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Search Results: 1 - 10 of 400726 matches for " M. Musztyfaga "
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Advisory system assisting selection of project structures and project team
M. Musztyfaga,B. Sko?ud
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: Purpose: The main aim of the paper is to investigate work effect of the advisory system, which helps theoperator to make a decision concerning an adjustment of structure and structure project team to a certain project,which was selected by operator.Design/methodology/approach: Exsys Professional program of Exsys Inc. was used to create the advisorysystem by rule processor.Findings: System operator can a very quickly adjusted to structures (organizational and project teams) into toa project on the basis of the advisory system only by answering short questions from the system. Moreover, anadvisory system shows graphic presentation of the results.Research limitations/implications: The built advisory system can be a great basis to create a tool, which willassist in making more complicated decisions.Practical implications: A disadvantage of Exsys Professional program are both, laborious and time-consumingdata introduction into an advisory system.Originality/value: The paper helps to understand the need of building advisory systems. It has a potential valuefor future entrepreneur.
Human resources management in a project type tasks
M. Musztyfaga,B. Sko?ud
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: Purpose: The paper describes theoretical issues concerning the scope of human resources management, as well as the pertinent advisory systems. Another main of the paper is to investigate work effect of the advisory system, which helps the operator to make a decision concerning an adjustment of structure and structure project team to a certain project, which was selected by operator.Design/methodology/approach: In this article the advisory system was created in Exsys Professional program. What is more, the system was upgraded with a help tool – a database, because it makes possible to collect and keep data. The database as such was created with the use of Microsoft Access 2000, an integral part of Microsoft Office for Windows.Findings: Based on comprehensive literature, the article reviewed the implementation of the advisory system in some small enterprises, because a system operator can very quickly adjust the structures (organizational and project teams) to a project. On the basis of the system the operator can both ask questions and get answers quickly. Moreover, an advisory system shows graphic presentation of the results.Research limitations/implications: In this paper an advisory system has been used. This exact advisory system could be used in bigger number of enterprises, but on one condition - it must be developed according to their needs.Originality/value: The advisory system was supplemented with a help tool – a database. The database is a source and a concise help tool, perfect completion during the use of advisory system. It allows the user to adjust into more detailed structures to a selected project.
Effect of the front electrode metallisation process on electrical parameters of a silicon solar cell
L.A. Dobrzański,M. Musztyfaga
Journal of Achievements in Materials and Manufacturing Engineering , 2011,
Abstract: Purpose: This paper shows that the laser micro-treatment of the silicon elements of solar cells with the different morphology of monocrystalline silicon, including the selective laser sintering of the front electrode to its surface using the CO2 laser, improves the quality by minimising the resistance of a joint between the electrode and the substrate. The influence of the properties achieved for the front electrode on the electrical properties of solar cells was assessed. A front electrode of photovoltaic cells deposited by the traditional screen printing method and by co-firing in the infrared conveyor furnace was prepared for comparative purposes.Design/methodology/approach: The topography of front contacts subjected to selective laser sintering and co-firing in the infrared conveyor furnace was investigated using the scanning electron microscope with the energy dispersive X-ray (EDS) spectrometer for a microchemical analysis and with the confocal laser scanning microscope. Both, the surface topography and cross section of the front contacts was examined with the SEM microscope. The phase composition analyses of the selected front contacts were carried out using the XRD method. The front contacts were formed on the surface with the different morphologies of solar cells: textured ones with a coated antireflection layer, textured ones without a coated antireflection layer, non-textured ones with a coated antireflection layer and non-textured ones without a coated antireflection layer. An average size of pyramids was measured using the atomic force microscope (AFM). The resistance of the front electrodes was investigated using the Transmission Line Model (TLM).Findings: The following technological recommendations for the laser micro-treatment technology such as optimal paste composition, the power and scanning speed of the laser beam, the morphology of the silicon substrate to produce the front electrode of silicon solar cells, were selected experimentally in order to produce a uniformly melted structure, well adhering to the substrate, with the low resistance of the front electrode-to-substrate joint zone.Research limitations/implications: The contact resistance of front metallisation established depends on the paste composition, morphology of the silicon substrate as well as the co-firing and laser micro-treatment conditions.Originality/value: This paper investigates the front contact production using different silver paste compositions on silicon solar cells in order to decrease contact resistance and increase efficiency in this way.
Influence of cooling rates on properties of pre-alloyed PM materials
L.A. Dobrzański,M. Musztyfaga
Journal of Achievements in Materials and Manufacturing Engineering , 2009,
Abstract: Purpose: The paper focuses on microstructural and mechanical properties of pre-alloyed Astaloy CrL and CrM sintered steels with high addition of carbon.Design/methodology/approach: The main objective of the present work was to establish the effect of cooling rates on the microstructure and properties such as: Charpy impact test, microhardness, wear resistance (disk on disk test) were evaluated depending on chemical composition. Compacts containing low amounts of chromium, molybdenum and high amount of graphite were sintered in a vacuum furnace at 1120oC in vacuum atmosphere and rapidly cooled in nitrogen with two different rates. Then compacts were tempered in vacuum, and cooled in nitrogen. Obtained samples were analysed by light optical microscopy (LOM) for microstructure observation and scanning electron microscopy (SEM) with EDS for chemical composition.Findings: Sinter hardening is a cost-effective process that consists of sintering and heat treatment in one step, so it minimizes the number of processing steps. It is known that the cooling rate following sintering greatly affect material microstructure, which determine the final properties of sinter-hardened materials. The objective was to understand how sintering conditions influence the development of microstructures and thereby control mechanical properties of materials.Practical implications: Changing the amount of graphite element and cooling rates, will affect the amount of ferrite, perlite, martensite and bainite in the microstructure. Further tests should be carried out in order to examine different cooling rates.Originality/value: Sinter-hardening of CrL and CrM pre-alloyed powders with addition of graphite was investigated to study cooling mechanism.
Effect of cooling rates on sinter-hardened steels
L.A. Dobrzański,M. Musztyfaga
Journal of Achievements in Materials and Manufacturing Engineering , 2009,
Abstract: Purpose: Purpose of this paper was to evaluate the differences between rapid, medium and low cooling rates on three systems and also to study cooling mechanism of known materials.Design/methodology/approach: Two different systems have been tested in order to investigate how the cooling rates influence on the microstructure and properties. The powders used in the present invention are pre-alloyed iron-base powders containing low amounts of chromium and molybdenum. The amount of graphite that was admixed to the iron-base powder was 0.6% and lubricant 0.75%. The amount of graphite which is mixed with the iron-base powder is 0.6% and lubricant is 0.75%. Green compact were sintered in a vacuum furnace at 1120oC for 30 minutes in vacuum atmosphere and rapidly cooled in nitrogen with three different rates: rapid cooling (7oC/s) and medium cooling (1.6oC/s), slow cooling (0.3oC/s). Next the samples were tempered in vacuum in the same furnace at 200oC for 60 minutes and then were cooled to room temperature in nitrogen, with the exception of slow cooling cycle.Findings: The effect of cooling and applied sintering were studied in terms of mechanical properties, hardness and wear resistance. The results achieved after the investigation sinter-hardened steels with low carbon content proved that applied process of sintering and different cooling rates brought expected outcome.Practical implications: According to the powders characteristic, the applied rapid and medium cooling rate seems to be a good compromise for mechanical properties and microstructure, nevertheless further tests should be carried out in order to examine different cooling rates.Originality/value: The effect of cooling rates on mechanical properties of pre-alloyed Astaloy CrL and CrM powders was investigated.
Thermovision systems used to improve a technological process for hot-rolled copper and brass strips
Z. Rdzawski,B. Krupińska,M. Musztyfaga
Journal of Achievements in Materials and Manufacturing Engineering , 2009,
Abstract: Purpose: This paper contains description made on thermovision testing with the use of Inframetrics 760B system. Measurements were executed on the surface of a heat furnace and also on the surface of material heated before and hot-rolled. The results of the investigations in a form of thermograpic pictures were taken down in working environment.Design/methodology/approach: The purpose of this research was to evaluate technological process of heating cooper and brass cakes, and hot-rolled strip in special passes assessment of the temperature modification. For basic criterion estimation of these processes, the maintenance at the demanded final rolling temperature in order to keep up adequate structure and narrow range of mechanical properties variation was accepted.Findings: The process of heating charge material is carried through in order to facilitate its machining in a rolling process. When the material does not obtain the adequate temperature or does not become uniformly heated, internal stresses which cause appearance of the rims of fracture and occurrence of other defects in structure appear in cold rolling, as the next. Because of this there is a need of temperature controlling. Research limitations/implications: If a temperature profile on heated to a hot-rolled cakes is not uniform and does not reach a given level, this can mean forming some defects, which can be revealed during a hot-rolled process, relatively during following technological operations leading to a quality decrease and in a consequence to product disqualificationOriginality/value: The use of thermovision system in processes of heating cakes evolution and also hot-rolling. These research enable a condition control of thermal furnace and hot-roll processes.
Selective laser sintering method of manufacturing front electrode of silicon solar cell
L.A. Dobrzański,M. Musztyfaga,A. Dryga?a
Journal of Achievements in Materials and Manufacturing Engineering , 2010,
Abstract: Purpose: The aim of the paper is to demonstrate a laser method of micro-machining front contacts of monocrystalline solar wafers. This means forming front electrodes in order to decrease their resistance. It was demonstrated, that laser processing is a promising technique for selective laser sintering (SLS) solar cell contacts compared conventional forming front grid methods.Design/methodology/approach: The topography of laser micro-machining contact formations and screen-printing were investigated using ZEISS SUPRA 25 scanning electron microscope. The materials used in the present invention are different granulation silver powders. The grain size analysis were used in order to determine their size. The transmission line model (TLM) patterns were fabricated by selective laser sintering. Findings: This work presents an initial analysis of a new selective laser sintering/melting process to contact crystalline silicon solar cells. The seed layer was created using both silver pastes and powders by a selective laser sintering, do not use up to now in Poland. These contact structures were investigated microscopically to gain a better understanding of the method and select laser micro-machining parameters, which will influence on electrical parameters of formed front side grids.Practical implications: SLS can produce parts from a relatively wide range of commercially available powder materials. The physical process can be full melting, partial melting, or liquid-phase sintering and depending on the material. The thickness of silicon solar wafer can cause some difficulties connected with adhesion electrode during contact formation process.Originality/value: In pursuing the purpose of increasing the efficiency η of industrial crystalline solar cells to reduce costs of PV electricity, a measure to improve the front side grid is interesting – decreasing contact resistance and increasing efficiency in this way.
Computer aided determination of porosity in sintered steels
L.A. Dobrzański,M. Musztyfaga,M. Actis Grande,M. Rosso
Archives of Materials Science and Engineering , 2009,
Abstract: Purpose: Purpose of this paper was to apply a computer method of open porosity analysis for determination of porosity in sintered Astaloy CrL and CrM powders.Design/methodology/approach: The powders used in the present papier are pre-alloyed iron-base powders containing low amounts of chromium and molybdenum. The amount of graphite which is mixed with the iron-base powder is 0.6% and lubricant is 0.75%. Green compacts were sintered in a vacuum furnace at 1120oC for 30 minutes in vacuum and rapidly cooled in nitrogen at four different rates: high cooling (7 oC/s and 6.5 oC/s) and medium cooling (1.6oC/s) low cooling (0.3 oC/s). Next the samples were tempered in vacuum in the same furnace at 200oC for 60 minutes and cooled in nitrogen, with the exception of low cooling. Obtained samples were examined by light optical microscopy (LOM) for microstructure observation and scanning electron microscopy (SEM).Findings: The investigations of porosity in the pre-alloyed steels were performed using ”Image-Pro Plus 4.5” computer program. Leica light microscope (MEFA4) was applied to prepare series of micrographs. The microstructures were observed at 100x magnification and recorded as*jpg files. After calibration of the digital images, the perimeter, area, diameter, roundness, Feret max were calculated.Practical implications: The program has some limitations (built in mathematical functions), which made difficult to obtain some results automatically.Originality/value: The obtained results prove that this program is very useful in the statistical analysis of microstructures, because it saves the time during calculations and is well suited for checking sintered materials.
Investigation of various properties of monocrystalline silicon solar cell
L.A. Dobrzański,M. Musztyfaga,M. Giedro?,P. Panek
Journal of Achievements in Materials and Manufacturing Engineering , 2012,
Abstract: Purpose: The aim of the paper was to apply Sherescan instrument, which is a valuable tool used for fault detection, error diagnosis and process optimization by cell manufacturers, paste suppliers, institutes and universities all over the world.Design/methodology/approach: Screen printed front side contacts and next to co-fired them in the infrared conveyor furnace were carried out at 920°C temperature. A commercial silver paste to form front side metallization was apply into investigations. The investigations were carried out on monocrystalline silicon wafers. Front side metallization of solar cell was formed on textured surface with coated antireflection layer. Investigated were both surface topography and cross section of front contacts using the SEM microscope. The size of textured silicon surface was measured using the AFM microscope. The thickness of tested front contacts was measured using SEM and CLSM microscope. The metal resistance of solar cells was investigated using the ‘Sherescan’ instrument. The I-V characteristics of solar cells were also investigated.Findings: The technological recommendations for the co-firing technology in order to produce a uniformly melted structure, well adhering to the substrate, with the low resistance of the front electrode-to-substrate joint zone.Research limitations/implications: The resistance of the metal-semiconductor connection zone depends on conductive paste composition from which the paths were made, as well as manufacturing conditions.Originality/value: The influence of the obtained front side metallization features on electrical properties of solar cell was estimated.
Investigation of the screen printed contacts of silicon solar cells using Transmission Line Model
L.A. Dobrzański,M. Musztyfaga,A. Dryga?a,P. Panek
Journal of Achievements in Materials and Manufacturing Engineering , 2010,
Abstract: Purpose: The aim of the paper is to analyze how to improve the quality of the screen printed contacts of silicon solar cells. This means forming front side grid in order to decrease contact resistance.Design/methodology/approach: The topography of screen printed contacts were investigated using ZEISS SUPRA 25 scanning electron microscope (SEM) with an energy dispersive X-ray (EDS) spectrometer for microchemical analysis. Front collection grid was created using two types of Ag pastes.The Transmission Line Model (TLM) patterns were fabricated by screen printing method on p – type Czochralski silicon Cz-Si wafer with n+ emitter without texture and with a titanium oxide (TiOx) layer as an antireflection coating (ARC). Electrical properties of contacts were investigated using TLM.Findings: This work presents a conventional analysis of a screen printing process for contact formation in the crystalline silicon solar cells. The seed layer was created using silver pasts by the screen printed metallization. These contact structures were investigated using SEM to gain a better understanding of the obtained electrical parameters.Research limitations/implications: The contact resistance of the screen-printed metallization depends not only on the kind of applied paste and firing conditions, but is also strongly influenced by the surface morphology of the silicon substrate.Practical implications: Contact formation is an important production step to be optimized in the development of high efficiency solar cells.Originality/value: The effect of co-firing different pasts (especially a past, which was prepared using silver nano-powder) on electrical properties of silicon wafers.
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