• Journal of Biomedical Engineering Research
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• v.33 no.2
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• pp.72-77
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• 2012

Phase Contrast MR Angiography(PC MRA) is excellent MRA technique for measuring the velocity of vessels in the human body. PC MRA need to at least four images for angiogram reconstruction and it caused longer scan time. Therefore, we used keyhole imaging combined PC MRA to reduce the scan time. However, keyhole imaging can lead the erroneous effects as loss of phase information or frequency discontinuous. In this study, we applied the keyhole imaging combined 2D PC MRA for improving the temporal resolution and also measured the velocity to evaluate the accuracy of phase information. We used 0.32T MRI scanner(Magfinder II, Scimedix, Korea). Using the 2D PC MRA pulse sequence, the vascular images for a human brain targeted on the Superior Sagittal Sinus(SSS) were obtained. We applied tukey window function for keyhole images to minimize the ringing artifact and erroneous factors that are induced frequency discontinuous and phase information loss. We also applied zero-padded algorithm to peripheral missing k-space lines to compare keyhole imaging results and the artifact power(AP) value was measured on the complex difference images to validate the image quality. Consider as based on our results, heavy image distortions and artifacts were shown until using at least 50% keyhole factor. Using above the 50% keyhole factors are shown well reconstructed and matched for magnitude images and velocity information measurements. In conclusion, we confirmed the image quality and velocity information of keyhole technique combined 2D PC MRA. Especially, measured velocity information through the keyhole imaging combination was similar to the velocity information of full sampled k-space image despite of frequency discontinuous and phase information loss in the keyhole imaging reconstruction process. Consequently, the keyhole imaging combined 2D PC MRA will give some clinical usefulness and advantages as improving the temporal resolution and measuring the velocity information via selecting the appropriate keyhole factor at low tesla MRI system.

• Journal of Forest and Environmental Science
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• v.24 no.1
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• pp.35-39
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• 2008

The present study was conducted to analyze the soil environment of planted areas around Sudokwon Landfill Site, and drew conclusions as follows. Among the physical properties of soil, bulk density ranged between 1.11~1.59 $g{\cdot}cm^{-3}$, which was higher than the average bulk density (1.05 $g{\cdot}cm^{-3}$) of the B layer of forest soil in Gyeonggido, Korea. This is probably because of treading by heavy equipment used to prepare the ground for planting, and measures should be taken to improve bulk density for the growth of the root system of trees. Among the chemical properties of soils, the organic matter content was only 1/5~1/10 of 30 $g{\cdot}kg^{-1}$, the adequate level for landscape planting. In addition, cation exchange capacity (CEC) ranged between 1~3 $cmol{\cdot}kg^{-1}$, which was much lower than 6 $cmol{\cdot}kg^{-1}$, the least capacity for landscape planting. Therefore, these problems need to be solved.

• The Journal of the Acoustical Society of Korea
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• v.21 no.8
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• pp.708-718
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• 2002

In this paper, the problems in identifying the noise sources by using the sound intensity technique are dealt with for the general radiated near-field from vibro-acoustic sources. For this purpose, a three-dimensional model structure resembling the engine room of a car or heavy equipment is considered. Similar to the practical situations, the model contains many mutually coherent and incoherent noise sources distributed on the complicated surfaces. The sources are located on the narrow, connected, reflecting planes constructed with rigid boxes, of which a small clearance exists between the whole box structure and the reflecting bottom. The acoustic boundary element method is employed to calculate the acoustic intensity at the near-field surfaces and interior spaces. The effects of relative source phases, frequencies, and locations are investigated, from which the results are illustrated by the contour map, vector plot, and energy streamlines. It is clearly observed that the application of sound intensity technique to the reactive or reverberant field, e.g., scanning over the upper engine room as is usually practiced, can yield the detection of fake sources. For the precise result for such a field, the field reactivity should be checked a priori and the proper effort should be directed to reduce or improve the reactivity of sound field.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.3
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• pp.467-475
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• 2018

The purpose of this study is to propose the evaluation criteria of asphalt pavement condition in narrow regional road considering the traffic environment in order to reduce road budget of local governments. In general, narrow regional roads are considered relatively less important because they have low travel speed and low traffic volume of heavy-vehicle. Generally, automatic surveying equipment is used for investigations of pavement condition, but the operating costs are not efficient for the narrow regional roads because the cost is too high. This study presents the pavement condition evaluation index suitable for narrow regional roads. In this study, the pavement condition evaluation index is presented considering the traffic environment of narrow regional roads. The pavement condition were classified into three classes based on the crack measured by visual inspection, and the validity of the pavement condition evaluation index presented through the expert's questionnaire survey was examined. Pavement condition for the narrow regional roads was classified into three grades based on the index values calculated by visual inspection. Expert's surveys were conducted to evaluate the validity of the proposed pavement condition evaluation. The proposed evaluation index shows a high correlation with questionnaire survey result ($R^2=0.88$). The proposed evaluation index which is obtained through visual crack inspection under limited conditions can be applied to narrow regional roads. In addition, it is expected that it will be effective not only for road management but also for road management budget by more economical evaluation method of pavement condition.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.854-867
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• 2014

In the circumstance that high oil price state is continued over the world, the investment in crude oil development by oil major is a trend of increasing. Recently the number of delivered drill-ship for 5 years has been sharply increased all over the world and about twice than that of past 30 years. As addition to the increase of the drill-ship demand, the operation of drill-ships which is delivered recently is about 3,000 meters, ultra deep sea, on average and the work area is expending. Accordingly the drilling system including the size and length of pipe for drilling has been bigger and bigger and the power supply equipment for operation system also has large capacity. Unlike merchant vessel, high power and high voltage of diesel generators are required for drill-ship for which the demand for V-type 320 bore of diesel generator has increased. It is on the raised that the importance of lubrication oil cleaning for diesel generator on drill-ship which has longer time for construction, and also long term low load operation is unavoidable during commissioning of equipments. Recently it was reported that engine crankpin was damaged due to the hard contact caused by the abnormal wear down(Cam wear) on crankpin and bearing. The same pattern of wear down was found through the inspection on series vessels and the other vessel under commissioning. The purpose of this paper is to analyze of the wear mechanism based on the observation and theories and objective research from actual cases and to prepare the counter measures to avoid foreseeable damage when the lubricating oil is not properly cleaned.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.294-301
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• 2017

In this study, we found the optimal manufacturing conditions of livestock manure sludge RDF with the oil-drying method. We performed oil evaporation, oil drying and pelletizing of the sludge to evaluate the value of the product (sludge RDF), and measured the performance of the product using calorimeter and PXRF equipment. Also, we conducted the calorie comparison test between sludge RDF manufactured in this study and wood RDF generally used in the field. Experimental results showed that 30g of the sludge treated by vegetable oil at $130^{\circ}C$ for 25 minutes were the optimal conditions to make the sludge RDF (considering the aspects of eco-friendly and mass production). The caloric value of the sludge RDF manufactured in this study was 5211kcal/kg which is higher than that of wood RDF used widely in the market. Finally, PXRF results showed sludge RDF contains no heavy metals with the exception of sulfur. Therefore, we recommend more study about the sulfur control process for future development of the industrial manufacturing process.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.6
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• pp.553-560
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• 2014

The road tunnel install a vent for the purpose of ventilation and smoke control. Ventilation equipment capacity(number of jet fans) depends on from the condition that of the pressure and ventilation resistance. Pressure and the resistance under operating vehicle have affected on the drag coefficient. The drag coefficient of the tunnel have affected by the blockage effect and slipstream effects. However, when calculating the ventilation fan, are not properly consider taking into account such effects. Therefore, ventilation force may have been slightly overestimated. This paper describes the drag coefficient through a numerical analysis to calculate the equivalent resistance area that reflects the vehicle distance, and examined the equivalent resistance area. The ventilation coefficient corresponding to the result heavy vehicle mixing ratio of the present study was not clear. Equivalent resistance area had reduced by about 86% compared to the road design handbook current standards. Also it had analyzed and reduced to 62.2% compared to Korea Highway Corporation ventilation design criteria ratio, which is the old standard.

• Journal of Navigation and Port Research
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• v.40 no.4
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• pp.173-181
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• 2016

From 2016, controls on reduction of NOx and SOx emissions from the vessels that are operated in the emission control area were tightened. The selectivity catalytic reduction system of the denitrification equipment which NOx among the above controlled materials is very effective and used commercially very much. But it has the disadvantage that CSR is activated at high temperatures. Therefore, the SCR and SCR activation instrument that can react even at low temperatures by using micro-nano bubbles so that the above problems can be minimized were developed. And the computational fluid dynamics technique was used by ANSYS-CFX package to prepare the plan that improves the SCR system's efficiency. Simulation for the viscous flow analysis of the SCR system was executed by applying the Navier-Stokes equation to it as a governing equation. For the SCR system's shape, 3D modeling was done by using CATIA V5. SCR jet nozzle's position was checked by changing it to the intervals of 1/3, 1/2, and 2/3 from the inlet of the vent pipe to compare the SCR system's efficiency. And the number of nozzles was compared and analyzed by simulating 4, 6, and 8 holes to check an effect of the number on the SCR system's efficiency. The simulation result has found that the closer nozzles are to the inlet of the vent pipe and the more nozzles are, the more efficiency is improved.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.557-564
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• 2017

The purpose of the thermal imaging observation device mounted on the K's tank in the Republic of Korea military is to convert infrared rays into visual information to provide information about the environment under conditions of restricted visibility. Among the various performance indicators of thermal observation devices, such as the view, magnification, resolution, MTF, NETD, and Minimum Resolvable Temperature Difference (MRTD), the MRTD is the most important, because it can indicate both the spatial frequency and temperature resolvable. However, the standard method of measuring the MRTD in NATO contains many subjective factors. As the measurement result can vary depending on subjective factors such as the human eye, metal condition and measurement conditions, the MRTD obtained is not stable. In this study, these qualitative MRTD measurement systems are converted into quantitative indicators based on a gray scale using imaging processing. By converting the average of the gray scale differences of the black and white images into the MRTD, the mean values can be used to determine whether the performance requirements required by the defense specification are met. The (mean) value can also be used to discriminate between detection, recognition and identification and the detectable distance of the thermal equipment can be analyzed under various environmental conditions, such as altostratus, heavy rain and fog.

• Fire Science and Engineering
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• v.22 no.2
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• pp.20-29
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• 2008

The traffic accident of Fire engine takes place very much, compared with that of the past. The reason is that there is a lot of the increase of the demand in the fire, rescue, first aid, and the public request. Also, because the Fire engine should go out at the place of the accident very quickly, it should inevitably violate the traffic regulations. Therefore, this is due to the traffic accident. Despite the urgent situation in the infringement motive of traffic regulations, the outbreak of the traffic accident does not vary largely from the degree of the disadvantage. Accordingly, a fire officer should take charge of his social and economic disadvantage by himself. In this situation, a fire officer has no choice but to start moving passively not to be afflicted with his own disadvantage. Most of the situations concerning the fire fighting are the ones to be controlled urgently. Nevertheless, because of the disadvantage of the traffic accident, passive mobilization of the fire fighting equipment is the heavy burden of all the people of the nation. Therefore, Special institutional safety device should be ready for the protection of the life and property of all people. The special law concerning the processing in the accident of the emergency car needs to be revised. By establishing this special law, the government should not provide the officer who drives the fire engine with the disadvantage caused by traffic accident.