• Progress in Superconductivity
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• v.8 no.1
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• pp.33-39
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• 2006

We have developed a second-order double relaxation oscillation SQUID(DROS) gradiometer with a baseline of 35 mm, and constructed a poorly magnetically-shielded room(MSR) with an aluminum layer and permalloy layers for magnetocardiography(MCG). The 2nd-order DROS gradiometer has a noise level of 20 $fT/{\surd}Hz$ at 1 Hz and 8 $fT/{\surd}Hz$ at 200 Hz inside the heavily-shielded MSR with a shielding factor of $10^3$ at 1 Hz and $10^4-10^5$ at 100 Hz. The poorly-shielded MSR, built of a 12-mm-thick aluminum layer and 4-6 permalloy layers of 0.35 mm thickness, is 2.4mx2.4mx2.4m in size, and has a shielding factor of 40 at 1 Hz, $10^4$ at 100 Hz. Our 64-channel second-order gradiometer MCG system consists of 64 2nd-order DROS gradiometers, flux-locked loop electronics, and analog signal processors. With the 2nd-order DROS gradiometers and flux-locked loop electronics installed inside the poorly-shielded MSR, and with the analog signal processor installed outside it, the noise level was measured to be 20 $fT/{\surd}Hz$ at 1 Hz and 8 $fT/{\surd}Hz$ at 200 Hz on the average even though the MSR door is open. This result leads to a low noise level, low enough to obtain a human MCG at the same level as that measured in the heavily-shielded MSR. However, filters or active shielding is needed fur clear MCG when there is large low-frequency noise from heavy air conditioning or large ac power consumption near the poorly-shielded MSR.

• Wind and Structures
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• v.3 no.3
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• pp.177-191
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• 2000

This paper presents an approach for evaluating directionality effects for both wind speeds and wind loads in hurricane-prone regions. The focus of this study is on directional wind loads on low-rise structures. Using event-based simulation, hurricane directionality effects are determined for an open-terrain condition at various locations in the southeastern United States. The wind speed (or wind load) directionality factor, defined as the ratio of the N-year mean recurrence interval (MRI) wind speed (or wind load) in each direction to the non-directional N-year MRI wind speed (or wind load), is less than one but increases toward unity with increasing MRI. Thus, the degree of conservatism that results from neglecting directionality effects decreases with increasing MRI. It may be desirable to account for local exposure effects (siting effects such as shielding, orientation, etc.) in design. To account for these effects in a directionality adjustment, the factor described above for open terrain would need to be transformed to other terrains/exposures. A "local" directionality factor, therefore, must effectively combine these two adjustments (event directionality and siting or local exposure directionality). By also considering the direction-specific aerodynamic coefficient, a direction-dependent wind load can be evaluated. While the data necessary to make predictions of directional wind loads may not routinely be available in the case of low-rise structures, the concept is discussed and illustrated in this paper.

• Progress in Superconductivity
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• v.10 no.2
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• pp.139-143
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• 2009

We have fabricated a low-noise 61-channel axial-type first-order gradiometer system for measuring fetal magnetocardiography(MCG) signals. Superconducting quantum interference device(SQUID) sensor was based on double relaxation oscillation SQUID(DROS) for detecting biomagnetic signal, such as MCG, magnetoencphalogram(MEG) and fetal-MCG. The SQUID sensor detected axial component of fetal MCG signal. The pickup coil of SQUID sensor was wound with 120 ${\mu}m$ NbTi wire on bobbin(20 mm diameter) and was a first-order gradiometer to reject the environment noise. The sensors have low white noise of 3 $fT/Hz^{1/2}$ at 100 Hz on average. The fetal MCG was measured from $24{\sim}36$ weeks fetus in a magnetically shielded room(MSR) with shielding factor of 35 dB at 0.1 Hz and 80 dB at 100 Hz(comparatively mild shielding). The MCG signal contained maternal and fetal MCG. Fetal MCG could be distinguished relatively easily from maternal MCG by using independent component analysis(ICA) filter. In addition, we could observe T peak as well as QRS wave, respectively. It will be useful in detecting fetal cardiac diseases.

• Nuclear Engineering and Technology
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• v.51 no.8
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• pp.2018-2025
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• 2019

This study systematically compared two hybrid deterministic/Monte Carlo transport codes, ADVANTG/MCNP and MAVRIC, in solving a difficult shielding problem for a real-world spent fuel storage cask. Both hybrid codes were developed based on the consistent adjoint driven importance sampling (CADIS) methodology but with different implementations. The dose rate distributions on the cask surface were of primary interest and their predicted results were compared with each other and with a straightforward MCNP calculation as a baseline case. Forward-Weighted CADIS was applied for optimization toward uniform statistical uncertainties for all tallies on the cask surface. Both ADVANTG/MCNP and MAVRIC achieved substantial improvements in overall computational efficiencies, especially for gamma-ray transport. Compared with the continuous-energy ADVANTG/MCNP calculations, the coarse-group MAVRIC calculations underestimated the neutron dose rates on the cask's side surface by an approximate factor of two and slightly overestimated the dose rates on the cask's top and side surfaces for fuel gamma and hardware gamma sources because of the impact of multigroup approximation. The fine-group MAVRIC calculations improved to a certain extent and the addition of continuous-energy treatment to the Monte Carlo code in the latest MAVRIC sequence greatly reduced these discrepancies. For the two continuous-energy calculations of ADVANTG/MCNP and MAVRIC, a remaining difference of approximately 30% between the neutron dose rates on the cask's side surface resulted from inconsistent use of thermal scattering treatment of hydrogen in concrete.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.12 s.354
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• pp.83-88
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• 2006

In this paper, we propose a new cross bar embedded structure for improvement of attenuation characteristics along the different lossy media. A general characterization procedure based on the extraction of the characteristic impedance and propagation constant for analyzing a single MIS(Metal-Insulator-Semiconductor) transmission line used and an analysis for a new substrate shielding MIS structure consisting of grounded crossbars at the interface between Si and Sio2 layer using the Finite-Difference Time-Domain(FDTD) technique is used. In order to reduce the substrate effects on the transmission line characteristics, a shielding structure consisting of grounded cross bar lines over time-domain signal has been examined. The extracted, distributed frequency-dependent transmission line parameters as well as the line voltages and currents, and also corresponding equivalent circuit parameters have been examined as function of frequency. It is shown that the quality factor of the transmission line can be improved without significant changes in the characteristic impedance and effective dielectric constant.

• Nuclear Engineering and Technology
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• v.47 no.7
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• pp.791-803
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• 2015

The effective cross sections (XSs) in the direct whole core calculation code nTRACER are evaluated by the equivalence theory-based resonance-integral-table method using the WIMS-based library as an alternative to the subgroup method. The background XSs, as well as the Dancoff correction factors, were evaluated by the enhanced neutron-current method. A method, with pointwise microscopic XSs on a union-lethargy grid, was used for the generation of resonance-interference factors (RIFs) for mixed resonant absorbers. This method was modified by the intermediate-resonance approximation by replacing the potential XSs for the non-absorbing moderator nuclides with the background XSs and neglecting the resonance-elastic scattering. The resonance-escape probability was implemented to incorporate the energy self-shielding effect in the spectrum. The XSs were improved using the proposed method as compared to the narrow resonance infinite massbased method. The RIFs were improved by 1% in $^{235}U$, 7% in $^{239}Pu$, and >2% in $^{240}Pu$. To account for thermal feedback, a new feature was incorporated with the interpolation of pre-generated RIFs at the multigroup level and the results compared with the conventional resonance-interference model. This method provided adequate results in terms of XSs and k-eff. The results were verified first by the comparison of RIFs with the exact RIFs, and then comparing the XSs with the McCARD calculations for the homogeneous configurations, with burned fuel containing a mixture of resonant nuclides at different burnups and temperatures. The RIFs and XSs for the mixture showed good agreement, which verified the accuracy of the RIF evaluation using the proposed method. The method was then verified by comparing the XSs for the virtual environment for reactor applicationbenchmark pin-cell problem, as well as the heterogeneous pin cell containing burned fuel with McCARD. The method works well for homogeneous, as well as heterogeneous configurations.

• Journal of the Korean earth science society
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• v.38 no.7
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• pp.481-495
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• 2017

The purpose of this study is to investigate and analyze the relationship between meteorologicalclimatic factors and fruit property data from Aronia sampling points during May to August 2016 in the Danyang area. For this purpose, we investigated the meteorological factor, the physicalchemical property of fruit and soil, and the property change of fruit according to the setting of rain and daylight shielding from Aronia sampling points. The result indicate that first, meteorologicalclimatic factors such as the maximum air temperature, the accumulated precipitation, the relative humidity, and daylight hours are a positive influence on products and maintenance of quality of Aronia as well as a suitable field for cultivating Aronia in the Danyang. However, a strong wind in April and May deeply affects the falling phenomenon of the flowering and blooming season. Second, the quality and products of Aronia show the high correlation coefficients of more than 0.9 with agricultural meteorologicalclimatic factors such as daily maximum temperature, daily soil temp, daily soil pH, cumulated precipitation, and daily soil humidity. Also, they can be predicted by the regression equations using these factors. Third, it is necessary to maintain the rain shielding in these fields because antocyanin and saccharinity components within Aronia decreased in case of heavy rainfalls. And, the result of regression analysis saccharinity and antocyanin within aronia from normal fields and rain shieldingfields at Aronia sampling points show a high correlation, respectively.

• Journal of the Korean Society of Radiology
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• v.8 no.7
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• pp.449-454
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• 2014

The purpose of this study is(was) to investigate the shielding ratio of 1 mmPb and the off axis ratio outside the field edge at depth of 1 cm from a phantom surface for 6 MV photon beam. A dose of 180 cGy was delivered to a depth of 10 cm for a $10{\times}10cm^2$ and $15{\times}15cm^2$ field in the SAD technique. The off axis ratio was calculated by measuring the dose of optically stimulated luminescent nanoDot dosimeters(OSLnDs) positioned at 2, 4 and 6 cm from the field edge, and the center axis of field. And the shielding ratio of 1 mmPb was calculated by measuring the dose of OSLnDs positioned at 2, 4 and 6 cm from the field edge.. As a result, for a $10{\times}10cm^2$ and $15{\times}15cm^2$ field, the off axis ratios were acquired 0.008-0.023 and 0.011-0.028, respectively. Also the shielding ratios of 1 mmPb were acquired 0.868-0.888 and 0.807-0.842, respectively. These results provide data to protect organs at risk outside the radiation treatment field.

• Journal of the Korean Society of Radiology
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• v.3 no.3
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• pp.23-25
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• 2009

Gd-157 material has very large neutron capture cross section in the thermal region. So it is very useful to shield material for thermal neutrons. Futhermore, in the neutron capture experiment and calculation, the neutron absorption and scattering are very important. Especially these effects are conspicuous in the resonance energy region and below the thermal energy region. In the case of very narrow resonance, the effect of scattering is to be more considerable factor. In the present study, we obtained energy dependent neutron absorption ratios of natural indium in energy region from 0.003 to 100 keV by MCNP-4B Code. The coefficients for neutron absorption was calculated for circular type and 1 mm thickness. In the lower energy region, neutron absorption is larger than higher region, because of large capture cross section (1/v). Furthermore it seems very different neutron absorption in the large resonance energy region. These results are very useful to decide the thickness of sample and shielding materials.

• Proceedings of the KWS Conference
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• v.43
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• pp.171-173
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• 2004

Electromagnetic force is one of the most important factor that effect on metal transfer mode, short-circuit rate, spatter generation rate and mechanical properties of weld metal etc. Also, shielding gas and welding current have influence on metal transfer mode in GMAW. In this paper, different ways for external electromagnetic forces are applied by attaching cylindrically rounded conducting wire solenoid on touch tip holding. With the applied electromagnetic field, the arc transfer mode changes from normal mode to rotating mode and spatter generation decreased in electromagnetic fields(N-pole). In MIG welding, the influences of electromagnetic force on the spatter generation showed different tendency as in the $CO_2$ welding. It is possible reasons were discussed.