• Imaging Science in Dentistry
• /
• v.48 no.3
• /
• pp.201-212
• /
• 2018

Purpose: The aim of this study was to compare cone-beam computed tomography (CBCT) and digital panoramic radiography (DPR) for the detection of pulp stones. Materials and Methods: DPR and CBCT images of 202 patients were randomly selected from the database of our department. All teeth were evaluated in sagittal, axial, and coronal sections in CBCT images. The systemic condition of patients, the presence of pulp stones, the location of the tooth, the group of teeth, and the presence and depth of caries and restorations were recorded. The presence of pulp stones in molar teeth was compared between DPR and CBCT images. Results: Pulp stones were identified in 105 (52.0%) of the 202 subjects and in 434 (7.7%) of the 5,656 teeth examined. The prevalence of pulp stones was similar between the sexes and across various tooth locations and groups of teeth (P>.05). A positive correlation was observed between age and the number of pulp stones(${\rho}=0.277$, P<.01). Pulp stones were found significantly more often in restored or carious teeth (P<.001). CBCT and DPR showed a significant difference in the detection of pulp stones(P<.001), which were seen more often on DPR than on CBCT. Conclusion: DPR, as a 2D imaging system, has inherent limitations leading to the misinterpretation of pulp stones. Restored and carious teeth should be carefully examined for the presence of pulp stones. CBCT imaging is recommended for a definitive assessment in cases where there is a suspicion of a pulp stone on DPR.

• The Journal of Korean Academy of Prosthodontics
• /
• v.37 no.4
• /
• pp.506-515
• /
• 1999

Dental practice can produce and spread some infectious diseases from patients to dentist, dental assistant, and dental labors. One possible method for preventing these cross-contamination is to immerse dental impression in chemical disinfectants. So for many investigators studied on the dimensional changes of dental impressions and on the surface qualities of stone casts made from impression following immersion in disinfectants. This study was proposed to evaluate some popular impression disinfectant combination from the point of dimensional stability. Impression was taken from dental arch-shaped metal model. Irreversible hydrocolloid and 3 elastomers(polyvinyl siloxane, polysulfide, polyether) were immersed in 3 disinfectants (2% glutaraldehyde, 1% povidone-iodine, 0.5% sodium hypochlorite) for 10 minutes and measured both cross-arch and anterior-posterior distance under stereo microscope to evaluate dimensional change. The results obtained were as follows: 1. Dimensional changes of irreversible hydrocolloid impression was statistically different in cross-arch and anterior-posterior distance when immersed in 2% glutaraldehyde solution and in anterior-posterior distance when immersed in 0.5% sodium hypochlorite solution from control group (p<0.05). 2. Dimensional changes of polyvinyl siloxane and polysulfide impression were not statistically different from control group (p>0.05). 3. Dimensional changes of polyether impression was statistically different in cross-arch distance when immersed in 0.5% sodium hypochlorite solution and in anterior-posterior distance when immersed in 1% povidone-iodine solution from control group (p<0.05). 4. In all cases, dimensional changes were less than 0.1% from the original dimension and concluded clinically acceptable.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.52 no.8
• /
• pp.348-353
• /
• 2003

This paper was the research of high voltage suspension insulator (400 [kN]) including pottery stone, feldspar, clay and alumina of 17 [wt%]. The slurry was fabricated after ball milling mixed raw materials. Green compacts were made by the extrusion of jiggering method and were sintered at 1300[$^{\circ}C$] for 50 [min.] in the tunnel kiln. The sintered density was reached to 97% of theoretical density, and the bending strength was 1658 [k $g_{f}$/$\textrm{cm}^2$] and hardness and fracture toughness which was measured by ICL( indentation crack length ) method were 1658 (kgf/$\textrm{cm}^2$) and 27.5 [Gpa], respectively. In measurement of tana and insulation break voltage of 400 (kN) porcelain, tan$\delta$ took some numerical value between 17${\times}$10$_{-3}$ and 61${\times}$10$_{-3}$ and insulation break voltage value was 19.9$\pm$1.4 [㎸/mm]. The test was performed to research whether the shape of pin affect a overvoltage break load or not As a consequence, when a pin was designed a pin diameter 51 [mm] with the bottom form of two-step constructed with straight in the suspension insulator, Insulator showed overvoltage break load 52 [ton] of the highest value and reflected a fine characteristic in aged deterioration test which is one of the accelerated aging test. Also it could be confirmed a fine characteristic through performing the test that electrical property of insulator was established correctly in accordance with IEC 60383-1 standards.s.

• Acta Via Serica
• /
• v.4 no.2
• /
• pp.119-128
• /
• 2019

This paper attempts to reveal little-known pages from the history of relations between the peoples of Central Asia and Korea based on materials derived from written sources and modern scientific literature, as well as from medieval wall paintings from the early medieval Afrasiab Palace of Varhuman, the ruler of Samarkand, and from stone sculptures of Sogdian figures contained in Silla royal tombs. Korea's interest in the western lands led to its contact with Buddhism, which spread and later flourished in all three Korean kingdoms (Koguryo, Paekche and Silla). The spread of Buddhism in turn motivated a number of Korean monks to undertake pilgrimages to India via Central Asia. Hyecho, a young Silla pilgrim, left evidence of his journey via the South China Sea to India in 723 AD. Paul Pelliot discovered a report from Hyecho's journey entitled Notes on Pilgrimage to Five Regions in India (Wang Wu Tianzhuguo zhuan) in the Dunhuang caves in 1908. Hyecho's contributions are worthy of attention, substantially complementing knowledge available for this little-studied period in the history of South and Central Asia. The information contained in Hyecho's manuscript is, in fact, considered the most significant work of the first half of the 8th century. Research regarding the relationship between Central Asia and Korea remains underdeveloped. Existing historical evidence, however, including the above mentioned Samarkand wall paintings, depicts the visits of two Korean ambassadors to Samarkand, and evidence from Silla tombs suggests the presence of diplomatic relations in addition to trade between the two regions. Overall, the history of the relationship between Central Asia and Korea yields new insights into how and why these distant countries sustained trade and diplomatic and cultural exchange during this early period. Taking into account Korea's growing interest in Uzbekistan, especially in its history and culture, this article can act as a catalyst for studying the history of the two country's relations.

• Journal of the Korean GEO-environmental Society
• /
• v.5 no.1
• /
• pp.13-25
• /
• 2004

Granular compaction piles increase the load bearing capacity of the soft ground and reduce the settlement of foundation built on the reinforced soil. The granular compaction group piles also accelerate the consolidation of the soft ground and prevent the liquefaction caused by earthquake using the granular materials such as sand, gravel, stone etc. However, this method is one of unuseful method in Korea. In the present study, the optimum locations of granular compaction group piles using genetic algorithm are proposed. The results were shown that the bearing capacity was increased in the case concentrated on the central part of the group piles. Also, the optimum design for total weight of granular compaction group piles was carried out in consideration of the economical efficiency and parametric studies were performed to examine the effects of parameters at the design of granular compaction group piles.

• Korean Journal of Environment and Ecology
• /
• v.22 no.2
• /
• pp.145-151
• /
• 2008

The purpose of this study was to understand users' attitudes for trail structure conditions in Dobong district, Bukhansan National Park, Korea. For this purpose, the research conducted a respondent's-personal entry-method based questionnaire survey on 250 visitors using inquiry routes in Dobong areas in Bukhansan National Park in July, 2007. The survey result showed that the 6 types of pedestrian trail structures were relatively in better shape in its quality and quantity while the responses for 3 types of structures, such as wood deck, wood railings, and stone paving, were positive in terms of harmony with landscape, preservation of resources, and user convenience. In conclusion, it is considered to be essential to bring in nature-friendly materials for walking facilities in National Parks and also necessary to consider the visual effect arising from the harmony with landscape together with the functions of conservation of resources and inquiry convenience.

• Fashion & Textile Research Journal
• /
• v.8 no.3
• /
• pp.258-268
• /
• 2006

The purpose of this study is to consider incense culture found in costume and life in forms of carrying and decoration. Here, incense for carrying and decoration is classified into two cases, using it as a costume accessory and life space. Hyangjumony, Hyangnorigae, Hyangjul, Hyangdae and Hyangseonchu were costume accessories. Hyangjumony was not only used for the royal palanguin, but also for bedroom. When Poetic Literature, and other ancient publications were reviewed in regard to incense for carrying and decoration, it was estimated that incense began to be carried for the first time before the late period of Shilla(9C). In addition, it was found that incense was not just a personal taste, but one of important gifts exchanged between states, envoys of different nations and between sovereign and subject and that incense was a necessary costume accessory for men. Types of incense for carrying and decoration used in this nation are classified into Hyangjumony, Hyangnorigae, Hyangjul and Hyangseonchu. Hyangjumony is a fabric pouch that contains incense. Hyangnorigae is Norigae whose main material is incense. Hyangjul is a string to which incense is hanged. Hyangseonchu is Seonchu whose main material is incense. Incense for carrying and decoration was based on five colors that symbolize cosmic order and harmony, of which red and purple were mostly used. Red strongly suggests expelling Yin with Yang, or exorcism. The color gives a strong impression, so it was often used to make a carried incense more decorating. Main materials of incense for carrying and decoration were gold, silver, precious stone and horsehair. They are different in characteristics, but were used appropriately for incense fragrance and decoration. Patterns mainly used for the incense had shapes of animal, plant, sipjangsaeng and letter. These were all auspicious patterns that symbolize human wishes and desires, especially individual and family happiness.

• Solar Energy
• /
• v.15 no.1
• /
• pp.13-28
• /
• 1995

In this study, the history of Korean traditional Ondol was investigated and the latent heat materials and bioceramics were selected to develop the latent heat storage-bioceramics Ondol system based on the Korean traditional Ondol(sensible heat storage type), and the thermal characteristics of Ondol were analyzed experimentally The results could be summarized as follows; 1. Korean traditional Ondol has been originated in "Whaduk" which had been utilized continuously for about $2{\times}10^6$ years from the Old Stone Age to the Bronze Age, and Korean traditional Ondol using in these days has been utilized for about 976 years from the Koryu Dynasty to the Modern Ages. 2. $Na_2SO_4{\cdot}10H_2O(SSD)$ was selected as latent heat material for the latent heat storage Ondol. 3. Ondol unit was filled with the latent heat material of 0.63 kg and the dimension of Ondol unit was $400mm{\times}400mm{\times}27mm(width{\t\imes}depth{\times}height)$. 4. The comfortable surface temperature($23{\sim}29^{\circ}C$) of the latent heat storage Ondol was lasted 5 hours at the room temperature of $16{\sim}18^{\circ}C$, whereas that of sensible heat storage Ondol was lasted only 1.0 hours in the same conditions. 5. For the thermal effect of bioceramics, the Ondol air temperature i.n case of bioceramics treatment on the pannel was higher than that of without bioceramics treatment.

• Journal of Forest and Environmental Science
• /
• v.33 no.4
• /
• pp.330-341
• /
• 2017

Tropical forests play a key role for functioning of the planet and maintenance of life. These forests support more than half of the world's species, serve as regulators of global and regional climate, act as carbon sinks and provide valuable ecosystem services. Forest floor biomass and litterfall dynamics was measured in different sites influenced by fire in a seasonally dry tropical forest of Bhoramdeo wildlife sanctuary of Chhattisgarh, India. The forest floor biomass was collected randomly placed quadrats while the litterfall measured by placing stone-block lined denuded quadrat technique. The seasonal mean total forest floor biomass across the fire regimes varied from $2.00-3.65t\;ha^{-1}$. The total litterfall of the study sites varied from $4.75-7.56t\;ha^{-1}\;yr^{-1}$. Annual turnover of litter varied from 70-74% and the turnover time between 1.35-1.43 years. Monthly pattern of forest floor biomass indicated that partially decayed litter, wood litter and total forest floor were differed significantly. The seasonal variation showed that leaf fall differed significantly in winter season only among the fire regimes while the wood litter was found non significant in all the season. This study shows that significant variation among the site due to the forest fire. Decomposition is one of the ecological processes critical to the functioning of forest ecosystems. The decomposing wood serves as a saving account of nutrients and organic materials in the forest floor. Across the site, high fire zone was facing much of the deleterious effects on forest floor biomass and litter production. Control on such type of wildfire and anthropogenic ignition could allow the natural recovery processes to enhance biological diversity. Chronic disturbances do not provide time for ecosystem recovery; it needs to be reduced for ecosystem health and maintaining of the high floral and faunal biodiversity.

• The Journal of Advanced Prosthodontics
• /
• v.5 no.2
• /
• pp.179-186
• /
• 2013

PURPOSE. One of the most important factors in evaluating the quality of fixed dental prostheses (FDPs) is their gap. The purpose of this study was to compare the marginal and internal gap of two different metal-ceramic crowns, casting and selective laser sintering (SLS), before and after porcelain firing. Furthermore, this study evaluated whether metal-ceramic crowns made using the SLS have the same clinical acceptability as crowns made by the traditional casting. MATERIALS AND METHODS. The 10 study models were produced using stone. The 20 specimens were produced using the casting and the SLS methods; 10 samples were made in each group. After the core gap measurements, 10 metal-ceramic crowns in each group were finished using the conventional technique of firing porcelain. The gap of the metal-ceramic crowns was measured. The marginal and internal gaps were measured by two-dimensional and three-dimensional replica techniques, respectively. The Wilcoxon signed-rank test, the Wilcoxon rank-sum test and nonparametric ANCOVA were used for statistical analysis (${\alpha}$=.05). RESULTS. In both groups, the gap increased after completion of the metal-ceramic crown compared to the core. In all measured areas, the gap of the metal cores and metal-ceramic crowns produced by the SLS was greater than that of the metal cores and metal-ceramic crowns produced using the casting. Statistically significant differences were found between cast and SLS (metal cores and metal-ceramic crown). CONCLUSION. Although the gap of the FDPs produced by the SLS was greater than that of the FDPs produced by the conventional casting in all measured areas, none exceeded the clinically acceptable range.