• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.749-757
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• 1999

Holographic interferornetric tomography can provide reconstruction of instantaneous three dimensional gross flow fields. The technique however confronts ill-posed reconstruction problems in practical applications. Experimental data are usually limited in projection and angular scanning when a field is captured instantaneously or under the obstruction of test models and test section enclosures. An algorithm, based on a series expansion method, has been developed to improve the reconstruction under the ill-posed conditions. A three-dimensional natural convection flow around two interacting isothermal cubes is experimentally investigated. The flow can provide a challenging reconstruction problem and lend itself to accurate numerical solution for comparison. The refractive index fields at two horizontal sections of the thermal plume with and without an opaque object are reconstructed at a limited view angle of 80" The experimental reconstructions are then compared with those from numerical calculation and thermocouple thermometry. It confirms that the technique is applicable to reconstruction of reasonably complex, three-dimensional flow fields.elds.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11C
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• pp.1592-1599
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• 2004

In this paper, we proposed the 3D mesh watermarking using projection onto convex sets (POCS). 3D mesh is projected iteratively onto two constraint convex sets until it satisfy the convergence condition. These sets consist of the robustness set and the invisibility set that designed to embed watermark Watermark is extracted without original mesh by using the decision values and the index that watermark is embedded. Experimental results verified that the watermarked mesh have the robustness against mesh simplification, cropping, affine transformation, and vertex randomization as well as the invisibility.

• Journal of the Korean earth science society
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• v.44 no.4
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• pp.255-263
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• 2023

Western coastal area of Chungnam, including Cheonsu Bay and Garorim Bay, has suffered from hot and cold extremes. In this study, the extreme sea surface temperature on the western coast of Chungnam was analyzed using the quantile regression method, which extracts the linear regression values in all quantiles. The regional MOHID (MOdelo HIDrodinâmico) model, with a high resolution on a 1/60° grid, was constructed to reproduce the extreme sea surface temperature. For future prediction, the SSP5-8.5 scenario data of the CMIP6 model were used to simulate sea surface temperature variability. Results showed that the extreme sea surface temperature of Cheonsu Bay in August 2017 was successfully simulated, and this extreme sea surface temperature had a significant negative correlation with the Pacific decadal variability index. As a result of future climate prediction, it was found that an average of 2.9℃ increased during the simulation period of 86 years in the Chungnam west coast and there was a seasonal difference (3.2℃ in summer, 2.4℃ in winter). These seasonal differences indicate an increase in the annual temperature range, suggesting that extreme events may occur more frequently in the future.

• Journal of Environmental Policy
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• v.7 no.4
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• pp.35-55
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• 2008

Assessing vulnerability to climate change is the first step to take when setting up appropriate adaptation strategies. Adaptive capacity to climate change is the important factor comprising vulnerability. An adaptive capacity index in agricultural water management system was developed considering agricultural water supply and demand for rice production in Jeolla-do, Korea. The agricultural water supply was assumed to be equal to the amount of water stored in the major agricultural reservoirs, while data on the agricultural water demand was obtained from the dynamic simulation results by Korea Agriculture Corporation(KAC). The spatial unit for analysis was conducted at the county(Si, Gun, Gu) level and temporal scale was based on every month from 1991-2003. Adaptive capacity for drought stress index(ACDS index) was calculated as the percentage of data points where the irrigated water supply was greater than the crop water demand. The ACDS index was compared with SWSCI(Standard Water Storage Capacity Index) and the relationship showed high degree of fit($R^2$=0.84) using the exponential function, indicating that the developed ACDS index is useful for evaluating the status of the balance between agricultural water supply and demand, especially for the small sized agricultural reservoirs. This study provided the methodological basis for developing climate change vulnerability index in agricultural water system which is projected to be more frequently exposed to drought condition in the future due to climate change. Further research should be extended to the study on the water demand of the crops other than rice and to the projection of the change in ACDS index in the future.

• Journal of the Korean Society of Radiology
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• v.11 no.2
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• pp.79-85
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• 2017

The purpose of this study is to investigate the cause analysis according to the difference between the pre exposure tube voltage and actual exposure tube voltage in mammography in connection with breast pressure thickness, breast size and body mass index and to find the improvement. The study tracked 377 women age 40 and older among the mammography examiners conducted by the National Health Insurance Corporation. It was analyzed that breast pressure thickness, breast size and body mass index according to the difference between the pre exposure tube voltage and actual exposure tube voltage among the parameters of dose report been sent to the picture archiving communication system with reference to the image with cranio-caudal projection in mammography. As are result, it shows that the thicker the breast thickness, smaller the breast size and lower body mass index, the higher the difference of tube voltage. In conclusion, the minimum tube voltage of mammography machine should be reset in order to set the tube voltage according to breast pressure thickness and breast size that are suitable for our country in mammography, in addition, it was considered that radiologist should make an effort to reduce radiation exposure and make a good quality image with reducing the difference of mammography condition by making a correct exposure condition in case of examining the patients with thin breast pressure and small breast size.

• Journal of the Korean Society of Radiology
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• v.83 no.3
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• pp.669-679
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• 2022

Purpose To evaluate the feasibility of pediatric low-dose facial CT reconstructed with filtered back projection (FBP) using adequate kernels. Materials and Methods We retrospectively reviewed the clinical and imaging data of children aged < 10 years who underwent facial CT at our emergency department. The patients were divided into two groups: low-dose CT (LDCT; Group A, n = 73) with a fixed 80-kVp tube potential and automatic tube current modulation (ATCM) and standard-dose CT (SDCT; Group B, n = 40) with a fixed 120-kVp tube potential and ATCM. All images were reconstructed with FBP using bone and soft tissue kernels in Group A and only bone kernel in Group B. The groups were compared in terms of image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Two radiologists subjectively scored the overall image quality of bony and soft tissue structures. The CT dose index volume and dose-length product were recorded. Results Image noise was higher in Group A than in Group B in bone kernel images (p < 0.001). Group A using a soft tissue kernel showed the highest SNR and CNR for all soft tissue structures (all p < 0.001). In the qualitative analysis of bony structures, Group A scores were found to be similar to or higher than Group B scores on comparing bone kernel images. In the qualitative analysis of soft tissue structures, there was no significant difference between Group A using a soft tissue kernel and Group B using a bone kernel with a soft tissue window setting (p > 0.05). Group A showed a 76.9% reduction in radiation dose compared to Group B (3.2 ± 0.2 mGy vs. 13.9 ± 1.5 mGy; p < 0.001). Conclusion The addition of a soft tissue kernel image to conventional CT reconstructed with FBP enables the use of pediatric low-dose facial CT protocol while maintaining image quality.

• Journal of the Korean Society of Radiology
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• v.9 no.7
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• pp.467-471
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• 2015

This study's purpose is improve image quality to keep accurate tube angle in order to recognize distortion degree conditions by patient's position or tube angle and to provide exact clinical informations when taking chest AP projection for patient which have L-tube in stomach. The experimental equipment was ELMO-T6S by SHIMADZU corporation, then we put L-tube which attached 1 mm gap scales ruler on chest phantom surface. The experiment set by 90 kVp, 4 mAs, 120 cm distance. Each phantom position which changed supine, 30degree, 45degree, 60degree on the table exposured direct, ${\pm}5degree$, ${\pm}10degree$, ${\pm}15degree$ to head and feet directions. As a result, L-tube tip's position was changed by patient's position and tube angle. When patient's position is supine, tip's position change was lower than 30degree, 45degree, 60degree. We have to adjust patient's position or tube angle in order to occur image distortion by fault tube angle when confirming correct position L-tube tip through chest x-ray. Also, Radiological technologist try to make accurate evaluation index for satisfied L-tube insertion.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.3
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• pp.162-169
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• 2016

The agrometeorological reference index means 'the agrometeorological damage possibility' or the possibility of the normal year climate condition to damage the crop cultivation in a certain region. It is a reference used to compare the cultivation risk of a crop by region. The global climate warming is expected to increase the winter temperature. At the same time, the frequency of extreme weather events will also increase. Therefore, people pay attention to the potential of low temperature-induced damages (e.g., frost damage and injury) to fruit trees under the future climate condition. However, simple damage projection based on climate conditions does not help the climate change adaptation in the practical aspect because the climate change affects the phenology of fruit trees as well. This study predicted the phenology of the pear, peach, and apple trees by using the climate change scenarios of major regions. Furthermore, low temperature induced agrometeorological reference indices were calculated based on the effects of temperature on each plant growth stage to predict the damage possibility. It was predicted that the breaking rest would delay more in the future while the bud-burst date and flowering date will be earlier. In Daegu, Jeonju, and Mokpo, the breaking rest delayed more as time passed. The bud-burst date and flowering date of Seoul and Incheon regions were later than other regions. Seoul and Incheon showed a similar pattern, while Daegu and Jeonju revealed a similar pattern. Busan and Mokpo also showed a similar pattern. All regions were safe from the frost damage during the dormancy period. However, plants were vulnerable to frost damage between the breaking rest and the bud-burst period. Regions showed different frost damage patterns between the bud-burst period and the flowering period. During the bud-burst and flowering period, the risk level decreased in general, although the risk of some areas tended to increase.

• Progress in Medical Physics
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• v.27 no.2
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• pp.93-97
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• 2016

In this study, we evaluate the effect of respiration on the dose distribution in patient target volume (PTV) during intensity-modulated radiation therapy (IMRT) and research methods to reduce this impact. The dose distributions, homogeneity index (HI), coverage index (CVI), and conformity index of the PTV, which is calculated from the dose-volume histogram (DVH), are compared between the maximum intensity projection (MIP) image-based plan and other images at respiration phases of 30%, 60% and 90%. In addition, the reducing effect of complication caused by patient respiration is estimated in the case of a bolus and the expended PTV on the skin. The HI is increased by approximately twice, and the CVI is relatively decreased without the bolus at other respiration phases. With the bolus and expended PTV, the change in the dose distribution of the PTV is relatively small with patient respiration. Therefore, the usage of the bolus and expended PTV can be considered as one of the methods to improve the accuracy of IMRT in the treatment of breast cancer patients with respiratory motion.

• The Journal of Korean Society for Radiation Therapy
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• v.27 no.1
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• pp.1-11
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• 2015

Purpose : Evaluating absorbed dose related to 2D and 3D imaging confirmation devices Materials and Methods : According to the radiographic projection conditions, absorbed doses are measured that 3 glass dosimeters attached to the centers of 0', 90', 180' and 270' in the head, thorax and abdomen each with Rando phantom are used in field size $26.6{\times}20$, $15{\times}15$. In the same way, absorbed doses are measured for width 16cm and 10cm of CBCT each. OBI(version 1.5) system and calibrated glass dosimeters are used for the measurement. Results : AP projection for 2D imaging check, In $0^{\circ}$ degree absorbed doses measured in the head were $1.44{\pm}0.26mGy$ with the field size $26.6{\times}20$, $1.17{\pm}0.02mGy$ with the field size $15{\times}15$. With the same method, absorbed doses in the thorax were $3.08{\pm}0.86mGy$ to $0.57{\pm}0.02mGy$ by reducing field size. In the abdomen, absorbed dose were reduced $8.19{\pm}0.54mGy$ to $4.19{\pm}0.09mGy$. Finally according to the field size, absorbed doses has decreased by average 5~12%. With Lateral projection, absorbed doses showed average 5~8% decrease. CBCT for 3D imaging check, CBDI in the head were $4.39{\pm}0.11mGy$ to $3.99{\pm}0.13mGy$ by reducing the width 16cm to 10cm. In the same way in thorax the absorbed dose were reduced $34.88{\pm}0.93(10.48{\pm}0.09)mGy$ to $31.01{\pm}0.3(9.30{\pm}0.09)mGy$ and $35.99{\pm}1.86mGy$ to $32.27{\pm}1.35mGy$ in the abdomen. With variation of width 16cm and 10cm, they showed 8~11% decrease. Conclusion : By means of reducing 2D field size, absorbed dose were decreased average 5~12% in 3D width size 8~11%. So that it is necessary for radiation therapists to recognize systematical management for absorbed dose for Imaging confirmation. and also for frequent CBCT, it is considered whether or not prescribed dose for RT refer to imaging dose.