CO2 will probably not help to save Venice from the sea

It has been proposed to rise Venice by injecting CO₂ into an aquifer lying 600–800 m below its lagoon. It is shown that because of the prevailing ambient conditions in the aquifer phase change of CO₂ cannot be avoided. The ensuing change of specific volume and compressibility will inhibit a uniform uplift pattern which is needed to avoid cracks in historical buildings. Further, both liquid and gaseous CO₂ produce capillary effects at the contact surface with water in the voids of the reservoir rock and this affects its mechanical response. Hence further non homogeneity in the uplift pattern will be produced. This prevents the use of CO₂ in the proposed conditions.     

三峡库区滑坡的时空分布特征与成因探讨

三峡库区地质灾害频繁发生,地质历史上大型滑坡广泛发育。近年库区滑坡灾害有逐年增加趋势。这些滑坡形成的堆积体成因复杂,不能单纯从传统的外动力或内动力作用来解释,给库区灾害的防治工程带来了很大困难。三峡库区大型古滑坡主要沿长江干流和支流的深切河谷两岸分布,与河流发育演化史密切相关。15万年以来,长江三峡地区经历了新构造期以来抬升速率最快的一次构造幕,山原期夷平面上升了100m,河流强烈下切,形成高陡岸坡,卸荷效应显著;同时,该时期三峡地区的气候受到青藏高原环境变化的影响,在间冰期可能存在相似的暖湿古气候环境,降水极为丰富。三峡库区的大型古滑坡在新构造快速抬升时期广泛发育,并且与暖湿多雨期相对应,表明库区滑坡的发育演化是新构造运动和气候变化内外动力耦合作用的结果。     

Solidification or Melting Initiation over a Limited Portion of an Edge in a Plate

This paper proposes a method for obtaining short-time analytical solutions to problems in pure heat conduction, and heat conduction with phase change. The method employs the notion of fictitious initial temperatures in some fictitious extensions of the original phase region. Analytical results obtained in the case of a heat conduction problem in a rectangular plate are presented first and compared with numerical solutions. This analytical solution is also required later in the determination of liquid temperature in the phase change problem. The method is then extended to a two-phase solidification problem in which solidification starts over a limited portion of one of the vertical edges of the rectangular plate. The freezing front in this case consists of spread along the vertical edge and growth towards the interior. The spread along the edge can have asymptotic behaviour not commonly found. The method is applicable to other geometries, e.g. inside and outside of a long cylinder, a three-dimensional slab, etc.     

毫瓦计──功率变化量测量仪

本文介绍的毫瓦计是测量陀螺马达轴承摩擦力矩稳定性的一种新型仪器，为该仪器专门设计了功率测量和变化量测量方案，其优点是测量精度高、简单、可靠、实用性强。     

Phase-Transformation Fronts Evolution for Stress- and Strain-Controlled Tension Tests in TiNi Shape Memory Alloy

Nucleation and development of phase transformation fronts in TiNi shape memory alloy subjected to the stress- and strain-controlled tension tests were investigated. A thermovision camera was applied to register the distribution of infrared radiation emitted by the specimen and to find its temperature variations. During the loading, narrow bands of considerably higher temperature corresponding to the martensitic phase, starting from the central part of the specimen and developing towards the specimen grips, under both approaches, were registered. The inclined bands of heterogeneous temperature distribution were observed also during the unloading process of the SMA, while the reverse transformation accompanied by temperature decrease took place. Thermomechanical aspects of martensitic and reverse transformations for various strain rates were analyzed under both stress- and strain-controlled tests.     

Fabrication and performance of microencapsulated phase change materials with hybrid shell by in situ polymerization in Pickering emulsion

Microencapsulated phase change materials (MePCMs) using melamine–formaldehyde resin/SiO₂ as shell were investigated in this paper. Organically modified SiO₂ particles were employed to stabilize Pickering emulsion, and in situ polymerization of melamine and formaldehyde was carried out to form hybrid shell. The performances of resultant MePCMs with hybrid shell were investigated comparatively with the MePCMs with polymer shell. SiO₂ particles raise the microencapsulation efficiency by improving the stability of emulsion and providing a precipitation site for melamine–formaldehyde resin. Also, the mechanical strength, thermal reliability, and anti‐osmosis performance of MePCMs were improved significantly by SiO₂ particles in the shell. Our study shows that Pickering emulsion is a simple and robust template for MePCMs with polymer‐inorganic hybrid shell. Copyright © 2015 John Wiley & Sons, Ltd.     

Halogen‐bonded adduct of 1,2‐dibromo‐1,1,2,2‐tetrafluoroethane and 1,4‐diazabicyclo[2.2.2]octane

Halogen bonding is an intermolecular interaction capable of being used to direct extended structures. Typical halogen‐bonding systems involve a noncovalent interaction between a Lewis base, such as an amine, as an acceptor and a halogen atom of a halofluorocarbon as a donor. Vapour‐phase diffusion of 1,4‐diazabicyclo[2.2.2]octane (DABCO) with 1,2‐dibromotetrafluoroethane results in crystals of the 1:1 adduct, C₂Br₂F₄·C₆H₁₂N₂, which crystallizes as an infinite one‐dimensional polymeric structure linked by intermolecular N...Br halogen bonds [2.829 (3) Å], which are 0.57 Å shorter than the sum of the van der Waals radii.     

Active dielectric metasurface based on phase‐change medium

We propose all‐dielectric metasurfaces that can be actively re‐configured using the phase‐change material Ge₂Sb₂Te₅ (GST) alloy. With selectively controlled phase transitions on the composing GST elements, metasurfaces can be tailored to exhibit varied functionalities. Using phase‐change GST rod as the basic building block, we have modelled metamolecules with tunable optical response when phase change occurs on select constituent GST rods. Tunable gradient metasurfaces can be realized with variable supercell period consisting of different patterns of the GST rods in their amorphous and crystalline states. Simulation results indicate a range of functions can be delivered, including multilevel signal modulating, near‐field coupling of GST rods, and anomalous reflection angle controlling. This work opens up a new space in exploring active meta‐devices with broader applications that cannot be achieved in their passive counterparts with permanent properties once fabricated.

     

Experimental Investigation on Binary Phase Diagram of the Thermotropic Phase Transitions Compounds (n‐CnH2n+1R3)2ZnCl4

The thermotropic phase transitions compounds (n‐C_nH_2n+1R₃)₂ZnCl₄ as well as a series of their binary mixtures were prepared by a solution reflux method from their ethanol solutions. The experimental subsolidus binary phase diagram of [n‐C₁₈H₃₇N(CH₃)₃]₂ZnCl₄‐[n‐(C₁₈H₃₇)₂N(CH₃)₂]₂ZnCl₄ is constructed over the entire composition range by differential scanning calorimetry(DSC) and X‐ray. Experi‐ mental results indicate one stable intermediate phase [n‐C₁₈H₃₇N(CH₃)₃] [n‐(C₁₈H₃₇)₂N(CH₃)₂]ZnCl₄ at W_C18C3Zn %=59.75 %, and two invariant three phase equilibria, which shows two eutectoid temperatures: Te₁ at 310±1 K for eutectoid point W_C18C3Zn %=36.24 %, Te₂ at 313±1 K for eutectoid point W_C18C3Zn %=80.17 %. These three noticeable solid‐solution ranges are α‐phase at the left, ?‐phase at the right, and ψ‐phase in the middle of the phase diagram. It is (n‐C_nH_2n+1R₃)₂ZnCl₄ systems as phase change materials that are characterized the phase transition temperatures T in the range of 310 to 340 K, the transition enthalpies ΔH in the range of 38.40 and 168.72 J/g between two polymorphic forms.     

有机相变材料的发展及在纺织领域的应用

相变材料因为其优良的热性能,被广泛应用于纺织品、航空航天、交通运输、农业、国防、建材、太阳能系统和医疗设备等领域。近年来,开发应用新型相变材料已经成为研究热点。本文首先概括介绍了相变材料发展进程,着重介绍了有机相变材料,包括它的分类、性能和应用。详细介绍了有机相变材料在纺织行业的应用,以及对调温纺织品测试手段的研究和建立的相关数学模型的建立。