西北干旱区土建筑遗址加固概述

西北干旱区土建筑遗址很多, 有些还是世界文化遗产。由于风蚀风化作用强烈, 西北干旱区大批的土建筑遗址已破坏严重, 因而开展土建遗址加固研究十分必要。钾水玻璃 (PS)是一种水溶性的无机胶结加固材料, 本文全面详尽地总结了PS加固土建筑遗址技术, 就加固机理作了初步探讨。认识到PS是西北干旱地区土遗址加固的一种有效方法, 可达到较理想的加固效果。     

考虑植被影响的陆气耦合模式

以黄淮海平原大气边界层的观测数据为基础，发展了一个土壤－植被－大气多层模式，对大气和地表进行耦合模拟．模式对植被冠层作多层划分，以助于细致了解植被冠层沿高度分布的各物理量，为非均匀下垫面的参数化提供依据．运用观测结果对数值模拟结果进行验证，表明该模式较成功地模拟了陆气相互作用过程．同时，对模拟进行了敏感性数值试验，以了解植被在陆气相互作用中的影响大小     

Spatial dynamics of a vegetation model in an arid flat environment

Self-organized vegetation patterns in space were found in arid and semi-arid areas. In this paper, we modelled a vegetation model in an arid flat environment using reaction-diffusion form and investigated the pattern formation. By using Hopf and Turing bifurcation theory, we obtain Turing region in parameters space. It is found that there are different types of stationary patterns including spotted, mixed, and stripe patterns by amplitude equation. Moreover, we discuss the changes of the wavelength with respect to biological parameters. Specifically, the wavelength becomes smaller as rainfall increases and larger as plant morality increases. The results may well explain the vegetation pattern observed in the real world and provide some new insights on preventing from desertification.     

干旱区土遗址病害的分类研究

我国西北干旱区分布大量的土遗址,在分析干旱区土遗址病害的基础上,建立了按病害成因、病害表现形式和形成机理分类的土遗址病害3级分类体系和定义。将土遗址的病害分为两大类即自然破坏和人为破坏。自然破坏有5个亚类14个病害表现形式,包括片状剥蚀:雨蚀剥离病害、风蚀剥离病害和裂隙剥离病害;淘蚀:酥碱、风力淘蚀和流水淘蚀;裂隙(缝):卸荷裂隙、构造缝、变形裂隙、建筑工艺裂缝;冲沟:裂隙型冲沟和径流型冲沟;生物破坏:动物病害和植物病害。人为破坏有两种即历史破坏和近现代破坏。     

COAL DRY BENEFICIATION TECHNOLOGY IN CHINA：THE STATE—OF—THE—ART

In China, coal is the major source of energy and its leading role in energy consumption would not change in the next 50 years. Coal preparation is the essential component of Clean Coal Technology. In China more than two-thirds of available coal reserves are in arid areas, which results in the unfeasibility with conventional wet processing for coal preparation. The uniqueness of dry coal beneflciation technology with air-dense medium fluidized bed is dis-cussed in this paper and a detailed survey of the current status of theoretical study, commercial application and development of the new technoloav is aiven in this paper.     

基于强度与稳定性的端头加固理论模型及敏感性分析

为确保盾构始发与到达的顺利进行,避免施工过程中发生端头土体失稳,引发地表沉陷、塌方等工程事故,基于土体强度与稳定性的基本理论,作者就如何确定端头土体纵向加固范围和建立砂土复合地层端头滑动模型进行了研究。在具体分析了现有端头加固理论模型的优缺点后,提出一种基于强度理论的荷载等效模型和基于稳定性理论的砂性土端头滑动模型。该端头加固理论模型,与已有的计算模型相比,更真实地反映了端头土体的受力状况,因而与工程实际情况更为接近,且具有地层适应性。同时,为了检验新强度理论模型的合理性,分别对新旧模型进行实例比算,并对2种模型的主要影响因素进行了敏感性分析。研究结果表明:当盾构隧道直径较小时,已有模型和新提出模型的计算结果误差较小,计算结果较为接近; 随着盾构隧道直径的不断增大,已有模型的荷载简化会引起较大的计算结果误差,如将其结果应用于工程,可能会引发较严重的工程事故; 对于大直径盾构,特别是盾构隧道直径大于10m时,建议采用本文提出的改进理论模型进行端头加固设计和验算,由此得出的加固范围更加符合工程实际情况,对工程有很强的指导意义。同时基于强度理论提出的荷载等效模型为非对称荷载问题的研究提出了一种新的研究方法和求解思路,对今后类似问题的求解具有较好的借鉴意义。     

桁架结构非概率可靠性拓扑优化

考虑非概率可靠性的拓扑优化对于非确定参数和荷载条件下结构的概念设计具有重要意义,有关研究国内外少见报道.本文利用凸模型理论,考虑优化迭代过程的需要,提出改进的非概率可靠性指标的定义,并针对桁架结构拓扑优化设计问题建立了以杆件截面积为设计变量、结构重量极小化为目标、具有非概率可靠性指标约束的广义尺寸优化数学模型.本文指出,考虑桁架结构参数的不确定性的条件下所得到的最优杆件布局与确定性优化所得到的结果可能有显著不同.对文中提出的数学模型,采用数学规划算法求解,数值算例结果令人满意.本文工作表明了桁架结构非概率可靠性拓扑优化设计的可行性和所提出算法的有效性.     

泥沙输运模拟综述——现状及其发展趋势

随着流体力学中数值方法的飞速发展,计算模型已经成为研究流体运动,泥沙输运和不同环境(诸如河流,湖泊及沿海地区)中相应污染物归趋过程等方面非常有吸引力的工具,在过去的30多年里,发展了许多计算水动力学/泥沙输运模型.文章追溯当前具有代表性的(一维、二维、三维)模型的发展历程,描述他们各自的特点,优势及局限,力图作为对模型方面感兴趣读者的第一指南,同时也为大家讨论模型的局限性,未来的发展趋势和研究需求方面搭建一个平台.给出了模型的表达,时空特性,水动力学和沉积物的耦合方式,处理非恒定流,推移质和悬移质,泥沙交换过程,泥沙类型(粘性或非粘性)及非均匀泥沙输运的能力.总结了不同模型的应用实例,读者可以运用这些例子作为研究模型设置,模型率定及模型验证的参考.给出了选择泥沙输运模型应遵循的原则,模型输入及率定方面存在的问题及改进的途径.探讨了现有水动力学/泥沙输运模型在处理复杂湍流,泥沙携带,流动与输沙耦合,非均匀泥沙,离散和扩散系数,河岸来沙处理等方面的局限性及改进的方向.最后,对基于多相流思想的泥沙输运模型及其它一些交叉性问题作了评述与展望.     

Application of a POD-Galerkin based method to time resolved and time unresolved data for the determination of the Convective Velocity of Large-Scale Coherent Structures in High Speed Flows

Motivated by the aero-acoustic feedback loop phenomenon in high speed free jets and impinging jets, a thorough examination of a POD (Proper Orthogonal Decomposition)-Galerkin method to determine the average convection velocity of coherent structures in the shear layer is presented in this paper. The technique is shown to be applicable to both time resolved as well as time unresolved data, if the data set meets certain requirements. Using a detailed sensitivity analysis on a synthetic data set, a quantitative estimate on the required time resolution for the technique has been found, which can be useful for both experimental, as well as numerical studies investigating the aero-acoustic feedback loop in high speed flows. Moreover, some innovative ways to apply the technique are also demonstrated using a simulated data set, showing the effectiveness of the technique to any general problem in supersonic jets, heat transfer, combustion or other areas in fluid mechanics, where an advection process can be identified.     

非饱和膨胀土的土-水特征曲线研究

在干旱和半干旱地区 ,土体中含水量的变化常会引发各种工程问题。研究表明 ,非饱和土的工程性质不仅取决于土的组成、结构和应力状态 ,还与土中的吸力密切相关。非饱和土的土 -水特征曲线表达了土体中含水量与吸力的关系 ,是非饱和土研究的重要内容之一。     

基于Delaunay三角化的无网格法计算结果后处理

最近新发展起来的无网格方法由于不需要显式网格，节省了网格生成所需的大量时间，并且避免了网格畸变问题，所以在处理一些特殊问题如移动边界、大变形、高梯度等方面显示出特殊的优越性。但另一方面也使得计算结果的全域后处理遇到困难。提出了一种基于Delaunay三角形背景网格的实用无网格计算结果后处理方法，以无网格离散节点为顶点生成Delaunay三角形，将无网格法计算得到的节点应力值映射插值得到三角形内的应力场云图颜色。给出的二维线弹性应力分析算例表明方法可靠实用。     

Separation performance of fine low-rank coal by vibrated gas–solid fluidized bed for dry coal beneficiation

Vibrational energy was introduced to a dense medium gas–solid fluidized bed to improve the separation performance of 1–6 mm fine low-rank coal. The setup was termed a vibrated gas–solid fluidized bed and could provide a stable fluidization state and uniform density distribution for dry coal beneficiation by the transfer of vibrational energy and the interaction between vibrations and the gas phase. Favorable segregation of the ash content of the 1–6-mm-sized lignite samples is achieved under suitable operating conditions. Higher yields of cleaning coal were acquired when the ash content was reduced. The probable error values were 0.065 and 0.055 at separating densities of 1.68 and 1.75 g/cm³ for the 1–3- and 3–6-mm-sized lignite samples, respectively. Effective beneficiation of 1–6-mm-sized fine lignite could be achieved using the vibrated gas–solid fluidized bed, which provides an alternative technique for the separation of fine low-rank coal in arid areas.     

The General Mathematical Theory of Plasticity and the Il’yushin Postulates of Macroscopic Definability and Isotropy

The physical laws characterizing the relation between stresses and strains are considered and analyzed in the general modern theory of elastoplastic deformations and in its postulates of macroscopic definability and isotropy for initially isotropic continuous media. The fundamentals of this theory in continuum mechanics were developed by A.A. Il’yushin in the mid-twentieth century. His theory of small elastoplastic deformations under simple loading became a generalization of Hencky’s deformation theory of flow, whereas his theory of elastoplastic processes which are close to simple loading became a generalization of the Saint-Venant–Mises flow theory to the case of hardening media. In these theories, the concepts of simple arid complex loading processes arid the concept of directing form change tensors are introduced; the Bridgman law of volume elastic change and the universal Roche–Eichinger laws of a single hardening curve under simple loading are adopted; and the Odquist hardening for plastic deformations is generalized to the case of elastoplastic hardening media for the processes of almost simple loading without consideration of a specific history of deformations for the trajectories with small arid mean curvatures. In this paper we discuss the possibility of using the isotropy postulate to estimate the effect of forming parameters in the stress-strain state appeared due to the strain-induced anisotropy during the change of the internal structures of materials. We also discuss the possibility of representing the second-rank symmetric stress and strain tensors in the form of vectors in the linear coordinate six-dimensional Euclidean space. An identity principle is proposed for tensors and vectors.     

非均匀脆性材料数值试验CA计算模型

以自动元胞机CA(Cellular Automata)理论为基础,提出了一种CA计算模型,模拟混凝土、岩石等非均匀脆性材料的开裂过程,研究分析材料的变形性质和力学性能。文中给出了空间随机杆件方向余弦常量,推导了等效杆件截面面积计算公式,并通过数值试验证明了方法的有效性。     

Entropy-satisfying scheme for a hierarchy of dispersive reduced models of free surface flow

This work is devoted to the numerical resolution in the multidimensional framework of a hierarchy of reduced models of the water wave equations, such as the Serre-Green-Naghdi model. A particular attention is paid to the dissipation of mechanical energy at the discrete level, which acts as a stability argument of the scheme, even with source terms such space and time variation of the bathymetry. In addition, the analysis leads to a natural way to deal with dry areas without leakage of energy. To illustrate the accuracy and the robustness of the strategy, several numerical experiments are carried out. In particular, the strategy is capable of treating dry areas without special treatment.     

高耸异型烟囱结构风压和风振系数试验研究

本文在模拟的大气边界层中,对某一发电厂高耸异型烟囱的刚性模型进行了测压试验研究,得到了这一结构的平均风压系数、最大和最小风压系数分布,以及该结构的风荷载体型系数;结果表明在烟囱外形明显变化的局部区域,风压绝对值较大,与理论分析一致。同时,对动态测力试验模型进行了高频动态天平测力试验研究,详细介绍了试验及数据处理方法,根据试验结果计算得到了该烟囱在风作用下的动力响应和风振系数;根据试验结果计算所得的风振系数值大于按规范公式估算值。这些结果不仅为结构的风荷载计算提供了依据,也有助于进一步认识该类异性烟囱结构的风荷载和风振特性。     

钨合金弹体对混凝土靶的超高速侵彻机理

为研究钨合金弹体超高速侵彻混凝土靶的相关机理,构建了适用于超高速撞击的金属强度模型、失效模型和混凝土的本构模型,对93钨合金弹体超高速撞击混凝土靶问题进行了数值模拟。开展了钨合金弹体超高速撞击混凝土靶实验,分析了靶板成坑特性,研究了侵彻总深度和残余弹体长度随撞击速度的变化规律,理论分析了长杆钨弹超高速撞击混凝土的侵彻模型和混凝土靶内的应力波传播。得到以下主要结论:（1）利用金属及混凝土的新本构模型获得的超高速撞击混凝土靶的破坏形貌数值模拟结果与实验结果一致;（2）超高速撞击条件下混凝土靶成坑为“弹坑＋弹洞”形,成坑体积与弹体动能近似成正比;（3）超高速撞击条件下,侵彻深度随弹速提高呈现先增大后减小的现象,高速段侵深降低是弹体经历销蚀侵彻后“刚体侵彻阶段”减少造成的;（4）建立的钨合金超高速撞击混凝土侵彻分析模型,可用来预估侵彻深度、残余弹长、蘑菇头直径等参数;（5）采用建立的超高速撞击混凝土靶内应力波传播理论模型得到的计算结果与实验结果吻合较好。     

颗粒附壁燃烧机理及模拟方法探讨

在燃用固体燃料，如生物质、煤、固体废弃物时，都存在一定程度的附壁燃烧现象，以燃煤液排渣燃烧器为例，探讨了颗粒在熔融面上的沉积、流动以及燃烧机理。并针对现有煤粉燃烧程序在液排渣燃烧器模拟上的局限，开发了一种考虑液渣流动的附壁燃烧模型，给出了总体的计算框架．通过对不同壁面处理方式下计算结果的比较，分析了不同手法的优劣和特点，为液排渣燃烧器的正确模拟提供一种完整的思路，对生物质或固体废弃物燃烧模拟起到一定的参考作用。     

Tire-ice model development for the simulation of rubber compounds effect on tire performance

The material properties of the rubber compounds, which are highly dependent on temperature, have a vital role in the tire behavior. A comprehensive study on the effect of the rubber properties on tire performance, for different temperatures, as well as different road conditions is required to adequately predict the performance of tires on ice.In this study, a theoretical model has been developed for the tire-ice interaction. The temperature changes obtained from the model are used to calculate the height of the water film created by the heat generated due to the friction force. Next, the viscous friction coefficient at the contact patch is obtained. By using the thermal balance equation at the contact patch, the dry friction is obtained. Knowing the friction coefficients for the dry and wet regions, the equivalent friction coefficient is calculated. The model has been validated using experimental results for three similar tires with different rubber compounds properties. The model developed can be used to predict the temperature changes at the contact patch, the tire friction force, the areas of wet and dry regions, the height of the water film for different ice temperatures, different normal load, etc.     

环境因素对PS加固土遗址效果的影响

通过PS加固的高昌故城遗址土样崩解试验,耐风蚀的风洞模拟试验,冻融破坏,温差破坏,干湿破坏对力学强度影响等试验,模拟古丝绸之路特殊的自然环境对土遗址的影响,研究PS保护加固土遗址的效果。结果表明,经PS加固以后,样品的初始崩解时间延长,崩解速度大幅降低,抗风蚀能力提高10倍,抗冻融能力也有所增强。在高温养护下力学得到强度提高,干湿循环降低了样品的强度,但表现出良好的加固效果。试验证明PS可以有效地降低环境因素对干旱区土遗址的破坏,起到明显的加固保护效果。