• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.914-919
• /
• 2000

In most case high temperature components in fossil power plant are damaged by fatigue, creep and degradation. Design of power plant components is based on ideal loading such as temperature, pressure and so on. But in many cases unexpected loadings are applied at components. A key ingredient in plant life extension is the preventive diagnosis technology and remaining-life-assessment technology. This paper describes diagnosis technology and life-assessment technology for power plant boiler. It helps in setting up proper inspection schedules, maintenance procedures, and operating procedure.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.33 no.5
• /
• pp.373-380
• /
• 2009

The evaporation process of multi-component fuel is different from one of a single component, because the properties of each component affects among the components. In actual engine, the spatial distribution of fuel vapor concentration dominates auto-ignition and initial combustion, and depends on the volatility and diffusivity of each component fuel contained in the multi-component fuel. Then, this study proposes a simplified numerical scheme for analysis of evaporation process of multi-component fuel sprays. Evaporation process is calculated by KIVA-II code based on the simple two-phases region that is approximated by modified saturated liquid-vapor line, which was obtained by connecting the 50% distillation temperature for each component under several pressure fields. Consequently, it can be quantitatively simulated that vapor of low boiling fuel component mostly exists around nozzle and spray tip region, the high boiling duel component, on the other hand, mostly appears near the spray tip.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.258-263
• /
• 2000

River water is higher in temperature than the surrounding environment during the winter. It is highly suitable a heat source for heat pump system. Despite its suitability, however, it is not widely used, due to its fouling and corrosive nature in heat exchanger tubes of evaporator. It is designed prior-treatment system which come into direct contact with the river water, such as auto-seamer, ozone generator for bactericidal test and auto-cleaning system. And it is analyzed treatment effects for its operation. It is designed two-stage compression heat pump system using R-134a with heating load 35.16kW, ad analyzed its performance. As a result it is obtained 3.08 COP when mid-point pressure is 1,200kPa, and bypass ratio of flowing refreigerant to high-stage compressor is 25.1%

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.12
• /
• pp.1027-1031
• /
• 2001

A new constant growth technique to conserve an initial grating height of V-groove AlGaAs/InGaAs quantum nanostructures above 1.0 $\mu\textrm{m}$ thickness has been successfully embodied on submicron gratings using low pressure metalorganic chemical vapor deposition. A GaAs buffer prior to an AlGaAs barrier layer on submicron gratings plays an important role in overcoming mass transport effects and improving the uniformity of gratings. Transmission electron microscopy (TEM) image shows that high-density V-groove InGaAs quantum wires (QWRs) are well confined at the bottom of gratings. The photoluminescence (PL) peak of the InGaAs QWRs is observed in the temperature range from 10 to 280 K with a relatively narrow full width at half maximum less than 40 meV at room temperature PL. The constant growth technique is an important step to realize complex optoelectronic devices such as one-step grown distributed feedback lasers and two-dimensional photonic crystal.

• Proceedings of the KIEE Conference
• /
• 2002.07c
• /
• pp.1413-1415
• /
• 2002

The Displacement current measurement system used in this experiment because detecting the dynamic behavior of monolayers at the air-water interface is possible. It basically consists of a film balance, a pair of electrodes connected to each other through a sensitive ammeter. Here, one electrode is suspended in air and the other electrode is placed in the water. PBLG phase transformation measured by Maxwell-displacement-current-measurement method in surface of the water. Measured (surfacc pressure, displacement current and dipole moment) of monolayers of PBLG on the water surface. We measured displacement current that occur when changed temperature(15, 20, 25$^{\circ}$ ) and the compression speed(30, 40, 50(mm/min)). From the result, it is known that curren generated in the range of high surface pressur compression velocity and temperature become faste.

• Proceedings of the KIEE Conference
• /
• 1999.11d
• /
• pp.888-890
• /
• 1999

ZnO thin films on (001) sapphire substrates have been deposited by pulsed laser deposition using a Nd:YAG laser with the wavelength of 355 nm at an oxygen pressure of 350 mTorr. In order to investigate the effect of the substrate temperature on the properties of ZnO thin films, the experiment has been performed at various substrate temperatures in the range of $200^{\circ}C$ to $700^{\circ}C$. According to XRD, (002) textured ZnO films of high crystalline quality have been obtained by pulsed laser deposition technique. However, the intensity of UV emission is mostly depending on the stoichiometry of ZnO films.

• Proceedings of the SAREK Conference
• /
• 2005.11a
• /
• pp.451-456
• /
• 2005

The mathematical model for the heat exchangers of absorber and desorber is made in the elementary control volume method and the thermodynamic properties of working fluid. water/ammonia mixture. are calculated by some fundamental subroutines in RefProp 7.0 and flash subroutines made by authors The simulation results show that two-stage cycle has higher COP than single stage if temperature lift is high: the performance of single stage compression cycle can be improved by increase of absorber pressure. but the performance of two-stage compression cycle can not be improved in this way : the compressor discharging temperature of two-stage compression is much lower than that of single stage cycle. which is very important to the safety operation of CA heat pump. Major parameter comparison between the cycles at their optimal configurations is also given.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.7
• /
• pp.1075-1078
• /
• 2005

Hydrogen adsorption on various porous materials have been studied with a volumetric method at low temperature in the pressure of 0-760 torr. Their hydrogen uptakes depend at least partly on microporosity rather than total porosity. However, it is also necessary to consider other parameters such as pore size and pore architecture to explain the adsorption capacity. The heat of adsorption and adsorption-desorption-readsorption experiments show that the hydrogen adsorption over the porous materials are composed of physisorption with negligible contribution of chemisorption. Among the porous materials studied in this work, SAPO-34 has the highest adsorption capacity of 160 mL/g at 77 K and 1 atm probably due to high micropore surface area, micropore volume and narrow pore diameter.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.10 no.2
• /
• pp.3-8
• /
• 1973

In a recent year, welding is known as a most powerful process in production of pipe. For the conventional purpose, pipe is welded in axial direction to minimize the welding cost. And for the high pressure pipe, welding is done in helical direction to increase a allowable hoop stress. An analytical welding temperature distributions in a metal tube are obtained as a two dimensional case in quasi-stationary state. Numerical values which have been obtained by the analytical investigation shows a good agreement with the isocromatic lines which have been appeared at oxidized zone along the welds. Therefore it is thought that the analytical result can be used in estimating the heat effect upon the material such as a residual stress and strain, metallurgical change and etc..

• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.2186-2188
• /
• 2000

A fiberoptic sensor using an SLD as a light source has been studied. The sensor system employs an intrinsic fiber Fabry-Perot interferometer as a sensing tip and a fiber Mach-Zehnder interferometer as a processing one. A free loading test for temperature application shows that the fiberoptic sensor has a wide-dynamic range as well as high resolution. Due to the inherent property of the optical fiber itself and the intrinsic Fabry-Perot interferometer. the fiberoptic sensor gives obvious benefits when it is applied to harsh environments to monitor some physical parameters such as temperature, strain, pressure and vibration.