• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.595-596
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• 2006

Electro-magnetic launcher(EML)는 전자기력을 이용하여 발사체를 추진시키는 장치이다. EML은 크게 레일건의 형태와 코일건의 형태로 구분되며, 본 논문에서는 코일건의 형태로 설계, 제작하였다. 코일건의 형태인 EML은 솔레노이드에 여자되는 전류에 의해서 발사체에 흡인력이 발생하여 추진, 가속되므로 솔레노이드의 최적형태를 설계하고, 이를 바탕으로 제작하여 EML의 스위칭 시간에 따른 속도를 측정하여 여자전류의 스위칭 시간에 따른 동작특성을 해석, 실험하여 분석하였다.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.5
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• pp.27-35
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• 2010

A loader used for uploading materials into truck is a kind of construction equipment. Mainly, a wheel loader is applied to construction work. Recently, an automatic transmission for the wheel loader is used to help drivers get the repetitive works done comfortably. It is composed of geartrain, clutch pack, hydraulic control system and TCU. Especially, a high-performance proportional control valve and its control algorithm is demanded to achieve the shift quality during a change of speed. In this paper, the commercial package program was used in order to justify model of the proportional control valve and simulate it. Steady-state and dynamic characteristics of PCV were analyzed to classify attractive forces and hydraulic control characteristics. This model also was verified the validity compared to the experimental result. Using the developed model, performances of PCV were predicted as studying design parameters.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.5
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• pp.37-42
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• 1998

This study was performed to evaluate the characteristics of volume change is unsaturated clayed soil. The medium-plastic clay was selected and compacted by 50% of Proctor standard compaction energy at 6% higher moisture content than its OMC. A series of isotropic compression tests and triaxial shear tests were performed. The results of the study are summarized as follows. At each matric suction, when the matric suction was increased, the yield stress was increased and slope of volume change was decreased. The more net mean stress was, the less the quantity of volume change was. In shear test, the volumetric strain was much rapidly changed in large matric than in low matric suctions. But the effect of matric suction to volume change disappeared under high net mean stress. At lower deviator stress the more matric suction was, the higher volume change was. But As the matric suction was increasing, the behavior of the unsaturated clayey soil was similar to that of saturated clayey soil. Volume change in the unsaturated clayey soil can be represented as a unique plane in three-dimensional space, which is the axes of net mean stress, matric suction and void ratio.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.3
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• pp.101-110
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• 1996

The aim of the work described in this paper is to develope a constitutive model for the prediction of an unsaturated clayey soil and to confirm the application of the model. To this end a series of suction controlled isotropic and triaxial compression tests are conducted on clayey soils. Matric suction is controlled by the axis translation technique using high air entry ceramic disk. Total volume change, air and water volume changes are measured by the device made for the experiment. The specimens are compacted by dynamic compaction using a half of Proctor compaction energy with the water contents of 5% drier than the optimum moisture contents. From test results, volume changes and deviator stresses are analyzed at each state and their relationships are formulated. And the application of the model to clayey soils is confirmed by the comparison between test and predicted results. During drying-wetting and loading-unloading processes for isotropic states, the agreement between predicted and test results are satisfactory. And predicted deviator stresses are well agreed with the test results in shearing process, but volumetric strain is not well agreed with the test results in high suctions.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.1
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• pp.26-32
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• 1997

In this paper, numerical analysis of dynamic characteristics for the plunger-type solenoid was used for a high speed solenoid valve with fast switching is discussed. The theoretic analysis of the electromagnetic field including eddy currents in the solenoid is studied by using permeance. The optimum value of design parameters which are a mass and an area of the plunger, a source voltage, a elastic modulus of the spring, a stroke, a number of turns, are obtained by the results of the investigation on effect of a parameter on others. And dynamic characteristics of acting solenoid that is the variation of magnetic force, displacement, solenoid current are investigated.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1721-1722
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• 2006

Electro-magnetic launcher(EML)는 전자기력을 이용하여 발사체를 추진시키는 장치이다. EML은 크게 레일건의 형태와 코일건의 형태로 구분되며, 본 논문에서는 코일건의 형태로 설계, 제작하였다. 코일건의 형태인 EML은 솔레노이드에 여자되는 전류에 의해서 발사체에 흡인력이 발생하여 추진, 가속되므로 솔레노이드의 최적형태를 설계하고, 이를 바탕으로 제작하여 EML의 스위칭 시간에 따른 속도를 측정하여, 여자전류의 스위칭 시간에 따른 동작특성을 해석, 실험하여 분석하였다.

• Journal of the Korean Geotechnical Society
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• v.24 no.1
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• pp.5-13
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• 2008

The coefficient of permeability for a soil can be determined by the direct or the indirect method. The direct method of permeability can be performed either in the laboratory or in the field. The indirect method can be predicted from the soil-water characteristic curve. In this study, the coefficient of permeability for an unsaturated soil was determined by the modified apparatus of steady-state method (Klute, 1972) and was predicted from the equations of Brooks & Corey (1964) and van Genuchten (1980). The experimental results were compared with predicted coefficient of permeability and the applicability of the two equations (from Brooks & Corey, van Genuchten) was reviewed.

• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.57-64
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• 2007

Since matric suction of unsaturated soil was related to soil and ground water contaminations, it is very important to analyze its mechanism that was represented by shear characteristics. In three phases of soil, a little air makes the condition of unsaturated soil on contract or shrinkage surface between water and air. Capillarity and suction in pore of unsaturated soil cause surface tension and surface force so it makes negative pore water pressure and increases effective stress as a result. Therefore, negative pore water pressure in partially saturated soil affects the soil structure and degree of saturation and it is important to evaluate accurately unsaturate flow and behavior. In this study, the shear strength characteristics of the seven sandy soils were investigated using consolidated drained triaxial tests with special emphasis on the effects of the negative pore pressure and the matric suction. These tests involved shearing under either a constant net confining pressure and varying matric suction or under a constant matric suction and varying net normal stress.

• Pediatric Infection and Vaccine
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• v.30 no.3
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• pp.159-164
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• 2023

A brain abscess is a potentially life-threatening infection of the brain that can be challenging to diagnose, especially in children. In this report, we describe a case of a central nervous system infection caused by rare pathogens in an immunocompetent child. A 10-year-old female presented with a severe headache lasting 10 days, along with flashing lights, nausea, and vomiting. The patient was diagnosed with secundum atrial septal defect 7 years ago and underwent dental work for cavities one month prior to admission. Brain magnetic resonance imaging (MRI) showed a 4.2 cm sized brain abscess in the right parietal lobe, causing left inferior quadrantanopia. A craniotomy and abscess aspiration surgery were performed, and cultures from the aspirated pus and tissue revealed Aggregatibacter aphrophilus. Additionally, Actinomyces georgiae was identified through 16S rRNA sequencing. After 8 weeks of antimicrobial therapy with ampicillin-sulbactam, the patient was discharged without any complications. A follow-up brain MRI showed complete resolution of the abscess and edema.

• Journal of Veterinary Clinics
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• v.25 no.4
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• pp.257-262
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• 2008

Renal ischemia-reperfusion injury is great clinical important because viability of the transplanted organ depends on the tolerance of the graft to ischemia-reperfusion injury, an inevitable processing during surgery. The purpose of this study was to investigate the effects of irrigation-aspiration in ischemia-reperfusion injury model induced by cross-clamping of renal vessels. Blood samples were collected from these dogs for measurement of kidney function and antioxidant enzyme activity, and RI at the intrarenal artery was measured at different time intervals. And the kidneys were taken for histopathologic evaluation at day 14. Kidney function (Cr and BUN) showed a significant increasing in untreated group compared to treated group. Resistive index of intrarenal artery was no significant difference among the groups. Activity of antioxidant enzymes in plasma was significant decrease in untreated group compare to control group while in treated group was no significant difference compared to control group. In histopathologic finding, treated group was showed less damage than that of untreated group. This result suggests that the processing of irrigation-aspiration is useful to reducing ischemia-reperfusion injury.