• 대한기계학회논문집A
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• 제20권1호
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• pp.189-205
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• 1996

The twin-roll type strip continuous casting process(or direct rolling process) of steel materials is characterized by two rotating water cooled rolls receiving a steady supply of molten metal which solidifies onto the rolls. A solidification analysis of molten metal considering phase transformation and thermofluid is performed using finite diffefence method with curvilinear coordinate to reduce computing time and molten region analysis with arbitrary shape. An enthalpy-specific heat method is used to determine the temperatures inthe roll and the steel. The temperature distribution of cooling roll is calculated using two dimensional finite element method, because of complex roll shape due to cooling hole in rolls and improvemnt accuracy of calculation result. The energy equaiton of cooling roll is solved simultanuously with the conservation equaiton of molten metal in order to consider heat transfer through the cooling roll. The calculated roll temperature is compared to experimental results and the heat transfer coefficient between cooling roll surface and rolling material(steel) is also determined from comparison of measured roll temperature and calculated temperature.

• 한국대기환경학회지
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• 제13권4호
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• pp.257-267
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• 1997

This study focuses on the health risk assessment of airborne volatile organic compounds (VOCs) in a petrochemical complex, with several emphases on a risk assessment method. The first emphasis is on the importance of hazard identification to determine the likely carcinogenic potential of a VOC. Without considering this type of information, a direct comparison of the carcinogenic risks of two pollutants is meaningless. Therefore, wer suggest that this type of information be prepared and be listed with the estimate of cancer risk in parallel. The second emphasis is on the selection of a better dose-response model to estimate unit risk or cancer potency factor of a carcinogenic VOC. Finally, probilistic risk assessment method is discussed and recommended to use within a comparison of conventional point-estimate method. A health risk assessment has also been carried out. For non-carcinogenic risk, even the highest hazard index for carbon tetrachloride is estimated to be less than 1 with the other VOCs less than 0.03. However, the lifetime cancer risk from the inhalation of airborne VOCs is estimated to be about $2.6 \times 10^{-4}$ which is higher than the risk standard of $10^{-6}$ or even $10^{-5}$. Therefore, the investigation into domestic petrochemical complexes should be strengthened to obtain more fine long-term airborne VOC data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.602-606
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• 2000

A general procedure for the design sensitivity analysis of structural dynamic problems has been presented in frame of the FRF-based substructuring formulation. In the procedure, the direct differentiation method is used for the sensitivity formula. For a system response function, the proposed method gives a parametric design sensitivity formula in terms of the partial derivatives of the connection element properties and the transfer matrix of the subsystems. The derived design sensitivity formula is applied to a numerical example. The comparison of sensitivities derived by the proposed method and the finite difference method shows that the proposed method is efficient and accurate.

• 대한전기학회논문지
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• 제39권1호
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• pp.22-28
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• 1990

This paper is a study on the reduction of computation time in case of nonlinear magnetic field analysis by finite element method and Newton-Raphson method. For the purpose, the nonlinear convergence equation is computed by the conjugate gradient method which is known to be applicable to symmetric positive definite matrix equations only. As the results, we can not prove mathematically that the system Jacobian is positive definite, but when we applied this method, the diverging case did not occur. And the computation time is reduced by 25-55% and 15-45% in comparison with the case of direct and successive over-relaxation method, respectively. Therefore, we proved the utility of conjugate gradient method.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.791-794
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• 2004

In this article, we present a method to measure precisely the performances of direct-lit CCFL backlights using a luminance meter and dedicated image analysis software. The array of CCFL tubes alone can be measured directly and the luminance of each tube can be extracted along its main dimension. So, comparison of the different tubes on the same backlight can be made easily and the performances in terms of backlight uniformity improved. The influence of the diffuser sheet can be probed in the same way and the homogeneity of the entire surface of the backlight can be automatically extracted and quantified.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2002년도 학술논문발표회
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• pp.37-40
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• 2002

The purpose of this study is promote perfect of construction and progress of packing ability through comparison and analysis with quality, as placing ways and placing direction are changed. Kinds of concrete are general, high fluidity, and high Performance concrete. Classified with concrete as placing ways - direct ways, sheath way - and placing directing - flange direction, web direction - is analyzed section and strength of hardened concrete. The results of this study is belows the more fluid of concrete, the more useful to top-down method.

• 환경영향평가
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• 제19권6호
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• pp.563-571
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• 2010

In carrying out the prior review on environmental conditions for basic plan of public waters reclamation, the important item is review on conditions of location on prearranged reclaimed land. In this study, environmental assessment which needs careful consideration in the first stage of selecting location is presented by analyzing environmental impact assessment on public waters reclamation projects for about 10 years. The assessment index for alternative comparison is divided into two parts according to importance level. What is most important in alternative comparison is the comparison on direct influence due to reclamation. In other words, it figures out damaged extent of natural shoreline as well as intertidal and infralittoral zones. Comparing influence extent due to reclamation through the 1st comparison on this is regarded as to be important. In case there is no significant difference by alternatives through the 1st assessment, the 2nd assessment should be carried out. In the 2nd assessment indexes are damaged quantity of benthic organism, change in seawater current, erosion, accumulation and exchangeable rate of seawater. The plan for selecting optimal location which minimizes environmental influence in establishing public waters reclamation plan is demonstrated through model cases. For this, 3 districts which have similar environment and scale are selected, and then comparison on location alternative is made through environmental assessment index. In addition, the comparison on 3 arrangement alternatives are conducted, targeting certain areas. It is thought that carrying out comparison review on respective areas in the same cities and counties, not merely comparing arrangement plan by selecting 1 targeting area in advance, is the most appropriate. Besides, selection of arrangement plan considering environment, which minimizes damage of natural shoreline and influence due to change of seawater current is required in alternative comparison on arrangement plan as well. In case of the prior review on environmental conditions though alternative comparison method presented in this study is carried out, it is safely said that the influence on ocean environment due to public waters reclamation can be minimized.

• Journal of Power Electronics
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• 제12권1호
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• pp.128-135
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• 2012

In this paper, different switching tables proposed for the Direct Torque Controlled (DTC) of a six-phase induction machine are simulated and implemented. A six-phase induction motor has 64 space voltage vectors which result in increased complexity in the selecting of inverters switching. The unsuitable selection of a switching table leads to large harmonics especially at low speed and it also reduces drive efficiency. A six-phase induction machine has large zero sequence harmonic currents of the order $6{\kappa}{\pm}1$. These harmonic currents are varied in various techniques. Decreasing this loss is essential in a six-phase induction machine. The main purpose of this paper is to improve the ST-DTC of six-phase induction machines to reduce the voltage and current harmonics and the torque pulsation. Selecting a suitable method for minimizing these harmonics is very important.

• 대한간호학회지
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• 제33권2호
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• pp.246-255
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• 2003

Purpose: This study was designed to compare direct cost and indirect cost between home care and hospital care according to subject's characteristics. Method: The subjects of this study were patients with cerebrovascular disease. They were 50 patients in six university hospitals and 49 in four home care centers. Data were collected by using two type of questionnaires and reviewing medical records, home care service records and medical-fee claims from April 4th to September 13th, 2001. Result: The results were as follows; First, there was a statistically significant difference of direct cost between home care and hospital care, however, there was not a statistically significant difference of indirect cost. Second, according to subject's characteristics, six variables had statistically significant differences; sex, age, marital status, economy, job and diagnosis. Conclusion: It was found that cost-saving effect of home care was affected by subject's characteristic factors. More study needs to be done to develop a more detailed selection criteria for home care subjects.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.494-497
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• 2005

Direct velocity feedback (DVFB) control with a collocated distributed actuator and point sensor pair is known that it offers a good stability with high performance when the control strategy is applied at the suppression of structural vibration. Also decentralized control method introduced to offer to reduce implementaion effort and malfunction due to failure in sensors and actuators of control system has become an important position in DVFB. In this paper, the decentralized control is compared with centralized control in terms of vibrational velocity reduction in a clamped-clamped beam.