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排序方式: 共有764条查询结果,搜索用时 15 毫秒
1.
Victor Chabanenko Roman Puźniak Adam Nabiałek Sergei Vasiliev Vladimir Rusakov Loh Huanqian Ritta Szymczak Henryk Szymczak Jan Jun Janusz Karpiński Vitaly Finkel 《Journal of Low Temperature Physics》2003,130(3-4):175-191
We present a study of magneto-thermal instabilities in polycrystalline MgB2 superconductor, by magnetic hysteresis loop measurements and by investigations of magnetic flux dynamics with a miniature Hall probe. Temperature and magnetic field ranges where the flux jumps may be observed have been determined. On the basis of measurements of the magnetic flux dynamics, an average magnetic diffusivity describing the process of the flux jump is estimated. This parameter is compared with the thermal and magnetic diffusivities calculated on the basis of available data for thermal conductivity, heat capacity and resistivity. It is shown that the estimated value of the field of the first flux jump is influenced significantly by the field dependence of specific heat. In order to explain the observed phenomenon, the temperature reached by the sample during the flux jump at different magnetic fields is calculated. 相似文献
2.
Marek Markowski Ireneusz Bialobrzewski Janusz Bowszys Stanislaw Suchecki 《Drying Technology》2007,25(9):1527-1536
A neural-deterministic simulation model applied for calculating distributions of temperatures and moisture content in a bed of wheat stored in a steel silo without aeration is presented in the article. The model consists of differential equations of heat and moisture transfer, initial and boundary conditions, and three artificial neural networks used during simulated ambient air conditions. Experiments and computer simulations were carried out in order to determine temperature fields in wheat grain stored in a steel silo for two months. The computer simulations were carried using MATLAB and FEMLAB software. The difference between measured and simulated temperature in grain near the silo wall at a height of 2.5 m from the bottom was less than 3.0°C. On the basis of the analysis performed it was concluded that the temperature distributions obtained with the model were consistent with the measured results obtained for grain stored in a steel silo without aeration. 相似文献
3.
The objective of the present work is to further explore the problem of selection of the flow stress function which will give the best agreement with experiments for a wide range of the Zener‐Hollomon parameter. Analysis of various flow stress functions was performed, with particular emphasis on the Zerilli‐Armstrong model. Inverse analysis was successfully applied to identify the flow stress model for microalloyed steels deformed in ferrite, two‐phase and austenite regions. Inverse method is applied to interpret the results of the axisymmetrical compression tests performed for HSLA steel samples on a Gleeble 3800 and Split Hopkinson Pressure Bar. Sensitivity analysis is performed based on local and global methods. The objective of the sensitivity analysis in the present study is the evaluation to what extent the selected coefficients in the rheological model influence the result of simulations. In the considered tests this result is represented by two dependent variables, the load and the shape of the sample (barrelling). It is confirmed that the Zerilli‐Armstrong equations should be applied at very high strain rates. Physical meaning is an advantage of this model. Difficulties with identification are the main disadvantage. 相似文献
4.
Janusz Holowaty 《计算机技术与应用:英文》2013,(11):592-598
This paper presents comparison of numerical models used in an analysis of a road bridge deck. The models were adapted for computing the live load distribution coefficients in composite concrete bridge deck. The load distribution method was chosen for assessment of the usability of different numerical model in slab bridge deck analysis. The goal of the study is to determine a simplest but still accurate numerical model to estimate live load effects on composite slab bridge. In the analysis, the well-established grillage approach was adapted for representation of the bridge deck as a basic model as well as more sophisticated three-dimensional models which was supposed to better represent the real behavior of the deck under concentrated wheel loads. The bridge deck was effectively modeled using beam and shell elements. The grillage method compares well with the finite-element method. This finding is allowed to establish simplification in numerical modeling of slab bridge decks for live load effect computations. 相似文献
5.
In the paper, the approximate controllability of linear abstract second-order infinite-dimensional dynamical systems is considered. It is proved using the frequency-domain method, that approximate controllability of second-order system can be verified by the approximate controllability conditions for the corresponding simplified first-order system. General results are then applied for approximate controllability investigation of a vibratory dynamical system modeling flexible mechanical structure. Some special cases are also considered. Moreover, remarks and comments on the relationships between different concepts of controllability are given. The paper extends earlier results on approximate controllability of second-order abstract dynamical systems. 相似文献
6.
This paper presents an overview and discusses the role of certification in safety-critical computer systems focusing on software,
and partially hardware, used in the civil aviation domain. It discusses certification activities according to RTCA DO-178B
“Software Considerations in Airborne Systems and Equipment Certification” and touches on tool qualification according to RTCA
DO-254 “Design Assurance Guidance for Airborne Electronic Hardware.” Specifically, certification issues as related to real-time
operating systems and programming languages are reviewed, as well as software development tools and complex electronic hardware
tool qualification processes are discussed. Results of an independent industry survey done by the authors are also presented. 相似文献
7.
8.
Janusz Sokó? 《Computers & Mathematics with Applications》2011,62(2):611-619
This paper presents a new class of functions analytic in the open unit disc, and closely related to the class of starlike functions. Besides being an introduction to this field, it provides an interesting connections defined class with well known classes. The paper deals with several ideas and techniques used in geometric function theory. The order of starlikeness in the class of convex functions of negative order is also considered here. 相似文献
9.
Janusz Szczepanski 《Information Sciences》2009,179(9):1217-1220
Investigations of complexity of sequences lead to important applications such as effective data compression, testing of randomness, discriminating between information sources and many others. In this paper we establish formulae describing the distribution functions of random variables representing the complexity of finite sequences introduced by Lempel and Ziv in 1976. It is known that this quantity can be used as an estimator of entropy. We show that the distribution functions depend affinely on the probabilities of the so-called “exact” sequences. 相似文献
10.
A class of artificial neural networks with a two‐layer feedback topology to solve nonlinear discrete dynamic optimization problems is developed. Generalized recurrent neuron models are introduced. A direct method to assign the weights of neural networks is presented. The method is based on Bellmann's Optimality Principle and on the interchange of information which occurs during the synaptic chemical processing among neurons. A comparative analysis of the computational requirements is made. The analysis shows advantages of this approach as compared to the standard dynamic programming algorithm. The technique has been applied to several important optimization problems, such as shortest path and control optimal problems. 相似文献