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Cho, Yongbeom,Cho, Seongjae,Park, Byung-Gook,Harris, James S. Jr. The Institute of Electronics and Information Engin 2017 Journal of semiconductor technology and science Vol.17 No.5
Ge is on increasing demand in the advanced Si-compatible high-speed integrated circuits due to its high carrier mobilities. In particular, its hole mobility is much higher than those of other group-IV and III-V compound semiconductor materials. At the same time, Ge has the local minimum at the ${\Gamma}$ valley, which enables the utilization for optical applications. The fact that Ge becomes a direct-bandgap semiconductor material by applying tensile strain can be a good merit in obtaining higher spontaneous radiation probability. However, engineering the electronic structure of Ge by external mechanical stress through stressors with different thermal expansion coefficients might require a complicated set of processes. Efforts were made to turn it into a direct-bandgap one by incorporating Sn. Carrier mobilities are further enhanced when Sn is substitutionally incorporated into the Ge matrix. Thus, advantageous features are expected in improving both optical and electrical performances. Furthermore, the small bandgap energy and bandgap tunability make $Ge_{1-x}Sn_x$ alloy a promising material for components making up the optical interconnect on Si platform including optical source of near-infrared wavelength. In this work, we study the electrical and optical characteristics of $Ge_{1-x}Sn_x$ alloy as a function of Sn content. To achieve this goal, ab initio calculations of energy-band structures of $Ge_{1-x}Sn_x$ with different Sn fractions have been carried out based on linearized augmented plane wave (LAPW) method with modified Becke-Johnson potential model for more accurate bandgap energy. Then, a novel coding method has been adopted for more reliable overall band structures. The minimum Sn content required for direct- and indirect-bandgap material transition of $Ge_{1-x}Sn_x$, electrical and optical energy bandgaps to investigate the bandgap tunability, as well as effective masses, have been extracted as a function of Sn content. The transition point was found to be 6.9% and succinct reductions of effective masses of electron and hole have been confirmed.
Yongbeom Cho,Seongjae Cho,Byung-Gook Park,James S. Harris 대한전자공학회 2017 Journal of semiconductor technology and science Vol.17 No.5
Ge is on increasing demand in the advanced Si-compatible high-speed integrated circuits due to its high carrier mobilities. In particular, its hole mobility is much higher than those of other group-IV and III-V compound semiconductor materials. At the same time, Ge has the local minimum at the Γ valley, which enables the utilization for optical applications. The fact that Ge becomes a direct-bandgap semiconductor material by applying tensile strain can be a good merit in obtaining higher spontaneous radiation probability. However, engineering the electronic structure of Ge by external mechanical stress through stressors with different thermal expansion coefficients might require a complicated set of processes. Efforts were made to turn it into a direct-bandgap one by incorporating Sn. Carrier mobilities are further enhanced when Sn is substitutionally incorporated into the Ge matrix. Thus, advantageous features are expected in improving both optical and electrical performances. Furthermore, the small bandgap energy and bandgap tunability make Ge1-xSnx alloy a promising material for components making up the optical interconnect on Si platform including optical source of near-infrared wavelength. In this work, we study the electrical and optical characteristics of Ge1-xSnx alloy as a function of Sn content. To achieve this goal, ab initio calculations of energy-band structures of Ge1-xSnx with different Sn fractions have been carried out based on linearized augmented plane wave (LAPW) method with modified Becke-Johnson potential model for more accurate bandgap energy. Then, a novel coding method has been adopted for more reliable overall band structures. The minimum Sn content required for direct- and indirect-bandgap material transition of Ge1-xSnx, electrical and optical energy bandgaps to investigate the bandgap tunability, as well as effective masses, have been extracted as a function of Sn content. The transition point was found to be 6.9% and succinct reductions of effective masses of electron and hole have been confirmed.
증강현실을 이용한 실시간 구조 진동 디지털 트윈 시각화
조용범(Yongbeom Cho),오승인(Seungin Oh),김진균(Jin-Gyun Kim) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
This study presents a method for visualizing real-time digital twin models using augmented reality. The proposed system compresses the physical data calculated by finite element (FE) model, such as displacement and stress, with the reduced order modeling technique. A server solves the FE equation in real-time and transmits physical data in a compressed form. Then, a mobile device receives the data and restores to its original form through the pre-saved transformation matrix. As a result, it overcomes limitations of communication and hardware performance in the computational points of view, and achieves real-time visualization in augmented reality environment.
공개 교통사고 데이터베이스와 기계 학습을 이용한 탑승자의 상해 등급 예측에 관한 연구
이용범(Yongbeom Lee),조은기(Eungi Cho),윤창용(Changyong Yoon),박성근(Seongkeun Park) 대한전기학회 2019 전기학회논문지 Vol.68 No.7
In this paper, we propose a prediction model for traffic accident injury grade using machine learning algorithm. We used machine learning models such as Decision Tree, Support Vector Machine, and Logistic Regression to predict injury grade. And to improve performance, Principal Component Analysis(PCA) or Linear Discriminant Analysis(LDA) was applied to each machine learning model. The data used in this study are based on NASS-CDS data that collects traffic accident investigation data and medical records of accident victims. According to the results, the proposed method is expected to be used in the automatic traffic accident notification system because of its reliable accuracy.
라이다를 이용한 장애물 검출 및 자동차 경로계획에 관한 연구
이용범(Yongbeom Lee),조은기(EunGi Cho),최혁두(Hyukdoo Choi),박성근(Seongkeun Park) 한국지능시스템학회 2019 한국지능시스템학회논문지 Vol.29 No.1
본 논문에서는 자율주행 자동차 주행의 안전성 및 정확성 확보를 위해 LiDAR와 GPS를 사용한 장애물 검출 및 경로계획 시스템을 제안한다. 자율주행 자동차의 현재 위치를 추정하고 주변 환경에 대한 정보를 획득하여 차량의 경로를 계획하면 주행상황에 따라 능동적으로 반응하는 자율주행이 가능하다. GPS data의 오차를 줄여 정확한 차량의 위치를 추정하고 미리 취득한 경유점을 이용하여 현재 위치로부터의 전역경로를 계획한다. 또한, LiDAR data로부터 차량 주변의 장애물을 인식 및 검출하고 거리를 산출하여 주행상황에 최적화된 지역경로를 계획한다. 직선 구간에 장애물을 설치하고 차량이 장애물을 회피 주행하는 실험을 통해 제안한 시스템의 성능을 검증한다. In this paper, we propose an obstacle detection and path planning system using LiDAR and GPS to secure the safety and accuracy of autonomous driving car. It is possible to autonomously drive in response to the driving situation by estimating the current position of the car and acquiring information about the surrounding environment and planning the path of the vehicle. Estimating the position of the accurate vehicle by reducing the error of the GPS data, and planning the global path from the current position by using the previously acquired waypoint. In addition, using LiDAR data, we recognizes and detects obstacles around the vehicle and we calculates the distance to plan the optimal route for the driving situation. The performance of the proposed system is verified through an experiment in which obstacles are installed in a straight section and the vehicle avoids obstacles.