Larger Reaction Force Research Articles

水冷却Er: YAGレーザ骨きりでの低熱侵襲のための照射重複数最適化

Lasers have the capability to remove or cut bone precisely without large reaction forces. However, surgeons have had many difficulties with using lasers during operations because of the thermal damage. In this paper, we propose an optimization the overlapping ratio, using water cooling; for the efficiency of laser bone ablations per unit time without thermal damages for operational application. A water-cooling Er: YAG laser (18.5 J/cm2, λ=2.94μm, 20Hz, 200μs) using optical fiber was operated at 0.5-3.0mm/s moving velocities and repetitions. We focused specifically on the overlapping irradiated area and the interval time between the laser irradiations. Swine scapulae were ablated and its rate and performance were evaluated. The water-cooling Er: YAG laser obtained optimal ablation results when the moving velocity was set at 2.0mm/s; the overlapping ratio is 0.89, and the ablated area along the troughs per unit time was optimized to 0.50mm2/s. Carbonization was not evident at this velocity. Controlling of the laser's moving velocity, we can optimize the ablation ability to 0.50mm2/s at 2.0 mm/s. At this velocity, the mass removal efficiency was at 208 μg/J. This result was almost same with previously conducted results accomplished by free running without water cooling.

The Role of Biomechanics in Maximising Distance and Accuracy of Golf Shots

Golf biomechanics applies the principles and technique of mechanics to the structure and function of the golfer in an effort to improve golf technique and performance. A common recommendation for technical correction is maintaining a single fixed centre hub of rotation with a two-lever one-hinge moment arm to impart force on the ball. The primary and secondary spinal angles are important for conservation of angular momentum using the kinetic link principle to generate high club-head velocity. When the golfer wants to maximise the distance of their drives, relatively large ground reaction forces (GRF) need to be produced. However, during the backswing, a greater proportion of the GRF will be observed on the back foot, with transfer of the GRF on to the front foot during the downswing/acceleration phase. Rapidly stretching hip, trunk and upper limb muscles during the backswing, maximising the X-factor early in the downswing, and uncocking the wrists when the lead arm is about 30 degrees below the horizontal will take advantage of the summation of force principle. This will help generate large angular velocity of the club head, and ultimately ball displacement. Physical conditioning will help to recruit the muscles in the correct sequence and to optimum effect. To maximise the accuracy of chipping and putting shots, the golfer should produce a lower grip on the club and a slower/shorter backswing. Consistent patterns of shoulder and wrist movements and temporal patterning result in successful chip shots. Qualitative and quantitative methods are used to biomechanically assess golf techniques. Two- and three-dimensional videography, force plate analysis and electromyography techniques have been employed. The common golf biomechanics principles necessary to understand golf technique are stability, Newton's laws of motion (inertia, acceleration, action reaction), lever arms, conservation of angular momentum, projectiles, the kinetic link principle and the stretch-shorten cycle. Biomechanics has a role in maximising the distance and accuracy of all golf shots (swing and putting) by providing both qualitative and quantitative evidence of body angles, joint forces and muscle activity patterns. The quantitative biomechanical data needs to be interpreted by the biomechanist and translated into coaching points for golf professionals and coaches. An understanding of correct technique will help the sports medicine practitioner provide sound technical advice and should help reduce the risk of golfing injury.

Running on water: Three-dimensional force generation by basilisk lizards

Water provides a unique challenge for legged locomotion because it readily yields to any applied force. Previous studies have shown that static stability during locomotion is possible only when the center of mass remains within a theoretical region of stability. Running across a highly yielding surface could move the center of mass beyond the edges of the region of stability, potentially leading to tripping or falling. Yet basilisk lizards are proficient water runners, regularly dashing across bodies of water to evade predators. We present here direct measurements of time-averaged force produced by juvenile plumed basilisk lizards (Basiliscus plumifrons) while running across water. By using digital particle image velocimetry to visualize fluid flow induced by foot movement, we show that sufficient support force is generated for a lizard to run across water and that novel strategies are also required to run across a highly yielding surface. Juvenile basilisk lizards produce greatest support and propulsive forces during the first half of the step, when the foot moves primarily vertically downwards into the water; they also produce large transverse reaction forces that change from medial (79% body weight) to lateral (37% body weight) throughout the step. These forces may act to dynamically stabilize the lizards during water running. Our results give insight into the mechanics of how basilisk lizards run across water and, on a broader scale, provide a conceptual basis for how locomotor surface properties can challenge established rules for the mechanics of legged locomotion.

101 中間階免震建物用エレベーターの構造最適化技術の開発

The mid-story seismic isolated building has isolators at the mid-story and it is expected to apply for the seismic retrofit. The elevator for the mid-story seismic isolated building receives strong rail bending stress by the large deformation at the isolated story. To reduce the rail stress, the rail fixing span makes longer at the isolated story. This method has a big advantage for the elevator shaft space, but to realize the long rail fixing span, it is necessary to prevent a large reaction force excited by the car swing motion during an earthquake. To resolve the above problem, we developed a nonlinear finite element model to evaluate the earthquake transient behavior and checked the rail bending stress. The simulation result was evaluated by the experiment.

Sequential pattern load modeling and warning-system plan in modular falsework

This paper investigates the structural behavior of modular falsework system under sequential pattern loads. Based on the studies of 25 construction sites, the pattern load sequence modeling is defined as models R (rectangle), L and U. The study focuses on the system critical loads, regions of largest reaction forces, discrepancy between the pattern load and the uniform load, and the warning-system plan. The analysis results show that the critical loads of modular falsework systems with sequential pattern loads are very close to those with the uniform load used in design. The regions of largest reaction forces are smaller than those calculated by the uniform load. However, the regions of largest reaction forces of three models under sequential pattern loads can be considered as the crucial positions of warning-system based on the measured index of loading. The positions of the sensors for the warning-system for these three different models are not identical.

Efficient Estimation of Effective Mass for Complex Structures under Base Excitations

Traditionally, the two key roles of the effective mass have been (1) for definition of the predominant modes having large reaction forces, especially in relation to the coupling between a spacecraft or a launch vehicle with its payload, and (2) for verification and updating of finite-element models. More recently, the effective-mass concept found its way into the field of vibration testing of space hardware. The main role of vibration testing is to ensure that the structure will survive the launch environment. In the last decade, NASA Jet Propulsion Laboratory (JPL) has led the development and implementation of the force-limited vibration (FLV) method aimed at reducing the overtesting associated with conventional vibration testing. Two of the approaches for defining the reaction-force limits used by FLV are based on the concept of effective mass.This paper presents first an overview of the concept of effective mass. Then, it describes an efficient methodology, which has been implemented for extracting effective-mass values from the reaction force frequency response function and initial data processing with commercial modal analysis software. The paper includes the results of an experimental demonstration of the approach on a complex test article. The results are also been compared with those obtained from a finite-element method.

Relation between ankle joint dynamics and patellar tendinopathy in elite volleyball players.

Ankle joint complex dynamics developed during volleyball spike jumps take-offs and landings were quantified to assess potential relations between these joint dynamics and patellar tendinopathy. Three-dimensional kinematic data provided information about movements of the lower limbs, while the kinetic data permitted analysis of ground reaction forces as players took-off and landed from full-speed spike jumps. Simulated volleyball court with net in a biomechanics research laboratory. 10 members of the Canadian Men's National Volleyball Team. From history and physical examination, 3 of the 10 players had patellar tendon pain associated with activity and were diagnosed with patellar tendinopathy at the time of the study. Investigators were blinded about the injury status of the players. None. Three-dimensional kinematics and joint moments of the ankle, knee, and hip joints. Our analysis revealed that maximal external tibial rotation occurred at or near maximal dorsiflexion while maximal internal tibial rotation coincided with maximal plantarflexion. The plantarflexion moment was 3 to 10 times greater than all the other moments measured, with the maximal plantarflexor moment being calculated at 0.4 BWm (360 Nm). In blinded logistic regression analyses, we found one of the dynamics variables (inversion moment during the landing of the spike jump) was a significant predictor of patellar tendinopathy. Coupling the results of the current analysis of ankle joint complex dynamics with previously reported results of knee joint dynamics related to patellar tendinopathy suggests that a cluster of variables linked to patellar tendinopathy includes: high ankle inversion-eversion moments, high external tibial rotation and plantarflexion moments, large vertical ground reaction forces, and high rate of knee extensor moment development.

Measures to prevent cricket injuries: an overview.

Cricket is a major international sport, generally played in British Common-wealth nations. Although strictly a non-contact sport, injuries in cricket can result in a number of ways. In high level cricket, overuse injuries are common and related to the physical demands of the sport, particularly in the delivery of the ball. The bowling action involves repetitive twisting, extension and rotation of the trunk at the same time as absorption of large ground reaction forces over a short period of time. These movements, if performed incorrectly or too frequently, can lead to overuse injuries of the back, particularly in elite and high level cricketers. Cross-sectional studies have demonstrated that spinal overuse injuries occur more frequently to cricketers adopting a mixed bowling action than to those who favour a front- or side-on bowling technique. Strategies to ensure that cricketers do not adopt the mixed action or bowl too fast for extended periods can prevent these back injuries. Injuries resulting from impacts, generally from the cricket ball, can also occur and are more common during low level competition or informal participation. Because of the potential severity of these impacts, a range of protective equipment ranging from body padding to gloves and face protectors are now common features of standard cricket equipment. Although a number of measures to prevent cricket injuries have been widely suggested in the literature, there have been very few studies that have formally assessed their effectiveness in preventing injury. Further research is needed to gain a greater understanding of the biomechanics of cricket actions, the mechanisms of resultant injuries and the role of various risk factors in injury causation.

State switched transducers: A new approach to high-power, low-frequency, underwater projectors

In order to produce high-amplitude, low-frequency signals, an underwater transducer must generate a relatively large volume displacement. Since water exerts a large reaction force back on the transducer, “conventional wisdom” dictates that such a transducer would have to be a high Q resonant device and thus not be broadband. However, a transducer does not have to be broadband in the conventional sense to meet the requirements of communication and sonar systems. A transducer that is capable of instantaneously switching between two discrete frequencies is adequate for communication and transmission of coded signals; one that is capable of switching among several frequencies could produce the chirp signals commonly used in active sonars. Ordinarily, a broadband transducer is needed to accomplish the frequency switching rapidly. A way around this difficulty is the “state-switched” source concept originally proposed by Walter Munk in 1980 which permits instantaneous frequency switching of a high Q resonant transducer while always maintaining the resonance state. The objective of this research has been to investigate this novel approach to the design of high-power, low-frequency, broadband transducers for use in long-range underwater communication, active sonar, and underwater research applications. This paper presents a practical realization of a “state-switched” source.

Discomfort from pneumatic tool torque reaction: Acceptability limits

Pneumatic shut-off nut runners may produce large reaction forces to the operator's hand, especially at the end of the securing of threaded fasteners. These reaction forces depend on the shut-off mechanism, the joint hardness, tool torque level and to some extent the physical properties of the tool. The objective of this study was to find acceptability limits for the discomfort from pneumatic tool torque reaction forces that could be related to technical test measures of the tools. In a study at a truck assembly industry 38 workers participated. Reaction forces, tool handle displacements and subjective discomfort ratings were measured. The tools were first tested according to ISO 6544 in the laboratory and the tool torque impulse was calculated. Strong correlations between tool handle displacements ( r = 0.952), reaction forces ( r = 0.981, vertical force) and ratings were found. Acceptability limits for ratings, tool handle displacements and reaction forces were also determined. No subject would accept to work a whole workday at a discomfort level over 9 on a 20-point scale and all would work a whole workday at a discomfort level of 2. These limits could then be correlated to the tool torque impulse measures from the technical test, thus making it possible to predict how many of the assemblers would work within acceptance limits.

State switched acoustic source

To produce high amplitude low-frequency signals, an underwater transducer must generate a relatively large volume displacement. Since water exerts a large reaction force back on the transducer, ‘‘conventional wisdom’’ dictates that such a transducer would have to be a high Q resonant device and thus not be broadband as seemingly required for many applications. However, a transducer does not have to be broadband in the conventional sense to work in communication and SONAR systems. A transducer capable of switching between two discrete frequencies is adequate for communication and one capable of switching among several frequencies could produce chirp signals for active sonars. Ordinarily, a broadband transducer is needed to switch frequencies rapidly. It is theoretically possible, however, to instantaneously switch frequencies with a high Q resonant system provided that the system’s resonant and drive frequencies are altered simultaneously. Such a ‘‘state-switched’’ transducer [Munk, Webb, Birdsall, unpublished (1980), (1981)] would retain the advantages (high power, high efficiency, and large displacements) of a high Q resonant transducer without the accompanying disadvantage of slow response time. A state-switched acoustic source with an active spring of PZT has been built to demonstrate the state switching concept. [Research supported by ONR 334.]

片側性変形股関節症患者の歩行解析 同一人の術前・術後の比較

We studied 6 unilateral osteoarthritic hip patients before and after total hip replacement, and compared them, using a large floor reaction force plate. The average age of patients was 56.4 years at operation. The mean follow-up was 13.8 months after the last T. H. R.. The “weighing-off” effect ratio, indicating smooth ambulation of the bodies center of gravity, increased (p=0.075) after T. H. R. in comparison with before surgery. The stance phase duration ratio increased (p=0.10), but maximal walking speed did not increase after T. H. R. in comparison with before surgery. This improvement can be quantified, documented, and followed by using a system of gait evaluation.

Functional anatomy of the head of the large aquatic predatorRhomaleosaurus zetlandicus(Plesiosauria, Reptilia) from the Toarcian (Lower Jurassic) of Yorkshire, England

The skull and mandible of the type specimen of the large pliosauroid plesiosaurRhomaleosaurus zetlandicusfrom the Toarcian of England are elongate, and adapted for powerful predatory activity in water. The mandible contains all elements found in primitive reptilian mandibles. The broadly caniniform dentition suggests thatRhomaleosaurusfed on a wide range of active prey, and forcibly dismembered larger prey by shaking and twisting them. The cranial musculature is reconstructed for the first time in plesiosaurs. It was adapted for feeding in water. The adductor musculature included a large anterior pterygoideus attached to the suborbital fenestra, a large posterior pterygoideus, and a group of large dorsal muscles including the adductor mandibulae externus. The anterior pterygoideus exerted maximum torque when the jaws were wide open, snapping them shut quickly, and the dorsal muscle mass exerted maximum torque when the jaws were closed on prey to subdue and dismember it. The role of the posterior pterygoideus is uncertain or intermediate. The musculature combines elements of the "kinetic inertial’ system ascribed to aquatic tetrapods by Olson (1961), with his ‘static, pressure’ system ascribed to terrestrial tetrapods. Olson suggested that the large pterygoideus musculature typical of the ‘kinetic inertial’ system functioned to confer kinetic energy on the mandible. However, its function may instead have been to compensate for the inertia and drag of the mandible. The depressor musculature comprised the depressor mandibulae and the longitudinal pharyngeal muscles, and opened the jaw quickly against drag. The cervical musculature cannot be reconstructed in detail. There was a strong nuchal ligament. The forces within the head are analysed by using box and girder beams as analogues. Gross form, shape of constituent bones, and sutural morphology confirm adaptations to resist great bending moments arising from the action of the muscles when biting on prey. When the jaws were closed, the pterygoid flange supported the mandible against the inward component of the adductor muscle force.Rhomaleosauruswas a visual predator. The eyes were large. The stapes is present. Underwater olfaction was likely. There is no evidence for an eardrum, but it is not known whether this is the plesiomorphic reptilian state or secondarily derived from a tympanate ancestor. The ears were not acoustically isolated from the braincase, so underwater directional hearing was poor, and sonar was not possible. The structure of the head ofRhomaleosaurusis a functional compromise between the needs to maximize structural strength and to maximize swimming and feeding efficiency. Especially important were the ability to sustain large muscle and reaction forces to provide an adequate bite force at the end of a long snout, and the wide gape allowing the swallowing of large pieces of prey. Even larger items were dismembered into smaller pieces by shake and twist feeding. The major unresolved problems are the effects of scaling factors, and the torsional loadings induced when biting asymmetrically, or twisting large prey to pieces.

Assembly Performance of a Robotic Vibratory Wrist

In precision assembly, even small misalignment between two mating parts can cause large reaction forces and thus make the assembly task be impossible. This paper considers a vibratory assembly method which can compensate such misalignment for successful insertion task. For this purpose a PWM controller-based pneumatic vibratory wrist is used to investigate assembly performance such as search time, assembly force and correctable error range. Since they are critically dependent upon various system parameters, they were experimentally investigated for a chamferless peg-in-hole assembly task. Experimental results show that the proposed method yields good assembly performance; compensation of large initial error, fast searching and small reaction forces.

Hybrid Control of a Manipulator and its Application

In complex asks such as sewing or assembly, where a robot has a mechanical interaction with its environments, we cannot expect to get a good result only by using the conventional positioning control of the robot. This is because that even the smallest positioning error may cause a large reaction force between the robot and its object, then it will stop the motion required for the task or, the worst case, it will damage the object as well as the robot itself. From this point of view, various kinds of control methods which enable a robot to move compliantly to avoid producing an excessive force when there is an interaction between the robot and objects In this paper we will propose a hybrid control method which can control both position and force of the manipulator in the given task-oriented coordinates. We can expect to have a good task quality by using this method compared with the conventional positioning control. The experiments of some actual tasks using an articulated manipulator with 2 d.o.f. will be also shown to demonstrate the feasibility and applicability of the proposed method.