• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.4
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• pp.287-295
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• 2022

As low altitude long-range artillery threat has been strengthened, the development of anti-artillery interception system to protect assets against its attacks will be kicked off. We view the defense of long-range artillery attacks as a typical dynamic weapon target assignment (DWTA) problem. DWTA is a sequential decision process in which decision making under future uncertain attacks affects the subsequent decision processes and its results. These are typical characteristics of Markov decision process (MDP) model. We formulate the problem as a MDP model to examine the assignment policy for the defender. The proximity of the capital of South Korea to North Korea border limits the computation time for its solution to a few second. Within the allowed time interval, it is impossible to compute the exact optimal solution. We apply approximate dynamic programming (ADP) approach to check if ADP approach solve the MDP model within processing time limit. We employ Shoot-Shoot-Look policy as a baseline strategy and compare it with ADP approach for three scenarios. Simulation results show that ADP approach provide better solution than the baseline strategy.

• 대한핵의학회:학술대회논문집
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• 1997.05a
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• pp.183-183
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• 1997

• Nuclear Medicine and Molecular Imaging
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• v.41 no.1
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• pp.62-63
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• 2007

• 대한핵의학회:학술대회논문집
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• 1987.05a
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• pp.129.2-130
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• 1987

• 대한핵의학회:학술대회논문집
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• 1996.05a
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• pp.211-211
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• 1996

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.5
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• pp.1036-1057
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• 2013

Wireless body area network (WBAN) is a promising candidate for future health monitoring system. Nevertheless, the path to mature solutions is still facing a lot of challenges that need to be overcome. Energy efficient scheduling is one of these challenges given the scarcity of available energy of biosensors and the lack of portability. Therefore, researchers from academia, industry and health sectors are working together to realize practical solutions for these challenges. The main difficulty in WBAN is the uncertainty in the state of the monitored system. Intelligent learning approaches such as a Markov Decision Process (MDP) were proposed to tackle this issue. A Markov Decision Process (MDP) is a form of Markov Chain in which the transition matrix depends on the action taken by the decision maker (agent) at each time step. The agent receives a reward, which depends on the action and the state. The goal is to find a function, called a policy, which specifies which action to take in each state, so as to maximize some utility functions (e.g., the mean or expected discounted sum) of the sequence of rewards. A partially Observable Markov Decision Processes (POMDP) is a generalization of Markov decision processes that allows for the incomplete information regarding the state of the system. In this case, the state is not visible to the agent. This has many applications in operations research and artificial intelligence. Due to incomplete knowledge of the system, this uncertainty makes formulating and solving POMDP models mathematically complex and computationally expensive. Limited progress has been made in terms of applying POMPD to real applications. In this paper, we surveyed the existing methods and algorithms for solving POMDP in the general domain and in particular in Wireless body area network (WBAN). In addition, the papers discussed recent real implementation of POMDP on practical problems of WBAN. We believe that this work will provide valuable insights for the newcomers who would like to pursue related research in the domain of WBAN.

• The Korean Journal of Nuclear Medicine
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• v.25 no.2
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• pp.211-218
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• 1991

1983년 1월부터 1991년 2월까지 서울대학교 병원에서 진단된 위 암환자를 대상으로 시행한 359예의 골스캔을 후향적으로 재검토하여 골전이 빈도와 양상을 관찰하였으며 환자들의 의무기록을 검토하여 위암의 임상상과 비교하였다. 그 결과는 다음과 같았다. 1) 359예의 골스캔 중에서 골전이에 부합되는 이상소견은 167예(46.5%)이었다. 2) 관찰된 167예의 이상소견 빈도는 척추(66%)에 가장 많이 관찰되었고, 늑골(58%), 골반부(43%), 대퇴골(31%), 두개골(22%)순이었다. 3) 척추전이에서 흉추(65.6%)와 요추(64.5%)의 전이빈도는 거의 비슷하였고, 경추(23.6%)는 낮았다. 4) 골전이 빈도는 임상적 병기 3기 환자에서 진단후 1년 이내에 급격히 증가되었고 그 이후는 증가되지 않았다. 5) 골전이는 임상적 병기가 증가됨에 따라 증가되었으나, 조직학적 세포형태와는 무관하였다. 6) 혈청 alkaline phosphatase 치와 골스캔 상의 골전이 유무와 통제적으로 유의 한 상관관계가 관찰되었다. 이상의 결과로 위암환자의 상당 수에서 골전이가 진단되었으며 위 암환자, 특히 진행암 환자에서 골전이에 대한 주기적인 추적 검사가 필요할 것으로 생각된다.

• The Korean Journal of Nuclear Medicine
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• v.22 no.2
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• pp.215-220
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• 1988

폐암은 비록 그 예후가 나쁜 것으로 되어 있으나, 각 환자에서의 정확한 병기결정은 치료방침과 예후결정에 중요하다. $^{99m}Tc-MDP$를 이용한 골스캔은 단순 방사선학적 검사보다 골전이의 조기진단에 예민하므로, 병기결정에 유용하다고 인정되어 왔다. 저자들은 최근 2년간 조직학적으로 확진된 폐암 환자중 치료전의 골스캔을 구할 수 있었던 202예를 대상으로 후향적 분석을 하였다. 1) 전체적인 골스캔의 골전이 양성율은 43%(87/202)였으며, 비소세포폐암에서 44%(60/135), 소세포폐암에서 40%(27/67)로 나타났다. 2) 비소세포폐암 중에는 선암이 61%(19/31)의 가장높은 골전이 양성율을 보였고, 비소세포폐암의 임상적 stage II에사 29%, stage II에서 50%의 골전이 양성율을 보였다. 3) 87예의 골전이 양성중에서 고립성인 경우가 18예였으며, 다발성 69예의 골분포양상는 늑골이 가장 빈번했으며 요추, 대퇴골, 흉추 그리고 골반 순서로 나타났다. 4) 골통증이 있었던 환자 67예중 골스캔상 골전이가 양성인 경우가 57예, 골통증이 없었던 107예증 골전이 양성인 경우가 17예였고, 혈청 alkaline phosphatase가 증가되었던 65예중 47예에서 골스캔 양성이었고, 그 수치가 정상이었던 137예중 40예서 골스캔상 전이 소견을 보였다. 5) 전체적으로 증가추세에 있는 폐암 환자에 있어서 치료전의 골 스캔은 병기결정에 많은 도움을 줄 수 있는 유용한 검사라 하겠다.

• Journal of KIISE:Software and Applications
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• v.29 no.11
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• pp.785-794
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• 2002

Automatic stock trading systems should be able to solve various kinds of optimization problems such as market trend prediction, stock selection, and trading strategies, in a unified framework. But most of the previous trading systems based on supervised learning have a limit in the ultimate performance, because they are not mainly concerned in the integration of those subproblems. This paper proposes a stock trading system, called R-Trader, based on reinforcement teaming, regarding the process of stock price changes as Markov decision process (MDP). Reinforcement learning is suitable for Joint optimization of predictions and trading strategies. R-Trader adopts two popular reinforcement learning algorithms, temporal-difference (TD) and Q, for selecting stocks and optimizing other trading parameters respectively. Technical analysis is also adopted to devise the input features of the system and value functions are approximated by feedforward neural networks. Experimental results on the Korea stock market show that the proposed system outperforms the market average and also a simple trading system trained by supervised learning both in profit and risk management.

• The Korean Journal of Physiology
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• v.22 no.2
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• pp.219-230
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• 1988

The effect of glycine, structurally the most simple amino acid was investigated on the electrophysiological characteristics of the isolated superfused atrial muscle and sinus node cells of the rabbit heart. Superfusion of the sinus node cell with glycine solution (3, 5 and 8 mM) produced concentration-dependent increments of OS (overshoot potential) and MDP (maximum diastolic potential). Generally action potential amplitude increased as a result of greater increment of OS than that of MDP. The changes in action potential of the sinus node cell peaked in $7{\sim}10{\;}minutes$ after onset of superfusioin. On the contrary to the response to intravenously administered glycine, the rate of spontaneous firing of sinus node cell was invariably increased following superfusion with glycine. Action potential duration manifested as $APD_{60}$ (time to 60% repolarization) was significantly shortened by glycine. And the electrophysiological effects of glycine on the atrial muscle cell were similar to that on the sinus node cells. The results of present study suggest that glycine can exert direct effects on the atrial muscle and sinus node cells of the rabbit heart.