• Journal of applied mathematics & informatics
• /
• 제13권1_2호
• /
• pp.335-351
• /
• 2003

Spatial distribution of groundwater contaminant concentration has special characteristics such as approximate symmetric profile, for example, in the transversal direction to groundwater flow direction, a certain ratio in directional propagation distances, etc. To obtain a geophysically appropriate semivariogram which is a key factor in estimation of groundwater contaminant concentration at desired locations, these special characteristics should be considered. In this paper, a method for finding appropriate symmetric axes is introduced. Statistical analyses for the choices of symmetric axes and mathematical models for semivariograrns are performed. After implementing symmetry, the corresponding semivariograrns, kriging variances, and final estimated results show significant improvement compared with those obtained by conventional approaches which usually do not account for symmetry.

• The Journal of the Acoustical Society of Korea
• /
• 제16권1E호
• /
• pp.64-74
• /
• 1997

In many decision making systems, rule-based approaches are used to solve complex problems in the areas of pattern analysis and computer vision. In this paper, we present methods for generating fuzzy IF-THEN rules automatically from training data for pattern classification and high-level computer vision. The rules are generated by construction minimal approximate fuzzy aggregation networks and then training the networks using gradient descent methods. The training data that represent features are treated as linguistic variables that appear in the antecedent clauses of the rules. Methods to generate the corresponding linguistic labels(values) and their membership functions are presented. In addition, an inference procedure is employed to deduce conclusions from information presented to our rule-base. Two experimental results involving synthetic and real are given.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2010년도 춘계학술대회 논문집
• /
• pp.18-24
• /
• 2010

철도차량의 동특성 해석을 위한 기존의 연구는 대부분 2차원 접촉해석에 근거한 근사해법에 의존해 왔다. 최근에 휠-접촉해석에 대한 정확한 해를 구하기 위해 3차원적 접근방법이 제시되고 있지만, 계산시간의 과다로 인해 실제 시뮬레이션 적용에는 효과적이지 못했다. 본 연구의 주요 관점은 효율적인 3차원 휠-레일 접촉 해석을 통해 휠-레일 접촉력을 계산하여 철도차량의 동특성 해석의 새로운 방법을 제시하고자 하는 것이다. 이를 통해, 3차원 휠-레일 접촉해석 및 휠셋의 동적 계산식이 제시된다.

• Rapid Communication in Photoscience
• /
• 제5권1호
• /
• pp.8-10
• /
• 2016

The potential curves of OH bonds of liquid water are inhomogeneous because of a variety of interactions with other molecules and this leads to a wide distribution of vibrational frequency which hampers our understanding of the structure and dynamics of water molecules. Mixed quantum/classical (QM/CM) calculation methods are powerful theoretical techniques to help us analyze experimental data of various vibrational spectroscopies to study such inhomogeneous systems. In a type of those approaches, the interaction energy between OH bonds and other molecules is approximately represented by the interaction between the charges located at the appropriate interaction sites of water molecules. For this purpose, we re-calculated the values of charges by comparing the approximate interaction energies with quantum chemical interaction energies. We determined a set of charges at the TIP4P charge sites which better represents the quantum mechanical potential curve of OH bonds of liquid water.

• Communications for Statistical Applications and Methods
• /
• 제24권1호
• /
• pp.29-41
• /
• 2017

The estimation problem of expected time to failure of units is studied in a discrete set up. A simple step-stress accelerated life testing is considered with a Type-I censored sample from geometric distribution that is a commonly used distribution to model the lifetime of a device in discrete case. Maximum likelihood estimators as well as the associated distributions are derived. Exact, approximate and bootstrap approaches construct confidence intervals that are compared via a simulation study. Optimal confidence intervals are suggested in view of the expected width and coverage probability criteria. An illustrative example is also presented to explain the results of the paper. Finally, some conclusions are stated.

• Journal of applied mathematics & informatics
• /
• 제28권3_4호
• /
• pp.813-821
• /
• 2010

In this paper, the tenth-order linear boundary value problems are solved using reproducing kernel method. The algorithm developed approximates the solutions, and their higher-order derivatives, of differential equations and it avoids the complexity provided by other numerical approaches. First a new reproducing kernel space is constructed to solve this class of tenth-order linear boundary value problems; then the approximate solutions of such problems are given in the form of series using the present method. Three examples compared with those considered by Siddiqi, Twizell and Akram [S.S. Siddiqi, E.H. Twizell, Spline solutions of linear tenth order boundary value problems, Int. J. Comput. Math. 68 (1998) 345-362; S.S.Siddiqi, G.Akram, Solutions of tenth-order boundary value problems using eleventh degree spline, Applied Mathematics and Computation 185 (1)(2007) 115-127] show that the method developed in this paper is more efficient.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
• /
• pp.401-408
• /
• 2001

The main objective of this study is to analyze the distortion of curved steel box girders. For the distortional analysis of steel box girders, two approaches are presented. One is the development of approximate formulas obtained by applying Ritz method. The other is the formulation of stiffness matrix which is derived from the exact solution of the differential equation for distortion. Distortional analysis is carried out by utilizing 3-dimensional elements of a structural analysis computer program (SAP2000). The present analysis focuses on the distortional stress and the effects of the diaphragm. The results of several example cases are compared with those by the Nakai, Sakai, Heins, and Oleinik's theory and get the effect of diaphragm spacing on the distortional warping stress of the curved steel box girder.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제9권1호
• /
• pp.29-36
• /
• 2009

Power supply noise is fundamentally caused by large current peaks. Since large current peaks are induced by simultaneous switching of many circuit elements, power supply noise can be minimized by deliberate clock scheduling which utilizes nonzero clock skew. In this paper, nonzero skew clock scheduling is used to avoid the large peak current and consequently reduce power supply noise. While previous approaches require extra characterization efforts to acquire current waveform of a circuit, we approximate it only with existing cell library information to be easily adapted to conventional design flow. A simulated annealing based algorithm is performed, and the peak current values are estimated for feasible clock schedules found by the algorithm. The clock schedule with the minimum peak current is selected for a solution. Experimental results on ISCAS89 benchmark circuits show that the proposed method can effectively reduce the peak current.

• 한국통신학회논문지
• /
• 제30권12C호
• /
• pp.1125-1132
• /
• 2005

초광대역 신호의 높은 시간해상도는 복잡한 다중경로 환경에서의 정밀한 거리추정 및 위치추적 을 가능하게 한다. 그러나 신호의 도착신호 추정시 발생하는 큰 추정오차의 발생은 거리추정의 정확도를 저하시키는 요인이 된다. 본 논문에서는 다중경로, 다중사용자 환경에서 초광대역 거리추정의 성능을 평가한다. 상호상관을 이용한 직렬검색 알고리듬을 적용할 때 발생하는 추정오차를 분석하고 모의실험 결과를 개시한다.

• 전자공학회논문지B
• /
• 제29B권1호
• /
• pp.34-42
• /
• 1992

This paper presents two fast least-squares lattice algorithms for adaptive nonlinear filters equipped with bilinear system models. The lattice filters perform a Gram-Schmidt orthogonalization of the input data and have very good numerical properties. Furthermore, the computational complexity of the algorithms is an order of magnitude snaller than previously algorithm is an order of magnitude smaller than previously available methods. The first of the two approaches is an equation error algorithm that uses the measured desired response signal directly to comprte the adaptive filter outputs. This method is conceptually very simple`however, it will result in biased system models in the presence of measurement noise. The second approach is an approximate least-squares output error solution. In this case, the past samples of the output of the adaptive system itself are used to produce the filter output at the current time. Results of several experiments that demonstrate and compare the properties of the adaptive bilinear filters are also presented in this paper. These results indicate that the output error algorithm is less sensitive to output measurement noise than the squation error method.