• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.2
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• pp.59-61
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• 2006

In our country most of transmission lines are double-circuit lines. In these lines, the combining method of increasing conductor height and installation of passive shield-loop to mitigate magnetic field near a transmission line, is a good and feasible method. The basic principle of passive shield loop is that the field from the current induced in the shield loop conductors counteracts the field from the phase conductors. This method applied to domestic transmission lines to meet the magnetic field level, 100, 30, 10 and 4 mG, respectively. In each magnetic field level, the minimum conductor height and passive loop height are presented for the implementation of the practical design.

• Journal of Korean Society for Atmospheric Environment
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• v.8 no.2
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• pp.93-99
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• 1992

Recently a passive $NO_2$ samplers have been frequently used for the measurement of $NO_2$ concentration in the atmosphere because of its simplicity and high accuracy. But these samplers have a defect that the amount of $NO_2$ adsorbed is increased by wind. In this study, the inlet of sampler was covered with a draft shield made by 325 mesh stainless sieve to eliminate the effect. But it was expected that $NO_2$ diffusion was interrupted by the draft shield. In order to conform this phenomenon, samplers with and without draft shield were exposed to a box filled with 1-1.1ppm $NO_2$. The result indicated that draft shield nearly did not disturb $NO_2$ diffusion. To protect samplers from dust, sunshine, precipitation and vertical wind effects, these samplers were placed into a shelter during the field test. The data obtained in this study was compared with the data from the ambient air monitoring network. The coefficient of correlation(r) between the two data was 0.9995 for the test period of up to 35days. The results of this study indicate that the type of $NO_2$ samplers with draft shield in shelter used in this study can be used for measuring $NO_2$ concentrations in the ambient air relatively for a long period over 30 days.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.6
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• pp.421-430
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• 2000

This paper describes an optimal design method which is applied a weighted least square (WLS) method for Magnetic Resonance Imaging (MRI) system. An optimal design approach is presented for a homogeneity superconducting magnet with the superconducting active shield especially for a magnetic resonance imaging system. The WLS is used to obtain the optimal configurations using the least amount and minimum volume of conductor, exhibiting the smallest level of field inhomogeneity and resulting in the least level of stray field. The proposed model is used to design a multiple-shield configuration for a 1.5 T MRI magnet. The field homogeneity is required less than 5 gauss stray field contour within 4m axially and 3m radially from origin. The designed magnet with the actively magnetic shielding coil out of main coils is analyzed by FEM and theoretical analysis method, investigated the field homogeneity.

• Journal of Magnetics
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• v.18 no.1
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• pp.9-13
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• 2013

Shielding effects in conductive and magnetic materials were investigated as a function of properties, thickness and diameter. In this work, evaluations on passive conductive and magnetic shield specimens were achieved through experimentation set-up using 50 Hz single and three phase induction field sources. Analysis on material microstructure properties and characteristics of shielding specimens were performed with the use of vibrating sample magnetometer (VSM) and field emission scanning electron microscopy (FESEM). An induction field at $136{\mu}T$ of single phase system and $50{\mu}T$ of three phase systems were observed to the shield specimens with the thickness ranged of 0.2 mm to 0.4 mm. It is observed that shield specimen efficiency becomes inversely proportionate to the increment of induction fields. The decrease was attributed to the surface structure texture which relates to the crystallization and non-crystallization geometrical effects.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.4
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• pp.470-480
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• 2016

The reversal of a silicon chip to find out its security structure is common and possible at the present time. Thanks to reversing, it is possible to use a probing attack to obtain useful information such as personal information or a cryptographic key. For this reason, security-related blocks such as DES (Data Encryption Standard), AES (Advanced Encryption Standard), and RSA (Rivest Shamir Adleman) engines should be located in the lower layer of the chip to guard against a probing attack; in this regard, the addition of a silicon-surface-protection layer onto the chip surface is a crucial protective measure. But, for manufacturers, the implementation of an additional silicon layer is burdensome, because the addition of just one layer to a chip significantly increases the overall production cost; furthermore, the chip size is increased due to the bulk of the secure logic part and routing area of the silicon protection layer. To resolve this issue, this paper proposes a practical silicon-surface-protection method using a metal layer that increases the security level of the chip while minimizing its size and cost. The proposed method uses a shift register for the alternation and variation of the metal-layer data, and the inter-connection area is removed to minimize the size and cost of the chip in a more extensive manner than related methods.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1199-1213
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• 2011

Slurry type shield would be very effective for the tunnelling in a sandy ground, but low slurry pressure could cause a tunnel face failure or a ground settlement in front of the tunnel face. Thus, the stability of tunnel face could be maintained by applying an excess slurry pressure that is larger than the active earth pressure. However, the slurry pressure should increase properly because an excessively high slurry pressure could cause the slurry flow out or the passive failure of the frontal ground. It is possible to apply the high slurry pressure without passive failure if a horizontal impermeable layer is located in the ground in front of the tunnel face, but its location, size, and effects are not clearly known yet. In this research, two-dimensional model tests were carried out in order to find out the effect of a horizontal impermeable layer for the slurry shield tunnelling in a saturated sandy ground. As results, larger slurry pressure could be applied to increase the stability of the tunnel face when the impermeable layer was located in the ground above the crown in front of the tunnel face. The most effective length of the impermeable grouting layer was 1.0~1.5D, and the location was 1.0D above the crown level. The safety factor could be suggested as the ratio of the maximum slurry pressure to the active earth pressure at the tunnel face. It could also be suggested that the slurry pressure in the magnitude of 3.5~4.0 times larger than the active earth pressure at the initial tunnel face could be applied if the impermeable layer was constructed at the optimal location.

• Journal of Biomedical Engineering Research
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• v.16 no.3
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• pp.301-308
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• 1995

A high-precision pre-amplifier is designed for general use in EEG measurement system. It consists of signal generator, signal amplifier with a impedance converter, shield driver, body driver, differential amplifier, and isolation amplifier. The combination of minimum use of inaccurate passive components and the appropriate matching of each monolithic amplifiers results in good noise behavior, low leakage current, high CMRR, high input impedance, and high IMRR. The performance of EEG pre-amplifier has been verified by showing the typical EEG pattevn of a nomad person through the clinical experiments.

• Nuclear Engineering and Technology
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• v.30 no.1
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• pp.26-39
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• 1998

The containment pressure and temperature transient analysis computer code CONTEMPT4/MOD5 is modified to incorporate the passive containment cooling models. The correlations are selected from the existing experimental heat transfer correlations to model the natural and mixed convection in annular space between the containment shell and the shield building. The evaporative heat transfer of the water film on the outer shell of the containment is modeled using the correlations derived from the analogy between the heat and mass transfer. The modified code is applied to the Ap600 containment transient analysis for the model verification and the results are compared to the results of GOTHIC calculation done by Westinghouse. Also, d series of parametric sensitivity studies of heat transfer correlations, water film ratio and delay time of the wet cooling on the containment peak pressure and temperature following LOCA are performed for the containment of 1000MWe passive plant, KP1000.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2361-2369
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• 2020

Compton cameras using large scintillators have been developed for high imaging sensitivity. These scintillator-based Compton cameras, however, mainly due to relatively low energy resolution, suffer from undesired background-radiation signals, especially when radioactive materials' activity is very low or their location is far from the Compton camera. To alleviate this problem for a large-size Compton camera, in the present study, a hybrid-type shielding system was designed that combines an active shield with a veto detector and a passive shield that surrounds the active shield. Then, the performance of the hybrid shielding system was predicted, by Monte Carlo radiation transport simulation using Geant4, in terms of minimum detectable activity (MDA), signal-to-noise ratio (SNR), and image resolution. Our simulation results show that, for the most cases, the hybrid shielding system significantly improves the performance of the large-size Compton camera. For the cases investigated in the present study, the use of the shielding system decreased the MDA by about 1.4, 1.6, and 1.3 times, increased the SNR by 1.2-1.9, 1.1-1.7, and 1.3-2.1 times, and improved the image resolution (i.e., reduced the FWHM) by 7-8, 1-6, and 3-5% for ¹³⁷Cs, ⁶⁰Co, and ¹³¹I point source located at 1-5 m from the imaging system, respectively.

• Nuclear Engineering and Technology
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• v.45 no.4
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• pp.459-468
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• 2013

During a station blackout (SBO), the initiating event is a loss of Class IV and Class III power, causing the loss of the pumps, used in systems such as the primary heat transporting system (PHTS), moderator cooling, shield cooling, steam generator feed water, and re-circulating cooling water. The reference case of the SBO case does not credit any of these active heat sinks, but only relies on the passive heat sinks, particularly the initial water inventories of the PHTS, moderator, steam generator secondary side, end shields, and reactor vault. The reference analysis is followed by a series of sensitivity cases assuming certain system availabilities, in order to assess their mitigating effects. This paper also establishes the strategies to mitigate SBO accidents. Current studies and strategies use the computer code of the Integrated Severe Accident Analysis Code (ISAAC) for Wolsong plants. The analysis results demonstrate that appropriate strategies to mitigate SBO accidents are established and, in addition, the symptoms of the SBO processes are understood.