• Korean Journal of Materials Research
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• v.29 no.6
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• pp.363-370
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• 2019

The recent development of information and communication technologies brings new changes to automobile traffic systems. The most typical example is the advancement of dedicated short range communication(DSRC). DSRC mainly consists of an intelligent transportation system(ITS), an electronic toll collection system(ETCS) and an advanced traveler information system(ATIS). These wireless communications often cause unnecessary electromagnetic waves, and these electromagnetic waves, in turn, cause frequent system malfunction. To solve this problem, an absorber of electromagnetic waves is suggested. In this research, various materials, such as powdered metal and iron oxides, are used to test the possibility for an effective absorption of the unnecessary electromagnetic waves. The various metal powders are made into a thin sheet form by compositing through processing. The electromagnetic characteristics(complex permittivity, complex permeability) of the fabricated sheet are measured. As a result, we achieve -6.5 dB at 940 MHz(77.6 % absorption rate) with a 1.0 mm-thickness electromagnet wave absorber, and -9.5 dB at 940 MHz(88.8 % absorption rate) with a 2.0 mm-thickness absorber.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.105-108
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• 2002

Materials, matrices mixed with various kinds of conductive or magnetic powder, such as ferrite, have been used as the electromagnetic wave absorbing ones, so called RAM(radar absorbing material). The structure that does not only have electromagnetic waves absorbing property like RAM but also supports loads is called RAS(radar absorbing structure). One of the existing manufacturing process of RAS is to compound with conductive powders the glass fiber-reinforced composite with good permeability and the ability to support loads. The process, however, causes a number of problems, such as the degradation in the mechanical properties of the composite, especially, interlamina shear strength. In this study, mechanical properties of glass fabric/epoxy composite containing 7wt% carbon black powders were measured and compared with pure glass fabric/epoxy composites.

• Journal of electromagnetic engineering and science
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• v.4 no.2
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• pp.51-55
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• 2004

With the progress of the electronics industry and radio communication technology, certain problems, such as electromagnetic interference(EMI), have arisen due to the increased use of electromagnetic(EM) waves. International organizations such as CISPR, FCC, and ANSI have provided the standards for the EM wave environment and for the countermeasure of the electromagnetic compatibility(EMC). EM wave absorbers are used for constructing an anechoic chamber to test and measure EMI and electromagnetic susceptibility(EMS). In this paper, we have designed an one-body EM(electromagnetic) wave ferrite absorber, based on the equivalent material constants method for both normally and obliquely incident waves, whose absorption abilities are superior to that of the conventional ones. The fabricated absorber has a thickness of 27.68 mm and shows an absorption ability over 20 ㏈ in the frequency from 30 MHz to 6 ㎓.

• Journal of the Korea Society of Computer and Information
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• v.25 no.10
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• pp.231-240
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• 2020

Countries around the world have already taken direct and indirect measures to warn of the harmful effects of mobile phone electromagnetic waves. On the other hand, in the Republic of Korea the installation of Wi-Fi has been expandedwithout restrictions by location, and there is a widespread atmosphere of protesting human rights violations even if young students cannot use mobile phones, ignoring problems caused by the use of mobile phones. Human brain cells are increasingly exposed to electromagnetic waves of mobile phones as the penetration rate of smartphones grows.In order to solve the long-lasting question of whether electromagnetic waves from mobile phones will harm the human body, many studies are being conducted in various countries around the world, andthe recently published findingshave warned of the potential for harm. The labeling of electromagnetic waves alone is not sufficient to raise awareness about the dangers of electromagnetic waves. It is necessary that the Republic of Korea organize and operate a national electromagnetic wave research center in line with its status as an IT powerhouse, along with the revision of the Radio Wave Act, which directly warns the public about the hazards of mobile phone electromagnetic waves and can directly impose obligations on the mobile phone industry.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.2
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• pp.143-148
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• 2022

For the purpose of treating health checkups and recovery of patients in a super-aged society, hospitals use devices designed with a reduction circuit of electromagnetic waves associated with the specific absorption rate of electromagnetic waves absorbed by the human body. In this paper, we proposed a filter improvement design method capable of reducing electromagnetic waves. As a result of confirming the validity of the proposed technique through simulation and experimental results, the following result values were obtained. Applying the common-mode (CM) inductor 4 mH to a calibration circuit, noise decreased in a multiband spectrum. Using the differential mode(DM) inductor 40 µH element in the primary calibration circuit, the noise decreased by 15 dB or more in the 3 MHz band spectrum. Also, applying the Admittance Capacitance (Y-Cap) 10 nF element in the secondary calibration circuit resulted in the decrease by more than 30 dB in the band spectrum before 2 MHz. After using a common-mode inductor 4 mH element in the tertiary calibration circuit, it decreased by more than 15 dB in the band spectrum after 2 MHz.

• Journal of Digital Convergence
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• v.10 no.1
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• pp.271-276
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• 2012

As applications of electromagnetic waves increase, biological effects caused by the EM waves are worried about. Many studies about the biological effects are reported. However, there are only a few reports on protection against the EM waves. The protection should be considered for the researchers who use strong EM waves in their experiments. In this paper, a method of reducing SAR in a cylindrical human model by a shield plate is proposed for RF engineers exposed to strong electromagnetic waves. The shield plate modeled as an arc structure is shown effectively to protect the cylindrical human model from the exposed field.

• Advances in concrete construction
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• v.3 no.2
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• pp.103-111
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• 2015

The foam concrete was fabricated by adding the foaming agent which composite ordinary Portland cement with plant and animal protein into cement paste, and the electromagnetic wave absorption properties were studied for the first time as well. The studies showed that the electromagnetic waves can be absorbed by multiple reflections and scattering within the porous material. Thickness and filling ratio have a great influence on the electromagnetic wave absorbing properties in 2-18 GHz of the foam concrete, the greater the thickness, the better the performance of absorption; filling ratio was about 52 vol.%, the absorbing properties achieved the best.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1570_1571
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• 2009

본 논문에서는 초고주파를 이용하여 하지정맥류(Varicose vein)의 초기증상인 모세혈관 확장증(Telangiectasia)을 치료하는 데에 목적을 두었다. 유전율 차이에 따라 전자파(Electromagnetic waves)를 흡수하는 양이 다르다는 것을 전제하에 다리 모델링에 필요한 피부, 혈관, 혈액, 피하조직의 유전율을 구하였고, 혈관과 피부의 유전율에 비해 혈액의 유전율이 높다는 것을 통해 다른 조직에 비해 혈액의 전자파 흡수율이 높다는 것을 확인하였다. 피부의 구조와 유전율을 이용하여 모델링 한 후, 시뮬레이션을 통해 SAR(Specific Absorption rate)분포를 확인하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.4
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• pp.611-616
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• 2018

RFID-based Smart cabinets can make a recognition error owing to the electromagnetic wave interference. This paper proposes and implements a smart cabinet system for inventory management using RFID, especially which can be applied to biological laboratories. We calculate the optimal value of partition distance for the higher recognition rate between RFID tags and the reader, and the optimal partition thickness for electromagnetic wave absorption to achieve the higher recognition rate, in which two kinds of the partitions have been tested, a pure steel partition with various thickness and a thin steel partition attached with electromagnetic waves absorber. The experimental results show that the most recommended partition structure for the smart cabinets is one with the partition distance of 30cm and the partition thickness of 1mm attached with the electromagnetic wave absorption tapes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.688-697
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• 2008

In this paper, an analysis method for indoor optical wireless channel properties based on photon model is presented for characterization of communication environment. In contrast to radio waves, optical waves have very short wave-lengths and very high frequencies, so that material properties become important. Channel models including diffuse reflections and absorption effects due to material surface textures make conventional electromagnetic wave analysis methods based on ray tracing consume enormous time. To overcome these problems, an analysis method using photon model is presented that approximates light intensity by a density of photons. The photon model ensures that simulation time is within a predictable limit.