分解MP3：一种节俭的收听装置技术

在我买了一个激光打印机碳粉盒之后,一张“赠送价值75美元物品”优惠券还给我家带来了一台O D-128MP3,也就是人们熟知的MP3-818便携式数字音频播放器。这个价格在我听来如同音乐,特别是考虑到OfficeDe-pot对这种播放器的正常标价是69.99美元。它的特性也不算太平庸:对MP3和WMA(     

领会无成本之路

之前,EDN分析了一个削价至20美元(原价为50美元)的USB音频外设。这次我们继续对ABS打折后的NW-203-RT 802．11g与四端口开关式路由器进行财务分析。在这个淡紫色塑料壳内都有些什么东西?卖20美元ABS还赚钱吗?     

Cavity Development During Creep Deformation in Alumina with a Bimodal Grain Size Distribution

An alumina sample, codoped with equimolar proportions of magnesia and zirconia, exhibited a bimodal grain size distribution after hot-pressing. Flexural creep experiments were performed on this material at temperatures of 1673 and 1773 K in air. Inspection of the deformed specimens revealed extensive creep cavitation, with cavities developing preferentially in the coarse-grained regions. The nucleation, growth, and interlinkage of the cavities led to the formation of cracks. Crack growth occurred in the coarse-grained regions by the linkage of cavities with the crack tip. However, several cracks were observed to terminate after extending up to a fine-grained region of a specimen. A model has been developed to rationalize the observation that preferential cavitation occurs in the coarse-grained regions of a specimen undergoing creep deformation.     

影响农机购买的因素

购买农机的用户可分为集团购买和个人购买.集团购买农机时主要考虑的因素为产品的技术参数、性能特点、售后服务、价格等.农民个人购买农机除了考虑以上的因素外,他们还把品牌的社会影响力以及周围农机户的口碑也作为重要的因素.尽管有人认为集团购买更为理性,个人购买时感性的成分更多一些,但实际上所有的购买行为都会受到决策者心理因素的影响.     

Some circuit theory concepts revisited†

The concept of causality is introduced in a generalized form. Related system properties are then developed in an axiomatic manner. The unification of the development is illustrated through examples and discussions on related literature     

Asymptotic properties of linear multivariable continuous-time tracking systems incorporating high-gain error-actuated controllers

In this paper, the asymptotic properties of tracking systems incorporating linear multivariable plants which are amenable to high-gain error-actuated control (Porter and Bradshaw 1979) are characterized in terms of the eigenstructure of the closed-loop plant matrices. It is shown that the closed-loop eigenstructure is such that the tracking behaviour of systems incorporating high-gain error-actuated controllers designed in accordance with the synthesis technique of Porter and Bradshaw (1979) is increasingly dominated by the modes associated with the first-order infinito characteristic roots as the gain is increased and that increasingly ‘ tight ’ control is therefore achieved. These theoretical results are illustrated in the case of a closed-loop system incorporating a third-order plant and a high-gain error-actuated controller by the presentation of the computed closed-loop eigenstructure and of the results of computer simulation studies.     

Minimum settling-time control policies for cascaded production-inventory systems

In this paper, the technique of entire eigenstructure assignment is used to derive minimum settling-time control policies for a class of production—inventory systems which can be described by linear multivariate discrete-time state equations. It is shown that this technique can be readily used to derive minimum settling-time control policies for production-inventory systems which consist of a set of production-inventory sub-systems connected in cascade. The advantage obtained by using control policies derived in this way, compared with control policies derived by consideration of each sub-system in isolation, is clearly demonstrated.     

Singular perturbation methods in the design of tracking systems incorprating inner-loop compensators and fast-sampling error-actuated controllers

Singular perturbation methods are used to exhibit the asymptotic structure of the transfer function matrices of discrete-time tracking systems incorporating linear multivariate plants which are amenable to fast-sampling error-actuated digital control only if extra plant output measurements are generated by the introduction of appropriate transducers and processed by inner-loop compensators. It is shown that these results greatly facilitate the determination of controller and transducer matrices which ensure that the closed-loop behaviour of such discrete-time tracking systems becomes increasingly non-interacting as the sampling frequency is increased. These general results are illustrated by designing a fast-sampling error-actuated digital controller for an aircraft.