• Journal of Periodontal and Implant Science
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• v.40 no.1
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• pp.3-10
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• 2010

Purpose: Periodontal regenerative therapies for defects created by severe periodontitis are mainly focused on bone regeneration. Although cementum regeneration needs to be better understood, it is believed to play an important role in periodontal regeneration. The first step toward a full understanding of cementum regeneration is to compare repaired cementum to pristine cementum. This study, which used histological techniques, was designed to focus on cementum regeneration and to compare pristine cementum to repaired cementum after surgical procedures with 8 and 24 week healing periods in a canine model. Methods: Buccal and lingual mucoperiosteal flaps of 10 beagle dogs were surgically reflected to create critical-sized defects. Intrabony one-wall defects, of which dimension is 4 mm width and 5 mm depth, were made at the distal aspect of mandibular second premolars and the mesial aspect of mandibular fourth premolars in the right and left jaw quadrants. Animals were sacrificed after 8 and 24 weeks post-surgery for histological specimen preparation and histometric analysis. Results: The repaired cementum was composed mostly of acellular cementum and cellular mixed fiber cementum and was thicker in the apical area than in the coronal area. The acellular cementum of the supracrestal area appeared to be amorphous. The newly formed cellular cementum was partially detached from the underlying circumpulpal dentin, which implied a weak attachment between new cementum and dentin, and this split was observed to a lesser extent in the 24 week group than in the 8 week group. The vertical height of the repaired cementum was greater in the 24 week group than in the 8 week group. Conclusions: Within the limitations of this study, we can conclude that repaired cementum after root planing was mainly acellular cementum and cementum tissue that matured to a shape similar to pristine cementum as the healing progressed from 8 to 24 weeks.

• Journal of Gastric Cancer
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• v.12 no.3
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• pp.149-155
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• 2012

Purpose: Although serosal invasion is a critical predisposing factor for peritoneal dissemination in advanced gastric cancer, the accuracy of preoperative assessment using routine imaging studies is unsatisfactory. This study was conducted to identify high-risk group for serosal invasion using preoperative factors in patients with advanced gastric cancer. Materials and Methods: We retrospectively analyzed clinicopathological features of 3,529 advanced gastric cancer patients with Borrmann type I/II/III who underwent gastrectomy at Korea Cancer Center Hospital between 1991 and 2005. We stratified patients into low-(${\leq}40%$), intermediate-(40~70%), and high-risk (>70%) groups, according to the probability of serosal invasion. Results: Borrmann type, size, longitudinal and circumferential location, and histology of tumors were independent risk factors for serosal invasion. Most tumors of whole stomach location or encircling type had serosal invasion, so they belonged to high-risk group. Patients were subdivided into 12 subgroups in combination of Borrmann type, size, and histology. A subgroup with Borrmann type II, large size (${\geq}7$ cm), and undifferentiated histology and 2 subgroups with Borrmann type III, large size, and regardless of histology belonged to high-risk group and corresponded to 25% of eligible patients. Conclusions: This study have documented high-risk group for serosal invasion using preoperative predictors. And risk stratification for serosal invasion through the combination with imaging studies may collaboratively improve the accuracy of preoperative assessment, reduce the number of eligible patients for further staging laparoscopy, and optimize therapeutic strategy for each individual patient prior to surgery.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.307-317
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• 1999

The purpose of this study is to utilize conventional procedures for evaluation of liquefaction potential and to compare the results obtained by modified detailed method based on Korean earthquake magnitude (M=6.5). Liquefaction potential is assessed by comparing liquefaction strength of soil and cyclic shear stress generated in the soil layers during earthquakes. The cyclic shear stress is computed from the earthquake response analysis, and liquefaction strength of soil is evaluated by using results from cyclic triaxial tests. The cyclic triaxial tests are performed on many different conditions of sample ; relative densities(50%, 60%, and 70%), initial effective confining pressures (70kPa, 100kPa, and 150kPa), and fine contents(10%, 20%, and 30%). From the result of comparing the conventional procedure with the modified detailed method, it is found that the modified detailed method tends to evaluate larger safety factor against liquefaction in the weak sand site$(FS \leq1.5)$. Therefore in this case, it is suggested that liquefaction potential should be evaluated by using the modified detailed method based on cyclic triaxial tests. It is also found that in modified detailed method based on earthquake magnitude 6.5, critical depth where liquefaction can be generated is around 15m from the ground surface.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.4
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• pp.57-63
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• 2008

In this paper, the dependence of MOSFET performance on the channel stress is characterized in depth. The tensile and compressive stresses are applied to CMOSFET using a nitride film which is used for the contact etch stop layer (CESL). Drain current of NMOS and PMOS is increased by inducing tensile and compressive stress, respectively, due to the increased mobility as well known. In case of NMOS with tensile stress, both decrease of the back scattering ratio ($\tau_{sat}$) and increase of the thermal injection velocity ($V_{inj}$) contribute the increase of mobility. It is also shown that the decrease of the $\tau_{sat}$ is due to the decrease of the mean free path ($\lambda_O$). On the other hand, the mobility improvement of PMOS with compressive stress is analyzed to be only due to the so increased $V_{inj}$ because the back scattering ratio is increased by the compressive stress. Therefore it was confirmed that the device performance has a strong dependency on the channel back scattering of the inversion layer and thermal injection velocity at the source side and NMOS and PMOS have different dependency on them.

• The Journal of Engineering Geology
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• v.24 no.3
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• pp.423-429
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• 2014

Development of a reservoir pressure core sampler (PCS) with a built-in data logging system (DLS) for recording real-time temperature and pressure observations is critical in domestic hydrocarbon production to accurately measure and monitor reserves of shale gas, coalbed methane, and gas-hydrate. Another purpose of this new technology is to minimize the loss of gas from the core as the drill core is collected. This is accomplished by maintaining the pressure of the sample from the moment the drill core is obtained at depth, thus allowing an accurate analysis of shale gas, coalbed methane gas, and gashydrate within the core. Currently, the United States and European countries have monopolized the development and marketability of PCS technologies. We are thus developing a reservoir PCS by analyzing the operating principle and mechanisms of the existing PCS, and by conducting tests on the existing PCS. We further aim to develop a PCS with a maximum operating pressure of 100 bar, a maximum operating temperature of $-20^{\circ}C$ to $40^{\circ}C$, and a pressure loss rate of 10%.

• Journal of Gifted/Talented Education
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• v.21 no.4
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• pp.927-943
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• 2011

What are the critical factors in deciding future career to the gifted and talented students? The present study started with this question, and was to develop a career decision-making scale for scientifically gifted undergraduates. For this, literatures related to the scientifically gifted/talent and scientists' career decision-making were reviewed and examined in depth. Based on the review of the related literature, the developed scale of career decision-making was comprised of 26 items in 6 factors, such as individual aptitude & self-realization, economic aspect, work & leisure, familial influence, parents/teachers' recommendation, and experience of science activity during the school days. For the preliminary exploratory factor analysis, 153 undergraduate students who were majoring in natural sciences and engineer participated in the study. For the confirmatory factor analysis, 264 undergraduates who were awarded the presidential scholarships and 93 undergraduates who completed a university-affiliated gifted education center participated. The results of the study are as follows. The fit of measurement model was found to be $x^{2}$=645.157 (df=279, p=.00), TLI=.924, CFI= .935, RMSEA=.061, indicating most of fit indexes were acceptable. Cronbach's ${\alpha}$ in each sub-factor was quite high, .82 for individual aptitude & self-realization, .94 for economic aspect, .84 for work and leisure, .88 for familial influence, .79 for patents/ teachers' recommendation, and .79 for experience of science activity during the school days. The results of the study were discussed whether the developed scale could be used as a valid and reliable tool for measuring career decision-making factors of the scientifically gifted undergraduates in our country.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.4
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• pp.371-382
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• 1999

This paper presents the results of recent nutrients measurement and analysis in relation to other environmental parameters such as temperature, salinity, AOU and pH in the South Sea, Korea. In summer, temperature showed stronger correlation with nutrients than salinity and also did the parameters related to biological activities such as pH and AOU. Implications of above results exemplify that primary producers in the vicinity of salt front actively consumed nutrients so that nutrients-salinity correlation is strongly modified in the salt front. Nutrient in winter showed significant correlation only with temperature. Nutrient distribution seems governed by the location of thermal front between vertically mixed cold water in northern area and warm waters flowing north. Due to weak biological activity in winter pH-nutrients correlation, which was strongest in summer ($R^2$ >0.6) dropped sharply in winter ($R^2$ <0.5). Depth integrated nitrate+nitrite, phosphate and silicate values are 321 $mmol{\cdot}m^{-2}$, 23 $mmol{\cdot}m^{-2}$, 637 $mmol{\cdot}m^{-2}$ in summer and 261 $mmol{\cdot}m^{-2}$, 31 $mmol{\cdot}m^{-2}$, 742 $mmol{\cdot}m^{-2}$ in winter, respectively. NIP values in summer exhibit phosphorus deficiency, however, winter situation is reversed for nitrogen. Nitrogen input via precipitation and riverine discharge in wet season seems potentially critical for maintaining the South Sea ecosystem.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.5
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• pp.2149-2162
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• 2011

Currently practical examination can't function as a practical technique ability evaluation', so there is a contradiction which even though a radiologist passed an examination for license, he has to complete a training course. To improve this problem, this study tried to deduce the most reasonable plan from the analysis of propriety of currently practical examination and what improvement points are. This conduct study was compared and analyzed the performance or practical examination of radiology from leading advanced countries within the samples of 634 radiologists, 56 professors of radiology. From the result of this study, it showed that radiology practical examination was difficult to be substituted by radiology clinical training since there were some critical differences between conditions of domestic and advanced countries. Therefore, the introduction of the radiology practical examination is inevitable and necessary. However the currently practical examination can't evaluate actual practical ability, so we could conclude that converting it into OSCE (objective structured clinical examination) form is essential. From now on, we should consider more about an in-depth study on types of advanced practical examination and how to suggest and present them in order to become an one of the advanced countries for radiologic technologist.

• Journal of the Korean earth science society
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• v.28 no.7
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• pp.857-870
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• 2007

The structure and evolution of a thunderstorm outflow in two dimensions with no environmental wind are investigated using a cloud-resolving model with explicit liquid-ice phase microphysical processes (ARPS: Advanced Regional Prediction System). The turbulence structure of the outflow is explicitly resolved with a high-resolution grid size of 50m. The simulated single-cell storm and its associated Kelvin-Helmholtz (KH) billows are found to have the lift stages of development maturity, and decay. The secondary pulsation and splitting of convective cells resulted from interactions between cloud dynamics and microphysics are observed. The cooled downdrafts caused by the evaporation of rain and hail in the relatively dry lower atmosphere result in thunderstorm cold-air outflow. The outflow head propagates with almost constant speed. The KH billows formed by the KH instability cause turbulence mixing from the top of the outflow and control the structure of the outflow. Ihe KH billows are initiated at the outflow head, and pow and decay as moving rearward relative to the gust front. The numerical simulation results of the ratio of the horizontal wavelength of the fastest growing perturbation to the critical shear-layer depth and the ratio of the horizontal wavelength of the billow to its maximum amplitude are matched well with the results of other studies.

• International Journal of Highway Engineering
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• v.18 no.5
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• pp.117-125
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• 2016

PURPOSES : The density in uninterrupted traffic flow facilities plays an important role in representing the current status of traffic flow. For example, the density is used for the primary measures of effectiveness in the capacity analysis for freeway facilities. Therefore, the estimation of density has been a long and tough task for traffic engineers for a long time. This study was initiated to evaluate the performance of density values that were estimated using VDS data and two traditional methods, including a method using traffic flow theory and another method using occupancy by comparing the density values estimated using vehicular trajectory data generated from a radar detector. METHODS : In this study, a radar detector which can generate very accurate vehicular trajectory within the range of 250 m on the Joongbu expressway near to Dongseoul tollgate, where two VDS were already installed. The first task was to estimate densities using different data and methods. Thus, the density values were estimated using two traditional methods and the VDS data on the Joongbu expressway. The density values were compared with those estimated using the vehicular trajectory data in order to evaluate the quality of density estimation. Then, the relationship between the space mean speed and density were drawn using two sets of densities and speeds based on the VDS data and one set of those using the radar detector data. CONCLUSIONS : As a result, the three sets of density showed minor differences when the density values were under 20 vehicles per km per lane. However, as the density values become greater than 20 vehicles per km per lane, the three methods showed a significant difference among on another. The density using the vehicular trajectory data showed the lowest values in general. Based on the in-depth study, it was found out that the space mean speed plays a critical role in the calculation of density. The speed estimated from the VDS data was higher than that from the radar detector. In order to validate the difference in the speed data, the traffic flow models using the relationships between the space mean speed and the density were carefully examined in this study. Conclusively, the traffic flow models generated using the radar data seems to be more realistic.