A DYNAMIC SPECTRUM ACCESS NETWORK BASED ON COGNITIVE RADIO

Dynamic spectrum access technologies based on Cognitive Radio(CR) is under intensive research carried out by the wireless communication society and is expected to solve the problem of spectrum scarcity.However,most enabling technologies related to dynamic spectrum access are con-sidered individually.In this paper,we consider these key technologies jointly and introduce a new implementation scheme for a Dynamic Spectrum Access Network Based on Cognitive Radio(DSAN-BCR).We start with a flexible hardware platform for DSAN-BCR,as well as a flexible protocol structure that dominates the operation of DSAN-BCR.We then focus on the state of the art of key technologies such as spectrum sensing,spectrum resources management,dynamic spectrum access,and routing that are below the network layer in DSAN-BCR,as well as the development of technologies related to higher layers.Last but not the least,we analyze the challenges confronted by these men-tioned technologies in DSAN-BCR,and give the perspectives on the future development of these technologies.The DSAN-BCR introduced is expected to provide a system level guidance to alleviate the problem of spectrum scarcity.

Flow Field and Temperature Field in GaN-MOCVD Reactor Based on Computational Fluid Dynamics Modeling

Metal organic chenlical vapor deposition （AIOCVD） growth systems arc one of the. main types of equipment used for growing single crystal materials, such as GaN. To obtain fihn epitaxial materials with uniform performanee, the flow field and ternperature field in a GaN-MOCVD reactor are investigated by modeling and simulating. To make the simulation results more consistent with the actual situation, the gases in the reactor are considered to be compressible, making it possible to investigate the distributions of gas density and pressure in the reactor. The computational fluid dynamics method is used to stud,v the effects of inlet gas flow velocity, pressure in the reactor, rotational speed of graphite susceptor, and gases used in the growth, which has great guiding~ significance for the growth of GaN fihn materials.

Dynamics of Bottom Boundary Layers in the Yellow River Subaqueous Delta Based on Long-Term In-Situ Observations

Objective In geo-marine science,the generalized bottom boundary layer（BBL）represents a layer between sediments and seawater.The BBL plays an important role in geological,geobiochemical,geophysical and geotechnical research because it is the connection region of hydrosphere,

A dynamic knowledge base based search engine

Search engines have greatly helped us to find the desired information from the Internet. Most search engines use keywords matching technique. This paper discusses a Dynamic Knowledge Base based Search Engine （DKBSE）, which can expand the user＇s query using the keywords＇ concept or meaning. To do this, the DKBSE needs to construct and maintain the knowledge base dynamically via the system＇s searching results and the user＇s feedback information. The DKBSE expands the user＇s initial query using the knowledge base, and returns the searched information after the expanded query.

Analysis on Rules of Investment Decision Based on Payback Period of Dynamic Investment

The index of payback period of dynamic investment is an improvement on index of payback period of static investment, which is the problem that the rules to evaluate the project are feasible or not. This paper proves that rules shall be apt when using payback period of dynamic investment to evaluate the project feasibility under the condition of keeping the dynamic evaluation index to evaluate the same scheme and the consistent feasibility.

POWER-AWARE ROUTING BASED ON DSR FOR MOBILE AD HOC NETWORKS

Energy consumption is a crucial design concern in Mobile Ad hoc NETworks (MANETs) since nodes are powered by batteries with limited energy, whereas Dynamic Source Routing (DSR) protocol does not take the energy limitation of MANET nodes into account. This paper proposes an energy-saving routing algorithm based on DSR: Power Aware Routing protocol based on DSR (PAR-DSR). The design objective of PAR-DSR is to select energy-efficient paths. The main features of PAR-DSR are: (1) Nodes use the Signal Attenuation Rate (SAR) to conduct power control operations; (2) Minimum path cost as metric to balance the traffic and energy consumption of wireless nodes. The simulation results show that PAR-DSR can greatly reduce the energy consumption of MANET nodes. The average node lifetime of PAR-DSR is 50%-77% longer than that of DSR.

Study on the Medical Image Distributed Dynamic Processing Method

To meet the challenge of implementing rapidly advanced, time-consuming medical image processing algorithms, it is necessary to develop a medical image processing technology to process a 2D or 3D medical image dynamically on the web. But in a premier system, only static image processing can be provided with the limitation of web technology. The development of Java and CORBA (common object request broker architecture) overcomes the shortcoming of the web static application and makes the dynamic processing of medical images on the web available. To develop an open solution of distributed computing, we integrate the Java, and web with the CORBA and present a web-based medical image dynamic processing methed, which adopts Java technology as the language to program application and components of the web and utilies the CORBA architecture to cope with heterogeneous property of a complex distributed system. The method also provides a platform-independent, transparent processing architecture to implement the advanced image routines and enable users to access large dataset and resources according to the requirements of medical applications. The experiment in this paper shows that the medical image dynamic processing method implemented on the web by using Java and the CORBA is feasible.

ESKD-A New Structure of Expert System Based on Knowledge Discovery

A new structure of ESKD (expert system based on knowledge discovery system KD (D&K)) is first presented on the basis of KD (D&K)-a synthesized knowledge discovery system based on double-base (database and knowledge base) cooperating mechanism. With all new features, ESKD may form a new research direction and provide a great probability for solving the wealth of knowledge in the knowledge base. The general structural frame of ESKD and some sub-systems among ESKD have been described, and the dynamic knowledge base based on double-base cooperating mechanism has been emphased on. According to the result of demonstrative experi- ment, the structure of ESKD is effective and feasible.

Optimal PV array reconfiguration under partial shading condition through dynamic leader based collective intelligence

This paper applies the innovative idea of DLCI to PV array reconfiguration under various PSCs to capture the maxi-mum output power of a PV generation system.DLCI is a hybrid algorithm that integrates multiple meta-heuristic algo-rithms.Through the competition and cooperation of the search mechanisms of different metaheuristic algorithms,the local exploration and global development of the algorithm can be effectively improved to avoid power mismatch of the PV system caused by the algorithm falling into a local optimum.A series of discrete operations are performed on DLCI to solve the discrete optimization problem of PV array reconfiguration.Two structures(DLCI-I and DLCI-II)are designed to verify the effect of increasing the number of sub-optimizers on the optimized performance of DLCI by simulation based on 10 cases of PSCs.The simulation shows that the increase of the number of sub-optimizers only gives a relatively small improvement on the DLCI optimization performance.DLCI has a significant effect on the reduction in the number of power peaks caused by PSC.The PV array-based reconstruction system of DLCI-II is reduced by 4.05%,1.88%,1.68%,0.99%and 3.39%,when compared to the secondary optimization algorithms.

High-Performance Recyclable Furan-based Epoxy Resin and Its Carbon Fiber Composites with Dense Hydrogen Bonding

The emerging biomass-based epoxy vitrimers hold great potential to fulfill the requirements for sustainable development of society.Since the existence of dynamic chemical bonds in vitrimers often reduces both the thermal and mechanical properties of epoxy resins, it is challenging to produce recyclable epoxy vitrimers with both excellent mechanical properties and good thermal stability. Herein, a monomer 4-(((5-(hydroxymethyl)furan-2-yl)methylene)amino)phenol(FCN) containing furan ring with potential to form high density of hydrogen bonding among repeating units is designed and copolymerized with glycerol triglycidyl ether to yield epoxy resin(FCN-GTE), which intrinsically has dual hydrogen bond networks, dynamic imine structure and resultant high performance. Importantly, as compared to the BPA-GTE, the FCN-GTE exhibits significantly improved mechanical properties owing to the increased density of hydrogen bond network and physical crosslinking interaction. Furthermore, density functional theory(DFT) calculation and in situ FTIR analysis is conducted to decipher the formation mechanism of hydrogen bond network. In addition, the FCN-GTE possesses superior UV shielding, chemical degradation, and recyclability because of the existence of abundant imine bonds. Notably, the FCN-GTE-based carbon fiber composites could be completely recycled in an amine solution.This study provides a facile strategy for synthesizing recyclable biomass-based high-performance epoxy vitrimers and carbon fiber composites.

Planning and Control for Passive Dynamics Based Walking of 3D Biped Robots

Efficient walking is one of the main goals of research on biped robots. Passive Dynamics Based Walking （PDBW） has been proven to be an efficient pattern in numerous previous approaches to 2D biped walking. The goal of this study is to develop feasible method for the application of PDBW to 3D robots. First a hybrid control method is presented, where a previously proposed two-point-foot walking pattern is employed to generate a PDBW gait in the sagittal plane and, in the frontal plane, a systematic balance control algorithm is applied including online planning of the landing point of the swing leg and feedback control of the stance foot. Then a multi-space planning structure is proposed to implement the proposed method on a 13-link 3D robot. Related kinematics and planning details of the robot are presented. Furthermore, a simulation of the 13-link biped robot verifies that stable and highly efficient walking can be achieved by the proposed control method. In addition, a number of features of the biped walking, including the transient powers and torques of the joints are explored.

Comparative analysis of flower-meristem-identity gene APETALA2 (AP2) codon in different plant species

The flower-meristem-identity gene APETALA2(AP2), one of class-A genes, is involved in the establishment of the floral meristem and the forming of sepals and petals. Codon usage bias(CUB) identifies differences among species, meanwhile dynamic analysis of base composition can identify the molecular mechanisms and evolutionary relationships of a specific gene. In this study, eight coding sequences(CDS) of AP2 gene were selected from different plant species using the Gen Bank database. Their nucleotide composition(GC content), genetic index, relative synonymous codon usage(RSCU) and relative codon usage bias(RCUB) were calculated with R Software to compare codon bias and base composition dynamics of AP2 gene codon usage patterns in different plant species. The results showed that the usage of AP2 gene codons from different plant species were influened by GC bias, especially GC3 s. Overall, base composition analysis indicated that the usage frequency of codon AT in the gene coding sequence was higher than GC among AP2 gene CDS from different plant species. Furthermore, most AP2 gene CDSs ended with AT; AGA, GCU and UGU had relatively high RSCU values as the most dominant codon; the usage characteristic of the AP2 gene codon in Malus domestica was similar to that of Vitis vinifera; Paeonia lactiflora was similar to Paeonia suffruticosa and Solanum lycopersicum was similar to Petunia×hybrida. There was a moderate preference in the usage of AP2 gene codon among different plant species from relatively low frequency of optimal codon(Fop) values and high effective number of codons(ENC) value. This study has revealed the usage characteristics of the AP2 gene codon from the comparision of AP2 gene codon preference and base dynamics in different plant species and provide a platform for further study towards transgenic engineering and codon optimization.

PMD compensation based on a new type dynamic first-order PMD compensator

A dynamic first-order polarization mode dispersion （PMD） compensator based on garnet and yttrium vanadate crystal has been proposed and implemented. Consisting of a differential group delay （DGD） generator and a Faraday rotator （FR）, this PMD compensator has only two degrees of freedom. Feedback control and compensation algorithm are both very simple. Experimental results reveal the compensator behaviors to be excellent for PMD compensation in 40-Gb/s optical time domain multiplexing （OTDM） system.

Dynamic Gain Equalizer Based on the H-PDLC Volume Phase Grating

The structure and Bragg diffraction characteristics of volume phase gratings based on H-PDLC technology are presented, and the principles and simulation aided design of dynamic gain equalizers with the gratings are discussed.

Dynamic multicast sharing protection algorithm based on fuzzy game in multi-domain optical network

Aiming at the problem of dynamic multicast service protection in multi-domain optical network, this paper proposes a dynamic multicast sharing protection algorithm based on fuzzy game in multi-domain optical network. The algorithm uses the minimum cost spanning tree strategy and fuzzy game theory. First, it virtualizes two planes to calculate the multicast tree and the multicast protection tree respectively. Then, it performs a fuzzy game to form a cooperative alliance to optimize the path composition of each multicast tree. Finally, it generates a pair of optimal multicast work tree and multicast protection tree for dynamic multicast services. The time complexity of the algorithm is O(k3 m2 n), where n represents the number of nodes in the networks, k represents the number of dynamic multicast requests, and m represents the number of destination nodes for each multicast request. The experimental results show that the proposed algorithm reduces significantly the blocking rate of dynamic multicast services, and improves the utilization of optical network resources within a certain number of dynamic multicast request ranges.

Experimental realization of a switchable filter based on a dynamically transformable array

We introduce a geometrically reconfigurable metasurface whose artificial ＂atoms＂ will reorient within unit ceils in response to a thermal stimulus in the microwave spectrum. It can alternate between two contrasting behaviors under different temperatures and serve as a switchable filter that allows the incident energy to be selectively transmitted or reflected with an excess of 10 dB isolation at certain frequencies for both polarizations. The ex- perimental results are consistent with the theoretical simulations, verifying the availability of an innovative method for manipulating electromagnetic waves with the merits of higher controllability for dynamic behavior and greater flexibility in the design process.

Source dynamics of carbonaceous aerosol during the haze bloom-decay process in China based on radiocarbon and organic molecular tracer

With the support by the National Natural Science Foundation of China and the Chinese Academy of Sciences,the research team led by Prof.Li Jun(李军)at the State Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,illustrated the source dynamics of carbonaceous aerosol during the haze bloom-decay process in Beijing and Guangzhou based on

A novel downshifting strategy based on medium-time-distance information for hybrid electric bus

Vehicle downshifting during braking for the hybrid electric vehicle(HEV) equipped with the automatic mechanical transmission(AMT) could adjust work points of the motor. Thus, downshifting has great potential to effectively improve the efficiency of braking energy recovery. However, the power interruption during shifting could cause some loss of regenerative energy meanwhile.Hence, the choice of the downshifting point during vehicle braking which has crucial effect on energy recovery efficiency needs to be intensively studied. Moreover, the real-time application of the high-efficiency braking energy recovery strategy is a challenging problem to be tackled. Therefore, this paper proposes a dynamic-programming-rule-based(DPRB) downshifting strategy for a specific hybrid electric bus(HEB) driving condition. Firstly, the braking characteristic of the HEB during the process of pulling in is analyzed. Secondly, the medium-time-distance(MTD) demonstrating the dimension of time and space is proposed to define the boundary condition of the running bus. Then, look-up tables are established based on a dynamic programming algorithm offline using multiple sets of historical data. Thus, Based on the real-time driving data, whether to enter the optimal gear selection process can be decided online. Finally, simulations and hardware-in-the-loop(HIL) tests are carried out, and the results show that the proposed method can be indeed effective for braking energy recovery.

Injectable self-healing hydrogel with siRNA delivery property for sustained STING silencing and enhanced therapy of intervertebral disc degeneration

Inflammatory responses of nucleus pulposus(NP)can induce imbalanced anabolism and catabolism of extracellular matrix,and the cytosolic dsDNA accumulation and STING-NF-κB pathway activation found in NP inflammation are considered as fairly important cause of intervertebral disc(IVD)degeneration.Herein,we constructed a siSTING delivery hydrogel of aldehyde hyaluronic acid(HA-CHO)and poly(amidoamine)PAMAM/siRNA complex to intervene the abnormal STING signal for IVD degeneration treatment,where the formation of dynamic Schiff base bonds in the system(siSTING@HPgel)was able to overcome the shortcomings such as low cellular uptake,short half-life,and rapid degradation of siRNA-based strategy.PAMAM not only formed complexes with siRNA to promote siRNA transfection,but also served as dynamic crosslinker to construct hydrogel,and the injectable and self-healing hydrogel efficiently and steadily silenced STING expression in NP cells.Finally,the siSTING@HPgel significantly eased IVD inflammation and slowed IVD degeneration by prolonging STING knockdown in puncture-induced IVD degeneration rat model,revealing that STING pathway was a therapeutic target for IVD degeneration and such novel hydrogel had great potential for being applied to many other diseases for gene delivery.