• Journal of Communications and Networks
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• v.16 no.2
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• pp.193-201
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• 2014

In cognitive radio networks, the packet transmissions of the secondary users (SUs) can be interrupted randomly by the primary users (PUs). That is to say, the PU packets have preemptive priority over the SU packets. In order to enhance the quality of service (QoS) for the SUs, we propose a spectrum access strategy with an ${\alpha}$-Retry policy. A buffer is deployed for the SU packets. An interrupted SU packet will return to the buffer with probability ${\alpha}$ for later retrial, or leave the system with probability (1-${\alpha}$). For mathematical analysis, we build a preemptive priority queue and model the spectrum access strategy with an ${\alpha}$-Retry policy as a two-dimensional discrete-time Markov chain (DTMC).We give the transition probability matrix of the Markov chain and obtain the steady-state distribution. Accordingly, we derive the formulas for the blocked rate, the forced dropping rate, the throughput and the average delay of the SU packets. With numerical results, we show the influence of the retrial probability for the strategy proposed in this paper on different performance measures. Finally, based on the trade-off between different performance measures, we construct a cost function and optimize the retrial probabilities with respect to different system parameters by employing an iterative algorithm.

• The Journal of Korean Institute of Next Generation Computing
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• v.13 no.2
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• pp.49-61
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• 2017

Transactional Memory (TM) has greatly changed the parallel programming paradigm for transaction processing and is classified into STM, HTM, HyTM according to hardware or software frameworks. However, the existing studies have a problem that they provide static retry policy for all workloads. To solve the problems, we propose an hybrid transactional memory scheme using sampling-based adaptive retry policy in multi-core environment. First, the proposed scheme determines whether to use STM or HTM according to the characteristic of a transaction. Otherwise, it executes HTM and STM concurrently by using a bloom filter. Second, the proposed scheme provides adaptive retry policy for HTM according to the characteristic of transactions in each workload. Finally, through the experimental performance evaluation using STAMP, the proposed scheme shows 10~20% better performance than the existing schemes.

• KIISE Transactions on Computing Practices
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• v.23 no.8
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• pp.466-472
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• 2017

Hardware Transactional Memory (HTM) has greatly changed the parallel programming paradigm for transaction processing. Since Intel has recently proposed Transactional Synchronization Extension (TSX), a number of studies based on HTM have been conducted. However, the existing studies support conflict prediction for a single cause of the transaction processing and provide a standardized TSX environment for all workloads. To solve the problems, we propose an efficient hardware transactional memory scheme for processing transactions in multi-core in-memory environment. First, the proposed scheme determines whether to use Software Transactional Memory (STM) or the serial execution as a fallback path of HTM by using a prediction matrix to collect the information of previously executed transactions. Second, the proposed scheme performs efficient transaction processing according to the characteristic of a given workload by providing a retry policy based on machine learning algorithms. Finally, through the experimental performance evaluation using Stanford transactional applications for multi-processing (STAMP), the proposed scheme shows 10~20% better performance than the existing schemes.

• The Korean Society of Law and Medicine
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• v.20 no.2
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• pp.261-285
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• 2019

The essential policy of suicide prevention is to continuously manage and treat suicide attempted people through data base related to suicide retry rate and follow-up study report. In Korea, only few people are allowed to follow-up by the Personal Information Protection Act. As a result, the research participation rate and the service participation rate are rather low, so that the research participants is limited to a part of the suicide attempted people. Therefore, the policy proposals to be improved in the Ministry of Health and Welfare Act were examined comparatively in order to increase the practical utilization of the suicide prevention about Article 14 and Article 20 of the Suicide Prevention Act. As a criterion for policy improvement, measures for non-discrimination of information to be considered in terms of technical and ethical dimensions and non-profit research and medical information for medical purposes were suggested. In addition to the severity of the suicide, the suicide risk was assessed and the criteria for the objective assessment of the follow-up observation were considered in consideration of the severity of the suicide.

• The Journal of the Korea Contents Association
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• v.20 no.7
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• pp.149-160
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• 2020

The purpose of this study is to analyze factors affecting a grade maintenance of the non-graded group by LTCI(Long-Term Care Insurance, NHIS). The predictors were examined grade maintenance of the non-graded group(non-grade of A, B, C). The results were as follows: this study found that predisposing factors of the grade maintenance of non-graded of LTCI were significantly related to age, sex, death. Enabling factors of the grade maintenance of non-graded of LTCI were significantly related to household state, income level. Need factors of the grade maintenance of non-graded of LTCI were significantly related to dementia, grade of first grading, retry of applying for long-term care assessment. Based on the finding of study, implications and future research directions were discussed for policy considerations.