智慧矿山工业广场三维自动建模技术研究

为打破煤矿工业广场建模模式目前存在的高度依赖人工操作的现状,实现数字矿山规模化规范化建设、煤矿地面建筑设备模型量产化。本文对煤矿工业广场生产建筑群进行空间结构分析,着重分析煤矿井口、煤矿车间、煤矿办公楼的几何空间结构及生产设施的空间几何构型元素,提出一种分体分面组合模型自动建模技术。首先,通过将复杂的生产建筑群进行个体解构和几何拆分,将整套地上生产线设备及建筑拆分为最小规则(不规则)几何单元体,构建顶视投影弧段索引拓扑图;其次,通过线性封闭弧段环高程拉伸生成几何体空间组合关系构建建筑群;最后,以灵新煤矿为实验区域进行验证。结果表明:本文方法能够模拟建筑结构与设备的几何独特性,且纹理外观满足数字化要求;总建模工时由原来的每10栋建筑3.25人天降低到0.78人天,产能提升达到预期。

Investigation of droplet breakup in liquid–liquid dispersions by CFD–PBM simulations：The influence of the surfactant type

The accurate prediction of the droplet size distribution(DSD)in liquid–liquid turbulent dispersions is of fundamental importance in many industrial applications and it requires suitable kernels in the population balance model.When a surfactant is included in liquid–liquid dispersions,the droplet breakup behavior will change as an effect of the reduction of the interfacial tension.Moreover,also the dynamic interfacial tension may be different with respect to the static,due to the fact that the surfactant may be easily desorbed from the droplet surface,generating additional disruptive stresses.In this work,the performance of five breakup kernels from the literature is assessed,to investigate their ability to predict the time evolution of the DSD and of the mean Sauter diameter,when different surfactants are employed.Simulations are performed with the Quadrature Method of Moments for the solution of the population balance model coupled with the two-fluid model implemented in the compressible Two Phase Euler Foam solver of the open-source computational fluid dynamics(CFD)code Open FOAM v.2.2.x.The time evolution of the mean Sauter diameter predicted by these kernels is validated against experimental data for six test cases referring to a stirred tank with different types of surfactants(Tween 20 and PVA 88%)at different concentrations operating under different stirrer rates.Our results show that for the dispersion containing Tween 20 additional stress is generated,the multifractal breakup kernel properly predicts the DSD evolution,whereas two other kernels predict too fast breakup of droplets covered by adsorbed PVA.Kernels derived originally for bubbles completely fail.

A new solution method for black-body radiation inversion and the solar area-temperature distribution

The effective temperature of the solar photosphere is usually obtained according to the solar constant, based on the Stefan-Boltzmann law. However its temperature distribution is not homogeneous. A hopeful way to obtain the area-temperature distribution of the solar photosphere is to solve the Black-body Radiation Inversion (BRI) problem. In this paper, a new practical solution method for BRI is developed. The theoretical analysis and numerical calculations show the low-temperature distribution difficulty of BRI is solved by this new method. Then the area-temperature distribution of the solar photosphere is obtained, according to the measured absolute solar spectral irradiance. It is the first realization of BRI for a real system after almost three decades of efforts. The results are comparable to that from the Stefan-Boltzmann law.

A hexahedron element formulation with a new multi-resolution analysis

A multiresolution hexahedron element is presented with a new multiresolution analysis(MRA)framework.The MRA framework is formulated out of a mutually nesting displacement subspace sequence,whose basis functions are constructed of scaling and shifting on element domain of a basic node shape function.The basic node shape function is constructed from shifting to other seven quadrants around a specific node of a basic isoparametric element in one quadrant and joining the corresponding node shape functions of eight elements at the specific node.The MRA endows the proposed element with the resolution level(RL)to adjust structural analysis accuracy.As a result,the traditional 8-node hexahedron element is a monoresolution one and also a special case of the proposed element.The meshing for the monoresolution finite element model is based on the empiricism while the RL adjusting for the multiresolution is laid on the solid mathematical basis.The simplicity and clarity of shape function construction with the Kronecker delta property and the rational MRA enable the proposed element method to be more rational,easier and efficient in its implementation than the conventional mono-resolution solid element method or other MRA methods.The multiresolution hexahedron element method is more adapted to dealing with the accurate computation of structural problems.

How different are the surfaces of semiconductor Ag_(2)Se quantum dots with various sizes?

The surface of nanocrystals plays a dominant role in many of their physical and chemical properties.However,controllability and tunability of nanocrystal surfaces remain unsolved.Herein,we report that the surface chemistry of nanocrystals,such as near-infrared Ag_(2)Se quantum dots(QDs),is sizedependent and composition-tunable.The Ag_(2)Se QDs tend to form a stable metal complex on the surface to minimize the surface energy,and therefore the surface chemistry can be varied with particle size.Meanwhile,changes in surface inorganic composition lead to reorganization of the surface ligands,and the surface chemistry also varies with composition.Therefore,the surface chemistry of Ag_(2)Se QDs,responsible for the photoluminescence(PL)quantum yield and photostability,can be tuned by changing their size or composition.Accordingly,we demonstrate that the PL intensity of the Ag_(2)Se QDs can be tuned reversely by adjusting the degree of surface Ag^(+) enrichment via light irradiation or the addition of AgNO_(3).This work provides insight into the control of QD surface for desired PL properties.

Interfacial assembly of a series of Cu(Ⅱ)-coordinated Schiff bases complexes:Orderly nanostructures and supramolecular chirality

Four achiral Cu(Ⅱ)-coordinated Schiff bases complexes containing aromatic structures were synthesized and their supramolecular assemblies at the air/water interface were investigated.All the compounds could be spread on water surface although they have no alkyl chains.The Schiff base complex molecules with naphthyl groups tended to form J-aggregate in the Langmuir-Blodgett(LB) films transferred from water surface.By investigation of atomic force microscopy,a multilayer film or three-dimensional structures were observed.It was interesting to note that the LB films of achiral compound Cu-NA with naphthyl segment and without methyl groups transferred from water surface showed chirality.The supramolecular chirality in the present LB films was suggested to be due to a cooperative stereoregular-stacking of the functional groups in a helical sense.This research work provides a helpful clue for regulating the nanostructures and supramolecular chiral assembly in organized films.