Concentric and eccentric shoulder rehabilitation biomechanics

The use of an impulse-momentum (IM) exercise technique was investigated for end-stage shoulder rehabilitation. The objectives of this study were to: (a) quantify the net shoulder joint forces and moments while using an IM system and (b) test the influence of gender and muscle loading type (concentric or eccentric) on kinetic and kinematic parameters. Fourteen healthy adults (eight males, six females) performed a repeated measures experiment on an instrumented device utilizing a cabled shuttle system. While maintaining 90 degrees of shoulder abduction and 90 degrees of elbow flexion, the subjects externally rotated their upper arm from 0 degrees to 90 degrees (concentric acceleration) and then internally rotated their upper arm back from 90 degrees to the 0 degrees position (eccentric deceleration). Shoulder joint forces and moments as well as rotational work and power were calculated using inverse dynamics (free-body forces and moments calculated at intersegmental joint centres). Overall concentric peak forces and moments were greater than eccentric peak forces and moments (P < 0.0001). Joint forces and moments reached a maximum during the initial phase of concentric loading (0 degrees to 45 degrees) compared with any other rotational position in the loading cycle (concentric 45 degrees to 90 degrees or eccentric 90 degrees to 0 degrees). The results also indicate that males experienced higher (P < 0.0001) average resultant peak joint forces (concentric 0 degrees to 45 degrees = 108.0 N and eccentric 90 degrees to 45 degrees = 87.2 N) than females (concentric 0 degrees to 45 degrees = 74.7 N and eccentric 45 degrees to 0 degrees = 56.0 N). In addition, males experienced higher (P < 0.0001) average resultant peak joint moments (concentric 0 degrees to 45 degrees = 30.4 N m and eccentric 45 degrees to 0 degrees = 21.0 N m) than females (concentric 0 degrees to 45 degrees = 19.7 N m and eccentric 45 degrees to 0 degrees = 12.8 N m).     

The development of pivot bearing with multiple degrees of freedom: 2nd Report: Prototype of pivot bearing with three degrees of freedom

In this paper, we report a prototype of a new pivot bearing having three degrees of freedom. The idea of the pivot bearing is based on a constant velocity joint (CVJ). In the first report, two types of pivot bearing were designed and produced. Then, the static performance was examined. In this second paper, we have achieved three degrees of freedom by adding a ball bearing mechanism. However, this bearing with three degrees of freedom was larger than the bearing with two degrees of freedom. Then, in order to improve the internal structure, a full complement ball bearing was applied. Thus, the size of the bearing with three degrees of freedom was conformed to the bearing with two degrees of freedom. Furthermore, process accuracy was evaluated.     

一种可应用于板壳成形过程模拟的绝对-相对自由度壳单元

相对自由度壳单元是采用有限元法分析板壳成形过程的一种有效单元形式。它不仅可以解决采用实体单元模拟板壳成形过程所存在的问题 ,同时它与主从自由度壳单元相比还具有简单易用的特点。然而 ,目前尚未见到对该单元边界条件如何进行具体处理的方法的报道。作者的研究表明 ,该类单元应用于模拟薄壁件成形过程时尚不能直接采用置“1”法或置大数法处理其边界条件。为此 ,本文在该单元的基础上提出了一种绝对自由度和相对自由度相结合的壳单元。将该单元应用于薄壁管弯曲过程模拟的结果表明 ,它不仅继承了相对自由度壳单元的优势 ,而且可直接采用置“1”法或置大数法处理边界条件。     

Rheology of bovine bone marrow

The viscosity of bovine bone marrow was measured using samples taken from proximal and distal sites of five radii. The viscosity was found to be independent of shear rate and temperature above 37 degrees C (distal samples) and 42 degrees C (proximal samples). The viscosity of all samples fell to a lower limit of 0.04 Pas above these temperatures, irrespective of the treatments used. Below them the measured viscosity of the proximal marrow was some ten times that of the distal marrow at 35 degrees C and some 15 times that of the distal marrow at 30 degrees C. Below 30 degrees C the proximal marrow solidified. Distal marrow remained liquid to below 20 degrees C.     

五自由度磁悬浮电主轴结构与有限元分析

提出一种五自由度稳定悬浮的电主轴,由二自由度磁悬浮异步电机与三自由度轴向混合磁轴承实现五个自由度的稳定悬浮。其中,三自由度混合磁轴承采用四个定子磁极来控制轴向悬浮力与径向扭转力,可有效减少轴向长度。文中介绍了五自由度磁悬浮电主轴工作原理,建立磁悬浮异步电机和混合磁轴承的数学模型,并用电磁场分析软件welll5．0分析其磁场和悬浮力,验证电主轴的可行性,最后运用biatlab软件建立基于转子磁场定向的无轴承异步电机控制系统,仿真结果表明该控制方法可有效稳定控制电机。     

Self-Alignment Systems for Heavily Loaded,Compliant, Hydrodynamic Air Bearings

Internal and external self-alignment system for compliant-foil journal bearings have been developed and tested at 35000 rpm in ambient air. These system have been shown to substantially improve the self-alignment capabilities of the compliant-foil bearings. The standard bearings with center-split bump have a misaligned capacity of 0.07 degrees at 55 kPa and 0.03 degrees at 83 kPa. Bearings with an internal self-alignment system were shown to have 0.15-degree misalignment capability at 55-kPa loading and 0.06 degrees at 90 kPa. A bearing with an external self-alignment system tolerated 0.43 degrees of misalignment at 69 kPa and 0.37 degrees at 110 kPa. Self-alignment capabilities of the bearings were improved at higher speed. Limited testing at 288°C showed that the temperature had no influence on the bearing performance.     

Cytochrome oxidase activity and confocal laser scanning microscopic analysis of the hamster submandibular gland using microwave irradiated fixation

Submandibular glands of the hamster were irradiated in 2% paraformaldehyde (pFA)-0.5% pure glutaraldehyde (PGA) with a microwave (MW) processor at temperatures of 10 degrees and 37 degrees C. Electron microscopy showed that cytochrome oxidase activity was taking place in the mitochondrial intermembrane-intracristal space of the granular duct cell when the temperature of the MW-irradiated fixatives was at 10 degrees C. However, a decrease of this activity was observed when we took care to keep the temperature of the MW-irradiated fixatives at 37 degrees C. The distinct reduction of cytochrome oxidase activity allowed by MW irradiation seems to be due the thermal affects of fixatives. Of course, the possibility cannot be excluded that MW irradiation caused other undetectable membrane damage. Then, we used confocal laser scanning microscopy for the preservation check of the mitochondrial membrane for cytochemistry with MW-irradiated fixation. The fluorescence of rhodamine 123 was observed in the inner spaces of the mitochondria at temperatures of 10 degrees and 37 degrees C. When the same tissues were fixed with 2% pFA using an MW processor as the sole fixative at 10 degrees C, no mitochondrial fluorescence was observed. Cytochrome oxidase activity, by contrast, could be seen in the mitochondrial intermembrane-intracristal spaces in the same condition. Formaldehyde is not the best aldehyde for the purpose of ultrastructural preservation. On the other hand, light and electron microscopy showed that the endogenous peroxidase activity was localized in the nuclear envelope, endoplasmic reticulum, secretory granules, and Golgi apparatus of the hamster submandibular gland using 2% pFA-0.5% PGA fixative with and without MW irradiations at temperatures of 10 degrees and 37 degrees C. Some of the same cells were fixed with only 2% pFA under MW irradiation at 10 degrees C; however, marked diffuseness of the peroxidase activity was observed. Therefore, these results indicated that cytochrome oxidase activity was sensitive to heat with MW-irradiated fixation. Peroxidase activity was very resistant to heat with MW-irradiated fixation but not with pFA solo fixation, therefore, PGA had to be used.     

Echo-Doppler angle determination for noninvasive transmitral blood velocity calculations in normal and porcine bioprosthetic mitral valves

Doppler incident angle (DA) determination is a critical factor in the noninvasive attempt to measure transmitral blood velocity (TMBV) and to estimate volumetric flow. The error in TMBV varies with the cosine of DA. Using an echo-Doppler duplex scanner (DS), we studied transmitral flow velocities in 10 normal subjects (Group I) and 10 asymptomatic patients with procine mitral valve (PMV) bioprostheses. A 3-MHz scanhead with three medium focused rotating transducers was positioned at the left ventricular apex, and standard apical four-chamber views of the heart were obtained. The position of the Doppler sample volume (SV) was adjusted within the valve orifice until the maximal power of the Doppler audio spectra reflecting TMBV was recorded by a spectral analyzer. At this location of the SV, images were recorded and protractors were used to estimate DA. DA ranged from 10 to 40 degrees (x = 22.5 degrees +/- 10.8 degrees) in Group I and from 0 to 15 degrees (x = 4.5 degrees +/- 5.0 degrees) in Group II. Mean values of DA in Groups I and II were significantly different (p less than 0.01). We conclude: (1) in normal subjects, DA measured from the apex into the MV varies significantly and thus may compromise the accuracy of TMBV measurements; (2) the truncated funnel shape of the stent of the PMV bioprosthesis allows a DA less than 15 degrees and thus a smaller error in TMBV calculations.     

A kinematic model of the wrist based on maximization of joint contact area

The wrist is a complex joint and the factors governing its behaviour are poorly understood. A hypothesis that the movement of the carpal bones could be predicted using a minimum energy principle was tested. Carpal bones were dissected from a cadaveric forearm and their shapes were laser-digitized to obtain three-dimensional computer models. A computer program was created to measure contact area between neighbouring articular surfaces and to maximize this quantity by adjusting the six degrees of freedom of the bone models. This procedure was performed for 1.0 degree increments of rotation applied to the capitate bone up to 20 degrees of ulnar and 10 degrees of radial deviation. The model correctly predicted certain aspects of the complex behaviour of the carpal bones. The results for the scaphoid in particular displayed characteristics in common with known behaviour of this bone. During 20 degrees of unlar deviation and 10 degrees of radial deviation, the bone demonstrated 11.3 degrees of extension and 9.4 degrees of flexion respectively. The novelty of the study lay in the fact that the model did not rely upon ligamentous constraints. The results are encouraging, considering the only information used by the algorithm was the shape of the articular surfaces.     

特殊情况下机构自由度的计算方法

对于实际工程问题,机构自由度的确定往往不能简单地套用计算公式,除了需要综合考虑复合铰链,局部自由度和虚约束等问题外,还必须具体问题具体分析。本文讨论了一种特殊情况下的机构自由度计算问题,并给出了相应的计算方法。     

The thermal behavior of electrolyte-coated metal-foil dispersive electrodes

The thermal properties of electrolyte-coated aluminum (Al) and copper (Cu) foil dispersive electrodes carrying 700 mA of electrosurgical current for 1 min were studied on seven human subjects ranging in weight from 46 to 84 kg. Calibrated thermographic imaging was used for data analyses. The mean skin temperature rise for the Al-foil electrode was 1 degrees C and for the Cu-foil electrode was 0.5 degrees C. The maximum temperatures occurred at the perimeter of both electrode types and were 3.5 degrees C for the Al-foil and 2.5 degrees C for the Cu-foil electrode. Both electrodes performed adequately under these severe test conditions.     

Thermal quenching sample chamber for grazing incidence small angle x-ray scattering studies of polymer films

The second generation of a sample chamber designed for in situ measurement of temperature- and time-dependent polymer film nanostructure using the method of grazing incidence small angle x-ray scattering is presented. An increased operating temperature limit (from 260 to 400 degrees C) with precise control (+/-0.1 degrees C) at fixed temperatures as well as a fourfold increase in maximum instantaneous cooling rate (up to 73 degrees C/s) relative to the first generation chamber [M. N. Groves et al, J. Appl. Crystallogr. 39, 120 (2006)] are reported. Thermal quenches from 220 to 90 degrees C are shown to be reproducible to within +/-1 degrees C of the final temperature. Experimental tests on spin-coated films of symmetric diblock styrene-butadiene copolymer demonstrate the ability to resolve the kinetics of orientation of lamellar domains parallel to the silicon substrate, distinct from the initial formation of randomly oriented lamellar domains immediately following the thermal quench.     

非统计方法估计的不确定度分量的自由度

本文讨论了不确定度评定中非统计法估计的不确定度分量自由度的分析和计算，给出了由扩展不确定度计算自由度的表达式。     

Numerical study on the pulsatile flow characteristics of proximal anastomotic models

Haemodynamics was widely believed to correlate with anastomosis restenosis. Utilizing the haemodynamic parameters as indicator functions, distal anastomosis was redesigned by some researchers so as to improve the long-term graft patency rate. However, there were few studies upon the proximal anastomosis. Therefore, in this study, flow characteristics and distributions of the haemodynamic parameters in proximal anastomosis under physiological flow condition have been investigated numerically for three different grafting angles: namely, 45 degrees forward facing, 45 degrees backward facing, and 90 degrees anastomotic joints. The simulation results showed a flow separation region along the graft inner wall immediately after the heel at peak flow phase and it decreased in size with the grafting angle shifting from 45 degrees forward facing to 45 degrees backward facing. At the same time, a pair of vortex was found in the cross-sectional planes of the 45 degrees backward facing and 90 degrees grafts. In addition, stagnation point was found along the graft outer wall with small shifting during the physiological cycle. High spatial and temporal wall shear stresses gradients (WSSG) were observed around the anastomotic joint. Low time-averaged wall shear stress (WSS) with elevated oscillation shear index (OSI) was found near the middle of anastomosis at the aorta wall and along the graft inner wall respectively, while high time-averaged WSS with low OSI was found at the heel, the toe, and the region downstream of the toe. These regions correlated to early lesion growth. Elevated time-averaged WSSG was found at the same region, where the elevated low-density lipoprotein (LDL) permeability was observed as reported in the literature. The existence of nearly fixed stagnating location, flow separation, vortex, high time-averaged WSS with low OSI, low time-averaged WSS with elevated OSI, and high time-averaged WSSG may lead to graft stenosis. Moreover, the simulation results obtained were consistent with those of experimental measurements. Based on the validated simulation results, the 45 degrees backward-facing graft was found to have the lowest variation range of time-averaged WSS and the lowest segmental average of WSSG among the three models investigated. The 45 degrees backward-facing graft is thus recommended for the bypass operation with expected higher patency rate.     

关于自由度的计算

关于自由度的计算,已经引起了世界上许多学者的注意。本文提出了“根据机械系统的闭合特点,割断机架分析末杆运动,在同一瞬间把末杆与机架焊接,重新形成原机械系统”的理论,来计算机械系统（包括机构、结构）的自由度。本文阐明了机械系统中的静不定次数和自由度数的内在联系;为判断机械系统能否实现有限位移提供了必要性判据,同时为判定机械系统是否能作为结构提供了充分性判据;揭示了静不定和自由度的物理意义;严格地说明了把机构分成六个族是错误的,机构分族的观点是毫无意义的。根据上述理论,我们导出了闭合数计算公式、自由度数计算公司以及静不定次数计算公式。用这些公式可以毫无例外地按机械系统（包括机构、结构）的构造,正确地计算出它的自由度数和静不定次数。     

Dynamic analysis of non-uniform beams and plates by finite elements with generalized degrees of freedom

A finite element with generalized degrees of freedom (FEGDOF) and a finite strip with generalized degrees of freedom (FSGDOF) are developed for the dynamic analyses of beams and plates with cross-section varying in a continuous or discontinuous manner. The degrees of freedom (DOF) of the finite element are transformed into generalized degrees of freedom (GDOF). The admissible interpolating functions for the FEGDOF and FSGDOF are derived accordingly. To the best knowledge of the authors, it is the first time that the second order polynomials are employed in the dynamic analysis of flexural beams and plates, which simplifies the derivation of finite element or finite strip formulation. Numerical examples demonstrate the satisfactory accuracy, efficiency and versatility of the presented approach.     

A high pressure cell for dynamic light scattering up to 2 kbars with conservation of plane of polarization

We report on a high pressure cell with six optical windows which can be used up to 2 kbars for laser light scattering applications at scattering angles of 45 degrees , 90 degrees , and 135 degrees of liquid samples in a temperature range between -20 and 150 degrees C. The pressure transmitting medium is compressed nitrogen. The window material used is SF57 NSK, a glass with an extremely low stress optical coefficient in the order of about 10(-5) which allows thus to maintain the plane of polarization even under the action of high pressure. In order to demonstrate the functioning of the cell we show Rayleigh-Brillouin spectra of poly(methylphenylsiloxane) at different polarizations and pressures.     

Thermovoltaic properties of hornet silk

In silk from the larval silk caps of the Oriental hornet Vespa orientalis (Hymenoptera, Vespinae), temperature-dependent changes in the electric voltage have been recorded, with rise in the voltage occurring mainly upon rise in the temperature between 10-36 degrees C. The peak voltage was measured between 32-38 degrees C and attained 240-360 mV, but with further increase in temperature, the voltage decreased, dropping to 0 mV at about 45-50 degrees C. Upon second measurement (of same silk specimen), the voltage peak usually occurred later (by 8-9 degrees C) and at higher temperature than in the first measurement. Continuous measurements during warming up to 30 degrees C followed by cooling down to 15 degrees C yielded an hysteresis between the warming "line" and the cooling "line", the former often straight and the latter usually curved. Maintaining the silk specimen at a fixed temperature for a prolonged period (hours) initially causes the voltage to rise, then remain steady, and finally drop. Boiling the silk caps in tap water for 7-10 min exerts some changes in the silk properties, mainly a decrease in voltage level. The general behavior of the silk suggests that it is a polymer endowed with the qualities of an organic semiconductor. The various properties of the larval silk are discussed in great detail.     

High-temperature electron backscatter diffraction and scanning electron microscopy imaging techniques: in-situ investigations of dynamic processes

In-situ heating experiments have been conducted at temperatures of approximately 1200 K utilising a new design of scanning electron microscope, the CamScan X500. The X500 has been designed to optimise the potential for electron backscatter diffraction (EBSD) analysis with concomitant in-situ heating experimentation. Features of the new design include an inclined field emission gun (FEG) column, which affords the EBSD geometrical requirement of a high (typically 160 degrees) angle between the incoming electron beam and specimen surface, but avoids complications in heating-stage design and operation by maintaining it in a horizontal orientation. Our studies have found that secondary electron and orientation contrast imaging has been possible for a variety of specimen materials up to a temperature of at least 900 degrees C, without significant degradation of imaging quality. Electron backscatter diffraction patterns have been acquired at temperatures of at least 900 degrees C and are of sufficient quality to allow automated data collection. Automated EBSD maps have been produced at temperatures between 200 degrees C and 700 degrees C in aluminium, brass, nickel, steel, quartz, and calcite, and even at temperatures >890 degrees C in pure titanium. The combination of scanning electron microscope imaging techniques and EBSD analysis with high-temperature in-situ experiments is a powerful tool for the observation of dynamic crystallographic and microstructural processes in metals, semiconductor materials, and ceramics.     

TC4板孔冷挤压强化残余应力分布与疲劳寿命

开展了不同挤压量下TC4钛合金板孔冷挤压强化有限元仿真研究,得到了挤压强化后最小截面的切向残余应力分布规律,分析了挤压量对受载试样孔边应力分布的影响,探讨了挤压量、残余应力和疲劳增益三者之间的内在关系。采用开缝衬套冷挤压强化工艺对TC4带孔板件进行冷挤压和疲劳验证试验。研究结果表明,挤压强化后的孔边切向压缩残余应力可以有效降低孔周应力集中程度,优化受拉试样最小截面应力分布,改变裂纹源的位置并延长疲劳裂纹的萌生和扩展寿命,有效提高试样疲劳寿命。综合仿真和疲劳试验得到TC4板孔最优挤压量为4%。