• Geomechanics and Engineering
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• v.20 no.5
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• pp.421-432
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• 2020

Cutting of rocks is very common encountered in tunneling and mining during underground excavations. A deep understanding of rock-tool interaction can promote industrial applications significantly. In this paper, a distinct element method based approach, PFC^3D, is adopted to simulate the rock cutting under different operation conditions (cutting velocity, depth of cut and rake angle) and with various tool geometries (tip angle, tip wear and tip shape). Simulation results showed that the cutting force and accumulated number of cracks increase with increasing cutting velocity, cut depth, tip angle and pick abrasion. The number of cracks and cutting force decrease with increasing negative rake angle and increase with increasing positive rake angle. The numerical approach can offer a better insight into the rock-tool interaction during the rock cutting process. The proposed numerical method can be used to assess the rock cuttability, to estimate the cutting performance, and to design the cutter head.

• Clinical and Experimental Pediatrics
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• v.50 no.2
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• pp.127-131
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• 2007

Fever of unknown origin (FUO) has been a convenient term used to classify patients who warrant a particular systemic approach to diagnostic evaluation and management. The greatest clinical concern in evaluating FUO is identifying patients whose fever has a serious or life-threatening cause when a delay in diagnosis could jeopardize successful intervention. Thorough history and complete physical examination are critical to uncover the etiologic diagnosis. Most cases of FUO in children are caused by atypical presentations of common diseases rather than by typical manifestations of rare disorders. Selection of diagnostic tests and speed of investigation should be guided by a knowledge of the disease severity, patient age, epidemiologic and geographic information, and any positive findings from a detailed history and physical examination. The three most common causes of FUO in children are infectious diseases, connective tissue diseases, and malignancy. In general, the prognosis of FUO in children is better than that of adults. Although the outcome is dependent on the primary disease process, fever abates spontaneously in most cases in whom the cause of fever remains unclear.

• Journal of the Korean Society of Food Culture
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• v.27 no.5
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• pp.445-458
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• 2012

This study was conducted to approach the Korean new food words for the years 1994-2005 from the stance of food ethics. The new food words were categorized into food industry, foodstuffs, cooking, various foods, processed foods, distribution, and consumer health. The principles of food ethics applied to new food words include a respect for life, justice, environmental preservation, priority of safety, and dynamic equilibrium. Seventy percent of new food words were ethically neutral, while 30% had significant ethical meaning. There were more words with a negative ethical meaning than with a positive one. All of the principles, except respect for life, could be successfully applied to new food words. Dynamic equilibrium was the most appropriate principle for the new food words, followed by a priority for safety, justice, and environmental preservation. The results of this study implied that moderation and balance is required in our modern dietary life.

• The Journal of the Korean dental association
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• v.51 no.11
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• pp.604-609
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• 2013

Crown fractures are relatively common trauma to anterior teeth, and should be restored immediately in most cases. For those who suffer from unfortunate traumatic episode, the best treatment option should be minimally invasive approach. In the presence of fractured tooth fragment, reattachment procedure creates positive emotional response in the patient and simplifies the procedure and maintenance of the patient's original tooth anatomy and occlusion. Without fractured tooth fragment, next conservative option could be direct composite restoration which is based on minimal invasion concept. This article proposes simple and very conservative techniques that anyone can do in daily practice.

• KIEE International Transactions on Power Engineering
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• v.4A no.4
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• pp.178-191
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• 2004

This paper presents a new approach to HVDC system control for damping subsynchronous oscillation (SSO) involving HVDC converters and turbine generator shaft systems. This requires a novel eigenvalue analysis (NEA) program, derivation of HVDC system modeling considering steady-state conditions and dynamic conditions in the combined AC/DC system, and an appropriate control scheme. The method suggested makes possible the design of a subsynchronous oscillation damping controller (SODC) to provide positive damping torque for the range of torsional modes in combined AC/DC systems. There are three steps involved in the design of a SODC； first the worst torsional mode is determined using the NEA program, next the SODC parameters are designed for the range of that torsional mode, and then finally an off-line simultaneous time domain program such as PSCAD/EMTDC is used to verify the parameters of the SODC. The suggested SODC design method is applied to two AC/DC systems, and its practicality is verified using the PSCAD/EMTDC simulation program.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.95-100
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• 2013

This paper presents a new state feedback control approach for communication networks based control systems in which control input and output observation time-delay natures are generally occurred in practice. We first establish a generic state feedback control framework based on well-known linear system theory. A maximum time-delay value which allows critical stability of whole control system are defined to make a positive definite Lyapunov function which is mathematically composed of controlled system states. We analytically derive its control parameters by using a steepest descent optimization method in order to guarantee a stability condition through Lyapunov theory. Computer simulation is numerically carried out for demonstrating reliability of the proposed NCS algorithm and a comparative study is accomplished to prove its superiority for which the traditional control approach for NCS is made use of under same simulation scenarios.

• Journal of Information Technology Services
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• v.9 no.4
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• pp.135-150
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• 2010

In the age of digital convergence, it is expected that quality of life of human beings can be improved by converged devices and services. Researches concerning change of buying patterns and consumer behaviors in these contexts have to be progressed actively. To investigate future trend of consumer behaviors, we used focus group interview for Qualitative approach in the first step and then conducted questionnaire survey for experts in order to get validity and feasibility of research results. As result of research we suggested eight propositions by FGI for 20s target consumers. Additionally, on the basis of qualitative research, by questionnaire survey for 22 experts two perspectives of positive and negative views In future trends were proposed. Results can give lots of Implications and research motivations to academia, practices and workers in public policies who have interests in change of consumer behaviors, thinking styles, and life style under digital convergent environment.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.7
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• pp.44-51
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• 1998

Two-step neural network is designed for determining electrical discharge machining parameters in low erosion. The first neural network, which is used as a classification network, checks whether the current conditions are appropriate to electrical discharge machining in low tool erosion. If the conditions are appropriate to EDM in low erosion, suitable EDM parameters are generated by the second neural network. Theoretically known EDM conditions are produced and also utilized for training the second neural network. The trained neural network is tested how well suitable EDM machining conditions are generated under unknown machining situations Experimental result shows that the proposed two-step neural network approach could be effectively used for determining EDM parameters in low tool erosion. The results also have a practical contribution to EDM area in that it could be applied for maintaining low tool wear as well as obtaining maximum machining rates simultaneously.

• Journal of the Korea Safety Management & Science
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• v.14 no.4
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• pp.13-21
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• 2012

This paper tried to apply psychosocial factors in industrial safety research. Since Zohar's(1980) publication of safety climate in the field of safety research, this approach have been done by many researchers. Here, this paper reviewed the relationship between safety climate factors(safety rule, prevention, superior attitude, social support) and safety compliance, and the moderating effects of work condition, required skill and age. Based on the responses from 233 employees in Kangwon province industry, hierarchical regressional analysis showed that all safety climate factors(safety rule, prevention, superior attitude, social support) have positive relationship with safety compliance. Safety rule appeared to be more positively related with safety compliance, while work condition is more favorable and worker is older. But social support appeared to be more positively with safety compliance, while work condition is more unfavorable, and also prevention appeared to be more positively with safety compliance, while worker is more younger.

• International Journal of Advanced Culture Technology
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• v.8 no.4
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• pp.200-206
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• 2020

Digital storytelling, a 21st century educational tool that combines digital media with storytelling, is considered as a powerful tool to learn foreign languages in an authentic and meaningful way. This study explored cyber university students' perceptions and experiences with a digital storytelling project implemented to enhance their English writing and speaking skills. The results of 9 week-long research indicated that most of the students' attitudes were positive: the digital storytelling project was effective to increase their English skills, learning motivation and interest in learning English. Most students perceived that the process writing approach and videotaping tasks provided them with good opportunities to develop their English writing and speaking skills. Although many students had difficulties selecting a topic and writing a script in the initial stage, they could handle with these challenges with the help of professors' feedback and successfully completed their projects. After completing the project, most students expressed a strong sense of accomplishment. These results suggest that the digital storytelling project effectively met cyber university students' learning needs and facilitate their English learning.