• 한국자동차공학회논문집
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• 제9권1호
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• pp.102-111
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• 2001

To describe the air flow characteristics within an air cleaner cover and mass air flow sensor (MAFS) entry region installed in a 3.0L engine air induction system, flow visualization, velocity and turbulence intensity measurements were taken in several view planes. A detailed knowledge of the interaction between the design parameters and the flow structures will enhance our understanding of the motions within the flow field and enable engineers to optimize the induction system and reduce the signal-to-noise ratio in the MAFS output. Emphasis is placed on the analysis of coherent motions and the controlling parameters which affect the air flow in the MAFS entrance region over a flow rate of 13-240 kg/hr. The high speed motion pictures illustrated that the air flow generated within the air cleaner cover under steady state condition is quite complex. In both axial and radial planes of the main passage it was found that the flow pattern is remarkably influenced by the air cleaner cover and main passage configuration. A comparison of the flow patterns and measurements in the original and modified air cleaner cover is presented. Measurements from the MAFS indicated an significant reduction in pressure drop and signal noise for the modified cover as compared with the original cover, over an air flow rate of 13-240 kg/hr.

• 대한의용생체공학회:의공학회지
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• 제19권2호
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• pp.177-182
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• 1998

본 연구에서는 체내의 티타늄, 보철물, malalignment, 측정범위, 그리고 보철물 distal flare등이 전산화단층(CT) 촬영으로 골밀도를 축정할때에 미치는 영향을 조사하였다. 8구의 남성 사체로부터 대퇴골과 경골을 각각 8개씩 얻었으며 경골의 상부에 위치해있는 해면골 부분에서 15개의 평행사변형 시편을 만들었다. 평행사변형 시편과 대퇴골을 CT 스캔받침대의 중앙에 바로 놓았을때와 조금 떨어져 놓았을 때 그리고 티타늄 보철물을 체내에 넣었을 경우와 그렇지 않았을 경우 모두에 대해서 각각 스캔하였다. 이때 얻어진 CT 영상자료는 측정범위를 10cm와 30cm로 해서 재구성 하였다. 그리고 골밀도는 영상분석 소프트웨어을 사용하여 측정하였다. 그 결과 시편을 CT 스캔받침의 중앙에 놓았을 경우에는 그렇지 않았을 경우에 비해 골밀도 평균값의 상대차이가 피질골과 해면골 모두에 대해서 1% 미만이었다. 그러나 보철물의 malalignment와 distal flare는 골밀도의 측정값에 상당히 영향을 미쳤다. 체내에 티타늄 보철물의 존재여부는 시편을 CT 스캔받침대의 중앙에 놓았을 경우에는 피질골 뿐만 아니라 해면골 골밀도 측정값에 영향을 미치지 않았다. 그러나 체내에 티타늄 보철물의 존재가 malalignment 효과와 합쳐졌을때에는 골밀도 측정값이 많은 차이를 드러내었다.

• 천문학회지
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• 제37권5호
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• pp.355-359
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• 2004

Differential Faraday Rotation measurements between the images of same background source, of multiply-imaged gravitational lens systems can be effectively used to provide a valuable probe to establish the existence of large-scale ordered magnetic fields in lensing galaxies as well as galaxy clusters. Estimates of the magnetic field in lens galaxies, based on the radio polarization measurements do not appear to show any clear evidence for evolution with redhsift of the coherent large scale magnetic field between redshift of 0.9 and the present epoch. However, our method clearly establishes the presence of coherent large scale magnetic field in giant ellitpical galaxies.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.271-273
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• 2002

The ac loss in Bi-2223 tapes has been studied by a magnetic method. A brief overview of the theoretical background and the experimental set-up is presented. Measurements are made at 77 K in a magnetic fields. The magnitude of the ac loss indicates that filaments are fully coupled, which agrees with theory. As in other measurements, the loss in perpendicular field is larger than that in the parallel field by about a factor 10, which is close to the aspect ratio of the tape.

• Journal of Electrical Engineering and Technology
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• 제2권3호
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• pp.306-311
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• 2007

The transient fields generated during switching operations in a Gas Insulated Substation (GIS) are associated with high frequency components in the order of few tens of MHz. These transient fields leak into the external environment of the gas-insulated equipment and can interfere with the nearby electronics. Measurements of the transient fields are thus required to characterise the interference caused by switching phenomena in such substations. In view of the above, E-field emission measurement during a switching operation has been carried out for a 245 kV GIS model, using a resonant dipole antenna and D-dot sensor. The characteristics of the E-fields i.e., frequency spectra and their levels have been analysed and are reported in the paper. Suitability of the measurements has been confirmed by comparing frequency spectra of the measured and computed transient fields.

• Wind and Structures
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• 제6권3호
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• pp.221-248
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• 2003

The design of high-rise building is often influenced by wind-induced motions such as accelerations and lateral deflections. Consequently, the building's structural stiffness and dynamic (vibration periods and damping) properties become important parameters in the determination of such motions. The approximate methods and empirical expressions used to quantify these parameters at the design phase tend to yield values significantly different from each other. In view of this, there is a need to examine how actual buildings in the field respond to dynamic wind loading in order to ascertain a more realistic model for the dynamic behavior of buildings. This paper describes the findings from full-scale measurements of the wind-induced response of typical high-rise buildings in Singapore, and recommends an empirical forecast model for periods of vibration of typical buildings in Singapore, an appropriate computer model for determining the periods of vibration, and appropriate expressions which relate the wind speed to accelerations in buildings based on wind tunnel force balance model test and field results.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권5호
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• pp.455-462
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• 2015

H-field EMI measurements have been performed for the single-ended, the differential, and the pseudo-differential signaling on a 11" FR4 microstrip line. The pseudo-differential signaling reduces EMI by more than 10 dB compared to the single-ended signaling if the delay mismatch is lower than 5% of a period for a 3 GHz clock signal. Empirical H-field equations for both differential and single-ended signaling showed fair agreements with measurements.

• 설비공학논문집
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• 제16권4호
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• pp.383-389
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• 2004

Magnetic refrigeration is based on the magnetocaloric effect (MCE) - the ability of some materials to heat up when magnetized and cool down when removed from the magnetic field. The available techniques for studying the MCE we: (1) direct measurements by monitoring the change in the material's temperature during the application or removal of the magnetic field; and (2) indirect calculations from the experimental data of magnetization and/or specific heat as a function of the temperature and magnetic field. The MCE of gadolinium (Gd) has been demonstrated by direct measurements of temperature change, and isothermal magnetic entropy changes and adiabatic temperature changes have been calculated.

• Carbon letters
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• 제13권4호
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• pp.248-253
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• 2012

Dielectrophoretic filtering and alignment of single-walled carbon nanotubes (SWCNTs) were tested using deuterium oxide as a solvent. A solution of deuterium oxide-SWCNTs was dropped on top of a silicon chip and an ac electric field was applied between pre-defined electrodes. Deuterium oxide was found to be a better solvent than hydrogen oxide for the dielectrophoresis process with higher efficiency of filtering. This was demonstrated by comparing Raman spectra measured on the initial solution with those measured on the filtered solution. We found that the aligned nanotubes along the electric field were not deposited on the substrate but suspended in solution, forming chain-like structures along the field lines. This so-called pearl chain formation of CNTs was verified by electrical measurements through the aligned tubes. The solution was frozen in liquid nitrogen prior to the electrical measurements to maintain the chain formation. The current-voltage characteristics for the sample demonstrate the existence of conduction channels in the solution, which are associated with the SWCNT chain structures.

• 한국지반공학회논문집
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• 제20권6호
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• pp.119-126
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• 2004

본 논문에서는 현장계측을 통해 관측된 소일네일링 벽체의 거동을 분석하였다. 연구의 주요내용으로는 인발시험을 통해 산정한 네일과 지반의 경계면에서 전단강도의 발생, 지반의 수평변위, 네일에 발생하는 인장력의 분포 및 경계면에서의 전단강도의 발현 등이다. 특히, 경계면에서의 전단응력 발생 과정 및 전단강도 발현에 대한 심도있는 분석을 실시하였다. 본 연구에서 분석된 자료는 국내 소일네일링의 예비설계 단계시 참고 자료로 활용될 수 있을 것으로 기대된다.