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Found 6273 publications

Analysis and test results of quasi-resonant converters

Z. Puklus Peter Korondi Peter Csaba Szilagyi László Hodossy

Publication Name: Telescon 1997 2nd International Telecommunications Energy Special Conference

Publication Date: 1997-01-01

Volume: Unknown

Issue: Unknown

Page Range: 185-190

Description:

This paper presents the test results and simplified design method of a new type symmetrical resonant DC/DC converter. The realised converter operates in the frequency range of 30-300 kHz. This paper contributes the theoretical results of the resonant type DC/DC converters and shows the hits of their usage. The output voltage-current curve (Uo-Io) shows the typical features of the converter operation.

Open Access: Yes

DOI: 10.1109/TELESC.1997.655714

The generalization of pascal’s triangle from algebraic point of view

Gabor Kallos

Publication Name: Annales Mathematicae Et Informaticae

Publication Date: 1997-01-01

Volume: 24

Issue: Unknown

Page Range: 11-18

Description:

In this paper we generalize Pascal’s Triangle and examine the connections between the generalized triangles and powering integers and polynomials respectively.

Open Access: Yes

DOI: DOI not available

The generalization of pascal’s triangle from algebraic point of view

No authors available

Publication Name: Annales Mathematicae et Informaticae

Publication Date: 1997-01-01

Volume: 24

Issue:

Page Range: 11-18

Description:

In this paper we generalize Pascal’s Triangle and examine the connections between the generalized triangles and powering integers and polynomials respectively.

Open Access: No

DOI: DOI not available

Object-oriented database schema analysis and inheritance processing: A graph-theoretic approach

M. Missikoff A. Formica H. D. Groger

Publication Name: Data and Knowledge Engineering

Publication Date: 1997-01-01

Volume: 24

Issue: 2

Page Range: 157-181

Description:

In this paper we address the inheritance process in the context of strongly typed Object-oriented database (OODB) systems, allowing multiple inheritance and overriding. For such powerful systems, it is important to analyse the inheritance hierarchy to identify a number of significant properties. The first, schema consistency, is connected to the inheritance conflicts. In the presence of an unsolvable inheritance conflict there is a contradiction in the schema. The second property is related to the termination of the inheritance process. We expect that all the subtypes in the schema, if consistent, can be rewritten in expanded form, after inheritance, in a finite time. Schemas that guarantee these two formal properties will be referred to as correct schemas. In the paper a graph-theoretic method is provided, aimed at supporting the designer in checking the correctness and deriving the expanded form of a schema. Furthermore, from the analysis of the complexity of the inheritance process, a third formal property has been defined, concerning the degree of compactness achievable in a schema, by using inheritance hierarchies. In particular, a class of schemas has been defined, referred to as logarithmic schemas, whose expanded forms, after inheritance, become exponential in the size of the original schemas.

Open Access: Yes

DOI: 10.1016/S0169-023X(97)00018-9

A simple and accurate contactless frequency and amplitude meter

Tolnai László Marczy László

Publication Name: Review of Scientific Instruments

Publication Date: 1997-01-01

Volume: 68

Issue: 2

Page Range: 1303-1306

Description:

This study describes a measuring instrument based on the Michelson interferometer. It is able to measure the amplitude-time function or the resonance curve in a wide frequency range simultaneously depending on the amplitude of the vibration without any kind of mechanical contacts. Compared with other instruments based on similar principles, it has the advantage of not being a heterodyne interferometer, that is of using only the phenomenon of classic interference instead of the frequency of Doppler shift of the reflected light. The reflective surface of the oscillating object or the mirror glued thereon may turn, which is often the case. The software performs a correction to the errors arising from the turning of the mirror. In the realized instrument the allowed maximum angle of rotation of the mirror is ±5°, measuring range of the amplitude is 5 micron to 1 mm, measuring range of the frequency is 1 Hz to 5×104 Hz depending on the amplitude. © 1997 American Institute of Physics.

Open Access: Yes

DOI: 10.1063/1.1147888

Comprehensive method for the test calculation of complex digital circuits

Jozsef Sziray

Publication Name: Periodica Polytechnica Electrical Engineering

Publication Date: 1997-01-01

Volume: 41

Issue: 4

Page Range: 251-257

Description:

The paper presents a general test calculation principle which serves for producing tests for a wide range of possible faults: stuck-at-constant logic level (single, multiple), bridging (single), as well as behavioral (functional, single) faults. The proposed method handles multi-valued logic, where the number of logic values is unlimited. The level of circuit modeling is also allowed to vary in a wide range: switch level, gate level, functional level, etc. are equally allowed. Both combinational and sequential circuits are considered. The principle is comparatively simple, and it yields an opportunity to be realized by an efficient computer program.

Open Access: Yes

DOI: DOI not available

Ownership and control in the bus industry: The case of Hungary

John D. Nelson Wafaa Saleh István Prileszky

Publication Name: Journal of Transport Geography

Publication Date: 1997-01-01

Volume: 5

Issue: 2

Page Range: 137-146

Description:

In Hungary, the impending expiry of existing operating licences for both urban and interurban bus services is leading to considerable pressure for change in the current system of ownership and control. Furthermore, the transport sector in Hungary faces several endemic problems. Consequently, this paper analyses the experience of the public transport sector in Hungary with respect to the current situation noting changes after 1990. At the national level, reference is made to both road-based transport (including car ownership and use) and (briefly) to railways. The situation in Budapest is then considered in detail. Next, the structure of the public transport sector in Hungary is discussed both before and after 1990 when the move towards a free market economy received new impetus. The paper examines, as a case-study, the recent experience of private bus operators in Hungary. Finally, drawing on experience elsewhere with possible models for privatization and deregulation in the case of bus operations, suggestions are offered on lessons to be learned by the governments of countries in Central and Eastern Europe as they assess the possibilities for alternative methods of ownership and control. © 1997 Elsevier Science Ltd.

Open Access: Yes

DOI: 10.1016/s0966-6923(97)84102-6

Analysis of railway vehicles' bogies with different wheel forces

László Bozóky Vince Nagy

Publication Name: Proceedings of the Mini Conference on Vehicle System Dynamics Identification and Anomalies

Publication Date: 1996-12-01

Volume: Unknown

Issue: Unknown

Page Range: 203-213

Description:

For the past ten years, geometry and loaded tests on railway bogies are in progress at the Department for Automotive and Railway Engineering of Szechenyi Istvan College. Following analysis of running and driven bogies and laboratory measurements, operating test of running vehicles has also been conducted. Initial results made it possible to perform different theoretical and computer analysis.

Open Access: Yes

DOI: DOI not available

Residual elimination algorithm for solving linear equations and application for sparse systems

B. Török G. Y. Molnarka

Publication Name: ZAMM Zeitschrift Fur Angewandte Mathematik Und Mechanik

Publication Date: 1996-12-01

Volume: 76

Issue: SUPPL. 1

Page Range: 485-486

Description:

A new direct algorithm for solving linear system of equations will be presented. Short theoretical background and analysis of the proposed method will be given. We formulate an optimized version of the proposed algorithm, which also works for sparse matrices. The complexity of the suggested algorithm for full matrix systems is n3/3 H- O(n2) where n is the dimension of the problem. The numerical experiments show that some versions of the residual elimination algorithm can be competitive with the Gaussian elimination both in complexity and precision. Moreover the sparse linear solver based on this algorithm has some advantages in parallel environment.

Open Access: Yes

DOI: DOI not available