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On the basis of Wyner–Ziv video coding in transform domain, this paper studies the coding method of key frame and proposes a method of coding mode selection based on partition of frequency band: First of all, the key frames are transformed by DCT and they are divided into low-frequency band and high-frequency band according to the characteristics of frequency band. Then the low-frequency band and high-frequency band are encoded and decoded by Wyner–Ziv and intraframe, respectively. In this paper, the decision of coding mode is transferred to the decoder to be completed, which further improves the performance of the system without increasing the complexity of the encoder. Compared with the reference algorithm, the peak signal-to-noise ratio obtained by the proposed coding mode selection algorithm based on partition of frequency band is improved by 1–5 dB.

Zeolites have been widely used in industry owing to their ordered micropores and stable frameworks. The pore sizes and shapes are the key parameters that affect the selectivity and efficiency in their applications in catalysis, sorption, and separation. Zeolites with pores defined by 10 and 12 TO4 tetrahedra are often used for various catalytic processes. To optimize the performance of zeolites, it is extremely desirable to fine-tune the pore sizes/shapes. The first germanosilicate zeolite with a three-dimensional 11×11×12-ring channel system, PKU-16 (PKU, Peking University) is presented. Nanosized PKU-16 was structurally characterized by the new three-dimensional rotation electron diffraction (RED) technique. PKU-16 is structurally related to the zeolite β polymorph C (BEC, 12×12×12-ring channels) by rotating half of the four-rings in double mtw units.

A new porous vanadoborate was synthesized by employing the scale chemistry theory with the vanadoborate cluster V10B28. The twofold interpenetrated lvt network was assembled with zinc-containing elliptical vanadoborate clusters and Zn polyhedra. The single lvt framework contains a three-dimensional 38×38×20 ring channel system with the pore size (24.7×12.7 Å) reaching the mesoscale, thus indicating the possibility of constructing 3D ordered mesopores with vanadoborate clusters. The porosity of the SUT-7 structure was confirmed by CO2 adsorption of the as-synthesized materials.

Three three-dimensional (3D) open-framework vanadoborates, denoted as SUT-6-Zn, SUT-6-Mn, and SUT-6-Ni, were synthesized using diethylenetriamine as a template. SUT-6-Zn, SUT-6-Mn, and SUT-6-Ni are ...

The single crystal of the extra-large pore zeolite, ITQ-33, was obtained and used to explore its crystal structure details. The ITQ-33 structure was found to be disordered with the columnar periodi ...

Two new polymorphs of zeolite beta, denoted as SU-78A and SU-78B, were synthesized by employing dicyclohexylammonium hydroxides as organic structure-directing agents. The structure was solved by combining transmission electron microscopy and single-crystal X-ray diffraction. SU-78 is an intergrowth of SU-78A and SU-78B and contains interconnected 12-ring channels in three directions. The two polymorphs are built from the same building layer, similar to that for the zeolite beta family. The layer stacking in SU-78, however, is different from those in zeolite beta polymorph A, B, and C, showing new zeolite framework topologies. SU-78 is thermally stable up to 600 °C.

Three isostructures [C16H8O4·2(CH6N3)·4(H2O)] (1), [C16H10O4·2(CH6N3)·4(H2O)] (2) and [C14H8N2O4·2(CH6N3)·4(H2O)] (3) were prepared by the complexation of guanidinium with 4,4′-(ethyne-1,2-diyl)dibenzoic acid, 4,4′-(ethene-1,2-diyl)dibenzoic acid and 4,4′-(diazene-1,2-diyl)dibenzoic acid, respectively. The strong charge-assisted +N–H⋯O−hydrogen bonds cause the assembly of guanidinium and these different acids following almost the same procedure. The hydrogen-bonded water wire is incorporated in zwitterionic channels of organic salts.

Aiming at the significance of the energy controls of wireless sensor networks, an economical energy consumption algorithm for wireless communicating in Wireless Sensor Networks (WSN) is presented. Based on the algorithm, the maximal system throughput of WSN is analyzed, and the upper bound of throughput of WSN is proposed and proved. Some numerical simulations are conducted and analyzed. The conclusions include that the transmitting radius of sensor node and the parameters of the energy cost function have significant influence upon the throughput, but the monitoring region radius has little influence. For the same transmitting distance, the more the hopping of information transmitting, the better the throughput of WSN. On the other hand, for the energy optimization of the whole WSN, the trade-off problem between the throughput capacity and the relay nodes is proposed, and the specific expression of relay hops that minimized the energy consumptions and the maximal throughput of WSN under the specific situation is derived.

Throughput of mobile ad hoc network (MANET) is limited by collision avoidance. In CDMA-based MANET, this limitation can be overcome by multiuser detection (MUD) because conventional colliding packets can be detached and detected by MUD so that multi-packet reception (MPR) is possible. This paper introduces the principles of MUD algorithm for MANET, and proposes an adaptive blind MUD algorithm. A special medium access control (MAC) protocol is designed to make MANET more efficient. This is achieved by sending more packets to a destination simultaneously. The proposed MUD algorithm and MAC protocol allow CDMA-based MANET to support MPR. Simulations show a remarkable improvement in the throughput performance of MANET.

An emerging strategy for exploring the application of polyoxometalates (POMs) is to assemble POM clusters into open-framework materials, especially inorganic-organic hybrid three-dimensional (3D) open-framework materials, via the introduction of different organic linkers between the POM clusters. This strategy has yielded a few 3D crystalline POMs of which a typical class is the group of polyoxometalate metal-organic frameworks (POMMOFs). However, for reported POMMOFs, only coordination bonds are involved between the linkers and POM clusters, and it has not yet produced any covalently bonded polyoxometalate frameworks. Here, the concept of "covalently bonded POMs (CPOMs)" is developed. By using vanadoborates as an example, we showed that the 3D CPOMs can be obtained by a condensation reaction through the oxolation mechanism of polymer chemistry. In particular, suitable single crystals were harvested and characterized by single-crystal X-ray diffraction. This work forges a link among polymer science, POM chemistry, and open-framework materials by demonstrating that it is possible to use covalent bonds according to polymer chemistry principles to construct crystalline 3D open-framework POM materials.

Firstly, a multilevel trust algorithm for MANET (mobile ad hoc networks) is presented in this paper and the trust level is defined as a three-tuple type in this multilevel trust algorithm. The paper introduces the multilevel trust into MANET, thereby controlling restricted classified information flows among nodes that have different trust levels. Secondly, the infrastructure of MANET that suit to our multi-level trust is presented. Some conclusions are given at lastly.

Two layered V–B–O contained polyoxometalate (POM) net structures, denoted as SUT-12 and SUT-13, are reported here. SUT-12 was synthesized by the boric acid flux method, and it represents the first 2D structure constructed from the V6B20 vanadoborate cluster. SUT-13 was synthesized by the hydrothermal method and constructed from V12B6P12 vanadium borophosphate clusters. In both structures, the vanadoborate or vanadium borophosphate clusters were linked through in situ formed Zn(DETA)2 or Cu(DETA)2 complexes. Surprisingly, for all DETA molecules in the two metal complexes, there is one dangling amine group when it is coordinated to the metal. The phenomenon of the dangling amine group feature is abnormal and the Cu(DETA)2 complexes in SUT-13 were taken as an example and studied by the density functional theory (DFT) calculations in order to understand this unusual feature.

In recent years there has been a growing interest in sparse representation of signals based on overcomplete dictionaries. Selecting few atoms that best match the signal structure, the signal is described by linear combination of these atoms. In this paper, we propose a novel overcomplete dictionary design algorithm for sparse representation of piecewise stationary signals. An effective and easy-to-use overcomplete dictionary is constructed in accordance with the parametric autocorrelation function model of piecewise stationary processes. Furthermore, a sparse decomposition algorithm in terms of nonlinear approximation is designed to obtain sparse representation of piecewise stationary signals, which has lower computational complexity and better practicability than the conventional sparse decomposition algorithms. The experimental results demonstrate that the proposed method avails for higher sparsiry of signal representation and better reconstruction performance than sparse representation of signals based on overcomplete DCT dictionary.

Cognitive radio (CR), promote the efficient utilization of the licensed spectrum, and solve the problem of increasing demands for the wireless radio spectrum with the emergency of many new wireless communication networks. In this paper, we against a backdrop of cognitive radio technology, proposed a new opportunistic cooperative transmission scheme based on AF combining spectrum sensing and data transmission in Cognitive Networks (CNs). Besides, closed-form expressions of BER (bit error ratio) of secondary user for the proposed opportunistic cooperative transmission scheme and tradition non-cooperative scheme are presented over Rayleigh fading channels. Then, numerical simulations are conducted to compare our scheme with the non-cooperative transmission, showing the merits of the proposed opportunistic cooperative transmission in terms of BER, and transmission performance of secondary user in CNs can be improved without interfering the regular transmissions of the primary users (PU).

In this paper, we investigate joint cooperation diversity and symbol mapping diversity strategies for cooperative communication systems that employ nonbinary linear modulations such as phase-shift keying (PSK) and quadrature amplitude modulation (QAM). Substantial symbol error rate gains results from designing different symbol mappings for each packet transmission (symbol mapping diversity) and delivering them through independent paths to the final destination (cooperation diversity). These joint diversity schemes can provide substantial symbol error rate gains with only a small increase in receiver complexity and combat the effects of fading induced by multipath propagation effectively.

The importance of multiuser detection for CDMA-based mobile ad hoc networks is addressed in this paper. Conventionally, terminals in CDMA-based ad hoc networks use matched filters to receive packets, so the throughput of the network suffers from multi-access interference (MAI). Different from above scheme, in this paper, each terminal of the ad hoc network is equipped with an adaptive blind linear multiuser detector, so the ability of MAI-resistance is gained. Based on fully-connected network model, the throughput of ad hoc network with multiuser detection is studied in link-level. Theoretic analysis and simulation results show that multiuser detection can remarkably increase the throughput of ad hoc networks

A MANET (mobile ad hoc network) is a collection of wireless mobile nodes dynamically forming a temporary communication network without the use of any existing infrastructure or centralized administration. It is characterized by both highly dynamic network topology and limited energy. So, the efficiency of MANET depends not only on its control protocol, but also on its topology and energy management. A clustering strategy can improve the performance of flexibility and scalability in the network. With the aid of graph theory and a genetic annealing hybrid optimization algorithm, this paper proposes a new clustering strategy to perform topology management and energy conservation. A performance comparison is made between the original algorithms and our algorithm, named genetic algorithm and simulated annealing based clustering strategy (GASA-CS for short), in the aspects of average cluster number, topology stability, load balance and network lifetime. The experimental results show that our GASA-CS has a better performance on average.

A novel multitarget constant modulus array structure is proposed for CDMA systems in this paper. The new algorithm for the structure is called predespreading and wavelet denoising constant modulus algorithm (D-WD-CMA). In the new algorithm, the predespreading and wavelet denoising are applied for multitarget arrays to remove some multiple access. Simulation results illustrate the good performance for the proposed algorithm, compared with the traditional CMA algorithm.

As the use of small portable and mobile computing devices increases, ad hoc networks have become an increasingly popular topic of research and development activities. Cross-layer design and power conservation are two new technologies in this area. Both of them can make the ad hoc network more robust and more adaptive. The relation between them is improvable. A power control based cross-layer architecture is presented.

As the use of small portable and mobile computing devices increases, the MANET (mobile ad hoc network) is becoming an increasingly popular topic of research and development activities. MANET is power constrained since nodes operate with limited battery energy. To maximize the lifetime of these networks at the same time of holding the conventional network performance, a new DSR-base energy saving routing is proposed and analyze in this paper.