• International Journal of Aerospace System Engineering
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• 제2권2호
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• pp.29-33
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• 2015

The multidisciplinary design optimization (MDO) of a launch vehicle (LV) with a hybrid rocket engine (HRE) was carried out to investigate the ability of an HRE for a single-stage LV. The non-dominated sorting genetic algorithm-II (NSGA-II) was employed to solve two design problems. The design problems were formulated as two-objective cases involving maximization of the downrange distance over the target flight altitude and minimization of the gross weight, for two target altitudes: 50.0 km and 100.0 km. Each objective function was empirically estimated. Several non-dominated solutions were obtained using the NSGA-II for each design problem, and in each case, a trade-off was observed between the two objective functions. The results for the two design problem indicate that economical performance of the LV is limited with the HRE in terms of the maximum downrange distances achievable. The LV geometries determined from the non-dominated solutions were examined.

• 한국문헌정보학회지
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• 제38권2호
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• pp.49-74
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• 2004

본 연구에서는 한국과학기술정보연구원(KISTI)에서 지정하여 지원하고 있는 우리나라 과학기술분야 전문정보센터를 대상으로 정보서비스 체계 전반에 대한 현황 및 문제점을 분석$\cdot$파악하고 이를 토대로 최신의 정보기술을 반영$\cdot$적용한 우리나라 과학기술분야 전문정보센터의 효율적인 정보서비스 방안을 제시하였다. 이를 위하여 본 연구에서는 선행연구 분석, 설문조사, 해당기관 직접방문을 통한 관련자 면담, 해당기관 홈페이지의 관련 사이트 분석, 그리고 관련 전문가로 구성된 상시협의체의 회의를 통한 Brainstorming 방범 등을 병행하여 실시하였다.

• 아태비즈니스연구
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• 제10권4호
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• pp.77-86
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• 2019

The purpose of this study is to examine how the characteristics of family firms affect stock price crash risk. Prior studies argued that the opacity of information due to agency problem causes a plunge in stock prices. The governance characteristics of family firms can increase information opacity which leads to crash risk. Therefore, this study verifies whether family firms have a high possibility of stock price crash risk. We use a logistic regression model to test the relationship between family firms and stock price crash risk using listed firms listed on the Korean Stock Exchange during the fiscal years 2011 through 2017. The family firm is defined as the case where the controlling shareholder is the chief executive officer or the registered executive. If the controlling shareholder's share is less than 5%, it is not considered a family business. We found that family firms are more likely to experience a plunge in stock prices. This supports the hypothesis of this study that passive information disclosure behavior and information opacity of family firms increase stock price crash risk.

• 한국군사과학기술학회지
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• 제21권2호
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• pp.225-234
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• 2018

In this paper, we consider a problem of partitioning a search area into smaller rectangular regions, so that multiple platforms can conduct search operations independently without requiring unnecessary coordination among themselves. The search area consists of cells where each cell has some prior information regarding the probability of target existence. The detection probability in particular cell is evaluated by multiplying the observation probability of the platform and the target existence probability in that cell. The total detection probability within the search area is defined as the cumulative detection probability for each cell. However, since this search area partitioning problem is NP-Hard, we decompose the problem into three sequential phases to solve this computationally intractable problem. Additionally, we discuss a special case of this problem, which can provide an optimal analytic solution. We also examine the performance of the proposed approach by comparing our results with the optimal analytic solution.

• International Journal of Advanced Culture Technology
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• 제10권1호
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• pp.160-169
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• 2022

This qualitative study aimed to investigate ways to improve effective cooperative learning from students' perspective by understanding and analyzing the learning experiences of nursing students who participated in a collaborative problem-solving learning model. Data were collected through focus group interviews and reflection journals of six second-year nursing students from G-university in J-city who participated in a collaborative problem-solving learning model course. The interview data were analyzed and divided into 3 categories and 10 subcategories according to the six-step thematic analysis method proposed by Braun and Clarke. The results of analyzing the interviews were considered based on three areas: preparation before learning, the process of collaborating as a cooperative learning experience, and solutions and expectations after learning. The participants felt frustrated because collaborative problem-solving took more time for individual learning than traditional methods did and would not allow them to check the correct answers immediately. However, they gained new experiences by solving problems and engaging in discussions within their learning community. The participants' expectations included material that could help their learning, measures to prevent free-riders, and consideration of the learning process in evaluation factors. Although this study has sample limitations by targeting nursing students in only one region, it can be used to help operate collaborative problem-solving classes, as it reflects the real experiences and opinions of students.

• International Journal of Advanced Culture Technology
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• 제10권4호
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• pp.8-18
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• 2022

Objectives: The objective of this study was to explore the effects of the simulation-based learning program on stress, problem-solving ability, self-efficacy, and resilience of final-year nursing students in a college in South Korea. Methods: The design of the study was a one-group pretest-posttest. The participants of this study were final-year nursing students in 2018. A total of 105 students completed it. The intervention was an 8-week simulation-based practice course. The primary and secondary outcome measures were baseline and follow-up questionnaires regarding demographic factors, stress, problem-solving ability, self-efficacy, and resilience. Results: Problem-solving ability (t=6.567, p<.001), self-efficacy in four situations (p<.001) and resilience (t=2.352, p=.021) increased after simulation-based learning than before learning. Stress also increased after simulation-based learning compared to before learning (t=5.960, p<.001). The level of stress, self-efficacy, and resilience were mainly related to participants' satisfaction with their clinical placement, and interpersonal relationships (p<.05). Conclusions: Simulation-based learning is expected to improve nursing students' problem-solving ability, self-efficacy, and resilience. This can lead to induce learning motivation of nursing students, improve their coping strategies for solving problems, and ultimately provide high-quality care.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권10호
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• pp.5062-5079
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• 2017

Malicious insider threats have increased recently, and methods of the threats are diversifying every day. These insider threats are becoming a significant problem in corporations and governments today. From a technology standpoint, detecting potential insider threats is difficult in early stage because it is unpredictable. In order to prevent insider threats in early stage, it is necessary to collect all of insiders' data which flow in network systems, and then analyze whether the data are potential threat or not. However, analyzing all of data makes us spend too much time and cost. In addition, we need a large repository in order to collect and manage these data. To resolve this problem, we develop an indicator-based behavior ontology (IB2O) that allows us to understand and interpret insiders' data packets, and then to detect potential threats in early stage in network systems including social networks and company networks. To show feasibility of the behavior ontology, we developed a prototype platform called Insider Threat Detecting Extractor (ITDE) for detecting potential insider threats in early stage based on the behavior ontology. Finally, we showed how the behavior ontology would help detect potential inside threats in network system. We expect that the behavior ontology will be able to contribute to detecting malicious insider threats in early stage.

• 전자공학회논문지
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• 제51권4호
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• pp.18-24
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• 2014

본 논문에서는 무인항공기의 운용 범위 내에서 데이터링크 두절을 최소화할 수 있는 탑재 가시선 데이터링크 방향성 안테나의 최적 위치를 EM(Electromagnetic) 시뮬레이션을 통하여 분석하였다. 무인항공기의 급격한 거동 시 동체 Blockage로 인한 전자파 왜곡 및 손실로 데이터링크 두절이 발생할 수 있다. 이와 같은 데이터링크 두절을 방지하기 위하여 무인항공기의 거동범위를 제한하면 선회 반경이 커지게 되고, 이로 인하여 임무 수행에 많은 제약이 발생할 수 있다. 이를 해결하기 위하여 1축 방향성 안테나의 동체 상/하부 장착을 고려한 최적위치에 대하여 EM시뮬레이션을 수행하였다. 장착된 방향성 안테나는 수직빔폭이 넓은 1축 안테나를 적용하여 수직 빔폭 만큼 무인항공기가 데이터링크 두절 없이 거동할 수 있도록 설계하였다. 또한, 2축이 아닌 1축 안테나 탑재로 인하여 탑재 중량도 크게 줄일 수 있는 장점을 갖고 있다.

• 한국컴퓨터정보학회논문지
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• 제13권1호
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• pp.203-212
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• 2008

현재 운영되고 있는 경찰청 정보화 체계로는 내부 사용자와 국민들에게 편리성을 도모하지 못하는 문제점이 제기되어 왔다. 본 논문에서는 이 문제점에 대한 대책으로 외국의 경찰청 IT 정보화 조직이 주는 시사점을 분석한 후, 우리나라 경찰청 내부 사용자들에 대한 설문조사를 실시하여 개선점을 분석하여 경찰청 정보화 통합을 위한 효율적인 전략 방안을 도출하였다. 그 결과 경찰청 조직의 정보화 비전과 목표를 설정하고, 데이터연계 및 공동 활용 기반구축과 정보기술체계 등을 수립하는 효율적인 경찰청 IT 정보화 통합 모델을 설계하게 되었다. 또한 객관적인 경찰청의 업무지원시스템 고도화와 대민 서비스 강화를 위한 정보화 통합모델을 설계하고 타 기관과의 연계성을 염두에 두고 경찰청 정보업무의 효율성을 위한 개선방안을 제시하여 경찰청 정보화의 품질향상을 이룩할 수 있을 것으로 기대한다.

• 한국산학기술학회논문지
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• 제20권8호
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• pp.181-189
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• 2019

항공기용 전원 분배 장치는 발전기에서 생성된 전원을 분배 및 제어하고, 과전류를 보호하는 역할을 한다. 항공기 비행 중에 교류 전원 분배 장치의 결함으로 인해 교류 전원 분배가 불가능해지는 현상이 다수 발생하였다. 이로 인해 정상적인 교류 전원 분배가 불가능하고 일부 전자장비가 구동을 상실하는 문제점이 제기되었다. 본 논문에서는 결함 발생 조건인 항공기 비행 중 진동 조건을 진동 시험 장비로 모의하여, 결함의 근본 원인을 도출한 과정을 기술하였다. 이를 통해 결함의 원인이 교류 전원 분배 장치의 접촉기가 진동에 의해 내부 배선 손상이 발생한 것임을 확인하였으며, 결함 해소를 위해 접촉기 개선 형상을 도출하였다. 또한 결함이 내재된 접촉기를 검출하기 위해, 진동 시험 장비를 활용한 결함 검출 시험을 수행하는 방식으로 시험 절차를 개선하였다. 개선활동 결과 교류 전원 분배 장치의 결함 현상이 개선되었음을 구성품 인증 시험 및 비행 시험을 통해 입증하였다.