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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 26-28 (Oct. 2007), p. 1049-1052 
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this study, numerical analysis applying the finite element method (FEM) was used toinvestigate the effect of heat flux and temperature on thermal strain of aluminum alloy casting mold.For numerical analysis, analysis model was considered the effect of shrinkage, rapid temperaturevariation on the casting mold and was applied the temperature calibration to reduce the deformationand stress by temperature difference of inside and outside the mold during the cooling process. Indetail, temperature, deformation and stress distributions occurred inside of casting mold predicted bynumerical method and then investigated the correlations between the heat flux and temperaturevariation during the cooling process. As a result, aluminum alloy casting mold is occurreddeformation and stress because of rapid temperature difference in the initial of cooling, but it can bereduced the thermal strain through the heat flux control and temperature calibration. Accordingly, thetechnique of this numerical study will be helped to make the effective and the good quality of castingmold products
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 326-328 (Dec. 2006), p. 1145-1148 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The present study is investigated the causes of enhanced heat transfer during the meltingprocess of solid-liquid PCM (Phase Change Material) using an ultrasonic vibration. Paraffin (noctadecane)was selected as a PCM and experimental studies were performed as following. Heattransfer coefficient and enhancement ratio of heat transfer was measured, acoustic streaminginduced by ultrasonic waves observed using a PIV (Particle Image Velocimetry) and thermallyoscillating flow phenomenon observed using an infrared thermal camera during the melting process.For the numerical study, a coupled FE-BEM (Finite Element-Boundary Element Method) wasapplied to investigate acoustic pressure occurred by acoustic streaming in a medium. And then, theprofiles of pressure variation compared with the enhancement ratio of heat transfer. The results ofthis study revealed that ultrasonic vibrations accompanied the effects like acoustic streaming andthermally oscillating flow. Such effects are a prime mechanism in the overall melting process whenultrasonic vibrations are applied. Also, as the acoustic pressure occurred by acoustic streamingincreases, the higher enhancement ratio of heat transfer is obtained
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 324-325 (Nov. 2006), p. 1075-1078 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The present study was investigated on the melting phenomena and the accelerative factorsof phase change material (PCM) by acoustic streaming induced ultrasonic vibrations. To investigatethe melting phenomena and accelerative factors, the experimental study was measured the liquidtemperature and melting time of PCM and was observed the velocity vectors and thermal fluid flowinduced acoustic streaming to investigate the heat transfer using particle image velocimetry (PIV) andinfrared thermo vision camera, respectively. Also, the numerical study based on a coupled finiteelement-boundary element method (Coupled FE-BEM) was performed to investigate the analysis ofpressure field in the PCM. The results of experimental works revealed that acoustic streamingobserved by PIV and infrared thermo vision camera is one of the prime effects accelerating phasechange heat transfer. And, the final temperature of PCM is lower and melting speed is 2.6 times fasterthan that without ultrasonic vibrations when ultrasonic vibrations are applied. The results ofnumerical work presented that acoustic pressure is higher near the ultrasonic transducer than otherpoints where no ultrasonic transducer was installed and develops more intensive flow such as acousticstreaming, destroying the flow instability. Moreover, the profile of acoustic pressure variation isconsistent with that of enhancement of heat transfer
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 324-325 (Nov. 2006), p. 1087-1090 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In the present study, numerical work applying a finite element method (FEM) is used toanalyze the characteristics of aluminum (Al) alloy mold for thermal strain control. In the concrete, thetemperature distribution on the inside of Al alloy mold, the contraction rate and stress occurred bytemperature variations are investigated to predict the accurate measurement variation of Al alloy moldduring the cooling process. In addition, the numerical result of the Al alloy mold were compared withthose of mild steel mold in order to obtain the improvement and good quality of mold. In the end, thenumerical results such as temperature distributions, contraction rate and stress are presented to help tomake the effective and the best mold products. Besides, the introduced technique of numericalanalysis applying a FEM is very useful and important things in the fracture and damage mechanics,especially needs the accuracy improvement such as Al alloy mold products
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 47-50 (June 2008), p. 1039-1042 
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This study was numerically and experimentally investigated on improvement capturevelocity for increasing inhalation efficiency of hood in local ventilation system. The inhalationefficiency of hood was studied to improve by increasing inhalation force of the hood that attached thenew device named “Gas-Guide-Device (GGD)”. Also, harmful material that couldn’t inhale in hoodwas removed by increasing capture velocity at the edge of hood. For the numerical study,computational fluid dynamic (CFD) was used to predict the improvement of flow velocity withattached GGD in hood. To verify the numerical result, the flow velocity was experimentally measuredusing a hot-wire type anemometer. As a result of the numerical and experimental study for improvingthe effect of the GGD on the inhalation efficiency of the hood, it was verified that the capture velocityaround the hood inlet was relatively higher for the hood with the GGD than for the one without it
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 47-50 (June 2008), p. 1043-1046 
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper investigates on three-dimensional thermal deformation of aluminum casting tiremold applying metal casting method by numerical analysis and experiment. In this study, thenumerical analysis was performed based on finite element method (FEM) in order to predict thermaldeformation in tread part of tire mold by completely cooling about 50°C. For the numerical analysis,“COMSOL Multiphysics 3.3 Ver.” a commercial program for heat transfer and thermal-structuralanalysis, was used. In order to verify the results calculated by the numerical analysis, the experimentwas carried out applying metal casting method on the same condition of numerical analysis. For theexperiment, the temperature profile inside the aluminum casting tire mold was measured usingthermocouples by completely cooling. When the temperature profile calculated by the numericalanalysis and measured by the experiment were compared with each other, it appeared that was a slighttemperature difference between the two results by latent heat of aluminum alloy, but their coolingpatterns were almost similar
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 544-545 (May 2007), p. 179-182 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The present study was experimentally investigated the effect of ultrasonic vibrations onboiling heat transfer augmentation during the heating process. The experiments were carried outunder the constant wall temperature condition and were divided into two cases applying with andwithout ultrasonic vibrations, respectively. Also, the temperature distributions in a vessel filled withwater were measured using thermocouples during the heating process, heat transfer coefficient andaugmentation ratio of heat transfer on states of convection, subcooled boiling and saturated boilingwere calculated from obtained temperature profiles. In addition, the profiles of pressure variationsmeasured using a hydrophone were compared with the augmentation ratio of heat transfer in acousticfields. The results of experimental study were revealed that general profiles of heat transfercoefficient and augmentation ratio of heat transfer is more increased the convection state than theothers states. Moreover, the profiles of acoustic pressure is relatively higher near ultrasonic transducerthan other points where is no installed it and affects the augmentation ratio of heat transfer. In the end,as well as known “acoustic streaming” induced by ultrasonic vibrations is one of the prime effectsacoustically augmented boiling heat transfer or phase change heat transfer
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 580-582 (June 2008), p. 139-142 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In the present study, AC7A aluminum alloy casting mold which consist of 8 pieces isintroduced as an analysis model. Also, numerical work using a finite element method was applied toinvestigate the thermal strain that included the temperature distribution, stress and strain during thecooling process in AC7A casting mold. In addition, the numerical work was carried out that analysisresults of the AC7A casting mold were compared with those of mild steel casting mold to prove theimprovement and good quality. The numerical results such as temperature distributions, stress andstrain are presented to help to make the effective and the best tire mold. In addition, the introducedtechnique of numerical work using a finite element method is very useful and especially needs toimprove the precision of tire mold such as sectional type or puzzle type
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 449 (2007), S. 781-781 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Sir James E. Lovelock and Chris G. Rapley, in their Correspondence 'Ocean pipes could help the Earth to cure itself' (Nature 449, 403; doi:10.1038/449403a 2007) propose a variant on some well-publicized schemes to ...
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 447 (2007), S. 999-1002 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The flux of organic material sinking to depth is a major control on the inventory of carbon in the ocean. To first order, the oceanic system is at equilibrium such that what goes down must come up. Because the export flux is difficult to measure directly, it is routinely estimated indirectly ...
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