• 한국환경과학회지
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• 제9권3호
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• pp.193-199
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• 2000

This study is carried out the analysis of the runoff characteristics for the design of the interior drainage systems by SWMM in urbanization basin. The basin analyzed in this study is Bumuh-chun basin which is located in Susung-gu of Taegu city. Huff method is used for rainfall distribution analysis. The optimal rainfall duration in Bumuh-chun basin is analyzed as about 90 minutes decided from comparison of arrival time and critical duration. Flood flow variation pattern is proposed through the comparison of the results of peak flow and peak time analyzed by SWMM about pre-urbanization and post-urbanization of Bumuh-chun basin. It is known that the variation of arrival time caused by the rapid increase of pavement rate in the upper area shows about 20∼25 minutes faster than pre- urbanization. Therefore, the management of surface water for design of water supply and drainage, and channel alteration has to considered the variation of geological factors according to urbanization.

• Ocean Systems Engineering
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• 제2권4호
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• pp.239-255
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• 2012

Analysis of ship parametric roll has generally been restricted to simple analytical models and sophisticated time domain simulations. Simple analytical models do not capture all the critical dynamics while time-domain simulations are often time consuming to implement. The model presented in this paper captures the essential dynamics of the system without over simplification. This work incorporates various important aspects of the system and assesses the significance of including or ignoring these aspects. Special consideration is given to the fact that a hull form asymmetric about the design waterline would not lead to a perfectly harmonic variation in metacentric height. Many of the previous works on parametric roll make the assumption of linearized and harmonic behaviour of the time-varying restoring arm or metacentric height. This assumption enables modelling the roll motion as a Mathieu equation. This paper provides a critical assessment of this assumption and suggests modelling the roll motion as a Hills equation. Also the effects of non-linear damping are included to evaluate its effect on the bounded parametric roll amplitude in a simplified manner.

• Journal of Trauma and Injury
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• 제28권4호
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• pp.241-247
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• 2015

Purpose: To evaluate the influence of how the trauma care system is applied on the management of trauma patients. Methods: We divided the patients into a pre-trauma system group and a post-trauma system group according to the time when we began to apply the trauma care system in our institution. We compared the general characteristics, injury severity score, initial response time to the trauma patients, number of preventable deaths, and clinical outcomes between the two groups. Results: The numbers of patients in the pre-trauma system group and the post-trauma system group were 188 and 257, respectively. No differences in the patient's median ages, trauma scores (ISS, RTS, TRISS) and proportions of severe trauma patients (ISS>15) were observed between the two groups. The number and the proportion of patients who were admitted to our hospital were increased in the post-trauma system group. The time interval from trauma CP activation to emergency surgery or angio-embolization, and the patient's time spent in emergency room were shortened in the post-trauma system group. However, the lengths of the ICU stay and the hospital stay, and the number of in-hospital mortalities were not improved in the post-trauma system group. In severe trauma patients (ISS>15), there were no differences between the two groups in the number and the proportion of admitted patients, and the time interval from trauma CP activation to performing a diagnostic and therapeutic procedure was not shortened in the post-trauma system group. Conclusion: Application of the trauma care system has shortened the time between the initial response and patient management. However, this improvement was not enough to result in better clinical outcomes. More trauma physicians, multidisciplinary cooperation, and a well-organized trauma management process will be needed if the maximum efficacy of the trauma system is to be achieved.

• Steel and Composite Structures
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• 제37권4호
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• pp.463-479
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• 2020

Currently, there are many lateral resisting systems utilized in resisting lateral loads being produced in an earthquake. Such systems can significantly reduce the roof's displacement when placed at an optimum location. Since in the design of tall buildings, the minimum distance between adjacent buildings is important. In this paper, the critical excitation method is used to determine the best location of the belt truss system while calculating the minimum required distance between two adjacent buildings. For this purpose, the belt truss system is placed at a specific story. Then the critical earthquakes are computed so that the considered constraints are satisfied, and the value of roof displacement is maximized. This procedure is repeated for all stories; i.e., for each, a critical acceleration is computed. From this set of computed roof displacement values, the story with the least displacement is selected as the best location for the belt truss system. Numerical studies demonstrate that absolute roof displacements induced through critical accelerations range between 5.36 to 1.95 times of the San Fernando earthquake for the first example and 7.67 to 1.22 times of the San Fernando earthquake for the second example. This method can also be used to determine the minimum required distance between two adjacent buildings to eliminate the pounding effects. For this purpose, this value is computed based on different standard codes and compared with the results of the critical excitation method to show the ability of the proposed method.

• International Journal of Quality Innovation
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• 제9권2호
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• pp.39-56
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• 2008

Six Sigma has been one of main quality improvement approaches since Motorola first invented Six Sigma in 1987. Many scholars and consult experts have discussed the critical success factors of implementing Six Sigma management, but most of them are based on related theories or qualitative analyses. In the paper, we first review critical success factor of Six Sigma status quo based on literature. Then we design the questionnaire and survey China manufacturing enterprises that have introduced Six Sigma management. And finally, we analyze the critical success factors of China manufacturing industry implementing Six Sigma management by using structural equation model and find that leadership and Six Sigma strategy, focus on market and customer, evaluation and motivation, selecting, managing and implementing Six Sigma projects are four critical success factors of China manufacturing enterprises implementing Six Sigma management. At the same time, the paper also presents the relationships between the critical success factors. The results are of important role in China manufacturing industry locating resources, eliminating waste and improving Six Sigma performance.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.483-488
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• 2003

Frictional heating in brakes causes thermoelastic distortion of the contacting bodies and hence affects the contact pressure distribution. The resulting thermo-mechanical coupling can cause thermoelastic instability (TEI) if the sliding speed is sufficiently high, leading to non-uniform heating called hot spots and low frequency vibration known as hot judder. The vibration of brakes to the known phenomenon of frictionally-excited thermoelastic instability is estimated studying the interface temperature and pressure evolution with time. A simple model has been considered where a layer with half-thickness ${\alpha}$ slides with speed V between two half-planes which are rigid and non-conducting. The advantage of this properly simple model permits us to deduce analytically the critical conditions for the onset of instability, which is the relation between the critical speed and the growth rate of the interface temperature and pressure. Symmetrical component of pressure and temperature distribution at the layer interfaces can be more unstable than antisymmetrical component. As the thickness ${\alpha}$ reduces, the system becomes more apt to thermoelastic instability. Moreover, the evolution of the system beyond the critical conditions has shown that even if low frequency perturbations are associated with low critical speed, it might be less critical than high frequency perturbations if the working sliding speed is much larger than the actual critical speed of the system.

• Tribology and Lubricants
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• 제36권6호
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• pp.324-331
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• 2020

Wedging in a frictional elastic system is defined if the state of stick exists after the external loading on the system is removed. This paper presents a method to determine the critical coefficient of wedging for an elastic frictional system by considering the separation state. Wedging is always possible if the coefficient of friction exceeds a critical value known as the critical wedging coefficient. This method requires two concepts: a necessary and sufficient condition for wedging, which can be interpreted as positive spanning sets of constraint vectors existing in the wedged system, and the minimal positive basis that enables a minimum wedging coefficient. The algorithm based on the positive spanning concept is repeatedly executed after eliminating nodes from the contact stiffness matrix, for which the separation states are impending. The simulation results show that once a node enters the separation state, it never returns to the contact state again and the critical wedging coefficient reduces during repeated algorithm execution. The benefit of this method is that the computation time permits handling models with large numbers of contact nodes. The algorithm can also numerically find the critical wedging coefficient, thereby contributing to fastening and assembly performance improvements in mechanical systems.

• 대한기계학회논문집B
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• 제40권10호
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• pp.653-658
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• 2016

본 연구에서는 비정상 열전도 역산문제의 해석이 가능한 프로그램을 이용하여 온도측정의 시간간격, 측정위치가 분무냉각 열유속의 측정결과에 미치는 영향에 대한 연구를 수행하였다. 그 결과 다음과 같은 결론을 얻을 수 있었다. CHF 부근에서는 온도측정의 시간간격이 커질수록 비정상 열전도 역산법을 이용하여 계산한 열유속은 점차 감소하고 있음을 알 수 있었다. CHF 부근에서는 열유속이 매우 빠르게 변화하기 때문에 시간간격을 일정 값 이하로 작게 측정하여 열유속을 계산하는 것이 매우 중요할 것으로 판단된다. 온도측정위치는 비정상 열전도 역산법을 이용한 CHF 부근의 계산결과에 큰 영향을 미치지 않는 것으로 파악되었다. 실험결과로부터 CHF 과열도는 열전대의 측정위치가 전열면 표면에 가까울수록 약간 고온으로 이동하는 경향이 있음을 알 수 있었다.

• 한국농공학회논문집
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• 제65권4호
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• pp.25-32
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• 2023

KDS (Korean Design Standard) for agricultural drainage is a planning standard that helps determine the appropriate capacity and type of drainage facilities. The objective of this study was to analyze the inundation of the agricultural basin considering the current design standard and the critical rainfall duration. This study used the rainfall durations of 1-48 hour, and the time distribution method with the Chicago and the modified Huff model. For the runoff model, the NRCS (Natural Resources Conservation Service) unit hydrograph method was applied, and the inundation depth and duration were analyzed using area-elevation data. From the inundation analysis using the modified Huff method with different rainfall durations, 4 hours showed the largest peak discharge, and 11 hours showed the largest inundation depth. From the comparison analysis with the current method (Chicago method with a duration of 48 hours) and the modified Huff method applying critical rainfall duration, the current method showed less peak discharge and lower inundation depth compared to the modified Huff method. From the simulation of changing values of drainage rate, the duration of 11 hours showed larger inundation depth and duration compared to the duration of 4 hours. Accordingly, the modified Huff method with the critical rainfall duration would likely be a safer design than the current method. Also, a process of choosing a design hydrograph considering the inundation depth and duration is needed to apply the critical rainfall duration. This study is expected to be helpful for the theoretical basis of the agricultural drainage design standards.

• 한국식품위생안전성학회지
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• 제11권3호
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• pp.177-187
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• 1996

Time-temperature relationship and microbiological quality were assessed and critical control points were identified through hazard analysis during the phases of production in two different packaged meals (Dosirak) manufacturing establishments (A, B:Kim Pab). Microbiological tests on foods, equipments and utensils were done according to standard procedures and included total plate count, coliforms and fecal coliforms. The results of the study are summarized as follows : time-temperature control management was needed because time-temperature abuse more than 8 hours at dangerous temperature zone (5-6$0^{\circ}C$) was observed from pre-preperation to distribution phase; Poor sanitary practices of employees were observed in hand washing and using disposable gloves; Microbiological analysis results of equirpments and utensils showed possible cross-contamination risks when foods were contacted with them; Kim Pab needed thorough quality control because it included various mixed ingredients of cooked and uncooked and had many apportunities of cross-contamination either by equipments or hands through whole production processes.