• Composites Research
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• v.37 no.3
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• pp.219-225
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• 2024

It is essential to develop a light-weight, high-performance structure for the deployable reflector antenna, which is the payload of a reconnaissance satellite, considering launch and orbital operation performance. Among them, the composite main reflector is a key component that constitutes a deployable reflector antenna. In particular, the development of a high-performance main reflector is required to acquire high-quality satellite images after agile attitude control maneuvers during satellite missions. To develop main reflector, the initial design of the main reflector was confirmed considering the structural performance according to the laminate stacking design and material properties of the composite main reflector that constitutes the deployable reflector antenna. Based on the initial design, four types of composite main reflectors were manufactured with the variable for manufacturing process. As variables for manufacturing process, the curing process of the composite structure, the application of adhesive film between the carbon fiber composite sheet and the honeycomb core, and the venting path inside the sandwich composite were selected. After manufacture main reflector, weight measurement, non-destructive testing(NDT), surface error measurement, and modal test were performed on the four types of main reflectors produced. By selecting a manufacturing process that does not apply adhesive film and includes venting path, for a composite main reflector with light weight and structural performance, we developed and verified a main reflector that can be applied to the SAR(Synthetic Aperture Rader) satellite.

• Journal of Korea Water Resources Association
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• v.57 no.9
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• pp.571-583
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• 2024

Forecasting dam inflows in the medium to long term is crucial for effective dam operation and the prevention of water-related disasters such as floods and droughts. However, the increasing frequency of extreme weather events due to climate change has made hydrological forecasting more challenging. Since 2000, seasonal weather forecasts, which provide predictions for weather variables up to about seven months ahead, and their hydrological interpretation, known as Seasonal Flow Forecasts (SFFs) have gained significant global interest. This study utilises seasonal weather forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF), converting them into inflow forecasts using a hydrological model for 12 multipurpose dams in South Korea from 2011 to 2020. We then compare the performance of these SFFs with the Ensemble Streamflow Prediction (ESP). Our results indicate that while SFFs are more effective for short-term predictions of 1-2 months, ESP outperforms SFFs for long-term predictions. Seasonally, the performance of SFFs is higher in October-November but lower from December to February. Moreover, our findings demonstrate that SFFs are highly effective in quantitatively predicting dry conditions, although they tend to underestimate inflows under wet conditions.

• Explosives and Blasting
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• v.30 no.2
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• pp.29-42
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• 2012

Variables influencing the free face movement due to rock blasting include the physical and mechanical properties, in particular the discontinuity characteristics, explosive type, charge weight, burden, blast-hole spacing, delay time between blast-holes or rows, stemming conditions. These variables also affects the blast vibration, air blast and size of fragmentation. For the design of surface blasting, the priority is given to the safety of nearby buildings. Therefore, blast vibration has to be controlled by analyzing the free face movement at the surface blasting sites and also blasting operation needs to be optimized to improve the fragmentation size. High-speed digital image analysis enables the analyses of the initial movement of free face of rock, stemming optimality, fragment trajectory, face movement direction and velocity as well as the optimal detonator initiation system. Even though The high-speed image analysis technique has been widely used in foreign countries, its applications can hardly be found in Korea. This thesis aims at carrying out a fundamental study for optimizing the blast design and evaluation using the high-speed digital image analysis. A series of experimentation were performed at two large surface blasting sites with the rock type of shale and granite, respectively. Emulsion and ANFO were the explosives used for the study. Based on the digital images analysis, displacement and velocity of the free face were scrutinized along with the analysis fragment size distribution. In addition, AUTODYN, 2-D FEM model, was applied to simulate detonation pressure, detonation velocity, response time for the initiation of the free face movement and face movement shape. The result show that regardless of the rock type, due to the displacement and the movement velocity have the maximum near the center of charged section the free face becomes curved like a bow. Compared with ANFO, the cases with Emulsion result in larger detonation pressure and velocity and faster reaction for the displacement initiation.

• Archives of design research
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• v.18 no.2 s.60
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• pp.155-164
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• 2005

Home-service robots need to have sufficient spatial information about the surroundings for interacting with human intelligently and performing services efficiently. It is very important to investigate the efficient interaction style that supports map building task through human-robot collaboration. We first analyzed map building task with a cleaning robot and drew 4 design factors and tentative solutions, including map building procedure (task-preferred procedure/space- preferred procedure), LCD display installation (robot/robot+remote control), navigation method (push type/pull type), feedback modality(GUI/GUI+TTS). The design factors and tentative solutions were defined as independent variables and levels. This research investigated how those variables affect to the human task performance and behavior in map building tast. 8 kinds of experiment prototypes were built and usability test among 16 house wives was conducted for acquiring empirical data. As the experiment result, in terms of map building procedure, space-preferred procedure indicated better task performance than task-proffered procedure as we expected. For the LCD display installation factor, remote control with LCD display indicated higher task performance and subjective satisfaction. In robot navigation method, it was very difficult to find a significant difference between push type and pull type which contrary to our expectation. In fact, push type indicated higher subjective satisfaction. Also in feedback modality, we have acquired negative feedback an additional TTS operation guidance. It seems that robot's autonomy before achieving spatial information is rudiment condition which means users are just interacting with a mobile appliance. Thus they prefer remote-control-based interaction style in robot map building process as they used in traditional appliance control.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.6 no.3
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• pp.414-433
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• 1999

The purpose of this study is to identify the needs which are perceived by one of the familiy members who have head injury parients by traffic accidents in the intensive care units. Subjects were 70 families members of head injury patients admitted to 2 general hospitals NICU located Pusan city, 1 general hospital NICU located Ulsan city from December 1. 1998 to February 28. 1999. For this study, 70 family members were interviewed with aid of a Likert scale which was developed by researcher for this study. For development of the survey instrument, literature review and open questionnaire technique with family members and the nurses working in NICU. The 50needs-items were classified into 7 groups according to the homogeneity of the items with the support of literature review. For the content validity, the instrument was reviewed by 1 nursing professor and the internal reliability of this instrument was Cronbach alpha=0.94 which is highly accepted. Data was analyzed by a SPSS computer program. Data analysis included frequency. percentage, mean, standard variance and t-test or ANOVA. The results were as followings : 1. The general characteristics of head injury patients shows that the male was 74.3%, the female was 25.7% and age distribution shows that the fifty-fifty nine years was 30%, the highest. Of religion the buddhism was the most, The diagnosis distribution shows that epidural hematoma was 32.9% and subdural hematoma was 24.3%. The mentalility distribution shows that semicoma was 31.4% and stupor was 31.4%. Hemiplegia was 42.9% 2. The general charaterisrics of the family needs of head injury patients shows that thirty-thirty nine years was 31.4%, the highest. sex distribution shows that the male was 20%, the female was 80%. Of religion the buddism was the most. 3. The family needs of head injury patients was $3.03{\pm}0.42$, needs for the information of a patient's condition was $3.65{\pm}0.48$, the highest. And needs for the information of care and treatment was $3.48{\pm}0.48$, needs to be supplied with comfortable facilities for family was $3.04{\pm}0.66$, needs to be participate in a patient's care was $2.90{\pm}0.55$, needs to be informed about the available resources was $2.83{\pm}0.59$, needs to be supported emotionally for family was $2.79{\pm}0.55$, needs for religious assistance was $2.51{\pm}0.85$. 4. Examining the family needs of head injury patients according to patient's characteristics, mentality, plegia degree and operation were shown be variables to make an effect on the needs for the head injury patients family. At all, according to severity of head. injury, the family needs of head injury patients was high. 5. Examining the family needs of head injury patients according to their general characteristics, we could know that religion, job. income were shown to be variables to make an effect on the family needs. Through the examination it can be seen that the characteristics of head injury patients and the family needs of head injury patients. In conclusion, the family needs of head injury patients was almost same the family needs of ICU patients. Therefore we must involve the family's care of head injury patients and we must provide exact and repeated explanation, education and support the family of head injury patients. As this study was resulted in selecting the families admitted to NICU of some general hospital, we couldn't stretch the result in our favor. Therefore, continuous studies are suggested.

• Journal of Korean Academy of Nursing Administration
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• v.7 no.2
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• pp.265-284
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• 2001

The case management has been applied to improve the quality of care and the cost-effectiveness in the most health care institutions. In a way of case management, the critical pathway(CP) has been executed in many acute care settings, focused on the diagnoses with high cost, high volume, and high risk. This study was conducted to develop a case management program using CP as an intervention of patients with lumbar spinal stenosis for the surgery of posterolateral fusion, and to find out the effects of the critical pathway on the quality of nursing care, patient satisfaction as an outcome of care, length of stay and medical charge, and nurses' job satisfaction. At the same time, patients' functional states were checked with the Oswestry Low Back Pain Index, to show that the CP would not decrease the patients' function compared to the control group. The subjects were 25 control patients with a usual operation of lumbar fusion and 25 experimental patients with CP. They were all female, aged $50s{\sim}70s$, admitted in the Orthopedic surgery ward of a university hospital. Also nurses on the floor using CP were asked to respond to measurement tool of job satisfaction before and after the application of CP, and compared with other nurses on the different wards. Data were analyzed with t-test for continuous variables and chi-square for non-parametric variables in addition to the reliability test of the measurement tools. The results of this study were as followings: 1. Patients' functional states The differences in Oswestry scores of the experimental and control groups assessed at preoperation and at discharge were not statistically significant. The change in scores of the experimental group measured at preoperation and at discharge was larger than that of the control group, however the difference was not statistically significant. The results indicate that the CP did not decrease the patients' functional status. 2. The quality of nursing care The total of quality of nursing care given to the experimental group was better than that of the control group(P=.000). In addition, the experimental group showed better scores of quality of every item of care than the control group(P=.000 -.004). 3. Patient satisfaction Patients of the experimental group were not more satisfied with general care than the control group. But they were more satisfied with discharge care of 'explanation about medication, body posture, and brace application' and 'explanation about the adjustment of daily living and exercise during recovery'(P= .047, P=.028). 4. Nurses' job satisfaction Nurses working with the CP showed more job satisfaction than before the CP introduction(P=.048). But the control group of nurses on a different floor showed no change in job satisfaction at the same period of time. 5. Length of stay and medical charge The mean length of stay of the experimental group was shorter than that of the control group without statistical significance. The charge of medication and treatment of the experimental group were smaller than that of the control group(P=.011, P=.000). The results of the study support that the case management using critical pathway enables to improve the quality of care and job satisfaction, to reduce the medical charge, and consequently to increase satisfaction with care. However, the case management should be instituted focusing on the quality improvement of nursing and the client satisfaction, not just for the purpose of cost-effectiveness of health care facilities.

• Journal of the Korean Institute of Landscape Architecture
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• v.16 no.2
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• pp.43-57
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• 1988

The purpose of this thesis is to suggest objective basic data for park management proposal through the quantitative analysis of users' behaviors and satisfaction for the actual conditions of management in the Chiri Mountain National Park. For this users' behaviors and socio-economic characteristics have been cross-analyzed. Specifically, it attempts to investigate users' anticipate and degree of satisfaction applied Expectancy Theory by Likert attitude scale. Users'behaviors patterns of each site have been analyzed by the factor analysis algorithm, and each factor scores of sites have been clustered by the cluster method. And also user' satisfaction for the actual conditions of management have been analyzed by using the multiple regression. The major user groups were students and youth groups accompanied by their friends ranging from 3 to 10. The values of user'post occupancy-evaluation for such as rockwall climbing and praying on the mountain of each site showed higher than those of anticipated, but evaluation values of other activities were lower. The user'behaviors of each site have been analyzed five factors by factor analysis algorithm. By using the control method for the number of factors, T.V. has been obtained as 50.58%. The factor score of factor covering the behavior patterns of student and youth yield high EV. and C.V.. On the analysis of cluster using factor score, factor IV in Hwaomsa temple site and Ssanggyesa temple site, factor II, v in Jungsanri Valley site, factor, I, III in Bangmudong valley site and factor I. IV in Baemsagol vallry site showed very high values, respectively. According to the multiple regression analysis, the major variables related to the satisfaction for the actual conditions of vegetation and landscape managements were reservation of groundcover, recovery of artificial injury, the surroundings of camping and temple site. In the park facilities and operation, the major variables related to the satisfaction were conditions of management such amenity facilities as privy, sign board, junk yard, camping site, and guidance of excursion, campaign and preservation of nature.

• Journal of Korea Port Economic Association
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• v.37 no.4
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• pp.127-144
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• 2021

The purpose of this study is to derive service factors based on the "Rail Statistical Yearbook" data of railroad service providers from 1990 to 2019, and to analyze the effect of the service factors on the operating profit ratio(OPR), a representative management performance variable of railroad transport service providers. In particular, it has academic significance in terms of empirical research to evaluate whether the management innovation of the KoRail has changed in line with the purpose of establishing the corporation by dividing the research period into the first period (1990-2003) and the latter (2004-2019). The contents of this study investigated previous studies on the quality of railway passenger transportation service and analyzed the contents of government presentation data related to the management performance evaluation of the KoRail. As an empirical analysis model, a research model was constructed using OPR as a dependent variable and service factor variables of infrastructure, economy, safety, connectivity, and business diversity as explanatory variables based on the operation and management activity information during the analysis period 30 years. On the results of research analysis, OPR is that the infrastructure factor is improved by structural reform or efficiency improvement. And economic factors are the fact that operating profit ratio improves by reducing costs. The safety factor did not reveal the significant explanatory power of the regression coefficient, but the sign of influence was the same as the prediction. Connectivity factor reveals a influence on differences between first period and latter, but OPR impact direction is changed from negative in before to positive in late. This is an evironment in which connectivity is actually realized in later period. On diversity factor, there is no effect of investment share in subsidiaries and government subsidies on OPR.

• Journal of Korea Port Economic Association
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• v.37 no.4
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• pp.161-173
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• 2021

The shipping industry plummeted and was depressed due to the global economic crisis caused by the bankruptcy of Lehman Brothers in the US in 2008. In 2020, the shipping market also suffered from a collapse in the unstable global economic situation due to the COVID-19 pandemic, but unexpectedly, it changed to an upward trend from the end of 2020, and in 2021, it exceeded the market of the boom period of 2008. According to the Clarksons report published in May 2021, the decrease in cargo volume due to the COVID-19 pandemic in 2020 has returned to the pre-corona level by the end of 2020, and the tramper bulk carrier capacity of 103~104% of the Panamax has been in the ports due to congestion. Earnings across the bulker segments have risen to ten-year highs in recent months. In this study, as factors affecting BDI, the capacity and congestion ratio of Cape and Panamax ships on the supply side, iron ore and coal seaborne tonnge on the demand side and Granger causality test, IRF(Impulse Response Function) and FEVD(Forecast Error Variance Decomposition) were performed using VAR model to analyze the impact on BDI by congestion caused by strengthen quarantine at the port due to the COVID-19 pandemic and the loading and discharging operation delay due to the infection of the stevedore, etc and to predict the shipping market after the pandemic. As a result of the Granger causality test of variables and BDI using time series data from January 2016 to July 2021, causality was found in the Fleet and Congestion variables, and as a result of the Impulse Response Function, Congestion variable was found to have significant at both upper and lower limit of the confidence interval. As a result of the Forecast Error Variance Decomposition, Congestion variable showed an explanatory power upto 25% for the change in BDI. If the congestion in ports decreases after With Corona, it is expected that there is down-risk in the shipping market. The COVID-19 pandemic occurred not from economic factors but from an ecological factor by the pandemic is different from the past economic crisis. It is necessary to analyze from a different point of view than the past economic crisis. This study has meaningful to analyze the causality and explanatory power of Congestion factor by pandemic.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.18 no.2
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• pp.187-200
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• 2023

The purpose of this study is to examine how the start-up education, start-up support system, and start-up mentoring directly and indirectly conducted in universities affects entrepreneurial Intention, and to present programs and directions that can increase the possibility of start-up for college students. This study analyzed the effects of college students' satisfaction with university entrepreneurship education, awareness of the entrepreneurship support system, and entrepreneurship mentoring on entrepreneurial will, and then analyzed how entrepreneurship efficacy affects entrepreneurial will as a moderating effect. The recognition of the start-up support system was divided into the government start-up support policy and the university start-up support project, and start-up mentoring was divided into mentoring function (problem-solving function, networking function, communication function, motivation function) and mentor trust (cognitive trust, emotional trust). Regression analysis was performed on satisfaction with college entrepreneurship education, perception of entrepreneurship support system, entrepreneurship mentoring as independent variables, and willingness to entrepreneurship as dependent variables. In addition, entrepreneurship efficacy was designated as a moderating variable and analyzed. As a result of the study, first, it was found that satisfaction with start-up education had a positive (+) effect on college students' willingness to start a business. Second, among the start-up support systems, university start-up support projects were found to have a positive (+) effect on college students' willingness to start a business. Third, as a result of verifying whether entrepreneurial self-efficacy has a moderating effect on the relationship between college start-up support projects and college students' willingness to start a business while recognizing the start-up support system, it was found to have a moderating effect. The following implications can be derived based on the analysis results of this study. First, efforts to improve start-up education will be needed to increase the satisfaction of start-up education. Second, Through the operation of the start-up counseling center in the university, it will be possible to recognize the education system supported by the university, the university start-up support project that can carry out the indirect experience of start-up, and the government start-up support policy that supports funds. Third, It will be necessary to open a program that can provide start-up mentoring through connection with mentors in the start-up field, such as professors, employees, and senior start-ups in universities. Fourth, It is necessary to develop thorough education on the preparation process of start-ups, start-up special lectures where senior start-ups can indirectly experience the failure of start-ups, and programs for customized start-up education according to college students' major and individual tendencies.