• The Journal of Advanced Prosthodontics
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• v.12 no.2
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• pp.100-106
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• 2020

PURPOSE. The purpose of this in vitro study was to evaluate the fitting accuracy of single crowns made from a novel presintered Co-Cr alloy prepared with a computer-aided design and computer-aided manufacturing (CAD/CAM) technique, as compared with crowns manufactured by other digital and the conventional casting technique. Additionally, the influence of oxide layer on the fitting accuracy of specimens was tested. MATERIALS AND METHODS. A total of 40 test specimens made from Co-Cr alloy were investigated according to the fitting accuracy using a replica technique. Four different methods processing different materials were used for the manufacture of the crown copings (milling of presintered (Ceramill Sintron-group_cer_sin) or rigid alloy (Tizian NEM-group_ti_nem), selective laser melting (Ceramill NPL-group_cer_npl), and casting (Girobond NB-group_gir_nb)). The specimens were adapted to a resin model and the outer surfaces were airborne-particle abraded with aluminum oxide. After the veneering process, the fitting accuracy (absolute marginal discrepancy and internal gap) was evaluated by the replica technique in 2 steps, before removing the oxide layer from the intaglio surface of the crowns, and after removing the layer with aluminum oxide airborne-particle abrasion. Statistical analysis was performed by multifactorial analysis of variance (ANOVA) (α=.05). RESULTS. Mean absolute marginal discrepancy ranged between 20 ㎛ (group_cer_npl for specimens of Ceramill NPL) and 43 ㎛ (group_cer_sin for crowns of Ceramill Sintron) with the oxide layer and between 19 ㎛ and 28 ㎛ without the oxide layer. The internal gap varied between 33 ㎛ (group_ti_nem for test samples of Tizian NEM) and 75 ㎛ (group_gir_nb for the base material Girobond NB) with the oxide layer and between 30 ㎛ and 76 ㎛ without the oxide layer. The absolute marginal discrepancy and the internal gap were significantly influenced by the fabrication method used (P<.05). CONCLUSION. Different manufacturing techniques had a significant influence on the fitting accuracy of single crowns made from Co-Cr alloys. However, all tested crowns showed a clinically acceptable absolute marginal discrepancy and internal gap with and without oxide layer and could be recommended under clinical considerations. Especially, the new system Ceramill Sintron showed acceptable values of fitting accuracy so it can be suggested in routine clinical work.

• Korean Institute of Interior Design Journal
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• v.21 no.6
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• pp.224-232
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• 2012

Although evolution of construction materials brought about development of modern architecture, they caused destruction of the environment and pollution. This problem is not a new one in terms of ecological esthetics and materials of sustainable architecture in light of the Eastern view of nature and this idea became a background of this study. The basic concept is to try to find out their characteristics from a perspective of ecological esthetics in relation to traditional building materials that nature, architecture, and humans coexist and live with each other to balance. Based on ecological esthetics and precedent studies on materials of traditional architecture, we investigated connections, expressive methods and characteristics in traditional residential construction space. This attempt has meanings in that it can propose a new framework of forming various viewpoints and spatial perceptions in relation to esthetics and traditional construction materials. The current study examined the characteristics by dividing them into tangible and intangible elements based on expressive features of elements of nature. The characteristics found by this process are not simply notion of physical materials, but plays a key role aesthetically and ecologically. Nature and materials take circulation of the law of nature, regulate energy, increase efficiency and play a major role in an economic way. Nature in itself becomes natural alternative energy, and plays its role in an invisible fashion. It examined how expressive characteristics of construction materials are reflected through analyzing residential space and Korean traditional garden having relationships with Eastern viewpoint of nature in relation to Korean traditional construction materials from a perspective of ecological esthetics. Findings of the above study indicate that expressive characteristics of Korean traditional construction materials from a perspective of ecological esthetics are that nature, space, humans coexist and live together and they will provide a clue to an alternative to solve ecological and environmental problems modern society will have in the future. Through this process, it provided a possibility that traditional space and materials can be succeeded in creative and new ways, and it found out the way for nature, space, and humans to coexist and a possibility of ecological esthetics. It addition, it will provide a key base as an alternative of sustainable design of the future.

• Plant Journal
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• v.10 no.2
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• pp.48-59
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• 2014

Coupons which have same figure as weld joint of the forged steel valves and 1 inch nominal weld thickness were manufactured using ASTM A182 F92 material. After welding with GTAW method, the welded specimens have been post-weld heat treated at $705^{\circ}C$, $735^{\circ}C$, $750^{\circ}C$, $765^{\circ}C$, $795^{\circ}C$ and $825^{\circ}C$ for 1 hour per 1 inch nominal weld thickness each (Group 1) to evaluate characteristics of welds based on various holding temperature. Indeed, 3 welded specimens were post-weld heat treated for 30 minutes, 1 hour and 2 hour (Group 2) at $735^{\circ}C$ to evaluate characteristics of welds based on various holding time. Hardness values were measured at the weld metal, heat affected zone and base metal to observe hardness change depending on the condition. As a result of the evaluation, appropriate holding temperature for PWHT is proved as $750^{\circ}C$ and $765^{\circ}C$ for 1hour per 1 inch nominal weld thickness. Indeed, holding for 1 hour per 1 inch nominal weld thickness was insufficient for PWHT effect when the holding temperature was at $735^{\circ}C$. The microstructure of post-weld heat treated weld metal was determined as tempered-martensite structure.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.26 no.2
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• pp.133-145
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• 1996

Aspirating or swallowing foreign bodies is a common occurrence. If they are wholly or partly radiopaque, their localization in and progress through the gastrointestinal tract can be more effective. Of the dental origin foreign materials swallowed, the most common things are fragments of anterior maxillary partial denture. But the radiopacity of denture base resins is not sufficient to determine the location of the objects. The purpose of this study was to develop a radiopaque dental acrylic resin, which has clinically detectible radiopacity with minimal change of mechanical properties and color. The radiopacity, color change(CIE 6..E) and microhardness of acrylic resins were determined after mixing barium sulfate or iodide compound. Thermocycling course was conducted to determine the change of characteristic of resins after using for a long time in the mouth. Five or ten percent of barium sulfate to total weight of cured material was mixed with heat curing dental acrylic resin or chemically curing orthodontic resin. In the case of iodide compound, the mixing ratio was two or three percent. After mixing the high radiopaque materials, resin was cured to 20×20×2 mm plate, polished with #600 sand paper and finally polished with Microcloth(Buehler). The specimens were thermocycled in 5 and 55 t distilled water for 2,000 times, and the measurement of radiopacity, color and Vickers hardness was repeated every 500 times thcrmocycling. The radiopacity of specimens on the X -ray films was measured with densitometer(X-rite). The color change was detennined with differential colorimeter(Model TC-6FX, Tokyo Denshoku), and the Vickers hardness number was measured with microhardness tester(Mitsuzawa). The following results were obtained : 1. All the three variables, the kinds of acrylic resins, the mixing or the kinds of high radiopaque materials and thermocycling, had combined effect on the radiopacity of the dental acrylic resins(p<0.0l). 2. The two variables, the mixing or the kinds of high radiopaque materials and thermocycling, influenced on the radiopacity of the dental acrylic resins(p<0.01). But the kinds of acrylic resins did not influence on the color change of mixed dental acrylic resins(p>0.05). 3. Each of the three variables, the kinds of acrylic resins, the mixing or the kinds of high radiopaque materials and thermocycling, influenced on the radiopacity of dental acrylic resins(p<0.0l). 4. The high radiopaque materials used in this study did not yield clinically usable radiopacity, and the color change was great after mixing those materials.

• Journal of dental hygiene science
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• v.16 no.1
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• pp.93-100
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• 2016

The purpose of this study was to compare the changes of retentive force in different stud attachment systems for implant retained overdenture. Two commercially available attachments with different retentive forces were investigated: Kerator (pink, blue, red) and O-ring (orange, red). Two implant fixtures were vertically embedded in base mountings. Five pairs of each attachment were evaluated. A universal testing machine was used to evaluate the retentive force of two attachments during wear simulation. Surface characteristics of each attachment system were evaluated with scanning electron microscopy. Five pairs of each attachment were evaluated. Kerator pink showed the highest initial retention. After 2,500 cycles of wear-simulation, Kerator pink noted the largest decrease in retention. According to results of surface analysis, Worn surfaces were obtained in matrices and patrices. Heavy wears were observed in matrices. After 2 year-wear simulation, most attachments exhibited retention loss. Attachments using different kind of material exhibited dissimilar surface alterations.

• Journal of Korean Elementary Science Education
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• v.18 no.1
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• pp.19-28
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• 1999

This study aims to analyze tile research trends of science education in Korea, and suggest the direction of the desirable research, which is to help the improvement of science education practically. To achieve these aims, the papers related to the science education (paper;1288, master′s thesis;724, doctoral thesis;59), which were published from 1992 to 1996 in Korea, are classified by the criteria for the analysis and summed up. The condensed results of this study are as follows, 1. The papers published through this period, maintains the stability in aspect of quantity compared with 1980s. It is owing to the efforts of the prime investigator so that "the science education," as a part of normal science, may settle down in Korea. 2. In the case of thesis for the academic degree, the doctoral theses are rare, as the ratio of the doctoral vs. the master′s is 1:13. Even so, most of the theses were produced by a few universities(master′s thesis/Kor. Nat. Univ. of Edu.;28.3%, Ewha Woman′ Univ.;16.2%, doctoral thesis/Seoul Nat. Univ.;57.6%, Kor. Nat. Univ. of Edu.;22.0%). 3. Most of papers are preponderant at three categories among the ten categories proposed by this study (science teaching-learning material;23.5%, science teaching methods;21.4%, psychology of science education;21.1%). 4. Concerning the subject of research, these papers are not diversity and intensive, that is; the subject related to scientific concepts, scientific thinking and attitude, and analysis of scientific textbook is 17.7%, 14.3%, and 10.5% of the total, respectively. 5. Though not including this study, among the theses for the master of science education, many of theses are related to the subject of pure science. There are some suggestions related to tile results of this study. The severe preponderance ill the training process, the subject, and area of research, can be pointed out one of the flimsy in our researches of science education. Because these cannot be considered separately, the policy and support of educational administration must be needed to remove this phenomena. To improve the present situation of science education, the research funds have to be given to the practical than the theoretical subjects. Which can make promptly a settlement of tile problems and difficulties from the field of science education, and encourage the reseal,:h activities that tile front teachers take part in. Lately, the accumulation of literature and references are a prior condition in the development of academic knowledge. Therefore the data base system for the information of science education and translation of foreign literature related to science education must be achieved. In addition, the programs that tile teacher and the investigator can make good use of such an information without limited conditions, must be prepared.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.45-53
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• 2016

This study examined pruritus to provide the data based on burn patient pruritus. A self-report questionnaire survey was conducted among ninety five burn survivors, who were over 18 years of age with admission periods longer than two weeks. The results indicated that the average burn range was $18.95{\pm}17.10%$, severity was $48.83{\pm}23.96$, and distress was $46.42{\pm}25.80$. A significant difference in pruritus consequences was observed according to frequency. The patients consistently experienced pruritus, even if it happened less often, difficulty in falling asleep (F=4.817, p=.004), poor mood (F= 5.955, p=.015)), and loss of concentration (F=6.483, p<.000). A significant difference in the pruritus consequences according to duration was observed, lasting for 30 minutes for all groups, more than the population and less than 30 minutes, difficulty in falling asleep (F=7.452, p<.000), poor mood (F=3.655, p<.015), and loss of concentration (F=12.564, p<.000). The frequency, duration (r=.29, p=.004), severity (r=.45, p<.000), distress (r=.44, p<.000), and consequences of pruritus in burn patients (r=.29, p=.004) showed a positive correlation. The results of this study could be used as a base material for the care of burn patients experiencing pruritus.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.121-129
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• 2017

In this paper, the shake table test for the masonry infilled reinforced concrete frame with non-seismic details was carried out in order to evaluate its dynamic behaviour and damage under seismic condition. The tested specimens were the RC frame and the masonry infilled RC frame and the dynamic characteristics, such as a resonant period, acceleration response, displacement response and base shear force response, were compared between them. As a result of the shake table test, RC frame specimen had flexural cracks at the top and bottom of the column and shear cracks at the joints. In the case of masonry infilled RC frame, the damage of the frame was relatively minor but the sliding cracks and diagonal shear cracks on the masonry wall were severe at the final excitation. The resonant period of infilled RC frame specimen was shorter than that of the RC frame specimen because the masonry infill contributed to increase the stiffness. The maximum displacement response of the infilled RC frame specimen was decreased by about 20% than the RC frame specimen. It was analyzed that the masonry infill wall applied in this study contributed to increase the lateral strength of the RC frame with non - seismic detail by about 2.2 times and the stiffness by about 1.6 times.

• Journal of the Korean Institute of Gas
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• v.2 no.2
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• pp.48-54
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• 1998

In this study a computerized prototype system was developed with Safety Management Information System(SMIS version 1.0) as a main system and database as subsystems to handle information. Safety management information consists of management aspects and technical elements, but SMIS consists of 4 modules of technical elements to interrelate safety technologies closely. SMIS enables gas industries to manage process safety information effectively and to evaluate hazards. The results from SMIS can be used to the operation manual and the emergency plan. Data base consists of 3 modules of accident data, material data, and equipment data to support SMIS. Also, the case study results proved the usefulness of SMIS for searching and accumulating process safety data. Especially, MIS which has the database suggests a formal structure for scattered raw safety data in gas industries and brings reduction of man power and time.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.6
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• pp.291-298
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• 2016

Electrochemical water treatment process as a useful treatment method for the removal of non-degradable matter has been consistently studied for several decades. Key process of electrochemical water treatment are oxidation reaction from an anode and reduction from a cathode. In this study, the effect of pre-treatment methods in the insoluble electrode manufacturing process for the water treatment has been evaluated for the life time of electrode The results of this study showed that pre-treatment methods of a base metal such as surface roughness, clean method and interlayer formation influenced to life time of electrode when the same condition (catalyst electrode layer coating method and material system) was applied for pre-treatment methods. This study was conducted by using $IrO_2/Ti$ electrode In the test of sand-blasting process, an electrode manufactured by using sanding media of different sizes resulted in the most effective electrode life time when the size of alumina was used for $212{\sim}180{\mu}m$ praticle size (#80). The most effective method was considered using arc plasma in the additional roughness control and cleaning process, sputtering method to form Ta type interlayer formation process.