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.

Climate Implications of the Heterogeneity of Anthropogenic Aerosol Forcing

NASA Astrophysics Data System (ADS)

Persad, Geeta Gayatri

Short-lived anthropogenic aerosols are concentrated in regions of high human activity, where they interact with radiation and clouds, causing horizontally heterogeneous radiative forcing between polluted and unpolluted regions. Aerosols can absorb shortwave energy in the atmosphere, but deplete it at the surface, producing opposite radiative perturbations between the surface and atmosphere. This thesis investigates climate and policy implications of this horizontal and vertical heterogeneity of anthropogenic aerosol forcing, employing the Geophysical Fluid Dynamics Laboratory's AM2.1 and AM3 models, both at a global scale and using East Asia as a regional case study. The degree of difference between spatial patterns of climate change due to heterogeneous aerosol forcing versus homogeneous greenhouse gas forcing deeply impacts the detection, attribution, and prediction of regional climate change. This dissertation addresses a gap in current understanding of these two forcings' response pattern development, using AM2.1 historical forcing simulations. The results indicate that fast atmospheric and land-surface processes alone substantially homogenize the global pattern of surface energy flux response to heterogeneous aerosol forcing. Aerosols' vertical redistribution of energy significantly impacts regional climate, but is incompletely understood. It is newly identified here, via observations and historical and idealized forcing simulations, that increased aerosol-driven atmospheric absorption may explain half of East Asia's recent surface insolation decline. Further, aerosols' surface and atmospheric effects counteract each other regionally---atmospheric heating enhances summer monsoon circulation, while surface dimming suppresses it---but absorbing aerosols' combined effects reduce summer monsoon rainfall. This thesis constitutes the first vertical decomposition of aerosols' impacts in this high-emissions region and elucidates the monsoonal response to aerosols' surface versus atmospheric forcing. Future aerosol emissions patterns will affect the distribution of regional climate impacts. This dissertation interrogates how international trade affects existing assumptions about East Asia's future black carbon aerosol emissions, using integrated assessment modeling, emissions and economic data, and AM3 simulations. Exports emerge as a uniquely large and potentially growing source of Chinese black carbon emissions that could impede projected regional emissions reductions, with substantial climate and health consequences. The findings encourage greater emissions projection sophistication and illustrate how societal decisions may influence future aerosol forcing heterogeneity.

Vertical Impact of a Sphere Falling into Water

ERIC Educational Resources Information Center

Cross, Rod

2016-01-01

The nature of the drag force on an object moving through a fluid is well documented and many experiments have been described to allow students to measure the force. For low speed flows the drag force is proportional to the velocity of the object, while at high flow speeds the drag force is proportional to the velocity squared. The basic physics…

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.

Apparatus for encapsulating a photovoltaic module

DOEpatents

Albright, Scot P.; Dugan, Larry M.

1995-10-24

The subject inventions concern various photovoltaic module designs to protect the module from horizontal and vertical impacts and degradation of solar cell efficiency caused by moisture. In one design, a plurality of panel supports that are positioned adjacent to the upper panel in a photovoltaic module absorb vertical forces exerted along an axis perpendicular to the upper panel. Other designs employ layers of glass and tempered glass, respectively, to protect the module from vertical impacts. A plurality of button-shaped channels is used around the edges of the photovoltaic module to absorb forces applied to the module along an axis parallel to the module and direct moisture away from the module that could otherwise penetrate the module and adversely affect the cells within the module. A spacer is employed between the upper and lower panels that has a coefficient of thermal expansion substantially equivalent to the coefficient of thermal expansion of at least one of the panels.

Techniques for determination of impact forces during walking and running in a zero-G environment

NASA Technical Reports Server (NTRS)

Greenisen, Michael; Walton, Marlei; Bishop, Phillip; Squires, William

1992-01-01

One of the deleterious adaptations to the microgravity conditions of space flight is the loss of bone mineral content. This loss appears to be at least partially attributable to the minimal skeletal axial loading concomitant with microgravity. The purpose of this study was to develop and fabricate the instruments and hardware necessary to quantify the vertical impact forces (Fz) imparted to users of the space shuttle passive treadmill during human locomotion in a three-dimensional zero-gravity environment. The shuttle treadmill was instrumented using a Kistler forceplate to measure vertical impact forces. To verify that the instruments and hardware were functional, they were tested both in the one-G environment and aboard the KC-135 reduced gravity aircraft. The magnitude of the impact loads generated in one-G on the shuttle treadmill for walking at 0.9 m/sec and running at 1.6 and 2.2 m/sec were 1.1, 1.7, and 1.7 G, respectively, compared with loads of 0.95, 1.2, and 1.5 G in the zero-G environment.

Rearfoot and midfoot or forefoot impacts in habitually shod runners.

PubMed

Boyer, Elizabeth R; Rooney, Brandon D; Derrick, Timothy R

2014-07-01

Shear loading rates (LR) have not been investigated in runners with a mid- or forefoot strike (FFS) versus rearfoot strike (RFS). The purpose of this study was to compare three-dimensional ground reaction forces (GRF) and LR during impact in habitual rearfoot strikers (hRF) and habitual forefoot strikers (hFF) strikers. Thirty competitive runners performed 10 overground running trials with both foot strike styles. Peak three-dimensional and resultant GRF and instantaneous LR during impact were compared. Vertical LR significantly decreased for hRF using an FFS (RFS = 148 ± 36 body weight [BW]·s(-1), FFS = 98 ± 31 BW·s(-1)) but was similar for hFF running with either foot strike (FFS = 136 ± 35 BW·s(-1), RFS = 135 ± 28 BW·s(-1)). Posterior impact forces were present during FFS but not during RFS, and posterior LR was significantly greater for both groups during FFS (-58 ± 17 vs -19 ± 6 BW·s(-1)). Medial impact forces were also present during FFS but not during RFS, and medial LR was significantly larger for both groups during FFS (-21 ± 7 vs -6 ± 6 BW·s(-1)). Interestingly, hFF had greater impact peaks and LR in all directions compared with hRF during FFS. This may be explained by hFF using a smaller strike index (hFF = 62% ± 9%, hRF = 67% ± 9%; P = 0.02), which was significantly inversely related to vertical LR and impact peak. Peak resultant and vertical LR are not ubiquitously lower when using a shod FFS versus RFS despite an absence of resultant and vertical impact peaks. Furthermore, there were impact peaks in the posterior and medial directions, leading also to greater LR in these directions during FFS. Therefore, transitioning from RFS to FFS in traditional running shoes may not offer long-term protection against impact-related running injuries because hFF running with an FFS demonstrated many GRF and LR similar to or greater than RFS.

Instrumented figure skating blade for measuring on-ice skating forces

NASA Astrophysics Data System (ADS)

Acuña, S. A.; Smith, D. M.; Robinson, J. M.; Hawks, J. C.; Starbuck, P.; King, D. L.; Ridge, S. T.; Charles, S. K.

2014-12-01

Competitive figure skaters experience substantial, repeated impact loading during jumps and landings. Although these loads, which are thought to be as high as six times body weight, can lead to overuse injuries, it is not currently possible to measure these forces on-ice. Consequently, efforts to improve safety for skaters are significantly limited. Here we present the development of an instrumented figure skating blade for measuring forces on-ice. The measurement system consists of strain gauges attached to the blade, Wheatstone bridge circuit boards, and a data acquisition device. The system is capable of measuring forces in the vertical and horizontal directions (inferior-superior and anterior-posterior directions, respectively) in each stanchion with a sampling rate of at least 1000 Hz and a resolution of approximately one-tenth of body weight. The entire system weighs 142 g and fits in the space under the boot. Calibration between applied and measured force showed excellent agreement (R > 0.99), and a preliminary validation against a force plate showed good predictive ability overall (R ≥ 0.81 in vertical direction). The system overestimated the magnitude of the first and second impact peaks but detected their timing with high accuracy compared to the force plate.

The scaling and dynamics of a projectile obliquely impacting a granular medium.

PubMed

Wang, Dengming; Ye, Xiaoyan; Zheng, Xiaojing

2012-01-01

In this paper, the dynamics of a spherical projectile obliquely impacting into a two-dimensional granular bed is numerically investigated using the discrete element method. The influences of projectile's initial velocities and impacting angles are mainly considered. Numerical results show that the relationship between the final penetration depth and the initial impact velocity is very similar to that in the vertical-impact case. However, the dependence of the stopping time on the impact velocity of the projectile exhibits critical characteristics at different impact angles: the stopping time approximately increases linearly with the impact velocity for small impact angles but decreases in an exponential form for larger impact angles, which demonstrates the existence of two different regimes at low and high impact angles. When the impact angle is regarded as a parametric variable, a phenomenological force model at large impact angles is eventually proposed based on the simulation results, which can accurately describe the nature of the resistance force exerted on the projectile by the granular medium at different impact angels during the whole oblique-impact process. The degenerate model agrees well with the existing experimental results in the vertical-impact cases.

The effect of hardhats on head and neck response to vertical impacts from large construction objects.

PubMed

Suderman, Bethany L; Hoover, Ryan W; Ching, Randal P; Scher, Irving S

2014-12-01

We evaluated the effectiveness of hardhats in attenuating head acceleration and neck force in vertical impacts from large construction objects. Two weight-matched objects (lead shot bag and concrete block) weighing 9.1 kg were dropped from three heights (0.91 m, 1.83 m and 2.74 m) onto the head of a 50th percentile male Hybrid III anthropomorphic test device (ATD). Two headgear conditions were tested: no head protection and an ANSI Type-I, Class-E hardhat. A third headgear condition (snow sport helmet) was tested at 1.83 m for comparison with the hardhat. Hardhats significantly reduced the resultant linear acceleration for the concrete block impacts by 70-95% when compared to the unprotected head condition. Upper neck compression was also significantly reduced by 26-60% with the use of a hardhat when compared to the unprotected head condition for the 0.91 and 1.83 m drop heights for both lead shot and concrete block drop objects. In this study we found that hardhats can be effective in reducing both head accelerations and compressive neck forces for large construction objects in vertical impacts. Copyright © 2014 Elsevier Ltd. All rights reserved.

Enhanced vertical mixing within mesoscale eddies due to high frequency winds in the South China Sea

NASA Astrophysics Data System (ADS)

Cardona, Yuley; Bracco, Annalisa

The South China Sea is a marginal basin with a complex circulation influenced by the East Asian Monsoon, river discharge and intricate bathymetry. As a result, both the mesoscale eddy field and the near-inertial energy distribution display large spatial variability and they strongly influence the oceanic transport and mixing. With an ensemble of numerical integrations using a regional ocean model, this work investigates how the temporal resolution of the atmospheric forcing fields modifies the horizontal and vertical velocity patterns and impacts the transport properties in the basin. The response of the mesoscale circulation in the South China Sea is investigated under three different forcing conditions: monthly, daily and 6-hourly momentum and heat fluxes. While the horizontal circulation does not display significant differences, the representation of the vertical velocity field displays high sensitivity to the frequency of the wind forcing. If the wind field contains energy at the inertial frequency or higher (daily and 6-hourly cases), then submesoscale fronts, vortex Rossby waves and near inertial waves are excited as ageostrophic expression of the vigorous eddy field. Those quasi- and near-inertial waves dominate the vertical velocity field in the mixed layer (vortex Rossby waves) and below the first hundred meters (near inertial waves) and they are responsible for the differences in the vertical transport properties under the various forcing fields as quantified by frequency spectra, vertical velocity profiles and vertical dispersion of Lagrangian tracers.

Wagon instability in long trains

NASA Astrophysics Data System (ADS)

Cole, Colin; McClanachan, Mitchell; Spiryagin, Maksym; Sun, Yan Quan

2012-01-01

Lateral force components and impacts from couplers can adversely affect wagon stability. These issues are significant in longer and heavier trains increasing the risk of wagon rollover, wheel climb, wagon body pitch, bogie pitch and wagon lift-off. Modelling of coupler angles has been added to normal longitudinal train simulation to allow comprehensive study of lateral components of coupler forces. Lateral coupler forces are then combined with centripetal inertia calculations to determine quasi-static lateral forces, quasi-static vertical forces and quasi-static bogie lateral to vertical ratio, allowing the study of stringlining, buckling and wagon rollover risks. The approach taken allows for different rolling stock lengths, overhang and coupling lengths, and allows the study of angles occurring in transitions. Wagon body and bogie pitch are also studied with enhancements added to previous modelling to allow the study of wagon lift-off.

Influence of sports flooring and shoes on impact forces and performance during jump tasks.

PubMed

Malisoux, Laurent; Gette, Paul; Urhausen, Axel; Bomfim, Joao; Theisen, Daniel

2017-01-01

We aim to determine the influence of sports floorings and sports shoes on impact mechanics and performance during standardised jump tasks. Twenty-one male volunteers performed ankle jumps (four consecutive maximal bounds with very dynamic ankle movements) and multi-jumps (two consecutive maximal counter-movement jumps) on force plates using minimalist and cushioned shoes under 5 sports flooring (SF) conditions. The shock absorption properties of the SF, defined as the proportion of peak impact force absorbed by the tested flooring when compared with a concrete hard surface, were: SF0 = 0% (no flooring), SF1 = 19%, SF2 = 26%, SF3 = 37% and SF4 = 45%. Shoe and flooring effects were compared using 2x5 repeated-measures ANOVA with post-hoc Bonferroni-corrected comparisons. A significant interaction between SF and shoe conditions was found for VILR only (p = 0.003). In minimalist shoes, SF influenced Vertical Instantaneous Loading Rate (VILR) during ankle jumps (p = 0.006) and multi-jumps (p<0.001), in accordance with shock absorption properties. However, in cushioned shoes, SF influenced VILR during ankle jumps only (p<0.001). Contact Time was the only additional variable affected by SF, but only during multi-jumps in minimalist shoes (p = 0.037). Cushioned shoes induced lower VILR (p<0.001) and lower Contact Time (p≤0.002) during ankle jumps and multi-jumps compared to minimalist shoes. During ankle jumps, cushioned shoes induced greater Peak Vertical Ground Reaction Force (PVGRF, p = 0.002), greater Vertical Average Loading Rate (p<0.001), and lower eccentric (p = 0.008) and concentric (p = 0.004) work. During multi-jumps, PVGRF was lower (p<0.001) and jump height was higher (p<0.001) in cushioned compared to minimalist shoes. In conclusion, cushioning influenced impact forces during standardised jump tasks, whether it was provided by the shoes or the sports flooring. VILR is the variable that was the most affected.

Influence of sports flooring and shoes on impact forces and performance during jump tasks

PubMed Central

Urhausen, Axel; Bomfim, Joao

2017-01-01

We aim to determine the influence of sports floorings and sports shoes on impact mechanics and performance during standardised jump tasks. Twenty-one male volunteers performed ankle jumps (four consecutive maximal bounds with very dynamic ankle movements) and multi-jumps (two consecutive maximal counter-movement jumps) on force plates using minimalist and cushioned shoes under 5 sports flooring (SF) conditions. The shock absorption properties of the SF, defined as the proportion of peak impact force absorbed by the tested flooring when compared with a concrete hard surface, were: SF0 = 0% (no flooring), SF1 = 19%, SF2 = 26%, SF3 = 37% and SF4 = 45%. Shoe and flooring effects were compared using 2x5 repeated-measures ANOVA with post-hoc Bonferroni-corrected comparisons. A significant interaction between SF and shoe conditions was found for VILR only (p = 0.003). In minimalist shoes, SF influenced Vertical Instantaneous Loading Rate (VILR) during ankle jumps (p = 0.006) and multi-jumps (p<0.001), in accordance with shock absorption properties. However, in cushioned shoes, SF influenced VILR during ankle jumps only (p<0.001). Contact Time was the only additional variable affected by SF, but only during multi-jumps in minimalist shoes (p = 0.037). Cushioned shoes induced lower VILR (p<0.001) and lower Contact Time (p≤0.002) during ankle jumps and multi-jumps compared to minimalist shoes. During ankle jumps, cushioned shoes induced greater Peak Vertical Ground Reaction Force (PVGRF, p = 0.002), greater Vertical Average Loading Rate (p<0.001), and lower eccentric (p = 0.008) and concentric (p = 0.004) work. During multi-jumps, PVGRF was lower (p<0.001) and jump height was higher (p<0.001) in cushioned compared to minimalist shoes. In conclusion, cushioning influenced impact forces during standardised jump tasks, whether it was provided by the shoes or the sports flooring. VILR is the variable that was the most affected. PMID:29020108

Impact differences in ground reaction force and center of mass between the first and second landing phases of a drop vertical jump and their implications for injury risk assessment.

PubMed

Bates, Nathaniel A; Ford, Kevin R; Myer, Gregory D; Hewett, Timothy E

2013-04-26

The drop vertical jump (DVJ) task is commonly used to assess biomechanical performance measures that are associated with ACL injury risk in athletes. Previous investigations have solely assessed the first landing phase. We examined the first and second landings of a DVJ for differences in the magnitude of vertical ground reaction force (vGRF) and position of center of mass (CoM). A cohort of 239 adolescent female basketball athletes completed a series of DVJ tasks from an initial box height of 31 cm. Dual force platforms and a three dimensional motion capture system recorded force and positional data for each trial. There was no difference in peak vGRF between landings (p=0.445), but side-to-side differences increased from the first to second landing (p=0.007). Participants demonstrated a lower minimum CoM during stance in the first landing than the second landing (p<0.001). The results have important implications for the future assessment of ACL injury risk behaviors in adolescent female athletes. Greater side-to-side asymmetry in vGRF and higher CoM during impact indicate the second landing of a DVJ may exhibit greater perturbation and better represent in-game mechanics associated with ACL injury risk. Copyright © 2013 Elsevier Ltd. All rights reserved.

A finite element analysis of the stress distribution to the mandible from impact forces with various orientations of third molars*

PubMed Central

Liu, Yun-feng; Wang, Russell; Baur, Dale A.; Jiang, Xian-feng

2018-01-01

Objective: To investigate the stress distribution to the mandible, with and without impacted third molars (IM3s) at various orientations, resulting from a 2000-Newton impact force either from the anterior midline or from the body of the mandible. Materials and methods: A 3D mandibular virtual model from a healthy dentate patient was created and the mechanical properties of the mandible were categorized to 9 levels based on the Hounsfield unit measured from computed tomography (CT) images. Von Mises stress distributions to the mandibular angle and condylar areas from static impact forces (Load I-front blow and Load II left blow) were evaluated using finite element analysis (FEA). Six groups with IM3 were included: full horizontal bony, full vertical bony, full 450 mesioangular bony, partial horizontal bony, partial vertical, and partial 450 mesioangular bony impaction, and a baseline group with no third molars. Results: Von Mises stresses in the condyle and angle areas were higher for partially than for fully impacted third molars under both loading conditions, with partial horizontal IM3 showing the highest fracture risk. Stresses were higher on the contralateral than on the ipsilateral side. Under Load II, the angle area had the highest stress for various orientations of IM3s. The condylar region had the highest stress when IM3s were absent. Conclusions: High-impact forces are more likely to cause condylar rather than angular fracture when IM3s are missing. The risk of mandibular fracture is higher for partially than fully impacted third molars, with the angulation of impaction having little effect on facture risk. PMID:29308606

Vertical drag force acting on intruders of different shapes in granular media

NASA Astrophysics Data System (ADS)

Zaidi, Ali Abbas; Müller, Christoph

2017-06-01

The penetration of large objects into granular media is encountered commonly both in nature (e.g. impacts of meteors and projectiles) and engineering applications (e.g. insertion of tractor blades into sand). The motion of the impacting intruder in granular media is resisted by a granular drag force. In this work, we assess the effect of intruder shape on the granular drag force using discrete element modelling (DEM). The following intruder shapes were modelled: spherical, conical, cylindrical and cubical. We observed that the drag force can be described well by a power-law relationship with intrusion depth, independent of the intruder shape. However, the exponent of the power-law expression increases with increasing "flatness" of the intruder's impacting surface due to an increasing fraction of the granular media affected by the impact of the intruder.

Measurement of the effect of playground surface materials on hand impact forces during upper limb fall arrests.

PubMed

Choi, Woochol J; Kaur, Harjinder; Robinovitch, Stephen N

2014-04-01

Distal radius fractures are common on playgrounds. Yet current guidelines for the selection of playground surface materials are based only on protection against fall-related head injuries. We conducted "torso release" experiments to determine how common playground surface materials affect impact force applied to the hand during upper limb fall arrests. Trials were acquired for falls onto a rigid surface, and onto five common playground surface materials: engineered wood fiber, gravel, mulch, rubber tile, and sand. Measures were acquired for arm angles of 20 and 40 degrees from the vertical. Playground surface materials influenced the peak resultant and vertical force (P<.001), but not the peak horizontal force (P=.159). When compared with the rigid condition, peak resultant force was reduced 17% by sand (from 1039 to 864 N), 16% by gravel, 7% by mulch, 5% by engineered wood fiber, and 2% by rubber tile. The best performing surface provided only a 17% reduction in peak resultant force. These results help to explain the lack of convincing evidence from clinical studies on the effectiveness of playground surface materials in preventing distal radius fractures during playground falls, and highlight the need to develop playground surface materials that provide improved protection against these injuries.

Impact Forces of Plyometric Exercises Performed on Land and in Water

PubMed Central

Donoghue, Orna A.; Shimojo, Hirofumi; Takagi, Hideki

2011-01-01

Background: Aquatic plyometric programs are becoming increasingly popular because they provide a less stressful alternative to land-based programs. Buoyancy reduces the impact forces experienced in water. Purpose: To quantify the landing kinetics during a range of typical lower limb plyometric exercises performed on land and in water. Study Design: Crossover design. Methods: Eighteen male participants performed ankle hops, tuck jumps, a countermovement jump, a single-leg vertical jump, and a drop jump from 30 cm in a biomechanics laboratory and in a swimming pool. Land and underwater force plates (Kistler) were used to obtain peak impact force, impulse, rate of force development, and time to reach peak force for the landing phase of each jump. Results: Significant reductions were observed in peak impact forces (33%-54%), impulse (19%-54%), and rate of force development (33%-62%) in water compared with land for the majority of exercises in this study (P < 0.05). Conclusions: The level of force reduction varies with landing technique, water depth, and participant height and body composition. Clinical Relevance: This information can be used to reintroduce athletes to the demands of plyometric exercises after injury. PMID:23016022

Self-bridging of vertical silicon nanowires and a universal capacitive force model for spontaneous attraction in nanostructures.

PubMed

Sun, Zhelin; Wang, Deli; Xiang, Jie

2014-11-25

Spontaneous attractions between free-standing nanostructures have often caused adhesion or stiction that affects a wide range of nanoscale devices, particularly nano/microelectromechanical systems. Previous understandings of the attraction mechanisms have included capillary force, van der Waals/Casimir forces, and surface polar charges. However, none of these mechanisms universally applies to simple semiconductor structures such as silicon nanowire arrays that often exhibit bunching or adhesions. Here we propose a simple capacitive force model to quantitatively study the universal spontaneous attraction that often causes stiction among semiconductor or metallic nanostructures such as vertical nanowire arrays with inevitably nonuniform size variations due to fabrication. When nanostructures are uniform in size, they share the same substrate potential. The presence of slight size differences will break the symmetry in the capacitive network formed between the nanowires, substrate, and their environment, giving rise to electrostatic attraction forces due to the relative potential difference between neighboring wires. Our model is experimentally verified using arrays of vertical silicon nanowire pairs with varied spacing, diameter, and size differences. Threshold nanowire spacing, diameter, or size difference between the nearest neighbors has been identified beyond which the nanowires start to exhibit spontaneous attraction that leads to bridging when electrostatic forces overcome elastic restoration forces. This work illustrates a universal understanding of spontaneous attraction that will impact the design, fabrication, and reliable operation of nanoscale devices and systems.

Global and Regional Radiative Forcing from 20 Reductions in BC, OC and SO4 an HTAP2 Multi-Model Study

NASA Technical Reports Server (NTRS)

Stjern, Camilla Weum; Samset, Bjorn Hallvard; Myhre, Gunnar; Bian, Huisheng; Chin, Mian; Davila, Yanko; Dentener, Frank; Emmons, Louisa; Flemming, Johannes; Haslerud, Amund Sovde;

Crashworthy Gunner Seat Testing Program

DTIC Science & Technology

1977-03-01

147 5 LIST OF ILLUSTRATIONS Page 1. Swivel Gunner Seat Mock-up 14 2. Ceiling and Floor Swivel Rings .... ........... 16 3. Wire - Bending Tension...History . 57 37. Test 1 - Vertical Acceleration, Dummy Pelvis . 58 38. Upper Wire - bending Attenuators, Force/Duflection 59 39 Pre-test 2, 900 to Impact...unobstructed depth to permit lateral movement in the seat for gunnery operations. Wire - bending energy attenuators are located at the top of the two vertical

Multi-component ground motion response spectra for coupled horizontal, vertical, angular accelerations, and tilt

USGS Publications Warehouse

Kalkan, E.; Graizer, V.

2007-01-01

Rotational and vertical components of ground motion are almost always ignored in design or in the assessment of structures despite the fact that vertical motion can be twice as much as the horizontal motion and may exceed 2g level, and rotational excitation may reach few degrees in the proximity of fault rupture. Coupling of different components of ground excitation may significantly amplify the seismic demand by introducing additional lateral forces and enhanced P-?? effects. In this paper, a governing equation of motion is postulated to compute the response of a SDOF oscillator under a multi-component excitation. The expanded equation includes secondary P-?? components associated with the combined impacts of tilt and vertical excitations in addition to the inertial forcing terms due to the angular and translational accelerations. The elastic and inelastic spectral ordinates traditionally generated considering the uniaxial input motion are compared at the end with the multi-component response spectra of coupled horizontal, vertical and tilting motions. The proposed multi-component response spectrum reflects kinematic characteristics of the ground motion that are not identifiable by the conventional spectrum itself, at least for the near-fault region where high intensity vertical shaking and rotational excitation are likely to occur.

The effect of socks on vertical and anteroposterior ground reaction forces in walking and running.

PubMed

Blackmore, Tim; Ball, Nick; Scurr, Joanna

2011-03-01

Previous research suggests that socks may have the potential for injury protection through the absorption and/or redistribution of impact forces. However, there is limited research regarding the shock attenuation qualities of athletic socks in sporting populations and previously observed pressure reductions have not been quantified using a force plate. Firstly to identify the effect of specialist athletic socks on vertical and anteroposterior ground reaction forces (GRFs) during walking and running. Secondly, to compare GRFs between specialist socks, non-specialist socks and barefoot walking and running conditions. Following ethical approval participants (n=5) completed five walking (1.52-1.68 m s(-1)) and running (3.8-4.2 m s(-1)) trials, unshod, over a force plate. This was completed before and after a 5000 m run (3.2 m s(-1)) in their own trainers in three conditions; barefoot, non-specialist socks and specialist running socks. Significant differences were identified between barefoot and specialist sock conditions for pre-intervention time to impact peak (F=3.110((2)), P=.05, r=.11) and maximum propulsive force (F=8.126((2)), P=.001, r=.25) when walking. Post hoc analysis identified an increase of .0016 s in time to impact peak when walking barefoot compared to the specialist sock condition (T=-7.402((4)), P=.002, r=.71). During walking the specialist sock also demonstrated a significant decrease of .075 BWs in maximum propulsive force when compared to the barefoot condition (T=-7.624((4)), P=.002, r=.79). Both significant effects diminished following the 5000 m run. Findings suggest that the specialist running sock has limited effects on GRFs and therefore may be responsible for a limited degree of shock attenuation experienced during walking. Copyright © 2010 Elsevier Ltd. All rights reserved.

Foot forces induced through Tai Chi push-hand exercises.

PubMed

Wong, Shiu Hong; Ji, Tianjian; Hong, Youlian; Fok, Siu Lun; Wang, Lin

2013-08-01

The low impact forces of Tai Chi push-hand exercises may be particularly suited for older people and for those with arthritis; however, the biomechanics of push-hand exercises have not previously been reported. This paper examines the ground reaction forces (GRFs) and plantar force distributions during Tai Chi push-hand exercises in a stationary stance with and without an opponent. Ten male Tai Chi practitioners participated in the study. The GRFs of each foot were measured in three perpendicular directions using two force plates (Kistler). The plantar force distribution of each foot was measured concurrently using an insole sensor system (Novel). The results showed that the average maximum vertical GRF of each foot was not more than 88% ± 6.1% of the body weight and the sum of the vertical forces (103% ± 1.4%) generated by the two feet approximately equals the body weight at any one time. The horizontal GRFs generated by the two feet were in the opposite directions and the measured mean peak values were not more than 12% ± 2.8% and 17% ± 4.3% of the body weight in the medio-lateral and antero-posterior directions respectively. Among the nine plantar areas, the toes sustained the greatest plantar force. This study indicates that push-hand exercises generate lower vertical forces than those induced by walking, bouncing, jumping and Tai Chi gait, and that the greatest plantar force is located in the toe area, which may have an important application in balance training particularly for older adults.

Isokinetic analysis of ankle and ground reaction forces in runners and triathletes

PubMed Central

Luna, Natália Mariana Silva; Alonso, Angelica Castilho; Brech, Guilherme Carlos; Mochizuki, Luis; Nakano, Eduardo Yoshio; Greve, Júlia Maria D'Andréa

2012-01-01

OBJECTIVE: To analyze and compare the vertical component of ground reaction forces and isokinetic muscle parameters for plantar flexion and dorsiflexion of the ankle between long-distance runners, triathletes, and non-athletes. METHODS: Seventy-five males with a mean age of 30.26 (±6.5) years were divided into three groups: a triathlete group (n = 26), a long-distance runner group (n = 23), and a non-athlete control group. The kinetic parameters were measured during running using a force platform, and the isokinetic parameters were measured using an isokinetic dynamometer. RESULTS: The non-athlete control group and the triathlete group exhibited smaller vertical forces, a greater ground contact time, and a greater application of force during maximum vertical acceleration than the long-distance runner group. The total work (180°/s) was greater in eccentric dorsiflexion and concentric plantar flexion for the non-athlete control group and the triathlete group than the long-distance runner group. The peak torque (60°/s) was greater in eccentric plantar flexion and concentric dorsiflexion for the control group than the athlete groups. CONCLUSIONS: The athlete groups exhibited less muscle strength and resistance than the control group, and the triathletes exhibited less impact and better endurance performance than the runners. PMID:23018298

Educational Mismatches and Labor Market Outcomes: Evidence from Both Vertical and Horizontal Mismatches in Thailand

ERIC Educational Resources Information Center

Pholphirul, Piriya

2017-01-01

Purpose: Educational mismatches constitute negative impacts on labor markets in most countries, Thailand is no exception. The purpose of this paper is to quantify the degree of educational mismatch in Thailand and its impacts on labor market outcomes. Design/methodology/approach: This study analyzes data obtained from Thailand's Labor Force Survey…

Effects of shoe cushioning upon ground reaction forces in running.

PubMed

Clarke, T E; Frederick, E C; Cooper, L B

1983-11-01

To determine the effects of widely varying amounts of cushioning upon vertical force (VF) parameters, ten male subjects, (mean weight = 68.0 kg) ran at a speed of 4.5 m . s-1 (6 min/mile pace) and contacted a Kistler force platform. Two shoes were tested: a hard one and a softer shoe that had 50% more cushioning as measured by an instrumented impact tester. Five right footfalls were collected for each shoe on each subject during which the ground reaction forces were sampled at 500 HZ using a PDP 11/34 minicomputer. Eight parameters from the VF data obtained for each trial were selected for analysis and compared statistically using a paired difference t test. It was found [force magnitudes expressed in multiples of body weight (BW)] that the time to the vertical force impact peak (VFIP) was significantly longer (hard = 22.5 ms, soft = 26.6 ms) in the soft shoe; however, no differences were seen in the magnitudes (hard = 2.30 BW, soft = 2.34 BW). The minimum after the VFIP was also significantly delayed in the soft shoe (hard = 33.8 ms, soft = 37.9 ms) and was significantly greater in the soft shoe (hard = 1.46 BW, soft = 1.90 BW). The peak VF propulsive force occurred statistically at the same time in both shoes (hard = 85.7 ms, soft = 84.0 ms), but was significantly greater in the soft shoe (hard = 2.73 BW, soft = 2.83 BW).(ABSTRACT TRUNCATED AT 250 WORDS)

Numerical modeling and preliminary validation of drag-based vertical axis wind turbine

NASA Astrophysics Data System (ADS)

Krysiński, Tomasz; Buliński, Zbigniew; Nowak, Andrzej J.

2015-03-01

The main purpose of this article is to verify and validate the mathematical description of the airflow around a wind turbine with vertical axis of rotation, which could be considered as representative for this type of devices. Mathematical modeling of the airflow around wind turbines in particular those with the vertical axis is a problematic matter due to the complex nature of this highly swirled flow. Moreover, it is turbulent flow accompanied by a rotation of the rotor and the dynamic boundary layer separation. In such conditions, the key aspects of the mathematical model are accurate turbulence description, definition of circular motion as well as accompanying effects like centrifugal force or the Coriolis force and parameters of spatial and temporal discretization. The paper presents the impact of the different simulation parameters on the obtained results of the wind turbine simulation. Analysed models have been validated against experimental data published in the literature.

Black carbon vertical profiles strongly affect its radiative forcing uncertainty

NASA Astrophysics Data System (ADS)

Samset, B. H.; Myhre, G.; Schulz, M.; Balkanski, Y.; Bauer, S.; Berntsen, T. K.; Bian, H.; Bellouin, N.; Diehl, T.; Easter, R. C.; Ghan, S. J.; Iversen, T.; Kinne, S.; Kirkevåg, A.; Lamarque, J.-F.; Lin, G.; Liu, X.; Penner, J.; Seland, Ø.; Skeie, R. B.; Stier, P.; Takemura, T.; Tsigaridis, K.; Zhang, K.

2012-11-01

The impact of black carbon (BC) aerosols on the global radiation balance is not well constrained. Here twelve global aerosol models are used to show that at least 20% of the present uncertainty in modeled BC direct radiative forcing (RF) is due to diversity in the simulated vertical profile of BC mass. Results are from phases 1 and 2 of the global aerosol model intercomparison project (AeroCom). Additionally, a significant fraction of the variability is shown to come from high altitudes, as, globally, more than 40% of the total BC RF is exerted above 5 km. BC emission regions and areas with transported BC are found to have differing characteristics. These insights into the importance of the vertical profile of BC lead us to suggest that observational studies are needed to better characterize the global distribution of BC, including in the upper troposphere.

Black carbon vertical profiles strongly affect its radiative forcing uncertainty

NASA Astrophysics Data System (ADS)

Samset, B. H.; Myhre, G.; Schulz, M.; Balkanski, Y.; Bauer, S.; Berntsen, T. K.; Bian, H.; Bellouin, N.; Diehl, T.; Easter, R. C.; Ghan, S. J.; Iversen, T.; Kinne, S.; Kirkevåg, A.; Lamarque, J.-F.; Lin, G.; Liu, X.; Penner, J. E.; Seland, Ø.; Skeie, R. B.; Stier, P.; Takemura, T.; Tsigaridis, K.; Zhang, K.

2013-03-01

The impact of black carbon (BC) aerosols on the global radiation balance is not well constrained. Here twelve global aerosol models are used to show that at least 20% of the present uncertainty in modeled BC direct radiative forcing (RF) is due to diversity in the simulated vertical profile of BC mass. Results are from phases 1 and 2 of the global aerosol model intercomparison project (AeroCom). Additionally, a significant fraction of the variability is shown to come from high altitudes, as, globally, more than 40% of the total BC RF is exerted above 5 km. BC emission regions and areas with transported BC are found to have differing characteristics. These insights into the importance of the vertical profile of BC lead us to suggest that observational studies are needed to better characterize the global distribution of BC, including in the upper troposphere.

Black Carbon Vertical Profiles Strongly Affect Its Radiative Forcing Uncertainty

NASA Technical Reports Server (NTRS)

Samset, B. H.; Myhre, G.; Schulz, M.; Balkanski, Y.; Bauer, S.; Berntsen, T. K.; Bian, H.; Bellouin, N.; Diehl, T.; Easter, R. C.;

Vertical and lateral forces applied to the bar during the bench press in novice lifters.

PubMed

Duffey, Michael J; Challis, John H

2011-09-01

The purpose of this study was to determine the vertical and lateral forces applied to the bar during a maximal and a submaximal effort bench press lifts. For this study, 10 male and 8 female recreational lifters were recruited (mean height: 1.71 ± 0.08 m; mass: 73.7 ± 13.6 kg) and were asked to perform a maximal and submaximal (80% of maximal lift) bench press. These lifts were performed with a bar instrumented to record forces applied to it, via the hands, in the vertical direction and along the long axis of the bar. To determine the position of the bar and timing of events, 3D kinematic data were recorded and analyzed for both lifts. The subjects in this study averaged a maximal lift of 63 ± 29 kg (90 ± 31% bodyweight). The peak vertical force was 115 ± 22% (percentage of load), whereas for the submaximal condition it was 113 ± 20%; these forces were statistically different between conditions; they were not when expressed as a percentage of the load (p > 0.05). During all the lifts, the lateral forces were always outward along the bar. The lateral force profile was similar to that of the vertical force, albeit at a lesser magnitude. During the lift phase, the peak lateral force was on average 26.3 ± 3.9% of the vertical force for the maximal lift and 23.7 ± 3.9% of the vertical force for the submaximal lift. Given that the amount of force applied laterally to the bar was a similar percentage of vertical force irrespective of load, it appears that the generation of lateral forces during the bench press is a result of having the muscles engaged in generating vertical force.

SPH Simulation of Impact of a Surge on a Wall

NASA Astrophysics Data System (ADS)

Diwakar, Manoj Kumar; Mohapatra, Pranab Kumar; Tripathi, Shivam

2014-05-01

Structures located on the downstream of a dam are prone to impact of the surge due to dam break flow. Ramsden (1996) experimentally studied the run-up height on a vertical wall due to propagation of bore and surge on dry bed and measured their impact on the wall. Mohapatra et al. (2000) applied Navier Stokes equations to numerically study the impact of bore on vertical and inclined walls. They also obtained the evolution of surge on dry bed. In the present work, the impact of a surge wave due to dam break flow against the wall is modeled with a two-dimensional smoothed particle hydrodynamics (SPH) model. SPH is a mesh-free method that relies on the particle view of the field problem and approximates the continuity and momentum equations on a set of particles. The method solves the strong form of Navier-Stokes equations. The governing equations are solved numerically in the vertical plane. The propagation of the surge wave, its impact and the maximum run-up on the wall located at the boundary are analyzed. Surface profile, velocity field and pressure distributions are simulated. Non-dimensional run-up height obtained from the present numerical model is 0.86 and is in good agreement with the available experimental data of Ramsden (1996) which is in the range of 0.75-0.9. Also, the simulated profile of the surge tip was comparable to the empirical equations refereed in Ramsden (1996). The model is applied to the study the maximum force and the run-up height on inclined walls with different inclinations. The results indicate that the maximum force and the run-up height on the wall increase with the increment of wall inclination. Comparison of numerical results with analytical solutions derived from shallow water equations clearly shows the breakdown of shallow water assumption during the impact. In addition to these results, the numerical simulation yields the complete velocity and pressure ?elds which may be used to design structures located in the path of a dam-break wave. The study shows that the smoothed particle hydrodynamics can effectively simulate fluid flow dynamics. References: Mohapatra, P. K., Bhallamudi, S. M., and Eswaran, V. (2000). 'Numerical simulation of impact of bores against inclined walls.' J. Hydraulic. Engg., ASCE, 126(12), 942-945. Ramsden, J. D. (1996). 'Forces on a vertical wall due to long waves, bores, and dry-bed surges.' J. Waterway, Port, Coastal, and Ocean Engg., ASCE, 122(3), 134-141.

Impact of the Lower Atmosphere on the Ionosphere Response to a Geomagnetic Superstorm

NASA Astrophysics Data System (ADS)

Pedatella, N. M.

2016-12-01

Numerical simulations in the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) are performed to elucidate the impacts of lower atmosphere forcing on the ionosphere response to a geomagnetic superstorm. In particular, how the ionosphere variability due to the October 2003 Halloween storm would be different if it occurred in January coincident with a major sudden stratosphere warming (SSW) event is investigated. The TIE-GCM simulations reveal that the E x B vertical drift velocity and total electron content (TEC) respond differently to the geomagnetic disturbance when the lower atmosphere forcing is representative of SSW conditions compared to climatological lower atmosphere forcing conditions. Notably, the storm time variations in the E x B vertical drift velocity differ when the effects of the SSW are considered, and this is in part due to effects of the SSW on the equatorial ionosphere being potentially misinterpreted as being of geomagnetic origin. Differences in the TEC response to the geomagnetic storm can be up to 100% ( 30 TECU) of the storm induced TEC change, and the temporal variability of the TEC during the storm recovery phase is considerably different if SSW effects are considered. The results demonstrate that even during periods of extreme geomagnetic forcing it is important to consider the effects of lower atmosphere forcing on the ionosphere variability.

Validation of the iPhone app using the force platform to estimate vertical jump height.

PubMed

Carlos-Vivas, Jorge; Martin-Martinez, Juan P; Hernandez-Mocholi, Miguel A; Perez-Gomez, Jorge

2018-03-01

Vertical jump performance has been evaluated with several devices: force platforms, contact mats, Vertec, accelerometers, infrared cameras and high-velocity cameras; however, the force platform is considered the gold standard for measuring vertical jump height. The purpose of this study was to validate an iPhone app called My Jump, that measures vertical jump height by comparing it with other methods that use the force platform to estimate vertical jump height, namely, vertical velocity at take-off and time in the air. A total of 40 sport sciences students (age 21.4±1.9 years) completed five countermovement jumps (CMJs) over a force platform. Thus, 200 CMJ heights were evaluated from the vertical velocity at take-off and the time in the air using the force platform, and from the time in the air with the My Jump mobile application. The height obtained was compared using the intraclass correlation coefficient (ICC). Correlation between APP and force platform using the time in the air was perfect (ICC=1.000, P<0.001). Correlation between APP and force platform using the vertical velocity at take-off was also very high (ICC=0.996, P<0.001), with an error margin of 0.78%. Therefore, these results showed that application, My Jump, is an appropriate method to evaluate the vertical jump performance; however, vertical jump height is slightly overestimated compared with that of the force platform.

A Low Temperature Scanning Force Microscope with a Vertical Cantilever and Interferometric Detection Scheme

NASA Astrophysics Data System (ADS)

Kim, Jeehoon; Williams, T. L.; Chu, Sang Lin; Korre, Hasan; Chalfin, Max; Hoffman, J. E.

2008-03-01

We have developed a fiber-optic interferometry system with a vertical cantilever for scanning force microscopy. A lens, mounted on a Pan-type walker, was used to collect the interference signal in the cavity between the cantilever and the single mode fiber. This vertical geometry has several advantages: (1) it is directly sensitive to lateral forces; (2) low spring constant vertical cantilevers may allow increased force sensitivity by solving the ``snap-in'' problem that occurs with soft horizontal cantilevers. We have sharpened vertical cantilevers by focused ion beam (FIB), achieving a tip radius of 20 nm. We will show test results of a magnetic force microscope (MFM) with this vertical cantilever system.

On the impact of forced roll convection on vertical turbulent transport in cold air outbreaks

NASA Astrophysics Data System (ADS)

Gryschka, Micha; Fricke, Jens; Raasch, Siegfried

2014-11-01

We investigated the impact of roll convection on the convective boundary layer and vertical transports in different cold air outbreak (CAO) scenarios using large eddy simulations (LES). The organization of convection into rolls was triggered by upstream heterogeneities in the surface temperature, representing ice and water. By changing the sea ice distribution in our LES, we were able to simulate a roll and a nonroll case for each scenario. Furthermore, the roll wavelength was varied by changing the scale of the heterogeneity. The characteristics of the simulated rolls and cloud streets, such as aspect ratios, orientation of the roll axes, and downstream extensions of single rolls agreed closely with observations in CAO situations. The vertical turbulent fluxes, calculated for each simulation, were decomposed into contributions from rolls and from unorganized turbulence. Even though our results confirmed that rolls triggered by upstream heterogeneities can substantially contribute to vertical turbulent fluxes, the total fluxes were not affected by the rolls.

Improving Vertical Jump Profiles Through Prescribed Movement Plans.

PubMed

Mayberry, John K; Patterson, Bryce; Wagner, Phil

2018-06-01

Mayberry, JK, Patterson, B, and Wagner, P. Improving vertical jump profiles through prescribed movement plans. J Strength Cond Res 32(6): 1619-1626, 2018-Developing practical, reliable, and valid methods for monitoring athlete wellness and injury risk is an important goal for trainers, athletes, and coaches. Previous studies have shown that the countermovement vertical jump (CMJ) test is both a reliable and valid metric for evaluating an athlete's condition. This study examines the effectiveness of prescribed workouts on improving the quality of movement during CMJ. The data set consists of 2,425 pairs of CMJ scans for high school, college, and professional athletes training at a privately owned facility. During each scan, a force plate recorded 3 ground reaction force (GRF) measurements known to impact CMJ performance: eccentric rate of force development (ERFD), average vertical concentric force (AVCF), and concentric vertical impulse (CVI). After an initial scan, coaches either assigned the athlete a specific 1- or 2-strength movement plan (treatment group) or instructed the athlete to choose their own workouts (control group) before returning for a follow-up scan. A multivariate analysis of covariance (MANCOVA) revealed significant differences in changes to GRF measurements between athletes in the 2 groups after adjusting for the covariates sex, sport, time between scans, and rounds of workout completed. A principal component analysis of GRF measurements further identified 4 primary groups of athlete needs and the results provide recommendations for effective workout plans targeting each group. In particular, split squats increase CVI and decrease ERFD/AVCF; deadlifts increase AVCF and decrease CVI; alternating squats/split squats increase ERFD/CVI and decrease AVCF; and alternating squats/deadlifts increase ERFD/AVCF and decrease CVI.

Impact of disturbance electric fields in the evening on prereversal vertical drift and spread F developments in the equatorial ionosphere

NASA Astrophysics Data System (ADS)

Abdu, Mangalathayil A.; Nogueira, Paulo A. B.; Santos, Angela M.; de Souza, Jonas R.; Batista, Inez S.; Sobral, Jose H. A.

2018-04-01

Equatorial plasma bubble/spread F irregularity occurrence can present large variability depending upon the intensity of the evening prereversal enhancement in the zonal electric field (PRE), that is, the F region vertical plasma drift, which basically drives the post-sunset irregularity development. Forcing from magnetospheric disturbances is an important source of modification and variability in the PRE vertical drift and of the associated bubble development. Although the roles of magnetospheric disturbance time penetration electric fields in the bubble irregularity development have been studied in the literature, many details regarding the nature of the interaction between the penetration electric fields and the PRE vertical drift still lack our understanding. In this paper we have analyzed data on F layer heights and vertical drifts obtained from digisondes operated in Brazil to investigate the connection between magnetic disturbances occurring during and preceding sunset and the consequent variabilities in the PRE vertical drift and associated equatorial spread F (ESF) development. The impact of the prompt penetration under-shielding eastward electric field and that of the over-shielding, and disturbance dynamo, westward electric field on the evolution of the evening PRE vertical drift and thereby on the ESF development are briefly examined.

The influence of rail surface irregularities on contact forces and local stresses

NASA Astrophysics Data System (ADS)

Andersson, Robin; Torstensson, Peter T.; Kabo, Elena; Larsson, Fredrik

2015-01-01

The effect of initial rail surface irregularities on promoting further surface degradation is investigated. The study concerns rolling contact fatigue formation, in particular in the form of the so-called squats. The impact of surface irregularities in the form of dimples is quantified by peak magnitudes of dynamic contact stresses and contact forces. To this end simulations of two-dimensional (later extended to three-dimensional) vertical dynamic vehicle-track interaction are employed. The most influencing parameters are identified. It is shown that even very shallow dimples might have a large impact on local contact stresses. Peak magnitudes of contact forces and stresses due to the influence of rail dimples are shown to exceed those due to rail corrugation.

Influence of Manual Screwdriver Design in Combination With and Without Predrilling on Insertion Torque of Orthodontic Mini-Implants.

PubMed

Katalinic, Andrej; Trinajstic Zrinski, Magda; Roksandic Vrancic, Zlatka; Spalj, Stjepan

2017-02-01

The study focused on the influence of screwdriver design in combination with and without predrilling a pilot hole of inner implant diameter on insertion torque of orthodontic mini-implants, controlling for cortical thickness and vertical insertion force as cofactors. One hundred twenty mini-implants (Forestadent) of 1.7 mm in diameter and 6 and 8 mm in length were manually inserted into 120 swine rib bone samples. Maximal insertion torque as a measure of primary stability and vertical force were measured. The study included procedures with and without pilot hole and different screwdriver handles and shaft length and 2 implant lengths. Design of manual screwdriver does not modify insertion torque to a significant extent. In multiple linear regression model, significant predictors of insertion torque are thicker cortical bone (explaining 16.6% of variability), higher vertical force at maximal torque (13.5%), 6-mm implant length (2.5%), and the presence of pilot hole (2.3%). Handle type and shaft length of manual screwdriver do not significantly influence insertion torque, whereas predrilling a pilot hole has low impact on torque values of manually inserted self-drilling orthodontic mini-implants.

Heel impact forces during barefoot versus minimally shod walking among Tarahumara subsistence farmers and urban Americans

PubMed Central

Koch, Elizabeth; Holowka, Nicholas B.; Lieberman, Daniel E.

2018-01-01

Despite substantial recent interest in walking barefoot and in minimal footwear, little is known about potential differences in walking biomechanics when unshod versus minimally shod. To test the hypothesis that heel impact forces are similar during barefoot and minimally shod walking, we analysed ground reaction forces recorded in both conditions with a pedography platform among indigenous subsistence farmers, the Tarahumara of Mexico, who habitually wear minimal sandals, as well as among urban Americans wearing commercially available minimal sandals. Among both the Tarahumara (n = 35) and Americans (n = 30), impact peaks generated in sandals had significantly (p < 0.05) higher force magnitudes, slower loading rates and larger vertical impulses than during barefoot walking. These kinetic differences were partly due to individuals' significantly greater effective mass when walking in sandals. Our results indicate that, in general, people tread more lightly when walking barefoot than in minimal footwear. Further research is needed to test if the variations in impact peaks generated by walking barefoot or in minimal shoes have consequences for musculoskeletal health. PMID:29657826

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.

Dynamic impact force and association with structural damage to the knee joint: an ex-vivo study.

PubMed

Brill, Richard; Wohlgemuth, Walther A; Hempfling, Harald; Bohndorf, Klaus; Becker, Ursula; Welsch, Ulrich; Kamp, Alexander; Roemer, Frank W

2014-12-01

No systematic, histologically confirmed data are available concerning the association between magnitude of direct dynamic impact caused by vertical impact trauma and the resulting injury to cartilage and subchondral bone. The aim of this study was to investigate the association between dynamic impact and the resulting patterns of osteochondral injury in an ex-vivo model. A mechanical apparatus was employed to perform ex-vivo controlled dynamic vertical impact experiments in 110 pig knees with the femur positioned in a holding fixture. A falling body with a thrust plate and photo sensor was applied. The direct impact to the trochlear articular surface was registered and the resulting osteochondral injuries macroscopically and histologically correlated and categorized. The relationship between magnitude of direct impact and injury severity could be classified as stage I injuries (impact <7.3MPa): elastic deformation, no histological injury; stage II injuries (impact 7.3-9.6MPa): viscoelastic imprint of the cartilaginous surface, subchondral microfractures; stage III injuries (impact 9.6-12.7MPa): disrupted cartilage surface, chondral fissures and subchondral microfractures; stage IV injuries (impact >12.7MPa): osteochondral impression, histologically imprint and osteochondral macrofractures. The impact ranges and histologic injury stages determined from this vertical dynamic impact experiment allowed for a biomechanical classification of direct, acute osteochondral injury. In contrast to static load commonly applied in ex-vivo experiments, dynamic impact more realistically represents actual trauma to the knee joint.

3D numerical modelling of a willow vegetated river/floodplain system

NASA Astrophysics Data System (ADS)

Wilson, C. A. M. E.; Yagci, O.; Rauch, H.-P.; Olsen, N. R. B.

2006-07-01

SummaryUsing a three-dimensional finite volume code with standard k- ɛ turbulence closure the hydraulic impact of willow stands ( Salix alba and Salix fragilis) on the velocity distribution was modelled. The additional hydraulic resistance of the willow stands was modelled separately to the bed resistance using a drag force term that was introduced into the Navier-Stokes equations. Two flood events of varying magnitude and stages of plant development were simulated using this approach. The river comprises an asymmetric compound channel with vegetated floodplain of reach length 170 m. The willow development has been monitored annually and this information was used to define the density of the willow stands (average number per m 2) and its variation as a function of stand height. During both flood events the willow stands were submerged and in pronation. The willow stands were modelled in bending as well as in their undisturbed vertical state. Modelling the willow stands as vertical or in bending was found to have a major impact on the computed velocity profiles. The impact of using a drag-force approach based on a non-uniform projected area distribution was found to be greater when the plants are modelled vertically than when the plants are modelled in high degrees of bending. In field studies involving flexible plants without leaves, the determination of the drag coefficient is of less importance compared to the need to quantify the degree by which plants are in pronation.

Heel-toe running: A new look at the influence of foot strike pattern on impact force.

PubMed

Mercer, John A; Horsch, Sarah

2015-06-01

It is important to understand the factors that influence the impact force observed during running, since the impact force is likely to be related to overuse injuries. The purpose of this study was to compare the impact force during running when participants were instructed to use different foot strike patterns: obvious heel strike (Obvious-HS), subtle heel strike (Subtle-HS), midfoot strike (Mid-FS), and fore foot strike (Fore-FS) patterns. Participants ( n  = 10, 25 ± 5.7 years, 70.2 ± 12.1 kg, 174.6 ± 7.2 cm) completed four foot strike patterns while running over ground: Obvious-HS, Subtle-HS, Mid-FS, and Fore-FS. Speed was controlled between conditions (random order). Vertical ground reaction forces were recorded (1000 Hz) along with the impact force, peak force, and stance time for analysis. A repeated measures analysis of variance was used to compare each variable across foot strike instructions, with post hoc comparisons contrasting Obvious-HS to each of the other conditions. Impact force was influenced by foot strike instructions, with Obvious-HS being greater than Subtle-HS and Fore-FS ( p  < 0.05) but not different from Mid-FS ( p  > 0.05). The peak force was not influenced by foot strike instructions ( p  > 0.05); stance time was longer during Obvious-HS than during Mid-FS or Fore-FS ( p  < 0.05), but not different from Subtle-HS ( p  > 0.05). The unique observation of this study was that impact force was different when participants were instructed to run with either an Obvious-HS or a Subtle-HS at contact. Both these foot strike patterns would have been considered rear foot strike patterns, suggesting that something other than which specific part of the foot strikes the ground initially influenced impact force.

Myoelectric activation and kinetics of different plyometric push-up exercises.

PubMed

García-Massó, Xavier; Colado, Juan C; González, Luis M; Salvá, Pau; Alves, Joao; Tella, Víctor; Triplett, N Travis

2011-07-01

The kinetic and myoelectric differences between 3 types of plyometric push-ups were investigated. Twenty-seven healthy, physically active men served as subjects and completed both familiarization and testing sessions. During these sessions, subjects performed 2 series of 3 plyometric push-up variations in a counterbalanced order according to the following techniques: Countermovement push-ups (CPUs) were push-ups performed with the maximum speed of movement; jump push-ups (JPUs) were similar to clapping push-ups; and fall push-ups (FPUs) required kneeling subjects to drop and then attempt to return to their initial position. Vertical ground reaction forces were determined by using a force plate. Myoelectric activity was recorded by means of electromyography. Impact force and impact rate of force development were significantly (p < 0.05) higher for FPUs than for JPUs. The maximum rate of force development was higher for CPUs (p < 0.05) than for JPUs, and the maximum force was higher for the CPUs than for the FPUs (p < 0.05). There were differences among exercises for the mean muscle activation of the pectoralis major (PM; p < 0.001), triceps brachii (p < 0.001), external oblique (p < 0.005) and anterior deltoid (p < 0.001), and in the maximum muscle activation of the PM (p < 0.001). Plyometric push-ups with countermovement achieved a higher maximum force and rate of force and did not cause impact forces. Thus, this type of push-up exercise may be regarded as the best for improving explosive force. The FPU exercise achieved higher levels of muscular activation in the agonist and synergist muscle groups, and greater impact forces and impact force development rates.

Dynamic forces over the interface between a seated human body and a rigid seat during vertical whole-body vibration.

PubMed

Liu, Chi; Qiu, Yi; Griffin, Michael J

2017-08-16

Biodynamic responses of the seated human body are usually measured and modelled assuming a single point of vibration excitation. With vertical vibration excitation, this study investigated how forces are distributed over the body-seat interface. Vertical and fore-and-aft forces were measured beneath the ischial tuberosities, middle thighs, and front thighs of 14 subjects sitting on a rigid flat seat in three postures with different thigh contact while exposed to random vertical vibration at three magnitudes. Measures of apparent mass were calculated from transfer functions between the vertical acceleration of the seat and the vertical or fore-and-aft forces measured at the three locations, and the sum of these forces. When sitting normally or sitting with a high footrest, vertical forces at the ischial tuberosities dominated the vertical apparent mass. With feet unsupported to give increased thigh contact, vertical forces at the front thighs were dominant around 8Hz. Around 3-7Hz, fore-and-aft forces at the middle thighs dominated the fore-and-aft cross-axis apparent mass. Around 8-10Hz, fore-and-aft forces were dominant at the ischial tuberosities with feet supported but at the front thighs with feet unsupported. All apparent masses were nonlinear: as the vibration magnitude increased the resonance frequencies decreased. With feet unsupported, the nonlinearity in the apparent mass was greater at the front thighs than at the ischial tuberosities. It is concluded that when the thighs are supported on a seat it is not appropriate to assume the body has a single point of vibration excitation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electromagnetic interference impact of the proposed emitters for the High Frequency Active Auroral Research Program (HAARP). Interim report

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

Robertshaw, G.A.; Snyder, A.L.; Weiner, M.M.

1993-05-14

The proposed HAARP emitters at the Gakona (Alaska) preferred site and at the Clear AFS (Alaska) alternative site are the Ionospheric Research Instrument (IRI), the Incoherent Scatter Radar (ISR), and the Vertical Incidence Sounder(VIS). The electromagnetic interference (EMI) impact of those emitters on receiving systems in the vicinity of the sites is estimated in this study. The results are intended for use as an input to the Air Force Environmental Impact Statement as part of the Environmental Impact Analysis Process.

State of the art in protection of erosion-corrosion on vertical axis tidal current turbine

NASA Astrophysics Data System (ADS)

Musabikha, Siti; Utama, I. Ketut Aria Pria; Mukhtasor

2018-05-01

Vertical axis tidal current turbine is main part of ocean energy devices which converts the tidal current energy into electricity. Its development is arising too due to increased interest research topic concerning climate change mitigation. Due to its rotating movement, it will be induced mechanical forces, such as shear stress and/or particle impact. Because of its natural operations, vertical axis turbine is also being exposed to harsh and corroding marine environment itself. In order to secure the vertical tidal turbine devices from mechanical wear and corrosion effects which is lead to a material loss, an appropriate erosion-corrosion protection needs to be defined. Its protection actionscan be derived such as design factors, material selections, inhibitors usage, cathodic protections, and coatings. This paper aims to analyze protection method which is necessary to control erosion-corrosion phenomenon that appears to the vertical axis tidal current turbine.

Differences in pediatric vertical ground reaction force between planovalgus and neutrally aligned feet.

PubMed

Pauk, Jolanta; Szymul, Joanna

2014-01-01

Ground reaction forces (GRF) reflect the force history of human body contact with the ground. The purpose of this study was to explore human gait abnormalities due to planovalgus by comparing vertical GRF data between individuals with planovalgus and those with neutrally aligned feet. Second we estimated associations between various measurements and vertical GRF parameters in a pediatric population. Boys and girls between the ages of 4 and 18 years (72 planovalgus feet and 74 neutrally aligned feet) took part in this study. Ground reaction forces were recorded by two Kistler platforms and normalized to body weight. Comparison of vertical GRF between planovalgus and neutrally aligned feet suggests that the first and the second peaks of vertical force (Fz1, Fz2) are most affected by planovalgus. The results also indicate that neutrally aligned feet display a different ground reaction force pattern than planovalgus, and that differences between boys and girls may be observed. The shape of the vertical GRF curve can help in clinical interpretation of abnormal gait.

A reduction of the saddle vertical force triggers the sit-stand transition in cycling.

PubMed

Costes, Antony; Turpin, Nicolas A; Villeger, David; Moretto, Pierre; Watier, Bruno

2015-09-18

The purpose of the study was to establish the link between the saddle vertical force and its determinants in order to establish the strategies that could trigger the sit-stand transition. We hypothesized that the minimum saddle vertical force would be a critical parameter influencing the sit-stand transition during cycling. Twenty-five non-cyclists were asked to pedal at six different power outputs from 20% (1.6 ± 0.3 W kg(-1)) to 120% (9.6 ± 1.6 W kg(-1)) of their spontaneous sit-stand transition power obtained at 90 rpm. Five 6-component sensors (saddle tube, pedals and handlebars) and a full-body kinematic reconstruction were used to provide the saddle vertical force and other force components (trunk inertial force, hips and shoulders reaction forces, and trunk weight) linked to the saddle vertical force. Minimum saddle vertical force linearly decreased with power output by 87% from a static position on the bicycle (5.30 ± 0.50 N kg(-1)) to power output=120% of the sit-stand transition power (0.68 ± 0.49 N kg(-1)). This decrease was mainly explained by the increase in instantaneous pedal forces from 2.84 ± 0.58 N kg(-1) to 6.57 ± 1.02 N kg(-1) from 20% to 120% of the power output corresponding to the sit-stand transition, causing an increase in hip vertical forces from -0.17 N kg(-1) to 3.29 N kg(-1). The emergence of strategies aiming at counteracting the elevation of the trunk (handlebars and pedals pulling) coincided with the spontaneous sit-stand transition power. The present data suggest that the large decrease in minimum saddle vertical force observed at high pedal reaction forces might trigger the sit-stand transition in cycling. Copyright © 2015 Elsevier Ltd. All rights reserved.

H-60A/L Passenger Airbag Protection: Vertical and Horizontal Impact Tests

DTIC Science & Technology

2013-04-30

aft facing seating . While impact testing has been widely performed on ejection seats , only limited testing has been done on helicopter seating ...manikins with the LARD scaled to represent large occupants in the aerospace environment. LARD is also used by the Air Force and JSF in ejection seat ...for all rigid seat tests, resulting in no notable differences (manikin motion , manikin response) between the standard and airbag restraints. The

Climate Impacts of CALIPSO-Guided Corrections to Black Carbon Aerosol Vertical Distributions in a Global Climate Model

NASA Astrophysics Data System (ADS)

Kovilakam, Mahesh; Mahajan, Salil; Saravanan, R.; Chang, Ping

2017-10-01

We alleviate the bias in the tropospheric vertical distribution of black carbon aerosols (BC) in the Community Atmosphere Model (CAM4) using the Cloud-Aerosol and Infrared Pathfinder Satellite Observations (CALIPSO)-derived vertical profiles. A suite of sensitivity experiments are conducted with 1x, 5x, and 10x the present-day model estimated BC concentration climatology, with (corrected, CC) and without (uncorrected, UC) CALIPSO-corrected BC vertical distribution. The globally averaged top of the atmosphere radiative flux perturbation of CC experiments is ˜8-50% smaller compared to uncorrected (UC) BC experiments largely due to an increase in low-level clouds. The global average surface temperature increases, the global average precipitation decreases, and the ITCZ moves northward with the increase in BC radiative forcing, irrespective of the vertical distribution of BC. Further, tropical expansion metrics for the poleward extent of the Northern Hemisphere Hadley cell (HC) indicate that simulated HC expansion is not sensitive to existing model biases in BC vertical distribution.

Versatile Clinical Application of the Spike Screw: Direct Anchorage Versus Indirect Anchorage.

PubMed

Kim, Kyung A; Chen, Yu; Kwon, Soon-Yong; Seo, Kyung Won; Park, Ki-Ho; Kim, Seong-Hun

2015-10-01

This article represents clinical application of spike screw, novel design of miniscrew, for direct anchorage and indirect anchorage in orthodontic treatment. Accompanied by easy placement and removal, the spike screw provides good stability for the orthodontic anchorage. The spike screw consists of 6 spikes attached to a washer with laser welded stainless-steel hook that is placed by self-drilling fixation miniscrew. The spike screws were applied to correct malocclusions in patients as follows: traction of impacted canines and protraction of posterior teeth as a direct anchorage and correction of midline discrepancy as an indirect anchorage. For orthodontic traction of impacted canines, spike screws were placed in the mandibular labial mucosal area to create extrusive forces. Afterward, it was utilized for the protraction of posterior teeth. In the second case of the indirect anchorage, spike screw was applied on the midpalatal area to correct midline discrepancy that occurred during orthodontic treatment. The extended hook of a washer was prebended along the curvature of the palate and then secured with a mini screw. The extended hook was bonded to maxillary left first molar. In the first case, the spike screw provided adequate anchorage for the vertical traction of horizontally impacted canine. Since the spike screws were placed in the mandibular anterior lesion, the vertical traction force was applied simply with orthodontic elastics. Also, enough distance was achieved for up-down elastics to work by placing the spike screw in the opposite arch. The force of vertical traction was adjusted with selection of size and force of up-down elastics. Later, it was used to provide anchorage for protraction of mandibular molars without changing orientation of the spike screws. In the second case, the spike screw placed in the midpalatal area was attached to the left first molar and worked as an indirect anchorage. The midline discrepancy was resolved by consolidating the spaces to the left with securing the left first molar location. The novel design of the spike screw permits clinicians to have minimum invasive and easy placement and removal of the appliance while maintaining a good control over tooth movement with improved stability in various clinical cases.

The relationship between quadriceps muscle force, knee flexion, and anterior cruciate ligament strain in an in vitro simulated jump landing.

PubMed

Withrow, Thomas J; Huston, Laura J; Wojtys, Edward M; Ashton-Miller, James A

2006-02-01

An instrumented cadaveric knee construct was used to quantify the association between impact force, quadriceps force, knee flexion angle, and anterior cruciate ligament relative strain in simulated unipedal jump landings. Anterior cruciate ligament strain will correlate with impact force, quadriceps force, and knee flexion angle. Descriptive laboratory study. Eleven cadaveric knees (age, 70.8 [19.3] years; 5 male; 6 female) were mounted in a custom fixture with the tibia and femur secured to a triaxial load cell. Quadriceps, hamstring, and gastrocnemius muscle forces were simulated using pretensioned steel cables (stiffness, 7 kN/cm), and the quadriceps tendon force was measured using a load cell. Mean strain on the anteromedial bundle of the anterior cruciate ligament was measured using a DVRT. With the knee in 25 degrees of flexion, the construct was vertically loaded by an impact force initially directed 4 cm posterior to the knee joint center. Tibiofemoral kinematics was measured using a 3D optoelectronic tracking system. The increase in anterior cruciate ligament relative strain was proportional to the increase in quadriceps force (r(2) = 0.74; P < .00001) and knee flexion angle (r(2) = 0.88; P < .00001) but was not correlated with the impact force (r(2) = 0.009; P = .08). The increase in knee flexion and quadriceps force during this simulated 1-footed landing strongly influenced the relative strain on the anteromedial bundle of the anterior cruciate ligament. These results suggest that even in the presence of knee flexor muscle forces, the increase in quadriceps force required to prevent the knee from flexing during landing can place the anterior cruciate ligament at risk for large strains.

Prediction of Impact Pressures, Forces, and Moments During Vertical and Oblique Water Entry

DTIC Science & Technology

1977-01-15

2y2 )r W 3zqr 7 P y2 +2 z 4x2 q w x2 + z2 4y 2 A-2 NSWC/WOL/TR 77-16 i|. fx , Y,) I) III 4 4𔄁 41 FIG. A-1 SYMBOLS FIG. A-I COORDINATE SYSTEM A-3...total load (force). The output for each depth is concluded by providing: FX force along the x axis D2 CX X force coefficient ( FX /((m-.)1/2 p VI ) FD...Martucelli Applied Physics Rm. 33-211 Pierce Hall Prof. M. Finston Oxford Street Prof. J. Baron, Dept. Cambridge, MA 02138 of Aero. & Astro . Illinois

On the impact of the resolution on the surface and subsurface Eastern Tropical Atlantic warm bias

NASA Astrophysics Data System (ADS)

Martín-Rey, Marta; Lazar, Alban

2016-04-01

The tropical variability has a great importance for the climate of adjacent areas. Its sea surface temperature anomalies (SSTA) affect in particular the Brazilian Nordeste and the Sahelian region, as well as the tropical Pacific or the Euro-Atlantic sector. Nevertheless, the state-of the art climate models exhibits very large systematic errors in reproducing the seasonal cycle and inter-annual variability in the equatorial and coastal Africa upwelling zones (up to several °C for SST). Theses biases exist already, in smaller proportions though, in forced ocean models (several 1/10th of °C), and affect not only the mixed layer but also the whole thermocline. Here, we present an analysis of the impact of horizontal and vertical resolution changes on these biases. Three different DRAKKAR NEMO OGCM simulations have been analysed, associated to the same forcing set (DFS4.4) with different grid resolutions: "REF" for reference (1/4°, 46 vertical levels), "HH" with a finer horizontal grid (1/12°, 46 v.l.) and "HV" with a finer vertical grid (1/4°, 75 v.l.). At the surface, a more realistic seasonal SST cycle is produced in HH in the three upwellings, where the warm bias decreases (by 10% - 20%) during boreal spring and summer. A notable result is that increasing vertical resolution in HV causes a shift (in advance) of the upwelling SST seasonal cycles. In order to better understand these results, we estimate the three upwelling subsurface temperature errors, using various in-situ datasets, and provide thus a three-dimensional view of the biases.

Ground Reaction Forces of the Lead and Trail Limbs when Stepping Over an Obstacle

PubMed Central

Bovonsunthonchai, Sunee; Khobkhun, Fuengfa; Vachalathiti, Roongtiwa

2015-01-01

Background Precise force generation and absorption during stepping over different obstacles need to be quantified for task accomplishment. This study aimed to quantify how the lead limb (LL) and trail limb (TL) generate and absorb forces while stepping over obstacle of various heights. Material/Methods Thirteen healthy young women participated in the study. Force data were collected from 2 force plates when participants stepped over obstacles. Two limbs (right LL and left TL) and 4 conditions of stepping (no obstacle, stepping over 5 cm, 20 cm, and 30 cm obstacle heights) were tested for main effect and interaction effect by 2-way ANOVA. Paired t-test and 1-way repeated-measure ANOVA were used to compare differences of variables between limbs and among stepping conditions, respectively. The main effects on the limb were found in first peak vertical force, minimum vertical force, propulsive peak force, and propulsive impulse. Results Significant main effects of condition were found in time to minimum force, time to the second peak force, time to propulsive peak force, first peak vertical force, braking peak force, propulsive peak force, vertical impulse, braking impulse, and propulsive impulse. Interaction effects of limb and condition were found in first peak vertical force, propulsive peak force, braking impulse, and propulsive impulse. Conclusions Adaptations of force generation in the LL and TL were found to involve adaptability to altered external environment during stepping in healthy young adults. PMID:26169293

Does trampoline or hard surface jumping influence lower extremity alignment?

PubMed

Akasaka, Kiyokazu; Tamura, Akihiro; Katsuta, Aoi; Sagawa, Ayako; Otsudo, Takahiro; Okubo, Yu; Sawada, Yutaka; Hall, Toby

2017-12-01

[Purpose] To determine whether repetitive trampoline or hard surface jumping affects lower extremity alignment on jump landing. [Subjects and Methods] Twenty healthy females participated in this study. All subjects performed a drop vertical jump before and after repeated maximum effort trampoline or hard surface jumping. A three-dimensional motion analysis system and two force plates were used to record lower extremity angles, moments, and vertical ground reaction force during drop vertical jumps. [Results] Knee extensor moment after trampoline jumping was greater than that after hard surface jumping. There were no significant differences between trials in vertical ground reaction force and lower extremity joint angles following each form of exercise. Repeated jumping on a trampoline increased peak vertical ground reaction force, hip extensor, knee extensor moments, and hip adduction angle, while decreasing hip flexion angle during drop vertical jumps. In contrast, repeated jumping on a hard surface increased peak vertical ground reaction force, ankle dorsiflexion angle, and hip extensor moment during drop vertical jumps. [Conclusion] Repeated jumping on the trampoline compared to jumping on a hard surface has different effects on lower limb kinetics and kinematics. Knowledge of these effects may be useful in designing exercise programs for different clinical presentations.

Does trampoline or hard surface jumping influence lower extremity alignment?

PubMed Central

Akasaka, Kiyokazu; Tamura, Akihiro; Katsuta, Aoi; Sagawa, Ayako; Otsudo, Takahiro; Okubo, Yu; Sawada, Yutaka; Hall, Toby

2017-01-01

[Purpose] To determine whether repetitive trampoline or hard surface jumping affects lower extremity alignment on jump landing. [Subjects and Methods] Twenty healthy females participated in this study. All subjects performed a drop vertical jump before and after repeated maximum effort trampoline or hard surface jumping. A three-dimensional motion analysis system and two force plates were used to record lower extremity angles, moments, and vertical ground reaction force during drop vertical jumps. [Results] Knee extensor moment after trampoline jumping was greater than that after hard surface jumping. There were no significant differences between trials in vertical ground reaction force and lower extremity joint angles following each form of exercise. Repeated jumping on a trampoline increased peak vertical ground reaction force, hip extensor, knee extensor moments, and hip adduction angle, while decreasing hip flexion angle during drop vertical jumps. In contrast, repeated jumping on a hard surface increased peak vertical ground reaction force, ankle dorsiflexion angle, and hip extensor moment during drop vertical jumps. [Conclusion] Repeated jumping on the trampoline compared to jumping on a hard surface has different effects on lower limb kinetics and kinematics. Knowledge of these effects may be useful in designing exercise programs for different clinical presentations. PMID:29643592

Impact and intrusion of the foot of a lizard running rapidly on sand

NASA Astrophysics Data System (ADS)

Li, Chen; Hsieh, Tonia; Umbanhowar, Paul; Goldman, Daniel

2012-11-01

The desert-dwelling zebra-tailed lizard (Callisaurus draconoides, 10 cm, 10 g) runs rapidly (~10 BL/s) on granular media (GM) like sand and gravel. On loosely packed GM, its large hind feet penetrate into the substrate during each step. Based on above-ground observation, a previous study (Li et al., JEB 2012) hypothesized that the hind foot rotated in the vertical plane subsurface to generate lift. To explain the observed center-of-mass dynamics, the model assumed that ground reaction force was dominated by speed-independent frictional drag. Here we use x-ray high speed video to obtain subsurface foot kinematics of the lizard running on GM, which confirms the hypothesized subsurface foot rotation following rapid foot impact at touchdown. However, using impact force measurements, a resistive force model, and the observed foot kinematics, we find that impact force during initial foot touchdown and speed-independent frictional drag during rotation only account for part of the required lift to support locomotion. This suggests that the rapid foot rotation further allows the lizard to utilize inertial forces from the local acceleration of the substrate (particles), similar to small robots running on GM (Qian et al., RSS 2012) and the basilisk (Jesus) lizard running on water.

Quadriceps force and anterior tibial force occur obviously later than vertical ground reaction force: a simulation study.

PubMed

Ueno, Ryo; Ishida, Tomoya; Yamanaka, Masanori; Taniguchi, Shohei; Ikuta, Ryohei; Samukawa, Mina; Saito, Hiroshi; Tohyama, Harukazu

2017-11-18

Although it is well known that quadriceps force generates anterior tibial force, it has been unclear whether quadriceps force causes great anterior tibial force during the early phase of a landing task. The purpose of the present study was to examine whether the quadriceps force induced great anterior tibial force during the early phase of a landing task. Fourteen young, healthy, female subjects performed a single-leg landing task. Muscle force and anterior tibial force were estimated from motion capture data and synchronized force data from the force plate. One-way repeated measures analysis of variance and the post hoc Bonferroni test were conducted to compare the peak time of the vertical ground reaction force, quadriceps force and anterior tibial force during the single-leg landing. In addition, we examined the contribution of vertical and posterior ground reaction force, knee flexion angle and moment to peak quadriceps force using multiple linear regression. The peak times of the estimated quadriceps force (96.0 ± 23.0 ms) and anterior tibial force (111.9 ± 18.9 ms) were significantly later than that of the vertical ground reaction force (63.5 ± 6.8 ms) during the single-leg landing. The peak quadriceps force was positively correlated with the peak anterior tibial force (R = 0.953, P < 0.001). Multiple linear regression analysis showed that the peak knee flexion moment contributed significantly to the peak quadriceps force (R 2  = 0.778, P < 0.001). The peak times of the quadriceps force and the anterior tibial force were obviously later than that of the vertical ground reaction force for the female athletes during successful single-leg landings. Studies have reported that the peak time of the vertical ground reaction force was close to the time of anterior cruciate ligament (ACL) disruption in ACL injury cases. It is possible that early contraction of the quadriceps during landing might induce ACL disruption as a result of excessive anterior tibial force in unanticipated situations in ACL injury cases.

A kinetic comparison of back-loading and head-loading in Xhosa women.

PubMed

Lloyd, R; Parr, B; Davies, S; Cooke, C

2011-04-01

The purpose of this study was to compare the kinetic responses associated with ground reaction force measurements to both head-loading and back-loading in a group of Xhosa women. Altogether, 16 women were divided into two groups based on their experience of head-loading. They walked over a force plate in three conditions: unloaded or carrying 20 kg in either a backpack or on their head. The most striking finding was that there was no difference in kinetic response to head-loading as a consequence of previous experience. Considering the differences between the load carriage methods, most changes were consistent with increasing load. Head-loading was, however, associated with a shorter contact time, smaller thrust maximum and greater vertical force minimum than back-loading. Both loading conditions differed from unloaded walking for a number of temporal variables associated with the ground contact phase, e.g. vertical impact peak was delayed whilst vertical thrust maximum occurred earlier. STATEMENT OF RELEVANCE: Consideration of the kinetics of head and back load carriage in African women is important from a health and safety perspective, providing an understanding of the mechanical adaptations associated with both forms of load carriage for a group of people for whom such load carriage is a daily necessity.

Lidar characterizations of atmospheric aerosols and clouds

NASA Astrophysics Data System (ADS)

Ferrare, R. A.; Hostetler, C. A.; Hair, J. W.; Burton, S. P.

2017-12-01

Knowledge of the vertical profile, composition, concentration, and size distribution of aerosols is required to quantify the impacts of aerosols on human health, global and regional climate, clouds and precipitation. In particular, radiative forcing due to anthropogenic aerosols is the most uncertain part of anthropogenic radiative forcing, with aerosol-cloud interactions (ACI) as the largest source of uncertainty in current estimates of global radiative forcing. Improving aerosol transport model predictions of the vertical profile of aerosol optical and microphysical characteristics is crucial for improving assessments of aerosol radiative forcing. Understanding how aerosols and clouds interact is essential for investigating the aerosol indirect effect and ACI. Through its ability to provide vertical profiles of aerosol and cloud distributions as well as important information regarding the optical and physical properties of aerosols and clouds, lidar is a crucial tool for addressing these science questions. This presentation describes how surface, airborne, and satellite lidar measurements have been used to address these questions, and in particular how High Spectral Resolution Lidar (HSRL) measurements provide profiles of aerosol properties (backscatter, extinction, depolarization, concentration, size) important for characterizing radiative forcing. By providing a direct measurement of aerosol extinction, HSRL provides more accurate aerosol measurement profiles and more accurate constraints for models than standard retrievals from elastic backscatter lidar, which loses accuracy and precision at lower altitudes due to attenuation from overlying layers. Information regarding particle size and abundance from advanced lidar retrievals provides better proxies for cloud-condensation-nuclei (CCN), which are required for assessing aerosol-cloud interactions. When combined with data from other sensors, advanced lidar measurements can provide information on aerosol and cloud properties for addressing both direct and indirect radiative forcing.

The aerodynamic benefit of wing-wing interaction depends on stroke trajectory in flapping insect wings.

PubMed

Lehmann, Fritz-Olaf; Pick, Simon

2007-04-01

Flying insects may enhance their flight force production by contralateral wing interaction during dorsal stroke reversal ('clap-and-fling'). In this study, we explored the forces and moments due to clap-and-fling at various wing tip trajectories, employing a dynamically scaled electromechanical flapping device. The 17 tested bio-inspired kinematic patterns were identical in stroke amplitude, stroke frequency and angle of attack with respect to the horizontal stroke plane but varied in heaving motion. Clap-and-fling induced vertical force augmentation significantly decreased with increasing vertical force production averaged over the entire stroke cycle, whereas total force augmentation was independent from changes in force produced by a single wing. Vertical force augmentation was also largely independent of forces produced due to wing rotation at the stroke reversals, the sum of rotational circulation and wake capture force. We obtained maximum (17.4%) and minimum (1.4%) vertical force augmentation in two types of figure-eight stroke kinematics whereby rate and direction of heaving motion during fling may explain 58% of the variance in vertical force augmentation. This finding suggests that vertical wing motion distinctly alters the flow regime at the beginning of the downstroke. Using an analytical model, we determined pitching moments acting on an imaginary body of the flapping device from the measured time course of forces, the changes in length of the force vector's moment arm, the position of the centre of mass and body angle. The data show that pitching moments are largely independent from mean vertical force; however, clap-and-fling reinforces mean pitching moments by approximately 21%, compared to the moments produced by a single flapping wing. Pitching moments due to clap-and-fling significantly increase with increasing vertical force augmentation and produce nose-down moments in most of the tested patterns. The analytical model, however, shows that algebraic sign and magnitude of these moments may vary distinctly depending on both body angle and the distance between the wing hinge and the animal's centre of mass. Altogether, the data suggest that the benefit of clap-and-fling wing beat for vertical force enhancement and pitch balance may change with changing heaving motion and thus wing tip trajectory during manoeuvring flight. We hypothesize that these dependencies may have shaped the evolution of wing kinematics in insects that are limited by aerodynamic lift rather than by mechanical power of their flight musculature.

The Effect of Variation of Plyometric Push-Ups on Force-Application Kinetics and Perception of Intensity.

PubMed

Dhahbi, Wissem; Chaouachi, Anis; Dhahbi, Anis Ben; Cochrane, Jodie; Chèze, Laurence; Burnett, Angus; Chamari, Karim

2017-02-01

To examine differences between ground-reaction-force (GRF)-based parameters collected from 5 types of plyometric push-ups. Between-trials reliability and the relationships between parameters were also assessed. Thirty-seven highly active commando soldiers performed 3 trials of 5 variations of the plyometric push-up in a counterbalanced order: standard countermovement push-up (SCPu), standard squat push-up (SSPu), kneeling countermovement push-up (KCPu), kneeling squat push-up (KSPu), and drop-fall push-up (DFPu). Vertical GRF was measured during these exercises using a portable Kistler force plate. The GRF applied by the hands in the starting position (initial force supported), peak GRF and rate of force development during takeoff, flight time, impact force, and rate of force development impact on landing were determined. During standard-position exercises (SCPu and SSPu) the initial force supported and impact force were higher (P < .001) than with kneeling exercises (KCPu, KSPu, and DFPu). The peak GRF and rate of force development during takeoff were higher (P < .001) in the countermovement push-up exercises ([CMP] SCPu, KCPu, and DFPu) than squat push-up exercises ([SP] SSPu and KSPu). Furthermore, the flight time was greater (P < .001) during kneeling exercises than during standard-position exercises. A significant relationship (P < .01) between impact force and the rate of force development impact was observed for CMP and SP exercises (r = .83 and r = .62, respectively). The initial force supported was also negatively related (P < .01) to the flight time for both CMP and SP (r = -.74 and r = -.80, respectively). It was revealed that the initial force supported and the peak GRF during takeoff had excellent reliability; however, other parameters had poor absolute reliability. It is possible to adjust the intensity of plyometric push-up exercises and train athletes' muscle power by correctly interpreting GRF-based parameters. However, caution is required as some parameters had marginal absolute reliability.

The Relationship Between Latent Heating, Vertical Velocity, and Precipitation Processes: the Impact of Aerosols on Precipitation in Organized Deep Convective Systems

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Li, Xiaowen

2016-01-01

A high-resolution, two-dimensional cloud-resolving model with spectral-bin microphysics is used to study the impact of aerosols on precipitation processes in both a tropical oceanic and a midlatitude continental squall line with regard to three processes: latent heating (LH), cold pool dynamics, and ice microphysics. Evaporative cooling in the lower troposphere is found to enhance rainfall in low cloud condensation nuclei (CCN) concentration scenarios in the developing stages of a midlatitude convective precipitation system. In contrast, the tropical case produced more rainfall under high CCN concentrations. Both cold pools and low-level convergence are stronger for those configurations having enhanced rainfall. Nevertheless, latent heat release is stronger (especially after initial precipitation) in the scenarios having more rainfall in both the tropical and midlatitude environment. Sensitivity tests are performed to examine the impact of ice and evaporative cooling on the relationship between aerosols, LH, and precipitation processes. The results show that evaporative cooling is important for cold pool strength and rain enhancement in both cases. However, ice microphysics play a larger role in the midlatitude case compared to the tropics. Detailed analysis of the vertical velocity-governing equation shows that temperature buoyancy can enhance updraftsdowndrafts in the middlelower troposphere in the convective core region; however, the vertical pressure gradient force (PGF) is of the same order and acts in the opposite direction. Water loading is small but of the same order as the net PGF-temperature buoyancy forcing. The balance among these terms determines the intensity of convection.

Segmental and Kinetic Contributions in Vertical Jumps Performed with and without an Arm Swing

ERIC Educational Resources Information Center

Feltner, Michael E.; Bishop, Elijah J.; Perez, Cassandra M.

2004-01-01

To determine the contributions of the motions of the body segments to the vertical ground reaction force ([F.sub.z]), the joint torques produced by the leg muscles, and the time course of vertical velocity generation during a vertical jump, 15 men were videotaped performing countermovement vertical jumps from a force plate with and without an arm…

Evaluation of changes in vertical ground reaction forces as indicators of meniscal damage after transection of the cranial cruciate ligament in dogs.

PubMed

Trumble, Troy N; Billinghurst, R Clark; Bendele, Alison M; McIlwraith, C Wayne

2005-01-01

To determine whether decreases in peak vertical force of the hind limb after transection of the cranial cruciate ligament (CrCL) would be indicative of medial meniscal damage in dogs. 39 purpose-bred adult male Walker Hounds. The right CrCL was transected arthroscopically. Force plate measurements of the right hind limb were made prior to and 2, 4, 10, and 18 weeks after transection of the CrCL. Only dogs with > or =10% decreases in peak vertical force after week 2 were considered to have potential meniscal damage. Dogs that did not have > or =10% decreases in peak vertical force at any time point after week 2 were assigned to group 1. Group 2 dogs had > or =10% decreases in peak vertical force from weeks 2 to 4 only. Group 3 and 4 dogs had > or =10% decreases in peak vertical force from weeks 4 to 10 only or from weeks 10 to 18 only, respectively. Damage to menisci and articular cartilage was graded at week 18, and grades for groups 2 to 4 were compared with those of group 1. The percentage change in peak vertical force and impulse area was significantly different in groups 2 (n = 4), 3 (4), and 4 (4) at the end of each measurement period (weeks 4, 10, and 18, respectively) than in group 1 (27). The meniscal grade for groups 2 to 4 was significantly higher than for group 1. A > or =10% decrease in peak vertical force had sensitivity of 52% and accuracy of 72% for identifying dogs with moderate to severe medial meniscal damage. In dogs with transected or ruptured CrCLs, force plate analysis can detect acute exacerbation of lameness, which may be the result of secondary meniscal damage, and provide an objective noninvasive technique that delineates the temporal pattern of medial meniscal injury.

Data Impact of the DMSP F18 SSULI UV Data on the Operational GAIM Model

NASA Astrophysics Data System (ADS)

Dandenault, P. B.; Metzler, C. A.; Nicholas, A. C.; Coker, C.; Budzien, S. A.; Chua, D. H.; Finne, T. T.; Dymond, K.; Walker, P. W.; Schunk, R. W.; Scherliess, L.; Gardner, L. C.

2011-12-01

The Naval Research Laboratory (NRL) has developed five ultraviolet remote sensing instruments for the United States Air Force (USAF) Defense Meteorological Satellite Program (DMSP). The DMSP satellites are launched in a near-polar, sun-synchronous orbit at an altitude of approximately 830 km. Each Special Sensor Ultraviolet Limb Imager (SSULI) instrument measures vertical profiles of the natural airglow radiation from atoms, molecules and ions in the upper atmosphere and ionosphere by viewing the earth's limb within a tangent altitude range of approximately 50 km to 750 km. Limb observations are made from the extreme ultraviolet (EUV) to the far ultraviolet (FUV) over the wavelength range of 80 nm to 170 nm, with 1.8 nm resolution. Data products from SSULI observations include nightglow and dayglow Sensor Data Records (SDRs), as well as Environmental Data Records (EDRs) which contain vertical profiles of electron (Ne) densities, N2, O2, O, O+, and Temperature, hmF2, NmF2 and vertical Total Electron Content (TEC). On October 18, 2009, the third SSULI sensor launched from Vandenberg Air Force Base aboard the DMSP F18 spacecraft. The Calibration and Validation of the F18 instrument has completed and the SSULI program is scheduled to go operational at the Air Force Weather Agency (AFWA) in Fall 2011. The SSULI F18 data are ingested by the Global Assimilation of Ionospheric Measurements (GAIM) space weather model, which was developed by Utah State University and has been used operationally at AFWA since February 2006. A brief overview of the SSULI F18 SDR data assimilation process with GAIM is provided and the impact of the SSULI 1356 Å emission on the GAIM model is examined for spring and summer 2011 nightside data in the low-latitude region.

Effect of walking velocity on ground reaction force variables in the hind limb of clinically normal horses.

PubMed

Khumsap, S; Clayton, H M; Lanovaz, J L

2001-06-01

To measure the effect of subject velocity on hind limb ground reaction force variables at the walk and to use the data to predict the force variables at different walking velocities in horses. 5 clinically normal horses. Kinematic and force data were collected simultaneously. Each horse was led over a force plate at a range of walking velocities. Stance duration and force data were recorded for the right hind limb. To avoid the effect of horse size on the outcome variables, the 8 force variables were standardized to body mass and height at the shoulders. Velocity was standardized to height at the shoulders and expressed as velocity in dimensionless units (VDU). Stance duration was also expressed in dimensionless units (SDU). Simple regression analysis was performed, using stance duration and force variables as dependent variables and VDU as the independent variable. Fifty-six trials were recorded with velocities ranging from 0.24 to 0.45 VDU (0.90 to 1.72 m/s). Simple regression models between measured variables and VDU were significant (R2 > 0.69) for SDU, first peak of vertical force, dip between the 2 vertical force peaks, vertical impulse, and timing of second peak of vertical force. Subject velocity affects vertical force components only. In the future, differences between the forces measured in lame horses and the expected forces calculated for the same velocity will be studied to determine whether the equations can be used as diagnostic criteria.

The Zig-zag Instability of Streamlined Bodies

NASA Astrophysics Data System (ADS)

Guillet, Thibault; Coux, Martin; Quere, David; Clanet, Christophe

2017-11-01

When a floating bluff body, like a sphere, impacts water with a vertical velocity, its trajectory is straight and the depth of its dive increases with its initial velocity. Even though we observe the same phenomenon at low impact speed for axisymmetric streamlined bodies, the trajectory is found to deviate from the vertical when the velocity overcomes a critical value. This instability results from a competition between the destabilizing torque of the lift and the stabilizing torque of the Archimede's force. Balancing these torques yields a prediction on the critical velocity above which the instability appears. This theoretical value is found to depend on the position of the gravity center of the projectile and predicts with a full agreement the behaviour observed in our different experiments. Project funded by DGA.

Large General Purpose Frame for Studying Force Vectors

ERIC Educational Resources Information Center

Heid, Christy; Rampolla, Donald

2011-01-01

Many illustrations and problems on the vector nature of forces have weights and forces in a vertical plane. One of the common devices for studying the vector nature of forces is a horizontal "force table," in which forces are produced by weights hanging vertically and transmitted to cords in a horizontal plane. Because some students have…

A Comparison of 2 Current-Issue Army Boots.

DTIC Science & Technology

2000-01-01

at 3.5 mph, mean (SD) 32 21 .Maximum heel- strike vertical force (N) while walking at 3.5 mph, mean (SD) 33 22 Maximum heel- strike braking force...while running at 6.5 mph, mean (SD) 38 34 Maximum force on the hip (N) while running at 6.5 mph, mean (SD) 38 35 Maximum vertical heel- strike force (N...during 6.5 mph running, mean (SD) 39 36. Maximum heel- strike braking force (N) while running at 6.5 mph, mean (SD) 39 37. Maximum vertical push

Influence of loading forces on the vertical accuracy of interocclusal records.

PubMed

Ghazal, Muhamad; Kern, Matthias

2010-02-01

To evaluate the influence of loading forces on the vertical discrepancies caused by interocclusal recording materials. A custom-made apparatus was used to simulate the maxilla and mandible. Eight interocclusal records were made in each of the following groups: G1-Aluwax (aluminum wax; Aluwax), G2-Beauty Pink wax (hydrocarbon wax compound; Miltex), G3-Futar D, G4-Futar D Fast, G5-Futar Scan (polyvinyl siloxanes; Kettenbach), and G6-Ramitec (polyether; 3M ESPE). The vertical discrepancies were measured by an inductive displacement transducer connected to a carrier frequency amplifier after storage of the records for 1 hour at room temperature. Different compressive loading forces up to 1 kg were applied onto the upper part of the apparatus to evaluate the influence on the vertical discrepancies of the records. Two-way ANOVA was used for statistical analysis. The compressive loading force had a statistically significant influence on the vertical discrepancies (P<.01) (ie, higher forces reduced the vertical discrepancies). When a compressive force of 1 kg was applied to the upper part of the apparatus, the mean vertical discrepancies for G1 (11+/-3 microm) and G2 (12+/-3 microm) were statistically significantly higher than in groups G3 (1+/-1 microm), G4 (2+/-1 microm), G5 (0+/-1 microm), and G6 (-2+/-2 microm). A compressive force of 1 kg could be used to stabilize the cast during mounting procedures in an articulator using an interocclusal record made of polyvinyl siloxane without vertically changing the interocclusal relationships.

Concurrent Validity of a Portable Force Plate Using Vertical Jump Force-Time Characteristics.

PubMed

Lake, Jason; Mundy, Peter; Comfort, Paul; McMahon, John J; Suchomel, Timothy J; Carden, Patrick

2018-05-29

This study examined concurrent validity of countermovement vertical jump (CMJ) reactive strength index modified and force-time characteristics recorded using a one dimensional portable and laboratory force plate system. Twenty-eight men performed bilateral CMJs on two portable force plates placed on top of two in-ground force plates, both recording vertical ground reaction force at 1000 Hz. Time to take-off, jump height, reactive strength index modified, braking and propulsion impulse, mean net force, and duration were calculated from the vertical force from both force plate systems. Results from both systems were highly correlated (r≥.99). There were small (d<.12) but significant differences between their respective braking impulse, braking mean net force, propulsion impulse, and propulsion mean net force (p<.001). However, limits of agreement yielded a mean value of 1.7% relative to the laboratory force plate system (95% CL: .9% to 2.5%), indicating very good agreement across all of the dependent variables. The largest limits of agreement belonged to jump height (2.1%), time to take-off (3.4%), and reactive strength index modified (3.8%). The portable force plate system provides a valid method of obtaining reactive strength measures, and several underpinning force-time variables, from unloaded CMJ and practitioners can use both force plates interchangeably.

On the relationship between lower extremity muscles activation and peak vertical and posterior ground reaction forces during single leg drop landing.

PubMed

Mahaki, M; Mi'mar, R; Mahaki, B

2015-10-01

Anterior cruciate ligament (ACL) injury continues to be an important medical issue for athletes participating in sports. Vertical and posterior ground reaction forces have received considerable attention for their potential influence on ACL injuries. The purpose of this study was to examine the relationship between electromyographic activity of lower extremity muscles and the peak vertical and posterior ground reaction forces during single leg drop landing. Thirteen physical education male students participated in this correlation study. Electromyographic activities of gluteus medius, biceps femoris, medial gastrocnemius, soleus as well as anterior tibialis muscles along with ground reaction forces were measured. Participants performed single-leg landing from a 0.3 m height on to a force platform. Landing was divided into two phases: 100 ms preceding ground contact and 100 ms proceeding ground contact. Pearson correlation test was used to determine the relationships between these muscles activity and peak vertical and posterior ground reaction forces. The results of the study indicated that the activity of soleus and tibialis anterior in pre-landing phase were positively correlated with peak vertical ground reaction force ([P≤0.04], [P≤0.008], respectively). However, no significant correlation was found between the activities of other muscles in pre-landing phase and peak vertical as well as peak posterior ground reaction forces. Also, no significant correlation was found between the activities of muscles in post-landing phase and peak vertical as well as peak posterior ground reaction forces. Soleus loading shifts the proximal tibia posterior at the knee joint and tibialis anterior prevent hyperporonation of the ankle, a mechanisms of ACL injury. Hence, neuromuscular training promoting preparatory muscle activity in these muscles may reduce the incidence of ACL injuries.

Musculoskeletal loading during the round-off in female gymnastics: the effect of hand position.

PubMed

Farana, Roman; Jandacka, Daniel; Uchytil, Jaroslav; Zahradnik, David; Irwin, Gareth

2014-06-01

Chronic elbow injuries from tumbling in female gymnastics present a serious problem for performers. This research examined how the biomechanical characteristics of impact loading and elbow kinematics and kinetics change as a function of technique selection. Seven international-level female gymnasts performed 10 trials of the round-off from a hurdle step to flic-flac with 'parallel' and 'T-shape' hand positions. Synchronized kinematic (3D-automated motion analysis system; 247 Hz) and kinetic (two force plates; 1,235 Hz) data were collected for each trial. Wilcoxon non-parametric test and effect-size statistics determined differences between the hand positions examined in this study. Significant differences (p < 0.05) and large effect sizes (ES > 0.8) were observed for peak vertical ground reaction force (GRF), anterior-posterior GRF, resultant GRF, loading rates of these forces and elbow joint angles, and internal moments of force in sagittal, transverse, and frontal planes. In conclusion, the T-shape hand position reduces vertical, anterior-posterior, and resultant contact forces and has a decreased loading rate indicating a safer technique for the round-off. Significant differences observed in joint elbow moments highlighted that the T-shape position may prevent overloading of the joint complex and consequently reduce the potential for elbow injury.

Vertical and lateral forces when a permanent magnet above a superconductor traverses in arbitrary directions

NASA Astrophysics Data System (ADS)

Yang, Yong

2008-12-01

In an actual levitation system composed of high temperature superconductors (HTSs) and permanent magnets (PMs), the levitating bodies may traverse in arbitrary directions. Many previous researchers assumed that the levitating bodies moved in a vertical direction or a lateral direction in order to simplify the problem. In this paper, the vertical and lateral forces acting on the PM are calculated by the modified frozen-image method when a PM above an HTS traverses in arbitrary directions. In order to study the effects of the movement directions on the vertical and lateral forces, comparisons of the forces that act on a PM traversing in a tilted direction with those that act on a PM traversing in a vertical direction or a lateral direction have been presented.

Magnetic Levitation Force Measurement System at Any Low Temperatures From 20 K To 300 K

NASA Astrophysics Data System (ADS)

Celik, Sukru; Guner, S. Baris; Coskun, Elvan

2015-03-01

Most of the magnetic levitation force measurements in previous studies were performed at liquid nitrogen temperatures. For the levitation force of MgB2 and iron based superconducting samples, magnetic levitation force measurement system is needed. In this study, magnetic levitation force measurement system was designed. In this system, beside vertical force versus vertical motion, lateral and vertical force versus lateral motion measurements, the vertical force versus temperature at the fixed distance between permanent magnet PM - superconducting sample SS and the vertical force versus time measurements were performed at any temperatures from 20 K to 300 K. Thanks to these measurements, the temperature dependence, time dependence, and the distance (magnetic field) and temperature dependences of SS can be investigated. On the other hand, the magnetic stiffness MS measurements can be performed in this system. Using the measurement of MS at different temperature in the range, MS dependence on temperature can be investigated. These measurements at any temperatures in the range help to the superconductivity properties to be characterized. This work was supported by TUBTAK-the Scientific and technological research council of Turkey under project of MFAG - 110T622. This system was applied to the Turkish patent institute with the Application Number of 2013/13638 on 22/11/2013.

Countermovement strategy changes with vertical jump height to accommodate feasible force constraints.

PubMed

Kim, Seyoung; Park, Sukyung; Choi, Sangkyu

2014-09-22

In this study, we developed a curve-fit model of countermovement dynamics and examined whether the characteristics of a countermovement jump can be quantified using the model parameter and its scaling; we expected that the model-based analysis would facilitate an understanding of the basic mechanisms of force reduction and propulsion with a simplified framework of the center of mass (CoM) mechanics. Ten healthy young subjects jumped straight up to five different levels ranging from approximately 10% to 35% of their body heights. The kinematic and kinetic data on the CoM were measured using a force plate system synchronized with motion capture cameras. All subjects generated larger vertical forces compared with their body weights from the countermovement and sufficiently lowered their CoM position to support the work performed by push-off as the vertical elevations became more challenging. The model simulation reasonably reproduced the trajectories of vertical force during the countermovement, and the model parameters were replaced by linear and polynomial regression functions in terms of the vertical jump height. Gradual scaling trends of the individual model parameters were observed as a function of the vertical jump height with different degrees of scaling, depending on the subject. The results imply that the subjects may be aware of the jumping dynamics when subjected to various vertical jump heights and may select their countermovement strategies to effectively accommodate biomechanical constraints, i.e., limited force generation for the standing vertical jump. Copyright © 2014 Elsevier Ltd. All rights reserved.

Can Assimilation of Satellite Ozone Data Contribute to the Understanding of the Lower Stratospheric Ozone?

NASA Technical Reports Server (NTRS)

Stajner, I.; Wargan, K.; Pawson, S.; Hayashi, H.; Chang, L.-P.; Rood, R.

2004-01-01

We study the quality of lower stratospheric ozone fields from a three- dimensional global ozone assimilation system. Ozone in this region is important for the forcing of climate, but its global distribution is not fully known because of its large temporal and vertical variability. Modeled fields often have biases due to the inaccurate representation of transport processes in this region with strong gradients. Accurate ozonesonde or satellite occultation measurements have very limited coverage. Nadir measurements, such as those from the Solar Backscatter Ultraviolet/2 (SBUV/2) instrument that provide wide latitudinal coverage, lack the vertical resolution needed to represent sharp vertical features. Limb measurements, such as those from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), provide a finer vertical resolution. We show that assimilation of MIPAS data in addition to SBUV/2 data leads to better estimates of ozone in comparison with independent high quality satellite, aircraft, and ozone sonde measurements. Other modifications to the statistical analysis that have an impact on the lower stratospheric ozone will be mentioned: error covariance modeling and data selection. Direct and indirect impacts of transport and chemistry models will be discussed. Implications for multi-year analyses and short-tern prediction will be addressed.

Effects of Jaw Clenching and Jaw Alignment Mouthpiece Use on Force Production During Vertical Jump and Isometric Clean Pull.

PubMed

Allen, Charles R; Fu, Yang-Chieh; Cazas-Moreno, Vanessa; Valliant, Melinda W; Gdovin, Jacob R; Williams, Charles C; Garner, John C

2018-01-01

Allen, CR, Fu, Y-C, Cazas-Moreno, V, Valliant, MW, Gdovin, JR, Williams, CC, and Garner, JC. Effects of jaw clenching and jaw alignment mouthpiece use on force production during vertical jump and isometric clean pull. J Strength Cond Res 32(1): 237-243, 2018-This study examined the effects of jaw clenching, a self-adapted, jaw-repositioning mouthpiece on force production during maximum countermovement vertical jump and maximum isometric midthigh clean pull assessments in an attempt to determine any ergogenic effect attributable to clenching, jaw-repositioning mouthpiece use, or the combination of both. Thirty-six male subjects performed vertical jump and isometric clean pull assessments from a force platform under various mouthpiece and clench conditions. A 3 × 2 (mouthpiece × clench) repeated-measures analysis of variance was conducted to analyze each of the following force production variables for both assessments: peak force, normalized peak force, and rate of force development. In addition, jump height was analyzed for the vertical jump. Results revealed improvements in peak force (F1,35 = 15.84, p ≤ 0.001, (Equation is included in full-text article.)= 0.31), normalized peak force (F1,35 = 16.28, p ≤ 0.001, (Equation is included in full-text article.)= 0.32), and rate of force development (F1,35 = 12.89, p = 0.001, (Equation is included in full-text article.)= 0.27) during the isometric clean pull assessment when participants maximally clenched their jaw, regardless of mouthpiece condition. There were no statistically significant differences in jump height, peak force, normalized peak force, or rate of force development during the vertical jump for any treatment condition. This study supports previous research demonstrating that the implementation of remote voluntary contractions such as jaw clenching can lead to concurrent activation potentiation and a resulting ergogenic effect during activities involving and requiring high-force production.

Variability of vertical ground reaction forces collected with one and two force plates in healthy dogs.

PubMed

Stejskal, M; Torres, B T; Sandberg, G S; Sapora, J A; Dover, R K; Budsberg, S C

2015-01-01

To compare peak vertical force (PVF) and vertical impulse (VI) data collected with one and two force plates during the same collection time period in healthy dogs at a trot. Seventeen healthy client-owned adult dogs. Vertical ground reaction force (GRF) data were collected in a crossover study design, with four sessions on two consecutive days, and then two weeks apart (days 1, 2, 15, and 16) using both one and two force plates collection methods. A repeated measures model analysis of variance (ANOVA) was used to test for differences in force plate PVF, VI, and average time per trial (ATT) between days, weeks, and systems (1 plate versus 2 plates). Coefficients of variation for PVF and VI were also calculated separately by forelimbs and hindlimbs, plates, day, and week. The time required to obtain a valid trial was significantly longer using a single force plate when compared with two force plates. Comparing GRF data for all dogs, significant differences in PVF data were found between one and two force plates, however, these differences were diminutive in absolute magnitude, and of unknown clinical importance. Examination of the coefficients of variation for PVF and VI during the different collection periods yielded similar results. Use of two force plates decreased trial repetition and collection time. Vertical GRF data had a similar coefficient of variation with either one or two force plates collection techniques in healthy dogs.

Dynamically adjustable foot-ground contact model to estimate ground reaction force during walking and running.

PubMed

Jung, Yihwan; Jung, Moonki; Ryu, Jiseon; Yoon, Sukhoon; Park, Sang-Kyoon; Koo, Seungbum

2016-03-01

Human dynamic models have been used to estimate joint kinetics during various activities. Kinetics estimation is in demand in sports and clinical applications where data on external forces, such as the ground reaction force (GRF), are not available. The purpose of this study was to estimate the GRF during gait by utilizing distance- and velocity-dependent force models between the foot and ground in an inverse-dynamics-based optimization. Ten males were tested as they walked at four different speeds on a force plate-embedded treadmill system. The full-GRF model whose foot-ground reaction elements were dynamically adjusted according to vertical displacement and anterior-posterior speed between the foot and ground was implemented in a full-body skeletal model. The model estimated the vertical and shear forces of the GRF from body kinematics. The shear-GRF model with dynamically adjustable shear reaction elements according to the input vertical force was also implemented in the foot of a full-body skeletal model. Shear forces of the GRF were estimated from body kinematics, vertical GRF, and center of pressure. The estimated full GRF had the lowest root mean square (RMS) errors at the slow walking speed (1.0m/s) with 4.2, 1.3, and 5.7% BW for anterior-posterior, medial-lateral, and vertical forces, respectively. The estimated shear forces were not significantly different between the full-GRF and shear-GRF models, but the RMS errors of the estimated knee joint kinetics were significantly lower for the shear-GRF model. Providing COP and vertical GRF with sensors, such as an insole-type pressure mat, can help estimate shear forces of the GRF and increase accuracy for estimation of joint kinetics. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

Comparison of Aerosol Classification Results from Airborne High Spectral Resolution Lidar (HSRL) Measurements and the Calipso Vertical Feature Mask

NASA Technical Reports Server (NTRS)

Burton, S. P.; Ferrare, R. A.; Hostetler, C. A.; Hair, J. W.; Rogers, R. R.; Obland, M. D.; Butler, C. F.; Cook, A. L.; Harper, D. B.; Froyd, K. D.;

Climate Impacts of CALIPSO-Guided Corrections to Black Carbon Aerosol Vertical Distributions in a Global Climate Model

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

Kovilakam, Mahesh; Mahajan, Salil; Saravanan, R.

Here, we alleviate the bias in the tropospheric vertical distribution of black carbon aerosols (BC) in the Community Atmosphere Model (CAM4) using the Cloud-Aerosol and Infrared Pathfinder Satellite Observations (CALIPSO)-derived vertical profiles. A suite of sensitivity experiments are conducted with 1x, 5x, and 10x the present-day model estimated BC concentration climatology, with (corrected, CC) and without (uncorrected, UC) CALIPSO-corrected BC vertical distribution. The globally averaged top of the atmosphere radiative flux perturbation of CC experiments is ~8–50% smaller compared to uncorrected (UC) BC experiments largely due to an increase in low-level clouds. The global average surface temperature increases, the globalmore » average precipitation decreases, and the ITCZ moves northward with the increase in BC radiative forcing, irrespective of the vertical distribution of BC. Further, tropical expansion metrics for the poleward extent of the Northern Hemisphere Hadley cell (HC) indicate that simulated HC expansion is not sensitive to existing model biases in BC vertical distribution.« less

Climate Impacts of CALIPSO-Guided Corrections to Black Carbon Aerosol Vertical Distributions in a Global Climate Model

DOE PAGES

Kovilakam, Mahesh; Mahajan, Salil; Saravanan, R.; ...

2017-09-13

Here, we alleviate the bias in the tropospheric vertical distribution of black carbon aerosols (BC) in the Community Atmosphere Model (CAM4) using the Cloud-Aerosol and Infrared Pathfinder Satellite Observations (CALIPSO)-derived vertical profiles. A suite of sensitivity experiments are conducted with 1x, 5x, and 10x the present-day model estimated BC concentration climatology, with (corrected, CC) and without (uncorrected, UC) CALIPSO-corrected BC vertical distribution. The globally averaged top of the atmosphere radiative flux perturbation of CC experiments is ~8–50% smaller compared to uncorrected (UC) BC experiments largely due to an increase in low-level clouds. The global average surface temperature increases, the globalmore » average precipitation decreases, and the ITCZ moves northward with the increase in BC radiative forcing, irrespective of the vertical distribution of BC. Further, tropical expansion metrics for the poleward extent of the Northern Hemisphere Hadley cell (HC) indicate that simulated HC expansion is not sensitive to existing model biases in BC vertical distribution.« less

Vertical force and torque analysis during mechanical preparation of extracted teeth using hand ProTaper instruments.

PubMed

Glavičić, Snježana; Anić, Ivica; Braut, Alen; Miletić, Ivana; Borčić, Josipa

2011-08-01

The purpose was to measure and analyse the vertical force and torque developed in the wider and narrower root canals during hand ProTaper instrumentation. Twenty human incisors were divided in two groups. Upper incisors were experimental model for the wide, while the lower incisors for the narrow root canals. Measurements of the force and torque were done by a device constructed for this purpose. Differences between the groups were statistically analysed by Mann-Whitney U-test with the significance level set to P<0.05. Vertical force in the upper incisors ranged 0.25-2.58 N, while in the lower incisors 0.38-6.94 N. Measured torque in the upper incisors ranged 0.53-12.03 Nmm, while in the lower incisor ranged 0.94-10.0 Nmm. Vertical force and torque were higher in the root canals of smaller diameter. The increase in the contact surface results in increase of the vertical force and torque as well in both narrower and wider root canals. © 2010 The Authors. Australian Endodontic Journal © 2010 Australian Society of Endodontology.

The impact of urban canopy meteorological forcing on summer photochemistry

NASA Astrophysics Data System (ADS)

Huszár, Peter; Karlický, Jan; Belda, Michal; Halenka, Tomáš; Pišoft, Petr

2018-03-01

The regional climate model RegCM4.4, including the surface model CLM4.5, was offline coupled to the chemistry transport model CAMx version 6.30 in order to investigate the impact of the urban canopy induced meteorological changes on the longterm summer photochemistry over central Europe for the 2001-2005 period. First, the urban canopy impact on the meteorological conditions was calculated performing a reference experiment without urban landsurface considered and an experiment with urban surfaces modeled with the urban parameterization within the CLM4.5 model. In accordance with expectations, strong increases of urban surface temperatures (up to 2-3 K), decreases of wind speed (up to -1 ms-1) and increases of vertical turbulent diffusion coefficient (up to 60-70 m2s-1) were found. For the impact on chemistry, these three components were considered. Additionally, we accounted for the effect of temperature enhanced biogenic emission increase. Several experiments were performed by adding these effects one-by-one to the total impact: i.e., first, only the urban temperature impact was considered driving the chemistry model; secondly, the wind impact was added and so on. We found that the impact on biogenic emission account for minor changes in the concentrations of ozone (O3), oxides of nitrogen NOx = NO + NO2 and nitric acid (HNO3). On the other hand, the dominating component acting is the increased vertical mixing, resulting in up to 5 ppbv increase of urban ozone concentrations while causing -2 to -3 ppbv decreases and around 1 ppbv increases of NOx and HNO3 surface concentrations, respectively. The temperature impact alone results in reduction of ozone, increase in NO, decrease in NO2 and increases of HNO3. The wind impact leads, over urban areas, to ozone decreases, increases of NOx and a slight increase in HNO3. The overall impact is similar to the impact of increased vertical mixing alone. The Process Analysis (PA) technique implemented in CAMx was adopted to investigate the causes of the modeled impacts in more details. It showed that the main process contributing to the temperature impact on ozone is a dry-deposition enhancement, while the dominating process controlling the wind impact on ozone over cities is the advection reduction. In case of the impact of enhanced turbulence, PA suggests that ozone increases are, again as assumed, the result of increased downward vertical mixing supported by reduced chemical loss. Comparing the model concentrations with measurements over urban areas, a slight improvement of the model performance was achieved during afternoon hours if urban canopy forcing on chemistry via meteorology was accounted for. The study demonstrates that disregarding the urban canopy induced meteorological effects in air-quality oriented modeling studies can lead to erroneous results in the calculated species concentrations. However, it also shows that the individual components are not equally important: urban canopy induced turbulence effects dominate while the wind-speed and temperature related ones are of considerably smaller magnitude.

Impact of Official Matches on Soccer Referees' Power Performance.

PubMed

Castillo, Daniel; Yanci, Javier; Cámara, Jesús

2018-03-01

The evaluation of match officials' neuromuscular performance is now an important consideration and the vertical jump test is considered suitable for assessing lower limb power, partly because it is directly related to refereeing. The aim of this study, therefore, was to determine the effect of soccer matches on match officials' vertical jump performance by assessing various biomechanical variables. Eighteen field referees (FRs) and 36 assistant referees (ARs) who officiated in 18 official matches participated in this study. Before the match, at half time and immediately after the match, officials performed two countermovement jumps. Flight phase time (FT), maximum force production (MFpropulsion), time to production of maximum force (TMFpropulsion), production of maximum power (MP), maximum landing force (MFlanding) and time to stabilization (TTS) were calculated for all jumps. There was a tendency for match officials' jumping performance to improve after matches than beforehand (FR: effect size (ES) = 0.19 ± 0.36, possibly trivial; AR: ES = 0.07 ± 0.17, likely trivial). There were also likely small and very likely moderate differences between FRs' MP in pre-match and half-time jumps (ES = 0.46 ± 0.47) and in their pre- and post-match jumps (ES = 0.71 ± 0.48). These results indicate that refereeing soccer matches does not reduce vertical jump performance; the subsequent neuromuscular fatigue is not sufficient to affect landing technique.

Gait-related intrinsic risk factors for patellofemoral pain in novice recreational runners.

PubMed

Thijs, Y; De Clercq, D; Roosen, P; Witvrouw, E

2008-06-01

To determine prospectively gait-related intrinsic risk factors for patellofemoral pain (PFP) in a population of novice recreational runners. Prospective cohort study. 102 novice recreational runners (89 women) with no history of knee or lower leg complaints. The standing foot posture of the subjects was examined and plantar pressure measurements during running were collected. The subjects then participated in a 10-week "start to run" programme. During this period all sports injuries were registered by a sports medicine physician. The relationship between the standing foot posture and PFP was investigated and gait-related intrinsic risk factors for PFP were determined. The 17 runners who developed PFP exerted a significantly higher vertical peak force underneath the lateral heel and metatarsals 2 and 3. Logistic regression analysis showed that a significantly higher vertical peak force underneath the second metatarsal and shorter time to the vertical peak force underneath the lateral heel were predictors for PFP. No significant evidence was found for an association between an excessively pronated or supinated foot posture and the development of PFP. The findings suggest that an excessive impact shock during heel strike and at the propulsion phase of running may contribute to an increased risk of developing PFP. The hypothesis that persons at risk for PFP show an altered static foot posture in comparison with non-afflicted persons is not supported by the results of this study.

Pilot investigation - Nominal crew induced forces in zero-g

NASA Technical Reports Server (NTRS)

Klute, Glenn K.

1992-01-01

This report presents pilot-study data of test subject forces induced by intravehicular activities such as push-offs and landings with both hands and feet. Five subjects participated in this investigation. Three orthogonal force axes were measured in the NASA KC-135 research aircraft's 'zero-g' environment. The largest forces were induced during vertical foot push-offs, including one of 534 newtons (120 lbs). The mean vertical foot push-off was 311 newtons (70 lbs). The vertical hand push-off forces were also relatively large, including one of 267 newtons (60 lbs) with a mean of 151 newtons (34 lbs). These force magnitudes of these forces would result in a Shuttle gravity environment of about 1 x exp 10 -4 g's.

Fighter Pilot Ejection Study as an Educational Tool

ERIC Educational Resources Information Center

Robinson, Garry; Jovanoski, Zlatko

2010-01-01

In this article, we apply the well-known equations of projectile motion to the case of a fighter pilot ejecting from an aircraft, the aim being to establish under what conditions there is danger of impact with the rear vertical stabilizer. The drag force on the pilot after ejection is assumed to vary as the velocity squared and the aircraft motion…

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.

The influence of lateral forces on the cell stiffness measurement by optical tweezers vertical indentation

NASA Astrophysics Data System (ADS)

Ndoye, Fatou; Sulaiman Yousafzai, Muhammad; Coceano, Giovanna; Bonin, Serena; Scoles, Giacinto; Ka, Oumar; Niemela, Joseph; Cojoc, Dan

2016-01-01

We studied the lateral forces arising during the vertical indentation of the cell membrane by an optically trapped microbead, using back focal plane interferometry to determine force components in all directions. We analyzed the cell-microbead interaction and showed that indeed the force had also lateral components. Using the Hertz model, we calculated and compared the elastic moduli resulting from the total and vertical forces, showing that the differences are important and the total force should be considered. To confirm our results we analyzed cells from two breast cancer cell lines: MDA-MB-231 and HBL-100, known to have different cancer aggressiveness and hence stiffness.

Impacts of wave-induced circulation in the surf zone on wave setup

NASA Astrophysics Data System (ADS)

Guérin, Thomas; Bertin, Xavier; Coulombier, Thibault; de Bakker, Anouk

2018-03-01

Wave setup corresponds to the increase in mean water level along the coast associated with the breaking of short-waves and is of key importance for coastal dynamics, as it contributes to storm surges and the generation of undertows. Although overall well explained by the divergence of the momentum flux associated with short waves in the surf zone, several studies reported substantial underestimations along the coastline. This paper investigates the impacts of the wave-induced circulation that takes place in the surf zone on wave setup, based on the analysis of 3D modelling results. A 3D phase-averaged modelling system using a vortex force formalism is applied to hindcast an unpublished field experiment, carried out at a dissipative beach under moderate to very energetic wave conditions (Hm 0 = 6m at breaking and Tp = 22s). When using an adaptive wave breaking parameterisation based on the beach slope, model predictions for water levels, short waves and undertows improved by about 30%, with errors reducing to 0.10 m, 0.10 m and 0.09 m/s, respectively. The analysis of model results suggests a very limited impact of the vertical circulation on wave setup at this dissipative beach. When extending this analysis to idealized simulations for different beach slopes ranging from 0.01 to 0.05, it shows that the contribution of the vertical circulation (horizontal and vertical advection and vertical viscosity terms) becomes more and more relevant as the beach slope increases. In contrast, for a given beach slope, the wave height at the breaking point has a limited impact on the relative contribution of the vertical circulation on the wave setup. For a slope of 0.05, the contribution of the terms associated with the vertical circulation accounts for up to 17% (i.e. a 20% increase) of the total setup at the shoreline, which provides a new explanation for the underestimations reported in previously published studies.

Ankle taping does not impair performance in jump or balance tests.

PubMed

Abián-Vicén, Javier; Alegre, Luis M; Fernández-Rodríguez, J Manuel; Lara, Amador J; Meana, Marta; Aguado, Xavier

2008-01-01

This study aimed to investigate the influence of prophylactic ankle taping on two balance tests (static and dynamic balance) and one jump test, in the push off and the landing phase. Fifteen active young subjects (age: 21.0 ± 4.4 years) without previous ankle injuries volunteered for the study. Each participant performed three tests in two different situations: with taping and without taping. The tests were a counter movement jump, static balance, and a dynamic posturography test. The tests and conditions were randomly performed. The path of the center of pressures was measured in the balance tests, and the vertical ground reaction forces were recorded during the push-off and landing phases of the counter movement jump. Ankle taping had no influence on balance performance or in the push off phase of the jump. However, the second peak vertical force value during the landing phase of the jump was 12% greater with ankle taping (0.66 BW, 95% CI -0.64 to 1.96). The use of prophylactic ankle taping had no influence on the balance or jump performance of healthy young subjects. In contrast, the taped ankle increased the second peak vertical force value, which could be related to a greater risk of injury produced by the accumulation of repeated impacts in sports where jumps are frequently performed. Key pointsAnkle taping has no influence on balance performance.Ankle taping does not impair performance during the push-off phase of the jump.Ankle taping could increase the risk of injury during landings by increasing peak forces.

Ankle Taping Does Not Impair Performance in Jump or Balance Tests

PubMed Central

Abián-Vicén, Javier; Alegre, Luis M.; Fernández-Rodríguez, J. Manuel; Lara, Amador J.; Meana, Marta; Aguado, Xavier

2008-01-01

This study aimed to investigate the influence of prophylactic ankle taping on two balance tests (static and dynamic balance) and one jump test, in the push off and the landing phase. Fifteen active young subjects (age: 21.0 ± 4.4 years) without previous ankle injuries volunteered for the study. Each participant performed three tests in two different situations: with taping and without taping. The tests were a counter movement jump, static balance, and a dynamic posturography test. The tests and conditions were randomly performed. The path of the center of pressures was measured in the balance tests, and the vertical ground reaction forces were recorded during the push-off and landing phases of the counter movement jump. Ankle taping had no influence on balance performance or in the push off phase of the jump. However, the second peak vertical force value during the landing phase of the jump was 12% greater with ankle taping (0.66 BW, 95% CI -0.64 to 1.96). The use of prophylactic ankle taping had no influence on the balance or jump performance of healthy young subjects. In contrast, the taped ankle increased the second peak vertical force value, which could be related to a greater risk of injury produced by the accumulation of repeated impacts in sports where jumps are frequently performed. Key pointsAnkle taping has no influence on balance performance.Ankle taping does not impair performance during the push-off phase of the jump.Ankle taping could increase the risk of injury during landings by increasing peak forces. PMID:24149902

Minor loop dependence of the magnetic forces and stiffness in a PM-HTS levitation system

NASA Astrophysics Data System (ADS)

Yang, Yong; Li, Chengshan

2017-12-01

Based upon the method of current vector potential and the critical state model of Bean, the vertical and lateral forces with different sizes of minor loop are simulated in two typical cooling conditions when a rectangular permanent magnet (PM) above a cylindrical high temperature superconductor (HTS) moves vertically and horizontally. The different values of average magnetic stiffness are calculated by various sizes of minor loop changing from 0.1 to 2 mm. The magnetic stiffness with zero traverse is obtained by using the method of linear extrapolation. The simulation results show that the extreme values of forces decrease with increasing size of minor loop. The magnetic hysteresis of the force curves also becomes small as the size of minor loop increases. This means that the vertical and lateral forces are significantly influenced by the size of minor loop because the forces intensely depend on the moving history of the PM. The vertical stiffness at every vertical position when the PM vertically descends to 1 mm is larger than that as the PM vertically ascents to 30 mm. When the PM moves laterally, the lateral stiffness during the PM passing through any horizontal position in the first time almost equal to the value during the PM passing through the same position in the second time in zero-field cooling (ZFC), however, the lateral stiffness in field cooling (FC) and the cross stiffness in ZFC and FC are significantly affected by the moving history of the PM.

Depth-dependent resistance of granular media to vertical penetration.

PubMed

Brzinski, T A; Mayor, P; Durian, D J

2013-10-18

We measure the quasistatic friction force acting on intruders moving downwards into a granular medium. By utilizing different intruder geometries, we demonstrate that the force acts locally normal to the intruder surface. By altering the hydrostatic loading of grain contacts by a sub-fluidizing airflow through the bed, we demonstrate that the relevant frictional contacts are loaded by gravity rather than by the motion of the intruder itself. Lastly, by measuring the final penetration depth versus airspeed and using an earlier result for inertial drag, we demonstrate that the same quasistatic friction force acts during impact. Altogether this force is set by a friction coefficient, hydrostatic pressure, projectile size and shape, and a dimensionless proportionality constant. The latter is the same in nearly all experiments, and is surprisingly greater than one.

Forces on stationary particles in near-bed turbulent flows

NASA Astrophysics Data System (ADS)

Schmeeckle, Mark W.; Nelson, Jonathan M.; Shreve, Ronald L.

2007-06-01

In natural flows, bed sediment particles are entrained and moved by the fluctuating forces, such as lift and drag, exerted by the overlying flow on the particles. To develop a better understanding of these forces and the relation of the forces to the local flow, the downstream and vertical components of force on near-bed fixed particles and of fluid velocity above or in front of them were measured synchronously at turbulence-resolving frequencies (200 or 500 Hz) in a laboratory flume. Measurements were made for a spherical test particle fixed at various heights above a smooth bed, above a smooth bed downstream of a downstream-facing step, and in a gravel bed of similarly sized particles as well as for a cubical test particle and 7 natural particles above a smooth bed. Horizontal force was well correlated with downstream velocity and not correlated with vertical velocity or vertical momentum flux. The standard drag formula worked well to predict the horizontal force, but the required value of the drag coefficient was significantly higher than generally used to model bed load motion. For the spheres, cubes, and natural particles, average drag coefficients were found to be 0.76, 1.36, and 0.91, respectively. For comparison, the drag coefficient for a sphere settling in still water at similar particle Reynolds numbers is only about 0.4. The variability of the horizontal force relative to its mean was strongly increased by the presence of the step and the gravel bed. Peak deviations were about 30% of the mean force for the sphere over the smooth bed, about twice the mean with the step, and 4 times it for the sphere protruding roughly half its diameter above the gravel bed. Vertical force correlated poorly with downstream velocity, vertical velocity, and vertical momentum flux whether measured over or ahead of the test particle. Typical formulas for shear-induced lift based on Bernoulli's principle poorly predict the vertical forces on near-bed particles. The measurements suggest that particle-scale pressure variations associated with turbulence are significant in the particle momentum balance.

Forces on stationary particles in near-bed turbulent flows

USGS Publications Warehouse

Schmeeckle, M.W.; Nelson, J.M.; Shreve, R.L.

2007-01-01

In natural flows, bed sediment particles are entrained and moved by the fluctuating forces, such as lift and drag, exerted by the overlying flow on the particles. To develop a better understanding of these forces and the relation of the forces to the local flow, the downstream and vertical components of force on near-bed fixed particles and of fluid velocity above or in front of them were measured synchronously at turbulence-resolving frequencies (200 or 500 Hz) in a laboratory flume. Measurements were made for a spherical test particle fixed at various heights above a smooth bed, above a smooth bed downstream of a downstream-facing step, and in a gravel bed of similarly sized particles as well as for a cubical test particle and 7 natural particles above a smooth bed. Horizontal force was well correlated with downstream velocity and not correlated with vertical velocity or vertical momentum flux. The standard drag formula worked well to predict the horizontal force, but the required value of the drag coefficient was significantly higher than generally used to model bed load motion. For the spheres, cubes, and natural particles, average drag coefficients were found to be 0.76, 1.36, and 0.91, respectively. For comparison, the drag coefficient for a sphere settling in still water at similar particle Reynolds numbers is only about 0.4. The variability of the horizontal force relative to its mean was strongly increased by the presence of the step and the gravel bed. Peak deviations were about 30% of the mean force for the sphere over the smooth bed, about twice the mean with the step, and 4 times it for the sphere protruding roughly half its diameter above the gravel bed. Vertical force correlated poorly with downstream velocity, vertical velocity, and vertical momentum flux whether measured over or ahead of the test particle. Typical formulas for shear-induced lift based on Bernoulli's principle poorly predict the vertical forces on near-bed particles. The measurements suggest that particle-scale pressure variations associated with turbulence are significant in the particle momentum balance. Copyright 2007 by the American Geophysical Union.

Magnitude and Spatial Distribution of Impact Intensity Under the Foot Relates to Initial Foot Contact Pattern.

PubMed

Breine, Bastiaan; Malcolm, Philippe; Segers, Veerle; Gerlo, Joeri; Derie, Rud; Pataky, Todd; Frederick, Edward C; De Clercq, Dirk

2017-12-01

In running, foot contact patterns (rear-, mid-, or forefoot contact) influence impact intensity and initial ankle and foot kinematics. The aim of the study was to compare impact intensity and its spatial distribution under the foot between different foot contact patterns. Forty-nine subjects ran at 3.2 m·s -1 over a level runway while ground reaction forces (GRF) and shoe-surface pressures were recorded and foot contact pattern was determined. A 4-zone footmask (forefoot, midfoot, medial and lateral rearfoot) assessed the spatial distribution of the vertical GRF under the foot. We calculated peak vertical instantaneous loading rate of the GRF (VILR) per foot zone as the impact intensity measure. Midfoot contact patterns were shown to have the lowest, and atypical rearfoot contact patterns the highest impact intensities, respectively. The greatest local impact intensity was mainly situated under the rear- and midfoot for the typical rearfoot contact patterns, under the midfoot for the atypical rearfoot contact patterns, and under the mid- and forefoot for the midfoot contact patterns. These findings indicate that different foot contact patterns could benefit from cushioning in different shoe zones.

Kinematic Patterns Associated with the Vertical Force Produced during the Eggbeater Kick.

PubMed

Oliveira, Nuno; Chiu, Chuang-Yuan; Sanders, Ross H

2015-01-01

The purpose of this study was to determine the kinematic patterns that maximized the vertical force produced during the water polo eggbeater kick. Twelve water polo players were tested executing the eggbeater kick with the trunk aligned vertically and with the upper limbs above water while trying to maintain as high a position as possible out of the water for nine eggbeater kick cycles. Lower limb joint angular kinematics, pitch angles and speed of the feet were calculated. The vertical force produced during the eggbeater kick cycle was calculated using inverse dynamics for the independent lower body segments and combined upper body segments, and a participant-specific second-degree regression equation for the weight and buoyancy contributions. Vertical force normalized to body weight was associated with hip flexion (average, r = 0.691; maximum, r = 0.791; range of motion, r = 0.710), hip abduction (maximum, r = 0.654), knee flexion (average, r = 0.716; minimum, r = 0.653) and knee flexion-extension angular velocity (r = 0.758). Effective orientation of the hips resulted in fast horizontal motion of the feet with positive pitch angles. Vertical motion of the feet was negatively associated with vertical force. A multiple regression model comprising the non-collinear variables of maximum hip abduction, hip flexion range of motion and knee flexion angular velocity accounted for 81% of the variance in normalized vertical force. For high performance in the water polo, eggbeater kick players should execute fast horizontal motion with the feet by having large abduction and flexion of the hips, and fast extension and flexion of the knees.

An investigation of improved airbag performance by vent control and gas injection

NASA Astrophysics Data System (ADS)

Lee, Calvin; Rosato, Nick; Lai, Francis

Airbags are currently being investigated as an impact energy absorber for U.S. Army airdrop. Simple airbags with constant vent areas have been found to be unsatisfactory in yielding high G forces. In this paper, a method of controlling the vent area and a method of injecting gas into the airbag during its compression stroke to improve airbag performance are presented. Theoretical analysis of complex airbags using these two methods show that they provide lower G forces than simple airbags. Vertical drop tests of a vent-control airbag confirm this result. Gas-injection airbags are currently being tested.

Fringe Field Effects on Bending Magnets, Derived for TRANSPORT/TURTLE

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

Molloy, Riley; Blitz, Sam

2013-08-05

A realistic magnetic dipole has complex effects on a charged particle near the entrance and exit of the magnet, even with a constant and uniform magnetic field deep within the interior of the magnet. To satisfy Maxwell's equations, the field lines near either end of a realistic magnet are significantly more complicated, yielding non-trivial forces. The effects of this fringe field are calculated to first order, applying both the paraxial and thin lens approximations. We find that, in addition to zeroth order effects, the position of a particle directly impacts the forces in the horizontal and vertical directions.

Regional difference of the vertical structure of seasonal thermocline and its impact on sea surface temperature in the North Pacific

NASA Astrophysics Data System (ADS)

Yamaguchi, R.; Suga, T.

2016-12-01

Recent observational studies show that, during the warming season, a large amount of heat flux is penetrated through the base of thin mixed layer by vertical eddy diffusion, in addition to penetration of solar radiation [1]. In order to understand this heat penetration process due to vertical eddy diffusivity and its contribution to seasonal variation of sea surface temperature, we investigated the evolution of thermal stratification below the summertime thin mixed layer (i.e. evolution of seasonal thermocline) and its vertical structure in the North Pacific using high vertical resolution temperature profile observed by Argo floats. We quantified the vertical structure of seasonal thermocline as deviations from the linear structure where the vertical gradient of temperature is constant, that is, "shape anomaly". The shape anomaly is variable representing the extent of the bend of temperature profiles. We found that there are larger values of shape anomaly in the region where the seasonal sea surface temperature warming is relatively faster. To understand the regional difference of shape anomalies, we investigated the relationship between time changes in shape anomalies and net surface heat flux and surface kinetic energy flux. From May to July, the analysis indicated that, in a large part of North Pacific, there's a tendency for shape anomalies to develop strongly (weakly) under the conditions of large (small) downward net surface heat flux and small (large) downward surface kinetic energy flux. Since weak (strong) development of shape anomalies means efficient (inefficient) downward heat transport from the surface, these results suggest that the regional difference of the downward heat penetration below mixed layer is explained reasonably well by differences in surface heat forcing and surface wind forcing in a vertical one dimensional framework. [1] Hosoda et al. (2015), J. Oceanogr., 71, 541-556.

Analysis of Instantaneous Attractive-Normal Force and Vertical Vibration Control of Combined-Levitation-and-Propulsion SLIM Vehicle

NASA Astrophysics Data System (ADS)

Yoshida, Takashi

Combined-levitation-and-propulsion single-sided linear induction motor (SLIM) vehicle can be levitated without any additional levitation system. When the vehicle runs, the attractive-normal force varies depending on the phase of primary current because of the short primary end effect. The ripple of the attractive-normal force causes the vertical vibration of the vehicle. In this paper, instantaneous attractive-normal force is analyzed by using space harmonic analysis method. And based on the analysis, vertical vibration control is proposed. The validity of the proposed control method is verified by numerical simulation.

Cornering characteristics of the main-gear tire of the space shuttle orbiter

NASA Technical Reports Server (NTRS)

Daugherty, Robert H.; Stubbs, Sandy M.; Robinson, Martha P.

1988-01-01

An experimental investigation was conducted at the NASA Langley Research Center to study the effects of various vertical load and yaw angle conditions on the cornering behavior of the Space Shuttle Orbiter main gear tire. Measured parameters included side and drag force, side and drag force coefficients, aligning torque, and overturning torque. Side force coefficient was found to increase as yaw angle was increased, but decreased as the vertical load was increased. Drag force was found to increase as vertical load was increased at constant yaw angles. Aligning torque measurements indicated that the tire is stable in yaw.

Stride length: the impact on propulsion and bracing ground reaction force in overhand throwing.

PubMed

Ramsey, Dan K; Crotin, Ryan L

2018-03-26

Propulsion and bracing ground reaction force (GRF) in overhand throwing are integral in propagating joint reaction kinetics and ball velocity, yet how stride length effects drive (hind) and stride (lead) leg GRF profiles remain unknown. Using a randomised crossover design, 19 pitchers (15 collegiate and 4 high school) were assigned to throw 2 simulated 80-pitch games at ±25% of their desired stride length. An integrated motion capture system with two force plates and radar gun tracked each throw. Vertical and anterior-posterior GRF was normalised then impulse was derived. Paired t-tests identified whether differences between conditions were significant. Late in single leg support, peak propulsion GRF was statistically greater for the drive leg with increased stride. Stride leg peak vertical GRF in braking occurred before acceleration with longer strides, but near ball release with shorter strides. Greater posterior shear GRF involving both legs demonstrated increased braking with longer strides. Conversely, decreased drive leg propulsion reduced both legs' braking effects with shorter strides. Results suggest an interconnection between normalised stride length and GRF application in propulsion and bracing. This work has shown stride length to be an important kinematic factor affecting the magnitude and timing of external forces acting upon the body.

The Impact of the Aerosol Direct Radiative Forcing on Deep Convection and Air Quality in the Pearl River Delta Region

NASA Astrophysics Data System (ADS)

Liu, Z.; Yim, Steve H. L.; Wang, C.; Lau, N. C.

2018-05-01

Literature has reported the remarkable aerosol impact on low-level cloud by direct radiative forcing (DRF). Impacts on middle-upper troposphere cloud are not yet fully understood, even though this knowledge is important for regions with a large spatial heterogeneity of emissions and aerosol concentration. We assess the aerosol DRF and its cloud response in June (with strong convection) in Pearl River Delta region for 2008-2012 at cloud-resolving scale using an air quality-climate coupled model. Aerosols suppress deep convection by increasing atmospheric stability leading to less evaporation from the ground. The relative humidity is reduced in middle-upper troposphere due to induced reduction in both evaporation from the ground and upward motion. The cloud reduction offsets 20% of the aerosol DRF. The weaker vertical mixing further increases surface aerosol concentration by up to 2.90 μg/m3. These findings indicate the aerosol DRF impact on deep convection and in turn regional air quality.

Impact of soil moisture on regional spectral model simulations for South America

Treesearch

Shyh-Chin Chen; John Roads

2005-01-01

A regional simulation using the regional spectral model (RSM) with 50-km grid space increment over South America is described. NCEP/NCAR 28 vertical levels T62 spectral resolution reanalyses were used to initialize and force the regional model for a two-year period from March 1997 through March 1999. Initially, the RSM had a severe drying trend in the soil moisture...

Impact of aerosol vertical distribution on aerosol direct radiative effect and heating rate in the Mediterranean region

NASA Astrophysics Data System (ADS)

Pappas, Vasileios; Hatzianastassiou, Nikolaos; Matsoukas, Christos; Koras Carracca, Mario; Kinne, Stefan; Vardavas, Ilias

2015-04-01

It is now well-established that aerosols cause an overall cooling effect at the surface and a warming effect within the atmosphere. At the top of the atmosphere (TOA), both positive and negative forcing can be found, depending on a number of other factors, such as surface albedo and relative position of clouds and aerosols. Whilst aerosol surface cooling is important due to its relation with surface temperature and other bio-environmental reasons, atmospheric heating is of special interest as well having significant impacts on atmospheric dynamics, such as formation of clouds and subsequent precipitation. The actual position of aerosols and their altitude relative to clouds is of major importance as certain types of aerosol, such as black carbon (BC) above clouds can have a significant impact on planetary albedo. The vertical distribution of aerosols and clouds has recently drawn the attention of the aerosol community, because partially can account for the differences between simulated aerosol radiative forcing with various models, and therefore decrease the level of our uncertainty regarding aerosol forcing, which is one of our priorities set by IPCC. The vertical profiles of aerosol optical and physical properties have been studied by various research groups around the world, following different methodologies and using various indices in order to present the impact of aerosols on radiation on different altitudes above the surface. However, there is still variability between the published results as to the actual effect of aerosols on shortwave radiation and on heating rate within the atmosphere. This study uses vertical information on aerosols from the Max Planck Aerosol Climatology (MAC-v1) global dataset, which is a combination of model output with quality ground-based measurements, in order to provide useful insight into the vertical profile of atmospheric heating for the Mediterranean region. MAC-v1 and the science behind this aerosol dataset have already been presented and its validity has been tested against satellite-based retrievals. A detailed spectral radiative transfer model (RTM), already used in a number of planetary and regional studies, has been used in the present study to calculate the vertically distributed aerosol direct radiative effects (DREs) and the associated aerosol heating/cooling profiles within the troposphere. Specific emphasis is given to assessment of the crucial issue of the differences between modeling the aerosol DREs using either columnar aerosol optical properties, as usually done, or vertically layered information on those properties, which is the state of the art and ideal practice. To address this problem, the following experiment has been performed: the same RTM has been used twice with the same meteorological conditions but in the first run (set1) columnar values for aerosol optical depth (AOD) have been used while using vertically distributed AOD in the second run (set2). In the second run vertically layered information for AOD is considered for 20 layers extending from the surface to 20 km a.m.s.l.. The vertical profile of AOD has been mainly based on ECHAM model. The aerosol DREs are computed at the Earth's surface, at TOA and at various levels in the atmosphere. Apart from AOD, the model also requires single-scattering albedo (SSA) and asymmetry parameter (ASY) in 18 different wavelengths, which are obtained by linear interpolation from the available wavelengths in HAC. The comparison between the obtained two sets of DRE (set1 and set2) reveal small, but notable differences which vary from one place to another. Within the atmosphere, the difference -averaged over the four seasons - ranges from -0.3 to 1.7 Wm-2 with a mean value of 0.32 Wm-2. Given the fact that the average column-integrated DREAtm values for the entire Mediterranean region based on columnar aerosol optical properties is 11.44 Wm-2, there is an average variance of 3.7 %, which locally could get to 14.9 %. Differences between the columnar and the vertically layered versions of the model also exist for DRE(TOA) and DRE(NetSurface) calculations.

Impact of biomass burning plume on radiation budget and atmospheric dynamics over the arctic

NASA Astrophysics Data System (ADS)

Lisok, Justyna; Pedersen, Jesper; Ritter, Christoph; Markowicz, Krzysztof M.; Malinowski, Szymon; Mazzola, Mauro; Udisti, Roberto; Stachlewska, Iwona S.

2018-04-01

The aim of the research was to determine the impact of July 2015 biomass burning event on radiative budget, atmospheric stratification and turbulence over the Arctic using information about the vertical structure of the aerosol load from the ground-based data. MODTRAN simulations indicated very high surface radiative cooling (forcing of -150 Wm-2) and a heating rate of up to 1.8 Kday-1 at 3 km. Regarding LES results, a turbulent layer at around 3 km was clearly seen after 48 h of simulation.

Violent transient sloshing-wave interaction with a baffle in a three-dimensional numerical tank

NASA Astrophysics Data System (ADS)

Xue, Mi-An; Zheng, Jinhai; Lin, Pengzhi; Xiao, Zhong

2017-08-01

A finite difference model for solving Navier Stokes equations with turbulence taken into account is used to investigate viscous liquid sloshing-wave interaction with baffles in a tank. The volume-of-fluid and virtual boundary force methods are employed to simulate free surface flow interaction with structures. A liquid sloshing experimental apparatus was established to evaluate the accuracy of the proposed model, as well as to study nonlinear sloshing in a prismatic tank with the baffles. Damping effects of sloshing in a rectangular tank with bottom-mounted vertical baffles and vertical baffles touching the free surface are studied numerically and experimentally. Good agreement is obtained between the present numerical results and experimental data. The numerical results match well with the current experimental data for strong nonlinear sloshing with large free surface slopes. The reduction in sloshing-wave elevation and impact pressure induced by the bottom-mounted vertical baffle and the vertical baffle touching the free surface is estimated by varying the external excitation frequency and the location and height of the vertical baffle under horizontal excitation.

Landing gear energy absorption system

NASA Technical Reports Server (NTRS)

Hansen, Christopher P. (Inventor)

1994-01-01

A landing pad system is described for absorbing horizontal and vertical impact forces upon engagement with a landing surface where circumferentially arranged landing struts respectively have a clevis which receives a slidable rod member and where the upper portion of a slidable rod member is coupled to the clevis by friction washers which are force fit onto the rod member to provide for controlled constant force energy absorption when the rod member moves relative to the clevis. The lower end of the friction rod is pivotally attached by a ball and socket to a support plate where the support plate is arranged to slide in a transverse direction relative to a housing which contains an energy absorption material for absorbing energy in a transverse direction.

Towards a footwear design tool: influence of shoe midsole properties and ground stiffness on the impact force during running.

PubMed

Ly, Quoc Hung; Alaoui, Amina; Erlicher, Silvano; Baly, Laurent

2010-01-19

Several spring-damper-mass models of the human body have been developed in order to reproduce the measured ground vertical reaction forces during human running (McMahon and Cheng, 1990; Ferris et al., 1999; Liu and Nigg, 2000). In particular, Liu and Nigg introduced at the lower level of their model, i.e. at the interface between the human body and the ground, a nonlinear element representing simultaneously the shoe midsoles and the ground flexibility. The ground reaction force is modelled as the force supported by this nonlinear element, whose parameters are identified from several sets of experimental data. This approach proved to be robust and quite accurate. However, it does not explicitly take into account the shoe and the ground properties. It turns out to be impossible to study the influence of shoe materials on the impact force, for instance for footwear design purposes. In this paper, a modification of the Liu and Nigg's model is suggested, where the original nonlinear element is replaced with a bi-layered spring-damper-mass model: the first layer represents the shoe midsole and the second layer is associated with the ground. Ground is modelled as an infinite elastic half-space. We have assumed a viscoelastic behaviour of the shoe material, so the damping of shoe material is taken into account. A methodology for the shoe-soles characterization is proposed and used together with the proposed model. A parametric study is then conducted and the influence of the shoe properties on the impact force is quantified. Moreover, it is shown that impact forces are strongly affected by the ground stiffness, which should therefore be considered as an essential parameter in the footwear design. Copyright 2009 Elsevier Ltd. All rights reserved.

Impact of Mantle Wind on Subducting Plate Geometry and Interplate Pressure: Insights From Physical Modelling.

NASA Astrophysics Data System (ADS)

Boutelier, D.; Cruden, A. R.

2005-12-01

New physical models of subduction investigate the impact of large-scale mantle flow on the structure of the subducted slab and deformation of the downgoing and overriding plates. The experiments comprise two lithospheric plates made of highly filled silicone polymer resting on a model asthenosphere of low viscosity transparent silicone polymer. Subduction is driven by a piston that pushes the subducting plate at constant rate, a slab-pull force due to the relative density of the slab, and a basal drag force exerted by flow in the model asthenosphere. Large-scale mantle flow is imposed by a second piston moving at constant rate in a tunnel at the bottom of the experiment tank. Passive markers in the mantle track the evolution of flow during the experiment. Slab structure is recorded by side pictures of the experiment while horizontal deformation is studied via passive marker grids on top of both plates. The initial mantle flow direction beneath the overriding plate can be sub-horizontal or sub-vertical. In both cases, as the slab penetrates the mantle, the mantle flow pattern changes to accommodate the subducting high viscosity lithosphere. As the slab continues to descend, the imposed flow produces either over- or under-pressure on the lower surface of the slab depending on the initial mantle flow pattern (sub-horizontal or sub-vertical respectively). Over-pressure imposed on the slab lower surface promotes shallow dip subduction while under-pressure tends to steepen the slab. These effects resemble those observed in previous experiments when the overriding plate moves horizontally with respect to a static asthenosphere. Our experiments also demonstrate that a strong vertical drag force (due to relatively fast downward mantle flow) exerted on the slab results in a decrease in strain rate in both the downgoing and overriding plates, suggesting a decrease in interplate pressure. Furthermore, with an increase in drag force deformation in the downgoing plate can switch from compression to extension. The density contrast between the downgoing plate and asthenosphere is varied from 0% to ~2% in order to investigate the relative contributions of mantle flow and slab pull force on the geometry of the slab and tectonic regime (compressional or extensional).

Ground Contact Modeling for the Morpheus Test Vehicle Simulation

NASA Technical Reports Server (NTRS)

Cordova, Luis

2014-01-01

The Morpheus vertical test vehicle is an autonomous robotic lander being developed at Johnson Space Center (JSC) to test hazard detection technology. Because the initial ground contact simulation model was not very realistic, it was decided to improve the model without making it too computationally expensive. The first development cycle added capability to define vehicle attachment points (AP) and to keep track of their states in the lander reference frame (LFRAME). These states are used with a spring damper model to compute an AP contact force. The lateral force is then overwritten, if necessary, by the Coulomb static or kinetic friction force. The second development cycle added capability to use the PolySurface class as the contact surface. The class can load CAD data in STL (Stereo Lithography) format, and use the data to compute line of sight (LOS) intercepts. A polygon frame (PFRAME) is computed from the facet intercept normal and used to convert the AP state to PFRAME. Three flat plane tests validate the transitions from kinetic to static, static to kinetic, and vertical impact. The hazardous terrain test will be used to test for visual reasonableness. The improved model is numerically inexpensive, robust, and produces results that are reasonable.

Ground Contact Modeling for the Morpheus Test Vehicle Simulation

NASA Technical Reports Server (NTRS)

Cordova, Luis

2013-01-01

The Morpheus vertical test vehicle is an autonomous robotic lander being developed at Johnson Space Center (JSC) to test hazard detection technology. Because the initial ground contact simulation model was not very realistic, it was decided to improve the model without making it too computationally expensive. The first development cycle added capability to define vehicle attachment points (AP) and to keep track of their states in the lander reference frame (LFRAME). These states are used with a spring damper model to compute an AP contact force. The lateral force is then overwritten, if necessary, by the Coulomb static or kinetic friction force. The second development cycle added capability to use the PolySurface class as the contact surface. The class can load CAD data in STL (Stereo Lithography) format, and use the data to compute line of sight (LOS) intercepts. A polygon frame (PFRAME) is computed from the facet intercept normal and used to convert the AP state to PFRAME. Three flat plane tests validate the transitions from kinetic to static, static to kinetic, and vertical impact. The hazardous terrain test will be used to test for visual reasonableness. The improved model is numerically inexpensive, robust, and produces results that are reasonable.

Lower extremity mechanics during landing after a volleyball block as a risk factor for anterior cruciate ligament injury.

PubMed

Zahradnik, David; Jandacka, Daniel; Uchytil, Jaroslav; Farana, Roman; Hamill, Joseph

2015-02-01

To compare lower extremity mechanics and energy absorption during two types of landing after a successful or unsuccessful block in volleyball and assess the risks of anterior cruciate ligament (ACL) injury. Cohort study. Fourteen elite male volleyball players (aged 24.5 ± 4.6 years; height 1.94 ± 0.06 m; mass 86.6 ± 7.6 kg). Subjects were required to land on force platforms using stick landing or step-back landing (with the right lower extremity stepping back away from the net) techniques after performing a standing block jump movement. Vertical ground reaction force (body weight); knee flexion (degrees); knee moments (Nm/kg); and hip, knee and ankle energy absorption (J/kg). The right lower extremity showed a greater first peak of vertical ground reaction force, a greater valgus moment, lower energy absorption by the knee, and higher energy absorption by the hip and ankle joints during step-back landing. The lower extremity may be exposed to a greater risk of ACL injury when stepping back from the net during the initial impact phase after a step-back landing. Copyright © 2014 Elsevier Ltd. All rights reserved.

Thigh Muscle Activity, Knee Motion, and Impact Force During Side-Step Pivoting in Agility-Trained Female Basketball Players

PubMed Central

Wilderman, Danielle R; Ross, Scott E; Padua, Darin A

2009-01-01

Context: Improving neuromuscular control of hamstrings muscles might have implications for decreasing anterior cruciate ligament injuries in females. Objective: To examine the effects of a 6-week agility training program on quadriceps and hamstrings muscle activation, knee flexion angles, and peak vertical ground reaction force. Design: Prospective, randomized clinical research trial. Setting: Sports medicine research laboratory. Patients or Other Participants: Thirty female intramural basketball players with no history of knee injury (age  =  21.07 ± 2.82 years, height  =  171.27 ± 4.66 cm, mass  =  66.36 ± 7.41 kg). Intervention(s): Participants were assigned to an agility training group or a control group that did not participate in agility training. Participants in the agility training group trained 4 times per week for 6 weeks. Main Outcome Measure(s): We used surface electromyography to assess muscle activation for the rectus femoris, vastus medialis oblique, medial hamstrings, and lateral hamstrings for 50 milliseconds before initial ground contact and while the foot was in contact with the ground during a side-step pivot maneuver. Knee flexion angles (at initial ground contact, maximum knee flexion, knee flexion displacement) and peak vertical ground reaction force also were assessed during this maneuver. Results: Participants in the training group increased medial hamstrings activation during ground contact after the 6-week agility training program. Both groups decreased their vastus medialis oblique muscle activation during ground contact. Knee flexion angles and peak vertical ground reaction force did not change for either group. Conclusions: Agility training improved medial hamstrings activity in female intramural basketball players during a side-step pivot maneuver. Agility training that improves hamstrings activity might have implications for reducing anterior cruciate ligament sprain injury associated with side-step pivots. PMID:19180214

Mechanisms of the intensification of the upwelling-favorable winds during El Niño 1997-1998 in the Peruvian upwelling system

NASA Astrophysics Data System (ADS)

Chamorro, Adolfo; Echevin, Vincent; Colas, François; Oerder, Vera; Tam, Jorge; Quispe-Ccalluari, Carlos

2018-01-01

The physical processes driving the wind intensification in a coastal band of 100 km off Peru during the intense 1997-1998 El Niño (EN) event were studied using a regional atmospheric model. A simulation performed for the period 1994-2000 reproduced the coastal wind response to local sea surface temperature (SST) forcing and large scale atmospheric conditions. The model, evaluated with satellite data, represented well the intensity, seasonal and interannual variability of alongshore (i.e. NW-SE) winds. An alongshore momentum budget showed that the pressure gradient was the dominant force driving the surface wind acceleration. The pressure gradient tended to accelerate the coastal wind, while turbulent vertical mixing decelerated it. A quasi-linear relation between surface wind and pressure gradient anomalies was found. Alongshore pressure gradient anomalies were caused by a greater increase in near-surface air temperature off the northern coast than off the southern coast, associated with the inhomogeneous SST warming. Vertical profiles of wind, mixing coefficient, and momentum trends showed that the surface wind intensification was not caused by the increase of turbulence in the planetary boundary layer. Moreover, the temperature inversion in the vertical mitigated the development of pressure gradient due to air convection during part of the event. Sensitivity experiments allowed to isolate the respective impacts of the local SST forcing and large scale condition on the coastal wind intensification. It was primarily driven by the local SST forcing whereas large scale variability associated with the South Pacific Anticyclone modulated its effects. Examination of other EN events using reanalysis data confirmed that intensifications of alongshore wind off Peru were associated with SST alongshore gradient anomalies, as during the 1997-1998 event.

Estimation of aerosol direct radiative forcing in Lecce during the 2013 ADRIMED campaign

NASA Astrophysics Data System (ADS)

Barragan, Ruben; Romano, Salvatore; Sicard, Michaël.; Burlizzi, Pasquale; Perrone, Maria-Rita; Comeron, Adolfo

2015-10-01

In the framework of the ChArMEx (Chemistry-Aerosol Mediterranean Experiment, http://charmex.lsce.ipsl.fr/) initiative, a field campaign took place in the western Mediterranean Basin between 10 June and 5 July 2013 within the ADRIMED (Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) project. The scientific objectives of ADRIMED are the characterization of the typical "Mediterranean aerosol" and its direct radiative forcing (column closure and regional scale). This work is focused on the multi-intrusion Saharan dust transport period of moderate intensity that occurred over the western and central Mediterranean Basin during the period 14 - 27 June. The dust plumes were detected by the EARLINET/ACTRIS (European Aerosol Research Lidar Network / Aerosols, Clouds, and Trace gases Research InfraStructure Network, http://www.actris.net/) lidar stations of Barcelona (16 and 17 June) and Lecce (22 June). First, two well-known and robust radiative transfer models, parametrized by lidar profiles for the aerosol vertical distribution, are validated both in the shortwave and longwave spectral range 1) at the surface with down- and up-ward flux measurements from radiometers and 2) at the top of the atmosphere with upward flux measurements from the CERES (Clouds and the Earth's Radiant Energy System) radiometers on board the AQUA and TERRA satellites. The differences between models and their limitations are discussed. The instantaneous and clear-sky direct radiative forcing of mineral dust is then estimated using lidar data for parametrizing the particle vertical distribution at Lecce. The difference between the obtained forcings is discussed in regard to the mineralogy and vertical structure of the dust plume.

Dynamic vehicle-track interaction in switches and crossings and the influence of rail pad stiffness - field measurements and validation of a simulation model

NASA Astrophysics Data System (ADS)

Pålsson, Björn A.; Nielsen, Jens C. O.

2015-06-01

A model for simulation of dynamic interaction between a railway vehicle and a turnout (switch and crossing, S&C) is validated versus field measurements. In particular, the implementation and accuracy of viscously damped track models with different complexities are assessed. The validation data come from full-scale field measurements of dynamic track stiffness and wheel-rail contact forces in a demonstrator turnout that was installed as part of the INNOTRACK project with funding from the European Union Sixth Framework Programme. Vertical track stiffness at nominal wheel loads, in the frequency range up to 20 Hz, was measured using a rolling stiffness measurement vehicle (RSMV). Vertical and lateral wheel-rail contact forces were measured by an instrumented wheel set mounted in a freight car featuring Y25 bogies. The measurements were performed for traffic in both the through and diverging routes, and in the facing and trailing moves. The full set of test runs was repeated with different types of rail pad to investigate the influence of rail pad stiffness on track stiffness and contact forces. It is concluded that impact loads on the crossing can be reduced by using more resilient rail pads. To allow for vehicle dynamics simulations at low computational cost, the track models are discretised space-variant mass-spring-damper models that are moving with each wheel set of the vehicle model. Acceptable agreement between simulated and measured vertical contact forces at the crossing can be obtained when the standard GENSYS track model is extended with one ballast/subgrade mass under each rail. This model can be tuned to capture the large phase delay in dynamic track stiffness at low frequencies, as measured by the RSMV, while remaining sufficiently resilient at higher frequencies.

49 CFR 213.333 - Automated vehicle-based inspection systems.

Code of Federal Regulations, 2014 CFR

2014-10-01

... the contact point of wheels carrying a vertical load of no less than 10 kips per wheel, unless... enable field forces to easily locate indicated exceptions. (f) Following a track inspection performed by... reference loads of 16 kips of lateral force and 33 kips of vertical force. (j) As further specified for the...

49 CFR 213.333 - Automated vehicle-based inspection systems.

Code of Federal Regulations, 2013 CFR

2013-10-01

... the contact point of wheels carrying a vertical load of no less than 10 kips per wheel, unless... enable field forces to easily locate indicated exceptions. (f) Following a track inspection performed by... reference loads of 16 kips of lateral force and 33 kips of vertical force. (j) As further specified for the...

Physical Determinants of Interval Sprint Times in Youth Soccer Players

PubMed Central

Amonette, William E.; Brown, Denham; Dupler, Terry L.; Xu, Junhai; Tufano, James J.; De Witt, John K.

2014-01-01

Relationships between sprinting speed, body mass, and vertical jump kinetics were assessed in 243 male soccer athletes ranging from 10–19 years. Participants ran a maximal 36.6 meter sprint; times at 9.1 (10 y) and 36.6 m (40 y) were determined using an electronic timing system. Body mass was measured by means of an electronic scale and body composition using a 3-site skinfold measurement completed by a skilled technician. Countermovement vertical jumps were performed on a force platform - from this test peak force was measured and peak power and vertical jump height were calculated. It was determined that age (r=−0.59; p<0.01), body mass (r=−0.52; p<0.01), lean mass (r=−0.61; p<0.01), vertical jump height (r=−0.67; p<0.01), peak power (r=−0.64; p<0.01), and peak force (r=−0.56; p<0.01) were correlated with time at 9.1 meters. Time-to-complete a 36.6 meter sprint was correlated with age (r=−0.71; p<0.01), body mass (r=−0.67; p<0.01), lean mass (r=−0.76; p<0.01), vertical jump height (r=−0.75; p<0.01), peak power (r=−0.78; p<0.01), and peak force (r=−0.69; p<0.01). These data indicate that soccer coaches desiring to improve speed in their athletes should devote substantive time to fitness programs that increase lean body mass and vertical force as well as power generating capabilities of their athletes. Additionally, vertical jump testing, with or without a force platform, may be a useful tool to screen soccer athletes for speed potential. PMID:25031679

Analysis of Impact of Tropical Cyclone Blance on Rainfall at Kupang Region Based on Atmospheric Condition and Satellite Imagery

NASA Astrophysics Data System (ADS)

Roguna, S.; Saragih, I. J. A.; Siregar, P. S.; Julius, A. M.

2018-04-01

The Tropical Depression previously identified on March 3, 2017, at Arafuru Sea has grown to Tropical Cyclone Blance on March 5, 2017. The existence of Tropical Cyclone Blance gave impacts like increasing rainfall for some regions in Indonesia until March 7, 2017, such as Kupang. The increase of rainfall cannot be separated from the atmospheric dynamics related to convection processes and the formation of clouds. Analysis of weather parameters is made such as vorticity to observe vertical motion over the study area, vertical velocity to see the speed of lift force in the atmosphere, wind to see patterns of air mass distribution and rainfall to see the increase of rainfall compared to several days before the cyclone. Analysis of satellite imagery data is used as supporting analysis to see clouds imagery and movement direction of the cyclone. The results of weather parameters analysis show strong vorticity and lift force of air mass support the growth of Cumulonimbus clouds, cyclonic patterns on wind streamline and significant increase of rainfall compared to previous days. The results of satellite imagery analysis show the convective clouds over Kupang and surrounding areas when this phenomena and cyclone pattern moved down from Arafuru Sea towards the western part of Australia.

The application of musculoskeletal modeling to investigate gender bias in non-contact ACL injury rate during single-leg landings.

PubMed

Ali, Nicholas; Andersen, Michael Skipper; Rasmussen, John; Robertson, D Gordon E; Rouhi, Gholamreza

2014-01-01

The central tenet of this study was to develop, validate and apply various individualised 3D musculoskeletal models of the human body for application to single-leg landings over increasing vertical heights and horizontal distances. While contributing to an understanding of whether gender differences explain the higher rate of non-contact anterior cruciate ligament (ACL) injuries among females, this study also correlated various musculoskeletal variables significantly impacted by gender, height and/or distance and their interactions with two ACL injury-risk predictor variables; peak vertical ground reaction force (VGRF) and peak proximal tibia anterior shear force (PTASF). Kinematic, kinetic and electromyography data of three male and three female subjects were measured. Results revealed no significant gender differences in the musculoskeletal variables tested except peak VGRF (p = 0.039) and hip axial compressive force (p = 0.032). The quadriceps and the gastrocnemius muscle forces had significant correlations with peak PTASF (r = 0.85, p < 0.05 and r = - 0.88, p < 0.05, respectively). Furthermore, hamstring muscle force was significantly correlated with peak VGRF (r = - 0.90, p < 0.05). The ankle flexion angle was significantly correlated with peak PTASF (r = - 0.82, p < 0.05). Our findings indicate that compared to males, females did not exhibit significantly different muscle forces, or ankle, knee and hip flexion angles during single-leg landings that would explain the gender bias in non-contact ACL injury rate. Our results also suggest that higher quadriceps muscle force increases the risk, while higher hamstring and gastrocnemius muscle forces as well as ankle flexion angle reduce the risk of non-contact ACL injury.

Strength and Power Qualities Are Highly Associated With Punching Impact in Elite Amateur Boxers.

PubMed

Loturco, Irineu; Nakamura, Fabio Y; Artioli, Guilherme G; Kobal, Ronaldo; Kitamura, Katia; Cal Abad, Cesar C; Cruz, Igor F; Romano, Felipe; Pereira, Lucas A; Franchini, Emerson

2016-01-01

This study investigated the relationship between punching impact and selected strength and power variables in 15 amateur boxers from the Brazilian National Team (9 men and 6 women). Punching impact was assessed in the following conditions: 3 jabs starting from the standardized position, 3 crosses starting from the standardized position, 3 jabs starting from a self-selected position, and 3 crosses starting from a self-selected position. For punching tests, a force platform (1.02 × 0.76 m) covered by a body shield was mounted on the wall at a height of 1 m, perpendicular to the floor. The selected strength and power variables were vertical jump height (in squat jump and countermovement jump), mean propulsive power in the jump squat, bench press (BP), and bench throw, maximum isometric force in squat and BP, and rate of force development in the squat and BP. Sex and position main effects were observed, with higher impact for males compared with females (p ≤ 0.05) and the self-selected distance resulting in higher impact in the jab technique compared with the fixed distance (p ≤ 0.05). Finally, the correlations between strength/power variables and punching impact indices ranged between 0.67 and 0.85. Because of the strong associations between punching impact and strength/power variables (e.g., lower limb muscle power), this study provides important information for coaches to specifically design better training strategies to improve punching impact.

Vertical vibration and shape oscillation of acoustically levitated water drops

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

Geng, D. L.; Xie, W. J.; Yan, N.

2014-09-08

We present the vertical harmonic vibration of levitated water drops within ultrasound field. The restoring force to maintain such a vibration mode is provided by the resultant force of acoustic radiation force and drop gravity. Experiments reveal that the vibration frequency increases with the aspect ratio for drops with the same volume, which agrees with the theoretical prediction for those cases of nearly equiaxed drops. During the vertical vibration, the floating drops undergo the second order shape oscillation. The shape oscillation frequency is determined to be twice the vibration frequency.

Experimental estimation of energy absorption during heel strike in human barefoot walking.

PubMed

Baines, Patricia M; Schwab, A L; van Soest, A J

2018-01-01

Metabolic energy expenditure during human gait is poorly understood. Mechanical energy loss during heel strike contributes to this energy expenditure. Previous work has estimated the energy absorption during heel strike as 0.8 J using an effective foot mass model. The aim of our study is to investigate the possibility of determining the energy absorption by more directly estimating the work done by the ground reaction force, the force-integral method. Concurrently another aim is to compare this method of direct determination of work to the method of an effective foot mass model. Participants of our experimental study were asked to walk barefoot at preferred speed. Ground reaction force and lower leg kinematics were collected at high sampling frequency (3000 Hz; 1295 Hz), with tight synchronization. The work done by the ground reaction force is 3.8 J, estimated by integrating this force over the foot-ankle deformation. The effective mass model is improved by dropping the assumption that foot-ankle deformation is maximal at the instant of the impact force peak. On theoretical grounds it is clear that in the presence of substantial damping that peak force and peak deformation do not occur simultaneously. The energy absorption results, due the vertical force only, corresponding to the force-integral method is similar to the results of the improved application of the effective mass model (2.7 J; 2.5 J). However the total work done by the ground reaction force calculated by the force-integral method is significantly higher than that of the vertical component alone. We conclude that direct estimation of the work done by the ground reaction force is possible and preferable over the use of the effective foot mass model. Assuming that energy absorbed is lost, the mechanical energy loss of heel strike is around 3.8 J for preferred walking speeds (≈ 1.3 m/s), which contributes to about 15-20% of the overall metabolic cost of transport.

Aerial dispersal of particles emitted inside plant canopies: Application to the spread of plant diseases

NASA Astrophysics Data System (ADS)

Pan, Ying

This work combines numerical, experimental, and theoretical methods to investigate the dispersion of particles inside and above plant canopies. The large-eddy simulation (LES) approach is used to reproduce turbulence statistics and three-dimensional particle dispersion within the canopy roughness sublayer. The Eulerian description of conservation laws of fluid momentum and particle concentration implies that the continuous concentration field is advected by the continuous flow field. Within the canopy, modifications are required for the filtered momentum and concentration equations, because spatial filtering of flow variables and concentration field is inapplicable to a control volume consisting of both fluid and solid elements. In this work, the canopy region is viewed as a space occupied by air only. The sink of airflow momentum induced by forces acting on the surfaces of canopy elements is parameterized as a non-conservative virtual body force that dissipates the kinetic energy of the air. This virtual body force must reflect the characteristic of the surface forces exerted by canopy elements within the control volume, and is parameterized as a "drag force" following standard practice in LES studies. Specifically, the "drag force" is calculated as a product of a drag coefficient, the projected leaf area density, and the square of velocity. Using a constant drag coefficient, this model allows first-order accuracy in reproducing the vertically integrated sink of momentum within the canopy layer for airflows of high Reynolds number. The corresponding LES results of first- and second-order turbulence statistics are in good agreement with experimental data obtained in the field interior, within and just above mature maize canopies. However, the distribution of momentum sink among weak and strong events has not been well reproduced, inferred from the significant underestition of streamwise and vertical velocity skewness as well as the fractions of vertical momentum flux transported by strong events. Using a velocity-dependent drag coefficient that accounts for the effect of plant reconfiguration, the "drag force" model leads to LES results of streamwise and vertical velocity skewness as well as the fractions of vertical momentum flux transported by strong events in better agreement with field experimental data. The link between plant reconfiguration and turbulence dynamics within the canopy roughness sublayer is further investigated. The "reconfiguration drag model" using velocity-dependent drag coefficient is revised to incorporate a theoretical model of the force balance on individual crosswind blades. In the LES, the dimension and degree of the reconfiguration of canopy elements affect the magnitude and position of peak streamwise velocity skewness within the canopy as well as the fractions of vertical momentum flux transported by strong events. The streamwise velocity skewness is shown to be related to the penetration of strong events into the canopy, which is associated with the passage of canopy-scale coherent eddies. With the profile of mean vertical momentum flux constrained by field experimental data, changing the model of drag coefficient induces negligible changes in the vertically integrated "drag force" within the canopy layer. Consequently, first- and second-order turbulence statistics remain approximately the same. However, enhancing the rate of decrease of drag coefficient with increasing velocity increases the streamwise and vertical velocity skewness, the fractions of vertical momentum flux transported by strong events, as well as the ratio between vertical momentum flux transported by relatively strong head-down "sweeps" and relatively weak head-up "ejections." These results confirmed the inadequacy of describing the effects of canopy-scale coherent structures using just first- and second-order turbulence statistics. The filtered concentration equation is applied to the dispersion of particles within the canopy roughness sublayer, assuming that a virtual continuous concentration field is advected by a virtual continuous velocity field. A canopy deposition model is used to model the sink of particle concentration associated with the impaction, sedimentation, retention, and re-entrainment of particles on the surfaces of canopy elements. LES results of mean particle concentration field and mean ground deposition rate were evaluated against data obtained during an artificial continuous point-source release experiment. Accounting for the effect of reconfiguration by using a velocity dependent drag coefficient leads to better agreement between LES results and field experimental data of the mean particle concentration field, suggesting the importance of reproducing the distribution of momentum sink among weak and strong events for reproducing the dispersion of particles. LES results obtained using a velocity-dependent drag coefficient are analyzed to estimate essential properties for the occurrence of plant disease epidemics. The most interesting finding is that an existing analytical function can be used to model the crosswind-integrated mean concentration field above the canopy normalized by the escape fraction for particles released from the field interior. (Abstract shortened by ProQuest.).

Peak vertical force in a stabilized canine cranial cruciate deficient stifle model: A one-year follow-up.

PubMed

Lussier, Bertrand; Gagnon, Alexandre; Moreau, Maxim; Pelletier, Jean-Pierre; Troncy, Éric

2018-04-01

This study aimed to describe the peak vertical force (PVF) over a 1-year period in a stabilized canine cranial cruciate deficient stifle model. Our hypothesis was that PVF would be restored to Baseline (intact) at the end of the follow-up. Fifteen (> 20 kg) mixed-breed dogs were included in this study. Cranial cruciate ligament was transected on Day (D) 0 followed by lateral suture stabilization at D28. Peak vertical force was acquired at D-1, D14, D26, D91, D210 and D357. When compared to Baseline, the PVF was significantly decreased at D14, D26, and D91. Values at D210 and D357 were not statistically different to Baseline. This study suggests a return to normal baseline peak vertical force in a canine cranial cruciate deficient stifle model when lateral suture stabilization has been performed 28 days after surgical transection.

The Impact of Internal Wave Seasonality on the Continental Shelf Energy Budget

NASA Astrophysics Data System (ADS)

Wihsgott, Juliane U.; Sharples, Jonathan; Hopkins, Joanne; Palmer, Matthew R.; Mattias Green, J. A.

2017-04-01

Heating-stirring models are widely used to simulate the timing and strength of stratification in continental shelf environments. Such models are based on bulk potential energy (PE) budgets: the loss of PE due to thermal stratification is balanced by wind and tidal mixing. The model often fails to accurately predict the observed vertical structure, as it only considers forces acting on the surface and bottom boundary of the water column. This highlights the need for additional internal energy sources to close this budget, and produce an accurate seasonal cycle of stratification. We present new results that test the impact of boundary layer and internal wave forcing on stratification and vertical density structure in continental shelves. A new series of continuous measurements of full water depth vertical structure, dynamics and meteorological data spanning 17 months (March'14-July'15) provide unprecedented coverage over a full seasonal cycle at a station 120 km north-east from the continental shelf break. We observe a highly variable but energetic internal wave field from the onset of stratification that suggests a continuous supply of internal PE. The heating-stirring model reproduces bulk characteristics of the seasonal cycle. While it accurately predicts the timing of the onset in spring and peak stratification in late summer there is a persistent 20 J m-3 positive offset between the model and observations throughout this period. By including a source of internal energy in the model we improve the prediction for the strength of stratification and the vertical distribution of heat. Yet a constant source of PE seems to result in a seasonal discrepancy resulting in too little mixing during strong stratification and too much mixing during transient periods. The discrepancy seen in the model is consistent with the seasonality observed in the internal wave field. We will establish the role that changing stratification (N2) exerts on the internal wave field and vice versa. Ultimately, we will demonstrate how the strength and vertical range of shear varies seasonally and what effect it has on supplying PE to midwater mixing.

Crashworthy Evaluation of a 1/5-Scale Model Composite Fuselage Concept

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Fasanella, Edwin L.

1999-01-01

A 1/5-scale model composite fuselage concept for light aircraft and rotorcraft has been developed to satisfy structural and flight loads requirements and to satisfy design goals for improved crashworthiness. The 1/5-scale model fuselage consists of a relatively rigid upper section which forms the passenger cabin, a stiff structural floor, and an energy absorbing subfloor which is designed to limit impact forces during a crash event. The focus of the present paper is to describe the crashworthy evaluation of the fuselage concept through impact testing and finite element simulation using the nonlinear, explicit transient dynamic code, MSC/DYTRAN. The energy absorption behavior of two different subfloor configurations was determined through quasi-static crushing tests. For the dynamic evaluation, each subfloor configuration was incorporated into a 1/5-scale model fuselage section, which was impacted at 31 ft/s vertical velocity onto a rigid surface. The experimental data demonstrate that the fuselage section with a foam-filled subfloor configuration satisfied the impact design requirement. In addition, the fuselage section maintained excellent energy absorption behavior for a 31 ft/s vertical drop test with a 15 deg-roll impact attitude. Good correlation was obtained between the experimental data and analytical results for both impact conditions.

Influence of Lorentz force, Cattaneo-Christov heat flux and viscous dissipation on the flow of micropolar fluid past a nonlinear convective stretching vertical surface

NASA Astrophysics Data System (ADS)

Gnaneswara Reddy, Machireddy

2017-12-01

The problem of micropolar fluid flow over a nonlinear stretching convective vertical surface in the presence of Lorentz force and viscous dissipation is investigated. Due to the nature of heat transfer in the flow past vertical surface, Cattaneo-Christov heat flux model effect is properly accommodated in the energy equation. The governing partial differential equations for the flow and heat transfer are converted into a set of ordinary differential equations by employing the acceptable similarity transformations. Runge-Kutta and Newton's methods are utilized to resolve the altered governing nonlinear equations. Obtained numerical results are compared with the available literature and found to be an excellent agreement. The impacts of dimensionless governing flow pertinent parameters on velocity, micropolar velocity and temperature profiles are presented graphically for two cases (linear and nonlinear) and analyzed in detail. Further, the variations of skin friction coefficient and local Nusselt number are reported with the aid of plots for the sundry flow parameters. The temperature and the related boundary enhances enhances with the boosting values of M. It is found that fluid temperature declines for larger thermal relaxation parameter. Also, it is revealed that the Nusselt number declines for the hike values of Bi.

Are Atmospheric Updrafts a Key to Unlocking Climate Forcing and Sensitivity?

DOE PAGES

Donner, Leo J.; O'Brien, Travis A.; Rieger, Daniel; ...

2016-06-08

Both climate forcing and climate sensitivity persist as stubborn uncertainties limiting the extent to which climate models can provide actionable scientific scenarios for climate change. A key, explicit control on cloud-aerosol interactions, the largest uncertainty in climate forcing, is the vertical velocity of cloud-scale updrafts. Model-based studies of climate sensitivity indicate that convective entrainment, which is closely related to updraft speeds, is an important control on climate sensitivity. Updraft vertical velocities also drive many physical processes essential to numerical weather prediction. Vertical velocities and their role in atmospheric physical processes have been given very limited attention in models for climatemore » and numerical weather prediction. The relevant physical scales range down to tens of meters and are thus frequently sub-grid and require parameterization. Many state-of-science convection parameterizations provide mass fluxes without specifying vertical velocities, and parameterizations which do provide vertical velocities have been subject to limited evaluation against what have until recently been scant observations. Atmospheric observations imply that the distribution of vertical velocities depends on the areas over which the vertical velocities are averaged. Distributions of vertical velocities in climate models may capture this behavior, but it has not been accounted for when parameterizing cloud and precipitation processes in current models. New observations of convective vertical velocities offer a potentially promising path toward developing process-level cloud models and parameterizations for climate and numerical weather prediction. Taking account of scale-dependence of resolved vertical velocities offers a path to matching cloud-scale physical processes and their driving dynamics more realistically, with a prospect of reduced uncertainty in both climate forcing and sensitivity.« less

Relative net vertical impulse determines jumping performance.

PubMed

Kirby, Tyler J; McBride, Jeffrey M; Haines, Tracie L; Dayne, Andrea M

2011-08-01

The purpose of this investigation was to determine the relationship between relative net vertical impulse and jump height in a countermovement jump and static jump performed to varying squat depths. Ten college-aged males with 2 years of jumping experience participated in this investigation (age: 23.3 ± 1.5 years; height: 176.7 ± 4.5 cm; body mass: 84.4 ± 10.1 kg). Subjects performed a series of static jumps and countermovement jumps in a randomized fashion to a depth of 0.15, 0.30, 0.45, 0.60, and 0.75 m and a self-selected depth (static jump depth = 0.38 ± 0.08 m, countermovement jump depth = 0.49 ± 0.06 m). During the concentric phase of each jump, peak force, peak velocity, peak power, jump height, and net vertical impulse were recorded and analyzed. Net vertical impulse was divided by body mass to produce relative net vertical impulse. Increasing squat depth corresponded to a decrease in peak force and an increase in jump height and relative net vertical impulse for both static jump and countermovement jump. Across all depths, relative net vertical impulse was statistically significantly correlated to jump height in the static jump (r = .9337, p < .0001, power = 1.000) and countermovement jump (r = .925, p < .0001, power = 1.000). Across all depths, peak force was negatively correlated to jump height in the static jump (r = -0.3947, p = .0018, power = 0.8831) and countermovement jump (r = -0.4080, p = .0012, power = 0.9050). These results indicate that relative net vertical impulse can be used to assess vertical jump performance, regardless of initial squat depth, and that peak force may not be the best measure to assess vertical jump performance.

Automatic feed system for ultrasonic machining

DOEpatents

Calkins, Noel C.

1994-01-01

Method and apparatus for ultrasonic machining in which feeding of a tool assembly holding a machining tool toward a workpiece is accomplished automatically. In ultrasonic machining, a tool located just above a workpiece and vibrating in a vertical direction imparts vertical movement to particles of abrasive material which then remove material from the workpiece. The tool does not contact the workpiece. Apparatus for moving the tool assembly vertically is provided such that it operates with a relatively small amount of friction. Adjustable counterbalance means is provided which allows the tool to be immobilized in its vertical travel. A downward force, termed overbalance force, is applied to the tool assembly. The overbalance force causes the tool to move toward the workpiece as material is removed from the workpiece.

A Comparison of Golf Shoe Designs Highlights Greater Ground Reaction Forces with Shorter Irons

PubMed Central

Worsfold, Paul; Smith, Neal A.; Dyson, Rosemary J.

2007-01-01

In an effort to reduce golf turf damage the traditional metal spike golf shoe has been redesigned, but shoe-ground biomechanical evaluations have utilised artificial grass surfaces. Twenty-four golfers wore three different golf shoe traction designs (traditional metal spikes, alternative spikes, and a flat-soled shoe with no additional traction) when performing shots with a driver, 3 iron and 7 iron. Ground action forces were measured beneath the feet by two natural grass covered force platforms. The maximum vertical force recorded at the back foot with the 3 iron and 7 iron was 0.82 BW (body weight) and at the front foot 1.1 BW approximately in both the metal spike and alternative spike golf shoe designs. When using the driver these maximal vertical values were 0.49 BW at the back foot and 0.84 BW at the front foot. Furthermore, as performance of the backswing and then downswing necessitates a change in movement direction the range of force generated during the complete swing was calculated. In the metal spike shoe the vertical force generated at the back foot with both irons was 0.67 BW and at the front foot 0.96 BW with the 3 iron and 0.92 BW with the 7 iron. The back foot vertical force generated with the driver was 0.33 BW and at the front foot 0.83 BW wearing the metal spike shoe. Results indicated the greater force generation with the irons. When using the driver the more horizontal swing plane associated with the longer club reduced vertical forces at the back and front foot. However, the mediolateral force generated across each foot in the metal and alternative spike shoes when using the driver was greater than when the irons were used. The coefficient of friction was 0. 62 at the back and front foot whichever shoe was worn or club used. Key pointsDuring the golf swing ground reaction forces at the golf shoe to natural grass turf interface were greater with irons than with the longer driver.In the golf swing maximal vertical forces were greater at the front (left) foot in the than at the back foot for a right handed golfer.Similar maximum vertical ground reaction forces were recorded with each club when a 8 mm metal spike golf shoe or an alternative spike golf shoe were worn.Force generation and coefficients of friction were similar for the alternative spike design and traditional metal seven spike golf shoe on natural grass turf.Data collection possible due to application of technical developments to golf from work on other natural turf based sports. PMID:24149482

Analysis of the Vertical Ground Reaction Forces and Temporal Factors in the Landing Phase of a Countermovement Jump

PubMed Central

Ortega, Daniel Rojano; Rodríguez Bíes, Elisabeth C.; Berral de la Rosa, Francisco J.

2010-01-01

In most common bilateral landings of vertical jumps, there are two peak forces (F1 and F2) in the force-time curve. The combination of these peak forces and the high frequency of jumps during sports produce a large amount of stress in the joints of the lower limbs which can be determinant of injury. The aim of this study was to find possible relationships between the jump height and F1 and F2, between F1 and F2 themselves, and between F1, F2, the time they appear (T1 and T2, respectively) and the length of the impact absorption phase (T). Thirty semi-professional football players made five countermovement jumps and the highest jump of each player was analyzed. They were instructed to perform the jumps with maximum effort and to land first with the balls of their feet and then with their heels. All the data were collected using a Kistler Quattro Jump force plate with a sample rate of 500 Hz. Quattro Jump Software, v.1.0.9.0., was used. There was neither significant correlation between T1 and F1 nor between T1 and F2. There was a significant positive correlation between flight height (FH) and F1 (r = 0.584, p = 0.01) but no significant correlation between FH and F2. A significant positive correlation between F1 and T2 (r = 0.418, p < 0.05) and a significant negative correlation between F2 and T2 (r = -0.406, p < 0.05) were also found. There is a significant negative correlation between T2 and T (r = -0. 443, p < 0.05). T1 has a little effect in the impact absorption process. F1 increases with increasing T2 but F2 decreases with increasing T2. Besides, increasing T2, with the objective of decreasing F2, makes the whole impact absorption shorter and the jump landing faster. Key points In the landing phase of a jump there are always sev-eral peak forces. The combination of these peaks forces and the high frequency of jumps during sports produces a large amount of stress in the joints of the lower limbs which can be determinant of injury. In the most common two-footed landings usually appear two peak forces (F1 and F2) in the force-time curve and the second one is usually related to injury’s risk. In this article it is shown that increasing the time F2 appears decrease F2. Increasing landing times could be counterproductive with respect to the goals of the sport. In this article it is shown that increasing the time F2 appears makes, however, the whole impact absorption shorter in du-ration. PMID:24149697

Control and prediction components of movement planning in stuttering vs. nonstuttering adults

PubMed Central

Daliri, Ayoub; Prokopenko, Roman A.; Flanagan, J. Randall; Max, Ludo

2014-01-01

Purpose Stuttering individuals show speech and nonspeech sensorimotor deficiencies. To perform accurate movements, the sensorimotor system needs to generate appropriate control signals and correctly predict their sensory consequences. Using a reaching task, we examined the integrity of these control and prediction components, separately, for movements unrelated to the speech motor system. Method Nine stuttering and nine nonstuttering adults made fast reaching movements to visual targets while sliding an object under the index finger. To quantify control, we determined initial direction error and end-point error. To quantify prediction, we calculated the correlation between vertical and horizontal forces applied to the object—an index of how well vertical force (preventing slip) anticipated direction-dependent variations in horizontal force (moving the object). Results Directional and end-point error were significantly larger for the stuttering group. Both groups performed similarly in scaling vertical force with horizontal force. Conclusions The stuttering group's reduced reaching accuracy suggests limitations in generating control signals for voluntary movements, even for non-orofacial effectors. Typical scaling of vertical force with horizontal force suggests an intact ability to predict the consequences of planned control signals. Stuttering may be associated with generalized deficiencies in planning control signals rather than predicting the consequences of those signals. PMID:25203459

Case Studies of the Vertical Structure of the Direct Shortwave Aerosol Radiative Forcing During TARFOX

NASA Technical Reports Server (NTRS)

Redemann, J.; Turco, R. P.; Liou, K. N.; Hobbs, P. V.; Hartley, W. S.; Bergstrom, R. W.; Browell, E. V.; Russell, P. B.

2000-01-01

The vertical structure of aerosol-induced radiative flux changes in the Earth's troposphere affects local heating rates and thereby convective processes, the formation and lifetime of clouds, and hence the distribution of chemical constituents. We present observationally based estimates of the vertical structure of direct shortwave aerosol radiative forcing for two case studies from the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) which took place on the U.S. east coast in July 1996. The aerosol radiative forcings are computed using the Fu-Liou broadband radiative transfer model. The aerosol optical properties used in the radiative transfer simulations are calculated from independent vertically resolved estimates of the complex aerosol indices of refraction in two to three distinct vertical layers, using profiles of in situ particle size distributions measured aboard the University of Washington research aircraft. Aerosol single-scattering albedos at 450 nm thus determined range from 0.9 to 0.985, while the asymmetry factor varies from 0.6 to 0.8. The instantaneous shortwave aerosol radiative forcings derived from the optical properties of the aerosols are of the order of -36 Wm(exp -2) at the top of the atmosphere and about -56 Wm(exp -2) at the surface for both case studies.

Oceanic response to tropical cyclone `Phailin' in the Bay of Bengal

NASA Astrophysics Data System (ADS)

Pant, V.; Prakash, K. R.

2016-02-01

Vertical mixing largely explains surface cooling induced by Tropical Cyclones (TCs). However, TC-induced upwelling of deeper waters plays an important role as it partly balances the warming of subsurface waters induced by vertical mixing. Below 100 m, vertical advection results in cooling that persists for a few days after the storm. The present study investigates the integrated ocean response to tropical cyclone `Phaillin' (10-14 October 2013) in the Bay of Bengal (BoB) through both coupled and stand-alone ocean-atmosphere models. Two numerical experiments with different coupling configurations between Regional Ocean Modelling System (ROMS) and Weather Research and Forecasting (WRF) were performed to investigate the impact of Phailin cyclone on the surface and sub-surface oceanic parameters. In the first experiment, ocean circulation model ROMS observe surface wind forcing from a mesoscale atmospheric model (WRF with nested damin setup), while rest forcing parameters are supplied to ROMS from NCEP data. In the second experiment, all surface forcing data to ROMS directly comes from WRF. The modeling components and data fields exchanged between atmospheric and oceanic models are described. The coupled modeling system is used to identify model sensitivity by exchanging prognostic variable fields between the two model components during simulation of Phallin cyclone (10-14 October 2013) in the BoB.In general, the simulated Phailin cyclone track and intensities agree well with observations in WRF simulations. Further, the inter-comparison between stand-alone and coupled model simulations validated against observations highlights better performance of coupled modeling system in simulating the oceanic conditions during the Phailin cyclone event.

29 CFR 1926.1436 - Derricks.

Code of Federal Regulations, 2013 CFR

2013-07-01

... and guying must be designed to withstand maximum horizontal and vertical forces encountered when... be designed to withstand maximum horizontal and vertical forces encountered when operating within...”). (D) Applicable terms in section 7-0.2 (“Definitions”). (ii) Load tests for new hoists. The employer...

29 CFR 1926.1436 - Derricks.

Code of Federal Regulations, 2012 CFR

2012-07-01

... and guying must be designed to withstand maximum horizontal and vertical forces encountered when... be designed to withstand maximum horizontal and vertical forces encountered when operating within...”). (D) Applicable terms in section 7-0.2 (“Definitions”). (ii) Load tests for new hoists. The employer...

29 CFR 1926.1436 - Derricks.

Code of Federal Regulations, 2011 CFR

2011-07-01

... and guying must be designed to withstand maximum horizontal and vertical forces encountered when... be designed to withstand maximum horizontal and vertical forces encountered when operating within...”). (D) Applicable terms in section 7-0.2 (“Definitions”). (ii) Load tests for new hoists. The employer...

29 CFR 1926.1436 - Derricks.

Code of Federal Regulations, 2014 CFR

2014-07-01

... and guying must be designed to withstand maximum horizontal and vertical forces encountered when... be designed to withstand maximum horizontal and vertical forces encountered when operating within...”). (D) Applicable terms in section 7-0.2 (“Definitions”). (ii) Load tests for new hoists. The employer...

Single-limb force data for two lemur species while vertically clinging.

PubMed

Johnson, Laura E; Hanna, Jandy; Schmitt, Daniel

2015-11-01

Vertical clinging and climbing have been integral to hypotheses about primate origins, yet little is known about how an animal with nails instead of claws resists gravity while on large, vertical, and cylindrical substrates. Here we test models of how force is applied to maintain posture, predicting (1) the shear component force (Fs ) at the hands will be higher than the feet; (2) the normal component force (Fn ) at the feet will be relatively high compared to the hands; (3) the component force resisting gravity (Fg ) at the feet will be relatively high compared to the hands; (4) species with a high frequency of vertical clinging postures will have low Fg at the hands due to relatively short forelimbs. Using a novel instrumented support, single-limb force data were collected during clinging postures for the hands and feet and compared across limbs and species for Propithecus verreauxi (N = 2), a habitual vertical clinger and leaper, and Varecia variegata (N = 3), a habitual above-branch arboreal quadruped. For both species, hand Fs were significantly higher than at the feet and Fn and Fg at the feet were significantly higher than at the hands. Between species, P. verreauxi has relatively low Fg at the hands and Fn at the feet than V. vareigata. These results support previous models and show that hindlimb loading dominance, characteristic of primate locomotion, is found during clinging behaviors and may allow the forelimbs to be used for foraging while clinging. These findings provide insight into selective pressures on force distribution in primates and primate locomotor evolution. © 2015 Wiley Periodicals, Inc.

Clap-and-fling mechanism in a hovering insect-like two-winged flapping-wing micro air vehicle.

PubMed

Phan, Hoang Vu; Au, Thi Kim Loan; Park, Hoon Cheol

2016-12-01

This study used numerical and experimental approaches to investigate the role played by the clap-and-fling mechanism in enhancing force generation in hovering insect-like two-winged flapping-wing micro air vehicle (FW-MAV). The flapping mechanism was designed to symmetrically flap wings at a high flapping amplitude of approximately 192°. The clap-and-fling mechanisms were thereby implemented at both dorsal and ventral stroke reversals. A computational fluid dynamic (CFD) model was constructed based on three-dimensional wing kinematics to estimate the force generation, which was validated by the measured forces using a 6-axis load cell. The computed forces proved that the CFD model provided reasonable estimation with differences less than 8%, when compared with the measured forces. The measurement indicated that the clap and flings at both the stroke reversals augmented the average vertical force by 16.2% when compared with the force without the clap-and-fling effect. In the CFD simulation, the clap and flings enhanced the vertical force by 11.5% and horizontal drag force by 18.4%. The observations indicated that both the fling and the clap contributed to the augmented vertical force by 62.6% and 37.4%, respectively, and to the augmented horizontal drag force by 71.7% and 28.3%, respectively. The flow structures suggested that a strong downwash was expelled from the opening gap between the trailing edges during the fling as well as the clap at each stroke reversal. In addition to the fling phases, the influx of air into the low-pressure region between the wings from the leading edges also significantly contributed to augmentation of the vertical force. The study conducted for high Reynolds numbers also confirmed that the effect of the clap and fling was insignificant when the minimum distance between the two wings exceeded 1.2c (c = wing chord). Thus, the clap and flings were successfully implemented in the FW-MAV, and there was a significant improvement in the vertical force.

Clap-and-fling mechanism in a hovering insect-like two-winged flapping-wing micro air vehicle

PubMed Central

Phan, Hoang Vu; Au, Thi Kim Loan

2016-01-01

This study used numerical and experimental approaches to investigate the role played by the clap-and-fling mechanism in enhancing force generation in hovering insect-like two-winged flapping-wing micro air vehicle (FW-MAV). The flapping mechanism was designed to symmetrically flap wings at a high flapping amplitude of approximately 192°. The clap-and-fling mechanisms were thereby implemented at both dorsal and ventral stroke reversals. A computational fluid dynamic (CFD) model was constructed based on three-dimensional wing kinematics to estimate the force generation, which was validated by the measured forces using a 6-axis load cell. The computed forces proved that the CFD model provided reasonable estimation with differences less than 8%, when compared with the measured forces. The measurement indicated that the clap and flings at both the stroke reversals augmented the average vertical force by 16.2% when compared with the force without the clap-and-fling effect. In the CFD simulation, the clap and flings enhanced the vertical force by 11.5% and horizontal drag force by 18.4%. The observations indicated that both the fling and the clap contributed to the augmented vertical force by 62.6% and 37.4%, respectively, and to the augmented horizontal drag force by 71.7% and 28.3%, respectively. The flow structures suggested that a strong downwash was expelled from the opening gap between the trailing edges during the fling as well as the clap at each stroke reversal. In addition to the fling phases, the influx of air into the low-pressure region between the wings from the leading edges also significantly contributed to augmentation of the vertical force. The study conducted for high Reynolds numbers also confirmed that the effect of the clap and fling was insignificant when the minimum distance between the two wings exceeded 1.2c (c = wing chord). Thus, the clap and flings were successfully implemented in the FW-MAV, and there was a significant improvement in the vertical force. PMID:28083112

Periodic Comet Showers, Mass Extinctions, and the Galaxy

NASA Technical Reports Server (NTRS)

Rampino, M. R.; Stothers, R. B.

2000-01-01

Geologic data on mass extinctions of life and evidence of large impacts on the Earth are thus far consistent with a quasi-periodic modulation of the flux of Oort cloud comets. Impacts of large comets and asteroids are capable of causing mass extinction of species, and the records of large impact craters and mass show a correlation. Impacts and extinctions display periods in the range of approximately 31 +/- 5 m.y., depending on dating methods, published time scales, length of record, and number of events analyzed. Statistical studies show that observed differences in the formal periodicity of extinctions and craters are to be expected, taking into consideration problems in dating and the likelihood that both records would be mixtures of periodic and random events. These results could be explained by quasi-periodic showers of Oort Cloud comets with a similar cycle. The best candidate for a pacemaker for comet showers is the Sun's vertical oscillation through the plane of the Galaxy, with a half-period over the last 250 million years in the same range. We originally suggested that the probability of encounters with molecular clouds that could perturb the Oort comet cloud and cause comet showers is modulated by the Sun's vertical motion through the galactic disk. Tidal forces produced by the overall gravitational field of the Galaxy can also cause perturbations of cometary orbits. Since these forces vary with the changing position of the solar system in the Galaxy, they provide a mechanism for the periodic variation in the flux of Oort cloud comets into the inner solar system. The cycle time and degree of modulation depend critically on the mass distribution in the galactic disk. Additional information is contained in the original extended abstract.

Hypohydration Reduces Vertical Ground Reaction Impulse But Not Jump Height

DTIC Science & Technology

2010-01-01

countermovement jump from a 660 9 660 9 60 mm dual force plate plat- form (Leonardo v3.07, Orthometrix, Inc.) connected to a PC for the purpose of collecting... force data and calculating jump height (described below). Subjects stood still on the platform with one foot on each force plate for approxi- mately 10...study examined vertical jump performance using a force platform and weighted vest to determine why hypohydration (~4% body mass) does not improve jump

Effect of vertical ground motions on shear demand and capacity in bridge columns.

DOT National Transportation Integrated Search

2012-03-01

The objective of this project was to examine the effects of axial force variation in bridge columns due to strong vertical : ground motions and the influence of these axial force fluctuations on shear strength degradation. : Two quarter scale specime...

[The effect of verticalization of the resulting force (R) of weight bearing in the hip joint on morphologic characteristics of the medullary canal in the femoral shaft in patients with coxarthrosis].

PubMed

Jovanović, S

1992-01-01

An influence of verticalization of the resulting force of weight-bearing on the hip joint "R" on the morphological characteristics of the medullar canal on the proximal edge of the shaft of femur was researched. Progressive degenerative changes of the hip joint with a consequent sideways limping or changes of the collodiaphysial angle (ccd angle) were the cause of the verticalization of the resulting force "R". The analysis of patients treated and operated on The Orthopaedic Department of the General Hospital Osijek and The Orthopaedic Clinic of The Medical Faculty of The University of Zagreb. The research, undoubtedly, proved that the patients with coxarthrosis and side-ways in the hip or with changed collodiaphysial angle experienced verticalization of the resulting force of weigh-bearing of the hip joint and the proximal edge of femur which caused morphological changes of the medular canal of the shaft of femur.

A comparison between the dynamics of horizontal and vertical axis offshore floating wind turbines.

PubMed

Borg, M; Collu, M

2015-02-28

The need to further exploit offshore wind resources in deeper waters has led to a re-emerging interest in vertical axis wind turbines (VAWTs) for floating foundation applications. However, there has been little effort to systematically compare VAWTs to the more conventional horizontal axis wind turbine (HAWT). This article initiates this comparison based on prime principles, focusing on the turbine aerodynamic forces and their impact on the floating wind turbine static and dynamic responses. VAWTs generate substantially different aerodynamic forces on the support structure, in particular, a potentially lower inclining moment and a substantially higher torque than HAWTs. Considering the static stability requirements, the advantages of a lower inclining moment, a lower wind turbine mass and a lower centre of gravity are illustrated, all of which are exploitable to have a less costly support structure. Floating VAWTs experience increased motion in the frequency range surrounding the turbine [number of blades]×[rotational speed] frequency. For very large VAWTs with slower rotational speeds, this frequency range may significantly overlap with the range of wave excitation forces. Quantitative considerations are undertaken comparing the reference NREL 5 MW HAWT with the NOVA 5 MW VAWT. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Ground reaction forces and kinematics in distance running in older-aged men.

PubMed

Bus, Sicco A

2003-07-01

The biomechanics of distance running has not been studied before in older-aged runners but may be different than in younger-aged runners because of musculoskeletal degeneration at older age. This study aimed at determining whether the stance phase kinematics and ground reaction forces in running are different between younger- and older-aged men. Lower-extremity kinematics using three-dimensional motion analysis and ground reaction forces (GRF) using a force plate were assessed in 16 older-aged (55-65 yr) and 13 younger-aged (20-35 yr) well-trained male distance runners running at a self-selected (SRS) and a controlled (CRS) speed of 3.3 m.s-1. The older subjects ran at significantly lower self-selected speeds than the younger subjects (mean 3.34 vs 3.77 m.s-1). In both speed conditions, the older runners exhibited significantly more knee flexion at heel strike and significantly less knee flexion and extension range of motion. No age group differences were present in subtalar joint motion. Impact peak force (1.91 vs 1.70 BW) and maximal initial loading rate (107.5 vs 85.5 BW.s-1) were significantly higher in the older runners at the CRS. Maximal peak vertical and anteroposterior forces and impulses were significantly lower in the older runners at the SRS. The biomechanics of running is different between older- and younger-aged runners on several relevant parameters. The larger impact peak force and initial loading rate indicate a loss of shock-absorbing capacity in the older runners. This may increase their susceptibility to lower-extremity overuse injuries. Moreover, it emphasizes the focus on optimizing cushioning properties in the design and prescription of running shoes and suggests that older-aged runners should be cautious with running under conditions of high impact.

Specialized neuromuscular training to improve neuromuscular function and biomechanics in a patient with quiescent juvenile rheumatoid arthritis.

PubMed

Myer, Gregory D; Brunner, Hermine I; Melson, Paula G; Paterno, Mark V; Ford, Kevin R; Hewett, Timothy E

2005-08-01

The purpose of this case report is to describe a novel multidisciplinary approach for evaluating and preparing a patient with quiescent juvenile rheumatoid arthritis (JRA) for safe sports participation. The patient was a 10-year-old girl with a history of bilateral knee arthritis who desired to participate in soccer and basketball. Range of motion and manual muscle testing of the lower extremity were within normal limits. Neuromuscular testing included kinematic and kinetic testing, isokinetic assessment, and postural stability testing. The patient's gait was near normal; however, she had narrowed step width and increased knee flexion at heel-strike. Landing analysis during a box drop vertical jump task showed increased and imbalanced (right versus left lower extremity) peak impact forces. The testing was followed by specialized neuromuscular training (SNT). Following SNT, heel-strike and step width were within normal limits, peak impact forces on the box drop test decreased by 31%, imbalance decreased by 46%, and vertical jump increased 15%. The isokinetic strength ratio between knee flexors and extensors and the overall balance measures were within normal limits and equal bilaterally. Patients with quiescent JRA may have abnormal biomechanics, which could place them at increased risk for injury or future articular cartilage damage. Specialized neuromuscular training may have helped to decrease the patient's risk for future injury or disease progression.

CLouds, and Aerosols Radiative Impacts and Forcing: Year 2016 (CLARIFY-2016)

NASA Astrophysics Data System (ADS)

Haywood, J. M.; Bellouin, N.; Carslaw, K. S.; Coe, H.; Field, P.; Highwood, E. J.; Redemann, J.; Stier, P.; Wood, R.; Zuidema, P.

2013-12-01

Strongly absorbing biomass burning aerosols (BBAs) exist above highly reflectant stratocumulus clouds in the SE Atlantic with implications on the direct (e.g. Haywood et al., 2003), semi-direct (e.g. Johnson et al., 2006), and indirect effect of aerosols, implications on the remote sensing of cloud optical properties, development of clouds and feedback processes. Here, we present an analysis of modelled estimates of the direct effect using twelve models from the AEROCOM project (Myhre et al., 2013) to show that estimates of the direct effect in SE Atlantic range from strongly negative to strongly positive. Furthermore, we evaluate the performance of the HadGEM2 model and show it cannot replicate the extreme values of positive forcing inferred from high spectral resolution satellite retrievals. By examining patterns of deposition, we infer that the indirect effect from biomass burning aerosols is very limited in the model, but without detailed measurements we are unsure of the validity of this inference. We conclude that the SE Atlantic is therefore of key importance in determining the radiative forcing of biomass burning aerosols and provides a very stringent test for global climate models as they need to accurately represent the geographic distribution of the aerosol optical depth, the wavelength dependent aerosol single scattering albedo, the vertical profile of the aerosol, the geographic distribution of the cloud, the cloud fraction, the cloud liquid water content, the cloud droplet effective radii, and the vertical profile of the cloud. These results are used as scientific rationale to justify a new measurement campaign: CLouds and Aerosol Radiative Impacts and Forcing: Year-2016 (CLARIFY-2016). Haywood, J.M., Osborne, S.R. Francis, P.N., Keil, A., Formenti, P., Andreae, M.O., and Kaye, P.H., The mean physical and optical properties of regional haze dominated by biomass burning aerosol measured from the C-130 aircraft during SAFARI 2000, J. Geophys. Res., 108(D13), 8473, doi:10.1029/2002JD002226, 2003. Johnson, B.T., K.P. Shine, and P.M. Forster, The semi-direct aerosol effect: Impact of absorbing aerosols on marine stratocumulus, QJRMS, DOI: 10.1256/qj.03.61, 2006. Myhre, G. et al. Radiative forcing of the direct aerosol effect from AeroCom Phase II simulations, Atmos. Chem. Phys., 13, 1853-1877, doi:10.5194/acp-13-1853-2013, 2013

Effect of Ankle Joint Contact Angle and Ground Contact Time on Depth Jump Performance.

PubMed

Phillips, Joshua H; Flanagan, Sean P

2015-11-01

Athletes often need to both jump high and get off the ground quickly, but getting off the ground quickly can decrease the vertical ground reaction force (VGRF) impulse, impeding jump height. Energy stored in the muscle-tendon complex during the stretch-shortening cycle (SSC) may mitigate the effects of short ground contact times (GCTs). To take advantage of the SSC, several coaches recommend "attacking" the ground with the foot in a dorsiflexed (DF) position at contact. However, the efficacy of this technique has not been tested. This investigation tested the hypotheses that shorter GCTs would lead to smaller vertical depth jump heights (VDJH), and that this difference could be mitigated by instructing the athletes to land in a DF as opposed to a plantar flexed (PF) foot position. Eighteen healthy junior college athletes performed depth jumps from a 45-cm box onto force platforms under instruction to achieve one of the 2 objectives (maximum jump height [hmax] or minimal GCT [tmin]), with one of the 2 foot conditions (DF or PF). These variations created 4 distinct jump conditions: DF-hmax, DF-tmin, PF-hmax, and PF-tmin. For all variables examined, there were no significant interactions. For all 4 conditions, the ankle was PF during landing, but the DF condition was 28.87% less PF than the PF condition. The tmin conditions had a 23.48% shorter GCT than hmax. There were no significant main effects for jump height. The peak impact force for tmin was 22.14% greater than hmax and 19.11% greater for DF compared with PF conditions. A shorter GCT did not necessitate a smaller jump height, and a less PF foot did not lead to improvements in jump height or contact time during a depth jump from a 45-cm box. The same jump height was attained in less PF and shorter GCT conditions by larger impact forces. To decrease contact time while maintaining jump height, athletes should be instructed to "get off the ground as fast as possible." This cue seems to be more important than foot position. However, it should be acknowledged that this technique leads to larger impact forces, which should be considered when prescribing the number of foot contacts in a plyometrics program. The ability of athletes to truly land in a DF position during depth jumps is questioned and needs further investigation.

Influence of different abutment diameter of implants on the peri-implant stress in the crestal bone: A three-dimensional finite element analysis--In vitro study.

PubMed

Aradya, Anupama; Kumar, U Krishna; Chowdhary, Ramesh

2016-01-01

The study was designed to evaluate and compare stress distribution in transcortical section of bone with normal abutment and platform switched abutment under vertical and oblique forces in posterior mandible region. A three-dimensional finite element model was designed using ANSYS 13.0 software. The type of bone selection for the model was made of type II mandibular bone, having cortical bone thickness ranging from 0.595 mm to 1.515 mm with the crestal region measuring 1.5 mm surrounding dense trabecular bone. The implant will be modulated at 5 mm restorative platform and tapering down to 4.5 mm wide at the threads, 13 mm long with an abutment 3 mm in height. The models will be designed for two situations: (1) An implant with a 5 mm diameter abutment representing a standard platform in the posterior mandible region. (2) An implant with a 4.5 mm diameter abutment representing platform switching in the posterior mandible region. Force application was performed in both oblique and vertical conditions using 100 N as a representative masticatory force. For oblique loading, a force of 100 N was applied at 15° from the vertical axis. von Mises stress analysis was evaluated. The results of the study showed cortical stress in the conventional and platform switching model under oblique forces were 59.329 MPa and 39.952 MPa, respectively. Cortical stress in the conventional and platform switching model under vertical forces was 13.914 MPa and 12.793 MPa, respectively. Results from this study showed the platform switched abutment led to relative decrease in von Mises stress in transcortical section of bone compared to normal abutment under vertical and oblique forces in posterior mandible region.

PMHS impact response in 3 m/s and 8 m/s nearside impacts with abdomen offset.

PubMed

Miller, Carl S; Madura, Nathaniel H; Schneider, Lawrence W; Klinich, Kathleen D; Reed, Matthew P; Rupp, Jonathan D

2013-11-01

Lateral impact tests were performed using seven male post-mortem human subjects (PMHS) to characterize the force-deflection response of contacted body regions, including the lower abdomen. All tests were performed using a dual-sled, side-impact test facility. A segmented impactor was mounted on a sled that was pneumatically accelerated into a second, initially stationary sled on which a subject was seated facing perpendicular to the direction of impact. Positions of impactor segments were adjusted for each subject so that forces applied to different anatomic regions, including thorax, abdomen, greater trochanter, iliac wing, and thigh, could be independently measured on each PMHS. The impactor contact surfaces were located in the same vertical plane, except that the abdomen plate was offset 5.1 cm towards the subject. The masses of the sleds and the force- deflection characteristics of the energy-absorbing interface material between the sleds were set to provide the impactor sled with a velocity profile that matched the average driver door velocity history produced in a series of side NCAP tests. Impactor padding was also selected so that average ATD pelvis and thorax responses from the same series of side NCAP tests were reproduced when the ATD used in these tests was impacted using the average door-velocity history. Each subject was first impacted on one side of the body using an initial impactor speed of 3 m/s. If a post-test CT scan and strain-gage data revealed two or fewer non-displaced rib fractures, then the PMHS was impacted on the contralateral side of the body at a speed of 8 m/s or 10 m/s. The results of tests in the 3 m/s and 8 m/s conditions were used to develop force-deflection response corridors for the abdomen, force history response corridors for the pelvis (iliac wing and greater trochanter), the midthigh, and the thorax. Response corridors for the lateral acceleration of the pelvis were also developed. Future work will compare side impact ATD responses to these response corridors.

49 CFR 178.345-3 - Structural integrity.

Code of Federal Regulations, 2014 CFR

2014-10-01

... accelerative force equal to 0.35 times the vertical reaction at the suspension assembly of a trailer; or the... the suspension assembly of a trailer, and the horizontal pivot of the upper coupler (fifth wheel) or... normal operating accelerative force equal to 0.35 times the vertical reaction at the suspension assembly...

49 CFR 178.345-3 - Structural integrity.

Code of Federal Regulations, 2012 CFR

2012-10-01

... accelerative force equal to 0.35 times the vertical reaction at the suspension assembly of a trailer; or the... the suspension assembly of a trailer, and the horizontal pivot of the upper coupler (fifth wheel) or... normal operating accelerative force equal to 0.35 times the vertical reaction at the suspension assembly...

49 CFR 178.345-3 - Structural integrity.

Code of Federal Regulations, 2013 CFR

2013-10-01

... accelerative force equal to 0.35 times the vertical reaction at the suspension assembly of a trailer; or the... the suspension assembly of a trailer, and the horizontal pivot of the upper coupler (fifth wheel) or... normal operating accelerative force equal to 0.35 times the vertical reaction at the suspension assembly...

Sarcopenia Is Negatively Related to High Gravitational Impacts Achieved From Day-to-day Physical Activity.

PubMed

Hartley, April; Gregson, Celia L; Hannam, Kimberly; Deere, Kevin C; Clark, Emma M; Tobias, Jon H

2018-04-17

Sarcopenia has been associated with reduced physical activity (PA). We aimed to determine if sarcopenia, and specific components of muscle size, function, and physical performance, are associated with high impacts achieved during habitual PA, as these are related to bone strength in community-dwelling older women. Participants were older women from the Cohort of Skeletal Health in Bristol and Avon. We defined sarcopenia using the EWGSOP criteria. Lower limb peak muscle power and force were assessed using Jumping Mechanography (JM). High vertical impacts were assessed by tri-axial accelerometry (at least 1.5g above gravity). Cross-sectional associations were analyzed by linear regression, adjusting for age, height and weight (or fat mass for models including appendicular lean mass index), comorbidities, smoking, alcohol, and Index of Multiple Deprivation. Our analyses included 380 participants, with mean age 76.7 (SD 3.0) years; 242 (64%) also completed JM. In age-adjusted analysis, a negative relationship was observed between severity of sarcopenia and high, but not medium or low, impacts (p = .03 for trend). Regarding components of sarcopenia underlying this relationship, multivariable analyses revealed that gait speed (β 1.47 [95% CI 1.14, 1.89], [β-1] reflects the proportionate increase in high impacts per SD increase in exposure) and peak force (1.40 [1.07, 1.84]) were independently associated with high impacts. Older women with sarcopenia experienced fewer bone-strengthening high impacts than those with presarcopenia or without sarcopenia. To increase bone strengthening activity in older women, interventions need to improve both lower limb muscle force and walking speed.

Kinetic factors of vertical jumping for heading a ball in flexible flatfooted amateur soccer players with and without insole adoption.

PubMed

Arastoo, Ali Asghar; Aghdam, Esmaeil Moharrami; Habibi, Abdoul Hamid; Zahednejad, Shahla

2014-06-01

According to literature, little is known regarding the effects of orthotic management of flatfoot on kinetics of vertical jump. To compare the kinetic and temporal events of two-legged vertical jumping take-off from a force plate for heading a ball in normal and flexible flatfoot subjects with and without insole. A functional based interventional controlled study. Random sampling method was employed to draw a control group of 15 normal foot subjects to a group of 15 flatfoot subjects. A force platform was used to record kinetics of two-legged vertical jump shots. Results indicate that insole did not lead to a significant effect on kinetics regarding anterior-posterior and mediolateral directions (p > 0.05). Results of kinetics related to vertical direction for maximum force due to take-off and stance duration revealed significant differences between the normal and flexible flatfoot subjects without insole (p < 0.05) and no significant differences between the normal foot and flexible flatfoot subjects with insole adoption (p > 0.05). These results suggest that the use of an insole in the flexible flatfoot subjects led to improved stance time and decrease of magnitude of kinetics regarding vertical direction at take-off as the main feature of two-legged vertical jumping function. Adoption of the insole improved the design of the shoe-foot interface support for the flexible flatfoot athletes, enabling them to develop more effective take-off kinetics for vertical jumping in terms of ground reaction force and stance duration similar to that of normal foot subjects without insole. © The International Society for Prosthetics and Orthotics 2013.

Is midsole thickness a key parameter for the running pattern?

PubMed

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

2014-01-01

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

Foot force production and asymmetries in elite rowers.

PubMed

Buckeridge, Erica M; Bull, Anthony M J; McGregor, Alison H

2014-03-01

The rowing stroke is a leg-driven action, in which forces developed by the lower limbs provide a large proportion of power delivered to the oars. In terms of both performance and injury, it is important to initiate each stroke with powerful and symmetrical loading of the foot stretchers. The aims of this study were to assess the reliability of foot force measured by footplates developed for the Concept2 indoor ergometer and to examine the magnitude and symmetry of bilateral foot forces in different groups of rowers. Five heavyweight female scullers, six heavyweight female sweep rowers, and six lightweight male (LWM) rowers performed an incremental step test on the Concept2 ergometer. Vertical, horizontal, and resultant forces were recorded bilaterally, and asymmetries were quantified using the absolute symmetry index. Foot force was measured with high consistency (coefficient of multiple determination > 0.976 +/- 0.010). Relative resultant, vertical, and horizontal forces were largest in LWM rowers, whilst average foot forces significantly increased across stroke rates for all three groups of rowers. Asymmetries ranged from 5.3% for average resultant force to 28.9% for timing of peak vertical force. Asymmetries were not sensitive to stroke rate or rowing group, however, large inter-subject variability in asymmetries was evident.

The influence of cricket fast bowlers' front leg technique on peak ground reaction forces.

PubMed

Worthington, Peter; King, Mark; Ranson, Craig

2013-01-01

High ground reaction forces during the front foot contact phase of the bowling action are believed to be a major contributor to the high prevalence of lumbar stress fractures in fast bowlers. This study aimed to investigate the influence of front leg technique on peak ground reaction forces during the delivery stride. Three-dimensional kinematic data and ground reaction forces during the front foot contact phase were captured for 20 elite male fast bowlers. Eight kinematic parameters were determined for each performance, describing run-up speed and front leg technique, in addition to peak force and time to peak force in the vertical and horizontal directions. There were substantial variations between bowlers in both peak forces (vertical 6.7 ± 1.4 body weights; horizontal (braking) 4.5 ± 0.8 body weights) and times to peak force (vertical 0.03 ± 0.01 s; horizontal 0.03 ± 0.01 s). These differences were found to be linked to the orientation of the front leg at the instant of front foot contact. In particular, a larger plant angle and a heel strike technique were associated with lower peak forces and longer times to peak force during the front foot contact phase, which may help reduce the likelihood of lower back injuries.

Developing Soil Models for Dynamic Impact Simulations

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Lyle, Karen H.; Jackson, Karen E.

2009-01-01

This paper describes fundamental soils characterization work performed at NASA Langley Research Center in support of the Subsonic Rotary Wing (SRW) Aeronautics Program and the Orion Landing System (LS) Advanced Development Program (ADP). LS-DYNA(Registered TradeMark)1 soil impact model development and test-analysis correlation results are presented for: (1) a 38-ft/s vertical drop test of a composite fuselage section, outfitted with four blocks of deployable energy absorbers (DEA), onto sand, and (2) a series of impact tests of a 1/2-scale geometric boilerplate Orion capsule onto soil. In addition, the paper will discuss LS-DYNA contact analysis at the soil/structure interface, methods used to estimate frictional forces, and the sensitivity of the model to density, moisture, and compaction.

Use of a tibial accelerometer to measure ground reaction force in running: A reliability and validity comparison with force plates.

PubMed

Raper, Damian P; Witchalls, Jeremy; Philips, Elissa J; Knight, Emma; Drew, Michael K; Waddington, Gordon

2018-01-01

The use of microsensor technologies to conduct research and implement interventions in sports and exercise medicine has increased recently. The objective of this paper was to determine the validity and reliability of the ViPerform as a measure of load compared to vertical ground reaction force (GRF) as measured by force plates. Absolute reliability assessment, with concurrent validity. 10 professional triathletes ran 10 trials over force plates with the ViPerform mounted on the mid portion of the medial tibia. Calculated vertical ground reaction force data from the ViPerform was matched to the same stride on the force plate. Bland-Altman (BA) plot of comparative measure of agreement was used to assess the relationship between the calculated load from the accelerometer and the force plates. Reliability was calculated by intra-class correlation coefficients (ICC) with 95% confidence intervals. BA plot indicates minimal agreement between the measures derived from the force plate and ViPerform, with variation at an individual participant plot level. Reliability was excellent (ICC=0.877; 95% CI=0.825-0.917) in calculating the same vertical GRF in a repeated trial. Standard error of measure (SEM) equalled 99.83 units (95% CI=82.10-119.09), which, in turn, gave a minimum detectable change (MDC) value of 276.72 units (95% CI=227.32-330.07). The ViPerform does not calculate absolute values of vertical GRF similar to those measured by a force plate. It does provide a valid and reliable calculation of an athlete's lower limb load at constant velocity. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Hemispheric aerosol vertical profiles: anthropogenic impacts on optical depth and cloud nuclei.

PubMed

Clarke, Antony; Kapustin, Vladimir

2010-09-17

Understanding the effect of anthropogenic combustion upon aerosol optical depth (AOD), clouds, and their radiative forcing requires regionally representative aerosol profiles. In this work, we examine more than 1000 vertical profiles from 11 major airborne campaigns in the Pacific hemisphere and confirm that regional enhancements in aerosol light scattering, mass, and number are associated with carbon monoxide from combustion and can exceed values in unperturbed regions by more than one order of magnitude. Related regional increases in a proxy for cloud condensation nuclei (CCN) and AOD imply that direct and indirect aerosol radiative effects are coupled issues linked globally to aged combustion. These profiles constrain the influence of combustion on regional AOD and CCN suitable for challenging climate model performance and informing satellite retrievals.

Vertical Propagation and Temporal Growth of Perturbations in the Winter Atmosphere

NASA Astrophysics Data System (ADS)

Christiansen, B.

2001-12-01

We present a general circulation model study of the temporal growth and vertically propagation of perturbations following vertical confined forcings. Both transient and sustained forcings are considered. The motivation for the study is the recent recognition of downward propagation of anomalies from the stratosphere to the troposphere and its implications both for medium range forecasts and for a possible physical mechanism for stratospheric impacts on weather and climate. The dynamical link might also offer a mechanism for changes in the upper atmosphere to affect the tropospheric climate. Here we are thinking of changes in trace gases such as ozone, but also of modulations of the upper atmospheric structure related to the 11-year solar cycle. The model atmosphere is chaotic and shows growth of perturbations no matter which level is forced. The perturbations grow to a size comparable to the variability of the unperturbed atmosphere on a time-scale of 20 - 25 days in the troposphere and 30 - 40 days in the stratosphere. After the initial period of growth the perturbations have the same structure as the unperturbed atmosphere. Although the forcing is restricted to the northern hemisphere the perturbations encompass the whole atmosphere and develop on the same time scale on both hemispheres. Perturbations grow with time squared both when zonal mean and single cell values are considered. Such a power law growth suggest the existence of a finite predictability time which is independent of the initial perturbation as long as it is small. In the unperturbed atmosphere the stratospheric variability has the form of downward propagating stratospheric vacillations. However, in the initial period of growth the perturbations do not propagate downward and seem in general uncoupled to the background vacillations. This suggests that the downward propagation is a robust feature determined more by the processes in the troposphere than the state of the stratosphere. We note that downward propagation may still be a source for enhanced predictability of near-surface weather.

Evolution of aerosol vertical distribution during particulate pollution events in Shanghai

NASA Astrophysics Data System (ADS)

Zhang, Yunwei; Zhang, Qun; Leng, Chunpeng; Zhang, Deqin; Cheng, Tiantao; Tao, Jun; Zhang, Renjian; He, Qianshan

2015-06-01

A set of micro pulse lidar (MPL) systems operating at 532 nm was used for ground-based observation of aerosols in Shanghai in 2011. Three typical particulate pollution events (e.g., haze) were examined to determine the evolution of aerosol vertical distribution and the planetary boundary layer (PBL) during these pollution episodes. The aerosol vertical extinction coefficient (VEC) at any given measured altitude was prominently larger during haze periods than that before or after the associated event. Aerosols originating from various source regions exerted forcing to some extent on aerosol loading and vertical layering, leading to different aerosol vertical distribution structures. Aerosol VECs were always maximized near the surface owing to the potential influence of local pollutant emissions. Several peaks in aerosol VECs were found at altitudes above 1 km during the dust- and bioburning-influenced haze events. Aerosol VECs decreased with increasing altitude during the local-polluted haze event, with a single maximum in the surface atmosphere. PM2.5 increased slowly while PBL and visibility decreased gradually in the early stages of haze events; subsequently, PM2.5 accumulated and was exacerbated until serious pollution bursts occurred in the middle and later stages. The results reveal that aerosols from different sources impact aerosol vertical distributions in the atmosphere and that the relationship between PBL and pollutant loadings may play an important role in the formation of pollution.

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

Donner, Leo J.; O'Brien, Travis A.; Rieger, Daniel

Both climate forcing and climate sensitivity persist as stubborn uncertainties limiting the extent to which climate models can provide actionable scientific scenarios for climate change. A key, explicit control on cloud-aerosol interactions, the largest uncertainty in climate forcing, is the vertical velocity of cloud-scale updrafts. Model-based studies of climate sensitivity indicate that convective entrainment, which is closely related to updraft speeds, is an important control on climate sensitivity. Updraft vertical velocities also drive many physical processes essential to numerical weather prediction. Vertical velocities and their role in atmospheric physical processes have been given very limited attention in models for climatemore » and numerical weather prediction. The relevant physical scales range down to tens of meters and are thus frequently sub-grid and require parameterization. Many state-of-science convection parameterizations provide mass fluxes without specifying vertical velocities, and parameterizations which do provide vertical velocities have been subject to limited evaluation against what have until recently been scant observations. Atmospheric observations imply that the distribution of vertical velocities depends on the areas over which the vertical velocities are averaged. Distributions of vertical velocities in climate models may capture this behavior, but it has not been accounted for when parameterizing cloud and precipitation processes in current models. New observations of convective vertical velocities offer a potentially promising path toward developing process-level cloud models and parameterizations for climate and numerical weather prediction. Taking account of scale-dependence of resolved vertical velocities offers a path to matching cloud-scale physical processes and their driving dynamics more realistically, with a prospect of reduced uncertainty in both climate forcing and sensitivity.« less

A mathematical model of an active control landing gear for load control during impact and roll-out

NASA Technical Reports Server (NTRS)

Mcgehee, J. R.; Carden, H. D.

1976-01-01

A mathematical model of an active control landing gear (ACOLAG) was developed and programmed for operation on a digital computer. The mathematical model includes theoretical subsonic aerodynamics; first-mode wing bending and torsional characteristics; oleo-pneumatic shock strut with fit and binding friction; closed-loop, series-hydraulic control; empirical tire force-deflection characteristics; antiskid braking; and sinusoidal or random runway roughness. The mathematical model was used to compute the loads and motions for a simulated vertical drop test and a simulated landing impact of a conventional (passive) main landing gear designed for a 2268-kg (5000-lbm) class airplane. Computations were also made for a simply modified version of the passive gear including a series-hydraulic active control system. Comparison of computed results for the passive gear with experimental data shows that the active control landing gear analysis is valid for predicting the loads and motions of an airplane during a symmetrical landing. Computed results for the series-hydraulic active control in conjunction with the simply modified passive gear show that 20- to 30-percent reductions in wing force, relative to those occurring with the modified passive gear, can be obtained during the impact phase of the landing. These reductions in wing force could result in substantial increases in fatigue life of the structure.

Blood Back Spatter Caused by a Blunt Bullet Gunshot: Theory and Experiments

NASA Astrophysics Data System (ADS)

Comiskey, Patrick; Yarin, Alexander; Kim, Sungu; Attinger, Daniel

A theoretical model describing the blood back spatter pattern resulting from a blunt bullet gunshot is proposed and compared to experimental data. It is shown that the blunt bullet impact results in blood accelerating towards air opposite of the bullet motion creating a situation for the Rayleigh-Taylor instability which determines droplet sizes and initial velocities. Then, drop trajectories can be predicted accounting for all forces involved: air drag and gravity forces, as well as for the collective effect of drop-drop interaction through air which diminishes the drag force on drops moving in the wake of the others. Experimental data was acquired by shooting a blunt bullet into a porous substrate impregnated with swine blood and the spatter pattern was collected on a vertical surface located between the target and the shooter. The spatter pattern was analyzed for the number of droplets, the area of blood stains, total stain area, and location. Comparisons with the theoretical results reveal satisfactory agreement. The theory also predicts the impact angle at the collection surface, the Weber number corresponding to the drop impact onto the collection surface, and the stain ellipticity. Support of this work by the US National Institute of Justice (award NIJ 2014-DN-BX-K036) is greatly appreciated.

Sex differences in lower extremity biomechanics during single leg landings.

PubMed

Schmitz, Randy J; Kulas, Anthony S; Perrin, David H; Riemann, Bryan L; Shultz, Sandra J

2007-07-01

Females have an increased incident rate of anterior cruciate ligament tears compared to males. Biomechanical strategies to decelerate the body in the vertical direction have been implicated as a contributing cause. This study determined if females would exhibit single leg landing strategies characterized by decreased amounts of hip, knee, and ankle flexion resulting in greater vertical ground reaction forces and altered energy absorption patterns when compared to males. Recreationally active males (N=14) and females (N=14), completed five single leg landings from a 0.3m height onto a force platform while three-dimensional kinematics and kinetics were simultaneously collected. Compared to males, females exhibited (1) less total hip and knee flexion displacements (40% and 64% of males, respectively, P<0.05) and less time to peak hip and knee flexion (48% and 78% of males, respectively, P<0.05), (2) 9% greater peak vertical ground reaction forces (P<0.05), (3) less total lower body energy absorption (76% of males, P<0.05), and (4) 11% greater relative energy absorption at the ankle (P<0.05). Females in this study appear to adopt a single leg landing style using less hip and knee flexion, absorbing less total lower body energy with more relative energy at the ankle resulting in a landing style that can be described as stiff. This may potentially cause increased demands on non-contractile components of the lower extremity. Preventative training programs designed to prevent knee injury may benefit from the biomechanical description of sex-specific landing methods demonstrated by females in this study by focusing on the promotion of more reliance on using the contractile components to absorb impact energy during landings.

Impact of errors in short wave radiation and its attenuation on modeled upper ocean heat content

DTIC Science & Technology

Photosynthetically available radiation (PAR) and its attenuation with the depth represent a forcing (source) term in the governing equation for the...and vertical attenuation of PAR have on the upper ocean model heat content. In the Monterey Bay area, we show that with a decrease in water clarity...attenuation coefficient. For Jerlov’s type IA water (attenuation coefficient is 0.049 m1), the relative error in surface PAR introduces an error

Lift vs. drag based mechanisms for vertical force production in the smallest flying insects.

PubMed

Jones, S K; Laurenza, R; Hedrick, T L; Griffith, B E; Miller, L A

2015-11-07

We used computational fluid dynamics to determine whether lift- or drag-based mechanisms generate the most vertical force in the flight of the smallest insects. These insects fly at Re on the order of 4-60 where viscous effects are significant. Detailed quantitative data on the wing kinematics of the smallest insects is not available, and as a result both drag- and lift-based strategies have been suggested as the mechanisms by which these insects stay aloft. We used the immersed boundary method to solve the fully-coupled fluid-structure interaction problem of a flexible wing immersed in a two-dimensional viscous fluid to compare three idealized hovering kinematics: a drag-based stroke in the vertical plane, a lift-based stroke in the horizontal plane, and a hybrid stroke on a tilted plane. Our results suggest that at higher Re, a lift-based strategy produces more vertical force than a drag-based strategy. At the Re pertinent to small insect hovering, however, there is little difference in performance between the two strategies. A drag-based mechanism of flight could produce more vertical force than a lift-based mechanism for insects at Re<5; however, we are unaware of active fliers at this scale. Copyright © 2015 Elsevier Ltd. All rights reserved.

Vertical force and wrist deviation angle in a sample of elderly people using walkers.

PubMed

Leung, Cherng-Yee; Yeh, Po-Chan

2013-02-01

Walkers are frequently used by elderly people with weak lower limbs and limited balance, but the ergonomic relationship between the use of a walker and stress on the upper limbs is relatively unstudied. The current study assessed wrist deviation and vertical force among elderly individuals using a walker for assistance in walking. 60 elderly volunteers (M age = 81.0 yr., SD = 8.8) participated, 30 of whom frequently used a walker, and 30 who had no such prior experience. Data were obtained from four load cells and a twin-axis wrist goniometer during assisted ambulation using the walker. No significant group difference was found in gait cycle. Significant wrist deviation occurred, with ulnar deviation/dorsiflexion of the right hand, which was greater than that of the left. Non-experienced participants had larger dorsiflexion than experienced participants. Experienced participants produced larger vertical force than non-experienced participants. The greaterthe wrist deviation, the greater was the vertical force. The horizontal handles of most marketed walkers cause wrist deviations. This is a concern for users, clinicians, and related industries. Improvements in walker design should be considered.

Ground reaction forces on stairs: effects of stair inclination and age.

PubMed

Stacoff, Alex; Diezi, Christian; Luder, Gerhard; Stüssi, Edgar; Kramers-de Quervain, Inès A

2005-01-01

The goals of the study were to compare data of vertical ground reaction force (GRF) parameters during level walking, stair ascent and descent on three different stair inclinations and three different age groups. Twenty healthy subjects of three age groups (young 33.7 years; middle 63.6 years; old 76.5 years) were tested during the seven test conditions with 8-10 repetitions. Vertical forces were measured during two consecutive steps with force plates embedded in the walkway and the staircase. The results showed that during level walking the vertical GRF curves were very regular and repetitive, the trail-to-trial variability and left-right asymmetry of defined test parameters being around 2-5% and 3-5%. During stair ascent the vertical GRF force pattern was found to change slightly compared to level gait, but considerably compared to stair descent. On the steep stair the average vertical load increased up to 1.6 BW, and variability (5-10%) and asymmetry (5-15%) were increased significantly. The steep stair descent condition was found to be the most demanding test showing the largest variability and asymmetry and thus, the least stable gait pattern. Age was found to be a factor which should be considered, because the young age group walked faster and produced larger vertical GRF maxima during level walking and on stair ascent than the middle and old age group. Differences between the middle and old age group were found to be small. The present investigation is the first to provide normative data of GRF parameters on gait variability and symmetry of two consecutive steps during level gait and stair ambulation. It is the intention that the results of this study may be used as a basis for comparison with patient data.

Validity and reliability of Optojump photoelectric cells for estimating vertical jump height.

PubMed

Glatthorn, Julia F; Gouge, Sylvain; Nussbaumer, Silvio; Stauffacher, Simone; Impellizzeri, Franco M; Maffiuletti, Nicola A

2011-02-01

Vertical jump is one of the most prevalent acts performed in several sport activities. It is therefore important to ensure that the measurements of vertical jump height made as a part of research or athlete support work have adequate validity and reliability. The aim of this study was to evaluate concurrent validity and reliability of the Optojump photocell system (Microgate, Bolzano, Italy) with force plate measurements for estimating vertical jump height. Twenty subjects were asked to perform maximal squat jumps and countermovement jumps, and flight time-derived jump heights obtained by the force plate were compared with those provided by Optojump, to examine its concurrent (criterion-related) validity (study 1). Twenty other subjects completed the same jump series on 2 different occasions (separated by 1 week), and jump heights of session 1 were compared with session 2, to investigate test-retest reliability of the Optojump system (study 2). Intraclass correlation coefficients (ICCs) for validity were very high (0.997-0.998), even if a systematic difference was consistently observed between force plate and Optojump (-1.06 cm; p < 0.001). Test-retest reliability of the Optojump system was excellent, with ICCs ranging from 0.982 to 0.989, low coefficients of variation (2.7%), and low random errors (±2.81 cm). The Optojump photocell system demonstrated strong concurrent validity and excellent test-retest reliability for the estimation of vertical jump height. We propose the following equation that allows force plate and Optojump results to be used interchangeably: force plate jump height (cm) = 1.02 × Optojump jump height + 0.29. In conclusion, the use of Optojump photoelectric cells is legitimate for field-based assessments of vertical jump height.

Running stride peak forces inversely determine running economy in elite runners.

PubMed

Støren, Øyvind; Helgerud, Jan; Hoff, Jan

2011-01-01

The present study investigated the relationship between running economy (RE) at 15 km/h(-1) , 3.000-m race time, maximal strength, and a number of physiological, anthropometrical, and mechanical variables. The variables measured included RE, maximal oxygen consumption, heart rate, step length and frequency, contact time, and the peak horizontal and vertical forces of each step. Maximal strength was measured as the 1 repetition maximum (1RM) half-squat using a leg press machine. Eleven male elite endurance athletes with a V(O2)max of 75.8 ± 6.2 mL/kg(-1)/min(-1) participated in this study. After the anthropometric data were collected, they were tested for RE, running characteristics, and force measures on a level treadmill at 15 km/h(-1). The athletes wore contact soles, and the treadmill was placed on a force platform. Maximal oxygen consumption and 1RM were tested after the RE measurements. The sum of horizontal and vertical peak forces revealed a significant inverse correlation (p < 0.05) both with 3,000-m performance (R = 0.71) and RE (R = 0.66). Inverse correlations were also found (p < 0.05) between RE and body height (R = 0.61) and between RE and body fat percentage (R = 0.62). In conclusion, the sum of horizontal and vertical peak forces was found to be negatively correlated to running economy and 3,000-m running performance, indicating that avoiding vertical movements and high horizontal braking force is crucial for a positive development of RE.

Effects of spine flexion and erector spinae maximal force on vertical squat jump height: a computational simulation study.

PubMed

Blache, Yoann; Monteil, Karine

2015-03-01

The purpose of this study was to evaluate the single and combined effects of initial spine flexion and maximal isometric force of the erector spinae on maximal vertical jump height during maximal squat jumping. Seven initial flexions of the 'thorax-head-arm' segment (between 20.1° and 71.6°) and five maximal isometric forces of the erector spinae (between 5600 and 8600 N) were tested. Thus, 35 squat jumps were simulated using a 2D simulation model of the musculoskeletal system. Vertical jump height varied at most about 0.094 and 0.021 m when the initial flexion of the 'thorax-head-arm' segment and the maximal force of the erector spinae were, respectively, maximal. These results were explained for the most part by the variation of total muscle work. The latter was mainly influenced by the work produced by the erector spinae which increased at most about 57 and 110 J when the initial flexion of the 'thorax-head-arm' segment and the maximal force of the erector spinae were, respectively, maximal. It was concluded that the increase in the initial flexion of the 'thorax-head-arm' segment and in the maximal isometric force of the erector spinae enables an increase in maximal vertical jump height during maximal squat jumping.

Increased medial longitudinal arch mobility, lower extremity kinematics, and ground reaction forces in high-arched runners.

PubMed

Williams, D S Blaise; Tierney, Robin N; Butler, Robert J

2014-01-01

Runners with high medial longitudinal arch structure demonstrate unique kinematics and kinetics that may lead to running injuries. The mobility of the midfoot as measured by the change in arch height is also suspected to play a role in lower extremity function during running. The effect of arch mobility in high-arched runners is an important factor in prescribing footwear, training, and rehabilitating the running athlete after injury. To examine the effect of medial longitudinal arch mobility on running kinematics, ground reaction forces, and loading rates in high-arched runners. Cross-sectional study. Human movement research laboratory. A total of 104 runners were screened for arch height. Runners were then identified as having high arches if the arch height index was greater than 0.5 SD above the mean. Of the runners with high arches, 11 rigid runners with the lowest arch mobility (R) were compared with 8 mobile runners with the highest arch mobility (M). Arch mobility was determined by calculating the left arch height index in all runners. Three-dimensional motion analysis of running over ground. Rearfoot and tibial angular excursions, eversion-to-tibial internal-rotation ratio, vertical ground reaction forces, and the associated loading rates. Runners with mobile arches exhibited decreased tibial internal-rotation excursion (mobile: 5.6° ± 2.3° versus rigid: 8.0° ± 3.0°), greater eversion-to-tibial internal-rotation ratio (mobile: 2.1 ± 0.8 versus rigid: 1.5 ± 0.5), decreased second peak vertical ground reaction force values (mobile: 2.3 ± 0.2 × body weight versus rigid: 2.4 ± 0.1 × body weight), and decreased vertical loading rate values (mobile: 55.7 ± 14.1 × body weight/s versus rigid: 65.9 ± 11.4 × body weight/s). Based on the results of this study, it appears that runners with high arch structure but differing arch mobility exhibited differences in select lower extremity movement patterns and forces. Future authors should investigate the impact of arch mobility on running-related injuries.

Spring-mass behavior during exhaustive run at constant velocity in elite triathletes.

PubMed

Rabita, Giuseppe; Slawinski, Jean; Girard, Olivier; Bignet, Frank; Hausswirth, Christophe

2011-04-01

The aims of this study were i) to evaluate changes in leg-spring behavior during an exhaustive run in elite triathletes and ii) to determine whether these modifications were related to an increase in the energy cost of running (Cr). Nine elite triathletes ran to exhaustion on an indoor track at a constant velocity corresponding to 95% of the velocity associated with the maximal oxygen uptake (mean ± SD = 5.1 ± 0.3 m·s(-1), time to exhaustion = 10.7 ± 2.6 min). Vertical and horizontal ground reaction forces were measured every lap (200 m) by a 5-m-long force platform system. Cr was measured from pulmonary gas exchange using a breath-by-breath portable gas analyzer. Leg stiffness (-13.1%, P < 0.05) and peak vertical (-9.2%, P < 0.05) and propulsive (-7.5%, P < 0.001) forces decreased significantly with fatigue, whereas vertical stiffness did not change significantly. Leg and vertical stiffness changes were positively related with modifications of aerial time (R(2) = 0.66, P < 0.01 and R(2) = 0.72, P < 0.01, respectively) and negatively with contact time (R(2) = 0.71, P < 0.01 and R(2) = 0.74, P < 0.01, respectively). Alterations of vertical forces were related with the decrease of the angle of velocity vector at toe off (R(2) = 0.73, P < 0.01). When considering mean values of oxygen uptake, no change was observed from 33% to 100% of the time to exhaustion. However, between one-third and two-thirds of the fatiguing run, negative correlations were observed between oxygen consumption and leg stiffness (R(2) = 0.83, P < 0.001) or vertical stiffness (R(2) = 0.50, P < 0.03). During a constant run to exhaustion, the fatigue induces a stiffness adaptation that modifies the stride mechanical parameters and especially decreases the maximal vertical force. This response to fatigue involves greater energy consumption.

Estimation of actomyosin active force maintained by tropomyosin and troponin complex under vertical forces in the in vitro motility assay system

PubMed Central

Ishii, Shuya; Kawai, Masataka; Ishiwata, Shin'ichi

2018-01-01

The interaction between actin filaments and myosin molecular motors is a power source of a variety of cellular functions including cell division, cell motility, and muscular contraction. In vitro motility assay examines actin filaments interacting with myosin molecules that are adhered to a substrate (e.g., glass surface). This assay has been the standard method of studying the molecular mechanisms of contraction under an optical microscope. While the force generation has been measured through an optically trapped bead to which an actin filament is attached, a force vector vertical to the glass surface has been largely ignored with the in vitro motility assay. The vertical vector is created by the gap (distance) between the trapped bead and the glass surface. In this report, we propose a method to estimate the angle between the actin filament and the glass surface by optically determining the gap size. This determination requires a motorized stage in a standard epi-fluorescence microscope equipped with optical tweezers. This facile method is applied to force measurements using both pure actin filaments, and thin filaments reconstituted from actin, tropomyosin and troponin. We find that the angle-corrected force per unit filament length in the active condition (pCa = 5.0) decreases as the angle between the filament and the glass surface increases; i.e. as the force in the vertical direction increases. At the same time, we demonstrate that the force on reconstituted thin filaments is approximately 1.5 times larger than that on pure actin filaments. The range of angles we tested was between 11° and 36° with the estimated measurement error less than 6°. These results suggest the ability of cytoplasmic tropomyosin isoforms maintaining actomyosin active force to stabilize cytoskeletal architecture. PMID:29420610

Analysis of seismic body waves excited by the Mount Saint Helens eruption of May 18, 1980

NASA Technical Reports Server (NTRS)

Kanamori, H.; Given, J. W.; Lay, T.

1982-01-01

Seismic body waves which were excited by eruption of Mt. St. Helens, and recorded by the Global Digital Seismographic Network (GDSN) stations are analyzed to determine the nature and the time sequence of the events associated with the eruption. The polarity of teleseismic P waves (period 20 sec) is identical at six stations which are distributed over a wide azimuthal range. This observation, together with a very small S to P amplitude ratio (at 20 sec), suggests that the source is a nearly vertical single force that represents the counter force of the eruption. The time history of the vertical force suggests two distinct groups of events, about two minutes apart, each consisting of several subevents with a duration of about 25 sec. The magnitude of the force is approximately 2.6 to the 17th power dyne. this vertical force is in contrast with the long period (approximately 150 sec) southward horizontal single force which was determined by a previous study and interpreted to be due to the massive landslide.

Effective Swimmer’s Action during the Grab Start Technique

PubMed Central

Mourão, Luis; de Jesus, Karla; Roesler, Hélio; Machado, Leandro J.; Fernandes, Ricardo J.; Vilas-Boas, João Paulo; Vaz, Mário A. P.

2015-01-01

The external forces applied in swimming starts have been often studied, but using direct analysis and simple interpretation data processes. This study aimed to develop a tool for vertical and horizontal force assessment based on the swimmers’ propulsive and structural forces (passive forces due to dead weight) applied during the block phase. Four methodological pathways were followed: the experimented fall of a rigid body, the swimmers’ inertia effect, the development of a mathematical model to describe the outcome of the rigid body fall and its generalization to include the effects of the inertia, and the experimental swimmers’ starting protocol analysed with the inclusion of the developed mathematical tool. The first three methodological steps resulted in the description and computation of the passive force components. At the fourth step, six well-trained swimmers performed three 15 m maximal grab start trials and three-dimensional (3D) kinetic data were obtained using a six degrees of freedom force plate. The passive force contribution to the start performance obtained from the model was subtracted from the experimental force due to the swimmers resulting in the swimmers’ active forces. As expected, the swimmers’ vertical and horizontal active forces accounted for the maximum variability contribution of the experimental forces. It was found that the active force profile for the vertical and horizontal components resembled one another. These findings should be considered in clarifying the active swimmers’ force variability and the respective geometrical profile as indicators to redefine steering strategies. PMID:25978370

Three-Axis Ground Reaction Force Distribution during Straight Walking.

PubMed

Hori, Masataka; Nakai, Akihito; Shimoyama, Isao

2017-10-24

We measured the three-axis ground reaction force (GRF) distribution during straight walking. Small three-axis force sensors composed of rubber and sensor chips were fabricated and calibrated. After sensor calibration, 16 force sensors were attached to the left shoe. The three-axis force distribution during straight walking was measured, and the local features of the three-axis force under the sole of the shoe were analyzed. The heel area played a role in receiving the braking force, the base area of the fourth and fifth toes applied little vertical or shear force, the base area of the second and third toes generated a portion of the propulsive force and received a large vertical force, and the base area of the big toe helped move the body's center of mass to the other foot. The results demonstrate that measuring the three-axis GRF distribution is useful for a detailed analysis of bipedal locomotion.

Steerable vertical to horizontal energy transducer for mobile robots

DOEpatents

Spletzer, Barry L.; Fischer, Gary J.; Feddema, John T.

2001-01-01

The present invention provides a steerable vertical to horizontal energy transducer for mobile robots that less complex and requires less power than two degree of freedom tilt mechanisms. The present invention comprises an end effector that, when mounted with a hopping actuator, translates along axis (typically vertical) actuation into combined vertical and horizontal motion. The end effector, or foot, mounts with an end of the actuator that moves toward the support surface (typically a floor or the earth). The foot is shaped so that the first contact with the support surface is off the axis of the actuator. Off-axis contact with the support surface generates an on-axis force (typically resulting in vertical motion) and a moment orthogonal to the axis. The moment initiates a horizontal tumbling motion, and tilts the actuator so that its axis is oriented with a horizontal component and continued actuation generates both vertical and horizontal force.

Vertical Distribution of Black and Brown Carbon over Shanghai during Winter

NASA Astrophysics Data System (ADS)

Zheng, M.; Yan, C.; Wang, D.; Fu, Q.

2016-12-01

Carbonaceous aerosols (i.e., black carbon, BC, and organic aerosol, OA) have significant impact on Earth's energy budget by scattering and absorbing solar radiation. Extensive carbonaceous aerosols have been emitted in mainland China. It is essential to study the column burden of carbonaceous aerosol and associated light absorption to better understand its radiative forcing. In this study, a tethered balloon-based field campaign was conducted over a Chinese megacity, Shanghai, in December of 2015, with the primary goal to investigate the vertical profile of air pollutants within the lower troposphere, especially during the polluted days. A 7-wavelength Aethalometer (AE-31) were adopted in the observation to obtain vertical profiles of atmospheric carbonaceous aerosols within the lower troposphere. Light absorption by black and brown carbon, the light absorbing organic components, were distinguished and separated based on difference between light absorption at 450 nm versus 880 nm. Light absorption of brown carbon relative to black carbon were also estimated to pose the importance of brown carbon. Besides, diurnal variation of black and brown carbon vertical profiles would also be discussed, with consideration of variation of height of planetary boundary layer.

Vertical plasmonic nanowires for 3D nanoparticle trapping

NASA Astrophysics Data System (ADS)

Wu, Jingzhi; Gan, Xiaosong

2011-12-01

Nanoparticle trapping is considered to be more challenging than trapping micron-sized objects because of the diffraction limit of light and the severe Brownian motion of the nanoparticles. We introduce a nanoparticle trapping approach based on plasmonic nanostructures, which consist of nanopillars with high aspect ratio. The plasmonic nanopillars behave as plasmonic resonators that rely on paired nano-pillars supporting gap plasmon modes. The localized surface plasmon resonance effect provides strong electromagnetic field enhancement and enables confinement of nanoparticles in three dimensional space. Numerical simulations indicate that the plasmonic structure provides stronger optical forces for trapping nanoparticles. The study of thermal effect of the plasmonic structure shows that the impact of the thermal force is significant, which may determine the outcome of the nanoparticle trapping.

KSC-2014-2402

NASA Image and Video Library

2014-03-28

VANDENBERG AIR FORCE BASE, Calif. – The United Launch Alliance Delta II rocket for NASA's Orbiting Carbon Observatory-2 mission, or OCO-2, is lifted into a vertical position beside the mobile service tower at Space Launch Complex 2 on Vandenberg Air Force Base in California. Launch is scheduled for July 1, 2014. The observatory will collect precise global measurements of carbon dioxide in the Earth's atmosphere and provide scientists with a better idea of the chemical compound's impacts on climate change. Scientists will analyze this data to improve our understanding of the natural processes and human activities that regulate the abundance and distribution of this important atmospheric gas. To learn more about OCO-2, visit http://oco.jpl.nasa.gov. Photo credit: NASA/Mark Mackley, 30th Space Wing

OCO-2 Booster on Stand

NASA Image and Video Library

2014-03-28

VANDENBERG AIR FORCE BASE, Calif. – The United Launch Alliance Delta II rocket for NASA's Orbiting Carbon Observatory-2 mission, or OCO-2, is lifted into a vertical position beside the mobile service tower at Space Launch Complex 2 on Vandenberg Air Force Base in California. Launch is scheduled for July 2014. The observatory will collect precise global measurements of carbon dioxide in the Earth's atmosphere and provide scientists with a better idea of the chemical compound's impacts on climate change. Scientists will analyze this data to improve our understanding of the natural processes and human activities that regulate the abundance and distribution of this important atmospheric gas. To learn more about OCO-2, visit http://oco.jpl.nasa.gov. Photo credit: NASA/Randy Beaudoin

KSC-2014-2401

NASA Image and Video Library

2014-03-28

VANDENBERG AIR FORCE BASE, Calif. – The United Launch Alliance Delta II rocket for NASA's Orbiting Carbon Observatory-2 mission, or OCO-2, is lifted into a vertical position beside the mobile service tower at Space Launch Complex 2 on Vandenberg Air Force Base in California. Launch is scheduled for July 1, 2014. The observatory will collect precise global measurements of carbon dioxide in the Earth's atmosphere and provide scientists with a better idea of the chemical compound's impacts on climate change. Scientists will analyze this data to improve our understanding of the natural processes and human activities that regulate the abundance and distribution of this important atmospheric gas. To learn more about OCO-2, visit http://oco.jpl.nasa.gov. Photo credit: NASA/Mark Mackley, 30th Space Wing

OCO-2 Booster on Stand

NASA Image and Video Library

2014-03-28

VANDENBERG AIR FORCE BASE, Calif. – The United Launch Alliance Delta II rocket for NASA's Orbiting Carbon Observatory-2 mission, or OCO-2, hangs in a vertical position beside the mobile service tower at Space Launch Complex 2 on Vandenberg Air Force Base in California. Launch is scheduled for July 2014. The observatory will collect precise global measurements of carbon dioxide in the Earth's atmosphere and provide scientists with a better idea of the chemical compound's impacts on climate change. Scientists will analyze this data to improve our understanding of the natural processes and human activities that regulate the abundance and distribution of this important atmospheric gas. To learn more about OCO-2, visit http://oco.jpl.nasa.gov. Photo credit: NASA/Randy Beaudoin

Lyapunov stability analysis for the generalized Kapitza pendulum

NASA Astrophysics Data System (ADS)

Druzhinina, O. V.; Sevastianov, L. A.; Vasilyev, S. A.; Vasilyeva, D. G.

2017-12-01

In this work generalization of Kapitza pendulum whose suspension point moves in the vertical and horizontal planes is made. Lyapunov stability analysis of the motion for this pendulum subjected to excitation of periodic driving forces and stochastic driving forces that act in the vertical and horizontal planes has been studied. The numerical study of the random motion for generalized Kapitza pendulum under stochastic driving forces has made. It is shown the existence of stable quasi-periodic motion for this pendulum.

Vertical Force-deflection Characteristics of a Pair of 56-inch-diameter Aircraft Tires from Static and Drop Tests with and Without Prerotation

NASA Technical Reports Server (NTRS)

Smiley, Robert F; Horne, Walter B

1957-01-01

The vertical force-deflection characteristics were experimentally determined for a pair of 56-inch-diameter tires under static and drop-test conditions with and without prerotation. For increasing force, the tires were found to be least stiff for static tests, almost the same as for the static case for prerotation drop tests as long as the tires remain rotating, and appreciably stiffer for drop tests without prerotation.

Three-dimensional force measurements with mandibular overdentures connected to implants by ball-shaped retentive anchors. A clinical study.

PubMed

Mericske-Stern, R

1998-01-01

The purpose of this in vivo study was to determine maximum and functional forces simultaneously in three dimensions on mandibular implants supporting overdentures. The anchorage system for overdenture connection was the ball-shaped retentive anchor. Five edentulous patients, each with two mandibular ITI implants, were selected as test subjects. A novel miniaturized piezo-electric force transducer was developed for specific use with ITI implants. Force magnitudes and directions were registered under various test conditions by means of electrostatic plotter records. The test modalities were maximum biting in centric occlusion, maximum biting on a bite plate, grinding, and chewing bread. Maximum forces measured in centric occlusion and on the ipsilateral implant when using a bite plate were slightly increased in vertical and backward-forward dimension (z-, y-axis) compared to the lateral-medial direction (x-axis). On the contralateral implant, equally low values were found in all three dimensions. This may be the effect of a nonsplinted anchorage device. With the use of a bite plate, force magnitudes on the ipsilateral implant were significantly higher on the z- and y-axis than mean maximum forces in centric occlusion (P < .001). Chewing and grinding resulted in lower forces compared to maximum biting, particularly in the vertical direction. The transverse force component in backward-forward direction, however, reached magnitudes that exceeded the vertical component by 100% to 300% during chewing function. This chewing pattern had not been observed in previous investigations with bars and telescopes, and therefore appears to be specific for retentive ball anchors. The prevalent or exclusive force direction registered on both implants in the vertical direction was downward under all test conditions. In the transverse direction during maximum biting the forward direction was more frequently registered, while no obvious prevalence of transverse force direction was observed during chewing and grinding.

Sarcopenia Is Negatively Related to High Gravitational Impacts Achieved From Day-to-day Physical Activity

PubMed Central

Hartley, April; Gregson, Celia L; Hannam, Kimberly; Deere, Kevin C; Clark, Emma M; Tobias, Jon H

2018-01-01

Abstract Background Sarcopenia has been associated with reduced physical activity (PA). We aimed to determine if sarcopenia, and specific components of muscle size, function, and physical performance, are associated with high impacts achieved during habitual PA, as these are related to bone strength in community-dwelling older women. Methods Participants were older women from the Cohort of Skeletal Health in Bristol and Avon. We defined sarcopenia using the EWGSOP criteria. Lower limb peak muscle power and force were assessed using Jumping Mechanography (JM). High vertical impacts were assessed by tri-axial accelerometry (at least 1.5g above gravity). Cross-sectional associations were analyzed by linear regression, adjusting for age, height and weight (or fat mass for models including appendicular lean mass index), comorbidities, smoking, alcohol, and Index of Multiple Deprivation. Results Our analyses included 380 participants, with mean age 76.7 (SD 3.0) years; 242 (64%) also completed JM. In age-adjusted analysis, a negative relationship was observed between severity of sarcopenia and high, but not medium or low, impacts (p = .03 for trend). Regarding components of sarcopenia underlying this relationship, multivariable analyses revealed that gait speed (β 1.47 [95% CI 1.14, 1.89], [β-1] reflects the proportionate increase in high impacts per SD increase in exposure) and peak force (1.40 [1.07, 1.84]) were independently associated with high impacts. Conclusions Older women with sarcopenia experienced fewer bone-strengthening high impacts than those with presarcopenia or without sarcopenia. To increase bone strengthening activity in older women, interventions need to improve both lower limb muscle force and walking speed. PMID:29182712

Model space exploration for determining landslide source history from long period seismic data

NASA Astrophysics Data System (ADS)

Zhao, Juan; Mangeney, Anne; Stutzmann, Eléonore; Capdeville, Yann; Moretti, Laurent; Calder, Eliza S.; Smith, Patrick J.; Cole, Paul; Le Friant, Anne

2013-04-01

The seismic signals generated by high magnitude landslide events can be recorded at remote stations, which provides access to the landslide process. During the "Boxing Day" eruption at Montserrat in 1997, the long period seismic signals generated by the debris avalanche are recorded by two stations at distances of 450 km and 1261 km. We investigate the landslide process considering that the landslide source can be described by single forces. The period band 25-50 sec is selected for which the landslide signal is clearly visible at the two stations. We first use the transverse component of the closest station to determine the horizontal forces. We model the seismogram by normal mode summation and investigate the model space. Two horizontal forces are found that best fit the data. These two horizontal forces have similar amplitude, but opposite direction and they are separated in time by 70 sec. The radiation pattern of the transverse component does not enable to determine the exact azimuth of these forces. We then model the vertical component of the seismograms which enable to retrieve both the vertical and horizontal forces. Using the parameter previously determined (amplitude ratio and time shift of the 2 horizontal forces), we further investigate the model space and show that a single vertical force together with the 2 horizontal forces enable to fit the data. The complete source time function can be described as follows: a horizontal force toward the opposite direction of the landslide flow is followed 40 sec later by a vertical downward force and 30 more seconds later by a horizontal force toward the direction of the flow. Inverting directly the seismograms in the period band 25-50sec enable to retrieve a source time function that is consistent with the 3 forces determined previously. The source time function in this narrow period band alone does not enable easily to recover the corresponding single forces. This method can be used to determine the source parameters using only 2 distant stations. It is successfully tested also on Mount St. Helens (1980) event which are recorded by more broadband stations.

Equatorial waves in a stratospheric GCM: Effects of vertical resolution. [GCM (general circulation model)

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

Boville, B.A.; Randel, W.J.

1992-05-01

Equatorially trapped wave modes, such as Kelvin and mixed Rossby-gravity waves, are believed to play a crucial role in forcing the quasi-biennial oscillation (QBO) of the lower tropical stratosphere. This study examines the ability of a general circulation model (GCM) to simulate these waves and investigates the changes in the wave properties as a function of the vertical resolution of the model. The simulations produce a stratopause-level semiannual oscillation but not a QBO. An unfortunate property of the equatorially trapped waves is that they tend to have small vertical wavelengths ([le] 15 km). Some of the waves, believed to bemore » important in forcing the QBO, have wavelengths as short as 4 km. The short vertical wavelengths pose a stringent computational requirement for numerical models whose vertical grid spacing is typically chosen based on the requirements for simulating extratropical Rossby waves (which have much longer vertical wavelengths). This study examines the dependence of the equatorial wave simulation of vertical resolution using three experiments with vertical grid spacings of approximately 2.8, 1.4, and 0.7 km. Several Kelvin, mixed Rossby-gravity, and 0.7 km. Several Kelvin, mixed Rossby-gravity, and inertio-gravity waves are identified in the simulations. At high vertical resolution, the simulated waves are shown to correspond fairly well to the available observations. The properties of the relatively slow (and vertically short) waves believed to play a role in the QBO vary significantly with vertical resolution. Vertical grid spacings of about 1 km or less appear to be required to represent these waves adequately. The simulated wave amplitudes are at least as large as observed, and the waves are absorbed in the lower stratosphere, as required in order to force the QBO. However, the EP flux divergence associated with the waves is not sufficient to explain the zonal flow accelerations found in the QBO. 39 refs., 17 figs., 1 tab.« less

Optimal flapping wing for maximum vertical aerodynamic force in hover: twisted or flat?

PubMed

Phan, Hoang Vu; Truong, Quang Tri; Au, Thi Kim Loan; Park, Hoon Cheol

2016-07-08

This work presents a parametric study, using the unsteady blade element theory, to investigate the role of twist in a hovering flapping wing. For the investigation, a flapping-wing system was developed to create a wing motion of large flapping amplitude. Three-dimensional kinematics of a passively twisted wing, which is capable of creating a linearly variable geometric angle of attack (AoA) along the wingspan, was measured during the flapping motion and used for the analysis. Several negative twist or wash-out configurations with different values of twist angle, which is defined as the difference in the average geometric AoAs at the wing root and the wing tip, were obtained from the measured wing kinematics through linear interpolation and extrapolation. The aerodynamic force generation and aerodynamic power consumption of these twisted wings were obtained and compared with those of flat wings. For the same aerodynamic power consumption, the vertical aerodynamic forces produced by the negatively twisted wings are approximately 10%-20% less than those produced by the flat wings. However, these twisted wings require approximately 1%-6% more power than flat wings to produce the same vertical force. In addition, the maximum-force-producing twisted wing, which was found to be the positive twist or wash-in configuration, was used for comparison with the maximum-force-producing flat wing. The results revealed that the vertical aerodynamic force and aerodynamic power consumption of the two types of wings are almost identical for the hovering condition. The power loading of the positively twisted wing is only approximately 2% higher than that of the maximum-force-producing flat wing. Thus, the flat wing with proper wing kinematics (or wing rotation) can be regarded as a simple and efficient candidate for the development of hovering flapping-wing micro air vehicle.

Dynamic investigation of a locomotive with effect of gear transmissions under tractive conditions

NASA Astrophysics Data System (ADS)

Chen, Zaigang; Zhai, Wanming; Wang, Kaiyun

2017-11-01

Locomotive is used to drag trailers to move or supply the braking forces to slow the running speed of a train. The electromagnetic torque of the motor is always transmitted by the gear transmission system to the wheelset for generation of the tractive or braking forces at the wheel-rail contact interface. Consequently, gear transmission system is significant for power delivery of a locomotive. This paper develops a comprehensive locomotive-track vertical-longitudinal coupled dynamics model with dynamic effect of gear transmissions. This dynamics model enables considering the coupling interactions between the gear transmission motion, the vertical and the longitudinal motions of the vehicle, and the vertical vibration of the track structure. In this study, some complicated dynamic excitations, such as the gear time-varying mesh stiffness, nonlinear gear tooth backlash, the nonlinear wheel-rail normal contact force and creep force, and the rail vertical geometrical irregularity, are considered. Then, the dynamic responses of the locomotive under the tractive conditions are demonstrated by numerical simulations based on the established dynamics model and by experimental test. The developed dynamics model is validated by the good agreement between the experimental and the theoretical results. The calculated results reveal that the gear transmission system has strong dynamic interactions with the wheel-rail contact interface including both the vertical and the longitudinal motions, and it has negligible effect on the vibrations of the bogie frame and carbody.

Dynamics of the liquid film around elongated bubbles rising in vertical capillaries

NASA Astrophysics Data System (ADS)

Magnini, Mirco; Khodaparast, Sepideh; Matar, Omar K.; Stone, Howard A.; Thome, John R.

2017-11-01

We performed a theoretical, numerical and experimental study on elongated bubbles rising in vertical tubes in co-current liquid flows. The flow conditions were characterized by capillary, Reynolds and Bond numbers within the range of Ca = 0.005 - 0.1 , Re = 1 - 2000 and Bo = 0 - 20 . Direct numerical simulations of the two-phase flows are run with a self-improved version of OpenFOAM, implementing a coupled Level Set and Volume of Fluid method. A theoretical model based on an extension of the traditional Bretherton theory, accounting for inertia and the gravity force, is developed to obtain predictions of the profiles of the front and rear menisci of the bubble, liquid film thickness and bubble velocity. Different from the traditional theory for bubbles rising in a stagnant liquid, the gravity force impacts the flow already when Bo < 4 . Gravity effects speed up the bubble compared to the Bo = 0 case, making the liquid film thicker and reducing the amplitude of the undulation on the surface of the bubble near its tail. Gravity effects are more apparent in the visco-capillary regime, i.e. when the Reynolds number is below 1.

Sit-to-stand ground reaction force characteristics in blind and sighted female children.

PubMed

Faraji Aylar, Mozhgan; Jafarnezhadgero, Amir Ali; Salari Esker, Fatemeh

2018-03-05

The association between visual sensory and sit-to-stand ground reaction force characteristics is not clear. Impulse is the amount of force applied over a period of time. Also, free moment represents the vertical moment applied in the center of pressure (COP). How the ground reaction force components, vertical loading rate, impulses and free moment respond to long and short term restricted visual information? Fifteen female children with congenital blindness and 45 healthy girls with no visual impairments participated in this study. The girls with congenital blindness were placed in one group and the 45 girls with no visual impairments were randomly divided into three groups of 15; eyes open, permanently eyes closed, and temporary eyes closed. The participants in the permanently eyes closed group closed their eyes for 20 min before the test, whereas temporary eyes closed group did tests with their eyes closed throughout, and those in the eyes open group kept their eyes open. Congenital blindness was associated with increased vertical loading rate, range of motion of knee and hip in the medio-lateral plane. Also, medio-lateral and vertical ground reaction force impulses. Similar peak negative and positive free moments were observed in three groups. In conclusion, the results reveal that sit-to-stand ground reaction force components in blind children may have clinical importance for improvement of balance control of these individuals. Copyright © 2018 Elsevier B.V. All rights reserved.

Multiple sclerosis affects the frequency content in the vertical ground reaction forces during walking.

PubMed

Wurdeman, Shane R; Huisinga, Jessie M; Filipi, Mary; Stergiou, Nicholas

2011-02-01

Multiple sclerosis is a progressive neurological disease that results in a high incident of gait disturbance. Exploring the frequency content of the ground reaction forces generated during walking may provide additional insights to gait in patients with multiple sclerosis that could lead to specific tools for differential diagnosis. The purpose of this study was to investigate differences in the frequency content of these forces in an effort to contribute to improved clinical management of this disease. Eighteen patients and eighteen healthy controls walked across a 10 meter long walkway. The anterior-posterior and vertical ground reaction forces generated during the stance phase of gait were evaluated in the frequency domain using fast Fourier transformation. T-tests were utilized for comparison of median frequency, the 99.5% frequency, and the frequency bandwidth between patients and healthy controls and also for comparisons between patients with mild and moderate severity. Patients with multiple sclerosis had significantly lower 99.5% frequency (P=0.006) and median frequency (P<0.001) in the vertical ground reaction force. No differences were found in the anterior-posterior reaction force frequency content. There were no differences between patients with mild and moderate severity. The lower frequency content suggests lesser vertical oscillation of the center of gravity. Lack of differences between severities may suggest presence of differences prior to currently established diagnosis timelines. Analysis of the frequency content may potentially serve to provide earlier diagnostic assessment of this debilitating disease. Copyright © 2010 Elsevier Ltd. All rights reserved.

A Comparison of Accelerometers for Predicting Energy Expenditure and Vertical Ground Reaction Force in School-Age Children

ERIC Educational Resources Information Center

Garcia, Anne W.; Langenthal, Carla R.; Angulo-Barroso, Rosa M.; Gross, M. Melissa

2004-01-01

In this pilot study of 16 children, we evaluated the reliability and validity of three accelerometers (Mini-Motionlogger [MML], Computer Science Applications, Inc. Actigraph [CSA], and BioTrainer) as indicators of energy expenditure and vertical ground reaction force. The children wore 2 of each type of monitor while they walked, ran, and…

Vertical force and wrist deviation angle when using a walker to stand up and sit down.

PubMed

Leung, Cherng-Yee; Yeh, Po-Chan

2011-08-01

Research investigating walkers suggests that safety and assistance for the elderly with weak lower limbs were important. However, the relationship between the use of a walker and the upper limbs has received little investigation. Standing up and sitting down are important daily activities. Therefore, the aim of this study was to explore wrist deviation and vertical force among elderly individuals using a walker for assistance to stand up and sit down. In total, 64 elderly volunteers (M age = 80.22, SD = 9.36) were enrolled. Data were obtained from four load cells and a twin-axis wrist goniometer. Wrist deviation and vertical force were examined when participants used a walker with horizontal handles to assist in standing up and sitting down. Significant wrist angle deviation occurred with the use of a walker, with dorsiflexion of the right hand greater than that of the left. Males exerted significantly greater vertical force. In the sitting position, greater ulnar deviation was seen among experienced walker users, whereas during standing, experienced users exhibited greater dorsiflexion. The horizontal handles of most marketed walkers may cause user wrist deviations, suggesting researchers should pursue improvements in walker design.

Decoding the Vertical Phase Separation and Its Impact on C8-BTBT/PS Transistor Properties.

PubMed

Pérez-Rodríguez, Ana; Temiño, Inés; Ocal, Carmen; Mas-Torrent, Marta; Barrena, Esther

2018-02-28

Disentangling the details of the vertical distribution of small semiconductor molecules blended with polystyrene (PS) and the contact properties are issues of fundamental value for designing strategies to optimize small-molecule:polymer blend organic transistors. These questions are addressed here for ultrathin blends of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) and PS processed by a solution-shearing technique using three different blend composition ratios. We show that friction force microscopy (FFM) allows the determination of the lateral and vertical distribution of the two materials at the nanoscale. Our results demonstrate a three-layer stratification of the blend: a film of C8-BTBT of few molecular layers with crystalline order sandwiched between a PS-rich layer at the bottom (a few nm thick) acting as a passivating dielectric layer and a PS-rich skin layer on the top (∼1 nm) conferring stability to the devices. Kelvin probe force microscopy (KPFM) measurements performed in operating organic field-effect transistors (OFETs) reveal that the devices are strongly contact-limited and suggest contact doping as a route for device optimization. By excluding the effect of the contacts, field-effect mobility values in the channel as high as 10 cm 2 V -1 s -1 are obtained. Our findings, obtained via a combination of FFM and KPFM, provide a satisfactory explanation of the different electrical performances of the OFETs as a function of the blend composition ratio and by doping the contacts.

The role of the meridional sea surface temperature gradient in controlling the Caribbean low-level jet

NASA Astrophysics Data System (ADS)

Maldonado, Tito; Rutgersson, Anna; Caballero, Rodrigo; Pausata, Francesco S. R.; Alfaro, Eric; Amador, Jorge

2017-06-01

The Caribbean low-level jet (CLLJ) is an important modulator of regional climate, especially precipitation, in the Caribbean and Central America. Previous work has inferred, due to their semiannual cycle, an association between CLLJ strength and meridional sea surface temperature (SST) gradients in the Caribbean Sea, suggesting that the SST gradients may control the intensity and vertical shear of the CLLJ. In addition, both the horizontal and vertical structure of the jet have been related to topographic effects via interaction with the mountains in Northern South America (NSA), including funneling effects and changes in the meridional geopotential gradient. Here we test these hypotheses, using an atmospheric general circulation model to perform a set of sensitivity experiments to examine the impact of both SST gradients and topography on the CLLJ. In one sensitivity experiment, we remove the meridional SST gradient over the Caribbean Sea and in the other, we flatten the mountains over NSA. Our results show that the SST gradient and topography have little or no impact on the jet intensity, vertical, and horizontal wind shears, contrary to previous works. However, our findings do not discount a possible one-way coupling between the SST and the wind over the Caribbean Sea through friction force. We also examined an alternative approach based on barotropic instability to understand the CLLJ intensity, vertical, and horizontal wind shears. Our results show that the current hypothesis about the CLLJ must be reviewed in order to fully understand the atmospheric dynamics governing the Caribbean region.

Dynamic Torque and Vertical Force Analysis during Nickel-titanium Rotary Root Canal Preparation with Different Modes of Reciprocal Rotation.

PubMed

Tokita, Daisuke; Ebihara, Arata; Nishijo, Miki; Miyara, Kana; Okiji, Takashi

2017-10-01

The purpose of the present study was to compare 2 modes of reciprocal movement (torque-sensitive and time-dependent reciprocal rotation) with continuous rotation in terms of torque and apical force generation during nickel-titanium rotary root canal instrumentation. A custom-made automated root canal instrumentation and torque/force analyzing device was used to prepare simulated canals in resin blocks and monitor the torque and apical force generated in the blocks during preparation. Experimental groups (n = 7, each) consisted of (1) torque-sensitive reciprocal rotation with torque-sensitive vertical movement (group TqR), (2) time-dependent reciprocal rotation with time-dependent vertical movement (group TmR), and (3) continuous rotation with time-dependent vertical movement (group CR). The canals were instrumented with TF Adaptive SM1 and SM2 rotary files (SybronEndo, Orange, CA), and the torque and apical force were measured during instrumentation with SM2. The mean and maximum torque and apical force values were statistically analyzed using 1-way analysis of variance and the Tukey test (α = 0.05). The recordings showed intermittent increases of upward apical force and clockwise torque, indicating the generation and release of screw-in forces. The maximum upward apical force values in group TmR were significantly smaller than those in group CR (P < .05). The maximum torque values in clockwise and counterclockwise directions in groups TqR and TmR were significantly smaller than those in group CR (P < .05). Under the present experimental conditions using TF Adaptive instruments, both torque-sensitive and time-dependent reciprocal rotation generated significantly lower maximum torque and may have advantages in reducing stress generation caused by screw-in forces when compared with continuous rotation. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Modeling equine race surface vertical mechanical behaviors in a musculoskeletal modeling environment.

PubMed

Symons, Jennifer E; Fyhrie, David P; Hawkins, David A; Upadhyaya, Shrinivasa K; Stover, Susan M

2015-02-26

Race surfaces have been associated with the incidence of racehorse musculoskeletal injury, the leading cause of racehorse attrition. Optimal race surface mechanical behaviors that minimize injury risk are unknown. Computational models are an economical method to determine optimal mechanical behaviors. Previously developed equine musculoskeletal models utilized ground reaction floor models designed to simulate a stiff, smooth floor appropriate for a human gait laboratory. Our objective was to develop a computational race surface model (two force-displacement functions, one linear and one nonlinear) that reproduced experimental race surface mechanical behaviors for incorporation in equine musculoskeletal models. Soil impact tests were simulated in a musculoskeletal modeling environment and compared to experimental force and displacement data collected during initial and repeat impacts at two racetracks with differing race surfaces - (i) dirt and (ii) synthetic. Best-fit model coefficients (7 total) were compared between surface types and initial and repeat impacts using a mixed model ANCOVA. Model simulation results closely matched empirical force, displacement and velocity data (Mean R(2)=0.930-0.997). Many model coefficients were statistically different between surface types and impacts. Principal component analysis of model coefficients showed systematic differences based on surface type and impact. In the future, the race surface model may be used in conjunction with previously developed the equine musculoskeletal models to understand the effects of race surface mechanical behaviors on limb dynamics, and determine race surface mechanical behaviors that reduce the incidence of racehorse musculoskeletal injury through modulation of limb dynamics. Copyright © 2015 Elsevier Ltd. All rights reserved.

Vertical Distribution of Radiation Stress for Non-linear Shoaling Waves

NASA Astrophysics Data System (ADS)

Webb, B. M.; Slinn, D. N.

2004-12-01

The flux of momentum directed shoreward by an incident wave field, commonly referred to as the radiation stress, plays a significant role in nearshore circulation and, therefore, has a profound impact on the transport of pollutants, biota, and sediment in nearshore systems. Having received much attention since the seminal work of Longuet-Higgins and Stewart in the early 1960's, use of the radiation stress concept continues to be refined and evidence of its utility is widespread in literature pertaining to coastal and ocean science. A number of investigations, both numerical and analytical in nature, have used the concept of the radiation stress to derive appropriate forcing mechanisms that initiate cross-shore and longshore circulation, but typically in a depth-averaged sense due to a lack of information concerning the vertical distribution of the wave stresses. While depth-averaged nearshore circulation models are still widely used today, advancements in technology have permitted the adaptation of three-dimensional (3D) modeling techniques to study flow properties of complex nearshore circulation systems. It has been shown that the resulting circulation in these 3D models is very sensitive to the vertical distribution of the nearshore forcing, which have often been implemented as either depth-uniform or depth-linear distributions. Recently, analytical expressions describing the vertical structure of radiation stress components have appeared in the literature (see Mellor, 2003; Xia et al., 2004) but do not fully describe the magnitude and structure in the region bound by the trough and crest of non-linear, propagating waves. Utilizing a three-dimensional, non-linear, numerical model that resolves the time-dependent free surface, we present mean flow properties resulting from a simulation of Visser's (1984, 1991) laboratory experiment on uniform longshore currents. More specifically, we provide information regarding the vertical distribution of radiation stress components (Sxx and Sxy) resulting from obliquely incident, non-linear shoaling waves. Vertical profiles of the radiation stress components predicted by the numerical model are compared with published analytical solutions, expressions given by linear theory, and observations from an investigation employing second-order cnoidal wave theory.

The Coupled Mars Dust and Water Cycles: Understanding How Clouds Affect the Vertical Distribution and Meridional Transport of Dust and Water.

NASA Technical Reports Server (NTRS)

Kahre, M. A.

2015-01-01

The dust and water cycles are crucial to the current Martian climate, and they are coupled through cloud formation. Dust strongly impacts the thermal structure of the atmosphere and thus greatly affects atmospheric circulation, while clouds provide radiative forcing and control the hemispheric exchange of water through the modification of the vertical distributions of water and dust. Recent improvements in the quality and sophistication of both observations and climate models allow for a more comprehensive understanding of how the interaction between the dust and water cycles (through cloud formation) affects the dust and water cycles individually. We focus here on the effects of clouds on the vertical distribution of dust and water, and how those vertical distributions control the net meridional transport of water. For this study, we utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) combined with the NASA ARC Mars Global Climate Model (MGCM). We demonstrate that the magnitude and nature of the net meridional transport of water between the northern and southern hemispheres during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. We further examine how clouds influence the atmospheric thermal structure and thus the vertical structure of the cloud belt. Our goal is to identify and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

The Mars Dust and Water Cycles: Investigating the Influence of Clouds on the Vertical Distribution and Meridional Transport of Dust and Water.

NASA Technical Reports Server (NTRS)

Kahre, M. A.; Haberle, R. M.; Hollingsworth, J. L.; Brecht, A. S.; Urata, R.

2015-01-01

The dust and water cycles are critical to the current Martian climate, and they interact with each other through cloud formation. Dust modulates the thermal structure of the atmosphere and thus greatly influences atmospheric circulation. Clouds provide radiative forcing and control the net hemispheric transport of water through the alteration of the vertical distributions of water and dust. Recent advancements in the quality and sophistication of both climate models and observations enable an increased understanding of how the coupling between the dust and water cycles (through cloud formation) impacts the dust and water cycles. We focus here on the effects of clouds on the vertical distributions of dust and water and how those vertical distributions control the net meridional transport of water. We utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) and the NASA ARC Mars Global Climate Model (MGCM) to show that the magnitude and nature of the hemispheric exchange of water during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. Further, we investigate how clouds influence atmospheric temperatures and thus the vertical structure of the cloud belt. Our goal is to isolate and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

The Mars Dust and Water Cycles: Investigating the Influence of Clouds on the Vertical Distribution and Meridional Transport of Dust and Water

NASA Astrophysics Data System (ADS)

Kahre, Melinda A.; Haberle, Robert M.; Hollingsworth, Jeffery L.; Brecht, Amanda S.; Urata, Richard A.

2015-11-01

The dust and water cycles are critical to the current Martian climate, and they interact with each other through cloud formation. Dust modulates the thermal structure of the atmosphere and thus greatly influences atmospheric circulation. Clouds provide radiative forcing and control the net hemispheric transport of water through the alteration of the vertical distributions of water and dust. Recent advancements in the quality and sophistication of both climate models and observations enable an increased understanding of how the coupling between the dust and water cycles (through cloud formation) impacts the dust and water cycles. We focus here on the effects of clouds on the vertical distributions of dust and water and how those vertical distributions control the net meridional transport of water. We utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) and the NASA ARC Mars Global Climate Model (MGCM) to show that the magnitude and nature of the hemispheric exchange of water during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. Further, we investigate how clouds influence atmospheric temperatures and thus the vertical structure of the cloud belt. Our goal is to isolate and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

Rare Occurrence of the Left Maxillary Horizontal Third Molar Impaction, the Right Maxillary Third Molar Vertical Impaction and the Left Mandibular Third Molar Vertical Impaction with Inferior Alveolar Nerve Proximity in a 30 Year Old Female: A Case Report.

PubMed

Shunmugavelu, Karthik

2017-01-01

A combination of horizontal and vertical third molar impaction is a rare occurrence.When the tooth is unable to erupt to its proper position and fail to achieve a normal occlusion, it is known as impacted tooth. In this scientific article, case report of a female patient aged 30 years reported with acombination of horizontally and vertically impacted third molars in the maxilla and mandible has been presented. The treatment included surgical removal of the impacted teeth without any damage to underlying structures. Horizontal impaction of left maxillary third molar, vertical impaction of right maxillary third molar and left mandibular third molar is a rare occurrence. If symptomatic, surgical removal has to be planned as earlier as possible rather than late complications.

Development of a metrological atomic force microscope with a tip-tilting mechanism for 3D nanometrology

NASA Astrophysics Data System (ADS)

Kizu, Ryosuke; Misumi, Ichiko; Hirai, Akiko; Kinoshita, Kazuto; Gonda, Satoshi

2018-07-01

A metrological atomic force microscope with a tip-tilting mechanism (tilting-mAFM) has been developed to expand the capabilities of 3D nanometrology, particularly for high-resolution topography measurements at the surfaces of vertical sidewalls and for traceable measurements of nanodevice linewidth. In the tilting-mAFM, the probe tip is tilted from vertical to 16° at maximum such that the probe tip can touch and trace the vertical sidewall of a nanometer-scale structure; the probe of a conventional atomic force microscope cannot reach the vertical surface because of its finite cone angle. Probe displacement is monitored in three axes by using high-resolution laser interferometry, which is traceable to the SI unit of length. A central-symmetric 3D scanner with a parallel spring structure allows probe scanning with extremely low interaxial crosstalk. A unique technique for scanning vertical sidewalls was also developed and applied. The experimental results indicated high repeatability in the scanned profiles and sidewall angle measurements. Moreover, the 3D measurement of a line pattern was demonstrated, and the data from both sidewalls were successfully stitched together with subnanometer accuracy. Finally, the critical dimension of the line pattern was obtained.

Dynamic properties of a dirt and a synthetic equine racetrack surface measured by a track-testing device.

PubMed

Setterbo, J J; Fyhrie, P B; Hubbard, M; Upadhyaya, S K; Stover, S M

2013-01-01

Racetrack surface is a risk factor for Thoroughbred racehorse injury and death that can be engineered and managed. To investigate the relationship between surface and injury, the mechanical behaviour of dirt and synthetic track surfaces must be quantified. To compare dynamic properties of a dirt and a synthetic surface in situ using a track-testing device designed to simulate equine hoof impact; and to determine the effects of impact velocity, impact angle and repeated impact on dynamic surface behaviour. A track-testing device measured force and displacement during impact into a dirt and a synthetic surface at 3 impact velocities (1.91, 2.30, 2.63 m/s), 2 impact angles (0°, 20° from vertical), and 2 consecutive impacts (initial, repeat). Surfaces were measured at 3 locations/day for 3 days. The effects of surface type, impact velocity, impact angle and impact number on dynamic surface properties were assessed using analysis of variance. Synthetic surface maximum forces, load rates and stiffnesses were 37-67% of dirt surface values. Surfaces were less stiff with lower impact velocities, angled impacts and initial impacts. The magnitude of differences between dirt and synthetic surfaces increased for repeat impacts and higher impact velocities. The synthetic surface was generally softer than the dirt surface. Greatly increased hardness for repeat impacts corroborates the importance of maintenance. Results at different impact velocities suggest that surface differences will persist at higher impact velocities. For both surfaces it is clearly important to prevent horse exposure to precompacted surfaces, particularly during high-speed training when the surface has already been trampled. These data should be useful in coordinating racetrack surface management with racehorse training to prevent injuries. © 2012 EVJ Ltd.

Use of an instrument sandwiched between the hoof and shoe to measure vertical ground reaction forces and three-dimensional acceleration at the walk, trot, and canter in horses.

PubMed

Kai, M; Aoki, O; Hiraga, A; Oki, H; Tokuriki, M

2000-08-01

To develop an instrument that could be sandwiched between the hoof and shoe of horses and that would reliably measure vertical ground reaction forces and three-dimensional acceleration at the walk, trot, and canter. 5 clinically sound Thoroughbreds. The recording instrument (weight, 350 g) consisted of 2 metal plates, 2 bolts, 4 load cells, and 3 accelerometers. It was mounted to the hoof with a glue-on shoe and devised to support as much load exerted by a limb as possible. The load cells and accelerometers were wired to a 16-channel transmitter, and transmitted signals were received and amplified with a telemetry receiver. The recording instrument could measure in real time the 4 components of the ground reaction force or their resultant force along with acceleration in 3 dimensions as horses walked, trotted, or cantered on a treadmill. Patterns of force-time curves recorded for consecutive strides were similar to each other and to those previously reported, using a force plate. The recording instrument developed for use in the present study allowed us to record vertical ground reaction force and acceleration in 3 dimensions in horses at the walk, trot, and canter.

Tsunami-driven gravity waves in the presence of vertically varying background and tidal wind structures

NASA Astrophysics Data System (ADS)

Laughman, B.; Fritts, D. C.; Lund, T. S.

2017-05-01

Many characteristics of tsunami-driven gravity waves (TDGWs) enable them to easily propagate into the thermosphere and ionosphere with appreciable amplitudes capable of producing detectable perturbations in electron densities and total electron content. The impact of vertically varying background and tidal wind structures on TDGW propagation is investigated with a series of idealized background wind profiles to assess the relative importance of wave reflection, critical-level approach, and dissipation. These numerical simulations employ a 2-D nonlinear anelastic finite-volume neutral atmosphere model which accounts for effects accompanying vertical gravity wave (GW) propagation such as amplitude growth with altitude. The GWs are excited by an idealized tsunami forcing with a 50 cm sea surface displacement, a 400 km horizontal wavelength, and a phase speed of 200 ms-1 consistent with previous studies of the tsunami generated by the 26 December 2004 Sumatra earthquake. Results indicate that rather than partial reflection and trapping, the dominant process governing TDGW propagation to thermospheric altitudes is refraction to larger and smaller vertical scales, resulting in respectively larger and smaller vertical group velocities and respectively reduced and increased viscous dissipation. Under all considered background wind profiles, TDGWs were able to attain ionospheric altitudes with appreciable amplitudes. Finally, evidence of nonlinear effects is observed and the conditions leading to their formation is discussed.

An experimental comparative study of the efficiency of twisted and flat flapping wings during hovering flight.

PubMed

Phan, Hoang Vu; Truong, Quang Tri; Park, Hoon Cheol

2017-04-19

This work presents a parametric study to find a proper wing configuration for achieving economical flight using unsteady blade element theory, which is based on the 3D kinematics of a flapping wing. Power loading was first considered as a performance parameter for the study. The power loadings at each wing section along the wingspan were obtained for various geometric angles of attack (AoAs) by calculating the ratios of the vertical forces generated and the power consumed by that particular wing section. The results revealed that the power loading of a negatively twisted wing could be higher than the power loading that a flat wing can have; the power loading of the negatively twisted wing was approximately 5.9% higher. Given the relatively low average geometric AoA (α A,root   ≈  44° and α A,tip   ≈  25°), the vertical force produced by the twisted wing for the highest power loading was approximately 24.4% less than that produced by the twisted wing for the strongest vertical force. Therefore, for a given wing geometry and flapping amplitude, a flapping-wing micro air vehicle required a 13.5% increase in flapping frequency to generate the same strongest cycle-average vertical force while saving about 24.3% power. However, when force 3 /power 2 and force 2 /power ratios were considered as performance indices, the twisted wings for the highest force 3 /power 2 (α A,root   ≈  43° and α A,tip   ≈  30°) and force 2 /power (α A,root   ≈  43° and α A,tip   ≈  36°) required only 6.5% and 4% increases in flapping frequency and consumed 26.2% and 25.3% less power, respectively. Thus, it is preferable to use a flapping wing operating at a high frequency using the geometric AoAs for the highest power loading, force 3 /power 2 ratio, and force 2 /power ratio over a flapping wing operating at a low frequency using a high geometric AoA with the strongest vertical force. Additionally, by considering both aerodynamic and inertial forces, this study obtained average geometric AoAs in the range of 30° to 40°, which are similar to those of a typical hovering insect's wings. Therefore, the operation of an aerodynamically uneconomical, high AoA in a hovering insect's wings during flight is explainable.

Development of a structural concept to resist impacts from multiyear ice floes, ridges, and icebergs

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

Gerwick, B.C.; Potter, R.E.; Rojansky, M.

1984-05-01

Large multi-year ice features and icebergs may have masses ranging up to 20 million tons or more and may move in the open water at speeds up to 1 knot, thus developing tremendous kinetic energy. A stepped structure concept has been developed to resist these impacts and to transfer the resultant forces and moments into the foundation thus developing a relatively high concentrated reaction force against the ice tending to spall and split it, thus causing a multi-modal failure of the ice, as well as using up kinetic energy at a relatively controlled rate. Calculated ice forces and ice failuremore » modes will be presented. The stepped structure concept is primarily applicable to production platforms in water depths of 50 to 200 meters, which are subject to impact of large ice features such as multi-year ridges, floes, and icebergs The resulting global ice loads are reduced by 50 percent or more as compared to those developed by a vertical or a steep sided structure. Overturning moments are reduced, thus reducing maxima soil bearing values. The structure itself is efficient in its use of structural materials, and is practicable for construction in prestressed reinforced concrete or steel/ concrete hybrid construction. It has acceptable draft during tow and can carry a fully outfitted deck. It is stable during all stages of installation.« less

49 CFR 179.14 - Coupler vertical restraint system.

Code of Federal Regulations, 2010 CFR

2010-10-01

... mating coupler (or simulated coupler) having only frictional vertical force resistance at the mating interface; or a mating coupler (or simulated coupler) having the capabilities described in paragraph (a) of this section; (2) The testing apparatus shall simulate the vertical coupler performance at the mating...

Drop and Flight Tests on NY-2 Landing Gears Including Measurements of Vertical Velocities at Landing

NASA Technical Reports Server (NTRS)

Peck, W D; Beard, A P

1933-01-01

This investigation was conducted to obtain quantitative information on the effectiveness of three landing gears for the NY-2 (consolidated training) airplane. The investigation consisted of static, drop, and flight tests on landing gears of the oleo-rubber-disk and the mercury rubber-chord types, and flight tests only on a landing gear of the conventional split-axle rubber-cord type. The results show that the oleo gear is the most effective of the three landing gears in minimizing impact forces and in dissipating the energy taken.

Reversible Solid Adhesion for Defense Applications

DTIC Science & Technology

2008-01-31

sensitive. Referring to Fig. 2(a), using the two closed-loop piezoelectric ( PZT ) actuators, the vertical and horizontal velocities of the...approaching/retracting contacting surfaces can be independently controlled. The displacement resolution of the vertical PZT actuator is 0.6 nm, and the total...interfacial forces are measured using the prototype custom-made capacity-type force transducer which is attached directly on the upper PZT actuator. In order

The skeletal trauma resulting from a fatal B.A.S.E jump: A case study showing the impact of landing feet-first under extreme vertical deceleration.

PubMed

Rowbotham, Samantha K; Blau, Soren; Hislop-Jambrich, Jacqueline

2018-05-01

The term 'B.A.S.E jump' refers to jumping from a building, antenna, span (i.e., bridge) or earth (i.e., cliff) structure, and parachuting to the ground. There are numerous hazards associated with B.A.S.E jumps which often result in injury and, occasionally, fatality. This case report details the skeletal trauma resulting from a fatal B.A.S.E jump in Australia. In this case, the jumper impacted the ground from a fall of 439m in a feet-first landing position, as a result of a partially deployed parachute, under extreme vertical deceleration. Skeletal trauma was analyzed using full-body post mortem computed tomography (PMCT) and contextual information related to the circumstances of the jump as reported by the Coroner. Trauma to 61 skeletal elements indicates the primary impact was to the feet (i.e., feet-first landing), followed by an anterior impact to the body (i.e., fall forwards). Details of the individual fracture morphologies indicate the various forces and biomechanics involved in this fall event. This case presents the types of fractures that result from a B.A.S.E jump, and highlights the value of using PMCT and coronial data as tools to augment skeletal trauma interpretations. Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.

Trunk Muscle Activation and Estimating Spinal Compressive Force in Rope and Harness Vertical Dance.

PubMed

Wilson, Margaret; Dai, Boyi; Zhu, Qin; Humphrey, Neil

2015-12-01

Rope and harness vertical dance takes place off the floor with the dancer suspended from his or her center of mass in a harness attached to a rope from a point overhead. Vertical dance represents a novel environment for training and performing in which expected stresses on the dancer's body are different from those that take place during dance on the floor. Two male and eleven female dancers with training in vertical dance performed six typical vertical dance movements with electromyography (EMG) electrodes placed bilaterally on rectus abdominus, external oblique, erector spinae, and latissimus dorsi. EMG data were expressed as a percentage of maximum voluntary isometric contraction (MVIC). A simplified musculoskeletal model based on muscle activation for these four muscle groups was used to estimate the compressive force on the spine. The greatest muscle activation for erector spinae and latissimus dorsi and the greatest trunk compressive forces were seen in vertical axis positions where the dancer was moving the trunk into a hyper-extended position. The greatest muscle activation for rectus abdominus and external oblique and the second highest compressive force were seen in a supine position with the arms and legs extended away from the center of mass (COM). The least muscle activation occurred in positions where the limbs were hanging below the torso. These movements also showed relatively low muscle activation compression forces. Post-test survey results revealed that dancers felt comfortable in these positions; however, observation of some positions indicated insufficient muscular control. Computing the relative contribution of muscles, expressed as muscle activation and estimated spinal compression, provided a measure of how much the muscle groups were working to support the spine and the rest of the dancer's body in the different movements tested. Additionally, identifying typical muscle recruitment patterns in each movement will help identify key exercises for training that should promote injury prevention.

External Load Affects Ground Reaction Force Parameters Non-uniformly during Running in Weightlessness

NASA Technical Reports Server (NTRS)

DeWitt, John; Schaffner, Grant; Laughlin, Mitzi; Loehr, James; Hagan, R. Donald

2004-01-01

Long-term exposure to microgravity induces detrimefits to the musculcskdetal system (Schneider et al., 1995; LeBlanc et al., 2000). Treadmill exercise is used onboard the International Space Station as an exercise countermeasure to musculoskeletal deconditioning due to spaceflight. During locomotive exercise in weightlessness (0G), crewmembers wear a harness attached to an external loading mechanism (EL). The EL pulls the crewmember toward the treadmill, and provides resistive load during the impact and propulsive phases of gait. The resulting forces may be important in stimulating bone maintenance (Turner, 1998). The EL can be applied via a bungee and carabineer clip configuration attached to the harness and can be manipulated to create varying amounts of load levels during exercise. Ground-based research performed using a vertically mounted treadmill found that peak ground reaction forces (GRF) during running at an EL of less than one body weight (BW) are less than those that occur during running in normal gravity (1G) (Davis et al., 1996). However, it is not known how the GRF are affected by the EL in a true OG environment. Locomotion while suspended may result in biomechanics that differ from free running. The purpose of this investigation was to determine how EL affects peak impact force, peak propulsive force, loading rate, and impulse of the GRF during running in 0G. It was hypothesized that increasing EL would result in increases in each GRF parameter.

Ground reaction forces on stairs. Part II: knee implant patients versus normals.

PubMed

Stacoff, Alex; Kramers-de Quervain, Inès A; Luder, Gerhard; List, Renate; Stüssi, Edgar

2007-06-01

The goal of this study was to compare selected parameters of vertical ground reaction forces (GRF) of good outcome patients with different prosthesis designs with a matched control group during level walking, stair ascent and descent. Forty subjects, 29 with three main implant designs (including four subjects with a passive knee flexion restriction), and 11 healthy controls were measured with 8-10 repetitions. Vertical ground reaction forces were measured during two consecutive steps with force plates embedded in the walkway and the staircase. Defined parameters of the force signals were used to compare the results of the test groups. The results show, that, postoperatively, good outcome patients produce gait patterns of the vertical ground reaction force which are comparable to normal healthy subjects with the exception of a few distinct differences: a significant reduction (p<0.05) in the vertical loading on the operated side during level walking at take-off, at weight acceptance and take-off during stair ascent of the normal stair. During stair descent, the patients did not reduce load on the operated side, but increased load variation and side-to-side asymmetry; thus, the mechanical loads on the implants were high, which may be important information with respect to loading protocols of knee implant simulators. No systematic differences in any of the test parameters were found between posterior cruciate-retaining (LCS MB and Innex CR) versus non-retaining (LCS RP and Innex UCOR) implant designs. The restricted group showed significant reductions (p<0.05) of several loading parameters as well as an increased side-to-side asymmetry. About one third of the force parameters of the good outcome patients showed a side-to-side asymmetry between two consecutive steps, which was over a proposed level of acceptance.

Model space exploration for determining landslide source history from long period seismic data

NASA Astrophysics Data System (ADS)

Zhao, J.; Mangeney, A.; Stutzmann, E.; Capdeville, Y.; Moretti, L.; Calder, E. S.; Smith, P. J.; Cole, P.; Le Friant, A.

2012-12-01

The seismic signals generated by high magnitude landslide events can be recorded at remote stations, which provides access to the landslide process. During the "Boxing Day" eruption at Montserrat in 1997, the long-period seismic signals generated by the debris avalanche are recorded by two stations at distances of 450km and 1261km. We investigate the landslide process considering that the landslide source can be described by single forces. The period band 25-50 sec is selected for which the landslide signal is clearly visible at the two stations. We first use the transverse component of the closest station to determine the horizontal forces. We model the seismogram by normal mode summation and investigate the model space. Two horizontal forces are found that best fit the data. These two horizontal forces have similar amplitude, but opposite direction and they are separated in time by 70 sec. The radiation pattern of the transverse component does not enable to determine the exact azimuth of these forces. We then model the vertical component of the seismograms which enable to retrieve both the vertical and horizontal forces. Using the parameter previously determined (amplitude ratio and time shift of the 2 horizontal forces), we further investigate the model space and show that a single vertical force together with the 2 horizontal forces enable to fit the data. The complete source time function can be described as follows: a horizontal force toward the opposite direction of the landslide flow is followed 40 sec later by a vertical downward force and 30 more seconds later by a horizontal force toward the direction of the flow. The volume of the landslide estimated from the force magnitude is compatible with the volume determined by field survey. Inverting directly the seismograms in the period band 25-50sec enable to retrieve a source time function that is consistent with the 3 forces determined previously. The source time function in this narrow period band alone does not enable easily to recover the corresponding single forces. This method can be used to determine the source parameters using only 2 distant stations. It is successfully tested also on other landslides such as Mount St. Helens (1980) event and Mount Steller event (2005) which are recorded by more broadband stations.

Depletion forces on circular and elliptical obstacles induced by active matter

NASA Astrophysics Data System (ADS)

Leite, L. R.; Lucena, D.; Potiguar, F. Q.; Ferreira, W. P.

2016-12-01

Depletion forces exerted by self-propelled particles on circular and elliptical passive objects are studied using numerical simulations. We show that a bath of active particles can induce repulsive and attractive forces which are sensitive to the shape and orientation of the passive objects (either horizontal or vertical ellipses). The resultant force on the passive objects due to the active particles is studied as a function of the shape and orientation of the passive objects, magnitude of the angular noise, and distance between the passive objects. By increasing the distance between obstacles the magnitude of the repulsive depletion force increases, as long as such a distance is less than one active particle diameter. For longer distances, the magnitude of the force always decreases with increasing distance. We also found that attractive forces may arise for vertical ellipses at high enough area fraction.

Vertical Magnetic Levitation Force Measurement on Single Crystal YBaCuO Bulk at Different Temperatures

NASA Astrophysics Data System (ADS)

Celik, Sukru; Guner, Sait Baris; Ozturk, Kemal; Ozturk, Ozgur

Magnetic levitation force measurements of HTS samples are performed with the use of liquid nitrogen. It is both convenient and cheap. However, the temperature of the sample cannot be changed (77 K) and there is problem of frost. So, it is necessary to build another type of system to measure the levitation force high Tc superconductor at different temperatures. In this study, we fabricated YBaCuO superconducting by top-seeding-melting-growth (TSMG) technique and measured vertical forces of them at FC (Field Cooling) and ZFC (Zero Field Cooling) regimes by using our new designed magnetic levitation force measurement system. It was used to investigate the three-dimensional levitation force and lateral force in the levitation system consisting of a cylindrical magnet and a permanent cylindrical superconductor at different temperatures (37, 47, 57, 67 and 77 K).

Depletion forces on circular and elliptical obstacles induced by active matter.

PubMed

Leite, L R; Lucena, D; Potiguar, F Q; Ferreira, W P

2016-12-01

Depletion forces exerted by self-propelled particles on circular and elliptical passive objects are studied using numerical simulations. We show that a bath of active particles can induce repulsive and attractive forces which are sensitive to the shape and orientation of the passive objects (either horizontal or vertical ellipses). The resultant force on the passive objects due to the active particles is studied as a function of the shape and orientation of the passive objects, magnitude of the angular noise, and distance between the passive objects. By increasing the distance between obstacles the magnitude of the repulsive depletion force increases, as long as such a distance is less than one active particle diameter. For longer distances, the magnitude of the force always decreases with increasing distance. We also found that attractive forces may arise for vertical ellipses at high enough area fraction.

Load redistribution in walking and trotting Beagles with induced forelimb lameness.

PubMed

Abdelhadi, Jalal; Wefstaedt, Patrick; Galindo-Zamora, Vladimir; Anders, Alexandra; Nolte, Ingo; Schilling, Nadja

2013-01-01

To evaluate the load redistribution mechanisms in walking and trotting dogs with induced forelimb lameness. 7 healthy adult Beagles. Dogs walked and trotted on an instrumented treadmill to determine control values for peak and mean vertical force as well as vertical impulse for all 4 limbs. A small sphere was attached to the ventral pad of the right forelimb paw to induce a reversible lameness, and recordings were repeated for both gaits. Additionally, footfall patterns were assessed to test for changes in temporal gait variables. During walking and trotting, peak and mean vertical force as well as vertical impulse were decreased in the ipsilateral forelimb, increased in the contralateral hind limb, and remained unchanged in the ipsilateral hind limb after lameness was induced. All 3 variables were increased in the contralateral forelimb during trotting, whereas only mean vertical force and vertical impulse were increased during walking. Stance phase duration increased in the contralateral forelimb and hind limb during walking but not during trotting. Analysis of the results suggested that compensatory load redistribution mechanisms in dogs depend on the gait. All 4 limbs should be evaluated in basic research and clinical studies to determine the effects of lameness on the entire body. Further studies are necessary to elucidate specific mechanisms for unloading of the affected limb and to determine the long-term effects of load changes in animals with chronic lameness.

The generation of tire cornering forces in aircraft with a free-swiveling nose gear

NASA Technical Reports Server (NTRS)

Daugherty, R. H.; Stubbs, S. M.

1985-01-01

An experimental investigation was conducted to study the effect of various parameters on the cornering forces produced by a rolling aircraft tire installed on a tilted, free-swiveling nose gear. The parameters studied included tilt angle, trial, tire inflation pressure, rake angle, vertical load, and whether or not a twin tire configuration corotates. These parameters were evaluated by measuring the cornering force produced by an aircraft tire installed on the nose gear of a modified vehicle as it was towed slowly. Cornering force coefficient increased with increasing tilt angle. Increasing trial or rake angle decreased the magnitude of the cornering force coefficient. Tire inflation pressure had no effect on the cornering force coefficient. Increasing vertical load decreased the cornering force coefficient. When the tires of a twin tire system rotated independently, the cornering force coefficients were the same as those for the single-tire configuration. When the twin tire system was made to corotate, however, the cornering force coefficients increased significantly.

A study of the cornering forces generated by aircraft tires on a tilted, free-swiveling nose gear

NASA Technical Reports Server (NTRS)

Daugherty, R. H.; Stubbs, S. M.

1985-01-01

An experimental investigation was conducted to study the effect of various parameters on the cornering forces produced by a rolling aircraft tire installed on a tilted, free-swiveling nose gear. The parameters studied included tilt angle, trial, tire inflation pressure, rake angle, vertical load, and whether or not a twin tire configuration corotates. These parameters were evaluated by measuring the cornering force produced by an aircraft tire installed on the nose gear of a modified vehicle as it was towed slowly. Cornering force coefficient increased with increasing tilt angle. Increasing trial or rake angle decreased the magnitude of the cornering force coefficient. Tire inflation pressure had no effect on the cornering force coefficient. Increasing vertical load decreased the cornering force coefficient. When the tires of a twin tire system rotated independently, the cornering force coefficients were the same as those for the single-tire configuration. When the twin tire system was made to corotate, however, the cornering force coefficients increased significantly.

Ground reaction forces of Olympic and World Championship race walkers.

PubMed

Hanley, Brian; Bissas, Athanassios

2016-01-01

Race walking is an Olympic event where no visible loss of contact should occur and the knee must be straightened until midstance. The purpose of this study was to analyse ground reaction forces of world-class race walkers and associate them with key spatiotemporal variables. Nineteen athletes race walked along an indoor track and made contact with two force plates (1000 Hz) while being filmed using high-speed videography (100 Hz). Race walking speed was correlated with flight time (r = .46, p = .049) and flight distance (r = .69, p = .001). The knee's movement from hyperextension to flexion during late stance meant the vertical push-off force that followed midstance was smaller than the earlier loading peak (p < .001), resulting in a flattened profile. Athletes with narrower stride widths experienced reduced peak braking forces (r = .49, p = .046), peak propulsive forces (r = .54, p = .027), peak medial forces (r = .63, p = .007) and peak vertical push-off forces (r = .60, p = .011). Lower fluctuations in speed during stance were associated with higher stride frequencies (r = .69, p = .001), and highlighted the importance of avoiding too much braking in early stance. The flattened trajectory and consequential decrease in vertical propulsion might help the race walker avoid visible loss of contact (although non-visible flight times were useful in increasing stride length), while a narrow stride width was important in reducing peak forces in all three directions and could improve movement efficiency.

Are atmospheric updrafts a key to unlocking climate forcing and sensitivity?

DOE PAGES

Donner, Leo J.; O'Brien, Travis A.; Rieger, Daniel; ...

2016-10-20

Both climate forcing and climate sensitivity persist as stubborn uncertainties limiting the extent to which climate models can provide actionable scientific scenarios for climate change. A key, explicit control on cloud–aerosol interactions, the largest uncertainty in climate forcing, is the vertical velocity of cloud-scale updrafts. Model-based studies of climate sensitivity indicate that convective entrainment, which is closely related to updraft speeds, is an important control on climate sensitivity. Updraft vertical velocities also drive many physical processes essential to numerical weather prediction. Vertical velocities and their role in atmospheric physical processes have been given very limited attention in models for climatemore » and numerical weather prediction. The relevant physical scales range down to tens of meters and are thus frequently sub-grid and require parameterization. Many state-of-science convection parameterizations provide mass fluxes without specifying Vertical velocities and their role in atmospheric physical processes have been given very limited attention in models for climate and numerical weather prediction. The relevant physical scales range down to tens of meters and are thus frequently sub-grid and require parameterization. Many state-of-science convection parameterizations provide mass fluxes without specifying vs in climate models may capture this behavior, but it has not been accounted for when parameterizing cloud and precipitation processes in current models. New observations of convective vertical velocities offer a potentially promising path toward developing process-level cloud models and parameterizations for climate and numerical weather prediction. Taking account of the scale dependence of resolved vertical velocities offers a path to matching cloud-scale physical processes and their driving dynamics more realistically, with a prospect of reduced uncertainty in both climate forcing and sensitivity.« less

Are atmospheric updrafts a key to unlocking climate forcing and sensitivity?

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

Donner, Leo J.; O'Brien, Travis A.; Rieger, Daniel

Both climate forcing and climate sensitivity persist as stubborn uncertainties limiting the extent to which climate models can provide actionable scientific scenarios for climate change. A key, explicit control on cloud–aerosol interactions, the largest uncertainty in climate forcing, is the vertical velocity of cloud-scale updrafts. Model-based studies of climate sensitivity indicate that convective entrainment, which is closely related to updraft speeds, is an important control on climate sensitivity. Updraft vertical velocities also drive many physical processes essential to numerical weather prediction. Vertical velocities and their role in atmospheric physical processes have been given very limited attention in models for climatemore » and numerical weather prediction. The relevant physical scales range down to tens of meters and are thus frequently sub-grid and require parameterization. Many state-of-science convection parameterizations provide mass fluxes without specifying Vertical velocities and their role in atmospheric physical processes have been given very limited attention in models for climate and numerical weather prediction. The relevant physical scales range down to tens of meters and are thus frequently sub-grid and require parameterization. Many state-of-science convection parameterizations provide mass fluxes without specifying vs in climate models may capture this behavior, but it has not been accounted for when parameterizing cloud and precipitation processes in current models. New observations of convective vertical velocities offer a potentially promising path toward developing process-level cloud models and parameterizations for climate and numerical weather prediction. Taking account of the scale dependence of resolved vertical velocities offers a path to matching cloud-scale physical processes and their driving dynamics more realistically, with a prospect of reduced uncertainty in both climate forcing and sensitivity.« less

Bilateral asymmetries in max effort single-leg vertical jumps.

PubMed

Stephens, Thomas M; Lawson, Brooke R; Reiser, Raoul F

2005-01-01

While asymmetries in the lower extremity during jumping may have implications during rehabilitation, it is not clear if healthy subjects should be expected to jump equivalently on each leg. Therefore, the goal of this study was to determine if asymmetries exist in maximal effort single-leg vertical jumps. After obtaining university-approved informed consent, 13 men and 12 women with competitive volleyball playing experience and no injuries of the lower-extremity that would predispose them to asymmetries participated. After thorough warm-up, five maximal effort vertical jumps with countermovement were performed on each leg (random order) with ground reaction forces and lower extremity kinematics recorded. The best three jumps from each leg were analyzed, assigning the leg with the highest jump height average as the dominant side. Asymmetry was assessed by determining statistical significance in the dominant versus non-dominant sides (p < 0.05). A significant interaction existed between side and gender for thigh length and peak vertical ground reaction force. Women had a significantly shorter thigh and men a greater peak vertical ground reaction force on their dominant side. All other parameters were assessed as whole group. Jumps were significantly greater off the dominant leg (2.8 cm on average). No other differences between sides were observed. Significant differences in magnitude (p < 0.05) existed between the men and women in jump height, several anthropometric parameters, minimum ankle and hip angles, and vertical ground reaction forces (peak and average). In conclusion, though a person may jump slightly higher on one leg relative to the other, and women may jump slightly differently than men, the magnitude of the difference should be relatively small and due to the multi-factorial nature of jump performance, individual parameters related to performance may not be consistently different.

An ocean large-eddy simulation of Langmuir circulations and convection in the surface mixed layer

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

Skyllingstad, E.D.; Denbo, D.W.

Numerical experiments were performed using a three-dimensional large-eddy simulation model of the ocean surface mixed layer that includes the Craik-Leibovich vortex force to parameterize the interaction of surface waves with mean currents. Results from the experiments show that the vortex force generates Langmuir circulations that can dominate vertical mixing. The simulated vertical velocity fields show linear, small-scale, coherent structures near the surface that extend downwind across the model domain. In the interior of the mixed layer, scales of motion increase to eddy sizes that are roughly equivalent to the mixed-layer depth. Cases with the vortex force have stronger circulations nearmore » the surface in contrast to cases with only heat flux and wind stress, particularly when the heat flux is positive. Calculations of the velocity variance and turbulence dissipation rates for cases with and without the vortex force, surface cooling, and wind stress indicate that wave-current interactions are a dominant mixing process in the upper mixed layer. Heat flux calculations show that the entrainment rate at the mixed-layer base can be up to two times greater when the vortex force is included. In a case with reduced wind stress, turbulence dissipation rates remained high near the surface because of the vortex force interaction with preexisting inertial currents. In deep mixed layers ({approximately}250 m) the simulations show that Langmuir circulations can vertically transport water 145 m during conditions of surface heating. Observations of turbulence dissipation rates and the vertical temperature structure support the model results. 42 refs., 20 figs., 21 tabs.« less

Subatomic deformation driven by vertical piezoelectricity from CdS ultrathin films.

PubMed

Wang, Xuewen; He, Xuexia; Zhu, Hongfei; Sun, Linfeng; Fu, Wei; Wang, Xingli; Hoong, Lai Chee; Wang, Hong; Zeng, Qingsheng; Zhao, Wu; Wei, Jun; Jin, Zhong; Shen, Zexiang; Liu, Jie; Zhang, Ting; Liu, Zheng

2016-07-01

Driven by the development of high-performance piezoelectric materials, actuators become an important tool for positioning objects with high accuracy down to nanometer scale, and have been used for a wide variety of equipment, such as atomic force microscopy and scanning tunneling microscopy. However, positioning at the subatomic scale is still a great challenge. Ultrathin piezoelectric materials may pave the way to positioning an object with extreme precision. Using ultrathin CdS thin films, we demonstrate vertical piezoelectricity in atomic scale (three to five space lattices). With an in situ scanning Kelvin force microscopy and single and dual ac resonance tracking piezoelectric force microscopy, the vertical piezoelectric coefficient (d 33) up to 33 pm·V(-1) was determined for the CdS ultrathin films. These findings shed light on the design of next-generation sensors and microelectromechanical devices.

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.

Mechanical energy generation and transfer in the racket arm during table tennis topspin backhands.

PubMed

Iino, Yoichi; Kojima, Takeji

2016-06-01

The ability to generate a high racket speed and a large amount of racket kinetic energy on impact is important for table tennis players. The purpose of this study was to understand how mechanical energy is generated and transferred in the racket arm during table tennis backhands. Ten male advanced right-handed table tennis players hit topspin backhands against pre-impact topspin and backspin balls. The joint kinetics at the shoulder, elbow and wrist of the racket arm was determined using inverse dynamics. A majority of the mechanical energy of the racket arm acquired during forward swing (65 and 77% against topspin and backspin, respectively) was due to energy transfer from the trunk. Energy transfer by the shoulder joint force in the vertical direction was the largest contributor to the mechanical energy of the racket arm against both spins and was greater against backspin than against topspin (34 and 28%, respectively). The shoulder joint force directed to the right, which peaked just before impact, transferred additional energy to the racket. Our results suggest that the upward thrust of the shoulder and the late timing of the axial rotation of the upper trunk are important for an effective topspin backhand.

Mechanical Alterations during 800-m Self-Paced Track Running.

PubMed

Girard, Olivier; Millet, Gregoire P; Micallef, Jean-Paul

2017-04-01

We assessed the time course of running mechanical alterations during an 800-m. On a 200-m indoor track, 18 physical education students performed an 800-m self-paced run. Once per lap, ground reaction forces were measured by a 5-m-long force platform system, and used to determine running kinetics/kinematics and spring-mass characteristics. Compared with 100 m (19.4±1.8 km.h -1 ) running velocity progressively decreased at 300, 500 m but levelled-off at 700 m marks (-5.7±4.6, -10.4±8.3, and -9.1±13.5%, respectively; P<0.001). Stride length (-8.5±2.3%, P<0.01) and frequency (-1.0±1.5%, P=0.05) along with peak braking (-7.5±4.4%, P<0.05) and push-off forces (-5.1±7.2%, P<0.05) decreased from 100 m to 700 m. Peak vertical forces (-3.0±2.7%; P>0.05) and leg compression (+2.8±3.9%; P>0.05) remained unchanged, whereas centre of mass vertical displacement (+24.0±7.0%; P<0.001) increased during the run. Vertical stiffness decreased (-18.1±4.4%; P<0.001), whereas leg stiffness was unchanged (-3.2±4.6%; P>0.05). During an 800 m by physical education students, highest running velocity was achieved early during the run, with a progressive decrease in the second half of the trial. While vertical ground force characteristics remained unchanged, non-specialist runners produced lower peak braking and push-off forces, in turn leading to shorter stride length. Spring-mass model characteristics changed toward lower vertical stiffness values, whereas leg stiffness did not change. © Georg Thieme Verlag KG Stuttgart · New York.

On the Vertical Nature of Biomass Burning Plumes by the California Coast and Their Relationship with Marine Boundary Layer Clouds

NASA Astrophysics Data System (ADS)

Hu, L.; Montzka, S. A.; Godwin, D.; Andrews, A. E.; Thoning, K. W.; Miller, B. R.; Sweeney, C.; Miller, J. B.; Lehman, S.; Siso, C.; Mondeel, D. J.; Hall, B. D.; Nance, J. D.; Tans, P. P.; Elkins, J. W.

2016-12-01

Biomass burning (BB) plumes can significantly impact stratocumulus clouds (Sc), the dominant cloud type by global area, by altering their microphysical properties. The California (CA) coast is home to one of the three major semi-permanent stratocumulus (Sc) cloud decks in the world and BB emissions are of growing concern in the western United States, owing to both a warmer climate and fire-control strategies over recent decades. The thickness and vertical position of BB plumes, especially relative to clouds, is critical to understand how the aerosol will affect the thermodynamic structure of the atmosphere, cloud properties, and radiative forcing. This study reports on the characterization of the vertical, spatial, and temporal nature of BB aerosol over coastal CA, based on airborne data collected in the months of July and August for 2013 and 2016. Results from over 100 soundings indicate that multiple BB plume layers exist above clouds, with the thickness of BB plumes and their vertical position relative to cloud top varying significantly as a function of distance from coastline. Comparison of soundings at a given location at two different times of day reveals significant variation in BB characteristics. Intercomparisons for BB plume characteristics are explored between the field data, NAAPS, and CALIPSO.

On the Vertical Nature of Biomass Burning Plumes by the California Coast and Their Relationship with Marine Boundary Layer Clouds

NASA Astrophysics Data System (ADS)

Hossein Mardi, A.; MacDonald, A. B.; Dadashazar, H.; Crosbie, E.; WANG, Z.; Lynch, P.; Campbell, J. R.; Jonsson, H.; Sorooshian, A.

2017-12-01

Biomass burning (BB) plumes can significantly impact stratocumulus clouds (Sc), the dominant cloud type by global area, by altering their microphysical properties. The California (CA) coast is home to one of the three major semi-permanent stratocumulus (Sc) cloud decks in the world and BB emissions are of growing concern in the western United States, owing to both a warmer climate and fire-control strategies over recent decades. The thickness and vertical position of BB plumes, especially relative to clouds, is critical to understand how the aerosol will affect the thermodynamic structure of the atmosphere, cloud properties, and radiative forcing. This study reports on the characterization of the vertical, spatial, and temporal nature of BB aerosol over coastal CA, based on airborne data collected in the months of July and August for 2013 and 2016. Results from over 100 soundings indicate that multiple BB plume layers exist above clouds, with the thickness of BB plumes and their vertical position relative to cloud top varying significantly as a function of distance from coastline. Comparison of soundings at a given location at two different times of day reveals significant variation in BB characteristics. Intercomparisons for BB plume characteristics are explored between the field data, NAAPS, and CALIPSO.

Comparison of JET AVDE disruption data with M3D simulations and implications for ITER

DOE PAGES

Strauss, H.; Joffrin, E.; Riccardo, V.; ...

2017-10-02

Nonlinear 3D MHD asymmetric vertical displacement disruption simulations have been performed using JET equilibrium reconstruction initial data. There were several experimentally measured quantities compared with the simulation. These include vertical displacement, halo current, toroidal current asymmetry, and toroidal rotation. The experimental data and the simulations are in reasonable agreement. Also compared was the correlation of the toroidal current asymmetry and the vertical displacement asymmetry. The Noll relation between asymmetric wall force and vertical current moment is verified in the simulations. Also verified is the toroidal flux asymmetry. Though, JET is a good predictor of ITER disruption behavior, JET and ITERmore » can be in different parameter regimes, and extrapolating from JET data can overestimate the ITER wall force.« less

Comparison of JET AVDE disruption data with M3D simulations and implications for ITER

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

Strauss, H.; Joffrin, E.; Riccardo, V.

Nonlinear 3D MHD asymmetric vertical displacement disruption simulations have been performed using JET equilibrium reconstruction initial data. There were several experimentally measured quantities compared with the simulation. These include vertical displacement, halo current, toroidal current asymmetry, and toroidal rotation. The experimental data and the simulations are in reasonable agreement. Also compared was the correlation of the toroidal current asymmetry and the vertical displacement asymmetry. The Noll relation between asymmetric wall force and vertical current moment is verified in the simulations. Also verified is the toroidal flux asymmetry. Though, JET is a good predictor of ITER disruption behavior, JET and ITERmore » can be in different parameter regimes, and extrapolating from JET data can overestimate the ITER wall force.« less

Nutations of sunflower seedlings on tilted clinostats

NASA Technical Reports Server (NTRS)

Brown, A. H.; Chapman, D. K.

1977-01-01

The kinetics of hypocotyl nutations in Helianthus annuus L. were measured on plants which were rotated on clinostats with axes of rotation inclined at various angles, alpha, away from the vertical. The g-force component acting in the direction of the plant axis was taken as g cos alpha. The average period and average amplitude of nutation were constant for all such axially directed g-forces between 1.0 and 0.2 g (vertical to about 80 inclination). On the horizontal clinostat (90 inclination) nutation was neither initiated nor sustained. The g-force just sufficient fully to activate nutational oscillations should be sought for g-force parameter values ranging from 0 to 0.2.

Can the Ocean's Heat Engine Control Horizontal Circulation? Insights From the Caspian Sea

NASA Astrophysics Data System (ADS)

Bruneau, Nicolas; Zika, Jan; Toumi, Ralf

2017-10-01

We investigate the role of the ocean's heat engine in setting horizontal circulation using a numerical model of the Caspian Sea. The Caspian Sea can be seen as a virtual laboratory—a compromise between realistic global models that are hampered by long equilibration times and idealized basin geometry models, which are not constrained by observations. We find that increases in vertical mixing drive stronger thermally direct overturning and consequent conversion of available potential to kinetic energy. Numerical solutions with water mass structures closest to observations overturn 0.02-0.04 × 106 m3/s (sverdrup) representing the first estimate of Caspian Sea overturning. Our results also suggest that the overturning is thermally forced increasing in intensity with increasing vertical diffusivity. Finally, stronger thermally direct overturning is associated with a stronger horizontal circulation in the Caspian Sea. This suggests that the ocean's heat engine can strongly impact broader horizontal circulations in the ocean.

Flight Investigation of Effect of Various Vertical-Tail Modifications on the Directional Stability and Control Characteristics of the P-63A-1 Airplane (AAF No. 42-68889)

NASA Technical Reports Server (NTRS)

Johnson, Harold I.

1946-01-01

Because the results of preliminary flight tests had indicated. the P-63A-1 airplane possessed insufficient directional stability, the NACA and the manufacturer (Bell Aircraft Corporation) suggested three vertical-tail modifications to remedy the deficiencies in the directional characteristics. These modifications included an enlarged vertical tail formed by adding a tip extension to the original vertical tail, a large sharp-edge ventral fin, and a small dorsal fin. The enlarged vertical tail involved only a slight increase in total vertical-tail area from 23.73 to 26.58 square feet but a relatively much larger increase in geometric aspect ratio from 1.24 to 1.73 based on height and area above the horizontal tail. At the request of the Air Material Command, Army Air Forces, flight tests were made to determine the effect of these modifications and of some combinations of these modifications on the directional stability and control characteristics of the airplane, In all, six different vertical-tail. configurations were investigated to determine the lateral and directional oscillation characteristics of the airplane, the sideslip characteristics, the yaw due to ailerons in rudder-fixed rolls from turns and pull-outs, the trim changes due to speed changes; and the trim changes due to power changes. Results of the tests showed that the enlarged vertical tail approximately doubled the directional stability of the airplane and that the pilots considered the directional stability provided by the enlarged vertical tail to be satisfactory. Calculations based on sideslip data obtained at an indicated airspeed of 300 miles per hour showed that the directional stability of the airplane with the original vertical tail corresponded to a value of 0(sub n beta) of -0.00056 whereas for the enlarged vertical tail the estimated va1ue of C(sub n beta) was -0.00130, The ventral fin was found to increase by a moderate amount the directional stability of the airplane with the original vertical tail for smal1 sides1ip angles at low speeds but little consistent change in directional stability was effected by the ventral fin at higher speeds, The effectiveness of the ventral fin was generally much less when used with the enlarged vertical tail than when used with the original vertical tail. The ventral and dorsal fins were found to be very effective in eliminating rudder-force reversals which occurred in low-speed, high-engine-power, sideslipped conditions of flight . Sideslip tests at two altitudes for approximately the sane engine power and indicated airspeed showed that a small decrease in static directional stability occurred with increasing altitude and this decrease in stability was attributed to the increased propeller blade angles required at high altitudes. The variations of rudder pedal force with indicated airspeed using normal rated power and a constant rudder tab setting through the speed range were desirably small for all the configurations tested. The rudder pedal force changed by about 50 pounds for a power change from engine idling power, to normal rated power and this pedal force change was largely independent of airspeed or of vertical-tail configuration for the various configurations tested.

The collision forces and lower-extremity inter-joint coordination during running.

PubMed

Wang, Li-I; Gu, Chin-Yi; Wang, I-Lin; Siao, Sheng-Wun; Chen, Szu-Ting

2018-06-01

The purpose of this study was to compare the lower extremity inter-joint coordination of different collision forces runners during running braking phase. A dynamical system approach was used to analyse the inter-joint coordination parameters. Data were collected with six infra-red cameras and two force plates. According to the impact peak of the vertical ground reaction force, twenty habitually rearfoot-strike runners were categorised into three groups: high collision forces runners (HF group, n = 8), medium collision forces runners (MF group, n = 5), and low collision forces runners (LF group, n = 7). There were no significant differences among the three groups in the ankle and knee joint angle upon landing and in the running velocity (p > 0.05). The HF group produced significantly smaller deviation phase (DP) of the hip flexion/extension-knee flexion/extension during the braking phase compared with the MF and LF groups (p < 0.05). The DP of the hip flexion/extension-knee flexion/extension during the braking phase correlated negatively with the collision force (p < 0.05). The disparities regarding the flexibility of lower extremity inter-joint coordination were found in high collision forces runners. The efforts of the inter-joint coordination and the risk of running injuries need to be clarified further.

A Physics Based Vehicle Terrain Interaction Model for Soft Soil off-Road Vehicle Simulations

DTIC Science & Technology

2012-01-01

assumed terrain deformation, use of empirical relationships for the deformation, or finite/discrete element approaches for the terrain. A real-time...vertical columns of soil, and the deformation of each is modeled using visco-elasto-plastic compressibility relationships that relate subsoil pressures to...produced by tractive and turning forces will also be incorporated into the model. Both the vertical and horizontal force/displacement relationships

A flexible and biocompatible triboelectric nanogenerator with tunable internal resistance for powering wearable devices

PubMed Central

Zhu, Yanbo; Yang, Bin; Liu, Jingquan; Wang, Xingzhao; Wang, Luxian; Chen, Xiang; Yang, Chunsheng

2016-01-01

Recently, triboelectric energy nanogenerators (TENGs) have been paid the most attention by many researchers to convert mechanical energy into electrical energy. TENGs usually have a simple structure and a high output voltage. However, their high internal resistance results in low output power. In this work, we propose a flexible triboelectric energy nanogenerator with the double-side tribological layers of polydimethlysiloxane (PDMS) and PDMS/multiwall carbon nanotube (MWCNT). MWCNTs with different concentrations have been doped into PDMS to tune the internal resistance of triboelectric nanogenerator and optimize its output power. The dimension of the fabricated prototype is ~3.6 cm3. Three-axial force sensor is used to monitor the applied vertical forces on the device under vertical contact-separation working mode. The Prototype with 10 wt% MWCNT (Prototype I) produces higher output voltage than one with 2 wt% MWCNT (Prototype II) due to its higher dielectric parameter measured by LRC impedance analyzer. The triboelectric output voltages of Prototype I and Prototype II are 30 V and 25 V under the vertical force of 3.0 N, respectively. Their maximum triboelectric output powers are ~130 μW at 6 MΩ and ~120 μW at 8.6 MΩ under vertical forces, respectively. PMID:26916819

Analysis of Rail Vehicle Suspension Spring with Special Emphasis on Curving, Tracking and Tractive Efforts

NASA Astrophysics Data System (ADS)

Kumbhalkar, M. A.; Bhope, D. V.; Vanalkar, A. V.

2016-09-01

The dynamics of the rail vehicle represents a balance between the forces acting between wheel and rail, the inertia forces and the forces exerted by suspension and articulation. Axial loading on helical spring causes vertical deflection at straight track but failures calls to investigate for lateral and longitudinal loading at horizontal and vertical curves respectively. Goods carrying vehicle has the frequent failures of middle axle inner suspension spring calls for investigation. The springs are analyzed for effect of stress concentration due to centripetal force and due to tractive and breaking effort. This paper also discusses shear failure analysis of spring at curvature and at uphill at various speeds for different loading condition analytically and by finite element analysis. Two mass rail vehicle suspension systems have been analyzed for vibration responses analytically using mathematical tool Matlab Simulink and the same will be evaluated using FFT vibration analyzer to find peak resonance in vertical, lateral and longitudinal direction. The results prove that the suspension acquires high repeated load in vertical and lateral direction due to tracking and curving causes maximum stress concentration on middle axle suspension spring as height of this spring is larger than end axle spring in primary suspension system and responsible for failure of middle axle suspension spring due to high stress acquisition.

Further study on the wheel-rail impact response induced by a single wheel flat: the coupling effect of strain rate and thermal stress

NASA Astrophysics Data System (ADS)

Jing, Lin; Han, Liangliang

2017-12-01

A comprehensive dynamic finite-element simulation method was proposed to study the wheel-rail impact response induced by a single wheel flat based on a 3-D rolling contact model, where the influences of the structural inertia, strain rate effect of wheel-rail materials and thermal stress due to the wheel-rail sliding friction were considered. Four different initial conditions (i.e. pure mechanical loading plus rate-independent, pure mechanical loading plus rate-dependent, thermo-mechanical loading plus rate-independent, and thermo-mechanical loading plus rate-dependent) were involved into explore the corresponding impact responses in term of the vertical impact force, von-Mises equivalent stress, equivalent plastic strain and shear stress. Influences of train speed, flat length and axle load on the flat-induced wheel-rail impact response were discussed, respectively. The results indicate that the maximum thermal stresses are occurred on the tread of the wheel and on the top surface of the middle rail; the strain rate hardening effect contributes to elevate the von-Mises equivalent stress and restrain the plastic deformation; and the initial thermal stress due to the sliding friction will aggravate the plastic deformation of wheel and rail. Besides, the wheel-rail impact responses (i.e. impact force, von-Mises equivalent stress, equivalent plastic strain, and XY shear stress) induced by a flat are sensitive to the train speed, flat length and axle load.

Single-leg drop landing motor control strategies following acute ankle sprain injury.

PubMed

Doherty, C; Bleakley, C; Hertel, J; Caulfield, B; Ryan, J; Delahunt, E

2015-08-01

No research currently exists investigating the effect of acute injury on single-limb landing strategies. The aim of the current study was to analyze the coordination strategies of participants in the acute phase of lateral ankle sprain (LAS) injury. Thirty-seven participants with acute, first-time LAS and 19 uninjured participants completed a single-leg drop landing task on both limbs. Three-dimensional kinematic (angular displacement) and sagittal plane kinetic (moment-of-force) data were acquired for the joints of the lower extremity from 200 ms pre-initial contact (IC) to 200 ms post-IC. The peak magnitude of the vertical component of the ground reaction force (GRF) was also computed. Injured participants displayed a bilateral increase in hip flexion, with altered transverse plane kinematic profiles at the knee and ankle for both limbs (P < 0.05). This coincided with a reduction in the net-supporting flexor moment of the lower extremity (P < 0.05) and magnitude of the peak vertical GRF for the injured limb (21.82 ± 2.44 N/kg vs 24.09 ± 2.77 N/kg; P = 0.013) in injured participants compared to control participants. These results demonstrate that compensatory movement strategies are utilized by participants with acute LAS to successfully reduce the impact forces of landing. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Force-chain evolution in a two-dimensional granular packing compacted by vertical tappings

NASA Astrophysics Data System (ADS)

Iikawa, Naoki; Bandi, M. M.; Katsuragi, Hiroaki

2018-03-01

We experimentally study the statistics of force-chain evolution in a vertically-tapped two-dimensional granular packing by using photoelastic disks. In this experiment, the tapped granular packing is gradually compacted. During the compaction, the isotropy of grain configurations is quantified by measuring the deviator anisotropy derived from fabric tensor, and then the evolution of force-chain structure is quantified by measuring the interparticle forces and force-chain orientational order parameter. As packing fraction increases, the interparticle force increases and finally saturates to an asymptotic value. Moreover, the grain configurations and force-chain structures become isotropically random as the tapping-induced compaction proceeds. In contrast, the total length of force chains remains unchanged. From the correlations of those parameters, we find two relations: (i) a positive correlation between the isotropy of grain configurations and the disordering of force-chain orientations, and (ii) a negative correlation between the increasing of interparticle forces and the disordering of force-chain orientations. These relations are universally held regardless of the mode of particle motions with or without convection.

Initial forces experienced by the anterior and posterior teeth during dental-anchored or skeletal-anchored en masse retraction in vitro.

PubMed

Lee, David; Heo, Giseon; El-Bialy, Tarek; Carey, Jason P; Major, Paul W; Romanyk, Dan L

2017-07-01

To investigate initial forces acting on teeth around the arch during en masse retraction using an in vitro Orthodontic SIMulator (OSIM). The OSIM was used to represent the full maxillary arch in a case wherein both first premolars had been extracted. Dental and skeletal anchorage to a posted archwire and skeletal anchorage to a 10-mm power arm were all simulated. A 0.019 × 0.025-inch stainless steel archwire was used in all cases, and 15-mm light nickel-titanium springs were activated to approximately 150 g on both sides of the arch. A sample size of n = 40 springs were tested for each of the three groups. Multivariate analysis of variance (α = 0.05) was used to determine differences between treatment groups. In the anterior segment, it was found that skeletal anchorage with power arms generated the largest retraction force (P < .001). The largest vertical forces on the unit were generated using skeletal anchorage, followed by skeletal anchorage with power arms, and finally dental anchorage. Power arms were found to generate larger intrusive forces on the lateral incisors and extrusive forces on the canines than on other groups. For the posterior anchorage unit, dental anchorage generated the largest protraction and palatal forces. Negligible forces were measured for both skeletal anchorage groups. Vertical forces on the posterior unit were minimal in all cases (<0.1 N). All retraction methods produced sufficient forces to retract the anterior teeth during en masse retraction. Skeletal anchorage reduced forces on the posterior teeth but introduced greater vertical forces on the anterior teeth.

Characterization and validation of a split belt treadmill for measuring hindlimb ground-reaction forces in able-bodied and spinalized felines

PubMed Central

Dimiskovski, Marko; Scheinfield, Richard; Higgin, Dwight; Krupka, Alexander; Lemay, Michel A.

2017-01-01

BACKGROUND The measurement of ground reaction forces (GRFs) in animals trained to locomote on a treadmill after spinal cord injury (SCI) could prove valuable for evaluating training outcomes; however, quantitative measures of the GRFs in spinal felines are limited. NEW METHOD A split belt treadmill was designed and constructed to measure the GRFs of feline hindlimbs during stepping. The treadmill consists of two independent treadmill assemblies, each mounted on a force plate. The design allows measurements of the vertical (Fz), fore-aft (Fy) and mediolateral (Fx) ground-reaction forces for both hindlimbs while the forelimbs are resting on a platform. RESULTS Static and dynamic noise tests revealed little to no noise at frequencies below 6 Hz. Validation of the force plate measurements with a hand-held force sensor force showed good agreement between the two force readings. Peak normalized (to body mass) vertical GRFs for intact cats were 4.89±0.85N/Kg for the left hindlimb and 4.79±0.97N/Kg for the right. In comparison, trained spinalized cats peak normalized vertical GRFs were 2.20±0.94N/Kg for the left hindlimb and 2.85±0.99N/Kg for the right. COMPARISON WITH OTHER EXISTING METHODS Previous methods of measuring GRFs used stationary single force plates or treadmill mounted to single force plate. Using independent treadmills for each hindlimb allows measurement of the individual hindlimb’s GRFs in spinalized cats following body-weight supported treadmill training. CONCLUSIONS The split belt force treadmill enables the simultaneous recording of ground-reaction forces for both hindlimbs in cats prior to spinalization, and following spinalization and body-weight-supported treadmill training (BWST). PMID:28069392

49 CFR 581.7 - Test procedures.

Code of Federal Regulations, 2014 CFR

2014-10-01

... is vertical and the impact line is horizontal at the specified height. (3) For impacts at a height... Figure 1 so that Plane A is vertical and the impact line is horizontal at the specified height. (3) For... that Plane A is vertical and the impact line is horizontal at a height within the range. (4) Align the...

Effects of modified short-leg walkers on ground reaction force characteristics.

PubMed

Keefer, Maria; King, Jon; Powell, Douglas; Krusenklaus, John H; Zhang, Songning

2008-11-01

Although short-leg walkers are often used in the treatment of lower extremity injuries (ankle and foot fractures and severe ankle sprains), little is known about the effect the short-leg walker on gait characteristics. The purpose was to examine how heel height modifications in different short-leg walkers and shoe side may affect ground reaction forces in walking. Force platforms were used to collect ground reaction force data on 10 healthy participants. Five trials were performed in each of six conditions: lab shoes, gait walker, gait walker with heel insert on shoe side, gait walker modified with insert on walker side, equalizer walker, and equalizer walker with heel insert on shoe side. Conditions were randomized and walking speed was standardized between conditions. A 2x6 (sidexcondition) repeated analysis of variance was used on selected ground reaction force variables (P<0.05). The application of a walker created peak vertical and anteroposterior ground reaction forces prior to the normal peaks associated with the loading response. Wearing a walker introduced an elevated minimum vertical ground reaction force in all conditions except the equalizer walker when compared to shoe on the shoe side. Peak propulsive anteroposterior ground reaction forces were smaller in all walker conditions compared to shoe on walker side. The application of heel insert in gait walker with heel insert (on shoe side) and gait walker modified (on walker side) does not diminish the minimum vertical ground reaction force as hypothesized. Wearing a walker decreases the peak propulsive anteroposterior ground reaction force on the walker side and induces asymmetrical loading.

Proximal arm kinematics affect grip force-load force coordination

PubMed Central

Vermillion, Billy C.; Lum, Peter S.

2015-01-01

During object manipulation, grip force is coordinated with load force, which is primarily determined by object kinematics. Proximal arm kinematics may affect grip force control, as proximal segment motion could affect control of distal hand muscles via biomechanical and/or neural pathways. The aim of this study was to investigate the impact of proximal kinematics on grip force modulation during object manipulation. Fifteen subjects performed three vertical lifting tasks that involved distinct proximal kinematics (elbow/shoulder), but resulted in similar end-point (hand) trajectories. While temporal coordination of grip and load forces remained similar across the tasks, proximal kinematics significantly affected the grip force-to-load force ratio (P = 0.042), intrinsic finger muscle activation (P = 0.045), and flexor-extensor ratio (P < 0.001). Biomechanical coupling between extrinsic hand muscles and the elbow joint cannot fully explain the observed changes, as task-related changes in intrinsic hand muscle activation were greater than in extrinsic hand muscles. Rather, between-task variation in grip force (highest during task 3) appears to contrast to that in shoulder joint velocity/acceleration (lowest during task 3). These results suggest that complex neural coupling between the distal and proximal upper extremity musculature may affect grip force control during movements, also indicated by task-related changes in intermuscular coherence of muscle pairs, including intrinsic finger muscles. Furthermore, examination of the fingertip force showed that the human motor system may attempt to reduce variability in task-relevant motor output (grip force-to-load force ratio), while allowing larger fluctuations in output less relevant to task goal (shear force-to-grip force ratio). PMID:26289460

Evapotranspiration versus oxygen intrusion: which is the main force in alleviating bioclogging of vertical-flow constructed wetlands during a resting operation?

PubMed

Hua, Guofen; Chen, Qiuwen; Kong, Jun; Li, Man

2017-08-01

Clogging is the most significant challenge limiting the application of constructed wetlands. Application of a forced resting period is a practical way to relieve clogging, particularly bioclogging. To reveal the alleviation mechanisms behind such a resting operation, evapotranspiration and oxygen flux were studied during a resting period in a laboratory vertical-flow constructed wetland model through physical simulation and numerical model analysis. In addition, the optimum theoretical resting duration was determined based on the time required for oxygen to completely fill the pores, i.e., formation of a sufficiently thick and completely dry layer. The results indicated that (1) evapotranspiration was not the key factor, but was a driving force in the alleviation of bioclogging; (2) the rate of oxygen diffusion into the pores was sufficient to oxidize and disperse the flocculant biofilm, which was essential to alleviate bioclogging. This study provides important insights into understanding how clogging/bioclogging can be alleviated in vertical-flow constructed wetlands. Graphical abstract Evapotranspiration versus oxygen intrusion in alleviating bioclogging in vertical flow constructed wetlands.

A Model for Space Shuttle Orbiter Tire Side Forces Based on NASA Landing Systems Research Aircraft Test Results

NASA Technical Reports Server (NTRS)

Carter, John F.; Nagy, Christopher J.; Barnicki, Joseph S.

1997-01-01

Forces generated by the Space Shuttle orbiter tire under varying vertical load, slip angle, speed, and surface conditions were measured using the Landing System Research Aircraft (LSRA). Resulting data were used to calculate a mathematical model for predicting tire forces in orbiter simulations. Tire side and drag forces experienced by an orbiter tire are cataloged as a function of vertical load and slip angle. The mathematical model is compared to existing tire force models for the Space Shuttle orbiter. This report describes the LSRA and a typical test sequence. Testing methods, data reduction, and error analysis are presented. The LSRA testing was conducted on concrete and lakebed runways at the Edwards Air Force Flight Test Center and on concrete runways at the Kennedy Space Center (KSC). Wet runway tire force tests were performed on test strips made at the KSC using different surfacing techniques. Data were corrected for ply steer forces and conicity.

Scattering of SH wave by a semi-cylindrical salient near vertical interface in the bi-material half space

NASA Astrophysics Data System (ADS)

Qi, Hui; Zhang, Xi-meng

2017-10-01

With the aid of the Green function method and image method, the problem of scattering of SH-wave by a semi-cylindrical salient near vertical interface in bi-material half-space is considered to obtain its steady state response. Firstly, by the means of the image method, Green function which is the essential solution of displacement field is constructed to satisfy the stress-free condition on the horizontal boundary in a right-angle space including a semi-cylindrical salient and bearing a harmonic out-of-plane line source force at any point on the vertical boundary. Secondly, the bi-material is separated into two parts along the vertical interface, then unknown anti-plane forces are applied on the vertical interface, and according to the continuity condition, the first kind of Fredholm integral equations is established to determine unknown anti-plane forces by "the conjunction method", then the integral equations are reduced to the linear algebraic equations by effective truncation. Finally, the dynamic stress concentration factor (DSCF) around the edge of semi-cylindrical salient is calculated, and the influences of incident wave number, incident angle, effect of interface and different combination of material parameters, etc. on DSCF are discussed.

Design and evaluation of a deformable wing configuration for economical hovering flight of an insect-like tailless flying robot.

PubMed

Phan, Hoang Vu; Park, Hoon Cheol

2018-04-18

Studies on wing kinematics indicate that flapping insect wings operate at higher angles of attack (AoAs) than conventional rotary wings. Thus, effectively flying an insect-like flapping-wing micro air vehicle (FW-MAV) requires appropriate wing design for achieving low power consumption and high force generation. Even though theoretical studies can be performed to identify appropriate geometric AoAs for a wing for achieving efficient hovering flight, designing an actual wing by implementing these angles into a real flying robot is challenging. In this work, we investigated the wing morphology of an insect-like tailless FW-MAV, which was named KUBeetle, for obtaining high vertical force/power ratio or power loading. Several deformable wing configurations with various vein structures were designed, and their characteristics of vertical force generation and power requirement were theoretically and experimentally investigated. The results of the theoretical study based on the unsteady blade element theory (UBET) were validated with reference data to prove the accuracy of power estimation. A good agreement between estimated and measured results indicated that the proposed UBET model can be used to effectively estimate the power requirement and force generation of an FW-MAV. Among the investigated wing configurations operating at flapping frequencies of 23 Hz to 29 Hz, estimated results showed that the wing with a suitable vein placed outboard exhibited an increase of approximately 23.7%  ±  0.5% in vertical force and approximately 10.2%  ±  1.0% in force/power ratio. The estimation was supported by experimental results, which showed that the suggested wing enhanced vertical force by approximately 21.8%  ±  3.6% and force/power ratio by 6.8%  ±  1.6%. In addition, wing kinematics during flapping motion was analyzed to determine the reason for the observed improvement.

Effects of cloud condensate vertical alignment on radiative transfer calculations in deep convective regions

NASA Astrophysics Data System (ADS)

Wang, Xiaocong

2017-04-01

Effects of cloud condensate vertical alignment on radiative transfer process were investigated using cloud resolving model explicit simulations, which provide a surrogate for subgrid cloud geometry. Diagnostic results showed that the decorrelation length Lcw varies in the vertical dimension, with larger Lcw occurring in convective clouds and smaller Lcw in cirrus clouds. A new parameterization of Lcw is proposed that takes into account such varying features and gives rise to improvements in simulations of cloud radiative forcing (CRF) and radiative heating, i.e., the peak of bias is respectively reduced by 8 W m- 2 for SWCF and 2 W m- 2 for LWCF in comparison with Lcw = 1 km. The role of Lcw in modulating CRFs is twofold. On the one hand, larger Lcw tends to increase the standard deviation of optical depth στ, as dense and tenuous parts of the clouds would be increasingly aligned in the vertical dimension, thereby broadening the probability distribution. On the other hand, larger στ causes a decrease in the solar albedo and thermal emissivity, as implied in their convex functions on τ. As a result, increasing (decreasing) Lcwleads to decreased (increased) CRFs, as revealed by comparisons among Lcw = 0, Lcw = 1 km andLcw = ∞. It also affects the vertical structure of radiative flux and thus influences the radiative heating. A better representation of στ in the vertical dimension yields an improved simulation of radiative heating. Although the importance of vertical alignment of cloud condensate is found to be less than that of cloud cover in regards to their impacts on CRFs, it still has enough of an effect on modulating the cloud radiative transfer process.

A multilinear regression methodology to analyze the effect of atmospheric and surface forcing on Arctic clouds

NASA Astrophysics Data System (ADS)

Boeke, R.; Taylor, P. C.; Li, Y.

2017-12-01

Arctic cloud amount as simulated in CMIP5 models displays large intermodel spread- models disagree on the processes important for cloud formation as well as the radiative impact of clouds. The radiative response to cloud forcing can be better assessed when the drivers of Arctic cloud formation are known. Arctic cloud amount (CA) is a function of both atmospheric and surface conditions, and it is crucial to separate the influences of unique processes to understand why the models are different. This study uses a multilinear regression methodology to determine cloud changes using 3 variables as predictors: lower tropospheric stability (LTS), 500-hPa vertical velocity (ω500), and sea ice concentration (SIC). These three explanatory variables were chosen because their effects on clouds can be attributed to unique climate processes: LTS is a thermodynamic indicator of the relationship between clouds and atmospheric stability, SIC determines the interaction between clouds and the surface, and ω500 is a metric for dynamical change. Vertical, seasonal profiles of necessary variables are obtained from the Coupled Model Intercomparison Project 5 (CMIP5) historical simulation, an ocean-atmosphere couple model forced with the best-estimate natural and anthropogenic radiative forcing from 1850-2005, and statistical significance tests are used to confirm the regression equation. A unique heuristic model will be constructed for each climate model and for observations, and models will be tested by their ability to capture the observed cloud amount and behavior. Lastly, the intermodel spread in Arctic cloud amount will be attributed to individual processes, ranking the relative contributions of each factor to shed light on emergent constraints in the Arctic cloud radiative effect.

Adaptive cellular structures and devices with internal features for enhanced structural performance

NASA Astrophysics Data System (ADS)

Pontecorvo, Michael Eugene

This dissertation aims to develop a family of cellular and repeatable devices that exhibit a variety of force-displacement behaviors. It is envisioned that these cellular structures might be used either as stand-alone elements, or combined and repeated to create multiple types of structures (i.e. buildings, ship hulls, vehicle subfloors, etc.) with the ability to passively or actively perform multiple functions (harmonic energy dissipation, impact mitigation, modulus change) over a range of loading types, amplitudes, and frequencies. To accomplish this goal, this work combines repeatable structural frameworks, such as that provided by a hexagonal cellular structure, with internal structural elements such as springs, viscous dampers, buckling plates, bi-stable von Mises trusses (VMTs), and pneumatic artificial muscles (PAMs). The repeatable framework serves to position damping and load carrying elements throughout the structure, and the configuration of the internal elements allow each cell to be tuned to exhibit a desired force-displacement response. Therefore, gradient structures or structures with variable load paths can be created for an optimal global response to a range of loads. This dissertation focuses on the development of cellular structures for three functions: combined load-carrying capability with harmonic energy dissipation, impact mitigation, and cell modulus variation. One or more conceptual designs are presented for devices that can perform each of these functions, and both experimental measurements and simulations are used to gain a fundamental understanding of each device. Chapter 2 begins with a presentation of a VMT model that is the basis for many of the elements. The equations of motion for the VMT are derived and the static and dynamic behavior of the VMT are discussed in detail. Next, two metrics for the energy dissipation of the VMT - hysteresis loop area and loss factor - are presented. The responses of the VMT to harmonic displacement and force inputs are contrasted in relation to these metrics. The key innovation to the early structural elements presented here is the combination of the VMT with the pin-jointed hexagonal cell. Chapter 3 explores several prototypes of repeatable structural elements for simultaneous load-carrying capability and energy dissipation that are based on this innovation. The final demonstration prototype presented in this chapter is a column-like element that is based on a hexagonal cell containing two horizontal springs and one vertical damper. The unit is enclosed by a pair of buckling plates that serve to give the prototype a high initial stiffness and load carrying capability. The prototype is tested in both displacement and force input and its behavior is compared to simulation. Chapter 4 builds on the conceptual designs of Chapter 3 with the introduction of a plate-like element, that contains two compact VMTs connected by a horizontally oriented damper. Pre-loaded springs are used in the prototype to perform the same load carrying function as the buckling plates in the column-like prototype with increased predictability. The plate-like prototype is studied under impact to demonstrate its effectiveness as a protective layer. It is shown to reduce peak impact loads transmitted to the base of the device by over 60%. In most cases, the prototype compares well with a conventional protective rubber layer, and in cases of extreme impact loads, it exceeds the performance of the rubber layer. In addition to impact testing, the prototype is also experimentally tested under harmonic displacement input, and is simulated under both harmonic displacement and force input. The experiments illustrate that while the VMT parameters of a single layer can be optimized to a particular harmonic load amplitude, having two layers with softer and stiffer VMTs allows the system to show good energy dissipation characteristics at different harmonic load amplitude levels. Chapter 5 examines using PAM inclusions within planar hexagonal cells as variable stiffness springs to create a variable modulus cellular structure. The proposed concept is envisioned as a first step toward a structural unit cell whose in-plane modulus in a given direction can be tuned based on the orientation of PAMs within the cell and the pressure supplied to the individual muscles. To begin, a pin-jointed cell is considered, loaded in the horizontal direction, with three PAMs (one vertical PAM and two horizontal PAMs) oriented in an "H" configuration between the vertices of the cell. A method for calculation of the hexagonal cell modulus is introduced, as is an expression for the balance of tensile forces between the horizontal and vertical PAMs. An aluminum hexagonal unit cell is fabricated and simulation of the hexagonal cell with PAM inclusions is then compared to experimental measurement of the unit cell modulus in the horizontal direction over a pressure range up to 682 kPa. An increase in cell modulus of 200% and a corresponding change in cell angle of 1.53 degrees are demonstrated experimentally. A design study via simulation predicts that differential pressurization of the PAMs up to 1992 kPa can increase the cell modulus in the horizontal direction by a factor of 6.66 with a change in cell angle of only 2.75 degrees. Additionally, simulation predicts that variation of unpressurized cell equilibrium angle and vertical wall length coefficient can result in changes in cell modulus greater than 1000%. A drawback of the pin-jointed cell with PAM inclusions is that it is inherently underconstrained. To solve this problem, the pin-jointed cell walls are replaced with a continuous Delrin hexagon which gives the cell kinematic stability and allows for experimental measurement of modulus in both the horizontal and vertical directions. The Delrin cell is designed to have a modulus on the same order as that of the pin-jointed cell at zero pressure and is experimentally measured without the PAM inclusions. These measurements validate the use of a combined flexural/hinging analytical model that accurately simulates the cell modulus. This analysis is then combined with the PAM force equations to model the complete hexagonal cell with PAM inclusions. Simulation and experimental measurement of the cell modulus with the PAM inclusions are compared in both the horizontal and vertical directions over an expanded pressure range up to 1302 kPa. The interplay between the contraction ratio and pressure in orthogonal sets of PAMs is highlighted as the primary driver of overall cell modulus.

Composition and daytime vertical distribution of the ichthyoplankton assemblage in the Central Cantabrian Sea shelf, during summer: An Eulerian study

NASA Astrophysics Data System (ADS)

Rodriguez, J. M.; Gonzalez-Pola, C.; Lopez-Urrutia, A.; Nogueira, E.

2011-09-01

During summer, wind driven coastal upwelling dominates in the Central Cantabrian Sea (southern Bay of Biscay). Nevertheless, atmospheric forcing is highly variable and wind pulses may cause noticeable and fast hydrographic responses in the shelf region. In this paper, the composition and vertical distribution of the summer ichthyoplankton assemblage during the daytime at a fixed station, located on the Central Cantabrian Sea shelf, are documented. Also, the impact of a short-time scale hydrographic event on the abundance and structure of the larval fish assemblage is examined. Significant small-scale temporal hydrographic variability was observed. Currents showed changes in speed and direction and significant changes in thermocline depth were also observed. A total of 34 taxa of fish larvae were identified. Engraulis encrasicolus eggs and larvae of the shelf-dwelling species Trachurus trachurus, Capros aper and E. encrasicolus dominated the ichthyoplankton assemblage. The distribution of E. encrasicolus eggs and fish larvae was vertically structured. E. encrasicolus egg concentration increased exponentially towards the surface. Fish larvae showed a subsurface peak of concentration and their vertical distribution was not conditioned by thermocline depths. The short term hydrographic event did not affect the vertical distribution of fish larvae but it accounted for significant temporal changes in larval fish assemblage structure and abundance. Results suggest that temperature and light intensity are important factors in the vertical distribution of fish larvae. They also indicate that the temporal monitoring of the larval fish assemblage in this region requires multiple sampling sites.

Quasi-steady vortical structures in vertically vibrating soap films

NASA Astrophysics Data System (ADS)

Vega, José M.; Higuera, F. J.; Weidman, P. D.

1998-10-01

An analysis of the quasi-steady streaming of the liquid in a vertically vibrated horizontal soap film is reported. The air around the soap film is seen to play a variety of roles: it transmits normal and tangential oscillatory stresses to the film, damps out Marangoni waves, and forces non-oscillatory deflection of the film and tangential motion of the liquid. Non-oscillatory volume forcing originating inside the liquid is also analysed. This forcing dominates the quasi-steady streaming when the excitation frequency is close to the eigenfrequency of a Marangoni mode of the soap film, while both volume forcing in the liquid and surface forcing of the gas on the liquid are important when no Marangoni mode resonates. Different manners by which the combined forcings can induce quasi-steady streaming motion are discussed and some numerical simulations of the quasi-steady liquid flow are presented.

Utilization of satellite cloud information to diagnose the energy state and transformations in extratropical cyclones

NASA Technical Reports Server (NTRS)

Smith, P. J.

1984-01-01

A study of the contribution of latent heat release to the synoptic scale vertical motions in the Jan. 9-11, 1975 extratropical cyclone case study was completed. Results indicate that early cyclone development was dominated by dry dynamical forcing. However, as the cyclone matured, the influence of latent heating became more significant. This influence appeared to be of two types, (1) the direct impact of heating causing a lowering of surface pressures, and (2) an indirect role in which the heating altered thermal and vorticity gradients and lead to subsequent increases in dry dynamical forcing. The kinetic energy budget was completed and extended to include an available potential energy budget. Focusing on the eddy component of the budgets, results indicate that kinetic energy increased throughout the cyclone's development, with the increase being most pronounced after the onset of significant latent heat release. Latent heating played a strong role not only in generating available potential energy, but also in forcing baroclinic release of potential energy.

Ground reaction forces and plantar pressure distribution during occasional loaded gait.

PubMed

Castro, Marcelo; Abreu, Sofia; Sousa, Helena; Machado, Leandro; Santos, Rubim; Vilas-Boas, João Paulo

2013-05-01

This study compared the ground reaction forces (GRF) and plantar pressures between unloaded and occasional loaded gait. The GRF and plantar pressures of 60 participants were recorded during unloaded gait and occasional loaded gait (wearing a backpack that raised their body mass index to 30); this load criterion was adopted because is considered potentially harmful in permanent loaded gait (obese people). The results indicate an overall increase (absolute values) of GRF and plantar pressures during occasional loaded gait (p < 0.05); also, higher normalized (by total weight) values in the medial midfoot and toes, and lower values in the lateral rearfoot region were observed. During loaded gait the magnitude of the vertical GRF (impact and thrust maximum) decreased and the shear forces increased more than did the proportion of the load (normalized values). These data suggest a different pattern of GRF and plantar pressure distribution during occasional loaded compared to unloaded gait. Copyright © 2012 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Development of a mobile sensor for robust assessment of river bed grain forces

NASA Astrophysics Data System (ADS)

Maniatis, G.; Hoey, T.; Sventek, J.; Hodge, R. A.

2013-12-01

The forces experienced by sediment grains at entrainment and during transport, and those exerted on river beds, are significant for the development of river systems and landscape evolution. The assessment of local grain forces has been approached using two different methodologies. The first approach uses static impact sensors at points or cross-sections to measure velocity and/or acceleration. A second approach uses mobile natural or artificial 'smart' pebbles instrumented with inertia micro-sensors for directly measuring the local forces experienced by individual grains. The two approaches have yielded significantly different magnitudes of impact forces. Static sensors (piezoelectric plates connected to accelerometers) temporally smooth the impacts from several grains and infrequently detect the higher forces (up to ×100g) generated by direct single-grain impacts. The second method is currently unable to record the full range of impacts in real rivers due to the low measurement range of the deployed inertia sensors (×3g). Laboratory applications have required only low-range accelerometers, so excluding the magnitude of natural impacts from the design criteria. Here we present the first results from the development of a mobile sensor, designed for the purpose of measuring local grain-forces in a natural riverbed. We present two sets of measurements. The first group presents the calibration of a wide range micro-accelerometer from a set of vertical drop experiments (gravitational acceleration) and further experiments on a shaking table moving with pre-defined acceleration. The second group of measurements are from incipient motion experiments performed in a 9m x0.9m flume (slope 0.001 to 0.018) under steadily increasing discharge. Initially the spherical sensor grain was placed on an artificial surface of hemispheres of identical diameter to the sensor (111mm). Incipient motion was assessed under both whole and half-diameter exposure for each slope. Subsequently, the sensor was placed on a bed of natural gravel of equivalent mean diameter under low slope conditions (0.001). Incipient motion was monitored over a fully covered stable bed and over a partially covered bed developed over an artificial surface constructed to simulate a natural bedrock surface. Statistical analysis of the results describes the relationship between flow conditions and pre-entrainment grain vibration and the acceleration threshold for incipient motion. Finally we perform a preliminary analysis to assess the degree of dependency of the same threshold on the different degrees of alluvial coverage of a river bed and so illustrate the potential to evaluate existing models describing grain entrainment and transport.

Semi-analytical model of the axial movements of an oil-well drillstring in vertical wellbores

NASA Astrophysics Data System (ADS)

Hovda, Sigve

2018-03-01

A lumped element model for the axial movement of an oil-well drillstring is presented. In this paper, the model is restricted to vertical holes, where damping is due to skin friction from time dependent Newtonian annular Couette-Poiseuille flow. The drillstring is constructed of pipes with different diameters and the diameter of the hole varies as a function of depth. Under these assumptions, the axial movement anywhere in the drillstring is basically a convolution between the axial movement on the top and a semi-analytical function that is derived in this paper. Expressions are given for transfer functions for downhole movements and pressures (surge and swab). In a vertical drilling situation, the motion is clearly underdamped, even when the hole is tight. The semi-analytical model illuminates various factors that are shown to be important for describing downhole pressure and motion. In particular the effect of added mass, the steady state viscous forces, the Basset viscous forces and the distribution of pipe sizes in the hole. The latter have non-neglectable impacts on where the resonant frequencies are located, how much they are amplified and what happens to the downhole pressure. Together with statistical power spectra of ocean wave patterns and the response amplitude operators for a floating structure, this model illustrates design concerns related to heave motion and how fast one can run the drillstring into the hole. Moreover, because of the computational simplicity of computing the convolution, the model is well suited for a real-time implementation.

Age-related differences in lower-limb force-time relation during the push-off in rapid voluntary stepping.

PubMed

Melzer, I; Krasovsky, T; Oddsson, L I E; Liebermann, D G

2010-12-01

This study investigated the force-time relationship during the push-off stage of a rapid voluntary step in young and older healthy adults, to study the assumption that when balance is lost a quick step may preserve stability. The ability to achieve peak propulsive force within a short time is critical for the performance of such a quick powerful step. We hypothesized that older adults would achieve peak force and power in significantly longer times compared to young people, particularly during the push-off preparatory phase. Fifteen young and 15 older volunteers performed rapid forward steps while standing on a force platform. Absolute anteroposterior and body weight normalized vertical forces during the push-off in the preparation and swing phases were used to determine time to peak and peak force, and step power. Two-way analyses of variance ('Group' [young-older] by 'Phase' [preparation-swing]) were used to assess our hypothesis (P ≤ 0.05). Older people exerted lower peak forces (anteroposterior and vertical) than young adults, but not necessarily lower peak power. More significantly, they showed a longer time to peak force, particularly in the vertical direction during the preparation phase. Older adults generate propulsive forces slowly and reach lower magnitudes, mainly during step preparation. The time to achieve a peak force and power, rather than its actual magnitude, may account for failures in quickly performing a preventive action. Such delay may be associated with the inability to react and recruit muscles quickly. Thus, training elderly to step fast in response to relevant cues may be beneficial in the prevention of falls. Copyright © 2010 Elsevier Ltd. All rights reserved.

The Relationship Between the Push Off Ground Reaction Force and Ball Speed in High School Baseball Pitchers.

PubMed

Oyama, Sakiko; Myers, Joseph B

2018-05-01

Oyama, S and Myers, JB. The relationship between the push off ground reaction force and ball speed in high school baseball pitchers. J Strength Cond Res 32(5): 1324-1328, 2018-Baseball pitching is a sequential movement that requires transfer of momentum from the lower extremity to the throwing arm. Therefore, the ground reaction force (GRF) during push off is suggested to play a role in production of ball speed. The purpose of this study was to investigate the correlation between GRF characteristics during push off and ball speed in high school baseball pitchers. A total of 52 pitchers performed fast pitches from an indoor pitching mound. A force plate embedded in an indoor mound was used to capture the push off GRF. The GRF characteristics (peak anterior, vertical, and resultant forces, vertical and resultant forces at the time of peak anterior GRF, and impulse produced by the anterior GRF) from the 3 fastest strike pitches from each pitcher were used for analyses. Spearman's rank correlation coefficients were used to describe the relationships between ball speed and the GRF characteristics. Ball speed was only weakly correlated with peak resultant force (ρ = 0.32, p = 0.02) and vertical (ρ = 0.45, p < 0.001) and resultant (ρ = 0.42, p = 0.002) forces at the time of peak anterior force. The ball speed was not correlated with other variables. The correlation between ball speed and push off force in high school pitchers was weak, especially when compared with what was reported for adult pitchers in other studies. Unlike for adult pitchers, higher push off force is only weakly correlated with ball velocity in high school pitchers, which suggests that training to better use body momentum may help high school pitchers improve ball speed.

Subatomic deformation driven by vertical piezoelectricity from CdS ultrathin films

PubMed Central

Wang, Xuewen; He, Xuexia; Zhu, Hongfei; Sun, Linfeng; Fu, Wei; Wang, Xingli; Hoong, Lai Chee; Wang, Hong; Zeng, Qingsheng; Zhao, Wu; Wei, Jun; Jin, Zhong; Shen, Zexiang; Liu, Jie; Zhang, Ting; Liu, Zheng

2016-01-01

Driven by the development of high-performance piezoelectric materials, actuators become an important tool for positioning objects with high accuracy down to nanometer scale, and have been used for a wide variety of equipment, such as atomic force microscopy and scanning tunneling microscopy. However, positioning at the subatomic scale is still a great challenge. Ultrathin piezoelectric materials may pave the way to positioning an object with extreme precision. Using ultrathin CdS thin films, we demonstrate vertical piezoelectricity in atomic scale (three to five space lattices). With an in situ scanning Kelvin force microscopy and single and dual ac resonance tracking piezoelectric force microscopy, the vertical piezoelectric coefficient (d33) up to 33 pm·V−1 was determined for the CdS ultrathin films. These findings shed light on the design of next-generation sensors and microelectromechanical devices. PMID:27419234

Effect of gravitational and inertial forces on vertical distribution of pulmonary blood flow

NASA Technical Reports Server (NTRS)

Chevalier, P. A.; Reed, J. H., Jr.; Vandenberg, R. A.; Wood, E. H.

1978-01-01

Vertical distribution of pulmonary blood flow (VDPBF) was studied, using radioactive microsphere emboli, in dogs without thoracotomy in the right decubitus position during exposure to lateral accelerations of 1, 2, 4, and 6 G. At all levels of force environment studied, an inverse linear relationship was observed between vertical height in the thorax and pulmonary blood flow (ml/min/ml lung tissue) with a decrease in flow to the most dependent region of the lung despite large increases in intravascular pressures at this site. Changes in blood flow were smallest at the mid-lung level, the hydrostatic 'balance point' for vascular and pleural pressures. These force environment-dependent changes in VDPBF are not readily explainable by the Starling resistor analog. Gravity-dependent regional differences in pleural and associated interstitial pressures, plus possible changes in vascular tone resulting from inadequate aeration of blood in the most dependent regions of the lung, probably also affect VDPBF.

Three Dimensional Vibration Characteristics of the Permanent Magnet-HTSC Magnetic Bearing

NASA Astrophysics Data System (ADS)

Ohashi, Shunsuke

The three dimensional vibration of the rotor in a HTSC-permanent magnet bearing system is studied. We have developed the magnetic bearing system which can revolve up to 12,000rpm, and three dimensional vibration of the rotor is measured with laser displacement sensors. To consider the rotor vibration under the mechanical resonance state, static lateral and vertical pinning force of the magnetic bearing is measured. From the results, resonance frequency is given. There are two factors of mechanical resonance caused by the magnetic bearing. One is lateral equivalent spring and the other is vertical one. Influence of the resonance caused by the lateral spring is large, and that by the vertical one is small. Three dimensional vibration of the rotor position around the mechanical resonance frequency is measured. Because revolution of the rotor increases lateral force to the center, resonance frequency given from the free revolution experiment becomes larger than that from pinning force measurement.

14 CFR 25.493 - Braked roll conditions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... used if it is substantiated that an effective drag force of 0.8 times the vertical reaction cannot be... landing weight and 1.0 at the design ramp weight. A drag reaction equal to the vertical reaction multiplied by a coefficient of friction of 0.8, must be combined with the vertical ground reaction and...

14 CFR 25.493 - Braked roll conditions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... used if it is substantiated that an effective drag force of 0.8 times the vertical reaction cannot be... landing weight and 1.0 at the design ramp weight. A drag reaction equal to the vertical reaction multiplied by a coefficient of friction of 0.8, must be combined with the vertical ground reaction and...

14 CFR 25.493 - Braked roll conditions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... used if it is substantiated that an effective drag force of 0.8 times the vertical reaction cannot be... landing weight and 1.0 at the design ramp weight. A drag reaction equal to the vertical reaction multiplied by a coefficient of friction of 0.8, must be combined with the vertical ground reaction and...

Modeling lateral circulation and its influence on the along-channel flow in a branched estuary

NASA Astrophysics Data System (ADS)

Zhu, Lei; He, Qing; Shen, Jian

2018-02-01

A numerical modeling study of the influence of the lateral flow on the estuarine exchange flow was conducted in the north passage of the Changjiang estuary. The lateral flows show substantial variabilities within a flood-ebb tidal cycle. The strong lateral flow occurring during flood tide is caused primarily by the unique cross-shoal flow that induces a strong northward (looking upstream) barotropic force near the surface and advects saltier water toward the northern part of the channel, resulting in a southward baroclinic force caused by the lateral density gradient. Thus, a two-layer structure of lateral flows is produced during the flood tide. The lateral flows are vigorous near the flood slack and the magnitude can exceed that of the along-channel tidal flow during that period. The strong vertical shear of the lateral flows and the salinity gradient in lateral direction generate lateral tidal straining, which are out of phase with the along-channel tidal straining. Consequently, stratification is enhanced at the early stage of the ebb tide. In contrast, strong along-channel straining is apparent during the late ebb tide. The vertical mixing disrupts the vertical density gradient, thus suppressing stratification. The impact of lateral straining on stratification during spring tide is more pronounced than that of along-channel straining during late flood and early ebb tides. The momentum balance along the estuary suggests that lateral flow can augment the residual exchange flow. The advection of lateral flows brings low-energy water from the shoal to the deep channel during the flood tide, whereas the energetic water is moved to the shoal via lateral advection during the ebb tide. The impact of lateral flow on estuarine circulation of this multiple-channel estuary is different from single-channel estuary. A model simulation by blocking the cross-shoal flow shows that the magnitudes of lateral flows and tidal straining are reduced. Moreover, the reduced lateral tidal straining results in a decrease in vertical stratification from the late flood to early ebb tides during the spring tide. By contrast, the along-channel tidal straining becomes dominant. The model results illustrate the important dynamic linkage between lateral flows and estuarine dynamics in the Changjiang estuary.

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

Tang, Shuaiqi; Zhang, Minghua; Xie, Shaocheng

Large-scale forcing data, such as vertical velocity and advective tendencies, are required to drive single-column models (SCMs), cloud-resolving models, and large-eddy simulations. Previous studies suggest that some errors of these model simulations could be attributed to the lack of spatial variability in the specified domain-mean large-scale forcing. This study investigates the spatial variability of the forcing and explores its impact on SCM simulated precipitation and clouds. A gridded large-scale forcing data during the March 2000 Cloud Intensive Operational Period at the Atmospheric Radiation Measurement program's Southern Great Plains site is used for analysis and to drive the single-column version ofmore » the Community Atmospheric Model Version 5 (SCAM5). When the gridded forcing data show large spatial variability, such as during a frontal passage, SCAM5 with the domain-mean forcing is not able to capture the convective systems that are partly located in the domain or that only occupy part of the domain. This problem has been largely reduced by using the gridded forcing data, which allows running SCAM5 in each subcolumn and then averaging the results within the domain. This is because the subcolumns have a better chance to capture the timing of the frontal propagation and the small-scale systems. As a result, other potential uses of the gridded forcing data, such as understanding and testing scale-aware parameterizations, are also discussed.« less

Stress distribution in maxillary first molar periodontium using straight pull headgear with vertical and horizontal tubes: A finite element analysis.

PubMed

Feizbakhsh, Masood; Kadkhodaei, Mahmoud; Zandian, Dana; Hosseinpour, Zahra

2017-01-01

One of the most effective ways for distal movement of molars to treat Class II malocclusion is using extraoral force through a headgear device. The purpose of this study was the comparison of stress distribution in maxillary first molar periodontium using straight pull headgear in vertical and horizontal tubes through finite element method. Based on the real geometry model, a basic model of the first molar and maxillary bone was obtained using three-dimensional imaging of the skull. After the geometric modeling of periodontium components through CATIA software and the definition of mechanical properties and element classification, a force of 150 g for each headgear was defined in ABAQUS software. Consequently, Von Mises and Principal stresses were evaluated. The statistical analysis was performed using T-paired and Wilcoxon nonparametric tests. Extension of areas with Von Mises and Principal stresses utilizing straight pull headgear with a vertical tube was not different from that of using a horizontal tube, but the numerical value of the Von Mises stress in the vertical tube was significantly reduced ( P < 0/05). On the other hand, the difference of the principal stress between both tubes was not significant ( P > 0/05). Based on the results, when force applied to the straight pull headgear with a vertical tube, Von Mises stress was reduced significantly in comparison with the horizontal tube. Therefore, to correct the mesiolingual movement of the maxillary first molar, vertical headgear tube is recommended.

Correlation of prostaglandin E2 concentrations in synovial fluid with ground reaction forces and clinical variables for pain or inflammation in dogs with osteoarthritis induced by transection of the cranial cruciate ligament.

PubMed

Trumble, Troy N; Billinghurst, R Clark; McIlwraith, C Wayne

2004-09-01

To evaluate the temporal pattern of prostaglandin (PG) E2 concentrations in synovial fluid after transection of the cranial cruciate ligament (CCL) in dogs and to correlate PGE2 concentrations with ground reaction forces and subjective clinical variables for lameness or pain. 19 purpose-bred adult male Walker Hounds. Force plate measurements, subjective clinical analysis of pain or lameness, and samples of synovial fluid were obtained before (baseline) and at various time points after arthroscopic transection of the right CCL. Concentrations of PGE2 were measured in synovial fluid samples, and the PGE2 concentrations were correlated with ground reaction forces and clinical variables. The PGE2 concentration increased significantly above the baseline value throughout the entire study, peaking 14 days after transection. Peak vertical force and vertical impulse significantly decreased by day 14 after transection, followed by an increase over time without returning to baseline values. All clinical variables (eg, lameness, degree of weight bearing, joint extension, cumulative pain score, effusion score, and total protein content of synovial fluid, except for WBC count in synovial fluid) increased significantly above baseline values. Significant negative correlations were detected between PGE2 concentrations and peak vertical force (r, -0.5720) and vertical impulse (r, -0.4618), and significant positive correlations were detected between PGE2 concentrations and the subjective lameness score (r, 0.5016) and effusion score (r, 0.6817). Assessment of the acute inflammatory process by measurement of PGE2 concentrations in synovial fluid may be correlated with the amount of pain or lameness in dogs.

Force system generated by elastic archwires with vertical V bends: a three-dimensional analysis.

PubMed

Upadhyay, Madhur; Shah, Raja; Peterson, Donald; Asaki, Takafumi; Yadav, Sumit; Agarwal, Sachin

2017-04-01

Our previous understanding of V-bend mechanics is primarily from two-dimensional (2D) analysis of archwire bracket interactions in the second order. These analyses do not take into consideration the three-dimensional (3D) nature of orthodontic appliances involving the third order. To quantify the force system generated in a 3D two bracket set up involving the molar and incisors with vertical V-bends. Maxillary molar and incisor brackets were arranged in a dental arch form and attached to load cells capable of measuring forces and moments in all three planes (x, y, and z) of space. Symmetrical V-bends (right and left sides) were placed at 11 different locations along rectangular beta-titanium archwires of various sizes at an angle of 150degrees. Each wire was evaluated for the 11 bend positions. Specifically, the vertical forces (Fz) and anterio-posterior moments (Mx) were analysed. Descriptive statistics were used to interpret the results. With increasing archwire size, Fz and Mx increased at the two brackets (P < 0.05). The vertical forces were linear and symmetric in nature, increasing in magnitude as the bends moved closer to either bracket. The Mx curves were asymmetric and non-linear displaying higher magnitudes for molar bracket. As the bends were moved closer to either bracket a distinct flattening of the incisor Mx curve was noted, implying no change in its magnitude. This article provides critical information on V-bend mechanics involving second order and third order archwire-bracket interactions. A model for determining this force system is described that might allow for easier translation to actual clinical practice. © The Author 2016. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com

Optimization of damping in the passive automotive suspension system with using two quarter-car models

NASA Astrophysics Data System (ADS)

Lozia, Z.; Zdanowicz, P.

2016-09-01

The paper presents the optimization of damping in the passive suspension system of a motor vehicle moving rectilinearly with a constant speed on a road with rough surface of random irregularities, described according to the ISO classification. Two quarter-car 2DoF models, linear and non-linear, were used; in the latter, nonlinearities of spring characteristics of the suspension system and pneumatic tyres, sliding friction in the suspension system, and wheel lift-off were taken into account. The smoothing properties of vehicle tyres were represented in both models. The calculations were carried out for three roads of different quality, with simulating four vehicle speeds. Statistical measures of vertical vehicle body vibrations and of changes in the vertical tyre/road contact force were used as the criteria of system optimization and model comparison. The design suspension displacement limit was also taken into account. The optimum suspension damping coefficient was determined and the impact of undesirable sliding friction in the suspension system on the calculation results was estimated. The results obtained make it possible to evaluate the impact of the structure and complexity of the model used on the results of the optimization.

On occlusal forces in dentitions with implant-supported fixed cantilever prostheses.

PubMed

Falk, H

1990-01-01

The main aims of this thesis were (1) to study the functional characteristics of dentitions with mandibular implant-supported fixed cantilever prostheses - IFCP s- occluding with complete dentures, (2) to study in detail the magnitudes and distributions of axially directed closing and chewing forces in such dentitions, (3) to study the influence of number and distribution of occlusal contacts on the magnitude and distribution of closing and chewing forces, (4) to assess the vertical bending moment and the resulting vertical bending stress in the cantilever joints and (5) to find out whether the force distribution over the cantilever beams and the resulting vertical bending stress in the cantilever joint are influenced by the type of prosthetic construction in the opposing jaw. Closing and chewing forces were registered in altogether seventeen subjects by means of miniature strain gauge transducers mounted bilaterally and symmetrically in performed matrices in prosthetic appliances. Four, six or eight transducers, evenly distributed over the tooth-arch, permitted registrations of axially directed occlusal forces in several occluding areas simultaneously. In Papers I-IV, the implant-supported prostheses were installed in the mandible and occluded with complete dentures. In Paper V, group A, the fixture-supported prostheses were installed in the maxilla and occluded with tooth-supported fixed partial dentures whereas in group B, the arrangements were analogous to those in Papers I-IV. All subjects exhibited a rhythmic chewing pattern and preferred one side for chewing although both sides were used. Most chewing sequences were terminated with swallowing with occlusal force development. The mean total forces acting over the tooth-arch varied somewhat between groups and occlusal arrangements but averaged 350 and 170 N for closing and chewing respectively. Closing and chewing forces increased distally along the cantilever beams when occluding with complete dentures and decreased distally when occluding with fixed partial dentures. The distally increasing force distribution pattern could be altered to a distally decreasing force distribution pattern by infraoccluding the second cantilever unit by as little as 100 microns. Calculated vertical bending moments and stresses in the cantilever joints of the preferred chewing sides created by closing and chewing forces were larger in dentitions where the IFCP occluded with a complete denture than in dentitions where the IFCP occluded with a tooth-supported fixed partial denture.

Response of Ocean Circulation to Different Wind Forcing in Puerto Rico and US Virgin Islands

NASA Astrophysics Data System (ADS)

Solano, Miguel; Garcia, Edgardo; Leonardi, Stafano; Canals, Miguel; Capella, Jorge

2013-11-01

The response of the ocean circulation to various wind forcing products has been studied using the Regional Ocean Modeling System. The computational domain includes the main islands of Puerto Rico, Saint John and Saint Thomas, located on the continental shelf dividing the Caribbean Sea and the Atlantic Ocean. Data for wind forcing is provided by an anemometer located in a moored buoy, the Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) model and the National Digital Forecast Database (NDFD). Hindcast simulations have been validated using hydrographic data at different locations in the area of study. Three cases are compared to quantify the impact of high resolution wind forcing on the ocean circulation and the vertical structure of salinity, temperature and velocity. In the first case a constant wind velocity field is used to force the model as measured by an anemometer on top of a buoy. In the second case, a forcing field provided by the Navy's COAMPS model is used and in the third case, winds are taken from NDFD in collaboration with the National Centers for Environmental Prediction. Validated results of ocean currents against data from Acoustic Doppler Current Profilers at different locations show better agreement using high resolution wind data as expected. Thanks to CariCOOS and NOAA.

On the Effect of Offshore Wind Parks on Ocean Dynamics

NASA Astrophysics Data System (ADS)

Ludewig, E.; Pohlmann, T.

2012-12-01

Nowadays renewable energy resources play a key role in the energy supply discussion and especially an increasingly interest in wind energy induces intensified installations of wind parks. At this offshore wind energy gains in popularity in the course of higher and more consistent energy availability than over land. For example Germany's government adopted a national interurban offshore wind energy program comprising the construction of hundreds of wind turbines within Germany's Exclusive Economic Zone to ensure up to 50% of Germany's renewable energy supply. The large number of installation in coastal regions asks for analyzing the impact of offshore wind parks (OWPs) on the atmosphere and the ocean. As known from literature such wind parks excite also-called wake-effect and such an influence on the wind field in turn affects ocean circulation. To cover OWP's impact on ocean dynamics we evaluate model simulations using the Hamburg Shelf-Ocean-Model (HAMSOM). All simulations were driven with a wind forcing produced by the Mesoscale Atmosphere Model of the Hamburg University (METRAS) which has implemented wind turbines. Wind forcing data were generated in collaboration with and by courtesy of the Meteorological Institute of the University of Hamburg, Department Technical Meteorology, Numeric Modeling-METRAS. To evaluate dynamical changes forced by the OWP's wind wake-effect we did a sensitivity study with a theoretical setup of a virtual ocean of 60m depth with a flat bottom and a temperature and salinity stratification according to common North Sea's conditions. Here our results show that already a small OWP of 12 wind turbines, placed in an area of 4 km^2, lead to a complex change in ocean dynamics. Due to the wake-effect zones of upwelling and downwelling are formed within a minute after turning-on wind turbines. The evolving vertical cells have a size of around 15x15 kilometers with a vertical velocity in order of 10^-2 mm/sec influencing the dynamic of an area being hundred times bigger than the wind park itself. The emerged vertical structure is generated due to a newly created geostrophic balance resulting in a redistribution of the ocean mass field. A number of additional upwelling and downwelling cells around the wind park support an intensified vertical dispersion through all layers and incline the thermocline which also influences the lower levels. The disturbances of mass show a dipole structure across the main wind direction with a maximum change in thermocline depth of some meters close to the OWP. Diffusion, mostly driven by direct wind induced surface shear is also modified by the wind turbines and supports a further modification of the vertical patterns. Considering that wind turbines operate only in a special window of wind speed, i.e. wind turbines will stop in case of too weak or too strong wind speeds as well as in case of technical issues, the averaged dimension and intensity of occurring vertical cells depend on the number of rotors and expected wind speeds. Finally we will focus on scenario runs for the North Sea under fully realistic conditions to estimate possible changes in ocean dynamics due to OWPs in future and these results will be further used for process analyzes of the ecosystem. If we assume a continuous operation of North Sea's OWPs in future we expect a fundamental constant change in ocean dynamics and moreover in the ecosystem in its vicinity.

Worsened physical condition due to climate change contributes to the increasing hypoxia in Chesapeake Bay.

PubMed

Du, Jiabi; Shen, Jian; Park, Kyeong; Wang, Ya Ping; Yu, Xin

2018-07-15

There are increasing concerns about the impact of worsened physical condition on hypoxia in a variety of coastal systems, especially considering the influence of changing climate. In this study, an EOF analysis of the DO data for 1985-2012, a long-term numerical simulation of vertical exchange, and statistical analysis were applied to understand the underlying mechanisms for the variation of DO condition in Chesapeake Bay. Three types of analysis consistently demonstrated that both biological and physical conditions contribute equally to seasonal and interannual variations of the hypoxic condition in Chesapeake Bay. We found the physical condition (vertical exchange+temperature) determines the spatial and seasonal pattern of the hypoxia in Chesapeake Bay. The EOF analysis showed that the first mode, which was highly related to the physical forcings and correlated with the summer hypoxia volume, can be well explained by seasonal and interannual variations of physical variables and biological activities, while the second mode is significantly correlated with the estuarine circulation and river discharge. The weakened vertical exchange and increased water temperature since the 1980s demonstrated a worsened physical condition over the past few decades. Under changing climate (e.g., warming, accelerated sea-level rise, altered precipitation and wind patterns), Chesapeake Bay is likely to experience a worsened physical condition, which will amplify the negative impact of anthropogenic inputs on eutrophication and consequently require more efforts for nutrient reduction to improve the water quality condition in Chesapeake Bay. Copyright © 2018 Elsevier B.V. All rights reserved.

The Impact of Unsteady Reconfiguration on Turbulence Structure within a Flexible Canopy: Large-Eddy Simulation Study of a Cornfield

NASA Astrophysics Data System (ADS)

Chamecki, M.; Pan, Y.; Nepf, H. M.; Follett, E.

2014-12-01

Flexible plants bend in response to fluid motion and this reconfiguration mechanism allows plants to minimize the increase of drag force with increasing velocity, ensuring survival in flow-dominated habitats. The effect of reconfiguration on the flow field can be modeled by introducing a drag coefficient that decreases with increasing velocity. Typically, a power-law decrease of the drag coefficient with increasing velocity is used, and the negative exponent is known as the Vogel number. In practice, the Vogel number is a function of canopy rigidity and flow conditions. In this work we show that accounting for the effect of reconfiguration is required for large-eddy simulation (LES) models to reproduce the skewness of the streamwise and vertical velocity components and the distribution of sweeps and ejections observed in a large cornfield. Additional LES runs are conducted to investigate the structure of turbulence in different reconfiguration regimes, with mean vertical momentum flux constrained by measurements. The change of the Vogel number has negligible effects on LES predictions of the total vertical momentum flux and the components of turbulent kinetic energy, but produces profound changes in the mechanisms of momentum transport. This work demonstrates the necessity to model the effect of reconfiguration in LES studies of canopy flows. It also highlights the impacts of reconfiguration on the structure of turbulence and the dynamics of momentum fluxes, as well as any other process that depends on velocity fluctuations above and within the canopy region.

Analysis of the effects of gravity and wall thickness in a model of blood flow through axisymmetric vessels.

PubMed

Payne, S J

2004-11-01

The effects of gravitational forces and wall thickness on the behaviour of a model of blood flow through axisymmetric vessels were studied. The governing fluid dynamic equations were derived from the Navier-Stokes equations for an incompressible fluid and linked to a simple model of the vessel wall. A closed form of the hyperbolic partial differential equations was found, including a significant source term from the gravitational forces. The inclination of the vessel is modelled using a slope parameter that varied between -1 and 1. The wave speed was shown to be related to the wall thickness, and the time to first shock formation was shown to be directly proportional to this thickness. Two non-dimensional parameters were derived for the ratio of gravitational forces to viscous and momentum forces, respectively, and their values were calculated for the different types of vessel found in the human vasculature, showing that gravitational forces were significant in comparison with either viscous or momentum forces for every type of vessel. The steady-state solution of the governing equations showed that gravitational forces cause an increase in area of approximately 5% per metre per unit slope. Numerical simulations of the flow field in the aorta showed that a positive slope causes a velocity pulse to change in amplitude approximately linearly with distance: -4% per metre and +5% per metre for vessels inclined vertically upwards and downwards, respectively, in comparison with only +0.5% for a horizontal vessel. These simulations also showed that the change relative to the zero slope condition in the maximum rate of change of area with distance, which was taken to be a measure of the rate of shock formation, is proportional to both the slope and the wall thickness-to-inner radius ratio, with a constant of proportionality of 1.2. At a ratio of 0.25, typical of that found in human arteries, the distance to shock formation is thus decreased and increased by 30% for vessels inclined vertically downwards and upwards, respectively. Gravity and wall thickness thus have a significant impact on a number of aspects of the fluid and wall behaviour, despite conventionally being neglected.

Lidocaine permeation from a lidocaine NaCMC/gel microgel formulation in microneedle-pierced skin: vertical (depth averaged) and horizontal permeation profiles.

PubMed

Nayak, Atul; Short, Liam; Das, Diganta B

2015-08-01

Common local anaesthetics such as lidocaine are administered by the hypodermic parenteral route but it causes pain or anxiety to patients. Alternatively, an ointment formulation may be applied which involves a slow drug diffusion process. In addressing these two issues, this paper aims to understand the significance of the 'poke and patch' microneedle (MN) treatment on skin in conjunction to the lidocaine permeation, and in particular, the vertical (depth averaged) and horizontal (e.g. lateral) permeation profiles of the drug in the skin. The instantaneous pharmacokinetics of lidocaine in skin was determined by a skin denaturation technique coupled with Franz diffusion cell measurements of the drug pharmacokinetics. All pharmacokinetic profiles were performed periodically on porcine skin. Three MN insertion forces of 3.9, 7.9 and 15.7 N were applied on the MN to pierce the skin. For the smaller force (3.9 N), post MN-treated skin seems to provide an 'optimum' percutaneous delivery rate. A 10.2-fold increase in lidocaine permeation was observed for a MN insertion force of 3.9 N at 0.25 h and similarly, a 5.4-fold increase in permeation occurred at 0.5 h compared to passive diffusional delivery. It is shown that lidocaine permeates horizontally beyond the area of the MN-treated skin for the smaller MN insertion forces, namely, 3.9 and 7.9 N from 0.25 to 0.75 h, respectively. The lateral diffusion/permeation of lidocaine for larger MN-treated force (namely, 15.7 N in this work) seems to be insignificant at all recorded timings. The MN insertion force of 15.7 N resulted in lidocaine concentrations slightly greater than control (passive diffusion) but significantly less than 3.9 and 7.9 N impact force treatments on skin. We believe this likelihood is due to the skin compression effect that inhibits diffusion until the skin had time to relax at which point lidocaine levels increase.

A Novel Approach to Apply Gait Synchronized External Forces on the Pelvis using A-TPAD to Reduce Walking Effort

PubMed Central

Vashista, Vineet; Khan, Moiz; Agrawal, Sunil K.

2017-01-01

In this paper, we develop an intervention to apply external gait synchronized forces on the pelvis to reduce the user’s effort during walking. A cable-driven robot was used to apply the external forces and an adaptive frequency oscillator scheme was developed to adapt the timing of force actuation to the gait frequency during walking. The external forces were directed in the sagittal plane to assist the trailing leg during the forward propulsion and vertical deceleration of the pelvis during the gait cycle. A pilot experiment with five healthy subjects was conducted. The results showed that the subjects applied lower ground reaction forces in the vertical and anterior-posterior directions during the late stance phase. In summary, the current work provides a novel approach to study the role of external pelvic forces in altering the walking effort. These studies can provide better understanding for designing exoskeletons and prosthetic devices to reduce the overall walking effort. PMID:29623294

Gait ground reaction force characteristics of low back pain patients with pronated foot and able-bodied individuals with and without foot pronation.

PubMed

Farahpour, Nader; Jafarnezhad, AmirAli; Damavandi, Mohsen; Bakhtiari, Abbas; Allard, Paul

2016-06-14

The link between gait parameters and foot abnormalities in association with low back pain is not well understood. The objective of this study was to investigate the effects of excessive foot pronation as well as the association of LBP with excessive foot pronation on the GRF components during shod walking. Forty-five subjects were equally divided into a control group, a group of subjects with pronated feet only, and another group with pronated feet and LBP. Ground reaction forces were analyzed during shod walking. Foot pronation without low back pain was associated with increased lateral-medial ground reaction force, impulse, and time to peak of all reaction forces in heel contact phase (p<0.03). In low back pain patients with pronated foot, greater vertical reaction forces (p=0.001) and loading rate, and time to peak on propulsion force were observed compared to pronated foot without low back pain group. Impulse in posterior-anterior reaction force was smaller in the able-bodied group with normal foot than in the other groups (p<0.05). Positive peak of free moments of the LBP group was significantly greater than that in other groups (p<0.05). In conclusion, foot pronation alone was not associated with elevated vertical ground reaction forces. While, low back pain patients with foot pronation displayed higher vertical ground reaction force as well as higher loading rate. Present results reveal that gait ground reaction force components in low back pain patients with pronated foot may have clinical values on the prognosis and rehabilitation of mechanical LBP patients. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of occlusal splint therapy on maximum bite force in individuals with moderate to severe attrition of teeth.

PubMed

Jain, Veena; Mathur, Vijay Prakash; Abhishek, Kumar; Kothari, Mohit

2012-10-01

The purpose of the pilot study was to determine the effect of restoring lost occlusal vertical dimension (OVD) due to attrition on maximum bite force in humans. A total of 124 subjects in age range of 25-40 years, with moderate to severe attrition, having full complement of teeth were screened according to inclusion and exclusion criteria. After consent, occlusal vertical dimension was assessed by employing mechanical and physiological methods in the experimental group and a maxillary canine guided hard splint was fabricated for each subjects fulfilling inclusion criteria and with positive consent (78). Bite force in experimental group was measured before, immediately after delivery of splint and subsequently at an interval of four, eight, and twelve weeks. Due loss during follow up, only 50 subjects could be available for bite force recording till 12 weeks. Bite force of age, gender, height and weight matched controls with no signs of attrition was also measured for comparison. Bite force of the experimental group was found to be significantly less than the matched controls (P=0.000) initially. After delivery of splint, bite force values increased progressively till twelve weeks. However comparison of bite force values of experimental group with control group showed no significant difference at end of eight (P=0.008) and twelve weeks (P=0.162). It was concluded that maximum bite force increases with restoration of lost vertical using splint therapy. A time period of 8-12 weeks is required to restore the maximum bite force value approximately similar to matched controls. Copyright © 2012 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Total Longitudinal Moment Calculation and Reliability Analysis of Yacht Structures

NASA Astrophysics Data System (ADS)

Zhi, Wenzheng; Lin, Shaofen

In order to check the reliability of the yacht in FRP (Fiber Reinforce Plastic) materials, in this paper, the vertical force and the calculation method of the overall longitudinal bending moment on yacht was analyzed. Specially, this paper focuses on the impact of speed on the still water bending moment on yacht. Then considering the mechanical properties of the cap type stiffeners in composite materials, the ultimate bearing capacity of the yacht has been worked out, finally the reliability of the yacht was calculated with using response surface methodology. The result can be used in yacht design and yacht driving.

OH-58 Composite Main Rotor Blade Preliminary Design Investigation

DTIC Science & Technology

1978-11-01

of Damage on Root Loads. . . .... .......... 138 59 Effect of Damage on Fixed Hub Vertical Forces . . . 139 60 Schematic of Impact Test Fixture...LINE C •.. ~~OSTN .-- cs VRr -7 Ai . 60 (TYP)1.65] 3.30 "TWIST REp? LINE e ~ ~ ~ _l H,,i...%-.lORI.ZONTAL REF $UNE .- 2. 4 .. , +-+ Figure 4. OH-58C/A...I 0 -- . .. . . . . -- - -- _ . .. I-z _-- .. ~>0 co 0 0 4 wU) 04 C;C4t44 %0 400 a cH cmI C4 to co 4a co 60 c 0 1 o c4 % ol WA

Exploring coral reef responses to millennial-scale climatic forcings: insights from the 1-D numerical tool pyReef-Core v1.0

NASA Astrophysics Data System (ADS)

Salles, Tristan; Pall, Jodie; Webster, Jody M.; Dechnik, Belinda

2018-06-01

Assemblages of corals characterise specific reef biozones and the environmental conditions that change spatially across a reef and with depth. Drill cores through fossil reefs record the time and depth distribution of assemblages, which captures a partial history of the vertical growth response of reefs to changing palaeoenvironmental conditions. The effects of environmental factors on reef growth are well understood on ecological timescales but are poorly constrained at centennial to geological timescales. pyReef-Core is a stratigraphic forward model designed to solve the problem of unobservable environmental processes controlling vertical reef development by simulating the physical, biological and sedimentological processes that determine vertical assemblage changes in drill cores. It models the stratigraphic development of coral reefs at centennial to millennial timescales under environmental forcing conditions including accommodation (relative sea-level upward growth), oceanic variability (flow speed, nutrients, pH and temperature), sediment input and tectonics. It also simulates competitive coral assemblage interactions using the generalised Lotka-Volterra system of equations (GLVEs) and can be used to infer the influence of environmental conditions on the zonation and vertical accretion and stratigraphic succession of coral assemblages over decadal timescales and greater. The tool can quantitatively test carbonate platform development under the influence of ecological and environmental processes and efficiently interpret vertical growth and karstification patterns observed in drill cores. We provide two realistic case studies illustrating the basic capabilities of the model and use it to reconstruct (1) the Holocene history (from 8500 years to present) of coral community responses to environmental changes and (2) the evolution of an idealised coral reef core since the last interglacial (from 140 000 years to present) under the influence of sea-level change, subsidence and karstification. We find that the model reproduces the details of the formation of existing coral reef stratigraphic sequences both in terms of assemblages succession, accretion rates and depositional thicknesses. It can be applied to estimate the impact of changing environmental conditions on growth rates and patterns under many different settings and initial conditions.

A High Resolution Study of Black Sea Circulation and Hypothetical Oil Spills

NASA Astrophysics Data System (ADS)

Dietrich, D. E.; Bowman, M. J.; Korotenko, K. A.

2008-12-01

A 1/24 deg resolution adaptation of the DieCAST ocean model simulates a realistically intense Rim Current and ubiquitous mesoscale coastal anticyclonic eddies that result from anticyclonic vorticity generation by laterally differential bottom drag forces that are amplified near Black Sea coastal headlands. Climatological and synoptic surface forcings are compared. The effects of vertical momentum transfer by known (by Synop region fishermen, as reported by Ballard National Geographic article) big amplitude internal waves are parameterized by big vertical viscosity. Sensitivity to vertical viscosity is shown. Results of simulated hypothetical oil spills are shown. A simple method to nowcast/forecast the Black Sea currents is described and early results are shown.

Wave Shape and Impact Pressure Measurements at a Rock Coast Cliff

NASA Astrophysics Data System (ADS)

Varley, S. J.; Rosser, N. J.; Brain, M.; Vann Jones, E. C.

2016-02-01

Rock coast research focuses largely on wave behaviour across beaches and shore platforms but rarely considers direct wave interaction with cliffs. Hydraulic action is one of the most important drivers of erosion along rock coasts. The magnitude of wave impact pressure has been shown by numerical and laboratory studies to be related to the wave shape. In deep water, a structure is only subjected to the hydrostatic pressure due to the oscillating clapotis. Dynamic pressures, related to the wave celerity, are exerted in shallower water when the wave is breaking at the point of impact; very high magnitude, short duration shock pressures are theorised to occur when the approaching wavefront is vertical. As such, wave shape may directly influence the potential of the impact to weaken rock and cause erosion. Measurements of impact pressure at coastal cliffs are limited, and the occurrence and influence of this phenomenon is currently poorly constrained. To address this, we have undertaken a field monitoring study on the magnitude and vertical distribution of wave impact pressures at the rocky, macro-tidal coastline of Staithes, North Yorkshire, UK. A series of piezo-resistive pressure transducers and a camera were installed at the base of the cliff during low tide. Transducers were deployed vertically up the cliff face and aligned shore-normal to capture the variation in static and dynamic pressure with height during a full spring tidal cycle. Five minute bursts of 5 kHz pressure readings and 4 Hz wave imaging were sampled every 30 minutes for six hours during high tide. Pressure measurements were then compensated for temperature and combined with wave imaging to produce a pressure time series and qualitative wave shape category for each wave impact. Results indicate the presence of a non-linear relationship between pressure impact magnitude, the occurrence of shock pressures, wave shape and tidal stage, and suggest that breaker type on impact (and controls thereof) may be fundamental in dictating the effectiveness of hydraulic action in eroding rock coast cliffs. Our findings demonstrate the sensitivity of wave loading to changes in water depth and, hence, projected sea-level rise. This research leads directly into a wider project investigating the role of wave shape as a key control on marine forcing of erosion.

Impact absorption properties of carbon fiber reinforced bucky sponges

NASA Astrophysics Data System (ADS)

Thevamaran, Ramathasan; Saini, Deepika; Karakaya, Mehmet; Zhu, Jingyi; Podila, Ramakrishna; Rao, Apparao M.; Daraio, Chiara

2017-05-01

We describe the super compressible and highly recoverable response of bucky sponges as they are struck by a heavy flat-punch striker. The bucky sponges studied here are structurally stable, self-assembled mixtures of multiwalled carbon nanotubes (MWCNTs) and carbon fibers (CFs). We engineered the microstructure of the sponges by controlling their porosity using different CF contents. Their mechanical properties and energy dissipation characteristics during impact loading are presented as a function of their composition. The inclusion of CFs improves the impact force damping by up to 50% and the specific damping capacity by up to 7% compared to bucky sponges without CFs. The sponges also exhibit significantly better stress mitigation characteristics compared to vertically aligned CNT foams of similar densities. We show that delamination occurs at the MWCNT-CF interfaces during unloading, and it arises from the heterogeneous fibrous microstructure of the bucky sponges.

Assessing the vertical structure of baroclinic tidal currents in a global model

NASA Astrophysics Data System (ADS)

Timko, Patrick; Arbic, Brian; Scott, Robert

2010-05-01

Tidal forcing plays an important role in many aspects of oceanography. Mixing, transport of particulates and internal wave generation are just three examples of local phenomena that may depend on the strength of local tidal currents. Advances in satellite altimetry have made an assessment of the global barotropic tide possible. However, the vertical structure of the tide may only be observed by deployment of instruments throughout the water column. Typically these observations are conducted at pre-determined depths based upon the interest of the observer. The high cost of such observations often limits both the number and the length of the observations resulting in a limit to our knowledge of the vertical structure of tidal currents. One way to expand our insight into the baroclinic structure of the ocean is through the use of numerical models. We compare the vertical structure of the global baroclinic tidal velocities in 1/12 degree HYCOM (HYbrid Coordinate Ocean Model) to a global database of current meter records. The model output is a subset of a 5 year global simulation that resolves the eddying general circulation, barotropic tides and baroclinic tides using 32 vertical layers. The density structure within the simulation is both vertically and horizontally non-uniform. In addition to buoyancy forcing the model is forced by astronomical tides and winds. We estimate the dominant semi-diurnal (M2), and diurnal (K1) tidal constituents of the model data using classical harmonic analysis. In regions where current meter record coverage is adequate, the model skill in replicating the vertical structure of the dominant diurnal and semi-diurnal tidal currents is assessed based upon the strength, orientation and phase of the tidal ellipses. We also present a global estimate of the baroclinic tidal energy at fixed depths estimated from the model output.

16 Weeks of Progressive Barefoot Running Training Changes Impact Force and Muscle Activation in Habitual Shod Runners

PubMed Central

Mezêncio, Bruno; Amadio, Alberto Carlos; Serrão, Julio Cerca

2016-01-01

Short-term effects of barefoot and simulated barefoot running have been widely discussed in recent years. Consequences of adopting barefoot running for a long period, including as a training approach, still remain unknown. The present study evaluated the influence of 16 weeks of progressive barefoot running training on impact force and muscle activation in habitual shod runners. Six habitual shod runners (3 men and 3 women, 29.5 ± 7.3 years) were tested barefoot (BF) and shod (SH), before and after 16 weeks of progressive barefoot running training. Tests consisted of running on instrumented treadmill at 9 km/h, for 10 minutes in each experimental condition. Nine data acquisitions (10 s) of vertical ground reaction force (VGRF) and electromyographic (EMG) signal were conducted in each experimental condition for each test. BF training was effective to alter VGRF and EMG parameters of running in habitual shod runners, regardless of footwear condition (SH or BF). The magnitude of first peak of VGRF (Fy1) and the impulse of the first 50 ms decreased after training for BF and SH (p<0.01). The activation reduced from PRE to POST training for four muscles in BF running (p<0.001), whereas only muscle gastrocnemius lateralis decreased significantly its activation (p<0.01) in SH running. A 16-week progressive barefoot running training seems to be an effective training strategy to reduce impact force, improve shock attenuation and to decrease muscle activation intensity, not only in BF running, but also in SH running, although BF condition seems to be more influenced by BF training. PMID:27907069

Comparison of force plate gait analysis and owner assessment of pain using the Canine Brief Pain Inventory in dogs with osteoarthritis.

PubMed

Brown, D C; Boston, R C; Farrar, J T

2013-01-01

Lameness assessment using force plate gait analysis (FPGA) and owner assessment of chronic pain using the Canine Brief Pain Inventory (CBPI) are valid and reliable methods of evaluating canine osteoarthritis. There are no studies comparing these 2 outcome measures. Evaluate the relationship between CBPI pain severity (PS) and interference (PI) scores with the vertical forces of FPGA as efficacy measures in canine osteoarthritis. Sixty-eight client-owned dogs with osteoarthritis (50 hind limb and 18 forelimb). Double-blind, randomized. Owners completed the CBPI, and dogs underwent FPGA on days 0 and 14. Dogs received carprofen or placebo on days 1 through 14. The change in PS and PI scores from day 0 to 14 were compared to the change in peak vertical force (PVF) and vertical impulse (VI). PS and PI scores significantly decreased in carprofen- compared with placebo-treated dogs (P = .002 and P = .03, respectively). PVF and VI significantly increased in carprofen- compared with placebo-treated dogs (P = .006 and P = .02, respectively). There was no correlation or concordance between the PS or PI score changes and change in PVF or VI. In these dogs with hind limb or forelimb osteoarthritis, owner assessment of chronic pain using the CBPI and assessment of lameness using FPGA detected significant improvement in dogs treated with carprofen. The lack of correlation or concordance between the change in owner scores and vertical forces suggests that owners were focused on behaviors other than lameness when making efficacy evaluations in their dogs. Copyright © 2012 by the American College of Veterinary Internal Medicine.

A simple method of equine limb force vector analysis and its potential applications.

PubMed

Hobbs, Sarah Jane; Robinson, Mark A; Clayton, Hilary M

2018-01-01

Ground reaction forces (GRF) measured during equine gait analysis are typically evaluated by analyzing discrete values obtained from continuous force-time data for the vertical, longitudinal and transverse GRF components. This paper describes a simple, temporo-spatial method of displaying and analyzing sagittal plane GRF vectors. In addition, the application of statistical parametric mapping (SPM) is introduced to analyse differences between contra-lateral fore and hindlimb force-time curves throughout the stance phase. The overall aim of the study was to demonstrate alternative methods of evaluating functional (a)symmetry within horses. GRF and kinematic data were collected from 10 horses trotting over a series of four force plates (120 Hz). The kinematic data were used to determine clean hoof contacts. The stance phase of each hoof was determined using a 50 N threshold. Vertical and longitudinal GRF for each stance phase were plotted both as force-time curves and as force vector diagrams in which vectors originating at the centre of pressure on the force plate were drawn at intervals of 8.3 ms for the duration of stance. Visual evaluation was facilitated by overlay of the vector diagrams for different limbs. Summary vectors representing the magnitude (VecMag) and direction (VecAng) of the mean force over the entire stance phase were superimposed on the force vector diagram. Typical measurements extracted from the force-time curves (peak forces, impulses) were compared with VecMag and VecAng using partial correlation (controlling for speed). Paired samples t -tests (left v. right diagonal pair comparison and high v. low vertical force diagonal pair comparison) were performed on discrete and vector variables using traditional methods and Hotelling's T 2 tests on normalized stance phase data using SPM. Evidence from traditional statistical tests suggested that VecMag is more influenced by the vertical force and impulse, whereas VecAng is more influenced by the longitudinal force and impulse. When used to evaluate mean data from the group of ten sound horses, SPM did not identify differences between the left and right contralateral limb pairs or between limb pairs classified according to directional asymmetry. When evaluating a single horse, three periods were identified during which differences in the forces between the left and right forelimbs exceeded the critical threshold ( p  < .01). Traditional statistical analysis of 2D GRF peak values, summary vector variables and visual evaluation of force vector diagrams gave harmonious results and both methods identified the same inter-limb asymmetries. As alpha was more tightly controlled using SPM, significance was only found in the individual horse although T 2 plots followed the same trends as discrete analysis for the group. The techniques of force vector analysis and SPM hold promise for investigations of sidedness and asymmetry in horses.

Lateral forces exerted through ball or bar attachments in relation to the inclination of mini-implant underneath overdentures: in vitro study.

PubMed

Takagaki, Kyozo; Gonda, Tomoya; Maeda, Yoshinobu

2015-09-01

Lateral force to mini-implants should be avoided because mini-implants are weak mechanically because of its small diameter. Overdentures retained by mini-implants are usually formed using ball attachments. However, bar attachments can offer the advantage of splinting the mini-implants. This study examined the effect of attachments in withstanding these lateral forces in tilted mini-implants of overdentures. Strain gauges were attached to the mini-implants (2.5 × 18 mm) embedded in an acrylic resin block. Two mini-implants were inserted vertically (Control) or with one mini-implant inclined at 10° or 20° (10-inclined and 20-inclined, respectively). The female portions of the attachments were secured to the denture base. A prefabricated ball attachment and CAD/CAM-fabricated bar attachment were compared. A vertical load of 49 N was applied to the occlusal surface at a distance 10 mm away from the center of two mini-implants. The lateral force borne by the mini-implants was measured via the attached strain gauge. Mann-Whitney U-test and an analysis of Bonferroni correction were used to compare differences between the two attachments and among the three models (P < 0.05). The lateral force exerted to the inclined mini-implant was significantly greater than that borne by a vertical mini-implant for both attachment types. The lateral force on the 20° inclined mini-implants with bar attachments was smaller than that on mini-implants with ball attachments. Inclined mini-implants are subjected to greater stresses than vertical ones, and a bar attachment can reduce the lateral forces borne by the mini-implant when one mini-implant inclined at 20°. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

The roles of vertical mixing, solar radiation, and wind stress in a model simulation of the sea surface temperature seasonal cycle in the tropical Pacfic Ocean

NASA Technical Reports Server (NTRS)

Chen, Dake; Busalacchi, Antonio J.; Rothstein, Lewis M.

1994-01-01

The climatological seasonal cycle of sea surface temperature (SST) in the tropical Pacific is simulated using a newly developed upper ocean model. The roles of vertical mixing, solar radiation, and wind stress are investigated in a hierarchy of numerical experiments with various combinations of vertical mixing algorithms and surface-forcing products. It is found that the large SST annual cycle in the eastern equatorial Pacific is, to a large extent, controlled by the annually varying mixed layer depth which, in turn, is mainly determined by the competing effects of solar radiation and wind forcing. With the application of our hybrid vertical mixing scheme the model-simulated SST annual cycle is much improved in both amplitude and phase as compared to the case of a constant mixed layer depth. Beside the strong effects on vertical mixing, solar radiation is the primary heating term in the surface layer heat budget, and wind forcing influences SST by driving oceanic advective processes that redistribute heat in the upper ocean. For example, the SST seasonal cycle in the western Pacific basically follows the semiannual variation of solar heating, and the cycle in the central equatorial region is significantly affected by the zonal advective heat flux associated with the seasonally reversing South Equatorial Current. It has been shown in our experiments that the amount of heat flux modification needed to eliminate the annual mean SST errors in the model is, on average, no larger than the annual mean uncertainties among the various surface flux products used in this study. Whereas a bias correction is needed to account for remaining uncertainties in the annual mean heat flux, this study demonstrates that with proper treatment of mixed layer physics and realistic forcing functions the seasonal variability of SST is capable of being simulated successfully in response to external forcing without relying on a relaxation or damping formulation for the dominant surface heat flux contributions.

Quadrupedal galloping control for a wide range of speed via vertical impulse scaling.

PubMed

Park, Hae-Won; Kim, Sangbae

2015-03-25

This paper presents a bio-inspired quadruped controller that allows variable-speed galloping. The controller design is inspired by observations from biological runners. Quadrupedal animals increase the vertical impulse that is generated by ground reaction forces at each stride as running speed increases and the duration of each stance phase reduces, whereas the swing phase stays relatively constant. Inspired by this observation, the presented controller estimates the required vertical impulse at each stride by applying the linear momentum conservation principle in the vertical direction and prescribes the ground reaction forces at each stride. The design process begins with deriving a planar model from the MIT Cheetah 2 robot. A baseline periodic limit cycle is obtained by optimizing ground reaction force profiles and the temporal gait pattern (timing and duration of gait phases). To stabilize the optimized limit cycle, the obtained limit cycle is converted to a state feedback controller by representing the obtained ground reaction force profiles as functions of the state variable, which is monotonically increasing throughout the gait, adding impedance control around the height and pitch trajectories of the obtained limit cycle and introducing a finite state machine and a pattern stabilizer to enforce the optimized gait pattern. The controller that achieves a stable 3 m s(-1) gallop successfully adapts the speed change by scaling the vertical ground reaction force to match the momentum lost by gravity and adding a simple speed controller that controls horizontal speed. Without requiring additional gait optimization processes, the controller achieves galloping at speeds ranging from 3 m s(-1) to 14.9 m s(-1) while respecting the torque limit of the motor used in the MIT Cheetah 2 robot. The robustness of the controller is verified by demonstrating stable running during various disturbances, including 1.49 m step down and 0.18 m step up, as well as random ground height and model parameter variations.

Formation of correlated states and optimization of nuclear reactions for low-energy particles at nonresonant low-frequency modulation of a potential well

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

Vysotskii, V. I., E-mail: vivysotskii@gmail.com; Vysotskyy, M. V.

2015-02-15

A method for the formation of correlated coherent states of low-energy particles in a parabolic potential well owing to the full-scale low-frequency modulation ω(t) = ω{sub 0}sinΩt of the parameters of this well has been considered. It has been shown that such a modulation in the absence of a stochastic force acting on a particle results in the fast formation of correlated coherent states and in an increase in the correlation coefficient and transparency of the potential barrier to the limiting values vertical bar r(t) vertical bar {sub max} → 1 and D → 1. The presence of the stochasticmore » force significantly affects the evolution of correlated coherent states, decreasing the rate of an increase in the correlation coefficient vertical bar r(t) vertical bar {sub max} (at Ω ≤ 10{sup −4}ω{sub 0}) and limiting it at the level vertical bar r(∞) vertical bar {sub max} < 1 (at Ω = (0.001–0.1)ω{sub 0}); vertical bar r(∞) vertical bar {sub max} increases with a decrease in the frequency of modulation and decreases with an increase in the intensity of the stochastic force. It has been shown that, at a realistic relation between the parameters, low-frequency modulation can ensure such vertical bar r vertical bar {sub max} value that the transparency of the potential barrier for low-energy particles increases by a factor of 10{sup 50}–10{sup 100} or larger. The mechanism of the formation of correlated coherent states for charged particles in a gas or a low-pressure plasma placed in a low-frequency magnetic field has been considered. We have determined the relation between the magnetic field strength and modulation frequency, as well as the relation between the temperature and density of the gas (plasma), at which the method under consideration can be used to optimize nuclear reactions at low energies.« less

Forces Generated by Vastus Lateralis and Vastus Medialis Decrease with Increasing Stair Descent Speed.

PubMed

Caruthers, Elena J; Oxendale, Kassandra K; Lewis, Jacqueline M; Chaudhari, Ajit M W; Schmitt, Laura C; Best, Thomas M; Siston, Robert A

2018-04-01

Stair descent (SD) is a common, difficult task for populations who are elderly or have orthopaedic pathologies. Joint torques of young, healthy populations during SD increase at the hip and ankle with increasing speed but not at the knee, contrasting torque patterns during gait. To better understand the sources of the knee torque pattern, we used dynamic simulations to estimate knee muscle forces and how they modulate center of mass (COM) acceleration across SD speeds (slow, self-selected, and fast) in young, healthy adults. The vastus lateralis and vastus medialis forces decreased from slow to self-selected speeds as the individual lowered to the next step. Since the vasti are primary contributors to vertical support during SD, they produced lower forces at faster speeds due to the lower need for vertical COM support observed at faster speeds. In contrast, the semimembranosus and rectus femoris forces increased across successive speeds, allowing the semimembranosus to increase acceleration downward and forward and the rectus femoris to provide more vertical support and resistance to forward progression as SD speed increased. These results demonstrate the utility of dynamic simulations to extend beyond traditional inverse dynamics analyses to gain further insight into muscle mechanisms during tasks like SD.

Kinematics and Kinetics of Squats, Drop Jumps and Imitation Jumps of Ski Jumpers.

PubMed

Pauli, Carole A; Keller, Melanie; Ammann, Fabian; Hübner, Klaus; Lindorfer, Julia; Taylor, William R; Lorenzetti, Silvio

2016-03-01

Squats, drop jumps, and imitation jumps are commonly used training exercises in ski jumping to enhance maximum force, explosive force, and sport-specific skills. The purpose of this study was to evaluate the kinetics and kinematics of training exercises in ski jumping and to find objective parameters in training exercises that most correlate with the competition performance of ski jumpers. To this end, barbell squats, drop jumps, and imitation jumps were measured in a laboratory environment for 10 elite ski jumpers. Force and motion data were captured, and the influence of maximum vertical force, force difference, vertical take-off velocity, knee moments, knee joint power, and a knee valgus/varus index was evaluated and correlated with their season jump performance. The results indicate that, especially for the imitation jumps, a good correlation exists between the vertical take-off velocity and the personal jump performance on the hill (R = 0.718). Importantly, however, the more the athletes tended toward a valgus knee alignment during the measured movements, the worse their performance (R = 0.729 imitation jumps; R = 0.685 squats). Although an evaluation of the athletes' lower limb alignment during competitive jumping on the hill is still required, these preliminary data suggest that performance training should additionally concentrate on improving knee alignment to increase ski jumping performance.

Ultrasonic Measurement of Strain Distribution Inside Object Cyclically Compressed by Dual Acoustic Radiation Force

NASA Astrophysics Data System (ADS)

Odagiri, Yoshitaka; Hasegawa, Hideyuki; Kanai, Hiroshi

2008-05-01

One possible way to evaluate acupuncture therapy quantitatively is to measure the change in the elastic property of muscle after application of the therapy. Many studies have been conducted to measure mechanical properties of tissues using ultrasound-induced acoustic radiation force. To assess mechanical properties, strain must be generated in an object. However, a single radiation force is not effective because it mainly generates translational motion when the object is much harder than the surrounding medium. In this study, two cyclic radiation forces are simultaneously applied to a muscle phantom from two opposite horizontal directions so that the object is cyclically compressed in the horizontal direction. By the horizontal compression, the object is expanded vertically based on its incompressibility. The resultant vertical displacement is measured using another ultrasound pulse. Two ultrasonic transducers for actuation were both driven by the sum of two continuous sinusoidal signals at two slightly different frequencies [1 MHz and (1 M + 5) Hz]. The displacement of several micrometers in amplitude, which fluctuated at 5 Hz, was measured by the ultrasonic phased tracking method. Increase in thickness inside the object was observed just when acoustic radiation forces increased. Such changes in thickness correspond to vertical expansion due to horizontal compression.

Comparative Analysis of the Tour Jete and Aerial with Detailed Analysis of Aerial Takeoff Mechanics

NASA Astrophysics Data System (ADS)

Pierson, Mimi; Coplin, Kim

2006-10-01

Whether internally as muscle tension or from external sources, forces are necessary for all motion. This research focused on athletic rotations where conditions of flight are established during takeoff. By studying reaction forces that produce torques, moments of inertia, and linear and angular differences between distinct rotations around different principle axes of the body (tour jete in ballet - longitudinal axis; aerial in gymnastics - anteroposterior axis), and by looking at the values of angular momentum in the specific mechanics of aerial takeoff, we can gain insight into possible causes of injury, flaws in technique and limitations of athletes. Results showed significant differences in the horizontal and vertical components of takeoff between the tour jete and the aerial, and a realization that torque was produced in different biomechanical planes. Both rotations showed braking forces before takeoff to counteract forward momentum and increase vertical lift, but the angle of applied force varied, and the horizontal components of velocity and force and vertical velocity as well as moment of inertia throughout flight were consistently greater for the aerial. Breakdown of aerial takeoff highlighted the relative importance of the takeoff phases, showing that completion depends fundamentally upon the rotation of the rear foot and torso twisting during takeoff rather than the last foot in contact with the ground.

Ground reaction forces and heart rate profile of aerobic dance instructors during a low and high impact exercise programme.

PubMed

Rousanoglou, E N; Boudolos, K D

2005-06-01

The magnitude of ground reaction forces (GRF) has been associated, although never verified, with the high incidence of lower extremities injuries in aerobic dance (AD) instructors. Moreover, during their working activities AD instructors have demonstrated HR levels, such as 70% HRmax, values, more in training rather in working status. This study was designed to investigate GRF and heart rate (HR) exhibited by AD instructors of both genders, during a simulated AD instruction, from the perspective of accepted occupational workloads. Fourteen females and 14 males instructors performed a 35 min AD exercise programme (warm up--low impact (LI) interval--in high impact (HI) interval--cool down). Four GRF measurements were taken during LI and HI time intervals, respectively. HR was recorded throughout the whole experimental procedure and was synchronised to GRF measurements. All GRF and HR values were significantly increased in HI exercise (p<0.05) with a non significant (p>0.05) time effect for GRF. In both LI and HI exercises, females demonstrated significantly higher vertical but lower lateral GRF (p<0.05) and significantly shorter cycles of movement (p<0.05) while in HI exercise they had significant longer flight times (p<0.05). For both genders, HR was kept at 70% and 80% of HR(max-calc) and RHR was 60% and 70%, during LI and HI intervals respectively, with females showing a trend, though non-significant, for higher HR values. The gender specificity of the significant vertical and lateral GRF pattern differences, may possibly be associated with the significant anthropometric differences of male and female AD instructors. HR(max-calc) and RHR exceeded the accepted occupational levels rising to training status levels. We suggest that AD instructors take up such instructing methods which allow them to minimize the magnitude or the rate of GRF, as well as HR levels, developed in the course of their working hour.

Characterizing the Severe Turbulence Environments Associated with Commercial Aviation Accidents. Part 2; Hydrostatic Mesobeta Scale Numerical Simulations of Supergradient Wind Flow and Streamwise Ageostrophic Frontogenesis

NASA Technical Reports Server (NTRS)

Kaplan, Michael L.; Huffman, Allan W.; Lux, Kevin M.; Cetola, Jeffrey D.; Charney, Joseph J.; Riordan, Allen J.; Lin, Yuh-Lang; Waight, Kenneth T., III; Proctor, Fred (Technical Monitor)

2003-01-01

Simulation experiments reveal key processes that organize a hydrostatic environment conducive to severe turbulence. The paradigm requires juxtaposition of the entrance region of a curved jet stream, which is highly subgeostrophic, with the entrance region of a straight jet stream, which is highly supergeostrophic. The wind and mass fields become misphased as the entrance regions converge resulting in the significant spatial variation of inertial forcing, centripetal forcing, and along- and cross-stream pressure gradient forcing over a mesobeta scale region. This results in frontogenesis and the along-stream divergence of cyclonic and convergence of cyclonic ageostrophic vertical vorticity. The centripetally forced mesoscale front becomes the locus of large gradients of ageostrophic vertical vorticity along an overturning isentrope. This region becomes favorable for streamwise vorticity gradient formation enhancing the environment for organization of horizontal vortex tubes in the presence of buoyant forcing.

The response of an airplane to random atmospheric disturbances

NASA Technical Reports Server (NTRS)

Diederich, Franklin W

1957-01-01

The statistical approach to the gust-load problem which consists in considering flight through turbulent air to be a stationary random process is extended by including the effect of lateral variation of the instantaneous gust intensity on the aerodynamic forces. The forces obtained in this manner are used in dynamic analyses of rigid and flexible airplanes free to move vertically, in pitch, and in roll. The effect of the interaction of longitudinal, vertical, and lateral gusts on the wing stresses is also considered.

Are running speeds maximized with simple-spring stance mechanics?

PubMed

Clark, Kenneth P; Weyand, Peter G

2014-09-15

Are the fastest running speeds achieved using the simple-spring stance mechanics predicted by the classic spring-mass model? We hypothesized that a passive, linear-spring model would not account for the running mechanics that maximize ground force application and speed. We tested this hypothesis by comparing patterns of ground force application across athletic specialization (competitive sprinters vs. athlete nonsprinters, n = 7 each) and running speed (top speeds vs. slower ones). Vertical ground reaction forces at 5.0 and 7.0 m/s, and individual top speeds (n = 797 total footfalls) were acquired while subjects ran on a custom, high-speed force treadmill. The goodness of fit between measured vertical force vs. time waveform patterns and the patterns predicted by the spring-mass model were assessed using the R(2) statistic (where an R(2) of 1.00 = perfect fit). As hypothesized, the force application patterns of the competitive sprinters deviated significantly more from the simple-spring pattern than those of the athlete, nonsprinters across the three test speeds (R(2) <0.85 vs. R(2) ≥ 0.91, respectively), and deviated most at top speed (R(2) = 0.78 ± 0.02). Sprinters attained faster top speeds than nonsprinters (10.4 ± 0.3 vs. 8.7 ± 0.3 m/s) by applying greater vertical forces during the first half (2.65 ± 0.05 vs. 2.21 ± 0.05 body wt), but not the second half (1.71 ± 0.04 vs. 1.73 ± 0.04 body wt) of the stance phase. We conclude that a passive, simple-spring model has limited application to sprint running performance because the swiftest runners use an asymmetrical pattern of force application to maximize ground reaction forces and attain faster speeds. Copyright © 2014 the American Physiological Society.

Seismic-geodynamic constraints on three-dimensional structure, vertical flow, and heat transfer in the mantle

USGS Publications Warehouse

Forte, A.M.; Woodward, R.L.

1997-01-01

Joint inversions of seismic and geodynamic data are carried out in which we simultaneously constrain global-scale seismic heterogeneity in the mantle as well as the amplitude of vertical mantle flow across the 670 km seismic discontinuity. These inversions reveal the existence of a family of three-dimensional (3-D) mantle models that satisfy the data while at the same time yielding predictions of layered mantle flow. The new 3-D mantle models we obtain demonstrate that the buoyancy forces due to the undulations of the 670 km phase-change boundary strongly inhibit the vertical flow between the upper and lower mantle. The strong stabilizing effect of the 670 km topography also has an important impact on the predicted dynamic topography of the Earth's solid surface and on the surface gravity anomalies. The new 3-D models that predict strongly or partially layered mantle flow provide essentially identical fits to the global seismic data as previous models that have, until now, predicted only whole-mantle flow. The convective vertical transport of heat across the mantle predicted on the basis of the new 3-D models shows that the heat flow is a minimum at 1000 km depth. This suggests the presence at this depth of a globally defined horizon across which the pattern of lateral heterogeneity changes rapidly. Copyright 1997 by the American Geophysical Union.

One leg lateral jumps - a new test for team players evaluation.

PubMed

Taboga, P; Sepulcri, L; Lazzer, S; De Conti, D; Di Prampero, P E

2013-10-01

We assessed the subject's capacity to accelerate himself laterally in monopodalic support, a crucial ability in several team sports, on 22 athletes, during series of 10 subsequent jumps, between two force platforms at predetermined distance. Vertical and horizontal accelerations of the Centre of Mass (CM), contact and flight times were measured by means of force platforms and the Optojump-System®. Individual mean horizontal and vertical powers and their sum (total power) ranged between 7 and 14.5 W/kg. "Push angle", i.e., the angle with the horizontal along which the vectorial sum of all forces is aligned, was calculated from the ratio between vertical and horizontal accelerations: it varied between 38.7 and 49.4 deg and was taken to express the subject technical ability. The horizontal acceleration of CM, indirectly estimated as a function of subject's mass, contact and flight times, was essentially equal to that obtained from force platforms data. Since the vertical displacement can be easily obtained from flight and contact times, this allowed us to assess the Push angle from Optojump data only. The power developed during a standard vertical jump was rather highly correlated with that developed during the lateral jumps for right (R=0.80, N.=12) and left limb (R=0.72, N.=12), but not with the push angle for right (R=0.31, N.=12) and left limb (R=-0.43, N.=12). Hence standard tests cannot be utilised to assess technical ability. Lateral jumps test allows the coach to evaluate separately maximal muscular power and technical ability of the athlete, thus appropriately directing the training program: the optimum, for a team-sport player being high power and low push-angle, that is: being "powerful" and "efficient".

Gender, Vertical Height and Horizontal Distance Effects on Single-Leg Landing Kinematics: Implications for Risk of non-contact ACL Injury.

PubMed

Ali, Nicholas; Rouhi, Gholamreza; Robertson, Gordon

2013-01-01

There is a lack of studies investigating gender differences in whole-body kinematics during single-leg landings from increasing vertical heights and horizontal distances. This study determined the main effects and interactions of gender, vertical height, and horizontal distance on whole-body joint kinematics during single-leg landings, and established whether these findings could explain the gender disparity in non-contact anterior cruciate ligament (ACL) injury rate. Recreationally active males (n=6) and females (n=6) performed single-leg landings from a takeoff deck of vertical height of 20, 40, and 60 cm placed at a horizontal distance of 30, 50 and 70 cm from the edge of a force platform, while 3D kinematics and kinetics were simultaneously measured. It was determined that peak vertical ground reaction force (VGRF) and the ankle flexion angle exhibited significant gender differences (p=0.028, partial η(2)=0.40 and p=0.035, partial η(2)=0.37, respectively). Peak VGRF was significantly correlated to the ankle flexion angle (r= -0.59, p=0.04), hip flexion angle (r= -0.74, p=0.006), and trunk flexion angle (r= -0.59, p=0.045). Peak posterior ground reaction force (PGRF) was significantly correlated to the ankle flexion angle (r= -0.56, p=0.035), while peak knee abduction moment was significantly correlated to the knee flexion angle (r= -0.64, p=0.03). Rearfoot landings may explain the higher ACL injury rate among females. Higher plantar-flexed ankle, hip, and trunk flexion angles were associated with lower peak ground reaction forces, while higher knee flexion angle was associated with lower peak knee abduction moment, and these kinematics implicate reduced risk of non-contact ACL injury.

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.

NASA Goddard Earth Sciences Graduate Student Program. [FIRE CIRRUS-II examination of coupling between an upper tropospheric cloud system and synoptic-scale dynamics

NASA Technical Reports Server (NTRS)

Ackerman, Thomas P.

1994-01-01

The evolution of synoptic-scale dynamics associated with a middle and upper tropospheric cloud event that occurred on 26 November 1991 is examined. The case under consideration occurred during the FIRE CIRRUS-II Intensive Field Observing Period held in Coffeyville, KS during Nov. and Dec., 1991. Using data from the wind profiler demonstration network and a temporally and spatially augmented radiosonde array, emphasis is given to explaining the evolution of the kinematically-derived ageostrophic vertical circulations and correlating the circulation with the forcing of an extensively sampled cloud field. This is facilitated by decomposing the horizontal divergence into its component parts through a natural coordinate representation of the flow. Ageostrophic vertical circulations are inferred and compared to the circulation forcing arising from geostrophic confluence and shearing deformation derived from the Sawyer-Eliassen Equation. It is found that a thermodynamically indirect vertical circulation existed in association with a jet streak exit region. The circulation was displaced to the cyclonic side of the jet axis due to the orientation of the jet exit between a deepening diffluent trough and building ridge. The cloud line formed in the ascending branch of the vertical circulation with the most concentrated cloud development occurring in conjunction with the maximum large-scale vertical motion. The relationship between the large scale dynamics and the parameterization of middle and upper tropospheric clouds in large-scale models is discussed and an example of ice water contents derived from a parameterization forced by the diagnosed vertical motions and observed water vapor contents is presented.

Extended field observations of cirrus clouds using a ground-based cloud observing system

NASA Technical Reports Server (NTRS)

Ackerman, Thomas P.

1994-01-01

The evolution of synoptic-scale dynamics associated with a middle and upper tropospheric cloud event that occurred on 26 November 1991 is examined. The case under consideration occurred during the FIRE CIRRUS-II Intensive Field Observing Period held in Coffeyville, KS during Nov. and Dec., 1991. Using data from the wind profiler demonstration network and a temporally and spatially augmented radiosonde array, emphasis is given to explaining the evolution of the kinematically-derived ageostrophic vertical circulations and correlating the circulation with the forcing of an extensively sampled cloud field. This is facilitated by decomposing the horizontal divergence into its component parts through a natural coordinate representation of the flow. Ageostrophic vertical circulations are inferred and compared to the circulation forcing arising from geostrophic confluence and shearing deformation derived from the Sawyer-Eliassen Equation. It is found that a thermodynamically indirect vertical circulation existed in association with a jet streak exit region. The circulation was displaced to the cyclonic side of the jet axis due to the orientation of the jet exit between a deepening diffluent trough and building ridge. The cloud line formed in the ascending branch of the vertical circulation with the most concentrated cloud development occurring in conjunction with the maximum large-scale vertical motion. The relationship between the large scale dynamics and the parameterization of middle and upper tropospheric clouds in large-scale models is discussed and an example of ice water contents derived from a parameterization forced by the diagnosed vertical motions and observed water vapor contents is presented.

Stress distribution in maxillary first molar periodontium using straight pull headgear with vertical and horizontal tubes: A finite element analysis

PubMed Central

Feizbakhsh, Masood; Kadkhodaei, Mahmoud; Zandian, Dana; Hosseinpour, Zahra

2017-01-01

Background: One of the most effective ways for distal movement of molars to treat Class II malocclusion is using extraoral force through a headgear device. The purpose of this study was the comparison of stress distribution in maxillary first molar periodontium using straight pull headgear in vertical and horizontal tubes through finite element method. Materials and Methods: Based on the real geometry model, a basic model of the first molar and maxillary bone was obtained using three-dimensional imaging of the skull. After the geometric modeling of periodontium components through CATIA software and the definition of mechanical properties and element classification, a force of 150 g for each headgear was defined in ABAQUS software. Consequently, Von Mises and Principal stresses were evaluated. The statistical analysis was performed using T-paired and Wilcoxon nonparametric tests. Results: Extension of areas with Von Mises and Principal stresses utilizing straight pull headgear with a vertical tube was not different from that of using a horizontal tube, but the numerical value of the Von Mises stress in the vertical tube was significantly reduced (P < 0/05). On the other hand, the difference of the principal stress between both tubes was not significant (P > 0/05). Conclusion: Based on the results, when force applied to the straight pull headgear with a vertical tube, Von Mises stress was reduced significantly in comparison with the horizontal tube. Therefore, to correct the mesiolingual movement of the maxillary first molar, vertical headgear tube is recommended. PMID:28584535

Robot-Applied Resistance Augments the Effects of Body Weight-Supported Treadmill Training on Stepping and Synaptic Plasticity in a Rodent Model of Spinal Cord Injury.

PubMed

Hinahon, Erika; Estrada, Christina; Tong, Lin; Won, Deborah S; de Leon, Ray D

2017-08-01

The application of resistive forces has been used during body weight-supported treadmill training (BWSTT) to improve walking function after spinal cord injury (SCI). Whether this form of training actually augments the effects of BWSTT is not yet known. To determine if robotic-applied resistance augments the effects of BWSTT using a controlled experimental design in a rodent model of SCI. Spinally contused rats were treadmill trained using robotic resistance against horizontal (n = 9) or vertical (n = 8) hind limb movements. Hind limb stepping was tested before and after 6 weeks of training. Two control groups, one receiving standard training (ie, without resistance; n = 9) and one untrained (n = 8), were also tested. At the terminal experiment, the spinal cords were prepared for immunohistochemical analysis of synaptophysin. Six weeks of training with horizontal resistance increased step length, whereas training with vertical resistance enhanced step height and movement velocity. None of these changes occurred in the group that received standard (ie, no resistance) training or in the untrained group. Only standard training increased the number of step cycles and shortened cycle period toward normal values. Synaptophysin expression in the ventral horn was highest in rats trained with horizontal resistance and in untrained rats and was positively correlated with step length. Adding robotic-applied resistance to BWSTT produced gains in locomotor function over BWSTT alone. The impact of resistive forces on spinal connections may depend on the nature of the resistive forces and the synaptic milieu that is present after SCI.

Lower Extremity Movement Differences Persist After Anterior Cruciate Ligament Reconstruction and When Returning to Sports.

PubMed

Butler, Robert J; Dai, Boyi; Huffman, Nikki; Garrett, William E; Queen, Robin M

2016-09-01

To examine how landing mechanics change in patients after anterior cruciate ligament reconstruction (ACL-R) between 6 months and 12 months after surgery. Case-series. Laboratory. Fifteen adolescent patients after ACL-R participated. Lower extremity three-dimensional motion analysis was conducted during a bilateral stop jump task in patients at 6 and 12 months after ACL-R. Joint kinematic and kinetic data, in addition to ground reaction forces, were collected at each time point. During the stop jump landing, the peak joint moments and the initial and peak joint motion at the ankle, knee, and hip were examined. The peak vertical ground reaction force was also examined. Interactions were observed for both the peak knee (P = 0.03) and hip extension moment (P = 0.07). However, only the hip extension moment was symmetrical level at 12 months. Statistically significant (P < 0.05) side-to-side differences existed for the ankle angle at initial contact, peak plantarflexion moment, peak hip flexion angle, and peak impact vertical ground reaction force independent of time. The findings of this study suggest that sagittal plane moments at the knee and hip demonstrate an increase in symmetry between 6 months and 1 year after ACL-R surgery, however, symmetry of the knee extension moment is not established by 12 months after surgery. The lack of change in the variables across time was unexpected. As a result, it is inappropriate to expect a change in landing mechanics solely as a result of time alone after discharge from rehabilitation.

Biomechanical investigation of impact induced rib fractures of a porcine infant surrogate model.

PubMed

Blackburne, William B; Waddell, J Neil; Swain, Michael V; Alves de Sousa, Ricardo J; Kieser, Jules A

2016-09-01

This study investigated the structural, biomechanical and fractographic features of rib fractures in a piglet model, to test the hypothesis that fist impact, apart from thoracic squeezing, may result in lateral costal fractures as observed in abused infants. A mechanical fist with an accelerometer was constructed and fixed to a custom jig. Twenty stillborn piglets in the supine position were impacted on the thoracic cage. The resultant force versus time curves from the accelerometer data showed a number of steps indicative of rib fracture. The correlation between impact force and number of fractures was statistically significant (Pearson׳s r=0.528). Of the fractures visualized, 15 completely pierced the parietal pleura of the thoracic wall, and 5 had butterfly fracture patterning. Scanning electron microscopy showed complete bone fractures, at the zone of impact, were normal to the axis of the ribs. Incomplete vertical fractures, with bifurcation, occurred on the periphery of the contact zone. This work suggests the mechanism of rib failure during a fist impact is typical of the transverse fracture pattern in the anterolateral region associated with cases of non-accidental rib injury. The impact events investigated have a velocity of ~2-3m/s, approximately 2×10(4) times faster than previous quasi-static axial and bending tests. While squeezing the infantile may induce buckle fractures in the anterior as well as posterior region of the highly flexible bones, a fist punch impact event may result in anterolateral transverse fractures. Hence, these findings suggest that the presence of anterolateral rib fractures may result from impact rather than manual compression. Copyright © 2016 Elsevier Ltd. All rights reserved.

Clinical measurement of force systems upon activation of transpalatal arch in the treatment of unilateral crossbite.

PubMed

Yoshida, N; Koga, Y; Jost-Brinkmann, P G; Kobayashi, K

2003-01-01

in this study, forces and moments acting on the molars were theoretically determined by means of small-deflection analysis when an asymmetric third-order activation of the TPA was carried out. the transpalatal arch (TPA) is used to correct unilateral crossbites through the application of buccal root torque to the anchorage molar and lingual root torque to the contralateral molar in crossbite, combined with expansion. Unfortunately, the complex force systems created at the molars upon activation of the TPA cannot be easily estimated. our computations revealed that the vertical forces developed on the molars when both ends of the TPA are inserted into the lingual sheaths (two-couple system) is four-times greater than those when only one end is tied to the lingual sheath as a single-point contact (one-couple system). we propose a method of clinical estimation of the force system in a two-couple system by directly measuring the vertical force produced by the one-couple system.

Estimations of Vertical Velocities Using the Omega Equation in Different Flow Regimes in Preparation for the High Resolution Observations of the SWOT Altimetry Mission

NASA Astrophysics Data System (ADS)

Pietri, A.; Capet, X.; d'Ovidio, F.; Le Sommer, J.; Molines, J. M.; Doglioli, A. M.

2016-02-01

Vertical velocities (w) associated with meso and submesoscale processes play an essential role in ocean dynamics and physical-biological coupling due to their impact on the upper ocean vertical exchanges. However, their small intensity (O 1 cm/s) compared to horizontal motions and their important variability in space and time makes them very difficult to measure. Estimations of these velocities are thus usually inferred using a generalized approach based on frontogenesis theories. These estimations are often obtained by solving the diagnostic omega equation. This equation can be expressed in different forms from a simple quasi geostrophic formulation to more complex ones that take into account the ageostrophic advection and the turbulent fluxes. The choice of the method used generally depends on the data available and on the dominant processes in the region of study. Here we aim to provide a statistically robust evaluation of the scales at which the vertical velocity can be resolved with confidence depending on the formulation of the equation and the dynamics of the flow. A high resolution simulation (dx=1-1.5 km) of the North Atlantic was used to compare the calculations of w based on the omega equation to the modelled vertical velocity. The simulation encompasses regions with different atmospheric forcings, mesoscale activity, seasonality and energetic flows, allowing us to explore several different dynamical contexts. In a few years the SWOT mission will provide bi-dimensional images of sea level elevation at a significantly higher resolution than available today. This work helps assess the possible contribution of the SWOT data to the understanding of the submesoscale circulation and the associated vertical fluxes in the upper ocean.

Relative Roles of Deterministic and Stochastic Processes in Driving the Vertical Distribution of Bacterial Communities in a Permafrost Core from the Qinghai-Tibet Plateau, China.

PubMed

Hu, Weigang; Zhang, Qi; Tian, Tian; Li, Dingyao; Cheng, Gang; Mu, Jing; Wu, Qingbai; Niu, Fujun; Stegen, James C; An, Lizhe; Feng, Huyuan

2015-01-01

Understanding the processes that influence the structure of biotic communities is one of the major ecological topics, and both stochastic and deterministic processes are expected to be at work simultaneously in most communities. Here, we investigated the vertical distribution patterns of bacterial communities in a 10-m-long soil core taken within permafrost of the Qinghai-Tibet Plateau. To get a better understanding of the forces that govern these patterns, we examined the diversity and structure of bacterial communities, and the change in community composition along the vertical distance (spatial turnover) from both taxonomic and phylogenetic perspectives. Measures of taxonomic and phylogenetic beta diversity revealed that bacterial community composition changed continuously along the soil core, and showed a vertical distance-decay relationship. Multiple stepwise regression analysis suggested that bacterial alpha diversity and phylogenetic structure were strongly correlated with soil conductivity and pH but weakly correlated with depth. There was evidence that deterministic and stochastic processes collectively drived bacterial vertically-structured pattern. Bacterial communities in five soil horizons (two originated from the active layer and three from permafrost) of the permafrost core were phylogenetically random, indicator of stochastic processes. However, we found a stronger effect of deterministic processes related to soil pH, conductivity, and organic carbon content that were structuring the bacterial communities. We therefore conclude that the vertical distribution of bacterial communities was governed primarily by deterministic ecological selection, although stochastic processes were also at work. Furthermore, the strong impact of environmental conditions (for example, soil physicochemical parameters and seasonal freeze-thaw cycles) on these communities underlines the sensitivity of permafrost microorganisms to climate change and potentially subsequent permafrost thaw.

Relative Roles of Deterministic and Stochastic Processes in Driving the Vertical Distribution of Bacterial Communities in a Permafrost Core from the Qinghai-Tibet Plateau, China

PubMed Central

Tian, Tian; Li, Dingyao; Cheng, Gang; Mu, Jing; Wu, Qingbai; Niu, Fujun; Stegen, James C.; An, Lizhe; Feng, Huyuan

2015-01-01

Understanding the processes that influence the structure of biotic communities is one of the major ecological topics, and both stochastic and deterministic processes are expected to be at work simultaneously in most communities. Here, we investigated the vertical distribution patterns of bacterial communities in a 10-m-long soil core taken within permafrost of the Qinghai-Tibet Plateau. To get a better understanding of the forces that govern these patterns, we examined the diversity and structure of bacterial communities, and the change in community composition along the vertical distance (spatial turnover) from both taxonomic and phylogenetic perspectives. Measures of taxonomic and phylogenetic beta diversity revealed that bacterial community composition changed continuously along the soil core, and showed a vertical distance-decay relationship. Multiple stepwise regression analysis suggested that bacterial alpha diversity and phylogenetic structure were strongly correlated with soil conductivity and pH but weakly correlated with depth. There was evidence that deterministic and stochastic processes collectively drived bacterial vertically-structured pattern. Bacterial communities in five soil horizons (two originated from the active layer and three from permafrost) of the permafrost core were phylogenetically random, indicator of stochastic processes. However, we found a stronger effect of deterministic processes related to soil pH, conductivity, and organic carbon content that were structuring the bacterial communities. We therefore conclude that the vertical distribution of bacterial communities was governed primarily by deterministic ecological selection, although stochastic processes were also at work. Furthermore, the strong impact of environmental conditions (for example, soil physicochemical parameters and seasonal freeze-thaw cycles) on these communities underlines the sensitivity of permafrost microorganisms to climate change and potentially subsequent permafrost thaw. PMID:26699734

The Comfortable Roller Coaster--on the Shape of Tracks with a Constant Normal Force

ERIC Educational Resources Information Center

Nordmark, Arne B.; Essen, Hanno

2010-01-01

A particle that moves along a smooth track in a vertical plane is influenced by two forces: gravity and normal force. The force experienced by roller coaster riders is the normal force, so a natural question to ask is, what shape of the track gives a normal force of constant magnitude? Here we solve this problem. It turns out that the solution is…

76 FR 1121 - Proposed Flood Elevation Determinations

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-07

... approximately 410 feet of Lewis County. upstream of U.S. Route 61 Business. * National Geodetic Vertical Datum... intersection of Impact Drive and FM Road 2404. * National Geodetic Vertical Datum. + North American Vertical..., Environmental Consideration. An environmental impact assessment has not been prepared. Regulatory Flexibility...

Vertical Landing Aerodynamics of Reusable Rocket Vehicle

NASA Astrophysics Data System (ADS)

Nonaka, Satoshi; Nishida, Hiroyuki; Kato, Hiroyuki; Ogawa, Hiroyuki; Inatani, Yoshifumi

The aerodynamic characteristics of a vertical landing rocket are affected by its engine plume in the landing phase. The influences of interaction of the engine plume with the freestream around the vehicle on the aerodynamic characteristics are studied experimentally aiming to realize safe landing of the vertical landing rocket. The aerodynamic forces and surface pressure distributions are measured using a scaled model of a reusable rocket vehicle in low-speed wind tunnels. The flow field around the vehicle model is visualized using the particle image velocimetry (PIV) method. Results show that the aerodynamic characteristics, such as the drag force and pitching moment, are strongly affected by the change in the base pressure distributions and reattachment of a separation flow around the vehicle.

Vertical stiffness is not related to anterior cruciate ligament elongation in professional rugby union players.

PubMed

Serpell, Benjamin G; Scarvell, Jennie M; Pickering, Mark R; Ball, Nick B; Perriman, Diana; Warmenhoven, John; Smith, Paul N

2016-01-01

Novel research surrounding anterior cruciate ligament (ACL) injury is necessary because ACL injury rates have remained unchanged for several decades. An area of ACL risk mitigation which has not been well researched relates to vertical stiffness. The relationship between increased vertical stiffness and increased ground reaction force suggests that vertical stiffness may be related to ACL injury risk. However, given that increased dynamic knee joint stability has been shown to be associated with vertical stiffness, it is possible that modification of vertical stiffness could help to protect against injury. We aimed to determine whether vertical stiffness is related to measures known to load, or which represent loading of, the ACL. This was a cross-sectional observational study of 11 professional Australian rugby players. Knee kinematics and ACL elongation were measured from a 4-dimensional model of a hopping task which simulated the change of direction manoeuvre typically observed when non-contact ACL injury occurs. The model was generated from a CT scan of the participant's knee registered frame by frame to fluoroscopy images of the hopping task. Vertical stiffness was calculated from force plate data. There was no association found between vertical stiffness and anterior tibial translation (ATT) or ACL elongation (r=-0.05; p=0.89, and r=-0.07; p=0.83, respectively). ATT was related to ACL elongation (r=0.93; p=0.0001). Vertical stiffness was not associated with ACL loading in this cohort of elite rugby players but a novel method for measuring ACL elongation in vivo was found to have good construct validity.

Formulation of human-structure interaction system models for vertical vibration

NASA Astrophysics Data System (ADS)

Caprani, Colin C.; Ahmadi, Ehsan

2016-09-01

In this paper, human-structure interaction system models for vibration in the vertical direction are considered. This work assembles various moving load models from the literature and proposes extension of the single pedestrian to a crowd of pedestrians for the FE formulation for crowd-structure interaction systems. The walking pedestrian vertical force is represented as a general time-dependent force, and the pedestrian is in turn modelled as moving force, moving mass, and moving spring-mass-damper. The arbitrary beam structure is modelled using either a formulation in modal coordinates or finite elements. In each case, the human-structure interaction (HSI) system is first formulated for a single walking pedestrian and then extended to consider a crowd of pedestrians. Finally, example applications for single pedestrian and crowd loading scenarios are examined. It is shown how the models can be used to quantify the interaction between the crowd and bridge structure. This work should find use for the evaluation of existing and new footbridges.

Dynamics of unforced and vertically forced rocking elliptical and semi-elliptical disks

NASA Astrophysics Data System (ADS)

Wang, Xue-She; Mazzoleni, Michael J.; Mann, Brian P.

2018-03-01

This paper presents the results of an investigation on the dynamics of unforced and vertically forced rocking elliptical and semi-elliptical disks. The full equation of motion for both rocking disks is derived from first principles. For unforced behavior, Lamb's method is used to derive the linear natural frequency of both disks, and harmonic balance is used to determine their amplitude-dependent rocking frequencies. A stability analysis then reveals that the equilibria and stability of the two disks are considerably different, as the semi-elliptical disk has a super-critical pitchfork bifurcation that enables it to exhibit bistable rocking behavior. Experimental studies were conducted to verify the trends. For vertically forced behavior, numerical investigations show the disk's responses to forward and reverse frequency sweeps. Three modes of periodicity were observed for the steady state behavior. Experiments were performed to verify the frequency responses and the presence of the three rocking modes. Comparisons between the experiments and numerical investigations show good agreement.

Multimodal Kelvin Probe Force Microscopy Investigations of a Photovoltaic WSe2/MoS2 Type-II Interface.

PubMed

Almadori, Yann; Bendiab, Nedjma; Grévin, Benjamin

2018-01-10

Atomically thin transition-metal dichalcogenides (TMDC) have become a new platform for the development of next-generation optoelectronic and light-harvesting devices. Here, we report a Kelvin probe force microscopy (KPFM) investigation carried out on a type-II photovoltaic heterojunction based on WSe 2 monolayer flakes and a bilayer MoS 2 film stacked in vertical configuration on a Si/SiO 2 substrate. Band offset characterized by a significant interfacial dipole is pointed out at the WSe 2 /MoS 2 vertical junction. The photocarrier generation process and phototransport are studied by applying a differential technique allowing to map directly two-dimensional images of the surface photovoltage (SPV) over the vertical heterojunctions (vHJ) and in its immediate vicinity. Differential SPV reveals the impact of chemical defects on the photocarrier generation and that negative charges diffuse in the MoS 2 a few hundreds of nanometers away from the vHJ. The analysis of the SPV data confirms unambiguously that light absorption results in the generation of free charge carriers that do not remain coulomb-bound at the type-II interface. A truly quantitative determination of the electron-hole (e-h) quasi-Fermi levels splitting (i.e., the open-circuit voltage) is achieved by measuring the differential vacuum-level shift over the WSe 2 flakes and the MoS 2 layer. The dependence of the energy-level splitting as a function of the optical power reveals that Shockley-Read-Hall processes significantly contribute to the interlayer recombination dynamics. Finally, a newly developed time-resolved mode of the KPFM is applied to map the SPV decay time constants. The time-resolved SPV images reveal the dynamics of delayed recombination processes originating from photocarriers trapping at the SiO 2 /TMDC interfaces.

Pelvic kinematic method for determining vertical jump height.

PubMed

Chiu, Loren Z F; Salem, George J

2010-11-01

Sacral marker and pelvis reconstruction methods have been proposed to approximate total body center of mass during relatively low intensity gait and hopping tasks, but not during a maximum effort vertical jumping task. In this study, center of mass displacement was calculated using the pelvic kinematic method and compared with center of mass displacement using the ground-reaction force-impulse method, in experienced athletes (n = 13) performing restricted countermovement vertical jumps. Maximal vertical jumps were performed in a biomechanics laboratory, with data collected using an 8-camera motion analysis system and two force platforms. The pelvis center of mass was reconstructed from retro-reflective markers placed on the pelvis. Jump height was determined from the peak height of the pelvis center of mass minus the standing height. Strong linear relationships were observed between the pelvic kinematic and impulse methods (R² = .86; p < .01). The pelvic kinematic method underestimated jump height versus the impulse method, however, the difference was small (CV = 4.34%). This investigation demonstrates concurrent validity for the pelvic kinematic method to determine vertical jump height.

Combined Lorentz force and ultrasound Doppler velocimetry in a vertical convection liquid metal flow

NASA Astrophysics Data System (ADS)

Zürner, Till; Vogt, Tobias; Resagk, Christian; Eckert, Sven; Schumacher, Jörg

2017-11-01

We report experimental studies on turbulent vertical convection flow in the liquid metal alloy gallium-indium-tin. Flow measurements were conducted by a combined use of local Lorentz force velocimetry (LLFV) and ultrasound Doppler velocimetry (UDV). It is known that the forced convection flow in a duct generates a force on the LLFV magnet system, that grows proportional to the flow velocity. We show that for the slower flow of natural convection LLFV retains this linear dependence in the range of micronewtons. Furthermore experimental results on the scaling of heat and momentum transport with the thermal driving are presented. The results cover a range of Rayleigh numbers 3 ×105 < Ra < 3 ×107 at a Prandtl number Pr 0.032 . The Nusselt number Nu is found to scale as Nu Ra0.31 . A Reynolds number Rez based on the vertical velocities close the heated and cooled side walls scales with Rez Ra0.45 . Additionally a Reynolds number based on the horizontal flow component is scaling as Rex Ra0.67 . These results agree well with numerical simulations and theoretical predictions. This work is funded by the Deutsche Forschungsgemeinschaft under Grant No. GRK 1567.

Disuse bone loss in hindquarter suspended rats: partial weightbearing, exercise and ibandronate treatment as countermeasures

NASA Technical Reports Server (NTRS)

Schultheis, L.; Ruff, C. B.; Rastogi, S.; Bloomfield, S.; Hogan, H. A.; Fedarko, N.; Thierry-Palmer, M.; Ruiz, J.; Bauss, F.; Shapiro, J. R.

2000-01-01

The purpose of this study was to evaluate potential countermeasures for bone loss during long-term space missions in the hindquarter suspended rat, including partial weight bearing (surrogate for artificial gravity) episodic full weight bearing (2 hour/day full weight bearing) and treatment with the third generation bisphosphonate ibandronate (Roche). Graded mechanical loading was studied by housing the animals on a novel servo controlled force plate system which permitted the titration of mechanical force at varying frequency and amplitude and different levels of weight bearing. The force plate, which forms the cage floor, is a glass platform supported by an 18" diameter speaker cone filled with expanding polyurethane foam. An infrared optical sensor attached to the speaker cone yields a voltage linearly related to vertical displacement of the glass platform. The dynamic force on the paw was computed as a product of the apparent mass of the animal on the platform at rest and the acceleration of the platform determined from the second derivative of the optical sensor output. The mass of the animal on the platform was varied by adjusting tension on the tether suspending the animal. Mechanical impact loading was titrated with the force plate resonating at different frequencies, including 3 Hz and 16 Hz.

A virtual model of the bench press exercise.

PubMed

Rahmani, Abderrahmane; Rambaud, Olivier; Bourdin, Muriel; Mariot, Jean-Pierre

2009-08-07

The objective of this study was to design and validate a three degrees of freedom model in the sagittal plane for the bench press exercise. The mechanical model was based on rigid segments connected by revolute and prismatic pairs, which enabled a kinematic approach and global force estimation. The method requires only three simple measurements: (i) horizontal position of the hand (x(0)); (ii) vertical displacement of the barbell (Z) and (iii) elbow angle (theta). Eight adult male throwers performed maximal concentric bench press exercises against different masses. The kinematic results showed that the vertical displacement of each segment and the global centre of mass followed the vertical displacement of the lifted mass. Consequently, the vertical velocity and acceleration of the combined centre of mass and the lifted mass were identical. Finally, for each lifted mass, there were no practical differences between forces calculated from the bench press model and those simultaneously measured with a force platform. The error was lower than 2.5%. The validity of the mechanical method was also highlighted by a standard error of the estimate (SEE) ranging from 2.0 to 6.6N in absolute terms, a coefficient of variation (CV) < or =0.8%, and a correlation between the two scores > or =0.99 for all the lifts (p<0.001). The method described here, which is based on three simple parameters, allows accurate evaluation of the force developed by the upper limb muscles during bench press exercises in both field and laboratory conditions.

How Tidal Forces Cause Ocean Tides in the Equilibrium Theory

ERIC Educational Resources Information Center

Ng, Chiu-king

2015-01-01

We analyse why it is erroneous to think that a tidal bulge is formed by pulling the water surface directly up by a local vertical tidal force. In fact, ocean tides are caused by the global effect of the horizontal components of the tidal forces.

The reliability and validity of the Saliba Postural Classification System

PubMed Central

Collins, Cristiana Kahl; Johnson, Vicky Saliba; Godwin, Ellen M.; Pappas, Evangelos

2016-01-01

Objectives To determine the reliability and validity of the Saliba Postural Classification System (SPCS). Methods Two physical therapists classified pictures of 100 volunteer participants standing in their habitual posture for inter and intra-tester reliability. For validity, 54 participants stood on a force plate in a habitual and a corrected posture, while a vertical force was applied through the shoulders until the clinician felt a postural give. Data were extracted at the time the give was felt and at a time in the corrected posture that matched the peak vertical ground reaction force (VGRF) in the habitual posture. Results Inter-tester reliability demonstrated 75% agreement with a Kappa = 0.64 (95% CI = 0.524–0.756, SE = 0.059). Intra-tester reliability demonstrated 87% agreement with a Kappa = 0.8, (95% CI = 0.702–0.898, SE = 0.05) and 80% agreement with a Kappa = 0.706, (95% CI = 0.594–0818, SE = 0.057). The examiner applied a significantly higher (p < 0.001) peak vertical force in the corrected posture prior to a postural give when compared to the habitual posture. Within the corrected posture, the %VGRF was higher when the test was ongoing vs. when a postural give was felt (p < 0.001). The %VGRF was not different between the two postures when comparing the peaks (p = 0.214). Discussion The SPCS has substantial agreement for inter- and intra-tester reliability and is largely a valid postural classification system as determined by the larger vertical forces in the corrected postures. Further studies on the correlation between the SPCS and diagnostic classifications are indicated. PMID:27559288

The reliability and validity of the Saliba Postural Classification System.

PubMed

Collins, Cristiana Kahl; Johnson, Vicky Saliba; Godwin, Ellen M; Pappas, Evangelos

2016-07-01

To determine the reliability and validity of the Saliba Postural Classification System (SPCS). Two physical therapists classified pictures of 100 volunteer participants standing in their habitual posture for inter and intra-tester reliability. For validity, 54 participants stood on a force plate in a habitual and a corrected posture, while a vertical force was applied through the shoulders until the clinician felt a postural give. Data were extracted at the time the give was felt and at a time in the corrected posture that matched the peak vertical ground reaction force (VGRF) in the habitual posture. Inter-tester reliability demonstrated 75% agreement with a Kappa = 0.64 (95% CI = 0.524-0.756, SE = 0.059). Intra-tester reliability demonstrated 87% agreement with a Kappa = 0.8, (95% CI = 0.702-0.898, SE = 0.05) and 80% agreement with a Kappa = 0.706, (95% CI = 0.594-0818, SE = 0.057). The examiner applied a significantly higher (p < 0.001) peak vertical force in the corrected posture prior to a postural give when compared to the habitual posture. Within the corrected posture, the %VGRF was higher when the test was ongoing vs. when a postural give was felt (p < 0.001). The %VGRF was not different between the two postures when comparing the peaks (p = 0.214). The SPCS has substantial agreement for inter- and intra-tester reliability and is largely a valid postural classification system as determined by the larger vertical forces in the corrected postures. Further studies on the correlation between the SPCS and diagnostic classifications are indicated.

Forced Gravity Waves and the Tropospheric Response to Convection

NASA Astrophysics Data System (ADS)

Halliday, O. J.; Griffiths, S. D.; Parker, D. J.; Stirling, A.

2017-12-01

It has been known for some time that gravity waves facilitate atmospheric adjustment to convective heating. Further, convectively forced gravity waves condition the neighboring atmosphere for the initiation and / or suppression of convection. Despite this, the radiation of gravity waves in macro-scale models (which are typically forced at the grid-scale, by existing parameterization schemes) is not well understood. We present here theoretical and numerical work directed toward improving our understanding of convectively forced gravity wave effects at the mesoscale. Using the linear hydrostatic equations of motion for an incompressible (but non-Boussinesq) fluid with vertically varying buoyancy frequency, we find a radiating solution to prescribed sensible heating. We then interrogate the spatial and temporal sensitivity of the vertical velocity and potential temperature response to different heating functions, considering the remote and near-field forced response both to steady and pulsed heating. We find that the meso-scale tropospheric response to convection is significantly dependent on the upward radiation characteristics of the gravity waves, which are in turn dependent upon the temporal and spatial structure of the source, and stratification of the domain. Moving from a trapped to upwardly-radiating solution there is a 50% reduction in tropospherically averaged vertical velocity, but significant perturbations persist for up to 4 hours in the far-field. We find the tropospheric adjustment to be sensitive to the horizontal length scale which characterizes the heating, observing a 20% reduction in vertical velocity when comparing the response from a 10 km to a 100 km heat source. We assess the implications for parameterization of convection in coarse-grained models in the light of these findings. We show that an idealized `full-physics' nonlinear simulation of deep convection in the UK Met Office Unified Model is qualitatively described by the linear solution: departures are quantified and explored.

Vertical electrostatic force in MEMS cantilever IR sensor

NASA Astrophysics Data System (ADS)

Rezadad, Imen; Boroumand Azad, Javaneh; Smith, Evan M.; Alhasan, Ammar; Peale, Robert E.

2014-06-01

A MEMS cantilever IR detector that repetitively lifts from the surface under the influence of a saw-tooth electrostatic force, where the contact duty cycle is a measure of the absorbed IR radiation, is analyzed. The design is comprised of three parallel conducting plates. Fixed buried and surface plates are held at opposite potential. A moveable cantilever is biased the same as the surface plate. Calculations based on energy methods with position-dependent capacity and electrostatic induction coefficients demonstrate the upward sign of the force on the cantilever and determine the force magnitude. 2D finite element method calculations of the local fields confirm the sign of the force and determine its distribution across the cantilever. The upward force is maximized when the surface plate is slightly larger than the other two. The electrostatic repulsion is compared with Casimir sticking force to determine the maximum useful contact area. MEMS devices were fabricated and the vertical displacement of the cantilever was observed in a number of experiments. The approach may be applied also to MEMS actuators and micromirrors.

Three-dimensional modelling for assessment of far-field impact of tidal stream turbine: A case study at the Anglesey Coast, Wales, UK

NASA Astrophysics Data System (ADS)

Li, Xiaorong; Li, Ming; Wolf, Judith

2017-04-01

As a response to worldwide climate change, clean non-carbon renewable energy resources have been gaining significant attention. Among a range of renewable alternatives, tidal stream energy is considered very promising; due to its consistent predictability and availability. To investigate impacts of tidal stream devices on their surroundings, prototype experiments involving small scale laboratory studies have been implemented. Computational Flow Dynamics (CFD) modelling is also commonly applied to study turbine behaviours. However, these studies focus on impacts of the turbine in the near-field scale. As a result, in order to study and predict the far-field impacts caused by the operation of turbines, large scale 2D and 3D numerical oceanography models have been used, with routines added to reflect the impacts of turbines. In comparison to 2D models, 3D models are advantageous in providing complete prediction of vertical flow structures and hence mixing in the wake of a turbine. This research aims to deliver a thorough 3D tidal stream turbine simulation system, by considering major coastal processes, i.e. current, waves and sediment transport, based on a 3D wave-current-sediment fully coupled numerical oceanography model — the Unstructured Grid Finite Volume Community Ocean Model (FVCOM). The energy extraction of turbines is simulated by adding a body force to the momentum equations. Across the water depth, the coefficient related to the additional body force is given different values according to the turbine configuration and operation to reflect the vertical variation of the turbine's impacts on the passing flow. Three turbulence perturbation terms are added to the turbulence closure to simulate the turbine-induced turbulence generation, dissipation and interference for the turbulence length-scale. Impacts of turbine operation on surface waves are also considered by modification of wave energy flux across the device. A thorough validation study is carried out in which the developed model is tested; based on a combination of laboratory measured data and CFD simulated results. The developed turbine simulation system is then applied to the Anglesey coast, North Wales, UK for a case study. The validation study suggests that the developed turbine simulation system is able to accurately simulate both hydrodynamics and wave dynamics in the turbine wake. The case study with 18 turbines (diameter is 15 m) modelled individually in the waterway between the north-west Anglesey and the Skerries reveals impacts of the turbine farm on free surface elevation, flow field, turbulence kinetic energy (TKE), surface waves, bottom shear stress and suspended sediment transport. The wake is observable up to 4.5 km downstream of the device farm. Flow near the bed in the wake is accelerated, leading to enhanced bottom shear stress. The device farm has a strong influence on TKE and hence the vertical mixing of suspended sediment in the wake. Further, the eastwards directed residual sediment transport along the north coast of Anglesey is found to be weakened by the turbine farm.

Investigating the dependence of SCM simulated precipitation and clouds on the spatial scale of large-scale forcing at SGP [Investigating the scale dependence of SCM simulated precipitation and cloud by using gridded forcing data at SGP

DOE PAGES

Tang, Shuaiqi; Zhang, Minghua; Xie, Shaocheng

2017-08-05

Large-scale forcing data, such as vertical velocity and advective tendencies, are required to drive single-column models (SCMs), cloud-resolving models, and large-eddy simulations. Previous studies suggest that some errors of these model simulations could be attributed to the lack of spatial variability in the specified domain-mean large-scale forcing. This study investigates the spatial variability of the forcing and explores its impact on SCM simulated precipitation and clouds. A gridded large-scale forcing data during the March 2000 Cloud Intensive Operational Period at the Atmospheric Radiation Measurement program's Southern Great Plains site is used for analysis and to drive the single-column version ofmore » the Community Atmospheric Model Version 5 (SCAM5). When the gridded forcing data show large spatial variability, such as during a frontal passage, SCAM5 with the domain-mean forcing is not able to capture the convective systems that are partly located in the domain or that only occupy part of the domain. This problem has been largely reduced by using the gridded forcing data, which allows running SCAM5 in each subcolumn and then averaging the results within the domain. This is because the subcolumns have a better chance to capture the timing of the frontal propagation and the small-scale systems. As a result, other potential uses of the gridded forcing data, such as understanding and testing scale-aware parameterizations, are also discussed.« less

Associations of Region-Specific Foot Pain and Foot Biomechanics: The Framingham Foot Study

PubMed Central

Hagedorn, Thomas J.; Dufour, Alyssa B.; Hannan, Marian T.

2015-01-01

Background. Specific regions of the foot are responsible for the gait tasks of weight acceptance, single-limb support, and forward propulsion. With region foot pain, gait abnormalities may arise and affect the plantar pressure and force pattern utilized. Therefore, this study’s purpose was to evaluate plantar pressure and force pattern differences between adults with and without region-specific foot pain. Methods. Plantar pressure and force data were collected on Framingham Foot Study members while walking barefoot at a self-selected pace. Foot pain was evaluated by self-report and grouped by foot region (toe, forefoot, midfoot, or rearfoot) or regions (two or three or more regions) of pain. Unadjusted and adjusted linear regression with generalized estimating equations was used to determine associations between feet with and without foot pain. Results. Individuals with distal foot (forefoot or toes) pain had similar maximum vertical forces under the pain region, while those with proximal foot (rearfoot or midfoot) pain had different maximum vertical forces compared to those without regional foot pain (referent). During walking, there were significant differences in plantar loading and propulsion ranging from 2% to 4% between those with and without regional foot pain. Significant differences in normalized maximum vertical force and plantar pressure ranged from 5.3% to 12.4% and 3.4% to 24.1%, respectively, between those with and without regional foot pain. Conclusions. Associations of regional foot pain with plantar pressure and force were different by regions of pain. Region-specific foot pain was not uniformly associated with an increase or decrease in loading and pressure patterns regions of pain. PMID:25995291

A Comparison of the Habitual Landing Strategies from Differing Drop Heights of Parkour Practitioners (Traceurs) and Recreationally Trained Individuals.

PubMed

Standing, Regan J; Maulder, Peter S

2015-12-01

Parkour is an activity that encompasses methods of jumping, climbing and vaulting. With landing being a pertinent part of this practise, Parkour participants (traceurs) have devised their own habitual landing strategies, which are suggested to be a safer and more effective style of landing. The purpose of this study was to compare the habitual landing strategies of traceurs and recreationally trained individuals from differing drop heights. Comparisons between landing sound and mechanical parameters were also assessed to gauge the level of landing safety. Ten recreationally trained participants and ten traceurs performed three landings from 25% and 50% body height using their own habitual landing strategies. Results at 25% showed significantly lower maximal vertical force (39.9%, p < 0.0013, ES = -1.88), longer times to maximal vertical force (68.6%, p < 0.0015, ES = 1.72) and lower loading rates (65.1%, p < 0.0002, ES = -2.22) in the traceur group. Maximal sound was also shown to be lower (3.6%), with an effect size of -0.63, however this was not statistically significant (p < 0.1612). At 50%, traceurs exhibited significantly different values within all variables including maximal sound (8.6%, p < 0.03, ES = -1.04), maximal vertical force (49.0%, p < 0.0002, ES = -2.38), time to maximal vertical force (65.9%, p < 0.0067, ES = 1.32) and loading rates (66.3%, p < 0.0002, ES = -2.00). Foot strike analysis revealed traceurs landed using forefoot or forefoot-midfoot strategies in 93.2% of trials; whereas recreationally trained participants used these styles in only 8.3% of these landings. To conclude, the habitual landings of traceurs are more effective at lowering the kinetic landing variables associated with a higher injury risk in comparison to recreationally trained individuals. Sound as a measure of landing effectiveness and safety holds potential significance; however requires further research to confirm. Key pointsHabitual traceur landings were observed to be safer landing techniques in comparison to those utilised by recreationally trained individuals, due to the lower maximal vertical forces, slower times to maximal vertical force, lesser loading rates and lower maximal sound.Traceurs predominantly landed with the forefoot only, whereas recreationally trained individuals habitually utilised a forefoot to heel landing strategy.The habitual landing techniques performed by traceurs may be beneficial for other landing sports to incorporate into training to reduce injury.

Experimental and analytical determination of characteristics affecting light aircraft landing-gear dynamics

NASA Technical Reports Server (NTRS)

Fasanella, E. L.; Mcgehee, J. R.; Pappas, M. S.

1977-01-01

An experimental and analytical investigation was conducted to determine which characteristics of a light aircraft landing gear influence gear dynamic behavior significantly. The investigation focused particularly on possible modification for load control. Pseudostatic tests were conducted to determine the gear fore-and-aft spring constant, axial friction as a function of drag load, brake pressure-torque characteristics, and tire force-deflection characteristics. To study dynamic tire response, vertical drops were conducted at impact velocities of 1.2, 1.5, and 1.8 m/s onto a level surface; to determine axial-friction effects, a second series of vertical drops were made at 1.5 m/s onto surfaces inclined 5 deg and 10 deg to the horizontal. An average dynamic axial-friction coefficient of 0.15 was obtained by comparing analytical data with inclined surface drop test data. Dynamic strut bending and associated axial friction were found to be severe for the drop tests on the 10 deg surface.

A Vertically Lagrangian Finite-Volume Dynamical Core for Global Models

NASA Technical Reports Server (NTRS)

Lin, Shian-Jiann

2003-01-01

A finite-volume dynamical core with a terrain-following Lagrangian control-volume discretization is described. The vertically Lagrangian discretization reduces the dimensionality of the physical problem from three to two with the resulting dynamical system closely resembling that of the shallow water dynamical system. The 2D horizontal-to-Lagrangian-surface transport and dynamical processes are then discretized using the genuinely conservative flux-form semi-Lagrangian algorithm. Time marching is split- explicit, with large-time-step for scalar transport, and small fractional time step for the Lagrangian dynamics, which permits the accurate propagation of fast waves. A mass, momentum, and total energy conserving algorithm is developed for mapping the state variables periodically from the floating Lagrangian control-volume to an Eulerian terrain-following coordinate for dealing with physical parameterizations and to prevent severe distortion of the Lagrangian surfaces. Deterministic baroclinic wave growth tests and long-term integrations using the Held-Suarez forcing are presented. Impact of the monotonicity constraint is discussed.

Vertical structure of aerosol distribution and radiative properties over Svalbard - observations and modelling

NASA Astrophysics Data System (ADS)

Kaminski, Jacek W.; Struzewska, Joanna; Markowicz, Krzysztof; Jefimow, Maciej

2015-04-01

In the scope of the iAREA projects (Impact of absorbing aerosols on radiative forcing in the European Arctic - http://www.igf.fuw.edu.pl/iAREA) a field campaign was undertaken in March and April 2014 on Spitzbergen. Analysis of measurements was supported by the GEM-AQ model simulations. The GEM-AQ model is a chemical weather model. The core of the model is based on a weather prediction model with environmental processes (chemistry and aerosols) implanted on-line and are interactive (i.e. providing feedback of chemistry on radiation and dynamics). Numerical experiments were performed with the computational grid resolution of ˜15 km. The emission inventory developed by NILU in the ECLIPSE project was used. Preliminary analysis revealed small but systematic overestimation of modelled AOD and background BC levels. We will present the analysis of the vertical distribution of different aerosol species and its contribution to AOD for two stations on Svalbard. Also, changes of modelled chemical composition of aerosols with altitude will be analyzed.

Modeling methodology for a CMOS-MEMS electrostatic comb

NASA Astrophysics Data System (ADS)

Iyer, Sitaraman V.; Lakdawala, Hasnain; Mukherjee, Tamal; Fedder, Gary K.

2002-04-01

A methodology for combined modeling of capacitance and force 9in a multi-layer electrostatic comb is demonstrated in this paper. Conformal mapping-based analytical methods are limited to 2D symmetric cross-sections and cannot account for charge concentration effects at corners. Vertex capacitance can be more than 30% of the total capacitance in a single-layer 2 micrometers thick comb with 10 micrometers overlap. Furthermore, analytical equations are strictly valid only for perfectly symmetrical finger positions. Fringing and corner effects are likely to be more significant in a multi- layered CMOS-MEMS comb because of the presence of more edges and vertices. Vertical curling of CMOS-MEMS comb fingers may also lead to reduced capacitance and vertical forces. Gyroscopes are particularly sensitive to such undesirable forces, which therefore, need to be well-quantified. In order to address the above issues, a hybrid approach of superposing linear regression models over a set of core analytical models is implemented. Design of experiments is used to obtain data for capacitance and force using a commercial 3D boundary-element solver. Since accurate force values require significantly higher mesh refinement than accurate capacitance, we use numerical derivatives of capacitance values to compute the forces. The model is formulated such that the capacitance and force models use the same regression coefficients. The comb model thus obtained, fits the numerical capacitance data to within +/- 3% and force to within +/- 10%. The model is experimentally verified by measuring capacitance change in a specially designed test structure. The capacitance model matches measurements to within 10%. The comb model is implemented in an Analog Hardware Description Language (ADHL) for use in behavioral simulation of manufacturing variations in a CMOS-MEMS gyroscope.

Effect of foot type on knee valgus, ground reaction force, and hip muscle activation in female soccer players.

PubMed

Rath, Meghan E; Stearne, David J; Walker, Cameron R; Cox, Jaime C

2016-05-01

The purpose of this study was to determine the degree to which subtalar joint pronation resulting from a supple planus foot affects knee alignment, hip muscle activation and ground reaction force attenuation in female athletes during a broad jump-to-cut maneuver. Twelve National Collegiate Athletic Association (NCAA) Division II female soccer players (age=19.4±1.4 years, height=1.64±0.05 m, mass=64.10±4.8 kg) were identified as having either supple planus (SP) or rigid feet (RF). Participants completed three broad jump-to-cut trials onto a force plate while EMG and motion data were collected. Muscle activation levels (percentage of maximal voluntary contraction [%MVC]) in the gluteus maximus, gluteus medius, biceps femoris, and rectus femoris were calculated, and peak vertical and medial shear force, rate of loading, and valgus angle were collected for each trial. Mann-Whitney U tests revealed no statistical significance between foot-type groups, however, effect size statistics revealed practical significance for between-group %MVC biceps femoris (d=1.107), %MVC gluteus maximus (d=1.069), and vertical ground reaction force (d=1.061). Athletes with a SP foot type may experience decreased hip muscle activation associated with increased vertical ground reaction force during a broad jump-to-cut maneuver. This might result in reduced dynamic stability and neuromuscular control during deceleration, potentially increasing the risk of non-contact ACL injury in female soccer players.

The hindlimb in walking horses: 1. Kinematics and ground reaction forces.

PubMed

Hodson, E; Clayton, H M; Lanovaz, J L

2001-01-01

The objective was to study associations between kinematics and ground reaction forces in the hindlimb of walking horses. Video (60 Hz) and force (2000 Hz) data were gathered for 8 strides from each of 5 sound horses during the walk. Sagittal plane kinematics were measured concurrently with the vertical and longitudinal ground reaction forces. The hindlimb showed rapid loading and braking in the initial 10% stride. The stifle, tarsal and coffin joints flexed and the fetlock joint extended during this period of rapid loading. The vertical ground reaction force showed 2 peaks separated by a dip; this pattern was similar to the fetlock joint angle-time graph. Peaks in the longitudinal ground reaction force did not appear to correspond with kinematic events. Total braking impulse was equal to total propulsive impulse over the entire stride. Flexion and extension of the hip were responsible for protraction and retraction of the entire limb. Maximal protraction occurred shortly before the end of swing and maximal retraction occurred during breakover. During the middle part of stance the tarsal joint extended slowly, while the stifle began to flex when the limb was retracted beyond the midstance position at 28% stride. Flexion cycles of the stifle and tarsal joints were well coordinated during the swing phase to raise the distal limb as it was protracted. The results demonstrate a relationship between limb kinematics and vertical limb loading in the hindlimbs of sound horses. Future studies will elucidate the alterations in response to lameness.

A simple method of equine limb force vector analysis and its potential applications

PubMed Central

Robinson, Mark A.; Clayton, Hilary M.

2018-01-01

Background Ground reaction forces (GRF) measured during equine gait analysis are typically evaluated by analyzing discrete values obtained from continuous force-time data for the vertical, longitudinal and transverse GRF components. This paper describes a simple, temporo-spatial method of displaying and analyzing sagittal plane GRF vectors. In addition, the application of statistical parametric mapping (SPM) is introduced to analyse differences between contra-lateral fore and hindlimb force-time curves throughout the stance phase. The overall aim of the study was to demonstrate alternative methods of evaluating functional (a)symmetry within horses. Methods GRF and kinematic data were collected from 10 horses trotting over a series of four force plates (120 Hz). The kinematic data were used to determine clean hoof contacts. The stance phase of each hoof was determined using a 50 N threshold. Vertical and longitudinal GRF for each stance phase were plotted both as force-time curves and as force vector diagrams in which vectors originating at the centre of pressure on the force plate were drawn at intervals of 8.3 ms for the duration of stance. Visual evaluation was facilitated by overlay of the vector diagrams for different limbs. Summary vectors representing the magnitude (VecMag) and direction (VecAng) of the mean force over the entire stance phase were superimposed on the force vector diagram. Typical measurements extracted from the force-time curves (peak forces, impulses) were compared with VecMag and VecAng using partial correlation (controlling for speed). Paired samples t-tests (left v. right diagonal pair comparison and high v. low vertical force diagonal pair comparison) were performed on discrete and vector variables using traditional methods and Hotelling’s T2 tests on normalized stance phase data using SPM. Results Evidence from traditional statistical tests suggested that VecMag is more influenced by the vertical force and impulse, whereas VecAng is more influenced by the longitudinal force and impulse. When used to evaluate mean data from the group of ten sound horses, SPM did not identify differences between the left and right contralateral limb pairs or between limb pairs classified according to directional asymmetry. When evaluating a single horse, three periods were identified during which differences in the forces between the left and right forelimbs exceeded the critical threshold (p < .01). Discussion Traditional statistical analysis of 2D GRF peak values, summary vector variables and visual evaluation of force vector diagrams gave harmonious results and both methods identified the same inter-limb asymmetries. As alpha was more tightly controlled using SPM, significance was only found in the individual horse although T2 plots followed the same trends as discrete analysis for the group. Conclusions The techniques of force vector analysis and SPM hold promise for investigations of sidedness and asymmetry in horses. PMID:29492341

Physical Processes Contributing To Small-scale Vertical Movements During Changing Inplane Stresses In Rift Basins and At Passive Continental Margins

NASA Astrophysics Data System (ADS)

Paulsen, G. E.; Nielsen, S. B.; Hansen, D. L.

The vertical movements during a regional stress reversal in a rifted basin or on a passive continental margin are examined using a numerical 2D thermo-mechanical finite element model with a visco-elastic-plastic rheology. Three different physical mechanisms are recognized in small-scale vertical movements at small inplane force variations: elastic dilatation, elastic flexure, and permanent deformation. Their rela- tive importance depend on the applied force, the duration of the force, and the thermal structure of the lithosphere. Elastic material dilatation occurs whenever the stress state changes. A reversal from extension to compression therefore immediately leads to elastic dilatation, and re- sults in an overall subsidence of the entire profile. Simultaneously with dilatation the lithosphere reacts with flexure. The significance of the flexural component strongly depends on the thermal structure of the lithosphere. The polarity and amplitude of the flexure depends on the initial (before compression) loading of the lithosphere. Gener- ally, the flexural effects lead to subsidence of the overdeep in the landward part of the basin and a small amount of uplift at the basin flanks. The amplitudes of the flexural response are small and comparable with the amplitudes of the elastic dilatation. With continuing compression permanent deformation and lithospheric thickening becomes increasingly important. Ultimately, the thickened part of the lithosphere stands out as an inverted zone. The amount of permanent deformation is directly connected with the size and duration of the applied force, but even a relatively small force leads to inversion tectonics in the landward part of the basin. The conclusions are: 1) small stress induced vertical movements in rift basins and at passive continental margins are the result of a complex interaction of at least three different processes, 2) the total sediment loaded amplitudes resulting from these pro- cesses are small (2-300 m) for inplane forces up to 1.5·1012 N/m.

Instruction of jump-landing technique using videotape feedback: altering lower extremity motion patterns.

PubMed

Oñate, James A; Guskiewicz, Kevin M; Marshall, Stephen W; Giuliani, Carol; Yu, Bing; Garrett, William E

2005-06-01

Anterior cruciate ligament injury prevention programs have used videotapes of jump-landing technique as a key instructional component to improve landing performance. All videotape feedback model groups will increase knee flexion angles at initial contact and overall knee flexion motion and decrease peak vertical ground reaction forces and peak proximal anterior tibial shear forces to a greater extent than will a nonfeedback group. The secondary hypothesis is that the videotape feedback using the combination of the expert and self models will create the greatest change in each variable. Controlled laboratory study. Knee kinematics and kinetics of college-aged recreational athletes randomly placed in 3 different videotape feedback model groups (expert only, self only, combination of expert and self) and a nonfeedback group were collected while participants performed a basketball jump-landing task on 3 testing occasions. All feedback groups significantly increased knee angular displacement flexion angles [F(6,70) = 8.03, P = .001] and decreased peak vertical ground reaction forces [F(6,78) = 2.68, P = .021] during performance and retention tests. The self and combination groups significantly increased knee angular displacement flexion angles more than the control group did; the expert model group did not change significantly more than the control group did. All feedback groups and the nonfeedback group significantly reduced peak vertical forces across performance and retention tests. There were no statistically significant changes in knee flexion angle at initial ground contact (P = .111) and peak proximal anterior tibial shear forces (P = .509) for both testing sessions for each group. The use of self or combination videotape feedback is most useful for increasing knee angular displacement flexion angles and reducing peak vertical forces during landing. The use of self or combination modeling is more effective than is expert-only modeling for the implementation of instructional programs aimed at reducing the risk of jump-landing anterior cruciate ligament injuries.

Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures

PubMed Central

Schmidt, Matthew W.; Chang, Ping; Hertzberg, Jennifer E.; Them, Theodore R.; Ji, Link; Otto-Bliesner, Bette L.

2012-01-01

Both instrumental data analyses and coupled ocean-atmosphere models indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly linked to abrupt tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes. Although a slowdown of AMOC results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger warming because of rapid reorganizations of ocean circulation patterns at intermediate water depths. Here, we reconstruct high-resolution temperature records using oxygen isotope values and Mg/Ca ratios in both surface- and subthermocline-dwelling planktonic foraminifera from a sediment core located in the TNA over the last 22 ky. Our results show significant changes in the vertical thermal gradient of the upper water column, with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the Younger Dryas. Furthermore, we present new analyses of a climate model simulation forced with freshwater discharge into the North Atlantic under Last Glacial Maximum forcings and boundary conditions that reveal a maximum subsurface warming in the vicinity of the core site and a vertical thermal gradient change at the onset of AMOC weakening, consistent with the reconstructed record. Together, our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high-latitude North Atlantic climate to the tropical Atlantic during periods of reduced AMOC across the last deglacial transition. PMID:22908256

Impact of abrupt deglacial climate change on tropical Atlantic subsurface temperatures.

PubMed

Schmidt, Matthew W; Chang, Ping; Hertzberg, Jennifer E; Them, Theodore R; Ji, Link; J, Link; Otto-Bliesner, Bette L

2012-09-04

Both instrumental data analyses and coupled ocean-atmosphere models indicate that Atlantic meridional overturning circulation (AMOC) variability is tightly linked to abrupt tropical North Atlantic (TNA) climate change through both atmospheric and oceanic processes. Although a slowdown of AMOC results in an atmospheric-induced surface cooling in the entire TNA, the subsurface experiences an even larger warming because of rapid reorganizations of ocean circulation patterns at intermediate water depths. Here, we reconstruct high-resolution temperature records using oxygen isotope values and Mg/Ca ratios in both surface- and subthermocline-dwelling planktonic foraminifera from a sediment core located in the TNA over the last 22 ky. Our results show significant changes in the vertical thermal gradient of the upper water column, with the warmest subsurface temperatures of the last deglacial transition corresponding to the onset of the Younger Dryas. Furthermore, we present new analyses of a climate model simulation forced with freshwater discharge into the North Atlantic under Last Glacial Maximum forcings and boundary conditions that reveal a maximum subsurface warming in the vicinity of the core site and a vertical thermal gradient change at the onset of AMOC weakening, consistent with the reconstructed record. Together, our proxy reconstructions and modeling results provide convincing evidence for a subsurface oceanic teleconnection linking high-latitude North Atlantic climate to the tropical Atlantic during periods of reduced AMOC across the last deglacial transition.

Influence of running velocity on vertical, leg and joint stiffness : modelling and recommendations for future research.

PubMed

Brughelli, Matt; Cronin, John

2008-01-01

Human running can be modelled as either a spring-mass model or multiple springs in series. A force is required to stretch or compress the spring, and thus stiffness, the variable of interest in this paper, can be calculated from the ratio of this force to the change in spring length. Given the link between force and length change, muscle stiffness and mechanical stiffness have been areas of interest to researchers, clinicians, and strength and conditioning practitioners for many years. This review focuses on mechanical stiffness, and in particular, vertical, leg and joint stiffness, since these are the only stiffness types that have been directly calculated during human running. It has been established that as running velocity increases from slow-to-moderate values, leg stiffness remains constant while both vertical stiffness and joint stiffness increase. However, no studies have calculated vertical, leg or joint stiffness over a range of slow-to-moderate values to maximum values in an athletic population. Therefore, the effects of faster running velocities on stiffness are relatively unexplored. Furthermore, no experimental research has examined the effects of training on vertical, leg or joint stiffness and the subsequent effects on running performance. Various methods of training (Olympic style weightlifting, heavy resistance training, plyometrics, eccentric strength training) have shown to be effective at improving running performance. However, the effects of these training methods on vertical, leg and joint stiffness are unknown. As a result, the true importance of stiffness to running performance remains unexplored, and the best practice for changing stiffness to optimize running performance is speculative at best. It is our hope that a better understanding of stiffness, and the influence of running speed on stiffness, will lead to greater interest and an increase in experimental research in this area.

Seagrass ( Posidonia oceanica) vertical growth as an early indicator of fish farm-derived stress

NASA Astrophysics Data System (ADS)

Marbà, Núria; Santiago, Rocío; Díaz-Almela, Elena; Álvarez, Elvira; Duarte, Carlos M.

2006-04-01

The usefulness of vertical rhizome growth as an early indicator of fish farm impacts to Posidonia oceanica meadows was tested by comparing annual estimates of vertical rhizome growth, quantified retrospectively, at distances ranging between 5 and 1200 m from fish cages at four Mediterranean locations (Cyprus, Greece, Italy and Spain). The studied fish farms had been operating since, at least, 1997, producing between 150 and 1150 tons yr -1 of sea bream ( Sparus aurata) and sea bass ( Dicentrachus labrax), and, at Italy, also sharpsnout sea bream ( Diplodus puntazzo). The reconstructed vertical rhizome growth spanned from 19 to 25 years of growth, depending on sites, and the average vertical rhizome growth before the onset of fish farm operations ranged between 4.48 and 8.79 mm yr -1. The vertical rhizome growth after the onset of farming activities declined significantly ( t-test, P < 0.05) from the control station (at >800 m from the farm; vertical growth rate averaged 6.79, 5.52, 3.89 and 3.70 mm yr -1 at Cyprus, Greece, Italy and Spain control stations, respectively) to the impacted one (at 5-300 m from the farm; vertical growth rate was 4.82, 3.52, 2.77 and 1.92 mm yr -1 at Cyprus, Greece, Italy and Spain impacted stations, respectively) at each farm. Moreover, vertical growth significantly ( t-test, P < 0.05) declined by about twofold following the onset of fish farm operations for the extant meadow nearest to the cages, as well as those supporting intermediate impacts at distances 35-400 m from the cages. Vertical rhizome growth was not significantly affected after the onset of fish farm operations for the meadows located more than 800 m from the farm, except in those from the Italian site, the largest farm. Examination of the time course of vertical growth for individual rhizomes in the areas of the meadow nearest to the farms, except for those at Cyprus, showed that the decline in vertical growth was initiated within the year of the onset of farming activities, suggesting a negligible resistance of seagrass meadows to fish farm impacts. The results obtained confirm that fish farm activities strongly affect seagrass health on the surrounding meadows, and clearly demonstrate the value of reductions in vertical rhizome growth as an early warning symptom of stress and impacts to P. oceanica meadows.

Experimental Validation Data for Computational Fluid Dynamics of Forced Convection on a Vertical Flat Plate

DOE PAGES

Harris, Jeff R.; Lance, Blake W.; Smith, Barton L.

2015-08-10

We present computational fluid dynamics (CFD) validation dataset for turbulent forced convection on a vertical plate. The design of the apparatus is based on recent validation literature and provides a means to simultaneously measure boundary conditions (BCs) and system response quantities (SRQs). Important inflow quantities for Reynolds-Averaged Navier-Stokes (RANS). CFD are also measured. Data are acquired at two heating conditions and cover the range 40,000 < Re x < 300,000, 357 < Re δ2 < 813, and 0.02 < Gr/Re 2 < 0.232.

Are Brazil nuts attractive?

PubMed

Sanders, Duncan A; Swift, Michael R; Bowley, R M; King, P J

2004-11-12

We present event-driven simulation results for single and multiple intruders in a vertically vibrated granular bed. Under our vibratory conditions, the mean vertical position of a single intruder is governed primarily by a buoyancylike effect. Multiple intruders also exhibit buoyancy governed behavior; however, multiple neutrally buoyant intruders cluster spontaneously and undergo horizontal segregation. These effects can be understood by considering the dynamics of two neutrally buoyant intruders. We have measured an attractive force between such intruders which has a range of five intruder diameters, and we provide a mechanistic explanation for the origins of this force.

Impacts of Aerosol Direct Effects on the South Asian climate: Assessment of Radiative Feedback Processes Using Model Simulations and Satellite/surface Measurements

NASA Astrophysics Data System (ADS)

Wang, S.; Gautam, R.; Lau, W. K.; Tsay, S.; Sun, W.; Kim, K.; Chern, J.; Colarco, P. R.; Hsu, N. C.; Lin, N.

2011-12-01

Current assessment of aerosol radiative effect is hindered by our incomplete knowledge of aerosol optical properties, especially absorption, and our current inability to quantify physical and microphysical processes. In this research, we investigate direct aerosol radiative effect over heavy aerosol loading areas (e.g., Indo-Gangetic Plains, South/East Asia) and its feedbacks on the South Asian climate during the pre-monsoon season (March-June) using the Purdue Regional Climate Model (PRCM) with prescribed aerosol data derived by the NASA Goddard Earth Observing System Model (GEOS-5). Our modeling domain covers South and East Asia (60-140E and 0-50N) with spatial resolutions of 45 km in horizontal and 28 layers in vertical. The model is integrated from 15 February to 30 June 2008 continuously without nudging (i.e., only forced by initial/boundary conditions). Two numerical experiments are conducted with and without the aerosol-radiation effects. Both simulations are successful in reproducing the synoptic patterns on seasonal-to-interannual time scales and capturing a pre-monsoon feature of the northward rainfall propagation over Indian region in early June which shown in Tropical Rainfall Measuring Mission (TRMM) observation. Preliminary result suggests aerosol-radiation interactions mainly alter surface-atmosphere energetics and further result in an adjustment of the vertical temperature distribution in lower atmosphere (below 700 hPa). The modifications of temperature and associated rainfall and circulation feedbacks on the regional climate will be discussed in the presentation. In addition to modeling study, we will also present the most recent results on aerosol properties, regional aerosol absorption, and radiative forcing estimation based on NASA's operational satellite and ground-based remote sensing. Observational results show spatial gradients in aerosol loading and solar absorption accounting over Indo-Gangetic Plains during the pre-monsoon season. The direct radiative forcing of aerosols at surface to be -19-23 Wm-2 (12-15 % of the surface solar insolation) over NW India is estimated using an observational approach. A comparison of aerosol radiative forcing between numerical simulation and observational estimate will be presented. Overall, this work will demonstrate the aerosol direct effects from both modeling and observation perspectives, and further to assess the physical processes underlying the aerosol radiative feedbacks and possible impacts on the large-scale South Asian monsoon system.

A sensor fusion method for tracking vertical velocity and height based on inertial and barometric altimeter measurements.

PubMed

Sabatini, Angelo Maria; Genovese, Vincenzo

2014-07-24

A sensor fusion method was developed for vertical channel stabilization by fusing inertial measurements from an Inertial Measurement Unit (IMU) and pressure altitude measurements from a barometric altimeter integrated in the same device (baro-IMU). An Extended Kalman Filter (EKF) estimated the quaternion from the sensor frame to the navigation frame; the sensed specific force was rotated into the navigation frame and compensated for gravity, yielding the vertical linear acceleration; finally, a complementary filter driven by the vertical linear acceleration and the measured pressure altitude produced estimates of height and vertical velocity. A method was also developed to condition the measured pressure altitude using a whitening filter, which helped to remove the short-term correlation due to environment-dependent pressure changes from raw pressure altitude. The sensor fusion method was implemented to work on-line using data from a wireless baro-IMU and tested for the capability of tracking low-frequency small-amplitude vertical human-like motions that can be critical for stand-alone inertial sensor measurements. Validation tests were performed in different experimental conditions, namely no motion, free-fall motion, forced circular motion and squatting. Accurate on-line tracking of height and vertical velocity was achieved, giving confidence to the use of the sensor fusion method for tracking typical vertical human motions: velocity Root Mean Square Error (RMSE) was in the range 0.04-0.24 m/s; height RMSE was in the range 5-68 cm, with statistically significant performance gains when the whitening filter was used by the sensor fusion method to track relatively high-frequency vertical motions.

Loading forces in shallow water running in two levels of immersion.

PubMed

Haupenthal, Alessandro; Ruschel, Caroline; Hubert, Marcel; de Brito Fontana, Heiliane; Roesler, Helio

2010-07-01

To analyse the vertical and anteroposterior components of the ground reaction force during shallow water running at 2 levels of immersion. Twenty-two healthy adults with no gait disorders, who were familiar with aquatic exercises. Subjects performed 6 trials of water running at a self-selected speed in chest and hip immersion. Force data were collected through an underwater force plate and running speed was measured with a photocell timing light system. Analysis of covariance was used for data analysis. Vertical forces corresponded to 0.80 and 0.98 times the subject's body weight at the chest and hip level, respectively. Anteroposterior forces corresponded to 0.26 and 0.31 times the subject's body weight at the chest and hip level, respectively. As the water level decreased the subjects ran faster. No significant differences were found for the force values between the immersions, probably due to variability in speed, which was self-selected. When thinking about load values in water running professionals should consider not only the immersion level, but also the speed, as it can affect the force components, mainly the anteroposterior one. Quantitative data on this subject could help professionals to conduct safer aqua-tic rehabilitation and physical conditioning protocols.

The kinetics of rugby union scrummaging.

PubMed

Milburn, P D

1990-01-01

Two rugby union forward packs of differing ability levels were examined during scrummaging against an instrumented scrum machine. By systematically moving the front-row of the scrum along the scrum machine, kinetic data on each front-row forward could be obtained under all test conditions. Each forward pack was tested under the following scrummaging combinations: front-row only; front-row plus second-row; full scrum minus side-row, and full scrum. Data obtained from each scrum included the three orthogonal components of force at engagement and the sustained force applied by each front-row player. An estimate of sub-unit contributions was made by subtracting the total forward force on all three front-row players from the total for the complete scrum. Results indicated the primary role of the second-row appeared to be application of forward force. The back-row ('number eight') forward did not substantially contribute any additional forward force, and added only slightly to the lateral and vertical shear force experienced by the front-row. The side-row contributed an additional 20-27% to the forward force, but at the expense of increased vertical forces on all front-row forwards. Results of this investigation are discussed in relation to rule modification, rule interpretation and coaching.

Formation of well-mixed warm water column in central Bohai Sea during summer: Role of high-frequency atmospheric forcing

NASA Astrophysics Data System (ADS)

Ma, Weiwei; Wan, Xiuquan; Wang, Zhankun; Liu, Yulong; Wan, Kai

2017-12-01

The influence of high-frequency atmospheric forcing on the formation of a well-mixed summer warm water column in the central Bohai Sea is investigated comparing model simulations driven by daily surface forcing and those using monthly forcing data. In the absence of high-frequency atmospheric forcing, numerical simulations have repeatedly failed to reproduce this vertically uniform column of warm water measured over the past 35 years. However, high-frequency surface forcing is found to strongly influence the structure and distribution of the well-mixed warm water column, and simulations are in good agreement with observations. Results show that high frequency forcing enhances vertical mixing over the central bank, intensifies downward heat transport, and homogenizes the water column to form the Bohai central warm column. Evidence presented shows that high frequency forcing plays a dominant role in the formation of the well-mixed warm water column in summer, even without the effects of tidal and surface wave mixing. The present study thus provides a practical and rational way of further improving the performance of oceanic simulations in the Bohai Sea and can be used to adjust parameterization schemes of ocean models.

Aerodynamic forces and flow structures of the leading edge vortex on a flapping wing considering ground effect.

PubMed

Van Truong, Tien; Byun, Doyoung; Kim, Min Jun; Yoon, Kwang Joon; Park, Hoon Cheol

2013-09-01

The aim of this work is to provide an insight into the aerodynamic performance of the beetle during takeoff, which has been estimated in previous investigations. We employed a scaled-up electromechanical model flapping wing to measure the aerodynamic forces and the three-dimensional flow structures on the flapping wing. The ground effect on the unsteady forces and flow structures were also characterized. The dynamically scaled wing model could replicate the general stroke pattern of the beetle's hind wing kinematics during takeoff flight. Two wing kinematic models have been studied to examine the influences of wing kinematics on unsteady aerodynamic forces. In the first model, the angle of attack is asymmetric and varies during the translational motion, which is the flapping motion of the beetle's hind wing. In the second model, the angle of attack is constant during the translational motion. The instantaneous aerodynamic forces were measured for four strokes during the beetle's takeoff by the force sensor attached at the wing base. Flow visualization provided a general picture of the evolution of the three-dimensional leading edge vortex (LEV) on the beetle hind wing model. The LEV is stable during each stroke, and increases radically from the root to the tip, forming a leading-edge spiral vortex. The force measurement results show that the vertical force generated by the hind wing is large enough to lift the beetle. For the beetle hind wing kinematics, the total vertical force production increases 18.4% and 8.6% for the first and second strokes, respectively, due to the ground effect. However, for the model with a constant angle of attack during translation, the vertical force is reduced during the first stroke. During the third and fourth strokes, the ground effect is negligible for both wing kinematic patterns. This finding suggests that the beetle's flapping mechanism induces a ground effect that can efficiently lift its body from the ground during takeoff.

The ecological dynamics of Barra Bonita (Tietê River, SP, Brazil) reservoir: implications for its biodiversity.

PubMed

Tundisi, J G; Matsumura-Tundisi, T; Abe, D S

2008-11-01

Barra Bonita reservoir is located in the Tietê River Basin - São Paulo state - 22 degrees 29' to 22 degrees 44' S and 48 degrees 10 degrees W and it is the first of a series of six large reservoirs in this river. Built up in 1963 with the aim to produce hydroelectricity this reservoir is utilized for several activities such as fish production, irrigation, navigation, tourism and recreation, besides hydroelectricity production. The seasonal cycle of events in this reservoir is driven by the hydrological features of the basin with consequences on the retention time and on the limnological functions of this artificial ecosystem. The reservoir is polymitic with short periods of stability. Hydrology of the basin, retention time of the reservoir and cold fronts have an impact in the vertical and horizontal structure of the system promoting rapid changes in the planktonic community and in the succession of species. Blooms of Microcystis sp. are common during periods of stability. Superimposed to the climatological and hydrological forcing functions the human activities in the watershed produce considerable impact such as the discharge of untreated wastewater, the high suspended material contributions and fertilizers from the sugar cane plantations. The fish fauna of the reservoir has been changed extent due to the introduction of exotic fish species that exploit the pelagic zone of the reservoir. Changes in the primary productivity of phytoplankton in this reservoir, in the zooplankton community in the diversity and organization of trophic structure are a consequence of eutrophication and its increase during the last 20 years. Control of eutrophication by treating wastewater from urban sources, adequate agricultural practices in order to diminish the suspended particulate matter contribution, revegetation of the watershed and riparian forests along the tributaries are some possible restoration measures. Another action that can be effective is the protection of wetlands in the main tributaries as an effort to control eutrophication and particulate material load. Hydrology, climatic forcing and retention time are major forcing functions that promote the circulation (vertical and horizontal) in the reservoir and probably have a strong effect on dissolved and particulate material distribution. The 114 tributaries are systems that enhance spatial heterogeneity promoting diversity throughout ecological niches. Switches of control systems of this artificial ecosystem seems to be related with physical - physical forces; physical - biological forces during short periods of time, and biological - biological interactions at varying degrees during the seasonal cycle.

Atmospheric gravity waves with small vertical-to-horizotal wavelength ratios

NASA Astrophysics Data System (ADS)

Song, I. S.; Jee, G.; Kim, Y. H.; Chun, H. Y.

2017-12-01

Gravity wave modes with small vertical-to-horizontal wavelength ratios of an order of 10-3 are investigated through the systematic scale analysis of governing equations for gravity wave perturbations embedded in the quasi-geostrophic large-scale flow. These waves can be categorized as acoustic gravity wave modes because their total energy is given by the sum of kinetic, potential, and elastic parts. It is found that these waves can be forced by density fluctuations multiplied by the horizontal gradients of the large-scale pressure (geopotential) fields. These theoretical findings are evaluated using the results of a high-resolution global model (Specified Chemistry WACCM with horizontal resolution of 25 km and vertical resolution of 600 m) by computing the density-related gravity-wave forcing terms from the modeling results.

Atomic force microscope based on vertical silicon probes

NASA Astrophysics Data System (ADS)

Walter, Benjamin; Mairiaux, Estelle; Faucher, Marc

2017-06-01

A family of silicon micro-sensors for Atomic Force Microscope (AFM) is presented that allows to operate with integrated transducers from medium to high frequencies together with moderate stiffness constants. The sensors are based on Micro-Electro-Mechanical-Systems technology. The vertical design specifically enables a long tip to oscillate perpendicularly to the surface to be imaged. The tip is part of a resonator including quasi-flexural composite beams, and symmetrical transducers that can be used as piezoresistive detector and/or electro-thermal actuator. Two vertical probes (Vprobes) were operated up to 4.3 MHz with stiffness constants 150 N/m to 500 N/m and the capability to oscillate from 10 pm to 90 nm. AFM images of several samples both in amplitude modulation (tapping-mode) and in frequency modulation were obtained.

Vertical stiffness is not related to anterior cruciate ligament elongation in professional rugby union players

PubMed Central

Serpell, Benjamin G; Scarvell, Jennie M; Pickering, Mark R; Ball, Nick B; Perriman, Diana; Warmenhoven, John; Smith, Paul N

2016-01-01

Background Novel research surrounding anterior cruciate ligament (ACL) injury is necessary because ACL injury rates have remained unchanged for several decades. An area of ACL risk mitigation which has not been well researched relates to vertical stiffness. The relationship between increased vertical stiffness and increased ground reaction force suggests that vertical stiffness may be related to ACL injury risk. However, given that increased dynamic knee joint stability has been shown to be associated with vertical stiffness, it is possible that modification of vertical stiffness could help to protect against injury. We aimed to determine whether vertical stiffness is related to measures known to load, or which represent loading of, the ACL. Methods This was a cross-sectional observational study of 11 professional Australian rugby players. Knee kinematics and ACL elongation were measured from a 4-dimensional model of a hopping task which simulated the change of direction manoeuvre typically observed when non-contact ACL injury occurs. The model was generated from a CT scan of the participant's knee registered frame by frame to fluoroscopy images of the hopping task. Vertical stiffness was calculated from force plate data. Results There was no association found between vertical stiffness and anterior tibial translation (ATT) or ACL elongation (r=−0.05; p=0.89, and r=−0.07; p=0.83, respectively). ATT was related to ACL elongation (r=0.93; p=0.0001). Conclusions Vertical stiffness was not associated with ACL loading in this cohort of elite rugby players but a novel method for measuring ACL elongation in vivo was found to have good construct validity. PMID:27900192

Cognitive Demands Influence Lower Extremity Mechanics During a Drop Vertical Jump Task in Female Athletes.

PubMed

Almonroeder, Thomas Gus; Kernozek, Thomas; Cobb, Stephen; Slavens, Brooke; Wang, Jinsung; Huddleston, Wendy

2018-05-01

Study Design Cross-sectional study. Background The drop vertical jump task is commonly used to screen for anterior cruciate ligament injury risk; however, its predictive validity is limited. The limited predictive validity of the drop vertical jump task may be due to not imposing the cognitive demands that reflect sports participation. Objectives To investigate the influence of additional cognitive demands on lower extremity mechanics during execution of the drop vertical jump task. Methods Twenty uninjured women (age range, 18-25 years) were required to perform the standard drop vertical jump task, as well as drop vertical jumps that included additional cognitive demands. The additional cognitive demands were related to attending to an overhead goal (ball suspended overhead) and/or temporal constraints on movement selection (decision making). Three-dimensional ground reaction forces and lower extremity mechanics were compared between conditions. Results The inclusion of the overhead goal resulted in higher peak vertical ground reaction forces and lower peak knee flexion angles in comparison to the standard drop vertical jump task. In addition, participants demonstrated greater peak knee abduction angles when trials incorporated temporal constraints on decision making and/or required participants to attend to an overhead goal, in comparison to the standard drop vertical jump task. Conclusion Imposing additional cognitive demands during execution of the drop vertical jump task influenced lower extremity mechanics in a manner that suggested increased loading of the anterior cruciate ligament. Tasks utilized in anterior cruciate ligament injury risk screening may benefit from more closely reflecting the cognitive demands of the sports environment. J Orthop Sports Phys Ther 2018;48(5):381-387. Epub 10 Jan 2018. doi:10.2519/jospt.2018.7739.

Vertical feed stick wood fuel burning furnace system

DOEpatents

Hill, Richard C.

1984-01-01

A new and improved stove or furnace for efficient combustion of wood fuel including a vertical feed combustion chamber for receiving and supporting wood fuel in a vertical attitude or stack, a major upper portion of the combustion chamber column comprising a water jacket for coupling to a source of water or heat transfer fluid and for convection circulation of the fluid for confining the locus of wood fuel combustion to the bottom of the vertical gravity feed combustion chamber. A flue gas propagation delay channel extending from the laterally directed draft outlet affords delayed travel time in a high temperature environment to assure substantially complete combustion of the gaseous products of wood burning with forced air as an actively induced draft draws the fuel gas and air mixture laterally through the combustion and high temperature zone. Active sources of forced air and induced draft are included, multiple use and circuit couplings for the recovered heat, and construction features in the refractory material substructure and metal component superstructure.

Model of vertical plasma motion during the current quench

NASA Astrophysics Data System (ADS)

Breizman, Boris; Kiramov, Dmitrii

2017-10-01

Tokamak disruptions impair plasma position control, which allows the plasma column to move and hit the wall. These detrimental events enhance thermal and mechanical loads due to halo currents and runaway electron losses. Their fundamental understanding and prevention is one of the high-priority items for ITER. As commonly observed in experiments, the disruptive plasma tends to move vertically, and the timescale of this motion is rather resistive than Alfvenic. These observations suggest that the plasma column is nearly force-free during its vertical motion. In fact, the force-free constraint is already used in disruption simulators. In this work, we consider a geometrically simple system that mimics the tokamak plasma surrounded by the conducting structures. Using this model, we highlight the underlying mechanism of the vertical displacement events during the current quench phase of plasma disruption. We also address a question of ideal MHD stability of the plasma during its resistive motion. Work supported by the U.S. Department of Energy Contracts DEFG02-04ER54742 and DE-SC0016283.

Aerodynamic Loads at Mach Numbers from 0.70 to 2.22 on an Airplane Model Having a Wing and Canard of Triangular Plan Form and Either Single or Twin Vertical Tails Supplement I-Tabulated Data for the Model with Single Vertical Tails. Supplement 1; Tabulated Data for the Model with Single Vertical Tail

NASA Technical Reports Server (NTRS)

Peterson, Victor L.; Menees, Gene P.

1961-01-01

Tabulated results of a wind-tunnel investigation of the aerodynamic loads on a canard airplane model with a single vertical tail are presented for Mach numbers from 0.70 to 2.22. The Reynolds number for the measurements was 2.9 x 10(exp 6) based on the wing mean aerodynamic chord. The results include local static pressure coefficients measured on the wing, body, and vertical tail for angles of attack from -4 deg to + 16 deg, angles of sideslip of 0 deg and 5.3 deg, vertical-tail settings of 0 deg and 5 deg, and nominal canard deflections of 0 deg and 10 deg. Also included are section force and moment coefficients obtained from integrations of the local pressures and model-component force and moment coefficients obtained from integrations of the section coefficients. Geometric details of the model and the locations of the pressure orifices are shown. An index to the data contained herein is presented and definitions of nomenclature are given.

Aircraft Brake Systems Testing Handbook.

DTIC Science & Technology

1981-05-01

distribution is unlimited. AIR FORCE FLIGHT TEST CENTER EDWARDS AIR FORCE BASE , CALIFORNIA AIR FORCE SYSTEMS COMMAND UNITED STATES AIR FORCE A This handbook... Base , California 93523. This handbook has been reviewed and cleared for open publication and/or public release by the AFFTC Office of Public Affairs in...Force lbs Ft Engine Thrust lbs F vrt Vertical Force acting on the tire at the qround lbs 9 Acceleration due to gravity 32.17 ft/sec 2 h Distance

Muscle Force-Velocity Relationships Observed in Four Different Functional Tests.

PubMed

Zivkovic, Milena Z; Djuric, Sasa; Cuk, Ivan; Suzovic, Dejan; Jaric, Slobodan

2017-02-01

The aims of the present study were to investigate the shape and strength of the force-velocity relationships observed in different functional movement tests and explore the parameters depicting force, velocity and power producing capacities of the tested muscles. Twelve subjects were tested on maximum performance in vertical jumps, cycling, bench press throws, and bench pulls performed against different loads. Thereafter, both the averaged and maximum force and velocity variables recorded from individual trials were used for force-velocity relationship modeling. The observed individual force-velocity relationships were exceptionally strong (median correlation coefficients ranged from r = 0.930 to r = 0.995) and approximately linear independently of the test and variable type. Most of the relationship parameters observed from the averaged and maximum force and velocity variable types were strongly related in all tests (r = 0.789-0.991), except for those in vertical jumps (r = 0.485-0.930). However, the generalizability of the force-velocity relationship parameters depicting maximum force, velocity and power of the tested muscles across different tests was inconsistent and on average moderate. We concluded that the linear force-velocity relationship model based on either maximum or averaged force-velocity data could provide the outcomes depicting force, velocity and power generating capacity of the tested muscles, although such outcomes can only be partially generalized across different muscles.

Climate impact of supersonic air traffic: an approach to optimize a potential future supersonic fleet - results from the EU-project SCENIC

NASA Astrophysics Data System (ADS)

Grewe, V.; Stenke, A.; Ponater, M.; Sausen, R.; Pitari, G.; Iachetti, D.; Rogers, H.; Dessens, O.; Pyle, J.; Isaksen, I. S. A.; Gulstad, L.; Søvde, O. A.; Marizy, C.; Pascuillo, E.

2007-10-01

The demand for intercontinental transportation is increasing and people are requesting short travel times, which supersonic air transportation would enable. However, besides noise and sonic boom issues, which we are not referring to in this investigation, emissions from supersonic aircraft are known to alter the atmospheric composition, in particular the ozone layer, and hence affect climate significantly more than subsonic aircraft. Here, we suggest a metric to quantitatively assess different options for supersonic transport with regard to the potential destruction of the ozone layer and climate impacts. Options for fleet size, engine technology (nitrogen oxide emission level), cruising speed, range, and cruising altitude, are analyzed, based on SCENIC emission scenarios for 2050, which underlay the requirements to be as realistic as possible in terms of e.g., economic markets and profitable market penetration. This methodology is based on a number of atmosphere-chemistry and climate models to reduce model dependencies. The model results differ significantly in terms of the response to a replacement of subsonic aircraft by supersonic aircraft, e.g., concerning the ozone impact. However, model differences are smaller when comparing the different options for a supersonic fleet. Those uncertainties were taken into account to make sure that our findings are robust. The base case scenario, where supersonic aircraft get in service in 2015, a first fleet fully operational in 2025 and a second in 2050, leads in our simulations to a near surface temperature increase in 2050 of around 7 mK and with constant emissions afterwards to around 21 mK in 2100. The related total radiative forcing amounts to 22 mWm2 in 2050, with an uncertainty between 9 and 29 mWm2. A reduced supersonic cruise altitude or speed (from Mach 2 to Mach 1.6) reduces both, climate impact and ozone destruction, by around 40%. An increase in the range of the supersonic aircraft leads to more emissions at lower latitudes since more routes to SE Asia are taken into account, which increases ozone depletion, but reduces climate impact compared to the base case.

Aerosol properties computed from aircraft-based observations during the ACE- Asia campaign. 2; A case study of lidar ratio closure and aerosol radiative effects

NASA Technical Reports Server (NTRS)

Kuzmanoski, Maja; Box, M. A.; Schmid, B.; Box, G. P.; Wang, J.; Russell, P. B.; Bates, D.; Jonsson, H. H.; Welton, Ellsworth J.; Flagan, R. C.

2005-01-01

For a vertical profile with three distinct layers (marine boundary, pollution and dust), observed during the ACE-Asia campaign, we carried out a comparison between the modeled lidar ratio vertical profile and that obtained from collocated airborne NASA AATS-14 sunphotometer and shipborne Micro-Pulse Lidar (MPL) measurements. Vertically resolved lidar ratio was calculated from two size distribution vertical profiles - one obtained by inversion of sunphotometer-derived extinction spectra, and one measured in-situ - combined with the same refractive index model based on aerosol chemical composition. The aerosol model implies single scattering albedos of 0.78 - 0.81 and 0.93 - 0.96 at 0.523 microns (the wavelength of the lidar measurements), in the pollution and dust layers, respectively. The lidar ratios calculated from the two size distribution profiles have close values in the dust layer; they are however, significantly lower than the lidar ratios derived from combined lidar and sunphotometer measurements, most probably due to the use of a simple nonspherical model with a single particle shape in our calculations. In the pollution layer, the two size distribution profiles yield generally different lidar ratios. The retrieved size distributions yield a lidar ratio which is in better agreement with that derived from lidar/sunphotometer measurements in this layer, with still large differences at certain altitudes (the largest relative difference was 46%). We explain these differences by non-uniqueness of the result of the size distribution retrieval and lack of information on vertical variability of particle refractive index. Radiative transfer calculations for this profile showed significant atmospheric radiative forcing, which occurred mainly in the pollution layer. We demonstrate that if the extinction profile is known then information on the vertical structure of absorption and asymmetry parameter is not significant for estimating forcing at TOA and the surface, while it is of importance for estimating vertical profiles of radiative forcing and heating rates.

Numerical study of breakwater failure due to tsunami-like undular bore impacts: The case of the port of Soma.

NASA Astrophysics Data System (ADS)

Martin-Medina, Manuel; Morichon, Denis; Abadie, Stephane; Le Roy, Sylvestre; Lemoine, Anne

2017-04-01

The Tohoku tsunami, that impacted the Japanese coast in 2011, caused great damages on many offshore vertical breakwaters ranging from the erosion of the rubble mound to the partial displacement or total collapse of caissons. The breakwater failure mechanisms were function of the tsunami wave types that vary along the Japanese coast according to the bathymetry features. The Iwate coast, characterized by deep water depths and steep slopes, was mainly impacted by tsunami overflow leading in particular to the failure of the world's deepest breakwater of Kamaishi. In the shallow waters of the Sendai bay, observations showed that breakwaters protecting harbor entrances were impacted by short waves train resembling to undular bore. This work aims to investigate this latter type of tsunami wave impacts that are less reported in the literature. We chose to focus on the highly damaged offshore breakwater of Soma, located in the south part of the Sendai bay. The hydrodynamics conditions during the tsunami impact are investigated using the VARANS Thetis code (Desombre et al., 2012), which allows to simulate both the free surface flow and the flow inside the rubble mound simulated by a porous medium. The model is forced at the offshore boundaries by the Funwave Boussinesq code that describes the transformation of the tsunami waves from the source to the generation of undular bores in shallow waters. The study includes the computation of forces acting on the caissons. We discuss the relevance of describing the hydrodynamics at the short wave scale to assess breakwater stability in the course of tsunami-like undular bore impact. References Desombre, J., Morichon, D., & Mory, M. (2012). SIMULTANEOUS SURFACE AND SUBSURFACE AIR AND WATER FLOWS MODELLING IN THE SWASH ZONE. Coastal Engineering Proceedings, 1(33), 56.

Modeling the effects of UV variability and the QBO on the troposphere-stratosphere system. Part I: The middle atmosphere

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

Balachandran, N.K.; Rind, D.

1995-08-01

Results of experiments with a GCM involving changes in UV input ({plus_minus}25%, {plus_minus}10%, {plus_minus}5% at wavelengths below 0.3 {mu}m) and simulated equatorial QBO are presented, with emphasis on the middle atmosphere response. The UV forcing employed is larger than observed during the last solar cycle and does not vary with wavelength, hence the relationship of these results to those from actual solar UV forcing should be treated with caution. The QBO alters the location of the zero wind line and the horizontal shear of the zonal wind in the low to middle stratosphere, while the UV change alters the magnitudemore » of the polar jet and the vertical shear of the zonal wind. Both mechanisms thus affect planetary wave propagation. The east phase of the QBO leads to tropical cooling and high-latitude warming in the lower stratosphere, with opposite effects in the upper stratosphere. This quadrupole pattern is also seen in the observations. The high-latitude responses are due to altered planetary wave effects, while the model`s tropical response in the upper stratosphere is due to gravity wave drag. Increased UV forcing warms tropical latitudes in the middle atmosphere, resulting in stronger extratropical west winds, an effect which peaks in the upper stratosphere/lower mesosphere with the more extreme UV forcing but at lower altitudes and smaller wind variations with the more realistic forcing. The increased vertical gradient of the zonal wind leads to increased vertical propagation of planetary waves, altering energy convergences and temperatures. The exact altitudes affected depend upon the UV forcing applied. Results with combined QBO and UV forcing show that in the Northern Hemisphere, polar warming for the east QBO is stronger when the UV input is reduced by 25% and 5% as increased wave propagation to high latitudes (east QBO effect) is prevented from then propagating vertically (reduced UV effect). 30 refs., 14 figs., 6 tabs.« less

Comparative study of the surface characteristics, microstructure, and magnetic retentive forces of laser-welded dowel-keepers and cast dowel-keepers for use with magnetic attachments.

PubMed

Chao, Yonglie; Du, Li; Yang, Ling

2005-05-01

Information regarding the merits and problems associated with connecting a keeper to a dowel and coping using a laser welding technique has not been explored extensively in the dental literature. This in vitro study compared the surface characteristics, microstructure, and magnetic retentive forces for a dowel and coping-keeper mechanism fabricated using a laser welding process and a cast-to casting technique. Five cast-to and 6 laser-welded dowel and coping-keeper specimens were tested. Using 5 freestanding keepers as the control group, the surface characteristics and microstructures of the specimens were examined by means of stereomicroscopy, metallographic microscopy, and scanning electron microscopy (SEM). Energy-dispersive spectroscopic (EDS) microanalysis with SEM provided elemental concentration information for the test specimens. The vertical magnetic retentive forces (N) of the 3 groups were measured using a universal testing machine. The results were statistically compared using 1-way analysis of variance and the Newman-Keuls multiple range test (alpha =.05). The laser-welded dowel-keeper generally maintained its original surface smoothness as well as the original microstructure. Elements diffused readily through the fusion zone. The surface of the cast dowel-keeper became rough with the formation of an oxide layer, the microstructure changed, and there was only limited elemental diffusion in the fusion zone. The average vertical magnetic retentive force of the laser-welded group, the cast group, and the control group were 4.2 +/- 0.2 N, 3.8 +/- 0.3 N, and 5.6 +/- 0.3 N, respectively. Statistically significant differences in vertical magnetic retentive force were found between the control group and both the laser-welded and cast groups (P <.01). Compared with the cast dowel-keepers, the average vertical magnetic retentive force of the laser-welded dowel-keepers was significantly higher (P <.05). The laser welding technique had less influence on the surface characteristics, the microstructure, and the magnetic retentive forces of keepers relative to techniques that incorporate a keeper at the time of cast dowel and coping fabrication.

The influence of tyre transient side force properties on vehicle lateral acceleration for a time-varying vertical force

NASA Astrophysics Data System (ADS)

Takahashi, Toshimichi

2018-05-01

The tyre model which formerly developed by the author et al. and describes the tyre transient responses of side force and aligning moment under the time-varying vertical force was implemented to the vehicle dynamics simulation software and the influence of tyre side force transient property on the vehicle behaviour was investigated. The vehicle responses with/without tyre transient property on sinusoidally undulated road surfaces were simulated and compared. It was found that the average lateral acceleration of the vehicle at the sinusoidal steering wheel angle input decreases on the undulated road of long wavelength (3 m) for both cases, but when the wavelength becomes shorter (1 m), the average lateral acceleration increases only in the case that the transient property is considered. The cause of those changes is explained by using the tyre-related variables. Also the steady-state turning behaviour of the vehicle on undulated roads are shown and discussed.

Optimum dimensions of power solenoids for magnetic suspension

NASA Technical Reports Server (NTRS)

Kaznacheyev, B. A.

1985-01-01

Design optimization of power solenoids for controllable and stabilizable magnetic suspensions with force compensation in a wind tunnel is shown. It is assumed that the model of a levitating body is a sphere of ferromagnetic material with constant magnetic permeability. This sphere, with a radius much smaller than its distance from the solenoid above, is to be maintained in position on the solenoid axis by balance of the vertical electromagnetic force and the force of gravitation. The necessary vertical (axial) force generated by the solenoid is expressed as a function of relevant system dimensions, solenoid design parameters, and physical properties of the body. Three families of curves are obtained which depict the solenoid power for a given force as a function of the solenoid length with either outside radius or inside radius as a variable parameter and as a function of the outside radius with inside radius as a variable parameter. The curves indicate the optimum solenoid length and outside radius, for minimum power, corresponding to a given outside radius and inside radius, respectively.

Static Footprint Local Forces, Areas, and Aspect Ratios for Three Type 7 Aircraft Tires

NASA Technical Reports Server (NTRS)

Howell, William E.; Perez, Sharon E.; Vogler, William A.

1991-01-01

The National Tire Modeling Program (NTMP) is a joint NASA/industry effort to improve the understanding of tire mechanics and develop accurate analytical design tools. This effort includes fundamental analytical and experimental research on the structural mechanics of tires. Footprint local forces, areas, and aspect ratios were measured. Local footprint forces in the vertical, lateral, and drag directions were measured with a special footprint force transducer. Measurements of the local forces in the footprint were obtained by positioning the transducer at specified locations within the footprint and externally loading the tires. Three tires were tested: (1) one representative of those used on the main landing gear of B-737 and DC-9 commercial transport airplanes, (2) a nose landing gear tire for the Space Shuttle Orbiter, and (3) a main landing gear tire for the Space Shuttle Orbiter. Data obtained for various inflation pressures and vertical loads are presented for two aircraft tires. The results are presented in graphical and tabulated forms.

Concurrent validity of the Gyko inertial sensor system for the assessment of vertical jump height in female sub-elite youth soccer players.

PubMed

Lesinski, Melanie; Muehlbauer, Thomas; Granacher, Urs

2016-01-01

The aim of the present study was to verify concurrent validity of the Gyko inertial sensor system for the assessment of vertical jump height. Nineteen female sub-elite youth soccer players (mean age: 14.7 ± 0.6 years) performed three trials of countermovement (CMJ) and squat jumps (SJ), respectively. Maximal vertical jump height was simultaneously quantified with the Gyko system, a Kistler force-plate (i.e., gold standard), and another criterion device that is frequently used in the field, the Optojump system. Compared to the force-plate, the Gyko system determined significant systematic bias for mean CMJ (-0.66 cm, p  < 0.01, d  = 1.41) and mean SJ (-0.91 cm, p  < 0.01, d  = 1.69) height. Random bias was ± 3.2 cm for CMJ and ± 4.0 cm for SJ height and intraclass correlation coefficients (ICCs) were "excellent" (ICC = 0.87 for CMJ and 0.81 for SJ). Compared to the Optojump device, the Gyko system detected a significant systematic bias for mean CMJ (0.55 cm, p  < 0.05, d  = 0.94) but not for mean SJ (0.39 cm) height. Random bias was ± 3.3 cm for CMJ and ± 4.2 cm for SJ height and ICC values were "excellent" (ICC = 0.86 for CMJ and 0.82 for SJ). Consequently, apparatus specific regression equations were provided to estimate true vertical jump height for the Kistler force-plate and the Optojump device from Gyko-derived data. Our findings indicate that the Gyko system cannot be used interchangeably with a Kistler force-plate and the Optojump device in trained individuals. It is suggested that practitioners apply the correction equations to estimate vertical jump height for the force-plate and the Optojump system from Gyko-derived data.

Breaking tester for examining strength of consolidated starch

NASA Astrophysics Data System (ADS)

Stasiak, Mateusz; Molenda, Marek; Bańda, Maciej; Wiącek, Joanna; Dobrzański, Bohdan; Parafiniuk, Piotr

2017-04-01

A new method based on the measurement of force required to break by bending a vertical column of consolidated powder was elaborated, and its results were compared with the ones obtained from the Jenike shear test. A new apparatus was built based on a vertical cylindrical chamber divided into two cylinders connected with a horizontal hinge. The apparatus was tested with samples of potato, maize and wheat starches with moisture content of 6, 12 and 17% and with the addition of a lubricant. Results of testing revealed significant differences in measured force required to rotate the upper part of the cylinder away from the lower one. The average force varied from 0.138 N for maize starch to 0.143 N for potato starch, while, for various moisture contents, the measured force varied from 0.135 N for 6% to 0.143 N for 17% mc. The results were compared with the results of a direct shear test.

Modelling vertical human walking forces using self-sustained oscillator

NASA Astrophysics Data System (ADS)

Kumar, Prakash; Kumar, Anil; Racic, Vitomir; Erlicher, Silvano

2018-01-01

This paper proposes a model of a self-sustained oscillator which can generate reliably the vertical contact force between the feet of a healthy pedestrian and the supporting flat rigid surface. The model is motivated by the self-sustained nature of the walking process, i.e. a pedestrian generates the required inner energy to sustain its repetitive body motion. The derived model is a fusion of the well-known Rayleigh, Van der Pol and Duffing oscillators. Some additional nonlinear terms are added to produce both the odd and even harmonics observed in the experimentally measured force data. The model parameters were derived from force records due to twelve pedestrians walking on an instrumented treadmill at ten speeds using a linear least square technique. The stability analysis was performed using the energy balance method and perturbation method. The results obtained from the model show a good agreement with the experimental results.

Evaluation of the shear force of single cancer cells by vertically aligned carbon nanotubes suitable for metastasis diagnosis.

PubMed

Abdolahad, M; Mohajerzadeh, S; Janmaleki, M; Taghinejad, H; Taghinejad, M

2013-03-01

Vertically aligned carbon nanotube (VACNT) arrays have been demonstrated as probes for rapid quantifying of cancer cell deformability with high resolution. Through entrapment of various cancer cells on CNT arrays, the deflections of the nanotubes during cell deformation were used to derive the lateral cell shear force using a large deflection mode method. It is observed that VACNT beams act as sensitive and flexible agents, which transfer the shear force of cells trapped on them by an observable deflection. The metastatic cancer cells have significant deformable structures leading to a further cell traction force (CTF) than primary cancerous one on CNT arrays. The elasticity of different cells could be compared by their CTF measurement on CNT arrays. This study presents a nanotube-based methodology for quantifying the single cell mechanical behavior, which could be useful for understanding the metastatic behavior of cells.

Force and light tuning vertical tunneling current in the atomic layered MoS2.

PubMed

Li, Feng; Lu, Zhixing; Lan, Yann-Wen; Jiao, Liying; Xu, Minxuan; Zhu, Xiaoyang; Zhang, Xiankun; Wu, Hualin; Qi, Junjie

2018-07-06

In this work, the vertical electrical transport behavior of bilayer MoS 2 under the coupling of force and light was explored by the use of conductive atomic force microscopy. We found that the current-voltage behavior across the tip-MoS 2 -Pt junction is a tunneling current that can be well fitted by a Simmons approximation. The transport behavior is direct tunneling at low bias and Fowler-Nordheim tunneling at high bias, and the transition voltage and tunnel barrier height are extracted. The effect of force and light on the effective band gap of the junction is investigated. Furthermore, the source-drain current drops surprisingly when we continually increase the force, and the dropping point is altered by the provided light. This mechanism is responsible for the tuning of tunneling barrier height and width by force and light. These results provide a new way to design devices that take advantage of ultrathin two-dimensional materials. Ultrashort channel length electronic components that possess tunneling current are important for establishing high-efficiency electronic and optoelectronic systems.

The Effect of Fatigue-Induced Changes in Eggbeater-Kick Kinematics on Performance and Risk of Injury.

PubMed

Oliveira, Nuno; Saunders, David H; Sanders, Ross H

2016-01-01

To investigate the effects of fatigue on the vertical force and kinematics of the lower limbs during maximal water polo eggbeater kicking. Twelve male water polo players maintained as high a position as possible while performing the eggbeater kick with the upper limbs raised out of the water until they were unable to keep the top of the sternum (manubrium) above water. Data comprising 27 complete eggbeater-kick cycles were extracted corresponding to 9 cycles of the initial nonfatigued (0%), 50% time point (50%), and final fatigued (100%) periods of the trial. Vertical force, foot speed, and hip-, knee-, and ankle-joint angles were calculated. Mean vertical force (0%, 212.2 N; 50%, 184.5 N; 100%, 164.3 N) progressively decreased with time. Speed of the feet (0.4 m/s), hip abduction (2.9°), and flexion (3.6°) decreased with fatigue, while hip internal rotation (3.6°) and ankle inversion (4°) increased with fatigue. Average angular velocity decreased for all joint motions. Eggbeater-kick performance decreases with fatigue. Inability to maintain foot speeds and hip and ankle actions with progressing fatigue diminishes the ability of the player to produce vertical force during the cycle. Increased internal rotation of the hip when fatigued and the large eversion/abduction of the ankle during the cycle may be predisposing factors for the prevalence of patellofemoral pain syndrome observed among eggbeater-kick performers. Appropriate training interventions that can limit the effects of fatigue on performance and injury risk should be considered.

The evolution of vertical climbing in primates: evidence from reaction forces.

PubMed

Hanna, Jandy B; Granatosky, Michael C; Rana, Pooja; Schmitt, Daniel

2017-09-01

Vertical climbing is an essential behavior for arboreal animals, yet limb mechanics during climbing are poorly understood and rarely compared with those observed during horizontal walking. Primates commonly engage in both arboreal walking and vertical climbing, and this makes them an ideal taxa in which to compare these locomotor forms. Additionally, primates exhibit unusual limb mechanics compared with most other quadrupeds, with weight distribution biased towards the hindlimbs, a pattern that is argued to have evolved in response to the challenges of arboreal walking. Here we test an alternative hypothesis that functional differentiation between the limbs evolved initially as a response to climbing. Eight primate species were recorded locomoting on instrumented vertical and horizontal simulated arboreal runways. Forces along the axis of, and normal to, the support were recorded. During walking, all primates displayed forelimbs that were net braking, and hindlimbs that were net propulsive. In contrast, both limbs served a propulsive role during climbing. In all species, except the lorisids, the hindlimbs produced greater propulsive forces than the forelimbs during climbing. During climbing, the hindlimbs tends to support compressive loads, while the forelimb forces tend to be primarily tensile. This functional disparity appears to be body-size dependent. The tensile loading of the forelimbs versus the compressive loading of the hindlimbs observed during climbing may have important evolutionary implications for primates, and it may be the case that hindlimb-biased weight support exhibited during quadrupedal walking in primates may be derived from their basal condition of climbing thin branches. © 2017. Published by The Company of Biologists Ltd.

Comparison of immediate complete denture, tooth and implant-supported overdenture on vertical dimension and muscle activity

PubMed Central

Shah, Farhan Khalid; Gebreel, Ashraf; Elshokouki, Ali hamed; Habib, Ahmed Ali

2012-01-01

PURPOSE To compare the changes in the occlusal vertical dimension, activity of masseter muscles and biting force after insertion of immediate denture constructed with conventional, tooth-supported and Implant-supported immediate mandibular complete denture. MATERIALS AND METHODS Patients were selected and treatment was carried out with all the three different concepts i.e, immediate denture constructed with conventional (Group A), tooth-supported (Group B) and Implant-supported (Group C) immediate mandibular complete dentures. Parameters of evaluation and comparison were occlusal vertical dimension measured by radiograph (at three different time intervals), Masseter muscle electromyographic (EMG) measurement by EMG analysis (at three different positions of jaws) and bite force measured by force transducer (at two different time intervals). The obtained data were statistically analyzed by using ANOVA-F test at 5% level of significance. If the F test was significant, Least Significant Difference test was performed to test further significant differences between variables. RESULTS Comparison between mean differences in occlusal vertical dimension for tested groups showed that it was only statistically significant at 1 year after immediate dentures insertion. Comparison between mean differences in wavelet packet coefficients of the electromyographic signals of masseter muscles for tested groups was not significant at rest position, but significant at initial contact position and maximum voluntary clench position. Comparison between mean differences in maximum biting force for tested groups was not statistically significant at 5% level of significance. CONCLUSION Immediate complete overdentures whether tooth or implant supported prosthesis is recommended than totally mucosal supported prosthesis. PMID:22737309

Kinematic and kinetic comparison of running in standard and minimalist shoes.

PubMed

Willy, Richard W; Davis, Irene S

2014-02-01

The purpose of this study was to determine whether running in a minimalist shoe results in a reduction in ground reaction forces and alters kinematics over standard shoe running. The secondary purpose of this study was to determine whether within-session accommodation to a novel minimalist shoe occurs. Subjects were 14 male, rearfoot striking runners who had never run in a minimalist shoe. Subjects were tested while running 3.35 m·s(-1) for 10 min on an instrumented treadmill in a minimalist and a standard shoe as three-dimensional lower extremity kinematics and kinetics were evaluated. Data were collected at minute 1 and then again after 10 min of running in both shoe conditions to evaluate accommodation to the shoe conditions. Shoe-time interactions were not found for any of the variables of interest. Minimalist shoe running resulted in no changes in step length (P = 0.967) or in step rate (P = 0.230). At footstrike, greater knee flexion (P = 0.001) and greater dorsiflexion angle (P = 0.025) were noted in the minimalist shoe. Vertical impact peak (P = 0.017) and average vertical loading rate (P < 0.000) were greater during minimalist shoe running. There were main effects of time as dorsiflexion angle decreased (P = 0.035), foot inclination at footstrike decreased (P = 0.048), and knee flexion at footstrike increased (P = 0.002), yet the vertical impact peak (P = 0.002) and average vertical loading rate (P < 0.000) increased. Running in a minimalist shoe appears to, at least in the short term, increase loading of the lower extremity over standard shoe running. The accommodation period resulted in less favorable landing mechanics in both shoes. These findings bring into question whether minimal shoes will provide enough feedback to induce an alteration that is similar to barefoot running.

On Heels and Toes: How Ants Climb with Adhesive Pads and Tarsal Friction Hair Arrays

PubMed Central

Endlein, Thomas; Federle, Walter

2015-01-01

Ants are able to climb effortlessly on vertical and inverted smooth surfaces. When climbing, their feet touch the substrate not only with their pretarsal adhesive pads but also with dense arrays of fine hairs on the ventral side of the 3rd and 4th tarsal segments. To understand what role these different attachment structures play during locomotion, we analysed leg kinematics and recorded single-leg ground reaction forces in Weaver ants (Oecophylla smaragdina) climbing vertically on a smooth glass substrate. We found that the ants engaged different attachment structures depending on whether their feet were above or below their Centre of Mass (CoM). Legs above the CoM pulled and engaged the arolia (‘toes’), whereas legs below the CoM pushed with the 3rd and 4th tarsomeres (‘heels’) in surface contact. Legs above the CoM carried a significantly larger proportion of the body weight than legs below the CoM. Force measurements on individual ant tarsi showed that friction increased with normal load as a result of the bending and increasing side contact of the tarsal hairs. On a rough sandpaper substrate, the tarsal hairs generated higher friction forces in the pushing than in the pulling direction, whereas the reverse effect was found on the smooth substrate. When the tarsal hairs were pushed, buckling was observed for forces exceeding the shear forces found in climbing ants. Adhesion forces were small but not negligible, and higher on the smooth substrate. Our results indicate that the dense tarsal hair arrays produce friction forces when pressed against the substrate, and help the ants to push outwards during horizontal and vertical walking. PMID:26559941

On Heels and Toes: How Ants Climb with Adhesive Pads and Tarsal Friction Hair Arrays.

PubMed

Endlein, Thomas; Federle, Walter

2015-01-01

Ants are able to climb effortlessly on vertical and inverted smooth surfaces. When climbing, their feet touch the substrate not only with their pretarsal adhesive pads but also with dense arrays of fine hairs on the ventral side of the 3rd and 4th tarsal segments. To understand what role these different attachment structures play during locomotion, we analysed leg kinematics and recorded single-leg ground reaction forces in Weaver ants (Oecophylla smaragdina) climbing vertically on a smooth glass substrate. We found that the ants engaged different attachment structures depending on whether their feet were above or below their Centre of Mass (CoM). Legs above the CoM pulled and engaged the arolia ('toes'), whereas legs below the CoM pushed with the 3rd and 4th tarsomeres ('heels') in surface contact. Legs above the CoM carried a significantly larger proportion of the body weight than legs below the CoM. Force measurements on individual ant tarsi showed that friction increased with normal load as a result of the bending and increasing side contact of the tarsal hairs. On a rough sandpaper substrate, the tarsal hairs generated higher friction forces in the pushing than in the pulling direction, whereas the reverse effect was found on the smooth substrate. When the tarsal hairs were pushed, buckling was observed for forces exceeding the shear forces found in climbing ants. Adhesion forces were small but not negligible, and higher on the smooth substrate. Our results indicate that the dense tarsal hair arrays produce friction forces when pressed against the substrate, and help the ants to push outwards during horizontal and vertical walking.

Accuracy of a vertical jump contact mat for determining jump height and flight time.

PubMed

Whitmer, Tyler D; Fry, Andrew C; Forsythe, Charles M; Andre, Matthew J; Lane, Michael T; Hudy, Andrea; Honnold, Darric E

2015-04-01

Several devices are available to measure vertical jump (VJ) height based on flight time, VJ reach height, or ground reaction forces. The purpose of this study was to determine the accuracy of a VJ mat for measuring flight time and VJ height compared with a VJ tester or a force plate. Seventeen men and 18 women (X ± SD; age = 20.9 ± 0.7 years, height = 176.1 ± 0.9 cm, weight = 72.6 ± 13.5 kg) served as subjects. Subjects performed counter-movement vertical jumps while standing on both a force plate (1,000 Hz) and a VJ mat. A Vertec VJ tester was used to measure jump reach. Compared with the force plate, the VJ mat reported greater VJ height (VJ mat = 0.50 ± 0.12 m, force plate = 0.34 ± 0.10 m) and flight time (VJ mat = 0.629 ± 0.078 seconds, force plate = 0.524 ± 0.077 seconds). Comparison of VJ heights from the VJ mat and the Vertec revealed no significant differences (Vertec = 0.48 ± 0.11 m). Regression analyses indicated strong relationships between testing methods and suggested that high VJ performances may be underestimated with the VJ mat. This particular VJ mat compared favorably with the Vertec but not the force plate. It seems that the different flight times derived from the VJ mat may permit the VJ mat to be in closer agreement with VJ heights from the Vertec. Also, the VJ mat may not be an appropriate tool for assessing high VJ performances (i.e., ≥0.70 m; ≈28 inches). Practitioners and researchers using similar VJ mats may not obtain accurate flight times and may underestimate high performers.

Muscle Force-Velocity Relationships Observed in Four Different Functional Tests

PubMed Central

Zivkovic, Milena Z.; Djuric, Sasa; Cuk, Ivan; Suzovic, Dejan; Jaric, Slobodan

2017-01-01

Abstract The aims of the present study were to investigate the shape and strength of the force-velocity relationships observed in different functional movement tests and explore the parameters depicting force, velocity and power producing capacities of the tested muscles. Twelve subjects were tested on maximum performance in vertical jumps, cycling, bench press throws, and bench pulls performed against different loads. Thereafter, both the averaged and maximum force and velocity variables recorded from individual trials were used for force–velocity relationship modeling. The observed individual force-velocity relationships were exceptionally strong (median correlation coefficients ranged from r = 0.930 to r = 0.995) and approximately linear independently of the test and variable type. Most of the relationship parameters observed from the averaged and maximum force and velocity variable types were strongly related in all tests (r = 0.789-0.991), except for those in vertical jumps (r = 0.485-0.930). However, the generalizability of the force-velocity relationship parameters depicting maximum force, velocity and power of the tested muscles across different tests was inconsistent and on average moderate. We concluded that the linear force-velocity relationship model based on either maximum or averaged force-velocity data could provide the outcomes depicting force, velocity and power generating capacity of the tested muscles, although such outcomes can only be partially generalized across different muscles. PMID:28469742

Effect of the vertical position of the canine on the frictional/orthodontic force ratio of Ni-Ti archwires during the levelling phase of orthodontic treatment.

PubMed

Kato, Moeko; Namura, Yasuhiro; Yoneyama, Takayuki; Shimizu, Noriyoshi

2018-05-31

This study investigated the effect of the vertical position of the canine on changes in the frictional/orthodontic (F/O) force ratio of nickel-titanium (Ni-Ti) archwires during the initial levelling phase of orthodontic treatment. Frictional and orthodontic forces were measured by using low-friction brackets and Ni-Ti archwires with three different cross-sectional sizes and force types. To simulate canine malocclusion (first premolar extraction case), the upper right canine was displaced gingivally by 1 to 3 mm and the inter-bracket distance between the upper right lateral incisor and second premolar was set at 15 mm or 20 mm. A three-point bending test was performed to measure the orthodontic force of each Ni-Ti archwire. Frictional forces were measured with a universal testing machine and dental arch models by pulling parallel to the end of the archwire at a crosshead speed of 0.5 mm/min. F/O force ratio was calculated and analysed statistically. At a displacement of 3 mm, few archwires had F/O force ratios of less than 1.0, at which orthodontic force overcame frictional force, thus ensuring extrusion of the canine. For effective tooth movement, orthodontists should use Ni-Ti archwires with an F/O force ratio of less than 1.0.

Vertical dependence of black carbon, sulphate and biomass burning aerosol radiative forcing

NASA Astrophysics Data System (ADS)

Samset, Bjørn H.; Myhre, Gunnar

2011-12-01

A global radiative transfer model is used to calculate the vertical profile of shortwave radiative forcing from a prescribed amount of aerosols. We study black carbon (BC), sulphate (SO4) and a black and organic carbon mixture typical of biomass burning (BIO), by prescribing aerosol burdens in layers between 1000 hPa and 20 hPa and calculating the resulting direct radiative forcing divided by the burden (NDRF). We find a strong sensitivity in the NDRF for BC with altitude, with a tenfold increase between BC close to the surface and the lower part of the stratosphere. Clouds are a major contributor to this dependence with altitude, but other factors also contribute. We break down and explain the different physical contributors to this strong sensitivity. The results show a modest regional dependence of the altitudinal dependence of BC NDRF between industrial regions, while for regions with properties deviating from the global mean NDRF variability is significant. Variations due to seasons and interannual changes in cloud conditions are found to be small. We explore the effect that large altitudinal variation in NDRF may have on model estimates of BC radiative forcing when vertical aerosol distributions are insufficiently constrained, and discuss possible applications of the present results for reducing inter-model differences.

Turbulent structure of stably stratified inhomogeneous flow

NASA Astrophysics Data System (ADS)

Iida, Oaki

2018-04-01

Effects of buoyancy force stabilizing disturbances are investigated on the inhomogeneous flow where disturbances are dispersed from the turbulent to non-turbulent field in the direction perpendicular to the gravity force. Attaching the fringe region, where disturbances are excited by the artificial body force, a Fourier spectral method is used for the inhomogeneous flow stirred at one side of the cuboid computational box. As a result, it is found that the turbulent kinetic energy is dispersed as layered structures elongated in the streamwise direction through the vibrating motion. A close look at the layered structures shows that they are flanked by colder fluids at the top and hotter fluids at the bottom, and hence vertically compressed and horizontally expanded by the buoyancy related to the countergradient heat flux, though they are punctuated by the vertical expansion of fluids at the forefront of the layered structures, which is related to the downgradient heat flux, indicating that the layered structures are gravity currents. However, the phase between temperature fluctuations and vertical velocity is shifted by π/2 rad, indicating that temperature fluctuations are generated by the propagation of internal gravity waves.

Optical levitation and translation of a microscopic particle by use of multiple beams generated by vertical-cavity surface-emitting laser array sources.

PubMed

Ogura, Yusuke; Shirai, Nobuhiro; Tanida, Jun

2002-09-20

An optical levitation and translation method for a microscopic particle by use of the resultant force induced by multiple light beams is studied. We show dependence of the radiation pressure force on the illuminating distribution by numerical calculation, and we find that the strongest axial force is obtained by a specific spacing period of illuminating beams. Extending the optical manipulation technique by means of vertical-cavity surface-emitting laser (VCSEL) array sources [Appl. Opt. 40, 5430 (2001)], we are the first, to our knowledge, to demonstrate levitation of a particle and its translation while levitated by using a VCSEL array. The vertical position of the target particle can be controlled in a range of a few tens of micrometers with an accuracy of 2 microm or less. The analytical and experimental results suggest that use of multiple beams is an effective method to levitate a particle with low total illumination power. Some issues on the manipulation method that uses multiple beams are discussed.

Plasma Component of Self-gravitating Disks and Relevant Magnetic Configurations

NASA Astrophysics Data System (ADS)

Bertin, G.; Coppi, B.

2006-04-01

Astrophysical disks in which the disk self-gravity is more important than the gravity force associated with the central object can have significant plasma components where appreciable toroidal current densities are produced. When the vertical confinement of the plasma rotating structures that can form is kept by the Lorentz force rather than by the vertical component of the gravity force, the disk self-gravity remains important only in the radial equilibrium condition, modifying the rotation curve from the commonly considered Keplerian rotation. The equilibrium equations that are solved involve the vertical and the horizontal components of the total momentum conservation equations, coupled with the lowest order form of the gravitational Poisson's equation. The resulting poloidal field configuration can be visualized as a sequence [1] of Field Reverse Configurations, in the radial direction, consisting of pairs of oppositely directed current channels. The plasma density thus acquires a significant radial modulation that may grow to the point where plasma rings can form [2]. [1] B. Coppi, Phys. Plasmas, 12, 057302 (2005) [2] B. Coppi and F. Rousseau, to be published in Astrophys. J. (April 2006)

Performance Enhancement of a Vertical Tail Model with Sweeping Jet Actuators

NASA Technical Reports Server (NTRS)

Seele, Roman; Graff, Emilio; Lin, John; Wygnanski, Israel

2013-01-01

Active Flow Control (AFC) experiments performed at the Caltech Lucas Adaptive Wall Wind Tunnel on a 12%-thick, generic vertical tail model indicated that sweeping jets emanating from the trailing edge (TE) of the vertical stabilizer significantly increased the side force coefficient for a wide range of rudder deflection angles and yaw angles at free-stream velocities approaching takeoff rotation speed. The results indicated that 2% blowing momentum coefficient (C(sub mu) increased the side force in excess of 50% at the maximum conventional rudder deflection angle in the absence of yaw. Even C(sub mu) = 0.5% increased the side force in excess of 20% under these conditions. This effort was sponsored by the NASA Environmentally Responsible Aviation (ERA) project and the successful demonstration of this flow-control application could have far reaching implications. It could lead to effective applications of AFC technologies on key aircraft control surfaces and lift enhancing devices (flaps) that would aid in reduction of fuel consumption through a decrease in size and weight of wings and control surfaces or a reduction of the noise footprint due to steeper climb and descent.

Experimental study of vertical stress profiles of a confined granular bed under static and dynamic conditions.

PubMed

Mandato, S; Cuq, B; Ruiz, T

2012-07-01

In a wet agglomeration process inside a low shear mixer, the blade function is to induce i) homogenization of the liquid sprayed on the powder surface and ii) a stress field able to transfer the mechanical energy at the particle scale. In this work we study the mechanical state of a confined powder bed through the analysis of stress distributions (by force measurements) in a rectangular cell in two cases: for a classical model powder (i.e. glass beads) and a complex powder (i.e. wheat semolina). Two types of vertical stress profiles are obtained according to the type of measurements carried out in the powder bed, either locally (at different positions in the cell) or globally (at the entire base). The global vertical stress profile follows Janssen's model and the local vertical stress profile highlights a critical length, identified as the percolation threshold of the force network, and a shielding length near the bottom, which is similar to an influence length of the side walls. In the context of wet agglomeration, the results allow to consider the role of the characteristic lengths in the mixing bowl under vertical mechanical solicitation.

Measures of functional performance and their association with hip and thigh strength.

PubMed

Kollock, Roger; Van Lunen, Bonnie L; Ringleb, Stacie I; Oñate, James A

2015-01-01

Insufficient hip and thigh strength may increase an athlete's susceptibility to injury. However, screening for strength deficits using isometric and isokinetic instrumentation may not be practical in all clinical scenarios. To determine if functional performance tests are valid indicators of hip and thigh strength. Descriptive laboratory study. Research laboratory. Sixty-two recreationally athletic men (n = 30, age = 21.07 years, height = 173.84 cm, mass = 81.47 kg) and women (n = 32, age = 21.03 years, height = 168.77 cm, mass = 68.22 kg) participants were recruited. During session 1, we measured isometric peak force and rate of force development for 8 lower extremity muscle groups, followed by an isometric endurance test. During session 2, participants performed functional performance tests. Peak force, rate of force development, fatigue index, hop distance (or height), work (joules), and number of hops performed during the 30-second lateral-hop test were assessed. The r values were squared to calculate r (2). We used Pearson correlations to evaluate the associations between functional performance and strength. In men, the strongest relationship was observed between triple-hop work and hip-adductor peak force (r(2) = 50, P ≤ .001). Triple-hop work also was related to hip-adductor (r(2) = 38, P ≤ .01) and hip-flexor (r(2) = 37, P ≤ .01) rate of force development. For women, the strongest relationships were between single-legged vertical-jump work and knee-flexor peak force (r(2) = 0.44, P ≤ .01) and single-legged vertical-jump height and knee-flexor peak force (r(2) = 0.42, P ≤ .01). Single-legged vertical-jump height also was related to knee-flexor rate of force development (r(2) = 0.49, P ≤ .001). The 30-second lateral-hop test did not account for a significant portion of the variance in strength endurance. Hop tests alone did not provide clinicians with enough information to make evidence-based decisions about lower extremity strength in isolated muscle groups.

Comparison of the Hang High-Pull and Loaded Jump Squat for the Development of Vertical Jump and Isometric Force-Time Characteristics.

PubMed

Oranchuk, Dustin J; Robinson, Tracey L; Switaj, Zachary J; Drinkwater, Eric J

2017-04-15

Weightlifting movements have high skill demands and require expert coaching. Loaded jumps have a comparably lower skill demand, but may be similarly effective for improving explosive performance. The purpose of this study was to compare vertical jump performance, isometric force, and rate of force development (RFD) following a ten-week intervention employing the hang high-pull (hang-pull) or trap-bar jump squat (jump-squat). Eighteen NCAA Division II swimmers (8 males, 10 females) with at least one year of resistance training experience volunteered to participate. Testing included the squat jump (SJ), countermovement jump (CMJ) and the isometric mid-thigh pull (IMTP). Vertical ground reaction forces were analyzed to obtain jump height and relative peak power. Relative peak force, peak RFD and relative force at five time bands were obtained from the IMTP. Subjects were randomly assigned to either a hang-pull (n = 9) or jump-squat (n = 9) training group and completed a ten-week, volume-equated, periodized training program. While there was a significant main effect of training for both groups, no statistically significant between-group differences were found (p ≥ 0.17) for any of the dependent variables. However, medium effect sizes in favor of the jump-squat training group were seen in SJ height (d = 0.56) and SJ peak power (d = 0.69). Loaded jumps seem equally effective as weightlifting derivatives for improving lower-body power in experienced athletes. Since loaded jumps require less skill and less coaching expertise than weightlifting, loaded jumps should be considered where coaching complex movements is difficult.

Occlusal force, electromyographic activity of masticatory muscles and mandibular flexure of subjects with different facial types

PubMed Central

CUSTODIO, William; GOMES, Simone Guimarães Farias; FAOT, Fernanda; GARCIA, Renata Cunha Matheus Rodrigues; DEL BEL CURY, Altair Antoninha

2011-01-01

Objective The aim of this study was to evaluate whether vertical facial patterns influence maximal occlusal force (MOF), masticatory muscle electromyographic (EMG) activity, and medial mandibular flexure (MMF). Material and Methods Seventy-eight dentate subjects were divided into 3 groups by Ricketts's analysis: brachyfacial, mesofacial and dolychofacial. Maximum occlusal force in the molar region was bilaterally measured with a force transducer. The electromyographic activities of the masseter and anterior temporal muscles were recorded during maximal voluntary clenching. Medial mandibular flexure was calculated by subtracting the intermolar distance of maximum opening or protrusion from the distance in the rest position. The data were analyzed using ANOVA followed by Tukey's HSD test. The significance level was set at 5%. Results Data on maximum occlusal force showed that shorter faces had higher occlusal forces (P<0.0001). Brachyfacial subjects presented higher levels of masseter electromyographic activity and medial mandibular flexure, followed by the mesofacial and dolychofacial groups. Additionally, dolychofacial subjects showed significantly lower electromyographic temporalis activities (P<0.05). Conclusion Within the limitations of the study, it may be concluded that maximum occlusal force, masticatory muscle activity and medial mandibular flexure were influenced by the vertical facial pattern. PMID:21655772

Knee extensor dynamics in the volleyball approach jump: the influence of patellar tendinopathy.

PubMed

Sorenson, Shawn C; Arya, Shruti; Souza, Richard B; Pollard, Christine D; Salem, George J; Kulig, Kornelia

2010-09-01

Controlled laboratory study using a cross-sectional design. To evaluate knee joint dynamics in elite volleyball players with and without a history of patellar tendinopathy, focusing on mechanical energy absorption and generation. We hypothesized that tendinopathy would be associated withreduced net joint work and net joint power. Patellar tendinopathy is a common, debilitating injury affecting competitive volleyball players. Thirteen elite male players with and without a history of patellar tendinopathy (mean ± SD age, 27 ± 7 years) performed maximum-effort volleyball approach jumps. Sagittal plane knee joint kinematics, kinetics, and energetics were quantified in the lead limb, using data obtained from a force platform and an 8-camera motion analysis system. Vertical ground reaction forces and pelvis vertical velocity at takeoff were examined. Independent sample t tests were used to evaluate group differences (α = .05). The tendinopathy group, compared to controls, demonstrated significant reductions (approximately 30%) in net joint work and net joint power during the eccentric phase of the jump, with no differences in the concentric phase. Positive to-negative net joint work and net joint power ratios were significantly higher in the tendinopathy group, which had a net joint work ratio of 1.00 (95% CI: 0.77, 1.24) versus 0.76 (95% CI: 0.64, 0.88) for controls, and a net joint power ratio of 1.62 (95% CI: 1.15, 2.10) versus 1.00 (95% CI: 0.80, 1.21) for controls. There were no significant differences in net joint moment, angular velocity, or range of motion. Peak vertical ground reaction forces were lower for the tendinopathy group, while average vertical ground reaction forces and pelvis vertical velocity were similar. Patellar tendinopathy is associated with differences in sagittal plane mechanical energy absorption at the knee during maximum-effort volleyball approach jumps. Net joint work and net joint power may help define underlying mechanisms, adaptive effects, or rehabilitative strategies for individuals with patellar tendinopathy.

How much vertical displacement of the symphysis indicates instability after pelvic injury?

PubMed

Golden, Robert D; Kim, Hyunchul; Watson, Jeffrey D; Oliphant, Bryant W; Doro, Christopher; Hsieh, Adam H; Osgood, Greg M; O'Toole, Robert V

2013-02-01

Measures of pubic symphyseal widening are used by at least two classification systems as determinants of injury grade. Recent work has challenged the commonly used parameter of 2.5 cm of pubic symphysis as an accurate marker of pelvic injury grade and has suggested a role of rotation in the flexion-extension plane as a determinant of pelvic stability. We investigated pelvic stability in the flexion-extension plane to determine a threshold of rotational displacement of the hemipelvis above which the potential for instability exists. Cadaveric specimens were mounted onto a servohydraulic biaxial testing machine and subjected to a vertically directed flexion moment. Position of hemipelvis was recorded using a three-dimensional motion capture system and video recording. Displacement of the pubic symphysis and changes in length and position of the sacrospinous and sacrotuberous ligaments were recorded. Amount of force applied was measured and recorded. A yield point was determined as the first point at which the force plot exhibited a decrease in force and was correlated to the corresponding displacement. The mean vertical displacement of the pubic symphysis at the yield point was 16 mm (95% confidence interval, 11-22 mm). Mean sacrospinous ligament strain at yield point was 4% (range, 1.0-9.5%). Pelves with vertical rotational symphyseal displacement of less than 11 mm can reasonably be expected to have rotational stability in the flexion-extension plane. Those with displacement of greater than 22 mm can be expected to have lost some integrity regarding resistance to pelvic flexion. These values may allow clinicians to infer pelvic stability from amount of vertical symphyseal displacement.

Terminal Velocity of a Shuttlecock in Vertical Fall.

ERIC Educational Resources Information Center

Peastrel, Mark; And Others

1980-01-01

Describes a straightforward vertical fall experiment using a badminton shuttlecock, a tape measure, and a millisecond timer. The effects of air resistance are important and directly measurable. The experimental data best fit a predictive model which assumes a resistive force quadratic in the instantaneous speed of the falling object. (GS)

49 CFR 179.14 - Coupler vertical restraint system.

Code of Federal Regulations, 2011 CFR

2011-10-01

... system shall be tested under the following conditions: (1) The test coupler shall be tested with a mating coupler (or simulated coupler) having only frictional vertical force resistance at the mating interface; or a mating coupler (or simulated coupler) having the capabilities described in paragraph (a) of this...

Increase in Jumping Height Associated with Maximal Effort Vertical Depth Jumps.

ERIC Educational Resources Information Center

Bedi, John F.; And Others

1987-01-01

In order to assess if there existed a statistically significant increase in jumping performance when dropping from different heights, 32 males, aged 19 to 26, performed a series of maximal effort vertical jumps after dropping from eight heights onto a force plate. Results are analyzed. (Author/MT)

Vertical Integration of Geographic Information Sciences: A Recruitment Model for GIS Education

ERIC Educational Resources Information Center

Yu, Jaehyung; Huynh, Niem Tu; McGehee, Thomas Lee

2011-01-01

An innovative vertical integration model for recruiting to GIS education was introduced and tested following four driving forces: curriculum development, GIS presentations, institutional collaboration, and faculty training. Curriculum development was a useful approach to recruitment, student credit hour generation, and retention-rate improvement.…

An analytic model of the in-line and cross-axis apparent mass of the seated human body exposed to vertical vibration with and without a backrest

NASA Astrophysics Data System (ADS)

Zheng, Guangtai; Qiu, Yi; Griffin, Michael J.

2011-12-01

During vertical excitation of the seated human body there are vertical and fore-and-aft forces at the seat that are influenced by contact with a backrest, so it is desirable to take into account the effect of a backrest when developing models of the seated human body. Initially, a seven degree-of-freedom multi-body dynamic model was developed for the human body sitting with an upright posture unsupported by a backrest and exposed to vertical vibration. The model was optimized to fit the vertical apparent mass and the fore-and-aft cross-axis apparent mass measured on a seat. The model was then extended by the addition of vertical and fore-and-aft reaction forces to the upper lumbar spine to model the interaction between the human body and a backrest. By minimizing the least square error between experimental data and the analytical solution of the apparent masses on the seat and at the back, the human body model was able to represent both the vertical apparent mass and the fore-and-aft cross-axis apparent mass on the seat and at the back. Parameter sensitivity studies showed that the vertical apparent mass and the fore-and-aft cross-axis apparent mass on the seat and the backrest were all highly sensitive to the axial stiffness of the tissue beneath the pelvis. Pitch motion of the upper-body contributed to the vertical apparent mass and the fore-and-aft cross-axis apparent mass on the seat. The apparent mass at the back was more sensitive to the stiffness and damping of the lower back than the properties of the upper back.

A Sensor Fusion Method for Tracking Vertical Velocity and Height Based on Inertial and Barometric Altimeter Measurements

PubMed Central

Sabatini, Angelo Maria; Genovese, Vincenzo

2014-01-01

A sensor fusion method was developed for vertical channel stabilization by fusing inertial measurements from an Inertial Measurement Unit (IMU) and pressure altitude measurements from a barometric altimeter integrated in the same device (baro-IMU). An Extended Kalman Filter (EKF) estimated the quaternion from the sensor frame to the navigation frame; the sensed specific force was rotated into the navigation frame and compensated for gravity, yielding the vertical linear acceleration; finally, a complementary filter driven by the vertical linear acceleration and the measured pressure altitude produced estimates of height and vertical velocity. A method was also developed to condition the measured pressure altitude using a whitening filter, which helped to remove the short-term correlation due to environment-dependent pressure changes from raw pressure altitude. The sensor fusion method was implemented to work on-line using data from a wireless baro-IMU and tested for the capability of tracking low-frequency small-amplitude vertical human-like motions that can be critical for stand-alone inertial sensor measurements. Validation tests were performed in different experimental conditions, namely no motion, free-fall motion, forced circular motion and squatting. Accurate on-line tracking of height and vertical velocity was achieved, giving confidence to the use of the sensor fusion method for tracking typical vertical human motions: velocity Root Mean Square Error (RMSE) was in the range 0.04–0.24 m/s; height RMSE was in the range 5–68 cm, with statistically significant performance gains when the whitening filter was used by the sensor fusion method to track relatively high-frequency vertical motions. PMID:25061835

Immediate effects of modified landing pattern on a probabilistic tibial stress fracture model in runners.

PubMed

Chen, T L; An, W W; Chan, Z Y S; Au, I P H; Zhang, Z H; Cheung, R T H

2016-03-01

Tibial stress fracture is a common injury in runners. This condition has been associated with increased impact loading. Since vertical loading rates are related to the landing pattern, many heelstrike runners attempt to modify their footfalls for a lower risk of tibial stress fracture. Such effect of modified landing pattern remains unknown. This study examined the immediate effects of landing pattern modification on the probability of tibial stress fracture. Fourteen experienced heelstrike runners ran on an instrumented treadmill and they were given augmented feedback for landing pattern switch. We measured their running kinematics and kinetics during different landing patterns. Ankle joint contact force and peak tibial strains were estimated using computational models. We used an established mathematical model to determine the effect of landing pattern on stress fracture probability. Heelstrike runners experienced greater impact loading immediately after landing pattern switch (P<0.004). There was an increase in the longitudinal ankle joint contact force when they landed with forefoot (P=0.003). However, there was no significant difference in both peak tibial strains and the risk of tibial stress fracture in runners with different landing patterns (P>0.986). Immediate transitioning of the landing pattern in heelstrike runners may not offer timely protection against tibial stress fracture, despite a reduction of impact loading. Long-term effects of landing pattern switch remains unknown. Copyright © 2016 Elsevier Ltd. All rights reserved.

Distinguishing Nanobubbles from Nanodroplets with AFM: The Influence of Vertical and Lateral Imaging Forces.

PubMed

An, Hongjie; Tan, Beng Hau; Ohl, Claus-Dieter

2016-12-06

The widespread application of surface-attached nanobubbles and nanodroplets in biomedical engineering and nanotechnology is limited by numerous experimental challenges, in particular, the possibility of contamination in nucleation experiments. These challenges are complicated by recent reports that it can be difficult to distinguish between nanoscale drops and bubbles. Here we identify clear differences in the mechanical responses of nanobubbles and nanodroplets under various modes of AFM imaging that subject the objects to predominantly vertical or lateral forces. This allows us to distinguish among nanodroplets, nanobubbles, and oil-covered nanobubbles in water.

Letter: Symmetric instability drastically changes upon inclusion of the full Coriolis force

NASA Astrophysics Data System (ADS)

Zeitlin, V.

2018-06-01

It is shown that the classical symmetric instability drastically changes, if the usually neglected vertical component of the Coriolis force and the contribution of the vertical velocity into its horizontal components are taken into account. The influence of these "non-traditional" terms is different for flows with positive and negative horizontal relative vorticities. A critical value of the Richardson number appears in the second case, with the instability changing its character across it. Major differences appear between hydrostatic and non-hydrostatic versions of the instability. All these features are absent in the traditional approximation.

Influence of stretch-shortening cycle on mechanical behaviour of triceps surae during hopping.

PubMed

Belli, A; Bosco, C

1992-04-01

Six subjects performed a first series of vertical plantar flexions and a second series of vertical rebounds, both involving muscle triceps surae exclusively. Vertical displacements, vertical forces and ankle angles were recorded during the entire work period of 60 seconds per series. In addition, expired gases were collected during the test and recovery for determination of the energy expenditure. Triceps surae was mechanically modelled with a contractile component and with an elastic component. Mechanical behaviour and work of the different muscle components were determined in both series. The net muscular efficiency calculated from the work performed by the centre of gravity was 17.5 +/- 3.0% (mean +/- SD) in plantar flexions and 29.9 +/- 4.8% in vertical rebounds. The net muscle efficiency calculated from the work performed by the contractile component was 17.4 +/- 2.9% in plantar flexions and 16.1 +/- 1.4% in vertical rebounds. These results suggest that the muscular efficiency differences do not reflect muscle contractile component efficiency but essentially the storage and recoil of elastic energy. This is supported by the relationship (P less than 0.01) found in vertical rebounds between the extra work and the elastic component work. A detailed observation of the mechanical behaviour of muscle mechanical components showed that the strategy to maximize the elastic work depends also on the force-velocity characteristics of the movement and that the eccentric-concentric work of the contractile component does not always correspond respectively to the ankle extension-flexion.

Modeling dynamic behavior of superconducting maglev systems under external disturbances

NASA Astrophysics Data System (ADS)

Huang, Chen-Guang; Xue, Cun; Yong, Hua-Dong; Zhou, You-He

2017-08-01

For a maglev system, vertical and lateral displacements of the levitation body may simultaneously occur under external disturbances, which often results in changes in the levitation and guidance forces and even causes some serious malfunctions. To fully understand the effect of external disturbances on the levitation performance, in this work, we build a two-dimensional numerical model on the basis of Newton's second law of motion and a mathematical formulation derived from magnetoquasistatic Maxwell's equations together with a nonlinear constitutive relation between the electric field and the current density. By using this model, we present an analysis of dynamic behavior for two typical maglev systems consisting of an infinitely long superconductor and a guideway of different arrangements of infinitely long parallel permanent magnets. The results show that during the vertical movement, the levitation force is closely associated with the flux motion and the moving velocity of the superconductor. After being disturbed at the working position, the superconductor has a disturbance-induced initial velocity and then starts to periodically vibrate in both lateral and vertical directions. Meanwhile, the lateral and vertical vibration centers gradually drift along their vibration directions. The larger the initial velocity, the faster their vibration centers drift. However, the vertical drift of the vertical vibration center seems to be independent of the direction of the initial velocity. In addition, due to the lateral and vertical drifts, the equilibrium position of the superconductor in the maglev systems is not a space point but a continuous range.

Proportioning the airplane for lateral stability

NASA Technical Reports Server (NTRS)

Donlan, C. J.

1976-01-01

Proportioning for lateral aircraft control included: (1) directional stability (slope of curve of yawing moment coefficient against sideslip), and (2) effective dihedral factor (slope of curve of rolling moment coefficient against sideslip). Basic forces influencing the directional stability of aircraft are indicated. Propeller side force, basic fuselage yaw, and vertical tail side force contributed to yaw moment about center of gravity.

An Impulse-Momentum Method for Calculating Landing-Gear Contact Conditions in Eccentric Landings

NASA Technical Reports Server (NTRS)

Yntema, Robert T; Milwitzky, Benjamin

1952-01-01

An impulse-momentum method for determining impact conditions for landing gears in eccentric landings is presented. The analysis is primarily concerned with the determination of contact velocities for impacts subsequent to initial touchdown in eccentric landings and with the determination of the effective mass acting on each landing gear. These parameters determine the energy-absorption requirements for the landing gear and, in conjunction with the particular characteristics of the landing gear, govern the magnitude of the ground loads. Changes in airplane angular and linear velocities and the magnitude of landing-gear vertical, drag, and side impulses resulting from a landing impact are determined by means of impulse-momentum relationships without the necessity for considering detailed force-time variations. The effective mass acting on each gear is also determined from the calculated landing-gear impulses. General equations applicable to any type of eccentric landing are written and solutions are obtained for the particular cases of an impact on one gear, a simultaneous impact on any two gears, and a symmetrical impact. In addition a solution is presented for a simplified two-degree-of-freedom system which allows rapid qualitative evaluation of the effects of certain principal parameters. The general analysis permits evaluation of the importance of such initial conditions at ground contact as vertical, horizontal, and side drift velocities, wing lift, roll and pitch angles, and rolling and pitching velocities, as well as the effects of such factors as landing gear location, airplane inertia, landing-gear length, energy-absorption efficiency, and wheel angular inertia on the severity of landing impacts. -A brief supplementary study which permits a limited evaluation of variable aerodynamic effects neglected in the analysis is presented in the appendix. Application of the analysis indicates that landing-gear impacts in eccentric landings can be appreciably more severe than impacts in symmetrical landings with the same sinking speed. The results also indicate the effects of landing-gear location, airplane inertia, initial wing lift, side drift velocity, attitude, and initial rolling velocity on the severity of both initial and subsequent landing-gear impacts. A comparison of the severity of impacts on auxiliary gears for tricycle and quadricycle configurations is also presented.

Effects of Froude number and geometry on water entry of a 2-D ellipse

NASA Astrophysics Data System (ADS)

Zhang, Xu; Liu, Pei-qing; Qu, Qiu-lin; Wang, Rui; Agarwal, Ramesh K.

2018-05-01

By using the finite volume method with volume of fluid model and global dynamic mesh technique, the effects of Froude number and geometry on the water entry process of a 2-D ellipse are investigated numerically. For the time history of the vertical force, the computational fluid dynamics (CFD) results match the experimental data much better than the classical potential-flow theories due to the consideration of the viscosity, turbulence, surface tension, gravity, and compressibility. The results show that the position of peak pressure on ellipse shifts from the spray root to the bottom of ellipse at a critical time. The critical time changes with the geometry and Froude number. By studying the vertical force, the ellipse water entry process can be divided into the initial and late stages based on the critical dimensionless time of about 0.1. The geometry of the ellipse plays a dominant role in the initial stage, while the Froude number is more important in the late stage of entry. The classical Wagner theory is extended to the ellipse water entry, and the predicted maximum value of vertical force coefficient in the initial stage is 4πa/b that matches the CFD results very well, where a and b are the horizontal axis and vertical axis of the ellipse parallel and perpendicular to the initial calm water surface, respectively.

An Overview of Active Flow Control Enhanced Vertical Tail Technology Development

NASA Technical Reports Server (NTRS)

Lin, John C.; Andino, Marlyn Y.; Alexander, Michael G.; Whalen, Edward A.; Spoor, Marc A.; Tran, John T.; Wygnanski, Israel J.

2016-01-01

This paper summarizes a joint NASA/Boeing research effort to advance Active Flow Control (AFC) technology to enhance aerodynamic efficiency of a vertical tail. Sweeping jet AFC technology was successfully tested on subscale and full-scale models as well as in flight. The subscale test was performed at Caltech on a 14% scale model. More than 50% side force enhancement was achieved by the sweeping jet actuation when the momentum coefficient was 1.7%. AFC caused significant increases in suction pressure on the actuator side and associated side force enhancement. Subsequently, a full-scale Boeing 757 vertical tail model equipped with sweeping jets was tested at the National Full-Scale Aerodynamics Complex 40- by 80-Foot Wind Tunnel at NASA Ames Research Center. There, flow separation control optimization was performed at near flight conditions. Greater than 20% increase in side force were achieved for the maximum rudder deflection of 30deg at the key sideslip angles (0deg and -7.5deg) with a 31-actuator AFC configuration. Based on these tests, the momentum coefficient is shown to be a necessary, but not sufficient parameter to use for design and scaling of sweeping jet AFC from subscale tests to full-scale applications. Leveraging the knowledge gained from the wind tunnel tests, the AFC-enhanced vertical tail technology was successfully flown on the Boeing 757 ecoDemonstrator in the spring of 2015.

Convection Induced by Traveling Magnetic Fields in Semiconductor Melts

NASA Technical Reports Server (NTRS)

Konstantin, Mazuruk

2000-01-01

Axisymmetric traveling magnetic fields (TMF) can be beneficial for crystal growth applications. such as the vertical Bridgman, float zone or traveling heater methods. TMF induces a basic flow in the form of a single roll. This type of flow can enhance mass and heat transfer to the growing crystal. More importantly, the TMF Lorentz body force induced in the system can counterbalance the buoyancy forces, so the resulting convection can be much smaller and even the direction of it can be changed. In this presentation, we display basic features of this novel technique. In particular, numerical calculations of the Lorentz force for arbitrary frequencies will be presented along with induced steady-state fluid flow profiles. Also, numerical modeling of the TMF counter-balancing natural convection in vertical Bridgman systems will be demonstrated.

Rising dynamics of a bubble confined in vertical cells with rectangular cross-sections

NASA Astrophysics Data System (ADS)

Murano, Mayuko; Okumura, Ko

2017-11-01

Recently, the drag friction acting on a fluid drop in confined space has been actively studied. Here, we investigate the rising velocity of a bubble in a vertical cell with a rectangular cross-section, both theoretically and experimentally, in which understanding of the drag force acting on the rising bubble is crucial. Although the drag force in such confined space could involve several regimes, we study a special case in which the bubble is long and the aspect-ratio of the rectangular cross-section of the cell is high. As a result, we found new scaling law for the rising velocity and the drag force, and confirmed the laws experimentally. Crossover to the rising dynamics in a Hele-Shaw cell will be also discussed.

Arctic Black Carbon Loading and Profile Using the Single-Particle Soot Photometer (SP2) Field Campaign Report

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

Sedlacek, Arthur J

One of the major issues confronting aerosol climate simulations of the Arctic and Antarctic cryospheres is the lack of detailed data on the vertical and spatial distribution of aerosols with which to test these models. This is due, in part, to the inherent difficulty of conducting such measurements in extreme environments. However given the pronounced sensitivity of the polar regions to radiative balance perturbations, it is incumbent upon our community to better understand and quantify these perturbations, and their unique feedbacks, so that robust model predictions of this region can be realized. One class of under-measured radiative forcing agents inmore » the polar region is the absorbing aerosol—black carbon and brown carbon. Black carbon (BC; also referred to as light-absorbing carbon [LAC], refractory black carbon [rBC], and soot) is second only to CO2 as a positive forcing agent. Roughly 60% of BC emissions can be attributed to anthropogenic sources (fossil fuel combustion and open-pit cooking), with the remaining fraction being due to biomass burning. Brown carbon (BrC), a major component of biomass burning, collectively refers to non-BC carbonaceous aerosols that typically possess minimal light absorption at visible wavelengths but exhibit pronounced light absorption in the near-ultraviolet (UV) spectrum. Both species can be sourced locally or be remotely transported to the Arctic region and are expected to perturb the radiative balance. The work conducted in this field campaign addresses one of the more glaring deficiencies currently limiting improved quantification of the impact of BC radiative forcing in the cryosphere: the paucity of data on the vertical and spatial distributions of BC. By expanding the Gulfstream aircraft (G-1) payload for the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility-sponsored ACME-V campaign to include the Single-Particle Soot Photometer (SP2)) and leveraging the ACME-V campaign’s deployment within the Arctic Circle during the summer of 2015 (Deadhorse, Alaska [70° 12' 20" N, 148° 30' 42" W]), the truly unique opportunity presented itself to acquire profile data on BC loading at little additional cost. Since the SP2 is a particle-resolved measurement, the resulting data set provides refractory black carbon (rBC) mass loadings, size and mass distributions, and rBC-containing particle mixing state, all of which are expected to readily find value in the modeling community. As part of the ACME-V (http://www.arm.gov/campaigns/aaf2014armacmev) campaign, CO, CO2, and CH4 were also measured, providing the unique opportunity for carbon closure. We will also work closely with modelers who require such data and expect this collaboration will lead directly to a better understanding of the climate impacts of BC in the Arctic. The primary measurement objective was to acquire airborne data on the vertical and spatial distributions of refractory black carbon (rBC) loading, size and mass distribution, and particle mixing state. The primary scientific objective was to provide a targeted data set of rBC particle distributions to better understand and constrain the impact of black carbon radiative forcing in the cryosphere. The SP2-based data set during this campaign is available in the DOE-ARM archive (http://www.arm.gov/campaigns/aaf2015abclp).« less

Modelling, simulation and applications of longitudinal train dynamics

NASA Astrophysics Data System (ADS)

Cole, Colin; Spiryagin, Maksym; Wu, Qing; Sun, Yan Quan

2017-10-01

Significant developments in longitudinal train simulation and an overview of the approaches to train models and modelling vehicle force inputs are firstly presented. The most important modelling task, that of the wagon connection, consisting of energy absorption devices such as draft gears and buffers, draw gear stiffness, coupler slack and structural stiffness is then presented. Detailed attention is given to the modelling approaches for friction wedge damped and polymer draft gears. A significant issue in longitudinal train dynamics is the modelling and calculation of the input forces - the co-dimensional problem. The need to push traction performances higher has led to research and improvement in the accuracy of traction modelling which is discussed. A co-simulation method that combines longitudinal train simulation, locomotive traction control and locomotive vehicle dynamics is presented. The modelling of other forces, braking propulsion resistance, curve drag and grade forces are also discussed. As extensions to conventional longitudinal train dynamics, lateral forces and coupler impacts are examined in regards to interaction with wagon lateral and vertical dynamics. Various applications of longitudinal train dynamics are then presented. As an alternative to the tradition single wagon mass approach to longitudinal train dynamics, an example incorporating fully detailed wagon dynamics is presented for a crash analysis problem. Further applications of starting traction, air braking, distributed power, energy analysis and tippler operation are also presented.

Lower-extremity musculoskeletal geometry affects the calculation of patellofemoral forces in vertical jumping and weightlifting.

PubMed

Cleather, D I; Bull, A M J

2010-01-01

The calculation of the patellofemoral joint contact force using three-dimensional (3D) modelling techniques requires a description of the musculoskeletal geometry of the lower limb. In this study, the influence of the complexity of the muscle model was studied by considering two different muscle models, the Delp and Horsman models. Both models were used to calculate the patellofemoral force during standing, vertical jumping, and Olympic-style weightlifting. The patellofemoral forces predicted by the Horsman model were markedly lower than those predicted by the Delp model in all activities and represented more realistic values when compared with previous work. This was found to be a result of a lower level of redundancy in the Delp model, which forced a higher level of muscular activation in order to allow a viable solution. The higher level of complexity in the Horsman model resulted in a greater degree of redundancy and consequently lower activation and patellofemoral forces. The results of this work demonstrate that a well-posed muscle model must have an adequate degree of complexity to create a sufficient independence, variability, and number of moment arms in order to ensure adequate redundancy of the force-sharing problem such that muscle forces are not overstated.

Rail commuter vehicle curving performance

DOT National Transportation Integrated Search

2002-04-01

This report presents results of a program to design and install a wayside wheel-rail force measurement system. The test site is capable of developing a set of measurements of lateral and vertical forces exerted between the wheel and the rail at caref...

Changes in kinetics and kinematics of handwriting during a prolonged writing task in children with and without dysgraphia.

PubMed

Kushki, Azadeh; Schwellnus, Heidi; Ilyas, Faizah; Chau, Tom

2011-01-01

Handwriting difficulties or dysgraphia have a profound impact on children's psychosocial development, and yet, 10-30% of school-aged children are reported to experience difficulties mastering this skill. Several studies have examined the nature and biomechanical underpinnings of handwriting difficulties in children with and without dysgraphia. While the majority of these studies have considered short handwriting activities involving a sentence or a paragraph, handwriting quality and speed are reported to vary with the length of the writing task. Further, it is suggested that the biomechanics of handwriting also evolve over extended writing periods, and that these changes may be distinct between children with and without dysgraphia. The nature and specificity of these biomechanical alterations remain unknown. To address this knowledge gap, we examined changes in writing speed, grip forces on the pen barrel, and normal forces on the writing surface, over the course of a 10-min writing task, in a large cohort of 4th grade children with and without dysgraphia. Horizontal stroke speed, grip force and normal force increased over time while vertical stroke speed decreased in all children. These biomechanical changes may be attributable to physical and psychological fatigue and the corresponding compensatory processes invoked by the motor system. Copyright © 2011 Elsevier Ltd. All rights reserved.

Film flow and heat transfer during condensation of steam on inclined and vertical nonround tubes

NASA Astrophysics Data System (ADS)

Nikitin, N. N.; Semenov, V. P.

2008-03-01

We describe a mathematical model for calculating heat transfer during film condensation of stagnant steam on inclined and vertical smooth tubes with cross sections of arbitrary shape that takes into account the action of surface tension forces. The heat-transfer coefficients are calculated, and the hydrodynamic pattern is presented in which a condensate film flows over the surface of nonround inclined and vertical tubes with cross-section of different shapes.

Inconsistencies in the Weather Research and Forecasting Model of the Marine Boundary Layer Along the Coast of California

NASA Astrophysics Data System (ADS)

Fisher, Andrew M.

The late spring and summer low-level wind field along the California coast is primarily controlled by the pressure gradient between the Pacific high and the thermal low over the desert southwest. Strong northwesterly winds within the marine boundary layer (MBL) are common and the flow is often described as a two-layer shallow water hydraulic system, capped above by subsidence and bounded laterally by high coastal topography. Hydraulic features such as an expansion fan can occur near major coastal headlands. Numerical simulations using the Weather Research and Forecasting (WRF) modeling system were conducted over a two-month period and compared to observations from several buoy stations and aircraft measurements from the Precision Atmospheric Marine Boundary Layer Experiment (PreAMBLE). Model performance of the atmospheric adjustment near the Point Arguello and Point Conception (PAPC) headlands and into the Santa Barbara Channel (SBC) is assessed. Substantial inconsistencies are revealed, especially in the SBC. The strength of the synoptic forcing impacts model performance upstream of PAPC. The model maintains stronger winds than observed under weak forcing regimes, inadequately representing periods of wind relaxation. The large-scale forcing has minimal impact on the flow in the SBC, where poor modeling of the MBL characteristics exists throughout the entire period. Similar results are found in the coarser North American Mesoscale (NAM) model. In general, WRF overestimates the wind speed around PAPC and the expansion fan extends too far into the SBC. Previous conceptual models were based on similar flawed model results and limited observations. PreAMBLE measurements reveal a more complex lower atmosphere in the SBC than the simulations can represent. Mischaracterization of surface wind stress in the SBC has implications for forcing ocean models with WRF. Understanding model biases of the vertical profile of temperature and humidity are also critical to several national defense agencies with interests in atmospheric refractivity conditions and its impact on their operations.

Aerodynamic Loads at Mach Numbers from 0.70 to 2.22 on an Airplane Model Having a Wing and Canard of Triangular Plan Form and Either Single or Twin Vertical Tails. Supplement 2; Tabulated Data for the Model with Twin Vertical Tails

NASA Technical Reports Server (NTRS)

Peterson, Victor L.; Menees, Gene P.

1961-01-01

Tabulated results of a wind-tunnel investigation of the aerodynamic loads on a canard airplane model with twin vertical tails are presented for Mach numbers from 0.70 to 2.22. The Reynolds number for the measurements was 2.9 x 10(exp 6) based on the wing mean aerodynamic chord. The results include local static-pressure coefficients measured on the wing, body, and one of the vertical tails for angles of attack from -4 degrees to 16 degree angles of sideslip of 0 degrees and 5.3 degrees, and nominal canard deflections of O degrees and 10 degrees. Also included are section force and moment coefficients obtained from integrations of the local pressures and model-component force and moment coefficients obtained from integrations of the section coefficients. Geometric details of the model are shown and the locations of the pressure orifices are shown. An index to the data contained herein is presented and definitions of nomenclature are given. Detailed descriptions of the model and experiments and a brief discussion of some of the results are given. Tabulated results of measurements of the aerodynamic loads on the same canard model but having a single vertical tail instead of twin vertical tails are presented.

Design for Manufacturing for Energy Absorption Systems

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

Del Prete, A.; Primo, T.; Papadia, G.

2011-05-04

In the typical scenario of a helicopter crash, impact with the ground is preceded by a substantially vertical drop, with the result that a seated occupant of a helicopter experiences high spinal loads and pelvic deceleration during such crash due to the sudden arresting of vertical downward motion. It has long been recognized that spinal injuries to occupants of helicopters in such crash scenario can be minimized by seat arrangements which limit the deceleration to which the seated occupant is subjected, relative to the helicopter, to a predetermined maximum, by allowing downward movement of the seated occupant relative to themore » helicopter, at the time of impact with the ground, under a restraining force which, over a limited range of such movement, is limited to a predetermined maximum. In practice, significant benefits, in the way of reduced injuries and reduced seriousness of injuries, can be afforded in this way in such crash situations even where the extent of such controlled vertical movement permitted by the crashworthy seat arrangement is quite limited. Important increase of accident safety is reached with the installation of crashworthy shock absorbers on the main landing gear, but this solution is mostly feasible on military helicopters with long fixed landing gear. Seats can then give high contribution to survivability. Commonly, an energy absorber is a constant load device, if one excludes an initial elastic part of the load-stroke curve. On helicopter seats, this behavior is obtained by plastic deformation of a metal component or scraping of material. In the present work the authors have studied three absorption systems, which differ in relation to their shape, their working conditions and their constructive materials. All the combinations have been analyzed for applications in VIP helicopter seats.« less

Seasonality and intermittency of the ocean dynamics at scales smaller than 100 km in the world ocean: A scientific challenge for SWOT

NASA Astrophysics Data System (ADS)

Wang, J.; Su, Z.; Klein, P.; Thompson, A. F.; Menemenlis, D.; Fu, L. L.

2016-12-01

The major observational advance expected from the Surface Water and Ocean Topography (SWOT) altimeter, compared with existing altimeters, is that it will provide wide-swath (120 km) along-track data that permit the sampling of oceanic scales between 15 and 150km. The potential of this satellite mission is to understand the dynamical impact of these small scales on ocean dynamics. Such impact is known to affect the vertical velocity field (and therefore the vertical fluxes of ocean properties) and significantly affect both the inverse and direct kinetic energy cascades. The need to monitor these scales on a global scale is illustrated by the results of a realistic global ocean simulation. This model has 1/48-degree horizontal grid spacing, 90 vertical levels, and the inclusion of tidal forcing. This simulation reveals a strong seasonality of ocean dynamics at scales less than 100 km, not only in the previously documented regions, such as the Kuroshio extension, Gulf Stream, and subtropical gyres; but also in most other regions, such as most of the Southern Hemisphere and the North-East Atlantic. This strong seasonality, with a maximum amplitude consistently in winter, is associated with deep winter mixed-layer and energetic mesoscale eddies, pointing to mixed-layer instability as a major driver of the seasonality of dynamics at small scales. In addition to seasonal variations, strong intermittencies of ocean dynamics with a period of one to two weeks are also observed occasionally with the same amplitude as the seasonal variability. In this presentation, we discuss the consequences and the challenges posed by the strong spatial and temporal variability to SWOT data analysis.

Design for Manufacturing for Energy Absorption Systems

NASA Astrophysics Data System (ADS)

Del Prete, A.; Primo, T.; Papadia, G.; Manisi, B.

2011-05-01

In the typical scenario of a helicopter crash, impact with the ground is preceded by a substantially vertical drop, with the result that a seated occupant of a helicopter experiences high spinal loads and pelvic deceleration during such crash due to the sudden arresting of vertical downward motion. It has long been recognized that spinal injuries to occupants of helicopters in such crash scenario can be minimized by seat arrangements which limit the deceleration to which the seated occupant is subjected, relative to the helicopter, to a predetermined maximum, by allowing downward movement of the seated occupant relative to the helicopter, at the time of impact with the ground, under a restraining force which, over a limited range of such movement, is limited to a predetermined maximum. In practice, significant benefits, in the way of reduced injuries and reduced seriousness of injuries, can be afforded in this way in such crash situations even where the extent of such controlled vertical movement permitted by the crashworthy seat arrangement is quite limited. Important increase of accident safety is reached with the installation of crashworthy shock absorbers on the main landing gear, but this solution is mostly feasible on military helicopters with long fixed landing gear. Seats can then give high contribution to survivability. Commonly, an energy absorber is a constant load device, if one excludes an initial elastic part of the load-stroke curve. On helicopter seats, this behavior is obtained by plastic deformation of a metal component or scraping of material. In the present work the authors have studied three absorption systems, which differ in relation to their shape, their working conditions and their constructive materials. All the combinations have been analyzed for applications in VIP helicopter seats.

The ins and outs of modelling vertical displacement events

NASA Astrophysics Data System (ADS)

Pfefferle, David

2017-10-01

Of the many reasons a plasma discharge disrupts, Vertical Displacement Events (VDEs) lead to the most severe forces and stresses on the vacuum vessel and Plasma Facing Components (PFCs). After loss of positional control, the plasma column drifts across the vacuum vessel and comes in contact with the first wall, at which point the stored magnetic and thermal energy is abruptly released. The vessel forces have been extensively modelled in 2D but, with the constraint of axisymmetry, the fundamental 3D effects that lead to toroidal peaking, sideways forces, field-line stochastisation and halo current rotation have been vastly overlooked. In this work, we present the main results of an intense VDE modelling activity using the implicit 3D extended MHD code M3D-C1 and share our experience with the multi-domain and highly non-linear physics encountered. At the culmination of code development by the M3D-C1 group over the last decade, highlighted by the inclusion of a finite-thickness resistive vacuum vessel within the computational domain, a series of fully 3D non-linear simulations are performed using realistic transport coefficients based on the reconstruction of so-called NSTX frozen VDEs, where the feedback control was purposely switched off to trigger a vertical instability. The vertical drift phase, the evolution of the current quench and the onset of 3D halo/eddy currents are diagnosed and investigated in detail. The sensitivity of the current quench to parameter changes is assessed via 2D non-linear runs. The growth of individual toroidal modes is monitored via linear-complex runs. The intricate evolution of the plasma, which is decaying to large extent in force-balance with induced halo/wall currents, is carefully resolved via 3D non-linear runs. The location, amplitude and rotation of normal currents and wall forces are analysed and compared with experimental traces.

Theoretical calculations of the pressure, forces, and moments at supersonic speeds due to various lateral motions acting on thin isolated vertical tails

NASA Technical Reports Server (NTRS)

Margolis, Kenneth; Bobbitt, Percy J

1956-01-01

Velocity potentials, pressure, distributions, and stability derivatives are derived by use of supersonic linearized theory for families of thin isolated vertical tails performing steady rolling, steady yawing, and constant-lateral-acceleration motions. Vertical-tail families (half-delta and rectangular plan forms) are considered for a broad Mach number range. Also considered are the vertical tail with arbitrary sweepback and taper ratio at Mach numbers for which both the leading edge and trailing edge of the tail are supersonic and the triangular vertical tail with a subsonic leading edge and a supersonic trailing edge. Expressions for potentials, pressures, and stability derivatives are tabulated.

Impacts of the IOD-associated temperature and salinity anomalies on the intermittent equatorial undercurrent anomalies

NASA Astrophysics Data System (ADS)

Li, Junde; Liang, Chujin; Tang, Youmin; Liu, Xiaohui; Lian, Tao; Shen, Zheqi; Li, Xiaojing

2017-11-01

The study of Equatorial Undercurrent (EUC) has attracted a broad attention in recent years due to its strong response and feedback to the Indian Ocean Dipole. In this paper, we first produce a high-quality simulation of three-dimensional temperature, salinity and zonal current simulation from 1982 to 2014, using a high-resolution ocean general circulation model. On this basis, with two sensitivity experiments, we investigate the role of temperature and salinity anomalies in driving and enhancing the EUC during the positive IOD events by examining the variation of the EUC seasonal cycle and diagnosing the zonal momentum budget along the equatorial Indian Ocean. Our results show that during January-March, the EUC can appear along the entire equatorial Indian Ocean in all years, but during August-November, the EUC can appear and reach the eastern Indian Ocean only during the positive IOD events. The zonal momentum budget analysis indicates that the pressure gradient force contributes most to the variation of the eastward acceleration of zonal currents in the subsurface. During the positive IOD events, strong negative subsurface temperature anomalies exist in the eastern Indian Ocean, with negative surface salinity anomalies in the central and eastern Indian Ocean, resulting in a large pressure gradient force to drive EUC during the August-November. Further, the results of two sensitivity experiments indicate that the temperature anomalies significantly impact the pressure gradient force, playing a leading role in driving the EUC, while the surface salinity anomalies can secondarily help to intensify the eastward EUC through increasing the zonal density gradient in the eastern Indian Ocean and impacting the vertical momentum advection in the subsurface.

Mapping Impact of Urbanization in the Continental U.S. from 2001-2020

NASA Technical Reports Server (NTRS)

Bounoua, Lahouari; Nigro, Joseph; Zhang, Ping; Thome, Kurtis

2016-01-01

Data fusion, from Landsat and MODIS, was used to characterize US buildup and to derive a plausible 2020 impervious surface area (ISA) projection based on observed rates of ISA change as a function of population from 2006 to 2011. The analysis shows that urbanization in the U.S. implicitly includes a cultural character whereby depending on the region, cities are either built horizontally with large ISA per capita or vertically with a minimal spatial footprint. This cultural character can also be forced by land availability, topography and inland water. In other regions, cities seem to have adapted to their population growth and adjusted their ISA use per capita.

Predicting lower body power from vertical jump prediction equations for loaded jump squats at different intensities in men and women.

PubMed

Wright, Glenn A; Pustina, Andrew A; Mikat, Richard P; Kernozek, Thomas W

2012-03-01

The purpose of this study was to determine the efficacy of estimating peak lower body power from a maximal jump squat using 3 different vertical jump prediction equations. Sixty physically active college students (30 men, 30 women) performed jump squats with a weighted bar's applied load of 20, 40, and 60% of body mass across the shoulders. Each jump squat was simultaneously monitored using a force plate and a contact mat. Peak power (PP) was calculated using vertical ground reaction force from the force plate data. Commonly used equations requiring body mass and vertical jump height to estimate PP were applied such that the system mass (mass of body + applied load) was substituted for body mass. Jump height was determined from flight time as measured with a contact mat during a maximal jump squat. Estimations of PP (PP(est)) for each load and for each prediction equation were compared with criterion PP values from a force plate (PP(FP)). The PP(est) values had high test-retest reliability and were strongly correlated to PP(FP) in both men and women at all relative loads. However, only the Harman equation accurately predicted PP(FP) at all relative loads. It can therefore be concluded that the Harman equation may be used to estimate PP of a loaded jump squat knowing the system mass and peak jump height when more precise (and expensive) measurement equipment is unavailable. Further, high reliability and correlation with criterion values suggest that serial assessment of power production across training periods could be used for relative assessment of change by either of the prediction equations used in this study.

Influence of Familiarization and Competitive Level on the Reliability of Countermovement Vertical Jump Kinetic and Kinematic Variables.

PubMed

Nibali, Maria L; Tombleson, Tom; Brady, Philip H; Wagner, Phillip

2015-10-01

Understanding typical variation of vertical jump (VJ) performance and confounding sources of its typical variability (i.e., familiarization and competitive level) is pertinent in the routine monitoring of athletes. We evaluated the presence of systematic error (learning effect) and nonuniformity of error (heteroscedasticity) across VJ performances of athletes that differ in competitive level and quantified the reliability of VJ kinetic and kinematic variables relative to the smallest worthwhile change (SWC). One hundred thirteen high school athletes, 30 college athletes, and 35 professional athletes completed repeat VJ trials. Average eccentric rate of force development (RFD), average concentric (CON) force, CON impulse, and jump height measurements were obtained from vertical ground reaction force (VGRF) data. Systematic error was assessed by evaluating changes in the mean of repeat trials. Heteroscedasticity was evaluated by plotting the difference score (trial 2 - trial 1) against the mean of the trials. Variability of jump variables was calculated as the typical error (TE) and coefficient of variation (%CV). No substantial systematic error (effect size range: -0.07 to 0.11) or heteroscedasticity was present for any of the VJ variables. Vertical jump can be performed without the need for familiarization trials, and the variability can be conveyed as either the raw TE or the %CV. Assessment of VGRF variables is an effective and reliable means of assessing VJ performance. Average CON force and CON impulse are highly reliable (%CV: 2.7% ×/÷ 1.10), although jump height was the only variable to display a %CV ≤SWC. Eccentric RFD is highly variable yet should not be discounted from VJ assessments on this factor alone because it may be sensitive to changes in response to training or fatigue that exceed the TE.

The influence of different screw tightening forces on the vertical misfit of implant-supported frameworks.

PubMed

Vasconcellos, Diego Klee de; Bottino, Marco Antonio; Nishioka, Renato Sussumu; Valandro, Luiz Felipe; Costa, Elza Maria Valadares da

2005-06-01

The present in vitro study was designed to compare the differences in the vertical misfit of implant-supported frameworks using three different forces for tightening the bridge locking screws: fastening by hand until first resistance, and using torque drivers with 10 and 20Ncm. The investigation was conducted based on the results given by 9 six-unit nickel-chromium (2 abutments/ 4 pontics) screw-retained implant-supported frameworks. The structures were exposed to simulated porcelain firings. The marginal misfit measurements were made using a traveling measuring microscope at selected screw tightening forces: fastening by hand until first resistance, and using torque drivers with 10 and 20Ncm. The results were submitted to one-way ANOVA with repeated measures on one factor, and post hoc pairwise comparisons using Tukey test (5%). The mean marginal misfit of the frameworks, fastening the screws by hand until first resistance, was 41.56µm (SD±12.45µm). The use of torque driver devices caused a significant reduction in marginal opening (p<0.05). With the lowest torque available (10Ncm), the mean marginal discrepancy at the abutment-framework interface was reduced an average of 52% to a mean marginal opening of 19.71µm (SD±2.97µm). After the use of the 20Ncm torque driver, the mean marginal discrepancy of the frameworks was reduced an average of 69% to a mean marginal opening of 12.82µm (SD±4.0µm). Comparing the use of torque drivers with 10 and 20 Ncm torque, the means are not significantly different from one another. The seating force has an important effect on the vertical misfit measurements, once it may considerably narrow the vertical misfit gaps at the abutment-framework interface, thus leading to a misjudgment of the real marginal situation.

Warm-Core Intensification Through Horizontal Eddy Heat Transports into the Eye

NASA Technical Reports Server (NTRS)

Braun, Scott A.; Montgomery, Michael T.; Fulton, John; Nolan, David S.; Starr, David OC. (Technical Monitor)

2001-01-01

The mechanism for the formation and intensification of the hurricane warm core is not well understood. The generally accepted explanation is that the warm core forms as a result of gentle subsidence of air within the eye that warms as a result of adiabatic compression. Malkus suggested that this subsidence is part of a deep circulation in which air begins descent at high levels in the eye, acquires cyclonic angular momentum as it descends to lower levels, and then diverges at low levels, where it is entrained back into the eyewall. Inward mixing from the eyewall is hypothesized to force the subsidence and maintain the moisture and momentum budgets of the subsiding air. Willoughby suggested that air within the eye has remained so since it was first enclosed during the formation of the eyewall and that it subsides at most only a few kilometers rather than through the depth of the troposphere. He relates the subsidence to the low-level divergence and entrainment into the eyewall noted by Malkus, but suggests that shrinkage of the eye's volume is more than adequate to account for the air lost to the eyewall or converted to cloudy air by turbulent mixing across the eye boundary. Smith offered an alternative view of the subsidence forcing, suggesting that vertical motion in a mature hurricane eye is generated largely by imbalances between the downward vertical pressure gradient force and the upward buoyancy force. The vertical pressure gradient force is associated with the decay and/or radial spread of the tangential wind field with height at those levels were the winds are in approximate gradient wind balance. The rate of subsidence is just that required to warm the air sufficiently such that the buoyancy remains in close hydrostatic balance with an increasing vertical pressure gradient force. In this study, a very high-resolution simulation of Hurricane Bob using a cloud-resolving grid scale of 1.3 km is used to examine the heat budget within the storm with particular emphasis on the mechanisms for warming of the eye.

[Kinetics of heifers and cows walking on an instrumented treadmill].

PubMed

Nuss, K; Waldern, N M; Weishaupt, M A; Wiestner, T

2015-01-01

Kinetic data of stride characteristics and ground reaction forces of cattle become increasingly important as automated lameness detection may be installed in dairy cow housing systems in the future. Therefore, sound heifers and cows were measured on an instrumented treadmill to collect such basic data. Nine heifers and 10 cows were trained to walk on an instrumented treadmill. Vertical ground reaction forces as well as step and stride timing and length variables were measured for all limbs simultaneously. On average, 16 stride cycles in cows and 24 strides in heifers were analysed in each case. The cows walked on the treadmill at an average speed of 1.2 ± 0.05 m/s (mean ± standard deviation), with a stride rate of 43.0 ± 1.9/min and a stride length of 1.68 ± 0.1 m. The heifers had average values of 1.3 ± 0.04 m/s, 53.7 ± 2.2/min and 1.49 ± 0.05 m, respectively. The stance duration relative to stride duration (the duty factor) was for the cows significantly longer in the forelimbs (67%) than in the hind limbs (64%). Force-time-curves of all limbs showed two peaks, one after landing (FP1) and another during push off (FP2). Vertical ground reaction force was highest for FP1 in the hind limbs, but for FP2 in the forelimbs. At all limbs, force minimum between the peaks occurred shortly before midstance. The vertical impulse carried by both forelimbs amounted to 53.7% of the total stride impulse in cows and to 55.0% in heifers. The location of the centre of body mass varied during the stride cycle but was always located more towards the front limbs. Cows and heifers showed a symmetrical walk with minimal intra-individual variations. Relative stride impulse of the front limbs was higher than that of the hind limbs. Peak vertical force in the hind limbs was highest at landing and in the forelimbs at push off. The present study offers kinetic data of sound cows and heifers which might be helpful as guidelines for automated systems for lameness detection in cattle.

Design of a new engine mount for vertical and horizontal vibration control using magnetorheological fluid

NASA Astrophysics Data System (ADS)

Phu, D. X.; Choi, S. B.; Lee, Y. S.; Han, M. S.

2014-10-01

This paper presents a new design of a magnetorheological fluid (MR) mount for vibration control considering both vertical forces and horizontal moments such as are met in various engine systems, including a medium high-speed engine of ship. The newly designed mount, called a MR brake mount, offers several salient benefits such as small size and relatively high load capacity compared with a conventional MR engine mount that can control vertical vibration only. The principal design parameters of the proposed mount are optimally determined to achieve maximum torque with geometric and spatial constraints. Subsequently, the proposed MR mount is designed and manufactured based on the optimized design parameters. It is shown from experimental testing that the proposed mount, which combines MR mount with MR brake, can produce the desired force and torque to reduce unwanted vibration of a medium high-speed engine system of ship subjected to both vertical and horizontal exciting motions. In addition, it is verified that there is no large difference between experiment results and simulation results that are obtained from an analytical model derived in this work.

Residual-stress-induced grain growth of twinned grains and its effect on formability of magnesium alloy sheet at room temperature

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

Kim, Se-Jong; Kim, Daeyong, E-mail: daeyong@kims.re.kr; Lee, Keunho

2015-11-15

A magnesium alloy sheet was subjected to in-plane compression along with a vertical load to avoid buckling during compression. Pre-compressed specimens machined from the sheet were annealed at different temperatures and the changes in microstructure and texture were observed using electron back scattered diffraction (EBSD). Twinned grains preferentially grew during annealing at 300 °C, so that a strong texture with the < 0001 > direction parallel to the transverse direction developed. EBSD analysis confirmed that the friction caused by the vertical load induced inhomogeneous distribution of residual stress, which acted as an additional driving force for preferential grain growth ofmore » twinned grain during annealing. The annealed specimen showed excellent formability. - Highlights: • A magnesium alloy sheet subjected to in-plane compression under a vertical load • The vertical load induced inhomogeneous distribution of the residual stress. • The residual stress acted as an additional driving force for grain growth. • The annealed specimen with strong non-basal texture showed excellent formability.« less

Dynamic knee valgus alignment influences impact attenuation in the lower extremity during the deceleration phase of a single-leg landing.

PubMed

Tamura, Akihiro; Akasaka, Kiyokazu; Otsudo, Takahiro; Shiozawa, Jyunya; Toda, Yuka; Yamada, Kaori

2017-01-01

Dynamic knee valgus during landings is associated with an increased risk of non-contact anterior cruciate ligament (ACL) injury. In addition, the impact on the body during landings must be attenuated in the lower extremity joints. The purpose of this study was to investigate landing biomechanics during landing with dynamic knee valgus by measuring the vertical ground reaction force (vGRF) and angular impulses in the lower extremity during a single-leg landing. The study included 34 female college students, who performed the single-leg drop vertical jump. Lower extremity kinetic and kinematic data were obtained from a 3D motion analysis system. Participants were divided into valgus (N = 19) and varus (N = 15) groups according to the knee angular displacement during landings. The vGRF and angular impulses of the hip, knee, and ankle were calculated by integrating the vGRF-time curve and each joint's moment-time curve. vGRF impulses did not differ between two groups. Hip angular impulse in the valgus group was significantly smaller than that in the varus group (0.019 ± 0.033 vs. 0.067 ± 0.029 Nms/kgm, p<0.01), whereas knee angular impulse was significantly greater (0.093 ± 0.032 vs. 0.045 ± 0.040 Nms/kgm, p<0.01). There was no difference in ankle angular impulse between the groups. Our results indicate that dynamic knee valgus increases the impact the knee joint needs to attenuate during landing; conversely, the knee varus participants were able to absorb more of the landing impact with the hip joint.

Numerical Study of Splash Detail Due to Grain Impact on Granular Bed

NASA Astrophysics Data System (ADS)

Tanabe, Takahiro; Niiya, Hirofumi; Awazu, Akinori; Nishimori, Hiraku

2017-04-01

Massive sediment transport phenomena, such as sand storm and drifting snow, pose a considerable threat to human life. Further, the formation of geomorphological patterns on sand-desert and snowfield surfaces as a result of sediment transport, such as dunes and ripples, is of considerable research interest. Because the major component of the grain entrainment into the air is caused by both the collision and ejection, it is necessary to focus on the collisions between wind-blown grains and surface of sand field along with the resultant ejection grains from the surfaces, which processes are, as a whole, called a splash process. However, because of complexity of jumping grains over the ground surface, detailed measurement is very hard. Therefore, to investigate the splash process, we simulate detailed process of splash caused by 1-grain impact onto a randomly packed granular bed using discrete element method. As a result, we obtained good correspondence between our numerical results and the findings of previous experiments for the movement of ejected grains. Furthermore, the distributions of the ejection angle and the vertical ejection speed for individual grains vary depending on the relative timing at which the grains are ejected after the initial impact. Obvious differences are observed between the distributions of grains ejected during the earlier and later splash periods: the form of the vertical ejection-speed distribution varies from a power-law form to a lognormal form with time, and this difference is related to the grain trajectory after ejection [1]. In addition, we focus on the bulk dynamics inside the granular bed to relate the ejected grains behavior to the force propagations from the first impact to the ejection of each grain. [1] T. Tanabe, T. Shimada, N. Ito, and, H. Nishimori, (submitted)

Dynamics of an acoustically levitated particle using the lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Barrios, G.; Rechtman, R.

When the acoustic force inside a cavity balances the gravitational force on a particle the result is known as acoustic levitation. Using the lattice Boltzmann equation method we find the acoustic force acting on a rounded particle for two different single-axis acoustic levitators in two dimensions, the first with plane waves, the second with a rounded reflector that enhances the acoustic force. With no gravitational force, a particle oscillates around a pressure node; in the presence of gravity the oscillation is shifted a small vertical distance below the pressure node. This distance increases linearly as the density ratio between the solid particle and fluid grows. For both cavities, the particle oscillates with the frequency of the sound source and its harmonics and in some cases there is a much smaller second dominant frequency. When the momentum of the acoustic source changes, the oscillation around the average vertical position can have both frequencies mentioned above. However, if this quantity is large enough, the oscillations of the particle are aperiodic in the cavity with a rounded reflector.

Aerial Rotation Effects on Vertical Jump Performance Among Highly Skilled Collegiate Soccer Players.

PubMed

Barker, Leland A; Harry, John R; Dufek, Janet S; Mercer, John A

2017-04-01

Barker, LA, Harry, JR, Dufek, JS, and Mercer, JA. Aerial rotation effects on vertical jump performance among highly skilled collegiate soccer players. J Strength Cond Res 31(4): 932-938, 2017-In soccer matches, jumps involving rotations occur when attempting to head the ball for a shot or pass from set pieces, such as corner kicks, goal kicks, and lob passes. However, the 3-dimensional ground reaction forces used to perform rotational jumping tasks are currently unknown. Therefore, the purpose of this study was to compare bilateral, 3-dimensional, and ground reaction forces of a standard countermovement jump (CMJ0) with those of a countermovement jump with a 180° rotation (CMJ180) among Division-1 soccer players. Twenty-four participants from the soccer team of the University of Nevada performed 3 trials of CMJ0 and CMJ180. Dependent variables included jump height, downward and upward phase times, vertical (Fz) peak force and net impulse relative to mass, and medial-lateral and anterior-posterior force couple values. Statistical significance was set a priori at α = 0.05. CMJ180 reduced jump height, increased the anterior-posterior force couple in the downward and upward phases, and increased upward peak Fz (p ≤ 0.05). All other variables were not significantly different between groups (p > 0.05). However, we did recognize that downward peak Fz trended lower in the CMJ0 condition (p = 0.059), and upward net impulse trended higher in the CMJ0 condition (p = 0.071). It was concluded that jump height was reduced during the rotational jumping task, and rotation occurred primarily via AP ground reaction forces through the entire countermovement jump. Coaches and athletes may consider additional rotational jumping in their training programs to mediate performance decrements during rotational jump tasks.

The Effects of Caffeine on Vertical Jump Height and Execution in Collegiate Athletes.

PubMed

Bloms, Lucas P; Fitzgerald, John S; Short, Martin W; Whitehead, James R

2016-07-01

Bloms, LP, Fitzgerald, JS, Short, MW, and Whitehead, JR. The effects of caffeine on vertical jump height and execution in collegiate athletes. J Strength Cond Res 30(7): 1855-1861, 2016-Caffeine ingestion elicits a variety of physiological effects that may be beneficial to maximal-intensity exercise performance, although its effectiveness and physical mechanism of action enhancing ballistic task performance are unclear. The purpose of this study was to examine the effects of caffeine ingestion on vertical jump height and jump execution in Division I collegiate athletes. The study used a single-blind, randomized, crossover design. Athletes (n = 25) consumed either caffeine (5 mg·kg) or placebo. After a 60-minute waiting period, athletes performed 3 squat jumps (SJ) and 3 countermovement jumps (CMJ) while standing on a force platform. Jump height and execution variables were calculated from mechanography data. In comparison with placebo, caffeine increased SJ height (32.8 ± 6.2 vs. 34.5 ± 6.7 cm; p = 0.001) and CMJ height (36.4 ± 6.9 vs. 37.9 ± 7.4 cm; p = 0.001). Peak force (p = 0.032) and average rate of force development (p = 0.037) were increased during the CMJ in the caffeine trail compared with the control. Time to half peak force was the only execution variable improved with caffeine (p = 0.019) during the SJ. It seems that caffeine affects both height and execution of jumping. Our data indicate that the physical mechanism of jump enhancement is increased peak force production or rate of force development during jumping depending on technique. The physical mechanism of jump enhancement suggests that the ergogenic effects of caffeine may transfer to other ballistic tasks involving the lower-body musculature in collegiate athletes.

Galactoseismology and the local density of dark matter

DOE PAGES

Banik, Nilanjan; Widrow, Lawrence M.; Dodelson, Scott

2016-10-08

Here, we model vertical breathing mode perturbations in the Milky Way's stellar disc and study their effects on estimates of the local dark matter density, surface density, and vertical force. Evidence for these perturbations, which involve compression and expansion of the Galactic disc perpendicular to its midplane, come from the SEGUE, RAVE, and LAMOST surveys. We show that their existence may lead to systematic errors ofmore » $$10\\%$$ or greater in the vertical force $$K_z(z)$$ at $$|z|=1.1\\,{\\rm kpc}$$. These errors translate to $$\\gtrsim 25\\%$$ errors in estimates of the local dark matter density. Using different mono-abundant subpopulations as tracers offers a way out: if the inferences from all tracers in the Gaia era agree, then the dark matter determination will be robust. Disagreement in the inferences from different tracers will signal the breakdown of the unperturbed model and perhaps provide the means for determining the nature of the perturbation.« less

Coherent Structures and Extreme Events in Rotating Multiphase Turbulent Flows

NASA Astrophysics Data System (ADS)

Biferale, L.; Bonaccorso, F.; Mazzitelli, I. M.; van Hinsberg, M. A. T.; Lanotte, A. S.; Musacchio, S.; Perlekar, P.; Toschi, F.

2016-10-01

By using direct numerical simulations (DNS) at unprecedented resolution, we study turbulence under rotation in the presence of simultaneous direct and inverse cascades. The accumulation of energy at large scale leads to the formation of vertical coherent regions with high vorticity oriented along the rotation axis. By seeding the flow with millions of inertial particles, we quantify—for the first time—the effects of those coherent vertical structures on the preferential concentration of light and heavy particles. Furthermore, we quantitatively show that extreme fluctuations, leading to deviations from a normal-distributed statistics, result from the entangled interaction of the vertical structures with the turbulent background. Finally, we present the first-ever measurement of the relative importance between Stokes drag, Coriolis force, and centripetal force along the trajectories of inertial particles. We discover that vortical coherent structures lead to unexpected diffusion properties for heavy and light particles in the directions parallel and perpendicular to the rotation axis.

Snowboard Jumping, Newton's Second Law and the Force on Landing

ERIC Educational Resources Information Center

O'Shea, Michael J.

2004-01-01

An application of Newton's second law to a snowboarder dropping off a vertical ledge shows that the average normal force during landing (force exerted by the ground on the snowboarder) is determined by four factors. It is shown that the flexing of the legs, the softness of the snow, the angle of the landing surface and the forward motion of the…

Seasonal variations of aerosol optical properties, vertical distribution and associated radiative effects in the Yangtze Delta Region of China

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

Liu, Jianjun; Zheng, Youfei; Li, Zhanqing

2012-02-09

Four years of columnar aerosol particle optical properties (2006 to 2009) and one year database worth of aerosol particle vertical profile of 527 nm extinction coefficient (June 2008 to May 2009) are analyzed at Taihu in the central Yangtze Delta region in eastern China. Seasonal variations of aerosol optical properties, vertical distribution, and influence on shortwave radiation and heating rates were investigated. Multiyear variations of aerosol optical depths (AOD), Angstrom exponents, single scattering albedo (SSA) and asymmetry factor (ASY) are analyzed, together with the vertical profile of aerosol extinction. AOD is largest in summer and smallest in winter. SSAs exhibitmore » weak seasonal variation with the smallest values occurring during winter and the largest during summer. The vast majority of aerosol particles are below 2 km, and about 62%, 67%, 67% and 83% are confined to below 1 km in spring, summer, autumn and winter, respectively. Five-day back trajectory analyses show that the some aerosols aloft are traced back to northern/northwestern China, as far as Mongolia and Siberia, in spring, autumn and winter. The presence of dust aerosols were identified based on the linear depolarization measurements together with other information (i.e., back trajectory, precipitation, aerosol index). Dust strongly impacts the vertical particle distribution in spring and autumn, with much smaller effects in winter. The annual mean aerosol direct shortwave radiative forcing (efficiency) at the bottom, top and within the atmosphere are -34.8 {+-} 9.1 (-54.4 {+-} 5.3), -8.2 {+-} 4.8 (-13.1 {+-} 1.5) and 26.7 {+-} 9.4 (41.3 {+-} 4.6) W/m{sup 2} (Wm{sup -2} T{sup -1}), respectively. The mean reduction in direct and diffuse radiation reaching surface amount to 109.2 {+-} 49.4 and 66.8 {+-} 33.3 W/m{sup 2}, respectively. Aerosols significantly alter the vertical profile of solar heating, with great implications for atmospheric stability and dynamics within the lower troposphere.« less