Results 11 to 20 of about 308,970 (123)
Region‐wide retreats from lower elevations of range‐restricted birds across the Northern Andes
Conservation Biology, Volume 37, Issue 5, October 2023., 2023 Abstract Local studies show upslope shifts in the distribution of tropical birds in response to warming temperatures. Unanswered is whether these upward shifts occur regionally across many species. We considered a nearly 2000‐km length of the Northern Andes, where deforestation, temperature, and extreme weather events have increased during the past ...
Wilderson Medina +2 more
wiley +1 more source
Methods in Ecology and Evolution, Volume 14, Issue 6, Page 1443-1456, June 2023., 2023 Abstract Successful use of stable isotopes (δ2H and δ18O) in ecohydrological studies relies on the accurate extraction of unfractionated water from different types of soil samples. Cryogenic vacuum distillation (CVD) is a common laboratory‐based technique used for soil water extraction; however, the reliability of this technique in reflecting soil ...
Bin Yang +14 more
wiley +1 more source
Gaoya dianqi, 2023 文中针对高压开关温升预测缺少电流同温升关系模型这一难点，首次建立导电部位稳定温升τw与电流I的数学模型，得出τw与I的变化规律，通过高压开关柜系列电流下的温升试验，验证了该模型的合理性和准确性。阐述了电器发热基本理论中温升τ与时间t关系模型的推导过程，通过高压开关柜系列电流下的温升试验，进一步研究了该模型下不同试验时间段的拟合温升规律。在温升预测应用中，按文中τw与I的数学模型，求解形成稳定温升与电流标准曲线，作为温度在线监测的判断标准，从而实现故障提前预警。
兰剑, 韩冬, 冯英, 陆德鹏
doaj
Gaoya dianqi, 2020 为了验证晶闸管可否承受设计要求的最高结温及高低温循环应力,在出厂试验阶段需要开展换流阀温升试验。首先介绍了温升试验参数的计算方法,其次设计了采用直流电流加热原理的温升试验回路,最后结合某换流阀实例计算了温升试验参数,在试验室中开展了温升试验。试验结果显示温升试验参数的试验值和计算值基本一致,试验前后晶闸管性能未有下降。试验结果表明,结合给出的温升试验参数计算方法和温升试验回路可以完成温升试验,验证晶闸管的温升性能。
张翔 +5 more
doaj
, 2017 本发明涉及航天器地面热试验领域，公开了一种航天器热真空试验温度控制方法及系统。该方法包括步骤：使用两个测量区域不同的测温仪同时对准热源加热中心位置，测得两个不同的平均温度T1、T2；根据平均温度T1，得到平均温度T1与目标温度的差值作为增量式PID控制器的输入量进行PID控制；将两个平均温度的比值T1/T2作为额外的反馈量与PID控制结果线性叠加得到热源功率的变化值；根据所述变化值调整热试验热源的输出功率。本发明可以保证航天器热真空试验温度稳定且超调量可控 ...
甘政涛 +5 more
core +2 more sources
, 1965 高速飞机及飞航导弹在飞行过程中受到气动力的快速加热和快速加载.为了最充分地利用结构材料强度进行合理设计,必须研究金属结构材料在快速加载、快速加热下的力学性能.本文叙述了一种短时高温拉伸试验设备;这设备能以小于85 kg/s的速率对试件进行恒速加载,以小于80℃/s的速率进行快速升温;试件50mm标距内温度梯度小于5℃;整个加热控温过程和应力应变测量记录过程均系自动进行.在此设备上可进行高温快速拉伸和短时蠕变等实验,并已进行了低碳钢,等材料的短时拉伸、短时蠕变、恒裁等加热率的实验.文内列有图表 ...
柯受全 +3 more
core +2 more sources
Gaoya dianqi, 2021 以隔离开关关键零部件触头为研究对象,建立温升理论模型,通过±60℃高低温试验平台,测试了1 000次机械操作前后触头表面夹紧力、压紧弹簧力值、触头磨损率和回路电阻等通流参数,设计触头温升试验,定量研究高低温对触头通流能力的影响。建立温度与触头夹紧力、镀银层磨损量和接触电阻的关系曲线,分析了触头夹紧力、镀银层和接触电阻随温度变化情况,通过试验研究可知,低温环境对触头温升变化没有高温影响大,为隔离开关触头优化改进和通流能力的提升奠定理论基础。
徐刚 +9 more
doaj
Rare Metals, Volume 45, Issue 5, May 2026.ABSTRACT This study demonstrates a new strategy for modifying the boron content to address stress‐relief cracking (SRC) in the 7CrMoVTiB10.10 alloy. First, coarse‐grained heat‐affected zone (CGHAZ) specimens with different boron contents were prepared via simulated welding thermal cycles.
Dongdong Zhang +3 more
wiley +1 more source
Rare Metals, Volume 45, Issue 4, April 2026.ABSTRACT A comparative study was performed to elucidate the temperature‐dependent corrosion kinetics and the semiconductor/structural characteristics of the passive film formed on Fe40Ni7Cr17Mo12C13B9Y2 (at%) amorphous alloy coatings. The results indicate that increasing temperature accelerates the corrosion kinetics of the coating.
Yang Lv +12 more
wiley +1 more source
, 1995 为解决石油平台在辽东湾海域的低温疲劳问题，借助ＭＴＳ试验机，建立一套低温疲劳实验系统，实现了低温疲劳实验中疲劳裂纹的观察和测量，以获取平台结构钢在低温下的疲劳裂纹扩展速率的可靠数据 ...
方华灿 +4 more
core +2 more sources