多调和算子Dirichlet特征值下界的一种估计

通过构造热核函数的部分和,我们给出了多调和算子Dirichlet特征值的一个新的下界估计,新的估计式推广了已有的特征值估计的结果。     

热力学第二定律研究方法的评述

通过对热力学第二定律详细分析,从不同角度讨论了准静态绝热过程的微分方程,在对微分方程进行积分的过程中指出积分因子不是唯一的.     

灰体辐射问题的探究——一道典型灰体辐射问题的四种解法的探讨

在工程计算中常用灰体辐射模型来计算辐射传热,然而在大学本科教学中极少出现对灰体辐射的详细解法的讨论。文章对一道典型的灰体辐射题目进行了多种解法的探讨,为灰体辐射传热教学提供参考。     

WinPcap技术在网络流量计费中的应用

通过对WinPcap的结构和功能的介绍,实现对计算机进行有效流量计费的管理,从而提高管理效率和服务质量。     

半线性热方程解的熄灭与区域的相关性

研究半线性热方程第一初边值问题解的熄灭性，应用能量方法，对具零Dirichlet边界条件和非负初值的热方程u1-△u=u-λ|u|^p-1u，给出了一个导致解在有限时间内熄灭的与区域相关的充分条件。     

基于Java技术的网吧计费系统设计

针对c/s的特点,结合java技术的功能特性,本文介绍了一种基于java技术设计的网吧计费系统.通过对socket、多线程、向量和jdbc等java技术和网吧计费系统功能及特点的分析,提出设计网吧计费系统的思想、模式及实现方法,使系统具备更高的可靠性和容错能力.     

半导体激光器中散热问题的研究现状及最新进展

在半导体大功率激光器的各种关键技术中,散热问题的解决是一个极其关键的技术。在管芯焊接的地方产生的热流量大约为1KW/cm2。这种热负载是限制激光器正常工作的关键因素。文章分析了半导体激光器的发热因素,并对了几种常见的热沉类型进行了分析研究。     

外墙外保温挤塑板的施工工艺与质量控制

结合小高层外墙外保温系统的施工实践,分析和介绍了外墙外保温挤塑板的施工工艺与质量控制的要点。     

热损伤预防——军事训练上的展望

军事行动和训练经常在极端环境和高代谢的条件下实施,暴露在高温环境下,工作负荷大。环境因素和行为因素决定热应激。这些因素的结合可导致热相关的损伤。热相关的损伤代表着职业上的危险,特别是对于从温和区域迅速部署到热环境中的士兵。传统上,对热的适应被认为是生理上的适应,但是这些损伤应该被设定为可预见和可避免的损伤,通过遵循一些简单的指导、教育和行为上的适应,可有效地进行预防。     

Heat transfer variations of bicycle helmets

Abstract

Bicycle helmets exhibit complex structures so as to combine impact protection with ventilation. A quantitative experimental measure of the state of the art and variations therein is a first step towards establishing principles of bicycle helmet ventilation. A thermal headform mounted in a climate-regulated wind tunnel was used to study the ventilation efficiency of 24 bicycle helmets at two wind speeds. Flow visualization in a water tunnel with a second headform demonstrated the flow patterns involved. The influence of design details such as channel length and vent placement was studied, as well as the impact of hair. Differences in heat transfer among the helmets of up to 30% (scalp) and 10% (face) were observed, with the nude headform showing the highest values. On occasion, a negative role of some vents for forced convection was demonstrated. A weak correlation was found between the projected vent cross-section and heat transfer variations when changing the head tilt angle. A simple analytical model is introduced that facilitates the understanding of forced convection phenomena. A weak correlation between exposed scalp area and heat transfer was deduced. Adding a wig reduces the heat transfer by approximately a factor of 8 in the scalp region and up to one-third for the rest of the head for a selection of the best ventilated helmets. The results suggest that there is significant optimization potential within the basic helmet structure represented in modern bicycle helmets.