• 한국기계가공학회지
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• 제2권3호
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• pp.48-55
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• 2003

This study investigates the effect of temperature and electric field strength on the Bingham characteristics of Electro-Rheological(ER) fluids which change their Yield shear stress and viscosity by temperature and electric field strength. It is found that under constant temperature the Yield sheal stress and viscosity of ER fluids proportionally increase with the applied electric field strength, and under constant applied electric field strength the Yield shear stress and viscosity of ER fluids decrease with the increasing temperature. These results are considered to be applied to the fluid and pneumatic power industry.

• 방사선산업학회지
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• 제10권4호
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• pp.227-230
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• 2016

DWI of biological effects are independent of magnetic field strength in various regions. High field strength, however, does affect the signal to noise ratio (SNR) and artifacts of diffusion weighted imaging (DWI) images, which ultimately will influence the quantitative of diffusion imaging. In this study, the effects of field strength on DWI are reviewed. The effects of the diseases also are discussed. Comparing DWI in cerebellum, WM, GM, Hyperacute region measurements both as a function of field strength (1.5T and 3.0T). Overall, the SNR of the DWI roughly doubled going from 1.5 T to 3.0 T. In summary, DWI studies at 3.0 T is provided significantly improved DWI measurements relative to studies at 1.5T.

• 한국자기학회지
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• 제4권2호
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• pp.150-153
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• 1994

본 연구에서는 2쌍의 헬름홀쯔코일을 사용하여 비본형 시편의 종방향 및 횡방향으로 자기장 을 인가한 상태에서 열처리한 Co-계 비정질 합금 VITROVAC 6030의 보자력 노이즈를 측정하였다. 시편의 종방향 및 횡방향으로 dc 자기장을 인가한 상태에서 열처리한 시편의 경우, 보자력노이즈는 자화주파수 가 1~100 kHz 범위에서 거의 변화하지 않았으며, 시편의 종방향으로 ac 자기장을 횡방향으로는 dc자기 장을 인가한 상태에서 열처리한 시편의 경우의 보자력 노이즈는 자화주파수의 거듭제곱으로 감소하는 경 향을 보였다. 또한 자구핵형성이 일어날 경우 보자력 노이즈는 크게 증가하며 자화주파수의 거듭제곱으 로 감소하는 경향을 보였다.

• Agricultural and Biosystems Engineering
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• 제5권1호
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• pp.10-20
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• 2004

Precision agriculture aims to minimize costs and environmental damage caused by agriculture and to maximize crop yield and profitability, based on information collected at within-field locations. In this process, quantification of soil physical properties, including soil strength, would be useful. To quantify and manage variability in soil strength, there is need for a strength sensor that can take measurements continuously while traveling across the field. In this paper, preliminary analyses were conducted using two datasets available with current technology, (1) cone penetrometer readings collected at different compaction levels and for different soil textures and (2) tillage draft (TD) collected from an entire field. The objective was to provide information useful for design of an on-the-go soil strength profile sensor and for interpretation of sensor test results. Analysis of cone index (CI) profiles led to the selection of a 0.5-m design sensing depth, 10-MPa maximum expected soil strength, and 0.1-MPa sensing resolution. Compaction level, depth, texture, and water content of the soil all affected CI. The effects of these interacting factors on data obtained with the soil strength sensor should be investigated through experiments. Spatial analyses of CI and TD indicated that the on-the-go soil strength sensor should acquire high spatial-resolution, high-frequency ($\ge$ 4 Hz) measurements to capture within-field spatial variability.

• Journal of Positioning, Navigation, and Timing
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• 제3권2호
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• pp.83-90
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• 2014

In this study, to improve an existing ground-wave based time broadcasting system, a study that predicts the field distribution and field strength of the transmitted signal of a new ground-wave based time broadcasting system was performed. The prediction area was assumed to be the Korean peninsula; and to reflect the mountainous terrain of the Korean peninsula in the prediction of the variations of field distribution and field strength, a new prediction method based on the Monteath model was proposed and utilized. As field distribution changes depending on the position of a transmitter station, potential sites for the transmitter station were selected considering the geographical characteristics. In this regard, the ground conductivity information of North Korea cannot be obtained, and thus, the ground conductivity of the North Korean region was reflected considering the geological characteristics of South Korea and North Korea. Based on this, the variations of field distribution and field strength were predicted by setting the Korean peninsula as the prediction area, and the prediction results depending on the position of the transmitter station were discussed.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1997년도 가을 학술발표회 논문집
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• pp.19-36
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• 1997

This paper discusses the reduction and subsequent recovery and increase of shear strength of clay in the vicinity of soil-cement column. Laboratory and field tests were conducted to investigate the effects on surrounding clay during and after soil-cement column installation in soft Ariake clay. Discussions were made on the mechanism of strength changes of clay by considering the thixotropic recovery, reconsolidation effect, penetration of cement slurry and diffusion of exchangeable cations. On the basis of field and laboratory observations, 10 days after column installation, the decreased shear strength of surrounding clay during mixing was recovered and 30 days later, shear strength of surrounding clay increased 30% by average. Therefore, it is recommended that the increase of shear strength of clay can be taken into consideration in the bearing capacity and stability analysis of the composite ground.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 춘계 학술논문 발표대회 1부
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• pp.33-36
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• 2011

Recently, It has increased to use ultra high strength concrete. It is effective to mix organic fibers for preventing spalling. But if fiber mixed, flowability of concrete is decreases. The aim of this study is to evaluation of fire resistance performance for fiber-mixed ultra high strength concrete on field application. As a result, flowability of nylon fiber mixed concrete is better than polyethylene fiber mixed. In non-fiber and polyethylene fiber mixed concrete, spalling occurred. And strain converged at 0.004. Also, residual strength could not evaluate. Nylon fiber mixed concrete is effective to prevent spalling. And it remians 50% residual strength compare with compressive strength at room temperature.

• 방송공학회논문지
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• 제15권6호
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• pp.731-741
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• 2010

본 논문에서는 30 MHz ~ 3000 MHz 대역에서 1 kW ERP에 대해 점-대-지역 전파특성 예측에 이용되는 ITU-R 권고 P.1546 전파 모델을 이용하여 DTV 수신기의 전계강도 예측을 위한 방법을 제안한다. DTV 수신기의 유도된 전계강도 수식과 권고에서 기술된 절차를 이용하여 수치계산을 통한 결과를 제시한다. 또한 산출된 결과의 적절성 검증을 위해 Okumura-Hata 모델과 비교하였으며, 수신 전계강도가 약 6.9 ~ 11.5 % 범위 내에 오차가 있음을 확인할 수 있었다. 제시된 방법은 DTV 수신지역의 전계강도 예측을 통한 송신된 신호의 품질 분석은 물론, 양호한 전파환경 구축을 위한 적절한 국소 선정을 제공한다. 또한 동일 대역의 주파수 공유를 위한 보호비 또는 이격 거리 분석에도 직접 활용이 가능하다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 가을 학술발표회 논문집
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• pp.83-86
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• 1994

High strength concrete increasingly used in various countries. Recently, great attetion is also paid to the high strength concrete in this country. To promote the actual application of high strength concrete, several series of high strength concrete have been made and applied to actual structures. The mechanical properties and the temperature rise due to generation of hydration heat have been also studied. The present study provides a firm base for the actual application of high strength concrete in the field.

• 천문학회지
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• 제26권2호
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• pp.89-98
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• 1993

Magnetostatic models of starspots of late type main sequence stars$(G5V\~K5V)$ have been constructed to investigate their physical characteristics by using the similarity law suggested by Schluter and Temesvary(1958) and later employed by Deinzer(1965) and Yun(1968). The starspots are assumed to be single, circular and in horizontal magnetostatic equilibrium. In the present study we considered only those model spots whose area covers less than $12\%$ of the entire stellar surface as suggested by observations. The computed surface field strength of our model spots ranges from $10^3$\;to\;several\;10^3$ gauss and their magnetic flux is found to be $10\~100$ times that of sunspots. The field strength is sensitive to spectral type, which increases with later spectral type. In contrast to the field strength, the area of starspots depends strongly on the total magnetic flux. Finally, it is noted that the computed field strength of model spots belonging to $G0V\~G5V$ falls below the equipartition field strength at their parent stellar surface unless the coverage is less than $2\%$. This suggests that the observed spot on $G0V\~G5V$ stars is likely to be a group of small starspots.