Measurements of Hydrate Equilibrium Conditions for CH4, CO2, and CH4＋C2H6＋C3H8 in Various Systems by Step-heating Method

Phase equilibrium conditions of gas hydrate in several systems were measured by the step-heating method using the cylindrical transparent sapphire cell device.The experimental data for pure CH4 or CO2+deionized water systems showed good agreement with those in the literatures.This kind of method was then applied to CH4/CO2+sodium dodecyl sulfate(SDS)aqueous solution,CH4/CO2+SDS aqueous solution+silica sand,and(CH4+C2H6+C3H8)gas mixture+SDS aqueous solution systems,where SDS was added to increase the hydrate formation rate without evident influence on the equilibrium conditions.The feasibility and reliability of the step-heating method,especially for porous media systems and gas mixtures systems were determined.The experimental data for CO2+silica sand data shows that the equilibrium pressure will change significantly when the particle size of silica sand is less than 96μm.The formation equilibrium pressure was also measured by the reformation of hydrate.

GaN-based heterostructures： electric-static equilibrium and boundary conditions

In the GaN-based heterostructures, this paper reports that the strong electric fields induced by polarization effects at the structure boundaries complicate the electric-static equilibrium and the boundary conditions. The basic requirements of electric-static equilibrium for the heterostructure systems are discussed first, and it is deduced that in the application of the coupled Schroedinger-Poisson model to the heterostructures of electric static equilibrium state, zero external electric field guarantees the overall electric neutrality, and there is no need to introduce the charge balance equation. Then the relation between the screening of the polar charges in GaN-based heterostructures and the possible boundary conditions of the Poisson equation is analysed, it is shown that the various boundary conditions are equivalent to each other, and the surface charge, which can be used in studying the screening of the polar charges, can be precisely solved even if only the conduction band energy is correctly known at the surface. Finally, through the calculations on an AlGaN/GaN heterostructure with typical structure parameters by the coupled Schroedinger-Poisson model under the various boundary conditions, the correctness of the above analyses are validated.

Study on the mechanism of isotope fractionation in soil water during the evaporation process under equilibrium condition

In this study, with the method of vacuum extraction, two evaporative processes of soil water and free water under equilibrium condition were simulated. For each sample,water vapor was condensed by liquid nitrogen and was collected in four time intervals. From the analysis of hydrogen and oxygen isotopic compositions of the water collected at different times, it was discovered that the isotope fractionation of soil water also follows the mode, which is just the same as the evaporative process of free water. The relationship between the stable hydrogen and oxygen isotopes in residual water showed that the simulative evaporation line was close to the global meteoric water line (GMWL) under the equilibrium condition at about 20℃. Comparison of the two types of evaporative processes indicated that the isotope fractionation and evaporation velocity of soil water were only slightly modified by the Van der Waals force.

Expansive Behaviors of Self-stressing Concrete under Different Restraining Conditions

The expansive behaviors of the expensive concrete under different restraining conditions were systemically studied. The experimental results indicate that expansive deformation obviously increases before 10 days and tends to be constant after 25 days regardless of the restraining conditions. The mixture ratio of expansive cement and restraining conditions are the main factors affecting expansive deformation. Self-stress can be obtained when the expansive deformation is restrained. The higher self-stress could be obtained when the expensive concrete is restrained by steel tube. For specimens under steel tube restraining, the wall thickness and the length of the steel tube have important influence on self-stress. Both the radial self-stress and axial self-stress in concrete core increase when wall thickness or length of the steel tube increases.

THE CONTINUOUS CASTING PROBLEM WITH NON-EQUILIBRIUM CONDITIONS

We establish the existence and uniqueness of classical solutions of the continuous casting problem with surface tension and kinetic conditions in a short time interval.

Application of the Conditional Nonlinear Optimal Perturbations Method in a Theoretical Grassland Ecosystem

Using a simplified nonlinearly theoretical grassland ecosystem proposed by Zeng et al.,we study the sensitivity and nonlinear instability of the grassland ecosystem to finiteamplitude initial perturbations with the approach of conditional nonlinear optimal perturbation （CNOP）.The results show that the linearly stable grassland （desert or latent desert） states can turn to be nonlinearly unstable with finite amplitude initial perturbations.When the precipitation is between the two bifurcation points,a large enough finite amplitude initial perturbation can induce a transition between the grassland statethe desert state or the latent desert.

Necessary and Sufficient Conditions for Reactive Azeotropes in Multi-reaction Mixtures in Terms of Elemental Composition

Necessary and sufficient conditions for azeotropy in reactive mixtures are derived in terms of elemental composition, which shows that in the space of elemental compositions, they take the same functional form as the conditions for azeotropy in non-reactive mixtures. The production of methyl tert-butyl ether (MTBE) is taken as an example. It is found that there are a 'pseudo' intermediate-boiling ternary reactive azeotrope at p = 101.325kPa and two 'real' ternary reactive azeotropes at p = 101.325 Pa. The introduced elemental compositions also reduce the dimensionality of the phase diagrams and provide a natural set of variables for visualization of phase behavior.

Study on air formation to ground attack-defends decision making in fuzzy condition

With the development of modern military technology, uncertain decision-making problems become more and more exigent to be solved in military command and control. Based on game theory, and taking air formarion to ground attack-defends campaign as the background, this paper established an opposed dynamic decision-making model. As to the problems in military decision-making in fuzzy condition in uncertainty, this paper put forward a fuzzy-influence-factor, which reflects the fuzzy influence on battle units, and establishes a fuzzy opposed decision-making model in anticipant value and in correlative chance way farther to get strategy equilibrium. It can be seen from the simulating results that the model disposes the fuzzy status in battlefield reasonably, analyzes the fighting results objectively, and offers a powerful decision-making support for military operation. The method is practically and effectively.

Subgradient Extragradient Methods for Equilibrium Problems and Fixed Point Problems in Hilbert Space

Inspired by inertial methods and extragradient algorithms,two algorithms were proposed to investigate fixed point problem of quasinonexpansive mapping and pseudomonotone equilibrium problem in this study.In order to enhance the speed of the convergence and reduce computational cost,the algorithms used a new step size and a cutting hyperplane.The first algorithm was proved to be weak convergence,while the second algorithm used a modified version of Halpern iteration to obtain strong convergence.Finally,numerical experiments on several specific problems and comparisons with other algorithms verified the superiority of the proposed algorithms.

Dark current suppression in HOT LWIR HgCdTe heterostructures operating in non-equilibrium mode

Typically,infrared detectors require cryogenic cooling to limit dark current w hich is directly dependent on Auger generation-recombination mechanism and highly influential in Hg Cd Te-narrow band gap material.The Auger suppressed architectures have an advantage over conventional detectors allow ing operation at elevated temperatures>200 K.Architecture w ith combination of exclusion and extraction heterojunctions has been proposed to low er Auger contribution.The paper presents a new long-w ave(≈10μm)infrared Hg Cd Te architecture w ith graded gap/doping interfaces and extra barrier located in exclusion heterojunction to suppress dark current for high operating temperature conditions.Proper barrier implementation reduces dark current by more than 20 A/cm2for room temperature operation.

SCR脱硝系统的RBF条件积分滑模参数优化控制

针对选择性催化还原(SCR)脱硝系统在火电机组深度调峰下因系统特性随着机组负荷改变而难以控制的问题,提出基于径向基函数(RBF)的条件积分滑模优化控制方案,用条件积分滑模减少抖振与调节时间,用RBF实时逼近SCR脱硝系统特性改变下的未知扰动以提高系统鲁棒性。并提出一种纳什均衡量子粒子群寻优(NEQPSO)算法,以获得RBF条件积分滑模控制方案的最优参数,并在20%~100%的机组负荷下进行仿真实验。结果表明:优化后的RBF条件积分滑模控制与传统控制方案相比超调量降低50.26%、调节时间缩短13.55%,在干扰信号下超调量仅有1.50%,其响应速度更快、抗干扰能力更强、鲁棒性更好。

相平衡关系在《化工原理》单元过程强化中的应用

相平衡条件是传质过程的热力学极限,借此可以确定分离级数、液气比等操作参数,设计和优化分离工艺,探索体系极限。本文列举了蒸馏、吸收、萃取单元操作中相平衡的内容,说明通过改变温度、压力、浓度或增加促进剂可以改善相平衡,调整传质过程的控制步骤,从而对化工过程实现精准设计和调控,是过程强化的重要手段。对于这些能源密集型单元过程,相平衡模型的准确预测或模拟是高效分离或纯化、减少能耗和原料损失的必要保障。

开放经济动态随机一般均衡模型下最优货币政策和货币状况指数研究——基于1992—2022年中国数据的理论和实证分析

本文构建开放经济下的新凯恩斯动态随机一般均衡模型,模拟显示在外部冲击下,利率、汇率和最终目标高度相关。以理论模型为基础对最优货币政策进行探究,发现其政策权重受消费者、生产者和中央银行的行为等模型参数的影响。进一步构建货币状况指数(MCI),其权重不仅取决于商品市场、货币市场和利率平价参数等的变化,还依赖于最优货币政策参数的变化。根据1992—2022年数据进行实证研究发现,最优货币政策参数为1.1823,意味着我国央行的货币政策是逆周期操作的,且赋予经济增长以更大的权重;估计出MCI的权重为0.7867,意味着实际利率上升1%相当于实际汇率下降0.79%,实际利率变动的影响弱于实际汇率。最后本文研究表明货币状况指数可以作为宏观经济目标变动的先行指标。

某钼(铜)多金属矿排土场边坡稳定性分析

为了研究排土场边坡稳定性,以西藏天仁矿业有限公司邦铺矿区钼(铜)多金属矿排土场为研究对象。通过工程地质条件调研,并考虑自然工况、降雨工况、地震工况三种工况,最后采用极限平衡分析法中的简化Bishop法、Spencer法与Morgenstern-Prince法对该矿排土场边坡稳定性进行分析。结果表明:排土场1-1’剖面在自然工况、降雨工况及地震工况下以极限平衡法计算所得到的安全系数均大于规范值,据此排土场边坡处于稳定状态。研究结果对该矿其他排土场边坡稳定性分析提供一定的参考依据。

涟水高沟地区承压地下水可更新性研究

为合理开发利用和保护地下水资源,评价区域地下水可更新性成为当前首要解决的问题。本文从定性和定量两个角度进行分析研究,首先从区域水文地质条件与地下水水动力等方面,进行地下水系统划分及特征研究,分析含水层空间结构及补径排条件;其次在收集利用以往测试资料基础上,通过现场采样分析,开展不同水体环境同位素特征研究;最后利用水均衡法计算地下水可更新能力指标。研究结果表明:涟水高沟地区承压水具备地下水补给通道,主要接受上游山区侧向径流补给,且在开发利用过程中不会引发地面沉降等环境地质问题;地下水水龄2万年左右,水循环更新周期上千年,可认为其具有一定的更新能力,不属于难以更新的地下水;同时,地下水的合理开发利用有助于加快地下水循环速率,进一步提高地下水更新能力。

R13/R26矩方法的介观尺度壁面边界条件

宏观尺度NSF(Navier-Stokes-Fourier)、R13/R26矩方程边界条件在中、大克努森数Kn来流条件下计算精度大幅度降低,也极易发散。针对这一难题,提出R13/R26矩方程的介观尺度边界条件,在靠近壁面处重构速度分布函数,并输入介观尺度Boltzmann模型方程;基于离散速度法求解宏观参数,所得到的宏观参数作为R13/R26矩方程的壁面边界条件。仿真结果表明:基于介观尺度边界条件的R13/R26矩方法相较原边界条件计算精度最大提高59.84%,同时,所提出的边界条件将矩方法对Kn的适用范围拓展到1.0。

基于分层架构的退役电池可重构均衡控制研究

利用退役电池构建储能系统,充分利用其剩余价值,是解决大量退役电池再利用的重要途径。然而,经过多次充放电影响,退役电池不一致性问题较新电池更为突出。在此背景下,首先,针对退役电池储能系统提出了分层式可重构均衡拓扑。其次,基于该拓扑提出了分层式均衡控制策略。考虑组内部和组间两个层次的均衡控制,组内以SOC和端电压为均衡变量,通过重构实现电池单体状态均衡,组间以SOC为均衡变量,通过重构保证全电池簇均衡。同时考虑多种运行工况:静置过程中通过自均衡提高电池组的均衡效率和可用容量,放电过程中通过拓扑结构变换维持输出电压稳定,充电过程中考虑能量损耗和充电速度合理优化充电电流,缩短充电时间,减少温升,延长电池使用寿命。最后,在Matlab中验证了所提拓扑与均衡策略在不同工况下的有效性。

Shear strength degradation of gas hydrate-bearing sediment due to partial hydrate dissociation

Extraction of methane hydrate from subseafloor reservoir may potentially trigger seabed slides and induce subsidence.To address the problems,it is crucial to properly characterize the phase equilibrium condition of pore hydrate and the shear strength of the soil.As one of the key constitutive components,the phase equilibrium condition enforces a constraint over pore gas pressure,temperature and unhydrated water content.Such a constraint,however,has been traditionally ignored in analyzing the mechanical behavior of hydrate-bearing soil.In this paper,a series of stepwise hydrate dissociation tests was performed,and the phase equilibrium condition of pore hydrate was determined,providing an effective way to evaluate the unhydrated water content during hydrate dissociation.Meanwhile,a series of direct shear tests was also conducted to explore the shear strength characteristics of the soil.It is shown that the shear strength of the hydrate-bearing soil can be significantly influenced by pore gas pressure,unhydrated water content,hydrate saturation and several other factors.In particular,the measured shear strength depends upon the initial water content of the sample,pointing to a potential problem that the shear strength could be wrongly determined if not properly interpreted.A shear strength criterion,which enforces the equilibrium condition of pore hydrate,is developed for hydrate-bearing soil,establishing a link between the equilibrium condition and the shear strength.The proposed equation describes well the shear strength characteristics of hydrate-bearing soils,remarkably unifying the effects of pore pressure,temperature,water content and hydrate saturation.

非平衡热输运边界条件影响研究

当材料的特征尺寸小到与声子平均自由程相当,或特征时间短到与声子弛豫时间相当时,准平衡假设就不再有效,系统内会产生非局部效应。此时,边界条件将成为影响非平衡热输运的重要因素之一。超快速激光加热纳米薄膜是反映此类问题的典型案例,其传热过程中不仅热影响时间极短,而且作用区域还在纳米尺度。文章研究了不同边界条件对纳米硅薄膜非平衡热输运的影响,分析了声子从扩散状态向弹道状态转变的特性。结果表明:采用镜面边界条件与反弹边界条件具有相似的热输运过程,薄膜内部能量密度差异较小;对流边界条件下薄膜内部热量持续向外界流失,其能量密度最低;通过改变对流方式,发现强制对流相比于自然对流会带走更多的热量;随着薄膜尺寸减小,边界条件对热输运的影响会增大。

基于BIM技术的建筑群施工造价偏差预警

常规的建筑群施工造价偏差预警方法以竣工结算阶段的造价偏差预警为主,忽略了累积造价偏差,导致造价偏差预警存在明显差异。因此,设计了基于BIM技术的建筑群施工造价偏差预警方法。动态测算建筑群施工阶段工程造价偏差,将不确定性问题的造价价值信息提取出来,为造价偏差预警行为提供正确描述。基于BIM技术构建建筑群施工造价偏差预警模型,利用IFC描述BIM造价偏差预警的标准格式,为建筑群施工各阶段的造价偏差提供预警决策。约束建筑群施工造价阶段性预警变量,针对不同的施工阶段进行预警条件优化,将各预警变量进行均衡约束,确保施工造价偏差预警效果。采用实例分析,验证了该预警方法的效果更佳,能够应用于实际生活中。