• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.2
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• pp.138-144
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• 2014

Purpose: This study examined the water sorption of commonly used dual-cure resin cements and compared the change in the micro-hardness among the cements. Materials and Methods: Five types of dual-cure resin cements (Maxcem, Duo-link, Panavia F, Variolink II, Rely X Unicem) were selected. Fifty specimens were classified into five groups containing ten specimens in each group. The water sorption of the five specimens in each group was evaluated after being immersed in distilled water (DDW) for seven days. The following results were obtained by comparing the specimens immersed in DDW with those not immersed in DDW. Results: 1. The water sorption of Maxcem showed the highest score, followed by Panavia F. These two cements were followed by Duo-link and Rely X Unicem. The water sorption of Variolink II showed the lowest score among the cements used in this study. 2. Among the specimens not immersed in DDW, the micro-hardness of Rely X Unicem showed the highest score followed by Panavia F and Variolink II. These cements were followed in order by Duo-link and Maxcem. 3. Among the specimens immersed in DDW, the microhardness of Rely X Unicem showed the highest score followed by Maxcem, Panavia F and Variolink II. Duo-link shoed the lowest score among the cements used in this study. 4. Maxcem, Duo-link, Panavia F and Rely X Unicem showed significant differences in micro-hardness due to water resorption but Variolink II was unaffected by immersion in water. Conclusion: Using the resin cement which has lower water sorption and higher micro-hardness is recommended.

• Restorative Dentistry and Endodontics
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• v.12 no.1
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• pp.39-49
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• 1986

The purpose of this study was to observe characteristic properties through the polarization curves and SEM images from 4 different types of amalgam obtained by using the potentiostats (Princeton EG & G) & SEM (Jeol/35), and to investigate the degree of corrosion on the oxidation peak of the each phase of amalgam. After each amalgam alloy and Hg was triturated as the direction of the manufacturer by means of the mechanical amalgamator (Shofu Co.), the triturated mass was inserted into the cylindrical metal mold which was 12mm in diameter and 10.0mm in height and was condensed by using routine manner. The specimen was removed from the mold and stored at room temperature for about 24 hours. The standard surface preparation was routinely carried out. Anodic polarization measurement was employed to confirm the corrosion behaviour of the amalgams in a 0.9% saline solution (P.H: 6.8-7.0) at $37^{\circ}C$. The initial rest potential (corrosion potential) was determined after 30 minutes of immersion of specimen in electrolyte, and the potential scan was begun at the point of 100mV cathodic from the corrosion potential. The scan rate was 0.17mV/sec. in the study to observe the degree of corrosion of each phase. SEI and EPMA images on the determined oxidation peaks of each amalgam were observed. The results were as follows: 1. In the four anodic polarization curves, low copper amalgams have three oxidation peaks and high copper amalgams have two oxidation peaks, -270mV, +26mV and +179mV(SEC) in the low copper lathe cut, and -300mV, +39mV and +163mV(SEC) in the low copper spherical. -4mV and +154mV(SEC) in the Dispersalloy, and +17mV and +180mV(SEC) in the Tytin as high copper amalgams. 2. ${\gamma}_2$ phase in the low copper amalgam and ${\eta}$ phase in the high copper amalgam were the most corrodible phases and Ag-Cu eutectic in high copper amalgam was the most slowly corroded phase. 3. Low copper amalgam was more susceptible in corrosion than high copper amalgam.

• Restorative Dentistry and Endodontics
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• v.13 no.2
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• pp.221-235
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• 1988

The purpose of this study was to observe characteristic properties through the polarization curves and EMPA images from 4 different types of amalgam obtained by using the potentiostats (EG & G PARC) & EPMA (Jeol JSM-35), to investigate the degree of corrosion of each phase of amalgam on the oxidation peak, and to identify corrosion products from the corroded amalgam by use of X-ray diffractometer(Rigaku). After each amlgam alloy and Hg were triturated as the direction of the manufacturer by means of the mechanical amalgamator(Shofu), the triturated mass was inserted into the cylindrical metal mold which was 12mm in diameter and 10mm in height and was condensed by means of routine manner. The specimen was removed from the mold and stored at room temperature for about 7 days. The standard surface preparation was routinely carried out. Anodic polarization measurement was employed to compare the corrosion behaviours of the amalgams in 0.9% saline solution(pH6.8~7.0) and artificial saliva (pH6.8~7.0) at $37^{\circ}C$. The open circuit potential was determined after 30 minutes' immersion of specimen in electrolyte and the potential scan was begun at the potential of 100mV cathodic from the corrosion potential. The scan rate was 1mV/sec and the surface area of amalgam exposed to the solution was 0.64$cm^2$ for each specimen. All the potentials reported are with respect to a saturated calomel electrode (SCE). EPMA images on the determined oxidation peaks of each amalgam in artificial saliva were observed. X-ray diffraction patterns of each sample were recorded before and after polarization in artificial saliva (Aristaloy, Caulk Spherical, Dispersalloy and Tytin: at +770mV, +585mV, +8.10m V and +680m V respectively) by use of a recording diffractometer. Nickel filtered Cu $K_{{\alpha}_1}$ radiation was used and sample was scanned at $4^{\circ}(2{\theta})/min.$ from $25^{\circ}$ to $80^{\circ}$. The following results were obtained. 1. Oxidation peak potential in artificial saliva shifted to more anodic direction than that in saline solution. 2. The corrosion potential of high copper amalgam was more anodic than the potential of low copper amalgam. 3. The current density was lower in artificial saliva than in saline solution. 4. One of the corrosion products, AgCl was identified by X-ray diffraction analysis. 5. ${\gamma}_2$ phase was the most susceptible to corrosion and e phase was stable in low copper amalgam and ${\eta}$' phase and Ag-Cu eutectic were susceptible to corrosion in high copper amalgam.

• Restorative Dentistry and Endodontics
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• v.32 no.6
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• pp.542-549
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• 2007

The purpose of this study was to evaluate the difference in the surface roughness after polishing and to evaluate the difference in color stability after immersion in a dye solution among four types of composite resin materials. Four light-polymerized composite resins(Shade A2) with different sized filler content(a nanofilled, a hybrid, a microfilled, a flowble) were used. Average surface roughness (Ra) was measured with a surface roughness tester (Surftest Formtracer) before and after polishing with aluminum oxide abrasive discs(Super-Snap). Color of specimens before and after staining with 2% methylene blue solution were measured using spectrophotometer(CM-3700d) with SCI geometries. The results of Ra and ${\Delta}E$ were analyzed by one-way analysis of variance(ANOVA), a Scheffe multiple comparison test and Student t-test(p=0.05). After polishing, Ra values were decreased regardless of type of composite resins. In surface roughness after polishing and color stability after staining, nanofilled composite resin was not different with other composite resins except flowable resins.

• Elastomers and Composites
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• v.40 no.3
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• pp.166-173
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• 2005

Effect of thermal aging on the weight loss and water absorption of epoxy adhesives was investigated in the presence of three types of different hardeners, such as D-230, G-5022, and HN-2200. Thermal and mechanical properties of the cured epoxy resins were also studied througth the glass transition temperature and shear adhesion strength measurements. Weight losses of DGEBA/D-230 and DGEBA/HN- 2200 systems were not varied. However, the weight of DGEBA/G-5022 system was significantly decreased with increasing the thermal aging time. The water absorption of the specimens was increased as the thermal aging time increased except that using G-5022. DEGBA/HN-2200 system showed higher $T_g$ value than those of other systems, due to the formation of the fine three-dimensional network structure containing aliphatic ring. Shear adhesion strength of all systems was increased with increasing the thermal aging tine, which is attributed to increased degree of cure and fine three-dimensional network structure formation. And $T_g$ values and shear adhesion strength of all specimens exposed to water was decreased as the immersion time increased.

• Tuberculosis and Respiratory Diseases
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• v.42 no.4
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• pp.513-521
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• 1995

Background: Nucleolar organizer regions(NORs) are chromosomal segments encoding for ribosomal RNA and associated with argyrophilic nonhistone protein. Ribosomal RNA genes ultimately direct ribosome and protein synthesis, and it has been suggested the numbers of NORs detected in the cell may reflect nuclear and cellular activity. This study was performed to evaluate the applicability of AgNORs to the diagnosis of squamous cell carcinoma of the lung. Method: The one step silver methods(AgNORs) was used to stain NORs in the routinely processed, formalin fixed, paraffin embedded sections of 36 cases of squamous cell carcinoma of the lung obtained by surgical resection of primary tumor. In each specimen, 100 tumor cells and 100 normal cells adjacent to the tumor chosen at random were examined under an oil immersion lens at a magnification of ${\times}1000$. The mean number of AgNORs per nucleus was calculated for each specimen. Results: The mean number of AgNORs per nucleus(mAgNORs) of normal bronchial epithelium and squamous cell carcinoma of the lung was $1.74{\pm}0.25$ and $4.05{\pm}0.80$, respectively. The difference of mAgNOR between normal and tumor tissue was statistically significant(p<0.001). There was no statistical difference among tumors of different stages. The difference of mAgNOR between normal and tumor tissue was statistically significant in each TNM stage(p<0.05). Conclusion: Mean AgNOR count may be used as a useful marker for the differential diagnosis of benignancy and malignancy, and proliferative activity of the cell in squamous cell carcinoma of the lung. But there was no statistical difference in mean AgNOR count among tumors of different surgical stages. Further studies for the application of mAgNORs to the diagnosis of other histologic types and cytologic specimens of the lung cancer are needed.

• Korean Journal of Food Science and Technology
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• v.41 no.1
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• pp.11-15
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• 2009

Commercial tofu was cut and re-packed in a vacuum container, an airtight container and an open tofu tray in an effort to assess the effects of vacuum containers on the shelf life of leftover tofu. The re-packed tofu were stored at $5^{\circ}C$ and $25^{\circ}C$ for the enumeration of total bacteria and coliforms. We also measured changes in color, pH, and opacity. The vacuum retarded the bacterial growth under $10^5$ CFU/mL for up to 12 days at $5^{\circ}C$. The color of the tofu was unaffected by the container type at both storage temperatures, whereas the pH and opacity of the immersion solution were altered less profoundly by storage in the vacuum container at $5^{\circ}C$. However, we noted no significant differences in bacterial growths, pH, and opacity among container types at $25^{\circ}C$. The results of this study showed that the usage of vacuum containers may be a favorable method for the preservation of tofu under refrigerated conditions.

• Journal of Energy Engineering
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• v.23 no.2
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• pp.149-157
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• 2014

The steam generator tubes of nuclear power plants have various types of corrosion failures during the plant operation. The stress corrosion cracking which occurs on the outer surface of tube is called the secondary side stress corrosion cracking and mainly occurs in the expansion-transition area of tube. The causes are the concentration of impurities by the sludge pile-up related to the geometry of its region and the residual stress by tube expansion in the process of steam generator manufacturing. Especially the directionality and sizes of residual stresses are differed according to the tube expansion methods and the direction and the frequency of tube cracks depend on their characteristics. In bases on the plant experiences, it is notified that circumferential cracks of tubes expanded with explosive expansion method are dominantly occurred compared to those of tubes done with hydraulic expansion one. Therefore in this study, according to tube expansion methods frequencies and sizes of tube cracks with specific direction are compared by means of accelerated immersion test and also the crack morphology and the specific chemicals from water-chemistry environment are observed through the fracture surface examination.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2290-2299
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• 2009

This study aims to analyze the importances of various SCM adoption factors suggested in precedent researches with AHP. SCM adoption factors were categorized by four types: organization factor, transaction factor, relation factor, and information factor. Each factor has sub-factors. Organization factor has five sub-factors: adoption strategy, support of CEO, maturity of information technology, development of assessment system, and innovation leadership. Transaction factor has three sub-factors: transaction period, delivery/quality, and shared goal. Relation factor has five sub-factors: trust, collaboration, inter-dependence, conflict, and immersion. Information factor has three sub-factors: information quality, information share, and information exchange. There are sixteen sub-factors altogether. Analyzing the importances of SCM adoption factors with AHP, the importance of organization factor(.387) ranked the highest. Relation factor(.291), information factor(.167), and transaction factor(.155) followed. Putting the analysis results of primary hierarchy factors and secondary hierarchy factors together, support of CEO(.169) ranked the highest and trust(.124), adoption strateg (.089), share goal(.081), information exchange(.069), collaboration(.064), and information share (.057) followed.

• Journal of Digital Convergence
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• v.19 no.7
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• pp.397-408
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• 2021

The purpose of this study is to investigate the effect of teaching style of liberal arts physical education professors to class satisfaction, Class flow and physical education attitude of liberal arts students. A study was conducted on a total of 221 liberal arts students. For the collected data, a confirmatory factor analysis and reliability analysis (Cronbach' α) for the measurement tool were performed using the SPSS 26.0 and Amos 21.0 programs. And correlation analysis and multiple regression analysis were performed. The liberal arts physical education Professor's teaching stlye affects the student's class satisfaction (educational satisfaction, environmental satisfaction, psychosocial satisfaction, physical satisfaction), and students' class flow (class immersion, purpose experience, consciousness agreement, challenge, control, Integration). In addition, it has various effects on the student's attitude toward physical education(relationships, physical activity, active participation, health and physical fitness, positive emotions). Efforts to strengthen the competence of liberal arts physical education professors will be needed to revitalize the liberal arts physical education.