• Kyungpook Mathematical Journal
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• 제46권3호
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• pp.329-336
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• 2006

In the category of the group theoretic methods using invertible discrete group transformation, we give a useful relation between Emden-Fowler equations and nonlinear heat equation. In this paper, by means of appropriate transformations of discrete group analysis, the nonlinear hate equation transformed into the class of the Emden-Fowler equations. This approach shows that, under the group action, the solution of reference equation can be transformed into the solution of the transformed equation.

• Nuclear Engineering and Technology
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• 제22권2호
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• pp.151-158
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• 1990

새로운 중성자 수송방정식의 해법인 Discrete Elements Method(DEM)를 1차원 모델에 대 한 단일 에너지 중성자 수송방정식에 적용했다. 본 연구에서는 고정선원문제와 임계계산을 행하여, 각분할법과 DEM의 계산결과의 정확도를 비교했으며 세가지의 위치차등법(DD, SC그리고 LC Scheme)중 어떤 것이 DEM에서 가장 좋은지를 오차분석을 통해 정량적으로 알아보았다. 수행한 모든 계산결과에서 같은 위치차등법을 이용할 때 DEM결과의 정확도가 각분할법으로 얻은 결과보다 훨씬 좋았으며 위치차등법중에서는 각분할 법에서와 같이 DEM에서도 LC scheme이 가장 좋은 결과를 주었다.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.832-837
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• 2015

The group method of data handling (GMDH) algorithm has proven to be a powerful and effective way to extract rules or polynomials from an electric load pattern. However, because it is nonstationary, the load pattern needs to be decomposed using a discrete wavelet transform. In addition, if a load pattern has a complicated curve pattern, GMDH should use a higher polynomial, which requires complex computing and consumes a lot of time. This paper suggests a method for short-term electric load forecasting that uses a wavelet transform and a GMDH algorithm. Case studies with the proposed algorithm were carried out for one-day-ahead forecasting of hourly electric loads using data during the years 2008-2011. To prove the effectiveness of our proposed approach, the results were evaluated and compared with those obtained by Holt-Winters method and artificial neural network. Our suggested method resulted in better performance than either comparison group.

• 대한수학회지
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• 제52권4호
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• pp.797-819
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• 2015

A trapdoor discrete logarithm group is a cryptographic primitive with many applications, and an algorithm that allows discrete logarithm problems to be solved faster using a pre-computed table increases the practicality of using this primitive. Currently, the distinguished point method and one extension to this algorithm are the only pre-computation aided discrete logarithm problem solving algorithms appearing in the related literature. This work investigates the possibility of adopting other pre-computation matrix structures that were originally designed for used with cryptanalytic time memory tradeoff algorithms to work as pre-computation aided discrete logarithm problem solving algorithms. We find that the classical Hellman matrix structure leads to an algorithm that has performance advantages over the two existing algorithms.

• Communications for Statistical Applications and Methods
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• 제17권1호
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• pp.127-140
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• 2010

본 논문에서는 중간분석에서 사용되는 집단축차 검정법으로 이산형 반응변수인 경우, 오류 분배율 함수를 적용한 집단축차 검정법을 제안한다. 특히 제 1종 오류와 제 2종 오류를 모두 적용한 집단축차 검정법을 제안하며, 기존의 오류 분배율 함수를 포함하는 새로운 오류 분배율 함수를 제안한다. 반응변수가 이산형인 경우 정확한 크기 ${\alpha}$ 검정을 할 수 없으므로 각 검정단계에 사용될 오류율을 분배하는 대신 각 검정단계까지 사용되어야 할 누적 오류율을 이용한다. 오류 분배율 함수를 적용한 집단축차 검정은 기존의 집단축차 검정 보다 빠른 연산과 유연한 검정이 가능하다는 장점을 지니고 있으며, 본 논문에서 제시된 오류 분배율 함수를 이용해 특성을 비교한다.

• International Journal of Computer Science & Network Security
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• 제21권8호
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• pp.17-27
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• 2021

Non-abelian group based cryptosystems are a latest research inspiration, since they offer better security due to their non-abelian properties. In this paper, we propose a novel approach to non-abelian group based public-key cryptographic protocols using semidirect products of finite groups. An intractable problem of determining automorphisms and generating elements of a group is introduced as the underlying mathematical problem for the suggested protocols. Then, we show that the difficult problem of determining paths and cycles of Cayley graphs including Hamiltonian paths and cycles could be reduced to this intractable problem. The applicability of Hamiltonian paths, and in fact any random path in Cayley graphs in the above cryptographic schemes and an application of the same concept to two previous cryptographic protocols based on a Generalized Discrete Logarithm Problem is discussed. Moreover, an alternative method of improving the security is also presented.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제17권4호
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• pp.275-288
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• 2010

A one-holed torus ${\Sigma}$(l, 1) is a building block of oriented surfaces. In this paper we formulate the matrix presentations of the holonomy group of a one-holed torus ${\Sigma}$(1, 1) by the gluing method. And we present an algorithm for deciding the discreteness of the holonomy group of ${\Sigma}$(1, 1).

• 한국농공학회지
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• 제42권2호
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• pp.71-77
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• 2000

A multi-region model for solute transport through saturated soils has been developed to describe preferential flow. The model consists of numerous discrete pore groups, which are characterized by a discrete dispersion coefficient, flow velocity, and porosity . The hydraulic properties for each pore group are derived from a soil's hydraluic conductivity and soil water characteristic functions . Flow in pore group is described by the classical advection-disersion equation (ADE). An implict finite difference scheme was applied to the governing equation that results in a block-tridiagonal system of equations that is very efficient and allows the soil to be divided into any number of pore groups. The numerical technique is derived from methods used to solve coupled equations in fluid dynamics problems and can also be applied to the transport of interacting solutes. The results of the model are compared to the experimental data from published papers. This paper contributes on the characteristics of the method when applied to the parallel porosity model to describe preferential flow of solutes in soil.

• 한국전산구조공학회논문집
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• 제33권3호
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• pp.187-192
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• 2020

덤프 트럭 데크의 경량화를 통한 연료 소비를 줄이고 에코 친화적인 설계를 위해서는 정확한 구조 분석이 필요하다. 지금까지 데크의 하중은 정수압 또는 토압 이론을 기반으로 계산되었다. 이 방법으로 데크의 하중 불균일을 계산할 수 없다. 하중 분포는 골재 입자의 크기 분포 및 상호 작용에 따라 달라진다. 이산요소법은 유한요소법보다 효과적으로 골재의 거동을 시뮬레이션할 수 있다. 본 논문에서는 벌크 밀도와 안식각을 측정하여 주요 특성을 얻었다. 15톤 덤프 트럭 데크는 범핑, 브레이킹 및 회전 시의 운동 조건을 적용하여 얻은 하중을 사용했다. 시뮬레이션은 이산요소해석 소프트웨어인 EDEM을 사용했다. 데크의 응력 및 변형 분포는 NASTRAN에 의해 계산되었다. 측정된 값과 비교하였고, 이를 통해 DEM 시뮬레이션의 결과는 수학적 가정에 의한 결과보다 정확함을 확인하였다.

• 한국정밀공학회지
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• 제22권9호
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• pp.99-106
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• 2005

In recent years, vision sensors are widely used to mobile robot for navigation or exploration. The analog signal transmission of visual data being used in this area, however, has some disadvantages including noise weakness in view of the data storage. A large amount of data also makes it difficult to use this method for a mobile robot. In this paper, a digital data compressing technology based on MPEG4 which substitutes for analog technology is proposed to overcome the disadvantages by using DWT(Discreate Wavelet Transform) instead of DCT(Discreate Cosine Transform). The TI Company's DSP chip, TMS320C6711, is used for the image encoder, and the performance of the proposed method is evaluated by PSNR(Peake Signal to Noise Rates), QP(Quantization Parameter) and bitrate.