• Journal of Korean Neurosurgical Society
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• 제51권5호
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• pp.253-261
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• 2012

Objective : This study was performed to determine the anatomical landmarks and optimal dissection points of the facial nerve (FN) and the hypoglossal nerve (HGN) in the submandibular region to provide guidance for hypoglossal-facial nerve anastomosis (HFNA). Methods : Twenty-nine specimens were obtained from 15 formalin-fixed adult cadavers. Distances were measured based on the mastoid process tip (MPT), common carotid artery bifurcation (CCAB), and the digastric muscle posterior belly (DMPB). Results : The shortest distance from the MPT to the stylomastoid foramen was $14.1{\pm}2.9$ mm. The distance from the MPT to the FN origin was $8.6{\pm}2.8$ mm anteriorly and $5.9{\pm}2.8$ mm superiorly. The distance from the CCAB to the crossing point of the HGN and the internal carotid artery was $18.5{\pm}6.7$ mm, and that to the crossing point of the HGN and the external carotid artery was $15.1{\pm}5.7$ mm. The distance from the CCAB to the HGN bifurcation was $26.6{\pm}7.5$ mm. The distance from the digastric groove to the HGN, which was found under the DMPB, was about $35.8{\pm}5.7$ mm. The distance from the digastric groove to the HGN, which was found under the DMPB, corresponded to about 65.5% of the whole length of the DMPB. Conclusion : This study provides useful information regarding the morphometric anatomy of the submandibular region, and the presented morphological data on the nerves and surrounding structures will aid in understanding the anatomical structures more accurately to prevent complications of HFNA.

• 한국정보통신학회논문지
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• 제15권9호
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• pp.2013-2018
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• 2011

관상동맥 성형술과 관상동맥 우회술은 심근경색의 치료를 위해서 널리 이용되고 있는 방법이다. 특히 이 시술을 위해서 혈관의 협착 부위를 정확히 진단하는데 많은 어려움이 있다. 이러한 문제점을 개선하기 위해서 여러 연구자들에 의해서 에지 추출을 이용한 혈관의 협착부위를 검출하는 연구가 진행되고 있다. 그러나 이러한 방법들은 혈관의 구조나 영상의 질에 따라 그 성능의 차이가 발생한다. 따라서 본 연구는 이러한 문제점을 개선하기 위해 새로운 알고리즘을 제안한다. 제안된 알고리즘은 다중 샘플링과 쓰레쉬홀드, 퍼지 알고리즘을 이용한 혈관의 분기점과 끝점, 협착 부위를 검출하는 방법으로 구성되어 있다. 제안된 알고리즘의 성능을 평가하기 위해 다양한 혈관조영영상을 사용하였으며 그 결과 제안된 알고리즘에 의한 혈관의 분기점 및 끝점, 협착 부위 검출에 효과적이었다.

• 한국전산구조공학회논문집
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• 제18권3호
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• pp.277-289
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• 2005

본 논문은 강사장교의 극한강도를 다루고 있다. 강사장교의 극한강도를 평가하기 위하여 비선형 비탄성 해석 접근법과 분기점 좌굴 고유치해석 접근법인 유효접선탄성계수$(E_f)$법을 사용하여 예제를 수행하였다. 이를 위하여 초기형상을 고려한 실용적인 비선형 비탄성 해석기법을 제시하였다. 초기형상 해석 시각 형상해석 단계마다 보-기둥 부재의 부재력 대신 개선된 구조물형상을 고려하였다. 보-기둥 부재의 기하학적 비선형은 안정함수를 사용하여 고려하였고, 재료적 비선형은 CRC 접선계수와 포물선 함수를 사용하여 고려하였다. 또한, 케이블 부재의 기하학적 비선형은 할선탄성계수 값을 사용하여 고려하였다. 본 연구에서 제안한 해석기법으로 예측된 하중-변위 곡선들이 다른 연구에 의한 결과들과 비교 검증 되었으며, 제시된 3차원 강사장교 모델들에 대하여 제안한 해석기법과 비탄성 좌굴해석을 사용하여 극한강도를 비교하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 D
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• pp.2233-2235
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• 2004

This paper presents a therapy that uses a constant drug dosage for leading a HIV patient to a LTNP (Long-Tenn Non-Progressor). From analysis of CTLp (Cytotoxic T Lymphocyte precursor) concentration at equilibrium point and bifurcation of equilibrium points, we found the therapy with a drug whose efficacy is less than one brings higher CTLp concentration at the equilibrium point. From this fact, we propose a treatment with constant drug dosage. which can induce LTNP.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.381-386
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• 2007

The present study is concerned with the application of Constant arc-length method that proposed by Crisfield in the investigation of the geometrically nonlinear behaviour of spatial structures composed by truss or beam element. The arc-length method can trace the full nonlinear equilibrium path of Spatial structure far beyond the critical point such as limit or bifurcation point. So, we have developed the constant arc-length method of Crisfield to analysis spatial structure. The finite element formulation is used to develop the 3d truss/beam element including the geometrical nonlinear effect. In an effort to evaluate the merits of the methods, extensive numerical studies were carried out on a number of selected structural systems. The advantages of Constant arc length method in tracing the post-buckling behavior of spatial structures, are demonstrated.

• Structural Engineering and Mechanics
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• 제5권6호
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• pp.715-728
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• 1997

The aim of this paper is to investigate the secondary buckling behaviour and mode-coupling of spherical caps under uniformly external pressure. The analysis makes use of a rotational finite shell element on the basis of strain-displacement relations according to Koiter's shell theory (Small Finite Deflections). The post-buckling behaviours after a bifurcation point are analyzed precisely by considering multi-mode coupling between several higher order harmonic wave numbers: and on the way of post-buckling path the positive definiteness of incremental stiffness matrix of uncoupled modes is examined step by step. The secondary buckling point that has zero eigen-value of incremental stiffness matrix and the corresponding secondary mode are obtained, moreover, the secondary post-buckling path is traced.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.1078-1082
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• 1997

The distance in load parameter space to the closest voltage collapse point provides the worst case power margin and the left eigenvector identifies the most effective direction to steer the system to maximize voltage stability under contingency. This paper presents the results of the comparative performance study of the algorithms, which are applicable to a large scale power system, for computing the closest saddle node bifurcation (CSNB) point. Dobson's iterative method converges with robustness. However the slow process of updating the load increasing direction makes the algorithm less efficient. The direct method converges very quickly. But it diverges if the initial guess is not very close to CSNB. Zeng's method of estimating the approximate critical point in the pre-determined direction is attractive in the sense that it uses only using load flow equations. However, the method is found to be less efficient than Dobson's iterative method. It may be concluded from the above observation that the direct method with the initial values obtained by carrying out the iterative method twice is most efficient at this time and more efficient algorithms are needed for on-line application.

• 전자공학회논문지
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• 제53권3호
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• pp.151-159
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• 2016

본 연구의 목적은 가돌리늄 조영제를 사용한 Head & Neck MR Angio검사에 있어서 매개변수인 FA(Flip Angle)이 MR신호에 미치는 영향에 대해서 알아보고자 하였으며, 이에 따른 FA의 적정 값을 제시하는 것이다. 실험은 FA증가에 따른 MR팬텀실험과 임상실험으로 진행하였고, 이에 대한 정량적 분석이 이루어졌다. 실험결과 팬텀실험에서의 조영증강 반응시작 지점인 RSP(Reaction Starting Point)는 FA증가에 따라 300~400 mmol 사이에서 반응하였고, 최대 신호강도인 MPSI(Max Peak Signal Intensity)는 2,086, 3,705, 5,109, 6,194, 7.096, 7,192 [a.u]를 기록하였다. MPSI가 형성되는 몰농도 지점인 MPP(Max Peak Point)는 FA에 증가에 따라 40, 50, 50, 40, 50, 40 mmol에서 보였으며, MPSI의 증가율인 IRMPSI(Increase Rate of MPSI)는 77.6%, 37.9%, 21.2%, 14.6%, 1.4%임을 확인하였다. 임상실험에서의 평가기준인 SICB(Signal Intensity of Carotid artery Bifurcation)는 FA증가에 따라 각 평균값 2392.5, 4165.2, 4270, 3502.2, 3263.7, 3119.6 [a.u]를 기록하였고, 아티팩트 발생율인 ORA(Occurence Rate of Artifact)는 0, 0, 20, 40, 50, 70%로 점차 증가하였다. 본 연구를 통하여 FA의 증가는 혈관 내 가돌리늄과 결합한 H1스핀의 신호강도와 아티팩트에 영향을 미친다는 사실을 확인하였고, 이는 실제 임상에서의 CE(Contrast Enhanced)-Head&Neck MR Angio검사에 있어서 본 연구의 데이터를 활용한다면 진단학적으로 효율적인 MR Angiography 영상을 구현할 수 있을 것으로 사료된다.

• 한국공간구조학회논문집
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• 제13권1호
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• pp.87-96
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• 2013

This study investigated characteristics of buckling load and effective buckling length by member rigidity of dome-typed space frame which was sensitive to initial conditions. A critical point and a buckling load were computed by analyzing the eigenvalues and determinants of the tangential stiffness matrix. The hexagonal pyramid model and star dome were selected for the case study in order to examine the nodal buckling and member buckling in accordance with member rigidity. From the numerical results, an effective buckling length factor of adopted models was bigger than that of Euler buckling for the case of fixed boundary. These numerical models indicated that the influence of nodal buckling was greater than that of member buckling as member rigidity was higher. Besides, there was a tendency that the bifurcation appeared on the equilibrium path before limit point in the member buckling model.

• 대한전기학회논문지:전력기술부문A
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• 제48권8호
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• pp.951-957
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• 1999

The saddle node bifurcation (SNB) and the distance voltage instability are valuable information in power system planning and operation. This paper presents a new efficient, robust and unified strategy to compute the SNB by the combined use of the continuation power flow (CPF), Point of Collapse (PoC) method, and the method of a pair of multiple load flow solutions (PMLFS) with Lagrange interpolation utilizing only their advantages: the approximate nose curves and critical loading are determined fast by Lagrange-interpolating two stable and two unstable solutions obtained by using the robust CPF and PMLFS; the exact SNB is computed by the quadratically converging PoC method. The proposed method has been tested on Klos-Kerner 11-bus, New England 30-bus, IEEE 118-bus and KEPCO 791-bus systems. The method is found to be so efficient that computation time for determining the SNB of the KEPCO 791-bus system is 17.82 sec by a notebook PC with 300 MHz Pentium processor.