• Elastomers and Composites
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• v.44 no.2
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• pp.150-155
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• 2009

This study examined the effects of the concentration variation of the silyl hydride (Si-H) functional group in polymethylhydrogen siloxane cross-linker and the vinyl-functional group in silicone prepolymer on the physical properties of the dental polyvinylsiloxane impression materials (PVS). When the SiH/Vinyl ratio was 1.6 (Group $\underline{C6}$ containing ${\underline{C}}ross$-linker $\underline{6}$ parts), the setting rate was too slow even though their tensile strength was the highest within the tested groups. When the SiH/Vinyl ratio was 3.2 (Group C12), the setting rate was too fast to allow appropriate working time even though their mechanical properties were good. The C14 group showed rather lower tensile strength compared to the groups having lower cross-linker contents. Notably, too much incorporation of cross-linker, like C16 group, induced delay of the setting, by which the mechanical and manipulation properties were detrimentally affected.

• Journal of the Korean Solar Energy Society
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• v.40 no.4
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• pp.13-22
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• 2020

As the supply of photovoltaic (PV) increases worldwide, the cumulative installations in 2018 were 7.9 and 560 GW in Korea and the world, respectively. Typically, when the ground on commercial PV modules is installed, the area is limited; hence, new designs of PV modules are required to install additional PVs. Among the new design of PV modules, lightweight PV modules can be utilized in PV systems, such as buildings, farmlands, and floating PV. Concerning the investigation of lightweight PV modules, several studies on materials for replacing low-iron tempered glass, which comprises approximately 65% of the PV module weight, have been conducted. However, materials that are used as substitutes for glass should possess similar lightweight properties and reliability as glass. In this study, experimental tests were performed to evaluate the applicability of ethylene tetrafluoroethylene (ETFE) film with excellent resistance to water and aging as a front material of PV modules. The transmittance and ultraviolet properties of the ETFE film were determined and compared with those of glass. A 1-cell module and laboratory-scale 24-cell module were manufactured using the ETFE film and glass, and the electrical output was measured and analyzed. Furthermore, damp heat and thermal cycle tests were conducted to evaluate the reliability of the ETFE film module. Based on the experimental results, the electrical output and reliability of the ETFE film module were similar to those of the glass module, and the ETFE film could be used as the front material of PV modules.

• Korean Journal of Food Science and Technology
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• v.51 no.5
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• pp.438-446
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• 2019

To investigate the changes in volatile compounds of persimmon vinegar (PV) during aging, PVs aged for 3-25 years were analyzed using solid-phase microextraction-gas chromatography-mass spectrometry. In total, 90 volatile compounds were identified, and acids and esters were the most abundant, followed by ketones and alcohols. The concentration of acetic acid ranged from 8,925.0 to 26,132.3 ng/mL, depending on the aging period. Ethyl acetate concentration ranged from 32.5 to 50,681.7 ng/mL and ethanol was present only in PV aged for 3 years (PV-3). The volatile compound content was the highest in PV-3. The volatile profiles of PV aged for 22 years (PV-22) and 25 years (PV-25) were considerably similar. Acids were the most predominant in PV-15, PV-22, and PV-25, whereas esters were abundant in PV-3. The contents of acids, alcohols, and esters decreased, while the aldehyde and ketone content increased with aging.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.1
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• pp.45-58
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• 2013

The purpose of this study was to analyze the area of occlusal contact points using visual method. One subject was selected who had Angle Class I, normal dentition, without dental caries, periodontal disease and temporomandibular disorders. Forty times PVS impressions were taken and 10 pairs casts were fabricated using dental super hard stone. After mounting the casts with customized loading apparatus, 78.9kg/f force was loaded as a maximum biting force. In T-Scan method, occlusal contact points measurement was repeated twice. Then, using Photoshop program (Adobe photoshop CS3, Adobe. San Jose, USA), the pixels which indicated occlusal contact points by color was recognized, and the distribution of recognized pixels were calculated to area. In Add picture method, polyether bite material applied to the occlusal surface of the casts. Then, the image of the translucent areas was recorded and classified $0{\sim}10{\mu}m$, $0{\sim}30{\mu}m$, $0{\sim}60{\mu}m$ area by the amount of transmitted light. To acquire occlusal surface, the numbers of pixels from the photograph of the contact area indicated cast converted to $mm^2$. The mean occlusal contact area by two methods was statistically analyzed (paired t-test). Part of the red and pink area in T-Scan image were almost equivalent to the $0{\sim}10{\mu}m$, $0{\sim}30{\mu}m$, $0{\sim}60{\mu}m$ area in Add picture image. The distribution of occlusal contact points were similar, but the average area of occlusal contact points was wider in T-scan image (P<.05). Pink and red area in T-scan image was wider than $0{\sim}10{\mu}m$, $0{\sim}30{\mu}m$ area in Add picture image (P<.05), but similar to $0{\sim}60{\mu}m$area in Add picture image (P>.05). Occlusal contact points in T-scan image did not indicate real occlusal contact points. Occlusal contact areas in T-scan method were enlarged results comparing with those in Add picture method.

• Journal of Hospice and Palliative Care
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• v.14 no.1
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• pp.28-33
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• 2011

Purpose: Recognition of impending death is crucial not only for efficient communication with the caregiver of the patient, but also determination of the time to refer to a separate room. Current studies simply list the events 'that have already occurred' around 48 hours before the death. This study is to analyze the predictability of each event by comparing the time length from 'change' to death. Methods: Subjects included 160 patients who passed away in a palliative care unit in Incheon. The analysis was limited to 80 patients who had medical records for the last week of their lives. We determined 9 symptoms and 8 signs, and established the standard of 'significant change' of each event before death. Results: The most common symptom was increased sleeping (53.8%) and the most common sign was decreased blood pressure (BP) (87.5%). The mean time to death within 48 hours was 46.8% in the case of resting dyspnea, 13.6% in the ease of low oxygen saturation, and 36.9% in the case of decreased BP. The symptom(s) which had the highest positive predictive value (PV) for death within 48 hours was shown to be resting dyspnea (83%), whereas the combination of resting dyspnea and confusion/delirium (65%) had the highest negative PV. As for the most common signs before death within 48 hours, the positive PVs were more than 95%, and the negative PV was the highest when decreased BP and low oxygen saturation were combined. The difference in survival patterns between symptoms and signs was significant. Conclusion: The most reliable symptoms to predict the impending death are resting dyspnea and confusion/delirium, and decline of oxygen saturation and BP are the reliable signs to predict the event.

• Korean Journal of Food Science and Technology
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• v.7 no.1
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• pp.37-42
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• 1975

The color intensity (Absorbance at 490nm) and the antioxidant effects of absolute and 90% ethanol extracts obtained from a Maillard-type browning reaction mixture (0. 5M glucose and 0. 5M glycine mixture, heated at $100^{\circ}C$) were determined. The color intensity of the absolute and 90% ethanol extracts were compared with the length of reaction time and the antioxidant effects of the extracts of both types were compared one another. The results obtained are as follows. 1. The color intensity of the absolute ethanol extracts remained almost unchanged as the browning reaction proceeded. The color intensity of the 90% ethanol extracts appeared to increase nearly in proportion to the length of reaction time. 2. The absolute and the 90% ethanol extracts seemed to possess significant antioxidant activity on the autoxidation of an edible soybean oil. which was kept at $45{\pm}0.5^{\circ}C$ for 21 days. It was noteworthy that the absolute ethanol extracts showed stronger antioxidant effects than those of the 90% ethanol extracts, which contained a far greater amount of brown-colored pigments. Since the PVs of the controls in both groups, after the end of the storage period, did not differ much from one another, the possibility of residual water playing some prooxidant role in the substrates containing the 90% ethanol extracts should be ruled out. Extracts of both types obtained at earlier stages of the brownig reaction demonstrated less but comparable antioxidant activity to that of extracts taken at later stages of the reaction. 3. The results of the present study appeared to suggest that the effective antioxidant compounds, produced in the Maillard-type browning reaction, were probably intermediate products such as reductones formed at fairly earlier stages of the browning reaction.

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.4
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• pp.270-279
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• 2018

Purpose: The aim of this study was to assess the patients' perception, acceptance, and preference of the difference between a conventional impression and digital impression through questionnaire survey. Materials and Methods: Thirteen (6 male, 7 female) subjects who experienced both digital and conventional impression at the same day were enrolled in this study. Conventional impression were taken with polyvinylsiloxane and digital impression were performed using a newly developed intra-oral scanner. Immediately after the two impressions were made, a survey was conducted with the standardized questionnaires consisting of the following three categories; 1) general dental treatment 2) satisfaction of conventional impression 3) satisfaction of digital impression. The perceived source of satisfaction was evaluated using Likert scale. The distribution of the answers was assessed by percentages and statistical analyses were performed with the paired t-test, and P < 0.05 was considered significant. Results: There were significant differences of the overall satisfaction between two impression methods (P < 0.05). Digital impression showed high satisfaction in less shortness of breath and odor to participants compared to conventional impression. The use of an oral scanner resulted in a discomfort of TMJ due to prolonged mouth opening and in lower score of the scanner tip size. Conclusion: It was confirmed that the preference for the digital impression using intraoral scanner is higher than the conventional impression. Most survey participants said they would recommend the digital impression to others and said they preferred it for future prosthetic treatment.