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1.
2.
ZnO-based varistor samples were prepared by the direct mixing of the constituent phases (DMCP) and sintering at 1100 °C for 2 h. The influence of the starting powder mixture's composition – the amounts of the pre-reacted varistor compounds and their composition – and its preparation, either with or without mechano-chemical activation (MCA), on the microstructure, phase composition and electrical characteristics of the varistor samples was studied. It showed that MCA improved the density and microstructural homogeneity of the varistor samples. MCA strongly affected the grain growth: it enhanced the nucleation of inversion boundaries (IBs) in the ZnO grains and the IBs-induced grain-growth mechanism resulted in uniform grain growth and hence a microstructure with smaller ZnO grains and a narrower grain size distribution. The final phase composition of the samples prepared by the DMCP method mainly depended on the presence of varistor dopants that can prevent the formation of the pyrochlore phase, especially Cr2O3, while MCA can affect it mostly by providing a homogeneous distribution of those dopants. The DMCP varistor samples prepared with MCA had much better current–voltage characteristics than the samples of the same composition prepared from unactivated powders. 相似文献
3.
V Živica 《Bulletin of Materials Science》1995,18(2):115-124
The paper describes a method for the mathematical modelling of steel reinforcement corrosion rate. This method is based exclusively
on experimental results and expression of the influence of significant corrosion factors in the form of functional relations.
The method takes into account the reality of the effects of corrosion factors, their contigency and complexity, and various
circumstances occurring in practice. It represents one way towards the development of methods for the prediction of service
life of reinforced concrete and structures. 相似文献
4.
In this paper we focus on appearance features particularly the Local Binary Patterns describing the manual component of Sign Language. We compare the performance of these features with geometric moments describing the trajectory and shape of hands. Since the non-manual component is also very important for sign recognition we localize facial landmarks via Active Shape Model combined with Landmark detector that increases the robustness of model fitting. We test the recognition performance of individual features and their combinations on a database consisting of 11 signers and 23 signs with several repetitions. Local Binary Patterns outperform the geometric moments. When the features are combined we achieve a recognition rate up to 99.75% for signer dependent tests and 57.54% for signer independent tests. 相似文献
5.
6.
Inductive Logic Programming (ILP) deals with the problem of finding a hypothesis covering positive examples and excluding negative examples, where both hypotheses and examples are expressed in first-order logic. In this paper we employ constraint satisfaction techniques to model and solve a problem known as template ILP consistency, which assumes that the structure of a hypothesis is known and the task is to find unification of the contained variables. In particular, we present a constraint model with index variables accompanied by a Boolean model to strengthen inference and hence improve efficiency. The efficiency of models is demonstrated experimentally. 相似文献
7.
P. Žitňan 《Computing》1997,59(1):17-27
A discrete least-squares technique for computing the eigenvalues of differential equations is presented. The eigenvalue approximations
are obtained in two steps. Firstly, initial approximations of the desired eigenvalues are computed by solving a quadratic
matrix eigenvalue problem resulting from the least-squares method applied to the equation under consideration. Secondly, these
initial approximations, being of sufficient accuracy in some cases, are improved by using the Gauss-Newton method. Results
from numerical experiments are reported that show great efficiency of the proposed technique in solving both regular and singular
one-dimensional problems. The high flexibility of the technique enables one to use also the multidomain approach and the trial
functions not satisfying any of the prescribed boundary conditions. 相似文献
8.
An approach to the design of a digital algorithm for network frequency estimation is proposed. The algorithm is derived by using the Fourier and zero crossing techniques. The Fourier method is used for digital filtering and the zero crossing technique is applied to the cosine or sine components of the original signal, which is usually corrupted by higher harmonics. The algorithm showed a very high level of robustness as well as a high measurement accuracy over a wide range of frequency changes. It can be used for frequency tracking in power networks when higher harmonics are present in the voltage or current signals. The theoretical basis and practical implementation of the technique are described. The performance of the developed algorithm has been verified by the computer simulations, and the field and laboratory tests. 相似文献
9.
Juš Kocijan Gregor Žunič Stanko Strmčnik Damir Vrančić 《International journal of control》2013,86(14):1082-1091
In the paper an approach to the non-linear control of a gas-liquid separation plant is presented. To solve the problem the fuzzy gain-scheduling method was used and implemented on a programmable logic controller (PLC). Velocity-based linearization approach was used for control system design and implementation for the first time in process control application. Emphasis was placed on the appropriate adaptation of the method and some important implementation issues. The algorithm was carefully designed and tested by using ordinary simulation, hardware-in-the-loop simulation, and experiments on the real plant. The results show that the proposed approach substantially improves the closed-loop performance of the plant. 相似文献
10.
P. Žitňan 《Engineering Analysis with Boundary Elements》2013,37(5):860-867
The aim of this work is to show how the B-spline collocation method may be used for the approximate solution of Poisson problems considered on complex shaped planar domains in a simple and stable way. The most important aspect of this work consists in the use of approximate Fekete points recently developed by Sommariva and Vianello. Numerical experiments concerning the collocation solution of Poisson problems defined on an amoeba-like domain, star shaped domain and a square with eight holes subject to Dirichlet boundary conditions are presented. 相似文献