Performance investigation on a novel 3D wave flow channel design for PEMFC

Flow field structure can largely determine the output performance of Polymer electrolyte membrane fuel cell. Excellent channel configuration accelerates electrochemical reactions in the catalytic layer, effectively avoiding flooding on the cathode side. In present study, a three-dimensional, multi-phase model of PEMFC with a 3D wave flow channel is established. CFD method is applied to optimize the geometry constructions of three-dimensional wave flow channels. The results reveal that 3D wave flow channel is overall better than straight channel in promoting reactant gases transport, removing liquid water accumulated in microporous layer and avoiding thermal stress concentration in the membrane. Moreover, results show the optimal flow channel minimum depth and wave length of the 3D wave flow channel are 0.45 mm and 2 mm, respectively. Due to the periodic geometric characteristics of the wave channel, the convective mass transfer is introduced, improving gas flow rate in through-plane direction. Furthermore, when the cell output voltage is 0.4 V, the current density in the novel channel is 23.8% higher than that of conventional channel.     

大功率CO_2激光器非平衡态合成WO_3／Fe_2O_3新型陶瓷催化剂──Ⅱ．WO_3／Fe_2O_3烯烃歧化反应催化剂的催化活性

用大功率ＣＯ２激光器熔制ＷＯ３／Ｆｅ２Ｏ３新型烯烃歧化反应催化剂。考查了催化剂组成、激光功率及熔炼时间与丙烯歧化反应催化活性之间的关系。     

Dual-reflector configuration in varied line-space grating displacement sensor

A method to improve the accuracy of the wavelength encoding varied line-space grating displacement sensor is presented. Based on the detailed analysis of the measured displacement errors from the single-mirror configuration sensor, a dual-reflector configuration is used to replace the previous configuration, and greatly decreases its errors. Experiments are conducted in order to make comparison of the two configurations. The results show that the measured displacement error of the sensor with dual-reflector configuration is lower than 0.03 mm in full scale (0 to 50 mm), only about 10% of the sensor with single-mirror configuration.     

Plasmon-Assisted Self-Encrypted All-Optical Memory

All-optical responsive nanomaterials, which can rapidly switch between two stable states, have been regarded as the next-generation memories due to their potential to realize binary information storage and implement on-chip, integrated photonic neuromorphic systems. Rare earth oxides are preeminent candidates owing to their extraordinary luminescent stability and narrow optical transitions. However, due to the lack of simple and effective optical switches, it is difficult to realize all-optical data storage, encoding, and retrieval by pure rare earth-doped luminescent nanoparticles. Here, a rapid and high-contrast of 10⁴ luminescent switching of Y₂O₃:Eu³⁺ nanoparticle between the enhancement and quenching states is achieved by employing the strong light confinement and ultrafast thermal response of localized surface plasmon resonance. A self-encrypted all-optical memory is presented with optical information writing, encryption, reading, and re-writing, and a high-sensitivity synaptic response of emitters to frequency and light intensity flux, which can be harnessed to encrypt information flows and promote convenient and high-security information encryption. Such a convenient and secure plasmonic thermally assisted self-encrypting luminescent switch paves the way for constructing high-performance stimuli-responsive rare earth oxide crystals on demand and expanding their applications in various data encryption, anti-counterfeiting, and rewritable colouration devices.     

Effects of Fe/Ni Ratio on Microstructure and Properties of FeNiCrAlNb High-Entropy Alloys

Herein, the effects of Fe/Ni ratio on the microstructure, mechanical properties, and corrosion resistance in a 3.5 wt% NaCl solution of Fe_xNi_65−xCr₂₀Al₁₀Nb₅ are investigated systematically. It is found that the phases shifted from the FCC-dominated to the BCC-dominated with the molar ratio of the Fe/Ni increased. The strength of Fe_xNi_65−xCr₂₀Al₁₀Nb₅ increases with the molar ratio of Fe/Ni further increased, while the plasticity decreases. The yield strength reaches 1,653 MPa at x = 45. The alloy exhibits the best corrosion resistance when x = 35 which is attributed to the dominant FCC phases in the dendritic region.     

一个基于POS的燃气用户收费及管理系统的开发

本文介绍了一个基于POS的燃气用户收费及管理系统的设计和实现,给出了系统的总体结构,并对其主要组成的原理和功能作了阐述。     

Broadband dielectric microwave microscopy on micron length scales

We demonstrate that a near-field microwave microscope based on a transmission line resonator allows imaging in a substantially wide range of frequencies, so that the microscope properties approach those of a spatially resolved impedance analyzer. In the case of an electric probe, the broadband imaging can be used in a direct fashion to separate contributions from capacitive and resistive properties of a sample at length scales on the order of one micron. Using a microwave near-field microscope based on a transmission line resonator we imaged the local dielectric properties of a focused ion beam milled structure on a high-dielectric-constant Ba(0.6)Sr(0.4)TiO(3) thin film in the frequency range from 1.3 to 17.4 GHz. The electrostatic approximation breaks down already at frequencies above approximately 10 GHz for the probe geometry used, and a full-wave analysis is necessary to obtain qualitative information from the images.     

远程镜像中自适应异步模式的设计及讨论

在远程镜像系统中,通信链路的可用带宽和主站应用程序的I/O数据率都可能会不断变化,因此通信链路的负载也会随之改变。但现今一些基于存储设备块级别的远程镜像系统(如EMCSRDF,IBMPPRC,XRC等)在异步模式下并未涉及这些变化因素。该文综合考虑了这一点,简要地设计了一个异步远程镜像方案——自适应异步模式,它不但避免了rollingdisaster的产生,而且能够根据链路负载的变化动态地调整在链路中传输的数据量。     

A robust mixed‐conducting multichannel hollow fiber membrane reactor

To accelerate the commercial application of mixed‐conducting membrane reactor for catalytic reaction processes, a robust mixed‐conducting multichannel hollow fiber (MCMHF) membrane reactor was constructed and characterized in this work. The MCMHF membrane based on reduction‐tolerant and CO₂‐stable SrFe_0.8Nb_0.2O_3‐δ (SFN) oxide not only possesses a good mechanical strength but also has a high oxygen permeation flux under air/He gradient, which is about four times that of SFN disk membrane. When partial oxidation of methane (POM) was performed in the MCMHF membrane reactor, excellent reaction performance (oxygen flux of 19.2 mL min^?1 cm^?2, hydrogen production rate of 54.7 mL min^?1 cm^?2, methane conversion of 94.6% and the CO selectivity of 99%) was achieved at 1173 K. And also, the MCMHF membrane reactor for POM reaction was operated stably for 120 h without obvious degradation of reaction performance. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2592–2599, 2015     

Optical,electrochemical, and photovoltaic properties of conjugated polymers with dithiafulvalene as side chains

Three conjugated polymers, P1–P3, with dithiafulvalene (DTF) as side chains have been synthesized. All polymers have good thermal stabilities. The DTF unit could be oxidized to DTF?⁺ which was observed from cyclic voltammetry and ultraviolet–visible (UV–vis) spectra, and the oxidation process was independent of the conjugated backbone of the polymer. The strong π–π* transition absorbing band of the three polymers decreases gradually as increasing oxidation, and the resulting DTF?⁺ species give rise to an additional band at 750–1100 nm, which can be assigned to a distinguishing feature of the cation radical species. Photovoltaic device based on the blend of P2 and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PC₆₁BM) showed the power conversion efficiency of 1.05% with a fill factor of 42.8%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41508.