Integrating workload balancing and fault tolerance in distributed stream processing system

World Wide Web - Distributed Stream Processing Engine (DSPE) is designed for processing continuous streams so as to achieve the real-time performance with low latency guaranteed. To satisfy such...     

Fabrication of High Thermally Conductive and Electrical Insulating Composites by Boron Nitride-Nanosheet-Coated PEEK Fiber

The development of polyether ether ketone (PEEK)-based thermally conductive insulating composites is required in miniaturized electronic devices with a high power density where heat needs to be evacuated. However, the low thermal conductivity (TC) remains a great challenge, significantly restricting the large-scale applications of PEEK. Here, a novel class of boron nitride nanosheets (BNNSs)/PEEK composites with excellent heat dissipation properties through BNNS-coated PEEK fiber is developed, through simple hot-press sintering. A direct comparison of experimental measurements between the BNNSs/PEEK fiber composites and the BNNSs/PEEK powder composites indicates that the TC is greatly improved in the presence of the well-orientated structure of BNNSs. In addition, the composite with high loading of BNNSs exhibits a combination of high tensile strength and significant electrical insulation (volume electrical resistivity beyond 10⁹ Ω cm). The experimental data demonstrate that it has broad and bright prospects for application in a range of emerging electronic devices, which also provide great potential for enhancing the thermal management application of PEEK-based composites.     

关于阴极保护标准及工程测量方法的探讨

研究表明，在阴极保护实际工程应用中，传统的通电12s后断电3s的测量方法并不能得到准确的断电电位数据。IR降的正确测量可以通过专业仪器得到，也可在工程现场用万用表进行简单测量后进行修正得到。另外，在正常情况下，一100mV极化可以将电化学腐蚀速率降低到原来的2％；极端情况下也可以降低到原来的1／7。因此应该重视-100mV的极化标准，并将此准则同样视为阴极保护工程验收的一条重要标准。     

Retrieval,reporting and methodological characteristics for systematic reviews/meta-analyses of animal models: a meta-epidemiological study

The study aimed to analyze the reporting and methodological quality of systematic reviews (SRs)/metaanalyses (MAs) of animal models to provide references for later studies and avoid the waste of medical resources. EMBASE and MEDLINE databases were searched from inception to November 2017, with no language restriction. Two reviewers selected inclusion dependently and extracted the basic characteristics. Review Manager 5.3, stata 12.0, and SPSS 21 software were used to conduct analyses. A total of 46 SRs/MAs were included. The results showed that the English databases with high retrieval frequency are PubMed/MEDLINE, EMBASE, and Web of Science. 67.31% (31/46) of the articles reported the search strategy in the full text or the appendix. 65.22% (30/46) reported the literature screening flow diagram, and only 19.57% (9/46) reported the number of works of literature retrieved in each database. 60.87% (28/46) illustrated supplement retrieval. Through 2 subgroup analyses, it was found that there were no significant differences in the quality of reports of PRISMA items. But referring to the methodological quality or reporting of PRESS items, SCI was better than that of non-SCI, while there seemed a source of funding to have no significant impact on the methodological quality or the items of PRESS. The results of PRESS, AMSTAR 2, and PRISMA were correlated, and the correlation between PRISMA and AMSTAR 2 was strong. These results demonstrated that search strategies of animal model SRs/MAs are still not enough comprehensive, report specification and methodological quality still need to be ameliorated. To show users the scientificity and rigor of the study, future research should focus on these various guidelines like PRESS, PRISMA, and AMSTAR 2 checklists that have been issued, it can help to increase the value of research and improve the utilization of medical resources.     

Dynamic and Static Characteristics of Double Push Rods Electromechanical Converter

Due to the influence of material characteristics and winding power, single output electromagnet has limited ability to improve the dynamic characteristic of electro-hydraulic valve. Therefore, an electromechanical converter with double push rods is proposed in this paper, which can simultaneously output two electromagnetic forces, can push or pull the valve core and sleeve according to the current direction and realize rapid operation of load. According to the electromagnetic principle and the magnetic circuit analysis method, the mathematical model and equivalent circuit of the electromechanical converter with double push rods are established. Through the finite element simulation model of the electromechanical converter with double push rods with the same magnetization directions, the changing rules of its magnetic field distribution and force–displacement behaviors are studied and analyzed. According to the analysis results, the electromagnetic mechanical parameters and mechanical structure of the electromechanical converter with double push rods are determined, and the prototype is made. The test platform for the push-pull characteristics of the electromechanical converter with double push rods is built, and its static and dynamic characteristics are tested and analyzed. The results show that the thrust and pull output characteristics of the internal and external push rods are basically consistent with the simulation output, and proportional to the current density of the coil; the push-pull hysteresis of internal and external push rods output force is less than 5%; and the dynamic time response characteristics of the displacement and force are obtained. The hysteresis e ect of output force is improved e ectively through the H bridge drive control circuit modulated by PWM. Compared with the displacement response of a singlewinding electromagnet with a similar volume, it can e ectively improve the dynamic displacement response. Followup work will further optimize the structure of the electromechanical converter and test the corresponding pilot valve. The research results provide a new theory for improving the output characteristics of electro-hydraulic pilot valve and have an extremely high engineering application value and broad application prospect.     

一类卷积积分的图形解析法

卷积积分是一种线性运算,在概率理论、自动控制、信号处理、系统分析中有广泛的应用。提出了一类可以通过图形、并辅之以解析的卷积积分计算方法,简单明了,实用快速。     

One-pot solvothermal synthesis of PdCu nanocrystals with enhanced electrocatalytic activity toward glycerol oxidation and hydrogen evolution

The catalytic capability of bimetallic nanocatalysts is closely correlated with their size, shape, and crystal structures. Herein, a facile one-pot solvothermal strategy is designed to fabricate uniform spherical PdCu nanocrystals (NCs) assembled by many smaller grains. Oeylamine (OAm) is acted as the reaction solvent and reductant. KBr and hexadecylpyridinium chloride monohydrate (HDPC) are used as the capping agent and surfactant to avoid the aggregation, respectively. The architectures possess larger electrochemically active surface area (ECSA) of 13.6 m² g^?1 than commercial Pd black (4.4 m² g^?1), showing the improved catalytic ability for glycerol oxidation reaction (GOR) in alkaline electrolyte in contrast with Pd black. Besides, the obtained catalyst exhibits more positive onset potential (?56 mV) and Tafel slope (51 mV decade^?1) toward hydrogen evolution reaction (HER) in acidic media relative to commercial Pd/C, albeit with their performance bellow commercial Pt/C catalyst.     

The microstructure and mechanical properties of TaN/TiN and TaWN/TiN superlattice films

The microstructure and the microhardness of the TaN/TiN and TaWN/TiN superlattice films have been studied with X-ray diffraction, transmission electron microscopy and microhardness tester. The results showed that both TaN/TiN and TaWN/TiN superlattice films have a cubic crystal structure with an epitaxially grown mode of polycrystallinity. Lattice constants of superlattice films are between those of the constituent materials. The superhardness effect was found in TaN/TiN and TaWN/TiN superlattice films and the maximum hardness value was 40.0 GPa at a modulation period of 9.0 nm for TaN/TiN, and 50.0 GPa at a modulation period of 5.6 nm for TaWN/TiN. It is proposed that the lattice mismatch affects the microhardness value and the peak position of maximum hardness. The inhibition of dislocation motion by alternating stress fields of interfacial coherent strains is believed responsible for hardness anomalies.     

乙醛法合成乙酸乙酯

工业乙醛经４Ａ分子筛干燥至水分低于００３％，在乙醇铝作催化剂，无水氯化锌作助催化剂，２０～４０℃反应温度的条件下，直接合成乙酸乙酯，乙醛的转化率可达９９３％，乙酸乙酯的选择性可达９５３％。催化剂的合成和乙醛的干燥是实验的关键步骤。