• 대한교통학회지
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• 제28권6호
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• pp.75-84
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• 2010

신호교차로는 교통 네트워크 상에서 지체가 발생하는 중요 지점이며, 또한 신호교차로의 운영 효율성은 전체 네트워크 성능에 결정적인 영향을 끼친다. 신호 교차로 상에서의 MOE(Measure of Effectiveness)는 다양한 기준으로 측정되고 있으며, 그 중 교통류의 지체는 운전자와 교통 전문가들이 일반적으로 가장 잘 이해하기 쉽고 중요한 MOE라 할 수 있다. 따라서, 신호 교차로 상에서 교차로에 유입되는 차량의 지체에 대한 측정은 교차로의 교통 성능의 평가를 위한 중요한 기준이 되며, 그에 따라 지체를 측정하기 위한 다양한 지체 산정 모형들이 개발되었다. 그러나 실제 교통류가 혼합교통류인데 반해, 지금까지의 지체 측정 모형 대부분은 동질 교통류를 가정한 연구로 수행되었다. 그러므로, 본 연구에서는 버스와 승용차로 이루어진 비포화 혼합교통류 상황에서, 신호교차로와 버스 정류장에서 사이에서 발생하는 지체를 직접 산정하기 위한 모형을 개발하였다. 이 모형은 혼합교통류의 모든 교통상황을 반영한 모형이라기 보다는 2차로 도로에서 버스의 정차로 인한 지체현상을 설명하는데 주안점을 두었다. 모형의 검증은 지체 산정모형과 시뮬레이션인 INTEGRATION의 결과값을 비교하여 모형적용에 대한 유효성을 평가하였다. 평가결과 버스의 유입량에 대한 비교에서는 버스의 대수가 많아질수록 평균 지체량은 늘어나는 것으로 나타났다. 신호 교차로와 버스 정류장의 이격거리에 대한 비교에서는 버스가 전방차량의 영향을 받지 않는 경우 일정한 값을 유지하는 결과가 나타났다. INTEGRATION과 본 연구에서 개발한 모델과의 오차범위는 10% 내외로 나타났다.

• 대한교통학회지
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• 제28권6호
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• pp.109-120
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• 2010

본 연구는 도로점용공사가 신호교차로의 정지선에 인접하여 시행될 시, 물리적 차로점용으로 인하여 변화하는 포화교통류율을 산정하기 위한 수학적 논리모형 개발을 목적으로 한다. 우선 문헌조사와 사전 모의실험을 통하여 신호교차로에 인접한 도로의 포화교통류율이 도로점용공사의 위치, 차로 수, 신호주기, 유효녹색시간에 의해 민감하게 변화함을 확인하였다. 이러한 포화교통류율 변화요인을 독립변수로 선정하고, 기존 교통류이론을 활용한 수학적 논리모형을 개발하였으며, 개발모형은 도로점용공사의 위치(교차로 상/하류)에 따라 각각 달리 적용하도록 이원화하였다. 개발된 논리모형의 검증을 위하여 다양한 미시적 시뮬레이션을 수행하였으며, 논리모형 적용과 모의실험 수행을 통해 각각 얻어낸 포화교통류율 결과 값을 비교/분석하였다. 검증결과, 각각의 방법으로 얻어낸 포화교통류율의 절대적 차이가 다소 존재하였으나, 독립변수의 영향에 의한 포화교통류율 분포 형태가 통계적으로 유의함을 확인하였다.

• Journal of Chest Surgery
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• 제24권11호
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• pp.1081-1089
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• 1991

Atrial fibrillation is characterized by beat to beat irregularity of shape, size, conduction time and polarity. The mechanism of atrial fibrillation can be explained by so called "Multiple wavelet theory". The adverse effect of atrial fibrillation is the decrease of cardiac output by absence of atrial kick[10 ~ 15%] and the possibility of thrombosis in the left atrium which is dangerous to develop the thromboembolism is increased. The present study was designed to assess the effect of overdrive pacing on the suppression of recurring of atrial fibrillation after open heart surgery and the results were summarized as follows: 1. There were no significant differences of factors between converting patients and non-converting patients to normal sinus rhythm by electric cardioversion after open heart surgery. 2. Among converting patients to normal sinus rhythm, there were no significant differences of factors between study group and control group. 3. Cardiothoracic Ratio on the preoperative chest film was significantly larger in the patients of recurring atrial fibrillation within 72hrs than in the patients of maintaining normal sinus rhythm. [61.7$\pm$ 1.4% vs 67.7$\pm$2.4%, p=0.03] 4. There was a significant difference of suppressive effects between overdrive pacing group and control group among recurred cases until 24, 48, and 72hours [Fisher`s exact test ; p=0.037, p=0.076, p=0.53, respectively] 5. There was a difference of the delay of recurring of atrial fibrillation between study group and control group among recurred cases within 72 hours.[53.4$\pm$6.9hr vs. 19.3$\pm$3.8 hr, p<0.01] We think that the overdrive pacing may suppress the natural pacemaker and the converted normal sinus rhythm is maintained longer than control group during critical immediate postoperative period.ve period.

• 논리연구
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• 제13권2호
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• pp.27-59
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• 2010

작년 7월 28일 고(故) 김영정 교수의 갑작스러운 별세 이후 4편의 미발표 논문이 발견되었다. 그 논문에는 김영정 교수의 원대한 계획이 있었음이 확인되었다. 특히 그의 독자적인 개념과 이론이 확인되었는데, 김영정 교수가 "선제논리" 또는 "장논리"라고 부르는 것이다. 이 글에서는 김영정 교수의 그 계획을 "선제논리 프로그램"이라고 부르고자 한다. 김영정 교수는 논리학과 비판적 사고의 더욱 밀접한 연관관계의 필요성과 가능성을 실현하기 위하여 선제논리라는 새로운 논리체계를 모색하였다. 이 글에서는 김영정 교수의 "선제"와 선제논리가 무엇인지(2절), 왜 김영정 교수가 논리학의 관점에서 선제논리가 필요하다고 보았는지를(3절) 살펴볼 것이다. 이렇게 함으로써 우리는 김영정 교수가 마지막 학문적 열정과 투혼을 쏟아 부었던 작업 내용의 얼개를 파악할 수 있다. 이러한 파악을 바탕으로 나는 김영정 교수로 하여금 최후까지 고뇌에 싸이게 했던 문제를 비판적으로 조명하고자 한다(4절, 5절).

• 한국지반공학회논문집
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• 제16권3호
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• pp.5-13
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• 2000

본 연구에서 흙(사질토)-구조물의 경계면에 대한 거동특성을 분석하기 위하여 교란상태개념(DSC)을 수정 및 보완하였다. 제안한 DSC모델에서는 변형중인 재료는 상대적으로 손상되지 않은 상태(RI)와 완전 파괴된 상태(FA)가 혼합되어있다는 가정에 기초를 두고 있다. RI 상태는 HiSS모델을 이용하였고, FA 상태는 한계상태모델을 이용하였다. 이런 DSC 모델을 Biot이론에 기초한 기존 유한요소 프로그램에 접목하였다. 본 연구에서 수저한 유한요소 프로그램을 이용하여 실제 경계면 실험(두 가지 하중조건: 정하중, 동하중)에 대하여 모의실험을 수행하였다. 또한 그 결과와 실내시험결과를 비교 검토하였다. DSC모델을 이용한 유한요소해석은 실제 실내시험 결과와 유사한 경향을 보였다. 본 연구의 결과를 통하여, DSC모델을 흙-구조물 경계면 해석에 비교적 합리적인 결과를 제공한다고 판단된다.

• 한국초등과학교육학회지:초등과학교육
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• 제21권1호
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• pp.71-80
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• 2002

The purpose of this study was to develop children's creativity by applying creative problem solving model to elementary school science. Creative problem solving(CPS), the theoretical frame of model is proposed by Treffinger et al.(1994). CPS model is based on a substantial foundation of theory and research about creativity and problem solving. It is a well organized, deliberate set of methods you can call upon whenever you need new ideas or solutions and a process anyone can use to deal with many of life's everyday problems, opportunities, and challenges. CPS consists of three components. Within these three components, there are six specific stages during which creative and critical thinking abilities are used in harmony. Each stage involves both divergent and convergent thinking. The study was conducted for six week during the 1998 two semester in A elementary school which is located in Incheon. Eighty three 2nd grade students are selected for this study. The students were divided into two groups--experimental group and control group. The experimental group were taught in applying the CPS model, and the control group were taught by the traditional manner. Data for this study were collected by questionnaire which were developed by this researcher, and were analyzed by SPSSWIN 8.0. The results of this study were as follows: There was a significant difference on creativity between the instruction by applying CPS model and the traditional instruction. There was also gender differences on creativity between two groups. On fluency and flexibility as components of creativity, there was a signigicant difference between two groups. In conclusion, the instruction by applying CPS model was more effective in developing children's creativity than the traditional instruction.

• 한국실내디자인학회논문집
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• 제16권2호
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• pp.278-286
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• 2007

Postmodernism, the theory and philosophy that swayed the world in the late 20th century, can be interpreted in various ways as a critical reaction against modernism as well as, in one way, the logical extension of modernism itself. Thus, an extensive understanding of the social and temporal background of the birth of postmodernism and a macroscopic and correlative approach toward the related artistic circles, especially art, were carried out before a formative discussion on the furniture design of postmodernism. Postmodemism in the field of furniture design shares the history of birth and spirit with Memphis, the progressive design group established by Ettore Sottsass in Milan, 1980. This study identifies the formative features of pestrnodernistic furniture design around those works that express the trend of postmodernism, in particular, chairs, as well as the designers who participated in the first Memphis exhibition at the Milan Furniture Fair. By identifying such features, the correlation between postmodemism and those features expressed in the works of postmodernism paintings were examined. The works of Anselm Kiefer, a German nee-expressionist who became famous through the Venice Biennale 1980, and five young Italian trans-avant garde authors were selected as the scope of this case study. The characteristics of postmodernism in modern art were analyzed in terms of themes, shape, and content and were derived as follows; Firstly, borrowed and past-oriented themes, secondly, deconstructive, atypical, plural, emotional, and intuitional shapes, and thirdly, basic, metaphorical, and abstract content, The formative characteristics of chair design in postmodemism furniture design are as follows; Firstly, deconstructive, symbolic, and abstract shapes, past-oriented, reactionary, and primitive colors and closing, as well as the characteristic of delivering commercial and metaphorical messages. The subjects and motives of art have been succeeded by the characteristics of color and closing in furniture, the shape and techniques of fine arts by the characteristics of furniture shape, and the content of art by that of furniture. They share key words and characteristics.

• Journal of Communications and Networks
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• 제18권5호
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• pp.744-761
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• 2016

For about the past decade and a half research efforts into cognitive radio networks (CRNs) have increased dramatically. This is because CRN is recognized as a technology that has the potential to squeeze the most out of the existing spectrum and hence virtually increase the effective capacity of a wireless communication system. The resulting increased capacity is still a limited resource and its optimal allocation is a critical requirement in order to realize its full benefits. Allocating these additional resources to the secondary users (SUs) in a CRN is an extremely challenging task and integer programming based optimization tools have to be employed to achieve the goals which include, among several aspects, increasing SUs throughput without interfering with the activities of primary users. The theory of the optimization tools that can be used for resource allocations (RA) in CRN have been well established in the literature; convex programming is one of them, in fact the major one. However when it comes to application and implementation, it is noticed that the practical problems do not fit exactly into the format of well established tools and researchers have to apply approximations of different forms to assist in the process. In this survey paper, the optimization tools that have been applied to RA in CRNs are reviewed. In some instances the limitations of techniques used are pointed out and creative tools developed by researchers to solve the problems are identified. Some ideas of tools to be considered by researchers are suggested, and direction for future research in this area in order to improve on the existing tools are presented.

• 대기
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• 제17권4호
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• pp.315-326
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• 2007

The effects of windbreaks on the reduction of suspended particles are investigated using a computational fluid dynamics (CFD) model with the ${\kappa}-{\varepsilon}$ turbulence closure scheme based on the renormalization group (RNG) theory. In the control experiment, the recirculation zones behind the storage piles are generated and, as a whole, relatively monotonous flow patterns appear. When the windbreaks with the 0% porosity are constructed, the recirculation zones are generated by the windbreaks and very complicated flow patterns appear due to the interference between the windbreaks and storage piles. The porosity of the windbreaks suppresses the generation of the recirculation zone and decreases the wind velocity in the windbreaks as well as that outside the windbreaks. As the emission of suspended particles from the storage piles are closely related with the friction velocity at the surfaces of the storage piles, variation of the friction velocity and total amount of the emission of the suspended particles with the height and porosity of the windbreaks are investigated. The results show that higher and more porous windbreaks emit less suspended particles and that the reduction effect of the porosity is still more effective than that of the height. In the case of the windbreak with 30 m height and 50% porosity, friction velocities above the storage piles are smaller than the critical friction velocity above which particles would be suspended. As a result, total amount of suspended particles are much fewer than those in other cases.

• 복합신소재구조학회 논문집
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• 제4권2호
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• pp.39-44
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• 2013

This study is aimed to examine the influence of the rotational stiffness of U-shaped ribs on the local buckling behaviors of laminated composite plates. Applying the orthotropic plates with eight layers of the layup $[(0^{\circ})4]s$ and $[(0^{\circ}/90^{\circ})2]s$, 3-dimensional finite element models for the U-rib stiffened plates were setup by using ABAQUS and then a series of eigenvalue analyses were conducted. There is a need to develope a simple design equation to establish the rotational stiffness effect, which could be easily quantified by comparing the theoretical critical stress equation for laminated composite plates with elastic restraints based on the Classical laminated plate theory. Through the parametric numerical studies, it is confirmed that there should clearly exist an increasing effect of local plate buckling strength due to the rotational stiffness by closed-section ribs. An applicable coefficient for practical design should be verified and proposed for future study. This study will contribute to the future study for establishing an increasing coefficient for the design strength and optimum design of U-rib stiffened plates.