• Journal of Communications and Networks
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• 제13권6호
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• pp.639-654
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• 2011

In this paper, we present a channel access mechanism, referred to as the enhanced mesh coordinated channel access (eMCCA) mechanism, for IEEE 802.11s-based wireless mesh networks. The current draft of IEEE 802.11s includes an optional medium access control (MAC), denoted as MCCA, which is designed to provide collision-free and guaranteed channel access during reserved periods. However, the MCCA mechanism fails to achieve the desired goal in the presence of contending non-MCCA nodes; this is because non-MCCA nodes are not aware of MCCA reservations and have equal access opportunities during reserved periods. We first present a probabilistic analysis that reveals the extent to which the performance of MCCA may be affected by contending non-MCCA nodes. We then propose eMCCA, which allows MCCA-enabled nodes to enjoy collision-free and guaranteed channel access during reserved periods by means of prioritized and preemptive access mechanisms. Finally, we evaluate the performance of eMCCA through extensive simulations under different network scenarios. The simulation results indicate that eMCCA outperforms other mechanisms in terms of success rate, network throughput, end-to-end delay, packet-loss rate, and mesh coordinated channel access opportunity-utilization.

• 국제초고층학회논문집
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• 제1권2호
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• pp.99-105
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• 2012

The higher the building height and the larger the temperature difference between the outdoor and indoor space, the more remarkable is the draft driven by the stack effect in high-rise buildings. Moreover, the stack effect can bring about the deterioration of habitability and the degradation of the performance of the indoor control system in high-rise buildings. In this study, as a measure to attenuate the stack effect, the E/V shaft cooling method was proposed and its performance was compared with the conventional stack effect control method for strengthening the air-tightness of the building using a numerical simulation method. The total decreasing ratios on the stack effect in a building were compared, and the probabilities of the secondary problems were analyzed. The results show that the E/V shaft cooling is very effective to decrease the stack effect in a high-rise building in terms of the reduction performance and application. Moreover, this method does not cause secondary problems, such as stack pressure transition to other walls, unlike the conventional stack effect mitigation method.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.375-380
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• 2008

This study have processed the developing of vane damper with accurate control by using gear which is a flow-control equipment of marine boiler's FD fan on this research. For the developing of vane damper, we have corrected some problem from welding & assembly process by changing the design, and for the case of an emergency case, we have applied the easy disassembly & assembly on that vane damper. Compared to Rink type vane damper in current, we have focused on high efficiency with low price of that new developing damper. For selection of actuator, we have tried to find the propriety with our developing focus. Also, we have developed a jig of assembly processing for high productivity with quality, it caused the best assembly performance with heat-treated & processed parts.

• 한국항해항만학회지
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• 제32권1호
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• pp.1-7
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• 2008

최근 중국의 경제 활성화에 힘입어 물동량이 급증하게 되었고, 따라서 선박의 폭발적인 요구도 생기게 되었다. 그러나 조선소의 건조 능력은 드라이도크의 용량에 의하여 크게 의존할 수밖에 없는 실정이다. 드라이도크의 건조는 상당히 긴 기간을 필요로 하고, 또 건조 비용도 많이 들기 때문에 장기적인 조선의 수요의 관점에서 타당성을 검토할 필요가 있다. 더욱 시급한 것은 당장 목전에 와 있는 조선 수요를 적절히 감당해 주어야 한다는 점이다. 그래서 여러 조선소에서는 드라이도크의 부족을 메우기 위한 다양한 방안들이 검토되었다. 현대중공업에서는 육상 건조법을 도입하였고, 삼성중공업과 STX 조선소에서는 플로팅도크에서 건조하는 방법을 도입하였다. 본 논문은 육상에서 건조한 대블록을 플로팅도크에 밀어 넣는 Skid Launching System(SLS)을 위한 도크 제어 시뮬레이터를 개발하여 모의 조정한 결과를 보인다. 대형 블록을 플로팅도크에 밀어 넣기 전에 발라스트 순서도를 작성하여 모의 작업을 통하여 안정성을 확인한 뒤 실제 작업 시 이 순서대로 작업을 하여 플로팅도크의 안전성을 확보하기 위한 장치를 개발한 것이다.

• 아태비즈니스연구
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• 제10권3호
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• pp.125-142
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• 2019

The study wanted to verify the effect of emotional sub-compression, a negative variable of emotional labor, on job performance, on security personnel working at private security companies, and further to verify how the impact on emotional sub-compression can affect job performance through the first draft of regulation. Empirical analysis through the study model showed that emotional edema was not a significant effect, but a negative effect on job performance, and that it did not affect the control focus itself. This revealed that emotional harmony has been shown to have a negative impact on performance due to the present state and conflicting situations in one's emotions, which means that emotional harmony does not affect negative or positive effects depending on a person's attributes. It also showed that the temperamental control focus on job performance had a positive impact on employees with an improvement focus and had a negative impact on employees with a preventive focus, and that a temperamental control focus between emotional dissonance and job performance had an effect. This indicated that job performance was affected by a temperamental control focus and that employees with an improvement focus had a positive effect and had a positive effect on performance. The implications of the study in this study are that it can have target differentiation in the areas where the study was conducted on guard workers, a social issue related to the study of emotional labor, and it can be meaningful that the study of emotional labor had a control focus and measured both positive and negative tendencies. It is also believed that there will be contributions to the verification of differences in performance resulting from employee propensity and by linking it with a variable called emotional instability. However, the data collected have the limitations of the subject and region, and the emphasis on cross-sectional analysis and the representative of the various emotions to verify the negative effects of emotional labor, and the problem of securing reliability related to the adjustment focus verification are the limitations of the research.

• Journal of Nutrition and Health
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• 제31권8호
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• pp.1355-1364
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• 1998

This study was planned to investigate the effect of 40 plant ethanolic extracts on antioxidant activities in vitro. The total phenolics, $\beta$-carotene, $\alpha$-tocopherol and selenium contents were also determined . Antioxidant activities fo the ethanolic extracts(0.02%, w/w) in the soybean oil were measured both by determining the peroxide value (POV) during 35 days of storage at 4$0^{\circ}C$ in a forced draft air-incubator and by determining changes in conductivity at 11$0^{\circ}C$(Rancimat method.). Soybean oil without any additives was used as a control and that treated with 0.02% BHT was used as a positive control. Based on the POV determination, green tea extract was found to be the most effective in stabilizing soybean oil, then followed by long tea, which both of them showed higher antioxidant activities compared to the BHT treatment. The antioxidant activities of them showed higher antioxidant activities compared to the BHT treatment. the antioxidant activities of coffee, cinnamomi cortex, acanthopanacis cortex, black tea, orange peel , instant coffee, peony and crni fructus extracts were stronger compared to the control .By the Rancimat method, green tea leaf and oolong tea leaf, foxglove, acanthopanacis cortex and peony extracts. Compared to other extracts, green tea leaf, black tea leaf, foxglove, acanthopanacis cortex and peony extracts had stronger antioxidative effects in both the POV and Rancimat methods used in this study. ethanolic extracts which showed the stronger antioxidative effect also has the higher contents of total phenolics, $\beta$-carotene, and/or $\alpha$-tocopherol. The antioxidative effect of ethanolic extracts was found to be due to the combined effect of various antioxidants.

• 대한간호학회지
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• 제47권4호
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• pp.526-539
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• 2017

Purpose: This study was undertaken to develop and test a mastery learning program of nursing skills for undergraduate nursing students. Methods: In this methodological study, first, the preliminary draft of a mastery learning program to provide training for nursing skills was developed based on Bloom's framework for mastery learning. Second, to test the developed program, a single-blinded, nonequivalent control group nonsynchronized study was conducted on 50 senior nursing students in a University selected by convenient sampling. Thirteen students were assigned to a control group; 13, 12, and 13 of them were assigned to intravenous therapy, transfusion, and patient transfer groups, respectively. The achievement levels and performance scores of the selected nursing skills were measured before and after the completion of the program in all the groups. Lastly, the final program was confirmed based on the results of the program testing. Results: Intravenous therapy, transfusion, and patient transfer were selected as essential nursing skills for the program based on the priorities rated by clinical instructors and staff nurses. The achievement levels of selected nursing skills were determined by Angoff scores. After participating in the program, the proportion of passers and performance scores of the nursing skills in the experimental groups were significantly higher than those in the control group. The final program was confirmed which included a diagnostic test, enrichment activities for the passers and three repetitions of corrective activities and formative assessments for non-passers. Conclusion: The results suggest that a mastery learning program for undergraduate students can lead to better improvement and performance of essential nursing skills.

• 한국항해항만학회지
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• 제33권6호
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• pp.375-380
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• 2009

1년 전까지만 해도 조선시황은 한없는 호항을 누릴 것으로 보였다. 그러나 2008년 후반에 찾아든 글로벌 경제의 불황은 바로 해운시장을 뒤흔들었고 그 여파는 바로 조선 사장에도 한없는 추락을 가져오고 있다. 저자들은 이러한 사태를 예견하여 이미 드라이 도크의 건조에 신중을 기할 것을 주장한 바 있다. 여기에 비하여 Floating Dock는 건조 비용도 덜 들고, 건조 기간도 짧고, 이동성마저 갖추고 있기 때문에 훨씬 더 유연한 도크 건설 방법이 될 수 있다. 그러나 Floating Dock는 대형의 블록을 탑재할 때 갑작스런 중량의 이동으로 인한 중심의 큰 변화로 안정성이 크게 위협 받게 된다. 따라서 안전하게 블록을 탑재하기 위하여서는 아주 고도의 정밀한 발라스트 작업이 수행되어야 한다. 본 연구에서는 육상에서 만들어진 거대 블록을 플로팅도크에 밀어 넣는 Skid Launching System을 위한 플로팅도크 제어 시스템을 완성하여 안정적인 SLS를 구현하고자 한다. 이를 위하여 저자들은 우선 가상의 진수 절차를 만들어 모의 조정하는 시뮬레이터를 개발(Kim et al. 2008)한 바 있다. 본 논문에서는 이시뮬레이션을 바탕으로 실시간 모니터링하면서 실시간 제어하는 시스템을 만들고 실제 진수에 적용하고자 한다.

• 한국콘텐츠학회논문지
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• 제21권12호
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• pp.190-201
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• 2021

도로전광표지판(VMS : Variable Message Sign)은 도로이용자에게 교통, 도로, 기상상황 및 공사로 인한 통제 등에 대한 실시간 정보를 제공함으로써 교통흐름의 효율화와 통행의 안전성을 향상시키기 위한 장비이다. 일반국도 VMS의 대부분을 차지하는 문자식 VMS에서 표출 및 제공되는 소통정보 메시지 구성은 일반적으로 구간, 구간에 대한 통행시간, 소통상황에 대한 정보로 이루어진다. 본 연구에서는 수도권 일반국도에서 운영 중인 문자식 VMS를 대상으로 도로이용자 선호도 분석을 통해 도로관리자 위주의 기존 표출문안을 도로이용자 중심으로 개선안을 마련하였다. 아울러 도로이용자가 가장 선호하는 돌발상황에 대한 정보를 신속하고 효율적으로 제공할 수 있는 시스템 개선에 대한 방안을 제시함으로써 도로이용자 중심의 VMS 교통정보 제공 효용성을 향상시키고자 한다.

• 한국항해항만학회지
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• 제47권2호
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• pp.75-84
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• 2023

Ships need to ensure safety during their navigation, which makes route determination highly important. It must be accompanied by a route following controller that can accurately follow the route. This study proposes a method for automatically generating the ship route based on deep reinforcement learning algorithm and following it using a route following controller. To generate a ship route, under keel clearance was applied to secure the ship's safety and navigation chart information was used to apply ship navigation related regulations. For the experiment, a target ship with a draft of 8.23 m was designated. The target route in this study was to depart from Busan port and arrive at the pilot boarding place of the Ulsan port. As a route following controller, a velocity type fuzzy P ID controller that could compensate for the limitation of a linear controller was applied. As a result of using the deep Q network, a route with a total distance of 62.22 km and 81 waypoints was generated. To simplify the route, the Douglas-Peucker algorithm was introduced to reduce the total distance to 55.67 m and the number of way points to 3. After that, an experiment was conducted to follow the path generated by the target ship. Experiment results revealed that the velocity type fuzzy P ID controller had less overshoot and fast settling time. In addition, it had the advantage of reducing the energy loss of the ship because the change in rudder angle was smooth. This study can be used as a basic study of route automatic generation. It suggests a method of combining ship route generation with the route following control.