Evaluation of roundness error from coordinate data using curvature technique

Workpieces like a shaft or hole make contact on their functional boundaries and its circularity is obtained based on the functional boundaries by enveloping features. Data for evaluating roundness error can be obtained from coordinate measuring machines. A technique for roundness error based on the curvature has been proposed to deal with coordinate measurement data. The computational geometric concepts of convex hulls are used to reduce the computation. The method developed is implemented and validated with the data available in the literature.     

Optimal adjustment of a machine tool for improving the geometrical quality of machined parts

The manufacturing industry has to improve the quality of its manufactured products. It is the reason why industry needs tools and methods that make the control of that quality possible. In this paper, we propose a method that allows an optimal adjustment of the machine tools in order to respect at best a set of standard functional requirements applied to a part. The requirements have to use the maximal material requirement defined by ISO standard.The proposed method works out a geometrical model. Interchangeability boundaries enriched with adjustment parameters constitute the basis of the model. Comparison between this geometrical model and a first manufactured part allows us to obtain the variations of adjustment parameters. These variations directly correct the machine tool being certain that the following parts respect at the very best the functional requirements. At least, this method brings the first step to statistically control a process.     

Optimal adjustment of a machine tool for improving the geometrical quality of machined parts

The manufacturing industry has to improve the quality of its manufactured products. It is the reason why industry needs tools and methods that make the control of that quality possible. In this paper, we propose a method that allows an optimal adjustment of the machine tools in order to respect at best a set of standard functional requirements applied to a part. The requirements have to use the maximal material requirement defined by ISO standard.The proposed method works out a geometrical model. Interchangeability boundaries enriched with adjustment parameters constitute the basis of the model. Comparison between this geometrical model and a first manufactured part allows us to obtain the variations of adjustment parameters. These variations directly correct the machine tool being certain that the following parts respect at the very best the functional requirements. At least, this method brings the first step to statistically control a process.     

企业自建PKI基础设施的建设方案探讨

PKI体系可按功能域划分为三个可以独立构建的职责分嚷、边界清晰、接口规范的功能子体系,提出了在按需独立构建三个子体系的基础上,组合构建企业自建PKI基础设施的建设方案,从而为企业简化自建PKI基础设施的建设难度,更好地建设符合自身实际需要的PKI基础设施提供技术指引。     

Transmission loss estimation of three dimensional silencers with perforated internal structures using multi-domain BEM

The calculation of the transmission loss of the silencers with complicated internal structures by the conventional BEM combined with the transfer matrix method is incorrect at best or impossible for 3-dimensional silencers due to its inherent plane wave assumption. On this consideration, we propose an efficient practical means to formulate algebraic overall condensed acoustic equations for the whole acoustic structure, where particle velocities on the domain interface boundaries are unknowns, and the solutions are used later to compute the overall transfer matrix elements, based on the multi-domain BEM data. The transmission loss estimation by the proposed method is tested by comparison with the experimental one on an air suction silencer with perforated internal structures installed in air compressors. The method shows its viability by presenting the reasonably consistent anticipation of the experimental result.     

理想材料零件数字化设计制造研究现状

理想材料零件是由均质材料、复合材料、功能梯度材料和介观细结构构成的复杂非均质零件 ,其数字化设计制造是以 RPM工艺为基础、几何与材料同时制备的并行制造过程。本文介绍了理想材料零件在数字化设计制造中的 CAD建模、定向技术、切片技术、制造技术等关键技术 ,分析了国内外研究现状     

Identification potential of online handwritten signature verification

This paper presents a comparison of natural and artificial intelligences in identifying operators of information-processing systems and their functional state based on handwriting. The cause of the large scatter in the person identification error probability is determined. It is concluded that at the present level of knowledge, the best result achieved in solving the problem by artificial intelligence systems is close to that potentially possible. It is substantiated that online handwritten signature verification is suitable for identifying the functional state of operators of human-machine systems in professional activities.     

基于功能小区方法的电力系统负荷预测

电力系统负荷预测是电网规划的基本工作。介绍了回归预测模型、灰色系统理论预测模型、空间负荷预测法、曲线法、最优组合预测法等中长期电力负荷预测的方法,讨论了功能小区的划分及功能小区的功能分析,通过对功能小区负荷预测的实际计算,结果充分证明了功能小区负荷预测与湖南省衡阳市城区发展的实际情况相符合。说明了基于功能小区方法的电力系统负荷预测具有重要的现实意义和广泛的应用前景。     

基于AHP的产品概念设计研究

产品概念设计的基本目的是获得综合性能最好的设计方案。通过对产品功能的分解和结构要素的映射分析,求出的方案集的解,通过分析不同方案对功能要素的相对重要度大小并进行量化处理,再基于AHP进行归纳计算,找到综合权重最大的方案作为最佳设计方案。通过对电缆除冰装置概念设计的实例分析和计算,验证了该方法在产品概念设计方面应用的可行性和实用性。     

Electron backscattered diffraction as a tool to quantify subgrains in deformed calcite

In this work, we investigated processing methods to obtain subgrain sizes from electron backscattered diffraction data using samples of experimentally deformed calcite (CaCO₃) polycrystals. The domain boundary hierarchy method, based on area measurements of domains enclosed by boundaries larger than a given misorientation angle, was applied to these calcite samples and was found to be limited by: (i) topological problems; (ii) undersampling of large grains; and (iii) artefacts caused by nonindexing. We tested two alternative methods that may reduce the problems: (i) the measured linear intercept hierarchy method, based on measurements of linear intercept between boundaries having larger misorientations than a given minimum angle; and (ii) the calculated linear intercept hierarchy method, based on the total length of boundaries having misorientations larger than a given minimum angle. The measured linear intercept hierarchy method was found to produce results more representative for the microstructure than the calculated linear intercept hierarchy method, because the calculated linear intercept hierarchy method has a significant uncertainty related to the grid‐based nature of the measurements. Preliminary results on calcite suggest that the measured linear intercept hierarchy method is related, in a complex way, to deformation conditions such as stress, strain and temperature as well as to the characteristics of subgrain rotation and grain boundary migration processes.     

装配体ICT图象的内外边界识别研究

用小波变换提取装配体ＩＣＴ图象中的边界轮廓,提出基于简单环识别装配体ＩＣＴ图象的内外边界,该算法可用于装配体的结构形状分析并能正确地建立实体模型。     

钇元素及固溶处理对AZ31镁合金组织和性能的影响

通过力学性能检测、SEM和XRD分析,研究了钇元素及固溶处理对AZ31镁合金组织和性能的影响,并分析了其断裂方式。结果表明:稀土钇元素能够细化铸态α-Mg基体组织,对镁合金具有较好的细晶强化作用;钇元素和铝元素形成的Al2Y化合物,在细化晶粒的同时均匀分布于晶界处,可强化晶界,提高合金的力学性能;钇元素质量分数为1.0%时,合金的力学性能最佳;进行440℃×10h的固溶处理能使加入0.5%(质量分数)钇元素的合金组织最为均匀;加入钇元素后,合金以韧性断裂和准解理断裂相结合的方式断裂。     

Experimental analysis and computer simulation of a methodology for laser focusing in the solar cell characterization by laser beam induced current

This paper presents a quick methodology for focusing a laser beam on a photoactive surface based on performing a single line scan while simultaneously modifying the laser's position over the surface and the distance between the focusing lens and the active surface. The methodology was tested using the computer simulation technique. Several configurations were computer simulated by programming different experimental situations to discover the situations in which this focusing methodology would provide optimum results. The conclusions obtained from computer simulation methodology were checked by means of experimental tests using several solar cells, such as a thin-film amorphous silicon solar cell, a monocrystalline silicon solar cell, and a polycrystalline silicon solar cell. From the tests performed, we concluded that optimum focusing is achieved in systems in which the laser beam induced current signal generated by the photoactive surface has no large heterogeneities (e.g., fingers or grain boundaries), artefacts, or defects. Thus, the best results are achieved in systems where the surface of the photovoltaic device has a certain degree of homogeneity.     

基于边界控制的Gn连续过渡曲面的构造

讨论了基于重新参数化局部基曲面线性组合构造G^n连续过渡曲面时重新参数化局部基曲面的形状对于过渡曲面的边界和形状的影响；提出了采用能量最小法使过渡曲面的边界弯曲最小来确定重新参数化局部基曲面参数域的方法，并提出相应的重新参数化局部基曲面的确定方法，从而构造较好的过渡曲面。     

Experimental validation of numerical model for turbulent flow in a tangentially fired boiler with platen reheaters

A 1 : 20 laboratory scale test rig of a 200 MW tangentially fired boiler is built up with completely simulated structures such as platen heaters and burners. Iso-thermal turbulent flow in the boiler is mapped by 3-D PDA (Particle Dynamic Analyzer). The 3-D numerical models for the same case are proposed based on the solution ofk-ε model closed RANS (Reynolds time-Averaged Navier-Stokes) equations, which are written in the framework of general coordinates and discretized in the corresponding body-fitted meshes. Not only are the grid lines arranged to fit the inner/outer boundaries, but also to align with the streamlines to the best possibility in order to reduce the NDE (numerical diffusion errors). Extensive comparisons of profiles of mean velocities are carried out between experiment and calculation. Predicted velocities in burner region were quantitatively similar with measured ones, while those in other area have same tendency with experimental counterpart.     

Recrystallization behaviour of the nickel-based alloy 80 A during hot forming

The dynamic recrystallization as well as meta‐dynamic and static recrystallization of the nickel‐based alloy 80A was investigated by means of electron backscatter diffraction (EBSD). Specimens were hot compressed at a temperature of 1120°C and a strain rate of 0.1/s at varying strain and soak times to describe the recrystallization behaviour. Various approaches were tested in order to differentiate between recrystallized and deformed grains based on EBSD data. The grain orientation spread was clearly found to be the most reliable procedure. A high twinning of the recrystallized grains was observed, and as a consequence the measured grain size was strongly dependent on whether the coherent and incoherent twin boundaries were regarded as genuine boundaries or removed.     

基于质量功能配置的产品优化设计

提出了基于质量功能配置的产品优化设计。它既考虑来自自然科学定律的定量信息，又考虑来自质量屋分析的定性信息，对产品功能、特性、成本等多个目标进行综合优化，体现了由用户需求驱动的多目标优化设计的思想。最后，以齿轮减速器设计为例进行了应用分析。     

Study of the volumetric water content based on density,suction and initial water content

The practical application of determination of the soil water retention curves (SWRC) is in seepage modelling in unsaturated soil. The models based on the physics behind the seepage mechanism has been developed for predicting the SWRC. However, those models rarely consider the combined effects of initial volumetric water content and soil density. One of the best routes to study these effects is to formulate the SWRC models/functional relations with volumetric water content as an output and the soil density, initial volumetric water content and soil suction as input parameters. In light of this, the present work introduces the advanced soft computing methods such as genetic programming (GP), artificial neural network and support vector regression (SVR) to formulate the volumetric water content models based on the suction, density and initial volumetric water content. The performance of the three models is compared based on the standard measures and goodness-of-fit tests. The findings from the statistical validation reveals that the GP model performs the best in generalizing the volumetric water content values based on the suction, density and initial water content. Further, the 2-D and 3-D plots, evaluating the main and the interaction effects of the three inputs on the volumetric water content are generated based on the parametric procedure of the best model. The study reveals that the volumetric water content values behave non-linearly with respect to soil suction because it first decreases till a certain point of soil suction and then increases suddenly.     

Voronoi based discrete least squares meshless method for heat conduction simulation in highly irregular geometries

A new technique is used in Discrete Least Square Meshfree(DLSM) method to remove the common existing deficiencies of meshfree methods in handling of the problems containing cracks or concave boundaries. An enhanced Discrete Least Squares Meshless method named as VDLSM(Voronoi based Discrete Least Squares Meshless) is developed in order to solve the steady-state heat conduction problem in irregular solid domains including concave boundaries or cracks. Existing meshless methods cannot estimate precisely the required unknowns in the vicinity of the above mentioned boundaries. Conducted researches are limited to domains with regular convex boundaries. To this end, the advantages of the Voronoi tessellation algorithm are implemented. The support domains of the sampling points are determined using a Voronoi tessellation algorithm. For the weight functions, a cubic spline polynomial is used based on a normalized distance variable which can provide a high degree of smoothness near those mentioned above discontinuities. Finally, Moving Least Squares(MLS) shape functions are constructed using a varitional method. This straight-forward scheme can properly estimate the unknowns(in this particular study, the temperatures at the nodal points) near and on the crack faces, crack tip or concave boundaries without need to extra backward corrective procedures, i.e. the iterative calculations for modifying the shape functions of the nodes located near or on these types of the complex boundaries. The accuracy and efficiency of the presented method are investigated by analyzing four particular examples. Obtained results from VDLSM are compared with the available analytical results or with the results of the well-known Finite Elements Method(FEM) when an analytical solution is not available. By comparisons, it is revealed that the proposed technique gives high accuracy for the solution of the steady-state heat conduction problems within cracked domains or domains with concave boundaries and at the same time possesses a high convergence rate which its accuracy is not sensitive to the arrangement of the nodal points. The novelty of this paper is the use of Voronoi concept in determining the weight functions used in the formulation of the MLS type shape functions.     

TEM analysis of near-coincidence grain boundaries in silicon

High-precision characterization of grain boundaries with a deviation from the ideal coincidence is presented. The analysis is based on the shift of Kikuchi lines at grain boundaries. The accuracy was controlled using Frank's relationship applied to intrinsic secondary dislocations which accommodate the orientation deviation. An application is presented to coincidences with Σ = 25 and 3 observed in polycrystalline silicon.