In situ formation of multi scale reinforcing phases to improve performance of Al2O3-SiC C castables

In order to improve the physical properties and slag corrosion resistance of refractory materials for hot metal pretreatment, different contents of composite metal powders (CMP) were introduced into Al2O3-SiC-C refractory castables. The effect of CMP on the microstructure, physical properties and slag corrosion resistance of Al2O3-SiC-C refractory castables were studied. The results show that the multi scale reinforcing phases including flake crystals, rod shaped fibers, filamentous fibers and whiskers are in situ formed in the samples with addition of CMP, which result to the improvement of the cold modulus of rupture and cold crushing strength. When the addition of CMP is 6 wt.%, the high temperature modulus of rupture increases by 231%, the thermal shock resistance increases by 77% after thermal shock by water cooling 5 times and the percentage of the slag resistant area reduces by 37.2%.     

未增塑聚氯乙烯(PVC-U)异型材配方基础

PVC-U异型材配方十分复杂,常用原料通常在10种以上。根据大连实德集团实际生产情况,这10多种原料通常以7大组分的方式进行配料和生产。文中就该配方中7大组分的分类、特点及应用情况分别进行了详细介绍。     

书立复合冲裁模的设计

介绍了安装在液压试验机上的一种集冲裁、切口作用于一体的复合冲裁模的设计，解决了没有压力机的情况下冲裁件的加工问题。     

Forced Vertical Vibration of Circular Plate in Multilayered Poroelastic Medium

This paper considers the vertical vibrations of an elastic circular plate in a multilayered poroelastic half space. The plate is subjected to axisymmetric time–harmonic vertical loading and its response is governed by the classical thin-plate theory. The contact surface between the plate and the multilayered half space is assumed to be smooth and either fully permeable or impermeable. The half space under consideration consists of a number of layers with different thicknesses and material properties and is governed by Biot’s poroelastodynamic theory. The vertical displacement of the plate is represented by an admissible function containing a set of generalized coordinates. Contact stress and pore pressure jump are established in terms of generalized coordinates through the solution of flexibility equations based on the influence functions corresponding to vertical and pore pressure loading. Solutions for generalized coordinates are obtained by establishing the equation of motion of the plate through the application of Lagrange’s equations of motion. Selected numerical results are presented to portray the influence of various parameters on dynamic interaction between an elastic plate and a multilayered poroelastic half space.     

Formation of composites fabricated by exothermic dispersion reaction in A1-TiO2-B2O3 system

The formation of aluminum matrix composites fabricated by exothermic dispersion reaction in A1-TiO2-B2O3 system was investigated. The thermal analysis results show that the reactions are spontaneous and exothermic. The Gibbs free energy of α-Al2O3 is the lowest among all the combustion products, followed by TiB2 and Al3Ti. It is noted that when the B2O3/TiO2 mole ratio is below 1, the reaction products are composed of particle-like α-Al2O3, TiB2 and rod-like Al3Ti. The α-Al2O3 crystallites, resulting from the reaction between A1 and TiO2 or B2O3, are segregated at the grain boundaries due to a lower wettability with the matrix. SEM micrographs show that rod-like Al3Ti phase distributes uniformly in the matrix. When the BEO3/TiO2 mole ratio is around 1, the Al3Ti phase almost disappears in the composites, and the distribution of α-Al2O3 particulates is improved evidently.     

铁路桥梁横向振动模拟及适应快速行车结构型式的研究

针对铁路提速后出现的上承式简支钢板梁桥跨中横向振幅过大的问题,以羊楼司桥(L=32m单跨上承式简支钢板梁桥)为例进行实桥检测和数值模拟,建立车辆、线路、桥梁三者的联合模型,考虑轮轨接触力,应用MSC/DYTRAN大型结构分析程序进行车线桥动力相互作用的仿真分析。研究揭示我国用量最多的C62型货车以70∽80km/h的速度空载通过时,该跨度的钢板梁桥发生横向谐振的机理。此外,用该方法对32m跨长的组合梁结构进行桥梁动力特性及列车走行性分析,表明该结构满足提速货车和高速电动旅客列车走行的要求。研究结果对我国高速铁路桥梁建设和既有桥梁的改造具有积极意义。     

Breaking the search space symmetry in partitioning problems: An application to the graph coloring problem

Many problems consist in splitting a set of objects into different groups so that each group verifies some properties. In practice, a partitioning is often encoded by an array mapping each object to its group numbering. In fact, the group number of an object does not really matter, and one can simply rename each group to obtain a new encoding. That is what we call the symmetry of the search space in a partitioning problem. This property may be prejudicial for optimization methods such as evolutionary algorithms (EA) which require some diversity during the search.     

土工合成材料在辽宁省水利工程中应用效益分析

截止2003年辽宁省水利工程中应用土工合成材料已达1450万多m^2，尤其在河道护岸、堤(坝)护坡、防渗工程上这种新型工程材料得到了广泛应用。结合辽宁省水利工程上应用的实际，对其效益进行了分析，分析结果表明：采用土工织物软体排护岸比传统柴排护岸节省投资35％～80％；堤坝护坡采用土工织物滤层比传统砂砾料滤层节省投资30％以上；土工膜防渗可比粘土防渗节省投资30％～50％。同时还取得了保护生态平衡、节省能源、促进化纤工业发展等十分显的社会效益。     

Performance of natural‐fiber–plastic composites under stress for outdoor applications: Effect of moisture,temperature, and ultraviolet light exposure

The effects of moisture, temperature, and ultraviolet (UV) light on performance of natural‐fiber–plastic composites (NFPC) were assessed. We conducted short‐term tests in the laboratory and long‐term tests under natural exposure and measured changes in mechanical properties and color in samples of the composite. Chemical changes of the composite's materials were measured by X‐ray photoelectron spectroscopy to elucidate the mechanisms of chemical transformations on the material surface. Relative humidity highly affected the modulus of rupture (MOR) and the modulus of elasticity (MOE), and had a greater effect than temperature and UV exposure on performance of the composite. The lightness of the composite was increased by the UV effect in the short‐ and the long‐term tests. The X‐ray photoelectron spectroscopy (XPS) analysis suggested that the composite was protected by the UV absorber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2570–2577, 2006     

A stochastic realization algorithm via block LQ decomposition in Hilbert space

A stochastic realization problem of a stationary stochastic process is re-visited, and a new stochastically balanced realization algorithm is derived in a Hilbert space generated by second-order stationary processes. The present algorithm computes a stochastically balanced realization by means of the singular value decomposition of a weighted block Hankel matrix derived by a “block LQ decomposition”. Extension to a stochastic subspace identification method explains how the proposed abstract algorithm is implemented in system identification.