• 소성∙가공
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• 제27권2호
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• pp.115-122
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• 2018

Most domestic and international standards on the forming limit diagram (FLD) including ISO 12004-2, use a 'position-dependent method,' which determines the forming limit from a strain distribution measured on the specimen after necking or fracture. However, the position-dependent method has inherent problems such as the incidence of asymmetry of a strain distribution, the estimation of missing data near fracture, the termination time of test, and the deformation due to the new stress equilibrium after a fracture, which is blamed for causing sometimes a significant lab-to-lab variation. The 'time-dependent method,' which is anticipated to be a new international standard for evaluating the forming limit, is expected to greatly improve these intrinsic disadvantages of the position-dependent method. It is because the time-dependent method makes it possible to identify and accurately determine the forming limit, just before the necking point from the strain data as continuously measured in a short time interval. In this study, we propose a new time-dependent method based on a Gaussian fitting of strain acceleration with the introduction of 'normalized correlation coefficient.' It has been shown in this study that this method can determine the forming limit very stably and gives a higher value, which is in comparison with the results of the previously studied position-dependent and time-dependent methods.

• 설비공학논문집
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• 제7권2호
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• pp.171-183
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• 1995

Generally, among many kinds of shading devices such as venetian blind, sunscreen, louver and curtain, venetian blind is using widely because the mechanism is so simple and easy to use solar insolation by controlling the slat angle. Analysis of time dependent heat transfer through the window with venetian blind is very important in order to use it effectivly. Therefore, in this study, theoretical thermal analysis method was developed to analyze time dependent heat transfer through a double pane window with and without venetian blind, and was made one module of TRNSYS(A Transient Simulation Program)program. By this way, it was analyzed that how much the variation of slat angle, slat colour and slat absorptivity of venetian blind would be affected on the heating and cooling load of building, and also which colour and angle of slat was optimal for the heating and cooling load of building.

• Structural Engineering and Mechanics
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• 제22권2호
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• pp.197-222
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• 2006

In this paper, the non-linear time-dependent closed-form, discrete and combined solutions for the post-elastic response of a geometrically and physically non-linear suspended cable to a uniformly distributed load considering the creep effects, are presented. The time-dependent closed-form method for the particularly straightforward determination of a vertical uniformly distributed load applied over the entire span of a cable and the accompanying deflection at time t corresponding to the elastic limit and/or to the elastic region, post-elastic and failure range of a suspended cable is described. The actual stress-strain properties of steel cables as well as creep of cables and their rheological characteristics are considered. In this solution, applying the Irvine's theory, the direct use of experimental data, such as the actual stress-strain and strain-time properties of high-strength steel cables, is implemented. The results obtained by the closed-form solution, i.e., a load corresponding to the elastic limit, post-elastic and failure range at time t, enable the direct use in the discrete non-linear time-dependent post-elastic analysis of a suspended cable. This initial value of load is necessary for the non-linear time-dependent elastic and post-elastic discrete analysis, concerning incremental and iterative solution strategies with tangent modulus concept. At each time step, the suspended cable is analyzed under the applied load and imposed deformations originated due to creep. This combined time-dependent approach, based on the closed-form solution and on the FEM, allows a prediction of the required load that occurs in the post-elastic region. The application of the described methods and derived equations is illustrated by numerical examples.

• Journal of the Korean Data and Information Science Society
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• 제19권2호
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• pp.421-429
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• 2008

We consider a general semiparametric additive risk model that consists of three components. They are parametric, purely and smoothly nonparametric components. In parametric component, time dependent term is known up to proportional constant. In purely nonparametric component, time dependent term is an unknown function, and time dependent term in smoothly nonparametric component is an unknown but smoothly function. As an estimation method of this model, we use the weighted least square estimation by Huffer and McKeague (1991). We provide an illustrative example as well as a simulation study that compares the performance of our method with the ordinary least square method.

• Nuclear Engineering and Technology
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• 제43권3호
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• pp.243-256
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• 2011

This paper considers the concept of analog computing based on a cellular neural network (CNN) paradigm to simulate nuclear reactor dynamics using a time-dependent second order form of the neutron transport equation. Instead of solving nuclear reactor dynamic equations numerically, which is time-consuming and suffers from such weaknesses as vulnerability to transient phenomena, accumulation of round-off errors and floating-point overflows, use is made of a new method based on a cellular neural network. The state-of-the-art shows the CNN as being an alternative solution to the conventional numerical computation method. Indeed CNN is an analog computing paradigm that performs ultra-fast calculations and provides accurate results. In this study use is made of the CNN model to simulate the space-time response of scalar flux distribution in steady state and transient conditions. The CNN model also is used to simulate step perturbation in the core. The accuracy and capability of the CNN model are examined in 2D Cartesian geometry for two fixed source problems, a mini-BWR assembly, and a TWIGL Seed/Blanket problem. We also use the CNN model concurrently for a typical small PWR assembly to simulate the effect of temperature feedback, poisons, and control rods on the scalar flux distribution.

• 한국음향학회지
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• 제13권5호
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• pp.24-31
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• 1994

본 논문에서는 단어 조음결합의 음성학적 모델을 이용한 한국어 연속음성 인식에 관해 연구한다. 조음결합 현상에 의한 성능 감소를 줄이기 위해 단어내에서의 전이뿐만 아니라 단어간의 전이를 모델링하는 context-dependent (CD)단위를 사용한다. 모든 경우에서 각 단어의 첫 음소는 앞에 올 수 있는 모든 단어의 마지막 음소에 의해 지정되며, 각 단어의 마지막 음소도 유사한 방법으로 지정된다. Hidden Markov model (HMM) 파라미터들의 강인성을 개선하기 위해 공분산 행렬을 평활화한다. 또한 음성 단위들 사이의 분별력을 높이기 위해 position-dependent 단위를 사용한다. 실험 결과들은 개선된 조음결합 모델을 사용함으로서 intra-word 단위만을 사용하는 기본 인식 시스템에 비해 성능을 상당히 개선할 수 있음을 보여 주었다.

• 대한간호학회지
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• 제21권2호
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• pp.204-217
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• 1991

The purpose of this study is to verify the effect of lateral position and chest percussion on gas exchange in the decreased level of conscious patients. The Subjects for this study were 21 patients' admitted in ICU of CNUH from Dec 18th, 1989 to Aug 4th, 1990. The Data was analyzed by paired t - test. The results of this study as follows ; 1) In comparison of supine position, good -lung dependent position and good - lung dependent with chest percussion, the difference of PaO ㆍ was statistically significant (P＜0.05). 2) In comparison of supine position, good -lung dependent position and good - lung dependent with chest percussion, the difference of A-a Do ㆍ was statistically significant (p＜0.05). En conclusion, the use of good -lung dependent position and chest percussion was effective nursing intervention on decreased level of conscious patients in ICU.

• 산업경영시스템학회지
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• 제35권1호
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• pp.140-147
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• 2012

Vehicle routing problem is one of the traveling salesman problems with various conditions such as vehicle capacity limits, delivery time windows, as well as time dependent speeds in metropolitan area. In this research hourly vehicle moving speeds information in a typical metropolitan area are analyzed to use the results in the design procedure of VRP heuristic. Quality initial vehicle routing solutions can be obtained with adaption of the analysed results of the time periods with no vehicle speed changes. This strategy makes complicated time dependent vehicle speed simple to solve. Time dependent vehicle speeds are too important to ignore to obtain optimum vehicle routing search for real life logistics systems.

• Journal of Trauma and Injury
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• 제22권2호
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• pp.233-241
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• 2009

Purpose: Alcohol is a major risk factor for injuries, but little is known about the relationship between chronic drinking pattern and injuries. The purpose of this study was to evaluate the incidence of alcohol-related injuries and the differences in the characteristics of the injuries between Alcohol Use Disorder Identification Test (AUDIT) categories. Methods: Among a representative sample of the third Korea National Health and Nutrition Examination Survey. 7,697 adults answered questions about injuries, drinking patterns, and socioeconomic status. Incidences of alcohol-related injuries and of non-alcohol-related injuries were calculated, and the relative ratio of injuries between AUDIT categories was analyzed. Results: The incidences of all injuries and alcohol-related injuries were 69.2 and 6.8 per 1000 person-year. After adjustment, the incidences of non-alcohol-related injuries showed no differences between AUDIT categories. But the adjusted relative ratios (RRs) of alcohol-related injuries were 3.73 (95% CI: 1.54~8.99) and 7.70 (95% CI: 3.61~16.44) for risk drinkers and for alcohol-dependent drinkers respectively. No specific body part could be identified as being frequently injured in cases of risk drinkers and alcohol-dependent drinkers. In contrast, the adjusted RRs of fractures, bruises, and open wounds were 1.76 (95% CI: 1.03~3.02), 1.73 (95% CI: 1.15~2.61), and 1.85 (95% CI: 1.17~2.93) for alcohol-dependent drinkers. Assaults occurred 4.66 times more frequently in alcohol-dependent drinkers. Conclusion: Alcohol-related injuries occur more frequently as the person becomes more dependent on alcohol. Fractures, Bruises, open wounds, and assaults occur more frequently in alcohol-dependent drinker. This study suggests that efforts should be carried out in the ED to screen and treat alcohol-use disorders associated with patients injured after drinking.

• 정신신체의학
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• 제14권2호
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• pp.102-107
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• 2006

연구목적 : 본 연구는 메스암페타민 의존자의 우울감 정도를 알아보고, 이들의 우울감이 메스암페타민 사용행태와 관련이 있는지 알아보기 위해 실시되었다. 방법: 메스암페타민 의존자 43명과 대조군 40명을 대상으로 메스암페타민 사용행태를 조사하였고, Beck 우울척도(Beck Depression Inventory, BDI)를 이용하여 우울감에 대해 알아보았다. 결과: 메스암페타민 군의 평균 BDI 점수는$14.1{\pm}7.7$점으로 대조군의 $7.3{\pm}5.7$점에 비해 유의하게 높았다(t=4.04, df=65, p<0.001). 의미있는 우울감을 호소하는 이의 비율도 대조군(경도-중등도 : 22.6%, 중등도-중증 : 3.2%)에 비해 메스암페타민 의존자(경도-중등도 : 38.9% : 중등도-중증 : 27.8%)에서 더욱 컸다(p=0.001). 성별, 연령, 음주량과 흡연량을 보정한 후에도 메스암페타민 의존자에서 우울감을 호소하는 이가 더 많았다. (OR=300.7, p=0.012). 메스암페타민 의존자의 BDI점수는 메스암페타민 단약기간과 유의한 음의 상관관계를 보였지만(r=-0.35, n=36, p=0.042), 메스암페타민 사용 용량이나 사용 기간과는 유의한 상관관계를 보이지 않았다(r=-0.08, n=36, p=0.677 ; r=-0.08, n=36, p=0.658). 결론: 메스암페타민 의존자는 대조군에 비해 우울감이 심하며 의미있는 우울감을 보고하는 경우도 더 흔하였다. 메스암페타민 의존자의 우울감은 메스암페타민 사용 정도와는 관련이 없었으나, 장기간의 단약을 통해 감소할 가능성이 시사되었다.