• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12A
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• pp.1233-1241
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• 2008

We design, fabricate, and measure a MIMO antenna system mountable on a small PCB (such as UMPC). The proposed antenna system accommodates three radiation elements on the PCB area of $40mm\;{\times}\;100mm$. Two of them employ a slot type and one uses a modified monopole with an inverted L shape expecting high isolation and polarization purity. The bandwidth of each proposed MIMO antenna ranges from 80MHz and 200MHz at the center frequency of 1.8 GHz. The isolations between ports have been found to be greater than 10dB over the interested frequency band. Besides, the proposed MIMO system has been evaluated in terms of ARC(Active Reflection Coefficient, TARC(Total ARC), correlation, MEG, and etc. The envelope correlation is calculated to be much less than 0.04 and the ratio of the mean effective gain(MEG) between the antennas is found to be close to unity.

• Journal of the Korean Wood Science and Technology
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• v.48 no.1
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• pp.41-49
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• 2020

Jabon (Anthocephalus cadamba) is a fast-growing wood species that is widely utilized for light construction and other purposes in Indonesia. The objectives of the current study were to determine the effects of monoethylene glycol (MEG) and SiO₂ nanoparticles (nano SiO₂) impregnation treatment on the dimensional stability and density of jabon wood and to identify the characteristics of impregnated jabon wood. Wood samples were immersed in water (as untreated), MEG, 0.5% MEGSiO₂, then impregnated by applying 0.5 bar of vacuum for 60 min, and then applying 2.5 bar of pressure for 120 min. The results showed that impregnation with MEG and Nano SiO₂ had a significant effect on the dimensional stability of jabon wood. Polymers can fill cell walls in wood indicated by increasing weight percentgain, antiswelling efficiency, bulking effect, and density, then decreasing in water uptake value. Jabon wood morphology by using SEM showed that MEGSiO₂ polymers can cover part of the pitsin the wood vessel wall of jabon. This finding was reinforced by EDX results showing that the silicon content was increased due to the addition of SiO₂ nano. The XRD diffraction pattern indicated that MEGSiO₂ treatment increased the degree of crystallinity in wood samples. Overall, treatment with 0.5% MEGSiO₂ led to the most improvement in the dimensional stability of 5-year-old jabon wood in this study.

• Journal of electromagnetic engineering and science
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• v.13 no.1
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• pp.28-33
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• 2013

This paper proposes a miniaturized high-isolation diversity antenna for wearable wireless body area network (WBAN) applications. An inverted-F type radiating element is used to reduce the overall dimension of the proposed antenna to $30mm{\times}30mm{\times}2.5mm$. The antenna performance on the human body phantom is analyzed through simulation and the performance of the fabricated antenna is verified by comparing the measured data with that of the simulation when the antenna is placed on a semi-solid flat phantom with equivalent electrical properties of a human body. The fabricated antenna has a 10 dB return loss bandwidth over the Industrial Scientific Medical (ISM) band from 2.35 GHz to 2.71 GHz and isolation is higher than 28 dB at 2.45 GHz. The measured peak gain of antenna elements # 1 and # 2 is -0.43 dBi and -0.54 dBi, respectively. Performance parameters are analyzed, including envelope correlation coefficient (ECC), mean effective gain (MEG), and the MEG ratio. In addition, the specific absorption ratio (SAR) distributions of the proposed antenna are measured for consideration in use.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.467.1-467.1
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• 2014

Quantum dots (QD) solar cells has received considerable attention due to their potential of improving the overall conversion efficiency by harvesting excess energy via multiple excitons generation (MEG). Although there have been many reports which show MEG phenomena by using optical measurement of quantum dots themselves, carrier multiplication in real QD photovoltaic devices has been sparsely reported due to difficulty in dissociation of excitons and charge collection. In this reports, heterojunction QD solar cells composed of PbS QD monolayer on highly crystalline $TiO_2$ thin films were fabricated by using Langmuir-Blodgett deposition technique to significantly reduce charge recombination at the interfaces between each QD. The PbS CQDs monolayer was characterized by using UV-vis, transmission electron microscopy (TEM) and atomic force microscopy (AFM). The internal quantum efficiency (IQE) for the monolayer QD solar cells was obtained by measurement of external quantum efficiency and determining light absorption efficiency of active layer. Carrier multiplication was observed by measuring IQE greater than 100% over threshold photon energy. Our findings demonstrate that monolayer QD solar cell structure is potentially capable of realizing highly efficient solar cells based on carrier multiplication.

• Journal of the Korean Applied Science and Technology
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• v.20 no.1
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• pp.44-50
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• 2003

We studied on the preparation and evaluation of O/W type microemulsion containing "wax, liquid paraffine and quaternary ammonium salt". And also it was obtained to stability of microemulsions by mono ethylene glycol(MEG) addition. The microemulsions were generally prepared at 96${\sim}$97$^{\circ}C$ by the phase inversion method. We used polyoxyethylene(20) sorbitan monooleate(POE(20)SMO) and distearyl dimethyl ammonium chloride(D.D.A.C.) as the emulsifiers at microemulsion preparation. From the results, we could get best condition for microemulsion preparation, in case of oil phase, montanic ester wax ; 1.1wt%, paraffine wax ; 1.1wt%, liquid paraffine ; 3.1wt%, propylene glycol ; 0.6wt% and ethylene glycol monobutyl ether ; 0.6wt%, when the ratio(wt%) of D.D.A.C. and POE(20)SMO were 2 : 3. And also we could obtained that the distributed particle size of the final microemulsions were about 8${\pm}$1.5nm and the mean particle size was 7${\pm}$0.5nm. We got following results from final microemulsions that the percent of transmittance; 96${\sim}$98% at 700nm. And the microemulsion blended with MEG of 5${\sim}$15wt% showed smaller particle size and more stable distribution than non-containing MEG.

• Elastomers and Composites
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• v.47 no.2
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• pp.96-103
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• 2012

This paper reviews recent technologies for recycling poly (ethylene terephthalate) wastes. Wide application and non-biodegradability of the PET creates huge amounts of waste and disposal, leading to an environmental problem and economic loss. Chemical recycling can be a promising technology to deal with these problems by converting the waste into useful feedstock material for polyester production. Chemical recycling of polyethylene terephthalate are processes where the PET polymer chain is destructed by the impact of glycol (MEG) causing glycolysis, methanol causing methanolysis or water causing hydrolysis. After intensive purification polyester oligomers or the monomers MEG, dimethyl telephthalate (DMT) or purified terephthalic acid (PTA) are received which are re-used to produce polyester products.

• Journal of Biomedical Engineering Research
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• v.29 no.3
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• pp.231-238
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• 2008

Nelder-Mead downhill simplex method (DSM), a kind of deterministic optimization algorithms, has been used extensively for magnetoencephalography(MEG) dipolar source localization problems because it dose not require any functional differentiation. Like many other deterministic algorithms, however, it is very sensitive to the choice of initial positions and it can be easily trapped in local optima when being applied to complex inverse problems with multiple simultaneous sources. In this paper, some modifications have been made to make up for DSM's limitations and improve the accuracy of DSM. First of all, initial point determination method for DSM using magnetic fields on the sensor surface was proposed. Secondly, Univariant-DSM combined DSM with univariant method was proposed. To verify the performance of the proposed method, it was applied to simulated MEG data and practical MEG measurements.

• Journal of electromagnetic engineering and science
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• v.19 no.1
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• pp.20-30
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• 2019

A wide-band multiple-input multiple-output (MIMO) antenna with dual-band (2.4 and 5 GHz) operation is proposed for premium indoor access points (IAPs). Typically, an omni-directional pattern is used for dipole antennas and a directional radiation pattern is used for patch antennas. In this paper, both antenna types were used to compare their performance with that of the proposed $2{\times}2$ MIMO antenna. We simulated and measured the performance of the MIMO antenna, including the isolation, envelope correlation coefficient (ECC), mean effective gain (MEG) for the IAPs, and the throughput, in order to determine its communication quality. The performance of the antennas was analyzed according to the ECC and MEG. The proposed antenna has sufficient performance and excellent characteristics, making it suitable for IAPs. We analyzed the communication performance of wireless networks using the throughput data of a typical office environment. The network throughput of an 802.11n device was used for the comparison and was conducted according to the antenna type. The results showed that the values of the ECC, MEG, and the throughput have unique characteristics in terms of their directivity, antenna gains, isolation, etc. This paper also discusses the communication performance of various aspects of MIMO in multipath situations.

• Progress in Superconductivity
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• v.4 no.1
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• pp.19-26
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• 2002

We have earlier developed a 40-channel SQUID system. An important figure of merit of a MEG system is the localization error, within which the underlying current source can be localized. With this system, we investigated the localization error in terms of the standard deviation of the coordinates of the ECDs and the systematic error due to inadequate modeling. To do this, we made localization of single current dipoles from tangential components of auditory evoked fields. Equivalent current dipoles (ECD) at N1m peak were estimated based on a locally fitted spherical conductor model. In addition, we made skull phantom and simulation measurements to investigate the contribution of various errors to the localization error. It was found that the background noise was the main source of the errors that could explain the observed standard deviation. Further, the amount of systematic error, when modeling the head with a spherical conductor, was much less than the standard deviation due to the background noise. We also demonstrated the performance of the system by measuring the evoked fields to grammatical violation in sentence comprehension.

• The Magazine of the IEIE
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• v.36 no.11
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• pp.83-92
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• 2009