In vitro testing of the deformation pattern and initial stability of a cementless stem coupled to an experimental femoral head, with increased offset and altered femoral neck angles

The ability to vary femoral offset and neck angles in total hip arthroplasty increases the amount of flexibility in the mechanical reconstruction of the hip joint. The present study investigates the changes in strain pattern and bone-implant micromotion caused by increased femoral offset in combination with retroversion or reduced neck-shaft angle, made possible by a large experimental femoral head. A cementless femoral stem was inserted in 10 human cadaver femurs. Three femoral head configurations were tested: the standard situation, an increased offset combined with retroversion, and increased offset combined with reduced neck-shaft angle. The femurs were loaded in a hip simulator that was able to reproduce the conditions that correspond to one-legged stance and stair climbing. There was a statistically significant increase in strain for the experimental head at several strain gauge rosettes compared to the standard head. The largest significant increase in strain was 14.2 per cent on the anterior side of the femur. The largest mean total point motion was 44 microm in the distal coating area for the configuration with increased femoral offset and retroverted neck axis. The clinical relevance of the changes in strain distribution is uncertain. The femoral stem showed excellent initial stability for all test situations.     

Finite element analysis of the head–neck taper interface of modular hip prostheses

The purpose of this paper was to identify which parameters influence the micromotion at the head–neck taper interface of modular hip prostheses. Finite element analysis was performed where 3D models of the head–neck taper interface were subjected to an assembly force, 3300 N of compression, and 100 N of tension. The micromotion increased as the head size, assembly force, and taper size increased. The micromotion also increased when a mixed alloy material combination (CoCr head and Ti6Al4V neck) was used instead of all CoCr alloy prosthesis and when the center of the femoral head was in a more superior position relative to the center of the neck taper.     

The transmission of translational seat vibration to the head: the effect of measurement position at the head.

Head motion has been measured in six axes on twelve subjects exposed to vertical seat vibration in the frequency range 0.5-25 Hz. The subjects sat on a rigid flat seat in two postures: 'back-off' (no backrest) and 'back-on' (subject's back in contact with the seat backrest). Translational acceleration has been calculated for various locations on the head and transmissibilities between vertical seat vibration and translational head motion determined for each location and all axes. The translational motion of the head was most affected by pitch motion of the head. This caused variations in fore-and-aft motion with position along the vertical axis of the head and variations in vertical motion with position along the fore-and-aft axis of the head. These variations are illustrated for each subject in both postures. The individual data allow the identification of various modes of vibration and show that seat-to-head transmissibility is greatly affected by pitch modes of the head and neck. The magnitude of motion occurring in some modes is dependent on body posture.     

Wear of tribe-elements of video tape recorders

The helical scan magnetic recording equipment, like the video tape recorders (VTR), consist of many tribe-elements. The wear of these tribe-elements is an essential problem affecting the reliability of the equipment. The rotating magnetic head in high-speed rubbing with the magnetic tape needs a self-cleaning effect by mild wear. A simple trial of reducing the head wear often brings partial recession, friction polymer and brown stain. The summary of the current study of head wear is given by dividing it into the head factors, the tape factors, the system factors and the atmosphere factors. The computational analysis of head contour change caused by wear is compared with the experimental results. The outline of the tribology of motor, capstan and tape path in the VTR is introduced.     

Resonance phenomenon and its effects of laser texture disk

To achieve lower flying height for high areal recording density, the laser zone texturing of the disk needs to be designed to reduce glide height. One problem of the laser bump design is that the regular laser bump pattern often produces glide resonance phenomenon, which leads to failure of the glide height test. However, it was found in this study that glide resonance is an intrinsic problem of the glide head used and resonance phenomenon depends on the type of the head slider, that is, the natural frequency of the slider body. Therefore, higher glide height or glide failure caused by glide resonance does not lead to head/media interface problem in the real drive operating conditions in which the data head is used. Pseudo- random bump pattern greatly reduces the glide resonance. Smaller bump pitch will also help to reduce the glide resonance. However, as bump spacing becomes smaller, glide height will be increased due to increased air pressure developed around the bumps. Lowering bump height is the most effect way to reduce glide avalanche.     

A study on the influence of the seat and head restraint foam stiffnesses on neck injury in low speed offset rear impacts

Soft tissue neck injury (STNI) is thought to be related to automotive seat characteristics, and it is important to know how the stiffness of the seatback and head restraint foam affect the occupant’s motions in low speed rear impacts. The combined MADYMO(MAthematical DYnamic MOdel, TNO) 50th percentile facet male human body model with a detailed neck model was selected for this analysis. In order to determine the relationship between the occupant’s motions and seatback and head restraint foam stiffnesses, 40% offset rear impact simulations were performed by changing the stiffness of seatback and head restraint. Simulated results show that the maximum acceleration of head and trunk would tend to increase with those stiffnesses. Increased stiffness of the seatback and head restraint resulted in increased ligament and disc forces. On the other hand a proper combination of seatback and head restraint stiffness can reduce a possible neck injury. It is clear that an appropriate combination of stiffnesses between seatback and head restraint allows to minimize a neck injury.     

Simulation of transient flow in pipeline systems due to load rejection and load acceptance by hydroelectric power plants

In this paper, the implicit method of characteristics (IMOC) is extended to simulate the transient flow caused by load variation of hydroelectric power plants. The IMOC was proposed recently by the authors to remove the limitations of the commonly used conventional method of characteristics (MOC) and subsequently used for the simulation of transient flow caused by valve closure and pump failure. In the IMOC, an element-wise definition is used for all devices that may be used in a pipeline system and the corresponding equations are then assembled to form a system of equations that is solved for the unknown nodal heads and flows at each time step. In this paper, the IMOC is extended for the simulation of transient flow in the pipeline system upstream of a hydroelectric power plant. For this, an element-wise definition of the hydroelectric power plants and simple surge tank is proposed and their governing equations are derived in a matrix form required by the IMOC. Then these equations are assembled along with those of other devices of the pipeline system to construct a system of equations that is solved for the unknown head and flow. To further improve the convergence characteristics of the method, an improved formulation of the turbine is also proposed. In the proposed formulation, one of the turbine characteristic parameters, namely turbine net head, is used in addition to turbine head and discharges, to formulate the behavior of the turbine element. The method is applied to a problem of transient flow caused by load rejection and acceptance and the results are presented and compared with those of the explicit MOC. The results show the ability of the proposed method to accurately predict the variations of head and flow in the cases considered. It is also shown that the improved formulation of the turbine is computationally more efficient than the original formulation while producing the same results.     

弹性约束下颗粒碰撞阻尼器的理论与实验研究

为进一步研究弹性约束颗粒碰撞阻尼器的减振性能,提出了该阻尼系统的动力学模型,并模拟了该阻尼器对悬臂梁的减振效果。同时,对5种不同刚度的弹性约束颗粒碰撞阻尼器的减振效果进行了实验研究。结果表明：理论计算与实验的结果基本吻合,证明所建立的弹性约束下的颗粒碰撞阻尼系统的计算模型是可靠的;在弹性约束下的颗粒碰撞阻尼系统中,其刚度比对减振效果的影响是非线性的,且弹簧刚度对该碰撞系统的共振点存在影响。     

Theoretical relationships between component design, patient bone geometry and range-of-motion post hip resurfacing

Clinical studies indicate that range of motion until prosthetic impingement is important in understanding unexplained failures of hip resurfacings, yet the underlying biomechanical principles have received little attention. This study investigates the mathematical relationships between component design, position, patient bone geometry and range of motion in hip resurfaced prostheses. Variations in range of motion and impingement-free safe-zones for cup position were calculated using an established method of vector analysis that facilitated parametric analysis in a time efficient manner. The alpha angle, defined as the angle between the centreline of the femoral neck and the waist of the femoral head/neck junction, was used to represent the natural femoral neck. Range of motion and impingement-free safe-zones were inversely proportional to the alpha angle and cup inclusion angle. The size of the safe-zone was most sensitive to the alpha angle with a 6 degrees reduction, decreasing the range of cup positions without impingement by 80-100%. Lowering the upper limit of cup inclination from 55 degrees to 45 degrees reduced the range of cup positions that allow impingement-free motion by 47-94%. No common safe-zone was observed for the range of component sizes and positions investigated. This offers an explanation to why clinic studies have failed to associate outcome with standardised positioning criteria.     

Rigid-body modelling of shaken baby syndrome

Recent reassessment of the literature on the shaken baby syndrome (SBS) has revealed a lack of scientific evidence and understanding of all aspects of the syndrome. In particular, studies have been unable to clarify the mechanisms of injury, indicating that impact, rather than shaking alone, is necessary to cause the type of brain damage observed. Rigid-body modelling (RBM) was used to investigate the effect of neck stiffness on head motion and head-torso impacts as a possible mechanism of injury. Realistic shaking data obtained from an anthropometric test dummy (ATD) was used to simulate shaking. In each study injury levels for concussion were exceeded, though impact-type characteristics were required to do so in the neck stiffness study. Levels for the type of injury associated with the syndrome were not exceeded. It is unlikely that further gross biomechanical investigation of the syndrome will be able to significantly contribute to the understanding of SBS. Current injury criteria are based on high-energy, single-impact studies. Since this is not the type of loading in SBS it is suggested that their application here is inappropriate and that future studies should focus on injury mechanisms in low-energy cyclic loading.     

肉燃机阀门压缩弹簧遗传优化设计

首先对内燃机阀门压缩弹簧进行分析,建立优化数学模型,并应用遗传算法求出问题的最优解,探讨了将遗传算法应用于此类具有约束、多变量类型优化问题的可行性。     

弹头冲击盔-头-颈的数值模拟和运动仿真

这里根据盔-头-颈的结构特点建立了简化的有限元分析模型。利用LS—DYNA3D模拟了弹头冲击头盔时，头部加速度和速度的动态响应特性和颈部的受力过程。并在多参数条件下，对头、颈部的伤害进行了简单的评价。这里所采用的计算方法和模拟结果有助于头颈部组织损伤机理的分析研究，并为头盔内衬结构的优化设计和改进提供了理论参考。     

Etiopathogenesis and clinical presentation of carotid body tumors

The carotid body (CB) is a highly specialized small organ located at the bifurcation of the common carotid artery in the neck and plays an important role in acute adaptation to hypoxia. The most common diseased state of the carotid body is its enlargement (i.e., the CB paraganglioma), which can be caused by a genetic predisposition (hereditary paraganglioma, PGL) and by chronic hypoxic stimulation. The CB is the most common tumor site in head and neck paragangliomas. Currently, inactivating germline mutations in the mitochondrial complex II subunits SDHB, SDHC, and SDHD have been identified as genetic risk factors for CB tumors (CBTs). Another locus at chromosome 11q13, identified by linkage analysis in a single family, may harbor a fourth susceptibility gene. Although CBTs are mostly slow-growing and benign, they can cause significant morbidity because of their proximity to major arteries and nerves in the head and neck. Here, we review the etiological factors implicated in the development of CBTs and provide information pertaining to their clinical presentation. Although CBTs are rare, they have the potential to provide unique insights for tumorigenesis and oxygen sensing and signaling mechanisms.     

基于LS-DYNA驾驶座椅鞭打性能分析及优化

根据C-NCAP(2018)版鞭打试验评价规程和评分原则,利用仿真分析法研究了某驾驶座椅鞭打试验中假人的颈部伤害.依照鞭打试验规章建立了座椅鞭打试验的有限元分析模型,并与试验结果进行对标分析,验证仿真模型的有效性.研究结果表明:通过优化头枕杆的位置,减小头后高度,可改善鞭打试验中颈部伤害.     

新型自动平衡头的控制算法研究

介绍了一种新型释放液体式平衡头的设计思想,克服了传统注入液体式平衡头调节能力易饱和的问题。在前人的研究基础上改进了基于PID的控制策略,在PID控制器的设计中引进了内模控制原理．改善了常规PID控制器对系统参数变化适应性差的缺点,并通过仿真对改进前、后的控制方法进行比较分析。实验表明,改进后的控制方法不仅能快速有效地减小系统不平衡量,还大大加强了系统的鲁棒性和抗干扰性。     

基于STL模型的双面数控渐进成形干涉检查与修正

针对双面数控渐进成形中工具头与板材之间容易发生干涉的问题, 提出了基于STL模型的工具头与板材干涉检查与修正方法。对于主工具头，采用等距面生成无干涉的成形轨迹，以避免干涉；对于副工具头，将干涉类型分为工具头与板材非成形特征区的干涉和工具头与板材成形特征区的干涉两种类型，并通过判断副工具头刀位点与支撑面的位置关系来确定是否发生干涉。算法应用实例和成形实验结果表明，所提出的算法能够避免干涉，进而生成无干涉的工具头运动轨迹。     

多变量协调自适应控制器初步研究

本文初步研究了多变时过程控制器设计的优化目标和约束的统一表达体系,将模块多变量控制技术引入自适应控制器的设计过程,提出了多变量协调自适应控制器的概念,并初步解决了有约束的多目标优化控制的设计问题。     

Development of a high-performance laser-guided deep-hole boring tool:: Optimal determination of reference origin for precise guiding

A laser-guided deep-hole boring tool using piezoelectric actuators was developed to prevent hole deviation. To extend the depth of controllable boring further, the following were improved. The tool’s guiding error, caused by misalignment of the corner cube prism and the mirror in the optical head from the spindle axis, was eliminated using an adjustment jig that determined the reference origins of the two position-sensitive detectors (PSDs) precisely. A single-edge counter-boring head is used instead of the double-edge head used up to now. The former was thought to be better in attitude control than the latter. A new boring bar, which was lower in rigidity and better in controllability of tool attitude, was used. Experiments were conducted to examine the performance of the new tool in detail and to determine its practical application, using duralumin (A2017-T4) workpieces with a prebored 108-mm diameter hole. The experiments were performed with a rotating tool–stationary workpiece system. Rotational speed was 270 rpm and feed was 0.125 mm/rev. Tool diameter was 110 mm. As a result, controlled boring becomes possible up to a depth of 700 mm under the stated experimental conditions. 700 mm is the maximum machinable length of the machine tool. The tool can be put to practical use.     

盾构机刀盘的布刀方式及刀具位置误差分析

针对刀盘的工作性能问题,分析了盾构机刀盘的布刀方式,运用Solidworks建立了刀盘的虚拟样机模型;分析并计算了滚刀的受力情况。通过有限元分析了刀盘装配体的强度及布刀的合理性,分析了盘形滚刀位置误差对刀盘工作性能产生的影响等,并提出了改进方案。     

基于ARM和CPLD的横机机头电路测试系统

为解决电脑横机机头控制系统信号的测试可靠性问题,基于低成本、高效率的考虑,研究设计了机头控制系统电路板的批量测试系统。该系统采用TI公司的LM3S5R31芯片作为系统的核心部分,通过CPLD进行I／O扩展及辅助控制,使得系统功能灵活强大。将同一信号通路中的前后级元件信号进行编码,向待测板发送握手信号并使之发送反馈信号,该系统将反馈信号进行采样并在程序中比较计算,制作了实物并进行了大量实验。研究结果表明,该测试系统叮有效解决电脑横机机头控制系统的快速故障测试及定位问题。