Modelling of Al2O3 Powder Compaction with Hot Pressing in a Rigid Die

Computer modelling of hot pressing is provided. Kinetics are described for compaction during hot pressing in a rigid die, and the change in density distribution, irreversible solid phase strain accumulation, and equivalent stresses are studied by means of the finite element method. Shrinkage during the preparation of complex-shaped articles by hot pressing pure Al₂O₃ powder in a graphite die without a protective atmosphere and the physicomechanical properties of the finished article are studied. Calculated and experimental results agree satisfactorily.     

IMAGIS在数字校园建模中的应用

介绍了IMAGIS的功能和工作流程以及IMAGIS空间数据的获取途径,利用IMAGIS进行数字校园三维建模的实现,并以河南理工大学北校区数字校园建设为例介绍了IMAGIS在三维景观建模中的应用。     

Estimating thermal stress in BIPV modules

The thermal stress on building‐integrated photovoltaic modules (BIPV) in Espoo, Finland, was studied with field‐testing of amorphous silicon modules. Based on these results, the thermal stress at two other European locations (Paris and Lisbon) was estimated. The estimation procedure entailed thermal modelling of heat transfer in the façade with meteorological data as input. The results indicate that the thermal stress on BIPV modules in Lisbon is, in this case, approximately 50% higher that in Espoo and between 80 and 200% higher than in Paris, depending on the activation energy of the degradation process. The difference in stress between a BIPV module and a free‐standing module in Espoo was 50–200%. Copyright © 2006 John Wiley & Sons, Ltd.     

Autoregressive modelling in vector spaces: An application to narrow-bandwidth spectral estimation

A generalisation of the Burg algorithm to vector spaces is described. This can be used to subsample time series that have narrow frequency bandwidth, thereby reducing the computation time and the complexity of the autoregressive model required. The technique is preferable to conventional subsampling.     

重金属污染物动态吸附试验及数学模拟

本文采用泥沙动力学中Ｒｏｕｓｅ等人用来研究泥沙浓度沿垂线分布的装置。对泥沙吸附重金属污染物进行了动态模拟。试验分有底泥和无底泥两种情况。研究中发现在Ｒｏｕｓｅ装置的水力、泥沙条件下泥沙吸附重金属污染物达到平衡状态需要６小时以上，由极坐标下的重金属迁移转化数学模型方程，在本文具体试验条件下进行数值求解，计算结果和试验结果合良好，说明数学模型是正确合理的试验是可靠的。计算时依据室内静态试验结果，对动态     

Delivering Improvement from Truth — the Fragile Link Between Analysis and Effective Change

In the history of operations research in industry there has been an abundance of analyses and recommendations produced in millions of man hours by dedicated OR specialists. And yet the net improvement is significantly lower than expected. There are numerous reasons for this shortfall: incomplete analysis, too much theory, incomplete implementation, unreliable recommendations, or a combination of some of these reasons.
By describing several examples, the major reasons for the fragility of the link between recommendation and implementation will be reviewed. What has to be done today to increase the likelihood of implementing an OR recommendation and thus improve the performance of an industrial entity by using the power of OR tools will then be described.     

Boundary Constrained Swept Surfaces for Modelling and Animation

Due to their simplicity and intuitiveness, swept surfaces are widely used in many surface modelling applications. In this paper, we present a versatile swept surface technique called the boundary constrained swept surfaces. The most distinct feature is its ability to satisfy boundary constraints, including the shape and tangent conditions at the boundaries of a swept surface. This permits significantly varying surfaces to be both modelled and smoothly assembled, leading to the construction of complex objects. The representation, similar to an ordinary swept surface, is analytical in nature and thus it is light in storage cost and numerically very stable to compute. We also introduce a number of useful shape manipulation tools, such as sculpting forces, to deform a surface both locally and globally. In addition to being a complementary method to the mainstream surface modelling and deformation techniques, we have found it very effective in automatically rebuilding existing complex models. Model reconstruction is arguably one of the most laborious and expensive tasks in modelling complex animated characters. We demonstrate how our technique can be used to automate this process.     

SQL extension for spatio-temporal data

An SQL extension is formalized for the management of spatio-temporal data, i.e. of spatial data that evolves with respect to time. The extension is dedicated to applications such as topography, cartography, and cadastral systems, hence it considers discrete changes both in space and in time. It is based on the rigid formalization of data types and of SQL constructs. Data types are defined in terms of time and spatial quanta. The SQL constructs are defined in terms of a kernel of few relational algebra operations, composed of the well-known operations of the 1NF model and of two more, Unfold and Fold. In conjunction with previous work, it enables the uniform management of 1NF structures that may contain not only spatio-temporal but also either purely temporal or purely spatial or conventional data. The syntax and semantics of the extension is fully consistent with the {SQL:2003} standard.