• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.232-236
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• 2003

The anchor is laid on seabed and the main engine is worked to against incident environmental loads in typoon. As the main engine is broken down in the storm, the anchor chain is cutted and the vessel is drifted. Although a ship is moored by two point mooring lines to keep the her position, a ship is crashed into a rock because of typoon and the accident of oil spilling may be occured. In this paper, we studied the position-keeping of a ship which is analyized based on the slow motion maneuvering equations considering wave, current and wind. The direct integration method is employed to estimate wave loads. The current forces are calculated by using mathematical of MMG. The two point mooring forces are quasisatatically evaluated by using the catenary equation. The coefficeints of wind forces are modeled from Isherwood’s emperical data and the variation of wind speed is estimated by wind spectrum. The nonlinear motions of a two point moored ship are simulated considering wave, current, wind load in time domain.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1135-1139
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• 2006

가뭄은 홍수와 함께 인류역사상 가장 큰 재해로 인식되어 있다. 미해양대기청의 발표에 따르면 20세기 최대 자연재해의 상위 5위 안에 4개의 가뭄이 포함되어 있다. 이러한 기록은 가뭄이 동서고금을 막론하고 국가의 흥망성쇠를 좌우할 만큼 막대한 피해를 입혀왔음을 의미한다. 그러나 가뭄의 해석은 가뭄의 정의 자체가 확실하지 않고 서서히 찾아오는 자연재해이기 때문에 그 시작과 끝을 인식하기 어렵다. 아울러 그 진행속도도 굉장히 느리며 또한 장기간에 걸쳐 지속되는 특성을 가지고 있고 시공간적으로 전파된다. 따라서 가뭄의 해석은 굉장히 까다로운 것이라 할 수 있으며 그 해석방법 또한 다양할 수 밖에 없다. 본 연구에서는 우리나라 전역 59개 지점의 표준강수지수(Standard Precipitation Index) 시계열 자료에 대한 공간적 패턴분석과 시간적인 자료확장을 시도하였다. 경험적 직교함수(Emperical Orthogonal function) 해석을 이용하여 자료의 공간적인 패턴을 확인하였고 EOF 해석에서 나타난 EOF Coefficient Time Series를 추계학적 모형에 적용하여 시간적인 자료 확장을 수행하였다. 이렇게 확장된 긴 기간의 자료를 이용하면 재현기간에 대한 평균적인 가뭄심도를 추출할 수 있으며 실제 나타난 사상의 재현기간이 어느 정도인지 평가할 수 있다. 또한 이렇게 나타난 가뭄심도를 강수부족량으로 환산하여 우리나라 대권역별 물부족량을 평가하였다.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.1
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• pp.63-73
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• 2004

A simple analytical model has been presented for the study of the optical bistability using a $GaAs-Al_{0.32}Ga_{0.68}As$ multiple quantum well (MQW) p-i-n diode structure. The calculation of the optical absorption is based on a semi-emperical model which is accurately valid for a range of wells between 5 and 20 nm and the electric field F< 200kV/cm . The electric field dependent analytical expression for the responsivity is presented. An attempt has been made to derive the analytical relationship between the incident optical power ( $(P_{in})$ ) and the voltage V across the device when the diode is reverse biased by a power supply in series with a load resistor. The relationship between $P_{in}$ and $P_{out}$ (i.e. transmitted optical power) is also presented. Numerical results are presented for a typical case of well size $L_Z=10.5nm,\;barrier\;size\;L_B=9.5nm$ optical wave length l = 851.7nm and electric field F? 100kV/cm. It has been shown that for the values of $P_{in}$ within certain range, the device changes its state in such a way that corresponding to every value of $P_{in}$ , two stable states and one unstable state of V as well as of $P_{out}$ are obtained which shows the optically controlled bistable nature of the device.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.11
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• pp.1509-1520
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• 1998

An experiment was carried out for the fully developed turbulent flow of water in tube coils on the condition of uniform heat flux. The present work was conducted for various ranges for Dean number(1794~1321), Prandtl number (2.5~4.5), curvature ratio parameters (22~60). Heat transfer to steady viscous flow in coiled tubes of circular cross section was studied for fully developed velocity and temperature fields under the thermal boundary condition of uniform heat flux. The peripherally local Nusselt number correlated as a function of Dean and Prandtl numbers. We studied the flow in heat coiled tubes under the influence of both centrifugal and buoyancy forces in order to gain insight into the flow pattern. In the present study, we obtained three emperical formulas, $Nu_v=0.0231Re^{0.84}Pr^{0.4}(a/R)^{0.13}$ (vertical) $Nu_c=0.0241Re^{0.86}Pr^{0.4}(a/R)^{0.08}$ (corrugated) $Nu_h=0.0227Re^{0.84}Pr^{0.4}(a/R)^{0.09}$ (horizontal).

• Korea journal of population studies
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• v.20 no.1
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• pp.161-199
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• 1997

Unexceedingly rapid industrialization in Korea produced not only the improvement of living standards but many side effects including safety problems. This study, utilizing the survey data on 800 respondents on the quality of life and psycho-physical safety, reveals several findings as follows: 1) safety is one of the key dimensions of quality of life, 2) people usually take an equilibrium between risk and safety, although the equilibrium point differs by culture, social system, and other demographic traits, 3) accidents can be classified into three different types, demanding a different approach on the cause process, and solution in safety-related accidents. Major findings of this study implies that for the improvement of the quality of life, we should prescribe different policy measures according to the three different types of accidents.

• Journal of Korean Port Research
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• v.2 no.1
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• pp.75-106
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• 1988

As port transport system consists of subsystems such as navigation system, cargo handling system, storage system, inland transport system, and Management and Information system, the productivity of this system is determined by the minimum level of subsystem. From the viewpoint of elaborating the efficiency of integrated system, it is valuable to determine the optimal level of harbour tug boat which is the most important factor of navigation system. This paper treats the optimal amount of harbour tug boat by simulation, and applied to Pusan port. In the course of simulation, an emperical formula is introduced for determining the Horse Power (HP) of tug boat by the ship's gross tonnage (G/T) refering to the cases of various ports of other countries, that is ; $Y=9.96X^{0.6}+569$. X : The gross tonnage of vessel (G/T). Y : The Horse Power (HP) of tug boat. The results of the simulation are summarized as follows ; 1) In 1987, three or four low-powered harbour tug boats, five mid-powered harbour tug boats and four high-powered harbour tug boats are necessary in the mean level. But, five or seven low-powered harbour tug boats, ten mid-powered harbour tug boats and eight high-powered harbour tug boats are necessary lest delay should occur at all. 2) In 1992, 1lee or four low-powered harbour tug boats, six mid-powered harbour tug boats and seven high-powered harbour tug boats are estimated and be necessary in the mean level.

• Management & Information Systems Review
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• v.32 no.3
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• pp.285-297
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• 2013

In this study, price discovery among the KOSPI200 markets(KOSPI200 spot, KOSPI200 Futures and The ETFs) is investigated using the vector error correction model(VECM). The main findings are as follows. KODEX200(KOSEF200), KOSPI200 spot and Futures are cointegrated in most cases. Daily data from KODEX200(KOSEF200), KOSPI200 spot and KOSPI200 futures show that the movements of the three markets are interrelated. Specially, KODEX200 contains the most information, followed by the KOSPI200 spot and futures markets. KODEX200 contribute to the price discovery process. Namely KODEX200 plays a more dominant role in price discovery than the KOSPI200 spot and futures.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.172-178
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• 2003

As a typoon gets into harbour, a moored ships shows erratic motions and even mooring line failures is occurred. Such troubles may be caused by harbour resonance phenomena, result in large motion amplitudes at law frequency, which is closed to the natural frequency of the moored ship. The nonlinear motions of a moored ship beside quay are simulated under external forces due to wave, current including mooring forces in time domain. The forces due to waves are obtained from source and dipole distribution method in the frequency domain. The current forces are calculated by using slow motion maneuvering equation in the horizontal plane. The wind forces are calculated from emperical formula of ABS and the mooring forces of ropes and fenders are modeled as linear spring.

• Journal of the Korean Society for Precision Engineering
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• v.5 no.1
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• pp.40-49
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• 1988

The chip control problem is one of the important subjects to be studied in the metal cutting process. Especially, an important practical problem concerns the form of chips pro- duced in machining since this has important implications relative to : 1. Personal safety. 2. Possible damage to equipment and product. 3. Handling and disposal of swarf after machining. 4. Cutting forces, temperatures, and tool life. However, a dependable way to predict the form of chips in a wide range of cutting conditions has not been established satisfactorily. In this paper, the relationship between the form of chips and the ratios of cutting forces were studied experimentally. According to what the experiments have been carried out in the turning process the main results can be summarized as follows : 1. By use of the multiple linear regression model, emperical formulas which are suitable to wide ranges of cutting conditions with accuracy were obtained satisfactorily. 2. The correlations between the form of chips based upon the classification by Henriksen and the ratios of cutting forces, namely (feeding force/thrust force), (principal force/feeding force) were determined. 3. Using above results, the algorithms which predict the form of chips were constituted. With these algorithms, the form of chips in a wide range of cutting of cutting conditions can be predicted.

• Korean Journal of Food Science and Technology
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• v.6 no.1
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• pp.1-5
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• 1974

The extraction mode of orange-yellow pigment from Gardenia is depended upon the extraction time, extraction temperature and volume of solvent. The amounts of the extracted-pigment (C) is proportional to the log ${\theta}^{1.15}$ of extraction time $({\theta}:0{\cdots}{\cdots}{\cdots}60$ min.), the log $T^{3.73}$ of extraction temperature $(T:5{\cdots}{\cdots}{\cdots}60^{\circ}C)$ and the log $S^{3.7}$ of volume of solvent $(S:5{\cdots}{\cdots}{\cdots}50ml)$ at $18^{\circ}C$ for 10 minutes. Finally, the general emperical equation was derived as follows; C=1.15 log ${\theta}$+3.73 log T+3.7 log S-7.0