• Journal of Periodontal and Implant Science
• /
• v.35 no.3
• /
• pp.597-608
• /
• 2005

The aim of this study is to determine whether full-mouth disinfection therapy(FMT) in our clinical setting would show better improvement of clinical parameters than partial mouth disinfection therapy(PMT) in chronic periodontitis and aggressive periodontitis patients. Among 12 patients, 6 were treated FMT and other 6 were treated PMT. Clinical parameters were calculated 3 months and 6 months after initial therapy. 1. There were no statistically significant differences between FMT and PMT in the reduction rate of bleeding on probing after 3 months, 6 months 2. Initial probing depth was 4-6mm, the mean probing depth after 3 months was 2.2mm vs 2.5mm(FMT vs PMT), after 6 months was 2.4mm vs 2.8mm. This was significantly lower in the FMT groups. 3. Initial probing depth was ${\geqq}$ 7mm, the reduction rate of mean probing depth during first 3 months was 4.8mm vs 4.1mm(FMT vs PMT), and 3 to 6 months was 0.5mm vs 0.3mm. This was significantly larger in the FMT groups. 4. Initial probing depth was 4-6mm, the mean clinical attachment level after 3 months was 2.3mm vs 2.7mm(FMT vs PMT), after 6 months was 2.7mm vs 3.0mm. This was significantly lower in the FMT groups. 5. Initial probing depth was ${\geqq}$ 7mm, the reduction rate of mean probing depth during first 3 months was 4.0mm vs 3.0mm(FMT vs PMT), and 3 to 6 months was 0mm vs -0.1mm. This was significantly larger in the FMT groups. Although the results provided us with succeccful clinical improvement in aggressive periodontitis, further research is needed to prove its additional benefit in the treatment of chronic periodontitis

• Korean Journal of Digital Imaging in Medicine
• /
• v.10 no.1
• /
• pp.45-50
• /
• 2008

Recently, MR Cholangiography used mainly bu controlling of patient's breathing. There is breathing hold techniques to get images within shopt time and gating technique adjusted to respiration cycle for high resolution image. In this study, the aim of this experiment is to know on clinical usefulness compared with PACE and RTG thchniques. This study's period is from 2006 in November to 2007 in January. A total of 21 patients investigated at MAGNETOM Sonata 1.5T (SIEMENS Erlangen) with use of 12ch body coil. MR acquisition protocol used 3D turbo spin echo coronal sequence. Scan parameters applied to potimal setting in use as gating techniques, respectively. Analysis of consuming timing evaluated with rapidness. As analysis of quantity, the common bile duct, gall bladder measured in signal intensities, then these data were calculated by signal to noise ratio and contrast to noise ratio. Qualitative analysis, experienced 2radiologists and 3 RTs were evaluated into 3groups about artifact, accuracy of lesions, sharpness of the common bile duct or gall bladder. As a result of analysis, when compared to PACE, consuming time of the RTG took less than PACE, On both CNRs and SNRs, PACE technique was slightly high values than RTG(p<0.05). Qualitative analysis' results, discrimination of lesions in the common bile duct, gall bladder get a significance level in both RTG and PACE techniques but presence's artifact of breathing and pulsation highly demonstrate in PACE techniques. In conclusion, both PACE and RTG methods at MRCP provided prominently clinical information for the common bile duct, gall bladder. If machines have not limitation with performance, induction of breathing holding also will help getting diagnistic quality.

• Journal of radiological science and technology
• /
• v.33 no.4
• /
• pp.327-334
• /
• 2010

Exposure during childhood results in higher risk for certain detrimental cancers than exposure during adulthood. We measured entrance skin dose (ESD) under 7-year children undergoing chest imaging and compared the relationship between ESD and age, height, weight, chest thickness. Though it is important to measure chest thickness for setting up the exposure condition of chest examination, it is difficult to measure chest thickness of children. We set up exposure parameters according to age because chest thickness of children has correlation with age. In the exposure parameters, for chest A-P examination under 2 year-children, tube voltage (kVp) in hospital A was higher than that in hospital B while tube current (mAs) was higher in hospital B, thus the ESD values were about 1.7 times higher in hospital B. However, for chest P-A examination over 4 year-children, the tube voltage was 7 kVp higher in hospital B, the tube current were same in all two systems, and focus to image receptor distance (FID) in hospital B (180 cm) was longer than that in hospital A (130 cm), thus the ESD values were 1.4 times higher in hospital A. For same ages, the ESD values for chest A-P examinations were higher than those for chest P-A examinations. Comparing ESD according to age, ESD values were $154{\mu}Gy$, $194{\mu}Gy$ and $138{\mu}Gy$ for children under 1 year, 1 to under 4 years and 4 to under 7 years of age, respectively. These values were lower than reference level ($200{\mu}Gy$) recommended in JART (japan association of radiological technologists), however these were higher than reference values recommended by EC (european commission), NRPB (national radiological protection board) and NIFDS (national institute of food & drug safety evaluation). In conclusion, the values of ESD were affected by exposure parameters from radiographer's past experience more than x-ray system. ESD values for older children were not always higher than those for younger children. Therefore we need to establish our own DRLs (diagnostic reference levels) according to age of the children in order to optimize pediatric patient protection.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.31 no.3
• /
• pp.158-169
• /
• 2019

A probabilistic model that can predict the residual useful lifetime of structure is formulated by using the gamma process which is one of the stochastic processes. The formulated stochastic model can take into account both the sampling uncertainty associated with damages measured up to now and the temporal uncertainty of cumulative damage over time. A method estimating several parameters of stochastic model is additionally proposed by introducing of the least square method and the method of moments, so that the age of a structure, the operational environment, and the evolution of damage with time can be considered. Some features related to the residual useful lifetime are firstly investigated into through the sensitivity analysis on parameters under a simple setting of single damage data measured at the current age. The stochastic model are then applied to the rubble-mound breakwater straightforwardly. The parameters of gamma process can be estimated for several experimental data on the damage processes of armor rocks of rubble-mound breakwater. The expected damage levels over time, which are numerically simulated with the estimated parameters, are in very good agreement with those from the flume testing. It has been found from various numerical calculations that the probabilities exceeding the failure limit are converged to the constraint that the model must be satisfied after lasting for a long time from now. Meanwhile, the expected residual useful lifetimes evaluated from the failure probabilities are seen to be different with respect to the behavior of damage history. As the coefficient of variation of cumulative damage is becoming large, in particular, it has been shown that the expected residual useful lifetimes have significant discrepancies from those of the deterministic regression model. This is mainly due to the effect of sampling and temporal uncertainties associated with damage, by which the first time to failure tends to be widely distributed. Therefore, the stochastic model presented in this paper for predicting the residual useful lifetime of structure can properly implement the probabilistic assessment on current damage state of structure as well as take account of the temporal uncertainty of future cumulative damage.

• Journal of Korea Water Resources Association
• /
• v.46 no.8
• /
• pp.833-842
• /
• 2013

The quantile mapping is utilized to reproduce reliable GCM(Global Climate Model) data by correct systematic biases included in the original data set. This scheme, in general, projects the Cumulative Distribution Function (CDF) of the underlying data set into the target CDF assuming that parameters of target distribution function is stationary. Therefore, the application of stationary quantile mapping for nonstationary long-term time series data of future precipitation scenario computed by GCM can show biased projection. In this research the Nonstationary Quantile Mapping (NSQM) scheme was suggested for bias correction of nonstationary long-term time series data. The proposed scheme uses the statistical parameters with nonstationary long-term trends. The Gamma distribution was assumed for the object and target probability distribution. As the climate change scenario, the 20C3M(baseline scenario) and SRES A2 scenario (projection scenario) of CGCM3.1/T63 model from CCCma (Canadian Centre for Climate modeling and analysis) were utilized. The precipitation data were collected from 10 rain gauge stations in the Han-river basin. In order to consider seasonal characteristics, the study was performed separately for the flood (June~October) and nonflood (November~May) seasons. The periods for baseline and projection scenario were set as 1973~2000 and 2011~2100, respectively. This study evaluated the performance of NSQM by experimenting various ways of setting parameters of target distribution. The projection scenarios were shown for 3 different periods of FF scenario (Foreseeable Future Scenario, 2011~2040 yr), MF scenario (Mid-term Future Scenario, 2041~2070 yr), LF scenario (Long-term Future Scenario, 2071~2100 yr). The trend test for the annual precipitation projection using NSQM shows 330.1 mm (25.2%), 564.5 mm (43.1%), and 634.3 mm (48.5%) increase for FF, MF, and LF scenarios, respectively. The application of stationary scheme shows overestimated projection for FF scenario and underestimated projection for LF scenario. This problem could be improved by applying nonstationary quantile mapping.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.16 no.2
• /
• pp.47-56
• /
• 2008

The objective of this research is to evaluate the optimum recycling methods for the sewage sludge cakes at different microwave power-settings and for different periods of time. The dehydrated sewage sludge cakes used in this study was obtained from N wastewater treatment plan in the P City. The beginning drying processes were carried out in a microwave oven with 2,450 MHz frequency and power ranges of 1kW to 4 kW. The continuous conveyer drying system was also operated with 2,450 MHz frequency and power setting, ranging from of 1 kW to 6 kW. Initial moisture content of the sewage cake is 78~80%, and the moisture content decreased rapidly up to 0.2~2(wt%) within short periods due to breaking the cell walls. This study is also conducted to evaluate the characteristics of sewage sludge cakes with respect to important physical parameters effect on the thermal kinetics for evaporation water in the sludge which are operation times, moisture contents, drying rates, input amounts, flow rates and calorific values. It takes 60 minutes and 120 minutes to reach the critical moisture contents with power setting of 4 kW for 3kg/min and 6kg/min of the flow rates respectively. It takes 120 minutes and 110 minutes to reach the critical moisture contents with flow rates of 2.5 cm/min and sludge input of 6kg/min for the power settings of 4 kW and 6 kW respectively. The most effective value of the power for drying the sludge is 4 kW. Operation with 6kg/min and 4kW on 2cm of the sludge thickness can be effectively and inexpensively to reach the critical moisture contents, when you compare 2cm of the sludge thickness with 1cm and 3cm of the sludge thickness.

• Journal of radiological science and technology
• /
• v.31 no.4
• /
• pp.379-387
• /
• 2008

Among methods to eliminate aliasing effects, the method of increasing velocity scale gradually eliminated the phenomenon in which the direction of the blood flow appeared in reverse. It was done by increasing the velocity scale while maintaining other parameters in the same state. The method of setting the Doppler angle to $0^{\circ}$ did not show significant changes in the wave pattern of the spectrum according to the angle. In actual ultrasonography tests, more accurate tests are expected to be carried out by applying variations to the velocity scale under the considerations of speed, accuracy, and convenience of the examination. The results showed that blood flow velocity increases exponentially according to the Doppler Angle. When the angle goes over $70^{\circ}$, the velocity value increases to an unmeasurable state. This indicates that in blood flow velocity measurements, the blood flow velocity is very dependent on the Doppler Angle. It also shows that the error increases when the incidence angle to the direction of blood flow exceeds $60^{\circ}$, and when the angle exceeds $70^{\circ}$, the error becomes even greater. In addition, he experiment results showed that an angle below $60^{\circ}$ is appropriate and for blood flow velocity measurements in extremity vessels, the most appropriate Doppler Angle is from $45^{\circ}$ to $60^{\circ}$.

• Journal of Korea Water Resources Association
• /
• v.45 no.2
• /
• pp.203-215
• /
• 2012

The objective of this study is to develop a catchment hydrologic cycle assessment model which can assess the impact of urban development and designing water cycle improvement facilities. Developed model might contribute to minimize the damage caused by urban development and to establish sustainableurban environments. The existing conceptual lumped models have a potential limitation in their capacity to simulate the hydrologic impacts of land use changes and assess diverse urban design. The distributed physics-based models under active study are data demanding; and much time is required to gather and check input data; and the cost of setting up a simulation and computational demand are required. The Catchment Hydrologic Cycle Assessment Tool (hereinafter the CAT) is a water cycle analysis model based on physical parameters and it has a link-node model structure. The CAT model can assess the characteristics of the short/long-term changes in water cycles before and after urbanization in the catchment. It supports the effective design of water cycle improvement facilities by supplementing the strengths and weaknesses of existing conceptual parameter-based lumped hydrologic models and physical parameter-based distributed hydrologic models. the model was applied to Seolma-cheon catchment, also calibrated and validated using 6 years (2002~2007) hourly streamflow data in Jeonjeokbigyo station, and the Nash-Sutcliffe model efficiencies were 0.75 (2002~2004) and 0.89 (2005~2007).

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.144.2-144.2
• /
• 2016

Diamond-like carbon (DLC) coatings have been widely applied to the mechanical components, cutting tools due to properties of high hardness and wear resistance. Among them, hydrogenated amorphous carbon (a-C:H) coatings are well-known for their low friction properties, stable production of thin and thick film, they were reported to be easily worn away under high temperature. Non-hydrogenated tetrahedral amorphous carbon (ta-C) is an ideal for industrial applicability due to good thermal stability from high $sp^3$-bonding fraction ranging from 70 to 80 %. However, the large compressive stress of ta-C coating limits to apply thick ta-C coating. In this study, the thick ta-C coating was deposited onto Inconel alloy disk by the FCVA technique. The thickness of the ta-C coating was about $3.5{\mu}m$. The tribological behaviors of ta-C coated disks sliding against $Si_3N_4$ balls were examined under elevated temperature divided into 23, 100, 200 and $300^{\circ}C$. The range of temperature was setting up until peel off observed. The experimental results showed that the friction coefficient was decreased from 0.14 to 0.05 with increasing temperature up to $200^{\circ}C$. At $300^{\circ}C$, the friction coefficient was dramatically increased over 5,000 cycles and then delaminated. These phenomenon was summarized two kinds of reasons: (1) Thermal degradation and (2) graphitization of ta-C coating. At first, the reason of thermal degradation was demonstrated by wear rate calculation. The wear rate of ta-C coatings showed an increasing trend with elevated temperature. For investigation of relationship between hardness and graphitization, thick ta-C coatings(2, 3 and $5{\mu}m$) were additionally deposited. As the thickness of ta-C coating was increased, hardness decreased from 58 to 49 GPa, which means that graphitization was accelerated. Therefore, now we are trying to increase $sp^3$ fraction of ta-C coating and control the coating parameters for thermal stability of thick ta-C at high temperatures.

• Journal of the Korean Institute of Gas
• /
• v.20 no.5
• /
• pp.9-16
• /
• 2016

Buried pipe system is subject to leak or rupture due to internal and external defects with age. Especially, if the pipeline is designed for pressurized gas, the leak can wreak a devastating on its surrounding area. The current method of setting up underground gas pipeline is based on OGP criteria of applying one tenth of the inner pipe pressure. The criteria is applied irrespective of their burial depth or pipe's properties. At times, even the whole safety measures are totally ignored. Considering the magnitude of possible damage from a gas leakage, a precise analytical tool for the risk assessment is urgently needed. The study was conducted to assess possible scenarios of gas accidents and to develop a computer model to minimize the damage. The data from ETA was analyzed intensively, and the model was developed. The model is capable of predicting jet fire influence area with comprehensive input parameters, such as burial depth. The model was calibrated and verified by the historic accident data from Edison Township, New Jersey, the United States. The statistical model was also developed to compare the results of the model in this study and the existing OGP model. They were in good agreement with respect to damage predictions, such as radiation heat coming from 10 meters away from the heat source of gas flame.