• 한국CDE학회논문집
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• 제11권4호
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• pp.246-255
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• 2006

Ribs and fans are interesting geometric entities that are derived from an ordinary $B\'{e}zier$ curve or surface. A rib itself is a $B\'{e}zier$ curve or surface with a lower degree than the given curve or surface. A fan is a vector field whose degree is also lower than its origin. First, we present methods to transform the control points of a $B\'{e}zier$ curve or surface into the control points and vectors of its ribs and fans. Then, we show that a $B\'{e}zier$ curve of degree n is decomposed into a rib of degree (n-1), a fan of degree (n-2), and a scalar function of degree 2. We also show that a $B\'{e}zier$ surface of degree (m, n) is decomposed into a rib of degree (m-1, n-1) and three fans of degrees (m-1, n-2), (m-2, n-1), and (m-2, n-2), respectively. In addition, the lengths of the fans are further controlled by scalar functions of degree 2 and (2, 2). We present relevant notations and definitions, introduce theories, and present some of design examples.

• 천문학회지
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• 제25권1호
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• pp.11-21
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• 1992

Applying mass model to disk galaxy NGC 300, since the observed rotation curve of NGC 300 is flatter than Toomre's mass model n = 1, two cases are used; obtaining parameters $a^n$ and $b^n$ from the polynomial fitting of the observed rotation curve (case A) and from the least square fitting between the observed rotation curve and model rotation curve (case B). In any case, n bas a fixed value of 1. Brandt's mass model is also discussed. which has a shape parameter n = 1.4. Calculated total mass and total mass to luminosity ratio are $3.3{\times}10^{10}M_{\odot}$, l2.1 for case A and $2.8{\times}10^{10}M_{\odot}$, 10.3 for case B. In case of Brandt's model, the values are $4.2{\times}10^{10}M_{\odot}$ and 15.4. The rise in the local mass to luminosity ratio in the outer part of NGC 300 implies existence of massive halo. Other dynamical properties are also discussed.

• 수산해양기술연구
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• 제29권3호
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• pp.177-182
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• 1993

In order to estimate the mesh selectivity master curves and the optimum mesh size, experiments were made by the cover net method with the cod-ends of the five different the opening mesh sizes(51.2mm, 70.2mm, 77.6mm, 88.0mm and 111.3mm). After that 163 hauling were performed and there by investigated, on the training vessel Saebada in the Southern Korean Sea and East China Sea from June 1991 to August 1992. In this report, the mesh selectivity master curves were fitted by using logistic function(S=1/(1+exp super(-(aR+b))), R=(L-L sub(0))/(M-M sub(0)) and the optimum mesh sizes were estimated from each master curve. In this case, a and b are the selection parameters, M is the mesh size of each experimental cod-end. L is body length, L sub(0) and M sub(0) is the distance from the coordinate origine to intersection of linear regression between 25% and 50% selection length. The results obtained are summarized as follows; 1. Trachurus japonicus: Mesh selectivity master curve parameters: a and b were 2. 25, -4.73 respectively and optimum mesh size was estimated to be 79.3mm. 2. Trichiurus lepturus: Mesh selectivity master curve parameters: a and b were 0.81, -3.17 respectively and optimum mesh size was estimated to be 64.5mm. 3. Photololigo edulis: Mesh selectivity master curve parameters: a and b were 1.30m, -4.10 respectively and optimum mesh size was estimated to be 89.9mm. 4. Todarodes pacificus: Mesh selectivity master curve parameters: a and b were 1. 35, -3.45 respectively and optimum mesh size was estimated to be 89.4mm.

• 대한수학회논문집
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• 제9권4호
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• pp.905-915
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• 1994

Let $M_g$ be the moduli space of isomorphism classes of genus g smooth curves. It is a quasi-projective variety of dimension 3g - 3, when $g > 2$. It is known that a complete subvariety of $M_g$ has dimension $< g-1 [D]$. In general it is not known whether this bound is rigid. For example, it is not known whether $M_4$ has a complete surface in it. But one knows that there is a complete curve through any given finite points [H]. Recently, an explicit example of a complete curve in moduli space is given in [G-H]. In [G-H] they constructed a complete curve of $M_3$ as an intersection of five hypersurfaces of the Satake compactification of $M_3$. One way to get a complete curve of $M_3$ is to find a complete one dimensional family $p : X \to B$ of plane quartics which gives a nontrivial morphism from the base space B to the moduli space $M_3$. This is because every non-hyperelliptic smooth curve of genus three can be realized as a nonsingular plane quartic and vice versa. This paper has come out from the effort to find such a complete family of plane quartics. Since nonsingular quartics form an affine space some fibers of p must be singular ones. In this paper, due to the semistable reduction theorem [M], we search singular plane quartics which can occur as singular fibers of the family above. We first list all distinct plane quartics in terms of singularities.

• Journal of Gastric Cancer
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• 제18권2호
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• pp.182-188
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• 2018

Purpose: Despite the fact that there are several reports of single-port laparoscopic distal gastrectomy (SPDG), no analysis of its learning curve has been described in the literature. The aim of this study was to investigate the favorable factors for SPDG and to analyze the learning curve of SPDG. Materials and Methods: A total of 125 cases of SPDG performed from November 2011 to December 2015 were enrolled. All operations were performed by 2 surgeons (surgeon A and surgeon B). The moving average method was used for defining the learning curve. All cases were divided into 10 cases in a sequence, and the mean operative time and estimated blood loss data were extracted from each group. Results: Surgeon A performed 68 cases (female-to-male sex ratio, 91.1%:8.82%), and surgeon B performed 57 cases (female-to-male sex ratio, 61.4%:38.5%). The operative time of surgeon B significantly decreased after 30 cases ($157.8{\pm}38.4$ minutes vs. $118.1{\pm}34.5$ minutes, P=0.003); that of surgeon A did not significantly decrease before and after around 30 cases ($160.8{\pm}51.6$ minutes vs. $173.3{\pm}35.2$ minutes, P=0.6). The subgroup analysis showed that the operative time significantly decreased in the patients with body mass index (BMI) of <$25kg/m^2$ (<$25kg/m^2$:${\geq}25kg/m^2$, $159.3{\pm}41.7$ minutes: $194.25{\pm}81.1$ minutes; P=0.001). Conclusions: Although there was no significant decrease in the operative time for surgeon A, surgeon B reached the learning curve upon conducting 30 cases of SPDG. BMI of <$25kg/m^2$ was found to be a favorable factor for SPDG.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.61-63
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• 1998

A B-H curve measuring system for testing softmagnetic materials was constructed. This system can measure the B-H curve in the low frequency(0.1 - 1 Hz) range. The drift of the integrator can be moderately removed by software technique. The advantages of the developed system are easier to measure B-H curve compared with conventional measuring system and low cost.

• 한국자기학회지
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• 제21권1호
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• pp.15-22
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• 2011

강자성체를 정밀해석하기 위해서는 포화자화 현상과 히스테리시스 현상을 모두 고려해 주어야만 한다. Preisach 모델링은 변화율이 심한 히스테리시스 현상을 매우 잘 표현해 낼 수 있는 수치모사 방법이다. 하지만 정자기 유한요소법과 Preisach 모델링을 사용한 자화해석 반복 과정에서 수렴성이 떨어진다는 큰 문제점을 가지고 있다. 특히 자화율의 기울기가 급격히 변화할 경우 수렴에 많은 문제점을 가지고 있다. 이러한 문제점은 일반적인 M-H 변수를 사용하지 않고, M-B 변수를 사용하면 해결할 수 있다. 본 논문에서는 일반적인 M-H를 이용한 Preisach 모델링의 평면 분포로부터 M-H 변수를 M-B 변수화 시키는 방법을 제안하고 있고, 2차원 정자기 유한요소법과 M-H, M-B 변수를 이용한 Preisach 모델링을 비교 분석하여 Preisach 모델링의 수렴성 문제를 해결하는 방법에 대해 기술하였다.

• 한국수자원학회논문집
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• 제39권6호
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• pp.487-494
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• 2006

화원 지점의 홍수시 유량은 수위가 상승할 때와 하강할 때 동일한 수위에 대해 많은 차이를 나타내고, 이와 같이 이력효과의 크기가 클 경우에는 많은 오차가 발생할 수 있다. 유량 환산 오차를 줄이기 위해 낙동강 본류 화원 수위관측소 지점에 대한 고리모양 수위-유량 관계곡선을 작성하였다. 하천유량과 단순 환산된 유량의 편차를 계산하기 위해 부정류 모의 사례로부터 (수위, 유량) 자료쌍을 획득하여 단순 수위-유량 관계곡선식을 작성하였다. 이 관계에서 이탈하는 유량편차 ${\Delta}Q$와 수위변화 따른 하천폭과 시간변화율의 곱인 $B{\Delta}h/{\Delta}t$와의 관계로부터 고리모양 수위-유량 관계의 유량을 구하였다. ${\Delta}Q$와 $B{\Delta}h/{\Delta}t$는 높은 상관관계를 나타내었다. 이로부터 계산된 유량은 1997년의 수위 7m이상 관측유량 11개 중 7개가 고리모양 수위-유량 환산관계의 유량과 10% 이내의 차이를 보였고, 수위 9m이상의 1998년 관측유량은 고리모양에 근접하였다. 화원 지점과 같이 고리폭이 큰 지점은 단순 수위-유량 관계보다 고리모양 수위-유량 관계를 적용하는 것이 유량 환산의 오차를 줄 일 수 있을 것으로 기대된다.

• 한국정보통신학회논문지
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• 제4권1호
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• pp.131-138
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• 2000

This paper works on development of an algorithm for mapping of cerebral perfusion parameters using the gamma-variate curve fitting. The signal intensity variate curve according to time measured in each pixel of perfusion MRI is nonlinear, and various hemodynamic parameters are not computed accurately. Levenberg-Marquardt algorithm(LMA), nonlinear optimum algorithm with high convergent speed and stability, is used to compute them. That is, the signal intensity variate curve is fitted by the gamma-variate function. Various hemodynamic parameters - Cerebral Blood Volume(C.B.V), Mean Transit Time(M.T.T), Cerebral Blood Flow(C.B.F), Time-to-Peak(T.T.P), Bolus Arrival Time(B.A.T), Maximum Slope(M.S) - are computed using LMA.

• 한국수자원학회논문집
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• 제50권10호
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• pp.661-671
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• 2017

본 연구의 목적은 하천의 조도계수와 유량의 불확실성을 고려하여, 부정류 흐름에서 홍수위 해석에 미치는 영향을 정량적으로 분석하는 데 있다. 본 연구에서는 GLUE (Generalized Likelihood Uncertainty Estimation) 기법을 적용하여 조도계수와 유량의 불확실성이 홍수위 해석에 미치는 영향을 분석하고, 강우사상의 크기와 불확실성과의 관계를 분석하였다. 조도계수의 불확실성은 하천기본계획을 참고하여 0.025~0.040의 범위에서 분석하였다. 유량의 불확실성은 수위 h일 때의 유량을 Q라고 할 때, $Q=A(h-B)^C$로 표현되는 수위-유량관계식의 회귀계수 A, B, C를 통해 분석하였다. 수위-유량관계식의 회귀계수를 비선형 회귀분석을 통해 추정하였으며, 회귀계수는 t 분포를 가정하여 95% 신뢰도로 상한과 하한의 범위를 산정하였다. 산정된 회귀계수의 범위는 A는 5.138~18.442, B는 -0.524~0.104, C는 2.427~2.924로 산정되었다. 범위 내에서 10,000개의 매개변수 세트를 추출하여 HEC-RAS (Hydrologic Engineering Center's River Analysis System)에 적용하여 Monte Carlo 모의를 수행하였다. 강우사상 1~3에서 모의된 홍수위의 95% 신뢰구간의 평균적인 범위는 각각 0.39 m, 0.83 m, 0.96 m이며, 첨두 홍수위가 발생했을 때의 범위는 각각 0.52 m, 1.36 m, 1.75 m로 산정되었다. 또한 이천관측소의 1986~2015년의 일 강우에 대한 빈도해석을 수행하였으며, 수행 결과 GEV (Generalized Extreme Vlaue) 분포일 때 강우사상 1~3의 재현기간은 각각 1년, 10년, 25년 빈도에 해당되었다. 본 연구를 통해 강우사상의 크기와 불확실성의 관계를 분석하였으며, 향후 다양한 강우사상에 적용하여 검증한다면 홍수위의 불확실성을 예측하여, 하천관리 등을 위한 구조물의 계획 및 설계 시 의사 결정에 실질적인 도움이 될 수 있을 것으로 사료된다.