자기베어링 및 공기베어링 병용 소형고속스핀들

최정섭,경진호,노승국,박종권 한국공작기계학회 2006 한국공작기계학회 추계학술대회논문집 Vol.2006 No.-

The design of a miniaturized air spindle system suspended a magnetic bearing is discussed in this paper. We designed and manufactured for the machine tool of micro factory system. The proposed spindle is consisted of air bearing unit for supporting both side of the radial and axial direction and a magnetic bearing unit for controlling in the radial direction. The used air bearing is aero-static type and the equipped magnetic bearing is a homo-polar type magnetic bearing which has 4 poles and 4 coils. This magnetic bearing is located in the top side of the spindle for improvement of damping of air spindle. The diameter and length of the spindle are 84mm and 112mm, respectively. We discussed the performance of an air bearing and a magnetic bearing in analytical and experimental approach.

조혈모세포이식을 받은 급성 골수 백혈병 환자에서 발생한 cyclosporine에 의한 양측 시신경병증

정진권,김한조,박명진,하승주,최경식,이성진,박성희,이상철,이남수,박희숙,원종호 순천향대학교 의학연구소 2007 Journal of Soonchunhyang Medical Science Vol.13 No.2

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Streptomyces coelicolor의 pat 유전자 5'-Flanking Region의 염기서열

박경현,채영규,최영길,박영석 漢陽大學校 基礎科學硏究所 1994 基礎科學論文集 Vol.13 No.-

Streptomyces coelicolor의 phosphinothricin acetyltransferase (pat)유전자는 phosphinothricin(PPT) 저항성 유전자들로부터 고안된 primer를 사용하여 클로닝되었다. Southern blot 분석결과 S. coelicolor에서 얻어진 2.1-kb DNA 절편은 S. hygroscopicus의 bar유전자를 DNA-DNA hybridization 하였다. 본 논문은 S. coelicolor의 pat 유전자의 5'-flanking region의 염기서열을 분석하였다. The pat gene of Streptomyces coelicolor strain was cloned by using primers designed from the PPT resistant genes. Southern blot analysis was revealed a DNA-DNA hybridization between the obtained 2.1-kb DNA fragment from S. coelicolor and bar gene from S. hygroscopicus. This paper was analyzed for the nucleotide sequence about the 5'-flanking region of pat gene from S. coelicolor.

Plasma N-Terminal Pro-B-Type Natriuretic Peptide Is Predictive of Perioperative Cardiac Events in Patients Undergoing Vascular Surgery

( Ji Hyun Yang ),( Jin Ho Choi2 ),( Young Wook Ki ),( Dong Ik Kim ),( Duk Kyung Kim ),( Jeong Rang Park ),( Jae K. Oh ),( Seung Hyuk Choi ) 대한내과학회 2012 The Korean Journal of Internal Medicine Vol.27 No.3

Background/Aims: Identification of patients at high risk for perioperative cardiac events (POCE) is clinically important. This study aimed to determine whether preoperative measurement of plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) could predict POCE, and compared its predictive value with that of conventional cardiac risk factors and stress thallium scans in patients undergoing vascular surgery. Methods: Patients scheduled for non-cardiac vascular surgery were prospectively enrolled. Clinical risk factors were identified, and NT-proBNP levels and stress thallium scans were obtained. POCE was the composite of acute myocardial infarction, congestive heart failure including acute pulmonary edema, and primary cardiac death within 5 days after surgery. A modified Revised Cardiac Risk Index (RCRI) was proposed and compared with NT-proBNP; a positive result for ischemia and a significant perfusion defect (≥ 3 walls, moderate to severely decreased, reversible perfusion defect) on the thallium scan were added to the RCRI. Results: A total of 365 patients (91% males) with a mean age of 67 years had a median NT-proBNP level of 105.1 pg/ mL (range of quartile, 50.9 to 301.9). POCE occurred in 49 (13.4%) patients. After adjustment for confounders, an NTproBNP level of>302 pg/mL (odds ratio [OR], 5.7; 95% confidence interval [CI], 3.1 to 10.3; p<0.001) and a high risk by the modified RCRI (OR, 3.9; 95% CI, 1.6 to 9.3; p = 0.002) were independent predictors for POCE. Comparison of the area under the curves for predicting POCE showed no statistical differences between NT-proBNP and RCRI. Conclusions: Preoperative measurement of NT-proBNP provides information useful for prediction of POCE as a single parameter in high-risk patients undergoing noncardiac vascular surgery.

Enhanced superconductivity in surface-electron-doped iron pnictide Ba(Fe_1.94Co_0.06)₂As₂

Kyung, W. S.,Huh, S. S.,Koh, Y. Y.,Choi, K.-Y.,Nakajima, M.,Eisaki, H.,Denlinger, J. D.,Mo, S.-K.,Kim, C.,Kim, Y. K. Nature Publishing Group 2016 NATURE MATERIALS Vol.15 No.12

<P>The superconducting transition temperature (T-c) in a FeSe monolayer on SrTiO3 is enhanced up to 100 K (refs 1-4). High T-c is also found in bulk iron chalcogenides with similar electronic structure(5-7) to that of monolayer FeSe, which suggests that higher T-c may be achieved through electron doping, pushing the Fermi surface (FS) topology towards leaving only electron pockets. Such an observation, however, has been limited to chalcogenides, and is in contrast to the iron pnictides, for which the maximum T-c is achieved with both hole and electron pockets forming considerable FS nesting instability(8-11). Here, we report angle-resolved photoemission characterization revealing a monotonic increase of T-c from 24 to 41.5 K upon surface doping on optimally doped Ba(Fe1-xCox)(2)As-2. The doping changes the overall FS topology towards that of chalcogenides through a rigid downward band shift. Our findings suggest that higher electron doping and concomitant changes in FS topology are favourable conditions for the superconductivity, not only for iron chalcogenides, but also for iron pnictides.</P>

Design sensitivity analysis and optimization with industrial applications

Kyung K. Choi 대한기계학회 1996 대한기계학회 기타 간행물 Vol.1996 No.11

Cereblon Maintains Synaptic and Cognitive Function by Regulating BK Channel

Choi, Tae-Yong,Lee, Seung-Hyun,Kim, Yoon-Jung,Bae, Jae Ryul,Lee, Kwang Min,Jo, Youhwa,Kim, Soo-Jeong,Lee, A-Ram,Choi, Sekyu,Choi, La-Mee,Bang, Sunhoe,Song, Mi-Ryoung,Chung, Jongkyeong,Lee, Kyung Jin,K The Society 2018 The Journal of neuroscience Vol.38 No.14

<P>Mutations in the cereblon (CRBN) gene cause human intellectual disability, one of the most common cognitive disorders. However, the molecular mechanisms of CRBN-related intellectual disability remain poorly understood. We investigated the role of CRBN in synaptic function and animal behavior using male mouse and Drosophila models. Crbn knock-out (KO) mice showed normal brain and spine morphology as well as intact synaptic plasticity; however, they also exhibited decreases in synaptic transmission and presynaptic release probability exclusively in excitatory synapses. Presynaptic function was impaired not only by loss of CRBN expression, but also by expression of pathogenic CRBN mutants (human R419X mutant and Drosophila G552X mutant). We found that the BK channel blockers paxilline and iberiotoxin reversed this decrease in presynaptic release probability in Crbn KO mice. In addition, paxilline treatment also restored normal cognitive behavior in CrbnKOmice. These results strongly suggest that increased BK channel activity is the pathological mechanism of intellectual disability in CRBN mutations.</P>

Oncogenic Pathways of Mitogen-activated Protein Kinases and Phosphatidylinositol 3-kinase in Epithelial Ovarian Cancer

Jeung, Eui-Bae,Park, Se-Hyung,Leung, Peter C.K.,Yang, Hoe-Saeng,Sim, Jae-Chul,Kim, Kyung-Tai,Choi, Kyung-Chul 대한부인종양 콜포스코피학회 2003 Journal of Gynecologic Oncology Vol.14 No.4

Mitogen-activated protein kinases (MAPKs) are a group of serine/threonine kinases which are activated in response to a diverse array of extracellular stimuli, and mediate signal transduction from the cell surface to the nucleus. The chemotherapeutic agents, growth factors and reproductive hormones have been demonstrated to activate MAPKs, suggesting that the MAPK signaling pathway plays an important role in the regulation of proliferation, apoptosis, survival and differentiation in response to these external stimuli in ovarian cancer. In addition to MAPKs as an oncogenic pathway, phosphatidylinositol 3-kinase (PI3K) plays a role in a various range of important cellular processes associated with malignant characterestics including cell growth, survival and migration, which is a member of lipid kinases subfamily that phosphorylates and dephosphorylates the 3-position of the inositol ring of phosphoinositides in a membrane. In this review, recent results of the MAPK and PI3K signaling cascades by external stimuli, and potential roles of these oncogenic pathways as an oncogenic pathway are summarized in epithelial ovarian cancer.

부채비율과 경영자의 이익조절

최성규 ( Sung K. Choi ),김경민 ( Kyung Min Kim ) 한국회계학회 2005 會計學硏究 Vol.30 No.3

본 연구는 부채비율이 높을수록 경영자의 이익조절이 더 심하다는 명제를 실증하는데 필요한 두 개의 가설을 제시하고 이와 일관된 증거를 제시한다. 가설 1은 부채비율이 높은 기업일수록 재량발생의 절대값이 더 크다는 것이고 가설 2는 부채비율이 높은 기업일수록 재량발생의 시장반응이 더 작다는 것이다. 가설의 전개와 검증과정에서 본 연구는 정치적·경제적·법적 환경이 미국과 다른 우리나라 기업환경에서는 부채비율을 계약과정(contracting process)보다는 정치과정(political process)의 틀에서 이해하는 것이 더 타당하다는 논리와 이와 일관된 증거를 제시한다. 또한, 이익조절을 실증연구의 대상으로 한 대부분의 국내외 선행연구의 논리적·방법론적 문제점을 지적하고, 이익조절의 증거를 확보하기 위한 하나의 방법론을 제시한다. 가설검증은 1993년부터 2002년까지 10년 동안 560개의 상장 제조기업을 대상으로 하였다. 가설 1의 검증력을 높이기 위하여 경영자가 기업의 투자·생산·영업활동의 결과를 정상적으로 회계처리하는 과정에서 생기는 재량발생과 발생의 역전현상으로 인하여 생기는 재량발생을 종속변수(재량발생의 절대값)에서 제거할 수 있도록 영업현금흐름의 절대값과 전 년도의 총발생의 절대값을 회귀식에 추가하였다. 검증결과, 가설 1과 가설 2에 일관된 증거를 확보할 수 있었다. 즉, 부채비율이 높을수록 경영자의 이익조절이 더 심하다는 본 연구의 명제는 실증적 지지를 받고 있다. This study develops and tests hypotheses concerning the proposition that earnings management is more prevalent in firms with higher debt/asset ratio. Earnings management is conceptualized by many as an opportunistic/discretionary accounting choice(e.g., Schipper 1989, Healy and Wahlen 1999). Prior research indicates that managers can exercise accounting discretions to either properly signal the outcomes of firms` production/investment/operating activities or obtain personal gains. The former increases the usefulness of accounting information and, therefore, is not earnings management; yet, the latter, namely the opportunistic/discretionary accounting choice is. As such, the critical part of obtaining evidence of earnings management is to show that managers` discretionary accounting choices are indeed opportunistic. To this day, this fact is largely ignored by empirical researches in earnings management, with the notable exception of Choi and Kim(2001). Managers` discretionary accounting choices can be measured by discretionary accruals. However, whether or not such choices are opportunistic cannot be measured directly. Therefore, one must either ask managers about the opportunistic nature of their behaviors, or make inferences from the market assessments of the managers` discretionary accounting choices. This paper adopts the latter approach and provides a framework from which to infer such market assessments. In this study, empirically testing the proposition that earnings management is more prevalent in firms with higher debt/asset ratio essentially boils down to testing the two related hypotheses: hypothesis 1 asserts that the absolute value of discretionary accruals increases as the debt/asset ratio increases; hypothesis 2 states that the market response to discretionary accruals decreases as the debt/asset ratio increases. Hypothesis 1 serves to ascertain the evidence of discretionary accounting choices while hypothesis 2 infers whether such managerial discretions are opportunistic and related to market assessments. The rationale of such an inference is provided by the framework mentioned above. The hypotheses are tested by using a sample of 560 manufacturing firms listed in the Korean Stock Exchanges from the year of 1993 to the year of 2002 inclusively. To increase the power of the test of hypothesis 1, the portion of discretionary accruals that arise naturally in the course of normal accounting treatments of firms` production/investment/operating outcomes and the portion of discretionary accruals that arise from accrual reversals will be eliminated from the discretionary accrual measure. Results consistent with the hypotheses are obtained.

자기베어링을 이용한 마이크로 스핀들 형상 설계

최정섭(J. S. Choi),경진호(J. H. Kyung),노승국(S. K. Ro),김창기(C. K. Kim),박종권(J. K. Park) 한국생산제조학회 2006 한국공작기계학회 춘계학술대회논문집 Vol.2006 No.-

The design of a miniaturized spindle system applied active magnetic bearings(MB) is discussed. The proposed system is consisted of radial and axial magnetic bearings. The radial magnetic bearing is hybrid type, permanent magnet for bias magnetic flux and electromagnet for control current. And the axial magnetic bearing is only used electromagnet. Therefor this system is a 5 degrees of freedom active control system. In this paper, we suggest the design specification, such as stiffness, length and width of each part, including permanent magnet. We will apply this spindle system to micro machine tool system for micro factory.