• Journal of Energy Engineering
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• v.27 no.1
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• pp.21-32
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• 2018

In this paper, we reported the current technologies of water scaling removal and also water recovery from the flue gases, which are funded by Department of Energy (DOE), USA. Globally, water resources are limited due to the climate change. The potential impacts of climate change is food and water shortages. In the $21^{st}$ century, water shortages and pollution are expected to become more acute as populations grow and concentrate in cities. At present, the water stress increases over 62.0 ~ 75.8% of total water basin area and decreases over 19.7 ~ 29.0%. Many renewable energy sources demand secure water resources. Water is critical for successful climate change mitigation, as many efforts to reduce greenhouse gas emissions depend on reliable access to water resources. Water hardness is one of the major challenge to coal power plants. Department of energy (DOE) funded and encouraged for the development of advanced technologies for the removal of hardness of water (scaling) and also water recovery from the flue gases from coal power plants.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.20-27
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• 2017

This study investigated the problems in current practice of drive-train resonance analysis procedure and suggested solutions. The first problem is the resonance occurrence at the un-identified resonance point by the current practice, as for a solution the force spectrum analysis for each critical force transmitting component was suggested. The second one is the inaccurate estimation of potential resonance point in eigenfrequency analysis because of the non-consideration about the eigenfrequency dependency on rotor-speed, the fine linearization at each rotor speed point all over operational range was proposed to account for the affection. Lastly the insufficient time for resonance activation under run-up simulation condition was recognized as a problem in resonance load increasing analysis, as an alternative, steady state condition was suggested to estimate the maximum load increasing level.

• Proceedings of the KIEE Conference
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• 2006.05a
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• pp.48-50
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• 2006

SC(Static Condenser) in KEPCO is used in voltage control and power factor compensation. Currently KEPCO uses SC to 154kv 50MVA and 23kv SMVA. It is not important in old days because a SC bank accident has no effect on power system. But we are interested in the SC bank for power quality in these days. The SC Bank has a reactor and a condenser using series connection. It is operated in critical point for resonance circuit normally. Therefore the SC bank has a small reliability against other Power instruments. If a 4th harmonic frequency as a resonance frequency is supplied in system, the condenser is damaged because of a resonance current. And a trip and a closing for CB(Circuit Breaker) in many times will have a big influence of SC bank destruction. General OCR(Over Current Relay) observing SC bank is not useful for this protection We think that protection relay must be have the SC bank characteristics. A solution for this problem is active Power, resonance frequency and impedance.

• Progress in Superconductivity and Cryogenics
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• v.6 no.4
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• pp.5-8
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• 2004

A low cost MOD processing using YBCO oxide powder as a starting precursor was employed for fabrication of YBCO thin films. YBCO oxide is advantageous over metal acetates or TFA salts which are popular starting precursors for conventional MOD-TFA process. YBCO thin films were prepared by oxide-precursor-based MOD process and annealing condition was optimized. The YBCO thin film annealed at 78$0^{\circ}C$ shows no transport $I_c$ and poor microstructure. However, the YBCO thin film annealed at higher temperature shows improvement in microstructure and current transport property. In order to improve critical current, YBCO thin film was prepared by double coating method. YBCO thin film prepared with double coating approach shows enhanced superconducting performance ($I_c$>100A/cm-w).

• Journal of Communications and Networks
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• v.7 no.2
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• pp.126-134
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• 2005

Reducing energy consumption in mobile hosts (MHs) is one of the most critical issues in wireles/mobile networks. IP paging protocol at network layer and power saving mechanism (PSM) at link layer are two core technologies to reduce the energy consumption of MHs. First, we investigate the energy efficiency of the current IEEE 802.11 power saving mechanism (PSM) when IP paging protocol is deployed over IEEE 802.11 networks. The result reveal that the current IEEE 802.11 PSM with a fixed wakeup interval (i.e., the static PSM) exhibits a degraded performance when it is integrated with IP paging protocol. Therefore, we propose an adaptive power saving mechanism in IEEE 802.11-based wireless IP networks. Unlike the static PSM, the adaptive PSM adjusts the wake-up interval adaptively depending on the session activity at IP layer. Specifically, the MH estimates the idle periods for incoming sessions based on the exponentially weighted moving average (EWMA) scheme and sets its wake-up interval dynamically by considering the estimated idle period and paging delay bound. For performance evaluation, we have conducted comprehensive simulations and compared the total cost and energy consumption, which are incurred in IP paging protocol in conjunction with various power saving mechanisms: The static PSM, the adaptive PSM, and the optimum PSM. Simulation results show that the adaptive PSM provides a closer performance to the optimum PSM than the static PSM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10B
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• pp.880-890
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• 2004

As the side effects of information society, for example hacking, virus, etc., diffuse, the information security becomes one of the most important issues over the world. Information security manpower who produce the information security products, and who conduct the information security services are critical factor to complete secure information society In spite of many Plans formulated and implemented by government and civil sector, there is no systematic analysis on the current status of information security educational institutions. This article aims to analyze the current status of information security educational institutions - colleges, universities and graduate schools-with Statistical Yearbook of Education, and to predict the supply of information supply manpower.

• Journal of Smart Tourism
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• v.2 no.4
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• pp.25-34
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• 2022

Digital transformation plays a critical role in making hospitality and tourism organizations create new business processes and customer experiences. The hospitality and tourism industry thrives on creating unique experiences by offering exceptional and innovative customer services through innovative digital technologies. Thus, this study provides an overview of the current use of these technologies in the hospitality industry and their potential advantages and opportunities. In particular, the metaverse and immersive virtual reality (VR) technology are gaining popularity in the hospitality industry, offering new opportunities for innovation and driving core values. This study discusses the current use of VR and metaverse and potential advantages and opportunities for researchers and practitioners in the hospitality and tourism context. Thus, we provide suggestions and implications for hospitality and tourism industry stakeholders to increase core values and business performance and create sustainable competitive advantages over other market players through VR and metaverse.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2250-2254
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• 2007

Comprehensive analytical models focusing on the anode water loss, the cathode flooding, water equilibrium, and water management strategy are developed for polymer electrolyte fuel cells. Analytical solutions presented in this study are compared with two-dimensional computational results and shows a good agreement in predicting those critical characteristics of water. General features of water concentration profile as a function of membrane thickness and current density are presented to illustrate the net effect of the back-diffusion of water from the cathode to anode and the water production by the cathode catalytic reaction on water transport over a fuel cell domain. As one of practical applications, the required humidity level of feed streams for full saturation at the channel outlets are investigated as a function of the physical operating condition. These analytical models can provide good understanding on the characteristic water

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.18 no.4
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• pp.282-292
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• 2008

This study was conducted to evaluate work environment monitoring program(WMP) under Industrial Safety and Health Act in Korea. WMP was evaluated by focusing on five key elements, such as purpose, subject, scope, method and workers' participation. The operation status of WMP was evaluated by using questionnaire to workers and data published by Ministry of Labor(MOL). Compliance rate of WMP was less 13 % in manufacturing workplaces. Over-exposure rate was steady state by annual trend. The degree of workers' satisfaction to WMP was just 24 %. A critical problem with the current WMP is that the employer and workers are not acting as main players. For a fundamental improvement in working condition to take place, participation of workers should be expanded and be guaranteed by law.

• Korean Management Science Review
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• v.23 no.2
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• pp.93-107
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• 2006

This paper attempts to improve the typical DEA model that is often used as a performance evaluation method for service firms. The after-sales service system in a Korean electronic company is chosen as a sample case. The performance evaluation method currently practiced in the firm was reviewed and some critical issues of the current method were discussed. DEA model would be considered a solution for solving those Issues. However, typical DEA models has various drawbacks in determining the weights over evaluation criteria. Proposed is the priority-constrained DEA model that accommodates the strategic Importance of each evaluation criterion. The results of the proposed model are compared with those of typical DEA models. It is shown that the priority-constrained DEA model is superior to the others in terms of evaluation quality.