快速凝固高碳铁基合金脉冲激光非平衡热处理

利用脉冲Ｎｄ：ＹＡＧ激光辐照对快速凝固高碳铁基合金进行非平衡相变热处理，发现在高能脉冲激光辐照时，原快速凝固共晶碳化物（Ｆｅ３Ｃ）异常迅速地石墨化，获得了含超细石墨球和既含超细石墨球又含快速凝固共晶Ｆｅ３Ｃ的两种新材料，研究表明，这种快速石墨化及上述两类新型材料的形成主要归因于脉冲激光光速辐照产生强烈周期性起伏温度场的“微退火（ｍｉｃｒｏ－ａｎｎｅａｌｉｎｇ）效应。     

Thermal and nonequilibrium responses of superconductors for radiation detectors

This work summarizes the progress in the study of the superconductor response to optical radiation and in the development of infrared detectors. The recent advances in the design of high-T _c superconducting radiation detectors using silicon microfabrication technology are emphasized. Thermal and optical properties important for the detector performance are discussed. The mechanism of the nonequilibrium optical response and its potential use to build fast and sensitive radiation detectors are described. Future challenges and opportunities in the development of high-T _c superconducting radiation detectors are highlighted.     

Multidimensional Kinetics of Nucleation in Liquid-Vapor Systems

A metastable system is described as an ensemble of locally isolated statistically independent centers, with a possibility of one and only one nucleus of a close-to- critical radius emerging on each one of these centers. It is assumed that this event occurs as a result of fluctuations in a heterophase subsystem and leads to the formation of a viable nucleus at a given point in space. The process of the emergence of this nucleus is treated as the first crossing of the potential barrier by a Brownian particle. Proceeding from the principles of nonequilibrium thermodynamics, dynamic equations of bubble (droplet) growth are derived, which correspond to the Onsager relations. These formulas are used as Langevin equations in multidimensional phase space and are related to the respective Fokker-Planck equation whose solution enables one to determine the local rate of emergence of a viable nucleus and, as a consequence, the rate of its emergence in the entire system. An alternative expression is given for the rate of homogeneous steady-state nucleation, which differs from the classical expression by the pre-exponential factor and, in the case where one parameter (radius) may be sufficient, gives close limits of attainable superheat (supersaturation). Given the expression for the nonequilibrium work of bubble (droplet) and the distribution of heterogeneous centers, the obtained result may be readily generalized to the case of heterogeneous nucleation.     

Prediction of half reaction length for H2O2Ar detonation with an extended vibrational nonequilibrium Zel'dovich −von Neumann −Döring (ZND) model

An extended Zel'dovich–von Neumann–Döring (ZND) model has been proposed to address vibrational nonequilibrium mechanism. To expand the application of this extended ZND model in predicting flow characteristics under thermal nonequilibrium for hydrogen-related detonation simulations, a case of one-dimensional stoichiometric hydrogen-oxygen detonation with argon dilution is adopted for comparative study. A vibrational relaxation timescale is introduced in the extended ZND model together with simplified single-step and two-step chemical reaction models. In addition, a numerical simulation using the conservation element and solution element (CE/SE) algorithm and detailed chemistry with vibrational nonequilibrium coupling is conducted to serve as a benchmark for the model predictions. In this specific case study, predictions of half reaction length are in good agreement with simulations if the single-step Arrhenius model and the characteristic vibrational temperature of hydrogen are used. Compared with the detailed numerical simulations, the current extended ZND model and the simplified chemical models are demonstrated feasible and economical to predict the half reaction thickness under the vibrational nonequilibrium condition and can serve as one of the analytical tools in studying large-scale H₂O₂ detonation.     

Effects of Internal and External Connection of Electrodes in Diagonal Type Nonequilibrium Plasma MHD Generator

In this paper, by a two-dimensional analysis in the duct cross section perpendicular to the plasma flow, the authors investigate comparatively the current distribution, the electrical efficiency etc. in the diagonal type nonequilibrium plasma generator of the window frame construction and the one of the insulating sidewall. Their numerical computations are made for an example of the cesium-seeded helium in nonequilibrium ionization, where it is assumed that the ionization instability does not occur.

It is shown that the current in the generator duct of the diagonal conducting wall tends to flow uniformly in the cross section of the duct, and on the other hand, the current in the duct of the insulating sidewall does in its central part; thus the performance characteristics of the former becomes better than those of the latter. This tendency increases with the load factor and wall temperature of the generator. Also the generator characteristics are improved with increasing the inclination factor, and the electrode voltage drop decreases with the load factor.     

Optimal design of catalytic distillation columns: A case study on synthesis of TAEE

The design of catalytic distillation (CD) columns is a challenging task because of the superposition of chemical reaction and distillation in one apparatus. In this work, a method to design a cost-optimal CD column for chemical systems with large number of components and chemical reactions is presented. The method is based on the following steps: (1) estimation of the number of theoretical stages and catalyst volume by the decomposition of the CD column into a sequence of chemical reactors and non-reactive distillation columns, (2) estimation of the column diameter and operating conditions using an equilibrium stage model, and (3) design of the column applying an optimisation algorithm and using a rigorous non-equilibrium stage model to represent the CD process. The method is applied to determine the optimal column configuration and operating conditions for the synthesis of tert-amyl ethyl ether from ethanol and isoamylenes. Eight components and four chemical reactions were selected to represent the chemical system in the simulations.     

聚合物辅料对阿司匹林结晶动力学影响机制的非平衡热力学建模及预测

探究聚合物辅料对难溶性药物结晶的影响机制,是指导无定形固体分散体制剂设计和制备中辅料筛选的关键。研究了不同因素（温度、搅拌速率、聚合物浓度、聚合物分子量和聚合物种类等）对阿司匹林晶体生长动力学的影响。首先,采用基于三种不同晶体生长机制的化学势梯度模型结合UNIQUAC活度系数模型,描述和预测了阿司匹林在不同条件下的结晶动力学。进一步分析了不同因素对晶体生长速率常数k_t和结晶热力学推动力?\mu的影响以及对阿司匹林结晶动力学的影响机制。结果表明,阿司匹林晶体生长速率随着结晶温度、聚合物浓度的增加而降低,随搅拌速率的增加而升高;聚乙烯吡咯烷酮（PVP K25）和羟丙基甲基纤维素（HPMC E3）显著抑制了阿司匹林的晶体生长,在PVP K25和HPMC E3水溶液体系下阿司匹林的晶体生长属于二维成核机制,在纯水和PEGs水溶液体系下晶体生长属于粗糙生长机制。所采用的化学势梯度模型能很好预测不同温度和搅拌速率下阿司匹林的结晶动力学,可有效减少实验所需的人力、物力和财力。研究可为固体分散体制剂制备中聚合物的筛选提供理论研究基础。     

Study on Hydrolysis of Methyl Acetate in a Catalytic Distillation Column

A nonequilibrium stage model was used to simulate countercurrent multicomponent catalytic distillation processes for methyl acetate hydrolysis. Computations of stage efficiencies or height equivalent to a theoretical plate (HETP) were entirely avoided by this model. The consistency of simulated results and experimental data in conversions and concentration of each component along a column indicates that the model predicts the actual process well. The influences of operating parameters on hydrolytic conversions, such as feed molar ratios, feed locations, feed and reflux rates, heights of reactive and stripping sections, were analyzed adequately by simulating calculations. A good operating mode was then obtained, which is helpful to the development of a new process.     

Investigation of local thermal nonequilibrium effects on oil in situ combustion simulation

In the models developed for oil in situ combustion so far, local thermal equilibrium (LTE) was assumed between reservoir rock and fluids without being validated. As presence of a combustion zone makes the validation of this assumption questionable, in this study a new two-energy equations model is developed describing the temperature fields of rock and fluids separately. Investigating the effect of local thermal nonequilibrium between rock and fluids indicates that LTE will fail if the grain's diameter size order exceeds a millimeter. In this case, using LTE will lead to overestimating the heat and mass transfer rates.