Numerical investigation of a multichannel reactor for syngas production by methanol steam reforming at various operating conditions

A novel multichannel reactor with a bifurcation inlet manifold, a rectangular outlet manifold, and sixteen parallel minichannels with commercial CuO/ZnO/Al₂O₃ catalyst for methanol steam reforming was numerically investigated in this paper. A three-dimensional numerical model was established to study the heat and mass transfer characteristics as well as the chemical reaction rates. The numerical model adopted the triple rate kinetic model of methanol steam reforming which can accurately calculate the consumption and generation of each species in the reactor. The effects of steam to carbon molar ratio, weight hourly space velocity, operating temperature and catalyst layer thickness on the methanol steam reforming performance were evaluated and discussed. The distributions of temperature, velocity, species concentration, and reaction rates in the reactor were obtained and analyzed to explain the mechanisms of different effects. It is suggested that the operating temperature of 548 K, steam to carbon ratio of 1.3, and weight hourly space velocity of 0.67 h⁻¹ are recommended operating conditions for methanol steam reforming by the novel multichannel reactor with catalyst fully packed in the parallel minichannels.     

抗几何失真的视频Hashing算法研究

文中提出了一种基于视频灰度直方图形状的Hashing算法,能有效抵抗各种常见的几何失真和视频处理操作.算法的鲁棒性原理如下:1)由于直方图的形状与像素位置无关,故基于直方图的视频Hashing算法能有效抵抗各种常见的几何攻击;2)由于在计算Hashing前对视频帧进行了平滑预处理,故算法对加噪攻击、模糊滤波、有损压缩等处理操作有很好的鲁棒性;3)由于计算Hashing前在时间轴上进行了低通滤波预处理,故算法能抵抗帧率变化、帧丢失等时域同步攻击.实验结果表明,所提出的Hashing算法有良好的唯一性和鲁棒性能.     

Room-Temperature Solid-State Lithium Metal Batteries Using Metal Organic Framework Composited Comb-Like Methoxy Poly(ethylene glycol) Acrylate Solid Polymer Electrolytes

Solid polymer electrolyte with good thermal stability and flexibility is an excellent candidate for solid-state lithium metal batteries, while its low ionic conductivity caused by high crystallinity limits its application at ambient temperature. Here a metal organic framework (zeolitic imidazolate framework-8, ZIF-8) composited comb-like methoxy poly(ethylene glycol) acrylate polymer electrolyte (MCPE) with high ionic conductivity (9.96 × 10⁻⁵ S cm⁻¹ at 30 °C) is prepared by an in situ UV polymerization method. The as-prepared MCPE exhibits improved mechanical property due to the introduction of porous ZIF-8 nanofillers, which is beneficial to suppress the growth of lithium dendrites. Consequently, the LiFePO₄||MCPE||Li cells show a high capacity of 116 mAh g⁻¹ at 30 °C and 0.5 C, and maintain 89.4% of initial capacity after 150 cycles with the average Coulombic efficiency of 99.9%. These results demonstrate that the MCPE shows great potential in solid-state lithium metal batteries near room temperature.     

Na0.5Bi0.5TiO3 phase relations: Thermodynamics and phase equilibria in the systems Bi2O3 – TiO2, Na2O – TiO2, and Na2O – Bi2O3 – TiO2

The lead-free piezoelectric material sodium bismuth titanate (NBT, Na_0.5Bi_0.5TiO₃) has attracted considerable attention owing to its promising dielectric, piezoelectric, and electrical properties. However, the literature on the binary subsystems is contradictory and there are only limited data for the ternary system. The present work surveys all of the reports of the binary subsystems Bi₂O₃ – TiO₂ and Na₂O – TiO₂ and synthesizes these data into inclusive revised versions. The compatibilities for the ternary system Na₂O – Bi₂O₃ – TiO₂ were determined experimentally, thus enabling the construction of a complete isothermal section at 800 °C. The compatibilities associated with the problematic binary subsystem Na₂O – Bi₂O₃, which experiences extreme volatilisation, were determined through the generation of the absent standard-state thermodynamic functions for the relevant binary and ternary phases, thus providing a full suite of thermodynamic data for this system. The thermodynamic stability diagrams for Na₂O, Bi₂O₃, and TiO₂ thus were calculated. The isothermal section also addresses the contradictions in the literature concerning the formation of solid solutions of Bi₁₂TiO_20-x / Bi_12-xTi_1+xO_20+0.5x, pyrochlore (Bi₂Ti₂O₇ / Na_wBi_2-xTi_2-yO_7-z), BTO (Bi₄Ti₃O₁₂ / Na_xBi₄Ti₃O_12+0.5x), and NBT (Na_0.5Bi_0.5TiO₃ / Bi_1±xNa_xTiO_3.5±x). Further, it was observed that the congruent melting point of NBT, which was determined to be 1225 °C, was preceded by the onset of gradual structural destabilization at 940 °C. Also, the NBT rhombohedral → tetragonal phase transformation was observed at an onset temperature of ∼250 °C. The present work thus provides platform data for the fabrication and reactivities of materials in the ternary system Na₂O – Bi₂O₃· TiO₂ and its binary subsystems.     

Characterization of microwave and terahertz dielectric properties of single crystal La2Ti2O7 along one single direction

New generation wireless communication systems require characterisations of dielectric permittivity and loss tangent at microwave and terahertz bands. La₂Ti₂O₇ is a candidate material for microwave application. However, all the reported microwave dielectric data are average value from different directions of a single crystal, which could not reflect its anisotropic nature due to the layered crystal structure. Its dielectric properties at the microwave and terahertz bands in a single crystallographic direction have rarely been reported. In this work, a single crystal ferroelectric La₂Ti₂O₇ was prepared by floating zone method and its dielectric properties were characterized from 1 kHz to 1 THz along one single direction. The decrease in dielectric permittivity with increasing frequency is related to dielectric relaxation from radio frequency to microwave then to terahertz band. The capability of characterizing anisotropic dielectric properties of a single crystal in this work opens the feasibility for its microwave and terahertz applications.     

The influence of user cognition on consumption decision-making from the perspective of bounded rationality

Consumer decision-making is related to the success or failure of enterprises, and products that cater to the cognitive preferences of users have become a focus of current research. Based on the theory of bounded rationality, this paper explores the cognitive process of consumer decision-making. Then, how product shape affects consumption decision-making is analyzed with eye-tracking technology. Finally, the design principle of the product form is further explored. The results demonstrate the following: (1) the perceptual cognition of users has a driving effect on consumption behavior; (2) as a key factor affecting the perceptual cognition of users, product form affects consumer decision-making by influencing the degree of approach motivation; (3) by establishing the mapping relationship between product form elements and user images, the principles of product form design can be more consistent with user image preferences. This study provides useful suggestions for how to increase the purchase behavior of users from the perspective of bounded rationality.     

All-Visible-Light Triggered Photoswitch of Dithienylethene Derivatives with Molecular Conformation Changes Excess 5 Å

Developing new all-visible-light driven fluorescent molecular switches has attracted much interests due to their important application prospects in materials science and life science. Herein, three novel all-visible-light triggered fluorescent molecular photoswitches ( 2P3 , 4F , and 4Cl ) are designed and prepared, which are realized by prolonging π-conjugation length with aggregated-induced emission units. These photoswitches show reversible photochromic and fluorescent switching in dilute solutions and films under 420 nm and 560 nm irradiations. Meanwhile, upon alternating irradiations with 450 nm/560 nm light, effective photochromic and fluorescent switching in powder states are also achieved. More interestingly, two distinct conformations with different photochromic abilities can be altered by solvents polarity. The size difference of the two conformations is over 5 Å in the vertical direction which is one of the largest changes among photochromic molecules based on dithienylethene. The accompanying conformational changes are analysed to understand the relationship between solvent characteristics and crystal structure, as well as the intermolecular interaction in solid state for all-visible-light triggered photoswitching molecules.     

An interpretability security framework for intelligent decision support systems based on saliency map

International Journal of Information Security - Benefiting from the high-speed transmission and super-low latency, the Fifth Generation (5G) networks are playing an important role in contemporary...     

An improved lossless data hiding scheme based on image VQ-index residual value coding

Copyright protection and information security have become serious problems due to the ever growing amount of digital data over the Internet. Reversible data hiding is a special type of data hiding technique that guarantees not only the secret data but also the cover media can be reconstructed without any distortion. Traditional schemes are based on spatial, discrete cosine transformation (DCT) and discrete wavelet transformation (DWT) domains. Recently, some vector quantization (VQ) based reversible data hiding schemes have been proposed. This paper proposes an improved reversible data hiding scheme based on VQ-index residual value coding. Experimental results show that our scheme outperforms two recently proposed schemes, namely side-match vector quantization (SMVQ)-based data hiding and modified fast correlation vector quantization (MFCVQ)-based data hiding.     

External CFRP tendon members: Secondary reactions and moment redistribution

The response of prestress secondary reactions in the post-elastic range has been a topic of much controversy. Due to the brittleness of FRP (fiber reinforced polymer) composites, external FRP tendon members may have different moment redistribution characteristics compared to conventional concrete members. This paper presents a numerical investigation into the secondary reactions and moment redistribution in prestressed concrete continuous members with external CFRP tendons. The investigation parameters include the initial prestress level and the pattern of loading. The secondary reactions are computed using a newly developed method based on the linear transformation concept combined with a nonlinear finite element analysis. The results indicate that the secondary reactions increase quicker after concrete cracking and nonprestressed steel yielding. As a consequence, the secondary moment should be included in the design moment. The moment redistribution behavior for symmetrical loading is shown to be quite different from that for unsymmetrical loading. The study also shows that the effect of initial prestress on the moment redistribution is rather important.