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The 22nd issue of RECENT journal was edited and multiplied with support of:
CONTENTS
PARALLEL BETWEEN OBTAINING BARIUM TITANATE BY SOLID-STATE REACTION AND BY PRECIPITATION METHODS (2nd Part) » Abstract. This paper presents the experimental results of obtaining insulating barium titanate by two methods: the solid – state reaction method and the precipitation method. There are presented the technological routes corresponding to these two methods by which the material is processed. The material obtained by these two methods is characterized by derivatographic analysis (ATD, TG, DTG, T), microstructural analysis by X-Ray diffractometry (XRD), optics microscopy. The application of this material is very large in electronic industry for obtaining passive electronic components thus: as insulating is used in disks ceramic capacitors and multi-layer capacitors (MLCC), piezoelectric devices manufacture and as semiconductor (controlled doped barium titanate) in PTC thermistors manufacture. » Keywords: barium titanate, solid-state reaction, precipitation
ANALYTICAL APPROXIMATION OF THE ELASTIC STRAINS OF THE LATHE FRAMES » Abstract. This paper proposes a way of analytical deduction of the elastic strains that can occur during the splintering process at normal lathes, mostly for intense processing duties. The knowledge of these strains for various splintering forces is particularly useful mainly in case of the adaptive control setting up and usage. The elastic strain has been highlighted in this paper by using the method of the finite element. The subsequent deduction of an analytical law for this strain, as well, is possible by using the polynomial regression method. The analytical law thus obtained, as function of the length, can be used as reference quantity for the adaptive control. » Keywords: adaptive, frame, finite element, carrying element, rigidity
MULTI-CRITERIA ANALYSIS OF SOME INVESTMENTS IN ROMANIAN TOURISM » Abstract. The paper discusses a development strategy of Romanian tourism in the European context based on the construction of major tourist objectives. A number of seven such objectives are analyzed and the most investment-eligible one is established from the viewpoint of economic performance. The applied method is that of advanced multi-criteria analysis. The criteria underlying the analysis are established and their corresponding weighting coefficients computed. Finally the total value coefficients of performance are computed for all considered objectives, allowing their hierarchy. » Keywords: multi-criteria analysis, investment, tourism
RAPID ELECTRODE MANUFACTURE USING STEREOLITHOGRAPHY MODELS - A STATE OF THE ART » Abstract. Electrical discharge machining (EDM) is a non-conventional process for the manufacture of complex or hard material parts that are difficult to machine by conventional machining processes. During EDM, the electrode shape is mirrored in the workpiece. As a result, problems are transferred on the electrode manufacturing process. In order to reduce the product development time and the cost of tooling, layered manufacturing techniques were developed commonly known as rapid prototyping technology. This technology encompasses a group of manufacturing techniques, in which adding the material layer-by-layer generates the shape of the physical part. Rapid tooling is a progression from rapid prototyping. It is the ability to build prototype tools directly, as opposed to prototype products directly from the CAD model, resulting in compressed time to market solutions. The various methods of manufacturing RT electrodes, using Stereolithography (SL) models, with respect to supplementary processes, are classified in the present work. Recent international research work is reviewed and the results on the performance of RT electrodes are tabulated. » Keywords: EDM, stereolithography, rapid tooling, rapid prototyping
3D MODELING OF THE SHAFTS THROUGH TECHNOLOGICAL-CONSTRUCTIVE ENTITIES » Abstract. The hereby paper issues the constructive planning of the products, using the modern concept of 3D change through technological-constructive entities. The major objective taken into consideration is to insert concept activities with manufacturing. Going in this direction, the hereby paper is a constituent part of a series of papers which issue this subject as being very important. An effective instrument of constructive planning of products is presented herein and this is illustrated in a case study. » Keywords: CAD, CAD/CAM, 3D modeling, CAPP
ECOLOGICAL BRIQUETTE OBTAINED FROM WOODEN BIOMASS » Abstract. This paper has the aim to present the wooden briquette, obtained from biomass, by synthesis of pick-up-data from specialized literature, and find some new directions of researches. It is presented the ecological and energetic advantages for using of this wooden product. Finally, after an incursion in this field, is found that this product can be improved by lignin activation, for increasing of physical, mechanical, ecological and energetic properties. » Keywords: wooden biomass, briquettes, ecological combustion
A NEW FORMULA FOR COMPUTING THE CASTING SOLIDIFICATION CONSTANT » Abstract. It is established a formula for computing the solidification constant using the expansions in power series of the exponential function and error function. » Keywords: casting, solidification, error function
MOLYBDENUM IN STAINLESS STEELS » Abstract. The corrosion resistance of the stainless steels is directly influenced by the chemical composition and metallographic structure obtained by heat treatments and eventually cold–working plastic deformations. The present paper presents the in-house stainless steels alloyed with molybdenum and there are given relations for calculating the influence of the molybdenum over the martensitic transformation temperature Md and corrosion resistance. » Keywords: stainless steels, pit corrosion temperature (TPC), direct contact temperature (TCC), martensitic transformation Md
MEASUREMENT SYSTEMS AND METHODS FOR DETERMINING ELECTROMAGNETIC FIELD ATTENUATION IN NANOMATERIALS » Abstract. This paper presents number of measurement systems and experimental methods for the investigation of nanomaterials behavior inside electromagnetic field (EMF). Measurements were aimed at determining the attenuation of electromagnetic field in nanomaterials. Nanomaterials are new materials obtained by specific industrial processes of mixing and combining different types of materials. Knowing the characteristics and the behavior of nanomaterials inside different media creates wide opportunities for a variety of industrial applications. The measurements systems and methods presented in this paper were developed in order to investigate nanomaterials behavior relative to the influence of electromagnetic fields of different frequencies within a wide spectrum ranging from several tens of MHz up to tens / hundreds of GHz. This paper was written in the framework of the 429/2006 CNCSIS project “Study of the shielding properties of materials obtained by nanotechnologies and nanoprocessing in order to ensure their integration in electrical and elec-tronic systems aimed at improving environment quality”. » Keywords: nanomaterials study, attenuation, microwave systems
COMPARATIVE ANALYSIS OF EXPERIMENTAL AND SIMULATING RESEARCH WITH CAE SYSTEM MSC.VisualNASTRAN 4D OF THE SLIDING BEARINGS » Abstract. In deeper entering of CAD/CAE systems in engineering practice, processes connected with development and researching of different products are carrying in the virtual space. In that reason arise the question how far the results received from the investigation of different 3D models with CAE systems correspond to the real. In the paper is made comparison of the results from the experimental investigations of the journal - bearings with the sliding bearings at the different friction coefficients. The same investigation is done with the CAE system MSC.visualNASTRAN 4D. The received results show that the researches are comparative. » Keywords: journal - bearings, sliding bearings, kinematic analysis, CAD-CAE
THEORY OF CONSTRAINS APPLYING IN OPTIMIZATION OF PRODUCTION MANAGEMENT SYSTEMS AND AUTOMATION OF PRODUCTION SYSTEMS » Abstract. The goal of present research is to determine how and in what way the effectiveness of the production process in theory and practical in the wake of the built organizational structure in a middle large Bulgarian mineral water bottling company with 4% market quota in this industry can influence over the whole organization in production aspect, how far the effective management and material resources contribute to the success of the analyzed company, as well as the opportunities for systematical analysis making in basic production and organizational activities, priorities and trends of development in the concrete company environment. The main aspects in the production activity management are considered on the base of the practical and theoretical formulations as a strategy of management, company policy, motivation and complete process of a definite management philosophy adoption, connected with the specific character of every particular company. On the ground of the considered project is the decision finding for improving of the capacity of the company on the base of high level automated technological equipment adoption. » Keywords: TOC; logical thinking; cause and effect connect
EXPERIMENTAL RESEARCHES REGARDING WOOD COLOUR MEASUREMENT » Abstract. The wood colour is particularly important when it comes to refining the wood of some widespread species having a high rate of growth and a high productivity of wooden mass, such as the poplar wood. The paper presents an original method of measuring the wood colour by virtue of CorelDRAW. The experiments have been made on poplar wood samples, which have been scanned and examined as regards the colour by means of a PC-scanner-screen assembly. One of the advantages of this method is that one can determine the colour for small surfaces (1×1 pixels; 2×2 pixels and 5×5 pixels). This means that the errors resulted after measuring the colour for larger surfaces (when an average of the surface colour is made) are removed. » Keywords: measuring, colour, wood, PC
RESEARCH OF EFFECTIVENESS OF ASSEMBLY DEPENDING ON THE ANGLE OF SCREW GRADIENT IN RELATION TO THE AXIS OF THE HOLE IN THE PROCESS OF AUTOMATIC SCREW DRIVING » Abstract. The process ‘automatic screw driving’ is one of the most difficult and at the same time very spread because of the advantages of the threaded joints. A basic characteristic feature of the precision of the assembly process according to the classical understandings is the error in the relative disposition of the parts at the moment, right before starting the assembly – the displacement of the axes of the screw and the hole, as well as the angle of the screw gradient in relation to the hole. In the present work is described a method about measuring the angle of the screw gradient during gradually changing the displacement of the axes of the assembly parts. The results from the carried out works on a specialized device are given. The got experimental data are analyzed by a statistics program. » Keywords: automation, screw, assembly, an angle of screw gradient
DYNAMICAL MODELING OF MECHANICAL OSCILLATIONS IN MAGNETIC FIELD » Abstract. The paper deals with the problems of magneto-mechanical system consisting of elastic cantilever with ferromagnetic mass at its free end posed in a force potential field of the permanent magnet. The basic relations of the mechanical oscillations are worked out. A quality analysis of the dynamical model is done and the possibilities for influence and control of the magneto-mechanical system are shown. » Keywords: oscillations, natural frequency, permanent magnet, MEMS
AUTOMATED WORKSTATION FOR PRIOR-TO-PAINTING CLEANING OF METALLIC SURFACES » Abstract. The subject of the present report is an automatic shop for cleaning of metal surfaces before painting, which is a key factor for the quality of the varnish coating. A contemporary automatic technology is suggested by processing the metal surfaces with a flow of accelerated spherical shots providing cleaning from corrosion and surface texture improving the adhesion of the coating to the treated surface. » Keywords: automated workstation, metallic surfaces, cleaning, variability, methodology, optimal variant
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