Effects of repeated exposures to severely cold environments on thermal responses of humans

Abstract

This study was conducted to investigate the effects of different exposure rates on thermal responses with the total cold exposure time the same under each of the conditions. After resting in a warm room (25°C) for 10 minutes, six male students wearing standard cold protective clothing entered an adjoining cold room (— 25°C). Each 5-, 10- and 20-minute cold exposure was repeated 12, 6 and 3 times, respectively. Each cold exposure was followed by a similar duration of rest at 25°C. Total cold exposure time was the same under the three conditions. Rectal temperature, skin temperatures, blood pressure, 17-hydroxycoyticoids (OHCS), counting task and subjective responses were measured. At the end of the cold exposure skin temperatures in the shorter exposures were higher than those in the other conditions, except on the foot. Discomfort due to cold was less in the shorter exposures and manifestation of discomfort was delayed. However, there were no differences among the three conditions in the fall of rectal temperature and urinary excretion of 17-OHCS, which are good indices of cold stress, Moreover, increase in blood pressure and decrease in counting task due to cold were not different among the three conditions. Even though the cold exposure time for each stay was short, when cold exposures were repeated frequently, cold stress of the whole body and decrease in manual task performance were the same as in the longer cold exposure.     

Synthesis of WSi2 -SiC composite under the thermally activated combustion mode

Opportunities on combustion synthesizing the WSi2-SiC ceramic composites in a wide range of compositions under the thermal activated mode were studied. Tungsten, silicon powders and carbon black were used as initial reagents, and Magnesium–Teflon mixture was used as an activating additive. The stepwise character of the combustion process evolution, being characterized by low- and high-temperature regimes, was revealed. The end-products were subjected to SEM, XRD and DTA/TG analyses.     

浅淡漳州市住宅外墙保温施工

漳州的气候条件对于建筑节能来说,主要是夏季隔热的问题,本文对漳州目前采用的住宅外墙保温施工的问题进行了粗浅的探讨。     

Could sperm quality be affected by a building environment? A literature review

The human body responds psychologically and physiologically to the thermal environment to which it is exposed. Fanger's PMV model has been adopted for the design of built environments and building maintenance from the end of the 1960s. The sperm quality of humans has been decreasing since the 1970s. The thermal environment is one of the most important factors of the Sick Building Syndrome (SBS). It is well known that spermatogenesis is very sensitive to heat exposure. Mild thermal exposure increases tissue microcirculation and consequently produces an appropriate supply of nutrients and oxygen to tissue cells; thus, it can modulate the proliferation of Sertoli cells in which the spermatogonia stem cells develop into adult spermatozoa. Excessive exposure to heat is harmful to spermatogenesis, and excessive testicular cooling can cause the cessation of spermatogenesis.     

前苏联核电站用1000 MW四极汽轮发电机

介绍"电力"工厂20世纪80年代研制的TBB-1000-4型四极汽轮发电机的主要技术数据、结构以及厂内试验结果.图1表3     

Thermal stability of devices with molybdenum oxide doped organic semiconductors

We demonstrate the thermal stability of transition-metal-oxide (molybdenum oxide; MoO₃)-doped organic semiconductors. Impedance spectroscopy analysis indicated that thermal deformation of the intrinsic 1,4-bis[N-(1-naphthyl)-N′-phenylamino]-4,4′-diamine (NPB) layer is facilitated when the MoO₃-doped NPB layer is deposited on the intrinsic NPB layer. The resistance of the intrinsic NPB layer is reduced from 300 kΩ to 3 kΩ after thermal annealing at 100 °C for 30 min. Temperature-dependent conductance/angular frequency–frequency (G/w-f-T) analysis revealed that the doping efficiency of MoO₃, which is represented by the activation energy (E_a), is reduced after the annealing process.     

新型发射极指组合结构功率SiGe HBT热分析

提出了一种发射极指分段和非均匀发射极指长、指间距组合的新型器件结构,以改善多指功率硅锗异质结双极晶体管(SiGe HBT)的热稳定性。考虑器件具有多层热阻,发展建立了相应的热传导模型。以十指功率SiGe HBT为例,运用有限元方法对其进行热模拟,得到三维温度分布。与传统发射极结构器件相比,新结构器件最高结温从416.3 K下降到405 K,各个发射指上的高低温差从7 K～8 K下降为1.5 K～3 K,热阻值下降14.67 K/W,器件整体温度分布更加均匀。     

气密性陶瓷封装内热应力的ANSYS分析

采用有限元方法,运用ANSYS软件,分析计算了气密性陶瓷封装管壳内温度及热应力分布,比较了4种粘接剂对芯片温度及热应力分布的影响。热分析表明,芯片中心处温度最高,边角处最低;不同粘接剂都因为厚度较薄,对芯片温度的分布无较大影响。热应力分析表明,由于热分布不均匀,使芯片与粘接剂的接触处有较大的热应力,主要集中在粘接剂与芯片的下底面,此处也是最容易导致芯片脱落失效的部分。对比4种粘接剂的结果发现:采用H35作粘接剂时,应力峰值为17.0MPa,但芯片与粘接剂和底座之间的热应力较大;采用PbSnAg焊料作粘接剂时,应力峰值为41.9MPa,但芯片与粘接剂和底座之间的热应力较小。     

UHVCVD外延设备的热场设计

介绍了超高真空化学气相沉积(UHVCVD)锗硅外延设备的加热室设计方法,完善了相关的炉体设计,相关温度指标达到设计标准。