WorldWideScience
1

Analysis of dynamic foot pressure distribution and ground reaction forces  

Science.gov (United States)

The purpose of this study was to assess the relationship between forces derived from in-shoe pressure distribution and GRFs during normal gait. The relationship served to demonstrate the accuracy and reliability of the in-shoe pressure sensor. The in-shoe pressure distribution from Tekscan F-Scan system outputs vertical forces and Centre of Force (COF), while the Kistler force plate gives ground reaction forces (GRFs) in terms of Fz, Fx and Fy, as well as vertical torque, Tz. The two systems were synchronized for pressure and GRFs measurements. Data was collected from four volunteers through three trials for both left and right foot under barefoot condition with the in-shoe sensor. The forces derived from pressure distribution correlated well with the vertical GRFs, and the correlation coefficient (r2) was in the range of 0.93 to 0.99. This is a result of extended calibration, which improves pressure measurement to give better accuracy and reliability. The COF from in-shoe sensor generally matched well with the force plate COP. As for the maximum vertical torque at the forefoot during toe-off, there was no relationship with the pressure distribution. However, the maximum torque was shown to give an indication of the rotational angle of the foot.

Ong, F. R.; Wong, T. S.

2005-04-01

2

Ground reaction forces during level ground walking with body weight unloading  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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 w [...] ould 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.

Ana M. F., Barela; Paulo B. de, Freitas; Melissa L., Celestino; Marcela R., Camargo; José A., Barela.

2014-12-01

3

Treadmill motor current based anteroposterior force estimation using ground reaction force approximation depending on gait cycle.  

Science.gov (United States)

We have been developing a new vehicle, "Tread-Walk 2 (TW-2)", which supports walking for the elderly. TW-2 is controlled by the natural walking movement. In our previous work, we tried to estimate the user's anteroposterior force from the motor current value without a force sensor in order to possible to have a more intuitive operability of TW-2. But, a user of this vehicle experienced some discomfort both when he started walking and when he stopped walking. This problem is caused by inaccurate estimation of the user's anteroposterior force at the heel contact and the toe off. The estimation of the user's anteroposterior force is greatly related to inaccurate estimation of the vertical component of the ground reaction force, which is approximated by the square waveform in the stance phase. In order to construct a control algorithm to improve the operability of TW-2, we accurately estimated the user's anteroposterior force. We therefore proposed the new method to approximate the vertical force in order to estimate the user's anteroposterior force accurately. This paper describes the new method to approximate the waveforms of the vertical forces as isosceles trapezoidal waves with a slope changed depending on the change of the walking velocity. By comparing the estimated anteroposterior force using the new method with the measured value using the force plate, for two young subjects whose physical characteristics were different, the waveform pattern of the estimated force was found to be similar to that of the measured force. This showed that the proposed method could possibly be useful for accurate estimation of anteroposterior force. PMID:22254625

Nakashima, Yasutaka; Ando, Takeshi; Kobayashi, Yo; Fujie, Masakatsu G

2011-01-01

4

The effect of increasing inertia upon vertical ground reaction forces and temporal kinematics during locomotion.  

Science.gov (United States)

The addition of inertia to exercising astronauts could increase ground reaction forces and potentially provide a greater health benefit. However, conflicting results have been reported regarding the adaptations to additional mass (inertia) without additional net weight (gravitational force) during locomotion. We examined the effect of increasing inertia while maintaining net gravitational force on vertical ground reaction forces and temporal kinematics during walking and running. Vertical ground reaction force was measured for 10 healthy adults (five male/five female) during walking (1.34 m s(-1)) and running (3.13 m s(-1)) using a force-measuring treadmill. Subjects completed locomotion at normal weight and mass and at 10, 20, 30 and 40% of added inertial force. The added gravitational force was relieved with overhead suspension, so that the net force between the subject and treadmill at rest remained equal to 100% body weight. Ground reaction forces were affected by the added inertial force, but not to the magnitude predicted by the increase in mass, suggesting that adaptations in motion occurred. Vertical ground reaction force production and adaptations in gait temporal kinematics were different between walking and running. Peak vertical impact forces and loading rates increased with increased inertia during walking, and decreased during running. As inertia increased, peak vertical propulsive forces decreased during walking and did not change during running. Stride time increased during walking and running, and contact time increased during running. The increased inertial forces were utilized independently from gravitational forces by the motor control system when determining coordination strategies. PMID:18344482

De Witt, John K; Hagan, R Donald; Cromwell, Ronita L

2008-04-01

5

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

Directory of Open Access Journals (Sweden)

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.

Kluitenberg Bas

2012-11-01

6

Analysis of ground reaction force and electromyographic activity of the gastrocnemius muscle during double support.  

Science.gov (United States)

Mechanisms associated with energy expenditure during gait have been extensively researched and studied. According to the double-inverted pendulum model energy expenditure is higher during double support, as lower limbs need to work to redirect the centre of mass velocity. This study looks into how the ground reaction force of one limb affects the muscle activity required by the medial gastrocnemius of the contralateral limb during step-to-step transition. Thirty-five subjects were monitored as to the medial gastrocnemius electromyographic activity of one limb and the ground reaction force of the contralateral limb during double support. After determination of the Pearson correlation coefficient (r), a moderate correlation was observed between the medial gastrocnemius electromyographic activity of the dominant leg and the vertical (Fz) and anteroposterior (Fy) components of ground reaction force of the non-dominant leg (r = 0.797, p double support, ground reaction force is associated with the electromyographic activity of the contralateral medial gastrocnemius and that there is an increased dependence between the ground reaction force of the non-dominant leg and the electromyographic activity of the dominant medial gastrocnemius. PMID:22720393

Sousa, Andreia S P; Santos, Rubim; Oliveira, Francisco P M; Carvalho, Paulo; Tavares, João Manuel R S

2012-05-01

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

Science.gov (United States)

High ground reaction forces during the front foot contact phase of the bowling action are believed to be a major contributor to the high prevalence of lumbar stress fractures in fast bowlers. This study aimed to investigate the influence of front leg technique on peak ground reaction forces during the delivery stride. Three-dimensional kinematic data and ground reaction forces during the front foot contact phase were captured for 20 elite male fast bowlers. Eight kinematic parameters were determined for each performance, describing run-up speed and front leg technique, in addition to peak force and time to peak force in the vertical and horizontal directions. There were substantial variations between bowlers in both peak forces (vertical 6.7 ± 1.4 body weights; horizontal (braking) 4.5 ± 0.8 body weights) and times to peak force (vertical 0.03 ± 0.01 s; horizontal 0.03 ± 0.01 s). These differences were found to be linked to the orientation of the front leg at the instant of front foot contact. In particular, a larger plant angle and a heel strike technique were associated with lower peak forces and longer times to peak force during the front foot contact phase, which may help reduce the likelihood of lower back injuries. PMID:23098100

Worthington, Peter; King, Mark; Ranson, Craig

2013-01-01

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

Directory of Open Access Journals (Sweden)

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

William I. Sellers

2009-03-01

9

Forelimb and hindlimb ground reaction forces of walking cats: assessment and comparison with walking dogs.  

Science.gov (United States)

The primary aim of this study was to assess the potential of force plate analysis for describing the stride cycle of the cat. The secondary aim was to define differences in feline and canine locomotion based on force plate characteristics. Ground reaction forces of 24 healthy cats were measured and compared with ground reaction forces of 24 healthy dogs. Force-time waveforms in cats generated by force plate analysis were consistent, as reflected by intra-class correlation coefficients for peak vertical force, peak propulsive force and peak braking force (0.94-0.95, 0.85-0.89 and 0.89-0.90, respectively). Compared with dogs, cats had a higher peak vertical force during the propulsion phase (cat, 3.89?±?0.19?N/kg; dog, 3.03?±?0.16?N/kg), and a higher hindlimb propulsive force (cat, -1.08?±?0.13?N/kg; dog, (-0.87?±?0.13?N/kg) and hindlimb impulse (cat, -0.18?±?0.03?N/kg; dog, -0.14?±?0.02?N/kg). Force plate analysis is a valuable tool for the assessment of locomotion in cats, because it can be applied in the clinical setting and provides a non-invasive and objective measurement of locomotion characteristics with high repeatability in cats, as well as information about kinetic characteristics. Differences in force-time waveforms between cats and dogs can be explained by the more crouched position of cats during stance and their more compliant gait compared with dogs. Feline waveforms of the medio-lateral ground reaction forces also differ between cats and dogs and this can be explained by differences in paw supination-pronation. PMID:25155217

Corbee, R J; Maas, H; Doornenbal, A; Hazewinkel, H A W

2014-10-01

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In-Shoe Plantar Pressures and Ground Reaction Forces during Overweight Adults' Overground Walking  

Science.gov (United States)

Purpose: Because walking is highly recommended for prevention and treatment of obesity and some of its biomechanical aspects are not clearly understood for overweight people, we compared the absolute and normalized ground reaction forces (GRF), plantar pressures, and temporal parameters of normal-weight and overweight participants during…

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

2014-01-01

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Ground Reaction Force and Valgus Knee Loading during Landing after a Block in Female Volleyball Players  

OpenAIRE

A non-contact anterior cruciate ligament (ACL) injury is both a serious and very common problem in volleyball. The aim of the study was to determine the association between stick, step-back, and run-back landings after a block and select risk factors of ACL injuries for female professional volleyball players. The research sample involved fourteen female professional volleyball players. Two force plates were used to determine ground reaction forces. Eight infrared cameras were employed to coll...

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

2014-01-01

12

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

Science.gov (United States)

The goal of this study was to compare selected parameters of vertical ground reaction forces (GRF) of good outcome patients with different prosthesis designs with a matched control group during level walking, stair ascent and descent. Forty subjects, 29 with three main implant designs (including four subjects with a passive knee flexion restriction), and 11 healthy controls were measured with 8-10 repetitions. Vertical ground reaction forces were measured during two consecutive steps with force plates embedded in the walkway and the staircase. Defined parameters of the force signals were used to compare the results of the test groups. The results show, that, postoperatively, good outcome patients produce gait patterns of the vertical ground reaction force which are comparable to normal healthy subjects with the exception of a few distinct differences: a significant reduction (pUCOR) implant designs. The restricted group showed significant reductions (p<0.05) of several loading parameters as well as an increased side-to-side asymmetry. About one third of the force parameters of the good outcome patients showed a side-to-side asymmetry between two consecutive steps, which was over a proposed level of acceptance. PMID:16979893

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

2007-06-01

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Ground Reaction Force and Valgus Knee Loading during Landing after a Block in Female Volleyball Players.  

Science.gov (United States)

A non-contact anterior cruciate ligament (ACL) injury is both a serious and very common problem in volleyball. The aim of the study was to determine the association between stick, step-back, and run-back landings after a block and select risk factors of ACL injuries for female professional volleyball players. The research sample involved fourteen female professional volleyball players. Two force plates were used to determine ground reaction forces. Eight infrared cameras were employed to collect the kinematic data. The one-factor repeated-measures analysis of variance, where the landing type was the factor, was used for comparing the valgus moment and ground reaction force on the right lower limb. ANOVA showed that the type of landing has a main effect on the valgus moment on the right lower limb (F) = 5.96, p = 0.019df = 1.18, partial ?(2) = 0.239 and SP = 0.693). Furthermore, it did not show a main effect on the vertical reaction force on the right lower limb ((F)=2.77, p=0.090, df=1.55, partial ?(2)= 0.128 and SP=0.448). The highest valgus moment occurred during the run-back landing. This moment, however, did not have any effect within the first 100 ms after initial contact with the ground, but rather upon the subsequent motion carried out when stepping back off the net. A comparison between a run-back landing and a step-back landing showed relevant higher values of vertical ground reaction forces during the run-back landing. PMID:25031674

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

2014-03-27

14

Analysis of ground reaction force and electromyographic activity of the gastrocnemius muscle during double support  

OpenAIRE

Purpose: Mechanisms associated with energy expenditure during gait have been extensively researched and studied. According to the double-inverted pendulum model energy expenditure is higher during double support, as lower limbs need to work to redirect the centre of mass velocity. This study looks into how the ground reaction force (GRF) of one limb affects the muscle activity required by the medial gastrocnemius (MG) of the contralateral limb during step-to-step transition. Methods: Thirty-f...

Sousa, Andreia S. P.; Santos, Rubim; Oliveira, Francisco; Carvalho, Paulo; Tavares, Joa?o Manuel

2012-01-01

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

OpenAIRE

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 traditiona...

Puddle, Damien L.; Maulder, Peter S.

2013-01-01

16

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

Science.gov (United States)

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 (p<0.05), and MC were significantly higher than SC (p<0.05). DISCUSSION: Faster squat 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

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

2008-01-01

17

Number of Trials Necessary to Achieve Performance Stability of Selected Ground Reaction Force Variables During Landing  

OpenAIRE

The objectives were to determine the number of trials necessary to achieve performance stability of selected ground reaction force (GRF) variables during landing and to compare two methods of determining stability. Ten subjects divided into two groups each completed a minimum of 20 drop or step-off landings from 0.60 or 0.61 m onto a force platform (1000 Hz). Five vertical GRF variables (first and second peaks, average loading rates to these peaks, and impulse) were quantified during the init...

Roger James, C.; Herman, Joseph A.; Dufek, Janet S.; Bates, Barry T.

2007-01-01

18

NUMBER OF TRIALS NECESSARY TO ACHIEVE PERFORMANCE STABILITY OF SELECTED GROUND REACTION FORCE VARIABLES DURING LANDING  

OpenAIRE

The objectives were to determine the number of trials necessary to achieve performance stability of selected ground reaction force (GRF) variables during landing and to compare two methods of determining stability. Ten subjects divided into two groups each completed a minimum of 20 drop or step-off landings from 0.60 or 0.61 m onto a force platform (1000 Hz). Five vertical GRF variables (first and second peaks, average loading rates to these peaks, and impulse) were quantified during the init...

Roger James, C.; Herman, Joseph A.; Dufek, Janet S.; Bates, Barry T.

2007-01-01

19

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

OpenAIRE

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 platfo...

Natália Mariana Silva Luna; Angelica Castilho Alonso; Guilherme Carlos Brech; Luis Mochizuki; Eduardo Yoshio Nakano; Andrea Greve, Ju?lia Maria D.

2012-01-01

20

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

OpenAIRE

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...

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

2012-01-01

21

Kinetic analysis of ski turns based on measured ground reaction forces.  

Science.gov (United States)

The objective of this study was to devise a method of kinetic analysis of the ground reaction force that enables the durations and magnitudes of forces acting during the individual phases of ski turns to be described exactly. The method is based on a theoretical analysis of physical forces acting during the ski turn. Two elementary phases were defined: (1) preparing to turn (initiation) and (2) actual turning, during which the center of gravity of the skier-ski system moves along a curvilinear trajectory (steering). The starting point of the turn analysis is a dynamometric record of the resultant acting ground reaction force applied perpendicularly on the ski surface. The method was applied to six expert skiers. They completed a slalom course comprising five gates arranged on the fall line of a 26° slope at a competition speed using symmetrical carving turns (30 evaluated turns). A dynamometric measurement system was placed on the carving skis (168 cm long, radius 16 m, data were recorded at 100 Hz). MATLAB procedures were used to evaluate eight variables during each turn: five time variables and three force variables. Comparison of the turn analysis results between individuals showed that the method is useful for answering various research questions associated with ski turns. PMID:21904012

Vaverka, Frantisek; Vodickova, Sona; Elfmark, Milan

2012-02-01

22

Ability of Sagittal Kinematic Variables to Estimate Ground Reaction Forces and Joint Kinetics in Running  

Science.gov (United States)

Study Design Controlled laboratory study, cross sectional design. Objective To determine if sagittal kinematic variables can be used to estimate select running kinetics. Background Excessive loading during running has been implicated in a variety of injuries, yet this information is typically not assessed during a standard clinical examination. Developing a clinically feasible strategy to estimate ground reaction forces and joint kinetics may improve the ability to identify those at an increased risk of injury. Methods Three-dimensional kinematics and ground reaction forces of 45 participants were recorded during treadmill running at self-selected speed. Kinematic variables used to estimate specific kinetic metrics included: vertical excursion of the center of mass, foot inclination angle at initial contact, horizontal distance between the center of mass and heel at initial contact, knee flexion angle at initial contact, and peak knee flexion angle during stance. Linear mixed effects models were fitted to explore the association between the kinetic and kinematic measures, including step rate and gender, with final models created using backward variable selection. Results Models were developed to estimate peak knee extensor moment (R2=0.43), energy absorbed at the knee during loading response (R2=0.58), peak patellofemoral joint reaction force (R2=0.55), peak vertical ground reaction force (R2=0.48), braking impulse (R2=0.50), and average vertical loading rate (R2=0.04). Conclusions Our findings suggest that insights into important running kinetics can be obtained from a subset of sagittal plane kinematics common to a clinical running analysis. Of note, the limb posture at initial contact influenced subsequent loading patterns in stance. PMID:25156183

Wille, Christa; Lenhart, Rachel; Wang, Sijian; Thelen, Darryl; Heiderscheit, Bryan

2015-01-01

23

Prediction of ground reaction forces and moments during various activities of daily living.  

Science.gov (United States)

Inverse dynamics based simulations on musculoskeletal models is a commonly used method for the analysis of human movement. Due to inaccuracies in the kinematic and force plate data, and a mismatch between the model and the subject, the equations of motion are violated when solving the inverse dynamics problem. As a result, dynamic inconsistency will exist and lead to residual forces and moments. In this study, we present and evaluate a computational method to perform inverse dynamics-based simulations without force plates, which both improves the dynamic consistency as well as removes the model?s dependency on measured external forces. Using the equations of motion and a scaled musculoskeletal model, the ground reaction forces and moments (GRF&Ms) are derived from three-dimensional full-body motion. The method entails a dynamic contact model and optimization techniques to solve the indeterminacy problem during a double contact phase and, in contrast to previously proposed techniques, does not require training or empirical data. The method was applied to nine healthy subjects performing several Activities of Daily Living (ADLs) and evaluated with simultaneously measured force plate data. Except for the transverse ground reaction moment, no significant differences (P>0.05) were found between the mean predicted and measured GRF&Ms for almost all ADLs. The mean residual forces and moments, however, were significantly reduced (P>0.05) in almost all ADLs using our method compared to conventional inverse dynamic simulations. Hence, the proposed method may be used instead of raw force plate data in human movement analysis using inverse dynamics. PMID:24835471

Fluit, R; Andersen, M S; Kolk, S; Verdonschot, N; Koopman, H F J M

2014-07-18

24

Effects of different lifting cadences on ground reaction forces during the squat exercise.  

Science.gov (United States)

The purpose of this investigation was to determine the effect of different lifting cadences on the ground reaction force (GRF) during the squat exercise. Squats performed with greater acceleration will produce greater inertial forces; however, it is not well understood how different squat cadences affect GRF. The hypotheses were that faster squat cadences would result in greater peak GRF and that the contributions of the body and barbell, both of equivalent mass, to total system inertial force would not be different. Six experienced male subjects (31 +/- 4 years, 180 +/- 9 cm, 88.8 +/- 13.3 kg) performed 3 sets of 3 squats using 3 different cadences (fast cadence [FC] = 1-second descent/1-second ascent; medium cadence [MC] = 3-second descent/1-second ascent; and slow cadence [SC] = 4-second descent/2-second ascent) while lifting a barbell mass equal to their body mass. Ground reaction force and velocity sensor data were used to calculate inertial force contributions of both the body and barbell to total inertial force. Peak GRF were significantly higher in FC squats compared to MC (p = 0.0002) and SC (p = 0.0002). Ranges of GRF were also significantly higher in FC compared to MC (p < 0.05) and higher in MC compared to SC (p < 0.05). The inertial forces associated with the body were larger than those associated with the barbell, regardless of cadence. Faster squat cadences result in significantly greater peak GRF as a result of the inertia of the system. This study demonstrates that GRF was more dependent on descent cadence than on ascent cadence and that researchers should not use a single point on the body to approximate the location of the center of mass during squat exercise analysis. PMID:20386484

Bentley, Jason R; Amonette, William E; De Witt, John K; Hagan, R Donald

2010-05-01

25

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

Science.gov (United States)

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

Puddle, Damien L; Maulder, Peter S

2013-01-01

26

Ground reaction forces and lower-limb joint kinetics of turning gait in typically developing children.  

Science.gov (United States)

Turning is a common locomotor task essential to daily activity; however, very little is known about the forces and moments responsible for the kinematic adaptations occurring relative to straight-line gait in typically developing children. Thus, the aims of this study were to analyse ground reaction forces (GRFs), ground reaction free vertical torque (TZ), and the lower-limb joint kinetics of 90° outside (step) and inside (spin) limb turns. Step, spin, and straight walking trials from fifty-four typically developing children were analysed. All children were fit with the Plug-in Gait and Oxford Foot Model marker sets while walking over force plates embedded in the walkway. Net internal joint moments and power were computed via a standard inverse dynamics approach. All dependent variables were statistically analysed over the entire curves using the mean difference 95% bootstrap confidence band approach. GRFs were directed medially for step turns and laterally for spin turns during the turning phase. Directions were reversed and magnitudes decreased during the approach phase. Step turns showed reduced ankle power generation, while spin turns showed large TZ. Both strategies required large knee and hip coronal and transverse plane moments during swing. These kinetic differences highlight adaptations required to maintain stability and reorient the body towards the new walking direction during turning. From a clinical perspective, turning gait may better reveal weaknesses and motor control deficits than straight walking in pathological populations, such as children with cerebral palsy, and could potentially be implemented in standard gait analysis sessions. PMID:25311452

Dixon, Philippe C; Stebbins, Julie; Theologis, Tim; Zavatsky, Amy B

2014-11-28

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

Directory of Open Access Journals (Sweden)

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.

Natália Mariana Silva Luna

2012-09-01

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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 di [...] vided 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.

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

1023-10-01

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

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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

Damien L. Puddle

2013-03-01

30

Differences in Ground Reaction Forces and Shock Impacts Between Nordic Walking and Walking.  

Science.gov (United States)

The regular practice of Nordic walking (NW) has increased in recent years, in part thanks to the health benefits described by the scientific literature. However, there is no consensus on the effects of shock-impact absorption during its practice. Purpose: The aim of this study was to compare the levels of impact and ground reaction forces (GRF) between NW and walking (W). Method: Twenty physically active and experienced participants were assessed using a dynamometric platform and accelerometry analysis. Results: The results show statistically significantly higher levels of acceleration in the tibia (12%) and head (21%) during NW compared with W. Equally, GRF were significantly higher (27%) at the instant of strike compared with W, and a reduction of the forces at the instant of takeoff (8%) was observed. Conclusions: During NW, shock impacts and GRF levels increased compared with W, an aspect that should be considered when prescribing health improvement programs. PMID:25386664

Encarnación-Martínez, Alberto; Pérez-Soriano, Pedro; Llana-Belloch, Salvador

2014-11-11

31

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

Directory of Open Access Journals (Sweden)

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.

Bhargava P

2007-01-01

32

Test-retest reliability of vertical ground reaction forces during stair climbing in the elderly population.  

Science.gov (United States)

The purpose of the study was to determine the reliability of vertical ground reaction force (VGRF) parameters during stair ascent and descent in the elderly. Forty-two elderly subjects (80.1 SD 6.4 years) were asked to perform three stair ascents and descents at their self-selected normal speed. VGRF were measured during two consecutive steps on an instrumented staircase. Force-time curves where then parameterized into force, force-time and time variables, according to a previously suggested protocol. In addition, force and force-time variables were normalized to body weight. Intraclass correlation coefficients (ICC) type (2, 1) and coefficients of variation (CV) were calculated. Force variables showed moderate to good reliability for the normalized values with ICCs ranging from 0.537 to 0.836 and CVs between 2.52% and 6.51%. Variability of Fmax1 and Fmin appeared to be higher in stair descent with CVs of >5.20% as compared to stair ascent (<3.75%). Time variables showed good reliability in stair ascent but were clearly lower in stair descent (ICCs between 0.108 and 0.684 and CVs between 10.70% and 14.45%). Significant differences were found for the ICCs between the absolute and normalized values as well as for the ICCs of the time dependent and CVs of all variables between stair ascent and descent.It has been concluded that VGRF parameters can be used as a reliable measurement tool for the quantification of stair climbing in the elderly. The present data can be further used as reference values in future investigations. PMID:21764316

Leitner, Monika; Schmid, Stefan; Hilfiker, Roger; Radlinger, Lorenz

2011-07-01

33

Reducing ground reaction forces in gymnastics' landings may increase internal loading.  

Science.gov (United States)

The aim of this study was to use a subject-specific seven-link wobbling mass model of a gymnast, and a multi-layer model of a landing mat, to determine landing strategies that minimise ground reaction forces (GRF) and internal forces. Subject-specific strength parameters were determined that defined the maximum voluntary torque/angle/angular velocity relationship at each joint. These relationships were used to produce subject-specific 'lumped' linear muscle models for each joint. Muscle activation histories were optimised using a Simplex algorithm to minimise GRF or bone bending moments for forward and backward rotating vault landings. Optimising the landing strategy to minimise each of the GRF reduced the peak vertical and horizontal GRF by 9% for the backward rotating vault and by 8% and 48% for the forward rotating vault, compared to a matching simulation. However, most internal loading measures (bone bending moments, joint reaction forces and muscle forces) increased compared to the matching simulation. Optimising the landing strategy to minimise the peak bone bending moments resulted in reduced internal loading measures, and in most cases reduced GRF. Bone bending moments were reduced by 27% during the forward rotating vault and by 2% during the backward rotating vault landings when compared to the matching simulations. It is possible for a gymnast to modify their landing strategy in order to minimise internal forces and lower GRF. However, using a reduction in GRF, due to a change in landing strategy, as a basis for a reduction in injury potential in vaulting movements may not be appropriate since internal loading can increase. PMID:19281989

Mills, Chris; Pain, Matthew T G; Yeadon, Maurice R

2009-04-16

34

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

International Nuclear Information System (INIS)

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

35

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

Science.gov (United States)

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.

Liu, Tao; Inoue, Yoshio; Shibata, Kyoko

2010-08-01

36

Oxygen Uptake, Muscle Activity and Ground Reaction Force during Water Aerobic Exercises.  

Science.gov (United States)

This study aimed to compare the oxygen uptake (VO2), the muscle activity of lower limbs, and the vertical ground reaction force (V-GRF) of women performing water aerobic exercises at different intensities. 12 young women performed the experimental protocol, which consisted of 3 water exercises (stationary running [SR], frontal kick [FK] and cross country skiing [CCS]) at 3 intensities (first and second ventilatory thresholds and maximum effort). A two-way repeated measures ANOVA was used. Regarding VO2, different responses between intensities (pCCS compared to the SR and FK exercises (pCCS could be used to attenuate the V-GRF; if the purpose is to reduce the muscular activity of lower limbs at a specific intensity, SR could be recommended. PMID:25144436

Alberton, C L; Pinto, S S; Cadore, E L; Tartaruga, M P; Kanitz, A C; Antunes, A H; Finatto, P; Kruel, L F M

2014-12-01

37

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

Science.gov (United States)

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

Christina, Kathryn A; Cavanagh, Peter R

2002-04-01

38

Effects on motor unit potentiation and ground reaction force from treadmill exercise  

Science.gov (United States)

This study was conducted to analyze the characteristics of motor unit potentiation (MUP) and ground reaction force (GRF) in treadmill exercise at the inclines of 0, 5.5 and 11 percent with conjuctive speeds of 7.5, 6, and 5 mph respectively. These speeds and corresponding inclines were set to provide equivalent physiological workloads at 12.5 METS. EMG recordings were taken from the rectus femoris and gastrocnemius of the right leg from 5 subjects. Simultaneous GRF recordings were obtained from a Delmar Avionic treadmill rigged with load cells. Measures for MUP and GRF were taken over a period containing 10 strides at steady pace. It was concluded that the gastrocnemius was more evident in EMG activity in all speed/incline settings over the rectus femoris, and that inclines from 5.5 to 11 percent produced greater GRF's over 0 percent. Recommendations for future studies was made.

Elam, Reid P.

1989-01-01

39

Relations between compressive axial forces in an instrumented massive femoral implant, ground reaction forces, and integrated electromyographs from vastus lateralis during various 'osteogenic' exercises.  

Science.gov (United States)

A subject, who had undergone surgery to replace one hip joint and the proximal half of the femur with an instrumented titanium implant, performed brief exercises whilst simultaneous measurements were made of compressive axial force in the implant using short-range wireless telemetry, ground reactions using a Kistler force plate, and electromyographic activity of the vastus lateralis (VL) and erector spinae (ES) muscles using surface electrodes. Recordings were made barefoot and wearing 'trainers'. The exercises (slow jumping in counter movement style, fast continuous jumping, and jogging on the spot) have been found effective in controlled interventions for increasing bone mineral density in women. The implant forces were 250-400% BW. The values were about twice the magnitude of the ground reaction forces and significantly correlated with them for both peak force and its rate of rise but their relative magnitudes varied depending on mode of activity (jumping or jogging). Implant forces were significantly related to the muscle activity; in multiple regression analysis implant forces during take off from slow jumps VL contributed significantly in addition to the ground reaction (98% total explained variance). There was more activity in VL during jumping than jogging for the same implant force which may explain why jumping appears to be more osteogenic than jogging for the femur. For the same ground reaction, wearing trainers increased both the magnitude of the compressive loading of the femur and its rate of rise. PMID:9119820

Bassey, E J; Littlewood, J J; Taylor, S J

1997-03-01

40

Offensive and defensive agility: a sex comparison of lower body kinematics and ground reaction forces.  

Science.gov (United States)

The aim of this study was to compare biomechanical and perceptual-cognitive variables between sexes during an offensive and defensive agility protocol. Twelve male and female (n = 24) recreational team sport athletes participated in this study, each performing 12 offensive and defensive agility trials (6 left, 6 right) changing direction in response to movements of a human stimulus. Three-dimensional motion, ground reaction force (GRF), and impulse data were recorded across plant phase for dominant leg change of direction (COD) movements, while timing gates and high-speed video captured decision time, total running time, and post COD stride velocity. Subjects also performed a unilateral isometric squat to determine lower body strength and limb dominance. Group (sex) by condition (2 × 2) MANOVAs with follow-up ANOVAs were conducted to examine differences between groups (P ? .05). Male athletes demonstrated significantly greater lower body strength, vertical braking force and impulse application, knee and spine flexion, and hip abduction, as well as faster decision time and post COD stride velocity during both agility conditions compared with females. Differences between offensive and defensive movements appear to be attributed to differences in decision time between sexes. This study demonstrates that biomechanical and perceptual-cognitive differences exist between sexes and within offensive and defensive agility movements. PMID:24615296

Spiteri, Tania; Hart, Nicolas H; Nimphius, Sophia

2014-08-01

41

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

DEFF Research Database (Denmark)

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.

Ketabi, Shahin; Kersting, Uwe G.

2013-01-01

42

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

Science.gov (United States)

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.

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

2010-01-01

43

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

Science.gov (United States)

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 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.

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

2010-01-01

44

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

Science.gov (United States)

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 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.

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

2010-01-01

45

Low strength is related to diminished ground reaction forces and walking performance in older women  

Science.gov (United States)

The purpose of this study was to determine how lower-limb strength in older women affected gait speed, supportive forces, spatial, and temporal aspects of walking gait. Twenty-four women between 65 – 80 yr performed maximal voluntary isometric contractions for the knee extensors (KE), knee flexors (KF), ankle plantarflexors (PF) and ankle dorsiflexors (DF) and were separated into low strength and normal strength groups using a KE torque threshold of 1.5 Nm kg?1. They walked at both a standard speed of 0.8 m s?1 and at a self-selected maximal speed on an instrumented treadmill that recorded vertical ground reaction forces (vGRF) and spatiotemporal gait measures. Older women with low strength had 30% lower KE maximal torque, 36% lower PF maximal torque, 34% lower KE rate of torque development (RTD) and 30% lower KF RTD. Low strength women demonstrated slower maximal walking speeds (1.26 ± 0.20 vs. 1.56 ± 0.20 m s?1), lower vGRF during weight acceptance (1.15 ± 0.10 vs. 1.27 ± 0.13 BW), lower weight acceptance rates (11.3 ± 0.5 vs. 17.0 ± 5.5 BW s?1), slower stride rates, shorter stride lengths, and longer foot-ground and double-limb support times (all P vGRF and rate (r = 0.60 – 0.85, P < 0.01) and moderately related to lower-limb strength (r = 0.42 – 0.60, P < 0.05). In older women with low strength, diminished peak vGRFs were associated with slower walking speeds putting them at risk for mobility limitation, disability, poor health, and loss of independence. PMID:21458271

LaRoche, Dain P.; Millett, Erica D.; Kralian, Rachel J.

2011-01-01

46

Relationship between vertical ground reaction force and speed during walking, slow jogging, and running.  

Science.gov (United States)

OBJECTIVE: To obtain descriptive information between vertical ground reaction force (GRF)-time histories and gait speed, running style, and gender. DESIGN: GRF-time history measurements were obtained from male and female subjects during walking, slow jogging, jogging and running on an indoor platform. BACKGROUND: Previous studies have established GRF descriptor variables for male subjects running at speeds from 3 to 6 m s(-1), but very little descriptive data exists for slower or faster running, nor have previous studies reported GRF descriptors separately for female subjects. METHODS: GRF-time histories were recorded for 13 male and 10 female recreational athletes during walking and slow jogging at speeds between 1.5 and 3.0 m s(-1), and running at speeds between 3.5 and 6.0 m s(-1). Vertical GRF-time data for trials with speeds within 0.2 m s(-1) of the prescribed speed were analysed to determine thrust maximum GRF (F(z)) and loading rate (G(z)). RESULTS: In both male and female subjects, F(z) increased linearly during walking and running from 1.2 BW to approximately 2.5 BW at 6.0 m s(-1), remaining constant during forward lean sprinting at higher speeds. F(z) was linearly correlated to G(z), the latter ranging from 8 to 30 BW s(-1) over this speed range. Slow jogging was associated with a > 50% higher F(z) and G(z) in comparison to walking or fast running. CONCLUSIONS: Similar GRF descriptor data and velocity relationships were obtained for male and female subjects. Impact forces were greatest when the subjects adopted a higher, less fixed centre of gravity during slow jogging. RELEVANCE: These results suggest that vertical GRF norms can be established for male and female subjects alike, and that slow or fast running with a lower, fixed centre of gravity decreases impact forces. PMID:11415629

Keller, T S; Weisberger, A M; Ray, J L; Hasan, S S; Shiavi, R G; Spengler, D M

1996-07-01

47

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

Science.gov (United States)

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…

Hughes, Gerwyn; Watkins, James; Owen, Nick

2010-01-01

48

Effect of plantar flexion and eversion on mediolateral ground reaction force in subjects with functional ankle instability  

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Full Text Available Abstract   Background and Aim: The common mechanism for lateral ankle sprain is inversion, plantar flexion, or the combination of both, if untreated successfully can lead to chronic ankle instability. It seems that the foot position, while touching the ground, has an effective role to cause ankle sprain. Thus it is possible to prevent ankle sprain through limiting foot position. Therefore the aim of this research is to study the effect of plantar flexion and eversion on mediolateral ground reaction force while landing in individuals who suffering from functional ankle instability.    Materials and Methods: In this case-control research study 32 subjects (17 subjects with unilateral functional ankle instability (FAI and 15 control subjects, aged from 18 to 35 years, were tested. All subjects in instability group were selected by the orthopedic physician, then the anterior drawer and talar tilt tests were  performed for diagnosis of functional ankle instability and other physical examinations. Control group were matched with instability group by age, weight, height, gender and body mass index. The subjects standing with single leg on a 40 cm high platform in 25 cm front of a force-plate while the test leg relaxed and non-weight bearing. The subject landed on the test leg on the center of the force-plate. The subjects landed according to four types of position: A: neutral position of ankle and lateral foot wedge, B: neutral position of ankle, C: positive heel and lateral foot wedge and D: positive heel.   Results: Among control group, medial ground reaction force increased in the "C" position relative to "B" position (p=0.007 and "C" position relative to "D" position (p=0.018. In FAI group, lateral ground reaction force increased in "C" position relative to "B" position (p=0.001 and "C" position relative to "A" position (p=0.002. Also in FAI group medial ground reaction force decreased in "D" position relative to "A" position (p=0.014.   Conclusion: According to the findings, applying lateral foot wedge, while the ankle is in plantar flexion, increases the mediolateral ground reaction forces. Based on the results, position of plantar flexion is more possibly effective than inversion in ankle sprain. According to the study, the lateral foot wedge in ankle plantar flexion position may be more effective than in neutral one to change mediolateral ground reaction forces.   Key words: Functional ankle instability, Position of foot, Landing, Lateral foot wedge  

Ali Ashraf Jamshidi

2012-10-01

49

Using ground reaction force to predict knee kinetic asymmetry following anterior cruciate ligament reconstruction.  

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Asymmetries in sagittal plane knee kinetics have been identified as a risk factor for anterior cruciate ligament (ACL) re-injury. Clinical tools are needed to identify the asymmetries. This study examined the relationships between knee kinetic asymmetries and ground reaction force (GRF) asymmetries during athletic tasks in adolescent patients following ACL reconstruction (ACL-R). Kinematic and GRF data were collected during a stop-jump task and a side-cutting task for 23 patients. Asymmetry indices between the surgical and non-surgical limbs were calculated for GRF and knee kinetic variables. For the stop-jump task, knee kinetics asymmetry indices were correlated with all GRF asymmetry indices (P?

Dai, B; Butler, R J; Garrett, W E; Queen, R M

2014-12-01

50

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

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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

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

2008-12-01

51

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

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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

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

2014-01-01

52

NUMBER OF TRIALS NECESSARY TO ACHIEVE PERFORMANCE STABILITY OF SELECTED GROUND REACTION FORCE VARIABLES DURING LANDING  

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Full Text Available The objectives were to determine the number of trials necessary to achieve performance stability of selected ground reaction force (GRF variables during landing and to compare two methods of determining stability. Ten subjects divided into two groups each completed a minimum of 20 drop or step-off landings from 0.60 or 0.61 m onto a force platform (1000 Hz. Five vertical GRF variables (first and second peaks, average loading rates to these peaks, and impulse were quantified during the initial 100 ms post-contact period. Test-retest reliability (stability was determined using two methods: (1 intra-class correlation coefficient (ICC analysis, and (2 sequential averaging analysis. Results of the ICC analysis indicated that an average of four trials (mean 3.8 ± 2.7 Group 1; 3.6 ± 1.7 Group 2 were necessary to achieve maximum ICC values. Maximum ICC values ranged from 0.55 to 0.99 and all were significantly (p < 0. 05 different from zero. Results of the sequential averaging analysis revealed that an average of 12 trials (mean 11.7 ± 3.1 Group 1; 11.5 ± 4.5 Group 2 were necessary to achieve performance stability using criteria previously reported in the literature. Using 10 reference trials, the sequential averaging technique required standard deviation criterion values of 0.60 and 0.49 for Groups 1 and 2, 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 for determining stability, especially when compared to previous applications of the sequential averaging technique. Moreover, criteria for implementing the sequential averaging technique can be adjusted so that results closely approximate the results from ICC. In conclusion, subjects in landing experiments should perform a minimum of four and possibly as many as eight trials to achieve performance stability of selected GRF variables. Researchers should use this information to plan future studies and to report the stability of GRF data in landing experiments

C. Roger James

2007-03-01

53

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

OpenAIRE

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...

Kyoko Shibata; Yoshio Inoue; Tao Liu(Institut für Theoretische Teilchenphysik, Karlsruhe Institute of Technology (KIT), D-76128 Karlsruhe, Germany)

2010-01-01

54

An investigation into the vertical ground reaction force status in the coper and non-coper ACL-deficient knee subjects during walking on level ground  

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Full Text Available Background and Aim: An immaculate review of the literature reveals some changes on the vertical ground reaction force (VGRF in ACL deficient knee subjects. However, the details are not clear yet. The current study aimed to study these changes in the ACL-deficient and apparently healthy knees of the coper and non-coper ACL-deficient knee subjects in comparison with the normal knees. Materials and Methods: Sixteen unilateral ACL-torn subjects included 8 copers and 8 non-copers were recruited in this quasi-experimental study and were compared with 16 normal knee subjects (8 subjects matched to each coper and non-coper groups. All subjects walked barefoot and with their preferred speed in a 6-meter walkway and placed their wanted foot on the platform of a Zebris pedobarograph tool. The patients were asked to place their injured and healthy feet separately on the platform. The control group placed their foot matched to the ACL-deficient legs on the platform. The testes were repeated so much to have five acceptable trials. The outcome measures included the peak F1Z, F2Z, F3Z of the vertical ground reaction force values and the times to reach these peak values as well as total stance time of the tested feet. Results: The results showed only a significant lower F1Z value in the non-coper ACL-deficient knee subjects (p=0.008. No significant changes were shown in the F2Z, F3Z or the times reach to F1Z, F2Z and F3Z values (p>0.05. The stance time of the coper ACL-deficient knee subjects increased significantly in the non-coper ACL-deficeint knee subjects when compared to the coper and healthy knees (p=0.005. Conclusion: The reduced F1Z of the vertical ground reaction force at initial contact as well as increased total stance time seen only in non-coper ACL-deficient knee subjects reveals inadequate compensatory mechanism in these patients as a counter force stress at initial contact and weight bearing. However, the coper ACL-deficient knee subjects compensated these forces with good strategies and walked very similar to the control group. Keywords: Vercial ground reaction force (VGRF, Time to peak vertical ground reaction force components, Coper & non-coper ACL-deficient knee subjects, Pedobarography.

Narjes Soltani

2014-10-01

55

Influence of a commercially available orthotic device on rearfoot eversion and vertical ground reaction force when running in military footwear.  

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The objective of this study was to investigate the influence of a commercially available orthotic device on rearfoot movement and peak impact force variables during running in combat assault boots. Eight military trainees performed running trials under two running conditions: boot with standard-issue insole and boot with the test orthotic. For each trial, vertical ground reaction force and frontal plane rearfoot angle data were collected. It was found that peak eversion angle was not significantly influenced by the orthotic device (p > 0.05), but that this peak occurred later in stance (p force, average rate of loading, and peak rate of loading of impact force were all lower when the orthotic device was used (p < 0.05). The findings of this study highlight the potential of a commercially available orthotic to provide benefits more typically associated with molded prescription orthoses, providing a cost-effective option to the routine use of prescription orthotic devices. PMID:17484322

Dixon, Sharon J

2007-04-01

56

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

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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.

Wefstaedt Patrick

2009-11-01

57

The influence of an additional load on time and force changes in the ground reaction force during the countermovement vertical jump.  

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The aim of this study was to determine how an additional load influences the force-vs-time relationship of the countermovement vertical jump (CMVJ). The participants that took part in the experiment were 18 male university students who played sport recreationally, including regular games of volleyball. They were asked to perform a CMVJ without involving the arms under four conditions: without and with additional loads of 10%, 20%, and 30% of their body weight (BW). The vertical component of the ground reaction force (GRF) was measured by a force plate. The GRF was used to calculate the durations of the preparatory, braking, and acceleration phases, the total duration of the jump, force impulses during the braking and acceleration phases, average forces during the braking and acceleration phases, and the maximum force of impact at landing. Results were evaluated using repeated-measures ANOVA. Increasing the additional load prolonged both the braking and acceleration phases of the jump, with statistically significant changes in the duration of the acceleration phase found for an additional load of 20% BW. The magnitude of the force systematically and significantly increased with the additional load. The force impulse during the acceleration phase did not differ significantly between jumps performed with loads of 20% and 30% BW. The results suggest that the optimal additional load for developing explosive strength in vertical jumping ranges from 20% to 30% of BW, with this value varying between individual subjects. PMID:24235994

Vaverka, Frantisek; Jakubsova, Zlatava; Jandacka, Daniel; Zahradnik, David; Farana, Roman; Uchytil, Jaroslav; Supej, Matej; Vodicar, Janez

2013-01-01

58

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

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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.

Takahashi, Hidetoshi; Thanh-Vinh, Nguyen; Jung, Uijin G.; Matsumoto, Kiyoshi; Shimoyama, Isao

2014-06-01

59

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

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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.

S. Rafajlovi?

2009-06-01

60

Dimensional analysis and ground reaction forces for stair climbing: effects of age and task difficulty.  

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Altered perception-action capability is often associated with falls and diminished self-efficacy in older people. This study evaluated and compared perception-action capability in stair-climbing performance of 18 healthy volunteers assigned to two age groups (mean age, 26.3+/-4.3 years and 66.4+/-4.7 years, respectively). The experimental set-up included 14 stairs (50 cm wide, 60 cm deep, riser height 35-90 cm) positioned at the edge of a force platform. The task was to climb the stair with the greatest riser height subjects thought they could climb without outside support or use of hands. Dimensional and dynamic data were collected and analyzed to reveal the invariant relationships that sustain action preparation and execution. All subjects chose the same proportion between stair height and distance covered before mounting the stair, as expressed by the invariant angle (alpha). While the geometric invariant relationship was picked up as a visual guide prior to action, there was a dynamic invariance in the forces applied during actual execution. To establish whether the invariance still held in extreme cases, two perturbed conditions were introduced in which stair distances were changed, forcing subjects to execute a foot-strike, either very far from or near to the stair, before climbing it, so as to reveal any significant adaptations the climber would undertake to avoid slips or falls. Older and younger subjects applied appropriate visual and motor guidance by scaling their motor capabilities to the environmental dimensions. PMID:19019678

Bertucco, Matteo; Cesari, Paola

2009-02-01

61

A comparison of ground reaction forces during level and cross-slope walking in Labrador Retrievers.  

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BackgroundInclined or slippery surfaces and various other types of obstacles are common demands in our environment. Dogs with impaired locomotion might have difficulties to manage rough terrain. Gait analyses using force plates or pressure plates, which are well established to characterize limb loads in human medicine as well as in animals, are mostly limited to level surfaces. Therefore, the aim of this study was to investigate the effect of cross-slope walking in ten healthy Labrador Retrievers using a pressure plate walkway system. The dogs walked over the pressure plate on a level surface, with a lateral elevation angle of 10° (CS1) or 15° (CS2) until five valid trials were achieved. Three measurements were obtained at weekly intervals. Peak vertical force (PFz), vertical impulse (IFz), step length, and velocity were determined.ResultsCompared to level walking (LW), cross-slope walking was associated with a significant decrease in GRF of the up-slope (US) hindlimb, which was compensated for by the down-slope (DS) forelimb. The other diagonal limb pair showed less pronounced effects during CS1, but in CS2 more weight was shifted onto the DS hindlimb during the first two measurements, thus reducing weight on the US forelimb (for IFz). The effect diminished from trial to trial, with GRF values approaching LW standards finally. The IFz was a more sensitive measure than the PFz. The step length of the DS forelimb was significantly decreased in both cross-slope conditions, while the step length of the US forelimb only decreased during CS2.ConclusionsThe dogs adapted their gait pattern and step length to compensate for the discrepancy in apparent leg length caused by the cross-slope. The results suggest that cross-slope walking requires functional musculoskeletal adaptations that may be difficult for animals with impaired locomotion. Further, this knowledge might be of clinical impact for early diagnosis of neurological disorders, mild lameness and proprioceptive deficits. PMID:25262070

Strasser, Therese; Peham, Christian; Bockstahler, Barbara A

2014-09-28

62

Effects of fatigue on frontal plane knee motion, muscle activity, and ground reaction forces in men and women during landing.  

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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 fatigued landings. No other variables exhibited a fatigue main effect, although there was a significant (p 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. Key pointsFatigue reduces ground reaction forces in both men and women during drop-jump landings.There was no significant difference in frontal plane knee kinematics between men and women when they were fatigued.Men and women did show differences in frontal plane knee kinematics in the fatigued state compared to the pre-fatigued state and the increased motion was in the valgus direction and varus direction.Single subject analysis shows that both women and men exhibit characteristics that may predispose them to ACL injury. PMID:24150006

Smith, Michael P; Sizer, Phillip S; James, C Roger

2009-01-01

63

Vertical ground reaction force responses to different head-out aquatic exercises performed in water and on dry land.  

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Abstract The purpose was to analyse the vertical ground reaction forces (Fz) of head-out aquatic exercises [stationary running (SR), frontal kick (FK), cross-country skiing (CCS), jumping jacks (JJ), adductor hop (ADH) and abductor hop (ABH)] at two cadences in both aquatic and dry land environments. Twelve young women completed two sessions in each environment, each consisting of three exercises performed at two cadences (first and second ventilatory thresholds - C1 and C2, respectively). Two-way and three-way repeated measures analysis of variance were used to the statistical analysis. The results showed that the peak Fz and impulse were significantly lower in the aquatic environment, resulting in values from 28.2% to 58.5% and 60.4% to 72.8% from those obtained on dry land, respectively. In the aquatic environment, the peak Fz was lower and the impulse was higher at the C1 than at the C2. Furthermore, it was observed that SR and FK (0.9-1.1 BW) elicited a significantly higher peak Fz values compared to the ADH and JJ exercises (0.5-0.8 BW). It can be concluded that the aquatic environment reduces the Fz during head-out aquatic exercises. It should be noted that its magnitude is also dependent on the intensity and the identity of the exercise performed. PMID:25356625

Alberton, Cristine Lima; Finatto, Paula; Pinto, Stephanie Santana; Antunes, Amanda Haberland; Cadore, Eduardo Lusa; Peikriszwili Tartaruga, Marcus; Kruel, Luiz Fernando Martins

2014-10-30

64

Ground reaction forces and throwing performance in elite and novice players in two types of handball shot.  

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The purpose of this study was to examine the differences in the ground reaction force (GRF) patterns between elite and novice players during two types of handball shots, as well as the relationships between throwing performance and the GRF variables. Ball velocity and throwing accuracy were measured during jump shots and 3-step shots performed by 15 elite and 15 novice players. The GRF pattern was recorded for the vertical and the anterior-posterior GRF components (Kistler forceplate type-9281, 750Hz). One-way ANOVA was used for the group differences and the Pearson coefficient for the correlation between throwing performance and GRF variables (SPSS 21.0, p ? 0.05). The elite players performed better in both types of shot. Both groups developed consistent and similar GRF patterns, except for the novices' inconsistent Fz pattern in the 3-step shot. The GRF variables differed significantly between groups in the 3-step shot (p ? 0.05). Significant correlations were found only for ball velocity and predominantly for the novice players during the 3-step shot (p ? 0.05). The results possibly highlight a shortage in the novice ability to effectively reduce their forward momentum so as to provide a stable base of support for the momentum transfer up the kinetic chain, a situation that may predispose athletes to injury. PMID:25031672

Rousanoglou, Elissavet; Noutsos, Konstantinos; Bayios, Ioannis; Boudolos, Konstantinos

2014-03-27

65

Gait analysis by measuring ground reaction forces in children: changes to an adaptive gait pattern between the ages of one and five years.  

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The aim of this study was to look at the maturational profile of gait parameters by measuring ground reaction forces during independent walking in children. Fifty-four normal children aged 1 to 5 years were examined. The children walked with eight force transducers under each sole. Gait velocity and step length increased with age, whereas step frequency remained relatively constant. Phases of double ground contact expressed as percentages of the total gait cycle decreased significantly from age 1 to 5 with the steepest decrease occurring in the first year of independent walking. No asymmetry between left and right could be detected for any of these parameters. The pattern of ground reaction forces with a significant heel strike and obvious enrollment process resembling that in adults was achieved between the age of 2 and 3 years. Measuring ground reaction forces is a fast and easily manageable method of analysing gait pattern in children and is also a promising tool for detection of gait abnormalities in children with neurological disease. PMID:9183260

Preis, S; Klemms, A; Müller, K

1997-04-01

66

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

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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

Jasmes M.W. Brownjohn

2009-12-01

67

Biomechanical comparison of interfragmentary movements and ground reaction forces of two monolateral external fixators with different stiffness in a sheep model  

OpenAIRE

Biomechanical factors in fracture healing are yet not been completely finalised and current clinical methods for monitoring fracture healing are often invasive and inaccurate. This study evaluates the non-invasive measurement of the interfragmentary movements and ground reaction forces in two monolateral external fixators with different stiffness to define the ideal factors that optimise the fracture healing. Standardised 3 mm diaphyseal bone defects were created in the right tibia of 64 ...

Parwani, Abdul Shokor

2010-01-01

68

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

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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

Michael P. Smith

2009-09-01

69

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

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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.

Alessandro Haupenthal

2010-09-01

70

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

Directory of Open Access Journals (Sweden)

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.

Akashi Paula MH

2010-02-01

71

The effect of changing the inertia of a trans-tibial dynamic elastic response prosthesis on the kinematics and ground reaction force patterns.  

Science.gov (United States)

The aim of this study was to assess, by means of gait analysis, the effect on the gait of a trans-tibial amputee of altering the mass and the moment of inertia of a dynamic elastic response prosthesis. One male amputee was analysed for four to five walking trials at normal and fast cadences, using the VICON system of motion analysis and an AMTI force plate. The kinematic variables of cadence, swing time, single support time and joint angles for the knee and hip on the affected and intact sides were analysed. The ground reaction force was also analysed. The sample size was limited to one as an example to indicate the changes which are possible through simply changing the inertial characteristics. Descriptive statistics are used to demonstrate these changes. Three mass conditions for the prosthesis were analysed m1: 1080g; m2: 1080 + 530g; m3: 1080 + 1460g. The m1 condition is the mass of the prosthesis with no added weight while m2 and m3 were attachments of the same geometrical shape but were made from different materials. It was felt that the large mass range would highlight biomechanical adjustments as a result of its alteration. The effect on selected temporal characteristics were that as the speed increased the cadence changed and the affected side single support times as a percentage of the gait cycle were altered. The effect on the joint angles was also apparent at the hip and knee of both sides. The ground reaction force patterns were similar for all three mass conditions, though the impact peak which was evident in the intact limb was missing, indicating a shock absorbing property in the prosthesis. Clearly, changing the mass and moment of inertia has an effect on the kinematic variables of gait and should be considered when designing a prosthesis. PMID:9285955

Hillery, S C; Wallace, E S; McIlhagger, R; Watson, P

1997-08-01

72

Influence of pressure-relief insoles developed for loaded gait (backpackers and obese people) on plantar pressure distribution and ground reaction forces.  

Science.gov (United States)

The aims of this study were to test the effects of two pressure relief insoles developed for backpackers and obese people on the ground reaction forces (GRF) and plantar pressure peaks during gait; and to compare the GRF and plantar pressures among normal-weight, backpackers, and obese participants. Based on GRF, plantar pressures, and finite element analysis two insoles were manufactured: flat cork-based insole with (i) corkgel in the rearfoot and forefoot (SLS1) and with (ii) poron foam in the great toe and lateral forefoot (SLS2). Gait data were recorded from 21 normal-weight/backpackers and 10 obese participants. The SLS1 did not influence the GRF, but it relieved the pressure peaks for both backpackers and obese participants. In SLS2 the load acceptance GRF peak was lower; however, it did not reduce the plantar pressure peaks. The GRF and plantar pressure gait pattern were different among the normal-weight, backpackers and obese participants. PMID:24468683

Peduzzi de Castro, Marcelo; Abreu, Sofia; Pinto, Viviana; Santos, Rubim; Machado, Leandro; Vaz, Mario; Vilas-Boas, João Paulo

2014-07-01

73

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

DEFF Research Database (Denmark)

Lameness is a frequent disorder in dairy cows and in large dairy herds manual lameness detection is a time-consuming task. This study describes a method for automatic identification of stance phases in walking cows, and their classification as made by a front or a hind foot based on ground reaction 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 quadrupedal walking. The clusters were identified as full or truncated (incomplete) stance phases furthermore the stance phases were classified as originating from a front or hind foot. Data from 370 walking trials made by 9 cows on 5 experiment days were used to test the method. Four cows were moderately lame at experimental onset. On average 5.1 stance phases per cow per trial were obtained of which 3.2 were classified as full stance phases and therefore appropriate for further gait analysis (the latter not being the scope of this study). Of the 2617 identified clusters 1844 were classified as stance phases, of these 1146 (62%) were automatically identified as full stance phases and classified as made by a front or hind foot. As intended, the procedures did not favour identification of stance phases of healthy cows over lame cows. In addition, a human observer evaluated the stance phases by visual inspection, revealing a very low discrepancy (3.5%) between manual and automated approaches. Further, a sensitivity test indicated large robustness in the automatic procedures. In conclusion, the experimental setup combined with the computerized procedures described in the present study resulted in a high number of stance phases obtained per trial. It is thus a combination which has the potential to enable unsupervised gait analysis based on data collected automatically on-farm

SkjØth, F; Thorup, Vivi MØrkØre

2013-01-01

74

The Influence of an Additional Load on Time and Force Changes in the Ground Reaction Force During the Countermovement Vertical Jump  

OpenAIRE

The aim of this study was to determine how an additional load influences the force-vs-time relationship of the countermovement vertical jump (CMVJ). The participants that took part in the experiment were 18 male university students who played sport recreationally, including regular games of volleyball. They were asked to perform a CMVJ without involving the arms under four conditions: without and with additional loads of 10%, 20%, and 30% of their body weight (BW). The vertical component of t...

Vaverka, Frantisek; Jakubsova, Zlatava; Jandacka, Daniel; Zahradnik, David; Farana, Roman; Uchytil, Jaroslav; Supej, Matej; Vodicar, Janez

2013-01-01

75

Running-specific prostheses limit ground-force during sprinting  

OpenAIRE

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...

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

2010-01-01

76

Unmanned ground vehicles for integrated force protection  

Science.gov (United States)

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.

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

2004-09-01

77

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  

Directory of Open Access Journals (Sweden)

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.

Roberto Bianco

2011-12-01

78

Resonantly Forced Inhomogeneous Reaction-Diffusion Systems  

OpenAIRE

The dynamics of spatiotemporal patterns in oscillatory reaction-diffusion systems subject to periodic forcing with a spatially random forcing amplitude field are investigated. Quenched disorder is studied using the resonantly forced complex Ginzburg-Landau equation in the 3:1 resonance regime. Front roughening and spontaneous nucleation of target patterns are observed and characterized. Time dependent spatially varying forcing fields are studied in the 3:1 forced FitzHugh-Na...

Hemming, C. J.; Kapral, R.

2000-01-01

79

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  

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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.

Kelley George A

2012-09-01

80

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  

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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.

DL Vianna

2006-09-01

81

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  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese 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. Abstract in english 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.

DL, Vianna; JMD, Greve.

2006-09-01

82

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  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese 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 Abstract in english 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 plant [...] ar 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

Roberto, Bianco; Ana Paula da Silva, Azevedo; Carina Helena Wasem, Fraga; Fernanda Michelone, Acquesta; Luis, Mochizuki; Alberto Carlos, Amadio; Júlio Cerca, Serrão.

2011-12-01

83

Exercise Countermeasures for Bone Loss During Space Flight: A Method for the Study of Ground Reaction Forces and their Implications for Bone Strain  

Science.gov (United States)

Effective countermeasures to prevent loss of bone mineral during long duration space flight remain elusive. Despite an exercise program on MIR flights, the data from LeBlanc et al. (1996) indicated that there was still a mean rate of loss of bone mineral density in the proximal femur of 1.58% per month (n=18, flight duration 4 - 14.4 months). The specific mechanisms regulating bone mass are not known, but most investigators agree that bone maintenance is largely dependent upon mechanical demand and the resultant local bone strains. A plausible hypothesis is that bone loss during space flight, such as that reported by LeBlanc et al. (1996), may result from failure to effectively load the skeleton in order to generate localized bone strains of sufficient magnitude to prevent disuse osteoporosis. A variety of methods have been proposed to simulate locomotor exercise in reduced gravity. In such simulations, and in an actual microgravity environment, a gravity replacement load (GRL) must always be added to return the exercising subject to the support surface and the resulting skeletal load is critically dependent upon the magnitude of the GRL. To our knowledge, GRLs during orbital flight have only been measured once (on STS 81) and it is likely that most or all prior treadmill exercise in space has used GRLs that were less than one body weight. McCrory (1997) has shown that subjects walking and running in simulated zero-G can tolerate GRLs of 1 if an appropriate harness is used. Several investigators have attempted to measure in vivo strains and forces in the bones of humans, but have faced ethical and technical limitations. The anteromedial aspect of the tibial midshaft has been a common site for the placement of strain gauges; one reason to measure strains in the anterior tibia is that this region is surgically accessible. Aamodt et al. (1997) were able to measure strains on the lateral surface of the proximal femur only because their experimental subjects were already scheduled for hip surgery. Lu et al. (1997) used an instrumented massive proximal femoral prosthesis along with electromyographic measurements to demonstrate that femoral forces depend on muscular activity. These analyses of in vivo bone mechanics are valuable. The invasive nature of the procedures involved, however, limits both the number of subjects and the number of strain gauge locations. Further, the results of these studies may be confounded by the inclusion of subjects with pathological conditions. Gross et al. (1992) measured strain at three locations on the equine third metacarpal and used those data to construct a computer model of the internal strain environment of the bone. An analogous placement of multiple gauges in living humans would be difficult and potentially hazardous because of the depth of soft tissue overlying the tibia and femur.

Peterman, M.; McCrory, J. L.; Sharkey, N. A.; Piazza, S.; Cavanagh, P. R.

1999-01-01

84

Ground reaction force in basketball cutting maneuvers with and without ankle bracing and taping / Análise da força de reação do solo durante o cutting no basquetebol com e sem o uso de implementos no tornozelo  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese CONTEXTO E OBJETIVO: A lesão mais comum no basquetebol é a entorse de tornozelo. Assim, os atletas freqüentemente utilizam suportes externos como medidas profiláticas. O objetivo deste estudo é avaliar as respostas da força de reação do solo (FRS) durante a execução do movimento de cutting do basque [...] tebol com e sem acessórios de tornozelo. TIPO DE ESTUDO E LOCAL: Estudo comparativo. Delineamento experimental de grupo único com medidas repetidas; Divisão de Medicina de Reabilitação, Hospital das Clínicas, Faculdade de Medicina da Universidade de São Paulo, Brasil. MÉTODOS: Foram colhidas as forças vertical (Fy) e médio-lateral (Fz) em três condições (bandagem, Aircast e calçado esportivo) e analisados os picos de força e de propulsão no contato com o solo (Fymax1, Fzmax1, Fymax2 e Fzmax2), o gradiente de crescimento (pico/tempo) (GC Fymax1, GC Fzmax1, GC Fymax2 e GC Fzmax2) e o impulso após o contato. RESULTADOS: Os acessórios reduziram significativamente Fymax2 e GC Fymax2. GC FZmax1 foi maior na situação com tênis quando comparado com bandagem. No momento do impacto, a bandagem aumentou a Fy em relação ao calçado, mas em um intervalo de tempo maior, não aumentando a carga articular. Fz atingiu um pico em menor tempo, podendo gerar maior carga eversora/inversora. O Aircast exerceu um melhor efeito de absorção de impacto, pois gera menor Fy em um maior intervalo de tempo. CONCLUSÕES: Apesar do uso freqüente deste tipo de recurso pelos atletas, seu mecanismo de ação ainda é confuso. Mais estudos são necessários para esclarecer seus efeitos nas atividades esportivas a longo prazo. Abstract in english CONTEXT AND OBJECTIVE: In basketball, the most common injuries are ankle sprains. For this reason, players frequently use external ankle devices or taping as prophylactic and rehabilitation measures. The purpose of this study was to evaluate ground reaction force (GRF) responses in basketball player [...] s while performing typical cutting maneuvers with and without ankle bracing and ankle taping. DESIGN AND SETTING: Comparative study with experimental design of single-group repeated measurements, at Medical Rehabilitation Division, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo. METHODS: Vertical (Fy) and medial-lateral (Fz) GRF measurements were made under three conditions (taping, Aircast-type orthosis and basketball shoes alone), with analysis of peak forces at foot contact (Fymax1, Fzmax1, Fymax2 and Fzmax2), growth gradient (peak/time) (GG Fymax1, GG Fzmax1, GG Fymax2 and GG Fzmax2) and impulse after foot contact. RESULTS: Bracing significantly reduced Fymax2 and GG Fymax2. GG Fzmax1 was significantly higher for the sport shoe condition than for the taping condition. Taping increased Fy in relation to the sport shoe at foot contact, but over a longer time interval, without increasing excessive ankle loading. Fz reached a peak in less time, which might generate greater inversion/eversion loading on a player's foot. The Aircast exerted better shock-absorbing effect than did the other two conditions, since it generated less vertical force over longer time intervals and smaller medial-lateral forces in relation to taping. CONCLUSIONS: Ankle bracing and ankle taping action mechanisms are still unclear and therefore should be carefully prescribed. More studies are needed to clarify taping and bracing effects on sporting activities.

Isabel de Camargo Neves, Sacco; Henrique Yuji, Takahasi; Eneida Yuri, Suda; Linamara Rizzo, Battistella; Cristianne Akie, Kavamoto; José Augusto Fernandes, Lopes; Jeane Cintra Peixoto de, Vasconcelos.

85

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

DEFF Research Database (Denmark)

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.

Paik, Jeom Kee; Pedersen, Preben Terndrup

1996-01-01

86

A vacuum--generated inertia reaction force  

International Nuclear Information System (INIS)

A clear and succinct covariant approach shows that, in principle, there must be a contribution to the inertia reaction force on an accelerated object by the surrounding vacuum electromagnetic field in which the object is embedded. No details of the vacuum to object electromagnetic interaction need to be specified other than the fact that the object is made of electromagnetically interacting particles. Some interesting consequences of this feature are discussed. This analysis strongly supports the concept that inertia is indeed an opposition of the vacuum fields to any attempt to change the uniform state of motion of material bodies. This also definitely shows that inertia should be viewed as extrinsic to mass and that causing agents and/or mechanisms responsible for the inertia reaction force are neither intrinsic to the notion of mass nor to the entities responsible for the existence of mass in elementary particles (as, e.g., the Higgs field). In other words the mechanism that produces the inertia-reaction-force requires an explicit explanation. This explicit explanation is that inertia is an opposition of the vacuum fields to the accelerated motion of any material entities, i.e., of entities that possess mass. It is briefly commented why the existence of a Higgs field responsible for the generation of mass in elementary particles does not contradict the view presented here. It is also briefly discussed why a strict version of Mach's Principle does really contradict f Mach's Principle does really contradict this view, though a broad sense version of Mach's Principle may be in agreement

87

Tensor Forces and the Ground-State Structure of Nuclei  

Energy Technology Data Exchange (ETDEWEB)

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 {sup 1}S{sub 0} 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.

Rocco Schiavilla

2007-03-01

88

Hole saw drill attachment has zero force reaction  

Science.gov (United States)

Zero reaction tools require no force application by workers in space. The tool accomplishes hole cutting by holding the workpiece and feeding the cutting blade into and through it by forces entirely absorbed within the tool.

Holmes, A. E.; Riley, R. H., Jr.

1966-01-01

89

Ground state octupole correlation energies with effective forces  

CERN Document Server

The ground state octupole correlations energies obtained with the D1M variant of the Gogny force are analyzed in detail. First we consider the correlation energy gained at the mean field level by allowing reflection symmetry breaking. Next we consider the energy gain coming from symmetry (parity) restoration and finally we analyze the ground state correlation energy after configuration mixing with axially symmetric octupole states. We find that these correlations do not significantly affect the trends of binding energies and systematics near closed shells. In particular, the too-large shell gaps predicted by self-consistent mean field models are not altered by the correlations.

Robledo, Luis M

2014-01-01

90

Ground reaction curve based upon block theory  

International Nuclear Information System (INIS)

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

91

Tensor forces and the ground-state structure of nuclei.  

Science.gov (United States)

Two-nucleon momentum distributions are calculated for the ground states of nuclei with mass number Atensor 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). PMID:17501194

Schiavilla, R; Wiringa, R B; Pieper, Steven C; Carlson, J

2007-03-30

92

Analytical r-mode solution with gravitational radiation reaction force  

OpenAIRE

We present and discuss the analytical r-mode solution to the linearized hydrodynamic equations of a slowly rotating, Newtonian, barotropic, non-magnetized, perfect-fluid star in which the gravitational radiation reaction force is present.

Dias, O?scar J. C.; Sa?, Paulo M.

2005-01-01

93

Front explosion in a periodically forced surface reaction  

OpenAIRE

Resonantly-forced oscillatory reaction-diffusion systems can exhibit fronts with complicated interfacial structure separating phase-locked homogeneous states. For values of the forcing amplitude below a critical value the front "explodes" and the width of the interfacial zone grows without bound. Such front explosion phenomena are investigated for a realistic model of catalytic CO oxidation on a Pt(110) surface in the 2:1 and 3:1 resonantly-forced regimes. In the 2:1 regime,...

Davidsen, Jo?rn; Mikhailov, Alexander; Kapral, Raymond

2006-01-01

94

Vertical reaction forces and kinematics of backward walking underwater.  

Science.gov (United States)

The aim of this study was to compare the first and second peaks of the vertical ground reaction force (VGRF) and kinematics at initial contact (IC) and final stance (FS) during walking in one of two directions (forward×backward) and two environments (on land×underwater). Twenty-two adults (24.6±2.6 years) walking forward (FW) and backward (BW) on a 7.5m walkway with a central force plate. Underwater immersion was at the height of the Xiphoid process. Ten trials were performed for each condition giving a total of 40 trials where the VGRF and kinematic data were recorded. Two-way repeated measures analysis of covariance was used with a combination of environment and direction of walking: FW on land, FW underwater, BW on land and BW underwater (entered as between-subjects factor) and repeated measures of VGRF peaks (first and second) or angles (at IC and FS). Walking velocity was included as a covariate. Both VGRF peaks were reduced when participants walked underwater compared to on land (p<.001). For BW, in both environments, the second peak was lower than the first (p<.001; for both). During BW at IC the ankle is more dorsiflexed and the knee is more flexed, both on land and underwater. At FS, there was no difference between the ankle angle for FW and BW in both environments. At IC, in FW and BW the knee and hip are more flexed underwater. BW underwater involves a lower VGRF and more knee and hip flexion than BW on land. PMID:21993483

Carneiro, Leticia Calado; Michaelsen, Stella Maris; Roesler, Helio; Haupenthal, Alessandro; Hubert, Marcel; Mallmann, Eddy

2012-02-01

95

Government Applications Task Force ground truth study of WAG 4  

International Nuclear Information System (INIS)

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

96

Feedback Control of Floor Reaction Force Based on Force-Reflecting-Type Multilateral Control  

Science.gov (United States)

Real-world haptics is being studied not only for improving feedback on real-world haptic information in teleoperation but also for developing key technologies for future human support. For the remote operating of systems at distant places, haptic information is required in addition to visual information. The haptic information around a work environment can be the floor reaction force, which can be obtained using a movement-type haptic device. The floor reaction force from the environment that the mobile haptic device touches is fed back accurately to the operator. First, this paper proposes a general force-reflecting-type multilateral control. Second, this paper extends the control to feedback control of the floor reaction force by using force-reflecting-type multilateral control and a novel haptic device employing a biped robot with a slave system. The position response of a master system is transformed to a leg tip position command for the biped-type haptic device. In addition, the floor reaction force determined by the biped-type haptic device is fed back to the master system. The proposed method can determine the force feedback to the sole of the foot, which is not possible with a conventional stationary system. As a result, the floor reaction force from a large area can be obtained, and the operability of the control system is improved by using the proposed system.

Nagase, Kazuki; Katsura, Seiichiro

97

Government Applications Task Force ground truth study of WAG 4  

Energy Technology Data Exchange (ETDEWEB)

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.

Evers, T.K.; Smyre, J.L.; King, A.L.

1997-06-01

98

A thermodynamic force generated by chemical gradient and adsorption reaction  

CERN Document Server

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.

Sugawara, Takeshi

2009-01-01

99

Comparison of the electron-spin force and radiation reaction force  

Science.gov (United States)

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.

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

2015-02-01

100

Effect of proximity force on potential barrier in fusion reaction  

International Nuclear Information System (INIS)

The macroscopic deformed potential energies for fusion reactions are determined within a generalized liquid drop model (GLDM) which includes the volume-, surface-, and Coulomb-energies, the proximity effects, the mass asymmetry, and an accurate nuclear radius. In ordinary fission studies, it is assumed that the surface and Coulomb-energies control the height and width of the barrier. The surface energy ES takes into account only the effect of the surface tension force and does not include the contribution of the attractive nuclear forces between surfaces in regard to the neck or the gap between the nascent fragments. The nuclear proximity energy is adopted to take into account these additional surface effects in general liquid drop model. At the contact point, the proximity energy reaches maximum while it decreases both sides till to zero. The proximity energy decreases the barrier height by several MeV and moves the position of the barrier top forward, which corresponds to two separated fragments in unstable equilibrium by the balance between the attractive nuclear proximity force and the repulsive Coulomb force in the GDLM. It turns out that a wide macroscopic potential pocket in fusion process is formed due to proximity energy and appears at large deformation. This behavior does not appear at the barrier for the fusion reaction of light nucleus-nucleus collision. (author)

101

Identification of excitation and reaction forces spectra for offshore platforms  

Energy Technology Data Exchange (ETDEWEB)

Offshore platforms subjected to random waves are typically modelled as multi-degree of freedom systems. This paper presented a method of predicting damping and natural frequencies for fixed offshore platform subjected to random wind-generated waves. The method predicted the reaction forces and bending moment at the foundation of the platform. A random decrement signature was used to identify the parameters in the equation of motion. The free decay motion was derived from the stationary random response. The RD was used to describe the free decay response of the system. A simple beam was used to discuss the relationship between the natural frequency of the system and the range of the frequencies of the spectrum of the excitation. Results of the analysis indicated that the RD technique is best applied to lightly damp, linear systems with natural frequencies within the frequency range of the excitation spectrum. The methods can be used to predict the wave exciting force and its location on an offshore structure, as well as to predict reaction forces at the foundation of an offshore structure, and to estimate the total virtual mass of the structure in waves. 18 refs., 3 tabs., 20 figs.

Elshafey, A.A. [Minufiya Univ., Shebin Elkom (Egypt). Dept. of Civil Engineering; Haddara, M. [Ryerson Polytechnic Univ., Toronto, ON (Canada). Dept. of Civil Engineering; Marzouk, H. [Memorial Univ. of Newfoundland, St. John' s, NL (Canada). Dept. of Engineering and Applied Science

2010-01-15

102

Forced thermal cycling of catalytic reactions: experiments and modelling  

DEFF Research Database (Denmark)

Recent studies of catalytic reactions subjected to fast forced temperature oscillations have revealed a rate enhancement increasing with temperature oscillation frequency. We present detailed studies of the rate enhancement up to frequencies of 2.5 Hz. A maximum in the rate enhancement is observed 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 explained by dynamic thermal limitations of the reactor. (c) 2007 Elsevier B.V. All rights reserved.

Jensen, SØren; Olsen, Jakob Lind

2007-01-01

103

Compare and contrast the reaction coordinate diagrams for chemical reactions and cytoskeletal force generators  

OpenAIRE

Reaction coordinate diagrams are used to relate the free energy changes that occur during the progress of chemical processes to the rate and equilibrium constants of the process. Here I briefly review the application of these diagrams to the thermodynamics and kinetics of the generation of force and motion by cytoskeletal motors and polymer ratchets as they mediate intracellular transport, organelle dynamics, cell locomotion, and cell division. To provide a familiar biochemical context for di...

Scholey, Jonathan M.

2013-01-01

104

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

OpenAIRE

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...

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

2012-01-01

105

Resolution of Forces and Strain Measurements from an Acoustic Ground Test  

Science.gov (United States)

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.

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

2013-01-01

106

Microgravity Investigation of Crew Reactions in 0-G (MICR0-G): Ground-Based Development Effort  

Science.gov (United States)

This report describes the technology development of an advanced load sensor ground-based prototype and details the preliminary tests in microgravity during parabolic flights. The research effort is entitled, the Microgravity Investigation and Crew Reactions in 0-G (MICR0-G), a ground-based research effort funded by the National Aeronautics and Space Administration (NASA). The MICR0-G project was a follow-on to the Enhanced Dynamic Load Sensors (EDLS) spaceflight experiment flown on the Russian Space Station Mir. The technology development of the advanced load sensor prototype has been carried out by the Massachusetts Institute of Technology (MIT), with collaboration from Politecnico di Milano University and the Italian Space Agency (ASI). The key hardware of the advanced sensor prototype is a set of two types of load sensors - a hand-hold and foot restraints - similar in appearance to the mobility aids found in the Space Shuttle orbiter to assist the crew in moving inside the spacecraft, but able to measure the applied forces and moments about the x-, y-, and z- axes. The aim of Chapter 1 is to give a brief overview of the report contents. The first section summarizes the previous research efforts on astronaut-induced loads in microgravity. The second section provides information on the MICR0-G research project and the technology development work conducted at MIT. Section 1.3 details the motivation for designing a new generation of load sensors and describes the main enhancements and contributions of the MICR0-G advanced load sensors system compared to the EDLS system. Finally, the last section presents the outline of the report.

Newman, Dava J.

2002-01-01

107

Role of magnetic forces in electrochemical reactions at microstructures.  

Science.gov (United States)

The effect of an external magnetic field (up to 0.8 T) on the anodic dissolution of microstructures has been investigated systematically. Copper and silver wires (100 microm in diameter) were embedded in epoxy resin and dissolved potentiostatically while a magnetic field was periodically switched on and off. A special feature of the thus prepared structures is that they show a smooth transition from an inlaid disk to a recessed disk electrode. An increase or a decrease of the limiting current density in the presence of B was found depending on the orientation of the magnetic field and the hydrodynamic conditions in the cell (natural or forced convection). The magnetic forces which are responsible for this are the Lorentz force and the gradient force. We propose a model which discusses the interaction of these forces with the natural and the forced convection to explain the experimental results. PMID:16853566

Bund, A; Kuehnlein, H H

2005-10-27

108

The solar forcing on the 7Be-air concentration variability at ground level  

International Nuclear Information System (INIS)

This paper analyses the correlation between the temporal and spatial variability of 7Be-air concentration at ground level and the amount of precipitation. There were used the measured data from 26 stations distributed on North America, South America, Australia and Antarctica. The variability study was made using EOF and principal components analysis. The presented results show that the variability of 7 Be air concentration at ground level is simultaneously influenced by the solar cycle and some atmospheric processes like precipitation, turbulent transport, advection, etc. The solar forcing on the 7 Be variability at ground level was outlined for time-scales longer than 1 year and can be considered a global phenomenon. The atmospheric processes influence the 7 Be variability for scale shorter than one year and can be considered a local phenomenon. (author)

109

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

Energy Technology Data Exchange (ETDEWEB)

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.

1992-03-01

110

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

Energy Technology Data Exchange (ETDEWEB)

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.

1991-10-01

111

Use of ground clay brick as a pozzolanic material to reduce the alkali-silica reaction  

International Nuclear Information System (INIS)

The objective of this experimental study was to use ground clay brick (GCB) as a pozzolanic material to minimize the alkali-silica reaction expansion. Two different types of clay bricks were finely ground and their activity indices were determined. ASTM accelerated mortar bar tests were performed to investigate the effect of GCB when used to replace cement mass. The microstructure of the mortar was investigated using scanning electron microscopy (SEM). The results showed that the GCBs meet the strength activity requirements of ASTM. In addition, the GCBs were found to be effective in suppressing the alkali-silica reaction expansion. The expansion decreased as the amount of GCBs in the mortar increased

112

Resonance tongues and patterns in periodically forced reaction-diffusion systems  

CERN Document Server

Various resonant and near-resonant patterns form in a light-sensitive Belousov-Zhabotinsky (BZ) reaction in response to a spatially-homogeneous time-periodic perturbation with light. The regions (tongues) in the forcing frequency and forcing amplitude parameter plane where resonant patterns form are identified through analysis of the temporal response of the patterns. Resonant and near-resonant responses are distinguished. The unforced BZ reaction shows both spatially-uniform oscillations and rotating spiral waves, while the forced system shows patterns such as standing-wave labyrinths and rotating spiral waves. The patterns depend on the amplitude and frequency of the perturbation, and also on whether the system responds to the forcing near the uniform oscillation frequency or the spiral wave frequency. Numerical simulations of a forced FitzHugh-Nagumo reaction-diffusion model show both resonant and near-resonant patterns similar to the BZ chemical system.

Lin, A L; Meron, E; Swinney, H L; Lin, Anna L.; Hagberg, Aric; Meron, Ehud; Swinney, Harry L.

2004-01-01

113

Ground state transitions in (d,6Li) reactions on sd-shell nuclei  

International Nuclear Information System (INIS)

Alpha spectroscopic factors for nuclei of the sd shell are investigated in the case of the (d,6Li) reaction at Esub(d) = 80 MeV. The importance of a careful choice of optical potentials and the necessity of employing coupled channel calculations are demonstrated for transitions leading to the ground states. (author)

114

Comparison of Absolute Thresholds Derived from an Adaptive Forced-Choice Procedure and from Reaction Probabilities and Reaction Times in a Simple Reaction Time Paradigm  

OpenAIRE

An understanding of the auditory system's operation requires knowledge of the mechanisms underlying thresholds. In this work we compare detection thresholds obtained with a three-interval-three-alternative forced-choice paradigm with reaction thresholds extracted from both reaction probabilities (RP) and reaction times (RT) in a simple RT paradigm from the same listeners under otherwise nearly identical experimental conditions. Detection thresholds, RP, and RT to auditory stimuli exhibited su...

Heil, Peter; Neubauer, Heinrich; Tiefenau, Andreas; Von Specht, Hellmut

2006-01-01

115

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

Directory of Open Access Journals (Sweden)

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.

J. A. Santos

2013-07-01

116

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

Science.gov (United States)

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.

Santos, J. A.; Reis, M. A.; De Pablo, F.; Rivas-Soriano, L.; Leite, S. M.

2013-07-01

117

33 CFR 334.710 - The Narrows and Gulf of Mexico adjacent to Santa Rosa Island, Air Force Proving Ground Command...  

Science.gov (United States)

...2010-07-01 false The Narrows and Gulf of Mexico adjacent to Santa Rosa Island, Air Force Proving Ground Command, Eglin Air Force Base...334.710 The Narrows and Gulf of Mexico adjacent to Santa Rosa Island, Air Force Proving Ground Command, Eglin Air Force...

2010-07-01

118

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

Directory of Open Access Journals (Sweden)

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.

J. A. Santos

2012-03-01

119

Harmonic vs. subharmonic patterns in a spatially forced oscillating chemical reaction  

CERN Document Server

The effects of a spatially periodic forcing on an oscillating chemical reaction as described by the Lengyel-Epstein model are investigated. We find a surprising competition between two oscillating patterns, where one is harmonic and the other subharmonic with respect to the spatially periodic forcing. The occurrence of a subharmonic pattern is remarkable as well as its preference up to rather large values of the modulation amplitude. For small modulation amplitudes we derive from the model system a generic equation for the envelope of the oscillating reaction that includes an additional forcing contribution, compared to the amplitude equations known from previous studies in other systems. The analysis of this amplitude equation allows the derivation of analytical expressions even for the forcing corrections to the threshold and to the oscillation frequency, which are in a wide range of parameters in good agreement with the numerical analysis of the complete reaction equations. In the nonlinear regime beyond t...

Hammele, M; Hammele, Martin; Zimmermann, Walter

2006-01-01

120

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

Energy Technology Data Exchange (ETDEWEB)

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).

1991-10-01

121

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

International Nuclear Information System (INIS)

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

122

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

International Nuclear Information System (INIS)

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 verbeetle 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)

123

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

Science.gov (United States)

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)

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

1982-01-01

124

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

Energy Technology Data Exchange (ETDEWEB)

In April 1990, Wright-Patterson Air Force Base (WPAFB) initiated an effort for the evaluation of potential removal of ground water contamination at the Base. This report presents a current assessment of the nature and extent of the contamination believed to be migrating across the southwestern boundary of Area C and the northern boundary of Area B based upon analysis of existing environmental data obtained from several sources. The existing data base indicates widespread, low-level contamination moving across Base boundaries at levels that pose no immediate threat to the Mad River Valley well fields. An investigation by the City of Dayton in May and June 1990, however, implies that a more identifiable plume of PCE and TCE may be crossing the southwestern boundary of Area C immediately downgradient of Landfill 5. More data is needed to delineate ground water contamination and to design and implement a suitable control system. This report concludes that although an extensive study of the boundaries in question would be the preferred approach, a limited, focused investigation and subsequent feasibility study can be accomplished with a reasonable certainty of achieving the desired outcome of this project.

1991-10-01

125

Fine structure in the transition region: reaction force analyses of water-assisted proton transfers.  

Science.gov (United States)

We have analyzed the variation of the reaction force F(?) and the reaction force constant ?(?) along the intrinsic reaction coordinates ? of the water-assisted proton transfer reactions of HX-N = Y (X,Y = O,S). The profile of the force constant of the vibration associated with the reactive mode, k ? (?), was also determined. We compare our results to the corresponding intramolecular proton transfers in the absence of a water molecule. The presence of water promotes the proton transfers, decreasing the energy barriers by about 12 - 15 kcal mol(-1). This is due in part to much smaller bond angle changes being needed than when water is absent. The ?(?) profiles along the intrinsic reaction coordinates for the water-assisted processes show striking and intriguing differences in the transition regions. For the HS-N = S and HO-N = S systems, two ?(?) minima are obtained, whereas for HO-N = O only one minimum is found. The k ? (?) show similar behavior in the transition regions. We propose that this fine structure reflects the degree of synchronicity of the two proton migrations in each case. PMID:22733272

Yepes, Diana; Murray, Jane S; Santos, Juan C; Toro-Labbé, Alejandro; Politzer, Peter; Jaque, Pablo

2013-07-01

126

Stress-modulated driving force for lithiation reaction in hollow nano-anodes  

Science.gov (United States)

Lithiation of a crystalline silicon anode proceeds by the movement of an atomically sharp reaction front that separates a pristine crystalline phase and a fully-lithiated amorphous phase. The velocity of the reaction front is limited rather by the reaction rate at the lithiation front than by the diffusivity of lithium ions in the amorphous lithiated phase. Experiments on solid nanoparticle/nanowire silicon anodes show an initial rapid advancing of reaction front at the initial stage of lithiation, followed by an apparent slowing or even halting of the reaction front propagation. Lithiation-induced stresses during lithiation are attributed to alter the driving force of lithiation and thus result in the observed slowing of reaction front. Recent experiments on lithiation of hollow silicon nanowires reveals similar slowing of reaction front, however, quantitative study of the effect of lithiation-associated stress on the driving force of lithiation still lacks so far. Here, through chemo-mechanical modeling and theoretical formulation, we present a comprehensive study on lithiation-induced stress field and its contribution to the driving force of lithiation reaction in hollow silicon nanowire anodes. We show that hollow silicon nano-anodes could be fully lithiated with lower stress-induced energy barrier than solid silicon nano-anodes. As a result, it is expected that the hollow nanowires and nanoparticles may serve as an optimal structural design for high-performance anodes of lithium-ion batteries. Results from the present study shed light on a number of open questions of lithiation kinetics of silicon-based anodes in recent literature and offer insight on developing silicon-based anodes with high charging capacity and high charging rate.

Jia, Zheng; Li, Teng

2015-02-01

127

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

CERN Document Server

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 about 20MeV, 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 2pi-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 appl...

Witala, Henryk; Skibinski, Roman; Topolnicki, Kacper

2013-01-01

128

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

Directory of Open Access Journals (Sweden)

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?force and average poling force (p?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.

Martin Pšurný

2013-09-01

129

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

International Nuclear Information System (INIS)

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.)

130

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

Science.gov (United States)

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)

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

1986-01-01

131

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

OpenAIRE

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 support...

Josip Serti?; An Kozak, Dra X. E.; Ivan Samardži?

2014-01-01

132

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

Directory of Open Access Journals (Sweden)

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.

Giraux Pascal

2006-11-01

133

Nanostructuring on WSe2 with the atomic force microscope by a potential controlled electrochemical reaction  

OpenAIRE

We present a method for the controlled fabrication of stable nanostructures under ambient conditions. The surfaces under consideration, WSe2, are imaged by an atomic force microscope. By applying a voltage between the tip and the sample, we can control an etching process at the surface: different voltage thresholds for the creation and the growth of structures of one monolayer (Se W Se) depth are observed. Our measurements on p-doped WSe2 strongly support an electrochemical corrosion reaction...

Bo?hmisch, Mathias; Burmeister, Frank; Boneberg, Johannes; Leiderer, Paul

1996-01-01

134

Atomic force microscope based Kelvin probe measurements : application to an electrochemical reaction  

OpenAIRE

An atomic force microscope (AFM) was utilized as a Kelvin probe to determine work functions of several metals and semiconductors quantitarively. Most of the experimental data show excellent agreement with published values measured by photoemission. Variations in work functions as low as 5 mV could be detected with a typical lateral resolution of 20 nm. This method allowed us to analyze and explain the energetics of an electrochemical reaction on the surface of WSe2, which could be in situ ind...

Bo?hmisch, Mathias; Burmeister, Frank; Rettenberger, Armin; Zimmermann, Jo?rg; Boneberg, Johannes; Leiderer, Paul

1997-01-01

135

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

International Nuclear Information System (INIS)

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

136

External forces acting on wall type deep mixing ground improved up to a bearing stratum and its stabilizing mechanism; Chakuteigata kabeshiki shinso kongo kairyo jiban ni sayosuru gairyoku to antei no mechanism  

Energy Technology Data Exchange (ETDEWEB)

In the ground improved by DEEP MIXING (DM) method up to the bearing stratum, it is expected that the displacement of the improved ground is comparatively smaller so that external forces acting on the DM body are mobilized in the process of horizontal displacement of the DM body. External forces on the DM body were measured during the construction of reclaimed land. After various investigations on the stability of the DM ground as well as external forces, the following conclusions were derived. (1) The earth pressure in the active side developed to the active earth pressure as a result of small movement of DM body while that in the passive side remained as the earth pressure at rest. (2) The subgrade reaction forces on the base of the DM body found to be equivalent to the analyzed pressure considering the skin friction acting on the DM wall in the active side. (3) From these evidents, it was confirmed that the mobilizing process of external forces should be taken into account. (4) Further, some problems in the current design method were pointed out from this study. 26 refs., 13 figs., 1 tab.

Noriyasu, N.; Tahara, M. [Chuden Engineering Consultants Co. Ltd., Hiroshima (Japan); Hyodo, M. [Yamaguchi University, Yamaguchi (Japan). Faculty of Engineering; Hayashi, S. [Saga University, Saga (Japan). Faculty of Engineering; Shintani, N. [Chugoku Electric Power Co. Inc., Hiroshima (Japan); Nakasa, T. [Shimizu Corp., Tokyo (Japan)

1997-12-21

137

The reaction of benzene with a ground state carbon atom, C(3Pj)  

International Nuclear Information System (INIS)

The reaction between benzene and a single ground state carbon atom, C(3Pj), which yields a C7H5 radical without a barrier in the exit channel, has been studied using density functional theory (B3LYP), Moeller-Plesset perturbation theory, and the G2(B3LYP/MP2) and complete basis set (CBS) model chemistries. Comparing the computed reaction energies for the formation of various C7H5 radicals with experimental data suggests that the 1,2-didehydrocycloheptatrienyl radical (15) is observed in crossed-beams experiments at collision energies between 2 and 12 kcal mol-1. The carbon atom attacks the ?-electron density of benzene and forms without entrance barrier a Cs symmetric complex (17T) in which the carbon atom is bound to the edge of benzene. From 17T, the insertion of the C atom into a benzene CC bond to yield triplet cycloheptatrienylidene (9T) is associated with a much lower barrier than the insertion into a CH bond to give triplet phenylcarbene (7T). As both steps are strongly exothermic, high energy vinyl carbene rearrangements on the triplet C7H6 potential energy surface provide pathways between 9T and 7T below the energy of separated reactants. In addition, intersystem crossing in the vicinity of 17T and 9T might give rise to singlet cycloheptatetraene (12S). The monocyclic seven-membered ring compounds 9T or 12S are precursors of the 1,2-didehydrocyclohepe precursors of the 1,2-didehydrocycloheptatrienyl radical: the dissociation of a CH bond ? to the divalent carbon atom proceeds without an exit barrier, in agreement with experiment. In contrast, a direct carbon-hydrogen exchange reaction pathway analogous to the aromatic electrophilic substitution followed by rearrangement of phenylcarbyne (13) to 15 involves high barriers (39 kcal mol-1 with respect to separated reactants) and is thus not viable under the experimental conditions. (c) 2000 American Institute of Physics

138

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

Energy Technology Data Exchange (ETDEWEB)

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.

1992-03-01

139

Measurement of Centaur/Orbiter multiple reaction forces in a full-scale test rig  

Science.gov (United States)

A multiple component load cell for measuring load is described, and its capability and reliability are evaluated by utilizing it to measure the reaction forces between the Centaur and Centaur Support Structure. The system employs 11 six-component balances in a single test rig to react a combination of loads. The vehicle and balance loads, procedures for fabricating each balance, and the assembly of the balances are discussed. The calibration and testing of the balances are examined. It is noted that the multiple component load cell system is a cost-effective method for obtaining an accurate measurement of friction effects and primary loads.

Mole, Philip J.; Griffin, Stan A.

1986-01-01

140

In situ atomic force microscope observations of a dissolution– crystallisation reaction: The phosgenite– cerussite transformation  

OpenAIRE

The dissolution–reprecipitation reaction of phosgenite (Pb2Cl2CO3) to cerussite (PbCO3) has been observed in situ in a fluid cell of an atomic force microscope (AFM). The (001) face of phosgenite, in contact with static carbonated aqueous solutions, rapidly begins to dissolve. AFM observations show that dissolution occurs by generation and spread of square-shaped etch pits with sides parallel to (110) directions. The dissolution of the (110) steps is isotropic and the etch pits ...

Pina Marti?nez, Carlos Manuel; Ferna?ndez Di?az, Lourdes; Prieto Rubio, Manuel; Putnis, Andrew

2000-01-01

141

Identification of pseudodiatomic behavior in polyatomic bond dissociation: Reaction force analysis  

Science.gov (United States)

An interesting uniformity that has been observed for diatomic molecular dissociation has been demonstrated to apply to many single bonds in polyatomic molecules as well. The energy to reach a key point in the bond-breaking process, at which it changes from simply stretching to transition to products, is for most cases a nearly constant fraction of the dissociation energy. The point at which this change occurs corresponds to the minimum of the reaction force F(R ) for the dissociation, F(R ) being the negative gradient of the potential energy along the reaction coordinate. Thirty nine single bonds were analyzed at the B3PW91/6-31++G(3d,2p) level. Both adiabatic and vertical stretching were considered; those bonds for which these give essentially the same results are labeled "pseudodiatomic."

Murray, Jane S.; Toro-Labbé, Alejandro; Gutiérrez-Oliva, Soledad; Politzer, Peter

2010-04-01

142

Constructing a Mass-Current Radiation-Reaction Force For Numerical Simulations  

CERN Document Server

We present a new set of 3.5 Post-Newtonian equations in which Newtonian hydrodynamics is coupled to the nonconservative effects of gravitational radiation emission. Our formalism differs in two significant ways from a similar 3.5 Post-Newtonian approach proposed by Blanchet (1993, 1997). Firstly we concentrate only on the radiation-reaction effects produced by a time-varying mass-current quadrupole $S_{ij}$. Secondly, we adopt a gauge in which the radiation-reaction force densities depend on the fourth time derivative of $S_{ij}$, rather than on the fifth, as in Blanchet's approach. This difference makes our formalism particularly well-suited to numerical implementation and could prove useful in performing fully numerical simulations of the recently discovered $r$-mode instability for rotating neutron stars subject to axial perturbations.

Rezzolla, L; Asada, H; Baumgarte, T W; Shapiro, S L

1999-01-01

143

Development of Velocity Guidance Assistance System by Haptic Accelerator Pedal Reaction Force Control  

Science.gov (United States)

This research proposes a haptic velocity guidance assistance system for realizing eco-driving as well as enhancing traffic capacity by cooperating with ITS (Intelligent Transportation Systems). The proposed guidance system generates the desired accelerator pedal (abbreviated as pedal) stroke with respect to the desired velocity obtained from ITS considering vehicle dynamics, and provides the desired pedal stroke to the driver via a haptic pedal whose reaction force is controllable and guides the driver in order to trace the desired velocity in real time. The main purpose of this paper is to discuss the feasibility of the haptic velocity guidance. A haptic velocity guidance system for research is developed on the Driving Simulator of TUAT (DS), by attaching a low-inertia, low-friction motor to the pedal, which does not change the original characteristics of the original pedal when it is not operated, implementing an algorithm regarding the desired pedal stroke calculation and the reaction force controller. The haptic guidance maneuver is designed based on human pedal stepping experiments. A simple velocity profile with acceleration, deceleration and cruising is synthesized according to naturalistic driving for testing the proposed system. The experiment result of 9 drivers shows that the haptic guidance provides high accuracy and quick response in velocity tracking. These results prove that the haptic guidance is a promising velocity guidance method from the viewpoint of HMI (Human Machine Interface).

Yin, Feilong; Hayashi, Ryuzo; Raksincharoensak, Pongsathorn; Nagai, Masao

144

Effect of tensor force and one-nucleon exchange in the quasielastic (6Li, 6He) reaction  

International Nuclear Information System (INIS)

The effect of the tensor force and one-nucleon exchange is studied by applying the antisymmetrized DWBA method to the 48Ca(6Li,6He)48Sc (?fsub(7/2)?fsu6(7/2)-1)sub(J) reaction. The exchange effect increases the cross sections but does not change the angular shapes. In contrast to the tensor force with Gaussian shape, the TWOPEP tensor contribution is larger than that of the central force and dominates the reaction for large L-transfer. (Auth.)

145

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

OpenAIRE

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 stu...

Santos, J. A.; Reis, M. A.; Pablo, F.; Rivas-soriano, L.; Leite, S. M.

2013-01-01

146

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

DEFF Research Database (Denmark)

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 solution is based on contact microphones attached on the exterior part of each shoe, which capture the sound of a footstep. The second approach consists on using microphones placed on the floor. In both situations, the captured sound is analysed and used to control a sound synthesis engine. We discuss advantages and disadvantages of the two approaches.

Serafin, Stefania; Turchet, Luca

2009-01-01

147

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

OpenAIRE

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 solution is based on contact microphones attached on the exterior part of each shoe, which capture the sound of a footstep. The second approach consists on using microphones placed on the floor. In b...

Serafin, Stefania; Turchet, Luca; Nordahl, Rolf

2009-01-01

148

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

International Nuclear Information System (INIS)

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)

149

The benzene ground state potential surface. II. Harmonic force field for the planar vibrations  

Science.gov (United States)

A complete harmonic force field in terms of nonredundant coordinates has been generated from experimental frequencies for D6h, D3h, and D2h isotopically labeled benzenes and degenerate mode Coriolis constants predicting broken symmetry labeled benzene frequencies to ±0.1% and Coriolis constants to ±0.01 units, on the average. Exact solutions have been obtained for the six E1u force constants from D6h symmetry frequency data with the inclusion of 13C6H6 information. Some modes (e.g., the e2g mode ?8, in Wilson notation) are significantly altered from previous experimental force field predictions, rationalizing unclearly understood vibronic features of phosphorescence and two-photon spectra. A conundrum regarding the e1u Coriolis constant for ?18 (Wilson notation) is identified: no harmonic force field is capable of predicting the reported experimental magnitudes for this constant for both C6H6 and C6D6. The Pulay et al. scaled ab initio force field is in qualitative agreement with the experimental field for every symmetry class, with significant quantitative discrepancies involving CH stretching constants.

Ozkabak, Ali G.; Goodman, Lionel

1987-09-01

150

Iterated Perfect-set Forcing and a Transitive set in the Ground Model  

CERN Document Server

In this paper we show that, when we iteratively add Sacks reals to a model of ZFC we have for every two reals in the extension a continuous function defined in the ground model that maps one of the reals onto the other.

Hart, K P

2000-01-01

151

The benzene ground state potential surface. V. Criteria for theoretical modeling of the B2u harmonic force field  

Science.gov (United States)

We demonstrate that fundamental frequencies provide a poor criterion of the benzene B2u force field accuracy and that two-photon cross sections of the b2u fundamental bands in the 1B2u?1A1g electronic transition, which can be directly related to skeletal displacement magnitudes in the two b2u modes, provide an insightful physical criterion of harmonic force field quality. Another valid criterion for force field quality is isotopic frequency shifts combined with the fundamental frequencies. The frequency-generated force field of part II accurately predicts the measured cross sections and isotopic frequency shifts, indicating that the B2u force constants are known to ±0.01 mdyn/Å. These constants are used as benchmark quantities for calibrating theoretically modeled force fields. A systematic series of ab initio B2u harmonic force fields for ground state benzene using theoretical geometries are generated at Hartree-Fock and correlated second, third, and fourth order (with single, double, triple, and quadruple excitation) Møller-Plesset perturbation theory (MP2, MP3, MP4SDTQ) and configuration interaction theory with all single and double excitation (CISD) levels using basis sets from minimal double zeta to triple zeta plus diffuse and polarized functions. These theoretical models of the B2u force field all provide poor predictions for the three criteria: fundamental frequency accuracy 2%-3%; isotopic frequency shift accuracy 10%-300%; two-photon cross section accuracy 300%-1200% with the sense of isotopic effects on two-photon cross sections in some cases incorrectly predicted. The MP2 calculations, even using the largest basis set, are incapable of meeting any of the criteria, hence higher order approaches to the correlation problem are required. The inadequacies in frequencies, isotopic shifts, and mode forms arise because both the diagonal and off-diagonal force constants are not predicted by ab initio calculations with the sufficient 10-2 mdyn/Å accuracy required for reasonably accurate frequency and intensity predictions. A feature of the ab initio calculations is that carbon and hydrogen displacement phases for the b2u modes are unchanged by the basis set size or correlation level. The unmeasured 13C6D6?14 two-photon cross section and iosotope frequency shift from 12C6H6 are predicted to be larger than for any of the other D6h symmetry benzenes (˜30% higher than in C6H6 for the former and 72 cm-1 for the latter) by the benchmark field of part II.

Ozkabak, Ali G.; Goodman, Lionel; Wiberg, Kenneth B.

1990-04-01

152

Force  

Science.gov (United States)

Instructions: This is a webquest designed to help students understand force. It is specifically meant to teach the idea that the greater the force applied to an object the greater the change in speed or direction of the object depending on the mass. This is also known as Newton's Second Law of Motion. Lets Learn about Force! For this project your students will understand force. They will use Newton's second law to solve the problem presented. UT Core Curriculum: Science 3rd Grade. Standard 3- Students will understand the relationship between the force applied to an object and resulting motion of the ...

Mrs. Brownie

2010-04-07

153

The study of the ANC and spectroscopic factor of the 16O ground state using breakup reactions  

International Nuclear Information System (INIS)

In nuclear astrophysics, the charged particle thermonuclear reactions occurring in the stars are difficult to be reproduced in the laboratory. This is because the energies at which the rates or cross sections of these reactions are required to be measured are much below the Coulomb barrier of the interacting nuclei. However, the breakup method has not been applied to compact systems. It is well known that the 12C(?, ?) reaction is a very important alpha capture process in the helium burning stage of a star. The R matrix calculation of the E2 part of the capture cross section of this reaction requires the reduced alpha width and spectroscopic factors of the 2+ states (both unbound and sub threshold) and ground state of 16O. It is possible to extract the spectroscopic information of the unbound and the ground state of 16O from the breakup-CDCC method. In this work we study the ground state spectroscopic factor and ANC of 16O from the breakup method using a recent sequential breakup data of 16O at intermediate energies

154

Reaction forces due to the decompression of pressurized vessels filled with two-phase fluids  

International Nuclear Information System (INIS)

A unique fluid behavioral model which is applicable to many homogeneous multiphase fluids is used as a generic model to examine the reaction forces developed by the decompression of pressurized vessels filled with single component two-phase fluids. The decompression is the result of the sudden creation of an outflow area such as by the accidental puncture of the vessel shell or the rupture of a pipe connection at the vessel. The study includes the treatment of two basic initial conditions: the case of a vessel completely filled with a saturated liquid, and the case of a vessel partially filled with a saturated liquid and covered with its saturated vapor, that is, the two region stratified condition. The principal variables include an expansion parameter which characterizes the fluid behavior in the two-phase domain, the vapor volume fraction, and the location of the outflow area for the stratified case

155

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

CERN Document Server

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.

Siskind, J M

2011-01-01

156

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

OpenAIRE

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, a...

Siskind, J. M.

2011-01-01

157

Influence of mineral weathering reactions on the chemical composition of soil water, springs, and ground water, Catoctin Mountains, Maryland  

Science.gov (United States)

During 1983 and 1984, wet precipitation was primarily a solution of dilute sulphuric acid, whereas calcium and bicarbonate were the major ions in springs and ground water in two small watersheds with a deciduous forest cover in central Maryland. Dominant ions in soil water were calcium, magnesium, and sulphate. The relative importance of mineral weathering reactions on the chemical composition of these subsurface waters was compared to the contribution from wet precipitation, biological processes, and road deicing salts. -from Author

Katz, B.G.

1989-01-01

158

A wide field of view force protection system for ground vehicles  

Science.gov (United States)

The latest generation of heavily armored vehicles and the proliferation of IEDs in urban combat environments dictate that electro-optical systems play a greater role in situational awareness for ground vehicles. FLIR systems has been addressing the needs of the ground vehicle community by developing unique sensor systems combining thermal imaging and electro-optical sensors, advanced image processing, and networking capabilities into compact, cost effective packages. This paper will discuss one of those new products, the WideEye II. The WideEye II combines long wave infrared and electro-optical sensors in a 180 degree field of view, single integrated package to meet the critical needs of the warfighter. It includes seamless electronic stitching of the 180 degree image, and state of the art networking capability to allow it to be operated standalone or to be fully integrated with modern combat vehicle systems. The paper will discuss system tradeoffs and capabilities of this new product and show potential applications for its use.

Way, Scott; Archer, Cynthia; Jolivet, Noel; Cannon, Bruce; Hansen, Joel; Holt, Jordon; Olsen, Steven; Sarao, Jeremy

2009-05-01

159

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

OpenAIRE

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...

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

2013-01-01

160

Age, double porosity, and simple reaction modifications for the MOC3D ground-water transport model  

Science.gov (United States)

This report documents modifications for the MOC3D ground-water transport model to simulate (a) ground-water age transport; (b) double-porosity exchange; and (c) simple but flexible retardation, decay, and zero-order growth reactions. These modifications are incorporated in MOC3D version 3.0. MOC3D simulates the transport of a single solute using the method-ofcharacteristics numerical procedure. The age of ground water, that is the time since recharge to the saturated zone, can be simulated using the transport model with an additional source term of unit strength, corresponding to the rate of aging. The output concentrations of the model are in this case the ages at all locations in the model. Double porosity generally refers to a separate immobilewater phase within the aquifer that does not contribute to ground-water flow but can affect solute transport through diffusive exchange. The solute mass exchange rate between the flowing water in the aquifer and the immobile-water phase is the product of the concentration difference between the two phases and a linear exchange coefficient. Conceptually, double porosity can approximate the effects of dead-end pores in a granular porous media, or matrix diffusion in a fractured-rock aquifer. Options are provided for decay and zero-order growth reactions within the immobilewater phase. The simple reaction terms here extend the original model, which included decay and retardation. With these extensions, (a) the retardation factor can vary spatially within each model layer, (b) the decay rate coefficient can vary spatially within each model layer and can be different for the dissolved and sorbed phases, and (c) a zero-order growth reaction is added that can vary spatially and can be different in the dissolved and sorbed phases. The decay and growth reaction terms also can change in time to account for changing geochemical conditions during transport. The report includes a description of the theoretical basis of the model, a detailed description of input requirements and output options, and the results of model testing and evaluation. The model tests illustrate use of these modifications and demonstrate that accurate solutions can be obtained for these simple cases. Two test cases have no dispersion, illustrating the suitability of this method-of-characteristics model for simulation of advection-dominated transport in ground water.

Goode, Daniel J.

1999-01-01

161

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

International Nuclear Information System (INIS)

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

162

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

DEFF Research Database (Denmark)

Humans maneuver easily over uneven terrain. To maintain smooth and efficient gait the motor system needs to adapt the locomotor output to the walking environment. In the present study we investigate the role of sensory feedback in adjusting the soleus muscle activity during overground walking in 19 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 activity of -17.9% (SD 2) and -21.4% (SD 2), with an onset latency of 49 ms (SD 1) and 45 ms (SD 1) in midstance and late stance, respectively. Input to the vestibular apparatus (i.e., the head acceleration) occurred at a latency 10.0 ms (SD 2.4) following the drop and ankle dorsiflexion velocity was decreased starting 22 ms (SD 15) after the drop. To investigate the role of length- and velocity-sensitive afferents onthe 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 not observed, suggesting that spindle afferents may have a more significant effect on the output during this phase of the step cycle.

Af Klint, Richard; Nielsen, Jens Bo

2009-01-01

163

Alpha-cluster structure in the ground state of 40Ca displayed in a (p,p?) knockout reaction  

International Nuclear Information System (INIS)

The analyzing power is very sensitive to details of the reaction mechanism of (p, p?) knockout reactions in the incident energy range of approximately 100 MeV and higher. Whereas distorted wave impulse approximation calculations in the past proved to give an excellent reproduction of analyzing power angular distributions for quasifree (p, p?) reactions on light targets such as 6Li, 9Be and 12C, the situation for 40Ca was not as simple. It is now shown that the theory also offers good agreement with the experimental distribution of the heaviest target nucleus if care is taken to use proper distorted waves which treat ??36Ar properly as a system for which ?–elastic scattering is anomalous. Thus it is shown that 40Ca reveals its ground state ?–cluster structure in an unambiguous way similar to the light target nuclei.

164

Absolute rate parameters for the reaction of ground state atomic oxygen with carbonyl sulfide  

Science.gov (United States)

The rate parameters for the reaction of O(3P) with carbonyl sulfide, O(3P) + OCS yields CO + SO, have been determined directly by monitoring O(3P) using the flash photolysis-resonance fluorescence technique. The value for reaction rate was measured over a temperature range of 263-502 K and the data were fitted to an Arrhenius expression with good linearity. A comparison of the present results with those from previous studies of this reaction is also presented.

Klemm, R. B.; Stief, L. J.

1974-01-01

165

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

Energy Technology Data Exchange (ETDEWEB)

In April 1990, Wright-Patterson Air Force Base (WPAFB) initiated an effort for the evaluation of potential removal of ground water contamination at the Base. This report presents a current assessment of the nature and extent of the contamination believed to be migrating across the southwestern boundary of Area C and the northern boundary of Area B based upon analysis of existing environmental data obtained from several sources. The existing data base indicates widespread, low-level contamination moving across Base boundaries at levels that pose no immediate threat to the Mad River Valley well fields. An investigation by the City of Dayton in May and June 1990, however, implies that a more identifiable plume of PCE and TCE may be crossing the southwestern boundary of Area C immediately downgradient of Landfill 5. More data is needed to delineate ground water contamination and to design and implement a suitable control system. This report concludes that although an extensive study of the boundaries in question would be the preferred approach, a limited, focused investigation and subsequent feasibility study can be accomplished with a reasonable certainty of achieving the desired outcome of this project.

1991-10-01

166

The study of atmospheric aerosol characteristics and its radiative forcing over North China from ground and satellite observation  

Science.gov (United States)

Two comprehensive radiation sites (Xianghe and Liaozhong) have been established in North China. Instruments such as CIMEL sunphotometer, MFRSR, total sky imager, MPL and broadband radiometers are deployed. A robust data quality control algorithm is adopted to eliminate bad broadband radiation data. Clear conditions are distinguished on the basis of a clear-sky discrimination method. Aerosol optical properties such as aerosol optical thickness, single scattering albedo and phase function are derived under clear conditions and compared between different determinations. The comparison between measurements and radiative transfer model simulations shows a good agreement, not only for direct radiation, but also for diffuse radiation. Ground-based derivation of aerosol properties, broadband radiation data, and satellite observations such as MODIS and CERES are combined to characterize the distribution of atmospheric aerosol and its radiative forcing over North China. High quality data of aerosol characteristics from ground measurements and satellite remote sensing data are strongly required in order to better understand aerosols over China. Our research presents a good example and makes great progresses along this direction.

Wang, P.; Xia, X.; Zong, X.; Li, Z.; Chen, H.; Qiu, J.

2005-12-01

167

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

Science.gov (United States)

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.

Forcier, Bob

2003-09-01

168

Probing the {sup 8}He ground state via the {sup 8}He(p,t){sup 6}He reaction  

Energy Technology Data Exchange (ETDEWEB)

The weakly-bound {sup 8}He nucleus exhibits a neutron halo or thick neutron skin and is generally considered to have an {alpha}+4n structure in its ground state, with the four valence neutrons each occupying 1p{sub 3/2} states outside the {alpha} core. The {sup 8}He(p,t){sup 6}He reaction is a sensitive probe of the ground state structure of {sup 8}He, and we present a consistent analysis of new and existing data for this reaction at incident energies of 15.7 and 61.3A MeV, respectively. Our results are incompatible with the usual assumption of a pure (1p{sub 3/2}){sup 4} structure and suggest that other configurations such as (1p{sub 3/2}){sup 2}(1p{sub 1/2}){sup 2} may be present with significant probability in the ground state wave function of {sup 8}He.

Keeley, N. [CEA-Saclay DSM/DAPNIA/SPhN, F-91191 Gif-sur-Yvette (France)]. E-mail: nkeeley@cea.fr; Skaza, F. [CEA-Saclay DSM/DAPNIA/SPhN, F-91191 Gif-sur-Yvette (France); Lapoux, V. [CEA-Saclay DSM/DAPNIA/SPhN, F-91191 Gif-sur-Yvette (France); Alamanos, N. [CEA-Saclay DSM/DAPNIA/SPhN, F-91191 Gif-sur-Yvette (France); Auger, F. [CEA-Saclay DSM/DAPNIA/SPhN, F-91191 Gif-sur-Yvette (France); Beaumel, D. [Institut de Physique Nucleaire, IN2P3-CNRS, F-91406 Orsay (France); Becheva, E. [Institut de Physique Nucleaire, IN2P3-CNRS, F-91406 Orsay (France); Blumenfeld, Y. [Institut de Physique Nucleaire, IN2P3-CNRS, F-91406 Orsay (France); Delaunay, F. [Institut de Physique Nucleaire, IN2P3-CNRS, F-91406 Orsay (France); Drouart, A. [CEA-Saclay DSM/DAPNIA/SPhN, F-91191 Gif-sur-Yvette (France); Gillibert, A. [CEA-Saclay DSM/DAPNIA/SPhN, F-91191 Gif-sur-Yvette (France); Giot, L. [GANIL, Bld. Henri Becquerel, BP 5027, F-14021 Caen Cedex (France); Kemper, K.W. [Dept. of Physics, Florida State Univ., Tallahassee, FL 32306-4350 (United States); Nalpas, L. [CEA-Saclay DSM/DAPNIA/SPhN, F-91191 Gif-sur-Yvette (France); Pakou, A. [Dept. of Physics, Univ. of Ioannina, 45110 Ioannina (Greece); Pollacco, E.C.; Raabe, R. [CEA-Saclay DSM/DAPNIA/SPhN, F-91191 Gif-sur-Yvette (France); Roussel-Chomaz, P. [GANIL, Bld. Henri Becquerel, BP 5027, F-14021 Caen Cedex (France); Rusek, K. [Dept. of Nuclear Reactions, The Andrzej Soltan Institute for Nuclear Studies, ul. Hoza 69, PL-00681 Warsaw (Poland); Scarpaci, J.-A. [Institut de Physique Nucleaire, IN2P3-CNRS, F-91406 Orsay (France); Sida, J.-L. [CEA-Saclay DSM/DAPNIA/SPhN, F-91191 Gif-sur-Yvette (France); Stepantsov, S. [Flerov Lab. of Nuclear Reactions, JINR, Dubna, RU-141980 (Russian Federation); Wolski, R. [Flerov Lab. of Nuclear Reactions, JINR, Dubna, RU-141980 (Russian Federation)]|[Henryk Niewodniczanski Inst. of Nuclear Physics, PL-31342 Krakow (Poland)

2007-03-22

169

Treadmill walking and overground walking of human subjects compared by recording sole-floor reaction force.  

Science.gov (United States)

In order to clarify differences of treadmill from overground locomotion, experiments were carried out on 10 volunteers (five males and five females). Sole-floor reaction force was recorded from five anatomically discrete points with strain gauge transducers of 14 mm diameter attached firmly to the sole of bare-foot. At first the subject was asked to walk on the laboratory floor at his/her preferred velocity. After the average velocity was obtained, the subject was asked to walk on the treadmill at the same velocity of average overground walking. Stance period at treadmill walking shortened to 93.3% (P contact times were shorter in the treadmill walking; heel 81.2%, first metatarsal 93.5%, third metatarsal 93.6%, fifth metatarsal 90.6% and at great toe 93.2% of overground locomotion. Cadence during treadmill locomotion was significantly larger than overground walking (106.6%, P < 0.05). These results show that when subjects walk on the treadmill and on laboratory floor at the identical speed, stance period shortened by 6.7% while cadence increased by 6.6% on the treadmill. PMID:16182398

Warabi, Tateo; Kato, Masamichi; Kiriyama, Kiichi; Yoshida, Toshikazu; Kobayashi, Nobuyoshi

2005-11-01

170

Regulating emotions uniquely modifies reaction time, rate of force production, and accuracy of a goal-directed motor action.  

Science.gov (United States)

We investigated how emotion regulation (ER) strategies influence the execution of a memory guided, ballistic pinch grip. Participants (N=33) employed ER strategies (expressive suppression, emotional expression, and attentional deployment) while viewing emotional stimuli (IAPS images). Upon stimulus offset, participants produced a targeted pinch force aimed at 10% of their maximum voluntary contraction. Performance measures included reaction time (RT), rate of force production, and performance accuracy. As hypothesized, attentional deployment resulted in the slowest RT, largest rate of force production, and poorest performance accuracy. In contrast, expressive suppression reduced the rate of force production and increased performance accuracy relative to emotional expression and attentional deployment. Findings provide evidence that emotion regulation strategies uniquely influence human movement. Future work should further delineate the interacting role that emotion regulation strategies have in modulating both affective experience and motor performance. PMID:24576703

Beatty, Garrett F; Fawver, Bradley; Hancock, Gabriella M; Janelle, Christopher M

2014-02-01

171

A formula used to subtract the effect of excited state to ground state in measurement of cross section of nuclear reaction  

International Nuclear Information System (INIS)

According to the regulation of growing and decay of artificial radioactive nuclide, a general formula used to subtract the effect of excited state to ground state was deduced. Therefore, the problem of effect of excited state to ground state was solved in the measurement of cross section of nuclear reaction. (authors)

172

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

Directory of Open Access Journals (Sweden)

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.

Kyoko Shibata

2010-07-01

173

Reaction force/torque sensing in a master-slave robot system without mechanical sensors.  

Science.gov (United States)

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. PMID:22163595

Liu, Tao; Li, Chunguang; Inoue, Yoshio; Shibata, Kyoko

2010-01-01

174

The electronic behavior of a photosynthetic reaction center monitored by conductive atomic force microscopy.  

Science.gov (United States)

The conductivity of a photosynthetic reaction center (RC) from Rhodobacter sphaeroides was measured with conductive atomic force microscopy (CAFM) on SAM-modified Au(111) substrates. 2-mercaptoethanol (2ME), 2-mercaptoacetic acid (MAC), 2-mercaptopyridine (2MP) and 4-mercaptopyridine (4MP) were prepared as SAM materials to investigate the stability and morphology of RCs on the substrate by using near-IR absorption spectroscopy and AFM, respectively. The clear presence of the three well known RC near-IR absorption peaks indicates that the RCs were native on the SAM-modified Au(111). Dense grains with various diameters of 5-20 nm, which corresponded to mixtures of single RCs up to aggregates of 10, were observed in topographs of RCs adsorbed on all the different SAM-modified Au(111) substrates. The size of currents obtained from the RC using a bare conductive cantilever were produced in the following order for SAM molecules: 2MP > 2ME > 4MP > MAC. A clear rectification of this current was observed for the modification of the Au(111) substrate with the pi-conjugated thiol, 2MP, indicating that 2MP was effective in both promoting the specific orientation of the RCs on the electrode and electron injection into the RC. Cyclic voltammetry measurements indicate that the 2MP is better mediator for the electron transfer between a quinone and substrate. The current with 2MP-modified cantilever was twice as high as that obtained with the Au-coated one alone, indicating that 2MP has an important role in lowering the electron injection barrier between special pair side of RC and gold electrode. PMID:19441283

Mikayama, Takeshi; Iida, Kouji; Suemori, Yoshiharu; Dewa, Takehisa; Miyashita, Tokuji; Nango, Mamoru; Gardiner, Alastair T; Cogdell, Richard J

2009-01-01

175

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

Directory of Open Access Journals (Sweden)

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.

Ling XianZhang, Tang Liang and Xu Pengju

2011-04-01

176

Proton occupancies in the even Se ground states via the (d,3He) reaction  

International Nuclear Information System (INIS)

The spectroscopic factors for the levels of sup(73,75,77,79,81)As have been measured in the Se(d,3He)As reactions at 25.2 MeV. The proton occupation numbers deduced for the even Se isotopes show that the striking change in proton configuration, observed for the Ge isotopes between N=42, does persist for the Se isotopes. This change is not reproduced, either by a model calculation using spectral distribution methods or by proton wave functions recently suggested for the Se isotopes to explain the results of the Se(d,6Li)Ge reactions. (orig.)

177

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

Science.gov (United States)

The 2H( d, ?)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.

Arai, K.; Aoyama, S.; Suzuki, Y.; Descouvemont, P.; Baye, D.

2013-08-01

178

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

International Nuclear Information System (INIS)

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)

179

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

International Nuclear Information System (INIS)

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.)

180

Exciplexes versus Loose Ion Pairs: How Does the Driving Force Impact the Initial Product Ratio of Photoinduced Charge Separation Reactions?  

Science.gov (United States)

Many donor-acceptor systems can undergo a photoinduced charge separation reaction, yielding loose ion pairs (LIPs). LIPs can be formed either directly via (distant) electron transfer (ET) or indirectly via the dissociation of an initially formed exciplex or tight ion pair. Establishing the prevalence of one of the reaction pathways is challenging because differentiating initially formed exciplexes from LIPs is difficult due to similar spectroscopic footprints. Hence, no comprehensive reaction model has been established for moderately polar solvents. Here, we employ an approach based on the time-resolved magnetic field effect (MFE) of the delayed exciplex luminescence to distinguish the two reaction channels. We focus on the effects of the driving force of ET and the solvent permittivity. We show that, surprisingly, the exciplex channel is significant even for an exergonic ET system with a free energy of ET of -0.58 eV and for the most polar solutions studied (butyronitrile). Our findings demonstrate that exciplexes play a crucial role even in polar solvents and at moderate driving forces, contrary to what is usually assumed. PMID:25243054

Hoang, Hao Minh; Pham, Thi Bich Van; Grampp, Günter; Kattnig, Daniel R

2014-09-18

181

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

Science.gov (United States)

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

Serti?, Josip; Kozak, Dražan; Samardži?, Ivan

2014-01-01

182

Rate constants for the reaction of ground state atomic oxygen with methanol  

International Nuclear Information System (INIS)

The reaction of O(3P) with methanol has been studied using the complementary discharge flow and flash photolysis techniques. In both cases, resonance fluorescence detection of atomic oxygen was employed. The discharge flow (DF) apparatus was used in a temperature range of 298--998 K while the flash photolysis (FP) apparatus was used in the overlapping range of 329--527 K. The apparent bimolecular rate constants for the O-atom/methanol reaction obtained from DF experiments at low temperatures (T2 were added to the flow to intercept the primary reaction product (CH2OH), but had no apparent effect on the measured rate constant. Results from the two methods were in good agreement within this limited temperature range (approx.300--500 K). At temperatures above approx.450 K, the apparent rate constants obtained from DF experiments were increasingly sensitive to the O2 concentration, with the rate constants being smaller when determined in the presence of large [O2]. Since the initial O-atom concentrations were on the order of 1011 or less, a simple stoichiometry effect can be ruled out. However, the results of the present kinetic experiments indicated that heterogeneous pyrolysis of CH3OH may have occurred in the flow system. This observation is consistent with stem. This observation is consistent with studies of the adsorption of methanol on silica surfaces. This problem was apparently overcome by adding small amounts of O2 and the rate constants obtained in this way were seen to agree well with values extrapolated from the lower temperature DF and FP experiments. The rate data from DF and FP experiments were thus combined to obtain the following Arrhenius expression (298--998 K): k1 (T) = (2.70 +- 0.50) x 10-11 exp-5030 +- 160/RT cm3 molecule-1 s-1

183

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

Directory of Open Access Journals (Sweden)

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.

Palacios, M.

2012-12-01

184

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

Energy Technology Data Exchange (ETDEWEB)

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.

Ball, D

2005-04-29

185

Reaction of cyanoacetylene HCCCN(X 1?+) with ground-state carbon atoms C(3P) in cold molecular clouds  

Science.gov (United States)

The reaction of the simplest cyanopolyyne, cyanoacetylene [HCCCN(X?+1)], with ground-state atomic carbon C(P3) is investigated theoretically to explore the probable routes for the depletion of the famed interstellar molecule HCCCN, and the formation of carbon-nitrogen-bearing species in extraterrestrial environments particularly of ultralow temperature. Six collision complexes (c1-c6) without entrance barrier as a result of the carbon atom addition to the ? systems of HCCCN are located. The optimized geometries and harmonic frequencies of the intermediates, transition states, and products along the isomerization and dissociation pathways of each collision complex are obtained by utilizing the unrestricted B3YLP /6-311G(d,p) level of theory, and the corresponding CCSD(T)/cc-pVTZ energies are calculated. Subsequently, with the facilitation of Rice-Ramsperger-Kassel-Marcus (RRKM) and variational RRKM rate constants at collision energy of 0-10kcal/mol, the most probable paths for the titled reaction are determined, and the product yields are estimated. Five collision complexes (c1-c3, c5, and c6) are predicted to give the same products, a chained CCCCN (p2)+H, via the linear and most stable intermediate, HCCCCN (i2), while collision complex c4 is likely to dissociate back to C +HCCCN. The study suggests that this class of reaction is an important route to the destruction of cyanoacetylene and cyanopolyynes in general, and to the synthesis of linear carbon-chained nitriles at the temperature as low as 10K to be incorporated in future chemical models of interstellar clouds.

Li, H. Y.; Cheng, W. C.; Liu, Y. L.; Sun, B. J.; Huang, C. Y.; Chen, K. T.; Tang, M. S.; Kaiser, R. I.; Chang, A. H. H.

2006-01-01

186

In situ measurement of structural mass, stiffness, and damping using a reaction force actuator and a laser Doppler vibrometer  

International Nuclear Information System (INIS)

The problem of structural parameter measurements needs a total solution bridging theory and experiments. In this paper, a practical methodology for in situ measurements of structural mass, stiffness, and damping is presented for built-up structures. As for the experimental uniqueness of the methodology, a reaction force actuator and non-contact optical device are utilized respectively as an input force generator and output displacement measurer, providing a fundamental data set of the proposed numerical algorithm for data-driven structural parameter estimation. The algorithm autonomously estimates the diagonalized mass, symmetric stiffness, optimal non-proportional damping, and suboptimal proportional damping matrices for multi-degrees-of-freedom structures. Structural parameter measurements of two built-up structures followed by a comparison with conventional measurements are used as examples for verification of the accuracy of the proposed methodology. (paper)

187

Effect of baffle on slosh reaction forces in rotating liquid helium subjected to a lateral impulse in microgravity  

Science.gov (United States)

Sloshing dynamics within a partially filled rotating Dewar of superfluid He II are investigated in response to a lateral impulse. The study investigates several factors, including how the rotating bubble of superfluid He II reacts to the impulse in microgravity, how the amplitudes of slosh reaction forces act on the Dewar with various rotating speeds, how the frequencies of the sloshing modes excited differ in terms of differences in rotating speeds, and how the sloshing dynamics differ with and without a baffle. The numerical computation of sloshing dynamics is based on the noninertial frame spacecraft-bound coordinates. Results of the simulations are illustrated.

Hung, R. J.; Long, Y. T.

1995-01-01

188

Construction of cryptographic information protection in automated control systems for rapid reaction military forces  

Directory of Open Access Journals (Sweden)

Full Text Available New approaches to realizations of military operations are analyzed. The main factors that directly affect the construction and operation of information security subsystems in prospective automated command and control military systems are described. Possible ways of the construction of cryptographic subsystems of information protection in automated operation management systems for united military force groups are investigated.

Sergey Petrovich Evseev

2012-04-01

189

Construction of cryptographic information protection in automated control systems for rapid reaction military forces  

OpenAIRE

New approaches to realizations of military operations are analyzed. The main factors that directly affect the construction and operation of information security subsystems in prospective automated command and control military systems are described. Possible ways of the construction of cryptographic subsystems of information protection in automated operation management systems for united military force groups are investigated.

Sergey Petrovich Evseev; Oleksandr Vasilievich Dorokhov; Olga Grigorievna Korol

2012-01-01

190

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

Energy Technology Data Exchange (ETDEWEB)

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.

1991-10-01

191

Variational transition-state theory with multidimensional, semiclassical, ground-state transmission coefficients: Applications to secondary deuterium kinetic isotope effects in reactions involving methane and chloromethane  

International Nuclear Information System (INIS)

This article has two parts. The first provides an overview of variational transition state theory with multidimensional semiclassical ground-state transmission coefficients. The second provides an update of recent applications to three secondary deuterium kinetic isotope effects in gas-phase C1 reactions: hydrogen radicals reacting with deuterated methane, chlorine anions reacting with deuterated chloromethane, and hydrated chlorine anions reacting with chloromethane

192

Study of the ground-state wave function of {sup 6}He via the {sup 6}He(p, t){alpha} transfer reaction  

Energy Technology Data Exchange (ETDEWEB)

We have measured the {sup 6}He(p,t){alpha} transfer reaction in inverse kinematics at 25 MeV/nucleon. The data were compared to DWBA calculations in order to extract the spectroscopic amplitudes for {alpha}+2n and t+t configurations in the ground state of {sup 6}He. (orig.)

Giot, L.; Roussel-Chomaz, P.; Demonchy, Ch.E.; Mittig, W.; Pita, S.; Savajols, H. [GANIL (DSM/CEA, IN2P3/CNRS), B.P. 5027, Caen Cedex 5 (France); Alamanos, N.; Auger, F.; Gillibert, A.; Jouanne, C.; Lapoux, V.; Nalpas, L.; Pollacco, E.C.; Sida, J.L.; Skaza, F. [Saclay, CEA/DSM/DAPNIA/SPhN, Gif-sur-Yvette Cedex (France); Cortina-Gil, M.-D.; Fernandez, J. [Universidad Santiago de Compostela, Departamento de Fisica de Particulas, Santiago de Compostela (Spain); Mackintosh, R.S. [The Open University, Department of Physics and Astronomy, Milton Keynes (United Kingdom); Pakou, A. [The University of Ioannina, Department of Physics, Ioannina (Greece); Rodin, A.; Stepantsov, S.; Ter-Akopian, G. [Dubna, FLNR, JINR, P.O. Box 79, Moscow (Russian Federation); Rusek, K. [The Andrzej Soltan Institute for Nuclear Studies, Hoza 69, Department of Nuclear Reactions, Warsaw (Poland); Thompson, I. [University of Surrey, Department of Physics, Guildford (United Kingdom)

2005-09-01

193

A Q-GERT analysis of the space shuttle ground turnaround system at Vandenberg Air Force Base  

Science.gov (United States)

The efficient ground turnaround of the Space Shuttle is critical to the execution of national policies. Research identified four major subsystems within the Vandenberg Ground Turnaround System; the Orbiter Maintenance Subsystem, External Tank Subsystem, Solid Rocket Booster Subsystem, and Launch Pad Subsystem. A Q-GERT simulation of the ground Turnaround System was conducted to investigate the system and observe the interactions between the major subsystems. The Q-GERT model simulated the integration of Space Shuttle components to determine the subsystem most sensitive to change. The results indicate the Launch Pad Subsystem is the most critical in the Vandenberg Ground Turnaround System. However, further research is recommended in areas of logistics support, spares availability, and transportation of components.

Graham, S.; Jones, T. W.

1982-09-01

194

Wave packet and statistical quantum calculations for the He + NeH? ? HeH? + Ne reaction on the ground electronic state.  

Science.gov (United States)

A real wave packet based time-dependent method and a statistical quantum method have been used to study the He + NeH(+) (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. PMID:25240353

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

2014-09-21

195

Wave packet and statistical quantum calculations for the He + NeH+ ? HeH+ + Ne reaction on the ground electronic state  

Science.gov (United States)

A real wave packet based time-dependent method and a statistical quantum method have been used to study the He + NeH+ (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.

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

2014-09-01

196

Wave packet and statistical quantum calculations for the He + NeH+ ? HeH+ + Ne reaction on the ground electronic state  

International Nuclear Information System (INIS)

A real wave packet based time-dependent method and a statistical quantum method have been used to study the He + NeH+ (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

197

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

CERN Document Server

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.

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

2014-01-01

198

Finite size corrections to the radiation reaction force in classical electrodynamics  

CERN Document Server

We introduce an effective field theory approach that describes the motion of finite size objects under the influence of electromagnetic fields. We prove that leading order effects due to the finite radius $R$ of a spherically symmetric charge is order $R^2$ rather than order $R$ in any physical model, as widely claimed in the literature. This scaling arises as a consequence of Poincar\\'e and gauge symmetries, which can be shown to exclude linear corrections. We use the formalism to calculate the leading order finite size correction to the Abraham-Lorentz-Dirac force.

Galley, Chad R; Rothstein, Ira Z

2010-01-01

199

Reactions to reading “Remaining consistent with method? An analysis of grounded theory research in accounting”: A comment on Gurd  

OpenAIRE

Purpose: This paper is a comment on Gurd's paper published in QRAM 5(2) on the use of grounded theory in interpretive accounting research. Methodology: Like Gurd, we conducted a bibliographic study on prior pieces of research claiming the use of grounded theory. Findings: We found a large diversity of ways of doing grounded theory. There are as many ways as articles. Consistent with the spirit of grounded theory, the field suggested the research questions, methods and verifiability criteria. ...

Joannides, Vassili; Berland, Nicolas

2008-01-01

200

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

International Nuclear Information System (INIS)

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

201

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

International Nuclear Information System (INIS)

The objective of this project was to define the mechanisms, equilibria, kinetics, and extent of sorption of aqueous uranium onto hydroxyapatite (Ca5(PO4)3(OH)) for a range of pH, ionic strength, aqueous uranium concentration, dissolved carbon/air CO2, 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 CO2-free atmospheres, over 98% of initial uranium is sorbed to hydroxyapatite, (3) in waters in equilibrium with higher air CO2 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 uraniof 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 m2 of hydroxyapatite can sorb over 7.53 X 10-6 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 m2 as opposed to 0.083 mg of uranium sequestered per m2 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 (H2(UO2)2(PO4)2 x 10H20) dominates the sequestration process

202

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

Energy Technology Data Exchange (ETDEWEB)

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.

Taffet, M

2004-04-22

203

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

Directory of Open Access Journals (Sweden)

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.

Mohamed Ahmed Elbashir

2014-04-01

204

A Comparison of the vertical ground reaction force during forward and backward walking In athletes with ankle sprain  

Directory of Open Access Journals (Sweden)

Full Text Available Background and Aim: Diabetes has world wide prevalence and it is estimated that up to ten years later, more than 300 million people would suffer from it. The disease has serious secondary complications. Physical activity can decrease the complications by altering the blood profiles. Patients with diabetes are unwilling to do physical exercise. Whole Body Vibration (WBV might be a proper substitution for exercise. The effects of WBV on patients with diabetes have not been studied enough, so the aim of this study was to evaluate the effects of WBV on the blood profiles in patients with diabetes type 2. Materials and Methods: Twenty patients with diabetes were assigned using matched assignment either into control (n=10 or intervention (n=10 group. Intervention group received the WBV with frequency of 30 Hz and amplitude of 2.5 mm for six weeks twice a week. The control group did not receive any intervention during this period. Blood profiles were measured in both groups at the baseline and the end of the study. Results: FBS and HbA1C decreased in intervention group in comparison with the control group but the differences were not statistically significant (P=0.44.  There were not significant statistical differences in Cholesterol, HDL, LDL and TG before and after the treatment between the two groups.Conclusion: The application of WBV with the above parameters might reduce FBS and HbA1C in patients with diabetes type 2. Increase in the amount of Glucose Transporter protein 4 (GLUT-4 is one of the contributing factors that these changes can be ascribed to.

H Sadeghi

2013-05-01

205

A Comparison of the vertical ground reaction force during forward and backward walking In athletes with ankle sprain  

OpenAIRE

Background and Aim: Diabetes has world wide prevalence and it is estimated that up to ten years later, more than 300 million people would suffer from it. The disease has serious secondary complications. Physical activity can decrease the complications by altering the blood profiles. Patients with diabetes are unwilling to do physical exercise. Whole Body Vibration (WBV) might be a proper substitution for exercise. The effects of WBV on patients with diabetes have not been studied enough, so t...

Sadeghi, H.; Kh Mousavi, S.; Ghasempur, H.; Nabavinik, H.

2013-01-01

206

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

OpenAIRE

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...

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

2012-01-01

207

Core particles of hepatitis B virus and ground squirrel hepatitis virus. II. Characterization of the protein kinase reaction associated with ground squirrel hepatitis virus and hepatitis B virus.  

OpenAIRE

The recently described protein kinase activity in hepatitis B virus core antigen particles (Albin and Robinson, J. Virol. 34:297-302, 1980) has been demonstrated here in the liver-derived core particles of ground squirrel hepatitis virus. Both protein kinase activities were initially associated with DNA polymerase-positive heavy core particles in CsCl density equilibrium gradients and shifted to polymerase-negative cores during the course of purification. The major core-associated polypeptide...

Feitelson, M. A.; Marion, P. L.; Robinson, W. S.

1982-01-01

208

Tensor-force effects in the 2H(d-arrow-right,?) 4He reaction and the D state of 4He  

International Nuclear Information System (INIS)

Vector analyzing powers, tensor analyzing powers, and relative differential cross sections have been measured for the 2H(d-arrow-right,?) 4He reaction at an incident energy of 10 MeV. Multipole decomposition and partial-wave analysis reveal that about 15% of the cross section involves processes in which the tensor force plays a role, either in the entrance or exit channel. Contrary to earlier claims, the reaction cannot be used to determine the D-state admixture in the 4He wave function unless the D state of the deuteron and other tensor-force effects in the entrance channel are taken into account

209

[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  

Energy Technology Data Exchange (ETDEWEB)

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).

1991-10-01

210

Vertical force calibration of smart force platform using artificial neural networks  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english INTRODUCTION: The human body may interact with the structures and these interactions are developed through the application of contact forces, for instance due to walking movement. A structure may undergo changes in the dynamic behaviour when subjected to loads and human bodies. The aim of this paper [...] is to propose a methodology using Artificial Neural Networks (ANN) to calibrate a force platform in order to reduce uncertainties in the vertical Ground Reaction Force measurements and positioning of the applied force for the human gait. METHODS: Force platforms have been used to evaluate the pattern of applied human forces and to fit models for the interaction between pedestrians and structures. The designed force platform consists in two force plates placed side by side in the direction of walking. The reference voltages applied to the Wheatstone bridge were used for calibration as the input data to the ANN, while the output data were the estimated values of the standard weights applied to the force platform. RESULTS: It was presented a framework to enhance traditional calibration methods for force platforms (vertical component) using an ANN. The use of ANN shows significant improvements for the measured variables, leading to better results with lower uncertain values that are smaller than those using a simple traditional calibration. CONCLUSION: The results suggest that the calibration with the ANN method may be useful in obtaining more accurate vertical Ground Reaction Forces and positioning measurements in a force platform for human gait analysis.

Marcelo André, Toso; Herbert Martins, Gomes.

2014-12-01

211

Observations of forced oscillations of the magnetosphere by a geostationary satellite and an extensive ground magnetometer array  

International Nuclear Information System (INIS)

Results are presented from the analysis of magnetometer measurements of one of the clearest observations of a double resonance Pc4 pulsation to date. The Pc4, with a period of 55 s, was measured by 18 ground magnetometers and also on board the ATS-6 satellite at geostationary orbit. using a subsequent observation of a second harmonic guided poloidal mode pulsation at ATS-6, the plasma density at geostationary orbit has been estimated. Periods of theoretical cavity mode resonances in the plasmatrough and the eigenperiods of different wave modes and harmonics at geostationary orbit were calculated. A model was developed of the variation of plasma density, and hence eigenperiods, within the magnetosphere which is consistent with these calculations and with the amplitude, phase and ellipticity observations made over the array of ground observatories. In this model it is suggested that hydromagnetic field line resonances occur in the plasmatrough and in the plasmasphere, which are the second and fundamental harmonic guided toroidal mode resonances, respectively. The model also allows the evaluation of the damping experienced by hydromagnetic standing waves in the magnetosphere. The damping is found to be slightly higher than that previously suggested for daytime conditions. (author)

212

Effects of the tensor force on the ground and first $2^{+}$ states of the magic $^{54}$Ca nucleus  

OpenAIRE

The magic nature of the $^{54}$Ca nucleus is investigated in the light of the recent experimental results. We employ both HFB and HF+BCS methods using Skyrme-type SLy5, SLy5+T and T44 interactions. The evolution of the single-particle spectra is studied for the N=34 isotones: $^{60}$Fe, $^{58}$Cr, $^{56}$Ti and $^{54}$Ca. An increase is obtained in the neutron spin-orbit splittings of $p$ and $f$ states due to the effect of the tensor force which also makes $^{54}$Ca a magic...

Yu?ksel, E.; Giai, N.; Khan, E.; Bozkurt, K.

2014-01-01

213

The C-X bond force constant as a factor determining the activation energy of the X-atom radical abstraction reactions (X=Cl, Br, and I)  

International Nuclear Information System (INIS)

Experimental values of activation energies of the reactions H.+R'X ? HX + R'. and R. + R'X ? RX + RX + R'. (X=Cl, Br, K; R and R' -alkyl radicals) are analyzed in the framework of the model of transition state with two crossing Morse curves, one of which characterizes breaking bond and another-forming one. It is shown that thermoneutral activation energies of these reactions are directly proportional to force constant of R'-X bond. For reactions H. + X2 and R. + X2 there is parabolic dependence between X atom displacement in elementary act and this atom radius

214

Accurate quantum wave packet calculations for the F + HCl ? Cl + HF reaction on the ground 1(2)A' potential energy surface.  

Science.gov (United States)

We present converged exact quantum wave packet calculations of reaction probabilities, integral cross sections, and thermal rate coefficients for the title reaction. Calculations have been carried out on the ground 1(2)A' global adiabatic potential energy surface of Deskevich et al. [J. Chem. Phys. 124, 224303 (2006)]. Converged wave packet reaction probabilities at selected values of the total angular momentum up to a partial wave of J = 140 with the HCl reagent initially selected in the v = 0, j = 0-16 rovibrational states have been obtained for the collision energy range from threshold up to 0.8 eV. The present calculations confirm an important enhancement of reactivity with rotational excitation of the HCl molecule. First, accurate integral cross sections and rate constants have been calculated and compared with the available experimental data. PMID:22423835

Bulut, Niyazi; K?os, Jacek; Alexander, Millard H

2012-03-14

215

The benzene ground state potential surface. IV. Discrimination between multiple E1u force field solutions through infrared intensities  

Science.gov (United States)

Accurate values for integrated intensities of the infrared active 13C6H6 fundamentals, ?18, ?19, ?20, and ?11 (Wilson notation) have been measured and redetermined for ?18 and ?19 in C6H6 and C6D6. The 13C6H6 intensities are I18=6.52±0.15, I19=12.60±0.20, I20=55.6±1, and I11=74.6±3 km/mol. Unlike C6H6 and C6D6, interfering transitions in 13C6H6 are minor and these intensities can be used as a critical test for theoretical predictions of atomic polar tensors. The ?18 intensities in C6H6 and C6D6 (7.48±0.15 and 7.09±0.14 km/mol, respectively) and the ?19 intensity in C6D6 (2.51±0.12 km/mol) are measured to be substantially lower than the literature values. The qualitative intensity pattern of benzene in-plane fundamentals uniquely discriminate among the eight possible real E1u force field solutions obtained from frequency information alone. Isotopically invariant dipole moment derivatives, ??/?S18a, ??/?S19a, and ??/?S20a are 0.494±0.005, 0.395±0.016, and 0.770±0.008 D/Å, respectively, obtained from the 13C6H6 experimental intensities and the complete experimental force field of Part II. Using these quantities and the L-1 matrix (Table III), dipole moment gradients for C6H6 become ??/?Q018a =+0.298, ??/?Q019a =+0.371, and ??/?Q020a =+0.814 D/Å. Mode decomposition matrices expressing normal modes of benzene in terms of isotopically labeled molecule modes have been used to definitively determine the C6H6 dipole gradient signs. The signs are in agreement with theoretical calculations. The D6 isotopic labeling effect on C6H6 ?18 intensity provides a sensitive test of E1u force field quality and reveals the inadequacy of present theoretical force field approaches. Ab initio atomic polar tensors have been obtained both at the HF level, using several basis sets up to the 6-311+G(d,p) and at the MP2 level up to the 6-31+G(d) basis set. The dipole derivative for the CC stretch is highly sensitive to both basis set (particularly diffuse functions) and correlation effects. Qualitative CH and CC stretching dipole derivative and intensity predictions by the MP2/6-31+G(d) calculation are encouraging (i.e., within 15% of the experimental values). However, the same calculation yields 20% and 45% errors for the CH bending dipole derivative and fundamental intensity, respectively.

Goodman, Lionel; Ozkabak, Ali G.; Wiberg, Kenneth B.

1989-08-01

216

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

Science.gov (United States)

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

Barbaro, Jeffrey R.

2002-01-01

217

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

Science.gov (United States)

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.

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

2014-10-01

218

Ground-Level Ozone  

Science.gov (United States)

Ground level or "bad" ozone is not emitted directly into the air, but is created by chemical reactions between ... who have lung diseases such as asthma. Ground level ozone can also have harmful effects on sensitive ...

219

Estimation of the aerosol radiative forcing at ground level, over land, and in cloudless atmosphere, from METEOSAT-7 observation: method and case study  

Directory of Open Access Journals (Sweden)

Full Text Available A new method is proposed to estimate the spatial and temporal variability of the solar radiative flux reaching the surface over land (DSSF, as well as the Aerosol Radiative Forcing (ARF, in cloud-free atmosphere. The objective of regional applications of the method is attainable by using the visible broadband of METEOSAT-7 satellite instrument which scans Europe and Africa on a half-hourly basis. The method relies on a selection of best correspondence between METEOSAT-7 radiance and radiative transfer computations.

The validation of DSSF is performed comparing retrievals with ground-based measurements acquired in two contrasted environments: an urban site near Paris and a continental background site located South East of France. The study is concentrated on aerosol episodes occurring around the 2003 summer heat wave, providing 42 cases of comparison for variable solar zenith angle (from 59° to 69°, variable aerosol type (biomass burning emissions and urban pollution, and variable aerosol optical thickness (a factor 6 in magnitude. The method reproduces measurements of DSSF within an accuracy assessment of 20 W m?2 (5% in relative in 70% of the situations, and within 40 W m?2 in 90% of the situations, for the two case studies considered here.

Considering aerosol is the main contributor in changing the measured radiance at the top of the atmosphere, DSSF temporal variability is assumed to be caused only by aerosols, and consequently ARF at ground level and over land is also retrieved: ARF is computed as the difference between DSSF and a parameterised aerosol-free reference level. Retrievals are linearly correlated with the ground-based measurements of the aerosol optical thickness (AOT: sensitivity is included between 120 and 160 W m?2 per unity of AOT at 440 nm. AOT being an instantaneous measure indicative of the aerosol columnar amount, we prove the feasibility to infer instantaneous aerosol radiative impact at the ground level over land with METEOSAT-7 visible channel.

T. Elias

2008-02-01

220

Aerodynamic Lifting Force.  

Science.gov (United States)

Describes some experiments showing both qualitatively and quantitatively that aerodynamic lift is a reaction force. Demonstrates reaction forces caused by the acceleration of an airstream and the deflection of an airstream. Provides pictures of demonstration apparatus and mathematical expressions. (YP)

Weltner, Klaus

1990-01-01

221

Dynamics of low-energy nuclear forces for electromagnetic and weak reactions with the deuteron in the Nambu-Jona-Lasinio model of light nuclei  

OpenAIRE

A dynamics of low-energy nuclear forces is investigated for low-energy electromagnetic and weak nuclear reactions with the deuteron in the Nambu-Jona-Lasinio model of light nuclei by example of the neutron-proton radiative capture (M1-capture) n + p -> D + photon, the photomagnetic disintegration of the deuteron photon + D -> n + p and weak reactions of astrophysical interest. These are the solar proton burning p + p -> D + positron + nu_e, the pep-process p + electron + p -...

Ivanov, A. N.; Oberhummer, H.; Troitskaya, N. I.; Faber, M.

2000-01-01

222

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

OpenAIRE

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...

Schizas, C. G.; Kramers-de Quervain, I. A.; Stu?ssi, E.; Grob, D.

1998-01-01

223

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

International Nuclear Information System (INIS)

The 2H(d, ?)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)

224

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

Science.gov (United States)

The ^2H(d,?)^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.

Arai, K.; Aoyama, S.; Suzuki, Y.; Descouvemont, P.; Baye, D.

225

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

International Nuclear Information System (INIS)

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

226

The ground state mass of 147Gd from single-neutron-transfer reactions and its impact on derived mass values  

International Nuclear Information System (INIS)

Using a 148Gd radioactive target and the (p, d), (d, t), and (3He, ?) single neutron pick-up reactions we have measured the 147Gd mass excess as -75,366(4) keV, which differs by 139(24) keV from the adopted value of the 1983 mass table. From this result, and from recently reported first transfer-reaction mass determinations for 145Eu and 146Eu, we have recalculated the masses of nuclei above 146Gd from a previous shell model analysis of high-spin states. (orig.)

227

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

Science.gov (United States)

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 A y 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.

Maeda, Y.; Saito, T.; Miyasako, H.; Uesaka, T.; Ota, S.; Kawase, S.; Kikuchi, T.; Tokieda, H.; Kawabata, T.; Yako, K.; Wakasa, T.; Sakaguchi, S.; Chen, R.; Sakaguchi, H.; Shima, T.; Suzuki, T.; Tamii, A.

2014-08-01

228

The Ground Axiom (GA)  

CERN Document Server

A new axiom is proposed, the Ground Axiom, asserting that the universe is not a nontrivial set forcing extension of any inner model. The Ground Axiom is first-order expressible, and any model of ZFC has a class forcing extension which satisfies it. The Ground Axiom is independent of many well-known set-theoretic assertions including the Generalized Continuum Hypothesis, the assertion V=HOD that every set is ordinal definable, and the existence of measurable and supercompact cardinals. The related Bedrock Axiom, asserting that the universe is a set forcing extension of a model satisfying the Ground Axiom, is also first-order expressible, and its negation is consistent.

Reitz, J

2006-01-01

229

Variations and radiative forcing of atmospheric aerosols in the U. S. Southeast from ground and space based measurements over the past decade  

Science.gov (United States)

This study examines how aerosols measured from the ground and space over the U. S. Southeast change temporally over a regional scale and their radiative impacts. PM2.5 data consist of two datasets that represent the measurements that are used for regulatory purposes by the U.S. EPA and continuous measurements used for quickly disseminating air quality information. Aerosol optical depth (AOD) data come from three NASA sensors: the MODIS sensors onboard Terra and Aqua satellites and the MISR sensor onboard the Terra satellite. We analyze all available aerosol data over the state of Georgia from 2000 - 2009. In additional to aerosol data, we examine the surface albedo and cloud cover products from MODIS Terra over the same time period. Strong seasonality is detected in both the AOD and PM2.5 datasets; as evidenced by a threefold increase of AOD from mean winter values to mean summer values, and the increase in PM2.5 concentrations is almost twofold from over the same period. We found good agreement between MODIS and MISR onboard the Terra satellite during the spring and summer having correlation coefficients of 0.64 in spring and 0.71 in summer. Monthly anomalies were used to determine the presence of a trend in the both AODs and PM2.5 aerosol datasets. In addition, radiative transfer modeling was performed to assess the aerosol radiative forcing in the region over the past decade. The results of this analysis suggest that the Southeastern U.S. is experiencing solar brightening likely due to better air quality control policies. Our results also hint that if the brightening continues, the radiative forcing from these aerosols will become less negative, which could have potential impacts on climate for the region.

Alston, E. J.; Sokolik, I. N.

2011-12-01

230

Reaction of electric and meteorological states of the near-ground atmosphere during a geomagnetic storm on 5 April 2010  

Science.gov (United States)

The effects of a geomagnetic storm on 5 April 2010 on electric parameters of the atmospheric near-ground layer in Kamchatka have been investigated. Three processes over the course of the storm were identified. Air electroconductivity began to decrease 4 h before the storm, and this lasted for 20 h. The storm's sudden commencement caused potential gradient oscillations with amplitudes up to 300 V/m. During the stages of the storm, a significant increase in the atmosphere ion content unipolarity coefficient occurred.

Smirnov, Sergey

2014-12-01

231

The Ground Axiom (GA)  

OpenAIRE

A new axiom is proposed, the Ground Axiom, asserting that the universe is not a nontrivial set forcing extension of any inner model. The Ground Axiom is first-order expressible, and any model of ZFC has a class forcing extension which satisfies it. The Ground Axiom is independent of many well-known set-theoretic assertions including the Generalized Continuum Hypothesis, the assertion V=HOD that every set is ordinal definable, and the existence of measurable and supercompact ...

Reitz, Jonas

2006-01-01

232

The Ground Axiom  

OpenAIRE

A new axiom is proposed, the Ground Axiom, asserting that the universe is not a nontrivial set-forcing extension of any inner model. The Ground Axiom is first-order expressible, and any model of ZFC has a class-forcing extension which satisfies it. The Ground Axiom is independent of many well-known set-theoretic assertions including the Generalized Continuum Hypothesis, the assertion V=HOD that every set is ordinal definable, and the existence of measurable and supercompact ...

Reitz, Jonas

2006-01-01

233

Absolute rate parameters for the reaction of ground state atomic oxygen with carbonyl sulfide. [using O(3P) monitoring  

Science.gov (United States)

The rate parameters for the reaction of O(3P) with carbonyl sulfide, O(3P) + OCS yields CO + SO have been determined directly by monitoring O(3P) using the flash photolysis-resonance fluorescence technique. The value for k sub 1 was measured over a temperature range of 263 - 502 K and the data were fitted to an Arrhenuis expression with good linearity.

Klemm, R. B.; Stief, L. J.

1974-01-01

234

Tensor force manifestations in ab initio study of the 2H(d, ?)4He, 2H(d, p)3H and 2H(d, n)3He reactions  

International Nuclear Information System (INIS)

The 2H(d, ?)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, in which the 3H, 3He, and d clusters are given by the precise few-body wave functions with a realistic nucleon-nucleon force and the cluster relative motions are solved with the same 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.

235

Confining forces  

CERN Document Server

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.

Rollmann, Dirk

2015-01-01

236

Self-Force with a Stochastic Component from Radiation Reaction of a Scalar Charge Moving in Curved Spacetime  

OpenAIRE

We give a quantum field theoretical derivation of the scalar Abraham-Lorentz-Dirac (ALD) equation and the self-force for a scalar charged particle interacting with a quantum scalar field in curved spacetime. We regularize the causal Green's function using a quasi-local expansion in the spirit of effective field theory and obtain a regular expression for the self-force. The scalar ALD equation obtained in this way for the classical motion of the particle checks with the equat...

Galley, Chad R.; Hu, B. L.

2005-01-01

237

Proton ground-state correlations in 40Ca studied with the reaction 40Ca(e, e'p)39K  

International Nuclear Information System (INIS)

The spectral function of the reaction 40Ca(e,e'p) 39K was measured with special emphasis on the knockout of protons from the 1f7/2 and 2p3/2 orbits above the Fermi level. Particularly for the transition to the 3/2- state two-step processes were found to be not negliglible. The spectroscopic strength for the 1f and 2p knockout, integrated up to 10 MeV excitation energy, is much less than the missing strength in the 1d3/2 and 2s1/2 orbits, but it agrees with values expected from calculations involving ground-state correlations. (orig.)

238

The Ground Axiom  

CERN Document Server

A new axiom is proposed, the Ground Axiom, asserting that the universe is not a nontrivial set-forcing extension of any inner model. The Ground Axiom is first-order expressible, and any model of ZFC has a class-forcing extension which satisfies it. The Ground Axiom is independent of many well-known set-theoretic assertions including the Generalized Continuum Hypothesis, the assertion V=HOD that every set is ordinal definable, and the existence of measurable and supercompact cardinals. The related Bedrock Axiom, asserting that the universe is a set-forcing extension of a model satisfying the Ground Axiom, is also first-order expressible, and its negation is consistent. As many of these results rely on forcing with proper classes, an appendix is provided giving an exposition of the underlying theory of proper class forcing.

Reitz, J

2006-01-01

239

Effect of the tensor force on gamma-ray de-excitation angular distributions from dipole states populated in the 12C( p,p') reaction  

International Nuclear Information System (INIS)

Angular distributions have been measured for the de-excitation gamma rays from the isoscalar and isovector 1+ states populated in the 12C( p,p') reaction at E/sub p/(lab) =22--27 MeV. Fluctuations in the A0 coefficients, which measure the total excitation cross sections, are observed to decrease with energy toward the high end of the region investigated. The a2 coefficients are still fluctuating at 27 MeV, but exhibit reasonably well-defined average values of about -0.40 and 0.15 for the T=0 and T=1 levels, respectively. Microscopic distorted-wave calculations based on a realistic G matrix interaction, while not sufficient to completely describe the present data, suggest that the isospin dependence of the a2 coefficients is associated with the tensor force. The theoretical calculations have been extended to 50 MeV and this effect of the tensor force persists

240

Possible evidence for sensitivity to the two-body tensor force in the reaction d+p->p+p+n  

International Nuclear Information System (INIS)

For deuteron break-up by protons at kinematic conditions far from two-body enhancements, a region of sensitivity to higher partial wave components of the two-body interaction has been found. In particular, using two different nucleon-nucleon tensor forces, three-body calculations of break-up cross sections show statistically significant differences as compared with measured cross sections. Calculated tensor analyzing powers are seen to be highly sensitive to the tensor force. Experimental investigation of these is encouraged. (orig.)

241

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

242

A global ab initio potential energy surface for the X 2A' ground state of the Si + OH ? SiO + H reaction  

Science.gov (United States)

We report the first global potential energy surface (PES) for the X 2A' ground electronic state of the Si(3P) + OH(X2?) ? SiO(X^1? _g^+) + H(2S) 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(3P) and OH(X2?). 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.

Dayou, Fabrice; Duflot, Denis; Rivero-Santamaría, Alejandro; Monnerville, Maurice

2013-11-01

243

Application of Catalyst-free Click Reactions in Attaching Affinity Molecules to Tips of Atomic Force Microscopy for Detection of Protein Biomarkers  

Science.gov (United States)

Atomic Force Microscopy (AFM) has been extensively used in studies of biological interactions. Particularly, AFM based force spectroscopy and recognition imaging can sense biomolecules on a single molecule level, having great potential to become a tool for molecular diagnostics in clinics. These techniques, however, require affinity molecules to be attached to AFM tips in order to specifically detect their targets. The attachment chemistry currently used on silicon tips involves multiple steps of reactions and moisture sensitive chemicals, such as (3-aminopropyl)triethoxysilane (APTES) and N-hydroxysuccinimide (NHS) ester, making the process difficult to operate in aqueous solutions. In the present study, we have developed a user-friendly protocol to functionalize the AFM tips with affinity molecules. A key feature of it is that all reactions are carried out in aqueous solutions. In summary, we first synthesized a molecular anchor composed of cyclooctyne and silatrane for introduction of a chemically reactive function to AFM tips and a bi-functional polyethylene glycol linker that harnesses two orthogonal click reactions, copper free alkyne-azide cycloaddition and thiol-vinylsulfone Michael addition, for attaching affinity molecules to AFM tips. The attachment chemistry was then validated by attaching anti-thrombin DNA aptamers and cyclo-RGD peptides to silicon nitride (SiN) tips respectively, and measuring forces of unbinding these affinity molecules from their protein cognates human ?-thrombin and human ?5?1-integrin immobilized on mica surfaces. In turn, we used the same attachment chemistry to functionalize silicon tips with the same affinity molecules for AFM based recognition imaging, showing that the disease-relevant biomarkers such as ?-thrombin and ?5?1-integrin can be detected with high sensitivity and specificity by the single molecule technique. These studies demonstrate the feasibility of our attachment chemistry for the use in functionalization of AFM tips with affinity molecules. PMID:24180289

Senapati, Subhadip; Manna, Saikat; Lindsay, Stuart; Zhang, Peiming

2013-01-01

244

Application of catalyst-free click reactions in attaching affinity molecules to tips of atomic force microscopy for detection of protein biomarkers.  

Science.gov (United States)

Atomic force microscopy (AFM) has been extensively used in studies of biological interactions. Particularly, AFM based force spectroscopy and recognition imaging can sense biomolecules on a single molecule level, having great potential to become a tool for molecular diagnostics in clinics. These techniques, however, require affinity molecules to be attached to AFM tips in order to specifically detect their targets. The attachment chemistry currently used on silicon tips involves multiple steps of reactions and moisture sensitive chemicals, such as (3-aminopropyl)triethoxysilane (APTES) and N-hydroxysuccinimide (NHS) ester, making the process difficult to operate in aqueous solutions. In the present study, we have developed a user-friendly protocol to functionalize the AFM tips with affinity molecules. A key feature of it is that all reactions are carried out in aqueous solutions. In summary, we first synthesized a molecular anchor composed of cyclooctyne and silatrane for introduction of a chemically reactive function to AFM tips and a bifunctional polyethylene glycol linker that harnesses two orthogonal click reactions, copper free alkyne-azide cycloaddition and thiol-vinylsulfone Michael addition, for attaching affinity molecules to AFM tips. The attachment chemistry was then validated by attaching antithrombin DNA aptamers and cyclo-RGD peptides to silicon nitride (SiN) tips, respectively, and measuring forces of unbinding these affinity molecules from their protein cognates human ?-thrombin and human ?5?1-integrin immobilized on mica surfaces. In turn, we used the same attachment chemistry to functionalize silicon tips with the same affinity molecules for AFM based recognition imaging, showing that the disease-relevant biomarkers such as ?-thrombin and ?5?1-integrin can be detected with high sensitivity and specificity by the single molecule technique. These studies demonstrate the feasibility of our attachment chemistry for the use in functionalization of AFM tips with affinity molecules. PMID:24180289

Senapati, Subhadip; Manna, Saikat; Lindsay, Stuart; Zhang, Peiming

2013-11-26

245

Electron-transfer reactions involving two harmonic potentials with a different force constant: The Zusman approach versus the spin-boson model  

International Nuclear Information System (INIS)

Two approaches: (a generalized spin-boson model with a nonlinear spin-boson coupling and the Zusman's stochastic Liouville formalism) are employed to analyze the electron-transfer reactions involving two harmonic potentials with a different force constant. An analytical rate formula, expressed as a convoluted integral of the individual rate kernel for each mode, is derived with full consideration of quantum tunneling effects. For a dominant solvent mode at low frequency, the formula can be reduced to the results of the Zusman's theory, showing asymmetry of the Marcus rate plot between the normal and the inverted regions

246

A coupled reference interaction site model/molecular dynamics study of the potential of mean force curve of the SN2 Cl- + CH3Cl reaction in water.  

Science.gov (United States)

An application of the coupled reference interaction site model (RISM)/simulation methodology to the calculation of the potential of mean force (PMF) curve in aqueous solution for the identity nucleophilic substitution reaction Cl(-) + CH(3)Cl is performed. The free energy of activation is calculated to be 27.1 kcal/mol which compares very well with the experimentally determined barrier height of 26.6 kcal/mol. Furthermore, the calculated PMF is almost superimposed with that previously calculated using the computationally rigorous Monte Carlo with importance sampling method (Chandrasekhar, J.; Smith, S. F.; Jorgensen, W. L. J. Am. Chem. Soc. 1985, 107, 154). Using the calculated PMF, a crude estimate of the solvated kinetic transmission coefficient also compares well with that of previous more accurate simulations. These results indicate that the coupled RISM/simulation method provides a cost-effective methodology for studying reactions in solution. PMID:16851554

Freedman, Holly; Truong, Thanh N

2005-03-17

247

Reaction of cyanoacetylene HCCCN(X 1Sigma+) with ground-state carbon atoms C(3P) in cold molecular clouds.  

Science.gov (United States)

The reaction of the simplest cyanopolyyne, cyanoacetylene [HCCCN(X (1)Sigma(+))], with ground-state atomic carbon C((3)P) is investigated theoretically to explore the probable routes for the depletion of the famed interstellar molecule HCCCN, and the formation of carbon-nitrogen-bearing species in extraterrestrial environments particularly of ultralow temperature. Six collision complexes (c1-c6) without entrance barrier as a result of the carbon atom addition to the pi systems of HCCCN are located. The optimized geometries and harmonic frequencies of the intermediates, transition states, and products along the isomerization and dissociation pathways of each collision complex are obtained by utilizing the unrestricted B3YLP6-311G(d,p) level of theory, and the corresponding CCSD(T)/cc-pVTZ energies are calculated. Subsequently, with the facilitation of Rice-Ramsperger-Kassel-Marcus (RRKM) and variational RRKM rate constants at collision energy of 0-10 kcal/mol, the most probable paths for the titled reaction are determined, and the product yields are estimated. Five collision complexes (c1-c3, c5, and c6) are predicted to give the same products, a chained CCCCN (p2)+H, via the linear and most stable intermediate, HCCCCN (i2), while collision complex c4 is likely to dissociate back to C+HCCCN. The study suggests that this class of reaction is an important route to the destruction of cyanoacetylene and cyanopolyynes in general, and to the synthesis of linear carbon-chained nitriles at the temperature as low as 10 K to be incorporated in future chemical models of interstellar clouds. PMID:16460162

Li, H Y; Cheng, W C; Liu, Y L; Sun, B J; Huang, C Y; Chen, K T; Tang, M S; Kaiser, R I; Chang, A H H

2006-01-28

248

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  

International Nuclear Information System (INIS)

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)

249

Hybrid Quantum Mechanical and Molecular Mechanics Study of the SN2 Reaction of CCl4 + OH? in Aqueous Solution: The Potential of Mean Force, Reaction Energetics, and Rate Constants  

Energy Technology Data Exchange (ETDEWEB)

The bimolecular nucleophilic substitution reaction of CCl{sub 4} and OH{sup -} in aqueous solution was investigated on the basis of a combined quantum mechanical and molecular mechanics method. A multilayered representation approach is employed to achieve high accuracy results at the CCSD(T) level of theory. The potential of mean force calculations at the DFT level and CCSD(T) level of theory yield reaction barrier heights of 22.7 and 27.9 kcal/mol, respectively. Both the solvation effects and the solvent-induced polarization effect have significant contributions to the reaction energetics, for example, the solvation effect raises the saddle point by 10.6 kcal/mol. The calculated rate constant coefficient is 8.6 x 10{sup -28} cm{sup 3} molecule{sup -1} s{sup -1} at the standard state condition, which is about 17 orders magnitude smaller than that in the gas phase. Among the four chloromethanes (CH{sub 3}Cl, CH{sub 2}Cl{sub 2}, CHCl{sub 3}, and CCl{sub 4}), CCl{sub 4} has the lowest free energy activation barrier for the reaction with OH{sup -1} in aqueous solution, confirming the trend that substitution of Cl by H in chloromethanes diminishes the reactivity.

Wang, Ting; Yin, Hongyun; Wang, Dunyou; Valiev, Marat

2012-02-16

250

Self-Force with a Stochastic Component from Radiation Reaction of a Scalar Charge Moving in Curved Spacetime  

CERN Document Server

We give a quantum field theoretical derivation of the scalar Abraham-Lorentz-Dirac (ALD) equation and the self-force for a scalar charged particle interacting with a quantum scalar field in curved spacetime. We regularize the causal Green's function using a quasi-local expansion in the spirit of effective field theory and obtain a regular expression for the self-force. The scalar ALD equation obtained in this way for the classical motion of the particle checks with the equation obtained by Quinn earlier \\cite{Quinn}. We further derive a scalar ALD-Langevin equation with a classical stochastic force accounting for the effect of quantum fluctuations in the field, which causes small fluctuations on the particle trajectory. This equation will be useful for the study of stochastic motion of charges under the influence of both quantum or classical noise sources, derived either self-consistently (as done here) or put in by hand (with warnings). We show the possibility of secular effects from such stochastic influenc...

Galley, C R; Galley, Chad R.

2005-01-01

251

Self-force with a stochastic component from radiation reaction of a scalar charge moving in curved spacetime  

International Nuclear Information System (INIS)

We give a quantum field theoretical derivation of the scalar Abraham-Lorentz-Dirac (ALD) equation and the self-force for a scalar charged particle interacting with a quantum scalar field in curved spacetime. We regularize the causal Green's function using a quasilocal expansion in the spirit of effective field theory and obtain a regular expression for the self-force. The scalar ALD equation obtained in this way for the classical motion of the particle checks with the equation obtained by Quinn earlier [T. C. Quinn, Phys. Rev. D 62, 064029 (2000).]. We further derive a scalar ALD-Langevin equation with a classical stochastic force accounting for the effect of quantum fluctuations in the field, which causes small fluctuations on the particle trajectory. This equation will be useful for the study of stochastic motion of charges under the influence of both quantum and classical noise sources, derived either self-consistently (as done here) or put in by hand (with warnings). We show the possibility of secular effects from such stochastic influences on the trajectory that may impact on the present calculations of gravitational waveform templates

252

Solvent effects and potential of mean force: a multilayered-representation quantum mechanical/molecular mechanics study of the CH3Br + CN- reaction in aqueous solution.  

Science.gov (United States)

The bimolecular nucleophilic substitution (SN2) reaction of CH3Br and CN(-) in aqueous solution was investigated using a multilayered-representation quantum mechanical and molecular mechanics methodology. The reactant complex, transition state, and product complex are identified and characterized in aqueous solution. The potentials of mean force are computed at both DFT and CCSD(T) levels of theory for the reaction region. The CCSD(T)/MM level of theory presents a free energy activation barrier height at 19.1 kcal mol(-1) which agrees very well with the experimental value of 20.7 kcal mol(-1), while the DFT/MM level of theory underestimated the barrier height at 16.5 kcal mol(-1). The results show that the aqueous environment has a significant contribution to the potential of mean force. Both the solvation effect and the polarization effect increase the activation barrier height by ?14.5 kcal mol(-1) and the solvation effect plays a major role by providing about 70% of the contribution. PMID:25159052

Xu, Yulong; Zhang, Jingxue; Wang, Dunyou

2014-10-01

253

Reduction of frontal-plane hip joint reaction force via medio-lateral foot center of pressure manipulation: A pilot study.  

Science.gov (United States)

Footwear-generated biomechanical manipulation of lower-limb joints has been shown to influence lower-limb biomechanics. Numerous studies report the influence of such interventions on the knee, however little is known about the influence of these interventions on the hip. The present study analyzed kinetic and kinematic changes about the hip of 12 healthy young males who underwent biomechanical manipulation utilizing the APOS biomechanical device (APOS-Medical and Sports Technologies Ltd., Herzliya, Israel) allowing controlled foot center of pressure manipulation. Subjects underwent gait testing in four para-sagittal device configurations: Medial, lateral, neutral, and regular shoes. In the medial configuration, subjects demonstrated no change in step width (i.e., distance between right and left foot center of pressure), however inter-malleolar distance significantly increased. Likewise with the medial setting, greater hip abduction was recorded, while hip adduction moment and joint reaction force decreased significantly. We speculate that subjects adopt a modified gait pattern aimed to maintain constant base of support. As a result, hip abductor muscle moment arm increases and adduction moment and joint reaction force decreases. To the best of our knowledge this is the first study to show this relationship. These results contribute to the understanding of lower-limb biomechanics and warrant further investigation. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:261-269, 2015. PMID:25256253

Solomonow-Avnon, Deborah; Wolf, Alon; Herman, Amir; Rozen, Nimrod; Haim, Amir

2015-02-01

254

How Low-Energy Weak Reactions Can Constrain Three-Nucleon Forces and the Neutron-Neutron Scattering Length  

International Nuclear Information System (INIS)

We show that chiral symmetry and gauge invariance enforce relations between the short-distance physics that occurs in a number of electroweak and pionic reactions on light nuclei. Within chiral perturbation theory, this is manifested via the appearance of the same axial isovector two-body contact term in ?-d?nn?, p-wave pion production in NN collisions, tritium ? decay, pp fusion, ?d scattering, and the hep reaction. Using a Gamow-Teller matrix element obtained from calculations of pp fusion as input, we compute the neutron spectrum obtained in ?-d?nn?. With the short-distance physics in this process controlled from pp?de+?e, the theoretical uncertainty in the nn scattering length extracted from ?-d?nn? is reduced by a factor larger than 3, to < or approx. 0.05 fm

255

How low-energy weak reactions can constrain three-nucleon forces and the neutron-neutron scattering length.  

Science.gov (United States)

We show that chiral symmetry and gauge invariance enforce relations between the short-distance physics that occurs in a number of electroweak and pionic reactions on light nuclei. Within chiral perturbation theory, this is manifested via the appearance of the same axial isovector two-body contact term in pi(-)d --> nngamma, p-wave pion production in NN collisions, tritium beta decay, pp fusion, nud scattering, and the hep reaction. Using a Gamow-Teller matrix element obtained from calculations of pp fusion as input, we compute the neutron spectrum obtained in pi(-)d --> nngamma. With the short-distance physics in this process controlled from pp --> de(=)nu(e), the theoretical uncertainty in the nn scattering length extracted from pi(-)d --> nngamma is reduced by a factor larger than 3, to approximately < or = 0.05 fm. PMID:16803373

Gårdestig, A; Phillips, D R

2006-06-16

256

How low-energy weak reactions can constrain three-nucleon forces and the neutron-neutron scattering length  

CERN Document Server

We show that chiral symmetry and gauge invariance enforce relations between the short-distance physics that occurs in a number of electroweak and pionic reactions on light nuclei. Within chiral perturbation theory this is manifested via the appearance of the same axial isovector two-body contact term in pi- d -> n n gamma, p-wave pion production in NN collisions, tritium beta decay, pp fusion, nu d scattering, and the hep reaction. Using a Gamow-Teller matrix element obtained from calculations of pp fusion as input we compute the neutron spectrum obtained in pi- d -> n n gamma. With the short-distance physics in this process controlled from p p -> d e+ nu_e the theoretical uncertainty in the nn scattering length extracted from pi- d -> n n gamma is reduced by a factor larger than three, to <~0.05 fm.

Gardestig, A

2006-01-01

257

Gap Forcing  

CERN Document Server

Many of the most common reverse Easton iterations found in the large cardinal context, such as the Laver preparation, admit a gap at some small delta in the sense that they factor as P*Q, where P has size less than delta and Q is forced to be delta-strategically closed. In this paper, generalizing the Levy-Solovay theorem, I show that after such forcing, every embedding j:V[G]-->M[j(G)] in the extension which satisfies a mild closure condition is the lift of an embedding j:V-->M in the ground model. In particular, every ultrapower embedding in the extension lifts an embedding from the ground model and every measure in the extension which concentrates on a set in the ground model extends a measure in the ground model. It follows that gap forcing cannot create new weakly compact cardinals, measurable cardinals, strong cardinals, Woodin cardinals, strongly compact cardinals, supercompact cardinals, almost huge cardinals, huge cardinals, and so on.

Hamkins, J D

1998-01-01

258

Catalysis of Photochemical Reactions.  

Science.gov (United States)

Offers a classification system of catalytic effects in photochemical reactions, contrasting characteristic properties of photochemical and thermal reactions. Discusses catalysis and sensitization, examples of catalyzed reactions of excepted states, complexing ground state substrates, and catalysis of primary photoproducts. (JM)

Albini, A.

1986-01-01

259

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

International Nuclear Information System (INIS)

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.)

260

Linear Energy Relationships in Ground State Proton Transfer and Excited State Proton-Coupled Electron Transfer.  

Science.gov (United States)

Proton-coupled electron transfer (PCET) processes are elementary chemical reaction involved in a broad range of radical and redox reactions. Elucidating fundamental PCET reaction mechanisms are thus of central importance for chemical and biochemical research. Here we use quantum chemical density functional theory (DFT), time-dependent density functional theory (TDDFT), and the algebraic diagrammatic-construction through second-order (ADC(2)) to study the mechanism, thermodynamic driving force effects and reaction barriers of both ground state proton transfer (pT) and photo-induced proton-coupled electron transfer (PCET) between nitrosylated phenyl-phenol compounds and hydrogen-bonded t-butylamine as an external base. We show that the obtained reaction barriers for the ground state pT reactions depend linearly on the thermodynamic driving force, with a Brønsted slope of 1 or 0. Photo-excitation leads to a PCET reaction, for which we find that the non-adiabatic excited state reaction barrier depend on the thermodynamic driving force with a Brønsted slope of ½. To support the mechanistic picture arising from the static potential energy surfaces, we perform additional molecular dynamics simulations on the excited state energy surface, in which we observe a spontaneous PCET between the donor and acceptor groups. Our findings suggest that a Brønsted analysis may distinguish the ground state pT and excited state PCET processes. PMID:25485993

Gámiz-Hernández, Ana-Patricia; Magomedov, Artiom; Hummer, Gerhard; Kaila, Ville R I

2014-12-01

261

NRC Task Force report on review of the Federal/State program for regulation of commercial low-level radioactive waste burial grounds. Analysis of public comments  

International Nuclear Information System (INIS)

Correspondence after publication of NUREG-0217 in the Federal Register is listed by docket. A summary of the comments is given. Comments on the task force conclusions on federal/state roles, comprehensive regulator program, and need to study alternatives, provide adequate capacity, and avoid proliferation are analyzed. A breakdown of the comments of states, industry, and others on the task force conclusions and recommendations is tabulated

262

78 FR 20852 - Safety Zones; Marine Week Air Ground Demonstration, Lake Washington; Seattle, WA  

Science.gov (United States)

...Special Marine Air Ground Task Force Demonstration...vehicles, swimmers, combat equipment, and...The Marine Air Ground Task Force Demonstration...vehicles, swimmers, combat equipment, and...the Marine Air Ground Task Force...

2013-04-08

263

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

264

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

International Nuclear Information System (INIS)

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.

265

The separate reactions of the 2Psub(3/2) and 2Psub(1/2) ground states of Kr+ with a number of gases from 0.04 eV to several eV  

International Nuclear Information System (INIS)

The separate reactions of 2Psub(3/2) and 2Psup(1/2) ground states of Kr+ with O2, CO, N2O and OCS have been investigated over the mean relative kinetic energy range from 0.04 eV to several eV using a Flow-Drift-Tube (FDT) apparatus. The results have been interpreted in terms of transitions between states of the reaction intermediate that correlate adiabatically to either the reactants or charge transfer products. (Author)

266

Quasiclassical trajectory calculations of the thermal rate coefficient for the oxygen atom + hydroxyl .fwdarw. oxygen + hydrogen atom reaction on realistic double many-body expansion potential energy surfaces for ground-state hydroperoxy  

OpenAIRE

Quasi-classical trajectory calculations of the thermal rate coefficient for the title reaction have been carried out over the temperature range 250 5 T 5 2500 K by using two recently reported DMBE potential energy surfaces for the ground state of the hydroperoxyl radical. The results are compared with each other and with experiment. The agreement is god. Our results support previous theoretical calculations by Miller on the Melius-Blint potential energy surface in that nonstatistical...

Quintales, L. A. M.; Varandas, A. J. C.; Alvarin?o, J. M.

1988-01-01

267

Large atmospheric shortwave radiative forcing by Mediterranean aerosols derived from simultaneous ground-based and spaceborne observations and dependence on the aerosol type and single scattering albedo  

Science.gov (United States)

Aerosol optical properties and shortwave irradiance measurements at the island of Lampedusa (central Mediterranean) during 2004-2007 are combined with Clouds and the Earth's Radiant Energy System observations of the outgoing shortwave flux at the top of the atmosphere (TOA). The measurements are used to estimate the surface (FES), the top of the atmosphere (FETOA), and the atmospheric (FEATM) shortwave aerosol forcing efficiencies for solar zenith angle (?) between 15° and 55° for desert dust (DD), urban/industrial-biomass burning aerosols (UI-BB), and mixed aerosols (MA). The forcing efficiency at the different atmospheric levels is derived by applying the direct method, that is, as the derivative of the shortwave net flux versus the aerosol optical depth at fixed ?. The diurnal average forcing efficiency at the surface/TOA at the equinox is (-68.9 ± 4.0)/(-45.5 ± 5.4) W m-2 for DD, (-59.0 ± 4.3)/(-19.2 ± 3.3) W m-2 for UI-BB, and (-94.9 ± 5.1)/(-36.2 ± 1.7) W m-2 for MA. The diurnal average atmospheric radiative forcing at the equinox is (+7.3 ± 2.5) W m-2 for DD, (+8.4 ± 1.9) W m-2 for UI-BB, and (+8.2 ± 1.9) W m-2 for MA, suggesting that the mean atmospheric forcing is almost independent of the aerosol type. The largest values of the atmospheric forcing may reach +35 W m-2 for DD, +23 W m-2 for UI-BB, and +34 W m-2 for MA. FETOA is calculated for MA and 25° ? ? ? 35° for three classes of single scattering albedo (0.7 ? ? < 0.8, 0.8 ? ? < 0.9, and 0.9 ? ? ? 1) at 415.6 and 868.7 nm: FETOA increases, in absolute value, for increasing ?. A 0.1 increment in ? determines an increase in FETOA by 10-20 W m-2.

di Biagio, Claudia; di Sarra, Alcide; Meloni, Daniela

2010-05-01

268

Light induced electron transfer reactions of metal complexes  

Energy Technology Data Exchange (ETDEWEB)

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.

Sutin, N; Creutz, C

1980-01-01

269

Light induced electron transfer reactions of metal complexes  

International Nuclear Information System (INIS)

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

270

Estimation of the aerosol radiative forcing at ground level, over land, and in cloudless atmosphere, from METEOSAT-7 observation: method and case study  

OpenAIRE

A new method is proposed to estimate the spatial and temporal variability of the solar radiative flux reaching the surface over land (DSSF), as well as the Aerosol Radiative Forcing (ARF), in cloud-free atmosphere. The objective of regional applications of the method is attainable by using the visible broadband of METEOSAT-7 satellite instrument which scans Europe and Africa on a half-hourly basis. The method relies on a selection of best correspondence between METEOSAT-7 radiance and radiati...

Elias, T.; -l Roujean, J.

2008-01-01

271

Dynamical response of the Galileo Galilei on the ground rotor to test the equivalence principle: Theory, simulation, and experiment. II. The rejection of common mode forces  

International Nuclear Information System (INIS)

'Galileo Galilei on the ground' (GGG) is a fast rotating differential accelerometer designed to test the equivalence principle (EP). Its sensitivity to differential effects, such as the effect of an EP violation, depends crucially on the capability of the accelerometer to reject all effects acting in common mode. By applying the theoretical and simulation methods reported in Part I of this work, and tested therein against experimental data, we predict the occurrence of an enhanced common mode rejection of the GGG accelerometer. We demonstrate that the best rejection of common mode disturbances can be tuned in a controlled way by varying the spin frequency of the GGG rotor

272

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  

Energy Technology Data Exchange (ETDEWEB)

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)

Bashinov, Aleksei V; Gonoskov, Arkady A; Kim, A V; Marklund, Mattias; Mourou, G; Sergeev, Aleksandr M

2013-04-30

273

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

International Nuclear Information System (INIS)

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

274

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

DEFF Research Database (Denmark)

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 of sandals embedded with six pressure sensors each. Investigations of the relationships between recorded force and footstep sounds is presented, together with several possible applications of the system.

Grani, Francesco; Serafin, Stefania

2013-01-01

275

Estimation of the aerosol radiative forcing at ground level, over land, and in cloudless atmosphere, from METEOSAT-7 observation: method and first results  

OpenAIRE

A new method is proposed to estimate the spatial and temporal variability of the solar radiative flux reaching the surface (DSSF) over land, as well as the Aerosol Radiative Forcing (ARF), in cloud-free atmosphere. The objective of global applications of the method is fulfilled by using the visible broadband of METEOSAT-7 satellite which scans Europe and Africa on a half-hourly basis. The method relies on a selection of best correspondence between METEOSAT-7 radiance and DSSF computed with a ...

Elias, T.; -l Roujean, J.

2007-01-01

276

Frictional Forces Required for unrestrained locomotion in dairy cattle  

OpenAIRE

Most free-stall housing systems in the Netherlands are equipped with slatted or solid concrete floors with manure scrapers. A slipping incident occurs when the required coefficient of friction (RCOF) exceeds the coefficient of friction (COF) at the claw–floor interface. An experiment was conducted to measure ground reaction forces (GRF) of dairy cows (n = 9) performing various locomotory behaviors on a nonslippery rubber-covered concrete floor. The RCOF was determined as the ratio of the ho...

Tol, P. P. J.; Metz, J. H. M.; Noordhuizen-stassen, E. N.; Back, W.; Braam, C. R.

2005-01-01

277

Walking without impacts as a motion/force control problem  

OpenAIRE

The paper deals with the synthesis of control for impactless bipedal walking. In order of avoid impulses, both the specified motion of the biped and its ground reactions are controlled, yielding a combined motion and force control problem. A method for modeling and solving such problems is proposed. and then illustrated by the example of an impactless planar walk of a seven-link bipedal robot. Some numerical results of the motion simulation are reported.

Blajer, Wojciech; Schiehlen, Werner

1992-01-01

278

Relationship between the forces acting on the horse's back and the movements of rider and horse while walking on a treadmill  

OpenAIRE

Reasons for performing the study: The exact relationship between the saddle pressure pattern during one stride cycle and the movements of horse and rider at the walk are poorly understood and have never been investigated in detail. Hypothesis: The movements of rider and horse account for the force distribution pattern under the saddle. Method: Vertical ground reaction forces (GRF), kinematics of horse and rider as well as saddle forces (FS) were measured synchronously in 7 high level dr...

Von Peinen, K.; Wiestner, T.; Bogisch, S.; Roepstorff, L.; Weeren, R.; Weishaupt, M. A.

2009-01-01

279

Chemical Reactions (Netorials)  

Science.gov (United States)

Chemical Reactions: this is a resource in the collection "Netorials". The Netorials cover selected topics in first-year chemistry including: Chemical Reactions, Stoichiometry, Thermodynamics, Intermolecular Forces, Acids & Bases, Biomolecules, and Electrochemistry.

280

Grounding Bottom Damage and Ship Motion over a Rock  

DEFF Research Database (Denmark)

A model for prediction of damage to tankers during grounding is presented. The model takes into account the coupling between the external ship dynamics and the local damage process of the hull girder. The model for the local damage is based on a least upper bound solution with kinematic compatibility between all structural members. Friction is taken into account and it is shown how friction contributes to the horizontal resistance force and the vertical reaction force. The resistance of the structural members is expressed in closed forms thus requiring very small modeling time. The model was validated by small scale tests and a large scale test. Application of the theory is illustrated by a study of the grounding damage of a single hull VLCC.

Simonsen, Bo Cerup; Wierzbicki, Tomasz

1996-01-01

281

Transition from wing to leg forces during landing in birds.  

Science.gov (United States)

Transitions to and from the air are critical for aerial locomotion and likely shaped the evolution of flying animals. Research on take-off demonstrates that legs generate greater body accelerations compared with wings, and thereby contribute more to initial flight velocity. Here, we explored coordination between wings and legs in two species with different wingbeat styles, and quantified force production of these modules during the final phase of landing. We used the same birds that we had previously studied during take-off: zebra finch (Taeniopygia guttata, N=4) and diamond dove (Geopelia cuneata, N=3). We measured kinematics using high-speed video, aerodynamics using particle image velocimetry, and ground-reaction forces using a perch mounted on a force plate. In contrast with the first three wingbeats of take-off, the final four wingbeats during landing featured ~2 times greater force production. Thus, wings contribute proportionally more to changes in velocity during the last phase of landing compared with the initial phase of take-off. The two species touched down at the same velocity (~1 m s(-1)), but they exhibited significant differences in the timing of their final wingbeat relative to touchdown. The ratio of average wing force to peak leg force was greater in diamond doves than in zebra finches. Peak ground reaction forces during landing were ~50% of those during take-off, consistent with the birds being motivated to control landing. Likewise, estimations of mechanical energy flux for both species indicate that wings produce 3-10 times more mechanical work within the final wingbeats of flight compared with the kinetic energy of the body absorbed by legs during ground contact. PMID:24855670

Provini, Pauline; Tobalske, Bret W; Crandell, Kristen E; Abourachid, Anick

2014-08-01

282

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  

Energy Technology Data Exchange (ETDEWEB)

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.

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

283

Ab initio study of 2H(d,?)4He, 2H(d,p)3H, and 2H(d,n)4He reactions and the tensor force  

International Nuclear Information System (INIS)

The 2H(d,p)3H, 2H(d,n)3He, and 2H(d,?)4He 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.

284

Ab initio study of 2H(d,?)4He, 2H(d,p)3H, and 2H(d,n)4He reactions and the tensor force  

Science.gov (United States)

The 2H(d,p)3H, 2H(d,n)3He, and 2H(d,?)4He 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.

Arai, K.; Aoyama, S.; Suzuki, Y.; Descouvemont, P.; Baye, D.

2012-11-01

285

Tactical force protection  

Science.gov (United States)

The need for enhanced tactical force protection capabilities is evidenced from our recent experiences in Iraq and Afghanistan and occurs wherever U.S. Forces maintain a forward presence in a potentially hostile environment. Levels of force protection proficiency vary widely from combat units whose mission is to close with and destroy the enemy to combat support/combat service support units performing maintenance and logistics functions. We must provide force protection capabilities that are not only good enough to get the job done, but affordable for the entire force. Addressing the force protection challenge requires an investment in research and development to deliver affordable, scalable, modular and sustainable force protection equipment. This can be accomplished through an evolutionary acquisition strategy of capability upgrades in the near, mid and far-terms that leverage the Army's investments in unmanned ground sensors (UGS), unmanned ground vehicles (UGV) and surveillance radar and imaging technology. This approach addresses the field's immediate tactical force protection requirements, while working towards full integration with the Future Combat System. Futuristic Tactical Force Protection will consist of a fully integrated system of systems architecture that will include UGVs, UGS and Unmanned Aerial Vehicles (UAVs) that are networked with the Future Force.

Stockel, Eugene; Moneyhun, Jon C.

2004-09-01

286

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

International Nuclear Information System (INIS)

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.

287

Ground subgroups  

OpenAIRE

In this article we give a concept of ground subgroup for finite and countable groups. By our definition such a subgroup of a group depends on a given subset of the group and on a given partition of the subset. For finite and free groups we describe some sets of ground subgroups. We apply the ground subgroups to describe ground states of a model of statistical mechanics.

Rozikov, U. A.

2009-01-01

288

Determination of coefficient for subgrade reactions of an earth-retaining structure with consideration of effects of hard ground below the excavated bottom; Kaho ni sonzaisuru katai jiban no eikyo wo koryoshita kussaku dodomeko no suihei jiban hanryoku keisu no settei hoho no kenkyu  

Energy Technology Data Exchange (ETDEWEB)

With clayey ground as the object, the previous paper proposed a new method to establish soil pressure on backside, equilibrium pressure on excavation side, passive pressure on the excavation side, and subgrade reaction coefficient for the excavation side. These factors are used in the elasto-plasticity method which is used in designing excavation earth retaining structures. This paper discusses extension of the subgrade reaction coefficient setting method proposed in the previous and present papers, so that effects of hard ground existing below the excavation bottom can be considered. This paper also shows the results of discussions on applicability of the soil pressures and subgrade reaction coefficient proposed in the previous and present papers. As a result, a new proposal is made on a rational and practical setting method for soil pressures and subgrade reaction coefficient as input items of the elasto-plasticity method used in designing ordinary excavation earth retaining structures in clayey ground. In contrast to the conventional method, the proposed method includes shear resistance in surface of an earth retaining wall, excavation width, thickness of the subject ground, depth from the ground surface, distance from the hard ground below the excavation bottom, and the Poission ratio of the ground. 10 refs., 18 figs., 12 tabs.

Nakamura, H. [Pacific Consultants K.K., Tokyo (Japan); Hirashima, K. [Yamanashi University, Yamanashi (Japan). Faculty of Engineering

1998-06-20

289

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  

Science.gov (United States)

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.

Marchisio, Mario; Piroddi, Luca; Ranieri, Gaetano; Calcina, Sergio V.; Farina, Paolo

2014-10-01

290

Crystalline beam ground state  

International Nuclear Information System (INIS)

In order to employ Molecular Dynamics method, 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 has been performed to obtain the equilibrium structure. The effects 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 Rahman and Schiffer, 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

291

Crystalline beam ground state  

International Nuclear Information System (INIS)

In order to employ the Molecular Dynamics method, commonly used in condensed matter physics, the authors have derived the equations of motion for a beam of charged particles in the rotating rest frame of the reference particle. They 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 has been performed to obtain the equilibrium structure. The effects 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 Rahman and Schiffer, 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

292

Crystalline beam ground state  

International Nuclear Information System (INIS)

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

293

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  

CERN Document Server

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...

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

2006-01-01

294

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  

Science.gov (United States)

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.

Holloway, Owen G.; Waddell, Jonathan P.

2008-01-01

295

Time-dependent quantum wave packet study of the Ar+H{sub 2}{sup +}{yields}ArH{sup +}+H reaction on a new ab initio potential energy surface for the ground electronic state (1{sup 2}A Prime )  

Energy Technology Data Exchange (ETDEWEB)

A new global potential energy surface for the ground electronic state (1{sup 2}A Prime ) of the Ar+H{sub 2}{sup +}{yields}ArH{sup +}+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.

Hu Mei; Liu Xinguo; Tan Ruishan; Li Hongzheng [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Xu Wenwu [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China)

2013-05-07

296

Coupling between the bacteriorhodopsin photocycle and the protonmotive force in Halobacterium halobium cell envelope vesicles. II. Quantitation and preliminary modeling of the M----bR reactions.  

OpenAIRE

The cell membrane of Halobacterium halobium (H. halobium) contains the proton-pump bacteriorhodopsin, which generates a light-driven transmembrane protonmotive force. The interaction of the bacteriorhodopsin photocycle with the electric potential component of the protonmotive force has been investigated. H. halobium cell envelope vesicles have been prepared by sonication and further purified by ultracentrifugation on Ficoll/NaCl/CsCl density gradients. Under continuous illumination (550 +/- 5...

Groma, G. I.; Helgerson, S. L.; Wolber, P. K.; Beece, D.; Dancsha?zy, Z.; Keszthelyi, L.; Stoeckenius, W.

1984-01-01

297

Coaxial Atomic Force Microscope Tweezers  

OpenAIRE

We demonstrate coaxial atomic force microscope (AFM) tweezers that can trap and place small objects using dielectrophoresis (DEP). An attractive force is generated at the tip of a coaxial AFM probe by applying a radio frequency voltage between the center conductor and a grounded shield; the origin of the force is found to be DEP by measuring the pull-off force vs. applied voltage. We show that the coaxial AFM tweezers (CAT) can perform three dimensional assembly by picking u...

Brown, Keith Andrew; Aguilar, J. A.; Westervelt, Robert M.

2010-01-01

298

Tensor force manifestations in ab initio study of the 2H(d, ?)4He, 2H(d,p)3H, and 2H(d,n)3He reactions  

OpenAIRE

The 2H(d,p)3H, 2H(d,n)3He, and 2H(d,?)4He reactions are studied at low energies in a multi-channel 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 experiment. The most important channels...

Arai, Koji; Aoyama, Shigeyoshi; Suzuki, Yasuyuki; Descouvemont, Pierre; Baye, Daniel Jean

2011-01-01

299

An experimental guided-ion-beam and ab initio study of the ion-molecule gas-phase reactions between Li+ ions and iso-C3H7Cl in their ground electronic state  

International Nuclear Information System (INIS)

Reactive collisions between Li+ ions and i-C3H7Cl molecules have been studied in the 0.20-12.00 eV center-of-mass energy range using an octopole radio frequency guided-ion beam apparatus recently developed in our laboratory. At low collision energies, dehydrohalogenation reactions giving rise to Li(C3H6)+ and Li(HCl)+ are the main reaction channels, while at higher ones C3H7+ and C2H3+ become dominant, all their reactive cross sections having been measured as a function of the collision energy. To obtain information about the potential energy surfaces (PESs) on which the reactive processes take place, ab initio calculations at the MP2 level have been performed. For dehydrohalogenations, the reactive ground singlet PES shows ion-molecule adduct formation in both the reactant and product sides of the surface. Following the minimum energy path connecting both minima, an unstable intermediate and the corresponding barriers, both lying below the reactant's energy, have been characterized. The entrance channel ion-molecule adduct is also involved in the formation of C3H7+, which then generates C2H3+ via an CH4 unimolecular elimination. A qualitative interpretation of the experimental results based on ab initio calculations is also included.ations is also included.

300

A change in twist of actin provides the force for the extension of the acrosomal process in limulus sperm: the false-discharge reaction  

OpenAIRE

One of the most spectacular motions is the generation of the acrosomal process in the limulus sperm. On contact with the egg, the sperm generates a 60-mum-long process that literally drills its way through the jelly surrounding the egg. This irresversible reaction takes only a few seconds. We suggested earlier that this motion is driven by a change in twist of the actin filaments comprising the acrosomal process. In this paper we analyze the so-called false discharge, a reversible reaction, i...

Derosier, Dj; Tilney, Lg; Bonder, Em; Frankl, P.

1982-01-01

301

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  

Energy Technology Data Exchange (ETDEWEB)

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.

Bogen, K T

2001-05-24

302

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  

Energy Technology Data Exchange (ETDEWEB)

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.

Bogen, K.T.

1999-09-29

303

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  

International Nuclear Information System (INIS)

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 hay. 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

304

Detection by multiplex real-time polymerase chain reaction assays and isolation of Shiga toxin-producing Escherichia coli serogroups O26, O45, O103, O111, O121, and O145 in ground beef.  

Science.gov (United States)

Six Shiga toxin-producing Escherichia coli (STEC) serogroups, which include O26, O45, O103, O111, O121, and O145, are responsible for the majority of non-O157 STEC infections in the United States, representing a growing public health concern. Cattle and other ruminants are reservoirs for these pathogens; thus, food of bovine origin may be a vehicle for infection with non-O157 STEC. Methods for detection of these pathogens in animal reservoirs and in food are needed to determine their prevalence and to develop intervention strategies. This study describes a method for detection of non-O157 STEC in ground beef, consisting of enrichment in modified tryptic soy broth at 42°C, followed by real-time multiplex polymerase chain reaction (PCR) assays targeting stx(1), stx(2), and genes in the O-antigen gene clusters of the six serogroups, [corrected] and then immunomagnetic separation (IMS) followed by plating onto Rainbow® Agar O157 and PCR assays for confirmation of isolates. All ground beef samples artificially inoculated with 1-2 and 10-20 CFU/25?g of ground beef consistently gave positive results for all of the target genes, including the internal amplification control using the multiplex real-time PCR assays after enrichment in modified tryptic soy broth for a total of 24?h (6?h at 37°C and 18?h at 42°C). The detection limit of the real-time multiplex PCR assays was ?50 CFU per PCR. IMS for O26, O103, O111, and O145 was performed with commercially available magnetic beads, and the IMS beads for O45 and O121 were prepared using polyclonal antiserum against these serogroups. A large percentage of the presumptive colonies of each serogroup picked from Rainbow Agar O157 were confirmed as the respective serogroups; however, the percent recovery of STEC O111 was somewhat lower than that of the other serogroups. This work provides a method for detection and isolation in ground beef and potentially other foods of non-O157 STEC of major public health concern. PMID:21214490

Fratamico, Pina M; Bagi, Lori K; Cray, William C; Narang, Neelam; Yan, Xianghe; Medina, Marjorie; Liu, Yanhong

2011-05-01

305

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  

International Nuclear Information System (INIS)

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

306

Grounded theory  

OpenAIRE

No presente capítulo apresentamos a grounded theory como uma metodologia qualitativa, com progressiva utilização no âmbito da investigação em psicologia. A descrição da metodologia da grounded theory é enquadrada numa perspectiva histórica do desenvolvimento da investigação qualitativa em geral e em particular na psicologia. Apresentamos os princípios e procedimentos de codificação, de acordo com as propostas dos autores de referência para esta metodologia, exemplificando a su...

Fernandes, Euge?nia M.; Maia, A?ngela

2001-01-01

307

Determination of External Forces in Alpine Skiing Using a Differential Global Navigation Satellite System  

Directory of Open Access Journals (Sweden)

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.

Erich Müller

2013-08-01

308

Racial Composition of the Volunteer Armed Forces  

Science.gov (United States)

Analyzes Department of Defense statistics, noting that to examine the question of racial composition in the all-volunteer force is to focus on the enlisted personnel of the ground combat units; and asserting that, in the long run, the end of black over concentration in the ground combat forces necessitates effective racial equality and dignity in…

Janowitz, Morris; Moskos, Charles C., Jr.

1975-01-01

309

Motion synthesis and force distribution analysis for a biped robot.  

Science.gov (United States)

In this paper, the method of generating biped robot motion using recorded human gait is presented. The recorded data were modified taking into account the velocity available for robot drives. Data includes only selected joint angles, therefore the missing values were obtained considering the dynamic postural stability of the robot, which means obtaining an adequate motion trajectory of the so-called Zero Moment Point (ZMT). Also, the method of determining the ground reaction forces' distribution during the biped robot's dynamic stable walk is described. The method was developed by the authors. Following the description of equations characterizing the dynamics of robot's motion, the values of the components of ground reaction forces were symbolically determined as well as the coordinates of the points of robot's feet contact with the ground. The theoretical considerations have been supported by computer simulation and animation of the robot's motion. This was done using Matlab/Simulink package and Simulink 3D Animation Toolbox, and it has proved the proposed method. PMID:21761810

Trojnacki, Maciej T; Zieli?ska, Teresa

2011-01-01

310

Precision measurements of the pp??+pn and pp??+d reactions: Importance of long-range and tensor force effects  

International Nuclear Information System (INIS)

Inclusive measurements of pion production in proton-proton collisions in the forward direction were undertaken at 400 and 600 MeV at the cooler synchrotron (COSY) at Forschungszentrum Julich using the Big Karl spectrograph. The high resolution in the ?+ momentum ensured that there was an unambiguous separation of the pp??+d/?+pn channels. Using these and earlier data, the ratio of the production cross sections could be followed through the ? region and compared with the predictions of final state interaction theory. Deviations are strongly influenced by long-range terms in the production operator and the tensor force in the final pn system. These have been investigated in a realistic pp??+d/?+pn calculation that includes SD channel coupling between the final nucleons. A semiquantitative understanding of the observed effects is achieved.

311

The human foot and heel-sole-toe walking strategy: a mechanism enabling an inverted pendular gait with low isometric muscle force?  

Science.gov (United States)

Mechanically, the most economical gait for slow bipedal locomotion requires walking as an 'inverted pendulum', with: I, an impulsive, energy-dissipating leg compression at the beginning of stance; II, a stiff-limbed vault; and III, an impulsive, powering push-off at the end of stance. The characteristic 'M'-shaped vertical ground reaction forces of walking in humans reflect this impulse-vault-impulse strategy. Humans achieve this gait by dissipating energy during the heel-to-sole transition in early stance, approximately stiff-limbed, flat-footed vaulting over midstance and ankle plantarflexion (powering the toes down) in late stance. Here, we show that the 'M'-shaped walking ground reaction force profile does not require the plantigrade human foot or heel-sole-toe stance; it is maintained in tip-toe and high-heel walking as well as in ostriches. However, the unusual, stiff, human foot structure--with ground-contacting heel behind ankle and toes in front--enables both mechanically economical inverted pendular walking and physiologically economical muscle loading, by producing extreme changes in mechanical advantage between muscles and ground reaction forces. With a human foot, and heel-sole-toe strategy during stance, the shin muscles that dissipate energy, or calf muscles that power the push-off, need not be loaded at all--largely avoiding the 'cost of muscle force'--during the passive vaulting phase. PMID:22572024

Usherwood, J R; Channon, A J; Myatt, J P; Rankin, J W; Hubel, T Y

2012-10-01

312

Force feedback device / force properties  

OpenAIRE

Force feedback devices are, at first sight, a category of haptic devices that are able to exert a controlled force by the means of actuators in their mechanical (or gesture) interaction with a user. This definition, provided for the sake of simplicity, should be considered carefully. Anyhow, the expression force feedback device clearly relates with the idea of a controlled force. Hence, an important mean to evaluate these devices consists in considering their force properties.

Florens, Jean-loup; Hulin, Thomas; Gil, Jorge Juan; Davy, Pierre

2007-01-01

313

Army ground robotics research program  

Science.gov (United States)

The U.S. Army is undergoing a transformation from Cold War era "heavy" forward-deployed forces arrayed against a monolithic known enemy to lighter, more flexible, U.S.-based forces able to rapidly engage in a full spectrum of military operations. Unmanned systems can potentially contribute towards achieving this goal of a highly capable and flexible ground force. To support this effort, the U.S. Army Research Laboratory has undertaken a long-term research program to support technology development for unmanned ground vehicle systems. Over the course of the past year, this multifaceted effort has made significant technical strides, demonstrating sufficient technological maturity to potentially enable incorporation of semi-autonomous unmanned vehicles into the initial fielding of Future Combat Systems (FCS), while successfully conducting additional research directed toward improved capabilities for later increments of FCS and Land Warrior systems.

Bornstein, Jonathan A.; Shoemaker, Chuck M.

2003-09-01

314

Force,” ontology, and language  

OpenAIRE

We introduce a linguistic framework through which one can interpret systematically students’ understanding of and reasoning about force and motion. Some researchers have suggested that students have robust misconceptions or alternative frameworks grounded in everyday experience. Others have pointed out the inconsistency of students’ responses and presented a phenomenological explanation for what is observed, namely, knowledge in pieces. We wish to present a view that builds on and unifies...

Brookes, David T.; Eugenia Etkina

2009-01-01

315

Labor Force  

Science.gov (United States)

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…

Occupational Outlook Quarterly, 2012

2012-01-01

316

Reaction Control Engine for Space Launch Initiative  

Science.gov (United States)

Engineers at the Marshall Space Flight Center (MSFC) have begun a series of engine tests on a new breed of space propulsion: a Reaction Control Engine developed for the Space Launch Initiative (SLI). The engine, developed by TRW Space and Electronics of Redondo Beach, California, is an auxiliary propulsion engine designed to maneuver vehicles in orbit. It is used for docking, reentry, attitude control, and fine-pointing while the vehicle is in orbit. The engine uses nontoxic chemicals as propellants, a feature that creates a safer environment for ground operators, lowers cost, and increases efficiency with less maintenance and quicker turnaround time between missions. Testing includes 30 hot-firings. This photograph shows the first engine test performed at MSFC that includes SLI technology. Another unique feature of the Reaction Control Engine is that it operates at dual thrust modes, combining two engine functions into one engine. The engine operates at both 25 and 1,000 pounds of force, reducing overall propulsion weight and allowing vehicles to easily maneuver in space. The low-level thrust of 25 pounds of force allows the vehicle to fine-point maneuver and dock while the high-level thrust of 1,000 pounds of force is used for reentry, orbit transfer, and coarse positioning. SLI is a NASA-wide research and development program, managed by the MSFC, designed to improve safety, reliability, and cost effectiveness of space travel for second generation reusable launch vehicles.

2002-01-01

317

Leg adjustments during running across visible and camouflaged incidental changes in ground level.  

Science.gov (United States)

During running in a natural environment, humans must routinely negotiate varied and unpredictable changes in ground level. To prevent a fall, changes in ground level, especially those that are invisible, require a quick response of the movement system within a short time. For 11 subjects we investigated two consecutive contacts during running across visible (drop of 0, 5 and 10 cm) and camouflaged (drop of 0 and 10 cm) changes in ground level. For both situations, we found significant variances in their leg parameters and ground reaction forces (GRFs) during the perturbed second contact but also one step ahead, in the unperturbed first contact. At visible first contact, humans linearly adapt their GRF to lower and smooth their centre of mass. During the camouflaged situation, the GRF also decreased, but it seems that the runners anticipate a drop of approximately 5-10 cm. The GRF increased with drop height during the visible perturbed second contact. At the camouflaged second contact, GRFs differed noticeably from the observed reaction when crossing a similar visible drop, whereas the contact time decreased and the initial impact peak increased. This increased impact can be interpreted as a purely mechanical contribution to cope with the event. Furthermore, we observed an increased angle of attack and leg length with drop height for both situations. This is in accordance with results observed in birds running over a track with an unexpected drop, and suggests that adaptations in swing leg retraction form part of the strategy for running across uneven ground. PMID:22875771

Müller, Roy; Ernst, Michael; Blickhan, Reinhard

2012-09-01

318

14 CFR 27.497 - Ground loading conditions: landing gear with tail wheels.  

Science.gov (United States)

...1) The appropriate ground loads specified in...between the rear wheel ground reaction and the rotorcraft...probability of landing with initial contact on the rear wheel must...wheel contacting the ground. In this...

2010-01-01

319

14 CFR 29.497 - Ground loading conditions: landing gear with tail wheels.  

Science.gov (United States)

...1) The appropriate ground loads specified in...between the rear wheel ground reaction and the rotorcraft...probability of landing with initial contact on the rear wheel must...wheel contacting the ground. In this...

2010-01-01

320

Force cycles and force chains.  

Science.gov (United States)

We examine the coevolution of N cycles and force chains as part of a broader study which is designed to quantitatively characterize the role of the laterally supporting contact network to the evolution of force chains. Here, we elucidate the rheological function of these coexisting structures, especially in the lead up to failure. In analogy to force chains, we introduce the concept of force cycles: N cycles whose contacts each bear above average force. We examine their evolution around force chains in a discrete element simulation of a dense granular material under quasistatic biaxial loading. Three-force cycles are shown to be stabilizing structures that inhibit relative particle rotations and provide strong lateral support to force chains. These exhibit distinct behavior from other cycles. Their population decreases rapidly during the initial stages of the strain-hardening regime-a trend that is suddenly interrupted and reversed upon commencement of force chain buckling prior to peak shear stress. Results suggest that the three-force cycles are called upon for reinforcements to ward off failure via shear banding. Ultimately though, the resistance to buckling proves futile; buckling wins under the combined effects of dilatation and increasing compressive load. The sudden increase in three-force cycles may thus be viewed as an indicator of imminent failure via shear bands. PMID:20365363

Tordesillas, Antoinette; Walker, David M; Lin, Qun

2010-01-01

321

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  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese 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. Abstract in english 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.

Carlos E. S., Volpato; Oscar A., Braunbeck; Carlos A. A. de, Oliveira.

2005-08-01

322

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  

Directory of Open Access Journals (Sweden)

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.

Carlos E. S. Volpato

2005-08-01

323

Earth Force  

Science.gov (United States)

"Earth Force engages young people as active citizens who improve the environment and their communities now and in the future." Educators can learn about Earth Force's three programs: Community Action and Problem solving (CAPS), the Global Rivers Environmental Education Network (GREEN), and Earth Force After School. Users can discover students' many accomplishments such as creating reusable fabric grocery bags, recycling cell phones and ink cartridges to earn money, and cleaning up litter. The Tools for Teachers section offers evaluation results, a quality rubric, and a description of the six-step Earth Force community action and problem-solving process.

324

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  

Scientific Electronic Library Online (English)

Full Text Available SciELO Portugal | Language: Portuguese Abstract in portuguese 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.

Daniel Cury, Ribeiro; Jefferson Fagundes, Loss.

325

Influence of external force on properties and reactivity of disulfide bonds.  

Science.gov (United States)

The mechanochemistry of the disulfide bridge--that is, the influence of an externally applied force on the reactivity of the sulfur-sulfur bond--is investigated by unrestricted Kohn-Sham theory. Specifically, we apply the COGEF (constrained geometry simulates external force) approach to characterize the mechanochemistry of the disulfide bond in three different chemical environments: dimethyl disulfide, cystine, and a 102-atom model of the I27 domain in the titin protein. Furthermore, the mechanism of the thiol-disulfide reduction reaction under the effect of an external force is investigated by considering the COGEF potential for the adduct and transition-state clusters. With the unrestricted Becke-three-parameter-Lee-Yang-Parr (UB3LYP) exchange-correlation functional in the 6-311++G(3df,3pd) orbital basis, the rupture force of dimethyl disulfide is 3.8 nN at a disulfide bond elongation of 35 pm. The interaction with neighboring groups and the effect of conformational rigidity of the protein environment have little influence on the mechanochemical characteristics. Upon stretching, we make the following observations: the diradical character of the disulfide bridge increases; the energy difference between the singlet ground state and low-lying triplet state decreases; and the disulfide reduction is promoted by an external force in the range 0.1-0.4 nN. Our model of the interplay between force and reaction mechanism is in qualitative agreement with experimental observations. PMID:21366304

Iozzi, Maria Francesca; Helgaker, Trygve; Uggerud, Einar

2011-03-24

326

Correlations of quasi particles in the deformed nuclei ground states  

International Nuclear Information System (INIS)

The effect of ground state correlation on the properties of the one-phonon states in deformed nuclei is considered. The isoscalar and isovector multipole forces are taken into account. The calculations with fixed energies of first one-phonon states are shown that the ground state correlation leads to small increase of collectivity of these states. The isovector force inclusion decreases the role of correlations. On the whole, the effect of ground state correlations is small even for strongly collective states

327

Dam Forces  

Science.gov (United States)

Students learn how the force of water helps determine the size and shape of dams. They use clay to build models of four types of dams, and observe the force of the water against each type. They conclude by deciding which type of dam they, as Splash Engineering engineers, will design for Thirsty County.

Integrated Teaching And Learning Program And Laboratory

328

Buoyant Force  

Science.gov (United States)

This activity is a lab where students gather data on buoyant force and height of and object being submerged in two different types of fluids. The slope of the buoyant force and height is proportional to the density of the fluid. Students compare the densities of the fluids calculated with the actual densities.

Renae Garski, Bigfork High School, Bigfork, MN, based on an original activity from Science Workshop, p. 115

329

Role of tensor force in elastic scattering  

International Nuclear Information System (INIS)

We present a compact formulation of microscopic form factors for inelastic scattering due to the effective two-nucleon interaction with the tensor force along with the ordinary central force. The theory has been applied for 14C(p,n)14N reaction in which the role of tensor force turns out to be significant. (Author)

330

Strong Force  

CERN Multimedia

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?

331

EXTENDED HÜCKEL ORBITAL FORCES  

OpenAIRE

The forces acting on individual atoms in a molecule, arising from the distorting effect on the molecular framework of the electrons in the different populated molecular orbitals, are calculated within a simple Extended Hückel formalism. The method, which is strongly dependent on the properties of overlap integrals, is applied to the study of several processes and reactions of chemical interest, such as conformational stability of molecules, torsional stability for rotations around a single b...

Federico Eisner; María del Carmen González; Jorge Ricardo Letelier D

2003-01-01

332

The amazing normal forces  

CERN Document Server

This manuscript is written for students in introductory physics classes to address some of the common difficulties and misconceptions of the normal force, especially the relationship between normal and friction forces. Accordingly, it is intentionally informal and conversational in tone to teach students how to build an intuition to complement mathematical formalism. This is accomplished by beginning with common and everyday experience and then guiding students toward two realizations: (i) That real objects are deformable even when deformations are not easily visible, and (ii) that the relation between friction and normal forces follows from the action-reaction principle. The traditional formulae under static and kinetic conditions are then analyzed to show that peculiarity of the normal-friction relationship follows readily from observations and knowledge of physics principles.

Petrache, Horia I

2012-01-01

333

Weak Force  

CERN Multimedia

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...

334

Level locomotion in wood ants: evidence for grounded running.  

Science.gov (United States)

In order to better understand the strategies of locomotion in small insects, we have studied continuous level locomotion of the wood ant species Formica polyctena. We determined the three-dimensional centre of mass kinematics during the gait cycle and recorded the ground reaction forces of single legs utilising a self-developed test site. Our findings show that the animals used the same gait dynamics across a wide speed range without dissolving the tripodal stride pattern. To achieve higher velocities, the ants proportionally increased stride length and stepping frequency. The centre of mass energetics indicated a bouncing gait, in which horizontal kinetic and gravitational potential energy fluctuated in close phase. We determined a high degree of compliance especially in the front legs, as the effective leg length was nearly halved during the contact phase. This leads to only small vertical oscillations of the body, which are important in maintaining ground contact. Bouncing gaits without aerial phases seem to be a common strategy in small runners and can be sufficiently described by the bipedal spring-loaded inverted pendulum model. Thus, with our results, we provide evidence that wood ants perform 'grounded running'. PMID:24744414

Reinhardt, Lars; Blickhan, Reinhard

2014-07-01

335

Drug Reactions  

Science.gov (United States)

... version Drug Reactions Drug Reactions What is an adverse drug reaction? Medicines can treat or prevent illness and ... medicines can cause problems. These problems are called adverse drug reactions. You should know what to do if ...

336

Casimir forces  

OpenAIRE

The present notes are organized as the lectures given at the Les Houches Summer School "Quantum Optics and Nanophotonics" in August 2013. The first section contains an introduction and a description of the current state-of-the-art for Casimir force measurements and their comparison with theory. The second and third sections are a pedagogical presentation of the main features of the theory of Casimir forces for 1-dimensional model systems and for mirrors in 3-dimensional space.

Reynaud, S.; Lambrecht, A.

2014-01-01

337

Unbinding forces of single antibody-antigen complexes correlate with their thermal dissociation rates  

Science.gov (United States)

Point mutants of three unrelated antifluorescein antibodies were constructed to obtain nine different single-chain Fv fragments, whose on-rates, off-rates, and equilibrium binding affinities were determined in solution. Additionally, activation energies for unbinding were estimated from the temperature dependence of the off-rate in solution. Loading rate-dependent unbinding forces were determined for single molecules by atomic force microscopy, which extrapolated at zero force to a value close to the off-rate measured in solution, without any indication for multiple transition states. The measured unbinding forces of all nine mutants correlated well with the off-rate in solution, but not with the temperature dependence of the reaction, indicating that the same transition state must be crossed in spontaneous and forced unbinding and that the unbinding path under load cannot be too different from the one at zero force. The distance of the transition state from the ground state along the unbinding pathway is directly proportional to the barrier height, regardless of the details of the binding site, which most likely reflects the elasticity of the protein in the unbinding process. Atomic force microscopy thus can be a valuable tool for the characterization of solution properties of protein-ligand systems at the single molecule level, predicting relative off-rates, potentially of great value for combinatorial chemistry and biology.

Schwesinger, Falk; Ros, Robert; Strunz, Torsten; Anselmetti, Dario; Güntherodt, Hans-Joachim; Honegger, Annemarie; Jermutus, Lutz; Tiefenauer, Louis; Plückthun, Andreas

2000-08-01

338

On Grounding of Fast Ships  

DEFF Research Database (Denmark)

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 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 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 withthe ground, the paper presents experimental results from crushing tests of aluminium hull girder components with realistic full-scale scantlings. A comparison with existing simplified calculation procedures for ductile metallic structures show that these procedures cannot be used to predict the crushing behaviour of the fore body of high speed ships.

Simonsen, Bo Cerup; Pedersen, Preben Terndrup

1997-01-01

339

The human foot and heel–sole–toe walking strategy: a mechanism enabling an inverted pendular gait with low isometric muscle force?  

OpenAIRE

Mechanically, the most economical gait for slow bipedal locomotion requires walking as an ‘inverted pendulum’, with: I, an impulsive, energy-dissipating leg compression at the beginning of stance; II, a stiff-limbed vault; and III, an impulsive, powering push-off at the end of stance. The characteristic ‘M’-shaped vertical ground reaction forces of walking in humans reflect this impulse–vault–impulse strategy. Humans achieve this gait by dissipating energy during the heel-to-sole ...

Usherwood, J. R.; Channon, A. J.; Myatt, J. P.; Rankin, J. W.; Hubel, T. Y.

2012-01-01

340

Seismic Analysis of Elevated Water Storage Tanks Subjected to Six Correlated Ground Motion Components  

Directory of Open Access Journals (Sweden)

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.

L. Kalani Sarokolayi

2013-01-01

341

Crew station for ground combat vehicles  

Science.gov (United States)

Force XXI is the vision to synthesize the technology, doctrine, and organization of the U.S. Army so that it can fight and win the wars of the 21st Century. Digitization--taking advantage of the microprocessor revolution--is a key enabler of the Force XXI plan. In the Crewman's Associate Advanced Technology Demonstration, crew stations for ground combat vehicles are being developed that allow the soldier to use digitization to maximum weapon system performance.

Mariani, Daniele

1996-06-01

342

The Introduction of Fields in Relation to Force  

Science.gov (United States)

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.)

Brunt, Marjorie; Brunt, Geoff

2012-01-01

343

Constructivist Grounded Theory?  

OpenAIRE

In meinem Beitrag greife ich zurück auf den ausgezeichneten und inspirierenden Artikel von CHARMAZ zu konstruktivistischer Grounded Theory, um an diesem Beispiel zu diskutieren, dass und warum die Grounded Theory kein konstruktivistisches Unterfangen ist. Ich versuche zu zeigen, dass "konstruktivistische Daten" bzw. konstruktivistische Anwendungen der Grounded Theory, sofern sie überhaupt existieren bzw. sinnvoll sein könnten, nur einen verschwindend kleinen Teil der Grounded Theory ausmac...

Barney G Glaser, Phd

2002-01-01

344

Allergic Reactions  

Science.gov (United States)

Allergic Reactions: Tips to Remember Allergies often bring to mind sneezing, runny nose or watery eyes. While these ... symptoms of some types of allergic disease, an allergic reaction is actually a result of a chain reaction ...

345

Reaction Automata  

CERN Document Server

Reaction systems are a formal model that has been introduced to investigate the interactive behaviors of biochemical reactions. Based on the formal framework of reaction systems, we propose new computing models called reaction automata that feature (string) language acceptors with multiset manipulation as a computing mechanism, and show that reaction automata are computationally Turing universal. Further, some subclasses of reaction automata with space complexity are investigated and their language classes are compared to the ones in the Chomsky hierarchy.

Okubo, Fumiya; Yokomori, Takashi

2011-01-01

346

TARDEC's Intelligent Ground Systems overview  

Science.gov (United States)

The mission of the Intelligent Ground Systems (IGS) Area at the Tank Automotive Research, Development and Engineering Center (TARDEC) is to conduct technology maturation and integration to increase Soldier robot control/interface intuitiveness and robotic ground system robustness, functionality and overall system effectiveness for the Future Combat System Brigade Combat Team, Robotics Systems Joint Project Office and game changing capabilities to be fielded beyond the current force. This is accomplished through technology component development focused on increasing unmanned ground vehicle autonomy, optimizing crew interfaces and mission planners that capture commanders' intent, integrating payloads that provide 360 degree local situational awareness and expanding current UGV tactical behavior, learning and adaptation capabilities. The integration of these technology components into ground vehicle demonstrators permits engineering evaluation, User assessment and performance characterization in increasingly complex, dynamic and relevant environments to include high speed on road or cross country operations, all weather/visibility conditions and military operations in urban terrain (MOUT). Focused testing and experimentation is directed at reducing PM risk areas (safe operations, autonomous maneuver, manned-unmanned collaboration) and transitioning technology in the form of hardware, software algorithms, test and performance data, as well as User feedback and lessons learned.

Jaster, Jeffrey F.

2009-05-01

347

Grounding experiments on soft bottoms  

DEFF Research Database (Denmark)

To verify a theoretical analysis procedure for calculation of the hull girder response of ships running aground, a series of large-scale ship grounding experiments was performed on an artificial island made of engineered fill. The tests were conducted by running a condemned fishing vessel up on selected beaches of the island with velocities ranging between 2m/s and 5.5 m/s. During the tests, surge, heave, and pitch accelerations were measured and also the deformations of the beach and ship bow. Based on these accelerations, rigid body velocities and motions were determined. The forces arising from the interaction between the bow of the vessel and the seabed were determined by solving the equations of motions. This article describes the analysis of the measured results and a comparison of the results form the full-scale measurements with results from recently developed analysis procedure for grounding on soft bottoms.

Sterndorff, M.J.; Pedersen, Preben Terndrup

1996-01-01

348

Friction Force  

Science.gov (United States)

Students use LEGO® MINDSTORMS® robotics to help conceptualize and understand the force of friction. Specifically, they observe how different surfaces in contact result in different frictional forces. A LEGO robot is constructed to pull a two-wheeled trailer made of LEGO parts. The robot is programmed to pull the trailer 10 feet and trial runs are conducted on smooth and textured surfaces. The speed and motor power of the robot is kept constant in all trials so students observe the effect of friction between various combinations of surfaces and trailer wheels. To apply what they learn, students act as engineers and create the most effective car by designing the most optimal tires for given surface conditions.

AMPS GK-12 Program,

349

XMM Future Operational Ground Segment  

Science.gov (United States)

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.

Finn, T.; Kirsch, M.; Schmidt, F.; Pfeil, N.; Vasconcellos, A.; Martin, J.

2014-07-01

350

Picosecond-nanosecond laser photolysis studies on the photochemical reaction of excited benzophenone with 1,4-diazabicyclo[2.2.2]octane in acetonitrile solution: proton abstraction of the free benzophenone anion radical from the ground state amine  

Science.gov (United States)

Picosecond and nanosecond dynamics of the ion pair produced by the electron transfer reaction between the triplet state benzophenone ( 3BP*) and 1,4-diazabicyclo[2.2.2]octane (DABCO) was investigated by means of transient absorption spectroscopy and laser-induced photoconductivity measurement. It has been revealed that the solvated free anion radical of BP, produced by the rapid ionic dissociation of the ion pair within 2 ns, abstracts proton from the neutral DABCO giving benzophenone ketyl radical, competing with the charge recombination reaction at encounter with DABCO +, decomposition and/or impurity scavenging processes.

Miyasaka, Hiroshi; Morita, Kazuhiro; Kamada, Kenji; Mataga, Noboru

1991-04-01

351

New experimental approach to modern three-nucleon forces  

International Nuclear Information System (INIS)

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.

352

46 CFR 120.376 - Grounded distribution systems (Neutral grounded).  

Science.gov (United States)

...false Grounded distribution systems (Neutral grounded). 120.376 Section 120...376 Grounded distribution systems (Neutral grounded). (a) If a grounded...lighting, or distribution system having a neutral bus or conductor must have the...

2010-10-01

353

46 CFR 183.376 - Grounded distribution systems (neutral grounded).  

Science.gov (United States)

...false Grounded distribution systems (neutral grounded). 183.376 Section 183...376 Grounded distribution systems (neutral grounded). (a) If a grounded...lighting, or distribution system having a neutral bus or conductor must have the...

2010-10-01

354

gamma-decay of resonance-like structure observed in sup 3 sup 0 Si(p,gamma) sup 3 sup 1 P reaction  

CERN Document Server

gamma-Decay of a resonance-like structure observed in the reaction sup 3 sup 0 Si (p, gamma) sup 3 sup 1 P in the energy region E sub p = 1.4 - 2.7 MeV of accelerated protons is studied. The M1 resonance built on the ground state of sup 3 sup 1 P is identified. The position of the M1 resonance is explained taking into account pairing forces.

Kachan, A S; Korda, L P; Mishchenko, V M; Korda, V Y

2002-01-01

355

Study of few-body aspects of nuclear reactions in the break-up of deuterons by alpha-particles of 29.2 MeV  

International Nuclear Information System (INIS)

Alpha deuteron system, because of the very high binding energy of the alpha particle, is expected to be a very powerful testing ground in studying the off-shell behaviour involved in the underlying few-body nuclear reaction mechanism. Our aim is also to search for three-body force (3BF) effects if there is any, by exploiting the kinematical configuration favouring the condition of colinearity

356

Generative force of self-oscillating gel.  

Science.gov (United States)

We succeeded in measuring the generative force of a self-oscillating polymer gel in an aqueous solution comprising the three substrates of the Belousov-Zhabotinsky (BZ) reaction (malonic acid, sodium bromate, and nitric acid) under constant temperature. In this study, we developed an apparatus with a microforce sensor for measuring the generative force of small-sized gels (1 mm(3)). The self-oscillating polymer gel directly converts the chemical energy of the BZ reaction into mechanical work. It was determined that the generative force of the self-oscillating gel was 972 Pa, and the period of self-oscillation was 480 s at 18 °C. We demonstrated that the generative force of the gel was about a hundredth the generative force of a muscle in the body. We analyzed the time dependence of the color change in the self-oscillating polymer gel. The color of the gel changed periodically owing to the cyclic change in the redox state of the Ru moiety, induced by the BZ reaction. The peaks of the waveforms of the generative force and color change were almost identical. This result showed that the generative force was synchronized with the periodical change in the oxidation number of the Ru catalytic moiety in the gel. To understand a theoretical basis for the generative force of a self-oscillating gel, we considered a general theory that is based on the volume phase transition of gel and the two-parameter Oregonator model of the BZ reaction. PMID:24524539

Hara, Yusuke; Mayama, Hiroyuki; Morishima, Keisuke

2014-03-01

357

Gravitational self force and gauge transformations  

OpenAIRE

We explore how the gravitational self force (or ``radiation reaction'' force), acting on a pointlike test particle in curved spacetime, is modified in a gauge transformation. We derive the general transformation law, describing the change in the self force in terms of the infinitesimal displacement vector associated with the gauge transformation. Based on this transformation law, we extend the regularization prescription by Mino et al. and Quinn and Wald (originally formulat...

Barack, Leor; Ori, Amos

2001-01-01

358

15N(n,d)14C and 15N(n,t)13C ground state reactions as functions of energy and angle in the neutron energy range 13.6 to 14.8 MeV  

International Nuclear Information System (INIS)

This study was undertaken in order to determine the mechanism of the 15N(n,d)14C g.s. reaction and to investigate the 15N(n,t)13C g.s. reaction. Techniques were developed for producing neutron spectra having the characteristics needed for excitation function measurements. A method was also developed for measuring the neutron spectrum incident on a reaction target. The 15N reaction data were taken with a counter telescope which consisted of two gas differential energy detectors plus a scintillator. Excitation functions were measured at counter angle settings of 00 and 450 over the neutron energy range 13.6 through 14.8 meV. Cross section angular distributions were taken at anti E/sub n/ = 14.1 and 14.6 MeV. The direct mechanism was found to be completely dominant for the (n,d) reaction. A DWBA analysis gives a fairly good fit to the shape of the observed angular distribution for 15N(n,d)14C g.s., but predicts an energy dependence different from that observed. Spectroscopic factors extracted for the (n,d) reaction are ambiguous because of sensitivity to the choice of 14C + d optical potential. The absolute cross section observed for 15N(n,d)14C g.s. is contradictory to the results of earlier work on 14C(d,n)15N g.s. A significant variation seen in the 00 excitation function for 15N(n,t)1315N(n,t)13C g.s. was deduced to be a compound nucleus-related statistical fluctuation. Values for fractional direct mechanism contributions to the energy-averaged (n,t) cross sections were extracted, as were values for the mean level width of the 16N compound nucleus. Cross sections for 15N(n,t)13C g.s. were calculated in zero-range DWBA. The factors required to normalize the theoretical cross sections are in all cases several times larger than standard values

359

An ergonomic modular foot platform for isometric force/torque measurements in poststroke functional assessment: A pilot study  

Directory of Open Access Journals (Sweden)

Full Text Available The main goal of this article is to present the design, technical development, and preliminary validation of an innovative mechatronic device for force/torque measurements taken from the human foot using pilot data. The device, formed by a mobile platform equipped with two six-axis force/torque sensors, was used to perform accurate quantitative measurements during isometric exercises, aimed at performing functional assessment tests in poststroke patients undergoing a rehabilitation treatment. Results from pilot data provide a validation of the device. A large clinical trial has been planned to test whether the platform can be used in the clinical practice. We suggest that measurements of ground reaction forces taken from the foot of poststroke patients during the initiation of activities of daily living tasks can provide information about their motor recovery and enlighten possible areas of application, ranging from isometric motor exercise in neurorehabilitation to foot-based human-machine interface.

Stefano Mazzoleni, PhD

2012-08-01

360

Experimental Investigation of a Wing-in-Ground Effect Craft  

OpenAIRE

The aerodynamic characteristics of the wing-in-ground effect (WIG) craft model that has a noble configuration of a compound wing was experimentally investigated and Universiti Teknologi Malaysia (UTM) wind tunnel with and without endplates. Lift and drag forces, pitching moment coefficients, and the centre of pressure were measured with respect to the ground clearance and the wing angle of attack. The ground effect and the existence of the endplates increase the wing lift-to-drag ratio at low...

Mobassher Tofa, M.; Adi Maimun; Ahmed, Yasser M.; Saeed Jamei; Agoes Priyanto; Rahimuddin

2014-01-01

361

The ground based plan  

International Nuclear Information System (INIS)

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.)

362

Interfacial forces  

International Nuclear Information System (INIS)

The past few years have witnessed tremendous advances in experimental and theoretical techniques for probing both the static and dynamic properties of surfaces at the angstrom level. Here we review how these advances have furthered our fundamental understanding of adhesion-particularly those processes that contribute to energy dissipation during adhesion and separation (loading--unloading cycles), and friction-particularly how the dynamic (e.g., viscous and rheological) properties of liquids in ultrathin films differ from the bulk liquid properties, and how this affects the friction forces of lubricated contacts. The emphasis will be on ''ideal'' surfaces and interfaces, i.e., surfaces that are molecularly smooth, and interfacial films that are no more than a few molecular layers thick

363

Casimir-Polder forces on moving atoms  

International Nuclear Information System (INIS)

Polarizable atoms and molecules experience the Casimir-Polder force near magnetoelectric bodies, a force that is induced by quantum fluctuations of the electromagnetic field and the matter. Atoms and molecules in relative motion to a magnetoelectric surface experience an additional velocity-dependent force. We present a full quantum-mechanical treatment of this force and identify a generalized Doppler effect, the time delay between photon emission and reabsorption, and the Roentgen interaction as its three sources. For ground-state atoms, the force is very small and always decelerating, hence commonly known as quantum friction. For atoms and molecules in electronically excited states, on the contrary, both decelerating and accelerating forces can occur depending on the magnitude of the atomic transition frequency relative to the surface-plasmon frequency.

364

Safety Considerations in the Ground Environment  

Science.gov (United States)

In the history of humankind, every great space adventure has begun on the ground. While this seems to be stating the obvious, mission and spacecraft designers who have overlooked this fact have paid a high price, either in loss or damage to the spacecraft pre-launch, or in mission failure or reduction. Spacecraft personnel may risk not only their flight hardware, but they may also risk their lives, their co-workers lives and even the general public by not heeding safety on the ground. Their eyes may be on the stars but their feet are on the ground! One additional comment: Although the design requirements are very different for human rated and nonhuman rated flight hardware, while on the ground that flight hardware (and its ground support equipment) doesn't care about what it is flying on. On the ground, additional requirements are often levied to protect the work force and general public. (Authors' Note: The source material for this chapter is primarily taken from the Kennedy Space Center Handbook (KHB) 1700.7/45 SW Handbook S-100 Space Shuttle Payload Ground Safety Handbook and the authors' personal experiences.

Kirkpatrick, Paul D.; Palo, Thomas E.

2007-01-01

365

Chemical Reactions  

Science.gov (United States)

We don't often stop to think about it, but underlying many of our everyday activities are chemical reactions. From the cooking of an egg to the growth of a child, chemical reactions make things happen. Although many of the reactions that support our lives

National Science Teachers Association (NSTA)

2009-05-01

366

Army ground robotics technology development and experimentation program  

Science.gov (United States)

In the past year, the U.S. Army has committed to a paradigm shift in the way future ground military operations will be conducted. Increased emphasis upon the deployability of future forces has focused efforts towards reducing the weight, volume, and logistics requirements for proposed tactical systems. Extensive use of unmanned systems offer a potential means to achieve these goals, without reducing the lethality or survivability of this future ground combat force. To support this vision, the U.S. Army has embarked upon a concerted effort to develop required technology and demonstrate its maturity with the goal of incorporating this technology into the Future Combat Systems and the Objective Force.

Bornstein, Jonathan A.; Brendle, Bruce E., Jr.; Shoemaker, Chuck M.

2001-09-01

367

Rapid grounding line migration induced by internal ice stream variability  

Science.gov (United States)

Observations indicate that the grounding line position of West Antarctica is sensitive to both forced and unforced ice stream variabilities. This study endeavors to characterize and understand unforced ice stream variability and associated grounding line migration. We use a flowline ice stream model with an undrained plastic bed, lateral shear stresses, and a stretched grid refined in the grounding zone. This model exhibits parameter space structure and hysteresis behavior similar to simpler ice stream models. Low prescribed temperature at the ice surface or weak geothermal heating produces thermal oscillations between active and stagnant phases. As in previous spatially resolved ice flow models, thermal activation propagates as an "activation wave." This model's fine resolution of the grounding zone allows for accurate simulations of transient, unforced grounding line migration. Upstream of the grounding zone, horizontal grid spacing of 1 km is required to accurately resolve activation waves. Activation waves induce the grounding line to migrate over 100 km at a rate that can exceed 1 km/yr. This is followed during the active phase by retreat, which then continues for the duration of the stagnant phase. Grounding line retreat is the result of a negative mass balance near the grounding line but is not necessarily associated with negative mass balance for the entire ice stream in our simulations of internal variability. The novel approach and experiments described in this study show that there can be large excursions in grounding line position in the absence of either external forcing or retrograde slopes.

Robel, A. A.; Schoof, C.; Tziperman, E.

2014-11-01

368

Activation of C-O and C-C bonds and formation of novel HAlOH-ether complexes: an EPR study of the reaction of ground-state Al atoms with methylethyl ether and diethyl ether.  

Science.gov (United States)

Reaction mixtures, containing Al atoms and methylethyl ether (MEE) or diethyl ether (DEE) in an adamantane matrix, were prepared with the aid of a metal-atom reactor known as a rotating cryostat. The EPR spectra of the resulting products were recorded from 77-260 K, at 10 K intervals. Al atoms were found to insert into methyl-O, ethyl-O, and C-C bonds to form CH(3)AlOCH(2)CH(3), CH(3)OAlCH(2)CH(3), and CH(3)OCH(2)AlCH(3), respectively, in the case of MEE while DEE produced CH(3)CH(2)AlOCH(2)CH(3) and CH(3)AlCH(2)OCH(2)CH(3), respectively. From the intensity of the transition lines attributed to the Al atom C-O insertion products of MEE, insertion into the methyl-O bond is preferred. The Al hyperfine interaction (hfi) extracted from the EPR spectra of the C-O insertion products was greater than that of the C-C insertion products, that is, 5.4% greater for the DEE system and 7% greater for the MEE system. The increase in Al hfi is thought to arise from the increased electron-withdrawing ability of the substituents bonded to Al. Besides HAlOH, resulting from the reaction of Al atoms with adventitious water, novel mixed HAlOH:MEE and HAlOH:DEE complexes were identified with the aid of isotopic studies involving H(2)(17)O and D(2)O. The Al and H hfi of HAlOH were found to decrease upon complex formation. These findings are consistent with the nuclear hfi calculated using a density functional theory (DFT) method with close agreement between theory and experiment occurring at the B3LYP level using a 6-311+G(2df,p) basis set. PMID:22299675

Brunet, François D; Feola, Julie C; Joly, Helen A

2012-03-15

369

Informed grounded theory  

OpenAIRE

There is a widespread idea that in grounded theory (GT) research, the researcher has to delay the literature review until the end of the analysis to avoid contamination - a dictum that might turn educational researchers away from GT. Nevertheless, in this article the author (a) problematizes the dictum of delaying a literature review in classic grounded theory, (b) presents arguments for using extant literature in the substantive field within a constructivist grounded theory, and (c) suggests...

Thornberg, Robert

2012-01-01

370

The Grounded Theory Bookshelf  

OpenAIRE

The Grounded Theory Perspective III: Theoretical Coding, Barney G. Glaser (Sociology Press, 2005). Not intended for a beginner, this book further defi nes, describes, and explicates the classic grounded theory (GT) method. Perspective III lays out various facets of theoretical coding as Glaser meticulously distinguishes classic GT from other subsequent methods. Developed many years after Glaser’s classic GT, these methods, particularly as described by Strauss and Corbin, adopt the grounded ...

Dr Alvita Nathaniel, Dsn

2005-01-01

371

Biodiversity in ground waters.  

Science.gov (United States)

Despite the importance of ground waters in the global water cycle, their ecology and biodiversity have only recently received attention. Three areas are currently being studied: (I ) the origin and colonization ground ground waters, (2) the adaptation of animals to the subterranean environment, and (3) the role of ecotone between surface and ground waters. There are still several gaps in our knowledge of groundwater biodiversity (at the genetic level, the species level, the functional group level and the ecosystem level) to which future research must be directed. PMID:21236209

Marmonier, P; Vervier, P; Giber, J; Dole-Olivier, M J

1993-11-01

372

Simple Assessment of Post-Grounding Loads and Strength of Ships  

DEFF Research Database (Denmark)

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.

Paik, Jeom Kee; Pedersen, Preben Terndrup

1997-01-01

373

Nuclear reactions  

OpenAIRE

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 o...

???????, ???? ???????????; ???????, ???? ??????????; Diadechko, Alla Mykolaivna; Velytchenko, A.

2009-01-01

374

Grounded running in quails: simulations indicate benefits of observed fixed aperture angle between legs before touch-down.  

Science.gov (United States)

Many birds use grounded running (running without aerial phases) in a wide range of speeds. Contrary to walking and running, numerical investigations of this gait based on the BSLIP (bipedal spring loaded inverted pendulum) template are rare. To obtain template related parameters of quails (e.g. leg stiffness) we used x-ray cinematography combined with ground reaction force measurements of quail grounded running. Interestingly, with speed the quails did not adjust the swing leg's angle of attack with respect to the ground but adapted the angle between legs (which we termed aperture angle), and fixed it about 30ms before touchdown. In simulations with the BSLIP we compared this swing leg alignment policy with the fixed angle of attack with respect to the ground typically used in the literature. We found symmetric periodic grounded running in a simply connected subset comprising one third of the investigated parameter space. The fixed aperture angle strategy revealed improved local stability and surprising tolerance with respect to large perturbations. Starting with the periodic solutions, after step-down step-up or step-up step-down perturbations of 10% leg rest length, in the vast majority of cases the bipedal SLIP could accomplish at least 50 steps to fall. The fixed angle of attack strategy was not feasible. We propose that, in small animals in particular, grounded running may be a common gait that allows highly compliant systems to exploit energy storage without the necessity of quick changes in the locomotor program when facing perturbations. PMID:23831138

Andrada, Emanuel; Rode, Christian; Blickhan, Reinhard

2013-10-21

375

Perl Tools for Automating Satellite Ground Systems  

Science.gov (United States)

The freeware scripting language Pert offers many opportunities for automating satellite ground systems for new satellites as well as older, in situ systems. This paper describes a toolkit that has evolved from of the experiences gained by using Pert to automate the ground system for the Compton Gamma Ray Observatory (CGRO) and for automating some of the elements in the Earth Observing System Data and Operations System (EDOS) ground system at Goddard Space Flight Center (GSFC). CGRO is an older ground system that was forced to automate because of fund cuts. Three 8 hour shifts were cut back to one 8 hour shift, 7 days per week. EDOS supports a new mission called Terra, launched December 1999 that requires distribution and tracking of mission-critical reports throughout the world. Both of these ground systems use Pert scripts to process data and display it on the Internet as well as scripts to coordinate many of the other systems that make these ground systems work as a coherent whole. Another task called Automated Multimodal Trend Analysis System (AMTAS) is looking at technology for isolation and recovery of spacecraft problems. This effort has led to prototypes that seek to evaluate various tools and technology that meet at least some of the AMTAS goals. The tools, experiences, and lessons learned by implementing these systems are described here.

McLean, David; Haar, Therese; McDonald, James

2000-01-01

376

Relational grounding facilitates development of scientifically useful multiscale models  

Directory of Open Access Journals (Sweden)

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.

Lam Tai

2011-09-01

377

Convection in Drying and Freezing Ground  

CERN Document Server

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.

Faizal, Mir

2012-01-01

378

SEM Ground Spider Interactive  

Science.gov (United States)

This interactive look at a ground spider's anatomy has close-up images taken using the high-resolution technology of a scanning electron microscope (SEM). By mousing over the labeled images, students can view fifteen features of a generalized ground spider's anatomy.

379

Airport Ground Staff Scheduling  

DEFF Research Database (Denmark)

Modern airports are centers of transportation that service a large number of aircraft and passengers every day. To facilitate this large volume of transportation, airports are subject to many logistical and decision problems that must continuously be solved to make sure each flight and passenger travels safely and efficiently through the airport. When an aircraft lands, a significant number of tasks must be performed by different groups of ground crew, such as fueling, baggage handling and cleaning. These tasks must be complete before the aircraft is able to depart, as well as check-in and security services. These tasks are collectively known as ground handling, and are the major source of activity with airports. The business environments of modern airports are becoming increasingly competitive, as both airports themselves and their ground handling operations are changing to private ownership. As airports are in competition to attract airline routes, efficient and reliable ground handling operations are imperative for the viability and continued growth of both airports and airlines. The increasing liberalization of the ground handling market prompts ground handling operators to increase cost effectiveness and deliver fast and reliable service. This thesis presents models and algorithms for general optimization and decision problems arising within ground handling. The thesis contains an introductory part which provide an overview of the ground handling environment and reviews a series of optimization problems from the specific perspective of airport ground handling. In addition, the thesis contains five scientific papers, which consider specific optimization problems within ground handling in detail. The considered problems range from generalized approaches to workforce planning, to highly detailed scheduling problems arising in the highly dynamic environment of airports.

Clausen, Tommy

2010-01-01

380

Display integration for ground combat vehicles  

Science.gov (United States)

The United States Army's requirement to employ high resolution target acquisition sensors and information warfare to increase its dominance over enemy forces has led to the need to integrate advanced display devices into ground combat vehicle crew stations. The Army's force structure require the integration of advanced displays on both existing and emerging ground combat vehicle systems. The fielding of second generation target acquisition sensors, color digital terrain maps and high volume digital command and control information networks on these platforms define display performance requirements. The greatest challenge facing the system integrator is the development and integration of advanced displays that meet operational, vehicle and human computer interface performance requirements for the ground combat vehicle fleet. The subject of this paper is to address those challenges: operational and vehicle performance, non-soldier centric crew station configurations, display performance limitations related to human computer interfaces and vehicle physical environments, display technology limitations and the Department of Defense (DOD) acquisition reform initiatives. How the ground combat vehicle Program Manager and system integrator are addressing these challenges are discussed through the integration of displays on fielded, current and future close combat vehicle applications.

Busse, David J.

1998-09-01

381

Classical Helium Atom with Radiation Reaction  

OpenAIRE

We study a classical model of Helium atom in which, in addition to the Coulomb forces, the radiation reaction forces are taken into account. This modification brings in the model a new qualitative feature of a global character. Indeed, as pointed out by Dirac, in any model of classical electrodynamics of point particles involving radiation reaction one has to eliminate, from the a priori conceivable solutions of the problem, those corresponding to the emission of an infinite...

Carati, Andrea; Galgani, Luigi

2011-01-01

382

Handbook of force transducers  

CERN Document Server

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

Stefanescu, Dan Mihai

2011-01-01

383

Neutrino nuclear response and photo nuclear reaction  

OpenAIRE

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...

Ejiri, H.; Titov, A. I.; Boswell, M.; Young, A.

2013-01-01

384

A force calibration standard for magnetic tweezers  

Science.gov (United States)

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.

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

385

Nuclear reactions an introduction  

CERN Document Server

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 ...

Paetz gen. Schieck, Hans

2014-01-01

386

Reaction cross sections for proton scattering from stable and unstable nuclei based on a microscopic approach  

CERN Document Server

Microscopic optical model potential results for reaction cross sections of proton elastic scattering are presented. The applications cover the 10-1000 MeV energy range and consider both stable and unstable nuclei. The study is based on in-medium g-matrix full-folding optical model approach with the appropriate relativistic kinematic corrections needed for the higher energy applications. The effective interactions are based on realistic NN potentials supplemented with a separable non-Hermitian term to allow optimum agreement with current NN phase-shift analyzes, particularly the inelasticities above pion production threshold. The target ground-state densities are obtained from Hartree-Fock-Bogoliubov calculations based on the finite range, density dependent Gogny force. The evaluated reaction cross sections for proton scattering are compared with measurements and their systematics is analyzed. A simple function of the total cross sections in terms of the atomic mass number is observed at high energies. At low ...

Arellano, H F

2007-01-01

387

Effect of excited states on thermonuclear reaction rates  

International Nuclear Information System (INIS)

Values of the ratio of the thermonuclear reaction rate of a reaction, with target nuclei in a thermal distribution of energy states, to the reaction rate with all target nuclei in their ground states are tabulated for neutron, proton, and ? particle induced reactions on the naturally occurring nuclei from 20Ne to 70Zn, at temperatures of 1, 2, 3.5, and 5 x 109K. The ratios are determined from reaction rates based on statistical model cross sections

388

The Fifth Force, the Sixth Force and the Spring Force  

OpenAIRE

Upon  revisiting the famous Pound-Rebka-Snider experiments on the gravitational red-shift , the fifth and even the sixth force in nature are in fact the stretching and compression force of the spring , where the spring term is the cosmological constant in Einstein’s field equations.

Ling Man Tsang

2012-01-01

389

The Fifth Force, the Sixth Force and the Spring Force  

Directory of Open Access Journals (Sweden)

Full Text Available Upon  revisiting the famous Pound-Rebka-Snider experiments on the gravitational red-shift , the fifth and even the sixth force in nature are in fact the stretching and compression force of the spring , where the spring term is the cosmological constant in Einstein’s field equations.

Ling Man Tsang

2012-04-01

390

Private Ground Water Wells  

Science.gov (United States)

... questions about wells . Ground Water and Wells When rain falls, much of it is absorbed into the ... on Home Water Treatment Technologies Choosing Home Water Filters Step 1: Know Your Water Source Step 2: ...

391

Enzyme Reactions  

Science.gov (United States)

The enzyme reaction rate activity allows students to simulate the effects of variables such as temperature and pH on the reaction rate of the enzyme catalase. This computer simulation is best used after the students have done a wet lab experiment. The value of the simulation is that it requires the students to interpret and analyze the graphical representation of data and it enables the running of mutiple experiments in a short amount of time.

Maryland Virtual High School

392

Teaching Visual Grounded Theory  

OpenAIRE

The paper is based on personal 20-years experience of teaching methodology of grounded theory and qualitative methods. In the following paper I would like to show the usefulness of visual analysis in teaching methodology of grounded theory. A very important tool is to use pictures and a sequencing of pictures, which give a comparative insight into empirical data and teaches the comparative method that is so important to generate theory (Glaser 1965; Glaser, Straus...

Konecki, Krzysztof Tomasz

2009-01-01

393

Force Control in Monopod Hopping Robot While Landing  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, the issue of control of impact forces generated during the interaction between the hopping ro-bot toe and the ground while landing has been considered. The force thus generated can damage the robot altogether. With the objective to control these impact forces, impedance control strategy has been applied to the hopping robot system. The dynamics pertaining to the impact between robot toe and ground has been modeled as in case of a ball bouncing on the ground. Bond Graph theory has been used for the modeling of the hopping robot system. Simulation results show that impact forces generated during the landing has been controlled to a specified limiting value. This model and the corresponding analysis can be further extended for understanding the dynamics involved in continuous hopping of robot with constant height and velocity control.

Satish Chandra Jain

2010-11-01

394

Force and Its Representation  

Science.gov (United States)

This page is from a comprehensive and comprehensible tutorial in physics. Schematic drawings, animations, and links to animations are included. Use the link in the left navigation bar to explore the related topic of types of forces including frictional force, gravitational force, and magnetic force.

2010-01-01

395

Investigating Forces and Motion  

CERN Document Server

Forces can't be seen, but without them, nothing around us would happen! A force is a push or pull that usually causes movement. Friction is a force that opposes motion and slows things down or stops them. Famous scientist and mathematician Sir Isaac Newton wrote the rules about forces and motion.

Weir, Jane

2007-01-01

396

A comparison of methods for determining the rate of force development during isometric midthigh clean pulls.  

Science.gov (United States)

Haff, GG, Ruben, RP, Lider, J, Twine, C, and Cormie, P. A comparison of methods for determining the rate of force development during isometric midthigh clean pulls. J Strength Cond Res 29(2): 386-395, 2015-Twelve female division I collegiate volleyball players were recruited to examine the reliability of several methods for calculating the rate of force development (RFD) during the isometric midthigh clean pull. All subjects were familiarized with the isometric midthigh clean pull and participated in regular strength training. Two isometric midthigh clean pulls were performed with 2 minutes rest between each trail. All measures were performed in a custom isometric testing device that included a step-wise adjustable bar and a force plate for measuring ground reaction forces. The RFD during predetermined time zone bands (0-30, 0-50, 0-90, 0-100, 0-150, 0-200, and 0-250 milliseconds) was then calculated by dividing the force at the end of the band by the band's time interval. The peak RFD was then calculated with the use of 2, 5, 10, 20, 30, and 50 milliseconds sampling windows. The average RFD (avgRFD) was calculated by dividing the peak force (PF) by the time to achieve PF. All data were analyzed with the use of intraclass correlation alpha (ICC?) and the coefficient of variation (CV) and 90% confidence intervals. All predetermined RFD time bands were deemed reliable based on an ICC? >0.95 and a CV <4%. Conversely, the avgRFD failed to meet the reliability standards set for this study. Overall, the method used to assess the RFD during an isometric midthigh clean pull impacts the reliability of the measure and predetermined RFD time bands should be used to quantify the RFD. PMID:25259470

Haff, G Gregory; Ruben, Ryan P; Lider, Joshua; Twine, Corey; Cormie, Prue

2015-02-01

397

Transition from leg to wing forces during take-off in birds.  

Science.gov (United States)

Take-off mechanics are fundamental to the ecology and evolution of flying animals. Recent research has revealed that initial take-off velocity in birds is driven mostly by hindlimb forces. However, the contribution of the wings during the transition to air is unknown. To investigate this transition, we integrated measurements of both leg and wing forces during take-off and the first three wingbeats in zebra finch (Taeniopygia guttata, body mass 15 g, N=7) and diamond dove (Geopelia cuneata, body mass 50 g, N=3). We measured ground reaction forces produced by the hindlimbs using a perch mounted on a force plate, whole-body and wing kinematics using high-speed video, and aerodynamic forces using particle image velocimetry (PIV). Take-off performance was generally similar between species. When birds were perched, an acceleration peak produced by the legs contributed to 85±1% of the whole-body resultant acceleration in finch and 77±6% in dove. At lift-off, coincident with the start of the first downstroke, the percentage of hindlimb contribution to initial flight velocity was 93.6±0.6% in finch and 95.2±0.4% in dove. In finch, the first wingbeat produced 57.9±3.4% of the lift created during subsequent wingbeats compared with 62.5±2.2% in dove. Advance ratios were <0.5 in both species, even when taking self-convection of shed vortices into account, so it was likely that wing-wake interactions dominated aerodynamics during wingbeats 2 and 3. These results underscore the relatively low contribution of the wings to initial take-off, and reveal a novel transitional role for the first wingbeat in terms of force production. PMID:22972887

Provini, Pauline; Tobalske, Bret W; Crandell, Kristen E; Abourachid, Anick

2012-12-01

398

Macroscopic aspects of heavy-ion reactions  

International Nuclear Information System (INIS)

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)

399

Forces and gravity  

SCPinfonet

...Forces and gravity Forces and gravity This site uses cookies. By continuing to use this site you agree to our use of cookies....here Activities Public engagement Resources Physicists in Primary Schools Topics Forces and gravity Public engagement Resources Physicists in Primary Schools Topics Electricity Forces and ... gravity Experiments Apparatus Safety notes Forces and magnets Sound Solids Light Solids, liquids and gases Sunlight and space travel Forces and springs Earth ...and the Solar System Electricity generation: Part 1 Electricity generation: Part 2 Forces and gravity Is gravity real or does the Earth just suck? Supports ...

400

Surface and Interfacial Forces  

CERN Document Server

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.

Butt, Hans-Jurgen

2010-01-01

401

On the entropy of radiation reaction  

CERN Document Server

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.

Burton, David A

2013-01-01

402

On the entropy of radiation reaction  

OpenAIRE

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 expl...

Burton, David; Noble, Adam

2014-01-01

403

Direct Reactions  

International Nuclear Information System (INIS)

In order to give a unified presentation of one point of view, these lectures are devoted only to a detailed development of the standard theories of direct reactions, starting from basic principles. Discussion is given of the present status of the theories, of the techniques used for practical calculation, and of possible future developments. The direct interaction (DI) aspects of a reaction are those which involve only a few of the many degrees of freedom of a nucleus. In fact the minimum number of degrees of freedom which must be involved in a reaction are those required to describe the initial and final channels, and DI studies typically consider these degrees of freedom and no others. Because of this simplicity DI theories may be worked out in painstaking detail. DI processes concern only part of the wave function for a problem. The other part involves complicated excitations of many degrees of freedom, and gives the compound nucleus (CN) effects. While it is extremely interesting to learn how to separate DI and CN effects in an orderly manner, if they are both present in a reaction, no suitable method has yet been found. Instead, current work stresses the kinds of reactions and the kinds of final states in which DI effects dominate and in which CN effects may almost be forgotten. The DI cross-sections which are studied are often extremely large, comparable to elastic scattering cross-sections. (author)

404

Macroscopic QED in linearly responding media and a Lorentz-Force approach to dispersion forces  

Energy Technology Data Exchange (ETDEWEB)

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.)

Raabe, Christian

2008-07-08

405

Reinventing Grounded Theory: Some Questions about Theory, Ground and Discovery  

Science.gov (United States)

Grounded theory's popularity persists after three decades of broad-ranging critique. In this article three problematic notions are discussed--"theory," "ground" and "discovery"--which linger in the continuing use and development of grounded theory procedures. It is argued that far from providing the epistemic security promised by grounded theory,…

Thomas, Gary; James, David

2006-01-01

406

Reaction mechanisms  

International Nuclear Information System (INIS)

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

407

A Simple Derivation of Lorentz Self Force  

CERN Document Server

We derive the Lorentz self force for an arbitrarily moving charged particle via averaging the retarded fields. The derivation is simple and at the same time pedagogically accessible. We obtain the radiation reaction for a charged particle moving in a conic. We pin down the underlying concept of mass renormalization.

Haque, Asrarul

2014-01-01

408

Ground Water Contamination  

Science.gov (United States)

This detailed discussion explains that most ground water contamination is the result of human activity, and that several laws have been passed with an aim to minimize effects. The Clean Water Act and the Safe Drinking Water Act are explained along with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, or Superfund), the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), the Resource Conservation and Recovery Act (RCRA), and the Toxic Substances Control Act (TSCA). Other terms explained include zone of contribution, interaquifer leakage, and plume of contamination. Special tables included at this site are Typical Sources of Potential Ground Water Contamination by Land Use Category and Potential Harmful Components of Common Household Products. There is also a full page diagram showing some potential sources of ground water contamination.

409

Force-dependent chemical kinetics of disulfide bond reduction observed with single-molecule techniques  

OpenAIRE

The mechanism by which mechanical force regulates the kinetics of a chemical reaction is unknown. Here, we use single-molecule force–clamp spectroscopy and protein engineering to study the effect of force on the kinetics of thiol/disulfide exchange. Reduction of disulfide bonds through the thiol/disulfide exchange chemical reaction is crucial in regulating protein function and is known to occur in mechanically stressed proteins. We apply a constant stretching force to single engineered disu...

Wiita, Arun P.; Ainavarapu, Sri Rama Koti; Huang, Hector H.; Fernandez, Julio M.

2006-01-01

410

Reinventing grounded theory: some questions about theory, ground and discovery  

OpenAIRE

Grounded theory’s popularity persists after three decades of broad-ranging critique. In this article three problematic notions are discussed—‘theory,’ ‘ground’ and ‘discovery’—which linger in the continuing use and development of grounded theory procedures. It is argued that far from providing the epistemic security promised by grounded theory, these notions—embodied in continuing reinventions of grounded theory—constrain and distort qualitative inquiry, and that what is...

Thomas, Gary; James, David

2006-01-01

411

Effects of vertical ground motion on seismic performance verification system of RC underground structures. Discussion on response of RC structures embedded in horizontally layered ground  

International Nuclear Information System (INIS)

The objective of this study is how to estimate vertical ground motion on the seismic performance verification method for crucial civil engineering structures in nuclear power plants. This paper presents the numerical study about the effects of vertical ground motion on underground RC structures. Several soil-structure interaction models embedded in horizontally layered ground were prepared, and the nonlinear earthquake response of the models were discussed under observed earthquake ground motion. Based on the numerical results, the findings are summarized as follows: Horizontal component of earthquake load is hardly affected by vertical ground motion, then the deformation angle, section force (bending moment and shear force) and curvature in RC member cause by global shear deformation on structure almost coincide with them developed by horizontal ground motion. On the other hand, the vertical ground motion brings a slight increase of axial force on upward columns, however that has little effect on limit deformation angle and shear strength of RC member which are affected by axial force fluctuation. And response and limit state values on structure are almost stable regardless of time instant difference of the peak acceleration between horizontal and vertical ground motions. (author)

412

Simulated earthquake ground motions  

International Nuclear Information System (INIS)

The paper reviews current methods for generating synthetic earthquake ground motions. Emphasis is on the special requirements demanded of procedures to generate motions for use in nuclear power plant seismic response analysis. Specifically, very close argeement is usually sought between the response spectra of the simulated motions and prescribed, smooth design response spectra. The features and capabilities of the computer program SIMQKE, which has been widely used in power plant seismic work are described. Problems and pitfalls associated with the use of synthetic ground motions in sesmic safety assessment are also pointed out. (Auth.)

413

Screened Casimir forces  

OpenAIRE

We demonstrate that a very recently obtained formula for the force on a slab in a material planar cavity based on the calculation of the vacuum Lorentz force [C. Raabe and D.-G. Welsch, Phys. Rev. A 71, 013814 (2005)] describes a (medium) screened Casimir force and, in addition to it, a medium-assisted force. The latter force also describes the force on the cavity medium. For dilute media, it implies the atom-mirror interaction of the Casimir-Polder type at large and of the ...

Tomas, M. S.

2005-01-01

414

Screened Casimir forces  

CERN Document Server

We demonstrate that a very recently obtained formula for the force on a slab in a material planar cavity based on the calculation of the vacuum Lorentz force [C. Raabe and D.-G. Welsch, Phys. Rev. A 71, 013814 (2005)] describes a (medium) screened Casimir force and, in addition to it, a medium-assisted force. The latter force also describes the force on the cavity medium. For dilute media, it implies the atom-mirror interaction of the Casimir-Polder type at large and of the Coulomb type at small atom-mirror distances of which the sign is insensitive to the polarizability type (electric or magnetic) of the atom.

Tomas, M S

2005-01-01

415

Coding Issues in Grounded Theory  

Science.gov (United States)

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…

Moghaddam, Alireza

2006-01-01

416

Forces in general relativity  

International Nuclear Information System (INIS)

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 anance with general relativity and tensor analysis.

417

Earth's Water:Ground Water  

Science.gov (United States)

This USGS site contains graphs, tables, and charts for the following ground water topics: What is ground water, ground water flow diagrams, importance of groundwater, and trends in ground-water use. Ground water quality, pesticides, aquifers, waterwells, artesian wells, sinkholes, and land subsidence are also covered. There are a variety of links within all of the above topics and a very complete glossary, as well as numerous charts, maps, photographs and illustrations.

418

A Study of Winglet and Aerodynamic Interferences in 3-D Viscous Flow around a Flying-Boat in Ground Effect  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, the flow field about a complete flying-boat in ground effect is resolved. The influences of using winglet in ground and out of ground effects are compared and it is shown that ground affects this influence to a large extent. It is also shown that with careful shaping of the body and using a step underneath the body a propulsive force can be produced in vicinity of the ground. However, this causes an increase in drag force in free flight.

H. Afshar

2009-01-01

419

Coal and coffee grounds  

Energy Technology Data Exchange (ETDEWEB)

The Sopad Nestle plant in Dieppe is the number 1 plant in France producing soluble coffee and chicory. Since 1983, it recovers and uses a production byproduct, coffee grounds as fuel, with coal, with an ignifluid boiler (hot fluidized bed), built by Fives-Cail-Babcock.

Landais, C.

420

Informed Grounded Theory  

Science.gov (United States)

There is a widespread idea that in grounded theory (GT) research, the researcher has to delay the literature review until the end of the analysis to avoid contamination--a dictum that might turn educational researchers away from GT. Nevertheless, in this article the author (a) problematizes the dictum of delaying a literature review in classic…

Thornberg, Robert

2012-01-01

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