Self-Supported Nanoporous Au3Cu Electrode with Enriched Gold on Surface for Efficient Electrochemical Reduction of CO2

The key to the electrochemical conversion of CO₂ lies in the development of efficient electrocatalysts with ease of operation, good conductivity, and rich active sites that fulfil the desired reaction direction and selectivity. Herein, an oxidative etching of Au₂₀Cu₈₀ alloy is used for the synthesis of a nanoporous Au₃Cu alloy, representing a facile strategy for tuning the surface electronic properties and altering the adsorption behavior of the intermediates. HRTEM, XPS, and EXAFS results reveal that the curved surface of the synthesized nanoporous Au₃Cu is rich in gold with unsaturated coordination conditions. It can be used directly as a self-supported electrode for CO₂ reduction, and exhibits high Faradaic efficiency (FE) of 98.12 % toward CO at a potential of −0.7 V versus the reversible hydrogen electrode (RHE). The FE is 1.47 times that over the as-made single nanoporous Au. Density functional theory reveals that *CO has a relatively long distance on the surface of nanoporous Au₃Cu, making desorption of CO easier and avoiding CO poisoning. The Hirshfeld charge distribution shows that the Au atoms have a negative charge and the Cu atoms exhibit a positive charge, which separately bond to the C atom and O atom in the *COOH intermediate through a bidentate mode. This affords the lowest *COOH adsorption free energy and low desorption energy for CO molecules.     

偶应力问题的杂交／混合元分析

将弹性力学中Hellinger—Reissner交分原理推广到偶应力理论中，并以罚函数的形式引入其约束条件，提出了一种有效的杂交／混合单元。文中分别分析了带中心小孔平板在轴向均匀加载时的应力集中情况，以及含中问裂纹的无限平板单轴拉伸时的位移场和应力场。算例表明，该单元计算效率高，精度好，即使在材料本征长度很小时，仍然能够得到相当理想的结果。     

Comparison of resonances and spectral properties for microstructures incorporating singular layered metal dielectric subwavelength grating with different profiles

A multilayered structure incorporating a single metal-dielectric subwavelength grating is a structure with characteristic of polarization separation for visible light, enabling creating visible color aspect. Based on that, two specific structures separately with grating layers of rectangular and sinusoidal refractive index profiles are designed and their related resonant behaviors and spectral properties are compared respectively for s and p polarized incident lights. The impacts of structural parameters of the structures together with dielectric materials on their resonances and spectra in reflection are studied in detailed. Similarities of resonant behaviors, reflection spectra and variations in resonant locations and spectral profiles between both structures are also demonstrated for both polarizations, especially for s polarized light. Due to such similarities and convenience in fabrication, the structure with a sinusoidal grating can replace that with a rectangular grating in mass production for color-based various applications such as color security, image reproduction.     

Blocking probability analysis model for flexible spectrum optical networks

Compared to the traditional wavelength division multiplexing （WDM） optical networks with rigid and coarse granularities, flexible spectrum optical networks have high spectrum efficiency, which can support the service with various bandwidth requirements, such as sub and super channel. Among all network performance parameters, blocking probability is an important parameter for the performance evaluation and network planning in circuit~based optical networks including flexible spectrum optical networks. We propose an analytical method of blocking probability computation for flexible spectrum optical networks in this letter through mathematical analysis and theoretical derivation. Two blocking probability models are built respectively based on whether considering spectrum consecutiveness or not. Numerical results validate our proposed blocking probability models under different link capacity and traffic loads.     

基于元胞自动机的“右行左超车”规则作用与影响分析

研究“右行左超车”规则在高速公路不同交通负荷下对通行能力及安全性的影响。引入超车欲望值及状态改变率的概念,基于交通流元胞自动机模型,建立了“右行左超车”规则下的单向双车道和三车道换道规则及相应的超车规则。选取5个评价参数,针对两车道模型,将“右行左超车”规则与无规则下的换道超车对交通效率与安全表现的影响进行对照试验。试验结果表明：在安全表现方面,低负荷状态下“右行左超车”规则较无规则情形要差,而在高负荷状态下,该规则较无规则情形好;在通行能力方面二者差别不大;试验结果还表明：无论是有规则还是无规则,提高车道的最大与最小限速不仅可以提升道路的通行能力,而且可以提升安全性。最后分析了模型的优缺点,并指出了改进的方向。     

Magnetic and hydrophilic imprinted particles via ATRP at room temperature for selective separation of sulfamethazine

In this work, a facile route to prepare hydrophilic molecularly imprinted particles with magnetic susceptibility (MMIPs) was first reported via atom transfer radical precipitation polymerization (ATRPP) in a methanol/water solvent at low temperature (298 K), which can be considered as an environment-friendly system. During the process, 2-hydroxyethyl methacrylate and N, N-methylenebisacrylamide monomers were added to improve the hydrophilicity of the polymers. The obtained materials were characterized in detail by X-ray diffraction, transform infrared spectroscopy, thermogravimetric analysis, vibrating sample magnetometer, scanning electron microscopy and transmission electron microscopy, and then used for the selective separation of sulfamethazine (SMZ) from aqueous medium. The images showed Fe₃O₄ nanoparticles that were successfully embedded into the polymer particles with the size ranging from 450 to 650 nm, which exhibited great superparamagnetic susceptivity and high thermal stability. Batch adsorption experiments were performed to determine specific adsorption equilibrium, kinetics, and selective recognition and separation. The effect of the ratio of the double monomers used in the adsorption property was also studied. The equilibrium data of MMIPs toward SMZ was well fitted by the Langmuir isotherm model, and the maximum adsorption capacity estimated was 66.67 μmol g^?1. The adsorption kinetics rapidly achieved equilibrium within 1.0 h and was well described by the pseudo-second-order model. The MMIPs synthesized showed outstanding affinity and selectivity toward SMZ over structurally analogous antibiotics and easily achieved magnetic separation under an external magnetic field. In addition, the adsorption performance of the resulting MMIPs was no obviously decreased at least six repeated cycles.     

钨球侵彻防弹衣加红松木复合靶的研究

为研究钨球对防弹衣加人体等效靶的侵彻性能,利用12.7 mm弹道枪对钨球侵彻三级软体防弹衣加25 mm厚红松靶开展了实验研究;在此基础上,利用LS-DYNA3D软件对侵彻过程及破坏机理进行了分析,并研究了钨球质量变化对弹道极限及靶板能量吸收的影响;依据量纲分析建立了钨球侵彻防弹衣加红松木复合靶的穿靶能量公式,推导了钨球的弹道极限公式。研究结果表明:0.17、0.21、0.44 g的小钨球侵彻防弹衣加红松木复合靶的弹道极限分别为742.3、692.9、570.1 m/s;侵彻过程中,防弹衣以基体开裂、纤维断裂和拉伸分层破坏为主,纤维层面内出现类似“十”字型的损伤,松木靶以剪切和冲塞剥落破坏为主;随着钨球质量的增加,弹道极限呈幂函数形式降低,靶板的能量吸收率逐渐降低;钨球穿靶能量公式及弹道极限公式的计算结果与实验结果吻合良好,可分别用于计算不同侵彻速度下的穿靶能量和不同质量钨球的弹道极限。     

Bifurcation, amplitude death and oscillation patterns in a system of three coupled van der Pol oscillators with diffusively delayed velocity coupling

In this paper, we study a system of three coupled van der Pol oscillators that are coupled through the damping terms. Hopf bifurcations and amplitude death induced by the coupling time delay are first investigated by analyzing the related characteristic equation. Then the oscillation patterns of these bifurcating periodic oscillations are determined and we find that there are two kinds of critical values of the coupling time delay: one is related to the synchronous periodic oscillations, the other is related to eight branches of asynchronous periodic solutions bifurcating simultaneously from the zero solution. The stability of these bifurcating periodic solutions are also explicitly determined by calculating the normal forms on center manifolds, and the stable synchronous and stable phase-locked periodic solutions are found. Finally, some numerical simulations are employed to illustrate and extend our obtained theoretical results and numerical studies also describe the switches of stable synchronous and phase-locked periodic oscillations.     

Enhancing the performance of polymer light-emitting diode via methanol treatment

Enhanced performance of polymer light-emitting diodes (PLEDs) was realized by performing methanol treatment on the emissive layer. Experimental results show that with methanol treatment the electron current increased owing to the rougher surface topography of the emissive layer. Therefore, the balance between electron and hole current was improved. The maximum luminous efficiency and external quantum efficiency of PLEDs increased from 19.7 cd/A and 6.89% to 22.5 cd/A and 7.87%, respectively.     

Compensation control study based on impairment-aware for Wavelength Switched Optical Networks (WSON)

In an optical network, the optical signal transmitted along the lightpath may need to travel through a number of cross connect switches (OXCs), optical amplifiers, and fiber segments. While the signal propagates toward its destination, the optical components would continuously degrade the signal quality by inducing impairments. When the signal degradation is so severe that the received bit-error rate (BER) becomes unacceptably high, the lightpath would not be able to provide good service quality to a connection request. Such a lightpath, which has poor signal quality due to transmission impairments in the physical layer, should not be used for connection provisioning in the network layer. This paper presents an adaptive PID controller based on the power compensation of BP neural network to restrict the influence of the impairment power for a networked control system (NCS) with the presence of controller time-delay and power compensation at amplifiers' node firstly. Control algorithms continuously adjust their channel powers in response to dynamic information from the network links. And the controller could achieve the on-line adaptive power compensation without changing the parameters of PID controller. The results of simulation show that the proposed controller could adjust better channel power at the transmitter sites and achieve channel optical signal-to-noise ratio (OSNR) optimization with controller's time-delay.