• Progress in Medical Physics
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• v.23 no.4
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• pp.252-260
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• 2012

The reduction of radiation dose from x-ray is a main concern in computed tomography (CT) imaging due to the side-effect of the dose on human body. Recently, the various methods for dose reduction have been studied in CT and one of the method is a iterative reconstruction based on total variation (TV) minimization at few-views data. In this paper, we evaluated the image quality between total variation (TV) minimization algorithm and Feldkam-Davis-kress (FDK) algorithm in micro computed tomography (CT). To evaluate the effect of TV minimization algorithm, we produced a cylindrical phantom including contrast media, water, air inserts. We can acquire maximum 400 projection views per rotation of the x-ray tube and detector. 20, 50, 90, 180 projection data were chosen for evaluating the level of image restoration by TV minimization. The phantom and mouse image reconstructed with FDK algorithm at 400 projection data used as a reference image for comparing with TV minimization and FDK algorithm at few-views. Contrast-to-noise ratio (CNR), Universal quality index (UQI) were used as a image evaluation metric. When projection data are not insufficient, our results show that the image quality of reconstructed with TV minimization is similar to reconstructed image with FDK at 400 view. In the cylindrical phantom study, the CNR of TV image was 5.86, FDK image was 5.65 and FDK-reference was 5.98 at 90-views. The CNR of TV image 0.21 higher than FDK image CNR at 90-views. UQI of TV image was 0.99 and FDK image was 0.81 at 90-views. where, the number of projection is 90, the UQI of TV image 0.18 higher than FDK image at 90-views. In the mouse study UQI of TV image was 0.91, FDK was 0.83 at 90-views. the UQI of TV image 0.08 higher than FDK image at 90-views. In cylindrical phantom image and mouse image study, TV minimization algorithm shows the best performance in artifact reduction and preserving edges at few view data. Therefore, TV minimization can potentially be expected to reduce patient dose in clinics.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.3
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• pp.175-185
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• 2020

Three-dimensional registration is a process of matching data with or without a coordinate system to a reference coordinate system, which is used in various fields such as the absolute orientation of photogrammetry and data combining for producing precise road maps. Three-dimensional registration is divided into a method using points and a method using linear features. In the case of using points, it is difficult to find the same conjugate point when having different spatial resolutions. On the other hand, the use of linear feature has the advantage that the three-dimensional registration is possible by using not only the case where the spatial resolution is different but also the conjugate linear feature that is not the same starting point and ending point in point cloud type data. In this study, we proposed a method to determine the scale and the three-dimensional translation after determining the three-dimensional rotation angle between two data using quaternion to perform three-dimensional registration using linear features. For the verification of the proposed method, three-dimensional registration was performed using the linear features constructed an indoor and the linear features acquired through the terrestrial mobile mapping system in an outdoor environment. The experimental results showed that the mean square root error was 0.001054m and 0.000936m, respectively, when the scale was fixed and if not fixed, using indoor data. The results of the three-dimensional transformation in the 500m section using outdoor data showed that the mean square root error was 0.09412m when the six linear features were used, and the accuracy for producing precision maps was satisfied. In addition, in the experiment where the number of linear features was changed, it was found that nine linear features were sufficient for high-precision 3D transformation through almost no change in the root mean square error even when nine linear features or more linear features were used.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.3
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• pp.305-313
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• 2020

The use of cable tunnels for electric power transmission as well as their construction in difficult conditions such as in subsea terrains and large overburden areas has increased. So, in order to efficiently operate the small diameter shield TBM (Tunnel Boring Machine), the estimation of advance rate and development of a design model is necessary. However, due to limited scope of survey and face mapping, it is very difficult to match the rock mass characteristics and TBM operational data in order to achieve their mutual relationships and to develop an advance rate model. Also, the working mechanism of previously utilized linear cutting machine is slightly different than the real excavation mechanism owing to the penetration of a number of disc cutters taking place at the same time in the rock mass in conjunction with rotation of the cutterhead. So, in order to suggest the advance rate and machine design models for small diameter TBMs, an EPB (Earth Pressure Balance) shield TBM having 3.54 m diameter cutterhead was manufactured and 19 cases of full-scale tunneling tests were performed each in 87.5 ㎥ volume of artificial rock mass. The relationships between advance rate and machine data were effectively analyzed by performing the tests in homogeneous rock mass with 70 MPa uniaxial compressive strength according to the TBM operational parameters such as thrust force and RPM of cutterhead. The utilization of the recorded penetration depth and torque values in the development of models is more accurate and realistic since they were derived through real excavation mechanism. The relationships between normal force on single disc cutter and penetration depth as well as between normal force and rolling force were suggested in this study. The prediction of advance rate and design of TBM can be performed in rock mass having 70 MPa strength using these relationships. An effort was made to improve the application of the developed model by applying the FPI (Field Penetration Index) concept which can overcome the limitation of 100% RQD (Rock Quality Designation) in artificial rock mass.

• Journal of the Korean association of regional geographers
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• v.4 no.2
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• pp.31-47
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• 1998

This paper deals with the historical geography of land-use and agriculture along the Lower Nam-River floodplains. The reclamation process of the river floodplains, the cultivation methods on the reclaimed lands, and the land-use patterns and processes are investigated. The Nam River, one of the major tributaries of the Nakdong River, flows through the boundary between Ham-An and Eu-Ryong Guns. Larger floodplains are located in Ham-An Gun. The floodplains of Ham-An Gun have been surveyed intensively in this study. In South Korea, the alluvial plains, mostly located along the river valleys, have been reclaimed to provide fertile agricultural lands. Those along the upper river valleys were reclaimed before those along the lower river valleys. The flood-plains of Han-An Gun were reclaimed to be the largest agricultural lands of the Gun. The natural levees along the Lower Nam-River Valley were identified before the reclamation processes but now hardly identified. Relatively larger floodplains are located along the tributary streams of the Nam River. Often there are low-lying back swamps between the natural levees and the hills/mountains that rise above the floodplains. The back swamps, called 'natural bog lands' in this region, have been reduced in size and in number through reclamation for the purpose of agricultural and industrial land-uses. Now about ten 'natural bog lands' are found in the Ham-An floodplains, and some of them are being reclaimed for the industrial land-use. This study suggests the emergent need of conservation for the remaining 'natural bog lands' in terms of ecology. Seven agricultural fields of large size, originated from the Nam-River floodplains, are identified in this study: Kun(큰들), Chung-Am(정암들), Chang-chi(장지들), Baek-San(백산들), Ha-Ki(하기들), Gu-Hae(구혜들), and Chang-Po(장포들) fields. The Kun field was reclaimed during the Japanese control and the Gu-Hae, in the 1950s. All of those except the above two fields were reclaimed after the mid-1960s. The Nam-River Dam in Chinju, completed in 1969, contributed the reclamation processes along the Lower Nam-River floodplains. The rice acreage of the region has been reduced slowly since 1970 but the rice production of the region has been relatively stable (Table 4). Rice culture had been the most important agriculture on the reclaimed lands for decades before the greenhouse vegetable cultivation became more important in the 1980s. Among the vegetables cultivated in the greenhouse, the watermelon is the dominantly leading one. Watermelons are usually harvested two or three times in a year though it is possible to harvest four times in one year. The rotation of watermelons and rice is common in the region. It is known the physical conditions of the Nam-River floodplains in Ham-An Gun is the most suitable for watermelon cultivation in South Korea.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.4
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• pp.233-252
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• 2021

This paper is a study to improve the efficiency of mixing technology in the shield TBM chamber. Currently, the number of construction cases using the TBM method is increasing in Korea. According to the increasing use of TBM method, research on TBM method such as Disc Cutter, Cutter bit, and Segment also shows an increasing trend. However, there is little research on the mixing efficiency in chamber and chamber. In order to improve the smooth soil treatment and the behavior of the excavated soil, a study was conducted on the change of the mixing efficiency according to the effective mixing bar arrangement in the chamber. In the scale model experiment, the ground was composed using plastic materials of different colors for ease of identification. In addition, the mixing bar arrangement was different and classified into 4 cases, and the particle size distribution was classified into single particle size and multiple particle size, and the experiment was conducted with a total of 8 cases. The rotation speed of the cutter head of all cases was the same as 5 RPM, and the experiment time was also carried out in the same condition, 1 minute and 30 seconds. In order to check the mixing efficiency, samples at the upper, middle (left or right), and lower positions of each case were collected and analyzed. As a result of the scaled-down model experiment, the mixing efficiency of Case 4 and Case 4-1 increased compared to Case 1 and Case 1-1, which are actually used. Accordingly, it is expected that the mixing efficiency can be increased by changing the arrangement of the mixing bar in the chamber, and it is considered to be effective in saving air as the mixing efficiency increases. Therefore, this study is considered to be an important indicator for the use of shield TBM in Korea.

• Journal of vocational education research
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• v.37 no.6
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• pp.36-60
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• 2018

The purpose of this study is to explore the occupational personality required for high school graduates and to develop a scale to measure them objectively. In order to achieve the purpose of the study, this study constituted the delphi committee composed of the teacher group and the industrial personnel group. Afterwards, Delphi survey was conducted twice, and it was found that 12 jobs such as sincerity and honesty were related to occupational personality. As a result of the development of the scale based on the previous research and the expert group interview, 12 factors and 116 scales were developed for the pre - occupational personality test tool. In order to verify the validity and reliability of the developed preliminary test tool, we conducted a questionnaire survey of 700 students of vocational high school, and 514 questionnaires were used for final analysis. Parallel analysis was performed to determine the number of factors before exploratory factor analysis. As a result, eight factors were found to be appropriate. As a result of exploratory factor analysis using the 'maximum likelihood method' and 'direct oblimin rotation method', 78 items of 8 factors were found appropriate. However, in order to confirm whether the item reflects the contents of the factors, we conducted a content validity test for the expert group. As a result, feedback was obtained that 19 items were irrelevant or inadequate. Therefore, the validity of the existing job personality test tool and the modified job personality test tool were verified through confirmatory factor analysis. As a result, the fitness of the revised test tool was higher and the fitness level was generally good.

• The Journal of Korean Society for Radiation Therapy
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• v.25 no.2
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• pp.115-121
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• 2013

Purpose: Latest linear accelerator and the introduction of new measurement equipment to the agency that the introduction of this equipment in the future, by analyzing the process of confirming the usefulness of the preparation process for applying it in the clinical causes some problems, should be helpful. Materials and Methods: All measurements TrueBEAM STX (Varian, USA) was used, and a file specific to each energy, irradiation conditions, the dose distribution was calculated using a computerized treatment planning equipment (Eclipse ver 10.0.39, Varian, USA). Measuring performance and cause errors in MapCHECK 2 were analyzed and measured against. In order to verify the performance of the MapCHECK 2, 6X, 6X-FFF, 10X, 10X-FFF, 15X field size $10{\times}10$ cm, gantry $0^{\circ}$, $180^{\circ}$ direction was measured by the energy. IGRT couch of the CT values affect the measurements in order to confirm, CT number values : -800 (Carbon) & -950 (COUCH in the air), -100 & 6X-950 in the state for FFF, 15X of the energy field sizes $10{\times}10$, gantry $180^{\circ}$, $135^{\circ}$, $275^{\circ}$ directionwas measured at, MapPHAN allocated to confirm the value of HU were compared, using the treatment planning computer for, Measurement error problem by the sharp edges MapPHAN Learn gantry direction MapPHAN of dependence was measured in three ways. GANTRY $90^{\circ}$, $270^{\circ}$ in the direction of the vertically erected settings 6X-FFF, 15X respectively, and Setting the state established as a horizontal field sizes $10{\times}10$, $90^{\circ}$, $45^{\circ}$, $315^{\circ}$, $270^{\circ}$ of in the direction of the energy-6X-FFF, 15X, respectively, were measured. Without intensity modulated beam of the third open arc were investigated. Results: Of basic performance MapCHECK confirm the attenuation measured by Couch, measured from the measured HU values that are assigned to the MAP-PHAN, check for calculation accuracy for the angled edge of the MapPHAN all come in a range of valid measurement errors do not affect the could see. three ways for the Gantry direction dependence, the first of the meter built into the value of the Gantry $270^{\circ}$ (relative $0^{\circ}$), $90^{\circ}$ (relative $180^{\circ}$), 6X-FFF, 15X from each -1.51, 0.83% and -0.63, -0.22% was not affected by the AP/PA direction represented. Setting the meter horizontally Gantry $90^{\circ}$, $270^{\circ}$ from the couch, Energy 6X-FFF 4.37, 2.84%, 15X, -9.63, -13.32% the difference. By-side direction measurements MapPHAN in value is not within the valid range can not, because that could be confirmed as gamma pass rate 3% of the value is greater than the value shown. You can check the Open Arc 6X-FFF, 15X energy, field size $10{\times}10$ cm $360^{\circ}$ rotation of the dose distribution in the state to look at nearly 90% pass rate to emerge. Conclusion: Based on the above results, the MapPHAN gantry direction dependence by side in the direction of the beam relative dose distribution suitable for measuring the gamma value, but accurate measurement of the absolute dose can not be considered is. this paper, a more accurate treatment plan in order to confirm, Reduce the tolerance for VMAT, such as lateral rotation investigation in order to measure accurate absolute isodose using a combination of IMF (Isocentric Mounting Fixture) MapCHEK 2, will be able to minimize the impact due to the angular dependence.

• Korean Journal of Agricultural Science
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• v.10 no.1
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• pp.61-73
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• 1983

This study was conducted to obtain fundamental informations on the improvement of cropping system to increase in land utilization rate and crop production. In order to group the characteristics of areas, Chungnam province was classified into 4 classes: Suburb (Daedeog Gun, Cheonwon Gun), Plain (Nonsan Gun, Dangjin Gun) Coastal (Seosan Gun, Boryeong Gun) and Hilly region (Gongju Gun, Cheongyang Gun). 100 farm households were sampled from each region, and cropping system and utilization state of paddy and upland in 1982 were surveyed. The results obtained were summarized as follows: 1. Average utilization rate of upland was 161.9 % The utilization rate of upland at plain was highest (188.9 %), and that at suburb showed lowest value (152.0%). 2. Number of crops cultivated at upland was 32 kinds. Among the rate of planting area of each crop. soybean showed highest rate of 18.8%, barley 15.4%, red-pepper 13.1% and chinese' cabbage 10.1% respectively, but the red pepper showed highest rate of planting area at suburb, the barley at hilly region and the soybean at plain and coastal region. 3. Average utilization rate of paddy was 115.6% and the utilization rate of paddy at suburb showed the highest value (140.0%) and that at coastal region the lowest value (108.2%). 4. 12 kinds of crops were cultivated at paddy before or after rice cultivation. Among the crops cultivated at paddy before or after rice cultivation, barley showed the highest area rate (5.0%) of cultivation and strawberry the next but the strawberry showed the highest area rate of cultivation at suburb and barley at other regions. 5. The cropping systems at upland were divided into single cropping and double cropping. Types of double cropping at upland were classified into 38 types by the combinations of crops. Among the types of double cropping, the rate of cultivation area of soybean after barley combination was 35.0%, but at suburb the rate of this type of cropping system was low and the double cropping of vegetable combinations showed high rate. 6. Types of double cropping at paddy were classified into 6 types. As a whole, double cropping of barley after rice combination showed highest rate of cultivation area (42.8%) among crop combinations but at suburb, the area rate of this type cropping was low and cultivation of fruit vegetable after rice showed highest rate. The area rate of post - cropping to rice was 76.3% of whole double cropping area at paddy and significantly higher than the rate of precropping to rice. 7. Some kinds of crop combinations were consisted of same family or closely related crops and the characteristics of the crop rotation between those crops are almost same. The area cultivated those unreasonable crop combinations were 19.09 ha. 8. At upland, planting area of the cereal crops, vegetale crops and industrial crops crops and industrial crops was 88.92ha, 93.70ha and 21.80ha respectively. The Planting area of cereal crops was significantly less than that of vegetable crops. 9. Most of all the research reports on the cropping system from 1910 to 1980 were about the post cropping after rice harvest. The objectives of researches could be classified into 14 kinds and the important objectives of researches were the planting time, the amounting of manuring, the quantity of seeding, the transplanting time, the ridging method, the sowing method and the variety test.