• International Journal of Air-Conditioning and Refrigeration
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• 제14권3호
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• pp.94-101
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• 2006

A theoretical investigation to find thermodynamically optimum design conditions of conduction-cooled Peltier current leads is performed. A Peltier current lead (PCL) is composed of a thermoelectric element (TE), a metallic lead and a high temperature superconductor (HTS) lead in the order of decreasing temperature. Mathematical expressions for the minimum heat flow per unit current crossing the TE-metal interface and the minimum heat flow per unit current from the metal lead to the joint of the metal and the HTS leads are obtained. It is shown that the temperature at the TE -metal interface possesses a unique optimal value that minimizes the heat flow to the joint and that this optimal value depends on the material properties of the TE and the metallic lead but not the joint temperature nor electric current. It is also shown that there exists a unique optimal value for the joint temperature between the metal and the HTS leads that minimizes the sum of the power dissipated by ohmic heating in the current leads and the refrigerator power consumed to cool the lead, for a given length of the HTS.

• 열처리공학회지
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• 제7권4호
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• pp.233-243
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• 1994

Constitutive relation of thermoelasto-plastic material undergoing phase transformation during quenching process were developed on the basic of continuum thermodynamics. The metallic structure, temperature and residual stresses distributions were numerically calculated by the finite element technique. The metallic structure were defined by transformation from austenite to pearlite and characterized as a fuction of thermal history and mixture rule of phase. On the distribution of thermal stress along the radial direction, axial and tangential stresses are compressive in the surface, and tential in the inner part. Radial stress is tensile in the whole body. The reversion of residual stress takes plase at 11.5~15.5mm from the center.

• 한국기계가공학회지
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• 제10권4호
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• pp.57-63
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• 2011

The aim of this study is to analyze turning process using commercial FEM simulation code. Various simulation models of orthogonal cutting process for 3 layers of metallic material have been simulated and analyzed. The workpiece material used for the orthogonal plane-strain metal cutting simulation consists of three layers, which are Allow Tool Steel, Aluminum and Stainless Steel. The finite element model is composed of a deformable workpiece and a rigid tool. The tool penetrates through the workpiece at a constant speed and constant feed rate. As an analytical result, detailed cutting temperature, strain, pressure, residual stress for both a tool and each layer of workpiece were obtained during the turning process. It has been closely observed that the chip flow curve deforms continuously.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1996년도 제24회 추계학술대회
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• pp.183-188
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• 1996

Films and coatings are used for an enormous and diverse set of applications including mechanical, electronic and optical devices, protection at high temperature, cutting tools enhancement and automotive use. Many of these applications require the various properties associated with inorganic and metallic / non-metallic materials; i.e., with ceramics. Therefore, a large number of coatings have been developed and used for a long time in the various fields, especially in mechanical one. As one of the mutual surface actions, the problems of contact stresses are complex. The relationship between load and stress are nonlinear. Besides, the material is often apt to deform plastically under low load. However, analytical solutions exist only for some simple problems. If a material has a complicated shape or inhomogeneous properties, numerical method must be used. In this paper, the analysis of the contact stress of the coating layer was solved, using the finite element method.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.257-260
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• 2006

This paper presents electromagnetic finite element analysis of power cables for wind turbine application. Eddy current losses are calculated due to high currents along metallic part, and dielectric strength on power cables is investigated for case study, which suggests the optimal cabling configuration for wind turbine construction.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1992년도 제15회 학술강연회초록집
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• pp.1-20
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• 1992

1. Ceramics as engineering Materials Ceramic \ulcorner :'material based on inorganic non-metallic compounds' Oxygen, Carbon, Nitrogen with metal (Al, Si) -cheap, plentiful and widespread element in the Earth -dirt: ceramic

• 자원환경지질
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• 제53권2호
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• pp.133-145
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• 2020

본 연구는 대한민국 충청도에 위치한 폐광산을 대상으로 오염경로를 분석하기 위해 갱구, 하천 퇴적토 및 인근 농경지의 중금속 오염 확산 특성을 조사하였다. 연구대상지역에서 갱내수 유출지점으로부터 약 61 m까지 적화현상이 관찰되었고 총 1800 ㎥의 폐석 유실구간이 확인하였다. 갱내수는 우기기간동안 pH 4.9, 황산염의 농도 1557.8 mg/L를 나타냈다. 동일한 기간에 황산염 농도는 하천시료에서 평균 773.6 mg/L으로 나타났다. 하천에서 채취한 황갈색 시료를 분석한 결과 침철석과 페리하이드라이트(ferrihydrite)로 나타났다. 본 연구지역의 주요 오염원은 폐석 손실에 의한 것으로 여겨지며 토양오염우려기준을 초과한 오염 필지는 총 10,297 ㎡로 산정되었다.

• 한국환경보건학회지
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• 제27권4호
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• pp.63-71
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• 2001

PM 2.5/ samples were measured at two sites, Hadan(suburban site) and Anrak (roadside site) in Busan area. PM 2.5/ sampling was performed for 24-hour intervals by the FH9.5 particulate sampler. Aerosol samples were collected on PTFE filter. A total of 60 particulate samples were collected, dad samples were measured for Particulate mass concentration, metallic elements (Cr, Mn, Ni. Cu. Se, Fe, Pb, and Zn) and waer-soluble elements (C $l^{[-10]}$ , N $O_{3}$$^{[-10]}$ ,S $O_{4}$$^{2-}$, N $H_{4}$$^{+}$, $Ca_{2}$$^{+}$, $Mg_{2}$$^{+}$ and $^{+}$.Mass concentration in Hadan ranged 24.23~57.12 $\mu\textrm{g}$/㎥ and 60.22~72.12 $\mu\textrm{g}$/㎥m Yellow Sand Events. Major cations in Hadan and Anrak site is N $H_{4}$$^{+}$and N $a^{+}$ respectively. SO42$^{[-10]}$ was the abundant specie in the PM 2.5 fraction for Hadan site an dAnrak site. Hadan site showed igher concentration in S $O_{4}$$^{2.1}$ and N $H_{4}$ $^{+}$ In Anrak site the concentration of S $O_{4}$/sip 2-/and N $a^{+}$ was higher than other ions Prominent metallic elements were Fe and Pb in two sites. Principal component analysis showed that main source of PM 2.5 aerosol particles was non-metal related source which was resulted in relating elements as Cr, Ni, and Pb at Hadan site, Anrak site also has resulted PM2.5 aerosol paricles source, which was related its element like Zn, and Ni,. The SAS package analysis also showed that long-range transport effect at Hadan area due to Yellow Sand Event by the prevailing weaterlies.ling weaterlies.

• 소성∙가공
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• 제19권5호
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• pp.311-319
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• 2010

Rare earth metal Ce has a relatively low melting point and high specific gravity. Because of its significantly high affinity to oxygen, nitrogen and sulfur, it is highly usable as a steel refining agent. However, because Ce compound has relatively high specific gravity, it is difficult to be separated from molten steel through floatation, and it degrades the purity of molten steel, or may clog the nozzle in continuous casting. Such problem may be solved by using an appropriate deoxidation agent together with Ce and settling molten steel sufficiently after refining. Thus a fundamental study in the formation behavior of non-metallic inclusion in Ce added Hyper Duplex STS melts was investigated. The addition amount of Ce, melt temperature were considered as experimental variables. A main non-metallic inclusion in mother alloy is 51(wt%MnO) - 27.6(wt%SiO$_2$)- 10.9(wt%$Cr_2O_3$). Non-metallic inclusion was dramatically decreased and the particle size was fined as the amount of Ce increased. Moreover (%MnO) and (%SiO$_2$) of non-metallic inclusion were decreased. But (%$Al_2O_3$)were relatively increased. The number of non-metallic inclusion were decreased and the large particle size were increased by increasing the temperature of molten steel.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.130-133
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• 2005

Efficient finite element method has been introduced for metallic sandwich plates subject to 3-point bending. A full model 3-point bending FE-analysis shows that plastic behavior of inner structures appears only at the load point. So, Unit structures of sandwich plates are defined to numerically calculate the bending stiffness with recurrent boundary condition of pure bending. And then equivalent models with same bending stiffness and strength of full models are designed analytically. It is demonstrated that results of both models are almost same and FE analysis method with equivalent models can reduce analysis time effectively.