Wireless Power Transmission between Two Metamaterial-Inspired Loops at 300 ㎒

Gunyoung Kim,Youn-Kwon Jung,Bomson Lee 한국전자파학회JEES 2010 Journal of Electromagnetic Engineering and Science Vol.10 No.4

Based on a provided closed-form wireless power transmission (WPT) efficiency formula, which may be used for any value of load, we have analyzed the WPT efficiencies between two metamaterial-inspired loop antennas in various aspects. Due to the modeling based on low frequency circuit theory, the provided formula at the center resonant frequency has been found to be accurate until when the distance between the two loop antennas increases to 15 ㎝ (about λ?/6 at 300 ㎒). When the two loops get closer, the resonant frequency has been found to split into two in theory, simulations, and measurements. The EM-simulated and measured efficiencies at new resonant frequencies are 60.9 % and 46.3 %, respectively, at d=15 cm. With two extra rings around the loops, the maximum efficiency is enhanced to 93.7 % at d=15 ㎝. The effect of the additional two rings is about 30 %.

Ion chromatographic determination of chlorite and chlorate in chlorinated food using a hydroxide eluent

Kim, Dasom,Jung, Sungjin,Lee, Gunyoung,Yun, Sang Soon,Lim, Ho Soo,Kim, Hekap The Korean Society of Analytical Science 2017 분석과학 Vol.30 No.2

This study was conducted to develop an analytical technique for determination of chlorite and chlorate concentrations in fresh-cut food and dried fish products by an ion chromatography/conductivity detection method using a hydroxide mobile phase. Deionized water was added to homogenized samples, which were then extracted by ultrasound extraction and centrifuged at high speed (8,500 rpm). Subsequently, a Sep-Pak tC18 cartridge was used to purify the supernatant. Chlorite and chlorate ions were separated using 20 mM KOH solution as the mobile phase and Dionex IonPac AS27 column as the stationary phase. Ethylenediamine was used as sample preservative and dibromoacetate was added to adjust for the disparity in extraction efficiencies between the food samples. The method detection limit) for chlorite and chlorate were estimated to be 0.2 mg/kg and 0.1 mg/kg, respectively, and the coefficient of determination ($r^2$) that denotes the linearity of their calibration curves were correspondingly measured to be 0.9973 and 0.9987. The recovery rate for each ion was 92.1 % and 96.3 %, with relative standard deviations of 7.47 % and 6.18 %, respectively. Although neither chlorite nor chlorate was detected in the food samples, the analytical technique developed in this study may potentially be used in the analysis of disinfected food products.

Design of wideband absorbers using RLC screen

Gunyoung Kim,Bomson Lee IET 2015 Electronics letters Vol.51 No.11

<P>Design equations for wideband single-layer absorbers based on the condition of zero slope reactance (or susceptance) at a specific centre frequency are presented. Using the design equations, a microwave absorber is realised employing a cross-shaped strip structure as a unit on an FR-4 substrate with a relative permittivity of 4.6 and height of 3.2 mm. At a design centre frequency of 10.93 GHz, the size of each unit is 9.6 × 9.6 × 3.2 mm and the overall size of the fabricated absorber is 336 × 336 × 3.2 mm. The EM-simulated and measured absorptions are close to 100% at the design centre frequency and their 90% bandwidths are about 47% (the limit for the case of the layer with <I>ε</I><SUB>r</SUB> = 4.6). The absorption characteristics of the proposed absorber are shown to be almost unaffected by the polarisation angles of normally incident TEM waves.</P>

Effects of Metamaterial Slabs Applied to Wireless Power Transfer at 13.56 MHz

Kim, Gunyoung,Oh, Taek-Kyu,Lee, Bomson Hindawi Limited 2015 International journal of antennas and propagation Vol.2015 No.-

<P>This paper analyzes the effects of a metamaterial slab (or a practical “perfect lens”) with negative permeability applied to a two loop magnetically coupled wireless power transfer (WPT) system at 13.56 MHz, based on theory, full-wave electromagnetic- (EM-) simulations, and measurements. When using lossless slabs with ideal negative permeability in EM-simulations, the WPT efficiencies have been found to be enhanced close to 100% due to the magnetic field focusing. For the case of using a realistic slab made of ring resonators (RR)<SUB>μr</SUB>=-1-j0.23withs/d=0.5(<I>s</I>: slab width,<I>d</I>: distance between the transmitting and receiving loops), the WPT efficiency has been found to significantly decrease to about 20%, even lower than that of a free space case (32%) due to the heavy power absorption in the slab. However, some efficiency enhancement can be achieved whens/dis optimized between 0.1 and 0.3. Overall, the significant enhancement of efficiencies when using a lossless slab becomes moderate or only marginal when employing a realistic slab.</P>

Design of Wireless Power and Information Transfer Systems Considering Figure of Merit for Information

Gunyoung Kim,Bomson Lee 한국전자파학회JEES 2020 Journal of Electromagnetic Engineering and Science Vol.20 No.4

Inductively coupled resonant wireless power transfer (WPT) systems can be used as a wireless power and information transfer (WPIT) system by properly adding the function of varying Rx loads. A new metric for the figure of merit for information transfer from Rx to Tx is proposed as the ratio of Tx input impedances for the Rx shorted and optimum loads to systematically assess the information transfer. While most of WPT and near-field communication (NFC) devices have been adopted for very short distances between Tx and Rx, this work shows that the WPIT systems using inductively coupled resonant structures with high Q-factor coils enable much longer working distances with the best power transfer efficiency and information transfer capability. Several design examples show that the newly proposed figure of merit for information transfer is an essential metric in the understanding and design of WPIT systems. The theory is validated with circuit and electromagnetic simulations for various system configurations.

Changes in Korean Consumers' Perception on Food Preservatives by a Risk Communication Booklet

Kim, Suna,Kim, Ji-Sun,Kang, Hee-Jin,Lee, Gunyoung,Lim, Ho Soo,Yun, Sang Soon,Kim, Jeong-Weon The Korean Society of Food Hygiene and Safety 2018 한국식품위생안전성학회지 Vol.33 No.6

본 연구는 학부모를 대상으로 식품첨가물 및 보존료에 대한 인식 수준과 정보요구도를 파악하고 이를 바탕으로 학부모의 식품첨가물 및 보존료에 대한 올바른 이해와 안전한 식생활을 위한 교육자료를 개발하고자 하였다. 2014년 서울 경기지역 초등학생을 둔 학부모 381명을 대상으로 식품첨가물 및 보존료에 대한 인식 및 정보요구도에 대한 설문조사를 수행한 결과 응답자 중 가공식품 구입 시 안전성을 가장 중요한 요소라고 응답하였으며, 41.5%가 식품 첨가물을 가장 식품안전을 위협하는 것이라고 응답하였으며, 식품 첨가물 중에서는 보존료가 가장 위험하다고 응답하였다. 그러나 응답자의 90.6%가 식품첨가물 및 보존료에 대한 교육 경험이 없다고 응답하였다. 설문결과와 학부모들의 정보요구도에 따라 교육홍보책자인 '보존료 바르게 알기'를 개발하였다. '보존료 바르게 알기'는 '보존료란 어떤 물질인가요?', '보존료는 어떤 종류가 있나요?', '보존료는 안전한가요?', '가공식품, 어떻게 섭취해야 하나요?', '식품첨가물은 식약처가 철저히 관리하고 있어요' 등의 5장으로 구성하여 소비자인 학부모들이 알고 싶어하는 내용들을 알기 쉽고 재미있게 전달할 수 있도록 구성하였다. 개발된 교육홍보책자를 초등학교 학부모에게 시범 적용한 결과, 사전 18.9%만이 보존료가 무엇인지 알고 있다고 응답한 수준에서 사후 90.9%가 그 역할을 이해하고 72.7%가 안전하다고 응답하여 개발된 책자가 보존료에 대한 이해도를 크게 높이고 보존료에 대한 오해를 바로잡을 수 있는 것을 확인할 수 있었다. 따라서 본 연구에서 개발된 교육홍보책자는 학부모를 비롯한 일반소비자들에게 보존료에 대한 이해를 높일 수 있는 효과적인 정보전달매체로 활용될 수 있을 것이다. Food preservatives are very important food additives for the biological and chemical safety of processed foods. The purposes of this study were to investigate Korean consumer's perception and information needs on food preservatives, to develop an educational booklet as a risk communication material on food preservatives, and to assess the educational effect of the developed booklet. To understand perception on food preservatives, a self-administered questionnaire survey was conducted by 381 parents having elementary school students at Seoul and Geoynggi area in Korea. Based on the survey results, brain storming of the authors along with consultation from the professionals, we developed a risk communication booklet about food preservatives. It was exposed to 35 parents of elementary school children, and their evaluation was collected by using a questionnaire and analyzed statistically. Respondents considered food safety (44.8%) as the most important factor while purchasing processed foods. They still perceived food additives as the most hazardous one (41.5%), and among those, food preservatives were the most concerned (45.9%). Total 67.7% of the respondents considered the consumption of food preservatives as hazardous or very hazardous. However, 90.6% of respondents did not have any educational experience about food additives and food preservatives. Based on their information needs, a science-based booklet consisting of the definition, classification, safety, intake, and management of food preservatives was developed. When the booklet titled as 'Food preservatives, Just Know Them!' was exposed to the parents via elementary school teacher, their negative perceptions on food additives and food preservatives were changed positively by increasing the understanding level on preservatives from 18.9% to 90.9% and obtaining 72.7% positive answers on their safety. Therefore, it could be used as an effective risk communication material on food preservatives.

Metamaterial-Based Zeroth-Order Resonant Antennas for MIMO Applications

Gunyoung Kim,Bomson Lee 한국전자파학회JEES 2013 Journal of Electromagnetic Engineering and Science Vol.13 No.3

Control of Power Distribution for Multiple Receivers in SIMO Wireless Power Transfer System

Gunyoung Kim,Seunghyun Boo,Sanghoek Kim,Bomson Lee 한국전자파학회JEES 2018 Journal of Electromagnetic Engineering and Science Vol.18 No.4

A method to control the power distribution among receivers by the load values in a single-input, multiple-output (SIMO) wireless power transfer (WPT) system is investigated. We first derive the value of loads to maximize total efficiency. Next, a simple, but effective analytical formula of the load condition for the desired power distribution ratio is presented. The derived load solutions are simply given by system figure of merits and desired power ratios. The formula is validated with many numerical examples via electromagnetic simulations. We demonstrate that with the choice of loads from this simple formula, the power can be conveniently and accurately distributed among receivers for most practical requirements in SIMO WPT systems.

자계 결합 무선 전력 전송에서의 결합 계수 추출 방법

김건영(Gunyoung Kim),이범선(Bomson Lee) 한국전자파학회 2012 한국전자파학회논문지 Vol.23 No.9

본 논문에서는 손실을 고려한 등가 회로 분석을 통하여 자계 결합 무선 전력 전송 시스템에서의 결합 계수추출식을 유도하였다. 부하 저항을 고려한 유도된 추출식을 이용하여 결합 모드 이론을 이용한 기존의 추출식을 일반화시켰다. 따라서 우수/기수 모드 해석이 불필요하기 때문에 측정 과정에서 쉽게 결합 계수를 구할 수 있다. 또한, EM 시뮬레이션에서 두 루프를 통과하는 자속의 비를 이용하여 구한 결합 계수와 유도된 추출식을 이용하여 구한 결합 계수가 일치함을 확인할 수 있다. 자계 결합 무선 전력 전송에서의 정확한 결합 계수를 추출한다면, 시스템을 분석하고 최적화시키는 데 유용하게 활용할 수 있다. This paper presented the extraction solution for the coupling coefficient at the magnetically coupled wireless power transmission(WPT) system through the analysis of its equivalent circuit considering the loss. The conventoinal extraction solution using coupled mode theory is generalized employing the extracted solution considering the load resistance. Consequently, the measuring process of extracting coupling coefficient becomes convenient since the even/odd mode analysis is not necessary. Furthermore, the coupling coefficient obtained from the induced extraction method was in excellent agreement with the coupling coefficient obtained using the ratio of magnetic flux passing through the two loops. The extraction of the accurate coupling coefficient at the magnetically coupled WPT is an essential work to analyze and optimize the WPT system.

Ion chromatographic determination of chlorite and chlorate in chlorinated food using a hydroxide eluent

Dasom Kim,Sungjin Jung,Gunyoung Lee,Sang Soon Yun,Ho Soo Lim,Hekap Kim 한국분석과학회 2017 분석과학 Vol.30 No.2