Xichang Satellite Launch Center
Xichang Satellite Launch Center
Fan M.,PLA University of Science and Technology |
Zhang H.,PLA University of Science and Technology |
Hu H.,PLA Air Force Aviation University |
Wang Q.,Xichang Satellite Launch Center
2016 IEEE International Conference on Communication Systems, ICCS 2016 | Year: 2016
In RF-powered full-duplex cognitive radio networks (FD CRNs), with the help of FD technique and energy harvesting capability, secondary users (SUs) can conduct spectrum sensing, utilize the spectrum opportunistically and harvest energy from RF signals simultaneously. Since the circumstances whether secondary transmitters (STs) are transmitting or not are different, two detection thresholds for energy detector are employed. In this paper, we investigate the problem of optimizing detection thresholds to maximize both energy efficiency (EE) and harvesting efficiency (HE) in RF-powered FD CRNs under the constraint that the primary user (PU) is protected. We define a new objective function, i.e., the weighted sum of EE and HE and formulate the optimization problem mathematically. Further we optimize the defined objective function and obtain the optimal detection thresholds and the corresponding EE and HE. Simulation results are given to verify the proposed optimization scheme and the theoretical analyses. © 2016 IEEE.
Li G.,Xichang Satellite Launch Center |
Chen J.,CAS South China Sea Institute of Oceanology |
Wang X.,CAS South China Sea Institute of Oceanology |
Luo X.,PLA University of Science and Technology |
And 4 more authors.
Climate Dynamics | Year: 2017
As an important oceanic signal, the North Atlantic sea surface temperature (SST) affects not only the climate variability over East China and Northeast China but also can affect climate variability over southwestern China (SWC). Based on station rainfall data and reanalysis datasets, the present study investigates the relationship of North Atlantic SST with SWC rainfall during boreal spring for the period 1979–2016. The results show that there is a significant positive correlation between North Atlantic SST and SWC rainfall during boreal spring. The atmospheric circulation over southern Asia associated with North Atlantic SST is favorable for positive rainfall anomalies. Further analyses show that North Atlantic SST can induce a North Atlantic–western Russia–western Tibetan Plateau–SWC (NRTC) teleconnection wave train from upper level to low level. At low level, two anomalous anticyclones are found over the mid-high latitude of North Atlantic and the western Tibetan Plateau, and two anomalous cyclones are observed over the western Russia and Bay of Bengal (BOB), respectively. The NRTC teleconnection wave train plays a bridging role between the North Atlantic SST and SWC rainfall during boreal spring. Both the observational analysis and two numerical experiments suggest that the North Atlantic SST during boreal spring can induce an anomalous cyclone over BOB by the NRTC teleconnection pattern. The anomalous cyclone over BOB favors moisture transport to SWC, accompanying with significant anomalous ascending motion, and thus results in positive rainfall anomalies in SWC during boreal spring. © 2017 Springer-Verlag Berlin Heidelberg
Chen H.-X.,Xichang Satellite Launch Center |
Chen H.-X.,State Key Laboratory of NBC Protection |
Ren Y.,Spaceflight Project Command |
Yu S.-X.,Xichang Satellite Launch Center
Yuhang Xuebao/Journal of Astronautics | Year: 2017
Fuzzy fault tree analysis method is applied to study the reliability of the conventional temperature control system. Firstly, a fault tree model of the conventional rocket propellant temperature control system is established. Secondly, based on the fuzzy mathematics theory, the ascending method is applied to solve the minimum cut set of the fault tree. The expression of the bottom event occurrence probability is described by the normal type fuzzy numbers, and the calculation method of the top event fuzzy sets is put forward. Finally, a fault location and screening method based on the fuzzy probability importance is provided. The PLC communication faults are calculated and analyzed as an example. The results show that the troubleshooting methods based on the fuzzy probability importance can effectively improve the efficiency of fault location. © 2017, Editorial Dept. of JA. All right reserved.
News Article | November 6, 2015
China successfully launched a new communication satellite called ChinaSat 2C, which will be utilized to provide transmissions for radio, television and broadband services. The satellite was carried on-board the Long March 3B rocket on Wednesday from the Xichang Satellite Launch Center in southwest China's Sichuan province. Launched at 12:25 a.m., the experimental satellite for communication technology will provide signal transmission services for the country's television stations, radio stations, cable networks and wireless transmission devices across China. ChinaSat 2C was developed by China Academy of Space Technology and owned by China Satellite Communications Co., Ltd., a company that provides satellite space segment and satellite ground operation services. Generally, they provide transmissions through in-orbit satellites to broadcast television programs and radio stations. The launch was the 216th mission of the Long March carrier rocket series and 13th successful space launch by China this year. However, reports circulated that the satellite, which they called Zhongxing-2C was launched with a private payload believed by Western observers to be a military communications satellite. They speculated that this newly launched satellite is the second one of the second generation Shentong geostationary military communication satellites. China media did not release other information regarding the mission aside from preflight warnings for airplanes to avoid the area. Lately, a series of satellites for various purposes were launched by China. On Oct. 16, they launched the APSTAR-9 communications satellite which was also blasted off with a Long March-3B/G2 rocket which is the replacement satellite for APT Satellite's APSTAR-9A satellite. It was launched to provide quality satellite telecommunications and broadcasting services to the Asia-Pacific region. On Oct. 27, they launched a mapping satellite into the orbit. Tianhui-1C will be used mainly for scientific experiments, mapping, disaster relief and land resource surveys. A satellite intended to explore the dark matter is scheduled to be launched in December. First of the satellites in that series, the dark matter particle explorer will aid in the assessment of direction and electric charge of energy particles in space to search dark matter.
Wang D.,Xichang Satellite Launch Center |
Zhou J.,National University of Defense Technology |
Lin Z.-Y.,National University of Defense Technology
Tuijin Jishu/Journal of Propulsion Technology | Year: 2017
To analyze operating characteristics of two-phase continuous rotating detonation combustor fueled by kerosene more deeply, the time/frequency-domain characteristics of ignition and propagation processes in the combustor were acquired with experimental method when the oxidizer was air with more oxygen or pure oxygen. The droplet velocity and diameter distribution in different planes out of the injector were measured with the PDA system. The experimental results show that when the mass flow rates of kerosene, O2 and air are 78.0g/s, 224.0g/s and 72.5g/s, and the equivalent ratio of 1.083 respectively, the combustor steadily works in single-wave mode, and the detonation wave has an average frequency of 0.904kHz and an average velocity of 649m/s. When the mass flow rates of kerosene and O2 are 81.8g/s and 231.8g/s, and the equivalent ratio of 1.222 respectively, the combustor works in double-wave mode, where the detonation waves have an average frequency of 5.882kHz and an average velocity of 1848m/s, and the propagation process shows strong unsteadiness when the oxidizer is pure oxygen. The detonation velocity increases with the rise of oxygen content in oxidant when the equivalent ratio ranges from 0.805 to 0.908, reaching 2440m/s. As the equivalent ratio ranges from 1.057 to 1.220, the detonation velocity increases linearly with the rise of oxygen content. © 2017, Editorial Department of Journal of Propulsion Technology. All right reserved.
Zou J.,Tsinghua University |
Zhao Q.,Tsinghua University |
Yang W.,Tsinghua University |
Yang W.,Xichang Satellite Launch Center |
Wang F.,Tsinghua University
Energy and Buildings | Year: 2017
Indoor occupancy measurement plays an indispensable role in occupant-based intelligent control of building systems for energy conservation. In this paper, a novel algorithm is proposed to detect occupancy by analyzing the office surveillance videos. The algorithm uses a cascade classifier to detect human head, consisting of pre-classifier, main classifier and clustering analyzer. The pre-classifier uses three frame difference algorithm to search motion windows and employs a HOG-SVM module to filter most non-head areas quickly. The main classifier employs a convolution neural network to classify head windows with high recall and precision. The clustering analyzer utilizes K-means clustering to fuse sequential frames and verify the head detection result to further improve the accuracy. The advantages of the three stages are enhanced by separately determined parameters and then united by the particular combination. The innovation yields an outstanding overall performance. The algorithm is tested on the dataset of 80-h surveillance videos in an office. The experimental results show that the accuracy (correctness for presence of head) of occupancy measurement reaches up to 95.3% and the computational cost for a measurement is just 721 ms. It is applicable to both off-line data mining of stored videos and on-line detection of occupancy by intelligent video surveillance. © 2017 Elsevier B.V.
Yang W.,Tsinghua University |
Yang W.,Xichang Satellite Launch Center |
Zhao Q.,Tsinghua University
2014 IEEE Chinese Guidance, Navigation and Control Conference, CGNCC 2014 | Year: 2015
The increasing interconnectivity of industrial control system (ICS) networks has exposed them to a wide range of security problems. In recent years, efforts from industries and research communities have been made in addressing the security issues of ICSs. However, the ICSs security for critical infrastructures is still a challenging issue today. Controller, supervisory software and control network are critical components of ICS, and those components, many designed without security in mind, are vulnerable to cyber-attacks and any of them attacked easily lead to system collapse. Much research work about this subject has been done and a lot of vulnerabilities and countermeasures were presented. In this paper, we surveys ongoing research and provide an overview of the cyber security of controller, supervisory software and control network. © 2014 IEEE.
Guo Z.,Xichang Satellite Launch Center |
Li Q.,Beijing Institute of Technology
Proceedings of the International Astronautical Congress, IAC | Year: 2013
This paper focuses on system level EMC database modeling of spacecraft. Since there are many electromagnetic interference sources for the sensitive electron devices on the spacecraft, kinds of different EMI sources will be discussed at the beginning. The EMI radiated sources such as strong electromagnetic pulse, various payloads radiated emissions and high-power AC/DC conducted emissions etc will be analyzed in details. After that, as for sensitive devices easily to be interfered by others types of EMI sources, the EMI estimation formulae will be deduced. Following that, according to deduced EMI estimation formula, the EMI prediction models for sensitive devices will be given out. Because of several of sensitive devices on the spacecraft, different database estimation model should be made according to the allowed EMI safeguard levels. Based on which has been discussed spacecraft database of EMC, the subsystem (equipment) level devices EMC prediction can be simulation under this model. This design methodology can be used in spaceflight project of the various payloads to ensure compliance with the stringent EMI requirements.Copyright ©2013 by the International Astronautical Federation.
Kuang P.-C.,Xichang Satellite Launch Center |
Wang J.-G.,Electronic Engineering Institute |
Luo J.-Q.,Electronic Engineering Institute
Yuhang Xuebao/Journal of Astronautics | Year: 2011
The existing feature description of radar signal can not describe or recognize the complicated radar emitter efficiently. In order to solve the problem, a novel method of using Pulse Sequence Pattern (PSP) and the Vague Set is proposed in this paper. The problem of radar emitter recognition is transformed into the problem of multi-property decision of Vague Set. This technique not only can solve the problem of fuzziness in radar signal recognition, but also do not need a process of feature extraction as conventional method, so the process is reduced. In addition, in the PSP-based radar emitter recognition ordered multi-pulses are used for matching synchronously, so the recognition results are more accurate. Computer simulations show that this technique is practicable and effective and offers a new idea for radar emitter recognition.
PubMed | Xichang Satellite Launch Center and Tsinghua University
Type: Journal Article | Journal: Sensors (Basel, Switzerland) | Year: 2016
With the increasing demands for better transmission speed and robust quality of service (QoS), the capacity constrained backhaul gradually becomes a bottleneck in cooperative wireless networks, e.g., in the Internet of Things (IoT) scenario in joint processing mode of LTE-Advanced Pro. This paper focuses on resource allocation within capacity constrained backhaul in uplink cooperative wireless networks, where two base stations (BSs) equipped with single antennae serve multiple single-antennae users via multi-carrier transmission mode. In this work, we propose a novel cooperative transmission scheme based on compress-and-forward with user pairing to solve the joint mixed integer programming problem. To maximize the system capacity under the limited backhaul, we formulate the joint optimization problem of user sorting, subcarrier mapping and backhaul resource sharing among different pairs (subcarriers for users). A novel robust and efficient centralized algorithm based on alternating optimization strategy and perfect mapping is proposed. Simulations show that our novel method can improve the system capacity significantly under the constraint of the backhaul resource compared with the blind alternatives.