Time–Harmonic Behaviour of a Cracked Piezoelectric Solid by BIEM

ACM Computing Classification System (1998): J.2, G.1.9Time–harmonic behaviour of a cracked piezoelectric finite solid is studied by nonhypersingular traction Boundary Integral Equation Method (BIEM). A numerical solution for Crack Opening Displacement (COD) and Stress Intensity Factor (SIF) is obtained by using Mathematica. Several examples are presented to demonstrate the dependence of the solution on the crack position.The authors acknowledge the support of the Bulgarian NSF under the Grant No. DID 02/15

Rail freight in the EU: A problem-oriented survey (Part I)

This paper consists of a survey on rail freight in the EU, where the prime objective is to reveal the current situation of the rail freight in the EU and raises looming questions for discussion. The paper is organized in three chapters, as follows: 1.Overview reveals the current situation with the European railways and raises questions about the future of these systems; 2.Levels of Operation discusses how the European railways are viewed at both International and National level and suggests some steps for action; and 3.Synthesis. It should be noted that this paper is the Part I of III Problem-Oriented Surveys dedicated to rail freight issues of today

Przygotowanie specjalistów z zakresu turyzmu na Uniwersytecie Sofijskim

Gwałtowny rozwój turystyki w Bułgarii wymagał przygotowania wysoko kwalifikowanych kadr z wyższym w ykształceniem. Kształcenie takie rozpoczęto W 1965 r. w Wyższym Instytucie Ekonomicznym w Warnie w zakresie ekonomiki i organizacji turystyki, a od 1967 r. w zakresie geografii na Uniwersytecie Sofijskim. Specjalistów od turystyki przygotowuje także Wyższy Instytut Kultury Fizycznej oraz dwie szkoły typu półwyższego w Burgas i Warnie. W roku 1973 na Wydziale Geologiczno-Geograficznym Uniwersytetu Sofijskiego powołano samodzielną Katedrę Geografii Turyzmu, która prowadzi specjalizacyjne studia w zakiesie geografii turyzmu

Sinteza, spektroskopska karakterizacija i ab initio istraživanje tioanaloga spirohidantoina

Dithioanalogues of cycloalkanespiro-5-hydantoins were prepared by reaction of the respective spirohydantoins with Lawesson’s reagent or P4S10. Cycloalkanespiro-5-(2-thiohydantoins) and cycloalkanespiro-5-(4-hydantoins) were also synthesized from cycloalkanespiro-5-(2,4-dithiohydantoins) via different reaction pathways. The structures of the compounds obtained were verified by 1H, 13C NMR and IR spectroscopy. Quantum-chemical calculations at the ab initio level of molecular nonlinear characteristics were performed. Increase of polarizability α and the second hyperpolarizability γ with enlarging the saturated ring was observed in all the structures studied.Ditioanalozi cikloalkan-spiro-5-hidantoina pripravljeni su reakcijama odgovarajućih spirohidantoina i Lawesson-ovoga reagensa ili P4S10. Sintetizirani su i cikloalkan-spiro-5-(2-tiohidantoini) i cikloalkan-spiro-5- -(4-tiohidantoini), uporabom različitih reakcijskih putova. Strukture dobivenih spojeva potvrđene su 1H, 13C NMR i IR spektroskopijom. Nelinearne molekularne karakteristike predviđene su kvantno-kemijskim računima na ab initio razini. U svim proučavanim strukturama, s povećanjem zasićenog prstena došlo je do porasta polarizabilnosti α i druge hiperpolarizabilnosti γ

COMPUTER GRAFOANALITIC KINEMATICAL ANALYSIS FOR FOUR-BAR LINKAGE MECHANISM

In this work, a methodology for calculating a class of lever mechanisms is proposed using a current software product for solving algebraic equations. They are adapted in the environment of the theory of mechanisms, where the main kinematic parameters of the articulated four-link mechanism are presented in graphical form. These parameters are linear and angular velocities and linear and angular accelerations. The work is related to the course in general and mechanical engineering at the Technical University - Gabrovo.

Editorial:Introduction to group research projects developed within an intensive programme in railway and Logistics

This paper introduces a special issue of the Journal Transport Problems on group research projects developed within the RailNewcastle summer school organised and held in Newcastle upon Tyne, North East England. The participants (both educators and students) worked together in multinational and multidisciplinary groups to produce research projects. The topics of the group research projects were based around railway and logisticsrelated problems. As a result a collection of the best articles is produced for the purposes of this special issue

SYNTHESIS OF EIGHT MIDDLE LOST MECHANISMS FINALLY DISCHARGED DISCREET POSITIONS

The author has developed the algorithm for the synthesis of eight kinematic structures to generate random function of the positions by given n-number approximate nodes. Synthesis was performed at extreme distances at n≤6. In practice, an approximate synthesis is proposed, with the error being zero only in the approximate nodes, and in the remaining points the error is plotted graphically. According to preset 6 approximate nodes we determine the metric parameters of a family of mechanisms from which we choose the optimal (with the least relative error in the movement of the executive unit). The determination of the position, speed and acceleration function of the executive unit is shown graphically. To establish the authenticity of synthesis is an example.

VECTOR-MATRIX COMPUTER METHOD FOR DRAFTING CIRCLING-POINT CURVES AND CENTERING-POINT CURVES OF BURMESTER

The author suggests a method for drafting circling-point curves and centering-point curves of Burmester in the present paper. The geometrical compulsion makes the best use of synthesis of levers mechanisms by vector-matrix computer method under existing circumstances. Propose the drafting of the Burmester circling-point and centering-point curves are more applicable and more approach for engineers and constructors in the manufacture.