负热膨胀反钙钛矿锰氮化合物的研究综述

反钙钛矿结构锰氮化合物是近年发展起来的一类具有各向同性、负热膨胀系数及负热膨胀温度区间可调、金属性能及力学性能优良的新型负热膨胀材料,展现出重要的应用潜力.本文从负热膨胀材料的发展历史、化合物体系、制备方法、负热膨胀性能影响因素及微观机理等方面,阐述了反钙钛矿结构锰氮化合物负热膨胀材料的研究现状及最新发展动态,并对其发展前景进行了分析和展望.     

沿空巷破碎煤体自燃耗氧及升温特征数值模拟

为研究巷道顶煤和煤柱破碎后由漏风引起的自燃耗氧及升温规律,在质量、动量和热量守恒模型的基础上利用FLUENT软件求解了沿空巷周围破碎煤体的稳态氧气分布和温度的动态变化过程。计算结果表明：在煤柱较完整的情况下,顶煤的氧气浓度分布高于煤柱,但二者都具有自然发火的危险。由于散热作用,高温区离二者的漏风边界都有一定的距离,顶煤升温速率较煤柱更快。在改变漏风强度后,高温区位置和范围也会随之改变。此研究结论可以帮助缩小现场火源区的寻找范围,以便及时采取措施抑制自燃。     

Development of High Deformability Pipeline Steel

Based on strain-based design, high deformability X70 high strength pipeline steel with dual-phase microstructure has been developed, which can be laid in the seismic, the cold or the deepwater region. The results illustrated that the developed X70 steel has the stress-strain curve like round house and it shows good anti-transformation characteristic, high uniform deformation(≥10%), enhanced n-value(≥0.10), and the low yield-tensile ratio Y/T(≤0.85). The dual-phase microstructure of ferrite and bainite conta...     

Model updating based on incomplete modal data

The objective of model updating is to improve the accuracy of a dynamic model based on the correlation between the measured data and the analytical (finite element) model. In this paper, we intend to update the mass and stiffness matrices of an analytical model when only modal frequencies or spatially incomplete modal data are available. While the proposed method is systematic in nature, it also preserves the initial configuration of the analytical model, and physical equality and/or inequality constraints ...     

Removing coarse sediment by sorting of reservoirs

Reservoir sedimentation is an unsolved problem.In this paper,based on measured data,theoretical analysis and numerical computations,we prove that a proportion of the sediment coarser than 0.1 mm(CS) is sorted and deposited in specific reaches in the upper backwaters or in run-of-river reservoirs.The ratio of CS is usually small but it impacts the slope of deposition delta greatly and raises the backwater in later stages for a river shaped reservoir(RSR).Based on these facts,we propose to remove such CS from...     

Multi-level multi-area hybrid automatic voltage control system and its trial operation in Northeast China Grid

In order to coordinate automatic voltage control(AVC)systems of a large interconnected system,a multi-level multi-area hybrid automatic voltage control(MLMA-HAVC)system was constructed.This system began its trial operation in the Northeast China Grid in January 2010,and for the first time in China and abroad it realized automatic close-loop control of multi-area and multi-level interconnected power grid and multi-objective self-approaching optimization in aspects of security,high quality and economic operat...     

电冶矾土刚玉质自流浇注料的研究

以电冶矾土刚玉为骨料有利于提高浇注料的自流性能 ;六偏磷酸钠分散剂对Al2 O3泥浆流变性能有较理想的改善作用 ;电冶矾土刚玉质自流浇注料具有优良的抗渣性能 ,这主要同浇注料的显微结构和电冶矾土刚玉骨料的性能相关。     

硅粉粒度和含量对烧成Al2O3-ZrO2-C材料强度与结构的影响

选用4种不同粒度的硅粉,借助于压汞仪、扫描电子显微镜和能谱分析仪等测试手段,研究了硅粉粒度(粒度按A(d50=336.9μm)、B(d50=123.5μm)、C(d50=19.5μm)、D(d50=2.21μm)依次变小)和含量(分别为1%、3%、5%、7%)对埋炭烧成铝锆碳材料的耐压强度、孔径分布和显微结构的影响。结果表明:1)硅粉粒度和含量影响着材料的耐压强度,随着硅粉含量的增加,材料的耐压强度增大;硅粉粒度减小有利于提高强度,但硅粉粒度太细,强度反而大大降低;2)硅粉粒度和含量控制着材料的物相组成和显微结构,随着硅粉粒度减小,碳化硅晶须生成量增加,其长径比降低,逐渐形成良好网络结构,孔径分布范围也由宽变窄,气孔直径大大降低,但硅粉太细,晶须分布反而稀疏,小气孔的比孔容积也呈增加趋势;加入合适粒度和含量的硅粉还有利于氮化物在材料内部的形成。     

烧结气氛对合成MgAl2O4-Ti(C,N)复合陶瓷的影响

以金属铝粉、钛白粉和轻烧MgO细粉为原料,通过设计100%焦炭粒(简称C气氛),10%钛白粉 90%焦炭粒(简称TC气氛),以及10%硅微粉 90%焦炭粒(简称SC气氛)3种埋粉条件下的高温烧结还原性气氛,采用X射线衍射仪(XRD)、扫描电镜(SEM)和微区电子探针分析(EPMA)等手段,研究了铝热还原氮化法(1600℃3h)制备MgAl2O4-Ti(C,N)复合陶瓷在不同烧结气氛下的相组成和显微结构的变化。结果表明在不同气氛下,烧后试样的主要物相均为MgAl2O4和Ti(C,N),Ti(C,N)可能会固溶氧,气氛对Ti(C,N)的影响较大。和单纯埋炭气氛下相比,在TC气氛下有助于Ti(C,N)的生成,但晶粒细小;在SC气氛下不利于Ti(C,N)的生成,且有玻璃相存在。     

UHMWPE混炼接枝马来酸酐研究

讨论了超高相对分子质量聚乙烯(UHMWPE)混炼接枝马来酸酐(MAH)过程中，单体MAH用量、引发剂DCP用量、交联抑制剂己内酰胺(CAILA)用量、流动改性剂硬脂酸钙(CaSt2)用量及混炼温度、时间等工艺条件对UHMWPE接枝率和凝胶含量的影响。用红外光谱表征了接枝物的存在。并用滴定分析法和重量分析法测定了接枝物UHMWPE～g～MAH的接枝率和凝胶含量。实验表明，MAH用量为5份、DCP为0．15份、CALA为0．1份、CaSt2为1份时。混炼温度175∽180℃。混炼时间14min时，可得到接枝率0．75％、凝胶含量1．48%的UHMWPE接枝物。