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Network virtualization is a promising technology to enable multiple architectures to run on a single network. However, virtualization also introduces additional security vulnerabilities that may be exploited by attackers. It is necessary to ensure that the security requirements of virtual networks are met by the physical substrate, which however has not received much attention thus far. This paper...
IEEE 802.22 wireless regional area network (WRAN) standard employing cognitive radios is gaining much attention recently. The WRAN standard targets reuse of unused TV channels. We propose a device-to-device wireless regional area network (D2DWRAN) to extend the capacity of IEEE 802.22. Network capacity can be increased by supporting direct intra-cell device to device (D2D) communication through channel...
The ultra-low orbit satellites generally orbit at an altitude about 200km, and have better performance of observing the Earth and receiving information while using the same observation instrument, thus have good economic benefits and broad application prospects. However, the aerodynamic forces and moments interference to the ultra-low-orbit satellites are dozens of orders of magnitude higher than...
Spacecraft formation flying has different from the traditional spacecraft orbit control of a single satellite, which has a certain degree of autonomy to maintain specific formation geometries configuration. According to the existing satellite platform technology, a software implementation of autonomous orbit control is proposed as a supplement of the satellite onboard control system. With that same...
Flexible channelization can enhance spectrum efficiency by adapting channel bandwidth and center frequency compared with traditional fixed width channel. The key challenge of this new mechanism lies in how to determine proper channel width for each link in a distributed manner without coordination. In this work, we investigate the spectrum sharing problem with flexible channelization from game-theoretic...
A novel Y-cap. connection structure for Class II offline SMPS applications is proposed to suppress the common mode (CM) noise. With proposed concept, the size of the CM choke can be greatly reduced while satisfying the EMC standard. Furthermore, the inner shielding layer inside power transformer which is normally a must in product design to comply with the EMC standards can be eliminated for higher...
Against conventional wisdom, asymmetrical interleaving strategy is proposed for two-phase interleaved LLC resonant DC/DC running at the same switching frequency to guarantee the equilibrium point of current sharing under all operation condition. Basing this strategy, adaptive-voltage-positioning (AVP) concept is further proposed for passive current sharing realization, while satisfying output voltage...
Fuzzy keyword search is an important and necessary functionality for information retrieval in modern cloud storage services, since cloud users may submit queries with typos errors or have deficient knowledge about the underlying keywords of cloud data sets. However, for the purpose of privacy preservation, data is usually encrypted before outsourcing to the cloud, which greatly compromises the data...
We consider the distributed optimization problem of networked large-scale systems under specified constraints. In particular, we aim to optimize the steady-state performance of the system by making it (in a distributed manner) working at the optimal operation point. To solve the problem, a primal-dual method is employed to seek the optimal setpoint in conjunction with Extremum Seeking Control (ESC)...
Urban traffic congestions have become a financial and societal burden in many cities. Efficient traffic management solutions mitigating such congestions require a reliable modeling and estimation of traffic jams. In urban traffic, the modeling challenges are related to flow collisions and gridlocks created at intersections. In this paper, we propose a traffic light extended Cell Transmission Model...
We present a scalable large-area terahertz (THz) emitter designed for excitation with 1.55 µm pump radiation. It is based on an InGaAs heterostructure combined with a microstructured electrode pattern. Electric fields of more than 2.5 V/cm in the THz focus are reached, the spectrum of the pulses extends up to 3 THz.
In recent years, specialized R&D or management departments of service innovation have appeared in some large-size enterprises in China, which aim to effectively manage service innovation activities. This article studied on cases of ten leading enterprises in China and summarized the function of the specialized department in service innovation. Its functions include managing ideas and innovative...
Working principle of single-phase Boost-cascaded Boost-Buck(BoCBB) power factor correction converter is analyzed. On this basis, a new nonlinear current control method for buck converter is presented first, and a novel integrated control strategy constituting average current mode control and the above nonlinear current control method is proposed for BoCBB converter. With this control strategy, the...
Trajectory tracking control of a stratospheric satellite is investigated in this paper. A simplified dynamical model for the stratospheric satellite is established based on the Lagrange equation to design its longitudinal trajectory tracking controller. From the model it is proved that the tracking problem cannot be solved by direct input-output feedback linearization control strategy, so the stratospheric...
MapReduce framework and its open-source implementation Hadoop, a scalable and fault-tolerant infrastructure for big data analysis on large clusters, can achieve different performance with different data storage structures. This paper evaluates the performance about three kinds of data storage structures of MapReduce, namely row-store, column-store, and RCFile. The evaluating experiments are designed...
Enterprise WLAN consists of many APs connected to wired backbone network. Conventional DCF mechanism can not completely prevent conflicts between APs which cause large quantities of transmission failure and retransmission overhead. However, to keep compatible with 802.11-compliant clients, it is difficult to discard DCF. In this paper, we proposed a framework called DPS, which incorporates centralized...
For downlink multi-user multiple-input multiple-output (MU-MIMO) system, the precoding scheme of maximizing signal-to-leakage-and-noise (SLNR) at base station (BS) relies on channel covariance matrix. However, the CSI feedback defined in LTE/LTE-A does not directly correspond to channel covariance. Instead, precoding matrix indicator (PMI) and channel quality indicator (CQI) are fed back from user...
The 6-DOF dynamic model of a stratospheric satellite is established on the Lagrangian dynamic formulation for its longitudinal trajectory control. With the knowledge of direct input/output linearization feedback cannot be realized, the control system is decomposed into three serial subsystems on the functional principle of rudder controlling the sail, sail supporting the tether and tether dragging...
The spatial and temporal variations of licensed spectrum bands introduce new problems to cognitive wireless LANs. We propose a novel client-centric heterogeneous spectrum access mechanism to deal with these new challenges. All clients in a cell would not have to use the same channel to communicate with access point when there is no common available channel among these clients. In order to achieve...
Aiming at the subjective limitations of the traditional condition monitoring and evaluation methods for the power transformer, the condition assessment method of the transformer state based on the dynamic gray target theory is used to evaluate and diagnose the operating condition and the fault mode of the transformer. The probabilistic reasoning mechanism based on the distance measurement is constructed,...
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