• Journal of the Korean Mathematical Society
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• v.35 no.2
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• pp.399-422
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• 1998

A useful method of proving the finite decidability of an equationally definable class V of algebras (i.e., variety) is to prove the decidability of the class of finite directly indecomposable members of V. The validity of this method relies on the well-known result of Feferman-Vaught: if a class K of first-order structures is decidable, then so is the class {$\prod$$_{i}$＜n/ $A_{i}$│ $A_{i}$ $\in$ X (i < n), n $\in$ $\omega$}. In this paper we show that the converse of this does not necessarily hold.d.d.

• Journal of applied mathematics & informatics
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• v.7 no.2
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• pp.357-377
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• 2000

A parallel communicating automata system is an accepting device based on the communications between more automata working in parallel. It consists of several automata corking independently but communicating with each other by request. We survey several variants of parallel communicating automata systems with respect to their computational power. Other aspects like decidability and complexity matters are also briefly discussed. Some open problem sand directions for future research are finally pointed out.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.971-974
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• 2002

Petri net is an effective modeling tool for concurrent systems. Liveness problem is one of analysis problems in Petri net theory verifying whether the system is free from any local deadlocks. It is well known that computational complexity of liveness problem of general Petri net is deterministic exponential space. Some subclasses, such as marked graph and free choice net, are suggested where liveness problem is verified in less complexity. This paper studies liveness of siphon containing circuit (SCC) net. Liveness condition based on algebraic inequalities is shown. Then polynomial time decidability of liveness of SCC net is derived, if the given net is known to be an SCC net a priori.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10b
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• pp.372-377
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• 2006

유비쿼터스 컴퓨팅 시대의 도래와 시맨틱 웹에 대한 관심이 높아짐에 따라 관련 기술인 온톨로지와 이를 이용한 추론 기술에 대한 요구가 증가하고 있다. 따라서, 추론이 가능한 시맨틱 웹 기반의 모델링과 추론에 대한 연구가 필요하다. 모델링을 위해 사용되는 OWL-DL과 임의의 사용자 규칙을 표현하는 SWRL은 각각 W3C의 표준안으로서, 유비쿼터스 컴퓨팅 환경에 효율적으로 자동적인 개인화 서비스[1][2]를 제공하는데 있어서 적합하다. 그러나 OWL-DL과 SWRL의 단순한 결합은 질의응답(Query Answering)에 대한 처리가 비결정 가능한(undecidable) 문제를 야기한다. 본 논문에서는, 비결정가능성 문제의 원인인 무한반복의 가능성을 제거하기 위한 블록(blocking) 방법을 제안한다. OWL-DL이 지닌 서술논리(Description Logic)의 표현력을 유지하고, 그에 따른 추론의 질적인 성능을 유지하는 범위에서 블록방법을 사용하여 결정 가능한 질의응답을 수행하는데 궁극적인 목적을 두고 있다. OWL-DL의 TBox에 위치하는 존재 정량자(Existential Quantifier)를 대체하고 ABox에 삽입하여, 무한반복의 가능성을 없애는 해결 방법을 제시한다. 실험은 비결정가능성 문제를 DL-Safe 규칙을 통해 해결한 KAON2와 비교하여 진행한다.

• Korea Information Processing Society Review
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• v.11 no.6
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• pp.56-75
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• 2004

In this article we address some system characteristics and challenging issues in developing Context-aware Middleware for Ubiquitous Computing. The functionalities of a Context-aware Middleware includes gathering context data from hardware/software sensors, reasoning and inferring high-level context data, and disseminating/delivering appropriate context data to interested applications/services. The Middleware should facilitate the query, aggregation, and discovery for the contexts, as well as facilities to specify their privacy policy. Following a formal context model using ontology would enable syntactic and semantic interoperability, and knowledge sharing between different domains. Moddleware should also provide different kinds of context classification mechanical as pluggable modules, including rules written in different types of logic (first order logic, description logic, temporal/spatial logic, fuzzy logic, etc.) as well as machine-learning mechanical (supervised and unsupervised classifiers). Different mechanisms have different power, expressiveness and decidability properties, and system developers can choose the appropriate mechanism that best meets the reasoning requirements of each context. And finally, to promote the context-trigger actions in application level, it is important to provide a uniform and platform-independent interface for applications to express their need for different context data without knowing how that data is acquired. The action could involve adapting to the new environment, notifying the user, communicating with another device to exchange information, or performing any other task.

• Journal of the Korea Society of Computer and Information
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• v.15 no.10
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• pp.27-34
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• 2010

This paper proposes an efficient method for verifying palmprint which is captured at the natural interface without any physical restriction. The location and orientation of the region of interest (ROI) in palm images are variously appeared due to the translation and rotation of hand. Therefore, it is necessary to extract the ROI stably for palmprint recognition. This paper presents a method that can extract the ROI, which is based on the reference points that are located at the center of the crotch segments between index finger and middle finger and between ring finger and little finger. It also proposes a palmprint recognition method using the histogram of local binary patterns (LBP). Experiments for evaluating the performance of the proposed method were performed on 1,597 palmprint images acquired from 100 different persons. The experimental results showed that ROI was correctly extracted at the rate of 99.5% and the equal error rate (EER) and the decidability index d' indicating the performance of palmprint verification were 0.136 and 3.539, respectively. These results demonstrate that the proposed method is robust to the variations of the translation and rotation of hand.

• The Journal of the Korea Contents Association
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• v.12 no.12
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• pp.517-523
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• 2012

Biometrics is a study of identifying individual by using the features of human body. It has been studied for an alternative or complementary method for the classical method based on password, ID card, etc. In comparison with the fingerprint, iris, ear, palmprint, finger-knuckle print has been recently studied. This paper proposes an effective method for recognizing finger-knuckle print based on the feature of Gradient orientation. The main features of finger-knuckle print are the size and direction of winkles. In order to extract these features stably, we make a feature vector consisted of Gradient orientations after the preprocessing of enhancing non-uniform brightness and low contrast. Total 790 images acquired from 158 persons have been used at the experiment for evaluating the performance of the proposed method. The experimental results show the recognition rate of 99.69% and the relatively high decidability index of 1.882. These results demonstrate that the proposed method is effective in recognizing finger-knuckle print.

• Kyungpook Mathematical Journal
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• v.28 no.2
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• pp.185-196
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• 1988

We study existence of polynomial integrating factors and solutions F(x, y)=c of first order nonlinear differential equations. We characterize the homogeneous case, and give algorithms for finding existence of and a basis for polynomial solutions of linear difference and differential equations and rational solutions or linear differential equations with polynomial coefficients. We relate singularities to nature of the solution. Solution of differential equations in closed form to some degree might be called more an art than a science: The investigator can try a number of methods and for a number of classes of equations these methods always work. In particular integrating factors are tricky to find. An analogous but simpler situation exists for integrating inclosed form, where for instance there exists a criterion for when an exponential integral can be found in closed form. In this paper we make a beginning in several directions on these problems, for 2 variable ordinary differential equations. The case of exact differentials reduces immediately to quadrature. The next step is perhaps that of a polynomial integrating factor, our main study. Here we are able to provide necessary conditions based on related homogeneous equations which probably suffice to decide existence in most cases. As part of our investigations we provide complete algorithms for existence of and finding a basis for polynomial solutions of linear differential and difference equations with polynomial coefficients, also rational solutions for such differential equations. Our goal would be a method for decidability of whether any differential equation Mdx+Mdy=0 with polynomial M, N has algebraic solutions(or an undecidability proof). We reduce the question of all solutions algebraic to singularities but have not yet found a definite procedure to find their type. We begin with general results on the set of all polynomial solutions and integrating factors. Consider a differential equation Mdx+Ndy where M, N are nonreal polynomials in x, y with no common factor. When does there exist an integrating factor u which is (i) polynomial (ii) rational? In case (i) the solution F(x, y)=c will be a polynomial. We assume all functions here are complex analytic polynomial in some open set.