• Journal of the Korean Association of Geographic Information Studies
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• v.13 no.3
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• pp.14-28
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• 2010

The aim of this study is to investigate crime hotspot areas using the spatio-temporal cluster analysis which is possible to search simultaneously time range as well as space range as an alternative method of existing hotspot analysis only identifying crime occurrence distribution patterns in urban area. As for research method, first, crime data were collected from criminal registers provided by official police authority in M city, Gyeongnam and crime occurrence patterns were drafted on a map by using Geographic Information Systems(GIS). Second, by utilizing Ripley K-function and Space-Time Scan Statistics analysis, the spatio-temporal distribution of crime was examined. The results showed that the risk of crime was significantly clustered at relatively few places and the spatio-temporal clustered areas of crime were different from those predicted by existing spatial hotspot analysis such as kernel density analysis and k-means clustering analysis. Finally, it is expected that the results of this study can be not only utilized as a valuable reference data for establishing urban planning and crime prevention through environmental design(CPTED), but also made available for the allocation of police resources and the improvement of public security services.

• Tunnel and Underground Space
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• v.14 no.3
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• pp.167-174
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• 2004

This paper is to introduce an article published in Rock Mechanics and Rock Engineering, 2003. In this research, a fracture mechanics model is developed to illustrate the importance of time-dependence far brittle fractured rock. In particular a model is developed fer the time-dependent degradation of rock joint cohesion. Degradation of joint cohesion is modeled as the time-dependent breaking of intact patches or rock bridges along the joint surface. A fracture mechanics model is developed utilizing subcritical crack growth, which results in a closed-form solution for joint cohesion as a function of time. As an example, a rock block containing rock bridges subjected to plane sliding is analyzed. The cohesion is found to continually decrease, at first slowly and then more rapidly. At a particular value of time the cohesion reduces to value that results in slope instability. A second example is given where variations in some of the material parameters are assumed. A probabilistic slope analysis is conducted, and the probability of failure as a function of time is predicted. The probability of failure is found to increase with time, from an initial value of 5% to a value at 100 years of over 40%. These examples show the importance of being able to predict the time-dependent behavior of a rock mass containing discontinuities, even for relatively short-term rock structures.

• The Journal of Engineering Geology
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• v.24 no.4
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• pp.501-510
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• 2014

Volcanic eruptions alone may lead to serious natural disasters, but the associated release of water from a caldera lake may be equally damaging. There is both historical and geological evidence of the past eruptions of Mt. Baekdusan, and the volcano, which has not erupted for over 100 years, has recently shown signs of reawakening. Action is required if we are to limit the social, political, cultural, and economic damage of any future eruption. This study aims to identify the area that would be inundated following a volcanic flood from the Cheon-Ji caldera lake that lies within Mt. Baekdusan. A scenario-based numerical analysis was performed to generate a flood hydrograph, and the parameters required were selected following a consideration of historical records from other volcanoes. The amount of water at the outer rim as a function of time was used as an upper boundary condition for the downstream routing process for a period of 10 days. Data from the USGS were used to generate a DEM with a resolution of 100 m, and remotely sensed satellite data from the moderate-resolution imaging spectroradiometer (MODIS) were used to show land cover and use. The simulation was generated using the software FLO-2D and was superposed on the remotely sensed map. The results show that the inundation area would cover about 80% of the urban area near Erdaobaihezhen assuming a 10 m/hr collapse rate, and 98% of the area would be flooded assuming a 100 m/hr collapse rate.

• Journal of Environmental Impact Assessment
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• v.29 no.3
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• pp.219-229
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• 2020

This study evaluated the applicability of the convergence technology by deriving the optimum conditions about operating factors of electrical resistance heating to enhance the soil flushing effect on soil contaminated with bunker C oil in the coastal landfill area. As a result of the batch scale experiment, the flushing efficiency of the VG-2020 was higherthan that of the Tween-80, and the flushing efficiency increased by about 1.4 times at 60℃ compared to room temperature. As a result of the electrical resistance heating box experiment, soil temperature rose to 100℃ in about 40~80 minutes in soil with water content of 20~40%, and it was found that the heat transfer efficiency is excellent when the pipe-shaped electrode rod with STS 316 material is located in a triangular arrangement in saturated soil. In addition, it was confirmed that the interval between the electrode rods to maintain the soil temperature above 60℃ under the optimum conditions was 1.5 m, and the soil flushing box experiment accompanying electrical resistance heating showed TPH reduction efficiency of about 55% at 5 Pore Volume, and satisfied the Korean standard for the conservation of soil (less than TPH 2,000 mg/kg) at 10 Pore Volume.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.477-486
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• 2020

The purpose of this study was to evaluate the effects of reconstruction filters, X-ray source trajectories and intervals in the quality of digital tomosynthesis (DT) images, and the results was clinically validated. The filtered back-projection was implemented by using Ramp, Shepp-Logan, Cosine, Hamming, Hann and Blackman filters, and the X-ray source trajectories were simulated with 1 × 36, 2 × 18, 3 × 12, 4 × 9 and 6 × 6 arrays. The X-ray source intervals were 5, 10, 20, 30 and 40 mm. The depth resolution, spatial resolution and noise of DT image were evaluated by measuring artifact spread function (ASF), full width at half maximum (FWHM) and signal-to-noise ratio (SNR), respectively. The results showed that the spatial resolution and noise properties of DT images were maximized by the Ramp and Blackman filters, respectively, and the depth resolution and noise properties of the DT images obtained with a 1 × 36 X-ray source trajectory were superior to the other trajectories. The depth resolution and noise properties of DT images improved with an increase of X-ray source intervals, and the high X-ray source intervals degraded the spatial resolution of DT images. Therefore, the characteristics of DT images are highly dependent on reconstruction filters, X-ray source trajectories and intervals, and it is necessary to use optimal imaging parameters in accordance with diagnostic purpose.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.487-494
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• 2020

The distance between the source and the detector, the diameter of the detector, and the volume effect of the radiation source result in a change in solid angle at the detector entrance, which affects the determination of detection efficiency by causing a difference in path length within the detector. A typical analysis method for calculating solid angles was useful only for a source (⁶⁰Co) with a simple geometric structure, so in this experiment, the distance between the detector and the source was measured by switching on for up to 25 cm with the reference point of window cap 0.5 cm. In addition, 450 and 1000 ㎖ Marinelli beaker of standard volumetric sources were closely adhered to the detector. For circular point sources co-axial with the detector, the change in the solid angle to the distance from the detector window is equal to half the square radius of the source versus the square radius of the detector, if the resulting relationship of the calculation analysis results in the detector being less than the radius of the source. Since the solid angular difference is 0.5 the result of Monte Carlo is acceptable. The relationship between detector and source distance is shown. Solid angles have been verified to decrease rapidly with distance. Measurement and simulation results for a volumetric source show a difference of ±1.01% from a distance of 0 cm and less than 4 % when the distance is reduced to 5 and 10 cm. It can be seen that the longer distance, the smaller efficiency angle, and the exponential increase in attenuation as the energy decreases, is reflected in the calculation of efficiency. Thus, the detection efficiency has proved sufficient for the use of solid angle and Monte Carlo codes.

• Journal of the Korean Society of Radiology
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• v.11 no.3
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• pp.153-159
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• 2017

Chronic kidney disease can be treated if it is detected early, but as the disease progresses, it becomes impossible to recover. Finally, renal replacement therapy such as transplantation or dialysis should be used. Ultrasonography is used to diagnose kidney cancer, inflammatory disease, nodular disease, and chronic kidney disease. It is used to identify information about degree of inflammation using information such as kidney size, internal echo characteristics. Currently, the degree of disease in the clinic uses the value of glomerular filtration rate. However, even in ultrasound, changes in the degree of inflammation and disease can be observed. In this study, we used ultrasound images to quantify the changes in brightness, size, cortex, and subclinical changes of the kidney with progression of the disease, and compared them with the glomerular filtration rate used in clinical practice. In 105 cases, we performed 35 cases of normal kidney, 35 cases of early kidney disease, and 35 cases of terminal kidney. The brightness of the cortex of the image was obtained and the difference in brightness between the cortex and the proximal portion was obtained by the slope. The graph of the portion which was not smooth due to the ultrasonic characteristics was used as the function regrass. The size reduction was obtained from the original data. The results were as follows: It was proportional to the glomerular filtration rate. It is considered that the algorithm can be applied to the disease if the algorithm study continues.

• Communications of Mathematical Education
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• v.30 no.4
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• pp.515-530
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• 2016

Recently an extensive study of the mathematicians who have overcome the visually impaired and contribute to the academic in math was published. In the case of Korea, we can find there are mathematicians who have overcome physical disabilities such as cerebral palsy and polio. However there is no example of blind person who majored mathematics to become a mathematic's teacher or professor and have entered any mathematics related professions. This let us to study the reasons that caused difficulties to visually impaired students majoring in mathematics. We also suggest ways that may help blind students to have access to mathematics intuitively. In this study, we propose a tactile mathematics textbooks and teaching manuals utilizing 3D printing which the visually impaired students can touch and feel. We can supply such materials to visually impaired youth, special education teachers and parents in Korea. As a result, visually impaired students will be able to access mathematics easily and can build their confidence in mathematics. We hope that some blind students with mathematical talent do not hesitate to major mathematics and choose career in mathematical professions.

• Fire Science and Engineering
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• v.27 no.3
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• pp.1-7
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• 2013

The wildland fire intensity and scale are getting bigger owing to climate change in the world. In the case of domestic, the forest is distributed over approximately 63.7 % of country and the main facilities like a industrial facility or gas facility abuts onto it. Therefore there is potential that the wildland fire is developed to a large-scale disaster. In this study, the effect distances of the radiant heat flux from the crown fire are analysed according to the change of wind velocity. The safety criteria concerning the radiant heat flux to influence on the surrounding were researched to analyse the effect distances. The criteria of radiant heat flux were chosen $5kW/m^2$, $12.5kW/m^2$, $37.5kW/m^2$. WFDS, which is an extension of NIST's Fire Dynamics Simulator, was used to consequence analysis of the forest fire. In order to apply the analysis conditions, it is researched the forest conditions that is generally distributed in domestic region. As the result, the maximum effect distances by radiant heat were showed at the horizontal and vertical direction. When the wind velocity varied from 0 to 10 m/s, the maximum effect distance increased as the wind velocity increases. Interesting point is that the maximum effect distance were shown at the wind velocity of 8 m/s. The maximum effect distance was decreased according as the fuel moisture of trees increase. This study can contribute to analyse quantitative risk about the damage effect of the surrounding facilities caused by wildland fire.

• Food Science of Animal Resources
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• v.32 no.5
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• pp.669-677
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• 2012

The objective of this study was to analyze the flavor pattern of different varieties of cheeses. Four of the each following cheese varieties such as shred type pizza cheese, Cheddar cheese, Mozzarella block cheese, and white mold-ripened cheeses, stored at $4^{\circ}C$ during 2 wks were examined before and after cooking at $70^{\circ}C$ and $160^{\circ}C$. Flavor patterns of these cheeses were analyzed using an electronic nose system based on mass spectrometer. All data were treated by multivariate data processing based on discriminant function analysis (DFA). The results showed the discriminant model by DFA method. Data revealed that flavor patterns of pizza cheeses were well separated as storage prolonged and obviously discriminated as the higher the cooking temperature. The result of pattern recognition analysis based on discriminant function analysis showed that new brand of pizza cheese produced by Imsil Cheese Cooperative was located at middle between the flavors of the imported brands of pizza cheese and those of domestic brand of pizza cheeses. Imsil cheese has a unique flavor pattern among other variety of cheeses. Application of pattern recognition analysis by electronic nose might be useful and advanced technology for characterizing in flavor pattern of cheese products from different origins and different categories of cheeses.