• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.1
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• pp.66-71
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• 2004

Magnesium alloys have been widely used for many structural components of automobiles and aircraft because of high specific strength and good cast-ability in spite of hexagonal closed-packed crystal structure of pure magnesium. In this study, it is studied about the forming characteristics of press forging of AZ31 magnesium alloy by MSC/MARC in case of material having one boss and MSC/Supeiforge in case of material having multi-boss with heat transfer analysis during deformation at elevated temperature. For these results it is simulated about temperature distribution, strain distribution, and stress distribution of AZ31 Magnesium alloy. During the press forging, foot regions of bosses showed greater temperature rise than other areas of AZ31 sheet. Finally the plastic strain of AZ31 sheet did not remarkably vary with increasing temperature from 373 to 473K, while it significantly increased as the forming temperature increased from 473 to 573K, which is related with the change in micro-structures, such as dynamic re-crystallization occurring during the deformation process.

• Journal of the Korean Society of Visualization
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• v.16 no.2
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• pp.16-22
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• 2018

This study investigates dynamic wetting behaviors of a water droplet placed on surfaces with different wettability and nano-structures. Hydrophobic and hydrophilic properties on as-received silicon wafers were prepared by fabricating thin films of hydrophobic polymer and hydrophilic nanoparticles via layer-by-layer coating. Dynamic advancing contact angle of droplets on the prepared surfaces was measured at various moving velocities of triple contact line with a high-speed video camera. As advancing velocity of triple contact line increased, dynamic advancing contact angle on the as-received silicon and hydrophobic surfaces sharply increased up to $80^{\circ}$ in the range of order of mm/sec whereas the SiO2 nanoparticle-coated hydrophilic surface maintained low contact angles of about $30^{\circ}$ and then it gradually increased in the velocity range of order of hundred mm/sec. The improved dynamic wetting ability observed on the nanostructured hydrophilic surface can benefit the performance of various phase-change heat transfer phenomena under forced convective flow.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.3
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• pp.234-239
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• 2011

In this study, the heat transfer capability have been improved by using via-holes in FR4 PCB, when the LED lighting is designed to solve the thermal problem. The thermal resistance and junction temperature were measured by changing the dimension of FR4 PCB and size of via hole. As a result, when the dimension was increased initially, the thermal resistance and junction temperature was decreased rapidly, the ones was stabilized after the dimension of 200 $[mm^2]$. Also, the light output was improved up to maximum 17% by formation of via-hole and expansion of dimension in FR4 PCB. Therefore, the thermal resistance and junction temperature could be improved by expansion of PCB dimension and configuration of via-hole ability.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.965-973
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• 1992

Boilers, which are considered to be one of the basic equipment in industry, consume large potion of nation's petroleum and their demand is growing everyday. In recent, the technology improvement in production of high efficiency boilers and their effective utilization is needed for design of boiler which steam condition is the large capacity of high temperature and high pressure. It is necessary that boiler control system be studied for high efficiency, high reliability and smooth operation. The control of drum pressure and water level particularly becomes an important task for greater accuracy with the avail ability of boiler operation. To achieve this aim, dynamic analysis of a boiler is accomplished by choosing a boiler as a model. Transfer function thus obtained is made a comparison of measurement with reckoning to technical design data. The results of comparison makes it possible to verify thermodynamical analysis on the dynamic behavior of the overall system.

• Journal of Drive and Control
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• v.18 no.1
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• pp.1-8
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• 2021

This paper presents research on methods for the reduction of forklifts' noise level for the increased comfort and safety of its operator. A cooling fan with a high air volume flow rate installed in the forklift acts as an important design parameter which efficiently cools the heat exchanger system, helping to transfer internal heat from the engine room to the outdoors with both transmitted and diffracted opening noises. The cooling fan contributes significantly to both the forklift's emitted sound power and the operator room's noise level, thereby necessitating research on the forklift's reduction of acoustic power level and transmission. A noise analysis for various fan models with a biomimetic design based on eagle-wing geometry was conducted. In addition to the acoustic power generation, the aerodynamic performance of the cooling blade is also strongly influenced by the design of airfoil distribution, thereby requiring optimization. The cooling fans were fabricated and installed in the forklift in order to check the efficacy of the forklift engine's cooling, and the final version of the fan was measured for its ability to lower acoustic power level and cool the engine room. This study explains the aerodynamic and acoustic features of the designed fans with the use of BEM analysis and forklift test results.

• Journal of Navigation and Port Research
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• v.40 no.1
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• pp.7-14
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• 2016

Although the life jacket can provide the buoyance with the drowner, heat loss can make the drowned individual be subject to the hypothermia. In this study, The thermal insulation of two types life jacket including inflatable and foam type were evaluate by both experiments and numerical analysis. To estimate the thermal resistance of the jackets, experiments on the heat flux were conducted by the thermal manikin exposed to cold water. Heat flux loss on the surface of thermal manikin were measured for both foam and inflatable type life jacket. Also, finite element method is applied to a body section in order to understand the level of hypothermia of each life jacket. The segmental of human thigh is represented by a multi-layered section which considers the heat conduction within tissue, bone and fat. As a result, the thermal resistance and hypothermia time of each jackets have been compared based on the finite element analysis. It was found that the insulation ability of suggested life jackets is better than that of conventional type.

• Journal of Korean Society of Forest Science
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• v.63 no.1
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• pp.12-20
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• 1984

This research was performed to estimate the properties of particleboard based on the press time and temperature which was made of chip of larch that grows in Korea. The results in this study were as follows: 1) Even though the chips, 1:1-35 ratio between length and thickness, are relatively bad condition, the surface smoothness that can easily spread the adhesive evenly and thoroughly and bonding ability of chips can give proper physical properties. 2) It shows more mechanical properties at the press time of 10 min. in MOR (Modulus of Rupture), MOE (Modulus of Elasticity) and SHA (Screw Holding Ability). 3) It is not significant according to the press time 20 min. in MOR, IBS (Internal Bonding Strength) and SHA, for the reciprocal actions between the accelerating aging effect of chip and the softening effect of adhesion are occured. 4) IBS is rising according to the increasing temp at the press time of 10 min. Because it needs to transfer the plate heat to make the proper hardening temp. In the layer. 5) The heat treatment effects have greatly influenced the stahility of dimension by falling the absorption, anisotropy and inhomegenity. As a result of these the values of thickness and linear expansion ratio were respectively dropped by the increase of press temp and the time and so did absorption.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.727-736
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• 2017

In this study, the method of evaluation of moisturizing ability of cosmetics using specimens was studied as an alternative method of clinical tests. Cosmetic spreadability, surface drying, and moisture loss rate of four specimens (Japanese cake (Maru mochi), Garaetteok, wheat flour, and agar) were evaluated. Also, the water loss rate of the specimens and the transepidermal waterloss were analyzed for 10 kinds of lip make-up products (5 kinds of lipstick, 3 kinds of lip balm, 2 kinds of lip gloss). The moisture loss rate (moisture evaporation sensitivity) of the agar specimen was highest in the order of agar> Garaetteok> Japanese cake> wheat flour. Agar specimens are the most suitable in terms of spreadability, surface crack, and raw material supply. Containers for the preparation of agar specimens are suitable for plastic materials with low heat transfer, which can produce convex, smooth surface specimens. In the evaluation of moisturizing ability of lip makeup products, there was a strong correlation between the water loss rate and the transepidermal waterloss rate measured with agar specimens. These results show that the proposed method can be used as one of the useful alternative test methods.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.4
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• pp.419-424
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• 2012

In addition to respiration, the nose performs three other major physiological functions-air-conditioning, filtering, and smelling. On the basis of our experience in experimental investigations of nasal airflows in normal and abnormal nasal cavity models, airflows in the normal model and three artificially deformed models, which simulate the results of surgical treatments (inferior turbinectomy), are investigated by PIV and CFD. The left cavities of all three models are normal, and the right cavities are modified as follows: (1) excision of the head of the inferior turbinate, (2) resection of the lower fifth of the inferior turbinate, and (3) resection of almost the entire inferior turbinate. The use of high-resolution CT data and careful surface rendering of three-dimensional computer models with the help of an ENT doctor provide more sophisticated nasal cavity models. Nasal airflows for both normal and deformed cases are also compared.

• Journal of Energy Engineering
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• v.12 no.1
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• pp.1-10
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• 2003

Pressurized fluidized bed combustion unit is operated at pressures of 1~1.5 MPa with combustion temperatures of 850~87$0^{\circ}C$. The pressurized coal combustion system heats steam, in conventional heat transfer tubing, and produces a hot gas supplied to a gas turbine. Gas cleaning is a vital aspect of the system, as is the ability of the turbine to cope with some residual solids. The need to pressurize the feed coal, limestone and combustion air, and to depressurize the flue gases and the ash removal system introduces some significant operating complications. The proportion of power coming from the steam : gas turbines is approximately 80:20%. Pressurized fluidized bed combustion and generation by the combined cycle route involves unique control considerations, as the combustor and gas turbine have to be properly matched through the whole operating range. The gas turbines are rather special, in that the maximum gas temperature available from the FBC is limited by ash fusion characteristics. As no ash softening should take place, the maximum gas temperature is around 90$0^{\circ}C$. As a result a high pressure ratio gas turbine with compression intercooling is used. This is to offset the effects of the relatively low temperature at the turbine inlet.