高調波 低減形 整流回路의 最適化에 관한 硏究

柳喆魯,金聖中,李公熙,李星龍 全北大學校 1989 論文集 Vol.31 No.-

The harmonics involved in input AC line currents of thyristor converter apparatus have generated such serious problems as burning of power condenser, misaction of UFR(protective relay), and trouble of the automatic voltage controller, etc., in transmission and distribution of electric power system. In this study, we have analyzed the characteristics of the converter for reducing harmonics, which originate all sorts of obstacles. And in order to maximize the effect for the reduction of harmonics, we researched into the following items. A. From the side of reducing harmonics. 1) Optimum value of turn ratio and number according to the increment of switching tap on interphase reactor. 2) Optimum value of control angle of tap changing. 3) Development of new tap changing algorithm according to control angle of main converter. B. From the side in consideration of economical efficiency 1) Determination of the uppermost limit according to increment of switching tap on interphase reactor. 2) Turn ratio and capacity of main trasformer. 3) Turn ratio and capacity of interphase reactor. In comparison with optimum value by computer simulation about the above items, we have made this converter system in accordance with theory, and then proved this validity through experiments. Therefore, we developed the converter of optimal condition which could be used practically by applying this conclusion.

고분자 복합재료를 위한 액정중합체(I)

조철형,조성휴,조병욱,김정규,김숭평,권중근 조선대학교 생산기술연구소 1983 生産技術硏究 Vol.1983 No.-

Copolyesters containing oxybenzoate as a rigid rod molecule and methylene group and dimethyl tetramethyl disiloxane as flexible spacers were prepared by room temperature solution polymerization for the purpose of the developement of polymeric composite materials. The thermal properties and the characteristics of the polymers were investigated by DSC and a polarizing microscope. The polymers may be formed nematic liquid crystal phase, and the thermodynamic characteristics of their mesophase to isotropic phase transition could be explained on the basis of its structural features.

β係數를 利用한 投資決定方法에 관한 考察

金喆中 弘益大學校 1982 弘大論叢 Vol.14 No.1

The purpose of this paper is to explain the idea of Investment Decision Using β Coefficient. The theoretical framework is briefly summarized first, and then there are some computation examples of this idea. The condition that must hold if the project is to be acceptable is as follows. E(R^o_j)>R_f+[E(R_m)-R_f)β^o_j E(R^o_j) : Return on an individual project. R_f : Risk-free interest rate. E(R_m) : Return on the market. β^o_j : coefficient of an individual project. One great practical advantage of the market price of risk criterion is that all but one of its statistical factors are market constants, applicable to all firms and to all projects. But, because market price data are not available either for individual projects, the problem in this idea is the calculation of the betas for individual projects.

代理費用과 企業의 財務政策

金喆中 홍익대학교 경영연구소 1993 경영연구 Vol.17 No.-

백서 창상의 피복방법에 따르는 Muofibroblast의 생성 및 소실되는 과정의 실험적인 비교관찰

김한중,최희윤,조철현,이인승 大韓成形外科學會 1985 Archives of Plastic Surgery Vol.12 No.1

The question of how skin coverage affects contracting wounds has long been a significant problem in the study of wound contraction. Myofibroblasts appear to be well established as the cellular cause of wound contraction. Myofibroblasts are found in many types of contracting wounds, including granulating wounds and hypertrophic burn scars. Myofibroblasts in contracting wounds have definitive life cycles, being present when contraction is active and then disappearing when contraction has ceased. In this study, we observated comparatively quantitative changes in the surface area by planimetry and changes of myofibroblasts by electron microscope through 8 weeks according to the types of skin coverage. The purpose of this study was to evaluate the myofibroblast population in skin coveraged wounds in a rat model, which allowed frequent biopsies as well as precise identificaion of the interface of the skin coverage and the wound bed. The results of our experiments are as follows: 1. Granulating wound Contracted rapidly and had long persistence of myofibroblasts. 2. Split-thickness skin graft Contrated less and myofibroblasts were more rapidly decreased and were disappeared at 5 weeks later. 3. Full-thickness skin graft Minimum contracti aondnmyofibroblasts were very rapidly decreased and were disappeared at 4 weeks later. 4. Local flap No contraction and could not find myofibroblast. Slowly increase in size at begining. 5. Contraction was influenced by number and lasting time of myofibroblast.

초등학생들의 물질 개념에 관한 연구

김석중,남철우,김정길,송판섭,한광래,최도성,김숙희 光州敎育大學校 初等敎育硏究所 2002 初等敎育硏究 Vol.17 No.-

Over the past 20 years, research on students' conceptual development of science concepts has begun to inform educators about the roles that prior knowledge and experiences play in the development of conceptual understandings. Whereas many initial studies focused on identifying and cataloging naive of misconceptions, more recent research has focused on how student concept development research can inform teaching practice and curriculum design. In this study, we investigated children's (ages 11∼12) spontaneously constructed or naive understanding of the particulate nature of matter prior to any formal instruction in the domain. Thirty students were interviewed concerning their understanding of the macroscopic and microscopic properties of the states of matter(solid, liquid, and gas), as well as their macro/microscopic understanding of phase changes and dissolving. Children expressed ideas about states of matter which were categorized as macrocontinuous, macroparticulate, or microparticulate. Furthermore, a substantial number of the children provided explanations of properties and processes which were consistent with those beliefs. These children's beliefs about matter were not fully and consistently developed across the spectrum of substances from continuous solids to particulate solids to liquids to gases. We speculate that children first develop local frameworks particular to different classes of substances and then slowly expand these frameworks to include a wide range of substances and their properties as well as such processes as melting and freezing.

고지방식이가 백서 골격근 및 지방조직의 지방분해에 미치는 영향

김철희,정윤이,이성진,박중열,홍성관,김홍규,서교일,이기업 대한당뇨병학회 2002 Diabetes and Metabolism Journal Vol.24 No.6

연구배경:지방산화의 증가가 골격근에서 인슐린 저항성을 유발한다는 주장이 꾸준히 제기되어 나왔으나, 최근 제2형 당뇨병 환자나 인슐린저항성 상태에서 골격근의 지방산화능이 저하되어 있다는 보고도 있어 논란이 있는 상태이다. 본 연구에서는 고지방식이를 투여하여 인슐린저항성을 유발한 백서에서 microdialysis 기법을 이용하여 조직내의 지방분해 결과로 간질액내로 방출되는 글리세롤 농도를 골격근 및 지방조직에서 직접 측정하여 지방분해의 변화를 알아보고자 하였다. 방법:정상 Sprague­Dawley 백서를 두 군으로 나누어 4주간 고지방식이 및 저지방식이를 투여하였다. 4주간 기저상태 및 고인슐린 정상혈당 클램프 중의 골격근 및 지방조직에 microdialysis probe를 삽입하고 일정한 농도의 글리세롤을 포함하는 dialysate를 통과시켜 주입액과 유출액의 글리세롤 농도 차이로부터 조직 간질의 글리세롤 농도를 산출하엿다. 결과:기저상태에서 골격근 및 지방조직 간질의 글리세롤 농도는 저지방식이군에 비하여 고지방식이군에서 유의하게 낮았다. 고인슐린 정상혈당 클램프 중에는 골격근 및 지방조직 간질의 글리세롤 농도가 양군에서 모두 억제되었는데, 기저 상태와 마찬가지로 골격근 및 지방조직 모두에서 저지방식이군보다 고지방식이 군에서 더 낮았다. 기저 상태에 대한 고인슐린 클램프중의 글리세롤 방출 억제 정도는 저지방식이군에 비하여 고지방식이군에서 덜 억제되는 경향을 보였는데, 골격근조직에서만 통계적으로 유의하였다. 결론:본 연구 결과는 고지방식이에 의한 인슐린저항성 모델에서 골격근 및 지방조직내 지방분해가 억제되어 있음을 보여주며, 기존의 포도당­지방산 cycle 이론과는 달리 조직내 지방산화의 증가보다는 지방산화능의 감소에 따른 세포내 지방축척이 인슐린저항성과 관련될 가능성을 시사하였다. Background : It has been hypothesized that increased fat oxidation reduces glucose utilization in skeletal muscle, and is responsible for the insulin resistance associated with obesity or high-fat feeding. In contrast, there have been reports that fat oxidation capacity was decreased in skeletal muscles from insulin resistant subjects. This study was undertaken to examine whether insulin resistance in high-fat fed rats is associated with increased lipolysis in skeletal muscle and adipose tissue. Methods : Two groups of Sprague-Dawley rats were fed either high-fat or low-fat diets for 4 weeks. Lipolysis in skeletal muscle and adipose tissue was determined by measurement of interstitial 1 glycerol concentrations by a microdialysis method in basal and hyperinsuline mic-euglycemic clamp conditions. Results : In basal state, plasma glycerol levels and interstitial glycerol concentrations of skeletal muscle, and adipose tissue were lower in high-fat fed than in low-fat fed rats. The degree of suppression of glycerol release by the hyperinsuline mia was smaller in the high-fat diet than in the low-fat diet group. However, plasma and interstitial glycerol concentrations during the hyperinsuline mic euglycemic clamps were also lower in the high-fat diet group. Conclusion : Lipolysis was decreased in skeletal muscle and adipose tissue of insulin resistant, high-fat fed rats. These results support the idea that limited fat oxidation capacity resulting in lipid accumulation in tissues, rather than increased fat oxidation perse, is responsible for the insulin resistance associated with high-fat feeding (J Kor Diabetes Asso 24:641~651, 2000).

충남대학교 기초과학분야의 효율적 육성에 관한 연구

윤화중,진성일,윤민중,윤혜수,이영하,최철규,이천배,신대현 충남대학교 자연과학연구소 1986 忠南科學硏究誌 Vol.13 No.2

Chungnam National University (CNU) is located in Daeduk Science Town, a center of science and technology in Korea, and it is expected to play an important role in the development of science in Korea. With this in mind, the basic natural sciences at CNU should be more actively supported in both education and research. Accordingly analysis and comparison of the basic science program at major college in Korea as well as those in the USA and Europe has been performed. The current cooperative relationship between CNU and research institutes in the science town has also been analyzed. This study has resulted in propositions to make more efficient the upbringing of the basic sciences at CNU, by focusing on the following points ; a) to improve academic affairs, b) to make graduate studies substantial, c) to secure highly qualified faculty members, d) to increase cooperation in research between CNU and reserch institutes, e) to enlarge research laboratories and acquire more equipment and facilities.

유연한 조작기의 진동에 대한 최적 위치 제어

박중윤,황상철 金烏工科大學校 1993 論文集 Vol.14 No.-

Optimal position control of a flexible manipulator is studied. A slender flexible manipulator is modeled as Euler-Bernoulli beam with tip mass and a rigid hub. The vibration system of a flexible manipulator neglecting higher-order elastic vibrating modes is subject to become unstable because of the excitation of the residual modes. The classical control method is usually used is not suitable in this non-minimum phase system. It is shown that the PD control which is known as increasing the system damping is unstable. However, even in the non-minimum phase system, the system is stabilized by the optimal feedback control. LQG/LTR control law is more effective method for controller design of the physical control system than any other optimal control law. LQG/LTR design method and numerical results are presented.

환자에서 분리한 Klebsiella pneumoniae의 장독소 생성능 및 활성에 대하여

윤정중,이태연,박철희 단국대학교 신소재기술연구소 1997 신소재 Vol.7 No.-

임상에서 가져온 99주에 대한 재 실험 결과 40주의 분리균은 생물, 화학적 성상이 Klebsiella pneumoniae ATCC 13883과 동일한 성상을 나타내었으며, K99 균주의 장독소 생성능을 CYE 배지와 CAYE 배지에서 비교하였을 때, CYE 배지에서의 독소 생성능이 높았다. 또한 균주의 배양시간별 장독소 생성능 측정을 위해 배양 후 12시간부터 24시간까지 3시간 간격으로 측정해 본 결과, 21시간 배양했을 때 장독소 생성능이 가장 높았고 마우스 접종시간별 장 독성능을 알아보기 위해 접종 후 시간별로 장 독성능을 측정해 본 결과, 접종 후 4시간후에 장 독성능을 측정했을 때의 효과가 가장 높았다. 따라서 이상의 결과를 종합하면, 환자로부터 분리한 Klebsiella pneumoniae K99 균주는 기존에 보고된 것과는 다소 차이가 있는 생물 및 생화학적 특징을 나타내는 장독소를 생산하는 것을 알 수 있었다. In this study, the enterotoxin of Klebsiella pneumoniae isolated from clinical patients in Korea was characterized. Enterotoxin of Kelbsiella pneumoniae has been known to be secreted in the water and electrolytes in the small intestines of human resulted in diarrhea. For this reason, Klebsiella pneumoniae strains were isolated from patients at hospitals in Seoul, Korea and were investigated for their ability for enterotoxin production by the method of suckling mouse assay. The results were as follows; 1. For their ability of enterotoxin production by the culture media, the casamino acid yeast extract medium was more effective than the casamino acid yeast extract salt medium. 2. For their ability of enterotoxin production by the culture time, enterotoxin their peaked at 21 hrs of incubation. 3. Maximal cytotoxicity was achieved at 4 hrs after the administration of the enterotoxin into the mouse.