• Tribology and Lubricants
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• v.40 no.4
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• pp.111-117
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• 2024

Due to global CO₂ emission reductions and fuel efficiency regulations, the trend toward transitioning from internal combustion engine vehicles to electric vehicles (EVs) has accelerated. Consequently, the problem of EV failures has become a focal point of active research. The parasitic capacitance generated during motor-shaft rotation induces voltage that deteriorates the raceway and ball surfaces of bearings, causing electrical damage in EVs. Despite numerous attempts to address this issue, most studies have been conducted under high viscosity lubricant and low load conditions. However, due to factors such as high-speed operation, rapid acceleration and deceleration, motor heating, and motor system-decelerator integration, current EV applications have shown diminished stability in lubrication films of motor bearings, thereby leveraging the investigation to address the risk of electrical damage. This study investigates the electrical damage to rolling bearing elements in EV motor drive systems. The experimental analysis focuses on the effects of electric currents and operational loads on bearing integrity. A test rig is designed to generate high-rate voltage specific to a motor system's parasitic capacitance, and bearing samples are exposed to these currents for specified durations. Component evaluation involves visual inspections and vibration measurements. In addition, a predictive model for electrical failure is developed based on accumulated data, which demonstrates the ability to predict the likelihood of electrical failure relative to the duration and intensity of current exposure. This in turn reduces uncertainties in practical applications regarding electrical erosion modes.

• Journal of Practical Engineering Education
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• v.16 no.4
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• pp.491-497
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• 2024

Over the past five years, the proportion of patients with arrhythmia heart disease among teenagers and those in their 20s has been increasing. Heart disease has consistently remained the second leading cause of death in Korea and as the number has increased, electrocardiogram testing for arrhythmia has become important. However, specialized electrocardiogram medical devices are economically burdensome and are difficult to store individually in hospitals due to their large size and difficulty in operation. Testing is conducted through visits. Therefore, it is essential to enable individuals to perform ECG self-examinations using an Arduino-based ECG sensor that is affordable and easy to use in daily life, so that arrhythmia can be identified through individual ECG measurement. In this study, data is measured using an electrocardiogram sensor (AD8232), and changes in bio signals are visually provided through real-time monitoring, allowing users to make intuitive decisions and at the same time understand test results. To safeguard sensitive personal information, we have developed a web service that provides individual heart disease and customized health guides that can protect personal information through web vulnerability security using session and user authentication and SSL.

• Journal of the Health Care and Life Science
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• v.11 no.2
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• pp.271-277
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• 2023

This study targeted 125 prospective early childhood teachers at G University in G Metropolitan City to investigate their perceptions of safety care practices. The collected data were analyzed using One-way ANOVA and Scheffe's post hoc test. As a result of the study, there was a statistically significant difference in the overall awareness of safe care practices of prospective early childhood teachers according to grade. Statistically significant differences were found in the sub-factors 'Life Safety', 'Traffic Safety', 'Violence and Personal Safety', 'Drugs and Cyber Addiction', and 'Disaster Safety'. On the other hand, there was no statistically significant difference in 'occupational safety' and 'first aid'. Through these results, Through these results, we aim to increase safety competency by measuring safety care practices, expand practical training opportunities for prospective early childhood teachers, develop various media, and above all, improve class operation and content related to safety in early childhood teacher training courses. Based on this, we aim to provide basic data to develop a pre-service early childhood teacher education program.

• Smart Structures and Systems
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• v.33 no.4
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• pp.291-300
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• 2024

Uncertainty of the model, system delay and drive dynamics can be considered as normal uncertainties, and the main source of uncertainty in the seismic control system is related to the nature of the simulated seismic error. In this case, optimizing the management strategy for one particular seismic record will not yield the best results for another. In this article, we propose a framework for online management of active structural management systems with seismic uncertainty. For this purpose, the concept of reinforcement learning is used for online optimization of active crowd management software. The controller consists of a differential controller, an unplanned gain ratio, the gain of which is enhanced using an online reinforcement learning algorithm. In addition, the proposed controller includes a dynamic status forecaster to solve the delay problem. To evaluate the performance of the proposed controllers, thousands of ground motion data sets were processed and grouped according to their spectrum using fuzzy clustering techniques with spatial hazard estimation. Finally, the controller is implemented in a laboratory scale configuration and its operation is simulated on a vibration table using cluster location and some actual seismic data. The test results show that the proposed controller effectively withstands strong seismic interference with delay. The goals of this paper are towards access to adequate, safe and affordable housing and basic services, promotion of inclusive and sustainable urbanization and participation, implementation of sustainable and disaster-resilient buildings, sustainable human settlement planning and manage. Simulation results is believed to achieved in the near future by the ongoing development of AI and control theory.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.35 no.3
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• pp.210-217
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• 2024

Objectives: South Korea has the highest suicide rate among Organisation for Economic Co-operation and Development countries; there is an increasing trend in suicide attempts among middle and high school students. Various factors contribute to the risk of suicide among adolescents, and the perception of suicide prevention has emerged as a significant factor. This study aimed to investigate the association between emotional and behavioral difficulties among middle and high school students and their perceptions of suicide prevention and to explore differences in suicide perception according to age. Methods: A survey was conducted among community middle and high school students, including 530 participants, between 2020 and 2021. Emotional and behavioral difficulties were assessed using the Strengths and Difficulties Questionnaire-Korean version, and participants were asked to complete a questionnaire on the importance and possibility of suicide prevention. A correlation test and analysis of variance were used to examine the relationships between the variables, and suicide awareness was compared according to age. Results: The participants who displayed higher strength or lower difficulty were more likely to respond positively to suicide prevention measures. They also exhibited high strength and low difficulty levels, thus agreeing with the importance of suicide prevention. Regarding age-related perceptions of suicide, adults aged 20-29 years reported the lowest probability of suicide prevention. Conclusion: Suicide perceptions influence the incidence of suicide. Therefore, active societal engagement through suicide prevention campaigns and related education is essential to improve such perceptions. Continuous attention and support are required to address this issue.

• Korean Journal of Agricultural Science
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• v.51 no.3
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• pp.295-305
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• 2024

Due to the environment of irregular soil characteristic for agricultural fields, dynamic characteristic occurs in the tractor cabin during agricultural operations. Operator's fatigue is increased, and operation performance is decreased by these irregular environment conditions. This study was conducted to measure and analyze the dynamic characteristic of a tractor cabin, a major agriculture machinery, during agricultural operations. The specification of tractor used in the study was a 95 kW class tractor. To analyze the dynamic characteristics of the tractor cabin, the main agricultural operations, plow tillage and rotary tillage, were selected. To measure data of dynamic characteristic of the cabin, which continuously changes during operations, an Ellipse Series INS (inertia navigation system) with a built-in IMU (inertia measurement unit) was attached to the center of gravity of the cabin. During field test, the gear stages of plow tillage were B4 (4.3 km·h^-1) and B5 (5.6 km·h^-1), and the gear stages of rotary tillage were A3 (3.3 km·h^-1) and A4 (4.2 km·h^-1), which are the most commonly used. To analyze dynamic characteristic such as roll and pitch during operations according to the gear stages. As a result, the dynamic characteristics of pitch increased more than the dynamic characteristics of roll as the travel speed increased, and the dynamic characteristics of both agricultural operations were in the range of 2 to 5°.

• Progress in Medical Physics
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• v.35 no.2
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• pp.45-51
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• 2024

Purpose: Accurate operation of the multi-leaf collimator (MLC), a key technology in intensity modulated radiation therapy (IMRT), is essential for safe and optimal radiation treatment. The Halcyon^TM linear accelerator has a collimator with low leakage and radiation transmission, making it suitable for IMRT. The limitations of the existing Halcyon^TM MLC quality assurance (QA) method were supplemented with a mathematical method, and the results were analyzed. Methods: Electric portal imaging device (EPID) images obtained by performing the MLC QA plan on the Halcyon^TM was analyzed using Python. The picket fence tests were performed and compared using the maximum pixel value and mathematical methods. Dose rate, gantry speed, and leaf speed variation plan were performed for dose transmission comparison. Results: For the maximum pixel value, the minimum distance between leaf junctions was 13.86 mm, and the maximum was 16.06 mm. However, for the mathematical method, the minimum and maximum were 14.54 mm and 15.68 mm, respectively. This suggests that setting the peak value to the highest value may cause an error in interpretation due to the limitations of the pixels of the EPID image. Performing QA on the remaining items confirmed that the measured values were within 3% of tolerance. Conclusions: The presented analysis method applied to the MLC QA can derive more reasonable and valid values than existing methods, which will help with MLC monitoring by reducing errors in excessive interpretation.

• Journal of Chest Surgery
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• v.13 no.3
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• pp.174-185
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• 1980

It was my great nohour that I can be exposed to such plenty materials of the coronary bypass surgery. Here, I am summarizing the xoronary bypass surgery, clinically. The material is serial 101 patients who underwent coronary bypass surgery between July 17, 1979 to November 30, 1979 in Shadyside Hospital, University of Pittsburgh. 1. Incidence of the Atherosclerosis is frequent in white, male, fiftieth who are living in industrialized country. It has been told the etiologic factor of the atherosclerosis is hereditary, hyperlipidemia, hypertension, smoking, drinking, diabetes, obesity, stress, etc. 2. The main and most frequent complication of the coronary atherosclerosis is angina pectoris. Angina pectoris is the chief cause of coronary bypass surgery and the other causes of coronary bypass surgery are obstruction of the left main coronary artery, unstable angina, papillary muscle disruption or malfunction and ventricular aneurysm complicated by coronary artery disease. 3. The preoperative clinical laboratory examination shows abnormal elevation of plasma lipid in 82 patint, plasma glucose in 40 patient, total CPK-MB in 24 patient stotal LDH in 22 patient out of 101 patient. 4. Abnormal ECG findings in preoperative examine were 29.1% myocardial infarction, 25.8% ischemia and injury, 14.6T conduction defect. 5. Also we had done Echocardiography, Tread Mill Test, Myocardial Scanning, Vectorcardiography and Lung function test to get adjunctive benefit in prediction of prognosis and accurate diagnosis. 6. The frequency of coronary atherosclerosis in main coronary arteries were LAD, RCA and Circumflex in that order. 7. The patients' main complaints which were became as etiologic factor undergoing coronary bypass surgery were angina, dyspnea, diaphoresis, dizziness, nausea and etc. 8. For the coronary bypass surgery, we used cardiopulmonary bypass machine, non-blood, diluting prime, cold cardioplegic solution and moderate cooling for the myocardial protection. 9. We got the grafted veins from Saphenous and Cephalic vein. Reversed and anastomosed between aorta and distal coronary A. using 5-0 and 7-0 prolene continuous suture. Occasionally we used internal mammary A. as an arterial blood source and anastomosed to the distal coronary A. and to side fashion. 10. The average cardiopulmonary bypass time for every graft was 43.9 min. and aortic clamp time was 23 minute. We could Rt. coronary A. bypass surgery only by stand by the cardiopulmonary machine and in the state of pumping heart. 11. Rates by the noumbers of graft were as follow : 21.8% single, 33.7% double, 26.7% triple, 13.9% quadruple, 3% quintuple and 1% was sixtuple graft. 12. combined procedures with coronary bypass surgery were 6% aneurysmectomy, 3% AVR, 1% MVR, 13% pacer implantation and 1% intraaortic ballon setting. 13. We could see the complete abolition of anginal pain after operation in 68% of patient, improvement 25.8%, no change in 3.1%, and there was unknown in 3%. 14. There were 4% immediate postoperative deaths, 13.5% some kinds of heart complication, 51.3% lung complications 33.3% pleural complications as prognosis.

• Journal of Korean Neurosurgical Society
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• v.30 no.6
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• pp.717-723
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• 2001

Objective : Subarachnoid hemorrhage(SAH) is still one of the most serious disease with high morbidity and mortality in the neurosurgical field. Clipping of the aneurysmal neck is the gold standard of the surgical treatment of aneurysmal SAH. The purpose of this study was to investigate the role of the postoperative angiography and to assess the risk factors related to the incomplete clipping. Materials and Methods : From July 1995 to June 1998, the pre- and postoperative angiography were performed in 50 patients among total 81 patients who have underwent the aneurysmal surgery. We reviewed the various contributing factors including age, sex, Hunt-Hess grade, Fisher grade and the premature rupture of aneurysm during operation retrospectively. Careful evaluation of pre- and postoperative angiography focusing on the size, shape, and remnant neck of the aneurysms and vasospasm was performed. According to the angiographic findings, the patients were divided into two groups ; a complete clipping group and an incomplete clipping group. The data were analyzed by using unpaired independent sample t test after F-test to compare the significance between two groups. Results : Incomplete clipping of aneurysms was found in 6(12%) patients through the evaluation of postoperative angiography. Among them, three cases were located on the middle cerebral artery territory. Whereas the patient age, sex, Hunt-Hess grade, and Fisher grade were not significant(p>0.05), an intraoperative premature rupture had a statistical significance(p<0.05). A severe vasospasm occurred in 24(48%) cases and one patient with anterior communicating aneurysm was reoperated due to residual sac. Conclusion : According to our experience, the surgeons' judgement is the most reliable factor in deciding the postoperative angiography. During the aneurysmal surgery, the premature rupture always disturbs a complete clipping of aneurysms. Therefore, the temporary clipping of parent arteries is considered essential for a successful clipping. We believe that the postoperative angiography has a role in decreasing the re-bleeding risk due to clip migration and an inaccurate clipping only in the selected cases.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.269-269
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• 2012

A new ion source has been designed, fabricated, and installed at the NBTS (Neutral Beam Test Stand) at the KAERI (Korea Atomic Energy Research Institute) site. The goalis to provide a 100 keV, 2MW deuterium neutral beam injection as an auxiliary heating of KSTAR (Korea Super Tokamak Advanced Research). To cope with power demand, an ion current of 50 A is required considering the beam power loss and neutralization efficiency. The new ion source consists of a magnetic cusp bucket plasma generator and a set of tetrode accelerators with circular copper apertures. The plasma generator for the new ion source has the same design concept as the modified JAEA multi-cusp plasma generator for the KSTAR prototype ion source. The dimensions of the plasma generator are a cross section of $59{\times}25cm^2$ with a 32.5 cm depth. The anode has azimuthal arrays of Nd-Fe permanent magnets (3.4 kG at surface) in the bucket and an electron dump, which makes 9 cusp lines including the electron dump. The discharge properties were investigated preliminarily to enhance the efficiency of the beam extraction. The discharge of the new ion source was mainly controlled by a constant power mode of operation. The discharge of the plasma generator was initiated by the support of primary electrons emitted from the cathode, consisting of 12 tungsten filaments with a hair-pin type (diameter = 2.0 mm). The arc discharge of the new ion source was achieved easily up to an arc power of 80 kW (80 V/1000 A) with hydrogen gas. The 80 kW capacity seems sufficient for the arc power supply to attain the goal of arc efficiency (beam extracted current/discharge input power = 0.8 A/kW). The accelerator of the new ion source consists of four grids: plasma grid (G1), gradient grid (G2), suppressor grid (G3), and ground grid (G4). Each grid has 280 EA circular apertures. The performance tests of the new ion source accelerator were also finished including accelerator conditioning. A hydrogen ion beam was successfully extracted up to 100 keV /60 A. The optimum perveance is defined where the beam divergence is at a minimum was also investigated experimentally. The optimum hydrogen beam perveance is over $2.3{\mu}P$ at 60 keV, and the beam divergence angle is below $1.0^{\circ}$. Thus, the new ion source is expected to be capable of extracting more than a 5 MW deuterium ion beam power at 100 keV. This ion source can deliver ~2 MW of neutral beam power to KSTAR tokamak plasma for the 2012 campaign.