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Ground reaction forces during treadmill running in microgravity.  

Science.gov (United States)

Astronauts perform treadmill exercise during long-duration space missions to counter the harmful effects of microgravity exposure upon bone, muscle, and cardiopulmonary health. When exercising in microgravity, astronauts wear a harness and bungee system that provides forces that maintain attachment to the treadmill. Typical applied forces are less than body weight. The decreased gravity-replacement force could result in differences in ground-reaction force at a given running speed when compared to those achieved in normal gravity, which could influence the adaptive response to the performed exercise. Seven astronauts (6 m/1 f) who completed approximately 6-month missions on the International Space Station (ISS) completed a preflight (1G) and multiple in-flight (0G) data collection sessions. Ground-reaction forces were measured during running at speeds of 8.0kph and greater on an instrumented treadmill in the lab and on the ISS. Ground-reaction forces in 0G were less than in 1G for a given speed depending upon the gravity-replacement force, but did increase with increased speed and gravity-replacement force. Ground-reaction forces attained in 1G during slower running could be attained by increasing running speed and/or increasing gravity-replacement forces in 0G. Loading rates in 1G, however, could not be replicated in 0G. While current gravity-replacement force devices are limited in load delivery magnitude, we recommend increasing running speeds to increase the mechanical loads applied to the musculoskeletal system during 0G treadmill exercise, and to potentially increase exercise session efficiency. PMID:24835563

De Witt, John K; Ploutz-Snyder, Lori L

2014-07-18

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

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

Shahin Gohar Pay

2011-10-01

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The Effect of Increasing Inertia upon Vertical Ground Reaction Forces 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 kinematics during walking and running. Vertical ground reaction force was measured for ten healthy adults (5 male/5 female) during walking (1.34 m/s) and running (3.13 m/s) 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. 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. Vertical ground reaction force production and adaptations in gait kinematics were different between walking and running. The increased inertial forces were utilized independently from gravitational forces by the motor control system when determining coordination strategies.

DeWitt, John K.; Hagan, R. Donald; Cromwell, Ronita L.

2007-01-01

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

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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

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Validation of vertical ground reaction forces on individual limbs calculated from kinematics of horse locomotion  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The purpose of this study was to determine whether individual limb forces could be calculated accurately from kinematics of trotting and walking horses. We collected kinematic data and measured vertical ground reaction forces on the individual limbs of seven Warmblood dressage horses, trotting at 3.4 m s(-1) and walking at 1.6 m s(-1) on a treadmill. First, using a segmental model, we calculated from kinematics the total ground reaction force vector and its moment arm relative to each of the ...

Bobbert, M. F.; Gomez Alvarez, C. B.; Weeren, R.; Roepstorff, L.; Weishaupt, M. A.

2007-01-01

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RELATIONSHIPS AMONG SPRINT VELOCITIES, HORIZONTAL GROUND REACTION FORCE, AND ISOKINETIC TRUNK STRENGTH VARIABLES  

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Full Text Available The purpose of this study was to investigate the relationships among sprint velocities, horizontal ground reaction force, and isokinetic trunk strength variables. Voluntary 19 athletes were participated to the study [age (year= 20.9±2.3, training age (month= 91.3±48.2, body height (cm= 173.1±6.5, body weight (kg= 64.7±8.4] from different sports including in explosive strength. Sprints (10m, 20m, 30m, and 40m were tested on a non-motorized treadmill. Velocities (V10m, V20m, V30m, and V40m and horizontal ground reaction forces (HGRF-10m, HGRF-20m, HGRF-30m, and HGRF-40m of the sprints were calculated. Isokinetic trunk strength criteria (flexion-extension peak torques at 3 different angular velocities (30o.s-1, 90o.s-1, and 120o.s-1 were tested. Pearson Correlation Coefficient was used for statistical analysis. Probability level was p?0.05. All sprint velocities was correlated with all horizontal ground reaction forces (except the correlation between V10m and HGRF-20m and all isokinetic trunk flexion-extension peak torques (except the correlation between V10m and isokinetic trunk flexion peak torque at 120o.s-1. Statistically highest significant correlations have been found between V40m and all horizontal ground reaction forces and also between V40m and isokinetic trunk flexion-extension peak torques (30o.s-1, 90o.s-1, and 120o.s-1. There were significant relationships of horizontal ground reaction forces with isokinetic trunk extension-flexion peak torques at 30o.s-1, 90o.s-1, and 120o.s-1. In conclusion, isokinetic trunk flexion and extension strength values are crucial for improving sprint acceleration and horizontal component of ground reaction force.

Kale Mehmet

2013-12-01

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Effects of weighted sled towing on ground reaction force during the acceleration phase of sprint running.  

Science.gov (United States)

Athletes use weighted sled towing to improve sprint ability, but little is known about its biomechanics. The purpose of this study was to investigate the effect of weighted sled towing with two different loads on ground reaction force. Ten physically active men (mean ± SD: age 27.9 ± 1.9 years; stature 1.76 ± 0.06 m; body mass 80.2 ± 9.6 kg) performed 5 m sprints under three conditions; (a) unresisted, (b) towing a sled weighing 10% of body mass (10% condition) and (c) towing a sled weighing 30% of body mass (30% condition). Ground reaction force data during the second ground contact after the start were recorded and compared across the three conditions. No significant differences between the unresisted and 10% conditions were evident, whereas the 30% condition resulted in significantly greater values for the net horizontal and propulsive impulses (P < 0.05) compared with the unresisted condition due to longer contact time and more horizontal direction of force application to the ground. It is concluded that towing a sled weighing 30% of body mass requires more horizontal force application and increases the demand for horizontal impulse production. In contrast, the use of 10% body mass has minimal impact on ground reaction force. PMID:24576071

Kawamori, Naoki; Newton, Robert; Nosaka, Ken

2014-01-01

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

Science.gov (United States)

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. Key pointsGround reaction forces and joint moments during lateral stepping are smaller in magnitude than those experienced during moderate running.Force exposure in SS and XS gaits in normal play does not appear to contribute to the development of overuse injuryThe leading and trailing limbs perform distinct roles, acting as a generator of vertical force and shock absorber respectively.This distinct contribution may contribute to the development of muscular imbalances which may ultimately contribute to the development of overuse injury. PMID:24150549

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

2009-01-01

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

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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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The effect of ankle taping on the ground reaction force in vertical jump performance.  

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Koyama, K, Kato, T, and Yamauchi, J. The effect of ankle taping on the ground reaction force in vertical jump performance. J Strength Cond Res 28(5): 1411-1417, 2014-The purpose of this study was to investigate the effects of closed basket weave (CBW) ankle taping on the vertical ground reaction force during the contact phase before the take-off in vertical jump performance. We hypothesized that ankle taping would limit the capability for explosive force generation during the contact phase before the take-off in jump performance. Twelve healthy young men (age, 20.2 ± 1.3 years; height, 1.76 ± 0.05 m; body mass, 66.1 ± 6.1 kg; mean ± SD) performed a vertical jump performance on a force plate without (CON) or with ankle taping (CBW technique) of the right ankle joint. Vertical jump ability was assessed using 2 styles of vertical jump with no arm swing: a countermovement jump (CMJ) and squat jump (SJ). From the vertical ground reaction force (GRF), maximum jump height, vertical impulse (VI), rate of force development, maximum GRF (GRFmax), and time-series GRF (GRFts) during the contact phase before the take-off in jump performance were determined. Jump height was significantly lower for CBW (36.6 ± 6.6 cm) than CON (38.1 ± 6.7 cm) in CMJ, but not in SJ. Rate of force development and GRFts at 35, 40, 45, 50, 55, 60, and 65% of total time of the contact phase in jumping performance were also significantly smaller for CBW than CON in CMJ, but not in SJ. Conversely, VI and GRFmax were not significantly different between the groups in either jump condition. These results suggest that ankle taping impairs CMJ performance, because of a decreased ability to develop large force rapidly on the ground before the take-off. PMID:24126899

Koyama, Keiji; Kato, Tomoo; Yamauchi, Junichiro

2014-05-01

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Foot speed, foot-strike and footwear: linking gait mechanics and running ground reaction forces.  

Science.gov (United States)

Running performance, energy requirements and musculoskeletal stresses are directly related to the action-reaction forces between the limb and the ground. For human runners, the force-time patterns from individual footfalls can vary considerably across speed, foot-strike and footwear conditions. Here, we used four human footfalls with distinctly different vertical force-time waveform patterns to evaluate whether a basic mechanical model might explain all of them. Our model partitions the body's total mass (1.0Mb) into two invariant mass fractions (lower limb=0.08, remaining body mass=0.92) and allows the instantaneous collisional velocities of the former to vary. The best fits achieved (R(2) range=0.95-0.98, mean=0.97±0.01) indicate that the model is capable of accounting for nearly all of the variability observed in the four waveform types tested: barefoot jog, rear-foot strike run, fore-foot strike run and fore-foot strike sprint. We conclude that different running ground reaction force-time patterns may have the same mechanical basis. PMID:24737756

Clark, Kenneth P; Ryan, Laurence J; Weyand, Peter G

2014-06-15

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Sagittal plane ground reaction forces, centre of pressure and centre of mass in trotting horses.  

Science.gov (United States)

The aims of this study were to measure ground reaction forces (GRFs) of concurrently loaded limbs and to evaluate spatial relationships between the centre of pressure (COP) and centre of mass (COM) in trotting horses. Kinematic (120Hz) and GRF data were collected at trot from three trials of eight horses using four force plates (960 Hz). Forelimb and hind limb GRFs were measured, COP was calculated from the resultant vertical GRF vector and COM was calculated by summation of weighted segmental COMs. Peak total vertical force (19.3 ± 1.3N/kg at 45.1 ± 2.3% diagonal stance) coincided with zero total longitudinal force (45.1 ± 2.4% stance). Initially, COP position corresponded with the fore or hind hoof of the diagonal that contacted the ground earlier. During diagonal overlap, COP position reflected forelimb contribution to total vertical GRF; it maintained a fairly constant position relative to the base of support through the middle part of stance, then moved cranially in the last third of stance towards the fore hoof, which was always the last hoof to leave the ground. The COM moved forward continuously; its longitudinal velocity decreased with the net braking force in early stance and increased with the net propulsive force in late stance. The COM was caudal to the COP in early stance, coincident at 35.8 ± 4.4% stance and was maximally ahead of the COP at 67.6 ± 4.8% stance. Changes in the spatial relationship between COP and COM affect the moment arms of the forelimb and hind limb vertical GRFs and their effect in generating a pitching torque around the COM. PMID:24138935

Hobbs, Sarah J; Clayton, Hilary M

2013-12-01

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Control of ground reaction forces by hindlimb muscles during cat locomotion.  

Science.gov (United States)

It has been proposed that biarticular muscles are primarily responsible for the control of the direction of external forces, as their activation is closely related and highly sensitive to the direction of external forces. This functional role for biarticular muscles has been supported qualitatively by experimental evidence, but has never been tested quantitatively for lack of a mathematical/mechanical formulation of this theory and the difficulty of measuring individual muscle forces during voluntary movements. The purposes of this study were: (1) to define rules for muscular coordination based on the control of external forces; (2) to develop a model of the cat hindlimb that allows for the calculation of the magnitude and direction of the ground reaction forces (GRFs) produced by individual hindlimb muscles; and (3) to test if the coordination of mono- and biarticular cat hindlimb muscles is related to the control of the resultant GRF. We measured the GRF, hindlimb kinematics, selected muscle forces and activations during cat locomotion. Then, the measured muscle forces were used as input to the hindlimb model to compute the muscle-induced GRF. We assume that if activation (and possibly force) increased as the muscle-induced component of GRF approximated the resultant GRF, then that muscle was used by the central nervous system (CNS) to help control the direction of the external GRF. During cat walking, medial gastrocnemius (MG) and plantaris (PL) forces increased with increasing proximity to the GRF, while soleus (SOL) forces and vastus lateralis (VL) activations did not. SOL and VL activation were most strongly related to the vertical and parallel (braking/accelerating) component of the GRF, respectively. We concluded from these results that MG and PL are primarily responsible for the control of the direction of the GRF, while SOL primarily functions as an anti-gravity muscle, and VL as an acceleration/deceleration muscle. PMID:16310793

Kaya, Motoshi; Leonard, Tim R; Herzog, Walter

2006-01-01

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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.

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Three-dimensional kinematics and ground reaction forces during the instep and outstep soccer kicks in pubertal players  

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The purpose of the present study was to compare the three-dimensional kinematics of the lower extremities and ground reaction forces between the instep kick and the kick with the outside area of the foot (outstep kick) in pubertal soccer players. Ten pubertal soccer players performed consecutive kicking trials in random order after a two-step angled approach with the instep and the outstep portion of the foot. Three-dimensional data and ground reaction forces were measured during kicking. Pai...

Katis Athanasios; ??????, ??????????; Kellis, Eleftherios; ???????, ???????????

2010-01-01

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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

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

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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

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An investigation into the relation between step height and ground reaction forces in step exercise: a pilot study.  

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The aim of this study was to investigate the effect that changing step height had on ground reaction force. Using a randomised crossover design, 12 volunteers with no previous experience of step aerobics were recruited to perform at three different step heights: 6, 8 and 10 inches. Subjects performed a basic step at a cadence of 120 beats/min and performed three one minute trials during which ground reaction force was measured. Measurement of peak impact force, time to achieve peak impact, an...

Maybury, M. C.; Waterfield, J.

1997-01-01

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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

2010-08-01

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Comparison of ground reaction force asymmetry in one- and two-legged countermovement jumps.  

Science.gov (United States)

This study examined whether ground reaction force (GRF) asymmetry of 2-legged countermovement jumps (CMJ) is related to 1-legged CMJ asymmetry. The GRF asymmetry of a 2-legged CMJ has been suggested as a preferred test to the 1-legged CMJ for functional strength and power deficit assessment. Twenty-eight men and 30 women performed 5 trials each of a 1-legged CMJ with the right limband the left limb, and a 2-legged CMJ. Vertical GRFs were collected from each lower limb using 2 force platforms. Although several GRF variables were calculated, vertical impulse correlated most strongly with jump height in all conditions (p Halton exact p = 0.61) and women (Freeman-Halton exact p = 0.19). Only 11 women recorded the same dominant limb for both 1- and 2-legged CMJs. This suggests that impulse asymmetries found in the 1- and 2-legged CMJ were unrelated. As the 1-legged CMJ relies on the extension forces generated entirely from 1 limb, variations in jump heights and GRF impulses by left and right limbs separately were more indicative of functional strength differences between sides. Hence, it is recommended that the 1-legged CMJ is used when examining functional strength asymmetry in the lower limbs. In contrast, factors causing asymmetry in GRF impulses during 2-legged CMJs are more complicated and require further investigation. PMID:23287834

Benjanuvatra, Nat; Lay, Brendan S; Alderson, Jacqueline A; Blanksby, Brian A

2013-10-01

 
 
 
 
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Functional data analysis on ground reaction force of military load carriage increment  

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Analysis of ground reaction force on military load carriage is done through functional data analysis (FDA) statistical technique. The main objective of the research is to investigate the effect of 10% load increment and to find the maximum suitable load for the Malaysian military. Ten military soldiers age 31 ± 6.2 years, weigh 71.6 ± 10.4 kg and height of 166.3 ± 5.9 cm carrying different military load range from 0% body weight (BW) up to 40% BW participated in an experiment to gather the GRF and kinematic data using Vicon Motion Analysis System, Kirstler force plates and thirty nine body markers. The analysis is conducted in sagittal, medial lateral and anterior posterior planes. The results show that 10% BW load increment has an effect when heel strike and toe-off for all the three planes analyzed with P-value less than 0.001 at 0.05 significant levels. FDA proves to be one of the best statistical techniques in analyzing the functional data. It has the ability to handle filtering, smoothing and curve aligning according to curve features and points of interest.

Din, Wan Rozita Wan; Rambely, Azmin Sham

2014-06-01

22

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

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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

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Frequency domain analysis of ground reaction force in preadolescents with and without Down syndrome.  

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Children with Down syndrome (DS) display less stable and coordinated gait patterns in the time domain than their healthy peers. However, little is known about whether this group difference exists in the frequency domain. The purpose of this study was to investigate differences in vertical ground reaction force (GRF) in the frequency domain between preadolescents with and without DS. Twenty children at 7-10 years of age with and without DS participated in this study. Participants walked on an instrumented treadmill at two speeds with and without external ankle load. Vertical GRF was collected and the data was processed through a Fourier transform. Frequency content variables included fundamental frequency, power of the first five harmonics, and the frequency and number of harmonics at 95%, 99% and 99.5% of total power. Preadolescents with DS had a similar fundamental frequency as their healthy peers even though the DS group walked at slower speeds. The DS group displayed a different power spectrum of the first five harmonics and had the lower frequency and number of harmonics at 99% and 99.5% of total power. However, walking at a faster speed with external ankle load helped the DS group produce a power spectrum more similar to healthy children. Frequency content of vertical GRF provides additional assessment parameters in functional gait evaluation of children with DS. Treadmill intervention at a faster speed and with external ankle load appears to be clinically promising and needs further investigation. PMID:24685940

Wu, Jianhua; Beerse, Matthew; Ajisafe, Toyin

2014-06-01

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Estimation of ground reaction force and zero moment point on a powered ankle-foot prosthesis.  

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The ground reaction force (GRF) and the zero moment point (ZMP) are important parameters for the advancement of biomimetic control of robotic lower-limb prosthetic devices. In this document a method to estimate GRF and ZMP on a motorized ankle-foot prosthesis (MIT Powered Ankle-Foot Prosthesis) is presented. The method proposed is based on the analysis of data collected from a sensory system embedded in the prosthetic device using a custom designed wearable computing unit. In order to evaluate the performance of the estimation methods described, standing and walking clinical studies were conducted on a transtibial amputee. The results were statistically compared to standard analysis methodologies employed in a gait laboratory. The average RMS error and correlation factor were calculated for all experimental sessions. By using a static analysis procedure, the estimation of the vertical component of GRF had an averaged correlation coefficient higher than 0.94. The estimated ZMP location had a distance error of less than 1 cm, equal to 4% of the anterior-posterior foot length or 12% of the medio-lateral foot width. PMID:18003052

Martinez-Villalpando, Ernesto C; Herr, Hugh; Farrell, Matthew

2007-01-01

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

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

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

2010-01-01

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

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

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

2006-12-01

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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

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Adaptive locomotor training on an end-effector gait robot: evaluation of the ground reaction forces in different training conditions.  

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The main goal of robotic gait rehabilitation is the restoration of independent gait. To achieve this goal different and specific patterns have to be practiced intensively in order to stimulate the learning process of the central nervous system. The gait robot G-EO Systems was designed to allow the repetitive practice of floor walking, stair climbing and stair descending. A novel control strategy allows training in adaptive mode. The force interactions between the foot and the ground were analyzed on 8 healthy volunteers in three different conditions: real floor walking on a treadmill, floor walking on the gait robot in passive mode, floor walking on the gait robot in adaptive mode. The ground reaction forces were measured by a Computer Dyno Graphy (CDG) analysis system. The results show different intensities of the ground reaction force across all of the three conditions. The intensities of force interactions during the adaptive training mode are comparable to the real walking on the treadmill. Slight deviations still occur in regard to the timing pattern of the forces. The adaptive control strategy comes closer to the physiological swing phase than the passive mode and seems to be a promising option for the treatment of gait disorders. Clinical trials will validate the efficacy of this new option in locomotor therapy on the patients. PMID:22275689

Tomelleri, Christopher; Waldner, Andreas; Werner, Cordula; Hesse, Stefan

2011-01-01

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

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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...

Tao Liu; Yoshio Inoue; Kyoko Shibata

2010-01-01

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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

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Effects of sex and mode of carrying schoolbags on ground reaction forces and temporal characteristics of gait  

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The aim of this study was to examine the effects of different modes of carrying schoolbags on children. Ten girls and eight boys walked without a bag (NO-BAG), with a bag placed low at the back (LBACK), with a back placed high at the back (HBACK) and carrying the bag using the handle (HANDBAG). Ground reaction forces and temporal characteristics were recorded. When carrying a schoolbag, children walked with shorter strides, at lower speeds, with higher double support phase and increased verti...

2010-01-01

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

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Context: Runners with high medial longitudinal arch structure demonstrate unique kinematics and kinetics that may lead to running injuries. The mobility of the midfoot as measured by the change in arch height is also suspected to play a role in lower extremity function during running. The effect of arch mobility in high-arched runners is an important factor in prescribing footwear, training, and rehabilitating the running athlete after injury. Objective: To examine the effect of medial longitudinal arch mobility on running kinematics, ground reaction forces, and loading rates in high-arched runners. Design: Cross-sectional study. Setting: Human movement research laboratory. Patients or Other Participants: A total of 104 runners were screened for arch height. Runners were then identified as having high arches if the arch height index was greater than 0.5 SD above the mean. Of the runners with high arches, 11 rigid runners with the lowest arch mobility (R) were compared with 8 mobile runners with the highest arch mobility (M). Arch mobility was determined by calculating the left arch height index in all runners. Intervention(s): Three-dimensional motion analysis of running over ground. Main Outcome Measure(s): Rearfoot and tibial angular excursions, eversion-to-tibial internal-rotation ratio, vertical ground reaction forces, and the associated loading rates. Results: Runners with mobile arches exhibited decreased tibial internal-rotation excursion (mobile: 5.6° ± 2.3° versus rigid: 8.0° ± 3.0°), greater eversion-to-tibial internal-rotation ratio (mobile: 2.1 ± 0.8 versus rigid: 1.5 ± 0.5), decreased second peak vertical ground reaction force values (mobile: 2.3 ± 0.2 × body weight versus rigid: 2.4 ± 0.1 × body weight), and decreased vertical loading rate values (mobile: 55.7 ± 14.1 × body weight/s versus rigid: 65.9 ± 11.4 × body weight/s). Conclusions: Based on the results of this study, it appears that runners with high arch structure but differing arch mobility exhibited differences in select lower extremity movement patterns and forces. Future authors should investigate the impact of arch mobility on running-related injuries. PMID:24840580

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

2014-06-01

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Reliability of performance measurements derived from ground reaction force data during countermovement jump and the influence of sampling frequency.  

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Force platforms are used extensively to measure force and power output during countermovement jump (CMJ). The purpose of this study was to examine measurement reliability and validity of commonly used performance measurements derived from ground reaction force (GRF)-time data during CMJ and the influence of sampling at different frequencies. Twenty-four men performed 2 trials of CMJ on a force platform, and GRF-time data were sampled at a rate of 500 Hz. Data obtained at 500 Hz were considered as the reference, and then data were resampled at 400, 250, 200, 100, 50, and 25 Hz, using interpolation. Commonly used power, force, and velocity performance measures were obtained from GRF-time data. Reliability was assessed by intraclass correlation coefficient (ICC) and coefficient of variation (CV) between the 2 trials within the session. Peak power, peak force, and peak velocity were highly reliable across all sampling frequencies (ICC = 0.92-0.98, CV = 1.3-4.1). Percentage differences from 500-Hz reference values ranged from -0.85 to 0.20% at 400 Hz, -1.88 to 0.89% at 250 Hz, -1.80 to 1.31% at 200 Hz, -3.63 to 3.34% at 100 Hz, -11.37 to 6.51% at 50 Hz, and -13.17 to 9.03% at 25 Hz. In conclusion, peak power, force, and velocity measurements derived from GRF to assess leg extensor capabilities are reliable within a test session except for peak rate of force development and time to peak power. With regard to sampling frequency, scientists and practitioners may consider sampling as low as 200 Hz, depending on the purpose of measurement, because the percentage difference is not markedly enlarged until the frequency is 100 Hz or lower. PMID:19387390

Hori, Naruhiro; Newton, Robert U; Kawamori, Naoki; McGuigan, Michael R; Kraemer, William J; Nosaka, Kazunori

2009-05-01

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The effect of tibio-talar arthrodesis on foot kinematics and ground reaction force progression during walking.  

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Degenerative osteoarthritis in the subtalar and mid-tarsal joints occurring after tibio-talar arthrodesis is thought to be a consequence of abnormal foot dynamics. We hypothesized that the forward tilt of the tibia during stance induces early heel-off and alteration of the progression of ground reaction force (GRF) after ankle arthrodesis. Three-dimensional gait analysis was performed on nine patients who had an ankle arthrodesis fused in a neutral position and on ten control subjects. Patients walking barefoot were compared to controls. The GRF progression was shifted forward during mid-stance, heel-off occurred earlier and was associated with less anterior tilt of the tibia and a more posterior position of the GRF with reference to the metatarsal heads. The GRF progression, heel-off and tibial tilt were not significantly different between patients and controls when walking in shoes but the GRF was still more posterior at heel-off. Increasing the walking speed worsened the anomalies of foot dynamics. These alterations of foot dynamics are thought to be associated with pathogenic stresses applied to the mid-foot. PMID:15196525

Beyaert, C; Sirveaux, F; Paysant, J; Molé, D; André, J-M

2004-08-01

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

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

Kyoko Shibata

2010-11-01

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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

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The Effect of pPoron Layered Insole on Ground Reaction Force in Comparison with Common Insole on Subjects with Flexible Flat foot  

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Full Text Available Background: Flexible flat foot is a congenital common deformity in lower extremity associated with ligamentus laxity. This deformity may cause hammer toe, heel spur, inflammation of achille tendon, early muscle fatigue during sport, foot imbalance and pain in leg, knee and hip. The use of insole with medial arch support considered as one of the common treatments for patients. The purpose of this study was to determine the effect of a composite insole, Ethyl Vinyl Acetate (EVA with Poron layer on ground reaction force on subjects with flexible flat foot in comparison with common EVA insole. Materials and Methods: Fifty two subjects (14 Male and 38 female between 18-40 years of age with flexible flat foot participated in this study. Twenty six subjects received Poron insole (EVA with Poron layer and 26 subjects received common EVA insole. After assessment each subject asked to walk with normal speed across two force plate in two conditions, walking with insole and shoe and walking without insole. Then each subject asked to use insole for forty hours during two weeks. Vertical ground reaction force in the first session and after two weeks was assessed.Results: Impact force and first peak of vertical ground reaction force (F1 with Poron insole in comparison with shoe significantly increased in second session (P<0.05. The second peak (F3 with common insole in comparison with shoe significantly increased in second session (P<0.05. Significant reduction was noted in first peak (F1 with common insole in second session in comparison with first session (P<0.05. There was no observable significant difference in two groups before and after intervention.Conclusion: The results of this preliminary study show that both insoles change vertical ground reaction force in comparison with shoe alone. But using a composite Poron Layer on EVA insole has not demonstrated a significant difference with common arch support insoles. Therefore appli

F Khanmohammad

2012-01-01

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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

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

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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

 
 
 
 
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Ground Reaction Forces and Gait Parameters during Motorized and Non-Motorized Treadmill Walking and Runing on the International Space Station Treadmill  

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Both motorized (T-M) and non-motorized (T-NM) treadmill locomotion are used on the International Space Station (ISS) as countermeasures to the deleterious effects of prolonged weightlessness. However, the ground reaction forces (GRF) and gait parameters of these exercise modes have not been examined. The purpose of this study was to determine if differences in GRF and gait parameters exist while walking (1.34 m/s) and running (3.13 m/s) on T-M and T-NM. Dissimilar GRF and gait parameters suggest that T-M and T-NM locomotion may elicit different physiologic effects. T-NM may result in a reduced stimulus to bone formation due to a lower LR, but an increased energy cost as a result of shorter, more frequent strides. Therefore, the usage of each mode should depend upon the desired training stimulus.

Hagan, Ronald Donald; Norcross, Jason; DeWitt, John; Lee, Stuart M.; McCleary, Frank; Edwards, W. Brent

2006-01-01

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Força de reação do solo como subsídio para prescrição de exercícios aquáticos: estudo de caso / Ground reaction force as a subsidy for prescribing aquatic exercises: case study  

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Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: Comparar a componente vertical da força de reação do solo nos exercícios de caminhada, corrida com deslocamento, corrida estacionária e salto vertical, realizados em ambiente aquático em diferentes níveis de imersão. MÉTODO: Participou deste estudo de caso um sujeito do sexo masculino (27 [...] anos, 1,80 m e 84,3 kg). Utilizou-se para a coleta de dados uma plataforma subaquática de força posicionada no fundo de uma piscina térmica. O sujeito realizou 30 tentativas válidas de cada exercício, imerso nos níveis do processo xifoide e do quadril. Os dados foram analisados com a utilização da estatística descritiva, teste "t" de Student para amostras pareadas e ANOVA, para medidas repetidas (p Abstract in english OBJECTIVE: To compare the vertical component of the ground reaction force in the exercises of walking, running, stationary running and vertical jump in the water, performed in different levels of immersion. METHODS: This case study was conducted with one subject (male, 27 years, 1,80 m and 84,3 kg). [...] An underwater force plate was used for data collection, placed at the bottom of a thermal swimming pool. The subject performed 30 valid passages for each exercise in two immersion levels: xiphoid process and hip. Data were analyzed through descriptive statistics, Student's "t" test for paired samples and ANOVA for repeated measures (p

Alessandro, Haupenthal; Caroline, Ruschel; Marcel, Hubert; Heiliane de Brito, Fontana; Helio, Roesler.

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Comparative analysis of the ground reaction forces, during the support phase, in a group of pregnant women on their 3rd trimester of pregnancy and in a group of not pregnant women  

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PURPOSE: To analyze and compare the Ground Reaction Forces (GRF), during the stance phase of walking in pregnant women in the 3rd trimester of pregnancy, and non pregnant women. METHODS: 20 women, 10 pregnant and 10 non pregnant, voluntarily took part in this study. GRF were measured (1000 Hz) using a force platform (BERTEC 4060-15), an amplifier (BERTEC AM 6300) and an analogical-digital converter of 16 Bits (Biopac). RESULTS: The study showed that there were significant diffe...

Santos, Rubim; Gil, Belandina; Marques, Alda; Vilas Boas, Joa?o; Silva, Jose?

2008-01-01

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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

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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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 players 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, a...

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

2006-01-01

46

Grounding-Line Migration under Cyclical Forcing  

Science.gov (United States)

Modeling of grounding-line dynamics is critical to determining the stability and steady-state behavior of ice sheets as well as accurate climate projections (Weertman 1974 J.Glaciol.; Schoof 2007, JGR; Gladstone et al. 2010, JGR; Docquier et al. 2011, Surv. Geophys.; Pattyn et al. 2012, The Cryosphere). There have been numerous efforts to analyze the response of the grounding line to different parameter changes, e.g., buttressing, oceanic warming, orbital-scale climate cycling, sedimentation, basal friction or melting. In this work, we consider grounding-line migration under cyclical forcing, using vertically integrated momentum-balance (MacAyeal-Morland) equations. The numerical experiments are carried out using finite-element models (FEMs), where the grounding line is determined by using the basis functions within the partially-grounded elements. Preliminary results, using linear bases, show asymmetric grounding-line response under centennial-scale cyclical forcing of model parameters, such as basal friction or ice hardness. Combined cyclical forcing of parameters may lead to larger or smaller oscillations in grounding-line response, depending on the phase. Preliminary results will be extended by using quadratic bases, and considering different geometry and bed topographies.

Aykutlug, E.; Dupont, T. K.

2012-12-01

47

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

Directory of Open Access Journals (Sweden)

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

Giovana Levada

2012-06-01

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

Scientific Electronic Library Online (English)

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

Giovana, Levada; Paula Hentschel Lobo da, Costa.

49

Dynamics of grounding zones under tidal forcing  

Science.gov (United States)

We combine the dynamics of ice, bed and ocean in a new elastic model for the tidal-timescale migration of grounding lines on deformable foundations. Previous interpretations of tidal flexure using models of elastic ice shelves with fixed grounding lines were found to be inconsistent, suggesting an elasticity of ice that varies spatially and temporally and that is significantly smaller than measured experimentally. We argue that, with our model, a consistent, purely elastic interpretation can be made. Combining this new approach with remote-sensing measurements, we show that the grounding line migrates several kilometers during a tidal cycle, that we can infer the effective elastic properties of the bed, and that the elastic pressure of the ice leads to a hydrological barrier near the grounding line and controls subglacial hydrology. Our findings imply that subglacial lubrication and melting induced by the ocean thermal forcing can increase substantially during high tide. Consequently, these processes can combine to accelerate the mass transfer from ice sheets to the ocean, and contribute to sea level rise.

Sayag, Roiy; Worster, Grae

2014-05-01

50

The Origin of the Radiation Reaction Force  

CERN Multimedia

The emission of radiation from an accelerated charge is analyzed. It is found that at zero velocity, the radiation emitted from the charge imparts no counter momentum to the emitting charge, and no radiation reaction force is created by the radiation. A reaction force is created by the stress force that exists in the curved electric field of the charge, and the work done in overcoming this force is the source of the energy carried by the radiation.

Harpaz, A

2000-01-01

51

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  

Directory of Open Access Journals (Sweden)

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

52

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.

53

Low Reaction Force Nozzle Using Unsteady Flow.  

Science.gov (United States)

The use of unsteady flow concepts in reducing the reaction forces that accompany the flow through a firehose nozzle and an attached segment of hose is studied. These steady state reaction forces are primarily due to curvature of the attached portion of ho...

A. J. Bilanin A. H. Boschitsch A. E. Kaufman T. R. Quackenbush

1989-01-01

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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.

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

Directory of Open Access Journals (Sweden)

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

Alberto Carlos Amadio

2013-01-01

56

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

Scientific Electronic Library Online (English)

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

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

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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.

58

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

Science.gov (United States)

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

Powell, R. D.

2013-12-01

59

Ground reaction curve based upon block theory  

Energy Technology Data Exchange (ETDEWEB)

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.

Yow, J.L. Jr.; Goodman, R.E.

1985-09-01

60

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

1985-10-10

 
 
 
 
61

Muscle response to pneumatic hand tool torque reaction forces.  

Science.gov (United States)

Surface electromyography was used for studying the effects of torque reaction force acting against the hand, on forearm muscle activity and grip force for five subjects operating right angle, air shut-off nutrunners. Four tools having increasing spindle torque were operated using short and long torque reaction times. Nutrunner spindle torque ranged between 30 Nm and 100 Nm. Short torque reaction time was considered 0.5 s while long torque reaction time was 2 s. Peak horizontal force was the greatest component of the reaction force acting against the hand and accounted for more than 97% of the peak resultant hand force. Peak hand force increased from 89 N for the smallest tool to 202 N for the largest tool. Forearm muscle rms EMG, scaled for grip force, indicated average flexor activity during the Torque-reaction phase was more than four times greater than the Pre-start and Post Shut-off phases, and two times greater than the Run-down phase. Flexor EMG activity during the Torque-reaction phase increased for increasing tool peak spindle torque. Average flexor rms EMG activity, scaled for grip force, during the Torque-reaction phase increased from 372 N for the 30 Nm nutrunner to 449 N for the 100 Nm nutrunner. Flexor rms EMG activity averaged during the Torque-reaction phase and scaled for grip force was 390 N for long torque reaction times and increased to 440 N for short torque reaction times. Flexor rms EMG integrated over the torque reaction phase was 839 Ns for long torque reaction times and decreased to 312 Ns for short torque reaction times. The average latency between tool spindle torque onset and peak initial flexor rms EMG for long torque reaction times was 294 ms which decreased to 161 ms for short torque reaction times. The average latency between peak tool spindle torque, just prior to tool shut-off, and peak final rms EMG for long torque reaction times was 97 ms for flexors and 188 ms for extensors, which decreased for short torque reaction times to 47 ms for flexors and 116 ms for extensors. The results suggest that right angle nutrunner torque reaction forces can affect extrinsic hand muscles in the forearm, and hence grip exertions, by way of a reflex response.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2776745

Radwin, R G; VanBergeijk, E; Armstrong, T J

1989-06-01

62

How critical are the tibiofemoral joint reaction forces during frequent squatting in Asian populations?  

Science.gov (United States)

This study examines tibiofemoral joint moments and forces when performing a squat. The relevance of studying such an activity is to understand better the mechanical factors involved in the higher incidence of tibiofemoral osteoarthritis in Asian populations where squatting is a common daily activity. In this study, motion analysis data of walking versus squatting were compared, specifically looking at net external knee flexion moments, ground reaction forces and tibiofemoral contact forces. It was found that while squatting resulted in more than 2.5 times larger peak external moments compared with walking, tibiofemoral contact forces were not significantly different. This was due to reduced ground reaction forces recorded for the squatting phase compared to the larger dynamic effects of deceleration at heel strike during walking. The most significant finding of this study was that in squatting, there was a reversal in the tibiofemoral shear reaction force from posterior-directed to anterior-directed, occurring under full compressive load and within a fraction of a second. It is believed that repeated squatting results in many such reversals in shear reactions that may ultimately have significant implications to the long term mechanical function and structural integrity of the joint cartilage. PMID:18524597

Thambyah, Ashvin

2008-08-01

63

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

1997-01-01

64

Force, reaction time, and precision of Kung Fu strikes.  

Science.gov (United States)

The goal was to compare values of force, precision, and reaction time of several martial arts punches and palm strikes performed by advanced and intermediate Kung Fu practitioners, both men and women. 13 Kung Fu practitioners, 10 men and three women, participated. Only the men, three advanced and seven intermediate, were considered for comparisons between levels. Reaction time values were obtained using two high speed cameras that recorded each strike at 2500 Hz. Force of impact was measured by a load cell. For comparisons of groups, force data were normalized by participant's body mass and height. Precision of the strikes was determined by a high speed pressure sensor. The results show that palm strikes were stronger than punches. Women in the study presented, on average, lower values of reaction time and force but higher values of precision than men. Advanced participants presented higher forces than intermediate participants. Significant negative correlations between the values of force and precision and the values of force and reaction time were also found. PMID:19831109

Neto, Osmar Pinto; Bolander, Richard; Pacheco, Marcos Tadeu Tavares; Bir, Cynthia

2009-08-01

65

Flow reaction forces upon blowdown of safety valves  

Energy Technology Data Exchange (ETDEWEB)

The activation of safety valves causes the development of flow reaction forces that have to be transferred in an adequate way via the piping to the steel structure or via the connected vessel into the foundation. If the safety valve outlet piping is connected to a blowdown system or, in case of blowing off into the atmosphere, are equipped with a T-piece at the outlet, the stationary reaction forces are compensated completely. The transient opening process, however, develops flow reaction forces which culminate in peaks of short duration. In this article, a simple method will be proposed for the estimation of the resulting reaction forces as a function of the length of the pipe at the safety valve outlet. CFD calculations and blowdown tests executed with a full-lift safety valve have confirmed this method on principle. Special importance is attributed to the short duration of the effect of the reaction forces which seems to have only a negligible impact on the supporting steel structure. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

Muschelknautz, S.; Wellenhofer, A. [Linde AG, Verfahrenstechnik und Anlagenbau, Dr. Carl-von-Linde-Strasse 6-14, D-82049 Hoellriegelskreuth (Germany)

2003-07-01

66

Front explosion in a periodically forced surface reaction  

CERN Document Server

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, the fronts are stationary and the front explosion leads to a defect-mediated turbulent state. In the 3:1 resonantly-forced system, the fronts propagate. The front velocity tends to zero as the front explosion point is reached and the final asymptotic state is a 2:1 resonantly-locked labyrinthine pattern. The front dynamics described here should be observable in experiment since the model has been shown to capture essential features of the CO oxidation reaction.

Davidsen, J; Kapral, R E; Mikhailov, Alexander; Kapral, Raymond

2005-01-01

67

Radiation reaction force and unification of electromagnetic and gravitational fields  

International Nuclear Information System (INIS)

A unified theory of electromagnetic and gravitational fields should modify classical electrodynamics such that the radiation reaction force is accounted for. The analysis leads to a five-dimensional unified theory of five variables. The theory is supported by showing that, for the case of a charged particle moving in a constant magnetic field, the radiation reaction force is indeed included. Moreover, this example shows explicitly that physical changes are associated with the fifth variable. Thus, the notion of a physical five-dimensional space should be seriously taken into consideration

1981-01-01

68

TUNNEL LINING DESIGN METHOD BY FRAME STRUCTURE ANALYSIS USING GROUND REACTION CURVE  

Science.gov (United States)

Both of NATM and shield tunnelling method can be applied to Diluvial and Neogene deposit, on which mega cities are located in Japan. Since the lining design method for both tunnelling methods are much different, the unified concept for tunnel lining design is expected. Therefore, in this research, a frame structure analysis model for tunnel lining design using the ground reaction curve was developed, which can take into account the earth pressure due to excavated surface displacement to active side including the effect of ground self-stabilization, and the excavated surface displacement before lining installation. Based on the developed model, a parameter study was carried out taking coefficient of subgrade reaction and grouting rate as a parameter, and the measured earth pressure acting on the lining at the site was compared with the calculated one by the developed model and the conventional model. As a result, it was confirmed that the developed model can represent earth pressure acting on the lining, lining displacement, and lining sectional force at ground ranging from soft ground to stiff ground.

Sugimoto, Mitsutaka; Sramoon, Aphichat; Okazaki, Mari

69

Floating frame grounding system. [for wind tunnel static force measurement  

Science.gov (United States)

The development of a floating frame grounding system (FFGS) for the 40- by 80-foot low speed wind tunnel facility at the NASA Ames Research Center National Full Scale Aerodynamics Complex is addresssed. When electrical faults are detected, the FFGS ensures a ground path for the fault current. In addition, the FFGS alerts the tunnel operator when a mechanical foul occurs.

Forsyth, T. J.

1987-01-01

70

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

Energy Technology Data Exchange (ETDEWEB)

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

1991-10-01

71

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)

2004-10-01

72

Force-Restore Model of surface temperature using a new parameterization of ground heat flux  

Science.gov (United States)

The classical force-restore model (FRM) of soil surface (skin) temperature was reformulated by incorporating the recently developed maximum entropy production (MEP) model of ground heat flux for the study of the effect of radiation forcing on the land-atmosphere interaction. The use of MEP model of ground heat flux leads to a non-linear dynamic force-restore equation of soil surface temperature forced by net radiation independent of wind speed and surface roughness used for parameterizing latent and sensible heat flux based on bulk flux formulas. Preliminary test indicates that modified FRM performs well in capturing diurnal variations of soil surface temperature and ground heat flux. The modified FRM may be applied in remote sensing of surface energy budget and physical parameterization of land surface hydrology in regional and global climate models.

Huang, S.; Wang, J.

2013-12-01

73

Air Force Geophysics Laboratory portable PCM ground station  

Science.gov (United States)

The present paper is concerned with the development of a portable Pulse-Code Modulation (PCM) telemetry station for the Air Force Geophysics Laboratory (AFGL). A system description is provided, taking into account the system equipment, the interface, the decommutator (DECOM) section of the interface, the direct memory access (DMA) section, and system specifications and capabilities. In the context of selecting between two conflicting philosophies regarding software, it was decided to favor a small scale specialized approach. Attention is given to the operating system, aspects of setting up the software, the application software, and questions of portability.

Shaw, H.; Lawrence, F. A.

74

Ground-water-monitoring evaluation, Hughes Aircraft, US Air Force Plant No. 44. Tucson, Arizona  

Energy Technology Data Exchange (ETDEWEB)

This report summarizes the results of EPA investigations conducted during April 1987 at the Hughes Aircraft/Air Force Plant 44 in Tucson, Arizona to determine compliance with the regulatory requirements of ground-water monitoring, and for the hazardous and solid-waste amendments of RCRA, and the corresponding State regulations. Based on the results of these investigations, a number of requisite actions were identified to attain compliance.

Filippini, M.G.; Zuroski, D.

1988-04-01

75

(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

76

Importance of long-range forces on ion-molecule reactions  

International Nuclear Information System (INIS)

Chemical reactions in a gas phase are usually caused through a short-range intermolecular interaction. The author assumes that the reaction always occurs with unit probability under the influence of the short-range interaction. In that case, the cross section for reaction is just equal to the one for a close encounter, and a long-range force determines the reaction cross section. An ion-molecule system has a spherically-symmetric polarization force. Consideration of only a polarization force can give a sufficient estimation of the cross section of ion-molecule reactions. The idea is well known as the Langevine model. However, when a molecule has a permanent dipole moment, the Langevine model cannot be directly applied because a dipole force is usually much stronger than a polarization force and has large anisotropy. He summarizes the present status of theoretical studies on calculating the cross section for a close encounter of ion-molecule collisions

1989-12-17

77

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

Energy Technology Data Exchange (ETDEWEB)

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

1992-04-01

78

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

79

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)

1984-01-01

80

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 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)

2013-09-01

 
 
 
 
81

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

Science.gov (United States)

The aim of this work is to provide an insight into the aerodynamic performance of the beetle during takeoff, which has been estimated in previous investigations. We employed a scaled-up electromechanical model flapping wing to measure the aerodynamic forces and the three-dimensional flow structures on the flapping wing. The ground effect on the unsteady forces and flow structures were also characterized. The dynamically scaled wing model could replicate the general stroke pattern of the beetle's hind wing kinematics during takeoff flight. Two wing kinematic models have been studied to examine the influences of wing kinematics on unsteady aerodynamic forces. In the first model, the angle of attack is asymmetric and varies during the translational motion, which is the flapping motion of the beetle's hind wing. In the second model, the angle of attack is constant during the translational motion. The instantaneous aerodynamic forces were measured for four strokes during the beetle's takeoff by the force sensor attached at the wing base. Flow visualization provided a general picture of the evolution of the three-dimensional leading edge vortex (LEV) on the beetle hind wing model. The LEV is stable during each stroke, and increases radically from the root to the tip, forming a leading-edge spiral vortex. The force measurement results show that the vertical force generated by the hind wing is large enough to lift the beetle. For the beetle hind wing kinematics, the total vertical force production increases 18.4% and 8.6% for the first and second strokes, respectively, due to the ground effect. However, for the model with a constant angle of attack during translation, the vertical force is reduced during the first stroke. During the third and fourth strokes, the ground effect is negligible for both wing kinematic patterns. This finding suggests that the beetle's flapping mechanism induces a ground effect that can efficiently lift its body from the ground during takeoff. PMID:23851351

Van Truong, Tien; Byun, Doyoung; Kim, Min Jun; Yoon, Kwang Joon; Park, Hoon Cheol

2013-09-01

82

Forced periodic temperature cycling of chemical reactions in microstructure devices  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2008-01-01

83

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

Energy Technology Data Exchange (ETDEWEB)

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

Bellotti, U.; Bornatici, M. [Pavia Univ. (Italy). Dip. di Fisica `A. Volta`, Istituto Nazionale di Fisica Molecolare

1998-09-01

84

(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

85

Description of heavy ion reactions with medium dependent forces  

International Nuclear Information System (INIS)

The collision between two nuclei is calculated in the Quantum Molecular Dynamics (QMD) approach for C-C and Nb-Nb reactions using a collision term for the nucleon-nucleon cross section which is determined in the nuclear medium using the Brueckner G-matrix with the appropriate Pauli operator and the self consistent single particle energies for the densities of the projectile and the target at the collision point of the two nucleons. The QMD approach is very similar to the Vlasov-Uehling-Uhlenbeck or Boltzmann-Uehling-Uhlenbeck approach, but taking into account the finite extension of the wave packet representing a nucleon in position and momentum space. Usually one uses in the collision term a constant (40 mb) or the free nucleon-nucleon cross section. Using a local density approximation the Bethe-Goldstone equation is solved for two colliding nuclear matters of which the densities are determined by the local densities obtained in the QMD approach at the collision point of the two nucleons inside the nuclear medium. Comparing the momentum transfer in transverse and longitudinal direction and the number of emitted particles calculated with the G-matrix cross section and the isotropic constant cross section (40 mb) we find for this inclusive data only minor differences between the results in the C-C collision, but larger ones for the Nb-Nb case.f The double differential cross section for charge particle emission in the C-C reaction at Elab = 84 MeV/n is described in good agreement with the data. (orig.)

1989-05-01

86

Estimating the Radiative Forcing of Carbonaceous Aerosols over California based on Satellite and Ground Observations  

Energy Technology Data Exchange (ETDEWEB)

Carbonaceous aerosols have the potential to impact climate both through directly absorbing incoming solar radiation, and by indirectly affecting the cloud layer. To quantify this impact recent modeling studies have made great efforts to simulate both the spatial and temporal distribution of carbonaceous aerosols and their associated radiative forcing. This study makes the first observationally constrained assessment of the direct radiative forcing of carbonaceous aerosols at a regional scale over California. By exploiting multiple observations (including ground sites and satellites), we constructed the distribution of aerosol optical depths and aerosol absorption optical depths over California for a ten-year period (2000-2010). The total solar absorption was then partitioned into contributions from elemental carbon (EC), organic carbon (OC) and dust aerosols using a newly developed scheme. Aerosol absorption optical depth due to carbonaceous aerosols (EC and OC) at 440 nm is 50%-200% larger than natural dust, with EC contributing the bulk (70%-90%). Observationally constrained EC absorption agrees reasonably well with estimates from regional transport models, but the model underestimates the OC AAOD by at least 50%. We estimate that the TOA warming from carbonaceous aerosols is 0.7 W/m2 and the TOA forcing due to OC is close to zero. The atmospheric heating of carbonaceous aerosols is 2.2-2.9 W/m2, of which EC contributed about 80-90%. The atmospheric heating due to OC is estimated to be 0.1 to 0.4 W/m2, larger than model simulations. The surface brightening due to EC reduction over the last two decades is estimated to be 1.5-3.5 W/m2.

Xu, Yangyang; Bahadur, R.; Zhao, Chun; Leung, Lai-Yung R.

2013-10-04

87

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

2000-01-19

88

A study into the effects and viability of applying lateral force control to an air to ground rocket  

Science.gov (United States)

The effects of lateral force control on a previously unguided air to ground rocket were studied. A 5 deg aiming cone was required. The firing of masses out of the side of the rocket, to give a sideways impulse and the emission of a lateral jet to push the rocket across were analyzed. The disturbance of the flow on thrust position was changed by 9% or 12% with respect to the center of gravity. Lateral force control is shown to be feasible.

Halsey, J. C.

89

Population of ground-state rotational bands of superheavy nuclei produced in complete fusion reactions  

Science.gov (United States)

Using the statistical and quantum diffusion approaches, we study the population of ground-state rotational bands of superheavy nuclei produced in the fusion-evaporation reactions 208Pb(48Ca,2n)254No, 206Pb(48Ca,2n)252No, and 204Hg(48Ca,2n)250Fm. By describing the relative intensities of E2 transitions between the rotational states, the entry spin distributions of residual nuclei, and the excitation functions for these reactions, the dependence of fission barriers of shell-stabilized nuclei on angular momentum is investigated.

Zubov, A. S.; Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.

2011-10-01

90

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

91

Shortwave radiative forcing efficiency of urban aerosols--a case study using ground based measurements.  

Science.gov (United States)

Aerosols reduce the surface reaching solar flux by scattering the incoming solar radiation out to space. Various model studies on climate change suggest that surface cooling induced by aerosol scattering is the largest source of uncertainty in predicting the future climate. In the present study measurements of aerosol optical depth (AOD) and its direct radiative forcing efficiency has been presented over a typical tropical urban environment namely Hyderabad during December, 2003. Measurements of AOD have been carried out using MICROTOPS-II sunphotometer, black carbon aerosol mass concentration using Aethalometer, total aerosol mass concentration using channel Quartz Crystal Microbalance (QCM) Impactor Particle analyser and direct normal solar irradiance using Multifilter Rotating Shadow Band Radiometer (MFRSR). Diurnal variation of AOD showed high values during afternoon hours. The fraction of BC estimated to be approximately 9% in the total aerosol mass concentration over the study area. Results of the study suggest -62.5 Wm(-2) reduction in the ground reaching shortwave flux for every 0.1 increase in aerosol optical depth. The results have been discussed in the paper. PMID:15571753

Latha, K Madhavi; Badarinath, K V S

2005-01-01

92

Complementarity of reaction force and electron localization function analyses of asynchronicity in bond formation in Diels-Alder reactions.  

Science.gov (United States)

We have computationally compared three Diels-Alder cycloadditions involving cyclopentadiene and substituted ethylenes; one of the reactions is synchronous, while the others are slightly or highly asynchronous. Synchronicity and weak asynchronicity are characterized by the reaction force constant ?(?) having just a single minimum in the transition region along the intrinsic reaction coordinate ?, while for high asynchronicity ?(?) has a negative maximum with minima on both sides. The electron localization function (ELF) shows that the features of ?(?) can be directly related to the formation of the new C-C bonds between the diene and the dienophile. There is thus a striking complementarity between ?(?) and ELF; ?(?) identifies the key points along ? and ELF describes what is happening at those points. PMID:24589878

Yepes, Diana; Murray, Jane S; Pérez, Patricia; Domingo, Luis R; Politzer, Peter; Jaque, Pablo

2014-04-14

93

Theory for electron-transfer reactions involving two Marcus surfaces with a different force constant  

Energy Technology Data Exchange (ETDEWEB)

Theory for electron-transfer reactions at high temperature involving two Marcus parabolic surfaces with a different force constant is presented. The dynamic solvent effects are also considered using the stochastic Liouville equation, assuming an overdamped Debye solvent. An analytical expression for the adiabatic/nonadiabatic electron-transfer rate constant is derived.

Tang, Jau

1994-02-01

94

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

95

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

96

Large Ground-State Entropy Changes for Hydrogen Atom Transfer Reactions of Iron Complexes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Reported herein are the hydrogen atom transfer (HAT) reactions of two closely related dicationic iron tris ?-diimine complexes. FeII(H2bip) (iron(II) tris[2,2?-bi-1,4,5,6-tetra-hydropyrimidine]diperchlorate) and FeII(H2bim) (iron(II) tris[2,2?-bi-2-imidazoline]diperchlorate) both transfer H• to TEMPO (2,2,6,6-tetramethyl-1-piperidinoxyl) to yield the hydroxylamine, TEMPO-H, and the respective deprotonated iron(III) species, FeIII(Hbip) or FeIII(Hbim). The ground-state thermodynamic par...

Mader, Elizabeth A.; Davidson, Ernest R.; Mayer, James M.

2007-01-01

97

Determination and optimization of joint torques and joint reaction forces in therapeutic exercises with elastic resistance.  

Science.gov (United States)

A model has been developed to definitively characterize the resistance properties and the joint loading (i.e., shear and compressive components of the joint reaction force) in single-joint exercises with ideal elastic bands. The model accounts for the relevant geometric and elastic properties of the band, the band pre-stretching, and the relative positioning among the joint center of rotation and the fixation points of the band. All the possible elastic torque profiles of ascending-descending, descending, or ascending type were disclosed in relation to the different ranges of joint angles. From these results the elastic resistance setting that best reproduces the average-user's knee extensor torque in maximal isometric/isokinetic efforts was determined. In this optimized setting, the shear tibiofemoral reaction force corresponding to an anterior (posterior) tibial displacement was 65% smaller than (nearly the same as) that obtained in a cam-equipped leg-extension equipment for equal values of resistance torque peak, whereas the compressive tibiofemoral reaction force was 22% higher. Compared to a weight-stack leg-extension equipment, an elastic resistance optimized setting has the potential to give a more effective quadriceps activation across the range of motion, and greatly reduces the anterior cruciate ligament strain force, which represents the main drawback of existing open kinetic-chain knee-extension exercises. PMID:21757393

Biscarini, Andrea

2012-01-01

98

Higher Ground: Guidelines for the Air Force's Transition to the Space Environment.  

Science.gov (United States)

The following study examines some of the major issues facing the Air Force as it transitions from an 'air' to an 'air and space' force. International regimes currently preserve space as a peaceful operating environment. However, given the military advanta...

J. E. Lloyd

1999-01-01

99

Ground state proton capture reactions from 20 to 100 MeV  

International Nuclear Information System (INIS)

Proton capture reactions on targets of /sup 11/B, /sup 12/C, /sup 15/N, /sup 16/O, and /sup 27/Al were measured from E/sub p/ = 20 to 100 MeV. The energy dependence of the ?/sub ?/ = 600 differential cross sections are presented for captures populating the ground states of /sup 12/C, /sup 13/N, /sup 16/O, /sup 17/F, and /sup 28/Si. Differential-cross-section and analyzing-power angular distributions are presented at bombarding energies of E/sub p/ = 20.8, 28.35, 49.2, and 49.69 MeV. Calculations from two capture-reaction models are compared to the data

1988-01-01

100

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

Science.gov (United States)

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

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

2014-01-01

 
 
 
 
101

Amplitude equations for breathing spiral waves in a forced reaction-diffusion system  

Science.gov (United States)

Based on a multiple scale analysis of a forced reaction-diffusion system leading to amplitude equations, we explain the existence of spiral wave and its photo-induced spatiotemporal behavior in chlorine dioxide-iodine-malonic acid system. When the photo-illumination intensity is modulated, breathing of spiral is observed in which the period of breathing is identical to the period of forcing. We have also derived the condition for breakup and suppression of spiral wave by periodic illumination. The numerical simulations agree well with our analytical treatment.

Ghosh, Pushpita; Ray, Deb Shankar

2011-09-01

102

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

Science.gov (United States)

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

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

1995-01-01

103

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

104

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

International Nuclear Information System (INIS)

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

1985-01-01

105

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-03-10

106

Discussion on external force of lateral flow on in-ground duct and supporting pile; Chichu dodo / kokisokei ni sayo suru sokuho ryudo no gairyoku ni kansuru ichikosatsu  

Energy Technology Data Exchange (ETDEWEB)

Condition where ground duct is set in the lateral pile as a structure system was presumed. The method of making ground duct at supporting pile is effective for preventive measures of duct floating due to liquefaction of ground and there exist practical constructions. However, in spite of floating measures, there may occur the conditions where the ground surrounding the in-ground duct and supporting pile may be liquefied completely and as a lateral flow, may work as a parallel external force on the in-ground duct and supporting pile depending on the ground condition and earthquake intensity level. Research regarding the setting of external force of lateral flow corresponding to such cases has not been carried out so far. In this research, firstly, the external force characteristics of lateral flow working on in-ground duct and supporting pile were revealed using model shake table test and static test. Secondly, the maximum values of these external forces were paid attention and its evaluation was carried out using earth pressure coefficient. Further, effect of viscosity coefficient of liquefaction ground on the change in external force with time caused by lateral flow was studied. 16 refs., 19 figs., 1 tab.

Otomo, K. [Central Research Inst. of Electric Power Industry, Tokyo (Japan)

1998-10-21

107

A theoretical investigation of ground effects on USB configurations  

Science.gov (United States)

A formulation predicts the variation of circulation forces and jet reaction forces in ground proximity as a function of ground height. The predicted results agree well with available experimental data. It is shown that the wing-alone theory is not capable of predicting the ground effect for USB configurations.

Lan, C. E.

1979-01-01

108

Surface/subsurface observation and removal mechanisms of ground reaction bonded silicon carbide  

Science.gov (United States)

Reaction Bonded Silicon Carbide (RBSiC) has long been recognized as a promising material for optical applications because of its unique combination of favorable properties and low-cost fabrication. Grinding of silicon carbide is difficult because of its high hardness and brittleness. Grinding often induces surface and subsurface damage, residual stress and other types of damage, which have great influence on the ceramic components for optical application. In this paper, surface integrity, subsurface damage and material removal mechanisms of RBSiC ground using diamond grinding wheel on creep-feed surface grinding machine are investigated. The surface and subsurface are studied with scanning electron microscopy (SEM) and optical microscopy. The effects of grinding conditions on surface and subsurface damage are discussed. This research links the surface roughness, surface and subsurface cracks to grinding parameters and provides valuable insights into the material removal mechanism and the dependence of grind induced damage on grinding conditions.

Yao, Wang; Zhang, Yu-Min; Han, Jie-cai; Zhang, Yun-long; Zhang, Jian-han; Zhou, Yu-feng; Han, Yuan-yuan

2006-01-01

109

Gramicidin A Channel as a Test Ground for Molecular Dynamics Force Fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We use the well-known structural and functional properties of the gramicidin A channel to test the appropriateness of force fields commonly used in molecular dynamics (MD) simulations of ion channels. For this purpose, the high-resolution structure of the gramicidin A dimer is embedded in a dimyristoylphosphatidylcholine bilayer, and the potential of mean force of a K+ ion is calculated along the channel axis using the umbrella sampling method. Calculations are performed using two of the most...

Allen, Toby W.; Bas?tug?, Turgut; Kuyucak, Serdar; Chung, Shin-ho

2003-01-01

110

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

Energy Technology Data Exchange (ETDEWEB)

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

1992-04-01

111

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 ...

Brownie, Mrs.

2010-04-07

112

Electromagnetic-energy-density distribution around a ground-state hydrogen atom and connection with van der Waals forces  

International Nuclear Information System (INIS)

A spinless hydrogen atom coupled to the electromagnetic field is considered within the context of nonrelativistic quantum electrodynamics. The atom-field interaction is taken in the minimal-coupling form and the Coulomb gauge is used. When the coupled system is in its ground state the electromagnetic field fluctuates away from the vacuum state and the atom has virtual admixtures from its uncoupled lowest eigenstate. The electric- and magnetic-field-energy densities that arise from the fluctuations are determined as functions of the distance from the atom. The relationship between these field-energy densities and the retarded long-range van der Waals forces is also discussed

1987-01-01

113

Optimizing the third-and-a-half post-Newtonian gravitational radiation-reaction force for numerical simulations  

CERN Document Server

The gravitational radiation-reaction force acting on perfect fluids at 3.5 post-Newtonian order is cast into a form which is directly applicable to numerical simulations. Extensive use is made of metric-coefficient changes induced by functional coordinate transformations, of the continuity equation, as well as of the equations of motion. We also present an expression appropriate for numerical simulations of the radiation field causing the worked out reaction force.

Faye, G

2003-01-01

114

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 asses...

2007-01-01

115

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Figueiredo, Maria Cristina Pinto Leite Braamcamp

2011-01-01

116

Study of spin parts of three nucleon forces via d->p breakup reactions at intermediate energies  

Energy Technology Data Exchange (ETDEWEB)

Measurements of deuteron-proton breakup reactions at 135 MeV/A have been made at RIKEN Accelerator Research Facility, focusing on the specific coplanar configurations. The obtained results are compared with the Faddeev calculations based on the modern nucleon-nucleon forces together with the Tucson-Melbourne99, and UrbanaIX three nucleon forces.

Sekiguchi, K. [RIKEN, Institute of Physical and Chemical Research, Saitama 351-0198 (Japan); Sakai, H. [RIKEN, Institute of Physical and Chemical Research, Saitama 351-0198 (Japan); Department of Physics, University of Tokyo, 113-0033 (Japan); Sakamoto, N. [RIKEN, Institute of Physical and Chemical Research, Saitama 351-0198 (Japan); Kuboki, H. [Department of Physics, University of Tokyo, 113-0033 (Japan); Sasano, M. [Department of Physics, University of Tokyo, 113-0033 (Japan); Takahashi, Y. [Department of Physics, University of Tokyo, 113-0033 (Japan); Yako, K. [Department of Physics, University of Tokyo, 113-0033 (Japan); Kawabata, T. [Center for Nuclear Study, University of Tokyo, 113-0033 (Japan); Maeda, Y. [Center for Nuclear Study, University of Tokyo, 113-0033 (Japan); Sakaguchi, S. [Center for Nuclear Study, University of Tokyo, 113-0033 (Japan); Sasamoto, Y. [Center for Nuclear Study, University of Tokyo, 113-0033 (Japan); Suda, K. [Center for Nuclear Study, University of Tokyo, 113-0033 (Japan); Uesaka, T. [Center for Nuclear Study, University of Tokyo, 113-0033 (Japan); Okamura, H. [Research Center for Nuclear Physics, Osaka University, Osaka 567-0047 (Japan); Itoh, K. [Department of Physics, Saitama University, Saitama 338-8570 (Japan); Wakasa, T. [Department of Physics, Kyushu University, 812-8581 (Japan)

2007-06-15

117

Study of spin parts of three nucleon forces via d->p breakup reactions at intermediate energies  

International Nuclear Information System (INIS)

Measurements of deuteron-proton breakup reactions at 135 MeV/A have been made at RIKEN Accelerator Research Facility, focusing on the specific coplanar configurations. The obtained results are compared with the Faddeev calculations based on the modern nucleon-nucleon forces together with the Tucson-Melbourne99, and UrbanaIX three nucleon forces

2007-06-15

118

"Emergence" vs. "Forcing"? Ein grundlegendes Problem der Methodologie der "Grounded Theory" – neu überdacht  

Directory of Open Access Journals (Sweden)

Full Text Available Seit den späten 1960er Jahren haben Barney GLASER und Anselm STRAUSS, die Begründer der Methodologie der "Grounded Theory", eine Reihe von Versuchen unternommen, grundlegende Konzepte und Annahmen dieses Ansatzes zu explizieren und zu rekonzeptualisieren. Hieraus sind unterschiedliche und zum Teil einander widersprechende Konzeptionen hervorgegangen, die schließlich sogar einen Bruch zwischen GLASER und STRAUSS mit sich brachten. Wichtige Aspekte der Überarbeitung und Weiterentwicklung der "Grounded Theory" beziehen sich auf das Verhältnis zwischen empirischen Daten und theoretischen Konzepten und auf die Bedeutung theoretischen Vorwissens. Die Monographie, die die Popularität der methodologischen Ideen von GLASER und STRAUSS ursprünglich begründete, "The Discovery of Grounded Theory", enthält dabei zwei divergierende Konzepte des Empirie-Theorieverhältnisses: das Konzept des "Emergierens" theoretischer Konzepte einerseits und andererseits das Konzept der "theoretischen Sensibilität". Die späteren Entwicklungen der Grounded Theory lassen sich als Versuche verstehen diese ursprünglich konfligierenden Konzepte miteinander zu vereinbaren, wobei GLASER empfiehlt, bei der empirisch begründeten Theoriebildung auf eine große Zahl sog. "Kodierfamilien" zurückzugreifen, wohingegen STRAUSS die Verwendung einer allgemeinen Handlungstheorie als "Achse" der Konstruktion der entstehenden Theorie empfiehlt. Der Beitrag fasst zuerst die wichtigsten Entwicklungen der "Grounded Theory", die das Verhältnis zwischen Theorie und Daten betreffen, zusammen. Dabei werden die zentralen Unterschiede zwischen GLASERs und STRAUSS' Konzepten behandelt und ausführlich auf GLASERs Kritik eingegangen, wonach die von STRAUSS und CORBIN beschriebenen Begriffe des "Kodierparadigmas" und der "axialen Kodierung" dazu führen, dass den Daten theoretische Konzepte "aufgezwungen" werden, anstatt aus ihnen zu "emergieren". Es wird gezeigt, das GLASERs Kritik tatsächlich bestehende Schwächen des STRAUSS'schen und CORBIN'schen Ansatzes thematisiert, die hierin liegenden Risiken aber in ihrer Bedeutung weit überschätzt. Ein zentrales Argument dieses Beitrags lautet, dass grundlegende Probleme empirisch begründeter Theoriebildung wesentlich effektiver behandelt werden können, wenn man explizit Bezug nimmt auf zeitgenössische wissenschaftsphilosophische Debatten und auf dort entwickelte, heute allgemein akzeptierte Konzepte. Dies betrifft insbesondere die Kritik des Naiven Realismus und Empirismus, die Konzepte des hypothetischen und abduktiven Schließens und das Konzept des empirischen Gehalts bzw. der Falsifizierbarkeit von Aussagen. URN: urn:nbn:de:0114-fqs0502275

Udo Kelle

2005-05-01

119

Study of the ground-state wave function of 6He via the 6He(p, t)? transfer reaction  

International Nuclear Information System (INIS)

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

2005-09-01

120

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

 
 
 
 
121

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

122

Aerosol radiative forcing over east Asia determined from ground-based solar radiation measurements  

Science.gov (United States)

We developed a method of retrieving aerosol optical properties and their associated radiative forcing from simultaneously measured sky radiation and surface solar flux data. The method is then applied to data sets collected at Mandalgovi, Dunhuang, Yinchuan, and Sri-Samrong sites of the Skyradiometer Network (SKYNET), and at Anmyon, Gosan, and Amami-Oshima, to examine the aerosol characteristics of east Asia. From the analysis for the SKYNET sites it was found that aerosols in east Asia have smaller single scattering albedos (i.e., 0.89 for Asian dusts in Dunhuang, 0.9 for urban type aerosols in Yinchuan, and 0.88 for biomass burning aerosols in Sri-Samrong), compared to the single scattering albedo for the same type of aerosols found in other areas. Lower single scattering albedo suggests that the aerosols over east Asia absorb comparatively more solar radiation. The measurements taken during April at the latter three sites over the Korean peninsula and the East China Sea showed that the single scattering albedo of Asian dust becomes smaller during the course of its movement from the source region to east Asian seawaters (i.e., 0.86 at Anmyon, 0.84 at Gosan, and 0.80 in Amami-Oshima), compared with 0.89 found in the source region (i.e., Dunhuang). These findings strongly suggest that Asian dusts become blackened during the movement because of mixing with soot particles produced over the industrial/urban area of China. The overall atmospheric forcing efficiency (radiation flux per unit aerosol optical thickness at 0.5 ?m) of Asian dusts ranges from 65 to 94 W m-2 near the east Asian seaboard area, indicating that atmospheric heating by Asian dusts can be significantly enhanced by the mixing with soot particles.

Kim, Do-Hyeong; Sohn, B. J.; Nakajima, Teruyuki; Takamura, Tamio

2005-05-01

123

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

1985-01-01

124

Theoretical study of the reaction of carbon monoxide with oxygen molecules in the ground triplet and singlet delta states.  

Science.gov (United States)

Quantum chemical calculations were carried out to study the reaction of carbon monoxide with molecular oxygen in the ground triplet and singlet delta states. Transition states and intermediates that connect the reactants with products of the reaction on the triplet and singlet potential energy surfaces were identified on the base of coupled-cluster method. The values of energy barriers were refined by using compound techniques such as CBS-Q, CBS-QB3, and G3. The calculations showed that there exists an intersection of triplet and singlet potential energy surfaces. This fact leads to the appearance of two channels for the triplet CO+O(2)(X(3)?(g)(-)) reaction, which produces atomic oxygen in the ground O((3)P) and excited O((1)D) states. The appropriate rate constants of all reaction paths were estimated on the base of nonvariational transition-state theory. It was found that the singlet reaction rate constant is much greater than the triplet one and that the reaction channel CO+O(2)(a(1)?(g)) should be taken into consideration to interpret the experimental data on the oxidation of CO by molecular oxygen. PMID:21338155

Sharipov, Alexander; Starik, Alexander

2011-03-17

125

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

1994-10-09

126

[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

127

Removing systematic errors in interionic potentials of mean force computed in molecular simulations using reaction-field-based electrostatics  

Science.gov (United States)

The performance of reaction-field methods to treat electrostatic interactions is tested in simulations of ions solvated in water. The potential of mean force between sodium chloride pair of ions and between side chains of lysine and aspartate are computed using umbrella sampling and molecular dynamics simulations. It is found that in comparison with lattice sum calculations, the charge-group-based approaches to reaction-field treatments produce a large error in the association energy of the ions that exhibits strong systematic dependence on the size of the simulation box. The atom-based implementation of the reaction field is seen to (i) improve the overall quality of the potential of mean force and (ii) remove the dependence on the size of the simulation box. It is suggested that the atom-based truncation be used in reaction-field simulations of mixed media.

Baumketner, Andrij

2009-03-01

128

Removing systematic errors in interionic potentials of mean force computed in molecular simulations using reaction-field-based electrostatics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The performance of reaction-field methods to treat electrostatic interactions is tested in simulations of ions solvated in water. The potential of mean force between sodium chloride pair of ions and between side chains of lysine and aspartate are computed using umbrella sampling and molecular dynamics simulations. It is found that in comparison with lattice sum calculations, the charge-group-based approaches to reaction-field treatments produce a large error in the association energy of the i...

Baumketner, Andrij

2009-01-01

129

Numerical verification of B-WIM system using reaction force signals  

Energy Technology Data Exchange (ETDEWEB)

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

Chang, Sung Jin; Kim, Nam Sik [Pusan National Univ., Busan (Korea, Republic of)

2012-12-15

130

Squatting-Related Tibiofemoral Shear Reaction Forces and a Biomechanical Rationale for Femoral Component Loosening  

Science.gov (United States)

Previous gait studies on squatting have described a rapid reversal in the direction of the tibiofemoral joint shear reaction force when going into a full weight-bearing deep knee flexion squat. The effects of such a shear reversal have not been considered with regard to the loading demand on knee implants in patients whose activities of daily living require frequent squatting. In this paper, the shear reversal effect is discussed and simulated in a finite element knee implant-bone model, to evaluate the possible biomechanical significance of this effect on femoral component loosening of high flexion implants as reported in the literature. The analysis shows that one of the effects of the shear reversal was a switch between large compressive and large tensile principal strains, from knee extension to flexion, respectively, in the region of the anterior flange of the femoral component. Together with the known material limits of cement and bone, this large mismatch in strains as a function of knee position provides new insight into how and why knee implants may fail in patients who perform frequent squatting.

Thambyah, Ashvin

2014-01-01

131

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

132

Atomic force microscopic detection enabling multiplexed low-cycle-number quantitative polymerase chain reaction for biomarker assays.  

Science.gov (United States)

Quantitative polymerase chain reaction is the current "golden standard" for quantification of nucleic acids; however, its utility is constrained by an inability to easily and reliably detect multiple targets in a single reaction. We have successfully overcome this problem with a novel combination of two widely used approaches: target-specific multiplex amplification with 15 cycles of polymerase chain reaction (PCR), followed by single-molecule detection of amplicons with atomic force microscopy (AFM). In test experiments comparing the relative expression of ten transcripts in two different human total RNA samples, we find good agreement between our single reaction, multiplexed PCR/AFM data, and data from 20 individual singleplex quantitative PCR reactions. This technique can be applied to virtually any analytical problem requiring sensitive measurement concentrations of multiple nucleic acid targets. PMID:24918650

Mikheikin, Andrey; Olsen, Anita; Leslie, Kevin; Mishra, Bud; Gimzewski, James K; Reed, Jason

2014-07-01

133

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

134

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

International Nuclear Information System (INIS)

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

1983-01-01

135

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

136

(p,t) reaction on even-mass cadmium nuclei: Test for the admixture of intruder configurations in the ground states  

International Nuclear Information System (INIS)

The /sup 106,108,110,112,11/ /sup 4,116/Cd(p,t) reactions have been investigated at E/sub p/ = 26 MeV. Enhancement factors for the ground-state to ground-state transitions have been extracted and compared with predictions for two-nucleon transfer strengths. No evidence for a sizable admixture of the intruder configurations in the ground states is deduced from this experiment

1986-01-01

137

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

138

Role of electronic-vibrational mixing in enhancing vibrational coherences in the ground electronic states of photosynthetic bacterial reaction center.  

Science.gov (United States)

We describe polarization controlled two-color coherence photon echo studies of the reaction center complex from a purple bacterium Rhodobacter sphaeroides. Long-lived oscillatory signals that persist up to 2 ps are observed in neutral, oxidized, and mutant (lacking the special pair) reaction centers, for both (0°,0°,0°,0°) and (45°,-45°,90°,0°) polarization sequences. We show that the long-lived signals arise via vibronic coupling of the bacteriopheophytin (H) and accessory bacteriochlorophyll (B) pigments that leads to vibrational wavepackets in the B ground electronic state. Fourier analysis of the data suggests that the 685 cm(-1) mode of B may play a key role in the H to B energy transfer. PMID:24433029

Ryu, Ian Seungwan; Dong, Hui; Fleming, Graham R

2014-02-01

139

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

140

Mechanics of Ship Grounding  

DEFF Research Database (Denmark)

In these notes first a simplified mathematical model is presented for analysis of ship hull loading due to grounding on relatively hard and plane sand, clay or rock sea bottoms. In a second section a more rational calculation model is described for the sea bed soil reaction forces on the sea bottom. Finally, overall hull failure is considered first applying a quasistatic analysis model and thereafter a full dynamic model.

Pedersen, Preben Terndrup

1996-01-01

 
 
 
 
141

The reaction force constant as an indicator of synchronicity/nonsynchronicity in [4+2] cycloaddition processes.  

Science.gov (United States)

A variety of experimental and computational analyses support the concept that a chemical reaction has a transition region, in which the system changes from distorted states of the reactants to distorted states of the products. The boundaries of this region along the intrinsic reaction coordinate ?, which includes the traditional transition state, are defined unambiguously by the minimum and maximum of the reaction force F(?), which is the negative gradient of the potential energy V(?). The transition region is characterized by the reaction force constant ?(?), the second derivative of V(?), being negative throughout. It has recently been demonstrated that the profile of ?(?) in the transition region is a sensitive indicator of the degree of synchronicity of a concerted reaction: a single ?(?) minimum is associated with full or nearly full synchronicity, while a ?(?) maximum (negative) between two minima is a sign of considerable nonsynchronicity, i.e. a two-stage concerted process. We have now applied reaction force analysis to the Diels-Alder cycloadditions of the various cyanoethylenes to cyclopentadiene. We examine the relative energy requirements of the structurally- and electronically-intensive phases of the activation processes. We demonstrate that the variation of ?(?) in the transition region is again indicative of the level of synchronicity. The fully synchronous cycloadditions are those in which the cyanoethylenes are symmetrically substituted. Unsymmetrical substitution leads to minor nonsynchronicity for monocyanoethylene but much more - i.e. two stages - for 1,1-dicyano- and 1,1,2-tricyanoethylene. We also show that the ?(?) tend to become less negative as the activation energies decrease. PMID:23575799

Yepes, Diana; Donoso-Tauda, Oscar; Pérez, Patricia; Murray, Jane S; Politzer, Peter; Jaque, Pablo

2013-05-21

142

Effect of the Reaction Field on Molecular Forces and Torques Revealed by an Image-Charge Solvation Model  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We recently developed the Image-Charge Solvation Model (ICSM), which is an explicit/implicit hybrid model to accurately account for long-range electrostatic forces in molecular dynamics simulations [Lin et al., J. Chem. Phys., 131, 154103, 2009]. The ICSM has a productive spherical volume within the simulation cell for which key physical properties of bulk water are reproduced, such as density, radial distribution function, diffusion constants and dielectric properties. Although the reaction ...

Song, Wei; Lin, Yuchun; Baumketner, Andrij; Deng, Shaozhong; Cai, Wei; Jacobs, Donald J.

2013-01-01

143

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

144

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

145

Theoretical study of the reaction of ethane with oxygen molecules in the ground triplet and singlet delta states.  

Science.gov (United States)

Quantum chemical calculations are carried out to study the reaction of ethane with molecular oxygen in the ground triplet and singlet delta states. Transition states, intermediates, and possible products of the reaction on the triplet and singlet potential energy surfaces are identified on the basis of the coupled-cluster method. The basis set dependence of coupled-cluster energy values is estimated by the second-order perturbation theory. The values of energy barriers are also refined by using the compound CBS-Q and G3 techniques. It was found that the C(2)H(6) + O(2)(X(3)?(g)(-)) reaction leads to the formation of C(2)H(5) and HO(2) products, whereas the C(2)H(6) + O(2)(a(1)?(g)) process produces C(2)H(4) and H(2)O(2) molecules. The appropriate rate constants of these reaction paths are estimated on the basis of variational and nonvariational transition-state theories assuming tunneling and possible nonadiabatic transitions in the temperature range 500-4000 K. The calculations showed that the rate constant of the C(2)H(6) + O(2)(a(1)?(g)) reaction path is much greater than that of the C(2)H(6) + O(2)(X(3)?(g)(-)) one. At the same time, the singlet and triplet potential surface intersection is detected that leads to the appearance of the nonadiabatic quenching channel O(2)(a(1)?(g)) + C(2)H(6) ? O(2)(X (3)?(g)(-)) + C(2)H(6). The rate constant of this process is estimated with the use of the Landau-Zener model. It is demonstrated that, in the case of the existence of thermal equilibrium in the distribution of molecules over the electronic states, at low temperatures (T 1200 K) the situation is inverted. PMID:22823469

Sharipov, Alexander S; Starik, Alexander M

2012-08-23

146

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

147

Ground- and excited-state proton-transfer reaction of 3-Hydroxyflavone in aqueous micelles  

Science.gov (United States)

Photophysical studies on 3-Hydroxyflavone in aqueous micelles reveal the occurrence of both excited-state intramolecular proton transfer (ESIPT) as well as ground-state intermolecular proton transfer. The latter yields an anion responsible for the long-wavelength absorption band and 450-480 nm fluorescence of 3-Hydroxyflavone in aqueous micelles, and is independent of ESIPT. However, excitation at shorter wavelengths preferentially leads to fast, reversible, ESIPT and dual emission from an equilibrium mixture of excited normal (N ?) and tautomer (T ?) forms. The ESIPT dynamics of 3-Hydroxyflavone in aqueous micelles is similar to that in protic, hydrogen-bonding solvents like methanol and water, where dual emission is also observed.

Mondal, Samiran; Basu, Saswati; Mandal, Debabrata

2009-09-01

148

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)

1978-10-14

149

Micromorphology of zinc fluoride-induced reaction products on ground human enamel.  

Science.gov (United States)

Zinc in combination with hexetidine has been shown to be an effective chemical antiplaque agent clinically and in the laboratory. The effects of zinc fluoride on ground human enamel were studied by SEM and the sizes and numbers of the resulting globular structures measured from photomicrographs. Prepared enamel specimens were immersed in zinc fluoride solutions containing 250 and 750 ppm F- at pH 6 and 4 for 4 min. The specimens were examined as such or after washing in water for 5 min, 60 min or 24 h and the globuli categorized as larger or smaller than 0.5 um. The sizes and numbers of the globuli on the enamel were pH and concentration dependent. At pH 6, the two solutions tested produced few small globuli on enamel which were removed after 5 min (250 ppm F-) and after 60 min (750 ppm F-) in water. At pH 4, markedly more globuli were present, particularly with the 750 ppm F- solution. Large and small globuli were present after the 250 ppm F- treatment with most being removed between 5 and 60 min in water. After the 750 ppm F- treatment only small globuli were found on enamel and were removed between 60 min and 24 h of water washing. Zinc fluoride-induced globuli were generally smaller than those induced by sodium fluoride at the same pH values and fluoride concentrations. PMID:6583216

Barbakow, F; Scherle, W; Yankell, S

1984-01-01

150

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 (T< or =450 K) were independent of both the initial O-atom concentration and the mode of O-atom production. In addition, large excesses of O_2 were added to the flow to intercept the primary reaction product (CH_2OH), 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 O_2 concentration, with the rate constants being smaller when determined in the presence of large [O_2]. Since the initial O-atom concentrations were on the order of 10"1"1 or less, a simple stoichiometry effect can be ruled out. However, the results of the present kinetic experiments indicated that heterogeneous pyrolysis of CH_3OH may have occurred in the flow system. This observation is consistent with studies of the adsorption of methanol on silica surfaces. This problem was apparently overcome by adding small amounts of O_2 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): k_1 (T) = (2.70 +- 0.50) x 10"-"1"1 exp-5030 +- 160/RT cm"3 molecule"-"1 s"-"1

1981-09-15

151

[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

152

The challenge of distinguishing figure from ground: reaction to Gelso's work on the real relationship.  

Science.gov (United States)

The motives of the beginning psychotherapist for choosing his or her orientation are an underresearched issue in psychotherapy training. This study focuses on the role of personality-based factors, specifically the epistemological preferences of the therapist that Kolb (1984) has termed "learning style" (LS). The aim of the present study was to explore possible associations between psychology students' developing LSs and their choice of psychotherapeutic orientation (psychodynamic [PDT] vs. cognitive-behavioural [CBT]). Students in a psychologist's program (N = 175) took the Learning Style Inventory in their third semester and, before their formal choice, in their seventh semester. Besides a common trend toward radicalization or purification of their LS, the average PDT student tended to stick to the "feel and watch" style from the third semester to the seventh, whereas the CBT student tended to move toward "think and do." A cluster analysis revealed that the average movement among the CBT students was the result of the forces in two different subgroups, one toward "think" (and, more weakly, "watch"), the other toward "do" (and, more weakly, "feel"). PMID:20183388

McCullough, Leigh

2009-05-01

153

Transient kinetics measured with force steps discriminate between double-stranded DNA elongation and melting and define the reaction energetics  

Science.gov (United States)

Under a tension of ?65 pN, double-stranded DNA undergoes an overstretching transition from its basic (B-form) conformation to a 1.7 times longer conformation whose nature is only recently starting to be understood. Here we provide a structural and thermodynamic characterization of the transition by recording the length transient following force steps imposed on the ?-phage DNA with different melting degrees and temperatures (10–25°C). The shortening transient following a 20–35 pN force drop from the overstretching force shows a sequence of fast shortenings of double-stranded extended (S-form) segments and pauses owing to reannealing of melted segments. The lengthening transients following a 2–35 pN stretch to the overstretching force show the kinetics of a two-state reaction and indicate that the whole 70% extension is a B-S transition that precedes and is independent of melting. The temperature dependence of the lengthening transient shows that the entropic contribution to the B-S transition is one-third of the entropy change of thermal melting, reinforcing the evidence for a double-stranded S-form that maintains a significant fraction of the interstrand bonds. The cooperativity of the unitary elongation (22 bp) is independent of temperature, suggesting that structural factors, such as the nucleic acid sequence, control the transition.

Bongini, Lorenzo; Melli, Luca; Lombardi, Vincenzo; Bianco, Pasquale

2014-01-01

154

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(3P) 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 0-10 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.

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

155

Neutrino neutral reaction on 4He, effects of final state interaction and realistic NN force  

CERN Multimedia

The inelastic neutral reaction of neutrino on 4He is calculated microscopically, including full final state interaction among the four nucleons. The calculation is performed using the Lorentz integral transform (LIT) method and the hyperspherical-harmonic effective interaction approach (EIHH), with a realistic nucleon-nucleon interaction. A detailed energy dependent calculation is given in the impulse approximation. With respect to previous calculations, this work predicts an increased reaction cross-section by 10%-30% for neutrino temperature up to 15 MeV.

Gazit, D; Gazit, Doron; Barnea, Nir

2004-01-01

156

On the dynamics of a forced reaction-diffusion model for biological pattern formation.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ideas from the theory of dynamical systems are applied in biological pattern formation. By considering a simple reaction-diffusion model subjected to an external excitation, we find that the system can give rise to a great variety of periodic, quasiperiodic, and chaotic evolutions.

1989-01-01

157

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

Energy Technology Data Exchange (ETDEWEB)

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

1991-10-01

158

Kinesiological Study of Push-up Motion Using a Three-Dimensional Floor Reaction on a Force Plate  

Directory of Open Access Journals (Sweden)

Full Text Available To find an effective way to handle wheelchairs, 3-dimensional floor reactions of the hand and angular deviation of the elbow and wrist joints during push-up motion were studied in 10 healthy men. The push-up was carried out using 3 hand positions (fist, finger and palm and a push-up device. In all hand positions, anteroposterior force (Fx and the mediolateral force (Fy appeared after the vertical force (Fz. The end point of Fx and Fy was observed before that of Fz. Among the 4 different hand positions, Fx and Fy appeared first in the palm, followed by the finger and fist positions, and lastly in the push-up devices. The results indicate that the more unstable pushing-up the body is, the earlier and longer Fx and Fy are. Thus, Fx and Fy are considered to be good indicators of body balance during the push-up motion. The elbow joint showed a hyperextended position only when using the palm position in the maintenance phase. The wrist joint showed palmar flexion only when using the fist position.

Ikawa,Harutomo

1995-06-01

159

Uprooting force balance for pioneer woody plants: A quantification of the relative contribution of above- and below-ground plant architecture to uprooting susceptibility  

Science.gov (United States)

Cottonwood (Populus), willow (Salix), and tamarisk (Tamarix) populate riparian areas in many dryland regions, and their recruitment depends heavily on hydrogeomorphic conditions. The survival of pioneer woody seedlings depends in part on the establishment of root systems capable of anchoring plants in subsequent floods, and this root system development in turn influences the cohesion that plants provide to bars. The factors influencing the anchoring ability and resistance to scour of woody seedlings include plant frontal area and flexibility, root structure, and water table elevation. This study aims to quantify the factors comprising the force balance to uproot woody seedlings and saplings in two field sites characterized by different hydrologic conditions. The Bill Williams River (AZ) is an impounded river with elevated water table elevations produced by dam-released base flows. The Bitterroot River (MT) is an unimpounded river with a snowmelt hydrograph and seasonal fluctuations in river and water table elevation. We simulate uprooting from flooding events by saturating substrates and applying force near the base of the plant in a lateral, downstream direction until uprooting occurs, for a range of plant sizes but with a focus on small (<1 m high) seedlings. Preliminary results indicate a positive correlation between root diameter and stem length and the force required to pull out plants, with cottonwood and tamarisk seedlings showing greater variability than willow. In contrast, root length and stem diameter are only weakly correlated with pull-out force. By combining pull test results with measurements of geomorphic and groundwater conditions, this study provides insights into the relative contribution of a plant's above-ground and below-ground architecture to uprooting potential and into the feedbacks between vegetation and morphodynamics on river bars.

Bywater-Reyes, S.; Wilcox, A. C.; Lightbody, A.; Skorko, K.; Stella, J. C.

2012-12-01

160

Nonlocal field correlations and dynamical Casimir-Polder forces between one excited- and two ground-state atoms  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The problem of nonlocality in the dynamical three-body Casimir-Polder interaction between an initially excited and two ground-state atoms is considered. It is shown that the nonlocal spatial correlations of the field emitted by the excited atom during the initial part of its spontaneous decay may become manifest in the three-body interaction. The observability of this new phenomenon is discussed.

Passante, R.; Persico, F.; Rizzuto, L.

2006-01-01

 
 
 
 
161

Many-body GW Calculations of Ground-State Properties Quasi-2D Electron Systems and van der Waals Forces  

CERN Multimedia

We present GW many-body results for ground-state properties of two simple but very distinct families of inhomogenous systems in which traditional implementations of density-functional theory (DFT) fail drastically. The GW approach gives notably better results than the well-known random-phase approximation, at a similar computational cost. These results establish GW as a superior alternative to standard DFT schemes without the expensive numerical effort required by quantum Monte Carlo simulations.

García-Gonzalez, P

2002-01-01

162

Reactions to Reading 'Remaining Consistent with Method? An Analysis of Grounded Theory Research in Accounting': A Comment on Gurd  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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. ...

2008-01-01

163

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Purpose: The present paper is a comment on Gurd's paper published in QRAM 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...

2008-01-01

164

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

165

[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

166

Quantum radiation reaction force on a one-dimensional cavity with two relativistic moving mirrors  

International Nuclear Information System (INIS)

We consider a real massless scalar field inside a cavity with two moving mirrors in a two-dimensional spacetime, satisfying the Dirichlet boundary condition at the instantaneous position of the boundaries, for arbitrary and relativistic laws of motion. Considering vacuum as the initial field state, we obtain formulas for the exact value of the energy density of the field and the quantum force acting on the boundaries, which extend results found in previous papers [D. T. Alves, E. R. Granhen, H. O. Silva, and M. G. Lima, Phys. Rev. D 81, 025016 (2010); L. Li and B.-Z. Li, Phys. Lett. A 300, 27 (2002); L. Li and B.-Z. Li, Chin. Phys. Lett. 19, 1061 (2002); L. Li and B.-Z. Li, Acta Phys. Sin. 52, 2762 (2003); C. K. Cole and W. C. Schieve, Phys. Rev. A 64, 023813 (2001)]. For the particular cases of a cavity with just one moving boundary, nonrelativistic velocities, or in the limit of infinity length of the cavity (a single mirror), our results coincide with those found in the literature.

2010-08-15

167

Laboratory Scale Vacuum Energy Extraction Modeled on Weak Nuclear Force Reactions in a Spinning Black Hole System  

Science.gov (United States)

A spinning black hole with accreting disk of matter and axially directed jet(s) of ejecta may promote a catalytic process of vacuum energy extraction by weak nuclear force reactions. This process would have profound cosmological implications and offers rationale for a luminosity mechanism in jets, anti-matter emission in jets, disrupted regions in jets, and some deep space gamma emission peaks. Innovative interpretations of three known quantum level effects each offer rationale for laboratory scale matter/spacetime interaction using nuclear magnetic resonance techniques. The natural model of putative vacuum energy extraction represented by a spinning black hole may potentially be mimicked in a laboratory setting by exploiting the solar neutrino flux, using off-the-shelf equipment, in the near-term, with no major design challenges, and at relatively low cost.

Roser, Joseph J.

1999-01-01

168

Prediction of reaction barriers and force-induced instabilities under mechanochemical conditions with an approximate model: A case study of the ring opening of 1,3-cyclohexadiene  

Science.gov (United States)

Mechanochemistry, the use of mechanical stresses to activate chemical reactions, has emerged as a topic of significant interest. The present study examines the use of an approximate model for the prediction of reaction barriers under mechanochemical conditions using the ring opening of 1,3-cyclohexadiene along conrotatory and disrotatory directions as a specific test case. To do this, reaction barriers are evaluated using quantum chemical methods with an external force applied between various pairs of atoms. The results show that the consequent effects on the barrier exhibit a significant dependence on the locations of the atoms used to apply the external force, and in some cases, force-induced instabilities occur that alter the fundamental nature of the reaction pathway. The ability of an approximate model based on a second-order expansion of the force-modified potential energy with respect to nuclear coordinates to reproduce this behavior is then assessed. Good agreement between the results obtained through the quantum chemical calculations and approximate model is attained when force-induced instabilities do not occur. In addition, a strategy for predicting when such instabilities occur is presented and found to yield results that are in qualitative agreement with the quantum chemical calculations. Finally, the response of the system to the external force is interpreted in terms of the parameters entering the model, which correspond to interatomic distances and stiffnesses, and possibly sheds lights on ways to design molecules that exhibit a desired chemical response to mechanochemical conditions.

Bailey, Adrian; Mosey, Nicholas J.

2012-01-01

169

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 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

2004-01-01

170

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

171

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

CERN Document Server

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 nucleus candidate. QRPA calculations on top of HF+BCS are performed to investigate the first $J^{\\pi}$=$2^{+}$ states of the calcium isotopic chain. A good agreement for excitation energies is obtained when we include the tensor force in the mean-field part of the calculations. The first $2^{+}$ states indicate a subshell closure for both $^{52}$Ca and $^{54}$Ca nuclei. We confirm that the tensor part of the interaction is quite essential in explaining the neutron subshell closure in $^{52}$Ca and $^{54}$Ca nuclei.

Yüksel, E; Khan, E; Bozkurt, K

2014-01-01

172

Low-energy 2H(d,?)4He reaction and the D-state admixture in the 4He ground state  

International Nuclear Information System (INIS)

We have studied the low-energy 2H(d,?) 4He reaction based on a microscopic description of the nuclear wave functions. Our study reproduces the experimental reaction cross sections at E?3 MeV; it allows for an extrapolation of the data to energies relevant for big-bang nucleosynthesis resulting in a cross section about 35 times higher than given in present compilations. Our results indicate a D-state admixture in the 4He ground state of ?5--7 %

1987-01-01

173

A comparison of ground-based and space flight data: Atomic oxygen reactions with boron nitride and silicon nitride  

Energy Technology Data Exchange (ETDEWEB)

The effects of atomic oxygen on boron nitride (BN) and silicon nitride (Si{sub 3}N{sub 4}) have been studied in low Earth orbit (LEO) flight experiments and in a ground-based simulation facility at Los Alamos National Laboratory. Both the in-flight and ground-based experiments employed the materials coated over thin ({approx}250{Angstrom}) silver films whose electrical resistance was measured in situ to detect penetration of atomic oxygen through the BN and Si{sub 3}N{sub 4} materials. In the presence of atomic oxygen, silver oxidizes to form silver oxide, which has a much higher electrical resistance than pure silver. Permeation of atomic oxygen through BN, as indicated by an increase in the electrical resistance of the silver underneath, was observed in both the in-flight and ground-based experiments. In contrast, no permeation of atomic oxygen through Si{sub 3}N{sub 4} was observed in either the in-flight or ground-based experiments. The ground-based results show good qualitative correlation with the LEO flight results, thus validating the simulation fidelity of the ground-based facility in terms of reproducing LEO flight results. 9 refs., 3 figs.

Cross, J.B. (Los Alamos National Lab., NM (USA)); Lan, E.H.; Smith, C.A. (McDonnell Douglas Space Systems Co., Huntington Beach, CA (USA)); Whatley, W.J. (Sparta, Inc., Huntsville, AL (USA)); Koontz, S.L. (National Aeronautics and Space Administration, Houston, TX (USA). Lyndon B. Johnson Space Center)

1990-01-01

174

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

175

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

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 (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 radiative transfer code.

The validation of DSSF is performed comparing retrievals with ground-based measurements acquired in two contrasted environments, i.e. an urban site near Paris and a continental background site in 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. The method reproduces measurements of DSSF within an accuracy assessment of 20 Wm?2 (5% in relative in 70% of the cases, and within 40 Wm?2 in 90% of the cases.

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 the 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 Wm?2 per unity of AOT at 440 nm. AOT being an instantaneous measure indicative of the aerosol columnar amount, we therefore prove the feasibility to infer instantaneous aerosol radiative impact at the ground level over land with METEOSAT-7 visible channel.

T. Elias

2007-09-01

176

Ground effects on USB configurations. [Upper Surface Blowing  

Science.gov (United States)

Recent investigations of ground effects on aerodynamic characteristics have been stimulated by the interest in powered-lift STOL airplanes. The ground effects on upper-surface-blowing (USB) configurations may involve change in both the circulation forces and the jet reaction forces. In this note, a theoretical method is proposed for predicting these effects. It is shown that the predicted results agree well with available experimental data. In particular, the wing-alone method is shown to be incapable of predicting the ground effects of USB configurations.

Lan, C. E.

1979-01-01

177

A force measuring treadmill in clinical gait analysis.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This preliminary study presents the development and testing of an instrumented treadmill device measuring the ground reaction forces (GRFs) and the feasibility of using this force measuring treadmill (FMT) in clinical gait analysis. A commercially available treadmill was modified and fitted out with three-dimensional strain-gauge force transducers. Tests of linearity, centre of pressure position (CoP), cross talk, natural frequency, background noises, and belt speed were undertaken in order t...

Dierick, Fre?de?ric; Penta, Massimo; Renaut, David; Detrembleur, Christine

2004-01-01

178

(p,n) reaction to ground- and excited-state analogs on the samarium isotopes: Importance of two-phonon coupling effects  

International Nuclear Information System (INIS)

The (p,n) reaction to ground- and excited-state analogs on /sup 144,148,150,152/Sm is investigated at bombarding energies of 20.0, 24.5, and 26.0 MeV. Ground-state analog (p,n) angular distributions are measured at all three bombarding energies. Excited-analog 2+ and 3- (p,n) angular distributions are obtained at 24.5 and 26.0 MeV. For 152Sm, the ground- and 2+ excited-analog neutron groups are not resolved, but an angular distribution for one 4+ excited-analog transition is obtained. Coupled-channel calculations indicate substantial three-step destructive interference which reduces the ground-analog cross sections and accounts substantially for the departure of these cross sections from a simple proportionality on neutron excess. A corresponding effect on the 2+ excited-analogs due to a set of four-step processes proceeding through one- and two-phonon states interfering destructively with the dominant two-step excited-analog mechanism is found

1979-01-01

179

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-10-05

180

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

International Nuclear Information System (INIS)

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

1999-01-01

 
 
 
 
181

Psychological effects of disaster relief activities on Japan ground self-defense force personnel following the 2011 great East Japan earthquake.  

Science.gov (United States)

Objective: Disaster relief workers are potentially exposed to severe stressors on the job, resulting in a variety of psychological responses. This study aims to clarify the psychological effects of disaster relief activities on Japan Ground Self-Defense Force (JGSDF) personnel following the 2011 Great East Japan Earthquake. Method: A self-report questionnaire was administered to 606 JGSDF personnel one month after completing the disaster relief mission. Posttraumatic stress responses and general psychological distress were assessed using the Impact of Event Scale-Revised (IES-R) and the K10 scales. Associations between outcome variables and independent variables (age, gender, military rank, length of deployment, and exposure to dead bodies) were measured with univariate analyses and subsequent multiple logistic regression analyses. Results: The mean (± SD) IES-R score was 6.2 (± 8.1), and the mean K10 score was 12.8 (± 4.4). In the univariate analyses, exposure to dead bodies and age were identified as significant factors for IES-R and K10 scores, (p < 0.01). However, the multiple logistic regression analyses did not reveal any significant factors although body handlers' exposure approached significance for IES-R. Conclusions: The subjects reported very low psychological responses despite the severe nature of their disaster relief activities. Several factors may account for the low levels of psychological distress and posttraumatic symptoms observed in this study. PMID:24865200

Dobashi, Kosuke; Nagamine, Masanori; Shigemura, Jun; Tsunoda, Tomoya; Shimizu, Kunio; Yoshino, Aihide; Nomura, Soichiro

2014-01-01

182

New approach to radiation reaction in classical electrodynamics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The problem of self forces and radiation reaction is solved by conservation of energy methods. The longstanding problem of constant acceleration is solved, and it is shown that the self force does indeed affect the particle's motion, as expected on physical grounds. The relativistic generalization is also presented.

Hammond, Richard T.

2009-01-01

183

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)

2013-08-01

184

Ground- and excited-state electron-transfer reactions: photoinduced redox reactions of poly(pyridine)ruthenium(II) complexes and cobalt(III) cage compounds  

Energy Technology Data Exchange (ETDEWEB)

Rate constants for the quenching of poly(pyridine)ruthenium(II) (RuL/sub 3//sup 2 +/) excited states by caged cobalt(III) amine complexes (Co(cage)/sup 3 +/) range from 2 x 10/sup 8/ to 1 x 10/sup 9/ M/sup -1/ s/sup -1/ at 25/sup 0/C. The quenching process involves parallel energy transfer (k/sub en/ approx. 1 x 10/sup 8/ M/sup -1/ s/sup -1/) and electron transfer (k/sub el/ = (0.1-1) x 10/sup 9/ M/sup -1/ s/sup -1/) from RuL/sub 3//sup 2 +/ to Co(cage)/sup 3 +/. The rate constants for electron-transfer quenching are consistent with expectations based on an adiabatic semiclassical model. The yields of electron-transfer products range from 0.3 to 1.0, increasing as the rate constants for the back-reaction of RuL/sub 3//sup 3 +/ with Co(cage)/sup 2 +/ diminish. The relatively low magnitudes of the back-reaction rate constants, (0.08-8) x 10/sup 8/ M/sup -1/ s/sup -1/, are consistent with the high yields of electron-transfer products and derive from poor coupling of the RuL/sub 3//sup 3 +/ and Co(cage)/sup 2 +/ orbitals. 30 references, 3 figures, 4 tables.

Mok, C.Y.; Zanella, A.W.; Creutz, C.; Sutin, N.

1984-08-29

185

Calculations of kinetic isotope effects for S/sub N/2 bromine exchange reactions of alkyl bromides: development of transition-state force field for calculation of NPE effects  

International Nuclear Information System (INIS)

A transition-state force field for S/sub N/2 bromine-exchange reactions with a series of alkyl bromides has been developed and checked by calculation of 14C primary and (mostly) 2H secondary hydrogen isotope effects for these reactions in reasonable agreement with experimental values for related reactions

1981-01-28

186

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

International Nuclear Information System (INIS)

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

1987-01-01

187

Search for the $\\Delta^{++}$ component in $^{12}C$ ground state using $^{12}C(\\gamma , \\pi^{+}p)$ reaction  

CERN Multimedia

The differential cross section for the reaction $^{12}$C$(\\gamma ,\\pi ^{+}p)$ has been measured in the $\\Delta$ resonance region at high recoil momenta of the residual nuclear system. The data are analysed under the assumption that the formation of $\\pi^+p$ pairs may be interpreted as constituent in a target nucleus. As a result, the estimation $N_\\Delta=0.028\\pm 0.008$ deltas per nucleon in $^{12}$C was obtained.

Fix, A I; Krechetov, Yu F; Saigushkin, O K; Schuvalov, E N; Tabachenko, A N; Krechetov, Yu. F.

1999-01-01

188

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

Science.gov (United States)

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

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

2008-06-01

189

Search for $\\Delta^{++}$ component in $^{12}C$ ground state using $^{12}C(\\gamma, \\pi^{+} p)$ reaction  

CERN Multimedia

The differential cross section for the $^{12}$C$(\\gamma,\\pi^{+}p)$ reaction has been measured in the $\\Delta$(1232) resonance region at high recoil momenta of the residual nuclear system. The data are analyzed under the assumption that the formation of the $\\pi^+p$ pairs may be interpreted as a $\\gamma\\Delta^{++}\\to\\pi^+p$ process which takes place on a $\\Delta^{++}$ preexisting in the target nucleus. Estimates of the $\\Delta^{++}$ momentum distribution $\\rho_{\\Delta^{++}}(\\bar{p})$=0.17 fm$^3$ for a mean momentum $\\bar{p}=300\\pm49$ MeV/c as well as the number of $\\Delta$ isobars per nucleon $N_\\Delta=0.017$ were obtained for $^{12}$C.

Bystritsky, V M; Glavanakov, I V; Grabmayr, P; Krechetov, Yu F; Saigushkin, O K; Schuvalov, E N; Tabachenko, A N; Krechetov, Yu. F

2002-01-01

190

Momentum-space 3N Faddeev calculations of hadronic and electromagnetic reactions with proton-proton Coulomb and three-nucleon forces included  

CERN Document Server

We extend our approach to incorporate the proton-proton (pp) Coulomb force into the three-nucleon (3N) momentum-space Faddeev calculations of elastic proton-deuteron (pd) scattering and breakup to the case when also a three-nucleon force (3NF) is acting. In addition we formulate that approach in the application to electron- and gamma-induced reactions on 3He. The main new ingredient is a 3-dimensional screened pp Coulomb t-matrix obtained by a numerical solution of a 3-dimensional Lippmann-Schwinger equation (LSE). The resulting equations have the same structure as the Faddeev equations which describe pd scattering without 3NF acting. That shows the practical feasibility of both presented formulations.

Witala, H; Golak, J; Gloeckle, W

2010-01-01

191

Ground treatment  

Energy Technology Data Exchange (ETDEWEB)

This patent describes an apparatus for forming a stone column in the ground, which comprises: a pair of concentric tubes the inner one of which is open at its upper end, and at or near its lower end is integrally connected by an imperforate connecting member to the outer tube; and a driving plate attached at or close to the upper end of one of the inner and outer tubes, so as to extend around the one tube; and driving means for applying a downwardly acting force against the driving plate whereby the apparatus may be driven into or against the ground, and wherein the space within the inner tube defines a cavity for receiving stone.

Sliwinski, Z.J.; Fleming, W.G.K.

1988-03-15

192

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

1994-01-01

193

Effect of iso-spin averaging and finite range of the NN force on reaction cross section for neutron rich nuclei  

International Nuclear Information System (INIS)

The optical limit to Glauber theory is used to calculate the reaction cross section, ?R, for neutron rich nuclei. In-medium and iso-spin dependence of the effective nucleon-nucleon (NN) reaction cross-section, ?NN, are treated correctly assuming both finite and zero range NN interaction. We find that the combined effect of iso-spin dependence and finite range of NN force can increase up to 20% for neutron rich nuclei compared to ?R calculated using zero range approximation and constant matter density value 0.16 fm-3 in ?NN. The maximum percentage increase is reduced to 13% compared with ?R based on free NN cross section. (author)

2003-11-19

194

Investigation of nuclear forces in d + p elastic and p + d break-up reactions at intermediate energies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this thesis, the break-up and elastic channels of the reaction at a proton-beam energy of 190~MeV were studied using BINA. After accelerating the polarized-proton beam from POLIS with AGOR, reactions of protons with deuterons from a liquid-deuterium target took place at the center of BINA. The cross section and analyzing powers are measured as a function of the kinematical variable S for different combinations of the polar coordinates of the outgoing particles.

Mardanpour-mollalar, Hossein

2008-01-01

195

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

196

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

International Nuclear Information System (INIS)

We report the first global potential energy surface (PES) for the X?2A? ground electronic state of the Si(3P) + OH(X2?) ? SiO(X1?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

2013-11-28

197

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

198

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

199

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

200

A radial basis function (RBF) finite difference method for the simulation of reaction-diffusion equations on stationary platelets within the augmented forcing method  

Science.gov (United States)

We present a computational method for solving the coupled problem of chemical transport in a fluid (blood) with binding/unbinding of the chemical to/from cellular (platelet) surfaces in contact with the fluid, and with transport of the chemical on the cellular surfaces. The overall framework is the Augmented Forcing Point Method (AFM) (\\emph{L. Yao and A.L. Fogelson, Simulations of chemical transport and reaction in a suspension of cells I: An augmented forcing point method for the stationary case, IJNMF (2012) 69, 1736-52.}) for solving fluid-phase transport in a region outside of a collection of cells suspended in the fluid. We introduce a novel Radial Basis Function-Finite Difference (RBF-FD) method to solve reaction-diffusion equations on the surface of each of a collection of 2D stationary platelets suspended in blood. Parametric RBFs are used to represent the geometry of the platelets and give accurate geometric information needed for the RBF-FD method. Symmetric Hermite-RBF interpolants are used for enforcing the boundary conditions on the fluid-phase chemical concentration, and their use removes a significant limitation of the original AFM. The efficacy of the new methods are shown through a series of numerical experiments; in particular, second order convergence for the coupled problem is demonstrated.

Shankar, Varun; Wright, Grady B.; Fogelson, Aaron L.; Kirby, Robert M.

2014-05-01

 
 
 
 
201

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.)

1983-09-14

202

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.

2010-01-01

203

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

204

Forcing of Turing patterns in the chlorine dioxide-iodine-malonic acid reaction with strong visible light.  

Science.gov (United States)

We investigate the sensitivity of Turing patterns in the chlorine dioxide-iodine-malonic acid reaction to illumination by strong white light. Intense illumination results in an increase of [I(-)], in contrast to previous studies, which found only decreased [I(-)] for weak and intermediate intensities of illumination. We propose an expanded mechanism to explain the experimental observations. Both experimental and numerical results suggest that [ClO2] is the key parameter that determines whether the high iodide state is obtained under strong illumination. When strong illumination is applied through a spatially periodic mask with black and white stripes, a dark state with high [I(-)] is produced in the illuminated domain and a light state with low [I(-)] forms in the nonilluminated domain. Depending on the black:white ratio of the mask and its wavelength, Turing patterns can coexist with either the light or the dark state in the nonilluminated domain. PMID:23991763

Nagao, Raphael; Epstein, Irving R; Dolnik, Milos

2013-09-26

205

Grounding Ring for Ground Adapters.  

Science.gov (United States)

The present invention relates to a grounding ring which may be used in ground adapters. The grounding ring has a structure resembling a miniature box girder with an irregular hexagonal cross section and a hollow toroidal configuration. The grounding ring ...

N. F. Schade

1991-01-01

206

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

2006-03-01

207

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

1977-01-01

208

Effect of head and neck position on vertical ground reaction forces and interlimb coordination in the dressage horse ridden at walk and trot on a treadmill.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

REASONS FOR PERFORMING STUDY: Little is known in quantitative terms about the influence of different head-neck positions (HNPs) on the loading pattern of the locomotor apparatus. Therefore it is difficult to predict whether a specific riding technique is beneficial for the horse or if it may increase the risk for injury. OBJECTIVE: To improve the understanding of forelimb-hindlimb balance and its underlying temporal changes in relation to different head and neck positions. METHODS: Vertical g...

Weishaupt, M. A.; Wiestner, T.; Von Peinen, K.; Waldern, N.; Roepstorff, L.; Weeren, R.; Meyer, H.; Johnston, C.

2006-01-01

209

Three-body forces  

International Nuclear Information System (INIS)

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

1982-10-31

210

Comparative therapeutic efficacy and safety of type-II collagen (UC-II), glucosamine and chondroitin in arthritic dogs: pain evaluation by ground force plate.  

Science.gov (United States)

The investigation was conducted on client-owned moderately arthritic dogs with two objectives: (i) to evaluate therapeutic efficacy of type-II collagen (UC-II) alone or in combination with glucosamine hydrochloride (GLU) and chondroitin sulphate (CHO), and (ii) to determine their tolerability and safety. Dogs in four groups (n = 7-10), were treated daily for a period of 150 days with placebo (Group-I), 10 mg active UC-II (Group-II), 2000 mg GLU + 1600 mg CHO (Group-III), and UC-II + GLU + CHO (Group-IV). On a monthly basis, dogs were evaluated for observational pain (overall pain, pain upon limb manipulation, and pain after physical exertion) using different numeric scales. Pain level was also measured objectively using piezoelectric sensor-based GFP for peak vertical force and impulse area. Dogs were also examined every month for physical, hepatic (ALP, ALT and bilirubin) and renal (BUN and creatinine) functions. Based on observations, significant (p < 0.05) reduction in pain was noted in Group-II, III, and IV dogs. Using GFP, significant increases in peak vertical force (N/kg body wt) and impulse area (N s/kg body wt), indicative of a decrease in arthritis associated pain, were observed in Group-II dogs only. None of the dogs in any group showed changes in physical, hepatic or renal functions. In conclusion, based on GFP data, moderately arthritic dogs treated with UC-II (10 mg) showed a marked reduction in arthritic pain with maximum improvement by day 150. UC-II, GLU and CHO operate through different mechanisms of action, and were well tolerated over a period of 150 days. PMID:21623931

Gupta, R C; Canerdy, T D; Lindley, J; Konemann, M; Minniear, J; Carroll, B A; Hendrick, C; Goad, J T; Rohde, K; Doss, R; Bagchi, M; Bagchi, D

2012-10-01

211

"Emergence" vs. "Forcing"? Ein grundlegendes Problem der Methodologie der "Grounded Theory" – neu überdacht "Emergence" vs. "Forcing" of Empirical Data? A Crucial Problem of "Grounded Theory" Reconsidered ¿La "emergencia" vs. el "forzar" los datos empíricos? Un problema crucial de la reconsiderada "Teoría Fundamentada  

Directory of Open Access Journals (Sweden)

Full Text Available Seit den späten 1960er Jahren haben Barney GLASER und Anselm STRAUSS, die Begründer der Methodologie der "Grounded Theory", eine Reihe von Versuchen unternommen, grundlegende Konzepte und Annahmen dieses Ansatzes zu explizieren und zu rekonzeptualisieren. Hieraus sind unterschiedliche und zum Teil einander widersprechende Konzeptionen hervorgegangen, die schließlich sogar einen Bruch zwischen GLASER und STRAUSS mit sich brachten. Wichtige Aspekte der Überarbeitung und Weiterentwicklung der "Grounded Theory" beziehen sich auf das Verhältnis zwischen empirischen Daten und theoretischen Konzepten und auf die Bedeutung theoretischen Vorwissens. Die Monographie, die die Popularität der methodologischen Ideen von GLASER und STRAUSS ursprünglich begründete, "The Discovery of Grounded Theory", enthält dabei zwei divergierende Konzepte des Empirie-Theorieverhältnisses: das Konzept des "Emergierens" theoretischer Konzepte einerseits und andererseits das Konzept der "theoretischen Sensibilität". Die späteren Entwicklungen der Grounded Theory lassen sich als Versuche verstehen diese ursprünglich konfligierenden Konzepte miteinander zu vereinbaren, wobei GLASER empfiehlt, bei der empirisch begründeten Theoriebildung auf eine große Zahl sog. "Kodierfamilien" zurückzugreifen, wohingegen STRAUSS die Verwendung einer allgemeinen Handlungstheorie als "Achse" der Konstruktion der entstehenden Theorie empfiehlt. Der Beitrag fasst zuerst die wichtigsten Entwicklungen der "Grounded Theory", die das Verhältnis zwischen Theorie und Daten betreffen, zusammen. Dabei werden die zentralen Unterschiede zwischen GLASERs und STRAUSS' Konzepten behandelt und ausführlich auf GLASERs Kritik eingegangen, wonach die von STRAUSS und CORBIN beschriebenen Begriffe des "Kodierparadigmas" und der "axialen Kodierung" dazu führen, dass den Daten theoretische Konzepte "aufgezwungen" werden, anstatt aus ihnen zu "emergieren". Es wird gezeigt, das GLASERs Kritik tatsächlich bestehende Schwächen des STRAUSS'schen und CORBIN'schen Ansatzes thematisiert, die hierin liegenden Risiken aber in ihrer Bedeutung weit überschätzt. Ein zentrales Argument dieses Beitrags lautet, dass grundlegende Probleme empirisch begründeter Theoriebildung wesentlich effektiver behandelt werden können, wenn man explizit Bezug nimmt auf zeitgenössische wissenschaftsphilosophische Debatten und auf dort entwickelte, heute allgemein akzeptierte Konzepte. Dies betrifft insbesondere die Kritik des Naiven Realismus und Empirismus, die Konzepte des hypothetischen und abduktiven Schließens und das Konzept des empirischen Gehalts bzw. der Falsifizierbarkeit von Aussagen. URN: urn:nbn:de:0114-fqs0502275Since the late 1960s Barney GLASER and Anselm STRAUSS, developers of the methodology of "Grounded Theory" have made several attempts to explicate, clarify and reconceptualise some of the basic tenets of their methodological approach. Diverging concepts and understandings of Grounded Theory have arisen from these attempts which have led to a split between its founders. Much of the explication and reworking of Grounded Theory surrounds the relation between data and theory and the role of previous theoretical assumptions. The book which initially established the popularity of GLASER's and STRAUSS' methodological ideas, "The Discovery of Grounded Theory", contains two conflicting understandings of the relation between data and theory—the concept of "emergence" on the one hand and the concept of "theoretical sensitivity" on the other hand. Much of the later developments of Grounded Theory can be seen as attempts to reconcile these prima facie diverging concepts. Thereby GLASER recommends to draw on a variety of "coding families" while STRAUSS proposes the use of a general theory of action to build an axis for an emerging theory. This paper first summarises the most important developments within "Grounded Theory" concerning the understanding of the relation between empirical data and theoretical statements. Thereby special emphasis will be laid on

Udo Kelle

2005-05-01

212

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

213

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

1980-07-19

214

Column aerosol optical properties and aerosol radiative forcing during a serious haze-fog month over North China Plain in 2013 based on ground-based sunphotometer measurements  

Science.gov (United States)

In January 2013, North China Plain experienced several serious haze events. Cimel sunphotometer measurements at seven sites over rural, suburban and urban regions of North China Plain from 1 to 30 January 2013 were used to further our understanding of spatial-temporal variation of aerosol optical parameters and aerosol radiative forcing (ARF). It was found that Aerosol Optical Depth at 500 nm (AOD500 nm) during non-pollution periods at all stations was lower than 0.30 and increased significantly to greater than 1.00 as pollution events developed. The Angstrom exponent (Alpha) was larger than 0.80 for all stations most of the time. AOD500 nm averages increased from north to south during both polluted and non-polluted periods on the three urban sites in Beijing. The fine mode AOD during pollution periods is about a factor of 2.5 times larger than that during the non-pollution period at urban sites but a factor of 5.0 at suburban and rural sites. The fine mode fraction of AOD675 nm was higher than 80% for all sites during January 2013. The absorption AOD675 nm at rural sites was only about 0.01 during pollution periods, while ~0.03-0.07 and 0.01-0.03 during pollution and non-pollution periods at other sites, respectively. Single scattering albedo varied between 0.87 and 0.95 during January 2013 over North China Plain. The size distribution showed an obvious tri-peak pattern during the most serious period. The fine mode effective radius in the pollution period was about 0.01-0.08 ?m larger than during non-pollution periods, while the coarse mode radius in pollution periods was about 0.06-0.38 ?m less than that during non-pollution periods. The total, fine and coarse mode particle volumes varied by about 0.06-0.34 ?m3, 0.03-0.23 ?m3, and 0.03-0.10 ?m3, respectively, throughout January 2013. During the most intense period (1-16 January), ARF at the surface exceeded -50 W m-2, -180 W m-2, and -200 W m-2 at rural, suburban, and urban sites, respectively. The ARF readings at the top of the atmosphere were approximately -30 W m-2 in rural and -40-60 W m-2 in urban areas. Positive ARF at the top of the atmosphere at the Huimin suburban site was found to be different from others as a result of the high surface albedo due to snow cover.

Che, H.; Xia, X.; Zhu, J.; Li, Z.; Dubovik, O.; Holben, B.; Goloub, P.; Chen, H.; Estelles, V.; Cuevas-Agulló, E.; Blarel, L.; Wang, H.; Zhao, H.; Zhang, X.; Wang, Y.; Sun, J.; Tao, R.; Zhang, X.; Shi, G.

2014-02-01

215

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

216

Grounding of space structures  

Science.gov (United States)

Space structures, such as the Space Station solar arrays, must be extremely light-weight, flexible structures. Accurate prediction of the natural frequencies and mode shapes is essential for determining the structural adequacy of components, and designing a controls system. The tension pre-load in the 'blanket' of photovoltaic solar collectors, and the free/free boundary conditions of a structure in space, causes serious reservations on the use of standard finite element techniques of solution. In particular, a phenomenon known as 'grounding', or false stiffening, of the stiffness matrix occurs during rigid body rotation. This paper examines the grounding phenomenon in detail. Numerous stiffness matrices developed by others are examined for rigid body rotation capability, and found lacking. A force imbalance inherent in the formulations examined is the likely cause of the grounding problem, suggesting the need for a directed force formulation.

Bosela, P. A.; Fertis, D. G.; Shaker, F. J.

1992-01-01

217

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Reasons for performing 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 dressage hor...

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

2009-01-01

218

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

Directory of Open Access Journals (Sweden)

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

Vilar, JM

2012-01-01

219

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

Science.gov (United States)

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

Czakó, Gábor

2014-06-01

220

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

 
 
 
 
221

Theoretical study of Li2H. II. Correlation diagram, and collinear reactions of H with Li2 and Li with LiH in ground and excited states  

International Nuclear Information System (INIS)

A SCF correlation diagram is reported for low-lying linear and bent states of Li2H. SCF potential curves are computed for th colinear reactions H + Li2 and Li + LiH. These are related to the earlier study of C/sub 2v/ and collinear paths. Charge transfer is found to be important in all of the lowest states, and reactive charge transfer cones are discussed. Estimated electron-jump Li2H geometries are given. It is suggested that the reaction of Li with LiH may produce the as yet unobserved Li2H molecule

1977-04-21

222

Titanium(III) chemistry: electron-transfer reactions with ground-state poly(pyridine)osmium(III) complexes, quenching reactions with excited-state poly(pyridine)ruthenium(II) complexes, and formal reduction potentials  

International Nuclear Information System (INIS)

Potentiometric titrations of aquotitanium(III) with ferric ions have been performed in hydrochloric acid solution. The potentiometric data are described by E (V vs. NHE) = 0.03 - 0.059 log ([Ti(III)]/[Ti(IV)][H+]2) at 250C and 3.0 M ionic strength and are consistent with the interpretation that Ti3+(aq) and TiO2+ are the principal titanium(III) and titanium(IV) species, respectively, present at acid concentrations of 0.1 - 3.0 M. Rate constants for the oxidation of titanium(III) by a series of osmium(III) complexes, OsL33+, where L is a bipyridine or phenanthroline derivative, have been determined at 250C and 3.0 M ionic strength. The rates are interpreted in terms of the reactions of Ti3+(aq) and TiOH2+. The rate constants are correlated with the Marcus theory, and the exchange rate constants for the Ti4+ 3+(aq) and TiOH3+ 2+ couples are estimated. The rate constants for the reaction of titanium(III) with the excited states of the ruthenium(II) complexes RuL32+ are insensitive to the reduction potentials of the ruthenium(II) complexes. Arguments are presented to show that the quenching reactions proceed predominatly by energy-transfer mechanisms. The implications of these results for the production of Ti2+(aq) in quenching reactions are discussed. 6 figures, 5 tables

1979-01-01

223

Modification of the contact area of a standard force platform and runway for small breed dogs.  

Science.gov (United States)

Objectives: To develop a platform that used standard size force plates for large breed dogs to capture ground reaction force data from any size dog. Methods: A walkway platform was constructed to accommodate two force plates (60 cm x 40 cm) positioned in series to a variety of smaller sizes. It was constructed from a custom wood frame with thick aluminium sheet force plate covers that prevented transfer of load to the force plate, except for rectangular windows of three different dimensions. A friction study was performed to ensure plates did not translate relative to one another during gait trials. A prospective, observational, single crossover study design was used to compare the effect of force platform configuration (full plate size [original plate], half plate size [modified plate]) on ground reaction forces using eight adult healthy Labrador Retriever dogs. Results: Slippage of the steel plate on the force plate did not occur. Peak propulsion force was the only kinetic variable statistically different between the full size and half sized platforms. There were no clinically significant differences between the full and half force platforms for the variables and dogs studied. Discussion and conclusion: The modified force platform allows the original 60 x 40 cm force plate to be adjusted effectively to a 30 x 40 cm, 20 x 40 cm and 15 x 40 cm sized plate with no clinically significant change in kinetic variables. This modification that worked for large breed dogs will potentially allow kinetic analysis of a large variety of dogs with different stride lengths. PMID:24817147

Kapatkin, A S; Kim, J Y W; Garcia-Nolan, T C; Kim, S Y; Hayashi, K; Hitchens, P L; Stover, S M

2014-07-21

224

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 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

1999-01-01

225

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

226

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

227

Mechanochemical changes of Weinschenkite-type RPO4· 2H2O (R = DY, Y, Er, or YB) by grinding the thermal reactions of the ground specimens  

International Nuclear Information System (INIS)

The melting temperatures of monazite- and xenotime-type RPO4 (R = rare-earth elements) are about 2000 degrees C or higher in air. These properties may make the rare-earth orthophosphates attractive new materials for high-temperature applications. There have been few systematic studies on the preparation conditions and thermal changes of the rare-earth orthophosphates. This paper, discusses the mechanochemical changes of weinschenkite-type RPO4 · 2H2O (R = Dy, Y, Er, or Yb) at room temperature and the thermal reactions of the new rhabdophane-type YPO4 · 0.8H2O and ErPO4 · 0.9H2O at temperatures ranging from room temperature to 1800 degrees C in air

1989-01-01

228

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

229

Coaxial Atomic Force Microscope Tweezers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 versus applied voltage. We show that the coaxial AFM tweezers can perform three-dimensional assembly by picking up a specified silica ...

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

2010-01-01

230

Dispersion Forces  

CERN Document Server

In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...

Buhmann, Stefan Yoshi

2012-01-01

231

Wave propagation characteristics of subsurface irregular ground. Part 3. ; Forced vibration tests with a servohydraulic type vibrator. Fuseikei jiban no hado denpa tokusei. 3. ; Yuatsu seigyo kishinki ni yoru kyosei shindo shiken ni kansuru kenkyu  

Energy Technology Data Exchange (ETDEWEB)

Discussions were given on wave propagation characteristics of subsurface irregular ground with the topography and the ground bed construction changing extremely widely, using a newly developed servohydraulic-type vibrator. The method is composed of generating such waves as P-wave, S-wave and SH-wave from model footings forcibly vibrated in vertical or horizontal direction, measuring the wave distribution on the measuring points provided on a subsurface irregular ground, and evaluating particle orbits necessary for identifying the wave groups, coherence and phase between adjoining measuring points, and the distribution curves of phase velocity. The phase velocity between the measuring points inferred from the wave forms of the SH-wave or the Love wave on the measuring lines selected from the measurements agreed with the theoretical dispersion curves introduced from the plank hammering method. From this fact, these measuring lines are regarded to have the waves propagate through horizontally stratified ground. In other measuring lines, the particle orbit at the measuring points draws an ellipse, which anticipates propagation of the Rayleigh wave. However, no complete horizontally stratified ground is constructed in this case. 8 refs., 15 figs.

Shinozaki, Y.; KObori, T. (Kyoto University, Kyoto (Japan))

1992-01-30

232

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

233

Communication grounding facility  

International Nuclear Information System (INIS)

It is about communication grounding facility, which is made up twelve chapters. It includes general grounding with purpose, materials thermal insulating material, construction of grounding, super strength grounding method, grounding facility with grounding way and building of insulating, switched grounding with No. 1A and LCR, grounding facility of transmission line, wireless facility grounding, grounding facility in wireless base station, grounding of power facility, grounding low-tenton interior power wire, communication facility of railroad, install of arrester in apartment and house, install of arrester on introduction and earth conductivity and measurement with introduction and grounding resistance.

1998-01-01

234

Communication grounding facility  

Energy Technology Data Exchange (ETDEWEB)

It is about communication grounding facility, which is made up twelve chapters. It includes general grounding with purpose, materials thermal insulating material, construction of grounding, super strength grounding method, grounding facility with grounding way and building of insulating, switched grounding with No. 1A and LCR, grounding facility of transmission line, wireless facility grounding, grounding facility in wireless base station, grounding of power facility, grounding low-tenton interior power wire, communication facility of railroad, install of arrester in apartment and house, install of arrester on introduction and earth conductivity and measurement with introduction and grounding resistance.

Lee, Gye Seong

1998-06-15

235

Ship Grounding on Rock - I. Theory  

DEFF Research Database (Denmark)

This paper presents a set of analytical expressions which can be used to calculate the reaction force on a ship bottom deformed by a conical rock with a rounded tip. Closed form solutions are given for the resistance of inner and outer bottom plating, longitudinal stiffeners, girders and bulkheads and transverse frames, floors and bulkheads. The expressions are derived by use of an energy method or a type of 'upper bound' method which rigorously takes into account the effects of large plastic deformations, friction and fracture. A high level of generality for the methodology has been obtained by postulating a global mode of deformation for the structure around the rock with one free parameter, the plate split angle, related to the shape of thedeformation mode. It is assumed that intersections between structural components stay intact during the entire deformation process so the resistance of the individual structural members are derived according to the global deformation mode. The resistance of the entire structure is found by minimizing the energy disspiation from all the deformed members with respect to the plate split angle. In a subsequent paper it is shown that the theoreticl model predicts the damage of four large scale tests and an accidental grounding with errors less than 10%. Moreover, it is illustrated by an example that the model evaluation of a grounding scenario is sufficientlty fast to be used in a probabilistic framework in a Formal safety Assessment.

Simonsen, Bo Cerup

1997-01-01

236

Interactive forces  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This short article is devoted to the dynamics of controlled (and, therefore, open) systems. The internal forces, which appear only in the presence of external free controls and depend explicitely on them, are considered. Such interactive forces may be regarded as feedbacks generated in the system by the external free controls. In particular, one is able to interpret the interactive controls as couplings of free controls with the action of interactive forces; such dynamical a...

Juriev, Denis V.

1999-01-01

237

Analysing gait using a force-measuring walkway: intrasession repeatability in healthy children and adolescents.  

Science.gov (United States)

The goal of this study was to determine the repeatability of gait parameters measured by a force plate gait analysis system (Leonardo Mechanograph(®) GW) in healthy children. Nineteen healthy children and adolescents (age range: 7-17 years) walked at a self-selected speed on an 11-m-long walkway. Vertical ground reaction forces were measured in the central 6 m of the walkway. Each participant performed three blocks of three trials while walking barefoot and three blocks of three trials while wearing shoes. There were no differences between trials within each condition. All force and spatiotemporal parameters had intraclass correlation coefficients above 0.87 and coefficients of variation in the order of 1-6%. In this group of healthy children and adolescents, gait analysis with a force plate system produced repeatable intra-day results. PMID:23360226

Veilleux, Louis-Nicolas; Ballaz, Laurent; Robert, Maxime; Lemay, Martin; Rauch, Frank

2014-10-01

238

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

1984-01-01

239

``Force,'' ontology, and language  

Science.gov (United States)

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 aspects of this prior research. Our argument is that many students’ difficulties with force and motion are primarily due to a combination of linguistic and ontological difficulties. It is possible that students are primarily engaged in trying to define and categorize the meaning of the term “force” as spoken about by physicists. We found that this process of negotiation of meaning is remarkably similar to that engaged in by physicists in history. In this paper we will describe a study of the historical record that reveals an analogous process of meaning negotiation, spanning multiple centuries. Using methods from cognitive linguistics and systemic functional grammar, we will present an analysis of the force and motion literature, focusing on prior studies with interview data. We will then discuss the implications of our findings for physics instruction.

Brookes, David T.; Etkina, Eugenia

2009-06-01

240

Force,” ontology, and language  

Directory of Open Access Journals (Sweden)

Full Text Available 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 aspects of this prior research. Our argument is that many students’ difficulties with force and motion are primarily due to a combination of linguistic and ontological difficulties. It is possible that students are primarily engaged in trying to define and categorize the meaning of the term “force” as spoken about by physicists. We found that this process of negotiation of meaning is remarkably similar to that engaged in by physicists in history. In this paper we will describe a study of the historical record that reveals an analogous process of meaning negotiation, spanning multiple centuries. Using methods from cognitive linguistics and systemic functional grammar, we will present an analysis of the force and motion literature, focusing on prior studies with interview data. We will then discuss the implications of our findings for physics instruction.

David T. Brookes

2009-06-01

 
 
 
 
241

Design Optimization of Ground Clearance of Domestic Cars  

Directory of Open Access Journals (Sweden)

Full Text Available Drag and lift forces plays a vital role in the performance and stability of vehicles. Less drag means less fuel consumption and hence less vehicular pollution. Also, lower lift force means higher chance of adhesion of the car body with the ground causing less overturning of the vehicle, which improves the vehicle performance. Both drag and lift forces can be manipulated by varying the ground clearance of the cars. The present study concentrates on studying the effect of ground clearance on these aerodynamic forces experimentally. Wind tunnel studies with a notch-back car model revealed increase in drag and decrease in lift with increase in ground clearance. Therefore, optimization is required for designing the best ground clearance and a preferable value of the same is thus obtained.

Debojyoti Mitra

2010-07-01

242

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. PMID:10963664

Schwesinger, F; Ros, R; Strunz, T; Anselmetti, D; Güntherodt, H J; Honegger, A; Jermutus, L; Tiefenauer, L; Pluckthun, A

2000-08-29

243

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; Guntherodt, Hans-Joachim; Honegger, Annemarie; Jermutus, Lutz; Tiefenauer, Louis; Pluckthun, Andreas

2000-01-01

244

Investigation of ground state features of some medical radionuclides  

International Nuclear Information System (INIS)

In this study, ground state properties for some medical radionuclides used widely in medical applications have been investigated using Skyrme-Hartree-Fock (SHF) method. We calculated the proton, neutron and charge density RMS (root-mean-square) radii of some medical radionuclides such, as 42K 45Ca, 81Kr, 81Rb, 82Rb, 85Sr, 110In, 111In, 123Cs, 201Tl and 201Pb using the SHF calculations with the Skyrme force parameters. The calculated results are compared with the available experimental values for charge density RMS radii. The proton, neutron, charge and mass density distributions for all nuclei used in this study have also been calculated. The calculated conclusions can be used in estimating nuclear properties of the medical nuclei and for the calculations of pre-equilibrium reactions cross section data for the production of new medical radioisotopes. (orig.)

2012-03-01

245

Investigation of ground state features of some medical radionuclides  

Energy Technology Data Exchange (ETDEWEB)

In this study, ground state properties for some medical radionuclides used widely in medical applications have been investigated using Skyrme-Hartree-Fock (SHF) method. We calculated the proton, neutron and charge density RMS (root-mean-square) radii of some medical radionuclides such, as {sup 42}K {sup 45}Ca, {sup 81}Kr, {sup 81}Rb, {sup 82}Rb, {sup 85}Sr, {sup 110}In, {sup 111}In, {sup 123}Cs, {sup 201}Tl and {sup 201}Pb using the SHF calculations with the Skyrme force parameters. The calculated results are compared with the available experimental values for charge density RMS radii. The proton, neutron, charge and mass density distributions for all nuclei used in this study have also been calculated. The calculated conclusions can be used in estimating nuclear properties of the medical nuclei and for the calculations of pre-equilibrium reactions cross section data for the production of new medical radioisotopes. (orig.)

Tel, Eyyup; Kara, Ayhan [Osmaniye Korkut Ata Univ. (Turkey). Dept. of Physics; Aydin, Abdullah [Kirikkale Univ. (Turkey). Dept. of Physics; Kaplan, Abdullah [Sueleyman Demirel Univ., Isparta (Turkey). Dept. of Physics

2012-03-15

246

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.

Applying Mechatronics to Promote Science (AMPS) Program GK-12,

247

Forcing isomorphism  

CERN Document Server

A forcing extension may create new isomorphisms between two models of a first order theory. Certain model theoretic constraints on the theory and other constraints on the forcing can prevent this pathology. A countable first order theory is classifiable if it is superstable and does not have either the dimensional order property or the omitting types order property. Shelah [Sh:c] showed that if a theory T is classifiable then each model of cardinality lambda is described by a sentence of L_{infty, lambda}. In fact this sentence can be chosen in the L^*_{lambda}. (L^*_{lambda} is the result of enriching the language L_{infty, beth^+} by adding for each mu < lambda a quantifier saying the dimension of a dependence structure is greater than mu .) The truth of such sentences will be preserved by any forcing that does not collapse cardinals <= lambda and that adds no new countable subsets of lambda. Hence, if two models of a classifiable theory of power lambda are non-isomorphic, they are non-isomorphic afte...

Baldwin, J T; Shelah, S; Baldwin, John T.; Laskowski, Michael C.; Shelah, Saharon

1993-01-01

248

"Force," ontology, and language  

Science.gov (United States)

We introduce a linguistic framework through which one can interpret systematically studentsâ 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 studentsâ 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 aspects of this prior research. Our argument is that many studentsâ difficulties with force and motion are primarily due to a combination of linguistic and ontological difficulties. It is possible that students are primarily engaged in trying to define and categorize the meaning of the term âforceâ as spoken about by physicists. We found that this process of negotiation of meaning is remarkably similar to that engaged in by physicists in history. In this paper we will describe a study of the historical record that reveals an analogous process of meaning negotiation, spanning multiple centuries. Using methods from cognitive linguistics and systemic functional grammar, we will present an analysis of the force and motion literature, focusing on prior studies with interview data. We will then discuss the implications of our findings for physics instruction.

Brookes, David T.; Etkina, Eugenia

2010-06-30

249

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

250

Measurement of 241Am Ground State Radiative Neutron Capture Cross Section with Cold Neutron Beam. Progress Report on Research Contract HUN14318 for the CRP on Minor Actinide Neutron Reaction Data (MANREAD)  

International Nuclear Information System (INIS)

The ground state cross section of 242Am has been measured with beams of cold neutrons at the Budapest Research Reactor using the X-ray emission of the decay product of 242Pu. This methodology avoids the uncertainty caused by resonance neutrons in the pile activations. The target was characterized with gamma and X-ray spectrometry. The obtained ground state cross section is 540 ± 32 b, which is at the low end of the most recent literature values, but agrees with most of them within their uncertainty. (author)

2012-01-01

251

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

2012-01-01

252

Journal of Ground Water  

Science.gov (United States)

Ground Water is a leading technical publication strictly for ground water hydrogeologists. Each issue of the journal contains peer-reviewed scientific articles on pertinent ground water subjects. Non-members can read abstracts, book reviews and software spotlight columns. Members of the National Ground Water Association can view complete articles online.

Association, National G.

253

Grounding and noise coupling  

Energy Technology Data Exchange (ETDEWEB)

Grounding and Noise Coupling explains the purpose and techniques of electrically grounding electrical equipment and instrumentation systems to minimize or eliminate coupling of electrical noise. It covers the purpose of grounding, the signals to be grounded, the factors that affect these signals, threats that exist on systems, and noise coupling mechanisms. 9 figs., 1 tab.

Gunn, R.C.

1990-03-12

254

Constructivist Grounded Theory?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Glaser, Barney G.

2002-01-01

255

Force direction pattern stabilizes sagittal plane mechanics of human walking.  

Science.gov (United States)

The neural control and mechanics of human bipedalism are inadequately understood. The variable at the interface of neural control and body mechanics that is key to upright posture during human walking is the force of the ground on the foot (ground reaction force, F). We present a model that predicts sagittal plane F direction as passing through a divergent point (DP) fixed in a reference frame attached to the person. Four reference frames were tested to identify which provided the simplest and most accurate description of F direction. For all reference frames, the DP model predicted nearly all the observed variation in F direction and whole body angular momentum during single leg stance. The reference frame with vertical orientation and with origin on the pelvis provided the best combination of accuracy and simplicity. The DP was located higher than the CM and the predicted F produced a pattern of torque about the CM that caused body pitch oscillations that disrupted upright posture. Despite those oscillations, that torque was evidence of a stability mechanism that may be a critical component enabling humans to remain upright while walking and performing other tasks. PMID:21871681

Gruben, Kreg G; Boehm, Wendy L

2012-06-01

256

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

257

Nuclear reactions  

International Nuclear Information System (INIS)

This chapter of the textbook overviews nuclear reactions discussing the reaction mechanisms and the types of nuclear reactions, e.g. those induced by neutrons, by protons, by alpha particles and gamma photons, and finally, deuteron and thermonuclear reactions

1987-01-01

258

Reactions & Rates  

Science.gov (United States)

Explore what makes a reaction happen by colliding atoms and molecules. Design experiments with different reactions, concentrations, and temperatures. When are reactions reversible? What affects the rate of a reaction?

Simulations, Phet I.; Koch, Linda; Lemaster, Ron; Loeblein, Trish; Perkins, Kathy; Gratny, Mindy

2006-12-01

259

Hydrodynamic forces effecting steam bubbles while boiling  

International Nuclear Information System (INIS)

Hydrodynamic force values, effecting steam bubbles, on the water surface while boiling, n-pentane and methanol are investigated on the base of ''action function'' notion introduction. Grounded is use necessity while determining hydrodynamic forces of certain bubbles increase laws. It is shown, that depending on the nature of the acting hydrodynamic forces, the investigated steam bubbles can be divided into two groups with different separation conditions from the boiling surface. It is supposed, that the first group bubble growth is essentially influenced by the microlayer of the liquid under the bubble. Separation of the babbles of the second group is determined by evaporation force action and by the bubble dynamic instability

1978-01-01

260

Magnificent Ground Water Connection  

Science.gov (United States)

The Magnificent Ground Water Connection is a compilation of ground water-related activities for teaching and learning purposes. The teacher's activity guide is applicable to a wide range of subject matter and the ground water theme is integrated into stories, songs, math, social studies, art and writing. The topics include basic concepts of the water cycle, water distribution, treatment and stewardship. Other subjects include the water cycle and water conservation, New England's ground water resources, ground water contamination and protection. Sections are also available for wetlands, ground water, marine debris, waster, air quality, acid rain, and energy. Users can also access an on-line lending library for educational materials and videos.

 
 
 
 
261

Improved Torsion Pendulum for Ground Testing of LISA Displacement Sensors  

CERN Multimedia

We discuss a new torsion pendulum design for ground testing of prototype LISA (Laser Interferometer Space Antenna) displacement sensors. This new design is directly sensitive to net forces and therefore provides a more representative test of the noisy forces and parasitic stiffnesses acting on the test mass as compared to previous ground-based experiments. We also discuss a specific application to the measurement of thermal gradient effects.

Carbone, L; Dolesi, R; Hoyle, C D; Hüller, M; Vitale, S; Weber, W J

2004-01-01

262

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

263

Travelling-stripe forcing generates hexagonal patterns  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the response of Turing stripe patterns to a simple spatiotemporal forcing. This forcing has the form of a traveling wave and is spatially resonant with the characteristic Turing wavelength. Experiments conducted with the photosensitive chlorine dioxide-iodine-malonic acid reaction reveal a striking symmetry-breaking phenomenon of the intrinsic striped patterns giving rise to hexagonal lattices for intermediate values of the forcing velocity. The phenomenon is understood in the framew...

Mi?guez, D. G.; Nicola, E. M.; Mun?uzuri, A. P.; Casademunt I Viader, Jaume; Sague?s I Mestre, Francesc; Kramer, L.

2004-01-01

264

Private Ground Water Wells  

Science.gov (United States)

... Drinking Water Healthy Water Home Share Compartir Private Ground Water Wells Many people in the United States receive ... and answers to frequently asked questions about wells . Ground Water and Wells When rain falls, much of it ...

265

Electrical Subsurface Grounding Analysis  

Energy Technology Data Exchange (ETDEWEB)

The purpose and objective of this analysis is to determine the present grounding requirements of the Exploratory Studies Facility (ESF) subsurface electrical system and to verify that the actual grounding system and devices satisfy the requirements.

J.M. Calle

2000-11-01

266

HANDBOOK: GROUND WATER  

Science.gov (United States)

This document is provides information on ground-water contamination control and prevention technology to decision makers, field managers, and the scientific community. his 212-page resource document brings together available technical information on ground water in a convenient f...

267

National Ground Water Association  

Science.gov (United States)

This web site contains a wealth of information for the groundwater professional and for students of hydrogeology. The site features educational materials, information about conferences, courses and workshops, and a bookstore. There is also a searchable database of abstracts from the journals Ground Water, Ground Water Monitoring Review, Ground Water Monitoring and Remediation, and the Water Well Journal. Members of the National Ground Water Association may access these articles directly. Publications, fact sheets and industry links are also available.

Association, National G.

268

Ground water quality  

Energy Technology Data Exchange (ETDEWEB)

This book covers the sources, types, and quantities of contaminants in ground water, methods for ground water quality research, subsurface characterization in relation to ground water pollution, and transport and fate of subsurface contaminants. It focuses on the scientific and technological challenges and accomplishments in ground water quality research and assesses the state-of-the-art developments in this area on an international scale.

Ward, C.H.; McCarty, P.L.; Giger, W.

1985-01-01

269

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.)

1989-01-01

270

Grounding and necessity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The elucidations and regimentations of grounding offered in the literature standardly take it to be a necessary connection. In particular, authors often assert, or at least assume, that if some facts ground another fact, then the obtaining of the former necessitates the latter; and moreover, that grounding is an internal relation, in the sense of being necessitated by the existence of the relata. In this article, I challenge the necessitarian orthodoxy about grounding by offering two prima fa...

Leuenberger, S.

2013-01-01

271

Force Control in Monopod Hopping Robot While Landing  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 h...

Vaidyabhushan Leela Krishnan; Pushparaj Mani Pathak; Satish Chandra Jain

2010-01-01

272

Proximity forces  

International Nuclear Information System (INIS)

We have generalized a theorem according to which the force between two gently curved objects in close proximity is proportional to the interaction potential per unit area between two flat surfaces made of the same material, the constant of proportionality being a measure of the mean curvature of the two objects. This theorem leads to a formula for the interaction potential between curved objects (e.g., two smooth cylinders of mica or two atomic nuclei) which is a product of a simple geometrical factor and a universal function of separation, characteristic of the material of which the objects are made, and intimately related to the surface energy coefficient. We have calculated and tabulated this universal function for nuclear surfaces, using the nuclear Thomas- Fermi approximation. The results can be expressed by a simple cubic-exponential formula which gives the potential between any two nuclei in the separation degree of freedom. Even simpler expressions are found for the interaction energy associated with the ''crevice'' or neck in the nuclear configuration that would be expected immediately after contact of two nuclei. These ''proximity energies'' are used to supplement the usual expansion of the energy of a thin-skinned system into volume, surface, curvature, and higher-order terms. The resulting elementary formulas are tested against explicit models of interacting nuclei and against elastic scattering data, and are found to be useful for even quite small mass numbers

1977-01-01

273

Constructivist Grounded Theory?  

Directory of Open Access Journals (Sweden)

Full Text Available AbstractI refer to and use as scholarly inspiration Charmaz’s excellent article on constructivist grounded theory as a tool of getting to the fundamental issues on why grounded theory is not constructivist. I show that constructivist data, if it exists at all, is a very, very small part of the data that grounded theory uses.

Barney G. Glaser, PhD, Hon. PhD

2012-06-01

274

Electrical grounding prong socket  

Energy Technology Data Exchange (ETDEWEB)

This paper describes a socket for a grounding prong used in a three prong electrical plug. The socket being sufficiently spacious to prevent the socket from significantly stretching when a larger, U-shaped grounding prong is inserted into the socket, and having a ridge to allow a snug fit when a smaller tubular shape grounding prong is inserted into the socket. 11 figs.

Leong, R.

1989-09-12

275

Attractive optical forces from blackbody radiation.  

Science.gov (United States)

Blackbody radiation around hot objects induces ac Stark shifts of the energy levels of nearby atoms and molecules. These shifts are roughly proportional to the fourth power of the temperature and induce a force decaying with the third power of the distance from the object. We explicitly calculate the resulting attractive blackbody optical dipole force for ground state hydrogen atoms. Surprisingly, this force can surpass the repulsive radiation pressure and actually pull the atoms against the radiation energy flow towards the surface with a force stronger than gravity. We exemplify the dominance of the "blackbody force" over gravity for hydrogen in a cloud of hot dust particles. This overlooked force appears relevant in various astrophysical scenarios, in particular, since analogous results hold for a wide class of other broadband radiation sources. PMID:23889398

Sonnleitner, M; Ritsch-Marte, M; Ritsch, H

2013-07-12

276

Leg intramuscular pressures and in vivo knee forces during lower body positive and negative pressure treadmill exercise.  

Science.gov (United States)

Quantifying muscle and joint forces over a broad range of weight bearing loads during exercise may provide data required to improve prosthetic materials and better protect against muscle and bone loss. Collectively, leg intramuscular pressure (IMP), ground reaction force (GRF), and the instrumented tibial tray force measurements provide a comprehensive assessment of leg muscle and joint biomechanical effects of gravity during exercise. Titration of body weight (BW) by lower body negative pressure (LBNP) and lower body positive pressure (LBPP) can reproducibly modulate IMP within leg muscle compartments. In addition, previous studies document peak tibial forces during various daily activities of 2.2 to 2.5 BW. The study objective was to determine the IMPs of the leg, axial compressive force on the tibia in vivo, vertical GRF, and knee range of motion during altered BW levels using LBPP and LBNP treadmill exercise. We hypothesize that peak GRF, peak tibial forces, and peak IMPs of the leg correlate linearly with percent BW, as generated across a broad range of upright LBPP and supine LBNP exercise. When running at 2.24 m/s the leg IMPs significantly increased over the loading range of 60% to 140% BW with LBPP and LBNP (P IMPs were significantly higher when running compared with standing (P IMPs and peak tibial forces in vivo during upright LBPP, upright LBNP, and supine LBNP exercise. These data will aid the development of rehabilitation exercise hardware and prescriptions for patients and astronauts. PMID:22539171

Macias, Brandon R; D'Lima, Darryl D; Cutuk, Adnan; Patil, Shantanu; Steklov, Nick; Neuschwander, Timothy B; Meuche, Sabine; Colwell, Clifford W; Hargens, Alan R

2012-07-01

277

Predicting Ground Water Flow  

Science.gov (United States)

In this activity students learn how to draw ground water contours and understand how ground water flow may be predicted. As they complete this activity students will be able to draw a ground water contour map, have a basic understanding of how to predict the direction of ground water flow and understand the interrelated nature of ground water and surface water flow. They will also learn the difference between a gaining stream and a losing stream and why it is important to know the difference.

278

TFTR grounding system  

Energy Technology Data Exchange (ETDEWEB)

This paper outlines the rationale and concepts which led to the TFTR grounding system. Examples of induced voltages and voltage gradients expected during plasma disruption are presented. The methods of voltage gradient control and grounding connections are described. In addition to conventional grounding arrangements for equipment housings, fences, cable trays, special requirements for the vacuum vessel, TFTR coil cases, PF coil surfaces and umbrella-like support structures are described. Arrangements for diagnostic grounds which are designed to minimize interference from the facility ground also are described.

Faulkner, F.K.; Moo, W.; Neumeyer, C.; Zuvers, H.

1981-01-01

279

TFTR grounding system  

International Nuclear Information System (INIS)

This paper outlines the rationale and concepts which led to the TFTR grounding system. Examples of induced voltages and voltage gradients expected during plasma disruption are presented. The methods of voltage gradient control and grounding connections are described. In addition to conventional grounding arrangements for equipment housings, fences, cable trays, special requirements for the vacuum vessel, TFTR coil cases, PF coil surfaces and umbrella-like support structures are described. Arrangements for diagnostic grounds which are designed to minimize interference from the facility ground also are described

1981-10-29

280

A scaled quantum mechanical force field for tetranitromethane and its intermediates  

Science.gov (United States)

The quadratic force field of TNM has been calculated by AM1, PM3 and 3-21G Hamiltonians and then scaled according to Pulay's method. The computed vibrational frequencies fit the experiment within ±2 cm -1. On the other hand, the mechanism of thermolysis of TNM has been investigated by the mentioned methods and all possible reaction channels have been explored. Up to date, we have established that the first step in the thermal decomposition of TNM involves dissociation of a C-N bond. With this assumption, computed values for the activation energy agree satisfactorily with the experimental ones. Given that no experimental vibrational spectrum is available for transition states, the force field for the relevant activated complex has been quantum mechanically computed and then scaled by using scale factors obtained for TNM in its ground state, then numerical values for the preexponential factor have been computed.

Arenas, J. F.; Marcos, J. I.; Otero, J. C.; Soto, J.

1995-04-01

 
 
 
 
281

Naval Flanking in Ground Warfare  

Directory of Open Access Journals (Sweden)

Full Text Available The Mediterranean Sea, Israel’s only open border, also borders Israel’s enemies to the north and the Gaza Strip to the south, thereby linking it to enemy states. Thus, Israel’s control of this naval arena would enable it to project military strength from the sea, and afford it the capability to embark on landing operations of various types. “The shores of the State of Israel, the naval interface with each of our enemies, require us to expand our naval strength to the point of being able to land forces from the sea. David Ben-Gurion even said that we are bound to view the sea as Israel’s extended western territory.” The naval arena is the Achilles’ heel of Israel’s enemies and therefore also an opportunity for the IDF.However, even if Israel enjoys superiority in the naval arena, it is clear that the battle cannot be decided at sea. In fact, the IDF has aerial and naval superiority, two essential components for the existence of a naval ?anking option. In constructing a larger amphibious force, the IDF would be able to translate its naval superiority into a signi?cant contribution for attaining decisions in ground battles. The essay below examines the components of the landing process and offers some recommendations on construction of this type of force.

Gideon Raz

2011-05-01

282

Radiation Reaction at Extreme Intensity  

Directory of Open Access Journals (Sweden)

Full Text Available The radiation reaction force is examined for an idealized short pulse ofelectromagnetic radiation and for a plane wave. Exact solutions (without radiation reactionare discussed, the total radiated power is calculated. A new and simpler approach to theapproximate form of the equation of motion is presented that automatically removes the runawaysolutions. Finally, analytical solutions are presented for the equations of motion that includethe radiation reaction forces in the very high intensity regime. A classical scattering angle isde¯ned and it shows that the electron is scattered in a small cone in the forward direction. Theradiation reaction corrections to this angle are also considered.

Richard T. Hammond

2008-03-01

283

Protecting our ground water  

Energy Technology Data Exchange (ETDEWEB)

The nation's health and prosperity are irrevocably linked to the supply of clean, safe ground water. The key to ensuring future availability of the critical resource is to prevent its contamination. Private citizens should become familiar with the common sources of ground-water contamination. For more information about ground-water protection, contact your State or local department of natural resources, environmental protection, or public health. Information also is available at EPA regional offices.

1985-09-01

284

Electrical grounding prong socket  

Energy Technology Data Exchange (ETDEWEB)

The invention is a socket for a grounding prong used in a three prong electrical plug and a receptacle for the three prong plug. The socket being sufficiently spacious to prevent the socket from significantly stretching when a larger, U-shaped grounding prong is inserted into the socket, and having a ridge to allow a snug fit when a smaller tubular shape grounding prong is inserted into the socket. 17 figs.

Leong, R.

1990-12-31

285

Electrical grounding prong socket  

Energy Technology Data Exchange (ETDEWEB)

This patent describes a socket for a grounding prong used in a three prong electrical plug and a receptacle for the three prong plug. The socket being sufficiently spacious to prevent the socket from significantly stretching when a larger, U-shaped grounding prong is inserted into the socket, and having a ridge to allow a snug fit when a smaller tubular shape grounding prong is inserted into the socket.

Leong, R.

1991-06-18

286

Electrical grounding prong socket  

Energy Technology Data Exchange (ETDEWEB)

The invention is a socket for a grounding prong used in a three prong electrical plug and a receptacle for the three prong plug. The socket being sufficiently spacious to prevent the socket from significantly stretching when a larger, U-shaped grounding prong is inserted into the socket, and having a ridge to allow a snug fit when a smaller tubular shape grounding prong is inserted into the socket. 17 figs.

Leong, R.

1990-01-01

287

Performance and Stability of a Winged Vehicle in Ground Effect  

CERN Multimedia

Present work deals with the dynamics of vehicles which intentionally operate in the ground proximity. The dynamics in ground effect is influenced by the vehicle orientation with respect to the ground, since the aerodynamic force and moment coefficients, which in turn depend on height and angle of attack, also vary with the Euler angles. This feature, usually neglected in the applications, can be responsible for sizable variations of the aircraft performance and stability. A further effect, caused by the sink rate, determines unsteadiness that modifies the aerodynamic coefficients. In this work, an analytical formulation is proposed for the force and moment calculation in the presence of the ground and taking the aircraft attitude and sink rate into account. The aerodynamic coefficients are firstly calculated for a representative vehicle and its characteristics in ground effect are investigated. Performance and stability characteristics are then discussed with reference to significant equilibrium conditions, w...

de Divitiis, Nicola

2009-01-01

288

Hyperspherical calculations with Skyrme-like forces  

International Nuclear Information System (INIS)

The first approximation of the hyperspherical harmonic method is used to describe in a unified way the ground state and the breathing mode of several doubly-magic nuclei with Skyrme-like forces. A comparison is made with other methods

1975-01-01

289

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

290

The Grounded Theory Bookshelf  

Directory of Open Access Journals (Sweden)

Full Text Available 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 theory name and engender ongoing confusion about the very premises of grounded theory. Glaser distinguishes between classic GT and the adscititious methods in his writings, referring to remodeled grounded theory and its offshoots as Qualitative Data Analysis (QDA models.

Dr. Alvita Nathaniel, DSN, APRN, BC

2005-06-01

291

Grounding of electrical circuits  

Energy Technology Data Exchange (ETDEWEB)

This paper reports that the National Electrical Safety Code covers basic provisions for safeguarding of persons from hazards arising from the installation, operation or maintenance of (1) conductors and equipment in electric supply stations, and (2) overhead and underground electric supply and communication lines. It also includes work rules for the construction, maintenance and operation of electric supply and communication lines and equipment. This standard is applicable to the systems and equipment operated by utilities or similar systems and equipment of an industrial establishment or complex under the control of qualified persons. The intent of the NESC is to provide guidelines and direction towards safety of personnel. Grounding methods and proper grounding methods of equipment and apparatus can vary widely and can be the difference between a hazard and no hazard. Often the erroneous conception is that if there is a ground rod installed or the apparatus is grounded to a pipe, it is grounded and considered safe.

Reinhard, E.E. (PSI Energy Inc., Plainfield, IN (US))

1992-01-01

292

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

293

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

294

Three-nucleon forces and the trinucleon bound states  

International Nuclear Information System (INIS)

A summary of the bound-state working group session of the ''International Symposium on the Three-Body Force in the Three-Nucleon System'' is presented. The experimental evidence for three-nucleon forces has centered on two ground state properties: the tritium binding energy and the trinucleon form factors. Both are discussed

1986-04-24

295

Enzyme Reactions  

Science.gov (United States)

This video shows an enzyme reaction lab. The teacher demonstrates how the enzyme, catalase, reacts with hydrogen peroxide (a substrate found in cells). The teacher first demonstrates a normal enzyme reaction. He or she then goes on to show how manipulating temperature and pH will affect the reaction of an enzyme.

School, Minerva D.

2011-10-03

296

A biomechanical analysis of applied pinch force during periodontal scaling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

One of the factors associated with the high prevalence of upper extremity musculoskeletal disorders, such as carpal tunnel syndrome, among dental practitioners is the repeated high pinch force applied during periodontal scaling. The goal of this study was to determine the relationship between the pinch force applied during periodontal scaling and the forces generated at the tip of the tool. A linear biomechanical model that incorporated tool reaction forces and a calculated safety margin was ...

Villanueva, Alfredo; Dong, Hui; Rempel, David

2007-01-01

297

Parametric Time-Dependent Navier-Stokes Computations for a YAV-8B Harrier in Ground Effect  

Science.gov (United States)

The Harrier Jump Jet has the distinction of being the only powered-lift aircraft in the free world to achieve operational status and to have flown in combat. This V/STOL aircraft can take-off and land vertically or utilize very short runways by directing its four exhaust nozzles towards the ground. Transition to forward flight is achieved by rotating these nozzles into a horizontal position. Powered-lift vehicles have certain advantages over conventional strike fighters. Their V/STOL capabilities allow for safer carrier operations, smaller carrier size, and quick reaction time for troop support. Moreover, they are not dependent on vulnerable land-based runways. The AV-8A Harrier first entered service in the British Royal Air Force (RAF) during 1969, and the U.S. Marine Corps (USMC) in 1971. The AV-8B was a redesign to achieve improved payload capacity, range, and accuracy. This modified design first entered service with the USMC and RAF in 1985. The success and unique capabilities of the Harrier has prompted the design of a powered-lift version of the Joint Strike Fighter (JSF). The flowfield for the Harrier near the ground during low-speed or hover flight operations is very complex and time-dependent. A sketch of this flowfield is shown. Warm air from the fan is exhausted from the front nozzles, while a hot air/fuel mixture from the engine is exhausted from the rear nozzles. These jets strike the ground and move out radially forming a ground jet-flow. The ambient freestream, due to low-speed forward flight or - headwind during hover, opposes the jet-flow. This interaction causes the flow to separate and form a ground vortex. The multiple jets also interact with each other near the ground and form an upwash or jet fountain, which strikes the underside of the fuselage. If the aircraft is sufficiently close to the ground, the inlet can ingest ground debris and hot gases from the fountain and ground vortex. This Hot Gas Ingestion (HGI) can cause a sudden loss of thrust (powered lift), and the vehicle may crash. The high-speed jet flow along the ground can also entrain the ambient flow, resulting in a low pressure region underneath the vehicle. The accompanied loss of lift is referred to as the suckdown effect. The ground vortex may also be highly unsteady, dramatically changing its size and position with time at low frequencies, e.g., 1 Hz.

Chaderjian, Neal M.; Pandya, Shishir; Ahmad, Jasim; Murman, Scott; Kwak, Dochan (Technical Monitor)

2002-01-01

298

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

299

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

300

Forces and gravity  

...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 ...

 
 
 
 
301

Force-Clamp Spectroscopy of Single Proteins  

Science.gov (United States)

Force-clamp AFM, with its remarkable ability to manipulate short recombinant proteins, has become a useful probe of protein dynamics, allowing us to sense conformational changes down to the sub-Ångström scale. The single protein data is providing a new view that will help guide the development of theories on enzyme catalysis, the statistical dynamics of folding, and ab initio studies of a chemical reaction while placed under a stretching force; of common occurrence in nature.

Fernandez, Julio M.; Garcia-Manyes, Sergi; Dougan, Lorna

302

Electrical Protection Grounding Fundamentals.  

Science.gov (United States)

To provide technical information for use in the design, construction and operation of REA borrowers' telephone systems. The basic factors affecting earth resistivity and grounding are discussed. Information is also provided on the selection of an appropri...

1994-01-01

303

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

304

Topologically Invariant Reaction Coordinates for Simulating Multistate Chemical Reactions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

"Evaluating free energy profiles of chemical reactions in complex environments such as solvents and enzymes requires extensive sampling, which is usually performed by potential of mean force (PMF) techniques. The reliability of the sampling depends not only on the applied PMF method but also the reaction coordinate space within the dynamics is biased. In contrast to simple geometrical collective variables that depend only on the positions of the atomic coordinates of the reactants, the E...

Mones, Letif; Csanyi, Gabor

2012-01-01

305

The grounding system of TEXTOR  

International Nuclear Information System (INIS)

The modular design of the TEXTOR grounding system is described. The resistive grounding of major components is treated in detail. An insulation test procedure is proposed by using the grounding system. (author)

1981-01-01

306

A numerical investigation on the ground effect of a flapping-flying bird  

Science.gov (United States)

The flight of a small bird under the influence of the ground effect is numerically investigated with a complete three-dimensional model including the bird's body and wings. The flight mode is not the conventional steady gliding flight but an unsteady flight consisting of flapping, twisting, and folding motions. As the bird approaches the ground, the average lift force gradually increases while the average drag force decreases. At a particular distance, the average lift force increases by approximately 47%, whereas the average drag force decreases by nearly 20%, relative to the absence of the ground effect. Because of the ground, the improved aerodynamic performance in flapping flight is much more significant than in steady flight, in which the modification of the lift-drag ratio is typically less than 10%. On the basis of the flow field, regardless of the presence or absence of the ground, there exists no evidence for an obstruction of a wing-tip vortex, which is a remarkable phenomenon and accounts for the improved performance in steady flight. The extent of the region of high pressure beneath the wing in the near-ground case seems to surpass that in the far-ground case, accounting for the greater lift and thrust forces in the near-ground case. This air cushion beneath the wing, known as the cram effect, is the dominant factor of the ground effect on a flapping bird.

Su, Jian-Yuan; Tang, Jhen-Han; Wang, Ching-Hua; Yang, Jing-Tang

2013-09-01

307

A sum-rule approach to nuclear ground state correlations  

International Nuclear Information System (INIS)

By combining the sum-rule approximation to nuclear giant resonances with a generator-coorinate description of the collective ground-state we obtain a simple estimate of the collective ground-state correlations. We investigate the approach for a variety of nuclei and forces. The correlation effects are small but not negligible in view of the precision achieved in modern Skyrme-Hartree-Fock calculations. (orig.)

1985-07-01

308

Ground state energy fluctuations in the nuclear shell model  

Energy Technology Data Exchange (ETDEWEB)

Statistical fluctuations of the nuclear ground state energies are estimated using shell model calculations in which particles in the valence shells interact through well-defined forces, and are coupled to an upper shell governed by random 2-body interactions. Induced ground-state energy fluctuations are found to be one order of magnitude smaller than those previously associated with chaotic components, in close agreement with independent perturbative estimates based on the spreading widths of excited states.

Velazquez, Victor [Departamento de Fisica, Facultad de Ciencias, Universidad National Autonoma de Mexico, Apartado Postal 70-542, 04510 Mexico, DF (Mexico); Hirsch, Jorge G. [Instituto de Ciencias Nucleares, Universidad National Autonoma de Mexico, Apartado Postal 70-543, 04510 Mexico, DF (Mexico)]. E-mail: hirsch@nuclecu.unam.mx; Frank, Alejandro [Instituto de Ciencias Nucleares, Universidad National Autonoma de Mexico, Apartado Postal 70-543, 04510 Mexico, DF (Mexico); Barea, Jose [Instituto de Ciencias Nucleares, Universidad National Autonoma de Mexico, Apartado Postal 70-543, 04510 Mexico, DF (Mexico); Zuker, Andres P. [IReS, Bat t27-CNRS/Universite Louis Pasteur BP 28, F-67037 Strasbourg Cedex 2 (France)

2005-05-05

309

Ground state energy fluctuations in the Nuclear Shell Model  

CERN Document Server

Statistical fluctuations of the nuclear ground state energies are estimated using shell model calculations in which particles in the valence shells interact through well defined forces, and are coupled to an upper shell governed by random 2-body interactions. Induced ground-state energy fluctuations are found to be one order of magnitude smaller than those previously associated with chaotic components, in close agreement with independent perturbative estimates based on the spreading widths of excited states.

Velázquez, V; Frank, A; Barea, J; Zuker, A P; Velazquez, Victor; Hirsch, Jorge G.; Frank, Alejandro; Barea, Jose; Zuker, Andres P.

2005-01-01

310

Ground state energy fluctuations in the Nuclear Shell Model  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Statistical fluctuations of the nuclear ground state energies are estimated using shell model calculations in which particles in the valence shells interact through well defined forces, and are coupled to an upper shell governed by random 2-body interactions. Induced ground-state energy fluctuations are found to be one order of magnitude smaller than those previously associated with chaotic components, in close agreement with independent perturbative estimates based on the s...

Velazquez, Victor; Hirsch, Jorge G.; Frank, Alejandro; Barea, Jose; Zuker, Andres P.

2005-01-01

311

Acute effects of elastic bands during the free-weight barbell back squat exercise on velocity, power, and force production.  

Science.gov (United States)

The use of elastic bands in resistance training has been reported to be effective in increasing performance-related parameters such as power, rate of force development (RFD), and velocity. The purpose of this study was to assess the following measures during the free-weight back squat exercise with and without elastic bands: peak and mean velocity in the eccentric and concentric phases (PV-E, PV-C, MV-E, MV-C), peak force (PF), peak power in the concentric phase, and RFD immediately before and after the zero-velocity point and in the concentric phase (RFDC). Twenty trained male volunteers (age = 26.0 ± 4.4 years) performed 3 sets of 3 repetitions of squats (at 55% one repetition maximum [1RM]) on 2 separate days: 1 day without bands and the other with bands in a randomized order. The added band force equaled 20% of the subjects' 55% 1RM. Two independent force platforms collected ground reaction force data, and a 9-camera motion capture system was used for displacement measurements. The results showed that PV-E and RFDC were significantly (p elastic bands in terms of RFD. Practitioners concerned with improving RFD may want to consider incorporating this easily implemented training variation. PMID:20940640

Stevenson, Mark W; Warpeha, Joseph M; Dietz, Cal C; Giveans, Russell M; Erdman, Arthur G

2010-11-01

312

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 analysis.

2010-07-01

313

Hazardous potential differences in extensive grounding systems during ground faults  

Energy Technology Data Exchange (ETDEWEB)

A study of an extensive grounding network consisting of two generating station grounding systems which are located in a large generating plant has been carried out. Different analysis approaches are discussed and computation results compared. It is shown that the commonly used grounding analysis algorithms based on the assumption that the grounding system is an equipotential structure is not suitable for the analysis of this extensive grounding network. An appropriate analysis algorithm for this problem is based on a field theory approach, which takes into account not only the conductive interactions between ground conductors but also the inductive and capacitive interactions.The complete grounding network of the generating plant is modeled and numerical results presented, showing the ground potential rise at various locations of the grounding network and the ground potential differences between the two grounding systems during ground faults. Different interconnection schemes, which are used to reduce the ground potential differences, are also examined. The study presented in this paper clearly shows that hazardous potential differences can exist in extensive grounding systems during ground faults. The results presented in this paper provide useful information for the design of extensive grounding networks when interconnection problems have to be addressed.

Ma, J.; Dawalibi, F.P. [Safe Engineering Services and Technologies Ltd., Montreal, Quebec (Canada)

1996-11-01

314

Three-Nucleon Forces  

CERN Document Server

The role of three-nucleon forces in ab initio calculations of nuclear systems is investigated. The difference between genuine and induced many-nucleon forces is emphasized. Induced forces arise in the process of solving the nuclear many-body problem as technical intermediaries towards calculationally converged results. Genuine forces make up the Hamiltonian; they represent the chosen underlying dynamics. The hierarchy of contributions arising from two-, three- and many-nucleon forces is discussed. Signals for the need of the inclusion of genuine three-nucleon forces are studied in nuclear systems, technically best under control, especially in three-nucleon and four-nucleon systems. Genuine three-nucleon forces are important for details in the decription of some observables. Their contributions to observables are small on the scale set by two-nucleon forces.

Sauer, Peter U

2014-01-01

315

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.

316

External forcing of spiral waves.  

Science.gov (United States)

The effect of an external rhythm on rotating spiral waves in excitable media is investigated. Parameters of the unperturbed medium were chosen, such that the organizing spiral tip describes meandering (hypocyclic) trajectories, which are the most general shape for the experimentally observed systems. Periodical modulation of excitability in a model of the Belousov-Zhabotinsky (BZ) reaction forces meandering spiral tips to describe trajectories that are not found at corresponding stationary conditions. For different modulation periods, two types of resonance drift, phase-locked tip motion, a spectrum of hypocyclic trajectories, and complex multifrequency patterns were computed. The computational results are complemented by experimental data obtained for periodically changing illumination of the photosensitive BZ reaction. The observed drastic deformation of the tip trajectory is considered as an efficient means to study and to control wave processes in excitable media. PMID:12780127

Zykov, Vladimir S.; Steinbock, Oliver; Muller, Stefan C.

1994-09-01

317

Solvation force simulations in atomic force microscopy.  

Science.gov (United States)

Solvation force oscillation in octamethylcyclotetrasiloxane (OMCTS) versus the distance between an atomic force microscope (AFM) tip and mica substrate has been studied through molecular dynamics simulations. A driving spring model in a liquid-vapor molecular ensemble is used to explore the force oscillation mechanism. It has been found that OMCTS fluid in tip-substrate contact has a strong tendency to form a layered structure, starting from n = 8 layers. The force profile obtained from simulation is qualitatively similar to those in contact mode AFM experiments. However, the bulk-like diffusion and rotation of OMCTS molecules underneath the AFM tip suggest that, under the tip-substrate confinement geometry, the layered OMCTS film cannot form a solidified structure except under n = 2 extreme contact-layer confinement. PMID:24908030

Xu, Rong-Guang; Leng, Yongsheng

2014-06-01

318

Crossflow force transducer  

International Nuclear Information System (INIS)

A force transducer for measuring lift and drag coefficients for a circular cylinder in turbulent water flow is presented. In addition to describing the actual design and construction of the strain-gauged force- ring based transducer, requirements for obtained valid fluid force test data are discussed, and pertinent flow test experience is related

1982-01-01

319

Concepts of Force  

Science.gov (United States)

This book guides you through the history of the concept of force. Beginning in Acient Greece, Jammer analyzes their ideas about force and how it evolved through the centuries, leading in to the research of Newton, Liebniz, and Kepler, and showing how force applies in modern day physics.

Jammer, Max

2006-07-22

320

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

 
 
 
 
321

Unified approach to dispersion forces within macroscopic QED  

International Nuclear Information System (INIS)

We outline our Lorentz-force approach to the description of dispersion forces (see also C. Raabe and D.-G. Welsch, Phys. Rev. A 71:013814, 2005; Phys. Rev. A 73:063822, 2006). It is based on the ground-state Lorentz force density that acts on the charge and current densities attributed to the polarization and magnetization in linearly, locally, and causally responding media. Application of the theory to dielectric systems yields very general formulas for the Casimir force on dielectric bodies or parts of them. It is shown that well-known expressions for the Casimir-Polder force on a single atom and for the van der Waals force between atoms are also contained in our formula. The theory may thus be viewed as providing a unified basis for the calculation of dispersion forces from a macroscopic point of view.

2006-09-01

322

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

323

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)

2004-08-01

324

Neutrino nuclear response and photo nuclear reaction  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

325

Ground-water Aquifers  

Science.gov (United States)

This description of a ground-water aquifer has a graphic representation to accompany it. It is part of the U.S. Geologic Survey's Water Science for Schools website. Links to other parts of the site, such as definitions and types of wells, are included.

326

Ground Water Atlas  

Science.gov (United States)

Authored by the United States Geological Survey, the series consists of thirteen chapters which describes the ground-water resources of regional areas that collectively cover the 50 States, Puerto Rico, and the U.S. Virgin Islands. This is a nice reference tool for those interested in geology.

2008-02-07

327

Grounding in Instant Messaging  

Science.gov (United States)

In two experiments, we investigated predictions of the "collaborative theory of language use" (Clark, 1996) as applied to instant messaging (IM). This theory describes how the presence and absence of different grounding constraints causes people to interact differently across different communicative media (Clark & Brennan, 1991). In Study 1, we…

Fox Tree, Jean E.; Mayer, Sarah A.; Betts, Teresa E.

2011-01-01

328

Collison and Grounding  

DEFF Research Database (Denmark)

COMMITTEE MANDATE Concern for structural arrangements on ships and floating structures with regard to their integrity and adequacy in the events of collision and grounding, with the view towards risk assessment and management. Consideration shall be given to the frequency of occurrence, the probabilistic and physical nature of such accidents, and consequences on watertight integrity, structural integrity and environment.

Wang, G. USA

2006-01-01

329

POT for Bury Grounds  

…station POT Data for: IRWELL at Bury Grounds (69044) Note: Place the mouse cursor over a column heading to view a description of the data in that column Rank Date Time Stage Flow Rating Source Ref Comments 17 02/01/1976 17:45 1.468 116.89 In Range Estimated stage data from Bury Bridge (69035) 2b 74 30…

330

Quasielastic reactions  

International Nuclear Information System (INIS)

Quasielastic reaction studies, because of their capability to microscopically probe nuclear structure, are still of considerable interest in heavy-ion reactions. The recent progress in understanding various aspects of the reaction mechanism make this aim appear closer. The relation between microscopic and macroscopic behavior, as suggested, for example, by the single proton transfer data to individual final states or averaged excitation energy intervals, needs to be explored. It seems particularly useful to extend measurements to higher incident energies, to explore and understand nuclear structure aspects up to the limit of the energy range where they are important

1979-11-01

331

Anti-gravity treadmills are effective in reducing knee forces.  

Science.gov (United States)

Lower body positive pressure (LBPP) treadmills permit significant unweighting of patients and have the potential to enhance recovery following lower limb surgery. We determined the efficacy of an LBPP treadmill in reducing knee forces in vivo. Subjects, implanted with custom electronic tibial prostheses to measure forces in the knee, were tested on a treadmill housed within a LBPP chamber. Tibiofemoral forces were monitored at treadmill speeds from 1.5?mph (0.67?m/s) to 4.5?mph (2.01?m/s), treadmill incline from -10° to +10°, and four treadmill chamber pressure settings adjusted to decrease net treadmill reaction force from 100% to 25% of the subject's body weight (BW). The peak axial tibiofemoral force ranged from 5.1 times BW at a treadmill speed of 4.5?mph (2.01?m/s) and a pressure setting of 100% BW to 0.8 times BW at 1.5?mph (0.67?m/s) and a pressure setting of 25% BW. Peak knee forces were significantly correlated with walking speed and treadmill reaction force (R(2) ?=?0.77, p?=?0.04). The LBPP treadmill might be an effective tool in the rehabilitation of patients following lower-extremity surgery. The strong correlation between tibiofemoral force and walking speed and treadmill reaction forces allows for more precisely achieving the target knee forces desired during early rehabilitation. PMID:23239580

Patil, Shantanu; Steklov, Nikolai; Bugbee, William D; Goldberg, Timothy; Colwell, Clifford W; D'Lima, Darryl D

2013-05-01

332

Grounding equivalency of steel poles  

Energy Technology Data Exchange (ETDEWEB)

This article presents evidence that the embedded portion of a representative steel pole offer significant grounding capability. The Numerical Electromagnetics Code is used to compute the grounding resistance of a variety of grounding electrodes. The computational technique for determining ground resistance is first validated using standard ground rods. The computed results are then compared with the analytical equation for cylindrical ground rods as given in the IEEE Recommended Practices for Grounding Industrial and Commercial Power Systems. Since soil characteristics are of prime importance, two soil types are considered for each ground resistance computation: a relatively low conductivity sandy soil and a relatively high conductivity clay soil. Several different scenarios of grounding for the steel poles are considered. The ground resistance of the various electrodes considered here are computed using NEC-4 by applying the so-called fall-of-potential method. When the computed ground resistance of the coated steel pole is compared to that of a concrete pile, it is found that the coated steel pole is at least equal or better ground for bare lengths between four and five feet. Since the computed ground resistances on the coated steel pole are always larger than the actual grounding resistance, while concrete pile ground resistances are always smaller, the amount of bare length required on the coated steel pole to make it equivalent to the concrete pile ought to be significantly smaller than the given range of between four and five feet. 3 refs., 3 tabs., 5 figs.

Donohue, J. P.

2001-07-01

333

Force-Measuring Clamps  

Science.gov (United States)

Force-measuring clamps have been invented to facilitate and simplify the task of measuring the forces or pressures applied to clamped parts. There is a critical need to measure clamping forces or pressures in some applications for example, while bonding sensors to substrates or while clamping any sensitive or delicate parts. Many manufacturers of adhesives and sensors recommend clamping at specific pressures while bonding sensors or during adhesive bonding between parts in general. In the absence of a force-measuring clamp, measurement of clamping force can be cumbersome at best because of the need for additional load sensors and load-indicating equipment. One prior method of measuring clamping force involved the use of load washers or miniature load cells in combination with external power sources and load-indicating equipment. Calibrated spring clamps have also been used. Load washers and miniature load cells constitute additional clamped parts in load paths and can add to the destabilizing effects of loading mechanisms. Spring clamps can lose calibration quickly through weakening of the springs and are limited to the maximum forces that the springs can apply. The basic principle of a force-measuring clamp can be implemented on a clamp of almost any size and can enable measurement of a force of almost any magnitude. No external equipment is needed because the component(s) for transducing the clamping force and the circuitry for supplying power, conditioning the output of the transducers, and displaying the measurement value are all housed on the clamp. In other words, a force-measuring clamp is a complete force-application and force-measurement system all in one package. The advantage of unitary packaging of such a system is that it becomes possible to apply the desired clamping force or pressure with precision and ease.

Nunnelee, Mark

2003-01-01

334

Interactive forces between lignin and cellulase as determined by atomic force microscopy  

Science.gov (United States)

Background Lignin is a complex polymer which inhibits the enzymatic conversion of cellulose to glucose in lignocellulose biomass for biofuel production. Cellulase enzymes irreversibly bind to lignin, deactivating the enzyme and lowering the overall activity of the hydrolyzing reaction solution. Within this study, atomic force microscopy (AFM) is used to compare the adhesion forces between cellulase and lignin with the forces between cellulase and cellulose, and to study the moiety groups involved in binding of cellulase to lignin. Results Trichoderma reesei, ATCC 26921, a commercial cellulase system, was immobilized onto silicon wafers and used as a substrate to measure forces involved in cellulase non-productive binding to lignin. Attraction forces between cellulase and lignin, and between cellulase and cellulose were compared using kraft lignin- and hydroxypropyl cellulose-coated tips with the immobilized cellulase substrate. The measured adhesion forces between kraft lignin and cellulase were on average 45% higher than forces between hydroxypropyl cellulose and cellulase. Specialized AFM tips with hydrophobic, -OH, and -COOH chemical characteristics were used with immobilized cellulase to represent hydrophobic, H-bonding, and charge-charge interactions, respectively. Forces between hydrophobic tips and cellulase were on average 43% and 13% higher than forces between cellulase with tips exhibiting OH and COOH groups, respectively. A strong attractive force during the AFM tip approach to the immobilized cellulase was observed with the hydrophobic tip. Conclusions This work shows that there is a greater overall attraction between kraft lignin and cellulase than between hydroxypropyl cellulose and cellulase, which may have implications during the enzymatic reaction process. Furthermore, hydrophobic interactions appear to be the dominating attraction force in cellulase binding to lignin, while a number of other interactions may establish the irreversible binding.

2014-01-01

335

Sticking like sticky tape: tree frogs use friction forces to enhance attachment on overhanging surfaces.  

Science.gov (United States)

To live and clamber about in an arboreal habitat, tree frogs have evolved adhesive pads on their toes. In addition, they often have long and slender legs to facilitate not only long jumps, but also to bridge gaps between leaves when climbing. Both adhesive pads and long limbs are used in conjunction, as we will show in this study. Previous research has shown that tree frogs change from a crouched posture (where the limbs are close to the body) to a sprawled posture with extended limbs when clinging on to steeper inclines such as vertical or overhanging slopes. We investigated this change in posture in White's tree frogs (Litoria caerulea) by challenging the frogs to cling onto a tiltable platform. The platform consisted of an array of 24 three-dimensional force transducers, which allowed us to measure the ground reaction forces of the frogs during a tilt. Starting from a crouched resting position, the normal forces on the forelimbs changed sign and became increasingly negative with increasing slope angle of the platform. At about 106° ± 12°, tilt of the platform the frogs reacted by extending one or two of their limbs outwards. At a steeper angle (131° ± 11°), the frogs spread out all their limbs sideways, with the hindlimbs stretched out to their maximum reach. Although the extension was strongest in the lateral direction, limbs were significantly extended in the fore-aft direction as well. With the extension of the limbs, the lateral forces increased relative to the normal forces. The large contribution of the in-plane forces helped to keep the angle between the force vector and the platform small. The Kendall theory for the peeling of adhesive tape predicts that smaller peel angles lead to higher attachment forces. We compare our data with the predictions of the Kendall model and discuss possible implications of the sliding of the pads on the surface. The forces were indeed much larger for smaller angles and thus can be explained by peeling theory. PMID:23325755

Endlein, Thomas; Ji, Aihong; Samuel, Diana; Yao, Ning; Wang, Zhongyuan; Barnes, W Jon P; Federle, Walter; Kappl, Michael; Dai, Zhendong

2013-03-01

336

Correlations of Quasi Particles in the Deformed Nuclei Ground States.  

Science.gov (United States)

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 show t...

S. I. Bastrukov V. O. Nesterenko

1984-01-01

337

Networked unattended ground sensors: the road ahead  

Science.gov (United States)

With its focus on the Future Combat Systems (FCS), the U.S. Army has embarked on an important campaign to field a lighter force, capable of being deployed in a fraction of the time currently required. The survivability of this force, however, will be based more heavily on the use of integrated command and control capabilities with unsurpassed situational understanding for all levels of commanders. Arrays of small, low cost, low power sensors will play a key role in detecting, locating, tracking and identifying targets, particularly in areas where the terrain or other circumstances prevent traditional high performance sensors from providing critical information. There has been, and continues to be, a number of DoD programs aimed at fielding Unattended Ground Sensors (UGS). While much of the underpinning technology exists to field such systems, many technology and operational barriers still remain. This paper will attempt to discuss the challenges to overcoming these barriers.

Eicke, John; Kolodny, Michael A.

2002-08-01

338

Calculation of ground vibration spectra from heavy military vehicles  

Science.gov (United States)

The demand for reliable autonomous systems capable to detect and identify heavy military vehicles becomes an important issue for UN peacekeeping forces in the current delicate political climate. A promising method of detection and identification is the one using the information extracted from ground vibration spectra generated by heavy military vehicles, often termed as their seismic signatures. This paper presents the results of the theoretical investigation of ground vibration spectra generated by heavy military vehicles, such as tanks and armed personnel carriers. A simple quarter car model is considered to identify the resulting dynamic forces applied from a vehicle to the ground. Then the obtained analytical expressions for vehicle dynamic forces are used for calculations of generated ground vibrations, predominantly Rayleigh surface waves, using Green's function method. A comparison of the obtained theoretical results with the published experimental data shows that analytical techniques based on the simplified quarter car vehicle model are capable of producing ground vibration spectra of heavy military vehicles that reproduce basic properties of experimental spectra.

Krylov, V. V.; Pickup, S.; McNuff, J.

2010-07-01

339

Forced patterns near a Turing-Hopf bifurcation  

Science.gov (United States)

We study time-periodic forcing of spatially extended patterns near a Turing-Hopf bifurcation point. A symmetry-based normal form analysis yields several predictions, including that (i) weak forcing near the intrinsic Hopf frequency enhances or suppresses the Turing amplitude by an amount that scales quadratically with the forcing strength, and (ii) the strongest effect is seen for forcing that is detuned from the Hopf frequency. To apply our results to specific models, we perform a perturbation analysis on general two-component reaction-diffusion systems, which reveals whether the forcing suppresses or enhances the spatial pattern. For the suppressing case, our results are consistent with features of previous experiments on the chlorine dioxide-iodine-malonic acid chemical reaction. However, we also find examples of the enhancing case, which has not yet been observed in experiment. Numerical simulations verify the predicted dependence on the forcing parameters.

Topaz, Chad M.; Catllá, Anne J.

2010-02-01

340

Qualitative Force Structure Analysis of the Global Mobility Task Force.  

Science.gov (United States)

This paper examines the Global Mobility Task Force construct and the optimum force structure needed to implement this vision. The 'United States Air Force Transformation Flight Plan' provides the strategic guidance for the Global Mobility Task Force const...

M. J. Logar

2003-01-01

 
 
 
 
341

Trapping atoms using nanoscale quantum vacuum forces  

CERN Document Server

Quantum vacuum forces dictate the interaction between individual atoms and dielectric surfaces at nanoscale distances. For example, their large strengths typically overwhelm externally applied forces, which makes it challenging to controllably interface cold atoms with nearby nanophotonic systems. Here, we show that it is possible to tailor the vacuum forces themselves to provide strong trapping potentials. The trapping scheme takes advantage of the attractive ground state potential and adiabatic dressing with an excited state whose potential is engineered to be resonantly enhanced and repulsive. This procedure yields a strong metastable trap, with the fraction of excited state population scaling inversely with the quality factor of the resonance of the dielectric structure. We analyze realistic limitations to the trap lifetime and discuss possible applications that might emerge from the large trap depths and nanoscale confinement.

Chang, D E; Taylor, J M; Kimble, H J

2013-01-01

342

Contribution to the models for calculation and analysis of grounding grids and grounding systems  

International Nuclear Information System (INIS)

The aim of this dissertation is improving the existing models and finding new for calculating the conditions in the complex grounding systems and analyzing their performances. For that purpose, firstly, a model network of the grounding system is created, and the ways of modelling the separate elements are studied and elaborated also. Some methods for solving groundings with arbitrary complexity and dimensions are studied and worked out too. Afterwards the TL in models are worked out, with or without protective rope. Appropriate models are detail worked out and formed for the energetic cables, both for isolated and distributive outer shield - type PP, XHP, XHE, IPO, and IPZO. At the same time, the eventual presence of additional groundings like steel tapes and cooper ropes placed into the cable trench together with the cable is considered. Particular attention is dedicated on the cables with steel reinforcement, whose parameters of the 'unit length depends of the current in the shield and in the reinforcement, because they are sources of nonlinearity and also of the problems connected with its modelling and solving. Therefore an approach is made to the modelling of the mutual conductive couplings between the elements of the grounding system (ex. between two and more cables, the parts of one cable, the groundings of one substation and the cables in theirs immediate nearness and so on.). The electromagnetic couplings existing between the phases conductors, under the influence of the fault, like, (protective rope (TL), the metal shields, and the cables with electric protection, are included too. The mutual couplings are estimated over introducing inducted electro motor forces (EMF) in the transversal and/or longitudinal branches of the elements of the grounding system. (depending on what kind of coupling we are talking-conductive or inductive). These inductive EMF later are transformed into equivalent current generators and in that way the system will be harnessed. The number of the current generators that appear in the cycle with the procedure 'replacing of the current generators' are transferred easily into the node of the network where the fault is made previously. Further on, some modem numerical methods and procedures for calculating the grounding system, convenient for the use of the personal computers are studied. Some modem numerical procedures are adopted and worked out for calculating networks (cycles) with radial structure and/or with small number of loops. They are used for solving the condition in the network part of the grounding system, which means that up to now the researches are pointing to the adequacy of the use of the methods for summarizing admittances and summarizing current (MSAC). The next step, after the distribution of the whole system is defined, is passing to the estimation of the safety conditions from high touch and step voltages in the environment of the different groundings. For that purpose, the characteristics of the biggest number of typical groundings of the MV/LV substations, the characteristics of some kind's network groundings of the HV/N4V substation are studied. The tower TL groundings (ring shaped, square shaped, ray shaped) are analyzed in details. At the same time, a data multitude is calculated, necessary for the further analysis, and consisting theirs resistances to ground.(for a given value of a specific resistance of the soil), the maximum and the average values of touch and step potentials, as well as the frequencies of their appearances,. (frequent histograms FH) of the touch and step potential differences) and so on. All these quantities are depending on the geometry of the grounding. The calculating FH of different kinds of groundings is performed with a computer simulation-'simulation Monte Carlo'. In order to obtain them, an appropriate software is produced, which by making the number of experiments (simulations), defines the needed performances of the grounding statistically, and at the same time, accidentally generates the position of the human in the electro energetic

2003-01-01

343

Coulomb force as an entropic force  

Science.gov (United States)

Motivated by Verlinde’s theory of entropic gravity, we give a tentative explanation to the Coulomb’s law with an entropic force. When trying to do this, we find the equipartition rule should be extended to charges and the concept of temperature should be reinterpreted. If one accepts the holographic principle as well as our generalizations and reinterpretations, then Coulomb’s law, the Poisson equation, and the Maxwell equations can be derived smoothly. Our attempt can be regarded as a new way to unify the electromagnetic force with gravity, from the entropic origin. Possibly some of our postulates are related to the D-brane picture of black hole thermodynamics.

Wang, Tower

2010-05-01

344

GROUND WATER CONTAMINATION  

Energy Technology Data Exchange (ETDEWEB)

As required by the terms of the above referenced grant, the following summary serves as the Final Report for that grant. The grant relates to work performed at two separate sites, the Hoe Creek Underground Coal Gasification Site south of Gillette, Wyoming, and the Rock Springs In-Situ Oil Shale Retort Site near Rock Springs, Wyoming. The primary concern to the State of Wyoming at each site is ground water contamination (the primary contaminants of concern are benzene and related compounds), and the purpose of the grant has been to provide tiding for a Geohydrologist at the appropriate State agency, specifically the Land Quality Division (LQD) of the Wyoming Department of Environmental Quality. The LQD Geohydrologist has been responsible for providing technical and regulatory support to DOE for ground water remediation and subsequent surface reclamation. Substantial progress has been made toward remediation of the sites, and continuation of LQD involvement in the remediation and reclamation efforts is addressed.

Unknown

1999-09-01

345

Ground motion effects  

International Nuclear Information System (INIS)

Ground motion caused by natural earthquakes or by nuclear explosion causes buildings and other structures to respond in such manner as possibly to have high unit stresses and to be subject to damage or-in some cases-collapse. Even minor damage may constitute a hazard to persons within or adjacent to buildings. The risk of damage may well be the governing restraint on the uses of nuclear energy for peaceful purposes. Theory is advanced regarding structural-dynamic response but real buildings and structures are complex, highly variable, and often difficult to model realistically. This paper discusses the state of knowledge, the art of damage prediction and safety precautions, and shows ground motion effects from explosions of underground nuclear devices in the continental United States including events Salmon, Gasbuggy, Boxcar, Faultless and Benham. (author)

1969-04-07

346

The Symbol Grounding Problem  

CERN Multimedia

How can the semantic interpretation of a formal symbol system be made intrinsic to the system, rather than just parasitic on the meanings in our heads? How can the meanings of the meaningless symbol tokens, manipulated solely on the basis of their (arbitrary) shapes, be grounded in anything but other meaningless symbols? The problem is analogous to trying to learn Chinese from a Chinese/Chinese dictionary alone. A candidate solution is sketched: Symbolic representations must be grounded bottom-up in nonsymbolic representations of two kinds: (1) "iconic representations," which are analogs of the proximal sensory projections of distal objects and events, and (2) "categorical representations," which are learned and innate feature-detectors that pick out the invariant features of object and event categories from their sensory projections. Elementary symbols are the names of these object and event categories, assigned on the basis of their (nonsymbolic) categorical representations. Higher-order (3) "symbolic repre...

Harnad, S

1999-01-01

347

The Comparison on Grounding Characteristics for 3 Grounding Systems  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a comparison on the resistance and characteristics of transient response of grounding systems under surge currents using frequency domain electromagnetic field analysis software package and field test. Analysis is done by computer model, based on electromagnetic field theory approach, that accurately takes into account frequency dependent characteristics of the system. The transient performance of three grounding systems is analyzed by comparison of frequency dependent impedance and the maximal transient GPR. A double exponential lighting surge current is injected at one corner of the grounding systems. The transient GPRs of rod grounding systems are higher than mesh or electrolytic grounding systems. At field test, the result of resistance measurement and time-variant of ground resistance slightly reduce electrolytic grounding systems less than rod and mesh grounding systems. (author). 16 refs., 22 figs., 7 tabs.

Shin, Dong Ho; Kim, Yong; Baek, Soo Hyung; Lee, Eun Young [Dongguk University(Korea); Kim, Pill Soo [Daelim College of Technology(Korea)

2000-06-01

348

Association Kinetics from Single Molecule Force Spectroscopy Measurements  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Single molecule force spectroscopy is often used to study the dissociation of single molecules by applying mechanical force to the intermolecular bond. These measurements provide the kinetic parameters of dissociation. We present what to our knowledge is a new atomic force microscopy-based approach to obtain the activation energy of the association reaction and approximate grafting density of reactive receptors using the dependence of the probability to form molecular bonds on probe velocity ...

Guo, Senli; Lad, Nimit; Ray, Chad; Akhremitchev, Boris B.

2009-01-01

349

Interfacial Forces are Modified by the Growth of Surface Nanostructures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Nanostructures formed by chemical reaction can modify the interfacial forces present in aqueous solution near a surface. This study uses force-volume microscopy to explore this phenomenon for the growth of manganese oxide nanostructures on rhodochrosite. The interfacial forces above the oxide nanostructures are dominated by electrostatic repulsion for probe?surface separations greater than ca. 2 nm but are overtaken by van der Waals attraction for shorter distances. Across the investigated ...

Martin, Scot; Na, Chongzheng

2008-01-01

350

Remodeling Grounded Theory  

Directory of Open Access Journals (Sweden)

Full Text Available This paper outlines my concerns with Qualitative Data Analysis’ (QDAnumerous remodelings of Grounded Theory (GT and the subsequent eroding impact. I cite several examples of the erosion and summarize essential elements of classic GT methodology. It is hoped that the article will clarify my concerns with the continuing enthusiasm but misunderstood embrace of GT by QDA methodologists and serve as a preliminary guide to novice researchers who wish to explore the fundamental principles of GT.

Barney G. Glaser Ph.D., Hon. Ph.D.

2004-11-01

351

Airport Ground Staff Scheduling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Clausen, Tommy

2010-01-01

352

Physical Pendulum Forces  

Science.gov (United States)

The Physical Pendulum with Forces model displays the gravitational, normal, and friction forces acting on a mass attached to a pivoted rod.  These forces cause the mass to accelerate in the radially and tangentially with respect to pivot.  Although gravity is always downward, friction and normal force change direction in order to keep the mass in the same position on the stick.  The Physical Pendulum Forces model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_mech_newton_PhysicalPendulumForces.jar file will run the program if Java is installed.

Christian, Wolfgang

2010-02-01

353

Seals task force activities  

Energy Technology Data Exchange (ETDEWEB)

The Department of Energy (DOE) established the seals task force in 1986 to scope the extent of seals problems, develop guidelines and criteria, and recommend improvements. Recent task force activities have been to update the Safeguards Seals Reference manual produced in 1986, lay the groundwork for seal standardization, and make recommendations for general and specific seals problems in the field. This paper will discuss the manual updates and other general task force activities. 5 refs.

Waddoups, I.G.

1989-01-01

354

Drilling with force feedback  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Industrial robots have been used for a long time in the industry. Despite this thedevelopment of advanced force control system using industrial robots is relativelylimited. Using force controlled robot systems expands the possibility of what canbe done with industrial robots.Previously a force feedback system for a standard industrial robot from ABBhas been developed. The system is developed towards the aircraft industry, where amounted drill machine on the robot has to fulfill the requiremen...

Isaksson, Robert

2009-01-01

355

Force induced DNA melting  

International Nuclear Information System (INIS)

When pulled along the axis, double-strand DNA undergoes a large conformational change and elongates by roughly twice its initial contour length at a pulling force of about 70 pN. The transition to this highly overstretched form of DNA is very cooperative. Applying a force perpendicular to the DNA axis (unzipping), double-strand DNA can also be separated into two single-stranded DNA, this being a fundamental process in DNA replication. We study the DNA overstretching and unzipping transition using fully atomistic molecular dynamics (MD) simulations and argue that the conformational changes of double-strand DNA associated with either of the above mentioned processes can be viewed as force induced DNA melting. As the force at one end of the DNA is increased the DNA starts melting abruptly/smoothly above a critical force depending on the pulling direction. The critical force fm, at which DNA melts completely decreases as the temperature of the system is increased. The melting force in the case of unzipping is smaller compared to the melting force when the DNA is pulled along the helical axis. In the case of melting through unzipping, the double-strand separation has jumps which correspond to the different energy minima arising due to sequence of different base pairs. The fraction of Watson-Crick base pair hydrogen bond breaking as a function of force does not show smooth and continuous behavior and consists of plateaus followed by sharp jumps.

2009-01-21

356

Hydrostatic force sensor  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a theoretical and experimental investigation of a new kind of force sensor which detects forces by measuring an induced pressure change in a material of large Poisson`s ratio. In this investigation we develop mathematical expressions for the sensor`s sensitivity and bandwidth, and show that its sensitivity can be much larger and its bandwidth is usually smaller than those of existing strain-gage-type sensors. This force sensor is well-suited for measuring large but slowly varying forces. It can be installed in a space smaller than that required by existing sensors.

Evans, M.S.; Stoughton, R.S. [Pacific Northwest Lab., Richland, WA (United States); Kazerooni, H. [Univ. of California, Berkeley, CA (United States)

1994-08-01

357

Forcing Isomorphism II  

CERN Document Server

If T has only countably many complete types, yet has a type of infinite multiplicity then there is a ccc forcing notion Q such that, in any Q --generic extension of the universe, there are non-isomorphic models M_1 and M_2 of T that can be forced isomorphic by a ccc forcing. We give examples showing that the hypothesis on the number of complete types is necessary and what happens if `ccc' is replaced other cardinal-preserving adjectives. We also give an example showing that membership in a pseudo-elementary class can be altered by very simple cardinal-preserving forcings.

Laskowski, M C; Laskowski, Michael C.; Shelah, Saharon

1996-01-01

358

Dispersive forces on bodies and atoms: a unified approach  

CERN Document Server

A unified approach to the calculation of dispersive forces on ground-state bodies and atoms is given. It is based on the ground-state Lorentz force density acting on the charge and current densities attributed to the polarization and magnetization in linearly, locally, and causally responding media. The theory is applied to dielectric macro- and micro-objects, including single atoms. Existing formulas valid for weakly polarizable matter are generalized to allow also for strongly polarizable matter. In particular when micro-objects can be regarded as single atoms, well-known formulas for the Casimir-Polder force on atoms and the van der Waals interaction between atoms are recovered. It is shown that the force acting on medium atoms--in contrast to isolated atoms--is in general screened by the other medium atoms.

Raabe, C; Raabe, Christian; Welsch, Dirk-Gunnar

2006-01-01

359

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

1988-01-01

360

Piezonuclear Reactions  

CERN Multimedia

In this paper, we deal with the subject of piezonuclear reactions, namely nuclear reactions (of new type) triggered by pressure waves. We discuss the experimental evidences obtained in the last two decades, which can be summarized essentially as follows: experiments in cavitation of liquids, where transmutation of elements, creation of elements and emission of neutrons have been observed; emission of neutrons in brittle failure of solids subjected to mechanical pressure; alteration of the lifetime of un unstable element (thorium) subjected to cavitation. A theoretical model to explain these facts is proposed. Future perspectives of these experimental and theoretical investigations are also underlined.

Cardone, Fabio; Petrucci, Andrea

2010-01-01

 
 
 
 
361

Attractive optical forces from black-body radiation  

CERN Document Server

Black-body radiation around hot objects induces AC Stark shifts of the energy levels of nearby atoms and molecules. These shifts are roughly proportional to the fourth power of the temperature and induce a force decaying with the third power of the distance from the object's surface. We explicitly calculate the resulting attractive black-body optical dipole force for ground state hydrogen atoms. Surprisingly this force can surpass the repulsive radiation pressure and actually pull the atoms towards the surface with a force stronger than gravity. We exemplify the dominance of the "black-body force" over gravity for hydrogen in a cloud of hot dust particles. These forces, which have been neglected to date, appear highly relevant in various astrophysical scenarios, in particular since analogous results hold for a wide class of broadband radiation sources.

Sonnleitner, Matthias; Ritsch, Helmut

2013-01-01

362

Cross reaction and thermonuclear reaction rates forthe 58Ni(p,?)59Cu reaction  

International Nuclear Information System (INIS)

The yield from the 58Ni(p,?)59Cu reaction has been measured by detection of annihilation radiation in coincidence from the decay of 82 s 59Cu. Both thin (600?g cm-2) and thick (117 mg cm-2) targets have been used, the latter being thick enough to stop the proton beam at all incident energies. The cross section calculated from the thin target yield contains much structure and is in reasonably good agreement with previous studies. Thermonuclear reaction rates have been calculated from both thin and thick target yields for tempertures of interest in explosive nucleosynthesis. Both thin and thick target rates are in very good agreement with previous determinations but the thin rates are, on the average, 35% higher than thick target rates. The reaction rate for T99>=2 for both ground state and stellar reactions based on thin target measurements is recommended and analytic fits to the recommended rates are given. (auth)

1980-01-01

363

First observation of $^{13}$Li ground state  

CERN Document Server

The ground state of neutron-rich unbound $^{13}$Li was observed for the first time in a one-proton removal reaction from $^{14}$Be at a beam energy of 53.6 MeV/u. The $^{13}$Li ground state was reconstructed from $^{11}$Li and two neutrons giving a resonance energy of 120$^{+60}_{-80}$ keV. All events involving single and double neutron interactions in the Modular Neutron Array (MoNA) were analyzed, simulated, and fitted self-consistently. The three-body ($^{11}$Li+$n+n$) correlations within Jacobi coordinates showed strong dineutron characteristics. The decay energy spectrum of the intermediate $^{12}$Li system ($^{11}$Li+$n$) was described with an s-wave scattering length of greater than -4 fm, which is a smaller absolute value than reported in a previous measurement.

Kohley, Z; DeYoung, P A; Volya, A; Baumann, T; Bazin, D; Christian, G; Cooper, N L; Frank, N; Gade, A; Hall, C; Hinnefeld, J; Luther, B; Mosby, S; Peters, W A; Smith, J K; Snyder, J; Spyrou, A; Thoennessen, M

2013-01-01

364

Vector field statistical analysis of kinematic and force trajectories.  

Science.gov (United States)

When investigating the dynamics of three-dimensional multi-body biomechanical systems it is often difficult to derive spatiotemporally directed predictions regarding experimentally induced effects. A paradigm of 'non-directed' hypothesis testing has emerged in the literature as a result. Non-directed analyses typically consist of ad hoc scalar extraction, an approach which substantially simplifies the original, highly multivariate datasets (many time points, many vector components). This paper describes a commensurately multivariate method as an alternative to scalar extraction. The method, called 'statistical parametric mapping' (SPM), uses random field theory to objectively identify field regions which co-vary significantly with the experimental design. We compared SPM to scalar extraction by re-analyzing three publicly available datasets: 3D knee kinematics, a ten-muscle force system, and 3D ground reaction forces. Scalar extraction was found to bias the analyses of all three datasets by failing to consider sufficient portions of the dataset, and/or by failing to consider covariance amongst vector components. SPM overcame both problems by conducting hypothesis testing at the (massively multivariate) vector trajectory level, with random field corrections simultaneously accounting for temporal correlation and vector covariance. While SPM has been widely demonstrated to be effective for analyzing 3D scalar fields, the current results are the first to demonstrate its effectiveness for 1D vector field analysis. It was concluded that SPM offers a generalized, statistically comprehensive solution to scalar extraction's over-simplification of vector trajectories, thereby making it useful for objectively guiding analyses of complex biomechanical systems. PMID:23948374

Pataky, Todd C; Robinson, Mark A; Vanrenterghem, Jos

2013-09-27

365

Grounding Damage to Conventional Vessels  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The present paper is concerned with rational design of conventional vessels with regard to bottom damage generated in grounding accidents. The aim of the work described here is to improve the design basis, primarily through analysis of new statistical data for grounding damage. The current regulations for design of bottom compartment layout with regard to grounding damages are largely based on statistical damage data. New and updated damage statistics holding 930 grounding accident records ha...

Lu?tzen, Marie; Simonsen, Bo Cerup

2006-01-01

366

Three-nucleon forces and the trinucleon bound states  

Energy Technology Data Exchange (ETDEWEB)

A summary of the bound-state working group session of the ''International Symposium on the Three-Body Force in the Three-Nucleon System'' is presented. The paper includes a discussion of presently used calculational techniques, experimental evidence for three-nucleon forces in trinucleon ground states, future directions in theoretical research and future experimental research. (DWL)

Friar, J.L.; Frois, B.

1986-01-01

367

USGS Ground Water Information Pages  

Science.gov (United States)

The pages at this site are designed to provide useful information about groundwater resources and activities of the United States Geological Survey. Included are links to groundwater data, a publications section which gives access to Water Resources Publications, On-Line Fact Sheets, Ground Water Atlas, and Selected USGS Ground Water Publications, and a resource for field techniques and ground water models.

368

Ground Beef and Food Safety  

Science.gov (United States)

... ground meat is frozen at home. What causes ground beef patties to shrink while cooking? All meat will shrink ... on the same platter that held the raw patties unless you wash the platter ... bacteria, cook ground beef to a safe minimum internal temperature of 160 ° ...

369

Hand Interactions in Rapid Grip Force Adjustments Are Independent of Object Dynamics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Object manipulation requires rapid increase in grip force to prevent slippage when the load force of the object suddenly increases. Previous experiments have shown that grip force reactions interact between the hands when holding a single object. Here we test whether this interaction is modulated by the object dynamics experienced before the perturbation of the load force. We hypothesized that coupling of grip forces should be stronger when holding a single object than when holding separate o...

White, Olivier; Dowling, Noreen; Bracewell, R. Martyn; Diedrichsen, Jo?rn

2008-01-01

370

TFTR grounding scheme and ground-monitor system  

International Nuclear Information System (INIS)

The Tokamak Fusion Test Reactor (TFTR) grounding system utilizes a single-point ground. It is located directly under the machine, at the basement floor level, and is tied to the building perimeter ground. Wired to this single-point ground, via individual 500 MCM insulated cables, are: the vacuum vessel; four toroidal field coil cases/inner support structure quadrants; umbrella structure halves; the substructure ring girder; radial beams and columns; and the diagnostic systems. Prior to the first machine operation, a ground-loop removal program was initiated. It required insulation of all hangers and supports (within a 35-foot radius of the center of the machine) of the various piping, conduits, cable trays, and ventilation systems. A special ground-monitor system was designed and installed. It actively monitors each of the individual machine grounds to insure that there are no inadvertent ground loops within the machine structure or its ground and that the machine grounds are intact prior to each pulse. The TFTR grounding system has proven to be a very manageable system and one that is easy to maintain

1983-01-01

371

Allergic reactions  

Science.gov (United States)

... that don't bother most people (such as venom from bee stings and certain foods, medications, and pollens) can ... it. If the allergic reaction is from a bee sting, scrape the ... release more venom. If the person develops an itchy rash, apply ...

372

``Force-free'' electrophoresis?  

Science.gov (United States)

When a colloidal particle is exposed to an externally applied electric field, it acquires an electrophoretic velocity, resulting from fluid slip occurring across the Debye screening layer. When the field is uniformly applied, it is usually assumed that the net neutrality of the combined particle-layer system implies that the net electric force acting on it must vanish. This assumption of ``force-free'' phoretic motion has been employed extensively to describe electrophoresis in both unbounded and bounded fluid domains [J. L. Anderson, Annu. Rev. Fluid Mech. 21, 61 (1989)]. A careful inspection reveals here that this intuitive premise may fail when the fluid domain is bounded, in which case a nonzero electric force (resembling dielectrophoretic forces in nonuniformly applied fields) may actually exist. Such forces (represented via surface integrals of Maxwell stresses) result in particle motion above and beyond the one driven by the phoretic slip mechanism. A positive demonstration for the existence of a such a force is provided for a standard sphere-wall configuration, where the applied field acts parallel to the wall. In that scenario, particle motion consists of a (familiar) slip-driven contribution parallel to the wall, together with a superimposed force-driven drift away from the wall. An analogy with pressure forces occurring at incompressible and inviscid potential flows is presented.

Yariv, Ehud

2006-03-01

373

Conservative entropic forces  

Science.gov (United States)

Entropic forces have recently attracted considerable attention as ways to reformulate, retrodict, and perhaps even "explain" classical Newtonian gravity from a rather specific thermodynamic perspective. In this article I point out that if one wishes to reformulate classical Newtonian gravity in terms of an entropic force, then the fact that Newtonian gravity is described by a conservative force places significant constraints on the form of the entropy and temperature functions. (These constraints also apply to entropic reinterpretations of electromagnetism, and indeed to any conservative force derivable from a potential.) The constraints I will establish are sufficient to present real and significant problems for any reasonable variant of Verlinde's entropic gravity proposal, though for technical reasons the constraints established herein do not directly impact on either Jacobson'sor Padmanabhan's versions of entropic gravity. In an attempt to resolve these issues, I will extend the usual notion of entropic force to multiple heat baths with multiple "temperatures" and multiple "entropies".

Visser, Matt

2011-10-01

374

Umformungen der Grounded Theory  

Directory of Open Access Journals (Sweden)

Full Text Available In diesem Beitrag verdeutliche ich meine Besorgnis über zahlreiche Umformungen der Grounded Theory (GT, die mit deren Rezeption durch Methodologien der qualitative Datenanalyse (QDA einhergehen, und hieraus folgende Erosionen. Ich skizziere zunächst einige Beispiele hierfür, um danach die essentiellen Bestandteile der klassischen GT-Methodologie zusammenzufassen. Ich hoffe, dass dieser Beitrag meine Besorgnis über die wachsende, aber meines Erachtens missverstandene Einvernahme von GT durch QDA-Methodologien veranschaulicht und zugleich als einführender Leitfaden für Novizen und Novizinnen dient, die daran interessiert sind, die grundlegenden Prinzipien der GT nachzuvollziehen. URN: urn:nbn:de:0114-fqs040245

Barney G. Glaser

2004-05-01

375

GRC Ground Support Facilities  

Science.gov (United States)

The ISS Program is conducting an "ISS Research Academy' at JSC the first week of August 2010. This Academy will be a tutorial for new Users of the International Space Station, focused primarily on the new ISS National Laboratory and its members including Non-Profit Organizations, other government agencies and commercial users. Presentations on the on-orbit research facilities accommodations and capabilities will be made, as well as ground based hardware development, integration and test facilities and capabilities. This presentation describes the GRC Hardware development, test and laboratory facilities.

SaintOnge, Thomas H.

2010-01-01

376

Ground penetrating radar  

CERN Document Server

Ground-penetrating radar has come to public attention in recent criminal investigations, but has actually been a developing and maturing remote sensing field for some time. In the light of recent expansion of the technique to a wide range of applications, the need for an up-to-date reference has become pressing. This fully revised and expanded edition of the best-selling Surface-Penetrating Radar (IEE, 1996) presents, for the non-specialist user or engineer, all the key elements of this technique, which span several disciplines including electromagnetics, geophysics and signal processing. The

Daniels, David J

2004-01-01

377

Deep inelastic transfer reaction mechanism  

International Nuclear Information System (INIS)

This paper deals with reactions involving significant exchanges of matter or energy without leading to the complete fusion of the colliding nuclei. For relatively light projectiles (A<40), one observes deep inelastic transfer reactions with angular distribution of the light residues peaking forward in the c.m. system, and for heavier projectiles, quasi-fission reactions for which the angular distributions exhibit a peak in the vicinity of the grazing angle. The theoretical models which are used to explain these reactions are based on the assumption of the existence of friction (or viscosity) forces which are responsible for the large losses of kinetic energy observed. The transfer of matter is treated as a diffusion process by using transport equations in the frame of statistical mechanics

1975-06-30

378

Tips for effective building grounding  

Energy Technology Data Exchange (ETDEWEB)

With the proliferation of highly sensitive electronic equipment, grounding is taking on an increasingly important role. This paper explains the nature of grounding, recently introduced new products to help lower ground resistance, improve capacitance, and prolong system life, and provides some important suggestions for ensuring effective building grounding. The use of well-trained and equipped staff, measurement of site soil resistivity, concentrating critical electronic equipment in a single point configuration, guarding it with surge protection and isolation devices, and proper management and inspection of the grounding system are emphasized.

Arcand, L.; Sirola, W.

2000-05-01

379

Grounding of industrial power systems  

Energy Technology Data Exchange (ETDEWEB)

Grounding is one of two types: equipment grounding is defined as 'the connection of earth ground to non-current-carrying conductive materials such as conduits, cable trays, junction boxes, or motor frames' while system grounding is defined as 'the connection of earth ground to neutral points of current-carrying conductors such as the neutral point of a circuit, a transformer, rotating machinery or a system', either solidly or with a current limiting device. This article describes the characteristics of ungrounded systems, the benefits of proper system grounding such as simplified ground fault location, improved system and equipment fault protection, reduced maintenance time and expense, greater safety for personnel, and reduction in fault frequency, and the advantages of resistance-grounded neutral systems. The conclusion is that ungrounded delta systems have many operating disadvantages whereas solidly grounded neutral systems provide greater safety for personnel, limit the system potential to ground, and speed the detection and location of the ground fault.

Cochran, A.

2002-05-01

380

The Future of Grounded Theory  

Directory of Open Access Journals (Sweden)

Full Text Available I would like to speak about what I consider the future of grounded theory. I will discuss in whose hands the future of grounded theory appears to be and what accounts for its spread, its use and misuse, and where the majority of grounded theory studies are occurring. I will then briefly review poor grounded theory, qualitative grounded theory, social fictions, and theory bits. Finally, I will touch on the future structures in which grounded theory will be taught and centered.First, a few guidelines are necessary. Grounded theory refers to a specific methodology on how to get from systematically collecting data to producing a multivariate conceptual theory. It is a total methodological package. It provides a series of systematic, exact methods that start with collecting data and take the researcher to a theoretical piece that is publishable.

Barney G. Glaser, Ph.D., Hon. Ph.D.

2010-06-01

 
 
 
 
381

As forças transientes durante a marcha militar / Transient forces during military marching / Las fuerzas con efecto transiente durante la marcha militar  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese INTRODUÇÃO: O padrão vertical anormal da força de reação do solo (FRS) apresenta a assimetria ou mais de dois picos como marcha patológica típica. Uma força típica e assimétrica é a força transiente. Será que a marcha militar é uma espécie de marcha patológica? OBJETIVO: Descrever e analisar a força [...] de reação do solo vertical durante a fase de apoio da marcha militar. MÉTODO: Os participantes foram 20 soldados do Exército Brasileiro que tiveram anteriormente uma lesão nos membros inferiores relacionada com a marcha militar. Duas plataformas de força foram usadas para medir as componentes da FRS (mediolateral, anteroposterior e vertical) durante a marcha. Para cada lado e condição (andar e marcha), cinco amostras para cada pé foram registradas. A análise de variância foi utilizada para comparar os parâmetros da FRS durante o andar e marcha. RESULTADO: O primeiro pico de força foi o mais alto durante a condição de marcha. O pico de força transiente durante a marcha foi maior que o primeiro pico durante o andar. A força mínima foi a maior durante a marcha. CONCLUSÃO: A análise das forças de reação do solo marcha militar mostra uma força vertical transiente que não está normalmente presente no padrão de marcha normal. Abstract in spanish INTRODUCCIÓN: El estándar vertical anormal de la fuerza de reacción del suelo (FRS) presenta la asimetría, o más de dos picos, como marcha patológica típica. Una fuerza típica y asimétrica es la fuerza con efecto transiente. ¿Será que la marcha militar es un tipo de marcha patológica? Objetivo: Desc [...] ribir y analizar la fuerza vertical de reacción del suelo durante la fase de apoyo de la marcha militar. MÉTODO: Los participantes fueron 20 soldados del Ejército Brasileño, quienes tuvieron antes una lesión en los miembros inferiores relacionada con la marcha militar. Se usaron dos plataformas de fuerza para medir los componentes de la FRS (mediolateral, anteroposterior y vertical) durante la marcha. Para cada lado y condición (andar y marcha), se registraron cinco muestras para cada pie. El análisis de la variación fue utilizado para comparar los parámetros de la FRS durante el andar y la marcha. RESULTADO: El primer pico de fuerza fue el más alto durante la condición de marcha. El pico de fuerza, con efecto transiente durante la marcha, fue mayor que el primer pico durante el andar. La fuerza mínima fue mayor durante la marcha. CONCLUSIÓN: El análisis de las fuerzas de reacción del suelo, en la marcha militar, muestra una fuerza vertical, con efecto transiente, que normalmente no está presente en el estándar de marcha normal. Abstract in english INTRODUCTION: The abnormal vertical ground reaction force (GRF) pattern presents the asymmetry or the presence of more than two peaks as typical pathological gait. The typical asymmetric force is the transient force. Is the military marching a kind of pathological gait? OBJECTIVE: To describe and an [...] alyze the vertical ground reaction forces during the stance phase of the military marching. METHOD: Participants were 20 Brazilian Army soldiers who previously had an injury in the lower limbs related to the military marching. Two strain-gauge force platforms measured the GRF components (mediolateral, anterior posterior; and vertical components) during gait. To each side and condition (gait and marching) five samples for each foot were recorded. One-way analysis of variance (ANOVA) was used to compare the GRF parameters during gait and marching. RESULTS: The first force peak was the highest during the marching condition. The first force peak was the highest during marching condition. The peak transient force during marching was higher than the first peak during gait. The minimum force was higher during marching. CONCLUSION: The analysis of ground reaction forces in military marching shows a transient vertical force that is not usually present in normal gait pattern.

Thais Pereira, Guisande; Julio Cerca, Amadio; Alberto Carlos, Amadio; Luis, Mochizuki.

382

Direct SW aerosol radiative forcing over Portugal  

Directory of Open Access Journals (Sweden)

Full Text Available In this work, the evaluation of the aerosol radiative forcing at the top of the atmosphere as well as at the surface over the south of Portugal is made, particularly in the regions of Évora (38°34' N, 7°54' W and of Cabo da Roca (38°46' N, 9°38' W, during years 2004 and 2005.

The radiative transfer calculations, using the radiative transfer code Second Simulation of the Satellite Signal in the Solar Spectrum (6S, combine ground-based measurements, from Aerosol Robotic NETwork (AERONET, and satellite measurements, from MODerate Imaging Spectroradiometer (MODIS, to estimate the direct SW aerosol radiative forcing. The method developed to retrieve the surface spectral reflectance is also presented, based on ground-based measurements (AERONET of the aerosol optical properties combined with the satellite-measured radiances (MODIS.

The instantaneous direct SW aerosol radiative forcing values obtained at the top of the atmosphere are, in the majority of the cases, negative, indicating a tendency for cooling the Earth at the top of the atmosphere. For Desert Dust aerosols, over the Évora land region, the average forcing efficiency is estimated to be ?25 Wm?2/AOT0.55 whereas for the Cabo da Roca area, the average forcing efficiency is ?46 Wm?2/AOT0.55. In the presence of Forest Fire aerosols, both from short and long distances, the average value of forcing efficiency at the top of the atmosphere over Cabo da Roca is found to be ?28 Wm?2/AOT0.55 and, over Évora, ?27 Wm?2/AOT0.55. For specific situations, discussed in this work, the average surface direct SW aerosol radiative forcing efficiency due to the Desert Dust aerosols, in Évora region, is ?66 Wm?2/AOT0.55, whereas in Cabo da Roca region, the corresponding average value is ?38 Wm?2/AOT0.55. Considering the Forest Fire aerosols, over Évora region, the average surface direct SW aerosol radiative forcing efficiency can vary between ?36 and ?113 Wm?2/AOT0.55, the more negative value corresponding to forest fire aerosols coming only from shorter distances.

D. Santos

2008-10-01

383

Dilatonic Entropic Force  

Science.gov (United States)

We show in detail that the entropic force of the static spherically symmetric spacetimes with unusual asymptotics can be calculated through the Verlinde's arguments. We introduce three different holographic screen candidates, which are first employed thoroughly by Myung and Kim [Phys. Rev. D 81, 105012 (2010)] for Schwarzschild black hole solutions, in order to identify the entropic force arising between a charged dilaton black hole and a test particle. The significance of the dilaton parameter on the entropic force is highlighted, and shown graphically.

Sakalli, I.

2011-08-01

384

Dilatonic Entropic Force  

CERN Document Server

We show in detail that the entropic force of the static spherically symmetric spacetimes with unusual asymptotics can be calculated through the Verlinde's arguments. We introduce three different holographic screen candidates, which are first employed thoroughly by Myung and Kim [Phys. Rev. D 81, 105012 (2010)] for Schwarzschild black hole solutions, in order to identify the entropic force arising between a charged dilaton black hole and a test particle. The significance of the dilaton parameter on the entropic force is highlighted, and shown graphically.

Sakalli, I

2011-01-01

385

Notes on forcing axioms  

CERN Multimedia

In the mathematical practice, the Baire category method is a tool for establishing the existence of a rich array of generic structures. However, in mathematics, the Baire category method is also behind a number of fundamental results such as the Open Mapping Theorem or the Banach-Steinhaus Boundedness Principle. This volume brings the Baire category method to another level of sophistication via the internal version of the set-theoretic forcing technique. It is the first systematic account of applications of the higher forcing axioms with the stress on the technique of building forcing notions

Todorcevic, Stevo; Feng, Qi; Yang, Yue

2013-01-01

386

Solar Force-free Magnetic Fields  

Directory of Open Access Journals (Sweden)

Full Text Available The structure and dynamics of the solar corona is dominated by the magnetic field. In most areas in the corona magnetic forces are so dominant that all non-magnetic forces like plasma pressure gradient and gravity can be neglected in the lowest order. This model assumption is called the force-free field assumption, as the Lorentz force vanishes. This can be obtained by either vanishing electric currents (leading to potential fields or the currents are co-aligned with the magnetic field lines. First we discuss a mathematically simpler approach that the magnetic field and currents are proportional with one global constant, the so-called linear force-free field approximation. In the generic case, however, the relation between magnetic fields and electric currents is nonlinear and analytic solutions have been only found for special cases, like 1D or 2D configurations. For constructing realistic nonlinear force-free coronal magnetic field models in 3D, sophisticated numerical computations are required and boundary conditions must be obtained from measurements of the magnetic field vector in the solar photosphere. This approach is currently of large interests, as accurate measurements of the photospheric field become available from ground-based (for example SOLIS and space-born (for example Hinode and SDO instruments. If we can obtain accurate force-free coronal magnetic field models we can calculate the free magnetic energy in the corona, a quantity which is important for the prediction of flares and coronal mass ejections. Knowledge of the 3D structure of magnetic field lines also help us to interpret other coronal observations, e.g., EUV images of the radiating coronal plasma.

Thomas Wiegelmann

2012-09-01

387

Predicting Ground Illuminance  

Science.gov (United States)

Our Sun outputs 3.85 × 1026 W of radiation, of which ?37% is in the visible band. It is directly responsible for nearly all natural illuminance experienced on Earth's surface, either in the form of direct/refracted sunlight or in reflected light bouncing off the surfaces and/or atmospheres of our Moon and the visible planets. Ground illuminance, defined as the amount of visible light intercepting a unit area of surface (from all incident angles), varies over 7 orders of magnitude from day to night. It is highly dependent on well-modeled factors such as the relative positions of the Sun, Earth, and Moon. It is also dependent on less predictable factors such as local atmospheric conditions and weather. Several models have been proposed to predict ground illuminance, including Brown (1952) and Shapiro (1982, 1987). The Brown model is a set of empirical data collected from observation points around the world that has been reduced to a smooth fit of illuminance against a single variable, solar altitude. It provides limited applicability to the Moon and for cloudy conditions via multiplicative reduction factors. The Shapiro model is a theoretical model that treats the atmosphere as a three layer system of light reflectance and transmittance. It has different sets of reflectance and transmittance coefficients for various cloud types. Ground illuminance data from an observing run at the White Sands missile range were obtained from the United Kingdom Meteorology Office. Based on available weather reports, five days of clear sky observations were selected. These data are compared to the predictions of the two models. We find that neither of the models provide an accurate treatment during twilight conditions when the Sun is at or a few degrees below the horizon. When the Sun is above the horizon, the Shapiro model straddles the observed data, ranging between 90% and 120% of the recorded illuminance. During the same times, the Brown model is between 70% and 90% of the observed value. While the results are preliminary, the Shapiro model appears to have better predictive power than does the Brown model.

Lesniak, Michael V.

2014-01-01

388

Forces on the conductors of the Arc AG Magnet  

Energy Technology Data Exchange (ETDEWEB)

In the evaluation of the design of the support system for the Arc AG Magnets, factors which could deform or move the magnet have to be considered. Typically they are the ground movements, temperature effects, water vibrations, magnetic forces on the magnet and coil, and accidental human or equipment impacts. This note calculates the magnetic forces on the conductors at an excitation for a 50 GeV beam. It is found that the force is not negligible; therefore, a method to restrict the movement of the conductors should be introduced.

Weng, W.T.

1983-12-28

389

Approximate photochemical dynamics of azobenzene with reactive force fields  

Science.gov (United States)

We have fitted reactive force fields of the ReaxFF type to the ground and first excited electronic states of azobenzene, using global parameter optimization by genetic algorithms. Upon coupling with a simple energy-gap transition probability model, this setup allows for completely force-field-based simulations of photochemical cis?trans- and trans?cis-isomerizations of azobenzene, with qualitatively acceptable quantum yields. This paves the way towards large-scale dynamics simulations of molecular machines, including bond breaking and formation (via the reactive force field) as well as photochemical engines (presented in this work).

Li, Yan; Hartke, Bernd

2013-12-01

390

Force field development on pigments of photosystem 2 reaction centre.  

Czech Academy of Sciences Publication Activity Database

. Ro?. 43, ?. 3 (2005), s. 417-420. ISSN 0044-5231Grant CEP: GA ?R GP206/02/D177Výzkumný zám?r: CEZ:AV0Z50510513; CEZ:AV0Z60870520Klí?ová slova: photosystem 2Kód oboru RIV: CF - Fyzikální chemie a teoretická chemieImpakt faktor: 0.750, rok: 2005

Palen?ár, Peter

391

Ab initio theories of nuclear structure and reactions  

Science.gov (United States)

The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. In addition to the complex nature of nuclear forces with two-nucleon, three-nucleon and possibly even four-nucleon components, one faces the quantum-mechanical many-nucleon problem governed by an interplay between bound and continuum states. In recent years, significant progress has been made in ab initio nuclear structure and reaction calculations based on input from QCD employing Hamiltonians constructed within chiral effective field theory. I will discuss recent breakthroughs that allow for ab initio calculations for ground states and spectroscopy of nuclei throughout the p- and sd-shell and beyond with two- and three-nucleon interactions. I will highlight results obtained within the NCSM, CCM, QMC, and nuclear lattice EFT. I will also present new ab initio many-body approaches capable of describing both bound and scattering states in light nuclei simultaneously and discuss results for reactions important for astrophysics, such as ^7Be(p,?)^8B radiative capture, and for ^3H(d,n)^4He fusion.

Navratil, Petr

2012-10-01

392

Applying Grounded Theory  

Directory of Open Access Journals (Sweden)

Full Text Available Application of grounded theory (GT is a relatively neglected topic by my colleagues. I have written several chapters in my books on applying GT. Two colleagues, Odis Simmons and Barbara Artinian (2009, as well as Dirks and Mills (2011, and Walsh (2014, have also written about applying GT. In the first two chapters of this book I discuss at length properties of generally applying GT and then professional issues and personal matters when applying of GT. There follows in this book nine chapters, four by me and one by Simmons and one by Artinian and one by Dirks and Mills, that are already published in books on GT, and one by Walsh. Thus, this book ends like a reader which publishes in one place already written work. The reader of this book may experience some redundancy in these chapters, but that is the nature of reader texts as different authors discuss the same ideas and topics.

Barney G. Glaser, PhD, Hon. PhD

2014-06-01

393

RSOI: Force Deployment Bottleneck.  

Science.gov (United States)

This study uses The Theory Of Constraints (TOC) management methodology and recent military missions to show that RSOI operations are generally the limiting constraint to force deployment operations. This runs counter to the popular belief that strategic l...

M. A. D'Amato

1998-01-01

394

Yorkshire Forced Rhubarb  

than its counterparts, due to differing production techniques and traditional ... \\initially purchased from Nuclear stock Association (not now available). The only \\way to ... track of where roots come from and where they are planted forward. \\Forced ...

395

Packing force data correlations  

International Nuclear Information System (INIS)

One of the issues facing valve maintenance personnel today deals with an appropriate methodology for installing and setting valve packing that will minimize leak rates, yet ensure functionality of the the valve under all anticipated operating conditions. Several variables can affect a valve packing's ability to seal, such as packing bolt torque, stem finish, and lubrication. Stem frictional force can be an excellent overall indicator of some of the underlying conditions that affect the sealing characteristics of the packing and the best parameter to use when adjusting the packing. This paper addresses stem friction forces, analytically derives the equations related to these forces, presents a methodology for measuring these forces on valve stems, and attempts to correlate the data directly to the underlying variables

1994-07-01

396

SOFIE instrument ground calibration  

Science.gov (United States)

Space Dynamics Laboratory (SDL), in partnership with GATS, Inc., designed and built an instrument to conduct the Solar Occultation for Ice Experiment (SOFIE). SOFIE is the primary infrared sensor in the NASA Aeronomy of Ice in the Mesosphere (AIM) instrument suite. AIM's mission is to study polar mesospheric clouds (PMCs). SOFIE will make measurements in 16 separate spectral bands, arranged in eight pairs between 0.29 and 5.3 ?m. Each band pair will provide differential absorption limb-path transmission profiles for an atmospheric component of interest, by observing the sun through the limb of the atmosphere during solar occultation as AIM orbits Earth. A pointing mirror and imaging sun sensor coaligned with the detectors are used to track the sun during occultation events and maintain stable alignment of the sun on the detectors. Ground calibration experiments were performed to measure SOFIE end-to-end relative spectral response, nonlinearity, and spatial characteristics. SDL's multifunction infrared calibrator #1 (MIC1) was used to present sources to the instrument for calibration. Relative spectral response (RSR) measurements were performed using a step-scan Fourier transform spectrometer (FTS). Out-of-band RSR was measured to approximately 0.01% of in-band peak response using the cascaded filter Fourier transform spectrometer (CFFTS) method. Linearity calibration was performed using a calcium fluoride attenuator in combination with a 3000K blackbody. Spatial characterization was accomplished using a point source and the MIC1 pointing mirror. SOFIE sun sensor tracking algorithms were verified using a heliostat and relay mirrors to observe the sun from the ground. These techniques are described in detail, and resulting SOFIE performance parameters are presented.

Hansen, Scott; Fish, Chad; Romrell, Devin; Gordley, Larry; Hervig, Mark

2006-09-01

397

Decentralized Ground Staff Scheduling  

DEFF Research Database (Denmark)

Typically, ground staff scheduling is centrally planned for each terminal in an airport. The advantage of this is that the staff is efficiently utilized, but a disadvantage is that staff spends considerable time walking between stands. In this paper a decentralized approach for ground staff scheduling is investigated. The airport terminal is divided into zones, where each zone consists of a set of stands geographically next to each other. Staff is assigned to work in only one zone and the staff scheduling is planned decentralized for each zone. The advantage of this approach is that the staff work in a smaller area of the terminal and thus spends less time walking between stands. When planning decentralized the allocation of stands to flights influences the staff scheduling since the workload in a zone depends on which flights are allocated to stands in the zone. Hence solving the problem depends on the actual stand allocation but also on the number of zones and the layout of these. A mathematical model of the problem is proposed, which integrates the stand allocation and the staff scheduling. A heuristic solution method is developed and applied on a real case from British Airways, London Heathrow Airport. This study shows that decentralization generally increases the number of staff needed compared to centralized planning. The case study also shows that there is a trade-off between the extra staff needed and the quality of the stand allocation. Furthermore, the robustness of solutions with respect to disruptions deteriorates with the number of zones. In practice, the "cost" of introducing decentralization should therefore be weighted against the benefits gained.

Clausen, Jens

2002-01-01

398

Briefing from the Fruit and Vegetables Task Force – Soils 1 ...  

The task force aims to make domestic produce more competitive on grounds of \\cost, ... crops. The physical, chemical and biological properties of soil all \\contribute to the ... organic amendments, such as animal manures, have \\contributed to the poor physical ... and emissions of nitrous oxide, a potent \\greenhouse gas.

399

Force-Measuring Clamp  

Science.gov (United States)

A precision clamp that accurately measures force over a wide range of conditions is described. Using a full bridge or other strain gage configuration. the elastic deformation of the clamp is measured or detected by the strain gages. Thc strain gages transmit a signal that corresponds to the degree of stress upon the clamp. Thc strain gage signal is converted to a numeric display. Calibration is achieved by ero and span potentiometers which enable accurate measurements by the force-measuring clamp.

Nunnelee, Mark (Inventor)

2004-01-01

400

Enhanced radiometric forces  

CERN Document Server

Crookes' Radiometer exploits thermal forces arising from temperature gradients in rarefied gases. This instrument has remained confined to educational physics because of the very small size of the radiometric effect and because of the necessity of an evacuated environment for operation. In this article the physics of this instrument is reviewed, different theories are compared and some general principles are derived. A method for enhancing the radiometric effect and for generating radiometric forces at higher pressures is proposed.

Scandurra, M

2004-01-01