• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.305-314
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• 2017

Ocean wave energy harvesting is still too expensive despite developing a variety of wave energy converter (WEC) devices. For the cost-effective wave energy harvesting, it can be an effective measure to use existing breakwaters or newly installed breakwaters for both wave control and energy harvesting purposes. In this study, we investigated the functionality of both breakwater and wave-power generator for the oscillating water column (OWC)-type wave energy converter (WEC) installed in a pneumatic floating breakwater, which was originally developed as a floating breakwater. In order to verify the performance of the breakwater as a WEC, the air flow velocity from air-chamber to WEC has to be evaluated properly. Therefore, air flow velocity, wave transformation and motion of floating structure was numerically implemented based on BEM from linear velocity potential theory without considering the compressibility of air within the chamber. Air pressure, meanwhile, was assumed to be fluctuated by the motions of structure and the water level change within air-chamber. The validity of the obtained values can be determined by comparing the previous results from the numerical analysis for different shapes. Based on numerical model results, wave transformation characteristics around OWC system mounted on the fixed and floating breakwaters, and motions of the structure with air flow velocities are investigated. In summary, all numerical results are almost identical to the previous research considering air compressibility. Therefore, it can be concluded that this analysis not considering air compressibility in the air chamber is more efficient and practical method.

• Journal of Korea Water Resources Association
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• v.53 no.2
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• pp.89-96
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• 2020

Water management agencies under the Ministry of Environment produce and accumulate qualified basic data for major rivers. However, the integrated management of the river water has been weak since the artificial water circulation process, such as the intaking and drainage of agricultural water, has not been examined in the basin, which includes many agricultural land. In this study, a study was conducted on how the power usage method (operating time method) based on the running time can be applied and improved among indirect flow rate measurement methods used to investigate flow rates collected by the riverside for agricultural water purposes, and thus the resultant data of high reliability can be obtained at low cost. The operation time method is suitable for small-scale water pumping stations where it is difficult to secure real-time power supply data. The reliability of the data was verified through the correlation analysis with the actual flow rate, and it was found that the flow rate calculated by the operation time method reflecting the level of the stream to which the inlet of the pumping station is connected can be reasonably matched with the actual flow rate. In addition, it was confirmed that the investment cost at the time of initial installation of the facility was highly efficient by generating qualified flow data at low cost through comparison with direct flow rate measurement methods. If flow data is secured by applying the operation time method to large and small water farms located along the riverside, it is expected that more quantitative and integrated stream water management will be possible.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.3
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• pp.129-134
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• 2020

Moisture infiltration inside the solar cell module, filling of EVA sheet, melting of the frame seal, and deterioration of power generation performance in the module one year after installation are occurring. Whitening phenomenon, electrode corrosion phenomenon, and dielectric breakdown phenomenon are appearing in solar cell module installed in Korea before 5-7 years, leading to deterioration of power generation performance, and big problems for long-term reliability and long life technology are emerging. Therefore, in order to solve these problems, the development of a micro inverter (MiCrco Inverter Converter, MiC) including the function of securing the durability of the solar cell module and monitoring the aging progress and the solar cell based on the monitoring data from the MiC smart monitoring programs have been proposed to determine the aging of modules. In addition, in order to become a highly efficient solar smart monitoring system through systematic operation management through IT convergence with MiC that has enhanced monitoring function of solar cell module, SoC(System On Chip) in micro inverter is the environment for solar cell module. There is a demand for functions that can detect information in a complex manner and perform communication and control when necessary. Based on these requirements, this paper aims to develop SoC-based low-cost MiC smart photovoltaic system technology.

• Journal of Korean Society of Forest Science
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• v.70 no.1
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• pp.84-90
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• 1985

The objective of this study is to analyze the market structure and price formation status of imported log from overseas which has leadership of timber price decision mechanism in Korea. The results obtained are as follows; 1) The 53 percents of the total 134 log importing companies are the small scale companies which import less than ten thousand cubic meters per year, and are mainly aimed to do agent task of importing log. 2) The market structure of imported log formed high level 01 oligopolistic structure, but did not make excess profit of oligopoly because of excess import. 3) The bargaining power of Korea on the price decision process in the overseas log exporting market is very weak, because the market has the bilateral oligopoly structure, and the non-systematic importing behavior of Korean log importing companies make the bargaining power of Korea more weak. 4) It is analyzed that Korean domestic marketing system is comperatively simple, but reasonable marketing system is not established because of the disorder of the marketing behavior. From the results obtained above, it is proposed that the government has to establish the general institutional system to control the supply-demand and marketing problems of imported log, in order to establish the rational structure of market and price decision system of imported log.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.694-700
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• 2018

Korea has disposed of medium and low level radioactive waste generated by operating nuclear power plants permanently through the radioactive waste repository located in Gyeongju. However, the maritime transport of radioactive waste is exposed to the risk of marine accidents, and it will be necessary to introduce a system to secure safety from the viewpoint of the function and role of the Korea Coast Guard. Especially, Korea is affected by large-scale marine accidents, such as the Hebei Spirit or Sewol accidents. From this point of view, we analyzed the current status of Korea radioactive waste shipping and examined the response systems of major foreign countries. As a result of examining major cases of accidents, we have operated an Emergency Towing Vessel (ETV) fleet centering on European countries in order to respond urgently to marine casualties that may have social, regional and international effects, such as accidents of similar nuclear material carriers and dangerous cargo ships. It proves a partial effect. Based on this, we propose the introduction of the Korean ETV System. In other words, it is necessary to respond to large-scale marine accidents that could lead to enormous environmental, property, and personal damage, such as marine accidents involving nuclear material ships, large oil tankers, and large passenger ships. For this, it seems necessary to introduce Korea ETV, which can carry out emergency towing, oil pollution control function, large - scale rescue equipment and manpower. This will lead to the enhancement of the Korea Coast Guard response to marine accidents, and will not miss the golden time of the initial response to the national disaster, which will help protect precious people, property and the environment.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.90-102
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• 2017

In this study, various types of nutrient models were tested by using two tears's water quality data collected from the stormwater wetland in Korea. Based on results, most important factor influencing nitrogen removal was hydraulic loading rate, which indicates that surface area of wetland is more important than its volumetric capacity, and model proposed by WEF was found to give a least error between measured and calculated values. For the phosphorus, in case assuming a power relationship between rate constant and temperature, the best prediction result were obtained, but temperature was most sensitive parameter affecting phosphorus removal. In addition, denitrification was always a limiting step for the nitrogen removal in this particular wetland mostly due to the lack of carbon source and high dissolved oxygen concentration. In this paper, several alternatives to improve nitrogen removal, including proper arrangement and designation of wetland elements and use of floating plants or synthetic fiber mat to control oxygen level and to capture the algal particles were proposed and discussed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.12
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• pp.1091-1101
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• 2012

Device-to-device (D2D) communication is expected to offer local area services with low transmit power and short link distance, even not via any infrastructures. These advantages will lead to the deployment of D2D systems in a massive scale, where the order of magnitude of D2D user density is higher than that of cellular user density. Network-assisted D2D systems, where D2D resources are managed by cellular networks, are unable to support the large number of D2D devices, due to the signaling overhead for control signals. In this case, no coordination can be an answer. This paper considers uncoordinated D2D systems, which is implemented with a number of D2D devices in a large scale. By analyzing the transmission capacity of D2D systems, we found a feasibility condition under which the uncoordinated D2D communications possibly coexist within cellular networks, sharing the uplink spectrum. In addition, we provide guidelines for the operational points of massive D2D communications, giving some knowledge about proper transmit power level and link distance of uncoordinated D2D.

• Journal of Korean Academy of Nursing
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• v.26 no.3
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• pp.709-729
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• 1996

This study was done to analyze the trends of research on coping in Korea, to suggest future direction, for research on coping, and ultimately to contribute to an increase in explanation of adaptation. This article reviewed 79 nursing research papers on coping done since 1978 by examining them according to the period of publication or presentation, research design, type of subjects, measurement instruments, research for a degree or not, range of reliability, and association of coping and related variables. The results are as follows : The number of studies on coping increased rapidly from the mid-1980's and decreased slowly from the mid-1990's. The maority of the studies were surveys, comparative studies, or correlational studies. The subects of the 46 studies were healthy people, while those in the remaining studies were patients with a variety of illnesses. Thirth-eight studies on coping were done for master's thesis, three for dissertion, and 38 were not degrees. The Bell and Jalowiec coping scales have not been used since the early 1990's. In contrast, Lazarus and Folkman's W.C.C.L. has been used increasingly since that time. The reliabilities of the coping scale were reported in 37 cases and the Cronbach's alpha coefficients were .71 to .86. All subjects reported using more problem-oriented coping than emotion-oriented coping in short-term or emotion-oriented coping and healthy groups did more long-term coping. It was difficult to describe consistently the relationship between stress and coping according to the type of coping scale or research subjects, but generally moderate relationships were found. This was due to instrumental problems and no consideration of situational context. The subject group who used more short-term coping and less long-term coping reported poorer mental status, and higher scores in burnout and state anxiey than others. That is, the relationship between stress and adaptation increased the power of explanation with intervening the mediating effect of coping. The association of locus of control, mastery, social support, and self-concept with coping showed positive relationships : those of uncertainty and severity in illness with coping showed negativerelationships ; those of state anxiety and depression with short-term coping were positive, and those of self-esteem with long-term coping or problem-oriented coping were negative. There were significant differences in the scores of types of coping according to religion, level of education, and socio-economic status. That is, Presbyterians and Catholics, those with higher education levels and higher socio-economic status used more long-term or problem-oriented coping. On the basis of the above findings the following recommendations are made : 1. There is a need to test the mediating effect of coping variable in order to clarify the concept. 2. Longitudinal studies are needed to determine the patterns of change in coping strategies when stressful events are encountered. 3. It's necessary to develop a reliable and variable measurement tool for coping. 4. There is a need to identify subscales of coping to increase explanation of variance 5. It's necessary to consider personal, situational, and antecedent variables : the characteristics of subject populations, the natures of illness and treatment situations. 6. The power of explanation of studies designed to identify the stress-adaptation process should be increased using the combination model of process-oriented coping and cognitive-structural model.

• Korean Security Journal
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• no.16
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• pp.81-99
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• 2008

Despite its legal, systematic and quantitative growth, Korean private security has not been showing satisfactory level of qualitative growth comparing to quantitative growth as it socially shocked with recent occurrence of the events and accidents. People on demand of security are making use of private security service to offset insufficient supply of security power as, especially, the incendiarism at Sungryemun last February brought out security issues for nationally important facilities and cultural assets, and other cases showed that the police would not cope with the appropriate security services under the current security system for protecting the life and property of people. For the supplementation of security power, the private security service is prevalent, but lots of service providers would not overcome its small business scale, except some large-sized security providers. There are some problem occurred as some providers employed staff who would not have the stuff for performing security service and they even committed illegal actions. Some opinions pointed out that it should come up with measures as they socially lose their credit. Therefore, this research suggests the recognition of the importance and the improvement measures of human resources management as follows. Security Service needs: 1. control of criteria for the employment/recruitment of human resources; 2. inducement of qualitative improvement of security service by ensuring excellent quality of human resources; 3. elevation of morale of organizational members with the operation of efficient promotion system; 4. introduction of professional certification system for the inflow of excellent quality of human resources.

• Journal of Korea Water Resources Association
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• v.51 no.12
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• pp.1181-1194
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• 2018

This study suggests a novel approach of estimating stream flow discharge using the Synthetic Aperture Radar (SAR) images taken from 2015 to 2017 by European Space Agency Sentinel-1 satellite. Fifteen small to medium sized rivers in the Han River basin were selected as study area, and the SAR satellite images and flow data from water level and flow observation system operated by the Korea Institute of Hydrological Survey were used for model construction. First, we apply the histogram matching technique to 12 SAR images that have undergone various preprocessing processes for error correction to make the brightness distribution of the images the same. Then, the flow estimation model was constructed by deriving the relationship between the area of the stream water body extracted using the threshold classification method and the in-situ flow data. As a result, we could construct a power function type flow estimation model at the fourteen study areas except for one station. The minimum, the mean, and the maximum coefficient of determination ($R^2$) of the models of at fourteen study areas were 0.30, 0.80, and 0.99, respectively.