• Journal of KIISE:Computer Systems and Theory
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• v.31 no.9
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• pp.503-513
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• 2004

In large distributed systems, replications of data and service are needed to decrease communication cost, increase availability, and avoid single server bottleneck. Tree Quorum protocol is a representative replication protocol, which exploits a logical structure. Tree quorum protocol is one of the replication protocols allowing low read cost only in the best case, while the number of replicas exponentially increases as the level grows. In this paper, thus, we propose a new replication protocol, called symmetric tree protocol which efficiently solves the problem. The proposed symmetric tree protocol also requires much smaller read cost than previous protocols. We conduct cost and availability analysis of the protocols, and the proposed protocol displays comparable read availability to the tree protocol using much smaller number of nodes. Also, the symmetric tree protocol has much smaller response time than the logarithmic protocol.

• Journal of Power Electronics
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• v.16 no.1
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• pp.362-373
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• 2016

The on-line measurement of high-power IGBT collector current is important for the hierarchical control and short-circuit and overcurrent protection of its driver and the sensorless control of the converter. The conventional on-line measurement methods for IGBT collector current are not suitable for engineering measurement due to their large-size, high-cost, low-efficiency sensors, current transformers or dividers, etc. Based on the gate driver, this paper has proposed a current measuring circuit for IGBT collector current. The circuit is used to conduct non-intervention on-line measurement of IGBT collector current by detecting the voltage drop of the IGBT power emitter and the auxiliary emitter terminals. A theoretical analysis verifies the feasibility of this circuit. The circuit adopts an operational amplifier for impedance isolation to prevent the measuring circuit from affecting the dynamic performance of the IGBT. Due to using the scheme for integration first and amplification afterwards, the difficult problem of achieving high accuracy in the transient-state and on-state measurement of the voltage between the terminals of IGBT power emitter and the auxiliary emitter (u_Ee) has been solved. This is impossible for a conventional detector. On this basis, the adoption of a two-stage operational amplifier can better meet the requirements of high bandwidth measurement under the conditions of a small signal with a large gain. Finally, various experiments have been carried out under the conditions of several typical loads (resistance-inductance load, resistance load and inductance load), different IGBT junction temperatures, soft short-circuits and hard short-circuits for the on-line measurement of IGBT collector current. This is aided by the capacitor voltage which is the integration result of the voltage uEe. The results show that the proposed method of measuring IGBT collector current is feasible and effective.

• Design & Manufacturing
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• v.11 no.3
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• pp.19-24
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• 2017

In these days, increase requirement of TEM (Transmission Electro Microscope) in not only scientific field but also industrial field. Because TEM can measure inner-structure of specimen a variety of materials like metal, bio. etc. When use TEM, specimen should be thin about 50nm. So making for thin specimen, use Ion milling device that include specimen holder. The holder generally made of Aluminium Aluminium holder is worn away easily. For this reason, using time of ion milling with aluminum holder is too short. To solve the problem, we replace aluminium holer to molybdenum alloy holder. In this paper, we design molybdenum alloy holer for CAM and modify CAD modeling for effective machining process. So we array a specimen 3 by 4 and setup orientation for one-shot machining process. Next we make a CAM program for machining. we making a decision two machining strategy that chose condition of tool-path method, step-down, step-over. etc. And then conduct machining using CNC milling machining center. To make clear difference between case.1 and case.2, we fixed machining conditions like feed-rate, main spindle rpm, etc. After machining, we confirm the condition of workpiece and analysis the problems case by case. Finally, case.2 work piece that superior than case.1 cutting with WEDM because that method can not ant mechanical effect on workpiece.

• Journal of KIISE
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• v.42 no.5
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• pp.621-628
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• 2015

The rapid growth of network technology makes the high-tech weapon. Thus, in the modern war, the ability to immediately use of the high-tech weapon is important. To realize this ability, continuous trainning is necessary but, this trainning spends many money. To improve the budget efficiency, Modeling and Simulation(M&S) are used. However, they seriously decrease the reality. Recently, the system which can support the combination of Live with Virtual simulation is on the rise. The typical example is L-V-C Environment and many kind of middleware which can support the L-V-C Envrionment are already proposed. Previous middleware can support the interoperability between different simulations but, it cannot completely interoperate three(Live, Virtual, Constructive) simulation environments. In this paper, to solve this problem, we propose the scheme which is combination between different middlewares. And we conduct the API mapping between HLA and DDS which are typical middleware and verify the scheme.

• Communications of Mathematical Education
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• v.23 no.3
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• pp.523-543
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• 2009

We conduct a survey to find out the academic achievement factors for 484 second grade students at two middle schools in Busan city and Kyungsangnam Do, respectively. The survey questionnaire includes home environment and background, students' personal character, relationships with friends, learning attitudes towards improving problem solving, variables related to teaching methods and teachers, the school's computer facilities, mobile class by students levels, private education current situations, etc. Private education current situations are presented according to regions. Based on survey data we perform factor analysis to find major factors affecting mathematics academic achievement. We analyze the characteristics of the major factors. We also propose basic data and implications to mathematics educators and mathematics teachers at middle schools for improving middle school mathematics education quality.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.12
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• pp.3315-3337
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• 2012

Crowded scenes analysis is a challenging topic in computer vision field. How to detect diverse motion patterns in crowded scenarios from videos is the critical yet hard part of this problem. In this paper, we propose a novel approach to mining motion patterns by utilizing motion information during both long-term period and short interval simultaneously. To capture long-term motions effectively, we introduce Motion History Image (MHI) representation to access to the global perspective about the crowd motion. The combination of MHI and optical flow, which is used to get instant motion information, gives rise to discriminative spatial-temporal motion features. Benefitting from the robustness and efficiency of the novel motion representation, the following motion pattern mining is implemented in a completely unsupervised way. The motion vectors are clustered hierarchically through automatic hierarchical clustering algorithm building on the basis of graphic model. This method overcomes the instability of optical flow in dealing with time continuity in crowded scenes. The results of clustering reveal the situations of motion pattern distribution in current crowded videos. To validate the performance of the proposed approach, we conduct experimental evaluations on some challenging videos including vehicles and pedestrians. The reliable detection results demonstrate the effectiveness of our approach.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.2
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• pp.117-129
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• 2012

In this study, research was performed to establish the measurement and frequency of analysis for maintenance monitoring by investigation of tunnel maintenance monitoring system in the tunnel which was installed in the Seoul metro line 5, 7 and 8, using that the domestic and foreign application case, results of analyzed maintenance monitoring in the domestic tunnel and legal safety management standard of the facility. The results of the monitoring management about analysis frequency to the present are considered that the problem about measuring frequency does not occur. According to the analysis results of the maintenance monitoring which are located on the 5, 6th subway line, they are analyzed that the stress of concrete lining and reinforced bar are converged gradually after 45 months. Therefore Monitoring of measurement and analysis frequency is conduct more often within about 4 years after the measuring instrument installation. Four years later, slowing the frequency of measurement is considered reasonable.

• Journal of the Korean Society for Computer Game
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• v.31 no.4
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• pp.121-128
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• 2018

Virtual reality is a technology that enables users to implement environments that are separate from the real world, and immersion is an important factor in implementing separate environments. However, a variety of studies have been conducted to solve this problem as the lack of awareness of the surrounding environment can lead to an unstable virtual reality game environment. Most studies are focused on solving problems through visualization. On the other hand, because visualizations are generally information that is not relevant to the space of virtual reality, research is needed on the effect of the degree of immersion in virtual reality to which they are applied. The guidelines are necessary because there are differences in individual tendencies and the factors that influence the immersion. In order to solve these two problems, we are going to conduct experiments on two systems: a survey based on the immersion tendency and a visualized communication of information about the surrounding environment. Through these results, we will measure the immersion of individuals and identify the impact of visualizations on virtual reality games by dividing them by their propensity to do so to present guidelines on the creation of virtual reality game environments based on the individual's tendency to engage in immersion.

• Journal of East-West Nursing Research
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• v.27 no.2
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• pp.104-113
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• 2021

Purpose: The purpose of this study was to investigate the status of emotional labor of nursing personnel working in comprehensive nursing service ward and to suggest the way service improvement can be achieved. Methods: A total of 28 nurses working in comprehensive nursing service ward were divided into four groups to conduct focus group interview. All interviews were recorded and transcribed after the interview to perform data analysis in the order of data classification, topic categorization, and keyword derivation. Results: The five categories of subjects and relating keywords drawn from the focus group interviews are as follows: 1) Emotional labor experience: suppressing emotions, expressing emotions or actions that are different from reality, 2) Situations of emotional labor: verbal abuse and assault, sexual harassment, personal needs and errands, 3) Responses to emotional labor: responding directly, responding directly, receiving senior's help, using the organizational system, persevering, 4) Problems caused by emotional labor: work exhaustion, job change intention, job stress, 5) Protection plan against emotional labor: manual or education for nurses, education for patients and carers, compensation, tough sanctions though system strengthening. Conclusion: This study shows that although nurses working in comprehensive nursing service ward generally experience high levels of emotional labor, the problem solving of them relies mainly on personal response. Therefore, it is necessary to develop various measures to protect nurses in an organizational level response, thus to improve the comprehensive nursing service system.

• 한국사회정책
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• v.25 no.2
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• pp.305-332
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• 2018

This study explores the effectiveness of employment-oriented welfare state by analyzing the mediating role of employment rate on the relationship between public welfare effort and fiscal soundness. Notably, this study considers the quality of employment into the analysis: part-time work, involuntary part-time work and low-wage work in analysis. The data sample consists of 18 OECD countries which initiated employment-oriented welfare strategy after the crisis of welfare state. An analysis was conduct based on Baron & Kenny(1986)'s method and panel two-stage model to handle the endogeneity problem. The results show that while the high level of public welfare effort negatively affects the fiscal soundness if it contributes to boosting employment rates, it has positive effects on the fiscal soundness. However, when the incidence of involuntary part-time employment and low-wage employment is high, the mediating impact of employment rate on the fiscal soundness disappears. This study argues that unless the quality of employment is taken into consideration, the positive effect of employment-oriented welfare state strategy to improve the fiscal soundness is not fully guaranteed.