Interregional synaptic maps among engram cells underlie memory formation

Choi, Jun-Hyeok,Sim, Su-Eon,Kim, Ji-il,Choi, Dong Il,Oh, Jihae,Ye, Sanghyun,Lee, Jaehyun,Kim, TaeHyun,Ko, Hyoung-Gon,Lim, Chae-Seok,Kaang, Bong-Kiun American Association for the Advancement of Scienc 2018 Science Vol.360 No.6387

<P>Memory resides in engram cells distributed across the brain. However, the site-specific substrate within these engram cells remains theoretical, even though it is generally accepted that synaptic plasticity encodes memories. We developed the dual-eGRASP (green fluorescent protein reconstitution across synaptic partners) technique to examine synapses between engram cells to identify the specific neuronal site for memory storage. We found an increased number and size of spines on CA1 engram cells receiving input from CA3 engram cells. In contextual fear conditioning, this enhanced connectivity between engram cells encoded memory strength. CA3 engram to CA1 engram projections strongly occluded long-term potentiation. These results indicate that enhanced structural and functional connectivity between engram cells across two directly connected brain regions forms the synaptic correlate for memory formation.</P>

Four-Element Reconfigurable Coupled Loop MIMO Antenna Featuring LTE Full-Band Operation for Metallic-Rimmed Smartphone

Choi, Jaehyun,Hwang, Woonbong,You, Chisang,Jung, Byungwoon,Hong, Wonbin Institute of Electrical and Electronics Engineers 2019 IEEE transactions on antennas and propagation Vol.67 No.1

<P>This paper describes a low-profile <TEX>$2\times 2$</TEX> multi-input multi-output (MIMO) antenna system that is fully functional over the entire long-term evolution (LTE) spectrum 699–960 MHz (lower frequency spectrum) and 1710–2690 MHz (higher frequency spectrum) that is applicable to real-life metallic smartphone platforms. The presented methodology entails utilizing the longitudinal edges of the ground plane amid an extremely narrow ground clearance of 2 mm. The metallic frame of the smartphone is utilized along with a stub network to devise a reconfigurable coupled loop antenna topology. The proposed <TEX>$2\times 2$</TEX> MIMO antenna configuration is measured and confirmed to exhibit efficient envelope correlation coefficient (<0.5) and one of the highest radiation efficiencies to be reported in the literature across the entire LTE spectrum.</P>

Efficient Analysis of IT Facility Security Vulnerability Topics by Utilizing R Programming

Jaehyun Choi,Hoojin Lee 대한전자공학회 2019 IEIE Transactions on Smart Processing & Computing Vol.8 No.3

The recent development of domestic information and communications technologies (ICT) has made it possible to use the Internet anywhere in society, consequently exposing various security threats. Specifically, there is frequent leakage of personal information as well as system infringements, which are mainly caused by either internal or external security weaknesses. Besides, there is no exception for private companies or public corporations that have well-equipped security systems. In order to adequately prepare countermeasures against infringement incidents, security officers have been concerned every year. Hence, the government has designated information and communications infrastructures for major national facilities as a measure against the security threats and, since 2001, has enacted and promulgated the Information and Communication Infrastructure Protection Act. In this paper, we attempt to analyze the trends associated with the vulnerability status of information technology (IT) facilities, and to evaluate the weak points in IT facilities. And finally, we derive the most-mentioned vulnerabilities by effectively utilizing the R program to obtain statistical calculation and visualization, and thus, a common denominator for IT environments.

Genomic Analysis of Monkeypox Virus During the 2023 Epidemic in Korea

Choi Chi-Hwan,Lee Minji,Lee Sang Eun,Kim Jin-Won,Shin Hwachul,Choi Myung-Min,Yi Hwajung,Kim Min-Kyung,Jeon Jaehyun,Park Jun-Sun,Kim Yeonjae,Lim So Yun,Chin BumSik,Chung Yoon-Seok 대한의학회 2024 Journal of Korean medical science Vol.39 No.18

We aimed to characterize the genomes of monkeypox virus isolates from the Far East, providing insights into viral transmission and evolution. Genomic analysis was conducted on 8 isolates obtained from patients with monkeypox virus disease in the Republic of Korea between May 2022 and early 2023. These isolates were classified into Clade IIb. Distinct lineages, including B.1.1, A.2.1, and B.1.3, were observed in 2022 and 2023 isolates, with only the B.1.3 lineage detected in six isolates of 2023. These genetic features were specific to Far East isolates (the Republic of Korea, Japan, and Taiwan), distinguishing them from the diverse lineages found in the Americas, Europe, Africa, and Oceania. In early 2023, the prevalence of the B.1.3 lineage of monkeypox virus identified in six patients with no overseas travel history is considered as an indicator of the potential initiation of local transmission in the Republic of Korea.

High-Efficiency Crossed-Loop 4G LTE Antenna for All Display Metal-Rimmed Smartphones

Choi, Jaehyun,Hwang, Woonbong,You, Chisang,Jung, Byungwoon,Hong, Wonbin Hindawi Limited 2018 International journal of antennas and propagation Vol.2018 No.-

<P>A symmetrically crossed-loop antenna featuring very high radiation efficiency across the entire LTE frequency bands for metal-rimmed smartphones with only 2 mm ground clearance is proposed, analyzed, and verified. The employment of even and odd modes is utilized to achieve wide bandwidth across 698-960 MHz (low-frequency spectrum), 1710-2170 MHz (middle-frequency spectrum), and 2300-2690 MHz (high-frequency spectrum). Empirical analysis confirms the crossed-loop topology results in a 180° phase shift of the electric current distribution on the ground plane, resulting in enhancement of the radiation resistance. As a result, the devised LTE antenna exhibits more than 48% to 75% total system efficiency across the entire band of interest, which is the highest efficiency reported in literature for metal-rimmed smartphones with extremely small ground clearance.</P>

Global Grain Price Transmission to Korean Agricultural and Food Prices

( Jaehyun Choi ),( Doo Bong Han ) 한국농업경제학회 2017 農業經濟硏究 Vol.58 No.3

This study examines the price transmission of global grain prices on Korean agricultural and food markets. Furthermore, it tests the structural break points of global grain prices and analyzes whether their impact changes before and after the global financial crisis and agflation. The results are as follows. First, the structural break of global grain prices was found in May 2007. Second, causal relationships between global grain prices and domestic agricultural and food prices were also changed after the global financial crisis and agflation. Third, a significant price transmission from global soybeans price to domestic soybean price was observed only after 2007. Meanwhile, domestic wheat prices show significant price transmissions following the changes in global wheat prices in both periods. Fourth, the price transmission of global grain prices on domestic processed food prices was significant both before and after 2007. Lastly, an asymmetric price transmission between global and domestic prices was found only before 2007.

지속성장 가능한 기업 탐색을 위한 방법

최재현(Jaehyun Choi) 한국지능시스템학회 2018 한국지능시스템학회논문지 Vol.28 No.4

최근 창업기업을 지원하기 위한 다양한 정책들이 실시되고 있다. 정책에 의해 지원을 받는 기업은 미래 성장가능성이 높아야 한다. 즉, 이러한 정책들은 지속적인 성장이 가능한 기업들에게 지원되어야 한다. 지속 성장이 가능한 창업기업을 찾기 위해서는, 창업기업과 비슷한 구조를 가지고 있는 중소기업의 정보를 이용할 수 있다. 본 논문에서는 대전창조경제혁신센터에서 기술기반의 창업 및 중소기업 지원 프로그램을 제공받은 창업기업과 중소기업들에 대해 k-means 군집분석과 t-SNE를 이용하여 기업 군집화를 실시한다. k-means 군집분석을 이용하여 기업들의 군집화를 실시하고 t-SNE로 기업 정보를 학습하여 2차원 공간에 투영하여 군집별 기업 특성을 확인한다. 실험으로 창업기업과 중소기업 169개에 대해 적용한 결과, 성장 가능성이 높은 창업기업에 대한 군집을 찾을 수 있었다. Recently, various policies have been implemented to support start-up enterprises. Enterprises that are supported by policies should have a high potential for future growth. That is, these policies should be supported by enterprises that are capable of sustainable growth. In order to find a start-up enterprise capable of sustainable growth, information of SMEs having a structure similar to a start-up enterprise can be used. In this paper, we conduct enterprise clustering using k-means cluster analysis and t-SNE for start-up enterprises and SMEs that have been provided with technology-based start-up enterprises and SMEs support programs at Daejeon Center for Creative Economy & Innovation in South Korea. The clustering of companies using k-means cluster analysis is performed, and the enterprise information is learned by t-SNE and projected in a two-dimensional space to confirm the characteristics of each cluster. As a result of applying the experiment to 169 start-up enterprises and SMEs, we found clusters of start-up enterprises with high growth potential.

선분 그래프에서의 두 번째 모든 쌍 최단 경로 알고리즘에 관한 연구

구재현(Jaehyun Koo),최재현(Jaehyun Choi) 한국정보과학회 2015 한국정보과학회 학술발표논문집 Vol.2015 No.12

작업흐름도 기반 휴대전화 메시지 기능 사용성 평가

최재현(Jaehyun Choi),공용구(Yong?Ku Kong),정명철(Myung?Chul Jung) 대한인간공학회 2007 大韓人間工學會誌 Vol.26 No.4

This study evaluated the short message service (SMS) and multimedia message service (MMS) usability of mobile phones and wireless internet services by performance failure rates and flowcharts that adopted the concept of state diagrams. Forty-eight participants who had an experience of using mobile phones were recruited by posting an advertisement on websites for the experiment. They carried out both SMS and MMS tasks with the mobile phones of LG Cyon and Samsung Anycall as well as the wireless internet services of LGT ez-i, KTF magicN, and SKT NATE. In general, Cyon had the lower performance failure rate than Anycall for SMS, and ez-i had the lowest performance failure rate than the other services for MMS. More specifically through the workflow analysis, most participants used hot keys to take 7~8 steps to send a SMS including a symbol and had a difficulty in typing the symbol. They also took 10~11 steps to send a MMS after taking and attaching two pictures. Anycall, magicN, and NATE had significantly large error and failure rates due to the limited option of the menu paths that users could take and poor compatibilities of menu names and between menu and navigation keys. This study showed the possibility of use of flowcharts for systematic and specific usability evaluation methods and found the causes of performance errors and failures with mobile phones and wireless internet services to provide insight into their design.

머신러닝에 의한 기상상태와 COVID-19 감염 관계 분석

이재현(JaeHyun Lee),지승연(SeungYeon Ji),최원준(Wonjun Choi),강태훈(TaeHoon Kang),김상현(SangHyeon Kim),최지우(JiWoo Choi),강태원(TaeWon Kang) 한국정보기술학회 2021 Proceedings of KIIT Conference Vol.2021 No.11

COVID-19 사태의 심각성과 함께 역학조사의 중요성이 시간이 지난 지금까지도 대두되고 있다. 본 연구는 효과적인 역학조사를 위해 활동량에 영향을 끼치는 요인 중 기상정보를 선택하여 확진자의 발생 여부와 기상정보의 상관관계를 머신러닝 모델을 사용하여 분석하고자 한다. 사용한 모델은 SVM(Support Vector Machine) 으로 기본적인 기상정보와 추가적으로 추출한 특성들을 입력으로 다음날의 확진자의 발생 여부를 예측했으며 정확도 81.65%, 정밀도 98%, 재현율 71%의 성능을 보였다. 결과, 유의미한 성능향상을 보였던 대표적인 특성은 일정 기간동안의 확진자 수, 요일이 있었으며 기상정보의 경우 추가적인 특성추출에도 의미있는 성능향상을 보이지 않아 확진자 발생 여부와 기상정보의 관계가 뚜렷하지 않다는 것을 확인할 수 있었다. Along with the seriousness of the COVID-19 incident, the importance of epidemiological investigations is still emerging over time. This study aims to analyze the correlation between the occurrence of confirmed patients and weather information by selecting weather information among the factors influencing the amount of activity for effective epidemiological investigation using a machine learning model. The model used was SVM (Support Vector Machine), which predicted the occurrence of confirmed cases the next day by inputting basic weather information and additional extracted characteristics, and showed performance of 81.65%, precision 98%, and reproduction rate 71%. As a result, it was confirmed that the typical characteristics of significant performance improvement were the number of confirmed cases and days of the week, and in the case of weather information, there was no clear correlation between confirmed cases and weather information.