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  • Artikel  (1.322)
  • Emerald  (1.322)
  • American Association for the Advancement of Science (AAAS)
  • American Association of Petroleum Geologists (AAPG)
  • 1995-1999  (1.322)
  • Maschinenbau  (1.322)
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  • Artikel  (1.322)
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  • 1
    Digitale Medien
    Digitale Medien
    Corrosion effects on the electrical performance of silver metal contacts (1999)
    Bradford : Emerald
    Anti-corrosion 46 (1999), S. 85-94 
    Details
    ISSN: 0003-5599
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: In this work, commercial silver metal contacts welded on top of silver plated brass or brass substrates have been exposed to air rich in NaCl. Scanning electron microscopy and energy dispersive analysis of the exposed contact surfaces were performed to identify the corrosion by-products on top of the silver contacts, suspending wafers, and welding materials. Surface corrosion products were mainly found to consist of small spherules of Cu-Zn or Ag-Cu compounds which cover the surface of the contact proper with low adhesion properties. They mainly originate from the underplating wafer or welding materials. Electrical characterization of the contacting materials was based on dc temperature overheat tests, current switching cycle tests, and energy storage during ac current excitation. The experimental results display that the operating environment is indeed a very significant parameter determining the overall performance of the electrical contacts. New design rules as well as material selection properties may have to be systematically considered to allow for electrochemical induced degradation in saline operating environments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00035599910263152
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  • 2
    Digitale Medien
    Digitale Medien
    Experimental grease investigations from an energy point of view (1999)
    Bradford : Emerald
    Industrial lubrication & tribology 51 (1999), S. 246-251 
    Details
    ISSN: 0036-8792
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: This paper is concerned with the study of grease reaction by tribological stress. To observe the change of the viscoelastic properties by shearing the grease, rheometer tests were done. In addition to the flow behaviour, we investigated the friction process by using some tribometer. The tribological characteristics of the lubricant are determined with the help of energetic parameters. The interpretation of the results shows a correlation between viscoelastic properties and friction behaviour and an interesting dependence of storage modulus and shear stress. The results are considered to be useful information on the tribology of greases.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00368799910290935
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  • 3
    Digitale Medien
    Digitale Medien
    Black or white blues? (1999)
    Bradford : Emerald
    Industrial lubrication & tribology 51 (1999), S. 269-273 
    Details
    ISSN: 0036-8792
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: This paper discusses the lubrication of heavy load application and reports on a joint development project between the Technical University of Lulea in Sweden and Axel Christiernsson.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00368799910294760
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  • 4
    Digitale Medien
    Digitale Medien
    The influence of MoS on the mechanism of piston-ring wear during the running-in process (1999)
    Bradford : Emerald
    Industrial lubrication & tribology 51 (1999), S. 274-286 
    Details
    ISSN: 0036-8792
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: This report presents the results of a comparative test in which two similar new engines were run-in under identical conditions except that in one case a molybdenum disulphide suspension in oil was used as a crank case lubricant. The special testing rig is described and the results are presented in terms of comparative wear rates, determination of final ring profiles and SEM analyses of final ring surfaces. From this investigation it is concluded that the molybdenum disulphide additive is effective in modifying the mechanism of wear during running-in so that metal-to-metal contact is reduced and the change in surface topography is achieved mainly by plastic deformation rather than by an adhesive or abrasive wear process which mainly occurs when using conventional break-in oils.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00368799910294779
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  • 5
    Digitale Medien
    Digitale Medien
    Studies on tribological characteristics of alkylalkoxysilanes (1999)
    Bradford : Emerald
    Industrial lubrication & tribology 51 (1999), S. 294-300 
    Details
    ISSN: 0036-8792
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Different percentages of calcium and lithium stearate greases were prepared using dimethyldi-2-ethyl-1-hexoxysilane and dimethyldi-1-dodecoxysilane as base oils by open kettle process and then were characterised. The performance of different greases has been studied by determining their apparent viscosity, consistency, dropping point, oxidation stability, anti-wear characteristics and moisture resistance. These properties are compared with those of tetra-2-ethyl-1-hexoxysilane and polydimethylsiloxane greases. Lithium stearate thickened greases exhibit better lubrication and heat resistance properties than those of calcium stearate and can be used for extreme temperature conditions in the range between –70°C and +220°C for automotive ball joints, aircrafts, antifriction, ball bearings etc.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00368799910294797
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  • 6
    Digitale Medien
    Digitale Medien
    Use of Group II, Group III base stocks in hydraulic and industrial applications (1999)
    Bradford : Emerald
    Industrial lubrication & tribology 51 (1999), S. 287-293 
    Details
    ISSN: 0036-8792
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Use of hydrotreated, hydrocracked and catalytically dewaxed base oils in hydraulic and industrial applications is increasing on a global scale. The hydrogenation and dewaxing processes involved in the manufacture of these products can result in base oils of exceptionally low aromatic content and sulphur level and raised viscosity index (VI). The aromatic content, sulphur level and VI are parameters used by the American Petroleum Institute (API) to categorize the base oils as Group II or Group III. The performance of additives in these Groups II and III base stocks differs from that in Group I base stocks. In addition, different processes used by different manufacturers will not only create different base stock oxidative stability and solvency from that of Group I base stocks, it will also create differences between Group II base stocks and between Groups II and III base stocks. Several different base stocks have been examined using methods including mass spectrometry and aniline point. Variations in properties, such as aromatic content, cycloparaffinic content and aniline point, appear to relate to differences in oxidation stability and solvency. With the improved response of Groups II/III base stocks to antioxidants, a performance level of 10,000 hours or greater in the ASTM D 943 is common. This necessitates addition of specific antioxidants which result in extended oxidation performance but lead in some cases to the formation of insoluble degradation products in Group II/III base stocks, and more so in Group I base stocks. Phenolic- containing and phenolic-free antioxidant systems have been identified that allow for extended oxidation stability in a wide range of Group II base stocks without sludge formation in either Group I, II or III base stocks.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00368799910294788
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  • 7
    Digitale Medien
    Digitale Medien
    Study of the pigment type effect on the corrosion behaviour of epoxy painted steel/sea water systems (1999)
    Bradford : Emerald
    Anti-corrosion 46 (1999), S. 426-434 
    Details
    ISSN: 0003-5599
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The effect of different kind of pigments on the corrosion resistance properties of an epoxy paint has been investigated using electrochemical impedance spectroscopy and open circuit potential measurements. Painted naval steel samples were studied during the exposure to artificial sea water. The epoxy paint coatings were prepared employing red lead, zinc, red iron oxide or titanium dioxide as pigment with 0.8 of PVC/CPVC ratio. From the EIS and corrosion potential data analyis was found that the anticorrosive protection given by an anticorrosive (pigmented with red lead) and a top coat (pigmented with red iron oxide) epoxy painting scheme was both more lasting and more effective. This was attributed to the fact that both the effective adhesion provided by the chemical bonding between the steel surface and the epoxy paint groups and the constant high barrier effect afforded by this type of top coat were a perfect complement for the high corrosion inhibitive capacity of the red lead pigment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00035599910299388
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  • 8
    Digitale Medien
    Digitale Medien
    White oils and the food industry (1999)
    Bradford : Emerald
    Industrial lubrication & tribology 51 (1999), S. 6-12 
    Details
    ISSN: 0036-8792
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Manufacturing methods of white mineral oils are described, together with a summary of their major use areas. Recent toxicological studies using white mineral oils of various categories are covered. A summary of the current acceptable daily intake levels for such substances is included.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00368799910251686
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  • 9
    Digitale Medien
    Digitale Medien
    Extended drain intervals for crankcase lubricants (1999)
    Bradford : Emerald
    Industrial lubrication & tribology 51 (1999), S. 69-76 
    Details
    ISSN: 0036-8792
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The various approaches to achieving extended drain intervals in vehicle crankcase lubricants are described, with particular emphasis on commercial diesel engines. The various lubricant contaminants include soot, water, acids and particulate metals. Lubricant life may be prolonged by suitable design of the lubricant and of the engine, but more particularly by reducing the levels of contaminant in the lubricant such that the performance of the lubricant may be maintained. At the same time, wear rates within the engine must be within acceptable levels. The various options for reducing the levels of contaminant include lubricant by-pass filtration systems, including barrier filters, refiners and centrifugal filters.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00368799910261478
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  • 10
    Digitale Medien
    Digitale Medien
    Lubricating automotive engines (1999)
    Bradford : Emerald
    Industrial lubrication & tribology 51 (1999), S. 62-68 
    Details
    ISSN: 0036-8792
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Traditionally the development process has been used to optimise engine lubrication systems with a lot of hardware testing. This can lead to an expensive and time consuming process which can have major influences on the engine design. To complement engine development, design and analysis principles have been developed for further optimisation and understanding of the lubrication system. To demonstrate this a case study is used illustrating good use of analysis tools, offering clear ways towards system optimisation. In addition, while engine designers have been improving their techniques, new components and oil formulations have helped push the boundaries of the lubrication system, giving better wear and friction characteristics and also increasing oil life.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00368799910261469
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  • 11
    Digitale Medien
    Digitale Medien
    Oil analysis cost-effective machine condition monitoring technique (1999)
    Bradford : Emerald
    Industrial lubrication & tribology 51 (1999), S. 119-124 
    Details
    ISSN: 0036-8792
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: This paper describes the development of the use of lubricant analytical programmes and trend analysis to optimise oil change intervals and to predict equipment failure. The various analytical methods are covered, as are the most frequently occurring lubricant applications where such condition monitoring programmes are most appropriate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00368799910268066
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  • 12
    Digitale Medien
    Digitale Medien
    Fretting wear performance of diesel fuel lubricity additives (1999)
    Bradford : Emerald
    Industrial lubrication & tribology 51 (1999), S. 125-127 
    Details
    ISSN: 0036-8792
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The paper describes the evaluation of the fretting wear performance of diesel fuel additives as opposed to the sliding wear performance which is normally evaluated, and in fact forms part of the diesel fuel specification. Variations in load, frequency and running time were employed to ensure that all conditions which were like ly to be encountered were properly evaluated. Clear differences were observed between fretting wear performance and sliding wear performance, which is significant in view of the fact that fretting wear is often a factor for certain components of the fuel injection equipment. Further work on establishing the repeatability, reproducibility and participating in a "round robin" series of trials is indicated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00368799910268075
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  • 13
    Digitale Medien
    Digitale Medien
    The lead ban, lead replacement petrol, and the potential for engine damage (1999)
    Bradford : Emerald
    Industrial lubrication & tribology 51 (1999), S. 128-138 
    Details
    ISSN: 0036-8792
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The function of lead additives in petrol is described, together with the effects on various engine components of their removal. The corrosive wear mechanisms are described in detail, and the effect of alternative additives in reducing corrosion and wear are covered. A number of field case histories are described, including experiences in Sweden, where lead replacement petrol was introduced in 1992. The article concludes with a series of recommendations designed to minimise possible damage to engines caused by substitution of leaded petrol by LRP.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00368799910268093
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  • 14
    Digitale Medien
    Digitale Medien
    The influence of tribological properties of lubricating oils on the reliability of gears (1999)
    Bradford : Emerald
    Industrial lubrication & tribology 51 (1999), S. 170-179 
    Details
    ISSN: 0036-8792
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The main role of the gears is to ensure smoothness and noiseless service, required power transmission, precision of processing, necessary degree of efficiency and so on. Lubrication is of significant importance to the protection of gears from tribological processes which cause failure of gears. The aim of this study is to investigate the influence of lubricating oils on the reliability of gears. The experimental investigation of the influence of some industrial oils on the tribological behaviour of gears of machine tools has been carried out at a metalworking factory. The paper presents the following: the classification of industrial oils for gears; the flow-chart of the choice of the industrial oil for gears; the analysis of the symptoms and the causes of failure to gears; the reliability curves of gears in the function of tribological properties of lubricating oils under the operating conditions of investigation here presented. The reliability of gears was found to be affected by both the type of lubricating oil and the viscosity grade.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/00368799910276616
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  • 15
    Digitale Medien
    Digitale Medien
    Evaluation of pre-deposited (no-flow) underfill for flip chip and CSP assembly (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 8-12 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The benefits of a "no flow" process have been well documented in the recent past. The limitations of the previously reported materials in current use have been overcome via a unique chemistry which can be tailored to the application. Room temperature storage, effective fluxing, coupled with minimal outgassing, and a choice of reworkability after reflow or, if rework is not required, a full cure, can now be achieved within a single materials technology. This paper describes the properties of the new family of materials compared to conventional post-deposited underfills. The development sequence and the procedure for characterisation of material properties, including the evaluation of the effectiveness of the fluxing action on a range of solder alloys, is documented. A typical application is described, outlining how a minimum of two process steps can be eliminated and how improvements in materials handling, process robustness, and ultimate yield, have been realised. A simple rework regime is also proposed, and the almost "drop in replacement" aspect of the new material is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910254633
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  • 16
    Digitale Medien
    Digitale Medien
    An evaluation of the effect of ageing on the cleanability of solder flux residues (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 27-35 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The efficiency of cleaning of flux residues after various periods of ageing was assessed by measuring the ionic contamination removed in an Ionograph 500 SMD. The flux residues were removed from bare boards, and boards with through hole and surface mount components. The effect of different ageing temperature was also investigated. The work has shown that there is a maximum time interval following assembly during which cleaning should be carried out. The ionic contamination of aged assemblies with through hole and surface mount components were cleaned with varying efficiencies. The surface mount components were more difficult to clean. The use of brushing and scrubbing proved particularly beneficial for the through hole components. A proprietary cleaner proved more effective than the generic alternatives considered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910254912
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  • 17
    Digitale Medien
    Digitale Medien
    Towards the objective evaluation of garment appearance (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 151-160 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: As a first step towards objective evaluation of garment appearance, the present work considered seams on three-dimensional surfaces which simulate actual garment surfaces. The geometric profiles of the 3-D seams were scanned using a laser scanner. 1-D and 2-D digital filters were applied to obtain pucker signals from the geometric profiles by removing "high frequency" components due to fabric surface texture and "low frequency" components due to garment silhouette and drape. The advantages and disadvantages of the 1-D and 2-D digital filters are compared. Four physical parameters are examined to see their relevance to the subjective pucker grade. It was found that log(s2), i.e. the logarithm of the variance of the heights of pucker signals, is the best set of physical parameters for the objective evaluation of seam pucker. In addition, latest attempts at capturing and analyzing 3D garment image using a Cyberware laser scanner and Surfacer software are reported.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910282370
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  • 18
    Digitale Medien
    Digitale Medien
    Thermophysiological comfort of silicone softeners-treated woven textile materials (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 189-197 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: In this study the effect of the aminofunctional silicone softeners on fabrics' heat and moisture transport properties has been investigated by means of Alambeta and Permetest instruments. The silicone treated PES blended fabrics are warmer to the touch, but less comfortable as regards their reduced water-vapour permeability. The finishing stage of the fabrics has considerable influence on their thermal touch sensation and water-vapour permeability.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910281911
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  • 19
    Digitale Medien
    Digitale Medien
    A study of the effect of time variations for assembly line balancing in the clothing industry (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 181-188 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The problem of assembly line balancing is to assign different tasks to individual workstations for ensuring the sum of task times at any station not exceeding the station time. Standard minute time is generally used in the clothing industry as a predictor of sewing speed and production efficiency. In the clothing industry, the standard minute time derived from the work study methods is generally assumed as a constant for line balancing. However, a lot of factors cause variations on operational time of the same task such as the fabrics and sub-materials, performance of the machinery, working environment and quality level of the product. With the aid of an illustrating example selected from a men's shirt manufacturing factory, the effect of time variations for assembly line balancing has been studied in this paper.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910281894
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  • 20
    Digitale Medien
    Digitale Medien
    Solidification of a superheated fluid in a porous medium: effects of convection (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 72-91 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The solidification of a superheated fluid-porous medium contained in a rectangular cavity is studied numerically. The bottom and side walls of the cavity are insulated while the top wall is maintained at a constant temperature below the freezing point of the saturating fluid. The study is focused on the effects of superheat on the development of natural convection and heat transfer during the solidification process. For a fluid initially at a temperature above the freezing point, the results obtained by neglecting convection overpredicts the solidification time by about 12 percent for a Rayleigh number of 800. When convection is taken into account, it is found that the solidification process consists of three distinct regimes: the conduction regime, convection regime and the solidification of the remaining fluid that can be described by the Neumann solution for the solidification of a fluid at its freezing point. The numerical simulations are based on the Darcy-Boussinesq equations, using the front tracking method in a transformed coordinate system. The entire solidification process is described in terms of the evolutions of the streamlines and isotherm patterns, the maximum and average temperatures of the fluid, the interface position, and the heat transfer rate. The parametric domain covered by these simulations is 0 = Ra = 800, 0 = Stl = 0.67, Sts = 0.3 and XL = 1 where Ra is the Rayleigh number, Stl the liquid Stefan number, Sts the solid Stefan number, and XL the aspect ratio of the cavity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910251112
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  • 21
    Digitale Medien
    Digitale Medien
    Bifurcation to oscillatory flow of the natural convection around a vertical channel in rectangular enclosure (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 170-185 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Numerical computations were performed for the heat transfer and fluid flow characteristics of natural convection with an internal vertical channel composed by a pair of parallel plates in a rectangular enclosure. The inner plates and the bounding wall of the enclosure were maintained at uniform but different temperatures. The plates were symmetrically arranged. Unsteady computation was performed to simulate the evolution process of the natural convection developing from the zero initial field. The cases of Ra = 2 × 104, 2 × 105 and 106 were studied. A symmetrical steady solution was achieved for the case of Ra = 2 × 104. For Ra = 2 × 105 and 106, time dependent asymmetrical processes were observed. The flow oscillating process seemed to be more complex at Ra = 2 × 105 than that at Ra = 106, which is quasi-periodic with two frequencies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910256027
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  • 22
    Digitale Medien
    Digitale Medien
    Finite element modelling of radiation in a nonparticipating medium coupled with conduction and convection heat transfer with moving boundaries (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 257-270 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The radiation conduction coupling leads to particular problems due to computation time and high heat fluxes. Because of the hemispheric nature of the radiation, it is difficult to take into account symmetric or periodic conditions for the reduction of the modelled domain. We developed a finite element model of radiative heat transfers between grey diffuse surfaces with a nonparticipating medium with periodic or symmetric boundary conditions. The approaches used to decrease the computation time allowed the modelling of moving radiative surfaces. We introduced this model into a finite element convection diffusion code in order to simulate heat transfers in an electrical rotating engine. The main originality of this study lies in the use of periodic radiative conditions with moving surfaces and in the use of a method which is not based on the isothermal approximation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910260121
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  • 23
    Digitale Medien
    Digitale Medien
    Unsteady free convective flow in an enclosure with a stepwise periodically varying side-wall heat flux (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 214-225 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Free convective flow in a square enclosure with one of the vertical walls heated and with the opposite vertical wall cooled to a uniform temperature, the remaining walls being adiabatic, has been numerically studied. The heat flux at the heated wall is spatially uniform but is, in general, varying in a stepwise manner with time. The flow has been assumed to be laminar and two-dimensional. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces. The governing equations, expressed in terms of stream function and vorticity, have been written in dimensionless form. The resultant equations have been solved using the finite-element method. Because of the possible applications that motivated the study, results have only been obtained for a Prandtl number of 0.7. Results have then been obtained for modified Rayleigh numbers between 1,000 and 1,000,000 for a wide range of dimensionless amplitudes and periods of the heat flux variation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910260095
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  • 24
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    Digitale Medien
    Why you should consider object-oriented programming techniques for finite element methods (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 333-347 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Object-oriented programming, as an alternative to traditional, procedural programming methods for finite element analysis, is growing rapidly in importance as algorithms and programs become more complex. This paper reviews some of the literature and seeks to explain some of the concepts of object-oriented thinking most useful to the finite element programmer, using as an example a C++ implementation of a heat transfer and solidification program.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910260176
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  • 25
    Digitale Medien
    Digitale Medien
    Parallelization of the finite volume method for radiation heat transfer (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 388-406 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The finite volume method for radiative heat transfer calculations has been parallelized using two strategies, the angular domain decomposition and the spatial domain decomposition. In the first case each processor performs the calculations for the whole domain and for a subset of control angles, while in the second case each processor deals with all the control angles but only treats a spatial subdomain. The method is applied to three-dimensional rectangular enclosures containing a grey emitting-absorbing medium. The results obtained show that the number of iterations required to achieve convergence is independent of the number of processors in the angular decomposition strategy, but increases with the number of processors in the domain decomposition method. As a consequence, higher parallel efficiencies are obtained in the first case. The influence of the angular discretization, grid size and absorption coefficient of the medium on the parallel performance is also investigated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910266576
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  • 26
    Digitale Medien
    Digitale Medien
    A numerical simulation of measured transient temperatures in the walls, floor and surrounding soil of a buried structure (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 405-423 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Presents the results of a numerical simulation of measured heat transfer through a region surrounding a buried structure. The model applied in the study is a widely used whole building thermal simulation program of a type which predicts the thermal response of structures for building services requirements. A multi-dimensional numerical conductive heat transfer module has been added to this program but this does not specifically address earth-contact heat flows. This work attempts to assess the accuracy of the overall package when predicting earth-coupled heat transfer. It is common practice in the field of building services not to use specific earth-contact models and so it is important to assess the likely errors thus involved. The predictions of the finite-volume model are compared with one year of data from a basement test facility. The results are analysed using the Differential Sensitivity Analysis method and an attempt is made to correlate predictive errors with periods of rainfall and snow coverage. It seems that a purely conductive model may be capable, given accurate input data, of satisfactorily predicting the transient temperature variations in the soil/concrete envelope surrounding this structure for the period of the year when no snow coverage is present. However, if one is to accurately model regions of earth-contact (particularly at shallow depths) in a climate in which rainfall and snow are significant then these influences should be explicitly modelled.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910266585
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  • 27
    Digitale Medien
    Digitale Medien
    Axisymmetric finite element models for rotational molding (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 515-542 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: We present a new nonlinear axisymmetric finite element model for heat transfer and powder deposition in rotational molding. Arbitrary Lagrangian Eulerian techniques are employed to track the gradual growth of the plastic layer. Results using this approach compare well with earlier 1-D models and with experimental data. Using the model to study the effects of locally enhanced heat transfer on part wall thickness, we find that controlling the relative magnitudes of radial and circumferential heat transfer is crucial in order to obtain desired wall thickness profiles.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910276836
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  • 28
    Digitale Medien
    Digitale Medien
    Free convection flow of thermomicropolar fluid along a vertical plate with nonuniform surface temperature and surface heat flux (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 568-585 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: We determine the effects of micro-inertia density and the vortex viscosity on laminar free convection boundary layer flow of a thermomicropolar fluid past a vertical plate with exponentially varying surface temperature as well as surface heat flux. The governing nonsimilarity boundary layer equations are analyzed using: first, a series solution for small ? (a scaled streamwise distribution of micro-inertia density), second, an asymptotic solution for large ? and, third, a full numerical solution implicit finite difference method together with Keller-box scheme. Results are expressed in terms of local skin friction and local Nusselt number. The effects of varying the vortex viscosity parameter, ?, surface temperature and the surface heat flux gradient n and m respectively against ? for fluids having Prandtl number equals 0.72 and 7.0 are determined.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910276854
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  • 29
    Digitale Medien
    Digitale Medien
    Novel techniques for electronic component removal (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 7-11 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Component removal for rework and repair is traditionally achieved by re-melting of the solder, but the exposure of the assembly or its component parts to repeated soldering/ desoldering cycles may cause both immediate damage and create a significant long term reliability hazard. Rework is labour intensive and requires skilled operators. Area array components further increase the complexity of the rework process because of the number and inaccessibility of the solder joints. There is a growing requirement to recycle/reclaim electronic waste, creating the need for an effective process for dismantling of printed circuit board assemblies (PCBAs). This paper will present a brief review of alternative non-thermal techniques for rework or dismantling of conventional soldered assemblies, including both chemical etchants and mechanical techniques. Results will then be presented on trials of chemical etchants, where rates of solder removal consistent with realistic times for component removal have been readily achieved using commercially available tin-lead strippers. Electrochemical techniques are also shown to be usable in specific applications, i.e. where electrical contact can be readily made to the solder joints to be removed, and have the advantage of reclaiming the removed solder directly from the electrolyte.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910265622
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  • 30
    Digitale Medien
    Digitale Medien
    Characterization of a solder paste printing process and its optimization (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 23-26 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The objectives of this research are to model the screening process with planned experiments and to identify the optimal setting of the process parameters so as to minimize the printing defects. The percentage volume matching (PVM) and defects per unit (DPU) are the two quality characteristics of interest. A fractional factorial design was employed to study simultaneously the effects of eight process factors on the PVM and DPU and their possible interactions. Subsequent analysis shows that a low level of the stencil cleaning interval and low temperature results in the minimum DPU while maintaining a PVM very close to 100 per cent. Empirical relationships between these two quality characteristics and the important factors were formulated using regression analysis and close matches were found during subsequent validation experiments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910293838
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  • 31
    Digitale Medien
    Digitale Medien
    Interfacial reactions of tin-zinc-bismuth alloys (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 46-52 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A variety of lead-free solders are now commercially available. Of those suitable for mass soldering perhaps the ones closest to a direct, drop-in, replacement for tin-lead are the tin-zinc-bismuth alloys. For most tin-based solders it is the tin which is the active element and dominates the all-important interfacial reactions. As a result they have many properties in common. The addition of zinc, however, radically alters this picture. Zinc oxidation products are formed at the surfaces. Zinc intermetallic compounds are also formed in preference to tin-compounds at the substrate interfaces. The nature and implications of these changes are outlined for the common basis materials.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910293874
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  • 32
    Digitale Medien
    Digitale Medien
    Analysis of crack growth in solder joints (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 27-32 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Understanding crack growth in solder joints is important for predicting the fatigue life of solder interconnects. In this paper, crack propagation in solder joints made of two solder alloys, 62Sn/36Pb/2Ag (by weight), a commonly used solder paste for SMT reflow applications, and 96.5Sn/3.5Ag (by weight), a lead-free solder alloy, was examined during thermal cycling. Based on these observations, the rate of crack propagation was estimated. Microstructural changes in the solder during thermal cycling were also studied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910293847
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  • 33
    Digitale Medien
    Digitale Medien
    Survey of rework practices in the UK electronics assembly industry (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 12-22 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A survey of rework practices of the UK electronics assembly industry has been undertaken. Rework of electronics components in the UK was found to be dominated by the use of soldering irons. Many companies did not control tip temperatures, rework times, background heating or the number of rework operations which could be undertaken on any one component. Few companies followed the recommendations of the component manufacturers aimed at preventing damage to thermally sensitive components. It was found that those companies which did control rework temperatures, did reduce rework temperatures for surface mount components. In general, rework temperatures were much higher than those recommended by the component manufacturers. A great deal of cleaning was undertaken after rework, with most companies doing some form of local cleaning. Most companies reused components even if only on an occasional basis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910293829
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  • 34
    Digitale Medien
    Digitale Medien
    Simulation modeling of a garment production system using a spreadsheet to minimize production cost (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 287-299 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A methodology of structuring a garment production simulation model using a spreadsheet is described to minimize the average daily production cost through the investigation of various man-machine combinations. The capability and usability of an easily available modern spreadsheet Excel 7.0 to simulate a simple garment production system is accessed with an attempt to demonstrate the simulation model building in a user friendly environment rather than learning and using costly simulation programming languages or simulation software packages. Simulation has evaluated the resource utilization and measured the system performance and developed strategies for taking operational decisions in a logical and better way to minimize the garment production cost. It may also assist and benefit the garment production managers to plan, design and operate their systems in an efficient manner in a competitive environment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910297554
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  • 35
    Digitale Medien
    Digitale Medien
    An experimental study of needle heating in sewing heavy materials using infrared radiometry (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 300-314 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: This paper presents an experimental study on needle heating in sewing heavy materials such as upholstery fabrics. In the experiments, infrared (IR) radiometry, high speed line scanning IR radiometry, and high speed IR radiometry are used to obtain thermal images of the needle during sewing. In particular, IR radiometry was used in lower speed sewing (approximately 500rpm). High speed IR and high speed line scanning IR radiometry were used for medium speed sewing (1,000-2,000rpm). Using Taguchi's design of experiment method, the effects of various factors are studied including needle conditions (sharp or blunt), sewing speeds, number of stitches per inch, material being sewn, and thread tension. It is found that even with air vortex cooling the needle may still reach high enough temperatures that may affect the sewing quality and even cause thread breakage. This was confirmed via a thread tensile testing experiment. An empirical model of the mean needle temperature is also proposed and tested.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910297563
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  • 36
    Digitale Medien
    Digitale Medien
    Development of a large-eddy simulation open channel code (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 6-17 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Describes further development of a 3D finite difference code written to model turbulent flows in an open channel with a moving free surface. The code has been developed so that the computational domain can have side-walls and/or periodic directions and that the flow may also be buoyancy driven. Either a full simulation or large eddy simulation (LES) of the turbulence can be performed. Results are presented of a simulation of periodic streamwise flow in an open channel with parallel side-walls and also of a thermal jet into an open tank. Both simulations were carried out on a UNIX workstation using resolutions that enable the results to be viewed within an "engineering context". The LES application demands numerical approximations which conserve mass, momentum and total energy with high precision, and which permit wave motion with very little numerical dispersion or dissipation. The free surface is tracked using a split-merge technique which combines the volume of fluid (VOF) and height function methods in a way that is conservative.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910251077
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  • 37
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    Digitale Medien
    Equilibration of heat conduction simulation in a very thin film using molecular dynamics (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 60-71 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: This investigation deals with the equilibration of heat conduction simulation in a very thin film using molecular dynamics. Two parameters, the positional order parameter and the kinetic H-function, are employed simultaneously to monitor the evolution to the equilibrium. With the different boundary conditions, material parameters, and molecular lattice configurations, the results of the simulation show that the combination of the two parameters can give a consistent prediction to the approach of the equilibrium. At the equilibrium state, the process of heat conduction in a thin film is studied to understand the macroscopic behaviour from the standpoint of molecular dynamic motions. The method used can be applied to solve other microscopic flow and heat transfer problems using molecular dynamic simulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910251103
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  • 38
    Digitale Medien
    Digitale Medien
    Numerical prediction of enhanced heat flux due to shock-on-shock interaction in hypersonic nonequilibrium flow (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 114-135 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: This paper describes the numerical solutions of type-IV shock-on-shock interactions in hypersonic thermochemical nonequilibrium air flows around blunt bodies. The Navier-Stokes equation solver for a chemically reacting and vibrationally relaxing gas mixture was applied to the present problem, where the concepts of the Advection Upstream Splitting Method (AUSM) and the Lower-Upper Symmetric Gauss-Seidel (LU-SGS) method were basically employed along with the two-temperature thermochemical model of Park. The aerodynamic heating with or without the shock-on-shock interaction to a sphere and circular cylinders are simulated for a hypersonic nonequilibrium flow. The numerical results show that typical type-IV shock-on-shock interaction pattern with a supersonic jet structure is also formed in a high-enthalpy thermochemical nonequilibrium flow, and that the contribution of convective heat flux in the translational/rotational mode to the total heat flux is dominant. Furthermore, the inherent unsteadiness of nonequilibrium type-IV shock-on-shock interaction flowfield is discussed briefly.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910255992
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  • 39
    Digitale Medien
    Digitale Medien
    Numerical study of three-dimensional non-Darcy forced convection in a square porous duct (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 151-169 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The objective of the present work was to perform a detailed numerical study of laminar forced convection in a three-dimensional square duct packed with an isotropic granular material and saturated with a Newtonian fluid. Hydrodynamic and heat transfer results are reported for three different thermal boundary conditions. The flow in the porous medium was modeled using the semi-empirical Brinkman-Forchheimer-extended Darcy model which also included the effects of variable porosity and thermal dispersion. Empirical models for variable porosity and thermal dispersion were determined based on existing three-dimensional experimental measurements. Parametric studies were then conducted to investigate the effects of particle diameter, Reynolds number, Prandtl number and thermal conductivity ratio. The results showed that channeling phenomena and thermal dispersion effects are reduced considerably in a three-dimensional duct compared with previously reported results for a two-dimensional channel. It was found that the Reynolds number affects mainly the velocity gradient in the flow channeling region, while the particle diameter affects the width of the flow channeling region. As the Reynolds number increases or as the particle diameter decreases (i.e., when the inertia and thermal dispersion effects are enhanced), the Nusselt number increases. The effects of varing the Prandtl number on the magnitude of the Nusselt number were found to be more significant than those of the thermal conductivity ratio. Finally, the effects of varing the duct aspect ratio on the friction factor can be neglected for small particle diameter (Dp = 0.01) or for high particle Reynolds number (Red = 1000) due to the dominant bulk damping resistance from the porous matrix (Darcy term) or strong inertia effects (Forchheimer term), respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910256018
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  • 40
    Digitale Medien
    Digitale Medien
    Three-dimensional flows over backward facing s.tif (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 224-240 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Three-dimensional flows over backward facing s.tif are analysed by means of a finite element procedure, which shares many features with the SIMPLER method. In fact, given an initial or guessed velocity field, the pseudovelocities, i.e. the velocities that would prevail in the absence of the pressure field, are found first. Then, by enforcing continuity on the pseudovelocity field, the tentative pressure is estimated, and the momentum equations are solved in sequence for velocity components. Afterwards, continuity is enforced again to find corrections that are used to modify the velocity field and the estimated pressure field. Finally, whenever necessary, the energy equation is solved before moving to the next step.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/EUM0000000004563
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  • 41
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    Digitale Medien
    Solution of temperature field in DC cast aluminium alloy billet by the dual reciprocity boundary element method (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 269-297 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The axisymmetric steady-state convective-diffusive thermal field problem associated with direct-chill, semi-continuously cast billets has been solved using the dual reciprocity boundary element method. The solution is based on a formulation which incorporates the one-phase physical model, Laplace equation fundamental solution weighting, and scaled augmented thin plate splines for transforming the domain integrals into a finite series of boundary integrals. Realistic non-linear boundary conditions and temperature variation of all material properties are included. The solution is verified by comparison with the results of the classical finite volume method. Results for a 0.500[m] diameter Al 4.5 per cent Cu alloy billet at typical casting conditions are given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910260130
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  • 42
    Digitale Medien
    Digitale Medien
    Coupling heat conduction, radiation and convection in complex geometries (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 240-264 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: In many industrial applications, convection radiation and conduction participate simultaneously to the heat transfers. A numerical approach able to cope with such problems has been developed. The code SYRTHES is tackling conduction and radiation (limited to non participating medium). Radiation is solved by a radiosity approach, and conduction by a finite element method. Accurate and efficient algorithms based on a mixing of analytical/numerical integration, and ray tracing techniques are used to compute the view factors. The fluid part is solved by CFD codes like ESTET (Finite volumes) or N3S (Finite elements). SYRTHES relies on an explicit numerical scheme to couple all the phenomena. No stability problems have been encountered. To provide further flexibility, the three phenomena are solved on three independent grids. All data transfers being automatically taken care of by SYRTHES. Illustrating applications are shown.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910260112
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  • 43
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    Digitale Medien
    Modelling of heat transfer coupled with columnar dendritic growth in continuous casting of steel (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 296-317 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The general aim of this work is to calculate the extent of the equiaxed zone in continuously cast steel products. Free equiaxed grains can grow only in undercooled liquid regions. Undercooling of the bulk liquid occurs because the columnar dendrite tips growing from the mould reject solutes in the liquid. The specific aim of this contribution is to calculate the thermal and physical state of continuously cast steel long products assuming a columnar solidification mode, taking into account the tip undercooling at the solidification front. A 2-D heat transfer model has been developed where the columnar solidification mode is assumed. The calculation of the undercooling at the advancing solidification front is coupled with the heat transfer equation. The comparison between the results of the present model and the classical heat transfer model indicates the importance of modelling the undercooling phenomenon. The influence of the secondary cooling has also been studied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910260158
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  • 44
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    Digitale Medien
    Towards a formal theory of development/evolution and characterization of time discretized operators for heat transfer (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 348-381 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The time-discretization process of transient equation systems is an important concern in computational heat transfer applications. As such, the present paper describes a formal basis towards providing the theoretical concepts, evolution and development, and characterization of a wide class of time discretized operators for transient heat transfer computations. Therein, emanating from a common family tree and explained via a generalized time weighted philosophy, the paper addresses the development and evolution of time integral operators [IO], and leading to integration operators [InO] in time encompassing single-step integration operators [SSInO], multi-step integration operators [MSInO], and a class of finite element in time integration operators [FETInO] including the relationships and the resulting consequences. Also depicted are those termed as discrete numerically assigned [DNA] algorithmic markers essentially comprising of both: the weighted time fields, and the corresponding conditions imposed upon the dependent variable approximation, to uniquely characterize a wide class of transient algorithms. Thereby, providing a plausible standardized formal ideology when referring to and/or relating time discretized operators applicable to transient heat transfer computations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910260185
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  • 45
    Digitale Medien
    Digitale Medien
    Transient conjugate heat transfer in a porous medium in concentric annuli (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 444-462 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Transient conjugated forced convection in the thermal entry region of a thick-walled annulus, filled with a homogeneous and isotropic porous medium, has been numerically investigated using finite-difference techniques. Non-Darcian effects as well as axial conduction of heat have been considered. The flow is assumed to be hydrodynamically fully developed and steady but thermally developing and transient. The thermal transient is initiated by a step change in the prescribed isothermal temperature on the outer surface of the external tube of the annulus while the inner surface of the internal tube is kept adiabatic. A parametric study is carried out to explore the effects of the Darcy number, the inertia term, the Peclet number and the porous medium heat capacity ratio on the transient thermal behavior in a given annulus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910266602
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  • 46
    Digitale Medien
    Digitale Medien
    Numerical study on oscillatory convection of cold water in a tall vertical enclosure (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 487-508 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The stability of two-dimensional natural convection of water near its density maximum (cold water) inside a vertical rectangular enclosure with an aspect ratio of eight is investigated via a series of direct numerical simulations. The simulations aim to clarify, under the influence of density inversion, the physical nature of the instability mechanism responsible for the laminar buoyancy-driven flow transition from a steady state to an oscillatory state in the enclosure filled with cold water. Two values of the density inversion parameter, m= 0.4 and 0.5, where the density inversion of cold water may exert strong influence on the flow, are considered in the present study. The results show that the transition from steady state to periodically oscillatory convection arises in the cold-water-filled enclosure through a Hopf bifurcation. The oscillatory convection in the water-filled enclosure for both values of m is found to feature an oscillatory multicellular structure within the contra-rotating bicellular flow regions. A traveling wave motion accordingly results along the maximum density contour, which demarcates the contra-rotating bicellular flows in the enclosure. For both cases the nature of transition into unsteadiness is found to be buoyancy-driven. The critical Rayleigh number for the bifurcation at m = 0.4 is found to be markedly higher than that at m = 0.5.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910266639
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  • 47
    Digitale Medien
    Digitale Medien
    Estimation of numerical accuracy for the flow field in a draft tube (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 472-487 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The potential for overall efficiency improvements of modern hydro power turbines is a few percent. A significant part of the losses occurs in the draft tube. To improve the efficiency by analysing the flow in the draft tube, it is therefore necessary to do this accurately, i.e. one must know how large the iterative and the grid errors are. This was done by comparing three different methods to estimate errors. Four grids (122,976 to 4,592 cells) and two numerical schemes (hybrid differencing and CCCT) were used in the comparison. To assess the iterative error, the convergence history and the final value of the residuals were used. The grid error estimates were based on Richardson extrapolation and least square curve fitting. Using these methods we could, apart from estimate the error, also calculate the apparent order of the numerical schemes. The effects of using double or single precision and changing the under relaxation factors were also investigated. To check the grid error the pressure recovery factor was used. The iterative error based on the pressure recovery factor was very small for all grids (of the order 10–4 percent for the CCCT scheme and 10–10percent for the hybrid scheme). The grid error was about 10 percent for the finest grid and the apparent order of the numerical schemes were 1.6 for CCCT (formally second order) and 1.4 for hybrid differencing (formally first order). The conclusion is that there are several methods available that can be used in practical simulations to estimate numerical errors and that in this particular case, the errors were too large. The methods for estimating the errors also allowed us to compute the necessary grid size for a target value of the grid error. For a target value of 1 percent, the necessary grid size for this case was computed to 2 million cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910266620
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  • 48
    Digitale Medien
    Digitale Medien
    Preconditioning by approximations of the discrete Laplacian for 2-D non-linear free convection elliptic equations (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 586-600 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The paper analyses the preconditioning of non-linear nonsymmetric equations with approximations of the discrete Laplace operator. The test problems are non-linear 2-D elliptic equations that describe natural convection, Darcy flow, in a porous medium. The standard second order accurate finite difference scheme is used to discretize the models' equations. The discrete approximations are solved with a double iterative process using the Newton method as outer iteration and the preconditioned generalised conjugate gradient (PGCG) methods as inner iteration. Three PGCG algorithms, CGN, CGS and GMRES, are tested. The preconditioning with discrete Laplace operator approximations consists of replacing the solving of the equation with the preconditioner by a few iterations of an appropriate iterative scheme. Two iterative algorithms are tested: incomplete Cholesky (IC) and multigrid (MG). The numerical results show that MG preconditioning leads to mesh independence. CGS is the most robust algorithm but its efficiency is lower than that of GMRES.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910276863
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  • 49
    Digitale Medien
    Digitale Medien
    Numerical analysis of combined radiation and unsteady natural convection within a horizontal annular space (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 742-764 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The effect of radiation on unsteady natural convection in a two-dimensional participating medium between two horizontal concentric and vertically eccentric cylinders is investigated numerically. The equations of transfer are written by using a bicylindrical coordinates system, the stream function, and the vorticity. The finite volume radiation solution method and the control volume approach are used to discretize the coupled equations of radiative transfer, momentum, and energy. Original results are obtained for three eccentricities, Rayleigh number equal to 104, 105, and a wide range of radiation-conduction parameter. The effects of optical thickness, wall emissivity, and scattering on flow intensity and heat transfer are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910371119
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  • 50
    Digitale Medien
    Digitale Medien
    Natural convection of thermomicropolar fluid from an isothermal surface inclined at a small angle to the horizontal (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 814-832 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: An analysis is performed to study the skin-friction, the couple-stress and heat transfer characteristics of a laminar free-convection boundary layer flow of a micropolar fluid past an isothermal plate inclined at a small angle to the horizontal. When the inclination is positive, series solutions, one valid near the leading edge and the other at a large distance from it, are obtained. Introducing a strained coordinate transformation, the local nonsimilar boundary layer equations are also derived for the flow from the leading edge to downstream, solutions of which are obtained by using an implicit finite difference method. When the inclination is negative, the boundary layer separates. The effects of the material parameters on the skin-friction, the local couple-stress, the local Nusselt number and the point of separation for a negatively inclined plate have been investigated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910297888
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  • 51
    Digitale Medien
    Digitale Medien
    An explicit finite element algorithm for convection heat transfer problems (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 860-877 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A finite element algorithm is presented for the simulation of steady incompressible fluid flow with heat transfer using triangular meshes. The continuity equation is modified by employing the artificial compressibility concept to provide coupling between the pressure and velocity fields of the fluid. A standard Galerkin finite element method is used for spatial discretization and an explicit multistage Runge-Kutta scheme is used to march in the time domain. The resulting procedure is stabilized using an artificial dissipation technique. To demonstrate the performance of the proposed algorithm a wide range of test cases is solved including applications with and without heat transfer. Both natural and forced convection applications are studied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910297932
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  • 52
    Digitale Medien
    Digitale Medien
    Thermo-capillary driven flow in macrolayer at high wall heat fluxes (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 788-808 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The present work is to investigate nucleate boiling heat transfer at high heat fluxes, which is characterized by the existence of macrolayer. Two-region equations are proposed to simulate both thermo-capillary driven flow in the liquid layer and heat conduction in the solid wall. The numerical simulation results can clearly describe the activities of several multi vorticies in the macrolayer. These vorticies and evaporation at the vapor-liquid interface constitute a very efficient heat transfer mechanism to explain the high heat transfer coefficient of nucleate boiling heat transfer near CHF. This study also explores the flow pattern of macrolayer with a high conducting solid wall, e.g. copper, and hence the temperature is uniform at the liquid-solid interface, and the heat fluxes and the evaporation coefficient are found to have significant effect on flow pattern in the liquid layer. Furthermore, a parameter "evaporation fraction" as well as "aspect ratio" is proposed as an index to investigate the thermo-capillary driven flow system. The model prediction agrees reasonably well with the experimental data in the literature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910291163
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  • 53
    Digitale Medien
    Digitale Medien
    Nonsimilar solutions for free convection in non-Newtonian fluids along a vertical plate in a porous medium (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 847-859 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A nonsimilar boundary layer analysis is presented for the problem of free convection in power-law type non-Newtonian fluids along a permeable vertical plate with variable wall temperature or heat flux distribution. Numerical results are presented for the details of the velocity and temperature fields. A discussion is provided for the effect of viscosity index on the surface heat transfer rate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910297923
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  • 54
    Digitale Medien
    Digitale Medien
    Optimizing the reflow profile via defect mechanism analysis (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 13-20 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A reflow profile is proposed which is engineered to optimize soldering performance based on defect mechanism analysis. In general, a slow ramp-up rate is desired in order to minimize hot slump, bridging, tombstoning, skewing, wicking, opens, solder beading, solder balling, and components cracking. A minimized soaking zone reduces voiding, poor wetting, solder balling, and opens. Use of a low peak temperature lessens charring, delamination, intermetallics, leaching, dewetting, and voiding. A rapid cooling rate helps to reduce grain size as well as intermetallic growth, charring, leaching and dewetting. However, a slow cooling rate reduces solder or pad detachment. The optimized profile favors that the temperature ramps up slowly until reaching about 180°C. Implementation of the optimized profile requires the support of a heating-efficient reflow technology with a controllable heating rate. Emergence of the forced air convection reflow provides a controllable heating rate. In addition, it is not sensitive to variation in parts' features, thus allows the realization of the optimized profile.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910254642
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  • 55
    Digitale Medien
    Digitale Medien
    Solder joint reliability of plastic ball grid array packages (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 44-48 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Presents the results of a study of the effects of solder ball pad metallurgy, intermetallic compound (IMC) thickness and thermal cycling on the shear strengths of PBGA package solder balls. The study of the microstructures of solder balls revealed that only a very thin layer of intermetallic compound existed between solder balls and Ni or Ni alloy barrier layers immediately after ball placement and reflow. The protective Au layer was dissolved completely and a needle like AuSn4 intermetallic compound was then formed and dispersed evenly in the solder balls. The overall thickness of the IMC layers was thicker than 15µm after storage at 150°C for 1,000 hours. During the shear tests failure occurred at the interface of the two IMC layers. The fracture surfaces of solder balls with electrolytic Ni and thick Au layers were smooth and brittle fracture was observed. The ball shear strength decreased dramatically with the formation of IMC layers. For the solder balls with electroless Ni and thin Au layers, only a single IMC layer was formed at the interface and its thickness was only 2.5 µm after storage at 150°C for 1,000 hours.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910254930
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  • 56
    Digitale Medien
    Digitale Medien
    Surface insulation resistance (SIR) response to various processing parameters (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 30-34 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: SIR testing is in practice carried out under a wider range of experimental conditions than those detailed in standards. The work presented here explores some of the issues when using a range of fluxes with various processing conditions and also examines the influence of substrate finish, test bias and the reflow process. These results clearly show that care must be exercised when using different test set-ups, and when extrapolating between testing and use conditions. In particular the use of a 50V test bias voltage can produce anomalous results when compared to a 5V use environment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910265668
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  • 57
    Digitale Medien
    Digitale Medien
    Effect of the air on the motion of light fabric (the second paper): The added air mass of a membrane vibrating with fundamental mode (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 83-109 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The property of the added air mass of a plane membrane suspended between supports and vibrating in x-y plane with a half-sine fundamental mode is obtained again by analysis with a normal method which differs from that presented in the last proceedings. The method used in this paper is that based on a source distribution modeling approach (the last method was that based on a vortex distribution modeling approach). The calculated result of a, the ratio of the added air mass to the mass of the membrane itself, is 0.94/(m/(r)), where m is the mass per unit area of the membrane, r the density of the air flow and l the length of the membrane. This result is roughly equal to that obtained from the method in the last paper.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910276368
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  • 58
    Digitale Medien
    Digitale Medien
    The objective evaluation of blanket hand and durability: A preliminary investigation (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 90-108 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The purpose of this study is to investigate an objective method of evaluating the tactile comfort of blankets by a method of connecting the mechanical parameters of blankets to subjective evaluation. The two methods are preliminarily investigated as follows: (1) Transformation equations for the fabric hand of suiting, KN-101-W for primary hand values and KN-301-W for THV, are applied, with the mean and standard deviation applied to these equations replaced with new values for the blanket population. (2) A new prediction equation is constructed for deriving THV directly from the mechanical parameters and thermal properties. The prediction accuracy of method (2) is a little higher than that of (1). The durability of blankets during repeated use and repeated dry cleaning determined by the initial performance of blankets is also investigated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910276395
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  • 59
    Digitale Medien
    Digitale Medien
    Time-dependentcomputations of turbulent bluff-body diffusion flames close to extinction (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 39-59 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A two dimensional time-dependent Navier Stokes formulation that encompasses aspects from both the LES formalism and the conventional k-e approaches was employed to calculate a range of reacting bluff-body flows exhibiting high or low level large scale structure activity. Extensive regions of local flame extinction found in these bluff-body flame configurations were treated with a partial equilibrium/two-scalar exponential PDF combustion submodel combined with a local extinction criterion based on a comparison of the turbulent Damkohler number against the ratio of the scalar scale to the reaction zone thickness. A dual-mode description, burning/ non-burning, of combustion provided the local gas state. Comparisons between calculations and measurements indicated the ability of the method to capture all the experimentally observed variations in the momentum and reactive scalar mixing fields over a range of operating conditions from the lean to the rich blow-out limit.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910251095
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  • 60
    Digitale Medien
    Digitale Medien
    Finite difference modelling of natural convection flow with thermophoresis (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 692-705 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Deals with thermophoretic analysis in natural convection laminar flow over a cold vertical flat plate. The governing equations are solved by finite difference marching technique. Variation of wall concentration and wall flux with respect to the plate length is studied. Influence of Prandtl number, plate temperature on particle deposition and wall flux is presented in graphical form. An already established self-adaptive grid generation technique and variable grid size method are incorporated in the computer routine to get more accurate results. The nature of variation of particle concentration profile with respect to Prandtl number is found to be similar. For a cold plate it is observed that the wall concentration increases with decrease in Prandtl number.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910286033
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  • 61
    Digitale Medien
    Digitale Medien
    A hybrid finite element-finite difference method for thermal analysis in X-ray lithography (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 660-677 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: X-ray lithography is an important technique in micro fabrication used to obtain structures and devices with a high aspect ratio. The X-ray exposure takes place in a system composed of a mask and a photoresist deposited on a substrate (with a gap between mask and resist). Predictions of the temperature distribution in three dimensions in the different layers (mask, gap, photoresist and substrate) and of the potential temperature rise are essential for determining the effect of high flux X-ray exposure on distortions in the photoresist due to thermal expansion. In this study, we develop a three-dimensional numerical method for obtaining the temperature profile in an X-ray irradiation process by using a hybrid finite element-finite difference scheme for solving three-dimensional parabolic equations on thin layers. A domain decomposition algorithm is then obtained based on a parallel Gaussian elimination for solving block tridiagonal linear systems. The method is illustrated by a numerical method.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910276160
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  • 62
    Digitale Medien
    Digitale Medien
    Predictions of swirling flow in sudden-expansion dump combustor with flameholder side-inlet using two-step combustion model (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 764-787 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The swirling flow of sudden-expansion dump combustor with central V-gutter flameholder and six side-inlets is studied by employing the SIMPLE-C algorithm and Jones-Launder k-e two-equation turbulent model. Both combustion models of one-step with infinite chemical reaction rate and two-step with finite chemical reaction rate of eddy-breakup (EBU) model are used to solve the present problem. The results agreed well with available prediction data in terms of axial-velocity and total pressure coefficient along combustor centerline. The flowfield structure of combustor considered is strongly affected by swirling, flameholder and side-inlet flow. For the fixed strength of swirling, the length of central recirculation zone is decreased when the angle of V-gutter is increased. The outlet velocity of combustor in reacting flow is higher than that in cold flow because the released heat of combustion causes the decrease of density throughout the combustor flowfield. The distribution of mass fraction of various species in reacting process depends on the mixing effect, chemical kinetic and the geometric configuration of combustor.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910291154
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  • 63
    Digitale Medien
    Digitale Medien
    A transient analysis of incompressible fluid flow in vessels with moving boundaries (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 833-846 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: We present in this paper a finite element analysis of Navier-Stokes equations in a time-varying domain. The method of weighted residuals is used together with the semi-discretization approach to obtain the discrete equations. In this approach, where the physical domain is allowed to vary, care is taken to retain the space conservation law property. We describe in detail the transformation of equations between fixed and moving grids. The validity of this method has been tested against two problems which are amenable to analytic solutions. Time accurate results show favorable agreement with analytic solutions. Having verified the applicability of the Galerkin finite element code to problems involving moving grids, we consider the fluid flow in a vessel, where a portion of its boundary moves in time. Results are presented with emphasis on the depiction of vortical flow details.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910297905
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  • 64
    Digitale Medien
    Digitale Medien
    Mechanical stress and deformation of SMT components during temperature cycling and PCB bending (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 35-41 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A very common method to predict the reliability of components soldered on printed circuit board (PCB) or substrates is by bending tests and temperature cycle tests, for instance between -55°C and 125°C (up to 2,000 cycles at 1h cycle period). Sensitive SMD constructions such as chips with ball grid array mounting or multilayer chip capacitors (MLCC) are often a major issue due to their "flex cracking" problems. This paper describes the real behaviour of deformation at temperature cycling and PCB bending of chip components (body size 0603). By using the piezoresistive effect in thick film resistors the effects of stress on the alumina body can be determined and described for the whole temperature range of interest. The complete system of component, PCB/substrate and solder joint will be discussed and different influences will be isolated. It will be shown that CTE-matching of the component and substrate does not lead to an optimum situation. The influence of the solder joint plays an important part. Optimization potentials and design rules for the whole system will be given. The basis of this paper is a quite unusual "measurement tool" the effect of piezoresistivity. The investigation into that phenomenon will be described very thoroughly first.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910265677
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  • 65
    Digitale Medien
    Digitale Medien
    PBGA solder ball coplanarity impact evaluation (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 40-45 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A study was conducted to examine the sensitivity of solder joint integrity for PBGA assembly and post rework process yields to the change of the solder ball coplanarity specification from 0.15mm to 0.20mm as well as to increase the level of confidence with respect to the specification change. The study considered the following experimental variables: solder ball coplanarity; stencil thickness and aperture design; whether the assembly also experiences a wave soldering process; the rework method, i.e. whether there is dispensing of solder paste or just a flux. Electrical continuity tests were performed after PBGA assembly and rework. Accelerated thermal cycling and thermal shock tests were then used to evaluate the solder joint reliability. Additionally, standoff heights of PBGA solder joints were measured through cross sectioning samples. Statistical comparisons of the mean standoff height between different PBGA coplanarity groups, where different experiment variables were applied, allowed for determination of the variation of BGA solder joint integrity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910293865
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  • 66
    Digitale Medien
    Digitale Medien
    Qualification of flip chip fluxes by wetting balance and surface insulation resistance tests (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 21-26 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Owing to the incessant demand for reductions in the size of portable electronics, new dense packaging technologies are required. Reflow soldering is still mainly used for component joining on the substrate. In tiny joints such as those in flip chip (FC) assemblies the flux effect is vitally important and needs to pass a narrower performance window than in ordinary surface mount technology (SMT). The determination of the suitability of a flux, as reported in this paper, is twofold; first, the flux must perform well in its intended purpose and second, the flux must not leave harmful residues causing leakage or electromigration. The first test used was the wetting balance test for all fluxes. Fluxes accepted on the basis of the wetting tests were then subjected to the surface insulation resistance test (SIR).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910254651
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  • 67
    Digitale Medien
    Digitale Medien
    The impact of temperature and humidity conditions on surface insulation resistance values for various fluxes (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 36-43 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The surface insulation resistance (SIR) test has traditionally been performed by taking measurements at certain points during a seven-day test under well established environmental conditions. The work reported here explores the influence of test temperature and humidity when using a typical resin flux, a weak organic flux and glycol based fluxes when sampling SIR patterns every ten minutes. Results indicate that some fluxes are very sensitive to the test temperature, with volatilisation of flux residues an important issue. The frequent monitoring of the results also permitted the detection of dendrites during the SIR test. The results clearly show the importance of selecting the correct testing conditions and the benefit of frequent monitoring.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910254921
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  • 68
    Digitale Medien
    Digitale Medien
    Reduction of voiding in eutectic ball grid array solder joints (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 12-16 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The rapid progress of ball grid array (BGA) component technology has served to alleviate many problems associated with the placement and soldering of high lead count, fine pitch surface mount technology (SMT) packages. An unfortunate result of this process, however, is the occurrence of voids in the interconnecting eutectic solder balls of these packages. Large voids can affect the mechanical and thermal properties of the interconnect, which can reduce a component's mean time-to-failure and may also affect the transmission of high frequency electrical signals through the solder ball. For this reason, several experiments were conducted to investigate the manner and mechanisms in which voids are introduced into eutectic BGA solder ball joints. The following process parameters were found to be the primary parameters responsible for the voiding phenomenon: condition of the component's alloy and substrate, oxygen concentration in the reflow atmosphere, solder paste properties and the reflow profile. Through modification and optimization of process parameters in the manufacturing environment, BGA solder joint voiding was greatly reduced.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910265631
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  • 69
    Digitale Medien
    Digitale Medien
    TMA, DMA, DSC and TGA of lead free solders (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 17-24 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Most of the electronics packaging materials, especially solders, are temperature dependent. Their temperature-dependent material properties can be obtained by TMA (thermal mechanical analysis), DMA (dynamic mechanical analysis), DSC (differential scanning calorimetry), and TGA (thermogravimetric analysis). In this study, the thermal coefficient of expansion (TCE), storage modulus, moisture uptake, and melting point of two lead free solders, 96.5wt%Sn-3.5wt%Ag and 42wt%Sn-58wt%Bi provided from two different vendors, are measured by, respectively, TMA, DMA, TGA, and DSC. For comparison purpose, the 63wt%Sn-37wt%Pb solder is also considered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910265640
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  • 70
    Digitale Medien
    Digitale Medien
    CSP compatibility in the SMT assembly process (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 25-29 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: To achieve integration of chip scale package (CSP) devices into main stream surface mount technology (SMT) assembly, various experiments have been required. In process development, experiences learned from flip chip attach and ball grid array (BGA) assembly were utilized. Key process parameters for CSP assembly were defined and some of those key factors were optimized. They will be presented in this paper. Some observations during prototype build have been documented for correlation with reliability results in the future. The requirements for further CSP assembly studies will also be addressed in this paper.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910265659
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  • 71
    Digitale Medien
    Digitale Medien
    Materials behaviour and the reliability in performance of solder joints (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 8-11 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: While the implementation of lead-free solder technology has been the focus of much recent research, the challenge of joint structural integrity should not be overlooked. The paper summarises the significant variability in the mechanical properties of solders, both in terms of the prevailing testing conditions and between the alloys themselves. Using conventional routes to life prediction for an elementary creep situation, it demonstrates the critical importance of understanding the failure processes and utilising materials data that are appropriate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910293810
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  • 72
    Digitale Medien
    Digitale Medien
    Enhancement of underfill encapsulants for flip-chip technology (1999)
    Bradford : Emerald
    Soldering & surface mount technology 11 (1999), S. 33-39 
    Details
    ISSN: 0954-0911
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: This paper presents results on adding silane coupling agents to the underfill encapsulant to enhance the rheology and wetting of the underfill. These results include rheology measurements, contact angle measurements, and in situ flows using a simulated test chip on an FR4 with solder mask substrate. Three properties of the underfill encapsulant that can affect the mechanical reliability of the die and substrate assembly are: CTE; elastic modulus; and adhesion to the die and substrate surfaces. The approach taken in this paper is to add silane coupling agents with different chemistries to the underfill encapsulant to provide interfacial coupling of the underfill material to different die and substrate materials. This paper presents results on the enhancement of the adhesion of underfill encapsulant to silicon (Si), silicon nitride (SiN) die passivation, benzocyclobutene (BCB) die passivation, and solder mask surfaces. The adhesion strength was measured by die shear testing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09540919910293856
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  • 73
    Digitale Medien
    Digitale Medien
    The concept of virtual measurement: 3D fabric drapeability (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 10-18 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: This paper discusses the concept of virtual measurement in textiles and describes the development of a virtual 3D fabric drape measurement system. In this system, a physical based model is used to predict the draping performance, static and dynamic drape of a given fabric sample. Fabric mechanical properties are used for simulating the virtual 3D shape of the fabric samples, which produce a time-variable deformation of the virtual fabric drape. The 3D fabric drape can be observed under any view angle. An algorithm is developed, applied and integrated into the system for carrying out virtual fabric drape measurements in order to evaluate the drapeability of a given fabric. Important fabric aesthetic attributes such as number of fabric folds, fold variation and depth of fold are presented and implemented together with the drape co-efficient.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910258070
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  • 74
    Digitale Medien
    Digitale Medien
    Finite element analysis of sewing process (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 19-36 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Sewing is one of the most commonly used manufacturing processes in the world. Millions of parts are sewn every day ranging from cloths, shoes, furniture, to automobile seat covers. However, it is also one of the least understood processes. In fact, according to literature survey, few know how to calculate the sewing force or the fabric deformation during the sewing. This paper presents our research on using finite element model (FEM) to study the sewing process. The model is developed using ANSYS software system. In the model, the fabric is approximated by a number of perpendicular beam elements with elastic and plastic capabilities. On the other hand, the needle is modeled by a simple elastic beam. The contact between the two parts is modeled by contact elements. The variations of the needle geometry and the fabric material properties as well as the sewing conditions are also included in the model. The model can simulate the needle piercing through a material, and calculates the sewing forces as well as the fabric deformation forming a hole. It has been verified experimentally and can be used to study the effects of the key sewing parameters such as the fabric material properties and the needle geometry.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910258089
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  • 75
    Digitale Medien
    Digitale Medien
    Vibrations of a crank-shaft in a sewing machine induced by a zigzag mechanism (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 53-59 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Torsional vibrations of a shaft induced by a zigzag mechanism in a sewing machine with an oscillatory hook are studied in this paper. The dynamic equations of the motion are derived using the principle of virtual work. The discrete forms of the functions relating the motion of machine elements are found using Newton-Brent method. They are replaced locally by the continuous ones using Lagrange formula. The limit cycle trajectory is found by direct numerical integration and it is illustrated graphically. The presented mathematical model of the zigzag sewing machine makes it possible to choose the proper parameters of the machine at the preliminary state of design.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910258106
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  • 76
    Digitale Medien
    Digitale Medien
    Engineering of clothing systems for improved thermophysiological comfort: The effect of openings (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 37-52 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: To evaluate the effectiveness of ventilation systems in outdoor jackets, two jackets were purchased and modified, one made of PTFE laminated fabric and the other made of polyurethane coated fabric. Six male subjects undertook exercise routines simulating fell walking while wearing these jackets. The skin temperature at four different locations and the amount of perspiration generated during exercise were recorded for analysis. The experimental results were analysed using two- way analysis of variance. From the analysis it was found that during the exercise the design of the pit zip openings, especially with pit zip openings at both sleeve and side seams, in a jacket has an effect on thermal regulation, limiting the rate of temperature increase; however, during rest it is the fabric that plays the more important role. The results for the period of exercise suggest that the provision of ventilation at appropriate positions in the jacket could contribute considerably to heat loss irrespective of the use of breathable fabrics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910258098
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  • 77
    Digitale Medien
    Digitale Medien
    A mathematical model for predicting fabric loss during spreading (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 76-83 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Fabric loss is a major contribution to material utilization. Minimizing fabric loss during spreading can reduce the total production costs for garment manufacturing. A traditional method of predicting the fabric loss during spreading is mainly based on the experience of domain experts or the historical data of production orders. Such method is subjective, not systematic and non-repeatable. In this paper, assuming the spreading process is handled in a controlled manner and there are no flaws on the fabrics being spread, a mathematical model is constructed for predicting the total fabric loss in the spreading process. The total fabric loss includes the internal wastage (i.e. marker fallout), and the external wastage (including end loss, width loss, and splice loss). Other parameters such as marker length, number of splice lines, remnant, and roll length of fabric are also included in the model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910276359
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  • 78
    Digitale Medien
    Digitale Medien
    Using the compression properties of pillows to estimate sleeping comfort (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 160-169 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: In order to establish an objective method of evaluating pillow comfort, we investigate the relation between the sensory evaluation of pillows and the compression properties of pillows. The subjective evaluation values of hardness, fitness and total comfort were correlated with the compression energy WC and the displacement ? T at the maximum load of 50gf/cm2. Pillows which have large values of WC and ? T were regarded as softer, fitter and more comfortable. Pillows estimated as being soft and fit showed larger contact areas and less contact pressure on the head. For the pillows which have the same flat shape, a good agreement between the individual judges was shown in the assessments of hardness and height. The shape and packing density of polyethylene pipes affected the degree of the hardness of the pillows.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910282415
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  • 79
    Digitale Medien
    Digitale Medien
    Air permeability and light transmission of weaves (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 116-125 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The main aim of this contribution is characterization of fabric porosity by the light transmission and comparison of this characteristic with air permeability and idealized geometrical structure of selected weaves. For characterization of air permeability the classical apparatus has been used. The transmission of light through fabrics has been measured on the system LUCIA for image analysis. The porosity of textiles has been evaluated from corresponding construction parameters and idealized models of fabric geometry. The dependencies between the above mentioned characteristics were formalized by using regression analysis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910276331
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  • 80
    Digitale Medien
    Digitale Medien
    Optimisation of shirt fabrics' composition from the point of view of their appearance and thermal comfort (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 105-119 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: In this paper, the thermal contact comfort of a suddenly wetted shirt and some selected mechanical parameters of ten various woven shirt fabrics were measured with the aim of determining the effect of their composition on their complex quality level. In order to explain the thermal contact comfort of superficially wetted shirts, a new parameter called moisture absorptivity was introduced and a simple equation of the moisture transfer between the fabric and skin was derived. Since the direct measurement of the moisture absorptivity is complicated, an indirect method for its experimental determination was described and used for evaluation of thermal comfort. As regards the final complex evaluation of the measured shirt fabrics, it was found that shirts containing 25-40 per cent of classical PES fibres blended with cotton, compared with non-treated pure cotton shirts, have shown similar or even better water vapour permeability, fairly warmer feeling in dry state, better shear, fairly better ability to keep the form and a bit lower moisture absorptivity (worse thermal contact comfort feeling in the case of superficial wetting). Moreover, thermal comfort properties may be still improved by the application of special modified PES fibres.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910276250
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  • 81
    Digitale Medien
    Digitale Medien
    Effect of mechanical properties of fabrics on change of bloused line during cyclic wear: On front open part made up of fused composites (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 125-138 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: This study focuses on the objective evaluation of the silhouette of the front bloused line of women's blouses, in which fusible interlinings are used in the construction of the open part. The wearing test was carried out over three seasons and the bloused lines before and after the fatigue were observed and examined in relation to the mechanical properties of fused composites and their constituent fabrics. Since bending properties and KOSHI were found to play an important role in the change of the silhouette formation of bloused lines, those of fused fabrics were studied by applying the simple model. Finally, in the sensory test, applying the blouses fatigued and not fatigued, their open parts made up of fused composite are evaluated by 71 consumers for their preference. The essential concepts involved in the consumer preference were clarified.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910276269
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  • 82
    Digitale Medien
    Digitale Medien
    Surface appearance irregularity of nonwovens (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 141-152 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Visual and subjective methods for evaluation of surface appearance irregularity of chemically bonded nonwovens are compared. The image analysis system LUCIA is used for estimation of characteristics describing appearance. The analysis of subjective and objective estimates of surface appearance irregularity is realized by the coefficient of variation and by the ANOVA type model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910282280
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  • 83
    Digitale Medien
    Digitale Medien
    A guide line for manufacturing "ideal fabrics" (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 134-144 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: This paper reports the recent progress in the ideal fabrics project that started in 1996. The aim of this project is to initiate the engineered manufacturing of "ideal fabric". Ideal fabric is the fabric which satisfies the three conditions, good hand, good appearance of suit, and mechanical comfort for wear. The objective evaluation method of these three properties has been developed, and these objective method and fabric mechanics theories are fully applied to this project. Some ideal fabrics have been manufactured as the guideline for manufacturing ideal fabrics in the future. These trial fabrics are now being commercialized to assess the response of consumers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910276296
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  • 84
    Digitale Medien
    Digitale Medien
    Application of cluster analysis to fabric classification (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 206-215 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: This paper introduces a new way of classifying clothing fabrics objectively. Representative apparel fabrics were collected and measured by the Kawabata Evaluation System for Fabrics (KES-FB). The disjoint clustering method was used to divide fabrics into four clusters, each representing particular fabric performance and end-use characteristics. These classified clusters were further analyzed applying the method of principal-component analysis to acquire factor patterns that indicate the most important fabric properties for characterizing different fabric end-use. Extracted information from the instrumentally obtained data in terms of fabric physical properties is useful to fabric and garment producers, apparel designers, and consumers in specifying and categorizing fabric products, in insuring proper fabric use, and in controlling fabric purchase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910281966
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  • 85
    Digitale Medien
    Digitale Medien
    Made-to-measure garments for ladies - catering for wide ranging stature and length measurements for standard and outsize ladies (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 216-225 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A computer system for made-to-measure pattern production should have the capability of determining default measurements for sets of customer measurements input to the system where one or more of these measurements are missing. This paper recommends the use of default formulae rather than mathematical interpolation of size charts. These default formulae, when applied to a given size chart set, enable measurements to be determined efficiently over wide ranging customer sizes in both stature and girth. The specific default formulae for the German DOB charts are derived for Regular and Outsize charts and also for the full range of Height categories and Bust to Hip relationships, so that all sizes and shapes of customers are catered for. Default formulae have been applied in the MicroFit made-to-measure system from Garment Micro Systems and also implemented on this system for checking the validity of measurements entered into the system for each individual customer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910281975
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  • 86
    Digitale Medien
    Digitale Medien
    Water transfer properties of two-layer weft knitted fabric (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 198-205 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The aim of this study is to investigate the water (moisture vapor and liquid) transfer properties of two-layer weft knitted fabric and some related factors. Some experimental fabrics with specific yarns and stitch densities were prepared. Water vapor permeability rate through the fabrics and liquid water transfer from inner to outer layers were measured. The results show that the permeability rate is closely related to the porosity within the fabric while the transfer depends mainly upon the water absorption properties of the fibers on the two layers and degree of their difference.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910281948
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  • 87
    Digitale Medien
    Digitale Medien
    Microclimate ventilation of infant bedding (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 226-239 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The rate and volume of air exchanged between the bed microclimate and the ambient environment determines in part how much heat is lost from the human body. This study investigated the ventilatory characteristics of infant over-bedding to determine whether different combinations of bedding items (i.e. sheets, blankets, duvets) and types of tucking (i.e. loosely, firmly and swaddled/firmly tucked) affected microclimate ventilation. Microclimate volumes and air exchange rates were determined and used to calculate the ventilation indices. The presence of a duvet in the bedding combination resulted in lower ventilation indices than when bedding did not include a duvet. The type and combination of blankets did not significantly affect ventilation indices. The type of tucking had a significant effect on ventilation indices only when the assembly did not include a duvet.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910291677
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  • 88
    Digitale Medien
    Digitale Medien
    Effect of hem edges on the interface pressure of pressure garments (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 251-262 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Pressure garments are mainly made of elastic Lycra fabrics and tailor-made to individual patients' measurements to provide an appropriate amount of skin-garment interface pressure for burn rehabilitation. However, the fabric tension would be different at various locations from the hem edges of pressure garments, and thus the skin-garment interface pressure cannot be uniformly maintained over the interface surface. Aims to investigate the pattern of interface pressure changes caused by the different types of edge finish used for making pressure garments. The effect of garment sizes on the change of interface pressure was also examined. Experiments were carried out using two selected elastic Lycra fabrics, four types of hem finish and three different garment sizes. The results of the study provide a guideline for designing the edge finish of pressure garments, and a minimum margin from the hem edges of garments to the scar area is also recommended.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910297527
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  • 89
    Digitale Medien
    Digitale Medien
    Estimating thermal resistance of the bedding assembly from thickness of materials (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 262-276 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The purposes of this work were to determine: whether thickness of single layers can be used to accurately predict thickness and thermal resistance of multiple layer assemblies; and to identify variables affecting the total thickness (i.e. textile plus air layers) of bedding during simulated use. Thickness was determined when: materials were flat; and arranged over an infant manikin simulating use. Thermal resistance was measured using a guarded-hotplate similar to that specified in ISO 11092:1993(E). During simulated use, the site of measurement, body position, tucking, and product type significantly affected thickness of bedding. Equations for predicting thickness and thermal resistance (dry) of multiple-layer materials are described. While it was possible to predict thickness and thermal resistance of flat bedding from estimated values, extrapolation to bedding during simulated use was considered inappropriate, with significant differences of over 1,000 per cent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910297536
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  • 90
    Digitale Medien
    Digitale Medien
    Multiaxial determination of the resistance to creasing of clothing wool fabrics (1999)
    Bingley : Emerald
    International journal of clothing science & technology 11 (1999), S. 277-286 
    Details
    ISSN: 0955-6222
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: In this paper, values of deformation components (elastic, viscoelastic, plastic) of clothing wool fabrics by measuring the crease recovery angle in various directions to the warp direction (0°-warp, 30°, 45°, 60°, and 90°-weft) were determined. The size as well as the change of deformation component from warp to weft direction was presented through polar diagrams. On the basis of the results of investigation it is possible to conclude that all investigated fabrics (plain, 2/2 twill, cross twill), regardless of the biaxiality concerning quickly reversible (elastic) deformation, tend toward isotropy in total reversible deformation (elastic + viscoelastic). Concerning the plastic deformation value, mentioned investigated fabrics also express tendency toward isotropy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09556229910297545
    Standort Signatur Erwartet Verfügbarkeit
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  • 91
    Digitale Medien
    Digitale Medien
    Finite element analysis of radial cooled rotating electrical machines (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 18-38 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Accurate prediction of temperature distribution in an electrical machine at the design stage is becoming increasingly important. It is essential to know the locations and magnitudes of hot spot temperatures for optimum design of electrical machines. A methodology based on axi-symmetric finite element formulation has been developed to solve the conduction-convection problem in radial cooled machines using a new eight noded solid-fluid coupled element. The axi-symmetric model adopted is formulated purely from dimensional data, property data and published convective correlations. Steady state temperatures have been determined for 102 kW radial cooled motor at 100 percent and 75 percent loads and are validated with experimental results obtained from heat run tests. Parametric studies have been carried out to study the effect of critical parameters on temperature distribution and for optimising the design.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910251086
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  • 92
    Digitale Medien
    Digitale Medien
    A comparison study on fin surfaces in finned-tube heat exchangers (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 92-106 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A three-dimensional numerical study was conducted to assess the heat transfer performance of extended fins in a two-row finned tube heat exchanger. Fins under investigation were plane and slit types. A finite volume discretization method and a SIMPLE-based solution algorithm were, respectively, applied to working differential equations and their discrete counterparts to compute the gas velocities and pressure. The temperatures of solid and gas phases were computed from the same energy equation with different diffusivities and prescribed convective fluxes. The main objective of this study was to compare the transfer capabilities of the two investigated fin shapes. Their capabilities as a whole are presented in terms of the computed Nusselt number and the pressure drop across the flow passage.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910251149
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  • 93
    Digitale Medien
    Digitale Medien
    Flow over a slot-perforated flat surface between two parallel plates (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 136-150 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A theoretical and experimental study is performed to investigate unsteady, two-dimensional, incompressible fluid flow over both sides of a slot-perforated flat surface, which is placed in a two-dimensional channel. The governing boundary-layer equations are discretized by means of a finite-difference technique to determine streamwise and transverse velocity components. The roles of both the Reynolds number and the ratio of the slot width, d, to the plate thickness, d, on the velocity field are disclosed. It is found from the study that: (i) the flow pattern between two plates can be classified into four categories depending on a combination of Re and d/d, (ii) at a small value of Re and/or d/d, flow over the slot exhibits no timewise variation, (iii) when Re and d/d exceed certain values, an alternate crossing of flow from one side of the plate to the other occurs across the slot, and (iv) a further increase in Re results in a complex flow both inside the slot and on the plate downstream of the slot. These results are confirmed by the flow visualization using ion-exchange resins.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910256009
    Standort Signatur Erwartet Verfügbarkeit
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  • 94
    Digitale Medien
    Digitale Medien
    Radiation-natural convection interactions in partitioned cavities (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 186-203 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Heat transfer by radiation and natural convection in a two-dimensional, air-filled square enclosure with a vertical partition of finite thickness and varying height was investigated numerically in the laminar regime. The horizontal end walls are assumed to be adiabatic, and the vertical walls are at different temperatures. Calculations are made by using a finite volume method and an efficient numerical procedure is introduced for calculating the view factors, with shadow effects included. The results indicate that the partition does not significantly modify the heat transfer rate through the cavity, especially at high Rayleigh numbers, provided that its height is less than 90 per cent of the cavity height. The effects of radiation on the velocity and the temperature fields and the overall heat transfer rates as a function of the widths of the vents, solid/fluid conductivity ratio and Rayleigh number are documented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910256036
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    Digitale Medien
    Digitale Medien
    Lewis-Ransing correlation to optimally design the metal-mould heat transfer (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 318-334 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: Heat transfer across the metal-mould interface has been modelled by a generalized equation referred to as the Lewis-Ransing Correlation. It has been shown that the spatial as well as temporal variation of the interfacial heat transfer coefficient can be optimally designed to achieve a desired solidification pattern. The technique has been validated on two practical examples achieving a complex solidification pattern.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910260167
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    ADM-WENO scheme and its application in compressible mixing flows (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 461-471 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: High order schemes, which are widely used in DNS and LES, received increasing attention in recent years with a number of variants being developed. However most of these schemes have difficulties in achieving high order accuracy near the boundary points. In order to solve this problem, the analytical discrete method (ADM) is proposed and presented in this paper. In addition, this method is convenient to construct the higher order WENO (weighted essentially non-oscillatory) scheme. Application of the ADM-WENO scheme to shock-tube problems and compressible mixing flows has shown it is robust and accurate in both shock-capturing and complex flow structures detection.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910266611
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  • 97
    Digitale Medien
    Digitale Medien
    Interaction of surface radiation and variable property natural convection in a differentially heated square cavity - a finite element analysis (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 423-443 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A finite element solution on the interaction of surface radiation and variable property laminar natural convection is presented. Finite element formulation of the governing equations, associated with variable property natural convection, and incorporation of the radiative boundary conditions has been extensively discussed. The study also aims to highlight the limiting value of the terminal temperature difference (TTD), below which the natural convection heat transfer becomes the sole heat transfer mode, i.e. the effect of surface radiation can be neglected. The effects of variations of emissivity and TTD are also presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910266594
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  • 98
    Digitale Medien
    Digitale Medien
    Bifurcation in steady laminar mixed convection flow in uniformly heated inclined tubes (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 543-567 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The fully developed laminar mixed convection flow in inclined tubes subject to axially and circumferentially uniform heat flux has been studied numerically for a Boussinesq fluid. Dual solutions characterized by a two- and a four-vortex secondary flow structure in a cross-section normal to the tube's longitudinal axis have been found for different combinations of the Grashof number Gr and of the tube inclination a for all Prandtl numbers between 0.7 and 7. In the two-parameter space defined by Gr and a dual solutions occur: at a given a, if the Grashof number exceeds a critical value Grl (for horizontal tubes Grl is approximately 5.5 × 105, 1.7 × 105 and 1.7 × 104 respectively for Pr = 0.7, 7 and 70); at a given Gr, if the tube inclination is below a critical value ac (for Gr = 106 this critical angle is approximately 62.5° and 83.5° respectively for Pr = 0.7 and 7). Numerical experiments carried out for developing flows indicate that the two-vortex solution is the only stable flow structure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910276845
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  • 99
    Digitale Medien
    Digitale Medien
    An approximate method for oxygen diffusion in a sphere with simultaneous absorption (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 631-643 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: The oxygen diffusion problem is usually formulated in two stages: first, the steady state and second, the moving boundary stage. In this paper, we will consider the solution of the second stage in which a new semi-analytical method for solving such a problem was developed. The present method starts by assuming a polynomial representing the profile of oxygen concentration, and then by some mathematical manipulation a system of linear equations is obtained. Numerical solution for the system with a simple scheme relating the moving boundary and its velocity leads to the unknown functions in the assumed polynomial.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910276115
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  • 100
    Digitale Medien
    Digitale Medien
    Nonsimilar solutions for mixed convection in non-Newtonian fluids along a wedge with variable surface temperature in a porous medium (1999)
    Bradford : Emerald
    International journal of numerical methods for heat & fluid flow 9 (1999), S. 601-611 
    Details
    ISSN: 0961-5539
    Quelle: Emerald Fulltext Archive Database 1994-2005
    Thema: Maschinenbau
    Notizen: A nonsimilar boundary layer analysis is presented for the problem of mixed convection in power-law type non-Newtonian fluids along a vertical wedge with variable wall temperature distribution. The mixed convection regime is divided into two regions, namely, the forced convection dominated regime and the free convection dominated regime. The two solutions are matched. Numerical results are presented for the details of the velocity and temperature fields. A discussion is provided for the effect of viscosity index on the surface heat transfer rate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1108/09615539910276133
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