• Korean Journal of Materials Research
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• v.34 no.2
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• pp.111-115
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• 2024

Silicon carbide (SiC) has emerged as a promising material for next-generation power semiconductor materials, due to its high thermal conductivity and high critical electric field (~3 MV/cm) with a wide bandgap of 3.3 eV. This permits SiC devices to operate at lower on-resistance and higher breakdown voltage. However, to improve device performance, advanced research is still needed to reduce point defects in the SiC epitaxial layer. This work investigated the electrical characteristics and defect properties using DLTS analysis. Four deep level defects generated by the implantation process and during epitaxial layer growth were detected. Trap parameters such as energy level, capture-cross section, trap density were obtained from an Arrhenius plot. To investigate the impact of defects on the device, a 2D TCAD simulation was conducted using the same device structure, and the extracted defect parameters were added to confirm electrical characteristics. The degradation of device performance such as an increase in on-resistance by adding trap parameters was confirmed.

• Korean Journal of Social Welfare
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• v.58 no.4
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• pp.341-369
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• 2006

This study attempts to explain how the social-worker empowerment in the field of social work relates to social-work self-efficacy and whether or not the transactional leadership of the leader moderates the relationship between these two variables. Data from 390 social workers working with public and private sector agencies in Seoul were collected. For the questionnaire and analysis, this research uses the Social Worker Empowerment, Social Work Self-Efficacy, and Transactional Leadership scales. This research utilizes a wide range of statistical analyses, such as descriptive analysis, Pearson's correlation, reliability analysis, factor analysis, multiple regression, and general linear modeling. The calculations employed the use of SPSS/PC+ 12.0. This research indicates, among other things, that social workers with a high level of social worker empowerment and transactional leadership of the leader show a tendency toward higher social work self-efficacy and that the leader's transactional leadership level plays a moderating function in the relationship between social-worker empowerment and transactional leadership of the leader. In conclusion, a social worker with a low level of leader's transactional leadership shows a relatively greater tendency toward social work self-efficacy when compared to a social worker having a high level of leader's transactional leadership. Social workers and social-work organizations seeking professional practice can benefit from these findings on the relationship between professional behavior and social work self-efficacy with perceived transactional leadership about a team leader as a moderator.

• Korean Journal of Construction Engineering and Management
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• v.10 no.5
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• pp.113-122
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• 2009

The domestic construction market started to expand steadily since 1970s. The building market which utilizes a sandwich panel with advantages of economical construction expenses and convenient construction has grown rapidly in recent years. However, the companies which specialize in constructing sandwich panels are relatively small or medium size, compared with other construction companies. As a result, studies on the improvement of productivity have not been conducted sufficiently. In this study, the construction sites of sandwich panel are investigated, and the work processes by each team are analyzed. Additionally, the productivity and the construction cost of each work group are analyzed by constructing a model using the Web-Cyclone. It analyzed sensitivities about change of productivity and work costs following in processing place of the panel which is one of the productivity effect factors, so it assayed the optimized productivity by each work group and work costs. Analysis showed that 30% of productivity has improved compared with the factory processing work group, and analysis of work costs showed that about 15% of work costs was increased. Also sensitivity analysis of opening ratio showed that the work costs optimization will be accomplished when about 20% of opening was processed from the factory.

• Korea Journal of Hospital Management
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• v.7 no.2
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• pp.99-123
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• 2002

This study was conducted to determine whether follow-up management is carried out continuously following CQI activity and to analyze the factors behind the success and failure of follow-up management. Past presentations from 1994-1999 of CQI coordinators and lecturers from various institutions who presented at The Korean Society of Quality Assurance in Health Care(KoSQA) on the conditions of follow-up management in each institution were analyzed. The results of this study were as follows; Since the number of subjects on CQI increased each year at symposiums, this has expanded to all medical institutions. Although medical institutions usually conduct 11-20 subjects on CQI per year, there were many such occasions where more than 31 subjects were conducted. Moreover, institutions with less than 800 beds have come up with more projects than those with more than 800 beds, thus 23.3% of these institutions had at least 1 person involved in 4 projects. This had created an overload of responsibilities for specific persons' involvement, prompting them to incline toward formalities in their work rather than substantial activities. Among the projects presented at the symposiums, 51.7% demonstrated that follow-up management could be carried out. In particular, 55.3% of the projects from provincial regions could carry out follow-up management compared to 48.8% in Seoul. Moreover, it was demonstrated that 80% of the projects from institutions with 600-799 beds carried out follow-up management most effectively. With regards to previous presentations, the older they were, it was found that follow-up management could not be effectively carried out. Some institutions that responded that follow-up management was carried out effectively in their institutions were found to have conducted follow-up management without any inspection strategies or the appropriate tools. CQI activities were executed and terminated with no consistency and team members had no real concern for it. The most important factors that contribute to an effective follow-up management are the need for concern and interest from the directors of the hospitals, from the relevant departments and team members in addition to the role of the supervising department, follow-up management through management of target goals, consistency in tasks along with communication between all team members. The biggest problems were perceived to be overload of work due to accumulation of proposed projects in addition to lack of awareness pertaining to follow-up management. CQI is beneficial for all staff for the improvement of the mind and business administration and thus it is believed to be desirable. To carry out follow-up management effectively, leadership, analysis and application of information, follow-up management and planning, as well as quality management are perceived to be essential, on the other hand, the results showed a significant difference. To prevent CQI activities from becoming just an activity, the basic system should be reconstructed and augmented based on the problems derived from the results of this study. Moreover, we hope this study will be used as reference material that would encourage the administration of follow-up management after CQI activities in most hospitals. Furthermore, various studies on follow-up management should be conducted for CQI activities in the future.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.6
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• pp.628-638
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• 2017

In response to difficult employment conditions in the maritime industry and a desire to expand their career options, domestic mates are persuing DP operator training at institutions both domestically and abroad based on their shipboard experience. However, since the offshore plant service industry has not yet been established in Korea, those seeking to enter this field have difficulty acquiring qualifications and most seek work overseas for offshore shipping companies. Individuals wishing to work as DP operators are likely to face more conservative recruitment processes with overseas offshore shipping companies, focusing on career language restrictions as they will be non-native speakers relative to the foreign company, difficulty living in a multi-cultural environment, and lack of systematic information on essential job requirements. For these reasons, domestic mates have difficulty seeking jobs. Therefore, this study analyzes the capabilities and qualification required to be a DP operator to provide basic data for developing NCS standards representing a minimum level of competency. These standards can be applied by the government to develop plans for professional training for DP operators. In study, job classifications, competency standards and career development paths for DP operators have been proposed along with joint use of DP training vessels, to train specialized DP instructors. An NCS export model led by the government to activate professional training for DP operators is also presented.

• Fire Science and Engineering
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• v.33 no.6
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• pp.165-172
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• 2019

This study presents the design and manufacture of a self-contained breathing apparatus SCBA wireless communication module with a multipoint simultaneous full-duplex communication system to enable communication between team members wearing the SCBA system. It is necessary for fire-fighters to wear the SCBA system during extinguishing and rescue work at the fire site. Evaluation of the team communication module confirmed the feasibility of communication over more than 500 m in the test condition based on the line of sight. By implementing the Ad-hoc function, it was confirmed that the communication distance could be extended to 128 m by automatic routing up to 3 hoc. The vertical distance inside the building for successful communication was up to the 5th floor in the open staircase and up to the 3rd floor in the partitioned staircase. Furthermore, the performance testing of the communication module assuming a fire situation, confirmed that five team members correctly recognized the standard abbreviation of fire and wireless communication without a separate PTT key operation. In addition, the flame resistance was verified by exposing the module to a flame at 950 ± 50 ℃ for 5 s and then immediately extinguishing the flame.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.8
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• pp.692-700
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• 2014

In this work, satellite FE (finite element) model updating for the prediction of the effect of micro-vibration is described. In the case of satellites launched in low earth orbit, high agility and more mission accomplishments are required by the customer in order to procure many images from satellites. To achieve the goal, many mechanisms, including high capacity wheels and antennas with multi-axis gimbals have been widely adopted, but they become a source of micro-vibration which could significantly deteriorate the quality of images. To investigate the effect due to the micro-vibration in orbit on the ground, a prediction is conducted through an integrated model coupling the measured jitter sources with FE (finite element) model. Before prediction, the FE model is updated to match simulation results with the modal survey test. Subsequently, the quality of FE model is evaluated in terms of frequency deviation error, the resemblance of mode shapes and FRFs (frequency response functions) between test and analysis.

• 대한공업교육학회지
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• v.42 no.1
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• pp.87-105
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• 2017

The purpose of this study was to verify that students' interest in team activities for problem solving, the effect of interest on it, and students' changes in perceptions and their behavioral characteristics in the process of problem solving. The study reviewed documents prepared by students, such as work sheets, descriptive questionnaires, works and their photos, student activity photos and observation journals of teachers. The results of this research are as below. First, a problem solving team activity for making a model car was considered an interesting assignment by more than 90% of male/female students. The fact that female students could be more focused on this assignment than male students was discovered. Interest in the assignment not only had an influence on the points from the start (the blueprint) to the end (model cars completed based upon the designs) of problem solving, but also provided the traction power behind the assignment. Second, the problem solving team activity allowed the students to change their existing recognition (thoughts) while positively taking a lead or indirectly utilizing various learning experiences (including experiences of failure). Third, $2^{nd}$ graders in middle school had a tendency to solve problems in dependently rather than to receive help from others when they encountered problematic situations.

• Journal of Radiation Protection and Research
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• v.42 no.1
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• pp.33-41
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• 2017

Background: Phosphate rock and its by-product are widely used in various industries to produce phosphoric acid, gypsum, gypsum board, and fertilizer. Owing to its high level of natural radioactive nuclides (e.g., $^{238}U$ and $^{226}Ra$), the radiological safety of workers who work with phosphate rock should be systematically managed. In this study, $^{238}U$, $^{232}Th$, $^{226}Ra$, and $^{40}K$ levels were measured to analyze the transport characteristics of these radionuclides in the production cycle of phosphate rock. Materials and Methods: Energy dispersive X-ray fluorescence and gamma spectrometry were used to determine the activity of $^{238}U$, $^{232}Th$, $^{226}Ra$, and $^{40}K$. To evaluate the extent of secular disequilibrium, the analytical results were compared using statistical methods. Finally, the distribution of radioactivity across different stages of the phosphate rock production cycle was evaluated. Results and Discussion: The concentration ratios of $^{226}Ra$ and $^{238}U$ in phosphate rock were close to 1.0, while those found in gypsum and fertilizer were extremely different, reflecting disequilibrium after the chemical reaction process. The nuclide with the highest activity level in the production cycle of phosphate rock was $^{40}K$, and the median $^{40}K$ activity was $8.972Bq{\cdot}g^{-1}$ and $1.496Bq{\cdot}g^{-1}$, respectively. For the $^{238}U$ series, the activity of $^{238}U$ and $^{226}Ra$ was greatest in phosphate rock, and the distribution of activity values clearly showed the transport characteristics of the radionuclides, both for the byproducts of the decay sequences and for their final products. Conclusion: Although the activity of $^{40}K$ in k-related fertilizer was relatively high, it made a relatively low contribution to the total radiological effect. However, the activity levels of $^{226}Ra$ and $^{238}U$ in phosphate rock were found to be relatively high, near the upper end of the acceptable limits. Therefore, it is necessary to systematically manage the radiological safety of workers engaged in phosphate rock processing.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.1
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• pp.80-87
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• 2016

In this work, we conduct a thermal pointing error analysis of the observation satellites considering seasonal and daily temperature variation with interpolated temperature based on prescribed average temperature (PAT) method. Maximum 200 degree temperature excursion is applied to the observation satellites during on-orbit operation, which cause the line of sight (LOS) to deviate from the designated pointing direction due to thermo-elastic deformation. To predict and adjust such deviation, the thermo-elastic deformation analysis with a fine structural finite element model is accomplished with interpolated thermal maps calculated from the results of on-station thermal analysis with a coarse thermal model. After verifying the interpolated temperatures by PAT with two benchmark problems, we evaluate the thermal pointing error.