• 천문학회보
• /
• 제35권1호
• /
• pp.48.1-48.1
• /
• 2010

Four of nine exoplanets found by microlensing were detected by the resonant caustic, which represents the merging of the planetary and central caustics at the position when the projected separation of a host star and a bounded planet is s~1. One of the resonant caustic lensing events, OGLE-2005-BLG-169, was a caustic-crossing high-magnification event with A_max ~800 and the source star was much smaller than the caustic, nevertheless the perturbation was not obviously apparent on the light curve of the event. In this paper, we investigate the perturbation pattern of the resonant caustic to understand why the perturbations induced by the caustic do not leave strong traces on the light curves of high-magnification events despite a small source/caustic size ratio. From this study, we find that the regions with small magnification excess around the center of the resonant caustic are rather widely formed, and the event passing the small-excess region produces a high-magnification event with a weak perturbation that is small relative to the amplification caused by the star and thus does not noticeably appear on the light curve of the event. We also find that the positive excess of the inside edge of the resonant caustic and the negative excess inside the caustic become stronger and wider as q increases, and thus the resonant caustic-crossing high-magnification events with the weak perturbation occur in the range of q $\leq$ 10-4. We determine the probability of the occurrence of events with the small excess $|\varepsilon|{\leq}3%$ in high-magnification events induced by a resonant caustic. As a result, we find that for the Earth-mass planets with a separation of ~2.5 AU the resonant caustic high-magnification events with the weak perturbation can occur with a significant frequen.

• 대한기계학회논문집A
• /
• 제33권3호
• /
• pp.243-250
• /
• 2009

The adjoint variable method can reduce computation time and save computer resources because it can selectively provide the sensitivity information for the positions that designers wish to measure. However, the adjoint variable method commonly employs exact analytical differentiation with respect to the design variables. It can be cumbersome to precisely differentiate every given type of finite element. This trouble can be overcome only if the numerical differentiation scheme can replace this exact manner of differentiation. But, the numerical differentiation scheme causes of severe inaccuracy due to the perturbation size dilemma. For assuring the accurate sensitivity without any dependency of perturbation size, this paper employs a complex variable that has been mainly used for computational fluid dynamics problems. The adjoint variable method combined with complex variables is applied to obtain the shape and size sensitivity for structural optimization. Numerical examples demonstrate that the proposed method can predict stable sensitivity results and that its accuracy is remarkably superior to traditional sensitivity evaluation methods.

• Radiation Oncology Journal
• /
• 제13권4호
• /
• pp.397-402
• /
• 1995

Purpose : To determine the perturbation effect in the tissue downstream from surface layers of lesions located in the air/tumor-tissue interface of larynx using 6MV photon beam. Materials and Methods : Thermoluminescent dosimeters(TLDs), were embedded at 3 measurement locations in slab no. 7 of a humanoid phantom and exposed to forward and backward direction using various field sizes($4{\times}4cm^2\;-\;15{\times}15cm^2$). Results : At the air/tissue interface, forward dose perturbation factor(FDPF) is about 1.085 with $4{\times}4cm^2,\;1.05\;with\;7{\times}7cm^2,\;1.048\;with\;10{\times}10cm^2$ and $1.041\;with\;15{\times}15cm^2$. Backscatter dose perturbation factor(BDPF) is about 0.99 with $4{\times}4cm^2$, 0.981 with $7{\times}7cm^2$, 0.956 with $10{\times}10cm^2$ and 0.97 with $15{\times}15cm^2$. Conclusion : FDPF is greater as field size is smaller. And FDPF is smaller as the distance is further from the air/tissue interface.

• 전력전자학회논문지
• /
• 제16권5호
• /
• pp.521-531
• /
• 2011

본 논문은 그림자 영향을 고려한 PV(Photovoltaic) 시스템의 VPO(Variable Perturbation & Observation)MPPT(Maximum Power Point Tracking) 제어를 제시한다. 태양전지의 출력 특성은 비선형이고 온도, 일사량 및 그림자의 영향을 많이 받는다. MPPT 제어는 태양광발전 시스템의 출력 및 효율을 증가시키기 위한 매우 중요한 기술이다. 종래의 PO(Perturbation & Observation)와 IC(Incremental conductance) 등은 지속적인 자려진동에 의해 MPP(Maximum Power Point)를 찾는 방법으로 그림자 영향에 의해 출력이 급격하게 변할 경우 MPPT 제어를 수행하지 못한다. 이러한 문제점을 해결하기 위해 출력 변동에 따라 스텝 값이 변하는 새로운 제어 알고리즘을 제시한다. 제시한 알고리즘은 일사량, 온도 및 그림자 영향에 대해 종래의 제어 알고리즘과 응답특성을 비교하고 이를 통해 제시한 알고리즘의 타당성을 입증한다.

• 조명전기설비학회논문지
• /
• 제26권8호
• /
• pp.27-34
• /
• 2012

This paper proposes variable incremental conductance(IC) algorithm for maximum power point tracking(MPPT) control of photovoltaic. The conventional perturbation & observation(PO) and IC MPPT control algorithm generally uses fixed step size. A small step size reduces a tracking error in the steady state but slows a tracking speed in the transient state. Also, a large step size is fast a tracking speed but increases a tracking error. Therefore, this paper proposes variable IC MPPT algorithm that adjust automatically step size according to operating conditions. To improve a tracking speed and accuracy, when operating point is far from the maximum power point(MPP), the step size uses maximum value and when a operating point is near from the MPP, the step size uses variable step size that adjust according to slope of P-V curve. The validity of MPPT algorithm proposed in this paper prove through compare with conventional PO and IC MPPT algorithm.

• 조명전기설비학회논문지
• /
• 제27권11호
• /
• pp.20-26
• /
• 2013

This paper proposes the maximum power point tracking(MPPT) control of photovoltaic system using fuzzy based variable step size perturbation & observation(FVSS-PO) method. Conventional PO and incremental conductance(IC)MPPT control algorithm generally uses fixed step size. A small fixed step size will cause the tracking speed to decrease and tracking accuracy of the MPP will decrease due to large fixed step size. Therefore, the fixed step size can't be satisfying both the tracking speed and the tracking accuracy. This paper proposes FVSS-PO MPPT algorithm that adjusts automatically step size of PO by fuzzy control according to operating conditions. The validity of MPPT algorithm proposed in this paper prove through compare with conventional PO MPPT algorithm.

• 한국ITS학회:학술대회논문집
• /
• 한국ITS학회 2010년도 춘계학술대회
• /
• pp.96-97
• /
• 2010

• Journal of applied mathematics & informatics
• /
• 제20권1_2호
• /
• pp.35-59
• /
• 2006

In this paper, we generalized the results of [23, 26], and get the results of the condition number of the W-weighted Drazin-inverse solution of linear system W AW\chi=b, where A is an $m{\times}n$ rank-deficient matrix and the index of A W is $k_1$, the index of W A is $k_2$, b is a real vector of size n in the range of $(WA)^{k_2}$, $\chi$ is a real vector of size m in the range of $(AW)^{k_1}$. Let $\alpha$ and $\beta$ be two positive real numbers, when we consider the weighted Frobenius norm $\|[{\alpha}W\;AW,\;{\beta}b]\|$(equation omitted) on the data we get the formula of condition number of the W-weighted Drazin-inverse solution of linear system. For the normwise condition number, the sensitivity of the relative condition number itself is studied, and the componentwise perturbation is also investigated.

• Journal of the Korean Statistical Society
• /
• 제30권3호
• /
• pp.499-509
• /
• 2001

We investigate the influence of observations on a test of additional information about discrimination using the influence function and the derivative influence measures. the influence function for the test statistic is derived and this sample versions are used for influence analysis. The derivative influence measures for the test statistic under a perturbation scheme are derived. It will be seen that the influence function method and the derivative influence measures yield the same result. Furthermore, we will derive the relationships between the influence function and the derivative influence measures when the sample size is large. an illustrative example is given and we will compare the results provided by the influence function method and the derivative influence measures.

• Journal of applied mathematics & informatics
• /
• 제32권1_2호
• /
• pp.185-201
• /
• 2014

In this paper, we construct a numerical method to solve singularly perturbed one-dimensional parabolic convection-diffusion problems. We use Euler method with uniform step size for temporal discretization and exponential-spline scheme on spatial uniform mesh of Shishkin type for full discretization. We show that the resulting method is uniformly convergent with respect to diffusion parameter. An extensive amount of analysis has been carried out to prove the uniform convergence with respect to the singular perturbation parameter. The obtained numerical results show that the method is efficient, stable and reliable for solving convection-diffusion problem accurately even involving diffusion parameter.