基于化学监督的超(超)临界机组关键控制节能指标分析及建议

针对超(超)临界机组参数提高、材质升级,化学技术监督中的监督指标对机组经济性和可靠性影响较大的问题,本文通过机组典型案例分析、技术监督报告、现场实测等,对目前化学监督中影响较大的、关键的技术指标进行了系统性的分析研究。研究结果找出了6项化学监督中超(超)临界机组关键的、影响较大的控制监督指标,且提出了指标控制值和控制方法。这项系统性研究分析方法对指导超(超)临界机组化学监督具有重要的借鉴作用,以控制超(超)临界机组因参数提高和材质升级带来的新问题和新挑战。     

Systematic convergence of nonlinear stochastic estimators on the Special Orthogonal Group SO(3)

This paper introduces two novel nonlinear stochastic attitude estimators developed on the Special Orthogonal Group with the tracking error of the normalized Euclidean distance meeting predefined transient and steady‐state characteristics. The tracking error is confined to initially start within a predetermined large set such that the transient performance is guaranteed to obey dynamically reducing boundaries and decrease smoothly and asymptotically to the origin in probability from almost any initial condition. The proposed estimators produce accurate attitude estimates with remarkable convergence properties using measurements obtained from low‐cost inertial measurement units. The estimators proposed in continuous form are complemented by their discrete versions for the implementation purposes. The simulation results illustrate the effectiveness and robustness of the proposed estimators against uncertain measurements and large initialization error, whether in continuous or discrete form.     

Preparation and properties of chitosan/acidified attapulgite composite proton exchange membranes for fuel cell applications

A composite proton exchange membrane chitosan (CS)/attapulgite (ATP) was prepared with the organic–inorganic compounding of ATP and CS. The composite membranes were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR). The mechanical properties, thermal stability, water uptake, and proton conductivity of the composite membranes were fully investigated. The composite membranes exhibited an enhanced mechanical property, dimensional and thermal stability compared to CS membrane, owing to the interface interaction between ATP and CS. The maximum tensile strength of 53.1 MPa and decomposition temperature of 223.4°C was obtained, respectively. More importantly, the proton conductivity of the composite membrane is also enhanced, the composite membrane with 4 wt% ATP content (CS/ATP-4) exhibited the highest proton conductivity of 26.2 mS cm⁻¹ at 80°C with 100% relative humidity, which is 25.1% higher than pure CS membrane. These results may explore a simple and green strategy to prepare CS-based PEMs, which have a great potential in the application of proton exchange membrane fuel cells.     

基于差分进化算法的手眼标定方法

针对眼在手机器人视觉系统的手眼标定问题，提出了一种基于差分进化算法的手眼标定方法。首先建立了眼在手机器人视觉系统手眼标定的数学模型，通过李群李代数理论，将手眼标定问题转化为误差函数的优化问题，同时保证了优化问题的最优解落在特殊欧氏群ＳＥ（３）上。通过差分进化算法对优化问题进行求解，避免了求解过程中的局部最优问题。最后在实物平台上进行了手眼标定实验，实验结果验证了算法的可行性和有效性。     

带耐火衬里高温反应器密封锥结构的设计

耐火衬里及支撑结构设计的可靠性是保证高温反应器壳体温度小于设计温度的关键因素。针对耐火衬里结构失效导致反应器壳体温度超过设计温度的问题,提出了一种双金属焊接的密封锥结构。该结构具有支撑金属衬里的作用以及将耐火材料与金属衬里之间的膨胀空间分割成多个密闭空间以阻止高温气体的流动,进而提高隔热可靠性。采用ANSYS软件中APDL语言建立了密封锥连接结构的有限元模型,通过研究密封锥不同角度以及厚度对计算结果的影响,得出了密封锥的最佳结构参数,并满足ASME标准的应力强度评定要求。模拟结果可为此类高温反应器耐火衬里结构的设计提供参考依据。     

Enhanced mechanical toughness of carbon nanofibrous-coated surface modified Kevlar reinforced polyurethane/epoxy matrix hybrid composites

High-performance Kevlar fiber had extensively been explored to upgraded mechanical properties of the advanced composites. Therefore, this study aimed a challenging work to grow carbon nanofibers onto the Kevlar fiber to improve its fiber-matrix interaction properties. It was successfully done through inexpensive flame deposition as well as modification of matrix with hybrid resin using polyurethane-epoxy mixture. A hand-layup method had been adopted to manufacture the composite laminates. The chemical and surface structures of the prepared laminae were examined by scanning electron microscopy, Raman spectroscopy, X-ray diffraction, and the composite's properties were evaluated tensile test, compact tension (CT) fracture test, fractography, and differential scanning calorimetry. The surface modified Kevlar laminae with CNF were used as reinforcing layer in the epoxy and PU/epoxy hybrid resin matrices. CNF-coated heated Kevlar reinforced laminated PU/epoxy hybrid composites (CNF-Kev/PU-Epoxy) showed highest elongation 47% and fracture toughness (11.7 MPa√m) along with good UTS 139 MPa. Therefore, these hybrid nanocomposites developed by simple inexpensive method would be the potential candidates for several advanced applications particularly in defense, automobile, aerospace, and spacecraft applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48802.     

Synthesis and two-step sintering behavior of solution derived corundum abrasives with plate-like grains

Corundum abrasives with plate-like grains were fabricated by a two-step sintering technique using the solution-based process with the addition of the ternary compound additive Na₃AlF₆-CaO-SiO₂. The two-step sintering method showed obvious advantages over conventional sintering methods in promoting sample densification, suppressing grain growth, and homogenizing the microstructure of the corundum abrasives. The sample doped with 2.5?wt% Na₃AlF₆ and 4?wt% CaO + SiO₂ in the molar ratio of 1:1 possessed a relative density of 99.3%, average grain size of 0.54?µm, and single-particle compressive strength of 49?N. The introduction of seeds reduced the temperature of θ- to α-Al₂O₃ phase transformation. The relationship between the microstructure and the mechanical properties of the abrasives was also discussed.     

A Differentially Private Data Aggregation Method Based on Worker Partition and Location Obfuscation for Mobile Crowdsensing

With the popularity of sensor-rich mobile devices, mobile crowdsensing (MCS) has emerged as an effective method for data collection and processing. However, MCS platform usually need workers’ precise locations for optimal task execution and collect sensing data from workers, which raises severe concerns of privacy leakage. Trying to preserve workers’ location and sensing data from the untrusted MCS platform, a differentially private data aggregation method based on worker partition and location obfuscation (DP-DAWL method) is proposed in the paper. DP-DAWL method firstly use an improved K-means algorithm to divide workers into groups and assign different privacy budget to the group according to group size (the number of workers). Then each worker’s location is obfuscated and his/her sensing data is perturbed by adding Laplace noise before uploading to the platform. In the stage of data aggregation, DP-DAWL method adopts an improved Kalman filter algorithm to filter out the added noise (including both added noise of sensing data and the system noise in the sensing process). Through using optimal estimation of noisy aggregated sensing data, the platform can finally gain better utility of aggregated data while preserving workers’ privacy. Extensive experiments on the synthetic datasets demonstrate the effectiveness of the proposed method.     

Identification of Proteins Modulated in the Date Palm Stem Infested with Red Palm Weevil (Rhynchophorus ferrugineus Oliv.) Using Two Dimensional Differential Gel Electrophoresis and Mass Spectrometry

A state of the art proteomic methodology using Matrix Assisted Laser Desorption/Ionization-Time of Flight (MALDI TOF) has been employed to characterize peptides modulated in the date palm stem subsequent to infestation with red palm weevil (RPW). Our analyses revealed 32 differentially expressed peptides associated with RPW infestation in date palm stem. To identify RPW infestation associated peptides (I), artificially wounded plants (W) were used as additional control beside uninfested plants, a conventional control (C). A constant unique pattern of differential expression in infested (I), wounded (W) stem samples compared to control (C) was observed. The upregulated proteins showed relative fold intensity in order of I > W and downregulated spots trend as W > I, a quite interesting pattern. This study also reveals that artificially wounding of date palm stem affects almost the same proteins as infestation; however, relative intensity is quite lower than in infested samples both in up and downregulated spots. All 32 differentially expressed spots were subjected to MALDI-TOF analysis for their identification and we were able to match 21 proteins in the already existing databases. Relatively significant modulated expression pattern of a number of peptides in infested plants predicts the possibility of developing a quick and reliable molecular methodology for detecting plants infested with date palm.     

A directional mutation operator for differential evolution algorithms

Differential evolution (DE) is widely studied in the past decade. In its mutation operator, the random variations are derived from the difference of two randomly selected different individuals. Difference vector plays an important role in evolution. It is observed that the best fitness found so far by DE cannot be improved in every generation. In this article, a directional mutation operator is proposed. It attempts to recognize good variation directions and increase the number of generations having fitness improvement. The idea is to construct a pool of difference vectors calculated when fitness is improved at a generation. The difference vector pool will guide the mutation search in the next generation once only. The directional mutation operator can be applied into any DE mutation strategy. The purpose is to speed up the convergence of DE and improve its performance. The proposed method is evaluated experimentally on CEC 2005 test set with dimension 30 and on CEC 2008 test set with dimensions 100 and 1000. It is demonstrated that the proposed method can result in a larger number of generations having fitness improvement than classic DE. It is combined with eleven DE algorithms as examples of how to combine with other algorithms. After its incorporation, the performance of most of these DE algorithms is significantly improved. Moreover, simulation results show that the directional mutation operator is helpful for balancing the exploration and exploitation capacity of the tested DE algorithms. Furthermore, the directional mutation operator modifications can save computational time compared to the original algorithms. The proposed approach is compared with the proximity based mutation operator as both are claimed to be applicable to any DE mutation strategy. The directional mutation operator is shown to be better than the proximity based mutation operator on the five variants in the DE family. Finally, the applications of two real world engineering optimization problems verify the usefulness of the proposed method.