Chemical bath deposition synthesis of TiO2/Cu2O core/shell nanowire arrays with enhanced photoelectrochemical water splitting for H2 evolution and photostability

In this study, we have developed a facile chemical bath deposition (CBD) method to grow p-type Cu₂O nanoparticles on n-type TiO₂ nanowire arrays (TiO₂ NWAs) to fabricate TiO₂/Cu₂O core/shell heterojunction nanowire arrays (TiO₂/Cu₂O core/shell NWAs). When used as photoelectrode, the fabricated TiO₂/Cu₂O core/shell NWAs show improved photoelectrochemical (PEC) water splitting activity to pure TiO₂ NWAs. The effects of the CBD cycle times on the PEC activities have been studied. The TiO₂/Cu₂O core/shell heterojunction nanowire array photoelectrode prepared by cycling 5 times in the CBD process achieves the highest photocurrent of 2.5 mA cm^?2, which is 2.5 times higher than that of pure TiO₂ NWAs. In addition, the H₂ generation rate of this photoelectrode reaches to 32 μmol h^?1 cm^?2, 1.7 times higher than that of pure TiO₂ NWAs. Furthermore, the TiO₂/Cu₂O core/shell heterojunction nanowire array photoelectrode shows excellent photostability and achieves a stable photocurrent of over 2.3 mA cm^?2 during long light illumination time of 5 h. The enhanced photocatalytic activity of TiO₂/Cu₂O core/shell heterojunction nanowire array photoelectrode is attributed to the synergistic actions of TiO₂ and Cu₂O for improving visible light harvesting, and efficient transfer and separation of photogenerated electrons and holes.     

System level simulation of a micro resonant accelerometer with geometric nonlinear beams

Geometric nonlinear behaviors of micro resonators have attracted extensive attention of MEMS (microelectro-mechanical systems) researchers, and MEMS transducers utilizing these behaviors have been widely researched and used due to the advantages of essentially digital output.Currently, the design of transducers with nonlinear behaviors is mainly performed by numerical method and rarely by system level design method.In this paper, the geometric nonlinear beam structure was modeled and established as a reusable library component by system level modeling and simulation method MuPEN (multi port element network).A resonant accelerometer was constructed and simulated using this model together with MuPEN reusable library.The AC (alternating current) analysis results of MuPEN model agreed well with the results of architect model and the experiment results shown in the existing reference.Therefore, we are convinced that the beam component based on MuPEN method is valid, and MEMS system level design method and related libraries can effectively model and simulate transducers with geometric nonlinear behaviors if appropriate system level components are available.     

基于模糊逻辑的MEMS陀螺零漂温度补偿技术

针对MEMS陀螺在外界温度变化时,角速率输出误差较大且为非线性的特点,设计了一种基于模糊逻辑的MEMS陀螺温度补偿方法,采用一元Takagi-Sugeno模糊模型对陀螺零漂的温度误差进行辨识与实时补偿,并就陀螺在自身发热和外界温度变化两种情况下的补偿效果进行了实验验证,结果表明,经过温度补偿,陀螺零漂从0.01003°/s减小到0.007°/s,可满足工程应用的需要。     

Efficient Bipolar Blue AIEgens for High‐Performance Nondoped Blue OLEDs and Hybrid White OLEDs

Blue organic luminescent materials play a crucial role in full‐color display and white lighting but efficient ones meeting commercial demands are very rare. Herein, the design and synthesis of tailor‐made bipolar blue luminogens with an anthracene core and various functional groups are reported. The thermal stabilities, photophysical properties, electronic structures, electrochemical behaviors, carrier transport abilities, and electroluminescence performances are systematically investigated. The luminogen TPE‐TAPBI containing a tetraphenylethene moiety shows aggregation‐induced emission, while another luminogen TriPE‐TAPBI bearing a triphenylethene unit exhibits light aggregation‐caused quenching. In comparison with TriPE‐TAPBI, TPE‐TAPBI has stronger blue emission in neat film and functions more efficiently in nondoped organic light‐emitting diodes (OLEDs). High maxima current, power, and external quantum efficiencies of 7.21 cd A^?1, 6.78 lm W^?1, and 5.73%, respectively, are attained by the nondoped blue OLED of TPE‐TAPBI (CIE_x,y = 0.15, 0.16). Moreover, efficient two‐color hybrid warm white OLEDs (CIE_x,y = 0.457, 0.470) are achieved using TPE‐TAPBI neat film as the blue‐emitting component, which provide total current, power, external quantum efficiencies of up to 70.5 lm W^?1, 76.0 cd A^?1, and 28% at 1000 cd m^?2, respectively. These blue and white OLEDs are among the most efficient devices with similar colors in the literature.     

On providing wormhole‐attack‐resistant localization using conflicting sets

Wormhole attack is a severe attack that can be easily mounted on a wide range of wireless networks without compromising any cryptographic entity or network node. In the wormhole attack, an attacker sniffs packets at one point in the network and tunnels them through the wormhole link to another point. Such kind of attack can deteriorate the localization procedure in wireless sensor networks. In this paper, we first analyze the impacts of the wormhole attack on the localization procedure. Then, we propose a secure localization scheme against the wormhole attacks called SLAW including three phases: wormhole attack detection, neighboring locators differentiation, and secure localization. The main idea of the SLAW is to build a so‐called conflicting set for each locator based on the abnormalities during the message exchanges, which can be used to differentiate the dubious locators to achieve secure localization. We first consider the simplified system model in which there is no packet loss and all the nodes have the same transmission range. We further consider the general system model where the packet loss exists and different types of nodes have different transmission radii. We conduct the simulations to illustrate the effectiveness of the proposed secure localization scheme and compare it with the existing schemes under different network parameters. Copyright © 2014 John Wiley & Sons, Ltd.     

A New Approach to Tuning Carbon Ultramicropore Size at Sub‐Angstrom Level for Maximizing Specific Capacitance and CO2 Uptake

Ultramicroporous carbon materials with uniform pore size accurately adjusted to the dimension of electrolyte ions or CO₂ molecule are highly desirable for maximizing specific capacitance and CO₂ uptake. However, efficient ways to fine‐tuning ultramicropore size at angstrom level are scarce. A completely new approach to precisely tuning carbon ultramicropore size at sub‐angstrom level is proposed herein. Due to the varying activating strength and size of the alkali ions, the ultramicropore size can be finely tuned in the range of 0.60–0.76 nm as the activation ion varies from Li⁺ to Cs⁺. The carbons prepared by direct pyrolysis of alkali salts of carboxylic phenolic resins yield ultrahigh capacitances of up to 223 F g^‐1 (205 F cm^‐3) in ionic liquid electrolyte, and superior CO₂ uptake of 5.20 mmol g^‐1 at 1.0 bar and 25 °C. Such outstanding performance of the finely tuned carbons lies in its adjustable pore size perfectly adapted to the electrolyte ions and CO₂ molecule. This work paves the way for a new route to finely tuning ultramicropore size at the sub‐angstrom level in carbon materials.     

基板表面粗糙度对电阻薄膜微观形貌及电学性能的影响

不同表面粗糙度的基板显著影响其溅射膜层的微观形貌、电阻以及残余应力,同时其本身的制备成本也相差甚远。选择表面粗糙度适合的基板,能够在保证产品性能良好、可靠性高的同时,兼顾生产成本的有效调控。基于实际生产考量,通过磁控溅射工艺制备两种Ti、TaN功能薄膜,系统性评估了表面粗糙度大范围梯度（R_a=20—1000 nm）变化的氧化铝基板对溅射膜层的影响,包括镀膜前后表面粗糙度、室温电阻率以及电阻温度系数（TCR）。结果表明：当基板表面粗糙度R_a<350 nm,镀膜后R_a无显著变化;当R_a>350 nm,随着基板R_a增加其镀膜后R_a显著降低;不同于R_a,镀膜后功能薄膜层R_z明显低于基板值;Ti、TaN薄膜电阻率,随基板R_a的增加而增大;TaN功能薄膜TCR随基板R_a值的增加先增大后减小,负偏明显并保持在-500×10^-6—-550×10^-6 ℃^-1 区间。     

纳米银/PAMPS复合材料的微波合成及表征

在不加还原剂的条件下,采用微波辐射双原位聚合方法合成了纳米银/2-丙烯酰胺基-2-甲基丙磺酸均聚物(PAMPS)复合材料,并通过UV-Vis、XRD、FTIR、TEM、XPS和TG分析方法对其进行分析和表征。结果表明:纳米银粒子具有面心立方结构,且均匀地分散在聚合物基体中;微波辐射时间不影响纳米银粒子的形态;纳米银与基体PAMPS中的氮原子和羰基氧原子存在相互作用,降低了基体PAMPS的热稳定性。