• Korean Journal of Materials Research
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• v.27 no.12
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• pp.652-657
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• 2017

The use of continuous welded rail is increasing because of its many advantages, including vibration reduction, enhanced driving stability, and maintenance cost savings. In this work, two different types of continuous welded rails were examined to determine the influence of repeated wheel-rail contact on the crystal structure, microstructure and mechanical properties of the rails. The crystal structure was determined by x-ray diffraction, and the microstructure was examined using optical microscopy and scanning electron microscopy. Tensile and microhardness tests were conducted to examine the mechanical behaviors of prepared specimens taken from different positions in the cross section of both newly manufactured rail and worn rail. Analysis revealed that both the new and worn rail had a mixed microstructure consisting of ferrite and pearlite. The specimens from the top position of each rail exhibited decreased lamella spacing of the pearlite and increased yield strength, ultimate tensile strength and hardness, as compared with those from other positions of the rail. It is thought that the enhanced mechanical property on the top position of the worn rail might be explained by a mixed effect resulting from a directional microstructure, the decreased lamella spacing of pearlite, and work hardening by the repeated wheel-rail contact stress.

• Journal of the Korean Geotechnical Society
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• v.29 no.12
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• pp.87-94
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• 2013

In recent years, tunnel construction is being increased in order to resolve traffic congestion around urban area, however there are a lot of difficulties due to restrictions such as interference with existing alignment, adjacent structures and cost increase of land acquisition as well as public complaints for negative environmental impacts near the expected tunnel construction site. Therefore, applications of close parallel tunnel have been increasing greatly. But close parallel tunnels cannot guarantee the stability compared with normal parallel tunnel which has enough distance between tunnels. So various methods to strengthen the pillar have been introduced recently, however there is few methods which consider the pillar behaviour in the state of compression. In this paper, the reinforcement methods which reflect the behavior of pillar were reviewed with comparision and analysis by numerical method.

• International Area Studies Review
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• v.14 no.3
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• pp.35-60
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• 2010

In this paper, we develop a dynamic structural model based on a dynamic supergame and measure market power for the Dallas-Forth Worth fluid milk market in the U.S. In particular, we compare the conduct parameter estimates from a static model with that from the dynamic model and illustrate bias in the market-power measure in a static model. And we also analyze the cyclical behavior of firm conduct. We find that the conduct parameter in a static model underestimates true market power if firms' behaviors are posited by a dynamic oligopoly game. We also verify that firm conduct in the Dallas-Forth Worth fluid milk market is countercyclical against demand shocks and expected future cost shocks. Our results indicate that the firms' conduct in the Dallas-Forth Worth fluid milk market is consistent with what dynamic oligopoly models predict. This implies that the firms consider not only the contemporary reactions of the other firms' but also future market competition. Therefore, the measurement of market power requires the specification of fully dynamic pricing relationship.

• Journal of Korean Academy of Nursing
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• v.49 no.2
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• pp.113-125
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• 2019

Purpose: The purpose of this study was to examine the effects of a daily life-based physical activity enhancement program performed by middle-aged women at risk for cardiovascular disease. Methods: This study used a randomized control group pretest-posttest design. Middle-aged women aged 45 to 64 were recruited from two outpatient cardiology departments, and randomly assigned to an experimental group (n=28) and a control group (n=30). For the experimental group, after providing one-on-one counseling and education, we provided customized text messages to motivate them in daily life. To monitor the practice of physical activity, they also used an exercise diary and mobile pedometer for 12 weeks. Subjects' physical activities (MET-min/week) were measured using the International Physical Activity Questionnaire (IPAQ). Their physiological data were obtained by blood tests using a portable analyzer, and the data were analyzed using the SPSS 21.0/WIN program. Results: There were significant differences in exercise self-efficacy, health behavior, IPAQ score, body fat, body muscle, and fasting blood sugar between the two groups. However, there were no significant differences in total cholesterol, hemoglobin A1c, high-density lipoprotein cholesterol, and waist-to-hip ratio. Conclusion: Strengthening physical activity in daily life without being limited by cost burden and time and space constraints. Therefore, it is essential to motivate middle-aged women at risk for cardiovascular disease to practice activities that are easily performed in their daily lives.

• Tribology and Lubricants
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• v.35 no.2
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• pp.114-122
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• 2019

High-speed rotating machinery requires low cost and reliable bearing elements with low friction, stable rotordynamic characteristics, and a simple design. This study experimentally evaluates the effects of bearing-support elements on the vibrational characteristics of a small-sized, high-speed permanent magnetic motor. A series of coast down tests from 100 krpm characterize the vibrational behaviors, rotor displacement, and housing acceleration of motors supported by ball bearings, ball bearings with a metal mesh damper, and gas foil bearings, respectively. Two eddy-current sensors installed in the horizontal and vertical directions measure the displacement of the rotor at its front nut, and a 3-axis accelerometer attached to the motor housing measures the housing acceleration. The test results reveal that synchronous (1X) vibration components most significantly affect the rotor displacement and housing acceleration, independent of the bearing-support elements. The motor supported by the deep-groove ball bearings results in the largest rotor vibrations increasing with speed; this is due to the absence of a damping mechanism. Additionally, the metal mesh damper effectively reduces the rotor displacement, housing acceleration, and sound-pressure level in the high-speed region (i.e., above 40 krpm), thus implying its substantial damping performance when installed on the outer race of the ball bearing. Lastly, the gas foil bearing supported motor yields the smallest rotor displacement, housing acceleration, and lowest sound-pressure level because of its hydrodynamic airborne operation, which does not require rolling elements that may cause mechanical friction and vibrations.

• Tribology and Lubricants
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• v.37 no.5
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• pp.189-194
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• 2021

A straightforward, yet effective surface modification method of stainless steel mesh and its interesting anti-wetting characteristics are reported in this study. The stainless steel mesh is electrochemically etched, and the specimen has both micro and nano-scale structures on its surface. This process transforms the two types of mesh specimens known as the regular and dense specimens into hydrophobic specimens without applying any hydrophobic chemical coating process. The fundamental wettability of the modified mesh is analyzed through a dedicatedly designed experiment to investigate the waterproof characteristics, for instance, the penetration threshold. The waterproof characteristics are evaluated in a manner that the modified mesh resists as high as approximately 2.7 times the pressure compared with the bare mesh, i.e., the non-modified mesh. The results show that the penetration threshold depends primarily on the advancing contact angles, and the penetration stop behaviors are affected by the contact angle hysteresis on the surfaces. The findings further confirm that the inexpensive waterproof meshes created using the proposed straightforward electrochemical etching process are effective and can be adapted along with appropriate designs for various practical applications, such as underwater devices, passive valves, and transducers. In general, , additional chemical coatings are applied using hydrophobic materials on the surfaces for the applications that require water-repelling capabilities. Although these chemical coatings can often cause aging, the process proposed in this study is not only cost-effective, but also durable implying that it does not lose its waterproof properties over time.

• Journal of Korean Dental Hygiene Science
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• v.3 no.2
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• pp.1-8
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• 2020

This study investigated the relationship between oral health knowledge, behavior and orthodontic satisfaction in orthodontic patients visiting dental hospitals and clinics and provided suggestions to improve orthodontic patients' satisfaction. This study anayzed structured self-administered questionnaires collected from 245 patients who visited 5 dental clinics in Gwangju Metropolitan City. Regarding oral health knowledge, the highest percentage of correct answers was for the item "Cavities heal themselves over time" (97.1%), and the lowest percentage of correct answers was for the item "Cavity bacteria move from tooth to tooth" (16.7%). Five fluoride items showed a lower percentage of correct answers than those for cavity and gingival diseases. Regarding the survey on oral health behavior, the highest score was found for the item "I brush my teeth with a certain method and order" (3.78 out of 5), and the lowest score was found for the item "I use an electric toothbrush" (1.34 out of 5). Regarding the survey on orthodontic satisfaction, the highest score was found for the item "I would recommend receiving medical treatment at the department of orthodontics" (4.23), and the lowest score was found for the item "Orthodontic cost is reasonable" (3.46). While oral health behavior had on orthodontic satisfaction, oral health knowledge had no effect on it. Oral health behaviors should be improved to enhance orthodontic satisfaction. To improve oral health behavior, it is necessary to develop and activate education programs for tooth brushing and oral care for orthodontic patients.

• Asia-Pacific Journal of Business
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• v.10 no.4
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• pp.223-236
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• 2019

Governance can be defined as a concept that encompasses a series of processes including partner selection as well as control and coordination of collaboration to achieve common goals. The study examined efforts to mitigate the risks of opportunistic behaviors into partner selection, partner relationship, control mechanism, and conflict management. For cases that have achieved commercialization outputs with the participation of SMEs, data was collected and analyzed such as interviews with project managers and case records for seven months from October 2016. According to the analysis result, as the complexity increases, such as multilateral cooperation for the development of finished products, cooperation with a trusted partner rather than a partner who can perform a task well was preferred, and the process control was put ahead of the output control. Regarding the partner relationship, the relationship between the owner and the agent differed according to the point of view, and there was a lack of clear allocation of authority and responsibility as well as a reward for the result. In terms of the conflict management, most emphasis was on resolving conflicts or difficulties, and no attempt was made to utilize the positive aspects of the conflict. The structure of most industry-university-institute cooperation organizations is simply composed of the host and participating organizations, and the management regulations should be amended for companies, that put actual funds and use the outputs, to have the authority and responsibility as the owners, and be allowed to use the governance elements appropriately to take the lead as consumers.

• Korean Journal of Veterinary Research
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• v.62 no.3
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• pp.21.1-21.10
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• 2022

With the increasing population of companion dogs, the social cost derived from their behavioral problems is increasing. Therefore, it is important to understand the environment to provide experience for dogs via interactions with their owners to prevent and solve these problems. The parenting behavior of dog owners as an environmental factor has a profound impact on the behavior development of dogs, as does the parenting behavior on children. Therefore, this study aimed to develop a scale to assess the dog owner's parenting behavior. Exploratory factor analysis involving 300 participants resulted in a scale with four subscales, Positive Education, Involvement of Socialization, Intimacy, and Stable Responses, and 19 items. Confirmatory factor analysis was then performed to verify its reliability and validity. The result of parenting behaviors assessed by this scale was significantly different between a group with dogs with problematic behavior (n = 141) and those without (n = 159). Overall, a dog owner's parenting behavior involves affection and control aspects, but the role required specifically in the control aspect is distinguished from the parenting behavior with children. The findings in the present study will provide dog owners with effective education that will help prevent dogs from developing behavioral problems.

• Structural Engineering and Mechanics
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• v.80 no.5
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• pp.503-522
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• 2021

This paper investigates experimentally and numerically the influence of drilling process on the mechanical and thermomechanical behaviors of woven glass fiber reinforced polymer (GFRP) composite plate. Through the experimental analysis, a CNC machine with cemented carbide drill (point angles 𝜙=118° and 6 mm diameter) was used to drill a woven GFRP laminated squared plate with a length of 36.6 mm and different thicknesses. A produced temperature during drilling "heat affected zone (HAZ)" was measured by two different procedures using thermal IR camera and thermocouples. A thrust force and cutting torque were measured by a Kistler 9272 dynamometer. The delamination factors were evaluated by the image processing technique. Finite element model (FEM) has been developed by using LS-Dyna to simulate the drilling processing and validate the thrust force and torque with those obtained by experimental technique. It is found that, the present finite element model has the capability to predict the force and torque efficiently at various drilling conditions. Numerical parametric analysis is presented to illustrate the influences of the speeding up, coefficient of friction, element type, and mass scaling effects on the calculated thrust force, torque and calculation's cost. It is found that, the cutting time can be adjusted by drilling parameters (feed, speed, and specimen thickness) to control the induced temperature and thus, the force, torque and delamination factor in drilling GFRP composites. The delamination of woven GFRP is accompanied with edge chipping, spalling, and uncut fibers.