Linear shrinkage of metal powder compacts during sintering

Summary The influence exerted by various factors (particle size, particle size distribution, ultrafine powder addition, sintering temperature, etc.) on the linear shrinkage ratio during sintering was examined. Electrolytic, atomized, and ultrafine copper powders, as well as electrolytic iron powder, were used.     

Bending vibration of simply supported rectangular plates with internal rigid support

A previously derived invariant expression for the amplitude of the displacement of homogeneous, isotropic, harmonically vibrating plates with internal rigid supports or cracks is supplemented here by terms representing possible point discontinuities at the tips of the support or of the crack. This expression being given in tensor notation can be easily adapted to curvilinear plates with regular boundaries (separable coordinate systems) and arbitrary discontinuities and, in particular, to rectangular plates with curvilinear discontinuities. Vibration of a rectangular simply supported plate with arbitrarily located rectilinear rigid support is discussed as an example. The unknown discontinuity of the shear force across the support is described by a coupled system of integro-algebraic equations valid for any position and inclination of the rigid support. This system is subsequently reduced to an infinite system of linear-algebraic equations. Fundamental frequencies of natural vibration are obtained for a square plate with centrally located but arbitrarily inclined rigid support of any length. In the special cases—support parallel to one edge of the plate or diagonal support reaching the corners—the results show very good agreement with the ones known from previous analyses.     

PLANNING TO OPTIMIZE THE UMTS CALL SETUP FOR THE EXECUTION OF MOBILE APPLICATIONS

The third generation of mobile communication, the so-called UMTS, makes a broad variety of applications for mobile terminals available. This endeavor is the maintenance of several applications on one terminal: Radio bearers have restrictions in the quality of service (QoS) for applications due to limited resources. And the cell setup for the execution of several mobile applications may lead to unacceptable waiting periods for the user. As example considers WAP access, where the connection to the gateway takes, in general, approximately half a minute. This period increases if one is using several applications on one mobile terminal. Another hinderance is an insufficient QoS availability during the call setup. Here, the execution of the mobile application is shutdown.

In this paper, the optimization of the call setup for several mobile applications is investigated. The optimization applies scheduling to order and optimize the execution of the modules for UMTS for the call setup. This application is new for scheduling in artificial intelligence (AI). The premise is the modularization of the UMTS call setup based on agent technology, since the call setup of radio is basically a continuous process in the field of electrical engineering. As a result, the user has a shorter waiting period until the execution of several mobile applications is started and thus mobile terminals can be used more flexibly. Experiments for the execution of up to 20 mobile applications on the same mobile terminal demonstrate the optimization.     

Towards mesoscopic thermodynamics: Small systems in higher-order states

A higher-order generalization of the usual thermodynamic formalism is presented for systems with the number of particlesN large in comparison with 1, but sufficiently small that one or many higher-order fluctuations of energy (or other observables) are measurable, directly or indirectly. Then 1 «N «N _A , whereN _A is the Avogadro number, andn2, wheren is the highest order of fluctuations (central statistical moments). The systems are then open, finite and compact, and they have compact boundary surfaces, so that the energy is non-additive and temperatures are non-intensive, in general. Such systems will be called comesoscopic, while a finite or infinite super-system of such systems will be called mesoscopic. Three ideal models of comesoscopic systems are discussed in detail with one or two higher-order temperatures. General conclusions concerning hierarchical composite systems are drawn afterwards.

相似文献   

Dynamic contour: A texture approach and contour operations

The large morphometric variability in biomedical organs requires an accurate fitting method for a pregenerated contour model. We propose a physically based approach to fitting 2D shapes using texture feature vectors and contour operations that allow even automatic contour splitting. To support shrinkage of the contour and obtain a better fit for the concave parts an area force is introduced. When two parts of the active contour approach each other, it divides. The contour undergoing elastic deformation is considered as a set of masses linked by springs with their natural lengths set to zero. We also propose a method for automatic estimation of some model parameters based on a histogram of image forces along a contour.     

Kernel PCA for Feature Extraction and De-Noising in Nonlinear Regression

In this paper, we propose the application of the Kernel Principal Component Analysis (PCA) technique for feature selection in a high-dimensional feature space, where input variables are mapped by a Gaussian kernel. The extracted features are employed in the regression problems of chaotic Mackey–Glass time-series prediction in a noisy environment and estimating human signal detection performance from brain event-related potentials elicited by task relevant signals. We compared results obtained using either Kernel PCA or linear PCA as data preprocessing steps. On the human signal detection task, we report the superiority of Kernel PCA feature extraction over linear PCA. Similar to linear PCA, we demonstrate de-noising of the original data by the appropriate selection of various nonlinear principal components. The theoretical relation and experimental comparison of Kernel Principal Components Regression, Kernel Ridge Regression and ε-insensitive Support Vector Regression is also provided.     

Temperatures in linguistics as a model of thermodynamics

Natural languages have been taken as models of systems with strong statistical correlations. In such systems the usual probabilistic limiting laws (Gauss etc.) are no more valid and the concept of higher order temperatures can be applied. It has been shown that this is the case in such languages as English, German, French, Russian and Japanese, for letter and word statistics. The corresponding temperatures (up to the 5-th order), entropies and statistical moments have been calculated and their mutual relations have been checked.... erst wenn du plötzlich Fänger wirst des Balles, den eine ewige Mitspielerin dir zuwarf, ... erst dann ist Fangen-können ein Vermögen, nicht deines, einer Welt.(... only when you suddenly catch the ball which the eternal fellow player throws to you,... only then the catching ability is an accomplishment, not of you, but of the world.)R. M. Rilke (from the motto of [3])Supported by Committee of Scientific Research, Warsaw (KBN), Project Nr. 20412 91 01.     

Architecture-directed refinement

As critical computer systems continue to grow in complexity, the task of showing that they execute correctly becomes more difficult. For this reason, research in software engineering has turned to formal methods, i.e., rigorous approaches to demonstrating the correctness of software systems. Unfortunately, the formal methods currently used in the design of concurrent systems do not provide any mechanisms for specifying and reasoning about the mapping of software to hardware. As a result, architectural constraints, even though they play an important role in the design process, are left out of the formal framework. We show how to state architectural constraints in a formal notation, how to prove that programs are allocated correctly to the underlying architecture, and how to factor architectural considerations into a program derivation process which uses a mixture of specification and program refinements. The approach is illustrated by the derivation of two related programs that solve the same problem but are designed to work on distinct architectures     

Expressing and Enforcing Timing Constraints in a Dynamic Real-Time CORBA System

Distributed real-time applications have presented the need to extend the Object Management Group's Common Object Request Broker Architecture (CORBA) standard to support real-time. This paper describes a Dynamic Real-Time CORBA system, which supports the expression and enforcement of end-to-end timing constraints as an extension to a commercial CORBA system. The paper also describes performance tests that demonstrate the system's ability to enforce expressed timing constraints.     

On aspectualizing component models

Server‐side component models such as Enterprise JavaBeans (EJB) add powerful abstractions to the bare ‘business objects’ layer in order to support a clean separation of server‐side application logic from other concerns such as distribution, security, transaction management and persistence. An improved separation of concerns is also the main goal of aspect‐oriented programming (AOP). This paper compares the two approaches and reasons about the possibility of substituting (parts of) component models using AOP mechanisms. We conclude that AOP is a promising approach to eliminate important shortcomings of the container‐based component approach. However, our analysis of concrete aspect‐oriented languages shows that current AOP technology is not yet mature enough to supersede component models. Copyright © 2003 John Wiley & Sons, Ltd.