• 한국수학교육학회지시리즈A:수학교육
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• 제54권1호
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• pp.49-63
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• 2015

PISA 2012 showed that while Korean students achieved high-level math achievement in mathematics their levels are relatively lower in math self-efficacy. Students from Singapore, on the other hand, achieved high scores both in math achievement and in math self-efficacy. The results of the two countries differed although both countries has been sharing the same East Asian cultural sphere. This study analyzed the input and the process variables on the student- and school-level concerning math self-efficacy. The results were as follows. In Korea, math interest, instrumental motivation, elaboration strategies, applied and pure math tasks were the student-level variables that affected math self-efficacy. In Singapore, math interest, control strategies, elaboration strategies, applied and pure math tasks were the student-level variables that affected mathematics self-efficacy. Math club, teachers' low expectations were the school-level variables that affected math self-efficacy. For a higher-level of math self-efficacy in Korea, it is important to encourage students not only to use control strategies, but to participate in math clubs. It is equally important for teachers to have higher expectations towards students.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.152-161
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• 2022

We analyzed mitigation strategies for steam generator tube rupture (SGTR) accidents using MARS code under both full-power and low-power and shutdown (LPSD) conditions. In general, there are two approaches to mitigating SGTR accidents: supplementing the reactor coolant inventory using safety injection systems and depressurizing the reactor coolant system (RCS) by cooling it down using the intact steam generator. These mitigation strategies were compared from the viewpoint of break flow from the ruptured steam generator tube, the core integrity, and the possibility of the main steam safety valves opening, which is associated with the potential release of radiation. The "cooldown strategy" is recommended for break flow control, whereas the "RCS make-up strategy" is better for RCS inventory control. Under full power, neither mitigation strategy made a significant difference except for on the break flow while, in LPSD modes, the RCS cooldown strategy resulted in lower break and discharge flows, and thus less radiation release. As a result, using the cooldown strategy for an SGTR under LPSD conditions is recommended. These results can be used as a fundamental guide for mitigation strategies for SGTR accidents according to the operational mode.

• 한국정보통신학회논문지
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• 제1권1호
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• pp.105-111
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• 1997

This Paper Proposes a new efficient system design strategies for the acoustic-based underwater multiple modem and media access control protocol. The system aims to establish the acoustic-based communication network of an underwater vehicles for deep sea mining, which ensures a certain level of maximum throughput regardless of the propagation delay of acoustic and allows fast data transmission through the acoustic-based multiple channel. A media access control protocol for integrated communication network and it's acoustic-based communication modems that allows 'peer-to-peer' communication between a surface mining plant multiple underwater system is designed, and the proposed media access control protocol is implemented for its verification. Furthermore, a proposed design strategies which make it possible to control the multiple vehicle for an underwater mining is presented in this paper.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.511-513
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• 2005

The fuel cell system has inherent limitation such as slow response time and low fuel economy especially at the low power region, and thus, the battery system has come to be used to compensate for the fuel cell system. This type of hybrid configuration has many advantages, however, the energy management strategy is essentially required. The work in this paper presents survey on recent power management strategies for fuel cell hybrid electric vehicles. For three power management strategies: basic control method. object function-based control method, and fuzzy logic-based control method. each strategy is reviewed and discussed with other strategy.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제18권1호
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• pp.1-15
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• 2014

We have investigated optimal control strategies for prevention of ecstasy use. Ecstasy use has continued at raves and nightclubs in recent years and the reduction of ecstasy use has become one of the important issues in society. We apply optimal control theory to a model of the peer-driven dynamics of ecstasy use. Our goal is to minimize the ecstasy use class and the intervention cost. Optimal control is characterized in terms of the solution of optimality system, which is the state system coupled with the adjoint system and the optimality equations. The numerical simulations show the optimal prevention policies of ecstasy use in various scenarios.

• 자원ㆍ환경경제연구
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• 제1권1호
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• pp.115-149
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• 1991

In evaluating current environmental protection policy, economists often note that current regulations are more costly than necessary to meet environmental quality standards. While the a priori case can be made that current regulatory approaches entail higher-than-necessary costs to attain environmental standards, there is relatively little empirical evidence to support this claim in Korea. The purpose of this analysis is to supply some of the missing evidence by presenting the results of one study that assesses some of the potential savings associated with implementing economic, rather than command-and-control regulatory approaches to abate one type of air pollution in one region, in Korea, Specifically, the analysis examine the costs of meeting a long-term standard for TSP under the alternative control strategies for stationary sources of TSP in Ulsan Industrial Complex region. The alternative strategies that are considered are current command-and-control and various marketable permit designs. The analysis shows that the most efficient policy of emissions control is economic approaches, supporting results of previous empirical studies conducted in other countries.

• Smart Structures and Systems
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• 제13권3호
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• pp.419-434
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• 2014

In this paper, the electromagnetic damper (EMD), which is composed of a permanent-magnet rotary DC motor, a ball screw and a nut, is considered to be analyzed as a semi-active damper. The main objective pursued in the paper is to study the two degrees of freedom (DOF) model of the semi-active electromagnetic suspension system (SAEMSS) performance and energy regeneration controlled by on-off and continuous damping control strategies. The nonlinear equations of the SAEMSS must therefore be extracted. The effects of the EMD characteristics on ride comfort, handling performance and road holding for the passive electromagnetic suspension system (PEMSS) are first analyzed and damping control strategies effects on the SAEMSS performance and energy regeneration are investigated next. The results obtained from the simulation show that the SAEMSS provides better performance and more energy regeneration than the PEMSS. Moreover, the results reveal that the on-off hybrid control strategy leads to better performance in comparison with the continuous skyhook control strategy, however, the energy regeneration of the continuous skyhook control strategy is more than that of the on-off hybrid control strategy (except for on-off skyhook control strategy).

• Journal of Mechanical Science and Technology
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• 제19권7호
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• pp.1414-1423
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• 2005

This paper develops and evaluates several strategies for structural vibration control with the objective of attenuating broadband noise inside a rectangular enclosure. The strategies evaluated include model-independent collocated control, model-based feedback control and a new 'modal-estimate' feedback strategy. Collocated control requires no knowledge of model parameters and enjoys the advantage of robustness. However, effective broadband noise attenuation with colocated control requires a large number of sensor-actuator pairs. Model-based con-trollers, on the other hand, can be theoretically effective even with the use of a single actuator. However, they suffer from a lack of robustness and are unsuitable from a practical point of view for broadband structural vibration applications where the dynamic models are of large order and poorly known. A new control strategy is developed based on attenuating a few structural vibration modes that have the best coupling with the enclosure acoustics. Broadband attenuation of these important modes can be achieved using a single actuator, a limited number of accelerometers and limited knowledge of a few modal functions. Simulation results are presented to demonstrate the effectiveness of the developed strategy.

• 대한교통학회지
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• 제33권1호
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• pp.70-80
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• 2015

본 연구는 최근 국내 도입이 추진되고 있는 궤도교통수단인 트램이 일반교통류와 도로를 공유했을 때 발생할 수 있는 문제를 예상하고, 트램운영의 효율성과 안정성을 확보할 수 있는 신호운영 전략과 통합 신호운영이 가능한 신호제어기 시작품을 개발하는데 연구의 목적이 있다. 통합 신호운영을 위해 고정식 트램 우선신호와 능동식 트램 우선신호를 포함한 3단계의 유기적인 통합 신호제어 전략을 수립하였고, 각 단계별 전략수행을 위한 신호운영 알고리즘을 개발하였다. 개발된 신호제어 알고리즘을 S/W로 구현하고, 표준 신호제어기에 기반한 H/W로 제작하였고, 이를 평가하기 위한 통합 신호제어 시뮬레이터(Hardware in the Loop Simulation system: HILS)를 개발하였다. 미시적 시뮬레이션 프로그램을 통해 통합 신호제어 전략의 효과와 개발된 통합 신호제어기의 성능을 평가한 결과, 본 연구를 통해 개발된 신호제어 알고리즘으로 산출한 교차로 신호시간이 트램차량의 신호교차로 정지수와 통행시간을 감소시켰음을 확인하였고, 트램 우선신호에 따른 일반차량의 지체증가가 거의 나타나지 않음을 확인하였다. 또한 통합 신호제어 시뮬레이터를 통해 개발된 통합 신호제어기의 H/W와 S/W의 기능 수행 여부을 확인하였다.

• 한국직업건강간호학회지
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• 제18권2호
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• pp.219-231
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• 2009

Purpose: The purpose was to investigate the relations among job stress, depression, social support, and coping strategies of nurses. Method: The data were collected from 362 nurses. A self-administered questionnaire was used to assess general characteristics, job stress, depression, social support and coping strategies. Results: The prevalence of depression was 41.7%. Scores of job demand and insecurity, and organizational climate were very high. Logistic regressions showed that nurses, who were single, their 20s, had less than a career year, or working in private hospitals, associated with an increased risk of depression. The sub-scales of job stress except interpersonal conflict and lack of autonomy contributed to an increased risk of depression (lower group; OR=0.248, 95% CI:0.14-0.43). Also individual and organizational support and control coping strategies were associated with depression(lower group: OR=2.993, 95% CI: 2.11-6.30; OR=2.993, 95% CI: 1.51-5.65; OR=2.372, 95% CI=1.43-3.93). Conclusion: These findings indicated that the job stress, especially organizational climate, insecurity of job, lack of reward, individual and organizational support, and control coping strategies contributed to a risk of depression. In order to prevent the depression, the organizational support and strategies will be needed. The depression in specific context and organizational climate should be considered in future studies.