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

Mandal, A.; Gupta, Y. M.

To understand the elastic-plastic deformation response of shock-compressed molybdenum (Mo) – a body-centered cubic (BCC) metal, single crystal samples were shocked along the [100] crystallographic orientation to an elastic impact stress of 12.5 GPa. Elastic-plastic wave profiles, measured at different propagation distances ranging between ~0.23 to 2.31 mm using laser interferometry, showed a time-dependent material response. Within experimental scatter, the measured elastic wave amplitudes were nearly constant over the propagation distances examined. These data point to a large and rapid elastic wave attenuation near the impact surface, before reaching a threshold value (elastic limit) of ~3.6 GPa. Numerical simulations ofmore » the measured wave profiles, performed using a dislocation-based continuum model, suggested that {110}<111> and/or {112}<111> slip systems are operative under shock loading. In contrast to shocked metal single crystals with close-packed structures, the measured wave profiles in Mo single crystals could not be explained in terms of dislocation multiplication alone. A dislocation generation mechanism, operative for shear stresses larger than that at the elastic limit, was required to model the rapid elastic wave attenuation and to provide a good overall match to the measured wave profiles. However, the physical basis for this mechanism was not established for the high-purity single crystal samples used in this study. As a result, the numerical simulations also suggested that Mo single crystals do not work harden significantly under shock loading in contrast to the behavior observed under quasi-static loading.« less

Elastic-plastic deformation of molybdenum single crystals shocked along [100

DOE PAGES

Mandal, A.; Gupta, Y. M.

2017-01-24

To understand the elastic-plastic deformation response of shock-compressed molybdenum (Mo) – a body-centered cubic (BCC) metal, single crystal samples were shocked along the [100] crystallographic orientation to an elastic impact stress of 12.5 GPa. Elastic-plastic wave profiles, measured at different propagation distances ranging between ~0.23 to 2.31 mm using laser interferometry, showed a time-dependent material response. Within experimental scatter, the measured elastic wave amplitudes were nearly constant over the propagation distances examined. These data point to a large and rapid elastic wave attenuation near the impact surface, before reaching a threshold value (elastic limit) of ~3.6 GPa. Numerical simulations ofmore » the measured wave profiles, performed using a dislocation-based continuum model, suggested that {110}<111> and/or {112}<111> slip systems are operative under shock loading. In contrast to shocked metal single crystals with close-packed structures, the measured wave profiles in Mo single crystals could not be explained in terms of dislocation multiplication alone. A dislocation generation mechanism, operative for shear stresses larger than that at the elastic limit, was required to model the rapid elastic wave attenuation and to provide a good overall match to the measured wave profiles. However, the physical basis for this mechanism was not established for the high-purity single crystal samples used in this study. As a result, the numerical simulations also suggested that Mo single crystals do not work harden significantly under shock loading in contrast to the behavior observed under quasi-static loading.« less

Simultaneous, single-pulse, synchrotron x-ray imaging and diffraction under gas gun loading

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

Fan, D.; Luo, S. N., E-mail: sluo@pims.ac.cn; Key Laboratory of Advanced Technologies of Materials, Ministry of Education, Southwest Jiaotong University, Chengdu, Sichuan 610031

We develop a mini gas gun system for simultaneous, single-pulse, x-ray diffraction and imaging under high strain-rate loading at the beamline 32-ID of the Advanced Photon Source. In order to increase the reciprocal space covered by a small-area detector, a conventional target chamber is split into two chambers: a narrowed measurement chamber and a relief chamber. The gas gun impact is synchronized with synchrotron x-ray pulses and high-speed cameras. Depending on a camera’s capability, multiframe imaging and diffraction can be achieved. The proof-of-principle experiments are performed on single-crystal sapphire. The diffraction spots and images during impact are analyzed to quantifymore » lattice deformation and fracture; fracture is dominated by splitting cracks followed by wing cracks, and diffraction peaks are broadened likely due to mosaic spread. Our results demonstrate the potential of such multiscale measurements for studying high strain-rate phenomena at dynamic extremes.« less

Single quantum dot tracking reveals the impact of nanoparticle surface on intracellular state.

PubMed

Zahid, Mohammad U; Ma, Liang; Lim, Sung Jun; Smith, Andrew M

2018-05-08

Inefficient delivery of macromolecules and nanoparticles to intracellular targets is a major bottleneck in drug delivery, genetic engineering, and molecular imaging. Here we apply live-cell single-quantum-dot imaging and tracking to analyze and classify nanoparticle states after intracellular delivery. By merging trajectory diffusion parameters with brightness measurements, multidimensional analysis reveals distinct and heterogeneous populations that are indistinguishable using single parameters alone. We derive new quantitative metrics of particle loading, cluster distribution, and vesicular release in single cells, and evaluate intracellular nanoparticles with diverse surfaces following osmotic delivery. Surface properties have a major impact on cell uptake, but little impact on the absolute cytoplasmic numbers. A key outcome is that stable zwitterionic surfaces yield uniform cytosolic behavior, ideal for imaging agents. We anticipate that this combination of quantum dots and single-particle tracking can be widely applied to design and optimize next-generation imaging probes, nanoparticle therapeutics, and biologics.

Experimental study on Statistical Damage Detection of RC Structures based on Wavelet Packet Analysis

NASA Astrophysics Data System (ADS)

Zhu, X. Q.; Law, S. S.; Jayawardhan, M.

2011-07-01

A novel damage indicator based on wavelet packet transform is developed in this study for structural health monitoring. The response signal of a structure under an impact load is normalized and then decomposed into wavelet packet components. Energies of these wavelet packet components are then calculated to obtain the energy distribution. A statistical indicator is developed to describe the damage extent of the structure. This approach is applied to the test results from simply supported reinforced concrete beams in the laboratory. Cases with single damage are created from static loading, and accelerations of the structure from under impact loads are analyzed. Results show that the method can be used for the damage monitoring and assessment of the structure.

A Modified Split Hopkinson Pressure Bar Approach for Mimicking Dynamic Oscillatory Stress Fluctuations During Earthquake Rupture

NASA Astrophysics Data System (ADS)

Braunagel, M. J.; Griffith, W. A.

2017-12-01

Past experimental work has demonstrated that rock failure at high strain rates occurs by fragmentation rather than discrete fracture and is accompanied by a dramatic increase in rock strength. However, these observations are difficult to reconcile with the assertion that pulverized rocks in fault zones are the product of impulsive stresses during the passage of earthquake ruptures, as the distance from the principal slip zones of some pulverized rock is too great to exceed fragmentation transition. One potential explanation to this paradox that has been suggested is that repeated loading over the course of multiple earthquake ruptures may gradually reduce the pulverization threshold, in terms of both strain rate and strength. We propose that oscillatory loading during a single earthquake rupture may further lower these pulverization thresholds, and that traditional dynamic experimental approaches, such as the Split Hopkinson Pressure Bar (SHPB) wherein load is applied as a single, smooth, sinusoidal compressive wave, may not reflect natural loading conditions. To investigate the effects of oscillatory compressive loading expected during earthquake rupture propagation, we develop a controlled cyclic loading model on a SHPB apparatus utilizing two striker bars connected by an elastic spring. Unlike traditional SHPB experiments that utilize a gas gun to fire a projectile bar and generate a single compressive wave on impact with the incident bar, our modified striker bar assembly oscillates while moving down the gun barrel and generates two separate compressive pulses separated by a lag time. By modeling the modified assembly as a mass-spring-mass assembly accelerating due to the force of the released gas, we can predict the compression time of the spring upon impact and therefore the time delay between the generation of the first and second compressive waves. This allows us to predictably control load cycles with durations of only a few hundred microseconds. Initial experimental results demonstrate that fragmentation of Westerly Granite samples occurs at lower stresses and strain rates than those expected from traditional SHPB experiments.

Impact-damaged graphite-thermoplastic trapezoidal-corrugation sandwich and semi-sandwich panels

NASA Technical Reports Server (NTRS)

Jegley, D.

1993-01-01

The results of a study of the effects of impact damage on compression-loaded trapezoidal-corrugation sandwich and semi-sandwich graphite-thermoplastic panels are presented. Sandwich panels with two identical face sheets and a trapezoidal corrugated core between them, and semi-sandwich panels with a corrugation attached to a single skin are considered in this study. Panels were designed, fabricated and tested. The panels were made using the manufacturing process of thermoforming, a less-commonly used technique for fabricating composite parts. Experimental results for unimpacted control panels and panels subjected to impact damage prior to loading are presented. Little work can be found in the literature about these configurations of thermoformed panels.

Impact of Groundwater Flow and Energy Load on Multiple Borehole Heat Exchangers.

PubMed

Dehkordi, S Emad; Schincariol, Robert A; Olofsson, Bo

2015-01-01

The effect of array configuration, that is, number, layout, and spacing, on the performance of multiple borehole heat exchangers (BHEs) is generally known under the assumption of fully conductive transport. The effect of groundwater flow on BHE performance is also well established, but most commonly for single BHEs. In multiple-BHE systems the effect of groundwater advection can be more complicated due to the induced thermal interference between the boreholes. To ascertain the influence of groundwater flow and borehole arrangement, this study investigates single- and multi-BHE systems of various configurations. Moreover, the influence of energy load balance is also examined. The results from corresponding cases with and without groundwater flow as well as balanced and unbalanced energy loads are cross-compared. The groundwater flux value, 10(-7) m/s, is chosen based on the findings of previous studies on groundwater flow interaction with BHEs and thermal response tests. It is observed that multi-BHE systems with balanced loads are less sensitive to array configuration attributes and groundwater flow, in the long-term. Conversely, multi-BHE systems with unbalanced loads are influenced by borehole array configuration as well as groundwater flow; these effects become more pronounced with time, unlike when the load is balanced. Groundwater flow has more influence on stabilizing loop temperatures, compared to array characteristics. Although borehole thermal energy storage (BTES) systems have a balanced energy load function, preliminary investigation on their efficiency shows a negative impact by groundwater which is due to their dependency on high temperature gradients between the boreholes and surroundings. © 2014, National Ground Water Association.

PLA and single component silicone rubber blends for sub-zero temperature blown film packaging applications

NASA Astrophysics Data System (ADS)

Meekum, Utai; Khiansanoi, Apichart

2018-06-01

The poly(lactic acid) (PLA) blend with single component silicone rubber in the presence of reactive amino silane coupling agent and polyester polyols plasticizer were studied. The manufacturing of film packaging for sub-zero temperature applications from the PLA blend was the main objective. The mechanical properties, especially the impact strengths, of PLA/silicone blends were significantly depended on the silicone loading. The outstanding impact strengths, tested at sub-zero temperature, of the blend having silicone content of 8.0 phr was achieved. It was chosen as the best candidate for the processability improvement. Adding the talc filler into the PLA/silicone blend to enhance the rheological properties was investigated. The ductility of the talc filled blends were decreased with increasing the filler contents. However, the shear viscosity of the blend was raised with talc loading. The blend loaded with 40 phr of talc filler was justified as the optimal formula for the blown film process testing and it was successfully performed with a few difficulties. The obtained blown film showed relative good flexibility in comparison with LDPE but it has low transparency.

Simulations of X-ray diffraction of shock-compressed single-crystal tantalum with synchrotron undulator sources.

PubMed

Tang, M X; Zhang, Y Y; E, J C; Luo, S N

2018-05-01

Polychromatic synchrotron undulator X-ray sources are useful for ultrafast single-crystal diffraction under shock compression. Here, simulations of X-ray diffraction of shock-compressed single-crystal tantalum with realistic undulator sources are reported, based on large-scale molecular dynamics simulations. Purely elastic deformation, elastic-plastic two-wave structure, and severe plastic deformation under different impact velocities are explored, as well as an edge release case. Transmission-mode diffraction simulations consider crystallographic orientation, loading direction, incident beam direction, X-ray spectrum bandwidth and realistic detector size. Diffraction patterns and reciprocal space nodes are obtained from atomic configurations for different loading (elastic and plastic) and detection conditions, and interpretation of the diffraction patterns is discussed.

Simulations of X-ray diffraction of shock-compressed single-crystal tantalum with synchrotron undulator sources

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

Tang, M. X.; Zhang, Y. Y.; E, J. C.

Polychromatic synchrotron undulator X-ray sources are useful for ultrafast single-crystal diffraction under shock compression. Here, simulations of X-ray diffraction of shock-compressed single-crystal tantalum with realistic undulator sources are reported, based on large-scale molecular dynamics simulations. Purely elastic deformation, elastic–plastic two-wave structure, and severe plastic deformation under different impact velocities are explored, as well as an edge release case. Transmission-mode diffraction simulations consider crystallographic orientation, loading direction, incident beam direction, X-ray spectrum bandwidth and realistic detector size. Diffraction patterns and reciprocal space nodes are obtained from atomic configurations for different loading (elastic and plastic) and detection conditions, and interpretation of themore » diffraction patterns is discussed.« less

Development of postcompressional textural tests to evaluate the mechanical properties of medicated chewing gum tablets with high drug loadings.

PubMed

Al Hagbani, Turki; Nazzal, Sami

2018-02-01

Medicated chewing gum tablets (CGTs) represent a unique platform for drug delivery. Loading directly compressible gums with high concentrations of powdered medication, however, results in compacts with hybrid properties between a chewable gum and a brittle tablet. The aim of the present study was to develop textural tests that can identify the point at which CGTs begin to behave like a solid tablet upon drug incorporation. Curcumin (CUR) CGTs made with Health in gum were prepared with increasing CUR load from 0 to 100% and were characterized for their mechanical properties by a single-bite (knife) and a two-bite tests. From each test several parameters were extracted and correlated with drug loading. In the single-bite test, the change in the resistance of the compacts to plastic deformation was found to give a definitive guide on whether they behave as gums or tablets. A more in depth analysis of the impact of CUR loading on the chewability of the CGTs was provided by the two-bite test where CUR loading was found to have a nonlinear impact on the mechanical properties of compacts. An upper limit of 10% was found to yield compacts with gum-like properties, which were abolished at higher CUR loads. The textural test procedure outlined in this study are expected to assist those involved in the formulation of medicated gums for pharmaceutical applications in making an informed decision on the impact of drug loading on gum behavior before proceeding with clinical testing. There is a growing interest in utilizing medicated chewing gums for drug delivery, especially those made using directly compressible gum bases, such as Health in gum. Directly compressing a gum base with high amounts of solid drug powder, however, poses a challenge as it may result in compressed compacts with hybrid properties between a chewing gum and a hard tablet. Currently, official Pharmacopeias do not specify a testing procedure for the estimation of the mechanical and textural properties of chewing gum tablets. To fill in the knowledge gap, we demonstrated in the present study how complementing a single-bite (knife) test with a modified two-bite test could be used to discriminate between chewing gums and hard tablets that were prepared by directly compressing Health in gum base with increasing concentration of curcumin powder in the blend. By utilizing these two tests, it was possible to identify clear demarcations between conventional tablets and chewing gums. In this study, we found that a 10% load by weight is the upper limit for curcumin loading in a binary blend with Health in gum to maintain the mastication properties of the compacts, which become brittle tablets at 30% load. © 2017 Wiley Periodicals, Inc.

Effect of linear and non-linear blade modelling techniques on simulated fatigue and extreme loads using Bladed

NASA Astrophysics Data System (ADS)

Beardsell, Alec; Collier, William; Han, Tao

2016-09-01

There is a trend in the wind industry towards ever larger and more flexible turbine blades. Blade tip deflections in modern blades now commonly exceed 10% of blade length. Historically, the dynamic response of wind turbine blades has been analysed using linear models of blade deflection which include the assumption of small deflections. For modern flexible blades, this assumption is becoming less valid. In order to continue to simulate dynamic turbine performance accurately, routine use of non-linear models of blade deflection may be required. This can be achieved by representing the blade as a connected series of individual flexible linear bodies - referred to in this paper as the multi-part approach. In this paper, Bladed is used to compare load predictions using single-part and multi-part blade models for several turbines. The study examines the impact on fatigue and extreme loads and blade deflection through reduced sets of load calculations based on IEC 61400-1 ed. 3. Damage equivalent load changes of up to 16% and extreme load changes of up to 29% are observed at some turbine load locations. It is found that there is no general pattern in the loading differences observed between single-part and multi-part blade models. Rather, changes in fatigue and extreme loads with a multi-part blade model depend on the characteristics of the individual turbine and blade. Key underlying causes of damage equivalent load change are identified as differences in edgewise- torsional coupling between the multi-part and single-part models, and increased edgewise rotor mode damping in the multi-part model. Similarly, a causal link is identified between torsional blade dynamics and changes in ultimate load results.

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

Ruth, M.; Pratt, A.; Lunacek, M.

The combination of distributed energy resources (DER) and retail tariff structures to provide benefits to both utility consumers and the utilities is not well understood. To improve understanding, an Integrated Energy System Model (IESM) is being developed to simulate the physical and economic aspects of DER technologies, the buildings where they reside, and feeders servicing them. The IESM was used to simulate 20 houses with home energy management systems on a single feeder under a time-of-use (TOU) tariff to estimate economic and physical impacts on both the households and the distribution utilities. Home energy management systems (HEMS) reduce consumers’ electricmore » bills by precooling houses in the hours before peak electricity pricing. Utilization of HEMS reduce peak loads during high price hours but shifts it to hours with off-peak and shoulder prices, resulting in a higher peak load. used to simulate 20 houses with home energy management systems on a single feeder under a time-of-use (TOU) tariff to estimate economic and physical impacts on both the households and the distribution utilities. Home energy management systems (HEMS) reduce consumers’ electric bills by precooling houses in the hours before peak electricity pricing. Utilization of HEMS reduce peak loads during high price hours but shifts it to hours with off-peak and shoulder prices, resulting in a higher peak load.« less

Field Study of Performance, Comfort, and Sizing of Two Variable-Speed Heat Pumps Installed in a Single 2-Story Residence

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

Munk, Jeffrey D; Odukomaiya, Adewale O; Gehl, Anthony C

2014-01-01

With the recent advancements in the application of variable-speed (VS) compressors to residential HVAC systems, opportunities are now available to size heat pumps (HPs) to more effectively meet heating and cooling loads in many of the climate zones in the US with limited use of inefficient resistance heat. This is in contrast to sizing guidance for traditional single-speed HPs that limits the ability to oversize with regard to cooling loads, because of risks of poor dehumidification during the cooling season and increased cycling losses. VS-drive HPs can often run at 30-40% of their rated cooling capacity to reduce cycling losses,more » and can adjust fan speed to provide better indoor humidity control. Detailed air-side performance data was collected on two VS-drive heat pumps installed in a single unoccupied research house in Knoxville, TN, a mixed-humid climate. One system provided space conditioning for the upstairs, while the other unit provided space conditioning for the downstairs. Occupancy was simulated by operating the lights, shower, appliances, other plug loads, etc. to simulate the sensible and latent loads imposed on the building space by internal electric loads and human occupants according to the Building America Research Benchmark (2008). The seasonal efficiency and energy use of the units are calculated. Annual energy use is compared to that of the single speed minimum efficiency HPs tested in the same house previously. Sizing of the units relative to the measured building load and manual J design load calculations is examined. The impact of the unit sizing with regards to indoor comfort is also evaluated.« less

Delamination of Composite Cylinders

NASA Astrophysics Data System (ADS)

Davies, Peter; Carlsson, Leif A.

The delamination resistance of filament wound glass/epoxy cylinders has been characterized for a range of winding angles and fracture mode ratios using beam fracture specimens. The results reveal that the delamination fracture resistance increases with increasing winding angle and mode II (shear) fraction (GΠ/G). It was also found that interlaced fiber bundles in the filament wound cylinder wall acted as effective crack arresters in mode I loading. To examine the sensitivity of delamina-tion damage on the strength of the cylinders, external pressure tests were performed on filament-wound glass/epoxy composite cylinders with artificial defects and impact damage. The results revealed that the cylinder strength was insensitive to the presence of single delaminations but impact damage caused reductions in failure pressure. The insensitivity of the failure pressure to a single delamination is attributed to the absence of buckling of the delaminated sublaminates before the cylinder wall collapsed. The impacted cylinders contained multiple delaminations, which caused local reduction in the compressive load capability and reduction in failure pressure. The response of glass/epoxy cylinders was compared to impacted carbon reinforced cylinders. Carbon/epoxy is more sensitive to damage but retains higher implosion resistance while carbon/PEEK shows the opposite trend.

Finite-element nonlinear transient response computer programs PLATE 1 and CIVM-PLATE 1 for the analysis of panels subjected to impulse or impact loads

NASA Technical Reports Server (NTRS)

Spilker, R. L.; Witmer, E. A.; French, S. E.; Rodal, J. J. A.

1980-01-01

Two computer programs are described for predicting the transient large deflection elastic viscoplastic responses of thin single layer, initially flat unstiffened or integrally stiffened, Kirchhoff-Lov ductile metal panels. The PLATE 1 program pertains to structural responses produced by prescribed externally applied transient loading or prescribed initial velocity distributions. The collision imparted velocity method PLATE 1 program concerns structural responses produced by impact of an idealized nondeformable fragment. Finite elements are used to represent the structure in both programs. Strain hardening and strain rate effects of initially isotropic material are considered.

The breakage behaviour of Aspirin under quasi-static indentation and single particle impact loading: effect of crystallographic anisotropy.

PubMed

Olusanmi, D; Roberts, K J; Ghadiri, M; Ding, Y

2011-06-15

The influence of crystallographic structural anisotropy on the breakage behaviour of Aspirin under impact loading is highlighted. Under both quasi-static testing conditions, using nano-indentation, and dynamic impact tests, Aspirin demonstrates clear anisotropy in its slip and fracture behaviour. During nano-indentation on the (100) and (001) faces, cracks were propagated along the [010] direction. While the hardness was found to be comparatively similar for both these faces, it was observed that slip due to plastic deformation occurred more readily on the (100) than the (001) crystal planes suggesting the former as the preferred slip plane. Furthermore, the fracture toughness on the (001) planes was found to be distinctly lower than that of the (100) planes, indicating the former as the preferred cleavage plane. Observations of the crystal morphology of damaged particles after dynamic impact testing showed that both the chipping and fragmentation of Aspirin mostly occurred via cleavage in a manner consistent with the observed fracture behaviour following nano-indentation. This work highlights the importance of cleavage as a dominant factor underpinning the fracture mechanism of Aspirin under both quasi-static and impact loading conditions. Copyright © 2011 Elsevier B.V. All rights reserved.

Development of an epiphyte indicator of nutrient enrichment ...

EPA Pesticide Factsheets

Metrics of epiphyte load on macrophytes were evaluated for use as quantitative biological indicators for nutrient impacts in estuarine waters, based on review and analysis of the literature on epiphytes and macrophytes, primarily seagrasses, but including some brackish and freshwater rooted macrophyte species. An approach is presented that empirically derives threshold epiphyte loads which are likely to cause specified levels of decrease in macrophyte response metrics such as biomass, shoot density, percent cover, production and growth. Data from 36 studies of 10 macrophyte species were pooled to derive relationships between epiphyte load and -25 and -50% seagrass response levels, which are proposed as the primary basis for establishment of critical threshold values. Given multiple sources of variability in the response data, threshold ranges based on the range of values falling between the median and the 75th quantiles of observations at a given seagrass response level are proposed rather than single, critical point values. Four epiphyte load threshold categories - low, moderate, high, very high, are proposed. Comparison of values of epiphyte loads associated with 25 and 50% reductions in light to macrophytes suggest that the threshold ranges are realistic both in terms of the principle mechanism of impact to macrophytes and in terms of the magnitude of resultant impacts expressed by the macrophytes. Some variability in response levels was observed among

System ID modern control algorithms for active aerodynamic load control and impact on gearbox loading.

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

Berg, Jonathan Charles; Halse, Chris; Crowther, Ashley

2010-06-01

Prior work on active aerodynamic load control (AALC) of wind turbine blades has demonstrated that appropriate use of this technology has the potential to yield significant reductions in blade loads, leading to a decrease in wind cost of energy. While the general concept of AALC is usually discussed in the context of multiple sensors and active control devices (such as flaps) distributed over the length of the blade, most work to date has been limited to consideration of a single control device per blade with very basic Proportional Derivative controllers, due to limitations in the aeroservoelastic codes used to performmore » turbine simulations. This work utilizes a new aeroservoelastic code developed at Delft University of Technology to model the NREL/Upwind 5 MW wind turbine to investigate the relative advantage of utilizing multiple-device AALC. System identification techniques are used to identify the frequencies and shapes of turbine vibration modes, and these are used with modern control techniques to develop both Single-Input Single-Output (SISO) and Multiple-Input Multiple-Output (MIMO) LQR flap controllers. Comparison of simulation results with these controllers shows that the MIMO controller does yield some improvement over the SISO controller in fatigue load reduction, but additional improvement is possible with further refinement. In addition, a preliminary investigation shows that AALC has the potential to reduce off-axis gearbox loads, leading to reduced gearbox bearing fatigue damage and improved lifetimes.« less

Multiple versus single virus respiratory infections: viral load and clinical disease severity in hospitalized children

PubMed Central

Martin, Emily T.; Kuypers, Jane; Wald, Anna; Englund, Janet A.

2011-01-01

Please cite this paper as: Martin et al. (2012) Multiple versus single virus respiratory infections: viral load and clinical disease severity in hospitalized children. Influenza and Other Respiratory Viruses 6(1), 71–77. Background  Molecular testing for viral pathogens has resulted in increasing detection of multiple viruses in respiratory secretions of ill children. The clinical impact of multiple virus infections on clinical presentation and outcome is unclear. Objectives  To compare clinical characteristics and viral load between children with multiple virus versus single virus illnesses. Patients/methods  Eight hundred and ninety‐three residual nasal wash samples from children treated for respiratory illness at Children’s Hospital, Seattle, from September 2003 to September 2004 were evaluated by quantitative PCR for respiratory syncytial virus (RSV), human metapneumovirus (hMPV), influenza (Flu), parainfluenza, adenoviruses, and coronaviruses (CoV). Illness severity and patient characteristics were abstracted from medical charts. Results  Coinfections were identified in 103 (18%) of 566 virus‐positive samples. Adenovirus was most commonly detected in coinfections (52%), followed by CoV (50%). Illnesses with a single virus had increased risk of oxygen requirement (P = 0·02), extended hospital stays (P = 0·002), and admissions to the inpatient (P = 0·02) or intensive care units (P = 0·04). For Adv and PIV‐1, multiple virus illnesses had a significantly lower viral load (log10 copies/ml) than single virus illnesses (4·2 versus 5·6, P = 0·007 and 4·2 versus 6·9, P < 0·001, respectively). RSV, Flu‐A, PIV‐3, and hMPV viral loads were consistently high whether or not another virus was detected. Conclusions  Illnesses with multiple virus detections were correlated with less severe disease. The relationship between viral load and multiple virus infections was virus specific, and this may serve as a way to differentiate viruses in multiple virus infections. PMID:21668660

Investigation of Fundamental Processes and Crystal-Level Defect Structures in Metal-Loaded High-Explosive Materials under Dynamic Thermo-Mechanical Loads and their Relationships to Impact Survivability of Munitions (Thrust 4, Topic J)

DTIC Science & Technology

2014-06-01

to better represent the interactions at high compression . Monodisperse systems containing 64, 128, and 256 backbone carbon atoms were studied...was observed that for the sensitive orientation only elastic compression occurred, leading to the propagation of a single wave through the material...whereas for the insensitive direction elastic compression at and immediately behind the shock front was followed by inelastic deformation, leading to

Ultrafast dynamic response of single crystal β-HMX

NASA Astrophysics Data System (ADS)

Zaug, Joseph M.; Armstrong, Michael R.; Crowhurst, Jonathan C.; Radousky, Harry B.; Ferranti, Louis; Swan, Raymond; Gross, Rick; Teslich, Nick E.; Wall, Mark A.; Austin, Ryan A.; Fried, Laurence E.

2017-01-01

We report results from ultrafast compression experiments conducted on β-HMX single crystals. Results consist of nominally 12 picosecond time-resolved wave profile data, (ultrafast time domain interferometry -TDI measurements), that were analyzed to determine high-velocity wave speeds as a function of piston velocity. TDI results are used to validate calculations of anisotropic stress-strain behavior of shocked loaded energetic materials. Our previous results derived using a 350 ps duration compression drive revealed anisotropic elastic wave response in single crystal β-HMX from (110) and (010) impact planes. Here we present results using a 1.05 ns duration compression drive with a 950 ps interferometry window to extend knowledge of the anisotropic dynamic response of β-HMX within eight microns of the initial impact plane. We observe two distinct wave profiles from (010) and three wave profiles from (010) impact planes. The (110) impact plane wave speeds typically exceed (010) impact plane wave speeds at the same piston velocities. The development of multiple hydrodynamic wave profiles begins at 20 GPa for the (110) impact plane and 28 GPa for the (10) impact plane. We compare our ultrafast TDI results with previous gun and plate impact results on β-HMX and PBX9501.

On the shock response of Pisum Sativum (a.k.a the Common Pea)

NASA Astrophysics Data System (ADS)

Leighs, James; Hazell, Paul; Appleby-Thomas, Gareth

2011-06-01

The high strain-rate response of biological and organic structures is of interest to numerous fields ranging from the food industry (dynamic pasteurisation) to astrobiology (e.g. the theory of panspermia, which suggests that planets could be `seeded' with life `piggy-backing' of interplanetary bodies). Consequently, knowledge of the damage mechanisms and viability of shocked organic material is of paramount importance. In this study a single-stage gas-gun has been employed to subject samples of Pisum Sativum (the Common Pea) to semi-planar shock loading, corresponding to impact pressures of up to c.3 GPa. The experimental approach adopted is discussed along with results from Manganin gauges embedded in the target capsule which show the loading history. Further, the viability of the shock-loaded peas was investigated via attempts at germination. Finally, microscopic examination of the impacted specimens allowed a qualitative assessment of damage mechanisms to be made.

A multi-particle crushing apparatus for studying rock fragmentation due to repeated impacts

NASA Astrophysics Data System (ADS)

Huang, S.; Mohanty, B.; Xia, K.

2017-12-01

Rock crushing is a common process in mining and related operations. Although a number of particle crushing tests have been proposed in the literature, most of them are concerned with single-particle crushing, i.e., a single rock sample is crushed in each test. Considering the realistic scenario in crushers where many fragments are involved, a laboratory crushing apparatus is developed in this study. This device consists of a Hopkinson pressure bar system and a piston-holder system. The Hopkinson pressure bar system is used to apply calibrated dynamic loads to the piston-holder system, and the piston-holder system is used to hold rock samples and to recover fragments for subsequent particle size analysis. The rock samples are subjected to three to seven impacts under three impact velocities (2.2, 3.8, and 5.0 m/s), with the feed size of the rock particle samples limited between 9.5 and 12.7 mm. Several key parameters are determined from this test, including particle size distribution parameters, impact velocity, loading pressure, and total work. The results show that the total work correlates well with resulting fragmentation size distribution, and the apparatus provides a useful tool for studying the mechanism of crushing, which further provides guidelines for the design of commercial crushers.

An In Vivo Lapine Model for Impact-Induced Injury and Osteoarthritic Degeneration of Articular Cartilage

PubMed Central

Alexander, Peter G.; McCarron, Jesse A.; Levine, Matthew J.; Melvin, Gary M.; Murray, Patrick J.; Manner, Paul A.

2012-01-01

Objective: In this study, we applied a spring-loaded impactor to deliver traumatic forces to articular cartilage in vivo. Based on our recent finding that a 0.28-J impact induces maximal catabolic response in adult bovine articular cartilage in vitro using this device, we hypothesize that this impact will induce the formation of a focal osteoarthritic defect in vivo. Design: The femoral condyle of New Zealand White rabbits was exposed and one of the following procedures performed: 0.28 J impact, anterior cruciate ligament transection, articular surface grooving, or no joint or cartilage destruction (control). After 24 hours, 4 weeks, or 12 weeks (n = 3 for each time point), wounds were localized with India ink, and tissue samples were collected and characterized histomorphometrically with Safranin O/Fast green staining and Hoechst 33342 nuclear staining for cell vitality. Results: The spring-loaded device delivered reproducible impacts with the following characteristics: impact area of 1.39 ± 0.11 mm2, calculated load of 326 ± 47.3 MPa, time-to-peak of 0.32 ± 0.03 ms, and an estimated maximal displacement of 25.1% ± 4.5% at the tip apex. The impact resulted in immediate cartilage fissuring and cell loss in the surface and intermediate zones, and it induced the formation of a focal lesion at 12 weeks. The degeneration was defined and appeared more slowly than after anterior cruciate ligament transection, and more pronounced and characteristic than after grooving. Conclusion: A single traumatic 0.28 J impact delivered with this spring-loaded impactor induces focal cartilage degeneration characteristic of osteoarthritis. PMID:26069642

Effect of drug load and plate coating on the particle size distribution of a commercial albuterol metered dose inhaler (MDI) determined using the Andersen and Marple-Miller cascade impactors.

PubMed

Nasr, M M; Ross, D L; Miller, N C

1997-10-01

The purpose of this study is to investigate the effect of drug load, the coating of impactor stages, and the design of cascade impactors on albuterol MDIs particle size distribution measurements. The results of the investigation will be used to explain the "loading effect" recently reported. Particle size distribution parameters of a commercial albuterol MDI were measured using both Andersen (AI) and Marple-Miller (MMI) Cascade Impactors, where plates were either left uncoated or coated with silicone or glycerin. A previously validated HPLC-EC method was used for the assay of albuterol collected by the impactor and in single spray content determinations. Coating impactor collection plates had an impact on measured MMAD and GSD values for single puff measurements but very little or no effect for the multi puff measurements. Due to particle bounce, the percent of albuterol fine particles deposited in the filter and impactor finer stages (< 1.10 microns in AI and < 1.25 microns in MMI) in uncoated single puff experiments was much higher in comparison to either coated single puff or multi-puff (coated and uncoated) measurements. Evaluation of drug load and plate coating are necessary to determine whether observed particle size distributions are representative of the generated aerosol or are the result of particle bounce and reentrainment. In order to minimize particle bounce, especially for single puff determinations, it may be useful to apply a thin layer of a sticky coating agent to the surfaces of impactor plates.

Dynamic deformation and fracture of single crystal silicon: Fracture modes, damage laws, and anisotropy

DOE PAGES

Huang, J. Y.; E, J. C.; Huang, J. W.; ...

2016-05-25

Impact fracture of single-crystal Si is critical to long-term reliability of electronic devices and solar cells for its wide use as components or substrates in semiconductor industry. Single-crystal Si is loaded along two different crystallographic directions with a split Hopkinson pressure bar integrated with an in situ x-ray imaging and diffraction system. Bulk stress histories are measured, simultaneously with x-ray phase contrast imaging (XPCI) and Laue diffraction. Damage evolution is quantified with grayscale maps from XPCI. Single-crystal Si exhibits pronounced anisotropy in fracture modes, and thus fracture strengths and damage evolution. For loading along [11¯ 0] and viewing along [001],more » (1¯1¯0)[11¯ 0] cleavage is activated and induces horizontal primary cracks followed by perpendicular wing cracks. However, for loading along [011¯] and viewing along [111], random nucleation and growth of shear and tensile-splitting crack networks lead to catastrophic failure of materials with no cleavage. The primary-wing crack mode leads to a lower characteristic fracture strength due to predamage, but a more concentrated strength distribution, i.e., a higher Weibull modulus, compared to the second loading case. Furthermore, the sequential primary cracking, wing cracking and wing-crack coalescence processes result in a gradual increase of damage with time, deviating from theoretical predictions. Particle size and aspect ratios of fragments are discussed with postmortem fragment analysis, which verifies fracture modes observed in XPCI.« less

Data-Driven Residential Load Modeling and Validation in GridLAB-D

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

Gotseff, Peter; Lundstrom, Blake

Accurately characterizing the impacts of high penetrations of distributed energy resources (DER) on the electric distribution system has driven modeling methods from traditional static snap shots, often representing a critical point in time (e.g., summer peak load), to quasi-static time series (QSTS) simulations capturing all the effects of variable DER, associated controls and hence, impacts on the distribution system over a given time period. Unfortunately, the high time resolution DER source and load data required for model inputs is often scarce or non-existent. This paper presents work performed within the GridLAB-D model environment to synthesize, calibrate, and validate 1-second residentialmore » load models based on measured transformer loads and physics-based models suitable for QSTS electric distribution system modeling. The modeling and validation approach taken was to create a typical GridLAB-D model home that, when replicated to represent multiple diverse houses on a single transformer, creates a statistically similar load to a measured load for a given weather input. The model homes are constructed to represent the range of actual homes on an instrumented transformer: square footage, thermal integrity, heating and cooling system definition as well as realistic occupancy schedules. House model calibration and validation was performed using the distribution transformer load data and corresponding weather. The modeled loads were found to be similar to the measured loads for four evaluation metrics: 1) daily average energy, 2) daily average and standard deviation of power, 3) power spectral density, and 4) load shape.« less

High- and Low-Load Resistance Training: Interpretation and Practical Application of Current Research Findings.

PubMed

Fisher, James; Steele, James; Smith, Dave

2017-03-01

Our current state of knowledge regarding the load (lighter or heavier) lifted in resistance training programmes that will result in 'optimal' strength and hypertrophic adaptations is unclear. Despite this, position stands and recommendations are made based on, we propose, limited evidence to lift heavier weights. Here we discuss the state of evidence on the impact of load and how it, as a single variable, stimulates adaptations to take place and whether evidence for recommending heavier loads is available, well-defined, currently correctly interpreted or has been overlooked. Areas of discussion include electromyography amplitude, in vivo and in vitro methods of measuring hypertrophy, and motor schema and skill acquisition. The present piece clarifies to trainers and trainees the impact of these variables by discussing interpretation of synchronous and sequential motor unit recruitment and revisiting the size principle, poor agreement between whole-muscle cross-sectional area (CSA) and biopsy-determined changes in myofibril CSA, and neural adaptations around task specificity. Our opinion is that the practical implications of being able to self-select external load include reducing the need for specific facility memberships, motivating older persons or those who might be less confident using heavy loads, and allowing people to undertake home- or field-based resistance training intervention strategies that might ultimately improve exercise adherence.

Single Vector Calibration System for Multi-Axis Load Cells and Method for Calibrating a Multi-Axis Load Cell

NASA Technical Reports Server (NTRS)

Parker, Peter A. (Inventor)

2003-01-01

A single vector calibration system is provided which facilitates the calibration of multi-axis load cells, including wind tunnel force balances. The single vector system provides the capability to calibrate a multi-axis load cell using a single directional load, for example loading solely in the gravitational direction. The system manipulates the load cell in three-dimensional space, while keeping the uni-directional calibration load aligned. The use of a single vector calibration load reduces the set-up time for the multi-axis load combinations needed to generate a complete calibration mathematical model. The system also reduces load application inaccuracies caused by the conventional requirement to generate multiple force vectors. The simplicity of the system reduces calibration time and cost, while simultaneously increasing calibration accuracy.

Erosion of tungsten armor after multiple intense transient events in ITER

NASA Astrophysics Data System (ADS)

Bazylev, B. N.; Janeschitz, G.; Landman, I. S.; Pestchanyi, S. E.

2005-03-01

Macroscopic erosion by melt motion is the dominating damage mechanism for tungsten armour under high-heat loads with energy deposition W > 1 MJ/m 2 and τ > 0.1 ms. For ITER divertor armour the results of a fluid dynamics simulation of the melt motion erosion after repetitive stochastically varying plasma heat loads of consecutive disruptions interspaced by ELMs are presented. The heat loads for particular single transient events are numerically simulated using the two-dimensional MHD code FOREV-2D. The whole melt motion is calculated by the fluid dynamics code MEMOS-1.5D. In addition for the ITER dome melt motion erosion of tungsten armour caused by the lateral radiation impact from the plasma shield at the disruption and ELM heat loads is estimated.

Assessment of New Load Schedules for the Machine Calibration of a Force Balance

NASA Technical Reports Server (NTRS)

Ulbrich, N.; Gisler, R.; Kew, R.

2015-01-01

New load schedules for the machine calibration of a six-component force balance are currently being developed and evaluated at the NASA Ames Balance Calibration Laboratory. One of the proposed load schedules is discussed in the paper. It has a total of 2082 points that are distributed across 16 load series. Several criteria were applied to define the load schedule. It was decided, for example, to specify the calibration load set in force balance format as this approach greatly simplifies the definition of the lower and upper bounds of the load schedule. In addition, all loads are assumed to be applied in a calibration machine by using the one-factor-at-a-time approach. At first, all single-component loads are applied in six load series. Then, three two-component load series are applied. They consist of the load pairs (N1, N2), (S1, S2), and (RM, AF). Afterwards, four three-component load series are applied. They consist of the combinations (N1, N2, AF), (S1, S2, AF), (N1, N2, RM), and (S1, S2, RM). In the next step, one four-component load series is applied. It is the load combination (N1, N2, S1, S2). Finally, two five-component load series are applied. They are the load combination (N1, N2, S1, S2, AF) and (N1, N2, S1, S2, RM). The maximum difference between loads of two subsequent data points of the load schedule is limited to 33 % of capacity. This constraint helps avoid unwanted load "jumps" in the load schedule that can have a negative impact on the performance of a calibration machine. Only loadings of the single- and two-component load series are loaded to 100 % of capacity. This approach was selected because it keeps the total number of calibration points to a reasonable limit while still allowing for the application of some of the more complex load combinations. Data from two of NASA's force balances is used to illustrate important characteristics of the proposed 2082-point calibration load schedule.

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

Huang, J. Y.; E, J. C.; Huang, J. W.

Impact fracture of single-crystal Si is critical to long-term reliability of electronic devices and solar cells for its wide use as components or substrates in semiconductor industry. Single-crystal Si is loaded along two different crystallographic directions with a split Hopkinson pressure bar integrated with an in situ x-ray imaging and diffraction system. Bulk stress histories are measured, simultaneously with x-ray phase contrast imaging (XPCI) and Laue diffraction. Damage evolution is quantified with grayscale maps from XPCI. Single-crystal Si exhibits pronounced anisotropy in fracture modes, and thus fracture strengths and damage evolution. For loading along [11¯ 0] and viewing along [001],more » (1¯1¯0)[11¯ 0] cleavage is activated and induces horizontal primary cracks followed by perpendicular wing cracks. However, for loading along [011¯] and viewing along [111], random nucleation and growth of shear and tensile-splitting crack networks lead to catastrophic failure of materials with no cleavage. The primary-wing crack mode leads to a lower characteristic fracture strength due to predamage, but a more concentrated strength distribution, i.e., a higher Weibull modulus, compared to the second loading case. Furthermore, the sequential primary cracking, wing cracking and wing-crack coalescence processes result in a gradual increase of damage with time, deviating from theoretical predictions. Particle size and aspect ratios of fragments are discussed with postmortem fragment analysis, which verifies fracture modes observed in XPCI.« less

Effect of Footwear on Dynamic Stability during Single-leg Jump Landings.

PubMed

Bowser, Bradley J; Rose, William C; McGrath, Robert; Salerno, Jilian; Wallace, Joshua; Davis, Irene S

2017-06-01

Barefoot and minimal footwear running has led to greater interest in the biomechanical effects of different types of footwear. The effect of running footwear on dynamic stability is not well understood. The purpose of this study was to compare dynamic stability and impact loading across 3 footwear conditions; barefoot, minimal footwear and standard running shoes. 25 injury free runners (21 male, 4 female) completed 5 single-leg jump landings in each footwear condition. Dynamic stability was assessed using the dynamic postural stability index and its directional components (mediolateral, anteroposterior, vertical). Peak vertical ground reaction force and vertical loadrates were also compared across footwear conditions. Dynamic stability was dependent on footwear type for all stability indices (ANOVA, p<0.05). Post-hoc tests showed dynamic stability was greater when barefoot than in running shoes for each stability index (p<0.02) and greater than minimal footwear for the anteroposterior stability index (p<0.01). Peak vertical force and average loadrates were both dependent on footwear (p≤0.05). Dynamic stability, peak vertical force, and average loadrates during single-leg jump landings appear to be affected by footwear type. The results suggest greater dynamic stability and lower impact loading when landing barefoot or in minimal footwear. © Georg Thieme Verlag KG Stuttgart · New York.

Using single-step genomic best linear unbiased predictor to enhance the mitigation of seasonal losses due to heat stress in pigs.

PubMed

Fragomeni, B O; Lourenco, D A L; Tsuruta, S; Bradford, H L; Gray, K A; Huang, Y; Misztal, I

2016-12-01

The purposes of this study were to analyze the impact of seasonal losses due to heat stress in pigs from different breeds raised in different environments and to evaluate the accuracy improvement from adding genomic information to genetic evaluations. Data were available for 2 different swine populations: purebred Duroc animals raised in Texas and North Carolina and commercial crosses of Duroc and F females (Landrace × Large White) raised in Missouri and North Carolina; pedigrees provided links for animals from different states. Pedigree information was available for 553,442 animals, of which 8,232 pure breeds were genotyped. Traits were BW at 170 d for purebred animals and HCW for crossbred animals. Analyses were done with an animal model as either single- or 2-trait models using phenotypes measured in different states as separate traits. Additionally, reaction norm models were fitted for 1 or 2 traits using heat load index as a covariable. Heat load was calculated as temperature-humidity index greater than 70 and was averaged over 30 d prior to data collection. Variance components were estimated with average information REML, and EBV and genomic EBV (GEBV) with BLUP or single-step genomic BLUP (ssGBLUP). Validation was assessed for 146 genotyped sires with progeny in the last generation. Accuracy was calculated as a correlation between EBV and GEBV using reduced data (all animals, except the last generation) and using complete data. Heritability estimates for purebred animals were similar across states (varying from 0.23 to 0.26), and reaction norm models did not show evidence of a heat stress effect. Genetic correlations between states for heat loads were always strong (>0.91). For crossbred animals, no differences in heritability were found in single- or 2-trait analysis (from 0.17 to 0.18), and genetic correlations between states were moderate (0.43). In the reaction norm for crossbreeds, heritabilities ranged from 0.15 to 0.30 and genetic correlations between heat loads were as weak as 0.36, with heat load ranging from 0 to 12. Accuracies with ssGBLUP were, on average, 25% greater than with BLUP. Accuracies were greater in 2-trait reaction norm models and at extreme heat load values. Impacts of seasonality are evident only for crossbred animals. Genomic information can help producers mitigate heat stress in swine by identifying superior sires that are more resistant to heat stress.

Static and Dynamic Compaction of CL-20 Powders

NASA Astrophysics Data System (ADS)

Cooper, Marcia; Brundage, Aaron; Dudley, Evan

2009-06-01

Hexanitrohexaazaisowurtzitane (CL-20) powders were compacted under quasi-static and dynamic loading conditions. A uniaxial compression apparatus quasi-statically compressed the powders to 90% theoretical maximum density with applied stresses up to 0.5 GPa. Dynamic compaction measurements using low-density pressings (62-70% theoretical maximum density) were obtained in a single-stage gas gun at impact velocities between 0.17-0.70 km/s. Experiments were conducted in a reverse ballistic arrangement in which the CL-20 ladened projectile impacted a target consisting of an aluminized window. VISAR-measured particle velocities at the explosive-window interface determined the shock Hugoniot states for pressures up to 0.9 GPa. The powder compaction behavior is found to be stiffer under dynamic loading than under quasi-static loading. Additional gas gun tests were conducted in which the low-density CL-20 pressings were confined within a target cup by the aluminized window. This arrangement enabled temporal measurement of the transmitted wave profiles in which elastic wave precursors were observed.

Cells Respond to Distinct Nanoparticle Properties with Multiple Strategies As Revealed by Single-Cell RNA-Seq

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

Mitchell, Hugh D.; Markillie, Lye Meng; Chrisler, William B.

The impact of distinct nanoparticle (NP) properties on cellular response and ultimately human health is unclear. This gap is partially due to experimental difficulties in achieving uniform NP loads in the studied cells, creating heterogeneous populations with some cells “overloaded” while other cells are loaded with few or no NPs. Yet gene expression studies have been conducted in the population as a whole, identifying generic responses, while missing unique responses due to signal averaging across many cells, each carrying different loads. Here we applied single-cell RNA-Seq to alveolar epithelial cells carrying defined loads of aminated or carboxylated quantum dots (QDs),more » showing higher or lower toxicity, respectively. Interestingly, cells carrying lower loads responded with multiple strategies, mostly with upregulated processes, which were nonetheless coherent and unique to each QD type. In contrast, cells carrying higher loads responded more uniformly, with mostly downregulated processes that were shared across QD types. Strategies unique to aminated QDs showed strong upregulation of stress responses, coupled in some cases with regulation of cell cycle, protein synthesis and organelle activities. In contrast, strategies unique to carboxylated QDs showed upregulation of DNA repair and RNA activities, and decreased regulation of cell division, coupled in some cases with upregulation of stress responses and ATP related functions. Together, our studies suggest scenarios where higher NP loads lock cells into uniform responses, mostly shutdown of cellular processes, whereas lower loads allow for unique responses to each NP type that are more diversified, proactive defenses or repairs of the NP insults.« less

Hypervelocity impact response of aluminum multi-wall structures

NASA Technical Reports Server (NTRS)

Schonberg, William P.; Bean, Alan J.

1991-01-01

The results of an investigation in which the perforation resistance of aluminum multiwall structures is analyzed under a variety of hypervelocity impact loading conditions are presented. A comparative analysis of the impact damage in structural systems with two or more bumpers and the damage in single-bumper systems of similar weight is performed to determine the advantages and disadvantages of employing more than one bumper in structural wall systems for long-duration spacecraft. A significant increase in protection against perforation by hypervelocity projectiles can be achieved if a single bumper is replaced by two bumpers of similar weight while the total wall spacing is kept constant. It is found that increasing the number of bumpers beyond two while keeping the total stand-off distance constant does not result in a substantial increase in protection over that offered by two bumpers of similar weight.

Continuation Power Flow Analysis for PV Integration Studies at Distribution Feeders

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

Wang, Jiyu; Zhu, Xiangqi; Lubkeman, David L.

2017-10-30

This paper presents a method for conducting continuation power flow simulation on high-solar penetration distribution feeders. A load disaggregation method is developed to disaggregate the daily feeder load profiles collected in substations down to each load node, where the electricity consumption of residential houses and commercial buildings are modeled using actual data collected from single family houses and commercial buildings. This allows the modeling of power flow and voltage profile along a distribution feeder on a continuing fashion for a 24- hour period at minute-by-minute resolution. By separating the feeder into load zones based on the distance between the loadmore » node and the feeder head, we studied the impact of PV penetration on distribution grid operation in different seasons and under different weather conditions for different PV placements.« less

Wellbeing perception and the impact on external training output among elite soccer players.

PubMed

Malone, Shane; Owen, Adam; Newton, Matt; Mendes, Bruno; Tiernan, Leo; Hughes, Brian; Collins, Kieran

2018-01-01

The objective of the investigation was to observe the impact of player wellbeing on the training output of elite soccer players. Prospective cohort design. Forty-eight soccer players (age: 25.3±3.1years; height: 183±7cm; mass: 72±7kg) were involved in this single season observational study across two teams. Each morning, pre-training, players completed customised perceived wellbeing questionnaires. Global positioning technology devices were used to measure external load (total distance, total high-speed running distance, high speed running, player load, player load slow, maximal velocity, maximal velocity exposures). Players reported ratings of perceived exertion using the modified Borg CR-10 scale. Integrated training load ratios were also analysed for total distance:RPE, total high speed distance:RPE player load:RPE and player load slow:RPE respectively. Mixed-effect linear models revealed significant effects of wellbeing Z-score on external and integrated training load measures. A wellbeing Z-score of -1 corresponded to a -18±2m (-3.5±1.1%), 4±1m (-4.9±2.1%,) 0.9±0.1kmh -1 (-3.1±2.1%), 1±1 (-4.6±2.9%), 25±3AU (-4.9±3.1%) and 11±0.5AU (-8.9±2.9%) reduction in total high speed distance, high speed distance, maximal velocity, maximal velocity exposures, player load and player load slow respectively. A reduction in wellbeing impacted external:internal training load ratios and resulted in -0.49±0.12mmin -1 , -1.20±0.08mmin -1 ,-0.02±0.01AUmin -1 in total distance:RPE, total high speed distance:RPE and player load slow:RPE respectively. The results suggest that systematic monitoring of player wellbeing within soccer cohorts can provide coaches with information about the training output that can be expected from individual players during a training session. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Comparison of cyclic and impact-based reference point indentation measurements in human cadaveric tibia.

PubMed

Karim, Lamya; Van Vliet, Miranda; Bouxsein, Mary L

2018-01-01

Although low bone mineral density (BMD) is strongly associated with increased fracture risk, up to 50% of those who suffer fractures are not detected as high-risk patients by BMD testing. Thus, new approaches may improve identification of those at increased risk for fracture by in vivo assessment of altered bone tissue properties, which may contribute to skeletal fragility. Recently developed reference point indentation (RPI) allows for assessment of cortical bone indentation properties in vivo using devices that apply cyclic loading or impact loading, but there is little information available to assist with interpretation of RPI measurements. Our goals were to use human cadaveric tibia to determine: 1) the associations between RPI variables, cortical bone density, and morphology; 2) the association between variables obtained from RPI systems using cyclic, slow loading versus a single impact load; and 3) age-related differences in RPI variables. We obtained 20 human tibia and femur pairs from female donors (53-97years), measured total hip BMD using dual-energy X-ray absorptiometry, assessed tibial cortical microarchitecture using high-resolution peripheral quantitative computed tomography (HR-pQCT), and assessed cortical bone indentation properties at the mid-tibial diaphysis using both the cyclic and impact-based RPI systems (Biodent and Osteoprobe, respectively, Active Life Scientific, Santa Barbara, CA). We found a few weak associations between RPI variables, BMD, and cortical geometry; a few weak associations between measurements obtained by the two RPI systems; and no age-related differences in RPI variables. Our findings indicate that in cadaveric tibia from older women RPI measurements are largely independent of age, femoral BMD, and cortical geometry. Furthermore, measurements from the cyclic and impact loading RPI devices are weakly related to each other, indicating that each device reflects different aspects of cortical bone indentation properties. Copyright © 2016. Published by Elsevier Inc.

Spall behaviour of single crystal aluminium at three principal orientations

NASA Astrophysics Data System (ADS)

Owen, G. D.; Chapman, D. J.; Whiteman, G.; Stirk, S. M.; Millett, J. C. F.; Johnson, S.

2017-10-01

A series of plate impact experiments have been conducted to study the spall strength of the three principal crystallographic orientations of single crystal aluminium ([100], [110] and, [111]) and ultra-pure polycrystalline aluminium. The samples have been shock loaded at two impact stresses (4 GPa and 10 GPa). Significant differences have been observed in the elastic behaviour, the pullback velocities, and the general shape of the wave profiles, which can be accounted for by considerations of the microscale homogeneity, the dislocation density, and the absence of grain boundaries in the single crystal materials. The data have shown that there is a consistent order of spall strength measured for the four sample materials. The [111] orientation has the largest spall strength and elastic limit, followed closely by [110], [100], and then the polycrystalline material. This order is consistent with both quasi-static data and geometrical consideration of Schmid factors.

Impact of loaded sit-to-stand exercises at different speeds on the physiological cost of walking in children with spastic diplegia: A single-blind randomized clinical trial.

PubMed

Kusumoto, Yasuaki; Nitta, Osamu; Takaki, Kenji

2016-10-01

In the present study, we aimed to determine whether similarly loaded sit-to-stand exercises at different speeds improve the physiological cost of walking in children with spastic diplegia. This design was a single-blind randomized clinical trial. Sixteen children with cerebral palsy (CP), aged 12-18 years, with a diagnosis of spastic diplegia, were randomly allocated to a slow loaded sit-to-stand exercise group (n=8) and a self-paced loaded sit-to-stand exercise group (n=8). Loaded sit-to-stand exercise was conducted at home for 15min, 4 sets per day, 3-4days per week, for 6 weeks. The patients were evaluated immediately before the intervention and after the training. Lower limb muscle strength using a hand-held dynamometer, selective voluntary motor control using SCALE, 6-min walk distance (6MWD), and Physiological Cost Index (PCI) were measured. The 6MWD showed a significant difference before and after intervention. PCI showed a significant difference between the two groups and the two time points. 6MWD and the PCI improved after intervention in the slow sit-to-stand exercise group. Compared to loaded sit-to-stand exercise at a regular speed, slow low-loaded sit-to-stand exercise improved the 6MWD and PCI in children with CP, suggesting that this decrease in speed during exercise improves the physiological cost of walking in these children. Copyright © 2016 Elsevier Ltd. All rights reserved.

Structural Dynamic Behavior of Wind Turbines

NASA Technical Reports Server (NTRS)

Thresher, Robert W.; Mirandy, Louis P.; Carne, Thomas G.; Lobitz, Donald W.; James, George H. III

2009-01-01

The structural dynamicist s areas of responsibility require interaction with most other members of the wind turbine project team. These responsibilities are to predict structural loads and deflections that will occur over the lifetime of the machine, ensure favorable dynamic responses through appropriate design and operational procedures, evaluate potential design improvements for their impact on dynamic loads and stability, and correlate load and control test data with design predictions. Load prediction has been a major concern in wind turbine designs to date, and it is perhaps the single most important task faced by the structural dynamics engineer. However, even if we were able to predict all loads perfectly, this in itself would not lead to an economic system. Reduction of dynamic loads, not merely a "design to loads" policy, is required to achieve a cost-effective design. The two processes of load prediction and structural design are highly interactive: loads and deflections must be known before designers and stress analysts can perform structural sizing, which in turn influences the loads through changes in stiffness and mass. Structural design identifies "hot spots" (local areas of high stress) that would benefit most from dynamic load alleviation. Convergence of this cycle leads to a turbine structure that is neither under-designed (which may result in structural failure), nor over-designed (which will lead to excessive weight and cost).

Influences of Atmospheric Stability State on Wind Turbine Aerodynamic Loadings

NASA Astrophysics Data System (ADS)

Vijayakumar, Ganesh; Lavely, Adam; Brasseur, James; Paterson, Eric; Kinzel, Michael

2011-11-01

Wind turbine power and loadings are influenced by the structure of atmospheric turbulence and thus on the stability state of the atmosphere. Statistical differences in loadings with atmospheric stability could impact controls, blade design, etc. Large-eddy simulation (LES) of the neutral and moderately convective atmospheric boundary layer (NBL, MCBL) are used as inflow to the NREL FAST advanced blade-element momentum theory code to predict wind turbine rotor power, sectional lift and drag, blade bending moments and shaft torque. Using horizontal homogeneity, we combine time and ensemble averages to obtain converged statistics equivalent to ``infinite'' time averages over a single turbine. The MCBL required longer effective time periods to obtain converged statistics than the NBL. Variances and correlation coefficients among wind velocities, turbine power and blade loadings were higher in the MCBL than the NBL. We conclude that the stability state of the ABL strongly influences wind turbine performance. Supported by NSF and DOE.

Cells respond to distinct nanoparticle properties with multiple strategies as revealed by single-cell RNA-Seq

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

Mitchell, Hugh D.; Markillie, Lye Meng; Chrisler, William B.

The impact of distinct nanoparticle (NP) properties on cellular response and ultimately human health is unclear. This gap is partially due to experimental difficulties in achieving uniform NP loads in the studied cells, creating heterogeneous populations with some cells “overloaded” while other cells are loaded with few or no NPs. Yet gene expression studies have been conducted in the population as a whole, identifying generic responses, while missing unique responses due to signal averaging across many cells, each carrying different loads. In this paper, we applied single-cell RNA-Seq to alveolar epithelial cells carrying defined loads of aminated or carboxylated quantummore » dots (QDs), showing higher or lower toxicity, respectively. Interestingly, cells carrying lower loads responded with multiple strategies, mostly with up-regulated processes, which were nonetheless coherent and unique to each QD type. In contrast, cells carrying higher loads responded more uniformly, with mostly down-regulated processes that were shared across QD types. Strategies unique to aminated QDs showed strong up-regulation of stress responses, coupled in some cases with regulation of cell cycle, protein synthesis, and organelle activities. In contrast, strategies unique to carboxylated QDs showed up-regulation of DNA repair and RNA activities and decreased regulation of cell division, coupled in some cases with up-regulation of stress responses and ATP-related functions. Finally, together, our studies suggest scenarios where higher NP loads lock cells into uniform responses, mostly shutdown of cellular processes, whereas lower loads allow for unique responses to each NP type that are more diversified proactive defenses or repairs of the NP insults.« less

Cells respond to distinct nanoparticle properties with multiple strategies as revealed by single-cell RNA-Seq

DOE PAGES

Mitchell, Hugh D.; Markillie, Lye Meng; Chrisler, William B.; ...

2016-10-27

The impact of distinct nanoparticle (NP) properties on cellular response and ultimately human health is unclear. This gap is partially due to experimental difficulties in achieving uniform NP loads in the studied cells, creating heterogeneous populations with some cells “overloaded” while other cells are loaded with few or no NPs. Yet gene expression studies have been conducted in the population as a whole, identifying generic responses, while missing unique responses due to signal averaging across many cells, each carrying different loads. In this paper, we applied single-cell RNA-Seq to alveolar epithelial cells carrying defined loads of aminated or carboxylated quantummore » dots (QDs), showing higher or lower toxicity, respectively. Interestingly, cells carrying lower loads responded with multiple strategies, mostly with up-regulated processes, which were nonetheless coherent and unique to each QD type. In contrast, cells carrying higher loads responded more uniformly, with mostly down-regulated processes that were shared across QD types. Strategies unique to aminated QDs showed strong up-regulation of stress responses, coupled in some cases with regulation of cell cycle, protein synthesis, and organelle activities. In contrast, strategies unique to carboxylated QDs showed up-regulation of DNA repair and RNA activities and decreased regulation of cell division, coupled in some cases with up-regulation of stress responses and ATP-related functions. Finally, together, our studies suggest scenarios where higher NP loads lock cells into uniform responses, mostly shutdown of cellular processes, whereas lower loads allow for unique responses to each NP type that are more diversified proactive defenses or repairs of the NP insults.« less

30 CFR 77.905 - Connection of single-phase loads.

Code of Federal Regulations, 2012 CFR

2012-07-01

... COAL MINES Low- and Medium-Voltage Alternating Current Circuits § 77.905 Connection of single-phase loads. Single-phase loads shall be connected phase-to-phase in resistance grounded systems. ...

30 CFR 77.905 - Connection of single-phase loads.

Code of Federal Regulations, 2014 CFR

2014-07-01

... COAL MINES Low- and Medium-Voltage Alternating Current Circuits § 77.905 Connection of single-phase loads. Single-phase loads shall be connected phase-to-phase in resistance grounded systems. ...

30 CFR 77.905 - Connection of single-phase loads.

Code of Federal Regulations, 2013 CFR

2013-07-01

... COAL MINES Low- and Medium-Voltage Alternating Current Circuits § 77.905 Connection of single-phase loads. Single-phase loads shall be connected phase-to-phase in resistance grounded systems. ...

30 CFR 77.806 - Connection of single-phase loads.

Code of Federal Regulations, 2010 CFR

2010-07-01

... COAL MINES Surface High-Voltage Distribution § 77.806 Connection of single-phase loads. Single-phase loads, such as transformer primaries, shall be connected phase to phase in resistance grounded systems. ...

Double-Row Capsulolabral Repair Increases Load to Failure and Decreases Excessive Motion.

PubMed

McDonald, Lucas S; Thompson, Matthew; Altchek, David W; McGarry, Michelle H; Lee, Thay Q; Rocchi, Vanna J; Dines, Joshua S

2016-11-01

Using a cadaver shoulder instability model and load-testing device, we compared biomechanical characteristics of double-row and single-row capsulolabral repairs. We hypothesized a greater reduction in glenohumeral motion and translation and a higher load to failure in a mattress double-row capsulolabral repair than in a single-row repair. In 6 matched pairs of cadaveric shoulders, a capsulolabral injury was created. One shoulder was repaired with a single-row technique, and the other with a double-row mattress technique. Rotational range of motion, anterior-inferior translation, and humeral head kinematics were measured. Load-to-failure testing measured stiffness, yield load, deformation at yield load, energy absorbed at yield load, load to failure, deformation at ultimate load, and energy absorbed at ultimate load. Double-row repair significantly decreased external rotation and total range of motion compared with single-row repair. Both repairs decreased anterior-inferior translation compared with the capsulolabral-injured condition, however, no differences existed between repair types. Yield load in the single-row group was 171.3 ± 110.1 N, and in the double-row group it was 216.1 ± 83.1 N (P = .02). Ultimate load to failure in the single-row group was 224.5 ± 121.0 N, and in the double-row group it was 373.9 ± 172.0 N (P = .05). Energy absorbed at ultimate load in the single-row group was 1,745.4 ± 1,462.9 N-mm, and in the double-row group it was 4,649.8 ± 1,930.8 N-mm (P = .02). In cases of capsulolabral disruption, double-row repair techniques may result in decreased shoulder rotational range of motion and improved load-to-failure characteristics. In cases of capsulolabral disruption, repair techniques with double-row mattress repair may provide more secure fixation. Double-row capsulolabral repair decreases shoulder motion and increases load to failure, yield load, and energy absorbed at yield load more than single-row repair. Published by Elsevier Inc.

The Impact of Environmental and Endogenous Damage on Somatic Mutation Load in Human Skin Fibroblasts

PubMed Central

Saini, Natalie; Chan, Kin; Grimm, Sara A.; Dai, Shuangshuang; Fargo, David C.; Kaufmann, William K.; Taylor, Jack A.; Lee, Eunjung; Cortes-Ciriano, Isidro; Park, Peter J.; Schurman, Shepherd H.; Malc, Ewa P.; Mieczkowski, Piotr A.

2016-01-01

Accumulation of somatic changes, due to environmental and endogenous lesions, in the human genome is associated with aging and cancer. Understanding the impacts of these processes on mutagenesis is fundamental to understanding the etiology, and improving the prognosis and prevention of cancers and other genetic diseases. Previous methods relying on either the generation of induced pluripotent stem cells, or sequencing of single-cell genomes were inherently error-prone and did not allow independent validation of the mutations. In the current study we eliminated these potential sources of error by high coverage genome sequencing of single-cell derived clonal fibroblast lineages, obtained after minimal propagation in culture, prepared from skin biopsies of two healthy adult humans. We report here accurate measurement of genome-wide magnitude and spectra of mutations accrued in skin fibroblasts of healthy adult humans. We found that every cell contains at least one chromosomal rearrangement and 600–13,000 base substitutions. The spectra and correlation of base substitutions with epigenomic features resemble many cancers. Moreover, because biopsies were taken from body parts differing by sun exposure, we can delineate the precise contributions of environmental and endogenous factors to the accrual of genetic changes within the same individual. We show here that UV-induced and endogenous DNA damage can have a comparable impact on the somatic mutation loads in skin fibroblasts. Trial Registration ClinicalTrials.gov NCT01087307 PMID:27788131

CAD/CAM glass ceramics for single-tooth implant crowns: a finite element analysis.

PubMed

Akça, Kvanç; Cavusoglu, Yeliz; Sagirkaya, Elcin; Aybar, Buket; Cehreli, Murat Cavit

2013-12-01

To evaluate the load distribution of CAD/CAM mono-ceramic crowns supported with single-tooth implants in functional area. A 3-dimensional numerical model of a soft tissue-level implant was constructed with cement-retained abutment to support glass ceramic machinable crown. Implant-abutment complex and the retained crown were embedded in a Ø 1.5 × 1.5 cm geometric matrix for evaluation of mechanical behavior of mono-ceramic CAD/CAM aluminosilicate and leucite glass crown materials. Laterally positioned axial load of 300 N was applied on the crowns. Resulting principal stresses in the mono-ceramic crowns were evaluated in relation to different glass ceramic materials. The highest compressive stresses were observed at the cervical region of the buccal aspect of the crowns and were 89.98 and 89.99 MPa, for aluminosilicate and leucite glass ceramics, respectively. The highest tensile stresses were observed at the collar of the lingual part of the crowns and were 24.54 and 25.39 MPa, respectively. Stresses induced upon 300 N static loading of CAD/CAM aluminosalicate and leucite glass ceramics are below the compressive strength of the materials. Impact loads may actuate the progress to end failure of mono-ceramic crowns supported by metallic implant abutments.

Effects of age and loading rate on equine cortical bone failure.

PubMed

Kulin, Robb M; Jiang, Fengchun; Vecchio, Kenneth S

2011-01-01

Although clinical bone fractures occur predominantly under impact loading (as occurs during sporting accidents, falls, high-speed impacts or other catastrophic events), experimentally validated studies on the dynamic fracture behavior of bone, at the loading rates associated with such events, remain limited. In this study, a series of tests were performed on femoral specimens obtained post-mortem from equine donors ranging in age from 6 months to 28 years. Fracture toughness and compressive tests were performed under both quasi-static and dynamic loading conditions in order to determine the effects of loading rate and age on the mechanical behavior of the cortical bone. Fracture toughness experiments were performed using a four-point bending geometry on single and double-notch specimens in order to measure fracture toughness, as well as observe differences in crack initiation between dynamic and quasi-static experiments. Compressive properties were measured on bone loaded parallel and transverse to the osteonal growth direction. Fracture propagation was then analyzed using scanning electron and scanning confocal microscopy to observe the effects of microstructural toughening mechanisms at different strain rates. Specimens from each horse were also analyzed for dry, wet and mineral densities, as well as weight percent mineral, in order to investigate possible influences of composition on mechanical behavior. Results indicate that bone has a higher compressive strength, but lower fracture toughness when tested dynamically as compared to quasi-static experiments. Fracture toughness also tends to decrease with age when measured quasi-statically, but shows little change with age under dynamic loading conditions, where brittle "cleavage-like" fracture behavior dominates. Copyright © 2010 Elsevier Ltd. All rights reserved.

30 CFR 75.905 - Connection of single-phase loads.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Alternating Current Circuits § 75.905 Connection of single-phase loads. [Statutory Provisions] Single-phase... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Connection of single-phase loads. 75.905 Section 75.905 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE...

30 CFR 75.905 - Connection of single-phase loads.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Alternating Current Circuits § 75.905 Connection of single-phase loads. [Statutory Provisions] Single-phase... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Connection of single-phase loads. 75.905 Section 75.905 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE...

A new method for testing pile by single-impact energy and P-S curve

NASA Astrophysics Data System (ADS)

Xu, Zhao-Yong; Duan, Yong-Kang; Wang, Bin; Hu, Yi-Li; Yang, Run-Hai; Xu, Jun; Zhao, Jin-Ming

2004-11-01

By studying the pile-formula and stress-wave methods ( e.g., CASE method), the authors propose a new method for testing piles using the single-impact energy and P-S curves. The vibration and wave figures are recorded, and the dynamic and static displacements are measured by different transducers near the top of piles when the pile is impacted by a heavy hammer or micro-rocket. By observing the transformation coefficient of driving energy (total energy), the consumed energy of wave motion and vibration and so on, the vertical bearing capacity for single pile is measured and calculated. Then, using the vibration wave diagram, the dynamic relation curves between the force ( P) and the displacement ( S) is calculated and the yield points are determined. Using the static-loading test, the dynamic results are checked and the relative constants of dynamic-static P-S curves are determined. Then the subsidence quantity corresponding to the bearing capacity is determined. Moreover, the shaped quality of the pile body can be judged from the formation of P-S curves.

Single-source mechanical loading system produces biaxial stresses in cylinders

NASA Technical Reports Server (NTRS)

Flower, J. F.; Stafford, R. L.

1967-01-01

Single-source mechanical loading system proportions axial-to-hoop tension loads applied to cylindrical specimens. The system consists of hydraulic, pneumatic, and lever arrangements which produce biaxial loading ratios.

Void collapse under distributed dynamic loading near material interfaces

NASA Astrophysics Data System (ADS)

Shpuntova, Galina; Austin, Joanna

2012-11-01

Collapsing voids cause significant damage in diverse applications from biomedicine to underwater propulsion to explosives. While shock-induced void collapse has been studied extensively, less attention has been devoted to stress wave loading, which will occur instead if there are mechanisms for wave attenuation or if the impact velocity is relatively low. A set of dynamic experiments was carried out in a model experimental setup to investigate the effect of acoustic heterogeneities in the surrounding medium on void collapse. Two tissue-surrogate polymer materials of varying acoustic properties were used to create flowfield geometries involving a boundary and a void. A stress wave, generated by projectile impact, triggered void collapse in the gelatinous polymer medium. When the length scales of features in the flow field were on the same order of magnitude as the stress wave length scale, the presence of the boundary was found to affect the void collapse process relative to collapse in the absence of a boundary. This effect was quantified for a range of geometries and impact conditions using a two-color, single-frame particle image velocimetry technique. Research supported by NSF Award #0954769, ``CAREER: Dynamics and damage of void collapse in biological materials under stress wave loading'' with Prof. Henning Winter as Program Manager.

Measurement of peak impact loads differ between accelerometers - Effects of system operating range and sampling rate.

PubMed

Ziebart, Christina; Giangregorio, Lora M; Gibbs, Jenna C; Levine, Iris C; Tung, James; Laing, Andrew C

2017-06-14

A wide variety of accelerometer systems, with differing sensor characteristics, are used to detect impact loading during physical activities. The study examined the effects of system characteristics on measured peak impact loading during a variety of activities by comparing outputs from three separate accelerometer systems, and by assessing the influence of simulated reductions in operating range and sampling rate. Twelve healthy young adults performed seven tasks (vertical jump, box drop, heel drop, and bilateral single leg and lateral jumps) while simultaneously wearing three tri-axial accelerometers including a criterion standard laboratory-grade unit (Endevco 7267A) and two systems primarily used for activity-monitoring (ActiGraph GT3X+, GCDC X6-2mini). Peak acceleration (gmax) was compared across accelerometers, and errors resulting from down-sampling (from 640 to 100Hz) and range-limiting (to ±6g) the criterion standard output were characterized. The Actigraph activity-monitoring accelerometer underestimated gmax by an average of 30.2%; underestimation by the X6-2mini was not significant. Underestimation error was greater for tasks with greater impact magnitudes. gmax was underestimated when the criterion standard signal was down-sampled (by an average of 11%), range limited (by 11%), and by combined down-sampling and range-limiting (by 18%). These effects explained 89% of the variance in gmax error for the Actigraph system. This study illustrates that both the type and intensity of activity should be considered when selecting an accelerometer for characterizing impact events. In addition, caution may be warranted when comparing impact magnitudes from studies that use different accelerometers, and when comparing accelerometer outputs to osteogenic impact thresholds proposed in literature. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Characterization of pediatric wheelchair kinematics and wheelchair tiedown and occupant restraint system loading during rear impact.

PubMed

Fuhrman, Susan I; Karg, Patricia; Bertocci, Gina

2010-04-01

This study characterizes pediatric wheelchair kinematic responses and wheelchair tiedown and occupant restraint system (WTORS) loading during rear impact. It also examines the kinematic and loading effects of wheelchair headrest inclusion in rear impact. In two separate rear-impact test scenarios, identical WC19-compliant manual pediatric wheelchairs were tested using a seated Hybrid III 6-year-old anthropomorphic test device (ATD) to evaluate wheelchair kinematics and WTORS loading. Three wheelchairs included no headrests, and three were equipped with slightly modified wheelchair-mounted headrests. Surrogate WTORS properly secured the wheelchairs; three-point occupant restraints properly restrained the ATD. All tests used a 26km/h, 11g rear-impact test pulse. Headrest presence affected wheelchair kinematics and WTORS loading; headrest-equipped wheelchairs had greater mean seatback deflections, mean peak front and rear tiedown loads and decreased mean lap belt loads. Rear-impact tiedown loads differed from previously measured loads in frontal impact, with comparable tiedown load levels reversed in frontal and rear impacts. The front tiedowns in rear impact had the highest mean peak loads despite lower rear-impact severity. These outcomes have implications for wheelchair and tiedown design, highlighting the need for all four tiedowns to have an equally robust design, and have implications in the development of rear-impact wheelchair transportation safety standards. Copyright 2009 IPEM. Published by Elsevier Ltd. All rights reserved.

Impact of traffic intensity and pavement aggregate size on road dust particles loading

NASA Astrophysics Data System (ADS)

Amato, F.; Pandolfi, M.; Alastuey, A.; Lozano, A.; Contreras González, J.; Querol, X.

2013-10-01

Road dust emissions severely hamper PM10 urban air quality and their burden is expected to increase relatively to primary motor exhaust emissions. Beside the large influence of climate and meteorology, the emission potential varies widely also from one road to another due to numerous factors such as traffic conditions, pavement type and external sources. Nevertheless none of these factors is sufficiently known for a reliable description in emission modelling and for decision making in air quality management. In this study we carried out intensive road dust measurement campaigns in South Spain, with the aim of investigating the relationship between emission potential (i.e. road dust load) and traffic intensity, pavement aggregate size and distance from braking zones. Results indicate that, while no impact from braking activity can be drawn on the bulk road dust mass, an increase in traffic intensity or mean pavement aggregate size clearly reduce the single vehicle emission potential.

Spall Response of Additive Manufactured Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Brown, Andrew; Gregg, Adam; Escobedo, Jp; Hazell, Paul; East, Daniel; Quadir, Zakaria

2017-06-01

Additive manufactured (AM) Ti-6Al-4V was produced via electron beam melting (EBM) and laser melting deposition (LMD) techniques. The dynamic response of AM varieties of common aerospace and infrastructure metals are yet to be fully characterized and compared to their traditionally processed counterparts. Spall damage is one of the primary failure modes in metals subjected to shock loading from high velocity impact. Both EBM and LMD Ti-6Al-4V were shock loaded via flyer-target plate impact using a single-stage light gas gun. Target plates were subjected to pressures just above the spall strength of the material (3-5 GPa) to investigate the early onset of damage nucleation as a function of processing technique and shock orientation with respect to the AM-build direction. Post-mortem characterization of the spall damage and surrounding microstructure was performed using a combination of optical microscopy, scanning electron microscopy, and electron backscatter diffraction.

A High-Rate, Single-Crystal Model for Cyclotrimethylene Trinitramine including Phase Transformations and Plastic Slip

DOE PAGES

Addessio, Francis L.; Luscher, Darby Jon; Cawkwell, Marc Jon; ...

2017-05-14

A continuum model for the high-rate, thermo-mechanical deformation of single-crystal cyclotrimethylene trinitramine (RDX) is developed. The model includes the effects of anisotropy, large deformations, nonlinear thermo-elasticity, phase transformations, and plastic slip. A multiplicative decomposition of the deformation gradient is used. The volumetric elastic component of the deformation is accounted for through a free-energy based equation of state for the low- (α) and high-pressure (γ) polymorphs of RDX. Crystal plasticity is addressed using a phenomenological thermal activation model. The deformation gradient for the phase transformation is based on an approach that has been applied to martensitic transformations. Simulations were conducted andmore » compared to high-rate, impact loading of oriented RDX single crystals. The simulations considered multiple orientations of the crystal relative to the direction of shock loading and multiple sample thicknesses. Thirteen slip systems, which were inferred from indentation and x-ray topography, were used to model the α-polymorph. It is shown that by increasing the number of slip systems from the previously considered number of six (6) to thirteen (13) in the α-polymorph, better comparisons with data may be obtained. Simulations of impact conditions in the vicinity of the α- to γ-polymorph transformation (3.8 GPa) are considered. Eleven of the simulations, which were at pressures below the transformation value (3.0 GPa), were compared to experimental data. Comparison of the model was also made with available data for one experiment above the transformation pressure (4.4 GPa). Also, simulations are provided for a nominal pressure of 7.5 GPa to demonstrate the effect of the transformation kinetics on the deformation of a high-rate plate impact problem.« less

A High-Rate, Single-Crystal Model for Cyclotrimethylene Trinitramine including Phase Transformations and Plastic Slip

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

Addessio, Francis L.; Luscher, Darby Jon; Cawkwell, Marc Jon

A continuum model for the high-rate, thermo-mechanical deformation of single-crystal cyclotrimethylene trinitramine (RDX) is developed. The model includes the effects of anisotropy, large deformations, nonlinear thermo-elasticity, phase transformations, and plastic slip. A multiplicative decomposition of the deformation gradient is used. The volumetric elastic component of the deformation is accounted for through a free-energy based equation of state for the low- (α) and high-pressure (γ) polymorphs of RDX. Crystal plasticity is addressed using a phenomenological thermal activation model. The deformation gradient for the phase transformation is based on an approach that has been applied to martensitic transformations. Simulations were conducted andmore » compared to high-rate, impact loading of oriented RDX single crystals. The simulations considered multiple orientations of the crystal relative to the direction of shock loading and multiple sample thicknesses. Thirteen slip systems, which were inferred from indentation and x-ray topography, were used to model the α-polymorph. It is shown that by increasing the number of slip systems from the previously considered number of six (6) to thirteen (13) in the α-polymorph, better comparisons with data may be obtained. Simulations of impact conditions in the vicinity of the α- to γ-polymorph transformation (3.8 GPa) are considered. Eleven of the simulations, which were at pressures below the transformation value (3.0 GPa), were compared to experimental data. Comparison of the model was also made with available data for one experiment above the transformation pressure (4.4 GPa). Also, simulations are provided for a nominal pressure of 7.5 GPa to demonstrate the effect of the transformation kinetics on the deformation of a high-rate plate impact problem.« less

Microfluidics based manufacture of liposomes simultaneously entrapping hydrophilic and lipophilic drugs.

PubMed

Joshi, Sameer; Hussain, Maryam T; Roces, Carla B; Anderluzzi, Giulia; Kastner, Elisabeth; Salmaso, Stefano; Kirby, Daniel J; Perrie, Yvonne

2016-11-30

Despite the substantial body of research investigating the use of liposomes, niosomes and other bilayer vesicles for drug delivery, the translation of these systems into licensed products remains limited. Indeed, recent shortages in the supply of liposomal products demonstrate the need for new scalable production methods for liposomes. Therefore, the aim of our research has been to consider the application of microfluidics in the manufacture of liposomes containing either or both a water soluble and a lipid soluble drug to promote co-delivery of drugs. For the first time, we demonstrate the entrapment of a hydrophilic and a lipophilic drug (metformin and glipizide respectively) both individually, and in combination, using a scalable microfluidics manufacturing system. In terms of the operating parameters, the choice of solvents, lipid concentration and aqueous:solvent ratio all impact on liposome size with vesicle diameter ranging from ∼90 to 300nm. In terms of drug loading, microfluidics production promoted high loading within ∼100nm vesicles for both the water soluble drug (20-25% of initial amount added) and the bilayer embedded drug (40-42% of initial amount added) with co-loading of the drugs making no impact on entrapment efficacy. However, co-loading of glipizide and metformin within the same liposome formulation did impact on the drug release profiles; in both instances the presence of both drugs in the one formulation promoted faster (up to 2 fold) release compared to liposomes containing a single drug alone. Overall, these results demonstrate the application of microfluidics to prepare liposomal systems incorporating either or both an aqueous soluble drug and a bilayer loaded drug. Copyright © 2016 Elsevier B.V. All rights reserved.

Combined wind turbine fatigue and ultimate load reduction by individual blade control

NASA Astrophysics Data System (ADS)

Han, Y.; Leithead, W. E.

2014-06-01

If each blade of the wind turbine has individual pitch actuator, there is possibility of employing the pitch system to mitigate structural loads through advanced control methods. Previously, considerable reduction of blade lifetime equivalent fatigue loads has been achieved by Individual Blade Control (IBC) and in addition, it has also been shown the potential in blade ultimate loads reduction. However, both fatigue and ultimate loads impact on the design and life of wind turbine blades. In this paper, the design and application of IBC that concurrently reduce both blade fatigue and ultimate loads is investigated. The contributions of blade load spectral components, which are 1P, 2P and edgewise mode from blade in-plane and/or out-of-plane bending moments, are firstly explored. Four different control options for reducing various combinations of these load components are compared. In response to the different spectral peaks of both fatigue and ultimate loads, the controller has been designed so that it can act on different frequency components which vary with wind speed. The performance of the IBC controller on fatigue and ultimate load reduction is assessed by simulating a 5MW exemplar wind turbine. Simulation results show that with a proper selection of controlling inputs at different wind speed, the use of a single combined IBC can achieve satisfactory reduction on both fatigue and ultimate loads.

A novel integrated modelling framework to assess the impacts of climate and socio-economic drivers on land use and water quality.

PubMed

Zessner, Matthias; Schönhart, Martin; Parajka, Juraj; Trautvetter, Helene; Mitter, Hermine; Kirchner, Mathias; Hepp, Gerold; Blaschke, Alfred Paul; Strenn, Birgit; Schmid, Erwin

2017-02-01

Changes in climatic conditions will directly affect the quality and quantity of water resources. Further on, they will affect them indirectly through adaptation in land use which ultimately influences diffuse nutrient emissions to rivers and therefore potentially the compliance with good ecological status according to the EU Water Framework Directive (WFD). We present an integrated impact modelling framework (IIMF) to track and quantify direct and indirect pollution impacts along policy-economy-climate-agriculture-water interfaces. The IIMF is applied to assess impacts of climatic and socio-economic drivers on agricultural land use (crop choices, farming practices and fertilization levels), river flows and the risk for exceedance of environmental quality standards for determination of the ecological water quality status in Austria. This article also presents model interfaces as well as validation procedures and results of single models and the IIMF with respect to observed state variables such as land use, river flow and nutrient river loads. The performance of the IIMF for calculations of river nutrient loads (120 monitoring stations) shows a Nash-Sutcliffe Efficiency of 0.73 for nitrogen and 0.51 for phosphorus. Most problematic is the modelling of phosphorus loads in the alpine catchments dominated by forests and mountainous landscape. About 63% of these catchments show a deviation between modelled and observed loads of 30% and more. In catchments dominated by agricultural production, the performance of the IIMF is much better as only 30% of cropland and 23% of permanent grassland dominated areas have a deviation of >30% between modelled and observed loads. As risk of exceedance of environmental quality standards is mainly recognized in catchments dominated by cropland, the IIMF is well suited for assessing the nutrient component of the WFD ecological status. Copyright © 2016 British Geological Survey, NERC. Published by Elsevier B.V. All rights reserved.

Detection of Micro-Leaks Through Complex Geometries Under Mechanical Load and at Cryogenic Temperature

NASA Technical Reports Server (NTRS)

Rivers, H. Kevin; Sikora, J. G.; Sankaran, S. N.

2001-01-01

Polymer Matrix Composite (PMC) hydrogen tanks have been proposed as an enabling technology for reducing the weight of Single-Stage-to-Orbit reusable launch vehicles where structural mass has a large impact on vehicle performance. A key development issue of these lightweight structures is the leakage of hydrogen through the composite material. The rate of hydrogen leakage can be a function of the material used, method of 6 fabrication used to manufacture the tank, mechanical load the tank must react, internal damage-state of the material, and the temperatures at which the tank must operate. A method for measuring leakage through a geometrically complex structure at cryogenic temperature and under mechanical load was developed, calibrated and used to measure hydrogen leakage through complex X-33 liquid-hydrogen tank structure sections.

Investigation on pitch system loads by means of an integral multi body simulation approach

NASA Astrophysics Data System (ADS)

Berroth, J.; Jacobs, G.; Kroll, T.; Schelenz, R.

2016-09-01

In modern horizontal axis wind turbines the rotor blades are adjusted by three individual pitch systems to control power output. The pitch system consists of either a hydraulic or an electrical actuator, the blade bearing, the rotor blade itself and the control. In case of an electrical drive a gearbox is used to transmit the high torques that are required for blade pitch angle adjustment. In this contribution a new integral multi body simulation approach is presented that enables detailed assessment of dynamic pitch system loads. The simulation results presented are compared and evaluated with measurement data of a 2 MW-class reference wind turbine. Major focus of this contribution is on the assessment of non linear tooth contact behaviour incorporating tooth backlash for the single gear stages and the impact on dynamic pitch system loads.

The impact of pitch counts and days of rest on performance among major-league baseball pitchers.

PubMed

Bradbury, John C; Forman, Sean L

2012-05-01

Although the belief that overuse can harm pitchers is widespread, there exists little evidence to show that the number of pitches thrown and the days of rest affect future performance and injury among adults. The purpose of this study is to quantify the effects of pitches thrown and the days of rest on pitcher performance. We examined performances of major-league baseball starting pitchers from 1988 to 2009 using fractional polynomial multiple regression to estimate the immediate and cumulative impact of pitches thrown and the days of rest on performance, while controlling for other factors that likely affect pitcher effectiveness. Estimates indicate each pitch thrown in the preceding game increased earned run average (ERA) by 0.007 in the following game. Each pitch averaged in the preceding 5 and 10 games increased the ERA by 0.014 and 0.022, respectively. Older pitchers were more sensitive to cumulative pitching loads than younger pitchers were, but they were less affected by pitches thrown in the preceding game. Rest days were weakly associated with performance. In summary, we found that there is a negative relationship between past pitches thrown and future performance that is virtually linear. The impact of the cumulative pitching load is larger than the impact of a single game. Rest days do not appear to have a large impact on performance. This study supports the popular notion that high pitching loads can dampen future performance; however, because the effect is small, pitch-count benchmarks have limited use for maintaining performance and possibly preventing injury.

Application of nonlinear magnetic vibro-impact vibration suppressor and energy harvester

NASA Astrophysics Data System (ADS)

Afsharfard, Aref

2018-01-01

In the present study, application of a single unit vibro-impact system is improved. For this reason, in the so-called "magnetic impact damper" the impact mass is replaced by a permanent magnet, which moves in coil of gap enclosure. In the magnetic impact damper, wasting energy during inelastic contacts of masses and converting energy into electrical energy during the mass movement inside the coil, leads to suppress undesired vibrations. In this study it is shown that the magnetic impact dampers are not only good vibration suppressors but also they can harvest electrical energy. Effect of changing the main parameters of this system including gap size, load resistance and electromagnetic coupling coefficient is studied on the vibratory and energy behavior of the magnetic impact dampers. Finally using several user oriented charts, it is shown that energy-based and vibration-based design considerations can effectively improve application of the discussed vibro-impact system.

Effect of low-speed impact damage and damage location on behavior of composite panels

NASA Technical Reports Server (NTRS)

Jegley, Dawn C.

1992-01-01

The effect of low speed impact damage on the compression and tension strength of thin and moderately thick composite specimens was investigated. Impact speed ranged from 50 to 550 ft./sec., with corresponding impact energies from 0.25 to 30.7 ft. x lb. Impact locations were near the center of the specimen or near a lateral unloaded edge. In this study, thin specimens with only 90 degree and + or - 45 degree plies that were impacted away from the unloaded edge suffered less reduction in load carrying capability because of impact damage than of the same specimens impacted near the unloaded edge. Failure loads of thicker compression loaded specimens with a similar stacking sequence were independent of impact location. Failure loads of thin tension loaded specimens with 0 degree plies was independent of impact location, whereas failure loads of thicker compression loaded specimens with 0 degree plies were dependent upon impact location. A finite element analysis indicated that high axial strains occurred near the unloaded edges of the postbuckled panels. Thus, impacts near the unloaded edge would significantly affect the behavior of the postbuckled panel.

The Effect of Weaving on the Strength of Kevlar KM2 Single Fibers at Different Loading Rates

DTIC Science & Technology

2012-12-01

The Effect of Weaving on the Strength of Kevlar KM2 Single Fibers at Different Loading Rates by Brett Sanborn, Nicole Racine, and Tusit...Ground, MD 21005-5069 ARL-TR-6280 December 2012 The Effect of Weaving on the Strength of Kevlar KM2 Single Fibers at Different Loading Rates...Effect of Weaving on the Strength of Kevlar KM2 Single Fibers at Different Loading Rates 5a. CONTRACT NUMBER 1120-1120-99 5b. GRANT NUMBER 5c

Mechanical Properties of Shock Treated Aluminium Alloy Al 2024-T4

NASA Astrophysics Data System (ADS)

Joshi, K. D.; Mukhopadhyay, A. K.; Dey, A.; Rav, Amit S.; Biswas, S.; Gupta, Satish C.

2012-07-01

Plate impact experiment has been carried out on Al 2024-T4 alloy using single stage gas gun. The dynamic yield strength and spall strength of Al 2024-T4 sample has been determined to be 0.35 GPa and 1.43 GPa, respectively, from free surface velocity history measured using VISAR. The sample recovered after unloading from peak shock pressure of 4.4 GPa along with an unshocked sample is analyzed for mechanical properties using nano-indentation and scanning electron microscopy (SEM). The nano-indentation measurements reveal that the hardness and Young's modulus for unshocked sample remains unchanged as a function of load (equivalently depth), however, the same for shocked sample decreases monotonically with increase of load up to ~40 mN and on further increase of load it remains unchanged, suggesting the (i) increase in hardness of shock loaded sample; (ii) the increase in hardness is limited to certain depth, which in our case is 845.12 ± 43.16 nm.

Intrabilayer 64Cu Labeling of Photoactivatable, Doxorubicin-Loaded Stealth Liposomes.

PubMed

Luo, Dandan; Goel, Shreya; Liu, Hai-Jun; Carter, Kevin A; Jiang, Dawei; Geng, Jumin; Kutyreff, Christopher J; Engle, Jonathan W; Huang, Wei-Chiao; Shao, Shuai; Fang, Chao; Cai, Weibo; Lovell, Jonathan F

2017-12-26

Doxorubicin (Dox)-loaded stealth liposomes (similar to those in clinical use) can incorporate small amounts of porphyrin-phospholipid (PoP) to enable chemophototherapy (CPT). PoP is also an intrinsic and intrabilayer 64 Cu chelator, although how radiolabeling impacts drug delivery has not yet been assessed. Here, we show that 64 Cu can radiolabel the stable bilayer of preformed Dox-loaded PoP liposomes with inclusion of 1% ethanol without inducing drug leakage. Dox-PoP liposomes labeled with intrabilayer copper behaved nearly identically to unlabeled ones in vitro and in vivo with respect to physical parameters, pharmacokinetics, and CPT efficacy. Positron emission tomography and near-infrared fluorescence imaging visualized orthotopic mammary tumors in mice with passive liposome accumulation following administration. A single CPT treatment with 665 nm light (200 J/cm 2 ) strongly inhibited primary tumor growth. Liposomes accumulated in lung metastases, based on NIR imaging. These results establish the feasibility of CPT interventions guided by intrinsic multimodal imaging of Dox-loaded stealth PoP liposomes.

Three-Dimensional, Inelastic Response of Single-Edge Notch Bend Specimens Subjected to Impact Loading

DTIC Science & Technology

1993-08-01

measure the inherent fracture toughness of a material. A thor- ough understanding of the test specimen behavior is a prerequisite to the application of...measured material properties in structural applications . Three- dimensional dynamic analyses are performed for three different specimen configurations...derstanding of the test specimen behavior is a prerequisite to the application of measured ma- terial properties in structural applications . Three

Recruitment of single human low-threshold motor units with increasing loads at different muscle lengths.

PubMed

McNulty, P A; Cresswell, A G

2004-06-01

We investigated the recruitment behaviour of low threshold motor units in flexor digitorum superficialis by altering two biomechanical constraints: the load against which the muscle worked and the initial muscle length. The load was increased using isotonic (low load), loaded dynamic (intermediate load) and isometric (high load) contractions in two studies. The initial muscle position reflected resting muscle length in series A, and a longer length with digit III fully extended in series B. Intramuscular EMG was recorded from 48 single motor units in 10 experiments on five healthy subjects, 21 units in series A and 27 in series B, while subjects performed ramp up, hold and ramp down contractions. Increasing the load on the muscle decreased the force, displacement and firing rate of single motor units at recruitment at shorter muscle lengths (P<0.001, dependent t-test). At longer muscle lengths this recruitment pattern was observed between loaded dynamic and isotonic contractions, but not between isometric and loaded dynamic contractions. Thus, the recruitment properties of single motor units in human flexor digitorum superficialis are sensitive to changes in both imposed external loads and the initial length of the muscle.

High Strain Rate Deformation Mechanisms of Body Centered Cubic Material Subjected to Impact Loading

NASA Astrophysics Data System (ADS)

Visser, William

Low carbon steel is the most common grade of structural steel used; it has carbon content of 0.05% to 0.25% and very low content of alloying elements. It is produced in great quantities and provides material properties that are acceptable for many engineering applications, particularly in the construction industry in which low carbon steel is widely used as the strengthening phase in civil structures. The overall goal of this dissertation was to investigate the deformation response of A572 grade 50 steel when subjected to impact loading. This steel has a 0.23% by weight carbon content and has less than 2% additional alloying elements. The deformation mechanisms of this steel under shock loading conditions include both dislocation motion and twin formation. The goal of this work was achieved by performing experimental, analytical and numerical research in three integrated tasks. The first is to determine the relationship between the evolution of deformation twins and the impact pressure. Secondly, a stress criterion for twin nucleation during high strain rate loading was developed which can account for the strain history or initial dislocation density. Lastly, a method was applied for separating the effects of dislocations and twins generated by shock loading in order to determine their role in controlling the flow stress of the material. In this regard, the contents of this work have been categorically organized. First, the active mechanisms in body centered cubic (BCC) low carbon steel during shock loading have been determined as being a composed of the competing mechanisms of dislocations and deformation twins. This has been determined through a series of shock loading tests of the as-received steel. The shock loading tests were done by plate impact experiments at several impact pressures ranging from 2GPa up to 13GPa using a single stage light gas gun. A relationship between twin volume fraction and impact pressure was determined and an analytical model was utilized to simulate the shock loading and twin evolution for these loading conditions. The second part of this research ties into the modeling efforts. Within the model for predicting twin volume fraction is a twin growth equation and a constant describing the stress at which the twin nucleation will occur. By using a constant value for the twin nucleation stress modeling efforts fail to accurately predict the growth and final twin volume fraction. A second shock loading experimental study combined with high strain rate compression tests using a split Hopkinson pressure bar were completed to determine a twin nucleation stress equation as a function of dislocation density. Steel specimens were subjected to cold rolling to 3% strain and subsequently impacted using the gas gun at different pressures. The increase in dislocation density due to pre-straining substantially increased the twin nucleation stress indicating that twin nucleation stress in dependent upon prior strain history. This has been explained in terms of the velocity and generation rates of both perfect and partial dislocations. An explicit form of the critical twin nucleation stress was developed and parameters were determined through plate impact tests and low temperature (77K) SHPB compression tests. The final component in studying deformation twin mechanisms in BCC steel extends the research to the post-impact mechanical properties and how the twin volume fraction affects the dynamic flow stress. Compression tests between 293K and 923K at an average strain rate of 4700 s-1 were completed on the as-received and 3% pre-strained steels in both the initial condition and after being impacted at pressures of 6GPa and 11GPa. Results of the experimental testing were used in a thermal activation model in order to distinguish separate components in the microstructure contributing to the enhanced flow stress caused by the shock loading. It has been shown that the dislocations generated from shock loading are equivalent to those produced under lower rate straining and the addition of deformation twins in the microstructure contribute to the athermal stress by adding to the long range barriers.

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.

Estimating the Impacts of Direct Load Control Programs Using GridPIQ, a Web-Based Screening Tool

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

Pal, Seemita; Thayer, Brandon L.; Barrett, Emily L.

In direct load control (DLC) programs, utilities can curtail the demand of participating loads to contractually agreed-upon levels during periods of critical peak load, thereby reducing stress on the system, generation cost, and required transmission and generation capacity. Participating customers receive financial incentives. The impacts of implementing DLC programs extend well beyond peak shaving. There may be a shift of load proportional to the interrupted load to the times before or after a DLC event, and different load shifts have different consequences. Tools that can quantify the impacts of such programs on load curves, peak demand, emissions, and fossil fuelmore » costs are currently lacking. The Grid Project Impact Quantification (GridPIQ) screening tool includes a Direct Load Control module, which takes into account project-specific inputs as well as the larger system context in order to quantify the impacts of a given DLC program. This allows users (utilities, researchers, etc.) to test and compare different program specifications and their impacts.« less

Effect of Impaction Sequence on Osteochondral Graft Damage: The Role of Repeated and Varying Loads

PubMed Central

Kang, Richard W.; Friel, Nicole A.; Williams, James M.; Cole, Brian J.; Wimmer, Markus A.

2013-01-01

Background Osteochondral autografts and allografts require mechanical force for proper graft placement into the defect site; however, impaction compromises the tissue. This study aimed to determine the effect of impaction force and number of hits to seat the graft on cartilage integrity. Hypothesis Under constant impulse conditions, higher impaction load magnitudes are more detrimental to cell viability, matrix integrity and collagen network organization and will result in proteoglycan loss and nitric oxide release. Study Design Controlled laboratory study Methods Osteochondral explants, harvested from fresh bovine trochleas, were exposed to a series of consistent impact loads delivered by a pneumatically driven device. Each plug received the same overall impulse of 7 Ns, reflecting the mean of 23 clinically inserted plugs. Impaction loads of 37.5N, 75N, 150N, and 300N were matched with 74, 37, 21, and 11 hits respectively. Following impaction, the plugs were harvested and cartilage was analyzed for cell viability, histology by safranin-o and picosirius red, and release of sulfated glycosaminoglycans and nitric oxide. Data were compared with non-impacted control. Results Impacted plugs had significantly lower cell viability than non-impacted plugs. A dose response relationship in loss of cell viability with respect to load magnitude was seen immediately and after 4 days but lost after 8 days. Histologic analysis revealed intact cartilage surface in all samples (loaded or control), with loaded samples showing alterations in birefringence. While the sulfated GAG release was similar across varying impaction loads, release of nitric oxide increased with increasing impaction magnitudes and time. Conclusions Impaction loading parameters have a direct effect on the time course of the viability of the cartilage in the graft tissue. Clinical Relevance Optimal loading parameters for surgical impaction of osteochondral grafts are those with lower load magnitudes and a greater number of hits to ensure proper fit. PMID:19915099

Study on Mechanical Properties of Barite Concrete under Impact Load

NASA Astrophysics Data System (ADS)

Chen, Z. F.; Cheng, K.; Wu, D.; Gan, Y. C.; Tao, Q. W.

2018-03-01

In order to research the mechanical properties of Barite concrete under impact load, a group of concrete compression tests was carried out under the impact load by using the drop test machine. A high-speed camera was used to record the failure process of the specimen during the impact process. The test results show that:with the increase of drop height, the loading rate, the peak load, the strain under peak load, the strain rate and the dynamic increase factor (DIF) all increase gradually. The ultimate tensile strain is close to each other, and the time of impact force decreases significantly, showing significant strain rate effect.

Design and evaluation of a foam-filled hat-stiffened panel concept for aircraft primary structural applications

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.

1995-01-01

A structurally efficient hat-stiffened panel concept that utilizes a structural foam as stiffener core has been designed for aircraft primary structural applications. This stiffener concept utilizes a manufacturing process that can be adapted readily to grid-stiffened structural configurations which possess inherent damage tolerance characteristics due to their multiplicity of load paths. The foam-filled hat-stiffener concept in a prismatically stiffened panel configuration is more efficient than most other stiffened panel configurations in a load range that is typical for both fuselage and wing structures. The prismatically stiffened panel concept investigated here has been designed using AS4/3502 preimpregnated tape and Rohacell foam core and evaluated for its buckling and postbuckling behavior with and without low-speed impact damage. The results from single-stiffener and multi-stiffener specimens suggest that this structural concept responds to loading as anticipated and has good damage tolerance characteristics.

Response spectrum method for extreme wave loading with higher order components of drag force

NASA Astrophysics Data System (ADS)

Reza, Tabeshpour Mohammad; Mani, Fatemi Dezfouli; Ali, Dastan Diznab Mohammad; Saied, Mohajernasab; Saied, Seif Mohammad

2017-03-01

Response spectra of fixed offshore structures impacted by extreme waves are investigated based on the higher order components of the nonlinear drag force. In this way, steel jacket platforms are simplified as a mass attached to a light cantilever cylinder and their corresponding deformation response spectra are estimated by utilizing a generalized single degree of freedom system. Based on the wave data recorded in the Persian Gulf region, extreme wave loading conditions corresponding to different return periods are exerted on the offshore structures. Accordingly, the effect of the higher order components of the drag force is considered and compared to the linearized state for different sea surface levels. When the fundamental period of the offshore structure is about one third of the main period of wave loading, the results indicate the linearized drag term is not capable of achieving a reliable deformation response spectrum.

On the shock response of pisum sativum and lepidium sativum

NASA Astrophysics Data System (ADS)

Leighs, James Allen; Hazell, Paul; Appleby-Thomas, Gareth James

2012-03-01

The high strain-rate response of biological and organic structures is of interest to numerous fields ranging from the food industry to astrobiology. Consequently, knowledge of the damage mechanisms within, and the viability of shocked organic material are of significant importance. In this study, a single-stage gasgun has been employed to subject samples of Pisum sativum (common pea) and Lepidium sativum (curled cress) to planar shock loading. Impact pressures of up to ~11.5 GPa and ~0.5 GPa for pea and cress seed samples respectively have been reached. The development of the experimental approach is discussed and presented alongside results from modelled gauge traces showing the sample loading history. Viability of the shock-loaded pea and cress seeds was investigated via attempts at germination, which were unsuccessful with pea seeds but successful in all tests performed on cress seeds. This work suggests that organic structures could survive shockwaves that may be encountered during asteroid collisions.

A new drilling method—Earthworm-like vibration drilling

PubMed Central

Wang, Peng; Wang, Ruihe

2018-01-01

The load transfer difficulty caused by borehole wall friction severely limits the penetration rate and extended-reach limit of complex structural wells. A new friction reduction technology termed “earthworm-like drilling” is proposed in this paper to improve the load transfer of complex structural wells. A mathematical model based on a “soft-string” model is developed and solved. The results show that earthworm-like drilling is more effective than single-point vibration drilling. The amplitude and frequency of the pulse pressure and the installation position of the shakers have a substantial impact on friction reduction and load transfer. An optimization model based on the projection gradient method is developed and used to optimize the position of three shakers in a horizontal well. The results verify the feasibility and advantages of earthworm-like drilling, and establish a solid theoretical foundation for its application in oil field drilling. PMID:29641615

A new drilling method-Earthworm-like vibration drilling.

PubMed

Wang, Peng; Ni, Hongjian; Wang, Ruihe

2018-01-01

The load transfer difficulty caused by borehole wall friction severely limits the penetration rate and extended-reach limit of complex structural wells. A new friction reduction technology termed "earthworm-like drilling" is proposed in this paper to improve the load transfer of complex structural wells. A mathematical model based on a "soft-string" model is developed and solved. The results show that earthworm-like drilling is more effective than single-point vibration drilling. The amplitude and frequency of the pulse pressure and the installation position of the shakers have a substantial impact on friction reduction and load transfer. An optimization model based on the projection gradient method is developed and used to optimize the position of three shakers in a horizontal well. The results verify the feasibility and advantages of earthworm-like drilling, and establish a solid theoretical foundation for its application in oil field drilling.

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

Parab, Niranjan D.; Hudspeth, Matthew; Claus, Ben

Granular materials are widely used to resist impact and blast. Under these dynamic loadings, the constituent particles in the granular system fracture. To study the fracture mechanisms in brittle particles under dynamic compressive loading, a high speed X-ray phase contrast imaging setup was synchronized with a Kolsky bar apparatus. Controlled compressive loading was applied on two contacting particles using the Kolsky bar apparatus and fracture process was captured using the high speed X-ray imaging setup. Five different particles were investigated: soda-lime glass, polycrystalline silica (silicon dioxide), polycrystalline silicon, barium titanate glass, and yttrium stabilized zirconia. For both soda lime glassmore » and polycrystalline silica particles, one of the particles fragmented explosively, thus breaking into many small pieces. For Silicon and barium titanate glass particles, a finite number of cracks were observed in one of the particles causing it to fracture. For yttrium stabilized zirconia particles, a single meridonial crack developed in one of the particles, breaking it into two parts.« less

Effects of partial interlaminar bonding on impact resistance and loaded-hole behavior of graphite/epoxy quasi-isotropic laminates

NASA Technical Reports Server (NTRS)

Illg, W.

1986-01-01

A partial-bonding interlaminar toughening concept was evaluated for resistance to impact and for behavior of a loaded hole. Perforated Mylar sheets were interleaved between all 24 plies of a graphite/epoxy quasi-isotropic lay-up. Specimens were impacted by aluminum spheres while under tensile or compressive loads. Impact-failure thresholds and residual strengths were obtained. Loaded-hole specimens were tested in three configurations that were critical in bearing, shear, or tension. Partial bonding reduced the tensile and compressive strengths of undamaged specimens by about one-third. For impact, partial bonding did not change the threshold for impact failure under tensile preload. However, under compressive preload, partial bonding caused serious degradation of impact resistance. Partial bonding reduced the maximum load-carrying capacity of all three types of loaded-hole specimens. Overall, partial bonding degraded both impact resistance and bearing strength of holes.

Adult bone strength of children from single-parent families: the Midlife in the United States Study.

PubMed

Crandall, C J; Karlamangla, A S; Merkin, S S; Binkley, N; Carr, D; Greendale, G A; Seeman, T E

2015-03-01

Bone health may be negatively impacted by childhood socio-environmental circumstances. We examined the independent associations of single-parent childhood and parental death or divorce in childhood with adult bone strength indices. Longer exposure to a single-parent household in childhood was associated with lower bone strength in adulthood. Because peak bone mass is acquired during childhood, bone health may be negatively impacted by childhood socio-environmental disadvantage. The goal of this study was to determine whether being raised in a single-parent household is associated with lower bone strength in adulthood. Using dual-energy X-ray absorptiometry data from 708 participants (mean age 57 years) in the Midlife in the United States Biomarker Project, we examined the independent associations of composite indices of femoral neck bone strength relative to load (in three failure modes: compression, bending, and impact) in adulthood with the experience of single-parent childhood and parental death or divorce in childhood. After adjustment for gender, race, menopause transition stage, age, and body mass index, each additional year of single-parent childhood was associated with 0.02 to 0.03 SD lower indices of adult femoral neck strength. In those with 9-16 years of single-parent childhood, the compression strength index was 0.41 SD lower, bending strength index was 0.31 SD lower, and impact strength index was 0.25 SD lower (all p values < 0.05). In contrast, parental death or divorce during childhood was not by itself independently associated with adult bone strength indices. The magnitudes of these associations were unaltered by additional adjustment for lifestyle factors and socioeconomic status in childhood and adulthood. Independent of parental death or divorce, growing up in a single-parent household is associated with lower femoral neck bone strength in adulthood, and this association is not entirely explained by childhood or adult socioeconomic conditions or lifestyle choices.

Multi-barge flotilla impact forces on bridges.

DOT National Transportation Integrated Search

2008-06-01

The current AASHTO equations for barge impact loads are based on scale models of barges, and may not accurately predict impact loads on bridge piers. The results of this study produce more realistic flotilla impact design loads, potentially leading t...

Overview for Design and Construction of Drilled Shafts in Cohesive Soils.

DTIC Science & Technology

1981-08-01

water flowing around supporting columns of bridges. Methods for determining the lateral load -deflection behavior of drilled shafts are based on solutions...PROCEDURES. ..... ............... 22 Axial Load Behavior of Single Shafts .... ......... 22 Lateral Load Behavior of Single Shafts .... ........ 54 Load ...on the shaft (Patey 1977, Claessen and Horvat 1974). Large-diameter shafts can be more easily constructed to resist lateral loads than driven piles or

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

Stimpson, Shane G.

In this report, load-follow simulations using VERA-CS with one-way coupling to standalone BISON has been demonstrated including both a single rod with a full cycle of load-follow operations and a quarter-core model with a single month of load-follow.

Fatique crack growth behavior of a single crystal alloy as observed through an in situ fatigue loading stage

NASA Technical Reports Server (NTRS)

Telesman, Jack; Kantzos, Peter

1988-01-01

An in situ fatigue loading stage inside a scanning electron microscope (SEM) was used to determine the fatigue crack growth behavior of a PWA 1480 single-crystal nickel-based superalloy. The loading stage permits real-time viewing of the fatigue damage processes at high magnification. The PWA 1480 single-crystal, single-edge notch specimens were tested with the load axis parallel to the (100) orientation. Two distinct fatigue failure mechanisms were identified. The crack growth rate differed substantially when the failure occurred on a single slip system in comparison to multislip system failure. Two processes by which crack branching is produced were identified and are discussed. Also discussed are the observed crack closure mechanisms.

A PVDF-Based Sensor for Internal Stress Monitoring of a Concrete-Filled Steel Tubular (CFST) Column Subject to Impact Loads.

PubMed

Du, Guofeng; Li, Zhao; Song, Gangbing

2018-05-23

Impact loads can have major adverse effects on the safety of civil engineering structures, such as concrete-filled steel tubular (CFST) columns. The study of mechanical behavior and stress analysis of CFST columns under impact loads is very important to ensure their safety against such loads. At present, the internal stress monitoring of the concrete cores CFST columns under impact loads is still a very challenging subject. In this paper, a PVDF (Polyvinylidene Fluoride) piezoelectric smart sensor was developed and successfully applied to the monitoring of the internal stress of the concrete core of a CFST column under impact loads. The smart sensor consists of a PVDF piezoelectric film sandwiched between two thin steel plates through epoxy. The protection not only prevents the PVDF film from impact damages but also ensures insulation and waterproofing. The smart sensors were embedded into the circular concrete-filled steel tube specimen during concrete pouring. The specimen was tested against impact loads, and testing data were collected. The time history of the stress obtained from the PVDF smart sensor revealed the evolution of core concrete internal stress under impact loads when compared with the impact force⁻time curve of the hammer. Nonlinear finite element simulations of the impact process were also carried out. The results of FEM simulations had good agreement with the test results. The results showed that the proposed PVDF piezoelectric smart sensors can effectively monitor the internal stress of concrete-filled steel tubular columns under impact loads.

Effect of high strain rates on peak stress in a Zr-based bulk metallic glass

NASA Astrophysics Data System (ADS)

Sunny, George; Yuan, Fuping; Prakash, Vikas; Lewandowski, John

2008-11-01

The mechanical behavior of Zr41.25Ti13.75Cu12.5Ni10Be22.5 (LM-1) has been extensively characterized under quasistatic loading conditions; however, its mechanical behavior under dynamic loading conditions is currently not well understood. A Split-Hopkinson pressure bar (SHPB) and a single-stage gas gun are employed to characterize the mechanical behavior of LM-1 in the strain-rate regime of 102-105/s. The SHPB experiments are conducted with a tapered insert design to mitigate the effects of stress concentrations and preferential failure at the specimen-insert interface. The higher strain-rate plate-impact compression-and-shear experiments are conducted by impacting a thick tungsten carbide (WC) flyer plate with a sandwich sample comprising a thin bulk metallic glass specimen between two thicker WC target plates. Specimens employed in the SHPB experiments failed in the gage-section at a peak stress of approximately 1.8 GPa. Specimens in the high strain-rate plate-impact experiments exhibited a flow stress in shear of approximately 0.9 GPa, regardless of the shear strain-rate. The flow stress under the plate-impact conditions was converted to an equivalent flow stress under uniaxial compression by assuming a von Mises-like material behavior and accounting for the plane strain conditions. The results of these experiments, when compared to the previous work conducted at quasistatic loading rates, indicate that the peak stress of LM-1 is essentially strain rate independent over the strain-rate range up to 105/s.

The Load Capability of Piezoelectric Single Crystal Actuators

NASA Technical Reports Server (NTRS)

Xu, Tian-Bing; Su, Ji; Jiang, Xiaoning; Rehrig, Paul W.; Hackenberger, Wesley S.

2006-01-01

Piezoelectric lead magnesium niobate-lead titanate (PMN-PT) single crystal is one of the most promising materials for electromechanical device applications due to its high electrical field induced strain and high electromechanical coupling factor. PMN-PT single crystal-based multilayer stack actuators and multilayer stack-based flextensional actuators have exhibited high stroke and high displacement-voltage ratios. The actuation capabilities of these two actuators were evaluated using a newly developed method based upon a laser vibrometer system under various loading conditions. The measured displacements as a function of mechanical loads at different driving voltages indicate that the displacement response of the actuators is approximately constant under broad ranges of mechanical load. The load capabilities of these PMN-PT single crystal-based actuators and the advantages of the capability for applications will be discussed.

The Load Capability of Piezoelectric Single Crystal Actuators

NASA Technical Reports Server (NTRS)

Xu, Tian-Bing; Su, Ji; Jiang, Xiaoning; Rehrig, Paul W.; Hackenberger, Wesley S.

2007-01-01

Piezoelectric lead magnesium niobate-lead titanate (PMN-PT) single crystal is one of the most promising materials for electromechanical device applications due to its high electrical field induced strain and high electromechanical coupling factor. PMN-PT single crystal-based multilayer stack actuators and multilayer stack-based flextensional actuators have exhibited high stroke and high displacement-voltage ratios. The actuation capabilities of these two actuators were evaluated using a newly developed method based upon a laser vibrometer system under various loading conditions. The measured displacements as a function of mechanical loads at different driving voltages indicate that the displacement response of the actuators is approximately constant under broad ranges of mechanical load. The load capabilities of these PMN-PT single crystal-based actuators and the advantages of the capability for applications will be discussed.

Impact Damage and Strain Rate Effects for Toughened Epoxy Composite Structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Minnetyan, Levon

2006-01-01

Structural integrity of composite systems under dynamic impact loading is investigated herein. The GENOA virtual testing software environment is used to implement the effects of dynamic loading on fracture progression and damage tolerance. Combinations of graphite and glass fibers with a toughened epoxy matrix are investigated. The effect of a ceramic coating for the absorption of impact energy is also included. Impact and post impact simulations include verification and prediction of (1) Load and Impact Energy, (2) Impact Damage Size, (3) Maximum Impact Peak Load, (4) Residual Strength, (5) Maximum Displacement, (6) Contribution of Failure Modes to Failure Mechanisms, (7) Prediction of Impact Load Versus Time, and (8) Damage, and Fracture Pattern. A computer model is utilized for the assessment of structural response, progressive fracture, and defect/damage tolerance characteristics. Results show the damage progression sequence and the changes in the structural response characteristics due to dynamic impact. The fundamental premise of computational simulation is that the complete evaluation of composite fracture requires an assessment of ply and subply level damage/fracture processes as the structure is subjected to loads. Simulation results for the graphite/epoxy composite were compared with the impact and tension failure test data, correlation and verification was obtained that included: (1) impact energy, (2) damage size, (3) maximum impact peak load, (4) residual strength, (5) maximum displacement, and (6) failure mechanisms of the composite structure.

Structural Health Monitoring for Impact Damage in Composite Structures.

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

Roach, Dennis P.; Raymond Bond; Doug Adams

Composite structures are increasing in prevalence throughout the aerospace, wind, defense, and transportation industries, but the many advantages of these materials come with unique challenges, particularly in inspecting and repairing these structures. Because composites of- ten undergo sub-surface damage mechanisms which compromise the structure without a clear visual indication, inspection of these components is critical to safely deploying composite re- placements to traditionally metallic structures. Impact damage to composites presents one of the most signi fi cant challenges because the area which is vulnerable to impact damage is generally large and sometimes very dif fi cult to access. This workmore » seeks to further evolve iden- ti fi cation technology by developing a system which can detect the impact load location and magnitude in real time, while giving an assessment of the con fi dence in that estimate. Fur- thermore, we identify ways by which impact damage could be more effectively identi fi ed by leveraging impact load identi fi cation information to better characterize damage. The impact load identi fi cation algorithm was applied to a commercial scale wind turbine blade, and results show the capability to detect impact magnitude and location using a single accelerometer, re- gardless of sensor location. A technique for better evaluating the uncertainty of the impact estimates was developed by quantifying how well the impact force estimate meets the assump- tions underlying the force estimation technique. This uncertainty quanti fi cation technique was found to reduce the 95% con fi dence interval by more than a factor of two for impact force estimates showing the least uncertainty, and widening the 95% con fi dence interval by a fac- tor of two for the most uncertain force estimates, avoiding the possibility of understating the uncertainty associated with these estimates. Linear vibration based damage detection tech- niques were investigated in the context of structural stiffness reductions and impact damage. A method by which the sensitivity to damage could be increased for simple structures was presented, and the challenges of applying that technique to a more complex structure were identi fi ed. The structural dynamic changes in a weak adhesive bond were investigated, and the results showed promise for identifying weak bonds that show little or no static reduction in stiffness. To address these challenges in identifying highly localized impact damage, the possi- bility of detecting damage through nonlinear dynamic characteristics was also identi fi ed, with a proposed technique which would leverage impact location estimates to enable the detection of impact damage. This nonlinear damage identi fi cation concept was evaluated on a composite panel with a substructure disbond, and the results showed that the nonlinear dynamics at the damage site could be observed without a baseline healthy reference. By further developing impact load identi fi cation technology and combining load and damage estimation techniques into an integrated solution, the challenges associated with impact detection in composite struc- tures can be effectively solved, thereby reducing costs, improving safety, and enhancing the operational readiness and availability of high value assets.« less

A biomechanical comparison of single and double-row fixation in arthroscopic rotator cuff repair.

PubMed

Smith, Christopher D; Alexander, Susan; Hill, Adam M; Huijsmans, Pol E; Bull, Anthony M J; Amis, Andrew A; De Beer, Joe F; Wallace, Andrew L

2006-11-01

The optimal method for arthroscopic rotator cuff repair is not yet known. The hypothesis of the present study was that a double-row repair would demonstrate superior static and cyclic mechanical behavior when compared with a single-row repair. The specific aims were to measure gap formation at the bone-tendon interface under static creep loading and the ultimate strength and mode of failure of both methods of repair under cyclic loading. A standardized tear of the supraspinatus tendon was created in sixteen fresh cadaveric shoulders. Arthroscopic rotator cuff repairs were performed with use of either a double-row technique (eight specimens) or a single-row technique (eight specimens) with nonabsorbable sutures that were double-loaded on a titanium suture anchor. The repairs were loaded statically for one hour, and the gap formation was measured. Cyclic loading to failure was then performed. Gap formation during static loading was significantly greater in the single-row group than in the double-row group (mean and standard deviation, 5.0 +/- 1.2 mm compared with 3.8 +/- 1.4 mm; p < 0.05). Under cyclic loading, the double-row repairs failed at a mean of 320 +/- 96.9 N whereas the single-row repairs failed at a mean of 224 +/- 147.9 N (p = 0.058). Three single-row repairs and three double-row repairs failed as a result of suture cut-through. Four single-row repairs and one double-row repair failed as a result of anchor or suture failure. The remaining five repairs did not fail, and a midsubstance tear of the tendon occurred. Although more technically demanding, the double-row technique demonstrates superior resistance to gap formation under static loading as compared with the single-row technique. A double-row reconstruction of the supraspinatus tendon insertion may provide a more reliable construct than a single-row repair and could be used as an alternative to open reconstruction for the treatment of isolated tears.

Optimal load scheduling in commercial and residential microgrids

NASA Astrophysics Data System (ADS)

Ganji Tanha, Mohammad Mahdi

Residential and commercial electricity customers use more than two third of the total energy consumed in the United States, representing a significant resource of demand response. Price-based demand response, which is in response to changes in electricity prices, represents the adjustments in load through optimal load scheduling (OLS). In this study, an efficient model for OLS is developed for residential and commercial microgrids which include aggregated loads in single-units and communal loads. Single unit loads which include fixed, adjustable and shiftable loads are controllable by the unit occupants. Communal loads which include pool pumps, elevators and central heating/cooling systems are shared among the units. In order to optimally schedule residential and commercial loads, a community-based optimal load scheduling (CBOLS) is proposed in this thesis. The CBOLS schedule considers hourly market prices, occupants' comfort level, and microgrid operation constraints. The CBOLS' objective in residential and commercial microgrids is the constrained minimization of the total cost of supplying the aggregator load, defined as the microgrid load minus the microgrid generation. This problem is represented by a large-scale mixed-integer optimization for supplying single-unit and communal loads. The Lagrangian relaxation methodology is used to relax the linking communal load constraint and decompose the independent single-unit functions into subproblems which can be solved in parallel. The optimal solution is acceptable if the aggregator load limit and the duality gap are within the bounds. If any of the proposed criteria is not satisfied, the Lagrangian multiplier will be updated and a new optimal load schedule will be regenerated until both constraints are satisfied. The proposed method is applied to several case studies and the results are presented for the Galvin Center load on the 16th floor of the IIT Tower in Chicago.

Hugoniot-based equations of state for two filled EPDM rubbers

NASA Astrophysics Data System (ADS)

Pacheco, A. H.; Dattelbaum, D. M.; Orler, E. B.; Bartram, B. D.; Gustavsen, R. L.

2014-05-01

Particle-filled elastomers are commonly used as engineering components due to their ability to provide structural support via their elastic mechanical response. Even small amounts of particle fillers are known to increase the mechanical strength of elastomers due to polymer-filler interactions. In this work, the shock response of two filled (SiO2 or silica and KevlarTMfillers) ethylene-propylene-diene (EPDM) rubbers were studied using single and two-stage gas gun-driven plate impact experiments. Hugoniot states were determined using standard plate impact methods. Both filled-EPDM elastomers exhibit high compressibility under shock loading and have a response similar to adiprene rubber.

Ground reaction forces and knee kinetics during single and repeated badminton lunges.

PubMed

Lam, Wing Kai; Ding, Rui; Qu, Yi

2017-03-01

Repeated movement (RM) lunge that frequently executed in badminton might be used for footwear evaluation. This study examined the influence of single movement (SM) and RM lunges on the ground reaction forces (GRFs) and knee kinetics during the braking phase of a badminton lunge step. Thirteen male university badminton players performed left-forward lunges in both SM and RM sessions. Force platform and motion capturing system were used to measure GRFs and knee kinetics variables. Paired t-test was performed to determine any significant differences between SM and RM lunges regarding mean and coefficient of variation (CV) in each variable. The kinetics results indicated that compared to SM lunges, the RM lunges had shorter contact time and generated smaller maximum loading rate of impact force, peak knee anterior-posterior force, and peak knee sagittal moment but generated larger peak horizontal resultant forces (Ps < 0.05). Additionally, the RM lunges had lower CV for peak knee medial-lateral and vertical forces (Ps < 0.05). These results suggested that the RM testing protocols had a distinct loading response and adaptation pattern during lunge and that the RM protocol showed higher within-trial reliability, which may be beneficial for the knee joint loading evaluation under different interventions.

Model tests and numerical analyses on horizontal impedance functions of inclined single piles embedded in cohesionless soil

NASA Astrophysics Data System (ADS)

Goit, Chandra Shekhar; Saitoh, Masato

2013-03-01

Horizontal impedance functions of inclined single piles are measured experimentally for model soil-pile systems with both the effects of local soil nonlinearity and resonant characteristics. Two practical pile inclinations of 5° and 10° in addition to a vertical pile embedded in cohesionless soil and subjected to lateral harmonic pile head loadings for a wide range of frequencies are considered. Results obtained with low-to-high amplitude of lateral loadings on model soil-pile systems encased in a laminar shear box show that the local nonlinearities have a profound impact on the horizontal impedance functions of piles. Horizontal impedance functions of inclined piles are found to be smaller than the vertical pile and the values decrease as the angle of pile inclination increases. Distinct values of horizontal impedance functions are obtained for the `positive' and `negative' cycles of harmonic loadings, leading to asymmetric force-displacement relationships for the inclined piles. Validation of these experimental results is carried out through three-dimensional nonlinear finite element analyses, and the results from the numerical models are in good agreement with the experimental data. Sensitivity analyses conducted on the numerical models suggest that the consideration of local nonlinearity at the vicinity of the soil-pile interface influence the response of the soil-pile systems.

An experimental study on pile spacing effects under lateral loading in sand.

PubMed

Khari, Mahdy; Kassim, Khairul Anuar; Adnan, Azlan

2013-01-01

Grouped and single pile behavior differs owing to the impacts of the pile-to-pile interaction. Ultimate lateral resistance and lateral subgrade modulus within a pile group are known as the key parameters in the soil-pile interaction phenomenon. In this study, a series of experimental investigation was carried out on single and group pile subjected to monotonic lateral loadings. Experimental investigations were conducted on twelve model pile groups of configurations 1 × 2, 1 × 3, 2 × 2, 3 × 3, and 3 × 2 for embedded length-to-diameter ratio l/d = 32 into loose and dense sand, spacing from 3 to 6 pile diameter, in parallel and series arrangement. The tests were performed in dry sand from Johor Bahru, Malaysia. To reconstruct the sand samples, the new designed apparatus, Mobile Pluviator, was adopted. The ultimate lateral load is increased 53% in increasing of s/d from 3 to 6 owing to effects of sand relative density. An increasing of the number of piles in-group decreases the group efficiency owing to the increasing of overlapped stress zones and active wedges. A ratio of s/d more than 6d is large enough to eliminate the pile-to-pile interaction and the group effects. It may be more in the loose sand.

An Experimental Study on Pile Spacing Effects under Lateral Loading in Sand

PubMed Central

Khari, Mahdy; Kassim, Khairul Anuar; Adnan, Azlan

2013-01-01

Grouped and single pile behavior differs owing to the impacts of the pile-to-pile interaction. Ultimate lateral resistance and lateral subgrade modulus within a pile group are known as the key parameters in the soil-pile interaction phenomenon. In this study, a series of experimental investigation was carried out on single and group pile subjected to monotonic lateral loadings. Experimental investigations were conducted on twelve model pile groups of configurations 1 × 2, 1 × 3, 2 × 2, 3 × 3, and 3 × 2 for embedded length-to-diameter ratio l/d = 32 into loose and dense sand, spacing from 3 to 6 pile diameter, in parallel and series arrangement. The tests were performed in dry sand from Johor Bahru, Malaysia. To reconstruct the sand samples, the new designed apparatus, Mobile Pluviator, was adopted. The ultimate lateral load is increased 53% in increasing of s/d from 3 to 6 owing to effects of sand relative density. An increasing of the number of piles in-group decreases the group efficiency owing to the increasing of overlapped stress zones and active wedges. A ratio of s/d more than 6d is large enough to eliminate the pile-to-pile interaction and the group effects. It may be more in the loose sand. PMID:24453900

Coupling continuum dislocation transport with crystal plasticity for application to shock loading conditions

DOE PAGES

Luscher, Darby Jon; Mayeur, Jason Rhea; Mourad, Hashem Mohamed; ...

2015-08-05

Here, we have developed a multi-physics modeling approach that couples continuum dislocation transport, nonlinear thermoelasticity, crystal plasticity, and consistent internal stress and deformation fields to simulate the single-crystal response of materials under extreme dynamic conditions. Dislocation transport is modeled by enforcing dislocation conservation at a slip-system level through the solution of advection-diffusion equations. Nonlinear thermoelasticity provides a thermodynamically consistent equation of state to relate stress (including pressure), temperature, energy densities, and dissipation. Crystal plasticity is coupled to dislocation transport via Orowan's expression where the constitutive description makes use of recent advances in dislocation velocity theories applicable under extreme loading conditions.more » The configuration of geometrically necessary dislocation density gives rise to an internal stress field that can either inhibit or accentuate the flow of dislocations. An internal strain field associated with the internal stress field contributes to the kinematic decomposition of the overall deformation. The paper describes each theoretical component of the framework, key aspects of the constitutive theory, and some details of a one-dimensional implementation. Results from single-crystal copper plate impact simulations are discussed in order to highlight the role of dislocation transport and pile-up in shock loading regimes. The main conclusions of the paper reinforce the utility of the modeling approach to shock problems.« less

Clinical characteristics and viral load of respiratory syncytial virus and human metapneumovirus in children hospitaled for acute lower respiratory tract infection.

PubMed

Yan, Xiao-Li; Li, Yu-Ning; Tang, Yi-Jie; Xie, Zhi-Ping; Gao, Han-Chun; Yang, Xue-Mei; Li, Yu-Mei; Liu, Li-Jun; Duan, Zhao-Jun

2017-04-01

Respiratory syncytial virus (RSV) and human metapneumovirus (HMPV) are two common viral pathogens in acute lower respiratory tract infections (ALRTI). However, the association of viral load with clinical characteristics is not well-defined in ALRTI. To explore the correlation between viral load and clinical characteristics of RSV and HMPV in children hospitalized for ALRTI in Lanzhou, China. Three hundred and eighty-seven children hospitalized for ALRTI were enrolled. Nasopharyngeal aspirates (NPAs) were sampled from each children. Real-time PCR was used to screen RSV, HMPV, and twelve additional respiratory viruses. Bronchiolitis was the leading diagnoses both in RSV and HMPV positive patients. A significantly greater frequency of wheezing (52% vs. 33.52%, P = 0.000) was noted in RSV positive and negative patients. The RSV viral load was significant higher in children aged <1 year (P = 0.003), children without fever and wheezing (P = 0.015 and P = 0.000), days of illness <14 days (P = 0.002), children with bronchiolitis (P = 0.012) and children with RSV single infections (P = 0.000). No difference was found in the clinical features of HMPV positive and negative patients. The HMPV viral load had no correlation with any clinical characteristics. The incidences of severe disease were similar between single infection and coinfection for the two viruses (RSV, P = 0.221; HMPV, P = 0.764) and there has no statistical significance between severity and viral load (P = 0.166 and P = 0.721). Bronchiolitis is the most common disease caused by RSV and HMPV. High viral load or co-infection may be associated with some symptoms but neither has a significant impact on disease severity for the two viruses. J. Med. Virol. 89:589-597, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Effect of low-speed impact damage on the buckling properties of E-glass/epoxy laminates

NASA Astrophysics Data System (ADS)

Yapici, A.; Metin, M.

2009-11-01

The postimpact buck ling loads of E-glass/epoxy laminates have been measured. Composite samples with the stacking sequence [+45/-45/90/0]2s were subjected to low-speed impact loadings at various energy levels. The tests were conducted on a specially developed vertical drop-weight testing machine. The main impact parameters, such as the peak load, absorbed energy, deflection at the peak load, and damage area, were evaluated and com pared. The damaged specimens were subjected to compressive axial forces, and their buckling loads were determined. The relation between the level of impact energy and buck ling loads is investigated.

Biomechanical advantages of triple-loaded suture anchors compared with double-row rotator cuff repairs.

PubMed

Barber, F Alan; Herbert, Morley A; Schroeder, F Alexander; Aziz-Jacobo, Jorge; Mays, Matthew M; Rapley, Jay H

2010-03-01

To evaluate the strength and suture-tendon interface security of various suture anchors triply and doubly loaded with ultrahigh-molecular weight polyethylene-containing sutures and to evaluate the relative effectiveness of placing these anchors in a single-row or double-row arrangement by cyclic loading and then destructive testing. The infraspinatus muscle was reattached to the original humeral footprint by use of 1 of 5 different repair patterns in 40 bovine shoulders. Two single-row repairs and three double-row repairs were tested. High-strength sutures were used for all repairs. Five groups were studied: group 1, 2 triple-loaded screw suture anchors in a single row with simple stitches; group 2, 2 triple-loaded screw anchors in a single row with simple stitches over a fourth suture passed perpendicularly ("rip-stop" stitch); group 3, 2 medial and 2 lateral screw anchors with a single vertical mattress stitch passed from the medial anchors and 2 simple stitches passed from the lateral anchors; group 4, 2 medial double-loaded screw anchors tied in 2 mattress stitches and 2 push-in lateral anchors capturing the medial sutures in a "crisscross" spanning stitch; and group 5, 2 medial double-loaded screw anchors tied in 2 mattress stitches and 2 push-in lateral anchors creating a "suture-bridge" stitch. The specimens were cycled between 10 and 180 N at 1.0 Hz for 3,500 cycles or until failure. Endpoints were cyclic loading displacement (5 and 10 mm), total displacement, and ultimate failure load. A single row of triply loaded anchors was more resistant to stretching to a 5- and 10-mm gap than the double-row repairs with or without the addition of a rip-stop suture (P < .05). The addition of a rip-stop stitch made the repair more resistant to gap formation than a double row repair (P < .05). The crisscross double row created by 2 medial double-loaded suture anchors and 2 lateral push-in anchors stretched more than any other group (P < .05). Double-row repairs with either crossing sutures or 4 separate anchor points were more likely to fail (5- or 10-mm gap) than a single-row repair loaded with 3 simple sutures. The triple-loaded anchors with ultrahigh-molecular weight polyethylene-containing sutures placed in a single row were more resistant to stretching than the double-row groups. Copyright 2010 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Recovering bridge deflections from collocated acceleration and strain measurements

NASA Astrophysics Data System (ADS)

Bell, M.; Ma, T. W.; Xu, N. S.

2015-04-01

In this research, an internal model based method is proposed to estimate the displacement profile of a bridge subjected to a moving traffic load using a combination of acceleration and strain measurements. The structural response is assumed to be within the linear range. The deflection profile is assumed to be dominated by the fundamental mode of the bridge, therefore only requiring knowledge of the first mode. This still holds true under a multiple vehicle loading situation as the high mode shapes don't impact the over all response of the structure. Using the structural modal parameters and partial knowledge of the moving vehicle load, the internal models of the structure and the moving load can be respectively established, which can be used to form an autonomous state-space representation of the system. The structural displacements, velocities, and accelerations are the states of such a system, and it is fully observable when the measured output contains structural accelerations and strains. Reliable estimates of structural displacements are obtained using the standard Kalman filtering technique. The effectiveness and robustness of the proposed method has been demonstrated and evaluated via numerical simulation of a simply supported single span concrete bridge subjected to a moving traffic load.

Comparative Evaluation of Impact Strength of Fragment Bonded Teeth and Intact Teeth: An In Vitro Study

PubMed Central

Venugopal, L; Lakshmi, M Narasimha; Babu, Devatha Ashok; Kiran, V Ravi

2014-01-01

Background: To test and compare the impact strength of fragment bonded teeth with that of intact teeth by using impact testing machine (pendulum type) as a mode of load. Materials and Methods: Forty extracted, maxillary, central incisors selected for this study (20 control group and 20 experimental group). In experimental group, teeth crowns were fractured with a microtome at 2.5 mm from mesioincisal angle cervically, fractured portion is attached to original crown portion with 3 M single bond dentin bonding agent and 3 M Z ‘100’, composite resin. Impact strength of fragment bonded teeth and intact teeth tested with impact testing machine and compared. Results: Mean impact strength of fragment bonded teeth (30.76 KJ/M2 ) is not statistically significant deferent from mean impact strength of intact teeth (31.11 KJ/M2 ). Conclusion: Mean impact strength of fragment bonded teeth is not statistically different with that of intact teeth. Hence, after fracture of teeth if it is restored with fragment reattachment by using 3 M single bond dentin bonding agent and 3 M Z ‘100’ composite resin is having impact strength like that of intact teeth. How to cite the article: Venugopal L, Lakshmi MN, Babu DA, Kiran VR. Comparative evaluation of impact strength of fragment bonded teeth and intact teeth: An in vitro study. J Int Oral Health 2014;6(3):73-6. PMID:25083037

On the dynamic behavior of mineralized tissues

NASA Astrophysics Data System (ADS)

Kulin, Robb Michael

Mineralized tissues, such as bone and antler, are complex hierarchical materials that have adapted over millennia to optimize strength and fracture resistance for their in vivo applications. As a structural support, skeletal bone primarily acts as a rigid framework that is resistant to fracture, and able to repair damage and adapt to sustained loads during its lifetime. Antler is typically deciduous and subjected to large bending moments and violent impacts during its annual cycle. To date, extensive characterization of the quasi-static mechanical properties of these materials has been performed. However, very little has been done to characterize their dynamic properties, despite the fact that the majority of failures in these materials occur under impact loads. Here, an in depth analysis of the dynamic mechanical behavior of these two materials is presented, using equine bone obtained post-mortem from donors ranging in age from 6 months to 28 years, and antler from the North American Elk. Specimens were tested under compressive strain rates of 10-3, 100, and 103 sec-1 in order to investigate their strain rate dependent compressive response. Fracture toughness experiments were performed using a four-point bending geometry on single and double-notch specimens in order to measure fracture toughness, as well as observe differences in crack propagation between dynamic (˜2x105 MPa˙m1/2/s) and quasi-static (˜0.25 MPa˙m1/2/s) loading rates. After testing, specimens were analyzed using a combination of optical, electron and confocal microscopy. Results indicated that the mechanical response of these materials is highly dependent on loading rate. Decreasing quasi-static fracture toughness is observed with age in bone specimens, while dynamic specimens show no age trends, yet universally decreased fracture toughness compared to those tested quasi-statically. For the first time, rising R-curve behavior in bone was also shown to exist under both quasi-static and dynamic loading. Antler demonstrated itself to be extremely resistant to impact loading, often requiring multiple impacts to fracture a specimen. Microscopy observations of deformation and crack propagation mechanisms indicate that differences in mechanical behavior between bone and antler, and at varying strain rates, are the result of subtle differences in bulk composition and active microstructural toughening mechanisms.

Deformation, Fracture and Explosive Properties of Reactive Materials.

DTIC Science & Technology

1985-02-01

pump was adjusted such that the oressure inside the system did not exceed 10- 5 torr at maximum gas evol ut ion. c) Laser Initiation In a separate...of the impact and ignition processes. Laser - L speckle, used in conjun ion with a specimen loaded in the Brazilian test geometry which gives ten*le...by heating slowly, by fracturing single crystals and by laser irradiation.- Dfferent reaction pathways were found in each case and these are

Review of Rail Behavior Under Wheel/Rail Impact Loading

DOT National Transportation Integrated Search

1986-04-01

The report discusses several studies involving factors that significantly affect rail life, particularly wheel impact loads. Parameters that characterize the effect of wheel impact loads on rail behavior are examined in terms of system variables such...

Friction Stir Weld Failure Mechanisms in Aluminum-Armor Structures Under Ballistic Impact Loading Conditions

DTIC Science & Technology

2013-01-01

REPORT Friction Stir Weld Failure Mechanisms in Aluminum -Armor Structures Under Ballistic Impact Loading Conditions 14. ABSTRACT 16. SECURITY...Stir Weld Failure Mechanisms in Aluminum -Armor Structures Under Ballistic Impact Loading Conditions M. Grujicic, B. Pandurangan, A. Arakere, C-F. Yen...K.O. Pedersen, Fracture Mechanisms of Aluminum Alloy AA7075-T651 Under Various Loading Conditions , Int. J. Impact Eng., 2010, 37, p 537–551 24. T

Experimental Study on Impact Load on a Dam Due to Debris Flow

Treesearch

lwao Miyoshi

1991-01-01

When a dam is struck by mud or debris flow, it is put under a great impact load and sometimes is destroyed. To prevent such destruction, it is important to perform basic research about the impact load on a dam due to debris flow. Thus, we have made an experimental study and tried to establish a method to estimate such a impact load on the dam. The experiment was...

On Characterizing Particle Shape

NASA Technical Reports Server (NTRS)

Ennis, Bryan J.; Rickman, Douglas; Rollins, A. Brent; Ennis, Brandon

2014-01-01

It is well known that particle shape affects flow characteristics of granular materials, as well as a variety of other solids processing issues such as compaction, rheology, filtration and other two-phase flow problems. The impact of shape crosses many diverse and commercially important applications, including pharmaceuticals, civil engineering, metallurgy, health, and food processing. Two applications studied here include the dry solids flow of lunar simulants (e.g. JSC-1, NU-LHT-2M, OB-1), and the flow properties of wet concrete, including final compressive strength. A multi-dimensional generalized, engineering method to quantitatively characterize particle shapes has been developed, applicable to both single particle orientation and multi-particle assemblies. The two-dimension, three dimension inversion problem is also treated, and the application of these methods to DEM model particles will be discussed. In the case of lunar simulants, flow properties of six lunar simulants have been measured, and the impact of particle shape on flowability - as characterized by the shape method developed here -- is discussed, especially in the context of three simulants of similar size range. In the context of concrete processing, concrete construction is a major contributor to greenhouse gas production, of which the major contributor is cement binding loading. Any optimization in concrete rheology and packing that can reduce cement loading and improve strength loading can also reduce currently required construction safety factors. The characterization approach here is also demonstrated for the impact of rock aggregate shape on concrete slump rheology and dry compressive strength.

Parameterizing the Variability and Uncertainty of Wind and Solar in CEMs

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

Frew, Bethany

We present current and improved methods for estimating the capacity value and curtailment impacts from variable generation (VG) in capacity expansion models (CEMs). The ideal calculation of these variability metrics is through an explicit co-optimized investment-dispatch model using multiple years of VG and load data. Because of data and computational limitations, existing CEMs typically approximate these metrics using a subset of all hours from a single year and/or using statistical methods, which often do not capture the tail-event impacts or the broader set of interactions between VG, storage, and conventional generators. In our proposed new methods, we use hourly generationmore » and load values across all hours of the year to characterize the (1) contribution of VG to system capacity during high load hours, (2) the curtailment level of VG, and (3) the reduction in VG curtailment due to storage and shutdown of select thermal generators. Using CEM model outputs from a preceding model solve period, we apply these methods to exogenously calculate capacity value and curtailment metrics for the subsequent model solve period. Preliminary results suggest that these hourly methods offer improved capacity value and curtailment representations of VG in the CEM from existing approximation methods without additional computational burdens.« less

Estimating nitrogen loading and far-field dispersal potential from background sources and coastal finfish aquaculture: A simple framework and case study in Atlantic Canada

NASA Astrophysics Data System (ADS)

McIver, R.; Milewski, I.; Loucks, R.; Smith, R.

2018-05-01

Far-field nutrient impacts associated with finfish aquaculture have been identified as a topic of concern for regulators, managers, scientists, and the public for over two decades but disentangling aquaculture impacts from those caused by other natural and anthropogenic sources has impeded the development of monitoring metrics and management plans. We apply a bulk, steady-state nitrogen loading model (NLM) framework to estimate the annual input of Total Dissolved Nitrogen (TDN) from point and non-point sources to the watershed surrounding Port Mouton Bay, Nova Scotia (Canada). We then use the results of the NLM together with estimates of dissolved inorganic nitrogen (DIN) loading from a sea-cage trout farm in the Bay and progressive vector diagrams to illustrate potential patterns of DIN dispersal from the trout farm. Our estimated anthropogenic nitrogen contribution to Port Mouton Bay from all terrestrial and atmospheric sources is ∼211,703 kg TDN/year with atmospheric deposition accounting for almost all (98.6%). At a stocking level of ∼400,000 rainbow trout, the Port Mouton Bay sea-cage farm increases the annual anthropogenic TDN loading to the bay by 14.4% or 30,400 kg. Depending on current flow rates, nitrogen flux from the trout farm can be more than double the background concentrations of TDN near the farm site. Although it is unlikely that nitrogen loading from this single fish farm is saturating the DIN requirements of the entire bay, progressive vector diagrams suggest that the dispersal potential may be insufficient to mitigate potential symptoms of eutrophication associated with nitrogen fluxes. We present an accessible and user-friendly tool for managers to estimate baseline nutrient loading in relation to aquaculture and our use of progressive vector diagrams illustrate a practical and simple method for characterizing potential nutrient dispersal based on local conditions and spatial scales. Our study joins numerous studies which have highlighted the need for more effective monitoring and assessment methods to improve the detection of aquaculture effects at far-field scales and to assess those effects in relation to other natural and anthropogenic factors impacting coastal habitats.

Eye safety analysis for non-uniform retinal scanning laser trajectories

NASA Astrophysics Data System (ADS)

Schelinski, Uwe; Dallmann, Hans-Georg; Grüger, Heinrich; Knobbe, Jens; Pügner, Tino; Reinig, Peter; Woittennek, Franziska

2016-03-01

Scanning the retinae of the human eyes with a laser beam is an approved diagnosis method in ophthalmology; moreover the retinal blood vessels form a biometric modality for identifying persons. Medical applied Scanning Laser Ophthalmoscopes (SLOs) usually contain galvanometric mirror systems to move the laser spot with a defined speed across the retina. Hence, the load of laser radiation is uniformly distributed and eye safety requirements can be easily complied. Micro machined mirrors also known as Micro Electro Mechanical Systems (MEMS) are interesting alternatives for designing retina scanning systems. In particular double-resonant MEMS are well suited for mass fabrication at low cost. However, their Lissajous-shaped scanning figure requires a particular analysis and specific measures to meet the requirements for a Class 1 laser device, i.e. eye-safe operation. The scanning laser spot causes a non-uniform pulsing radiation load hitting the retinal elements within the field of view (FoV). The relevant laser safety standards define a smallest considerable element for eye-related impacts to be a point source that is visible with an angle of maximum 1.5 mrad. For non-uniform pulsing expositions onto retinal elements the standard requires to consider all particular impacts, i.e. single pulses, pulse sequences in certain time intervals and cumulated laser radiation loads. As it may be expected, a Lissajous scanning figure causes the most critical radiation loads at its edges and borders. Depending on the applied power the laser has to be switched off here to avoid any retinal injury.

Scattering and Imaging of Nonlinearly Loaded Antenna Structures in Half-Space and Complex-Room Environments

DTIC Science & Technology

2014-09-01

ABSTRACT The electromagnetic scattering responses of nonlinearly loaded antenna structures excited by single- tone or multi- tone incident fields are...3  Fig. 2 Monostatic scattered electric field strength for center array element: a) Single- tone excitation at 300 MHz...three diode-loaded targets and b) Two- tone excitation at 300 MHz and 305 MHz; two varactor-loaded targets

Mechanically metastable structures generated by single pulse laser-induced periodic surface structures (LIPSS) in the photoresist SU8.

PubMed

Reinhardt, Hendrik; Peschke, Patrick; Riedel, René; Hampp, Norbert

2018-07-27

Laser-induced periodic surface structures (LIPSS) with a periodicity of 351 nm are generated in the negative photoresist SU8 by single nanosecond laser pulse impact. Friction scans indicate the periodic pattern to comprise alternating regions of crosslinked and non-crosslinked SU8. Intriguingly, even minor mechanical stimuli in the order of nanonewtons cause the unfolding or rather the deletion of the characteristic periodic pattern similarly to the release of a pre-loaded spring. This feature combined with high resilience to heat and photon irradiation makes SU8-LIPSS attractive for applications such as mechanical stress monitors, self-destructing memory and passive micro actuators.

Mechanically metastable structures generated by single pulse laser-induced periodic surface structures (LIPSS) in the photoresist SU8

NASA Astrophysics Data System (ADS)

Reinhardt, Hendrik; Peschke, Patrick; Riedel, René; Hampp, Norbert

2018-07-01

Laser-induced periodic surface structures (LIPSS) with a periodicity of 351 nm are generated in the negative photoresist SU8 by single nanosecond laser pulse impact. Friction scans indicate the periodic pattern to comprise alternating regions of crosslinked and non-crosslinked SU8. Intriguingly, even minor mechanical stimuli in the order of nanonewtons cause the unfolding or rather the deletion of the characteristic periodic pattern similarly to the release of a pre-loaded spring. This feature combined with high resilience to heat and photon irradiation makes SU8-LIPSS attractive for applications such as mechanical stress monitors, self-destructing memory and passive micro actuators.

Thermal effect on the dynamic infiltration of water into single-walled carbon nanotubes.

PubMed

Zhao, Jianbing; Liu, Ling; Culligan, Patricia J; Chen, Xi

2009-12-01

Thermally induced variation in wetting ability in a confined nanoenvironment, indicated by the change in infiltration pressure as water molecules enter a model single-walled carbon nanotube submerged in aqueous environment, is investigated using molecular dynamics simulations. The temperature-dependent infiltration behavior is impacted in part by the thermally excited radial oscillation of the carbon nanotube, and in part by the variations of fundamental physical properties at the molecular level, including the hydrogen bonding interaction. The thermal effect is also closely coupled with the nanotube size effect and loading rate effect. Manipulation of the thermally responsive infiltration properties could facilitate the development of a next-generation thermal energy converter based on nanoporous materials.

Biomechanical Comparison of Standard and Linked Single-Row Rotator Cuff Repairs in a Human Cadaver Model.

PubMed

Meisel, Adam F; Henninger, Heath B; Barber, F Alan; Getelman, Mark H

2017-05-01

The purpose of this study was to evaluate the time zero cyclic and failure loading properties of a linked single-row rotator cuff repair compared with a standard simple suture single-row repair using triple-loaded suture anchors. Eighteen human cadaveric shoulders from 9 matched pairs were dissected, and full-thickness supraspinatus tears were created. The tendon cross-sectional area was recorded. In each pair, one side was repaired with a linked single-row construct and the other with a simple suture single-row construct, both using 2 triple-loaded suture anchors. After preloading, specimens were cycled to 1 MPa of effective stress at 1 Hz for 500 cycles, and gap formation was recorded with a digital video system. Samples were then loaded to failure, and modes of failure were recorded. There was no statistical difference in peak gap formation between the control and linked constructs (3.6 ± 0.9 mm and 3.6 ± 1.2 mm, respectively; P = .697). Both constructs averaged below a 5-mm cyclic failure threshold. There was no statistical difference in ultimate load to failure between the control and linked repair (511.1 ± 139.0 N and 561.2 ± 131.8 N, respectively; P = .164), and both groups reached failure at loads similar to previous studies. Constructs failed predominantly via tissue tearing parallel to the medial suture line. The linked repair performed similarly to the simple single-row repair. Both constructs demonstrated high ultimate load to failure and good resistance to gap formation with cyclic loading, validating the time zero strength of both constructs in a human cadaveric model. The linked repair provided equivalent resistance to gap formation and failure loads compared with simple suture single-row repairs with triple-loaded suture anchors. This suggests that the linked repair is a simplified rip-stop configuration using the existing suture that may perform similarly to current rotator cuff repair techniques. Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Impact of process parameters on the breakage kinetics of poorly water-soluble drugs during wet stirred media milling: a microhydrodynamic view.

PubMed

Afolabi, Afolawemi; Akinlabi, Olakemi; Bilgili, Ecevit

2014-01-23

Wet stirred media milling has proven to be a robust process for producing nanoparticle suspensions of poorly water-soluble drugs. As the process is expensive and energy-intensive, it is important to study the breakage kinetics, which determines the cycle time and production rate for a desired fineness. Although the impact of process parameters on the properties of final product suspensions has been investigated, scant information is available regarding their impact on the breakage kinetics. Here, we elucidate the impact of stirrer speed, bead concentration, and drug loading on the breakage kinetics via a microhydrodynamic model for the bead-bead collisions. Suspensions of griseofulvin, a model poorly water-soluble drug, were prepared in the presence of two stabilizers: hydroxypropyl cellulose and sodium dodecyl sulfate. Laser diffraction, scanning electron microscopy, and rheometry were used to characterize them. Various microhydrodynamic parameters including a newly defined milling intensity factor was calculated. An increase in either the stirrer speed or the bead concentration led to an increase in the specific energy and the milling intensity factor, consequently faster breakage. On the other hand, an increase in the drug loading led to a decrease in these parameters and consequently slower breakage. While all microhydrodynamic parameters provided significant physical insight, only the milling intensity factor was capable of explaining the influence of all parameters directly through its strong correlation with the process time constant. Besides guiding process optimization, the analysis rationalizes the preparation of a single high drug-loaded batch (20% or higher) instead of multiple dilute batches. Copyright © 2013 Elsevier B.V. All rights reserved.

Mother-to-child transmission of HIV-1: association with malaria prevention, anaemia and placental malaria.

PubMed

Naniche, D; Lahuerta, M; Bardaji, A; Sigauque, B; Romagosa, C; Berenguera, A; Mandomando, I; David, C; Sanz, S; Aponte, J; Ordi, J; Alonso, P; Menendez, C

2008-10-01

Malaria infection may impact on mother-to-child transmission (MTCT) of HIV-1. Prevention of malaria in pregnancy could thus potentially affect MTCT of HIV. We studied the impact of intermittent preventive treatment during pregnancy (IPTp) on HIV-1 MTCT in southern Mozambique. A total of 207 HIV-positive Mozambican pregnant women were enrolled in the study as part of a randomized placebo-controlled trial of two-dose sulfadoxine-pyrimethamine (SP) IPTp in women receiving single-dose nevirapine to prevent MTCT of HIV. HIV RNA viral load, maternal anaemia and peripheral and placental malaria were assessed at delivery. Infant HIV status was determined by DNA polymerase chain reaction (PCR) at 1 month of age. There were 19 transmissions of HIV in 153 mother-infant pairs. IPTp with SP did not have a significant impact on MTCT (11.8% in the SP group vs. 13.2% in the placebo group; P=0.784) or on maternal HIV RNA viral load [16 312 (interquartile range {IQR} 4076-69 296) HIV-1 RNA copies/mL in the SP group vs. 18 274 (IQR 5471-74 104) copies/mL in the placebo group; P=0.715]. In multivariate analysis, maternal HIV RNA viral load [adjusted odds ratio (AOR) 19.9; 95% confidence interval (CI) 2.3-172; P=0.006] and anaemia (haematocrit <33%; AOR 7.5; 95% CI 1.7-32.4; P=0.007) were independent risk factors for MTCT. Placental malaria was associated with a decrease in MTCT (AOR 0.23; 95% CI 0.06-0.89; P=0.034). IPTp with SP was not associated with a significant impact on MTCT of HIV. Maternal anaemia was an independent risk factor for MTCT.

Transient loads identification for a standoff metallic thermal protection system panel.

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

Hundhausen, R. J.; Adams, Douglas E.; Derriso, Mark

2004-01-01

Standoff thermal protection system (TPS) panels are critical structural components in future aerospace vehicles because they protect the vehicle from the hostile environment encountered during space launch and reentry. Consequently, the panels are exposed to a variety of loads including high temperature thermal stresses, thermal shock, acoustic pressure, and foreign object impacts. Transient impacts are especially detrimental because they can cause immediate and severe degradation of the panel in the form of, for example, debonding and buckling of the face sheet, cracking of the fasteners, or deformation of the standoffs. Loads identification methods for determining the magnitude and location ofmore » impact loads provide an indication of TPS components that may be more susceptible to failure. Furthermore, a historical database of impact loads encountered can be retained for use in the development of statistical models that relate impact loading to panel life. In this work, simulated inservice transient loads are identified experimentally using two methods: a physics-based approach and an inverse Frequency Response Function (FRF) approach. It is shown that by applying the inverse FRF method, the location and magnitude of these simulated impacts can be identified with a high degree of accuracy. The identified force levels vary significantly with impact location due to the differences in panel deformation at the impact site indicating that resultant damage due to impacts would vary with location as well.« less

Adult Bone Strength of Children from Single-Parent Families: The Midlife in the U.S. Study

PubMed Central

Crandall, Carolyn J.; Karlamangla, Arun S.; Merkin, Sharon Stein; Binkley, Neil; Carr, Deborah; Greendale, Gail A.; Seeman, Teresa E.

2015-01-01

Purpose Because peak bone mass is acquired during childhood, bone health may be negatively impacted by childhood socio-environmental disadvantage. The goal of this study was to determine whether being raised in a single-parent household is associated with lower bone strength in adulthood. Methods Using dual-energy x-ray absorptiometry data from 708 participants (mean age 57 years) in the Midlife in the United States Biomarker Project, we examined the independent associations of composite indices of femoral neck bone strength relative to load (in three failure modes: compression, bending, and impact) in adulthood with the experience of single-parent childhood and parental death or divorce in childhood. Results After adjustment for gender, race, menopause transition stage, age, and body mass index, each additional year of single-parent childhood was associated with 0.02 to 0.03 SD lower indices of adult femoral neck strength. In those with 9-16 years of single-parent childhood, the compression strength index was 0.41 SD lower, bending strength index was 0.31 SD lower, and impact strength index was 0.25 SD lower (all p-values < 0.05). In contrast, parental death or divorce during childhood was not by itself independently associated with adult bone strength indices. The magnitudes of these associations were unaltered by additional adjustment for lifestyle factors and socioeconomic status in childhood and adulthood. Conclusions Independent of parental death or divorce, growing up in a single-parent household is associated with lower femoral neck bone strength in adulthood, and this association is not entirely explained by childhood or adult socioeconomic conditions or lifestyle choices. PMID:25510582

The influence of impact direction and axial loading on the bone fracture pattern.

PubMed

Cohen, Haim; Kugel, Chen; May, Hila; Medlej, Bahaa; Stein, Dan; Slon, Viviane; Brosh, Tamar; Hershkovitz, Israel

2017-08-01

The effect of the direction of the impact and the presence of axial loading on fracture patterns have not yet been established in experimental 3-point bending studies. To reveal the association between the direction of the force and the fracture pattern, with and without axial loading. A Dynatup Model POE 2000 (Instron Co.) low energy pendulum impact machine was utilized to apply impact loading on fresh pig femoral bones (n=50). The bone clamp shaft was adjusted to position the bone for three-point bending with and without additional bone compression. Four different directions of the force were applied: anterior, posterior, lateral, and medial. The impacted aspect can be distinguished from the non-impacted aspects based on the fracture pattern alone (the most fractured one); the impact point can be identified on bare bones (the area from which all oblique lines radiate and/or the presence of a chip fragment). None of our experiments (with and without compression) yielded a "true" butterfly fracture, but instead, oblique radiating lines emerged from the point of impact (also known as "false" butterfly). Impacts on the lateral and anterior aspects of the bones produce more and longer fracture lines than impacts on the contralateral side; bones subjected to an impact with axial loading are significantly more comminuted and fragmented. Under axial loading, the number of fracture lines is independent of the impact direction. Our study presents an experimental model for fracture analysis and shows that the impact direction and the presence of axial loading during impact significantly affect the fracture pattern obtained. Copyright © 2017 Elsevier B.V. All rights reserved.

Single-Layer, All-Metal Patch Antenna Element with Wide Bandwidth

NASA Technical Reports Server (NTRS)

Chamberlain, Neil F.; Hodges, Richard E.; Zawardzki, Mark S.

2012-01-01

It is known that the impedance at the center of a patch antenna element is a short circuit, implying that a wire or post can be connected from the patch to the groundplane at this point without impacting radiation performance. In principle, this central post can be used to support the patch element, thus eliminating the need for dielectric. In spaceborne applications, this approach is problematic because a patch element supported by a single, thin post is highly susceptible to acoustic loads during launch. The technology reported here uses a large-diameter center post as its supporting structure. The supporting structure allows for the fabrication of a sufficiently rigid antenna element that can survive launch loads. The post may be either hollow or solid, depending on fabrication approach and/or mass constraints. The patch antenna element and support post are envisioned as being fabricated (milled) from a single piece of aluminum or other metal. Alternately, the patch plate and support column can be fabricated separately and then joined using fasteners, adhesive, or welding. Casting and electroforming are also viable techniques for manufacturing the metal patch part(s). The patch structure is then either bonded or fastened to the supporting groundplane. Arrays of patch elements can be fabricated by attaching several structures to a common groundplane/support structure.

Loading a single photon into an optical cavity

NASA Astrophysics Data System (ADS)

Du, Shengwang; Liu, Chang; Sun, Yuan; Zhao, Luwei; Zhang, Shanchao; Loy, M. M. T.

2015-05-01

Confining and manipulating single photons inside a reflective optical cavity is an essential task of cavity quantum electrodynamics (CQED) for probing the quantum nature of light quanta. Such systems are also elementary building blocks for many protocols of quantum network, where remote cavity quantum nodes are coupled through flying photons. The connectivity and scalability of such a quantum network strongly depends on the efficiency of loading a single photon into cavity. In this work we demonstrate that a single photon with an optimal temporal waveform can be efficiently loaded into a cavity. Using heralded narrow-band single photons with exponential growth wave packet whose time constant matches the photon lifetime in the cavity, we demonstrate a loading efficiency of more than 87 percent from free space to a single-sided Fabry-Perot cavity. Our result and approach may enable promising applications in realizing large-scale CQED-based quantum networks. The work was supported by the Hong Kong RGC (Project No. 601411).

Development, characterization, and modeling of ballistic impact on composite laminates under compressive pre-stress

NASA Astrophysics Data System (ADS)

Kerr-Anderson, Eric

Structural composite laminates were ballistically impacted while under in-plane compressive pre-stress. Residual properties, damage characterization, and energy absorption were compared to determine synergistic effects of in-plane compressive pre-stress and impact velocity. A fixture was developed to apply in-plane compressive loads up to 30 tons to structural composites during an impact event using a single-stage light-gas gun. Observed failure modes included typical conical delamination, the development of an impact initiated shear crack (IISC), and the shear failure of a pre-stressed composite due to impact. It was observed that the compressive failure threshold quadratically decreased in relation to the impact velocity up to velocities that caused partial penetration. For all laminates impacted at velocities causing partial or full penetration up to 350 ms-1, the failure threshold was consistent and used as an experimental normalization. Samples impacted below 65% of the failure threshold witnessed no significant change in damage morphology or residual properties when compared to typical conical delamination. Samples impacted above 65% of the failure threshold witnessed additional damage in the form of a shear crack extending perpendicular to the applied load from the point of impact. The presence of an IISC reduced the residual properties and even caused failure upon impact at extreme combinations. Four failure envelopes have been established as: transient failure, steady state failure, impact initiated shear crack, and conical damage. Boundaries and empirically based equations for residual compressive strength have been developed for each envelope with relation to two E-glass/vinyl ester laminate systems. Many aspects of pre-stressed impact have been individually examined, but there have been no comprehensive examinations of pre-stressed impact. This research has resulted in the exploration and characterization of compressively pre-stressed damage for impact velocities resulting in reflection, partial penetration, and penetration at pre-stress levels resulting in conical damage, shear cracking, and failure.

Structural Performance of a Compressively Loaded Foam-Core Hat-Stiffened Textile Composite Panel

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.; Dexter, Benson H.

1996-01-01

A structurally efficient hat-stiffened panel concept that utilizes a structural foam as a stiffener core material has been designed and developed for aircraft primary structural applications. This stiffener concept is fabricated from textile composite material forms with a resin transfer molding process. This foam-filled hat-stiffener concept is structurally more efficient than most other prismatically stiffened panel configurations in a load range that is typical for both fuselage and wing structures. The panel design is based on woven/stitched and braided graphite-fiber textile preforms, an epoxy resin system, and Rohacell foam core. The structural response of this panel design was evaluated for its buckling and postbuckling behavior with and without low-speed impact damage. The results from single-stiffener and multi-stiffener specimen tests suggest that this structural concept responds to loading as anticipated and has excellent damage tolerance characteristics compared to a similar panel design made from preimpregnated graphite-epoxy tape material.

Step-response of a torsional device with multiple discontinuous non-linearities: Formulation of a vibratory experiment

NASA Astrophysics Data System (ADS)

Krak, Michael D.; Dreyer, Jason T.; Singh, Rajendra

2016-03-01

A vehicle clutch damper is intentionally designed to contain multiple discontinuous non-linearities, such as multi-staged springs, clearances, pre-loads, and multi-staged friction elements. The main purpose of this practical torsional device is to transmit a wide range of torque while isolating torsional vibration between an engine and transmission. Improved understanding of the dynamic behavior of the device could be facilitated by laboratory measurement, and thus a refined vibratory experiment is proposed. The experiment is conceptually described as a single degree of freedom non-linear torsional system that is excited by an external step torque. The single torsional inertia (consisting of a shaft and torsion arm) is coupled to ground through parallel production clutch dampers, which are characterized by quasi-static measurements provided by the manufacturer. Other experimental objectives address physical dimensions, system actuation, flexural modes, instrumentation, and signal processing issues. Typical measurements show that the step response of the device is characterized by three distinct non-linear regimes (double-sided impact, single-sided impact, and no-impact). Each regime is directly related to the non-linear features of the device and can be described by peak angular acceleration values. Predictions of a simplified single degree of freedom non-linear model verify that the experiment performs well and as designed. Accordingly, the benchmark measurements could be utilized to validate non-linear models and simulation codes, as well as characterize dynamic parameters of the device including its dissipative properties.

Neck muscle load distribution in lateral, frontal, and rear-end impacts: a three-dimensional finite element analysis.

PubMed

Hedenstierna, Sofia; Halldin, Peter; Siegmund, Gunter P

2009-11-15

A finite element (FE) model of the human neck was used to study the distribution of neck muscle loads during multidirectional impacts. The computed load distributions were compared to experimental electromyography (EMG) recordings. To quantify passive muscle loads in nonactive cervical muscles during impacts of varying direction and energy, using a three-dimensional (3D) continuum FE muscle model. Experimental and numerical studies have confirmed the importance of muscles in the impact response of the neck. Although EMG has been used to measure the relative activity levels in neck muscles during impact tests, this technique has not been able to measure all neck muscles and cannot directly quantify the force distribution between the muscles. A numerical model can give additional insight into muscle loading during impact. An FE model with solid element musculature was used to simulate frontal, lateral, and rear-end vehicle impacts at 4 peak accelerations. The peak cross-sectional forces, internal energies, and effective strains were calculated for each muscle and impact configuration. The computed load distribution was compared with experimental EMG data. The load distribution in the cervical muscles varied with load direction. Peak sectional forces, internal energies, and strains increased in most muscles with increasing impact acceleration. The dominant muscles identified by the model for each direction were splenius capitis, levator scapulae, and sternocleidomastoid in lateral impacts, splenius capitis, and trapezoid in frontal impacts, and sternocleidomastoid, rectus capitis posterior minor, and hyoids in rear-end impacts. This corresponded with the most active muscles identified by EMG recordings, although within these muscles the distribution of forces and EMG levels were not the same. The passive muscle forces, strains, and energies computed using a continuum FE model of the cervical musculature distinguished between impact directions and peak accelerations, and on the basis of prior studies, isolated the most important muscles for each direction.

Characterization and development of truck load spectra and growth factors for current and future pavement design practices in Louisiana : technical summary report.

DOT National Transportation Integrated Search

2011-07-01

Current roadway pavement design practices follow the standards set by the American Society of State : Highway and Transportation Officials (AASHTO), which require the use of an equivalent single axle load : (ESAL-18 kip single axle load) for design t...

Crash-test dummy and pendulum impact tests of ice hockey boards: greater displacement does not reduce impact

PubMed Central

Schmitt, Kai-Uwe; Muser, Markus H; Thueler, Hansjuerg; Bruegger, Othmar

2018-01-01

Background One injury mechanism in ice hockey is impact with the boards. We investigated whether more flexible hockey boards would provide less biomechanical loading on impact than did existing (reference) boards. Methods We conducted impact tests with a dynamic pendulum (mass 60 kg) and with crash test dummies (ES-2 dummy, 4.76 m/s impact speed). Outcomes were biomechanical loading experienced by a player in terms of head acceleration, impact force to the shoulder, spine, abdomen and pelvis as well as compression of the thorax. Results The more flexible board designs featured substantial displacement at impact. Some so-called flexible boards were displaced four times more than the reference board. The new boards possessed less stiffness and up to 90 kg less effective mass, reducing the portion of the board mass a player experienced on impact, compared with boards with a conventional design. Flexible boards resulted in a similar or reduced loading for all body regions, apart from the shoulder. The displacement of a board system did not correlate directly with the biomechanical loading. Conclusions Flexible board systems can reduce the loading of a player on impact. However, we found no correlation between the displacement and the biomechanical loading; accordingly, displacement alone was insufficient to characterise the overall loading of a player and thus the risk of injury associated with board impact. Ideally, the performance of boards is assessed on the basis of parameters that show a good correlation to injury risk. PMID:29084724

Impact of a phenytoin loading dose program in the emergency department.

PubMed

Brancaccio, Adam; Giuliano, Christopher; McNorton, Kelly; Delgado, George

2014-11-01

The use of a combined physician-and pharmacist-directed phenytoin loading dose program in an emergency department (ED) was evaluated. This single-center, observational, preimplementation-postimplementation study evaluated adult patients who received a phenytoin loading dose in the ED. The primary outcome compared the proportion of optimal phenytoin loading doses in the preimplementation and postimplementation groups. The postimplementation group was further stratified into pharmacist- and prescriber-dosing groups. Other outcomes evaluated included the numbers of appropriate serum phenytoin concentrations measured, adverse drug reactions (ADRs), and recurrence of seizures within 24 hours of loading dose administration in the preimplementation and postimplementation groups. There was no difference in the proportion of optimal phenytoin loading doses between the preimplementation and postimplementation groups (50% versus 62%, respectively; p=0.19). When stratified by individual groups, the rate of optimal phenytoin loading doses increased by 64% in the postimplementation pharmacist group (50% versus 82%, p=0.007), while the rate in the prescriber-dosing group remained relatively unchanged (50% versus 49%, p=0.91). The number of appropriate serum phenytoin concentrations significantly improved in the postimplementation versus preimplementation group (65% versus 40%, p=0.025). Rates of ADRs and recurrence of seizures did not differ across the study groups. No change in the percentage of optimal phenytoin loading doses in the ED was observed after implementation of a combined pharmacist- and physician- dosing program. When stratified into pharmacist or prescriber dosing, the pharmacist-led dosing program significantly improved the proportion of patients who received optimal phenytoin loading doses. Copyright © 2014 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.

PubMed

Wellmann, Mathias; Wiebringhaus, Philipp; Lodde, Ina; Waizy, Hazibullah; Becher, Christoph; Raschke, Michael J; Petersen, Wolf

2009-12-01

The purpose of the study was to compare a single-row repair and a double-row repair technique for the specific characteristics of a complete subscapularis lesion. Ten pairs of human cadaveric shoulder human shoulder specimens were tested for stiffness and ultimate tensile strength of the intact tendons in a load to failure protocol. After a complete subscapularis tear was provoked, the specimens were assigned to two treatment groups: single-row repair (1) and a double-row repair using a "suture bridge" technique (2). After repair cyclic loading a subsequent load to failure protocol was performed to determine the ultimate tensile load, the stiffness and the elongation behaviour of the reconstructions. The intact subscapularis tendons had a mean stiffness of 115 N/mm and a mean ultimate load of 720 N. The predominant failure mode of the intact tendons was a tear at the humeral insertion site (65%). The double-row technique restored 48% of the ultimate load of the intact tendons (332 N), while the single-row technique revealed a significantly lower ultimate load of 244 N (P = 0.001). In terms of the stiffness, the double-row technique showed a mean stiffness of 81 N/mm which is significantly higher compared to the stiffness of the single-row repairs of 55 N/mm (P = 0.001). The double-row technique has been shown to be stronger and stiffer when compared to a conventional single-row repair. Therefore, this technique is recommended from a biomechanical point of view irrespectively if performed by an open or arthroscopic approach.

Properties of fiber reinforced plastics about static and dynamic loadings

NASA Astrophysics Data System (ADS)

Kudinov, Vladimir V.; Korneeva, Natalia V.

2016-05-01

A method for investigation of impact toughness of anisotropic polymer composite materials (reinforced plastics) with the help of CM model sample in the configuration of microplastic (micro plastic) and impact pendulum-type testing machine under static and dynamic loadings has been developed. The method is called "Break by Impact" (Impact Break IB). The estimation of impact resistance CFRP by this method showed that an increase in loading velocity ~104 times the largest changes occurs in impact toughness and deformation ability of a material.

Seat strength in rear body block tests.

PubMed

Viano, David C; White, Samuel D

2016-07-03

This study collected and analyzed available testing of motor vehicle seat strength in rearward loading by a body block simulating the torso of an occupant. The data were grouped by single recliner, dual recliner, and all belts to seat (ABTS) seats. The strength of seats to rearward loading has been evaluated with body block testing from 1964 to 2008. The database of available tests includes 217 single recliner, 65 dual recliner, and 18 ABTS seats. The trends in seat strength were determined by linear regression and differences between seat types were evaluated by Student's t-test. The average peak moment and force supported by the seat was determined by decade of vehicle model year (MY). Single recliner seats were used in motor vehicles in the 1960s to 1970s. The average strength was 918 ± 224 Nm (n = 26) in the 1960s and 1,069 ± 293 Nm (n = 65) in the 1980s. There has been a gradual increase in strength over time. Dual recliner seats started to phase into vehicles in the late 1980s. By the 2000s, the average strength of single recliner seats increased to 1,501 ± 335 Nm (n = 14) and dual recliner seats to 2,302 ± 699 Nm (n = 26). Dual recliner seats are significantly stronger than single recliner seats for each decade of comparison (P < .001). The average strength of ABTS seats was 4,395 ± 1,185 in-lb for 1989-2004 MY seats (n = 18). ABTS seats are significantly stronger than single or dual recliner seats (P < .001). The trend in ABTS strength is decreasing with time and converging toward that of dual recliner seats. Body block testing is an quantitative means of evaluating the strength of seats for occupant loading in rear impacts. There has been an increase in conventional seat strength over the past 50 years. By the 2000s, most seats are 1,700-3,400 Nm moment strength. However, the safety of a seat is more complex than its strength and depends on many other factors.

Linear and nonlinear dynamic analysis of redundant load path bearingless rotor systems

NASA Technical Reports Server (NTRS)

Murthy, V. R.

1985-01-01

The bearingless rotorcraft offers reduced weight, less complexity and superior flying qualities. Almost all the current industrial structural dynamic programs of conventional rotors which consist of single load path rotor blades employ the transfer matrix method to determine natural vibration characteristics because this method is ideally suited for one dimensional chain like structures. This method is extended to multiple load path rotor blades without resorting to an equivalent single load path approximation. Unlike the conventional blades, it isk necessary to introduce the axial-degree-of-freedom into the solution process to account for the differential axial displacements in the different load paths. With the present extension, the current rotor dynamic programs can be modified with relative ease to account for the multiple load paths without resorting to the equivalent single load path modeling. The results obtained by the transfer matrix method are validated by comparing with the finite element solutions. A differential stiffness matrix due to blade rotation is derived to facilitate the finite element solutions.

Fracture Behavior of Zr-BASED Bulk Metallic Glass Under Impact Loading

NASA Astrophysics Data System (ADS)

Shin, Hyung-Seop; Kim, Ki-Hyun; Oh, Sang-Yeob

The fracture behavior of a Zr-based bulk amorphous metal under impact loading using subsize V-shaped Charpy specimens was investigated. Influences of loading rate on the fracture behavior of amorphous Zr-Al-Ni-Cu alloy were examined. As a result, the maximum load and absorbed fracture energy under impact loading were lower than those under quasi-static loading. A large part of the absorbed fracture energy in the Zr-based BMG was consumed in the process for crack initiation and not for crack propagation. In addition, fractographic characteristics of BMGs, especially the initiation and development of shear bands at the notch tip were investigated. Fractured surfaces under impact loading are smoother than those under quasi-static loading. The absorbed fracture energy appeared differently depending on the appearance of the shear bands developed. It can be found that the fracture energy and fracture toughness of Zr-based BMG are closely related with the extent of shear bands developed during fracture.

Effect of unilateral and bilateral use of laterally wedged insoles with arch supports on impact loading in medial knee osteoarthritis.

PubMed

Abd El Megeid Abdallah, Amira Abdallah

2016-04-01

Increased impact loading is implicated in knee osteoarthritis development and progression. This study examined the impact ground reaction force (GRF) peak, its loading rate, its relative timing to stance phase timing, and walking speed during unilateral and bilateral use of laterally wedged insoles with arch supports. Within-subject design. Thirty-three female patients with medial knee osteoarthritis were examined with (unilateral 6° and 11°, and bilateral 0°, 6°, and 11°) and without insole use. Repeated measures MANOVA revealed that the impact force increased significantly in bilateral 11° versus unilateral 6° and without-insole conditions. The loading rate decreased significantly in unilateral 11° versus bilateral 6° insoles. The relative timing increased significantly in each of bilateral 6°, bilateral 11°, and unilateral 11° versus bilateral 0° insoles and in each of bilateral 11° and unilateral 11° versus without-insole condition. There were significant positive correlations between the walking speed and each of the force and loading rate. The Chi-square test revealed insignificant association between the insole condition and the presence of impact forces. Unilateral 11° insoles are capable of reducing impact loading possibly through increasing foot pronation. Walking slowly is another possible strategy to reduce loading. Unilaterally applied 11° laterally wedged insoles are capable of reducing and delaying the initial impact ground reaction forces and reducing their loading rates during walking in patients with medial knee osteoarthritis, thus reducing osteoarthritis progression. Walking slowly could also be used as a strategy to reduce impact loading. © The International Society for Prosthetics and Orthotics 2015.

Rough-water Impact-load Investigation of a Chine-immersed V-bottom Model Having a Dead-rise Angle of 10 Degrees

NASA Technical Reports Server (NTRS)

Markey, Melvin F; Carpini, Thomas D

1957-01-01

A hydrodynamic rough-water impact-loads investigation of a fixed-trim V-bottom float with a beam-loading coefficient of 5.78 and dead-rise angle of 10 degrees was made at the Langley impact basin. The size of the waves varied from approximately 10 to 60 feet in length and 1 to 2 feet in height. Time histories were obtained showing the position of the model relative to the wave throughout the impact and typical examples are presented. The load coefficient was found to vary primarily with the slope of the impacting wave.

Fundamental Research on Percussion Drilling: Improved rock mechanics analysis, advanced simulation technology, and full-scale laboratory investigations

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

Michael S. Bruno

This report summarizes the research efforts on the DOE supported research project Percussion Drilling (DE-FC26-03NT41999), which is to significantly advance the fundamental understandings of the physical mechanisms involved in combined percussion and rotary drilling, and thereby facilitate more efficient and lower cost drilling and exploration of hard-rock reservoirs. The project has been divided into multiple tasks: literature reviews, analytical and numerical modeling, full scale laboratory testing and model validation, and final report delivery. Literature reviews document the history, pros and cons, and rock failure physics of percussion drilling in oil and gas industries. Based on the current understandings, a conceptualmore » drilling model is proposed for modeling efforts. Both analytical and numerical approaches are deployed to investigate drilling processes such as drillbit penetration with compression, rotation and percussion, rock response with stress propagation, damage accumulation and failure, and debris transportation inside the annulus after disintegrated from rock. For rock mechanics modeling, a dynamic numerical tool has been developed to describe rock damage and failure, including rock crushing by compressive bit load, rock fracturing by both shearing and tensile forces, and rock weakening by repetitive compression-tension loading. Besides multiple failure criteria, the tool also includes a damping algorithm to dissipate oscillation energy and a fatigue/damage algorithm to update rock properties during each impact. From the model, Rate of Penetration (ROP) and rock failure history can be estimated. For cuttings transport in annulus, a 3D numerical particle flowing model has been developed with aid of analytical approaches. The tool can simulate cuttings movement at particle scale under laminar or turbulent fluid flow conditions and evaluate the efficiency of cutting removal. To calibrate the modeling efforts, a series of full-scale fluid hammer drilling tests, as well as single impact tests, have been designed and executed. Both Berea sandstone and Mancos shale samples are used. In single impact tests, three impacts are sequentially loaded at the same rock location to investigate rock response to repetitive loadings. The crater depth and width are measured as well as the displacement and force in the rod and the force in the rock. Various pressure differences across the rock-indentor interface (i.e. bore pressure minus pore pressure) are used to investigate the pressure effect on rock penetration. For hammer drilling tests, an industrial fluid hammer is used to drill under both underbalanced and overbalanced conditions. Besides calibrating the modeling tool, the data and cuttings collected from the tests indicate several other important applications. For example, different rock penetrations during single impact tests may reveal why a fluid hammer behaves differently with diverse rock types and under various pressure conditions at the hole bottom. On the other hand, the shape of the cuttings from fluid hammer tests, comparing to those from traditional rotary drilling methods, may help to identify the dominant failure mechanism that percussion drilling relies on. If so, encouraging such a failure mechanism may improve hammer performance. The project is summarized in this report. Instead of compiling the information contained in the previous quarterly or other technical reports, this report focuses on the descriptions of tasks, findings, and conclusions, as well as the efforts on promoting percussion drilling technologies to industries including site visits, presentations, and publications. As a part of the final deliveries, the 3D numerical model for rock mechanics is also attached.« less

30 CFR 77.905 - Connection of single-phase loads.

Code of Federal Regulations, 2011 CFR

2011-07-01

... COAL MINES Low- and Medium-Voltage Alternating Current Circuits § 77.905 Connection of single-phase... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Connection of single-phase loads. 77.905 Section 77.905 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE...

30 CFR 77.905 - Connection of single-phase loads.

Code of Federal Regulations, 2010 CFR

2010-07-01

... COAL MINES Low- and Medium-Voltage Alternating Current Circuits § 77.905 Connection of single-phase... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Connection of single-phase loads. 77.905 Section 77.905 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE...

Progressive cell-mediated changes in articular cartilage and bone in mice are initiated by a single session of controlled cyclic compressive loading

PubMed Central

Ko, Frank C.; Dragomir, Cecilia L.; Plumb, Darren A.; Hsia, Allison W.; Adebayo, Olufunmilayo O.; Goldring, Steven R.; Wright, Timothy M.; Goldring, Mary B.; van der Meulen, Marjolein C.H.

2017-01-01

We previously showed that repetitive cyclic loading of the mouse knee joint causes changes that recapitulate the features of osteoarthritis (OA) in humans. By applying a single loading session, we characterized the temporal progression of the structural and compositional changes in subchondral bone and articular cartilage. We applied loading during a single 5-minute session to the left tibia of adult (26-week-old) C57Bl/6 male mice at a peak load of 9.0N for 1200 cycles. Knee joints were collected at times 0, 1, and 2 weeks after loading. The changes in articular cartilage and subchondral bone were analyzed by histology, immunohistochemistry (caspase-3 and cathepsin K), and microcomputed tomography. At time 0, no change was evident in chondrocyte viability or cartilage or subchondral bone integrity. However, cartilage pathology demonstrated by localized thinning and proteoglycan loss occurred at 1 and 2 weeks after the single session of loading. Transient cancellous bone loss was evident at 1 week, associated with increased osteoclast number. Bone loss was reversed to control levels at 2 weeks. We observed formation of fibrous and cartilaginous tissues at the joint margins at 1 and 2 weeks. Our findings demonstrate that a single session of noninvasive loading leads to the development of OA-like morphological and cellular alterations in articular cartilage and subchondral bone. The loss in subchondral trabecular bone mass and thickness returns to control levels at 2 weeks, whereas the cartilage thinning and proteoglycan loss persist. PMID:26896841

Harmonic force spectroscopy measures load-dependent kinetics of individual human β-cardiac myosin molecules.

PubMed

Sung, Jongmin; Nag, Suman; Mortensen, Kim I; Vestergaard, Christian L; Sutton, Shirley; Ruppel, Kathleen; Flyvbjerg, Henrik; Spudich, James A

2015-08-04

Molecular motors are responsible for numerous cellular processes from cargo transport to heart contraction. Their interactions with other cellular components are often transient and exhibit kinetics that depend on load. Here, we measure such interactions using 'harmonic force spectroscopy'. In this method, harmonic oscillation of the sample stage of a laser trap immediately, automatically and randomly applies sinusoidally varying loads to a single motor molecule interacting with a single track along which it moves. The experimental protocol and the data analysis are simple, fast and efficient. The protocol accumulates statistics fast enough to deliver single-molecule results from single-molecule experiments. We demonstrate the method's performance by measuring the force-dependent kinetics of individual human β-cardiac myosin molecules interacting with an actin filament at physiological ATP concentration. We show that a molecule's ADP release rate depends exponentially on the applied load, in qualitative agreement with cardiac muscle, which contracts with a velocity inversely proportional to external load.

Harmonic force spectroscopy measures load-dependent kinetics of individual human β-cardiac myosin molecules

PubMed Central

Sung, Jongmin; Nag, Suman; Mortensen, Kim I.; Vestergaard, Christian L.; Sutton, Shirley; Ruppel, Kathleen; Flyvbjerg, Henrik; Spudich, James A.

2015-01-01

Molecular motors are responsible for numerous cellular processes from cargo transport to heart contraction. Their interactions with other cellular components are often transient and exhibit kinetics that depend on load. Here, we measure such interactions using ‘harmonic force spectroscopy'. In this method, harmonic oscillation of the sample stage of a laser trap immediately, automatically and randomly applies sinusoidally varying loads to a single motor molecule interacting with a single track along which it moves. The experimental protocol and the data analysis are simple, fast and efficient. The protocol accumulates statistics fast enough to deliver single-molecule results from single-molecule experiments. We demonstrate the method's performance by measuring the force-dependent kinetics of individual human β-cardiac myosin molecules interacting with an actin filament at physiological ATP concentration. We show that a molecule's ADP release rate depends exponentially on the applied load, in qualitative agreement with cardiac muscle, which contracts with a velocity inversely proportional to external load. PMID:26239258

Operating health analysis of electric power systems

NASA Astrophysics Data System (ADS)

Fotuhi-Firuzabad, Mahmud

The required level of operating reserve to be maintained by an electric power system can be determined using both deterministic and probabilistic techniques. Despite the obvious disadvantages of deterministic approaches there is still considerable reluctance to apply probabilistic techniques due to the difficulty of interpreting a single numerical risk index and the lack of sufficient information provided by a single index. A practical way to overcome difficulties is to embed deterministic considerations in the probabilistic indices in order to monitor the system well-being. The system well-being can be designated as healthy, marginal and at risk. The concept of system well-being is examined and extended in this thesis to cover the overall area of operating reserve assessment. Operating reserve evaluation involves the two distinctly different aspects of unit commitment and the dispatch of the committed units. Unit commitment health analysis involves the determination of which unit should be committed to satisfy the operating criteria. The concepts developed for unit commitment health, margin and risk are extended in this thesis to evaluate the response well-being of a generating system. A procedure is presented to determine the optimum dispatch of the committed units to satisfy the response criteria. The impact on the response wellbeing being of variations in the margin time, required regulating margin and load forecast uncertainty are illustrated. The effects on the response well-being of rapid start units, interruptible loads and postponable outages are also illustrated. System well-being is, in general, greatly improved by interconnection with other power systems. The well-being concepts are extended to evaluate the spinning reserve requirements in interconnected systems. The interconnected system unit commitment problem is decomposed into two subproblems in which unit scheduling is performed in each isolated system followed by interconnected system evaluation. A procedure is illustrated to determine the well-being indices of the overall interconnected system. Under normal operating conditions, the system may also be able to carry a limited amount of interruptible load on top of its firm load without violating the operating criterion. An energy based approach is presented to determine the optimum interruptible load carrying capability in both the isolated and interconnected systems. Composite system spinning reserve assessment and composite system well-being are also examined in this research work. The impacts on the composite well-being of operating reserve considerations such as stand-by units, interruptible loads and the physical locations of these resources are illustrated. It is expected that the well-being framework and the concepts developed in this research work will prove extremely useful in the new competitive utility environment.

Mechanical Characterization of the Human Lumbar Intervertebral Disc Subjected to Impact Loading Conditions

NASA Astrophysics Data System (ADS)

Jamison, David, IV

Low back pain is a large and costly problem in the United States. Several working populations, such as miners, construction workers, forklift operators, and military personnel, have an increased risk and prevalence of low back pain compared to the general population. This is due to exposure to repeated, transient impact shocks, particularly while operating vehicles or other machinery. These shocks typically do not cause acute injury, but rather lead to pain and injury over time. The major focus in low back pain is often the intervertebral disc, due to its role as the major primary load-bearing component along the spinal column. The formation of a reliable standard for human lumbar disc exposure to repeated transient shock could potentially reduce injury risk for these working populations. The objective of this project, therefore, is to characterize the mechanical response of the lumbar intervertebral disc subjected to sub-traumatic impact loading conditions using both cadaveric and computational models, and to investigate the possible implications of this type of loading environment for low back pain. Axial, compressive impact loading events on Naval high speed boats were simulated in the laboratory and applied to human cadaveric specimen. Disc stiffness was higher and hysteresis was lower than quasi-static loading conditions. This indicates a shift in mechanical response when the disc is under impact loads and this behavior could be contributing to long-term back pain. Interstitial fluid loss and disc height changes were shown to affect disc impact mechanics in a creep study. Neutral zone increased, while energy dissipation and low-strain region stiffness decreased. This suggests that the disc has greater clinical instability during impact loading with progressive creep and fluid loss, indicating that time of day should be considered for working populations subjected to impact loads. A finite element model was developed and validated against cadaver specimen subjected to impacts in the laboratory. Analysis showed greater total von Mises stress and pore pressure in the components of the disc under transient shocks compared to static or quasi-static loading. These findings support the idea that impact shocks cause a change in mechanical response and are potentially damaging to the disc in the long term.

Effect of loading orientations on the microstructure and property of Al−Cu single crystal during stress aging

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

Chen, Jiqiang; Chen, Zhiguo, E-mail: zgchen@mail.csu.edu.cn; Hunan University of Humanities, Science and Technology, Loudi 417000

The precipitation behavior and property of Al−Cu alloy during stress aging under various loading orientations were investigated using single crystals. The resulting microstructures and the strength property were examined by transmission electron microscope (TEM) and compression test, respectively, and the effect of the distribution of θ′-plates on strength property were discussed. The results show that the precipitation distribution of θ′ was significantly affected by the loading orientation during stress aging of Al−Cu single crystals. Loading along close to 〈011〉{sub Al} directions provided more uniform precipitation distribution of θ′ as compared to loading along close to 〈001〉{sub Al} directions, and thereforemore » provided higher strengthening stress of the θ′-plates for the stress aging sample. The results suggested that regulating the distribution of θ′ and therefore improving strength property are possible via controlling the loading orientation during stress aging. - Highlights: • We studied the effect of loading directions on stress aging of Al−Cu single crystal. • Precipitation distribution of θ′ was noticeably affected by the loading direction. • Loading along close to 〈011〉{sub Al} directions reduced the stress-orienting effect. • The strength property is closely related to the precipitation distribution of θ′. • It is possible to regulate the distribution of θ′ and improve strength property.« less

Flexural impact force absorption of mouthguard materials using film sensor system.

PubMed

Reza, Fazal; Churei, Hiroshi; Takahashi, Hidekazu; Iwasaki, Naohiko; Ueno, Toshiaki

2014-06-01

Several methods have been used to measure the impact force absorption capacities of mouthguard materials; however, the relationships among these measurement systems have not been clearly determined. The purpose of the present study was to evaluate the impact force-absorbing capability of materials using a drop-ball system with film sensors and load cells to clarify the relationship between these two sensor systems. Disk-shaped specimens (1, 2, and 3 mm thick) were prepared using three commercial thermoplastic mouthguard materials (Bioplast, Impact Guard, MG 21) and one experimental mouthguard material [mixture of Poly (ethyl methacrylate)]. Impact force was applied by letting a stainless steel ball drop free-fall onto the specimens and then measuring the impact load under each specimen using a film sensor system and a load cell sensor system. The total load measured with the film sensor system decreased with an increase in mouthguard thickness, while almost none of the transmitted impact forces measured with the load cell system were statistically different. The film sensor system was considered to be superior to the load cell system because the maximum stress and stress area could be determined. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Crash-test dummy and pendulum impact tests of ice hockey boards: greater displacement does not reduce impact.

PubMed

Schmitt, Kai-Uwe; Muser, Markus H; Thueler, Hansjuerg; Bruegger, Othmar

2018-01-01

One injury mechanism in ice hockey is impact with the boards. We investigated whether more flexible hockey boards would provide less biomechanical loading on impact than did existing (reference) boards. We conducted impact tests with a dynamic pendulum (mass 60 kg) and with crash test dummies (ES-2 dummy, 4.76 m/s impact speed). Outcomes were biomechanical loading experienced by a player in terms of head acceleration, impact force to the shoulder, spine, abdomen and pelvis as well as compression of the thorax. The more flexible board designs featured substantial displacement at impact. Some so-called flexible boards were displaced four times more than the reference board. The new boards possessed less stiffness and up to 90 kg less effective mass, reducing the portion of the board mass a player experienced on impact, compared with boards with a conventional design. Flexible boards resulted in a similar or reduced loading for all body regions, apart from the shoulder. The displacement of a board system did not correlate directly with the biomechanical loading. Flexible board systems can reduce the loading of a player on impact. However, we found no correlation between the displacement and the biomechanical loading; accordingly, displacement alone was insufficient to characterise the overall loading of a player and thus the risk of injury associated with board impact. Ideally, the performance of boards is assessed on the basis of parameters that show a good correlation to injury risk. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Oral health-related quality of life changes after placement of immediately loaded single implants in healed alveolar ridges or extraction sockets: a 5-year prospective follow-up study.

PubMed

Raes, Stefanie; Raes, Filiep; Cooper, Lyndon; Giner Tarrida, Luis; Vervaeke, Stijn; Cosyn, Jan; De Bruyn, Hugo

2017-06-01

The impact of single implants on oral health-related quality of life (OHRQoL) is scarcely investigated, especially when combined with immediate placement and loading in extraction sockets. The aim was to describe prospectively the changes of OHRQoL with single implants placed in the esthetic zone in healed ridges or in extraction sockets after 5 years. Ninety-six patients, enrolled at three clinical centers, received 102 single implants placed in a healed ridge (n = 54 implants/50 patients) or in extraction sockets (n = 48 implants/46 patients). Implants were immediately provisionalized, and permanent crowns were cemented after 12 weeks. Oral health impact profile questionnaires (OHIP-14) were completed before surgery, after 1 (provisional crown), 6 (permanent crown), 12 and 60 months, respectively. The overall OHIP-14 score pertains to seven domains with two items each and was assessed on a Likert scale of 0-4 (0 = never and 4 = very often). The evolution of the total OHIP-14 score and changes within all OHIP domains over time and between groups were assessed with a linear mixed-effect model analysis. After 5 years, overall implant survival was 98%. The total OHIP-14 score for both groups combined decreased from 0.50 at baseline to 0.17 at 6 months (P < 0.001), indicative of improvement. For both groups, this remained stable up to 5 years (P = 0.41). However, after 5 years, the total OHIP-14 score revealed a statistically significantly higher improvement in the healed group compared with the extraction group (P = 0.027). Missing a single tooth in the maxillary esthetic zone leads to limited OHRQoL problems as reflected by a low overall OHIP score. However, OHRQoL improves less in the extraction group, reflecting that replacing a missing tooth is perceived as more beneficial than replacing a present tooth. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Simulation of the dissolved nitrogen and phosphorus loads in different land uses in the Three Gorges Reservoir Region--based on the improved export coefficient model.

PubMed

Wang, Jinliang; Shao, Jing'an; Wang, Dan; Ni, Jiupai; Xie, Deti

2015-11-01

Nonpoint source pollution is one of the primary causes of eutrophication of water bodies. The concentrations and loads of dissolved pollutants have a direct bearing on the environmental quality of receiving water bodies. Based on the Johnes export coefficient model, a pollutant production coefficient was established by introducing the topographical index and measurements of annual rainfall. A pollutant interception coefficient was constructed by considering the width and slope of present vegetation. These two coefficients were then used as the weighting factors to modify the existing export coefficients of various land uses. A modified export coefficient model was created to estimate the dissolved nitrogen and phosphorus loads in different land uses in the Three Gorges Reservoir Region (TGRR) in 1990, 1995, 2000, 2005, and 2010. The results show that the new land use export coefficient was established by the modification of the production pollution coefficient and interception pollution coefficient. This modification changed the single numerical structure of the original land use export coefficient and takes into consideration temporal and spatial differentiation features. The modified export coefficient retained the change structure of the original single land use export coefficient, and also demonstrated that the land use export coefficient was not only impacted by the change of land use itself, but was also influenced by other objective conditions, such as the characteristics of the underlying surface, amount of rainfall, and the overall presence of vegetation. In the five analyzed years, the simulation values of the dissolved nitrogen and phosphorus loads in paddy fields increased after applying the modification in calculation. The dissolved nitrogen and phosphorus loads in dry land comprised the largest proportions of the TGRR's totals. After modification, the dry land values showed an initial increase and then a decrease over time, but the increments were much smaller than those of the paddy field. The dissolved nitrogen and phosphorus loads in the woodland and meadow decreased after modification. The dissolved nitrogen and phosphorus loads in the building lot were the lowest but showed an increase with the progression of time. These results demonstrate that the modified export coefficient model significantly improves the accuracy of dissolved pollutant load simulation for different land uses in the TGRR, especially the accuracy of dissolved nitrogen load simulation.

Engine-Operating Load Influences Diesel Exhaust Composition and Cardiopulmonary and Immune Responses

PubMed Central

Campen, Matthew J.; Harrod, Kevin S.; Seagrave, JeanClare; Seilkop, Steven K.; Mauderly, Joe L.

2011-01-01

Background: The composition of diesel engine exhaust (DEE) varies by engine type and condition, fuel, engine operation, and exhaust after treatment such as particle traps. DEE has been shown to increase inflammation, susceptibility to infection, and cardiovascular responses in experimentally exposed rodents and humans. Engines used in these studies have been operated at idle, at different steady-state loads, or on variable-load cycles, but exposures are often reported only as the mass concentration of particulate matter (PM), and the effects of different engine loads and the resulting differences in DEE composition are unknown. Objectives: We assessed the impacts of load-related differences in DEE composition on models of inflammation, susceptibility to infection, and cardiovascular toxicity. Methods: We assessed inflammation and susceptibility to viral infection in C57BL/6 mice and cardiovascular toxicity in APOE–/– mice after being exposed to DEE generated from a single-cylinder diesel generator operated at partial or full load. Results: At the same PM mass concentration, partial load resulted in higher proportions of particle organic carbon content and a smaller particle size than did high load. Vapor-phase hydrocarbon content was greater at partial load. Compared with high-load DEE, partial-load DEE caused greater responses in heart rate and T-wave morphology, in terms of both magnitude and rapidity of onset of effects, consistent with previous findings that systemic effects may be driven largely by the gas phase of the exposure atmospheres. However, high-load DEE caused more lung inflammation and greater susceptibility to viral infection than did partial load. Conclusions: Differences in engine load, as well as other operating variables, are important determinants of the type and magnitude of responses to inhaled DEE. PM mass concentration alone is not a sufficient basis for comparing or combining results from studies using DEE generated under different conditions. PMID:21524982

Hydrodynamic Impact of a System with a Single Elastic Mode II : Comparison of Experimental Force and Response with Theory

NASA Technical Reports Server (NTRS)

Miller, Robert W; Merten, Kenneth F

1952-01-01

Hydrodynamic impact tests were made on an elastic model approximating a two-mass spring system to determine experimentally the effects of structural flexibility on the hydrodynamic loads encountered during seaplane landing impacts and to correlate the results with theory. A flexible seaplane was represented by a two-mass spring system consisting of a rigid prismatic float connected to a rigid upper mass by an elastic structure. The model had a ratio of sprung mass to hull mass of 0.6 and a natural frequency of 3.0 cycles per second. The tests were conducted in smooth water at fixed trims and included both high and low flight-path angles and a range of velocity. Theoretical and experimental comparisons indicated that the theoretical results agreed well with the experimental results.

Microscopic modelling of ignition and burning for well-arranged energetic crystals in response to drop-weight impact

NASA Astrophysics Data System (ADS)

Wu, Yanqing; Huang, Fenglei; Zhou, Min

2014-05-01

To probe into impact sensitivity of energetic crystals, a theoretical approach was developed for modelling a single layer of energetic particles between upper striker and below base. Considering the particle plasticity, frictional heating, melting, fracture, and chemical reaction at particle level, effects of loading parameters and sample characteristics on time-to-ignition and burning rate were compared. Finite element numerical simulations were simultaneously performed to provide supporting evidence for thermo-mechanical interactions among energetic particles. Once hot- spots ignition occurred during impact, the macrokinetics of chemical reactions were formulated by hot-spots density, combustion wave velocity and geometric factor. The resulting reaction may or may not develop into a violent event, may be sustained or be extinguished, which can be revealed from the subsequent burn reaction rate.

40 CFR 63.9075 - What definitions apply to this subpart?

Code of Federal Regulations, 2010 CFR

2010-07-01

... loading, into a tank truck, railcar, ship, or barge, of liquid HCl from a transfer (or loading) rack (as... (or loading) rack is the material that is loaded by the transfer (or loading) rack in the greatest.... Transfer (or loading) rack means the collection of loading arms and loading hoses, at a single loading rack...

Double loaded self-decomposable SiO2 nanoparticles for sustained drug release

NASA Astrophysics Data System (ADS)

Zhao, Saisai; Zhang, Silu; Ma, Jiang; Fan, Li; Yin, Chun; Lin, Ge; Li, Quan

2015-10-01

Sustained drug release for a long duration is a desired feature of modern drugs. Using double-loaded self-decomposable SiO2 nanoparticles, we demonstrated sustained drug release in a controllable manner. The double loading of the drugs was achieved using two different mechanisms--the first one via a co-growth mechanism, and the second one by absorption. A two-phase sustained drug release was firstly revealed in an in vitro system, and then further demonstrated in mice. After a single intravenous injection, the drug was controllably released from the nanoparticles into blood circulation with a Tmax of about 8 h, afterwards a long lasting release pattern was achieved to maintain drug systemic exposure with a plasma elimination half-life of approximately 28 h. We disclosed that the absorbed drug molecules contributed to the initial fast release for quickly reaching the therapeutic level with relatively higher plasma concentrations, while the ``grown-in'' drugs were responsible for maintaining the therapeutic level via the later controlled slow and sustained release. The present nanoparticle carrier drug configuration and the loading/maintenance release mechanisms provide a promising platform that ensures a prolonged therapeutic effect by controlling drug concentrations within the therapeutic window--a sustained drug delivery system with a great impact on improving the management of chronic diseases.Sustained drug release for a long duration is a desired feature of modern drugs. Using double-loaded self-decomposable SiO2 nanoparticles, we demonstrated sustained drug release in a controllable manner. The double loading of the drugs was achieved using two different mechanisms--the first one via a co-growth mechanism, and the second one by absorption. A two-phase sustained drug release was firstly revealed in an in vitro system, and then further demonstrated in mice. After a single intravenous injection, the drug was controllably released from the nanoparticles into blood circulation with a Tmax of about 8 h, afterwards a long lasting release pattern was achieved to maintain drug systemic exposure with a plasma elimination half-life of approximately 28 h. We disclosed that the absorbed drug molecules contributed to the initial fast release for quickly reaching the therapeutic level with relatively higher plasma concentrations, while the ``grown-in'' drugs were responsible for maintaining the therapeutic level via the later controlled slow and sustained release. The present nanoparticle carrier drug configuration and the loading/maintenance release mechanisms provide a promising platform that ensures a prolonged therapeutic effect by controlling drug concentrations within the therapeutic window--a sustained drug delivery system with a great impact on improving the management of chronic diseases. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03029c

NASA experiments onboard the controlled impact demonstration

NASA Technical Reports Server (NTRS)

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

1985-01-01

The structural crashworthiness tests conducted by NASA on the December 1, 1984 controlled impact demonstration are discussed. The components and locations of the data acquisition and photographic systems developed by NASA to evaluate impact loads throughout the aircraft structure and the transmission of loads into the dummies are described. The effectiveness of the NASA designed absorbing seats and the vertical, longitudinal, and transverse impact loads are measured. Data that is extremely applicable to crash dynamics structural research was obtained by the data acquisition system and very low load levels were measured for the NASA energy absorbing seats.

Analytical and molecular dynamics studies on the impact loading of single-layered graphene sheet by fullerene

NASA Astrophysics Data System (ADS)

Hosseini-Hashemi, Shahrokh; Sepahi-Boroujeni, Amin; Sepahi-Boroujeni, Saeid

2018-04-01

Normal impact performance of a system including a fullerene molecule and a single-layered graphene sheet is studied in the present paper. Firstly, through a mathematical approach, a new contact law is derived to describe the overall non-bonding interaction forces of the "hollow indenter-target" system. Preliminary verifications show that the derived contact law gives a reliable picture of force field of the system which is in good agreements with the results of molecular dynamics (MD) simulations. Afterwards, equation of the transversal motion of graphene sheet is utilized on the basis of both the nonlocal theory of elasticity and the assumptions of classical plate theory. Then, to derive dynamic behavior of the system, a set including the proposed contact law and the equations of motion of both graphene sheet and fullerene molecule is solved numerically. In order to evaluate outcomes of this method, the problem is modeled by MD simulation. Despite intrinsic differences between analytical and MD methods as well as various errors arise due to transient nature of the problem, acceptable agreements are established between analytical and MD outcomes. As a result, the proposed analytical method can be reliably used to address similar impact problems. Furthermore, it is found that a single-layered graphene sheet is capable of trapping fullerenes approaching with low velocities. Otherwise, in case of rebound, the sheet effectively absorbs predominant portion of fullerene energy.

Impact kinetics associated with four common bilateral plyometric exercises.

PubMed

Stewart, Ethan; Kernozek, Thomas; Peng, Hsien-Te; Wallace, Brian

2018-04-20

This study quantified the peak vertical ground reaction force (VGRF), impulse, and average and instantaneous loading rates developed during bilateral plyometric exercises. Fourteen collegiate male athletes performed four different bilateral plyometric exercises within a single testing session. Depth jumps from thirty, sixty and ninety centimeter heights (DJ30, DJ60, and DJ90, respectively), and a two consecutive jump exercise (2CJ), were randomly performed. The subjects landed on and propelled themselves off two force platforms embedded into the floor. The stance phase of each plyometric movement was analyzed for vertical force characteristics. The dependent variables were normalized to body weight. One-way repeated-measures ANOVA revealed significant differences between exercises (p ≤ 0.05). For VGRF, only the DJ60 and 2CJ exercises were not different from each other. The impulses between DJ60 and DJ90, and DJ30 and 2CJ, were not different. All exercises were different from each other in regards to average and instantaneous loading rate except for DJ30 vs. DJ60, and DJ90 vs. 2CJ. The DJ90 condition reported the highest peak VGRF by approaching five times body weight. The 2CJ condition had similar impulse and loading rates as the DJ90 condition. A proper progression and detailed program planning should be utilized when implementing plyometric exercises due to their different impact kinetics and how they might influence the body upon ground contact.

Noncontact minimally invasive technique for the assessment of mechanical properties of single cardiac myocyte via magnetic field loading

NASA Astrophysics Data System (ADS)

Yin, Shizhuo; Zhang, Xueqian; Cheung, Joseph; Wu, Juntao; Zhan, Chun; Xue, Jinchao

2004-07-01

In this paper, a unique non-contact, minimum invasive technique for the assessment of mechanical properties of single cardiac myocyte is presented. The assessment process includes following major steps: (1) attach a micro magnetic bead to the cell to be measured, (2) measure the contractile performance of the cell under the different magnetic field loading, (3) calculate mechanical loading force, and (4) derive the contractile force from the measured contraction data under different magnetic field loading.

Progressive cell-mediated changes in articular cartilage and bone in mice are initiated by a single session of controlled cyclic compressive loading.

PubMed

Ko, Frank C; Dragomir, Cecilia L; Plumb, Darren A; Hsia, Allison W; Adebayo, Olufunmilayo O; Goldring, Steven R; Wright, Timothy M; Goldring, Mary B; van der Meulen, Marjolein C H

2016-11-01

We previously showed that repetitive cyclic loading of the mouse knee joint causes changes that recapitulate the features of osteoarthritis (OA) in humans. By applying a single loading session, we characterized the temporal progression of the structural and compositional changes in subchondral bone and articular cartilage. We applied loading during a single 5-minute session to the left tibia of adult (26-week-old) C57Bl/6 male mice at a peak load of 9.0N for 1,200 cycles. Knee joints were collected at times 0, 1, and 2 weeks after loading. The changes in articular cartilage and subchondral bone were analyzed by histology, immunohistochemistry (caspase-3 and cathepsin K), and microcomputed tomography. At time 0, no change was evident in chondrocyte viability or cartilage or subchondral bone integrity. However, cartilage pathology demonstrated by localized thinning and proteoglycan loss occurred at 1 and 2 weeks after the single session of loading. Transient cancellous bone loss was evident at 1 week, associated with increased osteoclast number. Bone loss was reversed to control levels at 2 weeks. We observed formation of fibrous and cartilaginous tissues at the joint margins at 1 and 2 weeks. Our findings demonstrate that a single session of noninvasive loading leads to the development of OA-like morphological and cellular alterations in articular cartilage and subchondral bone. The loss in subchondral trabecular bone mass and thickness returns to control levels at 2 weeks, whereas the cartilage thinning and proteoglycan loss persist. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1941-1949, 2016. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Optimized operation of dielectric laser accelerators: Multibunch

NASA Astrophysics Data System (ADS)

Hanuka, Adi; Schächter, Levi

2018-06-01

We present a self-consistent analysis to determine the optimal charge, gradient, and efficiency for laser driven accelerators operating with a train of microbunches. Specifically, we account for the beam loading reduction on the material occurring at the dielectric-vacuum interface. In the case of a train of microbunches, such beam loading effect could be detrimental due to energy spread, however this may be compensated by a tapered laser pulse. We ultimately propose an optimization procedure with an analytical solution for group velocity which equals to half the speed of light. This optimization results in a maximum efficiency 20% lower than the single bunch case, and a total accelerated charge of 1 06 electrons in the train. The approach holds promise for improving operations of dielectric laser accelerators and may have an impact on emerging laser accelerators driven by high-power optical lasers.

Investigation of impact phenomena on the marine structures: Part II - Internal energy of the steel structure applied by selected materials in the ship-ship collision incidents

NASA Astrophysics Data System (ADS)

Prabowo, A. R.; Baek, S. J.; Lee, S. G.; Bae, D. M.; Sohn, J. M.

2018-01-01

Phenomena of impact loads on the marine structures has attracted attention to be predicted regarding its influences to structural damage. This part demands sustainable analysis and observation as tendency may vary from one to others since impact involves various scenario models and the structure itself experiences continuous development. Investigation of the damage extent can be conducted by observation on the energy behaviour during two entities involve in a contact. This study aimed to perform numerical investigation to predict structural damage by assessing absorbed strain energy represented by the internal energy during a series of ship collisions. The collision target in ship-ship interactions were determined on the single and double hulls part of a passenger ship. Tendency of the internal energy by the steel structures was summarized, and verification was presented by several crashworthiness criteria. It was found that steel structures applied by the material grades A and B produced different tendencies compared to the material grades D and E. Effect of the structural arrangement to structural responses in terms of strain and stress indicated that the single hull presented contour expansion mainly on the longitudinal directions.

Shock Equation of State of Multi-Phase Epoxy-Based Composite (Al-MnO2-Epoxy)

DTIC Science & Technology

2010-10-01

single stage light gas gun , two...using three different loading techniques— single stage light gas gun , two stage light gas gun , and explosive loading—with multiple diagnostic...wave speed. B. Single stage gas gun loading experiments Four gas gun -driven equation of state experiments were conducted at NSWC-Indian Head using

SEE Transient Response of Crane Interpoint Single Output Point of Load DC-DC Converters

NASA Technical Reports Server (NTRS)

Sanders, Anthony B.; Chen, Dakai; Kim, Hak S.; Phan, Anthony M.

2011-01-01

This study was undertaken to determine the single event effect and transient susceptibility of the Crane Interpoint Maximum Flexible Power (MFP) Single Output Point of Load DC/DC Converters for transient interruptions in the output signal and for destructive and non destructive events induced by exposing it to a heavy ion beam..

Machined versus roughened immediately loaded and finally restored single implants inserted flapless: Preliminary 6-month data from a split- mouth randomised controlled trial.

PubMed

Cannizzaro, Gioacchino; Felice, Pietro; Loi, Ignazio; Viola, Paolo; Ferri, Vittorio; Leone, Michele; Lazzarini, Matteo; Trullenque-Eriksson, Anna; Esposito, Marco

To compare the outcome of immediately loaded single implants with a machined or a roughened surface. Fifty patients had two implant sites randomly allocated to receive flaplessplaced single Syra implants (Sweden & Martina), one with a machined and one with a roughened surface (sand-blasted with zirconia powder and acid etched), according to a split-mouth design. To be loaded immediately, implants had to be inserted with a torque superior to 50 Ncm. Implants were restored with definitive crowns in direct occlusal contact within 48 h. Patients were followed for 6 months after loading. Outcome measures were prosthetic and implant failures and complications. Two machined implants and four roughened implants were not loaded immediately. Six months after loading no dropout occurred. One implant loaded late, which had a rough implant surface, failed 20 days after loading (P (McNemar test) = 0.625; difference in proportions = -0.04; 95% CI: -0.15 to 0.07). Three crowns had to be remade on machined implants and four on roughened implants (P (McNemar test) = 1.000; difference in proportions = -0.02; 95% CI: -0.12 to 0.08). Three machined and five roughened implants experienced complications (P (McNemar test) = 0.625; difference in proportions = -0.04; 95% CI: -0.15 to 0.07). There were no statistically significant differences between groups for crown and implant losses as well as complications. Up to 6 months after loading both machined and roughened flapless-placed and immediately loaded single implants provided good and similar results, however, longer follow-ups are needed to evaluate the long-term prognosis of implants with different surfaces.

Static and Dynamic Compaction of CL-20 Powders

NASA Astrophysics Data System (ADS)

Cooper, Marcia A.; Brundage, Aaron L.; Dudley, Evan C.

2009-12-01

Hexanitrohexaazaisowurtzitane (CL-20) powders were compacted under quasi-static and dynamic loading conditions. A uniaxial compression apparatus quasi-statically compressed the powders to 90% theoretical maximum density with applied stresses up to 0.4 GPa. Dynamic compaction measurements using low-density pressings approximately 64% theoretical maximum density (TMD) were obtained in a single-stage gas gun at impact velocities between 0.17-0.95 km/s. Experiments were conducted in a reverse ballistic arrangement in which the projectile contained the CL-20 powder bed and impacted a target consisting of an aluminized window. VISAR-measured particle velocities at the explosive-window interface determined the shock Hugoniot states for pressures up to 1.3 GPa. Approved for public release, SAND2009-4810C.

Elastic response of (001)-oriented PWA 1480 single crystal - The influence of secondary orientation

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Abdul-Azis, Ali; Mcgaw, Michael

1991-01-01

The influence of secondary orientation on the elastic response of a zone axis (001)-oriented nickel-base single-crystal superalloy, PWA 1480, was investigated under mechanical loading conditions by applying finite element techniques. Elastic stress analyses were performed with a commercially available finite element code. Secondary orientation of the single-crystal superalloy was offset with respect to the global coordinate system in increments from 0 to 90 deg and stresses developed within the single crystal were determined for each loading condition. The results indicated that the stresses were strongly influenced by the angular offset between the secondary crystal orientation and the global coordinate system. The degree of influence was found to vary with the type of loading condition (mechanical, thermal, or combined) imposed on the single-crystal superalloy.

Dynamic Characteristics of Green Sandstone Subjected to Repetitive Impact Loading: Phenomena and Mechanisms

NASA Astrophysics Data System (ADS)

Li, S. H.; Zhu, W. C.; Niu, L. L.; Yu, M.; Chen, C. F.

2018-06-01

A split Hopkinson pressure bar apparatus driven by a pendulum hammer was used to perform uniaxial compression tests to examine the degradation process of green sandstone subjected to repetitive impact loading. The acoustic characteristics, dissipated energy, deformation characteristics, and microstructure evolution were investigated. The representative stress-strain curve can be broken into five stages that were characterized by changes in the axial strain response during impact loading. Both the ultrasonic wave velocity and cumulative dissipated energy exhibited obvious three-stage behavior with respect to the impact number. As the impact number increased, more than one peak was observed in the frequency spectra, and the relative weight of the peak frequency increased in the low-frequency range. According to the evolution of the ultrasonic wave velocity, the degradation process was divided into three stages. By comparing the intact stage I and early stage II microcrack development patterns, the initiation of new cracks and elongation of existing cracks were identified as the main degradation mechanisms. Furthermore, a slight increase in the number of cracks was observed, and microcrack lengths steadily increased. Moreover, due to the low level of microcrack damage, the deformation mechanism was mainly characterized by volume compression during impact loading. In late stage II, the main degradation mechanism was the elongation of existing cracks. Additionally, as microcracks accumulated in the rock samples, cracks were arranged parallel to the loading direction, which led to volume dilation. In stage III, microcracks continued to elongate nearly parallel to the loading direction and then linked to each other, which led to intense degradation in the rock samples. In this stage, rock sample deformation was mainly characterized by volume dilation during impact loading. Finally, rock samples were split into blocks with fractures oriented subparallel to the loading direction. These results can improve the understanding of the stability evaluations of rock structures subjected to repetitive impact loading.

The Extravehicular Suit Impact Load Attenuation Study for Use in Astronaut Bone Fracture Prediction

NASA Technical Reports Server (NTRS)

Lewandowski, Beth E.; Gilkey, Kelly M.; Sulkowski, Christina M.; Samorezov, Sergey; Myers, Jerry G.

2011-01-01

The NASA Integrated Medical Model (IMM) assesses the risk, including likelihood and impact of occurrence, of all credible in-flight medical conditions. Fracture of the proximal femur is a traumatic injury that would likely result in loss of mission if it were to happen during spaceflight. The low gravity exposure causes decreases in bone mineral density which heightens the concern. Researchers at the NASA Glenn Research Center have quantified bone fracture probability during spaceflight with a probabilistic model. It was assumed that a pressurized extravehicular activity (EVA) suit would attenuate load during a fall, but no supporting data was available. The suit impact load attenuation study was performed to collect analogous data. METHODS: A pressurized EVA suit analog test bed was used to study how the offset, defined as the gap between the suit and the astronaut s body, impact load magnitude and suit operating pressure affects the attenuation of impact load. The attenuation data was incorporated into the probabilistic model of bone fracture as a function of these factors, replacing a load attenuation value based on commercial hip protectors. RESULTS: Load attenuation was more dependent on offset than on pressurization or load magnitude, especially at small offsets. Load attenuation factors for offsets between 0.1 - 1.5 cm were 0.69 +/- 0.15, 0.49 +/- 0.22 and 0.35 +/- 0.18 for mean impact forces of 4827, 6400 and 8467 N, respectively. Load attenuation factors for offsets of 2.8 - 5.3 cm were 0.93 +/- 0.2, 0.94 +/- 0.1 and 0.84 +/- 0.5, for the same mean impact forces. Reductions were observed in the 95th percentile confidence interval of the bone fracture probability predictions. CONCLUSIONS: The reduction in uncertainty and improved confidence in bone fracture predictions increased the fidelity and credibility of the fracture risk model and its benefit to mission design and operational decisions.

The strength of polyaxial locking interfaces of distal radius plates.

PubMed

Hoffmeier, Konrad L; Hofmann, Gunther O; Mückley, Thomas

2009-10-01

Currently available polyaxial locking plates represent the consequent enhancement of fixed-angle, first-generation locking plates. In contrast to fixed-angle locking plates which are sufficiently investigated, the strength of the new polyaxial locking options has not yet been evaluated biomechanically. This study investigates the mechanical strength of single polyaxial interfaces of different volar radius plates. Single screw-plate interfaces of the implants Palmar 2.7 (Königsee Implantate und Instrumente zur Osteosynthese GmbH, Allendorf, Germany), VariAx (Stryker Leibinger GmbH & Co. KG, Freiburg, Germany) und Viper (Integra LifeSciences Corporation, Plainsboro, NJ, USA) were tested by cantilever bending. The strength of 0 degrees, 10 degrees and 20 degrees screw locking angle was obtained during static and dynamic loading. The Palmar 2.7 interfaces showed greater ultimate strength and fatigue strength than the interfaces of the other implants. The strength of the VariAx interfaces was about 60% of Palmar 2.7 in both, static and dynamic loading. No dynamic testing was applied to the Viper plate because of its low ultimate strength. By static loading, an increase in screw locking angle caused a reduction of strength for the Palmar 2.7 and Viper locking interfaces. No influence was observed for the VariAx locking interfaces. During dynamic loading; angulation had no influence on the locking strength of Palmar 2.7. However, reduction of locking strength with increasing screw angulation was observed for VariAx. The strength of the polyaxial locking interfaces differs remarkably between the examined implants. Depending on the implant an increase of the screw locking angle causes a reduction of ultimate or fatigue strength, but not in all cases a significant impact was observed.

Distributed dynamic load on composite laminates

NASA Astrophysics Data System (ADS)

Langella, A.; Lopresto, V.; Caprino, G.

2016-05-01

An experimental activity conducted in order to assess the impact behavior at room and low temperature of carbon fibre in vinylester resin laminates used in the shipbuilding industry, was reported. The conditions which reproduce the impact of a hull at low temperature with a solid body suspended in the water was reproduced. A test equipment was designed and realized to reproduce the real material behaviour in water to obtain a load distribution on the entire surface of the specimen. The results were obtained impacting the laminates placed between the cilyndrical steel impactor and a bag containing water. A falling weight machine, equipped with an instrumented steel impactor and a thermal chamber, was adopted for the experimental tests. The impact behaviour in hostile environments was compared to the behaviour at room temperature and the data obtained under distributed load conditions were compared with the results from concentrated loads: a completely different behaviour was observed between the two different loading conditions in terms of load-displacement curve. The effect of the impact on the laminates has been related with the delaminations, evaluated by ultrasonic scanning, and the indentation.

Cyclic loading of rotator cuff reconstructions: single-row repair with modified suture configurations versus double-row repair.

PubMed

Lorbach, Olaf; Bachelier, Felix; Vees, Jochen; Kohn, Dieter; Pape, Dietrich

2008-08-01

Double-row repair is suggested to have superior biomechanical properties in rotator cuff reconstruction compared with single-row repair. However, double-row rotator cuff repair is frequently compared with simple suture repair and not with modified suture configurations. Single-row rotator cuff repairs with modified suture configurations have similar failure loads and gap formations as double-row reconstructions. Controlled laboratory study. We created 1 x 2-cm defects in 48 porcine infraspinatus tendons. Reconstructions were then performed with 4 single-row repairs and 2 double-row repairs. The single-row repairs included transosseous simple sutures; double-loaded corkscrew anchors in either a double mattress or modified Mason-Allen suture repair; and the Magnum Knotless Fixation Implant with an inclined mattress. Double-row repairs were either with Bio-Corkscrew FT using modified Mason-Allen stitches or a combination of Bio-Corkscrew FT and PushLock anchors using the SutureBridge Technique. During cyclic load (10 N to 60-200 N), gap formation was measured, and finally, ultimate load to failure and type of failure were recorded. Double-row double-corkscrew anchor fixation had the highest ultimate tensile strength (398 +/- 98 N) compared to simple sutures (105 +/- 21 N; P < .0001), single-row corkscrews using a modified Mason-Allen stitch (256 +/- 73 N; P = .003) or double mattress repair (290 +/- 56 N; P = .043), the Magnum Implant (163 +/- 13 N; P < .0001), and double-row repair with PushLock and Bio-Corkscrew FT anchors (163 +/- 59 N; P < .0001). Single-row double mattress repair was superior to transosseous sutures (P < .0001), the Magnum Implant (P = .009), and double-row repair with PushLock and Bio-Corkscrew FT anchors (P = .009). Lowest gap formation was found for double-row double-corkscrew repair (3.1 +/- 0.1 mm) compared to simple sutures (8.7 +/- 0.2 mm; P < .0001), the Magnum Implant (6.2 +/- 2.2 mm; P = .002), double-row repair with PushLock and Bio-Corkscrew FT anchors (5.9 +/- 0.9 mm; P = .008), and corkscrews with modified Mason-Allen sutures (6.4 +/- 1.3 mm; P = .001). Double-row double-corkscrew anchor rotator cuff repair offered the highest failure load and smallest gap formation and provided the most secure fixation of all tested configurations. Double-loaded suture anchors using modified suture configurations achieved superior results in failure load and gap formation compared to simple suture repair and showed similar loads and gap formation with double-row repair using PushLock and Bio-Corkscrew FT anchors. Single-row repair with modified suture configurations may lead to results comparable to several double-row fixations. If double-row repair is used, modified stitches might further minimize gap formation and increase failure load.

Design and Modeling of a Variable Heat Rejection Radiator

NASA Technical Reports Server (NTRS)

Miller, Jennifer R.; Birur, Gajanana C.; Ganapathi, Gani B.; Sunada, Eric T.; Berisford, Daniel F.; Stephan, Ryan

2011-01-01

Variable Heat Rejection Radiator technology needed for future NASA human rated & robotic missions Primary objective is to enable a single loop architecture for human-rated missions (1) Radiators are typically sized for maximum heat load in the warmest continuous environment resulting in a large panel area (2) Large radiator area results in fluid being susceptible to freezing at low load in cold environment and typically results in a two-loop system (3) Dual loop architecture is approximately 18% heavier than single loop architecture (based on Orion thermal control system mass) (4) Single loop architecture requires adaptability to varying environments and heat loads

Splash evaluation of SRB designs

NASA Technical Reports Server (NTRS)

Counter, D. N.

1974-01-01

A technique is developed to optimize the shuttle solid rocket booster (SRB) design for water impact loads. The SRB is dropped by parachute and recovered at sea for reuse. Loads experienced at water impact are design critical. The probability of each water impact load is determined using a Monte Carlo technique and an aerodynamic analysis of the SRB parachute system. Meteorological effects are included and four configurations are evaluated.

Online Reading: A Preliminary Study of the Impact of Integrated and Split-Attention Formats on L2 Students' Cognitive Load

ERIC Educational Resources Information Center

Al-Shehri, Saleh; Gitsaki, Christina

2010-01-01

Cognitive load theory has been utilized by second language acquisition (SLA) researchers to account for differences in learner performance with regards to different learning tasks. Certain instructional designs were shown to have an impact on cognitive load and working memory, and this impact was found to be accentuated in a multimedia environment…

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

Rice, C. Keith; Shen, Bo; Shrestha, Som S.

This report describes an analysis to investigate representative heating loads for single-family detached homes using current EnergyPlus simulations (DOE 2014a). Hourly delivered load results are used to determine binned load lines using US Department of Energy (DOE) residential prototype building models (DOE 2014b) developed by Pacific Northwest National Laboratory (PNNL). The selected residential single-family prototype buildings are based on the 2006 International Energy Conservation Code (IECC 2006) in the DOE climate regions. The resulting load lines are compared with the American National Standards Institute (ANSI)/Air-Conditioning, Heating, and Refrigeration Institute (AHRI) Standard 210/240 (AHRI 2008) minimum and maximum design heating requirementmore » (DHR) load lines of the heating seasonal performance factor (HSPF) ratings procedure for each region. The results indicate that a heating load line closer to the maximum DHR load line, and with a lower zero load ambient temperature, is more representative of heating loads predicted for EnergyPlus prototype residential buildings than the minimum DHR load line presently used to determine HSPF ratings. An alternative heating load line equation was developed and compared to binned load lines obtained from the EnergyPlus simulation results. The effect on HSPF of the alternative heating load line was evaluated for single-speed and two-capacity heat pumps, and an average HSPF reduction of 16% was found. The alternative heating load line relationship is tied to the rated cooling capacity of the heat pump based on EnergyPlus autosizing, which is more representative of the house load characteristics than the rated heating capacity. The alternative heating load line equation was found to be independent of climate for the six DOE climate regions investigated, provided an adjustable zero load ambient temperature is used. For Region IV, the default DOE climate region used for HSPF ratings, the higher load line results in an ~28% increase in delivered heating load and an ~52% increase in the estimated heating operating cost over that given in the AHRI directory (AHRI 2014).« less

Safe Landing Strategies During a Fall: Systematic Review and Meta-Analysis.

PubMed

Moon, Yaejin; Sosnoff, Jacob J

2017-04-01

To systematically synthesize information on safe landing strategies for a fall, and quantitatively examine the effects of the strategies to reduce the risk of injury from a fall. PubMed, Web of Science, Cumulative Index to Nursing and Allied Health Literature, and Cochrane Library. Databases were searched using the combinations of keywords of "falls," "strategy," "impact," and "load." Randomized controlled trials, cohort studies, pre-post studies, and cross-sectional studies were included. Fall strategies were extracted and categorized by falling direction. Measurements of impact loads that reflect the risk of injuries were extracted (eg, impact velocity, impact force, fall duration, impact angle). Hedges' g was used as effect size to quantify the effect of a protective landing strategy to reduce the impact load. A total of 7 landing strategies (squatting, elbow flexion, forward rotation, martial arts rolling, martial arts slapping, relaxed muscle, stepping) in 13 studies were examined. In general, all strategies, except for the martial arts slapping technique, significantly reduced impact load (g values=.73-2.70). Squatting was an efficient strategy to reduce impact in backward falling (g=1.77), while elbow flexion with outstretched arms was effective in forward falling (g=.82). Also, in sideways falling strategies, martial arts rolling (g=2.70) and forward rotation (g=.82) were the most efficient strategies to reduce impact load. The results showed that landing strategies have a significant effect on reducing impact load during a fall and might be effective to reduce the impact load of falling. The current study also highlighted limitations of the previous studies that focused on a young population and self-initiated falls. Further investigation with elderly individuals and unexpected falls is necessary to verify the effectiveness and suitability of the strategies for at-risk populations in real-life falls. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Impact of overweight vehicles (with heavy axle loads) on bridge deck deterioration.

DOT National Transportation Integrated Search

2012-03-01

Bridge deck slabs develop compressive stresses from global flexural deformation and locally from high-level : wheel loads when it is subjected to overweight trucks. This study quantified the impact of overweight vehicles : with heavy axle loads on br...

PI and repetitive control for single phase inverter based on virtual rotating coordinate system

NASA Astrophysics Data System (ADS)

Li, Mengqi; Tong, Yibin; Jiang, Jiuchun; Liang, Jiangang

2018-03-01

Microgrid technology developed rapidly and nonlinear loads were connected increasingly. A new control strategy was proposed for single phase inverter when connected nonlinear loads under island condition. PI and repetitive compound controller was realized under synchronous rotating coordinate system and acquired high quality sinusoidal voltage output without voltage spike when loads step changed. Validity and correctness were verified by simulation using MATLAB/Simulink.

Ultrasonic impact peening for the surface properties’ management

NASA Astrophysics Data System (ADS)

Mordyuk, Bohdan N.; Prokopenko, Georgiy I.

2007-12-01

It is demonstrated that the ultrasonic impact peening (UIP) technique is a beneficial method for essential increase in the fatigue durability of metallic materials due to the surface nanocrystallization and hardening process provided for severe plastic deformation of surface via multiple impacts of high velocity impact pins. Nano-scale grain structures were obtained in the surface layers of stainless steel, low carbon steel weld and different titanium alloys using developed equipment for the UIP. Both the surface nanostructure and compressive residual stresses are shown to attribute to the essential hardness increase. It is revealed experimentally using profilometry that new modification of the UIP apparatus providing high velocity "sliding" impacts leads to marked diminution of the surface roughness, which is another important factor affecting to the fatigue cracks initiation process. The two-dimensional finite element model is used to simulate the indent formation process during single impaction. The solid steel pin and the Al alloy plate are modeled as a rigid material and an elasto-plastic material, respectively. It is shown that the surface roughness magnitude depends on the correlation of the vertical and lateral load components.

Lunar and Planetary Science XXXV: Effects of Impacts: Shock and Awe

NASA Technical Reports Server (NTRS)

Kyte, F. T.; Koeberl, C.

2004-01-01

This document discusses the following topics: Zircon as a Shock Indicator in Impactites of Drill Core Yaxcopoil-1, Chicxulub Impact Structure, Mexico; Experimental Investigation of Shock Effects in a Metapelitic Granulite; Experimental Reproduction of Shock Veins in Single-Crystal Minerals; Post-Shock Crystal-Plastic Processes in Quartz from Crystalline Target Rocks of the Charlevoix Impact Structure; Shock Reequilibration of Fluid Inclusions; How Does Tektite Glass Lose Its Water?; Assessing the Role of Anhydrite in the KT Mass Extinction: Hints from Shock-loading Experiments; A Mineralogical and Geochemical Study of the Nonmarine Permian/Triassic Boundary in the Southern Karoo Basin, South Africa; Extraterrestrial Chromium in the Permian-Triassic Boundary at Graphite Peak, Antarctica; Magnetic Fe,Si,Al-rich Impact Spherules from the P-T Boundary Layer at Graphite Peak, Antarctica; A Newly Recognized Late Archean Impact Spherule Layer in the Reivilo Formation, Griqualand West Basin, South Africa; Initial Cr-Isotopic and Iridium Measurements of Concentrates from Late Eocene Cpx-Spherule Deposits; An Ordinary Chondrite Impactor Composition for the Bosumtwi Impact Structure, Ghana, West Africa: Discussion of Siderophile Element Contents and Os and Cr Isotope Data.

The effect of loading time on flexible pavement dynamic response: a finite element analysis

NASA Astrophysics Data System (ADS)

Yin, Hao; Solaimanian, Mansour; Kumar, Tanmay; Stoffels, Shelley

2007-12-01

Dynamic response of asphalt concrete (AC) pavements under moving load is a key component for accurate prediction of flexible pavement performance. The time and temperature dependency of AC materials calls for utilizing advanced material characterization and mechanistic theories, such as viscoelasticity and stress/strain analysis. In layered elastic analysis, as implemented in the new Mechanistic-Empirical Pavement Design Guide (MEPDG), the time dependency is accounted for by calculating the loading times at different AC layer depths. In this study, the time effect on pavement response was evaluated by means of the concept of “pseudo temperature.” With the pavement temperature measured from instrumented thermocouples, the time and temperature dependency of AC materials was integrated into one single factor, termed “effective temperature.” Via this effective temperature, pavement responses under a transient load were predicted through finite element analysis. In the finite element model, viscoelastic behavior of AC materials was characterized through relaxation moduli, while the layers with unbound granular material were assumed to be in an elastic mode. The analysis was conducted for two different AC mixtures in a simplified flexible pavement structure at two different seasons. Finite element analysis results reveal that the loading time has a more pronounced impact on pavement response in the summer for both asphalt types. The results indicate that for reasonable prediction of dynamic response in flexible pavements, the effect of the depth-dependent loading time on pavement temperature should be considered.

[Watershed water environment pollution models and their applications: a review].

PubMed

Zhu, Yao; Liang, Zhi-Wei; Li, Wei; Yang, Yi; Yang, Mu-Yi; Mao, Wei; Xu, Han-Li; Wu, Wei-Xiang

2013-10-01

Watershed water environment pollution model is the important tool for studying watershed environmental problems. Through the quantitative description of the complicated pollution processes of whole watershed system and its parts, the model can identify the main sources and migration pathways of pollutants, estimate the pollutant loadings, and evaluate their impacts on water environment, providing a basis for watershed planning and management. This paper reviewed the watershed water environment models widely applied at home and abroad, with the focuses on the models of pollutants loading (GWLF and PLOAD), water quality of received water bodies (QUAL2E and WASP), and the watershed models integrated pollutant loadings and water quality (HSPF, SWAT, AGNPS, AnnAGNPS, and SWMM), and introduced the structures, principles, and main characteristics as well as the limitations in practical applications of these models. The other models of water quality (CE-QUAL-W2, EFDC, and AQUATOX) and watershed models (GLEAMS and MIKE SHE) were also briefly introduced. Through the case analysis on the applications of single model and integrated models, the development trend and application prospect of the watershed water environment pollution models were discussed.

A detailed study of gold-nanoparticle loaded cells using X-ray based techniques for cell-tracking applications with single-cell sensitivity

NASA Astrophysics Data System (ADS)

Astolfo, Alberto; Arfelli, Fulvia; Schültke, Elisabeth; James, Simon; Mancini, Lucia; Menk, Ralf-Hendrik

2013-03-01

In the present study complementary high-resolution imaging techniques on different length scales are applied to elucidate a cellular loading protocol of gold nanoparticles and subsequently its impact on long term and high-resolution cell-tracking utilizing X-ray technology. Although demonstrated for malignant cell lines the results can be applied to non-malignant cell lines as well. In particular the accumulation of the gold marker per cell has been assessed quantitatively by virtue of electron microscopy, two-dimensional X-ray fluorescence imaging techniques and X-ray CT with micrometric and sub-micrometric resolution. Moreover, utilizing these techniques the three dimensional distribution of the incorporated nanoparticles, which are sequestered in lysosomes as a permanent marker, could be determined. The latter allowed elucidation of the gold partition during mitosis and the cell size, which subsequently enabled us to define the optimal instrument settings of a compact microCT system to visualize gold loaded cells. The results obtained demonstrate the feasibility of cell-tracking using X-ray CT with compact sources.

Elastic response of zone axis (001)-oriented PWA 1480 single crystal: The influence of secondary orientation

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Abdul-Aziz, Ali; Mcgaw, Michael A.

1991-01-01

The influence of secondary orientation on the elastic response of a zone axis (001)-oriented nickel-base single-crystal superalloy, PWA 1480, was investigated under mechanical loading conditions by applying finite element techniques. Elastic stress analyses were performed with a commercially available finite element code. Secondary orientation of the single-crystal superalloy was offset with respect to the global coordinate system in increments from 0 to 90 deg and stresses developed within the single crystal were determined for each loading condition. The results indicated that the stresses were strongly influenced by the angular offset between the secondary crystal orientation and the global coordinate system. The degree of influence was found to vary with the type of loading condition (mechanical, thermal, or combined) imposed on the single-crystal superalloy.

Evaluation of a Compression-Loaded-Stitched-Multi-Bay Fuselage Panel With Barely Visible Impact Damage

NASA Technical Reports Server (NTRS)

Baker, Donald J.; Li, Ji-An

2005-01-01

The experimental results from a stitched VaRTM carbon-epoxy composite panel tested under uni-axial compression loading are presented along with nonlinear finite element analysis prediction of the response. The curved panel is divided by frames and stringers into six bays with a column of three bays along the compressive loading direction. The frames are supported at the frame ends to resist out-of-plane translation. Back-to-back strain gages are used to record the strain and displacement transducers were used to record the out-of-plane displacements. In addition a full-field-displacement measurement technique that utilizes a camera-based-stereo-vision system was used to record the displacements. The panel was loaded to 1.5 times the predicted initial buckling load (1st bay buckling load, P(sub er) from the nonlinear finite element analysis and then was removed from the test machine for impact testing. After impacting with 20 ft-lbs of energy using a spherical impactor to produce barely visible damage the panel was loaded in compression until failure. The buckling load of the first bay to buckle was 97% of the buckling load before impact. The stitching constrained the impact damage from growing during the loading to failure. Impact damage had very little overall effect on panel stiffness. Panel stiffness measured by the full-field-displacement technique indicated a 13% loss in stiffness after impact. The panel failed at 1.64 times the first panel buckling load. The barely visible impact damage did not grow noticeably as the panel failed by global instability due to stringer-web terminations at the frame locations. The predictions from the nonlinear analysis of the finite element modeling of the entire specimen were very effective in the capture of the initial buckling and global behavior of the panel. In addition, the prediction highlighted the weakness of the panel under compression due to stringer web terminations. Both the test results and the nonlinear predictions serve to reinforce the severe penalty in structural integrity caused by the low cost manufacturing technique to terminate the stringer webs, and demonstrates the importance of this type of sub-component testing and high fidelity failure analysis in the design of a composite fuselage.

A 24 h investigation of the hydrogeochemistry of baseflow and stormwater in an urban area impacted by mining: Butte, Montana

USGS Publications Warehouse

Gammons, Christopher H.; Shope, Christopher L.; Duaime, Terence E.

2005-01-01

Changes in water quality during a storm event were continuously monitored over a 24 h period at a single location along an urban stormwater drain in Butte, Montana. The Butte Metro Storm Drain (MSD) collects groundwater baseflow and stormwater draining Butte Hill, a densely populated site that has been severely impacted by 130 years of mining, milling, and smelting of copper-rich, polymetallic mineral deposits. On the afternoon of 26 June 2002, a heavy thunderstorm caused streamflow in the MSD to increase 100-fold, from 0·2 ft3 s−1 to more than 20 ft3 s−1. Hourly discharge and water quality data were collected before, during, and following the storm. The most significant finding was that the calculated loads (grams per hour) of both dissolved and particulate copper passing down the MSD increased more than 100-fold in the first hour following the storm, and remained elevated over baseline conditions for the remainder of the study period. Other metals, such as zinc, cadmium, and manganese, showed a decrease in load from pre-storm to post-storm conditions. In addition to the large flush of copper, loads of soluble phosphorus increased during the storm, whereas dissolved oxygen dropped to low levels (<2 mg l−1). These results show that infrequent storm events in Butte have the potential to generate large volumes of runoff that exceed Montana water quality standards for acute exposure of aquatic life to copper, as well as depressed levels of dissolved oxygen. This study has important implications to ongoing reclamation activities in the upper Clark Fork Superfund site, particularly with respect to management of storm flow, and may be applicable to other watersheds impacted by mining activities.

Weak and Habitat-Dependent Effects of Nutrient Pollution on Macrofaunal Communities of Southeast Australian Estuaries

PubMed Central

Nicastro, Andrea; Bishop, Melanie J.

2013-01-01

Among the impacts of coastal settlements to estuaries, nutrient pollution is often singled out as a leading cause of modification to the ecological communities of soft sediments. Through sampling of 48 sites, distributed among 16 estuaries of New South Wales, Australia, we tested the hypotheses that (1) anthropogenic nutrient loads would be a better predictor of macrofaunal communities than estuarine geomorphology or local sediment characteristics; and (2) local environmental context, as determined largely by sediment characteristics, would modify the relationship between nutrient loading and community composition. Contrary to the hypothesis, multivariate multiple regression analyses revealed that sediment grain size was the best predictor of macrofaunal assemblage composition. When samples were stratified according to median grain size, relationships between faunal communities and nitrogen loading and latitude emerged, but only among estuaries with sandier sediments. In these estuaries, capitellid and nereid polychaetes and chironomid larvae were the taxa that showed the strongest correlations with nutrient loading. Overall, this study failed to provide evidence of a differential relationship between diffuse nutrient enrichment and benthic macrofauna across a gradient of 7° of latitude and 4°C temperature. Nevertheless, as human population growth continues to place increasing pressure on southeast Australian estuaries, manipulative field studies examining when and where nutrient loading will lead to significant changes in estuarine community structure are needed. PMID:23799037

Biomechanical Analysis of Suture Anchor vs Tenodesis Screw for FHL Transfer.

PubMed

Drakos, Mark C; Gott, Michael; Karnovsky, Sydney C; Murphy, Conor I; DeSandis, Bridget A; Chinitz, Noah; Grande, Daniel; Chahine, Nadeen

2017-07-01

Chronic Achilles injury is often treated with flexor hallucis longus (FHL) tendon transfer to the calcaneus using 1 or 2 incisions. A single incision avoids the risks of extended dissections yet yields smaller grafts, which may limit fixation options. We investigated the required length of FHL autograft and biomechanical profiles for suture anchor and biotenodesis screw fixation. Single-incision FHL transfer with suture anchor or biotenodesis screw fixation to the calcaneus was performed on 20 fresh cadaveric specimens. Specimens were cyclically loaded until maximal load to failure. Length of FHL tendon harvest, ultimate load, stiffness, and mode of failure were recorded. Tendon harvest length needed for suture anchor fixation was 16.8 ± 2.1 mm vs 29.6 ± 2.4 mm for biotenodesis screw ( P = .002). Ultimate load to failure was not significantly different between groups. A significant inverse correlation existed between failure load and donor age when all specimens were pooled (ρ = -0.49, P < .05). Screws in younger specimens (fewer than 70) resulted in significantly greater failure loads ( P < .03). No difference in stiffness was found between groups. Modes of failure for screw fixation were either tunnel pullout (n = 6) or tendon rupture (n = 4). Anchor failure occurred mostly by suture breakage (n = 8). Adequate FHL tendon length could be harvested through a single posterior incision for fixation to the calcaneus with either fixation option, but suture anchor required significantly less graft length. Stiffness, fixation strength, and load to failure were comparable between groups. An inverse correlation existed between failure load and donor age. Younger specimens with screw fixation demonstrated significantly greater failure loads. Adequate harvest length for FHL transfer could be achieved with a single posterior incision. There was no difference in strength of fixation between suture anchor and biotenodesis screw.

Using squat repetition maximum testing to determine hamstring resistance training exercise loads.

PubMed

Ebben, William P; Long, Nicholas J; Pawlowski, Zach D; Chmielewski, Lauren M; Clewien, Rustin W; Jensen, Randall L

2010-02-01

The purpose of this study was to determine whether there is a linear relationship between the squat and a variety of hamstring resistance training exercises, and whether this relationship differs on the basis of sex. This study also sought to create prediction equations for the determination of hamstring exercise load based on the squat load. Repetition maximums of the squat, as well as 4 common hamstring resistance training exercises including the seated leg curl, stiff leg dead lift, single leg dead lift, and good morning exercise, were determined for each subject. Subjects included 21 men and 13 women collegiate athletes. Data were evaluated using linear regression analysis to predict hamstring exercise loads from 6 repetition maximum squat data. Results of the analysis of all subjects indicated that squat load was a significant predictor of loads for each of the hamstring exercises. However, separate analysis of women revealed that squat load was not a significant predictor of loads for any of the hamstring exercises. Analysis of the men revealed that squat was a significant predictor of load for the seated leg curl (R = 0.58, p < 0.001), stiff leg dead lift (R = 0.82, p < 0.001), single leg stiff leg dead lift (R = 0.80, p < 0.001), and good morning (R = 0.79, p < 0.001) exercises. On the basis of the analysis of the men, the following prediction equations were devised for each exercise: (1) seated leg curl load = squat load (0.186) + 10.935 kg, (2) stiff leg deadlift load = squat load (1.133) - 86.331 kg, (3) single leg stiff leg deadlift load = squat load (0.443) - 3.425 kg, and (4) good morning load = squat load (0.961) - 105.505 kg. Thus, results from testing core exercises such as the squat can provide useful data for the assignment of loads for assistance exercises.

Ovarian control of nectar collection in the honey bee (Apis mellifera).

PubMed

Siegel, Adam J; Freedman, Colin; Page, Robert E

2012-01-01

Honey bees are a model system for the study of division of labor. Worker bees demonstrate a foraging division of labor (DOL) by biasing collection towards carbohydrates (nectar) or protein (pollen). The Reproductive ground-plan hypothesis of Amdam et al. proposes that foraging DOL is regulated by the networks that controlled foraging behavior during the reproductive life cycle of honey bee ancestors. Here we test a proposed mechanism through which the ovary of the facultatively sterile worker impacts foraging bias. The proposed mechanism suggests that the ovary has a regulatory effect on sucrose sensitivity, and sucrose sensitivity impacts nectar loading. We tested this mechanism by measuring worker ovary size (ovariole number), sucrose sensitivity, and sucrose solution load size collected from a rate-controlled artificial feeder. We found a significant interaction between ovariole number and sucrose sensitivity on sucrose solution load size when using low concentration nectar. This supports our proposed mechanism. As nectar and pollen loading are not independent, a mechanism impacting nectar load size would also impact pollen load size.

HIV community viral load trends in South Carolina.

PubMed

Chakraborty, Hrishikesh; Weissman, Sharon; Duffus, Wayne A; Hossain, Akhtar; Varma Samantapudi, Ashok; Iyer, Medha; Albrecht, Helmut

2017-03-01

Community viral load is an aggregate measure of HIV viral load in a particular geographic location, community, or subgroup. Community viral load provides a measure of disease burden in a community and community transmission risk. This study aims to examine community viral load trend in South Carolina and identify differences in community viral load trends between selected population subgroups using a state-wide surveillance dataset that maintains electronic records of all HIV viral load measurements reported to the state health department. Community viral load trends were examined using random mixed effects models, adjusting for age, race, gender, residence, CD4 counts, HIV risk group, and initial antiretroviral regimen during the study period, and time. The community viral load gradually decreased from 2004 to 2013 ( p < 0.0001). The number of new infections also decreased ( p = 0.0001) over time. A faster rate of decrease was seen among men compared to women ( p < 0.0001), men who have sex with men ( p = 0.0001) compared to heterosexuals, patients diagnosed in urban areas compared to that in rural areas ( p = 0.0004), and patients prescribed single-tablet regimen compared to multiple-tablet regimen ( p < 0.0001). While the state-wide community viral load decreased over time, the decline was not uniform among residence at diagnosis, HIV risk group, and single-tablet regimen versus multiple-tablet regimen subgroups. Slower declines in community viral load among females, those in rural areas, and heterosexuals suggest possible disparities in care that require further exploration. The association between using single-tablet regimen and faster community viral load decline is noteworthy.

RF-MEMS Load Sensors with Enhanced Q-factor and Sensitivity in a Suspended Architecture.

PubMed

Melik, Rohat; Unal, Emre; Perkgoz, Nihan Kosku; Puttlitz, Christian; Demir, Hilmi Volkan

2011-03-01

In this paper, we present and demonstrate RF-MEMS load sensors designed and fabricated in a suspended architecture that increases their quality-factor (Q-factor), accompanied with an increased resonance frequency shift under load. The suspended architecture is obtained by removing silicon under the sensor. We compare two sensors that consist of 195 μm × 195 μm resonators, where all of the resonator features are of equal dimensions, but one's substrate is partially removed (suspended architecture) and the other's is not (planar architecture). The single suspended device has a resonance of 15.18 GHz with 102.06 Q-factor whereas the single planar device has the resonance at 15.01 GHz and an associated Q-factor of 93.81. For the single planar device, we measured a resonance frequency shift of 430 MHz with 3920 N of applied load, while we achieved a 780 MHz frequency shift in the single suspended device. In the planar triplet configuration (with three devices placed side by side on the same chip, with the two outmost ones serving as the receiver and the transmitter), we observed a 220 MHz frequency shift with 3920 N of applied load while we obtained a 340 MHz frequency shift in the suspended triplet device with 3920 N load applied. Thus, the single planar device exhibited a sensitivity level of 0.1097 MHz/N while the single suspended device led to an improved sensitivity of 0.1990 MHz/N. Similarly, with the planar triplet device having a sensitivity of 0.0561 MHz/N, the suspended triplet device yielded an enhanced sensitivity of 0.0867 MHz/N.

Sound-Intensity Feedback During Running Reduces Loading Rates and Impact Peak.

PubMed

Tate, Jeremiah J; Milner, Clare E

2017-08-01

Study Design Controlled laboratory study, within-session design. Background Gait retraining has been proposed as an effective intervention to reduce impact loading in runners at risk of stress fractures. Interventions that can be easily implemented in the clinic are needed. Objective To assess the immediate effects of sound-intensity feedback related to impact during running on vertical impact peak, peak vertical instantaneous loading rate, and vertical average loading rate. Methods Fourteen healthy, college-aged runners who ran at least 9.7 km/wk participated (4 male, 10 female; mean ± SD age, 23.7 ± 2.0 years; height, 1.67 ± 0.08 m; mass, 60.9 ± 8.7 kg). A decibel meter provided real-time sound-intensity feedback of treadmill running via an iPad application. Participants were asked to reduce the sound intensity of running while receiving continuous feedback for 15 minutes, while running at their self-selected preferred speed. Baseline and follow-up ground reaction force data were collected during overground running at participants' self-selected preferred running speed. Results Dependent t tests indicated a statistically significant reduction in vertical impact peak (1.56 BW to 1.13 BW, P≤.001), vertical instantaneous loading rate (95.48 BW/s to 62.79 BW/s, P = .001), and vertical average loading rate (69.09 BW/s to 43.91 BW/s, P≤.001) after gait retraining, compared to baseline. Conclusion The results of the current study support the use of sound-intensity feedback during treadmill running to immediately reduce loading rate and impact force. The transfer of within-session reductions in impact peak and loading rates to overground running was demonstrated. Decreases in loading were of comparable magnitude to those observed in other gait retraining methods. J Orthop Sports Phys Ther 2017;47(8):565-569. Epub 6 Jul 2017. doi:10.2519/jospt.2017.7275.

Synthesis, Characterization, and In Vivo Efficacy of Shell Cross-Linked Nanoparticle Formulations Carrying Silver Antimicrobials as Aerosolized Therapeutics

PubMed Central

2014-01-01

The use of nebulizable, nanoparticle-based antimicrobial delivery systems can improve efficacy and reduce toxicity for treatment of multi-drug-resistant bacteria in the chronically infected lungs of cystic fibrosis patients. Nanoparticle vehicles are particularly useful for applying broad-spectrum silver-based antimicrobials, for instance, to improve the residence time of small-molecule silver carbene complexes (SCCs) within the lung. Therefore, we have synthesized multifunctional, shell cross-linked knedel-like polymeric nanoparticles (SCK NPs) and capitalized on the ability to independently load the shell and core with silver-based antimicrobial agents. We formulated three silver-loaded variants of SCK NPs: shell-loaded with silver cations, core-loaded with SCC10, and combined loading of shell silver cations and core SCC10. All three formulations provided a sustained delivery of silver over the course of at least 2–4 days. The two SCK NP formulations with SCC10 loaded in the core each exhibited excellent antimicrobial activity and efficacy in vivo in a mouse model of Pseudomonas aeruginosa pneumonia. SCK NPs with shell silver cation-load only, while efficacious in vitro, failed to demonstrate efficacy in vivo. However, a single dose of core SCC10-loaded SCK NPs (0.74 ± 0.16 mg Ag) provided a 28% survival advantage over sham treatment, and administration of two doses (0.88 mg Ag) improved survival to 60%. In contrast, a total of 14.5 mg of Ag+ delivered over 5 doses at 12 h intervals was necessary to achieve a 60% survival advantage with a free-drug (SCC1) formulation. Thus, SCK NPs show promise for clinical impact by greatly reducing antimicrobial dosage and dosing frequency, which could minimize toxicity and improve patient adherence. PMID:23718195

Short rest between cyclic flexion periods is a risk factor for a lumbar disorder.

PubMed

Hoops, Heather; Zhou, Bing-He; Lu, Yun; Solomonow, Moshe; Patel, Vikas

2007-08-01

The epidemiology identifies cyclic lumbar loading as a risk factor for cumulative trauma disorder. Experimental biomechanical and physiological confirmation is lacking. The objective of this study was to asses the impact of different rest durations applied between periods of cyclic loading on the development of an acute lumbar disorder which, if continued to be subjected to loading, may develop into a cumulative disorder. Three groups of in vivo feline preparations were subjected to six sequential 10 min loading periods of cyclic lumbar flexion at 40 N with a frequency of 0.25 Hz applied to the L-4/5 level. The rest durations varied from 5 min in the first group, to 10 min in the second and to 20 min in the third. Reflexive EMG from the multifidi and lumbar displacement were used to identify significant (P<0.001) effects of time and rest duration for post-load EMG and displacement. Single-cycle test were performed hourly for 7 h post-loading to assess recovery. A model developed earlier was applied to represent the experimental data. The groups allowed 5 and 10 min rest exhibited an acute neuromuscular disorder expressed by a significant (P<0.001) delayed hyperexcitability 2-3 h into the 7 h recovery period with the intensity of the hyperexcitability significantly higher (P<0.001) for the group allowed only 5 min rest. The group allowed 20 min rest had a slow, uneventful recovery, free of delayed hyperexcitability. Occupational and sports activities requiring repetitive (cyclic) loading of the lumbar spine may be a risk factor for the development of a cumulative lumbar disorder and may require sufficient rest, as much as twice as long as the loading period, for prevention. Comparison to similar data for static lumbar loading shows that cyclic loading is more deleterious than static loading, requiring more rest to offset the negative effect of the repeated acts of stretch.

Loading capacity of zirconia implant supported hybrid ceramic crowns.

PubMed

Rohr, Nadja; Coldea, Andrea; Zitzmann, Nicola U; Fischer, Jens

2015-12-01

Recently a polymer infiltrated hybrid ceramic was developed, which is characterized by a low elastic modulus and therefore may be considered as potential material for implant supported single crowns. The purpose of the study was to evaluate the loading capacity of hybrid ceramic single crowns on one-piece zirconia implants with respect to the cement type. Fracture load tests were performed on standardized molar crowns milled from hybrid ceramic or feldspar ceramic, cemented to zirconia implants with either machined or etched intaglio surface using four different resin composite cements. Flexure strength, elastic modulus, indirect tensile strength and compressive strength of the cements were measured. Statistical analysis was performed using two-way ANOVA (p=0.05). The hybrid ceramic exhibited statistically significant higher fracture load values than the feldspar ceramic. Fracture load values and compressive strength values of the respective cements were correlated. Highest fracture load values were achieved with an adhesive cement (1253±148N). Etching of the intaglio surface did not improve the fracture load. Loading capacity of hybrid ceramic single crowns on one-piece zirconia implants is superior to that of feldspar ceramic. To achieve maximal loading capacity for permanent cementation of full-ceramic restorations on zirconia implants, self-adhesive or adhesive cements with a high compressive strength should be used. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Statistics concerning the Apollo command module water landing, including the probability of occurrence of various impact conditions, sucessful impact, and body X-axis loads

NASA Technical Reports Server (NTRS)

Whitnah, A. M.; Howes, D. B.

1971-01-01

Statistical information for the Apollo command module water landings is presented. This information includes the probability of occurrence of various impact conditions, a successful impact, and body X-axis loads of various magnitudes.

Configuration and Sizing of a Test Fixture for Panels Under Combined Loads

NASA Technical Reports Server (NTRS)

Lovejoy, Andrew E.

2006-01-01

Future air and space structures are expected to utilize composite panels that are subjected to combined mechanical loads, such as bi-axial compression/tension, shear and pressure. Therefore, the ability to accurately predict the buckling and strength failures of such panels is important. While computational analysis can provide tremendous insight into panel response, experimental results are necessary to verify predicted performances of these panels to judge the accuracy of computational methods. However, application of combined loads is an extremely difficult task due to the complex test fixtures and set-up required. Presented herein is a comparison of several test set-ups capable of testing panels under combined loads. Configurations compared include a D-box, a segmented cylinder and a single panel set-up. The study primarily focuses on the preliminary sizing of a single panel test configuration capable of testing flat panels under combined in-plane mechanical loads. This single panel set-up appears to be best suited to the testing of both strength critical and buckling critical panels. Required actuator loads and strokes are provided for various square, flat panels.

On Per-Phase Topology Control and Switching in Emerging Distribution Systems

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

Ding, Fei; Mousavi, Mirrasoul J.

This paper presents a new concept and approach for topology control and switching in distribution systems by extending the traditional circuit switching to laterals and single-phase loads. Voltage unbalance and other key performance indicators including voltage magnitudes, line loading, and energy losses are used to characterize and demonstrate the technical value of optimizing system topology on a per-phase basis in response to feeder conditions. The near-optimal per-phase topology control is defined as a series of hierarchical optimization problems. The proposed approach is respectively applied to IEEE 13-bus and 123-bus test systems for demonstration, which included the impact of integrating electricmore » vehicles (EVs) in the test circuit. It is concluded that the proposed approach can be effectively leveraged to improve voltage profiles with electric vehicles, the extent of which depends upon the performance of the base case without EVs.« less

A sealed capsule system for biological and liquid shock-recovery experiments.

PubMed

Leighs, James A; Appleby-Thomas, Gareth J; Stennett, Chris; Hameed, Amer; Wilgeroth, James M; Hazell, Paul J

2012-11-01

This paper presents an experimental method designed to one-dimensionally shock load and subsequently recover liquid samples. Resultant loading profiles have been interrogated via hydrocode simulation as the nature of the target did not allow for direct application of the diagnostics typically employed in shock physics (e.g., manganin stress gauges or Heterodyne velocimeter (Het-V)). The target setup has been experimentally tested using aluminium flyer plates accelerated by a 50-mm bore single-stage gas-gun reaching projectile impact velocities of up to ~500 ms(-1) (corresponding to peak pressures of up to ca. 4 GPa being experienced by fluid samples). Recovered capsules survived well showing only minor signs of damage. Modelled gauge traces have been validated through the use of a (slightly modified) experiment in which a Het-V facing the rear of the inner capsule was employed. In these tests, good correlation between simulated and experimental traces was observed.

How does spallation microdamage nucleate in bulk amorphous alloys under shock loading?

NASA Astrophysics Data System (ADS)

Huang, X.; Ling, Z.; Zhang, H. S.; Ma, J.; Dai, L. H.

2011-11-01

Specially designed plate-impact experiments have been conducted on a Zr-based amorphous alloy using a single-stage light gas gun. To understand the microdamage nucleation process in the material, the samples are subjected to dynamic tensile loadings of identical amplitude (˜ 3.18 GPa) but with different durations (83-201 ns). A cellular pattern with an equiaxed shape is observed on the spallation surface, which shows that spallation in the tested amorphous alloy is a typical ductile fracture and that microvoids have been nucleated during the process. Based on the observed fracture morphologies of the spallation surface and free-volume theory, we propose a microvoid nucleation model of bulk amorphous alloys. It is found that nucleation of microvoids at the early stage of spallation in amorphous alloys results from diffusion and coalescence of free volume, and that high mean tensile stress plays a dominant role in microvoid nucleation.

A sealed capsule system for biological and liquid shock-recovery experiments

NASA Astrophysics Data System (ADS)

Leighs, James A.; Appleby-Thomas, Gareth J.; Stennett, Chris; Hameed, Amer; Wilgeroth, James M.; Hazell, Paul J.

2012-11-01

This paper presents an experimental method designed to one-dimensionally shock load and subsequently recover liquid samples. Resultant loading profiles have been interrogated via hydrocode simulation as the nature of the target did not allow for direct application of the diagnostics typically employed in shock physics (e.g., manganin stress gauges or Heterodyne velocimeter (Het-V)). The target setup has been experimentally tested using aluminium flyer plates accelerated by a 50-mm bore single-stage gas-gun reaching projectile impact velocities of up to ˜500 ms-1 (corresponding to peak pressures of up to ca. 4 GPa being experienced by fluid samples). Recovered capsules survived well showing only minor signs of damage. Modelled gauge traces have been validated through the use of a (slightly modified) experiment in which a Het-V facing the rear of the inner capsule was employed. In these tests, good correlation between simulated and experimental traces was observed.

Pollution load index for heavy metals in Mian-Ab plain soil, Khuzestan, Iran.

PubMed

Jorfi, Sahand; Maleki, Rohangiz; Jaafarzadeh, Neemat; Ahmadi, Mehdi

2017-12-01

Soil pollution by heavy metals is a major concern in agricultural area. Potential impact of heavy metals in agricultural soil on human health by accumulating in food chain demonstrated elsewhere. In this regard Mian-Ab plain as a major agricultural site of Khuzestan province considered for Arsenic, cadmium and lead concentration as the main potential toxic pollutants in soil. 50 topsoil samples were collected and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Also Contamination level of selected heavy metals in Mian-Ab Plain, was assessed by single factor contaminant index (PI) and pollution load index (PLI). Results show mean concentration of arsenic, cadmium and lead were 2.52, 0.30 and 7.21 mg kg -1 . Base on PLI results 12 point (24%) of the studied area show moderately polluted and 38 point (76%) show unpolluted area.

The use of nanomodified concrete in construction of high-rise buildings

NASA Astrophysics Data System (ADS)

Prokhorov, Sergei

2018-03-01

Construction is one of the leading economy sectors. Currently, concrete is the basis of most of the structural elements, without which it is impossible to imagine the construction of a single building or facility. Their strength, reinforcement and the period of concrete lifetime are determined at the design stage, taking into account long-term operation. However, in real life, the number of impacts that affects the structural strength is pretty high. In some cases, they are random and do not have standardized values. This is especially true in the construction and exploitation of high-rise buildings and structures. Unlike the multi-storey buildings, they experience significant loads already at the stage of erection, as they support load-lifting mechanisms, formwork systems, workers, etc. The purpose of the presented article is to develop a methodology for estimating the internal fatigue of concrete structures based on changes in their electrical conductivity.

Modeling and Measurement of Sustained Loading and Temperature-Dependent Deformation of Carbon Fiber-Reinforced Polymer Bonded to Concrete.

PubMed

Jeong, Yoseok; Lee, Jaeha; Kim, WooSeok

2015-01-29

This paper aims at presenting the effects of short-term sustained load and temperature on time-dependent deformation of carbon fiber-reinforced polymer (CFRP) bonded to concrete and pull-off strength at room temperature after the sustained loading period. The approach involves experimental and numerical analysis. Single-lap shear specimens were used to evaluate temperature and short-term sustained loading effects on time-dependent behavior under sustained loading and debonding behavior under pull-off loading after a sustained loading period. The numerical model was parameterized with experiments on the concrete, FRP, and epoxy. Good correlation was seen between the numerical results and single-lap shear experiments. Sensitivity studies shed light on the influence of temperature, epoxy modulus, and epoxy thickness on the redistribution of interfacial shear stress during sustained loading. This investigation confirms the hypothesis that interfacial stress redistribution can occur due to sustained load and elevated temperature and its effect can be significant.

Modeling and Measurement of Sustained Loading and Temperature-Dependent Deformation of Carbon Fiber-Reinforced Polymer Bonded to Concrete

PubMed Central

Jeong, Yoseok; Lee, Jaeha; Kim, WooSeok

2015-01-01

This paper aims at presenting the effects of short-term sustained load and temperature on time-dependent deformation of carbon fiber-reinforced polymer (CFRP) bonded to concrete and pull-off strength at room temperature after the sustained loading period. The approach involves experimental and numerical analysis. Single-lap shear specimens were used to evaluate temperature and short-term sustained loading effects on time-dependent behavior under sustained loading and debonding behavior under pull-off loading after a sustained loading period. The numerical model was parameterized with experiments on the concrete, FRP, and epoxy. Good correlation was seen between the numerical results and single-lap shear experiments. Sensitivity studies shed light on the influence of temperature, epoxy modulus, and epoxy thickness on the redistribution of interfacial shear stress during sustained loading. This investigation confirms the hypothesis that interfacial stress redistribution can occur due to sustained load and elevated temperature and its effect can be significant. PMID:28787948

Experimental investigation of the effect of inlet particle properties on the capture efficiency in an exhaust particulate filter

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

Viswanathan, Sandeep; Rothamer, David; Zelenyuk, Alla

The impact of inlet particle properties on the filtration performance of clean and particulate matter (PM) laden cordierite filter samples was evaluated using PM generated by a spark-ignition direct-injection (SIDI) engine fuelled with tier II EEE certification gasoline. Prior to the filtration experiments, a scanning mobility particle spectrometer (SMPS) was used to measure the electrical-mobility based particle size distribution (PSD) in the SIDI exhaust from distinct engine operating conditions. An advanced aerosol characterization system that comprised of a centrifugal particle mass analyser (CPMA), a differential mobility analyser (DMA), and a single particle mass spectrometer (SPLAT II) was used to obtainmore » additional information on the SIDI particulate, including particle composition, mass, and dynamic shape factors (DSFs) in the transition () and free-molecular () flow regimes. During the filtration experiments, real-time measurements of PSDs upstream and downstream of the filter sample were used to estimate the filtration performance and the total trapped mass within the filter using an integrated particle size distribution method. The filter loading process was paused multiple times to evaluate the filtration performance in the partially loaded state. The change in vacuum aerodynamic diameter () distribution of mass-selected particles was examined for flow through the filter to identify whether preferential capture of particles of certain shapes occurred in the filter. The filter was also probed using different inlet PSDs to understand their impact on particle capture within the filter sample. Results from the filtration experiment suggest that pausing the filter loading process and subsequently performing the filter probing experiments did not impact the overall evolution of filtration performance. Within the present distribution of particle sizes, filter efficiency was independent of particle shape potentially due to the diffusion-dominant filtration process. Particle mobility diameter and trapped mass within the filter appeared to be the dominant parameters that impacted filter performance.« less

Space shuttle solid rocket booster recovery system definition. Volume 3: SRB water impact loads computer program, user's manual

NASA Technical Reports Server (NTRS)

1973-01-01

This user's manual describes the FORTRAN IV computer program developed to compute the total vertical load, normal concentrated pressure loads, and the center of pressure of typical SRB water impact slapdown pressure distributions specified in the baseline configuration. The program prepares the concentrated pressure load information in punched card format suitable for input to the STAGS computer program. In addition, the program prepares for STAGS input the inertia reacting loads to the slapdown pressure distributions.

Pitfalls in interpretation of CT-values of RT-PCR in children with acute respiratory tract infections.

PubMed

Wishaupt, Jérôme O; Ploeg, Tjeerd van der; Smeets, Leo C; Groot, Ronald de; Versteegh, Florens G A; Hartwig, Nico G

2017-05-01

The relation between viral load and disease severity in childhood acute respiratory tract infections (ARI) is not fully understood. To assess the clinical relevance of the relation between viral load, determined by cycle threshold (CT) value of real-time reverse transcription-polymerase chain reaction assays and disease severity in children with single- and multiple viral ARI. 582 children with ARI were prospectively followed and tested for 15 viruses. Correlations were calculated between CT values and clinical parameters. In single viral ARI, statistically significant correlations were found between viral loads of Respiratory Syncytial Virus (RSV) and hospitalization and between viral loads of Human Coronavirus (HCoV) and a disease severity score. In multiple-viral ARI, statistically significant correlations between viral load and clinical parameters were found. In RSV-Rhinovirus (RV) multiple infections, a low viral load of RV was correlated with a high length of hospital stay and a high duration of extra oxygen use. The mean CT value for RV, HCoV and Parainfluenza virus was significantly lower in single- versus multiple infections. Although correlations between CT values and clinical parameters in patients with single and multiple viral infection were found, the clinical importance of these findings is limited because individual differences in host-, viral and laboratory factors complicate the interpretation of statistically significant findings. In multiple infections, viral load cannot be used to differentiate between disease causing virus and innocent bystanders. Copyright © 2017 Elsevier B.V. All rights reserved.

Peri-anterior cruciate ligament reconstruction femur fracture: a biomechanical analysis of the femoral tunnel as a stress riser.

PubMed

Han, Yung; Sardar, Zeeshan; McGrail, Scott; Steffen, Thomas; Martineau, Paul A

2011-12-01

Sixteen case reports of distal femur fractures as post-operative complications after anterior cruciate ligament (ACL) reconstruction have been described in the literature. The femoral tunnel has been suggested as a potential stress riser for fracture formation. Additionally, double bundle ACL reconstructions may compound this risk. This is the first biomechanical study to examine the significance of a stress riser effect of the femoral tunnel(s) after ACL reconstruction. The hypotheses tested in this study are that the femoral tunnel acts as a stress riser for fracture and that this effect increases with the size of the tunnel (8 mm vs. 10 mm) and with the number of tunnels (1 vs. 2). Femoral tunnels simulating single bundle (SB) hamstring graft (8 mm), bone-patellar tendon-bone graft (10 mm), and double bundle (DB) ACL reconstruction (7, 6 mm) were drilled in fourth-generation saw bones. These three experimental groups and a control group consisting of native saw bones without tunnels were loaded to failure. All fractures occurred through the tunnels in the DB group, whereas fractures did not consistently occur through the tunnels in the SB groups. The mean fracture load was 6,145N ± 471N in the native group, 5,691N ± 198N in the 8 mm SB group, 5,702N ± 282N in the 10 mm SB group, and 4,744N ± 418N in the DB group. The mean fracture load for the DB group was significantly lower when compared to the native, 8 mm SB, and 10 mm SB groups independently (P value = 0.0016, 0.0060, and 0.0038, respectively). The mean fracture loads for neither SB groups were not significantly different from the native group. An anatomically placed femoral tunnel in single bundle ACL reconstruction in our experimental model was not a significant stress riser to fracture, whereas the two femoral tunnels in double bundle ACL reconstruction significantly decreased load to failure. The results support the sparsity of reported peri-ACL reconstruction femur fractures in single femoral tunnel techniques. However, the increased fracture risk in double bundle ACL reconstruction may be a cause for concern and impact patient selection.

Fabrication and Testing of High-Speed-Single-Rotor and Compound-Rotor Systems

DTIC Science & Technology

2016-05-04

pitch link loads, hub loads, rotor wakes and performance of high -speed single-rotor and compound-rotor systems to support 1. REPORT DATE (DD-MM-YYYY) 4...Public Release; Distribution Unlimited UU UU UU UU 05-04-2016 14-Jul-2014 13-Jan-2016 Final Report: Fabrication and Testing of High -Speed Single- Rotor and...Final Report: Fabrication and Testing of High -Speed Single-Rotor and Compound-Rotor Systems Report Title The Alfred Gessow Rotorcraft Center has

Fabrication and Testing of High-Speed Single-Rotor and Compound-Rotor Systems

DTIC Science & Technology

2016-04-05

pitch link loads, hub loads, rotor wakes and performance of high -speed single-rotor and compound-rotor systems to support 1. REPORT DATE (DD-MM-YYYY) 4...Public Release; Distribution Unlimited UU UU UU UU 05-04-2016 14-Jul-2014 13-Jan-2016 Final Report: Fabrication and Testing of High -Speed Single- Rotor and...Final Report: Fabrication and Testing of High -Speed Single-Rotor and Compound-Rotor Systems Report Title The Alfred Gessow Rotorcraft Center has

The Impact Response of Carbon/Epoxy Laminates (Center Director's Discretionary Fund, Project No. 94-13)

NASA Technical Reports Server (NTRS)

Nettles, A. T.; Hodge, A. J.

1997-01-01

Low velocity dropweight impact tests were conducted on carbon/epoxy laminates under various boundary conditions. The composite plates were 8-ply (+45,0,-45,90)s laminates supported in a clamped-clamped/free-free configuration with varying amounts of in-plane load, N(sub x), applied. Specimens were impacted at energies of 3.4, 4.5, and 6 Joules (2.5, 3.3, and 4.4 ft-lb). The amount of damage induced into the specimen was evaluated using instrumented impact techniques, x-ray inspection, and cross-sectional photomicroscopy. Some static identation tests were performed to examine if the impact events utilized in this study were of a quasi-static nature and also to gain insight into the shape of the deflected surface at various impact load combinations. Load-displacement curves from these tests were compared to those of the impact tests, as was damage determined from x-ray inspection. The finite element technique was used to model the impact event and determine the stress field within the laminae. Results showed that for a given impact energy level, more damage was induced into the specimen as the external in-plane load, N(sub x), was increased. The majority of damage observed consisted of back face splitting of the matrix parallel to the fibers in that ply, associated with delaminations emanating from these splits. The analysis showed qualitatively the results of impact conditions on maximum load of impact, maximum transverse deflection, and first failure mode and location.

Loading direction regulates the affinity of ADP for kinesin.

PubMed

Uemura, Sotaro; Ishiwata, Shin'ichi

2003-04-01

Kinesin is an ATP-driven molecular motor that moves processively along a microtubule. Processivity has been explained as a mechanism that involves alternating single- and double-headed binding of kinesin to microtubules coupled to the ATPase cycle of the motor. The internal load imposed between the two bound heads has been proposed to be a key factor regulating the ATPase cycle in each head. Here we show that external load imposed along the direction of motility on a single kinesin molecule enhances the binding affinity of ADP for kinesin, whereas an external load imposed against the direction of motility decreases it. This coupling between loading direction and enzymatic activity is in accord with the idea that the internal load plays a key role in the unidirectional and cooperative movement of processive motors.

An extravehicular suit impact load attenuation study to improve astronaut bone fracture prediction.

PubMed

Sulkowski, Christina M; Gilkey, Kelly M; Lewandowski, Beth E; Samorezov, Sergey; Myers, Jerry G

2011-04-01

Understanding the contributions to the risk of bone fracture during spaceflight is essential for mission success. A pressurized extravehicular activity (EVA) suit analogue test bed was developed, impact load attenuation data were obtained, and the load at the hip of an astronaut who falls to the side during an EVA was characterized. Offset (representing the gap between the EVA suit and the astronaut's body), impact load magnitude, and EVA suit operating pressure were factors varied in the study. The attenuation data were incorporated into a probabilistic model of bone fracture risk during spaceflight, replacing the previous load attenuation value that was based on commercial hip protector data. Load attenuation was more dependent on offset than on pressurization or load magnitude, especially at small offset values. Load attenuation factors for offsets between 0.1-1.5 cm were 0.69 +/- 0.15, 0.49 +/- 0.22, and 0.35 +/- 0.18 for mean impact forces of 4827, 6400, and 8467 N, respectively. Load attenuation factors for offsets of 2.8-5.3 cm were 0.93 +/- 0.2, 0.94 +/- 0.1, and 0.84 +/- 0.5 for the same mean impact forces. The mean and 95th percentile bone fracture risk index predictions were each reduced by 65-83%. The mean and 95th percentile bone fracture probability predictions were both reduced approximately 20-50%. The reduction in uncertainty and improved confidence in bone fracture predictions increased the fidelity and credibility of the fracture risk model and its benefit to mission design and in-flight operational decisions.

Pesticide load dynamics during stormwater flow events in Mediterranean coastal streams: Alexander stream case study.

PubMed

Topaz, Tom; Egozi, Roey; Eshel, Gil; Chefetz, Benny

2018-06-01

Cultivated land is a major source of pesticides, which are transported with the runoff water and eroded soil during rainfall events and pollute riverine and estuarine environments. Common ecotoxicological assessments of riverine systems are mainly based on water sampling and analysis of only the dissolved phase, and address a single pesticide's toxicological impact under laboratory conditions. A clear overview of mixtures of pesticides in the adsorbed and dissolved phases is missing, and therefore the full ecotoxicological impact is not fully addressed. The aim of this study was to characterize and quantify pesticide concentrations in both suspended sediment and dissolved phases, to provide a better understanding of pesticide-load dynamics during storm events in coastal streams in a Mediterranean climate. High-resolution sampling campaigns of seven flood events were conducted during two rainy seasons in Alexander stream, Israel. Samples of suspended sediments were separated from the solution and both media were analyzed separately for 250 pesticides. A total of 63 pesticides were detected; 18 and 16 pesticides were found solely in the suspended sediments and solution, respectively. Significant differences were observed among the pesticide groups: only 7% of herbicide, 20% of fungicide and 42% of insecticide load was transported with the suspended sediments. However, in both dissolved and adsorbed phases, a mix of pesticides was found which were graded from "mobile" to "non-mobile" with varied distribution coefficients. Diuron, and tebuconazole were frequently found in large quantities in both phases. Whereas insecticide and fungicide transport is likely governed by application time and method, the governing factor for herbicide load was the magnitude of the stream discharge. The results show a complex dynamic of pesticide load affected by excessive use of pesticides, which should be taken into consideration when designing projects to monitor riverine and estuarine water quality. Copyright © 2017 Elsevier B.V. All rights reserved.

Relative roles of weather variables and change in human population in malaria: comparison over different states of India.

PubMed

Goswami, Prashant; Murty, Upadhayula Suryanarayana; Mutheneni, Srinivasa Rao; Krishnan, Swathi Trithala

2014-01-01

Pro-active and effective control as well as quantitative assessment of impact of climate change on malaria requires identification of the major drivers of the epidemic. Malaria depends on vector abundance which, in turn, depends on a combination of weather variables. However, there remain several gaps in our understanding and assessment of malaria in a changing climate. Most of the studies have considered weekly or even monthly mean values of weather variables, while the malaria vector is sensitive to daily variations. Secondly, rarely all the relevant meteorological variables have been considered together. An important question is the relative roles of weather variables (vector abundance) and change in host (human) population, in the change in disease load. We consider the 28 states of India, characterized by diverse climatic zones and changing population as well as complex variability in malaria, as a natural test bed. An annual vector load for each of the 28 states is defined based on the number of vector genesis days computed using daily values of temperature, rainfall and humidity from NCEP daily Reanalysis; a prediction of potential malaria load is defined by taking into consideration changes in the human population and compared with the reported number of malaria cases. For most states, the number of malaria cases is very well correlated with the vector load calculated with the combined conditions of daily values of temperature, rainfall and humidity; no single weather variable has any significant association with the observed disease prevalence. The association between vector-load and daily values of weather variables is robust and holds for different climatic regions (states of India). Thus use of all the three weather variables provides a reliable means of pro-active and efficient vector sanitation and control as well as assessment of impact of climate change on malaria.

Relative Roles of Weather Variables and Change in Human Population in Malaria: Comparison over Different States of India

PubMed Central

Goswami, Prashant; Murty, Upadhayula Suryanarayana; Mutheneni, Srinivasa Rao; Krishnan, Swathi Trithala

2014-01-01

Background Pro-active and effective control as well as quantitative assessment of impact of climate change on malaria requires identification of the major drivers of the epidemic. Malaria depends on vector abundance which, in turn, depends on a combination of weather variables. However, there remain several gaps in our understanding and assessment of malaria in a changing climate. Most of the studies have considered weekly or even monthly mean values of weather variables, while the malaria vector is sensitive to daily variations. Secondly, rarely all the relevant meteorological variables have been considered together. An important question is the relative roles of weather variables (vector abundance) and change in host (human) population, in the change in disease load. Method We consider the 28 states of India, characterized by diverse climatic zones and changing population as well as complex variability in malaria, as a natural test bed. An annual vector load for each of the 28 states is defined based on the number of vector genesis days computed using daily values of temperature, rainfall and humidity from NCEP daily Reanalysis; a prediction of potential malaria load is defined by taking into consideration changes in the human population and compared with the reported number of malaria cases. Results For most states, the number of malaria cases is very well correlated with the vector load calculated with the combined conditions of daily values of temperature, rainfall and humidity; no single weather variable has any significant association with the observed disease prevalence. Conclusion The association between vector-load and daily values of weather variables is robust and holds for different climatic regions (states of India). Thus use of all the three weather variables provides a reliable means of pro-active and efficient vector sanitation and control as well as assessment of impact of climate change on malaria. PMID:24971510

Impacct of scalding duration and scalding water temperature on broiler processing wastewater loadings

USDA-ARS?s Scientific Manuscript database

The effects of scalding water temperature and immersion time on impact to poultry processing wastewater (PPW) loading were evaluated following the slaughter of commercially raised broilers. Based on previous research, the hypothesis was that immersion time would have a significant impact on PPW load...

Design and evaluation of a foam-filled hat-stiffened panel concept for aircraft primary structural applications

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.

1993-01-01

Geodesically stiffened structures are very efficient in carrying combined bending, torsion, and pressure loading that is typical of primary aircraft structures. They are also very damage tolerant since there are multiple load paths available to redistribute loads compared to prismatically stiffened structures. Geodesically stiffened structures utilize continuous filament composite materials which make them amenable to automated manufacturing processes to reduce cost. The current practice for geodesically stiffened structures is to use a solid blade construction for the stiffener. This stiffener configuration is not an efficient concept and there is a need to identify other stiffener configurations that are more efficient but utilize the same manufacturing process as the solid blade. This paper describes a foam-filled stiffener cross section that is more efficient than a solid-blade stiffener in the load range corresponding to primary aircraft structures. A prismatic hat-stiffener panel design is then selected for structural evaluation in uni-axial compression with and without impact damage. Experimental results for both single stiffener specimens and multi-stiffener panel specimens are presented. Finite element analysis results are presented that predict the buckling and postbuckling response of the test specimens. Analytical results for both the element and panel specimens are compared with experimental results.

Effects of Acute Aerobic Exercise on Rats Serum Extracellular Vesicles Diameter, Concentration and Small RNAs Content.

PubMed

Oliveira, Getúlio P; Porto, William F; Palu, Cintia C; Pereira, Lydyane M; Petriz, Bernardo; Almeida, Jeeser A; Viana, Juliane; Filho, Nezio N A; Franco, Octavio L; Pereira, Rinaldo W

2018-01-01

Physical exercise stimulates organs, mainly the skeletal muscle, to release a broad range of molecules, recently dubbed exerkines. Among them, RNAs, such as miRNAs, piRNAs, and tRNAs loaded in extracellular vesicles (EVs) have the potential to play a significant role in the way muscle and other organs communicate to translate exercise into health. Low, moderate and high intensity treadmill protocols were applied to rat groups, aiming to investigate the impact of exercise on serum EVs and their associated small RNA molecules. Transmission electron microscopy, resistive pulse sensing, and western blotting were used to investigate EVs morphology, size distribution, concentration and EVs marker proteins. Small RNA libraries from EVs RNA were sequenced. Exercise did not change EVs size, while increased EVs concentration. Twelve miRNAs were found differentially expressed after exercise: rno-miR-128-3p, 103-3p, 330-5p, 148a-3p, 191a-5p, 10b-5p, 93-5p, 25-3p, 142-5p, 3068-3p, 142-3p, and 410-3p. No piRNA was found differentially expressed, and one tRNA, trna8336, was found down-regulated after exercise. The differentially expressed miRNAs were predicted to target genes involved in the MAPK pathway. A single bout of exercise impacts EVs and their small RNA load, reinforcing the need for a more detailed investigation into EVs and their load as mediators of health-promoting exercise.

In Situ Observation of High-Pressure Phase Transitions in SiO2 Under Shock Loading Using Time Resolved X-Ray Diffraction

NASA Astrophysics Data System (ADS)

Tracy, S. J.; Turneaure, S.; Duffy, T. S.

2016-12-01

Quartz is one of the most abundant minerals in Earth's crust and serves as an archetype for silicate minerals generally. The shock metamorphism of silica is important for understanding and interpreting meteorite impact events. Shock compression of quartz is characterized by a phase transition occurring over a broad mixed-phase region ( 10-40 GPa). Despite decades of study, the nature of this transformation and the structure of the high-pressure phase remain poorly understood. In situ x-ray diffraction data on shock-compressed SiO2 was collected at the Dynamic Compression Sector at the Advanced Photon Source. The behavior both single crystal alpha-quartz and fused silica was investigated under dynamic loading through a series real-time synchrotron x-ray diffraction measurements during peak stresses up to 65 GPa. A two-stage light gas gun was used to accelerate LiF flyer plates that impacted the SiO2 samples resulting in a propagating step-like increase in pressure and temperature behind the shock front. Four consecutive x-ray frames, separated by 153 ns, were collected during the transient loading and unloading. These measurements allow for the determination of time-dependent atomic arrangements, demonstrating that both amorphous silica as well as crystalline alpha-quartz transform to stishovite above 36 GPa. These measurements reveal important information about the role of kinetics as well texture development and potential defect structures in the transformed material.

30 CFR 75.806 - Connection of single-phase loads.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Connection of single-phase loads. 75.806 Section 75.806 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Underground High-Voltage Distribution...

Control of impact loading during distracted running before and after gait retraining in runners.

PubMed

Cheung, Roy T H; An, Winko W; Au, Ivan P H; Zhang, Janet H; Chan, Zoe Y S; MacPhail, Aislinn J

2018-07-01

Gait retraining using visual biofeedback has been reported to reduce impact loading in runners. However, most of the previous studies did not adequately examine the level of motor learning after training, as the modified gait pattern was not tested in a dual-task condition. Hence, this study sought to compare the landing peak positive acceleration (PPA) and vertical loading rates during distracted running before and after gait retraining. Sixteen recreational runners underwent a two-week visual biofeedback gait retraining program for impact loading reduction, with feedback on the PPA measured at heel. In the evaluation of PPA and vertical loading rates before and after the retraining, the participants performed a cognitive and verbal counting task while running. Repeated measures ANOVA indicated a significant interaction between feedback and training on PPA (F = 4.642; P = 0.048) but not vertical loading rates (F > 1.953; P > 0.067). Pairwise comparisons indicated a significantly lower PPA and vertical loading rates after gait retraining (P < 0.007; Cohen's d > 0.68). Visual feedback after gait retraining reduced PPA and vertical loading rates during distracted running (P < 0.033; Cohen's d > 0.36). Gait retraining is effective in lowering impact loading even when the runners are distracted. In dual-task situation, visual biofeedback provided beneficial influence on kinetics control after gait retraining.

Aircraft Survivability: Rotorcraft Survivability. Summer 2010

DTIC Science & Technology

2010-01-01

Loading of the shafts was conducted using two techniques. The first tech- nique applied a torsion load up to the design limit load after the article...show the ballistic impact and impact damage. Figure 11 shows a 45-degree shaft failure, a common failure type, when loaded to design limit after...SUMMER 2010 ROTORCRAFT Survivability STUDY ON ROTORCRAFT SURVIVABILITY V-22 INTEGRATED SURVIVABILITY DESIGN CH-53K HEAVY LIFT HELICOPTER 9 20 25

Impact of ballistic body armour and load carriage on walking patterns and perceived comfort.

PubMed

Park, Huiju; Branson, Donna; Petrova, Adriana; Peksoz, Semra; Jacobson, Bert; Warren, Aric; Goad, Carla; Kamenidis, Panagiotis

2013-01-01

This study investigated the impact of weight magnitude and distribution of body armour and carrying loads on military personnel's walking patterns and comfort perceptions. Spatio-temporal parameters of walking, plantar pressure and contact area were measured while seven healthy male right-handed military students wore seven different garments of varying weight (0.06, 9, 18 and 27 kg) and load distribution (balanced and unbalanced, on the front and back torso). Higher weight increased the foot contact time with the floor. In particular, weight placement on the non-dominant side of the front torso resulted in the greatest stance phase and double support. Increased plantar pressure and contact area observed during heavier loads entail increased impact forces, which can cause overuse injuries and foot blisters. Participants reported increasingly disagreeable pressure and strain in the shoulder, neck and lower back during heavier weight conditions and unnatural walking while wearing unbalanced weight distributed loads. This study shows the potentially synergistic impact of wearing body armour vest with differential loads on body movement and comfort perception. This study found that soldiers should balance loads, avoiding load placement on the non-dominant side front torso, thus minimising mobility restriction and potential injury risk. Implications for armour vest design modifications can also be found in the results.

Dynamic strength of cylindrical fiber-glass shells and basalt plastic shells under multiple explosive loading

NASA Astrophysics Data System (ADS)

Syrunin, M. A.; Fedorenko, A. G.

2006-08-01

We have shown experimentally that, for cylindrical shells made of oriented fiberglass platic and basalt plastic there exists a critical level of deformations, at which a structure sustains a given number of explosions from the inside. The magnitude of critical deformation for cylindrical fiberglass shells depends linearly on the logarithm of the number of loads that cause failure. For a given type of fiberglass, there is a limiting level of explosive action, at which the number of loads that do not lead to failure can be sufficiently large (more than ˜ 102). This level is attained under loads, which are an order of magnitude lower than the limiting loads under a single explosive action. Basalt plastic shells can be repeatedly used even at the loads, which cause deformation by ˜ 30-50% lower than the safe value ˜ 3.3.5% at single loading.

Fracture load and failure analysis of zirconia single crowns veneered with pressed and layered ceramics after chewing simulation.

PubMed

Stawarczyk, Bogna; Ozcan, Mutlu; Roos, Malgorzata; Trottmann, Albert; Hämmerle, Christoph H F

2011-01-01

This study determined the fracture load of zirconia crowns veneered with four overpressed and four layered ceramics after chewing simulation. The veneered zirconia crowns were cemented and subjected to chewing cycling. Subsequently, the specimens were loaded at an angle of 45° in a Universal Testing Machine to determine the fracture load. One-way ANOVA, followed by a post-hoc Scheffé test, t-test and Weibull statistic were performed. Overpressed crowns showed significantly lower fracture load (543-577 N) compared to layered ones (805-1067 N). No statistical difference was found between the fracture loads within the overpressed group. Within the layered groups, LV (1067 N) presented significantly higher results compared to LC (805 N). The mean values of all other groups were not significantly different. Single zirconia crowns veneered with overpressed ceramics exhibited lower fracture load than those of the layered ones after chewing simulation.

A single-stage optical load-balanced switch for data centers.

PubMed

Huang, Qirui; Yeo, Yong-Kee; Zhou, Luying

2012-10-22

Load balancing is an attractive technique to achieve maximum throughput and optimal resource utilization in large-scale switching systems. However current electronic load-balanced switches suffer from severe problems in implementation cost, power consumption and scaling. To overcome these problems, in this paper we propose a single-stage optical load-balanced switch architecture based on an arrayed waveguide grating router (AWGR) in conjunction with fast tunable lasers. By reuse of the fast tunable lasers, the switch achieves both functions of load balancing and switching through the AWGR. With this architecture, proof-of-concept experiments have been conducted to investigate the feasibility of the optical load-balanced switch and to examine its physical performance. Compared to three-stage load-balanced switches, the reported switch needs only half of optical devices such as tunable lasers and AWGRs, which can provide a cost-effective solution for future data centers.

The effects of interstimulus interval on event-related indices of attention: an auditory selective attention test of perceptual load theory.

PubMed

Gomes, Hilary; Barrett, Sophia; Duff, Martin; Barnhardt, Jack; Ritter, Walter

2008-03-01

We examined the impact of perceptual load by manipulating interstimulus interval (ISI) in two auditory selective attention studies that varied in the difficulty of the target discrimination. In the paradigm, channels were separated by frequency and target/deviant tones were softer in intensity. Three ISI conditions were presented: fast (300ms), medium (600ms) and slow (900ms). Behavioral (accuracy and RT) and electrophysiological measures (Nd, P3b) were observed. In both studies, participants evidenced poorer accuracy during the fast ISI condition than the slow suggesting that ISI impacted task difficulty. However, none of the three measures of processing examined, Nd amplitude, P3b amplitude elicited by unattended deviant stimuli, or false alarms to unattended deviants, were impacted by ISI in the manner predicted by perceptual load theory. The prediction based on perceptual load theory, that there would be more processing of irrelevant stimuli under conditions of low as compared to high perceptual load, was not supported in these auditory studies. Task difficulty/perceptual load impacts the processing of irrelevant stimuli in the auditory modality differently than predicted by perceptual load theory, and perhaps differently than in the visual modality.

The impact of luminance on tonic and phasic pupillary responses to sustained cognitive load.

PubMed

Peysakhovich, Vsevolod; Vachon, François; Dehais, Frédéric

2017-02-01

Pupillary reactions independent of light conditions have been linked to cognition for a long time. However, the light conditions can impact the cognitive pupillary reaction. Previous studies underlined the impact of luminance on pupillary reaction, but it is still unclear how luminance modulates the sustained and transient components of pupillary reaction - tonic pupil diameter and phasic pupil response. In the present study, we investigated the impact of the luminance on these two components under sustained cognitive load. Fourteen participants performed a novel working memory task combining mathematical computations with a classic n-back task. We studied both tonic pupil diameter and phasic pupil response under low (1-back) and high (2-back) working memory load and two luminance levels (gray and white). We found that the impact of working memory load on the tonic pupil diameter was modulated by the level of luminance, the increase in tonic pupil diameter with the load being larger under lower luminance. In contrast, the smaller phasic pupil response found under high load remained unaffected by luminance. These results showed that luminance impacts the cognitive pupillary reaction - tonic pupil diameter (phasic pupil response) being modulated under sustained (respectively, transient) cognitive load. These findings also support the relationship between the locus-coeruleus system, presumably functioning in two firing modes - tonic and phasic - and the pupil diameter. We suggest that the tonic pupil diameter tracks the tonic activity of the locus-coeruleus while phasic pupil response reflects its phasic activity. Besides, the designed novel cognitive paradigm allows the simultaneous manipulation of sustained and transient components of the cognitive load and is useful for dissociating the effects on the tonic pupil diameter and phasic pupil response. Copyright © 2016 Elsevier B.V. All rights reserved.

Loads specification and embedded plate definition for the ITER cryoline system

NASA Astrophysics Data System (ADS)

Badgujar, S.; Benkheira, L.; Chalifour, M.; Forgeas, A.; Shah, N.; Vaghela, H.; Sarkar, B.

2015-12-01

ITER cryolines (CLs) are complex network of vacuum-insulated multi and single process pipe lines, distributed in three different areas at ITER site. The CLs will support different operating loads during the machine life-time; either considered as nominal, occasional or exceptional. The major loads, which form the design basis are inertial, pressure, temperature, assembly, magnetic, snow, wind, enforced relative displacement and are put together in loads specification. Based on the defined load combinations, conceptual estimation of reaction loads have been carried out for the lines located inside the Tokamak building. Adequate numbers of embedded plates (EPs) per line have been defined and integrated in the building design. The finalization of building EPs to support the lines, before the detailed design, is one of the major design challenges as the usual logic of the design may alter. At the ITER project level, it was important to finalize EPs to allow adequate design and timely availability of the Tokamak building. The paper describes the single loads, load combinations considered in load specification and the approach for conceptual load estimation and selection of EPs for Toroidal Field (TF) Cryoline as an example by converting the load combinations in two main load categories; pressure and seismic.

The impact of targeting repetitive BamHI-W sequences on the sensitivity and precision of EBV DNA quantification.

PubMed

Sanosyan, Armen; Fayd'herbe de Maudave, Alexis; Bollore, Karine; Zimmermann, Valérie; Foulongne, Vincent; Van de Perre, Philippe; Tuaillon, Edouard

2017-01-01

Viral load monitoring and early Epstein-Barr virus (EBV) DNA detection are essential in routine laboratory testing, especially in preemptive management of Post-transplant Lymphoproliferative Disorder. Targeting the repetitive BamHI-W sequence was shown to increase the sensitivity of EBV DNA quantification, but the variability of BamHI-W reiterations was suggested to be a source of quantification bias. We aimed to assess the extent of variability associated with BamHI-W PCR and its impact on the sensitivity of EBV DNA quantification using the 1st WHO international standard, EBV strains and clinical samples. Repetitive BamHI-W- and LMP2 single- sequences were amplified by in-house qPCRs and BXLF-1 sequence by a commercial assay (EBV R-gene™, BioMerieux). Linearity and limits of detection of in-house methods were assessed. The impact of repeated versus single target sequences on EBV DNA quantification precision was tested on B95.8 and Raji cell lines, possessing 11 and 7 copies of the BamHI-W sequence, respectively, and on clinical samples. BamHI-W qPCR demonstrated a lower limit of detection compared to LMP2 qPCR (2.33 log10 versus 3.08 log10 IU/mL; P = 0.0002). BamHI-W qPCR underestimated the EBV DNA load on Raji strain which contained fewer BamHI-W copies than the WHO standard derived from the B95.8 EBV strain (mean bias: - 0.21 log10; 95% CI, -0.54 to 0.12). Comparison of BamHI-W qPCR versus LMP2 and BXLF-1 qPCR showed an acceptable variability between EBV DNA levels in clinical samples with the mean bias being within 0.5 log10 IU/mL EBV DNA, whereas a better quantitative concordance was observed between LMP2 and BXLF-1 assays. Targeting BamHI-W resulted to a higher sensitivity compared to LMP2 but the variable reiterations of BamHI-W segment are associated with higher quantification variability. BamHI-W can be considered for clinical and therapeutic monitoring to detect an early EBV DNA and a dynamic change in viral load.

The impact of targeting repetitive BamHI-W sequences on the sensitivity and precision of EBV DNA quantification

PubMed Central

Fayd’herbe de Maudave, Alexis; Bollore, Karine; Zimmermann, Valérie; Foulongne, Vincent; Van de Perre, Philippe; Tuaillon, Edouard

2017-01-01

Background Viral load monitoring and early Epstein-Barr virus (EBV) DNA detection are essential in routine laboratory testing, especially in preemptive management of Post-transplant Lymphoproliferative Disorder. Targeting the repetitive BamHI-W sequence was shown to increase the sensitivity of EBV DNA quantification, but the variability of BamHI-W reiterations was suggested to be a source of quantification bias. We aimed to assess the extent of variability associated with BamHI-W PCR and its impact on the sensitivity of EBV DNA quantification using the 1st WHO international standard, EBV strains and clinical samples. Methods Repetitive BamHI-W- and LMP2 single- sequences were amplified by in-house qPCRs and BXLF-1 sequence by a commercial assay (EBV R-gene™, BioMerieux). Linearity and limits of detection of in-house methods were assessed. The impact of repeated versus single target sequences on EBV DNA quantification precision was tested on B95.8 and Raji cell lines, possessing 11 and 7 copies of the BamHI-W sequence, respectively, and on clinical samples. Results BamHI-W qPCR demonstrated a lower limit of detection compared to LMP2 qPCR (2.33 log10 versus 3.08 log10 IU/mL; P = 0.0002). BamHI-W qPCR underestimated the EBV DNA load on Raji strain which contained fewer BamHI-W copies than the WHO standard derived from the B95.8 EBV strain (mean bias: - 0.21 log10; 95% CI, -0.54 to 0.12). Comparison of BamHI-W qPCR versus LMP2 and BXLF-1 qPCR showed an acceptable variability between EBV DNA levels in clinical samples with the mean bias being within 0.5 log10 IU/mL EBV DNA, whereas a better quantitative concordance was observed between LMP2 and BXLF-1 assays. Conclusions Targeting BamHI-W resulted to a higher sensitivity compared to LMP2 but the variable reiterations of BamHI-W segment are associated with higher quantification variability. BamHI-W can be considered for clinical and therapeutic monitoring to detect an early EBV DNA and a dynamic change in viral load. PMID:28850597

An ex vivo mechanical evaluation of single versus double semitubular plate fixation of a transverse distal-third scapular osteotomy in the dog.

PubMed

Mair, Jacqueline J; Belkoff, Stephen M; Boudrieau, Randy J

2003-01-01

To compare single versus double semitubular plate fixation for scapular body fractures. Ex vivo mechanical study. Eighteen paired cadaveric canine scapulae. Transverse scapular body osteotomies were created in the distal third of 18 pairs of scapulae. One scapula of each pair was repaired with a single plate, whereas the contralateral scapula was repaired with 2 plates. Initial strength and stiffness of the constructs were measured in 10 pairs of scapulae. Eight pairs of scapulae underwent cyclic loading and then were subjected to failure testing. Double-plate fixation was significantly stronger (3,899 +/- 632 N) but not stiffer (614 +/- 130 N/mm) than the single-plate fixation (3,238 +/- 935 N and 537 +/- 202 N/mm, respectively). Cyclic loading variables were not significantly different between the 2 methods of fixation. After cyclic loading, double-plate fixation was significantly stronger (2,916 +/- 618 N) than single-plate fixation (2,347 +/- 495 N). There was no significant difference (P =.11) in stiffness between double- versus single-plate fixations: 734 +/- 247 N/mm and 595 +/- 139 N/mm, respectively. Double-plate fixation was generally stronger and stiffer than single-plate fixation. Because all constructs failed at loads that greatly exceeded those estimated to occur clinically, any difference between the 2 methods of fixation probably is not clinically relevant. Single-plate fixation may be of sufficient strength for fixation of scapular body fractures. Copyright 2003 by The American College of Veterinary Surgeons

A pulsed load model and its impact on a synchronous-rectifier system

NASA Astrophysics Data System (ADS)

Hou, Pengfei; Xu, Ye; Li, Jianke; Wang, Jinquan; Zhang, Haitao; Yan, Jun; Wang, Chunming; Chen, Jingjing

2017-02-01

The pulsed load has become a developing trend of power loading. Unlike traditional loads, pulsed loads with current abrupt and repeated charges will result in unstable Microgrid operations because of their small capacity and inertia. In this paper, an Average Magnitude Sum Function (AMSF) is proposed to calculate the frequency of the grid, and based on AMSF, the Relative Deviation Rate (RDR) that characterises the impact of pulsed load on the AC side of the grid is defined and its calculation process is described in detail. In addition, the system dynamic characteristics under a pulsed load are analysed using an Insulated Gate Bipolar Transistor (IGBT) to control the on/off state of the resistive load for simulating a pulsed load. Finally, the transient characteristics of a synchronous-rectifier system with a pulsed load are studied and validated experimentally.

Single Piezo-Actuator Rotary-Hammering (SPaRH) Drill

NASA Technical Reports Server (NTRS)

Sherrit, Stewart; Domm, Lukas; Bao, Xiaoqi; Bar-Cohen, Yoseph; Chang, Zensheu; Badescu, Mircea

2012-01-01

The search for present or past life in the Universe is one of the most important objectives of NASA's exploration missions. Drills for subsurface sampling of rocks, ice and permafrost are an essential tool for astrobiology studies on other planets. Increasingly, it is recognized that drilling via a combination of rotation and hammering offers an efficient and effective rapid penetration mechanism. The rotation provides an intrinsic method for removal of cuttings from the borehole while the impact and shear forces aids in the fracturing of the penetrated medium. Conventional drills that use a single actuator are based on a complex mechanism with many parts and their use in future mission involves greater risk of failure and/or may require lubrication that can introduce contamination. In this paper, a compact drill is reported that uses a single piezoelectric actuator to produce hammering and rotation of the bit. A horn with asymmetric grooves was design to impart a longitudinal (hammering) and transverse force (rotation) to a keyed free mass. The drill requires low axial pre-load since the hammering-impacts fracture the rock under the bit kerf and rotate the bit to remove the powdered cuttings while augmenting the rock fracture via shear forces. The vibrations 'fluidize' the powdered cuttings inside the flutes reducing the friction with the auger surface. This action reduces the consumed power and heating of the drilled medium helping to preserve the pristine content of the acquired samples. The drill consists of an actuator that simultaneously impacts and rotates the bit by applying force and torque via a single piezoelectric stack actuator without the need for a gearbox or lever mechanism. This can reduce the development/fabrication cost and complexity. In this paper, the drill mechanism will be described and the test results will be reported and discussed.

Triple-Loaded Suture Anchors Versus a Knotless Rip Stop Construct in a Single-Row Rotator Cuff Repair Model.

PubMed

Noyes, Matthew P; Lederman, Evan; Adams, Christopher R; Denard, Patrick J

2018-05-01

To compare the biomechanical properties of single-row repair with triple-loaded (TL) anchor repair versus a knotless rip stop (KRS) repair in a rotator cuff repair model. Rotator cuff tears were created in 8 cadaveric matched-pair specimens and repaired with a TL anchor or KRS construct. In the TL construct, anchors were placed in the greater tuberosity and then all suture limbs were passed through the rotator cuff as simple sutures and tied. In the KRS construct, a 2-mm suture tape was passed through the tendon in an inverted mattress fashion, and a free suture was passed medial to the suture tape to create a rip-stop. Then, the suture tape and free suture were secured with knotless anchors. Displacement was observed with video tracking after cyclic loading, and specimens were loaded to failure. The mean load to failure was 438 ± 59 N in TL anchor repairs compared with 457 ± 110 N in KRS repairs (P = .582). The mean displacement with cyclic loading was 3.8 ± 1.6 mm in TL anchor repairs versus 4.3 ± 1.8 mm in the KRS group (P = .297). Mode of failure was consistent in both groups, with 6 of 8 failures in the TL anchor group and 7 of 8 failures in KRS group occurring from anchor pullout. There is no statistical difference in load to failure and cyclic loading between TL anchor and KRS single-row repair techniques. KRS repair technique may be an alternative method of repairing full-thickness supraspinatus tendon tears with a single-row construct. Copyright © 2018 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

The role of embryo movement in the development of the furcula.

PubMed

Pollard, A S; Boyd, S; McGonnell, I M; Pitsillides, A A

2017-03-01

The pectoral girdle is a complex structure which varies in its morphology between species. A major component in birds is the furcula, which can be considered equivalent to a fusion of the paired clavicles found in many mammals, and the single interclavicle found in many reptiles. These elements are a remnant of the dermal skeleton and the only intramembranous bones in the trunk. Postnatally, the furcula plays important mechanical roles by stabilising the shoulder joint and acting as a mechanical spring during flight. In line with its mechanical role, previous studies indicate that, unlike many other intramembranous bones, furcula growth during development can be influenced by mechanical stimuli. This study investigated the response of individual aspects of furcula growth to both embryo immobilisation and hypermotility in the embryonic chicken. The impact of altered incubation temperature, which influences embryo motility, on crocodilian interclavicle development was also explored. We employed whole-mount bone and cartilage staining and 3D imaging by microCT to quantify the impact of rigid paralysis, flaccid paralysis and hypermobility on furcula growth in the chicken, and 3D microCT imaging to quantify the impact of reduced temperature (32-28 °C) and motility on interclavicle growth in the crocodile. This revealed that the growth rates of the clavicular and interclavicular components of the furcula differ during normal development. Total furcula area was reduced by total unloading produced by flaccid paralysis, but not by rigid paralysis which maintains static loading of embryonic bones. This suggests that dynamic loading, which is required for postnatal bone adaptation, is not a requirement for prenatal furcula growth. Embryo hypermotility also had no impact on furcula area or arm length. Furcula 3D shape did, however, differ between groups; this was marked in the interclavicular component of the furcula, the hypocleideum. Hypocleideum length was reduced by both methods of immobilisation, and interclavicle area was reduced in crocodile embryos incubated at 28 °C, which are less motile than embryos incubated at 32 °C. These data suggest that the clavicular and interclavicle components of the avian furcula respond differently to alterations in embryo movement, with the interclavicle requiring both the static and dynamic components of movement-related loading for normal growth, while static loading preserved most aspects of clavicle growth. Our data suggest that embryo movement, and the mechanical loading this produces, is important in shaping these structures during development to suit their postnatal mechanical roles. © 2016 Anatomical Society.

Numerical simulations of the occupant head response in an infantry vehicle under blunt impact and blast loading conditions.

PubMed

Sevagan, Gopinath; Zhu, Feng; Jiang, Binhui; Yang, King H

2013-07-01

This article presents the results of a finite element simulation on the occupant head response in an infantry vehicle under two separated loading conditions: (1) blunt impact and (2) blast loading conditions. A Hybrid-III dummy body integrated with a previously validated human head model was used as the surrogate. The biomechanical response of the head was studied in terms of head acceleration due to the impact by a projectile on the vehicle and intracranial pressure caused by blast wave. A series of parametric studies were conducted on the numerical model to analyze the effect of some key parameters, such as seat configuration, impact velocity, and boundary conditions. The simulation results indicate that a properly designed seat and internal surface of the infantry vehicle can play a vital role in reducing the risk of head injury in the current scenarios. Comparison of the kinematic responses under the blunt impact and blast loading conditions reveals that under the current loading conditions, the acceleration pulse in the blast scenario has much higher peak values and frequency than blunt impact case, which may reflect different head response characteristics.

Impact of sampling strategy on stream load estimates in till landscape of the Midwest

USGS Publications Warehouse

Vidon, P.; Hubbard, L.E.; Soyeux, E.

2009-01-01

Accurately estimating various solute loads in streams during storms is critical to accurately determine maximum daily loads for regulatory purposes. This study investigates the impact of sampling strategy on solute load estimates in streams in the US Midwest. Three different solute types (nitrate, magnesium, and dissolved organic carbon (DOC)) and three sampling strategies are assessed. Regardless of the method, the average error on nitrate loads is higher than for magnesium or DOC loads, and all three methods generally underestimate DOC loads and overestimate magnesium loads. Increasing sampling frequency only slightly improves the accuracy of solute load estimates but generally improves the precision of load calculations. This type of investigation is critical for water management and environmental assessment so error on solute load calculations can be taken into account by landscape managers, and sampling strategies optimized as a function of monitoring objectives. ?? 2008 Springer Science+Business Media B.V.

Subject-specific computer simulation model for determining elbow loading in one-handed tennis backhand groundstrokes.

PubMed

King, Mark A; Glynn, Jonathan A; Mitchell, Sean R

2011-11-01

A subject-specific angle-driven computer model of a tennis player, combined with a forward dynamics, equipment-specific computer model of tennis ball-racket impacts, was developed to determine the effect of ball-racket impacts on loading at the elbow for one-handed backhand groundstrokes. Matching subject-specific computer simulations of a typical topspin/slice one-handed backhand groundstroke performed by an elite tennis player were done with root mean square differences between performance and matching simulations of < 0.5 degrees over a 50 ms period starting from ball impact. Simulation results suggest that for similar ball-racket impact conditions, the difference in elbow loading for a topspin and slice one-handed backhand groundstroke is relatively small. In this study, the relatively small differences in elbow loading may be due to comparable angle-time histories at the wrist and elbow joints with the major kinematic differences occurring at the shoulder. Using a subject-specific angle-driven computer model combined with a forward dynamics, equipment-specific computer model of tennis ball-racket impacts allows peak internal loading, net impulse, and shock due to ball-racket impact to be calculated which would not otherwise be possible without impractical invasive techniques. This study provides a basis for further investigation of the factors that may increase elbow loading during tennis strokes.

Climate change impacts on runoff, sediment, and nutrient loads in an agricultural watershed in the Lower Mississippi River Basin

USDA-ARS?s Scientific Manuscript database

Projected climate change can impact various aspects of agricultural systems, including the nutrient and sediment loads exported from agricultural fields. This study evaluated the potential changes in runoff, sediment, nitrogen, and phosphorus loads using projected climate estimates from 2041 – 2070 ...

Ovarian Control of Nectar Collection in the Honey Bee (Apis mellifera)

PubMed Central

Siegel, Adam J.; Freedman, Colin; Page, Robert E.

2012-01-01

Honey bees are a model system for the study of division of labor. Worker bees demonstrate a foraging division of labor (DOL) by biasing collection towards carbohydrates (nectar) or protein (pollen). The Reproductive ground-plan hypothesis of Amdam et al. proposes that foraging DOL is regulated by the networks that controlled foraging behavior during the reproductive life cycle of honey bee ancestors. Here we test a proposed mechanism through which the ovary of the facultatively sterile worker impacts foraging bias. The proposed mechanism suggests that the ovary has a regulatory effect on sucrose sensitivity, and sucrose sensitivity impacts nectar loading. We tested this mechanism by measuring worker ovary size (ovariole number), sucrose sensitivity, and sucrose solution load size collected from a rate-controlled artificial feeder. We found a significant interaction between ovariole number and sucrose sensitivity on sucrose solution load size when using low concentration nectar. This supports our proposed mechanism. As nectar and pollen loading are not independent, a mechanism impacting nectar load size would also impact pollen load size. PMID:22558073

Comparison of Deterministic and Probabilistic Radial Distribution Systems Load Flow

NASA Astrophysics Data System (ADS)

Gupta, Atma Ram; Kumar, Ashwani

2017-12-01

Distribution system network today is facing the challenge of meeting increased load demands from the industrial, commercial and residential sectors. The pattern of load is highly dependent on consumer behavior and temporal factors such as season of the year, day of the week or time of the day. For deterministic radial distribution load flow studies load is taken as constant. But, load varies continually with a high degree of uncertainty. So, there is a need to model probable realistic load. Monte-Carlo Simulation is used to model the probable realistic load by generating random values of active and reactive power load from the mean and standard deviation of the load and for solving a Deterministic Radial Load Flow with these values. The probabilistic solution is reconstructed from deterministic data obtained for each simulation. The main contribution of the work is: Finding impact of probable realistic ZIP load modeling on balanced radial distribution load flow. Finding impact of probable realistic ZIP load modeling on unbalanced radial distribution load flow. Compare the voltage profile and losses with probable realistic ZIP load modeling for balanced and unbalanced radial distribution load flow.

Pain and discomfort following immediate and delayed loading by overdentures in the single mandibular implant study (SMIS).

PubMed

Mundt, T; Passia, N; Att, W; Heydecke, G; Freitag-Wolf, S; Luthardt, R G; Kappel, S; Konstantinidis, I K; Stiesch, M; Wolfart, S; Kern, M

2017-03-01

This randomized clinical trial compares immediate and delayed loading of single implants to support mandibular overdentures. The aim of this preliminary analysis is to test the hypothesis whether patients with immediate loading will experience less pain and discomfort through the intervention than patients with delayed loading. Edentulous patients in nine German dental schools received a midline implant with a length of 11 mm. Implants with a minimum insertion torque of 30 Ncm and an implant stability quotient of ≥60 were randomly allocated to group A for immediate loading using ball attachments or to group B for delayed loading after 3 months. Patients completed questionnaires with 100-mm visual analogue scales about the items pain, pain during chewing, swelling, bleeding, and perception of the intervention at the day of surgery and 1, 2, 3, and 7 days, thereafter. Groups were compared by Wilcoxon-Mann-Whitney tests (P ≤ 0.05). The questionnaires of 81 patients in group A and 74 patients in group B were completed. The medians for pain and discomfort were moderate (<30). Participants of group A felt significantly more pain from the first day and more swelling from the third day after implantation than participants of group B. The individual perception of interventions showed no significant differences between groups. Immediate loading evoked more postoperative pain and swelling than the two stages of delayed loading. Immediate loading of a single mandibular midline implant supporting overdentures should be carefully considered.

Harmonic force spectroscopy reveals a force-velocity curve from a single human beta cardiac myosin motor

NASA Astrophysics Data System (ADS)

Sung, Jongmin; Nag, Suman; Vestergaard, Christian; Mortensen, Kim; Flyvbjerg, Henrik; Spudich, James

2014-03-01

A muscle contracts rapidly under low load, but slowly under high load. Its molecular mechanisms remain to be elucidated, however. During contraction, myosins in thick filaments interact with actin in thin filaments in the sarcomere, cycling between a strongly bound (force producing) state and a weakly bound (relaxed) state. Huxley et al. have previously proposed that the transition from the strong to the weak interaction can be modulated by a load. We use a new method we call ``harmonic force spectroscopy'' to extract a load-velocity curve from a single human beta cardiac myosin II motor. With a dual-beam optical trap, we hold an actin dumbbell over a myosin molecule anchored to the microscope stage that oscillates sinusoidally. Upon binding, the motor experiences an oscillatory load with a mean that is directed forward or backward, depending on binding location We find that the bound time at saturating [ATP] is exponentially correlated with the mean load, which is explained by Arrhenius transition theory. With a stroke size measurement, we obtained a load-velocity curve from a single myosin. We compare the curves for wild-type motors with mutants that cause hypertrophic cardiomyopathies, to understand the effects on the contractile cycle

Impacting load control of floating supported friction plate and its experimental verification

NASA Astrophysics Data System (ADS)

Ning, Keyan; Wang, Yu; Huang, Dingchuan; Yin, Lei

2017-05-01

Friction plates are key components in automobile transmission system. Unfortunately, due to the tough working condition i.e. high impact, high temperature, fracture and plastic deformation are easily observed in friction plates. In order to reduce the impact load and increase the impact resistance and life span of the friction plate. This paper presents a variable damping design method and structure, by punching holes in the key position of the friction plate and filling it with damping materials, the impact load of the floating support friction plate can be controlled. Simulation is applied to study the effect of the position and number of damping holes on tooth root stress. Furthermore, physic test was designed and conducted to validate the correctness and effectiveness of the proposed method. Test result shows that the impact load of the new structure is reduced by 40% and its fatigue life is 4.7 times larger. The new structure provides a new way for floating supported friction plates design.

Impacts of climate change on TN load and its control in a River Basin with complex pollution sources.

PubMed

Yang, Xiaoying; Warren, Rachel; He, Yi; Ye, Jinyin; Li, Qiaoling; Wang, Guoqing

2018-02-15

It is increasingly recognized that climate change could affect the quality of water through complex natural and anthropogenic mechanisms. Previous studies on climate change and water quality have mostly focused on assessing its impact on pollutant loads from agricultural runoff. A sub-daily SWAT model was developed to simulate the discharge, transport, and transformation of nitrogen from all known anthropogenic sources including industries, municipal sewage treatment plants, concentrated and scattered feedlot operations, rural households, and crop production in the Upper Huai River Basin. This is a highly polluted basin with total nitrogen (TN) concentrations frequently exceeding Class V of the Chinese Surface Water Quality Standard (GB3838-2002). Climate change projections produced by 16 Global Circulation Models (GCMs) under the RCP 4.5 and RCP 8.5 scenarios in the mid (2040-2060) and late (2070-2090) century were used to drive the SWAT model to evaluate the impacts of climate change on both the TN loads and the effectiveness of three water pollution control measures (reducing fertilizer use, constructing vegetative filter strips, and improving septic tank performance) in the basin. SWAT simulation results have indicated that climate change is likely to cause an increase in both monthly average and extreme TN loads in February, May, and November. The projected impact of climate change on TN loads in August is more varied between GCMs. In addition, climate change is projected to have a negative impact on the effectiveness of septic tanks in reducing TN loads, while its impacts on the other two measures are more uncertain. Despite the uncertainty, reducing fertilizer use remains the most effective measure for reducing TN loads under different climate change scenarios. Meanwhile, improving septic tank performance is relatively more effective in reducing annual TN loads, while constructing vegetative filter strips is more effective in reducing annual maximum monthly TN loads. Copyright © 2017 Elsevier B.V. All rights reserved.

Refractive indices of CaF2 single crystals under elastic shock loading

NASA Astrophysics Data System (ADS)

Li, Y.; Zhou, X. M.; Liu, C. L.; Luo, S. N.

2017-07-01

Refractive indices and Hugoniots of CaF2 single crystals are investigated by laser displacement interferometry under shock loading below 5 GPa. Birefringence is observed for the [110] loading. We obtain the Hugoniot equation of states for [100], [110] and [111], and refractive indices for these orientations with consideration of their polarization. The measured refractive indices are in reasonable agreement with predictions based on the piezo-optic theory, and are used to refine the elasto-optic coefficients.

Analytical research on impacting load of aircraft crashing upon moveable concrete target

NASA Astrophysics Data System (ADS)

Zhu, Tong; Ou, Zhuocheng; Duan, Zhuoping; Huang, Fenglei

2018-03-01

The impact load of an aircraft impact upon moveable concrete target was analyzed in this paper by both theoretical and numerical methods. The aircraft was simplified as a one dimensional pole and stress-wave theory was used to deduce the new formula. Furthermore, aiming to compare with previous experimental data, a numerical calculation based on the new formula had been carried out which showed good agreement with the experimental data. The approach, a new formula with particular numerical method, can predict not only the impact load but also the deviation between moveable and static concrete target.

High-Power Broad-Area Diode Lasers and Laser Bars

NASA Astrophysics Data System (ADS)

Erbert, Goetz; Baerwolff, Arthur; Sebastian, Juergen; Tomm, Jens

This review presents the basic ideas and some examples of the chip technology of high-power diode lasers ( λ= 650,-1060,) in connection with the achievements of mounted single-stripe emitters in recent years.In the first section the optimization of the epitaxial layer structure for a low facet load and high conversion efficiency is discussed. The so-called broadened waveguide Large Optical Cavity (LOC) concept is described and also some advantages and disadvantages of Al-free material. The next section deals with the processing steps of epitaxial wafers to make single emitters and bars. Several possibilities to realize contact windows (implantation, insulators, and wet chemical oxidation) and laser mirrors are presented. The impact of heating in the CW regime and some aspects of reliability are the following topics. The calculation of thermal distributions in diode lasers, which shows the need for sophisticated mounting, will be given. In the last part the current state-of-the-art of single-stripe emitters will be reviewed.

Dissection of Influenza Infection In Vivo by Single-Cell RNA Sequencing.

PubMed

Steuerman, Yael; Cohen, Merav; Peshes-Yaloz, Naama; Valadarsky, Liran; Cohn, Ofir; David, Eyal; Frishberg, Amit; Mayo, Lior; Bacharach, Eran; Amit, Ido; Gat-Viks, Irit

2018-06-01

The influenza virus is a major cause of morbidity and mortality worldwide. Yet, both the impact of intracellular viral replication and the variation in host response across different cell types remain uncharacterized. Here we used single-cell RNA sequencing to investigate the heterogeneity in the response of lung tissue cells to in vivo influenza infection. Analysis of viral and host transcriptomes in the same single cell enabled us to resolve the cellular heterogeneity of bystander (exposed but uninfected) as compared with infected cells. We reveal that all major immune and non-immune cell types manifest substantial fractions of infected cells, albeit at low viral transcriptome loads relative to epithelial cells. We show that all cell types respond primarily with a robust generic transcriptional response, and we demonstrate novel markers specific for influenza-infected as opposed to bystander cells. These findings open new avenues for targeted therapy aimed exclusively at infected cells. Copyright © 2018 Elsevier Inc. All rights reserved.

Foot Forces during Treadmill Exercise on the International Space Station

NASA Technical Reports Server (NTRS)

Cavanagh, Peter R.; Rice, Andrea J.; Maender, Christian C.; Gopalakrishnan, Raghavan; Genc, Kerim O.; Kuklis, Matthew

2006-01-01

Exercise has been the primary countermeasure to combat musculoskeletal changes during the approximately 6 month missions to the International Space Station (ISS). However, these countermeasures have not been successful in preventing loss of bone mineral density in the spine and hip of astronauts. We examined lower extremity loading during typical bouts of on-orbit exercise performed by 4 ISS crew members on the ISS treadmill (TVIS) and during locomotor activities on earth (1g). In-shoe forces were monitored at 128Hz using force-measuring insoles placed inside the shoes of the exercising crewmember, stored temporarily on Flash cards, and down-linked via satellite for analysis. Custom software extracted peak forces from up to 30 minutes of locomotor activity. All on-orbit loading conditions for walking and running resulted in peak forces and impact loading rates that were significantly less than those measured in 1g. Typical single leg loads on-orbit in walking and running were 0.860 plus or minus 0.04 body weights (BW) and 1.339 plus or minus 0.07 BW compared to 1.2 plus or minus 0.036 BW and 2.36 plus or minus 0.07 BW in 1g BW respectively. These results indicate that typical exercise on the ISS treadmill does not generate 1g-like loading conditions. This may be partly responsible for the loss of bone mineral density that has been observed in these and other crew members. Since on-orbit treadmill exercise requires a restraining load to return the crew member to the treadmill surface, more studies are required to enable comfortable full body weight loading to be applied.

Wind Tunnel Strain-Gage Balance Calibration Data Analysis Using a Weighted Least Squares Approach

NASA Technical Reports Server (NTRS)

Ulbrich, N.; Volden, T.

2017-01-01

A new approach is presented that uses a weighted least squares fit to analyze wind tunnel strain-gage balance calibration data. The weighted least squares fit is specifically designed to increase the influence of single-component loadings during the regression analysis. The weighted least squares fit also reduces the impact of calibration load schedule asymmetries on the predicted primary sensitivities of the balance gages. A weighting factor between zero and one is assigned to each calibration data point that depends on a simple count of its intentionally loaded load components or gages. The greater the number of a data point's intentionally loaded load components or gages is, the smaller its weighting factor becomes. The proposed approach is applicable to both the Iterative and Non-Iterative Methods that are used for the analysis of strain-gage balance calibration data in the aerospace testing community. The Iterative Method uses a reasonable estimate of the tare corrected load set as input for the determination of the weighting factors. The Non-Iterative Method, on the other hand, uses gage output differences relative to the natural zeros as input for the determination of the weighting factors. Machine calibration data of a six-component force balance is used to illustrate benefits of the proposed weighted least squares fit. In addition, a detailed derivation of the PRESS residuals associated with a weighted least squares fit is given in the appendices of the paper as this information could not be found in the literature. These PRESS residuals may be needed to evaluate the predictive capabilities of the final regression models that result from a weighted least squares fit of the balance calibration data.

Inlay-retained cantilever fixed dental prostheses to substitute a single premolar: impact of zirconia framework design after dynamic loading.

PubMed

Shahin, Ramez; Tannous, Fahed; Kern, Matthias

2014-08-01

The purpose of this in-vitro study was to evaluate the influence of the framework design on the durability of inlay-retained cantilever fixed dental prostheses (IR-FDPs), made from zirconia ceramic, after artificial ageing. Forty-eight caries-free human premolars were prepared as abutments for all-ceramic cantilevered IR-FDPs using six framework designs: occlusal-distal (OD) inlay, OD inlay with an oral retainer wing, OD inlay with two retainer wings, mesial-occlusal-distal (MOD) inlay, MOD inlay with an oral retainer ring, and veneer partial coping with a distal box (VB). Zirconia IR-FDPs were fabricated via computer-aided design/computer-aided manufacturing (CAD/CAM) technology. The bonding surfaces were air-abraded (50 μm alumina/0.1 MPa), and the frameworks were bonded with adhesive resin cement. Specimens were stored for 150 d in a 37°C water bath during which they were thermocycled between 5 and 55°C for 37,500 cycles; thereafter, they were exposed to 600,000 cycles of dynamic loading with a 5-kg load in a chewing simulator. All surviving specimens were loaded onto the pontic and tested until failure using a universal testing machine. The mean failure load of the groups ranged from 260.8 to 746.7 N. Statistical analysis showed that both MOD groups exhibited significantly higher failure loads compared with the other groups (i.e. the three OD groups and the VB group) and that there was no significant difference in the failure load among the OD groups and the VB group. In conclusion, zirconia IR-FDPs with a modified design exhibited promising failure modes. © 2014 Eur J Oral Sci.

Performance improvements of single-engine business airplanes by the integration of advanced technologies

NASA Technical Reports Server (NTRS)

Kohlman, D. L.

1982-01-01

An assessment is presented of the performance gains and economic impact of the integration in general aviation aircraft of advanced technologies, relating to such aspects of design as propulsion, natural laminar flow, lift augmentation, unconventional configurations, and advanced aluminum and composite structures. All considerations are with reference to a baseline mission of 1300 nm range and 300-knot cruise speed with a 1300-lb payload, and a baseline aircraft with a 40 lb/sq ft wing loading and an aspect ratio of 8. Extensive analytical results are presented from the NASA-sponsored General Aviation Synthesis Program. Attention is given to the relative performance gains to be expected from the single-engined baseline aircraft's use of a low cost general aviation turbine engine, a spark-ignited reciprocating engine, a diesel engine, and a Wankel rotary engine.

Fatigue crack growth with single overload - Measurement and modeling

NASA Technical Reports Server (NTRS)

Davidson, D. L.; Hudak, S. J., Jr.; Dexter, R. J.

1987-01-01

This paper compares experiments with an analytical model of fatigue crack growth under variable amplitude. The stereoimaging technique was used to measure displacements near the tips of fatigue cracks undergoing simple variations in load amplitude-single overloads and overload/underload combinations. Measured displacements were used to compute strains, and stresses were determined from the strains. Local values of crack driving force (Delta-K effective) were determined using both locally measured opening loads and crack tip opening displacements. Experimental results were compared with simulations made for the same load variation conditions using Newman's FAST-2 model. Residual stresses caused by overloads, crack opening loads, and growth retardation periods were compared.

Electric power distribution and load transfer system

NASA Technical Reports Server (NTRS)

Bradford, Michael P. (Inventor); Parkinson, Gerald W. (Inventor); Grant, Ross M. (Inventor)

1987-01-01

A power distribution system includes a plurality of power sources and load transfer units including transistors and diodes connected in series and leading to a common power output, each of the transistors being controller switchable subject to voltage levels of the respective input and output sides of said transistors, and the voltage and current level of said common power output. The system is part of an interconnection scheme in which all but one of the power sources is connected to a single load transfer unit, enabling the survival of at least a single power source with the failure of one of the load transfer units.

Electric power distribution and load transfer system

NASA Technical Reports Server (NTRS)

Bradford, Michael P. (Inventor); Parkinson, Gerald W. (Inventor); Grant, Ross M. (Inventor)

1989-01-01

A power distribution system includes a plurality of power sources and load transfer units including transistors and diodes connected in series and leading to a common power output, each of the transistors being controller switchable subject to voltage levels of the respective input and output sides of said transistors, and the voltage and current level of said common power output. The system is part of an interconnection scheme in which all but one of the power sources is connected to a single load transfer unit, enabling the survival of at least a single power source with the failure of one of the load transfer units.

Wide-field in vivo neocortical calcium dye imaging using a convection-enhanced loading technique combined with simultaneous multiwavelength imaging of voltage-sensitive dyes and hemodynamic signals

PubMed Central

Ma, Hongtao; Harris, Samuel; Rahmani, Redi; Lacefield, Clay O.; Zhao, Mingrui; Daniel, Andy G. S.; Zhou, Zhiping; Bruno, Randy M.; Berwick, Jason; Schwartz, Theodore H.

2014-01-01

Abstract. In vivo calcium imaging is an incredibly powerful technique that provides simultaneous information on fast neuronal events, such as action potentials and subthreshold synaptic activity, as well as slower events that occur in the glia and surrounding neuropil. Bulk-loading methods that involve multiple injections can be used for single-cell as well as wide-field imaging studies. However, multiple injections result in inhomogeneous loading as well as multiple sites of potential cortical injury. We used convection-enhanced delivery to create smooth, continuous loading of a large area of the cortical surface through a solitary injection site and demonstrated the efficacy of the technique using confocal microscopy imaging of single cells and physiological responses to single-trial events of spontaneous activity, somatosensory-evoked potentials, and epileptiform events. Combinations of calcium imaging with voltage-sensitive dye and intrinsic signal imaging demonstrate the utility of this technique in neurovascular coupling investigations. Convection-enhanced loading of calcium dyes may be a useful technique to advance the study of cortical processing when widespread loading of a wide-field imaging is required. PMID:25525611

Wide-field in vivo neocortical calcium dye imaging using a convection-enhanced loading technique combined with simultaneous multiwavelength imaging of voltage-sensitive dyes and hemodynamic signals.

PubMed

Ma, Hongtao; Harris, Samuel; Rahmani, Redi; Lacefield, Clay O; Zhao, Mingrui; Daniel, Andy G S; Zhou, Zhiping; Bruno, Randy M; Berwick, Jason; Schwartz, Theodore H

2014-07-24

In vivo calcium imaging is an incredibly powerful technique that provides simultaneous information on fast neuronal events, such as action potentials and subthreshold synaptic activity, as well as slower events that occur in the glia and surrounding neuropil. Bulk-loading methods that involve multiple injections can be used for single-cell as well as wide-field imaging studies. However, multiple injections result in inhomogeneous loading as well as multiple sites of potential cortical injury. We used convection-enhanced delivery to create smooth, continuous loading of a large area of the cortical surface through a solitary injection site and demonstrated the efficacy of the technique using confocal microscopy imaging of single cells and physiological responses to single-trial events of spontaneous activity, somatosensory-evoked potentials, and epileptiform events. Combinations of calcium imaging with voltage-sensitive dye and intrinsic signal imaging demonstrate the utility of this technique in neurovascular coupling investigations. Convection-enhanced loading of calcium dyes may be a useful technique to advance the study of cortical processing when widespread loading of a wide-field imaging is required.

The irrelevant speech effect and working memory load.

PubMed

Gisselgård, Jens; Petersson, Karl Magnus; Ingvar, Martin

2004-07-01

Irrelevant speech impairs the immediate serial recall of visually presented material. Previously, we have shown that the irrelevant speech effect (ISE) was associated with a relative decrease of regional blood flow in cortical regions subserving the verbal working memory, in particular the superior temporal cortex. In this extension of the previous study, the working memory load was increased and an increased activity as a response to irrelevant speech was noted in the dorsolateral prefrontal cortex. We suggest that the two studies together provide some basic insights as to the nature of the irrelevant speech effect. Firstly, no area in the brain can be ascribed as the single locus of the irrelevant speech effect. Instead, the functional neuroanatomical substrate to the effect can be characterized in terms of changes in networks of functionally interrelated areas. Secondly, the areas that are sensitive to the irrelevant speech effect are also generically activated by the verbal working memory task itself. Finally, the impact of irrelevant speech and related brain activity depends on working memory load as indicated by the differences between the present and the previous study. From a brain perspective, the irrelevant speech effect may represent a complex phenomenon that is a composite of several underlying mechanisms, which depending on the working memory load, include top-down inhibition as well as recruitment of compensatory support and control processes. We suggest that, in the low-load condition, a selection process by an inhibitory top-down modulation is sufficient, whereas in the high-load condition, at or above working memory span, auxiliary adaptive cognitive resources are recruited as compensation. Copyright 2004 Elsevier Inc.

Voice Changes in Real Speaking Situations During a Day, With and Without Vocal Loading: Assessing Call Center Operators.

PubMed

Ben-David, Boaz M; Icht, Michal

2016-03-01

Occupational-related vocal load is an increasing global problem with adverse personal and economic implications. We examined voice changes in real speaking situations during a single day, with and without vocal loading, aiming to identify an objective acoustic index for vocal load over a day. Call center operators (CCOs, n = 27) and age- and gender-matched students (n = 25) were recorded at the beginning and at the end of a day, with (CCOs) and without (students) vocal load. Speaking and reading voice samples were analyzed for fundamental frequency (F0), sound pressure level (SPL), and their variance (F0 coefficient of variation [F0 CV], SPL CV). The impact of lifestyle habits on voice changes was also estimated. The main findings revealed an interaction, with F0 rise at the end of the day for the students but not for the CCOs. We suggest that F0 rise is a typical phenomenon of a day of normal vocal use, whereas vocal loading interferes with this mechanism. In addition, different lifestyle profiles of CCOs and controls were observed, as the CCOs reported higher incidence of dehydrating behaviors (eg, smoking, caffeine). Yet, this profile was not linked with voice changes. In sum, we suggest that F0 rise over a day can potentially serve as an index for typical voice use. Its lack thereof can hint on consequent voice symptoms and complaints. Copyright © 2016 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

Performance of Railway Sleepers with Holes under Impact Loading

NASA Astrophysics Data System (ADS)

Lim, Chie Hong; Kaewunruen, Sakdirat; Mlilo, Nhlanganiso

2017-12-01

Prestressed concrete sleepers are essential structural components of railway track structures, with the purpose of redistributing wheel loads from the rails to the ground. To facilitate cables and signalling equipment, holes are often generated in these prestressed concrete sleepers. However, the performance of these sleepers under impact loading may be a concern with the addition of these holes. Numerical modelling using finite element analysis (FEA) is an ideal tool that enables static and dynamic simulation and can perform analyses of basic/advanced linear and nonlinear problems, without incurring a huge cost in resources like standard experimental test methods would. This paper will utilize the three-dimensional FE modelling software ABAQUS to investigate the behaviour of the prestressed concrete sleepers with holes of varying sizes upon impact loading. To obtain the results that resemble real-life behaviour of the sleepers under impact loading, the material properties, element types, mesh sizes, contact and interactions and boundary conditions will be defined as accurately as possible. Both Concrete Damaged Plasticity (CDP) and Brittle Cracking models will be used in this study. With a better understanding of how the introduction of holes will influence the performance of prestressed sleepers under impact loading, track and railway engineers will be able to generate them in prestressed concrete sleepers without compromising the sleepers’ performance during operation

Can martial arts techniques reduce fall severity? An in vivo study of femoral loading configurations in sideways falls.

PubMed

van der Zijden, A M; Groen, B E; Tanck, E; Nienhuis, B; Verdonschot, N; Weerdesteyn, V

2012-06-01

Sideways falls onto the hip are a major cause of femoral fractures in the elderly. Martial arts (MA) fall techniques decrease hip impact forces in sideways falls. The femoral fracture risk, however, also depends on the femoral loading configuration (direction and point of application of the force). The purpose of this study was to determine the effect of fall techniques, landing surface and fall height on the impact force and the loading configuration in sideways falls. Twelve experienced judokas performed sideways MA and Block ('natural') falls on a force plate, both with and without a judo mat on top. Kinematic and force data were analysed to determine the hip impact force and the loading configuration. In falls from a kneeling position, the MA technique reduced the impact force by 27%, but did not change the loading configuration. The use of the mat did not change the loading configuration. Falling from a standing changed the force direction. In all conditions, the point of application was distal and posterior to the greater trochanter, but it was less distal and more posterior in falls from standing than from kneeling position. The present decrease in hip impact force with an unchanged loading configuration indicates the potential protective effect of the MA technique on the femoral fracture risk. The change in loading configuration with an increased fall height warrant further studies to examine the effect of MA techniques on fall severity under more natural fall circumstances. Copyright © 2012 Elsevier Ltd. All rights reserved.

An exploratory investigation of cumulative shock fatigue.

NASA Technical Reports Server (NTRS)

Simonson, D.; Byrne, J. G.

1972-01-01

A simple device for producing cumulative shock loading in solids is described. The device uses a ballistic-impact-driven projectile to introduce high-stress waves into a solid. The impact time and load amplitude can be varied to produce fracture in one or several impacts in PMMA rods. The wavefront approached a square wave shape. Materials other than PMMA were loaded to failure to demonstrate the versatility of the device. Fracture morphologies observed with optical and scanning-electron microscopy are described.

Allostatic Load: Single Parents, Stress-Related Health Issues, and Social Care

ERIC Educational Resources Information Center

Johner, Randy L.

2007-01-01

This article explores the possible relationships between allostatic load (AL) and stress-related health issues in the low-income single-parent population, using both a population health perspective (PHP) and a biological framework. A PHP identifies associations among such factors as gender, income, employment, and social support and their…

Missouri | Solar Research | NREL

Science.gov Websites

previous calendar year, 1% of utility's single-hour peak load (annually) and 5% of utility's single-hour peak load Credit: Net excess generation is credited at avoided-cost rate RECs: Renewable energy size limit: 100 kW Liability insurance: There are no requirements for systems <10 kW; systems >10

The influence of primary and secondary orientations on the elastic response of a nickel-base single-crystal superalloy

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali; Kalluri, Sreeramesh; Mcgaw, Michael A.

1993-01-01

The influence of primary orientation on the elastic response of a (001)-oriented nickel-base single-crystal superalloy, PWA 1480, was investigated under mechanical, thermal, and combined thermal and mechanical loading conditions using finite element techniques. Elastic stress analyses were performed using the MARC finite element code on a square plate of PWA 1480 material. Primary orientation of the single crystal superalloy was varied in increments of 2 deg, from 0 to 10 deg, from the (001) direction. Two secondary orientations (0 and 45 deg) were considered, with respect to the global coordinate system, as the primary orientation angle was varied. The stresses developed within the single crystal plate were determined for each loading condition. In this paper, the influence of the angular offset between the primary crystal orientation and the loading direction on the elastic stress response of the PWA 1480 plate is presented for different loading conditions. The influence of primary orientation angle, when constrained between the bounds considered, was not found to be as significant as the influence of the secondary orientation angle, which is not typically controlled.

Single-Specimen Technique to Establish the J-Resistance of Linear Viscoelastic Solids with Constant Poisson's Ratio

NASA Technical Reports Server (NTRS)

Gutierrez-Lemini, Danton; McCool, Alex (Technical Monitor)

2001-01-01

A method is developed to establish the J-resistance function for an isotropic linear viscoelastic solid of constant Poisson's ratio using the single-specimen technique with constant-rate test data. The method is based on the fact that, for a test specimen of fixed crack size under constant rate, the initiation J-integral may be established from the crack size itself, the actual external load and load-point displacement at growth initiation, and the relaxation modulus of the viscoelastic solid, without knowledge of the complete test record. Since crack size alone, of the required data, would be unknown at each point of the load-vs-load-point displacement curve of a single-specimen test, an expression is derived to estimate it. With it, the physical J-integral at each point of the test record may be established. Because of its basis on single-specimen testing, not only does the method not require the use of multiple specimens with differing initial crack sizes, but avoids the need for tracking crack growth as well.

77 FR 26714 - Transmission Planning Reliability Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-07

... non-consequential load loss that satisfies the relevant Commission's directives in Order No. 693 and... that would allow a transmission planner to plan for non-consequential load loss following a single...), footnote 12 that would allow a transmission planner to plan for ``non-consequential load loss,'' i.e., load...

Immediate functional loading of single implants: a multicenter study with 4 years of follow-up

PubMed Central

Raes, Filiep; Eccellente, Tammaro; Lenzi, Carolina; Ortolani, Michele; Luongo, Giuseppe; Mangano, Carlo; Mangano, Francesco

2018-01-01

Background. In the current scientific literature there are only few studies on the immediate functional loading of single implants. The aim of the present present study was to evaluate the 4-year survival rate, complication rate and peri-implant marginal bone loss (PIMBL) of immediately loaded single implants inserted in healed ridges and fresh post-extraction sites. Methods. Six centers were involved in this prospective study. The surgical and prosthetic protocol was defined in detail, before the start of recruiting patients. Recruitment of patients and performance of surgeries took place between February 2012 and February 2013. Criteria for inclusion were single-tooth gaps in healed ridges and fresh post-extraction sockets. All the fixtures (Anyridge®, Megagen Corporation, Gyeongbuk, South Korea) were functionally loaded immediately after insertion and followed for a period of 4 years. Outcome measures were implant survival, complications and PIMBL. Results. Forty-six patients (18‒73 years of age) were selected. In total, 57 fixtures were placed (10 in fresh post-extraction sockets). After 4 years of functional loading, only one fixture was lost; therefore, high survival rates (97.6% patient-based; 98.1% implant-based) were reported. In addition, a limited incidence of biologic (4.8% patient-based; 3.8% implant-based) and prosthetic (9.7% patient-based; 7.6% implant-based) complications was reported. The overall 4-year PIMBL amounted to 0.38±0.21 mm (healed ridges: 0.4±0.21 mm; fresh post-extraction sockets: 0.33±0.20 mm). Conclusion. Loading single implants immediately seems to be a highly successful treatment modality. However, long-term data are needed to confirm these positive outcomes. PMID:29732018

Simultaneous anatomic reconstruction of the acromioclavicular and coracoclavicular ligaments using a single tendon graft.

PubMed

Shin, Sang-Jin; Campbell, Sean; Scott, Jonathan; McGarry, Michelle H; Lee, Thay Q

2014-09-01

The purpose of this study was to introduce a novel surgical technique for simultaneous anatomic reconstruction of the acromioclavicular and coracoclavicular ligaments using a single tendon graft and to compare its biomechanical characteristics to those of a coracoid cerclage reconstruction of the coracoclavicular ligaments. Six matched pairs of human acromioclavicular joints with an average age of 54.8 ± 7.8 years were used. One shoulder from each pair received the single tendon acromioclavicular-coracoclavicular reconstruction; the contralateral shoulder received the coracoid cerclage reconstruction. Bovine extensor tendon was used for both techniques. The single tendon acromioclavicular-coracoclavicular reconstruction technique provided anatomic restoration of the two coracoclavicular ligaments and the superior and inferior acromioclavicular ligaments simultaneously using one coracoid hole, one acromion hole, and two clavicular holes with interference screws. Anterior-posterior and superior-inferior translations were quantified for all specimens before and after reconstruction, followed by load to failure testing. Following coracoid cerclage reconstruction, total anterior-posterior translation was significantly greater than intact (10.0 ± 5.7 mm; p = 0.008). Following single tendon acromioclavicular-coracoclavicular reconstruction, there was no significant difference in anterior-posterior translation compared to intact (-1.6 ± 2.2 mm; n.s.). The coracoid cerclage technique demonstrated significantly greater anterior-posterior translation than the single tendon acromioclavicular-coracoclavicular technique (p = 0.007). Both techniques restored superior-inferior translation to the intact condition (n.s.). Ultimate load, deformation at ultimate load, and energy absorbed at ultimate load were significantly greater after acromioclavicular-coracoclavicular reconstruction than after coracoid cerclage reconstruction (p < 0.05). This novel single tendon anatomic acromioclavicular-coracoclavicular reconstruction provided greater stability and stronger load to failure characteristics than the isolated coracoid cerclage reconstruction. A simultaneous acromioclavicular-coracoclavicular reconstruction technique using a single free tendon graft provided anatomic reconstruction of the conoid, trapezoid, and superior and inferior acromioclavicular ligaments and may reduce postoperative subluxation.

Surface effects on dynamic stability and loading during outdoor running using wireless trunk accelerometry.

PubMed

Schütte, Kurt H; Aeles, Jeroen; De Beéck, Tim Op; van der Zwaard, Babette C; Venter, Rachel; Vanwanseele, Benedicte

2016-07-01

Despite frequently declared benefits of using wireless accelerometers to assess running gait in real-world settings, available research is limited. The purpose of this study was to investigate outdoor surface effects on dynamic stability and dynamic loading during running using tri-axial trunk accelerometry. Twenty eight runners (11 highly-trained, 17 recreational) performed outdoor running on three outdoor training surfaces (concrete road, synthetic track and woodchip trail) at self-selected comfortable running speeds. Dynamic postural stability (tri-axial acceleration root mean square (RMS) ratio, step and stride regularity, sample entropy), dynamic loading (impact and breaking peak amplitudes and median frequencies), as well as spatio-temporal running gait measures (step frequency, stance time) were derived from trunk accelerations sampled at 1024Hz. Results from generalized estimating equations (GEE) analysis showed that compared to concrete road, woodchip trail had several significant effects on dynamic stability (higher AP ratio of acceleration RMS, lower ML inter-step and inter-stride regularity), on dynamic loading (downward shift in vertical and AP median frequency), and reduced step frequency (p<0.05). Surface effects were unaffected when both running level and running speed were added as potential confounders. Results suggest that woodchip trails disrupt aspects of dynamic stability and loading that are detectable using a single trunk accelerometer. These results provide further insight into how runners adapt their locomotor biomechanics on outdoor surfaces in situ. Copyright © 2016 Elsevier B.V. All rights reserved.

Biomechanical comparisons of single- and double-legged drop jumps with changes in drop height.

PubMed

Wang, L-I; Peng, H-T

2014-06-01

The purpose of this study was to compare the biomechanics of single- and double-legged drop jumps (SDJ vs. DDJ) with changes in drop height. Jumping height, ground contact time, reactive strength index, ground reaction force, loading rate of ground reaction force, joint power and stiffness were measured in 12 male college students during SDJ from 20-, 30-, 40-, and 50-cm heights and DDJ from of 20- and 40-cm heights. The peak impact force was increased with the incremental drop height during SDJs. The jumping height and leg and ankle stiffness of SDJ30 were greater than those of SDJ40 and SDJ50. The knee and hip stiffnesses of SDJ30 were greater than those of SDJ50. The impact forces of SDJ30-50 were greater than those of DDJ40. The leg, ankle, knee and hip joint stiffnesses of SDJ20-30 were greater than those of DDJ20 and DDJ40. The propulsive forces of SDJ20-50 were greater than those of DDJ20 and DDJ40. The jumping height of SDJ30 was greater than that of DDJ20. Drop height of 30 cm was recommended during single-legged drop jump with the best biomechanical benefit. Single-legged drop jump from 20-30 cm could provide comparable intensity to double-legged drop jump from 40 cm. © Georg Thieme Verlag KG Stuttgart · New York.

Damage Tolerance of Pre-Stressed Composite Panels Under Impact Loads

NASA Astrophysics Data System (ADS)

Johnson, Alastair F.; Toso-Pentecôte, Nathalie; Schueler, Dominik

2014-02-01

An experimental test campaign studied the structural integrity of carbon fibre/epoxy panels preloaded in tension or compression then subjected to gas gun impact tests causing significant damage. The test programme used representative composite aircraft fuselage panels composed of aerospace carbon fibre toughened epoxy prepreg laminates. Preload levels in tension were representative of design limit loads for fuselage panels of this size, and maximum compression preloads were in the post-buckle region. Two main impact scenarios were considered: notch damage from a 12 mm steel cube projectile, at velocities in the range 93-136 m/s; blunt impact damage from 25 mm diameter glass balls, at velocities 64-86 m/s. The combined influence of preload and impact damage on panel residual strengths was measured and results analysed in the context of damage tolerance requirements for composite aircraft panels. The tests showed structural integrity well above design limit loads for composite panels preloaded in tension and compression with visible notch impact damage from hard body impact tests. However, blunt impact tests on buckled compression loaded panels caused large delamination damage regions which lowered plate bending stiffness and reduced significantly compression strengths in buckling.

Biomechanical validation of load-sharing rip-stop fixation for the repair of tissue-deficient rotator cuff tears.

PubMed

Burkhart, Stephen S; Denard, Patrick J; Konicek, John; Hanypsiak, Bryan T

2014-02-01

Poor-quality tendon is one of the most difficult problems the surgeon must overcome in achieving secure fixation during rotator cuff repair. A load-sharing rip-stop construct (LSRS) has recently been proposed as a method for improving fixation strength, but the biomechanical properties of this construct have not yet been examined. To compare the strength of the LSRS construct to that of single-row fixation for rotator cuff repair. Controlled laboratory study. Rotator cuff tears were created in 6 cadaveric matched-pair specimens and repaired with a single row or an LSRS. In the LSRS repair, a 2-mm suture tape was placed as an inverted mattress stitch in the rotator cuff, and sutures from 2 anchors were placed as simple stitches that passed medial to the suture tape. The suture tape limbs were secured with knotless anchors laterally before sutures were tied from the medial anchors. Displacement was observed with video tracking after cyclic loading, and specimens were loaded to failure. The mean load to failure was 371 ± 102 N in single-row repairs compared with 616 ± 185 N in LSRS repairs (P = .031). There was no difference in displacement with cyclic loading between the groups (3.3 ± 0.8 mm vs. 3.5 ± 1.1 mm; P = .561). In the single-row group, 4 of 6 failures occurred at the suture-tendon interface. In the LSRS group, only 1 failure occurred at the suture-tendon interface. The ultimate failure load of the LSRS construct for rotator cuff repair was 1.7 times that of a single-row construct in a cadaveric model. The LSRS rotator cuff repair construct may be useful in the repair of difficult tears such as massive tears, medial tears, and tears with tendon loss.

Failure Behavior Characterization of Mo-Modified Ti Surface by Impact Test and Finite Element Analysis

NASA Astrophysics Data System (ADS)

Ma, Yong; Qin, Jianfeng; Zhang, Xiangyu; Lin, Naiming; Huang, Xiaobo; Tang, Bin

2015-07-01

Using the impact test and finite element simulation, the failure behavior of the Mo-modified layer on pure Ti was investigated. In the impact test, four loads of 100, 300, 500, and 700 N and 104 impacts were adopted. The three-dimensional residual impact dents were examined using an optical microscope (Olympus-DSX500i), indicating that the impact resistance of the Ti surface was improved. Two failure modes cohesive and wearing were elucidated by electron backscatter diffraction and energy-dispersive spectrometer performed in a field-emission scanning electron microscope. Through finite element forward analysis performed at a typical impact load of 300 N, stress-strain distributions in the Mo-modified Ti were quantitatively determined. In addition, the failure behavior of the Mo-modified layer was determined and an ideal failure model was proposed for high-load impact, based on the experimental and finite element forward analysis results.

On a concurrent element-by-element preconditioned conjugate gradient algorithm for multiple load cases

NASA Technical Reports Server (NTRS)

Watson, Brian; Kamat, M. P.

1990-01-01

Element-by-element preconditioned conjugate gradient (EBE-PCG) algorithms have been advocated for use in parallel/vector processing environments as being superior to the conventional LDL(exp T) decomposition algorithm for single load cases. Although there may be some advantages in using such algorithms for a single load case, when it comes to situations involving multiple load cases, the LDL(exp T) decomposition algorithm would appear to be decidedly more cost-effective. The authors have outlined an EBE-PCG algorithm suitable for multiple load cases and compared its effectiveness to the highly efficient LDL(exp T) decomposition scheme. The proposed algorithm offers almost no advantages over the LDL(exp T) algorithm for the linear problems investigated on the Alliant FX/8. However, there may be some merit in the algorithm in solving nonlinear problems with load incrementation, but that remains to be investigated.

The Effects of Geometric and Loading Imperfections on the Response and Lower-Bound Buckling Load of a Compression-Loaded Cylindrical Shell

NASA Technical Reports Server (NTRS)

Kriegesmann, Benedikt; Hilburger, Mark W.; Rolfes, Raimund

2012-01-01

Results from a numerical study of the buckling response of a thin-walled compressionloaded isotropic circular cylindrical shell with initial geometric and loading imperfections are used to determine a lower bound buckling load estimate suitable for preliminary design. The lower bound prediction techniques presented herein include an imperfection caused by a lateral perturbation load, an imperfection in the shape of a single stress-free dimple (similar to the lateral pertubation imperfection), and a distributed load imperfection that induces a nonuniform load in the shell. The ABAQUS finite element code is used for the analyses. Responses of the cylinders for selected imperfection amplitudes and imperfection types are considered, and the effect of each imperfection is compared to the response of a geometrically perfect cylinder. The results indicate that compression-loaded shells subjected to a lateral perturbation load or a single dimple imperfection, and a nonuniform load imperfection, exhibit similar buckling behavior and lower bound trends and the predicted lower bounds are much less conservative than the corresponding design recommendation NASA SP-8007 for the design of buckling-critical shells. In addition, the lateral perturbation technique and the distributed load imperfection produce response characteristics that are physically meaningful and can be validated via laboratory testing.

Short-term forecasting of individual household electricity loads with investigating impact of data resolution and forecast horizon

NASA Astrophysics Data System (ADS)

Yildiz, Baran; Bilbao, Jose I.; Dore, Jonathon; Sproul, Alistair B.

2018-05-01

Smart grid components such as smart home and battery energy management systems, high penetration of renewable energy systems, and demand response activities, require accurate electricity demand forecasts for the successful operation of the electricity distribution networks. For example, in order to optimize residential PV generation and electricity consumption and plan battery charge-discharge regimes by scheduling household appliances, forecasts need to target and be tailored to individual household electricity loads. The recent uptake of smart meters allows easier access to electricity readings at very fine resolutions; hence, it is possible to utilize this source of available data to create forecast models. In this paper, models which predominantly use smart meter data alongside with weather variables, or smart meter based models (SMBM), are implemented to forecast individual household loads. Well-known machine learning models such as artificial neural networks (ANN), support vector machines (SVM) and Least-Square SVM are implemented within the SMBM framework and their performance is compared. The analysed household stock consists of 14 households from the state of New South Wales, Australia, with at least a year worth of 5 min. resolution data. In order for the results to be comparable between different households, our study first investigates household load profiles according to their volatility and reveals the relationship between load standard deviation and forecast performance. The analysis extends previous research by evaluating forecasts over four different data resolution; 5, 15, 30 and 60 min, each resolution analysed for four different horizons; 1, 6, 12 and 24 h ahead. Both, data resolution and forecast horizon, proved to have significant impact on the forecast performance and the obtained results provide important insights for the operation of various smart grid applications. Finally, it is shown that the load profile of some households vary significantly across different days; as a result, providing a single model for the entire period may result in limited performance. By the use of a pre-clustering step, similar daily load profiles are grouped together according to their standard deviation, and instead of applying one SMBM for the entire data-set of a particular household, separate SMBMs are applied to each one of the clusters. This preliminary clustering step increases the complexity of the analysis however it results in significant improvements in forecast performance.

Evaluation of Material Models within LS-DYNA(Registered TradeMark) for a Kevlar/Epoxy Composite Honeycomb

NASA Technical Reports Server (NTRS)

Polanco, Michael A.; Kellas, Sotiris; Jackson, Karen

2009-01-01

The performance of material models to simulate a novel composite honeycomb Deployable Energy Absorber (DEA) was evaluated using the nonlinear explicit dynamic finite element code LS-DYNA(Registered TradeMark). Prototypes of the DEA concept were manufactured using a Kevlar/Epoxy composite material in which the fibers are oriented at +/-45 degrees with respect to the loading axis. The development of the DEA has included laboratory tests at subcomponent and component levels such as three-point bend testing of single hexagonal cells, dynamic crush testing of single multi-cell components, and impact testing of a full-scale fuselage section fitted with a system of DEA components onto multi-terrain environments. Due to the thin nature of the cell walls, the DEA was modeled using shell elements. In an attempt to simulate the dynamic response of the DEA, it was first represented using *MAT_LAMINATED_COMPOSITE_FABRIC, or *MAT_58, in LS-DYNA. Values for each parameter within the material model were generated such that an in-plane isotropic configuration for the DEA material was assumed. Analytical predictions showed that the load-deflection behavior of a single-cell during three-point bending was within the range of test data, but predicted the DEA crush response to be very stiff. In addition, a *MAT_PIECEWISE_LINEAR_PLASTICITY, or *MAT_24, material model in LS-DYNA was developed, which represented the Kevlar/Epoxy composite as an isotropic elastic-plastic material with input from +/-45 degrees tensile coupon data. The predicted crush response matched that of the test and localized folding patterns of the DEA were captured under compression, but the model failed to predict the single-cell three-point bending response.

Tradeoffs between impact loading rate, vertical impulse and effective mass for walkers and heel strike runners wearing footwear of varying stiffness.

PubMed

Addison, Brian J; Lieberman, Daniel E

2015-05-01

Humans experience repetitive impact forces beneath the heel during walking and heel strike running that cause impact peaks characterized by high rates and magnitudes of loading. Impact peaks are caused by the exchange of momentum between the ground and a portion of the body that comes to a full stop (the effective mass) during the period of the impact peak. A number of factors can influence this exchange of momentum, including footwear stiffness. This study presents and tests an impulse-momentum model of impact mechanics which predicts that effective mass and vertical impulse is greater in walkers and heel strike runners wearing less stiff footwear. The model also predicts a tradeoff between impact loading rate and effective mass, and between impact loading rate and vertical impulse among individuals wearing footwear of varying stiffness. We tested this model using 19 human subjects walking and running in minimal footwear and in two experimental footpads. Subjects walked and ran on an instrumented treadmill and 3D kinematic data were collected. As predicted, both vertical impulse (walking: F(2,54)=52.0, p=2.6E-13; running: F(2,54)=25.2, p=1.8E-8) and effective mass (walking: F(2,54)=12.1, p=4.6E-5; running: F(2,54)=15.5, p=4.7E-6) increase in less stiff footwear. In addition, there is a significant inverse relationship between impact loading rate and vertical impulse (walking: r=-0.88, p<0.0001; running: r=-0.78, p<0.0001) and between impact loading rate and effective mass (walking: r=-0.88, p<0.0001; running: r=-0.82, p<0.0001). The tradeoff relationships documented here raise questions about how and in what ways the stiffness of footwear heels influence injury risk during human walking and running. Copyright © 2015 Elsevier Ltd. All rights reserved.

Impacts of building geometry modeling methods on the simulation results of urban building energy models

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

Chen, Yixing; Hong, Tianzhen

We present that urban-scale building energy modeling (UBEM)—using building modeling to understand how a group of buildings will perform together—is attracting increasing attention in the energy modeling field. Unlike modeling a single building, which will use detailed information, UBEM generally uses existing building stock data consisting of high-level building information. This study evaluated the impacts of three zoning methods and the use of floor multipliers on the simulated energy use of 940 office and retail buildings in three climate zones using City Building Energy Saver. The first zoning method, OneZone, creates one thermal zone per floor using the target building'smore » footprint. The second zoning method, AutoZone, splits the building's footprint into perimeter and core zones. A novel, pixel-based automatic zoning algorithm is developed for the AutoZone method. The third zoning method, Prototype, uses the U.S. Department of Energy's reference building prototype shapes. Results show that simulated source energy use of buildings with the floor multiplier are marginally higher by up to 2.6% than those modeling each floor explicitly, which take two to three times longer to run. Compared with the AutoZone method, the OneZone method results in decreased thermal loads and less equipment capacities: 15.2% smaller fan capacity, 11.1% smaller cooling capacity, 11.0% smaller heating capacity, 16.9% less heating loads, and 7.5% less cooling loads. Source energy use differences range from -7.6% to 5.1%. When comparing the Prototype method with the AutoZone method, source energy use differences range from -12.1% to 19.0%, and larger ranges of differences are found for the thermal loads and equipment capacities. This study demonstrated that zoning methods have a significant impact on the simulated energy use of UBEM. Finally, one recommendation resulting from this study is to use the AutoZone method with floor multiplier to obtain accurate results while balancing the simulation run time for UBEM.« less

Impacts of building geometry modeling methods on the simulation results of urban building energy models

DOE PAGES

Chen, Yixing; Hong, Tianzhen

2018-02-20

We present that urban-scale building energy modeling (UBEM)—using building modeling to understand how a group of buildings will perform together—is attracting increasing attention in the energy modeling field. Unlike modeling a single building, which will use detailed information, UBEM generally uses existing building stock data consisting of high-level building information. This study evaluated the impacts of three zoning methods and the use of floor multipliers on the simulated energy use of 940 office and retail buildings in three climate zones using City Building Energy Saver. The first zoning method, OneZone, creates one thermal zone per floor using the target building'smore » footprint. The second zoning method, AutoZone, splits the building's footprint into perimeter and core zones. A novel, pixel-based automatic zoning algorithm is developed for the AutoZone method. The third zoning method, Prototype, uses the U.S. Department of Energy's reference building prototype shapes. Results show that simulated source energy use of buildings with the floor multiplier are marginally higher by up to 2.6% than those modeling each floor explicitly, which take two to three times longer to run. Compared with the AutoZone method, the OneZone method results in decreased thermal loads and less equipment capacities: 15.2% smaller fan capacity, 11.1% smaller cooling capacity, 11.0% smaller heating capacity, 16.9% less heating loads, and 7.5% less cooling loads. Source energy use differences range from -7.6% to 5.1%. When comparing the Prototype method with the AutoZone method, source energy use differences range from -12.1% to 19.0%, and larger ranges of differences are found for the thermal loads and equipment capacities. This study demonstrated that zoning methods have a significant impact on the simulated energy use of UBEM. Finally, one recommendation resulting from this study is to use the AutoZone method with floor multiplier to obtain accurate results while balancing the simulation run time for UBEM.« less

Biomechanical evaluation of arthroscopic rotator cuff repairs: double-row compared with single-row fixation.

PubMed

Ma, C Benjamin; Comerford, Lyn; Wilson, Joseph; Puttlitz, Christian M

2006-02-01

Recent studies have shown that arthroscopic rotator cuff repairs can have higher rates of failure than do open repairs. Current methods of rotator cuff repair have been limited to single-row fixation of simple and horizontal stitches, which is very different from open repairs. The objective of this study was to compare the initial cyclic loading and load-to-failure properties of double-row fixation with those of three commonly used single-row techniques. Ten paired human supraspinatus tendons were split in half, yielding four tendons per cadaver. The bone mineral content at the greater tuberosity was assessed. Four stitch configurations (two-simple, massive cuff, arthroscopic Mason-Allen, and double-row fixation) were randomized and tested on each set of tendons. Specimens were cyclically loaded between 5 and 100 N at 0.25 Hz for fifty cycles and then loaded to failure under displacement control at 1 mm/sec. Conditioning elongation, peak-to-peak elongation, ultimate tensile load, and stiffness were measured with use of a three-dimensional tracking system and compared, and the failure type (suture or anchor pull-out) was recorded. No significant differences were found among the stitches with respect to conditioning elongation. The mean peak-to-peak elongation (and standard error of the mean) was significantly lower for the massive cuff (1.1 +/- 0.1 mm) and double-row stitches (1.1 +/- 0.1 mm) than for the arthroscopic Mason-Allen stitch (1.5 +/- 0.2 mm) (p < 0.05). The ultimate tensile load was significantly higher for double-row fixation (287 +/- 24 N) than for all of the single-row fixations (p < 0.05). Additionally, the massive cuff stitch (250 +/- 21 N) was found to have a significantly higher ultimate tensile load than the two-simple (191 +/- 18 N) and arthroscopic Mason-Allen (212 +/- 21 N) stitches (p < 0.05). No significant differences in stiffness were found among the stitches. Failure mechanisms were similar for all stitches. Rotator cuff repairs in the anterior half of the greater tuberosity had a significantly lower peak-to-peak elongation and higher ultimate tensile strength than did repairs on the posterior half. In this in vitro cadaver study, double-row fixation had a significantly higher ultimate tensile load than the three types of single-row fixation stitches. Of the single-row fixations, the massive cuff stitch had cyclic and load-to-failure characteristics similar to the double-row fixation. Anterior repairs of the supraspinatus tendon had significantly stronger biomechanical behavior than posterior repairs.

Computer simulation of the effects of shoe cushioning on internal and external loading during running impacts.

PubMed

Miller, Ross H; Hamill, Joseph

2009-08-01

Biomechanical aspects of running injuries are often inferred from external loading measurements. However, previous research has suggested that relationships between external loading and potential injury-inducing internal loads can be complex and nonintuitive. Further, the loading response to training interventions can vary widely between subjects. In this study, we use a subject-specific computer simulation approach to estimate internal and external loading of the distal tibia during the impact phase for two runners when running in shoes with different midsole cushioning parameters. The results suggest that: (1) changes in tibial loading induced by footwear are not reflected by changes in ground reaction force (GRF) magnitudes; (2) the GRF loading rate is a better surrogate measure of tibial loading and stress fracture risk than the GRF magnitude; and (3) averaging results across groups may potentially mask differential responses to training interventions between individuals.

Influence of tibial shock feedback training on impact loading and running economy.

PubMed

Clansey, Adam Charles; Hanlon, Michael; Wallace, Eric S; Nevill, Alan; Lake, Mark J

2014-01-01

The purpose of this study was to determine whether real-time feedback (RTF) training would reduce impact loading variables previously linked with tibial stress fracture risk and whether these adaptations would influence running economy. Twenty-two male runners were randomly assigned to RTF (n = 12) and control (n = 10) groups. The RTF group received feedback based on their peak tibial axial accelerations (PTA) during six 20-min treadmill runs for 3 wk, whereas the control group adhered to the same training but without feedback. Unilateral three-dimensional kinematic and kinetic analysis and running economy measurements were conducted before, after, and at 1 month posttraining. The RTF group had significant reductions (P < 0.01) in PTA and average and instantaneous vertical force loading rates after training as compared with no changes in the control group. These modifications in impact loads were only maintained in PTA 1 month after the training. A significant increase (P = 0.0033) in ankle plantarflexion at initial contact and a significant change (P = 0.030) in foot strike pattern from a rearfoot to midfoot strike pattern and a significant decrease (P = 0.008) in heel vertical velocity at initial contact appeared to be the primary mechanical strategies adopted by runners to reduce impact loading after RTF training. Despite these gait adaptations, running economy was unaffected. The results of this study suggest that gait retraining using RTF is an effective means of eliciting reductions in impact loading without negatively affecting running economy. However, with loading rate reductions not being maintained 1 month posttraining, further research is required to determine how these reductions in impact severity can be retained long term.

Experimental Investigation of Fibre Reinforced Composite Materials Under Impact Load

NASA Astrophysics Data System (ADS)

Koppula, Sravani; Kaviti, Ajay kumar; Namala, Kiran kumar

2018-03-01

Composite materials are extensively used in various engineering applications. They have very high flexibility design which allows prescribe tailoring of material properties by lamination of composite fibres with reinforcement of resin to it. Complex failure condition prevail in the composite materials under the action of impact loads, major modes of failure in composite may include matrix cracking, fibre matrix, fibre breakage, de-bonding or de- lamination between composite plies. This paper describes the mechanical properties of glass fibre reinforced composite material under impact loading conditions through experimental setup. Experimental tests are performed according to ASTM standards using impact testing machines like Charpy test, computerized universal testing machine.

The Bactericidal Effect of Shock Waves

NASA Astrophysics Data System (ADS)

Leighs, James; Appleby-Thomas, Gareth; Wood, David; Goff, Michael; Hameed, Amer; Hazell, Paul

2013-06-01

There are a variety of theories relating to the origins of life on our home planet, some of which discuss the possibility that life may have been spread via inter-planetary impacts. There have been a number of investigations into the ability of life to withstand the likely conditions generated by asteroid impact (both contained in the impactor and buried beneath the planet surface). Previously published data regarding the ability of bacteria to survive such applied shock waves has produced conflicting conclusions. The work presented here used an established technique, in combination with a single stage gas gun to shock load and subsequently recover Escherichia coli populations suspended in a phosphate buffered saline solution. Peak pressure across the sample region was calculated via numerical modelling, validated via Heterodyne velocimetry measurements. Survival data against peak sample pressure for recovered samples is presented alongside control tests.

Initial load-to-failure and failure analysis in single- and double-row repair techniques for rotator cuff repair.

PubMed

Baums, M H; Buchhorn, G H; Gilbert, F; Spahn, G; Schultz, W; Klinger, H-M

2010-09-01

This experimental study aimed to compare the load-to-failure rate and stiffness of single- versus double-row suture techniques for repairing rotator cuff lesions using two different suture materials. Additionally, the mode of failure of each repair was evaluated. In 32 sheep shoulders, a standardized tear of the infraspinatus tendon was created. Then, n = 8 specimen were randomized to four repair methods: (1) Double-row Anchor Ethibond coupled with polyester sutures, USP No. 2; (2) Double-Row Anchor HiFi with polyblend polyethylene sutures, USP No. 2; (3) Single-Row Anchor Ethibond coupled with braided polyester sutures, USP No. 2; and (4) Single-Row Anchor HiFi with braided polyblend polyethylene sutures, USP No. 2. Arthroscopic Mason-Allen stitches were placed (single-row) and combined with medial horizontal mattress stitches (double-row). All specimens were loaded to failure at a constant displacement rate on a material testing machine. Group 4 showed lowest load-to-failure result with 155.7 +/- 31.1 N compared to group 1 (293.4 +/- 16.1 N) and group 2 (397.7 +/- 7.4 N) (P < 0.001). Stiffness was highest in group 2 (162 +/- 7.3 N/mm) and lowest in group 4 (84.4 +/- 19.9 mm) (P < 0.001). In group 4, the main cause of failure was due to the suture cutting through the tendon (n = 6), a failure case observed in only n = 1 specimen in group 2 (P < 0.001). A double-row technique combined with arthroscopic Mason-Allen/horizontal mattress stitches provides high initial failure strength and may minimize the risk of the polyethylene sutures cutting through the tendon in rotator cuff repair when a single load force is used.

Single-Phase Single-Stage Grid Tied Solar PV System with Active Power Filtering Using Power Balance Theory

NASA Astrophysics Data System (ADS)

Singh, Yashi; Hussain, Ikhlaq; Singh, Bhim; Mishra, Sukumar

2018-06-01

In this paper, power quality features such as harmonics mitigation, power factor correction with active power filtering are addressed in a single-stage, single-phase solar photovoltaic (PV) grid tied system. The Power Balance Theory (PBT) with perturb and observe based maximum power point tracking algorithm is proposed for the mitigation of power quality problems in a solar PV grid tied system. The solar PV array is interfaced to a single phase AC grid through a Voltage Source Converter (VSC), which provides active power flow from a solar PV array to the grid as well as to the load and it performs harmonics mitigation using PBT based control. The solar PV array power varies with sunlight and due to this, the solar PV grid tied VSC works only 8-10 h per day. At night, when PV power is zero, the VSC works as an active power filter for power quality improvement, and the load active power is delivered by the grid to the load connected at the point of common coupling. This increases the effective utilization of a VSC. The system is modelled and simulated using MATLAB and simulated responses of the system at nonlinear loads and varying environmental conditions are also validated experimentally on a prototype developed in the laboratory.

Single-Phase Single-Stage Grid Tied Solar PV System with Active Power Filtering Using Power Balance Theory

NASA Astrophysics Data System (ADS)

Singh, Yashi; Hussain, Ikhlaq; Singh, Bhim; Mishra, Sukumar

2018-03-01

In this paper, power quality features such as harmonics mitigation, power factor correction with active power filtering are addressed in a single-stage, single-phase solar photovoltaic (PV) grid tied system. The Power Balance Theory (PBT) with perturb and observe based maximum power point tracking algorithm is proposed for the mitigation of power quality problems in a solar PV grid tied system. The solar PV array is interfaced to a single phase AC grid through a Voltage Source Converter (VSC), which provides active power flow from a solar PV array to the grid as well as to the load and it performs harmonics mitigation using PBT based control. The solar PV array power varies with sunlight and due to this, the solar PV grid tied VSC works only 8-10 h per day. At night, when PV power is zero, the VSC works as an active power filter for power quality improvement, and the load active power is delivered by the grid to the load connected at the point of common coupling. This increases the effective utilization of a VSC. The system is modelled and simulated using MATLAB and simulated responses of the system at nonlinear loads and varying environmental conditions are also validated experimentally on a prototype developed in the laboratory.

Evaluation of Thin Kevlar-Epoxy Fabric Panels Subjected to Shear Loading

NASA Technical Reports Server (NTRS)

Baker, Donald J.

1996-01-01

The results of an analytical and experimental investigation of 4-ply Kevlar-49-epoxy panels loaded by in-plane shear are presented. Approximately one-half of the panels are thin-core sandwich panels and the other panels are solid-laminate panels. Selected panels were impacted with an aluminum sphere at a velocity of either 150 or 220 ft/sec. The strength of panels impacted at 150 ft/sec was not reduced when compared to the strength of the undamaged panels, but the strength of panels impacted at 220 ft/sec was reduced by 27 to 40 percent. Results are presented for panels that were cyclically loaded from a load less than the buckling load to a load in the postbuckling load range. The thin-core sandwich panels had a lower fatigue life than the solid panels. The residual strength of the solid and sandwich panels cycled more than one million cycles exceeded the baseline undamaged panel strengths. The effect of hysteresis in the response of the sandwich panels is not significant. Results of a nonlinear finite element analysis conducted for each panel design are presented.

The role of working memory in spatial S-R correspondence effects.

PubMed

Wühr, Peter; Biebl, Rupert

2011-04-01

This study investigates the impact of working memory (WM) load on response conflicts arising from spatial (non) correspondence between irrelevant stimulus location and response location (Simon effect). The dominant view attributes the Simon effect to automatic processes of location-based response priming. The automaticity view predicts insensitivity of the Simon effect to manipulations of processing load. Four experiments investigated the role of spatial and verbal WM in horizontal and vertical Simon tasks by using a dual-task approach. Participants maintained different amounts of spatial or verbal information in WM while performing a horizontal or vertical Simon task. Results showed that high load generally decreased, and sometimes eliminated, the Simon effect. It is interesting to note that spatial load had a larger impact than verbal load on the horizontal Simon effect, whereas verbal load had a larger impact than spatial load on the vertical Simon effect. The results highlight the role of WM as the perception-action interface in choice-response tasks. Moreover, the results suggest spatial coding of horizontal stimulus-response (S-R) tasks, and verbal coding of vertical S-R tasks.

Marine Propulsion Load Emulation.

DTIC Science & Technology

1985-06-01

single-entry centrifugal compressor mechanically coupled to a single-stage axial - flow turbine , two cross- connected can type combustion chambers, and...an accessory- drive section. The power output section incorporates a second axial - flow turbine , reduction gears and output shaft, and is driven by the... Flow .... ............. ... 36 4.7 Load Valve Characteristics ... ............. .38 4.8 Photograph of Turbine Test gell .......... 39, * 4.9

An Investigation of the Characteristics of Steel Diaphragms for Automatic Fuel-Injection Valves

NASA Technical Reports Server (NTRS)

Joachim, W F

1926-01-01

This research on steel diaphragms was undertaken at the Langley Memorial Aeronautical Laboratory, as a part of a general investigation on fuel injection engines for aircraft. The work determined the load-deflection, load- deformation and hysteresis characteristics for single diaphragms having thicknesses from 0.00s inch to 0.012 inch, and for similar diaphragms tested in multiple having total thicknesses from 0.012 inch to 0.180 inch. The elastic limit loads and deflections, and rupture points of single diaphragms were also determined. Some work was done on diaphragms having central orifices in order to determine the effect of orifice diameter upon the load deflection characteristics.

The prediction of the impact of climatic factors on short-term electric power load based on the big data of smart city

NASA Astrophysics Data System (ADS)

Qiu, Yunfei; Li, Xizhong; Zheng, Wei; Hu, Qinghe; Wei, Zhanmeng; Yue, Yaqin

2017-08-01

The climate changes have great impact on the residents’ electricity consumption, so the study on the impact of climatic factors on electric power load is of significance. In this paper, the effects of the data of temperature, rainfall and wind of smart city on short-term power load is studied to predict power load. The authors studied the relation between power load and daily temperature, rainfall and wind in the 31 days of January of one year. In the research, the authors used the Matlab neural network toolbox to establish the combinational forecasting model. The authors trained the original input data continuously to get the internal rules inside the data and used the rules to predict the daily power load in the next January. The prediction method relies on the accuracy of weather forecasting. If the weather forecasting is different from the actual weather, we need to correct the climatic factors to ensure accurate prediction.

SRM attrition rate study of the aft motor case segments due to water impact cavity collapse loading

NASA Technical Reports Server (NTRS)

Crockett, C. D.

1976-01-01

The attrition assessment of the aft segments of Solid Rocket Motor due to water impact requires the establishment of a correlation between loading occurrences and structural capability. Each discrete load case, as identified by the water impact velocities and angle, varies longitudinally and radially in magnitude and distribution of the external pressure. The distributions are further required to be shifted forward or aft one-fourth the vehicle diameter to assure minimization of the effect of test instrumentation location for the load determinations. The asymmetrical load distributions result in large geometric nonlinearities in structural response. The critical structural response is progressive buckling of the case. Discrete stiffeners have been added to these aft segments to aid in gaining maximum structural capability for minimum weight addition for resisting these loads. This report presents the development of the attrition assessment of the aft segments and includes the rationale for eliminating all assessable conservatisms from this assessment.

Three-dimensional nonlinear responses to impact loads on free-span pipeline: Torsional coupling and load steps

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

Chung, J.S.; Huttelmaier, H.P.; Cheng, B.R.

1995-12-31

For a heavy object falling on a free-span pipeline, this study assesses three-dimensional (3-D) pipe-span responses with the torsional ({theta}x-) coupling of a pipeline through the biaxial (y) bending responses. The static pipe-span equilibrium is achieved with its self-weight and buoyancy and the external torsional moment induced by the cross-flow (y-directional) current on the sagged pipe span. Load steps taken for 2 different sequences of applying static loads induced different pipe deformations, and the pipe twists in entirely different pattern. The two types of impact loads are applied in the vertical (z-) direction to excite the pipe span in itsmore » static equilibrium: (1) triangular impulse loading and (2) ramp loading. Boundary condition of the span supports is ``fixed-fixed`` at both ends in both displacement and rotation. 3-D coupled axial (x-), bending (y- and z-) and torsional ({theta}x-) responses, both state and dynamic, to the z-directional impact loadings, are modeled and analyzed by a nonlinear FEM method for a 16-in pipeline. The 3-D responses are compared with 2-D responses. The comparison shows significant torsional vibrations caused by the cross-flow current, especially for longer spans. The torsional ({theta}x-) coupling is very sensitive to the time-step size in achieving numerical stability and accuracy, particularly for the ramp loading and for a shorter span. For very large impact loads, the response frequencies differ from the fundamental frequencies of the span, exhibiting beatings and strong bending-to-axial and to-twist couplings. Also, the eigenvalues for the linear system are not necessarily the resonance frequencies for these nonlinear coupled responses.« less

Vertical load capacities of roof truss cross members.

PubMed

Gearhart, David F; Morsy, Mohamed Khaled

2016-05-01

Trusses used for roof support in coal mines are constructed of two grouted bolts installed at opposing forty-five degree angles into the roof and a cross member that ties the angled bolts together. The load on the cross member is vertical, which is transverse to the longitudinal axis, and therefore the cross member is loaded in the weakest direction. Laboratory tests were conducted to determine the vertical load capacity and deflection of three different types of cross members. Single-point load tests, with the load applied in the center of the specimen and double-point load tests, with a span of 2.4 m, were conducted. For the single-point load configuration, the yield of the 25 mm solid bar cross member was nominally 98 kN of vertical load, achieved at 42 cm of deflection. For cable cross members, yield was not achieved even after 45 cm of deflection. Peak vertical loads were about 89 kN for 17 mm cables and 67 kN for the 15 mm cables. For the double-point load configurations, the 25 mm solid bar cross members yielded at 150 kN of vertical load and 25 cm of deflection. At 25 cm of deflection individual cable strands started breaking at 133 and 111 kN of vertical load for the 17 and 15 mm cable cross members respectively.

Engineering Design of Safe Automobile Front Strut Tower Brace with Predetermined Destruction

NASA Astrophysics Data System (ADS)

Mironenko, R. Ye; Balaev, E. Yu; Blednova, Zh M.

2018-03-01

This paper shows the developed design of an automobile front strut tower brace instantly breakable on reaching a predetermined value impact load, which allows the impact load not to be transferred to the opposite strut. An automobile front strut tower brace with the directed destruction V-shaped element using the SolidWorks and SolidWorks Simulations software complex was developed, designed and analyzed. The obtained data were confirmed experimentally. By changing geometric features of the V-shaped element, it is possible to change the impact load value required for its destruction.

A Consistent Wave Impact Load Model for Studying Structure, Equipment Ruggedness, Shock Isolation Seats, and Human Comfort in Small High Speed Craft

DTIC Science & Technology

2016-11-01

acceleration at a cross-section was used as a measure of the wave impact load in units of g. Later developments included publication of the envelope...Republic, 4 – 7 October 2004. PICKFORD, E.V., MAHONE, R.R., WOLK, H.L. (1975). Slam/Shock Isolation Pedestal, United States Patent Number, 3,912,248, 14...accelerations. The rigid body peak acceleration is a measure of the impact load in units of g. In the following plots the data corresponds to head-sea

Study on aging of single pile in soft soil foundation

NASA Astrophysics Data System (ADS)

Chen, Tiejun; Cao, Haiying

2017-04-01

In this paper, the single pile under load is analyzed by using the Biot consolidation equation and the modified method of the coupling of the Komala - Huang model. The consolidation of soil is simulated by Biot consolidation theory, and the whole process of the deformation of single pile is presented in the paper by means of the modified Komala - Huang model. Some useful conclusions are obtained by analyzing the variation of the pore pressure and the settlement of the soil under the action of load.

Black carbon from ships: a review of the effects of ship speed, fuel quality and exhaust gas scrubbing

NASA Astrophysics Data System (ADS)

Lack, D. A.; Corbett, J. J.

2012-01-01

The International Maritime Organization (IMO) has moved to address the health and climate impact of the emissions from the combustion of low-quality residual fuels within the commercial shipping industry. Fuel sulfur content (FS) limits and an efficiency design index for future ships are examples of such IMO actions. The impacts of black carbon (BC) emissions from shipping are now under review by the IMO, with a particular focus on the potential impacts of future Arctic shipping. Recognizing that associating impacts with BC emissions requires both ambient and onboard observations, we provide recommendations for the measurement of BC. We also evaluate current insights regarding the effect of ship speed (engine load), fuel quality and exhaust gas scrubbing on BC emissions from ships. Observations demonstrate that BC emission factors (EFBC) increases 3 to 6 times at very low engine loads (<25% compared to EFBC at 85-100% load); absolute BC emissions (per nautical mile of travel) also increase up to 100% depending on engine load, even with reduced load fuel savings. If fleets were required to operate at lower maximum engine loads, presumably associated with reduced speeds, then engines could be re-tuned, which would reduce BC emissions. Ships operating in the Arctic are likely running at highly variable engine loads (25-100%) depending on ice conditions and ice breaking requirements. The ships operating at low load may be emitting up to 50% more BC than they would at their rated load. Such variable load conditions make it difficult to assess the likely emissions rate of BC. Current fuel sulfur regulations have the effect of reducing EFBC by an average of 30% and potentially up to 80% regardless of engine load; a removal rate similar to that of scrubbers. Uncertainties among current observations demonstrate there is a need for more information on (a) the impact of fuel quality on EFBC using robust measurement methods and (b) the efficacy of scrubbers for the removal of particulate matter by size and composition.

Black carbon from ships: a review of the effects of ship speed, fuel quality and exhaust gas scrubbing

NASA Astrophysics Data System (ADS)

Lack, D. A.; Corbett, J. J.

2012-05-01

The International Maritime Organization (IMO) has moved to address the health and climate impact of the emissions from the combustion of low-quality residual fuels within the commercial shipping industry. Fuel sulfur content (FS) limits and an efficiency design index for future ships are examples of such IMO actions. The impacts of black carbon (BC) emissions from shipping are now under review by the IMO, with a particular focus on the potential impacts of future Arctic shipping. Recognizing that associating impacts with BC emissions requires both ambient and onboard observations, we provide recommendations for the measurement of BC. We also evaluate current insights regarding the effect of ship speed (engine load), fuel quality and exhaust gas scrubbing on BC emissions from ships. Observations demonstrate that BC emission factors (EFBC) increases 3 to 6 times at very low engine loads (<25% compared to EFBC at 85-100% load); absolute BC emissions (per nautical mile of travel) also increase up to 100% depending on engine load, even with reduced load fuel savings. If fleets were required to operate at lower maximum engine loads, presumably associated with reduced speeds, then engines could be re-tuned, which would reduce BC emissions. Ships operating in the Arctic are likely running at highly variable engine loads (25-100%) depending on ice conditions and ice breaking requirements. The ships operating at low load may be emitting up to 50% more BC than they would at their rated load. Such variable load conditions make it difficult to assess the likely emissions rate of BC. Current fuel sulfur regulations have the effect of reducing EFBC by an average of 30% and potentially up to 80% regardless of engine load; a removal rate similar to that of scrubbers. Uncertainties among current observations demonstrate there is a need for more information on a) the impact of fuel quality on EFBC using robust measurement methods and b) the efficacy of scrubbers for the removal of particulate matter by size and composition.

Impact evaluation of conducted UWB transients on loads in power-line networks

NASA Astrophysics Data System (ADS)

Li, Bing; Månsson, Daniel

2017-09-01

Nowadays, faced with the ever-increasing dependence on diverse electronic devices and systems, the proliferation of potential electromagnetic interference (EMI) becomes a critical threat for reliable operation. A typical issue is the electronics working reliably in power-line networks when exposed to electromagnetic environment. In this paper, we consider a conducted ultra-wideband (UWB) disturbance, as an example of intentional electromagnetic interference (IEMI) source, and perform the impact evaluation at the loads in a network. With the aid of fast Fourier transform (FFT), the UWB transient is characterized in the frequency domain. Based on a modified Baum-Liu-Tesche (BLT) method, the EMI received at the loads, with complex impedance, is computed. Through inverse FFT (IFFT), we obtain time-domain responses of the loads. To evaluate the impact on loads, we employ five common, but important quantifiers, i.e., time-domain peak, total signal energy, peak signal power, peak time rate of change and peak time integral of the pulse. Moreover, to perform a comprehensive analysis, we also investigate the effects of the attributes (capacitive, resistive, or inductive) of other loads connected to the network, the rise time and pulse width of the UWB transient, and the lengths of power lines. It is seen that, for the loads distributed in a network, the impact evaluation of IEMI should be based on the characteristics of the IEMI source, and the network features, such as load impedances, layout, and characteristics of cables.

Fibrous cartilage of human menisci is less shock-absorbing and energy-dissipating than hyaline cartilage.

PubMed

Gaugler, Mario; Wirz, Dieter; Ronken, Sarah; Hafner, Mirjam; Göpfert, Beat; Friederich, Niklaus F; Elke, Reinhard

2015-04-01

To test meniscal mechanical properties such as the dynamic modulus of elasticity E* and the loss angle δ at two loading frequencies ω at different locations of the menisci and compare it to E* and δ of hyaline cartilage in indentation mode with spherical indenters. On nine pairs of human menisci, the dynamic E*-modulus and loss angle δ (as a measure of the energy dissipation) were determined. The measurements were performed at two different strain rates (slow sinusoidal and fast single impact) to show the strain rate dependence of the material. The measurements were compared to previous similar measurements with the same equipment on human hyaline cartilage. The resultant E* at fast indentation (median 1.16 MPa) was significantly higher, and the loss angle was significantly lower (median 10.2°) compared to slow-loading mode's E* and δ (median 0.18 MPa and 16.9°, respectively). Further, significant differences for different locations are shown. On the medial meniscus, the anterior horn shows the highest resultant dynamic modulus. In dynamic measurements with a spherical indenter, the menisci are much softer and less energy-dissipating than hyaline cartilage. Further, the menisci are stiffer and less energy-dissipating in the middle, intermediate part compared to the meniscal base. In compression, the energy dissipation of meniscus cartilage plays a minor role compared to hyaline cartilage. At high impacts, energy dissipation is less than on low impacts, similar to cartilage.

Volcanic Loading: The Dust Veil Index (1985) (NDP-013)

DOE Data Explorer

Lamb, H. H. [University of East Anglia, Norwich, United Kingdom; Boden, Thomas A. [CDIAC, Oak Ridge National Laboratory; Watts, Julia A. [Oak Ridge National Laboratory

1985-09-01

Lamb's Dust Veil Index (DVI) is a numerical index that quantifies the impact of a particular volcanic eruption's release of dust and aerosols over the years following the event, especially the impact on the Earth's energy balance. DVIs have been calculated for eruptions occurring from 1500 through 1983. The methods used to calculate the DVI have been intercalibrated to give a DVI of 1000 for the eruption of Krakatoa in 1883. The DVI for any volcanic eruption is based on a review of the observational, empirical, and theoretical studies of the possible impact on climate of volcanic dust veils. The DVI allows one to compare volcanic eruptions by a single numerical index. The data base includes the name of the erupting volcano, year of eruption, volcano latitude and longitude, maximum extent of the dust veil, veil duration, DVI for the entire globe, DVI for the Northern Hemisphere, and DVI for the Southern Hemisphere. The data are in one file (22.6 kB).

Impact of tensile strain on the thermal transport of zigzag hexagonal boron nitride nanoribbon: An equilibrium molecular dynamics study

NASA Astrophysics Data System (ADS)

Navid, Ishtiaque Ahmed; Intisar Khan, Asir; Subrina, Samia

2018-02-01

The thermal conductivity of single layer strained hexagonal boron nitride nanoribbon (h-BNNR) has been computed using the Green—Kubo formulation of Equilibrium Molecular Dynamics (EMD) simulation. We have investigated the impact of strain on thermal transport of h-BNNR by varying the applied tensile strain from 1% upto 5% through uniaxial loading. The thermal conductivity of h-BNNR decreases monotonically with the increase of uniaxial tensile strain keeping the sample size and temperature constant. The thermal conductivity can be reduced upto 86% for an applied uniaxial tensile strain of 5%. The impact of temperature and width variation on the thermal conductivity of h-BNNR has also been studied under different uniaxial tensile strain conditions. With the increase in temperature, the thermal conductivity of strained h-BNNR exhibits a decaying characteristics whereas it shows an opposite pattern with the increasing width. Such study would provide a good insight on the strain tunable thermal transport for the potential device application of boron nitride nanostructures.

Full-Scale Test and Analysis Results of a PRSEUS Fuselage Panel to Assess Damage Containment Features

NASA Technical Reports Server (NTRS)

Bergan, Andrew; Bakuckas, John G., Jr.; Lovejoy, Andrew; Jegley, Dawn; Linton, Kim; Neal, Bert; Korkosz, Gregory; Awerbuch, Jonathan; Tan, Tein-Min

2012-01-01

Integrally stitched composite technology is an area that shows promise in enhancing the structural integrity of aircraft and aerospace structures. The most recent generation of this technology is the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. The goal of the PRSEUS concept relevant to this test is to provide damage containment capability for composite structures while reducing overall structural weight. The National Aeronautics and Space Administration (NASA), the Federal Aviation Administration (FAA), and The Boeing Company have partnered in an effort to assess the damage containment features of a full-scale curved PRSEUS panel using the FAA Full-Scale Aircraft Structural Test Evaluation and Research (FASTER) facility. A single PRSEUS test panel was subjected to axial tension, internal pressure, and combined axial tension and internal pressure loads. The test results showed excellent performance of the PRSEUS concept. No growth of Barely Visible Impact Damage (BVID) was observed after ultimate loads were applied. With a two-bay notch severing the central stringer, damage was contained within the two-bay region well above the required limit load conditions. Catastrophic failure was well above the ultimate load level. Information describing the test panel and procedure has been previously presented, so this paper focuses on the experimental procedure, test results, nondestructive inspection results, and preliminary test and analysis correlation.

Effect of kenaf short fiber loading on mechanical properties of biocomposites

NASA Astrophysics Data System (ADS)

Andilolo, J.; Nikmatin, S.; Nugroho, N.; Alatas, H.; Wismogroho, A. S.

2017-05-01

The research of biocomposite product with kenaf (Hibiscus cannabinus) short fiber as a filler and Acrylonitrile Butadiene Styrene (ABS) as the matrix had been done to understand the mechanical properties of this material. Kenaf short fiber was obtained from mechanical sieving after doing the mechanical milling. TAPPI method has been done to determine the chemical properties. In order to form a granular biocomposite a single screw extruder was performed with a variation of particle loading 10 and 15%. The original of acrylonitrile butadiene styrene (ABS) has been used as matrix. The fabrication of speciment had been done by molding injection process. Mechanical properties test was done by ASTM standarization. The results showed the density of the fibers of 1.008 g/cm3 with a fiber length of 897.07 µm and a diameter of 66.38 µm. Tensile strength of kenaf short fiber loading 10 and 15% was 23.522 ± 8.36 MPa and 20.739 ± 6.79 MPa, respectively. The tensile properties showed a decreasing trend as the fiber loading was increased. The values of impact strength were 68.657 ± 4.89 kJ m-2 and 82.090 ± 5.56 kJ m-2, respectively and the hardness values were 96.60 ± 6.03 HR and 105.20 ± 13.17 HR, respectively. Kenaf fiber can be a good reinforcement candidate for high performance polymer bio-composites.

Spallation studies on shock loaded uranium

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

Tonks, D.L.; Hixson, R.; Gustavsen, R.L.

1997-12-31

Uranium samples at two different purity levels were used for spall strength measurements at three different stress levels. A 50 mm single-stage gas-gun was used to produce planar impact conditions using Z-cut quartz impactors. Samples of depleted uranium were taken from very high purity material and from material that had 300 ppm of carbon added. A pair of shots was done for each impact strength, one member of the pair with VISAR diagnostics and the second with soft recovery for metallographical examination. A series of increasing final stress states were chosen to effectively freeze the microstructural damage at three placesmore » in the development to full spall separation. This allowed determination of the dependence of spall mechanisms on stress level and sample purity. This report will discuss both the results of the metallurgical examination of soft recovered samples and the modeling of the free surface VISAR data. The micrographs taken from the recovered samples show brittle cracking as the spallation failure mechanism. Deformation induced twins are plentiful and obviously play a role in the spallation process. The twins are produced in the initial shock loading and, so, are present already before the fracture process begins. The 1 d characteristics code CHARADE has been used to model the free surface VISAR data.« less

Androgynous, Reconfigurable Closed Loop Feedback Controlled Low Impact Docking System With Load Sensing Electromagnetic Capture Ring

NASA Technical Reports Server (NTRS)

Lewis, James L. (Inventor); Carroll, Monty B. (Inventor); Morales, Ray H. (Inventor); Le, Thang D. (Inventor)

2002-01-01

The present invention relates to a fully androgynous, reconfigurable closed loop feedback controlled low impact docking system with load sensing electromagnetic capture ring. The docking system of the present invention preferably comprises two Docking- assemblies, each docking assembly comprising a load sensing ring having an outer face, one of more electromagnets, one or more load cells coupled to said load sensing ring. The docking assembly further comprises a plurality of actuator arms coupled to said load sensing ring and capable of dynamically adjusting the orientation of said load sensing ring and a reconfigurable closed loop control system capable of analyzing signals originating from said plurality of load cells and of outputting real time control for each of the actuators. The docking assembly of the present invention incorporates an active load sensing system to automatically dynamically adjust the load sensing ring during capture instead of requiring significant force to push and realign the ring.

Association of Borrelia and Rickettsia spp. and bacterial loads in Ixodes ricinus ticks.

PubMed

Raulf, Marie-Kristin; Jordan, Daniela; Fingerle, Volker; Strube, Christina

2018-01-01

In recent years, awareness of coinfections has increased as synergistic or antagonistic effects on interacting bacteria have been observed. To date, several reports on coinfections of ticks with Rickettsia and Borrelia spp. are available. However, associations are rarely described and studies are based on rather low sample sizes. In the present study, coinfections of Ixodes ricinus with these pathogens were investigated by determining their association in a meta-analysis. A total of 5079 tick samples examined for Rickettsia and Borrelia spp. via probe-based quantitative real-time PCR in previous prevalence studies or as submitted diagnostic material were included. In Borrelia-positive ticks, genospecies were determined by Reverse Line Blot. Determination of bacterial loads resulted in an increase between developmental tick stages with highest mean bacterial loads in female ticks (7.96×10 4 in Borrelia single-infected, 4.87×10 5 in Rickettsia single-infected and 3.22×10 5 in Borrelia-Rickettsia coinfected females). The determined Borrelia-Rickettsia tick coinfection rate was 12.3% (626/5079) with a significant difference to the expected coinfection rate of 9.0% (457/5079). A significant slight association as well as correlation between Borrelia and Rickettsia were determined. In addition, a significant interrelation of the bacterial load in coinfected ticks was shown. At the level of Borrelia genospecies, significant weak associations with Rickettsia spp. were detected for B. afzelii, B. garinii/bavariensis, B. valaisiana and B. lusitaniae. The positive association provides evidence for interactions between Borrelia and Rickettsia spp. in the tick vector, presumably resulting in higher bacterial replication rates in the tick vector and possibly the reservoir host. However, coinfection may impact the vector negatively as indicated by an absent increase in coinfection rates from nymphs to adults. Future studies are needed to investigate the underlying mechanisms of the positive association in ticks and possible associations in the vertebrate host as well as the potential influence of environmental factors. Copyright © 2017 Elsevier GmbH. All rights reserved.

Usage monitoring of electrical devices in a smart home.

PubMed

Rahimi, Saba; Chan, Adrian D C; Goubran, Rafik A

2011-01-01

Profiling the usage of electrical devices within a smart home can be used as a method for determining an occupant's activities of daily living. A nonintrusive load monitoring system monitors the electrical consumption at a single electrical source (e.g., main electric utility service entry) and the operating schedules of individual devices are determined by disaggregating the composite electrical consumption waveforms. An electrical device's load signature plays a key role in nonintrusive load monitoring systems. A load signature is the unique electrical behaviour of an individual device when it is in operation. This paper proposes a feature-based model, using the real power and reactive power as features for describing the load signatures of individual devices. Experimental results for single device recognition for 7 devices show that the proposed approach can achieve 100% classification accuracy with discriminant analysis using Mahalanobis distances.

Improving Strength of Postbuckled Panels Through Stitching

NASA Technical Reports Server (NTRS)

Jegley, Dawn C.

2007-01-01

The behavior of blade-stiffened graphite-epoxy panels with impact damage is examined to determine the effect of adding through-the-thickness stitches in the stiffener flange-to-skin interface. The influence of stitches is evaluated by examining buckling and failure for panels with failure loads up to 3.5 times greater than buckling loads. Analytical and experimental results from four configurations of panel specimens are presented. For each configuration, two panels were manufactured with skin and flanges held together with through-the-thickness stitches introduced prior to resin infusion and curing and one panel was manufactured with no stitches holding the flange to the skin. No mechanical fasteners were used for the assembly of any of these panels. Panels with and without low-speed impact damage were loaded to failure in compression. Buckling and failure modes are discussed. Stitching had little effect on buckling loads but increased the failure loads of impact-damaged panels by up to 30%.

Marrow fat may distribute the energy of impact loading throughout subchondral bone

PubMed Central

Simkin, Peter A

2018-01-01

Abstract Most students of articular mechanics consider impact loads to be compressive forces that are borne by an intraosseous, trabecular scaffold. The possible role of marrow fat, which comprises about 75% of the structure, is generally ignored, and the potential contribution of type 1 collagen, the prototypic tensile protein, is not considered. Here, I question the evidence underlying these omissions and reject the conclusion of exclusive trabecular compression. Instead, I suggest that impact loading pressurizes the fat in subchondral compartments, and those pressures stretch the elastic trabecular walls, which are thereby subjected to tensile loading. The load-driven pressure pulses then diminish as they pass from each compartment to its adjoining neighbours. The resulting pressure gradient distributes the burden throughout the subchondrium, stores energy for ensuing recovery and subjects individual trabeculae only to the net pressure differences between adjacent compartments. PMID:28977578

Simulation Study on the Deflection Response of the 921A Steel thin plate under Explosive Impact Load

NASA Astrophysics Data System (ADS)

Zhang, Yu-Xiang; Chen, Fang; Han, Yan

2018-03-01

The Ship cabin would be subject to high-intensity shock wave load when it is attacked by anti-ship weapons, causing its side board damaged. The time course of the deflection of the thin plate made of 921A steel in different initial conditions under the impact load is researched by theoretical analysis and numerical simulation. According to the theory of elastic-plastic deformation of the thin plate, the dynamic response equation of the thin plate under the explosion impact load is established with the method of energy, and the theoretical calculation value is compared with the result from the simulation method. It proved that the theoretical calculation method has better reliability and accuracy in different boundary size.

Assessment of dynamic effects on aircraft design loads: The landing impact case

NASA Astrophysics Data System (ADS)

Bronstein, Michael; Feldman, Esther; Vescovini, Riccardo; Bisagni, Chiara

2015-10-01

This paper addresses the potential benefits due to a fully dynamic approach to determine the design loads of a mid-size business jet. The study is conducted by considering the fuselage midsection of the DAEDALOS aircraft model with landing impact conditions. The comparison is presented in terms of stress levels between the novel dynamic approach and the standard design practice based on the use of equivalent static loads. The results illustrate that a slight reduction of the load levels can be achieved, but careful modeling of the damping level is needed. Guidelines for an improved load definition are discussed, and suggestions for future research activities are provided.

Ultimate compression after impact load prediction in graphite/epoxy coupons using neural network and multivariate statistical analyses

NASA Astrophysics Data System (ADS)

Gregoire, Alexandre David

2011-07-01

The goal of this research was to accurately predict the ultimate compressive load of impact damaged graphite/epoxy coupons using a Kohonen self-organizing map (SOM) neural network and multivariate statistical regression analysis (MSRA). An optimized use of these data treatment tools allowed the generation of a simple, physically understandable equation that predicts the ultimate failure load of an impacted damaged coupon based uniquely on the acoustic emissions it emits at low proof loads. Acoustic emission (AE) data were collected using two 150 kHz resonant transducers which detected and recorded the AE activity given off during compression to failure of thirty-four impacted 24-ply bidirectional woven cloth laminate graphite/epoxy coupons. The AE quantification parameters duration, energy and amplitude for each AE hit were input to the Kohonen self-organizing map (SOM) neural network to accurately classify the material failure mechanisms present in the low proof load data. The number of failure mechanisms from the first 30% of the loading for twenty-four coupons were used to generate a linear prediction equation which yielded a worst case ultimate load prediction error of 16.17%, just outside of the +/-15% B-basis allowables, which was the goal for this research. Particular emphasis was placed upon the noise removal process which was largely responsible for the accuracy of the results.

Test and analysis of a stitched RFI graphite-epoxy panel with a fuel access door

NASA Technical Reports Server (NTRS)

Jegley, Dawn C.; Waters, W. Allen, Jr.

1994-01-01

A stitched RFI graphite-epoxy panel with a fuel access door was analyzed using a finite element analysis and loaded to failure in compression. The panel was initially 56-inches long and 36.75-inches wide and the oval access door was 18-inches long and 15-inches wide. The panel was impact damaged with impact energy of 100 ft-lb prior to compressive loading; however, no impact damage was detectable visually or by A-scan. The panel carried a failure load of 695,000 Ib and global failure strain of .00494 in/in. Analysis indicated the panel would fail due to collapse at a load of 688,100 Ib. The test data indicate that the maximum strain in a region near the access door was .0096 in/in and analysis indicates a local surface strain of .010 in/in at the panel's failure load. The panel did not fail through the impact damage, but instead failed through bolt holes for attachment of the access door in a region of high strain.

Polymer matrix and graphite fiber interface study

NASA Technical Reports Server (NTRS)

Adams, D. F.; Zimmerman, R. S.; Odom, E. M.

1985-01-01

Hercules AS4 graphite fiber, unsized, or with EPON 828, PVA, or polysulfone sizing, was combined with three different polymer matrices. These included Hercules 3501-6 epoxy, Hercules 4001 bismaleimide, and Hexcel F155 rubber toughened epoxy. Unidirectional composites in all twelve combinations were fabricated and tested in transverse tension and axial compression. Quasi-isotropic laminates were tested in axial tension and compression, flexure, interlaminar shear, and tensile impact. All tests were conducted at both room temperature, dry and elevated temperature, and wet conditions. Single fiber pullout testing was also performed. Extensive scanning electron microphotographs of fracture surfaces are included, along with photographs of single fiber pullout failures. Analytical/experimental correlations are presented, based on the results of a finite element micromechanics analysis. Correlations between matrix type, fiber sizing, hygrothermal environment, and loading mode are presented. Results indicate that the various composite properties were only moderately influenced by the fiber sizings utilized.

Study of technology of pile foundation construction of no.5 main pier of Shoujiang bridge in Wenchuan County

NASA Astrophysics Data System (ADS)

Huang, Xianbin; Liu, Chenyang; Chen, Chunyang; Wangren, Yahong; Xu, Jialin; Xian, Jin

2018-03-01

The group of pile foundation of no.5 pier in Shoujiang Bridge needs to overcome the big load of large span continuous steel structure. The length of single pile foundation is 77m and the diameter of single pile foundation is 250cm. It not only faces the flood in the upstream of Shoujiang river, the construction obstacles during summer rain period, but also the reservoir clearance activity of Zipingpu reservoir and the high water level in winter and other water level fluctuation that have huge impact on platform of pile foundation construction. This article introduces the preparation in aspect of personnel, material, equipment and so on of pile foundation construction, and also conduct intensive research on leveling the field, assaying pile location, the embedment of the steel casing, installing the drill, mixing mud, drilling, final hole inspection and clearance, steel cage construction, perfusing concrete under water.

Is less really more: Does a prefrontal efficiency genotype actually confer better performance when working memory becomes difficult?

PubMed

Ihne, Jessica L; Gallagher, Natalie M; Sullivan, Marie; Callicott, Joseph H; Green, Adam E

2016-01-01

Perhaps the most widely studied effect to emerge from the combination of neuroimaging and human genetics is the association of the COMT-Val(108/158)Met polymorphism with prefrontal activity during working memory. COMT-Val is a putative risk factor in schizophrenia, which is characterized by disordered prefrontal function. Work in healthy populations has sought to characterize mechanisms by which the valine (Val) allele may lead to disadvantaged prefrontal cognition. Lower activity in methionine (Met) carriers has been interpreted as advantageous neural efficiency. Notably, however, studies reporting COMT effects on neural efficiency have generally not reported working memory performance effects. Those studies have employed relatively low/easy working memory loads. Higher loads are known to elicit individual differences in working memory performance that are not visible at lower loads. If COMT-Met confers greater neural efficiency when working memory is easy, a reasonable prediction is that Met carriers will be better able to cope with increasing demand for neural resources when working memory becomes difficult. To our knowledge, this prediction has thus far gone untested. Here, we tested performance on three working memory tasks. Performance on each task was measured at multiple levels of load/difficulty, including loads more demanding than those used in prior studies. We found no genotype-by-load interactions or main effects of COMT genotype on accuracy or reaction time. Indeed, even testing for performance differences at each load of each task failed to find a single significant effect of COMT genotype. Thus, even if COMT genotype has the effects on prefrontal efficiency that prior work has suggested, such effects may not directly impact high-load working memory ability. The present findings accord with previous evidence that behavioral effects of COMT are small or nonexistent and, more broadly, with a growing consensus that substantial effects on phenotype will not emerge from candidate gene studies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Relationship of polymorphisms and haplotype in interleukin-16 and adiponectin gene with late-onset Alzheimer’s disease risk

PubMed Central

Yin, Honglei; Zhang, Yuzhen; Hua, Linlin; Li, Jinfeng; Zeng, Zhilei; Yang, Xiaopeng; Gong, Bin; Geng, Shuang; Liu, Yajun; Zhang, Hui; Liu, Yanqiu; Zhao, Jing; Wang, Yunliang

2017-01-01

Aims To investigate the impact of Interleukin-16 (IL- 16) and Adiponectin (ANP) gene single nucleotide polymorphisms (SNPs), gene- gene interactions and haplotype on late-onset Alzheimer’s disease (LOAD) risk. Methods Hardy-Weinberg equilibrium (HWE), haplotype and pairwise linkage disequilibrium (LD) analysis were investigated by using SNPstats (available online at http://bioinfo.iconcologia.net/SNPstats). Generalized multifactor dimensionality reduction (GMDR) was used to examine interaction among 4 SNPs, odds ratio (OR) and 95% confident interval (95%CI) were calculated by logistic regression model. Results LOAD risk was significantly higher in carriers of rs266729- G allele than those with CC genotype (CG+ GG versus CC), OR (95%CI) =1.61 (1.26-1.96), and higher in carriers of rs1501299- T allele, OR (95%CI) = 1.62 (1.32-2.12), lower in carriers of rs4072111- T allele, adjusted OR (95%CI) =0.65 (0.44-0.93). We also found a significant gene- gene interaction between rs266729 and rs4072111. Participants with CG or GG of rs266729 and CC of rs4072111 genotype have the highest LOAD risk, OR (95%CI) = 2.62 (1.64 -3.58). Haplotype containing the rs266729- G and rs1501299- T alleles were associated with increased LOAD risk, OR (95%CI)= 1.83 (1.32- 2.43), and haplotype containing the rs1131445- C and rs4072111- T alleles were associated with decreased LOAD risk, OR (95%CI)= 0.53 (0.18- 0.95). Conclusions We concluded that rs266729 and rs1501299 minor alleles were associated with increased LOAD risk, but rs4072111 minor allele was associated with decreased LOAD risk. We also found that interaction involving rs266729 and rs4072111, and haplotype combinations were associated with LOAD risk. PMID:29108295

The WRAIR projectile concussive impact model of mild traumatic brain injury: re-design, testing and preclinical validation.

PubMed

Leung, Lai Yee; Larimore, Zachary; Holmes, Larry; Cartagena, Casandra; Mountney, Andrea; Deng-Bryant, Ying; Schmid, Kara; Shear, Deborah; Tortella, Frank

2014-08-01

The WRAIR projectile concussive impact (PCI) model was developed for preclinical study of concussion. It represents a truly non-invasive closed-head injury caused by a blunt impact. The original design, however, has several drawbacks that limit the manipulation of injury parameters. The present study describes engineering advancements made to the PCI injury model including helmet material testing, projectile impact energy/head kinematics and impact location. Material testing indicated that among the tested materials, 'fiber-glass/carbon' had the lowest elastic modulus and yield stress for providing an relative high percentage of load transfer from the projectile impact, resulting in significant hippocampal astrocyte activation. Impact energy testing of small projectiles, ranging in shape and size, showed the steel sphere produced the highest impact energy and the most consistent impact characteristics. Additional tests confirmed the steel sphere produced linear and rotational motions on the rat's head while remaining within a range that meets the criteria for mTBI. Finally, impact location testing results showed that PCI targeted at the temporoparietal surface of the rat head produced the most prominent gait abnormalities. Using the parameters defined above, pilot studies were conducted to provide initial validation of the PCI model demonstrating quantifiable and significant increases in righting reflex recovery time, axonal damage and astrocyte activation following single and multiple concussions.

Dynamic analysis of Apollo-Salyut/Soyuz docking

NASA Technical Reports Server (NTRS)

Schliesing, J. A.

1972-01-01

The use of a docking-system computer program in analyzing the dynamic environment produced by two impacting spacecraft and the attitude control systems is discussed. Performance studies were conducted to determine the mechanism load and capture sensitivity to parametric changes in the initial impact conditions. As indicated by the studies, capture latching is most sensitive to vehicle angular-alinement errors and is least sensitive to lateral-miss error. As proved by load-sensitivity studies, peak loads acting on the Apollo spacecraft are considerably lower than the Apollo design-limit loads.

Comparison Virtual Landing Gear Drop Test for Commuter Aircraft Utilize MSC ADAMS And Solidworks Motion Analysis

NASA Astrophysics Data System (ADS)

Hidayat, Dony; Istiyanto, Jos; Agus Sumarsono, Danardono

2018-04-01

Loads at main landing gear while touchdown impact is function of aircraft weight and ground reaction load factor. In regulation states ground reaction load factor at Vsink = 3.05 m/s is below 3. Contact/impact force from simulation using MSC ADAMS is 94680 N, while using Solidworks Motion Analysis is 97691 N. The difference between MSC ADAMS and Solidworks Motion Analysis is 3.08%. The ground reaction load factor in MSC ADAMS is 2.78 while in Solidworks Motion Analysis is 2.87.

SRB attrition rate study of the aft skirt due to water impact cavity collapse loading

NASA Technical Reports Server (NTRS)

Crockett, C. D.

1976-01-01

A methodology was presented so that realistic attrition prediction could aid in selecting an optimum design option for minimizing the effects of updated loads on the Space Shuttle Solid Rocket Booster (SRB) aft skirt. The updated loads resulted in water impact attrition rates greater than 10 percent for the aft skirt structure. Adding weight to reinforce the aft skirt was undesirable. The refined method treats the occurrences of the load distribution probabilistically, radially and longitudinally, with respect to the critical structural response.

Assessment of Head and Neck Injury Potential During Aircraft Longitudinal Impacts

DOT National Transportation Integrated Search

2017-02-02

The risk of head-neck injuries was evaluated for certain aircraft seat and interior configurations in aircraft longitudinal impacts. Two loading scenarios for the head-neck system were investigated: inertial (noncontact) loading in posterior-anterior...

The impact of a single round of community mass treatment with azithromycin on disease severity and ocular Chlamydia trachomatis load in treatment-naïve trachoma-endemic island communities in West Africa.

PubMed

Last, Anna R; Burr, Sarah E; Harding-Esch, Emma; Cassama, Eunice; Nabicassa, Meno; Roberts, Chrissy H; Mabey, David C W; Holland, Martin J; Bailey, Robin L

2017-12-28

Trachoma, a neglected tropical disease, is caused by ocular infection with Chlamydia trachomatis (Ct). The World Health Organization (WHO) recommends three annual rounds of community mass drug treatment with azithromycin (MDA) if the prevalence of follicular trachoma in 1-9 year olds (TF 1-9 ) exceeds 10% at district level to achieve an elimination target of district-level TF 1-9 below 5% after. To evaluate this strategy in treatment-naïve trachoma-endemic island communities in Guinea Bissau, we conducted a cross-sectional population-based trachoma survey on four islands. The upper tarsal conjunctivae of each participant were clinically assessed for trachoma and conjunctival swabs were obtained (n = 1507). We used a droplet digital PCR assay to detect Ct infection and estimate bacterial load. We visited the same households during a second cross-sectional survey and repeated the ocular examination and obtained conjunctival swabs from these households one year after MDA (n = 1029). Pre-MDA TF 1-9 was 22.0% (136/618). Overall Ct infection prevalence (CtI) was 18.6% (25.4% in 1-9 year olds). Post-MDA (estimated coverage 70%), TF 1-9 and CtI were significantly reduced (7.4% (29/394, P < 0.001) and 3.3% (34/1029, P < 0.001) (6.6% in 1-9 year olds, P < 0.001), respectively. Median ocular Ct load was reduced from 2038 to 384 copies/swab (P < 0.001). Following MDA cases of Ct infection were highly clustered (Moran's I 0.27, P < 0.001), with fewer clusters of Ct infection overall, fewer clusters of cases with high load infections and less severe disease. Despite a significant reduction in the number of clusters of Ct infection, mean Ct load, disease severity and presence of clusters of cases of high load Ct infection suggesting the beginning of trachoma control in isolated island communities, following a single round of MDA we demonstrate that transmission is still ongoing. These detailed data are useful in understanding the epidemiology of ocular Ct infection in the context of MDA and the tools employed may have utility in determining trachoma elimination and surveillance activities in similar settings.

Evidence for two attentional components in visual working memory.

PubMed

Allen, Richard J; Baddeley, Alan D; Hitch, Graham J

2014-11-01

How does executive attentional control contribute to memory for sequences of visual objects, and what does this reveal about storage and processing in working memory? Three experiments examined the impact of a concurrent executive load (backward counting) on memory for sequences of individually presented visual objects. Experiments 1 and 2 found disruptive concurrent load effects of equivalent magnitude on memory for shapes, colors, and colored shape conjunctions (as measured by single-probe recognition). These effects were present only for Items 1 and 2 in a 3-item sequence; the final item was always impervious to this disruption. This pattern of findings was precisely replicated in Experiment 3 when using a cued verbal recall measure of shape-color binding, with error analysis providing additional insights concerning attention-related loss of early-sequence items. These findings indicate an important role for executive processes in maintaining representations of earlier encountered stimuli in an active form alongside privileged storage of the most recent stimulus. PsycINFO Database Record (c) 2014 APA, all rights reserved.

Effects of Home Energy Management Systems on Distribution Utilities and Feeders Under Various Market Structures: Preprint

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

Ruth, Mark; Pratt, Annabelle; Lunacek, Monte

2015-07-17

The combination of distributed energy resources (DER) and retail tariff structures to provide benefits to both utility consumers and the utilities is poorly understood. To improve understanding, an Integrated Energy System Model (IESM) is being developed to simulate the physical and economic aspects of DER technologies, the buildings where they reside, and feeders servicing them. The IESM was used to simulate 20 houses with home energy management systems on a single feeder under a time of use tariff to estimate economic and physical impacts on both the households and the distribution utilities. HEMS reduce consumers’ electric bills by precooling housesmore » in the hours before peak electricity pricing. Household savings are greater than the reduction utility net revenue indicating that HEMS can provide a societal benefit providing tariffs are structured so that utilities remain solvent. Utilization of HEMS reduce peak loads during high price hours but shifts it to hours with off-peak and shoulder prices and resulting in a higher peak load.« less

Instrument Package Manipulation Through the Generation and Use of an Attenuated-Fluent Gas Fold

NASA Technical Reports Server (NTRS)

Breen, Daniel P.

2012-01-01

This document discusses a technique that provides a means for suspending large, awkward loads, instrument packages, components, and machinery in a stable, controlled, and precise manner. In the baseplate of the test machine, a pattern of grooves and ports is installed that when pressurized generates an attenuated- fluent gas fold providing a low-cost, near-zero-coefficient-of-friction lubrication boundary layer that supports the object evenly, and in a predictable manner. Package movement control requires minimal force. Aids to repeatable travel and positional accuracy can be added via the addition of simple guide bars and stops to the floor or object being moved. This allows easily regulated three-axis motions. Loads of extreme weight and size can be moved and guided by a single person, or by automated means, using minimal force. Upon removal of the attenuated fluent gas fold, the object returns to a stable resting position without impact forces affecting the object.

A Radiographic Comparison of Progressive and Conventional Loading on Crestal Bone Loss and Density in Single Dental Implants: A Randomized Controlled Trial Study

PubMed Central

Ghoveizi, Rahab; Alikhasi, Marzieh; Siadat, Mohammad-Reza; Siadat, Hakimeh; Sorouri, Majid

2013-01-01

Objective: Crestal bone loss is a biological complication in implant dentistry. The aim of this study was to compare the effect of progressive and conventional loading on crestal bone height and bone density around single osseointegrated implants in the posterior maxilla by a longitudinal radiographic assessment technique. Materials and Methods: Twenty micro thread implants were placed in 10 patients (two implants per patient). One of the two implants in each patient was assigned to progressive and the other to conventional loading groups. Eight weeks after surgery, conventional implants were restored with a metal ceramic crown and the progressive group underwent a progressive loading protocol. The progressive loading group took different temporary acrylic crowns at 2, 4 and 6 months. After eight months, acrylic crowns were replaced with a metal ceramic crown. Computer radiography of both progressive and conventional implants was taken at 2, 4, 6, and 12 months. Image analysis was performed to measure the height of crestal bone loss and bone density. Results: The mean values of crestal bone loss at month 12 were 0.11 (0.19) mm for progressively and 0.36 (0.36) mm for conventionally loaded implants, with a statistically significant difference (P < 0.05) using Wilcoxon sign rank. Progressively loaded group showed a trend for higher bone density gain compared to the conventionally loaded group, but when tested with repeated measure ANOVA, the differences were not statistically significant (P > 0.05). Conclusion: The progressive group showed less crestal bone loss in single osseointegrated implant than the conventional group. Bone density around progressively loaded implants showed increase in crestal, middle and apical areas. PMID:23724215

Dynamic testing of horseshoe designs at impact on synthetic and dirt Thoroughbred racetrack materials.

PubMed

Mahaffey, C A; Peterson, M L; Thomason, J J; McIlwraith, C W

2016-01-01

Different horseshoe designs have been developed in an attempt to optimise footing for equine athletes. Horseshoe performance is assumed to be dependent on the surface and gait, but there are limited data on horseshoe performance on different surfaces, independent of gait variation. To quantify the dynamic loading for 3 aluminium racing shoe designs on Thoroughbred racetrack surface materials, using a biomechanical surface tester. A flat racing plate, a serrated V-Grip and a shoe with a 6 mm toe grab and 10 mm heel calks were tested on synthetic and dirt surfaces under typical operating conditions of temperature and moisture content for the respective material samples. Samples were tested under laboratory conditions, replicating a track surface by compacting material into a latex-lined mould surrounded by silica sand for representative boundary conditions. Peak loading and loading rates were measured vertically and horizontally (craniocaudal), simulating aspects of primary and secondary impacts of the hoof in a galloping horse. Maximum vertical and shear loads and loading rates were not significantly different between shoe types, with the exception of a reduced craniocaudal loading rate for the V-Grip shoe on the synthetic surface. All other statistical significance was related to the surface material. These 3 different Thoroughbred racing shoes do not have a significant impact on loading and loading rate, with the exception of the V-Grip shoe on a synthetic surface. Although the V-Grip may reduce craniocaudal peak load rates in a synthetic material with relatively high wax and/or low oil content, the reduction in load rate is less than the difference found between materials. This study indicates that shoeing has little effect, and that a track's surface material and its preparation have a significant effect on the dynamic loading during the impact phase of the stance. © 2015 EVJ Ltd.

FIREX-Related Biomass Burning Research Using ARM Single-Particle Soot Photometer Field Campaign Report

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

Onasch, Timothy B; Sedlacek, Arthur J

The scientific focus of this study was to investigate and quantify the mass loadings, chemical compositions, and optical properties of biomass burning particulate emissions generated in the laboratory from Western U.S. fuels using a similar instrument suite to the one deployed on the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility Gulfstream-1 (G-1) aircraft during the 2013 Biomass Burning Observation Project (BBOP) field study (Kleinman and Sedlacek, 2013). We deployed the single-particle soot photometer (SP2) to make measurements of biomass burning refractory black carbon (rBC) mass loadings and size distributions to correlate with non-refractory particulate mattermore » (NR-PM; i.e., HR-AMS) and rBC (SP-AMS) measurements as a function of photo-oxidation processes in an environmental chamber. With these measurements, we will address the following scientific questions: 1. What are the emission indices (g/kg fuel) of rBC from various wildland fuels from the Pacific Northwest (i.e., relevant to BBOP analysis) as a function of combustion conditions and simulated atmospheric processing in an environmental chamber? 2. What are the optical properties (e.g., mass-specific absorption cross-section [MAC], single-scattering albedo [SSA], and absorption Angstrom exponent [AAE)] of rBC emitted from various wildland fuels and how are they impacted by atmospheric processing? 3. How does the mixing state of rBC in biomass-burning plumes relate to the optical properties? 4. How does the emitted rBC affect radiative forcing?« less

Modeling shock-driven reaction in low density PMDI foam

NASA Astrophysics Data System (ADS)

Brundage, Aaron; Alexander, C. Scott; Reinhart, William; Peterson, David

Shock experiments on low density polyurethane foams reveal evidence of reaction at low impact pressures. However, these reaction thresholds are not evident over the low pressures reported for historical Hugoniot data of highly distended polyurethane at densities below 0.1 g/cc. To fill this gap, impact data given in a companion paper for polymethylene diisocyanate (PMDI) foam with a density of 0.087 g/cc were acquired for model validation. An equation of state (EOS) was developed to predict the shock response of these highly distended materials over the full range of impact conditions representing compaction of the inert material, low-pressure decomposition, and compression of the reaction products. A tabular SESAME EOS of the reaction products was generated using the JCZS database in the TIGER equilibrium code. In particular, the Arrhenius Burn EOS, a two-state model which transitions from an unreacted to a reacted state using single step Arrhenius kinetics, as implemented in the shock physics code CTH, was modified to include a statistical distribution of states. Hence, a single EOS is presented that predicts the onset to reaction due to shock loading in PMDI-based polyurethane foams. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's NNSA under Contract DE-AC04-94AL85000.

14 CFR 23.525 - Application of loads.

Code of Federal Regulations, 2012 CFR

2012-01-01

... the loads corresponding to the load factors specified in § 23.527. (b) In applying the loads resulting from the load factors prescribed in § 23.527, the loads may be distributed over the hull or main float... on the seaplane during the impact is assumed to be 2/3 of the weight of the seaplane. [Doc. No. 26269...

14 CFR 23.525 - Application of loads.

Code of Federal Regulations, 2013 CFR

2013-01-01

... the loads corresponding to the load factors specified in § 23.527. (b) In applying the loads resulting from the load factors prescribed in § 23.527, the loads may be distributed over the hull or main float... on the seaplane during the impact is assumed to be 2/3 of the weight of the seaplane. [Doc. No. 26269...

14 CFR 23.525 - Application of loads.

Code of Federal Regulations, 2010 CFR

2010-01-01

... the loads corresponding to the load factors specified in § 23.527. (b) In applying the loads resulting from the load factors prescribed in § 23.527, the loads may be distributed over the hull or main float... on the seaplane during the impact is assumed to be 2/3 of the weight of the seaplane. [Doc. No. 26269...

14 CFR 23.525 - Application of loads.

Code of Federal Regulations, 2014 CFR

2014-01-01

... the loads corresponding to the load factors specified in § 23.527. (b) In applying the loads resulting from the load factors prescribed in § 23.527, the loads may be distributed over the hull or main float... on the seaplane during the impact is assumed to be 2/3 of the weight of the seaplane. [Doc. No. 26269...

Influence of Material Distribution on Impact Resistance of Hybrid Composites

NASA Technical Reports Server (NTRS)

Abatan, Ayu; Hu, Hurang

1998-01-01

Impact events occur in a wide variety of circumstances. A typical example is a bullet impacting a target made of composite material. These impact events produce time-varying loads on a structure that can result in damage. As a first step to understanding the damage resistance issue in composite laminates, an accurate prediction of the transient response during an impact event is necessary. The analysis of dynamic loadings on laminated composite plates has undergone considerable development recently. Rayleigh-Ritz energy method was used to determine the impact response of laminated plates. The impact response of composite plates using shear deformation plate theory was analyzed. In recent work a closed-form solution was obtained for a rectangular plate with four edges simply supported subjected to a center impact load using classical plate theory. The problem was further investigated and the analysis results compared of both classical plate theory and shear deformation theory, and found that classical plate theory predicts very accurate results for the range of small deformations considered. In this study, the influence of cross sectional material distribution on the comparative impact responses of hybrid metal laminates subjected to low and medium velocity impacts is investigated. A simple linear model to evaluate the magnitude of the impact load is proposed first, and it establishes a relation between the impact velocity and the impact force. Then a closed-form solution for impact problem is presented. The results were compared with the finite element analysis results. For an 11 layer-hybrid laminate, the impact response as a function of material distribution in cross-section is presented. With equal areal weight, the effect of the number of laminate layers on the impact resistance is also investigated. Finally, the significance of the presented results is discussed.

Lipid-load in peripheral blood mononuclear cells: Impact of food-consumption, dietary-macronutrients, extracellular lipid availability and demographic factors.

PubMed

Ameer, Fatima; Munir, Rimsha; Usman, Hina; Rashid, Rida; Shahjahan, Muhammad; Hasnain, Shahida; Zaidi, Nousheen

2017-04-01

Lipid-load in peripheral blood mononuclear cells (PBMCs) has recently gained attention of the researchers working on nutritional regulation of metabolic health. Previous works have indicated that the metabolic circuitries in the circulating PBMCs are influenced by dietary-intake and macronutrient composition of diet. In the present work, we analyzed the impact of diet and dietary macronutrients on PBMCs' lipid-load. The overall analyses revealed that dietary carbohydrates and fats combinatorially induce triglyceride accumulation in PBMCs. On the other hand, dietary fats were shown to induce significant decrease in PBMCs' cholesterol-load. The effects of various demographic factors -including age, gender and body-weight- on PBMCs' lipid-load were also examined. Body-weight and age were both shown to affect PBMC's lipid-load. Our study fails to provide any direct association between extracellular lipid availability and cholesterol-load in both, freshly isolated and cultured PBMCs. The presented work significantly contributes to the current understanding of the impact of food-consumption, dietary macronutrients, extracellular lipid availability and demographic factors on lipid-load in PBMCs. Copyright © 2017 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

Secondary orientation effects in a single crystal superalloy under mechanical and thermal loads

NASA Technical Reports Server (NTRS)

Kalluri, Sreeramesh; Abdul-Aziz, Ali; Mcgaw, Michael A.

1991-01-01

The nickel-base single crystal superalloy PWA 1480 is a candidate blading material for the advanced turbopump development program of the SSME. In order to improve thermal fatigue resistance of the turbine blades, the single crystal superalloy PWA 1480 is grown along the low modulus zone axes (001) crystal orientation by a directional solidification process. Since cubic single crystal materials such as PWA 1480 exhibit anisotropic elastic behavior, the stresses developed within the single crystal superalloy due to mechanical and thermal loads are likely to be affected by the exact orientation of the secondary crystallographic direction with respect to the geometry of the turbine blade. The effects of secondary crystal orientation on the elastic response of single crystal PWA 1480 superalloy were investigated.

The Aerodynamic and Dynamic Loading of a Slender Structure by an Impacting Tornado-Like Vortex: The Influence of Relative Vortex-to-Structure Size on Structural Loading

NASA Astrophysics Data System (ADS)

Strasser, Matthew N.

Structural loading produced by an impacting vortex is a hazardous phenomenon that is encountered in numerous applications ranging from the destruction of residences by tornados to the chopping of tip vortices by rotors. Adequate design of structures to resist vortex-induced structural loading necessitates study of the phenomenon that control the structural loading produced by an impacting vortex. This body of work extends the current knowledge base of vortex-structure interaction by evaluating the influence of the relative vortex-to-structure size on the structural loading that the vortex produces. A computer model is utilized to directly simulate the two-dimensional impact of an impinging vortex with a slender, cylindrical structure. The vortex's tangential velocity profile (TVP) is defined by a normalization of the Vatistas analytical (TVP) which realistically replicates the documented spectrum of measured vortex TVPs. The impinging vortex's maximum tangential velocity is fixed, and the vortex's critical radius is incremented from one to one-hundred times the structure's diameter. When the impinging vortex is small, it interacts with vortices produced on the structure by the free stream, and maximum force coefficient amplitudes vary by more than 400% when the impinging vortex impacts the structure at different times. Maximum drag and lift force coefficient amplitudes reach asymptotic values as the impinging vortex's size increases that are respectively 94.77% and 10.66% less than maximum force coefficients produced by an equivalent maximum velocity free stream. The vortex produces maximum structural loading when its path is shifted above the structure's centerline, and maximum drag and lift force coefficients are respectively up to 4.80% and 34.07% greater than maximum force coefficients produced by an equivalent-velocity free stream. Finally, the dynamic load factor (DLF) concept is used to develop a generalized methodology to assess the dynamic amplification of a structure's response to vortex loading and to assess the dynamic loading threat that tornados pose. Typical civil and residential structures will not experience significant response amplification, but responses of very flexible structures may be amplified by up to 2.88 times.

Effect of water temperature on cyclic fatigue properties of glass-fiber-reinforced hybrid composite resin and its fracture pattern after flexural testing.

PubMed

Kuroda, Soichi; Shinya, Akikazu; Vallittu, Pekka K; Nakasone, Yuji; Shinya, Akiyoshi

2013-02-01

To evaluate in vitro the influence of dynamic loading applied to a glass-fiber-reinforced hybrid composite resin on its flexural strength in a moist, simulated oral environment. Three-point flexural strength specimens were subjected to cyclic loading in water at 37°C and 55°C to investigate the influence of immersion temperature on impact fatigue properties. Specimens were subjected to cyclic impact loading at 1 Hz for up to 5 × 105 cycles to obtain the number of cycles to failure, the number of unbroken specimens after 5 × 105 cycles, and the residual flexural strength of unbroken specimens. Maximum loads of 100, 200, and 300 N were chosen for both the non-reinforced and the glass-fiber reinforced hybrid composite resins. The mean residual flexural strength for 100 N impact loading at temperatures of 37°C and 55°C was 634 and 636 MPa, respectively. All specimens fractured at fewer than 5 × 105 cycles for loads of 200 and 300 N. Reduced numbers of cycles to fracture and lower fatigue values were observed as both the maximum load and immersion temperature increased.

Can Exercise Positively Influence the Intervertebral Disc?

PubMed

Belavý, Daniel L; Albracht, Kirsten; Bruggemann, Gert-Peter; Vergroesen, Pieter-Paul A; van Dieën, Jaap H

2016-04-01

To better understand what kinds of sports and exercise could be beneficial for the intervertebral disc (IVD), we performed a review to synthesise the literature on IVD adaptation with loading and exercise. The state of the literature did not permit a systematic review; therefore, we performed a narrative review. The majority of the available data come from cell or whole-disc loading models and animal exercise models. However, some studies have examined the impact of specific sports on IVD degeneration in humans and acute exercise on disc size. Based on the data available in the literature, loading types that are likely beneficial to the IVD are dynamic, axial, at slow to moderate movement speeds, and of a magnitude experienced in walking and jogging. Static loading, torsional loading, flexion with compression, rapid loading, high-impact loading and explosive tasks are likely detrimental for the IVD. Reduced physical activity and disuse appear to be detrimental for the IVD. We also consider the impact of genetics and the likelihood of a 'critical period' for the effect of exercise in IVD development. The current review summarises the literature to increase awareness amongst exercise, rehabilitation and ergonomic professionals regarding IVD health and provides recommendations on future directions in research.

Behavior of single lap composite bolted joint under traction loading: Experimental investigation

NASA Astrophysics Data System (ADS)

Awadhani, L. V.; Bewoor, Anand

2018-04-01

Composite bolted joints are preferred connection in the composite structures to facilitate the dismantling for the replacements/ maintenance work. The joint behavior under tractive forces has been studied in order to understand the safety of the structure designed. The main objective of this paper is to investigate the behavior of single-lap joints in carbon fiber reinforced epoxy composites under traction loading conditions. The experiments were designed to identify the effect of bolt diameter, stacking sequence and loading rate on the properties of the joint. The experimental results show that the parameters influence the joint performance significantly.

Full Body Loading for Small Exercise Devices Project

NASA Technical Reports Server (NTRS)

Downs, Meghan; Hanson, Andrea; Newby, Nathaniel

2015-01-01

Protecting astronauts' spine, hip, and lower body musculoskeletal strength will be critical to safely and efficiently perform physically demanding vehicle egress, exploration, and habitat building activities necessary to expand human presence in the solar system. Functionally limiting decrements in musculoskeletal health are likely during Mars proving-ground and Earth-independent missions given extended transit times and the vehicle limitations for exercise devices (low-mass, small volume). Most small exercise device concepts are designed with single-cable loading, which inhibits the ability to perform full body exercises requiring two-point loading at the shoulders. Shoulder loading is critical to protect spine, hip, and lower body musculoskeletal strength. We propose a novel low-mass, low-maintenance, and rapid deploy pulley-based system that can attach to a single-cable small exercise device to enable two-point loading at the shoulders. This attachment could protect astronauts' health and save cost, space, and energy during all phases of the Journey to Mars.

The viscoelastic behavior of notched glassy polymers

NASA Technical Reports Server (NTRS)

Crook, R. A.; Letton, Alan

1993-01-01

In the bulk, glassy polymers exhibit a nonlinear viscoelastic response during deformation. Stress or strain induced damage (i.e. crazing, microshear banding) results in the production of nonrecoverable work and observed nonlinearity. Stress or strain dependent shift factors have been used to mathematically model the mechanical behavior of these polymers. Glassy polymers that have been notched, may exhibit very different load displacement response compared to the same material under bulk deformation. If a sharp notch is introduced into the body then loaded, the load displacement trace may appear to be single-valued in the absence of viscoelasticity and crack growth. This suggests the volume of damaged material is small compared to the overall dimensions of the specimen. The ability to produce a single-valued load-load-line displacement trace through the use of the Correspondence Principle may prove to be useful for fracture of viscoelastic materials.

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

Jones, David Robert; Fensin, Saryu Jindal; Dippo, Olivia

Here, we present a study on the spall strength of additive manufactured (AM) Ti-6Al-4V. Samples were obtained from two pieces of selective laser melted (SLM, a powder bed fusion technique) Ti-6Al-4V such that the response to dynamic tensile loading could be investigated as a function of the orientation between the build layers and the loading direction. A sample of wrought bar-stock Ti-6Al-4V was also tested to act as a baseline representing the traditionally manufactured material response. A single-stage light gas-gun was used to launch a thin flyer plate into the samples, generating a region of intense tensile stress on amore » plane normal to the impact direction. The rear free surface velocity time history of each sample was recorded with laser-based velocimetry to allow the spall strength to be calculated. The samples were also soft recovered to enable post-mortem characterization of the spall damage evolution. Results showed that when the tensile load was applied normal to the interfaces between the build layers caused by the SLM fabrication process the spall strength was drastically reduced, dropping to 60% of that of the wrought material. However, when loaded parallel to the AM build layer interfaces the spall strength was found to remain at 95% of the wrought control, suggesting that when loading normal to the AM layer interfaces, void nucleation is facilitated more readily due to weaknesses along these boundaries. Quasi-static testing of the same sample orientations revealed a much lower degree of anisotropy, demonstrating the importance of rate-dependent studies for damage evolution in AM materials.« less

Assessing the impact of non-tidal atmospheric loading on a Kalman filter-based terrestrial reference frame

NASA Astrophysics Data System (ADS)

Abbondanza, Claudio; Altamimi, Zuheir; Chin, Toshio; Collilieux, Xavier; Dach, Rolf; Gross, Richard; Heflin, Michael; König, Rolf; Lemoine, Frank; Macmillan, Dan; Parker, Jay; van Dam, Tonie; Wu, Xiaoping

2014-05-01

The International Terrestrial Reference Frame (ITRF) adopts a piece-wise linear model to parameterize regularized station positions and velocities. The space-geodetic (SG) solutions from VLBI, SLR, GPS and DORIS used as input in the ITRF combination process account for tidal loading deformations, but ignore the non-tidal part. As a result, the non-linear signal observed in the time series of SG-derived station positions in part reflects non-tidal loading displacements not introduced in the SG data reduction. In this analysis, we assess the impact of non-tidal atmospheric loading (NTAL) corrections on the TRF computation. Focusing on the a-posteriori approach, (i) the NTAL model derived from the National Centre for Environmental Prediction (NCEP) surface pressure is removed from the SINEX files of the SG solutions used as inputs to the TRF determinations; (ii) adopting a Kalman-filter based approach, two distinct linear TRFs are estimated combining the 4 SG solutions with (corrected TRF solution) and without the NTAL displacements (standard TRF solution). Linear fits (offset and atmospheric velocity) of the NTAL displacements removed during step (i) are estimated accounting for the station position discontinuities introduced in the SG solutions and adopting different weighting strategies. The NTAL-derived (atmospheric) velocity fields are compared to those obtained from the TRF reductions during step (ii). The consistency between the atmospheric and the TRF-derived velocity fields is examined. We show how the presence of station position discontinuities in SG solutions degrades the agreement between the velocity fields and compare the effect of different weighting structure adopted while estimating the linear fits to the NTAL displacements. Finally, we evaluate the effect of restoring the atmospheric velocities determined through the linear fits of the NTAL displacements to the single-technique linear reference frames obtained by stacking the standard SG SINEX files. Differences between the velocity fields obtained restoring the NTAL displacements and the standard stacked linear reference frames are discussed.

Recent development in the design, testing and impact-damage tolerance of stiffened composite panels

NASA Technical Reports Server (NTRS)

Williams, J. G.; Anderson, M. S.; Rhodes, M. D.; Starnes, J. H., Jr.; Stroud, W. J.

1979-01-01

Structural technology of laminated filamentary-composite stiffened-panel structures under combined inplane and lateral loadings is discussed. Attention is focused on: (1) methods for analyzing the behavior of these structures under load and for determining appropriate structural proportions for weight-efficient configurations; and (2) effects of impact damage and geometric imperfections on structural performance. Recent improvements in buckling analysis involving combined inplane compression and shear loadings and transverse shear deformations are presented. A computer code is described for proportioning or sizing laminate layers and cross-sectional dimensions, and the code is used to develop structural efficiency data for a variety of configurations, loading conditions, and constraint conditions. Experimental data on buckling of panels under inplane compression is presented. Mechanisms of impact damage initiation and propagation are described.

Single-Cycle Versus Multicycle Proof Testing

NASA Technical Reports Server (NTRS)

Hudak, S. J., Jr.; Mcclung, R. C.; Bartlett, M. L.; Fitzgerald, J. H.; Russell, D. A.

1992-01-01

Report compares single-cycle with multiple-cycle mechanical-stress tests of parts under mechanical stresses. Objective of proof testing: to screen out gross manufacturing or material deficiencies and provide additional assurance of quality. Report concludes that changes in distribution of crack sizes during multicycle proof testing depend on initial distribution, number of cycles, relationship between resistance of material and elastic/plastic fracture-mechanics parameter, relationship between load control and displacement control, and magnitude of applied load or displacement. Whether single-cycle or multicycle testing used depends on shape, material, and technique of fabrication of components tested.

Water depth effects on impact loading, kinematic and physiological variables during water treadmill running.

PubMed

Macdermid, Paul W; Wharton, Josh; Schill, Carina; Fink, Philip W

2017-07-01

The purpose of this study was to compare impact loading, kinematic and physiological responses to three different immersion depths (mid-shin, mid-thigh, and xiphoid process) while running at the same speed on a water based treadmill. Participants (N=8) ran on a water treadmill at three depths for 3min. Tri-axial accelerometers were used to identify running dynamics plus measures associated with impact loading rates, while heart rate data were logged to indicate physiological demand. Participants had greater peak impact accelerations (p<0.01), greater impact loading rates (p<0.0001), greater stride frequency (p<0.05), shorter stride length (p<0.01), and greater rate of acceleration development at toe-off (p<0.0001) for the mid-shin and mid-thigh compared to running immersed to the xiphoid process. Physiological effort determined by heart rate was also significantly less (p<0.0001) when running immersed to the xiphoid process. Water immersed treadmill running above the waistline alters kinematics of gait, reduces variables associated with impact, while decreasing physiological demand compared to depths below the waistline. Copyright © 2017 Elsevier B.V. All rights reserved.

Estimating load weights with Huber's Cubic Volume formula: a field trial.

Treesearch

Dale R. Waddell

1989-01-01

Log weights were estimated from the product of Huber's cubic volume formula and green density. Tags showing estimated log weights were attached to logs in the field, and the weights were tallied into a single load weight as logs were assembled for aerial yarding. Accuracy of the estimated load weights was evaluated by comparing the predicted with the actual load...

Stereo photo series for quantifying natural fuels. Volume XII: Post-hurricane fuels in forests of the Southeast United States.

Treesearch

Robert E. Vihnanek; Cameron S. Balog; Clinton S. Wright; Roger D. Ottmar; Jeffrey W. Kelly

2009-01-01

Two series of single and stereo photographs display a range of natural conditions and fuel loadings in post-hurricane forests in the southeastern United States. Each group of photos includes inventory information summarizing vegetation composition, structure and loading, woody material loading and density by size class, forest floor loading, and various site...

Single nucleotide polymorphisms in the bovine MHC region of Japanese Black cattle are associated with bovine leukemia virus proviral load.

PubMed

Takeshima, Shin-Nosuke; Sasaki, Shinji; Meripet, Polat; Sugimoto, Yoshikazu; Aida, Yoko

2017-04-04

Bovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis, a malignant B cell lymphoma that has spread worldwide and causes serious problems for the cattle industry. The BLV proviral load, which represents the BLV genome integrated into host genome, is a useful index for estimating disease progression and transmission risk. Here, we conducted a genome-wide association study to identify single nucleotide polymorphisms (SNPs) associated with BLV proviral load in Japanese Black cattle. The study examined 93 cattle with a high proviral load and 266 with a low proviral load. Three SNPs showed a significant association with proviral load. One SNP was detected in the CNTN3 gene on chromosome 22, and two (which were not in linkage disequilibrium) were detected in the bovine major histocompatibility complex region on chromosome 23. These results suggest that polymorphisms in the major histocompatibility complex region affect proviral load. This is the first report to detect SNPs associated with BLV proviral load in Japanese Black cattle using whole genome association study, and understanding host factors may provide important clues for controlling the spread of BLV in Japanese Black cattle.

Impact of daily supplementation of Spirulina platensis on the immune system of naïve HIV-1 patients in Cameroon: a 12-months single blind, randomized, multicenter trial.

PubMed

Ngo-Matip, Marthe-Elise; Pieme, Constant Anatole; Azabji-Kenfack, Marcel; Moukette, Bruno Moukette; Korosky, Emmanuel; Stefanini, Philippe; Ngogang, Jeanne Yonkeu; Mbofung, Carl Moses

2015-07-21

Micronutrient deficiencies occur early in Human Immunodeficiency Virus (HIV) infections they have reverse effects on the nutritional status. The diet supplementation with a natural nutraceutical rich in proteins and micronutrient like Spirulina platensis, may be effective and efficient in delaying HIV disease progression by frequently reported improvement in immune response. A prospective single-blind, randomized, multicenter study conducted on 320 HIV-1 ARV-naïve participants for 12 months. Participants received either S. platensis supplementation and standard care or standard care and local balanced diet without S. platenis. Selected hematological and biochemical as well as CD4 count cells, viral load copies were assessed at three separate times. Among the 169 ART-naïve participants enrolled in the study, the female was mostly represented (67.1%). The significant increase of CD4 count cells (596.32-614.92 cells count) and significant decrease of viral load levels (74.7 × 10(3)-30.87 × 10(3) copies/mL) of the patients who received a supplementation of S. platensis was found after 6 months of treatment. Haemoglobin level was also significantly higher in the same group while the fasting blood glucose concentration decreased after 12 months compared to control. A daily supplementation with S. platensis to diet combined with a reasonable balanced diet has significantly increased the CD4 cells and reduced the viral load after 6 months. Further studies are recommended among a large specific group of people infected by the HIV in order to investigate the mechanisms involved on the effect of S. platensis on immune system.

A conceptual framework: redefining forest soil's critical acid loads under a changing climate.

PubMed

McNulty, Steven G; Boggs, Johnny L

2010-06-01

Federal agencies of several nations have or are currently developing guidelines for critical forest soil acid loads. These guidelines are used to establish regulations designed to maintain atmospheric acid inputs below levels shown to damage forests and streams. Traditionally, when the critical soil acid load exceeds the amount of acid that the ecosystem can absorb, it is believed to potentially impair forest health. The excess over the critical soil acid load is termed the exceedance, and the larger the exceedance, the greater the risk of ecosystem damage. This definition of critical soil acid load applies to exposure of the soil to a single, long-term pollutant (i.e., acidic deposition). However, ecosystems can be simultaneously under multiple ecosystem stresses and a single critical soil acid load level may not accurately reflect ecosystem health risk when subjected to multiple, episodic environmental stress. For example, the Appalachian Mountains of western North Carolina receive some of the highest rates of acidic deposition in the eastern United States, but these levels are considered to be below the critical acid load (CAL) that would cause forest damage. However, the area experienced a moderate three-year drought from 1999 to 2002, and in 2001 red spruce (Picea rubens Sarg.) trees in the area began to die in large numbers. The initial survey indicated that the affected trees were killed by the southern pine beetle (Dendroctonus frontalis Zimm.). This insect is not normally successful at colonizing these tree species because the trees produce large amounts of oleoresin that exclude the boring beetles. Subsequent investigations revealed that long-term acid deposition may have altered red spruce forest structure and function. There is some evidence that elevated acid deposition (particularly nitrogen) reduced tree water uptake potential, oleoresin production, and caused the trees to become more susceptible to insect colonization during the drought period. While the ecosystem was not in exceedance of the CAL, long-term nitrogen deposition pre-disposed the forest to other ecological stress. In combination, insects, drought, and nitrogen ultimately combined to cause the observed forest mortality. If any one of these factors were not present, the trees would likely not have died. This paper presents a conceptual framework of the ecosystem consequences of these interactions as well as limited plot level data to support this concept. Future assessments of the use of CAL studies need to account for multiple stress impacts to better understand ecosystem response. Published by Elsevier Ltd.

The impacts of aerosol loading, composition, and water uptake on aerosol extinction variability in the Baltimore-Washington, D.C. region

NASA Astrophysics Data System (ADS)

Beyersdorf, A. J.; Ziemba, L. D.; Chen, G.; Corr, C. A.; Crawford, J. H.; Diskin, G. S.; Moore, R. H.; Thornhill, K. L.; Winstead, E. L.; Anderson, B. E.

2016-01-01

In order to utilize satellite-based aerosol measurements for the determination of air quality, the relationship between aerosol optical properties (wavelength-dependent, column-integrated extinction measured by satellites) and mass measurements of aerosol loading (PM2.5 used for air quality monitoring) must be understood. This connection varies with many factors including those specific to the aerosol type - such as composition, size, and hygroscopicity - and to the surrounding atmosphere, such as temperature, relative humidity (RH), and altitude, all of which can vary spatially and temporally. During the DISCOVER-AQ (Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality) project, extensive in situ atmospheric profiling in the Baltimore, MD-Washington, D.C. region was performed during 14 flights in July 2011. Identical flight plans and profile locations throughout the project provide meaningful statistics for determining the variability in and correlations between aerosol loading, composition, optical properties, and meteorological conditions. Measured water-soluble aerosol mass was composed primarily of ammonium sulfate (campaign average of 32 %) and organics (57 %). A distinct difference in composition was observed, with high-loading days having a proportionally larger percentage of sulfate due to transport from the Ohio River Valley. This composition shift caused a change in the aerosol water-uptake potential (hygroscopicity) such that higher relative contributions of inorganics increased the bulk aerosol hygroscopicity. These days also tended to have higher relative humidity, causing an increase in the water content of the aerosol. Conversely, low-aerosol-loading days had lower sulfate and higher black carbon contributions, causing lower single-scattering albedos (SSAs). The average black carbon concentrations were 240 ng m-3 in the lowest 1 km, decreasing to 35 ng m-3 in the free troposphere (above 3 km). Routine airborne sampling over six locations was used to evaluate the relative contributions of aerosol loading, composition, and relative humidity (the amount of water available for uptake onto aerosols) to variability in mixed-layer aerosol extinction. Aerosol loading (dry extinction) was found to be the predominant source, accounting for 88 % on average of the measured spatial variability in ambient extinction, with lesser contributions from variability in relative humidity (10 %) and aerosol composition (1.3 %). On average, changes in aerosol loading also caused 82 % of the diurnal variability in ambient aerosol extinction. However on days with relative humidity above 60 %, variability in RH was found to cause up to 62 % of the spatial variability and 95 % of the diurnal variability in ambient extinction. This work shows that extinction is driven to first order by aerosol mass loadings; however, humidity-driven hydration effects play an important secondary role. This motivates combined satellite-modeling assimilation products that are able to capture these components of the aerosol optical depth (AOD)-PM2.5 link. Conversely, aerosol hygroscopicity and SSA play a minor role in driving variations both spatially and throughout the day in aerosol extinction and therefore AOD. However, changes in aerosol hygroscopicity from day to day were large and could cause a bias of up to 27 % if not accounted for. Thus it appears that a single daily measurement of aerosol hygroscopicity can be used for AOD-to-PM2.5 conversions over the study region (on the order of 1400 km2). This is complimentary to the results of Chu et al. (2015), who determined that the aerosol vertical distribution from "a single lidar is feasible to cover the range of 100 km" in the same region.

Experimental Results From Stitched Composite Multi-Bay Fuselage Panels Tested Under Uni-Axial Compression

NASA Technical Reports Server (NTRS)

Baker, Donald J.

2004-01-01

The experimental results from two stitched VARTM composite panels tested under uni-axial compression loading are presented. The curved panels are divided by frames and stringers into five or six bays with a column of three bays along the compressive loading direction. The frames are supported at the ends to resist out-of-plane translation. Back-to-back strain gages are used to record the strain and displacement transducers were used to record the out-of-plane displacements. In addition a full-field measurement technique that utilizes a camera-based-stero-vision system was used to record displacements. The panels were loaded in increments to determine the first bay to buckle. Loading was discontinued at limit load and the panels were removed from the test machine for impact testing. After impacting at 20 ft-lbs to 25 ft-lbs of energy with a spherical indenter, the panels were loaded in compression until failure. Impact testing reduced the axial stiffness 4 percent and less than 1 percent. Postbuckled axial panel stiffness was 52 percent and 70 percent of the pre-buckled stiffness.

Impact of vocal load on breathiness: perceptual evaluation.

PubMed

Remacle, Angélique; Schoentgen, Jean; Finck, Camille; Bodson, Agnès; Morsomme, Dominique

2014-10-01

To evaluate the impact on voice of 2 hours of continuous oral reading. Fifty normophonic women underwent two sessions of voice loading in which the required intensity level varied: 60-65 dB(A) for the first session, and 70-75 dB(A) for the second session. Ten expert judges evaluated the breathiness of one sentence recorded before and after each loading session. Pairs of stimuli were presented randomly to the judges, who were asked to designate the breathiest sample. A significant decrease in breathiness was observed following both sessions, suggesting an improvement of voice subsequent to loading. When comparing the two intensity levels, no difference was found for breathiness after vocal loading.

Multi-scale Modeling of the Impact Response of a Strain Rate Sensitive High-Manganese Austenitic Steel

NASA Astrophysics Data System (ADS)

Önal, Orkun; Ozmenci, Cemre; Canadinc, Demircan

2014-09-01

A multi-scale modeling approach was applied to predict the impact response of a strain rate sensitive high-manganese austenitic steel. The roles of texture, geometry and strain rate sensitivity were successfully taken into account all at once by coupling crystal plasticity and finite element (FE) analysis. Specifically, crystal plasticity was utilized to obtain the multi-axial flow rule at different strain rates based on the experimental deformation response under uniaxial tensile loading. The equivalent stress - equivalent strain response was then incorporated into the FE model for the sake of a more representative hardening rule under impact loading. The current results demonstrate that reliable predictions can be obtained by proper coupling of crystal plasticity and FE analysis even if the experimental flow rule of the material is acquired under uniaxial loading and at moderate strain rates that are significantly slower than those attained during impact loading. Furthermore, the current findings also demonstrate the need for an experiment-based multi-scale modeling approach for the sake of reliable predictions of the impact response.

PVDF Gauge Piezoelectric Response under Two-Stage Light Gas Gun Impact Loading

NASA Astrophysics Data System (ADS)

Bauer, Francois

2002-07-01

Stress gauges based on ferroelectric polymer (PVDF) studies under very high pressure shock compression have shown that the piezoelectric response exhibits a precise reproducible behavior up to 25 GPa. Shock pressure profiles obtained with "in situ" PVDF gauges in porous H.E. (Formex) in a detonation regime have been achieved. Observations of a fast superpressure of a few nanoseconds followed by a pressure release have raised the question of the loading path dependence of the piezoelectric response of PVDF at high shock pressure levels. Consequently, studies of the piezoelectric behavior of PVDF gauges under impact loading using a two-stage light gas gun have been conducted recently. Symmetric impact as well as non symmetric impact and reverse impact techniques have been achieved. Strong viscoplastic behavior of some materials is observed. In typical experiments, the piezoelectric response of PVDF at shock equilibrium could be determined. These results show that the PVDF response appears independent of the loading path up to 30 GPa. Accurate measurements in situ H.E. are also reported with very low inductance PVDF gauges.

Nonlinear system identification of smart structures under high impact loads

NASA Astrophysics Data System (ADS)

Sarp Arsava, Kemal; Kim, Yeesock; El-Korchi, Tahar; Park, Hyo Seon

2013-05-01

The main purpose of this paper is to develop numerical models for the prediction and analysis of the highly nonlinear behavior of integrated structure control systems subjected to high impact loading. A time-delayed adaptive neuro-fuzzy inference system (TANFIS) is proposed for modeling of the complex nonlinear behavior of smart structures equipped with magnetorheological (MR) dampers under high impact forces. Experimental studies are performed to generate sets of input and output data for training and validation of the TANFIS models. The high impact load and current signals are used as the input disturbance and control signals while the displacement and acceleration responses from the structure-MR damper system are used as the output signals. The benchmark adaptive neuro-fuzzy inference system (ANFIS) is used as a baseline. Comparisons of the trained TANFIS models with experimental results demonstrate that the TANFIS modeling framework is an effective way to capture nonlinear behavior of integrated structure-MR damper systems under high impact loading. In addition, the performance of the TANFIS model is much better than that of ANFIS in both the training and the validation processes.

Vertical accelerator device to apply loads simulating blast environments in the military to human surrogates.

PubMed

Yoganandan, Narayan; Pintar, Frank A; Schlick, Michael; Humm, John R; Voo, Liming; Merkle, Andrew; Kleinberger, Michael

2015-09-18

The objective of the study was to develop a simple device, Vertical accelerator (Vertac), to apply vertical impact loads to Post Mortem Human Subject (PMHS) or dummy surrogates because injuries sustained in military conflicts are associated with this vector; example, under-body blasts from explosive devices/events. The two-part mechanically controlled device consisted of load-application and load-receiving sections connected by a lever arm. The former section incorporated a falling weight to impact one end of the lever arm inducing a reaction at the other/load-receiving end. The "launch-plate" on this end of the arm applied the vertical impact load/acceleration pulse under different initial conditions to biological/physical surrogates, attached to second section. It is possible to induce different acceleration pulses by using varying energy absorbing materials and controlling drop height and weight. The second section of Vertac had the flexibility to accommodate different body regions for vertical loading experiments. The device is simple and inexpensive. It has the ability to control pulses and flexibility to accommodate different sub-systems/components of human surrogates. It has the capability to incorporate preloads and military personal protective equipment (e.g., combat helmet). It can simulate vehicle roofs. The device allows for intermittent specimen evaluations (x-ray and palpation, without changing specimen alignment). The two free but interconnected sections can be used to advance safety to military personnel. Examples demonstrating feasibilities of the Vertac device to apply vertical impact accelerations using PMHS head-neck preparations with helmet and booted Hybrid III dummy lower leg preparations under in-contact and launch-type impact experiments are presented. Published by Elsevier Ltd.

Recent advances in vibro-impact dynamics and collision of ocean vessels

NASA Astrophysics Data System (ADS)

Ibrahim, Raouf A.

2014-11-01

The treatment of ship impacts and collisions takes different approaches depending on the emphasis of each discipline. For example, dynamicists, physicist, and mathematicians are dealing with developing analytical models and mappings of vibro-impact systems. On the other hand, naval architects and ship designers are interested in developing design codes and structural assessments due to slamming loads, liquid sloshing impact loads in liquefied natural gas tanks and ship grounding accidents. The purpose of this review is to highlight the main differences of the two disciplines. It begins with a brief account of the theory of vibro-impact dynamics based on modeling and mapping of systems experiencing discontinuous changes in their state of motion due to collision. The main techniques used in modeling include power-law phenomenological modeling, Hertzian modeling, and non-smooth coordinate transformations originally developed by Zhuravlev and Ivanov. In view of their effectiveness, both Zhuravlev and Ivanov non-smooth coordinate transformations will be described and assessed for the case of ship roll dynamics experiencing impact with rigid barriers. These transformations have the advantage of converting the vibro-impact oscillator into an oscillator without barriers such that the corresponding equation of motion does not contain any impact term. One of the recent results dealing with the coefficient of restitution is that its value monotonically decreases with the impact velocity and not unique but random in nature. Slamming loads and grounding events of ocean waves acting on the bottom of high speed vessels will be assessed with reference to the ship structural damage. It will be noticed that naval architects and marine engineers are treating these problems using different approaches from those used by dynamicists. The problem of sloshing impact in liquefied natural gas cargo and related problems will be assessed based on the numerical and experimental results. It is important for vessel designers to determine the capacity of ships to resist random slamming loads, sloshing loading impact, grounding accidents and ships collisions.

Dynamic fragmentation of cellular, ice-templated alumina scaffolds

DOE PAGES

Tan, Yi Ming; Cervantes, Octavio; Nam, SeanWoo; ...

2016-01-08

Here, we examine the dynamic failure of ice-templated freeze-cast alumina scaffolds that are being considered as biomimetic hierarchical structures. Three porosities of alumina freeze-cast structures were fabricated, and a systematic variation in microstructural properties such as lamellar width and thickness was observed with changing porosity. Dynamic impact tests were performed in a light-gas gun to examine the failure properties of these materials under high strain-rate loading. Nearly complete delamination was observed following impact, along with characteristic cracking across the lamellar width. Average fragment size decreases with increasing porosity, and a theoretical model was developed to explain this behavior based onmore » microstructural changes. Using an energy balance between kinetic, strain, and surface energies within a single lamella, we are able to accurately predict the characteristic fragment size using only standard material properties of bulk alumina.« less

Identification of Defects in Piles Through Dynamic Testing

NASA Astrophysics Data System (ADS)

Liao, Shutao T.; Roesset, Jose M.

1997-04-01

The objective of this work was to evaluate the theoretical capabilities of the non-destructive impact-response method in detecting the existence of a single defect in a pile, its location and its length. The cross-section of the pile is assumed to be circular and the defects are assumed to be axisymmetric in geometry. As mentioned in the companion paper, special codes utilizing one-dimensional (1-D) and three-dimensional (3-D) axisymmetric finite element models were developed to simulate the responses of defective piles to an impact load. Extensive parametric studies were then performed. In each study, the results from the direct use of time histories of displacements or velocities and the mechanical admittance (or mobility) function were compared in order to assess their capabilities. The effects of the length and the width of a defect were also investigated using these methods. Int. J. Numer. Anal. Meth. Geomech., vol. 21, 277-291 (1997)

Alkaline peroxide pretreatment of corn stover: effects of biomass, peroxide, and enzyme loading and composition on yields of glucose and xylose

PubMed Central

2011-01-01

Background Pretreatment is a critical step in the conversion of lignocellulose to fermentable sugars. Although many pretreatment processes are currently under investigation, none of them are entirely satisfactory in regard to effectiveness, cost, or environmental impact. The use of hydrogen peroxide at pH 11.5 (alkaline hydrogen peroxide (AHP)) was shown by Gould and coworkers to be an effective pretreatment of grass stovers and other plant materials in the context of animal nutrition and ethanol production. Our earlier experiments indicated that AHP performed well when compared against two other alkaline pretreatments. Here, we explored several key parameters to test the potential of AHP for further improvement relevant to lignocellulosic ethanol production. Results The effects of biomass loading, hydrogen peroxide loading, residence time, and pH control were tested in combination with subsequent digestion with a commercial enzyme preparation, optimized mixtures of four commercial enzymes, or optimized synthetic mixtures of pure enzymes. AHP pretreatment was performed at room temperature (23°C) and atmospheric pressure, and after AHP pretreatment the biomass was neutralized with HCl but not washed before enzyme digestion. Standard enzyme digestion conditions were 0.2% glucan loading, 15 mg protein/g glucan, and 48 h digestion at 50°C. Higher pretreatment biomass loadings (10% to 20%) gave higher monomeric glucose (Glc) and xylose (Xyl) yields than the 2% loading used in earlier studies. An H2O2 loading of 0.25 g/g biomass was almost as effective as 0.5 g/g, but 0.125 g/g was significantly less effective. Optimized mixtures of four commercial enzymes substantially increased post-AHP-pretreatment enzymatic hydrolysis yields at all H2O2 concentrations compared to any single commercial enzyme. At a pretreatment biomass loading of 10% and an H2O2 loading of 0.5 g/g biomass, an optimized commercial mixture at total protein loadings of 8 or 15 mg/g glucan gave monomeric Glc yields of 83% or 95%, respectively. Yields of Glc and Xyl after pretreatment at a low hydrogen peroxide loading (0.125 g H2O2/g biomass) could be improved by extending the pretreatment residence time to 48 h and readjusting the pH to 11.5 every 6 h during the pretreatment. A Glc yield of 77% was obtained using a pretreatment of 15% biomass loading, 0.125 g H2O2/g biomass, and 48 h with pH adjustment, followed by digestion with an optimized commercial enzyme mixture at an enzyme loading of 15 mg protein/g glucan. Conclusions Alkaline peroxide is an effective pretreatment for corn stover. Particular advantages are the use of reagents with low environmental impact and avoidance of special reaction chambers. Reasonable yields of monomeric Glc can be obtained at an H2O2 concentration one-quarter of that used in previous AHP research. Additional improvements in the AHP process, such as peroxide stabilization, peroxide recycling, and improved pH control, could lead to further improvements in AHP pretreatment. PMID:21658263

The dynamic behavior of mortar under impact-loading

NASA Astrophysics Data System (ADS)

Kawai, Nobuaki; Inoue, Kenji; Misawa, Satoshi; Tanaka, Kyoji; Hayashi, Shizuo; Kondo, Ken-Ichi; Riedel, Werner

2007-06-01

Concrete and mortar are the most fundamental structural material. Therefore, considerable interest in characterizing the dynamic behavior of them under impact-loading exists. In this study, plate impact experiments have been performed to determine the dynamic behavior of mortar. Longitudinal and lateral stresses have been directly measured by means of embedded polyvinylidene fluoride (PVDF) gauges up to 1 GPa. A 200 mm-cal. powder gun enable us to measure longitudinal and lateral stresses at several point from the impact surface, simultaneously. The shear strength under impact-loading has been obtained from measured longitudinal and lateral stresses. The longitudinal stress profile shows a two-wave structure. It is indicated that this structure is associated with the onset of pore compaction and failure of mortar by comparing with hydrocode simulations using an elastic-plastic damage model for concrete.

Dynamic Response of Acrylonitrile Butadiene Styrene Under Impact Loading (Open Access)

DTIC Science & Technology

2016-03-16

of contraction and expansion was observed as the impact load was applied. Thismultistage deformation behavior may be attributable to the ring formed ...ABS fabricated by FDM. Results of the experimental characterization show that rasters formed parallel to the loading direction fabricated in the... formed using a solid ABS block to determine the mechanical property at various strain rates (Fig. 1). Through the analysis of the solid ABS, a linear

Mechanical competence of ovariectomy-induced compromised bone after single or combined treatment with high-frequency loading and bisphosphonates

PubMed Central

Camargos G. V.; Bhattacharya P.; van Lenthe G. H.; Del Bel Cury A. A.; Naert I.; Duyck J.; Vandamme K.

2015-01-01

Osteoporosis leads to increased bone fragility, thus effective approaches enhancing bone strength are needed. Hence, this study investigated the effect of single or combined application of high-frequency (HF) loading through whole body vibration (WBV) and alendronate (ALN) on the mechanical competence of ovariectomy-induced osteoporotic bone. Thirty-four female Wistar rats were ovariectomized (OVX) or sham-operated (shOVX) and divided into five groups: shOVX, OVX-shWBV, OVX-WBV, ALN-shWBV and ALN-WBV. (Sham)WBV loading was applied for 10 min/day (130 to 150 Hz at 0.3g) for 14 days and ALN at 2 mg/kg/dose was administered 3x/week. Finite element analysis based on micro-CT was employed to assess bone biomechanical properties, relative to bone micro-structural parameters. HF loading application to OVX resulted in an enlarged cortex, but it was not able to improve the biomechanical properties. ALN prevented trabecular bone deterioration and increased bone stiffness and bone strength of OVX bone. Finally, the combination of ALN with HF resulted in an increased cortical thickness in OVX rats when compared to single treatments. Compared to HF loading, ALN treatment is preferred for improving the compromised mechanical competence of OVX bone. In addition, the association of ALN with HF loading results in an additive effect on the cortical thickness. PMID:26027958

Macroscopic inhomogeneous deformation behavior arising in single crystal Ni-Mn-Ga foils under tensile loading

NASA Astrophysics Data System (ADS)

Murasawa, Go; Yeduru, Srinivasa R.; Kohl, Manfred

2016-12-01

This study investigated macroscopic inhomogeneous deformation occurring in single-crystal Ni-Mn-Ga foils under uniaxial tensile loading. Two types of single-crystal Ni-Mn-Ga foil samples were examined as-received and after thermo-mechanical training. Local strain and the strain field were measured under tensile loading using laser speckle and digital image correlation. The as-received sample showed a strongly inhomogeneous strain field with intermittence under progressive deformation, but the trained sample result showed strain field homogeneity throughout the specimen surface. The as-received sample is a mainly polycrystalline-like state composed of the domain structure. The sample contains many domain boundaries and large domain structures in the body. Its structure would cause large local strain band nucleation with intermittence. However, the trained one is an ideal single-crystalline state with a transformation preferential orientation of variants after almost all domain boundary and large domain structures vanish during thermo-mechanical training. As a result, macroscopic homogeneous deformation occurs on the trained sample surface during deformation.

In-vitro development of a temporal abutment screw to protect osseointegration in immediate loaded implants.

PubMed

García-Roncero, Herminio; Caballé-Serrano, Jordi; Cano-Batalla, Jordi; Cabratosa-Termes, Josep; Figueras-Álvarez, Oscar

2015-04-01

In this study, a temporal abutment fixation screw, designed to fracture in a controlled way upon application of an occlusal force sufficient to produce critical micromotion was developed. The purpose of the screw was to protect the osseointegration of immediate loaded single implants. Seven different screw prototypes were examined by fixing titanium abutments to 112 Mozo-Grau external hexagon implants (MG Osseous®; Mozo-Grau, S.A., Valladolid, Spain). Fracture strength was tested at 30° in two subgroups per screw: one under dynamic loading and the other without prior dynamic loading. Dynamic loading was performed in a single-axis chewing simulator using 150,000 load cycles at 50 N. After normal distribution of obtained data was verified by Kolmogorov-Smirnov test, fracture resistance between samples submitted and not submitted to dynamic loading was compared by the use of Student's t-test. Comparison of fracture resistance among different screw designs was performed by the use of one-way analysis of variance. Confidence interval was set at 95%. Fractures occurred in all screws, allowing easy retrieval. Screw Prototypes 2, 5 and 6 failed during dynamic loading and exhibited statistically significant differences from the other prototypes. Prototypes 2, 5 and 6 may offer a useful protective mechanism during occlusal overload in immediate loaded implants.

Covalent and non-covalent curcumin loading in acid-responsive polymeric micellar nanocarriers

NASA Astrophysics Data System (ADS)

Gao, Min; Chen, Chao; Fan, Aiping; Zhang, Ju; Kong, Deling; Wang, Zheng; Zhao, Yanjun

2015-07-01

Poor aqueous solubility, potential degradation, rapid metabolism and elimination lead to low bioavailability of pleiotropic impotent curcumin. Herein, we report two types of acid-responsive polymeric micelles where curcumin was encapsulated via both covalent and non-covalent modes for enhanced loading capacity and on-demand release. Biodegradable methoxy poly(ethylene glycol)-poly(lactic acid) copolymer (mPEG-PLA) was conjugated with curcumin via a hydrazone linker, generating two conjugates differing in architecture (single-tail versus double-tail) and free curcumin was encapsulated therein. The two micelles exhibited similar hydrodynamic size at 95 ± 3 nm (single-tail) and 96 ± 3 nm (double-tail), but their loading capacities differed significantly at 15.0 ± 0.5% (w/w) (single-tail) and 4.8 ± 0.5% (w/w) (double-tail). Under acidic sink conditions (pH 5.0 and 6.0), curcumin displayed a faster release from the single-tail nanocarrier, which was correlated to a low IC50 of 14.7 ± 1.6 (μg mL-1) compared to the value of double-tail micelle (24.9 ± 1.3 μg mL-1) in HeLa cells. The confocal imaging and flow cytometry analysis demonstrated a superior capability of single-tail micelle for intracellular curcumin delivery, which was a consequence of the higher loading capacity and lower degree of mPEG surface coverage. In conclusion, the dual loading mode is an effective means to increase the drug content in the micellar nanocarriers whose delivery efficiency is highly dependent on its polymer-drug conjugate architecture. This strategy offers an alternative nanoplatform for intracellularly delivering impotent hydrophobic agents (i.e. curcumin) in an efficient stimuli-triggered way, which is valuable for the enhancement of curcumin’s efficacy in managing a diverse range of disorders.

Effect of low-velocity or ballistic impact damage on the strength of thin composite and aluminum shear panels

NASA Technical Reports Server (NTRS)

Farley, G. L.

1985-01-01

Impact tests were conducted on shear panels fabricated from 6061-T6 aluminum and from woven fabric prepreg of Du Pont Kevlara fiber/epoxy resin and graphite fiber/epoxy resin. The shear panels consisted of three different composite laminates and one aluminum material configuration. Three panel aspect ratios were evaluated for each material configuration. Composite panels were impacted with a 1.27-cm (0.05-in) diameter aluminum sphere at low velocities of 46 m/sec (150 ft/sec) and 67 m/sec (220 ft/sec). Ballistic impact conditions consisted of a tumbled 0.50-caliber projectile impacting loaded composite and aluminum shear panels. The results of these tests indicate that ballistic threshold load (the lowest load which will result in immediate failure upon penetration by the projectile) varied between 0.44 and 0.61 of the average failure load of undamaged panels. The residual strengths of the panels after ballistic impact varied between 0.55 and 0.75 of the average failure strength of the undamaged panels. The low velocity impacts at 67 m/sec (220 ft/sec) caused a 15 to 20 percent reduction in strength, whereas the impacts at 46 m/sec (150 ft/sec) resulted in negligible strength loss. Good agreement was obtained between the experimental failure strengths and the predicted strength with the point stress failure criterion.

Load relaxation of olivine single crystals

NASA Astrophysics Data System (ADS)

Cooper, Reid F.; Stone, Donald S.; Plookphol, Thawatchai

2016-10-01

Single crystals of ferromagnesian olivine (San Carlos, AZ, peridot; Fo88-90) have been deformed in both uniaxial creep and load relaxation under conditions of ambient pressure, T = 1500°C and pO2 = 10-10 atm; creep stresses were in the range 40 ≤ σ1 (MPa) ≤ 220. The crystals were oriented such that the applied stress was parallel to [011]c, which promotes single slip on the slowest slip system in olivine, (010)[001]. The creep rates at steady state match well the results of earlier investigators, as does the stress sensitivity (a power law exponent of n = 3.6). Dislocation microstructures, including spatial distribution of low-angle (subgrain) boundaries, additionally confirm previous investigations. Inverted primary creep (an accelerating strain rate with an increase in stress) was observed. Load relaxation, however, produced a singular response—a single hardness curve—regardless of the magnitude of creep stress or total accumulated strain preceding relaxation. The log stress versus log strain rate data from load-relaxation and creep experiments overlap to within experimental error. The load-relaxation behavior is distinctly different than that described for other crystalline solids, where the flow stress is affected strongly by work hardening such that a family of distinct hardness curves is generated, which are related by a scaling function. The response of olivine for the conditions studied, we argue, indicates flow that is rate limited by dislocation glide, reflecting specifically a high intrinsic lattice resistance (Peierls stress).

Load Relaxation of Olivine Single Crystals

NASA Astrophysics Data System (ADS)

Cooper, R. F.; Stone, D. S.; Plookphol, T.

2016-12-01

Single crystals of ferromagnesian olivine (San Carlos, AZ, peridot; Fo90-92) have been deformed in both uniaxial creep and load relaxation under conditions of ambient pressure, T = 1500ºC and pO2 = 10-10 atm; creep stresses were in the range 40 ≤ σ1 (MPa) ≤ 220. The crystals were oriented such that the applied stress was parallel to [011]c, which promotes single slip on the slowest slip system in olivine, (010)[001]. The creep rates at steady state match well the results of earlier investigators, as does the stress sensitivity (a power-law exponent of n = 3.6). Dislocation microstructures, including spatial distribution of low-angle (subgrain) boundaries, additionally confirm previous investigations. Inverted primary creep (an accelerating strain rate with an increase in stress) was observed. Load-relaxation, however, produced a singular response—a single hardness curve—regardless of the magnitude of creep stress or total accumulated strain preceding relaxation. The log-stress v. log-strain rate data from load-relaxation and creep experiments overlap to within experimental error. The load-relaxation behavior is distinctly different that that described for other crystalline solids, where the flow stress is affected strongly by work hardening such that a family of distinct hardness curves is generated, which are related by a scaling function. The response of olivine for the conditions studied, thus, indicates flow that is rate-limited by dislocation glide, reflecting specifically a high intrinsic lattice resistance (Peierls stress).

Impact of increasing freight loads on rail substructure from fracking sand transportation.

DOT National Transportation Integrated Search

2014-03-01

In this report the effect of surface infiltration of frac sand and heavy axle loads (HALs) were studied for their impact on the ballast layer. : Different combinations of ballast and fracking sand were constructed to observe long term trends of defor...

14 CFR 23.613 - Material strength properties and design values.

Code of Federal Regulations, 2011 CFR

2011-01-01

...: (1) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component; 99 percent probability... would result in applied loads being safely distributed to other load carrying members; 90 percent...

14 CFR 23.613 - Material strength properties and design values.

Code of Federal Regulations, 2012 CFR

2012-01-01

...: (1) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component; 99 percent probability... would result in applied loads being safely distributed to other load carrying members; 90 percent...

14 CFR 23.613 - Material strength properties and design values.

Code of Federal Regulations, 2013 CFR

2013-01-01

...: (1) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component; 99 percent probability... would result in applied loads being safely distributed to other load carrying members; 90 percent...

14 CFR 25.613 - Material strength properties and material design values.

Code of Federal Regulations, 2011 CFR

2011-01-01

... following probability: (1) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent... elements would result in applied loads being safely distributed to other load carrying members, 90 percent...

10 CFR 434.201 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... includes any non-heating season pilot input loss. Area of the space (A): the horizontal lighted area of a... doors of a building. Integrated part-load value (IPLV): a single-number figure of merit based on part-load EER or COP expressing part-load efficiency for air-conditioning and heat pump equipment on the...

14 CFR 27.613 - Material strength properties and design values.

Code of Federal Regulations, 2013 CFR

2013-01-01

...) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent probability with... elements would result in applied loads being safely distributed to other load-carrying members, 90 percent...

14 CFR 23.613 - Material strength properties and design values.

Code of Federal Regulations, 2014 CFR

2014-01-01

...: (1) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component; 99 percent probability... would result in applied loads being safely distributed to other load carrying members; 90 percent...

14 CFR 25.613 - Material strength properties and material design values.

Code of Federal Regulations, 2014 CFR

2014-01-01

... following probability: (1) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent... elements would result in applied loads being safely distributed to other load carrying members, 90 percent...

14 CFR 29.613 - Material strength properties and design values.

Code of Federal Regulations, 2014 CFR

2014-01-01

...) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent probability with... elements would result in applied loads being safely distributed to other load-carrying members, 90 percent...

14 CFR 25.613 - Material strength properties and material design values.

Code of Federal Regulations, 2012 CFR

2012-01-01

... following probability: (1) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent... elements would result in applied loads being safely distributed to other load carrying members, 90 percent...

14 CFR 27.613 - Material strength properties and design values.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent probability with... elements would result in applied loads being safely distributed to other load-carrying members, 90 percent...

14 CFR 25.613 - Material strength properties and material design values.

Code of Federal Regulations, 2010 CFR

2010-01-01

... following probability: (1) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent... elements would result in applied loads being safely distributed to other load carrying members, 90 percent...

14 CFR 29.613 - Material strength properties and design values.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent probability with... elements would result in applied loads being safely distributed to other load-carrying members, 90 percent...

14 CFR 27.613 - Material strength properties and design values.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent probability with... elements would result in applied loads being safely distributed to other load-carrying members, 90 percent...

14 CFR 27.613 - Material strength properties and design values.

Code of Federal Regulations, 2012 CFR

2012-01-01

...) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent probability with... elements would result in applied loads being safely distributed to other load-carrying members, 90 percent...

14 CFR 25.613 - Material strength properties and material design values.

Code of Federal Regulations, 2013 CFR

2013-01-01

... following probability: (1) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent... elements would result in applied loads being safely distributed to other load carrying members, 90 percent...

14 CFR 23.613 - Material strength properties and design values.

Code of Federal Regulations, 2010 CFR

2010-01-01

...: (1) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component; 99 percent probability... would result in applied loads being safely distributed to other load carrying members; 90 percent...

14 CFR 27.613 - Material strength properties and design values.

Code of Federal Regulations, 2014 CFR

2014-01-01

...) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent probability with... elements would result in applied loads being safely distributed to other load-carrying members, 90 percent...

14 CFR 29.613 - Material strength properties and design values.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent probability with... elements would result in applied loads being safely distributed to other load-carrying members, 90 percent...

14 CFR 29.613 - Material strength properties and design values.

Code of Federal Regulations, 2013 CFR

2013-01-01

...) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent probability with... elements would result in applied loads being safely distributed to other load-carrying members, 90 percent...

14 CFR 29.613 - Material strength properties and design values.

Code of Federal Regulations, 2012 CFR

2012-01-01

...) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99 percent probability with... elements would result in applied loads being safely distributed to other load-carrying members, 90 percent...

Prediction of load threshold of fibre-reinforced laminated composite panels subjected to low velocity drop-weight impact using efficient data filtering techniques

NASA Astrophysics Data System (ADS)

Farooq, Umar; Myler, Peter

This work is concerned with physical testing of carbon fibrous laminated composite panels with low velocity drop-weight impacts from flat and round nose impactors. Eight, sixteen, and twenty-four ply panels were considered. Non-destructive damage inspections of tested specimens were conducted to approximate impact-induced damage. Recorded data were correlated to load-time, load-deflection, and energy-time history plots to interpret impact induced damage. Data filtering techniques were also applied to the noisy data that unavoidably generate due to limitations of testing and logging systems. Built-in, statistical, and numerical filters effectively predicted load thresholds for eight and sixteen ply laminates. However, flat nose impact of twenty-four ply laminates produced clipped data that can only be de-noised involving oscillatory algorithms. Data filtering and extrapolation of such data have received rare attention in the literature that needs to be investigated. The present work demonstrated filtering and extrapolation of the clipped data using Fast Fourier Convolution algorithm to predict load thresholds. Selected results were compared to the damage zones identified with C-scan and acceptable agreements have been observed. Based on the results it is proposed that use of advanced data filtering and analysis methods to data collected by the available resources has effectively enhanced data interpretations without resorting to additional resources. The methodology could be useful for efficient and reliable data analysis and impact-induced damage prediction of similar cases' data.

Effects of Backpack Carriage on Dual-Task Performance in Children During Standing and Walking.

PubMed

Beurskens, Rainer; Muehlbauer, Thomas; Grabow, Lena; Kliegl, Reinhold; Granacher, Urs

2016-01-01

Primary school children perform parts of their everyday activities while carrying school supplies and being involved in attention-demanding situations. Twenty-eight children (8-10 years old) performed a 1-legged stance and a 10 m walking test under single- and dual-task situations in unloaded (i.e., no backpack) and loaded conditions (i.e., backpack with 20% of body mass). Results showed that load carriage did not significantly influence children's standing and walking performance (all p > .05), while divided attention affected all proxies of walking (all p < .001). Last, no significant load by attention interactions was detected. The single application of attentional but not load demand negatively affects children's walking performance. A combined application of both did not further deteriorate their gait behavior.

Single Event Effects and Total Dose Testing of the Intersil ISL 70003SEH Integrated Point of Load Converter

NASA Astrophysics Data System (ADS)

van Vonno, N. W.; White, J. D.; Pearce, L. G.; Thomson, E. J.; Gill, J. S.; Mansilla, O. E.

2014-08-01

Single-event transient (SET) phenomena in power management applications has evolved into a key issue, particularly in point of load (POL) buck regulators, as the loads driven by these devices are sensitive to even short-term overvoltage conditions. We preface this paper by a discussion of earlier destructive and nondestructive SEE testing of Intersil integrated point of load regulators, with emphasis on SET phenomena and some of the lessons learned in this work. We then report recent results of SET and destructive SEE testing of the ISL70003SEH POL converter, together with a brief discussion of the part's electrical and radiation hardness specifications. We conclude with a brief overview of low and high dose rate total dose testing of the part.

A technique for individual atom delivery into a crossed vortex bottle beam trap using a dynamic 1D optical lattice.

PubMed

Dinardo, Brad A; Anderson, Dana Z

2016-12-01

We describe a system for loading a single atom from a reservoir into a blue-detuned crossed vortex bottle beam trap using a dynamic 1D optical lattice. The lattice beams are frequency chirped using acousto-optic modulators, which causes the lattice to move along its axial direction and behave like an optical conveyor belt. A stationary lattice is initially loaded with approximately 6000 atoms from a reservoir, and the conveyor belt transports them 1.1 mm from the reservoir to a bottle beam trap, where a single atom is loaded via light-assisted collisions. Photon counting data confirm that an atom can be delivered and loaded into the bottle beam trap 13.1% of the time.

Evaluation of wheelchair seating system crashworthiness: "drop hook"-type seat attachment hardware.

PubMed

Bertocci, G; Ha, D; Deemer, E; Karg, P

2001-04-01

To evaluate the crashworthiness of commercially available hardware that attaches seat surfaces to the wheelchair frame. A low cost static crashworthiness test procedure that simulates a frontal impact motor vehicle crash. Safety testing laboratory. Eleven unique sets of drop-hook hardware made of carbon steel (4), stainless steel (4), and aluminum (3). Replicated seat-loading conditions associated with a 20g/48 kph frontal impact. Test criterion for seat loading was 16,680 N (3750 lb). Failure load and deflection of seat surface. None of the hardware sets tested met the crashworthiness test criterion. All failed at less than 50% of the load that seating hardware could be exposed to in a 20g/48 kph frontal impact. The primary failure mode was excessive deformation, leading to an unstable seat support surface. Results suggest that commercially available seating drop hooks may be unable to withstand loading associated with a frontal crash and may not be the best option for use with transport wheelchairs.

Initial load-to-failure and failure analysis in single- and double-row repair techniques for rotator cuff repair

PubMed Central

Buchhorn, G. H.; Gilbert, F.; Spahn, G.; Schultz, W.; Klinger, H.-M.

2010-01-01

Aim This experimental study aimed to compare the load-to-failure rate and stiffness of single- versus double-row suture techniques for repairing rotator cuff lesions using two different suture materials. Additionally, the mode of failure of each repair was evaluated. Method In 32 sheep shoulders, a standardized tear of the infraspinatus tendon was created. Then, n = 8 specimen were randomized to four repair methods: (1) Double-row Anchor Ethibond® coupled with polyester sutures, USP No. 2; (2) Double-Row Anchor HiFi® with polyblend polyethylene sutures, USP No. 2; (3) Single-Row Anchor Ethibond® coupled with braided polyester sutures, USP No. 2; and (4) Single-Row Anchor HiFi® with braided polyblend polyethylene sutures, USP No. 2. Arthroscopic Mason–Allen stitches were placed (single-row) and combined with medial horizontal mattress stitches (double-row). All specimens were loaded to failure at a constant displacement rate on a material testing machine. Results Group 4 showed lowest load-to-failure result with 155.7 ± 31.1 N compared to group 1 (293.4 ± 16.1 N) and group 2 (397.7 ± 7.4 N) (P < 0.001). Stiffness was highest in group 2 (162 ± 7.3 N/mm) and lowest in group 4 (84.4 ± 19.9 mm) (P < 0.001). In group 4, the main cause of failure was due to the suture cutting through the tendon (n = 6), a failure case observed in only n = 1 specimen in group 2 (P < 0.001). Conclusions A double-row technique combined with arthroscopic Mason-Allen/horizontal mattress stitches provides high initial failure strength and may minimize the risk of the polyethylene sutures cutting through the tendon in rotator cuff repair when a single load force is used. PMID:20049605

Stereo photo series for quantifying natural fuels Volume X: sagebrush with grass and ponderosa pine-juniper types in central Montana.

Treesearch

Roger D. Ottmar; Robert E. Vihnanek; Clinton S. Wright

2007-01-01

Two series of single and stereo photographs display a range of natural conditions and fuel loadings in sagebrush with grass and ponderosa pinejuniper types in central Montana. Each group of photos includes inventory information summarizing vegetation composition, structure, and loading; woody material loading and density by size class; forest floor depth and loading;...

Development and implementation of a novel measure for quantifying training loads in rowing: the T2minute method.

PubMed

Tran, Jacqueline; Rice, Anthony J; Main, Luana C; Gastin, Paul B

2014-04-01

The systematic management of training requires accurate training load measurement. However, quantifying the training of elite Australian rowers is challenging because of (a) the multicenter, multistate structure of the national program; (b) the variety of training undertaken; and (c) the limitations of existing methods for quantifying the loads accumulated from varied training formats. Therefore, the purpose of this project was to develop a new measure for quantifying training loads in rowing (the T2minute method). Sport scientists and senior coaches at the National Rowing Center of Excellence collaborated to develop the measure, which incorporates training duration, intensity, and mode to quantify a single index of training load. To account for training at different intensities, the method uses standardized intensity zones (T zones) established at the Australian Institute of Sport. Each zone was assigned a weighting factor according to the curvilinear relationship between power output and blood lactate response. Each training mode was assigned a weighting factor based on whether coaches perceived it to be "harder" or "easier" than on-water rowing. A common measurement unit, the T2minute, was defined to normalize sessions in different modes to a single index of load; one T2minute is equivalent to 1 minute of on-water single scull rowing at T2 intensity (approximately 60-72% VO2max). The T2minute method was successfully implemented to support national training strategies in Australian high performance rowing. By incorporating duration, intensity, and mode, the T2minute method extends the concepts that underpin current load measures, providing 1 consistent system to quantify loads from varied training formats.

User's manual for the Graphical Constituent Loading Analysis System (GCLAS)

USGS Publications Warehouse

Koltun, G.F.; Eberle, Michael; Gray, J.R.; Glysson, G.D.

2006-01-01

This manual describes the Graphical Constituent Loading Analysis System (GCLAS), an interactive cross-platform program for computing the mass (load) and average concentration of a constituent that is transported in stream water over a period of time. GCLAS computes loads as a function of an equal-interval streamflow time series and an equal- or unequal-interval time series of constituent concentrations. The constituent-concentration time series may be composed of measured concentrations or a combination of measured and estimated concentrations. GCLAS is not intended for use in situations where concentration data (or an appropriate surrogate) are collected infrequently or where an appreciable amount of the concentration values are censored. It is assumed that the constituent-concentration time series used by GCLAS adequately represents the true time-varying concentration. Commonly, measured constituent concentrations are collected at a frequency that is less than ideal (from a load-computation standpoint), so estimated concentrations must be inserted in the time series to better approximate the expected chemograph. GCLAS provides tools to facilitate estimation and entry of instantaneous concentrations for that purpose. Water-quality samples collected for load computation frequently are collected in a single vertical or at single point in a stream cross section. Several factors, some of which may vary as a function of time and (or) streamflow, can affect whether the sample concentrations are representative of the mean concentration in the cross section. GCLAS provides tools to aid the analyst in assessing whether concentrations in samples collected in a single vertical or at single point in a stream cross section exhibit systematic bias with respect to the mean concentrations. In cases where bias is evident, the analyst can construct coefficient relations in GCLAS to reduce or eliminate the observed bias. GCLAS can export load and concentration data in formats suitable for entry into the U.S. Geological Survey's National Water Information System. GCLAS can also import and export data in formats that are compatible with various commonly used spreadsheet and statistics programs.

Experiments and FE modeling of stress-strain state in ReBCO tape under tensile, torsional and transverse load

NASA Astrophysics Data System (ADS)

Ilin, K.; Yagotintsev, K. A.; Zhou, C.; Gao, P.; Kosse, J.; Otten, S. J.; Wessel, W. A. J.; Haugan, T. J.; van der Laan, D. C.; Nijhuis, A.

2015-05-01

For high current superconductors in high magnet fields with currents in the order of 50 kA, single ReBCO coated conductors must be assembled in a cable. The geometry of such a cable is mostly such that combined torsion, axial and transverse loading states are anticipated in the tapes and tape joints. The resulting strain distribution, caused by different thermal contraction and electromagnetic forces, will affect the critical current of the tapes. Tape performance when subjected to torsion, tensile and transverse loading is the key to understanding limitations for the composite cable performance. The individual tape material components can be deformed, not only elastically but also plastically under these loads. A set of experimental setups, as well as a convenient and accurate method of stress-strain state modeling based on the finite element method have been developed. Systematic measurements on single ReBCO tapes are carried out combining axial tension and torsion as well as transverse loading. Then the behavior of a single tape subjected to the various applied loads is simulated in the model. This paper presents the results of experimental tests and detailed FE modeling of the 3D stress-strain state in a single ReBCO tape under different loads, taking into account the temperature dependence and the elastic-plastic properties of the tape materials, starting from the initial tape processing conditions during its manufacture up to magnet operating conditions. Furthermore a comparison of the simulations with experiments is presented with special attention for the critical force, the threshold where the tape performance becomes irreversibly degraded. We verified the influence of tape surface profile non-uniformity and copper stabilizer thickness on the critical force. The FE models appear to describe the tape experiments adequately and can thus be used as a solid basis for optimization of various cabling concepts.

Study of free-piston Stirling engine driven linear alternators

NASA Technical Reports Server (NTRS)

Nasar, S. A.; Chen, C.

1987-01-01

The analysis, design and operation of single phase, single slot tubular permanent magnet linear alternator is presented. Included is the no-load and on-load magnetic field investigation, permanent magnet's leakage field analysis, parameter identification, design guidelines and an optimal design of a permanent magnet linear alternator. For analysis of the magnetic field, a simplified magnetic circuit is utilized. The analysis accounts for saturation, leakage and armature reaction.

Single cardiac ventricular myosins are autonomous motors

PubMed Central

Wang, Yihua; Yuan, Chen-Ching; Kazmierczak, Katarzyna; Szczesna-Cordary, Danuta

2018-01-01

Myosin transduces ATP free energy into mechanical work in muscle. Cardiac muscle has dynamically wide-ranging power demands on the motor as the muscle changes modes in a heartbeat from relaxation, via auxotonic shortening, to isometric contraction. The cardiac power output modulation mechanism is explored in vitro by assessing single cardiac myosin step-size selection versus load. Transgenic mice express human ventricular essential light chain (ELC) in wild- type (WT), or hypertrophic cardiomyopathy-linked mutant forms, A57G or E143K, in a background of mouse α-cardiac myosin heavy chain. Ensemble motility and single myosin mechanical characteristics are consistent with an A57G that impairs ELC N-terminus actin binding and an E143K that impairs lever-arm stability, while both species down-shift average step-size with increasing load. Cardiac myosin in vivo down-shifts velocity/force ratio with increasing load by changed unitary step-size selections. Here, the loaded in vitro single myosin assay indicates quantitative complementarity with the in vivo mechanism. Both have two embedded regulatory transitions, one inhibiting ADP release and a second novel mechanism inhibiting actin detachment via strain on the actin-bound ELC N-terminus. Competing regulators filter unitary step-size selection to control force-velocity modulation without myosin integration into muscle. Cardiac myosin is muscle in a molecule. PMID:29669825

A biomechanical comparison of tendon-bone interface motion and cyclic loading between single-row, triple-loaded cuff repairs and double-row, suture-tape cuff repairs using biocomposite anchors.

PubMed

Barber, F Alan; Drew, Otis R

2012-09-01

To compare tendon-bone interface motion and cyclic loading in a single-row, triple-loaded anchor repair with a suture-tape, rip-stop, double-row rotator cuff repair. Using 18 human shoulders from 9 matched cadaveric pairs, we created 2 groups of rotator cuff repairs. Group 1 was a double-row, rip-stop, suture-tape construct. Group 2 was a single-row, triple-loaded construct. Before mechanical testing, the supraspinatus footprint was measured with calipers. A superiorly positioned digital camera optically measured the tendon footprint motion during 60° of humeral internal and external rotation. Specimens were secured at a fixed angle not exceeding 45° in reference to the load. After preloading, each sample was cycled between 10 N and 100 N for 200 cycles at 1 Hz, followed by destructive testing at 33 mm/s. A digital camera with tracking software measured the repair displacement at 100 and 200 cycles. Ultimate load and failure mode for each sample were recorded. The exposed anterior footprint border (6.5% ± 6%) and posterior footprint border (0.9% ± 1.7%) in group 1 were statistically less than the exposed anterior footprint border (30.3% ± 17%) and posterior footprint border (29.8% ± 14%) in group 2 (P = .003 and P < .001, respectively). The maximal internal rotation and external rotation tendon footprint displacements in group 1 (1.6 mm and 1.4 mm, respectively) were less than those in group 2 (both 3.6 mm) (P = .007 and P = .004, respectively). Mean displacement after 100 cycles for group 1 and group 2 was 2.0 mm and 3.2 mm, respectively, and at 200 cycles, mean displacement was 2.5 mm and 4.2 mm, respectively (P = .02). The mean ultimate failure load in group 1 (586 N) was greater than that in group 2 (393 N) (P = .02). The suture-tendon interface was the site of most construct failures. The suture-tape, rip-stop, double-row rotator cuff repair had greater footprint coverage, less rotational footprint displacement, and a greater mean ultimate failure load than the triple-loaded, single-row repair on mechanical testing. No double-row or single-row constructs showed 5 mm of displacement after the first 100 cycles. The most common failure mode for both constructs was suture tearing through the tendon. Differences in cuff fixation influence rotational tendon movement and may influence postoperative healing. Stronger repair constructs still fail at the suture-tendon interface. Copyright © 2012 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Single-strain-gage force/stiffness buckling prediction techniques on a hat-stiffened panel

NASA Technical Reports Server (NTRS)

Hudson, Larry D.; Thompson, Randolph C.

1991-01-01

Predicting the buckling characteristics of a test panel is necessary to ensure panel integrity during a test program. A single-strain-gage buckling prediction method was developed on a hat-stiffened, monolithic titanium buckling panel. The method is an adaptation of the original force/stiffness method which requires back-to-back gages. The single-gage method was developed because the test panel did not have back-to-back gages. The method was used to predict buckling loads and temperatures under various heating and loading conditions. The results correlated well with a finite element buckling analysis. The single-gage force/stiffness method was a valid real-time and post-test buckling prediction technique.

HMSIW-based switchable units using super compact loaded shunt stubs and its applications on SIW/HMSIW switches

NASA Astrophysics Data System (ADS)

Chen, Haidong; Che, Wenquan; Zhang, Tianyu; Cao, Yue; Feng, Wenjie

2018-06-01

Half-mode substrate integrated waveguide (HMSIW) switchable unit, built by HMSIW section with loaded single or multi-microstrip shunt stub(s), was proposed in this work. Both shorted and opened stubs were studied, investigated and compared, bandwidth enhancement method for proposed switchable units was proposed and demonstrated. Based on these switchable units, narrowband and broadband HMSIW single-pole-single-through (SPST) switches, SIW SPST switch and SIW/HMSIW-based single-pole-double-through (SPDT) switch were designed, fabricated and measured. Good performances were observed experimentally for these proposed circuits, showing the advantages of proposed concept and an excellent candidate for switchable or reconfigurable SIW/HMSIW circuits or systems.

Opposing effects of perceptual versus working memory load on emotional distraction.

PubMed

Tavares, Tamara P; Logie, Kyle; Mitchell, Derek G V

2016-10-01

Throughout our day-to-day activities, we are subjected to numerous stimuli that compete for our attention; consequently, we must prioritize stimuli for further processing and influence over behaviour. Previous research has demonstrated that the extent to which task-irrelevant distractors are processed is mediated by the nature of the cognitive task, and the level of processing load. Importantly though, the interaction between cognitive task, processing load, and emotional distractor processing remains unclear. This is a particularly important question given the unique ways that emotion interacts with attention, and the fact that some other forms of processing load have been shown to reduce emotional distractor encoding. In the present study, participants were presented with emotional distractors during a perceptual and working memory task, under varying levels of load. In Experiment 1, we showed that the impact of emotional distractors on behaviour was reduced under conditions of high relative to low perceptual load. However, in sharp contrast, high working memory load was associated with increased emotional distraction. Importantly, these results were replicated in Experiment 2. Overall, the impact of processing load on emotional distraction varies according to the cognitive function being performed. These results raise the intriguing possibility that working memory operations deplete some of the cognitive resources needed to control the impact of emotion on behaviour. The findings, therefore, may have important implications for clinical populations featuring cognitive dysfunction and emotional dysregulation.

Cost analysis of centralized viral load testing for antiretroviral therapy monitoring in Nicaragua, a low-HIV prevalence, low-resource setting.

PubMed

Gerlach, Jay; Sequeira, Magda; Alvarado, Vivian; Cerpas, Christian; Balmaseda, Angel; Gonzalez, Alcides; de Los Santos, Tala; Levin, Carol E; Amador, Juan Jose; Domingo, Gonzalo J

2010-11-05

HIV viral load testing as a component of antiretroviral therapy monitoring is costly. Understanding the full costs and the major sources of inefficiency associated with viral load testing is critical for optimizing the systems and technologies that support the testing process. The objective of our study was to estimate the costs associated with viral load testing performed for antiretroviral therapy monitoring to both patients and the public healthcare system in a low-HIV prevalence, low-resource country. A detailed cost analysis was performed to understand the costs involved in each step of performing a viral load test in Nicaragua, from initial specimen collection to communication of the test results to each patient's healthcare provider. Data were compiled and cross referenced from multiple information sources: laboratory records, regional surveillance centre records, and scheduled interviews with the key healthcare providers responsible for HIV patient care in five regions of the country. The total average cost of performing a viral load test in Nicaragua varied by region, ranging from US$99.01 to US$124.58, the majority of which was at the laboratory level: $88.73 to $97.15 per specimen, depending on batch size. The average cost to clinics at which specimens were collected ranged from $3.31 to $20.92, depending on the region. The average cost per patient for transportation, food, lodging and lost income ranged from $3.70 to $14.93. The quantitative viral load test remains the single most expensive component of the process. For the patient, the distance of his or her residence from the specimen collection site is a large determinant of cost. Importantly, the efficiency of results reporting has a large impact on the cost per result delivered to the clinician and utility of the result for patient monitoring. Detailed cost analysis can identify opportunities for removing barriers to effective antiretroviral therapy monitoring programmes in limited-resource countries with low HIV prevalence.

Effects of Gasoline Direct Injection Engine Operating Parameters on Particle Number Emissions

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

He, X.; Ratcliff, M. A.; Zigler, B. T.

2012-04-19

A single-cylinder, wall-guided, spark ignition direct injection engine was used to study the impact of engine operating parameters on engine-out particle number (PN) emissions. Experiments were conducted with certification gasoline and a splash blend of 20% fuel grade ethanol in gasoline (E20), at four steady-state engine operating conditions. Independent engine control parameter sweeps were conducted including start of injection, injection pressure, spark timing, exhaust cam phasing, intake cam phasing, and air-fuel ratio. The results show that fuel injection timing is the dominant factor impacting PN emissions from this wall-guided gasoline direct injection engine. The major factor causing high PN emissionsmore » is fuel liquid impingement on the piston bowl. By avoiding fuel impingement, more than an order of magnitude reduction in PN emission was observed. Increasing fuel injection pressure reduces PN emissions because of smaller fuel droplet size and faster fuel-air mixing. PN emissions are insensitive to cam phasing and spark timing, especially at high engine load. Cold engine conditions produce higher PN emissions than hot engine conditions due to slower fuel vaporization and thus less fuel-air homogeneity during the combustion process. E20 produces lower PN emissions at low and medium loads if fuel liquid impingement on piston bowl is avoided. At high load or if there is fuel liquid impingement on piston bowl and/or cylinder wall, E20 tends to produce higher PN emissions. This is probably a function of the higher heat of vaporization of ethanol, which slows the vaporization of other fuel components from surfaces and may create local fuel-rich combustion or even pool-fires.« less

Relationships between watershed emergy flow and coastal New England salt marsh structure, function, and condition.

PubMed

Brandt-Williams, Sherry; Wigand, Cathleen; Campbell, Daniel E

2013-02-01

This study evaluated the link between watershed activities and salt marsh structure, function, and condition using spatial emergy flow density (areal empower density) in the watershed and field data from 10 tidal salt marshes in Narragansett Bay, RI, USA. The field-collected data were obtained during several years of vegetation, invertebrate, soil, and water quality sampling. The use of emergy as an accounting mechanism allowed disparate factors (e.g., the amount of building construction and the consumption of electricity) to be combined into a single landscape index while retaining a uniform quantitative definition of the intensity of landscape development. It expanded upon typical land use percentage studies by weighting each category for the intensity of development. At the RI salt marsh sites, an impact index (watershed emergy flow normalized for marsh area) showed significant correlations with mudflat infauna species richness, mussel density, plant species richness, the extent and density of dominant plant species, and denitrification potential within the high salt marsh. Over the 4-year period examined, a loading index (watershed emergy flow normalized for watershed area) showed significant correlations with nitrite and nitrate concentrations, as well as with the nitrogen to phosphorus ratios in stream discharge into the marshes. Both the emergy impact and loading indices were significantly correlated with a salt marsh condition index derived from intensive field-based assessments. Comparison of the emergy indices to calculated nitrogen loading estimates for each watershed also produced significant positive correlations. These results suggest that watershed emergy flow is a robust index of human disturbance and a potential tool for rapid assessment of coastal wetland condition.

Damage Characteristics and Residual Strength of Composite Sandwich Panels Impacted with and Without Compression Loading

NASA Technical Reports Server (NTRS)

McGowan, David M.; Ambur, Damodar R.

1998-01-01

The results of an experimental study of the impact damage characteristics and residual strength of composite sandwich panels impacted with and without a compression loading are presented. Results of impact damage screening tests conducted to identify the impact-energy levels at which damage initiates and at which barely visible impact damage occurs in the impacted facesheet are discussed. Parametric effects studied in these tests include the impactor diameter, dropped-weight versus airgun-launched impactors, and the effect of the location of the impact site with respect to the panel boundaries. Residual strength results of panels tested in compression after impact are presented and compared with results of panels that are subjected to a compressive preload prior to being impacted.

Electromechanical Characterization of Single GaN Nanobelt Probed with Conductive Atomic Force Microscope

NASA Astrophysics Data System (ADS)

Yan, X. Y.; Peng, J. F.; Yan, S. A.; Zheng, X. J.

2018-04-01

The electromechanical characterization of the field effect transistor based on a single GaN nanobelt was performed under different loading forces by using a conductive atomic force microscope (C-AFM), and the effective Schottky barrier height (SBH) and ideality factor are simulated by the thermionic emission model. From 2-D current image, the high value of the current always appears on the nanobelt edge with the increase of the loading force less than 15 nN. The localized (I-V) characteristic reveals a typical rectifying property, and the current significantly increases with the loading force at the range of 10-190 nN. The ideality factor is simulated as 9.8 within the scope of GaN nano-Schottky diode unity (6.5-18), therefore the thermionic emission current is dominant in the electrical transport of the GaN-tip Schottky junction. The SBH is changed through the piezoelectric effect induced by the loading force, and it is attributed to the enhanced current. Furthermore, a single GaN nanobelt has a high mechanical-induced current ratio that could be made use of in a nanoelectromechanical switch.

Electromechanical Characterization of Single GaN Nanobelt Probed with Conductive Atomic Force Microscope

NASA Astrophysics Data System (ADS)

Yan, X. Y.; Peng, J. F.; Yan, S. A.; Zheng, X. J.

2018-07-01

The electromechanical characterization of the field effect transistor based on a single GaN nanobelt was performed under different loading forces by using a conductive atomic force microscope (C-AFM), and the effective Schottky barrier height (SBH) and ideality factor are simulated by the thermionic emission model. From 2-D current image, the high value of the current always appears on the nanobelt edge with the increase of the loading force less than 15 nN. The localized ( I- V) characteristic reveals a typical rectifying property, and the current significantly increases with the loading force at the range of 10-190 nN. The ideality factor is simulated as 9.8 within the scope of GaN nano-Schottky diode unity (6.5-18), therefore the thermionic emission current is dominant in the electrical transport of the GaN-tip Schottky junction. The SBH is changed through the piezoelectric effect induced by the loading force, and it is attributed to the enhanced current. Furthermore, a single GaN nanobelt has a high mechanical-induced current ratio that could be made use of in a nanoelectromechanical switch.

Wrist loading patterns during pommel horse exercises.

PubMed

Markolf, K L; Shapiro, M S; Mandelbaum, B R; Teurlings, L

1990-01-01

Gymnastics is a sport which involves substantial periods of upper extremity support as well as frequent impacts to the wrist. Not surprisingly, wrist pain is a common finding in gymnasts. Of all events, the pommel horse is the most painful. In order to study the forces of wrist impact, a standard pommel horse was instrumented with a specially designed load cell to record the resultant force of the hand on the pommel during a series of basic skills performed by a group of seventeen elite male gymnasts. The highest mean peak forces were recorded during the front scissors and flair exercises (1.5 BW) with peaks of up to 2.0 BW for some gymnasts. The mean peak force for hip circles at the center or end of the horse was 1.1 BW. The mean overall loading rate (initial contact to first loading peak) ranged from 5.2 BWs-1 (hip circles) to 10.6 BW s-1 (flairs). However, many recordings displayed localized initial loading spikes which occurred during 'hard' landings on the pommel. When front scissors were performed in an aggressive manner, the initial loading spikes averaged 1.0 BW in magnitude (maximum 1.8 BW) with an average rise time of 8.2 ms; calculated localized loading rates averaged 129 BW s-1 (maximum 219 BW s-1). These loading parameters are comparable to those encountered at heel strike during running. These impact forces and loading rates are remarkably high for an upper extremity joint not normally exposed to weight-bearing loads, and may contribute to the pathogenesis of wrist injuries in gymnastics.

Priority substances in combined sewer overflows: case study of the Paris sewer network.

PubMed

Gasperi, J; Garnaud, S; Rocher, V; Moilleron, R

2011-01-01

This study was undertaken to supply data on both priority pollutant (PP) occurrence and concentrations in combined sewer overflows (CSOs). A single rain event was studied on 13 sites within the Paris sewer network. For each sample, a total of 66 substances, including metals, polycyclic aromatic hydrocarbons (PAHs), pesticides, organotins, volatile organic compounds, chlorobenzenes, phthalates and alkylphenols were analyzed. Of the 66 compounds analyzed in all, 40 PPs including 12 priority hazardous substances were detected in CSOs. As expected, most metals were present in all samples, reflecting their ubiquitous nature. Chlorobenzenes and most pesticides were never quantified above the limit of quantification, while the majority of the other organic pollutants, except DEHP (median concentration: 22 μg.l(-1)), were found to lie in the μg.l(-1) range. For the particular rain event studied, the pollutant loads discharged by CSOs were evaluated and then compared to pollutant loads conveyed by the Seine River. Under the hydraulic conditions considered and according to the estimations performed, this comparison suggests that CSOs are potentially significant local source of metals, PAHs and DEHP. Depending on the substance, the ratio between the CSO and Seine River loads varied from 0.5 to 26, underscoring the important local impact of CSOs at the scale of this storm for most pollutants.

Specific Cell Targeting Therapy Bypasses Drug Resistance Mechanisms in African Trypanosomiasis

PubMed Central

Unciti-Broceta, Juan D.; Arias, José L.; Maceira, José; Soriano, Miguel; Ortiz-González, Matilde; Hernández-Quero, José; Muñóz-Torres, Manuel; de Koning, Harry P.; Magez, Stefan; Garcia-Salcedo, José A.

2015-01-01

African trypanosomiasis is a deadly neglected disease caused by the extracellular parasite Trypanosoma brucei. Current therapies are characterized by high drug toxicity and increasing drug resistance mainly associated with loss-of-function mutations in the transporters involved in drug import. The introduction of new antiparasitic drugs into therapeutic use is a slow and expensive process. In contrast, specific targeting of existing drugs could represent a more rapid and cost-effective approach for neglected disease treatment, impacting through reduced systemic toxicity and circumventing resistance acquired through impaired compound uptake. We have generated nanoparticles of chitosan loaded with the trypanocidal drug pentamidine and coated by a single domain nanobody that specifically targets the surface of African trypanosomes. Once loaded into this nanocarrier, pentamidine enters trypanosomes through endocytosis instead of via classical cell surface transporters. The curative dose of pentamidine-loaded nanobody-chitosan nanoparticles was 100-fold lower than pentamidine alone in a murine model of acute African trypanosomiasis. Crucially, this new formulation displayed undiminished in vitro and in vivo activity against a trypanosome cell line resistant to pentamidine as a result of mutations in the surface transporter aquaglyceroporin 2. We conclude that this new drug delivery system increases drug efficacy and has the ability to overcome resistance to some anti-protozoal drugs. PMID:26110623

Influence of semipermanent cement application used in immediately loaded, implant-supported restorations on crestal bone resorption.

PubMed

Błaszczyszyn, Artur; Kubasiewicz-Ross, Paweł; Gedrange, Tomasz; Dominiak, Marzena

2013-01-01

The paper presents clinical-radiological research on the impact of the new semi-cement luting agent in the immediately loaded implant-supported restoration on alveolar ridge resorption. 25 patients with a partially edentulous alveolar ridge in the anterior section of the maxilla or mandible were included in the study. The implants were inserted with the application of traditional burs or with a Piezosurgery device supplied by Mectron. Taking into account the method of implant bed preparation, the scientific material was divided into two groups. The implants were loaded immediately with single crown restorations cemented with the Implantlink semi cement application. The following indices were taken into consideration: pocket depth around implant calculated at four measuring points, marginal alveolar bone loss measured using radio-visiography, the 3-degree Wachtel scale of healing of the soft tissue. In addition, the presence and possible width or height of any recession around the implants was measured. The success of the implant treatment was assessed according to the Albrektsson success criteria. The research results were subjected to statistical analysis. The results of our study revealed no influence of the Implant-link semi cement on the crestal bone level, regardless of the bone bed preparation technique.

Interface bonding of shotcrete reinforced brick masonry assemblages, volume 1

NASA Astrophysics Data System (ADS)

Robinson, D. W.; Kahn, L. F.

1982-09-01

Nine 9 sq ft. shotcrete reinforced brick masonry assemblages and one 9 sq ft brick masonry control specimen were tested under a single reversed cycle diagonal compression load similar to the ASTM E519-74 testing procedures. The interface surface conditions, between the brick and shotcrete were varied. The surfaces of the single sythe of old brick were either dry, wet, or epoxy coated before application of the 3-inch reinforced shotcrete layer. Ultimate load capacities of the specimens were similar, however, specimens with epoxy-enhanced interfaces were the most ductile; the dry brick specimens showed interface bond failure immediately after the ultimate inplane load was attained.

Knee Joint Loading during Single-Leg Forward Hopping.

PubMed

Krupenevich, Rebecca L; Pruziner, Alison L; Miller, Ross H

2017-02-01

Increased or abnormal loading on the intact limb is thought to contribute to the relatively high risk of knee osteoarthritis in this limb for individuals with unilateral lower limb loss. This theory has been assessed previously by studying walking, but knee joint loading during walking is often similar between individuals with and without limb loss, prompting assessment of other movements that may place unusual loads on the knee. One such movement, hopping, is a form of locomotion that individuals with unilateral lower limb loss may situationally use instead of walking, but the mechanical effects of hopping on the intact limb are unknown. Compare knee joint kinetics of healthy adults during single-leg forward hopping compared to walking, a more traditional form of locomotion. Twenty-four healthy adults walked and hopped at self-selected speeds of 1.5 and 2.3 m·s, respectively. Joint moments were calculated using inverse dynamics. A paired Student's t-test was utilized to compare peak, impulse, and loading rate (LR) of knee adduction moment (KAM), and peak knee flexion moment (KFM) between walking and hopping. Peak KFM and KAM LR were greater during hopping compared to walking (peak KFM: 20.73% vs 5.51% body weight (BW) × height (Ht), P < 0.001; KAM LR: 0.47 vs. 0.33 BW·Ht·s, P = 0.01). Kinetic measures affecting knee joint loading are greater in hopping compared to walking. It may be advisable to limit single-leg forward hopping in the limb loss population until it is known if these loads increase knee osteoarthritis risk.

Force spectroscopy of quadruple H-bonded dimers by AFM: dynamic bond rupture and molecular time-temperature superposition.

PubMed

Zou, Shan; Schönherr, Holger; Vancso, G Julius

2005-08-17

We report on the application of the time-temperature superposition principle to supramolecular bond-rupture forces on the single-molecule level. The construction of force-loading rate master curves using atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) experiments carried out in situ at different temperatures allows one to extend the limited range of the experimentally accessible loading rates and hence to cross from thermodynamic nonequilibrium to quasi-equilibrium states. The approach is demonstrated for quadruple H-bonded ureido-4[1H]-pyrimidinone (UPy) moieties studied by variable-temperature SMFS in organic media. The unbinding forces of single quadruple H-bonding (UPy)2 complexes, which were identified based on a polymeric spacer strategy, were found to depend on the loading rate in the range of 5 nN/s to 500 nN/s at 301 K in hexadecane. By contrast, these rupture forces were independent of the loading rate from 5 to 200 nN/s at 330 K. These results indicate that the unbinding behavior of individual supramolecular complexes can be directly probed under both thermodynamic nonequilibrium and quasi-equilibrium conditions. On the basis of the time-temperature superposition principle, a master curve was constructed for a reference temperature of 301 K, and the crossover force (from loading-rate independent to -dependent regimes) was determined as approximately 145 pN (at a loading rate of approximately 5.6 nN/s). This approach significantly broadens the accessible loading-rate range and hence provides access to fine details of potential energy landscape of supramolecular complexes based on SMFS experiments.

Retention Load of Telescopic Crowns with Different Taper Angles between Cobalt-Chromium and Polyetheretherketone Made with Three Different Manufacturing Processes Examined by Pull-Off Test.

PubMed

Wagner, Christina; Stock, Veronika; Merk, Susanne; Schmidlin, Patrick R; Roos, Malgorzata; Eichberger, Marlis; Stawarczyk, Bogna

2018-02-01

To investigate the retention loads of differently fabricated secondary telescopic polyetheretherketone (PEEK) crowns on cobalt-chromium primary crowns with different tapers. Cobalt-chromium primary crowns with 0°, 1°, and 2° tapers were constructed, milled, and sintered. Corresponding secondary crowns were fabricated by milling, pressing from pellets, and pressing from granules. For these nine test groups, the pull-off tests of each crown combination were performed 20 times, and the retention loads were measured (Zwick 1445, 50 mm/min). Data were analyzed using linear regression, covariance analysis, mixed models, Kruskal-Wallis, and Mann-Whitney U-test, together with the Benferroni-Holm correction. The mixed models covariance analysis reinforced stable retention load values (p = 0.162) for each single test sequence. There was no interaction between the groups and the separation cycles (p = 0.179). Milled secondary crowns with 0° showed the lowest mean retention load values compared to all tested groups (p = 0.003) followed by those pressed form pellets with 1°. Regarding the different tapers, no effect of manufacturing method on the results was observed within 1° and 2° groups (p = 0.540; p = 0.052); however, among the 0° groups, the milled ones showed significantly the lowest retention load values (p = 0.002). Among the manufacturing methods, both pressed groups showed no impact of taper on the retention load values (p > 0.324 and p > 0.123, respectively), whereas among the milled secondary crowns, the 0° taper showed significantly lower retention load values than the 1° and 2° taper (p < 0.002). Based on these results, telescopic crowns made of PEEK seem to show stable retention load values for each test sequence; however, data with thermo-mechanical aging are still required. In addition, further developments in CAD/CAM manufacturing of PEEK materials for telescopic crowns are warranted, especially for 0°. © 2016 by the American College of Prosthodontists.

Investigating the pros and cons of browns gas and varying EGR on combustion, performance, and emission characteristics of diesel engine.

PubMed

Thangaraj, Suja; Govindan, Nagarajan

2018-01-01

The significance of mileage to the fruitful operation of a trucking organization cannot be downplayed. Fuel is one of the biggest variable expenses in a trucking wander. An attempt is made in this research to improve the combustion efficiency of a diesel engine for better fuel economy by introducing hydroxy gas which is also called browns gas or HHO gas in the suction line, without compromising performance and emission. Brown's gas facilitates the air-fuel mixture to ignite faster and efficient combustion. By considering safety and handling issues in automobiles, HHO gas generation by electrolysis of water in the presence of sodium bicarbonate electrolytes (NaHCO 3 ) and usage was explored in this research work over compressed pure hydrogen, due to generation and capacity of immaculate hydrogen as of now confines the application in diesel engine operation. Brown's gas was utilized as a supplementary fuel in a single-cylinder, four-stroke compression ignition (CI) engine. Experiments were carried out on a constant speed engine at 1500 rpm, result shows at constant HHO flow rate of 0.73 liter per minute (LPM), brake specific fuel consumption (BSFC) decreases by 7% at idle load to 16% at full load, and increases brake thermal efficiency (BTE) by 8.9% at minimum load to 19.7% at full load. In the dual fuel (diesel +HHO) operation, CO emissions decreases by 19.4, 64.3, and 34.6% at 25, 50, and 75% load, respectively, and unburned hydrocarbon (UHC) emissions decreased by 11.3% at minimum load to 33.5% at maximum load at the expense of NO x emission increases by 1.79% at 75% load and 1.76% at full load than neat diesel operation. The negative impact of an increase in NO x is reduced by adding EGR. It was evidenced in this experimental work that the use of Brown's gas with EGR in the dual fuel mode in a diesel engine improves the fuel efficiency, performance, and reduces the exhaust emissions.

Impact of enzyme loading on the efficacy and recovery of cellulolytic enzymes immobilized on enzymogel nanoparticles.

PubMed

Samaratunga, Ashani; Kudina, Olena; Nahar, Nurun; Zakharchenko, Andrey; Minko, Sergiy; Voronov, Andriy; Pryor, Scott W

2015-03-01

Cellulase and β-glucosidase were adsorbed on a polyacrylic acid polymer brush grafted on silica nanoparticles to produce enzymogels as a form of enzyme immobilization. Enzyme loading on the enzymogels was increased to a saturation level of approximately 110 μg (protein) mg(-1) (particle) for each enzyme. Enzymogels with varied enzyme loadings were then used to determine the impact on hydrolysis rate and enzyme recovery. Soluble sugar concentrations during the hydrolysis of filter paper and Solka-Floc with the enzymogels were 45 and 53%, respectively, of concentrations when using free cellulase. β-Glucosidase enzymogels showed lower performance; hydrolyzate glucose concentrations were just 38% of those using free enzymes. Increasing enzyme loading on the enzymogels did not reduce net efficacy for cellulase and improved efficacy for β-glucosidase. The use of free cellulases and cellulase enzymogels resulted in hydrolyzates with different proportions of cellobiose and glucose, suggesting differential attachment or efficacy of endoglucanases, exoglucanases, and β-glucosidases present in cellulase mixtures. When loading β-glucosidase individually, higher enzyme loadings on the enzymogels produced higher hydrolyzate glucose concentrations. Approximately 96% of cellulase and 66 % of β-glucosidase were recovered on the enzymogels, while enzyme loading level did not impact recovery for either enzyme.

The Impact of Vocal Cool-down Exercises: A Subjective Study of Singers' and Listeners' Perceptions.

PubMed

Ragan, Kari

2016-11-01

Using subjective measures, this study investigated singers' and listeners' perceptions of changes in voice condition after vocal cool-down exercises. A single-subject crossover was designed to evaluate whether there were discernible differences in either singer or listener perceptions from pre (no vocal cool downs) to post (with cool downs) test. Subjective questionnaires were completed throughout the study. Twenty classically trained female singers documented self-ratings and perceptual judgments through the Evaluation of the Ability to Sing Easily survey, the Singing Voice Handicap Index, and Self-Perceptual Questionnaires after a 60-minute voice load. Recordings were made and assessed by four expert listeners. The assessed data from the Singing Voice Handicap Index, the Evaluation of the Ability to Sing Easily, and Daily Perceptual Questionnaires show 68%, 67%, and 74% of singers reported improvement, respectively. However, because of significant variability in the underlying scores, the amount of improvement was not deemed to be statistically significant. Expert listeners correctly identified the cool-down week 46% of the time. Singers strongly perceived positive impact from the cool-down exercises on both their speaking and singing voices. Even though the objective data were statistically insignificant, the singers' subjective data clearly indicates a perceived sense of vocal well-being after utilizing the vocal cool-down protocol. The variability in the daily life of a singer (eg, stress, menses, reflux, vocal load, and vocal hygiene) makes it difficult to objectively quantify the impact of vocal cool downs. Copyright © 2016 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

Single dental implant retained mandibular complete dentures – influence of the loading protocol: study protocol for a randomized controlled trial

PubMed Central

2014-01-01

Background Over the years, there has been a strong consensus in dentistry that at least two implants are required to retain a complete mandibular denture. It has been shown in several clinical trials that one single median implant can retain a mandibular overdenture sufficiently well for up to 5 years without implant failures, when delayed loading was used. However, other trials have reported conflicting results with in part considerable failure rates when immediate loading was applied. Therefore it is the purpose of the current randomized clinical trial to test the hypothesis that immediate loading of a single mandibular midline implant with an overdenture will result in a comparable clinical outcome as using the standard protocol of delayed loading. Methods/design This prospective nine-center randomized controlled clinical trial is still ongoing. The final patient will complete the trial in 2016. In total, 180 edentulous patients between 60 and 89 years with sufficient complete dentures will receive one median implant in the edentulous mandible, which will retain the existing complete denture using a ball attachment. Loading of the median implant is either immediately after implant placement (experimental group) or delayed by 3 months of submerged healing at second-stage surgery (control group). Follow-up of patients will be performed for 24 months after implant loading. The primary outcome measure is non-inferiority of implant success rate of the experimental group compared to the control group. The secondary outcome measures encompass clinical, technical and subjective variables. The study was funded by the Deutsche Forschungsgemeinschaft (German research foundation, KE 477/8-1). Discussion This multi-center clinical trial will give information on the ability of a single median implant to retain a complete mandibular denture when immediately loaded. If viable, this treatment option will strongly improve everyday dental practice. Trial registration The trial has been registered at Deutsches Register Klinischer Studien (German register of clinical trials) under DRKS-ID: DRKS00003730 since 23 August 2012. (http://www.germanctr.de). PMID:24884848

Fibrin Networks Support Recurring Mechanical Loads by Adapting their Structure across Multiple Scales.

PubMed

Kurniawan, Nicholas A; Vos, Bart E; Biebricher, Andreas; Wuite, Gijs J L; Peterman, Erwin J G; Koenderink, Gijsje H

2016-09-06

Tissues and cells sustain recurring mechanical loads that span a wide range of loading amplitudes and timescales as a consequence of exposure to blood flow, muscle activity, and external impact. Both tissues and cells derive their mechanical strength from fibrous protein scaffolds, which typically have a complex hierarchical structure. In this study, we focus on a prototypical hierarchical biomaterial, fibrin, which is one of the most resilient naturally occurring biopolymers and forms the structural scaffold of blood clots. We show how fibrous networks composed of fibrin utilize irreversible changes in their hierarchical structure at different scales to maintain reversible stress stiffening up to large strains. To trace the origin of this paradoxical resilience, we systematically tuned the microstructural parameters of fibrin and used a combination of optical tweezers and fluorescence microscopy to measure the interactions of single fibrin fibers for the first time, to our knowledge. We demonstrate that fibrin networks adapt to moderate strains by remodeling at the network scale through the spontaneous formation of new bonds between fibers, whereas they adapt to high strains by plastic remodeling of the fibers themselves. This multiscale adaptation mechanism endows fibrin gels with the remarkable ability to sustain recurring loads due to shear flows and wound stretching. Our findings therefore reveal a microscopic mechanism by which tissues and cells can balance elastic nonlinearity and plasticity, and thus can provide microstructural insights into cell-driven remodeling of tissues. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Design of an Orthodontic Torque Simulator for Measurement of Bracket Deformation

NASA Astrophysics Data System (ADS)

Melenka, G. W.; Nobes, D. S.; Major, P. W.; Carey, J. P.

2013-12-01

The design and testing of an orthodontic torque simulator that reproduces the effect of archwire rotation on orthodontic brackets is described. This unique device is capable of simultaneously measuring the deformation and loads applied to an orthodontic bracket due to archwire rotation. Archwire rotation is used by orthodontists to correct the inclination of teeth within the mouth. This orthodontic torque simulator will provide knowledge of the deformation and loads applied to orthodontic bracket that will aide clinicians by describing the effect of archwire rotation on brackets. This will also impact that design on new archwirebracket systems by providing an assessment of performance. Deformation of the orthodontic bracket tie wings is measured using a digital image correlation process to measure elastic and plastic deformation. The magnitude of force and moments applied to the bracket though the archwire is also measured using a six-axis load cell. Initial tests have been performed on two orthodontic brackets of varying geometry to demonstrate the measurement capability of the orthodontic torque simulator. The demonstration experiment shows that a Damon Q bracket had a final plastic deformation after a single loading of 0.022 mm while the Speed bracket deformed 0.071 mm. This indicates that the Speed bracket plastically deforms 3.2 times more than the Damon Q bracket for similar magnitude of applied moment. The demonstration experiment demonstrates that bracket geometry affect the deformation of orthodontic brackets and this difference can be detected using the orthodontic torque simulator.

Biomechanics of Polyhydroxyalkanoate Mesh-Augmented Single-Row Rotator Cuff Repairs.

PubMed

Tashjian, Robert Z; Kolz, Christopher W; Suter, Thomas; Henninger, Heath B

Polyhydroxyalkanoate (PHA) mesh is a bioresorbable scaffold used to reinforce the suture-tendon interface in rotator cuff repairs (RCRs). We conducted a study of cyclic and ultimate failure properties of PHA mesh-augmented single-row RCRs and nonaugmented RCRs. Eight pairs of fresh-frozen cadaver humeri (6 male, 2 female) were tested. Mean (SD) age was 61 (9) years. The supraspinatus tendon was resected and reattached in a single-row configuration using 2 triple-loaded suture anchors and 6 simple stitches. The opposite humerus underwent RCR augmented with 2 strips of 13-mm × 23-mm PHA mesh. Humeri were mounted in an Instron load frame, cycled 1000 times to 1.0 MPa of effective stress, and loaded to failure. Construct gapping and ultimate failure loads/displacements were recorded. Paired t tests compared augmented and nonaugmented RCRs (P ≤ .05 was significant). There was no difference in gapping over 1000 cycles (P = .879). Mean (SD) failure load was higher for PHA mesh-augmented RCRs, 571 (173) N, than for nonaugmented (control) RCRs, 472 (120) N (P = .042), and failures were consistent within pairs because of tissue failure at the knots or anchor pullout. This technique for arthroscopic augmentation can be used to improve initial biomechanical repair strength in tears at risk for failure.

Modeling of orthotropic plate fracture under impact load using various strength criteria

NASA Astrophysics Data System (ADS)

Radchenko, Andrey; Krivosheina, Marina; Kobenko, Sergei; Radchenko, Pavel; Grebenyuk, Grigory

2017-01-01

The paper presents the comparative analysis of various tensor multinomial criteria of strength for modeling of orthotropic organic plastic plate fracture under impact load. Ashkenazi, Hoffman and Wu strength criteria were used. They allowed fracture modeling of orthotropic materials with various compressive and tensile strength properties. The modeling of organic plastic fracture was performed numerically within the impact velocity range of 700-1500 m/s.

Measurement of gravel bed load using impact plates

USDA-ARS?s Scientific Manuscript database

Accurate determinations of the rate of bed load transport are difficult to make but important for determining the fate of sediment released after the removal of a dam. Two dams were removed from the Elwha River in the state of Washington beginning in 2011, and 72 impact plates were installed downst...

78 FR 30804 - Transmission Planning Reliability Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-23

... ``Non-Consequential Load Loss.'' 6. On the same day that the Commission issued Order No. 762, it issued... Non-Consequential Load Loss meets the conditions shown in Attachment 1. In no case can the planned Non...- consequential load loss following a single contingency provided that the plan is documented and vetted in an...

49 CFR 172.301 - General marking requirements for non-bulk packagings.

Code of Federal Regulations, 2012 CFR

2012-10-01

... container load, and the entire contents of the rail car, truck or freight container are shipped from one... quantities of a single hazardous material in non-bulk packages. A transport vehicle or freight container... loaded at one loading facility; (iv) The transport vehicle or freight container contains no other...

49 CFR 172.301 - General marking requirements for non-bulk packagings.

Code of Federal Regulations, 2011 CFR

2011-10-01

... container load, and the entire contents of the rail car, truck or freight container are shipped from one... quantities of a single hazardous material in non-bulk packages. A transport vehicle or freight container... loaded at one loading facility; (iv) The transport vehicle or freight container contains no other...

49 CFR 172.301 - General marking requirements for non-bulk packagings.

Code of Federal Regulations, 2010 CFR

2010-10-01

... container load, and the entire contents of the rail car, truck or freight container are shipped from one... or freight container containing only a single hazardous material in non-bulk packages must be marked... hazardous material is loaded at one loading facility; (iv) The transport vehicle or freight container...

Investigation of Low-Cycle Bending Fatigue of AISI 9310 Steel Spur Gears

NASA Technical Reports Server (NTRS)

Handschuh, Robert F.; Krantz, Timothy L.; Lerch, Bradley A.; Burke, Christopher S.

2007-01-01

An investigation of the low-cycle bending fatigue of spur gears made from AISI 9310 gear steel was completed. Tests were conducted using the single-tooth bending method to achieve crack initiation and propagation. Tests were conducted on spur gears in a fatigue test machine using a dedicated gear test fixture. Test loads were applied at the highest point of single tooth contact. Gear bending stresses for a given testing load were calculated using a linear-elastic finite element model. Test data were accumulated from 1/4 cycle to several thousand cycles depending on the test stress level. The relationship of stress and cycles for crack initiation was found to be semi-logarithmic. The relationship of stress and cycles for crack propagation was found to be linear. For the range of loads investigated, the crack propagation phase is related to the level of load being applied. Very high loads have comparable crack initiation and propagation times whereas lower loads can have a much smaller number of cycles for crack propagation cycles as compared to crack initiation.

Investigation of Low-Cycle Bending Fatigue of AISI 9310 Steel Spur Gears

NASA Technical Reports Server (NTRS)

Handschuh, Robert F.; Krantz, Timothy L.; Lerch, Bradley A.; Burke, Christopher S.

2007-01-01

An investigation of the low-cycle bending fatigue of spur gears made from AISI 9310 gear steel was completed. Tests were conducted using the single-tooth bending method to achieve crack initiation and propagation. Tests were conducted on spur gears in a fatigue test machine using a dedicated gear test fixture. Test loads were applied at the highest point of single tooth contact. Gear bending stresses for a given testing load were calculated using a linear-elastic finite element model. Test data were accumulated from 1/4 cycle to several thousand cycles depending on the test stress level. The relationship of stress and cycles for crack initiation was found to be semilogarithmic. The relationship of stress and cycles for crack propagation was found to be linear. For the range of loads investigated, the crack propagation phase is related to the level of load being applied. Very high loads have comparable crack initiation and propagation times whereas lower loads can have a much smaller number of cycles for crack propagation cycles as compared to crack initiation.

Analysis of Mesh Distribution Systems Considering Load Models and Load Growth Impact with Loops on System Performance

NASA Astrophysics Data System (ADS)

Kumar Sharma, A.; Murty, V. V. S. N.

2014-12-01

The distribution system is the final link between bulk power system and consumer end. A distinctive load flow solution method is used for analysis of the load flow of radial and weakly meshed network based on Kirchhoff's Current Law (KCL) and KVL. This method has excellent convergence characteristics for both radial as well as weakly meshed structure and is based on bus injection to branch current and branch-current to bus-voltage matrix. The main contribution of the paper is: (i) an analysis has been carried out for a weekly mesh network considering number of loops addition and its impact on the losses, kW and kVAr requirements from a system, and voltage profile, (ii) different load models, realistic ZIP load model and load growth impact on losses, voltage profile, kVA and kVAr requirements, (iii) impact of addition of loops on losses, voltage profile, kVA and kVAr requirements from substation, and (iv) comparison of system performance with radial distribution system. Voltage stability is a major concern in planning and operation of power systems. This paper also includes identifying the closeness critical bus which is the most sensitive to the voltage collapse in radial distribution networks. Node having minimum value of voltage stability index is the most sensitive node. Voltage stability index values are computed for meshed network with number of loops added in the system. The results have been obtained for IEEE 33 and 69 bus test system. The results have also been obtained for radial distribution system for comparison.

Creation of an Aeronautical Capstone Design Project Program at Ohio State University

DTIC Science & Technology

2014-12-08

Equation 12 below. As Figure 35 shows, a single adhesively bonded lap joint is considered. The epoxy only sees a load in the axial direction. In...lap joint [1] = = ( ) 12 =stress distribution factor = applied load in the axial direction ...Figure 11. The joints are designed to handle the bending loads of horizontal, vertical and angled deployment and are designed to directly load the carbon

Impact of remote sensing upon the planning, management and development of water resources. Summary of computers and computer growth trends for hydrologic modeling and the input of ERTS image data processing load

NASA Technical Reports Server (NTRS)

Castruccio, P. A.; Loats, H. L., Jr.

1975-01-01

An analysis of current computer usage by major water resources users was made to determine the trends of usage and costs for the principal hydrologic users/models. The laws and empirical relationships governing the growth of the data processing loads were described and applied to project the future data loads. Data loads for ERTS CCT image processing were computed and projected through the 1985 era. The analysis showns significant impact due to the utilization and processing of ERTS CCT's data.

Triple-Loaded Single-Row Versus Suture-Bridge Double-Row Rotator Cuff Tendon Repair With Platelet-Rich Plasma Fibrin Membrane: A Randomized Controlled Trial.

PubMed

Barber, F Alan

2016-05-01

To compare the structural healing and clinical outcomes of triple-loaded single-row with suture-bridging double-row repairs of full-thickness rotator cuff tendons when both repair constructs are augmented with platelet-rich plasma fibrin membrane. A prospective, randomized, consecutive series of patients diagnosed with full-thickness rotator cuff tears no greater than 3 cm in anteroposterior length were treated with a triple-loaded single-row (20) or suture-bridging double-row (20) repair augmented with platelet-rich plasma fibrin membrane. The primary outcome measure was cuff integrity by magnetic resonance imaging (MRI) at 12 months postoperatively. Secondary clinical outcome measures were American Shoulder and Elbow Surgeons, Rowe, Simple Shoulder Test, Constant, and Single Assessment Numeric Evaluation scores. The mean MRI interval was 12.6 months (range, 12-17 months). A total of 3 of 20 single-row repairs and 3 of 20 double-row repairs (15%) had tears at follow-up MRI. The single-row group had re-tears in 1 single tendon repair and 2 double tendon repairs. All 3 tears failed at the original attachment site (Cho type 1). In the double-row group, re-tears were found in 3 double tendon repairs. All 3 tears failed medial to the medial row near the musculotendinous junction (Cho type 2). All clinical outcome measures were significantly improved from the preoperative level (P < .0001), but there was no statistical difference between groups postoperatively. There is no MRI difference in rotator cuff tendon re-tear rate at 12 months postsurgery between a triple-loaded single-row repair or a suture-bridging double-row repair when both are augmented with platelet-rich plasma fibrin membrane. No difference could be demonstrated between these repairs on clinical outcome scores. I, Prospective randomized study. Copyright © 2016 Arthroscopy Association of North America. All rights reserved.

Biomechanical performance of different cable and wire cerclage configurations.

PubMed

Lenz, Mark; Perren, Stephan Marcel; Richards, Robert Geoff; Mückley, Thomas; Hofmann, Gunther Olaf; Gueorguiev, Boyko; Windolf, Markus

2013-01-01

Cerclage technology is regaining interest due to the increasing number of periprosthetic fractures. Different wiring techniques have been formerly proposed and have hibernated over years. Hereby, they are compared to current cerclage technology. Seven groups (n = 6) of different cable cerclage (Ø1.7 mm, crimp closure) configurations (one single cerclage looped once around the shells, one single cerclage looped twice, two cerclages each looped once) and solid wire cerclages (Ø1.5 mm, twist closure) (same configurations as cable cerclages, and two braided wires, twisted around each other looped once) fixed two cortical half shells of human femoral shaft mounted on a testing jig. Sinusoidal cyclic loading with constantly increasing force (0.1 N/cycle) was applied starting at 50 N peak load. Cerclage pretension (P), load leading to onset of plastic deformation (D) and load at total failure (T) were identified. Statistical differences between the groups were detected by univariate ANOVA. Double looped cables (P442N ± 129; D1334N ± 319; T2734N ± 330) performed significantly better (p < 0.05) than single looped cables (P292N ± 56; D646N ± 108; T1622N ± 171) and were comparable to two single cables (P392N ± 154; D1191N ± 334; T2675N ± 361). Double looped wires (P335N ± 49; D752N ± 119; T1359N ± 80) were significantly better (p < 0.05) than single looped wires (P181N ± 16; D343N ± 33; T606N ± 109) and performed similarly to single looped cables. Braided wires (P119N ± 26; D225N ± 55; T919N ± 197) exhibited early loss of pretension and plastic deformation. Double looped cerclages provided a better fixation stability compared to a single looped cerclage. Double looped wires were comparable to a single looped cable. The use of braided wires could not be recommended mechanically.

Operation costs and pollutant emissions reduction by definition of new collection scheduling and optimization of MSW collection routes using GIS. The case study of Barreiro, Portugal.

PubMed

Zsigraiova, Zdena; Semiao, Viriato; Beijoco, Filipa

2013-04-01

This work proposes an innovative methodology for the reduction of the operation costs and pollutant emissions involved in the waste collection and transportation. Its innovative feature lies in combining vehicle route optimization with that of waste collection scheduling. The latter uses historical data of the filling rate of each container individually to establish the daily circuits of collection points to be visited, which is more realistic than the usual assumption of a single average fill-up rate common to all the system containers. Moreover, this allows for the ahead planning of the collection scheduling, which permits a better system management. The optimization process of the routes to be travelled makes recourse to Geographical Information Systems (GISs) and uses interchangeably two optimization criteria: total spent time and travelled distance. Furthermore, rather than using average values, the relevant parameters influencing fuel consumption and pollutant emissions, such as vehicle speed in different roads and loading weight, are taken into consideration. The established methodology is applied to the glass-waste collection and transportation system of Amarsul S.A., in Barreiro. Moreover, to isolate the influence of the dynamic load on fuel consumption and pollutant emissions a sensitivity analysis of the vehicle loading process is performed. For that, two hypothetical scenarios are tested: one with the collected volume increasing exponentially along the collection path; the other assuming that the collected volume decreases exponentially along the same path. The results evidence unquestionable beneficial impacts of the optimization on both the operation costs (labor and vehicles maintenance and fuel consumption) and pollutant emissions, regardless the optimization criterion used. Nonetheless, such impact is particularly relevant when optimizing for time yielding substantial improvements to the existing system: potential reductions of 62% for the total spent time, 43% for the fuel consumption and 40% for the emitted pollutants. This results in total cost savings of 57%, labor being the greatest contributor, representing over €11,000 per year for the two vehicles collecting glass-waste. Moreover, it is shown herein that the dynamic loading process of the collection vehicle impacts on both the fuel consumption and on pollutant emissions. Copyright © 2012 Elsevier Ltd. All rights reserved.

The impact of benthic fauna on fluvial bed load transport: Challenges of upscaling laboratory experiments to river and landscape scales.

NASA Astrophysics Data System (ADS)

Rice, S. P.

2012-04-01

The impact on sediment transport processes and channel morphology of several relatively large, iconic animals including beaver and salmon is increasingly well understood. However, many other aquatic fauna are important zoogeomorphic agents and ecosystem engineers. These somewhat overlooked "Cinderella" species include benthic aquatic insect larvae, freshwater crustaceans and many species of fish. Despite relatively modest individual effects, the ubiquity, abundance and cumulative impact of these organisms makes them a potentially significant agency, with as yet undiscovered and unquantified impacts on channel morphology and sediment fluxes. Their actions (digging, foraging, moving, burrowing), constructions and secretions modify bed sediment characteristics (grain size distribution, interlock, imbrication, protrusion), alter bed topography (thence hydraulic roughness) and contribute to biogenic restraints on grain movement. In turn, they can affect the distribution of surface particle entrainment thresholds and bed shear stresses, with implications for bed load transport. Flume experiments have measured some of these impacts and provided direct observations of the mechanisms involved, but many of the most interesting research questions pertain to the impact of these animals at reach, catchment and even landscape scales: Not least, what is the impact of small aquatic animals on bed load flux and yield? This presentation will consider some of the challenges involved in answering this question; that is, of scaling up experimental understanding of how aquatic animals affect bed load transport processes to river scales. Pertinent themes include: (1) the potential impacts of experimental arrangements on the behaviours and activities that affect hydraulic or geomorphological processes; (2) field coincidence of the spatial and temporal distributions of (a) the animals and their behaviours with (b) the physical conditions (substrates, flows) under which those animals are understood to have an effect; (3) the magnitude of any demonstrable net field impact, relative to those other factors that control bed load transport rates.

Single-Event Transient Testing of Low Dropout PNP Series Linear Voltage Regulators

NASA Technical Reports Server (NTRS)

Adell, Philippe; Allen, Gregory

2013-01-01

As demand for high-speed, on-board, digital-processing integrated circuits on spacecraft increases (field-programmable gate arrays and digital signal processors in particular), the need for the next generation point-of-load (POL) regulator becomes a prominent design issue. Shrinking process nodes have resulted in core rails dropping to values close to 1.0 V, drastically reducing margin to standard switching converters or regulators that power digital ICs. The goal of this task is to perform SET characterization of several commercial POL converters, and provide a discussion of the impact of these results to state-of-the-art digital processing IC through laser and heavy ion testing

Apparatus for measurement of acoustic wave propagation under uniaxial loading with application to measurement of third-order elastic constants of piezoelectric single crystals.

PubMed

Zhang, Haifeng; Kosinski, J A; Karim, Md Afzalul

2013-05-01

We describe an apparatus for the measurement of acoustic wave propagation under uniaxial loading featuring a special mechanism designed to assure a uniform mechanical load on a cube-shaped sample of piezoelectric material. We demonstrate the utility of the apparatus by determining the effects of stresses on acoustic wave speed, which forms a foundation for the final determination of the third-order elastic constants of langasite and langatate single crystals. The transit time method is used to determine changes in acoustic wave velocity as the loading is varied. In order to minimize error and improve the accuracy of the wave speed measurements, the cross correlation method is used to determine the small changes in the time of flight. Typical experimental results are presented and discussed.

In-vitro development of a temporal abutment screw to protect osseointegration in immediate loaded implants

PubMed Central

2015-01-01

PURPOSE In this study, a temporal abutment fixation screw, designed to fracture in a controlled way upon application of an occlusal force sufficient to produce critical micromotion was developed. The purpose of the screw was to protect the osseointegration of immediate loaded single implants. MATERIALS AND METHODS Seven different screw prototypes were examined by fixing titanium abutments to 112 Mozo-Grau external hexagon implants (MG Osseous®; Mozo-Grau, S.A., Valladolid, Spain). Fracture strength was tested at 30° in two subgroups per screw: one under dynamic loading and the other without prior dynamic loading. Dynamic loading was performed in a single-axis chewing simulator using 150,000 load cycles at 50 N. After normal distribution of obtained data was verified by Kolmogorov-Smirnov test, fracture resistance between samples submitted and not submitted to dynamic loading was compared by the use of Student's t-test. Comparison of fracture resistance among different screw designs was performed by the use of one-way analysis of variance. Confidence interval was set at 95%. RESULTS Fractures occurred in all screws, allowing easy retrieval. Screw Prototypes 2, 5 and 6 failed during dynamic loading and exhibited statistically significant differences from the other prototypes. CONCLUSION Prototypes 2, 5 and 6 may offer a useful protective mechanism during occlusal overload in immediate loaded implants. PMID:25932315

Physics Features of TRU-Fueled VHTRs

DOE PAGES

Lewis, Tom G.; Tsvetkov, Pavel V.

2009-01-01

The current waste management strategy for spent nuclear fuel (SNF) mandated by the US Congress is the disposal of high-level waste (HLW) in a geological repository at Yucca Mountain. Ongoing efforts on closed-fuel cycle options and difficulties in opening and safeguarding such a repository have led to investigations of alternative waste management strategies. One potential strategy for the US fuel cycle would be to make use of fuel loadings containing high concentrations of transuranic (TRU) nuclides in the next-generation reactors. The use of such fuels would not only increase fuel supply but could also potentially facilitate prolonged operation modes (viamore » fertile additives) on a single fuel loading. The idea is to approach autonomous operation on a single fuel loading that would allow marketing power units as nuclear batteries for worldwide deployment. Studies have already shown that high-temperature gas-cooled reactors (HTGRs) and their Generation IV (GEN IV) extensions, very-high-temperature reactors (VHTRs), have encouraging performance characteristics. This paper is focused on possible physics features of TRU-fueled VHTRs. One of the objectives of a 3-year U.S. DOE NERI project was to show that TRU-fueled VHTRs have the possibility of prolonged operation on a single fuel loading. A 3D temperature distribution was developed based on conceivable operation conditions of the 600 MWth VHTR design. Results of extensive criticality and depletion calculations with varying fuel loadings showed that VHTRs are capable for autonomous operation and HLW waste reduction when loaded with TRU fuel.« less

The relations among upper-extremity loading characteristics and bone mineral density changes in young women.

PubMed

Wang, Man-Ying; Salem, George J

2004-06-01

The relations among the reaction forces engendered during an upper-extremity dynamic impact-loading exercise (DILE) program and bone mineral density adaptations (DeltaBMD) in the radius were investigated in 24 healthy premenopausal women (mean age = 29 +/- 6 years). Subjects performed DILE 36 cycles/day, 3 days/week for 24 weeks. The exercised arm was allocated randomly to either the dominant or the nondominant limb. In addition, subjects were assigned randomly into either damped or nondamped treatment arms to examine the effects of both higher- and lower-magnitude loading prescriptions. Measurements including anthropometrics, self-reported physical activity levels, hand-grip strength, radial BMD (DEXA, Hologic QDR1500, MA) at the ultradistal radius (UD), distal 1/3 radius (DR), and total distal radius (TOTAL), and exercise-related loading characteristics (impact load, loading rate, and impulse) were recorded at baseline and at 6 months. Simple linear regression models were used to fit the regional BMD changes to the reaction force, changes in hand-grip strength (DeltaGRIP), and changes in body weight (DeltaBW). Findings demonstrated that the damping condition utilized during DILE influenced the relations between loading events and BMD changes. Specifically, none of the reaction-force characteristics significantly predicted changes in BMD in participants performing DILE using the damped condition, whereas, in the nondamped condition, impact load accounted for 58% of the variance in BMD change at DR and 66% of the variance in BMD change at TOTAL. Thresholds of 345 and 285 N of impact force to promote BMD increases at DR and TOTAL, respectively, were obtained from the regression models in the nondamped group. Impulse was also an independent predictor of BMD changes at TOTAL, accounting for 56% of the variance. Neither DeltaGRIP nor DeltaBW significantly predicted DeltaBMD at any radial site. These findings, in young adult women, parallel previous reports identifying significant, regionally specific relations among external loading events and BMD changes in both animal and human models.

Gene expression levels as endophenotypes in genome-wide association studies of Alzheimer disease

PubMed Central

Zou, F.; Carrasquillo, M. M.; Pankratz, V. S.; Belbin, O.; Morgan, K.; Allen, M.; Wilcox, S. L.; Ma, L.; Walker, L. P.; Kouri, N.; Burgess, J. D.; Younkin, L. H.; Younkin, Samuel G.; Younkin, C. S.; Bisceglio, G. D.; Crook, J. E.; Dickson, D. W.; Petersen, R. C.; Graff-Radford, N.; Younkin, Steven G.; Ertekin-Taner, N.

2010-01-01

Background: Late-onset Alzheimer disease (LOAD) is a common disorder with a substantial genetic component. We postulate that many disease susceptibility variants act by altering gene expression levels. Methods: We measured messenger RNA (mRNA) expression levels of 12 LOAD candidate genes in the cerebella of 200 subjects with LOAD. Using the genotypes from our LOAD genome-wide association study for the cis-single nucleotide polymorphisms (SNPs) (n = 619) of these 12 LOAD candidate genes, we tested for associations with expression levels as endophenotypes. The strongest expression cis-SNP was tested for AD association in 7 independent case-control series (2,280 AD and 2,396 controls). Results: We identified 3 SNPs that associated significantly with IDE (insulin degrading enzyme) expression levels. A single copy of the minor allele for each significant SNP was associated with ∼twofold higher IDE expression levels. The most significant SNP, rs7910977, is 4.2 kb beyond the 3′ end of IDE. The association observed with this SNP was significant even at the genome-wide level (p = 2.7 × 10−8). Furthermore, the minor allele of rs7910977 associated significantly (p = 0.0046) with reduced LOAD risk (OR = 0.81 with a 95% CI of 0.70-0.94), as expected biologically from its association with elevated IDE expression. Conclusions: These results provide strong evidence that IDE is a late-onset Alzheimer disease (LOAD) gene with variants that modify risk of LOAD by influencing IDE expression. They also suggest that the use of expression levels as endophenotypes in genome-wide association studies may provide a powerful approach for the identification of disease susceptibility alleles. GLOSSARY AD = Alzheimer disease; CI = confidence interval; GWAS = genome-wide association study; LOAD = late-onset Alzheimer disease; mRNA = messenger RNA; OR = odds ratio; SNP = single nucleotide polymorphism. PMID:20142614

Bone anchors or interference screws? A biomechanical evaluation for autograft ankle stabilization.

PubMed

Jeys, Lee; Korrosis, Sotiris; Stewart, Todd; Harris, Nicholas J

2004-01-01

Autograft stabilization uses free semitendinosus tendon grafts to anatomically reconstruct the anterior talofibular ligament. Study aims were to evaluate the biomechanical properties of Mitek GII anchors compared with the Arthrex Bio-Tenodesis Screw for free tendon reconstruction of the anterior talofibular ligament. There are no differences in load to failure and percentage specimen elongation at failure between the 2 methods. Controlled laboratory study using porcine models. Sixty porcine tendon constructs were failure tested. Re-creating the pull of the anterior talofibular ligament, loads were applied at 70 degrees to the bones. Thirty-six tendons were fixed to porcine tali and tested using a single pull to failure; 10 were secured with anchors and No. 2 Ethibond, 10 with anchors and FiberWire, 10 with screws and Fiberwire, and 6 with partially gripped screws. Cyclic preloading was conducted on 6 tendons fixed by anchors and on 6 tendons fixed by screws before failure testing. Two groups of 6 components fixed to the fibula were also tested. The talus single-pull anchor group produced a mean load of 114 N and elongation of 37% at failure. The talus single-pull screw group produced a mean load of 227 N and elongation of 22% at failure (P <.05). Cyclic preloading at 65% failure load before failure testing produced increases in load and decreases in elongation at failure. Partially gripped screws produced a load of 133 N and elongation of 30% at failure. The fibula model produced significant increases in load to failure for both. The human anterior talofibular ligament has loads of 139 N at failure with instability occurring at 20% elongation. Interference screw fixation produced significantly greater failure strength and less elongation at failure than bone anchors. The improved biomechanics of interference screws suggests that these may be more suited to in vivo reconstruction of the anterior talofibular ligament than are bone anchors.

The tensile effect on crack formation in single crystal silicon irradiated by intense pulsed ion beam

NASA Astrophysics Data System (ADS)

Liang, Guoying; Shen, Jie; Zhang, Jie; Zhong, Haowen; Cui, Xiaojun; Yan, Sha; Zhang, Xiaofu; Yu, Xiao; Le, Xiaoyun

2017-10-01

Improving antifatigue performance of silicon substrate is very important for the development of semiconductor industry. The cracking behavior of silicon under intense pulsed ion beam irradiation was studied by numerical simulation in order to understand the mechanism of induced surface peeling observed by experimental means. Using molecular dynamics simulation based on Stillinger Weber potential, tensile effect on crack growth and propagation in single crystal silicon was investigated. Simulation results reveal that stress-strain curves of single crystal silicon at a constant strain rate can be divided into three stages, which are not similar to metal stress-strain curves; different tensile load velocities induce difference of single silicon crack formation speed; the layered stress results in crack formation in single crystal silicon. It is concluded that the crack growth and propagation is more sensitive to strain rate, tensile load velocity, stress distribution in single crystal silicon.