• Journal of dental hygiene science
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• v.17 no.4
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• pp.358-367
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• 2017

The purpose of this study was to evaluate the influence of water infiltration and flexural strength changes in dental porcelain with glazing treatment. The block specimens were prepared as experimental materials, using feldspar type commercial dental porcelain; then, these were fired at $940^{\circ}C$ for 1 minute. The fired specimens were polished with a dimension of $40{\times}5.5{\times}5mm$. The specimens were distributed to two experimental groups: with and without glazing treatment specimens (n=5), and they were immersed in a solution of pH 7 for 3, 7, and 20 days at $40^{\circ}C$ after fabrication. To evaluate the flexural strength changes with water infiltration treatment in specimens with and without glazing, the 3-point flexural test was performed, using a universal testing machine until failure occurred. Starting powder and fired specimens consisted of amorphous and leucite crystalline phase. The Vickers hardness of fired specimens was more than 1.6 times higher than that of the enamel of natural teeth. According to porosimeter results, the specimens without glazing treatment exhibited a porosity of about 14.7%, whereas the glazed specimens exhibited the lowest porosity at about 1.1%. The average flexural strength of glazed specimens was higher than the flexural strength of specimens without glazing treatment (p<0.05). The flexural strength of all specimens with and without glazing treatment deteriorated with accelerated aging in the solution. In addition, significant differences between these two treatment groups were observed in all of the specimens treated at various water infiltration periods (p<0.05). The exposure of internal pores and micro-cracks in the surface due to polishing of the fired specimens influenced mechanical behaviors. Especially, the flexural strength in specimens without glazing treatment has shown significant degradation with the infiltration of water. Therefore, this study suggests that glazing processes can improve mechanical properties of dental porcelain.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.4
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• pp.258-271
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• 2010

In order to figure out hydrodynamic and water quality changes after completion of dike construction of the Saemangeum, which behaves as a semi-enclosed estuarine lake, numerical simulations based on fine grid structure by using EFDC were intensively carried out. In this study some limitations of precedent study has been improved and gate operation were considered. Also 3 phases such as air-water-sediment interaction modeling was considered. It is clear that inner mixing of the Saemangeum is dominated by Mankyeong and Dongjin riverine discharges rather than the gate opening influence through the Lagrangian particle tracking simulations. Vertical DO structure after the dike completion shows steep gradient especially at Dongjin river estuary due to lessen of outer sea water exchange. Increasing SOD at stagnantly changed man-made reservoir might cause oxygen deficiency and accelerating degradation of water quality. According to TSI evaluation test representing eutrophication status, it shows high possibility of eutrophication along Mankyeong waterway in spite of dike completion, while the index is getting high after final closing along Dongjin waterway. Numerical tests with gate operations show significant differences in water quality. Thus it should be noted that proper gate operation plays a major role in preserving target water quality and management for inner development plan.

• The Korean Journal of Nuclear Medicine Technology
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• v.13 no.1
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• pp.116-119
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• 2009

Background: Preanalytical factors can affect reliability of hormone assay results. Adrenocorticotropic hormone (ACTH) in blood is considered highly unstable because of proteolytic degradation, so storage of blood samples on ice until analysis is recommended. In clinical practice, however, this procedure may present logistical problems because most samples for ACTH measurement must be shipped from the place of sample collection to the laboratory. Therefore, we studied the impact of time and temperature before plasma separation and analysis on the results of ACTH assays. Methods: A total number of 22 patients were enrolled in this study. We obtained 2 blood samples. ACTH concentrations were 35~126 pg/mL. ACTH concentrations were measured by immunoradiometric assay (IRMA) using commercial kits (CIS Biointernational, Gif-sur-Yvette, France). Results: ACTH levels showed a significant difference between the samples of $22^{\circ}C$ EDTA and $4^{\circ}C$ EDTA. Measured ACTH concentrations significantly decreased with time before freezing at $-20^{\circ}C$. ACTH levels showed no significant difference between the groups of after storage for 24 hr without centrifugation at $22^{\circ}C$ and $4^{\circ}C$. Conclusion: We recommend that blood samples be obtained on pre-chilled EDTA collection tubes. The shortest possible time between sample collection and processing is always the best laboratory practice.

• Journal of Veterinary Clinics
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• v.32 no.1
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• pp.5-8
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• 2015

D-dimer is a fibrin degradation product (FDP), a small protein fragment present in the blood after a blood clot is degraded by fibrinolysis. D-dimer concentration is widely used for determining thrombosis and thromboembolism. Because one major cause of thromboembolism is congestive heart failure in human, we investigated the degree and risk of thromboembolism in dogs with different stage of congestive heart failure caused by chronic mitral valvular insufficiency (CMVI). The plasma level of d-dimer was evaluated in 20 healthy dogs and 30 dogs with different stage of congestive heart failure caused by CMVI. The d-dimer concentrations were measured by a commercialized assay kit. The plasma levels of d-dimer were not significantly different between healthy and CMVI dogs. Furthermore, there was no association of d-dimer concentrations to left atrium to aorta (LA/Ao) ratio, left ventricular dimension at diastole to aorta (LVIDd/Ao) ratio and severity of heart failure in our study population. Our study results implied that the degree of thromboembolism in canine heart failure might be minimal or the plasma d-dimer test might not be reliable for detecting thromboembolism in dogs.

• Journal of Food Hygiene and Safety
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• v.14 no.3
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• pp.249-254
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• 1999

The present study was performed to investigate biodegradation rate of BPMC(2-sec-butylphenyl methyl carbamate) and chlorothalonil. In the biodegradation test of two pesticides by the modified river die-away method from June 17 to August 22, 1998, the biodegradation rate constants and half-life were determined in Nakdong(A) and Kumho River(B). Bio- degradation rate of BPMC was 27% in A sampling point, 40% in B sampling point after 7 days. Biodegradation rate constants and half-life of BPMC were 0.0460 and 15.1 days in A sampling point, 0.0749 and 9.3 days in B sampling point, respectively. Biodegradation rate of chlorothalonil was 100% in A and B sampling points after 7 days. Biodegradation rate constants and half-life of chlorothalonil were 0.1416 and 4.9 hours in A sampling point, 0.1803 and 3.8 hours in B sampling point, respectively. Biodegradation rate of chlorothalonil was faster than that of BPMC. Correlation analysis between biodegradation rate constants of pesticides and water quality(DO, BOD, SS, ABS, $NH_3-N\;and\;NO_3-N$) showed significant correlation with BOD, SS and $NH_3-N$. Furthermore, regression analysis with BOD, SS and $NH_3-N$ as independent variable and biodegradation rate constant as independent variable showed a significant linear equation. These results suggested that BPMC and chlorothalonil were mainly degraded by biodegradation, and the difference in biodegradation of two pesticides was due to difference of water quality.

• Particle and aerosol research
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• v.15 no.4
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• pp.191-202
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• 2019

In this study, performance (particle removal efficiency and breathing resistance) of several commercially available face masks (electrostatic filter masks (KF80 certified), a nanofiber filter mask (KF80 certified), and an uncertified mask) with their filter structure and composition were evaluated. Also, effects of relative humidity (RH) of incoming air, water and alcohol exposure, and reusability on performance of face masks were examined. Monodisperse and polydisperse sodium chloride particles were used as test aerosols. Except the uncertified mask filter, PM_2.5 removal efficiency was found to be higher than 90%, and the nanofiber filter mask had the highest quality factor due to the low pressure drop and high removal efficiency (nanofibers were arranged in a densely packed pore structure and contained a significant amount of fluorine in addition to carbon and oxygen). In the case of the KF80 certified mask, the removal efficiency was little affected when the RH of incoming air increased. When the mask filters were soaked in water, the removal efficiency of mask filters was degraded. In particular, the uncertified mask filter showed the highest removal efficiency degradation (26%). When the mask was soaked in alcohol, the removal efficiency also decreased with the greater degree than the water soaking case. The nanofiber mask filter showed the strongest resistance to alcohol exposure among tested mask filters. During evaluation of reusability of masks in real life, the removal efficiency of certified mask filter was less than 4% for 5 consecutive days (2 hours per day), while the removal efficiency of uncertified mask filter significantly decreased by 30% after 5 days.

• Journal of Navigation and Port Research
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• v.31 no.5 s.121
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• pp.409-414
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• 2007

The effect of multipath is especially serious in urban area and sea surface where buildings and water reflect GPS signal. Multipath brings about the performance degradation on many GPS application because the presence of multipath causes the diminution of pseudorange measurement accuracy in turn position accuracy. In this paper, a multipath mitigation named weighted correlation method is implemented on software GPS receiver, in which the asymmetric correlation function is compensated by modifying the late correlation value. Asymmetry compensation is obtained as weighted sum of two correlators which have different early-late chip spaces. This structure is adopted to lessen the computation load lower keeping up performance similar to that. The performance of implemented multipath mitigation technique is evaluated using GPS signal and multipath signal generated by GPS signal generator and software GPS receiver. The test results show that the weighted correlation method gives hefter performance than the standard correlator and the narrow correlator.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.58-65
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• 2016

This study was a preparatory experiment aimed the development of membrane scaffolds for tissue engineering. A PCL composite solution contained sodium chloride(NaCl). PCL porous membrane scaffolds were formed on a glass casting plate using a film applicator and immersed in distilled water to remove the NaCl reaching after drying. NaCl was used as a pore former for a 3 dimensional pore net-work. The dry condition parameters were $4^{\circ}C$, room temperature (RT) and $40^{\circ}C$ for each different temperatures in the drying experiment. SEM revealed the morphology of the pores in the membrane after drying and evaluated the in vitro cytotoxicity for basic bio-compatibility. The macro and micro pores existed together in the scaffold and showed a 3-dimensional pore net-working morphology at RT. The in vitro cytotoxicity test result was "grade 2" in accordance with the criterion for cytotoxicity by ISO 10993-5. The dry condition affected the formation of a 3 dimensional pore network and micro and macro pores. Therefore, these results are expected provide the basic process for the development of porous membrane scaffolds to control degradation and allow drug delivery.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6977-6984
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• 2015

It is faced with the necessity of multi roll forming process of the ball slide rail which is made by adding the separate manufacturing processes, piercing, bending, trimming, to the roll forming process of a continuous plastic deformation, to improve the quality. However, the vibration and noise of the press machine in this process leads to the quality degradation of slide rail manufactured in this process. In this study, the roll was designed considering the optimal strain rates by the roll forming program with finite element method. And to estimate the static stability of the multi process the Von-Mises stress and deformation on the press was calculated with a structural analysis program. Also, to avoid driving systems in the resonance region their natural frequencies in the 1st and 2nd mode were calculated through the modal analysis. To verify its dynamic stability improvement the magnitudes of noise and vibration in the existing and studied system were compared using a microphone and accelerometers. And the widths and surface roughnesses of the rails which had been produced in the existing and studied process were measured. Therefore, it is known that multi roll forming process is stable in the analytical and experimental study.

• Journal of the Korean Electrochemical Society
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• v.12 no.2
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• pp.181-188
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• 2009

Pt catalyst was adsorbed on Carbon nanofiber (CNF) by modified polyol method after acid treatment of the carbon support with $HNO_3$ and $H_{2}SO_{4}$. As the time for acid treatment increases, more oxygen functional groups on carbon surface were produced which improve the loading amount and dispersion of Pt catalyst on carbon supports. In order to inspect the effect of CNF acid treatment time on electrochemical corrosion, constant potential of 1.4 V was applied to a single cell for 30 min and the amount of $CO_2$ emitted was monitored with on-line mass spectrometry. According to the results of our experiment, more $CO_2$ was produced with Pt/ oxidized-CNF catalyst in compared to that with unoxidized-CNF. Increasing acid treatment time also induces the more $CO_2$ emission. Besides, performance degradation after corrosion test expanded with severer carbon corrosion. From the observed results, it can be concluded that the acid treatment of CNF is beneficial to catalyst loading, but it also is a significant factor declining the fuel cell durability by accelerating electrochemical oxidation of carbon support.