• Journal of Energy Engineering
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• v.24 no.4
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• pp.159-165
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• 2015

The article presents a parametric study on geometrical design optimization for coupling the joint between a large exhaust air chimney and electromagnetic pulse (EMP) shield for gas turbine electricity generator. We conducted computational fluid dynamics (CFD) simulations on hydraulic diameters of waveguide below cutoff(WBC) ranges 800mm~1025mm, the connection distance ranges 150~450mm, and exhaust gas flow velocities at 15, 20, and 25m/s. The results show that the diameter of main chimney, connection distance, and exhaust gas velocity had impacts on flow stream at the EMP shield. To provide a fully developed stream line at three different flow velocity cases, the WBC diameter and distance of connection should be larger than 1050mm and longer than 300mm, respectively.

• Journal of the Korea Institute of Building Construction
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• v.13 no.6
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• pp.579-584
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• 2013

The stable fueling and water supply should be prerequisites to guarantee the operational sustainment of military command post. Meanwhile, in terms of the operational sustainment, it is verified that the current wave-guided below cutoff (WBC) system cannot satisfy the requirement of control associated with water supply and fueling within the command post. In this study, as the dielectric substance can block electromagnetic pulse (EMP), it was tried to identify the shielding effectiveness of the multi WBCs filled with water and diesel for attenuating the EMP effect using experiment based on the MIL STD 188-125-1. According to the experimental results, used water in the experiment show the shielding effectiveness from around 640 MHz frequency because of minerals contained in the water. Furthermore, it was noted that EMP attenuating strength of the WBC filled with diesel was enlarged from around 1,680 MHz frequency. Resultingly, it could be concluded that it is enough to supply stable water and diesel through the multi WBC to block EMP within the military command post for guaranteeing the military operations sustainment.

• Journal of Energy Engineering
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• v.25 no.1
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• pp.86-91
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• 2016

Convenient design guideline for Waveguide-below-cutoff (WBC) array is proposed to obtain the minimum waveguide length for electromagnetic pulse (EMP) shielding. The analysis includes circular, rectangular, and hexagonal WBC, determine the total length of the waveguide. When the unit side of rectangular WBC and the diagonal line of hexagonal WBC are given as 30 mm, the length of hexagonal WBC is 5 mm shorter than rectangular case with shielding effectiveness (SE) 80 dB. The length difference is deepened with SE of 100 dB, which shows approximately 30 mm shorter length for hexagonal case than others. In addition, hexagonal WBC requires much shorter length than circular WBC. In conclusion, hexagonal case is the most effective with respect to flow velocity and pressure loss for equivalent SE.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.424-432
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• 2018

We herein analyze and study the shielding effectiveness characteristic of an open conveyor-belt-type microwave dryer that is widely used in industry. In particular, the electromagnetic wave leakage problem of the open-type conveyor belt dryer using a general-purpose 2.45-GHz magnetron was improved by applying the corrugated rectangular waveguide. We conducted the electromagnetic simulation of the optimal shielding effectiveness characteristic with regard to the proposed waveguide structure to analyze the attenuation characteristics of the corrugated rectangular waveguide. To verify the shielding effectiveness characteristic of the fabricated corrugated rectangular waveguide by IEEE standard 299, we achieved the shielding effectiveness of more than 30 dB in the practical microwave dryer with the proposed corrugated rectangular waveguide.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.367-373
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• 2020

Most of the spatial scattered dose caused by the scattered rays generated by the collision between the object and X-rays is relatively easily absorbed by the human body as electromagnetic waves in the low energy region, thereby increasing the degree of radiation exposure. Such spatial scattering dose is also used as an indicator of the degree of radiation exposure of radiation workers and patients, and there is a need for a method to reduce exposure by reducing the spatial scattered dose that occurs indirectly. Therefore, in this study, a lead-free radiation shielding sheet was proposed as a way to reduce the spatial scattering dose, and a Monte Carlo (MC) simulation was performed based on a chest X-ray examination. The absorbed dose was calculated and the measured value and the shielding rate were compared and evaluated.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.4
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• pp.311-315
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• 2006

We investigated X-ray radiated from the pulsed Plasma Focus device that translated from electric energy into electromagnetic wave by electric discharge. X-ray radiation is analysed by using pin photodiode and 0.5mm pinhole camera shielded by $25{\mu}m$ Be. The condition of X-ray radiation was that the discharging voltage was 15 kV and the working gas were 0.12 torr Argon. Reproducibility of X-ray radiation is investigated and X-ray temperature is calculated above 3keV.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.2
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• pp.151-161
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• 2019

In this study, to evaluate the High Altitude Electromagnetic Pulse(HEMP) protection performance of UHPC/CNT composites by the content of Carbon nanotubes(CNTs), Electromagnetic Shielding Effectiveness(SE) test was performed based on MIL-STD-188-125-1. And the results were verified by applying the Antenna theory. In the case of UHPC with a thickness of 200 mm mixed with 1 % CNT of cement weight, the SE was 28.98 dB at 10 kHz and 45.94 dB at 1 GHz. Then the Scabbing limit thickness for bullet proof was computed based on the result of compressive strength test which was 170 MPa, and it was examined whether it satisfied the HEMP protection criteria. As a result, the required HEMP shielding criteria were satisfied in all frequency ranges as well as the scabbing limit thickness was reduced by up to 43 % compared with that of ordinary concrete.

• 전자공학회논문지 IE
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• v.43 no.4
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• pp.122-127
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• 2006

A series of conductive filler were prepared with electroless plating method. Base conductive materials of the filler were nickel and copper. The cores were prepared with Nylon 6 and rayon in different aspect ratio. Also, various complexes were made with ABS resin and conductive filler with different filler feed ratio. The conductivity of the filler was measured with conductivity analyzer and the size distributions of fillers was measured with laser particle size analyzer. Electromagnetic wave shielding efficiency of each complex film was measured with flange circular coaxial transmission line sample holder within the 1MHz$\sim$1GHz bandwidth range. From this study, the conductivity of filers surpass that of other carbon films. It is available that the filler made of fibrous materials can be applied in plastic molding industry of electric appliances as a EMI filler.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.3
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• pp.384-391
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• 2012

In this paper, reinforced concrete structures are modeled and analyzed. Reinforced concrete has been an essential element in the construction and one that is provided for shielding effectiveness at particular frequencies by rebar placed as a set up in the form of a grid. Using commercial 3-dimensional electromagnetic(3D EM) tool to analyze the reinforced concrete structure, the procedure of analysis for reinforced concrete is computed by dividing concrete, rebar and entire reinforced concrete. The spacing of rebar is bigger, transmission coefficient is higher and the diameter of rebar is bigger, transmission coefficient is lower. Also, in case of two layers is analyzed by gap of layers. Using single layer rebar that thickness of rebar given by 10, 20 and 30 mm have transmission coefficient of -1.89, -2.73 and -4.76 dB/10 cm at 500 MHz. Also, two layers rebar obtain -1.89, -2.73 and -4.76 dB/10 cm for same conditions.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.3
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• pp.553-562
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• 2020

S-band, C-band and X-band radars are used for weather observation purposes. Since the Meteorological Administration, the Ministry of Environment, and Republic of Korea Air Force operate radars according to the purpose of observation by departments, the installation site and observation characteristics are different. From a meteorological point of view, blind observational areas in the low level with an elevation of less than 1 km around the mountainous terrain near Jirisan and Taebaeksan. Assuming a small radar installation, we simulated low-level observations. In order to monitor dangerous weather in North Korea, we analyzed the precipitation of North Korea and simulated a large radar network. Finally, a radar network for Korean Peninsula was proposed.