Evidence for correlation between spin and charge dynamics in La2Cu1−xLixO4

Park, Eunsung,Park, Tuson,Sarrao, J. L.,Thompson, J. D. American Institute of Physics 2009 JOURNAL OF APPLIED PHYSICS - Vol.105 No.7

Influence of an active vibration isolator and electrochemical cell design on electrochemical measurements to minimize natural convection

Park, Kyungsoon,Kim, Eunsung,Park, Jun Hui,Hwang, Seongpil Elsevier Inc. 2017 Electrochemistry Communications Vol.82 No.-

<P><B>Abstract</B></P> <P>The influence of an active vibration isolator (AVI) and electrochemical cell design on natural convection was investigated. The natural convection of an electrolyte caused by external vibrations and acoustic sounds is reduced by both an AVI and an acoustic enclosure. Slow scan voltammetry with an AVI shows a reproducible and predictable diffusion-controlled current down to 0.4mV/s. Reducing the distance between the working electrode and the glass wall also has a considerable effect on the voltammetric signal.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Vibration affects voltammetry at slow scan rates. </LI> <LI> Use of an active vibration isolator with an acoustic enclosure reduced natural convection. </LI> <LI> Reducing the gap between the electrode and the cell wall also reduced natural convection. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Spectroscopic evidence for two-gap superconductivity in the quasi-1D chalcogenide Nb₂Pd_0.81S₅

Park, Eunsung,Lee, Sangyun,Ronning, Filip,Thompson, Joe D,Zhang, Qiu,Balicas, Luis,Lu, Xin,Park, Tuson IOP 2018 Journal of Physics, Condensed Matter Vol.30 No.16

<P>Low-dimensional electronic systems with confined electronic wave functions have attracted interest due to their propensity toward novel quantum phases and their use in wide range of nanotechnologies. The newly discovered chalcogenide Nb<SUB>2</SUB>PdS<SUB>5</SUB> possesses a quasi-one-dimensional electronic structure and becomes superconducting. Here, we report spectroscopic evidence for two-band superconductivity, where soft point-contact spectroscopic measurements in the superconducting (SC) state reveal Andreev reflection in the differential conductance <I>G</I>. Multiple peaks in <I>G</I> are observed at 1.8 K and explained by the two-band Blonder–Tinkham–Klapwijk model with two gaps Δ<SUB>1</SUB>  =  0.61 meV and Δ<SUB>2</SUB>  =  1.20 meV. The progressive evolution of <I>G</I> with temperature and magnetic field corroborates the multiple nature of the SC gaps.</P>

Antenna Placement Optimization for Distributed Antenna Systems

Eunsung Park,Sang-Rim Lee,Inkyu Lee IEEE 2012 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.11 No.7

<P>In this paper, we propose new algorithms to determine the antenna location for downlink distributed antenna systems (DASs) in single-cell and two-cell environments. We consider the composite fading channel which includes small and large scale fadings. First, for the single-cell DAS, we formulate the optimization problem of distributed antenna (DA) port locations by maximizing the lower bound of the expected signal to noise ratio (SNR). In comparison to the conventional algorithm based on the squared distance criterion which requires an iterative method, our problem generates a closed form solution. Next, for the two-cell DAS, we propose a gradient ascent algorithm which determines the optimum DA locations by maximizing the lower bound of the expected signal to leakage ratio (SLR). In our work, we consider selection transmission, maximal ratio transmission and zero-forcing beamforming (ZFBF) under sum power constraint and study equal gain transmission and scaled ZFBF under per-antenna power constraint. Simulation results show that our proposed algorithms based on both the SNR and the SLR criteria offer a capacity gain over the conventional centralized antenna systems.</P>

Feedback Bit Allocation Schemes for Multi-User Distributed Antenna Systems

Eunsung Park,Heejin Kim,Haewook Park,Inkyu Lee IEEE 2013 IEEE COMMUNICATIONS LETTERS Vol.17 No.1

<P>In this paper, we propose a feedback bit allocation algorithm for multi-user downlink distributed antenna systems with limited feedback. We consider a composite fading channel with small scale fadings and path loss, and assume the case where each user is served by only one distributed antenna (DA) port while each DA port can support any number of users. In order to efficiently determine bit allocation, we propose an iterative algorithm which minimizes an upper bound of a mean rate loss. Compared to conventional bit allocation methods, the proposed algorithm can be applied to more general system configurations. Simulation results show that our proposed algorithm offers a performance gain of 20% over an equal bit allocation scheme.</P>

A Novel Bt-Plus Development to Control the Brassica Leaf beetle, Phaedon brassicae

Eunsung Kim,Youngjin Park,Yonggyun Kim 한국응용곤충학회 2015 한국응용곤충학회 학술대회논문집 Vol.2015 No.04

Cabbage is one of the major vegetable crops especially in Korea. Various insect pests intimidate the cabbage production. Moreover, an excessive spray of chemical insecticides leads to development of insecticide resistance as well adverse effects on environment and humans. The brassica leaf beetle, Phaedon brassicae, is a coleopteran pest. Both larval and adult stages feed cabbage. This study aimed to develop an effective microbial biopesticide against P. brassicae by adding immunosuppressive agent to Bacillus thurigiensis (Bt). To determine an optimal immunosuppressive agent, two bacterial species of Photorhabdus temperata subsp. temperata (Ptt) and Xenorhabdus nematophila were compared in their insecticidal activity against P. brassicae, and Ptt was selected. Among four subspecies of Bt, B. thuringiensis subsp. tenebrionis (Btt) was selected. Ptt bacterial culture broth possessed immunosuppressive agent(s) because the bacterial culture broth significantly increased other bacterial growth in P. brassicae hemolymph. When the Ptt broth was added to Btt, it significantly increased the insecticidal activity of Btt. Bt-Plus was prepared by mixing Btt and Ptt bacterial culture and sprayed the cabbage infested by P. brassicae. The Bt-Plus was much more effective than Btt treatment. This study reports a novel Bt insecticide to control P. brassicae.

스마트 케어 감시 시스템에서 한 대의 CCTV를 이용한 GPS 위치정보의 보정 방법

박은성(Park, Eunsung),김기용(Kim, Kiyong) 한국전기전자학회 2016 전기전자학회논문지 Vol.20 No.2

스마트 케어 감시 시스템은 스마트 디바이스에 내장된 GPS 수신 기능을 사용하여 이용자의 위치 정보를 획득하고 주변의 CCTV를 제어하여 이용자를 추적하는 시스템이다. 그러나 일반적인 스마트 디바이스의 GPS 위치 정보는 상당한 오차를 포함하고 있기 때문에 추적을 원활히 하기 위하여 GPS 위치 정보의 보정을 필요로 한다. 기존의 스마트 케어 시스템에서는 두 대 이상의 CCTV를 이용하여 이러한 GPS 위치 정보 오차를 보정하였다. 그러나 이러한 방법은 반드시 두 대 이상이 동일한 지점을 촬영해야 하는 단점이 있다. 본 논문에서는 위치 정보의 오차를 보정하기 위하여 단지 하나의 CCTV만을 이용하는 새로운 방법을 제안한다. 실험 결과, 하나의 CCTV만을 이용하더라도 두 대의 CCTV를 이용한 위치 정보 보정방법 만큼 정확도가 향상되었음을 확인할 수 있다. Smart care surveillance system can take the position information of the user and monitor by controlling neighbor CCTVs using GPS receiver built into smart device. But because the position information contains a significant error, in general smart device, it is necessary to be corrected for precise monitoring. In previous smart care system, this error is corrected by using a plurality of CCTV. But it has disadvantage that two or more CCTVs pointed toward the same point at the same time. In this paper, we propose the method to correct error of the GPS location information by using only one CCTV. With experiment result, we find that the accuracy of GPS location information corrected with only one CCTV is as improved as two CCTVs.

NAT 환경에서 SBC를 이용한 계층적 회의

박은성(Eunsung Park),윤상현(Sanghyun Yun),김기용(Kiyong Kim),성동수(Dongsu Seong),이건배(Keonbae Lee) 한국통신학회 2009 한국통신학회 학술대회논문집 Vol.2009 No.6

대학 내 새터민들의 영어 장벽

박은성(Park, Eunsung),김옥연(Kim, Okyeon) 한국열린교육학회 2014 열린교육연구 Vol.22 No.3

본 연구의 목적은 대학 내 새터민 학생들의 영어 장벽을 해소해 주기 위한 하나의 방안으로 새터민 대학생들의 어려움과 학습요구를 분석하여 그들에게 맞는 영어교육을 제공하고자 하는데 있다. 이를 위해 서울 소재 사립대학 교양영어 프로그램을 사례로 채택하여 교양영어 수업을 듣고 있는 새터민 학생들의 특징과 배경을 알아보았다. 또한 대학 내 교양영어 수업에서 이들이 어떠한 어려움을 겪고 있는지를 조사하고, 새터민 학생들을 위해 개설된 '기본'영어 수업의 피드백을 받아 분석하였다. 본 연구는 설문조사와 심층 면담조사를 통해 진행되었으며 연구결과는 다음과 같다. 다수의 새터민 학생들이 북한(58%)과 남한(90%)에서 영어교육을 받은 것으로 조사되었지만 대학 영어수업에서는 여전히 큰 어려움을 경험하고 있는 것으로 나타났다. 이는 무엇보다도 기초 지식 부족 및 생소한 영어교재와 교수방법이 가장 큰 원인으로 드러났다. 기본 교양영어 수업을 수강한 학생들은 기초실력의 향상과 수준에 맞는 수업으로 영어에 흥미를 느꼈고 동기부여가 되었다는 긍정적인 반응도 있었지만, '기본' 수업과 '일반' 필수수업의 수준차이로 인해 일반 영어수업의 수강에는 여전이 어려움이 많다고 응답했다. 영어는 '언어'이므로 새터민 학생들과 일반 학생들과의 격차를 단기간에 해소하기에는 무리가 있겠지만 새터민 학생들의 특별한 배경과 학습요구를 고려한 체계적이고 장기적인 지원이 절실히 요구된다. The number of North Korean defectors entering universities in the South has rapidly increased in the past decade. Their transition into the South Korean university system has been reported to be accompanied by a number of obstacles, one of which pertains to the difficulty with mandatory English classes offered in South Korean universities. The current study is an attempt to better understand the North Korean defectors' experiences and difficulties with English classes at a South Korean university, in an attempt to better cater to their unique English-learning needs. Data were collected from 31 North Korean defectors enrolled at a private university in Seoul via means of questionnaires and interviews. The survey and interview questions were aimed at gauging the participants' prior educational experiences including the type of English-language training they received in North Korea and after arriving in South Korea, as well as their difficulties and initial reactions to the General Education English classes offered by the university. The results revealed that the majority of students received some form of English education in the North (58%) as well as in the South (90%). Such experience notwithstanding, they still face a number of difficulties in English classes in the South Korean university system. Such difficulties may be attributed to factors such as their lack of knowledge in foundational English, inability to understand the professors' lectures and the English textbooks, and their lack of familiarity with the format of classroom activities and midterms, among others. The results also indicated that even after taking foundational English courses especially designed for North Korean defectors, these students still face difficulties in regular English classes where they have to compete with regular South Korean students. Results are discussed with pedagogical implications.

CMOS SPAD의 최대 수광 효율을 위한 가드링 최적화

박은성(Eunsung Park),하원용(Wonyong Ha),최우영(Woo-Young Choi),이명재(Myung-Jae Lee) 대한전자공학회 2021 대한전자공학회 학술대회 Vol.2021 No.6