• The korean journal of orthodontics
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• v.26 no.4
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• pp.455-467
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• 1996

This study was designed to evaluate the expression of type I collagen in periodontal tissue during the experimental movement of rat incisors. Twenty-one Sprague-Dawley rats were divided into a control group(3 rats), and experimental groups(18 rats) where a force(75g) from helical springs across the maxillary incisors was applied. Experimental groups were sacrificed at 12 hours, 1, 4, 7, 14 and 28 days after force application, respectively. And tissue slides of control and experimental groups were studied histologically and immunohistochemically by LSAB(Labelled streptavidine Biotin) immunohistochemical staining for type I collagen. The results were as follows: 1. Until 28-day after force application, periodontal fibers were strectched on the tension side, and compressed in pressure side, and the arrangement of periodontal fibers was not recovered by that time. 2. The degree of type I collagen expression in control group was rare in the oral epithelium, predentin, pulp and periodontal ligament, but was mildly positive in osteoblasts, acellular cementum, cementoblasts, intermaxillary suture. 3. At acellular cementum of experimental group, the expression of type I collagen was moderate in 1-day and severe in 7-day, which was maintained until 28-day. 4. Type I collagen was observed in the newly formed fibrous connective tissue and osteoblasts at intermaxillary suture, moderately in 1-day, and severely in 14-day. 5. The tension side of periodontal ligament showed a more positive expression of type I collagen than the pressure side in 4-day. The degree was highest in 7-day and was not differentiated between sides in 14-day. 6. In the side wall of bone matrix on which osteoblasts were attached, type I collagen was expressed severely, especially in 7-day. From the above findings, we could suggest that bone remodeling in tooth movement be intimately related to the cell differentiation and the resulting formation of type I collagen.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.388-395
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• 2016

This paper explores the photocatalytic sensitivity of cement mortar incorporated with recycled $TiO_2$ from waste water sludge. Basically, $TiO_2$ cluster sank down slowly to the bottom of cement mortar specimen before setting and hardening process. This leads the mismatch of $TiO_2$ concentration on the top and the bottom faces of a specimen. This poorly dispersed $TiO_2$-cement mortar naturally exhibits poor NOx removal efficiency especially on the top of cementitious structure. In architectural engineering application such as building or housing structures, one can simply filp over from the bottom so that more $TiO_2$ concentrated surface can be placed outward into the air. However, in highway pavement case, this could not be applicable due to in-situ installation of concrete pavement. Hence, the dispersion of $TiO_2$ cluster inside the cementitous material is getting important issue onto road construction application. To elaborate this issue, according to our results, silica fume, high-ranged water reducer, viscosity agent, blast furnace slag were not enhanced much of dispersion characteristics of $TiO_2$ cluster. The combination of foaming agent and accelerator of hardening with viscosity agent and small grain size of fine aggregate may help the dispersion of $TiO_2$ inside cementitious materials. Even though the enhanced dispersion were applied to the specimen, NOx removal efficiency doest not change much for the top surface of the specimen. This concurrently affected by the presence of tiny air voids and the dispersion of $TiO_2$ in that these voids could easily adsorbed NOx gas with the aid of large surface area.

• Economic and Environmental Geology
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• v.46 no.5
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• pp.411-424
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• 2013

Assessment and damage reduction strategy of acidic rock drainage were conducted in a section of ${\bigcirc}{\bigcirc}$ highway construction site. The geology of the studied section consists of Icheonri sandstone and intermediate to acidic volcanic rocks. Sulfides occur as a disseminated type in sandstone and volcanics which were altered by the hydrothermal solution of granite intrusion. Volcanics and sandstone with a high content of sulfide were classified as a potentially acid rock drainage(ARD) forming rock. The drainage originated from those rocks may acidify and contaminate the surrounding area during the highway construction. Therefore, the drainage should be treated before it is discharged. A slope landslide hazard due to the ARD was also expected and the coating technology was recommended for the reduction of ARD generation as a preemptive measure before reinforcement work for enhancing slope stability such as shotcrete and anchor. According to the ARD risk analysis, those rocks should not be used as cement aggregate, but only to be used as a bank fill material of a filling-up system that allows minimal contact with rainfall and groundwater.

• Journal of the Mineralogical Society of Korea
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• v.16 no.1
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• pp.75-90
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• 2003

Ettringite and thaumasite were observed in some concrete. The morphology and occurrence of these minerals were closely examined by performing SEM/EDAX analyses. We also experimentally induced the concrete deterioration using $Na_2SO_4$ solution with application of various environmental conditions. The stability of these minerals and deterioration characteristics under applied experimental conditions were determined. Abundant ettringite formed by“through solution reaction”occurred in many open spaces, and some microscopic ettringite formed by "tophochemical replacement" of calcium aluminate also occurred in cement paste. Severe cracking of cement paste causing premature deterioration was often associated with ettringite location. Under specific condition, ettringite was transformed to thaumasite, tricthloroaluminate, or decomposed. Thaumasite occurred with association of ettrinsite in concrete containing carbonate aggregate being subject to dedolomitization or in some concrete being subject to carbonation. Thaumasite appears to be formed under the similar condition to the general ettringite forming condition, but it formed solid solution with ettringite by substituting pre-existing ettringite. Ettringite can also be transformed to trichloroaluminate in the presence of abundant chlorides, but trichloroaluminate changed back to ettringite in late sulfate attack. It is considered that the substitution reaction direction solely depend on the concentration of chloride and sulfate ion.

• Journal of the Korean Geotechnical Society
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• v.31 no.10
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• pp.37-47
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• 2015

Recently, the quality of drilled shafts concrete has been improved significantly due to the improved concrete performance, upgraded concrete materials, and better management of on-site constructions. Despite the development, current conventional quality management on concrete constructions is still used without any criticism. In this study, compressive strength test results of more than 200 concrete specimens after 7 and 28 days of curing were collected from one site at Songdo area of Incheon. The concrete specimens were prepared from the concrete with aggregate maximum dimensions of 25 mm, target compressive strength of 40 MPa, and slump of 180 mm. Influential factors including concrete temperature, air temperature, amount of slump, amount of air, amount of salinity on concrete specimen were also examined. The database was established from collected information and statistical analyses were performed. Analyzed results confirm that "the difference between concrete temperature and air temperature" has the largest impact on the compressive strengths of specimens at the durations of 7 and 28 days.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.2
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• pp.207-217
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• 2016

Permeability can not be expressed as a function of porosity alone, it depends on the porosity, pore size and distribution, and tortuosity of pore channels in concrete. There has been considerable interest in the relationship between microstructure and transport in cementitious materials, however, it is very rare to deal with the theoretical study on gas permeability coefficient in connection with carbonation of concrete and the effect of volumetric fraction of cement paste or aggregate on the permeability coefficient. The majority of these researches have not dealt with this issue combined with carbonation of concrete, although carbonation can significantly impact on the permeability coefficient of concrete. In this study, fundamental approach to compute gas permeability of (non)carbonated concrete is suggested. For several compositions of cement pastes, the gas permeability coefficient was calculated with the analytical formulation, followed by a microstructure-based model. For carbonated concrete, reduced porosity was calculated and this was used for calculating the gas permeability coefficeint. As the result of calculation of gas permeability for carbonated concrete, carbonation leaded to the significant reduction of gas permeability coefficient and this was obvious for concrete with high w/c ratio. Meanwhile, the relationship between gas permeability and water permeability has a linear function for cement paste based on Klinkenberg effect, however, which is not effective for concrete. For the evidence of the modeling, YOON's test was accomplished and these results were compared to each other.

• The Journal of Engineering Geology
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• v.10 no.2
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• pp.52-74
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• 2000

The basement rock of upper stream of Keum River Valley consists of Precambrian gneiss which is resistant to weathering. That of mid and lower stream valley, however, is mainly composed of Mesozoic granites which are vulnerable to weathering. The upstream part of Geum River Basin is typified by the deeply-incised and steep meandering streams, whereas mid and lower part is characterized by wide floodplain and gently dipping river bottom toward the Yellow Sea. In particular flooding deposits, in which are imprinted a number of repetitions of erosion and sedimentation during the Holocene, are widely distributed in the lower stream of Geum River Basin. For understanding of erosions in the mid and lower stream of Geum River Basin, the rate of erosion of each small basins were estimated by using the data of field survey, erosional experiments and GIS ananlysis. It was revealed that erosion rate appeared highest in granite areas, and overall areas, in this field survey were represented by relatively high erosion rates. By implemeatation of remote sensing and imagery data, the temporal changes of river bed sediments for about last 11 years were successfully monitored. Observed as an important phenomenon is that the river bed has been risen since 1994 when an embankment (Dyke) was constructed in the estuarine river mouth. From the results derived from the detailed river bed topographical map made in this investigation, the sedimentation of the lower river basin is considered to be deposited with about 5 cm/year for the last 11 years. Based on this river bed profile analysis by HEC-6 module, it is predicted that Geum River bed of Ganggyeong area is continuously rising up in general until 2004. Although extraction of a large amount of aggregates from Gongju to Ganggyung areas, the Ganggyung lower stream shows the distinct sedimentation. Therefore, it is interpreted that the active erosions of tributary basins Geum drainage basins can affect general river bed rising changes of Geum River.

• International Journal of Highway Engineering
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• v.17 no.3
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• pp.49-58
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• 2015

PURPOSES : The use of environmentally friendly construction methods has been recently encouraged to reduce fuel consumption and the effects of global warming. For this purpose, the roller compacted concrete pavement (RCCP) construction method has been developed. RCCP is more environmentally friendly and economically efficient than general concrete by reducing the amount of CO2 generated through the application of a smaller amount of cement. RCCP has a number of advantages such as an easy construction method, low cost, high structural hydration performance, and aggregate interlocking. However, mix design standards and construction guidelines of RCCP are required for domestic application. In addition, a study on aggregate selection, which has an effect on the characteristics of RCCP, is necessary owing to a limited number of researches. Thus, the aggregate effect on the performance of RCCP in securing the required strength and workability was evaluated in consideration of domestic construction. METHODS : Sand and coarse aggregates of both 19mm and 13mm in maximum size were used in this study. Four types of aggregate gradations (s/a = 30%, 58%, and 70% for the sand and coarse aggregate of 19mm in maximum size, and s/a = 50% for a combination of the three types of aggregates) were set up to investigate the effects of the PCA band on the RCC characteristics. The conditions of s/a = 30% and 70% were evaluated to check the gradation effect outside of the recommended band. The conditions of s/a = 58% and 50% were used because they are the optimum combination of the two and three types of aggregates, respectively. RCCP gradation band was suggested gradation with a proper construction method of RCCP by synthetically comparing and analyzing the correlation of optimum water content, maximum dry density, and strength of requirements through its consistency and compaction test. RESULTS : The lower and upper limit lines are insufficient to secure a relatively strong development and workability compared to an aggregate gradation in the RCCP gradation band region. On the other hand, the line in the RCCP gradation band and the 0.45 power curve in the RCCP gradation band region were satisfactory, ensuring the required strength and workability. CONCLUSIONS : The suitable aggregate gradation on RCCP process should meet the RCCP gradation band area; however, fine particles passing through a #60 sieve do not need to be within the recommended gradation band because the influence of this region on such fine particles is small.

• Korean Journal of Ecology and Environment
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• v.37 no.2 s.107
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• pp.227-235
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• 2004

Fish fauna and community structure were surveyed in the Nakdong River, Gumi City, Kyeongpook province from April 2001 to July 2002. During the surveyed Period, 39 species, 32 genera belonging to 10 families were collected. Cyprinid fish occupied 64.1% (25 species) and cobitid fish had 7.7% (3 species). Fourteen species(35.9%) of observed species were known as endemic species. The exotic fish was Micropterus salmoides (2.5%) . The dominant species were Zacco platypus (relative abundance: 36.7%) and Opsariichthys uncirorstris amurensis (22.7%). Carassius aurafus and Microphysogobio rapidus were numerous (4.0${\sim}$4.3%). The rare species comprising less than 0.15% were Acheilognathus koreensis, Aphyocypris chinensis, Iksookimia longicorpus, Coreoleuciscus splendidus, Rhinogobius giurinus, Sarcocheilichthys variagatus wakiyae, Silurus asotus astus, and Channa argus. It was found that the population density of carnivorous Opsariichthys uncirostris amurensis increased drastically in the mid-reach of the Nakdong river since it had been introduced from the other native rivers in the middle 1990s. Gobiobotia nakdongensis inhabit riffle (water velocity : 0.43${\sim}$0.67 m $s^{-1}$) of which the river bed is mainly sand. This species is considered to be in need of conservation. As the result of analyzing fish community in the surveyed area, the species diversity, evenness and dominant indices were 1.008, 0.663 and 0.196 respectively. The findings showed that the tributary, which the waterside plants were abundant and had various habitats, had a higher species diversity (1.112) than the main river (0.787). Sand mining had been disturbing the river ecosystem of the study stations 3, 11, 13 & 14, and these stations showed a quite low species diversity (0.421 ${\sim}$0.574).

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.535-535
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• 2012

하천 환경의 변화는 자연적으로 일어나기도 하지만, 우리나라 경우 대부분 하천 정비, 골재 채취, 수중보와 하구둑 등 하천시설물의 건설, 그리고 댐 및 교량건설 등 인위적인 요인에 의한 변화가 지배적이다 이렇게 환경이 변화하면 하천의 평형 상태는 파괴되며 하천의 평형 상태를 복원하는 과정에서 하천의 침식 또는 퇴적이 일어나며 이러한 과정의 총체적인 결과로서 하상변동이 일어나게 된다. 하상변동은 단기적인 면에서는 하천에서의 취수, 배수, 주운동 하천관리에 직접적인 영향을 주며, 장기적인 면에서는 하천시설물의 안정, 홍수위 및 지하수위 변화, 홍수터와 같은 하천부지의 변화 등 하천 및 유역 관리에 광범위한 영향을 주고 있다 하천의 유황 및 하상재료의 인위적인 변화에 의한 장기적인 하상변동 효과를 예측하고 분석하는 것은 하천계획 및 관리 면에서 매우 중요하다. 또한 하천 정비사업 등에 의한 영향을 제대로 평가하기 위해서는 비교적 단기간의 홍수 또는 호우 사상에 대한 단기적인 하상변동 효과를 정확하게 예측하는 것은 필수적이다. 외국에서는 하상변동 예측의 필요성을 일찍이 인식하여 다수의 하상변동 예측모형이 개발되어 하천 실무에 사용되고 있으며, 국내에서도 하천 흐름의 등수 역학적 해석을 위해 여러 가지 수치 기법들에 대한 연구가 진행되고 발전되어져 왔다. 현재 국내에서는 측량 자료이용과 모형적용의 용이성을 이유로 1차원 점변 부정류 해석프로그램인 HEC-RAS 모형을 많이 사용하고 있으며 대부분의 하천 정비 기본계획 수립에 있어서도 1차원 해석 모형을 적용하고 있는 실정이다. 국내에 서 수행된 하상변동 예측에 관한 연구들은 대부분 1차원 모형이므로 하천의 사행의 진행이나 유사의 횡방향 분포 등은 고려할 수 없다. 또한 하상변동 계산 시 이동상 부분의 전체가 균일하게 상승 또는 하향하는 것으로 가정하기 때문에 흐름이 급변하는 데 적용하는 것은 적합하지 않다. 따라서 본 연구에서는 4대강살리기 사업이 진행중인 낙동강유역 구미보지점을 대상으로 2차원 흐름 및 하상변동 수치모형인 CCHE2D 모형을 적용하여 50년, 100년, 200년 빈도별로 모의를 실시, 보설치 전 후의 하상변동을 비교 분석 하였다. 모의 결과 보설치 후의 경우 보 상류단은 전반적으로 퇴적의 양상을 보였으며, 보 하류단의 만곡부의 경우 홍수량이 증가함에 따라 유속 및 소류력이 비슷한 패턴으로 증가하여 침식이 관찰되었다. 특히 보 직하류의 경우 수문을 기준으로 다량의 침식이 있음을 보였으며, 침식이 계속 진행된다면 보유실과 같은 심각한 결과를 초래할 수 있기 때문에 침식을 방지 할 수 있는 다양한 장치가 마련되어야 할 것으로 판단된다.