• 전자공학회논문지A
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• 제31A권4호
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• pp.77-83
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• 1994

In this paper we numerically approximated the field-effect mobility of a-Si:H TFT. Field-effect mobility, based on the charge-trapping model and new effective capacitance model in our study, used Chebyshev approximation was approximated as the function of gate potential(gate-to-channel voltage). Even though various external factors are changed, this formula can be applied by choosing the characteristic coefficients without any change of the approximation formula corresponding to each operation region. Using new approximated field-effect mobility formula, the dependences of field-effect mobility on materials and thickness of gate insulator, thickness of a-Si bulk, and operation temperature in inverted staggered-electrode a-Si:H TFT were estimated. By this was the usefulness of new approximated mobility formula proved.

• 한국수자원학회논문집
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• 제32권6호
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• pp.741-749
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• 1999

본 연구에서는 TDR의 반향파의 특성과 총토양전기전도도의 관계를 이용한 비포화 토양에서의 용존오염원 농도를 측정하는 방법을 개발하였다. 본 연구에서 제안한 방법은 두 가지 중요한 관계를 결합한 것으로 첫 번째는 함수량이 일정할 경우 전기전도도와 토양수 농도는 선형관계를 유지한다는 것이며, 두 번째는 천이상태의 용존여염원의 농도를 측정할 수 있게 하기 위해 함수량과 전기전도도의 관계를 설정하는 것이다. 함수량과 전기전도도의 관계를 추정하는 식들이 여러 연구자들에 의하여 제안되었으나, 본 연구에서는 측정의 정확도를 높이기 위하여 한계함수량의 개념을 도입한 새로운 추정식을 제안하였다. 한계함수량 개념을 이용하여 실험자료를 선형, 비선형 구간으로 나누어 분석하였는데, 실험자료의 반영정도를 증가시킬 수 있어 본 연구에서 제안된 식을 이용하여 추정된 전기전도도와 함수량관계는 다른 제안식에 비하여 개선된 결과를 보여 주었다. 본 연구에서 제안된 전기전도도와 함수량관계 추정식을 이용한 천이상태의 오염원 농도 측정법은 함수량이 급하게 변하는 토양에도 적용할 수 있는 매우 유용한 방법으로 판단된다.

• 화약ㆍ발파
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• 제24권1호
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• pp.29-37
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• 2006

최근 국내 터널현장에서 기계식 장전장비를 활용한 벌크에멀전 (bulk emulsion) 폭약의 수요가 증가되면서 국내 암반 및 주변여건에 적합한 발파의 합리적인 설계기준이 요구되고 있다. 본 연구에서는 현재까지 국내에서 기계식 장전장비를 활용한 벌크에멀젼 폭약을 적용하여 시공한 사례 중 굴진효율 및 여굴량이 양호한 발파결과를 근거로 암반등급별 최적 비장약량과 영역별 적정 장약량을 검토하였다. 또한, 조건을 만족하는 발파결과를 분석하여 RMR 암반분류와 벌크에멀젼 폭약의 최적 비장약량과의 상관식 $({\Upsilon}= 0.669 + (0.0154{\times}RMR),\;r=0.81)$을 얻었고, 영역별로 천공장 변화에 따른 적정 장약량 범위를 산출하였다.

• 조명전기설비학회논문지
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• 제21권6호
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• pp.19-25
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• 2007

특정한 배광 구현을 위하여 부피를 갖는 실제 광원에 대한 프리즘 설계법을 연구하였다. 입사각을 알고 목표 방향으로 광선을 보내려 할 때, 프리즘 정각을 구하는 수식을 유도하였고, 순차적으로 프리즘 정각을 구하였다. 점광원으로 가정한 설계 결과의 문제점을 분석한 후 이를 보완하여 부피를 갖는 광원에 적용할 수 있는 설계법을 도출하였다. 각각의 설계 결과로 나온 배광과 효율을 비교, 분석하였고 보완된 설계법을 통해 개선된 결과를 얻을 수 있었다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.73-78
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• 2004

For the preliminary stages of ship design it is necessary to develop a basic design, which specifies the main particulars of the vessel. based on the requirements given by the owner. An efficient design enables the shipyard to make a rough estimate of the construction costs and to put forward a favourable quote during the call for tenders. The parametric determination of the main particulars of the vessel involves the application of empirical formulae. These formulae have been created after detailed tests and research by maritime research institutions and researchers had been carried out. Here, the design of a medium sized Bulk Carrier (26000t dwt) with a service speed of 17 knots for carrying rice and rock phosphate has been illustrated. Medium sized Bulk Carriers (25,000t dwt - 50,000t dwt) are in steady demand among small shipping companies. They have a size advantage, in that port size restrictions do not affect their design tremendously. Nevertheless, structurally. they are one of the most difficult to build. During design, the rules of the maritime regulatory bodies were strictly adhered to.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권5호
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• pp.499-508
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• 2017

This paper uses optimization techniques to obtain bow hull form of a 66,000 DWT bulk carrier in calm water and in waves. Parametric modification functions of SAC and section shape of DLWL are used for hull form variation. Multi-objective functions are applied to minimize the wave-making resistance in calm water and added resistance in regular head wave of ${\lambda}/L=0.5$. WAVIS version 1.3 is used to obtain wave-making resistance. The modified Fujii and Takahashi's formula is applied to obtain the added resistance in short wave. The PSO algorithm is employed for the optimization technique. The resistance and motion characteristics in calm water and regular and irregular head waves of the three hull forms are compared. It has been shown that the optimal brings 13.2% reduction in the wave-making resistance and 13.8% reduction in the added resistance at ${\lambda}/L=0.5$; and the mean added resistance reduces by 9.5% at sea state 5.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1084-1089
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• 2000

The basic equations are derived for the analysis of a stepped labyrinth gas seal which are generally used in high performance compressors, gas turbines, and steam turbines. The Bulk-flow is assumed for a single cavity control volume and the flow is assumed to be completely turbulent in circumferential direction. Moody's wall-friction-factor formula is used for the calculation of wall shear stresses in the single cavity control volume. For the reaction force developed by the seal, linearized zeroth-order and first-order perturbation equations are developed for small motion about a centered position. Integration of the resultant first-order pressure distribution along and around the seal defines the rotordynamic coefficients of the stepped labyrinth gas seal. The leakage and rotordynamic characteristic results of the stepped labyrinth gas seal are presented and compared with Scharrer's theoretical analysis using Blasius' wall-friction-factor formula.

• Journal of Ship and Ocean Technology
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• 제12권1호
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• pp.45-56
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• 2008

Recently, International Association Classification Societies (IACS) has adopted the Common Structural Rules (CSR) for Bulk Carriers and Tankers, which specifies the requirement associated with the ultimate strength of hull girder structure. The theoretical background and the results of verification study are neither well summarized nor released. Furthermore, the requirement is not a form of deterministic formula but a form of program in which source code is not disclosed. The reliability of the non-linear structural analysis program is verified through the comparison with the results of the analysis and the model test. Then, the reliability of the ultimate strength requirement in CSR is checked by comparing with the results of rigorous non-linear analysis.

• 대한화학회지
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• 제6권2호
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• pp.113-116
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• 1962

In this study we have measured the activity coefficients of NaCl in solution by E.M.F. method, depending upon MacInnes' equation at 25 dog. The cell (electrodes) is same as MacInnes' except the cock which was designed by ourselves as figure 1.Additionally, we have calculated the hydration number of NaCl from the activity coefficients using Robinson's equation and ionic hydration number according to our new formula $\frac{n_M{^+}+0.8}{n_A{^-}-0.1}=n_{MA}$, which was mentioned our former thesis.We also have calculated the hydration number of some salts from the ionic hydration number using upper formula and have got reasonable series match with other's value.As the results of our studying, we conclude it as follow;1) Liquid junction potential depend only on the bulk concentration of the both solution.2) The formula $\frac{n_M{^+}+0.8}{{n_A{^-}}-0.1}=n_{MA}$ is reasonable one in deducing to ionic hydration number.3) From upper relation, we can calculate the hydration number of unknown salts from it's ionic hydration numbers.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.251-257
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• 2000

A numerical simulation of the temperature rise for sliding surface in dry contact is based on Jaeger's formula combined with a calculated heat input. A gear tooth temperature analysis was performed. The pressure distribution has the Hertzian pressure distribution on the heat source. The heat partition factor is calculated along line of action. A Temperature distribution of tooth surface is calculated about before and after profile modification. A Temperature of addendum and deddendum in modified gear have reduced.