• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(III)
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• pp.151-156
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• 2003

The Communication Based Train Control(CBTC) System generally used to improving existing lines in the world is efficient and stable for improvement. Also it is efficient for improvement because it does not cause any problems in operation of existing lines. We examined the mixed operation scheme for more efficient and stable improvement when improvement is implemented depending on aged equipment and the increased number of passengers in the Korean city railroad. The biggest point in the mixed operation is to implement a stable test without interfering with the operation of the existing lines. For this purpose, we deduced a method of installing the equipment, a method of testing depending on the installed equipment, and the types of mixed operation, and presented a scheme of execution of the methods depending on the mixed operation.

• Journal of the Korean Statistical Society
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• 제36권2호
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• pp.201-208
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• 2007

Evolutionary operation (EVOP) proposed by Box (1957) is a method for continuous monitoring and improvement of a full-scale manufacturing process with the objective of moving the operating conditions toward the better ones. EVOP consists of systematically making small changes in the levels of the two or three process variables under consideration. Data are collected on the response variable at each point of two level factorial design with the center point and a cycle is said to have been completed. The cycles are replicated sequentially until the decision is made on whether further cycle of experiments is needed to conclude the significance of any of main effects or interaction effects or the curvature. In this paper, an improved flow chart of EVOP is proposed and how to determine the number of cycles is studied based on the size of type II error. In order to reject the alternative hypothesis of interests with more confidence and conclude that we believe in the null hypothesis of no effects, we propose a counter measure $p^*-value$ corresponding to the p-value. The relationship of $p^*-value$ to the probability of type II error ${\beta}$ under the alternative hypothesis of interests is analogous to that of p-value to the probability of type I error ${\alpha}$. Also the implementation of EVOP with a mixture experiment is discussed.

• 대한산업공학회지
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• 제18권1호
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• pp.155-167
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• 1992

This paper presents an automatic setup planning system for turning operation of symmetric rotational parts. The proposed setup planning system determines workpiece holding method, number of setup, clamping surface, and workpiece holding device by using design data, part description database and part feature recognition information. The workpiece holding method is based on functional name and length/diameter ratio of the given part, and number of setup is determined by part profile type and its technological constraints. Clamping surface and workpiece holding device are determined by using information about the results of workpiece holding method and number of setup, and capacity of workpiece holding devices. A case study is performed to show the performance of the proposed system.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제26권5호
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• pp.507-513
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• 2000

Objective : The purpose of this study is to evaluate the vitality of the teeth in and adjacent to the mandibular fracture line according to variable conditions of fracture and to establish the protocol of treatment of fracture line teeth. Materials and Methods : The vitality of 97 teeth in fracture line and 104 teeth adjacent to fracture line of 52 patients were invested preoperatively. Of these, 66 teeth in fracture line and 72 teeth adjacent to fracture line were monitored at least 6 months after operation. An electric pulp tester was used to measure pulpal response. The relationships between the vitality of teeth in variable time(preoperation, immediate post-operation; within 1 week after operation, and 6 months after operation) and variable conditions of fracture(horizontal, vertical gap of fracture line, the number of fracture line)were evaluated statistically. Result : The vitality of fracture line teeth in the 6 months after operation statistically differed by the vertical gap of fracture line and the number of fracture line. The vitality of fracture line adjacent teeth in the immediate post-operation only statistically differed by the vertical gap of fracture line. There were statistically differences between preoperative EPT value and vitality of fracture line teeth on 6 months after operation. There were 5 cases of complications including periapical and periodontal abscess. Of these, only one tooth was extracted and the others were well treated with endodontic treatment and subgingival curettage. Conclusion : It is recommended to retain teeth and to monitor the vitality of teeth in and adjacent to fracture line, unless there is an absolute indication for extraction.

• 대한간호학회지
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• 제2권1호
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• pp.49-61
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• 1971

The purpose of this study is to observe the administering of analgesics and sedatives to cases of surgery, the influence of the patients'situational variables on the use of these drugs, and the required number of recovery days in relation to the patients'situational variables and general conditions. Fifty patients in the age range of 15 through 65 who had undergone general surgery at Seoul national University Hospital. Woo Sok University Hospital and Koryo Hospital between May and August of 1971 were chosen for this study. They were observed with regard to the frequency of postoperative uses of analgesics and sedatives age, the required period of recovery in comparison with the situational variables of patients such as sex, age, marital status, the type and duration of anesthesia, experience of previous operation, history of other diseases, preoperative period of hospitalizations and the general conditions of patients such as sleep, stomach condition, bowel condition, urination, interest in surroundings, strength and energy, self-assistance and appetite. The study results were reviewed in a statistical method to obtain the following findings: 1. There was a significant decrease in the frequency of analgesic uses according to the number of days passed after operation. 2. The mean postoperative recovery days were 5.31 days and mote than half of the patients have never used analgesics until recovery. 3. There was a significant decrease in the frequency of sedative uses according to the number of days passed after operation. 4. The rank-order correlation between the frequency of analgesic use and that of sedative use following surgery observes in relation to the number of postoperative days was a low and negative one. 5. All of the patients except one hate used sedatives only once a day for the whole recovery period. 6. The longer they stayed in the hospital before surgery, the less have they used analgesics after surgery. 7. There were significant differences in use of analgesics after surgery by age groups; the 25-44 age group used more analgesics than the 15-24 and 45-65 age groups. 8. There were no significant differences in use of analgesics after surgery by all situational variables except the number of days of hospitalization and age. 9. The longer they stayed in the hospital before surgery, the earlier have they recovered from the surgery. 10. There were no significant differences in the number of required recovery days by all situational variables except the length of preoperative hospitalization. 11. There were no significant differences in the number of required postoperative recordedly days by the general conditions of patients.

• 한국수학교육학회지시리즈A:수학교육
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• 제51권1호
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• pp.1-19
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• 2012

In this study, contents of 'the 2007 revised curriculum handbook' and 16 kinds of mathematics textbooks were analyzed first. The purpose of this study is to examine the understanding state of students at general high schools by making questionnaires to survey the understanding state on contents of chapter of complex number based on above analysis. Results of research can be summarized as follows. First, the content of chapter of complex number in textbook was not logically organized. In the introduction of imaginary number unit, two kinds of marks were presented without any reason and it has led to two kinds of notation of negative square root. There was no explanation of difference between delimiter symbol and operator symbol at all. The concepts were presented as definition without logical explanations. Second, students who learned with textbook in which problems were pointed out above did not have concept of complex number for granted, and recognized it as expansion of operation of set of real numbers. It meant that they were confused of operation of complex numbers and did not form the image about number system itself of complex number. Implications from this study can be obtained as follows. First, as we came over to the 7th curriculum, the contents of chapter of complex number were too abbreviated to have the logical configuration of chapter in order to remove the burden for learning. Therefore, the quantitative expansion and logical configuration fit to the level for high school students corresponding to the formal operating stage are required for correct configuration of contents of chapter. Second, teachers realize the importance of chapter of complex number and reconstruct the contents of chapter to let students think conceptually and logically.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2004년도 학술대회 논문집
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• pp.237-240
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• 2004

For the paralleled operation of DC/DC converters, the current sharing between each modules is the most important for the reliability of the power system. Interleaving method is commonly used with many paralleling schemes for the reduction of the ripple in the output voltage of paralleled converters and there are many commercial IC for interleaving application appliable. But for all of them, it is impossible to detect the number of module in operating and then change the phase of them automatically. In this paper, a novel paralleling method is proposed for the converter parallel operation, which detects the number of modules in active and sets the phases of PWM signals applied to each modules autonomously. This can greatly improve the output voltage ripple and reliability of the system. The expandibility of modular number can be done very easily by just adding several parts.

• 대한안전경영과학회지
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• 제10권3호
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• pp.99-107
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• 2008

Product liability(PL) is the producer's compensation to customers for damage incurred by product defects. This paper studies on the organizational culture, promotion process, system construction, system level, product safety review, product safety assurance, system operation, and its effectiveness and necessity of recognition for the PL system of small and medium-sized firms in Gangwon-Do province. The results show that the firms have product safety regulations, but the number of firms which its employees understand the regulations is less than the number of firms which do not understand. Also the number of firms which is preparing PL prevention and insurance, and counterplan for accidents seems to be not in large numbers.

• 대한교통학회지
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• 제30권2호
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• pp.21-27
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• 2012

이 연구는 신호교차로의 신호운영과 교통사고의 관계를 다루고 있다. 연구의 목적은 전적색신호시간(ARCI) 운영에 따른 교통사고 감소효과를 분석하는데 있다. 이를 위해 이 연구는 청주시 37개 신호교차로를 대상으로 비교그룹 방법을 사용하여 ARCI의 교통사고 감소효과를 평가하는데 중점을 두고 있다. 주요 결과는 다음과 같다. 첫째, 교통사고 건수와 사상자 수는 ARCI 도입 전 후가 다른 것으로 평가되었다. 둘째, 교통사고 감소효과를 비교그룹방법으로 분석한 결과, 사고건수는 20.0%, 그리고 사상자 수는 28.0% 감소한 것으로 분석되었다. 마지막으로, 전적색신호시간 운영에 따른 사고건수의 감소 효과는 6.0~35.0%, 사상자 수의 감소 효과는 18.0~37.0%로 평가되었다.

• 산업경영시스템학회지
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• 제47권2호
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• pp.190-197
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• 2024

By the recent fast growth of e-commerce markets, it has been stimulated to study order picking systems to improve their efficiency in distribution centers. Many companies and researchers have been developed various types of order picking systems and pursued the corresponding optimal operation policies. However, the performances of the systems with the optimal policies often depend on the structures of the centers and the operation environments. Based on a simulation model that mimics a unique zone picking system operated by a real company in the Republic of Korea, this study compares several operation policies and finds the most appropriate order selection rule and worker assignment policy for the system. Under all scenarios considered in this study, simulation results show that it is recommendable to assign more efficient workers to the zones with heavier workload. It also shows that selecting the order with the maximum number of non-repeatedly visited zones from the order list provides the most consistent and stable performances with respect to flow time, makespan, and utilization of the system even under the scenario with the breakdown zones. On the other hand, selecting the order with the minimum ratio of penalty to the number of zones performs the worst in all scenarios considered.