• 한국방재학회 논문집
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• 제7권3호
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• pp.1-7
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• 2007

중공 RC 기둥은 중실 RC 기둥에 비해 자중의 감소 및 재료 절감에 대한 장점을 가진다. 그러나 중공 RC 기둥은 안쪽면의 취성파괴로 인하여 낮은 연성 거동을 할 가능성이 있다. 이러한 문제점을 해결하기 위해 중공 부재 내의 콘크리트 3축 구속 상태로 존재하게 하는 강관으로 보강된 중공 RC 기둥이 개발되었으며, 본 연구에서는 강관으로 보강된 중공 RC 기둥의 중공비를 $0.50{\sim}0.85$까지 변화 시켜 중공비에 따른 작용하중에 대한 안전율, 연성도, 재료비, 교각 총 중량에 대한 거동 특성을 파악하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.423-425
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• 2017

많은 우주 발사체와 로켓에 분리가 필요한 순간에 작동하는 파이로 분리장치는 높은 신뢰도 및 에너지를 갖는다는 장점을 가져 널리 활용되어 왔다. 그 중 high-explosive 타입의 분리장치에서 발생하는 충격과 파편은 발사체 내부 탑재 장비에 치명적 손상을 야기 할 수 있고, 이러한 문제를 해결하기 위해 압력 카트리지 방식의 저충격 분리장치가 개발되어 왔다. 본 연구에서는 저충격 분리장치중 하나인 스플릿 타입 파이로락에 대하여 연소상태와 파이로락을 구성하는 4개의 독립적 내부 부품의 분리 거동을 모사하는 수학적 모델을 설립하고, 실험 결과와 비교를 통해 검증을 수행하였다.

• Advances in aircraft and spacecraft science
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• 제6권4호
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• pp.333-348
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• 2019

Low fuel regression rate is the main drawback of hybrid rocket which should be overcome. One of the improvement techniques to this problem is usage of a solid fuel grain with a complicated geometry port, which has been promoted owing to the recent development of additive manufacturing technologies. In the design of a hybrid rocket fuel grain with a complicated geometry port, the understanding of fuel regression behavior is very important. Numerical investigations of fuel regression behavior requires a capturing method of solid fuel surface, i.e. gas-solid interface. In this study, level set method is employed as such a method and the preliminary numerical tool for capturing a hybrid rocket solid fuel surface is developed. At first, to test the adequacy of the numerical modeling, the simulation results for circular port are compared to the experimental results in open literature. The regression rates and oxidizer to fuel ratios show good agreements between the simulations and the experiments, after passing enough time. However, during the early period of combustion, there are the discrepancies between the simulations and the experiments, owing to transient phenomena. Second, the simulations of complicated geometry ports are demonstrated. In this preliminary step, a star shape is employed as complicated geometry of port. The slot number effect in star port is investigated. The regression rate decreases with increasing the slot number, except for the star port with many slots (8 slots) in the latter half of combustion. The oxidizer to fuel ratio increases with increasing the slot number.

• Structural Engineering and Mechanics
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• 제81권6호
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• pp.769-780
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• 2022

This paper studies the dynamic behavior of laminated composite circular cylindrical shells interacting with a fluid. The mathematical formulation of the dynamic problem for an elastic body is developed based on the variational principle of virtual displacements and the relations of linear elasticity theory. The behavior of an ideal compressible fluid is described by the potential theory, the equations of which together with boundary conditions are transformed to a weak form. The hydrodynamic pressure exerted by the fluid on the internal surface of the shell is calculated according to the linearized Bernoulli equation. The numerical implementation of the mathematical formulation has been done using the semi-analytical finite element method. The influence of the ply angle and lay-up configurations of laminated composites on the natural vibration frequencies and the hydroelastic stability boundary have been analyzed for shells with different geometrical dimensions and under different kinematic boundary conditions set at their edges. It has been found that the optimal value of the ply angle depends on the level of filling of the shell with a fluid. The obtained results support the view that by choosing the optimal configuration of the layered composite material it is possible to change upwards or downwards the frequency and mode shape, as well as the critical velocity for stability loss over a wide range.

• 한국학교보건학회지
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• 제6권2호
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• pp.89-100
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• 1993

This study intended to examine closely the reasons which influence the health status and to health behavior of teenagers and plan the development of the school health education. The subject of this study was the boys, and girls' high school students in Chonguy city. The number of them was totally 632 and the period was from July 9 to 14, 1990. 1. The Health Status of Teenagers. I have examined closely the health status of teenagers. They answered they continued to go to school. ever though the majority of teenagers had troubles in their sleeping and felt sick As for one's health, most of teenagers were in a good condition and were sometimes worrying about their health condition. 2. The Degree of Interest and Responsibilities of Teenagers for Their Own Health. In the responsibility of teenagers for their own health the answer, 'my health depends on my taking care of it', had the highest grade, 4.67. And the answer, 'I am in a good health condition because I have taken of my health very well', had the lowest average, 4.1. In the degree of interest of teenagers for their own health, the problem of studying had the highest degree, 4.48 and the use of drugs, the smoking behavior, masturbation, the drinking behavior and the birth control were the lowest degree. 3. The Health Behavior of Teenagers. In this part, teenagers performed about 64 percent's health behavior on the point of 3.37. 4. The Comparison of the Health Behavior, the Health Responsibility and the Health Interest of the Subject According to the General Characteristics. The results were as follows: 1) There are significantly different in the health behavior according to sex (t=6.23, p<.001), smoking experience (t=5.33, p<.001), living place (t=5.09, p<.001), ranking of brothers (F=4.19, p<.01), economic situation(F=6.57, p<.001). 2) There is significantly different in the health responsibility according to sex(t=2.31, p<.05), experiencd by disease(t= 1.92, p<.05). 3) There are significantly different in the health interest according to the chronic disease experience of family (t=3.29, p<.001), smoking experience(t=2.71, p<.01). 5. The Correlation of the Health Behavior, the Health Responsibility, the Health Interest and the Health Locus of Control of the Subject. The health behavior showed the positive correlation with the health responsibility (r=.2906, p<.001), and the health responsibility showed the positive correlation with the health interest (r=.0938, p<.01). Also the health behavior showed the positive correlation with powerful others health locus of control (r=.2606, p<.001), and internal health locus of control (r=.2023, p<.001), the health responsibility showed the positive correlation with internal health locus of control (r=.4541, p<.001), and chance health locus of control(r=.1352, p<.001), and the health interest showed the positive correlation with internal health locus of ccntrol (r=.0920, p<.001), powerful others health iocus of control (r=.1907, p<.001 chance health locus of control (r=.1191, p<.01). On the basis of the above result, we can find the fact that the interest of teenagers for their own health is increasing. And so, it is necessary for the school health management to establish the new curriculum which strengthens the health education for the planning of one's desirable health management. Besides we need efforts to develop the standard scale through the analysis of all reasons which influences the tenagers' health status and health behavior.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권2호
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• pp.786-799
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• 2018

Recently, NFV has attracted attention as a next-generation network virtualization technology for hardware -independent and efficient utilization of resources. NFV is a technology that not only virtualize computing, server, storage, network resources based on cloud computing but also connect Multi-Tenant of VNFs, a software network function. Therefore, it is possible to reduce the cost for constructing a physical network and to construct a logical network quickly by using NFV. However, in NFV, when a new VNF is added to a running Tenant, authentication between VNFs is not performed. Because of this problem, it is impossible to identify the presence of Fake-VNF in the tenant. Such a problem can cause an access from malicious attacker to one of VNFs in tenant as well as other VNFs in the tenant, disabling the NFV environment. In this paper, we propose Auto-configurable Security Mechanism in NFV including authentication between tenant-internal VNFs, and enforcement mechanism of security policy for traffic control between VNFs. This proposal not only authenticate identification of VNF when the VNF is registered, but also apply the security policy automatically to prevent malicious behavior in the tenant. Therefore, we can establish an independent communication channel for VNFs and guarantee a secure NFV environment.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2005년도 추계학술대회 논문집
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• pp.111-116
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• 2005

An automobile engine has the Positive Crankcase Ventilation system (PCV system) for preventing air pollution as the environmental problem is important In this system, a PCV valve is the most important component to control the flow rate of Blowby gas which is generated by various engine powers. But, in the working place, the design of a PCV valve is very difficult because of interaction between fluid and solid motions. In this study, we investigated fluid flow characteristics using re-meshing method of a CFD technique to simulate spool behavior. As the results, a spool is periodically oscillated with time and is largely oscillated in proportion to the differential pressure between inlet and outlet. And, although the velocity at the orifice increases with the differential pressure, the flow rate of the outlet decreases. This research may give PCV designers visual flow information to help them

• 유통과학연구
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• 제13권6호
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• pp.105-118
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• 2015

Purpose - Currently, strengthening small and medium-sized enterprises (SME) in terms of competitiveness is a key economic issue. However, the problem is that many SMEs lack the internal competence required to cope with a rapidly changing market structure. Such problems can act as an obstacle to economic development, yet most SMEs in Korea are dealing with this problem today. A company's source of competitive advantage is changing from quantity to quality, facility to knowledge, and hardwork to creativity. Under such circumstances, a company should place learning and sharing of knowledge and continuously creating new knowledge as its priority. This study aims to identify the effect of a chief executive officer's (CEO) compassion and forgiveness - positive factors in organizational emotion - on learning organization activities and organizational performance, through a theoretical comparison. Research design, data, and methodology - For this study, SMEs based in Daejeon and Chungcheong area were selected. To secure credibility of the data, the subjects were selected among those who have been working at the business for six months or longer. The survey was conducted for 30 days from March 5, 2015 to April 5, 2015. Both offline and online surveys were conducted. Fifty companies were chosen and 700 questionnaires were distributed, with 506 used for analysis. Fifty subject companies (25 from Daejeon, 10 from Chungnam, 10 from Chungbuk, and five from Sejong) were selected and the objective, target, and survey content were explained to a manager at each company either face-to-face or on the phone. Of the total of 700 questionnaires distributed via mail or e-mail, 78.6% or 550 copies were returned. Excluding 44 insufficient questionnaires, the remainder, 506 questionnaires, were used for analysis. Results - This study analyzed how the CEO's compassion and forgiveness affects learning organization activities and organizational performance. First, compassion of the CEO at the SMEs directly affected the learning organization activities and indirectly affected the organizational performance. Second, forgiveness of the CEO at the SMEs did not affect the learning organization activities and organizational performance directly or indirectly. Conclusions - The study conclusions are as follows. First, CEO compassionate behavior at the SMEs was a significant variable that directly and indirectly affected learning organization activities and organizational performance. Therefore, the CEO of an SME can create a positive organizational atmosphere through compassionate behaviors in the organization. Second, the forgiving behavior of the CEO did not have direct or indirect effects on learning organization activities and organizational performance. However, the reason for a CEO to continue his or her forgiving behavior is because it strengthens employee resilience, commitment, and self-efficacy to protect the organization from negative influences such as layoffs, risks, and wrongdoings. The action of forgiveness does not have direct or indirect effects. However, the CEO shall continue such behavior to strengthen members' physiological resilience, commitment, and self - effectiveness, and to protect the organization from risks including layoff and external negative factors.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• 제22권4호
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• pp.271-286
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• 2011

Objectives : The purposes of this study were to develop a mental health screening questionnaire and the practical intervention programs or guidelines which can be used in middle and high schools by students and teachers. Methods : The Adolescent Mental health & Problem behavior Screening Questionnaire II (AMPQ-II) was developed and was tested for reliability and validity using nationwide data from 2,180 middle and high school students and 2,145 teachers. Results : The AMPQ-II was measured by both students and teachers. The correlation coefficient of the test-retest test was 0.567 and internal consistency was high (Cronbach's alpha=0.878). Five factors such as worry and thought, mood and suicide, academic and Internet-related problems, peer problems, and rule violations were proposed. We also developed a practical guideline and manuals which can be easily used by secondary school teachers to screen for and manage mental health problems at school. Conclusion : The AMPQ-II can be a useful and reliable tool to screen for mental health problems in middle and high schools in South Korea.

• 한국사회복지학
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• 제57권3호
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• pp.133-164
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• 2005

본 연구는 아동이 인지한 가정의 경제적 곤란과 가족갈등 스트레스가 문제행동과 학교적응에 미치는 영향을 아동의 스트레스와 대처방식 간의 상호작용에 관심을 두고 접근하였다. 자료는 C도에 거주하는 12세-15세의 아동 1,200명에 대한 설문조사를 통해 수집, 최종적으로 1,115부를 통계분석하였다. 자료분석결과, 아동의 문제행동과 학교적응에 차이를 가져오는 일반적 특성은 아동의 성, 학년과 성적이 대표적이었고, 가족유형에 따른 차이는 없었다. 경제적 곤란과 가족갈등 스트레스는 적응에 유의한 변수로 나타났으나 성에 따라 차이가 있어 남아는 내 외현화 문제행동에 경제적 곤란과 가족갈등이 영향을 미쳤으나 여아의 내재화 문제행동에는 경제적 곤란의 영향력은 유의하지 않았다. 상호작용에서도 남아의 경우 모든 적응문제에 스트레스 변인과 대처방식의 상호작용효과가 유의하였으며, 여아의 경우에는 공격성, 비행 및 불안 우울에서만 상호작용효과가 유의하게 나타났다. 아동의 스트레스 대처방식이 부적응 예방 프로그램의 한 영역으로서 연구 개발될 필요성이 논의되었다.