• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.4
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• pp.89-97
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• 2008

A downdraft gasifier was manufactured for biomass gasification. The gasifier was designed based on the principles of gasification presented in previous studies. The pipes of 25mm diameter were used for both supplying air and discharging producer gas. Wood charcoals were mostly used for fuels. The concentration of CO ranged from 25 to 35%, comparable to the values presented in other studies. The temperature outside wall of the gasifier was measured up to $400^{\circ}C$, indicating a great heat loss. When glass wool was cover over the wall, some parts of wire mesh located in the bottom of the reactor were molten down. There were several modifications that should be made in order to improve its efficiency and obtain more stable continuous gasification, including insulation, reduction in pressure loss, durable bottom meshes, the optimum length of reaction part, and safety.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.237-239
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• 2003

A high-temperature superconductor (HTS) journal bearing was studied for loss. Two HTS bearings support the rotor at top and bottom. The rotor weight is 4 kg and the length is about 300 mm. Both the top and bottom bearings have two permanent magnet (PM) rings with an iron pole piece separating them. Each HTS journal bearing is composed of six pieces of superconductor blocks of size 35$\times$25$\times$10 mm. The HTS blocks are encased in a cryochamber through which liquid nitrogen flows. The inner spool of the cryochamber is made from G-10 to reduce eddy current loss, and the rest of the cryochamber is stainless steel. The magnetic field from the PM rings ＜ 10 mT on the stainless part. The rotational drag was measured over the same speed range. Results indicate that the 10 mT design criteria for magnetic field on the stainless part of the cryochamber is too high.

• Magazine of the Korean Society of Agricultural Engineers
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• v.14 no.1
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• pp.2557-2569
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• 1972

Hydraulic computations to determine the elevation of canal bottom and mater surface for box type concrete culverts are discussed. Velocity and cross sectional area of flow are computed from Manning's formula. Aad then head loss and velocity head are considered to determine the elevation of bottom and water surface. For stress analysis, 13.5 ton live load and earth pressure are considered. Also longitudinal stress of box culverts is checked.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.2
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• pp.28-33
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• 2008

This paper presents a continuous-time equalizer adopting a clock loss tracking technique for digital display interface. This technique uses bottom hold circuit to detect the incoming clock loss. The generated loss signal is directly fed to equalizer filters, building adaptive feed-forward loops which contribute the stability of the system. The design was done in $0.18{\mu}m$ CMOS technology. Experimental results summarize that eye-width of minimum 0.7UI is achieved until -33dB channel loss at 1.65Gbps. The average power consumption of the equalizer is a maximum 10mW, a very low value in comparison to those of previous researches, and the effective area is $0.127mm^2$.

• KIEAE Journal
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• v.12 no.3
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• pp.95-100
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• 2012

Thermal phenomena has caused abnormal weather phenomena due to the lack of urban green spaces To solve these problems, the country of recorded a city business is actively evolving trends. but in all the land, most built-up city's green buildings unless the demolition of the composition is an impossible situation, green space in urban areas, with emphasis on composition. In this study, thermal power plants that occured in the evolution of vegetation by utilizing Bottom Ash was tried to develop a lightweight block. Bottom Ash block to take advantage of vegetation is focused create green space in urban areas Vegetation in the block was carried out manufacturing lightweight, porous, lightweight water ratio suitable for three types of blocks selected according to its kind study on the manufacturing and process. Bottom Ash from this study at the time of disposal of coal ash generated by recycling the landfill shortages, loss of landfill costs, environmental pollution and are trying to solve the same problem at the same time.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.5
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• pp.389-395
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• 2005

The etching technology of the high aspect ratio contact(HARC) is necessary at the critical contact processes of semiconductor devices. Etching the $SiO_{2}$ contact hole with the sub-micron design rule in manufacturing VLSI devices, the unexpected phenomenon of 'profile tilting' or 'bottom distortion' is often observed. This makes a short circuit between neighboring contact holes, which causes to drop seriously the device yield. As the aspect ratio of contact holes increases, the high C/F ratio gases, $C_{4}F_{6}$, $C_{4}F_{8}$ and $C_{5}F_{8}$, become widely used in order to minimize the mask layer loss during the etching process. These gases provide abundant fluorocarbon polymer as well as high selectivity to the mask layer, and the polymer with high sticking yield accumulates at the top-wall of the contact hole. During the etch process, many electrons are accumulated around the asymmetric hole mouth to distort the electric field, and this distorts the ion trajectory arriving at the hole bottom. These ions with the distorted trajectory induce the deformation of the hole bottom, which is called 'profile tilting' or 'bottom distortion'. To prevent this phenomenon, three methods are suggested here. 1) Using lower C/F ratio gases, $CF_{4}$ or $C_{3}F_{8}$, the amount of the Polymer at the hole mouth is reduced to minimize the asymmetry of the hole top. 2) The number of the neighboring holes with equal distance is maximized to get the more symmetry of the oxygen distribution around the hole. 3) The dual frequency plasma source is used to release the excessive charge build-up at the hole mouth. From the suggested methods, we have obtained the nearly circular hole bottom, which Implies that the ion trajectory Incident on the hole bottom is symmetry.

• The Journal of the Acoustical Society of Korea
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• v.21 no.3
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• pp.213-220
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• 2002

The sound wave in the sea propagates under the effect of water depth, sound velocity structure, sea surface and bottom roughness, and bottom sediment distribution. In particular the sound velocity structure in shallow water varies with time and space, an? the sediment distributes very variedly with place. In order to investigate the seasonal variation of low-frequency sound propagation in the Yellow Sea, the propagation experiments were conducted along the same track in the middle part of the Yellow Sea at various seasons of spring. summer, and autumn. In this paper we consider the measurement results on the propagation loss with the sound velocity structure, and investigate the seasonal variation of the propagation loss. As a result, the propagation losses measured in summer were larger than the losses in spring and autumn. And the propagation losses measured in autumn were smaller than the losses in spring. The seasonal change of the propagation loss increased with the rise of sound frequency and the propagation range.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.525-528
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• 2004

The annual consumption of coal by coal-fired power plants is increasing. Also a large amount of ash is produced. The disposal of this large amount of ash makes the serious environmental problems and economical loss. Fly ash among the ash produced is used in building industries as a substitute to cement in concrete. But bottom ash is not used because of its poor properties. This study is aimed at the production of foamed concrete using bottom ash, to examine the physical properties of foamed concrete is manufactured by autoc1aving, and to exhibit the fundamental data to use it in site.

• Journal of the Korea Institute of Building Construction
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• v.9 no.3
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• pp.73-78
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• 2009

Coal ash is a by-product of the combustion of pulverized coal, and much of this is dumped in landfills. The disposal of coal ash is one of the major issues for environmental problems. In this paper, the effects of the kinds and replacement ratio of coal ash on the durabilities of concrete mixtures are investigated. Fine aggregate was replaced with coal ash(fly ash and bottom ash) in five different ratios, of 0%, 10%, 20%, 35%, and 50% by volume. Test results indicated that the compressive strength increased with the increase in fly ash percentage. The loss of compressive strength of bottom ash concrete mixes after immersion in sulphuric acid solution was less than in the control mix(BA0). In addition, the carbonation depth of fly ash concrete mixes was lower than the control mix(FA0).

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.4 no.2
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• pp.153-163
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• 2000

The non-dimensional convective heat losses from each surface are investigated as a function of the non-dimensional fin length, width and the ratio of upper surface Biot number to bottom surface Biot number (Bi2/Bi1) using the three-dimensional separation of variables method. Heat loss ratio in view of each surface with the variation of Bi2/Bi1 is presented. The variation of the non-dimensioal temperare profile along the fin center line for a thermally asymmetric conditions is also presented.