• Journal of the Korean Society for Marine Environment & Energy
• /
• v.18 no.3
• /
• pp.223-232
• /
• 2015

The present paper considers the conceptual design of floating wave-offshore wind hybrid power generation system. The worldwide demand for ocean renewable energy is increasing rapidly. Wave and offshore wind energy have been attractive among the various ocean renewable energy sources, and the site to generate electricity from wave and offshore wind accords well together. This means that a hybrid power generation system, which uses wave and offshore wind energy simultaneously has many advantages and several systems have been already developed in Western Europe. A R&D project for a 10 MW class floating wave-offshore wind hybrid power generation system has been also launched in Korea. A semi-submersible platform, which has four vertical columns at each corner of the platform to be connected with horizontal pontoons, was designed for this system considering arrangements of multiple wind turbines and wave energy converters. A mooring system and power cable were also designed based on the metocean data of installation site. In the present paper, those results are presented, and the difficulties and design method in the design of hybrid power generation system are presented.

• The Journal of the Korea Contents Association
• /
• v.14 no.7
• /
• pp.550-558
• /
• 2014

The purposes of the study are to introduce and apply an activity that can help improve student-initiated learning on the TOEIC Speaking Test (TOEICST) performance and to see students' attitude toward the activity. Twenty-eight university students in Chungcheong province engaged in learning based on this activity. In the present study, the activity proposed by McCormick and Vercellotti (2013) and Stillwell, Curabba, Alexander, Kidd, Kim, Stone, & Wyle (2010) was modified and adapted[14][19]. The outline of the Task Recording Activity (TRA) consisted of three steps: preparation step, Task Recording Activity step, and evaluation step. As data collection of the study, a survey and students' journal were utilized and qualitatively analyzed. The results showed that student-initiated learning activity could be applied positively not only in communicative lessons, but in TOEICST specific lessons as well. Additionally, participants showed positive attitudes toward self-transcription and self-correction. Some implications of the study are that the TRA can be applied to generate autonomous learners studying for the TOEIC Speaking Test, that the guideline for different proficiency can be developed to help them improve their self-reflection, and that students need to have an active attitude to lead their own learning.

• The Journal of Industrial Distribution & Business
• /
• v.10 no.5
• /
• pp.27-36
• /
• 2019

Purpose - Naver has emerged as a new leader in the open market. While existing open markets such as Gmarket, 11th Street, and so on are suffering from profitability deterioration, Naver is attracting sellers based on low commission and powerful search engine. We would like to analyze the impact of Naver shopping on the national economy, especially on employment, in a situation where the market reaction to Naver's strength as a leader in online shopping is mixed. Research Design, Data, and Methodology - Through the demand inducing inter-industry analysis, we estimate the employment inducement effect by Naver shopping from its shopping transaction. In turn, through the supply inducing inter-industry analysis, we estimate the employment inducement effect by Naver shopping from its low commission and powerful search engine. For the purpose of inter-industry analysis, as of 2018, the most recently announced 2014 inter-industry table (extension table) from the Bank of Korea is used. Results - The results of this study are as follows. First, Naver Shopping is expected to generate 7.8 trillion won's trade in 2018, resulting in 244,225 of job inducement, and 158,598 of employment inducement. In addition, Naver Shopping is estimated to benefit KRW 213 billion to its sellers due to low commission and powerful search function, resulting in 8,667 of job inducement, and 5,655 of employment inducement. Second, in terms of job inducement and employment inducement due to Naver Shopping's trade, transportation, business support service, information and communication, broadcasting, restaurants and lodging were ranked. Third, in terms of job inducement and employment inducement due to Naver Shopping's low commission and powerful search function, restaurants and hospitality, f/b and cigarette manufacturing, construction, and transportation equipment manufacturing were ranked. Conclusions - The number of job inducement resulting from low commission and powerful search engine of Naver shopping in 2018 was 8,667 (3.7% of 244,225, which was caused by transaction in Naver shopping in 2018), and employment inducement was 5,655 (3.7% of 158,598, which was caused by transaction in Naver shopping in 2018), which can be considered as additional employment impacts of Naver Shopping compared to the other online shopping operators.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.26 no.1
• /
• pp.65-74
• /
• 2020

The purpose of this study was to investigate the physical characteristics of marine environment, and to predict the probability of the occurrence of hypoxia in the Dangdong bay. We predicted hypoxia using the logistic regression model analysis by observing the water temperature, salinity, and dissolved oxygen concentration. The analysis showed that the Brunt-Väisälä frequency which was shallow than the deep bay entrance, was higher inside the bay due to a lesser amount of fresh water inflow from the inner side of the bay, and density stratification was formed. The Richardson number, and Brunt-Väisälä frequency were very high occasionally from June to September; however, after September 2, the stratification had a tendency to decrease. Analysis of dissolved oxygen, water temperature, and salinity data observed in Dangdong bay showed that the dissolved oxygen concentration in the bottom layer was mostly affected by the temperature difference (dt) between the surface layer and bottom layer. Meanwhile, when the depth difference (dz) was set as a fixed variable, the probability of the occurrence of hypoxia varied with respect to the difference in water temperature. The depth difference (dz) was calculated to be 5 m, 10 m, 15 m, 20 m, and the difference in water temperature (dt) was found to be greater than 70 % at 8℃, 7℃, 5℃, and 3℃. This indicated that the larger the difference in depth in the bay, the smaller is the temperature difference required for the generation of hypoxia. In particular, the place in the bay, where the water depth dif erence was approximately 20 m, was found to generate hypoxia.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.9
• /
• pp.974-982
• /
• 2009

Photomixing techniques beating two optical signals with different wavelengths and strong correlations are also very useful techniques to make a continuous wave(CW) signals in the range of millimeter(mm) and terahertz(THz) frequencies. An optical double sideband-suppressed carrier(DSB-SC) technique is one of the popular techniques to generate two optical signals with different wavelengths and strong correlations. DSB-SC signals with strong correlations are generated by a CW modulation of an optical carrier with a local oscillator and an optical modulator. In the previous parers related the DSB-SC for producing the CW signals within the range of mm and THz frequencies, there have been no reports why the optical carrier should suppress. In order to clear that, we have analyzed and measured the characteristics of the mm-wave CW signals made by the DSB-SC photomixing in this paper. From our analysis and measurement results, compared with the case of the DSB with the maximized optical carrier, the power and phase noise have improved about 23.9 dB and 21 dBc/Hz(@ 1 MHz offset frequency) in the case of the DSB with the minimized optical carrier (that is to say, the DSB-SC). Consequently, it is evident reason that the optical carrier should sufficiently suppress to obtain the mm-wave CW signals with the high power and low noise. This paper has given very helpful data to make mm- and THz-wave CW signals using photomixing techniques with the DSB-SC because the reason why the optical carrier should be suppressed is reported in this paper based on the numerical and experimental results.

• Asia pacific journal of information systems
• /
• v.18 no.2
• /
• pp.73-94
• /
• 2008

When individuals collaborated in virtual settings, communication is medicated through a variety of communication technologies, and is associated not only with communication effectiveness but also with socio-emotional interactions among group members. In this regards, scholars have examined how technology-mediated communication systems can be designed and used to facilitated communication interaction. However, the empirical results of the previous studies have revealed inconsistencies in the effects of communication media on users' behavioral or attitudinal responses, and on their viable effectiveness in organizations. Some studies claim that computer-mediated communication(CMC) is task-oriented but not suitable for emotional expression since it hinders close interpersonal interaction. On the other hand, some studies argue that individuals are able to develop interpersonal relationships more effectively in a CMC environment than in an FtF-environment. Due to the different perspectives, a theoretical gap exists, and it leads to the inconsistent research findings. The purpose of this paper is to combine the two different perspectives into single unified model, thereby providing a more realistic and comprehensive understanding about virtual collaboration. The present study here sought to answers the following questions with organizational communication perspective: What are the major components of virtual collaboration? What factors affect the performance of virtual collaboration? And what kind of managerial efforts should organization make in order to facilitate CMC media effectiveness in virtual collaboration? Although there is a certain belief that new media, namely technology-mediated communication support would create new opportunities, the problem of "how" or "why" has been an important question that is still not fully addressed. In this regards, we collectively reexamined previous literatures with major issues which are still controversial and integrated various theoretical activity within computer-mediated communication domain: task-oriented approach, socio-emotional approach, and evolutionary psychological approach. Our first contribution is to develop a framework for virtual collaboration by combining two different perspectives into a single unified model, providing a more realistic and comprehensive understanding. The second main contribution is the joint modeling of both social presence and cognitive effort, and the effects on two distinct but important communication outcomes(i.e., take performance and relational development). We tested the research hypotheses which were developed based on the various CMC theories using data gathered through a self-administered mail survey of 127 individuals of 69 virtual workgroups. The proposed model was supported, providing preliminary evidence that the tension between two opposite view should be integrated. The results show that the individual's psychological processes(social presence and cognitive effort) in a virtual environment significantly mediated the effect of CMC inputs (media richness, user adaptation, and shared contest) on the CMC outputs (task performance and relational development). Furthermore, this study shows that the lack of perceived media richness of CMC media can be complemented by user adaptation and shared context. Based on the results, we discuss how communication system should be designed and implemented so as to promote virtual interaction as well as how a virtual workgroup should be composed to complement the lack of media richness. A virtual collaboration using CMC media may create new value by overcoming the logistical constraints. On the other hand, it may also generate various managerial risks such as communicational depersonalization, process dissatisfaction, and low cohesion. Therefore, this study suggests that organization managers should carefully choose the CMC mediums and monitor individual member's cognitive and affective psychological processes during virtual collaboration to reduce potential risks in virtual collaboration.

• Asian Pacific Journal of Cancer Prevention
• /
• v.16 no.17
• /
• pp.7785-7788
• /
• 2015

Utilization of high energy photons (>10MV) with an optimal weight using a mixed energy technique is a practical way to generate a homogenous dose distribution while maintaining adequate target coverage in intact breast radiotherapy. This study represents a model for estimation of this optimal weight for day to day clinical usage. For this purpose, treatment planning computed tomography scans of thirty-three consecutive early stage breast cancer patients following breast conservation surgery were analyzed. After delineation of the breast clinical target volume (CTV) and placing opposed wedge paired isocenteric tangential portals, dosimeteric calculations were conducted and dose volume histograms (DVHs) were generated, first with pure 6MV photons and then these calculations were repeated ten times with incorporating 18MV photons (ten percent increase in weight per step) in each individual patient. For each calculation two indexes including maximum dose in the breast CTV ($D_{max}$) and the volume of CTV which covered with 95% Isodose line ($V_{CTV,95%IDL}$) were measured according to the DVH data and then normalized values were plotted in a graph. The optimal weight of 18MV photons was defined as the intersection point of $D_{max}$ and $V_{CTV,95%IDL}$ graphs. For creating a model to predict this optimal weight multiple linear regression analysis was used based on some of the breast and tangential field parameters. The best fitting model for prediction of 18MV photons optimal weight in breast radiotherapy using mixed energy technique, incorporated chest wall separation plus central lung distance (Adjusted R2=0.776). In conclusion, this study represents a model for the estimation of optimal beam weighting in breast radiotherapy using mixed photon energy technique for routine day to day clinical usage.

• Journal of Korea Spatial Information System Society
• /
• v.10 no.2
• /
• pp.81-93
• /
• 2008

Current re-arrangement of river and waterway has been made uniformly ignoring characteristics of individual rivers thereby aggravating artificial river restructuring. Subsequently this severely affects the rivers' physical, chemical, and biological phenomenon. On the contrary, quantitative techniques to evaluate the aftermath of artificial river disturbance such as uprising of river bed, intrusion of foreign fisheries, and changes of ecological habitats are not available. To establish such quantitative techniques, analysis of river changes to evaluate the major causes of the river disturbance and its impacts is essential. Therefore, this study mainly focused on proposing a method which can be applied for the development of techniques to investigate river disturbance according to the major factors for the domestic rivers using airphotos and GIS techniques. For the analysis, the study area on the downstream of the river was selected and airphotos of the area were converted into GIS format to generate 'shape' files to secure waterways, river banks, and auxiliary data required for analyzing river disturbance. Trend analysis of the waterway sinuosity and changes of the flow path leaded to detailed verification of the river disturbance for specific location or time period, and this enabled to relatively accurate numbers representing sinuosity of the waterway and relevant changes. As the major results from the analysis, the relocation of waterways and the level of river sinuosity were quantified and used to verify the impacts on the stability of the waterways especially in the downstream of the dam. The results from this study enabled effective establishing proper measures against waterways' unstability, and emphasized subsequent researches for identifying better alternatives against river disturbances.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.16 no.4
• /
• pp.155-168
• /
• 2011

Coastal boundary current flows along the eastern boundary of the Yellow Sea and its speed was about 0.l m/s during the summer 2007. In order to find major factors that affect the coastal boundary current in the eastern Yellow Sea, three-dimensional numerical model experiments were performed. The model simulation results were validated against hydrographic and current meter data in the eastern Yellow Sea. The eastern boundary current flows along the bottom front over the upper part of slopping bottom. Strength and position of the current were affected by tides, winds, local river discharge, and solar radiation. Tidal stirring and surface wind mixing were major factors that control the summertime boundary currents along the bottom front. Tidal stirring was essential to generate the bottom temperature front and boundary current. Wind mixing made the boundary current wider and augmented its north-ward transport. Buoyancy forcing from the freshwater input and solar radiation also affected the boundary current but their contributions were minor. Strong (weak) tidal mixing during spring (neap) tides made the northward transport larger (smaller) in the numerical simulations. But offshore position of the eastern boundary current's major axis was not apparently changed by the spring-neap cycle in the mid-eastern Yellow Sea due to strong summer stratification. The mean position of coastal boundary current varied due to variations in the level of wind mixing.

• Korean Journal of Social Welfare
• /
• v.57 no.2
• /
• pp.351-374
• /
• 2005

This study examines dynamics of poverty in Korea, focusing on poverty duration and its determinants. Data come from Korean Labor and Income Panel Study(KLIPS), 1998-2003. KLIPS is a longitudinal survey of 5,000 families and their members which are representative of urban residents in Korea. Respondents of KLIPS annually report detailed information on their income, economic activities, and other socio-economic characteristics. This study use poverty exit probabilities to generate distributions of spell lengths, following Bane and Ellwood(1986)'s methodology. This study finds a high level of poverty exit rates in Korea. About three quarters of those beginning a poverty spell exit from poverty within two years. Only 14.3 percent of all the poverty spells consist of long spells which persists five years or more. Yet, a different picture emerges when spells of the poor persons at a given time are analysed. Persistent poor occupy a considerable share of all the poor. Almost 50 percent of those who would be in poverty at a given time are in the midst of poverty spells lasting five years or more. When repeat spells of poverty are also included in the analyses, the proportion of long-term poor increases further. 63 percent of persons poor at a given time are long-termers. The majority of long-term poor are members of families headed by the aged. They show both a low level of poverty exit rates and a high level of reentry rates, and thus are most likely to experience long-term poverty. In the first place, they occupy a substantial share of all the poor. The second who are likely to be poor longer is members of families headed by non-aged women. Researchers have recentlty paid much attention to the working poor who have increased since the economic crisis in 1997. Yet, it is very likely that families headed by non-aged male who largely consist of the working poor temporarily experience poverty. Findings for this study suggest that further studies and policy proposals addressing persistent poverty are necessary.