• Transactions of the Korean hydrogen and new energy society
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• v.19 no.5
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• pp.403-409
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• 2008

Polymer electrolyte membrane fuel cell (PEMFC) is very interesting power source due to high power density, simple construction and operation at low temperature. But it has problems such as high cost, improvement of performance, effect of temperature and initial start at low temperature. These problems can be approached to be solved by using experiment and mathematical method which are general principles for analysis and optimization of control system for heat and hydrogen detecting management. In this paper, insulation vessel and control system for stable operation of fuel cell at low temperature were developed for experiment. The constant temperature capability and the heating time at sub-zero temperatures with insulation control system were studied by using a heating bar of 60W class. PEMFC stack which was made by 4 cells with $50\;mc^2$ active area in each cell is a thermal source. Times which take to reach constant temperature by the state of insulation vacuum were measured at variable environment temperatures. The test was performed at two conditions: heating mode and cooling mode. Constant temperature capability was better at lower environment temperature and vacuum pressure. The results of this experiment could be used as basis data about stable operation of fuel cell stack in low temperature zone.

• Imaging Science in Dentistry
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• v.50 no.3
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• pp.245-253
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• 2020

Purpose: This study investigated the prevalence of temporomandibular joint osteoarthritis (TMJ-OA) using the Research Diagnostic Criteria for Temporomandibular Disorders image analysis criteria, assessed the severity of incidental osteoarthritic changes affecting the TMJ, and evaluated the correlations of sex and age with the prevalence and severity of TMJ-OA. Materials and Methods: This retrospective study assessed 145 randomly selected cone-beam computed tomography scans (261 TMJs) from the authors' institutional maxillofacial radiology archive following the application of inclusion and exclusion criteria. The criteria described by Ahmad et al. were used to determine whether each TMJ was affected by OA, and the severity of the osteoarthritic changes was scored for each joint based on the method described by Alexiou et al. The chi-square, McNemar, Bhapkar chi-square, and Stuart-Maxwell chi-square tests were applied to evaluate the significance of the relationships between variables(age and sex). Results: Sixteen TMJs (6.1%) had no OA, 74 (28.6%) were indeterminate for OA, and 171 (65.5%) had OA. Flattening and sclerosis were observed in 86.6% and 12.3% of cases, respectively, while resorption was observed in 7.3% of the joints. Only 21 (8.1%) of the examined TMJs had subchondral cysts. Erosion of the articular eminence was observed in 58 (22.1%) cases, while sclerosis and resorption were found in 68 (25.9%) and 16 (6.1%) TMJs, respectively. Conclusion: Female patients had a higher prevalence and severity of TMJ-OA than male patients. The prevalence and severity of TMJ-OA increased with age, with peaks in the fifth and seventh decades of life.

• Journal of Technologic Dentistry
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• v.40 no.2
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• pp.63-69
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• 2018

Purpose: The purpose of this study is to investigate the non-precious metal core materials used in the dental laboratory to fabricate the implant superstructure by CAD / CAM method. And to observe and compare the morphology and distribution of the osteoblasts in relation to implant osseointegration. Methods: In this study, the mandibular right first molar tooth model was selected as an international standard to produce a single core. Using this model, the impression was made with the silicone rubber, the tooth model was scanned, and a single core was designed and 5-axis milling was performed. The materials used were Cobalt-Chromium and Nickel-Chromium, and the cores for dental implant top structures were fabricated according to the procedures of the dental labs. After the fabrication, the marginal area of the core was separated and cell culture experiment was performed. The osteoblast cells used MC3T3-E1, which is currently widely used. For morphological analysis of osteoblasts, cells were posttreated and observed using CLSM (Confocal Laser Scanning Microscope) and compared. Results: The cell adhesion behavior of the specimen surface measured by CLSM was uniformly distributed in specimen A (Cobalt-Chromium) than in specimen B (Nickel-Chromium). The distribution and changes of the cells were different in the two specimens. Conclusion : It is possible to confirm that specimen A (Cobalt-Chromium) is suitable for the living body through adhesion and proliferation of osteoblasts related to implant osseointegration in the non-precious metal superstructure used after implantation. It is considered that it is preferable to use Co-Cr when fabricating the superstructure.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.3
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• pp.435-449
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• 1995

In this paper, pressure drop through a capillary tube is modeled to determine the length of a capillary tube for a given set of conditions. HCFC-22 and its alternatives, HFC-134a, R407B, and R410A are used as working fluids. The conditions on which the model is tested are as follows : condensing temperature; 40.0, 45.0, 50.0, $55.0^{\circ}C$, degree of subcooling;0.0, 2.5, $5.0^{\circ}C$, capillary tube exit condition;choked flow, capillary tube diameter;1.2~2.4mm, mass flow rate;5.0~50.0g/sec. The results justify the use of Stoecker's model which yields the results very close to the values in ASHRAE handbook. While McAdams' method yields much better results than Duckler's in calculating the viscosity of the fluid in 2-phase, the friction factor suggested by Stoecker seems to be the best for capillary tubes of large diameter used in residential air conditioners. For each refrigerant, 372 data with various variables are calculated by the model. The results show that capillary tube length varies very uniformly with changes in condensing temperature and degree of subcooling. Based on this fact, regression analysis is performed to determine the dependence of mass flow rate on the length and diameter of a capillary tube, condensing temperature, and degree of subcooling. Thus determined correlation yields a mean deviation of 2.36% for 1,488 data, showing an excellent agreement.

• Journal of the Korean Chemical Society
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• v.22 no.4
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• pp.202-220
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• 1978

Uniform semiclassical (WKB) solutions are obtained for nonseparable systems without using a close coupling formalism and are given explicitly in terms of well known analytic functions for various physically interesting and realistic cases. They do not become singular at turning points or surfaces and when taken in their asymptotic forms, they reduce to the usual WKB solutions that could be obtained if the Stokes phenomenon was properly taken care of for solutions. In obtaining such uniform solutions, the Schroedinger equations for nonseparable systems are suitably "renormalized" to solvable "normal" forms through certain transformations. Ehrenfest's adiabatic principle plays an important guiding role for obtaining such "renormalized" uniform solutions for nonseparable systems. The eigenvalues of the Hamiltonian can be calculated from the extended Bohr-Sommerfeld quantization rules when appropriate classical trajectories are obtained. An application is made to many-electron systems and for one of the simplest examples to show the utility of the method the approximate wavefunction is calculated of the ground state helium atom.

• Journal of the Korean Wood Science and Technology
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• v.29 no.4
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• pp.25-32
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• 2001

A microwave vacuum (MW/V) dryer was developed for drying short roundwoods, from which woodcraft souvenirs in Korean market are mostly made, and which were hardly dried without defects in a conventional kiln. It consisted of three 1.5 kW magnetrons of 2,450 MHz, a vacuum pump, a load cell of 100 kg and a cavity of $580{\times}580{\times}1,360\;mm^3$. A computer program was developed to switch on or off the magnetrons according to drying schedules, those were based on microwave injection time or the average of wood temperatures. To evaluate the new MW/V dryer the roundwood specimens of rigida pine, poplar and birch were dried. Their log diameters and lengths ranged from 125 to 25 em and from 25 to 50 cm, respectively. In spite of the presence of minor drying defects, the MW/V drying is found to be an effective method for drying short roundwoods. Wooden turneries made of red alder and ash logs were also MW/V dried from green to 4%MC without any degradation. The rates of the MW/V drying were examined for three different lengths of poplar logs.

• Journal of muscle and joint health
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• v.14 no.1
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• pp.26-32
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• 2007

Purpose: The purpose of this study was to determine if osteoarthritis patients would benefit in terms of pain, fatigue, difficulty with physical activity, joint stiffness, and flexibility of the joints from a structured self-help program. Method: This self-help program was carried out 2-3 hours once a week for 6 weeks in 2005-2006, and evaluated in one group pretest-posttest pre-experimental design. The subjects of this study who were diagnosed osteoarthritis were recruited at two different Community Health Centers in Kangwon. The subjects who agreed with the purpose of this study and participated both pretest and post-test were 55 patients. Mean age is 63.48 (9.48) years, mean duration of disease is 7.95 (7.66) years. The self-help program was consisted of weekly health contract, exercise, health education, group discussion, group counseling, and recreation. At every meeting, researcher and trained public health nurse evaluated the program, and prepared the next program. The measurement tools were pain rating scale (0-10), fatigue rating scale (0-10), Korean WOMAC (Western Ontario and McMaster University Osteoarthritis) Index, ruler, and goniometer. Results: At the completion of 6 weeks of self-help program, the subjects reported significantly less pain and difficulty with physical activity and more flexibility in both shoulder and knee joints compared to pretest. Conclusion: The self-help program would be helpful on pain, physical activity, and joint flexibility for arthritis patients.

• Journal of Arbitration Studies
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• v.12 no.2
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• pp.337-372
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• 2003

Given the difficulties investors would encounter in pleading and proving their claims in court, they may well be better off in a system where less attention is paid to the law and more to the equities of the actual dispute before the arbitration panel. While this is not a system where accountability and predictability of results can be achieved, investors may fare better than they might expect. It follows then that if equitable considerations enhance rather than subtract from investors' chances of recovery, then investors need not worry about the consequences of the arbitrators' failure to apply the law. This article tracked the evolution of the arbitration process, through amendments to the pertinent securities arbitration codes of procedure, from an informal proceeding into a quasi-judicial one. Subsequently, I examined the practical difficulties arbitrators encounter in their efforts to apply the law. The Court in McMahon assumed arbitrators would apply the law and that the “manifest disregard” standard would provide sufficient judicial oversight to ensure that they did. But there is no meaningful review of arbitration awards to assure arbitrators are applying the law. Arbitration awards have no value as precedent for future arbitrations. Accordingly, there appears to be little reason to write such an award, particularly if the end result is an award immune from challenge no matter how the panel ruled. In these days, securities arbitration as a disputes resolution system is becoming a more popular practice. The trend of the courts in America has been to enforce arbitration agreements. Moreover arbitration helps alleviate some of the burden of a heavy caseload from the judiciary and is a viable method to resolve disputes in a relatively quick and efficient manner. Therefore I think it would be necessary to introduce securities arbitration system to our disputes resolution system Compared to American practices, there could be, of course, many differences in recognition on arbitration and legal structure in our country. Thus it will be an assignment to consider seriously and carefully what kind of securities arbitration system will be proper for us.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.12 no.3
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• pp.284-289
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• 2005

Purpose: The purpose of this study was to explore changes in the test items in the preparation book for the national qualifying examination. Test items which developed in the year 2000 and 2004 through nationwide faculty workshop in Fundamentals of Nursing were examined. Method: Test items for the national qualifying examination for 2000 and 2004 in Fundamentals of Nursing were analyzed using frequencies and percent. Results: The test items for the national qualifying examination for 2004 in Fundamentals of Nursing showed an increase in the number of test item over the year 2000. According to McGuire's taxonomy, domains of the test items in 2000 were recall(65.1%), interpretation (22.0%), and problem solving(12.9%) in that order. In 2004 items for the recall domain(74.7%) increased 9.6% above the level of 2000, and interpretation and problem solving domains showed a slight decrease. With regard to type of test items, the proportion of A type in 2004 was the same with 37.6% as 2000, and that of K type(61.5%) increased by 0.7% over the year 2000(60.8%). Conclusion: The test items for the national qualifying examination of 2000 and 2004 were not different except for the increase in the number of test items.

• Journal of Korean Medicine Rehabilitation
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• v.21 no.3
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• pp.45-55
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• 2011

Objectives : The main purpose of this study is to investigate the efficacy of Kyejibokryong-whan(Guizhifuling-wan) and examine the blood stasis for patients with motor vehicle accident. Methods : Of the patients who have visited Dong-Shin university oriental hospital for general pan due to motor vehicle accident from June 2010 to November 2010, we enrolled 29 patients and performed blood stasis diagnosis. Patients were divided into groups according to blood stasis findings. Patients who had more than twenty blood stasis diagnosis point were classified as blood stasis group. Patients who had under twenty blood stasis diagnosis point were classified as non blood stasis group. We administered Kyejibokryong-whan(Guizhifuling-wan) to all group. The effect was assessed by VAS(visual analogue scale), SF-MPQ(short form-McGill pain questionnaire) ODI(Oswestry disability index) & NDI(neck disability index). Results : The pain & function index decreased in both groups after treatment. Conclusions : The difference between blood stasis group and non blood stasis group were not significant at after treatment stage. This data suggested that the method of classifying blood stasis is useful and the Kyejibokryong-whan(Guizhifuling-wan) can be effective means that decrease pain caused by motor vehicle accident.