粗颗粒流态化浮选Ⅰ:动力学分区及矿化气絮体稳定性分析

流态化浮选技术作为粗颗粒分选新技术,明晰其动力学分选过程、揭示粗颗粒回收强化机理可为调控粗颗粒流态化分选过程奠定理论基础。本文搭建了实验室粗颗粒流态化浮选试验系统,采用电阻层析成像(ERT)、高速摄像、深槽取样等测试方法系统地探讨了不同上升水流速度(8 L/min、10 L/min和12 L/min)下床层轴向浓度分布。结果表明,流化玻璃球浓度在不同水流速度下均呈现自底部向顶部逐渐递减的稳定分布,中部浓度随高度增加而显著降低。进一步提出了粗颗粒流态化浮选“四分区”动力学模型,揭示了稀相区和浓相区的矿化分离机制:稀相区的分选过程为“浮力-重力”耦合,依赖于微重力场的泡沫浮选;浓相区为“重力-浮力”耦合,基于密度差异的重力分选。此外,建立了颗粒气泡矿化气絮体稳定性计算模型,推导了矿化气絮体稳定存在下的最大颗粒尺寸(R_(max)),从理论上证明了流态化浮选的粗颗粒浮选粒度上限是传统机械搅拌式浮选的1.5~1.8倍。

放顶煤采场力学分区及支承压力分析

研究分析了综采放顶煤采煤工作面顶板、顶煤在支承压力的作用下活动和运移规律,总结出综放采煤工作面支架—围岩关系和采面围岩的空间分区特点,对综采放顶煤控制顶板、改善顶煤的冒放性有一定的参考作用。

基于分区支承力学模型的综放工作面顶板矿压演化与压架预测

为预测综放工作面压架灾害,在综放顶板分区支承力学模型基础上,提出了综放工作面大采厚顶板矿压演化计算方法和支架压架判据,编制了相应的计算程序,分析了综放工作面顶板矿压演化规律,研究结果表明:①综放工作面顶板矿压演化包括4个阶段,分别为缓慢增阻阶段、顶板断裂阶段、快速增阻阶段和失稳阶段。②缓慢增阻阶段顶板沉降量小,支架增阻量小,顶板来压不强烈;快速增阻阶段顶板沉降量大,支架增阻显著。③顶板断裂阶段是矿压从缓慢增阻向快速增阻转变的过渡阶段。顶板煤壁前方断裂时,顶板的边界条件改变,顶板来压剧烈,支架增阻量大,易于引起安全阀开启,若顶板沉降量超过支架活柱允许压缩量,引发大面积切顶压架事故。④当工作面推进至断裂线处,顶板失稳,支架急增阻,若垮落覆岩作用于支架上的荷载超过支架额定工作阻力,安全阀开启,易于引发大面积压架事故。⑤支架额定工作阻力和初撑力设计应遵循的原则是:在缓慢增阻和快速增阻阶段,支架承担的荷载不超过支架额定工作阻力;在顶板断裂阶段,支架应具有足够的可压缩空间卸位让压;在失稳阶段,支架应具有足够的额定工作阻力承担垮落覆岩作用荷载。⑥酸刺沟煤矿6105-2综放工作面采用ZF15000/26/42四柱支承掩护式支架,初撑力10800 kN,支架额定工作阻力不足,易于发生大面积压架事故。

深部巷道非对称变形的分区力学模型研究

针对深部巷道开挖后围岩非对称变形现象,基于结构力学相关理论,对巷道围岩变形破坏进行了不同分区岩体梁的力学模型构建及数值模拟分析。得出各分区岩体梁变形的弯矩方程和挠度方程,理论分析了各分区岩体梁的变形最大弯矩及最大挠度位置。模拟结果对构建的力学模型进行了有力验证,得出各分区岩体梁的危险位置,可对相关问题提供一定的理论参考。

CT技术在基岩力学参数分区中的应用

采用ＣＴ技术可从不同射线方向的孔间穿透的声波、地震波走时信息中反演求得测区岩体的波速分布特征，圈定测区地质构造及地下硐室的分布情况。通过对测区岩样的静力试验资料与动测资料的对比，求得适合具体工程特点的动静对比经验公式，可将测区波速分布换成测区岩体力学参数分布，从而达到对测区进行力学参数分区的目的，本方法在清江高坝洲工程左岸溶塌体溶洞分布调查及坝基岩力学参数分区中得到初步应用。

水库滑坡力学效应分区及稳定性计算方法研究

水库滑坡的稳定与否直接关系到水库的正常运营,而通用的水库滑坡稳定性计算方法未能考虑滑坡体与库水间的力学作用效应。基于以上考虑,在地下水与岩土体相互作用效应分析的基础上,将水库滑坡划分为干燥、渗流和浸没三个力学作用效应区。在此基础上,以不平衡推力法为基础,推导出了三个效应区的稳定性计算方法,并开发了与之相对应的计算程序,为水库滑坡稳定性分析提供了一套行之有效的计算工具。

滑坡体变形运动的多层次监测研究

滑坡的失稳是一个渐变到突变的过程,破坏前会有一些预兆,捕捉这些信息并及时发现问题、采取处理措施是滑坡监测的主要目的。对小浪底某滑坡进行综合监测研究,在滑坡的关键位置设置25个地表变形监测点和3个深部变形监测点,所有监测点组成多层次综合监测系统,进行监测研究。分析监测数据可知:该滑坡体地质结构大致分为前部滑塌体、中后部滑移体和后缘拉裂体。坡体的力学性质分区大致为崩坡积物、碎裂岩体、裂隙、基岩,由此分析了滑坡体表面及深部变形的趋势和影响因素。

Leaching process of selenium residue

A thermodynamics analysis on the leaching process of selenium residue and discussion on the behaviors of aqueous ionic in the leaching process were carried out. Through thermodynamical calculation, the values of AG and relevant potential expressions were obtained. According to these thermodynamical data, the φ-pH diagrams of Se-H2O system at 298 and 373 K were obtained; Simultaneously, the φ-pH diagrams of SO2-H2O and SO2-Se-H2O systems were drawn at 298 K. With increasing the temperature, the stable regions of HSeO3, SeO2- and SeO2- in the φ-pH diagram of Se-H2O system become gradually large, but the limits of pH in the stable region become gradually small. The stability area of reduction precipitation in the SO2-Se-H2O system was finally determined. The results of oxidization leaching experiments of selenium residue indicate that when the mass ratio of selenium residue to sodium chlorate is 2, the concentration of sulfuric acid is 300 g/L and the residue is agitated for 3 h at leaching temperature of 80 ℃, the leaching rate of selenium could reach 97.76 %. The experimental results conform the calculated results by φ-pH diagram. The selenium reduction precipitation in oxidization-leaching solution was analyzed under the conditions of acidity of 150 g/L, the sodium sulphite concentration of 35 g/L at the reductive temperature of 23 ℃ for 120 min. And this demonstrates the thermodynamics analysis.

The Origin of the 2008 Wenchuan Earthquake Determined by the Analysis on the Active Longmenshan Nappe in Terms of Rockmass Mechanics

On 12 May 2008, the magnitude 8.0 Wenchuan Earthquake occurred along the Longmen Shan nappe, Sichuan, China. This devastating earthquake led to a heavy death toll of greater than 80,000. The seismic origin of this earthquake is currently hotly debated. We suppose that it is a special type of intraplate earthquake called an active-nappe-type earthquake. Using a holistic methodology, incorporating rockmass structure cybernetics and Byerlee's law, we present a comprehensive study on the geological origin of macroseisms in the Longmen Shan area and the seismic origin of the 2008 Wenchuan earthquake. Previous studies of neotectonic activity indicate that the Longmen Shan nappe moves at a rate of 1~3 mm/yr, due to horizontal compressive stress from the Tibetan Plateau. The difference between movement rates in the Bayankala block, Longmen Shan nappe and Sichuan Basin cause slow shear stress and strain accumulation in the Longmen Shan nappe. It is exhibited a relatively simple linear relations for the shear strength and the buried depth of the structural planes, and the detachment layer of the nappe has a higher shearing-sliding strength compared to the overlying fault planes and the underlying ductile shear belts, thus making it more prone to stick-slip deformation. Therefore, the detachment layer was the main section responsible for the Wenchuan earthquake. The initial rupture burst in the detachment layer under the Yingxiu-Beichuan fault, the rupture area nearly 1.4454 × 104 km2,encompassed the cross point of the Yingxiu and the Anxian-Guanxian faults with the detachment layer, then caused the Yingxiu-Beichuan and Anxian-Guanxian faults took an active part in this earthquake, so this earthquake might consist of three chain-like earthquake stages, totally increasing the duration of this earthquake an unusually large amount, to 120 s. The focal depth spanned range of 10-20km,consistent with the observed result of this focal depth by several agencies.

Urban Economic Cluster Template and Its Dynamics of Beijing,China

Economic clusters have been a central focus of current urban and regional research, policies and practices. However, a methodology to identify and analyze policy-relevant economic cluster dynamics is still not well developed. Based on input-output(I-O) data of 1987, 1992, 1997, 2002 and 2007 of Beijing, this article presents an adapted principle component analysis for identifying the evolution of local economic cluster patterns. This research addresses the changes of economic interaction of industries with complementary and common activities over time. The identified clusters provide an insight into the reality of economic development in a diversifying urban economy: the increasing importance of services and the growing interaction between service and manufacturing industries. Our method therefore provides the analysts with a better understanding of the emergence, disappearance and development of economic clusters citywide. The results could be used to assist monitoring urban economic development and designing more practical urban economic strategies.

Parallel hydrodynamic finite element model with an N-Best refining partition scheme

We enhance a robust parallel finite element model for coasts and estuaries cases with the use of N-Best refinement algorithms,in multilevel partitioning scheme.Graph partitioning is an important step to construct the parallel model,in which computation speed is a big concern.The partitioning strategy includes the division of the research domain into several semi-equal-sized sub-domains,minimizing the sum weight of edges between different sub-domains.Multilevel schemes for graph partitioning are divided into three phases:coarsening,partitioning,and uncoarsening.In the uncoarsening phase,many refinement algorithms have been proposed previously,such as KL,Greedy,and Boundary refinements.In this study,we propose an N-Best refinement algorithm and show its advantages in our case study of Xiamen Bay.Compared with original partitioning algorithm in previous models,the N-Best algorithm can speed up the computation by 1.9 times,and the simulation results are in a good match with the in-situ data.

Analysis of Absorption and Reaction Kinetics in the Oxidation of Organics in Effluents Using a Porous Electrode Ozonator

A novel electrode design for the in situ generation of ozone in the reaction zone of a tubular reactor is described in this work.The ozone generator uses a porous inner electrode tube in the corona discharge assembly,and the ozone generated around the outer periphery of the porous tube diffuses into the tubular reactor and reacts with the contaminants in the fluid that is being treated.A mathematical model that includes absorption and second order reaction in the film is developed to describe ozonation kinetics of a contaminant dye in the tubular reactor.The model describes the experimental data for dye decolorization,oxidation byproducts,dissolved ozone,and ozone gas concentrations well.Model analysis indicates that the fast dye decolorization reaction occurs partly in the liquid film and partly in the bulk fluid.The model can be used in the selection of appropriate gas-liquid contactors for efficient oxidation of contaminants in effluents.

Thermodynamics of DBI Black Holes in Anti-de Sitter Spacetime

Through the gauge field theory, we obtain the solution of the DBI-AdS black hole, In the meantime, according to the relations between the action and the grand partition function, we obtain the grand partition function in the DBI-AdS black hole. The temperature and the potential of the DBI-AdS black hole are gained from differential of the grand partition function. With the thermodynamic relations, other thermodynamics are also obtained. The solution and the thermodynamics of the DBI-AdS black hole are turned out that they can reduce to the case of a charged black hole in four-dimensional spacetimes.

Effect of small tensile deformation on damping capacities of Mg-1%Al alloy

Tensile tests with small deformation amounts of 0.5%,1%,3%and 5%were performed at room temperature on as cast Mg-1%Al alloy.Microstructures of the Mg-1%Al alloys before and after deformation were observed by optical microscopy(OM) and transmission electron microscopy(TEM).The strain amplitude dependent and temperature dependent damping capacities of the as-cast and deformed Mg-1%Al alloys were investigated by dynamic mechanical analysis(DMA).The mechanism of deformation on damping capacity of Mg-1%Al alloy was discussed.The results show that the as-cast Mg-1%Al alloy has high damping value at high strain.When the tensile elongation is higher than 3%,the damping values of this alloy in high strain region are significantly decreased at room temperature.But the large amount of dislocations produced by tensile deformation are activated by heat,and then increase the damping value at high temperature.

De Haas-van Alphen Effect of Free Electron Gas Revisited

The free electron gas in a uniform magnetic field at low temperature is restudied. The grand partition function previously obtained by Landau＇s quantitative calculation contains three parts, which are all approximate. An improved calculation is presented, in which two of the three parts are obtained in exact forms. A simple remedy for Landau and Lifshitz＇s qualitative calculation in the textbook is also given, which turns the qualitative result into the same one as obtained by the improved quantitative calculation. The chemical potential is solved approximately and the thermodynamic quantities are caiculated explicitly in both a weak field and a strong field. The thermodynamic quantities in a strong field obtained here contain both non-oscillating and oscillating corrections to the corresponding results derived from Landau＇s grand partition function. In particular, Landau＇s grand partition function is not sufficiently accurate to yield our nonzero results for the specific heat and the entropy. An error in the Laplace-transform method for the problem is corrected. The results previously obtained by this method are also improved.

Multi-scale chemo-mechanical analysis of the slip surface of landslides in the Three Gorges, China

Multi-scale chemo-mechanical effects and microscopic failure modes are explored in the evolution of strength change of slip surface. Direct shear equipments, scanning electro-microscope and X-ray diffraction are used to trace the change in strength of remodeled soils of slip surfaces in the Three Gorges area. Results show that there is a release of alkali metals and concentration of clay minerals on the surface. During the tests, potassium ions were released, the cementation was reduced, and the ratio of interlayer minerals varied associated with strength change. Accordingly, illites or montmorillonite-illite mixtures turned into montmorillonite. So the strength change originates from the release of alkali metal ions on molecular scale that leads to the concentration and transition of clay minerals on meso-scale. The evolution of slip surface and soil strength is a typical process involving multi-scale processes of structure changes and chemo-mechanical coupling.

Stepping-quenching-partitioning treatment of 20SiMn2MoVA steel and effects of carbon and carbide forming elements

A novel heat treatment process,stepping quenching and partitioning(S-Q-P),has been developed to manipulate microstructure and mechanical properties of steels.Based on incomplete partitioning of carbon from martensite to austenite,volume fraction and distribution of the retained austenite resulting from the following quenching of the steels could be effectively controlled,and then the synthesized mechanical properties of the steels would be improved.In this paper,20SiMn2MoVA steel was treated with conventional quenching-tempering(Q-T),currently prevailing quenching-partitioning(Q-P) and S-Q-P processes,respectively.The results indicated that the volume fraction of the retained austenite of the steel treated by Q-P and S-Q-P processes increased significantly that resulted in the increase of ductility and decrease of strength.The product of strength and ductility of the steel treated by S-Q-P process reached 23.7GPa%,that was increased by about 13% and 7% compared with that after Q-T and Q-P processes,respectively.Compared with the great improvement of the synthesized mechanical property obtained by S-Q-P process with another steel 35SiMn,there would be some factors that deteriorated the effect of S-Q-P process on 20SiMn2MoVA steel.It was found by microstructural testing that the carbide forming elements V and Mo in the steel led to precipitation of carbides during partitioning period and lack of carbon in austenite.As a result,less austenite would remain after final quenching and mechanical properties of the steel would be influenced.The results would be beneficial for understanding the principle of S-Q-P process and improving the design of the S-Q-P steel compositions.

CHARACTERISTIC ALTERNATING-DIRECTION FINITE ELEMENT METHODS FOR NONRECTANGULAR REGIONS FOR COUPLED SYSTEM OF DYNAMICS OF FLUIDS IN POROUS MEDIA AND ITS ANALYSIS

For coupled system of multilayer dynamics of fluids in porous media, thecharacteristic alternating-direction finite element methods for nonrectangular regions applicable toparallel arithmetic are put forward and two-dimensional and three-dimensional schemes are used toform a complete set. Some techniques, such as calculus of variations, isoparametric transformation,patch approximation, operator-splitting, characteristic method, negative norm estimate, energymethod, the theory of prior estimates and techniques are used. For the nonrectangular regions case,optimal order estimates in L^2 norm are derived for the error in the approximation solution. Thusthe well-known theoretical problem has been thoroughly and completely solved. These methods havebeen successfully used in multilayer oil resources migration-accumulation numerical simulation.

Size-dependent transition of the deformation behavior of Au nanowires

Inspired by the controversy over tensile deformation modes of single-crystalline 〈110〉/{111} Au nanowires, we investigated the dependency of the deformation mode on diameters of nanowires using the molecular dynamics technique. A new criterion for assessing the preferred deformation mode-slip or twin propagation--of nanowires as a function of nanowire diameter is presented. The results demonstrate the size-dependent transition, from superplastic deformation mediated by twin propagation to the rupture by localized slips in deformed region as the nanowire diameter decreases. Moreover, the criterion was successfully applied to explain the superplastic deformation of Cu nanowires.