• Journal of the Korean Institute of Telematics and Electronics
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• 제12권5호
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• pp.1-5
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• 1975

접합형 트린지스터와 발광다이오드(LED) 및 광도전소자(CdS)로서 구성된 광결합 전류안정부저항회로를 진안하였다. 이는 일반적으로 광트랜지스터보다도 더 예민한 것을 이용하여, CdS와 LED를 밀착 시켜서 LED에 흐르는 전류와 CdS의 실효저항변화로써 결합된 광결합방식을 택하였다. 트랜지스터의 콜랙터-에미터간에 인위적인 누변저항을 삽입하는 방법을 도입함으로써 부저항치 및 최대입력단자전압치를 임의로 변화할 수 있게 하였으며, 제안한 회로를 분석하고 또 이를 실험적으로 확인하였다. 누변저항을 1KΩ에서 30KΩ까지 변화시켰을 때 최대입력단자전압은 1.65V에서 4.22V로 변하였고, 부저항치는 -1.0KΩ에서 -10.0KΩ까지 변하였다. 또 실험치에 대한 계산치에의 상대백분최대오차가 11%이었다. A current stable negative resistance circuit has been constucted with combination of coulplementary symmetrical transistors, a light emitting diode and a photoconductive cell. The negative resistance(Rn) and break-over voltage(VBo) can be set at a designed value according to adjustment of the artificial leakage resistance of p-n-p transistor. The RN and VBo calculated in this designed circuit are checked though the experiments, the errors are found less than 11%.

• The Korean Journal of Financial Management
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• 제20권1호
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• pp.233-260
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• 2003

This paper compares the underpricing of IPOs listed on KOSADQ with that of IPOs listed on KSE. When we consider the last day of upper price limit of IPOs, IPOs on KSE show higher initial excess return than IPOs on KOSDAQ. And AR2 which is the abnormal return based on the stock price of the last day recording upper limit after listing, IPOs on KOSDAQ exhibit larger abnormal return than IPOs on KSE. Our study also reports that the long-term performance of IPOs in two markets does not show any difference. That is, IPOs of both markets under performed in the long-run. The wealth relatives of IPOs are a little higher than market portfolio. We explored the reasons of the underpricing of IPOs in both markets through the multiple regression analysis. The business history is examined asstatistically significant variable to explain the underpricing.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제34권12호
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• pp.1079-1085
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• 2010

A steady-state analytical model was presented for a loop heat pipe (LHP) with an evaporator that has a flat geometry. On the basis of a series of reviews of the relevant literature, a sequence of calculations was proposed to predict the temperatures and pressures at each important part of the LHP: the evaporator, liquid reservoir (compensation chamber), liquid line, vapor line, and condenser. The analysis of the evaporator, which is the only part in the LHP that has a capillary structure, was emphasized. Thin-film theory is applied to account for the pressure and temperature in the region adjacent to the liquid-vapor interface in the evaporator. The present study introduced a unique method to estimate the liquid temperature at the interface. Relative freedom was assumed in the configuration of a condenser with a simplified liquid-vapor interface. Our steady-state model was validated by experimental results available in the literature. The relative error was within 3% on the absolute temperature scale, and reasonable agreement was obtained.

• Journal of Chest Surgery
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• 제35권3호
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• pp.235-238
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• 2002

Among the causes of SVC syndrome, intraluminal tumor, especially the leiomyosarcoma is very rare. We report a 39 year old female patient who had been suffering from headache and facial edema for 6 weeks before admission. On physical examination, facial edema and venous engorgement on upper extermities and upper chast wall were showed. The chest CT scan and SVC cavogram showed a long intraluminal mass lesion resulting in a near total obstruction of the SVC Surgery was performed through median sternotomy. For complete resection of the tumor and thrombus, we used partial and total CPB. The follow up SVC cavogram revealed no abnormality 14 months after the operation.

• Journal of Korean Society of Steel Construction
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• 제16권6호통권73호
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• pp.833-846
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• 2004

This study presents a non-prismatic beam element for modeling the elastic behavior of steel beams, which have the post-Northridge connections in steel moment frames. The elastic stiffness matrix, including the shear effects for non-prismatic members with reduced beam section (RBS) connection, is in closed form. A simplified approach is also suggested, which uses a prismatic beam element to model beams with the RBS connection. This method can estimate quiteexactly the maximum story drift ratios of frames with the RBS connection. The effects of reduced beam section connection on the elastic stiffness of steel moment frames were investigated. The selection of a proper model to account for deformations at the joint might have a more important role in estimating the maximum story drift ratios of frames with better accuracy than the RBS cutouts.

• Journal of Oral Medicine and Pain
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• 제38권4호
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• pp.367-372
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• 2013

To diagnose sensory nerve damage, patient values for thermal stimuli as quantitative sensory test (QST) can be compared with the values of the general population (absolute reference data) or to values measured at contralateral unaffected side (relative reference data). It is well know that relative reference data are more sensitive for detecting sensory abnormality than absolute reference data. However it is still lack of the studies for comparisons between relative and absolute data. This study aimed to evaluate the validity of relative reference data and compare the sensitivities of the two approaches in the orofacial region. In 19 young Korean women as normal subjects, quantitative somatosensory thermotest were done in the forehead, cheek, mentum, lower lip and tongue tip bilaterally. After we get the standard deviations (SD) of average reference data and relative reference data, the ratios SD absolute data/SD relative data were calculated. Our study showed that relative reference data for side to side comparisons in the same patient have the high ratios than the absolute reference data, i.e. the side to side comparisons with relative reference data exhibit gain in sensitivity in assessment of sensory abnormality.

• 한국지형공간정보학회:학술대회논문집
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• 한국지형공간정보학회 2003년도 창립 10주년 기념 국제학술대회 논문집
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• pp.195-199
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• 2003

대규모 토목공사에서 토량환산계수는 공사물량 및 공사비에 미치는 영향이 크므로 합리적인 토량환산계수의 설계가 요구된다. 그러나 토량환산계수의 산정에 있어서 선정시험에 의한 결과치가 아닌 통상적으로 사용하고 있는 설계기준서에 제시된 값을 적용함으로써 정확한 잔토 및 부족토량의 산정에 있어서 많은 어려움이 따르며, 이러한 경우 현장여건에 적합한 대규모 현장시험을 실시하여 토량환산계수를 산정하는 것이 바람직하다. 또한 대규모 현장시험에 있어서 굴착부분의 체적은 토량환산계수 산정에 있어 매우 중요한 요소가 된다. 따라서, 본 연구에서는 대규모 현장을 대상으로 절 성토부 풍화암의 굴착부분의 체적을 정확히 산정하기 위하여 수치사진측량기법을 적용하였으며, 이를 Total Station에 의한 측량방식과 비교 분석하였다. 그 결과, 교차에 대한 상대정확도는 평균 0.5%로 산출되었으며, 체적에서 0.5%의 상대정확도는 길이 측정에서 0.17% 상대정확도에 해당되므로 정확한 측량이라 판단된다.

• Journal of Korea Foresty Energy
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• 제17권1호
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• pp.23-29
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• 1998

This study was carried out to develop the regression model for estimating biomass of natural Pinus densiflora forests by stand density in northeast Chinese area of Mt. Paekdu. Four allometric regression models(W=aD$^b$, W=a(D$^2$H)$^b$. logW=a+b$\cdot$ logD+cD and logW=a+b$\cdot$log(D$^2$H)+c(D$^2$H)) were used to estimate biomass for each of the tree components. The suitable regression model for estimating biomass of stem, bark and whole tree above ground was logW=a+b$\cdot$log(D$^2$H)+c(D$^2$H), and that for biomass of branch, needle and needle area, logW=a+b$\cdot$logD+cD for all of the stand density classes.

• Journal of environmental and Sanitary engineering
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• 제15권4호
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• pp.4-13
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• 2000

산업공정에서 배출되는 대기오염물질 및 유독성가스를 제거하기 위한 방법에는 여러 가지가 적용되고 있으나, 본 연구에서는 충전탑을 이용한 흡수원리로써 오염물질을 처리하는데 후력학적 특성에 대해서 연구하였다. 즉 환경보호와 화학공업에서 에너지 절약 측면에 충전탑의 사용이 증가되고 있으며, 충전물의 재료로는 플라스틱, 금속 및 세라믹 등으로 제작되며 종류로는 VSP-ring, Hiflow-ring, Hackette, Top-packing, Envi-pac 등이 있고 사용범위는 정류와 증류, 흡수 및 탈착과 액체와 액체의 추출공정 등에 효율적으로 사용되고 있다. 산업현장에서는 과거에 주로 사용되어온 Intalox-saddle, Rasching-ring, Pall-ring 등의 재래적 충전물은 압력손실과 물질전달, 에너지 절약 및 효율성이 좋은 격자형 충전물의 개발로 인하여 점점 사용이 감소되고 있는 추세이며, 최근에는 합성수지로 제조된 충전물 NSW-ring, Hiflow-ring, Envi-pac 등은 실험 결과에 의해서 재래적인 충전물 Raschig-ring과 Pall-ring보다 높은 상대적인 공간체적과 충전높이에 따른 낮은 압력손실과 함께 높은 부하 한계치에 대하여 효율적이고 가벼운 분리작용에 의한 수력학적 특성이 증명되어졌다. 격자형 충전물이 산업에 적용되기 위해서는 압력손실과 액체함량, 부하 한계치 가스상 또는 액상 물질전달의 특성을 규명하는 것이 중요하다. 따라서 본 연구에서는 가수와 액체의 역류흐름에 의한 수력학적 특성과 물질전달 실험결과를 나타내었다.

• Transactions of the Korean Society of Mechanical Engineers
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• 제13권1호
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• pp.115-124
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• 1989

Near-threshold fatigue crack-growth behavior at room temperature for a duplex stainless steel weldments was investigated to evaluate the effect of load ratio, microstructural change, and residual stresses. Near-threshold fatigue crack propagation behavior is found to show a marked sensitivity to .alpha./.gamma. phase ratio, and little residual stress effects. Threshold values in the heat affected zones are higher than those of base metals and threshold values for crack growth decrease with increasing the load ratio in the base metals and weldments. The fractrographic features in base metals, weldments and heat affectred zones were discussed in terms mechanism of crack growth.