检索结果-南通市图书馆

A review on direct synthesis of dimethoxymethane

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2022年第10期50卷 43-55页

作者： Jia Ren feng xin Yongsheng Xu School of Chemical Engineering and Technology Tianjin UniversityTianjin 300050China

Polyoxymethylene dimethyl ethers are recognized as the prospective diesel additive to decrease the pollutant emission from the light-duty vehicles,which can be polymerize form the monomer of dimethoxymethane(DMM).The industrial synthesis of DMM is mainly involved two-step process:methanol is oxidized to form the formaldehyde in fixed bed reactor and then reacted with the generated formaldehyde through acetalization in continuous stirred-tank *** to huge energy consumption,this typical synthesis route of DMM needs to be upgraded and more green routes should be *** this review,four state-of-the-art one-step direct synthetic routes,including two upgrading routes(methanol direct oxidation and direct dehydrogenation)and two green routes(methanol diethyl ether direct oxidation and carbon oxides direct hydrogenation),have been summarized and *** with the reaction mechanism and catalytic performance on the different catalysts,the challenges and opportu nities for every synthetic route are *** relationships between catalyst structu re and property in different synthesis strategy are also investigated and then the suggestions of the design of catalyst are given about future research directions that efforts should be made ***,this review can bridge the gap between newly developed catalysts and synthesis technology to realize their commercial applications in the near future.

关键词： Dimethoxymethane(DMM) Direct synthesis Reaction mechanism Catalyst

Love wave propagation in one-dimensional piezoelectric quasicrystal multilayered nanoplates with surface effects

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2024年第4期45卷 619-632页

作者： xin feng Liaoliang KE Yang GAO College of Science China Agricultural UniversityBeijing 100083China School of Mechanical Engineering Tianjin UniversityTianjin 300350China

The exact solutions for the propagation of Love waves in one-dimensional(1D)hexagonal piezoelectric quasicrystal(PQC)nanoplates with surface effects are *** electro-elastic model is developed to investigate the anti-plane strain problem of Love wave *** introducing three shape functions,the wave equations and electric balance equations are decoupled into three uncorrelated *** the boundary conditions of the top surface on the covering layer,the interlayer interface,and the matrix,a dispersive equation with the influence of multi-physical field coupling is provided.A surface PQC model is developed to investigate the surface effects on the propagation behaviors of Love waves in quasicrystal(QC)multilayered structures with nanoscale thicknesses.A novel dispersion relation for the PQC structure is derived in an explicit closed form according to the non-classical mechanical and electric boundary *** examples are given to reveal the effects of the boundary conditions,stacking sequence,characteristic scale,and phason fluctuation characteristics on the dispersion curves of Love waves propagating in PQC nanoplates with surface effects.

关键词： piezoelectric quasicrystal(PQC)material multilayered plate dispersion characteristic surface effect

Verifying Contextual Refinement with Ownership Transfer

在线全文

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2021年第6期36卷 1342-1366页

作者： Zhao-Hui Li xin-Yu feng School of Computer Science and Technology University of Science and Technology of ChinaHefei 230026China Department of Computer Science and Technology Nanjing UniversityNanjing 210023China State Key Laboratory for Novel Software Technology Nanjing UniversityNanjing 210023China

Contextual refinement is a compositional approach to compositional verification of concurrent *** has been much work designing program logics to prove the contextual refinement between the object implementation and its abstract ***,these program logics for contextual refinement verification cannot support objects with resource ownership transfer,which is a common pattern in many concurrent objects,such as the memory management module in OS kernels,which transfers the allocated memory block between the object and *** this paper,we propose a new approach to give abstract and implementation independent specifications to concurrent objects with ownership *** also design a program logic to verify contextual refinement of concurrent objects *** abstract *** have successfully applied our logic to verifying an implementation of the memory management module,where the implementation is an appropriately simplified version of the original version from a real-world preemptive OS kernel.

关键词： contextual refinement program logic concurrent object ownership transfer verification

Conductive and tribological properties of TiN-Ag composite coatings under grease lubrication

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Friction 2021年第4期9卷 774-788页

作者： Feihu LIN Yanqiu XIA xin feng School of Energy Power and Mechanical Engineering North China

TiN-Ag composite coatings were prepared by pulsed bias arc ion plating.X-ray diffraction(XRD)and energy dispersive X-ray spectroscopy(EDS)were applied to analyze the compositions of the *** properties of the coatings were studied using an MFT-R4000 ball-on-disk friction tester in the presence of lubricating greases containing multilayer *** electron microscopy(SEM),Raman spectroscopy,and X-ray photoelectron spectroscopy(XPS)were used to analyze the worn surface compositions of the lubricating *** results show that with the decrease in Ag in the film,hardness increased but electrical conductivity *** coating with 10 at%Ag content shows the best friction-reducing and anti-wear properties,which can be attributed to the moderate content of Ag embedded in the TiN crystal gap that enhanced the grain bonding force to improve the anti-wear and self-lubricating *** can be adsorbed on the coating as a solid lubricant.

关键词： silver tribology contact resistance lubricating grease

A program logic for obstruction-freedom

在线全文

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2024年第6期18卷 1-16页

作者： LI Zhao-Hui feng xin-Yu School of Computer Science and Technology University of Science and Technology of China Department of Computer Science and Technology Nanjing University State Key Laboratory for Novel Software Technology Nanjing University

Though obstruction-free progress property is weaker than other non-blocking properties including lock-freedom and wait-freedom, it has advantages that have led to the use of obstruction-free implementations for software transactional memory (STM) and in anonymous and fault-tolerant distributed computing. However, existing work can only verify obstruction-freedom of specific data structures (e.g., STM and list-based algorithms).In this paper, to fill this gap, we propose a program logic that can formally verify obstruction-freedom of practical implementations, as well as verify linearizability, a safety property, at the same time. We also propose informal principles to extend a logic for verifying linearizability to verifying obstruction-freedom. With this approach, the existing proof for linearizability can be reused directly to construct the proof for both linearizability and ***, we have successfully applied our logic to verifying a practical obstruction-free double-ended queue implementation in the first classic paper that has proposed the definition of obstruction-freedom.

关键词： verification program logic progress properties obstruction-freedom concurrent objects

Tribological application and mechanism of epicuticular wax

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Friction 2019年第1期7卷 44-58页

作者： Xuwen ZHONG Yanqiu XIA xin feng School of Energy Power and Mechanical Engineering North China Electric Power University

The plant cuticle is a complex mixture of omnipresent, commonly monofunctional, fatty acid derivatives and taxon-specific, generally bifunctional, specialty compounds. This study explored expanded applications for these substances. Four types of plant cuticles were distilled from leaves and the resulting lipid mixtures were analyzed using gas chromatography-mass spectrometry. These were then used as additives for a synthetic ester lubricant. A reciprocating friction and wear testing machine was utilized to investigate the resulting tribological properties. The worn surfaces of the lower discs were observed and analyzed using optical microscopy and time-of-flight secondary ion mass spectrometry. The results reveal that cuticular waxes can modify the friction properties of the base oil. Furthermore, cuticular waxes demonstrate better performance when compared to the commercially available additive molybdenum dithiocarbamates. A protective adsorption film was identified as the reason for the improved friction reduction and anti-wear properties of the lubricant on the friction pair. This study provides a reference for the study of new types of non-sulfur, phosphorus, and other active element additives and demonstrates considerable potential for the economical utilization of plant leaf waxes.

关键词： epicuticular wax tribological application GC-MS TOF-SIMS adsorption

Self-normalized Cramer-type Moderate Deviations for Functionals of Markov Chain

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2020年第2期36卷 294-313页

作者： xin-wei feng Qi-Man SHAO Zhongtai Securities Institute for Financial Studies Shandong UniversityJinan 250100China Department of Statistics The Chinese University of Hong KongShatinN.T.Hong KongChina Department of Statistics and Data Science Southern University of Science and TechnologyShenzhen 518000China

Let{xn,n≥0}be a Markov chain with a countable state space S and let f(·)be a measurable function from S to R and consider the functionals of the Markov chain yn:=f(xn).We construct a new type of self-normalized sums based on the random-block scheme and establish a Crame′r-type moderate deviations for self-normalized sums of functionals of the Markov chain.

关键词： self-normalized partial sums Cramer-type moderate deviations Markov Chain ergodic

From waste to added-value product: A case of efficient separation and recovery of zinc and iron from spent galvanizing acid

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2024年第4期34卷 702-709页

作者： Jiguo Tu xin feng Bokun Zhang Libo Chen State Key Laboratory of Advanced Metallurgy University of Science and Technology Beijing Jianlong Group & USTB Joint Laboratory University of Science and Technology Beijing

Spent galvanizing acid solution contains high concentrations of zinc salts, ferrous salts, and residual acids,exhibiting extremely high value-added recovery potential. However, achieving the efficient extraction and separation of Zn over Fe becomes particularly challenging under elevated Zn ion concentration. Here, the key extraction parameters, such as modifier ratio, Cyanex 923 concentration and ratio of organic phase to aqueous phase（O/A）, are investigated. The stripping and regeneration of extractant, extraction mechanism, as well as high-value recovery of Zn and Fe resources are also comprehensively expounded. After the two-stage extraction,the extraction efficiency of Zn and Fe is 98.92 % and 2.09 %, respectively. Moreover, the stripping efficiency of Zn reaches 92.3 % with O/A ratio of 1 : 2, using oxalic acid as stripping agent. The predominant extracted species is confirmed to be ZnCl-3, resulting in the formation of HZnCl3· R3PO complex. More importantly, the regenerated extractant can be recycled back into the extraction process, and the reproduced HCl, high-value recovered ZnO and Fe2O3can be used for different industrial fields. These findings lay a solid foundation for the efficient separation and comprehensive recovery of high-concentration spent galvanizing acid solution.

关键词： Zinc recovery Iron recovery Solvent extraction Spent galvanizing acid Extraction efficiency

Classification and spectrum optimization method of grease based on infrared spectrum

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Friction 2024年第6期12卷 1154-1164页

作者： xin feng Yanqiu XIA Peiyuan XIE Xiaohe LI School of Energy Power and Mechanical Engineering North China Electric Power UniversityBeijing 102206China State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China

The infrared(IR)absorption spectral data of 63 kinds of lubricating greases containing six different types of thickeners were obtained using the IR *** Kohonen neural network algorithm was used to identify the type of the lubricating *** results show that this machine learning method can effectively eliminate the interference fringes in the IR spectrum,and complete the feature selection and dimensionality reduction of the high-dimensional spectral *** 63 kinds of greases exhibit spatial clustering under certain IR spectrum recognition spectral bands,which are linked to characteristic peaks of lubricating greases and improve the recognition accuracy of these *** model achieved recognition accuracy of 100.00%,96.08%,94.87%,100.00%,and 87.50%for polyurea grease,calcium sulfonate composite grease,aluminum(Al)-based grease,bentonite grease,and lithium-based grease,*** on the different IR absorption spectrum bands produced by each kind of lubricating grease,the three-dimensional spatial distribution map of the lubricating grease drawn also verifies the accuracy of classification while recognizing the *** paper demonstrates fast recognition speed and high accuracy,proving that the Kohonen neural network algorithm has an efficient recognition ability for identifying the types of the lubricating grease.

关键词： grease infrared(IR)spectroscopy layered Kohonen network species recognition spectrum band optimization