Synthesis of Mg-α-sialon from the mixture of silicon, aluminum and magnesia powders in a flowing nitrogen atmosphere

Synthesis of Mg-α-Sialon has been investigated by the mixture of silicon, aluminum and magnesia powders in a flowing nitrogen atmosphere in the range of 1300–1600 °C, when Mg-α-Sialon is designed with a chemical formulation of Mg _x Si_12−3x Al_3x O _x N_16−x in present work. The results showed that Mg-α-sialon initially occurred at 1400 °C and basically increased with elevated temperatures. For the samples of x = 0.6, 0.8 and 1.0 the products mainly consisted of Mg-α-Sialon with small amounts of Si, AlN and 21R AlN-polytypoid phases at 1600° C. However, in final products of x = 1.2, 1.4 and 1.6 only a little of Mg-α-Sialon formed and a great amount of Si remained in these samples at all the fired temperatures. Fortunately, the content of Mg-α-Sialon in these samples were obviously increased by adding a small amount of α-Si₃N₄ as seeds before nitridation.     

化学事故危害评估

根据化学事故危害的主要影响因素对化学事故进行危害评估,考查了危害纵深、人员杀伤率、危害地域估算、爆炸燃烧事故危害等内容。     

数码相机的性能特点

1数码相机的原理和主要性能 数码相机与传统相机相比,原理上主要的区别是:以CCD等光电转换器件和闪存卡代替胶卷,拍摄得到的不是银盐潜影,而是数字图像.机身和镜头等系统均与传统相机基本相同.数码相机近年来以惊人的速度得到普及推广,不仅民用型如此,专业数码单反机也越来越多地为专业和业余人士所使用.     

陶艺的文化性与功能

中国古陶艺制品造型,釉色,装饰等艺术符号都与每时期的阶段性精神和物质生活相联系,但在"现代艺术"文化认识领域中,往往从理论思维角度把陶艺实用目的的物质性排斥在文化范畴之外。艺术常常强调物质的观赏性,而陶艺的实用功能就是这种文化类型的主体,陶艺的文化性和功能性,具有实用和审美文化的高度叠合,永久地承载着实用功能和精神功能两大内容。     

Aging response of the young’s modulus and mechanical properties of Ti-29Nb-13Ta-4.6Zr for biomedical applications

Alloys for implant devices require improved strength but a reduced Young’s modulus, in order to become mechanically more compatible with adjacent bone tissues. In this study, a new metastable β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (wt pct), was subjected to aging treatment to produce different microstructures, and the resulting mechanical properties, including the Young’s modulus, were measured. The Young’s modulus of this alloy is found to be sensitive to microstructures generated by various heat treatments. For microstructures varying from (α + β) to (α + β + ω) and (β + ω), the Young’s modulus increases with an accompanying increase in tensile strength and hardness, but decreases in ductility. The (β + ω) microstructure has a low strength, high modulus, and poor ductility and cannot be used for biomedical applications. For an (α + β) microstructure, the volume fraction of the phases is shown to be the main factor that determines the mechanical properties.     

公司大门工程建设施工

大门小品建筑属多项目综合性工程。本文作者从管理者的角度 ,通过对公司大门及附属工程施工质量控制的总结 ,说明了质量控制应贯穿于工程施工的全过程     

新的启迪

说点心里的话，建筑设计对青年人来讲是一条漫长的道路。建筑是一个载体，有精神一面，也有物质一面。有些建筑师拿着模型或未建成的设计来炒作，为了求名，生怕别人不知道。这对个人是小事，但若贻误了青年学子，那就是不可取的。     

A generalized Bezoutian matrix with respect to a polynomial sequence of interpolatory type

In this note, a generalized Bezoutian matrix with respect to a polynomial sequence of interpolatory type is introduced. The operator representation relative to a pair of dual bases and the generalized Barnett-type factorization formula are derived. An intertwining relation and a Bezoutian reduction to a block diagonal form by congruence via a generalized Vandermonde matrix are presented. Fujiwara-Hermite and Routh-Hurwitz criteria in terms of this generalized Bezout matrix are obtained.     

Structured optimal and robust control with multiple criteria: a convex solution

In this paper, the design of controllers that incorporate structural and multiobjective performance requirements is considered. The control structures under study cover nested, chained, hierarchical, delayed interaction and communications, and symmetric systems. Such structures are strongly related to several modern-day and future applications including integrated flight propulsion systems, platoons of vehicles, micro-electro-mechanical systems, networked control, control of networks, production lines and chemical processes. It is shown that the system classes presented have the common feature that all stabilizing controllers can be characterized by convex constraints on the Youla-Kucera parameter. Using this feature, a solution to a general optimal performance problem that incorporates time domain and frequency domain constraints is obtained. A synthesis procedure is provided which at every step yields a feasible controller together with a measure of its performance with respect to the optimal. Convergence to the optimal performance is established. An example of a multinode network congestion control problem is provided that illustrates the effectiveness of the developed methodology.