• Restorative Dentistry and Endodontics
• /
• v.24 no.2
• /
• pp.408-415
• /
• 1999

When a zinc-oxide eugenol type sealer was placed in root canals treated previously with calcium hydroxide, acceleration of its setting and the yellowish discoloration were observed clinically. The purpose of this study was to evaluate the properties of calcium hydroxide-eugenol compound. Some physical properties of calcium hydroxide-eugenol compound were compared with a manufactured zinc-oxide eugenol based root canal sealer, Tubli-seal$^{(R)}$ in terms of water solubility, water sorption, film thickness and microleakage. Solubility and water sorption were determined by the use of the method described in American Dental Association Specification(ADAS) no. 57. Ten samples of each material were prepared into disks 20mm in diameter and 1.5mm in thickness. The samples were immersed in 50ml of distilled water at $37{\pm}1^{\circ}C$ for 7 days. The samples were then removed and placed in a desiccator. The values for solubility and water sorption were calculated using differences between the weights of same sample. Film thickness was determined by the use of the method described in ADAS no. 57 too. A small quantity of mixed cement was placed between two glass plates of which thickness was measured previously. 15Kg loading was applied and total thickness of the glass plates and the cement film was measured. The thickness difference was recorded as the material's film thickness. Microleakage was determined with a dye penetration method. Experimental materials were placed between the dentin surface of bovine tooth and the acrylic rod. These units were immersed in Pelican ink (W-Germany) for three days. Dye-penetrated dentin surfaces of bovine tooth were measured using the NIB Image 1.60 Macintosh program. The results are as follows: 1. Water solubility value of calcium hydroxide-eugenol compound (20.98${\pm}$2.94%) was statistically higher than those of Tubli-seal$^{(R)}$(2.52${\pm}$0.49%)(p<0.05). 2. Water sorption value of calcium hydroxide-eugenol compound (59.72${\pm}$17.75%) was statistically higher than those of Tubli-seal$^{(R)}$(3.15${\pm}$0.76%)(p<0.05). 3. Film thickness value of calcium hydroxide-eugenol compound (0.36${\pm}$0.03mm) was statistically higher than those of Tubli-seal$^{(R)}$(0.12${\pm}$0.1mm)(p<0.05). 4. Dye penetration value after 3 days-immersion of calcium hydroxide-eugenol compound(57.63${\pm}$25.85%) was statistically higher than those of Tubli-seal$^{(R)}$(28.05${\pm}$23.46%)(p<0.05).

• Journal of the Korean Institute of Landscape Architecture
• /
• v.44 no.4
• /
• pp.22-34
• /
• 2016

The purpose of this study was to analyze commemoration characteristics of fifty-nine Vietnam war memorials in Korea(VWMK) including monuments and national cemeteries from landscape architectural point of view such as location, spacial characteristic, landscape detail, sculpture, and interpretive text. Based on the commemoration characteristics of the analysis, the commemoration culture among Vietnam, the U.S.A., and Korea were studied and differences compared. The results are as follows. First, monuments were mainly located in public open space such as national cemeteries, parks, and plaza, and some of them were elected along with Korea war memorials to honor Vietnam war veterans at the national level. Second, because the monuments were relatively small and memorial towers were conventionally built on a square platform, the memorial style had been simply standardized to stereotype the commemoration characteristics. Third, outmoded memorial towers, stone plates, emblems, and memorial walls were used as main landscape details and standardized facilities were considered from an artistic and social point of view. Fourth, realistic soldier statues to show heroic and humanitarian image were in majority, while symbolic and abstract sculpture were small in number, they were mostly conventional and unexpressive. Fifth, the causes of participation in the Vietnam War were predominantly expressed as 'defending freedom', 'keeping world peace', and 'national economic development' based on anti-communism and patriotism, and also the collectivity of Vietnam War veterans by troop and local level was emphasized through engraving each veterans's name on towers, plates, and walls. VWMK are mostly conventional and stereotyped in style and show strongly national official memory and the collectivity of veterans from a sociopolitical perspective, and aim for anti-communistic patriotism ideologically. Further study and projects will be required to make creative and innovative memorials and to study how to rethink sublime fundamental themes like war, death, and the individual veteran's experience in VWMK.

• Journal of Navigation and Port Research
• /
• v.26 no.3
• /
• pp.323-328
• /
• 2002

Soil-steel structures have been used for the underpass, or drainage systems in the road embankment. This type of structures sustain external load using the correlations with the steel wall and engineered backfill materials. Buried flexible conduits made of corrugated steel plates for the coastal road was tested under vehicle loading to investigate the effects of live load. Testing conduits was a circular structure with a diameter of 6.25m. Live-load tests were conducted on two sections, one of which an attempt was made to reinforce the soil cover with the two layers of geo-gird. Hoop fiber strains of corrugated plate, normal earth pressures exerted outside the structure, and deformations of structure were instrumented during the tests. This paper describes the measured static and dynamic load responses of structure. Wall thrust by vehicle loads increased mainly at the crown and shoulder part of the conduit. However additional bending moment by vehicle loads was neglectable. The effectiveness of geogrid-reinforced soil cover on reducing hoop thrust is also discussed based on the measurements in two sections of the structure. The maximum thrusts at the section with geogrid-reinforced soil cover was 85-92% of those with un-reinforced soil cover in the static load tests of the circular structure; this confirms the beneficial effect of soil cover reinforcement on reducing the hoop thrust. However, it was revealed that the two layers of geogrid had no effect on reducing the overburden pressure at the crown level of structure. The obtained values of DLA decrease approximately in proportion to the increase in soil cover from 0.9m to 1.5m. These values are about 1.2-1.4 times higher than those specified in CHBDC.

• Journal of the Korean Institute of Gas
• /
• v.8 no.2 s.23
• /
• pp.15-27
• /
• 2004

The purpose of this paper is to improve the performance of Polymer electrolyte fuel cell(PEMFC) by studying the channel dimension of bipolar plates using commercial CFD program 'Fluent'. Simulations are done ranging from 0.5 to 3.0mm for different size in order to find the channel size which shoves the highst hydrogen consumption. The results showed that the smaller channel width, land width, channel depth, the higher hydrogen consumption in anode. When channel width is increased, the pressure drop in channel is decreased because total channel length Is decreased, and when land width is increased, the net hydrogen consumption is decreased because hydrogen is diffused under the land width. It is also found that the influence of hydrogen consumption is larger at different channel width than it at different land width. The change of hydrogen consumption with different channel depth isn't as large as it with different channel width, but channel depth has to be small as can as it does because it has influence on the volume of bipolar plates. however the hydrogen utilization among the channel sizes more than 1.0mm which can be machined in reality is the most at channel width 1.0, land width 1.0, channel depth 0.5mm and considered as optimum channel size. The fuel cell combined with 2cm${\times}$2cm diagonal or serpentine type flow field and MEA(Membrane Electrode Assembly) is tested using 100W PEMFC test station to confirm that the channel size studied in simulation. The results showed that diagonal and serpentine flow field have similarly high OCV and current density of diagonal (low field is higher($2-40mA/m^2$) than that of serpentine flow field under 0.6 voltage, but the current density of serpentine type has higher performance($5-10mA/m^2$) than that of diagonal flow field under 0.7-0.8 voltage.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.27 no.6
• /
• pp.875-882
• /
• 2021

To minimize occupational noise induced hearing loss, it is recommended that workers should not be exposed to noise levels exceeding 85 dBA for over 8 h. In the present study, noise exposure levels were measured for seven workers based on their tasks on a training ship. The A-weighted noise exposure level (L_ex,24h) was measured by taking into account the A-weighted equivalent continuous sound level (L_Aeq,i), duration (h) and noise contribution (L_ex,24h,i) from the workers' locations. Results are thus obtained for different job categories as follows: officer group L_ex,24h=56.1 dB, navigation crew L_ex,24h=58.9 dB, navigation cadet L_ex,24h=62.0 dB, ship's cook L_ex,24h=64.3 dB, engine cadet L_ex,24h=91.1 dB, engineer L_ex,24h=91.1 dB, and engine crew L_ex,24h=95.1 dB. It was determined that the engineers, engine crews, and engine cadets in charge of machinery must wear hearing protection devices. By wearing hearing protection devices when working in highly noisy engine rooms, it is estimated that the noise expose levels could be reduced by the following amounts: engineer L_ex,24h=23.1 dB, engine Crew L_ex,24h=24.4 dB, and engine cadet L_ex,24h=21.5 dB. Moreover, if the no. 2 lecture room and mess room bottom plates in the cadets accommodations were improved to the 64 mm A-60-class floating plates, then further reductions are possible as follows: navigation cadet L_ex,24h=4.3 dB and engine cadet L_ex,24h=1.8 dB.

• Economic and Environmental Geology
• /
• v.54 no.2
• /
• pp.233-245
• /
• 2021

Many studies on the microstructures in rocks have been conducted using experimental methods with various equipment as well as natural rock studies to see the development of microstructures and understand their mechanisms. Grain boundary migration of mineral aggregates in rocks could cause grain growth or grain size changes during metamorphism or deformation as one of the main recrystallization mechanisms. This study suggests improved ways regarding the analog material experiments with reformed equipment to see sequential observations of these grain boundary migration. It can be more efficient than the existing techniques and carry out an appropriate microstructure analysis. This reformed equipment was implemented to enable optical manipulation by mounting polarizing plates capable of rotating operation on a stereoscopic microscope and a deformation rig capable of experimenting with analog materials. The equipment can automatically control the temperature and strain rate of the deformation rig by microcontrollers and programming and can take digital photomicrographs with constant time intervals during the experiment to observe any microstructure changes. The composite images synthesized using images by rotated polarizing plates enable us to see more accurate grain boundaries. As a rock analog material, norcamphor(C7H10O) was used, which has similar birefringence to quartz. Static grain growth and simple shear deformation experiments were performed using the norcamphor to verify the effectiveness of the equipment. The static grain growth experiments showed the characteristics of typical grain growth behavior. The number of grains decreases and the average grain size increases over time. These case experiments also showed a clear difference between the growth curves with three temperature conditions. The result of the simple shear deformation experiment under the medium temperature-low strain rate showed no significant change in the average grain size but presented the increased elongation of grain shapes in the direction of about 53° regarding the direction perpendicular to the shearing direction as the shear strain increases over time. These microstructures are interpreted as both the plastic deformation and the internal recovery process in grains are balanced by the deformation under the given experimental conditions. These experiments using the reformed equipment represent the ability to sequentially observe changing the microstructure during experiments as desired in the tests with the analog material during the entire process.

• Tuberculosis and Respiratory Diseases
• /
• v.50 no.4
• /
• pp.426-436
• /
• 2001

Background : Chronic obstructive pulmonary disease(COPD) is one of the major contributors to morbidity and mortality among the adult population. Cigarette smoking(CS) is undoubtedly the single most important factor in the pathogenesis of COPD. However, its mechanism is unclear. The current hypothesis regarding the pathogenesis of COPD postulates that an imbalance between proteases and antiproteases leads to the destructive changes in the lung parenchyma. This study had two aims. First, to evaluate the effect of CS exposure on histologic changes of the lung parenchyme, and second, to evaluate the effect of CS exposure on the expression of the gelatinolytic enzymes in BAL fluid cells in guinea pigs. Methods : Two groups of five guinea pigs were exposed to the whole smoke of 20 commercial cigarettes per day, 5 hours/day, 5 days/week, for 6weeks, and 12 weeks, respectively, using a smoking apparatus. Five age-matched guinea pigs exposed to room air were used as controls. Five or more sections were microscopically extamined(${\times}400$) and the number of cellular infiltration of the alveolar wall was measured in order to evaluate the effect of CS exposure on the histologic changes of lung parenchyme. The statistical significance was analyzed by a linear regression method. To evaluate the expression of the gelatinolytic enzymes in intraalveolar cells, BAL fluid was obtained and the intraalveolar cells were separated by centrifugation (500 g for 10 min at $4^{\circ}C$). Two sets of culture plates were loaded with $1{\times}10^6$ intraalveolar cells. One plate, contained O.1mM EDTA, a inhibitor of matrix metalloproteases(MMPs), and the other plate had no EDTA. Both plates were incubated for 48 hours at $37^{\circ}C$. After incubation, gelatinolytic protease expression in the supernatants was analyzed by gelatin zymography. Results : At the end of CS exposure, the level of blood carboxy Hb had increased significantly(4.1g/dl in control group, 24g/dl immediately after CS exposure, 18g/dl 30 min after CS exposure, 15g/dl 1 hour after CS exposure). Alveolar inflammatory cells were identified in the CS exposed guinea pigs. The number of alveolar cellular cells observed in a microscopic field ($400{\times}$) was $121.4{\pm}7.2$, $158.0{\pm}20.2$, $196.8{\pm}32.8$, in the control, the 6 weeks, and the 12 weeks group, respectively. The increased extent of inflammatory cellular infiltration of the lung parenchema showed a statistically significant linear relationship with the duration of CS exposure(p=0.001, $r^2=0.675$). Several types of gelatinolytic enzymes in the intraalveolar cells of CS exposed guinea pigs were expressed, of which some were inhibited by EDT A. However, the gelatinolytic enzymes were not expressed in the control groups. Conclusion : CS exposure increases inflammatory cellular infiltration of the alveolar wall and the expression of gelatinolytic proteases in guinea pigs. EDTA inhibits some of the gelatinolytic proteases. These findings suggest a possibility that CS exposure may increase MMP expression in the lungs of guinea pigs.

• MISULJARYO - National Museum of Korea Art Journal
• /
• v.98
• /
• pp.104-129
• /
• 2020

Designated as a national treasure of Korea and inscribed on the UNESCO World Heritage List, the Tripitaka Koreana at Haeinsa Temple is the world's oldest and most comprehensive extant version of the Tripitaka in Hanja script (i.e., Chinese characters). The set consists of 81,352 carved woodblocks, some of which have two or more copies, which are known as "duplicate woodblocks." These duplicates are supplementary woodblocks (bogakpan) that were carved some time after the original production, likely to replace blocks that had been eroded or damaged by repeated printings. According to the most recent survey, the number of supplementary woodblocks is 118, or approximately 0.14% of the total set, which attests to the outstanding preservation of the original woodblocks. Research on the supplementary woodblocks can reveal important details about the preservation and management of the Tripitaka Koreana woodblocks. Most of the supplementary woodblocks were carved during the Joseon period (1392-1910) or Japanese colonial period (1910-1945). Although the details of the woodblocks from the Japanese colonial period have been recorded and organized to a certain extent, no such efforts have been made with regards to the woodblocks from the Joseon period. This paper analyzes the characteristics and production date of the supplementary woodblocks of the Tripitaka Koreana. The sutra with the most supplementary woodblocks is the Maha Prajnaparamita Sutra (Perfection of Transcendental Wisdom), often known as the Heart Sutra. In fact, 76 of the total 118 supplementary woodblocks (64.4%) are for this sutra. Hence, analyses of printed versions of the Maha Prajnaparamita Sutra should illuminate trends in the carving of supplementary woodblocks for the Tripitaka Koreana, including the representative characteristics of different periods. According to analysis of the 76 supplementary woodblocks of the Maha Prajnaparamita Sutra, 23 were carved during the Japanese colonial period: 12 in 1915 and 11 in 1937. The remaining 53 were carved during the Joseon period at three separate times. First, 14 of the woodblocks bear the inscription "carved in the mujin year by Haeji" ("戊辰年更刻海志"). Here, the "mujin year" is estimated to correspond to 1448, or the thirtieth year of the reign of King Sejong. On many of these 14 woodblocks, the name of the person who did the carving is engraved outside the border. One of these names is Seonggyeong, an artisan who is known to have been active in 1446, thus supporting the conclusion that the mujin year corresponds to 1448. The vertical length of these woodblocks (inside the border) is 21 cm, which is about 1 cm shorter than the original woodblocks. Some of these blocks were carved in the Zhao Mengfu script. Distinguishing features include the appearance of faint lines on some plates, and the rough finish of the bottoms. The second group of supplementary woodblocks was carved shortly after 1865, when the monks Namho Yeonggi and Haemyeong Jangung had two copies of the Tripitaka Koreana printed. At the time, some of the pages could not be printed because the original woodblocks were damaged. This is confirmed by the missing pages of the extant copy that is now preserved at Woljeongsa Temple. As a result, the supplementary woodblocks are estimated to have been produced immediately after the printing. Evidently, however, not all of the damaged woodblocks could be replaced at this time, as only six woodblocks (comprising eight pages) were carved. On the 1865 woodblocks, lines can be seen between the columns, no red paint was applied, and the prayers of patrons were also carved into the plates. The third carving of supplementary woodblocks occurred just before 1899, when the imperial court of the Korean Empire sponsored a new printing of the Tripitaka Koreana. Government officials who were dispatched to supervise the printing likely inspected the existing blocks and ordered supplementary woodblocks to be carved to replace those that were damaged. A total of 33 supplementary woodblocks (comprising 56 pages) were carved at this time, accounting for the largest number of supplementary woodblocks for the Maha Prajnaparamita Sutra. On the 1899 supplementary woodblocks, red paint was applied to each plate and one line was left blank at both ends.

• Applied Chemistry for Engineering
• /
• v.25 no.5
• /
• pp.481-486
• /
• 2014

This study was performed to test combustive properties of medium density fibreboard (MDF) plates treated with piperazinomethyl-bis-phosphonic acid (PIPEABP), methylpiperazinomethyl-bis-phosphonic acid (MPIPEABP), and N,N-dimethylethylenediaminomethyl-bis-phosphonic acid (MDEDAP). MDF specimens were painted three times with 15 wt% solution of the alkylenediaminoalkyl-bis-phosphonic acids at room temperature. After drying specimen treated with chemicals, combustive properties were examined using the cone calorimeter (ISO 5660-1). As a result, combustion-retardation properties increased due to the treatment of bare MDF with alkylenediaminoalkyl-bis-phosphonic acid solution. Especially, the specimens treated with chemicals showed the ignition (TTI) (148 s~116 s) was retarded and the flameout (Tf) (633 s~529 s) time increased, while the total heat release rate (THRR) (61.1~67.0) $MJ/m^2$ was lowered than those of using virgin plate by reducing the burnig rate. Compared with virgin MDF plate, the specimens treated with the alkylenediaminoalkyl-bis-phosphonic acids showed low combustive properties. However the specimens treated with bis-(dimethylaminomethyl) phosphinic acid (DMDP) showed the higher peak heat release rate (PHRR) ($185.08kW/m^2$) than that of the virgin plate.

• Journal of the Korean Geophysical Society
• /
• v.5 no.4
• /
• pp.283-292
• /
• 2002

The Korean peninsula is located at the edge of the East Asian active margin. The seismic activity in the Korean Peninsula is relatively low compared with the neighboring countries China and Japan. According to the available Seismic information, the Korean Peninsula is not totally safe from the Earthquake disaster. Moreover, the area is surrounded by varies tectonic forces which is resulted from the relative movements of the surrounding tectonic plates "Pacific, Philippine Sea, Eurasian and South China". Nowadays South Korea has 65 GPS stations belong to 5 governmental organizations "each organization figure out its own GPS stations for different requirements" In order to minimize the seismic hazard in the Korean Peninsula a program for monitoring the recent crustal movement has been designed considering the uses of the available GPS station "some selected stations from the previously mentioned stations" and the tectonic settings in and around the Korean Peninsula. This program is composed of two main parts, the first part to monitor the crustal deformation around the Korean Peninsula with the collaboration of the surrounding countries "China and Japan" this part is composed of two phases "East Sea Phase and Yellow Sea Phase". These phases will be helpful in determining the deformation parameters in the East Sea and the Yellow Sea respectively While the Second part of this program, is designed to determine the deformation parameters id and around the main faults in the Korean Peninsula and the relative movement between the Korean Peninsula and the Cheju Island. Through out this study the needs of crustal movement center rose up to collect the data from the previously mentioned stations and Organizations in order to use such reliable data in different geodynamical application.