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The 18th issue of RECENT journal was edited and multiplied with support of:
CONTENTS
Nicolae BOIAN
SPECIFICATIONS OF AUDIT AND DIAGNOSE ANALYSIS OF SMALL AND MEDIUM SIZE
COMPANIES » Abstract. This paper presents the specific elements of economical activities at small and medium companies, the way in which they influence the analysis process and audit, the results and their level of influence. Also it brings out the possible dangers or traps that specialists must avoid in the economical analysis operations of small and medium companies. » Keywords: diagnose analysis, audit, small and medium size companies, organization, entrepreneur Azzedine BOUZAOUIT, Rachid CHAÏB, I.A. Elias HADJADJ, Ion VERZEA
STATISTICAL STUDY ON THE BEARING'S DEGRADATION » Abstract. The various functions which one requests from bearings vary according to the kind of use of those. These functions must be provided the one prolonged period old court of continuous or intermittent operation. Even if the bearings were correctly assembled and are correctly used, they are likely to cease functioning correctly at a certain time, in consequence of an increase in the level of noise and vibration, of a loss of precision of operation, of a deterioration of grease, or a chipping of tiredness of the riding surfaces. The paper presents the experimental researches for establishing a statistical study on the bearing's degradation. » Keywords: analyze deterioration, statistical study, conditional preventive maintenance Constantin BUZATU, Daniel Ionuţ BĂNCILĂ
BATCH OPTIMIZATION INFLUENCE FACTORS » Abstract. This paper presents a synthetic analysis on the influence of the representative factors interacting with the optimal batch in the series and flexible production. The cost of production is also considered. » Keywords: optimal batch, costs, influence factors Romeo CIOARĂ, Vladimir MĂRĂSCU-KLEIN, Oana TOMA
PLANETARY BEARINGS. ORIGIN OF THE CONCEPT AND SOME CONSTRUCTIVE SOLUTIONS » Abstract. In machines manufacturing industry axles driven at high and very high speeds requiring adequate bearings are increasingly frequently used. For this purpose special bearings are built, which typically are expensive, due to their high precision and - quite frequently - due to their being produced in reduced series. The authors addressed the issue of manufacturing bearings capable of carrying high speeds, but available at reduced cost and without significant technological modifications in relation to the usual bearings deployed at present. A realistic solution satisfying to a great extent the imposed requirements is given by planetary bearings. This original concept is based on the „combination” of two bearings, one „mounted” within the other, thus yielding a bearing with two intermediary layers of roller bodies. The exterior race of the „interior bearing” and the interior race of the „exterior bearing” form a single body, the intermediary race, a machinery part characteristic for planetary bearings. The maximum speed of a planetary bearing is theoretically equal to the algebraic sum of the maximum limit speeds of the two component bearings. The paper presents the detailed concept of a planetary bearing, examples of constructive solutions and potential technical performance for various types of planetary bearings. » Keywords: planetary bearings, concept, invention Ioan CIOBANU, Mihai MAŞNIŢĂ, Vlad MONESCU
RESEARCH BY COMPUTER SIMULATION REGARDING THE INFLUENCE OF THE LIQUID ALLOY OVERHEAT ABOVE THE SOLIDIFICATION TIME OF A CASTING POURED FROM A GREY CAST IRON » Abstract. This paper presents the results of a research made by the authors regarding the influence of the pouring temperature over solidification kinetics. It was used a 2D mathematical model for the solidification simulation. It was analysed a cast bar with section 20×150mm poured from an eutectic grey cast iron. The overheat at pouring above liquidus temperature was between 0˚C and 250˚C. We did some observation regarding the overheat influence over the solidification time and temperature field from casting and from the mould. » Keywords: casting, solidification, modelling, simulation Ştefan DIMITRIU
A COMPARATIVE CALCULATION OF STRAIGHT BEAMS UNDER DISTRIBUTED LOADINGS USING BOTH RESISTANCE AND STIFFNESS CONDITIONS » Abstract. The aim of the calculus was to determine the mathematical model for the beam elements design from stiffness conditions. The first use is the design and deformation analysis of beam elements under mobile distributed loadings. The article deal with a mathematical analysis developed to evaluate displacement fields and design from stiffness conditions. » Keywords: strain, stiffness, calculus of mechanical structures Jörg M. ELSENBACH
RFID IN SUPPLY CHAIN EVENT MANAGEMENT: THREE PERSPECTIVES » Abstract. The application of innovative information and communication systems is an indispensable prerequisite for an efficient Supply Chain Management today. The application of the RFID technology, which had its origin outside the logistics area already in the fifties, was implemented from the beginning of the nineties. Independent of the opportunities of this new technology, issues concerning the unit costs of the transponders, the standardization, interoperability and portability with other information and communication systems had to be solved. The Supply Chain Management research is also characterized by missing cost benefit considerations. Meanwhile some of these issues could be reduced or even be removed. Therefore new application fields for the RFID technology came up in Supply Chain Management. In parallel, approaches of an event-based scheduling were summarized to a Supply Chain Event management concept. The status information for the decision making process is provided by Tracking & Tracing systems which are based on barcode technology. The medium-term replacement of the barcode by the RFID technology in some individual application fields leads to a discussion of the integration of the RFID technology in Supply Chain Event Management. The implications of the RFID technology on Supply Chain Event Management are therefore analyzed and evaluated. This article deals with the opportunities and issues based on the current status of the RFID technology. Furthermore, cost benefit considerations are included. Besides the discussion of the impact on the Supply Chain performance, the costs were therefore figured out. Using the example of vehicle outbound logistics, possible application fields of the RFID technology are discussed regarding the functions of Supply Chain Event Management. » Keywords: RFID technology, Supply Chain Event Management, Tracking & Tracing, Information Systems Pavlina KATSAROVA, Stolian NIKOLOV
DESIGN AND MAKING OF UNIVERSAL FORCE MEASURING FORK » Abstract. A universal force measuring fork for the loading force is designed. It differs from those having conventional construction in the removable force-introducing parts which give the possibilities of measuring forces of pressure and tension when the point of application is fixed. The fixation of the parts to the fork body is made by threaded joint. The measurement range is up to 2000 N at elastic deformations up to 2mm. An optimization of the suggested construction is made by using the CAE system COSMOS Works in order to minimize the arising during the work strain. After producing the force-measuring fork it has to be calibrated. » Keywords: elastic element, force measuring fork, calibration Stancho KAVALDJIEV
ANALYSIS OF THE MESHING LOSSES IN SPUR GEARS » Abstract. This work addresses the questions related to the meshing loss evaluation in spur gears. A numerical study of the losses accounting for both double meshing and modification of the gears was carried out. The results for the loss coefficient as a function of the number of teeth of the pinion, speed ratio, contact ratio, and correction coefficients are presented in graphical form. » Keywords: efficiency coefficient, loss coefficient, gear, gear meshing, contact ratio Ivaylo KOVATCHEV, Lubomir DIMITROV
LA MÉTHODE MECANO-FIABILISTE POUR LES CALCULS DE VÉRIFICATION D'UN ENGRENAGE A VIS SANS FIN » Abstract. The goal of the present paper is to evaluate the probability of continuous functioning of a worm-gear set. A specific feature of the particular set is that the transferred torque is very big but the central distance of the box is very small. This peculiarity reflects on the safety factors which are smaller than 1.0. In order to evaluate the functionality of this worm-gear set the authors suggest using of a quality index such as “probability of continuous work”, instead of the commonly used quantity index, such as "safety factor". For the assessment of "probability of continuous work", we can use the theory of probability. In this case the working and allowable stresses are considered to be accidental quantities and they can vary in given limits. We consider that the suggested index “probability of continuous work” represents more precisely the nature of the failure process in worm-gear sets. » Keywords: worm-gear set; safety factor, probability of continuous work Badea LEPĂDĂTESCU, Ion ENESCU
HONING FLEXIBLE EQUIPMENT DESIGNED FOR BATCH WORK PRODUCTION PURPOSES » Abstract. The paper presents honing equipment, single spindle, manual loaded and operated, designed for batch work production purposes especially for blind end brake body cylinders. This equipment is designed to work in a small production requirements in the application where is essential that the blind end cylinder need a surface finish of Ra = 0.4 mm. Although a short recess is provided for stroking purposes. The successful honing of these cylinders is only made possible by using specially designed tools combined with the reliable machine controls to permit a momentary dwell on the stroke reversal at the blind end of the bore. » Keywords: surface finish, close tolerances, batch production Dan LOZNEANU, Gheorghe PANĂ
ANALOGUE SIGNAL TRANSMISSION SYSTEM » Abstract. This article presents the construction and operating principles of a simplex in-current communication system with galvanic isolation. This system can be successfully employed for industrial control operations. The communication system in question works on a frequency range of 10 kHz and on a max. distance of a couple of hundreds of meters, this parameter being changed according to the user's purpose. The system's construction is based on two functional modules provided with operational amplifiers and specialised integrated circuits. » Keywords: communication system, galvanic isolation, U/I converter, I/U converter, DC/DC converter Ionel MARTINESCU
CONSIDERATIONS REGARDING THE IMPORTANCE OF THE PARALLEL STRUCTURE SYSTEMS' ELEMENTS » Abstract. The paper presents a quantitative evaluation of the importance of the parallel structure systems' elements, taking into consideration two cases of specification for the reliability parameters: constants; as a function of time. The exemplification of the elements' importance is made using diagrams and tables, taking into consideration a parallel connection system with three elements. » Keywords: system, reliability, parallel structure George NICOLAE
PROGRAMMABLE SYSTEM FOR CONTROLLING THE TELEVISION PROGRAMS TRANSMISSION » Abstract. This article presents the functioning and construction principle of a programmable system for controlling the TV programs transmission. A continuing scanning process of the TV programs achieves the TV transmission control. The TV transmission scanning is programmed and brought up to date by the operator. The TV scanning transmission has as purpose the functioning state’s establishing of the communication system for television. Thus can be known any moment what TV channels are in normal functioning parameters. In case of apparition of some transmission troubles there are generated warning signals and there are displayed the TV channels, whose functioning parameters do not correspond to the standards and cannot ensure a good reception. The measuring and scanning process takes place on the basis of a scanning process introduced in the system’s memory. The scanning process can be actualized any moment by using a serial program found on the application board. The system can control successively TV channels from all the frequency bands allocated to television or can scan only the TV channels established by the operator. The information concerning the TV signal level, the video and audio signal can be displayed on a LCD screen, or stocked in the system’s memory. The system allows the successively rendering of some TV programs on a TV screen. If the transmission on a TV channel is not in normal parameters, it is generated a shiny and acoustic warning signal. The proposed system is useful in the situations of TV cable programs’ transmission for monitor sing the transmission in a view to intervention. Also, the system can be used in the terrestrial television for establishing the quality of the TV program reception in different points in the covered area. The system is formed with specialized electronic circuits, which make up: the TV channels selector, the TV demodulator, the programmable microcontroller, the LCD indicator, the serial programmer and the keyboard. » Keywords: TV scanner, TV scanner system, TV transmission management, system with microprocessor Victoria TOMA
ASPECTS REGARDING THE MANAGEMENT OF THE INDUSTRIAL MAINTENANCE » Abstract. The economical globalization process emphasize the fact that quality products making, at reasonable prices, respecting delays, suppose the production equipment’s maintenance in a good functioning shape, simultaneously with reducing frequency and the duration of the accidental interruptions (stops). The present study extracts special elements connected to modern instruments of the maintenance optimization, distinguishing new trends in research and the application of new methods and techniques of maintenance. » Keywords: production system, maintenance, RCM, e-maintenance Radu ŢÂRULESCU, Stelian ŢÂRULESCU
THE INTERIOR NOISE ANALYSIS PRODUCED BY THE ROAD VEHICLES » Abstract. Traffic noise is probably the most serious and pervasive type of noise pollution. Studies have shown that on a daily basis almost 40% of population is exposed to undesirable levels of traffic noise and a further 10% is exposed to excessive levels. Traffic noise has become a serious problem now because of inadequate urban planning in the past. Homes, schools, hospitals, churches, libraries and other community buildings were routinely built on main roads without buffer zones or adequate soundproofing. We studied the vehicle noise pollution in urban and rural areas, on various kinds of road vehicles (buses, trolley buses, trams, cars). The annual medium levels of day noise pollution in the residences on the main streets in Brasov frequently pass over the 70 dB limits. The vehicle noise was measured with the noise analyzer Brüel & Kjær 2237 Controller. » Keywords: noise, pollution, vehicle, measurement, sound
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