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Recent 28

Vol. 11 (2010), No. 1 (28), March 2010

The 28th issue of RECENT journal was edited and multiplied with support of:

  • Transilvania University of Brasov, Romania

  • Romanian Association for Nonconventional Technologies

  • Brasov County Council (by Scientific Activities, Education, Culture, Cults Committee), Romania


CONTENTS


  • Rachid CHAÏB, Ahmed BELLAOUAR, Mohamed BÉNIDIR, Ion VERZEA

FOR A BETTER CONTROL OF THE AVAILABILITY OF THE INDUSTRIAL EQUIPMENTS

» Abstract. Each one can intuitively understand that maintenance is significant because if equipment breaks down, the production can be stopped. In a system with tended flows or there are few intermediate stocks, such a stop can put in layoff part of the workers and thus to have very expensive consequences. thus, the stoppage or the abnormal operation of the production equipment, and the non-observance of the deadlines which is followed from there, indeed generate costs which the companies are not any more in a position to support: wastes of time, losses of production, thus affect the costs, then losses of credibility near the customers, therefore affect competition and the confidence and finally losses of profitability and competitiveness, even losses of perenniality. This is why; the companies cannot wait any more until the breakdown occurs to cure it but must from now on be organized to proceed to the various operations, which make it possible to avoid it. Thus in the company, the function "maintenance" less and less often consists in giving in state the working tool but to more and more frequently anticipate its dysfunctions. Therefore, it is not advisable to develop immediately all good practices. Some can be more urgent than others, according to priorities' of the company. Indeed, if the maintenance activities are correctly planned, one can better prepare the tools and the necessary parts as well as the team concerned to the various interventions, even a better coordination between maintenance and production. This is why the objective of this work is the early detection of the dysfunctions of the critical machines, even the intervention advisedly, while following the evolution in the time of the symptoms of state drift of the equipment. Thus, one is able to rationally use the mechanical components until complete wear without any risk of sudden breakage and to practice selective maintenance.

» Keywords: early detection, vibratory analyzes, rotating machines, maintenance, availability, failure

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  • Romeo CIOARĂ, Ovidiu SÎRBU

A MOVEMENT AND STRAIN MODEL OF THE BICYCLE

» Abstract. The bicycle is an extremely popular, non-polluting means of transportation and leisure, of ancient tradition and high perspectives. Therefore, the interest in manufacturing perfected bicycles with improved characteristics is justified. Designing gearings that should allow the bicyclist to move along at the desired speed under various conditions of road and resistance to advancement is of high interest. The paper herein submits a brief history and a simple movement and strain model of the bicycle, as necessary initial stage to the purpose of a critical analysis upon the gearings currently used in bicycles. Based on the elaborated model, an analysis of the variation in the movement and strain parameters of the bicycle are performed, different correlations of their variations being enhanced.

» Keywords: bicycle, brief history, movement and strain model

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  • Konstantin DIMITROV, Dimitar NURKOV

EXPERIMENTAL PLATFORM FOR SIMULATION AND ANALYSIS OF SYSTEMS STATES AND FAULT DIAGNOSIS

» Abstract. The present paper describes the development of an advanced experimental platform, designated for process modeling, simulation and analysis of technical conditions and fault diagnosis in a real and/or simulated industrial processes and systems states. The developed experimental platform was applied in the research and development studies as well as in the teaching programs of research students and professors in Technical University - Sofia, Bulgaria.

» Keywords: experimental platform, simulation and analysis of systems states, fault diagnosis, reliability enhancement

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  • Aurel FRATU, Jean-François BRETHÉ, Mariana FRATU

REDUNDANT INVERSE KINEMATICS SYSTEM FOR OBSTACLES AVOIDANCE

» Abstract. In this paper, the authors relate to the robotic systems to avoid the obstacles while positioning end-effectors. A new strategy to on-line collision-avoidance of the redundant robots with obstacles is presented. The strategy allows the use of redundant degrees of freedom such that a manipulator can avoid obstacles while tracking the desired end-effectors trajectory. The strategy is based on the redundant inverse kinematics and leads to the favourable use of the abilities of redundant robots to avoid the collisions with obstacles. The effectiveness of the proposed method is discussed by theoretical considerations and illustrated by simulation of the motion of the four-joint planar manipulators between symmetric obstacles.

» Keywords: redundant inverse kinematics, avoid collision, motion simulation

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  • Aurel LUNGULEASA, Gavril BUDĂU

TWO FEATURES OF THE ECOLOGICAL WOODEN BRIQUETTES

» Abstract. This paper presents some features of the ecological and experimental briquettes realized from wooden biomass. There are presented some advantages of the wooden biomass use such as combustible material, raw material and the used machine. Inside of analysed feature, it distinguishes the density as physical characteristics and the compression as mechanical one. The knowing of these features is important because it offers some data about the compaction and consistence degree of briquettes, respectively about the quality of them, but also about the calorific power of them.

» Keywords: briquettes, wooden biomass, density, compressive strength

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  • Feiza MEMET, Osman Kamil SAG

DIMINISHING PORT EMISSIONS FROM FISHING VESSELS

» Abstract. Marine engine emission has a global, regional and local impact. On board the ships exist two types of engines: main engines and auxiliary engines. In ports, ships use their auxiliary engines to produce electricity for cruising, manoeuvring and hotteling. Port emissions are fled by the port surrounding community in a very negative way, especially if ports located inside the cities, as it happens in Turkey. The Turkish fleet has a number of 176 fishing vessels. Having in view the long Turkey’s coastline, fishing has the potential to become an important contributor to the economy. This paper assesses port emissions from fishing vessels. In order to reduce the environmental problems, consequent to the port activities, in this work is proposed an energy supply for the fishing vessels utilities from the national grid. Such a scenario allows a NOx diminishing at berth of about 97%.

» Keywords: engine, port, emissions, electricity

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  • Plamen PETROV, Lubomir DIMITROV

NONLINEAR PATH CONTROL FOR A DIFFERENTIAL DRIVE MOBILE ROBOT

» Abstract. A nonlinear feedback path controller for a differential drive mobile robot is presented in this paper. First, a kinematic model in error coordinates expressed in a moving reference frame partially linked to the robot is developed. The control law is designed using backstepping method yielding exponential stability of the closed-loop system. Stability analysis is performed via Lyapunov stability theory. Simulation results are presented to illustrate the effectiveness of the proposed controller.

» Keywords: differential drive mobile robot, path following, nonlinear control, integrator backstepping

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  • Kalin RADLOV, Nikolay KOTZEV

SYSTEM "GIRDER CRANE-BUILDING" DYNAMIC ANALYSIS IN CASE OF EARTHQUAKE

» Abstract. There is a methodology suggested for system "girder crane-building" dynamic analysis in case of earthquake, which is based on lumped masses dynamic model. There is created a lumped masses dynamic model, which is appropriate for system "girder crane-building" dynamic researches in case of earthquake, by using the analytic dynamic common methodology. The created model includes the mechanical properties of the girder crane and the building and is appropriate for the seismic loads as a function of time representation.

» Keywords: girder crane, dynamic model, seismic load

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  • Veselin TSONEV, Nikolay NIKOLOV

DEFINING THE LARSON-MILER PARAMETER FOR A NEW ALLOY STEEL

» Abstract. This article shows how the Larson-Miler parameter could be defined through tests and then used to prognosticate the time to rupture for materials, working for a long time at a constant load and elevated temperatures. The necessary theoretical information, the methodology for carrying out the experiment and the approach to the experimental results processing are provided. The methodology exposed has been demonstrated with a practical study of a new alloy steel. Being relatively simple, the proposed approach can be always used when such a prognosis is needed, provided that the Larson-Miler criterion is suitable for the studied material.

» Keywords: creep, rupture, strength, steel, Larson-Miler parameter

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