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Realistic Head Phantom for Evaluation of Brain Stroke Localization Methods Using 3D Printer
Juneseok Lee,Jihoon Bang,Jaehoon Choi 한국전자파학회JEES 2016 Journal of Electromagnetic Engineering and Science Vol.16 No.4
In this paper, a brain phantom for evaluating brain stroke localization is proposed. To evaluate brain stroke localization, a phantom imitating three-dimensional (3D) simulation environment is needed. Mold for the proposed phantom was printed by a 3D printer and the interior of the phantom consists of 5 different brain tissue materials. Each of the brain tissue materials has the conductivity and permittivity similar to those of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) standards for a frequency band from 0.5 to 2 GHz.
전자파 두뇌 영상장치용 비대칭형 Corrugated 테이퍼드 슬롯 안테나
이준석(Juneseok Lee),박중기(Joongki Park),최재훈(Jaehoon Choi) 한국전자파학회 2013 한국전자파학회논문지 Vol.24 No.3
최근 전자파를 이용하여 두뇌를 영상화하는 시스템이 제안되고 있다. 이러한 시스템은 초광대역 특성(0.5~2GHz)과 주빔의 방향이 모든 동작 주파수 대역에서 일정하게 유지되는 소형 안테나를 요구한다. 위의 요구 조건을 만족하기 위해서 본 논문에서는 비대칭형 corrugation들을 일반 TSA에 적용하여 안테나의 크기는 14 % 감소시키고, 요구되는 동작 주파수 대역인 0.5 GHz에서 2 GHz까지 반사 손실이 10 dB 이하의 값을 가지도록 설계하였다. 특히 대칭형 corrugation들을 적용한 TSA가 가지는 주빔의 방향이 주파수에 따라 변하는 점을 개선하였고, 이러한 비대칭형 corrugated TSA는 전자파를 이용한 두뇌 영상장치의 구현을 위해서 요구되는 조건을 모두 만족한다. Recently, a brain imaging system with microwave devices has been proposed. The brain imaging system requires a small antenna which has ultra wide band(UWB) operating frequency bandwidth(0.5~2 GHz) and non-varying boresight of antenna over the frequency band. This paper proposes asymmetric corrugations on a tapered slot antenna (TSA) so that the size of the TSA is reduced by 14 % while 10 dB return loss bandwidth is satisfied over the operating frequency band from 0.5 GHz to 2 GHz. A miniaturized TSA with symmetric corrugations shows tilted boresight whilst frequency is getting lower; however, the proposed TSA with asymmetric corrugations maintains direction of boresight for different frequencies. This enhancements make an asymmetric corrugated TSA meet the requirement of the brain imaing system.
Label-free detection of zinc oxide nanowire using a graphene wrapping method
You, Juneseok,Jang, Kuewhan,Lee, Sangmyung,Bang, Doyeon,Haam, Seungjoo,Choi, Chang-Hwan,Park, Jinsung,Na, Sungsoo Elsevier 2015 Biosensors & Bioelectronics Vol.68 No.-
<P><B>Abstract</B></P> <P>Zinc oxide nanowires (ZnO NWs) have been attempted to various applications, such as piezoelectric devices, energy harvesting devices, self-powered nanosensors, and biomedical devices. However, recent reports have shown the toxic effect of ZnO NWs. In this report, we described the detection of ZnO NWs, for the first time using reduced graphene oxide (RGO) wrapping method. By wrapping RGO to ZnO NW (RGO–ZnO NW), we are able to aggregate ZnO NWs and increase the sensing performance. The detection measurement is based on the resonance frequency shift derived from mass variation of RGO–ZnO NW adsorption on the DNA immobilized resonator. The resonator is able to detect ZnO NWs with detection limit of 100ngmL<SUP>−1</SUP> which is 2 order below the fatal toxic concentration of ZnO NWs in Human Monocyte Macrophages (HMMs). Furthermore, the resonator is able to detect ZnO NWs in real tap water, showing the potential as ZnO NWs screening platform in real environmental aqua system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Using reduced graphene oxide and ssDNA immobilized resonator, zinc oxide nanowire detection method was developed. </LI> <LI> By measuring resonance frequency shift of the resonator, high sensitivity is attained. </LI> <LI> This detection method was able to detect 100ngml<SUP>−1</SUP> of zinc oxide nanowire. </LI> <LI> Selective detection of zinc oxide nanowire was achieved. </LI> <LI> This detection method was able to detect zinc oxide nanowire in real sample of tap water. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Design of a Wideband Antipodal Vivaldi Antenna with an Asymmetric Parasitic Patch
Jihoon Bang,Juneseok Lee,Jaehoon Choi 한국전자파학회JEES 2018 Journal of Electromagnetic Engineering and Science Vol.18 No.1
An antipodal Vivaldi antenna with a compact parasitic patch to overcome radiation performance degradations in the high-frequency band is proposed. For this purpose, a double asymmetric trapezoidal parasitic patch is designed and added to the aperture of an antipodal Vivaldi antenna. The patch is designed to efficiently focus the beam toward the end-fire direction at high frequencies by utilizing field coupling between the main radiating patch and the inserted parasitic patch. As a result, this technique considerably improves the gain and stability of radiation patterns at high frequencies. The proposed antenna has a peak gain greater than 9 dBi over the frequency range of 6–26.5 GHz.
Comparison of media and membrane filtrations for seawater desalination pretreatment
Kim, Dongkwan,Choi, Juneseok,Lee, Wontae Balaban Publishers 2016 Desalination and Water Treatment Vol. No.
<P>We compared microfiltration (pressurized and submerged) and media filtration as pretreatment to increase the removal of organics and to reduce reverse osmosis (RO) membrane fouling. The studied plant (feed rate=2,500m(3)/d, production rate=1,000m(3)/d) was taking seawater from East Sea of Korea and originally consisted of strainers, coagulation, dissolved air flotation, dual media filters (DMF), and RO membrane processes. A pressurized microfiltration (MF) and a submerged microfiltration (SMF) were installed and compared with DMF as pretreatment to the RO process. Upon pilot test results over one year, MF exhibited higher removal of dissolved organic materials. Average removals of UVA(254) were 23, 19, and 13% at MF, SMF, and DMF, respectively. These results were confirmed with molecular weight distribution, and compositions of humic and fulvic acids. Silt density index (SDI) values were lower in membrane processed waters, and the SDI results correlated with transparent exopolymer particles (r=0.73). The results indicated that MF can be an effective pretreatment to reduce RO membrane fouling with higher removal of organic materials.</P>
인체 부착형 기기를 고려한 변형된 Alford 루프 안테나 설계
박중기(Joongki Park),이준석(Juneseok Lee),최재훈(Jaehoon Choi) 한국전자파학회 2014 한국전자파학회논문지 Vol.25 No.1
본 논문에서는 인체 내ㆍ외부간 근거리 통신망인 WBAN(Wireless Body Area Network)에서 인체 부착형 기기간 통신링크를 원활하게 구성하기 위한 변형된 Alford 안테나를 제안하였다. 제안된 안테나는 인체의 영향을 고려해 설계하였으며, ISM(The Industrial, Scientific and Medical, 2.4~2.485 ㎓) 대역에서 동작한다. 기존 Alford 루프 안테나는 low-profile인 장점이 있지만, 인체 부착용 시스템의 다른 부품을 설치할 접지면이 존재하지 않고 balanced 급전 구조를 사용하기 때문에 on-body 안테나로 적합하지 않다. 따라서 본 논문에서는 on-body 환경에서 동작할 수 있는 접지면이 포함된 unbalanced 급전 구조를 갖는 안테나를 제안하였다. 또한, 안테나가 인체에 부착되어 안테나 성능에 미치는 영향을 고려하기 위해 모의 인체를 통해 모의실험과 측정을 수행하였다. 제안된 안테나는 모노폴 형태의 방사 패턴을 갖는 low-profile 구조이며, ISM 대역 내에서 10 ㏈ 반사 손실을 만족한다. 안테나는 on-body 통신 환경에 적합한 표면지향성 특성을 갖는다. In this paper, a modified Alford loop antenna for on-body communication system is proposed. The proposed antenna operating in the ISM band is designed with consideration of human body effect. One of advantages of the Alford loop antenna structure is lowprofile, however the Alford loop antenna is not suitable for on-body devices since it does not have a ground plane for other electronic part of on-body system and requires balanced feeding structure. To be embedded on on-body devices, the proposed antenna is design with the unbalanced feed structure and ground. The performance of the proposed antenna is simulated and measured when it is placed on the human body phantom to consider the effect of the human body. The proposed antenna a 10 ㏈ return loss bandwidth over the ISM band and monopole-like radiation pattern with low-profile. The antenna has the surface of appropriate for on-body communication environment.
Jang, Kuewhan,You, Juneseok,Park, Chanhoo,Park, Hyunjun,Choi, Jaeyeong,Choi, Chang-Hwan,Park, Jinsung,Lee, Howon,Na, Sungsoo IOP 2016 Nanotechnology Vol.27 No.36
<P>Recent advancements of nanomaterials have inspired numerous scientific and industrial applications. Zinc oxide nanowires (ZnO NWs) is one of the most important nanomaterials due to their extraordinary properties. However, studies performed over the past decade have reported toxicity of ZnO NWs. Therefore, there has been increasing demand for effective detection of ZnO NWs. In this study, we propose a method for the detection of ZnO NW using a quartz crystal microbalance (QCM) and DNA probes. The detection method is based on the covalent interaction between ZnO NWs and the phosphoric acid group of single-stranded DNA (i.e., linker DNA), and DNA hybridization between the linker DNA and the probe DNA strand on the QCM electrode. Rapid, high sensitivity, <I>in situ</I> detection of ZnO NWs was demonstrated for the first time. The limit of detection was 10<SUP>−4</SUP> <I>μ</I>g ml<SUP>−1</SUP> in deionized water, which represents a sensitivity that is 100000 times higher than the toxic ZnO NW concentration level. Moreover, the selectivity of the ZnO NW detection method was demonstrated by comparison with other types of nanowires and the method was able to detect ZnO NWs in tap water sensitively even after stored for 14 d in a refrigerator. The performance of our proposed method was sufficient to achieve detection of ZnO NW in the ‘real-world’ environment.</P>