An experimental study on static solid-liquid phase equilibrium in the pores of a porous medium

The so-called Clausius-Clapeyron equation, that is, the static equation of state for “solid-liquid-porous media” systems without liquid flow through the pores, has been experimentally examined by measuring the pore liqiud pressure at the solid-liquid interface in order to verify the accuracy of our method of measuring unfrozen pore liquid pressure. Several series of experiments have been carried out using water-saturated Ohya-Tuff as a porous medium specimen cooled from the top down. In these experiments, the solid-liquid interface was always fixed at the top surface of the specimen. The experimental results imply that the measurement method should be useful in determining the relative value of the unfrozen pore water pressure. © 1998 Scripta Technica, Inc. Heat Trans Jpn Res, 26(2): 69–83, 1997     

橡胶改性碳纤维-多壁碳纳米管水泥复合材料性能试验与分析

水泥基复合材料已推广应用于水利工程中,探究其耐久性能是保证高寒地区高混凝土坝安全的关键。将碳纤维与多壁碳纳米管双导电相填料加入水泥材料,从导电性能、力学性能和抗冻性能3个方面研究其作用效果。同时,为充分利用废弃资源,将废弃轮胎制备成橡胶集料加入试件用于力学性能和抗冻性能的试验分析。试验结果表明：当碳纤维与多壁碳纳米管掺量为0.25%时,导电相填料对水泥复合材料的电阻率改变最为明显,在掺量为0.3%时复合材料的电阻率最低,同时,不同外加电场对电阻率的影响可以忽略不计;当碳纤维和多壁碳纳米管的掺量为0.3%、橡胶掺量为30%时,复合材料的抗冻性能最佳,此时,力学性能也满足工程应用需求,抗折和抗压强度分别超过7 MPa和30 MPa。研究结果为提升高寒地区混凝土结构的性能提供了新的技术手段。     

基于导电水凝胶的柔性应变传感器研究进展

导电水凝胶具有良好的电性能、机械性能、生物相容性等,在电容器、调制器、传感器等领域具有广阔的应用前景.本文对导电水凝胶的概述、传感机理及传感器的种类进行了综述.     

单向冻结条件下扩底桩抗冻拔能力试验研究

采用单向冻结的方法,针对季节冻土区扩底桩的抗冻拔能力,分别选取不同扩角(无扩角直桩、45o、60o、70o)和不同埋深(240、290、340 mm),以及不同扩底直径(74、98、114 mm)的扩底桩开展室内试验研究.根据试验及计算结果,3组试验的最终冻结深度分别为19.51、14.36、14.80 cm.不同扩角...     

How to Select Phase Change Materials for Tuning Condensation and Frosting? (Adv. Funct. Mater. 3/2023)

Synthetic surfaces engineered to regulate phase transitions of matter and exercise control over its undesired accrual (liquid or solid) play a pivotal role in diverse industrial applications. Over the years, the design of repellant surfaces has transitioned from solely modifying the surface texture and chemistry to identifying novel material systems. In this study, selection criteria are established to identify bio-friendly phase change materials (PCMs) from an extensive library of vegetable-based/organic/essential oils that can thermally respond by harnessing the latent heat released during condensation and thereby delaying ice/frost formation in the very frigid ambient that is detrimental to its functionality. Concurrently, a comprehensive investigation is conducted to elucidate the relation between microscale heat transport phenomena during condensation and the resulting macroscopic effects (e.g., delayed droplet freezing) on various solidified PCMs as a function of their inherent thermo-mechanical properties. In addition, to freeze protection, many properties that are responsive to the thermal reflex of the surface, such as the ability to dynamically tune optical transparency, moisture harvesting, ice shedding, and quick in-field repairability, are achievable, resulting in the development of protective coatings capable of spanning a wide range of functionalities and thereby having a distinctive edge over conventional solutions.     

基于脉冲神经网络的冷链制冷机结霜检测方法

针对传统基于图像处理技术的结霜检测方法难以对处于复杂生产环境的冷链制冷机组进行灵活且准确的检测，还易受光照、起雾等环境因素的影响而误判的问题，设计了一种基于脉冲神经网络的冷链制冷机结霜检测方法。该方法以制冷机图像为输入，自动检测制冷机蒸发器结霜区域的动态变化情况，修正因光照、起雾等干扰因素引起的异常，并以脉冲发放率累积值划分双阈值作为结霜程度的判断依据。在多个投入至生产环境的冷链制冷机上进行实验，结果表明所设计的脉冲神经网络能够在实际生产环境下自适应地对制冷机蒸发器的结霜区进行动态区域检测、划分的双阈值可准确判断蒸发器的结霜程度，检测效果良好，稳定性强，可为制定冷链制冷机组除霜策略提供可靠的除霜时刻依据。     

丰满混凝土重力坝的冻胀变形分析

根据混凝土结构的冻胀变形机理、典型混凝土试件冰冻变形过程并结合丰满大坝的温度过程特点,定性地解释了坝顶位移测值的历年＂双峰＂现象,界定了冻胀变形的涵义;采用温度等效变形的有限元分析说明受冻胀影响,坝顶廊道处的位移除上抬外还会有向上游的水平位移;利用包含冰冻因子的统计模型对坝顶位移的分析表明,丰满大坝的加固工程对减小冻胀变形的影响确实起到了一定作用,位移测值＂双峰＂现象已不明显,但仍存在冻胀变形,表现出季节性的冻胀变形且时效变形仍有一定的发展趋势.