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Recent 36

Vol. 13 (2012), No. 3 (36), November 2012

 

This issue of the RECENT® journal was edited and multiplied with support of:

  • Transilvania University of Brasov, Romania

  • Romanian Association for Nonconventional Technologies


CONTENTS



  • Christian ASTALOSCH, Cătălin George ATANASIU

Compression Grade Analysis of Automotive Door Seals Made From TPV-E

» Abstract

Reducing costs in the automotive industry can be achieved by using new materials able to satisfy technical requirements, but with economic advantage. Such materials are for inner door waist belt the combination TPV-E/PP (vulcanized thermoplastic elastomer / polypropylene). Like any new materials, TPV PP-E and bring along a series of questions on the nature of technology and design, to be resolved. One of these problems is the degree of compression of the material in later phase thermal processing (extrusion). This degree of compression is essential for compliance with length tolerances, typically ± 1 mm, functional requirements imposed by car. Studies conducted show a dependence between the environmental temperature (in the conditioning) and the degree, respectively the time of compression the waist belt. The conclusion of the authors is that tolerance of ± 1 mm length of the finished product can not be achieved without conditioning profiles cut to over dimension. This technological step to be implemented before final stamping. To remove the influence of environmental temperature in the conditioning on the time required to achieve maximum compression, the authors recommend between final extrusion and punching a conditioning window of at least 4 hours.

» Keywords

TPV-E, PP, EPDM, extrusion, cutting, tolerance, shrinkage

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  • Sorin Adrian BARABAŞ

Influence of Deep Carburizing Treatment on Hardness of Workpieces

» Abstract

In carburizing heat treatment was achieved a theoretical and experimental research of influence of carburizing time on hardness and depth. The study of obtained results through performed experiments leads to optimization of carburizing process by application of an annealing treatment of diffusion to obtain a corresponding carbon concentration on great depths. The carburizing atmosphere determines the rate of carbon transfer from the atmosphere to the steel surface, in the carburizing stage. In the annealing stage, the rate of carbon transfer becomes limited by the carbon diffusion in austenite, which is primarily determined by the carburizing temperature and alloy composition of the steel. Is established during the studies presented in this papers, possibility of successfully implementing a deep carburizing process concept with all the advantages derived from this and is presented the advantages of use of diffusion annealing and its influence on hardness of carburized layer.

» Keywords

deep carburizing, diffusion annealing process, carbon potential

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  • Azzedine BOUZAOUIT, Lakhdar KHOCHMANE, Mounir GAHGAH

The Dynamic Evolution Modeling of the Bearings State Change

» Abstract

Predictive maintenance is used to improve the availability of industrial bodies while minimizing maintenance costs. Monitoring the evolution of defects and early detection are based on periodic controls to avoid failures and to plan maintenance operations considered relevant which aims to guarantee normal operation later. So talking about the future is knowing the present. In this context, a stochastic model is discussed based on a type of Markov chain (Xn, n = 1, 2, 3). That is, if Xn = i then the process is said to state i at time n with the existence of a probability Pij that this process will be in State j at time (n + 1). Thus, the conditional distribution of a future state of Xn+1 is independent of the past but only the Xn present state-dependent States. In this study, is presented the methodology to model and simulate the evolution of the degradation occurring in mechanical parts, the cases studied its double row bearings installed on centrifugal fan of average power. Each bearing, we propose to associate a Markov chain describing the transition from one State (i) to another (j) State following the evolution of the overall level of vibration, knowing that according to standards (NF, ISO, VDI, API...) the degradation process of imports it what mechanical body passes by States such as: 'Good', 'Eligible', 'Yet eligible' and 'Ineligible' or 'Disentitled'. The proposed model to calculate the probability of having a bearing faded along life. In addition, it is possible to use the transition matrix associated with Markov chain analysis of operation for the determination of the mechanical system reliability.

» Keywords

conditional maintenance, vibration, modelling Markov chain

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  • Gabriel DIMA, Ion BALCU

Considerations regarding Light Weight Design (LWD) for Aerostructures

» Abstract

This article proposes an integrated view over the lightweight design of aerostructures, a fundamental problem of aircraft industry, this becoming also actual for other domains. Coming out from a direct experience in aerospace engineering and project management, this paper is aiming to identify few historical milestones, basic principles and problems. The end is an analysis of actual method of weight control and reduction for an aircraft.

» Keywords

aerostructures, lightweight design, weight reduction, conceptual design

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  • Konstantin D. DIMITROV

Fault Diagnosis in Industrial Systems via Causality Graphs

» Abstract

Some enhanced methods for definition of the diagnosis problems as well as for the creation of logic-based qualitative description of dynamical industrial processes are developed in the presented paper. Specific techniques for application of causality graphs structures for enhanced Fault Diagnosis (FD) in dynamic industrial systems are also proposed. A specific diagnosis algorithm DIACAUSE as well as a particular causality graph structure were developed and respectively implemented for enhanced FD in a real industrial system for treatment of technologic liquids in a hot dip galvanizing plant.

» Keywords

fault diagnosis, causality graphs, logic-based description, industrial systems

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  • Elena EFTIMIE

Solar Radiation Estimation under Clear Sky Conditions for Brasov Area (Romania) - Models Performance Estimation

» Abstract

The literature in this field offers a high number of models for estimating total solar radiation, because the world's most weather stations measure total solar radiation. However, it must be mention, diffuse radiation estimation models are few and these can be applied only to a specific geographic and climate location of which these have been determined. This paper proposes the determination of solar radiation estimation models (diffuse, direct and total components) for the urban area of Brasov. In this respect, the achieved study proposes a unitary approach of the solar radiation components modelling, in order to obtain models that can be used together. It is taken into account the fact that, in literature, models for estimating solar radiation are studied only for one component of it (often total radiation); thus the combination of direct radiation patterns with those of diffuse radiation, leads to high estimation errors. Models performance is analyzed using the Root Mean Square Error (RMSE), the Mean Bias Error (MBE), the Mean Percentage Error (MPE) and t-statistic.

» Keywords

diffuse radiation, direct radiation, Mean Bias Error MBE, Root Mean Square Error RMSE, t-statistic

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  • Aurel FRATU

Simulation of the Robot Systems for Virtual Prototyping in Assembly Operations

» Abstract

This paper deals with the simulation of a dynamical system in which the motion of each rigid robot is subject to the influence of virtual forces induced by geometric constraints. These constraints may impose joint connectivity and angle limits for articulated robots, spatial relationships between multiple collaborative robots, or have a robot follow an estimated path to perform certain tasks in a cycle. In this paper the author give a brief overview of a general simulation framework, describing the primary tasks which a simulator needs to implement. The robot behavioural simulation in the virtual environment enables us to predict the behaviour of a given real manipulator into real environment.

» Keywords

virtual prototype, virtual assembly, estimated path, multi-body systems

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  • Mariana FRATU, Aurel FRATU

Intelligent Design Solutions for Intelligent Buildings

» Abstract

This paper is focused on the various virtual architectures of the intelligent buildings. One of the actual challenges is to educate owners on the benefits of an intelligent building design. This makes the education of both owners and architects about the benefits of intelligent design solutions as virtual prototyping. In current quest for modernization designers need that the building owner receives the best product possible. Building designers face exciting new challenges in incorporating new and innovative technologies in designing an efficient integrated intelligent building in areas of the building structure and its mechanical and electrical systems. The innovative design technologies would need to ensure that the end users achieve the utilization of its abilities in optimization of the projects.

» Keywords

innovative design process, intelligent building, virtual building

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  • Mariana GORANOVA, Lyudmila STOYANOVA, Alexandra DIMITROVA, Iskren VLAYKOV

Web Services as Help for Test Construction and Variants Generation

» Abstract

The goal of this paper is to present the developed Web service for test variants generation. The method for test construction is based on the Bloom’s taxonomy. Each test includes several sections of the curricula. Each section may contain a number of questions and these questions are ordered. The idea is that each test variant contains only one question for each section. The lecturer has to determine one definite question for each section for the first variant. The next variant is automatically built. The question for every section is determined as the next question in the ordered set of the section. The set of questions for each section must correlate with the appropriate level of the Bloom’s taxonomy. The levels should be used according to the definite goals in education. In one discipline, the different sections of the curriculum could intend different cognitive levels. In the paper the keywords for the different cognitive levels have been cited because of their usage in the questions’ formulation in the experiments. This Web service for test variants generation has been used for printing on paper of generated variants.

» Keywords

education, testing, short answer questions, Bloom's taxonomy, Web services

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  • Daniela GOTSEVA, Loie Naser Mahmud NIMRAWI

Comparison between Object-Relational and Object-Oriented Databases

» Abstract

This paper discusses some concepts related to the object-relational and object-oriented database system such as object identity, row types, user-defined types (UDTs), user-defined routines, polymorphism, subtypes and supertypes, persistent stored modules, and large objects. At the end of the paper exists comparison between ORDBMS and OODBMS.

» Keywords

object-oriented database, object-relational database, database design, object query language

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  • Izabella ICHIM, Catrina CHIVU

Simulation of Pneumatic Directional Valve

» Abstract

There is well known the fact that to design and simulate a system there may be used two methods: mathematical modelling, using dynamics equation of the system, or using oriented software that includes predefined elements associated with different type of systems (electric/hydraulic or pneumatic components, controllers, mechanical components etc.). The present papers present the second method applied to a pneumatic directional valve. Simulation is done using a toolbox of Matlab software, Simscape.

» Keywords

function-generating mechanism, synthesis, pneumatic

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  • Daniela IONESCU, Maria STOICĂNESCU, Ioan CIOBANU, Aurel CRIŞAN

Evolution of the Solid Fraction at the Solidification of a 0.1 %C Steel

» Abstract

To achieve mathematical models and software for solidification simulation casted pieces it is necessary to know the fraction of the solid variation at solidification. In the case of the alloys form solid solution by solidification, this dependence is expressed with a better precision by a quadratic function. The quadratic function is determined on the on the equilibrium diagram. If you pursue to obtain simple mathematical models, the fraction of the solid variation at solidification is approximated by a linear function. In this case, the fraction of the solid variation at solidification is determined according to the liquidus and solidus temperature of the alloy. This paper illustrates how to determine these dependences for the steels with 0.1% C.

» Keywords

solidification simulation, mathematical model, steel

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  • Ionuţ IONESCU, Daniela IONESCU, Ioan CIOBANU, Vasile JIMAN

Computation of the Heat Exchange Coefficient in Cylindrical Coordinates Mathematical Modelling of Castings Solidification

» Abstract

The paper discusses the advantages of utilizing cylindrical coordinates in the mathematical modelling of the solidification of castings with rotational symmetry. In this case the mould - casting assembly is divided into elementary rings. It is shown that for elementary rings undergoing solidification the equivalent thermal conductibility coefficient is influenced by the direction of motion of the solidification front. The paper presents study results concerning this influence. Further study concerned the influence of ring radius and thickness on this coefficient. Eventually a working methodology is established for developing mathematical models considering these aspects.

» Keywords

casting, simulation, solidification, mathematical modelling

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  • Monika MOGA, Gavrilă CALEFARIU

Game Theory as a Method Used in the Study of Research and Development

» Abstract

Research and development are crucial factors in the survival of an enterprise. In an industry that is changing fast, companies must continually revise their projects and range of products. This paper presents some possibilities of using game theory as a method used in the study of research and development. The general context of the application of the method is the rapid change of technology, continuous development, and to compete and respond to changing customer preferences. The method is exemplified by a specific numerical application.

» Keywords

research and development, game theory, sustainable development

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  • Gheorghe MORARIU, Mihai MACHEDON-PISU, Micsandra DUTCĂ

Wireless Monitoring of a Metal Cutting Technological Process in an Industrial Environment, affected by Electromagnetic Noise

» Abstract

In industrial settings, which imply metal cutting with machine tools, these tools can be seen as high-intensity and density electromagnetic noise generators, thus causing errors to wireless transmissions. The authors present an experimental and partially analytic study regarding the extraction, conditioning and transmission of the signal produced by a cutting tool during the processing of different materials, by this, emphasizing the limitations of the radio channel.

» Keywords

wireless transmission, electromagnetic noise, metal cutting

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  • Gabriela NANOVA, Lubomir DIMITROV, Todor NESHKOV, Charis APOSTOLOPOULOS, Panayiotis Th. SAVVOPOULOS

Lean Manufacturing Approach in Aircraft Maintenance Repair and Overhaul

» Abstract

This paper aims to give an overview of the LEAN approach and more specifically its application in an Aircraft Maintenance, Repair and Overhaul business. There are some examples provided to make the picture more understandable in the field of the diagnosis of an enterprise which is going to be a subject to LEAN initiatives. The purpose is not to give a full list of the LEAN tools and practices that may be used in a production environment but more to give an overview and to provide examples for the necessity of adjustments to the standard practices. This is valid not only for a MRO (Maintenance Repair and Overhaul) but for each and every area in which LEAN is used. The main specifics of the Maintenance, Repair and Overhaul that concerns LEAN implementation are that it is project based and is dependent on the defects of the aircraft which is maintained. These are the greatest challenges when deciding to apply LEAN principles on such an environment but also may be considered as advantages. These specifics provide the LEAN practitioner with a lot of flexibility and the approach may be completely customized in order to serve the needs of the specific situation.

» Keywords

LEAN, diagnosis, adjustments, MRO maintenance, repair, overhaul

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  • Nikolay NIKOLOV

General Mathematical Model for Type-Dimensional Synthesis of Function-Generating Mechanisms with Four-Bar Topological Structure

» Abstract

The present work is devoted to the developing of a general mathematical model for type-dimensional synthesis of function-generating mechanisms with four-bar topological structure and rotation of the input and the output. The known cases of particular belt mechanisms and cam mechanisms can be obtained in corollary from the mathematical model.

» Keywords

function-generating mechanism, synthesis, model

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  • Florin-Cătălin OLTEANU, Gavrilă CALEFARIU, Flavius Aurelian SÂRBU

Aspects Regarding the Decision on Insuring Auto Fleets Belonging to Commercial Companies

» Abstract

The decisions that an insurance company has to make regarding the insurance of auto fleets belonging to various companies are decisions taken in conditions of uncertainty and risk. This paper presents the use of Bayes decision procedures in the case of such choices. These procedures include the Bayes decision procedure with no experimentation and initial probabilities as well as the Bayes decision procedures with experimentation and conditioned and post probabilities. The paper also presents a numerical application in which it is shown how an insurance company can evaluate, using these procedures, an insurance request against theft and damage for an auto fleet of an industrial production company.

» Keywords

theft and damage insurance, decision, uncertainty, risk, Bayes procedure, initial probabilities, conditioned probabilities, post probabilities

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  • Iulian Alexandru ORZAN, Constantin BUZATU

Multicriterial Optimization Applied for Choosing the Measuring Instrument

» Abstract

According to David C. Crosby, "If you don’t know the capability of your measurement system, you don’t know if your measurements, or your products, are good or bad". Starting from this basic it had been made an comparative analyze from the point of view of the capability of measuring of an interior diameter micrometer, indicating micrometer (caliper) and a 3D measuring machine in order to identify the optimal management measure for serial machining pieces to measure interior diameters. The test was made in a controlled environment, with different operators in order to see how each measuring system is affected by the variables: method of work and operator. The performance characteristics used to determine which measurement device is the best choice to be used in serial production were: cost of the system, quality, measurement system analyze or repeatability and reproducibility (R&R), efficiency and method of measurement for each device. From the case study made, the result was that the best cost effective, with the best efficiency, in quality and with the best MSA (Measurement system analysis) value is the caliper.

» Keywords

MSA, repeatability and reproducibility (R&R), measurement system, micrometer, calliper, 3D measuring machine

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  • Cosmina PÖLLNER, Cătălin CHIVU, Romeo CIOARĂ

Command and Control of an Experimental Model of a Mechanical Vulcanizing Press

» Abstract

Research conducted at Transilvania University of Brasov, Romania, was orientated to exploring the possibilities of designing mechanical vulcanizing press with same or higher performances of hydraulic vulcanizing presses currently used. It aims to preserve the advantages identified at these including the removal of some of the disadvantages. To validate practically the original concept of mechanical vulcanizing press with a single screw, including the drive and control system, as well as how to control the proper functioning of force as a response in real time at pressure variations determined in mold by vulcanization process was achieved an experimental model. The experimental model is equipped with a modern electronic controls based on finite state machine. The experimental model has a large enough gauge that pressing force capable to be support becomes of the same order of magnitude as that of some real vulcanizing presses.

» Keywords

experimental model, mechanical vulcanizing press, electronic system of command and control

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  • Sorina Dana VEISS

Efficiency and Effectiveness in the Public Sector

» Abstract

In the public sector, efficiency is measured by the degree of serving the citizen, which becomes "the clients" of the institution. An organization is efficient if the employees are efficient. Efficiency means discipline and competence, reliability and promptitude, organization and accountability of the public institutions in solving the problems and needs of the citizens. Effectiveness and efficiency are essential features required for the civil servants. With the growth and diversification of the citizen’s requirements, it is necessary to increase efficiency and effectiveness in the public sector.

» Keywords

public sector, efficiency, effectiveness, civil servant

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