粘性流体圆柱绕流的混合有限分析解

应用混合有限分析法拟合坐标系对粘性流体圆柱绕流进行了数值计算,得出Re<40形成的分离区长度和分离角同试验资料吻合很好。也计算了Re=100和200时,旋涡的形成和脱落,算得的脱落斯特罗哈数分别是0.16和0.19,同试验结果完全相符。     

Multi-factor cheating prevention in visual secret sharing by hybrid codebooks

Visual secret sharing, or the so-called visual cryptography, is a well-known scheme that encrypts a secret image into several meaningless share images, usually printed on transparencies, and decrypts as stacking some or all share images by the human visual system. More and more researches about visual secret sharing and its applications have been recently proposed. Unfortunately, the cheating attack in which malicious participants cheat the honest one(s) by forging a fake share image has existed. Since 2006, some cheating prevention schemes have been proposed but suffered from one or more disadvantages as follows: (1) maintaining extra share images used to verify the integrity of a share image prior to stacking, (2) introducing extra pixel expansion, (3) raising heavy computation cost, and (4) giving ambiguous cheating detection. In this paper, a multi-factor cheating–preventing scheme, aiming at exploiting the hybrid codebook to hide the additional verification images into the share images, has been proposed without suffering the above-mentioned deficiencies. Two-factor cheating–detection exploits the design of verification to both share images and stacked results to deter attackers’ cheating. The experimental results demonstrate the proposed scheme is feasible.     

光纤工业控制网的研究

本文介绍了电路交换和分组交换相结合的新型光纤工业控制环网的设计与研究,着重考虑了环网的拓扑结构、体系结构、ＭＡＣ协议、帧结构和混合环路控制。     

Organic solar cell based on photosystem I pigment-protein complex,fabrication and optimization

The trends of using biological materials in electronic devices have made great developments in the last few years. Furthermore, the appealed cost features of organic semiconductors represent a bright low-cost, environment compatible, and efficient future for bio & nanotechnologies, especially Bio-organic solar cells which may consider as a noteworthy option for photovoltaic applications. Here, we report a novel single junction organic solar cell based on photosystem I pigment-protein complex. The complex which operated either as photosensitizer and charge generator compound, surprisingly. Photosystem I complexes were extracted from young spinach leaves and used as the active layer of the intended solid-state solar cell device, subsequently. After the characterization of the final cell, our photovoltaic system showed the current density of 3470 μA cm⁻² which realizes as a notable approach in between photosystem- I based energy conversion systems.     

An efficient hybrid protection scheme with shared/dedicated backup paths on elastic optical networks

Fast recovery and minimum utilization of resources are the two main criteria for determining the protection scheme quality. We address the problem of providing a hybrid protection approach on elastic optical networks under contiguity and continuity of available spectrum constraints. Two main hypotheses are used in this paper for backup paths computation. In the first case, it is assumed that backup paths resources are dedicated. In the second case, the assumption is that backup paths resources are available shared resources. The objective of the study is to minimize spectrum utilization to reduce blocking probability on a network. For this purpose, an efficient survivable Hybrid Protection Lightpath (HybPL) algorithm is proposed for providing shared or dedicated backup path protection based on the efficient energy calculation and resource availability. Traditional First-Fit and Best-Fit schemes are employed to search and assign the available spectrum resources. The simulation results show that HybPL presents better performance in terms of blocking probability, compared with the Minimum Resources Utilization Dedicated Protection (MRU-DP) algorithm which offers better performance than the Dedicated Protection (DP) algorithm.     

Hybrid nanocomposite thin films deposited by emulsion-based resonant infrared matrix-assisted pulsed laser evaporation for photovoltaic applications

Emulsion-based, resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) was used to deposit CdSe nanoparticle films and hybrid nanocomposite films comprising colloidal CdSe nanoparticles embedded in a low band gap polymer, poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT). We show that, in contrast to traditional MAPLE deposition, the CdSe nanoparticle film deposited by emulsion based RIR-MAPLE is contiguous and uniform, and it maintains the optical properties of the nanoparticle solution. Moreover, we show that the RIR-MAPLE deposited PCPDTBT/CdSe hybrid nanocomposite film exhibits a relatively random and uniform distribution of CdSe nanoparticles without the significant phase segregation that is observed in hybrid nanocomposite films deposited by spin-casting. Finally, hybrid organic solar cells based on nanocomposite films deposited by the RIR-MAPLE technique were fabricated and characterized, showing 0.4% power conversion efficiency. This is the first demonstration of a polymer–nanoparticle hybrid organic solar cell fabricated by a MAPLE-related technique.     

Novel hybrid self-assembly of an ultralarge ZnO macroflower and defect intensity-induced photocurrent and photocatalytic properties by facile hydrothermal synthesis using CO(NH2)2–N2H4 as alkali sources

Different flower-like ZnO nanoarchitectures were synthesized by a facile hydrothermal method using CO(NH₂)₂ and N₂H₄ as alkali sources simultaneously. A novel ultralarge ZnO macroflower was constructed by the ultrathin leaf-like nanobelts, hollow semisphere-like, sphere-like and apple-shaped nanoparticles simultaneously. The diameter of an individual flower can reach 90 µm. Meanwhile, three or five flower-like ZnO nanostructures with different diameters, lengths and tips (Planar, semi-pyramid, and/ or pyramid tips) were formed simultaneously under the same reaction condition. XRD shows that all the ZnO crystals possess the hexagonal wurtzite structure. When the samples range from S1 to S5, the crystallinity is improved. EDX shows that the Zn/ O atom ratio of S1–S5 is close to the 1:1 stoichiometric ratio, and that of S3 is almost equal to 1:1. FTIR indicates that S4 and S5 are pure. However, the surface of S1, S2 and S3 adsorbs the CO₃²⁻ group. The reflectance of S1–S4 in the range of 300–370 nm is inversely proportional to that in visible region. Meanwhile, when the grain size of S1–S4 decreases, their band gap increases. The Raman results of S1 and S5 are different from those of S4 and exhibit the higher crystal quality, which are favorable for the improvement of photocatalytic performance. S1 and S5 exhibit the highest photocatalytic performance and decompose 65% and 70% of MB within 50 min respectively. The photocatalytic activity and photocurrent strongly depend on the defect intensity of the ZnO crystals. The ZnO photocatalyst of S5 is still stable and efficient after three cycles. However, the photocatalytic activity of S1 decreases continuously, due to its unique morphology and the adsorption of intermediates. In addition, A hybrid self-assembly process of the ultralarge ZnO macroflower was proposed.     

A Communication Paradigm for Hybrid Sensor/Actuator Networks*

This paper investigates an anycast communication service for a hybrid sensor/actuator network, consisting of both resource-rich and resource-impoverished devices. The key idea is to exploit the capabilities of resource-rich devices (called micro-servers) to reduce the communication burden on smaller, energy, bandwidth and memory constrained sensor nodes. The goal is to deliver sensor data to the nearest micro-server, which can (i) store it (ii) forward it to other micro-servers using out-of-band communication or (iii) perform the desired actuation. We propose and evaluate a reverse tree-based anycast mechanism tailored to deal with the unique event dynamics in sensor networks. Our approach is to construct an anycast tree rooted at each potential event source, which micro-servers can dynamically join and leave. Our anycast mechanism is self-organizing, distributed, robust, scalable, routing-protocol independent and incurs very little overhead. Simulations using Network Simulator (ns-2) show that: our anycast mechanism when added to Directed Diffusion can reduce the network’s energy consumption by more than 50%; can reduce both the mean end-to-end latency of the transmission and the mean number of transmissions by more than 50%; achieves 99% data delivery rate for low and moderate micro-server mobility rate; and handles network dynamics reasonably well.This paper is a comprehensive extension of our earlier work in [1].     

An ideal host-guest system to accomplish high-performance greenish yellow and hybrid white organic light-emitting diodes

Greenish yellow organic light-emitting diodes (GYOLEDs) have steadily attracted researcher's attention since they are important to our life. However, their performance significantly lags behind compared with the three primary colors based OLEDs. Herein, for the first time, an ideal host-guest system has been demonstrated to accomplish high-performance phosphorescent GYOLEDs, where the guest concentration is as low as 2%. The GYOLED exhibits a forward-viewing power efficiency of 57.0 lm/W at 1000 cd/m², which is the highest among GYOLEDs. Besides, extremely low efficiency roll-off and voltages are achieved. The origin of the high performance is unveiled and it is found that the combined mechanisms of host-guest energy transfer and direct exciton formation on the guest are effective to furnish the greenish yellow emission. Then, by dint of this ideal host-guest system, a simplified but high-performance hybrid white OLED (WOLED) has been developed. The WOLED can exhibit an ultrahigh color rendering index (CRI) of 92, a maximum total efficiency of 27.5 lm/W and a low turn-on voltage of 2.5 V (1 cd/m²), unlocking a novel avenue to simultaneously achieve simplified structure, ultrahigh CRI (>90), high efficiency and low voltage.     

SH320大闭塞量低噪声视频放大器

本文介绍了ＳＨ３２０大闭塞量低噪声视频放大器的设计和研制。从对主要技术指标的分析入手，确定了合理的方案，并对电路进行了优化设计。在制作上，根据性能和结构要求，采用了高密度布线、多芯片组装的薄膜工艺。最后实现的是一种ＭＣＭ（多芯片组件）电路，在电性能上优于用户的要求，在工艺实现上也是采用ＭＣＭ技术的有益尝试。