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Sample records for ground reaction force

  1. Ground reaction forces during caterpillar climbing

    Barry Andrew Trimmer

    2012-04-01

    Full Text Available Larval Manduca sexta, the tobacco hornworm, are remarkable climbers and crawlers. They have evolved to navigate up, down, and across the branched and highly variable terrain on vegetation. Their locomotion, therefore, must be robust to any possible orientation. Furthermore, caterpillars lack a rigid support structure and the control of their increased degrees of freedom is not well understood. Our research explores Manduca’s locomotion in two orthogonal crawling modes: horizontal and vertical. Previous studies have demonstrated that caterpillars do not necessarily change their kinematics for crawling in these two orientations. We hypothesize that they also do not change the pattern of proleg force exertion in these two orientations, effectively using the same strategy to both crawl horizontally and to climb. To measure proleg force exertions, we used a biaxial strain gauge array to sense ground reaction forces of a crawling Manduca in vertical and horizontal directions. By averaging forces and looking at the general force distributions, we found that there is no difference in the pattern of axial forces between the two crawling directions but more variations in the normal forces. While caterpillar ground reaction forces are highly variable in nature, trends and shapes often persist between trials. Our data show that caterpillars maintain net drag on the abdominal segments, keeping their bodies in tension during both modes of locomotion. Axial forces during climbing are equivalent to axial forces during crawling offset by the addition of bodyweight. This suggests that the variations in the normal forces are due to the physics of vertical climbing and that Manduca accounts for bodyweight passively. This result also supports the general finding that caterpillars can use an environmental skeleton: the animal does not actively force any posture and only the axial forces are under active control to achieve forward progression. In climbing, gravity exerts drag on the body, providing the force necessary to maintain body tension. The animal passively resists the pitch-back moment generated by its bodyweight using fail-safe grippers at the tip of each proleg. This allows the animal to use the same crawling pattern with no additional compensation for changing orientations. Another important finding of this study is that the thoracic legs are necessary for normal locomotion, providing a tensioning thrust force in both orientations. Based on these results, we propose that caterpillars have developed a single locomotor strategy that allows them to move in any orientation, effectively ignoring gravitational effects.

  2. Ground Reaction Forces in Alternative Footwear during Slip Events

    Harish Chander; John C. Garner; Chip Wade

    2015-01-01

    Slips, trips and falls are major causitive factors for occupational and non-occupational falls. Alternative footwear such has crocs and flip flops have been used in and around work places and communities that can be slip prone environments. The purpose of the study is to analyze the effects of alternative footwear [crocs (CC), flip-flops (FF)] and industry standard slip resistant shoes (LT) on ground reaction forces (GRFs) during slip events. Eighteen healthy male participants following a rep...

  3. Crouched Posture Maximizes Ground Reaction Forces Generated by Muscles

    Hoang, Hoa X.; Reinbolt, Jeffrey A.

    2012-01-01

    Crouch gait decreases walking efficiency due to the increased knee and hip flexion during the stance phase of gait. Crouch gait is generally considered to be disadvantageous for children with cerebral palsy; however, a crouched posture may allow biomechanical advantages that lead some children to adopt a crouch gait. To investigate one possible advantage of crouch gait, a musculoskeletal model created in OpenSim was placed in 15 different postures from upright to severe crouch during initial, middle, and final stance of the gait cycle for a total of 45 different postures. A series of optimizations was performed for each posture to maximize transverse plane ground reaction forces in the 8 compass directions by modifying muscle forces acting on the model. We compared the force profile areas across all postures. Larger force profile areas were allowed by postures from mild crouch (for initial stance) to crouch (for final stance). The overall ability to generate larger ground reaction force profiles represents a mechanical advantage of a crouched posture. This increase in muscle capacity while in a crouched posture may allow a patient to generate new movements to compensate for impairments associated with cerebral palsy, such as motor control deficits. PMID:22542242

  4. Ground Reaction Forces in Alternative Footwear during Slip Events

    Harish Chander

    2015-04-01

    Full Text Available Slips, trips and falls are major causitive factors for occupational and non-occupational falls. Alternative footwear such has crocs and flip flops have been used in and around work places and communities that can be slip prone environments. The purpose of the study is to analyze the effects of alternative footwear [crocs (CC, flip-flops (FF] and industry standard slip resistant shoes (LT on ground reaction forces (GRFs during slip events. Eighteen healthy male participants following a repeated measures design for each footwear condition, were tested for heel kinematics during normal dry surface gait (NG; unexpected slip (US, alert slip (AS and expected slip (ES. A 3x4 repeated measures ANOVA was used to analyze the dependent vertical GRFs parameters (Mean Z-GRF and Peak Z-GRF at p = 0.05. Significant interactions between footwear and gait trials were found for Mean Z-GRF and significant main effect in gait trials for Peak Z-GRF were evident. On average significantly lower GRFs were seen in slip trials compared to normal gait. FF exhibited significantly lower GRFs during slip trials while LT demonstrated lower GRFs in normal gait. The reduced ground reaction forces during all slip events compared to normal gait can be attributed to the incomplete weight transfer on the slipping foot during the unexpected and alert slips and to the anticipation of the slippery environment in expected slips. Flip flops which had greater incidence of slips also demonstrated reduced GRFs compared to CC and LT during slip events, further suggesting incomplete weight transfer, while during normal gait, LT demonstrated reduced GRFs compared to alternative footwear owing to its cushioning midsole properties. The LT with lowest incidence of slips demonstrates to be the choice of footwear for maneuvering slippery flooring conditions and for reducing impact reaction forces during non-slippery flooring conditions.Keywords: Slips, Falls, Alternative Footwear, Ground Reaction Forces, Perception of Slipperiness

  5. Systematic review of ground reaction force measurements in cats.

    Schnabl, E; Bockstahler, B

    2015-10-01

    Although orthopaedic abnormalities in cats are frequently observed radiographically, they remain clinically underdiagnosed, and kinetic motion analysis, a fundamental aspect of orthopaedic research in dogs and horses, is not commonly performed. More information obtained with non-invasive measurement techniques to assess normal and abnormal gait in cats would provide a greater insight into their locomotion and biomechanics and improve the objective measurement of disease alterations and treatment modalities. In this systematic review, 12 previously performed studies that investigated ground reaction force measurements in cats during locomotion were evaluated. The aims of these studies, the measurement methods and equipment used, and the outcomes of parameters used to assess both sound and diseased cats are summarised and discussed. All reviewed studies used pressure sensitive walkways to gain data and all provided an acclimatisation period as a prerequisite for measurements. In sound cats during walking, the forelimb peak vertical force was greater than in the hindlimb and the peak vertical force in the hindlimb was greater in cats than in dogs. This review confirms that ground reaction forces can be used to evaluate lameness and treatment effects in the cat. PMID:26118478

  6. Does an instrumented treadmill correctly measure the ground reaction forces?

    Patrick A. Willems

    2013-11-01

    Since the 1990s, treadmills have been equipped with multi-axis force transducers to measure the three components of the ground reaction forces during walking and running. These measurements are correctly performed if the whole treadmill (including the motor is mounted on the transducers. In this case, the acceleration of the treadmill centre of mass relative to the reference frame of the laboratory is nil. The external forces exerted on one side of the treadmill are thus equal in magnitude and opposite in direction to the external forces exerted on the other side. However, uncertainty exists about the accuracy of these measures: due to friction between the belt and the tread-surface, due to the motor pulling the belt, some believe that it is not possible to correctly measure the horizontal components of the forces exerted by the feet on the belt. Here, we propose a simple model of an instrumented treadmill and we demonstrate (1 that the forces exerted by the subject moving on the upper part of the treadmill are accurately transmitted to the transducers placed under it and (2 that all internal forces – including friction – between the parts of the treadmill are cancelling each other.

  7. System of gait analysis based on ground reaction force assessment

    František Vaverka

    2015-12-01

    Full Text Available Background: Biomechanical analysis of gait employs various methods used in kinematic and kinetic analysis, EMG, and others. One of the most frequently used methods is kinetic analysis based on the assessment of the ground reaction forces (GRF recorded on two force plates. Objective: The aim of the study was to present a method of gait analysis based on the assessment of the GRF recorded during the stance phase of two steps. Methods: The GRF recorded with a force plate on one leg during stance phase has three components acting in directions: Fx - mediolateral, Fy - anteroposterior, and Fz - vertical. A custom-written MATLAB script was used for gait analysis in this study. This software displays instantaneous force data for both legs as Fx(t, Fy(t and Fz(t curves, automatically determines the extremes of functions and sets the visual markers defining the individual points of interest. Positions of these markers can be easily adjusted by the rater, which may be necessary if the GRF has an atypical pattern. The analysis is fully automated and analyzing one trial takes only 1-2 minutes. Results: The method allows quantification of temporal variables of the extremes of the Fx(t, Fy(t, Fz(t functions, durations of the braking and propulsive phase, duration of the double support phase, the magnitudes of reaction forces in extremes of measured functions, impulses of force, and indices of symmetry. The analysis results in a standardized set of 78 variables (temporal, force, indices of symmetry which can serve as a basis for further research and diagnostics. Conclusions: The resulting set of variable offers a wide choice for selecting a specific group of variables with consideration to a particular research topic. The advantage of this method is the standardization of the GRF analysis, low time requirements allowing rapid analysis of a large number of trials in a short time, and comparability of the variables obtained during different research measurements.

  8. Comparison of vertical ground reaction forces during overground and treadmill running. A validation study

    Kluitenberg Bas; Bredeweg Steef W; Zijlstra Sjouke; Zijlstra Wiebren; Buist Ida

    2012-01-01

    Abstract Background One major drawback in measuring ground-reaction forces during running is that it is time consuming to get representative ground-reaction force (GRF) values with a traditional force platform. An instrumented force measuring treadmill can overcome the shortcomings inherent to overground testing. The purpose of the current study was to determine the validity of an instrumented force measuring treadmill for measuring vertical ground-reaction force parameters during running. Me...

  9. Ground reaction forces during level ground walking with body weight unloading

    Ana M. F. Barela

    2014-12-01

    Full Text Available Background: Partial body weight support (BWS systems have been broadly used with treadmills as a strategy for gait training of individuals with gait impairments. Considering that we usually walk on level ground and that BWS is achieved by altering the load on the plantar surface of the foot, it would be important to investigate some ground reaction force (GRF parameters in healthy individuals walking on level ground with BWS to better implement rehabilitation protocols for individuals with gait impairments. Objective: To describe the effects of body weight unloading on GRF parameters as healthy young adults walked with BWS on level ground. Method: Eighteen healthy young adults (27±4 years old walked on a walkway, with two force plates embedded in the middle of it, wearing a harness connected to a BWS system, with 0%, 15%, and 30% BWS. Vertical and horizontal peaks and vertical valley of GRF, weight acceptance and push-off rates, and impulse were calculated and compared across the three experimental conditions. Results: Overall, participants walked more slowly with the BWS system on level ground compared to their normal walking speed. As body weight unloading increased, the magnitude of the GRF forces decreased. Conversely, weight acceptance rate was similar among conditions. Conclusions: Different amounts of body weight unloading promote different outputs of GRF parameters, even with the same mean walk speed. The only parameter that was similar among the three experimental conditions was the weight acceptance rate.

  10. Measurement of Ground Reaction Forces During Forward and Backward Walking In Flat Foot Female Subjects

    Shahin Gohar Pay

    2011-10-01

    Full Text Available Background and aim: Flexible flat foot is a common deformity in lower extremity, the foot arch collapses and the ground reaction forces does not apply properly to the foot. Backward walking is a common rehabilitive technique and is utilized to improve strength and balance. The purpose of this present study is to compare the salient points vertical ground reaction force measurements in flat foot patients while walking forward and backward with those of healthy subjects using a force plate system.Materials and methods: 10 flexible falt foot female subjects and 10 healthy female subjects were recruited to participate in this study. Each Subject walked 5 times forward and 5 times backward and the vertical ground reaction force was measured by a force platform.Results: The results of this present study suggest a significant difference in kinetic pattern of forward walking compared to backward walking in both healthy and flexible flat foot participants. The force related to first peak of vertical ground reaction force was significantly less in forward walking compared to backward walking (p=0.000. Whereas the force related to trough and second peak of vertical ground reaction force were significantly high in forward walking compared to backward walking (p=0.000.Conclusion: The results of this study show that backward walking changes the ground reaction force compared to forward walking; and the main characteristic of this difference is due to decrease of forces applied to the heel of foot which may be important in flat foot patients.

  11. Comparison of vertical ground reaction forces during overground and treadmill running. A validation study

    Kluitenberg Bas

    2012-11-01

    Full Text Available Abstract Background One major drawback in measuring ground-reaction forces during running is that it is time consuming to get representative ground-reaction force (GRF values with a traditional force platform. An instrumented force measuring treadmill can overcome the shortcomings inherent to overground testing. The purpose of the current study was to determine the validity of an instrumented force measuring treadmill for measuring vertical ground-reaction force parameters during running. Methods Vertical ground-reaction forces of experienced runners (12 male, 12 female were obtained during overground and treadmill running at slow, preferred and fast self-selected running speeds. For each runner, 7 mean vertical ground-reaction force parameters of the right leg were calculated based on five successful overground steps and 30 seconds of treadmill running data. Intraclass correlations (ICC(3,1 and ratio limits of agreement (RLOA were used for further analysis. Results Qualitatively, the overground and treadmill ground-reaction force curves for heelstrike runners and non-heelstrike runners were very similar. Quantitatively, the time-related parameters and active peak showed excellent agreement (ICCs between 0.76 and 0.95, RLOA between 5.7% and 15.5%. Impact peak showed modest agreement (ICCs between 0.71 and 0.76, RLOA between 19.9% and 28.8%. The maximal and average loading-rate showed modest to excellent ICCs (between 0.70 and 0.89, but RLOA were higher (between 34.3% and 45.4%. Conclusions The results of this study demonstrated that the treadmill is a moderate to highly valid tool for the assessment of vertical ground-reaction forces during running for runners who showed a consistent landing strategy during overground and treadmill running. The high stride-to-stride variance during both overground and treadmill running demonstrates the importance of measuring sufficient steps for representative ground-reaction force values. Therefore, an instrumented treadmill seems to be suitable for measuring representative vertical ground-reaction forces during running.

  12. Comparison of vertical ground reaction forces during overground and treadmill running. A validation study

    2012-01-01

    Background One major drawback in measuring ground-reaction forces during running is that it is time consuming to get representative ground-reaction force (GRF) values with a traditional force platform. An instrumented force measuring treadmill can overcome the shortcomings inherent to overground testing. The purpose of the current study was to determine the validity of an instrumented force measuring treadmill for measuring vertical ground-reaction force parameters during running. Methods Vertical ground-reaction forces of experienced runners (12 male, 12 female) were obtained during overground and treadmill running at slow, preferred and fast self-selected running speeds. For each runner, 7 mean vertical ground-reaction force parameters of the right leg were calculated based on five successful overground steps and 30 seconds of treadmill running data. Intraclass correlations (ICC(3,1)) and ratio limits of agreement (RLOA) were used for further analysis. Results Qualitatively, the overground and treadmill ground-reaction force curves for heelstrike runners and non-heelstrike runners were very similar. Quantitatively, the time-related parameters and active peak showed excellent agreement (ICCs between 0.76 and 0.95, RLOA between 5.7% and 15.5%). Impact peak showed modest agreement (ICCs between 0.71 and 0.76, RLOA between 19.9% and 28.8%). The maximal and average loading-rate showed modest to excellent ICCs (between 0.70 and 0.89), but RLOA were higher (between 34.3% and 45.4%). Conclusions The results of this study demonstrated that the treadmill is a moderate to highly valid tool for the assessment of vertical ground-reaction forces during running for runners who showed a consistent landing strategy during overground and treadmill running. The high stride-to-stride variance during both overground and treadmill running demonstrates the importance of measuring sufficient steps for representative ground-reaction force values. Therefore, an instrumented treadmill seems to be suitable for measuring representative vertical ground-reaction forces during running. PMID:23186326

  13. Software for analysis of equine ground reaction force data

    Schamhardt, H.C.; Merkens, H.W.; Lammertink, J.L.M.A.

    1986-01-01

    Software for analysis of force plate recordings of the horse at normal walk is described. The data of a number of stance phases are averaged to obtain a representative tracing of that horse. The amplitudes of a number of characteristic peaks in the force-time curves are used to compare left and right front limbs and left and right hind limbs. The averaged tracings are plotted, default on the line printer or, via a separate program, on a high quality pen plotter. A version of the program appli...

  14. Does maximising ball speed in cricket fast bowling necessitate higher ground reaction forces?

    King, M A; Worthington, P J; Ranson, C A

    2016-04-01

    This study aimed to investigate whether high peak ground reaction forces and high average loading rates are necessary to bowl fast. Kinematic and kinetic bowling data were collected for 20 elite male fast bowlers. A moderate non-significant correlation was found between ball speed and peak vertical ground reaction force with faster bowlers tending to have lower peak vertical ground reaction force (r = -0.364, P = 0.114). Faster ball speeds were correlated with both lower average vertical and lower average horizontal loading rates (r = -0.452, P = 0.046 and r = -0.484, P = 0.031, respectively). A larger horizontal (braking) impulse was associated with a faster ball speed (r = 0.574, P = 0.008) and a larger plant angle of the front leg (measured from the vertical) at front foot contact was associated with a larger horizontal impulse (r = 0.706, P = 0.001). These findings suggest that there does not necessarily need to be a trade-off between maximum ball release speed and the forces exerted on fast bowlers (peak ground reaction forces and average loading rates). Furthermore, it appears that one of the key determinants of ball speed is the horizontal impulse generated at the ground over the period from front foot contact until ball release. PMID:26186222

  15. BILATERAL GROUND REACTION FORCES AND JOINT MOMENTS FOR LATERAL SIDESTEPPING AND CROSSOVER STEPPING TASKS

    William I. Sellers

    2009-03-01

    Full Text Available Racquet sports have high levels of joint injuries suggesting the joint loads during play may be excessive. Sports such as badminton employ lateral sidestepping (SS and crossover stepping (XS movements which so far have not been described in terms of biomechanics. This study examined bilateral ground reaction forces and three dimensional joint kinetics for both these gaits in order to determine the demands of the movements on the leading and trailing limb and predict the contribution of these movements to the occurrence of overuse injury of the lower limbs. A force platform and motion-analysis system were used to record ground reaction forces and track marker trajectories of 9 experienced male badminton players performing lateral SS, XS and forward running tasks at a controlled speed of 3 m·s-1 using their normal technique. Ground reaction force and kinetic data for the hip, knee and ankle were analyzed, averaged across the group and the biomechanical variables compared. In all cases the ground reaction forces and joint moments were less than those experienced during moderate running suggesting that in normal play SS and XS gaits do not lead to high forces that could contribute to increased injury risk. Ground reaction forces during SS and XS do not appear to contribute to the development of overuse injury. The distinct roles of the leading and trailing limb, acting as a generator of vertical force and shock absorber respectively, during the SS and XS may however contribute to the development of muscular imbalances which may ultimately contribute to the development of overuse injury. However it is still possible that faulty use of these gaits might lead to high loads and this should be the subject of future work

  16. Effects of Nordic walking and walking on spatiotemporal gait parameters and ground reaction force.

    Park, Seung Kyu; Yang, Dae Jung; Kang, Yang Hun; Kim, Je Ho; Uhm, Yo Han; Lee, Yong Seon

    2015-09-01

    [Purpose] The purpose of this study was to investigate the effects of Nordic walking and walking on spatiotemporal gait parameters and ground reaction force. [Subjects] The subjects of this study were 30 young adult males, who were divided into a Nordic walking group of 15 subjects and a walking group of 15 subjects. [Methods] To analyze the spatiotemporal parameters and ground reaction force during walking in the two groups, the six-camera Vicon MX motion analysis system was used. The subjects were asked to walk 12 meters using the more comfortable walking method for them between Nordic walking and walking. After they walked 12 meters more than 10 times, their most natural walking patterns were chosen three times and analyzed. To determine the pole for Nordic walking, each subject's height was multiplied by 0.68. We then measured the spatiotemporal gait parameters and ground reaction force. [Results] Compared with the walking group, the Nordic walking group showed an increase in cadence, stride length, and step length, and a decrease in stride time, step time, and vertical ground reaction force. [Conclusion] The results of this study indicate that Nordic walking increases the stride and can be considered as helping patients with diseases affecting their gait. This demonstrates that Nordic walking is more effective in improving functional capabilities by promoting effective energy use and reducing the lower limb load, because the weight of the upper and lower limbs is dispersed during Nordic walking. PMID:26504319

  17. Effect of dog breed and body conformation on vertical ground reaction forces, impulses, and stance times

    Voss, K; Wiestner, T; Galeandro, L; H��ssig, M; Montavon , P M

    2011-01-01

    OBJECTIVES: To assess whether fully normalised vertical ground reaction forces and stance times obtained at a trot depend on dog breed or body conformations. METHODS: Peak vertical forces (PVF), vertical impulses (VI), stance times (ST), and ratio of forelimb impulse to total impulse (RVI) of 54 dogs of seven different breeds were normalised to body weight and body size according to the theory of dynamic similarity, and were tested for differences between breeds. Breeds were Borzoi...

  18. Mechanical stimulation of the foot sole in a supine position for ground reaction force simulation

    Fang, Juan; Vuckovic, Aleksandra; Galen, Sujay; Conway, Bernard A.; Hunt, Kenneth J.

    2014-01-01

    Background: To promote early rehabilitation of walking, gait training can start even when patients are on bed rest. Supine stepping in the early phase after injury is proposed to maximise the beneficial effects of gait restoration. In this training paradigm, mechanical loading on the sole of the foot is required to mimic the ground reaction forces that occur during overground walking. A pneumatic shoe platform was developed to produce adjustable forces on the heel and the forefoot with an ...

  19. Sagittal Plane Knee Biomechanics and Vertical Ground Reaction Forces Are Modified Following ACL Injury Prevention Programs

    Padua, Darin A.; DiStefano, Lindsay J.

    2009-01-01

    Context: Injuries to the anterior cruciate ligament (ACL) occur because of excessive loading on the knee. ACL injury prevention programs can influence sagittal plane ACL loading factors and vertical ground reaction force (VGRF). Objective: To determine the influence of ACL injury prevention programs on sagittal plane knee biomechanics (anterior tibial shear force, knee flexion angle/moments) and VGRF. Data Sources: The PubMed database was searched for studies published between January 1988 an...

  20. The forelimb in walking horses: 1. Kinematics and ground reaction forces.

    Hodson, E; Clayton, H M; Lanovaz, J L

    2000-07-01

    Video (60 Hz) and force (2000 Hz) data were collected from 5 sound horses during walking. Forelimb data were analysed for 8 strides (4 left, 4 right) per horse to determine sagittal plane kinematics and ground reaction forces (GRFs). The results suggested that brachial rotation was responsible for protraction and retraction of the limb as a whole, while rotations of the scapula and antebrachium elevated the distal limb during breakover and early swing then lowered it in preparation for ground contact. The coffin joint was flexed maximally at the time of peak longitudinal braking force, which occurred during breakover of the contralateral forelimb. The metacarpus was vertical at 28% stride. This was considerably earlier than the change from a braking to a propulsive longitudinal force (34% stride), which coincided with maximal extension of the fetlock joint. The longitudinal propulsive force peaked just after contact of the contralateral forelimb. During the swing phase the joints distal to the shoulder showed a single flexion cycle that peaked at 76% stride at the carpus, 81% stride at the fetlock and 84% stride at the elbow and coffin joints. The coffin and shoulder joints began to extend in the terminal swing phase and continued to extend through ground contact and early stance. The results provide normative data that will be applied in detecting changes in kinematics and ground reaction forces that are associated with specific lamenesses. PMID:10952376

  1. Analysis of kinematic data and determination of ground reaction force of foot in slow squat

    Zhang, Xu-Shu; Guo, Yuan; An, Mei-Wen; Chen, Wei-Yi

    2013-02-01

    In the present paper, the ground reaction force (GRF) acting on foot in slow squat was determined through a force measuring system, and at the same time, the kinematic data of human squat were obtained by analyzing the photographed image sequences. According to the height and body weight, six healthy volunteers were selected, three men in one group and the other three women in another group, and the fundamental parameters of subjects were recorded, including body weight, height and age, etc. Based on the anatomy characteristics, some markers were placed on the right side of joints. While the subject squatted at slow speed on the force platform, the ground reaction forces on the forefoot and heel for each foot were obtained through calibrated force platform. The analysis results show that the reaction force on heel is greater than that on forefoot, and double feet have nearly constant force. Moreover, from processing and analyzing the synchronously photographed image sequences in squat, the kinematic data of human squat were acquired, including mainly the curves of angle, angular velocity and angular acceleration varied with time for knee, hip and ankle joints in a sagittal plane. The obtained results can offer instructive reference for photographing and analyzing the movements of human bodies, diagnosing some diseases, and establishing in the future appropriate mathematical models for the human motion.

  2. New method for assessment of gait variability based on wearable ground reaction force sensor.

    Liu, Tao; Inoue, Yoshio; Shibata, Kyoko

    2008-01-01

    In this paper, a new quantitative method of analyzing gait variability using a developed wearable ground reaction force (GRF) sensor system is presented. The design of the sensor system is based on the use of five small 3-axial sensors distributed on the underside of a shoe, so that in human dynamics analysis this system can continuously measure vertical pressure force and bio-directional friction forces referring to anterior-posterior friction force and mediolateral friction force. Compared to existing spatio-temporal evaluation methods using traditional force plates or instrumented treadmills, the new method was developed based on measurements of ambulatory or wearable force sensor which can continuously measure ground reaction force in various environments not limited to the laboratory environment. The area of the center of pressure (CoP) distribution on the foot-plate and the average coefficient of variation of the 3-axial GRF, which correlate strongly with the distribution of CoP, are suggested parameters for quantifying gait variability. To certify the effectiveness of these parameters, we conducted an experimental study on a group of volunteer subjects who walked under a designed experimental protocol. PMID:19163171

  3. A rolling constraint reproduces ground reaction forces and moments in dynamic simulations of walking, running, and crouch gait

    Hamner, Samuel R.; Seth, Ajay; Steele, Katherine M.; Scott L. Delp

    2013-01-01

    Recent advances in computational technology have dramatically increased the use of muscle-driven simulation to study accelerations produced by muscles during gait. Accelerations computed from muscle-driven simulations are sensitive to the model used to represent contact between the foot and ground. A foot-ground contact model must be able to calculate ground reaction forces and moments that are consistent with experimentally measured ground reaction forces and moments. We show here that a rol...

  4. Ground reaction force estimation using an insole-type pressure mat and joint kinematics during walking.

    Jung, Yihwan; Jung, Moonki; Lee, Kunwoo; Koo, Seungbum

    2014-08-22

    Kinetic analysis of walking requires joint kinematics and ground reaction force (GRF) measurement, which are typically obtained from a force plate. GRF is difficult to measure in certain cases such as slope walking, stair climbing, and track running. Nevertheless, estimating GRF continues to be of great interest for simulating human walking. The purpose of the study was to develop reaction force models placed on the sole of the foot to estimate full GRF when only joint kinematics are provided (Type-I), and to estimate ground contact shear forces when both joint kinematics and foot pressure are provided (Type-II and Type-II-val). The GRF estimation models were attached to a commercial full body skeletal model using the AnyBody Modeling System, which has an inverse dynamics-based optimization solver. The anterior-posterior shear force and medial-lateral shear force could be estimated with approximate accuracies of 6% BW and 2% BW in all three methods, respectively. Vertical force could be estimated in the Type-I model with an accuracy of 13.75% BW. The accuracy of the force estimation was the highest during the mid-single-stance period with an average RMS for errors of 3.10% BW, 1.48% BW, and 7.48% BW for anterior-posterior force, medial-lateral force, and vertical force, respectively. The proposed GRF estimation models could predict full and partial GRF with high accuracy. The design of the contact elements of the proposed model should make it applicable to various activities where installation of a force measurement system is difficult, including track running and treadmill walking. PMID:24917473

  5. Bilateral ground reaction forces and joint moments for lateral sidestepping and crossover stepping tasks

    Sellers, William I.; Gregor Kuntze; Mansfield, Neil J.

    2009-01-01

    Racquet sports have high levels of joint injuries suggesting the joint loads during play may be excessive. Sports such as badminton employ lateral sidestepping (SS) and crossover stepping (XS) movements which so far have not been described in terms of biomechanics. This study examined bilateral ground reaction forces and three dimensional joint kinetics for both these gaits in order to determine the demands of the movements on the leading and trailing limb and predict the contribution of thes...

  6. Ground reaction forces and osteogenic index of the sport of cyclocross

    TOLLY, BRIAN; CHUMANOV, ELIZABETH; Brooks, Alison

    2014-01-01

    Weight-bearing activity has been shown to increase bone mineral density. Our purpose was to measure vertical ground reaction forces (GRFs) during cyclocross-specific activities and compute their osteogenic index (OI). Twenty-five healthy cyclocross athletes participated. GRF was measured using pressure-sensitive insoles during seated and standing cycling and four cyclocross-specific activities: barrier flat, barrier uphill, uphill run-up, downhill run-up. Peak and mean GRF values, according t...

  7. Effects of Different Lifting Cadences on Ground Reaction Forces during the Squat Exercise

    Bentley, Jason R.; Amonette, William E.; Hagan, R. Donald

    2008-01-01

    The purpose of this investigation was to determine the effect of different cadences on the ground reaction force (GRF(sub R)) during the squat exercise. It is known that squats performed with greater acceleration will produce greater inertial forces; however, it is not well understood how different squat cadences affect GRF(sub R). It was hypothesized that faster squat cadences will result in greater peak GRF(sub R). METHODS: Six male subjects (30.8+/-4.4 y, 179.5+/-8.9 cm, 88.8+/-13.3 kg) with previous squat experience performed three sets of three squats using three different cadences (FC = 1 sec descent/1 sec ascent; MC = 3 sec descent/1 sec ascent; SC = 4 sec descent/2 sec ascent) with barbell mass equal to body mass. Ground reaction force was used to calculate inertial force trajectories of the body plus barbell (FI(sub system)). Forces were normalized to body mass. RESULTS: Peak GRF(sub R) and peak FI(sub system) were significantly higher in FC squats compared to MC (p=0.0002) and SC (p=0.0002). Range of GRF(sub R) and FI(sub system) were also significantly higher in FC compared to MC (psquat cadences result in significantly greater peak GRF(sub R) due to the inertia of the system. GRF(sub R) was more dependent upon decent cadence than on ascent cadence. PRACTICAL APPLICATION: This study demonstrates that faster squat cadences produce greater ground reaction forces. Therefore, the use of faster squat cadences might enhance strength and power adaptations to long-term resistance exercise training. Key Words: velocity, weight training, resistive exercise

  8. GROUND REACTION FORCE DIFFERENCES BETWEEN RUNNING SHOES, RACING FLATS, AND DISTANCE SPIKES IN RUNNERS

    Suzanna Logan; Ian Hunter; J. Ty Hopkins; J.T., J. Brent Feland; Parcell, Allen C.

    2010-01-01

    Various shoes are worn by distance runners throughout a training season. This study measured the differences in ground reaction forces between running shoes, racing flats, and distance spikes in order to provide information about the potential effects of footwear on injury risk in highly competitive runners. Ten male and ten female intercollegiate distance runners ran across a force plate at 6.7 m·s-1 (for males) and 5.7 m·s-1 (for females) in each of the three types of shoes. To control for ...

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

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

    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 plat...

  10. Peripheral Arterial Disease Affects the Frequency Response of Ground Reaction Forces During Walking

    McGrath, Denise; Judkins, Timothy N.; Pipinos, Iraklis I.; Johanning, Jason M.; Myers, Sara A.

    2012-01-01

    Background Walking is problematic for patients with Peripheral Arterial Disease. The purpose of this study was to investigate the frequency domain of the ground reaction forces during walking to further elucidate the ambulatory impairment of these patients. Methods Nineteen bilateral peripheral arterial disease patients and nineteen controls were included in this study. Subjects were matched for age and gait speed. Participants walked over a force plate sampling at 600Hz. PAD patients were tested before (pain-free condition) after the onset of claudication symptoms (pain). We calculated median frequency, frequency bandwidth, and frequency containing 99.5% of the signal for the vertical and anterior-posterior ground reaction forces. Findings Our results showed reduced median frequency in the vertical and anterior-posterior components of the ground reaction forces between the control group and both peripheral arterial disease conditions. We found reduced frequency bandwidth in the anterior-posterior direction between controls and the peripheral arterial disease pain-free condition. There were no differences in median frequency or bandwidth between peripheral arterial disease pain-free and pain conditions, but an increase in the frequency content for 99.5% of the signal was observed in the pain condition. Interpretation Reduced frequency phenomena during gait in peripheral arterial disease patients compared to velocity-matched controls suggests more sluggish activity within the neuromotor system. Increased frequency phenomena due to pain in these patients suggests a more erratic application of propulsive forces when walking. Frequency domain analysis thus offers new insights into the gait impairments associated with this patient population. PMID:22967739

  11. Ground reaction forces and loading rates associated with parkour and traditional drop landing techniques.

    Puddle, Damien L; Maulder, Peter S

    2013-01-01

    Due to the relative infancy of Parkour there is currently a lack of empirical evidence on which to base specific technique instruction upon. The purpose of this study was to compare the ground reaction forces and loading rates involved in two Parkour landing techniques encouraged by local Parkour instructors and a traditional landing technique recommended in the literature. Ten male participants performed three different drop landing techniques (Parkour precision, Parkour roll, and traditional) onto a force plate. Compared to the traditional technique the Parkour precision technique demonstrated significantly less maximal vertical landing force (38%, p Parkour roll technique compared to the traditional technique. It is unclear whether or not the Parkour precision technique produced lower landing forces and loading rates than the Parkour roll technique as no significant differences were found. The landing techniques encouraged by local Parkour instructors such as the precision and roll appear to be more appropriate for Parkour practitioners to perform than a traditional landing technique due to the lower landing forces and loading rates experienced. Key pointsParkour precision and Parkour roll landings were found to be safer than a traditional landing technique, resulting in lower maximal vertical forces, slower times to maximal vertical force and ultimately lesser loading rates.Parkour roll may be more appropriate (safer) to utilize than the Parkour precision during Parkour landing scenarios.The Parkour landing techniques investigated n this study may be beneficial for landing by non-Parkour practitioners in everyday life. PMID:24149735

  12. Foot-ground reaction force during resistive exercise in parabolic flight

    Lee, Stuart M C.; Cobb, Kendall; Loehr, James A.; Nguyen, Daniel; Schneider, Suzanne M.

    2004-01-01

    INTRODUCTION: An interim resistance exercise device (iRED) was designed to provide resistive exercise as a countermeasure to spaceflight-induced loss of muscle strength and endurance as well as decreased bone mineral density. The purpose of this project was to compare foot-ground reaction force during iRED exercise in normal gravity (1 G) vs. microgravity (0 G) achieved during parabolic flight. METHODS: There were four subjects who performed three exercises (squat, heel raise, and deadlift) using the iRED during 1 G and 0 G at a moderate intensity (60% of maximum strength during deadlift exercise). Foot-ground reaction force was measured in the three orthogonal axes (x, y, z) using a force plate, and the magnitude of the resultant force vector was calculated (r = square root(x2 + y2 + z2)). Linear displacement (LD) was measured using a linear transducer. Peak force (Fpeak) and an index of total work (TWi) were calculated using a customized computer program. Paired t-tests were used to test if significant differences (p exercise. RESULTS: Fpeak and TWi measured in the resultant axis were significantly less in 0 G for each of the exercises tested. During 0 G, Fpeak was 42-46% and TWi was 33-37% of that measured during 1 G. LD and average time to complete each repetition were not different from 1 G to 0 G. CONCLUSIONS: Crewmembers who perform resistive exercises during spaceflight that include the movement of a large portion of their body mass will require much greater external resistive force during 0 G than 1 G exercise to provide a sufficient stimulus to maintain muscle and bone mass.

  13. A Comparison of Ground Reaction Forces Determined by Portable Force-Plate and Pressure-Insole Systems in Alpine Skiing

    Nakazato, Kosuke; Scheiber, Peter; Müller, Erich

    2011-01-01

    For the determination of ground reaction forces in alpine skiing, pressure insole (PI) systems and portable force plate (FP) systems are well known and widely used in previous studies. The purposes of this study were 1) to provide reference data for the vertical component of the ground reaction forces (vGRF) during alpine skiing measured by the PI and FP systems, and 2) to analyze whether the differences in the vGRF measured by the PI and the FP depend on a skier’s level, skiing mode and pitch. Ten expert and ten intermediate level skiers performed 10 double turns with the skiing technique “Carving in Short Radii” as High Dynamic Skiing mode and “Parallel Ski Steering in Long Radii” as Low Dynamic Skiing mode on both the steep (23 °) and the flat (15 °) slope twice. All subjects skied with both the PI and the FP system simultaneously. During the outside phase, the mean vGRF and the maximum vGRF determined by the FP are greater than the PI (p skiing modes of Experts and Intermediates (p skiing mode performed and pitch. Key points Typically, during the steering phases of the ski turns the total vGRFs measured by the pressure-insole system were lower compared to the portable force-plate system. However, in some skiing modes during the edge changing phase, the pressure-insole system overestimates the total vGRF compared to the portable force-plate system. Differences between the forces determined by the both systems depend on the phase in the turn (inside, outside, edge changing) and are affected additionally by the skier’s level, the performed skiing mode and pitch. PMID:24149570

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

    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

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

    Natália Mariana Silva Luna

    2012-09-01

    Full Text Available 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 nonathletes. 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 (180º/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 (60º/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.

  16. GROUND REACTION FORCES AND LOADING RATES ASSOCIATED WITH PARKOUR AND TRADITIONAL DROP LANDING TECHNIQUES

    Damien L. Puddle

    2013-03-01

    Full Text Available Due to the relative infancy of Parkour there is currently a lack of empirical evidence on which to base specific technique instruction upon. The purpose of this study was to compare the ground reaction forces and loading rates involved in two Parkour landing techniques encouraged by local Parkour instructors and a traditional landing technique recommended in the literature. Ten male participants performed three different drop landing techniques (Parkour precision, Parkour roll, and traditional onto a force plate. Compared to the traditional technique the Parkour precision technique demonstrated significantly less maximal vertical landing force (38%, p < 0.01, ES = 1.76 and landing loading rate (54%, p < 0.01, ES = 1.22. Similarly, less maximal vertical landing force (43%, p < 0.01, ES = 2.04 and landing loading rate (63%, p < 0.01, ES = 1.54 were observed in the Parkour roll technique compared to the traditional technique. It is unclear whether or not the Parkour precision technique produced lower landing forces and loading rates than the Parkour roll technique as no significant differences were found. The landing techniques encouraged by local Parkour instructors such as the precision and roll appear to be more appropriate for Parkour practitioners to perform than a traditional landing technique due to the lower landing forces and loading rates experienced

  17. GROUND REACTION FORCE DIFFERENCES BETWEEN RUNNING SHOES, RACING FLATS, AND DISTANCE SPIKES IN RUNNERS

    Suzanna Logan

    2010-03-01

    Full Text Available Various shoes are worn by distance runners throughout a training season. This study measured the differences in ground reaction forces between running shoes, racing flats, and distance spikes in order to provide information about the potential effects of footwear on injury risk in highly competitive runners. Ten male and ten female intercollegiate distance runners ran across a force plate at 6.7 m·s-1 (for males and 5.7 m·s-1 (for females in each of the three types of shoes. To control for differences in foot strike, only subjects who exhibited a heel strike were included in the data analysis. Two repeated-measures ANOVAs with Tukey's post-hoc tests (p < 0.05 were used to detect differences in shoe types among males and females. For the males, loading rate, peak vertical impact force and peak braking forces were significantly greater in flats and spikes compared to running shoes. Vertical stiffness in spikes was also significantly greater than in running shoes. Females had significantly shorter stance times and greater maximum propulsion forces in racing flats compared to running shoes. Changing footwear between the shoes used in this study alters the loads placed on the body. Care should be taken as athletes enter different phases of training where different footwear is required. Injury risk may be increased since the body may not be accustomed to the differences in force, stance time, and vertical stiffness

  18. Foot-Ground Reaction Force During Resistance Exercise in Parabolic Flight

    Lee, Stuart M. C.; Cobb, Kendall; Loehr, James A.; Nguyen, Daniel; Schneider, Suzanne M.

    2003-01-01

    An interim Resistance Exercise Device (iRED) was designed to provide resistive exercise as a countermeasure to space flight-induced loss of muscle strength and endurance as well as decreased bone mineral density. The purpose of this project was to compare foot-ground reaction force during iRED exercise in normal gravity (l-g) versus micro gravity (O-g) achieved during parabolic flight. METHODS: Four subjects performed three exercises using the iRED (squat, heel raise, and deadlift) during I-g and O-g at a moderate intensity (60% of maximum strength during deadlift exercise). Foot-ground reaction force was measured in three axes (x,y,z) using a force plate, and the magnitude of the resultant force vector was calculated (r = X 2 + y2 + Z2 ). Range of motion (ROM) was measured using a linear encoder. Peak force (PkF) and total work (TW) were calculated using a customized computer program. Paired t-tests were used to test if significant differences (p.::::0.05) were observed between I-g and O-g exercise. RESULTS: PkF and TW measured in the resultant axis were significantly less in O-g for each of the exercises tested. During O-g, PkF was 42-46% and TW was 33- 37% of that measured during I-g. ROM and average time to complete each repetition were not different from I-g to O-g. CONCLUSIONS: When performing exercises in which body mass is a portion of the resistance during I-g, PkF and TW measured during resistive exercise were reduced approximately 60-70% during O-g. Thus, a resistive exercise device during O-g will be required to provided higher resistances to induce a similar training stimulus to that on Earth.

  19. A comparison of golf shoe designs highlights greater ground reaction forces with shorter irons.

    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

  20. Measurement differences between three versus five photocells during collection of ground reaction forces in dogs.

    Punke, J P; Speas, A L; Reynolds, L R; Andrews, C M; Budsberg, S C

    2007-01-01

    The differences between velocities and accelerations obtained from three and five photocells were examined when obtaining ground reaction force (GRF) data in dogs. Ground reaction force data was collected 259 times from 16 different dogs in two experimental phases. The first phase compared velocities and accelerations reported by the two systems based on trials accepted by the three photocell system. The second phase accepted trials based on data from five photocells. Three photocell data were calculated mathematically in the second phase in order to compare the values of both systems. The velocity and acceleration values obtained from each system were significantly different (at the hundredth of a meter per second). Differences in measured values did not result in acceptance of data by the three photocell system that would not have been acceptable with the five photocell system (false positives), but did result in rejection of acceptable data by the three photocell system (11% false negative rate). Given the small differences between the two systems, GRF data collected should not be significantly different, though the three photocell system is less efficient in gathering data due to the number of trials rejected as false negatives. PMID:17546209

  1. Assessment of changes in gait parameters and vertical ground reaction forces after total hip arthroplasty

    Bhargava P

    2007-01-01

    Full Text Available The principal objectives of arthroplasty are relief of pain and enhancement of range of motion. Currently, postoperative pain and functional capacity are assessed largely on the basis of subjective evaluation scores. Because of the lack of control inherent in this method it is often difficult to interpret data presented by different observers in the critical evaluation of surgical method, new components and modes of rehabilitation. Gait analysis is a rapid, simple and reliable method to assess functional outcome. This study was undertaken in an effort to evaluate the gait characteristics of patients who underwent arthroplasty, using an Ultraflex gait analyzer. Materials and Methods: The study was based on the assessment of gait and weight-bearing pattern of both hips in patients who underwent total hip replacement and its comparison with an age and sex-matched control group. Twenty subjects of total arthroplasty group having unilateral involvement, operated by posterior approach at our institution with a minimum six-month postoperative period were selected. Control group was age and sex-matched, randomly selected from the general population. Gait analysis was done using Ultraflex gait analyzer. Gait parameters and vertical ground reaction forces assessment was done by measuring the gait cycle properties, step time parameters and VGRF variables. Data of affected limb was compared with unaffected limb as well as control group to assess the weight-bearing pattern. Statistical analysis was done by′t′ test. Results: Frequency is reduced and gait cycle duration increased in total arthroplasty group as compared with control. Step time parameters including Step time, Stance time and Single support time are significantly reduced ( P value < .05 while Double support time and Single swing time are significantly increased ( P value < .05 in the THR group. Forces over each sensor are increased more on the unaffected limb of the THR group as compared to the control group. Vertical ground reaction force variables are also altered. Conclusion: Significant changes ( P value < .05 in gait parameters and vertical ground reaction forces show that gait pattern is not normalized after THR and weight-bearing is not equally shared by both hips. Patient walks with residual antalgic gait even after surgery, which results in abnormal loading around hip joints and the integrity of the prosthesis fixation could be compromised.

  2. A COMPARISON OF GROUND REACTION FORCES DETERMINED BY PORTABLE FORCE-PLATE AND PRESSURE-INSOLE SYSTEMS IN ALPINE SKIING

    Kosuke Nakazato

    2011-12-01

    Full Text Available For the determination of ground reaction forces in alpine skiing, pressure insole (PI systems and portable force plate (FP systems are well known and widely used in previous studies. The purposes of this study were 1 to provide reference data for the vertical component of the ground reaction forces (vGRF during alpine skiing measured by the PI and FP systems, and 2 to analyze whether the differences in the vGRF measured by the PI and the FP depend on a skier's level, skiing mode and pitch. Ten expert and ten intermediate level skiers performed 10 double turns with the skiing technique "Carving in Short Radii" as High Dynamic Skiing mode and "Parallel Ski Steering in Long Radii" as Low Dynamic Skiing mode on both the steep (23 ° and the flat (15 ° slope twice. All subjects skied with both the PI and the FP system simultaneously. During the outside phase, the mean vGRF and the maximum vGRF determined by the FP are greater than the PI (p < 0.01. Additionally during the inside phase, the mean vGRF determined by the FP were greater than the PI (p < 0.01. During the edge changing phases, the mean vGRF determined by the FP were greater than the PI (p < 0.01. However, the minimum vGRF during the edge changing phases determined by the FP were smaller than the PI (p < 0.01 in the High-Steep skiing modes of Experts and Intermediates (p < 0.001. We have found that generally, the PI system underestimates the total vGRF compared to the FP system. However, this difference depends not only the phase in the turn (inside, outside, edge changing, but also is affected by the skier's level, the skiing mode performed and pitch.

  3. Gender Differences among Sagittal Plane Knee Kinematic and Ground Reaction Force Characteristics during a Rapid Sprint and Cut Maneuver

    James, C. Roger; Sizer, Phillip S.; Starch, David W.; Lockhart, Thurmon E.; Slauterbeck, James

    2004-01-01

    Women are more prone to anterior cruciate ligament (ACL) injury during cutting sports than men. The purpose of this study was to examine knee kinematic and ground reaction forces (GRF) differences between genders during cutting. Male and female athletes performed cutting trials while force platform and video data were recorded (180 Hz).…

  4. Ground reaction forces and frictional demands during stair descent: effects of age and illumination.

    Christina, Kathryn A; Cavanagh, Peter R

    2002-04-01

    Stair descent is an inherently risky and demanding task that older adults often encounter in everyday life. It is believed that slip between the foot or shoe sole and the stair surface may play a role in stair related falls, however, there are no reports on slip resistance requirements for stair descent. The aim of this study was to determine the required coefficient of friction (RCOF) necessary for safe stair descent in 12 young and 12 older adults, under varied illuminance conditions. The RCOF during stair descent was found to be comparable in magnitude and time to that for overground walking, and thus, with adequate footwear and dry stair surfaces, friction does not appear to be a major determinant of stair safety. Illuminance level had little effect on the dependent variables quantified in this study. However, the older participants demonstrated safer strategies than the young during stair descent, as reflected by differences in the ground reaction forces and lower RCOF. PMID:11869909

  5. Habituation of healthy dogs to treadmill trotting: repeatability assessment of vertical ground reaction force.

    Fanchon, Laurent; Grandjean, Dominique

    2009-08-01

    To assess the repeatability of kinetic gait analysis with a treadmill, 28 sound adult dogs were made to trot on an instrumented system. Vertical ground reaction force variables (Peak PFz and Impulse IFz) were collected by 10-s recordings, once a week, 4 weeks in succession. Data were analysed using a repeated-measures two-way ANOVA to investigate habituation to treadmill locomotion. Recorded data were stabilized from the end of the first and second sessions for IFz and PFz, respectively. The percentages of variance attributable to dogs, weeks, minutes and repetitions were, respectively, 72%, 10%, 7%, and 11% for PFz and 84%, 7%, 3%, and 6% for IFz. Habituation occurred after a single training session. Good repeatability was determined by a low coefficient of variation (3.4-4.7%). Adding a treadmill to kinetic gait analysis deserves consideration: reliable data are easily recorded using appropriate habituation and statistical model. PMID:19121530

  6. Machine learning techniques for gait biometric recognition using the ground reaction force

    Mason, James Eric; Woungang, Isaac

    2016-01-01

    This book focuses on how machine learning techniques can be used to analyze and make use of one particular category of behavioral biometrics known as the gait biometric. A comprehensive Ground Reaction Force (GRF)-based Gait Biometrics Recognition framework is proposed and validated by experiments. In addition, an in-depth analysis of existing recognition techniques that are best suited for performing footstep GRF-based person recognition is also proposed, as well as a comparison of feature extractors, normalizers, and classifiers configurations that were never directly compared with one another in any previous GRF recognition research. Finally, a detailed theoretical overview of many existing machine learning techniques is presented, leading to a proposal of two novel data processing techniques developed specifically for the purpose of gait biometric recognition using GRF. This book · introduces novel machine-learning-based temporal normalization techniques · bridges research gaps concerning the effect of ...

  7. Analysis of Vertical Ground Reaction Force Variables during a Sit to Stand Task in Participants Recovering from a Hip Fracture

    Houck, Jeff; Kneiss, Janet; Bukata, Susan V.; Puzas, J. Edward

    2011-01-01

    Background A sit to stand task following a hip fracture may be achieved through compensations (e.g. bilateral arms and uninvolved lower extremity), not restoration of movement strategies of the involved lower extremity. The primary purpose was to compare upper and lower extremity movement strategies using the vertical ground reaction force during a sit to stand task in participants recovering from a hip fracture to control participants. The secondary purpose was to evaluate the correlation between vertical ground reaction force variables and validated functional measures. Methods Twenty eight community dwelling older adults, 14 who had a hip fracture and 14 control participants completed the Sit to Stand task on an instrumented chair designed to measure vertical ground reaction force, performance based tests (Timed up and go, Berg Balance Scale and gait speed) and a self report Lower Extremity Measure. A MANOVA was used to compare functional scales and vertical ground reaction force variables between groups. Bivariate correlations were assessed using Pearson Product Moment correlations. Findings The vertical ground reaction force variables showed significantly higher bilateral arm force, higher uninvolved side peak force and asymmetry between the involved and uninvolved sides for the participants recovering from a hip fracture (Wilks’ Lambda = 3.16, p = 0.019). Significant correlations existed between the vertical ground reaction force variables and validated functional measures. Interpretation Participants recovering from a hip fracture compensated using their arms and the uninvolved side to perform a Sit to Stand. Lower extremity movement strategies captured during a Sit to Stand task were correlated to scales used to assess function, balance and falls risk. PMID:21196069

  8. Validity and reliability of pressure-measurement insoles for vertical ground reaction force assessment in field situations.

    Koch, Markus; Lunde, Lars-Kristian; Ernst, Michael; Knardahl, Stein; Veiersted, Kaj Bo

    2016-03-01

    This study aimed to test the validity and reliability of pressure-measurement insoles (medilogic(®) insoles) when measuring vertical ground reaction forces in field situations. Various weights were applied to and removed from the insoles in static mechanical tests. The force values measured simultaneously by the insoles and force plates were compared for 15 subjects simulating work activities. Reliability testing during the static mechanical tests yielded an average interclass correlation coefficient of 0.998. Static loads led to a creeping pattern of the output force signal. An individual load response could be observed for each insole. The average root mean square error between the insoles and force plates ranged from 6.6% to 17.7% in standing, walking, lifting and catching trials and was 142.3% in kneeling trials. The results show that the use of insoles may be an acceptable method for measuring vertical ground reaction forces in field studies, except for kneeling positions. PMID:26674403

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

    Paul Worsfold; 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 platfo...

  10. Effect of surgery to implant motion and force sensors on vertical ground reaction forces in the ovine model.

    Herfat, Safa T; Shearn, Jason T; Bailey, Denis L; Greiwe, R Michael; Galloway, Marc T; Gooch, Cindi; Butler, David L

    2011-02-01

    Activities of daily living (ADLs) generate complex, multidirectional forces in the anterior cruciate ligament (ACL). While calibration problems preclude direct measurement in patients, ACL forces can conceivably be measured in animals after technical challenges are overcome. For example, motion and force sensors can be implanted in the animal but investigators must determine the extent to which these sensors and surgery affect normal gait. Our objectives in this study were to determine (1) if surgically implanting knee motion sensors and an ACL force sensor significantly alter normal ovine gait and (2) how increasing gait speed and grade on a treadmill affect ovine gait before and after surgery. Ten skeletally mature, female sheep were used to test four hypotheses: (1) surgical implantation of sensors would significantly decrease average and peak vertical ground reaction forces (VGRFs) in the operated limb, (2) surgical implantation would significantly decrease single limb stance duration for the operated limb, (3) increasing treadmill speed would increase VGRFs pre- and post operatively, and (4) increasing treadmill grade would increase the hind limb VGRFs pre- and post operatively. An instrumented treadmill with two force plates was used to record fore and hind limb VGRFs during four combinations of two speeds (1.0 m/s and 1.3 m/s) and two grades (0 deg and 6 deg). Sensor implantation decreased average and peak VGRFs less than 10% and 20%, respectively, across all combinations of speed and grade. Sensor implantation significantly decreased the single limb stance duration in the operated hind limb during inclined walking at 1.3 m/s but had no effect on single limb stance duration in the operated limb during other activities. Increasing treadmill speed increased hind limb peak (but not average) VGRFs before surgery and peak VGRF only in the unoperated hind limb during level walking after surgery. Increasing treadmill grade (at 1 m/s) significantly increased hind limb average and peak VGRFs before surgery but increasing treadmill grade post op did not significantly affect any response measure. Since VGRF values exceeded 80% of presurgery levels, we conclude that animal gait post op is near normal. Thus, we can assume normal gait when conducting experiments following sensor implantation. Ultimately, we seek to measure ACL forces for ADLs to provide design criteria and evaluation benchmarks for traditional and tissue engineered ACL repairs and reconstructions. PMID:21280882

  11. The effects of baseball bat mass properties on swing mechanics, ground reaction forces, and swing timing.

    Laughlin, Walter A; Fleisig, Glenn S; Aune, Kyle T; Diffendaffer, Alek Z

    2016-03-01

    Swing trajectory and ground reaction forces (GRF) of 30 collegiate baseball batters hitting a pitched ball were compared between a standard bat, a bat with extra weight about its barrel, and a bat with extra weight in its handle. It was hypothesised that when compared to a standard bat, only a handle-weighted bat would produce equivalent bat kinematics. It was also hypothesised that hitters would not produce equivalent GRFs for each weighted bat, but would maintain equivalent timing when compared to a standard bat. Data were collected utilising a 500 Hz motion capture system and 1,000 Hz force plate system. Data between bats were considered equivalent when the 95% confidence interval of the difference was contained entirely within ±5% of the standard bat mean value. The handle-weighted bat had equivalent kinematics, whereas the barrel-weighted bat did not. Both weighted bats had equivalent peak GRF variables. Neither weighted bat maintained equivalence in the timing of bat kinematics and some peak GRFs. The ability to maintain swing kinematics with a handle-weighted bat may have implications for swing training and warm-up. However, altered timings of kinematics and kinetics require further research to understand the implications on returning to a conventionally weighted bat. PMID:26836969

  12. Residual analysis of ground reaction forces simulation during gait using neural networks with different configurations.

    Leporace, Gustavo; Batista, Luiz Alberto; Metsavaht, Leonardo; Nadal, Jurandir

    2015-08-01

    The aim of the study was to analyze and compare the residuals obtained from ground reaction force (GRF) models developed using two different neural network configurations (one network with three outputs; and three networks with one output each), based on accelerometer data. Seventeen healthy subjects walked along a walkway, with a force plate embedded, with a three dimensional accelerometer attached to the shank. Multilayer perceptron networks (MLP) models were developed with the 3D accelerometer data as inputs to predict the GRF. The residuals of these models were evaluated graphically and numerically to verify the fitting. A visual analysis of the simulated signals suggests the model was able to adequately predict the GRF. The errors and correlations found in the MLP models for the 3D GRF is at least similar to other studies, although some of them showed higher errors. There was not difference between the two MLP configurations. However, despite the high correlation coefficient and closeness to a normal probability distribution, the residual analysis still presented a higher kurtosis and skewness, suggesting that the inclusion of other variables and the increase of the validation sample size could increase the fitting of the simulation. PMID:26736876

  13. A rolling constraint reproduces ground reaction forces and moments in dynamic simulations of walking, running, and crouch gait.

    Hamner, Samuel R; Seth, Ajay; Steele, Katherine M; Delp, Scott L

    2013-06-21

    Recent advances in computational technology have dramatically increased the use of muscle-driven simulation to study accelerations produced by muscles during gait. Accelerations computed from muscle-driven simulations are sensitive to the model used to represent contact between the foot and ground. A foot-ground contact model must be able to calculate ground reaction forces and moments that are consistent with experimentally measured ground reaction forces and moments. We show here that a rolling constraint can model foot-ground contact and reproduce measured ground reaction forces and moments in an induced acceleration analysis of muscle-driven simulations of walking, running, and crouch gait. We also illustrate that a point constraint and a weld constraint used to model foot-ground contact in previous studies produce inaccurate reaction moments and lead to contradictory interpretations of muscle function. To enable others to use and test these different constraint types (i.e., rolling, point, and weld constraints) we have included them as part of an induced acceleration analysis in OpenSim, a freely-available biomechanics simulation package. PMID:23702045

  14. Metabolic Rate and Ground Reaction Force During Motorized and Non-Motorized Treadmill Exercise

    Everett, Meghan E.; Loehr, James A.; DeWitt, John K.; Laughlin, Mitzi; Lee, Stuart M. C.

    2010-01-01

    PURPOSE: To measure vertical ground reaction force (vGRF) and oxygen consumption (VO2) at several velocities during exercise using a ground-based version of the ISS treadmill in the M and NM modes. METHODS: Subjects (n = 20) walked or ran at 0.89, 1.34, 1.79, 2.24, 2.68, and 3.12 m/s while VO2 and vGRF data were collected. VO2 was measured using open-circuit spirometry (TrueOne 2400, Parvo-Medics). Data were averaged over the last 2 min of each 5-min stage. vGRF was measured in separate 15-s bouts at 125 Hz using custom-fitted pressure-sensing insoles (F-Scan Sport Sensors, Tekscan, Inc). A repeated-measures ANOVA was used to test for differences in VO2 and vGRF between M and NM and across speeds. Significance was set at P < 0.05. RESULTS: Most subjects were unable to exercise for 5 min at treadmill speeds above 1.79 m/s in the NM mode; however, vGRF data were obtained for all subjects at each speed in both modes. VO2 was approx.40% higher during NM than M exercise across treadmill speeds. vGRF increased with treadmill speed but was not different between modes. CONCLUSION: Higher VO2 with no change in vGRF suggests that the additional metabolic cost associated with NM treadmill exercise is accounted for in the horizontal forces required to move the treadmill belt. Although this may limit the exercise duration at faster speeds, high-intensity NM exercise activates the hamstrings and plantarflexors, which are not specifically targeted or well protected by other in-flight countermeasures.

  15. A wearable force plate system for the continuous measurement of triaxial ground reaction force in biomechanical applications

    The ambulatory measurement of ground reaction force (GRF) and human motion under free-living conditions is convenient, inexpensive and never restricted to gait analysis in a laboratory environment and is therefore much desired by researchers and clinical doctors in biomedical applications. A wearable force plate system was developed by integrating small triaxial force sensors and three-dimensional (3D) inertial sensors for estimating dynamic triaxial GRF in biomechanical applications. The system, in comparison to existent systems, is characterized by being lightweight, thin and easy-to-wear. A six-axial force sensor (Nitta Co., Japan) was used as a verification measurement device to validate the static accuracy of the developed force plate. To evaluate the precision during dynamic gait measurements, we compared the measurements of the triaxial GRF and the center of pressure (CoP) by using the developed system with the reference measurements made using a stationary force plate and an optical motion analysis system. The root mean square (RMS) differences of the two transverse components (x- and y-axes) and the vertical component (z-axis) of the GRF were 4.3 ± 0.9 N, 6.0 ± 1.3 N and 12.1 ± 1.1 N, respectively, corresponding to 5.1 ± 1.1% and 6.5 ± 1% of the maximum of each transverse component and 1.3 ± 0.2% of the maximum vertical component of GRF. The RMS distance between the two systems' CoP traces was 3.2 ± 0.8 mm, corresponding to 1.2 ± 0.3% of the length of the shoe. Moreover, based on the results of the assessment of the influence of the system on natural gait, we found that gait was almost never affected. Therefore, the wearable system as an alternative device can be a potential solution for measuring CoP and triaxial GRF in non-laboratory environments

  16. The measurement of ground reaction force in dogs trotting on a treadmill: an investigation of habituation.

    Fanchon, L; Valette, J-P; Sanaa, M; Grandjean, D

    2006-01-01

    We studied the time necessary to obtain reliable kinetic data from healthy dogs trotting on a treadmill. Ten adult male Malinois Belgian Shepherd dogs were made to trot on an instrumented treadmill to record the ground reaction force for the entire body and to determine the vertical force variables (peak [PFz], impulse [IFz], stride time [Str], peak time [Tz] and contact time [Ct]). Data were collected from each dog, during three sequences per day, on three consecutive days. In order to determine the contribution of the sequence, day of measurement, and dog factors and the percentage of variance attributable to dogs, data were analyzed with a linear mixed model. The curve shapes were similar to those obtained with a floor-mounted force platform. Intra-dog coefficients of variation were between 1.57 and 3.46%. Inter-dog coefficients of variation were between 4.18 and 7.82%. A sequence effect was not noted. Each day had a significant effect on all of the data. All variables differed significantly from the first day compared to the other days. However there was not any difference between days 2 and 3. The percentage of the total variance attributable to dogs ranged from 37 to 88%. The coefficients of variation were lower than those obtained with common protocols. The treadmill locomotion remained consistent during a single session. Even if interday variation needs to be accounted for, reliable data can still be obtained after a single training session. The majority of the variation was attributable to the dog. An instrumented treadmill may be used for kinetic analysis. PMID:16810349

  17. Effects of slip-induced changes in ankle movement on muscle activity and ground reaction forces during running acceleration

    Ketabi, Shahin; Kersting, Uwe G.

    Ground contact in running is always linked to a minimum amount of slipping, e.g., during the early contact phase when horizontal forces are high compared to vertical forces. Studies have shown altered muscular activation when expecting slips [2-4]. It is not known what the mechanical effect of such...... slip episodes are on joint loading or performance. The aim of the present study was to examine the effect of changes in ankle movement on ankle joint loading, muscle activity, and ground reaction forces during linear acceleration....

  18. Sensors' Ground Reaction Force behavior for both Normal and Parkinson subjects - A qualitative study.

    Alkhatib, R; Corbier, C; El Badaoui, M; Moslem, B; Diab, M O

    2015-08-01

    Characterization of normal and abnormal Gait has been a major research field for decades, whether in fall prevention, sports biomechanics or even disease indication. In this paper, we assess time domain statistical properties of the Vertical Ground Reaction Force (VGRF) during moderate-pace walking, aiming eventually to create a reliable mathematical model of VGRF for normal and abnormal cases. For that endeavor, first order statistical analysis was performed upon signal segmentation in order to determine the degree of stationarity and base the model upon it. Furthermore, we performed curve fitting of the VGRF time series between present and past values, which led us to model the waveform with linear regression via Autoregressive Model for both Normal Walking Signals and Parkinson diseased patients' walking signals. However this is done only for one chosen sensor. However, it would be crucial to take the advantage of the array of sensors. Evaluating the cross-covariance between multi-sensor data of a given subject at different time lags capture the most important information. The seasonality in the values give a quite important indications of the behavior of data. The objective behind this analysis is to recommend a preliminary basis to create reliable mathematical model of normal walking signals versus pathological walking signals, that we will emphasize in a complementary work, in the simplest way available and creating fall prevention indicators for old patients. PMID:26737217

  19. Subject recognition based on ground reaction force measurements of gait signals.

    Moustakidis, Serafeim P; Theocharis, John B; Giakas, Giannis

    2008-12-01

    An effective subject recognition approach is designed in this paper, using ground reaction force (GRF) measurements of human gait. The method is a three-stage procedure: 1) The original GRF data are translated through wavelet packet (WP) transform in the time-frequency domain. Using a fuzzy-set-based criterion, we determine an optimal WP decomposition, involving feature subspaces with distinguishing gait characteristics. 2) A feature extraction scheme is employed next for wavelet feature ranking, according to discrimination power. 3) The classification task is accomplished by means of a kernel-based support vector machine. The design parameters of the classifier are tuned through a genetic algorithm to improve recognition rates. The method is evaluated on a database comprising GRF records obtained from 40 subjects. To account for the natural variability of human gait, the experimental setup is designed, allowing different walking speeds and loading conditions. Simulation results demonstrate that high recognition rates can be achieved with moderate number of features and for different training/testing settings. Finally, the performance of our approach is favorably compared with the one obtained using other traditional classification algorithms. PMID:19022720

  20. Abdominal Bracing Increases Ground Reaction Forces and Reduces Knee and Hip Flexion During Landing.

    Campbell, Amity; Kemp-Smith, Kevin; O'Sullivan, Peter; Straker, Leon

    2016-04-01

    Study Design Controlled laboratory study. Background Abdominal bracing (AB) is a widely advocated method of increasing spine stability, yet the influence of AB on the execution of sporting movements has not been quantified. Landing is a common task during sporting endeavors; therefore, investigating the effect of performing AB during a drop-landing task is relevant. Objective To quantify the effect of AB on kinematics (ankle, knee, hip, and regional lumbar spine peak flexion angles) and peak vertical ground reaction force (vGRF) during a drop-landing task. Methods Sixteen healthy adults (7 female, 9 male; mean ± SD age, 27 ± 7 years; height, 170.6 ± 8.1 cm; mass, 68.0 ± 11.3 kg) were assessed using 3-D motion analysis, electromyography (EMG), and a force platform while performing a drop-landing task with and without AB. Abdominal bracing was achieved with the assistance of real-time internal oblique EMG feedback. Lower-limb and regional lumbar spine kinematics, peak vGRF, and normalized EMG of the left and right internal obliques and lumbar multifidus were quantified. Paired-samples t tests were used to compare variables between the AB and no-AB conditions. Results Abdominal bracing resulted in significantly reduced knee and hip flexion and increased peak vGRF during landing. No differences in lumbar multifidus EMG or lumbar spine kinematics were observed. Conclusion Abdominal bracing reduces impact attenuation during landing. These altered biomechanics may have implications for lower-limb and spinal injury risk during dynamic tasks. J Orthop Sports Phys Ther 2016;46(4):286-292. Epub 8 Mar 2016. doi:10.2519/jospt.2016.5774. PMID:26954271

  1. Squat Ground Reaction Force on a Horizontal Squat Device, Free Weights, and Smith Machine

    Scott-Pandorf, Melissa M.; Newby, Nathaniel J.; Caldwell, Erin; DeWitt, John K.; Peters, Brian T.

    2010-01-01

    Bed rest is an analog to spaceflight and advancement of exercise countermeasures is dependent on the development of exercise equipment that closely mimic actual upright exercise. The Horizontal Squat Device (HSD) was developed to allow a supine exerciser to perform squats that mimic upright squat exercise. PURPOSE: To compare vertical ground reaction force (GRFv) on the HSD with Free Weight (FW) or Smith Machine (SM) during squat exercise. METHODS: Subjects (3F, 3M) performed sets of squat exercise with increasing loads up to 1-repetition (rep) maximum. GRF data were collected and compared with previous GRF data for squat exercise performed with FW & SM. Loads on the HSD were adjusted to magnitudes comparable with FW & SM by subtracting the subject s body weight (BW). Peak GRFv for 45-, 55-, 64-, & 73-kg loads above BW were calculated. Percent (%) difference between HSD and the two upright conditions were computed. Effect size was calculated for the 45-kg load. RESULTS: Most subjects were unable to lift >45 kg on the HSD; however, 1 subject completed all loads. Anecdotal evidence suggested that most subjects shoulders or back failed before their legs. The mean % difference are shown. In the 45-kg condition, effect sizes were 0.37 & 0.83 (p>0.05) for HSD vs. FW and HSD vs. SM, respectively, indicating no differences between exercise modes. CONCLUSION: When BW was added to the target load, results indicated that vertical forces were similar to those in FW and SM exercise. The exercise prescription for the HSD should include a total external resistance equivalent to goal load plus subject BW. The HSD may be used as an analog to upright exercise in bed rest studies, but because most subjects were unable to lift >45 kg, it may be necessary to prescribe higher reps and lower loads to better target the leg musculature

  2. Ground reaction force and 3D biomechanical characteristics of walking in short-leg walkers.

    Zhang, Songning; Clowers, Kurt G; Powell, Douglas

    2006-12-01

    Short-leg walking boots offer several advantages over traditional casts. However, their effects on ground reaction forces (GRF) and three-dimensional (3D) biomechanics are not fully understood. The purpose of the study was to examine 3D lower extremity kinematics and joint dynamics during walking in two different short-leg walking boots. Eleven (five females and six males) healthy subjects performed five level walking trials in each of three conditions: two testing boot conditions, Gait Walker (DeRoyal Industries, Inc.) and Equalizer (Royce Medical Co.), and one pair of laboratory shoes (Noveto, Adidas). A force platform and a 6-camera Vicon motion analysis system were used to collect GRFs and 3D kinematic data during the testing session. A one-way repeated measures analysis of variance (ANOVA) was used to evaluate selected kinematic, GRF, and joint kinetic variables (p<0.05). The results revealed that both short-leg walking boots were effective in minimizing ankle eversion and hip adduction. Neither walker increased the bimodal vertical GRF peaks typically observed in normal walking. However, they did impose a small initial peak (<1BW) earlier in the stance phase. The Gait Walker also exhibited a slightly increased vertical GRF during midstance. These characteristics may be related to the sole materials/design, the restriction of ankle movements, and/or the elevated heel heights of the tested walkers. Both walkers appeared to increase the demand on the knee extensors while they decreased the demand of the knee and hip abductors based on the joint kinetic results. PMID:16414263

  3. Estimating Youth Locomotion Ground Reaction Forces Using an Accelerometer-Based Activity Monitor

    Neugebauer, Jennifer M.; Hawkins, David A.; Beckett, Laurel

    2012-01-01

    To address a variety of questions pertaining to the interactions between physical activity, musculoskeletal loading and musculoskeletal health/injury/adaptation, simple methods are needed to quantify, outside a laboratory setting, the forces acting on the human body during daily activities. The purpose of this study was to develop a statistically based model to estimate peak vertical ground reaction force (pVGRF) during youth gait. 20 girls (10.9±0.9 years) and 15 boys (12.5±0.6 years) wore a Biotrainer AM over their right hip. Six walking and six running trials were completed after a standard warm-up. Average AM intensity (g) and pVGRF (N) during stance were determined. Repeated measures mixed effects regression models to estimate pVGRF from Biotrainer activity monitor acceleration in youth (girls 10–12, boys 12–14 years) while walking and running were developed. Log transformed pVGRF had a statistically significant relationship with activity monitor acceleration, centered mass, sex (girl), type of locomotion (run), and locomotion type-acceleration interaction controlling for subject as a random effect. A generalized regression model without subject specific random effects was also developed. The average absolute differences between the actual and predicted pVGRF were 5.2% (1.6% standard deviation) and 9% (4.2% standard deviation) using the mixed and generalized models, respectively. The results of this study support the use of estimating pVGRF from hip acceleration using a mixed model regression equation. PMID:23133564

  4. The Effects of Opposition and Gender on Knee Kinematics and Ground Reaction Force during Landing from Volleyball Block Jumps

    Hughes, Gerwyn; Watkins, James; Owen, Nick

    2010-01-01

    The aim of this study was to examine the effect of opposition and gender on knee kinematics and ground reaction force during landing from a volleyball block jump. Six female and six male university volleyball players performed two landing tasks: (a) an unopposed and (b) an opposed volleyball block jump and landing. A 12-camera motion analysis…

  5. The Effects of Opposition and Gender on Knee Kinematics and Ground Reaction Force during Landing from Volleyball Block Jumps

    Hughes, Gerwyn; Watkins, James; Owen, Nick

    2010-01-01

    The aim of this study was to examine the effect of opposition and gender on knee kinematics and ground reaction force during landing from a volleyball block jump. Six female and six male university volleyball players performed two landing tasks: (a) an unopposed and (b) an opposed volleyball block jump and landing. A 12-camera motion analysis…

  6. Effects of backpack weight on posture, gait patterns and ground reaction forces of male children with obesity during stair descent.

    Song, Qipeng; Yu, Bing; Zhang, Cui; Sun, Wei; Mao, Dewei

    2014-01-01

    This study investigates the effects of backpack weight on posture, gait pattern, and ground reaction forces for children with obesity in an attempt to define a safe backpack weight limit for them. A total of 16 obese (11.19 ± 0.66 years of age) and 21 normal body weight (11.13 ± 0.69 years of age) schoolboys were recruited. Two force plates and two video cameras were used. Multivariate analysis of variance with repeated measures was employed. Obese children showed increased trunk and head forward inclination angle, gait cycle duration and stance phase, decreased swing phase, and increased ground reaction force in the medial-lateral and anterior-posterior directions when compared with male children with a normal body weight. The changes were observed even with an empty backpack in comparison with normal body weight children and a 15% increase in backpack weight led to further instability and damage on their already strained bodies. PMID:24650337

  7. A COMPARISON OF GOLF SHOE DESIGNS HIGHLIGHTS GREATER GROUND REACTION FORCES WITH SHORTER IRONS

    Paul Worsfold

    2007-12-01

    Full Text Available 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

  8. Effects of Prophylactic Ankle Supports on Vertical Ground Reaction Force During Landing: A Meta-Analysis

    Niu, Wenxin; Feng, Tienan; Wang, Lejun; Jiang, Chenghua; Zhang, Ming

    2016-01-01

    There has been much debate on how prophylactic ankle supports (PASs) may influence the vertical ground reaction force (vGRF) during landing. Therefore, the primary aims of this meta-analysis were to systematically review and synthesize the effect of PASs on vGRF, and to understand how PASs affect vGRF peaks (F1, F2) and the time from initial contact to peak loading (T1, T2) during landing. Several key databases, including Scopus, Cochrane, Embase, PubMed, ProQuest, Medline, Ovid, Web of Science, and the Physical Activity Index, were used for identifying relevant studies published in English since inception to April 1, 2015. The computerized literature search and cross-referencing the citation list of the articles yielded 3,993 articles. Criteria for inclusion required that 1) the study was conducted on healthy adults; 2) the subject number and trial number were known; 3) the subjects performed landing with and without PAS; 4) the landing movement was in the sagittal plane; 5) the comparable vGRF parameters were reported; and 6) the F1 and F2 must be normalized to the subject’s body weight. After the removal of duplicates and irrelevant articles, 6, 6, 15 and 11 studies were respectively pooled for outcomes of F1, T1, F2 and T2. This study found a significantly increased F2 (.03 BW, 95% CI: .001, .05) and decreased T1 (-1.24 ms, 95% CI: -1.77, -.71) and T2 (-3.74 ms, 95% CI: -4.83, -2.65) with the use of a PAS. F1 was not significantly influenced by the PAS. Heterogeneity was present in some results, but there was no evidence of publication bias for any outcome. These changes represented deterioration in the buffering characteristics of the joint. An ideal PAS design should limit the excessive joint motion of ankle inversion, while allowing a normal range of motion, especially in the sagittal plane. Key points PAS can effectively protect the ligamentous structure from spraining by providing mechanical support and cutaneous proprioceptive benefits. Using of PAS can significantly elevate F2 and reduce T1 and T2 during landing. These changes represented deterioration in the buffering characteristics of the joint. An ideal PAS design should limit the excessive joint motion of the ankle inversion, while allow normal range of motion, especially in the sagittal plane. PMID:26957920

  9. Effects of Prophylactic Ankle Supports on Vertical Ground Reaction Force During Landing: A Meta-Analysis.

    Niu, Wenxin; Feng, Tienan; Wang, Lejun; Jiang, Chenghua; Zhang, Ming

    2016-03-01

    There has been much debate on how prophylactic ankle supports (PASs) may influence the vertical ground reaction force (vGRF) during landing. Therefore, the primary aims of this meta-analysis were to systematically review and synthesize the effect of PASs on vGRF, and to understand how PASs affect vGRF peaks (F1, F2) and the time from initial contact to peak loading (T1, T2) during landing. Several key databases, including Scopus, Cochrane, Embase, PubMed, ProQuest, Medline, Ovid, Web of Science, and the Physical Activity Index, were used for identifying relevant studies published in English since inception to April 1, 2015. The computerized literature search and cross-referencing the citation list of the articles yielded 3,993 articles. Criteria for inclusion required that 1) the study was conducted on healthy adults; 2) the subject number and trial number were known; 3) the subjects performed landing with and without PAS; 4) the landing movement was in the sagittal plane; 5) the comparable vGRF parameters were reported; and 6) the F1 and F2 must be normalized to the subject's body weight. After the removal of duplicates and irrelevant articles, 6, 6, 15 and 11 studies were respectively pooled for outcomes of F1, T1, F2 and T2. This study found a significantly increased F2 (.03 BW, 95% CI: .001, .05) and decreased T1 (-1.24 ms, 95% CI: -1.77, -.71) and T2 (-3.74 ms, 95% CI: -4.83, -2.65) with the use of a PAS. F1 was not significantly influenced by the PAS. Heterogeneity was present in some results, but there was no evidence of publication bias for any outcome. These changes represented deterioration in the buffering characteristics of the joint. An ideal PAS design should limit the excessive joint motion of ankle inversion, while allowing a normal range of motion, especially in the sagittal plane. Key pointsPAS can effectively protect the ligamentous structure from spraining by providing mechanical support and cutaneous proprioceptive benefits.Using of PAS can significantly elevate F2 and reduce T1 and T2 during landing. These changes represented deterioration in the buffering characteristics of the joint.An ideal PAS design should limit the excessive joint motion of the ankle inversion, while allow normal range of motion, especially in the sagittal plane. PMID:26957920

  10. Effects of Prophylactic Ankle Supports on Vertical Ground Reaction Force During Landing: A Meta-Analysis

    Wenxin Niu, Tienan Feng, Lejun Wang, Chenghua Jiang, Ming Zhang

    2016-03-01

    Full Text Available There has been much debate on how prophylactic ankle supports (PASs may influence the vertical ground reaction force (vGRF during landing. Therefore, the primary aims of this meta-analysis were to systematically review and synthesize the effect of PASs on vGRF, and to understand how PASs affect vGRF peaks (F1, F2 and the time from initial contact to peak loading (T1, T2 during landing. Several key databases, including Scopus, Cochrane, Embase, PubMed, ProQuest, Medline, Ovid, Web of Science, and the Physical Activity Index, were used for identifying relevant studies published in English since inception to April 1, 2015. The computerized literature search and cross-referencing the citation list of the articles yielded 3,993 articles. Criteria for inclusion required that 1 the study was conducted on healthy adults; 2 the subject number and trial number were known; 3 the subjects performed landing with and without PAS; 4 the landing movement was in the sagittal plane; 5 the comparable vGRF parameters were reported; and 6 the F1 and F2 must be normalized to the subject’s body weight. After the removal of duplicates and irrelevant articles, 6, 6, 15 and 11 studies were respectively pooled for outcomes of F1, T1, F2 and T2. This study found a significantly increased F2 (.03 BW, 95% CI: .001, .05 and decreased T1 (-1.24 ms, 95% CI: -1.77, -.71 and T2 (-3.74 ms, 95% CI: -4.83, -2.65 with the use of a PAS. F1 was not significantly influenced by the PAS. Heterogeneity was present in some results, but there was no evidence of publication bias for any outcome. These changes represented deterioration in the buffering characteristics of the joint. An ideal PAS design should limit the excessive joint motion of ankle inversion, while allowing a normal range of motion, especially in the sagittal plane.

  11. The effects of changes in the sagittal plane alignment of running-specific transtibial prostheses on ground reaction forces

    Tominaga, Shuichi; Sakuraba, Keisyoku; Usui, Fumio

    2015-01-01

    [Purpose] To verify the effects of sagittal plane alignment changes in running-specific transtibial prostheses on ground reaction forces (GRFs). [Subjects and Methods] Eight transtibial amputees who used running-specific prostheses during sprinting participated. The sprint movements were recorded using a Vicon-MX system and GRF measuring devices. The experiment levels were set as regularly recommended alignment (REG; the normal alignment for the subjects) and dorsiflexion or pl...

  12. Multi-body simulation of a canine hind limb: model development, experimental validation and calculation of ground reaction forces

    Wefstaedt Patrick

    2009-11-01

    Full Text Available Abstract Background Among other causes the long-term result of hip prostheses in dogs is determined by aseptic loosening. A prevention of prosthesis complications can be achieved by an optimization of the tribological system which finally results in improved implant duration. In this context a computerized model for the calculation of hip joint loadings during different motions would be of benefit. In a first step in the development of such an inverse dynamic multi-body simulation (MBS- model we here present the setup of a canine hind limb model applicable for the calculation of ground reaction forces. Methods The anatomical geometries of the MBS-model have been established using computer tomography- (CT- and magnetic resonance imaging- (MRI- data. The CT-data were collected from the pelvis, femora, tibiae and pads of a mixed-breed adult dog. Geometric information about 22 muscles of the pelvic extremity of 4 mixed-breed adult dogs was determined using MRI. Kinematic and kinetic data obtained by motion analysis of a clinically healthy dog during a gait cycle (1 m/s on an instrumented treadmill were used to drive the model in the multi-body simulation. Results and Discussion As a result the vertical ground reaction forces (z-direction calculated by the MBS-system show a maximum deviation of 1.75%BW for the left and 4.65%BW for the right hind limb from the treadmill measurements. The calculated peak ground reaction forces in z- and y-direction were found to be comparable to the treadmill measurements, whereas the curve characteristics of the forces in y-direction were not in complete alignment. Conclusion In conclusion, it could be demonstrated that the developed MBS-model is suitable for simulating ground reaction forces of dogs during walking. In forthcoming investigations the model will be developed further for the calculation of forces and moments acting on the hip joint during different movements, which can be of help in context with the in silico development and testing of hip prostheses.

  13. MEMS two-axis force plate array used to measure the ground reaction forces during the running motion of an ant

    A terrestrial insect can perform agile running maneuvers. However, the balance of ground reaction forces (GRFs) between each leg in an insect have remained poorly characterized. In this report, we present a micro force plate array for the simultaneous measurement of the anterior and vertical components of GRFs of multiple legs during the running motion of an ant. The proposed force plate, which consists of a 2000 µm × 980 µm × 20 µm plate base as the contact surface of an ant's leg, and the supported beams with piezoresistors on the sidewall and surface are sufficiently compact to be adjacently arrayed along the anterior direction. Eight plates arrayed in parallel were fabricated on the same silicon-on-insulator substrate to narrow the gap between each plate to 20 µm. We compartmented the plate surface into 32 blocks and evaluated the sensitivities to two-axis forces in each block so that the exerted forces could be detected wherever a leg came into contact. The force resolutions in both directions were under 1 µN within ±20 µN. Using the fabricated force plate array, we achieved a simultaneous measurement of the GRFs of three legs on one side while an ant was running. (paper)

  14. Measurement of velocity with a kinematic system versus a photocell system in the collection of canine ground reaction forces.

    Punke, J P; Andrews, C M; Speas, A L; Reynolds, L R; Budsberg, S C

    2007-01-01

    Velocities obtained from a five photocell system were compared to velocities of nine anatomical points on a handler and canine subject as reported by a kinematic system over the same distance. There was not a statistically significant difference between the velocities of the markers on the dogs' occipital protuberance and interscapular region compared with the velocity as reported by the photocell system. The average velocities of the three markers on the forelimb of the dogs and three markers on the handler's leg and one on the sacrum had statistically different values than the photocell system. Given these results, photocell systems with the same configuration in this study can be trusted to report accurate trunk velocities of canine subjects during the collection of ground reaction forces. PMID:18038009

  15. Reproducibility of the spatio-temporal variables and the ground reaction forces walking with fire fighting boots

    Jesús Cámara Tobalina

    2010-11-01

    Full Text Available AbstractThe aim of this study is to analyze the reproducibility of the spatio-temporal variables and the ground reaction forces (GRF when walking with fire fighting boots in comparison to walking with low calf shoes. Spatio-temporal parameters and the variables related to the three components of the GRF of 39 people were recorded under two different walking conditions. A T-test to contrast the difference between the coefficients of variation (CV in both conditions was used. The CV of the spatio-temporal variables (i.e velocity (V, condition I = 2.01%; condition II = 1.81%, of the vertical (i.e. contact force (FZA of the left foot, condition I = 2.54%; condition II = 2.73% and of the antero-posterior GRF (i.e. maximum force (FXMAX of the left foot, condition I = 4.47%; condition II = 4.59% was lower than 12.5%, suggesting that these variables could be used to analyze the influence of fire fighting boots on the gait. However, the low reproducibility showed by medium-lateral parameters does not allow to use them. Apart from the bipodal phase no differences were found between the two walking conditions. Key words: biomechanics, footwear, variability.

  16. Quantitative metrics of spinal cord injury recovery in the rat using motion capture, electromyography and ground reaction force measurement.

    Johnson, Will L; Jindrich, Devin L; Roy, Roland R; Edgerton, V Reggie

    2012-04-30

    Toward improving the quantitative tools available for evaluation of locomotion after a spinal cord injury, we characterized selected biomechanical and physiological parameters that could be used to assess the level of recovery of locomotion after a mid-thoracic spinal cord lateral hemisection. Specifically we defined quantitative measures of muscle activation and coordination, body weight support, propulsive force, and pre-toe contact activation. Generation of this ensemble of recovery measures was based on kinematics, ground reaction forces, and EMG in rats from the hindlimb ipsilateral to the hemisection during quadrupedal running on a trackway. We derived muscle activation levels using inverse dynamics and static optimization applied to a model of the hindlimb musculoskeletal system. Rats exhibited a phased recovery pattern: progressive recovery of general muscle activity beginning within 2-3 days post-injury, followed by recovery of propulsive force and intralimb coordination of antagonistic muscles 12-13 days post-injury. Even at 12-13 days post-injury however, body weight support and the normal pre-paw contact EMG burst were significantly impaired. These data are consistent with a differential rate of recovery of general motor pool recruitment, and coordination among motor pools. The results demonstrate the discriminative potential of these physiologically based measures in quantifying the progressive recovery of gait performance after a lateral spinal cord hemisection. PMID:22361571

  17. Changes in ground reaction force during a rebound-jump task after hip strength training for single-sided ankle dorsiflexion restriction

    Kondo, Hitoshi; Someya, Fujiko

    2016-01-01

    [Purpose] Lateral ankle sprains are common injuries suffered while playing sports, and abnormal forward- and inward-directed ground reaction force occurs during a jumping task. However, the influence of hip muscle strength training on jumping performance after ankle injuries has not been fully examined. This study thus examined changes in ground reaction force during a rebound-jump task after training to strengthen hip muscles. [Subjects and Methods] Ten of 30 female high school basketball players were assigned as subjects who showed a difference of 7 or more degrees in dorsiflexion ranges between the bilateral ankles. The subjects underwent 12 weeks of training to strengthen hip abductors and external rotators. Comparisons between before and after training were made regarding ground reaction force components, hip and knee joint angles, percentage of maximum voluntary contraction in leg muscles, and muscle strength of hip muscles during the rebound-jump task. [Results] After training, the subjects showed increased strength of external rotator muscles, increased percentage of maximum voluntary contraction in the gluteus medius muscle, decreased inward ground reaction force, and increased flexion angles of the hip and knee joints. [Conclusion] This study suggests that training to strengthen hip muscles may ameliorate the inward ground reaction force in athletes with ankle dorsiflexion restriction. PMID:27065513

  18. The relationship between bone mechanical properties and ground reaction forces in normal and hypermuscular mice

    Schmitt, Daniel; Zumwalt, Ann C.; Hamrick, Mark W.

    2010-01-01

    Understanding the relationship between external load and bone morphology is critical for understanding adaptations to load in extant animals and inferring behavior in extinct forms. Yet the relationship bony anatomy and load is poorly understood, with empirical studies often producing conflicting results. It is widely assumed in many ecological and paleontological studies that bone size and strength reflects the forces experience by the bone in-vivo. This study examines that assumption by pro...

  19. Gait Phases Recognition from Accelerations and Ground Reaction Forces: Application of Neural Networks

    S. Rafajlović

    2009-06-01

    Full Text Available The goal of this study was to test the applicability of accelerometer as the sensor for assessment of the walking. We present here the comparison of gait phases detected from the data recorded by force sensing resistors mounted in the shoe insoles, non-processed acceleration and processed acceleration perpendicular to the direction of the foot. The gait phases in all three cases were detected by means of a neural network. The output from the neural network was the gait phase, while the inputs were data from the sensors. The results show that the errors were in the ranges: 30 ms (2.7% – force sensors; 150 ms (13.6% – nonprocessed acceleration, and 120 ms (11% – processed acceleration data. This result suggests that it is possible to use the accelerometer as the gait phase detector, however, with the knowledge that the gait phases are time shifted for about 100 ms with respect the neural network predicted times.

  20. The influence of pain distribution on walking velocity and horizontal ground reaction forces in patients with low back pain.

    Simmonds, Maureen J; Lee, C Ellen; Etnyre, Bruce R; Morris, G Stephen

    2012-01-01

    Objective. The primary purpose of this paper was to evaluate the influence of pain distribution on gait characteristics in subjects with low back problems (LBP) during walking at preferred and fastest speeds. Design. Cross-sectional, observational study. Setting. Gait analysis laboratory in a health professions university. Participants. A convenience age- and gender-matched sample of 20 subjects with back pain only (BPO), 20 with referred leg pain due to back problems (LGP), and 20 pain-free individuals (CON). Methods and Measures. Subjects completed standardized self-reports on pain and disability and were videotaped as they walked at their preferred and fastest speeds along a walkway embedded with a force plate. Temporal and spatial gait characteristics were measured at the midsection of the walkway, and peak medial, lateral, anterior, and posterior components of horizontal ground reaction forces (hGRFs) were measured during the stance phase. Results. Patients with leg pain had higher levels of pain intensity and affect compared to those with back pain only (t = 4.91, P LGP group and differed between groups at both walking speeds (F(2.57) = 13.62, P LGP group generated significantly less lateral force at the fastest walking speed (P = .005) and significantly less posterior force at both walking speeds (P ≤ .01) compared to the control group. Conclusions. Pain intensity and distribution differentially influence gait velocity and hGRFs during gait. Those with referred leg pain tend to utilize significantly altered gait strategies that are more apparent at faster walking speeds. PMID:22550576

  1. The Influence of Pain Distribution on Walking Velocity and Horizontal Ground Reaction Forces in Patients with Low Back Pain

    Simmonds, Maureen J.; Lee, C. Ellen; Etnyre, Bruce R.; Morris, G. Stephen

    2012-01-01

    Objective. The primary purpose of this paper was to evaluate the influence of pain distribution on gait characteristics in subjects with low back problems (LBP) during walking at preferred and fastest speeds. Design. Cross-sectional, observational study. Setting. Gait analysis laboratory in a health professions university. Participants. A convenience age- and gender-matched sample of 20 subjects with back pain only (BPO), 20 with referred leg pain due to back problems (LGP), and 20 pain-free individuals (CON). Methods and Measures. Subjects completed standardized self-reports on pain and disability and were videotaped as they walked at their preferred and fastest speeds along a walkway embedded with a force plate. Temporal and spatial gait characteristics were measured at the midsection of the walkway, and peak medial, lateral, anterior, and posterior components of horizontal ground reaction forces (hGRFs) were measured during the stance phase. Results. Patients with leg pain had higher levels of pain intensity and affect compared to those with back pain only (t = 4.91, P < .001 and t = 5.80, P < 0.001, resp.) and walking had an analgesic effect in the BPO group. Gait velocity was highest in the control group followed by the BPO and LGP group and differed between groups at both walking speeds (F2.57 = 13.62, P < .001 and F2.57 = 9.09, P < .001, for preferred and fastest speed condition, resp.). When normalized against gait velocity, the LGP group generated significantly less lateral force at the fastest walking speed (P = .005) and significantly less posterior force at both walking speeds (P ? .01) compared to the control group. Conclusions. Pain intensity and distribution differentially influence gait velocity and hGRFs during gait. Those with referred leg pain tend to utilize significantly altered gait strategies that are more apparent at faster walking speeds. PMID:22550576

  2. A Wearable Ground Reaction Force Sensor System and Its Application to the Measurement of Extrinsic Gait Variability

    Kyoko Shibata

    2010-11-01

    Full Text Available Wearable sensors for gait analysis are attracting wide interest. In this paper, a wearable ground reaction force (GRF sensor system and its application to measure extrinsic gait variability are presented. To validate the GRF and centre of pressure (CoP measurements of the sensor system and examine the effectiveness of the proposed method for gait analysis, we conducted an experimental study on seven volunteer subjects. Based on the assessment of the influence of the sensor system on natural gait, we found that no significant differences were found for almost all measured gait parameters (p-values < 0.05. As for measurement accuracy, the root mean square (RMS differences for the two transverse components and the vertical component of the GRF were 7.2% ± 0.8% and 9.0% ± 1% of the maximum of each transverse component and 1.5% ± 0.9% of the maximum vertical component of GRF, respectively. The RMS distance between both CoP measurements was 1.4% ± 0.2% of the length of the shoe. The area of CoP distribution on the foot-plate and the average coefficient of variation of the triaxial GRF, are the introduced parameters for analysing extrinsic gait variability. Based on a statistical analysis of the results of the tests with subjects wearing the sensor system, we found that the proposed parameters changed according to walking speed and turning (p-values < 0.05.

  3. NUMBER OF SUCCESSIVE CYCLES NECESSARY TO ACHIEVE STABILITY OF SELECTED GROUND REACTION FORCE VARIABLES DURING CONTINUOUS JUMPING

    Jasmes M.W. Brownjohn

    2009-12-01

    Full Text Available Because of inherent variability in all human cyclical movements, such as walking, running and jumping, data collected across a single cycle might be atypical and potentially unable to represent an individual's generalized performance. The study described here was designed to determine the number of successive cycles due to continuous, repetitive countermovement jumping which a test subject should perform in a single experimental session to achieve stability of the mean of the corresponding continuously measured ground reaction force (GRF variables. Seven vertical GRF variables (period of jumping cycle, duration of contact phase, peak force amplitude and its timing, average rate of force development, average rate of force relaxation and impulse were extracted on the cycle-by-cycle basis from vertical jumping force time histories generated by twelve participants who were jumping in response to regular electronic metronome beats in the range 2-2.8 Hz. Stability of the selected GRF variables across successive jumping cycles was examined for three jumping rates (2, 2.4 and 2.8 Hz using two statistical methods: intra-class correlation (ICC analysis and segmental averaging technique (SAT. Results of the ICC analysis indicated that an average of four successive cycles (mean 4.5 ± 2.7 for 2 Hz; 3.9 ± 2.6 for 2.4 Hz; 3.3 ± 2.7 for 2.8 Hz were necessary to achieve maximum ICC values. Except for jumping period, maximum ICC values took values from 0.592 to 0.991 and all were significantly (p < 0.05 different from zero. Results of the SAT revealed that an average of ten successive cycles (mean 10.5 ± 3.5 for 2 Hz; 9.2 ± 3.8 for 2.4 Hz; 9.0 ± 3.9 for 2.8 Hz were necessary to achieve stability of the selected parameters using criteria previously reported in the literature. Using 10 reference trials, the SAT required standard deviation criterion values of 0.49, 0.41 and 0.55 for 2 Hz, 2.4 Hz and 2.8 Hz jumping rates, respectively, in order to approximate the ICC results. The results of the study suggest that the ICC might be a less conservative but more objective method to evaluate stability of the data. Based on these considerations, it can be recommended that a force time history due to continuous, repetitive countermovement jumping should include minimum of four (the average from the ICC analysis and possibly as many as nine successive jumping cycles (the upper limit of the ICC analysis to establish stable mean values of the selected GRF data. This information is important for both experimental measurements and analytical studies of GRF signals due to continuous, repetitive countermovement jumping

  4. EFFECTS OF FATIGUE ON FRONTAL PLANE KNEE MOTION, MUSCLE ACTIVITY, AND GROUND REACTION FORCES IN MEN AND WOMEN DURING LANDING

    Michael P. Smith

    2009-09-01

    Full Text Available Women tear their Anterior Cruciate Ligament (ACL 2-8 times more frequently than men. Frontal plane knee motion can produce a pathological load in the ACL. During a state of fatigue the muscles surrounding the knee joint may lose the ability to protect the joint during sudden deceleration while landing. The purpose of this study was to investigate the effects of fatigue and gender on frontal plane knee motion, EMG amplitudes, and GRF magnitudes during drop- jump landing. Pretest-posttest comparison group design was used. Twenty-six volunteers (14 women; 12 Men; Mean ± standard deviation age = 24.5 ± 2.7 yrs; height = 1.73 ± 0.09 m; mass = 74.3 ± 11.8 kg participated in the study. Knee frontal plane ranges of motion and positions, ground reaction force peak magnitudes, and surface EMG RMS amplitudes from five lower extremity muscles (vastus medialis, vastus lateralis, medial hamstring, lateral hamstring, and lateral gastrocnemius were obtained during the landing phase of a drop-jump. MANOVA and ANOVA indicated that peak GRF significantly (p < 0.05; 2.50 ± 0.75 BW vs. 2.06 ± 0.93 BW decreased during fatigued landings. No other variables exhibited a fatigue main effect, although there was a significant (p < 0.05 fatigue by gender interaction for the frontal plane range of motion from initial contact to max knee flexion variable. Follow-up analyses failed to reveal significant gender differences at the different levels of fatigue for this variable. Additionally, no variables exhibited a significant gender main effect. Single subject analysis indicated that fatigue significantly altered frontal plane knee motion, peak GRF, and EMG in some subjects and the direction of differences varied by individual. Fatigue altered some aspects of landing performance in both men and women, but there were no gender differences. Additionally, both group and single subject analyses provided valuable but different information about factors representing neuromuscular control during drop-jump landing

  5. Short communication: Changes in gait symmetry in healthy and lame dairy cows based on 3-dimensional ground reaction force curves following claw trimming.

    Thorup, V M; do Nascimento, O F; Skjøth, F; Voigt, M; Rasmussen, M D; Bennedsgaard, T W; Ingvartsen, K L

    2014-12-01

    Lameness is a frequent health problem in dairy cows. This preliminary study aimed to detect gait differences between healthy and lame walking cows using 3-dimensional force plates. We examined left-right leg symmetry changes of healthy and lame Holstein dairy cows following claw trimming. Gait scoring (GS) was performed on d -5, 0, 1, and 7 relative to claw trimming. Before the experiment, 5 cows walked normally (initial GS=1) and 4 cows limped moderately on a hind leg (initial GS=3). Gait was measured on d -2, -1, 0, 1, and 7 relative to trimming by obtaining ground reaction forces as cows walked repeatedly across 2 parallel 3-dimensional force plates. From the ground reaction forces, stance phase data were derived using computerized procedures. Left-right leg symmetries of entire curves in the 3 force directions were calculated. Effects of lameness and trimming were analyzed in a mixed model, using a low lameness threshold (GS>1). One week after claw trimming, only one cow was mildly lame. In addition, the symmetries of all 3 dimensions were significantly improved shortly after trimming. Importantly, lameness significantly worsened vertical symmetry. Lame cows walked significantly more slowly than healthy cows. In conclusion, all force symmetries seemed capable of detecting gait responses to claw trimming. Although our results are based on a small number of animals, vertical leg symmetry was affected by lameness. PMID:25306278

  6. A comparison of lower limb EMG and ground reaction forces between barefoot and shod gait in participants with diabetic neuropathic and healthy controls

    Akashi Paula MH

    2010-02-01

    Full Text Available Abstract Background It is known that when barefoot, gait biomechanics of diabetic neuropathic patients differ from non-diabetic individuals. However, it is still unknown whether these biomechanical changes are also present during shod gait which is clinically advised for these patients. This study investigated the effect of the participants own shoes on gait biomechanics in diabetic neuropathic individuals compared to barefoot gait patterns and healthy controls. Methods Ground reaction forces and lower limb EMG activities were analyzed in 21 non-diabetic adults (50.9 ± 7.3 yr, 24.3 ± 2.6 kg/m2 and 24 diabetic neuropathic participants (55.2 ± 7.9 yr, 27.0 ± 4.4 kg/m2. EMG patterns of vastus lateralis, lateral gastrocnemius and tibialis anterior, along with the vertical and antero-posterior ground reaction forces were studied during shod and barefoot gait. Results Regardless of the disease, walking with shoes promoted an increase in the first peak vertical force and the peak horizontal propulsive force. Diabetic individuals had a delay in the lateral gastrocnemius EMG activity with no delay in the vastus lateralis. They also demonstrated a higher peak horizontal braking force walking with shoes compared to barefoot. Diabetic participants also had a smaller second peak vertical force in shod gait and a delay in the vastus lateralis EMG activity in barefoot gait compared to controls. Conclusions The change in plantar sensory information that occurs when wearing shoes revealed a different motor strategy in diabetic individuals. Walking with shoes did not attenuate vertical forces in either group. Though changes in motor strategy were apparent, the biomechanical did not support the argument that the use of shoes contributes to altered motor responses during gait.

  7. The Influence of Optimal Handheld Load on the Technical Ability to Apply Ground Reaction Forces during Horizontal Jumping in Female Netball Players.

    McKenzie, C R; Brughelli, M; Whatman, C; Brown, S R

    2016-04-01

    Handheld load has been reported to enhance horizontal jump performance, however little is known about its influence on ground reaction forces (GRF), especially in female athletes. This study investigated the effects of individualized optimal handheld loading on the technical and physical ability to apply GRF during horizontal jumping in female netball players. Maximal effort, single standing, horizontal jumps were performed by 13 female netballers. Participants performed the jumps under 2 conditions: 1) unloaded, and 2) loaded. Eccentric mean horizontal GRF significantly increased with loading (pstrength and conditioning coach, trainer and athlete. PMID:26667926

  8. The Relationship Between Landing Sound, Vertical Ground Reaction Force, and Kinematics of the Lower Limb During Drop Landings in Healthy Men.

    Wernli, Kevin; Ng, Leo; Phan, Xuan; Davey, Paul; Grisbrook, Tiffany

    2016-03-01

    Study Design Controlled laboratory study, cross-sectional. Background Soft-landing instruction, which is advocated in several injury prevention programs, is thought to have a qualitative relationship with decreased vertical ground reaction forces (vGRFs) and increased lower-limb joint excursions. Objective To quantify the relationships among landing sound, vGRFs, and lower-limb kinematics during a drop-landing task. Methods Twenty-six asymptomatic men aged 18 to 35 years were asked to perform 15 single-leg drop landings from a 30-cm height. Five trials were collected under 3 sound conditions: normal, quiet, and loud. The vGRF, lower-limb kinematics (sagittal plane), and impact sound were recorded during the deceleration phase. Results A simple linear regression revealed a significant relationship between landing sound and vGRF (R(2) = 0.42, Pdoi:10.2519/jospt.2016.6041. PMID:26813751

  9. Estimating 3D L5/S1 moments and ground reaction forces during trunk bending using a full-body ambulatory inertial motion capture system.

    Faber, G S; Chang, C C; Kingma, I; Dennerlein, J T; van Dieën, J H

    2016-04-11

    Inertial motion capture (IMC) systems have become increasingly popular for ambulatory movement analysis. However, few studies have attempted to use these measurement techniques to estimate kinetic variables, such as joint moments and ground reaction forces (GRFs). Therefore, we investigated the performance of a full-body ambulatory IMC system in estimating 3D L5/S1 moments and GRFs during symmetric, asymmetric and fast trunk bending, performed by nine male participants. Using an ambulatory IMC system (Xsens/MVN), L5/S1 moments were estimated based on the upper-body segment kinematics using a top-down inverse dynamics analysis, and GRFs were estimated based on full-body segment accelerations. As a reference, a laboratory measurement system was utilized: GRFs were measured with Kistler force plates (FPs), and L5/S1 moments were calculated using a bottom-up inverse dynamics model based on FP data and lower-body kinematics measured with an optical motion capture system (OMC). Correspondence between the OMC+FP and IMC systems was quantified by calculating root-mean-square errors (RMSerrors) of moment/force time series and the interclass correlation (ICC) of the absolute peak moments/forces. Averaged over subjects, L5/S1 moment RMSerrors remained below 10Nm (about 5% of the peak extension moment) and 3D GRF RMSerrors remained below 20N (about 2% of the peak vertical force). ICCs were high for the peak L5/S1 extension moment (0.971) and vertical GRF (0.998). Due to lower amplitudes, smaller ICCs were found for the peak asymmetric L5/S1 moments (0.690-0.781) and horizontal GRFs (0.559-0.948). In conclusion, close correspondence was found between the ambulatory IMC-based and laboratory-based estimates of back load. PMID:26795123

  10. ANALYSIS OF THE VERTICAL GROUND REACTION FORCES AND TEMPORAL FACTORS IN THE LANDING PHASE OF A COUNTERMOVEMENT JUMP

    Daniel Rojano Ortega

    2010-06-01

    Full Text Available 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.

  11. Comparisons of knee and ankle joint angles and ground reaction force according to functional differences during single-leg drop landing

    Kim, Kewwan; Jeon, Kyoungkyu

    2016-01-01

    [Purpose] The purpose of this study was to determine potential predictors of functional instability of the knee and ankle joints during single-leg drop landing based on the prior history of injury. [Subjects and Methods] The subjects were 24 collegiate soccer players without pain or dysfunction. To compare the differences between the stable and unstable sides during single-leg drop landing, 8 motion analysis cameras and a force plate were used. The Cortex 4 software was used for a biomechanical analysis of 3 events. An independent t-test was used for statistical comparison between both sides; pknee joint movements showed gradual flexion in the sagittal plane. The unstable-side ankle joint showed plantar flexion of approximately 2° relative to the stable side. In the coronal plane, the unstable-side knee joint differed from the stable side in its tendency for valgus movement. The unstable-side ankle joint showed contrasting movement compared with the stable side, and the difference was significant. Regarding the vertical ground reaction force, the stable side showed maximum knee flexion that was approximately 0.1 BW lower than that of the unstable side. [Conclusion] Increasing the flexion angle of the knee joint can help prevent injury during landing.

  12. Ground Reaction Force and Mechanical Differences Between the Interim Resistive Exercise Device (iRED) and Smith Machine While Performing a Squat

    Amonette, William E.; Bentley, Jason R.; Lee, Stuart M. C.; Loehr, James A.; Schneider, Suzanne

    2004-01-01

    Musculoskeletal unloading in microgravity has been shown to induce losses in bone mineral density, muscle cross-sectional area, and muscle strength. Currently, an Interim Resistive Exercise Device (iRED) is being flown on board the ISS to help counteract these losses. Free weight training has shown successful positive musculoskeletal adaptations. In biomechanical research, ground reaction forces (GRF) trajectories are used to define differences between exercise devices. The purpose of this evaluation is to quantify the differences in GRF between the iRED and free weight exercise performed on a Smith machine during a squat. Due to the differences in resistance properties, inertial loading and load application to the body between the two devices, we hypothesize that subjects using iRED will produce GRF that are significantly different from the Smith machine. There will be differences in bar/harness range of motion and the time when peak GRF occurred in the ROMbar. Three male subjects performed three sets of ten squats on the iRED and on the Smith Machine on two separate days at a 2-second cadence. Statistically significant differences were found between the two devices in all measured GRF variables. Average Fz and Fx during the Smith machine squat were significantly higher than iRED. Average Fy (16.82 plus or minus.23; p less than .043) was significantly lower during the Smith machine squat. The mean descent/ascent ratio of the magnitude of the resultant force vector of all three axes for the Smith machine and iRED was 0.95 and 0.72, respectively. Also, the point at which maximum Fz occurred in the range of motion (Dzpeak) was at different locations with the two devices.

  13. Force approach to radiation reaction

    López, Gustavo V.

    2016-02-01

    The difficulty of the usual approach to deal with the radiation reaction is pointed out, and under the condition that the radiation force must be a function of the external force and is zero whenever the external force be zero, a new and straightforward approach to radiation reaction force and damping is proposed. Starting from the Larmor formula for the power radiated by an accelerated charged particle, written in terms of the applied force instead of the acceleration, an expression for the radiation force is established in general, and applied to the examples for the linear and circular motion of a charged particle. This expression is quadratic in the magnitude of the applied force, inversely proportional to the speed of the charged particle, and directed opposite to the velocity vector. This force approach may contribute to the solution of the very old problem of incorporating the radiation reaction to the motion of the charged particles, and future experiments may tell us whether or not this approach point is in the right direction.

  14. Reversal of radiation reaction force and instability of the ground state of an atom located above the surface of an active medium

    It is shown that spontaneous emission of an excited atom is suppressed, and electromagnetic instability of the ground state is possible, if an atom is located in the vicinity of an active medium which amplifies the propagating radiation. The effect is due to a modified and phase-shifted near field of an oscillating atomic dipole, which prevails over the usual radiation reaction field related to the wave zone. The necessary conditions for the reversal of the total electromagnetic back reaction are found, and possible experimental realizations are discussed. copyright 1996 The American Physical Society

  15. Radiation reaction force without runaway solutions

    An equation including radiation reaction effects without runaway solutions is derived by making the postulate that the radiation reaction force is evaluated at a different time than the external force.

  16. Reproducibility of the spatio-temporal variables and the ground reaction forces walking with fire fighting boots REPRODUCIBILIDAD DE LAS VARIABLES ESPACIO-TEMPORALES Y DE LAS COMPONENTES DE LA FUERZA DE REACCIÓN DEL SUELO EN LA MARCHA CON BOTAS DE BOMBERO [Reproducibility of the spatio-temporal variables and the ground reaction forces walking with fire fighting boo

    Begoña Gavilanes

    2010-11-01

    Full Text Available AbstractThe aim of this study is to analyze the reproducibility of the spatio-temporal variables and the ground reaction forces (GRF when walking with fire fighting boots in comparison to walking with low calf shoes. Spatio-temporal parameters and the variables related to the three components of the GRF of 39 people were recorded under two different walking conditions. A T-test to contrast the difference between the coefficients of variation (CV in both conditions was used. The CV of the spatio-temporal variables (i.e velocity (V, condition I = 2.01%; condition II = 1.81%, of the vertical (i.e. contact force (FZA of the left foot, condition I = 2.54%; condition II = 2.73% and of the antero-posterior GRF (i.e. maximum force (FXMAX of the left foot, condition I = 4.47%; condition II = 4.59% was lower than 12.5%, suggesting that these variables could be used to analyze the influence of fire fighting boots on the gait. However, the low reproducibility showed by medium-lateral parameters does not allow to use them. Apart from the bipodal phase no differences were found between the two walking conditions. Key words: biomechanics, footwear, variability.ResumenEl objetivo del presente trabajo es analizar la reproducibilidad de las variables espacio-temporales y de la fuerza de reacción del suelo (FRS durante la marcha con botas de bombero y compararla con la mostrada durante la marcha con calzado de cuero sin caña. Se registraron las variables espacio-temporales de 39 personas así como las variables que definen las tres componentes de la FRS con dos tipos de calzado diferente. Se utilizó la prueba T para contrastar la hipótesis referida a la diferencia del coeficiente de variación (CV entre los dos tipos de calzado. El CV de las variables espacio-temporales (p. ej. velocidad (V, condición I = 2,01%; condición II = 1,81%, así como de las que definen la componente vertical (p. ej. fuerza de apoyo (FZA del pie izquierdo, condición I = 2,54%; condición II = 2,73% y antero-posterior (p. ej. fuerza máxima (FXMAX del pie izquierdo, condición I = 4,47%; condición II = 4,59% de la FRS fue inferior a 12,5%, sugiriendo que estas variables pueden ser utilizadas para analizar la influencia de las botas de bombero sobre la marcha. La baja reproducibilidad mostrada por las variables que definen la componente medio-lateral desaconseja la utilización de las mismas para evaluar el efecto de las botas de bombero sobre la marcha. A excepción del tiempo de apoyo bipodal, el resto de variables durante la marcha con botas de bombero no mostró una variabilidad diferente a la obtenida durante la marcha con calzado de cuero sin caña.Palabras clave: biomecánica, calzado, variabilidad. AbstractThe aim of this study is to analyze the reproducibility of the spatio-temporal variables and the ground reaction forces (GRF when walking with fire fighting boots in comparison to walking with low calf shoes. Spatio-temporal parameters and the variables related to the three components of the GRF of 39 people were recorded under two different walking conditions. A T-test to contrast the difference between the coefficients of variation (CV in both conditions was used. The CV of the spatio-temporal variables (i.e velocity (V, condition I = 2.01%; condition II = 1.81%, of the vertical (i.e. contact force (FZA of the left foot, condition I = 2.54%; condition II = 2.73% and of the antero-posterior GRF (i.e. maximum force (FXMAX of the left foot, condition I = 4.47%; condition II = 4.59% was lower than 12.5%, suggesting that these variables could be used to analyze the influence of fire fighting boots on the gait. However, the low reproducibility showed by medium-lateral parameters does not allow to use them. Apart from the bipodal phase no differences were found between the two walking conditions.Key words: biomechanics, footwear, variability.

  17. Estudo da variabilidade das forças de reação do solo na aquisição do andar independente em bebês A study of ground reaction forces variability during acquisition of independent gait in toddlers

    Giovana Levada

    2012-06-01

    Full Text Available Este estudo avaliou o comportamento das forças de reação do solo (FRS nos primeiros meses do andar independente, a fim de identificar mudanças na capacidade infantil de propulsionar e equilibrar o corpo em condição dinâmica. Foram avaliadas no período de três meses dez crianças com idade de 13 meses na primeira avaliação. As crianças caminharam em uma passarela de cinco metros de comprimento com duas plataformas de força embutidas. Foram estudadas magnitudes máximas e mínimas das FRS e as respectivas variabilidades. As avaliações foram comparadas através do teste não-paramétrico ANOVA de Friedman (pThis study aimed to describe ground reaction forces' profiles during toddler's gait at the first months of the acquisition phase of independent walking, in order to identify whether there are changes in the ability to propel and balance the body in this dynamic condition. Ten thirteen-month old toddlers volunteered to the study and were evaluated three times in a three-month interval. The toddlers walked over a 5 m long walkway with two force plates fixed at ground level. Vertical and horizontal peak reaction forces and variability coefficients were selected for analysis. To compare the results of the three evaluations ANOVA Friedman's tests were used at 5% level of significance. The walking experience achieved by the toddlers month after month was not sufficient to significantly change the biomechanical selected variables and statistically significant differences were not found for the selected variables along three months. However, a reduction in the variability coefficient for the vertical reaction forces suggests development towards an increasingly mature gait pattern.

  18. Predição da força de reação do solo durante a corrida na água Prediction of ground reaction force during water immersion running

    Alessandro Haupenthal

    2010-09-01

    Full Text Available Este estudo visou desenvolver um modelo para a predição da força de reação do solo na corrida subaquática. Participaram 20 sujeitos (9 homens e 11 mulheres, que realizaram corrida subaquática em dois níveis de imersão e três velocidades. Para cada sujeito foram coletadas seis passagens válidas em cada condição, com a utilização de uma plataforma subaquática de força. O modelo para predição da força foi construído por regressão linear múltipla. Foram consideradas variáveis dependentes a componente vertical e a componente ântero-posterior da força de reação do solo. As variáveis imersão, sexo, velocidade, massa corporal, densidade corporal e percentual de gordura foram consideradas independentes. Permaneceu no modelo final de regressão para a componente vertical a velocidade (pThis study aimed at developing a model to predict ground reaction force during deep-water running. A total of 20 subjects ((9 men, 11 women ran in water at two immersion levels and three different speeds. Each subject performed six valid trials in each condition, data being captured by an underwater force plate. The force prediction model was build by multiple linear regression. Dependent variables were the vertical and anteroposterior components of the ground reaction force; independent variables were runners' immersion, sex, speed, body mass, body density, and percentage of fat. At the final regression model for the vertical component, only speed remained (p<0.001, while for the anteroposterior component, speed, immersion, and body mass were maintained (all at p<0.001. The obtained model for the anteroposterior component of ground reaction force may be found satisfactory, as adjusted determination coefficient was 0.79. However, the prediction model for the vertical component cannot be recommended for prediction during deep-water running, since that coefficient was 0.18. It must be noted that the proposed prediction model applies to subjects provided that they have similar characteristics to those who took part in this study.

  19. Unmanned ground vehicles for integrated force protection

    Carroll, Daniel M.; Mikell, Kenneth; Denewiler, Thomas

    2004-09-01

    The combination of Command and Control (C2) systems with Unmanned Ground Vehicles (UGVs) provides Integrated Force Protection from the Robotic Operation Command Center. Autonomous UGVs are directed as Force Projection units. UGV payloads and fixed sensors provide situational awareness while unattended munitions provide a less-than-lethal response capability. Remote resources serve as automated interfaces to legacy physical devices such as manned response vehicles, barrier gates, fence openings, garage doors, and remote power on/off capability for unmanned systems. The Robotic Operations Command Center executes the Multiple Resource Host Architecture (MRHA) to simultaneously control heterogeneous unmanned systems. The MRHA graphically displays video, map, and status for each resource using wireless digital communications for integrated data, video, and audio. Events are prioritized and the user is prompted with audio alerts and text instructions for alarms and warnings. A control hierarchy of missions and duty rosters support autonomous operations. This paper provides an overview of the key technology enablers for Integrated Force Protection with details on a force-on-force scenario to test and demonstrate concept of operations using Unmanned Ground Vehicles. Special attention is given to development and applications for the Remote Detection Challenge and Response (REDCAR) initiative for Integrated Base Defense.

  20. Running-specific prostheses limit ground-force during sprinting

    Grabowski, Alena M.; McGowan, Craig P.; McDermott, William J.; Beale, Matthew T.; Kram, Rodger; Herr, Hugh M

    2009-01-01

    Running-specific prostheses (RSP) emulate the spring-like behaviour of biological limbs during human running, but little research has examined the mechanical means by which amputees achieve top speeds. To better understand the biomechanical effects of RSP during sprinting, we measured ground reaction forces (GRF) and stride kinematics of elite unilateral trans-tibial amputee sprinters across a range of speeds including top speed. Unilateral amputees are ideal subjects because each amputee's a...

  1. Computerized identification and classification of stance phases as made by front og hind feet of walking cows based on 3-dimensional ground reaction forces

    Skjøth, F; Thorup, Vivi Mørkøre; do Nascimento, Omar Feix; Ingvartsen, Klaus Lønne; Rasmussen, Morten Dam; Voigt, Michael

    2013-01-01

    force information. Features were derived from measurements made using two parallel 3-dimensional force plates. The approach presented is based on clustering of Centre of Pressure (COP) trace points over space and time, combined with logical sequencing of stance phases based on the dynamics of...

  2. Effects of ground and joint reaction force exercise on lumbar spine and femoral neck bone mineral density in postmenopausal women: a meta-analysis of randomized controlled trials

    Kelley George A

    2012-09-01

    Full Text Available Abstract Background Low bone mineral density (BMD and subsequent fractures are a major public health problem in postmenopausal women. The purpose of this study was to use the aggregate data meta-analytic approach to examine the effects of ground (for example, walking and/or joint reaction (for example, strength training exercise on femoral neck (FN and lumbar spine (LS BMD in postmenopausal women. Methods The a priori inclusion criteria were: (1 randomized controlled trials, (2 exercise intervention ≥ 24 weeks, (3 comparative control group, (4 postmenopausal women, (5 participants not regularly active, i.e., less than 150 minutes of moderate intensity (3.0 to 5.9 metabolic equivalents weight bearing endurance activity per week, less than 75 minutes of vigorous intensity (> 6.0 metabolic equivalents weight bearing endurance activity per week, resistance training g was calculated for each FN and LS BMD result and pooled using random-effects models. Z-score alpha values, 95%confidence intervals (CI and number-needed-to-treat (NNT were calculated for pooled results. Heterogeneity was examined using Q and I2. Mixed-effects ANOVA and simple meta-regression were used to examine changes in FN and LS BMD according to selected categorical and continuous variables. Statistical significance was set at an alpha value ≤0.05 and a trend at >0.05 to ≤ 0.10. Results Small, statistically significant exercise minus control group improvements were found for both FN (28 g’s, 1632 participants, g = 0.288, 95% CI = 0.102, 0.474, p = 0.002, Q = 90.5, p I2 = 70.1%, NNT = 6 and LS (28 g’s, 1504 participants, g = 0.179, 95% CI = −0.003, 0.361, p = 0.05, Q = 77.7, p I2 = 65.3%, NNT = 6 BMD. Clinically, it was estimated that the overall changes in FN and LS would reduce the 20-year relative risk of osteoporotic fracture at any site by approximately 11% and 10%, respectively. None of the mixed-effects ANOVA analyses were statistically significant. Statistically significant, or a trend for statistically significant, associations were observed for changes in FN and LS BMD and 20 different predictors. Conclusions The overall findings suggest that exercise may result in clinically relevant benefits to FN and LS BMD in postmenopausal women. Several of the observed associations appear worthy of further investigation in well-designed randomized controlled trials.

  3. About Radiation Reaction with Force Approach

    Velazquez, Gustavo Lopez

    2015-01-01

    The difficulty of usual approach to radiation reaction is pointed out , and a possible approach based on the force acting to the charged particle which produces the acceleration itself, is presented. This approach brings about an expression such that acceleration is zero whenever the external force is zero.

  4. Ground reaction force and electromyographic activity of transfemoral amputee gait: a case series http://dx.doi.org/10.5007/1980-0037.2013v15n1p16

    Alberto Carlos Amadio

    2013-01-01

    Full Text Available Ground reaction forces (GRF and electromyographic activity form a part of the descriptive data that characterise the biomechanics of gait. The research of these parameters is important in establishing gait training and understanding the impact of amputation and prosthetic components on movement during the act of walking. Therefore, this case series describes the GRF and electromyographic activity in the gait of transfemoral amputees. A force plate was used to measure GRF, and an electromyographic system monitored the vastus lateralis, biceps femoris, tibialis anterior, and gastrocnemius lateralis muscles of the non-amputated leg. The average vertical and anteroposterior GRF time-curves, average electromyographic activity, and descriptor variables were then analysed. We observed decreases in vertical and anteroposterior GRF magnitudes as well as in anteroposterior GRF descriptor variables during the propulsive phase in the amputated leg. There were increases in phasic muscle activity and co-activation in the non-amputated leg. We concluded that, during walking, the unilateral transfemoral amputees (who were analysed in this case series developed lower GRF in the amputated limb and a longer period of electromyographic activity in the non-amputated limb.

  5. Self-force approach for radiation reaction

    Burko, Lior M.

    1999-01-01

    We overview the recently proposed mode-sum regularization prescription (MSRP) for the calculation of the local radiation-reaction forces, which are crucial for the orbital evolution of binaries. We then describe some new results which were obtained using MSRP, and discuss their importance for gravitational-wave astronomy.

  6. Dynamic input to determine hip joint moments, power and work on the prosthetic limb of transfemoral amputees: ground reaction vs knee reaction

    FROSSARD, Laurent; Cheze, Laurence; Dumas, Raphaël

    2011-01-01

    Background: Calculation of lower limb kinetics is limited by floor-mounted force-plates. Objectives: Comparison of hip joint moments, power and mechanical work on the prosthetic limb of a transfemoral amputee calculated by inverse dynamics using either the ground reactions (force-plates) or knee reactions (transducer). Study design: Comparative analysis. Methods: Kinematics, ground reaction and knee reaction data were collected using a motion analysis system, two forceplates, and a multi-axia...

  7. Ground reaction force and electromyographic activity of transfemoral amputee gait: a case series / Força de Reação do Solo e atividade eletromiográfica da marcha de amputados transfemorais: uma série de casos

    Alex Sandra Oliveira de, Cerqueira; Edward Yuji, Yamaguti; Luis, Mochizuki; Alberto Carlos, Amadio; Júlio Cerca, Serrão.

    2013-02-01

    Full Text Available O comportamento da Força de Reação do Solo (FRS) e a atividade eletromiográfica formam uma parte dos dados que caracterizam a biomecânica da marcha. O estudo destes parâmetros é importante para a recuperação da locomoção e para compreensão do impacto da amputação e dos componentes protéticos nos mov [...] imentos desenvolvidos no andar. Portanto, esta série de casos tem como objetivo descrever a atividade eletromiográfica e a FRS de amputados transfemorais. Para mensurar a FRS, foi utilizada uma plataforma de força e um sistema de eletromiografia monitorou os músculos vasto lateral, bíceps femoral, tibial anterior e gastrocnêmio lateral da perna não-amputada. As médias das componentes vertical e ânteroposterior da FRS, a atividade eletromiográfica e variáveis descritivas foram analisadas. Foi observado uma diminuição da magnitude da FRS vertical e ânteroposterior e das variáveis descritivas da componente ânteroposterior da FRS durante a fase de propulsão na perna amputada. Houve aumento na atividade fásica muscular e co-ativação na perna não-amputada. Pode-se concluir que os amputados transfemorais unilaterais analisados nesta série de casos desenvolveram menor FRS na perna amputada e longos períodos de atividade eletromiográfica na perna não amputada durante a marcha. Abstract in english Ground reaction forces (GRF) and electromyographic activity form a part of the descriptive data that characterise the biomechanics of gait. The research of these parameters is important in establishing gait training and understanding the impact of amputation and prosthetic components on movement dur [...] ing the act of walking. Therefore, this case series describes the GRF and electromyographic activity in the gait of transfemoral amputees. A force plate was used to measure GRF, and an electromyographic system monitored the vastus lateralis, biceps femoris, tibialis anterior, and gastrocnemius lateralis muscles of the non-amputated leg. The average vertical and anteroposterior GRF time-curves, average electromyographic activity, and descriptor variables were then analysed. We observed decreases in vertical and anteroposterior GRF magnitudes as well as in anteroposterior GRF descriptor variables during the propulsive phase in the amputated leg. There were increases in phasic muscle activity and co-activation in the non-amputated leg. We concluded that, during walking, the unilateral transfemoral amputees (who were analysed in this case series) developed lower GRF in the amputated limb and a longer period of electromyographic activity in the non-amputated limb.

  8. A COMPARISON OF UPPER-EXTREMITY REACTION FORCES BETWEEN THE YURCHENKO VAULT AND FLOOR EXERCISE

    Matthew Kirk Seeley

    2005-06-01

    Full Text Available The purpose of this study was to examine reaction forces transmitted to the upper extremities of high-level gymnasts during the round-off phase of the Yurchenko vault. A secondary purpose of this study was to compare reaction forces during the Yurchenko vault to reaction forces observed in a tumbling pass during the floor exercise. Ten high-level, female gymnasts volunteered to participate. Conditions of the independent variable were the Yurchenko vault and floor exercise; dependent variables were peak vertical and peak anterior-posterior reaction forces. Each participant performed three trials of both conditions with the trail hand contacting a force platform. Vertical and anterior-posterior reaction forces, normalized to body weight, were greater (p < 0.05 during the round-off phase of the Yurchenko vault (2.38 than during the floor exercise round-off (2.15. Vertical reaction forces during the round-off phase of the Yurchenko vault and floor exercise round-off are similar to reaction forces transmitted to upper extremities during other gymnastic skills and ground reaction forces transmitted to lower extremities while running and walking at various speeds. Results of this study reveal a need for further research considering methods aimed at reducing reaction forces transmitted to the upper extremities during the Yurchenko vault and floor exercise.

  9. Grounding-Induced Sectional Forces and Residual Strength of Grounded Ship Hulls

    Paik, Jeom Kee; Pedersen, Preben Terndrup

    The aim of the present study is to determine the sectional forces induced by ship grounding and also to assess the residual strength of groundedship hulls. An analytical approach is used to estimate the grounding-induced sectional forces of ships. The extent and location of structural damage due to...... grounding is defined based on the ABS Safe Hull guide. The residual strength of damaged hulls is calculated by using a simple analytical formula. The method is applied to residual strength assessment of a damaged double hull tanker of 38,400 dwt due to grounding....

  10. Tensor Forces and the Ground-State Structure of Nuclei

    Two-nucleon momentum distributions are calculated for the ground states of nuclei with mass number A (le) 8, using accurate variational Monte Carlo wave functions derived from a realistic Hamiltonian with two- and three-nucleon potentials. The momentum distribution of 'np' pairs is found to be much larger than that of 'pp' pairs for values of the relative momentum in the range (300--600) MeV/c and vanishing total momentum. This large difference, more than an order of magnitude, is seen in all nuclei considered, and has a universal character originating from the tensor components present in any realistic nucleon-nucleon potential. The correlations induced by the tensor force strongly influence the structure of 'np' pairs, which are known to be predominantly in deuteron-like states, while they are ineffective for 'pp' pairs, which are mostly in 1S0 states. These features should be easily observable in two-nucleon knock-out processes, for example in A(e,e(prime) np) and A(e,e(prime) pp) reactions

  11. Ground reaction curve based upon block theory

    Discontinuities in a rock mass can intersect an excavation surface to form discrete blocks (keyblocks) which can be unstable. Once a potentially unstable block is identified, the forces affecting it can be calculated to assess its stability. The normal and shear stresses on each block face before displacement are calculated using elastic theory and are modified in a nonlinear way by discontinuity deformations as the keyblock displaces. The stresses are summed into resultant forces to evaluate block stability. Since the resultant forces change with displacement, successive increments of block movement are examined to see whether the block ultimately becomes stable or fails. Two-dimensional (2D) and three-dimensional (3D) analytic models for the stability of simple pyramidal keyblocks were evaluated. Calculated stability is greater for 3D analyses than for 2D analyses. Calculated keyblock stability increases with larger in situ stress magnitudes, larger lateral stress ratios, and larger shear strengths. Discontinuity stiffness controls blocks displacement more strongly than it does stability itself. Large keyblocks are less stable than small ones, and stability increases as blocks become more slender

  12. Linear motion under constant force and radiation reaction

    The classical relativistic equation of motion with radiation reaction is solved exactly when the motion is along the lines of force due to a constant electric field. For physically admissible solutions, there is no contribution due to the radiation reaction. The general motion without radiation reaction is not linear. (author)

  13. Evaluating competing forces constraining glacial grounding-line stability (Invited)

    Powell, R. D.

    2013-12-01

    Stability of grounding lines of marine-terminating glaciers and ice sheets is of concern due to their importance in governing rates of ice mass loss and consequent sea level rise during global warming. Although processes are similar at tidewater and floating grounding zones their relative magnitudes in terms of their influence on grounding-line stability vary between these two end members. Processes considered Important for this discussion are ice dynamics, ice surface melting and crevassing, ocean dynamics, subglacial sediment and water dynamics, and subglacial bed geometries. Models have continued to improve in their representation of these complex interactions but reliable field measurements and data continue to be hard earned and too few to properly constrain the range of boundary conditions in this complicated system. Some data will be presented covering a range of regimes from Alaska, Svalbard and Antarctica. Certainly more data are required on subglacial sediment/water dynamics and fluxes to fully represent the spectrum of glacial regimes and to assess the significance of grounding-zone sediment systems in counteracting the other processes to force grounding-line stability. Especially important here is constraining the duration of the stability that could be maintained by sediment flux - present data appear to show that it is likely to be a limited period.

  14. Ground-state photoneutron reactions in 15N

    Photoneutron angular distributions were measured by time-of-flight techniques for the reaction 15N(#betta#,n0) 14N over the region of excitation energy from 15 to 25 MeV. Ground state cross sections were obtained by stepping the bremsstrahlung end point over the energy region of interest in 2 MeV intervals. By fitting the spectral data to a series of Legendre polynomials, angular distribution coefficients were extracted and interpreted on the basis of a simple single particle model. It appears that a large fraction of the photoabsorption strength leading to decays via the ground state channel is due to the formation of J/sup ?/ = (3/2)+, T = (1/2) states in 15N which decay by d-wave neutron emission. The data support an approximation of purely electric dipole absorption in the region measured. Some small amount of s-wave neutron emission interfering with the dominant p/sub 1/2/?d/sub 3/2/ transition is consistent with an observed value for the a2/a0 coefficient of -0.7 +- 0.2. The (#betta#,n0) cross section integrated between threshold and 30 MeV is estimated to represent about one-third of the total strength in the neutron channel. A state identified at 17.3 MeV is consistent in energy and composition with a theoretical prediction based on a shell model calculation using a residual interaction with a Soper mixture of exchange forces

  15. CHEMICAL REACTIONS SIMULATED BY GROUND-WATER-QUALITY MODELS.

    Grove, David B.; Stollenwerk, Kenneth G.

    1987-01-01

    Recent literature concerning the modeling of chemical reactions during transport in ground water is examined with emphasis on sorption reactions. The theory of transport and reactions in porous media has been well documented. Numerous equations have been developed from this theory, to provide both continuous and sequential or multistep models, with the water phase considered for both mobile and immobile phases. Chemical reactions can be either equilibrium or non-equilibrium, and can be quantified in linear or non-linear mathematical forms. Non-equilibrium reactions can be separated into kinetic and diffusional rate-limiting mechanisms. Solutions to the equations are available by either analytical expressions or numerical techniques. Saturated and unsaturated batch, column, and field studies are discussed with one-dimensional, laboratory-column experiments predominating. A summary table is presented that references the various kinds of models studied and their applications in predicting chemical concentrations in ground waters.

  16. Generalization of the Force Approach to Radiation Reaction

    Lopez, Gustavo V

    2016-01-01

    A generalization of the force approach to radiation reaction is given, taken into consideration an arbitrary motion of the charged particle . The expression obtained brings about the expression already given for the linear an the circular acceleration cases.

  17. Forced vibration tests of a model foundation on rock ground

    The effect of the dynamic soil-structure interaction was investigated experimentally by forced vibration tests of a model foundation resting on rock surface. The experiment was carried out in 1985 at Tomari nuclear power plant site, Hokkaido, Japan. The model foundation was made of reinforced concrete of 14m*14m in plan and 5m thick and the total weight was 2352 ton. The ground was made of two layers whose interface was inclined by certain degree from north-west to south-east. The forced vibration tests were carried out mainly by an exciter of maximum 4 ton force. Micro-tremor and micro-earthquake were also observed. In this experiment such special attention was paid for obtaining good traction data beneath the foundation as accurate calibration of pressure gauges at the site and the use of auxiliary exciter with larger capacity. Simulations are carried out by wave propagation theory and FEM. Simulated results can reasonably explain the experimental results and the dynamic soil-structure interaction effects in various aspects. Resultant forces and moments evaluated by experimentally obtained tractions with approximated polynomial distribution are in good agreement with those evaluated by displacements

  18. Can shoulder joint reaction forces be estimated by neural networks?

    de Vries, W H K; Veeger, H E J; Baten, C T M; van der Helm, F C T

    2016-01-01

    To facilitate the development of future shoulder endoprostheses, a long term load profile of the shoulder joint is desired. A musculoskeletal model using 3D kinematics and external forces as input can estimate the mechanical load on the glenohumeral joint, in terms of joint reaction forces. For long term ambulatory measurements, these 3D kinematics can be measured by means of Inertial Magnetic Measurement Systems. Recording of external forces under daily conditions is not feasible; estimations of joint loading should preferably be independent of this input. EMG signals reflect the musculoskeletal response and can easily be measured under daily conditions. This study presents the use of a neural network for the prediction of glenohumeral joint reaction forces based upon arm kinematics and shoulder muscle EMG. Several setups were examined for NN training, with varying combinations of type of input, type of motion, and handled weights. When joint reaction forces are predicted by a trained NN, for motion data independent of the training data, results show a high intraclass correlation (ICC up to 0.98) and relative SEM as low as 3%, compared to similar output of a musculoskeletal model. A convenient setup in which kinematics and only one channel of EMG were used as input for the NN׳s showed comparable predictive power as more complex setups. These results are promising and enable long term estimation of shoulder joint reaction forces outside the motion lab, independent of external forces. PMID:26654109

  19. Relação entre a mobilidade do tornozelo e pé e a magnitude da força vertical de reação do solo Relationship between ankle and foot mobility and the magnitude of the vertical ground reaction force

    DL Vianna

    2006-09-01

    Full Text Available OBJETIVO: Verificar a relação entre a mobilidade do tornozelo e do pé, e o pico da força vertical de reação do solo, considerada como porcentagem do peso corporal, gerada durante a fase de apoio da marcha. MÉTODOS: foram estudados pés normais do lado direito e esquerdo de 15 homens com 22,1±2,7 anos (19-28 e 15 mulheres 24,20±5,24 anos (19-34. Os parâmetros de exclusão foram: deformidades nos pés, doenças ou traumas, que pudessem acometer o sistema musculoesquelético e a marcha. A mobilidade do tornozelo e dos pés foi obtida através da goniometria da flexão plantar, dorsiflexão, extensão do hálux e extensão dos dedos, o pico da força vertical de reação do solo FRS, foi obtido pela baropodometria computadorizada do sistema FSCAN R. A correlação entre ambas foi feita pelo teste estatístico de Spearman. RESULTADOS: os indivíduos do grupo masculino apresentaram menores valores de mobilidade, e maiores valores do pico da força vertical de reação do solo, quando comparados com o grupo feminino. Não houve diferença entre os pés direito e esquerdo. No sexo feminino foi encontrada correlação negativa estatisticamente significante entre os valores da flexão plantar e a força vertical, e entre os valores da extensão dos dedos e a foça vertical. No sexo masculino, houve correlação negativa estatisticamente significante entre os valores da dorsiflexão e a força vertical. Entre os demais valores não foi encontrada correlação significante. CONCLUSÃO: Há relação entre a mobilidade e a força vertical gerada durante a marcha.OBJECTIVE: To investigate the relationship between ankle and foot mobility and the peak of the vertical ground reaction force, as a percentage of body weight, generated during the gait stance phase. METHOD: Fifteen men with mean age of 22.1 ± 2.7 years (range: 19-28 and fifteen women with mean age of 24.20 ± 5.24 years (range: 19-34 with normal feet were studied. The exclusion criteria were foot deformities or a history of trauma or diseases that might have harmed both the musculoskeletal system and gait pattern. The ankle and foot mobility was obtained by means of goniometry on the plantar flexion, dorsiflexion, hallux extension and toe extension. The peak of the vertical ground reaction force was obtained by baropodometry using the FSCAN TM system. The Spearman statistical test was used to identify correlations. RESULTS: Males presented lower mobility values and higher peak values for the vertical ground reaction force, in comparison with females. There was no difference between the right and left foot. For females, there were statistically significant negative correlations between the values for plantar flexion and vertical force, and between the values for toe extension and vertical force. For males, there were statistically significant negative correlations between the values for dorsiflexion and vertical force. Among the remaining values, no significant correlation was found. CONCLUSION: There was a relationship between mobility and the vertical force generated during gait.

  20. Computational Catalysis Using the Artificial Force Induced Reaction Method.

    Sameera, W M C; Maeda, Satoshi; Morokuma, Keiji

    2016-04-19

    The artificial force induced reaction (AFIR) method in the global reaction route mapping (GRRM) strategy is an automatic approach to explore all important reaction paths of complex reactions. Most traditional methods in computational catalysis require guess reaction paths. On the other hand, the AFIR approach locates local minima (LMs) and transition states (TSs) of reaction paths without a guess, and therefore finds unanticipated as well as anticipated reaction paths. The AFIR method has been applied for multicomponent organic reactions, such as the aldol reaction, Passerini reaction, Biginelli reaction, and phase-transfer catalysis. In the presence of several reactants, many equilibrium structures are possible, leading to a number of reaction pathways. The AFIR method in the GRRM strategy determines all of the important equilibrium structures and subsequent reaction paths systematically. As the AFIR search is fully automatic, exhaustive trial-and-error and guess-and-check processes by the user can be eliminated. At the same time, the AFIR search is systematic, and therefore a more accurate and comprehensive description of the reaction mechanism can be determined. The AFIR method has been used for the study of full catalytic cycles and reaction steps in transition metal catalysis, such as cobalt-catalyzed hydroformylation and iron-catalyzed carbon-carbon bond formation reactions in aqueous media. Some AFIR applications have targeted the selectivity-determining step of transition-metal-catalyzed asymmetric reactions, including stereoselective water-tolerant lanthanide Lewis acid-catalyzed Mukaiyama aldol reactions. In terms of establishing the selectivity of a reaction, systematic sampling of the transition states is critical. In this direction, AFIR is very useful for performing a systematic and automatic determination of TSs. In the presence of a comprehensive description of the transition states, the selectivity of the reaction can be calculated more accurately. For relatively large molecular systems, the computational cost of AFIR searches can be reduced by using the ONIOM(QM:QM) or ONIOM(QM:MM) methods. In common practice, density functional theory (DFT) with a relatively small basis set is used for the high-level calculation, while a semiempirical approach or a force field description is used for the low-level calculation. After approximate LMs and TSs are determined, standard computational methods (e.g., DFT with a large basis set) are used for the full molecular system to determine the true LMs and TSs and to rationalize the reaction mechanism and selectivity of the catalytic reaction. The examples in this Account evidence that the AFIR method is a powerful approach for accurate prediction of the reaction mechanisms and selectivities of complex catalytic reactions. Therefore, the AFIR approach in the GRRM strategy is very useful for computational catalysis. PMID:27023677

  1. Government Applications Task Force ground truth study of WAG 4

    This report documents the Government Applications Task Force (GATF) Buried Waste Project. The project was initiated as a field investigation and verification of the 1994 Strategic Environmental Research and Development Program's (SERDP) Buried Waste Identification Project results. The GATF project team included staff from three US Department of Energy (DOE) Laboratories [Oak Ridge National Laboratory (ORNL), Los Alamos National Laboratory (LANL), and the Savannah River Technology Center (SRTC)] and from the National Exploitation Laboratory. Similar studies were conducted at each of the three DOE laboratories to demonstrate the effective use of remote sensing technologies. The three locations were selected to assess differences in buried waste signatures under various environmental conditions (i.e., climate, terrain, precipitation, geology, etc.). After a brief background discussion of the SERDP Project, this report documents the field investigation (ground truth) results from the 1994--1995 GATF Buried Waste Study at ORNL's Waste Area Grouping (WAG) 4. Figures for this report are located in Appendix A

  2. Tensor Forces and the Ground-State Structure of Nuclei

    Two-nucleon momentum distributions are calculated for the ground states of nuclei with mass number A?8, using variational Monte Carlo wave functions derived from a realistic Hamiltonian with two- and three-nucleon potentials. The momentum distribution of np pairs is found to be much larger than that of pp pairs for values of the relative momentum in the range (300-600) MeV/c and vanishing total momentum. This order of magnitude difference is seen in all nuclei considered and has a universal character originating from the tensor components present in any realistic nucleon-nucleon potential. The correlations induced by the tensor force strongly influence the structure of np pairs, which are predominantly in deuteronlike states, while they are ineffective for pp pairs, which are mostly in 1S0 states. These features should be easily observable in two-nucleon knockout processes, such as A(e,e'np) and A(e,e'pp)

  3. A thermodynamic force generated by chemical gradient and adsorption reaction

    Sugawara, Takeshi

    2009-01-01

    Biological units such as macromolecules, organelles, and cells are directed to a proper location under gradients of relevant chemicals. By considering a macroscopic element that has binding sites for a chemical adsorption reaction to occur on its surface, we show the existence of a thermodynamic force that is generated by the gradient and exerted on the element. By assuming local equilibrium and adopting the grand potential from thermodynamics, we derive a formula for such a thermodynamic force, which depends on the chemical potential gradient and Langmuir isotherm. The conditions under which the formula can be applied are demonstrated to hold in intracellular reactions. The role of the force in the partitioning of bacterial chromosome/plasmid during cell division is discussed.

  4. The reaction force: Three key points along an intrinsic reaction coordinate

    Peter Politzer; Alejandro Toro-Labbé; Soledad Gutiérrez-Oliva; Bárbara herrera; Pablo Jaque; Monica C Concha; Jane S Murray

    2005-09-01

    The concept of the reaction force is presented and discussed in detail. For typical processes with energy barriers, it has a universal form which defines three key points along an intrinsic reaction coordinate: the force minimum, zero and maximum. We suggest that the resulting four zones be interpreted as involving preparation of reactants in the first, transition to products in the second and third, and relaxation in the fourth. This general picture is supported by the distinctive patterns of the variations in relevant electronic properties. Two important points that are brought out by the reaction force are that (a) the traditional activation energy comprises two separate contributions, and (b) the transition state corresponds to a balance between the driving and the retarding forces.

  5. A influência do uso acumulado de calçados de corrida sobre a força de reação do solo e as respostas de pressão plantar The influence of running shoes cumulative usage on the ground reaction forces and plantar pressure responses

    Roberto Bianco

    2011-12-01

    Full Text Available Acredita-se que a eficiência do calçado seja afetada pelo uso prolongado, mas as alterações biomecânicas ainda não estão bem compreendidas. O objetivo deste estudo é analisar a influência do uso de calçados de corrida na força de reação do solo e os parâmetros de pressão plantar. Três corredores do sexo masculino receberam quatro calçados de corrida para usarem em suas sessões de treinamento. O Sistema Gaitway e o Sistema de F-scan foram usados para registrar a força de reação do solo e parâmetros pressão plantar em diferentes regiões do pé. As coletas ocorreram em quatro momentos: novo e 100, 200 e 300 km de uso. O primeiro pico diminuiu da condição novo para os 300 km de uso (p The prolonged use of a running shoe is thought to affect the efficiency of its impact attenuation properties. However, its effect over biomechanical variables has yet not been well understood. The aim of this study was to examine the influence of running shoe usage on ground reaction force and plantar pressure parameters. Three male runners received four running shoes each to use at their training sessions. The Gaitway System was used to register the vertical component of the ground reaction force, whereas the contact area and peak plantar pressure at different regions of the foot were assessed via the the F-scan System. Data collection occurred at baseline (when the shoes were new - New and after 100, 200 and 300km of use. The first peak decreased significantly from New to 300km (p < 0.01 and the loading rate showed a significant decrease at 200km in relation to the New condition (p < 0.01. Total area increased significantly from New to 100km (p < 0.01 of use and maintained a similar value when compared with the other conditions. There was a continuous and significant decrease (p < 0.01 on forefoot peak pressure as the mileage increased from New to 300km. The hallux peak pressure values were significantly smaller (p < 0.01 at 300km when compared with the New condition. Considering that the first peak, loading rate and plantar peak pressure values did not increase and that the plantar total contact area increased, it can be concluded that the running shoe did not suffer consistent alterations in ground reaction force and in plantar pressure after 300km of use.

  6. Comparison of the electron-spin force and radiation reaction force

    Mahajan, Swadesh M.; Asenjo, Felipe A.; Hazeltine, Richard D.

    2015-02-01

    It is shown that the forces that originate from the electron-spin interacting with the electromagnetic field can play, along with the Lorentz force, a fundamentally important role in determining the electron motion in a high energy density plasma embedded in strong high-frequency radiation, a situation that pertains to both laser-produced and astrophysical systems. These forces, for instance, dominate the standard radiation reaction force as long as there is a `sufficiently' strong ambient magnetic field for affecting spin alignment. The inclusion of spin forces in any advanced modelling of electron dynamics pertaining to high energy density systems (for instance in particle-in-cell codes), therefore, is a must.

  7. A new derivation for the radiation reaction force

    A new derivation for the radiation reaction on a point charge is presented. The field of the charge is written as a superposition of plane waves. The plane wave spectrum of the field consists of homogeneous plane waves which propagate away from the charge at the speed of light, and inhomogeneous plane waves which constitute the Coulomb field of the point charge. The radiation field is finite at the orbit of the point charge. The force acting on the charge due to this field is the well known Abraham-Lorentz radiation reaction. (author)

  8. Quantum Vacuum and Inertial Reaction Force in Nonrelativistic QED

    Sunahata, Hiroki; Haisch, Bernard

    2013-01-01

    The possible connection between the electromagnetic zero-point field (ZPF) and the inertia reaction force was first pointed out by Haisch, Rueda, and Puthoff (Phys. Rev. A, 49, 678, 1994), and then by Rueda and Haisch following a totally different and more satisfactory approach (Found. Phys., 28, 1057, 1998; Phys. Letters A, 240, 115, 1998; Annalen der Physik, 10 (5), 393, 2001). In the present paper, the approach taken by Rueda and Haisch will be followed, but the analysis will be done within a formulation that uses nonrelativistic quantum electrodynamics with the creation and annihilation operators rather than the approach of Rueda and Haisch using stochastic electrodynamics. We analyze the interaction between the zero-point field and an object under hyperbolic motion (constant proper acceleration), and find that there arises a reaction force which is proportional in magnitude, and opposite in direction, to the acceleration. This is suggestive of what we know as inertia. We also point out that the equivalen...

  9. Experimental verification of a computational technique for determining ground reactions in human bipedal stance.

    Audu, Musa L; Kirsch, Robert F; Triolo, Ronald J

    2007-01-01

    We have developed a three-dimensional (3D) biomechanical model of human standing that enables us to study the mechanisms of posture and balance simultaneously in various directions in space. Since the two feet are on the ground, the system defines a kinematically closed-chain which has redundancy problems that cannot be resolved using the laws of mechanics alone. We have developed a computational (optimization) technique that avoids the problems with the closed-chain formulation thus giving users of such models the ability to make predictions of joint moments, and potentially, muscle activations using more sophisticated musculoskeletal models. This paper describes the experimental verification of the computational technique that is used to estimate the ground reaction vector acting on an unconstrained foot while the other foot is attached to the ground, thus allowing human bipedal standing to be analyzed as an open-chain system. The computational approach was verified in terms of its ability to predict lower extremity joint moments derived from inverse dynamic simulations performed on data acquired from four able-bodied volunteers standing in various postures on force platforms. Sensitivity analyses performed with model simulations indicated which ground reaction force (GRF) and center of pressure (COP) components were most critical for providing better estimates of the joint moments. Overall, the joint moments predicted by the optimization approach are strongly correlated with the joint moments computed using the experimentally measured GRF and COP (0.78 unity slope (experimental=computational results) for postures of the four subjects examined. These results indicate that this model-based technique can be relied upon to predict reasonable and consistent estimates of the joint moments using the predicted GRF and COP for most standing postures. PMID:16797023

  10. The meson-theory ground for the effective force

    The effective force was considered based on the meson theory of nuclear forces. For the NN-interaction, nucleon-nucleon potentials of the one-boson-exchange model were used. Using the Hartree-Fock expression for nuclear energy density obtained with the effective force in the sudden approximation, the nucleus-nucleus potential can be analytically expressed by nuclei densities and xk, yk (the coefficients xk and tk are determined by masses and coupling constants of the exchange mesons). Using the expression for nuclear energy density, the nuclear matter binding energy can easily be obtained. (Z.S.) 1 tab., 3 figs., 10 refs

  11. Forced vibration tests of a model foundation on rock ground

    The response of very stiff structures, such as nuclear reactor buildings, to earthquake ground motion is significantly affected by radiation damping due to the soil-structure interaction. The radiation damping can be computed by vibration admittance theory or dynamical ground compliance theory. In order to apply the values derived from these theories to the practical problems, comparative studies between theoretical results and experimental results concerning the soil-structure interaction, especially if the ground is rock, are urgently needed. However, experimental results for rock are less easily obtained than theoretical ones. The purpose of this paper is to describe the harmonic excitation tests of a model foundation on rock and to describe the results of comparative studies. (orig./HP)

  12. The solar forcing on the ground 7 Be concentration variability

    7 Be, natural radionuclide, is produced by the interaction of cosmic radiation with oxygen and nitrogen molecules. 7 Be production in atmosphere depends on the intensity of cosmic radiation which is influenced by the Earth's magnetosphere. The magnetosphere shape depends on solar activity. This paper presents the influence of sunspots number (11 years period) on the ground 7 Be concentration variability. (authors)

  13. (Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio)

    1991-10-01

    This report presents information concerning field procedures employed during the monitoring, well construction, well purging, sampling, and well logging at the Wright-Patterson Air Force Base. Activities were conducted in an effort to evaluate ground water contamination.

  14. (Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio)

    1992-03-01

    This report presents information related to the sampling of ground water at the Wright-Patterson Air Force Base. It is part of an investigation into possible ground water contamination. Information concerns well drilling/construction; x-ray diffraction and sampling; soil boring logs; and chain-of-custody records.

  15. Tethered satellite system control using electromagnetic forces and reaction wheels

    Alandi Hallaj, Mohammad Amin; Assadian, Nima

    2015-12-01

    In this paper a novel non-rotating space tethered configuration is introduced which its relative positions controlled using electromagnetic forces. The attitude dynamics is controlled by three reaction wheels in the body axes. The nonlinear coupled orbital dynamics of a dumbbell tethered satellite formation flight are derived through a constrained Lagrangian approach. These equations are presented in the leader satellite orbital frame. The tether is assumed to be mass-less and straight, and the J2 perturbation is included to the analysis. The forces and the moments of the electromagnetic coils are modeled based on the far-filed model of the magnetic dipoles. A guidance scheme for generating the desired positions as a function of time in Cartesian form is presented. The satellite tethered formation with variable length is controlled utilizing a linear controller. This approach is applied to a specified scenario and it is shown that the nonlinear guidance method and the linear controller can control the nonlinear system of the tethered formation and the results are compared with optimal control approach.

  16. Fore-Aft Ground Force Adaptations to Induced Forelimb Lameness in Walking and Trotting Dogs

    Abdelhadi, Jalal; Wefstaedt, Patrick; Nolte, Ingo; Schilling, Nadja

    2012-01-01

    Animals alter their locomotor mechanics to adapt to a loss of limb function. To better understand their compensatory mechanisms, this study evaluated the changes in the fore-aft ground forces to forelimb lameness and tested the hypothesis that dogs unload the affected limb by producing a nose-up pitching moment via the exertion of a net-propulsive force when the lame limb is on the ground. Seven healthy Beagles walked and trotted at steady speed on an instrumented treadmill while horizontal f...

  17. Visual planning aid for movement of ground forces in operations other than war

    Schrepf, Norbert.

    1999-01-01

    The fall of the Berlin Wall in 1989 marked the change of the political and military situation worldwide. Peace keeping missions became more likely than major regional conflicts. However, the conventional combat simulations, which were developed for the combat between heavily armored forces could not handle these new situations. In these new missions the movement of ground forces becomes a major task for any commander. This thesis develops a software architecture of loosely coupled software co...

  18. A Comparison of Upper-Extremity Reaction Forces between the Yurchenko Vault and Floor Exercise.

    Seeley, Matthew K; Bressel, Eadric

    2005-06-01

    The purpose of this study was to examine reaction forces transmitted to the upper extremities of high-level gymnasts during the round-off phase of the Yurchenko vault. A secondary purpose of this study was to compare reaction forces during the Yurchenko vault to reaction forces observed in a tumbling pass during the floor exercise. Ten high-level, female gymnasts volunteered to participate. Conditions of the independent variable were the Yurchenko vault and floor exercise; dependent variables were peak vertical and peak anterior-posterior reaction forces. Each participant performed three trials of both conditions with the trail hand contacting a force platform. Vertical and anterior-posterior reaction forces, normalized to body weight, were greater (p running and walking at various speeds. Results of this study reveal a need for further research considering methods aimed at reducing reaction forces transmitted to the upper extremities during the Yurchenko vault and floor exercise. Key PointsDespite high difficulty and increased risk, a dearth of information exists concerning reaction forces transmitted to upper-extremities of high-level gymnasts performing the Yurchenko vault.Reaction forces experienced by high-level gymnasts performing the Yurchenko vault are relatively high; aforementioned forces are comparable to forces transmitted to lower-extremities during various activities and may be responsible for upper-extremity injury.Reaction forces observed during this study will serve as a baseline in the evaluation of methods purporting to reduce forces transmitted to upper-extremities during the Yurchenko vault. PMID:24431965

  19. Resolution of Forces and Strain Measurements from an Acoustic Ground Test

    Smith, Andrew M.; LaVerde, Bruce T.; Hunt, Ronald; Waldon, James M.

    2013-01-01

    The Conservatism in Typical Vibration Tests was Demonstrated: Vibration test at component level produced conservative force reactions by approximately a factor of 4 (approx.12 dB) as compared to the integrated acoustic test in 2 out of 3 axes. Reaction Forces Estimated at the Base of Equipment Using a Finite Element Based Method were Validated: FEM based estimate of interface forces may be adequate to guide development of vibration test criteria with less conservatism. Element Forces Estimated in Secondary Structure Struts were Validated: Finite element approach provided best estimate of axial strut forces in frequency range below 200 Hz where a rigid lumped mass assumption for the entire electronics box was valid. Models with enough fidelity to represent diminishing apparent mass of equipment are better suited for estimating force reactions across the frequency range. Forward Work: Demonstrate the reduction in conservatism provided by; Current force limited approach and an FEM guided approach. Validate proposed CMS approach to estimate coupled response from uncoupled system characteristics for vibroacoustics.

  20. Decrease of reaction force of metal gaskets just after initial tightening

    Akamatsu, H.; Shimojo, J.; Mantani, K.; Morikawa, K. [Kobe Steel, Ltd., Hyogo (Japan); Taniuchi, H.; Yokoe, D. [Transnuclear, Ltd., Tokyo (Japan)

    2004-07-01

    The decrease of reaction force of some metal gaskets inserted into the test flange at room temperature, 120 C(real cask temperature) and 200 C(accelerated condition) are measured. The reaction forces of metal gaskets in the room temperature have been almost not changed. The reaction force of 120 C and 200 C metal gaskets has decreased according to the temperature increase. After the temperature became stable, the decrease of the reaction force gradually proceeded, this decrease have been as same as previous studies. The bolts of transport and storage casks are usually tightened just after the loading of spent fuels, and then the temperature of metal gaskets at that time is almost the room temperature. The reaction forces of the metal gasket tightened at this condition would be decreased after the temperature increase due to the decay heat of spent fuels. It is confirmed that the loosening of the bolts might be happened if the tightening torque of bolts is not appropriate. It is easy to evaluate that the reaction forces of the metal gasket in storage condition according to Larson-Miller parameter or relaxation of the gasket material, but the decrease of the reaction forces of the metal gasket just after the loading is not able to evaluate by these method. It is necessary to evaluate the reaction forces according to plastic deformation property of the metal gaskets so as to fasten the gaskets safety.

  1. Decrease of reaction force of metal gaskets just after initial tightening

    The decrease of reaction force of some metal gaskets inserted into the test flange at room temperature, 120 C(real cask temperature) and 200 C(accelerated condition) are measured. The reaction forces of metal gaskets in the room temperature have been almost not changed. The reaction force of 120 C and 200 C metal gaskets has decreased according to the temperature increase. After the temperature became stable, the decrease of the reaction force gradually proceeded, this decrease have been as same as previous studies. The bolts of transport and storage casks are usually tightened just after the loading of spent fuels, and then the temperature of metal gaskets at that time is almost the room temperature. The reaction forces of the metal gasket tightened at this condition would be decreased after the temperature increase due to the decay heat of spent fuels. It is confirmed that the loosening of the bolts might be happened if the tightening torque of bolts is not appropriate. It is easy to evaluate that the reaction forces of the metal gasket in storage condition according to Larson-Miller parameter or relaxation of the gasket material, but the decrease of the reaction forces of the metal gasket just after the loading is not able to evaluate by these method. It is necessary to evaluate the reaction forces according to plastic deformation property of the metal gaskets so as to fasten the gaskets safety

  2. Performance testing for the Marine Air Ground Task Force Tactical Warfare Simulation

    Sawyers, William Alan.

    1995-01-01

    The Marine Air Ground Task Force( MAGTF) Tactical Warfare Simulation (MTWS) is a computer-assisted wargame being developed to provide a cost effective, yet realistic, training environment for Marine commanders and their staffs. A Developmental Test, conducted in November 1994, highlighted the need to improve the overall performance of the system. However, performance testing methods, which were used to evaluate the timeliness of events and the responsiveness of the simulation processes, were ...

  3. Influence of joint models on lower-limb musculo-tendon forces and threedimensional joint reaction forces during gait

    Dumas, Raphaël; Moissenet, Florent; GASPARUTTO, Xavier; Cheze, Laurence

    2012-01-01

    Several three-dimensional (3D) lower-limb musculo-skeletal models have been developed for gait analysis and different hip, knee and ankle joint models have been considered in the literature. Conversely to the influence of the musculotendon geometry, the influence of the joint models - i.e. number of degrees of freedom and passive joint moments - on the estimated musculo-tendon forces and 3D joint reaction forces has not been extensively examined. In this paper musculo-tendon forces and 3D joi...

  4. The temporal-spatial and ground reaction impulses of turning gait: is turning symmetrical?

    Strike, Siobhan C; Taylor, Matthew J D

    2009-06-01

    This study had two aims. Firstly, to characterise the temporal-spatial and ground reaction impulse adjustments, compared to straight gait, required to complete step turns to the left and to the right and secondly, to assess if the turns were asymmetrical. Seven participants were instructed to perform 90 degrees step turns to the left and right. The actual angle turned was less for both turns (right 80.2+/-5.5 degrees , left 82.8+/-5.3 degrees ). Data were collected using a 7 camera VICON infra-red motion analysis system (120 Hz) and a Kistler force plate (600 Hz). Adjustments were made in the approach, turn and depart strides compared to straight gait. The mean velocity was significantly lower and the stride was significantly shorter in the approach stride before the turn (pbraking and propulsion. The turns to the left and right were statistically asymmetrical (p<0.0125) in 11 of the 18 variables. However, impulses were generally symmetrical, which does not generally support the functional asymmetry theory, though the contributions to propulsion were significantly greater when turning from the dominant limb. PMID:19195890

  5. (Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio)

    1991-10-01

    In April 1990 Wright-Patterson Air Force Base (WPAFB) initiated an investigation to evaluate a potential CERCLA removal action to prevent, to the extent practicable, the migration of ground-water contamination in the Mad River Valley Aquifer within and across WPAFB boundaries. The action will be based on a Focused Feasibility Study with an Action Memorandum serving as a decision document that is subject to approval by the Ohio Environmental Protection Agency. The first phase (Phase 1) of this effort involves an investigation of ground-water contamination migrating across the southwest boundary of Area C and across Springfield Pike adjacent to Area B. Task 4 of Phase 1 is a field investigation to collect sufficient additional information to evaluate removal alternatives. The field investigation will provide information in the following specific areas of study: water-level data which will be used to permit calibration of the ground-water flow model to a unique time in history; and ground-water quality data which will be used to characterize the current chemical conditions of ground water.

  6. (Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio)

    1992-03-01

    An environmental investigation of ground water conditions has been undertaken at Wright-Patterson Air Force Base (WPAFB), Ohio to obtain data to assist in the evaluation of a potential removal action to prevent, to the extent practicable, migration of the contaminated ground water across Base boundaries. Field investigations were limited to the central section of the southwestern boundary of Area C and the Springfield Pike boundary of Area B. Further, the study was limited to a maximum depth of 150 feet below grade. Three primary activities of the field investigation were: (1) installation of 22 monitoring wells, (2) collection and analysis of ground water from 71 locations, (3) measurement of ground water elevations at 69 locations. Volatile organic compounds including trichloroethylene, perchloroethylene, and/or vinyl chloride were detected in concentrations exceeding Maximum Contaminant Levels (MCL) at three locations within the Area C investigation area. Ground water at the Springfield Pike boundary of Area B occurs in two primary units, separated by a thicker-than-expected clay layers. One well within Area B was determined to exceed the MCL for trichloroethylene.

  7. Foot Reaction Forces during Long Duration Space Flight

    Gopalakrishnan, R.; Rice, A. J.; Genc, K. O.; Maender, C. C.; Kuklis, M. M.; Humphreys, B.; Cavanagh, P. R.

    2008-01-01

    Musculoskeletal changes, particularly in the lower extremities, are an established consequence of long-duration space flight despite exercise countermeasures. It is widely believed that disuse and reduction in load bearing are key to these physiological changes, but no quantitative data characterizing the on-orbit movement environments currently exist. Here we present data from the Foot Experiment (E318) regarding astronaut activity on the ground and on-orbit during typical days from 4 International Space Station (ISS) crew members who flew during increments 6, 8, 11, and 12.

  8. Forced periodic temperature cycling of chemical reactions in microstructure devices

    Luther, Martin; Brandner, Juergen J.; Kiwi-Minsker, Lioubov; Renken, Albert; Schubert, Klaus

    2008-01-01

    In this publication, several stainless steel microstructure reactors specially designed to obtain rapid and periodic temperature changes are presented. Different microstructure reactor designs have been manufactured and tested for their thermal behaviour and equally by running a test reaction under stationary and non-stationary temperature conditions. The devices were continuously electrically heated and periodically cooled by a deionized water flow. The objective of the experimental measurem...

  9. Thinking anew causality problems for the radiation reaction force

    Souza, Reinaldo de Melo e

    2015-01-01

    In this work, we analyze a Lagrangian formalism recently proposed to approach the issue of the Abraham-Lorentz force. Instead of involving only position and velocity, as usual in Classical Mechanics, this Lagrangian involves the acceleration of the charge. We find the conserved momentum of the charge in the absence of any field and show that it contains an acceleration term. This enables us to re-visit the well-known pre-acceleration problem and show that, contrary to what has been widely believed, it is not related to any violation of causality.

  10. Deterministic reaction models with power-law forces

    We study a one-dimensional particles system, in the overdamped limit, where nearest particles attract with a force inversely proportional to a power α of their distance and coalesce upon encounter. The detailed shape of the distribution function for the gap between neighbouring particles serves to discriminate between different laws of attraction. We develop an exact Fokker-Planck approach for the infinite hierarchy of distribution functions for multiple adjacent gaps and solve it exactly, at the mean-field level, where correlations are ignored. The crucial role of correlations and their effect on the gap distribution function is explored both numerically and analytically. Finally, we analyse a random input of particles, which results in a stationary state where the effect of correlations is largely diminished.

  11. [Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio

    This Removal Action System Design has been prepared as a Phase I Volume for the implementation of the Phase II removal action at Wright-Patterson Air Force Base (WPAFB) near Dayton, Ohio. The objective of the removal action is to prevent, to the extent practicable, the migration of ground water contaminated with chlorinated volatile organic compounds (VOCS) across the southwest boundary of Area C. The Phase 1, Volume 9 Removal Action System Design compiles the design documents prepared for the Phase II Removal Action. These documents, which are presented in Appendices to Volume 9, include: Process Design, which presents the 30 percent design for the ground water treatment system (GWTS); Design Packages 1 and 2 for Earthwork and Road Construction, and the Discharge Pipeline, respectively; no drawings are included in the appendix; Design Package 3 for installation of the Ground Water Extraction Well(s); Design Package 4 for installation of the Monitoring Well Instrumentation; and Design Package 5 for installation of the Ground Water Treatment System; this Design Package is incorporated by reference because of its size

  12. (Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio)

    1992-04-01

    This Removal Action System Design has been prepared as a Phase I Volume for the implementation of the Phase II removal action at Wright-Patterson Air Force Base (WPAFB) near Dayton, Ohio. The objective of the removal action is to prevent, to the extent practicable, the migration of ground water contaminated with chlorinated volatile organic compounds (VOCS) across the southwest boundary of Area C. The Phase 1, Volume 9 Removal Action System Design compiles the design documents prepared for the Phase II Removal Action. These documents, which are presented in Appendices to Volume 9, include: Process Design, which presents the 30 percent design for the ground water treatment system (GWTS); Design Packages 1 and 2 for Earthwork and Road Construction, and the Discharge Pipeline, respectively; no drawings are included in the appendix; Design Package 3 for installation of the Ground Water Extraction Well(s); Design Package 4 for installation of the Monitoring Well Instrumentation; and Design Package 5 for installation of the Ground Water Treatment System; this Design Package is incorporated by reference because of its size.

  13. [Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio

    The Phase I, Task 5, Focused Feasibility Study (FFS) has been prepared as part of the Environmental Investigation of Ground Water Contamination Project being conducted by Wright-Patterson Air Force Base (WPAFB). The primary objective of this FFS was to select a cost-effective method of preventing migration of contaminated ground water across the southwestern boundary of Area C of the Base. The FFS presented in this document is a portion of a much larger effort being conducted at WPAFB. The detailed analysis of alternatives for the extraction, treatment, and discharge of contaminated ground water migrating across the southwest boundary of Area C at WPAFB led to the selection of a preferred removal action alternative. Specifically, this alternative is that ground water be extracted utilizing a three well array pumping at a total of 400 to 800 gpm, removed water be treated via air stripping to achieve appropriate effluent concentrations, and treated water be discharged to the Mad River in accordance with a National Pollution Discharge Elimination System (NPDES) permit and other relevant permits

  14. An effective 3He-nucleon force for the (3He,t) charge exchange reaction

    The feasibility and limitations of a DWBA approach to the (3He, t) reaction formulated as a direct reaction in terms of an effective 3He-nucleon force is investigated. While the central V? and the tensor component VT? can well be determined, the spin-orbit force VLS? cannot be used without a spin dependent normalization. Analysis of the analyzing power of the 'free' process 3He(n vector, p,)t indicates the need of an imaginary LS?-component but does not solve the normalization problem. The evidence on energy dependence of the efective force component is discussed briefly. (orig.)

  15. Radiation Reaction as a Non-conservative Force

    Aashish, Sandeep

    2016-01-01

    We study a system of a finite-size charged particle and electromagnetic field by exploiting the Hamilton's principle for classical non-conservative systems introduced recently by Galley[1] and obtain the equation of motion of the charged particle which turns out to be the same as obtained by Jackson[2]. We show that radiation reaction stems from the non-conservative potential of the effective Lagrangian. We derive the Abraham-Lorentz equation using the effective non-conservative Lagrangian for a point charge. We establish a correspondence between a charge interacting with its own electromagnetic field and that of a particle interacting with infinite bath oscillators which in turn affords a way to justify the non-conservative nature of the former system.

  16. (Environmental investigation of ground water contamination at Wright- Patterson Air Force Base, Ohio)

    1991-10-01

    This Health and Safety Plan (HSP) was developed for the Environmental Investigation of Ground-water Contamination Investigation at Wright-Patterson Air Force Base near Dayton, Ohio, based on the projected scope of work for the Phase 1, Task 4 Field Investigation. The HSP describes hazards that may be encountered during the investigation, assesses the hazards, and indicates what type of personal protective equipment is to be used for each task performed. The HSP also addresses the medical monitoring program, decontamination procedures, air monitoring, training, site control, accident prevention, and emergency response.

  17. Radiated power and radiation-reaction force: A derivation based on Fourier transforms

    On making use of the Fourier transforms, general formulas for the time-averaged radiated power and radiation-reaction force are obtained in terms of either the spectral distribution of the source current density or the source charge and current density at the retarded time. The former expressions are particularly suited for the derivation of the Lienard formula for the radiated power as well as the Abraham-Becker form of the radiation-reaction force for a pointlike charge. The procedure of getting instantaneous radiation quantities from the corresponding time-averaged ones is discussed critically and the Abraham-Lorentz force, obtained on the basis of the Heaviside-Feynman fields, is identified as the instantaneous radiation-reaction force

  18. Forcing factors of cloud-to-ground lightning over Iberia: regional-scale assessments

    J. A. Santos

    2013-07-01

    Full Text Available Cloud-to-ground lightning in a sector covering the Iberian Peninsula, the Balearic Islands and nearby seas (36–44° N, 10° W–5° E is analysed in the period from 2003 to 2009 (7 yr. Two Iberian lightning detection networks, composed of 18 sensors over Portugal and Spain, are combined for the first time in the present study. The selected characteristics are cloud-to-ground flashes (CGFs, first stroke peak current, polarity and multiplicity (number of strokes in a given flash. This study examines the temporal (on hourly, monthly and seasonal timescales and spatial variability of CGFs. The influence of five forcing factors on lightning (elevation, lifted index, convective available potential energy and daily minimum and maximum near-surface air temperatures over the Iberian sector is also assessed. For regional-scale assessments, six subsectors with different climatic conditions were analysed separately. Despite important regional differences, the strongest lightning activity occurs from late spring to early autumn, and mostly in the afternoon. Furthermore, CGFs are mainly located over high-elevation areas in late spring to summer, while they tend to occur over the sea in autumn. The results suggest that (1 orographically forced thunderstorms over mountainous areas, mostly from May to September, (2 tropospheric buoyancy forcing over western-central and northern regions in summer and over the Mediterranean regions in autumn, and (3 near-surface thermal contrasts from October to February largely control the location of lightning in Iberia. There is no evidence of different forcings by polarity. A clear correspondence between summertime precipitation patterns and CGFs is also found.

  19. Evaluation of Dust Absorption and Radiative Forcing of Climate Using Satellite and Ground Based Remote Sensing

    Kaufman, Yoram J.

    1999-01-01

    Simultaneous spaceborne and ground based measurements of the scattered solar radiation, create a powerful tool for determination of dust absorption. Absorption of solar radiation is a key component in understanding dust impact on radiative forcing at the top of the atmosphere, on the temperature profile and on cloud formation. We use Landsat spaceborne measurements at seven spectral channels in the range of 0.47 to 2.2 microns over Senegal with corresponding measurements of the aerosol spectral optical thickness by ground based sunphotometers, to find that Saharan dust absorption of solar radiation is two to four times smaller than measured in situ and represented in models. Though dust was found to absorb in the blue (single scattering albedo wo = 0.88), almost no absorption, wo = 0.98, was found for 1 greater than 0.6 microns. The results are in agreement with dust radiative measurements reported in the literature, and explain some previously reported but unexplained dust radiative properties. Therefore, the new finding should be of general relevance. The new finding increases by 50% recently estimated solar radiative forcing by dust at the top of the atmosphere and decreases the estimated dust heating of the lower troposphere due to absorption of solar radiation. Dust transported from Asia shows slightly higher absorption for wavelengths under 1 @im, that can be explained by the presence of black carbon from urban/industrial pollution associated with the submicron size mode.

  20. Cloud-to-ground lightning in Portugal: patterns and dynamical forcing

    J. A. Santos

    2012-03-01

    Full Text Available An analysis of the cloud-to-ground discharges (CGD over Portugal is carried out using data collected by a network of sensors maintained by the Portuguese Meteorological Institute for 2003–2009 (7 yr. Only cloud-to-ground flashes are considered and negative polarity CGD are largely dominant. The total number of discharges reveals a considerable interannual variability and a large irregularity in their distribution throughout the year. However, it is shown that a large number of discharges occur in the May–September period (71%, with a bimodal distribution that peaks in May and September, with most of the lightning activity recorded in the afternoon (from 16:00 to 18:00 UTC. In spring and autumn the lightning activity tends to be scattered throughout the country, whereas in summer it tends to be more concentrated over northeastern Portugal. Winter generally presents low lightning activity. Furthermore, two significant couplings between the monthly number of days with discharges and the large-scale atmospheric circulation are isolated: a regional forcing, predominantly in summer, and a remote forcing. In fact, the identification of daily lightning regimes revealed three important atmospheric conditions for triggering lightning activity: regional cut-off lows, cold troughs induced by remote low pressure systems and summertime regional low pressures at low-tropospheric levels combined with a mid-tropospheric cold trough.

  1. Influence of Muscle-Tendon Wrapping on Calculations of Joint Reaction Forces in the Equine Distal Forelimb

    Pandy, Marcus G.; Colin Burvill; Davies, Helen M. S.; Jonathan S. Merritt

    2008-01-01

    The equine distal forelimb is a common location of injuries related to mechanical overload. In this study, a two-dimensional model of the musculoskeletal system of the region was developed and applied to kinematic and kinetic data from walking and trotting horses. The forces in major tendons and joint reaction forces were calculated. The components of the joint reaction forces caused by wrapping of tendons around sesamoid bones were found to be of similar magnitude to the reaction forces betw...

  2. (Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio)

    Thompson, Bill

    1991-10-01

    In April 1990, Wright-Patterson Air Force Base (WPAFB), initiated an investigation to evaluate a potential Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) removal action to prevent, to the extent practicable, the offsite migration of contaminated ground water from WPAFB. WPAFB retained the services of the Environmental Management Operations (EMO) and its principle subcontractor, International Technology Corporation (IT) to complete Phase 1 of the environmental investigation of ground-water contamination at WPAFB. Phase 1 of the investigation involves the short-term evaluation and potential design for a program to remove ground-water contamination that appears to be migrating across the western boundary of Area C, and across the northern boundary of Area B along Springfield Pike. Primarily, Task 4 of Phase 1 focuses on collection of information at the Area C and Springfield Pike boundaries of WPAFB. This Sampling and Analysis Plan (SAP) has been prepared to assist in completion of the Task 4 field investigation and is comprised of the Quality Assurance Project Plan (QAPP) and the Field Sampling Plan (FSP).

  3. Measurement of muscle actions and foot reaction forces from crew members during entire working days on the International Space Station (ISS)

    Snedeker, Jess G.; Cavanagh, Peter R.

    2000-01-01

    We present pilot work in preparation for ISS Experiment 318, which will investigate changes in lower limb daily mechanical loading and muscular activity profiles that have been implicated in bone mineral loss and muscle atrophy during spaceflight. Prototype equipment for the musculo-skeletal rack of the Human Research Facility (HRF) was used in conjunction with the Ambulatory Data Acquisition System to record and store data. Right foot ground reaction force profiles, right leg EMG activity profiles from the tibialis anterior and vastus medialis, and joint angular excursion profiles from the right knee and ankle were collected during five minutes each of forward and backward running in 1g as well as over a twelve hour period of activities during daily living. Ground reaction force profiles were analyzed to provide an estimate of 1g daily mechanical load stimulus, while EMG and joint angle profiles characterized the role of individual muscles in generating and absorbing energy. .

  4. Measurement of muscle actions and foot reaction forces from crew members during entire working days on the International Space Station (ISS)

    We present pilot work in preparation for ISS Experiment 318, which will investigate changes in lower limb daily mechanical loading and muscular activity profiles that have been implicated in bone mineral loss and muscle atrophy during spaceflight. Prototype equipment for the musculo-skeletal rack of the Human Research Facility (HRF) was used in conjunction with the Ambulatory Data Acquisition System to record and store data. Right foot ground reaction force profiles, right leg EMG activity profiles from the tibialis anterior and vastus medialis, and joint angular excursion profiles from the right knee and ankle were collected during five minutes each of forward and backward running in 1g as well as over a twelve hour period of activities during daily living. Ground reaction force profiles were analyzed to provide an estimate of 1g daily mechanical load stimulus, while EMG and joint angle profiles characterized the role of individual muscles in generating and absorbing energy

  5. Lower limb reaction force asymmetry in rowers with and without a history of back injury.

    An, Winko W; Wong, Vincy; Cheung, Roy T H

    2015-11-01

    Back injury is common in rowers. Asymmetrical lower limb reaction force on the foot stretchers during rowing may compromise trunk biomechanics and lead to back injury. However, such a mechanism remains putative. Therefore, this study examined lower limb reaction force in experienced rowers with and without a history of back injury. Six rowers who suffered from back injury for more than one week in the past year and another 19 rowers who were never injured performed maximal exertion rowing on a fixed-head rowing machine for 30 strokes. Peak force, average and peak loading rate of the lower limb reaction force during the middle 10-stroke were recorded using strain-gauge transducers placed at the foot stretchers. Asymmetries and intra-limb variability were quantified as asymmetry indices and coefficients of variation, respectively. No significant asymmetry was observed in all selected kinetic parameters between the injured and healthy rowers (p = 0.448-0.722, Hedges' g = 0.162-0.310). Subgroup analyses also did not reveal any significant kinetic differences between injured and healthy scullers or sweepers (p = 0.194-0.855, Hedges' g = 0.203-0.518). Rowers with a history of back injury, regardless of the rowing types, did not demonstrate greater lower limb reaction force asymmetry when compared with healthy rowers. PMID:26237029

  6. BALANCE : a computer program for calculating mass transfer for geochemical reactions in ground water

    Parkhurst, David L.; Plummer, L. Niel; Thorstenson, Donald C.

    1982-01-01

    BALANCE is a Fortran computer designed to define and quantify chemical reactions between ground water and minerals. Using (1) the chemical compositions of two waters along a flow path and (2) a set of mineral phases hypothesized to be the reactive constituents in the system, the program calculates the mass transfer (amounts of the phases entering or leaving the aqueous phase) necessary to account for the observed changes in composition between the two waters. Additional constraints can be included in the problem formulation to account for mixing of two end-member waters, redox reactions, and, in a simplified form, isotopic composition. The computer code and a description of the input necessary to run the program are presented. Three examples typical of ground-water systems are described. (USGS)

  7. Aerodynamic forces and flow structures of the leading edge vortex on a flapping wing considering ground effect

    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. (paper)

  8. Aerodynamic forces and flow structures of the leading edge vortex on a flapping wing considering ground effect.

    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. PMID:23851351

  9. Enabling Force Sensing During Ground Locomotion: A Bio-Inspired, Multi-Axis, Composite Force Sensor Using Discrete Pressure Mapping

    Chuah, Meng Yee; Kim, Sangbae

    2013-01-01

    This paper presents a new force sensor design approach that maps the local sampling of pressure inside a composite polymeric footpad to forces in three axes, designed for running robots. Conventional multiaxis force sensors made of heavy metallic materials tend to be too bulky and heavy to be fitted in the feet of legged robots, and vulnerable to inertial noise upon high acceleration. To satisfy the requirements for high speed running, which include mitigating high impact forces, protecting t...

  10. A test on reactive force fields for the study of silica dimerization reactions

    Moqadam, Mahmoud; Riccardi, Enrico; Trinh, Thuat T.; Åstrand, Per-Olof; van Erp, Titus S.

    2015-11-01

    We studied silica dimerization reactions in the gas and aqueous phase by density functional theory (DFT) and reactive force fields based on two parameterizations of ReaxFF. For each method (both ReaxFF force fields and DFT), we performed constrained geometry optimizations, which were subsequently evaluated in single point energy calculations using the other two methods. Standard fitting procedures typically compare the force field energies and geometries with those from quantum mechanical data after a geometry optimization. The initial configurations for the force field optimization are usually the minimum energy structures of the ab initio database. Hence, the ab initio method dictates which structures are being examined and force field parameters are being adjusted in order to minimize the differences with the ab initio data. As a result, this approach will not exclude the possibility that the force field predicts stable geometries or low transition states which are realistically very high in energy and, therefore, never considered by the ab initio method. Our analysis reveals the existence of such unphysical geometries even at unreactive conditions where the distance between the reactants is large. To test the effect of these discrepancies, we launched molecular dynamics simulations using DFT and ReaxFF and observed spurious reactions for both ReaxFF force fields. Our results suggest that the standard procedures for parameter fitting need to be improved by a mutual comparative method.

  11. Calculations of three-nucleon reactions with N3LO chiral forces: achievements and challenges

    We discuss the application of the chiral N3LO forces to three-nucleon reactions and point to the challenges which will have to be addressed. Present approaches to solve three-nucleon Faddeev equations are based on a partial-wave decomposition. A rapid increase of the number of terms contributing to the chiral three-nucleon force when increasing the order of the chiral expansion from N2LO to N3LO forced us to develop a fast and effective method of automatized partial-wave decomposition. At low energies of the incoming nucleon below ≈20 MeV, where only a limited number of partial waves is required, this method allowed us to perform calculations of reactions in the three-nucleon continuum using N3LO two- and three-nucleon forces. It turns out that inclusion of consistent chiral interactions, with relativistic 1/m corrections and short-range 2π-contact term omitted in the N3LO three-nucleon force, does not explain the long standing low energy Ay-puzzle. We discuss problems arising when chiral forces are applied at higher energies, where large three-nucleon force effects are expected. It seems plausible that at higher energies, due to a rapid increase of a number of partial waves required to reach convergent results, a three-dimensional formulation of the Faddeev equations which avoids partial-wave decomposition is desirable. (paper)

  12. A test on reactive force fields for the study of silica dimerization reactions

    We studied silica dimerization reactions in the gas and aqueous phase by density functional theory (DFT) and reactive force fields based on two parameterizations of ReaxFF. For each method (both ReaxFF force fields and DFT), we performed constrained geometry optimizations, which were subsequently evaluated in single point energy calculations using the other two methods. Standard fitting procedures typically compare the force field energies and geometries with those from quantum mechanical data after a geometry optimization. The initial configurations for the force field optimization are usually the minimum energy structures of the ab initio database. Hence, the ab initio method dictates which structures are being examined and force field parameters are being adjusted in order to minimize the differences with the ab initio data. As a result, this approach will not exclude the possibility that the force field predicts stable geometries or low transition states which are realistically very high in energy and, therefore, never considered by the ab initio method. Our analysis reveals the existence of such unphysical geometries even at unreactive conditions where the distance between the reactants is large. To test the effect of these discrepancies, we launched molecular dynamics simulations using DFT and ReaxFF and observed spurious reactions for both ReaxFF force fields. Our results suggest that the standard procedures for parameter fitting need to be improved by a mutual comparative method

  13. Knee joint reaction force during tibial diaphyseal lengthening: a study on a rabbit model.

    Yang, Lang; Cai, Gang; Coulton, Les; Saleh, Michael

    2004-07-01

    The in vivo passive knee joint reaction force was measured in a rabbit model of tibial diaphyseal lengthening. This was based on the assumption that limb lengthening creates soft tissue tension that compresses the joint surface and generates the joint contact force. A measurement method was developed that involved the distraction of the joint and the determination of the distraction force that just separates the joint surfaces. Sixteen immature (mean+/-SD age=9+/-0.6 weeks) New Zealand White rabbits underwent 30% (left) tibial diaphyseal lengthening at a rate of two 0.4mm incremental lengthenings per day. The knee joint reaction force was measured at the end of lengthening (8 rabbits, mean+/-SD age=14+/-0.6 weeks) and five weeks after lengthening (8 rabbits, mean+/-SD age=19+/-0.7 weeks). An instrumented bilateral distractor and an extensometer were fixed cross the knee joint. The joint distraction force and distraction displacement were measured when the joint was distracted in steps and after the section of the Achilles tendon. The joint reaction force on the lengthened side was significantly higher than the control side at both time points (mean+/-SD 44.4+/-7.8 N v. 27.2+/-4.0 N at the end of lengthening, 44.3+/-S6.5 N v. 31.3+/-3.0 N at 5 weeks after lengthening). The contribution of the gastrocnemius to the joint reaction force on the lengthened side was also significantly higher than the control side at both time points (mean+/-SD 9.0+/-1.3N v. 2.8+/-0.8 N at the end of lengthening, 5.3+/-1.4N v. 2.7+/-0.5N at 5 weeks after lengthening). There were significant knee and ankle joint contractures at the end of lengthening, as evidenced by decreased range of motion (mean+/-SD 27+/-8 degrees and 36+/-13 degrees, respectively), which remained 5 weeks after lengthening (mean+/-SD 26+/-6 degrees and 35+/-8 degrees, respectively). The gastrocnemius contributed about 20% of the joint reaction force, indicating that changes in the other intra- and extra-articular structures due to joint contracture may be more important in generating the joint reaction force. PMID:15165875

  14. Optimal control of the initiation of a pericyclic reaction in the electronic ground state

    Timm Bredtmann; Jörn Manz

    2012-01-01

    Pericyclic reactions in the electronic ground state may be initiated by down-chirped pump-dump sub-pulses of an optimal laser pulse, in the ultraviolet (UV) frequency and sub-10 femtosecond (fs) time domain. This is demonstrated by means of a quantum dynamics model simulation of the Cope rearrangement of Semibullvalene. The laser pulse is designed by means of optimal control theory, with detailed analysis of the mechanism. The theoretical results support the recent experimental initiation of a pericyclic reaction. The present approach provides an important step towards monitoring asynchronous electronic fluxes during synchronous nuclear pericyclic reaction dynamics, with femto-to-attosecond time resolution, as motivated by the recent prediction of our group.

  15. Modeling chemical reactions by forced limit-cycle oscillator: synchronization phenomena and transition to chaos

    The lattice limit-cycle (LLC) model is introduced as a minimal mean-field scheme which can model reactive dynamics on lattices (low dimensional supports) producing non-linear limit cycle oscillations. Under the influence of an external periodic force the dynamics of the LLC may be drastically modified. Synchronization phenomena, bifurcations and transitions to chaos are observed as a function of the strength of the force. Taking advantage of the drastic change on the dynamics due to the periodic forcing, it is possible to modify the output/product or the production rate of a chemical reaction at will, simply by applying a periodic force to it, without the need to change the support properties or the experimental conditions

  16. Electromagnetic radiation reaction force and radiation potential in general five-dimensional relativity

    A unified theory of electromagnetic and gravitational fields should modify classical electrodynamics to account for the radiation reaction force. A conjecture that the radiation reaction force and the Lorentz force should be distinct, but in unified forms, results in a five-dimensional unified theory of five variables. It is found that a semicylindrical condition can reconcile the apparent differences between a five-dimensional physical space and our four-dimensional perceptions. Analysis of the geodesic equations results in the notion of gauge dynamics which manifests the influence of the unrestricted fifth variable. The element g55 of the five-dimensional metric is identified as the radiation potential, which can directly determine the radiation reaction force. This gives a distinct physical origin for the radiation process in classical theory. The potential suggests that the electron can have excited states in quantum electrodynamics. This theory is supported with calculations which demonstrate that the motion of the fifth variable directly causes physical changes in the four-dimensional subspace

  17. Analysis of ground-water data for selected wells near Holloman Air Force Base, New Mexico, 1950-95

    Huff, G.F.

    1996-01-01

    Ground-water-level, ground-water-withdrawal, and ground- water-quality data were evaluated for trends. Holloman Air Force Base is located in the west-central part of Otero County, New Mexico. Ground-water-data analyses include assembly and inspection of U.S. Geological Survey and Holloman Air Force Base data, including ground-water-level data for public-supply and observation wells and withdrawal and water-quality data for public-supply wells in the area. Well Douglas 4 shows a statistically significant decreasing trend in water levels for 1972-86 and a statistically significant increasing trend in water levels for 1986-90. Water levels in wells San Andres 5 and San Andres 6 show statistically significant decreasing trends for 1972-93 and 1981-89, respectively. A mixture of statistically significant increasing trends, statistically significant decreasing trends, and lack of statistically significant trends over periods ranging from the early 1970's to the early 1990's are indicated for the Boles wells and wells near the Boles wells. Well Boles 5 shows a statistically significant increasing trend in water levels for 1981-90. Well Boles 5 and well 17S.09E.25.343 show no statistically significant trends in water levels for 1990-93 and 1988-93, respectively. For 1986-93, well Frenchy 1 shows a statistically significant decreasing trend in water levels. Ground-water withdrawal from the San Andres and Douglas wells regularly exceeded estimated ground-water recharge from San Andres Canyon for 1963-87. For 1951-57 and 1960-86, ground-water withdrawal from the Boles wells regularly exceeded total estimated ground-water recharge from Mule, Arrow, and Lead Canyons. Ground-water withdrawal from the San Andres and Douglas wells and from the Boles wells nearly equaled estimated ground- water recharge for 1989-93 and 1986-93, respectively. For 1987- 93, ground-water withdrawal from the Escondido well regularly exceeded estimated ground-water recharge from Escondido Canyon, and ground-water withdrawal from the Frenchy wells regularly exceeded total estimated ground-water recharge from Dog and Deadman Canyons. Water-quality samples were collected from selected Douglas, San Andres, and Boles public-supply wells from December 1994 to February 1995. Concentrations of dissolved nitrate show the most consistent increases between current and historical data. Current concentrations of dissolved nitrate are greater than historical concentrations in 7 of 10 wells.

  18. Single-drop reactive extraction/extractive reaction with forced convective diffusion and interphase mass transfer

    Kleinman, Leonid S.; Reed, X. B., Jr.

    1995-01-01

    An algorithm has been developed for the forced convective diffusion-reaction problem for convection inside and outside a droplet by a recirculating flow field hydrodynamically coupled at the droplet interface with an external flow field that at infinity becomes a uniform streaming flow. The concentration field inside the droplet is likewise coupled with that outside by boundary conditions at the interface. A chemical reaction can take place either inside or outside the droplet or reactions can take place in both phases. The algorithm has been implemented and results are shown here for the case of no reaction and for the case of an external first order reaction, both for unsteady behavior. For pure interphase mass transfer, concentration isocontours, local and average Sherwood numbers, and average droplet concentrations have been obtained as a function of the physical properties and external flow field. For mass transfer enhanced by an external reaction, in addition to the above forms of results, we present the enhancement factor, with the results now also depending upon the (dimensionless) rate of reaction.

  19. Influence of Muscle-Tendon Wrapping on Calculations of Joint Reaction Forces in the Equine Distal Forelimb

    Marcus G. Pandy

    2008-05-01

    Full Text Available The equine distal forelimb is a common location of injuries related to mechanical overload. In this study, a two-dimensional model of the musculoskeletal system of the region was developed and applied to kinematic and kinetic data from walking and trotting horses. The forces in major tendons and joint reaction forces were calculated. The components of the joint reaction forces caused by wrapping of tendons around sesamoid bones were found to be of similar magnitude to the reaction forces between the long bones at each joint. This finding highlighted the importance of taking into account muscle-tendon wrapping when evaluating joint loading in the equine distal forelimb.

  20. Influence of muscle-tendon wrapping on calculations of joint reaction forces in the equine distal forelimb.

    Merritt, Jonathan S; Davies, Helen M S; Burvill, Colin; Pandy, Marcus G

    2008-01-01

    The equine distal forelimb is a common location of injuries related to mechanical overload. In this study, a two-dimensional model of the musculoskeletal system of the region was developed and applied to kinematic and kinetic data from walking and trotting horses. The forces in major tendons and joint reaction forces were calculated. The components of the joint reaction forces caused by wrapping of tendons around sesamoid bones were found to be of similar magnitude to the reaction forces between the long bones at each joint. This finding highlighted the importance of taking into account muscle-tendon wrapping when evaluating joint loading in the equine distal forelimb. PMID:18509485

  1. Effects of brain polarization on reaction times and pinch force in chronic stroke

    Giraux Pascal

    2006-11-01

    Full Text Available Abstract Background Previous studies showed that anodal transcranial DC stimulation (tDCS applied to the primary motor cortex of the affected hemisphere (M1affected hemisphere after subcortical stroke transiently improves performance of complex tasks that mimic activities of daily living (ADL. It is not known if relatively simpler motor tasks are similarly affected. Here we tested the effects of tDCS on pinch force (PF and simple reaction time (RT tasks in patients with chronic stroke in a double-blind cross-over Sham-controlled experimental design. Results Anodal tDCS shortened reaction times and improved pinch force in the paretic hand relative to Sham stimulation, an effect present in patients with higher impairment. Conclusion tDCS of M1affected hemisphere can modulate performance of motor tasks simpler than those previously studied, a finding that could potentially benefit patients with relatively higher impairment levels.

  2. A method of hydraulic reaction force computation due to fluid jet at a steamline break

    A method of hydraulic jet reaction force computation is presented at a 100% steamline break. The steamline break analysis is performed by the use of NOTRUMP code. Formation of supersonic flow at the converging-diverging flow restrictor is computed with a homogeneous equilibrium model. However, consideration is given on the slip ratio of the liquid and steam phases, thermal non-equilibrium effects, and normal and oblique shocks

  3. A method of computing hydraulic reaction force due to a fluid jet at a steamline break

    A method of computing hydraulic jet reaction force at a 100% steamline break is presented. The steamline break analysis is performed by the use of the NOTRUMP code. Formation of supersonic flow at the converging-diverging flow restrictor is computed with a homogeneous equilibrium model. Consideration is given, however, to the slip ratio of the liquid and steam phases, thermal nonequilibrium effects, and normal and oblique shocks

  4. Reaction force of percussive corer, rotary-friction corer, and rotary-percussive corer

    Chang, Zensheu; Sherrit, Stewart; Badescu, Mircea; Bao, Xiaoqi; Bar-Cohen, Yoseph; Backes, Paul

    2006-01-01

    Future NASA exploration missions will increasingly require sampling, in-situ analysis and possibly the return of material to Earth for laboratory analysis. To address these objective, effective and optimized drilling techniques are needed. This requires developing comprehensive tools to be able to determine analytically what takes place during the operation and what are the control parameters that can be enhanced. In this study, three types of coring techniques were studied and were identified as potential candidates for operation from a possible future Mars Sample Return (MSR) mission rover. These techniques include percussive, rotary-friction, and rotary-percussive coring. Theoretical models were developed to predict the dynamic reaction forces transmitted from these three types of corers to the robotic arms that hold them. The predicted reaction forces will then be used in a dynamic simulation environment to simulate a representative corer tool to obtain a best estimate of a tool that can be operated from a small rover. The predicted dynamic reaction forces will be presented in this paper.

  5. Description of the ground-state pionic double charge exchange reaction on 128,130Te

    The pionic double charge exchange reactions 128,130Te(?+, ?-)128,130Xe are investigated within the proton-neutron random-phase approximation. The approach is found to give a satisfactory agreement of the calculated differential cross sections and angular distributions with recent data. A strong dependence of the calculated quantities on the strength gpp of the particle-particle force is observed. This behaviour is similar to that reported for the ?+ decay in neutron-deficient nuclei and the double beta decay. The role of the DCX for the interpretation of the ratio of the double beta decay half-lives of the tellurium isotopes is discussed. (orig.)

  6. Calculation of Reaction Forces in the Boiler Supports Using the Method of Equivalent Stiffness of Membrane Wall

    Josip Sertić; Dražan Kozak; Ivan Samardžić

    2014-01-01

    The values of reaction forces in the boiler supports are the basis for the dimensioning of bearing steel structure of steam boiler. In this paper, the application of the method of equivalent stiffness of membrane wall is proposed for the calculation of reaction forces. The method of equalizing displacement, as the method of homogenization of membrane wall stiffness, was applied. On the example of “Milano” boiler, using the finite element method, the calculation of reactions in the supports fo...

  7. Assessment of ground-water contamination at Wurtsmith Air Force Base, Michigan, 1982-85

    Cummings, T.R.; Twenter, F.R.

    1986-01-01

    Study of ground-water contamination at Wurtsmith Air Force Base, Michigan, defined the movement and distribution of volatile organic compounds in the glacial sand and gravel aquifer at known sites of contamination, and has defined new plumes at two other sites. The Arrow Street purge system, installed in 1982 to remove contaminants from the Building 43 plume, has lowered concentrations of trichloroethylene (TCE) in groundwater in the central part of the most contaminated area from a range of 1,000 to 2,000 microg/L to about 200 microg/L. TCE is not escaping off-Base from this area. In the southern part of the Base a plume containing principally TCE and dichloroethylene (DCE) has been delineated along Mission Drive. Maximum concentrations observed were 3,290 microg/L of TCE and 1,480 microg/L of DCE. Hydrologically suitable sites for purge wells were identified in the southern part of the plume using a new ground-water flow model of the Base. A benzene plume near the bulk-fuel storage area has shifted to a more northerly direction under influence of the Arrow Street purge system. Sites initially identified for purging the benzene plume have been repositioned because of the change in contaminant movement. JP-4 fuel was found to be accumulating in wells near the bulk-fuel storage area, largely in response to seasonal fluctuations in the water-table. It is thought to originate from a spill that occurred several years ago. In general, concentrations found in water do not differ greatly from those observed in 1981. Since 1981, concentrations of TCE have decreased significantly in the Alert Apron plume. Near the origin of the plume, the concentration of TCE has decreased from 1,000 microg/L in 1980 to 50 microg/L in 1984. Water from Van Etten Lake near the termination of the plume had only a trace of TCE at one site. Benzene detected in water from well AF2 seems to originate near the former site of buried fuel tanks west of the operational apron. During periods of normal purge pumping along Arrow Street, contaminants are drawn toward water-supply wells AF2, AF4, and AF5. (Author 's abstract)

  8. Trends in Ground-State Entropies for Transition Metal Based Hydrogen Atom Transfer Reactions

    Mader, Elizabeth A.; Manner, Virginia W.; Markle, Todd F.; Wu, Adam; Franz, James A.; Mayer, James M.

    2009-03-10

    Reported herein are thermochemical studies of hydrogen atom transfer (HAT) reactions involving transition metal H-atom donors MIILH and oxyl radicals. [FeII(H2bip)3]2+, [FeII(H2bim)3]2+, [CoII(H2bim)3]2+ and RuII(acac)2(py-imH) [H2bip = 2,2’-bi-1,4,5,6-tetrahydro¬pyrimidine, H2bim = 2,2’-bi-imidazoline, acac = 2,4-pentandionato, py-imH = 2-(2’-pyridyl)¬imidazole)] each react with TEMPO (2,2,6,6-tetramethyl-1-piperidinoxyl) or tBu3PhO• (2,4,6-tri-tert-butylphenoxyl) to give the deprotonated, oxidized metal complex MIIIL, and TEMPOH or tBu3PhOH. Solution equilibrium measurements for the reactions of Co and Fe complexes with TEMPO show a large, negative ground-state entropy for hydrogen atom transfer: ?SºHAT = -30 ± 2 cal mol-1 K-1 for the two iron complexes and -41 ± 2 cal mol-1 K-1 for [CoII(H2bim)3]2+. The ?SºHAT for TEMPO + RuII(acac)2(py-imH) is much closer to zero, 4.9 ± 1.1 cal mol-1 K-1. Calorimetric measurements quantitatively confirm the enthalpy of reaction for [FeII(H2bip)3]2+ + TEMPO, thus also confirming ?SºHAT. Calorimetry on TEMPOH + tBu3PhO• gives ?HºHAT = 11.2 ± 0.5 kcal mol-1 which matches the enthalpy predicted from the difference in literature solution BDEs. An evaluation of the literature BDEs of both TEMPOH and tBu3PhOH is briefly presented and new estimates are included on the relative enthalpy of solvation for tBu3PhO• vs. tBu3PhOH. The primary contributor to the large magnitude of the ground-state entropy |?SºHAT| for the metal complexes is vibrational entropy, ?Sºvib. The common assumption that ?SºHAT ? 0 for HAT reactions, developed for organic and small gas phase molecules, does not hold for transition metal based HAT reactions. The trend in magnitude of |?SºHAT| for reactions with TEMPO, RuII(acac)2(py-imH) << [FeII(H2bip)3]2+ = [FeII(H2bim)3]2+ < [CoII(H2bim)3]2+, is surprisingly well predicted by the trends for electron transfer half-reaction entropies, ?SºET, in aprotic solvents. ?SºET and ?SºHAT are both affected by ?Sºvib and vary significantly with the metal center involved. The close connection between ?SºHAT and ?SºET provides an important link between these two fields and provides a starting point from which to predict which HAT systems will have important ground-state entropy effects. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  9. The gravitational radiation reaction force of a continuous medium. I. Perturbation of a quasi-newtonian motion

    We determine, within the general theory of relativity, the equations of motion in the slow approximation of a continuous medium in which the forces from material stresses do not play a leading part with respect to the gravitational forces. The gravitational radiation reaction force appears as a disturbing force in the post-post-newtonian equations of motion. Then, we deduce the formula for the variation of the energy of the system due to the gravitational radiation

  10. Biomechanics of gecko locomotion: the patterns of reaction forces on inverted, vertical and horizontal substrates

    The excellent locomotion ability of geckos on various rough and/or inclined substrates has attracted scientists’ attention for centuries. However, the moving ability of gecko-mimicking robots on various inclined surfaces still lags far behind that of geckos, mainly because our understanding of how geckos govern their locomotion is still very poor. To reveal the fundamental mechanism of gecko locomotion and also to facilitate the design of gecko-mimicking robots, we have measured the reaction forces (RFs) acting on each individual foot of moving geckos on inverted, vertical and horizontal substrates (i.e. ceiling, wall and floor), have associated the RFs with locomotion behaviors by using high-speed camera, and have presented the relationships of the force components with patterns of reaction forces (PRFs). Geckos generate different PRF on ceiling, wall and floor, that is, the PRF is determined by the angles between the direction of gravity and the substrate on which geckos move. On the ceiling, geckos produce reversed shear forces acting on the front and hind feet, which pull away from the body in both lateral and fore-aft directions. They use a very large supporting angle from 21° to 24° to reduce the forces acting on their legs and feet. On the floor, geckos lift their bodies using a supporting angle from 76° to 78°, which not only decreases the RFs but also improves their locomotion ability. On the wall, geckos generate a reliable self-locking attachment by using a supporting angle of 14.8°, which is only about half of the critical angle of detachment. (paper)

  11. Force Limiting Vibration Tests Evaluated from both Ground Acoustic Tests and FEM Simulations of a Flight Like Vehicle System Assembly

    Smith, Andrew; LaVerde, Bruce; Waldon, James; Hunt, Ron

    2014-01-01

    Marshall Space Flight Center has conducted a series of ground acoustic tests with the dual goals of informing analytical judgment, and validating analytical methods when estimating vibroacoustic responses of launch vehicle subsystems. The process of repeatedly correlating finite element-simulated responses with test-measured responses has assisted in the development of best practices for modeling and post-processing. In recent work, force transducers were integrated to measure interface forces at the base of avionics box equipment. Other force data was indirectly measured using strain gauges. The combination of these direct and indirect force measurements has been used to support and illustrate the advantages of implementing the Force Limiting approach for equipment qualification tests. The comparison of force response from integrated system level tests to measurements at the same locations during component level vibration tests provides an excellent illustration. A second comparison of the measured response cases from the system level acoustic tests to finite element simulations has also produced some principles for assessing the suitability of Finite Element Models (FEMs) for making vibroacoustics estimates. The results indicate that when FEM models are employed to guide force limiting choices, they should include sufficient detail to represent the apparent mass of the system in the frequency range of interest.

  12. Radiation-Reaction Force on a Small Charged Body to Second Order

    Moxon, Jordan; Flanagan, Eanna

    2015-04-01

    In classical electrodynamics, an accelerating charge emits radiation and experiences a corresponding radiation reaction force, or self force. We extend to greater precision (higher order in perturbation theory) a previous rigorous derivation of the electromagnetic self force in flat spacetime by Gralla, Harte, and Wald. The method introduced by Gralla, Harte, and Wald computes the self-force from the Maxwell field equations and conservation of stress-energy, and does not require regularization of a singular point charge, as has been necessary in prior computations. For our higher order compuation, it becomes necessary to adopt an adjusted definition of the mass of the body to avoid including self-energy from the electromagnetic field sourced during the history of the body. We derive the evolution equations for the mass, spin, and center of mass position of an extended body through second order using our adjusted formalism. The final equations give an acceleration dependent evolution of the spin (self-torque), as well as a mixing between the extended body effects and the acceleration dependent effects on the overall body motion.

  13. Influence of radiation reaction force on ultraintense laser-driven ion acceleration

    Capdessus, R.; McKenna, P.

    2015-05-01

    The role of the radiation reaction force in ultraintense laser-driven ion acceleration is investigated. For laser intensities ˜1023W/cm 2 , the action of this force on electrons is demonstrated in relativistic particle-in-cell simulations to significantly enhance the energy transfer to ions in relativistically transparent targets, but strongly reduce the ion energy in dense plasma targets. An expression is derived for the revised piston velocity, and hence ion energy, taking account of energy loses to synchrotron radiation generated by electrons accelerated in the laser field. Ion mass is demonstrated to be important by comparing results obtained with proton and deuteron plasma. The results can be verified in experiments with cryogenic hydrogen and deuterium targets.

  14. Low-energy neutron-deuteron reactions with N3LO chiral forces

    Golak, J; Topolnicki, K; Witala, H; Epelbaum, E; Krebs, H; Kamada, H; Meissner, Ulf-G; Bernard, V; Maris, P; Vary, J; Binder, S; Calci, A; Hebeler, K; Langhammer, J; Roth, R; Nogga, A; Liebig, S; Minossi, D

    2014-01-01

    We solve three-nucleon Faddeev equations with nucleon-nucleon and three-nucleon forces derived consistently in the framework of chiral perturbation theory at next-to-next-to-next-to-leading order in the chiral expansion. In this first investigation we include only matrix elements of the three-nucleon force for partial waves with the total two-nucleon (three-nucleon) angular momenta up to 3 (5/2). Low-energy neutron-deuteron elastic scattering and deuteron breakup reaction are studied. Emphasis is put on Ay puzzle in elastic scattering and cross sections in symmetric-space-star and neutron-neutron quasi-free-scattering breakup configurations, for which large discrepancies between data and theory have been reported.

  15. Low-energy neutron-deuteron reactions with N{sup 3}LO chiral forces

    Golak, J.; Skibinski, R.; Topolnicki, K.; Witala, H. [Jagiellonian University, M. Smoluchowski Institute of Physics, Krakow (Poland); Epelbaum, E.; Krebs, H. [Ruhr-Universitaet Bochum, Institut fuer Theoretische Physik II, Bochum (Germany); Kamada, H. [Kyushu Institute of Technology, Department of Physics, Faculty of Engineering, Kitakyushu (Japan); Meissner, Ulf G. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Bonn (Germany); JARA - High Performance Computing Forschungszentrum Juelich, Institute for Advanced Simulation, Institut fuer Kernphysik, Juelich Center for Hadron Physics, Juelich (Germany); Bernard, V. [CNRS/Univ. Paris-Sud, Institut de Physique Nucleaire, Orsay (France); Maris, P.; Vary, J. [Iowa State University, Department of Physics and Astronomy, Ames, Iowa (United States); Binder, S.; Calci, A.; Langhammer, J.; Roth, R. [Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany); Hebeler, K. [Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Extreme Matter Institute EMMI, Darmstadt (Germany); Nogga, A. [Juelich Center for Hadron Physics, Forschungszentrum Juelich, Institut fuer Kernphysik, Institute for Advanced Simulation, Juelich (Germany); Liebig, S.; Minossi, D. [Juelich Center for Hadron Physics, Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (Germany)

    2014-11-15

    We solve three-nucleon Faddeev equations with nucleon-nucleon and three-nucleon forces derived consistently in the framework of chiral perturbation theory at next-to-next-to-next-to-leading order in the chiral expansion. In this first investigation we include only matrix elements of the three-nucleon force for partial waves with the total two-nucleon (three-nucleon) angular momenta up to 3 (5/2). Low-energy neutron-deuteron elastic scattering and deuteron breakup reaction are studied. Emphasis is put on A{sub y} puzzle in elastic scattering and cross sections in symmetric-space-star and neutron-neutron quasi-free-scattering breakup configurations, for which large discrepancies between data and theory have been reported. (orig.)

  16. Force

    Graybill, George

    2007-01-01

    Forces are at work all around us. Discover what a force is, and different kinds of forces that work on contact and at a distance. We use simple language and vocabulary to make this invisible world easy for students to ""see"" and understand. Examine how forces ""add up"" to create the total force on an object, and reinforce concepts and extend learning with sample problems.

  17. Intervertebral reaction force prediction using an enhanced assembly of OpenSim models.

    Senteler, Marco; Weisse, Bernhard; Rothenfluh, Dominique A; Snedeker, Jess G

    2016-04-01

    OpenSim offers a valuable approach to investigating otherwise difficult to assess yet important biomechanical parameters such as joint reaction forces. Although the range of available models in the public repository is continually increasing, there currently exists no OpenSim model for the computation of intervertebral joint reactions during flexion and lifting tasks. The current work combines and improves elements of existing models to develop an enhanced model of the upper body and lumbar spine. Models of the upper body with extremities, neck and head were combined with an improved version of a lumbar spine from the model repository. Translational motion was enabled for each lumbar vertebrae with six controllable degrees of freedom. Motion segment stiffness was implemented at lumbar levels and mass properties were assigned throughout the model. Moreover, body coordinate frames of the spine were modified to allow straightforward variation of sagittal alignment and to simplify interpretation of results. Evaluation of model predictions for level L1-L2, L3-L4 and L4-L5 in various postures of forward flexion and moderate lifting (8 kg) revealed an agreement within 10% to experimental studies and model-based computational analyses. However, in an extended posture or during lifting of heavier loads (20 kg), computed joint reactions differed substantially from reported in vivo measures using instrumented implants. We conclude that agreement between the model and available experimental data was good in view of limitations of both the model and the validation datasets. The presented model is useful in that it permits computation of realistic lumbar spine joint reaction forces during flexion and moderate lifting tasks. The model and corresponding documentation are now available in the online OpenSim repository. PMID:26031341

  18. Impact of walking speed and slope of the ground on axial force of poles in Nordic walking

    Martin Pšurný

    2013-09-01

    Full Text Available BACKGROUND: Nordic walking (NW, due to its attractiveness and convenience of equipment, is becoming more popular and utilised in the areas of sports, recreation and physiotherapy. Some of its impacts on load to the body have not yet been sufficiently explored. OBJECTIVE: The objective of the study was to determine the impact of walking speed and slope of the ground on the magnitude of axial forces, transferred to the poles by upper extremities during NW. METHODS: The study was participated in by 17 healthy subjects, aged 25.9 ± 3.6 years, who went through 12 independent measurements on a treadmill in various speeds (6.0; 6.6; 7.2 and 7.8 km • h–1 and slopes (0; 5 and 7.5%. These measurements provided us with values of basic spatiotemporal variables, characterizing NW performance and force variables, acting on the poles. RESULTS: Increased walking speed led to increase in cycle frequency (p < .001 and increase in peak poling force and average poling force (p < .001. Poling time reduced with increasing speed (p < .001. Increase in slope of ground had no significant impact on the magnitude of time and dynamic variables. CONCLUSIONS: Increased walking speed during NW increases the force, generated by the upper extremities on the poles. During NW it is possible to prefer walking speed rather than to change the slope of the ground for those patients, who are indicated to strengthen upper extremities.

  19. Ground-state widths of 5He and 5Li determined in the 3H(d,?)5He and the 3He(d,?)5Li reactions

    We have measured the widths of the 3/2- ground states of 5He and 5Li using the 3H(d,?)5He and the 3He(d,?)5Li reactions at Ed=8.6 MeV. The ?-ray spectra were fitted with a convolution of the NaI line-shape response function, as measured with the 3H(p,?)4He reaction, and a Breit-Wigner single-level expression. The widths extracted from the spectra were found to be ?n=1.36±0.19 MeV for 5He, and ?p=2.44±0.21 MeV for 5Li. These values, significantly different from previously quoted measurements, lead to reduced widths which are equal to within error, a result which is consistent with the charge-symmetry property of the nuclear force

  20. Referral of tactile stimuli to action points in virtual reality with reaction force.

    Moizumi, Shunjiro; Yamamoto, Shinya; Kitazawa, Shigeru

    2007-09-01

    When we touch something with a tool, we feel the touch at the tip of the tool rather than at the hand. Yamamoto and Kitazawa [Yamamoto, S., Kitazawa, S., 2001b. Sensation at the tips of invisible tools. Nat. Neurosci. 4, 979-980] previously showed that the judgment of the temporal order of two successive stimuli, delivered to the tips of sticks held in each hand, was dramatically altered by crossing the sticks without changing the positions of the hands. This provided evidence for the referral of tactile signals to the tip of a tool in hand. In this study, we examined importance of force feedback from the tool in the referral by manipulating the direction of force feedback in a virtual reality. The virtual tool consisted of a spherical action point that was moved with a stylus in hand. Subjects held two styli, one in each hand, put each action point on each of two buttons in the virtual reality, and were required to judge the order of successive taps, delivered to the two styli. We manipulated the direction of reaction force from each button so that it was congruent or incongruent to the visual configuration of the button. When the arms were uncrossed, judgment primarily depended on whether the action points were crossed or not in the visual space. But when the arms were crossed, judgment critically depended on the direction of force feedback. The results show that tactile signals can be referred to the action point in the virtual reality and that the force feedback becomes a critical factor when the arms are crossed. PMID:17617482

  1. [Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio]. Volume 5, Field Investigation report

    1992-03-01

    An environmental investigation of ground water conditions has been undertaken at Wright-Patterson Air Force Base (WPAFB), Ohio to obtain data to assist in the evaluation of a potential removal action to prevent, to the extent practicable, migration of the contaminated ground water across Base boundaries. Field investigations were limited to the central section of the southwestern boundary of Area C and the Springfield Pike boundary of Area B. Further, the study was limited to a maximum depth of 150 feet below grade. Three primary activities of the field investigation were: (1) installation of 22 monitoring wells, (2) collection and analysis of ground water from 71 locations, (3) measurement of ground water elevations at 69 locations. Volatile organic compounds including trichloroethylene, perchloroethylene, and/or vinyl chloride were detected in concentrations exceeding Maximum Contaminant Levels (MCL) at three locations within the Area C investigation area. Ground water at the Springfield Pike boundary of Area B occurs in two primary units, separated by a thicker-than-expected clay layers. One well within Area B was determined to exceed the MCL for trichloroethylene.

  2. Ab initio nuclear structure and reactions with chiral three-body forces

    Langhammer, Joachim; Roth, Robert; Calci, Angelo [Institut fuer Kernphysik - Theoriezentrum, TU Darmstadt (Germany); Navratil, Petr [TRIUMF, Vancouver (Canada)

    2014-07-01

    One major ambition of ab initio nuclear theory is the description of nuclear-structure and reaction observables on equal footing. This is accomplished by combining the no-core shell model (NCSM) with the resonating-group method (RGM) to a unified ab initio approach to bound and continuum states, which is developed further to the no-core shell model with continuum (NCSMC). We present the formal developments to include three-nucleon interactions in both the NCSM/RGM and NCSMC formalism. This provides the possibility to assess the predictive power of chiral two- and three-nucleon forces in the variety of scattering observables. We study three-nucleon force effects on phase-shifts, cross sections and analyzing powers in first ab-initio studies of nucleon-{sup 4}He scattering with chiral two- and three-nucleon forces. Finally, we focus on heavier target nuclei using the NCSMC, e.g., in neutron-{sup 8}Be scattering and study the impact of the continuum on the spectrum of {sup 9}Be.

  3. Extraction of ground reaction forces for real-time synthesis of walking sounds

    Serafin, Stefania; Turchet, Luca; Nordahl, Rolf

    A shoe-independent system to synthesize real-time footstep sounds on different materials has been developed. A footstep sound is considered as the result of an interaction between an exciter (the shoe) and a resonator (the floor). To achieve our goal, we propose two different solutions. The first...

  4. Ground Reaction Force Differences in the Countermovement Jump in Girls with Different Levels of Performance

    Floría, Pablo; Harrison, Andrew J.

    2013-01-01

    Purpose: The aim of this study was to ascertain the biomechanical differences between better and poorer performers of the vertical jump in a homogeneous group of children. Method: Twenty-four girls were divided into low-scoring (LOW; M [subscript age] = 6.3 ± 0.8 years) and high-scoring (HIGH; M [subscript age] = 6.6 ± 0.8 years) groups based on…

  5. Ground Reaction Force Differences in the Countermovement Jump in Girls with Different Levels of Performance

    Floría, Pablo; Harrison, Andrew J.

    2013-01-01

    Purpose: The aim of this study was to ascertain the biomechanical differences between better and poorer performers of the vertical jump in a homogeneous group of children. Method: Twenty-four girls were divided into low-scoring (LOW; M [subscript age] = 6.3 ± 0.8 years) and high-scoring (HIGH; M [subscript age] = 6.6 ± 0.8 years) groups based on…

  6. Influence of walking speed in backpacker's gait : ground reaction forces and plantar pressure analysis

    Figueiredo, Maria Cristina Pinto Leite Braamcamp

    2011-01-01

    O modo como nos deslocamos influencia os parâmetros biomecânicos da marcha, alterando-os, podendo vir a originar lesões a curto ou longo prazo. Com este trabalho pretendeu-se fazer, em primeiro lugar, uma revisão sistemática da literatura acerca do que consiste a influência da velocidade nos parâmetros biomecânicos da marcha e, depois, estudar o efeito que a velocidade tem nas forças de reacção ao solo e na pressão plantar durante a marcha quando se transporta, ou não, uma carga. Assim, um do...

  7. Self-consistent HF-RPA description of electron and photon nuclear reactions with Skyrme forces

    A mean-field nuclear dynamics is investigated in the analysis of nuclear electromagnetic processes at low and intermediate (q, ω) transfers. The theoretical framework is a self-consistent HF-RPA theory with Skyrme forces formulated in the one-nucleon energy continuum. We review the results obtained in the Skyrme HF-RPA model by focusing on some specific aspects of the theoretical frame and discussing their incidence in the prediction of data. Main points of interest are: (i) the quasiparticle formulation of the Skyrme HF-RPA nuclear dynamics with the identification of a quasi-particle effective mass, (ii) the gauge-invariance of the Skyrme Hamiltonian which produces nuclear electromagnetic currents satisfying the continuity equation, (iii) the excitation and decay properties of the one-nucleon energy continuum. The problems dealt with in the discussion of experimental data are the following: the quasi-deuteron effect in (γ, p) and (γ, n) reactions of closed shell nuclei at energies Eγ≤300 MeV, Giant Multipole Resonances versus momentum transfer in inclusive (e, e' x) responses, the reaction mechanism in polarized ( vector e, e' x) angular distributions at q≤200 MeV/c, the evaluation of the missing strength in inclusive (e, e') longitudinal responses at high momentum transfer, final state interactions and missing momentum distributions in coincidence (e, e' p) reactions in the quasi-elastic region. (orig.)

  8. Numerical simulation study of ground vibrations using forces from wheels of a running high-speed train

    Katou, Masafumi; Matsuoka, Toshifumi; Yoshioka, Osamu; Sanada, Yoshinori; Miyoshi, Takayuki

    2008-12-01

    A 3-D viscoelastic finite difference method (FDM) was adopted to study the mechanism of ground vibrations induced by a high-speed train. Time-series data of the forces acting on the railroad were observed from the wheels of a running Shinkansen train in Japan and were used to develop a realistic source function as an input to numerical simulations for a single wheel. This is because the measured forces include suitable frequency components. A 3-D numerical model of the embankment of the railroad was designed to mimic a test field site for which borehole logging data were available. Simple analytical discussions concluded that a rail length of 120 m and a grid spacing of 0.25 m were acceptable for stable FDM simulations without numerical dispersion, and a model with about 32 million grid points was adopted for this study. A staggered-grid FDM with fourth-order accuracy in space was used for the numerical simulations. Finally, the simulated ground vibration was compared with the observed vibrations at the test site. The simulated ground vibrations closely resembled the observed ones. At the test site, the quality factor ( Q) was not observed experimentally; however, the best match with field data was realized by assuming Q=5-50.

  9. Stabilization Control of Two-Wheels Driven Mobile Manipulator by Ground Reaction Torque Feedback

    Nozaki, Kohei; Murakami, Toshiyuki

    This paper describes a stabilization control method of a two-wheels driven mobile manipulator by ground reaction torque feedback. As the population ages and birthrates decline, many people are expecting robots to assist them in their daily lives, such as in homes, offices, and hospitals. However, there are some issues in robot development. Human environment is complex and dynamic, such as the presence of steps, slopes, narrow paths, and unknown obstacles. Therefore, the future robots will be required to have high mobility. The two-wheels driven mobile manipulator has excellent mobility and can realize rapid and smooth motion such as turning instantly. However, since it does not have any casters, its attitude is unstable and some attitude control is required. In addition, even if attitude control is implemented, there is a risk of falling down on rough terrains. Hence, in this paper, a stabilization control considering rough terrains is proposed. The validity of the proposed method is confirmed by simulation and experimental results.

  10. [Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio]. Volume 9, Removal action system design

    1992-04-01

    This Removal Action System Design has been prepared as a Phase I Volume for the implementation of the Phase II removal action at Wright-Patterson Air Force Base (WPAFB) near Dayton, Ohio. The objective of the removal action is to prevent, to the extent practicable, the migration of ground water contaminated with chlorinated volatile organic compounds (VOCS) across the southwest boundary of Area C. The Phase 1, Volume 9 Removal Action System Design compiles the design documents prepared for the Phase II Removal Action. These documents, which are presented in Appendices to Volume 9, include: Process Design, which presents the 30 percent design for the ground water treatment system (GWTS); Design Packages 1 and 2 for Earthwork and Road Construction, and the Discharge Pipeline, respectively; no drawings are included in the appendix; Design Package 3 for installation of the Ground Water Extraction Well(s); Design Package 4 for installation of the Monitoring Well Instrumentation; and Design Package 5 for installation of the Ground Water Treatment System; this Design Package is incorporated by reference because of its size.

  11. Nuclear ground-state properties and ion-ion potentials in semiclassical calculations with the Gogny force

    The ground-state properties of magic nuclei have been studied by means of the Gogny force within the Hartree-Fock Scheme using the Slater approximation for the exchange part. A similar analysis has been carried out within the semiclassical framework by considering the extended Thomas-Fermi approach for the kinetic energy density. Comparisons with the complete Hartree-Fock results are made. The ion-ion potential for two colliding nuclei has been obtained in the energy density functional and the double-folded model approaches by using self-consistent semiclassical densities calculated with the Gogny force. These potentials have been applied in the study of 40Ca-40Ca elastic scattering. (author)

  12. Ground State Reactions of nC60 with Free Chlorine in Water.

    Wu, Jiewei; Benoit, Denise; Lee, Seung Soo; Li, Wenlu; Fortner, John D

    2016-01-19

    Facile, photoenhanced transformations of water-stable C60 aggregates (nC60) to oxidized, soluble fullerene derivatives, have been described as key processes in understanding the ultimate environmental fate of fullerene based materials. In contrast, fewer studies have evaluated the aqueous reactivity of nC60 during ground-state conditions (i.e., dark conditions). Herein, this study identifies and characterizes the physicochemical transformations of C60 (as nC60 suspensions) in the presence of free chlorine, a globally used chemical oxidant, in the absence of light under environmentally relevant conditions. Results show that nC60 undergoes significant oxidation in the presence of free chlorine and the oxidation reaction rates increase with free chlorine concentration while being inversely related to solution pH. Product characterization by FTIR, XPS, Raman Spectroscopy, TEM, XRD, TOC, collectively demonstrates that oxidized C60 derivatives are readily formed in the presence of free chlorine with extensive covalent oxygen and even chlorine additions, and behave as soft (or loose) clusters in solution. Aggregation kinetics, as a function of pH and ionic strength/type, show a significant increase in product stabilities for all cases evaluated, even at pH values approaching 1. As expected with increased (surface) oxidation, classic Kow partitioning studies indicate that product clusters are relatively more hydrophilic than parent (reactant) nC60. Taken together, this work highlights the importance of understanding nanomaterial reactivity and the identification of corresponding stable daughter products, which are likely to differ significantly from parent material properties and behaviors. PMID:26651395

  13. [Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio]. Volume 5, Appendix A, Part 1, Field Investigation report

    1992-03-01

    This report presents information related to the sampling of ground water at the Wright-Patterson Air Force Base. It is part of an investigation into possible ground water contamination. Information concerns well drilling/construction; x-ray diffraction and sampling; soil boring logs; and chain-of-custody records.

  14. Sudden drop in ground support produces force-related unload response in human overground walking

    Af Klint, Richard; Nielsen, Jens Bo; Sinkjaer, Thomas; Grey, Michael J

    2009-01-01

    healthy volunteers. Subjects walked unrestrained over a hydraulically actuated platform. On random trials the platform was accelerated downward at 0.8 g, unloading the plantar flexor muscles in midstance or late stance. The drop of the platform resulted in a significant depression of the soleus muscle...... decreased starting 22 ms (SD 15) after the drop. To investigate the role of length- and velocity-sensitive afferents on the depression in soleus muscle activity, the ankle rotation was arrested by using an ankle foot orthotic as the platform was dropped. Preventing the ankle movement did not significantly...... change the soleus depression in late stance [-18.2% (SD 15)], whereas the depression in midstance was removed [+4.9% (SD 13)]. It is concluded that force feedback from ankle extensors increases the locomotor output through positive feedback in late stance. In midstance the effect of force feedback was...

  15. Grounding the Lexical Semantics of Verbs in Visual Perception using Force Dynamics and Event Logic

    Siskind, J M

    2011-01-01

    This paper presents an implemented system for recognizing the occurrence of events described by simple spatial-motion verbs in short image sequences. The semantics of these verbs is specified with event-logic expressions that describe changes in the state of force-dynamic relations between the participants of the event. An efficient finite representation is introduced for the infinite sets of intervals that occur when describing liquid and semi-liquid events. Additionally, an efficient procedure using this representation is presented for inferring occurrences of compound events, described with event-logic expressions, from occurrences of primitive events. Using force dynamics and event logic to specify the lexical semantics of events allows the system to be more robust than prior systems based on motion profile.

  16. The 4- and 5-nucleon system, a testing ground for nuclear forces

    It is tried to demonstrate that the 4- and 5-nucleon systems are well suited to study the spin-dependent nucleon-nucleon forces acting in few nucleon systems. Observables can be found which depend on one or at least two components of the spin-dependent nucleon-nucleon interaction only. Within the three-nucleon system it does not seem to be possible to select such quantities. Generally many phases, which are almost unsplitted in respect to J, contribute to an observable. The interpretation of parts of the very accurate data is therefore complicated and doubtful. It is shown that the 4- and 5-nucleon systems offer information on the spin depending nucleon-nucleon forces, acting there, in a more simple way

  17. Grounding the Lexical Semantics of Verbs in Visual Perception using Force Dynamics and Event Logic

    Siskind, J. M.

    2011-01-01

    This paper presents an implemented system for recognizing the occurrence of events described by simple spatial-motion verbs in short image sequences. The semantics of these verbs is specified with event-logic expressions that describe changes in the state of force-dynamic relations between the participants of the event. An efficient finite representation is introduced for the infinite sets of intervals that occur when describing liquid and semi-liquid events. Additionally, an efficient proced...

  18. Criteria for Side-Force Control in Air-to-Ground Target Acquisition and Tracking

    Sammonds, Robert I.; McNeill, Walter E.; Bunnell, John W.

    1982-01-01

    A moving-base simulator experiment conducted at Ames Research Center demonstrated that a wings-level-turn control mode improved flying qualities for air-to-ground weapons delivery compared with those of a conventional aircraft. Evaluations of criteria for dynamic response for this system have shown that pilot ratings correlate well with equivalent time constant of the initial response and with system bandwidth. Ranges of this time constant, as well as digital-system transport delays and lateral-acceleration control authorities that encompassed level 1 through level 3 handling qualities, were determined.

  19. Intra-Articular Knee Contact Force Estimation During Walking Using Force-Reaction Elements and Subject-Specific Joint Model2.

    Jung, Yihwan; Phan, Cong-Bo; Koo, Seungbum

    2016-02-01

    Joint contact forces measured with instrumented knee implants have not only revealed general patterns of joint loading but also showed individual variations that could be due to differences in anatomy and joint kinematics. Musculoskeletal human models for dynamic simulation have been utilized to understand body kinetics including joint moments, muscle tension, and knee contact forces. The objectives of this study were to develop a knee contact model which can predict knee contact forces using an inverse dynamics-based optimization solver and to investigate the effect of joint constraints on knee contact force prediction. A knee contact model was developed to include 32 reaction force elements on the surface of a tibial insert of a total knee replacement (TKR), which was embedded in a full-body musculoskeletal model. Various external measurements including motion data and external force data during walking trials of a subject with an instrumented knee implant were provided from the Sixth Grand Challenge Competition to Predict in vivo Knee Loads. Knee contact forces in the medial and lateral portions of the instrumented knee implant were also provided for the same walking trials. A knee contact model with a hinge joint and normal alignment could predict knee contact forces with root mean square errors (RMSEs) of 165?N and 288?N for the medial and lateral portions of the knee, respectively, and coefficients of determination (R2) of 0.70 and -0.63. When the degrees-of-freedom (DOF) of the knee and locations of leg markers were adjusted to account for the valgus lower-limb alignment of the subject, RMSE values improved to 144?N and 179?N, and R2 values improved to 0.77 and 0.37, respectively. The proposed knee contact model with subject-specific joint model could predict in vivo knee contact forces with reasonable accuracy. This model may contribute to the development and improvement of knee arthroplasty. PMID:26720762

  20. Coupling Satellite and Ground-Based Instruments to Map Climate Forcing by Anthropogenic Aerosols

    Charlson, Robert J.; Anderson, Theodore L.; Hostetler, Chris (Technical Monitor)

    2000-01-01

    Climate forcing by anthropogenic aerosols is a significant but highly uncertain factor in global climate change. Only satellites can offer the global coverage essential to reducing this uncertainty; however, satellite measurements must be coupled with correlative, in situ measurements both to constrain the aerosol optical properties required in satellite retrieval algorithms and to provide chemical identification of aerosol sources. This grant funded the first two years of a three-year project which seeks to develop methodologies for combining spaceborne lidar with in-situ aerosol data sets to improve estimates of direct aerosol climate forcing. Progress under this two-year grant consisted in the development and deployment of a new in-situ capability for measuring aerosol 180' backscatter and the extinction-to-backscatter ratio. This new measurement capacity allows definitive lidar/in-situ comparisons and improves our ability to interpret lidar data in terms of climatically relevant quantities such as the extinction coefficient and optical depth. Measurements were made along the coast of Washington State, in Central Illinois, over the Indian Ocean, and in the Central Pacific. Thus, this research, combined with previous measurements by others, is rapidly building toward a global data set of extinction-to-backscatter ratio for key aerosol types. Such information will be critical to interpreting lidar data from the upcoming PICASSO-CENA, or P-C, satellite mission. Another aspect of this project is to investigate innovative ways to couple the lidar-satellite signal with targeted in-situ measurements toward a direct determination of aerosol forcing. This aspect is progressing in collaboration with NASA Langley's P-C lidar simulator and radiative transfer modeling by the University of Lille, France.

  1. Mechanics of Ship Grounding

    Pedersen, Preben Terndrup

    1996-01-01

    In these notes first a simplified mathematical model is presented for analysis of ship hull loading due to grounding on relatively hard and plane sand, clay or rock sea bottoms. In a second section a more rational calculation model is described for the sea bed soil reaction forces on the sea bott...

  2. Force and Torque Analytical Models of a Reaction Sphere Actuator Based on Spherical Harmonic Rotation and Decomposition

    Rossini, L.; Chetelat, O.; Onillon, E.; Perriard, Y.

    2013-01-01

    This paper presents an analytical model for the force and torque developed by a reaction sphere actuator for satellite attitude control. The reaction sphere is an innovative momentum exchange device consisting of a magnetic bearings spherical rotor that can be electronically accelerated in any direction making all the three axes of stabilized spacecrafts controllable by a unique device. The spherical actuator is composed of an 8-pole permanent magnet spherical rotor and of a 20-coil stator. F...

  3. The (p,n) reaction on cadmium isotopes leading to the ground- and excited-state analogs

    The (p,n) reactions to ground- and excited-state analogs on 110,114,116Cd have been studied at a bombarding energy of 25 MeV. Angular distributions of emitted neutrons leading to ground-state analogs, and 2+, 3- and 4+ excited-state analogs were obtained for each target. Angular distributions of differential cross sections to the ground-state analog agree with the predictions obtained from macroscopic DWBA calculations in which a Lane potential is employed. Coupled-channel calculations indicate the importance of two-step processes in the (p,n) transition to an excited-state analog. Further, the calculation using a larger value for the deformation parameter of the isovector part than of the isoscalar one fairly well describes the 2+ excited-state analog. (orig.)

  4. Numerical verification of B-WIM system using reaction force signals

    Bridges are ones of fundamental facilities for roads which become social overhead capital facilities and they are designed to get safety in their life cycles. However as time passes, bridge can be damaged by changes of external force and traffic environments. Therefore, a bridge should be repaired and maintained for extending its life cycle. The working load on a bridge is one of the most important factors for safety, it should be calculated accurately. The most important load among working loads is live load by a vehicle. Thus, the travel characteristics and weight of vehicle can be useful for bridge maintenance if they were estimated with high reliability. In this study, a B-WIM system in which the bridge is used for a scale have been developed for measuring the vehicle loads without the vehicle stop. The vehicle loads can be estimated by the developed B-WIM system with the reaction responses from the supporting points. The algorithm of developed B-WIM system have been verified by numerical analysis

  5. Use of aquifer testing to complete ground water remedial design, shallow aquifer Nellis Air Force Base, Las Vegas, Nevada

    As part of a US Army Corps of Engineers-directed remedial action, a ground water treatment system is being installed at Site 27, Nellis Air Force Base, Las Vegas, Nevada. Twenty-three extraction wells were installed in the center and on the leading edge of a jet fuel plume of free and dissolved product in the uppermost (nonpotable) aquifer. The purpose of the extraction well system is to contain and remediate the plume, and to recover free product, which is over 10 feet thick in one well. Aquifer testing, including step and constant discharge tests, was conducted during well installation in order to (1) assist in location of subsequent wells, (2) obtain dynamic product thickness data for selection of wells in which skimmer pumps will be installed, (3) determine initial pumping rates, (4) determine aquifer parameters for modeling and optimization, and (5) provide baseline data on well performance to evaluate possible future biofouling

  6. Reaction Force/Torque Sensing in a Master-Slave Robot System without Mechanical Sensors

    Kyoko Shibata

    2010-07-01

    Full Text Available In human-robot cooperative control systems, force feedback is often necessary in order to achieve high precision and high stability. Usually, traditional robot assistant systems implement force feedback using force/torque sensors. However, it is difficult to directly mount a mechanical force sensor on some working terminals, such as in applications of minimally invasive robotic surgery, micromanipulation, or in working environments exposed to radiation or high temperature. We propose a novel force sensing mechanism for implementing force feedback in a master-slave robot system with no mechanical sensors. The system consists of two identical electro-motors with the master motor powering the slave motor to interact with the environment. A bimanual coordinated training platform using the new force sensing mechanism was developed and the system was verified in experiments. Results confirm that the proposed mechanism is capable of achieving bilateral force sensing and mirror-image movements of two terminals in two reverse control directions.

  7. Unattended wireless proximity sensor networks for counterterrorism, force protection, littoral environments, PHM, and tamper monitoring ground applications

    Forcier, Bob

    2003-09-01

    This paper describes a digital-ultrasonic ground network, which forms an unique "unattended mote sensor system" for monitoring the environment, personnel, facilities, vehicles, power generation systems or aircraft in Counter-Terrorism, Force Protection, Prognostic Health Monitoring (PHM) and other ground applications. Unattended wireless smart sensor/tags continuously monitor the environment and provide alerts upon changes or disruptions to the environment. These wireless smart sensor/tags are networked utilizing ultrasonic wireless motes, hybrid RF/Ultrasonic Network Nodes and Base Stations. The network is monitored continuously with a 24/7 remote and secure monitoring system. This system utilizes physical objects such as a vehicle"s structure or a building to provide the media for two way secure communication of key metrics and sensor data and eliminates the "blind spots" that are common in RF solutions because of structural elements of buildings, etc. The digital-ultrasonic sensors have networking capability and a 32-bit identifier, which provide a platform for a robust data acquisition (DAQ) for a large amount of sensors. In addition, the network applies a unique "signature" of the environment by comparing sensor-to-sensor data to pick up on minute changes, which would signal an invasion of unknown elements or signal a potential tampering in equipment or facilities. The system accommodates satellite and other secure network uplinks in either RF or UWB protocols. The wireless sensors can be dispersed by ground or air maneuvers. In addition, the sensors can be incorporated into the structure or surfaces of vehicles, buildings, or clothing of field personnel.

  8. The law of action and reaction for the effective force in a non-equilibrium colloidal system

    We study a non-equilibrium Langevin many-body system containing two 'test' particles and many 'background' particles. The test particles are spatially confined by a harmonic potential, and the background particles are driven by an external driving force. Using numerical simulations of the model, we formulate an effective description of the two test particles in a non-equilibrium steady state. In particular, we investigate several different definitions of the effective force acting between the test particles. We find that the law of action and reaction does not hold for the total mechanical force exerted by the background particles, but that it does hold for the thermodynamic force defined operationally on the basis of an idea used to extend the first law of thermodynamics to non-equilibrium steady states

  9. Collisional and photoinitiated reaction dynamics in the ground electronic state of Ca-HCl

    Ca+HCl(?,j) reactive collisions were studied for different rovibrational states of the HCl reactant using wave-packet calculations in reactant Jacobi coordinates. A recently proposed potential-energy surface was used with a barrier of ?0.4 eV followed by a deep well. The possibility of an insertion mechanism due to this last well has been analyzed and it was found that once the wave packet passes over the barrier most of it goes directly to CaCl+H products, which shows that the reaction dynamics is essentially direct. It was also found that there is no significant change in the reaction efficiency as a function of the initial HCl rovibrational state, because CaHCl at the barrier has an only little elongated HCl bond. Near the threshold for reaction with HCl(?=0), however, the reaction shows significant steric effects for j>0. In a complementary study, the infrared excitation from the Ca-HCl van der Waals well was simulated. The spectrum thus obtained shows several series of resonances which correspond to quasibound states correlating to excited HCl(?) vibrations. The Ca-HCl binding energies of these quasibound states increase dramatically with ?, from 75 to 650 cm-1, because the wave function spreads increasingly over larger HCl bond lengths. Thus it explores the region of the barrier saddle point and the deep insertion well. Although also the charge-transfer contribution increases with ?, the reaction probability for resonances of the ?=2 manifold, which are well above the reaction threshold, is still negligible. This explains the relatively long lifetimes of these ?=2 resonances. The reaction probability becomes significant at ?=3. Our simulations have shown that an experimental study of this type will allow a gradual spectroscopic probing of the barrier for the reaction

  10. Does foot pitch at ground contact affect parachute landing technique?

    Whitting, John W; Steele, Julie R; Jaffrey, Mark; Munro, Bridget J

    2009-08-01

    The Australian Defence Force Parachute Training School instructs trainees to make initial ground contact using a flat foot whereas United States paratroopers are taught to contact the ground with the ball of the foot first. This study aimed to determine whether differences in foot pitch affected parachute landing technique. Kinematic, ground reaction force and electromyographic data were analyzed for 28 parachutists who performed parachute landings (vertical descent velocity = 3.4 m x s(-1)) from a monorail apparatus. Independent t-tests were used to determine significant (p < 0.05) differences between variables characterizing foot pitch. Subjects who landed flat-footed displayed less knee and ankle flexion, sustained higher peak ground reaction forces, and took less time to reach peak force than those who landed on the balls of their feet. Although forefoot landings lowered ground reaction forces compared to landing flat-footed, further research is required to confirm whether this is a safer parachute landing strategy. PMID:19743739

  11. Assessment of concentrations of trace elements in ground water and soil at the Small-Arms Firing Range, Shaw Air Force Base, South Carolina

    Landmeyer, J.E.

    1994-01-01

    Ground-water samples were collected from four shallow water-table aquifer observation wells beneath the Small-Arms Firing Range study area at Shaw Air Force Base. Water-chemistry analyses indicated that total lead concentrations in shallow ground water beneath the study area do not exceed the U.S. Environmental Protection Agency maximum contaminant level established for lead in drinking water (0.05 milligrams per liter). All other trace element total concentrations in ground water beneath the study area were at or below the detection limit of the analytical methodology.

  12. 3D FEM Numerical Simulation of Seismic Pile-supported Bridge Structure Reaction in Liquefying Ground

    Ling XianZhang, Tang Liang and Xu Pengju

    2011-04-01

    Full Text Available This study examines the establishment of liquefied ground pile-soil-bridge seismic interaction analysis of three-dimensional finite element analysis method for the simulation of liquefied ground shaking table test of pile-soil seismic interaction analysis, undertake OpenSees finite element based numerical simulation platform, for the shaking table test based on two-phase saturated porous media, Comparative numerical and experimental results, detailed test pile dynamic response of bridge structure and dynamic properties, especially liquefaction pore pressure, liquefaction of pile foundation and the dynamic response of the free field. Finite element method can reasonably predict the site of pore pressure, dynamic response; despite the conventional beam element simulation of pile, pile dynamic response can still accurately simulated.

  13. Tensor force in single-nucleon knock-on exchange in heavy-ion reactions

    Heavy-ion form factors for single-nucleon knock-on exchange are calculated with a two-body force comprising both central and tensor components. Central forces were found to greatly influence the cross section magnitude while tensor components seem to be negligible. (orig.)

  14. Guiding-centre transformation of the radiation-reaction force in a non-uniform magnetic field

    Hirvijoki, E.; Decker, J.; Brizard, A. J.; Embréus, O.

    2015-10-01

    > In this paper, we present the guiding-centre transformation of the radiation-reaction force of a classical point charge travelling in a non-uniform magnetic field. The transformation is valid as long as the gyroradius of the charged particles is much smaller than the magnetic field non-uniformity length scale, so that the guiding-centre Lie-transform method is applicable. Elimination of the gyromotion time scale from the radiation-reaction force is obtained with the Poisson-bracket formalism originally introduced by Brizard (Phys. Plasmas, vol. 11, 2004, 4429-4438), where it was used to eliminate the fast gyromotion from the Fokker-Planck collision operator. The formalism presented here is applicable to the motion of charged particles in planetary magnetic fields as well as in magnetic confinement fusion plasmas, where the corresponding so-called synchrotron radiation can be detected. Applications of the guiding-centre radiation-reaction force include tracing of charged particle orbits in complex magnetic fields as well as the kinetic description of plasma when the loss of energy and momentum due to radiation plays an important role, e.g. for runaway-electron dynamics in tokamaks.

  15. Russian Military and Security Forces: A Postulated Reaction to a Nuclear Detonation

    Ball, D

    2005-04-29

    In this paper, we will examine how Russia's military and security forces might react to the detonation of a 10-kiloton nuclear weapon placed next to the walls surrounding the Kremlin. At the time of this 'big bang,' Putin is situated outside Moscow and survives the explosion. No one claims responsibility for the detonation. No other information is known. Numerous variables will determine how events ultimately unfold and how the military and security forces will respond. Prior to examining these variables in greater detail, it is imperative to elucidate first what we mean by Russia's military and security forces.

  16. Reassessment of psychological distress and post-traumatic stress disorder in United States Air Force Distributed Common Ground System operators.

    Prince, Lillian; Chappelle, Wayne L; McDonald, Kent D; Goodman, Tanya; Cowper, Sara; Thompson, William

    2015-03-01

    The goal of this study was to assess for the main sources of occupational stress, as well as self-reported symptoms of distress and post-traumatic stress disorder among U.S. Air Force (USAF) Distributed Common Ground System (DCGS) intelligence exploitation and support personnel. DCGS intelligence operators (n=1091) and nonintelligence personnel (n = 447) assigned to a USAF Intelligence, Surveillance, and Reconnaissance Wing responded to the web-based survey. The overall survey response rate was 31%. Study results revealed the most problematic stressors among DCGS intelligence personnel included high workload, low manning, as well as organizational leadership and shift work issues. Results also revealed 14.35% of DCGS intelligence operators' self-reported high levels of psychological distress (twice the rate of DCGS nonintelligence support personnel). Furthermore, 2.0% to 2.5% self-reported high levels of post-traumatic stress disorder symptoms, with no significant difference between groups. The implications of these findings are discussed along with recommendations for USAF medical and mental health providers, as well as operational leadership. PMID:25747649

  17. Gamow-Teller strength function for 90Zr: Effects of spin and isospin exchange forces, and ground-state correlations

    Shell-model calculations of the Gamow-Teller strength function for 90Zr have been performed utilizing a realistic finite-range two-body interaction in a model space consisting of the 2p and 1g shells. The effects of admixtures of two-particle two-hole excitations in 90Nb, mostly due to the spin and isospin exchange components of the nucleon-nucleon force, are discussed. Ground state correlations in 90Zr are also added via seniority-zero two-proton excitations from the 2p shell into the 1g/sub 9/2/ shell. With the correlations the Gamow-Teller strength function is in good agreement with the experimental results and accounts for essentially all of the observed dispersion of strength. The inclusion of these correlations does not, however, produce either a displacement of Gamow-Teller strength to higher excitation energies, or a significant change in the total strength. Thus, they cannot account for the observed Gamow-Teller quenching. The quenching factor derived by a comparison of our calculated results with experiment is 0.52

  18. Calculation of reaction forces in the boiler supports using the method of equivalent stiffness of membrane wall.

    Sertić, Josip; Kozak, Dražan; Samardžić, Ivan

    2014-01-01

    The values of reaction forces in the boiler supports are the basis for the dimensioning of bearing steel structure of steam boiler. In this paper, the application of the method of equivalent stiffness of membrane wall is proposed for the calculation of reaction forces. The method of equalizing displacement, as the method of homogenization of membrane wall stiffness, was applied. On the example of "Milano" boiler, using the finite element method, the calculation of reactions in the supports for the real geometry discretized by the shell finite element was made. The second calculation was performed with the assumption of ideal stiffness of membrane walls and the third using the method of equivalent stiffness of membrane wall. In the third case, the membrane walls are approximated by the equivalent orthotropic plate. The approximation of membrane wall stiffness is achieved using the elasticity matrix of equivalent orthotropic plate at the level of finite element. The obtained results were compared, and the advantages of using the method of equivalent stiffness of membrane wall for the calculation of reactions in the boiler supports were emphasized. PMID:24959612

  19. The brute-force polarization of 23Na and the 23N vectora(n vector,?)24Na reaction

    A Na target has been polarized by brute force to 22% and the ?-radiation produced by polarized thermal neutron capture has been investigated. The Jsup(?)=2+ channel spin contribution has been determined model-independently and unambiguously for 22 primary transitions. The average Jsup(?)=2+ channel contribution is 5.8(5)%. The data resulted in one spin assignment and two spin restrictions. The energies and lifetimes of positive-parity levels as well as branching ratios and the magnetic moment of the ground state are in agreement with a shell-model calculation in the complete sd shell. (orig.)

  20. Quadrupedal locomotion in squirrel monkeys (Cebidae: Saimiri sciureus): a cineradiographic study of limb kinematics and related substrate reaction forces.

    Schmidt, Manuela

    2005-10-01

    Quadrupedal locomotion of squirrel monkeys on small-diameter support was analyzed kinematically and kinetically to specify the timing between limb movements and substrate reaction forces. Limb kinematics was studied cineradiographically, and substrate reaction forces were synchronously recorded. Squirrel monkeys resemble most other quadrupedal primates in that they utilize a diagonal sequence/diagonal couplets gait when walking on small branches. This gait pattern and the ratio between limb length and trunk length influence limb kinematics. Proximal pivots of forelimbs and hindlimbs are on the same horizontal plane, thus giving both limbs the same functional length. However, the hindlimbs are anatomically longer than the forelimbs. Therefore, hindlimb joints must be more strongly flexed during the step cycle compared to the forelimb joints. Because the timing of ipsilateral limb movements prevents an increasing amount of forelimb retraction, the forelimb must be more protracted during the initial stance phase. At this posture, gravity acts with long moment arms at proximal forelimb joints. Squirrel monkeys support most of their weight on their hindlimbs. The timing of limb movements and substrate reaction forces shows that the shift of support to the hindlimbs is mainly done to reduce the compressive load on the forelimb. The hypothesis of the posterior weight shift as a dynamic strategy to reduce load on forelimbs, proposed by Reynolds ([1985]) Am. J. Phys. Anthropol. 67:335-349; [1985] Am. J. Phys. Anthropol. 67:351-362), is supported by the high correlation of ratios between forelimb and hindlimb peak vertical forces and the range of motion of shoulder joint and scapula in primates. PMID:15838834

  1. From the self-force problem to the radiation reaction formula

    We review recent theoretical progress in the so-called self-force problem of a general relativistic two-body system. Although a two-body system in Newtonian gravity is a very simple problem, some fundamental issues are involved in relativistic gravity. Besides, because of recent projects for gravitational wave detection, it has become possible to see those phenomena directly via gravitational waves, and the self-force problem becomes one of urgent and highly-motivated problems in general relativity. Roughly speaking, there are two approaches to investigate this problem; the so-called post-Newtonian approximation, and a black-hole perturbation. In this paper, we review theoretical progress in the self-force problem using a black-hole perturbation. Although the self-force problem seems to be just a problem to calculate a self-force, we discuss that the real problem is to define a gauge-invariant concept of a motion in a gauge-dependent metric perturbation

  2. The ground state mass of 147Gd from single-neutron transfer reactions

    Thin targets of radioactive 148Gd were used to determine a precise value for the mass of 147Gd. The (p,d), (d,t), and 3He,α) reactions were used with high-resolution charged-particle spectrometry to determine Q-values for the 148Gd target relative to several calibration targets having known Q-values. By combining the measured Q-value with the 148Gd mass, the mass defect, ΔM(147Gd) = 75356 +- 6 keV, 149 keV less than the value in the 1977 mass tabulation was obtained. 7 refs., 1 fig., 1 tab

  3. Measurement of the rates of reaction of the ground and metastable excited states of 02+, N0+ and 0+ with atmospheric gases at thermal energy

    Thermal-energy reaction rate coefficients and product ion distributions have been measured for reactions of both the ground state and metastable electronic states of 02+, N0+ and 0+ with several neutral species, using a selected-ion flow tube. In general the excited-ion reaction rates are fast, frequently approaching the Langevin limit. Collisional quenching occurs for the reactions of N0+sup(star) with N2,02 and H2 and the quenching rates have been determined. The ion source also provided a substantial yield of doubly charged 02 permitting some measurements of reaction rates of 022+. (author)

  4. Repulsion forces of superplasticizers on ground granulated blast furnace slag in alkaline media, from AFM measurements to rheological properties

    Palacios, M.

    2012-12-01

    Full Text Available The electrostatic and steric repulsion induced by different superplasticizers on ground granulated blast furnace slag in alkaline media have been studied. The superplasticizers were sulfonated naphthalene, sulfonated melamine, vinyl copolymer, and polycarboxylate- based admixtures. With these superplasticizers the slag suspensions had negative zeta potentials, ranging from -3 to -10 mV. For the first time the adsorbed layer thicknesses for superplasticizers on slag using colloidal probe atomic force microscopy has been measured. To model the interparticle force interactions an effective Hamaker constant was computed from dielectric properties measured on a dense slag sample produced by spark plasma sintering. The obtained results conclude that the dispersion mechanism for all the superplasticizers studied in the present work is mainly dominated by the steric repulsion. Results were then used in a yield stress model, YODEL, to predict the yield stress with and without the superplasticizers. Predictions of the yield stress agreed well with experimental results.

    En este trabajo se ha estudiado la repulsión electrostática y estérica inducida por diferentes aditivos superplastificantes en sistemas de escoria de horno alto en medios alcalinos. Se han estudiado aditivos superplastificantes basados en naftaleno, melamina, copolímeros vinílicos y basados en policarboxilato. Estos aditivos inducen en la escoria un potencial zeta negativo, entre -3 y -10 mV. Por primera vez, se ha determinado el grosor de la capa de aditivo adsorbido sobre la escoria mediante microscopía de fuerzas atómicas (AFM. Para modelizar las fuerzas de interacción entre partículas, se ha determinado la constante efectiva de Hamaker de la escoria a partir de las propiedades dieléctricas de una muestra de escoria obtenida mediante sinterización spark plasma sintering. Los resultados obtenidos concluyen que el mecanismo de dispersión de los superplastificantes estudiados en este trabajo está gobernado fundamentalmente por la repulsión estérica. Utilizando el modelo YODEL se ha podido predecir el esfuerzo de cizalla umbral de sistemas de escoria con y sin superplastificantes. Los resultados calculados están de acuerdo con los valores de esfuerzo de cizalla determinados experimentalmente.

  5. Students' Understanding on Newton's Third Law in Identifying the Reaction Force in Gravity Interactions

    Zhou, Shaona; Zhang, Chunbin; Xiao, Hua

    2015-01-01

    In the past three decades, previous researches showed that students had various misconceptions of Newton's Third Law. The present study focused on students' difficulties in identifying the third-law force pair in gravity interaction situations. An instrument involving contexts with gravity and non-gravity associated interactions was designed and…

  6. Students' Understanding on Newton's Third Law in Identifying the Reaction Force in Gravity Interactions

    Zhou, Shaona; Zhang, Chunbin; Xiao, Hua

    2015-01-01

    In the past three decades, previous researches showed that students had various misconceptions of Newton's Third Law. The present study focused on students' difficulties in identifying the third-law force pair in gravity interaction situations. An instrument involving contexts with gravity and non-gravity associated interactions was designed and…

  7. Cluster emission in superdeformed Sr isotopes in the ground state and formed in heavy-ion reaction

    K P Santhosh; Antony Joseph

    2005-01-01

    Cluster decay of superdeformed 76,78,80Sr isotopes in their ground state are studied taking the Coulomb and proximity potential as the interacting barrier for the post-scission region. The predicted 1/2 values are found to be in close agreement with those values reported by the preformed cluster model (PCM). Our calculation shows that these nuclei are stable against both light and heavy cluster emissions. We studied the decay of these nuclei produced as an excited compound system in heavy-ion reaction. It is found that inclusion of excitation energy increases the decay rate (decreases 1/2 value) considerably and these nuclei become unstable against decay. These findings support earlier observation of Gupta et al based on PCM.

  8. Cluster emission in superdeformed Sr isotopes in the ground state and formed in heavy-ion reaction

    Cluster decay of superdeformed 76,78,80Sr isotopes in their ground state are studied taking the Coulomb and proximity potential as the interacting barrier for the post-scission region. The predicted T1/2 values are found to be in close agreement with those values reported by the preformed cluster model (PCM). Our calculation shows that these nuclei are stable against both light and heavy cluster emissions. We studied the decay of these nuclei produced as an excited compound system in heavy ion reaction. It is found that inclusion of excitation energy increases the decay rate (decreases T1/2 value) considerably and these nuclei become unstable against decay. These findings support earlier observation of Gupta et al based on PCM. (author)

  9. Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria

    Yuan, Yajie; Zrake, Jonathan; East, William E; Blandford, Roger D

    2016-01-01

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short time scales. These are likely due to rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reaction. We focus on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The "flares" are accompanied by an increased pol...

  10. Experimental Studies of the Coulomb Force Effects in Deuteron-Proton Break-up Reaction at Medium Energy Regime

    Ciepał, I.; Parol, W.; Kalantar-Nayestanaki, N.; Khatri, G.; Kistryn, St.; Kłos, B.; Kozela, A.; Kulessa, P.; Messchendorp, J.; Skwira-Chalot, I.; Stephan, E.; Włoch, B.

    2016-03-01

    A set of differential cross-section data of the 1H(d, pp)n breakup reaction at 130 and 160 MeV deuteron beam energies has been measured in the forward polar angles domain. The data were collected with the use of the Germanium Wall (FZ Jülich) and BINA (KVI Groningen) detectors. This part of the phase-space is special with respect to the dominant Coulomb force influence on the system dynamics. The data are compared with the theoretical calculations based on the Argonne V18 potential supplemented with the long-range electromagnetic component. The predictions also include the Urbana IX three nucleon force model. The strongest Coulomb effects are found in regions where the relative energy of the two protons is the smallest.

  11. Trichloroethylene and 1,1-dichloroethylene concentrations in ground water after temporary shutdown of the reclamation well field at Air Force Plant 44, Tucson, Arizona, 1999

    Graham, D.D.; Allen, T.J.; Barackman, M.L.; DiGuiseppi, W.H.; Wallace, M.F.

    2001-01-01

    Industrial activities beginning in the early 1940s resulted in extensive contamination of ground water near the Tucson International Airport, Tucson, Arizona, including an area around Air Force Plant 44, an industrial facility located on land owned by the U.S. Air Force and operated by a defense contractor. Principal ground-water contaminants are volatile organic compounds, primarily trichloroethylene (also called trichloroethene) and 1,1-dichloroethylene (also called 1,1-dichloroethene). A ground- water reclamation system was put into operation in 1987 to extract and treat contaminated ground water at Air Force Plant 44 and the downgradient area that is south of Los Reales Road. The ground- water reclamation system consists of 25 extraction wells, 22 recharge wells, and a water-treatment facility. Soil-vapor extraction techniques are being used to remove volatile organic compounds from the unsaturated zone. More than 120,000 pounds of volatile organic compounds have been removed from the regional aquifer and overlying unsaturated zone at Air Force Plant 44 and adjacent downgradient areas south of Los Reales Road. Air Force Plant 44 and adjacent areas being remediated by the ground-water reclamation system are about 7 square miles. To assess ground-water cleanup progress at Air Force Plant 44 and surrounding areas south of Los Reales Road, and possibly to identify areas that are resistant to cleanup attempts, ground-water samples were collected and analyzed after water levels had returned to near-equilibrium conditions following a 3-week shutdown of extraction and recharge wells. Modifications of the standard ground-water sampling procedures used at the site also were tested. The modifications included tests of a reduced-flow purging and sampling method in six monitoring wells and vertical- profile sampling in five extraction wells at the reclamation well field. The water treatment facility and all extraction and recharge wells at the reclamation well field were shut down on April 15, 1999, and water levels were allowed to recover for about 3 weeks before samples of ground water were obtained from 102 wells at Air Force Plant 44 and surrounding areas. Concentrations of trichloroethylene and 1,1-dichloroethylene were determined for samples obtained during the sitewide sampling effort. Data for 101 wells sampled in February 1999 before shutdown were compared with data obtained for wells sampled in May 1999 after shutdown. Concentrations of trichloroethylene increased in 36 wells, remained the same in 32 wells, and decreased in 33 wells. Increases in concentrations of trichloroethylene of as much as 1,476 micrograms per liter and decreases of as much as 2,292 micrograms per liter were reported after shutdown. Concentrations of trichloroethylene remained the same for the two sampling periods in wells that had concentrations that were at, or close to, the lower reporting limit (0.5 micrograms per liter) before shutdown. Net change in concentrations of trichloroethylene after shutdown on a percentage basis ranged from an increase of 1,300 percent to a decrease of 100 percent. Increases in concentrations of 1,1-dichloroethylene after shutdown of the reclamation well field of as much as 66 micrograms per liter and decreases of as much as 411.6 micro- grams per liter were reported. Concentrations of 1,1-dichloroethylene remained the same for the two sampling periods in wells that had concentrations that were at, or close to, the lower reporting limit (0.5 micrograms per liter) before shutdown. Net change in concentrations of 1,1-dichloroethylene after shutdown on a percentage basis ranged from an increase of 660 percent to a decrease of 100 percent. Data obtained from the water samples indicate

  12. Control of chemical reaction pathways by femtosecond ponderomotive forces: Time-resolved multiphoton ionization spectroscopic study of OCIO photodissociation

    Femtosecond time-resolved multiphoton ionization spectroscopy is applied to the study of the photodissociation of OClO. The observed ratio of O2+/ClO+ signal increases 12-fold with a 3-fold increase of the pump laser intensity. They are attributed to the change in the branching ratio between the two independent reaction channels leading to Cl+O2 and ClO+O, respectively. We believe this is the first experimental demonstration of laser controlled chemical reactions by femtosecond ponderomotive forces. At low pump power, the photodissociation dynamics at 386 nm is shown to be a two-step process, with the OClO slowly approaching (time constant 4.6 ps) a transition state that falls apart rapidly (time constant 250 fs). copyright 1997 American Institute of Physics

  13. Control of chemical reaction pathways by femtosecond ponderomotive forces: Time-resolved multiphoton ionization spectroscopic study of OCIO photodissociation

    Blackwell, M.; Ludowise, P.; Chen, Y.

    1997-07-01

    Femtosecond time-resolved multiphoton ionization spectroscopy is applied to the study of the photodissociation of OClO. The observed ratio of O2+/ClO+ signal increases 12-fold with a 3-fold increase of the pump laser intensity. They are attributed to the change in the branching ratio between the two independent reaction channels leading to Cl+O2 and ClO+O, respectively. We believe this is the first experimental demonstration of laser controlled chemical reactions by femtosecond ponderomotive forces. At low pump power, the photodissociation dynamics at 386 nm is shown to be a two-step process, with the OClO slowly approaching (time constant 4.6 ps) a transition state that falls apart rapidly (time constant 250 fs).

  14. Kinetic Study of Radiation-Reaction-Limited Particle Acceleration During the Relaxation of Force-Free Equilibria

    Yuan, Yajie; Nalewajko, Krzysztof; Blandford, Roger D.; East, William E.; Zrake, Jonathan

    2016-01-01

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over short time scales. This might be due to prodigal dissipation in a highly magnetized outflow. In order to understand the generic behavior of relativistic plasma with high magnetization, we consider a class of prototypical force-free equilibria which are shown to be unstable to ideal modes (East et al 2015 PRL 115, 095002). Kinetic simulations are carried out to follow the evolution of the instability and to study the basic mechanisms of particle acceleration, especially in the radiation-reaction-limited regime. We find that the instability naturally produces current layers and these are sites for efficient particle acceleration. Detailed calculations of the gamma ray spectrum, the evolution of the particle distribution function and the dynamical consequences of radiation reaction will be presented.

  15. Complex mixed-mode oscillatory patterns in a periodically forced excitable Belousov-Zhabotinsky reaction model.

    Español, Malena I; Rotstein, Horacio G

    2015-06-01

    The Oregonator is the simplest chemically plausible model for the Belousov-Zhabotinsky reaction. We investigate the response of the Oregonator to sinusoidal inputs with amplitudes and frequencies within plausible ranges. We focus on a regime where the unforced Oregonator is excitable (with no sustained oscillations). We use numerical simulations and dynamical systems tools to both characterize the response patterns and explain the underlying dynamic mechanisms. PMID:26117137

  16. EMMI Rapid Reaction Task Force Meeting on 'Quark Matter in Compact Star'

    Buballa, Michael; Drago, Alessandro; Fraga, Eduardo; Haensel, Pawel; Mishustin, Igor; Pagliara, Giuseppe; Schaffner-Bielich, Jurgen; Schramm, Stefan; Sedrakian, Armen; Weber, Fridolin

    2014-01-01

    The recent measurement of two solar mass pulsars has initiated an intense discussion on its impact on our understanding of the high-density matter in the cores of neutron stars. A task force meeting was held from October 7-10, 2013 at the Frankfurt Institute for Advanced Studies to address the presence of quark matter in these massive stars. During this meeting, the recent oservational astrophysical data and heavy-ion data was reviewed. The possibility of pure quark stars, hybrid stars and the nature of the QCD phase transition were discussed and their observational signals delineated.

  17. A full cost analysis of the replacement of Naval Base, Guantanamo Bay's Marine ground defense force by the fleet antiterrorism security team

    Ordona, Placido C.

    2000-01-01

    Constrained defense budgets and manpower resources have motivated the United States Marine Corps and the United States Navy to seek initiatives that maximize the efficient use and allocation of these diminishing resources. One such initiative is the restructuring of the Marine security presence at Naval Station, Guantanamo Bay, Cuba, through the replacement of the 350 man Marine Ground Defense Force with a smaller, rotating unit consisting of two platoons from the Fleet Antiterrorism Security...

  18. Assessment of Clear Sky Radiative Forcing in the Caribbean Region Using an Aerosol Dispersion Model and Ground Radiometry During Puerto Rico Dust Experiment

    Gasso, Santiago; Qi, Qiang; Westpthal, Douglas; Reid, Jeffery; Tsay, Si-Chee

    2004-01-01

    This study investigates the surface and top of the atmosphere solar radiative forcing by long-range transport of Saharan dust. The calculations of radiative forcing are based on measurements collected in the Puerto Rico Dust Experiment (PRIDE) carried out during July, 2000. The purpose of the experiment was the characterization of the Saharan dust plume, which frequently reaches the Caribbean region during the summer. The experiment involved the use of three approaches to study the plume: space and ground based remote sensing, airborne and ground based in-situ measurements and aerosol dispersion modeling. The diversity of measuring platforms provides an excellent opportunity for determination of the direct effect of dust on the clear sky radiative forcing. Specifically, comparisons of heating rates, surface and TOA fluxes derived from the Navy global aerosol dispersion model NAAPS (NRL Aerosol Analysis and Prediction System) and actual measurements of fluxes from ground and space based platforms are shown. In addition, the direct effect of dust on the clear sky radiative forcing is modeled. The extent and time of evolution of the radiative properties of the plume are computed with the aerosol concentrations modeled by NAAPS. Standard aerosol parameterizations, as well as in-situ composition and size distributions measured during PRIDE, are utilized to compute the aerosol optical depth, single scattering albedo and asymmetry factor. Radiative transfer computations are done with an in-house modified spectral radiative transfer code (Fu-Liou). The code includes gas absorption and cloud particles (ice and liquid phase) and it allows the input of meteorological data. The code was modified to include modules for the aerosols contribution to the calculated fluxes. This comparison study helps to narrow the current uncertainty in the dust direct radiative forcing, as recently reported in the 2001 IPCC assessment.

  19. Radiated power and radiation reaction forces of coherently oscillating charged particles in classical electrodynamics

    Niknejadi, Pardis; Madey, John M. J.; Kowalczyk, Jeremy M. D.

    2015-05-01

    For the foreseeable future, the analysis and design of the complex systems needed to generate intense beams of radiation via the process of coherent emission into free-space will depend on the principles and methods of classical electrodynamics (CED). But the fields and forces predicted by the currently accepted CED theory are manifestly incompatible with Maxwell's equations' energy integral as applied to the process of coherent emission into free-space. It is the purpose of this paper to review the evidence for these limitations of conventional CED, to identify an alternative formulation of CED that does not suffer from these defects, and to describe how the predictions of this more physically realistic formulation of electrodynamics, including the role of the advanced interactions allowed by Maxwell's equations and thermodynamics, might be tested by experiment and applied to enhance the capabilities of devices and systems employing the mechanism of "radiation into free-space."

  20. Role of spin-orbit interaction and Skyrme forces in Ni-induced reactions

    In the present work, the Skyrme nucleus-nucleus interaction in the semiclassical extended Thomas Fermi (ETF) approach, under frozen density approximation is used. The nuclear potential is obtained as a sum of the spin-orbit density-dependent VJ part and spin-orbit density-independent VP part of the Skyrme Hamiltonian density. Within the ETF approach, it is of interest to study the variation of spin-orbit part with increase in N/Z ratio of the compound systems. In the following, this study of the role of spin-orbit density part of interaction potential on nine even-mass compound nuclei (CN) 156-172Yb* formed in 56-72Ni+100Mo reactions where both spherical and deformed nuclei are involved

  1. [Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio]. Volume 2, Work plan: Phase 1, Task 4, Field Investigation: Draft

    1991-10-01

    In April 1990 Wright-Patterson Air Force Base (WPAFB) initiated an investigation to evaluate a potential CERCLA removal action to prevent, to the extent practicable, the migration of ground-water contamination in the Mad River Valley Aquifer within and across WPAFB boundaries. The action will be based on a Focused Feasibility Study with an Action Memorandum serving as a decision document that is subject to approval by the Ohio Environmental Protection Agency. The first phase (Phase 1) of this effort involves an investigation of ground-water contamination migrating across the southwest boundary of Area C and across Springfield Pike adjacent to Area B. Task 4 of Phase 1 is a field investigation to collect sufficient additional information to evaluate removal alternatives. The field investigation will provide information in the following specific areas of study: water-level data which will be used to permit calibration of the ground-water flow model to a unique time in history; and ground-water quality data which will be used to characterize the current chemical conditions of ground water.

  2. Ground-water-level monitoring, basin boundaries, and potentiometric surfaces of the aquifer system at Edwards Air Force Base, California, 1992

    Rewis, D.L.

    1995-01-01

    A ground-water-level monitoring program was implemented at Edwards Air Force Base, California, from January through December 1992 to monitor spatial and temporal changes in poten-tiometric surfaces that largely are affected by ground-water pumping. Potentiometric-surface maps are needed to determine the correlation between declining ground- water levels and the distribution of land subsidence. The monitoring program focused on areas of the base where pumping has occurred, especially near Rogers Lake, and involved three phases of data collection: (1) well canvassing and selection, (2) geodetic surveys, and (3) monthly ground-water-level measurements. Construction and historical water- level data were compiled for 118 wells and pi-ezometers on or near the base, and monthly ground-water-level measurements were made in 82 wells and piezometers on the base. The compiled water-level data were used in conjunction with previously collected geologic data to identify three types of no-flow boundaries in the aquifer system: structural boundaries, a principal-aquifer boundary, and ground-water divides. Heads were computed from ground-water-level measurements and land-surface altitudes and then were used to map seasonal potentiometric surfaces for the principal and deep aquifers underlying the base. Pumping has created a regional depression in the potentiometric surface of the deep aquifer in the South Track, South Base, and Branch Park well-field area. A 15-foot decline in the potentiometric surface from April to September 1992 and 20- to 30-foot drawdowns in the three production wells in the South Track well field caused locally unconfined conditions in the deep aquifer.

  3. Where the Lorentz-Abraham-Dirac equation for the radiation reaction force fails, and why the "proofs" break down

    Gromes, Dieter

    2015-01-01

    We calculate the energy radiated coherently by a system of $N$ charged non relativistic particles. It disagrees with the energy loss which is obtained if one employs the Lorentz Abraham Dirac (LAD) equation for each particle, and sums up the contributions. This fact was already clearly stated in the classical literature long ago. The reason for the discrepancy is the omission of the mixing terms in the Poynting vector. For some simple systems we present a generalized equation for the radiation reaction force which cures this defect. The counter examples show that the LAD equation cannot be generally valid and that all "proofs" must fail somewhere. We demonstrate this failure for some popular examples in the literature.

  4. Wave packet and statistical quantum calculations for the He + NeH{sup +} → HeH{sup +} + Ne reaction on the ground electronic state

    Koner, Debasish; Panda, Aditya N., E-mail: adi07@iitg.ernet.in [Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039 (India); Barrios, Lizandra; González-Lezana, Tomás, E-mail: t.gonzalez.lezana@csic.es [Instituto de Física Fundamental, C.S.I.C., Serrano 123, Madrid 28006 (Spain)

    2014-09-21

    A real wave packet based time-dependent method and a statistical quantum method have been used to study the He + NeH{sup +} (v, j) reaction with the reactant in various ro-vibrational states, on a recently calculated ab initio ground state potential energy surface. Both the wave packet and statistical quantum calculations were carried out within the centrifugal sudden approximation as well as using the exact Hamiltonian. Quantum reaction probabilities exhibit dense oscillatory pattern for smaller total angular momentum values, which is a signature of resonances in a complex forming mechanism for the title reaction. Significant differences, found between exact and approximate quantum reaction cross sections, highlight the importance of inclusion of Coriolis coupling in the calculations. Statistical results are in fairly good agreement with the exact quantum results, for ground ro-vibrational states of the reactant. Vibrational excitation greatly enhances the reaction cross sections, whereas rotational excitation has relatively small effect on the reaction. The nature of the reaction cross section curves is dependent on the initial vibrational state of the reactant and is typical of a late barrier type potential energy profile.

  5. Driving forces and the influence of the buffer composition on the complexation reaction between ibuprofen and HPCD.

    Perlovich, German L; Skar, Merete; Bauer-Brandl, Annette

    2003-10-01

    Cyclodextrins are often used in order to increase the aqueous solubility of drug substances by complexation. In order to investigate the complexation reaction of ibuprofen and hydroxypropyl-beta-cyclodextrin, titration calorimetry was used as a direct method. The thermodynamic parameters of the complexation process (stability constant, K(11); complexation enthalpy, deltaH(c) degrees ) were obtained in two different buffer systems (citric acid/sodium-phosphate and phosphoric acid) at various pH values. Based on these data the relative contributions of the enthalpic and entropic terms of the Gibbs energy to the complexation process have been analyzed. In both buffers the enthalpic and entropic terms are of different sign and this case corresponds to a 'nonclassical' model of hydrophobic interaction. In citric buffer, the main driving force of complexation is the entropy, which increases from 60 to 67% while the pH of the solution increases from 3.2 to 8.0. However, for the phosphoric buffer the entropic term decreases from 60 to 45%, while the pH-value of the solution increases from 5.0 to 8.2, and the driving force of the complexation process changes from entropy to enthalpy. The experimental data of the present study are compared to results of other authors and discrepancies discussed in detail. PMID:14550885

  6. Comparative Finite Element Analysis of the Effects of Tillage Tool Geometry on Soil Disturbance and Reaction Forces

    Mohamed Ahmed Elbashir

    2014-04-01

    Full Text Available In this study a comparative finite element analysis was conducted to investigate the effects of tillage tool geometry on soil disturbance and reaction forces. A nonlinear three dimensional finite element model, using ANSYS software, was developed to study the soil cutting process by trapezoidal (T1 and rectangular (T2 flat tools that inclined to the horizontal at three rake angles (R1 = 30°, R2 = 60° and R3 = 90°, therefore a total of six treatments were considered in this analysis. The soil media was assumed as elastic-perfectly plastic material with Drucker-Prager’s model. Results of this study revealed that the maximum vertical soil displaced by T1 is greater than that of T2; hence T1 disturbed the soil better than T2 . Results also showed that a significant reduction in draft force was noticed when cutting the soil with T1 in comparison to T2 . Designing the tool in the form of T1 significantly reduces the surface area of the tool; thus conserving the engineering material.

  7. Kinematics and Ground Reaction Force Determination: A Demonstration Quantifying Locomotor Abilities of Young Adult, Middle-aged, and Geriatric Rats

    Webb, Aubrey A.; Kerr, Brendan; Neville, Tanya; Ngan, Sybil; Assem, Hisham

    2011-01-01

    Behavior, in its broadest definition, can be defined as the motor manifestation of physiologic processes. As such, all behaviors manifest through the motor system. In the fields of neuroscience and orthopedics, locomotion is a commonly evaluated behavior for a variety of disease models. For example, locomotor recovery after traumatic injury to the nervous system is one of the most commonly evaluated behaviors 1-3. Though locomotion can be evaluated using a variety of endpoint measurements (e....

  8. [Environmental investigation of ground water contamination at Wright- Patterson Air Force Base, Ohio]. Volume 4, Health and Safety Plan (HSP); Phase 1, Task 4 Field Investigation report: Draft

    1991-10-01

    This Health and Safety Plan (HSP) was developed for the Environmental Investigation of Ground-water Contamination Investigation at Wright-Patterson Air Force Base near Dayton, Ohio, based on the projected scope of work for the Phase 1, Task 4 Field Investigation. The HSP describes hazards that may be encountered during the investigation, assesses the hazards, and indicates what type of personal protective equipment is to be used for each task performed. The HSP also addresses the medical monitoring program, decontamination procedures, air monitoring, training, site control, accident prevention, and emergency response.

  9. [Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio]. Volume 3, Appendix A, Draft standard operating procedures and elements: Sampling and Analysis Plan (SAP): Phase 1, Task 4, Field Investigation, Draft

    1991-10-01

    This report presents information concerning field procedures employed during the monitoring, well construction, well purging, sampling, and well logging at the Wright-Patterson Air Force Base. Activities were conducted in an effort to evaluate ground water contamination.

  10. Study of the Reactions Controlling the Mobility of Uranium in Ground and Surface Water Systems in Contact with Apatite

    Taffet, M

    2004-04-22

    The objective of this project was to define the mechanisms, equilibria, kinetics, and extent of sorption of aqueous uranium onto hydroxyapatite (Ca{sub 5}(PO{sub 4}){sub 3}(OH)) for a range of pH, ionic strength, aqueous uranium concentration, dissolved carbon/air CO{sub 2}, and mineral surface area. We conducted chemical modeling, batch and flow-through experiments, chemical analysis, x-ray absorption and diffraction measurement, and electron microscopy. Our motivation was the need to immobilize U in water and soil to prevent it's entry into water supplies and ultimately, biological systems. Applying hydroxyapatite to in-situ treatment of uranium-bearing ground water could be an effective, low cost technology. We found that hydroxyapatite quickly, effectively, and reversibly sorbed uranium at a high capacity by inner-sphere complexation over a wide range of conditions. Our results indicate that at aqueous uranium concentrations below 10-20 ppb: (1) equilibrium sorption of uranium to hydroxyapatite occurs in hours, regardless of pH; (2) in ambient and CO{sub 2}-free atmospheres, over 98% of initial uranium is sorbed to hydroxyapatite, (3) in waters in equilibrium with higher air CO{sub 2} concentrations, sorption removed over 97% of aqueous uranium, except above pH 9, where aqueous uranium concentrations were reduced by less than 40%, and (4) at near-neutral pH, bicarbonate alkalinities in excess of 500 slightly retarded sorption of uranium to hydroxyapatite, relative to lower alkalinities. Uranium sorption and precipitation are reversible and are not appreciably affected by ionic strength. The reversibility of these reactions requires that in situ treatment be carefully monitored to avoid breakthrough and de-sorption of uranium unto ground water. At typical surface conditions, sorption is the only mode of uranium sequestration below 20-50 ppb U - above this range, precipitation of uranium phosphate minerals begins to dominate sequestration processes. We verified that one m{sup 2} of hydroxyapatite can sorb over 7.53 X 10{sup -6} moles or 1.8 mg of uranium in agreement with calculations based on phosphate and calcium oxide sites on the unit cell. Our work is significant because small masses of hydroxyapatite can sorb appreciable masses of uranium quickly over a wide range of chemistries. Preliminary work with ground water containing 260 ppb of uranium and cow bone char indicates that its sorptive capacity is appreciable less than pure hydroxyapatite. Pure crystalline hydroxyapatite sequestered 2.9 mg of uranium per m{sup 2} as opposed to 0.083 mg of uranium sequestered per m{sup 2} of cow bone char, or 27% versus 3.5% by surface area, respectively. Extended x-ray adsorption fine structure (EXAFS) spectroscopy defined mono- and bidentate sorption of uranium to phosphate and calcium oxide groups on the hydroxyapatite surface. The EXAFS data indicate that up to several thousand parts U per million parts hydroxyapatite, surface complexation, and not precipitation, is the predominant process. Above this uranium: hydroxyapatite mass ratio, precipitation of meta-autunite (H{sub 2}(UO{sub 2})2(PO{sub 4}){sub 2} x 10H{sub 2}0) dominates the sequestration process.

  11. Repulsion forces of superplasticizers on ground granulated blast furnace slag in alkaline media, from AFM measurements to rheological properties

    Palacios, M.; Bowen, P.; Kappl, M.; Butt, H.J.; Stuer, M.; Pecharromán, C.; Aschauer, U.; Puertas, F.

    2012-01-01

    The electrostatic and steric repulsion induced by different superplasticizers on ground granulated blast furnace slag in alkaline media have been studied. The superplasticizers were sulfonated naphthalene, sulfonated melamine, vinyl copolymer, and polycarboxylate- based admixtures. With these superplasticizers the slag suspensions had negative zeta potentials, ranging from -3 to -10 mV. For the first time the adsorbed layer thicknesses for superplasticizers on slag using colloidal probe atomi...

  12. Simulation of ground-water flow and application to the design of a contaminant removal system, Loring Air Force Base, Maine

    Starn, J.J.

    1997-01-01

    The fractured-bedrock aquifer underlying the former Fire Training Area at Loring Air Force Base, Maine, has been contaminated with petroleum products as a result of fire training activities. A numerical model of the ground-water-flow system near the Fire Training Area was developed to provide information for the design and operation of a contaminant removal system. The goals of the simulation modeling were to (1) determine the maximum pumping rate that could be sustained, giventhe constraint that water levels not rise above a specified altitude, and (2) determine the effect of seasonal variation in recharge on the ability of a transient pumping scenario to capture contaminants. A steady-state simulation model of ground-water flow was used to determine the optimal pumping rate at the site. The optimal pumping rate was 8,570 ft3/d (44 gal/min). Monthly recharge rates wereestimated for use in a transient simulation model. During a typical year, most recharge probably occurs during two periods-one during snowmelt in early spring and another, possibly less significant period, during the late fall. The transient response of the water table to 8.5 inches of recharge in April, 2 inches of recharge in October, and 0.25 inches of recharge per month for each remaining month wassimulated. Fluctuations in ground-water levels caused by simulated seasonal variation of recharge would have minimal effect on the operation of thecontaminant removal system because the system is not pumped when recharge is lowest, ground-water velocities are lowest, and ground-water flow past the trench is minimal.

  13. The physics of nuclear reactions

    This new edition of the author's 'Nuclear Reactions' gives a general account of the interactions between nuclei and is intended for use by students in the second or third year of honours course. The chapters are headed; introduction, particle accelerators, kinematics, reactions of light nuclei, wave-mechanical theory of scattering, resonant scattering and reactions, reaction mechanisms, nuclear reactors, thermonuclear reactions, nuclear forces, and nuclear spin. A number of problems are set on each section and answers given. In an appendix the main properties of known types of nuclei in their ground states are summarized. (UK)

  14. [Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio]. Volume 3, Sampling and analysis plan (SAP): Phase 1, Task 4, Field Investigation: Draft

    1991-10-01

    In April 1990, Wright-Patterson Air Force Base (WPAFB), initiated an investigation to evaluate a potential Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) removal action to prevent, to the extent practicable, the offsite migration of contaminated ground water from WPAFB. WPAFB retained the services of the Environmental Management Operations (EMO) and its principle subcontractor, International Technology Corporation (IT) to complete Phase 1 of the environmental investigation of ground-water contamination at WPAFB. Phase 1 of the investigation involves the short-term evaluation and potential design for a program to remove ground-water contamination that appears to be migrating across the western boundary of Area C, and across the northern boundary of Area B along Springfield Pike. Primarily, Task 4 of Phase 1 focuses on collection of information at the Area C and Springfield Pike boundaries of WPAFB. This Sampling and Analysis Plan (SAP) has been prepared to assist in completion of the Task 4 field investigation and is comprised of the Quality Assurance Project Plan (QAPP) and the Field Sampling Plan (FSP).

  15. Depletion kinetics of the ground state CrO generated from the reaction of unsaturated Cr(CO)x with O2 and N2O

    Unsaturated Cr(CO)x(1?x?5) molecules were generated in the gas phase from photolysis of Cr(CO)6 vapor in He using an unfocussed weak UV laser pulse and their reactions with O2 and N2O have been studied. The formation and disappearance of the ground state CrO molecules were identified by monitoring laser-induced fluorescence(LIF)intensities vs delay time between the photolysis and probe pulses. The photolysis laser power dependence as well as the delay time dependence of LIF intensities from the CrO orange system showed different behavior as those from ground state Cr atoms, suggesting that the ground state CrO molecules were generated from the reaction between O2/N2O and photo- fragments of Cr(CO)6 by one photon absorption. The depletion rate constants for the ground state CrO by O2 and N2O are 5.4±0.2x10-11 and 6.5±0.4x10-12 cm3 molecule-1s-1, respectively

  16. An experimental study on advancement of damping performance of foundations in soft ground. Pt.1: Forced vibration tests of a foundation block constructed on improved soil medium

    Purpose of this study is to enhance attenuation performance of structures that will be constructed in the soft ground area. We conducted material tests to obtain basic properties of the soil cement column. The forced vibration tests then were carried out to acquire dynamic feature of the reinforced concrete block constructed on improved soil mediums. Additional forced vibration tests for various conditions of trenches dug along the block were conducted to obtain fundamental features of damping effect of the side surfaces of the test block. According to results of the material testing, densities of the soil cement columns were 1.45-1.52 g/cm3 and the unconfined compressive strengths were 2.4-4.2 times as large as the specified design strength (1 MPa). In comparison of resonance curves by experiments and simulation analysis, simulation analysis results estimated by the hybrid approach were in good agreement with experiment ones for both the X and Y-directions. From the results of the forced vibration test focusing on various condition of the trenches dug along the test block, it was indicated that response of tamping by the rammer decreased compared with that of treading. (authors)

  17. Influence of Coulomb and nuclear forces on the pattern of the double differential cross section d2sigma/d theta dE for deep inelastic reactions

    The tremendous change in the pattern of the Wilczynski curves for deep inelastic reactions with the product Z1Z2 is interpreted within a model including both dissipation and statistical fluctuations. The competition between Coulomb and nuclear forces seems to account for this effect

  18. Analytical results from ground-water sampling using a direct-push technique at the Dover National Test Site, Dover Air Force Base, Delaware, June-July 2001

    Guertal, William R.; Stewart, Marie; Barbaro, Jeffrey R.; McHale, Timthoy J.

    2004-01-01

    A joint study by the Dover National Test Site and the U.S. Geological Survey was conducted from June 27 through July 18, 2001 to determine the spatial distribution of the gasoline oxygenate additive methyl tert-butyl ether and selected water-quality constituents in the surficial aquifer underlying the Dover National Test Site at Dover Air Force Base, Delaware. The study was conducted to support a planned enhanced bio-remediation demonstration and to assist the Dover National Test Site in identifying possible locations for future methyl tert-butyl ether remediation demonstrations. This report presents the analytical results from ground-water samples collected during the direct-push ground-water sampling study. A direct-push drill rig was used to quickly collect 115 ground-water samples over a large area at varying depths. The ground-water samples and associated quality-control samples were analyzed for volatile organic compounds and methyl tert-butyl ether by the Dover National Test Site analytical laboratory. Volatile organic compounds were above the method reporting limits in 59 of the 115 ground-water samples. The concentrations ranged from below detection limits to maximum values of 12.4 micrograms per liter of cis-1,2-dichloroethene, 1.14 micrograms per liter of trichloroethene, 2.65 micrograms per liter of tetrachloroethene, 1,070 micrograms per liter of methyl tert-butyl ether, 4.36 micrograms per liter of benzene, and 1.8 micrograms per liter of toluene. Vinyl chloride, ethylbenzene, p,m-xylene, and o-xylene were not detected in any of the samples collected during this investigation. Methyl tert-butyl ether was detected in 47 of the 115 ground-water samples. The highest methyl tert-butyl ether concentrations were found in the surficial aquifer from -4.6 to 6.4 feet mean sea level, however, methyl tert-butyl ether was detected as deep as -9.5 feet mean sea level. Increased methane concentrations and decreased dissolved oxygen concentrations were found in samples that contained methyl tert-butyl ether.

  19. Chemical reactions in low-g

    Grodzka, P. G.; Facemire, B. R.

    1978-01-01

    The Apollo-Soyuz flight experiment, 'Chemical Foams' demonstrated that foams and air/liquid dispersions are much more stable in low-gravity than on the ground. It thus should be possible to conduct unique chemical reactions in space foams. The low-g results and subsequent ground work on the formaldehyde clock reaction indicate that the reaction is strongly influenced by (1) dissociated and undissociated solution species being adsorbed at solid/liquid and gas/liquid surfaces and (2) chemical reaction rates apparently being affected by long-range forces determined by the liquid mass and the extent and nature of all surface interfaces.

  20. Assessment of natural attenuation of ground-water contamination at sites FT03, LF13, and WP14/LF15, Dover Air Force Base, Delaware

    Barbaro, Jeffrey R.

    2002-01-01

    Water-quality, aquifer-sediment, and hydro-logic data were used to assess the effectiveness of natural attenuation of ground-water contamination at Fire Training Area Three, the Rubble Area Landfill, the Liquid Waste Disposal Landfill, and the Receiver Station Landfill in the East Management Unit of Dover Air Force Base, Delaware. These sites, which are contaminated with chlorinated solvents and fuel hydrocarbons, are under-going long-term monitoring to determine if natural attenuation continues to sufficiently reduce contaminant concentrations to meet regulatory requirements. This report is the first assessment of the effectiveness of natural attenuation at these sites since long-term monitoring began in 1999, and follows a preliminary investigation done in 1995?96. This assessment was done by the U.S. Geological Survey in cooperation with the U.S. Air Force.Since 1995?96, additional information has been collected and used in the current assessment. The conclusions in this report are based primarily on ground-water samples collected from January through March 2000. Previous analytical results from selected wells, available geologic and geo-physical well logs, and newly acquired information such as sediment organic-carbon measurements, hydraulic-conductivity measurements determined from slug tests on wells in the natural attenuation study area, and water-level measurements from surficial-aquifer wells also were used in this assessment. This information was used to: (1) calculate retardation factors and estimate contaminant migration velocities, (2) improve estimates of ground-water flow directions and inferred contaminant migration pathways, (3) better define the areal extent of contamination and the proximity of contaminants to discharge areas and the Base boundary, (4) develop a better under-standing of the vertical variability of contaminant concentrations and redox conditions, (5) evaluate the effects of temporal changes on concentrations in the plumes and source areas, and (6) determine whether intrinsic biodegradation is occurring at these sites.The water-quality data indicate that intrinsic biodegradation is occurring at all three sites. The strongest indication of intrinsic biodegradation is the detection of tetrachloroethene and trichloroethene breakdown products within and down-gradient of the source areas. The patterns of electron acceptors and metabolic by-products indicate that contaminant biodegradation has changed the prevailing geochemistry of the surficial aquifer, creating the strongly reducing conditions necessary for chlorinated solvent bio-degradation. Geochemical changes include depleted dissolved oxygen and elevated ferrous iron and methane levels relative to concentrations in uncontaminated zones of the surficial aquifer. At Fire Training Area Three and the Rubble Area Landfill sites, natural attenuation appears to be adequate for controlling the migration of the contaminant plumes. At the third site, the Liquid Waste Disposal and Receiver Station Landfills, the plume is larger and the uncertainty about the effectiveness of natural attenuation in reducing contaminant concentrations and controlling plume migration is greater. Ground-water data indicate, however, that U.S. Environmental Protection Agency maximum contaminant levels were not exceeded in any point-of-compliance wells located along the Base boundary.The information presented in this report led to the development of improved conceptual models for these sites, and to the recognition of four issues that are currently unclear and may need further study. These issues include delineating the areal and vertical extent of the contaminant plumes in greater detail, determining the extent of intrinsic biodegradation downgradient of the Liquid Waste Disposal and Receiver Station Landfills, deter-mining the fate of contaminants in the ground-water discharge areas, and determining the effect of temporal variability in source concentrations and ground-water

  1. Large-eddy simulation of pollutant dispersion from a ground-level area source over urban street canyons with irreversible chemical reactions

    Du, T. Z.; Liu, C.-H.; Zhao, Y. B.

    2014-10-01

    In this study, the dispersion of chemically reactive pollutants is calculated by large-eddy simulation (LES) in a neutrally stratified urban canopy layer (UCL) over urban areas. As a pilot attempt, idealized street canyons of unity building-height-to-street-width (aspect) ratio are used. Nitric oxide (NO) is emitted from the ground surface of the first street canyon into the domain doped with ozone (O3). In the absence of ultraviolet radiation, this irreversible chemistry produces nitrogen dioxide (NO2), developing a reactive plume over the rough urban surface. A range of timescales of turbulence and chemistry are utilized to examine the mechanism of turbulent mixing and chemical reactions in the UCL. The Damköhler number (Da) and the reaction rate (r) are analyzed along the vertical direction on the plane normal to the prevailing flow at 10 m after the source. The maximum reaction rate peaks at an elevation where Damköhler number Da is equal or close to unity. Hence, comparable timescales of turbulence and reaction could enhance the chemical reactions in the plume.

  2. Solar energy assessment in the Alpine area: satellite data and ground instruments integration for studying the radiative forcing of aerosols.

    Castelli, M.; Petitta, M.; Emili, E.

    2012-04-01

    The primary objective of this work is to purpose an approach for estimating the effect of aerosols on surface incoming shortwave radiation (SIS) in the Alpine region, which is based on the integration of different instruments: we develop a GIS model, whose output is corrected by monthly atmospheric coefficients, and then we progressively add details by daily updated atmospheric information. The assessment of solar energy availability at the earth's surface over a specific geographic area is crucial for planning photovoltaic panels installation. When modeling SIS with GIS instruments or retrieving it from satellites measurements, we have to account for terrain shadowing and atmospheric extinction, both of which are difficult to describe in the Alpine area, because of the topographic complexity and the local atmospheric circulation influence on the atmospheric composition. While advanced methods were developed to carefully describe the effect of topography, the atmospheric attenuation was considered so far only through monthly turbidity values, and the question remains whether it be possible to develop a time-effective routine to model the atmospheric effect on SIS at daily scale. As a first step we produced a WebGIS for the town of Bressanone, Italy, showing a classification of the roofs of the buildings according to the yearly amount of global irradiance. Furthermore we provide the annual electricity production based on the efficiency of the most common PV technologies. At this stage clear sky irradiance was computed with a GIS based model, and afterwards monthly correction coefficients were applied to add real sky conditions to the merely geometrical computations, which were obtained from 20 years of measurement collected by the pyranometer in the closest meteorological station. As a second step we investigate the influence of aerosol optical properties on SIS by running the radiative transfer model libRadtran by using as input the aerosol model defined for the measurement site of Bolzano, where we installed an AERONET sun-photometer for measuring aerosol optical properties and column water-vapor amount. The impact of aerosols on the surface irradiance was already demonstrated, in fact the literature shows that the daily aerosol direct forcing on the surface radiation in the Italian Po valley amounts on average to -12.2 Wm-2, with extremes values beyond -70 Wm-2. In particular here we examine the role in the radiation budget of the Alpine valleys of aerosol microphysical characteristics, such as size distribution, and optical properties, such as phase function, derived from the inversion of spectrally resolved sky radiances. After provided evidence of the radiative impact of atmospheric aerosols on solar energy availability in the Alpine area, the final step will be the enhancement of the most advanced existent algorithm for retrieving SIS in the Alpine area from satellite data, developed by MeteoSwiss in the framework of CM-SAF, which thoroughly considers the effect of topography and clouds, while can still be improved in terms of atmospheric input data.

  3. Atomic force microscopy of photochemistry and the Baeyer-Villiger reaction of 4,4{sup '}-dimethylbenzophenone in the solid state

    Zeng, Q.D.; Wang, C.; Xu, S.D.; Bai, C.L. [Inst. of Chemistry, Chinese Academy of Sciences, Beijing (China); Li, Y.; Yan, X.J. [Inst. of Chemical Metallurgy, Chinese Academy of Sciences, Beijing (China)

    2001-08-01

    Nanostructures are formed by photodimerization of crystalline 4,4{sup '}-dimethylbenzophenone (1) through intermolecular hydrogen abstraction and Baeyer-Villiger reaction of 1 with m-chloroperoxybenzoic acid (MCPBA) (5) in the solid state. Atomic force microscopy (AFM) reveals that the crystal face (001) of 1 during photodimerization exhibits volcanoes, whereas the same face (001) of 1 yields both craters and volcanoes all over the surface from the contact edge of the crystals during the Baeyer-Villiger reaction. All the experimental results are correlated with the bulk crystal structure. Molecular interpretation of the AFM features of 1 is given. (orig.)

  4. A new type of power energy for accelerating chemical reactions: the nature of a microwave-driving force for accelerating chemical reactions

    Zhou, Jicheng; Xu, Wentao; You, Zhimin; Wang, Zhe; Luo, Yushang; Gao, Lingfei; Yin, Cheng; Peng, Renjie; Lan, Lixin

    2016-01-01

    The use of microwave (MW) irradiation to increase the rate of chemical reactions has attracted much attention recently in nearly all fields of chemistry due to substantial enhancements in reaction rates. However, the intrinsic nature of the effects of MW irradiation on chemical reactions remains unclear. Herein, the highly effective conversion of NO and decomposition of H2S via MW catalysis were investigated. The temperature was decreased by several hundred degrees centigrade. Moreover, the apparent activation energy (Ea’) decreased substantially under MW irradiation. Importantly, for the first time, a model of the interactions between microwave electromagnetic waves and molecules is proposed to elucidate the intrinsic reason for the reduction in the Ea’ under MW irradiation, and a formula for the quantitative estimation of the decrease in the Ea’ was determined. MW irradiation energy was partially transformed to reduce the Ea’, and MW irradiation is a new type of power energy for speeding up chemical reactions. The effect of MW irradiation on chemical reactions was determined. Our findings challenge both the classical view of MW irradiation as only a heating method and the controversial MW non-thermal effect and open a promising avenue for the development of novel MW catalytic reaction technology. PMID:27118640

  5. A new type of power energy for accelerating chemical reactions: the nature of a microwave-driving force for accelerating chemical reactions.

    Zhou, Jicheng; Xu, Wentao; You, Zhimin; Wang, Zhe; Luo, Yushang; Gao, Lingfei; Yin, Cheng; Peng, Renjie; Lan, Lixin

    2016-01-01

    The use of microwave (MW) irradiation to increase the rate of chemical reactions has attracted much attention recently in nearly all fields of chemistry due to substantial enhancements in reaction rates. However, the intrinsic nature of the effects of MW irradiation on chemical reactions remains unclear. Herein, the highly effective conversion of NO and decomposition of H2S via MW catalysis were investigated. The temperature was decreased by several hundred degrees centigrade. Moreover, the apparent activation energy (Ea') decreased substantially under MW irradiation. Importantly, for the first time, a model of the interactions between microwave electromagnetic waves and molecules is proposed to elucidate the intrinsic reason for the reduction in the Ea' under MW irradiation, and a formula for the quantitative estimation of the decrease in the Ea' was determined. MW irradiation energy was partially transformed to reduce the Ea', and MW irradiation is a new type of power energy for speeding up chemical reactions. The effect of MW irradiation on chemical reactions was determined. Our findings challenge both the classical view of MW irradiation as only a heating method and the controversial MW non-thermal effect and open a promising avenue for the development of novel MW catalytic reaction technology. PMID:27118640

  6. Measurement of the 2H(p, n) Breakup Reaction at 170 MeV and the Three-Nucleon Force Effects

    The effects of three nucleon force (3NF) have been actively studied via the nucleon–deuteron (Nd) scattering states. The differential cross sections and the vector analyzing powers Ay of the 2H(p, n) inclusive breakup reaction at 170 MeV were measured for the study of 3NF effects in the intermediate energy region. The polarized proton beam of 170 MeV was injected to the deuterated polyethylene (CD2) target and the energy of scattered neutrons were measured by using TOF method. The data were compared with the Faddeev calculations based on modern nucleon–nucleon (NN) forces with and without the 3NF. Concerning the differential cross sections, we can see large discrepancies between the data and the calculations in the region of scattered neutron energies are low, which is similar to the results of the 2H(p, p) inclusive breakup reaction at 250 MeV. (author)

  7. Ground states of molecules. XLIX. MINDO/3 study of the retro-diels-alder reaction of cyclohexene

    The retro-Diels-Alder reaction of cyclohexene to form ethylene and butadiene has been studied, using MINDO/3. The transition state is predicted to be very unsymmetric, corresponding to weakening of one of the two breaking CC bonds. The calculated entropy of activation agrees well with experiment and the calculated secondary isotope effects for 4,4-dideuteriocyclohexene and 4,4,5,5-tetradeuteriocyclohexene are similar to those measured for an analogous reaction by Taagepera and Thornton. Discrepancies between the conclusions reached here and those from recent ab-initio calculations are discussed. 4 tables, 3 figures, 53 references

  8. Quantum mechanical calculations of the S(1D)+HD reaction dynamics on the ground electronic state

    We present reaction probabilities and branching ratios for the title reaction calculated employing the real wavepacket approach as implemented in the DIFFREALWAVE code. Calculations for zero total angular momentum (J = 0) and also for some non-zero values, J = 10, 30 and 40 have been carried out including all Coriolis couplings. These preliminary results predict a branching ratio greater than unity for energies above 0.5 eV total energy while more partial waves are needed to predict the ratio for energies below 0.5 eV.

  9. Tensor Force Manifestations in ab Initio Study of the 2H(d, γ)4He, 2H(d, p)3H, and 2H(d, n)3He Reactions

    The 2H(d, γ)4He capture reaction and the 2H(d, p)3H and 2H(d, n)3He transfer reactions at very low energies are studied in an extended microscopic cluster model with a realistic nucleon–nucleon force. Our results show that the tensor force in realistic interactions plays an essential and indispensable role to reproduce the very low-energy astrophysical S factor of these reactions. (author)

  10. Ground-state correlations in 12C and the mechanism of the (e,e'p) reaction

    In this thesis the results of an investigation into two aspects of the mechanism of the quasi-elastic (e,e'p) reaction: the interaction between the incident electron and the bound proton and the residual nucleus (final-state interaction (FSI)), are presented and used in the extraction of nuclear-structure information from (e,e'p) measurements on 12C. The experiments were carried out at NIKHEF-K with a high-resolution spectrometer. Two kinds of experiments have been performed on 12C. The first was aimed at obtaining accurate momentum distributions for various final states in 11B. Some special measurements were carried out in order to vary the parameters influencing the FSI. The role of coupled-channels effects in the 12C(e,e'p)11Be reaction is discussed. It is discussed whether some of the weak transitions observed in this reaction, can be associated with knockout from normally unoccupied shell-model orbitals. The second experiment on 12C was devoted to the e-p coupling. These measurements were supplemented with data taken on 6Li. The latter measurement allowed for measuring simultaneously knockout from the relatively dense 4He core and the relatively dilute deuteron. In this way the density dependence of the e-p coupling in the nucleus could be studied. The results of these experiments have been compared to various models that take into account the effect of the nuclear medium upon the e-p coupling. The possible role of charge-exchange and meson-exchange currents in the interpretation of these experiments is also considered. A brief survey of the formalism of the quasi-elastic (e,e'p) reaction is also presented. (author). 196 refs.; 53 figs.; 21 tabs

  11. Quantum calculations for the S(1D)+H2 reaction employing the ground adiabatic electronic state

    We present exact quantum differential and total cross sections for the title reaction. We employ a time-dependent wavepacket method as implemented in the DIFFREALWAVE code including all Coriolis coupling and a new potential energy surface, the double many-body expansion/complete basis set (DMBE/CBS) surface. Our results show that the DMBE/CBS surface gives smaller cross section when compared to previous results employing the Ho surface.

  12. Procedures for addressing uncertainty and variability in exposure to characterize potential health risk from trichloroethylene contaminated ground water at Beale Air Force Base in California

    Daniels, J I; Bogen, K T; Hall, L C

    1999-10-05

    Conservative deterministic, screening-level calculations of exposure and risk commonly are used in quantitative assessments of potential human-health consequences from contaminants in environmental media. However, these calculations generally are based on multiple upper-bound point estimates of input parameters, particularly for exposure attributes, and can therefore produce results for decision makers that actually overstate the need for costly remediation. Alternatively, a more informative and quantitative characterization of health risk can be obtained by quantifying uncertainty and variability in exposure. This process is illustrated in this report for a hypothetical population at a specific site at Beale Air Force Base in California, where there is trichloroethylene (TCE) contaminated ground water and a potential for future residential use. When uncertainty and variability in exposure were addressed jointly for this case, the 95th-percentile upper-bound value of individual excess lifetime cancer risk was a factor approaching 10 lower than the most conservative deterministic estimate. Additionally, the probability of more than zero additional cases of cancer can be estimated, and in this case it is less than 0.5 for a hypothetical future residential population of up to 26,900 individuals present for any 7.6-y interval of a 70-y time period. Clearly, the results from application of this probabilistic approach can provide reasonable and equitable risk-acceptability criteria for a contaminated site.

  13. Procedures for addressing uncertainty and variability in exposure to characterize potential health risk from trichloroethylene contaminated ground water at Beale Air Force Base in California; TOPICAL

    Conservative deterministic, screening-level calculations of exposure and risk commonly are used in quantitative assessments of potential human-health consequences from contaminants in environmental media. However, these calculations generally are based on multiple upper-bound point estimates of input parameters, particularly for exposure attributes, and can therefore produce results for decision makers that actually overstate the need for costly remediation. Alternatively, a more informative and quantitative characterization of health risk can be obtained by quantifying uncertainty and variability in exposure. This process is illustrated in this report for a hypothetical population at a specific site at Beale Air Force Base in California, where there is trichloroethylene (TCE) contaminated ground water and a potential for future residential use. When uncertainty and variability in exposure were addressed jointly for this case, the 95th-percentile upper-bound value of individual excess lifetime cancer risk was a factor approaching 10 lower than the most conservative deterministic estimate. Additionally, the probability of more than zero additional cases of cancer can be estimated, and in this case it is less than 0.5 for a hypothetical future residential population of up to 26,900 individuals present for any 7.6-y interval of a 70-y time period. Clearly, the results from application of this probabilistic approach can provide reasonable and equitable risk-acceptability criteria for a contaminated site

  14. The gravitational radiation reaction force of a continuous medium. II. Perturbation of a quasi-minkowskian motion

    We determine, within the framework of the first approximation of general relativity, the equations of motion of a continuous medium in which the forces from material stresses play a leading part with respect to the gravitational forces. In the slow approximation, we deduce the formula for the variation of the energy of the system due to the gravitational radiation. We obtain the surprising result that it has exactly the same form that one determined in the preceding paper (not only when averaged over a quasi-periodic motion)

  15. Measurement of the ground-state gamma-ray branching ratio of the dt reaction at low energies

    The branching ratio GAMMA/sub gamma0//GAMMA/sub α/ for the d+t reaction has been measured between deuteron energies of 45 and 146 keV. Pair-coincidence spectrometry and pulse-shape discrimination were employed to reduce the neutron effects in the NaI(Tl) gamma-ray detector. The branching ratio is found to be constant over the energy range of the measurements with a best value GAMMA/sub γ/0/GAMMA/sub α/ = (5.4 +- 1.3) x 10-5. This value is significantly greater than cluster-model calculations of the branching ratio

  16. Confining forces

    Rollmann, Dirk; Miller, David E.

    2015-01-01

    We discuss the forces on the internal constituents of the hadrons based on the bag model. The ground state of the hadrons forms a color singlet so that the effects of the colored internal states are neutralized. From the breaking of the dilatation and conformal symmetries under the strong interactions the corresponding currents are not conserved. These currents give rise to the forces changing the motion of the internal particles which causes confinement.

  17. Quadriceps force generation in patients with osteoarthritis of the knee and asymptomatic participants during patellar tendon reflex reactions: an exploratory cross-sectional study

    Howe Tracey E

    2005-09-01

    Full Text Available Abstract Background It has been postulated that muscle contraction is slower in patients with osteoarthritis of the knee than asymptomatic individuals, a factor that could theoretically impair joint protection mechanisms. This study investigated whether patients with osteoarthritis of the knee took longer than asymptomatic participants to generate force during reflex quadriceps muscle contraction. This was an exploratory study to inform sample size for future studies. Methods An exploratory observational cross sectional study was carried out. Two subject groups were tested, asymptomatic participants (n = 17, mean (SD 56.7 (8.6 years, and patients with osteoarthritis of the knee, diagnosed by an orthopaedic surgeon, (n = 16, age 65.9 (7.8 years. Patellar tendon reflex responses were elicited from participants and measured with a load cell. Force latency, contraction time, and force of the reflex response were determined from digitally stored data. The Mann-Whitney U test was used for the between group comparisons in these variables. Bland and Altman within-subject standard deviation values were calculated to evaluate the measurement error or precision of force latency and contraction time. Results No significant differences were found between the groups for force latency (p = 0.47, contraction time (p = 0.91, or force (p = 0.72. The two standard deviation measurement error values for force latency were 27.9 ms for asymptomatic participants and 16.4 ms for OA knee patients. For contraction time, these values were 29.3 ms for asymptomatic participants and 28.1 ms for OA knee patients. Post hoc calculations revealed that the study was adequately powered (80% to detect a difference between the groups of 30 ms in force latency. However it was inadequately powered (59% to detect this same difference in contraction time, and 28 participants would be required in each group to reach 80% power. Conclusion Patients with osteoarthritis of the knee do not appear to have compromised temporal parameters or magnitude of force generation during patellar tendon reflex reactions when compared to a group of asymptomatic participants. However, these results suggest that larger studies are carried out to investigate this area further.

  18. Gait asymmetries in patients with idiopathic scoliosis using vertical forces measurement only

    Schizas, C. G.; Kramers-de Quervain, I. A.; Stüssi, E.; Grob, D

    1998-01-01

    This study aimed at identifying measurable asymmetries during gait and relating them to the spinal deformity in subjects with idiopathic scoliosis. We investigated 21 patients aged between 10 and 26 years for gait asymmetries using force plates. All subjects completed five walking cycles over two force plates measuring vertical ground reaction forces. Among the parameters measured were contact time and magnitude of the two peaks of the vertical forces as well as the rate of application of tho...

  19. Study of the Three-Nucleon Force Effects in the 2H(p, n) Breakup Reaction at 170 MeV

    For the study of three nucleon force (3NF) effects in the intermediate energy region, the differential cross sections and the vector analyzing power Ay were measured for the 2H(p, n) inclusive breakup reaction at 170 MeV. The polarized proton beam of 170 MeV was injected to the deuterated polyethylene (CD2) target and the energy of scattered neutrons were deduce by TOF method. The data was compared with the results of the Faddeev calculations with and without 3NFs. Concerning about the differential cross sections, we can see large discrepancies between the data and the calculations in the region where the energies of scattered neutrons are low, which are similar to the results of the 2H(p, p) inclusive breakup reaction at 250 MeV. (author)

  20. Ground and excited state intramolecular proton transfer controlled intramolecular charge separation and recombination: A new type of charge and proton transfer reaction

    A novel ?-diketone 1-(4-(9-carbazol)phenyl)-3-phenyl-1,3-propanedione (CDBM) has been synthesized. When excited at 380 nm, this molecule shows single fluorescence. However, when excited at 338 nm, it shows dual fluorescence. A Al3+ complex Al(CDBM)3 has been synthesized to investigate the dual fluorescence of CDBM. It is found that this complex shows single fluorescence under all excitation. This result indicated that the dual fluorescence of CDBM may relate to the intramolecular proton transfer reaction. Based on the experimental and theoretical studies of CDBM, N-(4-cyanophenyl)carbazole (CBN) and Al(CDBM)3, a 'ground and excited state intramolecular proton transfer controlled intramolecular charge separation and recombination' mechanism is proposed to explain the unusual excitation-dependent dual fluorescence of CDBM

  1. Ground and excited state intramolecular proton transfer controlled intramolecular charge separation and recombination: A new type of charge and proton transfer reaction

    Nie, Daobo; Bian, Zuqiang; Yu, Anchi; Chen, Zhuqi; Liu, Zhiwei; Huang, Chunhui

    2008-06-01

    A novel ?-diketone 1-(4-(9-carbazol)phenyl)-3-phenyl-1,3-propanedione (CDBM) has been synthesized. When excited at 380 nm, this molecule shows single fluorescence. However, when excited at 338 nm, it shows dual fluorescence. A Al 3+ complex Al(CDBM) 3 has been synthesized to investigate the dual fluorescence of CDBM. It is found that this complex shows single fluorescence under all excitation. This result indicated that the dual fluorescence of CDBM may relate to the intramolecular proton transfer reaction. Based on the experimental and theoretical studies of CDBM, N-(4-cyanophenyl)carbazole (CBN) and Al(CDBM) 3, a "ground and excited state intramolecular proton transfer controlled intramolecular charge separation and recombination" mechanism is proposed to explain the unusual excitation-dependent dual fluorescence of CDBM.

  2. Diffusion and reactivity of ground-state nitrogen atoms N(4S) between 3 and 15 K: application to the hydrogen abstraction reaction from methane under non-energetic conditions

    Nourry, Sendres; Krim, Lahouari

    2015-07-01

    We have characterized the CH4 + N(4S) reaction in solid phase, at very low temperature, under non-energetic conditions and where the CH4 and N reactants are in their ground states. A microwave-driven atomic source has been used to generate ground-state nitrogen atoms N(4S), and experiments have been carried out at temperatures as low as 3 K to reduce the mobility of the trapped species in solid phase and hence to freeze the first step of the CH4 + N reaction pathway. Leaving the formed solid sample in the dark for a while allows all trapped reactants to relax to the ground state, specifically radicals and excited species streaming from the plasma discharge. Such a method could be the only possibility of proving that the CH4 + N reaction occurs between CH4 and N reactants in their ground states without any additional energy to initiate the chemical process. The appearance of the CH3 reaction product, just by inducing the mobility of N atoms between 3 and 11 K, translates that a hydrogen abstraction reaction from methane, under non-energetic conditions, will start occurring at very low temperature. The formation of methyl radical, under these experimental conditions, is due to recombination processes N(4S)-N(4S) of ground-state nitrogen atoms without any contribution of cosmic ray particles or high-energy photons.

  3. The HNO3 forming branch of the HO2 + NO reaction: pre-industrial-to-present trends in atmospheric species and radiative forcings

    I. S. A. Isaksen

    2011-05-01

    Full Text Available Recent laboratory measurements have shown the existence of a HNO3 forming branch of the HO2 + NO reaction. This reaction is the main source of atmospheric O3, through the subsequent photolysis of NO2, as well as being a major source of OH. The branching of the reaction to HNO3 reduces the formation of these species significantly, affecting O3 abundances, climate and the oxidation capacity of the troposphere. The Oslo CTM2, a three-dimensional chemistry transport model, is used to calculate atmospheric composition and trends with and without the new reaction branch. Results for the present day atmosphere, when both temperature and pressure effects on the branching ratio are accounted for, show an increase of the global, annual mean methane lifetime by 10.9 %, resulting from a 14.1 % reduction in the global, annual mean OH concentration. Comparisons with measurements show that including the new branch improves the modelled O3, but that it is not possible to conclude whether the NOy distribution improves. We model an approximately 11 % reduction in the tropical tropospheric O3 increase since pre-industrial times, as well as an 8 % decrease in the trend of OH concentration, when the new branch is accounted for. The radiative forcing due to changes in O3 over the industrial era was calculated as 0.33 W m?2, reducing to 0.26 W m?2 with the new reaction branch. These results are significant, and it is important that this reaction branching is confirmed by other laboratory groups.

  4. A global ab initio potential energy surface for the X{sup ?2}A{sup ?} ground state of the Si + OH ? SiO + H reaction

    Dayou, Fabrice, E-mail: fabrice.dayou@obspm.fr [Laboratoire d' Etude du Rayonnement et de la Matière en Astrophysique (UMR 8112 du CNRS), Observatoire de Paris-Meudon, Université Pierre et Marie Curie, 92195 Meudon Cedex (France); Duflot, Denis; Rivero-Santamaría, Alejandro; Monnerville, Maurice [Laboratoire de Physique des Lasers, Atomes et Molécules (UMR 8523 du CNRS), Université Lille I Sciences et Technologies, 59655 Villeneuve d' Ascq Cedex (France)

    2013-11-28

    We report the first global potential energy surface (PES) for the X{sup ?2}A{sup ?} ground electronic state of the Si({sup 3}P) + OH(X{sup 2}?) ? SiO(X{sup 1}?{sub g}{sup +}) + H({sup 2}S) reaction. The PES is based on a large number of ab initio energies obtained from multireference configuration interaction calculations plus Davidson correction (MRCI+Q) using basis sets of quadruple zeta quality. Corrections were applied to the ab initio energies in the reactant channel allowing a proper description of long-range interactions between Si({sup 3}P) and OH(X{sup 2}?). An analytical representation of the global PES has been developed by means of the reproducing kernel Hilbert space method. The reaction is found barrierless. Two minima, corresponding to the SiOH and HSiO isomers, and six saddle points, among which the isomerization transition state, have been characterized on the PES. The vibrational spectra of the SiOH/HSiO radicals have been computed from second-order perturbation theory and quantum dynamics methods. The structural, energetic, and spectroscopic properties of the two isomers are in good agreement with experimental data and previous high quality calculations.

  5. Measurement of the reaction 3He(γ,pp)n and its relation to three-body forces

    The three-body photodisintegration of 3He has been measured at photon energies ranging from 90 to 250 MeV, in kinematic regions where three-body forces effects are expected to be maximized, and two-body mechanisms suppressed. The differential cross sections as a function of neutron momentum demonstrate that calculations using only one-body and two-body photoabsorption mechanisms cannot describe the data and that a two-pion-exchange, three-body absorption mechanism is needed to adequately describe the data

  6. The brute-force polarization of 23Na and the 23Na(n,?)24Na reaction

    A Na target has been polarized by brute force to 22% and the ? radiation produced by polarized thermal neutron capture has been investigated. The 2+ channel spin contribution has been determined model independently and unambiguously for 22 primary transitions. The average 2+ channel contribution is 5.8(5)%. Spins of final levels are in agreement with previous assignments. For three levels spin restrictions have been made. The energies of positive parity levels are in agreement with a shell model calculation in the complete sd shell. (Auth.)

  7. Two-phase flow characteristics of hot water discharged from a thin nozzle. 1st Report. Boiling two-phase flow rate in a nozzle and reaction force by two-phase jet

    An experimental and analytical study on the mass flux and reaction force of water single-phase and steam-water two-phase jets discharged from a thin nozzle was carried out. The mass flux of water jet is well predicted using the Bernoulli's equation with the contraction coefficient, but the recovery of contraction at the nozzle exit should be considered to evaluate the reaction force. The L/D of the nozzle affects the mass flux and reaction force of the two-phase jet, i.e., the mass flux decreases and the reaction force increases with the L/D. The behavior of high-temperature water jet is similar to that of the water jet if the L/D is smaller or nozzle inlet pressure is higher. The behaviors of the mass flux and the reaction force show hysteresis depending on the decrease or increase of nozzle inlet pressure. The mass flux and reaction force can be well predicted by the critical flow analysis based on a separated flow model with the non-equilibrium parameter. (author)

  8. Handling of impact forces in inverse dynamics.

    Bisseling, Rob W; Hof, At L

    2006-01-01

    In the standard inverse dynamic method, joint moments are assessed from ground reaction force data and position data, where segmental accelerations are calculated by numerical differentiation of position data after low-pass filtering. This method falls short in analyzing the impact phase, e.g. landing after a jump, by underestimating the contribution of the segmental accelerations to the joint moment assessment. This study tried to improve the inverse dynamics method for the assessment of knee moment by evaluating different cutoff frequencies in low-pass filtering of position data on the calculation of knee moment. Next to this, the effect of an inclusion of direct measurement of segmental acceleration using accelerometers to the inverse dynamics was evaluated. Evidence was obtained that during impact, the contribution of the ground reaction force to the sagittal knee moment was neutralized by the moments generated by very high segmental accelerations. Because the accelerometer-based method did not result in the expected improvement of the knee moment assessment during activities with high impacts, it is proposed to filter the ground reaction force with the same cutoff frequency as the calculated accelerations. When this precaution is not taken, the impact peaks in the moments can be considered as artifacts. On the basis of these findings, we recommend in the search to biomechanical explanations of chronic overuse injuries, like jumper's knee, not to consider the relation with impact peak force and impact peak moment. PMID:16209869

  9. Testing the cosmic censorship conjecture with point particles: The effect of radiation reaction and the self-force

    A classical thought-experiment to destroy black holes was envisaged by Wald in 1974: it consists of throwing particles with large angular momentum into an extremal black hole, checking whether their capture can overspin the black hole past the extremal limit and create a naked singularity. Wald showed that in the test-particle limit, particles that would be otherwise capable of producing naked singularities are simply scattered. Recently, Jacobson and Sotiriou showed that if one considers instead a black hole that is almost, but not exactly extremal, then in the absence of backreaction effects particle capture could indeed overspin the spacetime above the Kerr limit. Here we analyze backreaction effects and show that for some of the trajectories giving rise to naked singularities, radiative effects can be neglected. However, for these orbits the conservative self-force is important, and seems to have the right sign to prevent the formation of naked singularities.

  10. Lesiones de los sargentos alumnos del Ejército de Tierra y factores de riesgo lesional / Injuries of the Ground Forces Student Sergeants and injury risk factors

    F.A., Valero Capilla; L., Franco Bonafonte; F.J., Rubio Pérez.

    2014-12-01

    Full Text Available Antecedentes: los cursos de entrenamiento militar requieren un alto nivel de exigencia física y provocan un número importante de lesiones osteomusculares. Es de interés conocer el tipo de lesiones que se observan en estos cursos y los factores de riesgo lesional asociados, para poder implantar poste [...] riormente medidas preventivas adecuadas y correctas gestiones de los recursos que se disponen. Objetivo: presentar el tipo de lesiones observadas durante la fase común del primer curso de formación de los sargentos alumnos del Ejército de Tierra (ET) y analizar la frecuencia lesional y factores de riesgo relacionados. Material y Métodos: estudio descriptivo observacional de corte transversal de 15 semanas de duración, en el que se incluyeron 579 sargentos alumnos (49 mujeres), edad media de 25,9 años (Rango 18-31). Al inicio del curso, se obtuvieron los parámetros antropométricos de los alumnos y se midió su condición física mediante las marcas obtenidas en carrera de 6000, 1000 y 50 m, y pruebas de salto vertical y flexo extensiones en suelo. Durante el curso, se registraron las lesiones observadas, sus causas, localización y tiempo de recuperación. Al final del curso, se comparó la frecuencia lesional observada y sus causas entre hombres y mujeres, y en el grupo de hombres, se compararon las marcas obtenidas y los parámetros antropométricos entre los lesionados y no lesionados. Resultados: la edad media del grupo de mujeres vs hombres fue de 27,1 (3,18) vs 25,7 (3,03) años p Abstract in english Background: military training courses are very physically demanding and they cause a significant number of musculoskeletal injuries. It is of interest to know the type of injuries observed in these courses and the associated injury risk factors in order to subsequently implant appropriate preventive [...] measures and manage available resources. Objective: to present the type of injuries observed during the common phase of the first training course of the Ground Forces Student Sergeants and to analyze the frequency of injuries and related risk factors. Material and Methods: descriptive, observational, cross-sectional, 15 week duration study, which included 579 student sergeants (49 women), average age of 25.9 years (range 18-31). At the beginning of the course, the anthropometric parameters of students were obtained and their physical condition was measured through the marks obtained in 6000, 1000 and 50 m career, and through vertical jump and flexion/extension tests on the ground. During the course, observed injuries, their causes, location and recovery time were recorded. At the end of the course, the observed frequency of injuries and their causes were compared between men and women, and in the male group, the obtained marks and the anthropometric parameters were compared between the injured and not injured. Results: the average age of the women vs men´s group was 27.1 (3.18) vs. 25.7 (3.03) years p

  11. Prediction of forces and moments for flight vehicle control effectors. Part 2: An analysis of delta wing aerodynamic control effectiveness in ground effect

    Maughmer, Mark D.; Ozoroski, L.; Ozoroski, T.; Straussfogel, D.

    1990-01-01

    Many types of hypersonic aircraft configurations are currently being studied for feasibility of future development. Since the control of the hypersonic configurations throughout the speed range has a major impact on acceptable designs, it must be considered in the conceptual design stage. Here, an investigation of the aerodynamic control effectiveness of highly swept delta planforms operating in ground effect is presented. A vortex-lattice computer program incorporating a free wake is developed as a tool to calculate aerodynamic stability and control derivatives. Data generated using this program are compared to experimental data and to data from other vortex-lattice programs. Results show that an elevon deflection produces greater increments in C sub L and C sub M in ground effect than the same deflection produces out of ground effect and that the free wake is indeed necessary for good predictions near the ground.

  12. The CMS Experiment: on and under Ground Motions of Structures Due to the Magnetic Field Forces as Observed by the Link Alignment System

    Alberdi, J.; Arce, J.; Barcala, J. M.; Calvo, E.; Ferrando, A.; Josa, M. I.; Molinero, A.; Navarrete, J.; Oller, J. C.; Yuste, C.; Brochero, J.; Calderon, A.; Fernandez, M. G.; Gomez, G.; Gonzalez-Sanchez, F. J.; Martinez-Ribero, C.; Matorras, F.; Rodrigo, T.; Rui-Arbol, P.; Scodellaro, L.; Sobron, M.; Vila, I.; Virto, A. L.; Fernandez, J.

    2010-05-01

    This document describes results obtained from the Link Alignment System data recorded during the CMS Magnet Test (at SX5 on ground Hall) and the CRAFT08 and 09 periods data taking in the point P5 (UX5), 100 m underground. A brief description of the system is followed by the discussion of the detected relative displacements (from micrometres to centimetres) between detector elements and rotation of detector structures (from microradiants to milliradiants). Observed motions are studied as functions of the magnetic fi eld intensity. Comparisons between recorded data on and under ground are made. (Author) 23 refs.

  13. The CMS Experiment: on and under Ground Motions of Structures Due to the Magnetic Field Forces as Observed by the Link Alignment System

    This document describes results obtained from the Link Alignment System data recorded during the CMS Magnet Test (at SX5 on ground Hall) and the CRAFT08 and 09 periods data taking in the point P5 (UX5), 100 m underground. A brief description of the system is followed by the discussion of the detected relative displacements (from micrometres to centimetres) between detector elements and rotation of detector structures (from microradiants to milliradiants). Observed motions are studied as functions of the magnetic fi eld intensity. Comparisons between recorded data on and under ground are made. (Author) 23 refs.

  14. Hydroelastic response of pontoon type very large offshore structure. 4th report. Estimation method of slowly varying wave drift force and fender reaction force; Pontoon gata choogata futaishiki kaiyo kozobutsu no harochu dansei oto ni kansuru kenkyu. 4 hendoha hyoryuryoku no santei to keiryuryoku

    Ikoma, T.; Maeda, H.; Rheem, C. [Tokyo Univ. (Japan)] Masuda, K. [Nihon Univ., Tokyo (Japan)

    1998-12-31

    As regard to the present studies on estimation of fluid force of very large floating structures, highly accurate hydroelastic response analysis becomes possible. In this paper, a method calculating varying wave drift force that works on very large shallow draft floating structures having elastic deformation, is proposed. The proposed method is a calculation method applicable enough for the cases to which the shallow draft theory is applied. The following conclusions are obtained from several numerical calculations. The characteristics of the varying wave drift force in longitudinal waves are quite different depending on the combinations of the wave frequencies. As for the characteristics of the varying wave drift force in oblique waves, the difference caused by the combinations of the frequencies is small to the surge direction, but the steady element is remarkable to the sway direction. In irregular waves, elastic floating structure shows smaller fender reaction force in comparison with a rigid body. Therefore, it is favorable to consider the elastic response while estimating the maximum value of the fender reaction force. In the case of dolphin mooring, the distribution characteristics of the maximum value of the fender reaction force is similar to the Weibull distribution. 11 refs., 8 figs., 2 tabs.

  15. Significance of mat and shoe softness during prolonged work in upright position: based on measurements of low back muscle EMG, foot volume changes, discomfort and ground force reactions.

    Hansen, L; Winkel, J; Jørgensen, K

    1998-01-01

    The aim of the investigation was to study the significance of mat and shoe softness during prolonged work in an upright position based on some physiological, biomechanical and comfort measurements related to the lower extremities and the low back. Eight healthy female volunteers performed 2 h of simulated standing and 2 h of standing/walking work tasks in the laboratory using four combinations of soft shoes, clogs, soft mat and concrete. Thus, each subject performed a total of eight 2 h work tests. The following parameters were measured pre-experimentally and one or more times during 2 h: total foot volume, vascular volume and interstitial volume of the left foot, EMG from the lumbar paraspinals, movement of centre of gravity (only during standing), biomechanical heel impact (only during standing/walking), perceived discomfort in lumbar back, legs and feet, whole body oxygen uptake, arterial blood pressure and heart rate. Using soft shoes rather than clogs during standing/walking work implies approximately a halving of the foot oedema formation and the heel impact. The effects due to the introduction of the soft mat are negligible. The local circulatory responses in the feet and the EMG-signs of paravertebral muscle fatigue are larger during standing compared to standing/walking work. The two investigated work types in this study differ regarding exposures as well as responses. Thus, it is recommended to shift between these postures and seated work during the working hours to improve job exposures. PMID:9676339

  16. Electron acceleration and emission in a field of a plane and converging dipole wave of relativistic amplitudes with the radiation reaction force taken into account

    A comparative analysis is performed of the electron emission characteristics as the electrons move in laser fields with ultra-relativistic intensity and different configurations corresponding to a plane or tightly focused wave. For a plane travelling wave, analytical expressions are derived for the emission characteristics, and it is shown that the angular distribution of the radiation intensity changes qualitatively even when the wave intensity is much less than that in the case of the radiation-dominated regime. An important conclusion is drawn that the electrons in a travelling wave tend to synchronised motion under the radiation reaction force. The characteristic features of the motion of electrons are found in a converging dipole wave, associated with the curvature of the phase front and nonuniformity of the field distribution. The values of the maximum achievable longitudinal momenta of electrons accelerated to the centre, as well as their distribution function are determined. The existence of quasi-periodic trajectories near the focal region of the dipole wave is shown, and the characteristics of the emission of both accelerated and oscillating electrons are analysed. (extreme light fields and their applications)

  17. Three-body forces

    Three-body forces are defined and their properties discussed. Evidence for such forces in the trinucleon bound states and scattering reactions is reviewed. The binding energy defects of the trinucleon bound states, the 3He charge density, the Phillips line for doublet n-d scattering lengths, and three-nucleon breakup reactions are discussed, together with the possible influence of three-body forces on these observables

  18. Three-body forces

    Three-body forces are defined and their properties discussed. Evidence for such forces in the trinucleon bound states and scattering reactions is reviewed. The binding energy defects of the trinucleon bound states, the 3He charge density, the Phillips line for doublet n-d scattering lengths, and three-nucleon breakup reactions are discussed, together with the possible influence of three-body forces on these observables. 23 references, 6 figures, 1 table

  19. NRC Task Force report on review of the federal/state program for regulation of commercial low-level radioactive waste burial grounds

    The underlying issue explored in this report is that of Federal vs State regulation of commercial radioactive waste burial grounds. The need for research and development, a comprehensive set of standards and criteria, a national plan for low-level waste management, and perpetual care funding are closely related to the central issue and are also discussed. Five of the six commercial burial grounds are regulated by Agreement States; the sixth is regulated solely by the NRC (NRC also regulates Special Nuclear Material at the sites). The sites are operated commercially. The operators contribute to the perpetual care funds for the sites at varying rates. The States have commitments for the perpetual care of the decommissioned sites except for one site, located on Federally owned land. Three conclusions are reached. Federal control over the disposal of low-level waste should be increased by requiring joint Federal/State site approval, NRC licensing, Federal ownership of the land, and a Federally administered perpetual care program. The NRC should accelerate the development of its regulatory program for the disposal of low-level waste. The undisciplined proliferation of low-level burial sites must be avoided. NRC should evaluate alternative disposal methods, conduct necessary studies, and develop a comprehensive low-level waste regulatory program (i.e., accomplish the above recommendations) prior to the licensing of new disposal sites

  20. Calibration of CR-39 with atomic force microscope for the measurement of short range tracks from proton-induced target fragmentation reactions

    We studied the track response of CR-39 plastic nuclear track detectors (PNTD) for low (<6 MeV/n) and high (>100 MeV/n) energy heavy ions using the atomic force microscope (AFM). CR-39 PNTD was exposed to several heavy ion beams of different energy at HIMAC (Heavy Ion Medical Accelerator in Chiba). For AFM measurement, the amount of bulk etch was controlled to be ∼2 μm in order to avoid etching away of short range tracks. The response data obtained by AFM for ∼2 μm bulk etch was in good agreement with data obtained by the conventional optical microscope analysis for larger bulk etch. The response data from low energy beams (stopping near the surface) was also consistent with the data from high energy beams (penetrating the detector) as a function of REL (restricted energy loss) with the δ-ray cut off energy of ω0 = 200 eV. We experimentally verified that REL (ω0 = 200 eV) gives a universal function for wide energy range in CR-39 PNTD. This work has been done as part of a basic study in the measurement of secondary short range tracks produced by target fragmentation reactions in proton cancer therapy fields. - Highlights: ► Track response of CR-39 for low and high energy heavy ions was studied. ► Track measurement was carried out with AFM. ► Amount of bulk etch was controlled to be shallowly ∼2 μm ► REL model with the 200 eV δ-ray cut-off energy gives a universal function for wide energy range

  1. Theoretical researches on ?-transfer rates of ground states in medium and heavy nuclei

    The ?-transfer rates of ground states in medium and heavy nuclei are obtained analytically in a two-level pairing force model of j-j scheme. It is concluded that, like the pair-transfer, there is a blocking effect in ?-transfer reactions because of the single and unpaired nucleon. This is in accordance with the experimental facts

  2. Quenching of spin-M1 transition matrix elements and tensor force effect in the ground state in N=Z and even-even nuclei

    Quenching of spin-M1 transition matrix elements from even-even and N=Z nuclei across the sd shell region was studied by using high resolution (p, p') measurements at forward scattering angles including 0deg. The nuclear matrix elements corresponding to each excited state were deduced by using the differential cross section at 0deg estimated from unit cross section after sorting 1+ nuclear transition derived from the distinct form of angular distribution of differential scattering cross section measured. It was experimentally found from the comparison of the matrix elements calculated for the respective target nuclei with the shell-model calculation that the quenching was observed in the component of isovector, but not in the corresponding one of isoscalar. The difference between these isospins for M1 quenching is presumed to be resulted from the difference of tensor forces in the respective isospin transitions. (author)

  3. [Observation study on aerosol optical properties and radiative forcing using the ground-based and satellite remote sensing at background station during the regional pollution episodes].

    Zhang, Xiao-Ling; Xia, Xiang-Ao; Che, Hui-Zheng; Tang, Jie; Tang, Yi-Xi; Meng, Wei; Dong, Fan

    2014-07-01

    The significant effect of anthropogenic pollutants transportation on the physical and optical properties of regional background atmospheric aerosol was studied by using ground-based and satellite remote sensing data obtained at the atmospheric background station (Shangdianzi, Beijing) of North China during October 1 to 15 in 2011. The aerosol mass concentration and reactive gases concentration increased obviously during periods of October 4-5, October 7-9, and October 11-12. Comparing with the background period of October 1-3, volume concentration increased by a factor of 3-6 for reactive gases such as NO(x), and CO, and a factor of 10-20 for SO2. Mass concentration of PM2.5 was about 200 microg x m(-3) on October 9. During haze period, the AOD at 500 nm varied between 0.60 to 1.00. The single scattering albedo (SSA) was lower than 0.88. And the black carbon concentration increased 4-8 times, which suggested the aerosol absorption was very strong during this pollution episode. The absorption of aerosol particles could cause 100-400 W x m(-2) increase of atmospheric radiation. The surface radiation decreased by about 100-300 W x m(-2) due to the aerosol scattering and absorption. This could cause higher stability of atmosphere, which will significantly affect the cloud and precipitation, and thus the regional weather and climate. PMID:25247232

  4. Light induced electron transfer reactions of metal complexes

    Properties of the excited states of tris(2,2'-bipyridine) and tris(1,10-phenanthroline) complexes of chromium(III), iron(II), ruthenium(II), osmium(II), rhodium(III), and iridium(III) are described. The electron transfer reactions of the ground and excited states are discussed and interpreted in terms of the driving force for the reaction and the distortions of the excited states relative to the corresponding ground states. General considerations relevant to the conversion of light into chemical energy are presented and progress in the use of polypyridine complexes to effect the light decomposition of water into hydrogen and oxygen is reviewed

  5. Quantum, Statistical, and Quasiclassical Trajectory Studies For the Ne + HeH(+) → NeH(+) + He Reaction on the Ground Electronic State.

    Koner, Debasish; Barrios, Lizandra; González-Lezana, Tomás; Panda, Aditya N

    2015-12-17

    Real wave packet, statistical quantum, and quasiclassical trajectory methods were employed to study the dynamics of Ne + HeH(+)(v0,j0) → He + NeH(+) reaction on an ab initio potential energy surface [J. Phys. Chem. A 2013, 117, 13070-13078]. Quantum and statistical quantum calculations were performed within the centrifugal sudden (CS) approximation as well as including the Coriolis coupling (CC). Dense oscillatory structures of the quantum reaction probabilities and fair agreement between quantum and statistical cross sections suggest a complex forming mechanism for the reaction. No significant differences between cross sections obtained within the CS and CC approaches are observed. Quasiclassical trajectory results give an excellent average description of the quantum CC results. At low collision energies, there is a substantial decrease in reactivity for the reaction upon rovibrational excitation. Initial state selected rate constants for the title reaction are calculated between 20 and 1000 K, and the calculated value at 300 K agrees quite well with the available experimental result. Reaction cross sections and rate constants are also compared with those calculated via the Langevin capture model for exothermic reactions. PMID:26172109

  6. Communication: Direct comparison between theory and experiment for correlated angular and product-state distributions of the ground-state and stretching-excited O(3P) + CH4 reactions

    Motivated by a recent experiment [H. Pan and K. Liu, J. Chem. Phys. 140, 191101 (2014)], we report a quasiclassical trajectory study of the O(3P) + CH4(vk = 0, 1) → OH + CH3 [k = 1 and 3] reactions on an ab initio potential energy surface. The computed angular distributions and cross sections correlated to the OH(v = 0, 1) + CH3(v = 0) coincident product states can be directly compared to experiment for O + CH4(v3 = 0, 1). Both theory and experiment show that the ground-state reaction is backward scattered, whereas the angular distributions shift toward sideways and forward directions upon antisymmetric stretching (v3) excitation of the reactant. Theory predicts similar behavior for the O + CH4(v1 = 1) reaction. The simulations show that stretching excitation enhances the reaction up to about 15 kcal/mol collision energy, whereas the O + CH4(vk = 1) reactions produce smaller cross sections for OH(v = 1) + CH3(v = 0) than those of O + CH4(v = 0) → OH(v = 0) + CH3(v = 0). The former finding agrees with experiment and the latter awaits for confirmation. The computed cold OH rotational distributions of O + CH4(v = 0) are in good agreement with experiment

  7. On ground model definability

    Gitman, Victoria; Johnstone, Thomas A.

    2013-01-01

    Laver, and Woodin independently, showed that models of ${\\rm ZFC}$ are uniformly definable in their set-forcing extensions, using a ground model parameter. We investigate ground model definability for models of fragments of ${\\rm ZFC}$, particularly of ${\\rm ZF}+{\\rm DC}_\\delta$ and of ${\\rm ZFC}^-$, and we obtain both positive and negative results. Generalizing the results of Laver and Woodin, we show that models of ${\\rm ZF}+{\\rm DC}_\\delta$ are uniformly definable in their set-forcing exte...

  8. Investigating the relationship between pressure force and acoustic waveform in footstep sounds

    Grani, Francesco; Serafin, Stefania; Götzen, Amalia De; Overholt, Daniel; Topel, Spencer

    In this paper we present an inquiry into of the relationships between audio waveforms and ground reaction force in recorded footstep sounds. In an anechoic room, we recorded several footstep sounds produced while walking on creaking wood and gravel. The recordings were performed by using a pair o...

  9. Ab initio study of {sup 2}H(d,{gamma}){sup 4}He, {sup 2}H(d,p){sup 3}H, and {sup 2}H(d,n){sup 4}He reactions and the tensor force

    Arai, K.; Aoyama, S.; Suzuki, Y.; Descouvemont, P.; Baye, D. [Division of General Education, Nagaoka National College of Technology, 888 Nishikatakai, Nagaoka, Niigata, 940-8532 (Japan); Center for Academic Information Service, Niigata University, Niigata 950-2181 (Japan); Department of Physics, Niigata University, Niigata 950-2181, Japan and RIKEN Nishina Center, Wako 351-0198 (Japan); Physique Nucleaire Theorique et Physique Mathematique, C.P.229, Universite Libre de Bruxelles, B 1050 Brussels (Belgium); Physique Quantique, CP165/82, Universite Libre de Bruxelles, B-1050 Brussels (Belgium)

    2012-11-12

    The {sup 2}H(d,p){sup 3}H, {sup 2}H(d,n){sup 3}He, and {sup 2}H(d,{gamma}){sup 4}He reactions at low energies are studied with realistic nucleon-nucleon interactions in an ab initio approach. The obtained astrophysical S-factors are all in very good agreement with experiment. The most important channels for both transfer and radiative capture are all found to dominate thanks to the tensor force.

  10. Column Aerosol Optical Properties and Aerosol Radiative Forcing During a Serious Haze-Fog Month over North China Plain in 2013 Based on Ground-Based Sunphotometer Measurements

    Che, H.; Xia, X.; Zhu, J.; Li, Z.; Dubovik, O.; Holben, Brent N.; Goloub, P.; Chen, H.; Estelles, V.; Cuevas-Agullo, E.

    2014-01-01

    In January 2013, North China Plain experienced several serious haze events. Cimel sunphotometer measurements at seven sites over rural, suburban and urban regions of North China Plain from 1 to 30 January 2013 were used to further our understanding of spatial-temporal variation of aerosol optical parameters and aerosol radiative forcing (ARF). It was found that Aerosol Optical Depth at 500 nm (AOD500nm) during non-pollution periods at all stations was lower than 0.30 and increased significantly to greater than 1.00 as pollution events developed. The Angstrom exponent (Alpha) was larger than 0.80 for all stations most of the time. AOD500nm averages increased from north to south during both polluted and non-polluted periods on the three urban sites in Beijing. The fine mode AOD during pollution periods is about a factor of 2.5 times larger than that during the non-pollution period at urban sites but a factor of 5.0 at suburban and rural sites. The fine mode fraction of AOD675nm was higher than 80% for all sites during January 2013. The absorption AOD675nm at rural sites was only about 0.01 during pollution periods, while 0.03-0.07 and 0.01-0.03 during pollution and non-pollution periods at other sites, respectively. Single scattering albedo varied between 0.87 and 0.95 during January 2013 over North China Plain. The size distribution showed an obvious tri-peak pattern during the most serious period. The fine mode effective radius in the pollution period was about 0.01-0.08 microns larger than during nonpollution periods, while the coarse mode radius in pollution periods was about 0.06-0.38 microns less than that during nonpollution periods. The total, fine and coarse mode particle volumes varied by about 0.06-0.34 cu microns, 0.03-0.23 cu microns, and 0.03-0.10 cu microns, respectively, throughout January 2013. During the most intense period (1-16 January), ARF at the surface exceeded -50W/sq m, -180W/sq m, and -200W/sq m at rural, suburban, and urban sites, respectively. The ARF readings at the top of the atmosphere were approximately -30W/sq m in rural and -40-60W/sq m in urban areas.

  11. Tensor Force Manifestations in Ab Initio Study of the 2H(d,?)4He, 2H(d,p)3H, and 2H(d,n)3He Reactions

    The 2H(d,p)3H, 2H(d,n)3He, and 2H(d,?)4He reactions are studied at low energies in a multichannel ab initio model that takes into account the distortions of the nuclei. The internal wave functions of these nuclei are given by the stochastic variational method with the AV8' realistic interaction and a phenomenological three-body force included to reproduce the two-body thresholds. The obtained astrophysical S factors are all in very good agreement with the experiment. The most important channels for both transfer and radiative capture are identified by comparing to calculations with an effective central force. They are all found to dominate thanks to the tensor force.

  12. Applying the cost of generating force hypothesis to uphill running

    Wouter Hoogkamer; Paolo Taboga; Rodger Kram

    2014-01-01

    Historically, several different approaches have been applied to explain the metabolic cost of uphill human running. Most of these approaches result in unrealistically high values for the efficiency of performing vertical work during running uphill, or are only valid for running up steep inclines. The purpose of this study was to reexamine the metabolic cost of uphill running, based upon our understanding of level running energetics and ground reaction forces during uphill running. In contrast...

  13. Testing nuclear forces by polarization transfer coefficients in d(\\vec p, \\vec p)d and d(\\vec p,\\vec d)p reactions at E^{lab}_p = 22.7 MeV

    Witala, H; Glöckle, W; Golak, J; Kamada, H; Kievsky, A; Nogga, A; Skibinski, R; Viviani, M

    2006-01-01

    The proton to proton polarization transfer coefficients K_x^{x'}, K_y^{y'}, K_z^{x'} and the proton to deuteron polarization transfer coefficients K_x^{x'}, K_y^{y'}, K_z^{x'}, K_x^{y'z'}, K_y^{z'z'}, K_z^{y'z'}, K_y^{x'z'} and K_y^{x'x'-y'y'} have been measured in d(\\vec p, \\vec p)d and d(\\vec p, \\vec d)p reactions at E^{lab}_p = 22.7 MeV, respectively. The data have been compared to predictions of modern nuclear forces obtained by solving the three-nucleon Faddeev equations in momentum space. Realistic (semi) phenomenological nucleon-nucleon potentials combined with model three-nucleon forces and modern chiral nuclear forces have been used. The AV18, CD Bonn, Nijm I and II nucleon-nucleon interactions have been applied alone or combined with the Tucson-Melbourne 99 three-nucleon force, adjusted separately for each potential to reproduce the triton binding energy. For the AV18 potential also the Urbana IX three-nucleon force have been used. In addition chiral NN potentials in the next-to-leading-order and ch...

  14. Diatomics-in-molecules (DIM) formalism for the reaction AH+ +A'?A+A'H+: A ground state potential energy surface for collinear He2H+

    A valence-bond diatomics-in-molecules (DIM) formalism is applied to the study of proton rare-gas reactions of the type AH++A'?A +A'H+. The method is used to generate potential energy surfaces for the He2H+ system. The DIM potential surface for this system is in good quantitative agreement with an LCAO--SCF--MO surface for the collinear arrangement, He--H--He+

  15. Variability of a "force signature" during windmill softball pitching and relationship between discrete force variables and pitch velocity.

    Nimphius, Sophia; McGuigan, Michael R; Suchomel, Timothy J; Newton, Robert U

    2016-06-01

    This study assessed reliability of discrete ground reaction force (GRF) variables over multiple pitching trials, investigated the relationships between discrete GRF variables and pitch velocity (PV) and assessed the variability of the "force signature" or continuous force-time curve during the pitching motion of windmill softball pitchers. Intraclass correlation coefficient (ICC) for all discrete variables was high (0.86-0.99) while the coefficient of variance (CV) was low (1.4-5.2%). Two discrete variables were significantly correlated to PV; second vertical peak force (r(5)=0.81, p=0.03) and time between peak forces (r(5)=-0.79; p=0.03). High ICCs and low CVs support the reliability of discrete GRF and PV variables over multiple trials and significant correlations indicate there is a relationship between the ability to produce force and the timing of this force production with PV. The mean of all pitchers' curve-average standard deviation of their continuous force-time curves demonstrated low variability (CV=4.4%) indicating a repeatable and identifiable "force signature" pattern during this motion. As such, the continuous force-time curve in addition to discrete GRF variables should be examined in future research as a potential method to monitor or explain changes in pitching performance. PMID:26999033

  16. Comparison of natural and artificial forcing to study the dynamic behaviour of bell towers in low wind context by means of ground-based radar interferometry: the case of the Leaning Tower in Pisa

    The study of Cultural Heritage assets needs the application of non-destructive and non-invasive monitoring techniques. In particular, monuments and historical buildings which are open to the visitors and/or subject to important stress must be studied for their dynamic response. In the last 10 years the new ground-based radar interferometry technology has been developed allowing to monitor displacements from a point of sight far from the studied targets. It virtually provides a continuous mapping of displacements of the observed structures up to 10 µm with a range resolution of 0.75 m. In this paper, the application of ground-based interferometry on one very important historical building, the Leaning Tower of Pisa in Italy, is reported. The analysis of these kind of structures is important to catch their dynamic response to natural actions in general, and also to assess the effects due to pedestrian and users, and consequently to define functional capabilities and levels of acceptable dynamic stress. The studied structure was subject to artificial loading by synchronous movement of about 20 people. Artificial forcing led the structure to a resonance condition with the same frequency of the one due to the natural noise excitation, which was separately measured, and with an oscillation amplitude more than thirty times greater than the natural one (in conditions of weak wind). During the passive stages of the survey the recorded structural vibrations were very closed to the instrumental sensitivity, making difficult to distinguish vibration amplitudes amplifications of various segments at various heights. Through the spectral analysis of the acquired data it was possible to estimate the vibration frequencies of the first modal shapes of the structure along two orthogonal directions. The power spectra of the passive survey data have the same maximum frequency of the active but contain more noise at low frequency. (paper)

  17. Resonance-like structure observed in 22Ne(p?)23Na reaction

    One studied ?-disintegration of a resonance-like structure observed in 22Ne(p?)23Na reaction within Ep 0.8-2.5 MeV energy range of accelerated protons. One identified M1 resonance in the ground and the excited states (E* = 440 and 2982 keV) of 23Na nucleus. M1 resonance position in the ground state is explained with regard to pairing forces

  18. Design and Operation of a Borehole Straddle Packer for Ground-Water Sampling and Hydraulic Testing of Discrete Intervals at U.S. Air Force Plant 6, Marietta, Georgia

    Holloway, Owen G.; Waddell, Jonathan P.

    2008-01-01

    A borehole straddle packer was developed and tested by the U.S. Geological Survey to characterize the vertical distribution of contaminants, head, and hydraulic properties in open-borehole wells as part of an ongoing investigation of ground-water contamination at U.S. Air Force Plant 6 (AFP6) in Marietta, Georgia. To better understand contaminant fate and transport in a crystalline bedrock setting and to support remedial activities at AFP6, numerous wells have been constructed that include long open-hole intervals in the crystalline bedrock. These wells can include several discontinuities that produce water, which may contain contaminants. Because of the complexity of ground-water flow and contaminant movement in the crystalline bedrock, it is important to characterize the hydraulic and water-quality characteristics of discrete intervals in these wells. The straddle packer facilitates ground-water sampling and hydraulic testing of discrete intervals, and delivery of fluids including tracer suites and remedial agents into these discontinuities. The straddle packer consists of two inflatable packers, a dual-pump system, a pressure-sensing system, and an aqueous injection system. Tests were conducted to assess the accuracy of the pressure-sensing systems, and water samples were collected for analysis of volatile organic compound (VOCs) concentrations. Pressure-transducer readings matched computed water-column height, with a coefficient of determination of greater than 0.99. The straddle packer incorporates both an air-driven piston pump and a variable-frequency, electronic, submersible pump. Only slight differences were observed between VOC concentrations in samples collected using the two different types of sampling pumps during two sampling events in July and August 2005. A test conducted to assess the effect of stagnation on VOC concentrations in water trapped in the system's pump-tubing reel showed that concentrations were not affected. A comparison was conducted to assess differences between three water-sampling methods - collecting samples from the well by pumping a packer-isolated zone using a submersible pump, by using a grab sampler, and by using a passive diffusion sampler. Concentrations of tetrachloroethylene, trichloroethylene and 1,2-dichloropropane were greatest for samples collected using the submersible pump in the packed-isolated interval, suggesting that the straddle packer yielded the least dilute sample.

  19. Time-dependent quantum wave packet study of the Ar+H2+?ArH++H reaction on a new ab initio potential energy surface for the ground electronic state (12A?)

    A new global potential energy surface for the ground electronic state (12A?) of the Ar+H2+?ArH++H reaction has been constructed by multi-reference configuration interaction method with Davidson correction and a basis set of aug-cc-pVQZ. Using 6080 ab initio single-point energies of all the regions for the dynamics, a many-body expansion function form has been used to fit these points. The quantum reactive scattering dynamics calculations taking into account the Coriolis coupling (CC) were carried out on the new potential energy surface over a range of collision energies (0.03–1.0 eV). The reaction probabilities and integral cross sections for the title reaction were calculated. The significance of including the CC quantum scattering calculation has been revealed by the comparison between the CC and the centrifugal sudden approximation calculation. The calculated cross section is in agreement with the experimental result at collision energy 1.0 eV.

  20. ?-decay of resonance-like structure observed in 30Si(p,?)31P reaction

    ?-Decay of a resonance-like structure observed in the reaction 30Si (p, ?)31P in the energy region Ep = 1.4 - 2.7 MeV of accelerated protons is studied. The M1 resonance built on the ground state of 31P is identified. The position of the M1 resonance is explained taking into account pairing forces

  1. Effects of vascular infusion with a solution of saccharides; sodium chloride; phosphates; and vitamins C, E, or both on carcass traits, Warner-Bratzler shear force, and palatability traits of steaks and ground beef.

    Yancey, E J; Dikeman, M E; Addist, P B; Katsanidis, E; Pullen, M

    2002-07-01

    Three groups of 12 high percentage Charolais steers were slaughtered on three dates. Steers (n = 27) were infused immediately after exsanguination at 10% of BW with a solution containing saccharides, NaCl, and phosphates (MPSC solution; MPSC, Inc., St. Paul, MN) plus either 500 ppm vitamin C (MPSC+C), 500 ppm vitamin E (MPSC+E), or 500 ppm vitamin C plus 500 ppm vitamin E (MPSC+C+E). Noninfused controls (CON) were 9 steers. The longissimus thoracis (LT), semitendinosus (ST), and quadriceps femoris muscles were removed at 48-h postmortem, vacuum-packaged, and aged until 14-d postmortem. Steaks 2.54-cm thick were cut from the LT and ST. The quadriceps was utilized for ground-beef production. Infused steers had higher dressing percentages and heavier heart and liver weights (P infusion with vitamins C, E, or C plus E had no effect (P > 0.05) on USDA yield and quality-grade traits, LT and ST Warner-Bratzler shear force, descriptive-attribute traits, and freshly cooked steak flavor-profile traits. Vascular infusion had little effect on the flavor-profile traits of warmed-over steaks. Therefore, the results of our study indicate that vascular infusion with vitamins C, E, or C plus E can increase dressing percentage and organ weights, but have minimal effects on descriptive-attribute and flavor-profile sensory panel ratings. PMID:12162658

  2. Exact integral constraint requiring only the ground-state electron density as input on the exchange-correlation force - partial differential(V)(xc)(r)/partial differential(r) for spherical atoms.

    March, N H; Nagy, A

    2008-11-21

    Following some studies of integral(n)(r)inverted DeltaV(r)dr by earlier workers for the density functional theory (DFT) one-body potential V(r) generating the exact ground-state density, we consider here the special case of spherical atoms. The starting point is the differential virial theorem, which is used, as well as the Hiller-Sucher-Feinberg [Phys. Rev. A 18, 2399 (1978)] identity to show that the scalar quantity paralleling the above vector integral, namely, integral(n)(r) partial differential(V)(r)/partial differential(r)dr, is determined solely by the electron density n(0) at the nucleus for the s-like atoms He and Be. The force - partial differential(V)/ partial differential(r) is then related to the derivative of the exchange-correlation potential V(xc)(r) by terms involving only the external potential in addition to n(r). The resulting integral constraint should allow some test of the quality of currently used forms of V(xc)(r). The article concludes with results from the differential virial theorem and the Hiller-Sucher-Feinberg identity for the exact many-electron theory of spherical atoms, as well as for the DFT for atoms such as Ne with a closed p shell. PMID:19026052

  3. Charge exchange study with the 40Ca(7Li, 7Be)40K reaction

    Angular distributions have been measured for the (4-, 3-) and (2-, 5-) doublets at approximately 0.0 and 0.85 MeV excitation in 40K with the reaction 40Ca(7Li, 7Be) for 7Be in both its ground and first excited states at Esub(7Li) = 35 MeV. Microscopic distorted wave approximation calculations including only a central force do not reproduce the cross sections. Inclusion of a tensor force may resolve this disagreement. (Auth.)

  4. Toe-Out Gait Decreases the Second Peak of the Medial Knee Contact Force.

    Ogaya, Shinya; Naito, Hisashi; Iwata, Akira; Higuchi, Yumi; Fuchioka, Satoshi; Tanaka, Masao

    2015-08-01

    Toe-out angle alternation is a potential tactic for decreasing the knee adduction moment during walking. Published reports have not examined the medial knee contact force during the toe-out gait, although it is a factor affecting knee articular cartilage damage. This study investigated the effects of increased toe-out angle on the medial knee contact force, using musculoskeletal simulation analysis. For normal and toe-out gaits in 18 healthy subjects, the muscle tension forces were simulated based on the joint moments and ground reaction forces with optimization process. The medial knee contact force during stance phase was determined using the sum of the muscle force and joint reaction force components. The first and second peaks of the medial knee contact force were compared between the gaits. The toe-out gait showed a significant decrease in the medial knee contact force at the second peak, compared with the normal gait. In contrast, the medial knee contact forces at the first peak were not significantly different between the gaits. These results suggest that the toe-out gait is beneficial for decreasing the second peak of the medial knee contact force. PMID:25880695

  5. Crystalline beam ground state

    In order to employ molecular dynamics (MD) methods, commonly used in condensed matter physics, we have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. We include in the formalism that the particles are confined by the guiding and focusing magnetic fields, and that they are confined in a conducting vacuum pipe while interacting with each other via a Coulomb force. Numerical simulations using MD methods has been performed to obtain the equilibrium crystalline beam structure. The effect of the shearing force, centrifugal force, and azimuthal variation of the focusing strength are investigated. It is found that a constant gradient storage ring can not give a crystalline beam, but that an alternating-gradient (AG) structure can. In such a machine the ground state is, except for one-dimensional (1-D) crystals, time dependent. The ground state is a zero entropy state, despite the time-dependent, periodic variation of the focusing force. The nature of the ground state, similar to that found by Schiffer et al. depends upon the density and the relative focusing strengths in the transverse directions. At low density, the crystal is 1-D. As the density increases, it transforms into various kinds of 2-D and 3-D crystals. If the energy of the beam is higher than the transition energy of the machine, the crystalline structure can not be formed for lack of radial focusing

  6. Electroweak Force

    Murdin, P.

    2000-11-01

    The united force that encompasses the electromagnetic force and the weak nuclear force. The unification of these two forces is described by a theory that was devised during the 1960s by Sheldon Glashow, Steven Weinberg and Abdus Salam according to which, at high enough energies, the electromagnetic force and the weak nuclear interaction behave in exactly the same way....

  7. Grounded cognition.

    Barsalou, Lawrence W

    2008-01-01

    Grounded cognition rejects traditional views that cognition is computation on amodal symbols in a modular system, independent of the brain's modal systems for perception, action, and introspection. Instead, grounded cognition proposes that modal simulations, bodily states, and situated action underlie cognition. Accumulating behavioral and neural evidence supporting this view is reviewed from research on perception, memory, knowledge, language, thought, social cognition, and development. Theories of grounded cognition are also reviewed, as are origins of the area and common misperceptions of it. Theoretical, empirical, and methodological issues are raised whose future treatment is likely to affect the growth and impact of grounded cognition. PMID:17705682

  8. Half-Lives of ground states in Pm and Eu nuclei following the 154,152Sm (p,x) reactions at 25 MeV

    Watwood, N. J.; Beausang, C. W.; Humby, P.; Simon, A.; Gell, K.

    2014-09-01

    The primary experiment was designed to study low/medium spin states in Sm nuclei following the 154,152Sm (p,x) reactions where x = d or t. During the experiment the Sm target was irradiated by a 25 MeV proton beam, provided by the K150 Cyclotron at Texas A&M University, with an average beam current of ~1 nA for about one week. Following the experiment, residual radioactivity in the target was measured in the Environmental Radioactivity Laboratory at the University of Richmond using a 25% efficiency coaxial Ge detector enclosed in a 6-inch thick Pb shield. The gamma ray spectra were internally calibrated using a 152Eu source and the energies of known gamma-rays from the target decays and from long lived environmental radioactivity. The decays of three long lived (~1 month or more) mass A ~ 150 nuclei were identified (148Sm, 148Eu, and 147Eu), and half lives for their beta-decay were (re)measured. Work is still in progress and preliminary results will be presented at the APS conference.

  9. Unloading Reaction during Sudden Ankle Inversion in Healthy Adults

    Jain, Tarang Kumar; Wauneka, Clayton; Liu, Wen

    2013-01-01

    The purpose of this research study was to determine the dynamics of early human response from sudden ankle inversion (30° tilt). Changes in vertical ground reaction forces (GRFs) following trapdoor release in a group of healthy subjects were compared to those from the similar experiments using a chair with two U shaped steel legs and matched weights of the human subjects. The experiments with the chair were further repeated with additional foam paddings at their bases to introduce visco-elast...

  10. Methods for Addressing Uncertainty and Variability to Characterize Potential Health Risk From Trichloroethylene-Contaminated Ground Water Beale Air Force Base in California: Integration of Uncertainty and Variability in Pharmacokinetics and Dose-Response

    Bogen, K.T.

    1999-09-29

    Traditional estimates of health risk are typically inflated, particularly if cancer is the dominant endpoint and there is fundamental uncertainty as to mechanism(s) of action. Risk is more realistically characterized if it accounts for joint uncertainty and interindividual variability after applying a unified probabilistic approach to the distributed parameters of all (linear as well as nonlinear) risk-extrapolation models involved. Such an approach was applied to characterize risks to potential future residents posed by trichloroethylene (TCE) in ground water at an inactive landfill site on Beale Air Force Base in California. Variability and uncertainty were addressed in exposure-route-specific estimates of applied dose, in pharmacokinetically based estimates of route-specific metabolized fractions of absorbed TCE, and in corresponding biologically effective doses estimated under a genotoxic/linear (MA{sub g}) vs. a cytotoxic/nonlinear (MA{sub c}) mechanistic assumption for TCE-induced cancer. Increased risk conditional on effective dose was estimated under MA{sub G} based on seven rodent-bioassay data sets, and under MA, based on mouse hepatotoxicity data. Mean and upper-bound estimates of combined risk calculated by the unified approach were <10{sup -6} and <10{sup -4}, respectively, while corresponding estimates based on traditional deterministic methods were >10{sup -5} and >10{sup -4}, respectively. It was estimated that no TCE-related harm is likely occur due any plausible residential exposure scenario involving the site. The unified approach illustrated is particularly suited to characterizing risks that involve uncertain and/or diverse mechanisms of action.

  11. Methods for Addressing Uncertainty and Variability to Characterize Potential Health Risk From Trichloroethylene-Contaminated Ground Water Beale Air Force Base in California: Integration of Uncertainty and Variability in Pharmacokinetics and Dose-Response; TOPICAL

    Traditional estimates of health risk are typically inflated, particularly if cancer is the dominant endpoint and there is fundamental uncertainty as to mechanism(s) of action. Risk is more realistically characterized if it accounts for joint uncertainty and interindividual variability after applying a unified probabilistic approach to the distributed parameters of all (linear as well as nonlinear) risk-extrapolation models involved. Such an approach was applied to characterize risks to potential future residents posed by trichloroethylene (TCE) in ground water at an inactive landfill site on Beale Air Force Base in California. Variability and uncertainty were addressed in exposure-route-specific estimates of applied dose, in pharmacokinetically based estimates of route-specific metabolized fractions of absorbed TCE, and in corresponding biologically effective doses estimated under a genotoxic/linear (MA(sub g)) vs. a cytotoxic/nonlinear (MA(sub c)) mechanistic assumption for TCE-induced cancer. Increased risk conditional on effective dose was estimated under MA(sub G) based on seven rodent-bioassay data sets, and under MA, based on mouse hepatotoxicity data. Mean and upper-bound estimates of combined risk calculated by the unified approach were and lt;10(sup -6) and and lt;10(sup -4), respectively, while corresponding estimates based on traditional deterministic methods were and gt;10(sup -5) and and gt;10(sup -4), respectively. It was estimated that no TCE-related harm is likely occur due any plausible residential exposure scenario involving the site. The unified approach illustrated is particularly suited to characterizing risks that involve uncertain and/or diverse mechanisms of action

  12. Methods for Addressing Uncertainty and Variability to Characterize Potential Health Risk from Trichloroethylene-Contaminated Ground Water at Beale Air Force Base in California:Integration of Uncertainty and Variability in Pharmacokinetics and Dose-Response

    Bogen, K T

    2001-05-24

    Traditional estimates of health risk are typically inflated, particularly if cancer is the dominant endpoint and there is fundamental uncertainty as to mechanism(s) of action. Risk is more realistically characterized if it accounts for joint uncertainty and interindividual variability within a systematic probabilistic framework to integrate the joint effects on risk of distributed parameters of all (linear as well as nonlinear) risk-extrapolation models involved. Such a framework was used to characterize risks to potential future residents posed by trichloroethylene (TCE) in ground water at an inactive landfill site on Beale Air Force Base in California. Variability and uncertainty were addressed in exposure-route-specific estimates of applied dose, in pharmacokinetically based estimates of route-specific metabolized fractions of absorbed TCE, and in corresponding biologically effective doses estimated under a genotoxic/linear (MA{sub G}) vs. a cytotoxic/nonlinear (MA{sub c}) mechanistic assumption for TCE-induced cancer. Increased risk conditional on effective dose was estimated under MA{sub G} based on seven rodent-bioassay data sets, and under MA{sub c} based on mouse hepatotoxicity data. Mean and upper-bound estimates of combined risk calculated by the unified approach were <10{sup -6} and 10{sup -4}, respectively, while corresponding estimates based on traditional deterministic methods were >10{sup -5} and 10{sup -4}, respectively. It was estimated that no TCE-related harm is likely to occur due to any plausible residential exposure scenario involving the site. The systematic probabilistic framework illustrated is particularly suited to characterizing risks that involve uncertain and/or diverse mechanisms of action.

  13. Deuteration effect on the NH/ND stretch band of the jet-cooled 7-azaindole and its tautomeric dimers: Relation between the vibrational relaxation and the ground-state double proton-transfer reaction

    Highlights: • Deuteration effect on IR spectra of 7-azaindole tautomeric dimers is investigated. • The NH/ND stretch levels are found to relax basically within the monomer unit. • Only the NH stretch of the tautomeric dimer exhibits a drastic deuteration effect. • The deuteration effect is related to the double proton-transfer reaction. - Abstract: Infrared spectra of NH and ND stretch bands of the 7-azaindole (7-AI) dimer and its tautomeric dimer are observed to investigate a deuteration effect on the spectra and also a ground-state double proton-transfer (DPT) reaction. We examined the three isotopic species for each dimers; undeuterated one (NH–NH) and one or two hydrogen atom(s) of the NH groups is deuterated ones (NH–ND and ND–ND, respectively). It is found that the ND stretch band profiles of the NH–ND and ND–ND tautomeric dimers are very similar with each other. This result is very distinct from the result of the comparison of the NH stretch band profiles of the NH–NH and NH–ND dimers in our previous paper. For a further discussion, we examined the deuteration effect in the case of the 7-AI dimer. It is found that band profiles of the NH stretch of the NH–NH and the NH–ND dimers and also the ND stretch of the NH–ND and the ND–ND dimers exhibit similar patterns, respectively. These facts indicates that the vibrational relaxation from the NH/ND stretch level of the dimer basically proceed within a monomer unit. The large deuteration effect of the NH stretch band profile observed previously is found to be characteristic of the tautomeric dimer. This behavior is related to a large anharmonicity of the potential energy surface originating from an existence of the double-proton transfer reaction barrier

  14. Análisis cuantitativo de la evolución post-quirúrgica de la rotura de ligamento cruzado anterior mediante el uso de la plataforma de fuerza - Quantitative analysis of the evolution of post-surgical anterior cruciate ligament rupture using force platform

    Vilar, JM; Morales M; Morales, I.; Montoya, A.; Rodríguez, O; Turco, V

    2010-01-01

    ResumenEl analisis cinético mediante plataforma de fuerza es un método objetivo de cuantificar el apoyo de los miembros en los animales domésticos.SummarySummaryKinetic análisis by jeans of force platforms is an objetive method to measure weight - bearing or ground reaction force (GRF).

  15. Análisis cuantitativo de la evolución post-quirúrgica de la rotura de ligamento cruzado anterior mediante el uso de la plataforma de fuerza - Quantitative analysis of the evolution of post-surgical anterior cruciate ligament rupture using force platform

    Vilar, JM

    2012-01-01

    Full Text Available ResumenEl analisis cinético mediante plataforma de fuerza es un método objetivo de cuantificar el apoyo de los miembros en los animales domésticos.SummaryKinetic análisis by jeans of force platforms is an objetive method to measure weight - bearing or ground reaction force (GRF.

  16. Some applications of the virial theorem to molecular force fields: the zero virial reaction coordinate and diatomic potentials from the normalized kinetic field functions

    For a fixed-angle potential energy surface (PES), W(Q), following the zero virial path (ZVP), on which Σ/sub μ//sup N/Q/sub μ/ . del /sub μ/W(Q) = 0, provides an efficient way for locating the transition state and generating a good approximation to the minimum-energy reaction path; vector Q = (Q1, ..., Q/sub N/ stands for nuclear coordinates. An algorithm which employs the ZVP following is proposed for exploring PESs when starting from the reactant (or product) region. It seems that this approach allows one to avoid some discontinuities in the reaction coordinate, which often result from the bottom-following procedures. The implications of the integral forms of the virial theorem are examined and a new way of constructing potential energy functions W(R) for diatomic molecules is proposed. It starts with the normalization of the kinetic component T(R) of the potential: integral0/sup infinity/[T(R) - T(infinity)]dR = Z/sub A/Z/sub B/, where Z/sub A/ and Z/sub B/ are the nuclear charges and R is the internuclear distance. The modified potentials are derived for four different analytical representations of T(R), T/sub X(R)(X = M, R, RM, and HH) by the Morse, Rydberg, Rosen--Morse, and Hulbert--Hirschfelder functions, respectively. The three-parameter modified potentials (X = M, R, and RM) are tested against known spectroscopic data for H2+ and H2.The modified potentials require one less experimental constant to fit the potential parameters than do their original analogs. It follows that the Morse and Rydberg functions constitute satisfactory representations of the kinetic component T(R), and that enforcing its normalization improves predictions of spectroscopic constants and relations between them. 46 references

  17. Ground Wars

    Nielsen, Rasmus Kleis

    Political campaigns today are won or lost in the so-called ground war--the strategic deployment of teams of staffers, volunteers, and paid part-timers who work the phones and canvass block by block, house by house, voter by voter. Ground Wars provides an in-depth ethnographic portrait of two such...... campaigns, New Jersey Democrat Linda Stender's and that of Democratic Congressman Jim Himes of Connecticut, who both ran for Congress in 2008. Rasmus Kleis Nielsen examines how American political operatives use "personalized political communication" to engage with the electorate, and weighs the implications...... of ground war tactics for how we understand political campaigns and what it means to participate in them. He shows how ground wars are waged using resources well beyond those of a given candidate and their staff. These include allied interest groups and civic associations, party-provided technical...

  18. Assessment of Approximate Coupled-Cluster and Algebraic-Diagrammatic-Construction Methods for Ground- and Excited-State Reaction Paths and the Conical-Intersection Seam of a Retinal-Chromophore Model.

    Tuna, Deniz; Lefrancois, Daniel; Wolański, Łukasz; Gozem, Samer; Schapiro, Igor; Andruniów, Tadeusz; Dreuw, Andreas; Olivucci, Massimo

    2015-12-01

    As a minimal model of the chromophore of rhodopsin proteins, the penta-2,4-dieniminium cation (PSB3) poses a challenging test system for the assessment of electronic-structure methods for the exploration of ground- and excited-state potential-energy surfaces, the topography of conical intersections, and the dimensionality (topology) of the branching space. Herein, we report on the performance of the approximate linear-response coupled-cluster method of second order (CC2) and the algebraic-diagrammatic-construction scheme of the polarization propagator of second and third orders (ADC(2) and ADC(3)). For the ADC(2) method, we considered both the strict and extended variants (ADC(2)-s and ADC(2)-x). For both CC2 and ADC methods, we also tested the spin-component-scaled (SCS) and spin-opposite-scaled (SOS) variants. We have explored several ground- and excited-state reaction paths, a circular path centered around the S1/S0 surface crossing, and a 2D scan of the potential-energy surfaces along the branching space. We find that the CC2 and ADC methods yield a different dimensionality of the intersection space. While the ADC methods yield a linear intersection topology, we find a conical intersection topology for the CC2 method. We present computational evidence showing that the linear-response CC2 method yields a surface crossing between the reference state and the first response state featuring characteristics that are expected for a true conical intersection. Finally, we test the performance of these methods for the approximate geometry optimization of the S1/S0 minimum-energy conical intersection and compare the geometries with available data from multireference methods. The present study provides new insight into the performance of linear-response CC2 and polarization-propagator ADC methods for molecular electronic spectroscopy and applications in computational photochemistry. PMID:26642989

  19. Nuclear forces

    Machleidt, R. [Department of Physics, University of Idaho, Moscow, Idaho 83844 (United States)

    2013-06-10

    These lectures present an introduction into the theory of nuclear forces. We focus mainly on the modern approach, in which the forces between nucleons emerge from low-energy QCD via chiral effective field theory.

  20. A simple method for measuring power, force, velocity properties, and mechanical effectiveness in sprint running.

    Samozino, P; Rabita, G; Dorel, S; Slawinski, J; Peyrot, N; Saez de Villarreal, E; Morin, J-B

    2016-06-01

    This study aimed to validate a simple field method for determining force- and power-velocity relationships and mechanical effectiveness of force application during sprint running. The proposed method, based on an inverse dynamic approach applied to the body center of mass, estimates the step-averaged ground reaction forces in runner's sagittal plane of motion during overground sprint acceleration from only anthropometric and spatiotemporal data. Force- and power-velocity relationships, the associated variables, and mechanical effectiveness were determined (a) on nine sprinters using both the proposed method and force plate measurements and (b) on six other sprinters using the proposed method during several consecutive trials to assess the inter-trial reliability. The low bias (running. PMID:25996964

  1. Labor Force

    Occupational Outlook Quarterly, 2012

    2012-01-01

    The labor force is the number of people ages 16 or older who are either working or looking for work. It does not include active-duty military personnel or the institutionalized population, such as prison inmates. Determining the size of the labor force is a way of determining how big the economy can get. The size of the labor force depends on two…

  2. Determination of External Forces in Alpine Skiing Using a Differential Global Navigation Satellite System

    Erich Müller

    2013-08-01

    Full Text Available In alpine ski racing the relationships between skier kinetics and kinematics and their effect on performance and injury-related aspects are not well understood. There is currently no validated system to determine all external forces simultaneously acting on skiers, particularly under race conditions and throughout entire races. To address the problem, this study proposes and assesses a method for determining skier kinetics with a single lightweight differential global navigation satellite system (dGNSS. The dGNSS kinetic method was compared to a reference system for six skiers and two turns each. The pattern differences obtained between the measurement systems (offset ± SD were −26 ± 152 N for the ground reaction force, 1 ± 96 N for ski friction and −6 ± 6 N for the air drag force. The differences between turn means were small. The error pattern within the dGNSS kinetic method was highly repeatable and precision was therefore good (SD within system: 63 N ground reaction force, 42 N friction force and 7 N air drag force allowing instantaneous relative comparisons and identification of discriminative meaningful changes. The method is therefore highly valid in assessing relative differences between skiers in the same turn, as well as turn means between different turns. The system is suitable to measure large capture volumes under race conditions.

  3. Determination of external forces in alpine skiing using a differential global navigation satellite system.

    Gilgien, Matthias; Spörri, Jörg; Chardonnens, Julien; Kröll, Josef; Müller, Erich

    2013-01-01

    In alpine ski racing the relationships between skier kinetics and kinematics and their effect on performance and injury-related aspects are not well understood. There is currently no validated system to determine all external forces simultaneously acting on skiers, particularly under race conditions and throughout entire races. To address the problem, this study proposes and assesses a method for determining skier kinetics with a single lightweight differential global navigation satellite system (dGNSS). The dGNSS kinetic method was compared to a reference system for six skiers and two turns each. The pattern differences obtained between the measurement systems (offset ± SD) were -26 ± 152 N for the ground reaction force, 1 ± 96 N for ski friction and -6 ± 6 N for the air drag force. The differences between turn means were small. The error pattern within the dGNSS kinetic method was highly repeatable and precision was therefore good (SD within system: 63 N ground reaction force, 42 N friction force and 7 N air drag force) allowing instantaneous relative comparisons and identification of discriminative meaningful changes. The method is therefore highly valid in assessing relative differences between skiers in the same turn, as well as turn means between different turns. The system is suitable to measure large capture volumes under race conditions. PMID:23917257

  4. Ground water

    There is growing evidence that the Nation's ground water is contaminated by a variety of sources. These include unprotected industrial, municipal, and radioactive disposal sites, petroleum exploration and mining activities, agricultural operations such as insecticide spraying, high de-icing salts and others. As of March 1980, more than 8000 chemical tests have been performed on well water, with chlorinated organic solvents found most frequently. Because 100 million Americans may be threatened by unfit drinking water, EPA has developed a new ground water strategy. It will enlist the help of State and local governments who already have programs under way and it will involve broad public debate and participation

  5. Accurate Hellman-Feynman force method for the study of the first and second derivatives of potential energy hypersurface

    The authors review the method of calculating a reliable H-F-force, starting from the underlying theorem, and examine the accuracy of calculated H-F force. The authors then show some recent applications of the method to geometry optimizations of the molecules in ground and excited states and of the transition state of a chemical reaction. Further, when the H-F theorum is used, an analytic expression of the second derivative becomes much simpler than a straightforward second derivative of the energy. The authors report calculations of force constants by this method and explain the electronic origins of the second derivatives

  6. Dispersion Forces

    Buhmann, Stefan Yoshi

    2012-01-01

    In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...

  7. On Grounding of Fast Ships

    Simonsen, Bo Cerup; Pedersen, Preben Terndrup

    1997-01-01

    loads during grounding on plane, sloping, sandy bottoms for six different designs of fast monohull ships made from steel, aluminium or GRP sandwich materials. The results show that the effect of the hull flexibility is to reduce the overall dynamic sectional loads on the hull girder. The considered......The paper deals with analysis of grounding of high-speed crafts. It is the purpose to present a comprehensive mathematical model for calculation of the overall dynamic ship response during grounding. This procedure is applied to derive the motions, the time varying sectional forces and the local...... numerical examples also indicate that, even with impact speeds of 40 knots against a 1:10 sloping bottom, the global strength of the hull girder is not exceeded by the grounding induced loads.For the local deformation of high-speed ship hulls at the point of contact with the ground, the paper presents...

  8. Survival of the Fittest: Competitive Co-crystal Reactions in the Ball Mill.

    Fischer, Franziska; Joester, Maike; Rademann, Klaus; Emmerling, Franziska

    2015-10-12

    The driving forces triggering the formation of co-crystals under milling conditions were investigated by using a set of multicomponent competitive milling reactions. In these reactions, different active pharmaceutical ingredients were ground together with a further compound acting as coformer. The study was based on new co-crystals including the coformer anthranilic acid. The results of the competitive milling reactions indicate that the formation of co-crystals driven by intermolecular recognition are influenced and inhibited by kinetic aspects including the formation of intermediates and the stability of the reactants. PMID:26332316

  9. Force sensing

    Sanders, David

    2007-01-01

    A young child can explore and learn and compensate for unknown dynamics by prodding, pushing, touching, grasping and feeling. Force sensing and software research could soon allow artificial mechanisms to do the same. Force sensing has its roots in strain gauges, piezoelectrics, Wheatstone bridges, automation, robotics, grippers and virtual reality. That force sensing research has now become commonplace and has expanded from those roots to include so much more: video games, athletic equipment,...

  10. Ground Pollution Science

    This book deals with ground pollution science and soil science, classification of soil and fundamentals, ground pollution and human, ground pollution and organic matter, ground pollution and city environment, environmental problems of the earth and ground pollution, soil pollution and development of geological features of the ground, ground pollution and landfill of waste, case of measurement of ground pollution.

  11. Modelo dinâmico de simulação e otimização da força normal de reação do solo para um mecanismo de corte basal Dynamic model of simulation and optimization of the normal force of soil reaction for a mechanism of base cutter

    Carlos E. S. Volpato

    2005-08-01

    Full Text Available O modelo físico foi baseado no método de Newton-Euler, sendo o mesmo desenvolvido utilizando o programa computacional científico Mathematica®. Realizaram-se várias simulações, nas quais se procurou obter a força normal de reação do solo variando velocidades de avanço (0,69; 1,12; 1,48; 1,82 e 2,12 m s-1; perfis de solo (senoidal, rampa ascendente e descendente e altura do camalhão (0,025 e 0,05 m. Após as simulações iniciais, o mecanismo foi otimizado utilizando o programa computacional científico Matlab®, tendo como critério (função-objetivo a minimização da força normal de reação do perfil (F N e como variáveis de projeto os comprimentos das barras (L1y, L2, l3 e L4, altura da operação (L7, o comprimento inicial da mola (Lmo e a constante elástica da mola (k t. A falta de robustez do mecanismo em relação à variável altura de operação foi contornada por meio do uso de mola com baixa rigidez e grande comprimento. Os resultados demonstraram que o mecanismo otimizado obteve desempenho de flutuação muito bom, em relação ao mecanismo inicial.The physical model was based on the method of Newton-Euler. The model was developed by using the scientific computer program Mathematica®. Several simulations where tried varying the progress speeds (0.69; 1.12; 1.48; 1.82 and 2.12 m s-1; soil profiles (sinoidal, ascending and descending ramp and height of the profile (0.025 and 0.05 m to obtain the normal force of soil reaction. After the initial simulations, the mechanism was optimized using the scientific computer program Matlab® having as criterion (function-objective the minimization of the normal force of reaction of the profile (FN. The project variables were the lengths of the bars (L1y, L2, l3 and L4, height of the operation (L7, the initial length of the spring (Lmo and the elastic constant of the spring (k t. The lack of robustness of the mechanism in relation to the variable height of the operation was outlined by using a spring with low rigidity and large length. The results demonstrated that the mechanism optimized showed better flotation performance in relation to the initial mechanism.

  12. Modelo 3D para quantificação das forças articulares e momentos proximais resultantes para o membro superior / 3D model for analysis of resultant proximal reaction forces and moments for the upper limb

    Daniel Cury, Ribeiro; Jefferson Fagundes, Loss.

    Full Text Available Objetivos: Este estudo teve como objetivo implementar um modelo biomecânico, de segmentos articulados, associado à dinâmica inversa que permita a análise em três dimensões das forças de reação proximais e momentos proximais resultantes para diferentes gestos do membro superior. Método: Os gestos ava [...] liados foram: flexão, extensão e abdução de ombro e flexão de cotovelo, os quais foram realizados por um indivíduo do sexo masculino. O modelo implementado é composto por cinco segmentos rígidos (mão, antebraço, braço, escápula e tronco) conectados. As equações de movimento de Newton-Euler foram utilizadas para quantificação das forças e momentos proximais resultantes. Para registro cinemático foram utilizadas cinco câmeras digitais, com freqüência de amostragem de 50 campos/seg. A precisão estimada do sistema de videogrametria foi, em média, de 1,7 mm. Foi monitorada a atividade eletromiográfica dos músculos deltóide (anterior, médio e posterior), bíceps braquial, tríceps braquial e peitoral maior. O modelo foi avaliado através da comparação qualitativa dos resultados de momento proximal resultante, com a atividade eletromiográfica. Resultados: Os resultados sugerem que o modelo apresenta resultados coerentes. O sinal eletromiográfico e o momento proximal apresentam sincronismo temporal. Conclusão: O modelo foi capaz de estimar as forças de reacção e momentos proximais resultantes nos diferentes gestos. Abstract in english Objectives: The aim of this study was to implement a biomechanical model, with linked segments associated with inverse dynamics, to analyze proximal net forces and moments during different upper limbs’ activities. Methods: one male subject performed flexion, extension and abduction of the shoulder a [...] nd flexion of the elbow. The model is composed of five connected rigid segments (hand, forearm, arm, scapula and trunk). The Newton-Euler motion equations were used to quantify proximal net reaction forces and moments. For kinematics recording, five cameras with a frequency sample of 50 fps were used. Videogrammetry accuracy was, on average, 1,7mm. The following muscles had their activities monitored: deltoid (anterior, medial, posterior), biceps brachialis, triceps brachialis, pectoralis major. The model was evaluated by qualitative comparison of proximal net moments with electromyographic signal of agonist muscles. Results: The results showed a temporal synchronism between the proximal net moments and agonist EMG activity. Conclusions: The model was able to estimate proximal net forces and moments during different upper limbs’ activities.

  13. Different forces

    1982-01-01

    The different forces, together with a pictorial analogy of how the exchange of particles works. The table lists the relative strength of the couplings, the quanta associated with the force fields and the bodies or phenomena in which they have a dominant role.

  14. Strong Force

    Without the strong force, there could be no life. The carbon in living matter is synthesised in stars via the strong force. Lighter atomic nuclei become bound together in a process called nuclear fusion. A minor change in this interaction would make life impossible. As its name suggests, the strong force is the most powerful of the 4 forces, yet its sphere of influence is limited to within the atomic nucleus. Indeed it is the strong force that holds together the quarks inside the positively charged protons. Without this glue, the quarks would fly apart repulsed by electromagnetism. In fact, it is impossible to separate 2 quarks : so much energy is needed, that a second pair of quarks is produced. Text for the interactive: Can you pull apart the quarks inside a proton?

  15. Communication grounding facility

    It is about communication grounding facility, which is made up twelve chapters. It includes general grounding with purpose, materials thermal insulating material, construction of grounding, super strength grounding method, grounding facility with grounding way and building of insulating, switched grounding with No. 1A and LCR, grounding facility of transmission line, wireless facility grounding, grounding facility in wireless base station, grounding of power facility, grounding low-tenton interior power wire, communication facility of railroad, install of arrester in apartment and house, install of arrester on introduction and earth conductivity and measurement with introduction and grounding resistance.

  16. Weak Force

    Without the weak force, the sun wouldn't shine. The weak force causes beta decay, a form of radioactivity that triggers nuclear fusion in the heart of the sun. The weak force is unlike other forces: it is characterised by disintegration. In beta decay, a down quark transforms into an up quark and an electron is emitted. Some materials are more radioactive than others because the delicate balance between the strong force and the weak force varies depending on the number of particles in the atomic nucleus. We live in the midst of a natural radioactive background that varies from region to region. For example, in Cornwall where there is a lot of granite, levels of background radiation are much higher than in the Geneva region. Text for the interactive: Move the Geiger counter to find out which samples are radioactive - you may be surprised. It is the weak force that is responsible for the Beta radioactivity here. The electrons emitted do not cross the plastic cover. Why do you think there is some detected radioa...

  17. Acceleration capability in elite sprinters and ground impulse: Push more, brake less?

    Morin, Jean-Benoît; Slawinski, Jean; Dorel, Sylvain; de Villareal, Eduardo Saez; Couturier, Antoine; Samozino, Pierre; Brughelli, Matt; Rabita, Giuseppe

    2015-09-18

    Overground sprint studies have shown the importance of net horizontal ground reaction force impulse (IMPH) for acceleration performance, but only investigated one or two steps over the acceleration phase, and not in elite sprinters. The main aim of this study was to distinguish between propulsive (IMPH+) and braking (IMPH-) components of the IMPH and seek whether, for an expected higher IMPH, faster elite sprinters produce greater IMPH+, smaller IMPH-, or both. Nine high-level sprinters (100-m best times range: 9.95-10.60s) performed 7 sprints (2×10 m, 2×15 m, 20 m, 30 m and 40 m) during which ground reaction force was measured by a 6.60 m force platform system. By placing the starting-blocks further from the force plates at each trial, and pooling the data, we could assess the mechanics of an entire "virtual" 40-m acceleration. IMPH and IMPH+ were significantly correlated with 40-m mean speed (r=0.868 and 0.802, respectively; Pperformance. Similar results were obtained when considering these mechanical data averaged over the first half of the sprint, but not over the second half. In conclusion, faster sprinters were those who produced the highest amounts of horizontal net impulse per unit body mass, and those who "pushed more" (higher IMPH+), but not necessarily those who also "braked less" (lower IMPH-) in the horizontal direction. PMID:26209876

  18. Multiparticle transfer and frictional forces in heavy ion collisions

    We study the frictional forces in a low-energy heavy ion collision by solving the independent particle transfer between two potentials moving on prescribed trajectories. We conclude that, although one may extract both a tangential and a radial frictional force for the initial stage of the collision, they will be different in the final stage of the reaction and they depend on the shell structure. The strong coherence of the transfer process shows up in the probability of remaining in the initial ground state, which is strongly enhanced over the result obtained from incoherent transfer. This indicates that a measurement of the absorption in the entrance channel is a sensitive measure of the effect of two-body collisions and other relaxation mechanisms. (orig.)

  19. 'Grounded' Politics

    Schmidt, Garbi

    2012-01-01

    A prominent strand within current migration research argues that, to understand the participation of immigrants in their host societies, we must focus on their incorporation into the cities in which they settle. This article narrows the perspective further by focusing on the role that immigrants...... play within one particular neighbourhood: Nørrebro in the Danish capital, Copenhagen. The article introduces the concept of grounded politics to analyse how groups of Muslim immigrants in Nørrebro use the space, relationships and history of the neighbourhood for identity political statements. The...... article further describes how national political debates over the Muslim presence in Denmark affect identity political manifestations within Nørrebro. By using Duncan Bell’s concept of mythscape (Bell, 2003), the article shows how some political actors idealize Nørrebro’s past to contest the present...

  20. 'Grounded' Politics

    Schmidt, Garbi

    2012-01-01

    A prominent strand within current migration research argues that, to understand the participation of immigrants in their host societies, we must focus on their incorporation into the cities in which they settle. This article narrows the perspective further by focusing on the role that immigrants ...... ethnic and religious diversity of the neighbourhood and, further, to frame what they see as the deterioration of genuine Danish identity....... play within one particular neighbourhood: Nørrebro in the Danish capital, Copenhagen. The article introduces the concept of grounded politics to analyse how groups of Muslim immigrants in Nørrebro use the space, relationships and history of the neighbourhood for identity political statements. The...... article further describes how national political debates over the Muslim presence in Denmark affect identity political manifestations within Nørrebro. By using Duncan Bell’s concept of mythscape (Bell, 2003), the article shows how some political actors idealize Nørrebro’s past to contest the present...

  1. Modelling of Muscle Force Distributions During Barefoot and Shod Running.

    Sinclair, Jonathan; Atkins, Stephen; Richards, Jim; Vincent, Hayley

    2015-09-29

    Research interest in barefoot running has expanded considerably in recent years, based around the notion that running without shoes is associated with a reduced incidence of chronic injuries. The aim of the current investigation was to examine the differences in the forces produced by different skeletal muscles during barefoot and shod running. Fifteen male participants ran at 4.0 m·s-1 (± 5%). Kinematics were measured using an eight camera motion analysis system alongside ground reaction force parameters. Differences in sagittal plane kinematics and muscle forces between footwear conditions were examined using repeated measures or Freidman's ANOVA. The kinematic analysis showed that the shod condition was associated with significantly more hip flexion, whilst barefoot running was linked with significantly more flexion at the knee and plantarflexion at the ankle. The examination of muscle kinetics indicated that peak forces from Rectus femoris, Vastus medialis, Vastus lateralis, Tibialis anterior were significantly larger in the shod condition whereas Gastrocnemius forces were significantly larger during barefoot running. These observations provide further insight into the mechanical alterations that runners make when running without shoes. Such findings may also deliver important information to runners regarding their susceptibility to chronic injuries in different footwear conditions. PMID:26557186

  2. Modelling of Muscle Force Distributions During Barefoot and Shod Running

    Sinclair Jonathan

    2015-09-01

    Full Text Available Research interest in barefoot running has expanded considerably in recent years, based around the notion that running without shoes is associated with a reduced incidence of chronic injuries. The aim of the current investigation was to examine the differences in the forces produced by different skeletal muscles during barefoot and shod running. Fifteen male participants ran at 4.0 m·s-1 (± 5%. Kinematics were measured using an eight camera motion analysis system alongside ground reaction force parameters. Differences in sagittal plane kinematics and muscle forces between footwear conditions were examined using repeated measures or Freidman’s ANOVA. The kinematic analysis showed that the shod condition was associated with significantly more hip flexion, whilst barefoot running was linked with significantly more flexion at the knee and plantarflexion at the ankle. The examination of muscle kinetics indicated that peak forces from Rectus femoris, Vastus medialis, Vastus lateralis, Tibialis anterior were significantly larger in the shod condition whereas Gastrocnemius forces were significantly larger during barefoot running. These observations provide further insight into the mechanical alterations that runners make when running without shoes. Such findings may also deliver important information to runners regarding their susceptibility to chronic injuries in different footwear conditions.

  3. Common muscle synergies for control of center of mass and force in nonstepping and stepping postural behaviors

    Chvatal, Stacie A.; Torres-Oviedo, Gelsy; Safavynia, Seyed A.; Ting, Lena H.

    2011-01-01

    We investigated muscle activity, ground reaction forces, and center of mass (CoM) acceleration in two different postural behaviors for standing balance control in humans to determine whether common neural mechanisms are used in different postural tasks. We compared nonstepping responses, where the base of support is stationary and balance is recovered by returning CoM back to its initial position, with stepping responses, where the base of support is enlarged and balance is recovered by pushi...

  4. Nuclear reactions

    This chapter of the textbook overviews nuclear reactions discussing the reaction mechanisms and the types of nuclear reactions, e.g. those induced by neutrons, by protons, by alpha particles and gamma photons, and finally, deuteron and thermonuclear reactions

  5. Effect of increased pushoff during gait on hip joint forces.

    Lewis, Cara L; Garibay, Erin J

    2015-01-01

    Anterior acetabular labral tears and anterior hip pain may result from high anteriorly directed forces from the femur on the acetabulum. While providing more pushoff is known to decrease sagittal plane hip moments, it is unknown if this gait modification also decreases hip joint forces. The purpose of this study was to determine if increasing pushoff decreases hip joint forces. Nine healthy subjects walked on an instrumented force treadmill at 1.25 m/s under two walking conditions. For the natural condition, subjects were instructed to walk as they normally would. For the increased pushoff condition, subjects were instructed to "push more with your foot when you walk". We collected motion data of markers placed on the subjects' trunk and lower extremities to capture trunk and leg kinematics and ground reaction force data to determine joint moments. Data were processed in Visual3D to produce the inverse kinematics and model scaling files. In OpenSim, the generic gait model (Gait2392) was scaled to the subject, and hip joint forces were calculated for the femur on the acetabulum after computing the muscle activations necessary to reproduce the experimental data. The instruction to "push more with your foot when you walk" reduced the maximum hip flexion and extension moment compared to the natural condition. The average reduction in the hip joint forces were 12.5%, 3.2% and 9.6% in the anterior, superior and medial directions respectively and 2.3% for the net resultant force. Increasing pushoff may be an effective gait modification for people with anterior hip pain. PMID:25468661

  6. A superellipsoid-plane model for simulating foot-ground contact during human gait.

    Lopes, D S; Neptune, R R; Ambrósio, J A; Silva, M T

    2016-07-01

    Musculoskeletal models and forward dynamics simulations of human movement often include foot-ground interactions, with the foot-ground contact forces often determined using a constitutive model that depends on material properties and contact kinematics. When using soft constraints to model the foot-ground interactions, the kinematics of the minimum distance between the foot and planar ground needs to be computed. Due to their geometric simplicity, a considerable number of studies have used point-plane elements to represent these interacting bodies, but few studies have provided comparisons between point contact elements and other geometrically based analytical solutions. The objective of this work was to develop a more general-purpose superellipsoid-plane contact model that can be used to determine the three-dimensional foot-ground contact forces. As an example application, the model was used in a forward dynamics simulation of human walking. Simulation results and execution times were compared with a point-like viscoelastic contact model. Both models produced realistic ground reaction forces and kinematics with similar computational efficiency. However, solving the equations of motion with the surface contact model was found to be more efficient (~18% faster), and on average numerically ~37% less stiff. The superellipsoid-plane elements are also more versatile than point-like elements in that they allow for volumetric contact during three-dimensional motions (e.g. rotating, rolling, and sliding). In addition, the superellipsoid-plane element is geometrically accurate and easily integrated within multibody simulation code. These advantages make the use of superellipsoid-plane contact models in musculoskeletal simulations an appealing alternative to point-like elements. PMID:26325481

  7. Flexible propulsors in ground effect

    We present experimental evidence for the hydrodynamic benefits of swimming ‘in ground effect’, that is, near a solid boundary. This situation is common to fish that swim near the substrate, especially those that are dorsoventrally compressed, such as batoids and flatfishes. To investigate flexible propulsors in ground effect, we conduct force measurements and particle image velocimetry on flexible rectangular panels actuated at their leading edge near the wall of a water channel. For a given actuation mode, the panels swim faster near the channel wall while maintaining the same propulsive economy. In conditions producing net thrust, panels produce more thrust near the ground. When operating in resonance, swimming near the ground can also increase propulsive efficiency. Finally, the ground can act to suppress three-dimensional modes, thereby increasing thrust and propulsive efficiency. The planform considered here is non-biological, but the hydrodynamic benefits are likely to apply to more complex geometries, especially those where broad flexible propulsors are involved such as fish bodies and fins. Such fish could produce more thrust by swimming near the ground, and in some cases do so more efficiently. (paper)

  8. Allergic reactions

    ... may recommend over-the-counter medications, such as antihistamines. For a severe allergic reaction (anaphylaxis), check the ... reaction is getting worse. The person has a history of severe allergic reactions (check for a medical ...

  9. Forcing isomorphism

    Baldwin, J T; Shelah, S; Baldwin, John T.; Laskowski, Michael C.; Shelah, Saharon

    1993-01-01

    A forcing extension may create new isomorphisms between two models of a first order theory. Certain model theoretic constraints on the theory and other constraints on the forcing can prevent this pathology. A countable first order theory is classifiable if it is superstable and does not have either the dimensional order property or the omitting types order property. Shelah [Sh:c] showed that if a theory T is classifiable then each model of cardinality lambda is described by a sentence of L_{infty, lambda}. In fact this sentence can be chosen in the L^*_{lambda}. (L^*_{lambda} is the result of enriching the language L_{infty, beth^+} by adding for each mu < lambda a quantifier saying the dimension of a dependence structure is greater than mu .) The truth of such sentences will be preserved by any forcing that does not collapse cardinals <= lambda and that adds no new countable subsets of lambda. Hence, if two models of a classifiable theory of power lambda are non-isomorphic, they are non-isomorphic afte...

  10. A new bi-axial cantilever beam design for biomechanics force measurements.

    Lin, Huai-Ti; Trimmer, Barry A

    2012-08-31

    The demand for measuring forces exerted by animals during locomotion has increased dramatically as biomechanists strive to understand and implement biomechanical control strategies. In particular, multi-axial force transducers are often required to capture animal limb coordination patterns. Most existing force transducers employ strain gages arranged in a Wheatstone bridge on a cantilever beam. Bi-axial measurements require duplicating this arrangement in the transverse direction. In this paper, we reveal a method to embed a Wheatstone bridge inside another to allow bi-axial measurements without additional strain gages or additional second beams. This hybrid configuration resolves two force components from a single bridge circuit and simplifies fabrication for the simultaneous assessment of normal and transverse loads. This design can be implemented with two-dimensional fabrication techniques and can even be used to modify a common full bridge cantilever force transducer. As a demonstration of the new design, we built a simple beam which achieved bi-axial sensing capability that outperformed a conventional half-bridge-per-axis bi-axial strain gage design. We have used this design to measure the ground reaction forces of a crawling caterpillar and a caterpillar-mimicking soft robot. The simplicity and increased sensitivity of this method could facilitate bi-axial force measurements for experimental biologists. PMID:22776687

  11. Transition States from Empirical Force Fields

    Jensen, Frank; Norrby, Per-Ola

    2003-01-01

    This is an overview of the use of empirical force fields in the study of reaction mechanisms. EVB-type methods (including RFF and MCMM) produce full reaction surfaces by mixing, in the simplest case, known force fields describing reactants and products. The SEAM method instead locates approximate...... transition structures by energy minimization along the intersection of the component force fields. The TSFF approach (including Q2MM) designs a new force field mimicking the transition structure as an energy minimum. The scope and applicability of the various methods are compared....

  12. Joining Forces

    Christiansen, Anne Mette

    The interest in Corporate Social Responsibility (CSR) has grown dramatically over the last three years in Greenland. A vast geographical area with a tiny population, Greenland has recently obtained self-government status and is going through a rapid development economically and socially as the...... country moves towards embracing extractive industries (oil, gas and mining) as a path to development. Both government, civil society and business are increasingly looking for new and innovative ways of joining forces across sectors to solve some of the country's many critical social issues. Greenlandic...

  13. Design Optimization of Ground Clearance of Domestic Cars

    Debojyoti Mitra

    2010-07-01

    Full Text Available Drag and lift forces plays a vital role in the performance and stability of vehicles. Less drag means less fuel consumption and hence less vehicular pollution. Also, lower lift force means higher chance of adhesion of the car body with the ground causing less overturning of the vehicle, which improves the vehicle performance. Both drag and lift forces can be manipulated by varying the ground clearance of the cars. The present study concentrates on studying the effect of ground clearance on these aerodynamic forces experimentally. Wind tunnel studies with a notch-back car model revealed increase in drag and decrease in lift with increase in ground clearance. Therefore, optimization is required for designing the best ground clearance and a preferable value of the same is thus obtained.

  14. Estimation of joint forces and moments for the in-run and take-off in ski jumping based on measurements with wearable inertial sensors.

    Logar, Grega; Munih, Marko

    2015-01-01

    This study uses inertial sensors to measure ski jumper kinematics and joint dynamics, which was until now only a part of simulation studies. For subsequent calculation of dynamics in the joints, a link-segment model was developed. The model relies on the recursive Newton-Euler inverse dynamics. This approach allowed the calculation of the ground reaction force at take-off. For the model validation, four ski jumpers from the National Nordic center performed a simulated jump in a laboratory environment on a force platform; in total, 20 jumps were recorded. The results fit well to the reference system, presenting small errors in the mean and standard deviation and small root-mean-square errors. The error is under 12% of the reference value. For field tests, six jumpers participated in the study; in total, 28 jumps were recorded. All of the measured forces and moments were within the range of prior simulated studies. The proposed system was able to indirectly provide the values of forces and moments in the joints of the ski-jumpers' body segments, as well as the ground reaction force during the in-run and take-off phases in comparison to the force platform installed on the table. Kinematics assessment and estimation of dynamics parameters can be applied to jumps from any ski jumping hill. PMID:25985167

  15. Estimation of Joint Forces and Moments for the In-Run and Take-Off in Ski Jumping Based on Measurements with Wearable Inertial Sensors

    Grega Logar

    2015-05-01

    Full Text Available This study uses inertial sensors to measure ski jumper kinematics and joint dynamics, which was until now only a part of simulation studies. For subsequent calculation of dynamics in the joints, a link-segment model was developed. The model relies on the recursive Newton–Euler inverse dynamics. This approach allowed the calculation of the ground reaction force at take-off. For the model validation, four ski jumpers from the National Nordic center performed a simulated jump in a laboratory environment on a force platform; in total, 20 jumps were recorded. The results fit well to the reference system, presenting small errors in the mean and standard deviation and small root-mean-square errors. The error is under 12% of the reference value. For field tests, six jumpers participated in the study; in total, 28 jumps were recorded. All of the measured forces and moments were within the range of prior simulated studies. The proposed system was able to indirectly provide the values of forces and moments in the joints of the ski-jumpers’ body segments, as well as the ground reaction force during the in-run and take-off phases in comparison to the force platform installed on the table. Kinematics assessment and estimation of dynamics parameters can be applied to jumps from any ski jumping hill.

  16. Cluster forcing

    Christensen, Thomas Budde

    The cluster theory attributed to Michael Porter has significantly influenced industrial policies in countries across Europe and North America since the beginning of the 1990s. Institutions such as the EU, OECD and the World Bank and governments in countries such as the UK, France, The Netherlands......, Portugal and New Zealand have adopted the concept. Public sector interventions that aim to support cluster development in industries most often focus upon economic policy goals such as enhanced employment and improved productivity, but rarely emphasise broader societal policy goals relating to e.......g. sustainability or quality of life. The purpose of this paper is to explore how and to what extent public sector interventions that aim at forcing cluster development in industries can support sustainable development as defined in the Brundtland tradition and more recently elaborated in such concepts as eco...

  17. The Introduction of Fields in Relation to Force

    Brunt, Marjorie; Brunt, Geoff

    2012-01-01

    The introduction of force at age 14-16 years is considered, starting with elementary student experiments using magnetic force fields. The meaningless use of terms such as "action" and "reaction", or "agent" and "receiver" is discussed. (Contains 6 figures.)

  18. Radiation Reaction at Extreme Intensity

    Richard T. Hammond

    2008-03-01

    Full Text Available The radiation reaction force is examined for an idealized short pulse ofelectromagnetic radiation and for a plane wave. Exact solutions (without radiation reactionare discussed, the total radiated power is calculated. A new and simpler approach to theapproximate form of the equation of motion is presented that automatically removes the runawaysolutions. Finally, analytical solutions are presented for the equations of motion that includethe radiation reaction forces in the very high intensity regime. A classical scattering angle isde¯ned and it shows that the electron is scattered in a small cone in the forward direction. Theradiation reaction corrections to this angle are also considered.

  19. Seismic Analysis of Elevated Water Storage Tanks Subjected to Six Correlated Ground Motion Components

    L. Kalani Sarokolayi

    2013-01-01

    Full Text Available In this work, rotational components of ground motion acceleration were defined according toimproved method from the corresponding available translational components based on transversely isotropicelastic wave propagation in the soil. With such improvement, it becomes possible to consider frequencydependent wave velocities on rotational components of ground motion. For this purpose, three translationalcomponents of El Centro earthquake (24 January 1951 were adopted to generate their relative rotationalcomponents based on SV and SH wave incidence by Fast Fourier transform with 4096 discrete frequencies.The translational and computed rotational motions were then applied to the concrete elevated water storagetanks with different structural characteristics and water elevations. The finite element method is used for thenonlinear analysis of water storage tanks considering the fluid-structure interaction using Lagrangian-Lagrangian approach and the concrete material nonlinearities have been taken into account through William-Warnke model. The nonlinear response of these structures considering the six components of ground motionshowed that the rotational components of ground motion can increase or decrease the maximum displacementand reaction force of the structure. These variations are depending on the frequency of structure andpredominant frequencies of translational and rotational components of ground motion.

  20. Ground water and energy

    1980-11-01

    This national workshop on ground water and energy was conceived by the US Department of Energy's Office of Environmental Assessments. Generally, OEA needed to know what data are available on ground water, what information is still needed, and how DOE can best utilize what has already been learned. The workshop focussed on three areas: (1) ground water supply; (2) conflicts and barriers to ground water use; and (3) alternatives or solutions to the various issues relating to ground water. (ACR)

  1. New experimental approach to modern three-nucleon forces

    Spin observables in proton deuteron breakup reactions at low energies offer a rich testing ground for the modern theory of nuclear forces, the chiral effective field theory (EFT). In the three-nucleon continuum the experimental data and the theoretical predictions are today at variance. At the PAX facility at COSY we plan to make an extensive study of analyzing powers and spin correlation parameters in pd breakup reactions at low energies between 30 and 50 MeV, an energy range where previous measurements are scarce and limited while three-nucleon effects are expected to be significant. Furthermore it is an ideal energy for the predictive power of chiral EFT to be tested. The longstanding physics question of the nature of three-nucleon forces will be studied with large coverage provided by an optimized silicon detector barrel, and flexibility utilizing the sampling method, a technique for direct comparison between experiment and theory developed specifically for the complex analysis of three-particle final states. The proposed experiment will yield an independent determination of the low-energy constants D and E and enable tests of appearing three-nucleon interactions in chiral EFT, with possible implications also for the spectra of light nuclei.

  2. Ground Assisted Onboard Planning Autonomy with VAMOS

    Wörle, Maria Theresia; Lenzen, Christoph

    2013-01-01

    The typical ground based mission planning system for a low earth satellite mission has one major drawback: The reaction time to onboard detected events includes at least the two upcoming ground station contacts. To address this disadvantage, DLR/GSOC implements the software experiment VAMOS as part of the FireBIRD mission, in which mission planning autonomy will be transferred to the spacecraft up to some extent. This paper presents the outcome of the VAMOS design phas...

  3. XMM Future Operational Ground Segment

    Finn, T.; Kirsch, M.; Schmidt, F.; Pfeil, N.; Vasconcellos, A.; Martin, J.

    2014-07-01

    XMM-Newton has been operating for 14 years which have been characterised by an extraordinary scientific return leading to it being considered as one of the most important scientific missions operated by ESA. XMM-Newton has outlived its original operating lifetime and this has led to a new array of technical challenges which new software and operating strategies have greatly mitigated and have enabled XMM-Newton to continue to perform optimally. XMM-Newton relies on reaction wheels and thrusters to manoeuvre consuming on -board fuel and limiting XMM-Newtons operating life. As a result a new operating concept for the reaction wheels has been devised and reduces the fuel consumption by approximately 50% potentially allowing XMM-Newton to operate until 2028. This extension leads to a new set of challenges; firstly, a change in the orbital inclination causes XMM-Newtons ground station Kourou to develop a gap in coverage around perigee for a period of 5 years from mid-2014 and secondly, XMM-Newtons second prime ground station, Perth, is to be decommissioned at the end of 2015 due to regulation governing civil spectrum usage. This paper illustrates how these issues are resoled from a ground segment perspective and when implemented will ensure XMM-Newtons continuance into the next decade.

  4. Nuclear reactions

    In reviewing work at Harwell over the past 25 years on nuclear reactions it is stated that a balance has to be struck in both experiment and theory between work on cross-sections of direct practical relevance to reactors and on those relevant to an overall understanding of reaction processes. The compound nucleus and direct process reactions are described. Having listed the contributions from AERE, Harwell to developments in nuclear reaction research in the period, work on the optical model, neutron capture theory, reactions at doorway states with fine structure, and sum-rules for spectroscopic factors are considered in more detail. (UK)

  5. Ground state correlations and electron scattering

    The effect of random phase ground state correlations on charge densities and elastic electron scattering cross sections is studied for 208Pb and 40Ca. Modifications of the charge densities relative to densities obtained by Hartree-Fock calculations with a density dependent force are studied using different RPA wave functions. The differences with respect to the HF charge distributions are discussed. (orig.)

  6. Electrical Subsurface Grounding Analysis

    The purpose and objective of this analysis is to determine the present grounding requirements of the Exploratory Studies Facility (ESF) subsurface electrical system and to verify that the actual grounding system and devices satisfy the requirements

  7. Parental Reactions to Cleft Palate Children.

    Vanpoelvoorde, Leah

    This literature review examines parental reactions following the birth of a cleft lip/palate child, focusing primarily on the mother's reactions. The research studies cited have explored such influences on maternal reactions as her feelings of lack of control over external forces and her feelings of guilt that the deformity was her fault. Delays…

  8. The Metaphysics of Grounding

    Clark, Michael John

    2013-01-01

    The phrase ‘in virtue of’ is a mainstay of metaphysical discourse. In recent years, many philosophers have argued that we should understand this phrase, as metaphysicians use it, in terms of a concept of metaphysical dependence called ‘grounding’.This dissertation explores a range of central issues in the theory of grounding. Chapter 1 introduces the intuitive concept of grounding and discusses some compulsory questions in the theory of grounding. Chapter 2 focusses on scepticism on grounding...

  9. The ground based plan

    The paper presents a report of ''The Ground Based Plan'' of the United Kingdom Science and Engineering Research Council. The ground based plan is a plan for research in astronomy and planetary science by ground based techniques. The contents of the report contains a description of:- the scientific objectives and technical requirements (the basis for the Plan), the present organisation and funding for the ground based programme, the Plan, the main scientific features and the further objectives of the Plan. (U.K.)

  10. Feed forward and feedback control for over-ground locomotion in anaesthetized cats

    Mazurek, K. A.; Holinski, B. J.; Everaert, D. G.; Stein, R. B.; Etienne-Cummings, R.; Mushahwar, V. K.

    2012-04-01

    The biological central pattern generator (CPG) integrates open and closed loop control to produce over-ground walking. The goal of this study was to develop a physiologically based algorithm capable of mimicking the biological system to control multiple joints in the lower extremities for producing over-ground walking. The algorithm used state-based models of the step cycle each of which produced different stimulation patterns. Two configurations were implemented to restore over-ground walking in five adult anaesthetized cats using intramuscular stimulation (IMS) of the main hip, knee and ankle flexor and extensor muscles in the hind limbs. An open loop controller relied only on intrinsic timing while a hybrid-CPG controller added sensory feedback from force plates (representing limb loading), and accelerometers and gyroscopes (representing limb position). Stimulation applied to hind limb muscles caused extension or flexion in the hips, knees and ankles. A total of 113 walking trials were obtained across all experiments. Of these, 74 were successful in which the cats traversed 75% of the 3.5 m over-ground walkway. In these trials, the average peak step length decreased from 24.9 ± 8.4 to 21.8 ± 7.5 (normalized units) and the median number of steps per trial increased from 7 (Q1 = 6, Q3 = 9) to 9 (8, 11) with the hybrid-CPG controller. Moreover, within these trials, the hybrid-CPG controller produced more successful steps (step length ? 20 cm ground reaction force ? 12.5% body weight) than the open loop controller: 372 of 544 steps (68%) versus 65 of 134 steps (49%), respectively. This supports our previous preliminary findings, and affirms that physiologically based hybrid-CPG approaches produce more successful stepping than open loop controllers. The algorithm provides the foundation for a neural prosthetic controller and a framework to implement more detailed control of locomotion in the future.

  11. Constructivist Grounded Theory?

    Barney G. Glaser, PhD, Hon. PhD

    2012-06-01

    Full Text Available AbstractI refer to and use as scholarly inspiration Charmaz’s excellent article on constructivist grounded theory as a tool of getting to the fundamental issues on why grounded theory is not constructivist. I show that constructivist data, if it exists at all, is a very, very small part of the data that grounded theory uses.

  12. Nuclear Reactions

    Bertulani, C. A.

    2009-01-01

    Nuclear reactions generate energy in nuclear reactors, in stars, and are responsible for the existence of all elements heavier than hydrogen in the universe. Nuclear reactions denote reactions between nuclei, and between nuclei and other fundamental particles, such as electrons and photons. A short description of the conservation laws and the definition of basic physical quantities is presented, followed by a more detailed account of specific cases: (a) formation and decay of compound nuclei;...

  13. Calculation of excitation functions of the 54,56,57,58Fe(, ) reaction from threshold to 30 MeV

    Damewan Suchiang; J Joseph Jeremiah; B M Jyrwa

    2014-10-01

    The cross-sections for the formation of 54,56,57,58Co in the 54,56,57,58Fe(, ) reaction from threshold to 30 MeV protons have been theoretically calculated using the TALYS-1.4 nuclear model code, whereby we have studied major nuclear reaction mechanisms, including direct, preequilibrium and compound nuclear reaction. Subsequently, the level density and shell damping parameters have been adjusted and at the same time, the odd–even effects are well comprehended. The excitation functions have been compared with experimental nuclear data. It is observed that the theoretical cross-sections match fairly well. Proton-induced reaction cross-sections provide clues to understand the nuclear structure and offers a good testing ground for ideas about nuclear forces. In addition, complete information in this field is very much required for application in accelerator-driven subcritical system.

  14. An improved model for tidally modulated grounding-line migration

    Tsai, Victor C.; Gudmundsson, G. Hilmar

    2015-01-01

    Understanding grounding-line dynamics is necessary for predictions of long-term ice-sheet stability. However, despite growing observations of the tidal influence on grounding-line migration, this short-timescale migration is poorly understood, with most modeling attempts assuming beam theory to calculate displacements. Here we present an improved model of tidal grounding-line migration that treats migration as an elastic fracture problem, forced by the additional ocean water press...

  15. The reaction of Xenopus laevis daudin (South African Toad) to linear accelerations

    Neubert, J.; Schatz, A.; Bromeis, B.; Briegleb, W.

    1994-08-01

    Preparing the German Spacelab Mission D-2 project ``Gravity Perception and Neuronal Plasticity'' - STATEX II - ground based experiments have been performed with larvae of the amphibian vertebrate Xenopus laevis Daud. to study the reactions to different levels of acceleration forces and profiles. The larvae have been exposed to accelerations of up to 5 g for different time periods using a modified laboratory centrifuge and the NIZEMI (Niedergeschwindigeits-Zentrifugen-Mikroskop) which allows direct observation and video documentation. The results will be discussed and compared with those of the D1-Mission, parabolic flights, and simulated weightlessness.

  16. Force- and moment-generating capacities of muscles in the distal forelimb of the horse.

    Brown, Nicholas A T; Pandy, Marcus G; Kawcak, Christopher E; McIlwraith, C Wayne

    2003-07-01

    A detailed musculoskeletal model of the distal equine forelimb was developed to study the influence of musculoskeletal geometry (i.e. muscle paths) and muscle physiology (i.e. force-length properties) on the force- and moment-generating capacities of muscles crossing the carpal and metacarpophalangeal joints. The distal forelimb skeleton was represented as a five degree-of-freedom kinematic linkage comprised of eight bones (humerus, radius and ulna combined, proximal carpus, distal carpus, metacarpus, proximal phalanx, intermediate phalanx and distal phalanx) and seven joints (elbow, radiocarpal, intercarpal, carpometacarpal, metacarpophalangeal (MCP), proximal interphalangeal (pastern) and distal interphalangeal (coffin)). Bone surfaces were reconstructed from computed tomography scans obtained from the left forelimb of a Thoroughbred horse. The model was actuated by nine muscle-tendon units. Each unit was represented as a three-element Hill-type muscle in series with an elastic tendon. Architectural parameters specifying the force-producing properties of each muscle-tendon unit were found by dissecting seven forelimbs from five Thoroughbred horses. Maximum isometric moments were calculated for a wide range of joint angles by fully activating the extensor and flexor muscles crossing the carpus and MCP joint. Peak isometric moments generated by the flexor muscles were an order of magnitude greater than those generated by the extensor muscles at both the carpus and the MCP joint. For each flexor muscle in the model, the shape of the maximum isometric joint moment-angle curve was dominated by the variation in muscle force. By contrast, the moment-angle curves for the muscles that extend the MCP joint were determined mainly by the variation in muscle moment arms. The suspensory and check ligaments contributed more than half of the total support moment developed about the MCP joint in the model. When combined with appropriate in vivo measurements of joint kinematics and ground-reaction forces, the model may be used to determine muscle-tendon and joint-reaction forces generated during gait. PMID:12892409

  17. Inflight Performance of Cassini Reaction Wheel Bearing Drag in 1997-2013

    Lee, Allan Y.; Wang, Eric K.

    2013-01-01

    As the first spacecraft to achieve orbit at Saturn in 2004, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended missions through September 2017. Cassini is a three-axis stabilized spacecraft. It uses reaction wheels to achieve high level of spacecraft pointing stability that is needed during imaging operations of several science instruments. The Cassini flight software makes in-flight estimates of reaction wheel bearing drag torque and made them available to the mission operations team. These telemetry data are being trended for the purpose of monitoring the long-term health of the reaction wheel bearings. Anomalous drag torque signatures observed over the past 15 years are described in this paper. One of these anomalous drag conditions is bearing cage instability that appeared (and disappeared) spontaneously and unpredictably. Cage instability is an uncontrolled vibratory motion of the bearing cage that can produce high-impact forces internal to the bearing that will cause intermittent and erratic torque transients. Characteristics of the observed cage instabilities and other drag torque "spikes" are described in this paper. In day-to-day operations, the reaction wheels' rates must be neither too high nor too low. To protect against operating the wheels in any undesirable conditions (such as prolonged low spin rate operations), a ground software tool named Reaction Wheel Bias Optimization Tool (RBOT) was developed for the management of the wheels. Disciplined and long-term use of this ground software has led to significant reduction in the daily consumption rate of the wheels' low spin rate dwell time. Flight experience on the use of this ground software tool as well as other lessons learned on the management of Cassini reaction wheels is given in this paper.

  18. The swim force as a body force

    Yan, Wen; Brady, John

    2015-11-01

    Net (as opposed to random) motion of active matter results from an average swim (or propulsive) force. It is shown that the average swim force acts like a body force - an internal body force [Yan and Brady, Soft Matter, DOI:10.1039/C5SM01318F]. As a result, the particle-pressure exerted on a container wall is the sum of the swim pressure [Takatori et al., Phys. Rev. Lett., 2014, 113, 028103] and the `weight' of the active particles. A continuum mechanical description is possible when variations occur on scales larger than the run length of the active particles and gives a Boltzmann-like distribution from a balance of the swim force and the swim pressure. Active particles may also display `action at a distance' and accumulate adjacent to (or be depleted from) a boundary without any external forces. In the momentum balance for the suspension - the mixture of active particles plus fluid - only external body forces appear.

  19. Malaysia and forced migration

    Arzura Idris

    2012-01-01

    This paper analyzes the phenomenon of “forced migration” in Malaysia. It examines the nature of forced migration, the challenges faced by Malaysia, the policy responses and their impact on the country and upon the forced migrants. It considers forced migration as an event hosting multifaceted issues related and relevant to forced migrants and suggests that Malaysia has been preoccupied with the issue of forced migration movements. This is largely seen in various responses invoked from Malaysi...

  20. Handbook of force transducers

    Stefanescu, Dan Mihai

    2011-01-01

    Part I introduces the basic ""Principles and Methods of Force Measurement"" acording to a classification into a dozen of force transducers types: resistive, inductive, capacitive, piezoelectric, electromagnetic, electrodynamic, magnetoelastic, galvanomagnetic (Hall-effect), vibrating wires, (micro)resonators, acoustic and gyroscopic. Two special chapters refer to force balance techniques and to combined methods in force measurement. Part II discusses the ""(Strain Gauge) Force Transducers Components"", evolving from the classical force transducer to the digital / intelligent one, with the inco

  1. Electronic transitions and intermolecular forces

    This thesis describes two different subjects - electronic transitions and intermolecular forces - that are related mainly by the following observation: The wavenumber at which an electronic transition in an atom or molecule occurs, depends on the environment of that atom or molecule. This implies, for instance, that when a molecule becomes solvated its absorption spectrum may be shifted either to the blue or to the red side of the original gasphase spectrum. In part I attention is paid to the experimental aspects of VUV spectroscopy, both in the gasphase and in the condensed phase. In part II a series of papers are presented, dealing with the calculation of intermolecular forces (and some related topics) both for the ground state and for the excited state interactions, using different non-empirical methods. The calculations provide, among other results, a semiquantitative interpretation of the spectral blue shifts encountered in our experiments. (Auth.)

  2. A semimicroscopic model of nuclear vibrations with separable forces and the giant dipole resonsance of 12C

    In the generalized ph basis generated for the realistic nuclear ground state, the nuclear hamiltonian is approximated by an expression containing the separable effective forces and terms which can be estimated from the spectroscopic data. The model hamiltonian obtained is used to describe normal nuclear vibrations. The application of this approach in the shell-model theory of nuclear reactions is discussed. The S-matrix for nucleon-nucleus scattering is calculated explicitly. The 12C photodisintegration calculation is made as a test example. (orig.)

  3. Allergic Reactions

    ... rhinitis or asthma is present. Severe Allergic Reactions Anaphylaxis (an-a-fi-LAK-sis) is a serious, ... are to foods, insect stings, medications and latex. Anaphylaxis typically affects more than one part of the ...

  4. Calculating deformation of buildings on mining ground

    Anderman, F.; Fedorowicz, L.; Fedorowicz, J.

    1986-01-01

    Discusses a method for optimizing design of apartment buildings constructed in areas influenced by underground coal mining with caving and stowing. Effects of underground mining on ground subsidence and deformation are analyzed. Interaction of ground being deformed and building foundations and factors which influence this interaction are investigated. Behavior of construction elements (walls and partition walls, floors etc.) and forces which influence various elements are analyzed. Computer programs for calculating building deformation are characterized. Examples of calculating effects of underground coal mining on the W-70/SG apartment buildings constructed in Upper Silesia are analyzed. Recommendations for building construction in mining areas are made. 13 refs.

  5. Current status on design ground motion for buildings in Japan

    This paper firstly describes the design seismic force and design ground motion currently used in Japan. In the past, the static force representing the effect of earthquake motion on the structures was used directly for design. When computer technology advanced, and a precise analytical modelling became possible, analysis using time-dependent ground motion data became more common for seismic design analysis. The design static force is given considering some uncertainties due to variations of the ground motion properties, whereas the ground motion time history is regarded as a sample data picked up from the whole data set representing the average properties of design ground motions. In general, the design seismic force should be evaluated based on the ground motions corresponding to the site conditions and the specified occurrence rate of motion. However, the consideration of such characteristics has not been possible until recently, since the earthquake data was not sufficient and the simulation technique was not fully established either. These were made possible with many experiences of structural damage, accumulation of strong motion records with the recent advances in computing technology. Here, current evaluation practice of design ground motion is introduced and some problems to be solved in near future will be added. (author)

  6. Energy shift and Casimir-Polder force for an atom out of thermal equilibrium near a dielectric substrate

    Zhou, Wenting; Yu, Hongwei

    2014-09-01

    We study the energy shift and the Casimir-Polder force of an atom out of thermal equilibrium near the surface of a dielectric substrate. We first generalize, adopting the local source hypothesis, the formalism proposed by Dalibard, Dupont-Roc, and Cohen-Tannoudji [J. Phys. (Paris) 43, 1617 (1982), 10.1051/jphys:0198200430110161700; J. Phys. (Paris) 45, 637 (1984), 10.1051/jphys:01984004504063700], which separates the contributions of thermal fluctuations and radiation reaction to the energy shift and allows a distinct treatment of atoms in the ground and excited states, to the case out of thermal equilibrium, and then we use the generalized formalism to calculate the energy shift and the Casimir-Polder force of an isotropically polarizable neutral atom. We identify the effects of the thermal fluctuations that originate from the substrate and the environment and discuss in detail how the Casimir-Polder force out of thermal equilibrium behaves in three different distance regions in both the low-temperature limit and the high-temperature limit for both the ground-state and excited-state atoms, with special attention devoted to the distinctive features as opposed to thermal equilibrium. In particular, we recover the distinctive behavior of the atom-wall force out of thermal equilibrium at large distances in the low-temperature limit recently found in a different theoretical framework, and furthermore we give a concrete region where this behavior holds.

  7. Applying the cost of generating force hypothesis to uphill running

    Wouter Hoogkamer

    2014-07-01

    Full Text Available Historically, several different approaches have been applied to explain the metabolic cost of uphill human running. Most of these approaches result in unrealistically high values for the efficiency of performing vertical work during running uphill, or are only valid for running up steep inclines. The purpose of this study was to reexamine the metabolic cost of uphill running, based upon our understanding of level running energetics and ground reaction forces during uphill running. In contrast to the vertical efficiency approach, we propose that during incline running at a certain velocity, the forces (and hence metabolic energy required for braking and propelling the body mass parallel to the running surface are less than during level running. Based on this idea, we propose that the metabolic rate during uphill running can be predicted by a model, which posits that (1 the metabolic cost of perpendicular bouncing remains the same as during level running, (2 the metabolic cost of running parallel to the running surface decreases with incline, (3 the delta efficiency of producing mechanical power to lift the COM vertically is constant, independent of incline and running velocity, and (4 the costs of leg and arm swing do not change with incline. To test this approach, we collected ground reaction force (GRF data for eight runners who ran thirty 30-second trials (velocity: 2.0–3.0 m/s; incline: 0–9°. We also measured the metabolic rates of eight different runners for 17, 7-minute trials (velocity: 2.0–3.0 m/s; incline: 0–8°. During uphill running, parallel braking GRF approached zero for the 9° incline trials. Thus, we modeled the metabolic cost of parallel running as exponentially decreasing with incline. With that assumption, best-fit parameters for the metabolic rate data indicate that the efficiency of producing mechanical power to lift the center of mass vertically was independent of incline and running velocity, with a value of ?29%. The metabolic cost of uphill running is not simply equal to the sum of the cost of level running and the cost of performing work to lift the body mass against gravity. Rather, it reflects a constant cost of perpendicular bouncing, decreased costs of parallel braking and propulsion and of course the cost of lifting body mass against gravity.

  8. Modulating tibiofemoral contact force in the sheep hind limb via treadmill walking: Predictions from an opensim musculoskeletal model.

    Lerner, Zachary F; Gadomski, Benjamin C; Ipson, Allison K; Haussler, Kevin K; Puttlitz, Christian M; Browning, Raymond C

    2015-08-01

    Sheep are a predominant animal model used to study a variety of orthopedic conditions. Understanding and controlling the in-vivo loading environment in the sheep hind limb is often necessary for investigations relating to bone and joint mechanics. The purpose of this study was to develop a musculoskeletal model of an adult sheep hind limb and investigate the effects of treadmill walking speed on muscle and joint contact forces. We constructed the skeletal geometry of the model from computed topography images. Dual-energy x-ray absorptiometry was utilized to establish the inertial properties of each model segment. Detailed dissection and tendon excursion experiments established the requisite muscle lines of actions. We used OpenSim and experimentally-collected marker trajectories and ground reaction forces to quantify muscle and joint contact forces during treadmill walking at 0.25 m• s(-1) and 0.75 m• s(-1) . Peak compressive and anterior-posterior tibiofemoral contact forces were 20% (0.38 BW, p = 0.008) and 37% (0.17 BW, p = 0.040) larger, respectively, at the moderate gait speed relative to the slower speed. Medial-lateral tibiofemoral contact forces were not significantly different. Adjusting treadmill speed appears to be a viable method to modulate compressive and anterior-posterior tibiofemoral contact forces in the sheep hind limb. The musculoskeletal model is freely-available at www.SimTK.org. PMID:25721318

  9. Reaction Wheel Disturbance Model Extraction Software Project

    National Aeronautics and Space Administration — Reaction wheel mechanical noise is one of the largest sources of disturbance forcing on space-based observatories. Such noise arises from mass imbalance, bearing...

  10. Pesticides in Ground Water

    Bjerg, Poul Løgstrup

    1996-01-01

    Review af: Jack E. Barbash & Elizabeth A. Resek (1996). Pesticides in Ground Water. Distribution trends and governing factors. Ann Arbor Press, Inc. Chelsea, Michigan. pp 588.......Review af: Jack E. Barbash & Elizabeth A. Resek (1996). Pesticides in Ground Water. Distribution trends and governing factors. Ann Arbor Press, Inc. Chelsea, Michigan. pp 588....

  11. Stochastic ground motion simulation

    Rezaeian, Sanaz; Xiaodan, Sun

    2014-01-01

    Strong earthquake ground motion records are fundamental in engineering applications. Ground motion time series are used in response-history dynamic analysis of structural or geotechnical systems. In such analysis, the validity of predicted responses depends on the validity of the input excitations. Ground motion records are also used to develop ground motion prediction equations(GMPEs) for intensity measures such as spectral accelerations that are used in response-spectrum dynamic analysis. Despite the thousands of available strong ground motion records, there remains a shortage of records for large-magnitude earthquakes at short distances or in specific regions, as well as records that sample specific combinations of source, path, and site characteristics.

  12. A force calibration standard for magnetic tweezers

    Yu, Zhongbo; Dulin, David; Cnossen, Jelmer; Köber, Mariana; van Oene, Maarten M.; Ordu, Orkide; Berghuis, Bojk A.; Hensgens, Toivo; Lipfert, Jan; Dekker, Nynke H.

    2014-12-01

    To study the behavior of biological macromolecules and enzymatic reactions under force, advances in single-molecule force spectroscopy have proven instrumental. Magnetic tweezers form one of the most powerful of these techniques, due to their overall simplicity, non-invasive character, potential for high throughput measurements, and large force range. Drawbacks of magnetic tweezers, however, are that accurate determination of the applied forces can be challenging for short biomolecules at high forces and very time-consuming for long tethers at low forces below ˜1 piconewton. Here, we address these drawbacks by presenting a calibration standard for magnetic tweezers consisting of measured forces for four magnet configurations. Each such configuration is calibrated for two commonly employed commercially available magnetic microspheres. We calculate forces in both time and spectral domains by analyzing bead fluctuations. The resulting calibration curves, validated through the use of different algorithms that yield close agreement in their determination of the applied forces, span a range from 100 piconewtons down to tens of femtonewtons. These generalized force calibrations will serve as a convenient resource for magnetic tweezers users and diminish variations between different experimental configurations or laboratories.

  13. Modifying landing mat material properties may decrease peak contact forces but increase forefoot forces in gymnastics landings.

    Mills, Chris; Yeadon, Maurice R; Pain, Matthew T G

    2010-09-01

    This study investigated how changes in the material properties of a landing mat could minimise ground reaction forces (GRF) and internal loading on a gymnast during landing. A multi-layer model of a gymnastics competition landing mat and a subject-specific seven-link wobbling mass model of a gymnast were developed to address this aim. Landing mat properties (stiffness and damping) were optimised using a Simplex algorithm to minimise GRF and internal loading. The optimisation of the landing mat parameters was characterised by minimal changes to the mat's stiffness (<0.5%) but increased damping (272%) compared to the competition landing mat. Changes to the landing mat resulted in reduced peak vertical and horizontal GRF and reduced bone bending moments in the shank and thigh compared to a matching simulation. Peak bone bending moments within the thigh and shank were reduced by 6% from 321.5 Nm to 302.5Nm and GRF by 12% from 8626 N to 7552 N when compared to a matching simulation. The reduction in these forces may help to reduce the risk of bone fracture injury associated with a single landing and reduce the risk of a chronic injury such as a stress fracture. PMID:21162361

  14. Neutrino nuclear response and photo nuclear reaction

    Ejiri, H.; Titov, A. I.; Boswell, M.; Young, A

    2013-01-01

    Photo nuclear reactions are shown to be used for studying neutrino/weak nuclear responses involved in astro-neutrino nuclear interactions and double beta decays. Charged current weak responses for ground and excited states are studied by using photo nuclear reactions through isobaric analog states of those states, while neutral current weak responses for excited states are studied by using photo nuclear reactions through the excited states. The weak interaction strengths are studied by measur...

  15. Viscoelastic modelling of grounding line migration

    Beyer, Sebastian; Christmann, Julia; Müller, Ralf; Plate, Carolin; Rückamp, Martin; Humbert, Angelika

    2015-04-01

    Tides play an important role by moving ice shelves and modulating the flow of ice streams even far upstream the grounding line. The grounding line as the boundary between the shelf and the ice sheet plays a crucial role in the mass balance and general stability of an ice sheet. It has been observed to migrate in response to tidal forcing, but the exact mechanisms and consequences are not yet understood in detail. On short timescales, as present in tidal forcing, we need to account for the viscoelastic character of glacier ice and choose a Maxwell model as an appropriate rheological representation. A viscoelastic full stokes ice flow model was implemented in the finite element software COMSOL Multiphysics. We investigate the influence of tides on the dynamics of ice sheet--ice shelf systems and grounding line migration by means of numerical modelling. In our model we are able to identify two processes, which control ice flow variations with tides. Uplifting of the ice shelf leads to retreat of the grounding line and therefore less area of the ice base is in contact with the bedrock. This leads to smaller basal shear stress, resulting in an increase in flow velocity. Additionally high tide causes increased normal stress at the ice -- water boundary, which slows the ice flow. When forced with the S2 (12 h) and M2 (12.42 h) tidal constituents, we observe a non-linear interaction, which leads to a perturbation of the horizontal flow velocity close to the M_sf (14.76 d) constituent. By not including tides and viscoelasticity into ice models we commit significant errors for the estimation of the flux across the grounding line and the resulting mass balance. For our experimental setup this error depends on the elastic parameter and we obtain a maximal error of 3.75%. We also observe a general retreat of the grounding line due to tidal forcing. This implies that tides possibly lead to a different equilibrium of the grounding line position.

  16. Repulsive Casimir forces

    Kenneth, O.; Klich, I.; Mann, A.; Revzen, M.

    2002-01-01

    We discuss repulsive Casimir forces between dielectric materials with non trivial magnetic susceptibility. It is shown that considerations based on naive pair-wise summation of Van der Waals and Casimir Polder forces may not only give an incorrect estimate of the magnitude of the total Casimir force, but even the wrong sign of the force when materials with high dielectric and magnetic response are involved. Indeed repulsive Casimir forces may be found in a large range of parameters, and we su...

  17. Centrifugal force: an appreciation

    Kern E. Kenyon

    2011-01-01

    The centrifugal force is used to increase the physical understanding of five examples taken from fluid dynamics, geophysics and the solar system, as well as four hypothetical orbital problems. Each example involves a balance of forces between the centrifugal force and one or two other forces, such as a pressure gradient and a component of the force of gravity. Among the examples chosen for examination are: the orbital motion of fluid particles in surface grav-ity waves, the boundary layer cha...

  18. Surface and Interfacial Forces

    Butt, Hans-Jurgen

    2010-01-01

    This systematic introduction to the topic includes theoretical concepts to help readers understand and predict surface forces, while also integrating experimental techniques and practical applications with up-to-date examples plus motivating exercises. Starting with intermolecular forces, the authors discuss different surfaces forces, with a major part devoted to surface forces between solid surfaces in liquid media. In addition, they cover surface forces between liquid-vapor interfaces and between liquid-liquid interfaces.

  19. Convection in Drying and Freezing Ground

    Faizal, Mir

    2012-01-01

    In this paper we analyse the drying of a soil composed of particles, water and solute impurities, and study the occurrence of convective instabilities during evaporation. We find that the main driving force for instability is the formation of a concentration gradient at the soil surface due to the evaporation of water. A similar phenomenon may occur during the thawing of frozen ground in Arctic regions.

  20. Reaction mechanisms

    The 1988 progress report of the Reaction Mechanisms laboratory (Polytechnic School, France), is presented. The research topics are: the valence bond methods, the radical chemistry, the modelling of the transition states by applying geometric constraints, the long range interactions (ion - molecule) in gaseous phase, the reaction sites in gaseous phase and the mass spectroscopy applications. The points of convergence between the investigations of the mass spectroscopy and the theoretical chemistry teams, as well as the purposes guiding the research programs, are discussed. The published papers, the conferences, the congress communications and the thesis, are also reported

  1. Three-nucleon forces and the trinucleon bound states

    A summary of the bound-state working group session of the ''International Symposium on the Three-Body Force in the Three-Nucleon System'' is presented. The paper includes a discussion of presently used calculational techniques, experimental evidence for three-nucleon forces in trinucleon ground states, future directions in theoretical research and future experimental research

  2. Force Measurement on the GLAST Delta II Flight

    Gordon, Scott; Kaufman, Daniel

    2009-01-01

    This viewgraph presentation reviews the interface force measurement at spacecraft separation of GLAST Delta II. The contents include: 1) Flight Force Measurement (FFM) Background; 2) Team Members; 3) GLAST Mission Overview; 4) Methodology Development; 5) Ground Test Validation; 6) Flight Data; 7) Coupled Loads Simulation (VCLA & Reconstruction); 8) Basedrive Simulation; 9) Findings; and 10) Summary and Conclusions.

  3. Relational grounding facilitates development of scientifically useful multiscale models.

    Hunt, C Anthony; Ropella, Glen E P; Lam, Tai ning; Gewitz, Andrew D

    2011-01-01

    We review grounding issues that influence the scientific usefulness of any biomedical multiscale model (MSM). Groundings are the collection of units, dimensions, and/or objects to which a variable or model constituent refers. To date, models that primarily use continuous mathematics rely heavily on absolute grounding, whereas those that primarily use discrete software paradigms (e.g., object-oriented, agent-based, actor) typically employ relational grounding. We review grounding issues and identify strategies to address them. We maintain that grounding issues should be addressed at the start of any MSM project and should be reevaluated throughout the model development process. We make the following points. Grounding decisions influence model flexibility, adaptability, and thus reusability. Grounding choices should be influenced by measures, uncertainty, system information, and the nature of available validation data. Absolute grounding complicates the process of combining models to form larger models unless all are grounded absolutely. Relational grounding facilitates referent knowledge embodiment within computational mechanisms but requires separate model-to-referent mappings. Absolute grounding can simplify integration by forcing common units and, hence, a common integration target, but context change may require model reengineering. Relational grounding enables synthesis of large, composite (multi-module) models that can be robust to context changes. Because biological components have varying degrees of autonomy, corresponding components in MSMs need to do the same. Relational grounding facilitates achieving such autonomy. Biomimetic analogues designed to facilitate translational research and development must have long lifecycles. Exploring mechanisms of normal-to-disease transition requires model components that are grounded relationally. Multi-paradigm modeling requires both hyperspatial and relational grounding. PMID:21951817

  4. Relational grounding facilitates development of scientifically useful multiscale models

    Lam Tai

    2011-09-01

    Full Text Available Abstract We review grounding issues that influence the scientific usefulness of any biomedical multiscale model (MSM. Groundings are the collection of units, dimensions, and/or objects to which a variable or model constituent refers. To date, models that primarily use continuous mathematics rely heavily on absolute grounding, whereas those that primarily use discrete software paradigms (e.g., object-oriented, agent-based, actor typically employ relational grounding. We review grounding issues and identify strategies to address them. We maintain that grounding issues should be addressed at the start of any MSM project and should be reevaluated throughout the model development process. We make the following points. Grounding decisions influence model flexibility, adaptability, and thus reusability. Grounding choices should be influenced by measures, uncertainty, system information, and the nature of available validation data. Absolute grounding complicates the process of combining models to form larger models unless all are grounded absolutely. Relational grounding facilitates referent knowledge embodiment within computational mechanisms but requires separate model-to-referent mappings. Absolute grounding can simplify integration by forcing common units and, hence, a common integration target, but context change may require model reengineering. Relational grounding enables synthesis of large, composite (multi-module models that can be robust to context changes. Because biological components have varying degrees of autonomy, corresponding components in MSMs need to do the same. Relational grounding facilitates achieving such autonomy. Biomimetic analogues designed to facilitate translational research and development must have long lifecycles. Exploring mechanisms of normal-to-disease transition requires model components that are grounded relationally. Multi-paradigm modeling requires both hyperspatial and relational grounding.

  5. Simple Assessment of Post-Grounding Loads and Strength of Ships

    Paik, Jeom Kee; Pedersen, Preben Terndrup

    1997-01-01

    The aim of the present study is to determine the sectional forces induced by the ship grounding and also to assess the residual strength of grounded ship hulls. An analytical approach is used to estimate the grounding- induced sectional forces of ships. The extent and location of structural damage...... due to grounding is defined based on the ABS Safe Hull guide. The residual strength of damaged hulls is calculated by using a simple analytical formula. The method is applied to the residual strength assessment of a double-hull tanker of 38.400 dwt damaged due to grounding....

  6. Ground Source Heat Pumps

    Lale Valizade

    2013-01-01

    A heat pump is a device that is able to transfer heat from one fluid at a lower temperature to another at a higher temperature. Ground source heat pumps are generally classified by the type of ground loop. The coefficient of performance (COP) is used to define the heating performance of heat pumps. Both the COP and EER values are valid only at the specific test conditions used in the rating. A ground source pump could reach 450%, compared with an efficient gas boiler of 90% obviously this is ...

  7. Force modeling for incisions into various tissues with MRF haptic master

    Kim, Pyunghwa; Kim, Soomin; Park, Young-Dai; Choi, Seung-Bok

    2016-03-01

    This study proposes a new model to predict the reaction force that occurs in incisions during robot-assisted minimally invasive surgery. The reaction force is fed back to the manipulator by a magneto-rheological fluid (MRF) haptic master, which is featured by a bi-directional clutch actuator. The reaction force feedback provides similar sensations to laparotomy that cannot be provided by a conventional master for surgery. This advantage shortens the training period for robot-assisted minimally invasive surgery and can improve the accuracy of operations. The reaction force modeling of incisions can be utilized in a surgical simulator that provides a virtual reaction force. In this work, in order to model the reaction force during incisions, the energy aspect of the incision process is adopted and analyzed. Each mode of the incision process is classified by the tendency of the energy change, and modeled for realistic real-time application. The reaction force model uses actual reaction force information with three types of actual tissues: hard tissue, medium tissue, and soft tissue. This modeled force is realized by the MRF haptic master through an algorithm based on the position and velocity of a scalpel using two different control methods: an open-loop algorithm and a closed-loop algorithm. The reaction forces obtained from the proposed model are compared with a desired force in time domain.

  8. Does Bohm's Quantum Force Have a Classical Origin?

    Lush, David C.

    2014-01-01

    In the de Broglie - Bohm formulation of quantum mechanics, the electron is stationary in the ground state of hydrogenic atoms, because the quantum force exactly cancels the Coulomb attraction of the electron to the nucleus. In this paper it is shown that classical electrodynamics similarly predicts the Coulomb force can be effectively canceled by part of the magnetic force that occurs between two similar particles each consisting of a point charge moving with circulatory motion at the speed o...

  9. Force of an actin spring

    Shin, Jennifer; Mahadevan, L.; Matsudaira, Paul

    2003-03-01

    The acrosomal process of the horseshoe crab sperm is a novel mechanochemical molecular spring that converts its elastic stain energy to mechanical work upon the chemical activation by Ca2+. Twisted and bent, the initial state of the acrosomal bundle features a high degree of complexity in its structure and the energy is believed to be stored in the highly strained actin filaments as an elastic potential energy. When activated, the bundle relaxes from the coil of the highly twisted and bent filaments to its straight conformation at a mean velocity of 15um/s. The mean extension velocity increases dramatically from 3um/s to 27um/s when temperature of the medium is changed from 9.6C to 32C (respective viscosities of 1.25-0.75cp), yet it exhibits a very weak dependence on changes in the medium viscosity (1cp-33cp). These experiments suggest that the uncoiling of the actin spring should be limited not by the viscosity of the medium but by the unlatching events of involved proteins at a molecular level. Unlike the viscosity-limited processes, where force is directly related to the rate of the reaction, a direct measurement is required to obtain the spring force of the acrosomal process. The extending acrosomal bundle is forced to push against a barrier and its elastic buckling response is analyzed to measure the force generated during the uncoiling.

  10. An Ignored Mechanism for the Longitudinal Recoil Force in Railguns and Revitalization of the Riemann Force Law

    Su, C C

    2005-01-01

    The electric induction force due to a time-varying current is used to account for the longitudinal recoil force exerted on the rails of railgun accelerators. As observed in the experiments, this induction force is longitudinal to the rails and can be the strongest at the heads of the rails. Besides, for the force due to a closed circuit, it is shown that the Riemann force law, which is based on a potential energy depending on a relative speed and is in accord with Newton's law of action and reaction, can reduce to the Lorentz force law.

  11. Surface plasmon polariton assisted optical pulling force

    Petrov, M I; Bogdanov, A A; Shalin, A S; Dogariu, A

    2016-01-01

    We demonstrate both analytically and numerically the existence of optical pulling forces acting on particles located near plasmonic interfaces. Two main factors contribute to the appearance of this negative reaction force. The interference between the incident and reflected waves induces a rotating dipole with an asymmetric scattering pattern while the directional excitation of surface plasmon polaritons (SPP) enhances the linear momentum of scattered light. The strongly asymmetric SPP excitation is determined by spin-orbit coupling of the rotating dipole and surface plasmon polariton. As a result of the total momentum conservation, the force acting on the particle points in a direction opposite to the incident wave propagation. We derive analytical expressions for the force acting on a dipolar particles placed in the proximity of plasmonic surfaces. Analytical expressions for this pulling force are derived within the dipole approximation and are in excellent agreement with results of electromagnetic numerica...

  12. Ground State Spin Logic

    Whitfield, James; Faccin, Mauro; Biamonte, Jacob

    2013-03-01

    Designing and optimizing cost functions and energy landscapes is a problem encountered in many fields of science and engineering. These landscapes and cost functions can be embedded and annealed in experimentally controllable spin Hamiltonians. Using an approach based on group theory and symmetries, we examine the embedding of Boolean logic gates into the ground-state subspace of such spin systems. We describe parameterized families of diagonal Hamiltonians and symmetry operations which preserve the ground-state subspace encoding the truth tables of Boolean formulas. The ground-state embeddings of adder circuits are used to illustrate how gates are combined and simplified using symmetry. Our work is relevant for experimental demonstrations of ground-state embeddings found in both classical optimization as well as adiabatic quantum optimization.

  13. Intake Ground Vortex Aerodynamics

    Murphy, John

    2008-01-01

    When an aircraft is operating in static or near static conditions during taxiing or take-o a vortex can form between the ground and the intake. With engine diameters increasing, intakes are moving non-dimensionally closer to the ground and as a consequence the likelihood of vortex formation during the aircraft operating envelope is set to increase. To date there is little quantitative knowledge therefore a greater understanding is required. This research is aimed at providing ...

  14. Macroscopic aspects of heavy-ion reactions

    Experimental results on multi-nucleon transfer reactions and deep-inelastic reactions are presented. Boundary conditions following from the liquid-drop model are used to determine an asymmetric nucleus-nucleus interaction potential which includes deformation degrees of freedom in the exit reaction channel explicitly. The problem of competition between fusion and two-body reactions is formulated. A phenomenological model of deep-inelastic reactions is proposed. The model is constructed on the basis of classical equations of motion of the Lagrange-Rayleigh type (with inclusion of conservative and dissipative forces). (author)

  15. Forces in general relativity

    Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced by an observer in general coordinates. The general force is then applied to the local co-moving coordinate system of a uniformly accelerating observer, leading to an expression of the inertial force experienced by the observer. Next, applying the general force in Schwarzschild coordinates is shown to lead to familiar expressions of the gravitational force. As a more complex demonstration, the general force is applied to an observer in Boyer-Lindquist coordinates near a rotating, Kerr black hole. It is then shown that when the angular momentum of the black hole goes to zero, the force on the observer reduces to the force on an observer held stationary in Schwarzschild coordinates. As a final consideration, the force on an observer moving in rotating coordinates is derived. Expressing the force in terms of Christoffel symbols in rotating coordinates leads to familiar expressions of the centrifugal and Coriolis forces on the observer. It is envisioned that the techniques presented herein will be most useful to graduate level students, as well as those undergraduate students having experience with general relativity and tensor analysis.

  16. Forces in general relativity

    Ridgely, Charles T.

    2010-07-01

    Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced by an observer in general coordinates. The general force is then applied to the local co-moving coordinate system of a uniformly accelerating observer, leading to an expression of the inertial force experienced by the observer. Next, applying the general force in Schwarzschild coordinates is shown to lead to familiar expressions of the gravitational force. As a more complex demonstration, the general force is applied to an observer in Boyer-Lindquist coordinates near a rotating, Kerr black hole. It is then shown that when the angular momentum of the black hole goes to zero, the force on the observer reduces to the force on an observer held stationary in Schwarzschild coordinates. As a final consideration, the force on an observer moving in rotating coordinates is derived. Expressing the force in terms of Christoffel symbols in rotating coordinates leads to familiar expressions of the centrifugal and Coriolis forces on the observer. It is envisioned that the techniques presented herein will be most useful to graduate level students, as well as those undergraduate students having experience with general relativity and tensor analysis.

  17. Gamov-Teller transitions from 14N ground to 14C ground and excited states

    Kanada-En'yo, Yoshiko

    2014-01-01

    Gamov-Teller transitions from the $^{14}$N ground state to the $^{14}$C ground and excited states were investigated, based on the model of antisymmetrized molecular dynamics. The calculated strengths for the allowed transitions to the $0^+$, $1^+$, and $2^+$ states of $^{14}$C were compared with the experimental data measured by high-resolution charge-exchange reactions. The calculated GT transition to the $2^+_1$ state is strong while those to the $0^+_{2,3}$ and $2^+_{2,3}$ states having dominant $2\\hbar\\omega$ excited configurations are relatively weak. The present calculation can not describe the anonymously long life time of $^{14}$C, though the strength of the $^{14}$C ground state is somewhat suppressed because of the cluster (many-body) correlation in the ground states of $^{14}$C and $^{14}$N.

  18. Force modeling for incision surgery into tissue with haptic application

    Kim, Pyunghwa; Kim, Soomin; Choi, Seung-Hyun; Oh, Jong-Seok; Choi, Seung-Bok

    2015-04-01

    This paper presents a novel force modeling for an incision surgery into tissue and its haptic application for a surgeon. During the robot-assisted incision surgery, it is highly urgent to develop the haptic system for realizing sense of touch in the surgical area because surgeons cannot sense sensations. To achieve this goal, the force modeling related to reaction force of biological tissue is proposed in the perspective on energy. The force model describes reaction force focused on the elastic feature of tissue during the incision surgery. Furthermore, the force is realized using calculated information from the model by haptic device using magnetorheological fluid (MRF). The performance of realized force that is controlled by PID controller with open loop control is evaluated.

  19. On the entropy of radiation reaction

    Burton, David A

    2013-01-01

    The inexorable development of ever more powerful laser systems has re-ignited interest in electromagnetic radiation reaction and its significance for the collective behaviour of charged matter interacting with intense electromagnetic fields. The classical radiation reaction force on a point electron is non-conservative, and this has led some authors to question the validity of methods used to model ultra-intense laser-matter interactions including radiation reaction. We explain why such concern is unwarranted.

  20. On the entropy of radiation reaction

    The inexorable development of ever more powerful laser systems has re-ignited interest in electromagnetic radiation reaction and its significance for the collective behavior of charged matter interacting with intense electromagnetic fields. The classical radiation reaction force on a point electron is non-conservative, and this has led some authors to question the validity of methods used to model ultra-intense laser–matter interactions including radiation reaction. We explain why such concern is unwarranted.

  1. Macroscopic QED in linearly responding media and a Lorentz-Force approach to dispersion forces

    In this thesis, a very general quantization scheme for the macroscopic electromagnetic field in arbitrary linearly responding media is presented. It offers a unified approach to QED in such media. Applying the quantization scheme, a theory of the dispersion forces on the basis of the Lorentz force is developed. By regarding the dispersion force as the (ground-state or thermal-state) expectation value of the Lorentz force that acts on appropriately defined charge and current densities, Casimir, Casimir-Polder, and van der Waals forces are united in a very natural way that makes transparent their common physical basis. Application of the theory to planar structures yields generalizations of well-known Lifschitz and Casimir-type formulas. (orig.)

  2. Discussion about grounding of OVATION

    The requirements of Grounding of OVATION platform applied in Digital Control System of SANMEN Nuclear Station are introduced and explained the detail functions for each type of grounding. Also, grounding principles and points for attention in engineering are given. (author)

  3. Trois familles, quatre forces

    Augereau, J F

    2002-01-01

    ENSEMBLE DE QUATRE ARTICLES - LARGE HADRON COLLIDER: Le monde des particules tel que nous le connaissons aujourd'hui est constitue de trois familles de quatre membres. Ces particules sont collees les unes aux autres par des forces. Celles-ci, au nombre de quatre - gravitation, force forte, force electromagnetique et force faible -, sont " portees " par d'autres particules dont certaines sont a decouvrir (graviton) et d'autres deja identifiees (gluons, photons, bosons W et Z) (1/2 page).

  4. Crossflow force transducer

    A force transducer for measuring lift and drag coefficients for a circular cylinder in turbulent water flow is presented. In addition to describing the actual design and construction of the strain-gauged force- ring based transducer, requirements for obtained valid fluid force test data are discussed, and pertinent flow test experience is related

  5. Forces in General Relativity

    Ridgely, Charles T.

    2010-01-01

    Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced…

  6. Forces in General Relativity

    Ridgely, Charles T.

    2010-01-01

    Many textbooks dealing with general relativity do not demonstrate the derivation of forces in enough detail. The analyses presented herein demonstrate straightforward methods for computing forces by way of general relativity. Covariant divergence of the stress-energy-momentum tensor is used to derive a general expression of the force experienced…

  7. Debunking Coriolis Force Myths

    Shakur, Asif

    2014-01-01

    Much has been written and debated about the Coriolis force. Unfortunately, this has done little to demystify the paradoxes surrounding this fictitious force invoked by an observer in a rotating frame of reference. It is the purpose of this article to make another valiant attempt to slay the dragon of the Coriolis force! This will be done without…

  8. Isospin violation in the 12C(6Li,?)14N(2.31 MeV) reaction

    The isospin violating reaction 12C(6Li,?)14N(2.31 MeV) was investigated in the range of beam energies from 9.0 to 14.0 MeV. Excitation functions were measured for the ground state, 2.31-MeV state and 3.95-MeV state of 14N at 150, 200, 600, and 1600. Excitation functions were taken at 400 for the ground state and 3.95-MeV states. Angular distributions were obtained at 10.5-, 11.25-, 12.5-, 13.75-, and 20.0-MeV beam energies. The cross section for the isospin forbidden reaction to the 2.31-MeV state is 0.4 to 1.8% of that to the allowed ground state and 3.95-MeV state in the beam energy range 9 to 14 MeV. At 20.0 MeV the ground state and 3.95-MeV state in the beam energy range 9 to 14 MeV. At 20.0 MeV the yield to the forbidden state is only 0.02% of the allowed yield. Isospin mixing by the Coulomb force is believed responsible for the forbidden yield observed between 9 - 14 MeV

  9. Electromyographic and Force Plate Analysis of the Deadlift Performed With and Without Chains.

    Nijem, Ramsey M; Coburn, Jared W; Brown, Lee E; Lynn, Scott K; Ciccone, Anthony B

    2016-05-01

    Nijem, RM, Coburn, JW, Brown, LE, Lynn, SK, and Ciccone, AB. Electromyographic and force plate analysis of the deadlift performed with and without chains. J Strength Cond Res 30(5): 1177-1182, 2016-The purpose of this study was to determine the effects of deadlift chain variable resistance on surface electromyography (EMG) of the gluteus maximus, erector spinae, and vastus lateralis muscles, ground reaction forces (GRFs), and rate of force development (RFD). Thirteen resistance-trained men (24.0 ± 2.1 years, 179.3 ± 4.8 cm, 87.0 ± 10.6 kg) volunteered for the study. On day 1, subjects performed 1 repetition maximum (1RM) testing of the deadlift exercise. On day 2, subjects performed one set of 3 repetitions with a load of 85% 1RM with chains (CH) and without chains (NC). The order of the CH and NC conditions was randomly determined for each subject. For the CH condition, the chains accounted for approximately 20% (19.9 ± 0.6%) of the 85% 1RM load, matched at the top of the lift. Surface EMG was recorded to differentiate muscle activity between conditions (CH, NC), range of motion (ROM; bottom, top), and phase (concentric, eccentric). Peak GRFs and RFD were measured using a force plate. Electromyography results revealed that for the gluteus maximus there was significantly greater EMG activity during the NC condition vs. the CH condition. For the erector spinae, EMG activity was greater at the bottom than the top ROM (p ≤ 0.05). Force plate results revealed that deadlifting at 85% 1RM with an accommodating chain resistance of approximately 20% results in a reduction in GRFs (p ≤ 0.05) and no change in RFD (p > 0.05). Collectively, these results suggest that the use of chain resistance during deadlifting can alter muscle activation and force characteristics of the lift. PMID:26840441

  10. Ground Enterprise Management System Project

    National Aeronautics and Space Administration — Emergent Space Technologies Inc. proposes to develop the Ground Enterprise Management System (GEMS) for spacecraft ground systems. GEMS will provide situational...

  11. Associations of force plate and body-mounted inertial sensor measurements for identification of hind limb lameness in horses.

    Bell, Rhodes P; Reed, Shannon K; Schoonover, Mike J; Whitfield, Chase T; Yonezawa, Yoshiharu; Maki, Hiromitchi; Pai, P Frank; Keegan, Kevin G

    2016-04-01

    OBJECTIVE To investigate associations between inertial sensor and stationary force plate measurements of hind limb lameness in horses. ANIMALS 21 adult horses with no lameness or with mild hind limb lameness. PROCEDURES Horses were instrumented with inertial sensors and evaluated for lameness with a stationary force plate while trotting in a straight line. Inertial sensor-derived measurements of maximum and minimum pelvic height differences between right and left halves of the stride were compared with vertical and horizontal ground reaction forces (GRFs). Stepwise linear regression was performed to investigate the strength of association between inertial sensor measurements of hind limb lameness and amplitude, impulse, and time indices of important events in the vertical and horizontal GRF patterns. RESULTS Difference in minimum pelvic position was moderately (Ra(2) = 0.60) associated with the difference in peak vertical GRF but had little association with any horizontal GRF measurements. Difference in maximum pelvic position was strongly (Ra(2) = 0.77) associated with a transfer of vertical to horizontal ground reaction impulse in the second half of the stance but was not associated with difference in peak vertical GRF. CONCLUSIONS AND CLINICAL RELEVANCE Inertial sensor-derived measurements of asymmetric pelvic fall (difference in minimum pelvic position) indicated a decrease in vertical GRF, but similar measurements of asymmetric pelvis rise (difference in maximum pelvic position) indicated a transfer of vertical to horizontal force impulse in the second half of the stance. Evaluation of both pelvic rise and fall may be important when assessing hind limb lameness in horses. PMID:27027831

  12. Sprint Acceleration Mechanics: The Major Role of Hamstrings in Horizontal Force Production

    Morin, Jean-Benoît; Gimenez, Philippe; Edouard, Pascal; Arnal, Pierrick; Jiménez-Reyes, Pedro; Samozino, Pierre; Brughelli, Matt; Mendiguchia, Jurdan

    2015-01-01

    Recent literature supports the importance of horizontal ground reaction force (GRF) production for sprint acceleration performance. Modeling and clinical studies have shown that the hip extensors are very likely contributors to sprint acceleration performance. We experimentally tested the role of the hip extensors in horizontal GRF production during short, maximal, treadmill sprint accelerations. Torque capabilities of the knee and hip extensors and flexors were assessed using an isokinetic dynamometer in 14 males familiar with sprint running. Then, during 6-s sprints on an instrumented motorized treadmill, horizontal and vertical GRF were synchronized with electromyographic (EMG) activity of the vastus lateralis, rectus femoris, biceps femoris, and gluteus maximus averaged over the first half of support, entire support, entire swing and end-of-swing phases. No significant correlations were found between isokinetic or EMG variables and horizontal GRF. Multiple linear regression analysis showed a significant relationship (P = 0.024) between horizontal GRF and the combination of biceps femoris EMG activity during the end of the swing and the knee flexors eccentric peak torque. In conclusion, subjects who produced the greatest amount of horizontal force were both able to highly activate their hamstring muscles just before ground contact and present high eccentric hamstring peak torque capability. PMID:26733889

  13. Snow and Ground Temperature

    Harris, R. N.; Davis, M. G.; Bartlett, M. G.; Chapman, D. S.

    2007-12-01

    A numerical model of snow-ground thermal interactions has been developed to investigate the effect of seasonal snow cover on the mean annual ground temperature. The model is parameterized in terms of three snow event parameters: onset time of the annual snow event, duration of the event, and maximum depth of snow during the event. These parameters are commonly available from meteorological and remotely sensed data making the model broadly applicable. The model is validated using surface air temperature (SAT), surface ground temperature (SGT), and snow depth data from observations at Emigrant Pass climate observatory (EPO) in northwestern Utah and National Weather Service data from sites across North America. Measured subsurface temperature-time series compare well with changes predicted by the model. We define a "snow effect" as the difference in mean annual ground temperatures with and without a snow event and explore how the snow effect might change with a warming climate. During the period 1950-2002, the mean North American snow event onset (December 15) and duration (81 days) has remained relatively constant although interannual variation as much as 18 days (onset) and 15 days (duration) are present. Across all North American stations with snow cover during this period, the trend in mean annual SGT-SAT offset is about \\- 0.02 K/decade. One unanticipated finding is that snow can either raise or lower the mean annual ground temperature depending principally on the timing of the snow event.

  14. Spallation reactions

    Spallation reactions dominate the interactions of hadrons with nuclei in the GeV range (from ? 0.1 to ? 10 GeV). They correspond to a sometimes important ejection of light particles leaving most of the time a residue of mass commensurate with the target mass. The main features of the experimental data are briefly reviewed. The most successful theoretical model, namely the intranuclear cascade + evaporation model, is presented. Its physical content, results and possible improvements are critically discussed. Alternative approaches are shortly reviewed. (author)

  15. Staying Open: The use of theoretical codes in grounded theory

    Barney G. Glaser, PhD; with the assistance of Judith A. Holton

    2005-01-01

    Theoretical codes (TCs) are abstract models that emerge during the sorting and memoing stages of grounded theory (GT) analysis. They conceptualize the integration of substantive codes as hypotheses of a theory. In this article, I explore the importance of their emergence in the development of a grounded theory and I discuss the challenge of the researcher in staying open to their emergence and earned relevance rather than their preconceived forcing on the theory under development. I emphasize...

  16. Forces in molecules.

    Hernández-Trujillo, Jesús; Cortés-Guzmán, Fernando; Fang, De-Chai; Bader, Richard F W

    2007-01-01

    Chemistry is determined by the electrostatic forces acting within a collection of nuclei and electrons. The attraction of the nuclei for the electrons is the only attractive force in a molecule and is the force responsible for the bonding between atoms. This is the attractive force acting on the electrons in the Ehrenfest force and on the nuclei in the Feynman force, one that is countered by the repulsion between the electrons in the former and by the repulsion between the nuclei in the latter. The virial theorem relates these forces to the energy changes resulting from interactions between atoms. All bonding, as signified by the presence of a bond path, has a common origin in terms of the mechanics determined by the Ehrenfest, Feynman and virial theorems. This paper is concerned in particular with the mechanics of interaction encountered in what are classically described as 'nonbonded interactions'--are atoms that 'touch' bonded or repelling one another? PMID:17328425

  17. Quantum fictitious forces

    Bialynicki-Birula, I; Cirone, M.A.; Dahl, Jens Peder; Seligman, T.H.; Straub, F.; Schleich, W.P.

    We present Heisenberg's equation of motion for the radial variable of a free non-relativistic particle in D dimensions. The resulting radial force consists of three contributions: (i) the quantum fictitious force which is either attractive or repulsive depending on the number of dimensions, (ii) a...... singular quantum force located at the origin, and (iii) the centrifugal force associated with non-vanishing angular momentum. Moreover, we use Heisenberg's uncertainty relation to introduce a lower bound for the kinetic energy of an ensemble of neutral particles. This bound is quadratic in the number of...... atoms and can be traced back to the repulsive quantum fictitious potential. All three forces arise for a free particle: "Force without force"....

  18. A numerical investigation on the ground effect of a flapping-flying bird

    Su, Jian-Yuan; Tang, Jhen-Han; Wang, Ching-Hua; Yang, Jing-Tang

    2013-09-01

    The flight of a small bird under the influence of the ground effect is numerically investigated with a complete three-dimensional model including the bird's body and wings. The flight mode is not the conventional steady gliding flight but an unsteady flight consisting of flapping, twisting, and folding motions. As the bird approaches the ground, the average lift force gradually increases while the average drag force decreases. At a particular distance, the average lift force increases by approximately 47%, whereas the average drag force decreases by nearly 20%, relative to the absence of the ground effect. Because of the ground, the improved aerodynamic performance in flapping flight is much more significant than in steady flight, in which the modification of the lift-drag ratio is typically less than 10%. On the basis of the flow field, regardless of the presence or absence of the ground, there exists no evidence for an obstruction of a wing-tip vortex, which is a remarkable phenomenon and accounts for the improved performance in steady flight. The extent of the region of high pressure beneath the wing in the near-ground case seems to surpass that in the far-ground case, accounting for the greater lift and thrust forces in the near-ground case. This air cushion beneath the wing, known as the cram effect, is the dominant factor of the ground effect on a flapping bird.

  19. Ground motion predictions

    Nuclear generated ground motion is defined and then related to the physical parameters that cause it. Techniques employed for prediction of ground motion peak amplitude, frequency spectra and response spectra are explored, with initial emphasis on the analysis of data collected at the Nevada Test Site (NTS). NTS postshot measurements are compared with pre-shot predictions. Applicability of these techniques to new areas, for example, Plowshare sites, must be questioned. Fortunately, the Atomic Energy Commission is sponsoring complementary studies to improve prediction capabilities primarily in new locations outside the NTS region. Some of these are discussed in the light of anomalous seismic behavior, and comparisons are given showing theoretical versus experimental results. In conclusion, current ground motion prediction techniques are applied to events off the NTS. Predictions are compared with measurements for the event Faultless and for the Plowshare events, Gasbuggy, Cabriolet, and Buggy I. (author)

  20. Force Limited Vibration Testing

    Scharton, Terry; Chang, Kurng Y.

    2005-01-01

    This slide presentation reviews the concept and applications of Force Limited Vibration Testing. The goal of vibration testing of aerospace hardware is to identify problems that would result in flight failures. The commonly used aerospace vibration tests uses artificially high shaker forces and responses at the resonance frequencies of the test item. It has become common to limit the acceleration responses in the test to those predicted for the flight. This requires an analysis of the acceleration response, and requires placing accelerometers on the test item. With the advent of piezoelectric gages it has become possible to improve vibration testing. The basic equations have are reviewed. Force limits are analogous and complementary to the acceleration specifications used in conventional vibration testing. Just as the acceleration specification is the frequency spectrum envelope of the in-flight acceleration at the interface between the test item and flight mounting structure, the force limit is the envelope of the in-flight force at the interface . In force limited vibration tests, both the acceleration and force specifications are needed, and the force specification is generally based on and proportional to the acceleration specification. Therefore, force limiting does not compensate for errors in the development of the acceleration specification, e.g., too much conservatism or the lack thereof. These errors will carry over into the force specification. Since in-flight vibratory force data are scarce, force limits are often derived from coupled system analyses and impedance information obtained from measurements or finite element models (FEM). Fortunately, data on the interface forces between systems and components are now available from system acoustic and vibration tests of development test models and from a few flight experiments. Semi-empirical methods of predicting force limits are currently being developed on the basis of the limited flight and system test data. A simple two degree of freedom system is shown and the governing equations for basic force limiting results for this system are reviewed. The design and results of the shuttle vibration forces (SVF) experiments are reviewed. The Advanced Composition Explorer (ACE) also was used to validate force limiting. Test instrumentation and supporting equipment are reviewed including piezo-electric force transducers, signal processing and conditioning systems, test fixtures, and vibration controller systems. Several examples of force limited vibration testing are presented with some results.

  1. Nuclear reactions

    Nuclear reactions' marks a new development in the study of television as an agency of public policy debate. During the Eighties, nuclear energy became a major international issue. The disasters at Three-mile Island and Chernobyl created a global anxiety about its risks and a new sensitivity to it among politicians and journalists. This book is a case-study into documentary depictions of nuclear energy in television and video programmes and into the interpretations and responses of viewers drawn from many different occupational groupings. How are the complex and specialist arguments about benefit, risk and proof conveyed through the different conventions of commentary, interview and film sequence? What symbolic associations does the visual language of television bring to portrayals of the issue? And how do viewers make sense of various and conflicting accounts, connecting what they see and hear on the screen with their pre-existing knowledge, experience and 'civic' expectations. The authors examine some of the contrasting forms and themes which have been used by programme makers to explain and persuade, and then give a sustained analysis of the nature and sources of viewers' own accounts. 'Nuclear Reactions' inquires into the public meanings surrounding energy and the environment, spelling out in its conclusion some of the implications for future media treatments of this issue. It is also a key contribution to the international literature on 'television knowledge' and the processes of active viewing. (author)

  2. On gravity as an entropic force

    Chaichian, Masud; Oksanen, Markku; Tureanu, Anca

    2011-01-01

    We consider E. Verlinde's proposal that gravity is an entropic force -- we shall call this theory entropic gravity (EG) -- and reanalyze a recent claim that this theory is in contradiction with the observation of the gravitationally-bound ground state of neutrons in the GRANIT experiment. We find that EG does not necessarily contradict the existence of gravitationally-bound quantum states of neutrons in the Earth's gravitational field, since EG is equivalent to Newtonian gravity in this case....

  3. Measurement of T20(90 degree) in the 1H(d searrow,?)3He reaction below deuteron breakup threshold

    The tensor analyzing powers of the 1H(d searrow,?)3He reaction are sensitive to the tensor component of the nucleon-nucleon force, which mixes the L=2 D state into the 3He ground state wave function. Modern Faddeev calculations of this reaction allow a quantitative comparison to the parametrization of the tensor force in the trinucleon system. The T20 analyzing power was measured at an incident beam energy of 5.25 MeV and a laboratory angle of 90 degree (?c.m.=92.9 degree), where the comparison to theory is especially rigorous. The measured value of T20(90labdegree) is -0.035±0.004, which differs by ?3? from a recent Faddeev calculation which uses the separable expansion of the Paris potential. copyright 1996 The American Physical Society

  4. Grounded Theory approach

    Ali Rabbani Khorasghani

    2010-01-01

    Full Text Available AbstractAccording to social changes in global level, social scientist introduced new theories to explanation of socialphenomena. According to appearance new theories, research methods have changed. The Idea is that,Simultaneity with Appearance post positivist theories, research approaches such a grounded theory hasestablished. This method, acts in the base of qualitative methods and use systematic complex of multipleProcedures to gathering data for theory development upon induction. This method with characteristics as ifflexibility, reflexivity, has caused many of researchers used it. In the present article, we paid to introductionof grounded theory and its critics.

  5. Gamov-Teller transitions from 14N ground to 14C ground and excited states

    Kanada-En'yo, Yoshiko; Suhara, Tadahiro

    2014-01-01

    Gamov-Teller transitions from the $^{14}$N ground state to the $^{14}$C ground and excited states were investigated, based on the model of antisymmetrized molecular dynamics. The calculated strengths for the allowed transitions to the $0^+$, $1^+$, and $2^+$ states of $^{14}$C were compared with the experimental data measured by high-resolution charge-exchange reactions. The calculated GT transition to the $2^+_1$ state is strong while those to the $0^+_{2,3}$ and $2^+_{2,3}$ states having do...

  6. Coding Issues in Grounded Theory

    Moghaddam, Alireza

    2006-01-01

    This paper discusses grounded theory as one of the qualitative research designs. It describes how grounded theory generates from data. Three phases of grounded theory--open coding, axial coding, and selective coding--are discussed, along with some of the issues which are the source of debate among grounded theorists, especially between its…

  7. Singlet Ground State Magnetism:

    Loidl, A.; Knorr, K.; Kjems, Jørgen; Liithi, B.

    1979-01-01

    The magneticGamma 1 –Gamma 4 exciton of the singlet ground state system TbP has been studied by inelastic neutron scattering above the antiferromagnetic ordering temperature. Considerable dispersion and a pronounced splitting was found in the [100] and [110] directions. Both the band width and the...

  8. Four frequency ground scatterometer

    Dickerson, E. T.

    1982-01-01

    The FM-CW Radar, used as a microwave scatterometer is described. Scatterometer system design, scatterometer system calibration, parameter calculation and correction for data acquisition, ground scatterometer data acquistion at Jornada Experimental Range, and Kansas radar cross-calibration test are discussed.

  9. Grounding in Instant Messaging

    Fox Tree, Jean E.; Mayer, Sarah A.; Betts, Teresa E.

    2011-01-01

    In two experiments, we investigated predictions of the "collaborative theory of language use" (Clark, 1996) as applied to instant messaging (IM). This theory describes how the presence and absence of different grounding constraints causes people to interact differently across different communicative media (Clark & Brennan, 1991). In Study 1, we…

  10. Nuclear reactions. An introduction

    Modern, self-contained introduction to the subject matter. Emphasizes the interplay between theory and experiment. Course-tested tutorial style, contains many derivations. Nuclei and nuclear reactions offer a unique setting for investigating three (and in some cases even all four) of the fundamental forces in nature. Nuclei have been shown - mainly by performing scattering experiments with electrons, muons, and neutrinos - to be extended objects with complex internal structures: constituent quarks; gluons, whose exchange binds the quarks together; sea-quarks, the ubiquitous virtual quark-antiquark pairs and, last but not least, clouds of virtual mesons, surrounding an inner nuclear region, their exchange being the source of the nucleon-nucleon interaction. The interplay between the (mostly attractive) hadronic nucleon-nucleon interaction and the repulsive Coulomb force is responsible for the existence of nuclei; their degree of stability, expressed in the details and limits of the chart of nuclides; their rich structure and the variety of their interactions. Despite the impressive successes of the classical nuclear models and of ab-initio approaches, there is clearly no end in sight for either theoretical or experimental developments as shown e.g. by the recent need to introduce more sophisticated three-body interactions to account for an improved picture of nuclear structure and reactions. Yet, it turns out that the internal structure of the nucleons has comparatively little influence on the behavior of the nucleons in nuclei, and nuclear physics - especially nuclear structure and reactions - is thus a field of science in its own right, without much recourse to subnuclear degrees of freedom. This book collects essential material that was presented in the form of lectures notes in nuclear physics courses for graduate students at the University of Cologne. It follows the course's approach, conveying the subject matter by combining experimental facts and experimental methods and tools with basic theoretical knowledge. Emphasis is placed on the importance of spin and orbital angular momentum (leading e.g. to applications in energy research, such as fusion with polarized nuclei), and on the operational definition of observables in nuclear physics. The end-of-chapter problems serve above all to elucidate and detail physical ideas that could not be presented in full detail in the main text. Readers are assumed to have a working knowledge of quantum mechanics and a basic grasp of both non-relativistic and relativistic kinematics; the latter in particular is a prerequisite for interpreting nuclear reactions and the connections to particle and high-energy physics.

  11. Nuclear reactions. An introduction

    Paetz gen. Schieck, Hans [Koeln Univ. (Germany). Inst. fuer Kernphysik

    2014-03-01

    Modern, self-contained introduction to the subject matter. Emphasizes the interplay between theory and experiment. Course-tested tutorial style, contains many derivations. Nuclei and nuclear reactions offer a unique setting for investigating three (and in some cases even all four) of the fundamental forces in nature. Nuclei have been shown - mainly by performing scattering experiments with electrons, muons, and neutrinos - to be extended objects with complex internal structures: constituent quarks; gluons, whose exchange binds the quarks together; sea-quarks, the ubiquitous virtual quark-antiquark pairs and, last but not least, clouds of virtual mesons, surrounding an inner nuclear region, their exchange being the source of the nucleon-nucleon interaction. The interplay between the (mostly attractive) hadronic nucleon-nucleon interaction and the repulsive Coulomb force is responsible for the existence of nuclei; their degree of stability, expressed in the details and limits of the chart of nuclides; their rich structure and the variety of their interactions. Despite the impressive successes of the classical nuclear models and of ab-initio approaches, there is clearly no end in sight for either theoretical or experimental developments as shown e.g. by the recent need to introduce more sophisticated three-body interactions to account for an improved picture of nuclear structure and reactions. Yet, it turns out that the internal structure of the nucleons has comparatively little influence on the behavior of the nucleons in nuclei, and nuclear physics - especially nuclear structure and reactions - is thus a field of science in its own right, without much recourse to subnuclear degrees of freedom. This book collects essential material that was presented in the form of lectures notes in nuclear physics courses for graduate students at the University of Cologne. It follows the course's approach, conveying the subject matter by combining experimental facts and experimental methods and tools with basic theoretical knowledge. Emphasis is placed on the importance of spin and orbital angular momentum (leading e.g. to applications in energy research, such as fusion with polarized nuclei), and on the operational definition of observables in nuclear physics. The end-of-chapter problems serve above all to elucidate and detail physical ideas that could not be presented in full detail in the main text. Readers are assumed to have a working knowledge of quantum mechanics and a basic grasp of both non-relativistic and relativistic kinematics; the latter in particular is a prerequisite for interpreting nuclear reactions and the connections to particle and high-energy physics.

  12. Forced thermal cycling of catalytic reactions: experiments and modelling

    Jensen, Søren; Olsen, Jakob Lind; Thorsteinsson, Sune; Hansen, Ole; Quaade, Ulrich

    2007-01-01

    at about 1 Hz. A model for the rate enhancement that includes the surface kinetics and the dynamic partial pressure variations in the reactor is introduced. The model predicts a levelling off of the rate enhancement with frequency at about 1 Hz. The experimentally observed decrease above 1 Hz is...

  13. Force field development on pigments of photosystem 2 reaction centre

    Palenčár, Peter

    2005-01-01

    Roč. 43, č. 3 (2005), s. 417-420. ISSN 0044-5231 R&D Projects: GA ČR GP206/02/D177 Institutional research plan: CEZ:AV0Z50510513; CEZ:AV0Z60870520 Keywords : photosystem 2 Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.750, year: 2005

  14. Force field development on pigments of photosystem 2 reaction centre

    Palenčár, P.; Vácha, František; Kutý, Michal

    2005-01-01

    Roč. 43, - (2005), 417-420. ISSN 0300-3604 R&D Projects: GA ČR GP206/02/D177 Institutional research plan: CEZ:AV0Z50510513; CEZ:AV0Z60870520 Keywords : photosystem 2 Subject RIV: BO - Biophysics Impact factor: 0.810, year: 2005

  15. Quantum anticentrifugal force

    In a two-dimensional world, a free quantum particle of vanishing angular momentum experiences an attractive force. This force originates from a modification of the classical centrifugal force due to the wave nature of the particle. For positive energies the quantum anticentrifugal force manifests itself in a bunching of the nodes of the energy wave functions towards the origin. For negative energies this force is sufficient to create a bound state in a two-dimensional δ-function potential. In a counterintuitive way, the attractive force pushes the particle away from the location of the δ-function potential. As a consequence, the particle is localized in a band-shaped domain around the origin

  16. Variable Acceleration Force Calibration System (VACS)

    Rhew, Ray D.; Parker, Peter A.; Johnson, Thomas H.; Landman, Drew

    2014-01-01

    Conventionally, force balances have been calibrated manually, using a complex system of free hanging precision weights, bell cranks, and/or other mechanical components. Conventional methods may provide sufficient accuracy in some instances, but are often quite complex and labor-intensive, requiring three to four man-weeks to complete each full calibration. To ensure accuracy, gravity-based loading is typically utilized. However, this often causes difficulty when applying loads in three simultaneous, orthogonal axes. A complex system of levers, cranks, and cables must be used, introducing increased sources of systematic error, and significantly increasing the time and labor intensity required to complete the calibration. One aspect of the VACS is a method wherein the mass utilized for calibration is held constant, and the acceleration is changed to thereby generate relatively large forces with relatively small test masses. Multiple forces can be applied to a force balance without changing the test mass, and dynamic forces can be applied by rotation or oscillating acceleration. If rotational motion is utilized, a mass is rigidly attached to a force balance, and the mass is exposed to a rotational field. A large force can be applied by utilizing a large rotational velocity. A centrifuge or rotating table can be used to create the rotational field, and fixtures can be utilized to position the force balance. The acceleration may also be linear. For example, a table that moves linearly and accelerates in a sinusoidal manner may also be utilized. The test mass does not have to move in a path that is parallel to the ground, and no re-leveling is therefore required. Balance deflection corrections may be applied passively by monitoring the orientation of the force balance with a three-axis accelerometer package. Deflections are measured during each test run, and adjustments with respect to the true applied load can be made during the post-processing stage. This paper will present the development and testing of the VASC concept.

  17. Measurements of piping forces in a safety valve discharge line

    Measurements were made of support reactions to transient hydrodynamic forces on the discharge line of a nuclear reactor safety valve test facility. Data is presented for three different test conditions two with upstream loop seals and one with only steam. Sufficient information is provided to permit verification/development of hydrodynamic force predictive models

  18. The missing climate forcing

    Hansen, J; Sato, M.; Lacis, A.; Ruedy, R.

    1997-01-01

    Observed climate change is consistent with radiative forcings on several time-scales for which the dominant forcings are known, ranging from the few years after a large volcanic eruption to glacial-to-interglacial changes. In the period with most detailed data, 1979 to the present, climate observations contain clear signatures of both natural and anthropogenic forcings. But in the full period since the industrial revolution began, global warming is only about half of that expected due to the ...

  19. Relativistic Linear Restoring Force

    Clark, D.; Franklin, J.; Mann, N.

    2012-01-01

    We consider two different forms for a relativistic version of a linear restoring force. The pair comes from taking Hooke's law to be the force appearing on the right-hand side of the relativistic expressions: d"p"/d"t" or d"p"/d["tau"]. Either formulation recovers Hooke's law in the non-relativistic limit. In addition to these two forces, we…

  20. Relativistic Linear Restoring Force

    Clark, D.; Franklin, J.; Mann, N.

    2012-01-01

    We consider two different forms for a relativistic version of a linear restoring force. The pair comes from taking Hooke's law to be the force appearing on the right-hand side of the relativistic expressions: d"p"/d"t" or d"p"/d["tau"]. Either formulation recovers Hooke's law in the non-relativistic limit. In addition to these two forces, we…