Influence of two different modes of resistance training in female subjects

In resistance training, it has been empirically accepted that muscle hypertrophy is developed by low intensity and high volume training, while muscle strength and power are developed by high intensity and low volume training. The purpose of the present study was to investigate the influence of two different modes of resistance training on isokinetic strength and muscle cross-sect tonal area (CSA) in females. Eleven females, who had no experience in resistance training, participated in this study and were randomly divided into two groups. The former consisted of 4-5 sets of 15-20 RM (repetition maximum) with sufficient rest between sets (Group H), while the latter consisted of 8-9 sets of 4-6 RM with 90s of rest between sets (Group S). The former was assumed to be appropriate for muscle hypertrophy and the latter muscle strength, respectively. All subjects completed isotonic knee extension exercise three times a week for 8 weeks. Measurements were made on quadriceps muscle cross-sectional area (CSA) and isokinetic torques at 0, 60, 180, and 300°/s before training, at the fifth week and the end of training period. Muscle CSA was defined as the sum of CSA measured at 30, 50 and 70% of femur length, After training, muscle CSA had significantly increased in both groups: 3·3 ± 0·7% (p <·05) for group H and 3·6 ± 1·1% (p < ·05) for group S, respectively. While the changes in isokinetic torque were 43·4 ± 47·5% (p <·05) for group H and 27·4 ± 31·3% (p <·05) for group S, respectively. In both groups the percentage changes of the isokinetic strength were significantly higher than those of the CSA. No significant difference in these variables were found between the two groups. These results suggest that during the early phase of resistance training two different modes of resistance training may have similar effects on muscle CSA and isokinetic strength in untrained females.     

Optimum shapes of bar cross-sections

In this paper, the problems of optimization of cylindrical bar cross sections are formulated. The functional considered characterizes rigidities, maximum stress and the areas of the cross-section of the bar. The shape of the boundary of the cross-section is taken as a design variable and is found in the case of regular polygonal contours. Using minimax approaches optimal designs have been obtained for simply connected and doubly connected cross-sections having given convex holes. Investigations performed and complete solutions derived from the cross-sectional area minimization under rigidity and strength constraints show the changes of the optimal shapes as functions of the problem parameter. Received September 29, 2000     

Optimal cross-sectional area distribution of a high-speed train nose to minimize the tunnel micro-pressure wave

Optimization of the cross-sectional area distribution of a high-speed train nose is conducted for various nose lengths in order to minimize the micro-pressure wave intensity at a tunnel exit. To this end, an inviscid compressible flow solver is adopted with an axi-symmetric patched grid system. To improve the shape of the train nose, multi-step design optimization is performed using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) algorithm with a response surface model. The optimization reveals that the optimal nose shapes differ for different nose lengths. For a short nose, the shape has an extremely blunt front end, and the cross-sectional area decreases in the middle section. As the nose length increases, the nose shape flattens around the middle section. These optimal shapes divide one large compression wave into two small waves by causing a strong expansion effect between the front and rear ends. As a result, through the nose shape optimization, the intensity of the micro-pressure wave is reduced by 18–27% compared to a parabolic nose, which has a minimum variation of the cross-sectional area change. The optimized distribution of the cross-sectional area can be used as a guideline for the design of three-dimensional nose shapes of high-speed trains, further improving their aerodynamic performance.     

Design and modeling of a single-mass biaxial capacitive accelerometer based on the SUMMiT V process

This paper presents the design of a biaxial capacitive accelerometer that takes advantages of a single-mass configuration to provide two orthogonal axes of sensitivity. The accelerometer structure is based on the SUMMiT V fabrication process. A set of fixed electrodes provides reliable measurements of capacitance in the two orthogonal directions. An analytical model based on the Euler-Bernoulli stress theory is introduced for variable cross-sectional area beams and is validated with a finite element analysis. In order to avoid a short circuit between fixed and movable electrodes, four displacement limiters were designed. The displacement limiters prevent out-of-plane displacement of the seismic mass and can withstand an impact of 250,000 G. A two-dimensional transient analysis of the seismic mass was carried out to confirm a linear oscillation behavior for either direction on the operation plane. The natural frequencies in the vibration modes of the two axes of interest are 462.5 and 463.2 Hz. It is also shown that the principal stresses in the beams are smaller than the fracture strength of polysilicon.     

Weld contour measurement of fillet welds by the reverse engineering technique

The external geometry of a fillet weld plays an important role in the strength of the weld. Two factors that influence the external geometry of the fillet weld are weld size and profile. The fillet weld must be made to the weld size and profile as specified in the welding code. An unacceptable profile not only is a defect of the weld but also produces stress risers that reduce the fatigue strength. An insufficient weld that reduces the cross-sectional area of weld throat may cause premature failure. Visual inspection and weld gauges are two of the most widely used simple tools to provide a rapid assessment of the external geometry of the fillet weld. In this study, the reverse engineering technique, in which a laser scanning system integrates with CAD software, is used to provide a more accurate measurement of the weld contour. The weld samples were made of low-carbon steel plates with a T-joint using CO₂ welding. The weld volume, weld size, and convexity were determined from the CAD model to evaluate the weld quality. The reverse engineering technique provides a more accurate and efficient method to inspect the external geometry of the fillet weld.     

Modeling of transfer length of prestressing strands using genetic programming and neuro-fuzzy

In this study, the efficiency of neuro-fuzzy inference system (ANFIS) and genetic expression programming (GEP) in predicting the transfer length of prestressing strands in prestressed concrete beams was investigated. Many models suggested for the transfer length of prestressing strands usually consider one or two parameters and do not provide consistent accurate prediction. The alternative approaches such as GEP and ANFIS have been recently used to model spatially complex systems. The transfer length data from various researches have been collected to use in training and testing ANFIS and GEP models. Six basic parameters affecting the transfer length of strands were selected as input parameters. These parameters are ratio of strand cross-sectional area to concrete area, surface condition of strands, diameter of strands, percentage of debonded strands, effective prestress and concrete strength at the time of measurement. Results showed that the ANFIS and GEP models are capable of accurately predicting the transfer lengths used in the training and testing phase of the study. The GEP model results better prediction compared to ANFIS model.     

Surface micromachined polysilicon heart cell force transducer

A microelectromechanical systems (MEMS) force transducer system, with a volume less than 1 mm³ millimeter, has been developed to measure forces generated by living heart muscle cells. Cell attachment and measurement of contractile forces have been demonstrated with a commercially fabricated surface-micromachined hinged polysilicon device. Two freestanding polysilicon clamps, each suspended by a pair of microbeams, hold each end of a heart cell. When the cell contracts, the beam bend and force is determined from the measured deflection and the spring constant in the beams. The average maximal force over seven contractile experiments using a calcium solution stimulus was F_max =12.6±4.66 μN. Normalizing to a cross-sectional area, F _max/area was 23.7±8.6 mN/mm². These force data were also correlated to optically imaged striation pattern periodicity. Intermediate forces were also measured in response to a calcium solution gradient and showed similar behavior to those measured in other laboratories. This MEMS force transducer demonstrates the feasibility of higher fidelity measurements from muscle cells and, thus, an improved understanding of the mechanisms of muscle contraction     

Minimal area cross-sectional shape for a bar with prescribed lower bounds on stiffness in bending and torsion

This paper establishes the minimum cross-sectional area for an externally convex, hollow, prismatic bar subjected to minimum constraints on the second moment of area and on torsional rigidity. Some properties of the solution established by previous workers are assumed. Prandtl's stress function is expressed as a series in polar coordinates and the cross-sectional shapes are found by the semi-inverse method. The convexity constraint is expressed in a form suitable for application of mathematical programming methods. The optimal shapes were found by quadratic programming and generalized reduced gradient methods. Numerical results are given for typical examples, both for a circular hole and with the hole shape included in the optimization.     

The interaction between lid diameter,height and shape on wrist torque exertion in younger and older adults

The following study investigated wrist torque strength measurements of a group of younger and older adults. The aim of the study was to examine the impact of shape, diameter and height of lid on wrist torque opening strength. Forty participants took part in the study in four groups, younger males and females and older males and females. Data were collected for 12 test pieces. Anthropometric data were also obtained for stature, weight, hand breadth, hand length, chuck grip force, grip force, lateral grip force and pinch grip force. The analysis of the wrist torque strength measurements found that participants could exert greater force with square test pieces compared to circular test pieces of the same diameter. Examination of the circular test pieces found that as diameter and height increased, so did torque exertion data for the test pieces between 20 mm and 50 mm diameter. The surface area of the test pieces was found to be highly correlated with the level of torque exertion, thus a linear model was developed to describe this relationship. The model could be used to predict maximal torque closure levels for use in the packaging industry. The anthropometric data revealed that as height, weight, hand length and hand breadth increased, there was a correlation with the levels of torque exerted. Future research needs to further examine the relationship between surface area and torque exerted and the design of spherical lids to increase the contact area between the hand and the lid.     

The interaction between lid diameter,height and shape on wrist torque exertion in younger and older adults

The following study investigated wrist torque strength measurements of a group of younger and older adults. The aim of the study was to examine the impact of shape, diameter and height of lid on wrist torque opening strength. Forty participants took part in the study in four groups, younger males and females and older males and females. Data were collected for 12 test pieces. Anthropometric data were also obtained for stature, weight, hand breadth, hand length, chuck grip force, grip force, lateral grip force and pinch grip force. The analysis of the wrist torque strength measurements found that participants could exert greater force with square test pieces compared to circular test pieces of the same diameter. Examination of the circular test pieces found that as diameter and height increased, so did torque exertion data for the test pieces between 20 mm and 50 mm diameter. The surface area of the test pieces was found to be highly correlated with the level of torque exertion, thus a linear model was developed to describe this relationship. The model could be used to predict maximal torque closure levels for use in the packaging industry. The anthropometric data revealed that as height, weight, hand length and hand breadth increased, there was a correlation with the levels of torque exerted. Future research needs to further examine the relationship between surface area and torque exerted and the design of spherical lids to increase the contact area between the hand and the lid.     

On the optimal shape of a compressed column subjected to restrictions on the cross-sectional area

By using Pontryagin’s principle we study the optimal shape of an elastic compressed column with clamped ends and restrictions on cross-sectional area. The restrictions are imposed on either maximum or both minimal and maximum value of the cross-sectional area. We analyzed a column on elastic foundation of Winkler type and a column without foundation. It is shown that the optimization can be both bimodal and unimodal. We determine the transition value between unimodal and bimodal optimization for specified values of parameters.     

Geometrical integrity of micromold cavity sputtered by FIB using multilayer slicing approach

This paper discusses the investigation of geometrical integrity of micromold cavity produced by focused ion beam (FIB) sputtering slice by slice. Parabolic shaped micromold cavity was chosen as an example. Preliminary experiments were carried out to characterize the machine and select the optimum process parameters such as beam current, pixel spacing, aperture size, and dwell time. The geometrical integrity of the sputtered micromold cavity was analyzed based on three selected criteria such as aspect ratio, cross-sectional area, and area offset. The theoretical and sputtered profiles were compared. The investigation showed that the measured aspect ratio was almost equal to the theoretical aspect ratio for low aspect ratio microcavity. For high aspect ratio cavity, the measured aspect ratio was higher than the theoretical aspect ratio by 5–8%. The area offset was found to be 5–10% of the theoretical area. The variation in theoretical and sputtered cross-sectional area was 2–4%. The characterization showed that the geometrical integrity of micromold cavity sputtered by FIB using slicing approach was high.     

Isodynamic evaluation of trunk muscles and low-back pain among workers in a steel factory

A cross-sectional study was conducted to explore the relationship between dynamic parameters of trunk muscle strength and the occurrence of low-back pain (LBP). Isodynamic strength measurements were performed among 31 male maintenance workers with spells of low-back pain in the past 12 months and 28 maintenance workers without a history of low-back pain. In general, workers with low-back pain showed a lower trunk muscle performance than the workers without low-back pain. Only the measures of torque during lateral movement differed significantly between both groups. Regression analysis revealed the importance of the nature of low-back pain for trunk muscle strength. Most parameters of trunk muscle strength were significantly decreased among workers with chronic low-back pain of a rather severe nature, showing reductions from 18% to 50%. None of the work-related risk factors for low-back pain contributed significantly to the prediction of trunk strength measures. The study suggests that isodynamic evaluation of trunk muscle strength may assist in determining objective measures for the severity of low-back pain rather than in evaluating a subject's capability of successfully coping with a specific work load.     

Micro-scale truss optimization using genetic algorithm

This paper describes the development of a genetic algorithm that is capable of optimizing the mass of micro-scale trusses. Belonging to the group of periodic cellular materials, micro-scale trusses are characterized by the creation of a base cell with a pattern that is repeated in space until a global structure is obtained. Investigation in this field has generally been focused on the design of base cells and their resistance once the final structure is obtained. In this project we have attempted to optimize each individual cell and in particular its elements according to the loads and boundary conditions applied to the global structure. With this objective, we defined a dichotomic search algorithm that establishes a set of cross-sectional areas suitable for the micro-scale truss, formulated the penalty coefficient for the over-sized elements, and studied the clones and rebirth process in order to avoid stagnation of the genetic algorithm. The cell elements used in this project were equal to or less than to 1 mm long, with a cross-sectional area in the order of 10^− 9 m².     

The relationship between maximum isometric strength and intramuscular circulatory occlusion

Twenty male college students served as subjects for lhe study which investigated the relationship between maximum isometric strength and the isometric tension necessary to produce total occlusion of intramuscular circulation. Subjects performed a scries of progressively increasing static contractions by squeezing a hand dynamometer and the subsequent blood flow responses were measured. Blood flow was occluded at a mean of 63-5% maximum handgrip strength for the total group tested. To determine whether individuals of different maximum strength occlude at different percentages of their MVC, subjects were divided into high and low strength groups. The high strength group was found to occlude at 51-5% of MVC while the low strength group occluded at 75-5% of MVC. A significant negative correlation (r= -0.58) was found between maximum isometric strength and the per cent of maximum strength necessary to produce intra-muscular occlusion. There was no significant difference between the absolute tension producing occlusion in the high strength group (34-8 kg) and that of the low strength group (34 3 kg).     

基于RANSAC的公路路面坑槽提取方法

针对基于三维激光点云的坑槽扫描提取算法计算量大、效率低的问题,提出基于RANSAC思想的坑槽提取方法.首先,使用RANSAC计算横断面基准线,矫正横断面数据并初步识别坑槽点及其位置;其次,对坑槽区域使用RANSAC计算坑槽局部基准路面,由此标记出坑槽点及路面点;然后使用种子填充算法进行连通域求解,计算出坑槽点集;最后对...     

跨地区短时间序列的离散化方法

跨地区时间序列是由多个地区组成的多变量时间序列集合,每个地区有着相同的变量集。其时序长度通常比较短。跨地区时间序列在商业、经济、公共管理等领域广泛存在。离散化是时间序列关联规则挖掘的不可或缺的先行步骤。该文介绍了一个新颖的针对跨地区时间序列的离散化方法。相对没有考虑跨地区性质的方法,在跨地区短时序数据上,此方法可以更准确地提取出事件,完成离散化工作。     

一种矿井风量检测仪的设计

针对目前采用机械式或电子式风速计以及米尺或皮尺测量井巷风量方法存在效率低、精度低、准确性差等问题,提出了一种可实现多参数自动测量的矿井风量检测仪的设计方案,介绍了该检测仪的组成、测量原理及软件设计。该仪器采用超声波探头及超声波时差法测量井巷风速,采用激光脉冲法测量测点与巷壁的距离,经计算得出巷道断面积,将校正后的风速与巷道断面积相乘即得到风量值。试验结果表明,该检测仪测量快速,精度较高。下一步将在井下测试该检测仪的准确性。     

高速列车车体数值模拟和优化设计

针对高速列车车体的强度和疲劳损伤问题,对高速动车组车体结构进行有限元分析和强度校核.结果表明,头车和中间车的最大应力均发生在车钩载荷施加附近的极小区域内,且应力值大于许用应力值,此处结构可能产生局部破坏,在车体试验时需要重点关注.为增强车钩强度,采用灵敏度分析方法优化头车车钩载荷施加区域、更改圆孔弧度,在很大程度上降低局部应力峰值,优化设计后的车体满足强度要求.