• Journal of Periodontal and Implant Science
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• 제42권6호
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• pp.217-223
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• 2012

Purpose: Several parameters have been described for determining the success or failure of dental implants. The surface properties of transgingival implant components have had a great impact on the long-term success of dental implants. The purpose of this study was to compare the tendency of two periodontal pathogens to adhere to and colonize zirconia abutments and titanium alloys both in hard surfaces and soft tissues. Methods: Twelve patients participated in this study. Three months after implant placement, the abutments were connected. Five weeks following the abutment connections, the abutments were removed, probing depth measurements were recorded, and gingival biopsies were performed. The abutments and gingival biopsies taken from the buccal gingiva were analyzed using real-time polymerase chain reaction to compare the DNA copy numbers of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and total bacteria. The surface free energy of the abutments was calculated using the sessile water drop method before replacement. Data analyses used the Mann Whitney U-test, and P-values below 0.05 find statistical significance. Results: The present study showed no statistically significant differences between the DNA copy numbers of A. actinomycetemcomitans, P. gingivalis, and total bacteria for both the titanium and zirconia abutments and the biopsies taken from their buccal gingiva. The differences between the free surface energy of the abutments had no influence on the microbiological findings. Conclusions: Zirconia surfaces have comparable properties to titanium alloy surfaces and may be suitable and safe materials for the long-term success of dental implants.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.170-170
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• 2000

Synthetic polymers such as polyimide, polycarbonate, and poly(methyl methacrylate) are long chain molecules which consist of carbon, hydrogen, and heteroatom linked together chemically. Recently, polymer surface can be modified by using a high energy ion beam process. High energy ions are introduced into polymer structure with high velocity and provide a high degree of chemical bonding between molecular chains. In high energy beam process the modified polymers have the highly crosslinked three-dimensionally connected rigid network structure and they showed significant improvements in electrical conductivity, in hardness and in resistance to wear and chemicals. Polyimide films (Kapton, types HN) with thickness of 50~100${\mu}{\textrm}{m}$ were used for investigations. They were treated with two different surface modification techniques: Plasma Source Ion Implantation (PSII) and conventional Ion Implantation. Polyimide films were implanted with different ion species such as Ar+, N+, C+, He+, and O+ with dose from 1 x 1015 to 1 x 1017 ions/cm2. Ion energy was varied from 10keV to 60keV for PSII experiment. Polyimide samples were also implanted with 1 MeV hydrogen, oxygen, nitrogen ions with a dose of 1x1015ions/cm2. This work provides the possibility for inducing conductivity in polyimide films by ion beam bombardment in the keloelectronvolt to megaelectronvolt energy range. The electrical properties of implanted polyimide were determined by four-point probe measurement. Depending on ion energy, doses, and ion type, the surface resistivity of the film is reduced by several orders of magnitude. Ion bombarded layers were characterized by Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS), XPS, and SEM.

• 한국물환경학회지
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• 제22권3호
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• pp.546-556
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• 2006

The purpose of this study is to improve the polluted stream water quality by pilot-scale five different constructed wetlands (CWs). Cell 1 to 3 are newly designed 2SFCW (Surface-subsurface flow CW) with 1 to 3 flow shifters (FS) in the middle of the wetland system. Cell 4 and 5 are control CW (CCW), but Cell 5 is the same type as Cell 3. The FS, which converts the route of surface and subsurface flow between two wetlands connected in series, was able to enhance the treatability of TN via nitrification and denitrification and of SS due to filtration and sedimentation. The void fraction and dispersion number of Cell 1, 2 and 3 obtained from the RTD analysis were found to be 0.73 and 0.17, respectively. COD and TP removal efficiencies of Cell 1 to 3 were similar to that of Cell 4 and 5. SS removal efficiencies of Cell 1 to 3 and 5 with FS were 5-10% higher than that of Cell 4 without FS. TN removal efficiencies of Cell 1 to 3 were 3-14% higher than that of Cell 4 and 5. The average $R^2$ values of COD, SS, TN and TP obtained from nonlinear regression analysis were similar to the results of other researchers.

• Geosciences Journal
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• 제22권6호
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• pp.871-880
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• 2018

During and shortly after the 2017 Pohang Earthquake ($M_w$ 5.4), sand blows were observed around the epicenter for the first time since the beginning of instrumental seismic recording in South Korea. We carried out field surveys plus satellite and drone imagery analyses, resulting in observation of approximately 600 sand blows on Quaternary sediment cover in this area. Most were observed within 3 km of the epicenter, with the farthest being 15 km away. In order to investigate the ground's susceptibility to liquefaction, we conducted a trench study of a 30 m-long sand blow in a rice field 1 km from the earthquake epicenter. The physical characteristics of the liquified sediments (grain size, impermeable barriers, saturation, and low overburden pressure) closely matched the optimum ground conditions for liquefaction. Additionally, we found a series of soft sediment deformation structures (SSDSs) within the trench walls, such as load structures and water-escaped structures. The latter were vertically connected to sand blows on the surface, reflecting seismogenic liquefaction involving subsurface deformation during sand blow formation. This genetic linkage suggests that SSDS research would be useful for identifying prehistoric damage-inducing earthquakes ($M_w$ > 5.0) in South Korea because SSDSs have a lower formation threshold and higher preservational potential than geomorphic markers formed by surface ruptures. Thus, future combined studies of Quaternary surface faults and SSDSs are required to provide reliable paleoseismological information in Korea.

• Journal of Information Processing Systems
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• 제14권6호
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• pp.1445-1456
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• 2018

Environment perception and three-dimensional (3D) reconstruction tasks are used to provide unmanned ground vehicle (UGV) with driving awareness interfaces. The speed of obstacle segmentation and surrounding terrain reconstruction crucially influences decision making in UGVs. To increase the processing speed of environment information analysis, we develop a CPU-GPU hybrid system of automatic environment perception and 3D terrain reconstruction based on the integration of multiple sensors. The system consists of three functional modules, namely, multi-sensor data collection and pre-processing, environment perception, and 3D reconstruction. To integrate individual datasets collected from different sensors, the pre-processing function registers the sensed LiDAR (light detection and ranging) point clouds, video sequences, and motion information into a global terrain model after filtering redundant and noise data according to the redundancy removal principle. In the environment perception module, the registered discrete points are clustered into ground surface and individual objects by using a ground segmentation method and a connected component labeling algorithm. The estimated ground surface and non-ground objects indicate the terrain to be traversed and obstacles in the environment, thus creating driving awareness. The 3D reconstruction module calibrates the projection matrix between the mounted LiDAR and cameras to map the local point clouds onto the captured video images. Texture meshes and color particle models are used to reconstruct the ground surface and objects of the 3D terrain model, respectively. To accelerate the proposed system, we apply the GPU parallel computation method to implement the applied computer graphics and image processing algorithms in parallel.

• 정보보호학회논문지
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• 제33권6호
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• pp.939-946
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• 2023

IT 기술이 급속히 발전하는 현대 초연결 환경은 네트워크 장비들이 다양해지고 네트워크 구성이 복잡해짐에 따라 사이버 공격자가 침투경로로 활용될 수 있는 공격표면(attack surface) 또한 증가하게 되었다. 이러한 환경에서 사이버 공격을 원천적으로 방어하기 위해 공격표면을 변이하는 MTD(Moving Target Defense) 기술이 연구되고 있다. 그중에 네트워크를 통해 공격이 시작됨에 따라 주요 속성 네트워크 주소를 변이하는 기술이 있으나, 대부분 운용환경이 기존 고정 IP 기반으로 운용되기 때문에 주소변이 기술이 기존 네트워크 보호체계 내에 적용되었을 때 어떠한 영향이 있는지 연구가 필요하다. 본 논문에서는 기존 네트워크 보호체계에서 네트워크 주소변이 기술이 적용되었을 때의 영향성을 연구하였고 연구 결과로서 네트워크 보호체계의 주요 시스템인 방화벽, NAC, IPS와 네트워크 주소변이 기술이 동시 적용되었을 때 운용 측면에서 고려해야 할 요소를 도출하였다. 또한 사이버 대응체계 내에서 네트워크 분석시스템과의 연동성을 위해 네트워크 주소변이 기술에서 관리해야하는 요소를 제안하였다.

• 한국환경보건학회지
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• 제34권1호
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• pp.86-94
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• 2008

Lake Shiwha, an artificial lake located near metropolitan Seoul, offers a unique water environment and has been suspected to have high levels of chemical and microbiological contaminations. Lake Shiwha was originally connected to the sea but currently has four major surface water inputs from agricultural, municipal, industrial areas and in addition an occasional inflow from the sea. The objectives of this study are to investigate the relative contribution of microbial contaminants from each of the inflowing surface waters and to identify appropriate microbial indicator organisms in this unique water environment. We measured the levels of microbial contaminations in the four inflowing surface waters. A number of microbial indicator organisms including total coliform (TC), fecal coliform (FC), E. coli, Enterococci, somatic and male-specific coliphages were analyzed. Bacterial indicator microorganisms were detected and quantified by the $Colilert^{(R)},\;Enterolert^{(R)}$ kit. Surface water (50 l) was sampled by $ViroCap^{TM}\;5"$ cartridge filters and analyzed by the single agar layer method for detecting coliphages. The concentrations of TC, FC, E. coli, and Enterococci were 1543 CFU/100 ml${\sim}1.99{\times}10^6$ CFU/100 ml, 0 CFU/100 ml${\sim}202$ CFU/100ml, 0 CFU/100 ml${\sim}1.80{\sim}10^5$ CFU/100ml, 74 CFU/100 ml${\sim}3408$ CFU/100 ml, respectively. The male-specific and somatic coliphages were detected in three different inflowing surface waters. Isolated E. coli and Enterococci strains were further analyzed by 16s rDNA amplification and subsequent phylogenetic analysis from Jungwang-chun, Ansan-chun, Banwol-chun and penstock of inflowing surface water. Our results indicated that the concentrations of different fecal indicator microorganisms might not be highly correlated with each other. Multiple microbial indicator organisms should be used for monitoring microbial contamination and microbial source tracking methods.

• Parasites, Hosts and Diseases
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• 제25권2호
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• pp.129-140
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• 1987

The present study was undertaken to demonstrate the surface structure of Paragonimus westermani metacercaria in Korea with special reference to the distribution of sensory papillae. Metacercariae were isolated from crayfish, one of the second intermediate tost of P. westermani in Bogil island, Chollanam-do (Province), Korea, where has been known as an endemic area of human paragonimiasis. Isolated metacercariae were encysted and examined with light. scanning and transmission electron microscopes for morphological features. On the surface of iBetacercariae, three types of sensory FaFillae were identified. Large domed papillae ($3~5{\mu\textrm{m}}$), which were covered with wrinkled plasma n!embrane of the worm, were distributed on the oral and ventral suckers only. On the oral sucker, these large domed papillae were 12~13 in number. On the other hand large domed papillae on the ventral sucker were constantly 6 in number and hexagonal in distribution. Small domed papillae ($2~3{\mu\textrm{m}}$), of which surface was more smooth than those of large ones, were distributed symmetrically on the ventral (30~32 pairs) and dorsal surfaces (40~42 Pairs). Ciliated Papillae ($0.8~1.5{\mu\textrm{m}}$) were observed about 5~6 in number around the oral sucker and 3~5 pairs each on the ventral and dorsal surface of the body. Single Fcinted spines covered the entire surface of the body except around the excretory pore. Spines on the anterior fart of the body were 0.9~2.0${\mu\textrm{m}}$ in length and $45~55/100{\mu\textrm{m}}$2 in number, and were gradually reduced in length ($0.4~1.4{\mu\textrm{m}}$) and in nuns.her ($12~27/100{\mu\textrm{m}}$2) toward the posterior part. The body wall of p. westermoni metacercariae was consisted with anucleated syncytium layer, fibrous interstitial layer and musclar layer. In the anucleated syncytium, biconcave ($0.15~0.55{\mu\textrm{m}}$) and spherical ($0.08~0.16{\mu\textrm{m}}$) secretory granules, which were transferred from epidermal cells via protoplasmic tubules, mitochondria and rihoEorses, T-ere observed. Spines originated around the basement membrane protruded externally. Epidermal cells were consisted with a nucleus and a cytoplasm, and connected to syncytium with protoplasmic tubules. In the cytoplasm many secretory granules, mitochondria, Golgi complex, endoplasmic reticula, ribosomes and lipid droplets were observed.

• 한국지형학회지
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• 제25권3호
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• pp.43-55
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• 2018

This study aimed to identify different sedimentary environments of Gochang coast according to geomorphic conditions of each bore hole. To achieve the aim, this study utilized the classification of sedimentary environmental conditions of surface sediment, which was based on grain size distribution characteristics.In other words, three sedimentary environmental conditions ofsandy flat + sand beach, coastal sand dune and weathered bedrock soil, which were distinguished based on grain size distribution characteristics of mean-sorting for surface sediments, were applied to the sediments of bore holes. Four sedimentary environments could be identified in Gochang coast. First, the lake sedimentary environment originated from terrestrial sediments seems to have been dominated by weathered bedrock soil that the surface flow has deposited in a coastal wetland or a boundary, which is affected by the sea. Second, the lake sedimentary environment that is little affected by coastal sand dunes is located at the center of a valley, which is connected to the land, and the dune slack of Saban-ri. The surface flow of weather bedrock soil is the main source of deposits. However, there seems to have been a temporary influence of the sea. Third, the lake sedimentary environment that is strongly affected by coastal sand dunes is located at the dune slack of Yeongjeong-ri. This environment shows traces of a change from a coastal sand dune into the dune slack. Finally, the coastalsand dune sedimentary environment, which wasinvestigated by boring the current coastal sand dune, shows a temporary influence of the land but seems to have maintained the overall stability. Consequently, this study demonstrated that the grain size distribution characteristics of the present surface sediments could be effectively applied to identify the sedimentary environments of the paleo bore hole sediments. In addition, the paleo change of sedimentary environment could also be identified in many places of Gochang coast. If the results of this study are combined with the age dating and geochemical analysis in future works, the paleo environmental change in Gochang coast will be restored more precisely.

• 농촌의학ㆍ지역보건
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• 제13권1호
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• pp.19-25
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• 1988

It is very important to supply safe drinking water for rural area not only a prevention of entric diseases but also a promotion of health life. It is estimated that 6,981,000 rural inhabitants were covered by the simple piped water supply system at the end of 1987 in Korea. The programme for improvement of water supply system in rural villages was initiated by the government since 1967. But most of these systems have been operated carelessly by the hands of villagers who have no proper knowledge and experience. Since most of water sources were located nearby farmland, there might be a possibility that the sources could be contaminated by pesticides and fertilizers. For this reason, it is recommended to take underground water as a water source rather than surface water such as a pond or streamwater in rural areas. However, the system is supplied from the surface water, its water quality can be improved by using of simple sand filter and simple chlorinator inexpensively. On the basis of an on-site study, conducted during 1986-87, in San-Buk Village, Keum-Sa-Myon, Yeju-Gun, Kyong-Gi-Do, the new simple piped water supply system was designed by the Institute for Environmental Research, Yonsei University, and constructed by the villagers themselves in September 1987. This simple system which is protected by metal fences consists of three main parts, pump house, vertical sand filter and water tank. The pumped water from underground flows into the upper part of the sand filter, through the sand, and out the water tank which is connected to the bottom of vertical filter. And the simple plastic-bottle chlorinator was installed in the water tank for chlorination. The water quality was remarkably improved after completion of construction. The total bacterial count was not detected from the tap water in households distributed by this simple piped water supply system. The construction cost of this system which was connected 34 households in San-Buk Village, was 4,851,000 won (approximately 6,020 U.S. dollars : 1$=805.8 won) in 1987,77% of expenses was supported by the Community Development Foundation in Korea. This case study for simple piped water supply projects will be applicable to other programme for improvement of water supply system in rural areas of Korea, and other developing countries.