1/2 1999

Distributed Simulation

N. Ruskova, H. Valchanov, T. Ruskov

Key Words:Discrete event simulation; parallel and distributed simulation; conservative and optimistic simulation; adaptive simulation.

Abstract.The field of parallel and distributed simulation has developed over the past years to satisfy the need for simulating dynamic and complex systems. The current state of the methodologies for asynchronous discrete event distributed simulation is discussed in this survey


On 2D CAD-CAM Link Stand on Automated Feature Recognition

P. Goranov

Key Words: Feature-based modeling; feature recognition; orthographic projections; CAD-CAM link.

Abstract.Features as used in design can differ significantly from those used in manufacturing. Integration between CAD and CAM system require to bridge the gap between feature based design and feature based process planning. A solution of this multiple views’ problem is to use some way of feature conversion or mapping. Most methods that have so far been proposed use as their input a solid model. Comparative little previous work has been reported on feature recognition from 2D drawings, which is the form in which the majority of design data currently exists. This paper present initial efforts to employ experimental system to recognise manufacturing features from orthographic projections of part. It has been designed to meet the automated process-planning requirements of today rather then tomorrow and it has demonstrated on a range of simple prismatic machined parts


Representation of Symbolic Information in Monochrome 2D Images for Image Pattern Recognition

P. Rashev, M. Lazarov, Y. Assenov

Key Words: Image processing; image pattern

Abstract.Representation of symbolic information in monochrome 2D-images for image pattern recognition is reviewed herein. Conversion of the initial symbolic information is divided in two steps ­ horizontal and vertical symbol scanning. The first step defines vertical symbol edges (horizontal derivative extraction). During the second step horizontal symbol edges are defined (vertical derivative extraction). The final result is a binary image corresponding to the outline of the processed symbol all lines of which are one pixel wide.


Teoretical Treatment and Biosensor Error Analysis

A. Neykov

Key Words: Biosensor; errors; model; experiment.

Abstract.A conception and amperometric biosensor error model for teoretical treatment is developed in this paper. Mathematical description of absolute sumary biosensor error of one-enzyme two-substrate biosensor system is made. The biosensor non-linearity error is analysed, too, and maximal value is evaluated. An enzyme sensor for glucose concentration with immobilised dextrane and oxygen sensor is developed and non-linearity errors are experimentally research.


Multifunctional Board
for Computer-based Information-measurement and Control Systems

Z. Nenova, N. Zankov, T. Nenov, R. Vulchev

Key Words: Information-measurement and control systems; multifunctional PC-board; virtual instruments.

Abstract.A multifunctional board is proposed, which enables the realization of information-measurement and control systems based on personal computers of the type IBM PC/AT. The board consist of the following basic subsystems: analogue inputs, analogue outputs, a counter/timer subsystem and digital inputs/outputs. It allows the realization of greatly functional virtual instrumentats with a flexible user interface.



3 1999


Computer System for a Radiographic Evaluation

P.Penchev, E.Baltov, M.Dobrev, N.Iskiliev

Key Words: Femoral head; numerical rating system; X-ray images.

Abstract.This paper addresses two problems facing surgeons today. One problem is the overwhelming flow of images and imaging information available to the surgeon. Nearly 100 years have passed since Roentgen's discovery of X-rays, and imaging and the handling of image information is now a routine aspect of surgery. But today, image acquisition technology has developed so rapidly that a new method of handling the multipleimaging modalities and clinical information is now needed. The second problem is how does one surgeon compare his results with another. Now does one sift through the growing number of research reports detailing the clinical effectiveness of various implants. The paper provides the basic tools for analysing, reporting and stimulated the introduction of several numerical rating system to express the state of the femoral head before and after treatment.


Modulation Techniques in Wireless LAN Based on Difused Infrared Channel

G. Spassov, V. Furnadjiev

Key Words: Diffuse infrared wireless LAN; modulation techniques; time pulse modulation.

Abstract. The use of infrared radiation as a medium for high-speed, short-range wireless digital communication is discussed. Advantages and drawbacks of the infrared medium are compared to those of radio media. Physical characteristics of infrared channels using intensity modulation with direct detection are presented. Several modulation formats are discussed in detail, including on-off keying (OOK) and pulse-position modulation (PPM). A new alternative time pulse modulation (TPM) is presented.


A WWW-based Terminological Dictionary in Computer Science Using an Underlying Semantic Network

G. Angelova, E. Djerassi

Key Words: Terminology; dictionary; semantic network; ontology; World Wide Web.

Abstract. The emerging Information Society is a society of knowledge and innovation and the path to it implies research and development of knowledge-based systems. This paper presents a pilot project for development of a WWW-based terminological dictionary, which can be accessed by many users. The underlying semantic network of domain terms provides for innovative flexible searching through the dictionary. The obtained product is in fact a knowledge-based system for information service and retrieval. The paper describes the laboratory version of the software providing an user interface under a WWW-browser. We discuss ways for acquisition, usage, elaboration, and integration of such a knowledge-based dictionary into other software environments for text processing and evaluate the positive and the negative aspects of the new approach vs. the traditional ones.


Integrating of Components for Cleaning of the Active Surface of Conductive Microsensors

M. Marinov, V. Galabov, C. Schilling

Key Words: Microsensors; environmental control; design of experiments.

Abstract. Microsensors are already components of macrotechnical systems in various areas. The reduction of physical dimensions allows the usage of entirely different methods for signal processing. Generally the present research concerns the impact of the natural water environment on the microtechnologically developed sensors and the principle possibilities for reducing that influence. The specific sensor to be considered ­ the microsensor on silicium plate for conductivity measurement is exposed in environments with defined parameters for a long term of time. In the paper are presented the experimental setup and the technique for investigation of various reasons for the sensor parameter variations. The study of the stability of the microstructural measuring probes aims at the increase of their reliability in in-situ mode through integration of components for (self-) cleaning of the active sensor surface.


Special Postdetermination of Logical Functions: Optimisational Procedure BALAR in Sequential Synthesis

L. Balkandjiev, S. Arnaudov

Key Words: Special postdetermination of logical functions; automata finite; sequential synthesis and analysis; programmable logical devices.

Abstract.The problem of special postdetermination of excitative functions of triggers with two logical inputs as optimisational procedure in sequential synthesis is defined in this paper. The basic treatments and results from the analytic investigation are given. Cite as evidence is given for every one trigger with two logical inputs every time and unconditionally can be menaged only with one excitative function. The role and the place of the proved theorem BALAR and the same optimizing procedure in the theory and the practice in contemporary sequential analysis are illustrated.


A knowledge Representation Language for Training in Complex Dynamic System

G.Georgiev, I.Zheliazkova

Key Words: Knowledge representation language; Simulation-based training; complex dynamic systems; declarative knowledge; procedural knowledge; operational skills

Abstract. Due to the inability to explicitly represent declarative and procedural knowledge and operational skills in complex dynamic systems the traditional simulation languages can not be applied to the development of intelligent training systems. A knowledge representation language is presented which explicitly expresses the system structure, functions, and behaviour. The general structure of the tutor's program in this language is discussed in the paper. The syntax and semantics of three types of knowledge, i.e. declarative knowledge, procedural knowledge, and operational skills are commented in detail. Finally an example tutor's program in the field of electronics is presented. Different types of training tasks for quantitative modelling of continuous and discrete systems can be programmed in the knowledge representation language.

4 1999

The papers in the issue are without abstracts.


5 1999

Methods for Data Compressing without Information Loss

P. Konyarov, L. Dakovski

Key Words: Data compression; compressing algorithm.

Abstract. This paper gives a systematized description of the methods for data compressing without information loss. The comparison of diferent algorithms suggest volunteer where and how to use every method for information compression.


Practical Adaptive Image Compression Technique

B. Rachev, S. Jordanova

Key Words : Data compression; quantization; coding.

Abstract. An efficient image compression/decompression for complex scenes is presented. An image is first decorrelated by a full two-dimensional DCT. The resulting coeffficient map is weghted using properties of human visual system and finally encoded with a novel encoder. The result is converted into printable ASCII for transmission by electronic mail.


Interdependence between Efficiency of Compressing and Distribution of Robability Ranges in Statistic Arithmetical Data Compressing

B. Alexandrov, B. Bozhinov

Key Words: Data compression; arithmetic coding; compression technique.

Abstract. The study presents the analytical interdependence found in statistic arithmetical data compressing between array zise after compression, probability range distribution and the number of symbols marking each probability range.


Generation of Cyclic Symbol Sequences with Assigned Markov Characteristics

Y. Guenov

Key Words: Markov sources, pseudorandom sequences.

Abstract. An algorithm for generation of symbol sequences with specific Markov properties is presented. "Cyclic" refers to the way symbols are interpreted as a Markov sequence, hence the way the Markov model is constructed. The algorithm produces the full set of all possible sequences conforming to a given model. Formally, this can be thought of as a controlled source of pseudorandom Markov sequences.


Track Detection Using Hough Transform

K. Alexiev, R. Pachova

Key Words: Track initiation; radar data processing.

Abstract. Track initiation of multiple objects is considered. The association of measurements is performed upon incomplete, ambiguous, inaccurate stochastic data. The widely used approaches have an unavoidable drawback ­ the number of the arising optimization tasks increases exponentially when the number of input measurements increases linearly. A nontrivial suboptimal solution of track initiation problem is proposed here. The approach is based on the application of the Hough transform and it achieves significant reduction of the required computational load. The problems of parameter space determination and discretisation are discussed. A Monte Carlo verification of results is presented.


Development of a Low Area Custom Microprocessor Core

P. Manoilov, G. Kouzmanov, T. Stefanov, A. Popov

Key Words: Heuristic iterative methodology; base algorithms; System-on-Chip; total area; timing; pure combinational control and arithmetic-logic unit

Abstract. The aim of this work is to present the authors’ team experience in developing a low area custom microprocessor core (named Ims8NI) at a quick and efficient methodology called HSTD. The choice of the lowest area control unit type (fixed logic or micro-program control) was made after some research. An original timing was realized and an unusual design of the control unit and the arithmetic-logical unit was achieved. An FPGA (Altera-Flex10K10) prototype of the core was implemented and a simple silicon chip was also implemented as a soft- and/or hard-macro for further use in microprocessor based application specific integrated circuits (ASICs). The core Ims8NI is compared with some other kernels of the same class and the results are represented in this paper.


6/1999 Information Technologies and Computer Virology

Information Technologies and Computer Virology

E. Nickolov

Key Words: Information society; information technologies; convergation; computer virology; computer security.

Abstract. The purpose of this article is to give a review of the present condition of the computer virology in the light of the new information technologies. In the beginning attention has been paid to the information environment and its components. After that the basic principles of functioning and the methods of computer viruses’ investigation have been looked upon. Further on the means for detecting and removing computer viruses have been commented upon. The problems in data recovery have been discussed, too. In conclusion respective deductions have been made.


Three-vector Data Protection in Operating Memory Environment

B. Aleksandrov, N. Siniagina

Key Words: Error control coding; error detection; double error correction; multiple error correction.

Abstract. The presented material describes a specific algoritmic feature of 3V coordinate protection of data arrays. An approach is also suggestec there for eliminating the same feature.


Organization of Measurment Systems in an Event Programming Environment

I. Zheliazkova, G. Georgiev, M. Velikov, G. Rashkov

Key Words: Data AcQuisition; data analysis; data presentation; event programming enviroment; virtual instrument; driver; Dynamic Linked Library; user interface.

Abstract. In an event-driven programming environment the investigator becomes an active agent during the three stages of the measurment process: data acqusition, data analysis and data presentation. The paper deals with the main problems, arising when a DAQ-system is organized in such an environment, namely: necessary additional hardware, hardware control, and user interface. In parallel the autorsexperience concerning a given DAQ-system is shared.


Implementation of Low Bit Rate Coder for Speech Signals Using Wavelet Transform

M. Momchedjikov, G. Iliev, K. Kostadinov

Key Words: Wavelet transform; speech coding; speech compression; adaptive signal processing.

Abstract. In this work an efficient realization of low bit rate coder for speech signals is presented. The coder uses wavelet transform, and in addition ADPCM and statistical coding for better compression of the speech signal. The experiments show that the proposed coder has a SEG-SNR which is very close to the SEG-SNR of two coders based on ADPCM and subband coding respectively. At the same time the bit rate of this coder is two to four times lower than the bit rate of these very popular coders. These results make the presented coder very attractive for applications where the bit rate is critical, for example xDSL.