• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.20-24
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• 2003

The feasibility of hybrid motor as a first stage of the air launch vehicle is investigated, and the result shows the hybrid motor can replace the solid motor. Optimal design study has been performed for the hybrid motor as a first stage of nanosat air launch vehicle. The first stage hybrid motor of the nanosat air launch vehicle, which uses the F-4E Phantom as a mother plane is designed for given mission requirements. Selected design variables are the number of ports, the initial oxidizer flux, the combustion chamber pressure, and the nozzle expansion ratio. The design results show that a hybrid motor can be successfully applicable to very small air launch vehicles which have severe physical constraints of length and diameter imposed by the mother plane.

• Clinical Endoscopy
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• v.56 no.2
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• pp.229-238
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• 2023

Background/Aims: Shear wave elastography (SWE) is used for liver fibrosis staging based on stiffness measurements. It can be performed using endoscopic ultrasound (EUS) or a transabdominal approach. Transabdominal accuracy can be limited in patients with obesity because of the thick abdomen. Theoretically, EUS-SWE overcomes this limitation by internally assessing the liver. We aimed to define the optimal technique for EUS-SWE for future research and clinical use and compare its accuracy with that of transabdominal SWE. Methods: Benchtop study: A standardized phantom model was used. The compared variables included the region of interest (ROI) size, depth, and orientation and transducer pressure. Porcine study: Phantom models with varying stiffness values were surgically implanted between the hepatic lobes. Results: For EUS-SWE, a larger ROI size of 1.5 cm and a smaller ROI depth of 1 cm demonstrated a significantly higher accuracy. For transabdominal SWE, the ROI size was nonadjustable, and the optimal ROI depth ranged from 2 to 4 cm. The transducer pressure and ROI orientation did not significantly affect the accuracy. There were no significant differences in the accuracy between transabdominal SWE and EUS-SWE in the animal model. The variability among the operators was more pronounced for the higher stiffness values. Small lesion measurements were accurate only when the ROI was entirely situated within the lesion. Conclusions: We defined the optimal viewing windows for EUS-SWE and transabdominal SWE. The accuracy was comparable in the non-obese porcine model. EUS-SWE may have a higher utility for evaluating small lesions than transabdominal SWE.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.585-596
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• 2016

This study was designed to examine the relationships among the levels of perceived stress, dietary behaviors, physical exercise, drinking, smoking, and relief from fatigue through sleep which affect the subjective happiness in adolescents. Based on the study findings, this paper proposes the basic data required for offering practical solutions to improve the subjective happiness of adolescents. IBM SPSS 20 and AMOS 23 were used to conduct frequency and descriptive analyses, in conjunction with Pearson's correlation coefficients, the AMOS bootstrapping method and phantom variables, for the raw data obtained from the 9,599 participants included in the 11th Korea Youth Risk Behavior Web-based Survey. Those factors having a direct effect on the subjective happiness of the adolescents were the level of perceived stress, relief from fatigue through sleep, physical exercise, dietary behavior and smoking. Perceived stress had an indirect effect on subjective happiness, and the analysis of the indirect effect and significance level of multiple mediators by means of phantom variables showed that, as well as perceived stress, relief from fatigue through sleep, physical exercise, dietary behaviors, and smoking also had indirect effects on subjective happiness. Consequently, a multidisciplinary approach is needed to optimize the subjective happiness in adolescents and financial support for environmental improvements is particularly necessary.

• Human Ecology Research
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• v.55 no.6
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• pp.609-623
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• 2017

Fur apparel is a representative luxury item that displays wealth and social status; however, it is also recognized as an unethical product criticized for its animal maltreatment in the production process. Understanding consumer responses to an ambivalent object, such as fur apparel, is an important research topic both academically and practically. This study investigates the hierarchical effects of perceived benefits and risks of fur apparel on consumers' emotions and purchase intention by applying the ABC model of attitudes to identify the mediating effects of consumer emotions. An online survey was conducted on 390 female consumers that verified hypotheses through structural equation modeling and bootstrapping analysis using phantom variables. The initial results of the survey showed that the relationship between perceived conspicuous benefits and purchase intention towards fur apparel was partially mediated by positive emotion. Second, the relationship between perceived epistemic benefits and purchase intention was completely mediated by positive emotion. Third, the relationship between perceived ethical risk and purchase intention was completely mediated by positive and negative emotions. Fourth, perceived social risk did not affect the purchase intention of fur apparel significantly. The results support that cognitive beliefs about the subject have a significant positive effect on behavioral intentions through emotions as suggested in the ABC model of the attitude. This study provides an in-depth understanding of consumer responses to ambivalent objects by revealing the individual mediating effects of consumers' positive and negative emotions.

• Journal of East-West Nursing Research
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• v.24 no.2
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• pp.171-181
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• 2018

Purpose: The study aimed to validate a structural model of self-concept among children and adolescents from multicultural families. Methods: Data were collected from 325 mothers of multicultural families and their 417 children. Confirmatory factor analysis, path analysis and multiple mediation analysis with a phantom variable approach were used to assess construct validity and relations between model variables. Results: Goodness of fit indices of the modified theoretical model, the standardized ${\chi}^2$ (2.75), RMR (.02), RMSEA (.07), NFI (.90), TLI (.92), CFI (.94), GFI (.89), and AGFI (.87), met criteria. Social support and mental health problem had significant direct effects on self-concept, whereas residential environment and school adjustment had significant indirect effects, accounting in combination for 53% of the variance in self-concept. Conclusion: Based on the results, mental health problem mediated the relationships of self-concept and parenting stress.

• The Journal of Korean Society for Radiation Therapy
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• v.33
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• pp.25-33
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• 2021

Purpose : The purpose of this study is to evaluate the accuracy and usefulness of the Trigger mode for the Respiratory Gated Radiation Therapy (RGRT) Materials and methods : A QUASAR respiratory phantom that inserted a 3 mm fiducial marker (a gold marker) was used to estimate the accuracy of the Trigger mode. And the 20 bpm was used as reference respiration rate in this study. The marker that placed at the center of the phantom was contoured, and the lower threshold of a gating window was fixed at 2.0 mm using an OBI with Truebeam STx^TM. The upper threshold was measured every 0.5 mm from 1.0 mm to 3.0 mm. The respiration rates were changed every 10 bpm from 10 bpm to 60 bpm. We repeatedly measured five times to check the error rate of the trigger mode in the same condition. Result : The differences of a distance from a peak phase to upper threshold, 1.0 to 3.0 mm at a 20 bpm as a reference for 3 days in a row were 0.68±0.05 mm, 0.91±0.03 mm, 1.23±0.03 mm, 1.42±0.04 mm, and 1.66±0.06 mm, respectively. Measurement result of changes in respiratory rate compared to baseline respiratory rate in maximum absolute difference. The coefficient of determination (R2) to estimate the correlation between the respiration velocity and variation of absolute difference was on average 0.838, 0.887, 0.770, 0.850, and 0.906. The p-values of all the variables were below 0.05. Conclusion : Using Trigger mode during respiratory gated radiation therapy (RGRT), accuracy and usefulness of trigger mode at reference breathing rate were confirmed. However, inaccuracies depending on the rate of breathing it could be uncertain in case of respiration rate is faster than 20 bpm as a standard respiration rate compared to slower than 20 bpm. Consequently, when conducting a RGRT using the trigger mode, real time monitoring is required with well educated respiration.

• The Journal of Korean Society for Radiation Therapy
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• v.26 no.2
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• pp.163-170
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• 2014

Purpose : If electron, chosen for superficial oncotherapy, was applied with bolus, it could work as an important factor to a therapy result by showing a drastic change in surface dose. Hence the calculation value and the actual measurement value of surface dose of Treatment Planning System (TPS) according to four variables influencing surface dose when using bolus on an electron therapy were compared and analyzed in this paper. Materials and Methods : Four variables which frequently occur during the actual therapies (A: bolus thickness - 3, 5, 10 mm, B: field size - $6{\time}6$, $10{\time}10$, $15{\time}15cm2$, C: energy - 6, 9, 12 MeV, D: gantry angle - $0^{\circ}$, $15^{\circ}$) were set to compare the actual measurement value with TPS(Pinnacle 9.2, philips, USA). A computed tomography (lightspeed ultra 16, General Electric, USA) was performed using 16 cm-thick solid water phantom without bolus and total 54 beams where A, B, C, and D were combined after creating 3, 5 and 10 mm bolus on TPS were planned for a therapy. At this moment SSD 100 cm, 300 MU was investigated and measured twice repeatedly by placing it on iso-center by using EBT3 film(International Specialty Products, NJ, USA) to compare and analyze the actual measurement value and TPS. Measured film was analyzed with each average value and standard deviation value using digital flat bed scanner (Expression 10000XL, EPSON, USA) and dose density analyzing system (Complete Version 6.1, RIT, USA). Results : For the values according to the thickness of bolus, the actual measured values for 3, 5 and 10 mm were 101.41%, 99.58% and 101.28% higher respectively than the calculation values of TPS and the standard deviations were 0.0219, 0.0115 and 0.0190 respectively. The actual values according to the field size were $6{\time}6$, $10{\time}10$ and $15{\time}15cm2$ which were 99.63%, 101.40% and 101.24% higher respectively than the calculation values and the standard deviations were 0.0138, 0.0176 and 0.0220. The values according to energy were 6, 9, and 12 MeV which were 99.72%, 100.60% and 101.96% higher respectively and the standard deviations were 0.0200, 0.0160 and 0.0164. The actual measurement value according to beam angle were measured 100.45% and 101.07% higher at $0^{\circ}$ and $15^{\circ}$ respectively and standard deviations were 0.0199 and 0.0190 so they were measured 0.62% higher at $15^{\circ}$ than $0^{\circ}$. Conclusion : As a result of analyzing the calculation value of TPS and measurement value according to the used variables in this paper, the values calculated with TPS on 5 mm bolus, $6{\time}6cm2$ field size and low-energy electron at $0^{\circ}$ gantry angle were closer to the measured values, however, it showed a modest difference within the error bound of maximum 2%. If it was beyond the bounds of variables selected in this paper using electron and bolus simultaneously, the actual measurement value could differ from TPS according to each variable, therefore QA for the accurate surface dose would have to be performed.

• Radiation Oncology Journal
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• v.13 no.2
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• pp.199-203
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• 1995

Purpose: To evaluate the dose under lung block as a function of depth and the effectiveness of a block as a function of block width. Materials and Methods : Field size of mantle field was $22.8{\times}32.4cm^2.$ Dose distribution of the mantle field was measured with two dimensional water phantom system. To analyze the effectiveness of the lung block. central axis plane, 5cm off-axis plane, and 10cm off-axis plane were studied. Results: The dose under the lung block was recorded with maximum at the depth between 5cm and 10cm. In the central axis plane, dosimetric block width was $10-15\%$ less than physical block width. In the 5cm off-axis plane, dosimetric block width was $4-9\%$ less than physical block width. In the 10cm off-axis plane, dosimetric block width was $2\%$ less than physical block width. Conclusion: Depth dependence of the dose under the lung block was founded. Also, block width dependence of the lung block was founded. To induce the accurate relation between the physical block width and the 'effective' block width, it needs more detailed understanding of the variables involved.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.4
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• pp.53-60
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• 2004

Optimal design of the hybrid motor has been performed for the first stage of nanosat air launch vehicle using F-4E Phantom as mother plane. Selected design variables are number of ports, the initial oxidizer flux, the combustion chamber pressure, and the nozzle expansion ratio. GBM(Gradient Based Method) and GA(Genetic Algorithm) are simultaneously used to compare the versatility of each algorithm for optimal design in this problem. Also, two objective functions of motor weight, and length are treated separatedly in the optimization to study how the objective function can affect the optimal design. The design results show that the optimal design can be successfully achieved either using GBM or GA regardless of the choice of the objective function; motor weight or length. And nanosat air launch vehicle which has total mass of 704.74kg, and length of first stage 3.74m is designed.

• Journal of Digital Convergence
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• v.18 no.5
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• pp.485-495
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• 2020

The purpose of this study was to examine the role of self-esteem (SE) and cooperation (CO) in the effect of parental attitudes (PA) as perceived by children on the quality of peer relationships (PR). To this end, the data of 1299 boys and 1278 girls in 4th grade were analyzed using the Korean Children and Youth Panel Survey data. The correlation analysis, confirmatory factor analysis, structural equation modeling using phantom variables and bootstrapping were performed by using SPSS and AMOS programs. The results of this study are as follows. First, perceived PA had a significant effect on SE, CO, and PR, SE had a significant effect on CO and PR, and CO had a significant effect on PR. Second, the serial multi-mediating model that assumed that SE and CO mediate the relationship between PA and PR was found to be appropriate. These results suggest that it is important to consider the child's self-esteem and cooperation with parenting attitudes to improve the child's peer relationship. Future research and clinical implications were discussed.