• Corrosion Science and Technology
• /
• v.4 no.1
• /
• pp.33-38
• /
• 2005

Some feasibility studies are conducted to produce an advanced ceramic coating, which reveals superior chemical and mechanical strength, on metal base structure used in chemical plant. This advanced coating on metallic frame can replace ceramic delivery pipe and reaction chamber used in chemical plant, which are operated in hi-temperature and corrosive/erosive environment. An dual spraying is adopted to reduce the residual stress in order to increase the coating thickness and the residual stress is estimated by in-situ manner. Then new methodology is tried to form special coating of yttrium aluminum garnet(YAG), which reveals hi-strength and low-creep rates at hi-temperature, superior anti-corrosion property, hi-stability against Alkali-Vapor corrosion, and so on, on iron base structure. To verify the formation of YAG during thermal spraying, XRD(X ray diffraction) technique was used.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.765-766
• /
• 2006

[ $Mo_2FeB_2$ ] boride base cermets produced by a novel sintering technique, called reaction boronizing sintering through a liquid phase, have excellent mechanical properties and wear and corrosion-resistances. Hence, the cermets are applied to the injection molding die-casting machine parts and so on. We investigated that the effect of deoxidization and sintering temperature on mechanical properties and deformation of the MIM processed cermets. As a result, deoxidization temperature of 1323K and sintering temperature of 1518K were suitable. The MIM products of the cermets showed allowable dimensional accuracy and the same mechanical properties as the press-sintered ones.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.55 no.5
• /
• pp.278-285
• /
• 2006

A micro hotplate for micro gas sensor was fabricated by MEMS technology. In order to heat up the gas sensing material to a target temperature, a micro hotplate was built on the gas sensor. The sensing material was deposited on the heater and electrodes, and did not contact with the silicon base to minimize the heat loss to the silicon base. The electric power to heat up the gas sensor was measured. The temperature distribution of micro gas sensor was analyzed by a CFD program. The predicted electric power to heat up th sensing material showed a good agreement with the measured data. The design of micro gas sensor could be modified to increase the temperature uniformity and to decrease the electric power consumption by optimizing the layout of micro hotplate and electrodes.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2019.05a
• /
• pp.116-117
• /
• 2019

3D printing technology can be applied to various industries, and is trapped by major technologies that change existing manufacturing processes. 3D printing materials must satisfy designability, economy and productivity, and building materials are required to have strength and economy secured technology. 3D printing technology of construction field can be divided into structural materials and internal and external materials, and is mainly done by extruding and adapting. Particularly when it is applied as an exterior materials, it is mainly applied to an unstructured exterior materials and high accuracy is required. The exterior materials can be used as a cement composite materials, it is suitable also for a lamination type, and the role of a cement base composite material is important. In this research, we developed a cementitious base binder applicable as a 3D printing exterior materials, confirmed high temperature strength characteristics for application as an exterior materials of buildings and confirmed its possibility.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1388-1393
• /
• 2004

Investigators have been perplexed with the thermal phenomena behind the recently discovered nanofluids, fluids with unprecedented stability of suspended nanoparticles although huge difference in the density of nanoparticles and fluid. For example, nanofluids have anomalously high thermal conductivities at very low fraction, strongly temperature-dependent and size-dependent conductivities, and three-fold higher critical heat flux than that of base fluids. Traditional conductivity theories such as the Maxwell or other macroscale approaches cannot explain why nanofluids have these intriguing features. So in this paper, we devise a theoretical model that accounts for the fundamental role of dynamic nanoparticles in nanofluids. The proposed model not only captures the concentration and temperature-dependent conductivity, but also predicts strongly size-dependent conductivity. Furthermore, we physically explain the new phenomena for nanofluids. In addition, based on a proposed model, the effects of various parameters such as the ratio of thermal conductivity of nanofluids to that of a base fluid, volume fraction, nanoparticle size, and temperature on the thermal conductivities of nanofluids are investigated.

• Proceedings of the SAREK Conference
• /
• 2008.11a
• /
• pp.269-274
• /
• 2008

The present study has been studied on a thermal and flow characteristic of the microchannel waterblock with flow distributions in each channels. Results of a numerical analysis using the CFX-11 are compared with results of an experiment. Numerical analysis and experiment are conducted under a heat transfer rate of 150W, inlet temperature of $20^{\circ}C$ and mass flow rates of $0.7{\sim}2.0\;kg$/min. Base temperature and pressure drop are investigated with standard deviations of mass flow rates in each channels of samples at 0.7 kg/min.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.25-28
• /
• 2000

In this study, Transient Characteristics of the Punch-Through Insulated Gate Bipolar Transistor (PT-IGBT) has been studied. On the contraty to Non-Punch Through Insulated Gate Bipolar Transistor(NPT-IGBT), PT-IGBT has buffer layer It has a simple drive circuit controlled by the gate voltage of the MOSFET and the low on-state resistance of the bipolar junction transistor. In this paper, the transient characteristics with temperature of the PT-IGBT has been analyzed analytically. PT-IGBT is made to reduce switching power loss. Excess Minority carrier distribution inactive base region and base charge, the rate of voltage with time is expressed analytically to include buffer layer.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.4
• /
• pp.377-383
• /
• 2012

The temperature distribution of an asymmetric trapezoidal fin with various upper lateral surface slopes is investigated by using the two-dimensional analytic method. For this asymmetric fin, convection from the inner fluid to the inner wall, conduction from the inner wall to the fin base and conduction through the fin base are considered simultaneously. The temperature profile with the variation of dimensionless fin length and height coordinates is shown. Also, the temperature variation at the bottom tip of the fin is presented as a function of the fin shape factor. Heat losses through the fin base and from each side are compared for variations in fin length. One of the results shows that temperature at the fin bottom tip decreases linearly as the fin shape factor increases.

• Journal of the Korean Society for Heat Treatment
• /
• v.13 no.1
• /
• pp.1-9
• /
• 2000

The microstructural characteristics and low temperature tensile properties between $25^{\circ}C$ and $-196^{\circ}C$ for as-welded and age hardened specimen by using Al 5083-H321 for base metal, 5083-5356 and 5083-4043 weldments have been investigated. The hardness of 5083-5356 weldment decreases with aging treatment, whereas the weld region of 5083-4043 weldment shows remarkable increase in hardness after aging due to the precipitation of fine Si particle at the grain boundaries and interiors. Low temperature tensile properties of 5083 AI base metal, 5083-5356 and 5083-4043 weldments appear to be the increment of tensile strengths and elongations at the room temperature and $-196^{\circ}C$, while the decrement of tensile properties around $-50^{\circ}C$ is shown. Through the observation of fine serration to fracture in the stress-strain curve and tensile fractography, the increment of localized deformation leading to promote the neck initiation and the increment of the dimple size cause to decrease in tensile strengths and elongations around $-50^{\circ}C$. For the tensile specimen of the 5083 base metal, 5083-5356 and 5083-4043 weldments, the reason to increase in elongation after solution and aging treatment is the diminishment of fine pit, the resolution of Mg into the matrix and the spheridization of the eutectic Si.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.6 no.4
• /
• pp.325-330
• /
• 2005

A lever type CO micro gas sensor was fabricated by MEMS technology. In order to heat up the gas sensing material, $SnO_2$, to a target temperature, a micro heater was built on the gas sensor. The heater and electrodes were hanged on the air as a bridge type to minimize the heat loss to the silicon base. The sensing material laid on the heater and electrodes and did not contact with the silicons base. The temperature distribution of micro gas sensor was analyzed by a CFD program, FLUENT. The results showed that the temperature of silicon wafer base was almost similar to that of the room temperature, which indicates that the heat generated at the micro heater heated up effectively the sensing material. The required electric current of micro heater to heat up the sensing material to the target temperature could be predicted.