a recently proposed late transition to a fresh decelerated phase.

ACCELERATED FAILURE TIME MODELS PROVIDE A USEFUL STATISTICAL FRAMEWORK FOR AGING RESEARCH

PubMed Central

Swindell, William R.

2009-01-01

Survivorship experiments play a central role in aging research and are performed to evaluate whether interventions alter the rate of aging and increase lifespan. The accelerated failure time (AFT) model is seldom used to analyze survivorship data, but offers a potentially useful statistical approach that is based upon the survival curve rather than the hazard function. In this study, AFT models were used to analyze data from 16 survivorship experiments that evaluated the effects of one or more genetic manipulations on mouse lifespan. Most genetic manipulations were found to have a multiplicative effect on survivorship that is independent of age and well-characterized by the AFT model “deceleration factor”. AFT model deceleration factors also provided a more intuitive measure of treatment effect than the hazard ratio, and were robust to departures from modeling assumptions. Age-dependent treatment effects, when present, were investigated using quantile regression modeling. These results provide an informative and quantitative summary of survivorship data associated with currently known long-lived mouse models. In addition, from the standpoint of aging research, these statistical approaches have appealing properties and provide valuable tools for the analysis of survivorship data. PMID:19007875

Accelerated failure time models provide a useful statistical framework for aging research.

PubMed

Swindell, William R

2009-03-01

Survivorship experiments play a central role in aging research and are performed to evaluate whether interventions alter the rate of aging and increase lifespan. The accelerated failure time (AFT) model is seldom used to analyze survivorship data, but offers a potentially useful statistical approach that is based upon the survival curve rather than the hazard function. In this study, AFT models were used to analyze data from 16 survivorship experiments that evaluated the effects of one or more genetic manipulations on mouse lifespan. Most genetic manipulations were found to have a multiplicative effect on survivorship that is independent of age and well-characterized by the AFT model "deceleration factor". AFT model deceleration factors also provided a more intuitive measure of treatment effect than the hazard ratio, and were robust to departures from modeling assumptions. Age-dependent treatment effects, when present, were investigated using quantile regression modeling. These results provide an informative and quantitative summary of survivorship data associated with currently known long-lived mouse models. In addition, from the standpoint of aging research, these statistical approaches have appealing properties and provide valuable tools for the analysis of survivorship data.

An externally oriented style of thinking as a moderator of responses to affective films in women.

PubMed

Davydov, Dmitry M; Luminet, Olivier; Zech, Emmanuelle

2013-02-01

This study was conducted to test the hypothesis that differences in alexithymia would moderate coupling in physiological and subjective-experiential responses to two affective films, which were shown to induce a common negative (sad) feeling, but to provoke different hyper- or hypo-arousal physiological responses (e.g., heart rate acceleration or deceleration) associated with antipathic or empathic context, respectively (Davydov et al., 2011). Only women were studied as persons showing more reactivity to sad films than men. Reactivity was evaluated for facial behavior, physiological arousal, and subjective experience. Some other affective and cognitive disposition factors (e.g., depression and defensiveness) were considered for evaluating their probable mediation of the alexithymia's effects. While subjective experience was not affected by alexithymia, high scorers on the externally-oriented thinking factor showed reduced physiological reactivity in both film conditions. These effects were mediated through different disposition factors: either low affectivity (low depressed mood), which mediated alexithymia's effect on hyper-arousal responses (e.g., decrease of heart rate acceleration), or impression management (other-deception), which mediated alexithymia's effect on hypo-arousal responses (e.g., decrease of heart rate deceleration). Copyright © 2012 Elsevier B.V. All rights reserved.

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.

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

Georgieva, A. E.; Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Old Road Campus Research Building Oxford OX3 7DQ; Payne, S. J.

Electronic fetal heart rate (FHR) recording is a standard way of monitoring fetal health in labor. Decelerations and accelerations usually indicate fetal distress and normality respectively. But one type of acceleration may differ, namely an overshoot that may atypically reflect fetal stress. Here we describe a new method for detecting decelerations, accelerations and overshoots as part of a novel system for computerized FHR analysis (OxSyS). There was poor agreement between clinicians when identifying these FHR features visually, which precluded setting a gold standard of interpretation. We therefore introduced 'modified' Sensitivity (SE deg.) and 'modified' Positive Predictive Value (PPV deg.) asmore » appropriate performance measures with which the algorithm was optimized. The relation between overshoots and fetal compromise in labor was studied in 15 cases and 15 controls. Overshoots showed promise as an indicator of fetal compromise. Unlike ordinary accelerations, overshoots cannot be considered to be reassuring features of fetal health.« less

Spectrum Evolution of Accelerating or Slowing down Soliton at its Propagation in a Medium with Gold Nanorods

NASA Astrophysics Data System (ADS)

Trofimov, Vyacheslav A.; Lysak, Tatiana M.

2018-04-01

We investigate both numerically and analytically the spectrum evolution of a novel type soliton - nonlinear chirped accelerating or decelerating soliton - at a femtosecond pulse propagation in a medium containing noble nanoparticles. In our consideration, we take into account one- or two-photon absorption of laser radiation by nanorods, and time-dependent nanorod aspect ratio changing due to their melting or reshaping because of laser energy absorption. The chirped solitons are formed due to the trapping of laser radiation by the nanorods reshaping fronts, if a positive or negative phase-amplitude grating is induced by laser radiation. Accelerating or slowing down chirped soliton formation is accompanied by the soliton spectrum blue or red shift. To prove our numerical results, we derived the approximate analytical law for the spectrum maximum intensity evolution along the propagation coordinate, based on earlier developed approximate analytical solutions for accelerating and decelerating solitons.

The Role of Informal and Formal Leisure Activities in the Disablement Process

ERIC Educational Resources Information Center

Janke, Megan C.; Payne, Laura L.; Van Puymbroeck, Marieke

2008-01-01

The disablement process model has been used as a framework to investigate factors that accelerate or decelerate disablement among older adults. Although very little is known about the direct and moderating effects of involvement in leisure activities on the disablement process, research has suggested that participation in leisure activities may…

Landing characteristics in waves of three dynamic models of flying boats

NASA Technical Reports Server (NTRS)

Benson, James M; Havens, Robert F; Woodward, David R

1952-01-01

Powered models of three different flying boats were landed in oncoming waves of various heights and lengths. The effects of varying the trim at landing, the deceleration after landing, and the size of the waves were determined. Data are presented on the motions and accelerations obtained during landings in rough water.

Mathematical modelling of active safety system functions as tools for development of driverless vehicles

NASA Astrophysics Data System (ADS)

Ryazantsev, V.; Mezentsev, N.; Zakharov, A.

2018-02-01

This paper is dedicated to a solution of the issue of synthesis of the vehicle longitudinal dynamics control functions (acceleration and deceleration control) based on the element base of the vehicle active safety system (ESP) - driverless vehicle development tool. This strategy helps to reduce time and complexity of integration of autonomous motion control systems (AMCS) into the vehicle architecture and allows direct control of actuators ensuring the longitudinal dynamics control, as well as reduction of time for calibration works. The “vehicle+wheel+road” longitudinal dynamics control is complicated due to the absence of the required prior information about the control object. Therefore, the control loop becomes an adaptive system, i.e. a self-adjusting monitoring system. Another difficulty is the driver’s perception of the longitudinal dynamics control process in terms of comfort. Traditionally, one doesn’t pay a lot of attention to this issue within active safety systems, and retention of vehicle steerability, controllability and stability in emergency situations are considered to be the quality criteria. This is mainly connected to its operational limits, since it is activated only in critical situations. However, implementation of the longitudinal dynamics control in the AMCS poses another challenge for the developers - providing the driver with comfortable vehicle movement during acceleration and deceleration - while the possible highest safety level in terms of the road grip is provided by the active safety system (ESP). The results of this research are: universal active safety system - AMCS interaction interface; block diagram for the vehicle longitudinal acceleration and deceleration control as one of the active safety system’s integrated functions; ideology of adaptive longitudinal dynamics control, which enables to realize the deceleration and acceleration requested by the AMCS; algorithms synthesised; analytical experiments proving the efficiency and practicability of the chosen concept.

Temporal and quantitative associations of electronic fetal heart rate monitoring patterns and neonatal outcomes†.

PubMed

Ogunyemi, Dotun; Jovanovski, Andrew; Friedman, Perry; Sweatman, Brittany; Madan, Ichchha

2018-04-06

The objective of this study is to evaluate the associations of electronic fetal heart rate monitoring (EFM) patterns and adverse neonatal outcomes Study design: From 2013 to 2016; 12,067 term, singleton deliveries in labor ≥2 h with abnormal EFM defined as absent accelerations, variable, late or prolonged decelerations, tachycardia, bradycardia, or minimal variability were analyzed as any documentation during labor, in first hour and last hour of labor. Outcomes were composite neonatal adverse outcomes, neonatal intensive care unit (NICU) admission, neonatal hypoxia, neonatal hypoglycemia, umbilical artery pH, and base excess. Independent associations were ascertained using regression analysis. Significant independent associations occurred between any abnormal EFM during the last hour and five adverse neonatal outcomes; between abnormal EFM at any time and one adverse neonatal outcome while there was none with the first hour of labor. In the last hour, accelerations had significant negative associations with three adverse neonatal outcomes, while prolonged decelerations, late decelerations, tachycardia, and bradycardia had significant positive associations with three adverse neonatal outcomes. Throughout labor, increasing accelerations events were significantly negatively correlated with all adverse neonatal outcomes, while increasing frequency of late, variable, and prolonged decelerations were positively associated with five adverse neonatal outcomes. Hierarchical analysis showed that bradycardia/tachycardia contributed only 0.8%, while all EFM periodic changes contributed 1%; the addition of the frequencies of abnormal EFM events contributed 0.6% to the variance in umbilical artery pH and base excess. Terminal EFM patterns are independently associated with neonatal outcomes. Accelerations are protective of adverse neonatal outcomes. Increasing frequency of EFM patterns overtime contributes to neonatal outcome.

The cost of transport of human running is not affected, as in walking, by wide acceleration/deceleration cycles.

PubMed

Minetti, Alberto E; Gaudino, Paolo; Seminati, Elena; Cazzola, Dario

2013-02-15

Although most of the literature on locomotion energetics and biomechanics is about constant-speed experiments, humans and animals tend to move at variable speeds in their daily life. This study addresses the following questions: 1) how much extra metabolic energy is associated with traveling a unit distance by adopting acceleration/deceleration cycles in walking and running, with respect to constant speed, and 2) how can biomechanics explain those metabolic findings. Ten males and ten females walked and ran at fluctuating speeds (5 ± 0, ± 1, ± 1.5, ± 2, ± 2.5 km/h for treadmill walking, 11 ± 0, ± 1, ± 2, ± 3, ± 4 km/h for treadmill and field running) in cycles lasting 6 s. Field experiments, consisting of subjects following a laser spot projected from a computer-controlled astronomic telescope, were necessary to check the noninertial bias of the oscillating-speed treadmill. Metabolic cost of transport was found to be almost constant at all speed oscillations for running and up to ±2 km/h for walking, with no remarkable differences between laboratory and field results. The substantial constancy of the metabolic cost is not explained by the predicted cost of pure acceleration/deceleration. As for walking, results from speed-oscillation running suggest that the inherent within-stride, elastic energy-free accelerations/decelerations when moving at constant speed work as a mechanical buffer for among-stride speed fluctuations, with no extra metabolic cost. Also, a recent theory about the analogy between sprint (level) running and constant-speed running on gradients, together with the mechanical determinants of gradient locomotion, helps to interpret the present findings.

FRW cosmological models in Brans-Dicke theory of gravity with variable q and dynamical \\varLambda-term

NASA Astrophysics Data System (ADS)

Chand, Avtar; Mishra, R. K.; Pradhan, Anirudh

2016-02-01

Exact solution of modified Einstein's field equations are considered within the scope of spatially homogeneous and isotropic Fraidmann-Robertson-Walker (FRW) space-time filled with perfect fluid in the frame work of Brans-Dicke scalar-tensor theory of gravity. In this paper we have investigated the flat, open and closed FRW models and the effect of dynamic cosmological term on the evolution of the universe. Two types of FRW cosmological models are obtained by setting the power law between the scalar field φ and the scale factor a and deceleration parameter (DP) q as a time dependent. The concept of time dependent DP with some proper assumptions yield two type of the average scale factors (i) a(t)=[sinh(α t)]^{1/n} and (ii) a(t)=[t^{α}et]^{1/n}, α and n≠ 0 are arbitrary constants. In case (i), for 0 < n ≤ 1, it generates a class of accelerating models while for n > 1, the models of the universe exhibit phase transition from early decelerating to present accelerating phase and the transition redshift zt has been calculated and found to be in good agreement with the results from recent astrophysical observations. In case (ii), for n ≥ 2 and α = 1, we obtain a class of transit models of the universe from early decelerating to present accelerating phase. Taking into consideration the observational data, we conclude that the cosmological constant behaves as a positive decreasing function of time. The physical and geometric properties of the models are also discussed with the help of graphical presentations.

Vertical dynamics of a single-span beam subjected to moving mass-suspended payload system with variable speeds

NASA Astrophysics Data System (ADS)

He, Wei

2018-03-01

This paper presents the vertical dynamics of a simply supported Euler-Bernoulli beam subjected to a moving mass-suspended payload system of variable velocities. A planar theoretical model of the moving mass-suspended payload system of variable speeds is developed based on several assumptions: the rope is massless and rigid, and its length keeps constant; the stiffness of the gantry beam is much greater than the supporting beam, and the gantry beam can be treated as a mass particle traveling along the supporting beam; the supporting beam is assumed as a simply supported Bernoulli-Euler beam. The model can be degenerated to consider two classical cases-the moving mass case and the moving payload case. The proposed model is verified using both numerical and experimental methods. To further investigate the effect of possible influential factors, numerical examples are conducted covering a range of parameters, such as variable speeds (acceleration or deceleration), mass ratios of the payload to the total moving load, and the pendulum lengths. The effect of beam flexibility on swing response of the payload is also investigated. It is shown that the effect of a variable speed is significant for the deflections of the beam. The accelerating movement tends to induce larger beam deflections, while the decelerating movement smaller ones. For accelerating or decelerating movements, the moving mass model may underestimate the deflections of the beam compared with the presented model; while for uniform motion, both the moving mass model and the moving mass-payload model lead to same beam responses. Furthermore, it is observed that the swing response of the payload is not sensitive to the stiffness of the beam for operational cases of a moving crane, thus a simple moving payload model can be employed in the swing control of the payload.

Will there be again a transition from acceleration to deceleration in course of the dark energy evolution of the universe?

NASA Astrophysics Data System (ADS)

Pan, Supriya; Chakraborty, Subenoy

2013-09-01

In this work we consider the evolution of the interactive dark fluids in the background of homogeneous and isotropic FRW model of the universe. The dark fluids consist of a warm dark matter and a dark energy and both are described as perfect fluid with barotropic equation of state. The dark species interact non-gravitationally through an additional term in the energy conservation equations. An autonomous system is formed in the energy density spaces and fixed points are analyzed. A general expression for the deceleration parameter has been obtained and it is possible to have more than one zero of the deceleration parameter. Finally, vanishing of the deceleration parameter has been examined with some examples.

Pressure-dependent decomposition kinetics of the energetic material HMX up to 3.6 GPa.

PubMed

Glascoe, Elizabeth A; Zaug, Joseph M; Burnham, Alan K

2009-12-03

The effect of pressure on the global thermal decomposition rate of the energetic material HMX was studied. HMX was precompressed in a diamond anvil cell (DAC) and heated at various rates. The parent species population was monitored as a function of time and temperature using Fourier transform infrared (FTIR) spectroscopy. Global decomposition rates were determined by fitting the fraction reacted to the extended-Prout-Tompkins nucleation-growth model and the Friedman isoconversional method. The results of these experiments and analysis indicate that pressure accelerates the decomposition at low-to-moderate pressures (i.e., between ambient pressure and 0.1 GPa) and decelerates the decomposition at higher pressures. The decomposition acceleration is attributed to pressure-enhanced autocatalysis, whereas the deceleration at high pressures is attributed to pressure-inhibiting bond homolysis step(s), which would result in an increase in volume. These results indicate that both the beta- and delta-polymorphs of HMX are sensitive to pressure in the thermally induced decomposition kinetics.

Accelerating dark energy cosmological model in two fluids with hybrid scale factor

NASA Astrophysics Data System (ADS)

Mishra, B.; Sahoo, P. K.; Ray, Pratik P.

In this paper, we have investigated the anisotropic behavior of the accelerating universe in Bianchi V spacetime in the framework of General Relativity (GR). The matter field we have considered is of two non-interacting fluids, i.e. the usual string fluid and dark energy (DE) fluid. In order to represent the pressure anisotropy, the skewness parameters are introduced along three different spatial directions. To achieve a physically realistic solutions to the field equations, we have considered a scale factor, known as hybrid scale factor, which is generated by a time-varying deceleration parameter. This simulates a cosmic transition from early deceleration to late time acceleration. It is observed that the string fluid dominates the universe at early deceleration phase but does not affect nature of cosmic dynamics substantially at late phase, whereas the DE fluid dominates the universe in present time, which is in accordance with the observations results. Hence, we analyzed here the role of two fluids in the transitional phases of universe with respect to time which depicts the reason behind the cosmic expansion and DE. The role of DE with variable equation of state parameter (EoS) and skewness parameters, is also discussed along with physical and geometrical properties.

Asymmetric acceleration/deceleration dynamics in heart rate variability

NASA Astrophysics Data System (ADS)

Alvarez-Ramirez, J.; Echeverria, J. C.; Meraz, M.; Rodriguez, E.

2017-08-01

The heart rate variability (HRV) is an important physiological signal used either to assess the risk of cardiac death or to model the cardiovascular regulatory dynamics. Asymmetries in HRV data have been observed using 2D Poincare plots, which have been linked to a non-equilibrium operation of the cardiac autonomic system. This work further explores the presence of asymmetries but in the serial correlations of the dynamics of HRV data. To this end, detrended fluctuation analysis (DFA) was used to estimate the Hurst exponent both when the heart rate is accelerating and when it is decelerating. The analysis is conducted using data collected from subjects under normal sinus rhythm (NSR), congestive heart failure (CHF) and atrial fibrillation (AF) . For the NSR cases, it was found that correlations are stronger (p < 0 . 05) when the heart rate is accelerating than when it is decelerating over different scales in the range 20-40 beats. In contrast, the opposite behavior was detected for the CHF and AF patients. Possible links between asymmetric correlations in the dynamics and the mechanisms controlling the operation of the heart rate are discussed, as well as their implications for modeling the cardiovascular regulatory dynamics.

Estimated metabolic and mechanical demands during different small-sided games in elite soccer players.

PubMed

Gaudino, Paolo; Alberti, Giampietro; Iaia, F Marcello

2014-08-01

The present study examined the extent to which game format (possession play, SSG-P and game with regular goals and goalkeepers, SSG-G) and the number of players (5, 7 and 10 a-side) influence the physical demands of small-sided soccer games (SSGs) in elite soccer players. Training data were collected during the in-season period from 26 English Premier League outfield players using global positioning system technology. Total distance covered, distance at different speed categories and maximal speed were calculated. In addition, we focused on changes in velocity by reporting the number of accelerations and decelerations carried out during the SSGs (divided in two categories: moderate and high) and the absolute maximal values of acceleration and deceleration achieved. By taking into account these parameters besides speed and distance values, estimated energy expenditure and average metabolic power and distance covered at different metabolic power categories were calculated. All variables were normalized by time (i.e., 4min). The main findings were that the total distance, distances run at high speed (>14.4kmh(-1)) as well as absolute maximum velocity, maximum acceleration and maximum deceleration increased with pitch size (10v10>7v7>5v5; p<.05). Furthermore, total distance, very high (19.8-25.2kmh(-1)) and maximal (>25.2kmh(-1)) speed distances, absolute maximal velocity and maximum acceleration and deceleration were higher in SSG-G than in SSG-P (p<.001). On the other hand, the number of moderate (2-3ms(-2)) accelerations and decelerations as well as the total number of changes in velocity were greater as the pitch dimensions decreased (i.e., 5v5>7v7>10v10; p<.001) in both SSG-G and SSG-P. In addition, predicted energy cost, average metabolic power and distance covered at every metabolic power categories were higher in SSG-P compared to SSG-G and in big than in small pitch areas (p<.05). A detailed analysis of these drills is pivotal in contemporary football as it enables an in depth understanding of the workload imposed on each player which consequently has practical implications for the prescription of the adequate type and amount of stimulus during exercise training. Copyright © 2014 Elsevier B.V. All rights reserved.

Muscle activation patterns in acceleration-based phases during reach-to-grasp movement.

PubMed

Tokuda, Keisuke; Lee, Bumsuk; Shiihara, Yasufumi; Takahashi, Kazuhiro; Wada, Naoki; Shirakura, Kenji; Watanabe, Hideomi

2016-11-01

[Purpose] An earlier study divided reaching activity into characteristic phases based on hand velocity profiles. By synchronizing muscle activities and the acceleration profile, a phasing approach for reaching movement, based on hand acceleration profiles, was attempted in order to elucidate the roles of individual muscle activities in the different phases of the acceleration profile in reaching movements. [Subjects and Methods] Ten healthy volunteer subjects participated in this study. The aim was to electromyographically evaluate muscles around the shoulder, the upper trapezius, the anterior deltoid, the biceps brachii, and the triceps brachii, most of which have been used to evaluate arm motion, as well as the acceleration of the upper limb during simple reaching movement in the reach-to-grasp task. [Results] Analysis showed the kinematic trajectories of the acceleration during a simple biphasic profile of the reaching movement could be divided into four phases: increasing acceleration (IA), decreasing acceleration (DA), increasing deceleration (ID), and decreasing deceleration (DD). Muscles around the shoulder showed different activity patterns, which were closely associated with these acceleration phases. [Conclusion] These results suggest the important role of the four phases, derived from the acceleration trajectory, in the elucidation of the muscular mechanisms which regulate and coordinate the muscles around the shoulder in reaching movements.

Predictive value of late decelerations for fetal acidemia in unselective low-risk pregnancies.

PubMed

Sameshima, Hiroshi; Ikenoue, Tsuyomu

2005-01-01

We evaluated the clinical significance of late decelerations (LD) of intrapartum fetal heart rate (FHR) monitoring to detect low pH (< 7.1) in low-risk pregnancies. We selected two secondary and two tertiary-level institutions where 10,030 women delivered. Among them, 5522 were low-risk pregnancies. The last 2 hours of FHR patterns before delivery were interpreted according to the guidelines of the National Institute of Child Health and Human Development. The correlation between the incidence of LD (occasional, < 50%; recurrent, > or = 50%) and severity (reduced baseline FHR accelerations and variability) of LD, and low pH (< 7.1) were evaluated. Statistical analyses included a contingency table with chi2 and the Fisher test, and one-way analysis of variance with the Bonferroni/Dunn test. In the 5522 low-risk pregnancies, 301 showed occasional LD and 99 showed recurrent LD. Blood gases and pH values deteriorated as the incidence of LD increased and as baseline accelerations or variability was decreased. Positive predictive value for low pH (< 7.1) was exponentially elevated from 0% at no deceleration, 1% in occasional LD, and > 50% in recurrent LD with no baseline FHR accelerations and reduced variability. In low-risk pregnancies, information on LD combined with acceleration and baseline variability enables us to predict the potential incidence of fetal acidemia.

Effect of beta-blocker therapy on heart rate response in patients with hypertension and newly diagnosed untreated obstructive sleep apnea syndrome.

PubMed

Wolf, Jacek; Drozdowski, Jacek; Czechowicz, Krzysztof; Winklewski, Paweł J; Jassem, Ewa; Kara, Tomas; Somers, Virend K; Narkiewicz, Krzysztof

2016-01-01

Beta1-receptor antagonists (BBs) are commonly administered in the treatment of cardiovascular disease (CVD). The reported benefits of BB use in CVD patients with concomitant obstructive sleep apnea (OSA) may be limited by their impact on apnea-induced bradycardias. Therefore the aim of the study was to test the influence of BBs on periapneic heart rate (HR) fluctuations in hypertensive patients with newly-detected and untreated OSA. We studied 88 hypertensive patients (56 on BBs and 32 BB naive) with newly-diagnosed moderate-to-severe OSA who were free of major pulmonary comorbidities and did not require antiarrhythmic therapy. ECGs recorded during sleep were investigated for heart rate (HR) responses to apneas allowing to compare extreme HR accelerations and decelerations between the groups. Average sleep-time HR was comparable in BB-naive (BB-) and BB-treated (BB+) patients. Direct comparisons showed that HR decelerations were also similar in the two subgroups (53.8±9.6 vs. 54.4±7.8 bpm; P=0.78, for BB- and BB+, respectively) however, BBs blunted the OSA-induced HR accelerations (82.3±12.2 vs. 74.3±10.0; P=0.003). After adjusting for baseline HR and magnitude of desaturations, HR decelerations were more evident in BB-naive group whereas tachycardic responses remained blunted in the BB+ group. The incidence of ectopies and conduction abnormalities were comparable across two groups. Beta-blockers do not potentiate apnea-induced HR decelerations, attenuate apnea-induced increases in heart rate and do not influence incidence of ectopies and conduction abnormalities in patients with hypertension and moderate-to-severe, untreated OSA. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Measurements of Form and Frictional Drags over a Rough Topographic Bank

DTIC Science & Technology

2014-09-01

processes, Topographic effects Unclassified Unclassified Unclassified UU 24 Hemantha Wijesekera (228) 688-4845 Reset I PAI!fElNTATION RELEASE...sea surface height associated with the sea surface slope resulting from rota- tional effects . Here barotropic pressure gradients associ- ated with...surface elevation are balanced by the Coriolis force; hTi(x, y, t) is the surface elevation resulting from accelerations/decelerations of flow over the

Misidentification of maternal heart rate as fetal on cardiotocography during the second stage of labor: the role of the fetal electrocardiograph.

PubMed

Nurani, Raisha; Chandraharan, Edwin; Lowe, Virginia; Ugwumadu, Austin; Arulkumaran, Sabaratnam

2012-12-01

To identify the incidence of fetal heart rate (FHR) accelerations in the second stage of labor and the role of fetal electrocardiograph (ECG) in avoiding misidentification of maternal heart rate (MHR) as FHR. Retrospective observational study. University hospital labor ward, London, UK. Cardiotocograph (CTG) tracings of 100 fetuses monitored using external transducers and internal scalp electrodes. CTG traces that fulfilled inclusion criteria were selected from an electronic FHR monitoring database. Rate of accelerations during external and internal monitoring as well as decelerations for a period of 60 minutes prior to delivery were determined. The role of fetal ECG in differentiating between MHR and FHR trace was explored. Decelerations occurred in 89% of CTG traces during the second stage of labor. Accelerations indicating possible recording of FHR or MHR were found in 28.1 and 10.9% of cases recorded by an external ultrasound transducer as well as internal scalp electrode, respectively. Accelerations coinciding with uterine contractions occurred only in 11.7 and 4% of external and internal recording of FHR, respectively. Absence of 'p-wave' of the ECG waveform was associated with MHR trace. Decelerations were the commonest CTG feature during the second stage of labor. The incidence of accelerations coinciding with uterine contractions was less than half in fetuses monitored using a fetal scalp electrode. Analysing the ECG waveform for the absence of 'p-wave' helps in differentiating MHR from FHR. © 2012 The Authors Acta Obstetricia et Gynecologica Scandinavica© 2012 Nordic Federation of Societies of Obstetrics and Gynecology.

R&D for the Future

NASA Astrophysics Data System (ADS)

Hübner, Kurt; Treille, Daniel; Schulte, Daniel

The following sections are included: * The LHC and Beyond * Accelerator Magnets with Ever-Higher Fields * Teasing Performance from Superconductors Old and New * RF Power for CLIC: Acceleration by Deceleration * The Next Energy Frontier e+e- Collider: Innovation in Detectors * Hadron Collider Detectors: A Bright and Energetic Future * References

Tracking progress towards global drinking water and sanitation targets: A within and among country analysis.

PubMed

Fuller, James A; Goldstick, Jason; Bartram, Jamie; Eisenberg, Joseph N S

2016-01-15

Global access to safe drinking water and sanitation has improved dramatically during the Millennium Development Goal (MDG) period. However, there is substantial heterogeneity in progress between countries and inequality within countries. We assessed countries' temporal patterns in access to drinking water and sanitation using publicly available data. We then classified countries using non-linear modeling techniques as having one of the following trajectories: 100% coverage, linear growth, linear decline, no change, saturation, acceleration, deceleration, negative acceleration, or negative deceleration. We further assessed the degree to which temporal profiles follow a sigmoidal pattern and how these patterns might vary within a given country between rural and urban settings. Among countries with more than 10 data points, between 15% and 38% showed a non-linear trajectory, depending on the indicator. Overall, countries' progress followed a sigmoidal trend, but some countries are making better progress and some worse progress than would be expected. We highlight several countries that are not on track to meet the MDG for water or sanitation, but whose access is accelerating, suggesting better performance during the coming years. Conversely, we also highlight several countries that have made sufficient progress to meet the MDG target, but in which access is decelerating. Patterns were heterogeneous and non-linearity was common. Characterization of these heterogeneous patterns will help policy makers allocate resources more effectively. For example, policy makers can identify countries that could make use of additional resources or might be in need of additional institutional capacity development to properly manage resources; this will be essential to meet the forthcoming Sustainable Development Goals. Copyright © 2015 Elsevier B.V. All rights reserved.

Speed And Power Control Of An Engine By Modulation Of The Load Torque

DOEpatents

Ziph, Benjamin; Strodtman, Scott; Rose, Thomas K

1999-01-26

A system and method of speed and power control for an engine in which speed and power of the engine is controlled by modulation of the load torque. The load torque is manipulated in order to cause engine speed, and hence power to be changed. To accomplish such control, the load torque undergoes a temporary excursion in the opposite direction of the desired speed and power change. The engine and the driven equipment will accelerate or decelerate accordingly as the load torque is decreased or increased, relative to the essentially fixed or constant engine torque. As the engine accelerates or decelerates, its power increases or decreases in proportion.

Spatial Disorientation in Gondola Centrifuges Predicted by the Form of Motion as a Whole in 3-D

PubMed Central

Holly, Jan E.; Harmon, Katharine J.

2009-01-01

INTRODUCTION During a coordinated turn, subjects can misperceive tilts. Subjects accelerating in tilting-gondola centrifuges without external visual reference underestimate the roll angle, and underestimate more when backward-facing than when forward-facing. In addition, during centrifuge deceleration, the perception of pitch can include tumble while paradoxically maintaining a fixed perceived pitch angle. The goal of the present research was to test two competing hypotheses: (1) that components of motion are perceived relatively independently and then combined to form a three-dimensional perception, and (2) that perception is governed by familiarity of motions as a whole in three dimensions, with components depending more strongly on the overall shape of the motion. METHODS Published experimental data were used from existing tilting-gondola centrifuge studies. The two hypotheses were implemented formally in computer models, and centrifuge acceleration and deceleration were simulated. RESULTS The second, whole-motion oriented, hypothesis better predicted subjects' perceptions, including the forward-backward asymmetry and the paradoxical tumble upon deceleration. Important was the predominant stimulus at the beginning of the motion as well as the familiarity of centripetal acceleration. CONCLUSION Three-dimensional perception is better predicted by taking into account familiarity with the form of three-dimensional motion. PMID:19198199

Conveying Movement in Music and Prosody

PubMed Central

Hedger, Stephen C.; Nusbaum, Howard C.; Hoeckner, Berthold

2013-01-01

We investigated whether acoustic variation of musical properties can analogically convey descriptive information about an object. Specifically, we tested whether information from the temporal structure in music interacts with perception of a visual image to form an analog perceptual representation as a natural part of music perception. In Experiment 1, listeners heard music with an accelerating or decelerating temporal pattern, and then saw a picture of a still or moving object and decided whether it was animate or inanimate – a task unrelated to the patterning of the music. Object classification was faster when musical motion matched visually depicted motion. In Experiment 2, participants heard spoken sentences that were accompanied by accelerating or decelerating music, and then were presented with a picture of a still or moving object. When motion information in the music matched motion information in the picture, participants were similarly faster to respond. Fast and slow temporal patterns without acceleration and deceleration, however, did not make participants faster when they saw a picture depicting congruent motion information (Experiment 3), suggesting that understanding temporal structure information in music may depend on specific metaphors about motion in music. Taken together, these results suggest that visuo-spatial referential information can be analogically conveyed and represented by music and can be integrated with speech or influence the understanding of speech. PMID:24146920

Application of Fuzzy-Logic Controller and Neural Networks Controller in Gas Turbine Speed Control and Overheating Control and Surge Control on Transient Performance

NASA Astrophysics Data System (ADS)

Torghabeh, A. A.; Tousi, A. M.

2007-08-01

This paper presents Fuzzy Logic and Neural Networks approach to Gas Turbine Fuel schedules. Modeling of non-linear system using feed forward artificial Neural Networks using data generated by a simulated gas turbine program is introduced. Two artificial Neural Networks are used , depicting the non-linear relationship between gas generator speed and fuel flow, and turbine inlet temperature and fuel flow respectively . Off-line fast simulations are used for engine controller design for turbojet engine based on repeated simulation. The Mamdani and Sugeno models are used to expression the Fuzzy system . The linguistic Fuzzy rules and membership functions are presents and a Fuzzy controller will be proposed to provide an Open-Loop control for the gas turbine engine during acceleration and deceleration . MATLAB Simulink was used to apply the Fuzzy Logic and Neural Networks analysis. Both systems were able to approximate functions characterizing the acceleration and deceleration schedules . Surge and Flame-out avoidance during acceleration and deceleration phases are then checked . Turbine Inlet Temperature also checked and controls by Neural Networks controller. This Fuzzy Logic and Neural Network Controllers output results are validated and evaluated by GSP software . The validation results are used to evaluate the generalization ability of these artificial Neural Networks and Fuzzy Logic controllers.

Galvanometer scanning technology for laser additive manufacturing

NASA Astrophysics Data System (ADS)

Luo, Xi; Li, Jin; Lucas, Mark

2017-02-01

A galvanometer laser beam scanning system is an essential element in many laser additive manufacturing (LAM) technologies including Stereolithography (SLA), Selective Laser Sintering (SLS) and Selective Laser Melting (SLM). Understanding the laser beam scanning techniques and recent innovations in this field will greatly benefit the 3D laser printing system integration and technology advance. One of the challenges to achieve high quality 3D printed parts is due to the non-uniform laser power density delivered on the materials caused by the acceleration and deceleration movements of the galvanometer at ends of the hatching and outlining patterns. One way to solve this problem is to modulate the laser power as the function of the scanning speed during the acceleration or deceleration periods. Another strategy is to maintain the constant scanning speed while accurately coordinating the laser on and off operation throughout the job. In this paper, we demonstrate the high speed, high accuracy and low drift digital scanning technology that incorporates both techniques to achieve uniform laser density with minimal additional process development. With the constant scanning speed method, the scanner not only delivers high quality and uniform results, but also a throughput increase of 23% on a typical LAM job, compared to that of the conventional control method that requires galvanometer acceleration and deceleration movements.

Acceleratory match-play demands of a Super Rugby team over a competitive season.

PubMed

Owen, Shaun M; Venter, Rachel E; du Toit, Stephan; Kraak, Wilbur J

2015-01-01

The match-play demands of rugby union have increased over time, and these demands should be quantified so as to provide a basis for optimal player loading during training. The primary aim of this article was to quantify accelerations, decelerations, impacts and aggregated body demands during the first half of match-play in a Super Rugby team. The secondary aim was to determine whether these characteristics are position-specific. Thirty-three players were monitored for 14 matches using global positioning system units with inbuilt microtechnology. Players were grouped according to positional roles and data were analysed for those who completed the entire duration of the first half of a given match. Forwards sustained more (d = 0.44) high-intensity impacts and greater (d = 0.26) aggregated body demands, while backs had more moderate (d = 0.55) and heavy accelerations (d = 0.76), and moderate (d = 0.23) and heavy decelerations (d = 0.54). These differences suggest that conditioning and recovery strategies should reflect the physical demands placed on players in different playing positions. Forwards should be conditioned with a focus on impacts and require longer recovery for the same duration of playing time, whereas conditioning for backs should emphasise rapid accelerations and decelerations.

Generalized fractional diffusion equations for accelerating subdiffusion and truncated Lévy flights

NASA Astrophysics Data System (ADS)

Chechkin, A. V.; Gonchar, V. Yu.; Gorenflo, R.; Korabel, N.; Sokolov, I. M.

2008-08-01

Fractional diffusion equations are widely used to describe anomalous diffusion processes where the characteristic displacement scales as a power of time. For processes lacking such scaling the corresponding description may be given by diffusion equations with fractional derivatives of distributed order. Such equations were introduced in A. V. Chechkin, R. Gorenflo, and I. Sokolov [Phys. Rev. E 66, 046129 (2002)] for the description of the processes getting more anomalous in the course of time (decelerating subdiffusion and accelerating superdiffusion). Here we discuss the properties of diffusion equations with fractional derivatives of the distributed order for the description of anomalous relaxation and diffusion phenomena getting less anomalous in the course of time, which we call, respectively, accelerating subdiffusion and decelerating superdiffusion. For the former process, by taking a relatively simple particular example with two fixed anomalous diffusion exponents we show that the proposed equation effectively describes the subdiffusion phenomenon with diffusion exponent varying in time. For the latter process we demonstrate by a particular example how the power-law truncated Lévy stable distribution evolves in time to the distribution with power-law asymptotics and Gaussian shape in the central part. The special case of two different orders is characteristic for the general situation in which the extreme orders dominate the asymptotics.

Analysis of the Magneto-Hydrodynamic (MHD) Energy Bypass Engine for High-Speed Air-Breathing Propulsion

NASA Technical Reports Server (NTRS)

Riggins, David W.

2002-01-01

The performance of the MHD energy bypass air-breathing engine for high-speed propulsion is analyzed in this investigation. This engine is a specific type of the general class of inverse cycle engines. In this paper, the general relationship between engine performance (specific impulse and specific thrust) and the overall total pressure ratio through an engine (from inlet plane to exit plane) is first developed and illustrated. Engines with large total pressure decreases, regardless of cause or source, are seen to have exponentially decreasing performance. The ideal inverse cycle engine (of which the MHD engine is a sub-set) is then demonstrated to have a significant total pressure decrease across the engine; this total pressure decrease is cycle-driven, degrades rapidly with energy bypass ratio, and is independent of any irreversibility. The ideal MHD engine (inverse cycle engine with no irreversibility other than that inherent in the MHD work interaction processes) is next examined and is seen to have an additional large total pressure decrease due to MHD-generated irreversibility in the decelerator and the accelerator. This irreversibility mainly occurs in the deceleration process. Both inherent total pressure losses (inverse cycle and MHD irreversibility) result in a significant narrowing of the performance capability of the MHD bypass engine. The fundamental characteristics of MHD flow acceleration and flow deceleration from the standpoint of irreversibility and second-law constraints are next examined in order to clarify issues regarding flow losses and parameter selection in the MM modules. Severe constraints are seen to exist in the decelerator in terms of allowable deceleration Mach numbers and volumetric (length) required for meaningful energy bypass (work interaction). Considerable difficulties are also encountered and discussed due to thermal/work choking phenomena associated with the deceleration process. Lastly, full engine simulations utilizing inlet shock systems, finite-rate chemistry, wall cooling with thermally balanced engine (fuel heat sink), fuel injection and mixing, friction, etc. are shown and discussed for both the MHD engine and the conventional scramjet. The MHD bypass engine has significantly lower performance in all categories across the Mach number range (8 to 12.2). The lower performance is attributed to the combined effects of 1) additional irreversibility and cooling requirements associated with the MHD components and 2) the total pressure decrease associated with the inverse cycle itself.

Control of finger forces during fast, slow and moderate rotational hand movements.

PubMed

Kazemi, Hamed; Kearney, Robert E; Milner, Theodore E

2014-01-01

The goal of this study was to investigate the effect of speed on patterns of grip forces during twisting movement involving forearm supination against a torsional load (combined elastic and inertial load). For slow and moderate speed rotations, the grip force increased linearly with load torque. However, for fast rotations in which the contribution of the inertia to load torque was significantly greater than slower movements, the grip force-load torque relationship could be segmented into two phases: a linear ascending phase corresponding to the acceleration part of the movement followed by a plateau during deceleration. That is, during the acceleration phase, the grip force accurately tracked the combined elastic and inertial load. However, the coupling between grip force and load torque was not consistent during the deceleration phase of the movement. In addition, as speed increased, both the position and the force profiles became smoother. No differences in the baseline grip force, safety margin to secure the grasp during hold phase or the overall change in grip force were observed across different speeds.

Observations of the Coronal Mass Ejection with a Complex Acceleration Profile

NASA Astrophysics Data System (ADS)

Reva, A. A.; Kirichenko, A. S.; Ulyanov, A. S.; Kuzin, S. V.

2017-12-01

We study the coronal mass ejection (CME) with a complex acceleration profile. The event occurred on 2009 April 23. It had an impulsive acceleration phase, an impulsive deceleration phase, and a second impulsive acceleration phase. During its evolution, the CME showed signatures of different acceleration mechanisms: kink instability, prominence drainage, flare reconnection, and a CME–CME collision. The special feature of the observations is the usage of the TESIS EUV telescope. The instrument could image the solar corona in the Fe 171 Å line up to a distance of 2 {R}ȯ from the center of the Sun. This allows us to trace the CME up to the LASCO/C2 field of view without losing the CME from sight. The onset of the CME was caused by kink instability. The mass drainage occurred after the kink instability. The mass drainage played only an auxiliary role: it decreased the CME mass, which helped to accelerate the CME. The first impulsive acceleration phase was caused by the flare reconnection. We observed the two-ribbon flare and an increase of the soft X-ray flux during the first impulsive acceleration phase. The impulsive deceleration and the second impulsive acceleration phases were caused by the CME–CME collision. The studied event shows that CMEs are complex phenomena that cannot be explained with only one acceleration mechanism. We should seek a combination of different mechanisms that accelerate CMEs at different stages of their evolution.

Cylindrical effects on Richtmyer-Meshkov instability for arbitrary Atwood numbers in weakly nonlinear regime

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

Liu, W. H.; He, X. T.; LCP, Institute of Applied Physics and Computational Mathematics, Beijing 100088

2012-07-15

When an incident shock collides with a corrugated interface separating two fluids of different densities, the interface is prone to Richtmyer-Meshkov instability (RMI). Based on the formal perturbation expansion method as well as the potential flow theory, we present a simple method to investigate the cylindrical effects in weakly nonlinear RMI with the transmitted and reflected cylindrical shocks by considering the nonlinear corrections up to fourth order. The cylindrical results associated with the material interface show that the interface expression consists of two parts: the result in the planar system and that from the cylindrical effects. In the limit ofmore » the cylindrical radius tending to infinity, the cylindrical results can be reduced to those in the planar system. Our explicit results show that the cylindrical effects exert an inward velocity on the whole perturbed interface, regardless of bubbles or spikes of the interface. On the one hand, outgoing bubbles are constrained and ingoing spikes are accelerated for different Atwood numbers (A) and mode numbers k'. On the other hand, for ingoing bubbles, when |A|k'{sup 3/2} Less-Than-Or-Equivalent-To 1, bubbles are considerably accelerated especially at the small |A| and k'; otherwise, bubbles are decelerated. For outgoing spikes, when |A|k' Greater-Than-Or-Equivalent-To 1, spikes are dramatically accelerated especially at large |A| and k'; otherwise, spikes are decelerated. Furthermore, the cylindrical effects have a significant influence on the amplitudes of the ingoing spike and bubble for large k'. Thus, it should be included in applications where the cylindrical effects play a role, such as inertial confinement fusion ignition target design.« less

Centrifugal reciprocating compressor

NASA Technical Reports Server (NTRS)

High, W. H.

1980-01-01

Efficient compressor uses centrifugal force to compress gas. System incorporates two coupled dc motors, each driving separate centrifugal reciprocating-compressor assembly. Motors are synchronized to accelerate and decelerate alternately.

Bianchi type string cosmological models in f(R,T) gravity

NASA Astrophysics Data System (ADS)

Sahoo, P. K.; Mishra, B.; Sahoo, Parbati; Pacif, S. K. J.

2016-09-01

In this work we have studied Bianchi-III and - VI 0 cosmological models with string fluid source in f( R, T) gravity (T. Harko et al., Phys. Rev. D 84, 024020 (2011)), where R is the Ricci scalar and T the trace of the stress energy-momentum tensor in the context of late time accelerating expansion of the universe as suggested by the present observations. The exact solutions of the field equations are obtained by using a time-varying deceleration parameter. The universe is anisotropic and free from initial singularity. Our model initially shows acceleration for a certain period of time and then decelerates consequently. Several dynamical and physical behaviors of the model are also discussed in detail.

Observed stratospheric downward reflection, and its relation to upward pulses of wave activity

NASA Astrophysics Data System (ADS)

Harnik, N.

2009-04-01

We examine the differences between observed stratospheric vertical wave reflection and wave absorption events, which differ in that the wave induced deceleration remains confined to upper levels in the former. The two types of events signify two types of stratospheric winter dynamics, associated with different downward coupling to the troposphere (Perlwitz and Harnik, 2004). Using time lag composites, we find that the main factor influencing which event will occur is the duration, in time, of the upward pulse of wave activity entering the stratosphere from the troposphere. Short pulses accelerate the flow at their trailing edge in the lower stratosphere while they decelerate it at upper levels, resulting in a vertical shear reversal, and corresponding downward reflection, while long pulses continue decelerating the vortex at progressively lower levels. The confinement of deceleration to upper levels for short wave forcing pulses is also found in an idealized model of an interaction between a planetary wave and the stratospheric vortex, though some aspects of the wave geometry evolution, and thus vertical reflection, are not captured realistically in the model. The results suggest the stratospheric influence on the type of wave interaction, in reality, is indirect - through a possible effect on the duration of upward wave fluxes through the tropopause.

Flow stagnation at Enceladus: The effects of neutral gas and charged dust

NASA Astrophysics Data System (ADS)

Omidi, N.; Tokar, R. L.; Averkamp, T.; Gurnett, D. A.; Kurth, W. S.; Wang, Z.

2012-06-01

Enceladus is one of Saturn's most active moons. It ejects neutral gas and dust particles from its southern plumes with velocities of hundreds of meters per second. The interaction between the ejected material and the corotating plasma in Saturn's magnetosphere leads to flow deceleration in ways that remain to be understood. The most effective mechanism for the interaction between the corotating plasma and the neutral gas is charge exchange which replaces the hotter corotating ions with nearly stationary cold ions that are subsequently accelerated by the motional electric field. Dust particles in the plume can become electrically charged through electron absorption and couple to the plasma through the motional electric field. The objective of this study is to determine the level of flow deceleration associated with each of these processes using Cassini RPWS dust impact rates, Cassini Plasma Spectrometer (CAPS) plasma data, and 3-D electromagnetic hybrid (kinetic ions, fluid electrons) simulations. Hybrid simulations show that the degree of flow deceleration by charged dust varies considerably with the spatial distribution of dust particles. Based on the RPWS observations of dust impacts during the E7 Cassini flyby of Enceladus, we have constructed a dust model consisting of multiple plumes. Using this model in the hybrid simulation shows that when the dust density is high enough for complete absorption of electrons at the point of maximum dust density, the corotating flow is decelerated by only a few km/s. This is not sufficient to account for the CAPS observation of flow stagnation in the interaction region. On the other hand, charge exchange with neutral gas plumes similar to the modeled dust plumes but with base (plume opening) densities of ˜109 cm-3 result in flow deceleration similar to that observed by CAPS. The results indicate that charge exchange with neutral gas is the dominant mechanism for flow deceleration at Enceladus.

Energy recapture through deceleration - regenerative braking in electric vehicles from a user perspective.

PubMed

Cocron, Peter; Bühler, Franziska; Franke, Thomas; Neumann, Isabel; Dielmann, Benno; Krems, Josef F

2013-01-01

We report results from a 1-year field study (N = 80) on user interactions with regenerative braking in electric vehicles. Designed to recapture energy in vehicles with electric powertrains, regenerative braking has an important influence on both the task of driving and energy consumption. Results from user assessments and data from onboard data loggers indicate that most drivers quickly learned to interact with the system, which was triggered via accelerator. Further, conventional braking manoeuvres decreased significantly as the majority of deceleration episodes could only be executed through regenerative braking. Still, some drivers reported difficulties when adapting to the system. These difficulties could be addressed by offering different levels of regeneration so that the intensity of the deceleration could be individually modified. In general, the system is trusted and regarded as a valuable tool for prolonging range. Regenerative braking in electric vehicles has direct implications for the driving task. We found that drivers quickly learn to use and accept a system, which is triggered via accelerator. For those reporting difficulties in the interaction, it appears reasonable to integrate options to customise or switch off the system.

Designing cylindrical implosion experiments on NIF to study deceleration phase of Rayleigh-Taylor

NASA Astrophysics Data System (ADS)

Vazirani, N.; Kline, J. L.; Loomis, E.; Sauppe, J. P.; Palaniyappan, S.; Flippo, K.; Srinivasan, B.; Malka, E.; Bose, A.; Shvarts, D.

2017-10-01

The Rayleigh-Taylor (RT) hydrodynamic instability occurs when a lower density fluid pushes on a higher density fluid. This occurs in inertial confinement fusion (ICF) implosions at each of the capsule interfaces during the initial acceleration and the deceleration as it stagnates. The RT instabilities mix capsule material into the fusion fuel degrading the Deuterium-Tritium reactivity and ultimately play a key role in limiting target performance. While significant effort has focused on understanding RT at the outer capsule surface, little work has gone into understanding the inner surface RT instability growth during the deceleration phase. Direct measurements of the RT instability are difficult to make at high convergence in a spherical implosion. Here we present the design of a cylindrical implosion system for the National Ignition Facility for studying deceleration phase RT. We will discuss the experimental design, the estimated instability growth, and our outstanding concerns.

Investigation of Motorcycle Steering Torque Components

NASA Astrophysics Data System (ADS)

Cossalter, V.; Lot, R.; Massaro, M.; Peretto, M.

2011-10-01

When driving along a circular path, the rider controls a motorcycle mainly by the steering torque. This work addresses an in-depth analysis of the steady state cornering and in particular the decomposition of the motorcycle steering torque in its main components, such as road-tyre forces, gyroscopic torques, centrifugal and gravity effects. A detailed and experimentally validated multibody model of the motorcycle is used herein to analyze the steering torque components at different speeds and lateral accelerations. First the road tests are compared with the numerical results for three different vehicles and then a numerical investigation is carried out to decompose the steering torque. Finally, the effect of longitudinal acceleration and deceleration on steering torque components is presented.

Peculiar motions, accelerated expansion, and the cosmological axis

NASA Astrophysics Data System (ADS)

Tsagas, Christos G.

2011-09-01

Peculiar velocities change the expansion rate of any observer moving relative to the smooth Hubble flow. As a result, observers in a galaxy like our Milky Way can experience accelerated expansion within a globally decelerating universe, even when the drift velocities are small. The effect is local, but the affected scales can be large enough to give the false impression that the whole cosmos has recently entered an accelerating phase. Generally, peculiar velocities are also associated with dipolelike anisotropies, triggered by the fact that they introduce a preferred spatial direction. This implies that observers experiencing locally accelerated expansion, as a result of their own drift motion, may also find that the acceleration is maximized in one direction and minimized in the opposite. We argue that, typically, such a dipole anisotropy should be relatively small and the axis should probably lie fairly close to the one seen in the spectrum of the cosmic microwave background.

Stability condition for the drive bunch in a collinear wakefield accelerator

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

Baturin, S. S.; Zholents, A.

The beam breakup instability of the drive bunch in the structure-based collinear wakefield accelerator is considered and a stabilizing method is proposed. The method includes using the specially designed beam focusing channel, applying the energy chirp along the electron bunch, and keeping energy chirp constant during the drive bunch deceleration. A stability condition is derived that defines the limit on the accelerating field for the witness bunch.

Whole-Motion Model of Perception during Forward- and Backward-Facing Centrifuge Runs

PubMed Central

Holly, Jan E.; Vrublevskis, Arturs; Carlson, Lindsay E.

2009-01-01

Illusory perceptions of motion and orientation arise during human centrifuge runs without vision. Asymmetries have been found between acceleration and deceleration, and between forward-facing and backward-facing runs. Perceived roll tilt has been studied extensively during upright fixed-carriage centrifuge runs, and other components have been studied to a lesser extent. Certain, but not all, perceptual asymmetries in acceleration-vs-deceleration and forward-vs-backward motion can be explained by existing analyses. The immediate acceleration-deceleration roll-tilt asymmetry can be explained by the three-dimensional physics of the external stimulus; in addition, longer-term data has been modeled in a standard way using physiological time constants. However, the standard modeling approach is shown in the present research to predict forward-vs-backward-facing symmetry in perceived roll tilt, contradicting experimental data, and to predict perceived sideways motion, rather than forward or backward motion, around a curve. The present work develops a different whole-motion-based model taking into account the three-dimensional form of perceived motion and orientation. This model predicts perceived forward or backward motion around a curve, and predicts additional asymmetries such as the forward-backward difference in roll tilt. This model is based upon many of the same principles as the standard model, but includes an additional concept of familiarity of motions as a whole. PMID:19208962

Impact-induced acceleration by obstacles

NASA Astrophysics Data System (ADS)

Corbin, N. A.; Hanna, J. A.; Royston, W. R.; Singh, H.; Warner, R. B.

2018-05-01

We explore a surprising phenomenon in which an obstruction accelerates, rather than decelerates, a moving flexible object. It has been claimed that the right kind of discrete chain falling onto a table falls faster than a free-falling body. We confirm and quantify this effect, reveal its complicated dependence on angle of incidence, and identify multiple operative mechanisms. Prior theories for direct impact onto flat surfaces, which involve a single constitutive parameter, match our data well if we account for a characteristic delay length that must impinge before the onset of excess acceleration. Our measurements provide a robust determination of this parameter. This supports the possibility of modeling such discrete structures as continuous bodies with a complicated constitutive law of impact that includes angle of incidence as an input.

Numerical investigation on the effects of acceleration reversal times in Rayleigh-Taylor Instability with multiple reversals

NASA Astrophysics Data System (ADS)

Farley, Zachary; Aslangil, Denis; Banerjee, Arindam; Lawrie, Andrew G. W.

2017-11-01

An implicit large eddy simulation (ILES) code, MOBILE, is used to explore the growth rate of the mixing layer width of the acceleration-driven Rayleigh-Taylor instability (RTI) under variable acceleration histories. The sets of computations performed consist of a series of accel-decel-accel (ADA) cases in addition to baseline constant acceleration and accel-decel (AD) cases. The ADA cases are a series of varied times for the second acceleration reversal (t2) and show drastic differences in the growth rates. Upon the deceleration phase, the kinetic energy of the flow is shifted into internal wavelike patterns. These waves are evidenced by the examined differences in growth rate in the second acceleration phase for the set of ADA cases. Here, we investigate global parameters that include mixing width, growth rates and the anisotropy tensor for the kinetic energy to better understand the behavior of the growth during the re-acceleration period. Authors acknowledge financial support from DOE-SSAA (DE-NA0003195) and NSF CAREER (#1453056) awards.

Three-grid accelerator system for an ion propulsion engine

NASA Technical Reports Server (NTRS)

Brophy, John R. (Inventor)

1994-01-01

An apparatus is presented for an ion engine comprising a three-grid accelerator system with the decelerator grid biased negative of the beam plasma. This arrangement substantially reduces the charge-exchange ion current reaching the accelerator grid at high tank pressures, which minimizes erosion of the accelerator grid due to charge exchange ion sputtering, known to be the major accelerator grid wear mechanism. An improved method for life testing ion engines is also provided using the disclosed apparatus. In addition, the invention can also be applied in materials processing.

From cosmic deceleration to acceleration: new constraints from SN Ia and BAO/CMB

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

Giostri, R.; Santos, M. Vargas dos; Waga, I.

2012-03-01

We use type Ia supernovae (SN Ia) data in combination with recent baryonic acoustic oscillations (BAO) and cosmic microwave background (CMB) observations to constrain a kink-like parametrization of the deceleration parameter (q). This q-parametrization can be written in terms of the initial (q{sub i}) and present (q{sub 0}) values of the deceleration parameter, the redshift of the cosmic transition from deceleration to acceleration (z{sub t}) and the redshift width of such transition (τ). By assuming a flat space geometry, q{sub i} = 1/2 and adopting a likelihood approach to deal with the SN Ia data we obtain, at the 68%more » confidence level (C.L.), that: z{sub t} = 0.56{sup +0.13}{sub −0.10}, τ = 0.47{sup +0.16}{sub −0.20} and q{sub 0} = −0.31{sup +0.11}{sub −0.11} when we combine BAO/CMB observations with SN Ia data processed with the MLCS2k2 light-curve fitter. When in this combination we use the SALT2 fitter we get instead, at the same C.L.: z{sub t} = 0.64{sup +0.13}{sub −0.07}, τ = 0.36{sup +0.11}{sub −0.17} and q{sub 0} = −0.53{sup +0.17}{sub −0.13}. Our results indicate, with a quite general and model independent approach, that MLCS2k2 favors Dvali-Gabadadze-Porrati-like cosmological models, while SALT2 favors ΛCDM-like ones. Progress in determining the transition redshift and/or the present value of the deceleration parameter depends crucially on solving the issue of the difference obtained when using these two light-curve fitters.« less

Collective Deceleration: Toward a Compact Beam Dump

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

Wu, H.-C.; /Munich, Max Planck Inst. Quantenopt.; Tajima, T.

With the increasing development of laser accelerators, the electron energy is already beyond GeV and even higher in near future. Conventional beam dump based on ionization or radiation loss mechanism is cumbersome and costly, also has radiological hazards. We revisit the stopping power of high-energy charged particles in matter and discuss the associated problem of beam dump from the point of view of collective deceleration. The collective stopping length in an ionized gas can be several orders of magnitude shorter than the Bethe-Bloch and multiple electromagnetic cascades stopping length in solid. At the mean time, the tenuous density of themore » gas makes the radioactivation negligible. Such a compact and non-radioactivating beam dump works well for short and dense bunches, which is typically generated from laser wakefield accelerator.« less

Pollution reduction technology program small jet aircraft engines, phase 3

NASA Technical Reports Server (NTRS)

Bruce, T. W.; Davis, F. G.; Kuhn, T. E.; Mongia, H. C.

1981-01-01

A series of Model TFE731-2 engine tests were conducted with the Concept 2 variable geometry airblast fuel injector combustion system installed. The engine was tested to: (1) establish the emission levels over the selected points which comprise the Environmental Protection Agency Landing-Takeoff Cycle; (2) determine engine performance with the combustion system; and (3) evaulate the engine acceleration/deceleration characteristics. The hydrocarbon (HC), carbon monoxide (CO), and smoke goals were met. Oxides of nitrogen (NOx) were above the goal for the same configuration that met the other pollutant goals. The engine and combustor performance, as well as acceleration/deceleration characteristics, were acceptable. The Concept 3 staged combustor system was refined from earlier phase development and subjected to further rig refinement testing. The concept met all of the emissions goals.

Parallel Hybrid Vehicle Optimal Storage System

NASA Technical Reports Server (NTRS)

Bloomfield, Aaron P.

2009-01-01

A paper reports the results of a Hybrid Diesel Vehicle Project focused on a parallel hybrid configuration suitable for diesel-powered, medium-sized, commercial vehicles commonly used for parcel delivery and shuttle buses, as the missions of these types of vehicles require frequent stops. During these stops, electric hybridization can effectively recover the vehicle's kinetic energy during the deceleration, store it onboard, and then use that energy to assist in the subsequent acceleration.

Prenatal stress effects in a wild, long-lived primate: predictive adaptive responses in an unpredictable environment.

PubMed

Berghänel, Andreas; Heistermann, Michael; Schülke, Oliver; Ostner, Julia

2016-09-28

Prenatal maternal stress affects offspring phenotype in numerous species including humans, but it is debated whether these effects are evolutionarily adaptive. Relating stress to adverse conditions, current explanations invoke either short-term developmental constraints on offspring phenotype resulting in decelerated growth to avoid starvation, or long-term predictive adaptive responses (PARs) resulting in accelerated growth and reproduction in response to reduced life expectancies. Two PAR subtypes were proposed, acting either on predicted internal somatic states or predicted external environmental conditions, but because both affect phenotypes similarly, they are largely indistinguishable. Only external (not internal) PARs rely on high environmental stability particularly in long-lived species. We report on a crucial test case in a wild long-lived mammal, the Assamese macaque (Macaca assamensis), which evolved and lives in an unpredictable environment where external PARs are probably not advantageous. We quantified food availability, growth, motor skills, maternal caretaking style and maternal physiological stress from faecal glucocorticoid measures. Prenatal maternal stress was negatively correlated to prenatal food availability and led to accelerated offspring growth accompanied by decelerated motor skill acquisition and reduced immune function. These results support the 'internal PAR' theory, which stresses the role of stable adverse internal somatic states rather than stable external environments. © 2016 The Author(s).

Time domain characteristics of hoof-ground interaction at the onset of stance phase.

PubMed

Burn, J F

2006-11-01

Little is known about the interaction of the hoof with the ground at the onset of stance phase although is it widely believed that high power collisions are involved in the aetiopathology of several conditions causing lameness. To answer 3 questions regarding the fundamental nature of hoof-ground collision: (1) is the collision process deterministic for ground surfaces that present a consistent mechanical interface (2) do collision forces act on the hoof in a small or large range of directions and (3) Is the hoof decelerated to near-zero velocity by the initial deceleration peak following ground contact? Hoof acceleration during the onset of stance phase was recorded using biaxial accelerometry for horses trotting on a tarmac surface and on a sand surface. Characteristics of the collision process were identified both from vector plots and time series representations of hoof acceleration, velocity and displacement. The response of the hoof to collision with smooth tarmac was predominantly deterministic and consistent with the response of a spring-damper system following shock excitation. The response to collision with sand was predominantly random. The deceleration peak following ground contact did not decelerate the hoof to near-zero velocity on tarmac but appeared to on sand. On both surfaces, collision forces acted on the hoof in a wide range of directions. The study suggests the presence of stiff, viscoelastic structures within the foot that may act as shock absorbers isolating the limb from large collision forces. The study indicates objectives for future in vivo and in vitro research into the shock absorbing mechanism within the equine foot; and the effects of shoe type and track surface properties on the collision forces experienced during locomotion. Studies of this nature should help to establish a link between musculoskeletal injury, hoof function and hoof-ground interaction if, indeed, one exists.

Magnetized strange quark model with Big Rip singularity in f(R, T) gravity

NASA Astrophysics Data System (ADS)

Sahoo, P. K.; Sahoo, Parbati; Bishi, Binaya K.; Aygün, S.

2017-07-01

Locally rotationally symmetric (LRS) Bianchi type-I magnetized strange quark matter (SQM) cosmological model has been studied based on f(R, T) gravity. The exact solutions of the field equations are derived with linearly time varying deceleration parameter, which is consistent with observational data (from SNIa, BAO and CMB) of standard cosmology. It is observed that the model begins with big bang and ends with a Big Rip. The transition of the deceleration parameter from decelerating phase to accelerating phase with respect to redshift obtained in our model fits with the recent observational data obtained by Farook et al. [Astrophys. J. 835, 26 (2017)]. The well-known Hubble parameter H(z) and distance modulus μ(z) are discussed with redshift.

Visualization of entry flow separation for oscillating flow in tubes

NASA Technical Reports Server (NTRS)

Qiu, Songgang; Simon, Terence W.

1992-01-01

Neutrally buoyant helium-filled soap bubbles with laser illumination are used to document entry flow separation for oscillating flow in tubes. For a symmetric entry case, the size of the separation zone appears to mildly depend on Reynolds number in the acceleration phase, but is roughly Reynolds number independent in the deceleration phase. For the asymmetric entry case, the separation zone was larger and appeared to grow somewhat during the deceleration phase. The separation zones for both entry geometry cases remain relatively small throughout the cycle. This is different from what would be observed in all-laminar, oscillator flows and is probably due to the high turbulence of the flow, particularly during the deceleration phase of the cycle.

Apparatus and process for the separation of gases using supersonic expansion and oblique wave compression

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

VanOsdol, John G.

The disclosure provides an apparatus and method for gas separation through the supersonic expansion and subsequent deceleration of a gaseous stream. The gaseous constituent changes phase from the gaseous state by desublimation or condensation during the acceleration producing a collectible constituent, and an oblique shock diffuser decelerates the gaseous stream to a subsonic velocity while maintain the collectible constituent in the non-gaseous state. Following deceleration, the carrier gas and the collectible constituent at the subsonic velocity are separated by a separation means, such as a centrifugal, electrostatic, or impingement separator. In an embodiment, the gaseous stream issues from a combustionmore » process and is comprised of N.sub.2 and CO.sub.2.« less

Rolling Friction on a Wheeled Laboratory Cart

DTIC Science & Technology

2012-01-01

by gravity, and a vehicle (such as a car or bicycle) accelerating along a level road is driven by a motor or by pedalling. In such cases, static...is slowing down, its acceleration a points downhill). The normal force N, frictional force f and axle torque four wheels. θ υ N a θ ω τ ƒ mg...friction force pointed backward (to translationally decelerate the object), then it would simultaneously rotationally accelerate the cylinder about its

Influence of maneuverability on helicopter combat effectiveness

NASA Technical Reports Server (NTRS)

Falco, M.; Smith, R.

1982-01-01

A computational procedure employing a stochastic learning method in conjunction with dynamic simulation of helicopter flight and weapon system operation was used to derive helicopter maneuvering strategies. The derived strategies maximize either survival or kill probability and are in the form of a feedback control based upon threat visual or warning system cues. Maneuverability parameters implicit in the strategy development include maximum longitudinal acceleration and deceleration, maximum sustained and transient load factor turn rate at forward speed, and maximum pedal turn rate and lateral acceleration at hover. Results are presented in terms of probability of skill for all combat initial conditions for two threat categories.

Brain sparing effect in growth-restricted fetuses is associated with decreased cardiac acceleration and deceleration capacities: a case-control study.

PubMed

Stampalija, T; Casati, D; Monasta, L; Sassi, R; Rivolta, M W; Muggiasca, M L; Bauer, A; Ferrazzi, E

2016-11-01

Phase rectified signal averaging (PRSA) is a new method of fetal heart rate variability (fHRV) analysis that quantifies the average acceleration (AC) and deceleration capacity (DC) of the heart. The aim of this study was to evaluate AC and DC of fHR [recorded by trans-abdominal fetal electrocardiogram (ta-fECG)] in relation to Doppler velocimetry characteristics of intrauterine growth restriction (IUGR). Prospective case-control study. Single third referral centre. IUGR (n = 66) between 25 and 40 gestational weeks and uncomplicated pregnancies (n = 79). In IUGR the nearest ta-fECG monitoring to delivery was used for PRSA analysis and Doppler velocimetry parameters obtained within 48 hours. AC and DC were computed at s = T = 9. The relation was evaluated between either AC or DC and Doppler velocimetry parameters adjusting for gestational age at monitoring, as well as the association between either AC or DC and IUGR with or without brain sparing. In IUGRs there was a significant association between either AC and DC and middle cerebral artery pulsatility index (PI; P = 0.01; P = 0.005), but the same was not true for uterine or umbilical artery PI (P > 0.05). Both IUGR fetuses with and without brain sparing had lower AC and DC than controls, but this association was stronger for IUGRs with brain sparing. Our study observed for the first time that AC and DC at PRSA analysis are associated with middle cerebral artery PI, but not with uterine or umbilical artery PI, and that there is a significant decrease of AC and DC in association with brain sparing in IUGR fetuses from 25 weeks of gestation to term. Brain sparing in IUGR fetuses is associated with decreased acceleration and deceleration capacities of the heart. © 2015 Royal College of Obstetricians and Gynaecologists.

Deceleration of Antiprotons in Support of Antiproton Storage/Utilization Research

NASA Astrophysics Data System (ADS)

Howe, Steven D.; Jackson, Gerald P.; Pearson, J. Boise; Lewis, Raymond A.

2005-02-01

Antimatter has the highest energy density known to mankind. Many concepts have been studied that use antimatter for propulsion. All of these concepts require the development of high density storage. Hbar Technologies, under contract with the NASA Marshall Space Flight Center, has undertaken the first step toward development of high density storage. Demonstration of the ability to store antiprotons in a Penning Trap provides the technology to pursue research in alternative storage methods that may lead to eventually to high density concepts. Hbar Technologies has undertaken research activity on the detailed design and operations required to decelerate and redirect the Fermi National Accelerator Laboratory (FNAL) antiproton beam to lay the groundwork for a source of low energy antiprotons. We have performed a detailed assessment of an antiproton deceleration scheme using the FNAL Main Injector, outlining the requirements to significantly and efficiently lower the energy of antiprotons. This task shall require a combination of: theoretical/computation simulations, development of specialized accelerator controls programming, modification of specific Main Injector hardware, and experimental testing of the modified system. Testing shall be performed to characterize the system with a goal of reducing the beam momentum from 8.9 GeV/c to a level of 1 GeV/c or less. We have designed an antiproton degrader system that will integrate with the FNAL decelerated/transferred beam. The degrader shall be designed to maximize the number of low energy antiprotons with a beam spot sized for acceptance by the Mark I test hardware.

Investigation of large transit vehicle accidents and establishing appropriate protection for wheelchair riders.

PubMed

Shaw, Greg

2008-01-01

Securing wheelchairs and restraining wheelchair riders on buses is difficult for many wheelchair riders and transit providers. This study examined injury-producing events aboard large transit buses in general in an attempt to better understand the potential risks and required protection for wheelchair users. The study found that few injuries and fatalities occur on large transit buses. Examination of the relatively few injury-producing events advanced the understanding of these events in terms of acceleration/deceleration magnitude and direction. Low acceleration/deceleration, or low-g, events such as those involving abrupt braking or turning occur frequently and are associated with approximately half of onboard passenger injuries. Unfortunately, the actual frequency of high-g events was not determined. Most of the injurious events involved the bus rapidly decelerating because of frontal impacts with another vehicle or roadside object. Further study is needed to determine the magnitude and frequency of high-g events. This information is necessary to determine the level of protection commensurate with real-world risk necessary for wheelchair riders in the transit bus environment and may ultimately facilitate the development of easier-to-use safety systems that secure and restrain wheelchairs and their riders.

Vehicle classification using mobile sensors.

DOT National Transportation Integrated Search

2013-04-01

In this research, the feasibility of using mobile traffic sensors for binary vehicle classification on arterial roads is investigated. Features (e.g. : speed related, acceleration/deceleration related, etc.) are extracted from vehicle traces (passeng...

U.S. Army/FRG Army Mobility Symposium Proceedings held in April 1975

DTIC Science & Technology

1975-11-01

widths, etC.--and their interactions with soil strength, tree stems of various sizes and spacings, approach angles in ditches and streams, etc. At the...provides for their specific identification and user control so that the effects of various levels of driver motivation, associated with combat or...prevailing in the areal unit (braking-visility limit). d. Maneuvering to avoid trees and/or obstacles. e. Acceleration and deceleration between obstacles

40 CFR 86.515-78 - EPA urban dynamometer driving schedule.

Code of Federal Regulations, 2014 CFR

2014-07-01

... PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES Emission... nonrepetitive series of idle, acceleration, cruise, and deceleration modes of various time sequences and rates...

40 CFR 86.515-78 - EPA urban dynamometer driving schedule.

Code of Federal Regulations, 2012 CFR

2012-07-01

... PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES Emission... nonrepetitive series of idle, acceleration, cruise, and deceleration modes of various time sequences and rates...

40 CFR 86.515-78 - EPA urban dynamometer driving schedule.

Code of Federal Regulations, 2011 CFR

2011-07-01

... PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES Emission... nonrepetitive series of idle, acceleration, cruise, and deceleration modes of various time sequences and rates...

40 CFR 86.115-78 - EPA dynamometer driving schedules.

Code of Federal Regulations, 2014 CFR

2014-07-01

... PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES Emission..., acceleration, cruise, and deceleration modes of various time sequences and rates. (b) The driver should attempt...

40 CFR 86.515-78 - EPA urban dynamometer driving schedule.

Code of Federal Regulations, 2013 CFR

2013-07-01

... PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES Emission... nonrepetitive series of idle, acceleration, cruise, and deceleration modes of various time sequences and rates...

14 CFR 27.965 - Fuel tank tests.

Code of Federal Regulations, 2010 CFR

2010-01-01

... reaction of the contents, with the tank full, during maximum limit acceleration or emergency deceleration... both sides of the horizontal (30 degrees total), about the most critical axis, for 25 hours. If motion...

14 CFR 27.965 - Fuel tank tests.

Code of Federal Regulations, 2011 CFR

2011-01-01

... reaction of the contents, with the tank full, during maximum limit acceleration or emergency deceleration... both sides of the horizontal (30 degrees total), about the most critical axis, for 25 hours. If motion...

Player Load, Acceleration, and Deceleration During Forty-Five Competitive Matches of Elite Soccer.

PubMed

Dalen, Terje; Ingebrigtsen, Jørgen; Ettema, Gertjan; Hjelde, Geir Havard; Wisløff, Ulrik

2016-02-01

The use of time-motion analysis has advanced our understanding of position-specific work rate profiles and the physical requirements of soccer players. Still, many of the typical soccer activities can be neglected, as these systems only examine activities measured by distance and speed variables. This study used triaxial accelerometer and time-motion analysis to obtain new knowledge about elite soccer players' match load. Furthermore, we determined acceleration/deceleration profiles of elite soccer players and their contribution to the players' match load. The data set includes every domestic home game (n = 45) covering 3 full seasons (2009, 2010, and 2011) for the participating team (Rosenborg FC), and includes 8 central defenders (n = 68), 9 fullbacks (n = 83), 9 central midfielders (n = 70), 7 wide midfielders (n = 39), and 5 attackers (A, n = 50). A novel finding was that accelerations contributed to 7-10% of the total player load for all player positions, whereas decelerations contributed to 5-7%. Furthermore, the results indicate that other activities besides the high-intensity movements contribute significantly to the players' total match workload. Therefore, motion analysis alone may underestimate player load because many high-intensity actions are without a change in location at the pitch or they are classified as low-speed activity according to current standards. This new knowledge may help coaches to better understand the different ways players achieve match load and could be used in developing individualized programs that better meet the "positional physical demands" in elite soccer.

Fetal heart rate patterns at 20 to 24 weeks gestation as recorded by fetal electrocardiography

PubMed Central

Hofmeyr, F; Groenewald, CA; Nel, DG; Myers, MM; Fifer, WP; Signore, C; Hankins, GDV; Odendaal, HJ

2014-01-01

Introduction With advancing technology it has become possible to accurately record and assess fetal heart rate (FHR) patterns from gestations as early as 20 weeks. The aim of our study was to describe early patterns of FHR, as recorded by transabdominal fetal electrocardiogram according to the Dawes-Redman criteria. Accordingly, short-term variability, basal heart rate, accelerations and decelerations were quantified at 20-24 weeks gestation among women with uncomplicated pregnancies. Methods This study was conducted in a subset of participants enrolled in a large prospective pregnancy cohort study. Our final data set consisted of 281 recordings of women with good perinatal outcomes that had undergone fetal electrocardiographic assessment as part of the Safe Passage Study. Results The success rate of the recordings was 95.4%. The mean frequency of small and large accelerations was 0.5 and 0.1 per 10 minutes respectively and that of small and large decelerations 0.3 and 0.008 per 10 minutes respectively. The mean and basal heart rates were both equal to 148.0 bpm at a median gestation of 161 days. The mean short term variation was 6.2 (SD 1.4) milliseconds and mean minute range 35.1 (SD 7.1) milliseconds. Conclusion The 20 to 24 week fetus demonstrates FHR patterns with more accelerations and decelerations, as well as higher baseline variability than was anticipated. Information from this study provides an important foundation for further, more detailed, studies of early FHR patterns. PMID:23991757

Acceleration from short-duration blast

NASA Astrophysics Data System (ADS)

Ritzel, D. V.; Van Albert, S.; Sajja, V.; Long, J.

2018-01-01

The blast-induced motion of spheres has been studied experimentally where the shock wave is rapidly decaying during the period that quasi-steady acceleration would be developed in the case of a step-function shock wave as considered in most shock-tube studies. The motion of sphere models ranging from 39 to 251 mm in diameter and having a range of densities was assessed using the "free-flight" method in a simulator specially designed to replicate the decaying shock wave profile of spherical blast including negative phase and positive entropy gradient. A standardized blast-wave simulation of 125 kPa and 6-ms positive-phase duration was applied for all experiments. In all cases, there are three phases to the motion: a relatively low "kickoff" velocity from the shock diffraction, acceleration or deceleration during the positive duration, then deceleration through the negative phase and subsequent quiescent air. The unexpected deceleration of larger spheres after their kickoff velocity during the decaying yet high-speed flow of the blast wave seems associated with the persistence of a ring vortex on the downstream side of the sphere. The flow is entirely unsteady with initial forces dominated by the shock diffraction; therefore, the early motion of spheres under such conditions is not governed by quasi-steady drag as in classical aerodynamics. The work will help establish scaling rules for model studies of blast-induced motion relevant to improvised explosive devices, and preliminary results are shown for motion imparted to a human skull surrogate.

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

Not Available

One objective of the study is to assess the effects of all currently known deviations from normal of medical, physiological, and biochemical parameters which appear to be due to zero gravity (zero-g) environment and to acceleration and deceleration to be experienced, as outlined in the reference Solar Power Satellite (SPS) design, by space worker. Study results include identification of possible health or safety effects on space workers - either immediate or delayed - due to the zero gravity environment and acceleration and deceleration; estimation of the probability that an individual will be adversely affected; description of the possible consequence tomore » work efficiently in persons adversely affected; and description of the possible/probable consequences to immediate and future health of individuals exposed to this environment. A research plan, which addresses the uncertainties in current knowledge regarding the health and safety hazards to exposed SPS space workers, is presented. Although most adverse affects experienced during space flight soon disappeared upon return to the Earth's environment, there remains a definite concern for the long-term effects to SPS space workers who might spend as much as half their time in space during a possible five-year career period. The proposed 90-day up/90 day down cycle, coupled with the fact that most of the effects of weightlessness may persist throughout the flight along with the realization that recovery may occupy much of the terrestrial stay, may keep the SPS workers in a deviant physical condition or state of flux for 60 to 100% of their five-year career. (JGB)« less

Control of acceleration during sudden ankle supination in people with unstable ankles.

PubMed

Vaes, P; Van Gheluwe, B; Duquet, W

2001-12-01

Comparative study of differences in functional control during ankle supination in the standing position in matched stable and unstable ankles (ex post facto design). To document acceleration and deceleration during ankle supination in the standing position and to determine differences in control of supination perturbation between stable and unstable ankles. Repetitive ankle sprain can be explained by mechanical instability only in a minority of cases. Exercise therapy for ankle instability is based on clinical experience. Joint stability has not yet been measured in dynamic situations that are similar to the situations leading to a traumatic sprain. The process of motor control during accelerating ankle supination has not been adequately addressed in the literature. Patients with complaints of ankle instability (16 unstable ankles) and nonimpaired controls (18 stable ankles) were examined (N = 17 subjects, 10 women and 7 men). The average age was 23.7 +/- 5.0 years (range, 20-41 y). Control of supination speed was studied during 50 degrees of ankle supination in the standing position using accelerometry (total supination time and deceleration times) and electromyography (latency time). Timing of motor response was estimated by measuring electromechanical delay. The presence of an early, sudden, and presumably passive slowdown of ankle supination in the standing position was observed. Peroneal muscle motor response was detected before the end of the supination. Unstable ankles showed significantly shorter total supination time (109.3 ms versus 124.1 ms) and significantly longer latency time (58.9 ms versus 47.7 ms). Functional control in unstable ankles is less efficient in decelerating the ankle during the supination test procedures used in our study. Our conclusions are based on significantly faster total supination and significantly slower electromyogram response in unstable ankles. The results support the hypothesis that both decelerating the total supination movement during balance disturbance and enhancing the speed of evertor activation through exercise can be specific therapy goals.

A parametric analysis of visual approaches for helicopters

NASA Technical Reports Server (NTRS)

Moen, G. C.; Dicarlo, D. J.; Yenni, K. R.

1976-01-01

A flight investigation was conducted to determine the characteristic shapes of the altitude, ground speed, and deceleration profiles of visual approaches for helicopters. Two hundred thirty-six visual approaches were flown from nine sets of initial conditions with four types of helicopters. Mathematical relationships were developed that describe the characteristic visual deceleration profiles. These mathematical relationships were expanded to develop equations which define the corresponding nominal ground speed, pitch attitude, pitch rate, and pitch acceleration profiles. Results are applicable to improved helicopter handling qualities in terminal area operations.

Fetal Cardiac Responding: A Correlate of Birth Weight and Neonatal Behavior.

ERIC Educational Resources Information Center

Emory, Eugene K.; Noonan, John R.

1984-01-01

Explores whether an empirical classification of healthy fetuses as fetal heart rate accelerators or decelerators would predict birth weight and neonatal behavior scored with the Brazelton Neonatal Behavior Assessment Scale. (Author/RH)

Shock Control and Power Extraction by MHD Processes in Hypersonic Air Flow

DTIC Science & Technology

2006-11-01

green) directions. The lower curve is smoothed to remove the pulser induced oscillations. E. Modeling of Hypersonic Aerodynamic Control and Thrust ...combination of deceleration near the surface and acceleration of the outer flow at XzO. 5 , to only acceleration ( thrust ) at y=l (Fig. 19). 1 - 1 - f...7 8 9 10 M Figure 20. Thrust (F.) and lift (AL) forces, their ratio (AL/AD), and the MHD deposited power versus Mach number for MHD accelerator with X

On the connection between the 3HE-enrichment and spectral index of solar energetic particles

NASA Technical Reports Server (NTRS)

Kocharov, L. G.; Dvoryanchikov, Y. V.

1985-01-01

A model is presented which explains the observed tendency of events with large 3He/4He ratios to have steeper spectra. In this model preferential injection of 3He, acceleration by Alfven waves and Coulomb deceleration of ions are considered simultaneously. The observed tendency may be obtained as a result of competition between injection and acceleration processes.

Kinetics of the Shanghai Maglev: Kinematical Analysis of a Real "Textbook" Case of Linear Motion

ERIC Educational Resources Information Center

Hsu, Tung

2014-01-01

A vehicle starts from rest at constant acceleration, then cruises at constant speed for a time. Next, it decelerates at a constant rate.… This and similar statements are common in elementary physics courses. Students are asked to graph the motion of the vehicle or find the velocity, acceleration, and distance traveled by the vehicle from a given…

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

Stepping responses to treadmill perturbations vary with severity of motor deficits in human SCI.

PubMed

Chu, Virginia Way Tong; Hornby, T George; Schmit, Brian D

2018-04-18

In this study, we investigated the responses to tread perturbations during human stepping on a treadmill. Our approach was to test the effects of perturbations to a single leg using a split-belt treadmill in healthy participants and in participants with varying severity of spinal cord injury (SCI). We recruited 11 people with incomplete SCI and 5 noninjured participants. As participants walked on an instrumented treadmill, the belt on one side was stopped or accelerated briefly during mid to late stance. A majority of participants initiated an unnecessary swing when the treadmill was stopped in mid stance, although the likelihood of initiating a step was decreased in participants with more severe SCI. Accelerating or decelerating one belt of the treadmill during stance altered the characteristics of swing. We observed delayed swing initiation when the belt was decelerated (i.e. the hip was in a more flexed position at time of swing) and advanced swing initiation with acceleration (i.e. hip extended at swing initiation). Further, the timing and leg posture of heel strike appeared to remain constant, reflected by a sagittal plane hip angle at heel strike that remained the same regardless of the perturbation. In summary, our results supported the current understanding of the role of sensory feedback and central drive in the control of stepping in participants with incomplete SCI and noninjured participants. In particular, the observation of unnecessary swing during a stop perturbation highlights the interdependence of central and sensory drive in walking control.

Longitudinal train dynamics model for a rail transit simulation system

DOE PAGES

Wang, Jinghui; Rakha, Hesham A.

2018-01-01

The paper develops a longitudinal train dynamics model in support of microscopic railway transportation simulation. The model can be calibrated without any mechanical data making it ideal for implementation in transportation simulators. The calibration and validation work is based on data collected from the Portland light rail train fleet. The calibration procedure is mathematically formulated as a constrained non-linear optimization problem. The validity of the model is assessed by comparing instantaneous model predictions against field observations, and also evaluated in the domains of acceleration/deceleration versus speed and acceleration/deceleration versus distance. A test is conducted to investigate the adequacy of themore » model in simulation implementation. The results demonstrate that the proposed model can adequately capture instantaneous train dynamics, and provides good performance in the simulation test. Thus, the model provides a simple theoretical foundation for microscopic simulators and will significantly support the planning, management and control of railway transportation systems.« less

Reducing Traffic Congestions by Introducing CACC-Vehicles on a Multi-Lane Highway Using Agent-Based Approach

NASA Technical Reports Server (NTRS)

Arnaout, Georges M.; Bowling, Shannon R.

2011-01-01

Traffic congestion is an ongoing problem of great interest to researchers from different areas in academia. With the emerging technology for inter-vehicle communication, vehicles have the ability to exchange information with predecessors by wireless communication. In this paper, we present an agent-based model of traffic congestion and examine the impact of having CACC (Cooperative Adaptive Cruise Control) embedded vehicle(s) on a highway system consisting of 4 traffic lanes without overtaking. In our model, CACC vehicles adapt their acceleration/deceleration according to vehicle-to-vehicle inter-communication. We analyze the average speed of the cars, the shockwaves, and the evolution of traffic congestion throughout the lifecycle of the model. The study identifies how CACC vehicles affect the dynamics of traffic flow on a complex network and reduce the oscillatory behavior (stop and go) resulting from the acceleration/deceleration of the vehicles.

Longitudinal train dynamics model for a rail transit simulation system

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

Wang, Jinghui; Rakha, Hesham A.

The paper develops a longitudinal train dynamics model in support of microscopic railway transportation simulation. The model can be calibrated without any mechanical data making it ideal for implementation in transportation simulators. The calibration and validation work is based on data collected from the Portland light rail train fleet. The calibration procedure is mathematically formulated as a constrained non-linear optimization problem. The validity of the model is assessed by comparing instantaneous model predictions against field observations, and also evaluated in the domains of acceleration/deceleration versus speed and acceleration/deceleration versus distance. A test is conducted to investigate the adequacy of themore » model in simulation implementation. The results demonstrate that the proposed model can adequately capture instantaneous train dynamics, and provides good performance in the simulation test. Thus, the model provides a simple theoretical foundation for microscopic simulators and will significantly support the planning, management and control of railway transportation systems.« less

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.

Assessment of zero gravity effects on space worker health and safety

NASA Technical Reports Server (NTRS)

1980-01-01

One objective of the study is to assess the effects of all currently known deviations from normal of medical, physiological, and biochemical parameters which appear to be due to zero gravity (zero-g) environment and to acceleration and deceleration to be experienced, as outlined in the references Solar Power Satellites (SPS) design, by space worker. Study results include identification of possible health or safety effects on space workers either immediate or delayed due to the zero gravity environment and acceleration and deceleration; estimation of the probability that an individual will be adversely affected; description of the possible consequence to work efficiency in persons adversely affected; and description of the possible/probable consequences to immediate and future health of individuals exposed to this environment. A research plan, which addresses the uncertainties in current knowledge regarding the health and safety hazards to exposed SPS space workers, is presented. Although most adverse affects experienced during space flight soon disappeared upon return to the Earth's environment, there remains a definite concern for the long-term effects to SPS space workers who might spend as much as half their time in space during a possible five year career period. The proposed 90 day up/90 day down cycle, coupled with the fact that most of the effects of weightlessness may persist throughout the flight along with the realization that recovery may occupy much of the terrestrial stay, may keep the SPS workers in a deviant physical condition or state of flux for 60 to 100% of their five year career.

STANDING SHOCK INSTABILITY IN ADVECTION-DOMINATED ACCRETION FLOWS

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

Le, Truong; Wood, Kent S.; Wolff, Michael T.

2016-03-10

Depending on the values of the energy and angular momentum per unit mass in the gas supplied at large radii, inviscid advection-dominated accretion flows can display velocity profiles with either preshock deceleration or preshock acceleration. Nakayama has shown that these two types of flow configurations are expected to have different stability properties. By employing the Chevalier and Imamura linearization method and the Nakayama instability boundary conditions, we discover that there are regions of parameter space where disks/shocks with outflows can be stable or unstable. In regions of instability, we find that preshock deceleration is always unstable to the zeroth mode withmore » zero frequency of oscillation, but is always stable to the fundamental mode and overtones. Furthermore, we also find that preshock acceleration is always unstable to the zeroth mode and that the fundamental mode and overtones become increasingly less stable as the shock location moves away from the horizon when the disk half-height expands above ∼12 gravitational radii at the shock radius. In regions of stability, we demonstrate the zeroth mode to be stable for the velocity profiles that exhibit preshock acceleration and deceleration. Moreover, for models that are linearly unstable, our model suggests the possible existence of quasi-periodic oscillations (QPOs) with ratios 2:3 and 3:5. These ratios are believed to occur in stellar and supermassive black hole candidates, for example, in GRS 1915+105 and Sgr A*, respectively. We expect that similar QPO ratios also exist in regions of stable shocks.« less

Physical condition for the slowing down of cosmic acceleration

NASA Astrophysics Data System (ADS)

Zhang, Ming-Jian; Xia, Jun-Qing

2018-04-01

The possible slowing down of cosmic acceleration was widely studied. However, judgment on this effect in different dark energy parameterizations was very ambiguous. Moreover, the reason of generating these uncertainties was still unknown. In the present paper, we analyze the derivative of deceleration parameter q‧ (z) using the Gaussian processes. This model-independent reconstruction suggests that no slowing down of acceleration is presented within 95% C.L. from the Union2.1 and JLA supernova data. However, q‧ (z) from the observational H (z) data is a little smaller than zero at 95% C.L., which indicates that future H (z) data may have a potential to test this effect. From the evolution of q‧ (z), we present an interesting constraint on the dark energy and observational data. The physical constraint clearly solves the problem of why some dark energy models cannot produce this effect in previous work. Comparison between the constraint and observational data also shows that most of current data are not in the allowed regions. This implies a reason of why current data cannot convincingly measure this effect.

Accelerative Forces Associated with Routine Inhouse Transportation of Rodent Cages

PubMed Central

Hurst, Keriann; Litwak, Kenneth N

2012-01-01

Transportation of rodents has repeatedly been demonstrated to potentially affect research outcomes. In addition, rapid acceleration and deceleration have marked physiologic effects. The current study determined the accelerative forces associated with common types of animal transportation within the institution and means of reducing these effects. A rodent-sized (24 g) accelerometer was placed in a standard polycarbonate mouse cage, which then was hand-carried or loaded onto a plastic, small metal, or large metal cart. The cage then moved along a set path that included several flooring types and obstacles. Accelerative forces within the mouse cage varied by as much as 35 m/s2 in as little as 1 s, primarily along the vertical axis (Z-axis). Measured acceleration was greatest with the plastic cart and lowest during hand-carrying. The placement of a towel under the cage dampened in-cage acceleration due to cart use by more than 50%, whereas a similarly located underpad had no significant effect. These data document that small rodents typically are exposed to considerable motion during transportation. The resulting physical and physiologic effects could affect study outcomes. PMID:23312081

Birth Weight by Gestational Age for 76,710 Twins Born in the United States as a Result of In Vitro Fertilization: 2006 to 2010.

PubMed

Dickey, Richard P; Pridjian, Gabriella; Xiong, Xu; Klempel, Monica C

2017-01-01

Objective  The objective of this study was to establish twin-specific birth weight percentiles by gestational age using U.S. twin births resulting from in vitro fertilization (IVF). Study Design  A retrospective analysis of birth weight by completed weeks of gestation for 76,710 twin IVF births reported to the Society for Assisted Reproductive Technologies from 2006 to 2010. Mean and median birth weights and 3rd, 5th, 10th, 25th, 50th, 75th, 90th, and 97th percentiles were calculated by completed week of gestation and infant sex. Results  IVF twin birth weight accelerates until term and then declines. The deceleration in twin birth weight occurs at 39 completed weeks of gestation for larger twins, those at or above the 50th percentile in weight. For smaller twins, the growth deceleration occurs earlier, at 38 weeks of gestation. IVF female and male twin birth weights for gestational age were similar to all IVF twins, showing similar decelerations near term. Conclusion  Using U.S. IVF twin-specific growth charts, with known date of conception, twins demonstrate a deceleration in birth weight near term. Larger twins demonstrate a deceleration in birth weight by 39 completed weeks of gestation; smaller twins show a deceleration at 38 weeks. These data may assist in the clinical management of twins near term. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Continuous all-optical deceleration of molecular beams and demonstration with Rb atoms

NASA Astrophysics Data System (ADS)

Long, Xueping; Jayich, Andrew; Campbell, Wesley

2017-04-01

Ultracold samples of molecules are desirable for a variety of applications, such as many-body physics, precision measurement and quantum information science. However, the pursuit of ultracold molecules has achieved limited success: spontaneous emission into many different dark states makes it hard to optically decelerate molecules to trappable speed. We propose to address this problem with a general optical deceleration technique that exploits a pump-dump pulse pair from a mode-locked laser. A molecular beam is first excited by a counter-propagating ``pump'' pulse. The molecular beam is then driven back to the initial ground state by a co-propagating ``dump'' pulse via stimulated emission. The delay between the pump and dump pulse is set to be shorter than the excited state lifetimes in order to limit decays to dark states. We report progress benchmarking this stimulated force by accelerating a cold sample of neutral Rb atoms.

How does the ball influence the performance of change of direction and sprint tests in para-footballers with brain impairments? Implications for evidence-based classification in CP-Football

PubMed Central

2017-01-01

The aims of this study were: i) to analyze the reliability and validity of three tests that require sprinting (10 m, 25 m, 40 m), accelerations/decelerations (Stop and Go Test) and change of direction (Illinois Agility Test), with and without ball, in para-footballers with neurological impairments, and ii) to compare the performance in the tests when ball dribbling is required and to explore the practical implications for evidence-based classification in cerebral palsy (CP)-Football. Eighty-two international para-footballers (25.2 ± 6.8 years; 68.7 ± 8.3 kg; 175.3 ± 7.4 cm; 22.5 ± 2.7 kg·m-2), classified according to the International Federation of Cerebral Palsy Football (IFCPF) Classification Rules (classes FT5-FT8), participated in the study. A group of 31 players without CP was also included in the study as a control group. The para-footballers showed good reliability scores in all tests, with and without ball (ICC = 0.53–0.95, SEM = 2.5–9.8%). Nevertheless, the inclusion of the ball influenced testing reproducibility. The low or moderate relationships shown among sprint, acceleration/deceleration and change of direction tests with and without ball also evidenced that they measure different capabilities. Significant differences and large effect sizes (0.53 < ηp2 < 0.97; p < 0.05) were found when para-footballers performed the tests with and without dribbling the ball. Players with moderate neurological impairments (i.e. FT5, FT6, and FT7) had higher coefficients of variation in the trial requiring ball dribbling. For all the tests, we also obtained between-group (FT5-FT8) statistical and large practical differences (ηp2 = 0.35–0.62, large; p < 0.01). The proposed sprint, acceleration/deceleration and change of direction tests with and without ball may be applicable for classification purposes, that is, evaluation of activity limitation from neurological impairments, or decision-making between current CP-Football classes. PMID:29099836

The role of streamline curvature in sand dune dynamics: evidence from field and wind tunnel measurements

NASA Astrophysics Data System (ADS)

Wiggs, Giles F. S.; Livingstone, Ian; Warren, Andrew

1996-09-01

Field measurements on an unvegetated, 10 m high barchan dune in Oman are compared with measurements over a 1:200 scale fixed model in a wind tunnel. Both the field and wind tunnel data demonstrate similar patterns of wind and shear velocity over the dune, confirming significant flow deceleration upwind of and at the toe of the dune, acceleration of flow up the windward slope, and deceleration between the crest and brink. This pattern, including the widely reported upwind reduction in shear velocity, reflects observations of previous studies. Such a reduction in shear velocity upwind of the dune should result in a reduction in sand transport and subsequent sand deposition. This is not observed in the field. Wind tunnel modelling using a near-surface pulse-wire probe suggests that the field method of shear velocity derivation is inadequate. The wind tunnel results exhibit no reduction in shear velocity upwind of or at the toe of the dune. Evidence provided by Reynolds stress profiles and turbulence intensities measured in the wind tunnel suggest that this maintenance of upwind shear stress may be a result of concave (unstable) streamline curvature. These additional surface stresses are not recorded by the techniques used in the field measurements. Using the occurrence of streamline curvature as a starting point, a new 2-D model of dune dynamics is deduced. This model relies on the establishment of an equilibrium between windward slope morphology, surface stresses induced by streamline curvature, and streamwise acceleration. Adopting the criteria that concave streamline curvature and streamwise acceleration both increase surface shear stress, whereas convex streamline curvature and deceleration have the opposite effect, the relationships between form and process are investigated in each of three morphologically distinct zones: the upwind interdune and concave toe region of the dune, the convex portion of the windward slope, and the crest-brink region. The applicability of the model is supported by measurements of the rate of sand transport and the change of the dune surface in the field.

Comment on ;Acceleration of particles to high energy via gravitational repulsion in the Schwarzschild field; [Astropart. Phys. 86 (2017) 18-20

NASA Astrophysics Data System (ADS)

Spallicci, Alessandro D. A. M.

2017-09-01

Comments are due on a recent paper by McGruder III (2017) in which the author deals with the concept of gravitational repulsion in the context of the Schwarzschild-Droste solution. Repulsion (deceleration) for ingoing particles into a black hole is a concept proposed several times starting from Droste himself in 1916. It is a coordinate effect appearing to an observer at a remote distance from the black hole and when coordinate time is employed. Repulsion has no bearing and relation to the local physics of the black hole, and moreover it cannot be held responsible for accelerating outgoing particles. Thereby, the energy boost of cosmic rays cannot be produced by repulsion.

Enhanced data reduction of the velocity data on CETA flight experiment. [Crew and Equipment Translation Aid

NASA Technical Reports Server (NTRS)

Finley, Tom D.; Wong, Douglas T.; Tripp, John S.

1993-01-01

A newly developed technique for enhanced data reduction provides an improved procedure that allows least squares minimization to become possible between data sets with an unequal number of data points. This technique was applied in the Crew and Equipment Translation Aid (CETA) experiment on the STS-37 Shuttle flight in April 1991 to obtain the velocity profile from the acceleration data. The new technique uses a least-squares method to estimate the initial conditions and calibration constants. These initial conditions are estimated by least-squares fitting the displacements indicated by the Hall-effect sensor data to the corresponding displacements obtained from integrating the acceleration data. The velocity and displacement profiles can then be recalculated from the corresponding acceleration data using the estimated parameters. This technique, which enables instantaneous velocities to be obtained from the test data instead of only average velocities at varying discrete times, offers more detailed velocity information, particularly during periods of large acceleration or deceleration.

Detachment of secondary dendrite arm in a directionally solidified Sn-Ni peritectic alloy under deceleration growth condition

PubMed Central

Peng, Peng; Li, Xinzhong; Li, Jiangong; Su, Yanqing; Guo, Jingjie; Fu, Hengzhi

2016-01-01

In order to better understand the detachment mechanism of secondary dendrite arm during peritectic solidification, the detachment of secondary dendrite arm from the primary dendrite arms in directionally solidified Sn-36at.%Ni peritectic alloys is investigated at different deceleration rates. Extensive detachment of secondary dendrite arms from primary stem is observed below peritectic reaction temperature TP. And an analytical model is established to characterize the detachment process in terms of the secondary dendrite arm spacing λ2, the root radius of detached arms and the specific surface area (SV) of dendrites. It is found that the detachment mechanism is caused by not only curvature difference between the tips and roots of secondary branches, but also that between the thicker secondary branches and the thinner ones. Besides, this detachment process is significantly accelerated by the temperature gradient zone melting (TGZM) effect during peritectic solidification. It is demonstrated that the reaction constant (f) which is used to characterize the kinetics of peritectic reaction is crucial for the determination of the detachment process. The value of f not only changes with growth rate but also with solidification time at a given deceleration rate. In conclusion, these findings help the better understanding of the detachment mechanism. PMID:27270334

Use of induced acceleration to quantify the (de)stabilization effect of external and internal forces on postural responses.

PubMed

van Asseldonk, Edwin H F; Carpenter, Mark G; van der Helm, Frans C T; van der Kooij, Herman

2007-12-01

Due to the mechanical coupling between the body segments, it is impossible to see with the naked eye the causes of body movements and understand the interaction between movements of different body parts. The goal of this paper is to investigate the use of induced acceleration analysis to reveal the causes of body movements. We derive the analytical equations to calculate induced accelerations and evaluate its potential to study human postural responses to support-surface translations. We measured the kinematic and kinetic responses of a subject to sudden forward and backward translations of a moving platform. The kinematic and kinetics served as input to the induced acceleration analyses. The induced accelerations showed explicitly that the platform acceleration and deceleration contributed to the destabilization and restabilization of standing balance, respectively. Furthermore, the joint torques, coriolis and centrifugal forces caused by swinging of the arms, contributed positively to stabilization of the Center of Mass. It is concluded that induced acceleration analyses is a valuable tool in understanding balance responses to different kinds of perturbations and may help to identify the causes of movement in different pathologies.

Underbody Blast Models of TBI Caused by Hyper-Acceleration and Secondary Head Impact

DTIC Science & Technology

2016-02-01

discovery rate (FDR), which controls for the expected proportion of false rejected hypotheses. ANOVA was performed to evaluate the significance in gene...acceleration/deceleration11,27 and blast4,13 have also been designed for the purpose of evaluating coup-contrecoup and blast wave energies potentially... evaluation of different angles/ locations of the projectile impact to the surface of the rat head. Finally, pilot studies were conducted to provide further

Explaining the Supernova Data Without Accelerating Expansion

NASA Astrophysics Data System (ADS)

Stuckey, W. M.; McDevitt, T. J.; Silberstein, M.

2012-10-01

The 2011 Nobel Prize in Physics was awarded "for the discovery of the accelerating expansion of the universe through observations of distant supernovae." However, it is not the case that the type Ia supernova data necessitates accelerating expansion. Since we do not have a successful theory of quantum gravity, we should not assume general relativity (GR) will survive unification intact, especially on cosmological scales where tests are scarce. We provide a simple example of how GR cosmology may be modified to produce a decelerating Einstein-de Sitter cosmology (EdS) that accounts for the Union2 Compilation data as well as the accelerating ΛCDM (EdS plus a cosmological constant).

Novel shock absorber features varying yield strengths

NASA Technical Reports Server (NTRS)

Geier, D. J.

1964-01-01

A shock absorbent webbing of partially drawn synthetic strands is arranged in sections of varying density related to the varying mass of the human body. This is contoured to protect the body at points of contact, when subjected to large acceleration or deceleration forces.

Survivability of bare, individual Bacillus subtilis spores to high-velocity surface impact: Implications for microbial transfer through space

NASA Astrophysics Data System (ADS)

Barney, Brandon L.; Pratt, Sara N.; Austin, Daniel E.

2016-06-01

Laboratory experiments show that endospores of Bacillus subtilis survive impact against a solid surface at velocities as high as 299 ±28 m/s. During impact, spores experience and survive accelerations of at least 1010 m/s2. The spores were introduced into a vacuum chamber using an electrospray source and accelerated to a narrow velocity distribution by entrainment in a differentially pumped gas flow. Different velocity ranges were studied by modifying the gas flow parameters. The spores were electrically charged, allowing direct measurement of the velocity of each spore as it passed through an image charge detector prior to surface impact. Spores impacted a glass surface and were collected for subsequent analysis by culturing. Most spores survived impact at all measured velocities. These experiments differ fundamentally from other studies that show either shock or impact survivability of bacteria embedded within or on the surface of a projectile. Bacteria in the present experiments undergo a single interaction with a solid surface at the full impact velocity, in the absence of any other effects such as cushioning due to microbe agglomerations, deceleration due to air or vapor, or transfer of impact shock through solid or liquid media. During these full-velocity impact events, the spores experience extremely high decelerations. This study is the first reported instance of accelerations of this magnitude experienced during a bacteria impact event. These results are discussed in the context of potential transfer of viable microbes in space and other scenarios involving surface impacts at high velocities.

The Longitudinal Stability of Flying Boats as Determined by Tests of Models in the NACA Tank II : Effect of Variations in Form of Hull on Longitudinal Stability

NASA Technical Reports Server (NTRS)

Olson, Roland E.; Truscott, Starr

1942-01-01

Data taken from tests at constant speed to establish trim limits of stability, tests at accelerated speeds to determine stable limits of center of gravity shift, and tests at decelerated speeds to obtain landing characteristics of several model hull forms were used to establish hull design effect on longitudinal stability of porpoising. Results show a reduction of dead rise angle as being the only investigated factor reducing low trim limit. Various methods of reducing afterbody interference increased upper trim limit

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

Candel, Arno; Li, Z.; Ng, C.

The Compact Linear Collider (CLIC) provides a path to a multi-TeV accelerator to explore the energy frontier of High Energy Physics. Its novel two-beam accelerator concept envisions rf power transfer to the accelerating structures from a separate high-current decelerator beam line consisting of power extraction and transfer structures (PETS). It is critical to numerically verify the fundamental and higher-order mode properties in and between the two beam lines with high accuracy and confidence. To solve these large-scale problems, SLAC's parallel finite element electromagnetic code suite ACE3P is employed. Using curvilinear conformal meshes and higher-order finite element vector basis functions, unprecedentedmore » accuracy and computational efficiency are achieved, enabling high-fidelity modeling of complex detuned structures such as the CLIC TD24 accelerating structure. In this paper, time-domain simulations of wakefield coupling effects in the combined system of PETS and the TD24 structures are presented. The results will help to identify potential issues and provide new insights on the design, leading to further improvements on the novel CLIC two-beam accelerator scheme.« less

Differential longitudinal changes in cortical thickness, surface area and volume across the adult life span: regions of accelerating and decelerating change.

PubMed

Storsve, Andreas B; Fjell, Anders M; Tamnes, Christian K; Westlye, Lars T; Overbye, Knut; Aasland, Hilde W; Walhovd, Kristine B

2014-06-18

Human cortical thickness and surface area are genetically independent, emerge through different neurobiological events during development, and are sensitive to different clinical conditions. However, the relationship between changes in the two over time is unknown. Additionally, longitudinal studies have almost invariably been restricted to older adults, precluding the delineation of adult life span trajectories of change in cortical structure. In this longitudinal study, we investigated changes in cortical thickness, surface area, and volume after an average interval of 3.6 years in 207 well screened healthy adults aged 23-87 years. We hypothesized that the relationships among metrics are dynamic across the life span, that the primary contributor to cortical volume reductions in aging is cortical thinning, and that magnitude of change varies with age and region. Changes over time were seen in cortical area (mean annual percentage change [APC], -0.19), thickness (APC, -0.35), and volume (APC, -0.51) in most regions. Volume changes were primarily explained by changes in thickness rather than area. A negative relationship between change in thickness and surface area was found across several regions, where more thinning was associated with less decrease in area, and vice versa. Accelerating changes with increasing age was seen in temporal and occipital cortices. In contrast, decelerating changes were seen in prefrontal and anterior cingulate cortices. In conclusion, a dynamic relationship between cortical thickness and surface area changes exists throughout the adult life span. The mixture of accelerating and decelerating changes further demonstrates the importance of studying these metrics across the entire adult life span. Copyright © 2014 the authors 0270-6474/14/348488-11$15.00/0.

Impact of Inner Surface Perturbations on the Stability of Cylindrical Liner Implosion

NASA Astrophysics Data System (ADS)

Weis, Matthew; Peterson, Kyle; Hess, Mark; Lau, Y. Y.; Zhang, Peng; Gilgenbach, Ronald

2015-11-01

This paper studies the effects of initial perturbations on the inner liner surface (ILS) of an imploding cylindrical liner. In MagLIF, nonuniform preheat of the fuel could provide an additional source of spatial nonuniformity on the ILS. A blast wave generated by the laser preheat might trigger the Richtmyer-Meshkov instability (RM) on the ILS which then serves as another seed to the Rayleigh-Taylor instability (RT) during the stagnation (deceleration) phase of the implosion. Another scenario is that the shock initiated from the outer liner surface, during current rise, propagates inward and is reflected at the ILS. This reflected shock would carry the initial ILS perturbations which then serve as an additional seed for the magneto-RT (MRT) during the acceleration phase of the implosion. These potentially dangerous interactions are analyzed using the 2D HYDRA code. The effects of axial magnetic fields, of the initial surface roughness spectrum, and of gas fill or water fill (to examine deceleration phase RT) are studied. M. R. Weis was supported by the Sandia National Laboratories. This work was also supported by DoE Grant DE-SC0012328.

Impact Factors Analysis of the Hot Side Temperature of Thermoelectric Module

NASA Astrophysics Data System (ADS)

Zhang, Xingyu; Tan, Gangfeng; Yang, Bo

2018-03-01

The thermoelectric generator (TEG) plays a crucial role in converting the waste energy of exhaust into electricity, which ensures energy saving and increased fuel utilization efficiency. In the urban driving cycle, frequent vehicle operation, like deceleration or acceleration, results in continuous variation of the exhaust temperature. In order to make the operating performance stable, and to weaken the adverse effects of the frequent variation of the exhaust temperature on the lifetime and work efficiency of the electronic components of TEG systems, the output voltage of the thermoelectric (TE) module should stay more stable. This article provides an improved method for the temperature stability of the TE material hot side based on sandwiching material. From the view of the TEG system's average output power and the hot side temperature stability of the TE material, the analyzing factors, including the fluctuation frequency of the exhaust temperature and the physical properties and thickness of the sandwiching material are evaluated, respectively, in the sine and new European driving cycle (NEDC) fluctuation condition of the exhaust temperature. The results show few effects of sandwiching material thickness with excellent thermal conductivity on the average output power. During the 150-170 s of the NEDC test condition, the minimum hot side temperatures with a BeO ceramic thickness of 2 mm and 6 mm are, respectively, 537.19 K and 685.70 K, which shows the obvious effect on the hot side temperature stability of the BeO ceramic thickness in the process of acceleration and deceleration of vehicle driving.

Impact Factors Analysis of the Hot Side Temperature of Thermoelectric Module

NASA Astrophysics Data System (ADS)

Zhang, Xingyu; Tan, Gangfeng; Yang, Bo

2017-12-01

The thermoelectric generator (TEG) plays a crucial role in converting the waste energy of exhaust into electricity, which ensures energy saving and increased fuel utilization efficiency. In the urban driving cycle, frequent vehicle operation, like deceleration or acceleration, results in continuous variation of the exhaust temperature. In order to make the operating performance stable, and to weaken the adverse effects of the frequent variation of the exhaust temperature on the lifetime and work efficiency of the electronic components of TEG systems, the output voltage of the thermoelectric (TE) module should stay more stable. This article provides an improved method for the temperature stability of the TE material hot side based on sandwiching material. From the view of the TEG system's average output power and the hot side temperature stability of the TE material, the analyzing factors, including the fluctuation frequency of the exhaust temperature and the physical properties and thickness of the sandwiching material are evaluated, respectively, in the sine and new European driving cycle (NEDC) fluctuation condition of the exhaust temperature. The results show few effects of sandwiching material thickness with excellent thermal conductivity on the average output power. During the 150-170 s of the NEDC test condition, the minimum hot side temperatures with a BeO ceramic thickness of 2 mm and 6 mm are, respectively, 537.19 K and 685.70 K, which shows the obvious effect on the hot side temperature stability of the BeO ceramic thickness in the process of acceleration and deceleration of vehicle driving.

The association between later cortical potentials and later phases of postural reactions evoked by perturbations to upright stance.

PubMed

Quant, Sylvia; Maki, Brian E; McIlroy, William E

2005-06-24

Previous studies have suggested that early cortical potentials (e.g. N1) that are evoked by perturbations to upright stance are associated with sensory processing of the initial perturbation and that later potentials may represent cognitive processing of this perturbation. However, it has also been suggested that later cortical potentials could reflect sensory and motor processing of later phases of the postural reaction. The current study set out to provide additional insight into the association between perturbation-evoked cortical potentials and postural reactions evoked by whole-body perturbations. By altering the deceleration onset of the perturbation, which altered the timing of later postural responses, we determined whether changes in later postural responses were associated with changes in later potentials. Based on previous work, we hypothesized that later potentials would not be associated with changes in later postural responses. During stance, seven healthy young adults were instructed to maintain their balance following two types of perturbations: (1) acceleration phase immediately followed by a deceleration phase (TASK 1), and (2) acceleration phase followed by a delayed deceleration phase (TASK 2). In spite of profound task differences in later postural responses, results revealed no significant differences in later potentials. This work provides additional support for the idea that latter elements of perturbation-evoked cortical responses are likely independent of evoked motor reactions required to maintain stability.

Primordial perturbations in a rainbow universe with running Newton constant

NASA Astrophysics Data System (ADS)

Brighenti, Francesco; Gubitosi, Giulia; Magueijo, Joao

2017-03-01

We compute the spectral index of primordial perturbations in a rainbow universe. We allow the Newton constant G to run at (super-) Planckian energies and we consider both vacuum and thermal perturbations. If the rainbow metric is the one associated to a generalized Horava-Lifshitz dispersion relation, we find that only when G tends asymptotically to 0 can one match the observed value of the spectral index and solve the horizon problem, both for vacuum and thermal perturbations. For vacuum fluctuations the observational constraints imply that the primordial universe expansion can be both accelerating or decelerating, while in the case of thermal perturbations only decelerating expansion is allowed.

Empirical observation of the impact of traffic oscillations on freeway safety : final report, OTREC-RR-10-13, September 2010.

DOT National Transportation Integrated Search

2010-09-01

Traffic oscillations are typical features of congested traffic flow that are characterized by recurring decelerations : followed by accelerations (stop-and-go driving). The negative environmental impacts of these oscillations are widely : accepted, b...

Analytical tool for measuring emissions impact of acceleration and deceleration lanes : final report.

DOT National Transportation Integrated Search

2001-04-01

Air quality has become one of the important factors to be considered in making transportation improvement : decisions. Thus, tools are expected to help such decision-makings. On the other hand, MOBILE5 model, which : has been widely used in evaluatin...

The Perception of the Higher Derivatives of Visual Motion.

DTIC Science & Technology

1986-06-24

uniform velocity in one run with a target mov- ing with either an accelerating or decelerating motion on another run , and had to decide on which of...the two runs the motion was uniform. It was found that sensitivity to acceleration (as indicated by proportion of correct dis- criminations) decreased...20 subjects had 8 In an experiment by Runeson (1975), one target (the stan- tracking runs with each of the three tvpes of moving target. The third

OVRhyp, Scramjet Test Aircraft

NASA Technical Reports Server (NTRS)

Aslan, J.; Bisard, T.; Dallinga, S.; Draper, K.; Hufford, G.; Peters, W.; Rogers, J.

1990-01-01

A preliminary design for an unmanned hypersonic research vehicle to test scramjet engines is presented. The aircraft will be launched from a carrier aircraft at an altitude of 40,000 feet at Mach 0.8. The vehicle will then accelerate to Mach 6 at an altitude of 100,000 feet. At this stage the prototype scramjet will be employed to accelerate the vehicle to Mach 10 and maintain Mach 10 flight for 2 minutes. The aircraft will then decelerate and safely land.

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

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.

Ditching Investigation of a 1/12-Scale Model of the Douglas F4D-1 Airplane, TED No. NACA DE 384

NASA Technical Reports Server (NTRS)

Windham, John O.

1956-01-01

A ditching investigation was made of a l/l2-scale dynamically similar model of the Douglas F4D-1 airplane to study its behavior when ditched. The model was landed in calm water at the Langley tank no. 2 monorail. Various landing attitudes, speeds, and configurations were investigated. The behavior of the model was determined from visual observations, acceleration records, and motion-picture records of the ditchings. Data are presented in tables, sequence photographs, time-history acceleration curves, and attitude curves. From the results of the investigation, it was concluded that the airplane should be ditched at the lowest speed and highest attitude consistent with adequate control (near 22 deg) with landing gear retracted. In a calm-water ditching under these conditions the airplane will probably nose in slightly, then make a fairly smooth run. The fuselage bottom will sustain appreciable damage so that rapid flooding and short flotation time are likely. Maximum longitudinal deceleration will be about 4g and maximum normal acceleration will be about 6g in a landing run of about 420 feet, In a calm-water ditching under similar conditions with the landing gear extended, the airplane will probably dive. Maximum longitudinal decelerations will be about 5-1/2g and maximum normal accelerations will be about 3-1/2g in a landing run of about 170 feet.

Evolution of non-interacting entropic dark energy and its phantom nature

NASA Astrophysics Data System (ADS)

Mathew, Titus K.; Murali, Chinthak; Shejeelammal, J.

2016-04-01

Assuming the form of the entropic dark energy (EDE) as it arises from the surface term in the Einstein-Hilbert’s action, its evolution was analyzed in an expanding flat universe. The model parameters were evaluated by constraining the model using the Union data on Type Ia supernovae. We found that in the non-interacting case, the model predicts an early decelerated phase and a later accelerated phase at the background level. The evolutions of the Hubble parameter, dark energy (DE) density, equation of state parameter and deceleration parameter were obtained. The model hardly seems to be supporting the linear perturbation growth for the structure formation. We also found that the EDE shows phantom nature for redshifts z < 0.257. During the phantom epoch, the model predicts big rip effect at which both the scale factor of expansion and the DE density become infinitely large and the big rip time is found to be around 36 Giga years from now.

Acceleration or deceleration of self-motion by the Marangoni effect

NASA Astrophysics Data System (ADS)

Matsuda, Yui; Suematsu, Nobuhiko J.; Kitahata, Hiroyuki; Ikura, Yumihiko S.; Nakata, Satoshi

2016-06-01

We investigated the water-depth dependence of the self-motion of a camphor disk and camphor boat. With increasing water depth, the speed of motion of the camphor disk increased, but that of the camphor boat decreased in an annular one-dimensional system. We discussed the difference in the water-depth dependence of the speed of the camphor objects in relation to Marangoni flow. We concluded that Marangoni flow, which became stronger with increasing the water depth, positively and negatively affected the speed of the disk and boat, respectively.

NSEG, a segmented mission analysis program for low and high speed aircraft. Volume 1: Theoretical development

NASA Technical Reports Server (NTRS)

Hague, D. S.; Rozendaal, H. L.

1977-01-01

A rapid mission analysis code based on the use of approximate flight path equations of motion is presented. Equation form varies with the segment type, for example, accelerations, climbs, cruises, descents, and decelerations. Realistic and detailed characteristics were specified in tabular form. The code also contains extensive flight envelope performance mapping capabilities. Approximate take off and landing analyses were performed. At high speeds, centrifugal lift effects were accounted for. Extensive turbojet and ramjet engine scaling procedures were incorporated in the code.

Computation of laminar heat transfer from gaseous plasmas in electromagnetic fields

NASA Technical Reports Server (NTRS)

Bose, T. K.

1972-01-01

Heat transfer analysis procedure is presented for two-temperature gaseous plasma. Analysis is based on laminar flow of singly-ionized, quasineutral plasma with variable properties. Sheath analysis is described for species in accelerating field, decelerating field, emitted from wall, and recombining at wall.

Driving simulator study of J-Turn acceleration/deceleration lane and U-turn spacing.

DOT National Transportation Integrated Search

2016-11-01

Carlos Sun : http://orcid.org/0000-0002-8857-9648 : The J-turn, also known as RCUT (Restricted Crossing U-Turn) and Superstreet, is an innovative geometric design that can improve intersection safety. Even though this design has been in use in severa...

Interaction of reflected ions with the firehose marginally stable current sheet - Implications for plasma sheet convection

NASA Technical Reports Server (NTRS)

Pritchett, P. L.; Coroniti, F. V.

1992-01-01

The firehose marginally stable current sheet, which may model the flow away from the distant reconnection neutral line, assumes that the accelerated particles escape and never return to re-encounter the current region. This assumption fails on the earthward side where the accelerated ions mirror in the geomagnetic dipole field and return to the current sheet at distances up to about 30 R(E) down the tail. Two-dimensional particle simulations are used to demonstrate that the reflected ions drive a 'shock-like' structure in which the incoming flow is decelerated and the Bz field is highly compressed. These effects are similar to those produced by adiabatic choking of steady convection. Possible implications of this interaction for the dynamics of the tail are considered.

Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

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

Velikovich, A. L.; Schmit, P. F.

Bell-Plesset (BP) effects account for the influence of global convergence or divergence of the fluid flow on the evolution of the interfacial perturbations embedded in the flow. The development of the Rayleigh-Taylor instability in radiation-driven spherical capsules and magnetically-driven cylindrical liners necessarily includes a significant contribution from BP effects due to the time dependence of the radius, velocity, and acceleration of the unstable surfaces or interfaces. An analytical model is presented that, for an ideal incompressible fluid and small perturbation amplitudes, exactly evaluates the BP effects in finite-thickness shells through acceleration and deceleration phases. The time-dependent dispersion equations determining themore » “instantaneous growth rate” are derived. It is demonstrated that by integrating this approximate growth rate over time, one can accurately evaluate the number of perturbation e-foldings during the inward acceleration phase of the implosion. In the limit of small shell thickness, exact thin-shell perturbation equations and approximate thin-shell dispersion equations are obtained, generalizing the earlier results [E. G. Harris, Phys. Fluids 5, 1057 (1962); E. Ott, Phys. Rev. Lett. 29, 1429 (1972); A. B. Bud'ko et al., Phys. Fluids B 2, 1159 (1990)].« less

Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

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

Velikovich, A. L.; Schmit, P. F.

Bell-Plesset (BP) effects account for the influence of global convergence or divergence of the fluid flow on the evolution of the interfacial perturbations embedded in the flow. The development of the Rayleigh-Taylor instability in radiation-driven spherical capsules and magnetically-driven cylindrical liners necessarily includes a significant contribution from BP effects due to the time dependence of the radius, velocity, and acceleration of the unstable surfaces or interfaces. An analytical model is presented that, for an ideal incompressible fluid and small perturbation amplitudes, exactly evaluates the BP effects in finite-thickness shells through acceleration and deceleration phases. The time-dependent dispersion equations determining themore » “instantaneous growth rate” are derived. It is demonstrated that by integrating this approximate growth rate over time, one can accurately evaluate the number of perturbation e-foldings during the inward acceleration phase of the implosion. As a result, in the limit of small shell thickness, exact thin-shell perturbationequations and approximate thin-shell dispersion equations are obtained, generalizing the earlier results [E. G. Harris, Phys. Fluids 5, 1057 (1962); E. Ott, Phys. Rev. Lett. 29, 1429 (1972); A. B. Bud'ko et al., Phys. Fluids B 2, 1159 (1990)].« less

Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

DOE PAGES

Velikovich, A. L.; Schmit, P. F.

2015-12-28

Bell-Plesset (BP) effects account for the influence of global convergence or divergence of the fluid flow on the evolution of the interfacial perturbations embedded in the flow. The development of the Rayleigh-Taylor instability in radiation-driven spherical capsules and magnetically-driven cylindrical liners necessarily includes a significant contribution from BP effects due to the time dependence of the radius, velocity, and acceleration of the unstable surfaces or interfaces. An analytical model is presented that, for an ideal incompressible fluid and small perturbation amplitudes, exactly evaluates the BP effects in finite-thickness shells through acceleration and deceleration phases. The time-dependent dispersion equations determining themore » “instantaneous growth rate” are derived. It is demonstrated that by integrating this approximate growth rate over time, one can accurately evaluate the number of perturbation e-foldings during the inward acceleration phase of the implosion. As a result, in the limit of small shell thickness, exact thin-shell perturbationequations and approximate thin-shell dispersion equations are obtained, generalizing the earlier results [E. G. Harris, Phys. Fluids 5, 1057 (1962); E. Ott, Phys. Rev. Lett. 29, 1429 (1972); A. B. Bud'ko et al., Phys. Fluids B 2, 1159 (1990)].« less

Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

NASA Astrophysics Data System (ADS)

Velikovich, A. L.; Schmit, P. F.

2015-12-01

Bell-Plesset (BP) effects account for the influence of global convergence or divergence of the fluid flow on the evolution of the interfacial perturbations embedded in the flow. The development of the Rayleigh-Taylor instability in radiation-driven spherical capsules and magnetically-driven cylindrical liners necessarily includes a significant contribution from BP effects due to the time dependence of the radius, velocity, and acceleration of the unstable surfaces or interfaces. An analytical model is presented that, for an ideal incompressible fluid and small perturbation amplitudes, exactly evaluates the BP effects in finite-thickness shells through acceleration and deceleration phases. The time-dependent dispersion equations determining the "instantaneous growth rate" are derived. It is demonstrated that by integrating this approximate growth rate over time, one can accurately evaluate the number of perturbation e-foldings during the inward acceleration phase of the implosion. In the limit of small shell thickness, exact thin-shell perturbation equations and approximate thin-shell dispersion equations are obtained, generalizing the earlier results [E. G. Harris, Phys. Fluids 5, 1057 (1962); E. Ott, Phys. Rev. Lett. 29, 1429 (1972); A. B. Bud'ko et al., Phys. Fluids B 2, 1159 (1990)].

Effects of deceleration and rate of deceleration on live seated human subjects

DOT National Transportation Integrated Search

1977-10-01

This report describes the testing of live, seated human subjects to determine : the maximum deceleration and associated rate of change of deceleration (jerk) at : which the majority of potential users of automated guideway transportation (ACT) : syst...

How Do Changes in Speed Affect the Perception of Duration?

ERIC Educational Resources Information Center

Matthews, William J.

2011-01-01

Six experiments investigated how changes in stimulus speed influence subjective duration. Participants saw rotating or translating shapes in three conditions: constant speed, accelerating motion, and decelerating motion. The distance moved and average speed were the same in all three conditions. In temporal judgment tasks, the constant-speed…

Fetal Cardiac Responding: Maturational and Behavioral Correlates.

ERIC Educational Resources Information Center

Emory, Eugene K.; Noonan, John R.

1984-01-01

Classified fetuses as accelerators or decelerators based on intrapartum fetal heart rate (FHR). Explored the relationship of the classification with gestational age and neonatal behavior in clinically healthy neonates to provide an empirical basis for using FHR in the study of infant behavior. Subjects were 48 "healthy term" or…

Abusive Head Trauma: A Perpetrator Confesses

ERIC Educational Resources Information Center

Bell, Erica; Shouldice, Michelle; Levin, Alex V.

2011-01-01

Objectives: To present a detailed confession from a perpetrator of Shaken Baby syndrome. Methods: Case study. Results: We present a confession of Shaken Baby syndrome describing how the perpetrator severely injured a 3 year old with repeated bursts of acceleration-deceleration (shaking). The child sustained retinal and intracranial hemorrhage.…

49 CFR 325.39 - Measurement procedure; highway operations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... shall be made of the sound level generated by a motor vehicle operating through the measurement area on..., acceleration or deceleration. (b) The sound level generated by the motor vehicle is the highest reading observed on the sound level measurement system as the vehicle passes through the measurement area...

49 CFR 325.39 - Measurement procedure; highway operations.

Code of Federal Regulations, 2011 CFR

2011-10-01

... shall be made of the sound level generated by a motor vehicle operating through the measurement area on..., acceleration or deceleration. (b) The sound level generated by the motor vehicle is the highest reading observed on the sound level measurement system as the vehicle passes through the measurement area...

Suppression of the chain nuclear fusion reaction based on the p+{sup 11}B reaction because of the deceleration of alpha particles

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

Shmatov, M. L., E-mail: M.Shmatov@mail.ioffe.ru

2016-09-15

It is shown that a rapid deceleration of alpha particles in matter of electron temperature up to 100 keV leads a strong suppression of the chain nuclear fusion reaction on the basis of the p+{sup 11}B reaction with the reproduction of fast protons in the α+{sup 11}B and n+{sup 10}B reactions. The statement that the chain nuclear fusion reaction based on the p+{sup 11}B reaction with an acceleration of {sup 11}B nuclei because of elastic alpha-particle scattering manifests itself in experiments at the PALS (Prague Asterix Laser System) facility is analyzed.

Activation of Neck and Low-Back Muscles Is Reduced with the Use of a Neck Balance System Together with a Lumbar Support in Urban Drivers.

PubMed

Menotti, Federica; Labanca, Luciana; Laudani, Luca; Giombini, Arrigo; Pigozzi, Fabio; Macaluso, Andrea

2015-01-01

Driving is associated with high activation of low-back and neck muscles due to the sitting position and perturbations imposed by the vehicle. The aim of this study was to investigate the use of a neck balance system together with a lumbar support on the activation of low-back and neck muscles during driving. Twelve healthy male subjects (age 32±6.71 years) were asked to drive in two conditions: 1) with devices; 2) without devices. During vehicle accelerations and decelerations root mean square (RMS) of surface electromyography (sEMG) was recorded from the erector spinae, semispinalis capitis and sternocleidomastoid muscles and expressed as a percentage of maximal voluntary contraction (MVC). The pitch of the head was obtained by means of an inertial sensor placed on the subjects' head. A visual analog scale (VAS) was used to assess the level of perceived comfort. RMS of the low back muscles was lower with than without devices during both acceleration and deceleration of the vehicle (1.40±0.93% vs 29 2.32±1.90% and 1.88±1.45% vs 2.91±2.33%, respectively), while RMS of neck extensor muscles was reduced only during acceleration (5.18±1.96% vs 5.91±2.16%). There were no differences between the two conditions in RMS of neck flexor muscles, the pitch of the head and the VAS score. The use of these two ergonomic devices is therefore effective in reducing the activation of low-back and neck muscles during driving with no changes in the level of perceived comfort, which is likely due to rebalancing weight on the neck and giving a neutral position to lumbar segments.

Activity profile of high-level Australian lacrosse players.

PubMed

Polley, Chris S; Cormack, Stuart J; Gabbett, Tim J; Polglaze, Ted

2015-01-01

Despite lacrosse being one of the fastest growing team sports in the world, there is a paucity of information detailing the activity profile of high-level players. Microtechnology systems (global positioning systems and accelerometers) provide the opportunity to obtain detailed information on the activity profile in lacrosse. Therefore, this study aimed to analyze the activity profile of lacrosse match-play using microtechnology. Activity profile variables assessed relative to minutes of playing time included relative distance (meter per minute), distance spent standing (0-0.1 m·min), walking (0.2-1.7 m·min), jogging (1.8-3.2 m·min), running (3.3-5.6 m·min), sprinting (≥5.7 m·min), number of high, moderate, low accelerations and decelerations, and player load (PL per minute), calculated as the square root of the sum of the squared instantaneous rate of change in acceleration in 3 vectors (medio-lateral, anterior-posterior, and vertical). Activity was recorded from 14 lacrosse players over 4 matches during a national tournament. Players were separated into positions of attack, midfield, or defense. Differences (effect size [ES] ± 90% confidence interval) between positions and periods of play were considered likely positive when there was ≥75% likelihood of the difference exceeding an ES threshold of 0.2. Midfielders had likely covered higher (mean ± SD) meters per minute (100 ± 11) compared with attackers (87 ± 14; ES = 0.89 ± 1.04) and defenders (79 ± 14; ES = 1.54 ± 0.94) and more moderate and high accelerations and decelerations. Almost all variables across positions were reduced in quarter 4 compared with quarter 1. Coaches should accommodate for positional differences when preparing lacrosse players for competition.

Coronary Physiology During Exercise and Vasodilation in the Healthy Heart and in Severe Aortic Stenosis.

PubMed

Lumley, Matthew; Williams, Rupert; Asrress, Kaleab N; Arri, Satpal; Briceno, Natalia; Ellis, Howard; Rajani, Ronak; Siebes, Maria; Piek, Jan J; Clapp, Brian; Redwood, Simon R; Marber, Michael S; Chambers, John B; Perera, Divaka

2016-08-16

Severe aortic stenosis (AS) can manifest as exertional angina even in the presence of unobstructed coronary arteries. The authors describe coronary physiological changes during exercise and hyperemia in the healthy heart and in patients with severe AS. Simultaneous intracoronary pressure and flow velocity recordings were made in unobstructed coronary arteries of 22 patients with severe AS (mean effective orifice area 0.7 cm(2)) and 38 controls, at rest, during supine bicycle exercise, and during hyperemia. Stress echocardiography was performed to estimate myocardial work. Wave intensity analysis was used to quantify waves that accelerate and decelerate coronary blood flow (CBF). Despite a greater myocardial workload in AS patients compared with controls at rest (12,721 vs. 9,707 mm Hg/min(-1); p = 0.003) and during exercise (27,467 vs. 20,841 mm Hg/min(-1); p = 0.02), CBF was similar in both groups. Hyperemic CBF was less in AS compared with controls (2,170 vs. 2,716 cm/min(-1); p = 0.05). Diastolic time fraction was greater in AS compared with controls, but minimum microvascular resistance was similar. With exercise and hyperemia, efficiency of perfusion improved in the healthy heart, demonstrated by an increase in the relative contribution of accelerating waves. By contrast, in AS, perfusion efficiency decreased due to augmentation of early systolic deceleration and an attenuated rise in systolic acceleration waves. Invasive coronary physiological evaluation can be safely performed during exercise and hyperemia in patients with severe aortic stenosis. Ischemia in AS is not related to microvascular disease; rather, it is driven by abnormal cardiac-coronary coupling. Copyright © 2016 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

An accelerometry-based comparison of 2 robotic assistive devices for treadmill training of gait.

PubMed

Regnaux, Jean-Philippe; Saremi, Kaveh; Marehbian, Jon; Bussel, Bernard; Dobkin, Bruce H

2008-01-01

Two commercial robotic devices, the Gait Trainer (GT) and the Lokomat (LOKO), assist task-oriented practice of walking. The gait patterns induced by these motor-driven devices have not been characterized and compared. A healthy participant chose the most comfortable gait pattern on each device and for treadmill (TM) walking at 1, 2 (maximum for the GT), and 3 km/h and over ground at similar speeds. A system of accelerometers on the thighs and feet allowed the calculation of spatiotemporal features and accelerations during the gait cycle. At the 1 and 2 km/h speed settings, single-limb stance times were prolonged on the devices compared with overground walking. Differences on the LOKO were decreased by adjusting the hip and knee angles and step length. At the 3 km/h setting, the LOKO approximated the participant's overground parameters. Irregular accelerations and decelerations from toe-off to heel contact were induced by the devices, especially at slower speeds. The LOKO and GT impose mechanical constraints that may alter leg accelerations-decelerations during stance and swing phases, as well as stance duration, especially at their slower speed settings, that are not found during TM and overground walking. The potential impact of these perturbations on training to improve gait needs further study.

Seismic evidence for complex sedimentary control of Greenland Ice Sheet flow

PubMed Central

Kulessa, Bernd; Hubbard, Alun L.; Booth, Adam D.; Bougamont, Marion; Dow, Christine F.; Doyle, Samuel H.; Christoffersen, Poul; Lindbäck, Katrin; Pettersson, Rickard; Fitzpatrick, Andrew A. W.; Jones, Glenn A.

2017-01-01

The land-terminating margin of the Greenland Ice Sheet has slowed down in recent decades, although the causes and implications for future ice flow are unclear. Explained originally by a self-regulating mechanism where basal slip reduces as drainage evolves from low to high efficiency, recent numerical modeling invokes a sedimentary control of ice sheet flow as an alternative hypothesis. Although both hypotheses can explain the recent slowdown, their respective forecasts of a long-term deceleration versus an acceleration of ice flow are contradictory. We present amplitude-versus-angle seismic data as the first observational test of the alternative hypothesis. We document transient modifications of basal sediment strengths by rapid subglacial drainages of supraglacial lakes, the primary current control on summer ice sheet flow according to our numerical model. Our observations agree with simulations of initial postdrainage sediment weakening and ice flow accelerations, and subsequent sediment restrengthening and ice flow decelerations, and thus confirm the alternative hypothesis. Although simulated melt season acceleration of ice flow due to weakening of subglacial sediments does not currently outweigh winter slowdown forced by self-regulation, they could dominate over the longer term. Subglacial sediments beneath the Greenland Ice Sheet must therefore be mapped and characterized, and a sedimentary control of ice flow must be evaluated against competing self-regulation mechanisms. PMID:28835915

Seismic evidence for complex sedimentary control of Greenland Ice Sheet flow.

PubMed

Kulessa, Bernd; Hubbard, Alun L; Booth, Adam D; Bougamont, Marion; Dow, Christine F; Doyle, Samuel H; Christoffersen, Poul; Lindbäck, Katrin; Pettersson, Rickard; Fitzpatrick, Andrew A W; Jones, Glenn A

2017-08-01

The land-terminating margin of the Greenland Ice Sheet has slowed down in recent decades, although the causes and implications for future ice flow are unclear. Explained originally by a self-regulating mechanism where basal slip reduces as drainage evolves from low to high efficiency, recent numerical modeling invokes a sedimentary control of ice sheet flow as an alternative hypothesis. Although both hypotheses can explain the recent slowdown, their respective forecasts of a long-term deceleration versus an acceleration of ice flow are contradictory. We present amplitude-versus-angle seismic data as the first observational test of the alternative hypothesis. We document transient modifications of basal sediment strengths by rapid subglacial drainages of supraglacial lakes, the primary current control on summer ice sheet flow according to our numerical model. Our observations agree with simulations of initial postdrainage sediment weakening and ice flow accelerations, and subsequent sediment restrengthening and ice flow decelerations, and thus confirm the alternative hypothesis. Although simulated melt season acceleration of ice flow due to weakening of subglacial sediments does not currently outweigh winter slowdown forced by self-regulation, they could dominate over the longer term. Subglacial sediments beneath the Greenland Ice Sheet must therefore be mapped and characterized, and a sedimentary control of ice flow must be evaluated against competing self-regulation mechanisms.

Crash pulse optimization for occupant protection at various impact velocities.

PubMed

Ito, Daisuke; Yokoi, Yusuke; Mizuno, Koji

2015-01-01

Vehicle deceleration has a large influence on occupant kinematic behavior and injury risks in crashes, and the optimization of the vehicle crash pulse that mitigates occupant loadings has been the subject of substantial research. These optimization research efforts focused on only high-velocity impact in regulatory or new car assessment programs though vehicle collisions occur over a wide range of velocities. In this study, the vehicle crash pulse was optimized for various velocities with a genetic algorithm. Vehicle deceleration was optimized in a full-frontal rigid barrier crash with a simple spring-mass model that represents the vehicle-occupant interaction and a Hybrid III 50th percentile male multibody model. To examine whether the vehicle crash pulse optimized at the high impact velocity is useful for reducing occupant loading at all impact velocities less than the optimized velocity, the occupant deceleration was calculated at various velocities for the optimized crash pulse determined at a high speed. The optimized vehicle deceleration-deformation characteristics that are effective for various velocities were investigated with 2 approaches. The optimized vehicle crash pulse at a single impact velocity consists of a high initial impulse followed by zero deceleration and then constant deceleration in the final stage. The vehicle deceleration optimized with the Hybrid III model was comparable to that determined from the spring-mass model. The optimized vehicle deceleration-deformation characteristics determined at a high speed did not necessarily lead to an occupant deceleration reduction at a lower velocity. The maximum occupant deceleration at each velocity was normalized by the maximum deceleration determined in the single impact velocity optimization. The resulting vehicle deceleration-deformation characteristic was a square crash pulse. The objective function was defined as the number of injuries, which was the product of the number of collisions at the velocity and the probability of occupant injury. The optimized vehicle deceleration consisted of a high deceleration in the initial phase, a small deceleration in the middle phase, and then a high deceleration in the final phase. The optimized vehicle crash pulse at a single impact velocity is effective for reducing occupant deceleration in a crash at the specific impact velocity. However, the crash pulse does not necessarily lead to occupant deceleration reduction at a lower velocity. The optimized vehicle deceleration-deformation characteristics, which are effective for all impact velocities, depend on the weighting of the occupant injury measures at each impact velocity.

Magnetized string cosmological models of accelerated expansion of the Universe in f(R,T) theory of gravity

NASA Astrophysics Data System (ADS)

Pradhan, Anirudh; Jaiswal, Rekha

A class of spatially homogeneous and anisotropic Bianchi-V massive string models have been studied in the modified f(R,T)-theory of gravity proposed by Harko et al. [Phys. Rev. D 84:024020, 2011] in the presence of magnetic field. For a specific choice of f(R,T)=f1(R) + f2(T), where f1(R) = ν1R and f2(T) = ν2T; ν1, ν2 being arbitrary parameters, solutions of modified gravity field equations have been generated. To find the deterministic solution of the field equations, we have considered the time varying deceleration parameter which is consistent with observational data of standard cosmology (SNIa, BAO and CMB). As a result to study the transit behavior of Universe, we consider a law of variation for the specifically chosen scale factor, which yields a time-dependent deceleration parameter comprising a class of models that depicts a transition of the Universe from the early decelerated phase to the recent accelerating phase. In this context, for the model of the Universe, the field equations are solved and corresponding cosmological aspects have been discussed. The Energy conditions in this modified gravity theory are also studied. Stability analysis of the solutions through cosmological perturbation is performed and it is concluded that the expanding solution is stable against the perturbation with respect to anisotropic spatial direction. Some physical and geometric properties of the models are also discussed.

The properties of fast and slow oblique solitons in a magnetized plasma

NASA Astrophysics Data System (ADS)

McKenzie, J. F.; Doyle, T. B.

2002-01-01

This work builds on a recent treatment by McKenzie and Doyle [Phys. Plasmas 8, 4367 (2001)], on oblique solitons in a cold magnetized plasma, to include the effects of plasma thermal pressure. Conservation of total momentum in the direction of wave propagation immediately shows that if the flow is supersonic, compressive (rarefactive) changes in the magnetic pressure induce decelerations (accelerations) in the flow speed, whereas if the flow is subsonic, compressive (rarefactive) changes in the magnetic pressure induce accelerations (decelerations) in the flow speed. Such behavior is characteristic of a Bernoulli-type plasma momentum flux which exhibits a minimum at the plasma sonic point. The plasma energy flux (kinetic plus enthalpy) also shows similar Bernoulli-type behavior. This transonic effect is manifest in the spatial structure equation for the flow speed (in the direction of propagation) which shows that soliton structures may exist if the wave speed lies either (i) in the range between the fast and Alfven speeds or (ii) between the sound and slow mode speed. These conditions follow from the requirement that a defined, characteristic "soliton parameter" m exceeds unity. It is in this latter slow soliton regime that the effects of plasma pressure are most keenly felt. The equilibrium points of the structure equation define the center of the wave. The structure of both fast and slow solitons is elucidated through the properties of the energy integral function of the structure equation. In particular, the slow soliton, which owes its existence to plasma pressure, may have either a compressive or rarefactive nature, and exhibits a rich structure, which is revealed through the spatial structure of the longitudinal speed and its corresponding transverse velocity hodograph.

Effect of Solar Wind Drag on the Determination of the Properties of Coronal Mass Ejections from Heliospheric Images

NASA Astrophysics Data System (ADS)

Lugaz, N.; Kintner, P.

2013-07-01

The Fixed-Φ (FΦ) and Harmonic Mean (HM) fitting methods are two methods to determine the "average" direction and velocity of coronal mass ejections (CMEs) from time-elongation tracks produced by Heliospheric Imagers (HIs), such as the HIs onboard the STEREO spacecraft. Both methods assume a constant velocity in their descriptions of the time-elongation profiles of CMEs, which are used to fit the observed time-elongation data. Here, we analyze the effect of aerodynamic drag on CMEs propagating through interplanetary space, and how this drag affects the result of the FΦ and HM fitting methods. A simple drag model is used to analytically construct time-elongation profiles which are then fitted with the two methods. It is found that higher angles and velocities give rise to greater error in both methods, reaching errors in the direction of propagation of up to 15∘ and 30∘ for the FΦ and HM fitting methods, respectively. This is due to the physical accelerations of the CMEs being interpreted as geometrical accelerations by the fitting methods. Because of the geometrical definition of the HM fitting method, it is more affected by the acceleration than the FΦ fitting method. Overall, we find that both techniques overestimate the initial (and final) velocity and direction for fast CMEs propagating beyond 90∘ from the Sun-spacecraft line, meaning that arrival times at 1 AU would be predicted early (by up to 12 hours). We also find that the direction and arrival time of a wide and decelerating CME can be better reproduced by the FΦ due to the cancelation of two errors: neglecting the CME width and neglecting the CME deceleration. Overall, the inaccuracies of the two fitting methods are expected to play an important role in the prediction of CME hit and arrival times as we head towards solar maximum and the STEREO spacecraft further move behind the Sun.

Circulation patterns in active lava lakes

NASA Astrophysics Data System (ADS)

Redmond, T. C.; Lev, E.

2014-12-01

Active lava lakes provide a unique window into magmatic conduit processes. We investigated circulation patterns of 4 active lava lakes: Kilauea's Halemaumau crater, Mount Erebus, Erta Ale and Nyiragongo, and in an artificial "lava lake" constructed at the Syracuse University Lava Lab. We employed visual and thermal video recordings collected at these volcanoes and use computer vision techniques to extract time-dependent, two-dimensional surface velocity maps. The large amount of data available from Halemaumau enabled us to identify several characteristic circulation patterns. One such pattern is a rapid acceleration followed by rapid deceleration, often to a level lower than the pre-acceleration level, and then a slow recovery. Another pattern is periodic asymmetric peaks of gradual acceleration and rapid deceleration, or vice versa, previously explained by gas pistoning. Using spectral analysis, we find that the dominant period of circulation cycles at approximately 30 minutes, 3 times longer than the dominant period identified previously for Mount Erebus. Measuring a complete surface velocity field allowed us to map and follow locations of divergence and convergence, therefore upwelling and downwelling, thus connecting the surface flow with that at depth. At Nyiragongo, the location of main upwelling shifts gradually, yet is usually at the interior of the lake, for Erebus it is usually along the perimeter yet often there is catastrophic downwelling at the interior; For Halemaumau upwelling/downwelling position is almost always on the perimeter. In addition to velocity fields, we developed an automated tool for counting crustal plates at the surface of the lava lakes, and found a correlation, and a lag time, between changes if circulation vigor and the average size of crustal plates. Circulation in the artificial basaltic lava "lake" was limited by its size and degree of foaming, yet we measured surface velocities and identify patterns. Maximum surface velocity showed symmetrical peaks of acceleration and deceleration. In summary, extended observations at lava lakes reveal patterns of circulations at different time scales, yielding insight into different processes controlling the exchange of gas and fluids between the magma chamber and conduit, and the surface and atmosphere.

Kick processes in the merger of two colliding black holes

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

Aranha, R. F.; Soares, I. Damiao; Tonini, E. V.

2010-11-15

We examine numerically the process of momentum extraction by gravitational waves in the merger of two colliding black holes, in the realm of Robinson-Trautman spacetimes. The initial data have already a common horizon so that the evolution covers the post-merger phase up to the final configuration of the remnant black hole. The analysis of the momentum flux carried out by gravitational waves indicates that two distinct regimes are present in the post-merger phase: (i) an initial accelerated regime, followed by (ii) a deceleration regime in which the deceleration increases rapidly towards a maximum and then decreases to zero, when themore » gravitational wave emission ceases. The analysis is based on the Bondi-Sachs conservation law for the total momentum of the system. We obtain the total kick velocity V{sub k} imparted on the merged black hole during the accelerated regime (i) and the total antikick velocity V{sub ak} during the decelerated regime (ii), by evaluating the impulse of the gravitational wave flux during both regimes. The distributions of both V{sub k} and V{sub ak} as a function of the symmetric mass ratio {eta} satisfy a simple {eta}-scaling law motivated by post-Newtonian analytical estimates. In the {eta}-scaling formula the Newtonian factor is dominant in the decelerated regime, that generates V{sub ak}, contrary to the behavior in the initial accelerated regime. For an initial infalling velocity v/c{approx_equal}0.462 of each individual black hole we obtain a maximum kick V{sub k{approx_equal}}6.4 km/s at {eta}{approx_equal}0.209, and a maximum antikick V{sub ak{approx_equal}}109 km/s at {eta}{approx_equal}0.205. The net antikick velocity (V{sub ak}-V{sub k}) also satisfies a similar {eta}-scaling law with a maximum approximately 102 km/s also at {eta}{approx_equal}0.205, qualitatively consistent with results from numerical relativity simulations, and post-Newtonian evaluations of binary black hole inspirals. For larger values of the initial data parameter v/c substantial larger values of the net antikick velocity are obtained. Based on the several velocity variables obtained, we discuss a possible definition of the center-of-mass motion of the merged system.« less

Time-varying changes in the simulated structure of the Brewer-Dobson Circulation

NASA Astrophysics Data System (ADS)

Garfinkel, Chaim I.; Aquila, Valentina; Waugh, Darryn W.; Oman, Luke D.

2017-01-01

A series of simulations using the NASA Goddard Earth Observing System Chemistry Climate Model are analyzed in order to assess changes in the Brewer-Dobson Circulation (BDC) over the past 55 years. When trends are computed over the past 55 years, the BDC accelerates throughout the stratosphere, consistent with previous modeling results. However, over the second half of the simulations (i.e., since the late 1980s), the model simulates structural changes in the BDC as the temporal evolution of the BDC varies between regions in the stratosphere. In the mid-stratosphere in the midlatitude Northern Hemisphere, the BDC does not accelerate in the ensemble mean of our simulations despite increases in greenhouse gas concentrations and warming sea surface temperatures, and it even decelerates in one ensemble member. This deceleration is reminiscent of changes inferred from satellite instruments and in situ measurements. In contrast, the BDC in the lower stratosphere continues to accelerate. The main forcing agents for the recent slowdown in the mid-stratosphere appear to be declining ozone-depleting substance (ODS) concentrations and the timing of volcanic eruptions. Changes in both mean age of air and the tropical upwelling of the residual circulation indicate a lack of recent acceleration. We therefore clarify that the statement that is often made that climate models simulate a decreasing age throughout the stratosphere only applies over long time periods and is not necessarily the case for the past 25 years, when most tracer measurements were taken.

Time-Varying Changes in the Simulated Structure of the Brewer-Dobson Circulation

NASA Technical Reports Server (NTRS)

Garfinkel, Chaim I.; Aquila, Valentina; Waugh, Darryn W.; Oman, Luke D.

2017-01-01

A series of simulations using the NASA Goddard Earth Observing System Chemistry Climate Model are analyzed in order to assess changes in the Brewer-Dobson Circulation (BDC) over the past 55 years. When trends are computed over the past 55 years, the BDC accelerates throughout the stratosphere, consistent with previous modeling results. However, over the second half of the simulations (i.e., since the late 1980s), the model simulates structural changes in the BDC as the temporal evolution of the BDC varies between regions in the stratosphere. In the mid-stratosphere in the midlatitude Northern Hemisphere, the BDC does not accelerate in the ensemble mean of our simulations despite increases in greenhouse gas concentrations and warming sea surface temperatures, and it even decelerates in one ensemble member. This deceleration is reminiscent of changes inferred from satellite instruments and in situ measurements. In contrast, the BDC in the lower stratosphere continues to accelerate. The main forcing agents for the recent slowdown in the mid-stratosphere appear to be declining ozone-depleting substance (ODS) concentrations and the timing of volcanic eruptions. Changes in both mean age of air and the tropical upwelling of the residual circulation indicate a lack of recent acceleration. We therefore clarify that the statement that is often made that climate models simulate a decreasing age throughout the stratosphere only applies over long time periods and is not necessarily the case for the past 25 years, when most tracer measurements were taken.

A cellular automata traffic flow model for three-phase theory

NASA Astrophysics Data System (ADS)

Qian, Yong-Sheng; Feng, Xiao; Zeng, Jun-Wei

2017-08-01

This paper presents a newly-modified KKW model including the subdivided vehicles types, and introduces the changes for a driver's sensitivity into the speed fluctuation. By means of the numerical simulation the following conclusions are obtained herewith: 1. Velocity disturbance propagation in traffic flow is caused by the speed adaptation among vehicles. 2. In free flow phase, very fewer vehicles are affected by the velocity disturbance and the effect can be dissipated quickly thus the time of disturbance in a single vehicle is quite shorter. On the contrary, the impact duration time of the disturbance on a single vehicle is longer in synchronous flow phase, thus, it will affect more vehicles accordingly. 3. Under the free flow phase, the continuous deceleration behavior of a high speed vehicle to adapt the preceding car with slow speed can cause the reduction of the driver's sensitivity, lead to the vehicle over-deceleration and aggravate the effects of velocity perturbations While in the synchronous flow phase, though the reaction delay caused by the driver's sensitivity reduction can induce speed wave dissolving in essence, it increases the impact of disturbance on the traffic flow. 4. The large acceleration and deceleration tendency of an aggressive driver in the free flow phase always increase the influence of the velocity disturbance, while a conservative driver often weakens the influence. However, in the synchronized flow, since the high traffic density and the synchronization between vehicles is very strong, also the main factor which affects the driver's speed choice is the distance among vehicles, therefore the effect of a driver's behavior tendency to the spread of velocity perturbation is not obvious under this state.

Flight evaluation of advanced controls and displays for transition and landing on the NASA V/STOL systems research aircraft

NASA Technical Reports Server (NTRS)

Franklin, James A.; Stortz, Michael W.; Borchers, Paul F.; Moralez, Ernesto, III

1996-01-01

Flight experiments were conducted on Ames Research Center's V/STOL Systems Research Aircraft (VSRA) to assess the influence of advanced control modes and head-up displays (HUD's) on flying qualities for precision approach and landing operations. Evaluations were made for decelerating approaches to hover followed by a vertical landing and for slow landings for four control/display mode combinations: the basic YAV-8B stability augmentation system; attitude command for pitch, roll, and yaw; flightpath/acceleration command with translational rate command in the hover; and height-rate damping with translational-rate command. Head-up displays used in conjunction with these control modes provided flightpath tracking/pursuit guidance and deceleration commands for the decelerating approach and a mixed horizontal and vertical presentation for precision hover and landing. Flying qualities were established and control usage and bandwidth were documented for candidate control modes and displays for the approach and vertical landing. Minimally satisfactory bandwidths were determined for the translational-rate command system. Test pilot and engineer teams from the Naval Air Warfare Center, the Boeing Military Airplane Group, Lockheed Martin, McDonnell Douglas Aerospace, Northrop Grumman, Rolls-Royce, and the British Defense Research Agency participated in the program along with NASA research pilots from the Ames and Lewis Research Centers. The results, in conjunction with related ground-based simulation data, indicate that the flightpath/longitudinal acceleration command response type in conjunction with pursuit tracking and deceleration guidance on the HUD would be essential for operation to instrument minimums significantly lower than the minimums for the AV-8B. It would also be a superior mode for performing slow landings where precise control to an austere landing area such as a narrow road is demanded. The translational-rate command system would reduce pilot workload for demanding vertical landing tasks aboard ship and in confined land-based sites.

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.

The impact of surfactants on Fe(III)-TAML-catalyzed oxidations by peroxides: accelerations, decelerations, and loss of activity.

PubMed

Banerjee, Deboshri; Apollo, Frank M; Ryabov, Alexander D; Collins, Terrence J

2009-10-05

Iron(III) complexes of tetraamidato macrocyclic ligands (TAMLs), [Fe{4-XC(6)H(3)-1,2-(NCOCMe(2)NCO)(2)CR(2)}(OH(2))](-), 1 (1 a: X = H, R = Me; 1 b: X = COOH, R = Me); 1 c: X = CONH(CH(2))(2)COOH, R = Me; 1 d: CONH(CH(2))(2)NMe(2), R = Me; 1 e: X = CONH(CH(2))(2)NMe(3) (+), R = Me; 1 f: X = H, R = F), have been tested as catalysts for the oxidative decolorization of Orange II and Sudan III dyes by hydrogen peroxide and tert-butyl hydroperoxide in the presence of micelles that are neutral (Triton X-100), positively charged (cetyltrimethylammonium bromide, CTAB), and negatively charged (sodium dodecyl sulfate, SDS). The previously reported mechanism of catalysis involves the formation of an oxidized intermediate from 1 and ROOH (k(I)) followed by dye bleaching (k(II)). The micellar effects on k(I) and k(II) have been separately studied and analyzed by using the Berezin pseudophase model of micellar catalysis. The largest micellar acceleration in terms of k(I) occurs for the 1 a-tBuOOH-CTAB system. At pH 9.0-10.5 the rate constant k(I) increased by approximately five times with increasing CTAB concentration and then gradually decreased. There was no acceleration at higher pH, presumably owing to the deprotonation of the axial water ligand of 1 a in this pH range. The k(I) value was only slightly affected by SDS (in the oxidation of Orange II), but was strongly decelerated by Triton X-100. No oxidation of the water-insoluble, hydrophobic dye Sudan III was observed in the presence of the SDS micelles. The k(II) value was accelerated by cationic CTAB micelles when the hydrophobic primary oxidant tert-butyl hydroperoxide was used. It is hypothesized that tBuOOH may affect the CTAB micelles and increase the binding of the oxidized catalysts. The tBuOOH-CTAB combination accelerated both of the catalysis steps k(I) and k(II).

Beam deceleration for block-face scanning electron microscopy of embedded biological tissue.

PubMed

Ohta, Keisuke; Sadayama, Shoji; Togo, Akinobu; Higashi, Ryuhei; Tanoue, Ryuichiro; Nakamura, Kei-ichiro

2012-04-01

The beam deceleration (BD) method for scanning electron microscopes (SEM) also referred to as "retarding" was applied to back-scattered electron (BSE) imaging of the flat block face of a resin embedded biological specimen under low accelerating voltage and low beam current conditions. BSE imaging was performed with 0-4 kV of BD on en bloc stained rat hepatocyte. BD drastically enhanced the compositional contrast of the specimen and also improved the resolution at low landing energy levels (1.5-3 keV) and a low beam current (10 pA). These effects also functioned in long working distance observation, however, stage tilting caused uncorrectable astigmatism in BD observation. Stage tilting is mechanically required for a FIB/SEM, so we designed a novel specimen holder to minimize the unfavorable tilting effect. The FIB/SEM 3D reconstruction using the new holder showed a reasonable contrast and resolution high enough to analyze individual cell organelles and also the mitochondrial cristae structures (~5 nm) of the hepatocyte. These results indicate the advantages of BD for block face imaging of biological materials such as cells and tissues under low-voltage and low beam current conditions. Copyright © 2011 Elsevier Ltd. All rights reserved.

STUDY PROGRAM FOR TURBO-COOLER FOR PRODUCING ENGINE COOLING AIR.

DTIC Science & Technology

VANES , STAGNATION POINT, DECELERATION, ACCELERATION, SUPERSONIC DIFFUSERS, TURBINE BLADES , EVAPOTRANSPIRATION, LIQUID COOLED, HEAT TRANSFER, GAS BEARINGS, SEALS...HYPERSONIC AIRCRAFT , COOLING + VENTILATING EQUIPMENT), (*GAS TURBINES , COOLING + VENTILATING EQUIPMENT), HYPERSONIC FLOW, AIR COOLED, AIRCRAFT ... ENGINES , FEASIBILITY STUDIES, PRESSURE, SUPERSONIC CHARACTERISTICS, DESIGN, HEAT EXCHANGERS, COOLING (U) AXIAL FLOW TURBINES , DUCT INLETS, INLET GUIDE

Anisotropic Bianchi-V dark energy model under the new perspective of accelerated expansion of the universe in Brans-Dicke theory of gravitation

NASA Astrophysics Data System (ADS)

Jaiswal, Rekha; Zia, Rashid

2018-04-01

In this paper, we have proposed a cosmological model, which is consistent with the new findings of `The Supernova Cosmology project' headed by Saul Perlmutter, and the `High-Z Supernova Search team', headed by Brian Schimdt. According to these new findings, the universe is undergoing an expansion with an increasing rate, in contrast to the earlier belief that the rate of expansion is constant or the expansion is slowing down. We have considered spatially homogeneous and anisotropic Bianchi-V dark energy model in Brans-Dicke theory of gravitation. We have taken the scale factor a(t)=k t^α e^{β t} , which results into variable deceleration parameter (DP). The graph of DP shows a transition from positive to negative, which shows that universe has passed through the past decelerated expansion to the current accelerated expansion phase. In this context, we have also calculated and plotted various parameters and observed that these are in good agreement with physical and kinematic properties of the universe and are also consistent with recent observations.

Model and algorithm based on accurate realization of dwell time in magnetorheological finishing.

PubMed

Song, Ci; Dai, Yifan; Peng, Xiaoqiang

2010-07-01

Classically, a dwell-time map is created with a method such as deconvolution or numerical optimization, with the input being a surface error map and influence function. This dwell-time map is the numerical optimum for minimizing residual form error, but it takes no account of machine dynamics limitations. The map is then reinterpreted as machine speeds and accelerations or decelerations in a separate operation. In this paper we consider combining the two methods in a single optimization by the use of a constrained nonlinear optimization model, which regards both the two-norm of the surface residual error and the dwell-time gradient as an objective function. This enables machine dynamic limitations to be properly considered within the scope of the optimization, reducing both residual surface error and polishing times. Further simulations are introduced to demonstrate the feasibility of the model, and the velocity map is reinterpreted from the dwell time, meeting the requirement of velocity and the limitations of accelerations or decelerations. Indeed, the model and algorithm can also apply to other computer-controlled subaperture methods.

Project Longshot

NASA Technical Reports Server (NTRS)

West, J. Curtis; Chamberlain, Sally A.; Stevens, Robert; Pagan, Neftali

1989-01-01

Project Longshot is an unmanned probe to our nearest star system, Alpha Centauri, 4.3 light years away. The Centauri system is a trinary system consisting of two central stars (A and B) orbiting a barycenter, and a third (Proxima Centauri) orbiting the two. The system is a declination of -67 degrees. The goal is to reach the Centauri system in 50 years. This time space was chosen because any shorter time would be impossible of the relativistic velocities involved, and any greater time would be impossible because of the difficulty of creating a spacecraft with such a long lifetime. Therefore, the following mission profile is proposed: (1) spacecraft is assembled in Earth orbit; (2) spacecraft escapes Earth and Sun in the ecliptic with a single impulse maneuver; (3) spacecraft changed declination to point toward Centauri system; (4) spacecraft accelerates to 0.1c; (5) spacecraft coasts at 0.1c for 41 years; (6) spacecraft decelerates upon reaching Centauri system; and (7) spacecraft orbits Centauri system, conducts investigations, and relays data to Earth. The total time to reach the Centauri system, taking into consideration acceleration and deceleration, will be approximately 50 years.

Late time acceleration of the 3-space in a higher dimensional steady state universe in dilaton gravity

NASA Astrophysics Data System (ADS)

Akarsu, Özgür; Dereli, Tekin

2013-02-01

We present cosmological solutions for (1+3+n)-dimensional steady state universe in dilaton gravity with an arbitrary dilaton coupling constant w and exponential dilaton self-interaction potentials in the string frame. We focus particularly on the class in which the 3-space expands with a time varying deceleration parameter. We discuss the number of the internal dimensions and the value of the dilaton coupling constant to determine the cases that are consistent with the observed universe and the primordial nucleosynthesis. The 3-space starts with a decelerated expansion rate and evolves into accelerated expansion phase subject to the values of w and n, but ends with a Big Rip in all cases. We discuss the cosmological evolution in further detail for the cases w = 1 and w = ½ that permit exact solutions. We also comment on how the universe would be conceived by an observer in four dimensions who is unaware of the internal dimensions and thinks that the conventional general relativity is valid at cosmological scales.

Holographic Dark Energy in Brans-Dicke Theory with Logarithmic Form of Scalar Field

NASA Astrophysics Data System (ADS)

Singh, C. P.; Kumar, Pankaj

2017-10-01

In this paper, an interacting holographic dark energy model with Hubble horizon as an infra-red cut-off is considered in the framework of Brans-Dicke theory. We assume the Brans-Dicke scalar field as a logarithmic form ϕ = ϕ 0 l n( α + β a), where a is the scale factor, α and β are arbitrary constants, to interpret the physical phenomena of the Universe. The equation of state parameter w h and deceleration parameter q are obtained to discuss the dynamics of the evolution of the Universe. We present a unified model of holographic dark energy which explains the early time acceleration (inflation), medieval time deceleration and late time acceleration. It is also observed that w h may cross the phantom divide line in the late time evolution. We also discuss the cosmic coincidence problem. We obtain a time-varying density ratio of holographic dark energy to dark matter which is a constant of order one (r˜ O(1)) during early and late time evolution, and may evolve sufficiently slow at present time. Thus, the model successfully resolves the cosmic coincidence problem.

Effect of artificial gravity on thermoregulation, respiratory metabolism and intermediary metabolism of animals

NASA Technical Reports Server (NTRS)

Oyama, J.

1973-01-01

Metabolic alterations in animals exposed to radial acceleration are reported. Temperatures in acutely stressed animals dropped profoundly in correlation with decreased food consumption. Repeated exposure of the acutely stressed animal caused a decrease in hypothermic response whereas deceleration or reduction of G load did not significantly change body temperatures. Adrenal corticosteroids affected significantly the animal's recovery rate. No changes occured in body temperature patterns of chronically centrifuged animals after full adaptation; their respiratory rate increased very significantly in terms of CO2 output as did their glucose uptake by muscle tissues and their insulin responsiveness or sensitivity.

NSEG: A segmented mission analysis program for low and high speed aircraft. Volume 2: Program users manual

NASA Technical Reports Server (NTRS)

Hague, D. S.; Rozendaal, H. L.

1977-01-01

A rapid mission analysis code based on the use of approximate flight path equations of motion is described. Equation form varies with the segment type, for example, accelerations, climbs, cruises, descents, and decelerations. Realistic and detailed vehicle characteristics are specified in tabular form. In addition to its mission performance calculation capabilities, the code also contains extensive flight envelop performance mapping capabilities. Approximate take off and landing analyses can be performed. At high speeds, centrifugal lift effects are taken into account. Extensive turbojet and ramjet engine scaling procedures are incorporated in the code.

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

Properties of Asymmetric Detrended Fluctuation Analysis in the time series of RR intervals

NASA Astrophysics Data System (ADS)

Piskorski, J.; Kosmider, M.; Mieszkowski, D.; Krauze, T.; Wykretowicz, A.; Guzik, P.

2018-02-01

Heart rate asymmetry is a phenomenon by which the accelerations and decelerations of heart rate behave differently, and this difference is consistent and unidirectional, i.e. in most of the analyzed recordings the inequalities have the same directions. So far, it has been established for variance and runs based types of descriptors of RR intervals time series. In this paper we apply the newly developed method of Asymmetric Detrended Fluctuation Analysis, which so far has mainly been used with economic time series, to the set of 420 stationary 30 min time series of RR intervals from young, healthy individuals aged between 20 and 40. This asymmetric approach introduces separate scaling exponents for rising and falling trends. We systematically study the presence of asymmetry in both global and local versions of this method. In this study global means "applying to the whole time series" and local means "applying to windows jumping along the recording". It is found that the correlation structure of the fluctuations left over after detrending in physiological time series shows strong asymmetric features in both magnitude, with α+ <α-, where α+ is related to heart rate decelerations and α- to heart rate accelerations, and the proportion of the signal in which the above inequality holds. A very similar effect is observed if asymmetric noise is added to a symmetric self-affine function. No such phenomena are observed in the same physiological data after shuffling or with a group of symmetric synthetic time series.

Solar wind deceleration and MHD turbulence in the earth's foreshock region - ISEE 1 and 2 and IMP 8 observations

NASA Technical Reports Server (NTRS)

Bonifazi, C.; Moreno, G.; Russell, C. T.; Lazarus, A. J.; Sullivan, J. D.

1983-01-01

The interaction of the solar wind with ions backstreaming from the earth's bow shock is investigated using plasma and magnetic field measurements on ISEE 1 and 2 and IMP 8 at widely separated positions in the earth's foreshock. This technique separates temporal and spatial variations within the foreshock. It is found that the solar wind acceleration associated with backstreaming ions is correlated with the amplitude of the MHD turbulence, and that the largest decelerations are seen close to the bow shock. The density of the backstreaming ion beam is strongly correlated with distance from the shock, and decreases by about a factor of three in a distance of about 3R(e).

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

Lazkoz, Ruth; Escamilla-Rivera, Celia; Salzano, Vincenzo

Cosmography provides a model-independent way to map the expansion history of the Universe. In this paper we simulate a Euclid-like survey and explore cosmographic constraints from future Baryonic Acoustic Oscillations (BAO) observations. We derive general expressions for the BAO transverse and radial modes and discuss the optimal order of the cosmographic expansion that provides reliable cosmological constraints. Through constraints on the deceleration and jerk parameters, we show that future BAO data have the potential to provide a model-independent check of the cosmic acceleration as well as a discrimination between the standard ΛCDM model and alternative mechanisms of cosmic acceleration.

Dynamics of clade diversification on the morphological hypercube

PubMed Central

Gavrilets, S.

1999-01-01

Understanding the relationship between taxonomic and morphological changes is important in identifying the reasons for accelerated morphological diversification early in the history of animal phyla. Here, a simple general model describing the joint dynamics of taxonomic diversity and morphological disparity is presented and applied to the data on the diversification of blastozoans. I show that the observed patterns of deceleration in clade diversification can be explicable in terms of the geometric structure of the morphospace and the effects of extinction and speciation on morphological disparity without invoking major declines in the size of morphological transitions or taxonomic turnover rates. The model allows testing of hypotheses about patterns of diversification and estimation of rates of morphological evolution. In the case of blastozoans, I find no evidence that major changes in evolutionary rates and mechanisms are responsible for the deceleration of morphological diversification seen during the period of this clade's expansion. At the same time, there is evidence for a moderate decline in overall rates of morphological diversification concordant with a major change (from positive to negative values) in the clade's growth rate.

Model structure of a cosmic-ray mediated stellar or solar wind

NASA Technical Reports Server (NTRS)

Lee, M. A.; Axford, W. I.

1988-01-01

An idealized hydrodynamic model is presented for the mediation of a free-streaming stellar wind by galactic cosmic rays or energetic particles accelerated at the stellar wind termination shock. The spherically-symmetric stellar wind is taken to be cold; the only body force is the cosmic ray pressure gradient. The cosmic rays are treated as a massless fluid with an effective mean diffusion coefficient k proportional to radial distance r. The structure of the governing equations is investigated both analytically and numerically. Solutions for a range of values of k are presented which describe the deceleration of the stellar wind and a transition to nearly incompressible flow and constant cosmic ray pressure at large r. In the limit of small k the transition steepens to a strong stellar wind termination shock. For large k the stellar wind is decelerated gradually with no shock transition. It is argued that the solutions provide a simple model for the mediation of the solar wind by interstellar ions as both pickup ions and the cosmic ray anomalous component which together dominate the pressure of the solar wind at large r.

Holographic dark energy with linearly varying deceleration parameter and escaping big rip singularity of the Bianchi type-V universe

NASA Astrophysics Data System (ADS)

Sarkar, Sanjay

2014-08-01

The present work deals with the accretion of two minimally interacting fluids: dark matter and a hypothetical isotropic fluid as the holographic dark energy components onto black hole and wormhole in a spatially homogeneous and anisotropic Bianchi type-V universe. To obtain an exact solution of the Einstein's field equations, we use the assumption of linearly varying deceleration parameter. Solution describes effectively the actual acceleration and indicates a big rip type future singularity of the universe. We have studied the evolution of the mass of black hole and the wormhole embedded in this anisotropic universe in order to reproduce a stable universe protected against future-time singularity. It is observed that the accretion of these dark components leads to a gradual decrease and increase of black hole and wormhole mass respectively. Finally, we have found that contrary to our previous case (Sarkar in Astrophys. Space. Sci. 341:651, 2014a), the big rip singularity of the universe with a divergent Hubble parameter of this dark energy model may be avoided by a big trip.

The effects of different concentrations of cocoa in the chocolate intaken by the mother on fetal heart rate.

PubMed

Buscicchio, Giorgia; Lorenzi, Sara; Tranquilli, Andrea Luigi

2013-10-01

To analyze the effects of different concentrations (30% and 80%) of cocoa on fetal heart rate (FHR). One hundred pregnant women with uncomplicated gestation, matched for age and parity, underwent computerized FHR recording before and after the consumption of 30 g of 30% and 80% cocoa chocolate. After 1 week, those who had received 30% were shifted to 80% and vice versa to have a crossover. Computerized cardiotocography parameters (contractions, fetal movements, baseline FHR, accelerations greater than 15 bpm for 15 s, number of decelerations, minutes of high variability, short term variability in ms) were recorded and expressed as mean and SD. The differences were tested for statistical significance using the paired t test, with the significance at p < 0.05. The percent change after chocolate intake for accelerations and short-term FHR variation was calculated. The number of fetal movements, accelerations, the duration of episodes of high variation and the short-term FHR variation were significantly higher (p < 0.0001) after 80% cocoa intake. After 30% cocoa chocolate intake, only the number of accelerations was significantly increased. The percent change of the number of accelerations and the short-term FHR variation were significantly higher after 80% cocoa chocolate maternal intake. Maternal intake of dark chocolate has a stimulating action on fetal reactivity. The effect is more marked with high concentrations (80%) of cocoa. This finding is likely due to the pharmacological action of theobromine, a methilxanthine present in cocoa.

Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators

DOE PAGES

O’Shea, B. D.; Andonian, G.; Barber, S. K.; ...

2016-09-14

There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m –1) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347±0.020 GeV m –1 using a dielectric wakefield accelerator of 15 cmmore » length, with sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320±17 MeV m –1. As a result, both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons.« less

Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators

PubMed Central

O'Shea, B. D.; Andonian, G.; Barber, S. K.; Fitzmorris, K. L.; Hakimi, S.; Harrison, J.; Hoang, P. D.; Hogan, M. J.; Naranjo, B.; Williams, O. B.; Yakimenko, V.; Rosenzweig, J. B.

2016-01-01

There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m−1) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347±0.020 GeV m−1 using a dielectric wakefield accelerator of 15 cm length, with sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320±17 MeV m−1. Both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons. PMID:27624348

Numerical simulation of flows in a circular pipe transversely subjected to a localized impulsive body force with applications to blunt traumatic aortic rupture

NASA Astrophysics Data System (ADS)

Di Labbio, G.; Keshavarz-Motamed, Z.; Kadem, L.

2017-06-01

Much debate surrounds the mechanisms responsible for the occurrence of blunt traumatic aortic rupture in car accidents, particularly on the role of the inertial body force experienced by the blood due to the abrupt deceleration. The isolated influence of such body forces acting on even simple fluid flows is a fundamental problem in fluid dynamics that has not been thoroughly investigated. This study numerically investigates the fundamental physical problem, where the pulsatile flow in a straight circular pipe is subjected to a transverse body force on a localized volume of fluid. The body force is applied as a brief rectangular impulse in three distinct cases, namely during the accelerating, peak, and decelerating phases of the pulsatile flow. A dimensionless number, termed the degree of influence of the body force (Ψ), is devised to quantify the relative strength of the body force over the flow inertia. The impact induces counter-rotating cross-stream vortices at the boundaries of the forced section accompanied by complex secondary flow structures. This secondary flow is found to develop slowest for an impact occurring during an accelerating flow and fastest during a decelerating flow. The peak skewness of the velocity field, however, occurred at successively later times for the three respective cases. After the impact, these secondary flows act to restore the unforced state and such dominant spatial structures are revealed by proper orthogonal decomposition of the velocity field. This work presents a new class of problems that requires further theoretical and experimental investigation.

Lieutenant Colonel John Stapp Demonstrates the Rocket Sled

NASA Image and Video Library

1956-04-21

Howard Hasbrook volunteers for a demonstration of a scaled-down version of Lieutenant Colonel John Stapp’s rocket sled set up in the hangar at the National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory. In 1945 Stapp, an Air Force medical doctor, volunteered to participate in a deceleration program to study the human body’s tolerance to aircraft crash forces. A 1500-pound sled powered by rockets was installed in 1947 on a section of railroad track in the California desert. Stapp participated in 29 experiments over the next seven years and broke land and deceleration records. These tests studied the effects of acceleration, G-force, deceleration, and wind blast on humans. Stapp suffered broken bones and retinal hemorrhages, but suffered no permanent damage. NACA Lewis was conducting a series of crash impact studies in the mid-1950s using dummies in actual aircraft. Irving Pinkel, the director of the program, and Stapp became friends through their mutual interest in this field. In April 1956 Stapp visited the Cleveland lab to give a talk to the local section of the American Rocket Society that discussed issues relating to the escape of pilots from the cockpit of supersonic jet aircraft. That same week, NACA Lewis’ Pinkel, Gerard Pesman, Merritt Preston, and Dugald Black received the annual Laura Taber Barbour Air Safety Award for their work on the Crash Fire Program. Black and Preston are visible in the crowd in this photograph.

Implications of climate change on wind erosion of agricultural lands in the Columbia Plateau

USDA-ARS?s Scientific Manuscript database

Climate change may impact soil health and productivity as a result of accelerated or decelerated rates of erosion. Previous studies suggest a greater risk of wind erosion on arid and semi-arid lands due to loss of biomass under a future warmer climate. There have been no studies conducted to assess ...

Visual Images of Subjective Perception of Time in a Literary Text

ERIC Educational Resources Information Center

Nesterik, Ella V.; Issina, Gaukhar I.; Pecherskikh, Taliya F.; Belikova, Oxana V.

2016-01-01

The article is devoted to the subjective perception of time, or psychological time, as a text category and a literary image. It focuses on the visual images that are characteristic of different types of literary time--accelerated, decelerated and frozen (vanished). The research is based on the assumption that the category of subjective perception…

City transport of the future - the high speed pedestrian conveyor. Part 2: ergonomic considerations of complete conveyor systems.

PubMed

Browning, A C

1975-03-01

This is the second part of an article on an unusual form of passenger transport, the moving pavement or pedestrian conveyor running at speeds up to 16 km/h. Part 1, "Ergonomic considerations of acceleration, deceleration and transfer sections," was published in the December, 1974, issue.

Walkway Length Determination for Steady State Walking in Young and Older Adults

ERIC Educational Resources Information Center

Macfarlane, Pamela A.; Looney, Marilyn A.

2008-01-01

The primary purpose of this study was to determine acceleration (AC) and deceleration (DC) distances that would accommodate young and older adults walking at their preferred and fast speeds. A secondary purpose was to determine the minimal walkway length needed to record six steady state (SS) steps (three full gait cycles) for younger and older…

Optimization of motion control laws for tether crawler or elevator systems

NASA Technical Reports Server (NTRS)

Swenson, Frank R.; Von Tiesenhausen, Georg

1988-01-01

Based on the proposal of a motion control law by Lorenzini (1987), a method is developed for optimizing motion control laws for tether crawler or elevator systems in terms of the performance measures of travel time, the smoothness of acceleration and deceleration, and the maximum values of velocity and acceleration. The Lorenzini motion control law, based on powers of the hyperbolic tangent function, is modified by the addition of a constant-velocity section, and this modified function is then optimized by parameter selections to minimize the peak acceleration value for a selected travel time or to minimize travel time for the selected peak values of velocity and acceleration. It is shown that the addition of a constant-velocity segment permits further optimization of the motion control law performance.

Activity profiles in U17, U20 and senior women's Brazilian National soccer teams during international competitions: Are there meaningful differences?

PubMed

Ramos, Guilherme P; Nakamura, Fábio Y; Penna, Eduardo M; Wilke, Carolina Franco; Pereira, Lucas A; Loturco, Irineu; Capelli, Luciano; Mahseredjian, Fábio; Silami-Garcia, Emerson; Coimbra, Cândido C

2017-07-31

The aim of this study was to compare locomotor activity profiles of Brazilian top-class female soccer players competing at distinct age brackets (U17, U20, and Senior). External match load of 14 U17, 14 U20, and 17 Senior female soccer players competing in 6-7 full official international matches were assessed using global positioning systems (GPS). Total distance covered, distance covered in high intensity (HID:15.6-20 kmh), distance covered in sprints (sprint:>20 kmh), number of accelerations (Acc)>1 ms, decelerations (Dec) >-1 ms, and Player Load generally increased across the age brackets (U17

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 EMA analysis of the effect of increasing word length on consonant production in apraxia of speech: a case study.

PubMed

Bartle, Carly J; Goozée, Justine V; Murdoch, Bruce E

2007-03-01

The effect of increasing word length on the articulatory dynamics (i.e. duration, distance, maximum acceleration, maximum deceleration, and maximum velocity) of consonant production in acquired apraxia of speech was investigated using electromagnetic articulography (EMA). Tongue-tip and tongue-back movement of one apraxic patient was recorded using the AG-200 EMA system during word-initial consonant productions in one, two, and three syllable words. Significantly deviant articulatory parameters were recorded for each of the target consonants during one, two, and three syllables words. Word length effects were most evident during the release phase of target consonant productions. The results are discussed with respect to theories of speech motor control as they relate to AOS.

Evaporation Mechanism of Cu from Liquid Fe Containing C and S

NASA Astrophysics Data System (ADS)

Jung, Sung-Hoon; Kang, Youn-Bae

2016-08-01

A number of liquid-gas experiments were carried out in order to elucidate evaporation mechanism of Cu from liquid Fe containing C and S. Rate of Cu evaporation in liquid Fe droplets at 1873 K (1600 °C) was determined using electromagnetic levitation equipment. Evaporation rate of the Cu under various conditions (flow rate of gas mixtures, initial C, and S concentrations) was examined. It was found from a series of kinetic analyses of the experimental data that Cu evaporates in forms of Cu(g) and CuS(g). As was reported for the Sn evaporation from liquid iron (Jung et al. Met. Mater. Trans. 46B, 250-258, 2014), S plays two roles for the evaporation of Cu: accelerating the rate by forming CuS(g) and decelerating the rate by blocking evaporation sites. As a result of these combinatorial effects, the evaporation of Cu is decelerated at low S content, but is accelerated at high S content. Based on the elucidated mechanism, an evaporation model equation for Cu was developed in the present study, which takes into account (1) evaporation of Cu in the two forms (Cu(g) and CuS(g)), (2) surface blocking by S using ideal Langmuir adsorption, and (3) effect of C. The obtained rate constant of a reaction Cu i + S i = CuS i (g), k CuS R , is 1.37 × 10-9 m4 mol-1 s-1, and the residual rate constant, k CuS r , is 4.11 × 10-10 m4 mol-1 s-1 at 1873 K (1600 °C). Both of them were found to be one order lower than those for Sn evaporation.

The kinetics and mechanism of nanoconfined molten salt reactions: trimerization of potassium and rubidium dicyanamide.

PubMed

Yancey, Benjamin; Vyazovkin, Sergey

2015-04-21

This study highlights the effect of the aggregate state of a reactant on the reaction kinetics under the conditions of nanoconfinement. Our previous work (Phys. Chem. Chem. Phys., 2014, 16, 11409) has demonstrated considerable deceleration of the solid state trimerization of sodium dicyanamide in organically modified silica nanopores. In the present study we use FTIR, NMR, pXRD, TGA and DSC to analyze the kinetics and mechanism of the liquid state trimerization of potassium and rubidium dicyanamide under similar conditions of nanoconfinement. It is found that nanoconfinement accelerates dramatically the kinetics of the liquid state trimerization, whereas it does not appear to affect the reaction mechanism. Kinetic analysis indicates that the acceleration is associated with an increase in the preexponential factor. Although nanoconfinement has the opposite effects on the respective kinetics of solid and liquid state trimerization, both effects are linked to a change in the preexponential factor. The results obtained are consistent with our hypothesis that the effects differ because nanoconfinement may promote disordering of the solid and ordering of the liquid reaction media.

Inverse Leidenfrost effect: self-propelling drops on a bath

NASA Astrophysics Data System (ADS)

Gauthier, Anais; van der Meer, Devaraj; Lohse, Detlef; Physics of Fluids Team

2017-11-01

When deposited on very hot solid, volatile drops can levitate over a cushion of vapor, in the so-called Leidenfrost state. This phenomenon can also be observed on a hot bath and similarly to the solid case, drops are very mobile due to the absence of contact with the substrate that sustains them. We discuss here a situation of ``inverse Leidenfrost effect'' where room-temperature drops levitate on a liquid nitrogen pool - the vapor is generated here by the bath sustaining the relatively hot drop. We show that the drop's movement is not random: the liquid goes across the bath in straight lines, a pattern only disrupted by elastic bouncing on the edges. In addition, the drops are initially self-propelled; first at rest, they accelerate for a few seconds and reach velocities of the order of a few cm/s, before slowing down. We investigate experimentally the parameters that affect their successive acceleration and deceleration, such as the size and nature of the drops and we discuss the origin of this pattern.

Visual and non-visual motion information processing during pursuit eye tracking in schizophrenia and bipolar disorder.

PubMed

Trillenberg, Peter; Sprenger, Andreas; Talamo, Silke; Herold, Kirsten; Helmchen, Christoph; Verleger, Rolf; Lencer, Rebekka

2017-04-01

Despite many reports on visual processing deficits in psychotic disorders, studies are needed on the integration of visual and non-visual components of eye movement control to improve the understanding of sensorimotor information processing in these disorders. Non-visual inputs to eye movement control include prediction of future target velocity from extrapolation of past visual target movement and anticipation of future target movements. It is unclear whether non-visual input is impaired in patients with schizophrenia. We recorded smooth pursuit eye movements in 21 patients with schizophrenia spectrum disorder, 22 patients with bipolar disorder, and 24 controls. In a foveo-fugal ramp task, the target was either continuously visible or was blanked during movement. We determined peak gain (measuring overall performance), initial eye acceleration (measuring visually driven pursuit), deceleration after target extinction (measuring prediction), eye velocity drifts before onset of target visibility (measuring anticipation), and residual gain during blanking intervals (measuring anticipation and prediction). In both patient groups, initial eye acceleration was decreased and the ability to adjust eye acceleration to increasing target acceleration was impaired. In contrast, neither deceleration nor eye drift velocity was reduced in patients, implying unimpaired non-visual contributions to pursuit drive. Disturbances of eye movement control in psychotic disorders appear to be a consequence of deficits in sensorimotor transformation rather than a pure failure in adding cognitive contributions to pursuit drive in higher-order cortical circuits. More generally, this deficit might reflect a fundamental imbalance between processing external input and acting according to internal preferences.

Ditching Tests of a 1/20-Scale Model of the Northrop B-35 Airplane

NASA Technical Reports Server (NTRS)

Fisher, Lloyd J.

1948-01-01

Tests of a 1/20-scale dynamically similar model of the Northrop B-35 airplane were made to study its ditching characteristics. The model was ditched in calm water at the Langley tank no. 2 monorail. Various landing attitudes, speeds,and conditions of damage were simulated during the investigation. The ditching characteristics were determined by visual observation and from motion-picture records and time-history acceleration records. Both longitudinal and lateral accelerations were measured. Results are given in tabular form and time-history acceleration curves and sequence photographs are presented. Conclusions based on the model investigation are as follows: 1. The best ditching of the B-35 airplane probably can be made by contacting the water in a near normal landing attitude of about 9 deg with the landing flaps full down so as to have a low horizontal speed. 2. The airplane usually will turn or yaw but the motion will not be violent. The maximum lateral acceleration will be about 2g. 3. If the airplane does not turn or yaw immediately after landing, it probably will trim up and then make a smooth run or porpoise slightly. The maximum longitudinal decelerations that will be encountered are about 6g or 7g. 4. Although the decelerations are not indicated to be especially large, the construction of the airplane is such that extensive damage is to be expected, and it probably will be difficult to find ditching stations where crew members can adequately brace themselves and be reasonably sure of avoiding a large inrush of water.

Movement Demands of Elite Under-20s and Senior International Rugby Union Players

PubMed Central

Drawer, Scott; Pollard, Ben; Eager, Robin; Taylor, Neil; Cook, Christian J.

2016-01-01

This study compared the movement demands of elite international Under-20 age grade (U20s) and senior international rugby union players during competitive tournament match play. Forty elite professional players from an U20 and 27 elite professional senior players from international performance squads were monitored using 10Hz global positioning systems (GPS) during 15 (U20s) and 8 (senior) international tournament matches during the 2014 and 2015 seasons. Data on distances, velocities, accelerations, decelerations, high metabolic load (HML) distance and efforts, and number of sprints were derived. Data files from players who played over 60 min (n = 258) were separated firstly into Forwards and Backs, and more specifically into six positional groups; FR–Front Row (prop & hooker), SR–Second Row, BR–Back Row (Flankers & No.8), HB–Half Backs (scrum half & outside half), MF–Midfield (centres), B3 –Back Three (wings & full back) for match analysis. Linear mixed models revealed significant differences between U20 and senior teams in both the forwards and backs. In the forwards the seniors covered greater HML distance (736.4 ± 280.3 vs 701.3 ± 198.7m, p = 0.01) and severe decelerations (2.38 ± 2.2 vs 2.28 ± 1.65, p = 0.05) compared to the U20s, but performed less relative HSR (3.1 ± 1.6 vs 3.2 ± 1.5, p < 0.01), moderate (19.4 ± 10.5 vs 23.6 ± 10.5, p = 0.01) and high accelerations (2.2 ± 1.9 vs 4.3 ± 2.7, p < 0.01) and sprint•min-1 (0.11 ± 0.06 vs 0.11 ± 0.05, p < 0.01). Senior backs covered a greater relative distance (73.3 ± 8.1 vs 69.1 ± 7.6 m•min-1, p < 0.01), greater High Metabolic Load (HML) distance (1138.0 ± 233.5 vs 1060.4 ± 218.1m, p < 0.01), HML efforts (112.7 ± 22.2 vs 98.8 ± 21.7, p < 0.01) and heavy decelerations (9.9 ± 4.3 vs 9.5 ± 4.4, p = 0.04) than the U20s backs. However, the U20s backs performed more relative HSR (7.3 ± 2.1 vs 7.2 ± 2.1, p <0.01) and sprint•min-1 (0.26 ± 0.07 vs 0.25 ± 0.07, p < 0.01). Further investigation highlighted differences between the 6 positional groups of the teams. The positional groups that differed the most on the variables measured were the FR and MF groups, with the U20s FR having higher outputs on HSR, moderate & high accelerations, moderate, high & severe decelerations, HML distance, HML efforts, and sprints•min-1. For the MF group the senior players produced greater values for relative distance covered, HSR, moderate decelerations, HML distance and sprint•min-1. The BR position group was most similar with the only differences seen on heavy accelerations (U20s higher) and moderate decelerations (seniors higher). Findings demonstrate that U20s internationals appear to be an adequate ‘stepping stone’ for preparing players for movement characteristics found senior International rugby, however, the current study highlight for the first time that certain positional groups may require more time to be able to match the movement demands required at a higher playing level than others. Conditioning staff must also bear in mind that the U20s players whilst maintaining or improving match movement capabilities may require to gain substantial mass in some positions to match their senior counterparts. PMID:27824865

Movement Demands of Elite Under-20s and Senior International Rugby Union Players.

PubMed

Cunningham, Daniel J; Shearer, David A; Drawer, Scott; Pollard, Ben; Eager, Robin; Taylor, Neil; Cook, Christian J; Kilduff, Liam P

2016-01-01

This study compared the movement demands of elite international Under-20 age grade (U20s) and senior international rugby union players during competitive tournament match play. Forty elite professional players from an U20 and 27 elite professional senior players from international performance squads were monitored using 10Hz global positioning systems (GPS) during 15 (U20s) and 8 (senior) international tournament matches during the 2014 and 2015 seasons. Data on distances, velocities, accelerations, decelerations, high metabolic load (HML) distance and efforts, and number of sprints were derived. Data files from players who played over 60 min (n = 258) were separated firstly into Forwards and Backs, and more specifically into six positional groups; FR-Front Row (prop & hooker), SR-Second Row, BR-Back Row (Flankers & No.8), HB-Half Backs (scrum half & outside half), MF-Midfield (centres), B3 -Back Three (wings & full back) for match analysis. Linear mixed models revealed significant differences between U20 and senior teams in both the forwards and backs. In the forwards the seniors covered greater HML distance (736.4 ± 280.3 vs 701.3 ± 198.7m, p = 0.01) and severe decelerations (2.38 ± 2.2 vs 2.28 ± 1.65, p = 0.05) compared to the U20s, but performed less relative HSR (3.1 ± 1.6 vs 3.2 ± 1.5, p < 0.01), moderate (19.4 ± 10.5 vs 23.6 ± 10.5, p = 0.01) and high accelerations (2.2 ± 1.9 vs 4.3 ± 2.7, p < 0.01) and sprint•min-1 (0.11 ± 0.06 vs 0.11 ± 0.05, p < 0.01). Senior backs covered a greater relative distance (73.3 ± 8.1 vs 69.1 ± 7.6 m•min-1, p < 0.01), greater High Metabolic Load (HML) distance (1138.0 ± 233.5 vs 1060.4 ± 218.1m, p < 0.01), HML efforts (112.7 ± 22.2 vs 98.8 ± 21.7, p < 0.01) and heavy decelerations (9.9 ± 4.3 vs 9.5 ± 4.4, p = 0.04) than the U20s backs. However, the U20s backs performed more relative HSR (7.3 ± 2.1 vs 7.2 ± 2.1, p <0.01) and sprint•min-1 (0.26 ± 0.07 vs 0.25 ± 0.07, p < 0.01). Further investigation highlighted differences between the 6 positional groups of the teams. The positional groups that differed the most on the variables measured were the FR and MF groups, with the U20s FR having higher outputs on HSR, moderate & high accelerations, moderate, high & severe decelerations, HML distance, HML efforts, and sprints•min-1. For the MF group the senior players produced greater values for relative distance covered, HSR, moderate decelerations, HML distance and sprint•min-1. The BR position group was most similar with the only differences seen on heavy accelerations (U20s higher) and moderate decelerations (seniors higher). Findings demonstrate that U20s internationals appear to be an adequate 'stepping stone' for preparing players for movement characteristics found senior International rugby, however, the current study highlight for the first time that certain positional groups may require more time to be able to match the movement demands required at a higher playing level than others. Conditioning staff must also bear in mind that the U20s players whilst maintaining or improving match movement capabilities may require to gain substantial mass in some positions to match their senior counterparts.

Summary of the First High-Altitude, Supersonic Flight Dynamics Test for the Low-Density Supersonic Decelerator Project

NASA Technical Reports Server (NTRS)

Clark, Ian G.; Adler, Mark; Manning, Rob

2015-01-01

NASA's Low-Density Supersonic Decelerator Project is developing and testing the next generation of supersonic aerodynamic decelerators for planetary entry. A key element of that development is the testing of full-scale articles in conditions relevant to their intended use, primarily the tenuous Mars atmosphere. To achieve this testing, the LDSD project developed a test architecture similar to that used by the Viking Project in the early 1970's for the qualification of their supersonic parachute. A large, helium filled scientific balloon is used to hoist a 4.7 m blunt body test vehicle to an altitude of approximately 32 kilometers. The test vehicle is released from the balloon, spun up for gyroscopic stability, and accelerated to over four times the speed of sound and an altitude of 50 kilometers using a large solid rocket motor. Once at those conditions, the vehicle is despun and the test period begins. The first flight of this architecture occurred on June 28th of 2014. Though primarily a shake out flight of the new test system, the flight was also able to achieve an early test of two of the LDSD technologies, a large 6 m diameter Supersonic Inflatable Aerodynamic Decelerator (SIAD) and a large, 30.5 m nominal diameter supersonic parachute. This paper summarizes this first flight.

Aerodynamic Models for the Low Density Supersonic Decelerator (LDSD) Test Vehicles

NASA Technical Reports Server (NTRS)

Van Norman, John W.; Dyakonov, Artem; Schoenenberger, Mark; Davis, Jody; Muppidi, Suman; Tang, Chun; Bose, Deepak; Mobley, Brandon; Clark, Ian

2016-01-01

An overview of aerodynamic models for the Low Density Supersonic Decelerator (LDSD) Supersonic Flight Dynamics Test (SFDT) campaign test vehicle is presented, with comparisons to reconstructed flight data and discussion of model updates. The SFDT campaign objective is to test Supersonic Inflatable Aerodynamic Decelerator (SIAD) and large supersonic parachute technologies at high altitude Earth conditions relevant to entry, descent, and landing (EDL) at Mars. Nominal SIAD test conditions are attained by lifting a test vehicle (TV) to 36 km altitude with a helium balloon, then accelerating the TV to Mach 4 and 53 km altitude with a solid rocket motor. Test flights conducted in June of 2014 (SFDT-1) and 2015 (SFDT-2) each successfully delivered a 6 meter diameter decelerator (SIAD-R) to test conditions and several seconds of flight, and were successful in demonstrating the SFDT flight system concept and SIAD-R technology. Aerodynamic models and uncertainties developed for the SFDT campaign are presented, including the methods used to generate them and their implementation within an aerodynamic database (ADB) routine for flight simulations. Pre- and post-flight aerodynamic models are compared against reconstructed flight data and model changes based upon knowledge gained from the flights are discussed. The pre-flight powered phase model is shown to have a significant contribution to off-nominal SFDT trajectory lofting, while coast and SIAD phase models behaved much as predicted.

Aerocapture Inflatable Decelerator for Planetary Entry

NASA Technical Reports Server (NTRS)

Reza, Sajjad; Hund, Richard; Kustas, Frank; Willcockson, William; Songer, Jarvis; Brown, Glen

2007-01-01

Forward Attached Inflatable Decelerators, more commonly known as inflatable aeroshells, provide an effective, cost efficient means of decelerating spacecrafts by using atmospheric drag for aerocapture or planetary entry instead of conventional liquid propulsion deceleration systems. Entry into planetary atmospheres results in significant heating and aerodynamic pressures which stress aeroshell systems to their useful limits. Incorporation of lightweight inflatable decelerator surfaces with increased surface-area footprints provides the opportunity to reduce heat flux and induced temperatures, while increasing the payload mass fraction. Furthermore, inflatable aeroshell decelerators provide the needed deceleration at considerably higher altitudes and Mach numbers when compared with conventional rigid aeroshell entry systems. Inflatable aeroshells also provide for stowage in a compact space, with subsequent deployment of a large-area, lightweight heatshield to survive entry heating. Use of a deployable heatshield decelerator enables an increase in the spacecraft payload mass fraction and may eliminate the need for a spacecraft backshell.

Vestibular coriolis effect differences modeled with three-dimensional linear-angular interactions.

PubMed

Holly, Jan E

2004-01-01

The vestibular coriolis (or "cross-coupling") effect is traditionally explained by cross-coupled angular vectors, which, however, do not explain the differences in perceptual disturbance under different acceleration conditions. For example, during head roll tilt in a rotating chair, the magnitude of perceptual disturbance is affected by a number of factors, including acceleration or deceleration of the chair rotation or a zero-g environment. Therefore, it has been suggested that linear-angular interactions play a role. The present research investigated whether these perceptual differences and others involving linear coriolis accelerations could be explained under one common framework: the laws of motion in three dimensions, which include all linear-angular interactions among all six components of motion (three angular and three linear). The results show that the three-dimensional laws of motion predict the differences in perceptual disturbance. No special properties of the vestibular system or nervous system are required. In addition, simulations were performed with angular, linear, and tilt time constants inserted into the model, giving the same predictions. Three-dimensional graphics were used to highlight the manner in which linear-angular interaction causes perceptual disturbance, and a crucial component is the Stretch Factor, which measures the "unexpected" linear component.

Gauging the cosmic acceleration with recent type Ia supernovae data sets

NASA Astrophysics Data System (ADS)

Velten, Hermano; Gomes, Syrios; Busti, Vinicius C.

2018-04-01

We revisit a model-independent estimator for cosmic acceleration based on type Ia supernovae distance measurements. This approach does not rely on any specific theory for gravity, energy content, nor parametrization for the scale factor or deceleration parameter and is based on falsifying the null hypothesis that the Universe never expanded in an accelerated way. By generating mock catalogs of known cosmologies, we test the robustness of this estimator, establishing its limits of applicability. We detail the pros and cons of such an approach. For example, we find that there are specific counterexamples in which the estimator wrongly provides evidence against acceleration in accelerating cosmologies. The dependence of the estimator on the H0 value is also discussed. Finally, we update the evidence for acceleration using the recent UNION2.1 and Joint Light-Curve Analysis samples. Contrary to recent claims, available data strongly favor an accelerated expansion of the Universe in complete agreement with the standard Λ CDM model.

Cosmic transit and anisotropic models in f(R,T) gravity

NASA Astrophysics Data System (ADS)

Sahu, S. K.; Tripathy, S. K.; Sahoo, P. K.; Nath, A.

2017-06-01

Accelerating cosmological models are constructed in a modified gravity theory dubbed as $f(R,T)$ gravity at the backdrop of an anisotropic Bianchi type-III universe. $f(R,T)$ is a function of the Ricci scalar $R$ and the trace $T$ of the energy-momentum tensor and it replaces the Ricci scalar in the Einstein-Hilbert action of General Relativity. The models are constructed for two different ways of modification of the Einstein-Hilbert action. Exact solutions of the field equations are obtained by a novel method of integration. We have explored the behaviour of the cosmic transit from an decelerated phase of expansion to an accelerated phase to get the dynamical features of the universe. Within the formalism of the present work, it is found that, the modification of the Einstein-Hilbert action does not affect the scale factor. However the dynamics of the effective dark energy equation of state is significantly affected.

Transit Time and Normal Orientation of ICME-driven Shocks

NASA Astrophysics Data System (ADS)

Case, A. W.; Spence, H.; Owens, M.; Riley, P.; Linker, J.; Odstrcil, D.

2006-12-01

Interplanetary Coronal Mass Ejections (ICMEs) can drive shocks that accelerate particles to great energies. It is important to understand the acceleration, transport, and spectra of these particles in order to quantify this fundamental physical process operating throughout the cosmos. This understanding also helps to better protect astronauts and spacecraft in upcoming missions. We show that the ambient solar wind is crucial in determining characteristics of ICME-driven shocks, which in turn affect energetic particle production. We use a coupled 3-D MHD code of the corona and heliosphere to simulate ICME propagation from 30 solar radii to 1AU. ICMEs of different velocities are injected into a realistic solar wind to determine how the initial speed affects the shape and deceleration of the ICME-driven shock. We use shock transit time and shock normal orientation to quantify these dependencies. We also inject identical ICMEs into different ambient solar winds to quantify the effective drag force on an ICME.

Effectiveness of restraint equipment in enclosed areas.

DOT National Transportation Integrated Search

1972-02-01

A series of 20-g decelerations of a crash sled was conducted to determine the magnitude of head impact decelerations while wearing various types of restraint equipment in small confined areas. Restraint webbing loads and head impact decelerations are...

Low Density Supersonic Decelerator Flight Dynamics Test-1 Flight Design and Targeting

NASA Technical Reports Server (NTRS)

Ivanov, Mark

2015-01-01

NASA's Low Density Supersonic Decelerator (LDSD) program was established to identify, develop, and eventually qualify to Test [i.e. Technology] Readiness Level (TRL) - 6 aerodynamic decelerators for eventual use on Mars. Through comprehensive Mars application studies, two distinct Supersonic Inflatable Aerodynamic Decelerator (SIAD) designs were chosen that afforded the optimum balance of benefit, cost, and development risk. In addition, a Supersonic Disk Sail (SSDS) parachute design was chosen that satisfied the same criteria. The final phase of the multi-tiered qualification process involves Earth Supersonic Flight Dynamics Tests (SFDTs) within environmental conditions similar to those that would be experienced during a Mars Entry, Descent, and Landing (EDL) mission. The first of these flight tests (i.e. SFDT-1) was completed on June 28, 2014 with two more tests scheduled for the summer of 2015 and 2016, respectively. The basic flight design for all the SFDT flights is for the SFDT test vehicle to be ferried to a float altitude of 120 kilo-feet by a 34 thousand cubic feet (Mcf) heavy lift helium balloon. Once float altitude is reached, the test vehicle is released from the balloon, spun-up for stability, and accelerated to supersonic speeds using a Star48 solid rocket motor. After burnout of the Star48 motor the vehicle decelerates to pre-flight selected test conditions for the deployment of the SIAD system. After further deceleration with the SIAD deployed, the SSDS parachute is then deployed stressing the performance of the parachute in the wake of the SIAD augmented blunt body. The test vehicle/SIAD/parachute system then descends to splashdown in the Pacific Ocean for eventual recovery. This paper will discuss the development of both the test vehicle and the trajectory sequence including design trade-offs resulting from the interaction of both engineering efforts. In addition, the SFDT-1 nominal trajectory design and associated sensitivities will be discussed as well as an overview of the on-board flight software used to trigger and sequence the main flight events necessary to deploy the deceleration technologies. Finally, as-flown performance of the SFDT-1 system will be discussed.

High efficiency ion beam accelerator system

NASA Technical Reports Server (NTRS)

Aston, G.

1981-01-01

An ion accelerator system that successfully combines geometrical and electrostatic focusing principles is presented. This accelerator system uses thin, concave, multiple-hole, closely spaced graphite screen and focusing grids which are coupled to single slot accelerator and decelerator grids to provide high ion extraction efficiency and good focusing. Tests with the system showed a substantial improvement in ion beam current density and collimation as compared with a Pierce electrode configuration. Durability of the thin graphite screen and focusing grids has been proven, and tests are being performed to determine the minimum screen and focusing grid spacing and thickness required to extract the maximum reliable beam current density. Compared with present neutral beam injector accelerator systems, this one has more efficient ion extraction, easier grid alignment, easier fabrication, a less cumbersome design, and the capacity to be constructed in a modular fashion. Conceptual neutral beam injector designs using this modular approach have electrostatic beam deflection plates downstream of each module.

Radially dependent angular acceleration of twisted light.

PubMed

Webster, Jason; Rosales-Guzmán, Carmelo; Forbes, Andrew

2017-02-15

While photons travel in a straight line at constant velocity in free space, the intensity profile of structured light may be tailored for acceleration in any degree of freedom. Here we propose a simple approach to control the angular acceleration of light. Using Laguerre-Gaussian modes as our twisted beams carrying orbital angular momentum, we show that superpositions of opposite handedness result in a radially dependent angular acceleration as they pass through a focus (waist plane). Due to conservation of orbital angular momentum, we find that propagation dynamics are complex despite the free-space medium: the outer part of the beam (rings) rotates in an opposite direction to the inner part (petals), and while the outer part accelerates, the inner part decelerates. We outline the concepts theoretically and confirm them experimentally. Such exotic structured light beams are topical due to their many applications, for instance in optical trapping and tweezing, metrology, and fundamental studies in optics.

Separated-orbit bisected energy-recovered linear accelerator

DOEpatents

Douglas, David R.

2015-09-01

A separated-orbit bisected energy-recovered linear accelerator apparatus and method. The accelerator includes a first linac, a second linac, and a plurality of arcs of differing path lengths, including a plurality of up arcs, a plurality of downgoing arcs, and a full energy arc providing a path independent of the up arcs and downgoing arcs. The up arcs have a path length that is substantially a multiple of the RF wavelength and the full energy arc includes a path length that is substantially an odd half-integer multiple of the RF wavelength. Operation of the accelerator includes accelerating the beam utilizing the linacs and up arcs until the beam is at full energy, at full energy executing a full recirculation to the second linac using a path length that is substantially an odd half-integer of the RF wavelength, and then decelerating the beam using the linacs and downgoing arcs.

Singular F(R) cosmology unifying early- and late-time acceleration with matter and radiation domination era

NASA Astrophysics Data System (ADS)

Odintsov, S. D.; Oikonomou, V. K.

2016-06-01

We present some cosmological models which unify the late- and early-time acceleration eras with the radiation and the matter domination era, and we realize the cosmological models by using the theoretical framework of F(R) gravity. Particularly, the first model unifies the late- and early-time acceleration with the matter domination era, and the second model unifies all the evolution eras of our Universe. The two models are described in the same way at early and late times, and only the intermediate stages of the evolution have some differences. Each cosmological model contains two Type IV singularities which are chosen to occur one at the end of the inflationary era and one at the end of the matter domination era. The cosmological models at early times are approximately identical to the R 2 inflation model, so these describe a slow-roll inflationary era which ends when the slow-roll parameters become of order one. The inflationary era is followed by the radiation era and after that the matter domination era follows, which lasts until the second Type IV singularity, and then the late-time acceleration era follows. The models have two appealing features: firstly they produce a nearly scale invariant power spectrum of primordial curvature perturbations and a scalar-to-tensor ratio which are compatible with the most recent observational data and secondly, it seems that the deceleration-acceleration transition is crucially affected by the presence of the second Type IV singularity which occurs at the end of the matter domination era. As we demonstrate, the Hubble horizon at early times shrinks, as expected for an initially accelerating Universe, then during the matter domination era, it expands and finally after the Type IV singularity, the Hubble horizon starts to shrink again, during the late-time acceleration era. Intriguingly enough, the deceleration-acceleration transition, occurs after the second Type IV singularity. In addition, we investigate which F(R) gravity can successfully realize each of the four cosmological epochs.

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

Nakanotani, Masaru; Matsukiyo, Shuichi; Hada, Tohru

A shock–shock interaction is investigated by using a one-dimensional full particle-in-cell simulation. The simulation reproduces the collision of two symmetrical high Mach number quasi-perpendicular shocks. The basic structure of the shocks and ion dynamics is similar to that obtained by previous hybrid simulations. The new aspects obtained here are as follows. Electrons are already strongly accelerated before the two shocks collide through multiple reflection. The reflected electrons self-generate waves upstream between the two shocks before they collide. The waves far upstream are generated through the right-hand resonant instability with the anomalous Doppler effect. The waves generated near the shock aremore » due to firehose instability and have much larger amplitudes than those due to the resonant instability. The high-energy electrons are efficiently scattered by the waves so that some of them gain large pitch angles. Those electrons can be easily reflected at the shock of the other side. The accelerated electrons form a power-law energy spectrum. Due to the accelerated electrons, the pressure of upstream electrons increases with time. This appears to cause the deceleration of the approaching shock speed. The accelerated electrons having sufficiently large Larmor radii are further accelerated through the similar mechanism working for ions when the two shocks are colliding.« less

Speedometer app videos to provide real-world velocity-time graph data 1: rail travel

NASA Astrophysics Data System (ADS)

King, Julien

2018-03-01

The use of modern rail travel as a source of real-life velocity-time data to aid in the teaching of velocity and acceleration is discussed. A technique for using GPS speedometer apps to produce videos of velocity and time figures during a rail journey is described. The technique is applied to a UK rail journey, demonstrating how students can use its results to produce a velocity-time graph from which acceleration and deceleration figures can be calculated. These are compared with theoretical maximum figures, calculated from the train’s technical specification.

Reducing Secondary Insults in Traumatic Brain Injury

DTIC Science & Technology

2015-03-01

from external stimuli ( vibration , noise ) and from acceleration and deceleration forces. During transport, Critical Care Air transport Team crews...provide excess noise and vibration during flight. Hearing protection for patients and flight crew is required to avoid damage. Vibration experi- enced...decelerative forces. In addition, the noise , vibration , and patient agitation associated with the tactical takeoff and land- ing of military cargo

The effect of maternal methadone use on the fetal heart pattern: a computerised CTG analysis.

PubMed

Navaneethakrishnan, R; Tutty, S; Sinha, C; Lindow, S W

2006-08-01

Using a computerised analysis, the cardiotocograph (CTG) from women who use methadone (n= 25) when compared with women who do not use methadone (n= 25) showed a significant reduction in the fetal heart baseline rate, with a significant reduction in number of accelerations and episodes of high variation. The short-term variation, number of decelerations and episodes of low variation were not different between the two groups. The time taken to meet the standardised criteria was not different, and it is possible that a computer-assisted CTG analysis could be more accurate than a naked eye interpretation.

Efficient direct yaw moment control: tyre slip power loss minimisation for four-independent wheel drive vehicle

NASA Astrophysics Data System (ADS)

Kobayashi, Takao; Katsuyama, Etsuo; Sugiura, Hideki; Ono, Eiichi; Yamamoto, Masaki

2018-05-01

This paper proposes an efficient direct yaw moment control (DYC) capable of minimising tyre slip power loss on contact patches for a four-independent wheel drive vehicle. Simulations identified a significant power loss reduction with a direct yaw moment due to a change in steer characteristics during acceleration or deceleration while turning. Simultaneously, the vehicle motion can be stabilised. As a result, the proposed control method can ensure compatibility between vehicle dynamics performance and energy efficiency. This paper also describes the results of a full-vehicle simulation that was conducted to examine the effectiveness of the proposed DYC.

Cosmic transparency and acceleration

NASA Astrophysics Data System (ADS)

Holanda, R. F. L.; Pereira, S. H.; Jain, Deepak

2018-01-01

In this paper, by considering an absorption probability independent of photon wavelength, we show that current type Ia supernovae (SNe Ia) and gamma-ray burst (GRB) observations plus high-redshift measurements of the cosmic microwave background (CMB) radiation temperature support cosmic acceleration regardless of the transparent-universe assumption. Two flat scenarios are considered in our analyses: the Λ CDM model and a kinematic model. We consider τ (z )=2 ln (1 +z )ɛ, where τ (z ) denotes the opacity between an observer at z =0 and a source at z . This choice is equivalent to deforming the cosmic distance duality relation as DLDA-1=(1 +z )2+ɛ and, if the absorption probability is independent of photon wavelength, the CMB temperature evolution law is TCMB(z )=T0(1 +z )1+2 ɛ /3. By marginalizing on the ɛ parameter, our analyses rule out a decelerating universe at 99.99% C.L. for all scenarios considered. Interestingly, by considering only SNe Ia and GRBs observations, we obtain that a decelerated universe—indicated by ΩΛ≤0.33 and q0>0 —is ruled out around 1.5 σ C.L. and 2 σ C.L., respectively, regardless of the transparent-universe assumption.

Late Pleistocene climate change, nutrient cycling, and the megafaunal extinctions in North America

NASA Astrophysics Data System (ADS)

Faith, J. Tyler

2011-06-01

This study proposes an ecological mechanism for the terminal Pleistocene population collapse and subsequent extinction of North American megafauna. Observations of modern ecosystems indicate that feedback mechanisms between plant nutrient content, nitrogen cycling, and herbivore-plant interactions can vary between a nutrient accelerating mode favoring increased herbivore biomass and a nutrient decelerating mode characterized by reduced herbivore biomass. These alternate modes are determined largely by plant nitrogen content. Plant nitrogen content is known to be influenced by atmospheric CO 2 concentrations, temperature, and precipitation. It is argued that Lateglacial climate change, particularly increases in atmospheric CO 2, shifted herbivore-ecosystem dynamics from a nutrient accelerating mode to a nutrient decelerating mode at the end of the Pleistocene, leading to reduced megafaunal population densities. An examination of Sporormiella records - a proxy for megaherbivore biomass - indicates that megafaunal populations collapsed first in the east and later in the west, possibly reflecting regional differences in precipitation or vegetation structure. The fortuitous intersection of the climatically driven nitrogen sink, followed by any one or combination of subsequent anthropogenic, environmental, or extra-terrestrial mechanisms could explain why extinctions took place at the end of the Pleistocene rather than during previous glacial-interglacial cycles.

Stable Adaptive Inertial Control of a Doubly-Fed Induction Generator

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

Kang, Moses; Muljadi, Eduard; Hur, Kyeon

2016-11-01

This paper proposes a stable adaptive inertial control scheme of a doubly-fed induction generator. The proposed power reference is defined in two sections: the deceleration period and the acceleration period. The power reference in the deceleration period consists of a constant and the reference for maximum power point tracking (MPPT) operation. The latter contributes to preventing a second frequency dip (SFD) in this period because its reduction rate is large at the early stage of an event but quickly decreases with time. To improve the frequency nadir (FN), the constant value is set to be proportional to the rotor speedmore » prior to an event. The reference ensures that the rotor speed converges to a stable operating region. To accelerate the rotor speed while causing a small SFD, when the rotor speed converges, the power reference is reduced by a small amount and maintained until it meets the MPPT reference. The results show that the scheme causes a small SFD while improving the FN and the rate of change of frequency in any wind conditions, even in a grid that has a high penetration of wind power.« less

Are Global and Regional Improvements in Life Expectancy and in Child, Adult and Senior Survival Slowing?

PubMed Central

Hum, Ryan J.; Verguet, Stéphane; Cheng, Yu-Ling; McGahan, Anita M.; Jha, Prabhat

2015-01-01

Improvements in life expectancy have been considerable over the past hundred years. Forecasters have taken to applying historical trends under an assumption of continuing improvements in life expectancy in the future. A linear mixed effects model was used to estimate the trends in global and regional rates of improvements in life expectancy, child, adult, and senior survival, in 166 countries between 1950 and 2010. Global improvements in life expectancy, including both child and adult survival rates, decelerated significantly over the study period. Overall life expectancy gains were estimated to have declined from 5.9 to 4.0 months per year for a mean deceleration of -0.07 months/year2; annual child survival gains declined from 4.4 to 1.6 deaths averted per 1000 for a mean deceleration of -0.06 deaths/1000/year2; adult survival gains were estimated to decline from 4.8 to 3.7 deaths averted per 1000 per year for a mean deceleration of -0.08 deaths/1000/year2. Senior survival gains however increased from 2.4 to 4.2 deaths averted per 1000 per year for an acceleration of 0.03 deaths/1000/year2. Regional variation in the four measures was substantial. The rates of global improvements in life expectancy, child survival, and adult survival have declined since 1950 despite an increase in the rate of improvements among seniors. We postulate that low-cost innovation, related to the last half-century progress in health–primarily devoted to children and middle age, is reaping diminishing returns on its investments. Trends are uneven across regions and measures, which may be due in part to the state of epidemiological transition between countries and regions and disparities in the diffusion of innovation, accessible only in high-income countries where life expectancy is already highest. PMID:25992949

Tracking the behavior of Maillard browning in lysine/arginine-sugar model systems under high hydrostatic pressure.

PubMed

Ma, Xiao-Juan; Gao, Jin-Yan; Tong, Ping; Li, Xin; Chen, Hong-Bing

2017-12-01

High-pressure processing is gaining popularity in the food industry. However, its effect on the Maillard reaction during high-pressure-assisted pasteurization and sterilization is not well documented. This study aimed to investigate the effects of high hydrostatic pressure on the Maillard reaction during these processes using amino acid (lysine or arginine)-sugar (glucose or fructose) solution models. High pressure retarded the intermediate and final stages of the Maillard reaction in the lysine-sugar model. For the lysine-glucose model, the degradation rate of Amadori compounds was decelerated, while acceleration was observed in the arginine-sugar model. Increased temperature not only accelerated the Maillard reaction over time but also formed fluorescent compounds with different emission wavelengths. Lysine reacted with the sugars more readily than arginine under the same conditions. In addition, it was easier for lysine to react with glucose, whereas arginine reacted more readily with fructose under high pressure. High pressure exerts different effects on lysine-sugar and arginine-sugar models. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Investigation of Pneumatic Inlet and Diffuser Blowing on a Ducted Fan Propulsor in Static Thrust Operation

NASA Technical Reports Server (NTRS)

Kondor, Shayne; Englar, Robert J.; Lee, Warren J.

2003-01-01

Tilting ducted fans present a solution for the lifting and forward flight propulsion requirements of VTOL aircraft. However, the geometry of the duct enshrouding the propeller has great a effect on the efficiency of the fan in various flight modes. Shroud geometry controls the velocity and pressure at the face of the fan, while maintaining a finite loading out at the tips of the fan blades. A duct tailored for most efficient generation of static lifting thrust will generally suffer from performance deficiencies in forward flight. The converse is true as well, leaving the designer with a difficult trade affecting the overall performance and sizing of the aircraft. Ideally, the shroud of a vertical lifting fan features a generous bell mouth inlet promoting acceleration of flow into the face of the fan, and terminating in a converging nozzle at the exit. Flow entering the inlet is accelerated into the fan by the circulation about the shroud, resulting in an overall increase in thrust compared to an open propeller operating under the same conditions . The accelerating shroud design is often employed in lifting ducted fans to benefit from the thrust augmentation; however, such shroud designs produce significant drag penalties in axial flight, thus are unsuitable for efficient forward flight applications. Decelerating, or diffusing, duct designs are employed for higher speed forward flight configurations. The lower circulation on the shroud tends to decelerate the flow into the face of the fan, which is detrimental to static thrust development; however, net thrust is developed on the shroud while the benefits of finite blade loading are retained. With judicious shroud design for intended flight speeds, a net increase in efficiency can be obtained over an open propeller. In this experiment, conducted under contract to NASA LaRC (contract NAG-1-02093) circulation control is being applied to a mildly diffusing shroud design, intended for improved forward flight performance, to generate circulation in the sense of an accelerating duct design. The intent is to improve static thrust performance of a ducted fan tailored for high speed axial flight, while at the same time significantly reduce the pressure signature on the ground plane. Circulation control on the fan shroud is achieved by the Coanda effect.

Aerocapture Inflatable Decelerator (AID)

NASA Technical Reports Server (NTRS)

Reza, Sajjad

2007-01-01

Forward Attached Inflatable Decelerators, more commonly known as inflatable aeroshells, provide an effective, cost efficient means of decelerating spacecrafts by using atmospheric drag for aerocapture or planetary entry instead of conventional liquid propulsion deceleration systems. Entry into planetary atmospheres results in significant heating and aerodynamic pressures which stress aeroshell systems to their useful limits. Incorporation of lightweight inflatable decelerator surfaces with increased surface-area footprints provides the opportunity to reduce heat flux and induced temperatures, while increasing the payload mass fraction. Furthermore, inflatable aeroshell decelerators provide the needed deceleration at considerably higher altitudes and Mach numbers when compared with conventional rigid aeroshell entry systems. Inflatable aeroshells also provide for stowage in a compact space, with subsequent deployment of a large-area, lightweight heatshield to survive entry heating. Use of a deployable heatshield decelerator not only enables an increase in the spacecraft payload mass fraction and but may also eliminate the need for a spacecraft backshell and cruise stage. This document is the viewgraph slides for the paper's presentation.

Long-term administration of pDC-Stimulative Lactococcus lactis strain decelerates senescence and prolongs the lifespan of mice.

PubMed

Sugimura, Tetsu; Jounai, Kenta; Ohshio, Konomi; Suzuki, Hiroaki; Kirisako, Takayoshi; Sugihara, Yoshihiko; Fujiwara, Daisuke

2018-05-01

The decline in immune function caused by aging increases the risk of infectious diseases, tumorigeneses and chronic inflammation, resulting in accelerating senescence. We previously reported a lactic acid bacteria, Lactococcus lactis strain Plasma (synonym of Lactococcus lactis subsp. lactis JCM 5805, Lc-Plasma), that stimulates plasmacytoid dendritic cells (pDCs), which play a crucial role in phylaxis from viral infection. In this study, we investigated the anti-aging effects of long-term oral administration of Lc-Plasma in a senescence-accelerated mouse strain, SAMP6. Mice given Lc-Plasma showed a significant improvement in survival rate at 82 weeks and a decreased senescence score as compared with control mice throughout this study. Anatomic analysis at 82 weeks revealed that the frequency of altered hepatocellular foci was significantly lower, and the incidence of other pathological findings in the liver and lungs tended to be lower in Lc-Plasma mice than in control mice. Transcription level of the IL-1β gene in lungs also tended to be lower in Lc-Plasma mice. Furthermore, the thinning of skin and age-related decrease in muscle mass were also significantly suppressed in the Lc-Plasma group as compared with the control group. Consistent with these phenotypic features, pDCs activity was significantly higher in Lc-Plasma mice than in control mice. In conclusion, long-term administration of Lc-Plasma can decelerate senescence and prolong lifespan via maintenance of the immune system due to activation of pDCs. Copyright © 2018 Elsevier B.V. All rights reserved.

Steady state and dynamical structure of a cosmic-ray-modified termination shock

NASA Technical Reports Server (NTRS)

Donohue, D. J.; Zank, G. P.

1993-01-01

A hydrodynamic model is developed for the structure of a cosmic-ray-modified termination shock. The model is based on the two-fluid equations of diffuse shock acceleration (Drury and Volk, 1981). Both the steady state structure of the shock and its interaction with outer heliospheric disturbances are considered. Under the assumption that the solar wind is decelerated by diffusing interstellar cosmic rates, it is shown that the natural state of the termination shock is a gradual deceleration and compression, followed by a discontinuous jump to a downstream state which is dominated by the pressure contribution of the cosmic rays. A representative model is calculated for the steady state which incorporates both interstellar cosmic ray mediation and diffusively accelerated anomalous ions through a proposed thermal leakage mechanism. The interaction of large-scale disturbances with the equilibrium termination shock model is shown to result in some unusual downstream structure, including transmitted shocks and cosmic-ray-modified contact discontinuities. The structure observed may be connected to the 2-kHz outer heliospheric radio emission (Cairns et al., 1992a, b). The time-dependent simulations also demonstrate that interaction with solar wind compressible turbulence (e.g., traveling interplanetary shocks, etc.) could induce the termination shock to continually fluctuate between cosmic-ray-dominated and gas-dynamic states. This fluctuation may represent a partial explanation of the galactic cosmic ray modulation effect and illustrates that the Pioneer and Voyager satellites will encounter an evolving shock whose structure and dynamic properties are strongly influence by the mediation of interstellar and anomalous cosmic rays.

Steady state and dynamical structure of a cosmic-ray-modified termination shock

NASA Astrophysics Data System (ADS)

Donohue, D. J.; Zank, G. P.

1993-11-01

A hydrodynamic model is developed for the structure of a cosmic-ray-modified termination shock. The model is based on the two-fluid equations of diffuse shock acceleration (Drury and Volk, 1981). Both the steady state structure of the shock and its interaction with outer heliospheric disturbances are considered. Under the assumption that the solar wind is decelerated by diffusing interstellar cosmic rates, it is shown that the natural state of the termination shock is a gradual deceleration and compression, followed by a discontinuous jump to a downstream state which is dominated by the pressure contribution of the cosmic rays. A representative model is calculated for the steady state which incorporates both interstellar cosmic ray mediation and diffusively accelerated anomalous ions through a proposed thermal leakage mechanism. The interaction of large-scale disturbances with the equilibrium termination shock model is shown to result in some unusual downstream structure, including transmitted shocks and cosmic-ray-modified contact discontinuities. The structure observed may be connected to the 2-kHz outer heliospheric radio emission (Cairns et al., 1992a, b). The time-dependent simulations also demonstrate that interaction with solar wind compressible turbulence (e.g., traveling interplanetary shocks, etc.) could induce the termination shock to continually fluctuate between cosmic-ray-dominated and gas-dynamic states. This fluctuation may represent a partial explanation of the galactic cosmic ray modulation effect and illustrates that the Pioneer and Voyager satellites will encounter an evolving shock whose structure and dynamic properties are strongly influence by the mediation of interstellar and anomalous cosmic rays.

Experimental Modeling of a Formula Student Carbon Composite Nose Cone

PubMed Central

Fellows, Neil A.

2017-01-01

A numerical impact study is presented on a Formula Student (FS) racing car carbon composite nose cone. The effect of material model and model parameter selection on the numerical deceleration curves is discussed in light of the experimental deceleration data. The models show reasonable correlation in terms of the shape of the deceleration-displacement curves but do not match the peak deceleration values with errors greater that 30%. PMID:28772982

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

Brisk heart rate and EEG changes during execution and withholding of cue-paced foot motor imagery

PubMed Central

Pfurtscheller, Gert; Solis-Escalante, Teodoro; Barry, Robert J.; Klobassa, Daniela S.; Neuper, Christa; Müller-Putz, Gernot R.

2013-01-01

Cue-paced motor imagery (MI) is a frequently used mental strategy to realize a Brain-Computer Interface (BCI). Recently it has been reported that two MI tasks can be separated with a high accuracy within the first second after cue presentation onset. To investigate this phenomenon in detail we studied the dynamics of motor cortex beta oscillations in EEG and the changes in heart rate (HR) during visual cue-paced foot MI using a go (execution of imagery) vs. nogo (withholding of imagery) paradigm in 16 healthy subjects. Both execution and withholding of MI resulted in a brisk centrally localized beta event-related desynchronization (ERD) with a maximum at ~400 ms and a concomitant HR deceleration. We found that response patterns within the first second after stimulation differed between conditions. The ERD was significantly larger in go as compared to nogo. In contrast the HR deceleration was somewhat smaller and followed by an acceleration in go as compared to nogo. These findings suggest that the early beta ERD reflects visually induced preparatory activity in motor cortex networks. Both the early beta ERD and the HR deceleration are the result of automatic operating processes that are likely part of the orienting reflex (OR). Of interest, however, is that the preparatory cortical activity is strengthened and the HR modulated already within the first second after stimulation during the execution of MI. The subtraction of the HR time course of the nogo from the go condition revealed a slight HR acceleration in the first seconds most likely due to the increased mental effort associated with the imagery process. PMID:23908614

Responses to deceleration during car following: roles of optic flow, warnings, expectations, and interruptions.

PubMed

DeLucia, Patricia R; Tharanathan, Anand

2009-12-01

More than 25% of accidents are rear-end collisions. It is essential to identify the factors that contribute to such collisions. One such factor is a driver's ability to respond to the deceleration of the car ahead. In Experiment 1, we measured effects of optic flow information and discrete visual and auditory warnings (brake lights, tones) on responses to deceleration during car following. With computer simulations of car-following scenes, university students pressed a button when the lead car decelerated. Both classes of information affected responses. Observers relied on discrete warnings when optic flow information was relatively less effective as determined by the lead car's headway and deceleration rate. This is consistent with DeLucia's (2008) conceptual framework of space perception that emphasized the importance of viewing distance and motion (and task). In Experiment 2, we measured responses to deceleration after a visual interruption. Scenes were designed to tease apart the role of expectations and optic flow. Responses mostly were consistent with optic flow information presented after the interruption rather than with putative mental expectations that were set up by the lead car's motion prior to the interruption. The theoretical implication of the present results is that responses to deceleration are based on multiple sources of information, including optical size, optical expansion rate and tau, and discrete warnings that are independent of optic flow. The practical implication is that in-vehicle collision-avoidance warning systems may be more useful when optic flow is less effective (e.g., slow deceleration rates), implicating a role for adaptive collision-warning systems. Copyright 2009 APA

Expanding space-time and variable vacuum energy

NASA Astrophysics Data System (ADS)

Parmeggiani, Claudio

2017-08-01

The paper describes a cosmological model which contemplates the presence of a vacuum energy varying, very slightly (now), with time. The constant part of the vacuum energy generated, some 6 Gyr ago, a deceleration/acceleration transition of the metric expansion; so now, in an aged Universe, the expansion is inexorably accelerating. The vacuum energy varying part is instead assumed to be eventually responsible of an acceleration/deceleration transition, which occurred about 14 Gyr ago; this transition has a dynamic origin: it is a consequence of the general relativistic Einstein-Friedmann equations. Moreover, the vacuum energy (constant and variable) is here related to the zero-point energy of some quantum fields (scalar, vector, or spinor); these fields are necessarily described in a general relativistic way: their structure depends on the space-time metric, typically non-flat. More precisely, the commutators of the (quantum field) creation/annihilation operators are here assumed to depend on the local value of the space-time metric tensor (and eventually of its curvature); furthermore, these commutators rapidly decrease for high momentum values and they reduce to the standard ones for a flat metric. In this way, the theory is ”gravitationally” regularized; in particular, the zero-point (vacuum) energy density has a well defined value and, for a non static metric, depends on the (cosmic) time. Note that this varying vacuum energy can be negative (Fermi fields) and that a change of its sign typically leads to a minimum for the metric expansion factor (a ”bounce”).

Setting accelerated dissolution test for PLGA microspheres containing peptide, investigation of critical parameters affecting drug release rate and mechanism.

PubMed

Tomic, I; Vidis-Millward, A; Mueller-Zsigmondy, M; Cardot, J-M

2016-05-30

The objective of this study was development of accelerated in vitro release method for peptide loaded PLGA microspheres using flow-through apparatus and assessment of the effect of dissolution parameters (pH, temperature, medium composition) on drug release rate and mechanism. Accelerated release conditions were set as pH 2 and 45°C, in phosphate buffer saline (PBS) 0.02M. When the pH was changed from 2 to 4, diffusion controlled phases (burst and lag) were not affected, while release rate during erosion phase decreased two-fold due to slower ester bonds hydrolyses. Decreasing temperature from 45°C to 40°C, release rate showed three-fold deceleration without significant change in release mechanism. Effect of medium composition on drug release was tested in PBS 0.01M (200 mOsm/kg) and PBS 0.01M with glucose (380 mOsm/kg). Buffer concentration significantly affected drug release rate and mechanism due to the change in osmotic pressure, while ionic strength did not have any effect on peptide release. Furthermore, dialysis sac and sample-and-separate techniques were used, in order to evaluate significance of dissolution technique choice on the release process. After fitting obtained data to different mathematical models, flow-through method was confirmed as the most appropriate for accelerated in vitro dissolution testing for a given formulation. Copyright © 2016 Elsevier B.V. All rights reserved.

Procedure Selection and Patient Positioning Influence Spine Kinematics During High-Velocity, Low-Amplitude Spinal Manipulation Applied to the Low Back.

PubMed

Bell, Spencer; D'Angelo, Kevin; Kawchuk, Gregory N; Triano, John J; Howarth, Samuel J

This investigation compared indirect 3-dimensional angular kinematics (position, velocity, and acceleration) of the lumbar spine for 2 different high-velocity, low-amplitude (HVLA) spinal manipulation procedures (lumbar spinous pull or push), and altered initial patient lower limb posture. Twenty-four participants underwent 6 HVLA procedures directed toward the presumed L4 vertebra, reflecting each combination of 2 variants of a spinal manipulation application technique (spinous pull and push) and 3 initial hip flexion angles (0°, 45°, and 90°) applied using a right lateral recumbent patient position. All contact forces and moments between the patient and the external environment, as well as 3-dimensional kinematics of the patient's pelvis and thorax, were recorded. Lumbar spine angular positions, velocities, and accelerations were analyzed within the preload and impulse stages of each HVLA trial. Lumbar spine left axial rotation was greater for the pull HVLA. The pull HVLA also generated a greater maximum (leftward) and lower minimum (rightward) axial rotation velocity and deceleration and greater leftward and rightward lateral bend velocities, acceleration, and deceleration components. Not flexing the hip produced the greatest amount of extension, as well as the lowest axial rotation and maximum axial rotation acceleration during the impulse. This investigation provides basic kinematic information for clinicians to understand the similarities and differences between 2 HVLA side-lying manipulations in the lumbar spine. Use of these findings and novel technology can drive future research initiatives that can both affect clinical decision making and influence teaching environments surrounding spinal manipulative therapy skill acquisition. Copyright © 2017. Published by Elsevier Inc.

Statefinder diagnostic and constraints on the Palatini f(R) gravity theories

NASA Astrophysics Data System (ADS)

Cao, Shu-Lei; Li, Song; Yu, Hao-Ran; Zhang, Tong-Jie

2018-03-01

We focus on a series of f(R) gravity theories in Palatini formalism to investigate the probabilities of producing late-time acceleration for the flat Friedmann-Robertson-Walker (FRW) universe. We apply a statefinder diagnostic to these cosmological models for chosen series of parameters to see if they can be distinguished from one another. The diagnostic involves the statefinder pair {r, s}, where r is derived from the scale factor a and its higher derivatives with respect to the cosmic time t, and s is expressed by r and the deceleration parameter q. In conclusion, we find that although two types of f(R) theories: (i) f(R) = R + αRm – βR ‑n and (ii) f(R) = R + α ln R – β can lead to late-time acceleration, their evolutionary trajectories in the r – s and r – q planes reveal different evolutionary properties, which certainly justify the merits of the statefinder diagnostic. Additionally, we utilize the observational Hubble parameter data (OHD) to constrain these models of f(R) gravity. As a result, except for m = n = 1/2 in case (i), α = 0 in case (i) and case (ii) allow the ΛCDM model to exist in the 1σ confidence region. After applying the statefinder diagnostic to the best-fit models, we find that all the best-fit models are capable of going through the deceleration/acceleration transition stage with a late-time acceleration epoch, and all these models turn to the de Sitter point ({r, s} = {1, 0}) in the future. Also, the evolutionary differences between these models are distinct, especially in the r – s plane, which makes the statefinder diagnostic more reliable in discriminating cosmological models.

Randomized trial of intermittent or continuous amnioinfusion for variable decelerations.

PubMed

Rinehart, B K; Terrone, D A; Barrow, J H; Isler, C M; Barrilleaux, P S; Roberts, W E

2000-10-01

To determine whether continuous or intermittent bolus amnioinfusion is more effective in relieving variable decelerations. Patients with repetitive variable decelerations were randomized to an intermittent bolus or continuous amnioinfusion. The intermittent bolus infusion group received boluses of 500 mL of normal saline, each over 30 minutes, with boluses repeated if variable decelerations recurred. The continuous infusion group received a bolus infusion of 500 mL of normal saline over 30 minutes and then 3 mL per minute until delivery occurred. The ability of the amnioinfusion to abolish variable decelerations was analyzed, as were maternal demographic and pregnancy outcome variables. Power analysis indicated that 64 patients would be required. Thirty-five patients were randomized to intermittent infusion and 30 to continuous infusion. There were no differences between groups in terms of maternal demographics, gestational age, delivery mode, neonatal outcome, median time to resolution of variable decelerations, or the number of times variable decelerations recurred. The median volume infused in the intermittent infusion group (500 mL) was significantly less than that in the continuous infusion group (905 mL, P =.003). Intermittent bolus amnioinfusion is as effective as continuous infusion in relieving variable decelerations in labor. Further investigation is necessary to determine whether either of these techniques is associated with increased occurrence of rare complications such as cord prolapse or uterine rupture.

Numerical modelling of flow structures over idealized transverse aeolian dunes of varying geometry

NASA Astrophysics Data System (ADS)

Parsons, Daniel R.; Walker, Ian J.; Wiggs, Giles F. S.

2004-04-01

A Computational Fluid Dynamics (CFD) model (PHOENICS™ 3.5) previously validated for wind tunnel measurements is used to simulate the streamwise and vertical velocity flow fields over idealized transverse dunes of varying height ( h) and stoss slope basal length ( L). The model accurately reproduced patterns of: flow deceleration at the dune toe; stoss flow acceleration; vertical lift in the crest region; lee-side flow separation, re-attachment and reversal; and flow recovery distance. Results indicate that the flow field over transverse dunes is particularly sensitive to changes in dune height, with an increase in height resulting in flow deceleration at the toe, streamwise acceleration and vertical lift at the crest, and an increase in the extent of, and strength of reversed flows within, the lee-side separation cell. In general, the length of the separation zone varied from 3 to 15 h from the crest and increased over taller, steeper dunes. Similarly, the flow recovery distance ranged from 45 to >75 h and was more sensitive to changes in dune height. For the range of dune shapes investigated in this study, the differing effects of height and stoss slope length raise questions regarding the applicability of dune aspect ratio as a parameter for explaining airflow over transverse dunes. Evidence is also provided to support existing research on: streamline curvature and the maintenance of sand transport in the toe region; vertical lift in the crest region and its effect on grainfall delivery; relations between the turbulent shear layer and downward forcing of flow re-attachment; and extended flow recovery distances beyond the separation cell. Field validation is required to test these findings in natural settings. Future applications of the model will characterize turbulence and shear stress fields, examine the effects of more complex isolated dune forms and investigate flow over multiple dunes.

Magnetized strange quark matter in f(R, T) gravity with bilinear and special form of time varying deceleration parameter

NASA Astrophysics Data System (ADS)

Sahoo, P. K.; Sahoo, Parbati; Bishi, Binaya K.; Aygün, Sezgin

2018-04-01

In this paper, we have studied homogeneous and anisotropic locally rotationally symmetric (LRS) Bianchi type-I model with magnetized strange quark matter (MSQM) distribution and cosmological constant Λ in f(R, T) gravity where R is the Ricci scalar and T the trace of matter source. The exact solutions of the field equations are obtained under bilinear and special form of time varying deceleration parameter (DP). Firstly, we have considered two specific forms of bilinear DP with a single parameter of the form: q = α(1-t)/1+t and q = -αt/1+t, which leads to the constant or linear nature of the function based on the constant α. Second one is the special form of the DP as q = - 1 + β/1+aβ. From the results obtained here, one can observe that in the early universe magnetic flux has more effects and it reduces gradually in the later stage. For t → ∞, we get p → -Bc and ρ → Bc. The behaviour of strange quark matter along with magnetic epoch gives an idea of accelerated expansion of the universe as per the observations of the type Ia Supernovae.

Influence of automatic word reading on motor control.

PubMed

Gentilucci, M; Gangitano, M

1998-02-01

We investigated the possible influence of automatic word reading on processes of visuo-motor transformation. Six subjects were required to reach and grasp a rod on whose visible face the word 'long' or 'short' was printed. Word reading was not explicitly required. In order to induce subjects to visually analyse the object trial by trial, object position and size were randomly varied during the experimental session. The kinematics of the reaching component was affected by word presentation. Peak acceleration, peak velocity, and peak deceleration of arm were higher for the word 'long' with respect to the word 'short'. That is, during the initial movement phase subjects automatically associated the meaning of the word with the distance to be covered and activated a motor program for a farther and/or nearer object position. During the final movement phase, subjects modified the braking forces (deceleration) in order to correct the initial error. No effect of the words on the grasp component was observed. These results suggest a possible influence of cognitive functions on motor control and seem to contrast with the notion that the analyses executed in the ventral and dorsal cortical visual streams are different and independent.

High Efficiency Electron-Laser Interactions in Tapered Helical Undulators

NASA Astrophysics Data System (ADS)

Duris, Joseph Patrick

Efficient coupling of relativistic electron beams with high power radiation lies at the heart of advanced accelerator and light source research and development. The inverse free electron laser is a stable accelerator capable of harnessing very high intensity laser electric fields to efficiently transfer large powers from lasers to electron beams. In this dissertation, we first present the theoretical framework to describe the interaction, and then apply our improved understanding of the IFEL to the design and numerical study of meter-long, GeV IFELs for compact light sources. The central experimental work of the dissertation is the UCLA BNL helical inverse free electron laser experiment at the Accelerator Test Facility in Brookhaven National Laboratory which used a strongly tapered 54cm long, helical, permanent magnet undulator and a several hundred GW CO2 laser to accelerate electrons from 52 to 106MeV, setting new records for inverse free electron laser energy gain (54MeV) and average accelerating gradient (100MeV/m). The undulator design and fabrication as well as experimental diagnostics are presented. In order to improve the stability and quality of the accelerated electron beam, we redesigned the undulator for a slightly reduced output energy by modifying the magnet gap throughout the undulator, and we used this modified undulator to demonstrated capture of >25% of the injected beam without prebunching. In the study of heavily loaded GeV inverse free electron lasers, we show that a majority of the power may be transferred from a laser to the accelerated electron beam. Reversing the process to decelerate high power electron beams, a mechanism we refer to as tapering enhanced stimulated superradiant amplification, offers a clear path to high power light sources. We present studies of radiation production for a wide range of wavelengths (10mum, 13nm, and 0.3nm) using this method and discuss the design for a deceleration experiment using the same undulator used for acceleration in this experiment. By accounting for the evolving radiation field in the design of the undulator tapering, a large fraction of energy may be transferred between the electrons and laser, enabling compact, high-current GeV accelerators and various wavelength light-sources of unprecedented peak powers.

Disordered cellular automaton traffic flow model: phase separated state, density waves and self organized criticality

NASA Astrophysics Data System (ADS)

Fourrate, K.; Loulidi, M.

2006-01-01

We suggest a disordered traffic flow model that captures many features of traffic flow. It is an extension of the Nagel-Schreckenberg (NaSch) stochastic cellular automata for single line vehicular traffic model. It incorporates random acceleration and deceleration terms that may be greater than one unit. Our model leads under its intrinsic dynamics, for high values of braking probability pr, to a constant flow at intermediate densities without introducing any spatial inhomogeneities. For a system of fast drivers pr→0, the model exhibits a density wave behavior that was observed in car following models with optimal velocity. The gap of the disordered model we present exhibits, for high values of pr and random deceleration, at a critical density, a power law distribution which is a hall mark of a self organized criticality phenomena.

Cavitation luminescence in a water hammer: Upscaling sonoluminescence

NASA Astrophysics Data System (ADS)

Su, C.-K.; Camara, C.; Kappus, B.; Putterman, S. J.

2003-06-01

Oscillatory acceleration and deceleration of a column of water leads to a pipe hammer as well as cavitation. With a small amount of xenon gas dissolved in the water, we can detect a stream of predominantly ultraviolet subnanosecond flashes of light which are attributed to collapsing bubbles. The observed emission can exceed 108 photons for a single collapse and has a peak power over 0.4 W.

Velocity profiles of interplanetary shocks

NASA Technical Reports Server (NTRS)

Cane, H. V.

1983-01-01

The type 2 radio burst was identified as a shock propagating through solar corona. Radio emission from shocks travelling through the interplanetary (IP) medium was observed. Using the drift rates of IP type II bursts the velocity characteristics of eleven shocks were investigated. It is indicated that shocks in the IP medium undergo acceleration before decelerating and that the slower shocks take longer to attain their maximum velocity.

40 CFR 202.20 - Standards for highway operations.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) measured on an open site with fast meter response at 50 feet from the centerline of lane of travel on highways with speed limits of 35 MPH or less; or 90 dB(A) measured on an open site with fast meter response..., acceleration or deceleration generates a sound level in excess of 83 dB(A) measured on an open site with fast...

40 CFR 202.20 - Standards for highway operations.

Code of Federal Regulations, 2013 CFR

2013-07-01

...) measured on an open site with fast meter response at 50 feet from the centerline of lane of travel on highways with speed limits of 35 MPH or less; or 90 dB(A) measured on an open site with fast meter response..., acceleration or deceleration generates a sound level in excess of 83 dB(A) measured on an open site with fast...

40 CFR 202.20 - Standards for highway operations.

Code of Federal Regulations, 2014 CFR

2014-07-01

...) measured on an open site with fast meter response at 50 feet from the centerline of lane of travel on highways with speed limits of 35 MPH or less; or 90 dB(A) measured on an open site with fast meter response..., acceleration or deceleration generates a sound level in excess of 83 dB(A) measured on an open site with fast...

40 CFR 202.20 - Standards for highway operations.

Code of Federal Regulations, 2012 CFR

2012-07-01

...) measured on an open site with fast meter response at 50 feet from the centerline of lane of travel on highways with speed limits of 35 MPH or less; or 90 dB(A) measured on an open site with fast meter response..., acceleration or deceleration generates a sound level in excess of 83 dB(A) measured on an open site with fast...

40 CFR 202.20 - Standards for highway operations.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) measured on an open site with fast meter response at 50 feet from the centerline of lane of travel on highways with speed limits of 35 MPH or less; or 90 dB(A) measured on an open site with fast meter response..., acceleration or deceleration generates a sound level in excess of 83 dB(A) measured on an open site with fast...

Rf Feedback free electron laser

DOEpatents

Brau, Charles A.; Swenson, Donald A.; Boyd, Jr., Thomas J.

1981-01-01

A free electron laser system and electron beam system for a free electron laser which use rf feedback to enhance efficiency. Rf energy is extracted from an electron beam by decelerating cavities and returned to accelerating cavities using rf returns such as rf waveguides, rf feedthroughs, etc. This rf energy is added to rf klystron energy to lower the required input energy and thereby enhance energy efficiency of the system.

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

Liu, Ying D.; Luhmann, Janet G.; Moestl, Christian

We investigate how coronal mass ejections (CMEs) propagate through, and interact with, the inner heliosphere between the Sun and Earth, a key question in CME research and space weather forecasting. CME Sun-to-Earth kinematics are constrained by combining wide-angle heliospheric imaging observations, interplanetary radio type II bursts, and in situ measurements from multiple vantage points. We select three events for this study, the 2012 January 19, 23, and March 7 CMEs. Different from previous event studies, this work attempts to create a general picture for CME Sun-to-Earth propagation and compare different techniques for determining CME interplanetary kinematics. Key results are obtainedmore » concerning CME Sun-to-Earth propagation: (1) the Sun-to-Earth propagation of fast CMEs can be approximately formulated into three phases: an impulsive acceleration, then a rapid deceleration, and finally a nearly constant speed propagation (or gradual deceleration); (2) the CMEs studied here are still accelerating even after the flare maximum, so energy must be continuously fed into the CME even after the time of the maximum heating and radiation has elapsed in the corona; (3) the rapid deceleration, presumably due to interactions with the ambient medium, mainly occurs over a relatively short timescale following the acceleration phase; and (4) CME-CME interactions seem a common phenomenon close to solar maximum. Our comparison between different techniques (and data sets) has important implications for CME observations and their interpretations: (1) for the current cases, triangulation assuming a compact CME geometry is more reliable than triangulation assuming a spherical front attached to the Sun for distances below 50-70 solar radii from the Sun, but beyond about 100 solar radii we would trust the latter more; (2) a proper treatment of CME geometry must be performed in determining CME Sun-to-Earth kinematics, especially when the CME propagation direction is far away from the observer; and (3) our approach to comparing wide-angle heliospheric imaging observations with interplanetary radio type II bursts provides a novel tool in investigating CME propagation characteristics. Future CME observations and space weather forecasting are discussed based on these results.« less

Influence of custom-made and prefabricated insoles before and after an intense run

PubMed Central

2017-01-01

Each time the foot contacts the ground during running there is a rapid deceleration that results in a shock wave that is transmitted from the foot to the head. The fatigue of the musculoskeletal system during running may decrease the ability of the body to absorb those shock waves and increase the risk of injury. Insoles are commonly prescribed to prevent injuries, and both custom-made and prefabricated insoles have been observed to reduce shock accelerations during running. However, no study to date has included a direct comparison of their behaviour measured over the same group of athletes, and therefore great controversy still exists regarding their effectiveness in reducing impact loading during running. The aim of the study was to analyse the acute differences in stride and shock parameters while running on a treadmill with custom-made and prefabricated insoles. Stride parameters (stride length, stride rate) and shock acceleration parameters (head and tibial peak acceleration, shock magnitude, acceleration rate, and shock attenuation) were measured using two triaxial accelerometers in 38 runners at 3.33 m/s before and after a 15-min intense run while using the sock liner of the shoe (control condition), prefabricated insoles and custom-made insoles. No differences in shock accelerations were found between the custom-made and the control insoles. The prefabricated insoles increased the head acceleration rate (post-fatigue, p = 0.029) compared to the control condition. The custom-made reduced tibial (pre-fatigue, p = 0.041) and head acceleration rates (pre-fatigue and post-fatigue, p = 0.01 and p = 0.046) compared to the prefabricated insoles. Neither the stride nor the acceleration parameters were modified as a result of the intense run. In the present study, the acute use of insoles (custom-made, prefabricated) did not reduce shock accelerations compared to the control insoles. Therefore, their effectiveness at protecting against injuries associated with elevated accelerations is not supported and remains unclear. PMID:28245273

Dynamin phosphorylation controls optimization of endocytosis for brief action potential bursts

PubMed Central

Armbruster, Moritz; Messa, Mirko; Ferguson, Shawn M; De Camilli, Pietro; Ryan, Timothy A

2013-01-01

Modulation of synaptic vesicle retrieval is considered to be potentially important in steady-state synaptic performance. Here we show that at physiological temperature endocytosis kinetics at hippocampal and cortical nerve terminals show a bi-phasic dependence on electrical activity. Endocytosis accelerates for the first 15–25 APs during bursts of action potential firing, after which it slows with increasing burst length creating an optimum stimulus for this kinetic parameter. We show that activity-dependent acceleration is only prominent at physiological temperature and that the mechanism of this modulation is based on the dephosphorylation of dynamin 1. Nerve terminals in which dynamin 1 and 3 have been replaced with dynamin 1 harboring dephospho- or phospho-mimetic mutations in the proline-rich domain eliminate the acceleration phase by either setting endocytosis at an accelerated state or a decelerated state, respectively. DOI: http://dx.doi.org/10.7554/eLife.00845.001 PMID:23908769

Perturbations for transient acceleration

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

Vargas, Cristofher Zuñiga; Zimdahl, Winfried; Hipólito-Ricaldi, Wiliam S., E-mail: win_unac@hotmail.com, E-mail: hipolito@ceunes.ufes.br, E-mail: winfried.zimdahl@pq.cnpq.br

2012-04-01

According to the standard ΛCDM model, the accelerated expansion of the Universe will go on forever. Motivated by recent observational results, we explore the possibility of a finite phase of acceleration which asymptotically approaches another period of decelerated expansion. Extending an earlier study on a corresponding homogeneous and isotropic dynamics, in which interactions between dark matter and dark energy are crucial, the present paper also investigates the dynamics of the matter perturbations both on the Newtonian and General Relativistic (GR) levels and quantifies the potential relevance of perturbations of the dark-energy component. In the background, the model is tested againstmore » the Supernova type Ia (SNIa) data of the Constitution set and on the perturbative level against growth rate data, among them those of the WiggleZ survey, and the data of the 2dFGRS project. Our results indicate that a transient phase of accelerated expansion is not excluded by current observations.« less

Aerodynamic Decelerators for Planetary Exploration: Past, Present, and Future

NASA Technical Reports Server (NTRS)

Cruz, Juna R.; Lingard, J. Stephen

2006-01-01

In this paper, aerodynamic decelerators are defined as textile devices intended to be deployed at Mach numbers below five. Such aerodynamic decelerators include parachutes and inflatable aerodynamic decelerators (often known as ballutes). Aerodynamic decelerators play a key role in the Entry, Descent, and Landing (EDL) of planetary exploration vehicles. Among the functions performed by aerodynamic decelerators for such vehicles are deceleration (often from supersonic to subsonic speeds), minimization of descent rate, providing specific descent rates (so that scientific measurements can be obtained), providing stability (drogue function - either to prevent aeroshell tumbling or to meet instrumentation requirements), effecting further aerodynamic decelerator system deployment (pilot function), providing differences in ballistic coefficients of components to enable separation events, and providing height and timeline to allow for completion of the EDL sequence. Challenging aspects in the development of aerodynamic decelerators for planetary exploration missions include: deployment in the unusual combination of high Mach numbers and low dynamic pressures, deployment in the wake behind a blunt-body entry vehicle, stringent mass and volume constraints, and the requirement for high drag and stability. Furthermore, these aerodynamic decelerators must be qualified for flight without access to the exotic operating environment where they are expected to operate. This paper is an introduction to the development and application of aerodynamic decelerators for robotic planetary exploration missions (including Earth sample return missions) from the earliest work in the 1960s to new ideas and technologies with possible application to future missions. An extensive list of references is provided for additional study.

Ion accelerator systems for high power 30 cm thruster operation

NASA Technical Reports Server (NTRS)

Aston, G.

1982-01-01

Two and three-grid accelerator systems for high power ion thruster operation were investigated. Two-grid translation tests show that over compensation of the 30 cm thruster SHAG grid set spacing the 30 cm thruster radial plasma density variation and by incorporating grid compensation only sufficient to maintain grid hole axial alignment, it is shown that beam current gains as large as 50% can be realized. Three-grid translation tests performed with a simulated 30 cm thruster discharge chamber show that substantial beamlet steering can be reliably affected by decelerator grid translation only, at net-to-total voltage ratios as low as 0.05.

Eddy-current-damped microelectromechanical switch

DOEpatents

Christenson, Todd R.; Polosky, Marc A.

2007-10-30

A microelectromechanical (MEM) device is disclosed that includes a shuttle suspended for movement above a substrate. A plurality of permanent magnets in the shuttle of the MEM device interact with a metal plate which forms the substrate or a metal portion thereof to provide an eddy-current damping of the shuttle, thereby making the shuttle responsive to changes in acceleration or velocity of the MEM device. Alternately, the permanent magnets can be located in the substrate, and the metal portion can form the shuttle. An electrical switch closure in the MEM device can occur in response to a predetermined acceleration-time event. The MEM device, which can be fabricated either by micromachining or LIGA, can be used for sensing an acceleration or deceleration event (e.g. in automotive applications such as airbag deployment or seat belt retraction).

Eddy-current-damped microelectromechanical switch

DOEpatents

Christenson, Todd R [Albuquerque, NM; Polosky, Marc A [Tijeras, NM

2009-12-15

A microelectromechanical (MEM) device is disclosed that includes a shuttle suspended for movement above a substrate. A plurality of permanent magnets in the shuttle of the MEM device interact with a metal plate which forms the substrate or a metal portion thereof to provide an eddy-current damping of the shuttle, thereby making the shuttle responsive to changes in acceleration or velocity of the MEM device. Alternately, the permanent magnets can be located in the substrate, and the metal portion can form the shuttle. An electrical switch closure in the MEM device can occur in response to a predetermined acceleration-time event. The MEM device, which can be fabricated either by micromachining or LIGA, can be used for sensing an acceleration or deceleration event (e.g. in automotive applications such as airbag deployment or seat belt retraction).

Apparent cosmic acceleration from Type Ia supernovae

NASA Astrophysics Data System (ADS)

Dam, Lawrence H.; Heinesen, Asta; Wiltshire, David L.

2017-11-01

Parameters that quantify the acceleration of cosmic expansion are conventionally determined within the standard Friedmann-Lemaître-Robertson-Walker (FLRW) model, which fixes spatial curvature to be homogeneous. Generic averages of Einstein's equations in inhomogeneous cosmology lead to models with non-rigidly evolving average spatial curvature, and different parametrizations of apparent cosmic acceleration. The timescape cosmology is a viable example of such a model without dark energy. Using the largest available supernova data set, the JLA catalogue, we find that the timescape model fits the luminosity distance-redshift data with a likelihood that is statistically indistinguishable from the standard spatially flat Λ cold dark matter cosmology by Bayesian comparison. In the timescape case cosmic acceleration is non-zero but has a marginal amplitude, with best-fitting apparent deceleration parameter, q_{0}=-0.043^{+0.004}_{-0.000}. Systematic issues regarding standardization of supernova light curves are analysed. Cuts of data at the statistical homogeneity scale affect light-curve parameter fits independent of cosmology. A cosmological model dependence of empirical changes to the mean colour parameter is also found. Irrespective of which model ultimately fits better, we argue that as a competitive model with a non-FLRW expansion history, the timescape model may prove a useful diagnostic tool for disentangling selection effects and astrophysical systematics from the underlying expansion history.

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.

An improved car-following model considering velocity fluctuation of the immediately ahead car

NASA Astrophysics Data System (ADS)

Yu, Shaowei; Huang, Mengxing; Ren, Jia; Shi, Zhongke

2016-05-01

To better describe car-following behaviors in the adaptive cruise control strategy and further increase roadway traffic mobility and reduce fuel consumptions, the linkage between velocity fluctuation of the immediately ahead car and the following car's acceleration or deceleration is explored with respect to the measured car-following data by employing the gray correlation analysis theory and then an improved car-following model considering velocity fluctuation of the immediately ahead car on basis of the full velocity difference model is proposed. Numerical simulations are carried out and the effects of velocity fluctuation of the immediately ahead car on each car's velocity, acceleration, vehicular gap, fuel consumptions and the total fuel consumptions of the whole car-following system with different time window lengths are investigated in detail. The results show that velocity fluctuation of the immediately ahead car has significant effects on car-following behaviors and fuel consumptions, and that considering velocity fluctuation of the immediately ahead car in designing the adaptive cruise control system can improve traffic flow stability and reduce fuel consumptions.

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

Zhang, Yue J.; Malikopoulos, Andreas; Cassandras, Christos G.

We address the problem of coordinating online a continuous flow of connected and automated vehicles (CAVs) crossing two adjacent intersections in an urban area. We present a decentralized optimal control framework whose solution yields for each vehicle the optimal acceleration/deceleration at any time in the sense of minimizing fuel consumption. The solu- tion, when it exists, allows the vehicles to cross the intersections without the use of traffic lights, without creating congestion on the connecting road, and under the hard safety constraint of collision avoidance. The effectiveness of the proposed solution is validated through simulation considering two intersections located inmore » downtown Boston, and it is shown that coordination of CAVs can reduce significantly both fuel consumption and travel time.« less

Design and Test Criteria for Increased Energy-Absorbing Seat Effectiveness

DTIC Science & Technology

1983-03-01

condition . ........ 35 8 CAMI aled. . . . . . . . . . . 37 9 CAMI wire - bending decelerator mechanism.... 38 10 Typical baseline deceleration pulses for...8217. * A * (b) Sled and wires following test. "Fiigure 9. CAI wire - bending decelerator mechanism. 38 OF --. 9 O 9 ’ W W v v v v W ’W A𔃾 50 so- 40- 40

Bell-Plesset effects in Rayleigh-Taylor instability of finite-thickness spherical and cylindrical shells

NASA Astrophysics Data System (ADS)

Velikovich, A. L.; Schmit, P. F.

2015-11-01

Bell-Plesset effects accounting for the time dependence of the radius, velocity and acceleration of the Rayleigh-Taylor-unstable surface are ubiquitous in the instability of spherical laser targets and magnetically driven cylindrical liners. We present an analytical model that, for an ideal incompressible fluid and small perturbation amplitudes, exactly accounts for the Bell-Plesset effects in finite-thickness targets and liners through acceleration and deceleration phases. We derive the time-dependent dispersion equations determining the ``instantaneous growth rate'' and demonstrate that by integrating this growth rate over time (the WKB approximation) we accurately evaluate the number of perturbation e-foldings during the acceleration phase. In the limit of the small target/liner thickness, we obtain the exact thin-shell perturbation equations and approximate thin-shell dispersion relations, generalizing the earlier results of Harris (1962), Ott (1972) and Bud'ko et al. (1989). This research was supported by the US DOE/NNSA (A.L.V.), and in part by appointment to the Sandia National Laboratories Truman Fellowship in National Security Science and Engineering (P.F.S.), which is part of the Laboratory Directed Research and Development (LDRD) Program, Project No. 165746, and sponsored by Sandia Corporation (a wholly owned subsidiary of Lockheed Martin Corporation) as Operator of Sandia National Laboratories under its U.S. Department of Energy Contract No. DE-AC04-94AL85000.

Load dependence of left ventricular contraction and relaxation. Effects of caffeine.

PubMed

Leite-Moreira, A F; Correia-Pinto, J; Gillebert, T C

1999-08-01

Load dependence of left ventricular (LV) contraction and relaxation was investigated at baseline and after alteration of intracellular calcium handling by caffeine. Afterload was increased by aortic clamp occlusions (n = 281) in anesthetized open-chest dogs (n = 7). Control and first heartbeat after the intervention were considered for analysis. Caffeine (50 mg/kg, iv) had no inotropic effect. The systolic LV pressure (LVP), developed in response to aortic occlusion, decreased as ejection proceeded and this pressure generating capacity was not affected by caffeine. Late-systolic aortic occlusions induced premature onset and accelerated rate of initial LVP fall at baseline and similarly after caffeine. Graded diastolic aortic occlusions induced systolic LVP elevations of various magnitudes. Smaller LVP elevations prolonged ejection and accelerated LVP fall, while larger elevations had opposite effects. The transition from acceleration to deceleration was observed at 83.1 +/- 1.1% of peak isovolumetric LVP at baseline and at lower loads, at 77.6 +/- 1.2%, after caffeine (p < 0.01). Isovolumetric heartbeats prolonged the time constant tau by 238 +/- 70% at baseline and only by 155 +/- 44% after caffeine (p < 0.01). The relaxation-systolic pressure relation, which describes afterload dependence of relaxation, was also modified by caffeine. Caffeine affected LV relaxation without altering contractility. As a consequence contraction-relaxation coupling was modified by caffeine. These results might help to understand load dependence of relaxation in conditions where intracellular calcium handling is altered.

Ground Target Overflight and Orbital Maneuvering via Atmospheric Maneuvers

DTIC Science & Technology

2014-03-27

Total deceleration m ∙ s−2 Gravitational acceleration m ∙ s−2 ℎ Altitude m Inclination angle rad Vehicle mass kg Geocentric ...determine the longitude. By expanding and simplifying Eqs. (3.1) and (3.5) for a circular orbit, the position can be written in the Geocentric Equatorial...Altitude m Inclination angle rad Vehicle mass kg Geocentric radial distance from planet center of mass to vehicle m General time s

Gas turbine engine fuel control

NASA Technical Reports Server (NTRS)

Gold, H. S. (Inventor)

1973-01-01

A variable orifice system is described that is responsive to compressor inlet pressure and temperature, compressor discharge pressure and rotational speed of a gas-turbine engine. It is incorporated into a hydraulic circuit that includes a zero gradient pump driven at a speed proportional to the speed of the engine. The resulting system provides control of fuel rate for starting, steady running, acceleration and deceleration under varying altitudes and flight speeds.

Quadrennial Review of Military Compensation (5th). Executive Summary.

DTIC Science & Technology

1984-01-01

COMBINATION Any proposed legislation to modify the current retire- ment system by reducing retired pay must stress the absolute requirement that a form of...Hazardous Duty Incentive Pays: — Parachute Duty — Flight Deck Duty -- Demolition Duty — Toxic Fuels and — Experimental Stress Duty Propellants — Non...3) Experimental Stress Duty Pay - an incentive for performance of hazardous duty while participating in acceleration/ deceleration testing, thermal

A Multidisciplinary Evaluation of Traumatic Brain Injury: Early Predictors of Outcome

DTIC Science & Technology

2007-04-01

undergoing an acceleration/deceleration movement (i.e., whiplash ) without direct external trauma to the head . Computed tomography (CT...mild head injury. J Neurol Neurosurg Psychiatry. 1985;48:137-140. Geurts ACH , Ribbers GM, Knoop JA, van Limbeek J. Identification of static and...boney) Injury 30 Facial Injury 13 Skull Fracture/ Head CT Findings 7 Symptoms (i.e. dizziness, nausea, vomiting) 10 Past Medical History 6 The NBM

V-22 Osprey Tilt-Rotor Aircraft

DTIC Science & Technology

2009-01-02

Station, VA, killing seven people and destroying the aircraft. This accident was caused by a fire resulting from hydraulic component failures and...April 5, 2001, the Marine Corps reported that the crash was caused by a burst hydraulic line in one of the Osprey’s two engine casings, and a software...malfunction that caused the aircraft to accelerate and decelerate unpredictably and violently when the pilots tried to compensate for the hydraulic

Standard cosmology delayed

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

Choudhury, Debajyoti; Ghoshal, Debashis; Sen, Anjan Ananda, E-mail: debajyoti.choudhury@gmail.com, E-mail: dghoshal@mail.jnu.ac.in, E-mail: anjan.ctp@jmi.ac.in

2012-02-01

The introduction of a delay in the Friedmann equation of cosmological evolution is shown to result in the very early universe undergoing the necessary accelerated expansion in the usual radiation (or matter) dominated phase. Occurring even without a violation of the strong energy condition, this expansion slows down naturally to go over to the decelerated phase, namely the standard Hubble expansion. This may obviate the need for a scalar field driven inflationary epoch.

Rf feedback free electron laser

DOEpatents

Brau, C.A.; Swenson, D.A.; Boyd, T.J. Jr.

1979-11-02

A free electron laser system and electron beam system for a free electron laser are provided which use rf feedback to enhance efficiency. Rf energy is extracted from an electron beam by decelerating cavities and returned to accelerating cavities using rf returns such as rf waveguides, rf feedthroughs, etc. This rf energy is added to rf klystron energy to lower the required input energy and thereby enhance energy efficiency of the system.

Dependence of driving characteristics upon follower-leader combination

NASA Astrophysics Data System (ADS)

Nagahama, Akihito; Yanagisawa, Daichi; Nishinari, Katsuhiro

2017-10-01

The analysis of the microscopic view of mixed traffic offers a basis for resolving traffic jams which are inhomogeneous due to several types of vehicles. In this study, we research the dependence of driving characteristics upon vehicle order in a platoon. By focusing particularly upon the manner in which the driving characteristics of a follower are affected by both their own vehicle type and that of their leader, we measured the trajectories of platoons comprising two vehicles selected from motorcycles, passenger cars, and trucks on a test course. Analysis based on vehicle order showed that the vehicle types of both the leader and the follower as well as the leader's driving characteristics affected the velocity, acceleration, deceleration, operational delay of followers, and the distance gap between leaders and followers in different ways. In addition, we investigated the factors affecting driving characteristics by multiple regression analysis. We revealed that the operational delay and the maximum distance gap tend to be large when the length of leaders is large. Furthermore, as long as a follower can follow, we need not consider vehicle types among the parameters determining maximum velocity in car-following models. The vehicle types of the leader and the follower should be considered to determine maximum acceleration. When determining maximum deceleration, the vehicle types of the follower should be considered.

Metabolic Power in Team Sports - Part 1: An Update.

PubMed

di Prampero, Pietro Enrico; Osgnach, Cristian

2018-06-14

Team sports are characterised by frequent episodes of accelerated/decelerated running. The corresponding energy cost can be estimated on the basis of the biomechanical equivalence between accelerated/decelerated running on flat terrain and constant speed running uphill/downhill. This approach allows one to: (i) estimate the time course of the instantaneous metabolic power requirement of any given player and (ii) infer therefrom the overall energy expenditure of any given time window of a soccer drill or match. In the original approach, walking and running were aggregated and energetically considered as running, even if in team sports several walking periods are interspersed among running bouts. However, since the transition speed between walking and running is known for any given incline of the terrain, we describe here an approach to identify walking episodes, thus utilising the corresponding energy cost which is smaller than in running. In addition, the new algorithm also takes into account the energy expenditure against the air resistance, for both walking and running. The new approach yields overall energy expenditure values, for a whole match,≈14% smaller than the original algorithm; moreover, it shows that the energy expenditure against the air resistance is≈2% of the total. © Georg Thieme Verlag KG Stuttgart · New York.

Drivers’ Visual Characteristics when Merging onto or Exiting an Urban Expressway

PubMed Central

Cheng, Ying; Gao, Li; Zhao, Yanan; Du, Feng

2016-01-01

The aim of this study is to examine drivers’ visual and driving behavior while merging onto or exiting an urban expressway with low and high traffic densities. The analysis was conducted according to three periods (approaching, merging or exiting, and accelerating or decelerating). A total of 10 subjects (8 males and 2 females) with ages ranging from 25 to 52 years old (M = 30.0 years old) participated in the study. The research was conducted in a natural driving situation, and the drivers’ eye movements were monitored and recorded using an eye tracking system. The results show that the influence of traffic density on the glance duration and scan duration is more significant when merging than when exiting. The results also demonstrate that the number of glances and the mean glance duration are mainly related to the driving task (e.g., the merging period). Therefore, drivers’ visual search strategies mainly depend on the current driving task. With regard to driving behavior, the variation tendencies of the duration and the velocity of each period are similar. These results support building an automated driving assistant system that can automatically identify gaps and accelerate or decelerate the car accordingly or provide suggestions to the driver to do so. PMID:27657888

New Kinematical Constraints on Cosmic Acceleration

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

Rapetti, David; Allen, Steve W.; Amin, Mustafa A.

2007-05-25

We present and employ a new kinematical approach to ''dark energy'' studies. We construct models in terms of the dimensionless second and third derivatives of the scale factor a(t) with respect to cosmic time t, namely the present-day value of the deceleration parameter q{sub 0} and the cosmic jerk parameter, j(t). An elegant feature of this parameterization is that all {Lambda}CDM models have j(t)=1 (constant), which facilitates simple tests for departures from the {Lambda}CDM paradigm. Applying our model to redshift-independent distance measurements, from type Ia supernovae and X-ray cluster gas mass fraction measurements, we obtain clear statistical evidence for amore » late time transition from a decelerating to an accelerating phase. For a flat model with constant jerk, j(t)=j, we measure q{sub 0}=-0.81 {+-} 0.14 and j=2.16 +0.81 -0.75, results that are consistent with {Lambda}CDM at about the 1{sigma} confidence level. In comparison to dynamical analyses, the kinematical approach uses a different model set and employs a minimum of prior information, being independent of any particular gravity theory. The results obtained with this new approach therefore provide important additional information and we argue that both kinematical and dynamical techniques should be employed in future dark energy studies, where possible.« less

The pull in olympic weightlifting.

PubMed

Enoka, R M

1979-01-01

Data from five experienced weightlifters on the vertical forces applied to the barbell and system (barbell and lifter) during the pull were in excellent agreement with earlier displacement-time descriptions of the double knee bend as consisting of two stages of extension interrupted by a period of realignment (second knee bend). The vertical component of the ground reaction force (Rz) consisted of three phases: Weighting I, Unweighting, and Weighting II. The relative magnitude of the Rz impulse with respect to the system weight impulse (as an indicant of the proportion of the Rz impulse contributing to system acceleration) ranged from 118--141% for Weighting I, 74--89% for Unweighting, and 122--135% for Weighting II. In agreement with published theoretical calculations the most experienced and successful lifter produced the larger phase of positive acceleration first. The rebending of the knees was associated with the Unweighting phase. Although this latter interval corresponded to a phase of barbell deceleration, it appeared that the concomitant enhancement of the back, hip, and knee extensor activity outweighed any adverse effects.

Effect of High Impact or Non-impact Loading Activity on Bone Bending Stiffness and Mineral Density

NASA Technical Reports Server (NTRS)

Liang, Michael T. C.; Arnnud, Sara B.; Steele, Charles R.; Moreno, Alexjandro

2003-01-01

Material properties of conical bone, including mineral density (BMD) and its geometry is closely related to its load-carrying capacity. These two primary components determine the strength of conical bone. High impact loading involving acceleration and deceleration movements used in gymnastics induce higher BMD of the affected bone compared to the non-impact acceleration and deceleration movements used in swimming. Study of these two groups of athletes on bone bending stiffness has not been reported. The purpose of this study was to compare differences in bone bending stiffness and BMD between competitive female synchronized swimmers and female gymnasts. Thirteen world class female synchronized swimmers (SYN) and 8 female gymnasts (GYM), mean age 21 +/- 2.9 yr. were recruited for this study. We used a mechanical response tissue analyzer (Gaitscan, NJ) to calculate EI, where E is Young's modulus of elasticity and I is the cross-sectional moment of inertia. EI was obtained from tissue response to a vibration probe placed directly on the skin of the mid-region of tibia and ulna. BMD of the heel and wrist were measured with a probe densitometer (PIXI, Lunor, WI). The SYN were taller than (p < 0.05) the GYM but weighed the same as the GYM. EI obtained from tibia and ulna of the SYN (291 +/- 159 and 41 +/- 19.4, respectively) were not significantly different from thc GYM (285 +/- 140 and 44 +/- 18.3, respectively). BMD of the heel and wrist in GYM were higher than in SYN (p < 0.001). High impact weight-bearing activities promote similar bone strength but greater BMD response than non-impact activities performed in a buoyant environment.

Free-Weight Augmentation With Elastic Bands Improves Bench Press Kinematics in Professional Rugby Players.

PubMed

García-López, David; Hernández-Sánchez, Sonsoles; Martín, Esperanza; Marín, Pedro J; Zarzosa, Fernando; Herrero, Azael J

2016-09-01

García-López, D, Hernández-Sánchez, S, Martín, E, Marín, PJ, Zarzosa, F, and Herrero, AJ. Free-weight augmentation with elastic bands improves bench press kinematics in professional rugby players. J Strength Cond Res 30(9): 2493-2499, 2016-This study aimed to investigate the effects of combining elastic bands to free weight resistance (EB + FWR) on the acceleration-deceleration and velocity profiles of the bench press in professional rugby players and recreationally trained subjects. Sixteen male subjects (8 rugby players and 8 recreationally trained subjects) were randomly assigned to complete 2 experimental conditions in a crossover fashion: EB + FWR and FWR. In both conditions, subjects performed 1 bench press set to volitional exhaustion with a load equivalent to the 85% of 1 repetition maximum (1RM). In the EB + FWR condition, the contribution of elastic resistance was approximately 20% of the selected load (85% 1RM). Results indicate that EB + FWR condition increased significantly the range of concentric movement in which the barbell is accelerated. This increase was significantly higher in rugby players (35%) in comparison with recreationally trained subjects (13%). Maximal velocity was also increased in EB + FWR (17%), when compared with FWR condition. These results suggest that when combined with variable resistance (i.e., EB), the external resistance seems to be more evenly distributed over the full range of motion, decreasing the need for dramatic deceleration at the end of the concentric phase. The present data also indicate that the kinematic benefits of an EB + FWR approach seems to be more prominent in athletes from modalities in which high level of strength and power are required (i.e., rugby players).

Very Small Interstellar Spacecraft

NASA Astrophysics Data System (ADS)

Peck, Mason A.

2007-02-01

This paper considers lower limits of length scale in spacecraft: interstellar vehicles consisting of little more material than found in a typical integrated-circuit chip. Some fundamental scaling principles are introduced to show how the dynamics of the very small can be used to realize interstellar travel with minimal advancements in technology. Our recent study for the NASA Institute for Advanced Concepts provides an example: the use of the Lorentz force that acts on electrically charged spacecraft traveling through planetary and stellar magnetospheres. Schaffer and Burns, among others, have used Cassini and Voyager imagery to show that this interaction is responsible for some of the resonances in the orbital dynamics of dust in Jupiter's and Saturn's rings. The Lorentz force turns out to vary in inverse proportion to the square of this characteristic length scale, making it a more effective means of propelling tiny spacecraft than solar sailing. Performance estimates, some insight into plasma interactions, and some hardware concepts are offered. The mission architectures considered here involve the use of these propellantless propulsion techniques for acceleration within our solar system and deceleration near the destination. Performance estimates, some insight into plasma interactions, and some hardware concepts are offered. The mission architectures considered here involve the use of these propellantless propulsion techniques for acceleration within our solar system and deceleration near the destination. We might envision a large number of such satellites with intermittent, bursty communications set up as a one-dimensional network to relay signals across great distances using only the power likely from such small spacecraft. Conveying imagery in this fashion may require a long time because of limited power, but the prospect of imaging another star system close-up ought to be worth the wait.

Continuous all-optical deceleration of molecular beams

NASA Astrophysics Data System (ADS)

Jayich, Andrew; Chen, Gary; Long, Xueping; Wang, Anna; Campbell, Wesley

2014-05-01

A significant impediment to generating ultracold molecules is slowing a molecular beam to velocities where the molecules can be cooled and trapped. We report on progress toward addressing this issue with a general optical deceleration technique for molecular and atomic beams. We propose addressing the molecular beam with a pump and dump pulse sequence from a mode-locked laser. The pump pulse counter-propagates with respect to the beam and drives the molecules to the excited state. The dump pulse co-propagates and stimulates emission, driving the molecules back to the ground state. This cycle transfers 2 ℏk of momentum and can generate very large optical forces, not limited by the spontaneous emission lifetime of the molecule or atom. Importantly, avoiding spontaneous emission limits the branching to dark states. This technique can later be augmented with cooling and trapping. We are working towards demonstrating this optical force by accelerating a cold atomic sample.

History of suborbital spaceflight: medical and performance issues.

PubMed

Campbell, Mark R; Garbino, Alejandro

2011-04-01

The development of manned sub-orbital commercial space vehicles is rapidly occurring and flight testing followed by operational flights will soon begin. The experience of manned suborbital spaceflight at the designated altitude (100 km/62.14 mi) is very limited--two Mercury-Redstone flights, two X-15 flights, one inadvertent Soyuz launch abort, and three recent SpaceShipOne flights, with only 15 min of critical flight time each. All indications were that the sequence of acceleration-weightlessness-deceleration was well tolerated with minimal neurovestibular dysfunction. However, there are some indications that distraction and spatial disorientation did occur. Vertigo on transition from the boost phase to weightlessness was reported on most high-altitude X-15 flights. +Gz tolerance to re-entry deceleration forces (as high as 6 + Gz) after 4 min of weightlessness is still unknown. Only further suborbital spaceflight experience will clarify if pilot performance will be affected.

Can superhorizon cosmological perturbations explain the acceleration of the universe?

NASA Astrophysics Data System (ADS)

Hirata, Christopher M.; Seljak, Uroš

2005-10-01

We investigate the recent suggestions by Barausse et al. and Kolb et al. that the acceleration of the universe could be explained by large superhorizon fluctuations generated by inflation. We show that no acceleration can be produced by this mechanism. We begin by showing how the application of Raychaudhuri equation to inhomogeneous cosmologies results in several “no go” theorems for accelerated expansion. Next we derive an exact solution for a specific case of initial perturbations, for which application of the Kolb et al. expressions leads to an acceleration, while the exact solution reveals that no acceleration is present. We show that the discrepancy can be traced to higher-order terms that were dropped in the Kolb et al. analysis. We proceed with the analysis of initial value formulation of general relativity to argue that causality severely limits what observable effects can be derived from superhorizon perturbations. By constructing a Riemann normal coordinate system on initial slice we show that no infrared divergence terms arise in this coordinate system. Thus any divergences found previously can be eliminated by a local rescaling of coordinates and are unobservable. We perform an explicit analysis of the variance of the deceleration parameter for the case of single-field inflation using usual coordinates and show that the infrared-divergent terms found by Barausse et al. and Kolb et al. cancel against several additional terms not considered in their analysis. Finally, we argue that introducing isocurvature perturbations does not alter our conclusion that the accelerating expansion of the universe cannot be explained by superhorizon modes.

A cellular automata model for traffic flow based on kinetics theory, vehicles capabilities and driver reactions

NASA Astrophysics Data System (ADS)

Guzmán, H. A.; Lárraga, M. E.; Alvarez-Icaza, L.; Carvajal, J.

2018-02-01

In this paper, a reliable cellular automata model oriented to faithfully reproduce deceleration and acceleration according to realistic reactions of drivers, when vehicles with different deceleration capabilities are considered is presented. The model focuses on describing complex traffic phenomena by coding in its rules the basic mechanisms of drivers behavior, vehicles capabilities and kinetics, while preserving simplicity. In particular, vehiclés kinetics is based on uniform accelerated motion, rather than in impulsive accelerated motion as in most existing CA models. Thus, the proposed model calculates in an analytic way three safe preserving distances to determine the best action a follower vehicle can take under a worst case scenario. Besides, the prediction analysis guarantees that under the proper assumptions, collision between vehicles may not happen at any future time. Simulations results indicate that all interactions of heterogeneous vehicles (i.e., car-truck, truck-car, car-car and truck-truck) are properly reproduced by the model. In addition, the model overcomes one of the major limitations of CA models for traffic modeling: the inability to perform smooth approach to slower or stopped vehicles. Moreover, the model is also capable of reproducing most empirical findings including the backward speed of the downstream front of the traffic jam, and different congested traffic patterns induced by a system with open boundary conditions with an on-ramp. Like most CA models, integer values are used to make the model run faster, which makes the proposed model suitable for real time traffic simulation of large networks.

Fetal motion estimation from noninvasive cardiac signal recordings.

PubMed

Biglari, Hadis; Sameni, Reza

2016-11-01

Fetal motility is a widely accepted indicator of the well-being of a fetus. In previous research, it has be shown that fetal motion (FM) is coherent with fetal heart rate accelerations and an indicator for active/rest cycles of the fetus. The most common approach for FM and fetal heart rate (FHR) assessment is by Doppler ultrasound (DUS). While DUS is the most common approach for studying the mechanical activities of the heart, noninvasive fetal electrocardiogram (ECG) and magnetocardiogram (MCG) recording and processing techniques have been considered as a possible competitor (or complement) for the DUS. In this study, a fully automatic and robust framework is proposed for the extraction, ranking and alignment of fetal QRS-complexes from noninvasive fetal ECG/MCG. Using notions from subspace tracking, two measures, namely the actogram and rotatogram, are defined for fetal motion tracking. The method is applied to four fetal ECG/MCG databases, including twin MCG recordings. By defining a novel measure of causality, it is shown that there is significant coherency and causal relationship between the actogram/rotatogram and FHR accelerations/decelerations. Using this measure, it is shown that in many cases, the actogram and rotatogram precede the FHR variations, which supports the idea of motion-induced FHR accelerations/decelerations for these cases and raises attention for the non-motion-induced FHR variations, which can be associated to the fetal central nervous system developments. The results of this study can lead to novel perspectives of the fetal sympathetic and parasympathetic brain systems and future requirements of fetal cardiac monitoring.

Tuning Spatial Profiles of Selection Pressure to Modulate the Evolution of Drug Resistance

NASA Astrophysics Data System (ADS)

De Jong, Maxwell G.; Wood, Kevin B.

2018-06-01

Spatial heterogeneity plays an important role in the evolution of drug resistance. While recent studies have indicated that spatial gradients of selection pressure can accelerate resistance evolution, much less is known about evolution in more complex spatial profiles. Here we use a stochastic toy model of drug resistance to investigate how different spatial profiles of selection pressure impact the time to fixation of a resistant allele. Using mean first passage time calculations, we show that spatial heterogeneity accelerates resistance evolution when the rate of spatial migration is sufficiently large relative to mutation but slows fixation for small migration rates. Interestingly, there exists an intermediate regime—characterized by comparable rates of migration and mutation—in which the rate of fixation can be either accelerated or decelerated depending on the spatial profile, even when spatially averaged selection pressure remains constant. Finally, we demonstrate that optimal tuning of the spatial profile can dramatically slow the spread and fixation of resistant subpopulations, even in the absence of a fitness cost for resistance. Our results may lay the groundwork for optimized, spatially resolved drug dosing strategies for mitigating the effects of drug resistance.

[Effect of the development phase and growth rate of a Shigella sonnei population on the reproduction of homologous bacteriophage].

PubMed

Voroshilova, N N; Kazakova, T B

1983-04-01

This study showed that the minimum latent period (20 minutes) of the intracellular multiplication of dysentery bacteriophage S-9 in the population of S. sonnei substrate strain under the conditions of static heterogeneous surface batch cultivation was observed at the end of the lag phase and at the growth acceleration phase, in the first and second thirds of the exponential curve, while the maximum latent period (35-40 minutes) was observed at the stationary phase. The maximum yield of phage S-9 from one infected bacterial cell (628.3 +/- 116.8) was registered during the first third of the phase of the exponential growth of the bacterial population and the minimum yield (18.66 +/- 6.6), at the beginning of the lag phase. The significant direct correlation between the specific growth rate of the bacterial population and the yield of the phage from one infected bacterial cell at the end of the lag phase, at the growth acceleration and deceleration phases, as well as the significant inverse correlation between the yield of the phage and the time of the generation of the bacterial population at the growth acceleration phase were established.

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

Optimized Trajectories to the Nearest Stars Using Lightweight High-velocity Photon Sails

NASA Astrophysics Data System (ADS)

Heller, René; Hippke, Michael; Kervella, Pierre

2017-09-01

New means of interstellar travel are now being considered by various research teams, assuming lightweight spaceships to be accelerated via either laser or solar radiation to a significant fraction of the speed of light (c). We recently showed that gravitational assists can be combined with the stellar photon pressure to decelerate an incoming lightsail from Earth and fling it around a star or bring it to rest. Here, we demonstrate that photogravitational assists are more effective when the star is used as a bumper (I.e., the sail passes “in front of” the star) rather than as a catapult (I.e., the sail passes “behind” or “around” the star). This increases the maximum deceleration at α Cen A and B and reduces the travel time of a nominal graphene-class sail (mass-to-surface ratio 8.6× {10}-4 {{g}} {{{m}}}-2) from 95 to 75 years. The maximum possible velocity reduction upon arrival depends on the required deflection angle from α Cen A to B and therefore on the binary’s orbital phase. Here, we calculate the variation of the minimum travel times from Earth into a bound orbit around Proxima for the next 300 years and then extend our calculations to roughly 22,000 stars within about 300 lt-yr. Although α Cen is the most nearby star system, we find that Sirius A offers the shortest possible travel times into a bound orbit: 69 years assuming 12.5% c can be obtained at departure from the solar system. Sirius A thus offers the opportunity of flyby exploration plus deceleration into a bound orbit of the companion white dwarf after relatively short times of interstellar travel.

Short-term metal particulate exposures decrease cardiac acceleration and deceleration capacities in welders: a repeated-measures panel study.

PubMed

Umukoro, Peter E; Cavallari, Jennifer M; Fang, Shona C; Lu, Chensheng; Lin, Xihong; Mittleman, Murray A; Christiani, David C

2016-02-01

Acceleration (AC) and deceleration (DC) capacities measure heart rate variability during speeding up and slowing down of the heart, respectively. We investigated associations between AC and DC with occupational short-term metal PM2.5 exposures. A panel of 48 male welders had particulate matter less than 2.5 microns in diameter (PM2.5) exposure measurements over 4-6 h repeated over 5 sampling periods between January 2010 and June 2012. We simultaneously obtained continuous recordings of digital ECG using a Holter monitor. We analysed ECG data in the time domain to obtain hourly AC and DC. Linear mixed models were used to assess the associations between hourly PM2.5 exposure and each of hourly AC and DC, controlling for age, smoking status, active smoking, exposure to secondhand smoke, season/time of day when ECG reading was obtained and baseline AC or DC. We also ran lagged exposure response models for each successive hour up to 3 h after onset of exposure. Mean (SD) shift PM2.5 exposure during welding was 0.47 (0.43) mg/m(3). Significant exposure-response associations were found for AC and DC with increased PM2.5 exposure. In our adjusted models without any lag between exposure and response, a 1 mg/m(3) increase of PM2.5 was associated with a decrease of 1.46 (95% CI 1.00 to 1.92) ms in AC and a decrease of 1.00 (95% CI 0.53 to 1.46) ms in DC. The effect of PM2.5 on AC and DC was maximal immediately postexposure and lasted 1 h following exposure. There are short-term effects of metal particulates on AC and DC. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Effects of Changes in Food Supply at the Time of Sex Differentiation on the Gonadal Transcriptome of Juvenile Fish. Implications for Natural and Farmed Populations

PubMed Central

Díaz, Noelia; Ribas, Laia; Piferrer, Francesc

2014-01-01

Background Food supply is a major factor influencing growth rates in animals. This has important implications for both natural and farmed fish populations, since food restriction may difficult reproduction. However, a study on the effects of food supply on the development of juvenile gonads has never been transcriptionally described in fish. Methods and Findings This study investigated the consequences of growth on gonadal transcriptome of European sea bass in: 1) 4-month-old sexually undifferentiated fish, comparing the gonads of fish with the highest vs. the lowest growth, to explore a possible link between transcriptome and future sex, and 2) testis from 11-month-old juveniles where growth had been manipulated through changes in food supply. The four groups used were: i) sustained fast growth, ii) sustained slow growth, iii) accelerated growth, iv) decelerated growth. The transcriptome of undifferentiated gonads was not drastically affected by initial natural differences in growth. Further, changes in the expression of genes associated with protein turnover were seen, favoring catabolism in slow-growing fish and anabolism in fast-growing fish. Moreover, while fast-growing fish took energy from glucose, as deduced from the pathways affected and the analysis of protein-protein interactions examined, in slow-growing fish lipid metabolism and gluconeogenesis was favored. Interestingly, the highest transcriptomic differences were found when forcing initially fast-growing fish to decelerate their growth, while accelerating growth of initially slow-growing fish resulted in full transcriptomic convergence with sustained fast-growing fish. Conclusions Food availability during sex differentiation shapes the juvenile testis transcriptome, as evidenced by adaptations to different energy balances. Remarkably, this occurs in absence of major histological changes in the testis. Thus, fish are able to recover transcriptionally their testes if they are provided with enough food supply during sex differentiation; however, an initial fast growth does not represent any advantage in terms of transcriptional fitness if later food becomes scarce. PMID:25340342

Effects of changes in food supply at the time of sex differentiation on the gonadal transcriptome of juvenile fish. Implications for natural and farmed populations.

PubMed

Díaz, Noelia; Ribas, Laia; Piferrer, Francesc

2014-01-01

Food supply is a major factor influencing growth rates in animals. This has important implications for both natural and farmed fish populations, since food restriction may difficult reproduction. However, a study on the effects of food supply on the development of juvenile gonads has never been transcriptionally described in fish. This study investigated the consequences of growth on gonadal transcriptome of European sea bass in: 1) 4-month-old sexually undifferentiated fish, comparing the gonads of fish with the highest vs. the lowest growth, to explore a possible link between transcriptome and future sex, and 2) testis from 11-month-old juveniles where growth had been manipulated through changes in food supply. The four groups used were: i) sustained fast growth, ii) sustained slow growth, iii) accelerated growth, iv) decelerated growth. The transcriptome of undifferentiated gonads was not drastically affected by initial natural differences in growth. Further, changes in the expression of genes associated with protein turnover were seen, favoring catabolism in slow-growing fish and anabolism in fast-growing fish. Moreover, while fast-growing fish took energy from glucose, as deduced from the pathways affected and the analysis of protein-protein interactions examined, in slow-growing fish lipid metabolism and gluconeogenesis was favored. Interestingly, the highest transcriptomic differences were found when forcing initially fast-growing fish to decelerate their growth, while accelerating growth of initially slow-growing fish resulted in full transcriptomic convergence with sustained fast-growing fish. Food availability during sex differentiation shapes the juvenile testis transcriptome, as evidenced by adaptations to different energy balances. Remarkably, this occurs in absence of major histological changes in the testis. Thus, fish are able to recover transcriptionally their testes if they are provided with enough food supply during sex differentiation; however, an initial fast growth does not represent any advantage in terms of transcriptional fitness if later food becomes scarce.

New Concepts and Fermilab Facilities for Antimatter Research

NASA Astrophysics Data System (ADS)

Jackson, Gerald

2008-04-01

There has long been significant interest in continuing antimatter research at the Fermi National Accelerator Laboratory. Beam kinetic energies ranging from 10 GeV all the way down to the eV scale and below are of interest. There are three physics missions currently being developed: the continuation of charmonium physics utilizing an internal target; atomic physics with in-flight generated antihydrogen atoms; and deceleration to thermal energies and paasage of antiprotons through a grating system to determine their gravitation acceleration. Non-physics missions include the study of medical applications, tests of deep-space propulsion concepts, low-risk testing of nuclear fuel elements, and active interrogation for smuggled nuclear materials in support of homeland security. This paper reviews recent beam physics and accelerator technology innovations in the development of methods and new Fermilab facilities for the above missions.

BrainAGE score indicates accelerated brain aging in schizophrenia, but not bipolar disorder.

PubMed

Nenadić, Igor; Dietzek, Maren; Langbein, Kerstin; Sauer, Heinrich; Gaser, Christian

2017-08-30

BrainAGE (brain age gap estimation) is a novel morphometric parameter providing a univariate score derived from multivariate voxel-wise analyses. It uses a machine learning approach and can be used to analyse deviation from physiological developmental or aging-related trajectories. Using structural MRI data and BrainAGE quantification of acceleration or deceleration of in individual aging, we analysed data from 45 schizophrenia patients, 22 bipolar I disorder patients (mostly with previous psychotic symptoms / episodes), and 70 healthy controls. We found significantly higher BrainAGE scores in schizophrenia, but not bipolar disorder patients. Our findings indicate significantly accelerated brain structural aging in schizophrenia. This suggests, that despite the conceptualisation of schizophrenia as a neurodevelopmental disorder, there might be an additional progressive pathogenic component. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

Ghost Dark Energy with Sign-changeable Interaction Term

NASA Astrophysics Data System (ADS)

Zadeh, M. Abdollahi; Sheykhi, A.; Moradpour, H.

2017-11-01

Regarding the Veneziano ghost of QCD and its generalized form, we consider a Friedmann-Robertson-Walker (FRW) universe filled by a pressureless matter and a dark energy component interacting with each other through a mutual sign-changeable interaction of positive coupling constant. Our study shows that, at the late time, for the deceleration parameter we have q → -1, while the equation of state parameter of the interacting ghost dark energy (GDE) does not cross the phantom line, namely ω D ≥ -1. We also extend our study to the generalized ghost dark energy (GGDE) model and show that, at late time, the equation of state parameter of the interacting GGDE also respects the phantom line in both flat and non-flat universes. Moreover, we find out that, unlike the non-flat universe, we have q → -1 at late time for flat FRW universe. In order to make the behavior of the underlying models more clear, the deceleration parameter q as well as the equation of state parameter w D for flat and closed universes have been plotted against the redshift parameter, z. All of the studied cases admit a transition in the expansion history of universe from a deceleration phase to an accelerated one around z ≈ 0.6.

Contribution of NK(2) tachykinin receptors to propulsion in the rabbit distal colon.

PubMed

Onori, L; Aggio, A; Taddei, G; Tonini, M

2000-01-01

The role of the tachykinin neurokinin (NK)(2) receptors on rabbit distal colon propulsion was investigated by using two selective NK(2)-receptor antagonists, MEN-10627 and SR-48968. Experiments on colonic circular muscle strips showed that contractile responses to [beta-Ala(8)]NKA-(4-10) (1 nM-1 microM), a selective NK(2)-receptor agonist, were competitively antagonized by MEN-10627 (1-100 nM), whereas SR-48968 (0.1-10 nM) caused an insurmountable antagonism, thus confirming the difference in the mode of action of the two compounds. Colonic propulsion was elicited by distending a mobile rubber balloon with 0.3 ml (submaximal stimulus) or 1.0 ml (maximal stimulus) of water. The velocity of anal displacement of the balloon (mm/s) was considered the main propulsion parameter. At low concentrations (1.0-100 nM and 0.1-10 nM, respectively), MEN-10627 and SR-48968 facilitated the velocity of propulsion, whereas at high concentrations (100 nM and 1 microM, respectively) they decelerated propulsion. The excitatory and inhibitory effects of both antagonists were observed only with submaximal stimulus. We focused on the hypothesis that the facilitatory effect on propulsion may result from blockade of neuronal NK(2) receptors and the inhibitory effect from suppression of the excitatory transmission mediated by NK(2) receptors on smooth muscle cells. In the presence of N(G)-nitro-L-arginine (300 microM), a nitric oxide synthase inhibitor, MEN-10627, at a concentration (10 nM) that was found to accelerate propulsion in control experiments inhibited the velocity of propulsion. In the presence of threshold (1-10 nM) or full (1 microM) concentration of atropine, which inhibited to a great extent the velocity of propulsion, the inhibitory effect of MEN-10627 (1 microM) was markedly increased. In conclusion, in the rabbit distal colon NK(2) receptors may decelerate propulsion by activating a nitric oxide-dependent neuronal mechanism and may accelerate it by a postjunctional synergistic interaction with cholinergic muscarinic receptors.

The ΩDE-ΩM Plane in Dark Energy Cosmology

NASA Astrophysics Data System (ADS)

Qiang, Yuan; Zhang, Tong-Jie

The dark energy cosmology with the equation of state w=const. is considered in this paper. The ΩDE-ΩM plane has been used to study the present state and expansion history of the universe. Through the mathematical analysis, we give the theoretical constraint of cosmological parameters. Together with some observations such as the transition redshift from deceleration to acceleration, more precise constraint on cosmological parameters can be acquired.

V-22 Osprey Tilt-Rotor Aircraft

DTIC Science & Technology

2007-03-13

destroying the aircraft. This accident was caused by a fire resulting from hydraulic component failures and design problems in the engine nacelles.3 Flight...the Marine Corps reported that the crash was caused by a burst hydraulic line in one of the Osprey’s two engine casings, and a software malfunction...that caused the aircraft to accelerate and decelerate unpredictably and violently when the pilots tried to compensate for the hydraulic CRS-6 7 An un

Measurement of Forces and Moments Transmitted to the Residual Limb

DTIC Science & Technology

2010-10-01

forces, moments, and alignments. 15. SUBJECT TERMS Amputees, prosthesis alignment, socket pressure, gait, force and moment sensors 16. SECURITY...evaluate the feasibility of using a tri-axial transducer mounted to the pylon of a lower limb prosthesis directly below the socket to a.) Characterize...weighing up to nearly 500lbs, or activities which involve deceleration or acceleration forces of up to 500 lbs along the pylon of a prosthesis . Diameter

Metabolic Power Requirement of Change of Direction Speed in Young Soccer Players: Not All Is What It Seems

PubMed Central

Mendez-Villanueva, Alberto; Palazzi, Dino; Ahmaidi, Saïd

2016-01-01

Purpose The aims of this study were to 1) compare the metabolic power demand of straight-line and change of direction (COD) sprints including 45° or 90°-turns, and 2) examine the relation between estimated metabolic demands and muscular activity throughout the 3 phases of COD-sprints. Methods Twelve highly-trained soccer players performed one 25-m and three 20-m sprints, either in straight-line or with one 45°- or 90°-COD. Sprints were monitored with 2 synchronized 100-Hz laser guns to assess players’ velocities before, during and after the COD. Acceleration and deceleration were derived from changes in speed over time. Metabolic power was estimated based on di Prampero’s approach (2005). Electromyography amplitude (RMS) of 2 lower limb muscles was measured. The expected energy expenditure during time-adjusted straight-line sprints (matching COD sprints time) was also calculated. Results Locomotor-dependant metabolic demand was largely lower with COD (90°, 142.1±13.5 J.kg-1) compared with time-adjusted (effect size, ES = -3.0; 193.2±18.6 J.kg-1) and non-adjusted straight-line sprints (ES = -1.7; 168.4±15.3 J.kg-1). Metabolic power requirement was angle-dependent, moderately lower for 90°-COD vs. 45°-COD sprint (ES = -1.0; 149.5±10.4 J.kg-1). Conversely, the RMS was slightly- (45°, ES = +0.5; +2.1%, 90% confidence limits (±3.6) for vastus lateralis muscle (VL)) to-largely (90°, ES = +1.6; +6.1 (3.3%) for VL) greater for COD-sprints. Metabolic power/RMS ratio was 2 to 4 times lower during deceleration than acceleration phases. Conclusion Present results show that COD-sprints are largely less metabolically demanding than linear sprints. This may be related to the very low metabolic demand associated with the deceleration phase during COD-sprints that may not be compensated by the increased requirement of the reacceleration phase. These results also highlight the dissociation between metabolic and muscle activity demands during COD-sprints, which questions the use of metabolic power as a single measure of running load in soccer. PMID:26930649

Review of the trajectory and atmospheric structure reconstruction for Mars Pathfinder

NASA Astrophysics Data System (ADS)

Withers, Paul; Towner, Martin; Hathi, Brijen; Zarnecki, John

2004-02-01

Mars Pathfinder landed on Mars on July 4, 1997. It used a novel deceleration procedure, consisting of a hypersonic aeroshell, a transonic parachute, retro-rockets, and airbags, to reach the surface safely. Its aerodynamic properties passively maintained a near-zero angle of attack throughout its entry. There were no gyroscopes to monitor attitude. Several different trajectory reconstructions have been based on the assumptions that accelerations along its symmetry axis are directed along its flight path and that accelerations in other directions are insignificant. The aerodynamics of Pathfinder once its parachute opened are still not well-understood and the available observations are probably not sufficient to improve matters significantly in the future.

Accelerated acidosis in response to variable fetal heart rate decelerations in chronically hypoxic ovine fetuses.

PubMed

Amaya, Kevin E; Matushewski, Brad; Durosier, L Daniel; Frasch, Martin G; Richardson, Bryan S; Ross, Michael G

2016-02-01

Due to limitations of technology, clinicians are typically unable to determine if human fetuses are normoxic or moderately, chronically hypoxic. Risk factors for chronic hypoxia include fetal growth restriction, which is associated with an increased incidence of oligohydramnios and thus a risk for umbilical cord occlusion (UCO) and variable fetal heart rate (FHR) decelerations. At delivery, fetal growth restriction infants (<3rd percentile) have nearly twice the incidence of low Apgar scores and umbilical pH <7.0. Despite the risks of oligohydramnios and intermittent UCO, there is little understanding of the acid/base responses rates of chronically hypoxic fetuses to variable FHR decelerations as might occur during human labor. We sought to compare the increase in base deficit (BD) among chronically hypoxic as compared to normoxic ovine fetuses in response to simulated mild, moderate, and severe variable FHR decelerations. Near-term ovine fetuses were chronically prepared with brachial artery catheters and an inflatable umbilical cuff occluder. Following a recovery period, normoxic (n = 9) and spontaneously hypoxic (n = 5) fetuses were identified (arterial O2 saturation ≤55%). Both animal groups underwent graded, 1-minute occlusions every 2.5 minutes with 1 hour of mild (∼30 beats/min [bpm] decrease from baseline), 1 hour of moderate (∼60 bpm decrease from baseline), and up to 2 hours of severe (∼90 bpm decrease from baseline) variable FHR decelerations until fetal arterial pH reached 7.00, when occlusions were stopped. Repetitive UCO resulted in development of acidosis (pH <7.0) in both groups. Hypoxic and normoxic fetuses demonstrated similar BD increases in response to both mild (0.39, interquartile range [IQR] 0.28-0.45 vs 0.26, IQR 0.01-0.30 mEq/L/10 min, P = .25) and severe (1.97, IQR 1.50-2.43 vs 1.51, IQR 0.97-2.45 mEq/L/10 min, P = .63) variable decelerations. However, moderate variable decelerations increased BD in hypoxic fetuses at 2.5 times the rate of normoxic fetuses (0.97, IQR 0.52-1.72 vs 0.39, IQR 0.23-0.47 mEq/L/10 min, P = .03). During the recovery period, hypoxic fetuses cleared BD slower than normoxic fetuses (0.08 ± 0.02 vs 0.12 ± 0.03 mEq/L/min, P = .02). In comparison to normoxic fetuses, hypoxic fetuses can more rapidly progress to significant metabolic acidosis in response to moderate FHR variable decelerations, and more slowly recover with in utero resuscitation, likely a consequence of impaired placental function and fetal physiologic responses. Copyright © 2016 Elsevier Inc. All rights reserved.

Vlasov simulations of electron hole dynamics in inhomogeneous magnetic field

NASA Astrophysics Data System (ADS)

Kuzichev, Ilya; Vasko, Ivan; Agapitov, Oleksiy; Mozer, Forrest; Artemyev, Anton

2017-04-01

Electron holes (EHs) or phase space vortices are solitary electrostatic waves existing due to electrons trapped within EH electrostatic potential. Since the first direct observation [1], EHs have been widely observed in the Earth's magnetosphere: in reconnecting current sheets [2], injection fronts [3], auroral region [4], and many other space plasma systems. EHs have typical spatial scales up to tens of Debye lengths, electric field amplitudes up to hundreds of mV/m and propagate along magnetic field lines with velocities of about electron thermal velocity [5]. The role of EHs in energy dissipation and supporting of large-scale potential drops is under active investigation. The accurate interpretation of spacecraft observations requires understanding of EH evolution in inhomogeneous plasma. The critical role of plasma density gradients in EH evolution was demonstrated in [6] using PIC simulations. Interestingly, up to date no studies have addressed a role of magnetic field gradients in EH evolution. In this report, we use 1.5D gyrokinetic Vlasov code to demonstrate the critical role of magnetic field gradients in EH dynamics. We show that EHs propagating into stronger (weaker) magnetic field are decelerated (accelerated) with deceleration (acceleration) rate dependent on the magnetic field gradient. Remarkably, the reflection points of decelerating EHs are independent of the average magnetic field gradient in the system and depend only on the EH parameters. EHs are decelerated (accelerated) faster than would follow from the "quasi-particle" concept assuming that EH is decelerated (accelerated) entirely due to the mirror force acting on electrons trapped within EH. We demonstrate that EH propagation in inhomogeneous magnetic fields results in development of a net potential drop along an EH, which depends on the magnetic field gradient. The revealed features will be helpful for interpreting spacecraft observations and results of advanced particle simulations. In particular, our simulations suggest that slow EHs (which generation is usually attributed to the Buneman instability) can arise due to slowing down of fast EH generated by electron-beam instability. The estimate of the potential drop along EHs allow to estimate the parallel potential drop provided by EHs in a particular plasma system. 1. Matsumoto, H., H. Kojima, T. Miyatake, Y. Omura, M. Okada, I. Nagano, and M. Tsutsui, Electrotastic Solitary Waves (ESW) in the magnetotail: BEN wave forms observed by GEOTAIL, Geophys. Res. Lett., 21, 2915-2918, doi:10.1029/94GL01284, 1994. 2. Norgren, C., M. Andŕe, A. Vaivads, and Y. V. Khotyaintsev, Slow electron phase space holes: Magnetotail observations, Geophys. Res. Lett., 42, 1654-1661, doi:10.1002/2015GL063218, 2015. 3. Malaspina, D. M., J. R. Wygant, R. E. Ergun, G. D. Reeves, R. M. Skoug, and B. A. Larsen, Electric field structures and waves at plasma boundaries in the inner magnetosphere, Journal of Geophysical Research (Space Physics), 120, 4246-4263, doi:10.1002/2015JA021137, 2015. 4. Franz, J. R., P. M. Kintner, J. S. Pickett, and L.-J. Chen, Properties of small-amplitude electron phase-space holes observed by Polar, Journal of Geophysical Research (Space Physics), 110, A09212, doi:10.1029/2005JA011095, 2005. 5. Cattell, C., C. Neiman, J. Dombeck, J. Crumley, J. Wygant, C. A. Kletzing, W. K. Peterson, F. S. Mozer, and M. André (2003), Large amplitude solitary waves in and near the Earth's magnetosphere, magnetopause and bow shock: Polar and Cluster observations, Nonlinear Processes Geophys., 10, 13-26. 6. Mandrake, L., P. L. Pritchett, and F. V. Coroniti, Electron beam generated solitary structures in a nonuniform plasma system, Geophys. Res. Lett., 27, 2869-2872, doi:10.1029/2000GL003785, 2000. The work of I.K. was supported by Russian Foundation for Basic Research 16-32-00721 mol_a. The work of I.V., O.A. and F.M. was supported by JHU/APL contract 922613 (RBSPEFW).

A high flux source of swift oxygen atoms

NASA Technical Reports Server (NTRS)

Fink, M.; Kohl, D. A.; Keto, J. W.; Antoniewicz, P.

1987-01-01

A source of swift oxygen atoms is described which has several unique features. A high current ion beam is produced by a microwave discharge, accelerated to 10 keV and the mass selected by a modified Du Pont 21-110 mass spectrometer. The O(+) beam exciting the mass spectrometer is focused into a rectangular shape with an energy spread of less than 1 eV. The next section of the machine decelerates the ion beam into a counterpropagating electron beam in order to minimize space charge effects. After deceleration, the ion beam intersects at 90 deg, a neutral oxygen atom beam, which via resonant charge exchange produces a mixture of O(+) and O. Any remaining O(+) are swept out of the beam by an electric field and differentially pumped away while the desired O beam, collimated by slits, impinges on the target. In situ monitoring of the target surface is done by X-ray photoelectron or Auger spectroscopy. Faraday cups provide flux measurements in the ion sections while the neutral flux is determined by a special torsion balance or by a quadrupole mass spectrometer specially adapted for swift atoms. While the vacuum from the source through the mass spectrometer is maintained by diffusion pumps, the rest of the machine is UHV.

Cardiac responses predict decisions: an investigation of the relation between orienting response and decisions in the ultimatum game.

PubMed

Osumi, Takahiro; Ohira, Hideki

2009-10-01

Emotion-based behaviors in humans cannot be fully explained by economic rationality. Particularly, in the ultimatum game, which incorporates conflict between self-interest and fairness, negative emotions evoked by an unfair offer seem to promote an economically irrational decision. In accordance with this suggestion, the previous studies have reported that physiological arousal is associated with rejecting unfair offers. In the present study, we investigated electrocardiogram and electrodermal activities in individuals which received fair, advantageously unfair, and disadvantageously unfair offers to specify the relations of the orienting and the defensive responses with these offers and with the decisions to accept and reject them. The results indicated that when an offer that would be rejected was presented, heart rate initially decelerated more than when an offer that would be accepted was presented. Additionally, there was a linear relationship between the deceleration and unfairness of offers. On the other hand, such different patterns were not seen in late cardiac acceleration or electrodermal response. The results suggest that because of perception of disadvantage and unpleasantness in a social context, the orienting response is evoked when an offer will be rejected. In addition, these results are discussed regarding the effect of the autonomic activity in decision-making.

Doubling The Intensity Of An ERL Based Light Source

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

Andrew Hutton

2005-05-01

A light source based on an Energy Recovered Linac (ERL) [1] consists of a superconducting linac and a transfer line that includes wigglers and undulators to produce the synchrotron light. The transfer line brings the electron bunches back to the beginning of the linac so that their energy can be recovered when they traverse the linac a second time, {lambda}/2 out of RF phase. There is another interesting condition when the length of the transfer line is (n {+-} 1/4) {lambda}. In this case, the electrons drift through on the zero RF crossing, and make a further pass around themore » transfer line, effectively doubling the circulating current in the wigglers and undulators. On the third pass through the linac, they will be decelerated and their energy recovered. The longitudinal focusing at the zero crossing is a problem, but it can be canceled if the drifting beam sees a positive energy gradient for the first half of the linac and a negative gradient for the second half (or vice versa). This paper presents a proposal to use a double chicane at the center of the linac to provide this focusing inversion for the drifting beam while leaving the accelerating and decelerating beams on crest. [1] G. R. Neil, et al, Phys. Rev. Let. 84, 662 2000« less

Formation of hollow atoms above a surface

NASA Astrophysics Data System (ADS)

Briand, Jean Pierre; Phaneuf, Ronald; Terracol, Stephane; Xie, Zuqi

2012-06-01

Slow highly stripped ions approaching or penetrating surfaces are known to capture electrons into outer shells of the ions, leaving the innermost shells empty, and forming hollow atoms. Electron capture occurs above and below the surfaces. The existence of hollow atoms below surfaces e.g. Ar atoms whose K and L shells are empty, with all electrons lying in the M and N shells, was demonstrated in 1990 [1]. At nm above surfaces, the excited ions may not have enough time to decay before hitting the surfaces, and the formation of hollow atoms above surfaces has even been questioned [2]. To observe it, one must increase the time above the surface by decelerating the ions. We have for the first time decelerated O^7+ ions to energies as low as 1 eV/q, below the minimum energy gained by the ions due to the acceleration by their image charge. As expected, no ion backscattering (trampoline effect) above dielectric (Ge) was observed and at the lowest ion kinetic energies, most of the observed x-rays were found to be emitted by the ions after surface contact. [4pt] [1] J. P. Briand et al., Phys.Rev.Lett. 65(1990)159.[0pt] [2] J.P. Briand, AIP Conference Proceedings 215 (1990) 513.

Keeping brains young with making music.

PubMed

Rogenmoser, Lars; Kernbach, Julius; Schlaug, Gottfried; Gaser, Christian

2018-01-01

Music-making is a widespread leisure and professional activity that has garnered interest over the years due to its effect on brain and cognitive development and its potential as a rehabilitative and restorative therapy of brain dysfunctions. We investigated whether music-making has a potential age-protecting effect on the brain. For this, we studied anatomical magnetic resonance images obtained from three matched groups of subjects who differed in their lifetime dose of music-making activities (i.e., professional musicians, amateur musicians, and non-musicians). For each subject, we calculated a so-called BrainAGE score which corresponds to the discrepancy (in years) between chronological age and the "age of the brain", with negative values reflecting an age-decelerating brain and positive values an age-accelerating brain, respectively. The index of "brain age" was estimated using a machine-learning algorithm that was trained in a large independent sample to identify anatomical correlates of brain-aging. Compared to non-musicians, musicians overall had lower BrainAGE scores, with amateur musicians having the lowest scores suggesting that music-making has an age-decelerating effect on the brain. Unlike the amateur musicians, the professional musicians showed a positive correlation between their BrainAGE scores and years of music-making, possibly indicating that engaging more intensely in just one otherwise enriching activity might not be as beneficial than if the activity is one of several that an amateur musician engages in. Intense music-making activities at a professional level could also lead to stress-related interferences and a less enriched environment than that of amateur musicians, possibly somewhat diminishing the otherwise positive effect of music-making.

Flight-Path Characteristics for Decelerating From Supercircular Speed

NASA Technical Reports Server (NTRS)

Luidens, Roger W.

1961-01-01

Characteristics of the following six flight paths for decelerating from a supercircular speed are developed in closed form: constant angle of attack, constant net acceleration, constant altitude" constant free-stream Reynolds number, and "modulated roll." The vehicles were required to remain in or near the atmosphere, and to stay within the aerodynamic capabilities of a vehicle with a maximum lift-drag ratio of 1.0 and within a maximum net acceleration G of 10 g's. The local Reynolds number for all the flight paths for a vehicle with a gross weight of 10,000 pounds and a 600 swept wing was found to be about 0.7 x 10(exp 6). With the assumption of a laminar boundary layer, the heating of the vehicle is studied as a function of type of flight path, initial G load, and initial velocity. The following heating parameters were considered: the distribution of the heating rate over the vehicle, the distribution of the heat per square foot over the vehicle, and the total heat input to the vehicle. The constant G load path at limiting G was found to give the lowest total heat input for a given initial velocity. For a vehicle with a maximum lift-drag ratio of 1.0 and a flight path with a maximum G of 10 g's, entry velocities of twice circular appear thermo- dynamically feasible, and entries at velocities of 2.8 times circular are aerodynamically possible. The predominant heating (about 85 percent) occurs at the leading edge of the vehicle. The total ablated weight for a 10,000-pound-gross-weight vehicle decelerating from an initial velocity of twice circular velocity is estimated to be 5 percent of gross weight. Modifying the constant G load flight path by a constant-angle-of-attack segment through a flight- to circular-velocity ratio of 1.0 gives essentially a "point landing" capability but also results in an increased total heat input to the vehicle.

An original traffic additional emission model and numerical simulation on a signalized road

NASA Astrophysics Data System (ADS)

Zhu, Wen-Xing; Zhang, Jing-Yu

2017-02-01

Based on VSP (Vehicle Specific Power) model traffic real emissions were theoretically classified into two parts: basic emission and additional emission. An original additional emission model was presented to calculate the vehicle's emission due to the signal control effects. Car-following model was developed and used to describe the traffic behavior including cruising, accelerating, decelerating and idling at a signalized intersection. Simulations were conducted under two situations: single intersection and two adjacent intersections with their respective control policy. Results are in good agreement with the theoretical analysis. It is also proved that additional emission model may be used to design the signal control policy in our modern traffic system to solve the serious environmental problems.

MHD Jeffrey nanofluid past a stretching sheet with viscous dissipation effect

NASA Astrophysics Data System (ADS)

Zokri, S. M.; Arifin, N. S.; Salleh, M. Z.; Kasim, A. R. M.; Mohammad, N. F.; Yusoff, W. N. S. W.

2017-09-01

This study investigates the influence of viscous dissipation on magnetohydrodynamic (MHD) flow of Jeffrey nanofluid over a stretching sheet with convective boundary conditions. The nonlinear partial differential equations are reduced into the nonlinear ordinary differential equations by utilizing the similarity transformation variables. The Runge-Kutta Fehlberg method is used to solve the problem numerically. The numerical solutions obtained are presented graphically for several dimensionless parameters such as Brownian motion, Lewis number and Eckert number on the specified temperature and concentration profiles. It is noted that the temperature profile is accelerated due to increasing values of Brownian motion parameter and Eckert number. In contrast, both the Brownian motion parameter and Lewis number have caused the deceleration in the concentration profiles.

NSEG: A segmented mission analysis program for low and high speed aircraft. Volume 3: Demonstration problems

NASA Technical Reports Server (NTRS)

Hague, D. S.; Rozendaal, H. L.

1977-01-01

Program NSEG is a rapid mission analysis code based on the use of approximate flight path equations of motion. Equation form varies with the segment type, for example, accelerations, climbs, cruises, descents, and decelerations. Realistic and detailed vehicle characteristics are specified in tabular form. In addition to its mission performance calculation capabilities, the code also contains extensive flight envelope performance mapping capabilities. For example, rate-of-climb, turn rates, and energy maneuverability parameter values may be mapped in the Mach-altitude plane. Approximate take off and landing analyses are also performed. At high speeds, centrifugal lift effects are accounted for. Extensive turbojet and ramjet engine scaling procedures are incorporated in the code.

The Effects of Meperidine Analgesia during Labor on Fetal Heart Rate

PubMed Central

Sekhavat, Leila; Behdad, Shecoofah

2009-01-01

To estimate the effects of intramuscular meperidine analgesia on fetal heart rate (FHR) patterns compared with placebo. In a prospective randomized study, 150 healthy women with singleton term pregnancy requesting analgesia during active labor were planned to receive either intramuscular meperidin 50 mg (meperidin group) or normal saline (control group) when they requested analgesia. Fetal heart rate patterns occurring within 40 minutes of initiation of labor analgesia were retrospectively read by maternal fetal medicine specialist who was blind to type of labor analgesia. Meperidine, compared with placebo, was associated with statistically significantly less beat to beat variability (absent or less than 5 beats per minute) (28% versus 5% of fetuses, P<0.05), lower proportion of accelerations (37.3% versus 17.3% P<0.05) and of the FHR. Also FHR deceleration was significantly more than control group (25.5% versus 4%, P<0.05). Meperidine has deleterious effects on FHR. PMID:23675116

Generalized Wall Function for Complex Turbulent Flows

NASA Technical Reports Server (NTRS)

Shih, Tsan-Hsing; Povinelli, Louis A.; Liu, Nan-Suey; Chen, Kuo-Huey

2000-01-01

A generalized wall function was proposed by Shih et al., (1999). It accounts the effect of pressure gradients on the flow near the wall. Theory shows that the effect of pressure gradients on the flow in the inertial sublayer is very significant and the standard wall function should be replaced by a generalized wall function. Since the theory is also valid for boundary layer flows toward separation, the generalized wall function may be applied to complex turbulent flows with acceleration, deceleration, separation and recirculation. This paper is to verify the generalized wall function with numerical simulations for boundary layer flows with various adverse and favorable pressure gradients, including flows about to separate. Furthermore, a general procedure of implementation of the generalized wall function for National Combustion Code (NCC) is described, it can be applied to both structured and unstructured CFD codes.

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.

Investigation on Radio-Quiet and Radio-Loud Fast CMEs and Their Associated Flares During Solar Cycles 23 and 24

NASA Astrophysics Data System (ADS)

Suresh, K.; Shanmugaraju, A.

2015-03-01

We present the results of a detailed analysis on the differences between radio-loud (RL) and radio-quiet (RQ) fast coronal mass ejections (CMEs) ( V≥900 km s-1) observed during the period 1996 - 2012. The analysis consists of three different steps in which we examined the properties of (i) RL and RQ CMEs, (ii) accelerating (class-A) and decelerating (class-D) CMEs among RL and RQ CMEs, and (iii) associated flares. The last two steps and events from a longer period are the extensions of the earlier work on RL and RQ CMEs that mainly aimed to determine the reason for the radio-quietness of some fast CMEs. During this period, we found that 38 % of fast CMEs are RL and 62 % of fast CMEs are RQ. Moreover, fewer RQ CMEs occur around the disc centre. The average speeds of RL and RQ CMEs are 1358 km s-1 and 1092 km s-1. Around 10 % of the RQ events are halo CMEs, but ≈ 66 % of RL events are halo CMEs. The mean acceleration or deceleration value of RL-CMEs is slightly greater than that of RQ-CMEs. When we divide these events based on their acceleration behaviour into class A and class D, there are no considerable differences between classes A and D of RL-CMEs or between classes A and D of RQ CMEs, except for their initial acceleration values. But there are significant differences among their associated flare properties. According to our study here, the RQ CMEs are less energetic than RL CMEs, and they are not associated with flares as strong as those associated with RL CMEs. This confirms the previous results that RQ CMEs do not often exceed the critical Alfvén speed of 1000 km s-1 in the outer corona that is needed to produce type II radio bursts.

A 6% measurement of the Hubble parameter at z ∼0.45: direct evidence of the epoch of cosmic re-acceleration

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

Moresco, Michele; Cimatti, Andrea; Citro, Annalisa

2016-05-01

Deriving the expansion history of the Universe is a major goal of modern cosmology. To date, the most accurate measurements have been obtained with Type Ia Supernovae (SNe) and Baryon Acoustic Oscillations (BAO), providing evidence for the existence of a transition epoch at which the expansion rate changes from decelerated to accelerated. However, these results have been obtained within the framework of specific cosmological models that must be implicitly or explicitly assumed in the measurement. It is therefore crucial to obtain measurements of the accelerated expansion of the Universe independently of assumptions on cosmological models. Here we exploit the unprecedentedmore » statistics provided by the Baryon Oscillation Spectroscopic Survey (BOSS, [1-3]) Data Release 9 to provide new constraints on the Hubble parameter H ( z ) using the cosmic chronometers approach. We extract a sample of more than 130000 of the most massive and passively evolving galaxies, obtaining five new cosmology-independent H ( z ) measurements in the redshift range 0.3 < z < 0.5, with an accuracy of ∼11–16% incorporating both statistical and systematic errors. Once combined, these measurements yield a 6% accuracy constraint of H ( z = 0.4293) = 91.8 ± 5.3 km/s/Mpc. The new data are crucial to provide the first cosmology-independent determination of the transition redshift at high statistical significance, measuring z {sub t} = 0.4 ± 0.1, and to significantly disfavor the null hypothesis of no transition between decelerated and accelerated expansion at 99.9% confidence level. This analysis highlights the wide potential of the cosmic chronometers approach: it permits to derive constraints on the expansion history of the Universe with results competitive with standard probes, and most importantly, being the estimates independent of the cosmological model, it can constrain cosmologies beyond—and including—the ΛCDM model.« less

A New Maneuver for Escape Trajectories

NASA Technical Reports Server (NTRS)

Adams, Robert B.

2008-01-01

This presentation put forth a new maneuver for escape trajectories and specifically sought to find an analytical approximation for medium thrust trajectories. In most low thrust derivations the idea is that escape velocity is best achieved by accelerating along the velocity vector. The reason for this is that change in specific orbital energy is a function of velocity and acceleration. However, Levin (1952) suggested that while this is a locally optimal solution it might not be a globally optimal one. Turning acceleration inward would drop periapse giving a higher velocity later in the trajectory. Acceleration at that point would be dotted against a higher magnitude V giving a greater rate of change of mechanical energy. The author then hypothesized that decelerating from the initial orbit and then accelerating at periapse would not lead to a gain in greater specific orbital energy--however, the hypothesis was incorrect. After considerable derivation it was determined that this new maneuver outperforms a direct burn when the overall DeltaV budget exceeds the initial orbital velocity (the author has termed this the Heinlein maneuver). The author provides a physical explanation for this maneuver and presents optimization analyses.

Close to Kill: Vestigial Technologies and Combat Arms

DTIC Science & Technology

2012-06-01

greater distances. The mere thought of ramming a several-thousand-ton ship into another vessel, stabbing a blade into the chest of an adversary, or...Not until six months into the war did it contract for a third.41 The shortage in production capacity led to a significant iron deficit by the end...wind and sea, influence of wakes , and rates and acceleration and deceleration of ships of different displacements.” Robison, A History of Naval

Development of hybrid electric vehicle powertrain test system based on virtue instrument

NASA Astrophysics Data System (ADS)

Xu, Yanmin; Guo, Konghui; Chen, Liming

2017-05-01

Hybrid powertrain has become the standard configuration of some automobile models. The test system of hybrid vehicle powertrain was developed based on virtual instrument, using electric dynamometer to simulate the work of engines, to test the motor and control unit of the powertrain. The test conditions include starting, acceleration, and deceleration. The results show that the test system can simulate the working conditions of the hybrid electric vehicle powertrain under various conditions.

Baseline test data for the EVA electric vehicle. [low energy consumption automobiles

NASA Technical Reports Server (NTRS)

Harhay, W. C.; Bozek, J.

1976-01-01

Two electric vehicles from Electric Vehicle Associates were evaluated for ERDA at the Transportation Research Center of Ohio. The vehicles, loaded to a gross vehicle weight of 3750 pounds, had a range of 56.3 miles at a steady speed of 25 mph and a 27.4 miles range during acceleration-deceleration tests to a top speed of 30 mph. Energy consumption varied from 0.48 kw-hr/mi. to 0.59 kw-hr/mi.

Biodynamic Assessment of Pilot Knee-Board Configurations During Simulated T-38 Catapult Acceleration

DTIC Science & Technology

2015-04-01

Apple iPad Mini with a shock case. The T-38C ejection pulse was simulated using the Vertical Deceleration Tower (VDT) set-up with a Martin Baker Mk...Figure 6. Free-body Diagram to Illustrate Loading and Bending Moment at Mid-Point of Femur (Schematic from Kennedy, VPI Thesis , 2004...kneeboard configuration compared to the paper kneeboard configuration. The proposed kneeboard configuration consisted of an Apple iPad Mini with a

Single electron beam rf feedback free electron laser

DOEpatents

Brau, C.A.; Stein, W.E.; Rockwood, S.D.

1981-02-11

A free electron laser system and electron beam system for a free electron laser which uses rf feedback to enhance efficiency are described. Rf energy is extracted from a single electron beam by decelerating cavities and energy is returned to accelerating cavities using rf returns, such as rf waveguides, rf feedthroughs, resonant feedthroughs, etc. This rf energy is added to rf klystron energy to reduce the required input energy and thereby enhance energy efficiency of the system.

Assessment of Early Diastolic Strain-Velocity Temporal Relationships Using SPAMM-PAV (SPAtial Modulation of Magnetization with Polarity Alternating Velocity encoding)

PubMed Central

Zhang, Ziheng; Dione, Donald P.; Brown, Peter B.; Shapiro, Erik M.; Sinusas, Albert J.; Sampath, Smita

2011-01-01

A novel MR imaging technique, spatial modulation of magnetization with polarity alternating velocity encoding (SPAMM-PAV), is presented to simultaneously examine the left ventricular early diastolic temporal relationships between myocardial deformation and intra-cavity hemodynamics with a high temporal resolution of 14 ms. This approach is initially evaluated in a dynamic flow and tissue mimicking phantom. A comparison of regional longitudinal strains and intra-cavity pressure differences (integration of computed in-plane pressure gradients within a selected region) in relation to mitral valve inflow velocities is performed in eight normal volunteers. Our results demonstrate that apical regions have higher strain rates (0.145 ± 0.005 %/ms) during the acceleration period of rapid filling compared to mid-ventricular (0.114 ± 0.007 %/ms) and basal regions (0.088 ± 0.009 %/ms), and apical strain curves plateau at peak mitral inflow velocity. This pattern is reversed during the deceleration period, when the strain-rates in the basal regions are the highest (0.027 ± 0.003 %/ms) due to ongoing basal stretching. A positive base-to-apex gradient in peak pressure difference is observed during acceleration, followed by a negative base-to apex gradient during deceleration. These studies shed insight into the regional volumetric and pressure difference changes in the left ventricle during early diastolic filling. PMID:21630348

Universe without dark energy: Cosmic acceleration from dark matter-baryon interactions

NASA Astrophysics Data System (ADS)

Berezhiani, Lasha; Khoury, Justin; Wang, Junpu

2017-06-01

Cosmic acceleration is widely believed to require either a source of negative pressure (i.e., dark energy), or a modification of gravity, which necessarily implies new degrees of freedom beyond those of Einstein gravity. In this paper we present a third possibility, using only dark matter (DM) and ordinary matter. The mechanism relies on the coupling between dark matter and ordinary matter through an effective metric. Dark matter couples to an Einstein-frame metric, and experiences a matter-dominated, decelerating cosmology up to the present time. Ordinary matter couples to an effective metric that depends also on the DM density, in such a way that it experiences late-time acceleration. Linear density perturbations are stable and propagate with arbitrarily small sound speed, at least in the case of "pressure" coupling. Assuming a simple parametrization of the effective metric, we show that our model can successfully match a set of basic cosmological observables, including luminosity distance, baryon acoustic oscillation measurements, angular-diameter distance to last scattering, etc. For the growth history of density perturbations, we find an intriguing connection between the growth factor and the Hubble constant. To get a growth history similar to the Λ CDM prediction, our model predicts a higher H0, closer to the value preferred by direct estimates. On the flip side, we tend to overpredict the growth of structures whenever H0 is comparable to the Planck preferred value. The model also tends to predict larger redshift-space distortions at low redshift than Λ CDM .

Changes in apparent duration follow shifts in perceptual timing

PubMed Central

Bruno, Aurelio; Ayhan, Inci; Johnston, Alan

2015-01-01

It is well established that the apparent duration of moving visual objects is greater at higher as compared to slower speeds. Here we report the effects of acceleration and deceleration on the perceived duration of a drifting grating with average speed kept constant (10°/s).For acceleration, increasing the speed range progressively reduced perceived duration. The magnitude of apparent duration compression was determined by speed rather than temporal frequency and was proportional to speed range (independent of standard duration) rather than acceleration. The perceived duration reduction was also proportional to the standard length. The effects of increases and decreases in speed were highly asymmetric. Reducing speed through the interval induced a moderate increase in perceived duration. These results could not be explained by changes in apparent onset or offset or differences in perceived average speed between intervals containing increasing speed and intervals containing decreasing speed. Paradoxically, for intervals combining increasing speed and decreasing speed, compression only occurred when increasing speed occurred in the second half of the interval. We show that this pattern of results in the duration domain was concomitant with changes in the reported direction of apparent motion of Gaussian blobs, embedded in intervals of increasing or decreasing speed, that could be predicted from adaptive changes in the temporal impulse response function. We detected similar changes after flicker adaptation, suggesting that the two effects might be linked through changes in the temporal tuning of visual filters. PMID:26024450

Fetal and infant growth patterns associated with total and abdominal fat distribution in school-age children.

PubMed

Gishti, Olta; Gaillard, Romy; Manniesing, Rashindra; Abrahamse-Berkeveld, Marieke; van der Beek, Eline M; Heppe, Denise H M; Steegers, Eric A P; Hofman, Albert; Duijts, Liesbeth; Durmuş, Büşra; Jaddoe, Vincent W V

2014-07-01

Higher infant growth rates are associated with an increased risk of obesity in later life. We examined the associations of longitudinally measured fetal and infant growth patterns with total and abdominal fat distribution in childhood. We performed a population-based prospective cohort study among 6464 children. We measured growth characteristics in the second and third trimesters of pregnancy, at birth, and at 6, 12, and 24 months. Body mass index, fat mass index (body fat mass/height(2)), lean mass index (body lean mass/height(2)), android/gynoid fat ratio measured by dual-energy x-ray absorptiometry, and sc and preperitoneal abdominal fat measured by ultrasound at the median age of 6.0 years (90% range, 5.7-7.4). We observed that weight gain in the second and third trimesters of fetal life and in early, mid, and late infancy were independently and positively associated with childhood body mass index (P < .05). Only infant weight gain was associated with higher fat mass index, android/gynoid fat ratio, and abdominal fat in childhood (P < .05). Children with both fetal and infant growth acceleration had the highest childhood body mass index, fat mass index, and sc abdominal fat, whereas children with fetal growth deceleration and infant growth acceleration had the highest value for android/gynoid fat ratio and the lowest value for lean mass index (P < .05). Growth in both fetal life and infancy affects childhood body mass index, whereas only infant growth directly affects measured total body and abdominal fat. Fetal growth deceleration followed by infant growth acceleration may lead to an adverse body fat distribution in childhood.

Variability of activity profile during medium-sided games in professional soccer.

PubMed

Rago, Vincenzo; Silva, João R; Mohr, Magni; Barreira, Daniel; Krustrup, Peter; Rebelo, António N

2018-04-24

In Southern European countries it is very frequent to perform medium-sized games (MSG) as last training drill. We analyzed the individual variability and changes in activity patterns during MSG throughout the preseason. Activity profile during MSGs (10v10+goalkeepers, duration: 10-min, field length: 50 m, width: 90 m, area per player: 204.5 m2) was quantified using a GPS in 14 professional male players (6 defenders, 5 midfielders 5 and attackers). Inter-individual variability was higher for high-intensity (HIR), very-high speed (VHS), maximum acceleration (Accmax) and maximum deceleration (Decmax) distance (CV=25.2 to 43.3%), compared to total distance (TD), total acceleration (Acctot) and total deceleration (Dectot) distance (CV= 8.3 to 18.3 %). Defenders showed higher variability in TD, HIR, VHS, Acctot and Dectot (ES= 1.30 to 11.28) compared to the other field positions, whereas attackers showed higher variability in HIR, VHS Accmax and Decmax (ES=-4.92 to 2.07) than other the field positions. Variability in TD regularly increased (ES= -2.13 to -0.91) towards the end of the preseason, while HIR and VHS variability tended to increase over the 3rd and the 4th preseason week (ES=-0.94 to -3.05). However, the behavior of variability across the preseason period was more unpredictable for Acctot and Dectot, both decreasing in the 3rd week (ES= 0.70 to 1.20), while Decmax increased in the 4th week (ES=-0.91±0.59). During MSGs, individual variability of activity differs among field positions, and tends to increase with either speed or acceleration intensity, underlining the need of an individualized approach for training load monitoring.

New holographic dark energy model with constant bulk viscosity in modified f(R,T) gravity theory

NASA Astrophysics Data System (ADS)

Srivastava, Milan; Singh, C. P.

2018-06-01

The aim of this paper is to study new holographic dark energy (HDE) model in modified f(R,T) gravity theory within the framework of a flat Friedmann-Robertson-Walker model with bulk viscous matter content. It is thought that the negative pressure caused by the bulk viscosity can play the role of dark energy component, and drive the accelerating expansion of the universe. This is the motive of this paper to observe such phenomena with bulk viscosity. In the specific model f(R,T)=R+λ T, where R is the Ricci scalar, T the trace of the energy-momentum tensor and λ is a constant, we find the solution for non-viscous and viscous new HDE models. We analyze new HDE model with constant bulk viscosity, ζ =ζ 0= const. to explain the present accelerated expansion of the universe. We classify all possible scenarios (deceleration, acceleration and their transition) with possible positive and negative ranges of λ over the constraint on ζ 0 to analyze the evolution of the universe. We obtain the solutions of scale factor and deceleration parameter, and discuss the evolution of the universe. We observe the future finite-time singularities of type I and III at a finite time under certain constraints on λ . We also investigate the statefinder and Om diagnostics of the viscous new HDE model to discriminate with other existing dark energy models. In late time the viscous new HDE model approaches to Λ CDM model. We also discuss the thermodynamics and entropy of the model and find that it satisfies the second law of thermodynamics.

ON SUN-TO-EARTH PROPAGATION OF CORONAL MASS EJECTIONS: II. SLOW EVENTS AND COMPARISON WITH OTHERS

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

Liu, Ying D.; Hu, Huidong; Wang, Chi

As a follow-up study on Sun-to-Earth propagation of fast coronal mass ejections (CMEs), we examine the Sun-to-Earth characteristics of slow CMEs combining heliospheric imaging and in situ observations. Three events of particular interest, the 2010 June 16, 2011 March 25, and 2012 September 25 CMEs, are selected for this study. We compare slow CMEs with fast and intermediate-speed events, and obtain key results complementing the attempt of Liu et al. to create a general picture of CME Sun-to-Earth propagation: (1) the Sun-to-Earth propagation of a typical slow CME can be approximately described by two phases, a gradual acceleration out tomore » about 20–30 solar radii, followed by a nearly invariant speed around the average solar wind level; (2) comparison between different types of CMEs indicates that faster CMEs tend to accelerate and decelerate more rapidly and have shorter cessation distances for the acceleration and deceleration; (3) both intermediate-speed and slow CMEs would have speeds comparable to the average solar wind level before reaching 1 au; (4) slow CMEs have a high potential to interact with other solar wind structures in the Sun–Earth space due to their slow motion, providing critical ingredients to enhance space weather; and (5) the slow CMEs studied here lack strong magnetic fields at the Earth but tend to preserve a flux-rope structure with an axis generally perpendicular to the radial direction from the Sun. We also suggest a “best” strategy for the application of a triangulation concept in determining CME Sun-to-Earth kinematics, which helps to clarify confusions about CME geometry assumptions in the triangulation and to improve CME analysis and observations.« less

Earth’s Rotational Deceleration: Determination of Tidal Friction Independent of Timescales

NASA Astrophysics Data System (ADS)

Deines, Steven D.; Williams, Carol A.

2016-04-01

This paper determines Earth's rotational deceleration without relying on atomic or ephemeris timescales. Earth's rotation defines the civil time standard called Universal Time (UT). Our previous paper did not examine tidal friction in depth when analyzing the timescale divergence between UT and International Atomic Time (TAI). We examine all available paleontological fossils and deposits for the direct measurements of Earth's past rotation rates, because that record includes all contributing effects. We examine paleontological reports that date Earth's rotation rate using corals, bivalves, brachiopods, rhythmites, and stromatolites. Contributions that vary Earth's moment of inertia, such as continental plate drifts, coastline changes, ice age formations, and viscous glacial rebounds, are superimposed with the secular deceleration. The average deceleration of Earth's rotation rate from all available fossil data is found to be (5.969 ± 1.762) × 10-7 rad yr-2. Our value is 99.8% of the total rotational deceleration determined by Christodoulidis et al., who used artificial satellite data, and our value is 96.6% of the expected tidal friction value obtained by Stephenson and Morrison. Taking the derivative of conserved angular momentum, the predicted lunar orbital deceleration caused by the average rotational deceleration corresponds closely to lunar models. When evaluating the significant time gaps between UT and TAI, Earth's rotational deceleration is a minor contributing factor. Also, the secular deceleration rate is necessary to correctly date ancient astronomical events. We strongly encourage that more ocean paleontological evidence be found to supplement the record to separate the many periodic variations embedded in these data.

Accelerating Universe from Gravitational Leakage into Extra Dimensions: Testing with Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Zhu, Zong-Hong; Alcaniz, Jailson S.

2005-02-01

There is mounting observational evidence that the expansion of our universe is undergoing an acceleration. A dark energy component has usually been invoked as the most feasible mechanism for the acceleration. However, it is desirable to explore alternative possibilities motivated by particle physics before adopting such an untested entity. In this work, we focus our attention on an acceleration mechanism arising from gravitational leakage into extra dimensions. We test this scenario with high-z Type Ia supernovae compiled by Tonry and coworkers and recent measurements of the X-ray gas mass fractions in clusters of galaxies published by Allen and coworkers. A combination of the two databases gives, at a 99% confidence level, Ωm=0.29+0.04-0.02, Ωrc=0.21+/-0.08, and Ωk=-0.36+0.31-0.35, indicating a closed universe. We then constrain the model using the test of the turnaround redshift, zq=0, at which the universe switches from deceleration to acceleration. We show that, in order to explain that acceleration happened earlier than zq=0=0.6 within the framework of gravitational leakage into extra dimensions, a low matter density, Ωm<0.27, or a closed universe is necessary.

Independent Orbiter Assessment (IOA): Analysis of the landing/deceleration subsystem

NASA Technical Reports Server (NTRS)

Compton, J. M.; Beaird, H. G.; Weissinger, W. D.

1987-01-01

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results corresponding to the Orbiter Landing/Deceleration Subsystem hardware. The Landing/Deceleration Subsystem is utilized to allow the Orbiter to perform a safe landing, allowing for landing-gear deploy activities, steering and braking control throughout the landing rollout to wheel-stop, and to allow for ground-handling capability during the ground-processing phase of the flight cycle. Specifically, the Landing/Deceleration hardware consists of the following components: Nose Landing Gear (NLG); Main Landing Gear (MLG); Brake and Antiskid (B and AS) Electrical Power Distribution and Controls (EPD and C); Nose Wheel Steering (NWS); and Hydraulics Actuators. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode. Due to the lack of redundancy in the Landing/Deceleration Subsystems there is a high number of critical items.

Effects of historical and predictive information on ability of transport pilot to predict an alert

NASA Technical Reports Server (NTRS)

Trujillo, Anna C.

1994-01-01

In the aviation community, the early detection of the development of a possible subsystem problem during a flight is potentially useful for increasing the safety of the flight. Commercial airlines are currently using twin-engine aircraft for extended transport operations over water, and the early detection of a possible problem might increase the flight crew's options for safely landing the aircraft. One method for decreasing the severity of a developing problem is to predict the behavior of the problem so that appropriate corrective actions can be taken. To investigate the pilots' ability to predict long-term events, a computer workstation experiment was conducted in which 18 airline pilots predicted the alert time (the time to an alert) using 3 different dial displays and 3 different parameter behavior complexity levels. The three dial displays were as follows: standard (resembling current aircraft round dial presentations); history (indicating the current value plus the value of the parameter 5 sec in the past); and predictive (indicating the current value plus the value of the parameter 5 sec into the future). The time profiles describing the behavior of the parameter consisted of constant rate-of-change profiles, decelerating profiles, and accelerating-then-decelerating profiles. Although the pilots indicated that they preferred the near term predictive dial, the objective data did not support its use. The objective data did show that the time profiles had the most significant effect on performance in estimating the time to an alert.

Computational flow predictions for hypersonic drag devices

NASA Technical Reports Server (NTRS)

Tokarcik, Susan; Venkatapathy, Ethiraj; Candler, Graham; Palmer, Grant

1991-01-01

The effectiveness of two types of hypersonic decelerators are computationally examined: mechanically deployable flares and inflatable ballutes. CFD is used to predict the flowfield around a solid rocket motor (SRM) with a deployed decelerator. The computations are performed with an ideal gas solver using an effective specific heat ratio of 1.15. The surface pressure coefficients, the drag, and the extent of the compression corner separation zone predicted by the ideal gas solver compare well with those predicted by the nonequilibrium solver. The ideal gas solver is computationally inexpensive and is shown to be well suited for preliminary design studies. The computed solutions are used to determine the size and shape of the decelerator that are required to achieve a drag coefficient of 5 in order to assure that the SRM will splash down in the Pacific Ocean. Heat transfer rates to the SRM and the decelerators are predicted to estimate the amount of thermal protection required.

Simple scaling of catastrophic landslide dynamics.

PubMed

Ekström, Göran; Stark, Colin P

2013-03-22

Catastrophic landslides involve the acceleration and deceleration of millions of tons of rock and debris in response to the forces of gravity and dissipation. Their unpredictability and frequent location in remote areas have made observations of their dynamics rare. Through real-time detection and inverse modeling of teleseismic data, we show that landslide dynamics are primarily determined by the length scale of the source mass. When combined with geometric constraints from satellite imagery, the seismically determined landslide force histories yield estimates of landslide duration, momenta, potential energy loss, mass, and runout trajectory. Measurements of these dynamical properties for 29 teleseismogenic landslides are consistent with a simple acceleration model in which height drop and rupture depth scale with the length of the failing slope.

Bubble deformations and segmented flows in corrugated microchannels at large capillary numbers

NASA Astrophysics Data System (ADS)

Sauzade, Martin; Cubaud, Thomas

2018-03-01

We experimentally investigate the interaction between individual bubble deformations and collective distortions of segmented flows in nonlinear microfluidic geometries. Using highly viscous carrier fluids, we study the evolution of monodisperse trains of gas bubbles from a square to a smoothly corrugated microchannel characterized with a series of extensions and constrictions along the flow path. The hysteresis in the bubble shape between accelerating and decelerating flow fields is shown to increase with the capillary number. Measurements of instantaneous bubble velocities reveal the presence of a capillary pull that produces a nonmonotonic behavior for the front velocity in accelerating flow regions. Functional relationships are developed for predicting the morphology and dynamics of viscous multiphase flow patterns at the pore scale.

Measurement of ultra-low ion energy of decelerated ion beam using a deflecting electric field

NASA Astrophysics Data System (ADS)

Thopan, P.; Suwannakachorn, D.; Tippawan, U.; Yu, L. D.

2015-12-01

In investigation on ultra-low-energy ion bombardment effect on DNA, an ion beam deceleration lens was developed for high-quality ultra-low-energy ion beam. Measurement of the ion energy after deceleration was necessary to confirm the ion beam really decelerated as theoretically predicted. In contrast to conventional methods, this work used a simple deflecting electrostatic field after the deceleration lens to bend the ion beam. The beam bending distance depended on the ion energy and was described and simulated. A system for the measurement of the ion beam energy was constructed. It consisted of a pair of parallel electrode plates to generate the deflecting electrical field, a copper rod measurement piece to detect ion beam current, a vernier caliper to mark the beam position, a stepping motor to translate the measurement rod, and a webcam-camera to read the beam bending distance. The entire system was installed after the ion-beam deceleration lens inside the large chamber of the bioengineering vertical ion beam line. Moving the measurement rod across the decelerated ion beam enabled to obtain beam profiles, from which the beam bending distance could be known and the ion beam energy could be calculated. The measurement results were in good agreement with theoretical and simulated results.

Development of new platforms for hydrodynamic instability and asymmetry measurements in deceleration phase of indirectly-driven implosions on NIF

NASA Astrophysics Data System (ADS)

Pickworth, Louisa

2017-10-01

Hydrodynamic instabilities and asymmetries are a major obstacle in the quest to achieve ignition as they cause pre-existing capsule perturbations to grow and ultimately quench the fusion burn in experiments at the National Ignition Facility (NIF). This talk will review recent developments of the experimental platforms and techniques to measure high-mode instabilities and low-mode asymmetries in the deceleration phase of implosions. These new platforms provide a natural link between the acceleration-phase experiments and neutron performance of layered deuterium-tritium implosions. In one innovative technique, self-emission from the hot spot was enhanced with argon dopant to ``self-backlight'' the shell in-flight around peak compression. Experiments with pre-imposed 2-D perturbations measured instability growth factors, while experiments with 3-D, ``native-roughness'' perturbations measured shell integrity in the deceleration phase of implosions. In a complimentary technique, the inner surface of the shell, along with its low-mode asymmetries and high-mode perturbations were visualized in implosions using x-ray emission of a high-Z dopant added to the inner surface of the capsule. These new measurements were instrumental in revealing unexpected surprises and providing improved understanding of the role of instabilities and asymmetries on implosion performance. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Aerodynamic Models for the Low Density Supersonic Declerator (LDSD) Supersonic Flight Dynamics Test (SFDT)

NASA Technical Reports Server (NTRS)

Van Norman, John W.; Dyakonov, Artem; Schoenenberger, Mark; Davis, Jody; Muppidi, Suman; Tang, Chun; Bose, Deepak; Mobley, Brandon; Clark, Ian

2015-01-01

An overview of pre-flight aerodynamic models for the Low Density Supersonic Decelerator (LDSD) Supersonic Flight Dynamics Test (SFDT) campaign is presented, with comparisons to reconstructed flight data and discussion of model updates. The SFDT campaign objective is to test Supersonic Inflatable Aerodynamic Decelerator (SIAD) and large supersonic parachute technologies at high altitude Earth conditions relevant to entry, descent, and landing (EDL) at Mars. Nominal SIAD test conditions are attained by lifting a test vehicle (TV) to 36 km altitude with a large helium balloon, then accelerating the TV to Mach 4 and and 53 km altitude with a solid rocket motor. The first flight test (SFDT-1) delivered a 6 meter diameter robotic mission class decelerator (SIAD-R) to several seconds of flight on June 28, 2014, and was successful in demonstrating the SFDT flight system concept and SIAD-R. The trajectory was off-nominal, however, lofting to over 8 km higher than predicted in flight simulations. Comparisons between reconstructed flight data and aerodynamic models show that SIAD-R aerodynamic performance was in good agreement with pre-flight predictions. Similar comparisons of powered ascent phase aerodynamics show that the pre-flight model overpredicted TV pitch stability, leading to underprediction of trajectory peak altitude. Comparisons between pre-flight aerodynamic models and reconstructed flight data are shown, and changes to aerodynamic models using improved fidelity and knowledge gained from SFDT-1 are discussed.

Figuring the Acceleration of the Simple Pendulum

NASA Astrophysics Data System (ADS)

Lieberherr, Martin

2011-12-01

The centripetal acceleration has been known since Huygens' (1659) and Newton's (1684) time.1,2 The physics to calculate the acceleration of a simple pendulum has been around for more than 300 years, and a fairly complete treatise has been given by C. Schwarz in this journal.3 But sentences like "the acceleration is always directed towards the equilibrium position" beside the picture of a swing on a circular arc can still be found in textbooks, as e.g. in Ref. 4. Vectors have been invented by Grassmann (1844)5 and are conveniently used to describe the acceleration in curved orbits, but acceleration is more often treated as a scalar with or without sign, as the words acceleration/deceleration suggest. The component tangential to the orbit is enough to deduce the period of the simple pendulum, but it is not enough to discuss the forces on the pendulum, as has been pointed out by Santos-Benito and A. Gras-Marti.6 A suitable way to address this problem is a nice figure with a catch for classroom discussions or homework. When I plotted the acceleration vectors of the simple pendulum in their proper positions, pictures as in Fig. 1 appeared on the screen. The endpoints of the acceleration vectors, if properly scaled, seemed to lie on a curve with a familiar shape: a cardioid. Is this true or just an illusion?

Ice-sheet thinning and acceleration at Camp Century, Greenlan

NASA Astrophysics Data System (ADS)

Colgan, W. T.

2017-12-01

Camp Century, Greenland (77.18 °N, 61.12 °W, 1900 m), is located approximately 150 km inland from the ice-sheet margin in Northwest Greenland. In-situ and remotely-sensed measurements of ice-sheet elevation at Camp Century exhibit a thinning trend between 1964 and the present. A comparison of 1966 and 2017 firn density profiles indicates that a portion of this ice-sheet thinning is attributable to increased firn compaction rate. In-situ measurements of increasing ice surface velocity over the 1977-2017 period indicate that enhanced horizontal divergence of ice flux is also contributing to ice dynamic thinning at Camp Century. This apparent ice dynamic thinning could potentially result from a migrating local flow divide or decreasing effective ice viscosity. In a shorter-term context, observations of decadal-scale ice-sheet thinning and acceleration at Camp Century highlights underappreciated transience in inland ice form and flow during the satellite era. In a longer-term context, these multi-decadal observations contrast with inferences of millennial-scale ice-sheet thickening and deceleration at Camp Century.

MMS Observations of Protons and Heavy Ions Acceleration at Plasma Jet Fronts

NASA Astrophysics Data System (ADS)

Catapano, F.; Retino, A.; Zimbardo, G.; Cozzani, G.; Breuillard, H.; Le Contel, O.; Alexandrova, A.; Mirioni, L.; Cohen, I. J.; Turner, D. L.; Perri, S.; Greco, A.; Mauk, B.; Torbert, R. B.; Russell, C. T.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Ergun, R.; Giles, B. L.; Fuselier, S. A.; Moore, T. E.; Burch, J.

2017-12-01

Plasma jet fronts in the Earth's magnetotail are kinetic-scale boundaries separating hot fast plasma jets, generally attributed to reconnection outflows, from colder ambient plasma. Jet fronts are typically associated with a sharp increase of the vertical component of the magnetic field Bz, an increase of the plasma temperature and a drop of plasma density. Spacecraft observations and numerical simulations indicate that jet fronts are sites of major ion acceleration. The exact acceleration mechanisms as well as the dependence of such mechanisms on ion composition are not fully understood, yet. Recent high-resolution measurements of ion distribution functions in the magnetotail allow for the first time to study the acceleration mechanisms in detail. Here, we show several examples of jet fronts and discuss ion acceleration therein. We show fronts that propagate in the mid-tail magnetotail both as isolated laminar boundaries and as multiple boundaries embedded in strong magnetic fluctuations and turbulence. We also show fronts in the near-Earth jet braking region, where they interact with the dipolar magnetic field and are significantly decelerated/diverted. Finally, we study the acceleration of different ion species (H+, He++, O+) at different types of fronts and we discuss possible different acceleration mechanisms and how they depend on the ion species.

Travelling wave solutions of the homogeneous one-dimensional FREFLO model

NASA Astrophysics Data System (ADS)

Huang, B.; Hong, J. Y.; Jing, G. Q.; Niu, W.; Fang, L.

2018-01-01

Presently there is quite few analytical studies in traffic flows due to the non-linearity of the governing equations. In the present paper we introduce travelling wave solutions for the homogeneous one-dimensional FREFLO model, which are expressed in the form of series and describe the procedure that vehicles/pedestrians move with a negative velocity and decelerate until rest, then accelerate inversely to positive velocities. This method is expect to be extended to more complex situations in the future.

Generate stepper motor linear speed profile in real time

NASA Astrophysics Data System (ADS)

Stoychitch, M. Y.

2018-01-01

In this paper we consider the problem of realization of linear speed profile of stepper motors in real time. We considered the general case when changes of speed in the phases of acceleration and deceleration are different. The new and practical algorithm of the trajectory planning is given. The algorithms of the real time speed control which are suitable for realization to the microcontroller and FPGA circuits are proposed. The practical realization one of these algorithms, using Arduino platform, is given also.

Cosmography by GRBs: Gamma Ray Bursts as possible distance indicators

NASA Astrophysics Data System (ADS)

Capozziello, S.; Izzo, L.

2009-10-01

A new method to constrain the cosmological equation of state is proposed by using combined samples of gammaray bursts (GRBs) and supernovae (SNeIa). The Chevallier-Polarski-Linder parameterization is adopted for the equation of state in order to find out a realistic approach to achieve the deceleration/acceleration transition phase of dark energy models. As results, we find that GRBs, calibrated by SNeIa, could be, at least, good distance indicators capable of discriminating cosmological models with respect to ΛCDM at high redshift.

The role of energy conditions in f(R) cosmology

NASA Astrophysics Data System (ADS)

Capozziello, S.; Nojiri, S.; Odintsov, S. D.

2018-06-01

Energy conditions can play an important role in defining the cosmological evolution. Specifically acceleration/deceleration of cosmic fluid, as well as the emergence of Big Rip singularities, can be related to the constraints imposed by the energy conditions. Here we discuss this issue for f (R) gravity considering also conformal transformations. Cosmological solutions and equations of state can be classified according to energy conditions. The qualitative change of some energy conditions when transformation from the Jordan frame to the Einstein frame done is also observed.

Gravitational considerations with animal rhythms

NASA Technical Reports Server (NTRS)

Wunder, C. C.

1974-01-01

As established in the laboratory and largely confirmed by others, simulated high-g environments influence growth and development of animals as small as or smaller than baby turtles, sometimes accelerating and sometimes decelerating these processes. High-g environments result in many functional changes or adjustments in feeding, metabolism, circulation, fluid balances, and structures for support, and influence life expectancy. An assembly of equipment suitable for measuring oxygen consumption of small mammals as influenced by chronic centrifugation and/or by day-night rhythms is discussed.

Observational Properties of Coronal Mass Ejections

DTIC Science & Technology

2006-01-01

speeds 2.5. Masses and Energies of CMEs exceeded 2000 km s-1; the fastest CME speed measured thus far was 2657 km s-1 on 4 November 2000. When compiled The...accelerated. The average deceleration of the fastest (> 900 km s-1) The CME kinetic energies can also be calculated from the CME group is -16 m s-2...OBSERVATIONAL PROPERTIES OF CORONAL MASS EJECTIONS 15 *"...... .. ’..’... ... ’...... kinetic energy is 2.4 x 1030 ergs (5.0 x 1029 ergs) [Vourlidas, 2004

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS On control of kinematic parameters of ultracold neutrons in waveguides

NASA Astrophysics Data System (ADS)

Rivlin, Lev A.

2010-10-01

The possibility of controlling the kinematic parameters of ultracold neutrons (UCNs) is analysed by the example of a waveguide transfer and transformation of 2D images in ultracold neutrons and by the example of an increase in the concentration and deceleration/acceleration of ultracold neutrons during their transport in the waveguide with a variable cross section. The critical parameters of the problem are estimated, which indicates both consistency of the proposed approach and the emerging experimental limitations.

EARTH’S ROTATIONAL DECELERATION: DETERMINATION OF TIDAL FRICTION INDEPENDENT OF TIMESCALES

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

Deines, Steven D.; Williams, Carol A., E-mail: steven.deines@gmail.com, E-mail: cw@math.usf.edu

This paper determines Earth's rotational deceleration without relying on atomic or ephemeris timescales. Earth's rotation defines the civil time standard called Universal Time (UT). Our previous paper did not examine tidal friction in depth when analyzing the timescale divergence between UT and International Atomic Time (TAI). We examine all available paleontological fossils and deposits for the direct measurements of Earth's past rotation rates, because that record includes all contributing effects. We examine paleontological reports that date Earth's rotation rate using corals, bivalves, brachiopods, rhythmites, and stromatolites. Contributions that vary Earth's moment of inertia, such as continental plate drifts, coastline changes, icemore » age formations, and viscous glacial rebounds, are superimposed with the secular deceleration. The average deceleration of Earth's rotation rate from all available fossil data is found to be (5.969 ± 1.762) × 10{sup −7} rad yr{sup −2}. Our value is 99.8% of the total rotational deceleration determined by Christodoulidis et al., who used artificial satellite data, and our value is 96.6% of the expected tidal friction value obtained by Stephenson and Morrison. Taking the derivative of conserved angular momentum, the predicted lunar orbital deceleration caused by the average rotational deceleration corresponds closely to lunar models. When evaluating the significant time gaps between UT and TAI, Earth's rotational deceleration is a minor contributing factor. Also, the secular deceleration rate is necessary to correctly date ancient astronomical events. We strongly encourage that more ocean paleontological evidence be found to supplement the record to separate the many periodic variations embedded in these data.« less

Modeling experiments on the deceleration and reactivation of Kangerlussuup Sermusa, West Greenland

NASA Astrophysics Data System (ADS)

Rezvanbehbahani, S.; Stearns, L. A.; van der Veen, C. J.; Catania, G. A.

2015-12-01

Seasonal variations in outlet glacier velocity due to basal sliding are well-documented and typically involve acceleration early in the melt season due to enhanced sliding as a result of inefficient drainage of surface water reaching the bed. However, velocity observations from Kangerlussuup Sermusa (KS) in West Greenland contradict this pattern. Instead, ice velocity at KS shows no significant change in early spring compared with the previous winter. This sluggish response of the glacier to spring melt is often followed by an extreme, and short-lived, deceleration. For example, in August 2010, the lower 20 km of the trunk decelerated from about 1600 m a-1 to less than 250 m a-1; this event was followed by a rapid reactivation back to the previous velocity in less than 60 days. Available records since 2006 show that the sequence of steady spring velocity, followed by summer deceleration, and rapid fall reactivation occurs annually; however, the magnitudes of deceleration vary. In this regard, the response of KS to regional environmental forcings is unique compared to its neighboring glaciers. In this study, we investigate whether the unique behavior of KS can be explained by the interaction between changes in basal conditions and the local geometry of the glacier. We model the glacier flow by solving full-Stokes equations using the finite element method in the open-source FEniCS framework. Assuming isothermal ice within the lower trunk, we run experiments on the mechanical properties and boundary conditions of the glacier. These experiments include spatio-temporal changes in basal slipperiness, periodic melt-water influx to the bed, and ice viscosity variations due to changes in melt-water supply to the bed. We also conduct sensitivity analyses on the glacier flow with different ice geometries (e.g. thickness and surface slope) to investigate conditions under which we can produce the unique seasonal behavior of KS. Finally, we assess the impact of the combination of these parameters on the ice flow and evaluate the credibility of our hypothetical scenarios based on available measurements.

Rotorcraft air transportation

NASA Technical Reports Server (NTRS)

Gilbert, G. A.

1983-01-01

Intermodal relationships and the particular ways in which they affect public transportation applications of rotorcraft are addressed. Some aspects of integrated services and general comparisons with other transportation modes are reviewed. Two potential application scenarios are discussed: down-to-downtown rotorcraft service and urban public transport rotorcraft service. It is concluded that to integrate well with ground access modes community rotorcraft service should be limited stop service with published schedules, and operate on a few specific routes between a few specific destinations. For downtown-to-downtown service, time savings favorable to rotorcraft are benefits that reflect its more direct access, relatively higher line-haul travel speeds, and less circuitous travel. For the scenario of public transport within urban areas, first, improving cruise speeds has a limited potential due to allowing for a ""station spacing'' effect. Secondly, public acceptance of higher acceleration/deceleration rates may be just as effective as a technological innovation as achieving higher cruise speeds.

Repeated readings and science: Fluency with expository passages

NASA Astrophysics Data System (ADS)

Kostewicz, Douglas E.

The current study investigated the effects of repeated readings to a fluency criterion (RRFC) for seven students with disabilities using science text. The study employed a single subject design, specifically, two multiple probe multiple baselines across subjects, to evaluate the effects of the RRFC intervention. Results indicated that students met criterion (200 or more correct words per minute with 2 or fewer errors) on four consecutive passages. A majority of students displayed accelerations to correct words per minute and decelerations to incorrect words per minute on successive initial, intervention readings suggesting reading transfer. Students' reading scores during posttest and maintenance out performed pre-test and baseline readings provided additional measures of reading transfer. For a relationship to comprehension, students scored higher on oral retell measures after meeting criterion as compared to initial readings. Overall, the research findings suggested that the RRFC intervention improves science reading fluency for students with disabilities, and may also indirectly benefit comprehension.

Gunslinger Effect and Müller-Lyer Illusion: Examining Early Visual Information Processing for Late Limb-Target Control.

PubMed

Roberts, James W; Lyons, James; Garcia, Daniel B L; Burgess, Raquel; Elliott, Digby

2017-07-01

The multiple process model contends that there are two forms of online control for manual aiming: impulse regulation and limb-target control. This study examined the impact of visual information processing for limb-target control. We amalgamated the Gunslinger protocol (i.e., faster movements following a reaction to an external trigger compared with the spontaneous initiation of movement) and Müller-Lyer target configurations into the same aiming protocol. The results showed the Gunslinger effect was isolated at the early portions of the movement (peak acceleration and peak velocity). Reacted aims reached a longer displacement at peak deceleration, but no differences for movement termination. The target configurations manifested terminal biases consistent with the illusion. We suggest the visual information processing demands imposed by reacted aims can be adapted by integrating early feedforward information for limb-target control.

The Differential Effect of Arm Movements during Gait on the Forward Acceleration of the Centre of Mass in Children with Cerebral Palsy and Typically Developing Children.

PubMed

Meyns, Pieter; Molenaers, Guy; Duysens, Jacques; Jonkers, Ilse

2017-01-01

Background: We aimed to study the contribution of upper limb movements to propulsion during walking in typically developing (TD) children ( n = 5) and children with hemiplegic and diplegic cerebral palsy (CP; n = 5 and n = 4, respectively). Methods: Using integrated three-dimensional motion capture data and a scaled generic musculoskeletal model that included upper limbs, we generated torque driven simulations of gait in OpenSim. Induced acceleration analyses were then used to determine the contributions of the individual actuators located at the relevant degrees of freedoms of the upper and lower limb joints to the forward acceleration of the COM at each time point of the gait simulation. The mean values of the contribution of the actuators of upper limbs, lower limbs, and gravity in different phases of the gait cycle were compared between the three groups. Findings: The results indicated a limited contribution of the upper limb actuators to COM forward acceleration compared to the contribution of lower limbs and gravity, in the three groups. In diplegic CP, the contribution of the upper limbs seemed larger compared to TD during the preswing and swing phases of gait. In hemiplegic CP, the unaffected arm seemed to contribute more to COM deceleration during (pre)swing, while the affected side contributed to COM acceleration. Interpretation: These findings suggest that in the presence of lower limb dysfunction, the contribution of the upper limbs to forward propulsion is altered, although they remain negligible compared to the lower limbs and gravity.

Constraining the cosmic deceleration-acceleration transition with type Ia supernova, BAO/CMB and H(z) data

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

Santos, M. Vargas dos; Reis, R.R.R.; Waga, I., E-mail: vargas@if.ufrj.br, E-mail: ribamar@if.ufrj.br, E-mail: ioav@if.ufrj.br

2016-02-01

We revisit the kink-like parametrization of the deceleration parameter q(z) [1], which considers a transition, at redshift z{sub t}, from cosmic deceleration to acceleration. In this parametrization the initial, at z >> z{sub t}, value of the q-parameter is q{sub i}, its final, z=−1, value is q{sub f} and the duration of the transition is parametrized by τ. By assuming a flat space geometry we obtain constraints on the free parameters of the model using recent data from type Ia supernovae (SN Ia), baryon acoustic oscillations (BAO), cosmic microwave background (CMB) and the Hubble parameter H(z). The use of H(z) data introducesmore » an explicit dependence of the combined likelihood on the present value of the Hubble parameter H{sub 0}, allowing us to explore the influence of different priors when marginalizing over this parameter. We also study the importance of the CMB information in the results by considering data from WMAP7, WMAP9 (Wilkinson Microwave Anisotropy Probe—7 and 9 years) and Planck 2015. We show that the contours and best fit do not depend much on the different CMB data used and that the considered new BAO data is responsible for most of the improvement in the results. Assuming a flat space geometry, q{sub i}=1/2 and expressing the present value of the deceleration parameter q{sub 0} as a function of the other three free parameters, we obtain z{sub t}=0.67{sup +0.10}{sub −0.08}, τ=0.26{sup +0.14}{sub −0.10} and q{sub 0}=−0.48{sup +0.11}{sub −0.13}, at 68% of confidence level, with an uniform prior over H{sub 0}. If in addition we fix q{sub f}=−1, as in flat ΛCDM, DGP and Chaplygin quartessence that are special models described by our parametrization, we get z{sub t}=0.66{sup +0.03}{sub −0.04}, τ=0.33{sup +0.04}{sub −0.04} and q{sub 0}=−0.54{sup +0.05}{sub −0.07}, in excellent agreement with flat ΛCDM for which τ=1/3. We also obtain for flat wCDM, another dark energy model described by our parametrization, the constraint on the equation of state parameter −1.22 < w < −0.78 at more than 99% confidence level.« less

Hysteresis effect implicates calcium cycling as a mechanism of repolarization alternans.

PubMed

Walker, Mariah L; Wan, Xiaoping; Kirsch, Glenn E; Rosenbaum, David S

2003-11-25

T-wave alternans is due to alternation of membrane repolarization at the cellular level and is a risk factor for sudden cardiac death. Recently, a hysteresis effect has been reported in patients whereby T-wave alternans, once induced by rapid heart rate, persists even when heart rate is subsequently slowed. We hypothesized that alternans hysteresis is an intrinsic property of cardiac myocytes, directly related to an underlying mechanism for repolarization alternans that involves intracellular calcium cycling. Stepwise pacing was used to induce alternans in Langendorff-perfused guinea pig hearts from which optical action potentials were recorded simultaneously at 256 ventricular sites with voltage-sensitive dyes and in whole-cell patch-clamped cardiac myocytes treated with or without BAPTA-AM (1,2-bis[2-aminophenoxy]ethane-N,N,N',N'-tetraacetic acid tetrakis [acetoxymethyl ester]). Alternans hysteresis was observed in every isolated heart: threshold heart rate for alternans was 280+/-12 bpm, but during subsequent deceleration of pacing, alternans persisted to significantly slower heart rates (238+/-5 bpm, P<0.05). Optical mapping showed that this effect also applied to the threshold for spatially discordant alternans (313+/-2.2 bpm during acceleration versus 250+/-6.6 bpm during deceleration, P<0.05). Alternans hysteresis was also observed in isolated cardiac myocytes. Moreover, calcium chelation by BAPTA-AM raised the threshold for alternans and inhibited hysteresis in a dose-dependent manner with no effect on baseline action potential duration. Alternans hysteresis is an intrinsic property of cardiac myocytes that can lead to persistence of arrhythmogenic discordant alternans even after heart rate is slowed. These results also support an important underlying role of calcium cycling in the mechanism of alternans.

Flow Studies of Decelerators at Supersonic Speeds

NASA Technical Reports Server (NTRS)

1959-01-01

Wind tunnel tests recorded the effect of decelerators on flow at various supersonic speeds. Rigid parachute models were tested for the effects of porosity, shroud length, and number of shrouds. Flexible model parachutes were tested for effects of porosity and conical-shaped canopy. Ribbon dive brakes on a missile-shaped body were tested for effect of tension cable type and ribbon flare type. The final test involved a plastic sphere on riser lines.

Simulation evaluation of a speed-guidance law for Harrier approach transitions

NASA Technical Reports Server (NTRS)

Merrick, Vernon K.; Moralez, Ernesto; Stortz, Michael W.; Hardy, Gordon H.; Gerdes, Ronald M.

1991-01-01

An exponential-deceleration speed guidance law is formulated which mimics the technique currently used by Harrier pilots to perform decelerating approaches to a hover. This guidance law was tested along with an existing two-step constant deceleration speed guidance law, using a fixed-base piloted simulator programmed to represent a YAV-8B Harrier. Decelerating approaches to a hover at a predetermined station-keeping point were performed along a straight (-3 deg glideslope) path in headwinds up to 40 knots and turbulence up to 6 ft./sec. Visibility was fixed at one-quarter nautical mile and 100 ft. cloud ceiling. Three Harrier pilots participated in the experiment. Handling qualities with the aircraft equipped with the standard YAV-8B rate damped attitude stability augmentation system were adequate (level 2) using either speed guidance law. However, the exponential deceleration speed guidance law was rated superior to the constant-deceleration speed guidance law by a Cooper-Harper handling qualities rating of about one unit independent of the level of wind and turbulence. Replacing the attitude control system of the YAV-8B with a high fidelity model following attitude flight controller increased the approach accuracy and reduced the pilot workload. With one minor exception, the handling qualities for the approach were rated satisfactory (level 1). It is concluded that the exponential deceleration speed guidance law is the most cost effective.

Design of an electromagnetic accelerator for turbulent hydrodynamic mix studies

NASA Astrophysics Data System (ADS)

Susoeff, A. R.; Hawke, R. S.; Morrison, J. J.; Dimonte, G.; Remington, B. A.

1993-12-01

An electromagnetic accelerator in the form of a linear electric motor (LEM) has been designed to achieve controlled acceleration profiles of a carriage containing hydrodynamically unstable fluids for the investigation of the development of turbulent mix. The Rayleigh-Taylor instability is investigated by accelerating two dissimilar density fluids using the LEM to achieve a wide variety of acceleration and deceleration profiles. The acceleration profiles are achieved by independent control of rail and augmentation currents. A variety of acceleration-time profiles are possible including: (1) constant, (2) impulsive and (3) shaped. The LEM and support structure are a robust design in order to withstand high loads with deflections and to mitigate operational vibration. Vibration of the carriage during acceleration could create artifacts in the data which would interfere with the intended study of the Rayleigh-Taylor instability. The design allows clear access for diagnostic techniques such as laser induced fluorescence radiography, shadowgraphs and particle imaging velocimetry. Electromagnetic modeling codes were used to optimize the rail and augmentation coil positions within the support structure framework. Results of contemporary studies for non-arcing sliding contact of solid armatures are used for the design of the driving armature and the dynamic electromagnetic braking system. A 0.6MJ electrolytic capacitor bank is used for energy storage to drive the LEM. This report will discuss a LEM design which will accelerate masses of up to 3kg to a maximum of about 3000g(sub o), where g(sub o) is accelerated due to gravity.

Neutral beamline with ion energy recovery based on magnetic blocking of electrons

DOEpatents

Stirling, W.L.

1980-07-01

A neutral beamline generator with energy recovery of the full-energy ion component of the beam based on magnetic blocking of electrons is provided. Ions from a positive ion source are accelerated to the desired beam energy from a slightly positive potential level with respect to ground through a neutralizer cell by means of a negative acceleration voltage. The unneutralized full-energy ion component of the beam exiting the neutralizer are retarded and slightly deflected and the elecrons in the neutralizer are blocked by a magnetic field generated transverse to the beamline. An electron collector in the form of a coaxial cylinder surrounding and protruding axial a few centimeters beyond the neutralizer exit terminates the electrons which exit the neutralizer in an E x B drift to the collector when the collector is biased a few hundred volts positive with respect to the neutralizer voltage. The neutralizer is operated at the negative acceleration voltage. The neutralizer is operated at the negative acceleration voltage, and the deflected full energy ions are decelerated and the charge collected at ground potential thereby expending none of their energy received from the acceleration power supply.

Antigraviceptive neck muscle responses to "moving up and moving down" in human.

PubMed

Aoki, M; Han, X Y; Yamada, H; Muto, T; Satake, H; Ito, Y; Matsunami, K

2000-07-01

The responses of neck muscle to sudden transit from one 'g' to hyper 'g', work to support the head and remain the relative position of head on trunk as common observed: i.e. in sudden acceleration or deceleration by car or ejection of pilot from aircraft. Accordingly it is highly possible that the neck muscle responses to moving up may be important to prevent the neck injury due to sudden linear acceleration such as moving up against gravity. However little is known about the evaluation of mechanism of this reflex. Therefore the present study was conducted with two aims. The first aim was to investigate the neck muscle responses to vertical linear acceleration bv 0.4 g produced with an electro-hydraulic servo-system. We chose the vertical linear acceleration because it activates mainly sacculus, from which afferents have been demonstrated to be connected directly to sternocleidomastoid muscle in animals and human. The second aim was to determine whether there is a difference of neck muscle response to moving down and moving up.

Antigraviceptive neck muscle responses to "moving up and moving down" in human

NASA Technical Reports Server (NTRS)

Aoki, M.; Han, X. Y.; Yamada, H.; Muto, T.; Satake, H.; Ito, Y.; Matsunami, K.

2000-01-01

The responses of neck muscle to sudden transit from one 'g' to hyper 'g', work to support the head and remain the relative position of head on trunk as common observed: i.e. in sudden acceleration or deceleration by car or ejection of pilot from aircraft. Accordingly it is highly possible that the neck muscle responses to moving up may be important to prevent the neck injury due to sudden linear acceleration such as moving up against gravity. However little is known about the evaluation of mechanism of this reflex. Therefore the present study was conducted with two aims. The first aim was to investigate the neck muscle responses to vertical linear acceleration bv 0.4 g produced with an electro-hydraulic servo-system. We chose the vertical linear acceleration because it activates mainly sacculus, from which afferents have been demonstrated to be connected directly to sternocleidomastoid muscle in animals and human. The second aim was to determine whether there is a difference of neck muscle response to moving down and moving up.

Neutral beamline with ion energy recovery based on magnetic blocking of electrons

DOEpatents

Stirling, William L.

1982-01-01

A neutral beamline generator with energy recovery of the full-energy ion ponent of the beam based on magnetic blocking of electrons is provided. Ions from a positive ion source are accelerated to the desired beam energy from a slightly positive potential level with respect to ground through a neutralizer cell by means of a negative acceleration voltage. The unneutralized full-energy ion component of the beam exiting the neutralizer are retarded and slightly deflected and the electrons in the neutralizer are blocked by a magnetic field generated transverse to the beamline. An electron collector in the form of a coaxial cylinder surrounding and protruding axial a few centimeters beyond the neutralizer exit terminates the electrons which exit the neutralizer in an E x B drift to the collector when the collector is biased a few hundred volts positive with respect to the neutralizer voltage. The neutralizer is operated at the negative acceleration voltage, and the deflected full energy ions are decelerated and the charge collected at ground potential thereby expending none of their energy received from the acceleration power supply.

Computational flow predictions for hypersonic drag devices

NASA Technical Reports Server (NTRS)

Tokarcik, Susan A.; Venkatapathy, Ethiraj

1993-01-01

The effectiveness of two types of hypersonic decelerators is examined: mechanically deployable flares and inflatable ballutes. Computational fluid dynamics (CFD) is used to predict the flowfield around a solid rocket motor (SRM) with a deployed decelerator. The computations are performed with an ideal gas solver using an effective specific heat ratio of 1.15. The results from the ideal gas solver are compared to computational results from a thermochemical nonequilibrium solver. The surface pressure coefficient, the drag, and the extend of the compression corner separation zone predicted by the ideal gas solver compare well with those predicted by the nonequilibrium solver. The ideal gas solver is computationally inexpensive and is shown to be well suited for preliminary design studies. The computed solutions are used to determine the size and shape of the decelerator that are required to achieve a drag coefficient of 5. Heat transfer rates to the SRM and the decelerators are predicted to estimate the amount of thermal protection required.

Radiative transfer calculations of ultra-relativistic shock breakout in circumstellar medium: Dependence on the central engine activity

NASA Astrophysics Data System (ADS)

Ohtani, Yukari; Suzuki, Akihiro; Shigeyama, Toshikazu

2015-08-01

Core collapse supernovae radiate bright X-ray or UV flashes imediately after their explosion, because shock waves emerge on the surfaces of the progenitors. Due to their short duration, a very small number of such events (so called shock breakouts) have been observed, and the maximum shock velocities are likely to be significantly smaller than the speed of light. In principle, we can consider the shocks with ultra-relativistic velocities breakout stellar surfaces and generate gamma-ray photons. A recently popular theory of gamma-ray bursts argues that the thermal radiation produced in the jet may play important roles in the prompt emission. Therefore, for understanding of the relation between jets and the central engine, studying properties of breakouts in the relativistic limit will be interesting. To obtain some information concerning the temporal evolution of the photospheric emission from jets, we make a radiative transfer calculation of ultra-relativistic shock breakout in circumstellar medium by using a Monte Carlo method. We use a self-similar solution constructed by Blandford & McKee (1976), in which the shock Lorentz factor is assumed to follow a simple power law relation determined by the central engine activity. By comparing the calculation results of the accelerating shock and the decelerating shock, we find that influence of the beaming effect and the scattering angular distribution cause two apparent differences in light curves and temporal spectral evolution. One is that the ratio of the time between the onset and the peak to the duration is much smaller in light curves of decelerating shocks. The other one is that the spectral shape does not significantly change with time if the shock accelerates, otherwise the first half of the emerging photons contains much more high energy photons (above 1 MeV) than the second half.

Using GPS-derived speed patterns for recognition of transport modes in adults.

PubMed

Huss, Anke; Beekhuizen, Johan; Kromhout, Hans; Vermeulen, Roel

2014-10-11

Identification of active or sedentary modes of transport is of relevance for studies assessing physical activity or addressing exposure assessment. We assessed in a proof-of-principle study if speed as logged by GPSs could be used to identify modes of transport (walking, bicycling, and motorized transport: car, bus or train). 12 persons commuting to work walking, bicycling or with motorized transport carried GPSs for two commutes and recorded their mode of transport. We evaluated seven speed metrics: mean, 95th percentile of speed, standard deviation of the mean, rate-of-change, standardized-rate-of-change, acceleration and deceleration. We assessed which speed metric would best identify the transport mode using discriminant analyses. We applied cross validation and calculated agreement (Cohen's Kappa) between actual and derived modes of transport. Mode of transport was reliably classified whenever a person used a mode of transport for longer than one minute. Best results were observed when using the 95th percentile of speed, acceleration and deceleration (kappa 0.73). When we combined all motorized traffic into one category, kappa increased to 0.95. GPS-measured speed enable the identification of modes of transport. Given the current low costs of GPS devices and the built-in capacity of GPS tracking in most smartphones, the use of such devices in large epidemiological studies may facilitate the assessment of physical activity related to transport modes, or improve exposure assessment using automated travel mode detection.

Hyporheic hot moments: Dissolved oxygen dynamics in the hyporheic zone in response to surface flow perturbations

NASA Astrophysics Data System (ADS)

Kaufman, Matthew H.; Cardenas, M. Bayani; Buttles, Jim; Kessler, Adam J.; Cook, Perran L. M.

2017-08-01

Dissolved oxygen (DO) is a key environmental variable that drives and feeds back with numerous processes. In the aquatic sediment that makes up the hyporheic zone, DO may exhibit pronounced spatial gradients and complex patterns which control the distribution of a series of redox processes. Yet, little is known regarding the dynamics of hyporheic zone DO, especially under transitional flow regimes. Considering the natural tendency of rivers to be highly responsive to external forcing, these temporal dynamics are potentially just as important and pronounced as the spatial gradients. Here we use laboratory flume experiments and multiphysics flow and reactive transport modeling to investigate surface flow controls on the depth of oxygen penetration in the bed as well as the area of oxygenated sediment. We show that the hyporheic zone DO conditions respond over time scales of hours-to-days when subjected to practically instantaneous surface flow perturbations. Additionally, the flume experiments demonstrate that hyporheic zone DO conditions respond faster to surface flow acceleration than to deceleration. Finally, we found that the morphology of the dissolved oxygen plume front depends on surface flow acceleration or deceleration. This study thus shows that the highly dynamic nature of typical streams and rivers drives equally dynamic redox conditions in the hyporheic zone. Because the redox conditions and their distribution within the hyporheic zone are important from biological, ecological, and contaminant perspectives, this hyporheic redox dynamism has the potential to impact system scale aquatic chemical cycles.

Transit car demonstration test program on the roll dynamics unit. Volume 2. Demonstration of a transit car performance test on the roll dynamic unit. Final report

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

Arnold, G.; Nelson, S.; Cooperrider, N.K.

1982-02-11

This report, Volume II, contains the results, conclusions, and recommendations of the first performance test of a transit care on the RDU. This report is limited to performance tests. The objective is to identify advantages and disadvantages of performance testing on the rollers of the RDU as highlighted by the SOAC test. The report involved separate testing, done by TTC personnel, in such traditional performance areas of transit vehicle operation ass traction, acceleration/deceleration, energy consumption, and spin/slide performance. The results of the successful performance test of a transit car on a roller unit is presented and the advantages of thismore » method of testing is discussed. Acceleration, deceleration, spin/slide, and power consumption tests, although of limited scope in comparison to the track tests performed on the same transit car, did show the feasibility of roller testing. It is concluded that the RDU is most suited for developmental testing of transit car systems particularly for power consumption and for cars with non-standard wheel gage. Tests should be of such scope as to justify the cost of car setup on the RDU. The following two test are recommended: (1) a power consumption study for a standard/non-standard gage transit car which investigates methods of reducing power consumption and (2) a non-standard gage full performance test.« less

Complex contagions with timers

NASA Astrophysics Data System (ADS)

Oh, Se-Wook; Porter, Mason A.

2018-03-01

There has been a great deal of effort to try to model social influence—including the spread of behavior, norms, and ideas—on networks. Most models of social influence tend to assume that individuals react to changes in the states of their neighbors without any time delay, but this is often not true in social contexts, where (for various reasons) different agents can have different response times. To examine such situations, we introduce the idea of a timer into threshold models of social influence. The presence of timers on nodes delays adoptions—i.e., changes of state—by the agents, which in turn delays the adoptions of their neighbors. With a homogeneously-distributed timer, in which all nodes have the same amount of delay, the adoption order of nodes remains the same. However, heterogeneously-distributed timers can change the adoption order of nodes and hence the "adoption paths" through which state changes spread in a network. Using a threshold model of social contagions, we illustrate that heterogeneous timers can either accelerate or decelerate the spread of adoptions compared to an analogous situation with homogeneous timers, and we investigate the relationship of such acceleration or deceleration with respect to the timer distribution and network structure. We derive an analytical approximation for the temporal evolution of the fraction of adopters by modifying a pair approximation for the Watts threshold model, and we find good agreement with numerical simulations. We also examine our new timer model on networks constructed from empirical data.

Redshift-Drift as a Test for Discriminating Between Decelerating Inhomogeneous and Accelerating Universe Models

NASA Astrophysics Data System (ADS)

Mishra, Priti; Célérier, Marie-Noëlle Singh, Tejinder P.

2015-01-01

Exact inhomogeneous solutions of Einstein's equations have been used in the literature to build models reproducing the cosmological data without dark energy. However, owing to the degrees of freedom pertaining to these models, it is necessary to get rid of the degeneracy often exhibited by the problem of distinguishing between them and accelerating universe models. We give an overview of redshift drift in inhomogeneous cosmologies, and explain how it serves to this purpose. One class of models which fits the data is the Szekeres Swiss-cheese class where non-spherically symmetric voids exhibit a typical size of about 400 Mpc. We present our calculation of the redshift drift in this model, and compare it with the results obtained by other authors for alternate scenarios.

Response of Metal Core Piezoelectric Fibers to Unsteady Airflows

NASA Astrophysics Data System (ADS)

Qiu, J. H.; Ji, H. L.; Zhu, K. J.; Park, M. J.

In the previous study, possible applications of metal core piezoelectric fibers with a diameter of 200 to 250 µm as bionic airflow sensors mimicking the flow sensitive receptor hairs of crickets have been proposed. This study aims to investigate the dynamic responses of the metal core piezoelectric fibers to unsteady airflow. The metal core piezoelectric fiber is half coated on the outer surface and is used in the bending mode. Wind tunnel tests were carried out and the output voltage of the fiber under the excitation of the unsteady aerodynamic force during flow acceleration and deceleration was measured when the wind tunnel was suddenly closed or opened by a shutter. The relationship between the maximum voltage and the steady-state velocity and that between the voltage and the acceleration of flow were also obtained.

Narrow bandwidth Laser-Plasma Accelerator driven Thomson photon source development

NASA Astrophysics Data System (ADS)

Geddes, C. G. R.; Tsai, H.-E.; Otero, G.; Liu, X.; van Tilborg, J.; Toth, Cs.; Vay, J.-L.; Lehe, R.; Schroeder, C. B.; Esarey, E.; Friedman, A.; Grote, D. P.; Leemans, W. P.

2017-10-01

Compact, high-quality photon sources at MeV energies can be provided by Thomson scattering of a laser from the electron beam of a Laser-Plasma Accelerator (LPA). Recent experiments and simulations demonstrate controllable LPAs in the energy range appropriate to MeV sources. Simulations indicate that high flux with narrow energy spread can be achieved via control of the scattering laser pulse shape and laser guiding, and that undesired background bremsstrahlung can be mitigated by plasma based deceleration of the electron beam after photon production. Construction of experiments and laser capabilities to combine these elements will be presented, along with initial operations, towards a compact photon source system. Work supported by US DOE NNSA DNN R&D and by Sc. HEP under contract DE-AC02-05CH11231.

High gradient tests of metallic mm-wave accelerating structures

DOE PAGES

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

2017-05-10

This study explores the physics of vacuum rf breakdowns in high gradient mm-wave accelerating structures. We performed a series of experiments with 100 GHz and 200 GHz metallic accelerating structures, at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory. This paper presents the experimental results of rf tests of 100 GHz travelling-wave accelerating structures, made of hard copper-silver alloy. The results are compared with pure hard copper structures. The rf fields were excited by the FACET ultra-relativistic electron beam. The accelerating structures have open geometries, 10 cm long, composed of two halves separated bymore » a variable gap. The rf frequency of the fundamental accelerating mode depends on the gap size and can be changed from 90 GHz to 140 GHz. The measured frequency and pulse length are consistent with our simulations. When the beam travels off-axis, a deflecting field is induced in addition to the decelerating longitudinal field. We measured the deflecting forces by observing the displacement of the electron bunch and used this measurement to verify the expected accelerating gradient. We present the first quantitative measurement of rf breakdown rates in 100 GHz copper-silver accelerating structure, which was 10 –3 per pulse, with peak electric field of 0.42 GV/m, an accelerating gradient of 127 MV/m, at a pulse length of 2.3 ns. The goal of our studies is to understand the physics of gradient limitations in order to increase the energy reach of future accelerators.« less

High gradient tests of metallic mm-wave accelerating structures

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 high gradient mm-wave accelerating structures. We performed a series of experiments with 100 GHz and 200 GHz metallic accelerating structures, at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory. This paper presents the experimental results of rf tests of 100 GHz travelling-wave accelerating structures, made of hard copper-silver alloy. The results are compared with pure hard copper structures. The rf fields were excited by the FACET ultra-relativistic electron beam. The accelerating structures have open geometries, 10 cm long, composed of two halves separated bymore » a variable gap. The rf frequency of the fundamental accelerating mode depends on the gap size and can be changed from 90 GHz to 140 GHz. The measured frequency and pulse length are consistent with our simulations. When the beam travels off-axis, a deflecting field is induced in addition to the decelerating longitudinal field. We measured the deflecting forces by observing the displacement of the electron bunch and used this measurement to verify the expected accelerating gradient. We present the first quantitative measurement of rf breakdown rates in 100 GHz copper-silver accelerating structure, which was 10 –3 per pulse, with peak electric field of 0.42 GV/m, an accelerating gradient of 127 MV/m, at a pulse length of 2.3 ns. The goal of our studies is to understand the physics of gradient limitations in order to increase the energy reach of future accelerators.« less

Turbulent pipe flows subjected to temporal decelerations

NASA Astrophysics Data System (ADS)

Jeong, Wongwan; Lee, Jae Hwa

2016-11-01

Direct numerical simulations of temporally decelerating turbulent pipe flows were performed to examine effects of temporal decelerations on turbulence. The simulations were started with a fully developed turbulent pipe flow at a Reynolds number, ReD =24380, based on the pipe radius (R) and the laminar centerline velocity (Uc 0). Three different temporal decelerations were imposed to the initial flow with f= | d Ub / dt | =0.00127, 0.00625 and 0.025, where Ub is the bulk mean velocity. Comparison of Reynolds stresses and turbulent production terms with those for steady flow at a similar Reynolds number showed that turbulence is highly intensified with increasing f due to delay effects. Furthermore, inspection of the Reynolds shear stress profiles showed that strong second- and fourth-quadrant Reynolds shear stresses are greatly increased, while first- and third-quadrant components are also increased. Decomposition of streamwise Reynolds normal stress with streamwise cutoff wavelength (λx) 1 R revealed that the turbulence delay is dominantly originated from delay of strong large-scale turbulent structures in the outer layer, although small-scale motions throughout the wall layer adjusted more rapidly to the temporal decelerations. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2014R1A1A2057031).

A mixture theory approach to model co- and counter-current two-phase flow in porous media accounting for viscous coupling

NASA Astrophysics Data System (ADS)

Qiao, Y.; Andersen, P. Ø.; Evje, S.; Standnes, D. C.

2018-02-01

It is well known that relative permeabilities can depend on the flow configuration and they are commonly lower during counter-current flow as compared to co-current flow. Conventional models must deal with this by manually changing the relative permeability curves depending on the observed flow regime. In this paper we use a novel two-phase momentum-equation-approach based on general mixture theory to generate effective relative permeabilities where this dependence (and others) is automatically captured. In particular, this formulation includes two viscous coupling effects: (i) Viscous drag between the flowing phases and the stagnant porous rock; (ii) viscous drag caused by momentum transfer between the flowing phases. The resulting generalized model will predict that during co-current flow the faster moving fluid accelerates the slow fluid, but is itself decelerated, while for counter-current flow they are both decelerated. The implications of these mechanisms are demonstrated by investigating recovery of oil from a matrix block surrounded by water due to a combination of gravity drainage and spontaneous imbibition, a situation highly relevant for naturally fractured reservoirs. We implement relative permeability data obtained experimentally through co-current flooding experiments and then explore the model behavior for different flow cases ranging from counter-current dominated to co-current dominated. In particular, it is demonstrated how the proposed model seems to offer some possible interesting improvements over conventional modeling by providing generalized mobility functions that automatically are able to capture more correctly different flow regimes for one and the same parameter set.

Decelerated medical education.

PubMed

McGrath, Brian; McQuail, Diane

2004-09-01

The aim of the study was to obtain information regarding the prevalence, structure, student characteristics and outcomes of formal decelerated medical education programs. A 13-item survey was mailed to all US medical schools examining characteristics of decelerated curricular programs. Responses were received from 77 schools (62% response). Some 24 (31%) indicated a formal decelerated option; 13 (57%) decelerate the first year while four (17%) decelerate year 1 or year 2. Participants may be selected before matriculation or after difficulty in 14 (61%) programs while four (17%) select only after encountering difficulty. Students may unilaterally choose deceleration in 10 (43%); 4.3% (0.1-12) of total matriculants were decelerated. The proportion of decelerated students identified as underrepresented minority (URM) was 37% (0-100), representing 10.5% (0-43) of total URM enrollment. Twelve (52%) programs do not provide unique support beyond deceleration. Standards for advancement are identical for decelerated and regular students in 17 schools (81%). In total, 10% (0-100) of decelerated students were dismissed within the last five years, representing 24% (0-90) of all dismissals. Few schools provided grade point average (GPA) or Medical College Admissions Test (MCAT) data but the limited responses indicate that many decelerated students are at risk for academic difficulty. It is concluded that decelerated curricular options are available at a significant number of US medical schools. Decelerated students comprise a small proportion of total enrollment but URM matriculants represent a disproportionate share of participants. Decelerated programs appear to be successful as measured by dismissal rates if one accepts attrition which exceeds that for regular MD students. Variation in dismissal rates is difficult to interpret given the lack of GPA and MCAT data. One half of all programs offer no additional support activities beyond deceleration. More data are needed to determine the relative contribution of deceleration vs. other support measures to the advancement of students at academic risk.

Comparing Global Positioning System (GPS) and Global Navigation Satellite System (GNSS) Measures of Team Sport Movements.

PubMed

Jackson, Benjamin M; Polglaze, Ted; Dawson, Brian; King, Trish; Peeling, Peter

2018-02-21

To compare data from conventional GPS and new GNSS-enabled tracking devices, and to examine the inter-unit reliability of GNSS devices. Inter-device differences between 10 Hz GPS and GNSS devices were examined during laps (n=40) of a simulated game circuit (SGC) and during elite hockey matches (n=21); GNSS inter-unit reliability was also examined during the SGC laps. Differences in distance values and measures in three velocity categories (low <3 m.s -1 ; moderate 3-5 m.s -1 ; high >5 m.s -1 ) and acceleration/deceleration counts (>1.46 m.s -2 and < -1.46 m.s -2 ) were examined using one-way ANOVA. Inter-unit GNSS reliability was examined using the coefficient of variation (CV) and intra-class correlation coefficient (ICC). Inter-device differences (P <0.05) were found for measures of peak deceleration, low-speed distance, % total distance at low speed, and deceleration count during the SGC, and for all measures except total distance and low-speed distance during hockey matches. Inter-unit (GNSS) differences (P <0.05) were not found. The CV was below 5% for total distance, average and peak speeds and distance and % total distance of low-speed running. The GNSS devices had a lower HDoP score than GPS devices in all conditions. These findings suggest that GNSS devices may be more sensitive than GPS in quantifying the physical demands of team sport movements, but further study into the accuracy of GNSS devices is required.

Ablative Rayleigh-Taylor and Richtmyer-Meshkov Instabilities in Laser-Accelerated Colliding Foils

NASA Astrophysics Data System (ADS)

Aglitskiy, Y.; Metzler, N.; Karasik, M.; Serlin, V.; Weaver, J.; Obenschain, S. P.; Oh, J.; Schmitt, A. J.; Velikovich, A. L.; Zalesak, S. T.; Gardner, J. H.; Harding, E. C.

2008-11-01

In our experiments done on the Nike KrF laser, we study instability growth at shock-decelerated interfaces in planar colliding-foil experiments. We use streaked monochromatic (1.86 keV) x-ray face-on imaging diagnostics to measure the areal mass modulation growth caused by the instability. Higher x-ray energies up to 5.25 keV are used to follow the shock propagation as well as the 1D dynamics of the collision. While a laser-driven foil is accelerated towards the stationary low-density foam layer, an ablative RT instability develops. Having reached a high velocity, the foil hits the foam layer. The impact generates strong shocks in the plastic and in the foam. The reflected shock wave re-shocks the ablation front, its acceleration stops, and so does the observed RT growth. This is followed by areal mass oscillations due to the ablative RM instability and feedout mechanisms, of which the latter dominates.

LATTICES FOR HIGH-POWER PROTON BEAM ACCELERATION AND SECONDARY BEAM COLLECTION AND COOLING.

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

WANG, S.; WEI, J.; BROWN, K.

2006-06-23

Rapid cycling synchrotrons are used to accelerate high-intensity proton beams to energies of tens of GeV for secondary beam production. After primary beam collision with a target, the secondary beam can be collected, cooled, accelerated or decelerated by ancillary synchrotrons for various applications. In this paper, we first present a lattice for the main synchrotron. This lattice has: (a) flexible momentum compaction to avoid transition and to facilitate RF gymnastics (b) long straight sections for low-loss injection, extraction, and high-efficiency collimation (c) dispersion-free straights to avoid longitudinal-transverse coupling, and (d) momentum cleaning at locations of large dispersion with missing dipoles.more » Then, we present a lattice for a cooler ring for the secondary beam. The momentum compaction across half of this ring is near zero, while for the other half it is normal. Thus, bad mixing is minimized while good mixing is maintained for stochastic beam cooling.« less

Modeling mechanical restriction differences between car and heavy truck in two-lane cellular automata traffic flow model

NASA Astrophysics Data System (ADS)

Li, Xin; Li, Xingang; Xiao, Yao; Jia, Bin

2016-06-01

Real traffic is heterogeneous with car and truck. Due to mechanical restrictions, the car and the truck have different limited deceleration capabilities, which are important factors in safety driving. This paper extends the single lane safety driving (SD) model with limited deceleration capability to two-lane SD model, in which car-truck heterogeneous traffic is considered. A car has a larger limited deceleration capability while a heavy truck has a smaller limited deceleration capability as a result of loaded goods. Then the safety driving conditions are different as the types of the following and the leading vehicles vary. In order to eliminate the well-known plug in heterogeneous two-lane traffic, it is assumed that heavy truck has active deceleration behavior when the heavy truck perceives the forming plug. The lane-changing decisions are also determined by the safety driving conditions. The fundamental diagram, spatiotemporal diagram, and lane-changing frequency were investigated to show the effect of mechanical restriction on heterogeneous traffic flow. It was shown that there would be still three traffic phases in heterogeneous traffic condition; the active deceleration of the heavy truck could well eliminate the plug; the lane-changing frequency was low in synchronized flow; the flow and velocity would decrease as the proportion of heavy truck grows or the limited deceleration capability of heavy truck drops; and the flow could be improved with lane control measures.

[Investigation of emission characteristics for light duty vehicles with a portable emission measurement system].

PubMed

Wang, Hai-Kun; Fu, Li-Xin; Zhou, Yu; Lin, Xin; Chen, Ai-Zhong; Ge, Wei-hu; Du, Xuan

2008-10-01

Emission from 7 typical light-duty vehicles under actual driving conditions was monitored using a portable emission measurement system to gather data for characterization of the real world vehicle emission in Shenzhen, including the effects of driving modes on vehicle emission, comparison of fuel consumption based emission factors (g x L(-1) with mileage based emission factors (g x km(-1)), and the average emission factors of the monitored vehicles. The acceleration and deceleration modes accounted for 66.7% of total travel time, 80.3% of traveling distance and 74.6%-79.2% of vehicle emission; the acceleration mode contributed more than other driving modes. The fuel based emission factors were less dependent on the driving speed; they may be utilized in building macro-scale vehicle emission inventory with smaller sensitivity to the vehicle driving conditions. The effect of vehicle technology on vehicle emission was significant; the emission factors of CO, HC and NO(x) of carbureted vehicles were 19.9-20.5, 5.6-26.1 and 1.8-2.0 times the more advanced vehicles of Euro II, respectively. Using the ECE + EUDC driving cycle would not produce the desired real-world emission rates of light duty vehicles in a typical Chinese city.

Effects of plyometric training on soccer players

PubMed Central

Wang, Ying-Chun; Zhang, Na

2016-01-01

Plyometric training (PT) is a technique used to increase strength and explosiveness. It consists of physical exercises in which muscles exert maximum force at short intervals to increase dynamic performances. In such a training, muscles undergo a rapid elongation followed by an immediate shortening (stretch-shortening contraction), utilizing the elastic energy stored during the stretching phase. There is consensus on the fact that when used, PT contributes to improvement in vertical jump performance, acceleration, leg strength, muscular power, increase of joint awareness and overall sport-specific skills. Consequently, PT which was primarily used by martial artists, sprinters and high jumpers to improve performances has gained in popularity and has been used by athletes in all types of sports. However, although PT has been shown to increase performance variables in many sports, little scientific information is currently available to determine whether PT actually enhances skill performance in soccer players, considering that soccer is an extremely demanding sport. Soccer players require dynamic muscular performance for fighting at all levels of training status, including rapid movements such as acceleration and deceleration of the body, change of direction, vertical and horizontal jumps, endurance, speed as well as power for kicking and tackling. In this review we discussed the effects of PT on soccer players by considering gender and age categories. PMID:27446242

Examining the cosmic acceleration with the latest Union2 supernova data

NASA Astrophysics Data System (ADS)

Li, Zhengxiang; Wu, Puxun; Yu, Hongwei

2011-01-01

In this Letter, by reconstructing the Om diagnostic and the deceleration parameter q from the latest Union2 Type Ia Supernova sample with and without the systematic error along with the baryon acoustic oscillation (BAO) and the cosmic microwave background (CMB), we study the cosmic expanding history, using the Chevallier-Polarski-Linder (CPL) parametrization. We obtain that Union2+BAO favor an expansion with a decreasing of the acceleration at z<0.3. However, once the CMB data is added in the analysis, the cosmic acceleration is found to be still increasing, indicating a tension between low redshift data and high redshift. In order to reduce this tension significantly, two different methods are considered and thus two different subsamples of Union2 are selected. We then find that two different subsamples+BAO+CMB give completely different results on the cosmic expanding history when the systematic error is ignored, with one suggesting a decreasing cosmic acceleration, the other just the opposite, although both of them alone with BAO support that the cosmic acceleration is slowing down. However, once the systematic error is considered, two different subsamples of Union2 along with BAO and CMB all favor an increasing of the present cosmic acceleration. Therefore a clear-cut answer on whether the cosmic acceleration is slowing down calls for more consistent data and more reliable methods to analyze them.

Inhibition of PTEN and activation of Akt by menadione.

PubMed

Yoshikawa, Kyoko; Nigorikawa, Kiyomi; Tsukamoto, Mariko; Tamura, Namiko; Hazeki, Kaoru; Hazeki, Osamu

2007-04-01

Menadione (vitamin K(3)) has been shown to activate Erk in several cell lines. This effect has been shown to be due to the activation of EGF receptors (EGFR) as a result of inhibition of some protein tyrosine phosphatases. In the present study, we examined the effects of menadione on Akt in Chinese hamster ovary cells. The phosphorylation of Akt by menadione was not inhibited by AG1478, an inhibitor of EGFR. Menadione inhibited the lipid phosphatase activity of PTEN in a cell-free system. In an intact cell system, menadione inhibited the effect of transfected PTEN on Akt. Thus, one mechanism of its action was considered the accelerated activation of Akt through inhibition of PTEN. This was not the sole mechanism responsible for the EGFR-independent activation of Akt, because menadione attenuated the rate of Akt dephosphorylation even in PTEN-null PC3 cells. The decelerated inactivation of Akt, probably through inhibition of some tyrosine phosphatases, was considered another mechanism of its action.

Extra projection data identification method for fast-continuous-rotation industrial cone-beam CT.

PubMed

Yang, Min; Duan, Shengling; Duan, Jinghui; Wang, Xiaolong; Li, Xingdong; Meng, Fanyong; Zhang, Jianhai

2013-01-01

Fast-continuous-rotation is an effective measure to improve the scanning speed and decrease the radiation dose for cone-beam CT. However, because of acceleration and deceleration of the motor, as well as the response lag of the scanning control terminals to the host PC, uneven-distributed and redundant projections are inevitably created, which seriously decrease the quality of the reconstruction images. In this paper, we first analyzed the aspects of the theoretical sequence chart of the fast-continuous-rotation mode. Then, an optimized sequence chart was proposed by extending the rotation angle span to ensure the effective 2π-span projections were situated in the stable rotation stage. In order to match the rotation angle with the projection image accurately, structure similarity (SSIM) index was used as a control parameter for extraction of the effective projection sequence which was exactly the complete projection data for image reconstruction. The experimental results showed that SSIM based method had a high accuracy of projection view locating and was easy to realize.

Effects of volcano profile on dilute pyroclastic density currents: Numerical simulations

NASA Astrophysics Data System (ADS)

Doronzo, D. M.; Valentine, G. A.; Dellino, P.; de Tullio, M. D.

2012-04-01

Explosive activity and lava dome collapse at stratovolcanoes can lead to pyroclastic density currents (PDCs; mixtures of volcanic gas, air, and volcanic particles) that produce complex deposits and pose a hazard to surrounding populations. Two-dimensional numerical simulations of dilute PDCs (characterized by a turbulent suspended load and deposition through a bed load) are carried out with the Euler-Lagrange approach of multiphase physics. The fluid phase is modeled as a dusty gas (1.88 kg/m3 dense), and the solid phase is modeled as discrete particles (1 mm, 5 mm, and 10 mm; 1500 kg/m3 dense and irregularly-shaped), which are two-way coupled to the gas, i.e. they affect the fluid turbulence. The initial PDC, which enters a volcano domain 5 km long and 1.9 km high, has the following characteristics: thickness of 200 m, velocity of 20 m/s, temperature of 573 K, turbulence of 5 %, and sediment concentration of 3 % by volume. The actual physics of flow boundary zone is simulated at the PDC base, by monitoring the sediment flux toward the substrate, which acts through the flow boundary zone, and the grain-size distribution. Also, the PDC velocity and dynamic pressure are calculated. The simulations show that PDC transport, deposition, and hazard potential are sensitive to the shape of the volcano slope (profile) down which they flow. In particular, three generic volcano profiles, straight, concave-upward, and convex-upward are focused on. Dilute PDCs that flow down a constant slope gradually decelerate over the simulated run-out distance (5 km in the horizontal direction) due to a combination of sedimentation, which reduces the density of the PDC, and mixing with the atmosphere. However, dilute PDCs down a concave-upward slope accelerate high on the volcano flanks and have less sedimentation until they begin to decelerate over the shallow lower slopes. A convex-upward slope causes dilute PDCs to lose relatively more of their pyroclast load on the upper slopes of a volcano, and although they accelerate as they reach the lower, steeper slopes, the acceleration is reduced because of the upstream loss of pyroclasts (lower density contrast with the atmosphere). The dynamic pressure, a measure of the damage that can be caused by PDCs, reflects these complex relations. Details are found in Valentine et al. (2011). Reference Valentine G.A., Doronzo D.M., Dellino P., de Tullio M.D. (2011), Effects of volcano profile on dilute pyroclastic density currents: Numerical simulations, Geology, 39, 947-950.

Heart Rate Fragmentation: A Symbolic Dynamical Approach.

PubMed

Costa, Madalena D; Davis, Roger B; Goldberger, Ary L

2017-01-01

Background: We recently introduced the concept of heart rate fragmentation along with a set of metrics for its quantification. The term was coined to refer to an increase in the percentage of changes in heart rate acceleration sign, a dynamical marker of a type of anomalous variability. The effort was motivated by the observation that fragmentation, which is consistent with the breakdown of the neuroautonomic-electrophysiologic control system of the sino-atrial node, could confound traditional short-term analysis of heart rate variability. Objective: The objectives of this study were to: (1) introduce a symbolic dynamical approach to the problem of quantifying heart rate fragmentation; (2) evaluate how the distribution of the different dynamical patterns ("words") varied with the participants' age in a group of healthy subjects and patients with coronary artery disease (CAD); and (3) quantify the differences in the fragmentation patterns between the two sample populations. Methods: The symbolic dynamical method employed here was based on a ternary map of the increment NN interval time series and on the analysis of the relative frequency of symbolic sequences (words) with a pre-defined set of features. We analyzed annotated, open-access Holter databases of healthy subjects and patients with CAD, provided by the University of Rochester Telemetric and Holter ECG Warehouse (THEW). Results: The degree of fragmentation was significantly higher in older individuals than in their younger counterparts. However, the fragmentation patterns were different in the two sample populations. In healthy subjects, older age was significantly associated with a higher percentage of transitions from acceleration/deceleration to zero acceleration and vice versa (termed "soft" inflection points). In patients with CAD, older age was also significantly associated with higher percentages of frank reversals in heart rate acceleration (transitions from acceleration to deceleration and vice versa , termed "hard" inflection points). Compared to healthy subjects, patients with CAD had significantly higher percentages of soft and hard inflection points, an increased percentage of words with a high degree of fragmentation and a decreased percentage of words with a lower degree of fragmentation. Conclusion: The symbolic dynamical method employed here was useful to probe the newly recognized property of heart rate fragmentation. The findings from these cross-sectional studies confirm that CAD and older age are associated with higher levels of heart rate fragmentation. Furthermore, fragmentation with healthy aging appears to be phenotypically different from fragmentation in the context of CAD.

Surface analysis by means of high resolution energy loss spectroscopy of 180° elastic scattered protons in the 100 keV regime

NASA Astrophysics Data System (ADS)

Jun-ichi, Kanasaki; Noriaki, Matsunami; Noriaki, Itoh; Tomoki, Oku; Kensin, Kitoh; Masahiko, Aoki; Koji, Matsuda

1988-06-01

The design and computer simulation of the performance of a new ion-beam surface analyzer has been presented. The analyzer has the capability of analyzing the energy of ions incident at 100 keV and scattered by 180° at surfaces with a resolution of 5 eV. The analyzer consists of an ion source, an accelerating-decelerating tube and a multichannel analyzer. Computer simulation of the energy spectra of ions scattered from GaAs is reported.

Simultaneous aortic and tricuspid valve rupture after fall injury

PubMed Central

Sabzi, Feridoun; Niazi, Mojtaba; Ahmadi, Alireza

2013-01-01

Abstract: This case study concerns a patient with disruption of both tricuspid and aortic valves: a previously healthy, adult man, who sustained a 5-meter fall from a building under construction. The mechanism of the injury was acceleration and deceleration, acting in two different phases of the cardiac cycle, i.e. systole and diastole. Simultaneous occurrence of these injuries is exceedingly rare and in a careful literature review, we did not find any such combination of injury. The possible mechanisms of this injury, as well as surgical techniques are discussed. PMID:23511124

Simultaneous aortic and tricuspid valve rupture after fall injury.

PubMed

Sabzi, Feridoun; Niazi, Mojtaba; Ahmadi, Alireza

2013-07-01

This case study concerns a patient with disruption of both tricuspid and aortic valves: a previously healthy, adult man, who sustained a 5-meter fall from a building under construction. The mechanism of the injury was acceleration and deceleration, acting in two different phases of the cardiac cycle, i.e. systole and diastole. Simultaneous occurrence of these injuries is exceedingly rare and in a careful literature review, we did not find any such combination of injury. The possible mechanisms of this injury, as well as surgical techniques are discussed.

[Nystagmus].

PubMed

Jutila, Topi; Hirvonen, Timo P

2013-01-01

Physiological nystagmus stabilizes gaze during head movements and pathological nystagmus reflects a disorder of the vestibulo-ocular reflex (VOR). Pathological nystagmus appears or strengthens usually during change in head position. Therefore, dizziness or nystagmus associated with head movements is not specific to benign paroxysmal positional vertigo unless it is verified in specific positional test. Peripheral nystagmus decelerates during visual fixation, accelerates when gaze is turned towards the fast phase, does not change direction, and is usually composed of several directional components unlike central nystagmus. The velocity and frequency of the slow phase of nystagmus can be measured with electronystagmography or video-oculography.

NASA general aviation crashworthiness seat development

NASA Technical Reports Server (NTRS)

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

1979-01-01

Three load limiting seat concepts for general aviation aircraft designed to lower the deceleration of the occupant in the event of a crash were sled tested and evaluated with reference to a standard seat. Dummy pelvis accelerations were reduced up to 50 percent with one of the concepts. Computer program MSOMLA (Modified Seat Occupant Model for Light Aircraft) was used to simulate the behavior of a dummy passenger in a NASA full-scale crash test of a twin engine light aircraft. A computer graphics package MANPLOT was developed to pictorially represent the occupant and seat motion.

Impact papers on aging in 2009

PubMed Central

Blagosklonny, Mikhail V.; Campisi, Judy; Sinclair, David A.; Bartke, Andrzej; Blasco, Maria A.; Bonner, William M.; Bohr, Vilhelm A.; Jr, Robert M. Brosh; Brunet, Anne; DePinho, Ronald A.; Donehower, Lawrence A.; Finch, Caleb E.; Finkel, Toren; Gorospe, Myriam; Gudkov, Andrei V.; Hall, Michael N.; Hekimi, Siegfried; Helfand, Stephen L.; Karlseder, Jan; Kenyon, Cynthia; Kroemer, Guido; Longo, Valter; Nussenzweig, Andre; Osiewacz, Heinz D.; Peeper, Daniel S.; Rando, Thomas A.; Rudolph, K Lenhard; Sassone-Corsi, Paolo; Serrano, Manuel; Sharpless, Norman E.; Skulachev, Vladimir P.; Tilly, Jonathan L.; Tower, John; Verdin, Eric; Vijg, Jan

2010-01-01

The editorial board of Aging reviews research papers published in 2009, which they believe have or will have a significant impact on aging research. Among many others, the topics include genes that accelerate aging or in contrast promote longevity in model organisms, DNA damage responses and telomeres, molecular mechanisms of life span extension by calorie restriction and pharmacologic interventions into aging. The emerging message in 2009 is that aging is not random but determined by a genetically-regulated longevity network and can be decelerated both genetically and pharmacologically. PMID:20351400

Experimental verification of an eddy-current bearing

NASA Technical Reports Server (NTRS)

Nikolajsen, Jorgen L.

1989-01-01

A new type of electromagnetic bearing was built and tested. It consists of fixed AC-electromagnets in a star formation surrounding a conducting rotor. The bearing works by repulsion due to eddy-currents induced in the rotor. A single bearing is able to fully support a short rotor. The rotor support is inherently stable in all five degrees of freedom. No feedback control is needed. The bearing is also able to accelerate the rotor up to speed and decelerate the rotor back to standstill. The bearing design and the experimentation to verify its capabilities are described.

A user-driven treadmill control scheme for simulating overground locomotion.

PubMed

Kim, Jonghyun; Stanley, Christopher J; Curatalo, Lindsey A; Park, Hyung-Soon

2012-01-01

Treadmill-based locomotor training should simulate overground walking as closely as possible for optimal skill transfer. The constant speed of a standard treadmill encourages automaticity rather than engagement and fails to simulate the variable speeds encountered during real-world walking. To address this limitation, this paper proposes a user-driven treadmill velocity control scheme that allows the user to experience natural fluctuations in walking velocity with minimal unwanted inertial force due to acceleration/deceleration of the treadmill belt. A smart estimation limiter in the scheme effectively attenuates the inertial force during velocity changes. The proposed scheme requires measurement of pelvic and swing foot motions, and is developed for a treadmill of typical belt length (1.5 m). The proposed scheme is quantitatively evaluated here with four healthy subjects by comparing it with the most advanced control scheme identified in the literature.

Survey of NASA research on crash dynamics

NASA Technical Reports Server (NTRS)

Thomson, R. G.; Carden, H. D.; Hayduk, R. J.

1984-01-01

Ten years of structural crash dynamics research activities conducted on general aviation aircraft by the National Aeronautics and Space Administration (NASA) are described. Thirty-two full-scale crash tests were performed at Langley Research Center, and pertinent data on airframe and seat behavior were obtained. Concurrent with the experimental program, analytical methods were developed to help predict structural behavior during impact. The effects of flight parameters at impact on cabin deceleration pulses at the seat/occupant interface, experimental and analytical correlation of data on load-limiting subfloor and seat configurations, airplane section test results for computer modeling validation, and data from emergency-locator-transmitter (ELT) investigations to determine probable cause of false alarms and nonactivations are assessed. Computer programs which provide designers with analytical methods for predicting accelerations, velocities, and displacements of collapsing structures are also discussed.

Relative brain displacement and deformation during constrained mild frontal head impact.

PubMed

Feng, Y; Abney, T M; Okamoto, R J; Pless, R B; Genin, G M; Bayly, P V

2010-12-06

This study describes the measurement of fields of relative displacement between the brain and the skull in vivo by tagged magnetic resonance imaging and digital image analysis. Motion of the brain relative to the skull occurs during normal activity, but if the head undergoes high accelerations, the resulting large and rapid deformation of neuronal and axonal tissue can lead to long-term disability or death. Mathematical modelling and computer simulation of acceleration-induced traumatic brain injury promise to illuminate the mechanisms of axonal and neuronal pathology, but numerical studies require knowledge of boundary conditions at the brain-skull interface, material properties and experimental data for validation. The current study provides a dense set of displacement measurements in the human brain during mild frontal skull impact constrained to the sagittal plane. Although head motion is dominated by translation, these data show that the brain rotates relative to the skull. For these mild events, characterized by linear decelerations near 1.5g (g = 9.81 m s⁻²) and angular accelerations of 120-140 rad s⁻², relative brain-skull displacements of 2-3 mm are typical; regions of smaller displacements reflect the tethering effects of brain-skull connections. Strain fields exhibit significant areas with maximal principal strains of 5 per cent or greater. These displacement and strain fields illuminate the skull-brain boundary conditions, and can be used to validate simulations of brain biomechanics.

Extrapolation of vertical target motion through a brief visual occlusion.

PubMed

Zago, Myrka; Iosa, Marco; Maffei, Vincenzo; Lacquaniti, Francesco

2010-03-01

It is known that arbitrary target accelerations along the horizontal generally are extrapolated much less accurately than target speed through a visual occlusion. The extent to which vertical accelerations can be extrapolated through an occlusion is much less understood. Here, we presented a virtual target rapidly descending on a blank screen with different motion laws. The target accelerated under gravity (1g), decelerated under reversed gravity (-1g), or moved at constant speed (0g). Probability of each type of acceleration differed across experiments: one acceleration at a time, or two to three different accelerations randomly intermingled could be presented. After a given viewing period, the target disappeared for a brief, variable period until arrival (occluded trials) or it remained visible throughout (visible trials). Subjects were asked to press a button when the target arrived at destination. We found that, in visible trials, the average performance with 1g targets could be better or worse than that with 0g targets depending on the acceleration probability, and both were always superior to the performance with -1g targets. By contrast, the average performance with 1g targets was always superior to that with 0g and -1g targets in occluded trials. Moreover, the response times of 1g trials tended to approach the ideal value with practice in occluded protocols. To gain insight into the mechanisms of extrapolation, we modeled the response timing based on different types of threshold models. We found that occlusion was accompanied by an adaptation of model parameters (threshold time and central processing time) in a direction that suggests a strategy oriented to the interception of 1g targets at the expense of the interception of the other types of tested targets. We argue that the prediction of occluded vertical motion may incorporate an expectation of gravity effects.

Accelerations and Passenger Harness Loads Measured in Full-Scale Light-Airplane Crashes

NASA Technical Reports Server (NTRS)

Eiband, A. Martin; Simpkinson, Scott H.; Black, Dugald O.

1953-01-01

Full-scale light-airplane crashes simulating stall-spin accidents were conducted to determine the decelerations to which occupants are exposed and the resulting harness forces encountered in this type of accident. Crashes at impact speeds from 42 to 60 miles per hour were studied. The airplanes used were of the familiar steel-tube, fabric-covered, tandem, two-seat type. In crashes up to an impact speed of 60 miles per hour, crumpling of the forward fuselage structure prevented the maximum deceleration at the rear-seat location from exceeding 26 to 33g. This maximum g value appeared independent of the impact speed. Restraining forces in the seatbelt - shoulder-harness combination reached 5800 pounds. The rear-seat occupant can survive crashes of the type studied at impact speeds up to 60 miles per hour, if body movement is restrained by an adequate seatbelt-shoulder-harness combination so as to prevent injurious contact with obstacles normally present in the cabin. Inwardly collapsing cabin structure, however, is a potential hazard in the higher-speed crashes.

Poynting vector, energy densities, and pressure of collective transverse electromagnetic fluctuations in unmagnetized plasmas

NASA Astrophysics Data System (ADS)

Schlickeiser, R.

2012-01-01

A systematic calculation of the electromagnetic properties (Poynting vector, electromagnetic energy, and pressure) of the collective transverse fluctuations in unmagnetized plasmas with velocity-anisotropic plasma particle distributions functions is presented. Time-averaged electromagnetic properties for monochromatic weakly damped wave-like fluctuations and space-averaged electromagnetic properties for monochromatic weakly propagating and aperiodic fluctuations are calculated. For aperiodic fluctuations, the Poynting vector as well as the sum of the space-averaged electric and magnetic field energy densities vanish. However, aperiodic fluctuations possess a positive pressure given by its magnetic energy density. This finite pressure density pa of aperiodic fluctuations has important consequences for the dynamics of cosmic unmagnetized plasmas such as the intergalactic medium after reionization. Adopting the standard cosmological evolution model, we show that this additional pressure changes the expansion law of the universe leading to further deceleration. Negative vacuum pressure counterbalances this deceleration to an accelerating universe provided that the negative vacuum pressure is greater than 1.5pa, which we estimate to be of the order 2.1 . 10-16 dyn cm-2.

Inflationary universe in deformed phase space scenario

NASA Astrophysics Data System (ADS)

Rasouli, S. M. M.; Saba, Nasim; Farhoudi, Mehrdad; Marto, João; Moniz, P. V.

2018-06-01

We consider a noncommutative (NC) inflationary model with a homogeneous scalar field minimally coupled to gravity. The particular NC inflationary setting herein proposed, produces entirely new consequences as summarized in what follows. We first analyze the free field case and subsequently examine the situation where the scalar field is subjected to a polynomial and exponential potentials. We propose to use a canonical deformation between momenta, in a spatially flat Friedmann-Lemaî tre-Robertson-Walker (FLRW) universe, and while the Friedmann equation (Hamiltonian constraint) remains unaffected the Friedmann acceleration equation (and thus the Klein-Gordon equation) is modified by an extra term linear in the NC parameter. This concrete noncommutativity on the momenta allows interesting dynamics that other NC models seem not to allow. Let us be more precise. This extra term behaves as the sole explicit pressure that under the right circumstances implies a period of accelerated expansion of the universe. We find that in the absence of the scalar field potential, and in contrast with the commutative case, in which the scale factor always decelerates, we obtain an inflationary phase for small negative values of the NC parameter. Subsequently, the period of accelerated expansion is smoothly replaced by an appropriate deceleration phase providing an interesting model regarding the graceful exit problem in inflationary models. This last property is present either in the free field case or under the influence of the scalar field potentials considered here. Moreover, in the case of the free scalar field, we show that not only the horizon problem is solved but also there is some resemblance between the evolution equation of the scale factor associated to our model and that for the R2 (Starobinsky) inflationary model. Therefore, our herein NC model not only can be taken as an appropriate scenario to get a successful kinetic inflation, but also is a convenient setting to obtain inflationary universe possessing the graceful exit when scalar field potentials are present.

Catalac free electron laser

DOEpatents

Brau, Charles A.; Swenson, Donald A.; Boyd, Jr., Thomas J.

1982-01-01

A catalac free electron laser using a rf linac (catalac) which acts as a catalyst to accelerate an electron beam in an initial pass through the catalac and decelerate the electron beam during a second pass through the catalac. During the second pass through the catalac, energy is extracted from the electron beam and transformed to energy of the accelerating fields of the catalac to increase efficiency of the device. Various embodiments disclose the use of post linacs to add electron beam energy extracted by the wiggler and the use of supplementary catalacs to extract energy at various energy peaks produced by the free electron laser wiggler to further enhance efficiency of the catalac free electron laser. The catalac free electron laser can be used in conjunction with a simple resonator, a ring resonator or as an amplifier in conjunction with a master oscillator laser.

Catalac free electron laser

DOEpatents

Brau, C.A.; Swenson, D.A.; Boyd, T.J. Jr.

1979-12-12

A catalac free electron laser using a rf linac (catalac) which acts as a catalyst to accelerate an electron beam in an initial pass through the catalac and decelerate the electron beam during a second pass through the catalac is described. During the second pass through the catalac, energy is extracted from the electron beam and transformed to energy of the accelerating fields of the catalac to increase efficiency of the device. Various embodiments disclose the use of post linacs to add electron beam energy extracted by the wiggler and the use of supplementary catalacs to extract energy at various energy peaks produced by the free electron laser wiggler to further enhance efficiency of the catalac free electron laser. The catalac free electron laser can be used in conjunction with a simple resonator, a ring resonator, or as an amplifier in conjunction with a master oscillator laser.

Multiscale Dynamics of Aseismic Slip on Central San Andreas Fault

NASA Astrophysics Data System (ADS)

Khoshmanesh, M.; Shirzaei, M.

2018-03-01

Understanding the evolution of aseismic slip enables constraining the fault's seismic budget and provides insight into dynamics of creep. Inverting the time series of surface deformation measured along the Central San Andreas Fault obtained from interferometric synthetic aperture radar in combination with measurements of repeating earthquakes, we constrain the spatiotemporal distribution of creep during 1992-2010. We identify a new class of intermediate-term creep rate variations that evolve over decadal scale, releasing stress on the accelerating zone and loading adjacent decelerating patches. We further show that in short-term (<2 year period), creep avalanches, that is, isolated clusters of accelerated aseismic slip with velocities exceeding the long-term rate, govern the dynamics of creep. The statistical properties of these avalanches suggest existence of elevated pore pressure in the fault zone, consistent with laboratory experiments.

Piezoelectric-based self-powered electronic adjustable impulse switches

NASA Astrophysics Data System (ADS)

Rastegar, Jahangir; Kwok, Philip

2018-03-01

Novel piezoelectric-based self-powered impulse detecting switches are presented. The switches are designed to detect shock loading events resulting in acceleration or deceleration above prescribed levels and durations. The prescribed acceleration level and duration thresholds are adjustable. They are provided with false trigger protection logic. The impulse switches are provided with electronic and logic circuitry to detect prescribed impulse events and reject events such as high amplitude but short duration shocks, and transportation vibration and similar low amplitude and relatively long duration events. They can be mounted directly onto electronics circuit boards, thereby significantly simplifying the electrical and electronic circuitry, simplifying the assembly process and total cost, significantly reducing the occupied volume, and in some applications eliminating the need for physical wiring to and from the impulse switches. The design of prototypes and testing under realistic conditions are presented.

Effects of longitudinal speed reduction markings on left-turn direct connectors.

PubMed

Zhao, Xiaohua; Ding, Han; Lin, Zhanzhou; Ma, Jianming; Rong, Jian

2018-06-01

Longitudinal speed reduction markings (LSRMs) are designed to alert drivers to an upcoming change in roadway geometry (e.g. direct connectors with smaller radii). In Beijing, LSRMs are usually installed on direct connectors of urban expressways. The objective of this paper is to examine the influence of LSRMs on vehicle operation and driver behavior, and evaluate the decelerating effectiveness of LSRMs on direct connectors with different radii. Empirical data were collected in a driving simulator, and indicators representing vehicle operation status and driving behavior were proposed. To examine the influence of LSRMs, an analysis segment was defined, which begins 500 m prior to the entering point of the connector and ends at the exiting point of the connector. Furthermore, the analysis segment was evenly divided into a series of subsections; the length of each subsection is 50 m. This definition is introduced based on the assumption that drivers would decelerate smoothly in advance of the connector. The analysis results show that drivers tend to decelerate earlier when the radii were 200 m or 300 m. When approaching the connector, drivers tend to decelerate at 500 m thru 250 m in advance of the connector with a 200 m radius; deceleration happens at 300 m-0 m in advance of the connector with a 300 m radius. On the connector, drivers controlled the throttle pedal use at 100 thru 300 m after the entering point when the radius was 200 m; deceleration occurred in two regions when the radius was 300 m: 0 m-900 m from the entering point, and the last 1,000 m of the connector. The analytical results further revealed that LSRMs would be effective at reducing speeds when the radius of the direct connector was 300 m. Copyright © 2018. Published by Elsevier Ltd.

A marine dynamic penetrometer for the determination of sea floor geotechnical properties

NASA Astrophysics Data System (ADS)

Stephan, S.; Kaul, N. E.; Villinger, H. W.

2013-12-01

We present a seafloor lance penetration monitoring system: the Lance Insertion Retardation Meter (LIRmeter). The device can be used to infer geotechnical seafloor properties, such as bearing capacity by monitoring the deceleration of a free-fall penetrating lance. The deceleration record can be furthermore used to estimate mean grain size and mud content of the sea floor as well as total penetration depth. The LIRmeter is contained in a pressure vessel (440 x 110 mm) and equipped with accelerometers of different sensitivities to (i) determine sea floor resistance during penetration and (ii) to generate a depth axis. Typically, measurements are carried out in a pogo style fashion to allow a rapid measurement progress during field campaigns. The LIRmeter is intended to determine sea floor properties on the sole basis of deceleration measurements in order to achieve a mechanically and electronically robust system. Data is sampled at a resolution of 16 bit and at a rate of typically 500 Hz for each channel. The device can either be installed in any type of lance i.e. marine heat flow probes, gravity corers, piston corers or can be used in combination with a purpose built lance as a standalone instrument. It has a usable length of four meters, a total weight of 280 kg in air and can be operated up to full ocean depth (6000m). The bearing capacity of the sea floor is a critical factor for marine engineering projects such as burial of marine cables, pipeline laying and foundations. Knowledge of the mud content can provide constraints for the estimation of hydraulic conductivity. The identification of weak zones along a slope can moreover provide vital information for risk assessment studies. Traditionally, frame based, quasi static Cone Penetration Tests (CPT) or sampling methods like gravity coring are used to conduct these types of investigation. In comparison to established but time consuming and rather costly methods, the LIRmeter is intended (i) for near surface investigations and/or (ii) to complement and connect conventional but isolated CPT measurements in a very efficient and rapid way. We show results from measurements in the North Sea, as well as results of laboratory experiments. During sea trials, the LIRmeter was equipped with an additional CPT sensor, which delivered data for cone (tip) resistance, sleeve friction and pore pressure, thus allowing a direct comparison between results of the acceleration measurements and results from conventional CPT sensors. The laboratory measurements were also carried out using both acceleration and tip resistance sensors. Resulting values show a very good agreement between tip resistance calculated from deceleration data and tip resistance from direct laboratory and field measurements. The influence of sediment type (mainly mud content) will be discussed within the context of laboratory measurements.

Comparing Experiment and Computation of Hypersonic Laminar Boundary Layers with Isolated Roughness

NASA Technical Reports Server (NTRS)

Bathel, Brett F.; Iyer, Prahladh S.; Mahesh, Krishnan; Danehy, Paul M.; Inman, Jennifer A.; Jones, Stephen B.; Johansen, Craig T.

2014-01-01

Streamwise velocity profile behavior in a hypersonic laminar boundary layer in the presence of an isolated roughness element is presented for an edge Mach number of 8.2. Two different roughness element types are considered: a 2-mm tall, 4-mm diameter cylinder, and a 2-mm radius hemisphere. Measurements of the streamwise velocity behavior using nitric oxide (NO) planar laser-induced fluorescence (PLIF) molecular tagging velocimetry (MTV) have been performed on a 20-degree wedge model. The top surface of this model acts as a flat-plate and is oriented at 5 degrees with respect to the freestream flow. Computations using direct numerical simulation (DNS) of these flows have been performed and are compared to the measured velocity profiles. Particular attention is given to the characteristics of velocity profiles immediately upstream and downstream of the roughness elements. In these regions, the streamwise flow can experience strong deceleration or acceleration. An analysis in which experimentally measured MTV profile displacements are compared with DNS particle displacements is performed to determine if the assumption of constant velocity over the duration of the MTV measurement is valid. This assumption is typically made when reporting MTV-measured velocity profiles, and may result in significant errors when comparing MTV measurements to computations in regions with strong deceleration or acceleration. The DNS computations with the cylindrical roughness element presented in this paper were performed with and without air injection from a rectangular slot upstream of the cylinder. This was done to determine the extent to which gas seeding in the MTV measurements perturbs the boundary layer flowfield.

Geographic variation in floral allometry suggests repeated transitions between selfing and outcrossing in a mixed mating plant.

PubMed

Summers, Holly E; Hartwick, Sally M; Raguso, Robert A

2015-05-01

Isometric and allometric scaling of a conserved floral plan could provide a parsimonious mechanism for rapid and reversible transitions between breeding systems. This scaling may occur during transitions between predominant autogamy and xenogamy, contributing to the maintenance of a stable mixed mating system. We compared nine disjunct populations of the polytypic, mixed mating species Oenothera flava (Onagraceae) to two parapatric relatives, the obligately xenogamous species O. acutissima and the mixed mating species O. triloba. We compared floral morphology of all taxa using principal component analysis (PCA) and developmental trajectories of floral organs using ANCOVA homogeneity of slopes. The PCA revealed both isometric and allometric scaling of a conserved floral plan. Three principal components (PCs) explained 92.5% of the variation in the three species. PC1 predominantly loaded on measures of floral size and accounts for 36% of the variation. PC2 accounted for 35% of the variation, predominantly in traits that influence pollinator handling. PC3 accounted for 22% of the variation, primarily in anther-stigma distance (herkogamy). During O. flava subsp. taraxacoides development, style elongation was accelerated relative to anthers, resulting in positive herkogamy. During O. flava subsp. flava development, style elongation was decelerated, resulting in zero or negative herkogamy. Of the two populations with intermediate morphology, style elongation was accelerated in one population and decelerated in the other. Isometric and allometric scaling of floral organs in North American Oenothera section Lavauxia drive variation in breeding system. Multiple developmental paths to intermediate phenotypes support the likelihood of multiple mating system transitions. © 2015 Botanical Society of America, Inc.

Metabolic and mechanical aspects of foot landing type, forefoot and rearfoot strike, in human running.

PubMed

Ardigò, L P; Lafortuna, C; Minetti, A E; Mognoni, P; Saibene, F

1995-09-01

The study was undertaken to assess the metabolic and the mechanical aspects of two different foot strike patterns in running, i.e. forefoot and rearfoot striking (FFS and RFS), and to understand whether there is some advantage for a runner to use one or the other of the two landing styles. Eight subjects performed two series of runs (FFS and RFS) on a treadmill at an average speed of 2.50, 2.78, 3.06, 3.33, 3.61, 3.89, 4.17 m s-1. Step frequency, oxygen uptake, mechanical work, and its two components, external and internal, were measured. No differences were found for step frequency, mechanical internal work per unit time and oxygen uptake, while external and total mechanical work per unit time were significantly higher, 7-12%, for FFS. The higher external work was the result of an increase of the work performed against both gravitational and inertial forces. As the energy expenditure was the same it has been speculated that a higher storage and release of energy takes place in the elastic structures of the lower leg with FFS. In a different series of experiments on six subjects contact time, time of deceleration and time of acceleration were measured by means of a video camera while running on the treadmill at 2.50, 3.33 and 4.17 m s-1, both FFS and RFS. Time of deceleration is similar for FFS and RFS, but contact time and time of acceleration are shorter, respectively 12 and 25%, for FFS.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of Competitive Game Demands of NCAA Division I College Football Players Using Global Positioning Systems.

PubMed

Wellman, Aaron D; Coad, Sam C; Goulet, Grant C; McLellan, Christopher P

2016-01-01

The aim of the present study was to examine the competitive physiological movement demands of National Collegiate Athletic Association (NCAA) Division I college football players using portable global positioning system (GPS) technology during games and to examine positional groups within offensive and defensive teams, to determine if a player's physiological requirements during games are influenced by playing position. Thirty-three NCAA Division I Football Bowl Subdivision football players were monitored using GPS receivers with integrated accelerometers (GPSports) during 12 regular season games throughout the 2014 season. Individual data sets (n = 295) from players were divided into offensive and defensive teams and subsequent position groups. Movement profile characteristics, including total, low-intensity, moderate-intensity, high-intensity, and sprint running distances (m), sprint counts, and acceleration and deceleration efforts, were assessed during games. A one-way ANOVA and post-hoc Bonferroni statistical analysis were used to determine differences in movement profiles between each position group within offensive and defensive teams. For both offensive and defensive teams, significant (p ≤ 0.05) differences exist between positional groups for game physical performance requirements. The results of the present study identified that wide receivers and defensive backs completed significantly (p ≤ 0.05) greater total distance, high-intensity running, sprint distance, and high-intensity acceleration and deceleration efforts than their respective offensive and defensive positional groups. Data from the present study provide novel quantification of position-specific physical demands of college football games and support the use of position-specific training in the preparation of NCAA Division I college football players for competition.

Movement Demands of Elite U20 International Rugby Union Players

PubMed Central

Drawer, Scott; Eager, Robin; Taylor, Neil; Cook, Christian

2016-01-01

The purpose of this study was to quantify movement demands of elite international age grade (U20) rugby union players during competitive tournament match play. Forty elite professional players from an U20 international performance squad were monitored using 10Hz global positioning systems (GPS) during 15 international tournament matches during the 2014/15 and 2015/16 seasons. Data on distances, velocities, accelerations, decelerations, high metabolic load (HML) distance and efforts, and number of sprints were derived. Data files from players who played over 60 min (n = 161) were separated firstly into Forwards and Backs, and more specifically into six positional groups; FR—Front Row (prop & hooker), SR—Second Row, BR—Back Row (Flankers & No.8), HB—Half Backs (scrum half & outside half), MF—Midfield (centres), B3 –Back Three (wings & full back) for match analysis. Analysis revealed significant differences between forwards and backs positions. Backs scored higher on all variables measured with the exception of number of moderate accelerations, decelerations (no difference). The centres covered the greatest total distance with the front row covering the least (6.51 ± 0.71 vs 4.97 ± 0.75 km, p < 0.001). The front row also covered the least high speed running (HSR) distance compared to the back three (211.6 ± 112.7 vs 728.4 ± 150.2 m, p < 0.001) who covered the most HSR distance, affirming that backs cover greater distances but forwards have greater contact loads. These findings highlight for the first time differences in the movement characteristics of elite age grade rugby union players specific to positional roles. PMID:27055230

Comparison of Activity Profiles and Physiological Demands Between International Rugby Sevens Matches and Training.

PubMed

Higham, Dean G; Pyne, David B; Anson, Judith M; Hopkins, Will G; Eddy, Anthony

2016-05-01

The specificity of contemporary training practices of international rugby sevens players is unknown. We quantified the positional group-specific activity profiles and physiological demands of on-field training activities and compared these with match demands. Twenty-two international matches and 63 rugby-specific training drills were monitored in 25 backs and 17 forwards from a national squad of male rugby sevens players over a 21-month period. Drills were classified into 3 categories: low-intensity skill refining (n = 23 drills, 560 observations), moderate- to high-intensity skill refining (n = 28 drills, 600 observations), and game simulation (n = 12 drills, 365 observations). Movement patterns (via Global Positioning System devices) and physiological load (via heart rate monitors) were recorded for all activities, and the differences between training and matches were quantified using magnitude-based inferential statistics. Distance covered in total and at ≥3.5 m·s, maximal velocity, and frequency of accelerations and decelerations were lower for forwards during competition compared with those for backs by a small but practically important magnitude. No clear positional group differences were observed for physiological load during matches. Training demands exceeded match demands only for frequency of decelerations of forwards during moderate- to high-intensity skill-refining drills and only by a small amount. Accelerations and distance covered at ≥6 m·s were closer to match values for forwards than for backs during all training activities, but training drills consistently fell below the demands of international competition. Coaches could therefore improve physical and physiological specificity by increasing the movement demands and intensity of training drills.

Movement Demands of Elite U20 International Rugby Union Players.

PubMed

Cunningham, Daniel; Shearer, David A; Drawer, Scott; Eager, Robin; Taylor, Neil; Cook, Christian; Kilduff, Liam P

2016-01-01

The purpose of this study was to quantify movement demands of elite international age grade (U20) rugby union players during competitive tournament match play. Forty elite professional players from an U20 international performance squad were monitored using 10 Hz global positioning systems (GPS) during 15 international tournament matches during the 2014/15 and 2015/16 seasons. Data on distances, velocities, accelerations, decelerations, high metabolic load (HML) distance and efforts, and number of sprints were derived. Data files from players who played over 60 min (n = 161) were separated firstly into Forwards and Backs, and more specifically into six positional groups; FR--Front Row (prop & hooker), SR--Second Row, BR--Back Row (Flankers & No.8), HB--Half Backs (scrum half & outside half), MF--Midfield (centres), B3--Back Three (wings & full back) for match analysis. Analysis revealed significant differences between forwards and backs positions. Backs scored higher on all variables measured with the exception of number of moderate accelerations, decelerations (no difference). The centres covered the greatest total distance with the front row covering the least (6.51 ± 0.71 vs 4.97 ± 0.75 km, p < 0.001). The front row also covered the least high speed running (HSR) distance compared to the back three (211.6 ± 112.7 vs 728.4 ± 150.2 m, p < 0.001) who covered the most HSR distance, affirming that backs cover greater distances but forwards have greater contact loads. These findings highlight for the first time differences in the movement characteristics of elite age grade rugby union players specific to positional roles.

Intermittent torsion of a normal ovary in a child associated with use of a trampoline.

PubMed

Yancey, Lynne M

2012-04-01

Ovarian torsion is rare in children. It usually occurs in the presence of ovarian or pelvic pathology. The course of symptoms is typically hours to days. Some authors have speculated that sudden acceleration/deceleration movements may precipitate torsion. The objective of this report is to describe a case of intermittent abdominal pain lasting nearly 6 months, which started when the child began playing regularly on a trampoline, and was ultimately diagnosed as intermittent ovarian torsion of an otherwise normal ovary. A 12-year-old girl presented to the Emergency Department (ED) with 2 h of abdominal pain and vomiting. She reported similar episodes over the previous 6 months. Initial ultrasound, obtained between episodes, was normal. Repeat ultrasound at ED presentation showed no blood flow to the left adnexa. Surgery confirmed the ovary to be twisted 1080 degrees and markedly edematous due to vascular engorgement. The family retrospectively identified the onset of the first episode as happening the same week the child had begun playing regularly on a trampoline. After surgery, she no longer played on the trampoline. At follow-up 22 months later, she had had no recurrence of her symptoms. Intermittent ovarian torsion should be considered as a rare cause of recurrent abdominal pain in children. The presence of blood flow with Doppler ultrasound during acute symptoms does not exclude the diagnosis. Clinicians might also ask about unusual physical activities because several authors have theorized that ovarian torsion could be precipitated by sudden acceleration/deceleration movements. Copyright © 2012. Published by Elsevier Inc.

Modeling of patient's blood pressure variation during ambulance transportation

NASA Astrophysics Data System (ADS)

Sakatani, Kenji; Ono, Takahiko; Kobayasi, Yasuhide; Hikita, Shinichi; Saito, Mitsuyuki

2007-12-01

In an emergency transportation by ambulance, a patient is transported in a supine position. In this position, a patient's blood pressure (BP) variation depending on an inertial force which occurs when an ambulance accelerates or decelerates. This BP variation causes a critical damage for a patent with brain disorder. In order to keep a patient stable during transportation, it is required to maintain small BP variation. To analyze the BP variation during transportation, a model of the BP variation has so far been made. But, it can estimate the BP variation only in braking. The purpose of this paper is to make a dynamical model of the BP variation which can simulate it in both braking and accelerating. First, to obtain the data to construct the model, we used a tilting bed to measure a head-to-foot acceleration and BP of fingertip. Based on this data, we build a mathematical model whose input is the head-to-foot acceleration and output is the Mean BP variation. It is a switched model which switches two models depending on the jerk. We add baroreceptor reflex to the model as a offset value.

Magnet design for the splitter/combiner regions of CBETA, the Cornell-Brookhaven Energy-Recovery-Linac Test Accelerator

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

Crittendon, J. A.; Burke, D. C.; Fuentes, Y. L.P.

2017-01-06

The Cornell-Brookhaven Energy-Recovery-Linac Test Accelerator (CBETA) will provide a 150-MeV electron beam using four acceleration and four deceleration passes through the Cornell Main Linac Cryomodule housing six 1.3-GHz superconducting RF cavities. The return path of this 76-m-circumference accelerator will be provided by 106 fixed-field alternating-gradient (FFAG) cells which carry the four beams of 42, 78, 114 and 150 MeV. Here we describe magnet designs for the splitter and combiner regions which serve to match the on-axis linac beam to the off-axis beams in the FFAG cells, providing the path-length adjustment necessary to energy recovery for each of the four beams.more » The path lengths of the four beamlines in each of the splitter and combiner regions are designed to be adapted to 1-, 2-, 3-, and 4-pass staged operations. Design specifi- cations and modeling for the 24 dipole and 32 quadrupole electromagnets in each region are presented. The CBETA project will serve as the first demonstration of multi-pass energy recovery using superconducting RF cavities with FFAG cell optics for the return loop.« less