• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.188.2-188.2
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• 2015

The presence of the conduction interface in epitaxial $LaAlO_3/SrTiO_3$ thin films has opened up challenging applications which can be expanded to next-generation nano-electronics. The metallic conduction path is associated with two adjacent insulating materials. Such device structure is applicable to frequency-dependent impedance spectroscopy. Impedance spectroscopy allows for simultaneous measurement of resistivity and dielectric constants, systematic identification of the underlying electrical origins, and the estimation of the electrical homogeneity in the corresponding electrical origins. Such unique capability is combined with the intentional control on the interface composition composed of $SrTiO_3$ and $CaTiO_3$, which can be denoted by $SrxCa1-_xTiO_3$. The underlying $Sr_xCa1-_xTiO_3$ interface was deposited using pulsed-laser deposition, followed by the epitaxial $LaAlO_3$ thin films. The platinum electrodes were constructed using metal shadow masks, in order to accommodate 2-point electrode configuration. Impedance spectroscopy was performed as the function of the relative ratio of Sr to Ca. The respective impedance spectra were analyzed in terms of the equivalent circuit models. Furthermore, the impedance spectra were monitored as a function of temperature. The ac-based characterization in the 2-dimensional conduction path supplements the dc-based electrical analysis. The artificial manipulation of the interface composition will be discussed towards the electrical application of 2-dimensional materials to the semiconductor devices in replacement for the current Si-based devices.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.399-407
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• 2010

The flexural behaviors of two types of beam members exposed to freeze-thaw cycles were evaluated. This study aims to examine the effect of freeze-thaw cycles on the behavior characteristics of reinforced concrete (RC) beams. For the purpose, a part of the beam specimens were damaged until yielding of tension reinforcement was reached, before they were exposed to 150 and 300 cycles of freeze-thaw. Cyclic tests, as well as monotonic tests, were conducted to evaluate the stiffness degradation characteristics when same cycle is repeated. The material tests showed that relative dynamic modulus of concrete exposed to 300 cycles of freeze-thaw moderately decreased to 86.8% of normal concrete, indicating that concrete used in this study has good durability against freeze and thaw damage. The results of monotonic tests showed reduction of flexural strength, ductility and stiffness of the beam specimens exposed to freeze-thaw cycles compared with those of the control speciments. In particular, BDF13 specimens, which had been subjected to artificial cracking damage, did not showed enough flexural strength to satisfy nominal moment required by current concrete structure design code. In the monotonic tests results, BF75 specimens exposed to freeze-thaw cycles showed 10% or more cyclic stiffness degradation. Therefore, it was thought that deformation of concrete in compression have to be considered in design process of members under cyclic load, such as seismic device.

• Journal of Korea Water Resources Association
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• v.36 no.3 s.134
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• pp.507-520
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• 2003

A V-shaped riffle is an artificial hydraulic structure haying two wings from the streamside with a narrow opening in between. It is usually made of crushed stones or large boulders. It limits channel width and accelerates the flow through the constricted section causing a local scour just downstream. The V-shaped riffle provides with a unique aquatic habitat by forming a pool and sandbars around the pool edge, increasing local morphologic, hydraulic and sedimentological diversity. This study investigates experimentally the scour characteristics of the V-shaped riffle in the sandbed stream and proposes a predictive equation for the scour. Total 45 cases of experiments were conducted to examine the effect of hydraulic factors and configuration of V-shaped riffle on the geometry of scour holes. From the comparison of the experimental results of this study with the predictive equation of spur dike by Breusers and Raudkivi(1991), it is found that their predictive equation of spur dike underestimates the maximum scour depth downstream of the V-shaped riffle. h new predictive equation for the maximum scour depth was developed using the non-dimensional hydraulic and geometrical variables. The parameters used in the proposed equations were determined using the experimental data. The analysis reveals that the scour depth is dependent dominantly on the Froude number at the opening of the V-shaped riffle, while the angle of riffle and the opening width also affect the scour depth. The proposed equation for the scour of V-shaped riffle well agrees with the experimental data. It can be used for estimating the scour of the V-shaped riffle in sandbed streams.

• Journal of the Korean Association of Geographic Information Studies
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• v.3 no.2
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• pp.1-10
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• 2000

The purpose of this study is to develope a parcel-based automatic simulation system of land price through the integration of urban mathematical model and GIS. The appraisal process of public land price by the local government is simple but is a great time-consuming task. Moreover, it doesn't provide any statistical analysis and spatial presentation tools. So, it is difficult for planners or administrative officials to analyze the variation of land price with spatial idea. From these, a system is developed combining two sub-systems, they are ANN(Artificial Neural Network) for the calculation of land price and GIS for visual presentation. Using Matlab application, ANN model was designed having 3-layer structure and was trained with the sample data taken from Chinju city. With the trained network, the impact of 'road', 'parks', 'height control district' and 'beauty district' on land price in 9 regions(dong) are simulated. The results of the simulation were visualized with ArcView GIS. The automatic simulation system operated through the DDE(Dynamic Data Exchange) conversation between two applications. ArcView was set as client and Matlab as server. Scripting in ArcView and customizing a window of ArcView, this system can execute the whole process of simulation by just clicking a button with mouse. As a conclusion, this system was proved to be an effective and easily controllable planning support system for the land price simulation.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.11 no.1
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• pp.101-116
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• 1989

Proplast and Porous Polyethylene which have porous structures as low-modulus polymers have been recently used in maxillofacial plastic and reconstructive surgery. The purpose of this study was to compare the response of adajacent tissue, new bone formation and stability after augmentation by differen methods of subperiosteal graft using proplast and purous polythylene in rabbit mandible. The augmentation procedure was carried out by dividing into two groups, A and B. A group consisted of subperiosteal graft on the cortex, and the other B group was made up only graft following artificial decortication in the mandibular body of rabbit. The experimental animals were sacrificed on the 1st, 2nd, 4th and 8th week after grafting for macroscopic and light microscopic examination. The samples extracted at the 6th postgrafting week were also used for biometric testing and scanning electron microscopic examination. The results obtained from this study were as follows : 1. Macroscopically, infection of graft site, deformation and migration of graft material were not observed in all experimental groups. 2. B group showed more rapid and increased bone formation and the greater stability than A group, and tissue response was similar to each other. 3. In the tissue response, macrophages and cellular infiltrations were observed in Proplast group, but few in PHDPE group. 4. In bone formation of A group, Proplast group showed no bone formation until the 8th week, but PHDPE group showed small quantity of osteoid tissue from the 2nd week and appositional bone growth with new bone formation at the 8th week. 5. In bone formation of B group, both Proplast and PHDPE group showed bone formation, but PHDPE group showed more rapid and larger bone formation. 6. In pattern of bone formation, Proplast group mainly showed appositional bone growth pattern connected with graft site. On the other hand, PHDPE group showed mixed pattern of new bone formation in the pore connective tissue with appositional bone growth from graff site. 7. The maximum mean values of shear stress were serially $111.3gf/mm^{2}$ in PHDPE of B group, $84.8gf/mm^{2}$ in PHDPE of A group, $32.9gf/mm^{2}$ in Proplast B group, and $15.7gf/mm^{2}$ in Proplast of A group. From above results, It was suggested that the capacity of bone formation and stability between bone and graft material were dependent on the pore size and structure of graft material itself, the state of graft site and tissue response.

• The Journal of Engineering Geology
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• v.22 no.1
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• pp.113-121
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• 2012

The mechanical characteristics of a fault gouge from near Mt. Kumjung in Kumjung-Gu, Busan, were estimated from laboratory tests on different joint models. Fault gouge samples and joint samples in biotite granite were obtained from boreholes in the study area that had penetrated small faults associated with the Dongnae and Yangsan faults. XRD and SEM analyses revealed that for the fault gouge consists of several clay minerals with tabular structure (kaolinite, montmorillonite, illite, sericite), which could cause the considerable reduction of shear strength when wet. The shear strength of the fault gouge was obtained from direct shear tests of the fault gouge itself and from direct shear tests of several natural/artificial joint surfaces coated with fault gouge. The results indicate that the reduction of shear strength is more abrupt for the joint surfaces coated with fault gouge compared with uncoated joint surfaces, and that the friction angle of the fault gouge between joint surfaces is much lower than the internal friction angle of the fault gouge itself. Fault gouges in contact with rock, therefore, could have a stronger negative effect on the stability of structures in rock masses than the fault gouge itself.

• Analytical Science and Technology
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• v.24 no.6
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• pp.544-555
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• 2011

The acute toxicity in the rainbow trout (Oncorhynchus mykiss) was analyzed and predicted using quantitative structure-activity relationships (QSAR). The aquatic toxicity, 96h $LC_{50}$ (median lethal concentration) of 275 organic pesticides, was obtained from EU-funded project DEMETRA. Prediction models were derived from 558 2D molecular descriptors, calculated in PreADMET. The linear (multiple linear regression) and nonlinear (support vector machine and artificial neural network) learning methods were optimized by taking into account the statistical parameters between the experimental and predicted p$LC_{50}$. After preprocessing, population based forward selection were used to select the best subsets of descriptors in the learning methods including 5-fold cross-validation procedure. The support vector machine model was used as the best model ($R^2_{CV}$=0.677, RMSECV=0.887, MSECV=0.674) and also correctly classified 87% for the training set according to EU regulation criteria. The MLR model could describe the structural characteristics of toxic chemicals and interaction with lipid membrane of fish. All the developed models were validated by 5 fold cross-validation and Y-scrambling test.

• The Journal of the Korean Society for Microbiology
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• v.34 no.6
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• pp.519-532
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• 1999

Helicobacter pylori is a causative agent of type B gastritis and plays a central role in the pathogenesis of gastroduodenal ulcer and gastric cancer. To elucidate the host-parasite relationship of the H. pylori infection on the basis of molecular biology, we tried to evaluate the genomic diversity of H. pylori. An ordered overlapping bacterial artificial chromosome (BAC) library of a Korean isolate, H. pylori 51 was constructed to set up a genomic map. A circular physical map was constructed by aligning ApaI, NotI and SfiI-digested chromosomal DNA. When the physical map of H. pylori 51 was compared to that of unrelated strain, H. pylori 26695, completely different restriction patterns were shown. Fifteen known genes were mapped on the chromosome of H. pylori 51 and the genetic map was compared with those of strain 26695 and J99, of which the entire genomic sequences were reported. There were some variability in the gene location as well as gene order among three strains. For further analysis on the genomic diversity of H. pylori, when comparing the genomic structure of 150 H. pylori Korean isolates with one another, genomic macrodiversity of H. pylori was characterized by several features: whether or not susceptible to restriction digestion of the chromsome, variation in chromosomal restriction fingerprint and/or high frequency of gene rearrangement. We also examined the extent of allelic variation in nucleotide or deduced amino acid sequences at the individual gene level. fucT, cagA and vacA were confirmed to carry regions of high variation in nucleotide sequence among strains. The plasticity zone and strain-specific genes of H. pylori 51 were analyzed and compared with the former two genomic sequences. It should be noted that the H. pylori 51-specific sequences were dispersed on the chromosome, not congregated in the plasticity zone unlike J99- or 26695-specific genes, suggesting the high frequency of gene rearrangement in H. pylori genome. The genome of H. pylori 51 shows differences in the overall genomic organization, gene order, and even in the nucleotide sequences among the H. pylori strains, which are far greater than the differences reported on the genomic diversity of H. pylori.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.4
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• pp.11-20
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• 2009

By using the artificial lightweight aggregate for the natural aggregate depletes and destruction of environment and the application of lightweight concrete in structure, the lightweight concrete is manufactured. The fundamental characteristics by the waterbinder ratio was evaluated. It is suggested the method to control of pre-absorbed water of the lightweight aggregate. Lightweight concrete with pre-absorbed aggregate has similar characteristics compared to normal weight concrete regardless of water-binder ratio. According to the water-binder ratio, the drying condition, and the rebar, the unit mass of the lightweight concrete showed the reduction of 14.6${\sim}$21.0% as the range of 1,668${\sim}$1,998 $kg/m^3$ in comparison to the normal weight concrete. The lightweight aggregate pre-absorbed water showed the deferent evaporation quantity according to the water-binder ratio. As the water-binder ratio is lower, the oven dry vapour water is larger, therefore the internal curing water is increasing. In the same water-binder, comparing the normal concrete the lightweight concrete shows lower compressive strength which is due to the different strength of an aggregate. In the air dry curing, the normal weight concrete has a lower strength improvement effect in w/c 0.3 than the ratio 0.4 and 0.5. However, the strength improvement effect has increasing as the water-binder ratio was low in the light concrete.

• Korean Journal of Microbiology
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• v.34 no.3
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• pp.169-174
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• 1998

To define the structure and diversity of bacterial communities in the aqutic ecosystem, Lake Soyang, the largest artificial reservoir in Korea, a new method, fluorescent in situ hybridization was applied. This technique relies on the specific hybridization of the nucleic acid probes to the naturally amplified intracellular rRNA. By this method, the bacterial community composition of Lake Soyang and bacterial numbers belong to eubacteria, proteobacteria and Cytophaga-Flavobacterium group were estimated. Total bacterial numbers ranged from $0.3{\times}10^6{\sim}2.0{\times}10^6cells{\cdot}ml^{-1}$, and vertical profile of total bacteria showed the peak at 2 and 5 m depths. The ratio of eubacteria to total bacteria were 22~100% and varied with depth and season. The percentage of Proteobacteria ${\alpha}$-group ranged 2.6~66.7%, ${\beta}$-group 4.5~53.5%, ${\gamma}$-group 4.6~76.7% and Cytophaga-Flavobacterium group 2.1~35.9%. Also, bacteria] community had spatial and temporal characteristics. The dominant groups were ${\beta}$-group in winter, ${\gamma}$-group in spring and early summer and ${\alpha}$-group in summer.