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Asymptotic Performance Analysis of Free-Space Optical Links with Transmit Diversity
Jianfeng Feng,Xiaohui Zhao 한국광학회 2016 Current Optics and Photonics Vol.20 No.4
The misalignment errors and fluctuations in irradiance due to atmospheric turbulence can severelydegrade the performance of free-space optical (FSO) systems. In this paper, we investigate the asymptoticbit error rate (BER) performance and diversity orders of FSO links using parallel transmit-diversity schemes. The BER expressions of FSO links with the switch-and-examine transmit (SET), switch-and-examinetransmit with post-selection (SETps), dual-branch transmit laser selection (Dual-TLS), and group transmitlaser selection (Group-TLS) schemes are derived, based on an approximate channel model. Then numericalsimulations for these four schemes in the region of high average signal-to-noise ratio (SNR) are presentedunder different channel conditions. The results show that the four transmit-diversity schemes can reducesystem complexity and overcome the limitation of peak power, without much BER deterioration.
Performance Analysis of FSO Communication Systems with Photodetector Multiplexing
Jianfeng Feng,Xiaohui Zhao 한국광학회 2017 Current Optics and Photonics Vol.1 No.5
In this paper, we carry out a performance analysis of a two-user free-space optical (FSO) communicationsystem with photodetector multiplexing, in which the two users are defined as the primary user (PU) andsecondary user (SU). Unlike common single-user FSO systems, our photodetector multiplexing FSO systemdeploys a shared detector at the receiver and enables PU and SU to send their own data synchronously. We conduct the performance analysis of this FSO system for two cases: (1) in the absence of backgroundradiation, and (2) in the presence of background radiation. Decision strategies for PU and SU are presentedaccording to the two scenarios above. Exact and approximate conditional symbol-error probability (SEP)expressions for both PU and SU are derived, in an ideal channel with no fading. Average SEP expressionsare also presented in the no-background-radiation scenario. Additionally, in some particular cases wherethe power ratio tends to 0.5 or 1, approximate SEP expressions are also obtained. Finally, numericalsimulations are presented under different conditions, to support the performance analysis.
Shi Jianfeng,Feng Ying,Tao Yangji,Guo Weican,Yao Riwu,Zheng Jinyang 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.9
High-density polyethylene (HDPE) pipelines in nuclear power plants (NPPs) have to meet high requirements for seismic performance. HDPE pipes have been proved to have good seismic performance, but joints are the weak links in the pipelines, and pipeline failures usually initiate from the defects inside the joints. Limited data are available on the seismic performance of butt-fusion joints of HDPE pipelines in NPPs, especially in terms of defects changes inside the joints after earthquakes. In this paper, full-scale shaking table tests were performed on a test section of suspended HDPE pipelines in an NPP, which included straight pipes, elbows, and 10 butt-fusion joints. During the tests, the seismic load-induced strain of the joints was analyzed by strain gauges, and it was much smaller than the internal pressure and self-weight-induced strain. Before and after the shaking table tests, phased array ultrasonic testing (PA-UT) was conducted to detect defects inside the joints. The locations, numbers, and dimensions of the defects were analyzed. It was found that defects were more likely to occur in elbows joints. No new defect was observed after the shaking table tests, and the defects showed no significant growth, indicating the satisfactory seismic performance of the butt-fusion joints.
Cheng Wu,Jianfeng Hu,Dan Xie,Endi Fan,Junlin Yang,Xiaolong You,Pingyan Cheng,Wei Huang,Feng Hu,Diqiang Wang 한국식품과학회 2024 Food Science and Biotechnology Vol.33 No.8
Mechanized, automated and intelligent brewing is an important trend of innovation and transition in Jiang-flavor baijiu industry. In this study, physicochemical parameters, microbial community composition and flavor substances during 3rd round heap fermentation between mechanical and traditional workshop were investigated and compared based on traditional culturable methods, high-throughput sequencing technology and gas chromatography analysis. The dominant bacterial and fungal genera were consistent between the two workshops, but mechanized brewing had a significant impact on the composition of fungal communities. Rhodococcus and Monascus were special genera in mechanical workshop. The interaction relationship between physicochemical parameters and dominant microorganisms in mechanized workshop was different from traditional workshop as well. This study provided a scientific basis for further analyzing the mechanism of mechanized brewing of Jiang-flavor baijiu.
CQDs as emerging trends for future prospect in enhancement of photocatalytic activity
Syed Noureen,Huang Jianfeng,Feng Yongqiang 한국탄소학회 2022 Carbon Letters Vol.32 No.1
Carbon quantum dots (CQDs) as a rising class of carbon family have gained widespread attention in view of their multiple properties such as great photoluminescence (PL) properties, facile synthesis route, needing economical and cheap raw material, high physiochemical stability, and simple functionalization. This makes CQDs highly versatile and with potential for different applications. To date, CQDs-enabled photocatalysts are regarded as one of the most efficient technologies to degrade pollutants in water; however, poor activity under visible light and the recombination of photogenerated electron and hole pairs hinder getting an ideal performance that may be applied on a large scale. Conventional techniques have been modified via a new advanced method. In this review, we highlighted the strategies to improve the activity of conventional semiconductor photocatalysis via coupling with CQDs, and strategies to improve the photocatalytic activity such as functionalization, doping, and Z-scheme heterojunctions were discussed in detail. This review also covered the CQDs heterojunction application in pollutant degradation and discussed several examples with high-performance photocatalytic activity.
ENERGY-SAVING MODEL PREDICTIVE CRUISE CONTROL COMBINED WITH VEHICLE DRIVING CYCLES
SiLun Peng,ZhiHao Xu,JianHua Li,Feng Xiao,Xu Zhang,ShiXin Song,Da Wang,ChunYang Qi,JianFeng Wang 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.2
This study analyzes the problem of adaptive cruise control of vehicles in different driving cycles and divides diverse weight coefficient intervals for the vehicles under the different driving cycles to improve the adaptability of the vehicles in various environments. This paper first describes the driving environment of the adaptive cruise vehicle, and a model prediction algorithm with fixed weight coefficients is established to control the vehicle state. Then, a neural network is established to identify the vehicle driving cycles, the weight intervals are divided in accordance with different driving cycles, and the weight value is dynamically adjusted through fuzzy control. Lastly, the variable weight coefficients of different driving cycles are combined with the model prediction controller. The software cosimulation shows that the method designed in this paper plays a positive role in the fuel economy of adaptive cruise.
Design and Implementation of Embedded Serial Communication Based on Finite State Machine
Jian Feng,Yuanyuan Ding 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.9
In order to solve problems of poor real-time capability, poor reliability and low fault tolerance for data transmission in embedded serial communication, a serial communication protocol based on finite state machine (FSM) was designed and implemented, and was applied in communications of network management. The packet format and the communication control mechanism of the serial communication protocol are described, and complete framework for the application is given. Process of receiving and transmitting FSM models in serial communication are abstracted, combined with the interrupt service routine. In practical application, the serial communication program can meet the functional and performance requirements of serial communication between embedded devices and network management system (NMS).