반사형 쌍안정 카이랄 스플레이 네마틱 액정표시소자

김태형,이중하,신정국,장지향,김정수,전철규,권순범,윤태훈,김재창,Kim, Tae-Hyung,Lee, Joong-Ha,Shen, Zheng-Guo,Jang, Ji-Hyang,Kim, Jeong-Soo,Jhun, Chul-Gyu,Kwon, Soon-Bum,Yoon, Tae-Hoon,Kim, Jae-Chang 한국광학회 2011 한국광학회지 Vol.22 No.1

쌍안정 카이랄 스플레이 네마틱 액정표시소자는 스플레이 상태와 $-\pi$ 꼬인 상태를 쌍안정 상태로 사용하는 메모리 액정표시소자이다. 셀 갭/피치의 값이 0.25일 경우 완전한 쌍안정 상태를 갖지만, $-\pi$ 꼬인 상태에서 스플레이 상태로 전이시키기 위하여 fringe 전계를 인가할 경우 픽셀영역은 전계의 왜곡에 의해서 완전한 스플레이 상태가 아니라 $-\pi$ 꼬인 상태를 부분적으로 유지하게 된다. 본 논문에서는 화소영역에서 두 안정한 상태가 공존하지 않는 $-\pi$ 꼬인 상태를 어두운 상태로 사용하는 반사형 쌍안정 카이랄 스플레이 네마틱 액정표시소자를 제안한다. 제작된 반사형 액정표시소자는 30:1의 고명암비를 나타냈으며, 응답속도는 수직전압 8 V, fringe 전압 12 V의 구동 전압으로 각각 쓰기 응답시간이 950 ms, 리셋 응답시간이 450 ms였다. 또한 제안된 셀은 +C 광학 보상 필름을 사용하여 좌우 방향에서 $180^{\circ}$의 광시야각을 나타냈다. Bistable chiral splay nematic liquid crystal display (BCSN LCD) is a memory type liquid crystal display using splay and $-\pi$ twist states as two stable states. When the cell thickness to pitch (d/p) ratio is 0.25, splay and $-\pi$ twist states have permanent memory time. However, when the transition from $-\pi$ twist state to splay state is caused by a fringe field, pixel regions show that the splay state is not perfect, but rather includes a contribution from the $-\pi$ twist state. In this paper, we propose a reflective BCSN LCD using $-\pi$ twist state in which the two stable states do not coexist. The fabricated reflective BCSN LC cell shows a high contrast ratio of over 30:1 and response times of 950 ms and 450 ms in vertical and fringe field switching, respectively. The proposed cell also shows wide viewing angle characteristics of $180^{\circ}$ in left- and right directions.

Modeling of the Tensile Strength of Unsaturated Granular Soil Using Soil-water Characteristic Curve

김태형,김찬기,김태훈,Kim Tae-Hyung,Kim Chan-Kee,Kim Tae-Hoon Korean Geotechnical Society 2004 한국지반공학회논문집 Vol.20 No.7

본 연구는 불포화 상태 전 범위에 대한 사질토의 인장강도 모델화 가능성을 조사하기 위해 실시 되었다. 새로 개발된 직접인장시험기법을 이용하여 인장시험이 실시되었다. 측정된 결과는 Rumpf 및 Schubert가 동일크기의 이상적인 구에 대해 개발한 이론적인 인장강도 모델들에 의한 예측 값과 비교 되었다. 이를 위해 석션-포화실험을 통해 얻어진 흙-수분특성곡선을 이용하여 이론모델에 있어 중요한 요소인 불포화상태(pendular, funicular, capillary) 구분 및 음의 간극수압 값을 산정하는데 사용하였다. Pendular 상태에서 불포화모래의 비선형 거동이 Rumpf의 모델에 의해 적절이 묘사되었다. Funicular 및 capillary상태의 경우, 함수비가 증가함에 따라 인장강도가 증가하다 최고 값이 도달한 후 다시 감소하는 실험 측정치의 경향도 Schubert의 모델에 의해 적절히 묘사되었다. 본 비교 연구는 이상적인 단일 크기의 입자에 대해 개발된 이론적인 모델이 다양한 크기를 갖는 불포화 사질토의 인장강도를 예측할 수 있다는 가능성을 뒷받침해준다. This study was conducted to explore the tensile strength models in granular soil at the full range of unsaturated state. Direct tension experiments were carried out with a newly developed direct tension technique. The measured experimental data were compared with theoretical models developed by Rumpf and Schubert for monosized ideal particulate solids at the unsaturated state. To do this, the soil-water characteristic curve obtained from a suction-saturation experiment was used to define the unsaturation state and the negative pore water pressure with different water content levels, which are important factors in theoretical tensile strength models. The nonlinear behavior of the tensile strength for unsaturated granular soil at the pendular state is appropriately simulated with Rumpf's model. For the funicular and capillary states, the predicted trend by Schubert's model is properly matched with the experimental data: tensile strength steadily increases and reaches a maximum value and then decreases until it reaches zero. This comparison supports the concept that the tensile strength of unsaturated real granular soil can be approximately simulated with theoretical models.

생쥐와 인간배아의 완만동결-급속융해 후 생존률과 배아발생에 미치는 Ethylene Glycol (EG)과 1,2-Propanediol (PROH)의 영향

김태형,차수경,이동률,한지은,이우식,윤태기,차광렬,정형민,Kim, Tae-Hyung,Cha, Soo-Kyung,Lee, Dong-Ryul,Han, Jee-Eun,Lee, Woo-Sik,Yoon, Tai-Ki,Cha, Kwang-Yul,Chung, Hyung-Min 대한생식의학회 2004 Clinical and Experimental Reproductive Medicine Vol.31 No.1

Objective: The aim of this study were to compare the effects of EG and PROH on cryopreservation of mouse and human embryos, and to find the optimal protocol for embryo freezing. Methods: Human embryos derived from fertilized eggs showing 3 pronuclei (PN) and mouse embryos were divided into two groups respectively: dehydrated with 1.5 M EG + 0.2 M sucrose or 1.5 M PROH + 0.2 M sucrose using the slow freezing method. Moreover mouse embryos were controlled the exposure time of cryoprotectant during dehydration or rehydration steps. Results: The survival rates of human embryos were 79.2% (84/106) in EG group and 77.9% (88/113) in PROH group. In mouse embryos, the survival and development rates up to blastocyst were 70.6% (245/347), 44.1% (123/279) in EG group and 62.1% (198/319), 45.1% (123/279) in PROH group, respectively. However, in EG group, partially damaged embryos after thawing were decreased compared to PROH group. In combination group, when the exposure time during dehydration and rehydration were reduced, the survival and embryonic developments were increased slightly, but not significant. Conclusion: Cryopreservation of mouse and human embryos at cleavage stage by using EG or PROH exhibited no statistical difference in the survival rate and/or developmental rate to blastocyst. However, the use of EG for cryopreservation of embryos might reduce the exposure time of the cryoprotectant because of a high permeation of EG and result in lessen its toxic effects.

로브곡선을 이용한 자동차용 신강재의 저항 점 용접성 평가 기술 개발

김태형,이동옥,이세헌,Kim, Tae-Hyung,Lee, Dong-Ock,Rhee, Se-Hun 대한용접접합학회 2005 대한용접·접합학회지 Vol.23 No.4

The resistance spot welding is one of the most commonly used welding process for joining the sheet metal in automotive manufacturing process due to higher deposition rates and higher economy achieved. Control variables in the resistance spot welding for achieving high quality are welding current, welding force and welding time. Generally at the manufacturing scene, welding current Vs welding time lobe diagram is used to estimate weldability because controlling welding force is not practical due to economical reasons. However new automotive steel plates have been developed to make lightweight automobiles and to improve resistance against rusting. Also the weldability of these steel plates are worst than the existing steel plates because of changing bare metal and surface plating effect. In consequence of above mentioned reasons, it is necessary to use welding force to present the lobe diagram. In this study, we obtained the welding force Vs welding current lobe diagram for commonly used GA steel plate and found that the second order repression model of tensile shear strength was useful in reducing the number of experiments, and the indentation, and thickness change during welding were used as a response to estimate quantitatively expulsion.

교사 직업군에서의 음성장애와 악화요인에 관한 연구

김태형,진성민,송윤경,이승석,이경철,권기환,Kim, Tae-Hyung,Jin, Sung-Min,Song, Yun-Kyung,Lee, Seung-Suk,Lee, Kyung-Chul,Kwon, Kee-Hwan 대한후두음성언어의학회 2004 대한후두음성언어의학회지 Vol.15 No.1

Background and Objective : Voice disorders are one of the major occupational hazards of school teaching. Prolonged voice use through verbal instruction has been implicated as a cause of vocal impairment among members of this profession. They all depend on their voice for their livelihood and are greatly alarmed by slightest alteration in voice quality. Despite considerable research in the area of voice problems in teachers, the prevalence of voice disorders in this group is unknown. Severe voice problems can affect teacher's ability to teach in the classroom. Materials and Method : This study investigated the prevalence of self-reported voice problems in teachers using a survey of a simple random sample of middle school teachers (n=1000). As part of the survey, teachers were asked to report voice problems for the day of the survey, duration, main symptom, smoking, caffeine, alcohol history etc. Results : The reponse rate was 91%(n=94) with 89.7%(n=812) teachers reporting voice problems on the day of the survey, and 40%(n=330) of these group reporting the history of medical consult. Conclusion : These finding indicate a need for vocal hygiene education in teachers and for the development of educational programs aimed at preventing voice problems in this group of professional voice users.

후복막 접근법을 통한 복강경 부신절제술의 초기 경험

김태형,이초록,박슬기,박재현,정준수,강상욱,정종주,남기현,정웅윤,박정수,Tae Hyung Kim,M.D.,Cho Rok Lee,M.D.,Seulkee Park,M.D.,Jae Hyun Park,M.D.,Jun Soo Jeong,M.D.,Sang-Wook Kang,M.D.,Jong Ju Jeong,M.D.,Kee- Hyun Nam,M.D.,Woong Youn 대한갑상선-내분비외과학회 2011 The Koreran journal of Endocrine Surgery Vol.11 No.4

Purpose: Posterior retroperitoneoscopic adrenalectomy (PRA) for small adrenal tumors has recently been in the spotlight due to its several benefits. Compelling advantages for endoscopic surgeons include direct, safe, and fast approach to the adrenal gland without trespass to the intraperitoneal organ. This study reports our initial experiences of PRA for the management of adrenal tumors. Methods: From December 2009 to August 2011, 63 patients underwent PRA for the management of adrenal tumor. Among these patients, laparoscopic adrenalectomy and robotic adrenalectomy were performed in 54 and nine patients, respectively. We retrospectively reviewed records of all surgical outcomes. Results: Of the 54 patients, 22 were male and 32 were female, and mean age was 51.7±14.0 years. Mean body mass index was 24.6±3.6 kg/m<SUP>2</SUP> and mean dimension of the tumors was 2.66±1.36 cm. Six patients were diagnosed with Cushing's disease, 22 patients with primary aldosteronism, seven patients with pheochromocytoma, one patient with metastatic adrenal gland cancer, and 18 patients with nonfunctioning adrenal tumors. Mean operative time was 88.5±27.1 min, mean blood loss was 17.4±37.4 ml, and mean duration to first oral intake was 0.83±0.4 days. Mean number of postoperative analgesics used was 2.28±2.54, and mean postoperative hospital stay was 2.85±1.43 days. There was no open conversion during the operation and no post-operative complication. Conclusion: PRA is a safe and fast procedure. In experienced hands, PRA represents one of the ideal approaching methods in the adrenal gland surgery. (Korean J Endocrine Surg 2011;11:287-291)

자동차 차체 제조 공정에서 용접 공정 오류 검출을 위한 지능형 모니터링 시스템 개발

김태형,유지영,이세헌,박영환,Kim, Tae-Hyung,Yu, Ji-Young,Rhee, Se-Hun,Park, Young-Whan 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.4

In resistance spot welding, regardless of the optimal condition, bad weld quality was still produced due to complicated manufacturing processes such as electrode wear, misalignment between the electrode and workpiece, poor part fit-up, and etc.. Therefore, the goal of this study was to measure the process signal which contains weld quality information, and to develop the process fault monitoring system. Welding force signal obtained through variety experimental conditions was analyzed and divided into three categories: good, shunt, and poor fit-up group. And then a monitoring algorithm made up of an artificial neural network that could estimate the process fault of each different category based on pattern was developed.

편측 신장 무형성 및 쇄항을 동반한 Mayer-Rokitansky-Kuster-Hauser(MRKH) 증후군 1례

김태형,김진희,김수영,Kim, Tae-Hyung,Kim, Jin-Hee,Kim, Soo-Yung 대한소아신장학회 2006 Childhood kidney diseases Vol.10 No.2

MRKH 증후군은 비뇨생식기계 및 골격계에 기형을 동반하지만 쇄항에 대한 동반 기형유무 검사상에서 MRKH 증후군으로 진단된 경우는 거의 보고되고 있지 않다. 이에 저자들은 쇄항을 주소로 내원한 34주 미숙아에서 MRKH 증후군으로 진단된 본 증례를 경험하였기에 문헌고찰과 함께 보고하는 바이다. The clinical features of the Mayer-Rokitansky-K$\ddot{u}$ster-Hauser(MRKH) syndrome include normal female secondary sex characteristics, normal genitalia, congenital absence of vagina, rudimentary or bipartite uterus, normal ovarian function and normal ovulation, 46, XX, karyotype, frequent association of renal, skeletal and other congenital anomalies. We experienced a case of a premature infant with MRKH syndrome who had imperforate anus and unilateral renal agenesis.

결막 내 이식했던 양막을 이용한 난치성 각막 윤부결핍 질환 치료 1예

김태형,정재훈,전연숙,김재찬,Tae Hyung Kim,Jae Hoon Jeong,Yeoun Sook Chun,Jae Chan Kim 대한안과학회 2011 대한안과학회지 Vol.52 No.9

Purpose: To report the use of amniotic membrane (AM) as a mesenchymal stem cell (MSC) carrier in cornea perforation with severe limbal stem cell deficiency due to a chemical burn on both eyes. Case summary: The patient in the present study is a 43-year-old man with a history of bilateral alkaline chemical injury six years previously. The patient suffered from total limbal stem cell deficiency (LSCD) in the injured eyes and underwent numerous operations including autologous conjunctival flap, AM graft, penetrating keratoplasty, keratolimbal autograft and ex vivo expanded limbal allogrft. However, the patient’s ocular condition deteriorated due to persistent LSCD, which led to corneal perforation resulting in the need for an urgent therapeutic operation. In the patient’s past ocular history, Ahmed valve implantation was performed for uncontrolled IOP. Revision of the Ahmed tube due to exposure and conjunctival erosion was performed again via placement of an AM over the exposed tube one year previous to presentation to our hospital. The authors performed a transplanted AM graft at the cornea perforation using sub-conjunctival AM believed to contain MSCs. Six months postoperatively, the ocular surface was well mainatained and the graft remained healthy. Transplanted AM showed morphological and immunohistochemical findings similar to those of MSCs. Conclusions: Results from the present study confirm that AM transplanted into the conjunctiva is a useful carrier of bone marrow-derived MSCs in severe ocular surface diseases. J Korean Ophthalmol Soc 2011;52(9):1104-1108

분류모형을 이용한 여신회사 고객대출 분석에 관한 연구

김태형,김영화,Kim, Tae-Hyung,Kim, Yeong-Hwa 한국데이터정보과학회 2013 한국데이터정보과학회지 Vol.24 No.3

데이터마이닝이란 대용량의 자료로부터 의미있는 패턴과 규칙을 찾기 위해서 자동화되거나 반자 동화된 도구를 이용하여 데이터를 탐색하고 분석하는 과정이다. 이러한 데이터마이닝 기법을 통해 정보의 연관성을 파악함으로써 가치 있는 정보를 만들어 합리적인 의사 결정이 가능하게 된다. 금융분야에서도 데이터베이스 마케팅, 신용평가, 서비스 품질개선, 부정행위 적발 등에 데이터마이닝 기법이 다양하게 사용되고 있다. 금융거래에서 대출의 중요도와 필요성이 시간이 지날수록 점점 높아지고 있으나, 대출을 이용하는 사람과 대출건수가 증가할수록 부실대출의 위험이 함께 증가하기 때문에 대출을 해주는 여신기관의 손실을 막기 위해서는 대출여부를 정확하게 예측할 필요성이 존재한다. 본 연구에서는 국내 A 여신기관의 실제 데이터를 사용하여 대출심사에 관한 연구를 진행하였으며, 모형 구축에 있어서 안정적이고 정확한 예측을 보이는 모형을 찾기 위하여 원 데이터에서의 샘플 정제와 여러가지 모형, 데이터마이닝 기법 등을 사용하여 다양한 모형을 구축하고 비교, 평가하였다. The importance and necessity of the credit loan are increasing over time. Also, it is a natural consequence that the increase of the risk for borrower increases the risk of non-performing loan. Thus, we need to predict accurately in order to prevent the loss of a credit loan company. Our final goal is to build reliable and accurate prediction model, so we proceed the following steps: At first, we can get an appropriate sample by using several resampling methods. Second, we can consider variety models and tools to fit our resampling data. Finally, in order to find the best model for our real data, various models were compared and assessed.