• Plant Journal
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• v.8 no.4
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• pp.34-39
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• 2012

This study presents how low quality coal combustion affects the desulfurizer draft system by correlating of draft loss in a coal-fired thermal power plant and predicts the stall occurrence time of a booster fan. In case of low quality coal, a lot of coal is needed to generate equivalent output power, thereby the rating of increasing draft loss was faster than designed amount of coal. We surely confirmed that draft loss affects the specific energy of a booster fan strongly. On this basis, it is possible to predict the occurring time of stall for a booster fan from current operation specific energy to stall limit specific energy. This study suggests increasing speed of draft loss in each caloric value and the impact of specific energy at a booster fan, it expects to help safe operating in a thermal power plant.

• 한국지구물리탐사학회:학술대회논문집
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• 2002.09a
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• pp.126-138
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• 2002

Designing the bridge with wider span is the present-day trends. Therefore, constructing the foundation on the suitable ground is one of the important factor for the safety of bridge. But, getting a subsurface information under the river is not easy problem. This paper shows results of electrical resistivity survey at the river. Electrical resistivity survey have revealed geoelectrical structure successfully. The result is well matched with boring and can provide useful information on the geological structure such as fault fracture zone for suitable location of foundation. It is expected that application of electrical resistivity survey at the river will be helpful in preventing modification of design due to unexpected ground condition during the construction, or water contamination and increment of costs accompanied with ground reinforcement.

• Journal of the Korean Geotechnical Society
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• v.26 no.4
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• pp.59-68
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• 2010

Piping, a common form of internal embankment erosion, is caused by progressive movement of soil particles through an embankment. The phenomenon commonly occurs with precursory signs of development of fractures in dam structures, but also occurs without any noticeable signs in dams that showed satisfactory dam performance for several years, due to dissolution of soluble material in an embankment. While piping accounts for nearly 50% of the causes for dam failure, few studies have been made for systematic evaluation of the phenomenon. In this study, we attempted to monitor the changes in electrical resistivities of fill-dam material while a saddle dam is dismantled for the construction of emergency spillways of Daechung dam. Two artificial subhorizontal boreholes were drilled into the embankment structure to simulate piping along the two artificial flow channels. Monitoring of changes in electrical resistivity showed an increase in resistivity values during piping. Thus, the investigation of resistivity over time could be an effective method for piping prediction.

• Weed & Turfgrass Science
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• v.2 no.4
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• pp.352-357
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• 2013

A survey was performed to investigate major paddy field weeds and frequently used herbicides in Gyeonggi province, Korea in order to establish a system to efficiently control herbicide-resistant weeds. The dominant paddy field weeds included Echinochloa spp. (22%), Eleocharis kuroguwai (14%), Sagittaria trifolia (13%), Scirpus juncoides (12%), Monochoria vaginalis (9%) and Sagittaria pygmaea (7%), and the most widely used herbicides were butachlor 33% CS (25%), benzobicyclon + fentrazamide + imazosulfuron 11.5% SC (9%), cyclosulfamuron + mefenacet 22.2% SC (9%), butachlor 5% GR (6%), and oxadiazon 12% EC (6%) in Gyeonggi province, Korea. Many paddy rice growers considered S. juncoides, M. vaginalis, S. pygmaea and C. difformis as herbicide-resistant weeds. An extensive research deserves to be conducted to monitor occurrence of herbicideresistant paddy weeds in Gyeonggi province, Korea.

• Journal of Navigation and Port Research
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• v.34 no.10
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• pp.741-746
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• 2010

It is necessary to estimate more accurately the resistance of barge in still water and waves to compute the break load of towline and towing power for safety towing performance. The method proposed by government has calculated the total resistance of barge which is composed of frictional resistance, wave making resistance and air resistance considering the shape of hull and towing speed. However, the added resistance is equally applied with the significant wave height regardless of the type of vessels. In this study, we have carried out the numerical calculation to estimate the added resistance of wigley model in waves and compared with the experiment data to confirm the accuracy of the method. Then the computation was executed for the barge varying shape of the bow. As a result, added resistance of barge was differently occurred i.e. 0.3∼1.1 ton according to encounter angle, 0.4∼1.2 ton according to towing speed and 0.5∼1.1 ton according to shape of bow.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.5
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• pp.103-110
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• 2003

The grounding system is necessary to provide means to dissipate electric currents into the earth without exceeding any operating and equipment limits. The ground is composed of various soils and the resistivity of the soil depends on many parameters. It depends on the type of soil and varies with distance as well as with depth. Especially, soil resistivity of volcanic area such as Jeju is ve교 high and it is difficult to acquire necessary grounding resistivity. This paper introduces the efficient grounding construction using coring technique for proper grounding resistance in high resistivity area. Because it is difficult to measure the accurate resistivity of soils, their resistivities are estimated using measured value of ground resistance and equivalent radius method. Estimated resistivities are used for grounding resistance in scheduled construction region.

• Korean Journal of Materials Research
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• v.7 no.12
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• pp.1058-1062
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• 1997

강유전체 전계효과를 관찰하기 위해 LaCoO$_{3}$/Pb(Zr, Ti)O$_{3}$(La, Sr)CoO$_{3}$ 다층구조를 LcOo$_{3}$가 기판 위에 pulsed laser deposition(PLD)법으로 에피택셜하게 성장시켰다. 이러한 다층구조에서는 전도성 채널층으로 Si대신 반도성 LaCoO$_{3}$가 사용 되었다. LaCoO$_{3}$(LCO)의 비저항은 산소 분위기에 의하여 변화되었는데 특히 증착시 산소 분위기에 의존함을 보였다. LCO의 비저항은 0.1-100Ωcm범위에서 변화되었다. LCO층에 유도되는 강유전체 전계효과는 Pb(Zr, Ti)O$_{3}$(PZT)의 분극 상태에 따른 LCO의 저항 변화를 측정함으로써 관찰되었는데 1020$\AA$ 두께를 가진 LCO층에서는 4%의 저항 변화를 얻었으며 680$\AA$의 LCO에서는 9%의 증가된 저항 변화를 얻었다. DC 바이어스(-5V)를 가한 후에는 저항 변화가 45%까지 증가하였다. 이러한 결과는 적당한 비저항을 갖는 LCO를 사용한 LCO/PZT/LSCO다층구조가 강유전체 전계효과 트랜지스터로 사용될 수 있다는 가능성을 제시하고 있다.

• Journal of the Korean Magnetics Society
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• v.5 no.6
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• pp.963-967
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• 1995

Ultra thin layers of NiFeCo or NiFe were inserted at the interfaces of Ni and Cu to form a multilayer structure. In case of inserting a NiFe layer, the magnetoresistance was about 6%, the saturation magnetic field was 50 Oe and the hysteresis of R-H (resistance-magnetic field) was very small. In case of inserting a NiFeCo layer, the magnetoresistance increased to about 7% but the saturation magnetic field and hysteresis were also increased. The increase of the output under biased magnetic field was much larger in case of inserting a NiFe layer because of relatively smaller hysteresis in R-H behavior.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.124-131
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• 2003

The concentration of nitrous oxide in dental environment has increased especially in pediatric department. In pediatric department frequently met the behavior disordered patients who need the deep sedation. As the deeply sedated patients could not respond well to verbal command, the amount of mouth breathing would be increased especially with mouth prop which backward transposition of mandible. Inhalation of low concentration of nitrous oxide for a long duration has caused various side effects such as spontaneous abortion and inhibition of methionine synthetase activity which is harmful to DNA synthesis. For evaluation of factors of mouth breathing during deep sedation. The author measured the concentration of nitrous oxide in breathing zone by the change of the scavenging methods. One is drain the gas through the tail part of reservoir bag of Jackson Ree's system naturally. Another is scavenge from tail portion of reservoir bag with negative pressure. Last one is scavenge from nasal mask with negative pressure. The nitrous oxide concentration in breathing zone was the lowest in nasal part drainage but high above the recommended concentration of NIOSH. The order of nitrous concentration in breathing zone was: natural drainage, tail part with negative pressure, nasal part with negative pressure. This would reflect the order of resistance of nasal airway and showed the amount of mouth breathing. From the above experiment, the resistance of nasal airway by the increment of gas flow in corrugating tube and reservoir bag would be one of the causative factors of mouth breathing in deeply sedated patients.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.6
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• pp.69-77
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• 2000

In this paper, the effects of the positions of the potential and current probes on the measurements of the ground resistance and potential gradients with the fall-of-potential method are described and the testing techniques to minimize the measuring errors are proposed. The fall-of-potential method is theoretically based on the potential and current measuring principle and the measuring error is primarily caused by the position and ground resistance of the measuring probes. The ground resistance is calculated by applying the 61.8% and rule in the fall-of-potential method, and then the potential probe is located on the straight line between the grounding electrode to be measured and the current probe. However, sometimes the grounding electrode to be measured and the measuring probes in on-site test might not be arranged on the straight line with adequate distance because there are building, road block, construction and other establishments. Provided that the grounding electrode to be measured and the measuring probes ar out of position on the straight line or have inadequate distance, the measurement of the ground resistance classically falls into an error and the measured ground resistance should be corrected. Measurements were focused on the grounding electrode system made by the ground rods of 2.4m long. It was found that the suitable separation between the grounding electrode to be measured and the current probe is more than 5 times of the length of the grounding electrode to be measured.