• Title/Summary/Keyword: Support performance

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A 2×2 MIMO Spatial Multiplexing 5G Signal Reception in a 500 km/h High-Speed Vehicle using an Augmented Channel Matrix Generated by a Delay and Doppler Profiler

  • Suguru Kuniyoshi;Rie Saotome;Shiho Oshiro;Tomohisa Wada
    • International Journal of Computer Science & Network Security
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    • v.23 no.10
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    • pp.1-10
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    • 2023
  • This paper proposes a method to extend Inter-Carrier Interference (ICI) canceling Orthogonal Frequency Division Multiplexing (OFDM) receivers for 5G mobile systems to spatial multiplexing 2×2 MIMO (Multiple Input Multiple Output) systems to support high-speed ground transportation services by linear motor cars traveling at 500 km/h. In Japan, linear-motor high-speed ground transportation service is scheduled to begin in 2027. To expand the coverage area of base stations, 5G mobile systems in high-speed moving trains will have multiple base station antennas transmitting the same downlink (DL) signal, forming an expanded cell size along the train rails. 5G terminals in a fast-moving train can cause the forward and backward antenna signals to be Doppler-shifted in opposite directions, so the receiver in the train may have trouble estimating the exact channel transfer function (CTF) for demodulation. A receiver in such high-speed train sees the transmission channel which is composed of multiple Doppler-shifted propagation paths. Then, a loss of sub-carrier orthogonality due to Doppler-spread channels causes ICI. The ICI Canceller is realized by the following three steps. First, using the Demodulation Reference Symbol (DMRS) pilot signals, it analyzes three parameters such as attenuation, relative delay, and Doppler-shift of each multi-path component. Secondly, based on the sets of three parameters, Channel Transfer Function (CTF) of sender sub-carrier number n to receiver sub-carrier number l is generated. In case of n≠l, the CTF corresponds to ICI factor. Thirdly, since ICI factor is obtained, by applying ICI reverse operation by Multi-Tap Equalizer, ICI canceling can be realized. ICI canceling performance has been simulated assuming severe channel condition such as 500 km/h, 8 path reverse Doppler Shift for QPSK, 16QAM, 64QAM and 256QAM modulations. In particular, 2×2MIMO QPSK and 16QAM modulation schemes, BER (Bit Error Rate) improvement was observed when the number of taps in the multi-tap equalizer was set to 31 or more taps, at a moving speed of 500 km/h and in an 8-pass reverse doppler shift environment.

Review on Rock-Mechanical Models and Numerical Analyses for the Evaluation on Mechanical Stability of Rockmass as a Natural Barriar (천연방벽 장기 안정성 평가를 위한 암반역학적 모델 고찰 및 수치해석 검토)

  • Myung Kyu Song;Tae Young Ko;Sean S. W., Lee;Kunchai Lee;Byungchan Kim;Jaehoon Jung;Yongjin Shin
    • Tunnel and Underground Space
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    • v.33 no.6
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    • pp.445-471
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    • 2023
  • Long-term safety over millennia is the top priority consideration in the construction of disposal sites. However, ensuring the mechanical stability of deep geological repositories for spent fuel, a.k.a. radwaste, disposal during construction and operation is also crucial for safe operation of the repository. Imposing restrictions or limitations on tunnel support and lining materials such as shotcrete, concrete, grouting, which might compromise the sealing performance of backfill and buffer materials which are essential elements for the long-term safety of disposal sites, presents a highly challenging task for rock engineers and tunnelling experts. In this study, as part of an extensive exploration to aid in the proper selection of disposal sites, the anticipation of constructing a deep geological repository at a depth of 500 meters in an unknown state has been carried out. Through a review of 2D and 3D numerical analyses, the study aimed to explore the range of properties that ensure stability. Preliminary findings identified the potential range of rock properties that secure the stability of central and disposal tunnels, while the stability of the vertical tunnel network was confirmed through 3D analysis, outlining fundamental rock conditions necessary for the construction of disposal sites.

Investigation of thermal hydraulic behavior of the High Temperature Test Facility's lower plenum via large eddy simulation

  • Hyeongi Moon ;Sujong Yoon;Mauricio Tano-Retamale ;Aaron Epiney ;Minseop Song;Jae-Ho Jeong
    • Nuclear Engineering and Technology
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    • v.55 no.10
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    • pp.3874-3897
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    • 2023
  • A high-fidelity computational fluid dynamics (CFD) analysis was performed using the Large Eddy Simulation (LES) model for the lower plenum of the High-Temperature Test Facility (HTTF), a ¼ scale test facility of the modular high temperature gas-cooled reactor (MHTGR) managed by Oregon State University. In most next-generation nuclear reactors, thermal stress due to thermal striping is one of the risks to be curiously considered. This is also true for HTGRs, especially since the exhaust helium gas temperature is high. In order to evaluate these risks and performance, organizations in the United States led by the OECD NEA are conducting a thermal hydraulic code benchmark for HTGR, and the test facility used for this benchmark is HTTF. HTTF can perform experiments in both normal and accident situations and provide high-quality experimental data. However, it is difficult to provide sufficient data for benchmarking through experiments, and there is a problem with the reliability of CFD analysis results based on Reynolds-averaged Navier-Stokes to analyze thermal hydraulic behavior without verification. To solve this problem, high-fidelity 3-D CFD analysis was performed using the LES model for HTTF. It was also verified that the LES model can properly simulate this jet mixing phenomenon via a unit cell test that provides experimental information. As a result of CFD analysis, the lower the dependency of the sub-grid scale model, the closer to the actual analysis result. In the case of unit cell test CFD analysis and HTTF CFD analysis, the volume-averaged sub-grid scale model dependency was calculated to be 13.0% and 9.16%, respectively. As a result of HTTF analysis, quantitative data of the fluid inside the HTTF lower plenum was provided in this paper. As a result of qualitative analysis, the temperature was highest at the center of the lower plenum, while the temperature fluctuation was highest near the edge of the lower plenum wall. The power spectral density of temperature was analyzed via fast Fourier transform (FFT) for specific points on the center and side of the lower plenum. FFT results did not reveal specific frequency-dominant temperature fluctuations in the center part. It was confirmed that the temperature power spectral density (PSD) at the top increased from the center to the wake. The vortex was visualized using the well-known scalar Q-criterion, and as a result, the closer to the outlet duct, the greater the influence of the mainstream, so that the inflow jet vortex was dissipated and mixed at the top of the lower plenum. Additionally, FFT analysis was performed on the support structure near the corner of the lower plenum with large temperature fluctuations, and as a result, it was confirmed that the temperature fluctuation of the flow did not have a significant effect near the corner wall. In addition, the vortices generated from the lower plenum to the outlet duct were identified in this paper. It is considered that the quantitative and qualitative results presented in this paper will serve as reference data for the benchmark.

How Korean children and adolescents perceive their parents: Indigenous psychological analysis (아동과 청소년의 부모에 대한 지각: 토착심리학적 접근)

  • Young-Shin Park;Uichol Kim;Kee Hye Han
    • Korean Journal of Culture and Social Issue
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    • v.9 no.2
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    • pp.127-164
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    • 2003
  • This study investigates how Korean children and adolescents perceive their parents using the indigenous psychological approach. An open-ended questionnaire was developed by the first two authors to investigate reasons why children and adolescents feel grateful, respect, indebted, close, conflict, and distance with their parents. A total of 763 participants (212 grade three students, 267 grade eight students, and 284 grade eleven students) completed the questionnaire. The results can be summarized into three main points. First, the vast majority of children and adolescents feel grateful, respect, and indebted to their parents. They feel grateful, respect and indebted for the sacrifice and suffering they experience looking after the family. Moreover, they respects their parents because of their sincerity, blood relationship, benevolence, guidance and educational support. They feel indebted since they did not obey them, were not able to meet their expectations, and were not diligent in their schoolwork. They felt especially close to their mother. The conflict they felt was due to generational gap and in their academic performance. Second, age affects how they perceive their parents. The parent-child conflict increases with age. The feeling of indebtedness also increase with age. However, the feeling of gratefulness and respects decreases with age. The feeling of closeness with father also decreases with age. Third, socio-economic status and educational achievement of children and adolescent affect the perception of their parents. Those with higher academic grade and socio-economic status are more likely to feel respect and indebtedness and less likely to feel conflict and distance.

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A Study on the Development of an Indoor Positioning Support System for Providing Landmark Information (랜드마크 정보 제공을 위한 실내위치측위 지원 시스템 구축에 관한 연구)

  • Ock-Woo NAM;Chang-Soo SHIN;Yun-Soo CHOI
    • Journal of the Korean Association of Geographic Information Studies
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    • v.26 no.4
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    • pp.130-144
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    • 2023
  • Recently, various positioning technologies are being researched based on signal-based positioning and image-based positioning to obtain accurate indoor location information. Among these, various studies are being conducted on image positioning technology that determines the location of a mobile terminal using images acquired through cameras and sensor data collected as needed. For video-based positioning, a method of determining indoor location is used by matching mobile terminal photos with virtual landmark images, and for this purpose, it is necessary to build indoor spatial information about various landmarks such as billboards, vending machines, and ATM machines. In order to construct indoor spatial information on various landmarks, a panoramic image in the form of a road view and accurate 3D survey results were obtained through c 13 buildings of the Electronics and Telecommunications Research Institute(ETRI). When comparing the 3D total station final result and the terrestrial lidar panoramic image coordinates, the coordinates and distance performance were obtained within about 0.10m, confirming that accurate landmark construction for use in indoor positioning was possible. By utilizing these terrestrial lidar achievements to perform 3D landmark modeling necessary for image positioning, it was possible to more quickly model landmark information that could not be constructed only through 3D modeling using existing as-built drawings.

A Study on Real-time Autonomous Driving Simulation System Construction based on Digital Twin - Focused on Busan EDC - (디지털트윈 기반 실시간 자율주행 시뮬레이션 시스템 구축 방안 연구 - 부산 EDC 중심으로 -)

  • Kim, Min-Soo;Park, Jong-Hyun;Sim, Min-Seok
    • Journal of Cadastre & Land InformatiX
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    • v.53 no.2
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    • pp.53-66
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    • 2023
  • Recently, there has been a significant interest in the development of autonomous driving simulation environment based on digital twin. In the development of such digital twin-based simulation environment, many researches has been conducted not only performance and functionality validation of autonomous driving, but also generation of virtual training data for deep learning. However, such digital twin-based autonomous driving simulation system has the problem of requiring a significant amount of time and cost for the system development and the data construction. Therefore, in this research, we aim to propose a method for rapidly designing and implementing a digital twin-based autonomous driving simulation system, using only the existing 3D models and high-definition map. Specifically, we propose a method for integrating 3D model of FBX and NGII HD Map for the Busan EDC area into CARLA, and a method for adding and modifying CARLA functions. The results of this research show that it is possible to rapidly design and implement the simulation system at a low cost by using the existing 3D models and NGII HD map. Also, the results show that our system can support various functions such as simulation scenario configuration, user-defined driving, and real-time simulation of traffic light states. We expect that usability of the system will be significantly improved when it is applied to broader geographical area in the future.

Study on Predicting the Designation of Administrative Issue in the KOSDAQ Market Based on Machine Learning Based on Financial Data (머신러닝 기반 KOSDAQ 시장의 관리종목 지정 예측 연구: 재무적 데이터를 중심으로)

  • Yoon, Yanghyun;Kim, Taekyung;Kim, Suyeong
    • Asia-Pacific Journal of Business Venturing and Entrepreneurship
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    • v.17 no.1
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    • pp.229-249
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    • 2022
  • This paper investigates machine learning models for predicting the designation of administrative issues in the KOSDAQ market through various techniques. When a company in the Korean stock market is designated as administrative issue, the market recognizes the event itself as negative information, causing losses to the company and investors. The purpose of this study is to evaluate alternative methods for developing a artificial intelligence service to examine a possibility to the designation of administrative issues early through the financial ratio of companies and to help investors manage portfolio risks. In this study, the independent variables used 21 financial ratios representing profitability, stability, activity, and growth. From 2011 to 2020, when K-IFRS was applied, financial data of companies in administrative issues and non-administrative issues stocks are sampled. Logistic regression analysis, decision tree, support vector machine, random forest, and LightGBM are used to predict the designation of administrative issues. According to the results of analysis, LightGBM with 82.73% classification accuracy is the best prediction model, and the prediction model with the lowest classification accuracy is a decision tree with 71.94% accuracy. As a result of checking the top three variables of the importance of variables in the decision tree-based learning model, the financial variables common in each model are ROE(Net profit) and Capital stock turnover ratio, which are relatively important variables in designating administrative issues. In general, it is confirmed that the learning model using the ensemble had higher predictive performance than the single learning model.

Current Research Trends in Entrepreneurship Based on Topic Modeling and Keyword Co-occurrence Analysis: 2002~2021 (토픽모델링과 동시출현단어 분석을 이용한 기업가정신에 대한 연구동향 분석: 2002~2021)

  • Jang, Sung Hee
    • Asia-Pacific Journal of Business Venturing and Entrepreneurship
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    • v.17 no.3
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    • pp.245-256
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    • 2022
  • The purpose of this study is to provide comprehensive insights on the current research trends in entrepreneurship based on topic modeling and keyword co-occurrence analysis. This study queried Web of Science database with 'entrepreneurship' and collected 14,953 research articles between 2002 and 2021. The study used R program for topic modeling and VOSviewer program for keyword co-occurrence analysis. The results of this study are as follows. First, as a result of keyword co-occurrence analysis, 5 clusters divided: entrepreneurship and innovation cluster, entrepreneurship education cluster, social entrepreneurship and sustainability cluster, enterprise performance cluster, and knowledge and technology transfer cluster. Second, as a result of the topic modeling analysis, 12 topics found: start-up environment and economic development, international entrepreneurship, venture capital, government policy and support, social entrepreneurship, management-related issues, regional city planning and development, entrepreneurship research, and entrepreneurial intention. Finally, the study identified two hot topics(venture capital and entrepreneurship intention) and a cold topic(international entrepreneurship). The results of this study are useful to understand current research trends in entrepreneurship research and provide insights into research of entrepreneurship.

A Study on the Investment Effect of Public Accelerator (공공 액셀러레이터 투자 효과에 관한 연구)

  • Hong, JungOh;Kim, Moon-Kyum
    • Asia-Pacific Journal of Business Venturing and Entrepreneurship
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    • v.17 no.3
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    • pp.19-31
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    • 2022
  • Currently, the role of public accelerators in the domestic accelerator market is gradually expanding. Accordingly, in order to establish relevant policies properly, it is necessary to check the effect and validity of public accelerators' investment. However, there is no quantitative research conducted on domestic accelerators, using their financial data, as domestic accelerators have a short history and quantitative data on them are not disclosed. Therefore, this study conducted an empirical analysis with financial data of the startups that received equity investments from public accelerators to confirm the effect of public accelerators'investment in startups. A regression analysis was conducted with financial data from 112 startups that acquired investments from public accelerators in the period of 2016~2020. And the findings are as follows: First, it was found that the initial investment of public accelerators had an effect on the growth and profitability of startups. Specifically, it was confirmed that the initial investment of public accelerators had a positive (+) effect on sales growth rates and total asset growth rates, which are growth indicators. Second, it was found that the joint investment of public accelerators had a significant positive (+) effect on profit margin, an indicator of profitability, rather than on growth. Therefore, it is deemed that it will be a great force for growth if investment in the early-stage startups that showed significant investment results in this study is continuously expanded in combination with support projects, which are a strength of public accelerators. Since this study has confirmed the investment effect of public accelerators, it is deemed necessary to actively promote policies that direct public accelerators' projects toward improving the performance of startups through joint investment with the private sector and supplementing private accelerators' deficiencies.

Key Factors of Talented Scientists' Growth and ExpeI1ise Development (과학인재의 성장 및 전문성 발달과정에서의 영향 요인에 관한 연구)

  • Oh, Hun-Seok;Choi, Ji-Young;Choi, Yoon-Mi;Kwon, Kwi-Heon
    • Journal of The Korean Association For Science Education
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    • v.27 no.9
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    • pp.907-918
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    • 2007
  • This study was conducted to explore key factors of expertise development of talented scientists who achieved outstanding research performance according to the stages of expertise development and dimensions of individual-domain-field. To fulfill the research purpose, 31 domestic scientists who were awarded major prizes in the field of science were interviewed in-depth from March to September, 2007. Stages of expertise development were analyzed in light of Csikszentmihalyi's IDFI (individual-domain-field interaction) model. Self-directed learning, multiple interests and finding strength, academic and liberal home environment, and meaningful encounter were major factors affecting expertise development in the exploration stage. In the beginner stage, independence, basic knowledge on major, and thirst for knowledge at university affected expertise development. Task commitment, finding flow, finding their field of interest and lifelong research topic, and mentor in formal education were the affecting factors in the competent stage. Finally, placing priority, communication skills, pioneering new domain, expansion of the domain, and evaluation and support system affected talented scientists' expertise development in the leading stage. The meaning of major patterns of expertise development were analyzed and described. Based on these analyses, educational implications for nurturing scientists were suggested.