• 정보보호학회논문지
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• 제29권1호
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• pp.225-234
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• 2019

비트코인은 탈중앙화와 분산원장을 특징으로 하는 암호화폐로서 "작업증명"이라는 채굴시스템을 통해 유지된다. 채굴 시스템에서는 블록 생성시간을 일정하게 유지하기 위해 채굴 난이도를 조정하게 되는데, 기존의 채굴 난이도 변경 방식은 미래의 해시파워를 반영할 수 없다는 문제가 있다. 따라서 실제시간과 예정시간 사이에 발생하는 오차로 인해 블록생성과 실세계 시간의 불일치를 가중시키게 되고, 결국 거래 기한을 맞추지 못하거나 코인 호핑 공격에 취약점을 노출시키게 된다. 블록 생성시간을 일정하게 유지시키기 위한 기존 연구도 여전히 오차 문제를 갖는다. 본 연구에서는 이러한 오차를 줄이기 위한 기계학습 기반 채굴 난이도 예측 방안을 제시한다. 이전 해시파워를 학습하여 미래의 해시파워를 예측하고 예측한 값을 이용하여 채굴 난이도를 조정한다. 우리의 실험 결과는 이와 같은 경우 기존 채굴 난이도 조정방식보다 오차율을 약 36% 더 줄일 수 있음을 보여준다.

• 통상정보연구
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• 제12권1호
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• pp.35-54
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• 2010

This article explored the bank's responsibilities in electronic payment system between Korea and U.S.A. In order to complete my research object, I used Article 4A of the U.C.C. and EFTA of 1978 and by Electronic Financial Transaction Act of Korea as a analytic instruments. I also adapted America's various regulations to regulate concerned parties(banks). The system of this article is going to display as fellows; First, I presented recent trend and legal stabilities of electronic payment in this article. Second, I focuses on the allocation of risk of loss caused by ambiguous term in payment orders that do not express the subjective intention of the senders. I also did analyze the solution procession of error occurring in course of send of payment order. Third, In any action which involves a customers's liability for an unauthorized electronic fund transfer, the burden of proof is upon the financial institution to show that the electronic fund transfer was authorized. Forth, Customers have to report the error and unauthorized electronic fund transfer after awaring of it. Then bank will be liable for such a unauthorized electronic fund transfer. But If customer's failure to report, the bank has exemptions. Lastly, In order to prevent or detect the unauthorized electronic fund transfer, bank will agree with custom to establish a commercially reasonable security procedure, while bank has duties to notify in order to decrease the loss resulted from unauthorized payment order in korea law.

• Communications for Statistical Applications and Methods
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• 제22권3호
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• pp.295-304
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• 2015

This paper considers the problem of estimation of the Hurst parameter H ${\in}$ (1/2, 1) from longitudinal data with the error term of a fractional Brownian motion with Hurst parameter H that gives the amount of the long memory of its increment. We provide a new estimator of Hurst parameter H using a two scale sampling method based on $A{\ddot{i}}t$-Sahalia and Jacod (2009). Asymptotic behaviors (consistent and central limit theorem) of the proposed estimator will be investigated. For the proof of a central limit theorem, we use recent results on necessary and sufficient conditions for multi-dimensional vectors of multiple stochastic integrals to converges in distribution to multivariate normal distribution studied by Nourdin et al. (2010), Nualart and Ortiz-Latorre (2008), and Peccati and Tudor (2005).

• 대한수학회보
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• 제46권4호
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• pp.627-644
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• 2009

The gauge-Uzawa method which has been constructed in [11] is a projection type method to solve the evolution Navier-Stokes equations. The method overcomes many shortcomings of projection methods and displays superior numerical performance [11, 12, 15, 16]. However, we have obtained only suboptimal accuracy via the energy estimate in [11]. In this paper, we study semi-discrete gauge-Uzawa method to prove optimal accuracy via energy estimate. The main key in this proof is to construct the intermediate equation which is formed to gauge-Uzawa algorithm. We will estimate velocity errors via comparing with the intermediate equation and then evaluate pressure errors via subtracting gauge-Uzawa algorithm from Navier-Stokes equations.

• 제어로봇시스템학회논문지
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• 제4권5호
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• pp.608-615
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• 1998

In this paper a second-order iterative learning control algorithm with feedback is proposed for the trajectory-tracking control of nonlinear dynamic systems with unidentified parameters. In contrast to other known methods, the proposed teaming control scheme utilize more than one past error history contained in the trajectories generated at prior iterations, and a feedback term is added in the learning control scheme for the enhancement of convergence speed and robustness to disturbances or system parameter variations. The convergence proof of the proposed algorithm is given in detail, and the sufficient condition for the convergence of the algorithm is provided. We also discuss the convergence performance of the algorithm when the initial condition at the beginning of each iteration differs from the previous value of the initial condition. The effectiveness of the proposed algorithm is shown by computer simulation result. It is shown that, by adding a feedback term in teaming control algorithm, convergence speed, robustness to disturbances and robustness to unmatched initial conditions can be improved.

• 대한임상독성학회지
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• 제3권1호
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• pp.1-10
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• 2005

Gastric lavage is now known to be ineffective, unnecessary or hazardous in some circumstances where it used to be performed as a routine. This article concerns the medico-legal aspect of forced gastric lavage. The Supreme Court 2005.1.28, 2003da14119 is the case where a patient, who ingested the organophosphate insecticide to attempt suicide and refused lavage. At first we discuss the effectiveness or hazards of lavage because a very high degree of proof -of negligence, not error of clinical judgment - would be required. Lavage, with or without the informed consent, performed negligently which result in harm could, of course, give rise to a claim in negligence. A doctor might also be held negligent in failing to perform an act which he/she had a duty to perform.

• 전자공학회논문지S
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• 제36S권2호
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• pp.88-95
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• 1999

스텍필터는 신호복원성이 뛰어난 디지털 비선형 필터의 일종이다. 그러나 기존의 적응형 설계기법을 이요하면 순차적인 특성 때문에 윈도우의 크기가 큰 스텍필터의 설계시 많은 계산량으로 그 응용에 한계가 있었다. 본 논문에서는 평균적대오차를 최소화하는 최적의 스텍필터를 설계하기 위한 병렬구조의 기법을 제안하였고 제안된 기법을 사용하면 적응특성 즉 학습의 반복적인 특성을 가지면서 최적의 필터로 수령하는데 필요한 반복 횟수를 줄임으로써 기존의 설계기법보다 설계시간을 단축할 수 있다는 사실과 제안된 기법이 최적의 스텍필터로 수렴한다는 사실을 증명하였다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제18권4호
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• pp.305-316
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• 2014

The Hodge-Helmholtz decomposition splits a vector field into the unique sum of a divergence-free vector field (solenoidal part) and a gradient field (irrotational part). In a bounded domain, a boundary condition needs to be supplied to the decomposition. The decomposition with the non-penetration boundary condition is equivalent to solving the Poisson equation with the Neumann boundary condition. The Gibou-Min method is an application of the Poisson solver by Purvis and Burkhalter to the decomposition. Using the $L^2$-orthogonality between the error vector and the consistency, the convergence for approximating the divergence-free vector field was recently proved to be $O(h^{1.5})$ with step size h. In this work, we analyze the convergence of the irrotattional in the decomposition. To the end, we introduce a discrete version of the Poincare inequality, which leads to a proof of the O(h) convergence for the scalar variable of the gradient field in a domain with general intersection property.

• 디지털산업정보학회논문지
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• 제7권2호
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• pp.29-37
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• 2011

Java bytecode verification is a critical process to guarantee the safety of transmitted Java applet on the web or contemporary embedded devices. We propose a design of framework which enables to analyze and verify java bytecode. The designed framework translates from a java bytecode into the intermediate representation which can specify a properties of program without using an operand stack. Using the framework is able to produce automatically error specifications that could be occurred in a program and express specifications annotated in intermediate representation by a user. Furthermore we design a verification condition generator which converts from an intermediate representation to a verification condition, a verification engine which verifies verification conditions from verification condition generator, and a result reporter which displays results of verification.

• KIEE International Transaction on Systems and Control
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• 제2D권2호
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• pp.108-114
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• 2002

This paper describes the design of a robust adaptive controller for a nonlinear dynamical system with unknown nonlinearities. These unknown nonlinearities are approximated by multilayered neural networks (MNNs) whose parameters are adjusted on-line, according to some adaptive laws far controlling the output of the nonlinear system, to track a given trajectory. The main contribution of this paper is a method for considering input constraint with a rigorous stability proof. The Lyapunov synthesis approach is used to develop a state-feedback adaptive control algorithm based on the adaptive MNN model. An overall control system guarantees that the tracking error converges at about zero and that all signals involved are uniformly bounded even in the presence of input saturation. Theoretical results are illustrated through a simulation example.