동영상 전송을 위한 고속 영상 부호화 알고리즘에 관한 연구

최영철 淸州大學校 1999 국내석사

效率的인 認證書 狀態 및 經路 檢證 시스템에 관한 硏究

최영철 成均館大學校 大學院 2002 국내박사

Nowadays PKI(Public Key Infrastructure) is known as very general security infrastructure for establishment of secure internet environment. Many countries already established their Digital Signature Act and have designated several licensed CAs under the law. Through such a PKI environment, many users already deployed PKI-enabled applications or are considering to do them. Nevertheless, in terms of general network environment's prospective, there is a critical problem should be solved relating for certificate status check and certification path validation. Although lots of technologies relating to certificate verification issues have been developed and standardized, definitely exact and perfect solution did not develop yet. We propose an efficient certificate status check and certification path validation method for specially real-time based client/server environment with huge scale in Internet environment. The proposed system provides an outstanding efficiency and cost-effectiveness in viewpoint of relying party such as large-scaled server of a internet banking, and so on. The concept of proposed scheme is that before a sender will send a digital signature to a recipient who is big server with lots of client, he/she contacts the VA(Validation Authority) server and gets some initial information from it. And then he/she receives a VC(Validation Certificate) with a result of checking certificate status and path validation. After received VC, he/she sends a digital signature made by him/her and VC to the target server. At that time, the target server, that is relying party, is no need to check the authenticity of the used certificate based on CRL, and so on. Instead of it, the server only checks the authenticity of the VC only using one-time hash operation. By using the proposed scheme, the users can establish an efficient PKI enabled application and system for large-scaled real-time client/server system based on Internet. Through such the implementation, the relying party gets rid of a critical risk that could be happened in real-time client/server environment, and had bad influence on stable operation of the system.

AEㆍDRA방법을 이용한 초기응력의 크기와 방향성 결정 연구

최영철 강원대학교 대학원 2008 국내석사

현재 초기응력 측정을 위한 다양한 방법들이 시도되고 있다. 이 중 AE·DRA 방법으로 초기응력 측정에 관한 검증을 수행한 사례는 많이 있지만, 주응력의 크기와 방향성을 결정한 사례는 많지 않다. 따라서 본 연구에서는 AE·DRA방법으로부터 주응력의 방향성과 크기를 결정하기 위한 시도를 하였다. 그리고 그 결과를 수압파쇄법과 비교하였다. 본 연구는 부산대학교 양산 캠퍼스 내에 위치한 시추공에서 채취된 화강암 시료를 사용하였다. 총 시추 심도는 300m이며, 심도 100m에서부터 약 50m 구간마다 시험하였다. 3차원 상의 응력텐서를 결정하기 위한 근사해를 도출하기 위해서 서로 다른 9방향으로 재시추하여 시험하였다. AE·DRA시험으로부터 결정된 을 이용하여 지하 응력의 3차원 해석을 시도하였다. 그 결과, 주응력의 크기와 방향성은 상이하게 분석이 되었다. 오차 원인을 분석하기 위해서 검증을 수행하였다. 그 결과 ±10% 이내의 작은 수직응력() 변화로도 3차원 응력의 크기와 방향성이 민감하게 변하는 것을 발견하였다. 수압파쇄법의 가정을 도입하여 2차원 검증을 수행한 결과 ±10%의 응력 변화에서는 응력의 크기와 방향성의 평균이 유사하게 분석되었다. 이 방법으로 2차원 해석을 수행하였다. 최대주응력의 방향은 대략 E-W 방향으로 분석되었으며, 측압계수(K)는 1.5~1.9의 분포를 보였다. AE·DRA 분석결과는 수압파쇄법의 결과와 비교했을 때, 대체로 응력의 크기와 방향이 일치하였다. 결론적으로 AE·DRA시험으로 주응력의 방향성과 크기를 결정할 때는 3차원 해석은 어려우며, 수압파쇄법의 가정을 이용하여 2차원 해석을 하는 것이 유용할 것이라고 판단된다. In-situ stress is very important in design of engineering structure and several methods, such as hydraulic fracturing method and overcoring method, have been used to measure in-situ stress. Recently, several new methods are tried to measure in-situ stress and acoustic emission(AE) and deformation rate analysis(DRA) methods are considered as one of the most inexpensive and accurate methods. I measured orientation and magnitude of in-situ stress at Yangsan area using AE and DRA methods from the drilled cores and compared the results with in-situ stress measured by hydraulic fracturing method to investigate the availability of AE and DRA methods. I re-drilled the oriented core along 9 directions and applied uniaxial compressive stress to measure acoustic emission and strain. In-situ normal stress along the direction of drilling was estimated based on the principle of the Kaiser effect. Orientation and magnitude of the principal in-situ stress were calculated using tensor transformation and were compared with those measured by hydraulic fracturing method. The principal in-situ stress estimated using AE and DRA methods are quite different from those measured by hydraulic fracturing method. I added 5%, 10% and 20% of error into the calculated normal stress along 9 directions and estimated the three principal stresses to investigate the discrepancy. The maximum differences were 18%, 50% and 100% of exact stress, indicating that a small error in measurement of AE result in wrong in-situ stress. Since hydraulic fracturing method measures only 2 horizontal principal stresses, I added 5%, 10% and 20% of error into the exact normal stress along 3 directions and calculated 2 horizontal principal stresses. The differences were very small when 5% and 10% of error were added. The difference of 2 horizontal principal stresses was only 18% when 20% of error were added, indicating that this method can be useful. Two horizontal principal stresses estimated from AE and DRA are within 2.8%-35.7% of those measured by hydraulic fracturing method and the difference in orientation was within 5°- 37.7°.

高等學校 統合 敎科의 討論式 敎授-學習 方法에 關한 硏究 : 大邱·慶北 地域을 中心으로

최영철 경주대학교 행정경영대학원 2000 국내석사

The purpose of this study was to develop more complete discussion-based teaching model for integrated subject, by surveying high school teachers' awareness of integrated subject education and discussion-based teaching-learning approach and their opinion of how that approach was actually utilized in the city of Taegu and North Kyongsang Province. Social change requires the change of education, which is taken into shape in educational reform policies. Building an open, life-long education society, where everyone can receive education he or she want at any time, is the very way to realize the ideal of education. And now, it's absolutely needed to improve classroom instruction to meet the requirement. There might be a number of approaches to do it, but it's particularly desirable to explore how to teach integrated subject and to develop discussion-based teaching- learning approach for that subject, because it can contribute to elevating the effect of education. It's intended in this study to discuss the political and economic background of educational reform, the theory and application of open education, the significance, concept, model and types of integrated subject, and the cases of applying integrated subject principles to the Academic Aptitude Test. And it's also planned to discuss the actual condition, essence, significance and type of discussion instruction, as it's assumed that integrated subject could be taken into shape in high school through discussion-based teaching-learning approach. The subjects in this study were 332 selected teachers who were in charge of regular subjects in high schools in the city of Taegu or North Kyongsang Province. The instrument used in this study was questionnaire covering teacher awareness of discussion-based teaching- learning approach toward integrated subject in high school and the actual use of that method. The collected data were analyzed with frequency, percentage and x2 test. The findings of this study were as below: Most of the teachers investigated in the region of Taegu and North Kyongsang still sticked to lecture method. And they didn't know well about how to teach integrated subject, and scarcely carried it out, either. They thought student's interest and need should be taken into account the most when selecting integrated-subject approach. The biggest difficulty in choosing integrated-subject approach was the lack of time required for teaching preparation. As a whole, integrating two subjects into one was most favored. It was approximately 60% who had ever used integrated-subject approach toward teaching-learning activity. Concerning discussion instruction, their awareness of discussion was very poor. Discussion instruction and discussion-centered student activity were regarded as the most necessary thing to settle down discussion culture in our society, and the discussion instriction was viewed fairly effective to attain the objective of education. In particular, they thought that the preparation of discussion data served to enlarge data-inquiring experience and opportunity for dialogue and expressing one's idea, and that this eventually contributed to raising student's interest and participation in instruction. The reason discussion instruction was not implemented successfully was that the given condition was not good enough and the opportunity of speaking was entirely possessed by some students. What should be done first to make successful discussion instruction was to change teacher's thought or to fix discussion culture into student activities. They wanted the theme of discussion would be determined by teacher in conjunction with curriculum, and that the time for releasing a selected theme would depend on the nature of the theme. The subject for which discussion instruction was most effective was social studies, ethics and Korean language, and the mass media giving the biggest impact on it was television, followed by newspaper and the Internet in the order named. As they didn't think students were interested a lot in discussion instruction, it's necessary to make systematic research efforts to addressing this problem. Based on the above-mentioned findings, the essential factor of discussion instruction can be listed as cooperative learning, student interest, open education, teacher role, and principle of composite art. A discussion instruction model could be developed based on the factors. The appropriate model was, among various discussion instruction models, pro-con teaching model, debate model, or direct debate model. What I have in mind is an applied direct debate model, and the concrete teaching method of this model is suggested in theoretical background section. In the future, it's required to make continuing researches in producing the best discussion instruction model by integrating those models.

Theoretical approach to designing nanoelectronic devices: Metal clusters, 1D nanowires, Molecular devices, and Graphene spin-valves : 나노전자소자 설계에 관한 이론적 연구: 금속뭉치, 1차원 나노선, 분자소자, 그리고 그래핀 스핀밸브

최영철 포항공과대학교 2009 국내박사

휴대전화의 가상 제품 구현을 통한 사용성 평가 방법의 연구

최영철 한양대학교 대학원 2005 국내석사

교사의 가치관 연구 : 근대화개념 이해를 중심으로

최영철 고려대학교 교육대학원 교육행정전공 1985 국내석사

조선시대 상류거주공간의 지속적 건축특성에 관한 연구

최영철 아주대학교 2001 국내석사

Truss의 節點剛性과 2次應力에 관한 硏究

최영철 東亞大學校 大學院 1988 국내석사

Ordinarily when a truss is analyzed, its members are assumed to be subject to direct or primary stress only. However, in the case of a truss with bolted or welded connections, bending of the truss as a whole also induces some bending of the individual members because of the rigidity of the joints. Stated in another way, such bending of the members of a truss superimposes additional bending stresses, which are called secondary s tresses. For common member design of the idealized truss, the secondary stresses generally are neglected. But the actual connections of the truss do give some rigidity to the joint and high secondary stresses exist only in some of the members. Hence, the resulting secondary stresses (Mc/I) should be added to the primary stress (P/A). That is, for combined bending and direct stress should be applied in the design of the members. For that reason, the purpose of this thesis is a study on mechanical behavior of truss members considering primary and secondary stress. This study consists of six chapters, each of which maybe summarized as follows : Chapter Ⅰ presents a general description of this study including its purpose, its methodology and its structure. Chapter Ⅱ describes the general stress analysis for steel trusses and definition of the secondary stress. Chapter Ⅲ describes the secondary stress analysis for steel trusses with respect to joint rigidity. Chapter Ⅳ considers the relation between secondary stress and mechanical behavior for steel trusses. In chapter Ⅴ, Secondary stress are compared and investigated through the model study based on the theory and hypothesis pres crib ed in chapter Ⅲ. The results are as follow : 1. When a truss with welded connections is analyzed, existing stress of its members is calculated to consider the effect of secondary stress . 2. Primary stress and deflection have no relation to joint rigidity. 3. Secondary stress analysis for the variation of joint rigidity is required. 4. The establishment of joint rigidity factor (φ) require experimental data.

미계측 유역의 확률홍수량 산정 절차 개선에 관한 연구

최영철 경남대학교 산업경영대학원 2018 국내석사

최근 발생하는 수해의 양상을 살펴보면 기상학적, 지형학적 취약성 외에도 도시화와 산업화에 따른 토지이용의 변화 등으로 인하여 그 위험성이 한층 고조되고 있는 실정으로 하천설계, 치수시설규모결정, 개발 사업에 따른 유출변화 검토 및 재해복구사업 등 수자원분야에서 홍수량 산정이 차지하는 비중이 매우 크다. 홍수량 산정을 위하여 계측을 통한 확률홍수량을 산정함이 원칙이나 홍수량 계측을 위한 시설이 매우 부족하여 강우와 유역특성에 따라 홍수량을 추정하고 있는 실정으로 홍수량 미계측 유역에 대한 홍수량 산정을 위한 연구가 지속되고 있다. 그러나 홍수량 산정을 위한 기준 및 지침이 지속적인 연구 성과에 따라 자주 변경이 되고 있으며 이에 따른 홍수량 산정 시스템을 구축하여야 하며 홍수량 산정을 위한 입력인자의 결정과 입력오류 등에 의해 홍수량 산정 결과가 다르게 나타나게 되므로 주관적 판단을 최소화 하도록 홍수량 산정에 필요한 주요인자 산출의 표준화, 데이터 입력의 단순화, 단계별 산출과정 검증 등으로 신뢰성을 확보하고자 하였다. 본 연구에서 개발된 VBA(Visual Basic for Application)를 이용한 확률홍수량 산정 개선 기법 연구 결과를 이용하여 미계측 유역에 대한 유출분석을 한 결과 다음과 같은 결론을 얻었다. 첫째, 설계홍수량산정 요령에 따라 연구대상지역에 대한 홍수량 산정을 수행하였고 그 결과 HEC-1을 이용한 홍수량 산정 결과와 비교하여 상대오차가 ±0.4% 미만인 것으로 검토 되었다. 둘째, 국내 홍수량 산정지침에 따른 홍수량 매개변수 산정을 수행하고 그 결과를 별도의 처리과정을 최소화하여 다음 계산과정의 데이터로 활용할 수 있도록 하여 데이터 입력에 따른 오류를 최소화 하였다. 셋째, 홍수량 산정지점 개수, 강우개수 등에 따른 데이터 입력, 계산 및 검토에 대한 반복수행이 용이하였다. 넷째, 본 연구에서 산정된 확률홍수량 결과를 적용하여 하천 및 관거 등 계획에 활용할 수 있으며, 강우사상별 수문곡선을 적용하여 효율적으로 저수지(저류지) 및 배수펌프장 계획 등에 활용할 수 있다. In the patterns of recent flood damages, the flood risk has been heightened much further due to land use changes according to urbanization and industrialization with meteorological and topographical vulnerabilities. Flood discharge estimation holds huge significance across the area of water resources including river design, determination of flood control facility size, review of spill changes according to a development project, and disaster restoration project. It is the principle to estimate probability flood discharges based on measurements for flood discharge estimation, but the actual reality is to estimate flood discharges according to rainfall and watershed characteristics since facilities used to measure flood discharges are in extreme shortage. There has been ongoing research on flood discharge estimation in watershed whose flood discharges have not measured. The criteria and guidelines for flood discharge estimation have, however, been changed frequently according to continuous research findings, which means that a new system should be established to estimate flood discharges accordingly. Since flood discharge estimation results can vary according to input factors and errors, this study tried out obtain reliability by standardizing the identification of major factors needed in flood discharge estimation, simplifying data inputs, and testing the estimation process by the stage so that subjective judgments can be reduced to the minimum. The investigator analyzed spills in unmeasured watershed with the findings about the technique developed in the study to improve the estimation of probability flood discharges based on VBA and reached the following conclusions: Firstly, the study area was estimated for its flood discharges according to the estimation procedure of design flood discharges, and the results had a relative error of under ±0.4% compared with the results of flood discharge estimation based on HEC-1. Secondly, flood discharge parameters were estimated according to the guidelines for flood discharge estimation in the nation, and errors from data inputs were minimized to make use of the results as data in the next calculation process through the minimization of a separate treatment process. Thirdly, it was easy to perform data input, calculation, and review repeatedly according to the number of points for flood discharge estimation and the frequency of rainfall. Finally, the results of probability flood discharges estimated in the study can be applied and used in river and sewage plans, and the hydrograph of each rainfall event can be applied and utilized efficiently in reservoir(detention facility) and drainage pump station plans.