Biomechanical analysis of circles on pommel horse

The aim of this study was to analyse the principal mechanics of circles. Seventeen university male gymnasts performed circles on an instrumented pommel horse model that enabled the pommel reaction forces to be recorded at 1000 Hz with two force plates. The circles were also videotaped using two digital video cameras operating at 60 frames per second. During circles, the vertical component of the reaction forces peaked in the double-hand support phases. Changes in the velocity of the centre of mass corresponded to the change in the tangential components of horizontal reaction forces. The velocity of the centre of mass had its peaks in the single-hand support phases and its local minimums in the double-hand support phases. The velocity of the ankles and that of the centre of mass of the head and trunk were minimal in the single-hand support phases and were maximal in the double-hand support phases. These results suggest that the circles were composed of vertical movements and two kinds of rotations: rotation of the centre of mass and rotation of the body itself about the centre of mass. These two kinds of rotations, which influence the legs' rotational velocity, are phase dependent. To further our understanding of circles, research on circles in different orientations on the pommel horse will be beneficial.     

Circles on pommel horse with a suspended aid: influence of expertise

In the third study of this series, we examined how circles with a suspended aid would vary depending of the gymnast's level of expertise. We analysed circles with the aid performed by three groups of eight gymnasts: expert, intermediate, and developing groups. The gymnasts for the expert and intermediate groups were selected from the previous studies based on judges' evaluation of their non-aid circles. The developing group of eight gymnasts, who were unable to perform circles on pommel horse without an aid, were added to this study and performed three sets of 10 circles on the pommel horse with the aid. Discriminative biomechanical variables identified in the previous two studies were used to compare circles with the aid among the three groups. As a result, the expert group demonstrated a larger pommel reaction force and a smaller aid reaction force than the other two groups, implying that they were less dependent on the aid. The smaller aid reaction force resulted in a smaller net hip joint moment. Furthermore, the expert group showed a shorter total duration and a greater shoulder excursion. In summary, the suspended aid can be used in a progressive manner depending on the gymnast's level of expertise.     

Generalized procedure of the reduction method for vibrating problems of orthotropic plates

A reduction method is proposed for deriving an approximate formula for estimating the natural frequency of an orthotropic plate by using the results of an isotropic one. To justify the method, approximate formulae for estimating the natural frequency of clamped orthotropic rectangular and elliptical plates are derived from results previously reported for clamped isotropic rectangular and elliptical ones, respectively. The accuracy of the approximate formulae is discussed.     

Circles on pommel horse with a suspended aid: Mass-centre rotation and hip joint moment

Abstract

This is the second study of the series, and its aim was to investigate the influence of using the suspended aid on circle kinetics. In addition to the kinematic data recorded for part one (Fujihara & Gervais, 2012), the pommel reaction forces and the force applied from the suspended aid (aid reaction force) were analysed in relation to the motion of a whole-body mass centre. The hip joint moment was also computed by combining all segments in the lower extremities into a single rigid segment. Generally, the use of the aid changed the magnitude of the mass-centre trajectory or horizontal pommel reaction forces but not their patterns. The results also showed that the net hip joint moment was altered during circles with the aid. In summary, a suspended aid can be used as a progression for a variety of goals because it allows gymnasts to practise circles which would not be possible without the aid. When a suspended aid is used, however, practitioners should be aware of the possible kinetic alteration caused by the external force from the aid.     

Inverting microwell array chip for the cultivation of human induced pluripotent stem cells with controlled aggregate size and geometrical arrangement

We present a novel cell culture chip, namely, “inverting microwell array chip,” for cultivation of human induced pluripotent stem cells. The chip comprises a lower hydrogel microwell array and an upper polystyrene culture surface. We demonstrate the formation of uniform cellular aggregates in the microwell array, and after inversion, a culture with controlled aggregate size and geometrical arrangement on the polystyrene surface. Here, we report effects of cell concentrations on a cultivation sequence in the chip.     

Demonstration of pelvic anatomy by modified midline transection that maintains intact internal pelvic organs

Gross dissection for demonstrating anatomy of the human pelvis has traditionally involved one of two approaches, each with advantages and disadvantages. Classic hemisection in the median plane through the pelvic ring transects the visceral organs but maintains two symmetric pelvic halves. An alternative paramedial transection compromises one side of the bony pelvis but leaves the internal organs intact. The authors propose a modified technique that combines advantages of both classical dissections. This novel approach involves dividing the pubic symphysis and sacrum in the median plane after shifting all internal organs to one side. The hemipelvis without internal organs is immediately available for further dissection of the lower limb. The hemipelvis with intact internal organs is ideal for showing the complex spatial relationships of the pelvic organs and vessels relative to the intact pelvic floor. Anat Sci Educ 3:254–260, 2010. © 2010 American Association of Anatomists.     

日本建筑节能对策

通过对日本建筑节能对策的介绍,从法规、技术标准、评价制度、节能服务等方面分析了日本当前建筑节能状况.借鉴日本的经验,认为我国在完善建筑节能法规体系的同时,应制定有效的建筑节能评价体系和节能认证制度,实施节能建筑建设的经济激励政策,加强建筑节能知识的普及与教育.     

差分精度对液压滑阀内流体数值解析的影响

：以液压控制系统中常用的滑阀为研究对象，通过对滑阀内流体流动的仿真计算，对本中采用的数值解析手法的差分方法、空间计算格子系等计算参数对计算结果的影响进行了分析和讨论。结果表明，上述计算参数对流场构造以及流量的计算结果影响相对较小。2种不同计算方法对滑阀轴向流体力的分析比较得出：作用在滑阀轴方向上的流体力对差分方法、空间计算格子系等计算参数非常敏感。如要得到较高精度的计算结果，采用压强和壁面切应力来直接计算流体力要比应用控制体内流体的动量守恒原理需要更密的计算格子系。这一结果有助于我们在进行流场数值计算时，根据不同的对象选取合适的解析手法和计算参数，节省计算时间，提高计算效率。     

The perceptions of information systems designers from the United States, Japan, and Korea on success and failure factors

This study examined the views of information systems (IS) designers from the United States, Japan and Korea on the importance of IS development factors in terms of how they contribute to both the success and failure of IS projects. IS designers from the US viewed Communication of the Project Goals and Characteristics of the IS Designers as more important than did the IS designers from Japan and Korea, but rated Characteristics of the Project Leader as less important. The results also indicated that the IS designers did not view the relative importance of the IS development factors, the same in terms of contributing to the success and failure of IS projects. Results obtained from the US sample were consistent with a self-serving bias, while the results obtained from IS designers from Japan were consistent with a self-effacing bias. No significant differences between the success and failure factors were observed for the Korean sample. It was noted that a self-serving bias may prevent IS designers from learning based on past experiences with IS failure.