超声动载荷下三维随机骨料混凝土的损伤

混凝土是一种由粗骨料与水泥砂浆组成的非均质复合材料。本研究利用APDL语言程序编写三维水泥混凝土骨料随机投放程序并导入ABAQUS中,同时赋予各相材料塑性损伤本构关系来研究混凝土动态加载下的破坏规律,运用超声波在混凝土破碎中的作用机理对混凝土动态损伤破坏过程进行模拟研究。结果表明:随着超声动态载荷的增大,粗骨料体积分数为40%的混凝土始终能够承受最大应力载荷;随着超声应力波幅值增大,混凝土在动载荷下的损伤值逐渐增大,且粗骨料体积分数为40%时,其抗损伤能力最优;当粗骨料最大粒径逐渐增大,或者当粗骨料最小粒径增大,混凝土级配不合理导致性能不稳定,更易损伤破坏。     

Aggregation‐Induced Emission of Hexaphenyl‐1,3‐butadiene

A new type of AIE molecules based on hexaphenyl‐1,3‐butadienes was reported with respect to the synthesis and characterization. This material exhibited different maximum emission wavelength and enhanced emission intensity at different aggregate state (amorphous and crystalline state).     

Using flow field-flow fractionation (Fl-FFF) for observation of salinity effect on the size distribution of humic acid aggregates

Flow field-flow fractionation (Fl-FFF) was used to investigate the effect of salinity on the size distribution of humic acid (HA) aggregates in estuarine water. In water with high salinity as estuarine water, size distributions were slightly broadened with increasing contact time between HA and estuarine water. At the longest contact times (89 days) and highest salinity value (28 psu, g kg^?1), the peak maxima were observed at 1.7 and 8.6 nm when detected at 254 nm, and at 1.9 and 9.1 nm when detected at 400 nm. In addition, Fl-FFF with an inductively coupled plasma mass spectrometry was applied to examine the effect of salinity on the size distribution of Cd, Ce, Cu, Mn and Pb-binding HA aggregates in estuarine water with different salinity values. At 1 day contact time, the peak maxima of Cd, Ce, Cu, Mn and Pb-binding HA aggregates in water with increased salinity values were increased and gave the larger breadth of size distribution. The larger size fraction of HA aggregates showed more affinity for Pb, Cd, Ce and Mn than Cu whereas the smaller size fraction of humic aggregates showed preferential binding towards Cu.     

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A Markov observation model with dividend is defined and the interpretation of the practical significance is given. We try to use an irreducible and homogeneous discrete-time Markov chain to modulate the inter-observation times and embed a dividend strategy. In the Markov observation model with dividend, a system of liner equations for the expected discounted value of dividends until ruin time is derived. Moreover, an explicit expression is obtained and proved. Finally, some interesting properties are illustrated by numerical analysis and by comparing with the complete compound binomial model with dividend.     

Kinetic study on solute permeation at the interface of molecular aggregates by partial filling capillary electrophoresis

Moment analysis method using partial filling CE was developed for the kinetic study on solute permeation at the interface of spherical molecular aggregates. Moment equations for partial filling CE were developed by classifying CE systems into five categories according to the migration velocities of solute and molecular aggregate. The method was applied to the study on the dissolution of electrically neutral solutes into SDS micelles. Elution peaks were measured by partial filling CE while changing the concentration of SDS and the filling ratio of SDS micellar zone to the capillary (ϕ_M). Partition equilibrium constants (K_p) and rate constants of interfacial solute permeation of SDS micelles (k_in and k_out) were determined from the first absolute and second central moments of the elution peaks by using the moment equations. Their values were comparable irrespective of ϕ_M and were almost the same as those previously measured by complete filling CE. The positive correlation of K_p with the hydrophobicity of the solutes was explained in terms of the change in k_in and k_out. It was demonstrated that the moment analysis method using partial filling CE is effective for studying solute permeation kinetics at the interface of spherical molecular aggregates.     

水岩作用对川藏公路102滑坡形成与演化的影响

10 2滑坡频繁活动造成了川藏公路运营的多次中断。本文立足于翔实的野外考察,从 10 2滑坡水岩作用的影响因素入手,指出川藏公路地区滑坡的水岩作用强烈且形式多样,并分析了水岩作用对 10 2滑坡形成与演化全过程的影响。最后,提出在 10 2滑坡防治中应重点考虑滑坡的水岩作用。     

骨料对混凝土材料冲击压缩行为的影响

利用大尺寸Hopkinson压杆，以实验数据为依据，研究了四种不同骨料尺寸的普通混凝土材料和两种不同配比的钢纤维增强混凝土材料在冲击载荷下的压缩强度，从唯象的角度分析了骨料性质及其粒径对混凝土材料动态压缩性能的影响及可能的力学机理，为在工程上更好地利用混凝土材料提供一定的理论和实验的支持。     

Analysis for some properties of discrete time Markov decision processes

This paper investigates properties of the optimality equation and optimal policies in discrete time Markov decision processes with expected discounted total rewards under weak conditions that the model is well defined and the optimality equation is true. The optimal value function is characterized as a solution of the optimality equation and the structure of optimal policies is also given.     

Ionic effects on the behavior of thermoresponsive PEO–PNIPAAm block copolymers

The temperature‐dependent aggregation and recovery of the copolymer poly(ethylene oxide)₂₂‐b‐poly(N‐isopropylacrylamide)₂₉ with a C₁₂ end‐cap in aqueous solutions of salts and acids are investigated. Salt solutions affected the critical aggregation temperature of the copolymer in a manner predictable according to the Hofmeister series, with the kosmotropic adipic ion lowering the critical aggregation temperature and the chaotropic iodide raising it. Also, both salts and acids increased the size of copolymer aggregates formed with heating, due to the electrostatic shielding of aggregated structures provided by the electrolytes. Additionally, the presence of ionic additives caused a thermohysteretic increase in the size of copolymer aggregates with temperature cycling. The transitions of polymer structure with increasing temperature were surprisingly sharp with the C₁₂ end‐cap present, and particularly broad in samples in which the end cap had been cleaved. This observation suggested that the hydrophobic end group was responsible for imparting some degree of order to the polymer at low temperatures, which allowed for rapid reconfiguration with increasing temperature. Finally, in addition to the transitions expected from the least critical solution temperature behavior of the polymer blocks, we have observed an unexpected additional transition which we attribute to the contraction of the poly(ethylene oxide) chains of the copolymer aggregates at higher temperatures. This work illustrates the importance of considering the environment and composition of thermoresponsive block copolymers in certain applications, particularly in solutions with even modest electrolyte concentrations (1–10 mM), as it can have a profound effect on transition temperatures and morphology. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 507–516