Study of human–seat interface pressure distribution under vertical vibration

The influence of whole-body vertical vibration on the dynamic human–seat interface pressure is investigated using a flexible grid of pressure sensors. The ischium pressure and the overall pressure distribution at the human–seat interface are evaluated as functions of the magnitude and frequency of vibration excitation, and seated posture and height. The dynamic pressure at the seat surface is measured under sinusoidal vertical vibration of different magnitudes in the 1–10 Hz frequency range. Two methods based on ischium pressure and ischium force are proposed to study the influence of seat height, posture and characteristics of vibration. The results of the study reveal that the amplitude of dynamic pressure component increases with an increase in the excitation amplitude in almost entire frequency range considered in this study. The dynamic components of both the ischium pressure and the ischium force reveal peaks in the 4 to 5 Hz frequency band, the range of primary resonant frequency of the seated human body in the vertical mode. The mean values of the dynamic ischium pressure and the ischium force remain constant, irrespective of the excitation frequency and amplitude. The magnitudes of mean pressure and force at the human–seat interface, however, are dependent upon the seat height and the subject's posture. The inter-subject variability of the static ischium pressure and effective contact area are presented as functions of the subject weight and subject weight-to-height ratio. It was found that heavy subjects tend to induce low ischium pressure as a result of increased effective contact area.

Relevance to industry

Pressure distribution at the human–seat interface has been found to be an important factor affecting the seating comfort and work efficiency of various workers. The study of human–seat interface pressure distribution under vibration is specifically critical to the comfort, work efficiency and health of vehicle drivers, who are regularly exposed to vibration. The results reported in this paper will be useful to study dynamic response of the interface pressure and design vehicle seats.     

Mobile robot localization using a self-organized visual environment representation

Owing to the upcoming applications in the field of service robotics mobile robots are currently receiving increasing attention in industry and the scientific community. Applications in the area of service robotics demand a high degree of system autonomy, which robots without learning capabilities will not be able to meet. Learning is required in the context of action models and appropriate perception procedures. In both areas flexible adaptivity is difficult to achieve especially when high bandwidth sensors (e.g. video cameras) - which are needed in the envisioned unstructured worlds - are used. This paper proposes a new methodology for image-based navigation using a self-organized visual representation of the environment. Self-organization leads to internal representations, which can be used by the robot, but are not transparent to the user. It is shown how this conceptual gap can be bridged.     

Automatic reconstruction of 3D human arm motion from a monocular image sequence

A model-based approach to reconstruction of 3D human arm motion from a monocular image sequence taken under orthographic projection is presented. The reconstruction is divided into two stages. First, a 2D shape model is used to track the arm silhouettes and second-order curves are used to model the arm based on an iteratively reweighted least square method. As a result, 2D stick figures are extracted. In the second stage, the stick figures are backprojected into the scene. 3D postures are reconstructed using the constraints of a 3D kinematic model of the human arm. The motion of the arm is then derived as a transition between the arm postures. Applications of these results are foreseen in the analysis of human motion patterns. Received: 26 January 1996 / Accepted: 17 July 1997     

交错BCH码在移动窄带图像信道中的性能研究

文章在详述ＢＣＨ码编译码过程的基础上，对交错ＢＣＨ码在移动瞧道压缩图像传输系统中的应用进行了计算机仿真，直观地显示出产错ＢＣＨ码在窄带图像传输系统中的优良性能，并为移动图像传输中码型的选用提供参考。     

三维空间控制器及其在三维空间交互技术中的应用

为提高人机交互的效率帮自然性，近年来多媒体，多通道交互和虚拟现实技术迅速兴起，而三维空间交互技术在其中占重要地位，并广泛应用于ＣＡＤ／ＣＡＭ和科学计算可视化等领域，本文指出三维空间交互的直接操纵本质，介绍操纵三维对象所需的六自由度三维空间控制器的原理和应用。     

手机用扁平振动马达寿命的提高

以电刷及换向器为焦点,介绍了提高手机用永磁直流电动机寿命的方法。     

一个移动进程演算的互模拟同余定义框架

并发计算模型是理论计算机科学研究的重要领域之一。以π演算为代表的移动进程演算是目前并发理论的研究热点。互模拟等价定义是移动进程演算研究中的核心概念和问题，而传名机制使得移动进程演算中的互模拟同余关系更加复杂和有趣。本文在分析了常见的互模拟同余定义的基础上，通过抽取定义的核心要素，提出了一个三维的互模拟同余定义模型，从而将一般文献中常见的互模拟定义纳入到一个统一的框架中来，加深了我们对移动进程演算中互模拟概念的理解；同时本文利用这个模型，系统分析了各种互模拟之阿的关系。模型的优点在于它的普适性和开放性。     

一种基于指向路径分次删剪的移动Agent通信算法

在移动agent环境下，agent的移动为应用程序的开发提供了更灵活的通信处理方式，但也同时对通信算法的设计提出了许多挑战，其中最突出的就是由于消息传输和agent移动之间的异步性而造成的通信不可靠问题。针对目前解决该问题的各种机制和算法的不足之处，该文提出了一种新的agent通信算法——S—COMP，它综合采用了Home寻址、途经节点转发、指向路径分次删剪和集中同步等手段，能够适应具有不同移动和通信特点的agent的通信需要，在确保消息传输可靠性的同时兼顾了效率和适应性。     

移动计算环境中缓存失效策略的归类研究法

缓存失效报告法是在移动计算环境中普遍采用的缓存方案，即服务器定期广播缓存失效报告，该报告中包含了最近被更新的对象，根据报告内容，客户可使缓存中被更新对象失效，以保证缓存的有效性。缓存失效报告技术可采用多种策略，本文在研究多种缓存策略的基础上，提出了一种针对缓存失效方案的归类研究法，可对具体策略加以分析和评估，在此基础上对其性能进行改良，以形成更适应特定移动计算环境要求的缓存方案。