장섬유강화 고분자 복합판의 프레스 성형에 있어서 니트라인에 관한 연구

조선형,이국웅,안종윤,윤성운 한국공작기계학회 2001 한국생산제조학회지 Vol.10 No.2

In recent years, compression molding of lone fiber-reinforced thermoplastics has been increased in commercial aspects. In the process of compression molding of composites, the flow analysis must he developed in order to accurately predict the finished part properties as a function of the molding process parameters. In this model FRTP is assumed to be nonisothermal fluid, which has different viscosities in extensional and in shear. For verification of the model, the formation of a knit line in the L-shaped parts is compared with that of experiments results. In this paper we will discuss the effects of extensional & shears viscosity ratio ξ and slip parameter α on the other mold fill-ing parameters

섬유강화 플라스틱 복합재의 성형공정에 관한 연구 : 일방향 섬유강화 복합재의 점도측정 및 유동해석 Flow analysis and Measurement of viscosity of Unidirectional Fiber Reinforced Plastic Composites

조선형,안종윤,이국웅,윤성운 한국공작기계학회 2001 한국생산제조학회지 Vol.10 No.2

During a compression molding process of Unidirectional Fiber Reinforced Thermoplastic Composites, control of filling patterns in mold and distribution of fiber is needed to predict the effects of molding parameters on the flow characteristics. To obtain an excellent product and decide optimum molding conditions, it is important to know the relationship between molding conditions and viscosity. In this study, the anisotropic viscosity of the Unidirectional Fiber-Reinforced Polymeric Composites is measured by using the parallel plastometer. The model for flow state has been simulated by using the viscosity. The composites is treated as an incompressible New-tonian fluid. The effects of longitudinal transverse viscosity ratio A and slip parameter α on buldging phenomenon and mold filling patterns, are also discussed.

Roe 기법을 이용한 Navier-Stokes 유동장 해석에서 벽면 경계조건이 정확도에 미치는 영향 고찰

김형국,김문상 한국 항공대학교 항공산업기술연구소 2000 航空宇宙産業技術硏究所 硏究誌 Vol.10 No.-

Navies-Stokes 방정식을 사용하여 점성 유동장을 해석할 때 어떤 벽면 경계조건이 가장 정확도가 좋은 결과를 주게되는지를 파악하기 위해서 물체 벽면 온도를 1000˚K로 유지한 채 본 연구에서 선정한 서로 다른 3종류의 벽면 경계조건을 각각 사용하여 마하수 3.0에서 마하수 6.0까지의 속도 범위에서 원형 실린더 주위의 유동장을 해석해 보았다. 그 결과 가장 바람직한 해석 결과를 보여주는 벽면 경계조건을 도출할 수 있었으며, 본 연구를 위해서 비점성 항은 Roe 기법을, 점성 항은 중심차분법을 사용하여 플럭스를 계산하도록 하는 유한체적법의 2차원 Navier-Stokes 프로그램을 개발하였다. A comparative study of different wall boundary conditions' effect on the Navier-Stokes' solution accuracy is accomplished to find the best wall boundary condition in the viscous flowfield. Flowfields are analyzed around a circular cylinder geometry with 1000˚K fixed wall temperature condition from Mach number 3.0 to 6.0 using the three different wall boundary conditions. Through this research, The best wall boundary condition is deduced. A two-dimensional wavier-Stokes solver is developed. The inviscid flux is calculated using the Roe scheme and the viscous flux is calculated by centered scheme.

中登 英語敎科書에 收錄된 語彙 檢討 : 主로 第一學年 敎科書 單語를 中心으로

全炯國 연세대학교 인문과학연구소 1957 人文科學 Vol.1 No.-

In addition to several books of English composition and grammar, there are twenty six diffrent kinds of English readers compiled for the use of middle school students in Korea. According to the syllabus of English education promulgated in 1955, all the English readers have been published with the approval of the Minister of Education. Many English teachers who have used the new textbooks published in 1956 have pointed out that they were inadequate. On the assumption that the quality of these textbooks should be examined, this paper is an attempt to investigate the words listed in each textbook and to find out the word frequency in them. Although scientific analysis and discussions of textbooks require many shades of investigation, word frequencies are also one of the important elememts in editing textbooks. After carefully inspecting the six tables. I have come to certain conclusions, and I wish to make a suggestion for the improvement of English textbooks. Although the number of words to teach in the 1st year of middle school is 400 according to the syllabus of English education, most authors of textbooks have neglected this figure. And there is such a amall number of words used in common in these textbooks, that the students will be faced with great difficulty in learning English when they transfer from one school to another or change their textbooks. On the assumption that the words from Thorndike and Lorge's Word Book and from Basic English are most useful and practical, approximately half of the words appearing in all these textbooks are not suitable words for the beginning student of English. Therefore, it is necessary to select the words for the textbook writers on the basic of scientific methods and furthermore that some way be found to ensure observance of this selection. For the purpose of compiling English textbooks and improving English education it is urgently required that the frequency of words, as well as the selection of words, should be carefully taken into account as many linguistics have already suggested.

유동장 해석의 정확도 증진을 위한 풍상차분법의 비교 연구

김형국,김문상 한국항공대학교 2000 論文集 Vol.38 No.-

본 논문에서는 유동장 해석 결과의 정확도 증진을 위한 비점성 플럭스 계산 기법에 대한 비교 연구를 수행하였다. 플럭스를 계산하는 대표적인 방법으로 풍상차분법과 중심차분법이 있는데 최근에는 풍상차분법이 주로 사용되고 있다. 특히 풍상차분법 중에서도 FVS와 FDS의 장점만을 선택하여 개발된 AUSM 계열 기법이 많이 사용되고 있는 추세이다. 본 논문에서는 마하수 5.0으로 비행하는 무딘 물체 주위에서의 유동장을 FVS, FDS, 그리고 AUSM 계열의 풍상차분법들을 사용하여 해의 정확성을 비교 연구하였다. 본 연구를 위해서 일반 곡면 좌표계에서 유도된 2차원 압축성 오일러 방정식을 사용한 전산 프로그램을 개발하였으며, 시간 전진법으로 음해법과 양해법 모두를 사용할 수 있게 하였고 MUSCL 기법을 사용하여 2차 공간 정확도를 가질 수 있도록 하였다. 해석 결과 가장 수치적 점성 효과가 큰 기법은 FVS 기법이었으며 FDS 기법은 엔트로피 보정이 없을 경우 정체점 부근에서 carbuncle 현상이 발생하였으며 엔트로피 보정에 의해서 올바른 해를 구할 수 있었다. AUSM 계열 기법은 가장 정확한 해석 결과를 보여주었으나 AUSM 및 AUSM+ 기법의 경우 충격파 후의 압력에 overshoot 현상이 발생하였고 이런 측면에서 AUSMPW가 가장 좋은 해석 결과를 보여주었다. In this paper, a comparative study of different upwind schemes is accomplished to figure out the solution accuracy enhancement in inviscid flux calculations. The upwind schemes are more popular than the centered schemes to calculate the inviscid fluxes. The AUSM family which takes the merits of FVS and FDS is the most frequently used scheme. The flowfield around a blunt body at Mach 5.0 in inviscid flow is analyzed by using the FVS, FDS, and AUSM family schemes to compare the solution accuracy. Two-dimensional compressible Euler equations derived in general curvilinear coordinate systems are used to develop the flowfield analysis code. Implicit and explicit method are built in this code and MUSCL approach is implemented to increase the solution accuracy up to the second order in space. The most diffusive results are shown when FVS is used. The FDS shows a carbuncle phenomena near the stagnation point. This undesirable result is removed by introducing the entropy fixing technique. The AUSM family shows the best solution even though the AUSM and AUSM+ yield the overshoot pressure right after the shock. The AUSMPW is considered as the best scheme in this sense.

펄스폭제어방식을 이용한 Switching Regulator에 관한 연구

박규태,윤형로,최승국 연세대학교 산업기술연구소 1981 논문집 Vol.13 No.2

본 논문에서는 Switching Regulator 내의 PWM 시스템에서의 위상지연과 스위칭소자의 지연에 의한 위상지연을 고찰하였고 출력필터의 연속전류모드와 불연속전류모드의 궤환에 의한 시스템의 특성을 분석하였다. 또한 Surge에 의한 Normal mode 잡음과 Ground 잡음전류에 의한 Common mode spike 잡음의 원인을 분석하고 그 대책을 강구하였으며 실제 스위칭 레귤레이터의 제작에 필요한 회로구성과 소자의 선정요건을 고찰하여 효율 82.6%, spike 잡음 10mvp-p 이내의 안정되고 특성이 우수한 레귤레이터를 설계하였다. The phase shift in PWM System due to the time delay in the switching elements has been studied. Employing the normal model, various performance characteristics of the converter for both continuous current operation and discontinuous current operation are compared. The normal mode noise generated by surge and common mode noise generated by ground noise current have been studied. To decrease the noise, several methods are introduced. Hardware circuits are built and in experimental measurements, it shows a high efficiency of 82.6% and low spike noise of 10mv p-p max.

유동층을 이용한 탈황제의 마모특성에 관한 연구

오광중,김형국,최은화,조기철 부산대학교 환경문제연구소 1999 環境硏究報 Vol.17 No.1

For the efficient energy use and the protection of environmental pollution, attrition characteristics, depending on the component and the condition of sorbent for the purification of fuel gas, were analyzed by a fluidized-bed tester. Results of these studies can be summarized follows. 1) When Mn-based sorbent(M, MT, MFT) prepared with varying addictives and induration conditions was compared in terms of particle size distribution and AI(Attrition Index), MT and MFT possessing TiO2 and Fe203 had much higher attrition resistance than M. Attrition resistance of M, MT and MFT increased as bentonite contents and induration temperature increased, when bentonite contents induration temperature were changed from 2 to 5% and from 1000 to 1100℃, respectively. Therefore when powdery catalysts are prepared, the attrition rate can be considerably affected by the controls of addictive, binder and induration temperature. 2) Attrition tests using MT1100-5 were performed under the conditions that particle size distribution was uniform and had much more over +270mesh and under -325mesh. AI due to attrition was 8.83, 21.54 and 1.67%, respectively. Thus, initial particle size distribution showed a great influence on both produced fines distribution and attrition loss. Therefore, the size distribution of particles injected initially and the particle size that carried over showed be considered to reduce the loss of particulate materials and the replacement cost due to attrition. 3) An experiment using MT1100-5 sorbent was also carried out to predict AI as a function of time and particle size distribution during 23hr. AI of prepared sorbent was 4.54, 7.73, 9.08, 11.35 and 12.48 after 1.5, 3, 5, 9 and 23hr. respectively. Thus, it was shown that the amount of produced fines during the same time was shorten with the increase of time. The operating condition of dust capturing equipment and the rate of powder exchange needs to be considered because most of the fines due to fluidization of particulate material was generated at initial operation.

마약길항제의 방출 제어형 제제 (제2보) : 나록손 이식제제의 생체적합성 및 약물속도론적 평가 Biocompatibility and Pharmacokinetics of Naloxone Implant

문미란,박주애,이승진,김형국,김길수 梨花女子大學校 藥學硏究所 1995 藥學硏究論文集 Vol.- No.5

For the effective administration of narcotic antagonist, the application of sustained release implantable systems with biodegradable polyphosphazene was examined. Using poly[(diethyl glutamate)-co-(ethyl glycinate) phosphazene]. the implantable devices containing naloxone hydrochloride were prepared and in vivo implantation studies were carried out subcutaneously in rat and rabbit with this preparation for the biocompatibility and pharmacokinetics. The histological finding in rats at initial time period was the inflammation that occurred focally around the implants, but they were showed subsequent mild and limited chronic inflammations and the irreversible changes such as necrosis and degeneration of the muscle or connective tissues were not observed. Therefore the placebo and naloxone implants are considered to be biocompatible formulations histologically. In pharmacokinetic studies, the release of naloxone from the naloxone implants into blood plasma was maintained in 192 hours, but the initial burst effect was observed. If this problem was solved, the application for the narcotic antagonist sustained release systems can be expected.

유리협점막이식술의 임상적 연구

김웅비,김 호,박형국,권혁진,김용각 大韓顎顔面成形再建外科學會 1995 Maxillofacial Plastic Reconstructive Surgery Vol.17 No.3

Free grafting of oral mucosa for minor oral reconstruction was first described by Propper in ridge extension surgery. Situation calling for mucosal grafting procedures may relate to periodontal surgery, minor and major preprosthetic surgery, implant surgery, reconstruction in deformity cases after trauma, congenital cleft, gross atrophy and ablative tumor surgery. In the cases of 9 patients with mucosal defect of intraoral or orbital cavity after wide excision of tumor, preprosthetic surgery, and orbitoplasty, full-thickness mucosal graft were used to close a large defect. Four patients received buccal mucosal graft for preprosthetic surgery or orbitoplasty, one patient had benign tumor and the others had malignant tumors located on the palate or upper alveolus. Buccal mucosal graft donor site morbidity and trismus were minimal and healing of surgical defect was satisfactory. So we present the case with review of literatures.

마약길항제의 방출 제어형 제제 (제1보) : 생체분해성 polyphosphazenes의 합성과 나록손 이식제제의 제조 및 용출특성 Synthesis of Biodegradable Polyphosphazenes and Preparation and Release Characteristics of Naloxone Implant

박주애,이승진,김형국,김길수 梨花女子大學校 藥學硏究所 1995 藥學硏究論文集 Vol.- No.5

For the administration of narcotic antagonist with short half-life and low patient compliance. the sustained release system using biodegradable matrix is effective. Polyphosphazenes are of considerable interest as biodegradable matrix systems for controlled release of drugs. In this study. biodegradable polyphosphazenes available for the sustained release implantable device were synthesized. and their application was examined. Poly〔dichlorophosphazene〕 was synthesized by solution polymerization method and confirmed with IR spectrum. Poly〔bis(ethyl glycinate) phosphazene〕 and poly[(diethyl glutamate)-co-(ethyl glycinate)phosphazene] were then produced by substitution of amino acid alkyl esters for chloride side groups. Using these polymers. the implantable devices of 1 ㎜ thickness and l0 × 10 ㎜ size containing naloxone hydrochloride were prepared and their release and degradation profiles were measured. In the case of poly〔bis(ethyl glycinate)phosphazene〕 with swelling characteristics, degradation rate was slower than the release rate, showing that the release rate is partly dependent on the swelling rate. In contrast, the degradation rate of poly〔(diethyl glutamate)-co-(ethyl glycinate)phos-phazene〕 matrix was identical with release rate of naloxone hydrochloride. On the basis of these results, it is expected that these polymers can be applied to sustained release implantable systems delivering narcotic antagonist.