• The Journal of the Korea Contents Association
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• v.11 no.9
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• pp.26-44
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• 2011

The Study was carreid out to see whether the intensity of electromagnetic waves in each floor of a building where the sharing base station has been established is harmful to a human body, and to expect the intensity of the waves in the building. The investigate was performed on both of sharing base station either with many scatterers or without any of them. To satisfy the international standard and the domestic TTA standard, rms for each of the electromagnetic wave of every floor in the building with the station was measured from 3 location of 3 heights(1.1m,1.5m, and 1.7m). Max of the measured rsm from the each of the frequencies in the nine location was confirmed to be 48.12%(the rooftop measured value) at most, compared to the human body protection standard. The value was confirmed to satisfy the human body protection standard for each frequency. And the total value of the calculated exposure indexes for each frequency was determined to be more than 7 times lower at most, which was 0.1445, compared to the 1 standard. Since P value in both of 868MHz and 2.14GHz electromagnetic waves intensity for each base station and floor was less than 0.05, it was revealed to be meaningful, and since R-Sq(adj) value showed a value more than 50%, the regression equation was determined to fully absorb the data information. However, although the P value of both of 868MHz and 2.14GHz electromagnetic waves intensities under the integrating terms of the base station data and the floor data was showed to be less than 0,05, since R-Sq(adj) value of 868MHz electromagnetic waves intensity presented a value smaller than 50%(34.15%), it was determined that the 868MHz electromagnetic waves intensity is very much influenced by an environment with a base station. Because the electromagnetic waves intensity of 2.14GHz show R-Sq(adj) value bigger then 50%(51.8%), The regression equation model of 2.14GHz electromagnetic waves intensity was confirmed to be proper. It also turned out not to be effected by the surrounding environment near a building with the base station and the intensity of electromagnetic waves for each floor of such building was expectable by the regression equation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.244-248
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• 2001

According to the progress of the electronic industry and radio communication technologies, mankind might enjoy its abundant life. On the other hand, many social problems such as EMI, and unnecessary electromagnetic wave occur due to the increased use of electromagnetic wave. Therefore, the organizations such as CISPR, FCC, ANSI, etc. have provided the standard of electromagnetic wave environment for the countermeasure of the EMC. It had been required that the absorbing ability of an electromagnetic wave absorber is more than 20dB, the bandwidth of which is required through 30 MHz to 1,000 MHz for satisfying the international standard about an anechoic chamber for EMI/EMS measurement. From November of 1998, however, the CISPR11 has accepted the extended frequency band from 1 GHz to 18 GHz additionally in the bandwidth of EMI measurement[1]. In this paper, we proposed a new type absorber satisfying the above requirements and carried out broadband design using the equivalent material constants method. Futhermore, the experiments were carried out over the frequency band from 30 MHz to 2 GHz, and hence, the validity of the proposed design theory was confirmed.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1162-1166
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• 2001

NiZn-ferrite was synthesized from waste catalysts, which were produced from styrene monomer process and buried underground as an industrial wastes, and its magnetic properties were investigated. Nickel oxide and zinc oxide powders were mixed with finely ground waste catalysts, and spinel type ferrite was obtained by calcination at 900$\^{C}$ and sintering at 1230$\^{C}$ for 5 hours. The intial permeability was measured and reflection loss was calculated from S-parameters for the composition of Ni$\_$x/Zn$\_$1-x/Fe$_2$O$_4$(x=0.36, 0.50, 0.66). NiZn-ferrite synthesized from waste iron oxide catalyst showed a feasibility for the use as electromagnetic wave absorber in X-band.

• Journal of the Korea Institute of Building Construction
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• v.19 no.3
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• pp.209-217
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• 2019

EMP (Electromagnetic Pulse) usually means High Power Electromagnetic Wave (HPEM). In the case of the shielding plate against the EMP, there is a possibility of deterioration of the electromagnetic wave shielding performance due to the skill of the constructor, bad construction, deformation of the shielding plate at the connection portion (joint portion). The inefficient use of space due to the separation distance is also pointed out as a problem. Therefore, this study aims to derive the optimum electromagnetic shielding condition by applying ATMSM to concrete as a part of securing electromagnetic wave shielding performance with reflection loss against concrete wall. Experimental parameters included concrete wall thickness and application of Zn-Al ATMSM. For the concrete wall, the wall thickness was 100 to 300mm, which is generally applied, and experimental parameters were set for the application of Zn-Al metal spraying method to evaluate electromagnetic shielding performance. Experimental results showed that as the thickness increases, the electromagnetic shielding performance increases due to the increase of absorption loss. In addition, after the application of Zn-Al ATMSM, the average shielding performance increased by 56.68 dB on average, which is considered to be increased by the reflection loss of the ATMSM. In addition, it is considered that the shielding performance will be better than that when the conductive mixed material and the ATMSM are simultaneously applied.

• Resources Recycling
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• v.12 no.6
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• pp.32-37
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• 2003

For the reduction of electromagnetic biological effects from cellular phones, the electrical field radiation from cellular phone antenna is reduced by using partial ferrite material added on the phone case as ground plane. On the given properties (permittivity, permeability and conductivity) of ferrite material, the characteristics of monopole antenna is analysed depending on the variation of ferrite added configuration(thickness and shape). According to this analysis, the design method and direction to minimize the biological effects to human head is proposed in 1.7 GHz band PCS phones. For the exact analysis involving the permittivity, per-meability and conductivity of ferrite material, FDTD numerical method is used.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.3 s.106
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• pp.239-248
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• 2006

In this paper, the cryogenically cooled low noise amplifier module for radio telescope receiver front-end using pHE-MT MMIC is designed and fabricated. In the selection of MMIC, the MMIC fabricated with the pHEMTS providing successful cryogenic operation are chosen. They are mounted in the housing using the thin film substrate. In the design of the housing, the absorber and the elimination of the gap between the carrier and the housing as well removed the unnecessary oscillations by its structure. The mismatch is improved by ribbon-tuning to provide the best performance at room temperature. The fabricated module shows the gain of $35dB{\pm}1dB$ and the noise figure of $2.37{\sim}2.57dB$ at room temperature over $21.5{\sim}23.5GHz$. In the cryogenic temperature of $15^{\circ}K$ cooled by He gas, the measured gain was above 35 dB and flatness ${\pm}2dB$ and the noise temperatures of $28{\sim}37^{\circ}K$.

• Journal of the Korean Magnetics Society
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• v.18 no.5
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• pp.195-199
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• 2008

Composites of $Fe_{93.5}Si_{6.5}$ powder and epoxy were prepared using a thermal curing process. Scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and network analyzer were used to analyze the structure, electromagnetic properties and microwave absorption of the composites. Results show that the saturation magnetization depends on the fraction of the $Fe_{93.5}Si_{6.5}$ powder in the composite, which affects initial permeability. It is believed that the eddy current loss is a dominant factor over 1 GHz and that the resonance frequency of the composite decreases with increasing fractions of $Fe_{93.5}Si_{6.5}$ powder. Finally, reflection loss was calculated from the permeability and permittivity of these composites. Composite with 50 wt.% $Fe_{93.5}Si_{6.5}$ powder fractions and 5 mm thickness showed reflection loss below -20 dB from 3.66 GHz to 4.16 GHz. Therefore, it is believed that thin Fe-Si/epoxy composites may be a good candidate for microwave absorption application.

• Proceedings of the Korea Crystallographic Association Conference
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• 2003.05a
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• pp.26-26
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• 2003

산업 폐기물로서 전량 매립되고 있는 styrene monomer (SM) 공정에서 발생되는 산화철 폐촉매를 사용하여 NiZn-페라이트를 합성하였고, 그 자기적 특성을 조사하였다. 평균입경 0.5㎛로 미분쇄된 산화철 폐촉매에 NiO 및 ZnO를 혼합하여 900℃에서 하소한후 1230℃에서 5시간 동안 소결하여 스핀넬형 페라이트 소결체를 얻었다. Ni/sub x/Zn/ub 1-x/Fe₂O₄(x=0.36, 0.50, 0.66) 및 (Ni/sub 0.5/Zn/sub 0.5/)/sub 1-y/Fe/sub 2+y/O₄(y=-0.02, 0, 0.02) 조성에 대하여 초투자율을 측정하였다. S-parameter를 측정하여 반사 감쇄량을 계산하였다. Ni/sub 0.5/Zn/sub 0.5/fe₂O₄ 조성의 경우 밀도 5.38 g/㎤ kHz에서의 초투자율이 59인 특성을 얻었다. 산화철 폐촉매를 이용하여 X-band 주파수 영역에서 높은 전자파 흡수능을 갖는 전파흡수체를 제조할 수 있음을 확인하였다. Ni/sub 0.5/Zn/sub 0.5/Fe₂O₄ 조성에 대하여 1100℃에서 하소한 분말을 사용하여 실리콘 고무에 복합시킨 후 전파흡수능을 측정하였다. 폐촉매에는 산화철 이외에 CeO₂가 주된 첨가물로 함유되어 있어서 페라이트의 합성 후에도 2차상으로서 존재하였다. 출발 원료인 산화철 폐촉매에 존재하는 K₂O 및 CeO₂를 제거하기 위하여 산처리와 분산제를 이용한 CeO₂ 분리과정을 행하였다. 정제된 산화철 폐촉매에 NiO 및 ZnO를 혼합하여 900℃에서 하소하여 스핀넬형 페라이트를 합성하고 1325℃에서 5시간 소결하였다. 위와 마찬가지로 Ni/sub x/Zn/sub 1-x/Fe₂O₄(x=0.36, 0.50, 0.66)과 (Ni/sub 0.5/Zn/sub 0.5/)/sub 1-y/Fe/sub 2+y/O₄(y=-0.02, 0, 0.02) 조성에 대하여 자기적 특성을 조사하였다.화된 중성자빔으로 측정하였다 BPC-Si를 구부려 슬랩의 곡률반경을 변화시키면서 단색기-시료-검출기가 평행파 반평행배치일 때 Cu(111), (200), (220), (311), (331), (420)면의 회절선을 측정하여 각 조건에서 분해능과 강도를 평가하였다.료의 가시적 변화를 통해 illumination angle 1.25mrad(Dose rate : 334 × 10³ e/sup -//sec·n㎡)일 경우 약 3초 이내에 비정질화가 시작됨을 알 수 있었고 이는 약 1 × 10/sup 6/ e/sup -//sec·n㎡ 의 전자선량에 해당되며 이를 기준으로 각각의 illumination angle에 대한 임계전자선량을 평가할 수 있었다. 실질적으로 Cibbsite와 같은 무기수화물의 직접가열실험 시 전자빔 조사에 의해 야기되는 상전이 영향을 배제하고 실험을 수행하려면 illumination angle 0.2mrad (Dose rate : 8000 e/sup -//sec·n㎡)이하로 관찰하고 기록되어야 함을 본 자료로부터 알 수 있었다.운동횟수에 의한 영향으로써 운동시간을 1일 6시간으로 설정하여, 운동횟수를 결정하기 위하여 오전, 오후에 각 3시간씩 운동시키는 방법과 오전부터 6시간동안 운동시키는 두 방법을 이용하여 품질을 비교하였다. 각 조건에 따라 운동시킨 참돔의 수분함량을 나타낸 것으로, 2회(오전 3시간, 오후 3시간)에 나누어서 운동시키기 위한 육의 수분함량은 73.37±2.02%를 나타냈으며, 1회(6시간 운동)운동시키기 위한 육은 71.74±1.66%을 나타내었다. 각각의 운동조건에서 양식된 참돔은 사육초기에는 큰 변화가 없었으나, 사육 5일 이후에는 수분함량이 증가하여 15일에는 76.40±0.14, 75.62±0.98%의 수분함량을 2회와 1회 운동시킨 참돔의 육에서 각각 나타났다. 운동횟수에 따른 지질함량은 2회 운동시킨 참돔은 5.83±2.08, 1회 운

• Journal of Powder Materials
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• v.16 no.4
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• pp.291-295
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• 2009

The electromagnetic wave absorption sheets were fabricated by mixing of $Fe_{73}Si_{16}B_7Nb_3Cu_1$ nanocrystalline soft magnetic powder, charcoal powder and polymer based binder. The complex permittivity, complex permeability, and scattering parameter have been measured using a network analyzer in the frequency range of 10 MHz$\sim$10 GHz. The results showed that complex permittivity of sheets was largely dependent on the frequency and the amount of charcoal powder : The permittivity was improved up to 100 MHz, however the value was decreased above 1 GHz. The power loss of electromagnetic wave absorption data showed almost the same tendency as the results of complex permittivity. However, the complex permeability was not largely affected by the frequency, and the values were decreased with the addition of charcoal powder. Based on the results, it can be summarized that the addition of charcoal powder was very effective to improve the EM wave absorption in the frequency range of 10 MHz$\sim$1 GHz.