• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.15-20
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• 2015

To examine the magnetic shielding effect for carbon-based materials at extremely low frequencies (60 Hz), two types of carbon black (Super-P and Denka Black) and a natural graphite (HC-198) were mixed into organic binder at 10 wt.% to produce a coating solution, and a powder coating with varying thickness was applied on an aluminum disk measuring 88 mm in radius. A device was developed to measure the sheielding effect at extremely low frequencies. A closed circuit was achieved by connecting a transformer and a resistor. The applied voltage was fixed at 65 V, and the magnetic field was measured to being the range of 4.95~5.10 mG. Depending on the thickness of the coating layer, the magnetic field showed a decreasing trend. The maximum decrease in the magnetic field of 38.3% was measured when natural graphite was coated with specimens averaging $455{\mu}m$. This study confirmed that carbon-based materials enable magnetic shielding at extremely low frequencies, and that the magnetic shielding effect can be enhanced by varying the coating thickness.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.7
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• pp.963-969
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• 2018

According to the dictionary definition Augmented Reality Technology is "an enhanced version of reality where live direct or indirect views of physical real-world environments are augmented with superimposed computer-generated images over a user's view of the real-world, thus enhancing one's current perception of reality". Since civilian property damages, noise and accidents during the field exercise by military or drills so that AR technology are indispensible with small units drills in Army. However because AR technology which Army has adopted are usually use for special units or need separate spaces which costs lots of budgets, those are not fit for small unit drills or tactics in regular Army. In this regards this paper suggests the AR technology which can apply small unit drill field and the efficiency and legal concerns thereof as well.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.4
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• pp.37-44
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• 2013

We have examined the effect of rice straw mat (RSM) on the reduction of non-point source (NPS) pollution loads at soybean cultivations. The slope of the experimental plot was about 3 %. Monitoring was carried out for four years at conventional tillage (CT) in 2008~2009 years and RSM covered tillage in 2010~2011 years. Thirty-two rainfall events were monitored and analyzed during the study period. During the 2 years of 2008 and 2009, 20 rainfall runoff events were monitored. But in 2010 years, only 2 rainfall runoff events could be monitored. And in 2011 years, 10 rainfall runoff events was monitored. It was because the RSM cover enhanced infiltration and reduce runoff in 2010 and 2011. Average NPS pollution load (organic matters) of the RSM covered field was reduced by 72.1~94.2 % compared to that of CT field. NPS pollution load of TN and TP reduced by 67.5 % and 55.7 %, respectively. Especially, SS pollution load was reduced by 97.3 %. Based on the results, rice straw mat cover was considered as a promising best management practices (BMP) to reduce NPS pollution load. However, it was recommended that the results are limited to the field conditions and the same experiments must be performed on different soil textures, slopes, and crops if it is applied to the development of policies.

• Korean Journal of Materials Research
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• v.20 no.3
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• pp.137-141
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• 2010

The $(1-x)La_{0.7}Sr_{0.3}MnO_3(LSMO)/xZnFe_2O_4$(ZFO) (x = 0, 0.01, 0.03, 0.06 and 0.09) composites were prepared by a conventional solid-state reaction method. We investigated the structural properties, magnetic properties and electrical transport properties of (1-x)LSMO/xZFO composites using X-ray diffraction (XRD), scanning electron microscopy (SEM), field-cooled dc magnetization and magnetoresistance (MR) measurements. The XRD and SEM results indicate that LSMO and ZFO coexist in the composites and the ZFO mostly segregates at the grain boundaries of LSMO, which agreed well with the results of the magnetic measurements. The resistivity of the samples increased by the increase of the ZFO doping level. A clear metal-to-insulator (M-I) transition was observed at 360K in pure LSMO. The introduction of ZFO further downshifted the transition temperature (350K-160K) while the transition disappeared in the sample (x = 0.09) and it presented insulating/semiconducting behavior in the measured temperature range (100K to 400K). The MR was measured in the presence of the 10kOe field. Compared with pure LSMO, the enhancement of low-field magnetoresistance (LFMR) was observed in the composites. It was clearly observed that the magnetoresistance effect of x = 0.03 was enhanced at room temperature range. These phenomena can be explained using the double-exchange (DE) mechanism, the grain boundary effect and the intrinsic transport properties together.

• Journal of Ocean Engineering and Technology
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• v.38 no.4
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• pp.187-198
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• 2024

Autonomous underwater vehicles (AUVs) have a limited bandwidth for real-time communication, limiting rapid responses to unexpected obstacles. This study addressed how AUVs can navigate to a target without a pre-existing obstacle map by generating one in real-time and avoiding obstacles. This paper proposes using forward-looking sonar with an occupancy grid map (OGM) for real-time obstacle mapping and a potential field algorithm for avoiding obstacles. The OGM segments the map into grids, updating the obstacle probability of each cell for precise, quick mapping. The potential field algorithm attracts the AUV towards the target and uses repulsive forces from obstacles for path planning, enhancing computational efficiency in a dynamic environment. Experiments were conducted in coastal waters with obstacles to verify the real-time obstacle mapping and avoidance algorithm. Despite the high noise in sonar data, the experimental results confirmed effective obstacle mapping and avoidance. The OGM-based potential field algorithm was computationally efficient, suitable for single-board computers, and demonstrated proper parameter adjustments through two distinct scenarios. The experiments also identified some of challenges, such as dynamic changes in detection rates, propulsion bubbles, and changes in repulsive forces caused by sudden obstacles. An enhanced algorithm to address these issues is currently under development.

• Journal of Auto-vehicle Safety Association
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• v.16 no.3
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• pp.64-71
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• 2024

With the advent of Level 4 autonomous vehicles, the need for effective communication between these vehicles and pedestrians has become increasingly important. To address this, eHMI (Enhanced Human-Machine Interface) technology has been proposed to replace traditional driver-pedestrian interactions. eHMI plays a crucial role in conveying the vehicle's status and intentions to pedestrians, thereby improving interaction. Globally, automobile manufacturers and technology companies are investing in visual eHMI technologies, advancing in tandem with the automotive industry. This study developed a methodology for field evaluation of communication technologies between pedestrians and Level 4 autonomous vehicles in urban settings. A three-stage message and display system, tailored to the pedestrian crossing process (recognition, judgment, response), was established. In experiments without message displays, 42.2% (38 out of 90) of participants abandoned crossing. Most who crossed did so only after the vehicle stopped, with some groups crossing irrespective of vehicle approach. When the 'yield' message was introduced, crossing patterns and speed distributions changed significantly. All 38 participants who initially abandoned crossing decided to cross, and the elderly who previously ran or walked quickly crossed at a normal pace, reducing overall crossing time. Field experiments are crucial as real-world conditions may elicit different behaviors than controlled settings. Continued research in field evaluations is essential to develop and assess effective eHMI messages. By observing and analyzing actual pedestrian movements, we can reliably evaluate the effectiveness of these communication technologies, thereby enhancing interaction between autonomous vehicles and pedestrians.

• The Journal of Korean Society for Radiation Therapy
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• v.16 no.2
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• pp.43-61
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• 2004

Purpose : For qualify improvement in radiotherapy, it is important to set up and evaluate equipment (linac) accurately. In addition, technicians are needed to be fully aware of the equipment's detailed quality and its manual. Therefore, the result of ATP is evaluated and introduced, in order that the technicians are skilled by participating in quality assurance (QA) and understanding the quality of the equipment before clinical use. Method and Material : QA for LINAC 21EX (Varian, US) was done with suppliers its procedure was divided into radiation survey, mechanical test, radiation isocenter test, bean performance, dosimetry, and enhanced dynamic wedge and using X-omat film (Kodak), multidata, densitometer, and electrometer. QA of MLC (Millennium, 120 leaf) attached to LINAC and EPID (Portal vision) were done separately. Result : The leakage dose by survey meter was below the tolerance. In mechanical test, collimater, gantry, and couch rotation were less than 1mm, and the angles were ${\pm}0.1^{\circ}$ for digital and ${\pm}0.5^{\circ}$ for mechanical. The alignment test of the light field and crosshair were evaluated less than 1mm. The (a)symmetrical jaw field was less than ${\pm}0.5mm$. The radiation isocenter test using X-mat film was less than 1mm. The consistency of light field and radiation field was less than ${\pm}0.1mm$. PDD for photon energy was less than ${\pm}1\%$ and for electron energy of $90\%,\;80\%,\;50\%,\;and\;30\%$ were evaluated within the tolerance. Flatness for photon and electron energy was evaluated $2.3\%$ (tolerance $3\%$) and $3\%$ (tolerance $4.5\%$), respectively, and symmetry was $0.45\%$ (tolerance $2\%$) and $0.3\%$ (tolerance $2\%$), respectively. Dosimetry test for short term, MU setting, rep rate, and dose rate accuracy of photon and electron energy was within the tolerance depending on energy, MU, and gantry angle. Conclusion : Accuracy and safety for clinical use of Clinac 21EX was verified through customer acceptance procedure and the quality of the equipment was found out. These can reduce the difficulties in using the equipment. Furthermore, it is useful for clinically treatment of patients by technicians' active participations.

• Korean Journal of Optics and Photonics
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• v.19 no.6
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• pp.394-399
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• 2008

An integral imaging system enabling enhanced depth of field by incorporating a pair of liquid-crystal (LC) lens arrays was proposed and demonstrated. The lens arrays exhibit two different refractive indexes depending on the light polarization. The proposed LC lens array I and II were implemented by depositing a ZLI-4119 LC and an E-7 LC, respectively, on top of a lens-array substrate in glass. When the two LC lens arrays were aligned appropriately, a birefringence was obtained for a specific light polarization in such a way that the incoming light sees different refractive indexes for them. As a result, the focal length associated with the imaging system utilizing the LC lens arrays was adaptively varied, thereby enhancing the depth of field for the image reconstruction. We have theoretically analyzed the proposed integral imaging system with the $LightTools^{(R)}$ to confirm that the focal length could be adjusted with the help of the birefringent lens array. Finally the proposed imaging system successfully reconstructed the objects. The birefringent lens array employing the ZLI-4119 LC produced a real image with the focal length of 680 mm, while the other using the E-7 LC yielded a virtual image with the focal length of -29 mm.

• Progress in Medical Physics
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• v.5 no.1
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• pp.55-66
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• 1994

After proving home-made imaging pulse sequences including tailored RF pulse by phantom, susceptibility-contrast-enhanced MR venograms of cat brain were obtained using tailored RF gradient-echo(TRGE) method. Sagittal MR imaging of the cat brain obtained by TRGE technique shows several veins, for example, dorsal sagittal sinus, straight sinus, vein of corpus callosum and internal cerebral vein, etc., compared with cats anatomical figure. Tailored RF waveform was generated by PASCAL language in ASPECT 3000 computer(Switzland, Bruker). Rectangular-shaped slice profile with bi-linear ramp function as phase distribution in the slice, at which maximum value was 2$\pi$, was fourier transformed to make tailored RF pulse. Experimental MR imaging parameters were TR/TE=205/10 msec, slice thickness TH=7mm, maxtrix size=256$\times$256, in-plane resolution=0.62$\times$0.31mm$^2$, and field of view(FOV)=8cm for both conventional gradient-echo(GE) imaging and TRGE imaging techniques.

• Journal of the Korean earth science society
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• v.25 no.8
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• pp.754-763
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• 2004

This study was aimed to examine the Landsat Enhanced Thematic Mapper Plus (ETM+) index, which matches well with the field survey data in the wildfire area of Gangneung, Gangweon Province, Korea. In the wildfire area NDVI (Normalized Difference Vegetation Index), SAVI (Soil Adjusted Vegetation Index), and Tasseled Cap Transformation Index (Brightness, Wetness, Greenness) were compared with field survey data. NDVI and SAVI were very useful in detecting the difference between the wildfire and non-wildfire area, but not so in classify the soil types in the wildfire area. The soil plane based on the Tasseled Cap Transformation showed a better result in classifying the soil types in the wildfire areas than NDVI and SAVI, and corresponded well with field survey data. Using a linear function based on greenness and wetness in the Tasseled Cap Transformation is expected to provide a more efficient and quicker method to classify wildfire areas.