• Journal of Astronomy and Space Sciences
• /
• v.26 no.2
• /
• pp.171-186
• /
• 2009

Various Earth-Moon transfer trajectories are designed and analyzed to prepare the future Korea's Lunar missions. Minimum fuel trajectory solutions are obtained for the departure year of 2017, 2020, 2022, and every required mission phases are analyzed from Earth departure to the final lunar mission orbit. N-body equations of motion are formulated which include the gravitational effect of the Sun, Earth and Moon. In addition, accelerations due to geopotential harmonics, Lunar J2 and solar radiation pressures are considered. Impulsive high thrust is assumed as the main thrusting method of spacecraft with launcher capability of KSLV-2 which is planned to be developed. For the method of injecting a spacecraft into a trans Lunar trajectory, both direct shooting from circular parking orbit and shooting from the multiple elliptical intermediate orbits are adapted, and their design results are compared and analyzed. In addition, spacecraft's visibility from Deajeon ground station are constrained to see how they affect the magnitude of TLI(Trans Lunar Injection) maneuver. The results presented in this paper includes launch opportunities, required optimal maneuver characteristics for each mission phase as well as the trajectory characteristics and numerous related parameters. It is confirmed that the final mass of Korean lunar explorer strongly depends onto the initial parking orbit's altitude and launcher's capability, rather than mission start time.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.10
• /
• pp.6722-6742
• /
• 2015

This study is intended to look for implications through longitudinal exploratory research on the change of children's problem behaviors for their temperament and parenting behaviors. The results are as follows. The factors influencing children's problem behaviors rose to 62 factors between 1990 and 2000, and 93 factors between 2000 and 2010 from total 41 factors between 1970 and 1990, which they were more than doubled after the 2000s compared with the earlier studies, subdividing children's problem behaviors. The proportion of the factors influencing children's problem behaviors showed that parents' moral thinking had the highest, and their negative thinking or emotion for children were higher than their moral thinking, which their problem behaviors were more greatly affected by parenting attitudes toward them than their own temperament or attitudes. The earlier studies were more likely to find the cause of children's problem behaviors for looking into the factors and causes influencing children's problem behaviors in terms of children's personal mental health, but there was more proportion of social environment, peer and teacher relationship while soaring family, relationship, home environment and child care center environment factors as well as children's personal factors after the 2000s. Consequently, the alternative resources or the environments of the times should be applied in other ways.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.11 no.4
• /
• pp.149-165
• /
• 2016

The objectives of this study is to assess the influence of individual characteristics and economic environment on the entrepreneurship such as entrepreneurial Intention and behavior based on the theory of Planned behaviors. This study used a country-level merged data set composed of GEM(Global Entrepreneurship Monitor) data and the OECD Statistics data. And this used the fixed effect model to analyze the panel data of 31 OECD countries during the period from 2005 to 2014. Our findings show that subjective norm has a significantly positive effect on entrepreneurial intention. In individual characteristics, the perceived opportunities has a significantly positive effect on early-stage entrepreneurial activity(TEA) and improvement-driven opportunity entrepreneurial activity. We identify the differences of between necessity-driven and improvement-driven opportunity entrepreneurial activity. For example, the effect on necessity-driven entrepreneurial activity is significantly negative. We also find the differences of between necessity-driven and improvement-driven opportunity entrepreneurial activity in economic environment variables. While real GDP growth as a demand variable has a significantly positive effect on necessity-driven entrepreneurial activity, unemployment rate as a supply variable has a significantly negative effect on early-stage entrepreneurial activity(TEA) and improvement-driven opportunity entrepreneurial activity. And GDP per capita as a supply variable has a significantly positive effect on early-stage entrepreneurial activity(TEA) and improvement-driven opportunity entrepreneurial activity. But the effect on necessity-driven entrepreneurial activity is significantly negative. We provide an interpretation of these empirical findings, emphasizing the importance of considering individual characteristics and economic environment simultaneously in promoting entrepreneurship.

• Korean Journal of Remote Sensing
• /
• v.38 no.5_3
• /
• pp.851-861
• /
• 2022

In this study, we analyzed the effects of trees planted in urban areas on PM_2.5 reduction using a computational fluid dynamics (CFD) model. For realistic numerical simulations, the meteorological components(e.g., wind velocity components and air temperatures) predicted by the local data assimilation and prediction system (LDAPS), an operational model of the Korea Meteorological Administration, were used as the initial and boundary conditions of the CFD model. The CFD model was validated against, the PM_2.5 concentrations measured by the sensor networks. To investigate the effects of trees on the PM_2.5 reduction, we conducted the numerical simulations for three configurations of the buildings and trees: i) no tree (NT), ii) trees with only drag effect (TD), and iii) trees with the drag and dry-deposition effects (DD). The results showed that the trees in the target area significantly reduced the PM_2.5 concentrations via the dry-deposition process. The PM_2.5 concentration averaged over the domain in DD was reduced by 5.7 ㎍ m^-3 compared to that in TD.

• 한국벤처창업학회:학술대회논문집
• /
• 2019.04a
• /
• pp.175-179
• /
• 2019

1년에도 수십 수백 개씩 스타트업이 생겨나고 있다. 아마도 모두 미래의 구글과 페이스북, 그리고 아마존이 되길 희망하며 하루하루 가열차게 달리고 있다. 하지만 그 많은 스타트업 중 소위 성공했다 불릴 수 있는 기업은 손에 꼽는다. 능력 있는 창업가, 기발한 사업 모델과 아이디어 그리고 이를 뒷받침해 줄 기술력과 자본이 있다고 성공할 수 없다. 스타트업 기업을 굴러가게 하는 힘은 결국 그 조직의 구성원에게서 나오기에 성공한 스타트업에겐 모두 그들 만의 '조직문화'가 있다. 그게 모두에게 좋은 문화일 필요는 없을 것이다. 그 조직에 가장 접합한, 그래서 구성원의 구성원의 공감대를 사 '일하고 싶은 회사'가 될 수 있게 하는 '조직 문화'가 있는 스타트업이 수많은 인재를 모아 성장을 거듭해 올 수 있었고 그것이 결국 스타트업을 성공으로 이끌었던 것이다. 이런 조직 문화는 회사 초창기에 세팅할수록 해당 기업의 성공 확률도 높아진다. 7년 미만의 초기 스타트업 기업을 대상으로 조직문화 유형이 스타트업 구성원의 조직 몰입과 조직성과에 어떠한 영향을 주는지에 대한 실증분석을 목적으로 하였다. 초기 스타트업 기업의 조직문화 차원은 경쟁가치모형의 혁신문화와 위계문화로 구분하였으며, 조직성과는 스타트업의 서비스, 제품을 경험한 이용자들의 서비스 만족도를 활용하였다. 조직문화는 외부환경에 대한 적응과 조직내부 통합의 문제를 해결하기 위하여 구성원들에 의해 창조 발전되어 학습되는 기본가정으로서 스타트업 구성원들에 의해 공유된 가치(values), 신념(beliefs), 규범(norms)의 체계로 정의한다. 따라서 어떠한 조직문화를 갖는냐에 따라 조직 구성원의 몰입, 충성심, 직무동기, 직무성과는 물론 조직성과와 혁신을 포함하는 여러 조직 요인도 직 갑적인 영향을 받는다. 7년 미만의 초기 스타트업 혁신문화가 스타트업 구성원의 조직몰입에 긍정적인 영향을 미치며, 조직몰입이 스타트업 서비스, 제품을 경험한 이용자들의 서비스 만족도에도 긍정적인 효과가 있는 것으로 나타났다.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.17 no.3
• /
• pp.55-67
• /
• 2007

In ad hoc network, especially in the environment which the system authority only exists at the beginning of the network, it is very important problem how to issue the certificates in self-initialized public key scheme that a node generates its certificate with public and private key pair and is signed that by the system authority. In order to solve this problem, early works present some suggestions; remove the system authority itself and use certificate chain, or make nodes as system authorities for other nodes' certificates. In this paper, we suggest another solution, which can solve many problem still in those suggestions, using proxy signature and threshold signature, and prove its performance using simulation and analyse its security strength in many aspects.

• Journal of Korean Public Health Nursing
• /
• v.28 no.3
• /
• pp.484-494
• /
• 2014

Purpose: The purpose of this study is to verify the direct influences of the risk factors of the family environment on the problem behaviors of early adolescents, and the indirect influences of the same by the mediation of ego resilience. Method: After random extraction of five elementary schools located in D metropolitan city, we conducted a survey of 5th and 6th-grade male and female students. For the analysis, we used data from the questionnaire results of 450 students. For the data analysis, we performed t-test of independent samples, one-way ANOVA, path analysis and Sobel test, utilizing SPSS/WIN 19.0 program. Result: The direct influence of the risk factors of the family environment on the problem behaviors of the early adolescents was 0.447, while the indirect influence by the mediation of ego resilience was 0.146. Conclusion: It was found that the risk factors of the family environment not only exert direct influences on the problem behaviors of early adolescents, they also have indirect influences on the problem behaviors of early adolescents by way of the mediation of ego resilience.

• 한국벤처창업학회:학술대회논문집
• /
• 2016.04a
• /
• pp.88-92
• /
• 2016

2008년 글로벌 금융위기 이후 세계 주요 국가들은 이러한 상황의 생존전략으로 창업 및 기업가정신의 부활을 강조하고 있다. 우리나라도 경기침체 및 청년실업률 증가와 같은 장기불황을 극복하기 위해 '국민행복, 희망의 새 시대'라는 국정비전하에 '일자리 중심의 창조경제' 실현을 제1의 국정목표로 설정하였다. 2016년 4년차에 접어드는 창조경제는 수많은 예산과 인력을 투입하여 창업지원사업을 하고 있지만, 그 효과성에 대해서는 의문이 든다. 이에 본 연구는 실제 창업을 하거나 준비 중인 창업가, (예비)창업가, 학생을 중심으로 현 창업생태계의 문제점을 분석하였고, 이 분석결과를 토대로 정부, 지방자치단체 및 민간의 창업지원사업에 바람직한 지원방향을 제시하여 건강한 창업생태계 구축을 위한 방안을 제시하고자 한다. 분석결과, 정부의 창업지원 정책의 문제점은 보겨 주기식 창업지원사업 및 행사라고 응답한 비율이 41.5%로 가장 높은 응답률을 보였고, 국내 창업생태계 조성을 위해 제 역할을 충분히 하지 않은 당사자는 34.1%가 중앙정부, 28.3% 국내 대기업이라고 응답하였다. 창업경험 유무에 따른 창업과정의 애로사항은 자금조달이 46.1%로 가장 높았고, 창업 초기자금 조달방법은 응답자의 절반인 50.4%가 개인자금으로 창업 초기자금을 조달한다고 응답하였다. 창업이 주저되는 주요 이유로는 창업자금 마련 및 기회비용이 40.4%로 가장 높은 응답률을 보였고, 창업 시 가장 필요하고 중요하다고 생각되는 지원정책으로는 자금 및 투자 지원이 26.6%, 사무실공간지원 13.5%, 마케팅 및 판로 지원이 13.5%의 응답률을 보였다.

• Geophysics and Geophysical Exploration
• /
• v.1 no.1
• /
• pp.49-56
• /
• 1998

Seismic tomography has been widely used as high resolution subsurface imaging techniques in engineering applications. Although most of the techniques have been using travel time inversion, waveform method is being driven forward owing to the progress of computational environments. Although full-waveform inversion method has been known as the best method in terms of model resolving power without high-frequency restriction and weak scattering approximation, it has practical disadvantage that it is apt to get stuck in local minimum if the initial guess is far from the actual model and it consumes so much time to calculate. In this study, 2-D full-waveform inversion algorithm in acoustic medium is developed, which uses result of traveltime tomography as initial model. From the application on synthetic data, it is proved that this approach can efficiently reduce the problem of conventional approaches: our algorithm shows much faster convergence rate and improvement of model resolution. Result of application on physical modeling data also shows much improvement. It is expected that this algorithm can be applicable to real data.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2005.05a
• /
• pp.297-300
• /
• 2005

최근 웹 관련 기술들의 개발 및 표준화로 인하여 서비스 지향 아키텍처(SOA: Service Oriented Architecture)기반의 비즈니스 어플리케이션 개발이 가능해짐에 따라 SOA 가 개발 방법의 새로운 패러다임으로 IT 분야의 주목을 받고 있다. 이와 관련하여 SOA 기반의 소프트웨어 개발에 대한 많은 연구가 진행되었으며, 이를 바탕으로 IT 분야에서 시장 형성이 진행되고 있다. 그러나 시장 측면에서 볼 때 SOA 기반의 비즈니스 어플리케이션 개발을 실제 적용하기에는 이용 가능한 서비스들이 아직은 부족한 상태이며, 사용자들에게 서비스 이용에 대한 신뢰성과 안정성에 대한 요구를 충족 시키지 못하고 있다는 점이다. 이는 SOC 환경의 활성화를 저해하는 결정적 장애요인이며, 더욱 심각한 문제는 대다수의 연구들이 서비스 시장에서 대체 서비스가 존재한다는 가정하에 진행되고 있어 웹 서비스의 도입 초기에 발생할 수 있는 대체 서비스가 존재하지 않는 문제점에 대해서는 간과하고 있는 점이다. 이러한 문제를 해결하기 위해 본 논문에서는 확장된 서비스 중개자(Extended Broker) 개념과 구현 방안을 제시함으로써 성숙되지 않은 웹 서비스 환경에서 서비스 요청자에게 제공되는 서비스 사용에 대한 안정성과 신뢰성을 보장하고자 한다.