지능형 용접 결함 분류를 위한 초음파 특징에 관한 연구

이현 조선대학교 대학원 1998 국내석사

Flaw classification is one of the fundamental issues in ultrasonic nondestructive evaluation (NDE) of the various materials and structures, since the effect of flaws on structural integrity is largely dependent on their types. Cracks are usually considered more dangerous than volumetric flaws. Thus, it is common to discriminate only between more crack-like and less volumetric flaws. For weldments, however, it is desirable to introduce more flaw categories such as cracks, porosity and slag inclusions not only for the evaluation of structural integrity of the weld but also for the improvement of weld process performance. Most of the intelligent ultrasonic flaw classification softwares proposed until now- are turned out to be very sensitive to the operational variables of ultrasonic testing such as transducer characteristics and pulser/receiver settings. This is the very reason for the application of ultrasonic pattern recognition approaches to be still quite rare in realistic field inspections even after the appearance of these softwares. In this study, we has constructed a database which contains 760 waveforms from crack, porosity and slag inclusion and proposed the "normalized features" which are very robust to the training set. Normalized features propose in this study demonstrates their capability to reduce the effect of the operational variables not only on the ultrasonic features but also on the bias in the classification due to the variation in the training and the test sets. Thus we feel that using these normalized features an invariant ultrasonic pattern recognition can be realized very efficiently.

순환구조(順換構造)에의 예술 행위적 접근에 대한 고찰 : 본인 작품 '만다라' 시리즈에 관한 연구

이현비 (李賢妃) 弘益大學校 大學院 2006 국내석사

I believe that when an artist speculates about something they are drawing for, they really mean to get some truth of their origin by focusing on their real being and their soul. We as a part of the world are not able to catch anything without first realizing their true self. And true self can not be understood without knowing the things around linked with self. As to encounter of internal world of humans and external world surrounding it can be said that the realization of such encounter itself is ultimate goal of contemporary artistic action. Pursuing establishment of new relationship of such encounter may be considered as essential element which makes contemporary art exist on various shapes today. This study defines the way I understand the meaning of self and of life, and examines the methods to express it in my paintings. Life is 'action itself' which can not be depicted as a stopped scene with any language. Matter exists individually but is not separable from the others. Anything in life persistently keeps changing, developing, evolving, circulating, and passing its own features onto upcoming generation. In other words, life can not be understood as something which is separated from the whole cycle of action. Therefore we can say that this world, everything in the universe is mere an instant shape appeared as a result of one whole action. From this kind of view, there is no complete world of existence. There are instead plural worlds of existence which are created by constantly including and re-structuring moving cycle. Clearly one can not exist without the relationship with the others. The others can not also exist without one either. In this relationship, we as a whole create an action. Through the relationships, life as action is created and destroyed and re-structured. Therefore, first step to approach to the meaning of life is to realize the relationships in our every day life. The relationships is what my interest in and is what initiated the series of 'Mandala'. The term mandala has Hindu origins but has been widely applied to various tangible objects which represents the cosmos metaphysically or symbolically, a microcosm of the universe from the standpoint of man. In the West the term is also used to refer to the "personal world" in which one lives. The various elements of the mandala indicate the activities and interests in which one engages. The title, 'mandala' of my paintings, is not particularly related to any religion. It refers to my wish for the Enlightened Mind in harmonious relationship with one another. This study is about my personal esthetic approach to the structure of circulation which indicates the self-consistency of the universe and its interrelationship. In attempting this approach, this study examines first, mandala as a symbol in general, theoretical opinions regarding mandala by Carl Gustav Jung (the aspect of psychology), Giuseppe Tucci (that of archeology), and Arguelles Miriam (that of iconology), and the meaning of the structure of circulation which mandala symbolizes as circle. In the support of the understanding the structure of circulation as our life, I have based on the phenomenological method of cognition. According to Carl Ransom Rogers(1902~1987, American psychologist), 'Phenomenological self' is of self-concept. When this self-concept is so obstinate, any organismic experience or sensory and visceral experience can not involve with 'self'. In this case, any experience comes against self-concept tends to be denied or distorted. This kind of state is, what Roger calls, 'self-incongruence' or 'maladjustment'. But the most important thing is that the obstinate self-concept doesn't hesitate to accept this 'self-incongruence' or 'maladjustment' when it doesn't hurt or harm 'self' with or without involving organismic experience. The denied and distorted experiences make one's self-concept sink into oblivion and indifference. The second chapter explains the importance of realizing 'self' in life, the meaning of 'self' in action through the relationships. And finally how the evolution of consciousness is suggested as the possibility of cure for existential frustration we today suffer from modern society is discussed. The details of how the structure of circulation is expressed in painting is the subject matter of the third chapter. This chapter explains the meaning of each material chosen to be applied directly on canvas, of repetition as the technique on the materials, and of erasing-in-becoming throughout the process of work as the evidence, the marks, and the symbol of everyday life. As I mentioned above, this study is to examine the possibility of the esthetic approach to the structure of circulation in my paintings. 'Repetition' and 'Erasing' are the main techniques as metaphor for everyday life and creativeness. A. Reinhardt views that repetition is painting and repainting the same thing several times, long repetition of actions, preparation and intention are followed by refinement, tension in arts and the completion of perception, and completeness in arts depends on repetitive actions. The main intention of repetition in my works is to bring out the sense of meditation and raise attention to the relationship among human body employed in creating works, time and the space. In this context, human body is not simply a tool but the subject which receives and perceives the substances actively. As to erasing my intention is to demonstrate an expression which is to be read. Erasing is an active action for creating an existence which is possible by my action along with my self-concept and the relationships I have with the materials. Completed works by repeatedly erased is now open and free to be engaged with the other relationships by itself. It is now ready for being erased or included and transcended in the cycle of life. I, as a whole, is the fuel of life. Life, as a whole, is the reason of I, 'the self'. In my paintings, the structure of circulation in relationship is not symbolized as circle in figure. What the circle symbolizes, I should say, are in the expression of my paintings, and in the way a viewer engages with my paintings. 현대인은 그 어느 시대보다 광범위하고 밀접한 정보와 물적 연결 관계 속에서 생활하고 있다. 이러한 연계 속에서 마치 사람과 사람사이의 교류가 활발하고 풍요롭게 이뤄지고 있는 듯이 느끼기 쉽다. 그러나 인터넷의 확산으로 잉태된 대다수 익명(匿名)의 개인은 이러한 관계의 엄청난 속도와 양에 휩쓸리며 현실과 그 안의 자신을 망각(忘却)하기 쉽다. 망각된 개체들 간의 위태로운 연대감은 정보와 물적 소유에 대한 강박관념, 주체로서의 자아 상실감, 상대에 대한 불신감으로 인한 불안을 익명의 개인들에게 부추기고, 급기야는 양심의 가책 없는 폭력에 무감각해지도록 길들인다. 욕망과 불안, 자아 상실감과 고립감, 무관심과 무감각, 이러한 것들은 분명 인식되고 치유되어야 할 문제이다. 병이 든 사람이 치유를 위해 가장 먼저 해야 할 일은 자신의 병을 인식하고 인정하는 것이라고들 한다. 현대 사회의 문제점, 그 사회와 그 안에서의 우리 모습을 인식하고 인정하는 것. 그것으로부터 우리는 우리의정체성을 확인하고 자아를 찾을 수 있다고 생각한다. 그렇게 되찾은 자아가 바로 사회를 치유하는 원동력이라고 믿는다. 사실 삶의 부조리성이 우리 시대만의 고민은 아니다. 주어진 삶의 조건으로부터의 탈피는 많은 정신적인 스승들의 예지에 의해 그 방법이 여러 가지로 제시되어 왔다. 그런데 동양 철학이나 종교에서 특히우리는 자기 자신을 찾음으로서 도달할 수 있는 진정한 자유와 만난다. 우주 만물의 서로 관계함을 깨달음으로써 전체의 조화를 위해 중심으로부터 탈주할 수 있는 것, 이 진정한 자유를 득한다는 것은 어쩌면 대단히 단순하고 쉬운 것일지도 모른다. 어렵게 생각하는 자체가 그 이해를 방해하는 요소일수도 있다. 쉬울 수도 있고 어려울 수도 있는 진정한 자유로의 과정은 어쨌건 그 이해의 과정이라고 생각되는 일련의 수련을 통해 가능할 것이다. 그 일련의 수련, 이에 본인에게 '만다라'라는 시리즈의 의미가 있다. 신의 죽음이 선언되고 존재하는 모든 것들이 과학적으로 분석되고 물질로 환원된 과학적 세계관 아래서 미술 또한 더 이상 정신의 영역을 언급하지 않는다. 물질성과 개념성에 관점을 둔 모더니즘과 미술과 문화의 정치적 의미와 위치를 모색하는 포스트모더니즘을 거치면서 현대미술은 현실의 거울로서 그 역할이 축약되어 왔다. 그러나 정신의 영역을 언급하지 않는다고 해서 현대미술에서 일종의 종교적 경험이나 정신성이 발견되지 않는다고 단언할 수 없다. 정신성 혹은 내면지향성의 추구야 말로 미술의 본래적 특성 중 하나이며 작가들에게 있어 빼놓을 수 없는 관심사이기 때문이다. 정신성만 가지고서 현실의 거울을 논할 수 없겠지만, 정신과 분리하여 신체만으로도 현실의 거울은 거론될 수 없다. 신체는 주변의 모든 것과 관계한다. 물론 정신성과도 긴밀한 관계를 유지하며 다른 사물과의 연계성을 가진다. 이런 의미에서 현대 미술에서 정신성을 배제할 수 없는 것이다. 이에 본인은 본 논문을 통해 치유로서의 순환구조, 작품을 통한 정신성을 표현 양식으로서 고찰하는 본인의 작품에 관해 논하고자 한다.

中華人民共和國의 정치적 주제의 中國畵 연구 : 1949~1976년 中國畵를 중심으로

이현아 (李賢俄) 홍익대학교 대학원 2006 국내석사

This thesis looks at the Chinese Paintings of Political theme in the People's Republic of China by dividing them on the basis of theme and examines their character and significance. The People's Republic of China carried out the radical reform policies in all sectors in order to establish an ideal Socialist State and these policies changed according to political situations. Art also was so contingent thoroughly on social-political consideration that the government directly controlled not only art creations but also art administrations, art executions and art criticisms. For these reason, in understanding arts in the People's Republic of China, it may be key point of view to examine relation between arts and politics. Unlike oil painting affected by western, the keynote that art should serve Party and People is hard especially for the traditional chinese paintings to follow, as it had been developed and refined focusing on the xieyi(寫意) style by the literati or scholar-official class. Therefore this thesis has examined how the traditional chinese paintings reflected political demands and theoretical premises were practically applied to the traditional chinese paintings. I focused on the period, from establishment of the People's republic of China in 1949 to the death of Mao Zedong(毛澤東) and the end of Cultural Revolution in 1976, when political constrains upon arts was the strictest. The theoretical guideline of arts in the People's Republic of China based on Mao's Yan'an Talks on the Literature and Art in 1942. That laid the foundation for artistic policy after establishment of the People's Republic of China, and artistic policies between 1949 and 1976 were thoroughly executed according to his theory. The most important points were that art should unify and educate the masses and should serve for the masses. He defined arts as a political weapon, stressed politic was prior to arts and proposed Socialist Realism as a artistic model. Socialist Realism derived from the Soviet. Its most important character is the Revolutionary Romanticism that means art should participate in Socialist construction actively and consciously, have optimistic view and express the bright sides of the society Following Mao theory, the government resolutely took steps to reform the art world and changed artistic policies on political considerations. Artistic policies were applied to art organizations, education, exhibitions and publications in order to carry out party policies systematically. Art was used as a mean to justify and propaganda party policies under government control. In the case of traditional chinese paintings, the core of reform movement was combining traditional chinese materials and techniques with Socialist Realist themes and styles. Traditional chinese painters applied optimistic themes reflecting new society and western realistic techniques to figure paintings, landscape paintings, and flowers and birds paintings so as to follow new demands for traditional chinese paintings. The traditional chinese paintings which were produced under the party's control showed themes reflecting new society demands in accordance with the guideline. Most works tended to fall into one or more of the four categories according to political content. First, chinese paintings that glorified party leader Mao Zedong produced reflecting the stress upon Mao's personality cult. Mao was depicted as a deification, heroic leader, people's great teacher, party's theorist, kind leader image according to various political situations and his images changed accordingly. Second, the chinese paintings that symbolized Communist Party and Revolution were produced. In those works, the red color was mainly used as a symbol of the Communist Party and Revolution. Most of them adopted Mao's poem as the title or represented the content of Mao's poem as various symbolic motives so that they could get the political justness. Third, the traditional chinese paintings that depicted a ideal Socialist State were produced. Those works exaggeratively depicted the scene of constructing a Socialist State, the result of constructing a Socialist State and scene of an ideal Socialist State in which people live peacefully harmonizing with nature. Finally, the works depicting socialist heroes or ideal people expressed the people who accomplish their revolutionary projects for the party and nation. In those works, children and women were used as a main icon to present ideal people. All themes which mentioned above are characterized that the bright side of Socialism, far from the realities of life, were represented and they followed party policies in order to suit for the mean of political propaganda. As is generally known, the political arts in the People's Republic of China were influenced by Soviet Socialist Realist art. Although chinese paintings were influenced by Soviet art, they didn't give up traditional chinese materials based on ink and brushwork and kept original characters of traditional chinese painting. Therefore, the chinese paintings of political theme have the significance in the sense that they ensured the original field as well as followed political demands. 본 논문은 중화인민공화국의 정치적 주제의 中國畵를 주제별로 분류하여 살펴보고 그 성격과 의의를 연구한 것이다. 중화인민공화국은 사회주의 국가 건설을 목표로 사회의 모든 영역에 있어서 과감한 개혁 정책을 펼쳤으며, 그러한 정책들은 정치적 상황에 따라 변화되었다. 미술도 역시 철저히 정치적 이해관계에 따라 좌우되어, 정부는 미술 창작 뿐 아니라 미술의 행정, 집행 그리고 평가에 있어서도 직접적인 통치를 가하였다. 이러한 상황속에서 이시기 중화인민공화국의 미술을 이해하는데 있어 정치와의 관계를 중심으로 고찰하는 것은 핵심적인 시각이라 생각된다. 특히 미술이 당과 인민을 위해 복무해야 한다는 기본 방침은 서양의 영향을 받은 사실적인 油畵와는 달리 사의적인 文人畵를 중심으로 한 전통 中國畵의 경우에는 따르기 어려운 문제였다. 따라서 본 논문은 전통적으로 중국 미술사에서 핵심을 이루었던 中國畵가 어떻게 정치적 요구를 반영하여 이를 中國畵로 제작하였는지 살펴보았다. 이를 위해 정치적 영향력이 어느 때보다 강조되었던 시기인 중화인민공화국이 성립된 1949년부터 毛澤東이 사망하고 文化大革命이 종결된 1976년까지의 中國畵를 중심으로 연구하였다. 중화인민공화국의 미술정책은 이론적 지침은 1942년 毛澤東이 延安에서 행했던 ‘延安文藝講話’에 두고 있다. 그것은 중화인민공화국 설립 이후 행해진 문예 정책의 기초를 형성했으며, 이시기 미술 정책은 철저히 그의 이론에 따라 수행되었다. 가장 핵심적 사항은 미술은 인민을 단결하고 교육하게 하며, 인민을 위해 복무해야 한다는 것이었다. 그는 미술을 정치적 도구로서 정의했고, 정치가 미술에 우선하며, 지향해야할 예술 원칙으로서 사회주의 리얼리즘을 제시하였다. 사회주의 리얼리즘은 소련에 연원을 두고 있는 것으로, 가장 중요한 특징은 예술이 능동적으로 그리고 의식적으로 새로운 사회의 건설에 참여해야 하며, 낙관적인 시각을 취해 사회의 밝은 면을 표현해야 한다는 혁명적 낭만주의였다. 毛澤東의 이론에 따라 정부는 미술계 전반에 걸쳐 과감한 개혁을 단행하였고, 정치적 입장에 따라 미술정책을 변화시켰다. 당의 정책을 조직적으로 수행할 수 있도록 미술정책은 미술 조직, 교육, 전시, 출판 등에 적용되었으며, 미술은 철저히 정부의 통제하에 당의 정책을 정당화하고 이를 선전하기 위한 수단으로 사용되었다. 특히 中國畵의 경우 개혁정책의 핵심은 중국 전통의 재료와 기법으로 사회주의 리얼리즘의 주제와 양식을 접목하는 것이었다. 中國畵에 대한 새로운 요구에 따라, 國畵家들은 人物畵, 山水畵, 花鳥畵에 새로운 사회를 반영하는 낙관적인 주제와 서양의 사실적인 기법을 결합함으로써 이를 따랐다. 철저한 당의 통제아래 제작된 中國畵는 정치를 위해 복무해야 한다는 지침에 따라 새로운 사회의 요구를 반영하는 주제들이 나타났다. 우선, 당의 지도자인 毛澤東 개인우상화 정책을 반영하여 그를 우상화한 주제의 中國畵가 제작되었다. 毛澤東은 정치적 상황에 따라 신격화 · 영웅화된 지도자의 이미지, 인민의 교사이자 당의 사상가의 이미지, 인민과 융화되어 인자한 지도자로 묘사된 이미지, 毛澤東 자신이 인민의 한 사람으로 묘사된 이미지 등 정치선전을 위해 그 시대가 요구하는 이미지들로 대체되었다. 둘째로, 공산당과 혁명을 상징적으로 표현한 주제의 中國畵가 제작되었다. 이러한 中國畵들은 共産黨과 革命을 상징하는 붉은 색의 두드러진 사용이 주된 특징이었으며, 대부분 그 상징에 대한 근거로서 毛澤東의 싯귀를 畵題로 사용하거나, 그것의 내용을 여러 상징적인 소재로 표현하여 정치적 정당성을 획득하고 있었다. 세 번째로, 大躍進運動과 文化大革命을 반영하는 사회주의 조국의 이상적인 모습을 표현한 주제의 中國畵가 제작되었다. 이러한 中國畵들은 사회주의 조국 건설과 건설 후의 만족감, 이러한 이상적인 사회속에서 자연과 하나되어 살아가는 이상적인 사회주의 국가의 모습을 과장하여 표현하였다. 또한 인민의 이상화․영웅화된 모습을 표현한 주제는 당과 조국을 위해 혁명적인 사업을 수행하는 인민들의 모습이 주로 나타났으며, 이를 위해 여성과 어린이와 같은 도상들을 사용하여 이상적 인민의 모습을 제시하였다. 전술한 모든 주제들은 모두 사회주의의 밝은 이상이 현실과 괴리된 모습으로 표현되었고, 정치적 선전 수단에 적합하도록 당의 지침을 철저히 따르고 있다. 주지하다시피 중화인민공화국의 정치적 미술은 소련 사회주의 리얼리즘 미술에서 많은 영향을 받았다. 그러나 정치적 주제의 中國畵는 소련의 영향을 받았다 할지라도 먹을 기본으로 하는 전통적인 중국의 재료와 먹선을 중시하는 전통적인 筆法을 포기하지 않고 전통 中國畵의 고유한 특성을 유지하여 타 장르에서는 볼 수 없는 독창적인 영역을 확보하였다는 점에서 의의가 있다.

Salmonella enterica serotype Typhimurium 내에 있는 salmonella pathogenicity islands 1-5의 유전자 변이 연구

이현 전남대학교 대학원 2007 국내석사

Salmonella enterica serotype Typhimurium is a major cause of human gastroenteritis. Five Salmonella pathogenicity islands (SPIs) have been characterized in detail for S. typhimurium. The aim of this study was to examine these regions, shown to be crucial in virulence, in pathogenic serotype Typhimurium to identify any major possession that may explain variation in virulence and provide further understanding of the elements involved in the evolution of these regions. Total strain thirty seven of S. typhimurium were isolated from clinical specimens of diarrhea patients during 2001-2004 in Gwang-ju area, Korea. It was compared by polymerase chain reaction (PCR) amplification using a series of primers that together encompassed the full length of all five SPIs. All strains were identified in all five SPIs. As time goes on from 2001 to 2004, S. typhimurium has a plenty of large blocks of virulence gene, as S. typhimurium in 2001 compared to S. typhimurium in 2004 together. The distribution of these differences suggests that there have been a number of relatively recent horizontal transfers of genes into strains. It seems that existence sequence are likely to be involved in continuing evolution of the pathogenicity islands of pathogenic S. typhimurium.

CAN 기반의 동적 ID 할당을 이용한 선박엔진 모니터링 시스템

이현 부산대학교 2012 국내박사

This thesis proposes a marine engine state monitoring system using dynamic ID application and scheduling method of network sensors which collects the state of bearings temperature and pressure of engine through the CAN network. This thesis proposes the effective monitoring method for marine engine system, which is implemented based upon CAN (Controller Area Network) network. As the marine engine monitoring system requires various kind of information, a lot of sensor nodes are distributed to several places. The dynamic application mechanism of CAN protocol ensures, which all nodes are transferred according to the priority of node identifiers. All the CAN modules are connected to the SCU (Signal Control Unit) module for the efficient communication and processing. SCU module of the time master is responsible for the transmission of CAN module message. Through these methods, message with low-priority were ensured to transmit message and node balancing on CAN bus. This design reduces the cost for wiring and improves the data transmission reliability by recognizing the sensor errors and data transmission errors. Conventional communication method as RS232 and RS485 is supported for compatibility with the existing Marine Engine State Monitoring System. Therefore state of marine is able to be checked in ER(Engine Room).

韓國 現代詩에 나타난 原型心像 硏究 : 에로스적 모티브를 중심으로

이현 慶南大學校 大學院 1984 국내석사

일부 지역 주민의 연령에 따른 난시성분의 변화

이현 충남대학교 대학원 2011 국내박사

Astigmatism is a refractive error commonly encountered in clinics. The prevalence of astigmatism changes with age, ethnicity, and environmental factors. And the number of astigmatism is also associated with degrees of myopia. For these reasons, there are many studies on the prevalence of astigmatism, particularly focusing on refractive astigmatism, but there are limited data on the distribution of corneal and internal astigmatism. To improve our understanding of astigmatism, it is important to know the distribution of all the components of astigmatism, their association with each other, and age-related changes. Therefore, in this study I have (1) reported the frequency of astigmatism, changes in components of astigmatism and its axis for age groups, (2) estimated the relationship between the components of astigmatism, and (3) documented the relationship between astigmatism and spherical power. The following are the major results of this study: 1. The frequency of astigmatism in all subjects was 24.6% for the right eye, 25.5% for the left eye and 32.9% for either the right or the left eye. The frequency of astigmatism did not significantly differ due to gender and laterality. 2. There was a significant difference in the frequency of astigmatism with age. The frequency of astigmatism changed with the highest prevalence of astigmatism found in the 60+ age group, and the second highest in the 20~29 age group, while the lowest prevalence was shown by the group between 20~29 and 60+. There was low frequency of astigmatism in 30~39 and 40~49 age groups, because the astigmatic axis changes from WTR astigmatism to ATR astigmatism. On the other hand, the frequency of astigmatism in 50~59 and 60+ age groups increased because ATR astigmatism was more frequently found. 3. There was a significant difference in the number of astigmatism in the astigmatic components based on age difference. The number of refractive and corneal astigmatism increased from 5~9 age group to 20~29 age group, and then it decreased with increasing age. The number of internal astigmatism was constant up to the 40s but it increased with increasing age after the 50s. 4. There were also changes in the astigmatic axis with age. The frequency of WTR astigmatism was predominant up to the 30s. However, the frequency of WTR astigmatism decreased with increasing age, while the frequency of ATR astigmatism was predominant even after the 30s. The frequency of oblique astigmatism was relatively constant with age. 5. There were age-related changes in astigmatic components and their axes due to the change of the corneal shape. The results indicated that corneal steepening occurred at the weak meridian commonly horizontal meridian and such changes began in the 30s. 6. J0 components of refractive, corneal and internal astigmatism in the astigmatism group were changed with age but they did not change in the non-astigmatism group. In the astigmatism group, J0 components of refractive astigmatism decreased remarkably from the 20s to the 50s, which is 0.77 D for the 20s age group and -0.63 D for the 50s age group. And J0 components of corneal astigmatism decreased from 0.93 D (in the 20s group to -0.14 D in the 50s group. It indicated a decrease in corneal astigmatism. The J0 components of internal astigmatism also decreased from -0.27 D in the 30s age group to -0.99 D in the 50s age group, which indicated to increase the internal astigmatism. However, J45 components of refractive, corneal and internal astigmatism did not changed among the age groups. 7. It is apparent that compensation occurs between corneal astigmatism and internal astigmatism to minimize the magnitude of refractive astigmatism in the non-astigmatic group. However, this did not occur in the astigmatic group. 8. There is an association between the components of astigmatism and the spherical power of ametropia. Refractive astigmatism and corneal astigmatism were increased with increasing absolute spherical power in both myopia and hyperopia. However, internal astigmatism was decreased with increasing absolute spherical power. It is possible to accelerate the progression of myopia when the compensation between corneal astigmatism and internal astigmatism is not suitable. In summary, there was a significant difference in the frequency of astigmatism with age because there were age-related changes in astigmatic components and their axes due to the change in the corneal shape. After 20 years of age, the number of corneal astigmatism was decreased with increasing age, whereas internal astigmatism increased with age. The compensation occurs between corneal astigmatism and internal astigmatism to minimize the magnitude of refractive astigmatism in the non-astigmatic group but this is not the case in the astigmatic group. Refractive astigmatism and corneal astigmatism increased with higher absolute spherical power in spherical error but internal astigmat decreased with increasing absolute spherical power. Therefore, the progression of myopia may accelerate if the compensation between corneal astigmatism and internal astigmatism is not suitable.

Performance analysis of hybrid random access in broadband wireless communications system

이현 Chungbuk National Univ. 2012 국내박사

WirelessMAN으로 알려져 있는 IEEE 802.16-2009 무선 접속 규격은 WirelessMAN-OFDM의 메시지 기반 랜덤 액세스 방식과 WirelessMAN-OFDMA의 CDMA 기반 랜덤 액세스 방식을 지원한다. 3단계 절차를 사용하는 메시지 기반 랜덤 액세스는 랜덤 액세스 부하가 낮을 때 액세스 딜레이를 줄이려고 사용한다. 메시지 기반 랜덤 액세스 방식 에서는 MS가 상향링크 대여폭 할당이 필요할 때 대여폭 할당 요구 메시지를 보낸다. 이 대여폭 할당 요구 메시지는 MS가 요청하는 바이트 수를 포함한다. 이 방식은 단순한 시그널링 절차를 가진다. 그렇지만, MS의 수가 증가함에 따라, 랜덤 액세스 시도의 충돌은 시스템 성능을 열화시킬 수 있다. 이에 반하여, 5단계 절차를 사용하는 CDMA 기반 랜덤 액세스는 랜덤 액세스의 부하가 증가하면 메시지 기반 랜덤 액세스는 실패하기 때문에 딜레이 성능을 희생하고도 낮은 충돌 확률을 위해 사용된다. CDMA 기반 랜덤 액세스에서 MS가 상향링크 요구가 필요할 때, MS는 CDMA 코드를 전송한다. CDMA 코드를 감지한 후, BS는 CDMA_Allocation_IE와 함께 상향링크 대여폭을 제공한다. MS는 이 할당을 대여폭 요구 메시지를 전송하는 데 사용한다. BS는 대역폭 요구 메시지에 대한 상향링크 자원을 할당한다. CDMA 코드는 대역폭 할당 요구 메시지에 대한 자원 할당을 요구하기 위해 사용한다. 그래서 상향링크 자원을 할당하는 절차에 추가적인 단계가 포함된다. 이것이 데이터 전송 딜레이를 증가시킨다. 또한 WirelessMAN-Advanced로 알려져 있는 IEEE 802.16m 무선 접속 규격은 하디브리드 랜덤 액세스 방식을 사용한다. 이 방식은 CDMA 기반 랜덤 액세스의 낮은 충돌 확률 장점과 메시지 기반 랜덤 액세스의 짧은 딜레이 성능 장점을 이용하기 위하여 이 두 랜덤 엑세스 방식을 혼합하여 사용한다. 지금까지 여러 연구 논문에서 낮은 랜덤 액세스 부하에서 메시지 기반 랜덤 액세스 방식이 장점을 가지고 높은 랜덤 액세스 부하에서 CDMA 기반 랜덤 액세스 방식이 장점을 가지고 있는 것에 대하여 보여주었다. WirelessMAN-Advance 시스템에서 새로운 하이브리드 랜덤 엑세스 방식을 채택하여 사용하였지만 이 방식에 대한 성능에 대한 연구가 없었다. 따라서, 새로운 하이브리드 랜덤 액세스 방식에 대한 성능 평가가 필요하다. 이 논문은 CDMA 기반 랜덤 액세스와 더불어 메시지 기반 랜덤 액세스를 지원하는 WirelessMAN-Advance 시스템의 향상된 랜덤 액세스 성능을 분석한다. BE 서비스 클래스와 nrtPS 클래스를 위한 WirelessMAN-Advanced 시스템의 랜덤 엑세스 방식의 수학적 모델을 개발하고 컴퓨터 시뮬레이션을 통하여 검증하였다. 이러한 하이브리드 랜덤 엑세스 방식에 대한 수치분석 결과와 시뮬레이션 결과는 짧은 딜레이 성능의 장점과 낮은 충돌 확률의 장점을 가지는 WirelessMAN-Advanced의 랜덤 액세스을 이해하는데 도움이 될 것이고 이 시스템의 랜덤 엑세스 파라미터에 대한 최적화 값을 제공할 수 있을 것이다. The WirelessMAN air interface known as IEEE 802.16-2009 supports a message-based random access in an orthogonal frequency division mode and a CDMA-based random access in an orthogonal frequency division multiple access mode. The 3-step message-based random access is intended to reduce access delay when random access load is low. Mobiles stations send bandwidth request messages, when they need uplink bandwidth allocation. The bandwidth request message includes the number of bytes requested by the mobile stations. This scheme has a simple signaling procedure. The collisions of random access trials, however, can make the system performance degrade as the number of mobile stations increases. The 5-step CDMA-based random access has lower collision probability than that of the 3-step message-based random access has, but it causes the delay for data transmission to increase. The procedure of the CDMA-based random access is as follows. When mobile stations need uplink request for resource allocation, they transmit a CDMA bandwidth request code. After detecting the CDMA code, the base station allocates a resource for an uplink bandwidth. The mobile station uses the allocated resource to transmit a bandwidth request message. The base station allocates an uplink resource for the bandwidth request message. The CDMA code is used to request resource allocation for the bandwidth request message and additional two communication steps support the procedure of the uplink bandwidth allocation. The delay for data transmission increases regardless of access load. WirelessMAN-Advanced air interface known as IEEE 802.16m-2011 adopts a hybrid random access. The hybrid random access scheme uses both the CDMA-code and message to take advantage of both the low collision probability of the CDMA-based random access and the short delay performance of the message-based random access. It has been analyzed that the message-based random access method had a 3-step short procedure for low random access load and the CDMA-based random access method for high random access loads. The performance evaluation of the hybrid random access has not been studied, while the new hybrid random access was adopted by the WirelessMAN-Advanced system. Its performance needs to be analyzed for system optimization purposes. This thesis analyzes the performance of the enhanced random access of the WirelessMAN-Advanced system which supports the message-based random access as well as the CDMA-based random access. An analysis model of random access of the WirelessMAN-Advanced system is developed for the best effort service class and the non real-time polling service class. The computer simulations verify the accuracy of the numerical model. The numerical analysis and the simulation results of the hybrid random access will help to understand the random access performance of the WirelessMAN-Advanced system. The WirelessMAN-Advanced system finds short delay and low collision probability. The optimal parameters of the random access of the Wireless MAN-Advanced system can be suggested. 

매입형 영구자석 전동기의 효율특성 향상을 위한 영구자석 형상설계

이현 창원대학교 2010 국내석사

매입형 영구자석 전동기는 영구자석을 회전자 내부에 삽입하는 형태로 자기적 공극 축소와 고속에서의 영구자석 비산방지가 주요 이점이었다. 매입형 영구자석 전동기의 큰 특징은 표면자석형 영구자석 전동기와는 다르게 릴럭턴스 토크가 존재하게 되어 마그네틱 토크에 더해지는 형태로 단위무게당 토크가 높은 이점이 있다. 높은 자속밀도와 릴럭턴스 차이에 의해 코깅토크가 다른 형태의 모터에 비하여 상대적으로 매우 크게 발생하여 전동기의 운전특성에 리플로 작용하고 전동기의 진동과 소음의 원인이 되는 단점을 가진다. 유압조절용 전동기의 경우에는 빠른 응답속도와 정확한 토크특성을 요구한다. 정확한 토크특성을 위해 전동기가 적용될 부분의 특성을 분석하여 최고속도와 최저속도에 따른 토크를 분석하고 목표로 설정하였다. 차량 내부에 사용되는 유압조절용 전동기의 형상을 재설계하여 설계목표를 만족시키고자 한다. 일반적인 형태가 아닌 영구자석의 형상을 실험계획법을 통해 정현적인 역기전력을 생성하는 직사각형 형태로 변형하고 특성해석을 통해 전동기의 특성지표인 속도-토크 특성을 도출하여 설계목표를 만족하는 지를 분석하였다.

페르미 입자의 혼합에 관한 연구

이현 建國大學校 大學院 2003 국내박사

One of the most peculiar and unexplained phenomena in the Standard Model is the repetition of generations. It is known that there are three generations of quarks and leptons. The famous electron-muon-tau universality is a distinguishing example of the repetition of generations. The weak interactions can distinguish one generation from another, because they depend on the quark flavours, and the various lepton numbers. This implies that the generations are not the eigenstates of the weak interactions. In fact, the fermionic states that are diagonal with respect to the weak interactions are not the eigenstates of the mass matirx of the corresponding fermions. Since the weak eigenstates are not identical with the mass eigenstates, there inevitably occurs the oscillation phenomena and mixing between them. This kind of mixing has been well observed in the quark sector through the Cabibbo-Kobayashi-Maskawa matrix. On the other hand, until recently, the lepton sector has been immune to the mixing, principally because the neutrinos are massless. However, as the recent result from the SuperKamiokande experiment has shown the hint of oscillations among neutrinos, it becomes quite likely that the neutrinos have non-zero masses, and thus it is reasonable to expect that mixings may also occur in the lepton sector. We review the mixings in the quark sector as well as in the lepton sector. The mechanisim and the basic ideas of the mixings are discussed.