• Restorative Dentistry and Endodontics
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• v.25 no.4
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• pp.599-605
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• 2000

Among the effects of tooth bleaching on composite resins, degree of color change and dye deposition onto composite resins after office bleaching were investigated in vitro. Seventy two disc-shaped resin samples were fabricated with hybrid type composite resin, Z-100 under 3 different environments(24 samples for each environment) characterized by 3 kinds of light-curing intensity and duration($250mW/cm^2$-20sec., $250mW/cm^2$-40sec., $550mW/cm^2$-20sec.). As control, one-third samples of each group were not treated with bleaching agent. The remaining two-thirds samples of each group were treated with bleaching agent(bleaching group). Then, before thermocycling procedure in coffee bath, the half of the samples treated with bleaching agent were polished(polishing group) with polishing system. SofLex, but the other half(not-polishing group) and control group were not polished. Another 72 samples were also made with microfilled type composite resin. Sillux Plus and treated according to the experimental procedures mentioned above. The color of each resin sample was measured before bleaching, after bleaching, and after thermocycling preceded by bleaching. And color difference was evaluated. It was concluded as follows: 1. The amount of color change of resin samples after office bleaching was not statistically significant(p>0.05). But the samples which were treated with bleaching agent showed more color change than that of control group. 2. After thermocycling in coffee bath, the amount of color change of resin samples between control and bleaching group was not statistically significant(p>0.05). 3. After thermocycling in coffee bath, the polishing procedure of resin samples showed no statistically significant difference(p>0.05) between polishing and not-polishing group in the aspect of color change.

• Journal of Korean Society of Rural Planning
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• v.3 no.1
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• pp.68-76
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• 1997

The purpose of this study is to suggest the spatial model which can be applied to the tourism farm plan. This study includes : (1) the analysis of existing facilities and activities of 22 tourism farms in Kyunggido and (2) the survey questionnaire about user's attitudes in 3 tourism farms. The results can be summarized as follows : 1) The .Major activities in the tourism farm are the resting/playing based on the natural environment and group meeting. 2) Average area is 17879.4uf (5418 坪). The most frequent facility is restaurant and lodge. 3) It is necessary to propose various types of tourism farm considering both natural conservation and development of rural region and users'various wants. The tourism farms are officially classified into four types Natural education type, Mind and body training type, Weekend farm type, Recreation type. 4) The space for tourism farm is divided into an area of production, and area of processing, and an area of convenience/recreation. 5) It is desired the convenience facilities are located in front of a farm, and the area of production is located at the back of a farm, and simple rest facilities are located all of the farm. 6) The weekend farm model and processing/convenient facility model are proposed in this study. Three types of the weekend farm models are proposed - simple type, composite type, and garden type. Three types of the processing/convenient models are proposed one building type, adjacent building type, and scattered building type.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.2
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• pp.85-93
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• 2018

This study investigated the structural behavior and field applicability of sandwich type GFRP arches with polymer mortar in core. As a result, in case of crack loading and failure loading, total strains at crown were the highest; the fracture strain at crown was 0.01690, which is 4.2 times greater than the fracture strain (0.004) of cement concrete. The 3 % deflection load was 17.42 kN, the flexural strength was $163.98{\times}10^{-3}GPa$, and the flexural elastic modulus was 11.884 GPa. From load-deflection relationship up to 3.5 % deflection, 3D analysis results and experimental values were observed to be almost identical. It was considered reasonable to set a deflection rate limit to be 3 % for structural safety purpose. The standard external flexural strength of semicircular arch used in this study was approximately 2.64 times higher than that of hume pipe (2 type standard) and tripled composite pipe. The external pressure strength at fracture was approximately 1.57 times higher than that of hume pipe. It was confirmed that the implementing semicircular arch had mechanically more advantage than the circular pipe. Optimum member thickness was 8~53 mm according to arch radius of 450~1,800 mm and cover depth of 2~10 m. It was found that the larger strength could be obtained even if the thickness of member was smaller than that of concrete structure. In field application study, figures and equations were derived for obtaining applicable cover depth and optimum member thickness according to loading conditions. These would be useful data for design and manufacture of sandwich type semicircular arch.

• Clinical and Experimental Pediatrics
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• v.65 no.1
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• pp.47-52
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• 2022

Background: An adequate large-scale pediatric cohort based on nationwide administrative data is lacking in Korea. Purpose: This study aimed to differentiate patients with VVS by autonomic dysfunction severity using the composite autonomic severity score (CASS) and compare the clinical manifestations and prognosis between patient subgroups. Methods: We retrospectively reviewed the medical records of 66 VVS patients divided into 3 groups by CASS. To compare the differences between these groups, we analyzed VVS type, triggers, prodromal symptoms, management of syncope, and prognosis between patients with mild versus moderate autonomic dysfunction. Results: Of our 66 patients with VVS, 41 had mild autonomic dysfunction (62.1%) and 25 had moderate autonomic dysfunction (37.9%). We found no significant intergroup differences in age, sex, inducible factor (P=0.172), prodromal symptoms, laboratory findings, head-up tilt test, type of syncope, or prognosis (P=0.154). Conclusion: We found no evidence that autonomic dysfunction degree is affected by VVS characteristics, test findings, parameters, or prognosis; therefore, no further evaluations are needed to classify autonomic dysfunction severity.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.4
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• pp.324-332
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• 2018

We conducted a questionnaire survey to analyze the current status of the coastal composite fisheries, as well as the improvement point in designing a new type coastal composite fishing boat suitable for Korean fishing environments from April to August 2017. The questionnaire composed of 20 questions about the features of the coastal composite fishing boat and fishing work. The survey sites were selected to cover all parts of the country by considering the geographical position. The significance testing for the response results was accessed by ${\chi}^2$ test and ANOVA. The results revealed that more than half (59.1%) of the fishermen operated one day per voyage and operating alone topped with 22.5% in the number of crews, followed by 2 persons (20.3%) and 5 persons (22.1%). The navigation devices had a high rate of installation and GPS plotter ranked first in the devices. In addition, fish finder ranked first in fishing equipment, followed by net hauler. The most inconvenient work that they felt during the fishing operation was fish handing at 49.8% and other general fishing works like setting and hauling line, deck cleaning accounted for about 25%. The hardest work was the accident by ropes wrapped around propeller and the engine trouble came in second. The most inconvenient facilities to the present design of fishing boat was wheelhouse (76.7%), followed by fish hold (38.5%), and deck (35.1%). Furthermore, inconvenient points related to the movement of fishing gear, noise and vibration of engine, slippery deck and small fish hold exceeded 50%.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.6
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• pp.271-275
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• 2001

We investigated preparation of 1-3 PZT composites for medical ultrasonic transducer array (briefly UTA) using micro pressing method. The proposed process was using pressing PZT green sheet by PMMA micro mold obtained from X-ray lithography. Microstructures, electriacl and electro-mechanical properties of fabricated composites were analyzed. Dielectric constant at 1kHz and thickness mode electro-mechanical coupling coefficient of $6.2mm{\times}6.2mm{\times}422{\mu}m$ UTA sample were 1754 and 51%, respectively. Microstructures of sintered PZT showed dense and uniform. And PZT phases were well crystallized. Micro pressing method is a mass productive process in case of using injection molded PMMA by batch type LIGA process.

• Composites Research
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• v.19 no.5
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• pp.7-11
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• 2006

The improved SWNTs/PANi composite actuator films applicable to an artificial muscle were fabricated successfully using a new process of manufacture that consists of 90% pure single-walled carbon nanotubes (SWNT) and chemical polymerization. PANi is electrically conducting polyaniline polymer. The conductivities of the composite SWNTs/PANi film-type actuators and the pure PANi films fabricated were measured as 56.15 S/cm and 17.38 S/cm, respectively, by the 4-prove method. The conductivity of the composite actuator is 3.2 times higher than the pure PANi film. The fabricated composite actuator showed higher conductivity than any other similar ones. The quality of samples was investigated by an electron scanning microscope (SEM). To measure the actuating strains, a specially designed beam balance apparatus was developed and strains of the composite actuators was measured by a laser displacement sensor subjected to electric currents. During the operation, the sample was soaked in the $NaNO_3$ solution and the sine-wave voltage in the range of $+1V{\sim}-1V$ was applied. The length of the composite actuator changed from $l_0=12.690$ mm to $l_1=12.733$ so that the change of length was l=0.043 mm and the strain was 0.34 %. This is a very high strain for this kind of a composite actuator. Other result reported by Tahhan showed 0.23 % strain, so that the present result is improved by 48%.

• Restorative Dentistry and Endodontics
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• v.13 no.1
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• pp.53-67
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• 1988

An investigation was carried out to compare the pulp responses against a few type of composite and streptococcus mutans contamination under the zinc oxide eugenol cement, and also confirmed pulpal responses of various composites with or without base. Seventy eight teeth from 6 dogs were employed and divided into 6 groups. Class V cavities were prepared on each tooth routinely with low speed dental engine. Paper disc about 0.3mm thick was immersed in the BHI broth in which streptococcus mutans had been enriched and the disc was inserted on the cavity floor prior to filling. Scotch bond puls Silux as Bis-GMA system composite resin and Helimolar as urethane system composite resin were adopted. Control group: Zinc-Oxide Eugenol cement filling Experimental groups: Group 1. Scotch bond + Silux filling with Dycal base Group 2. Heliomolar filling with Dycal base Group 3. Scotch bond + Silux filling without base Group 4. Heliomolar filling without base Group 5. Streptococcus mutans application. All cavities were sealed with thick ZOE cement to avoid marginal leakage. Postoperative intervals of 1, 2, 3, 4, 5 and 6 weeks teeth were carefully extracted, processed and stained with Hematoxylin and Eosin. The results were as follows: 1. S. mutans application group and composites without any base showed more severe pupal response than control group and dyca based groups. 2. The experimental group of S. mutans application showed severe response in the early stage compared to the two groups of composite resin without base, but no significant difference was found following periods. 3. The difference of pulpal response is not significant between Bis-GMA system and urethane system. 4. Streptococcus mutans application group and composites without base groups showed the evidence of histologic recovery at the six week cases and the large amount of reparative dentin was the prominent feature. 5. Pulp responses against every material were inclined to normal according to the time elapsed.

• Journal of Korean Society of Rural Planning
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• v.1 no.2
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• pp.67-76
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• 1995

The actual condition of farmstead, mainly livestock facility, was surveyed in ChungChongBukDo in order to find out factors and problems of farmstead planning design. From the data collected, a type, plot, size and scope of farmstead, relationship of house and farmstead, topography, climate, proprietor's opinion on them were analyzed or obtained as the basic design criteria for planning: designs. The best type of farmsteads was individual farm having livestock facilities. They were mostly breeding a kind of livestock without their plan and Bone planning at residing area. The south aspect of the facility was extremely much and slope of the land was mostly 15。 below. Wind blows from East-South in summer and winter wind are West-North extremely much. Sun heat was mostly above 6 hours. In the case of collective and composite farmstead, proprietors wanted that a head of cow has 1,000-3,000 pyeong, the area of facility has 1,500-2,000 pyeong, total area of farmstead has 45,000-400,000 pyeong and an estimated expense is 0.2 - 1.5 billion won. Farmstead planning design was proposed through field survey results and contents of'references. Examples of farmstead planning design were composite and concentrated type and existed according to the situation of road(North, South, East, and West).

• Journal of the Microelectronics and Packaging Society
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• v.9 no.2
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• pp.11-17
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• 2002

Polymer/ceramic composite is of great interest as a dielectric material for embedded capacitors. This paper is concerned in the effects of $BaTiO_3$ particle size on epoxy/$BaTiO_3$ composite films for embedded capacitors. 6 different size powders smaller than 1 $\mu\textrm{m}$ in diameter and bisphenol-A type epoxy were used for this experiment. Dielectric constant of the epoxy/$BaTiO_3$ composite capacitors increases as the powder size increases at the same powder loading, which is due to the increase of tetragonality of the powders as particle size increases. And leakage current of the capacitors also increases dramatically as the powder size increases. It was explained that this is due to the decrease of the number of $BaTiO_3$epoxy/$BaTiO_3$ potential barriers per unit length and, moreover, the enhancement of potential barrier lowering effects caused by increase of potential drop per one barrier. As a result, there is tradeoff between high dielectric constant and low leakage current in the epoxy/$BaTiO_3$ composite capacitors. So it is important to select proper size $BaTiO_3$ powders in accordance with needs.