• Tunnel and Underground Space
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• v.18 no.2
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• pp.149-161
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• 2008

It is nearly impossible to estimate the exact state of the current rock stress of interest site by the theoretical and physical approaches except some specific geological situations. This means that in-situ stress measurement is a unique way to obtain reliable information on rock stress especially for civil and mining engineering related problems. Since late in the 90's, in-situ rock stress tests have been widely conducted to provide the quantitative information on the stress state of engineering site at the design stage of an underground rock structure in the Kyungsang Basin, Korea. The study area is the near surface regions at the depth less than 300 m in the Kyungsang Basin. It includes Yeosoo to the west and Busan to the east. Totally, 270 in-situ stress measurements were conducted in the surface test boreholes at the depth from 14 m to 300 m by hydraulic fracturing method. In this paper, based on the measurement data set, the overall characteristics of the current in-situ rock stress fields in the study area are briefly described. And also the investigation results on the difference between the stress distributions for the granitoid and the andesitic rock region are also introduced. Finally, the distributions of the regional horizontal stress directions in Busan and the Yangsan faults area are shown.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.645-653
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• 2013

Seoul National University flap(SNUF) blade is a small-scale rotor blade incorporating a small trailing-edge flap control surface driven by piezoelectric actuators at higher harmonics for vibration attenuation. Initially, the blade was designed using two-dimensional cross-section analysis and geometrically exact one-dimensional beam analysis, and its material configuration was finalized. A flap-deflection angle of ${\pm}4^{\circ}$ was established as the criterion for enhanced vibration reduction based on an earlier simulation. The flap-linkage mechanism was designed and static bench tests were conducted for verifying the performance of the flap-actuation mechanism. Different versions of test beds were developed and tested with the designed flap and the selected APA 200M piezoelectric actuators. Through significant improvements, a maximum deflection of ${\pm}3.7^{\circ}$ was achieved. High-frequency experiments were conducted for evaluating the performance, and the transfer function of the test bed was determined experimentally. With the static tests almost complete, the rotor power required for testing the blade in a whirl tower (centrifugal environment) was calculated, and further preparations are underway.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.3
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• pp.255-264
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• 2019

Endodontic treatment of primary molars is a great challenge to the dentists because of their complex morphology. However, there have been limited controlled in vivo studies about filling materials for primary teeth. Hence, the aim of this study is to evaluate and compare histologic responses of different calcium hydroxide canal filling materials that are used in daily clinical practice. Pulpectomies were performed in 132 teeth of the dogs. The root canals were randomly filled with either $Vitapex^{(R)}$ (n = 44), $Metapex^{(R)}$ (n = 44), or $Metapaste^{(R)}$ (n = 44). After 4 or 13 weeks, respectively after operation, the dogs were sacrificed, and teeth were processed for histologic examinations. Inflammatory reaction was evaluated and scored in a blind manner. The Fisher's exact test and Kruskal-Wallis test were used to compare the tested groups. In 4-week-group, all inflammatory responses were in normal range except for fibrosis. In 13-week-group, increased response to various inflammation reaction was shown compared to the 4-week-group. However, there were no statically significant differences between the tested groups in all inflammatory reaction. Overall, there were no significant differences among three materials in responses of apical tissues and all of them showed favorable tissue responses.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.20-25
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• 2019

In this paper, the structural weakness analysis and quality improvement of small fixed wing UAV of the hard landing type were studied. Unlike conventional aircraft, small UAV does not use runways because of its small size. Instead, small UAV use hand launch takeoff and hard landings. This type has many operational advantages because it can take off and land in a narrow space. But, the hard landing has a strong impact on the structure of the UAV and can cause serious damage. In order to analyze the exact cause of this phenomenon, the structural analysis was carried out using the 3D structural analysis program (ABAQUS) to identify the location of the fracture. And to improve the accuracy of the structural analysis, properties of the material were obtained through specimen test. As a result of the analysis, structural weaknesses were identified and improved. Thus, the validity of the study was verified by demonstrating the quality of enhanced structure through a real impact test at a higher level of 1.5 times the maximum impact during operation.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.1
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• pp.29-37
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• 2019

The purpose of this study was to investigate the characteristics of intrusion in primary dentition and to evaluate factors influencing complications of primary and permanent dentition during long-term follow-up period. 61 patients (84 teeth) were selected in this study. Medical records of 61 patients were reviewed and age, gender, cause of injury, site of injury, severity of traumatic injury, other injuries associated with trauma, treatment method, and complications of primary and permanent dentition were examined. Collected data were statistically evaluated using Chi-square test and Fisher's exact test. Intrusion in primary anterior teeth was predominant in boys over girls and fall was the most common cause of trauma. It was most common at home and occurred most in the primary maxillary central incisors. Severity had an effect on the incidence of sequelae in permanent successors (p = 0.014). The incidence of complications was significantly lower in patients with soft tissue injuries than in patients with other periodontal injuries (p = 0.000).

• Investigative Magnetic Resonance Imaging
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• v.25 no.1
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• pp.35-42
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• 2021

Purpose: To evaluate and analyze the adequacy of breast magnetic resonance imaging (MRI)s taken before publication of the 2018 recommendation in South Korea. Materials and Methods: We enrolled 87 cases of breast MRIs, from January 2010 to November 2013, taken at external hospitals in the study. Breast MRI protocol elements are divided into three categories based on the recommendation by the Breast Imaging Study Group of the Korean Society of Magnetic Resonance: (1) Essential elements for breast MRI protocol; (2) Element to consider when evaluating imaging quality; and (3) Optional element for breast MRI protocol. Also, we divided enrolled cases into three groups based on their conducting locations -- (1) Primary hospitals, (2) Secondary hospitals, and (3) Tertiary hospitals-and analyzed them for the adequacy of imaging protocols based on the 2018 recommendation. We used a Chi-square test and Fisher's exact test to identify differences between categorical variables. Results: Over 98% of the criteria for 'essential elements for breast MRI protocol' were satisfied when compared with the 2018 Recommendation. Over 96% of the criteria for 'elements to consider when evaluating imaging quality' were also satisfied, except for the slice thickness (83.9%). Optional elements for breast MRI protocol were satisfied with various percentages. There were no statistically significant differences between groups of tertiary, secondary, and primary hospitals; however, 3 tesla of MRI (P = 0.04), subtraction image protocol (P = 0.032), and DWI protocol (P = 0.03) were used more frequently in the tertiary hospitals than in the others. Conclusion: We found that the categories of 'essential elements' and 'elements to consider when evaluating imaging quality' were satisfied at 98% and 96%, respectively, when compared with the 2018 Recommendation by the Breast Imaging Study Group of the Korean Society of Magnetic Resonance.

• Journal of the Korean Applied Science and Technology
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• v.39 no.1
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• pp.115-131
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• 2022

The purpose of this study was to develop and examine the effect of the Health Promotion Education Program for the Auxiliary Police based on the PRECEDE-PROCEED Model. This study was conducted using a nonequivalent control group pretest-posttest design. Twenty-five participants were selected by convenience sampling method and assigned to the experimental group, and 26 participants were assigned to the control group. The data were collected from Auxiliary Police officer in D provincial Police Agency. All of participations completed questionnaires about self-efficacy, social support, availability of resources, health promotion behavior, quality of life and received the objective stress test. In addition, the experimental group completed 7 sessions of health promotion Education programs according to PRECEDE-PROCEED model for 5 weeks. Data were analyzed using the SPSS/WIN 21.0 Program. There was significant differences over time between the groups in terms of health promotion behavior (F=7.63, p<.001), autonomic nervous activity (F=29.24, p<.001), stress resistance (F=31.22, p<.001), stress index (F=22.42, p<.001), fatigue (F=12.87, p<.001), and quality of life (F=3.49, p=.042). The results may be crucial to develop strategy in order to decrease the disease prevalence as well as increase the participants' overall quality of life. As a result, the Health Promotion Education Program for the auxiliary police was proved to be an effective intervention in order to improve the quality of life. Therefore, the program may be a useful intervention for the auxiliary police.

• Journal of Hospice and Palliative Care
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• v.25 no.1
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• pp.12-24
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• 2022

Purpose: This descriptive study compared the perceptions, determinants, and needs of patients, family members, nurses, and physicians regarding life-sustaining treatment decisions for patients with hematologic malignancies in the hematology-oncology department of a tertiary hospital in Seoul, Korea. Methods: In total, 147 subjects were recruited, gave written consent, and provided data by completing a structured questionnaire. Data were analyzed using analysis of variance, the chi-square test, and the Fisher exact test. Results: Nurses (F=3.35) and physicians (F=3.57) showed significantly greater familiarity with the Act on Decisions on Life-Sustaining Treatment than patients (F=2.69) and family members (F=2.59); (F=19.58, P<0.001). Many respondents, including 19 (51.4%) family members, 16 (43.2%) physicians, and 11 (29.7%) nurses, agreed that the patient's opinion had the greatest effect when making life-sustaining treatment decisions. Twelve (33.3%) patients answered that mental, physical, and financial burdens were the most important factors in life-sustaining treatment decisions, and there was a significant difference among the four groups (P<0.001). Twenty-four patients (66.7%), 27 (73.0%) family members, and 21(56.8%) nurses answered that physicians were the most appropriate people to provide information regarding life-sustaining treatment decisions. Unexpectedly, 19 (51.4%) physicians answered that hospice nurse practitioners were the most appropriate people to talk to about life-sustaining treatment (P<0.001). Conclusion: It is of utmost importance that the patient and physician determine when life-sustaining treatment should be withdrawn, with the patient making the ultimate decision. Doctors and nurses have the responsibility to provide detailed information. The goal of end-of-life planning is to ensure patients' dignity and respect their values.

• Journal of the Korean Society of Safety
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• v.37 no.2
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• pp.28-34
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• 2022

This study analyzes the impact that accidents and near misses have on clients' and contractors' awareness of safety culture. Due to the unique characteristic of employment structure in Korea, the occurrence of accidents differs by company size, which has relevant implications for the establishment of safety culture. Attention has been drawn to the importance of the management of accidents and near misses, with safety awareness acting as a core factor. A positive effect on the prevention of accidents could be achieved by noting the difference in safety awareness between clients and contractors and suggesting an associated suitable safety management system. In support of this study, a survey was distributed to workers in the automobile manufacturing industry (May-August 2020), and data from a total of 574 workers was collected and analyzed, including 399 clients' worksers and 175 contractors' workers. The questionnaire addressed participants' experiences of accidents and near misses as well as 50 items from the Nordic Occupational Safety Climate Questionnaire. Analysis of the responses was conducted using the methods of frequency analysis, Fisher's exact test, t-test, correlation analysis, and regression analysis. The results demonstrated that clients had more experiences with accidents and near misses compared to contractors. Additional differences between clients and contractors were noted in terms of the safety culture factors of learning, communication, and trust. A correlation was observed between the experience of accidents and safety justice management: for clients and contractors who experienced accidents, safety justice management was 9.4 times higher. Furthermore, clients' and contractors' awareness of employees' commitment to safety was determined to be 28.5 times higher in those who had experienced near misses This study concludes that, in order to improve accident prevention through the management of accidents and near misses, clients must focus on overseeing safety justice management and aspects of safety culture factors, while contractors must focus efforts on managing employees' commitment to safety. In further applications, this study could provide baseline data for health and safety activities in terms of the safety culture of clients and contractors. Further study on the establishment of safety culture as related to employment structure is proposed for future research.

• The Korean Journal of Emergency Medical Services
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• v.26 no.2
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• pp.97-111
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• 2022

Purpose: Automated External Defibrillator (AED) usage in out-of-hospital cardiac arrests (OHCAs) improves the survival of patients. In Singapore, public AEDs are protected by locked boxes with a 'break glass' mechanism to deter theft. Community responders have sustained injuries while breaking glass to retrieve AEDs. This unprecedented study aimed to elucidate the factors influencing successful retrieval of an AED and to document the prevalence of injuries. Methods: A survey was created and distributed. Participants were required to have responded to an OHCA in the past 12 months. Comparison tests were performed with the Fischer-Freeman-Halton Exact test or Pearson chi square test at 5% significance levels, and with multiple logistic regression with a logit link function. Results: Eighty-eight participants were eligible. The success of retrieving an AED was found not to be impacted by occupation, age, gender or time. Participants who responded to an OHCA because of activation by the myResponder App were more likely to retrieve an AED successfully. (AOR 11.111, 95% CI: 2.141-58.824) Conclusion: Use of the myResponder mobile application is associated with the greater success of retrieving an AED. Successful retrieval of an AED is not impacted by time, gender, age, or the occupation of the responder. Community responders in Singapore remain motivated to respond to Cardiac Arrests despite risk of injury.