基于SnO2中空纳米球的低温氢气传感器的研究

采用水热法一步合成SnO2纳米材料,采用XRD、SEM、TEM和氮吸附-脱附对材料的结构和形貌进行表征。表征结果表明所制备SnO2纳米材料是由直径150~200 nm的中空纳米球组成,且具有较大比表面积(82.6 m2/g)。采用丝网印刷技术将SnO2气敏浆料涂覆到叉指电极上,制成厚膜型气体传感器器件,研究其对氢气的气敏性能。结果表明SnO2中空纳米球在较低温度(200℃)下对5~200μl/L氢气具有较高的响应值及较快的响应速度,这归因于所制备的SnO2材料的中空结构和较大比表面积,利于氢气气体的吸附与扩散。     

Inferring kinetic dissolution of NaCl in aqueous glycol solution using a low-cost apparatus and population balance model

An experimental methodology for inferring brine dissolution rate in monoethylene glycol (MEG) solutions at different temperatures using a webcam combined with a mathematical model is presented. The measurement system is designed to track the RGB (red, green, and blue) colour variations during the dissolution process. A dynamic model augmented with the population balance equation is applied to describe the dissolution process. Moreover, the dissolution rate is consistently related to the temperature and MEG concentration through the driving force based on the Gibbs energy and chemical affinity. The applied low-cost measurement apparatus proved to be a useful resource for tracking the dissolution dynamics in a wide range of undersaturation.     

智能变电站设备管控大数据分析系统研究

结合数据挖掘、大数据技术在电力系统中的应用现状，分析和设计了一种智能变电站设备管控大数据分析系统。对变电站设备运行状态的大数据特征及基本框架进行了分析，并重点阐述了变电站设备运行状态大数据分析系统的数据集成与预处理、数据存储与处理、设备状态评估模型以及数据可视化展示。实验结果表明，所设计的大数据分析系统能够大幅度提升变电站设备数据分析智能化水平，为变电站管控稳定运行提供更加有效和实用性的技术支撑。     

Structural properties and sensing performance of CeTiO3 ceramic films as a solid-state pH sensor

In this paper, we have studied the impact of postannealing treatment on the structural properties and sensing characteristics of CeTiO₃ ceramic membranes deposited on Si substrate by sputtering for solid-state electrolyte-insulator-semiconductor (EIS) pH sensors. X-ray photoelectron spectroscopy, Auger electron spectroscopy, X-ray diffraction, and atomic force microscopy were used to study the chemical compositions, elemental depth profiles, film structures, and surface morphologies of CeTiO₃ ceramic membranes treated at three rapid thermal annealing (RTA) temperatures of 700, 800 and 900?°C. The sensing performance of the CeTiO₃ ceramic membranes annealed at three different RTA temperatures is strongly correlated to their structural properties. The CeTiO₃ EIS device after RTA at 800?°C exhibited the best sensing characteristics (pH sensitivity, hysteresis voltage and drift rate) among these RTA temperatures. We attribute this behavior to the optimal RTA temperature enhancing the Ce³⁺/Ce⁴⁺ ratio of CeTiO₃ ceramic membrane, reducing an interfacial layer at the CeTiO₃-Si interface, and increasing its surface roughness.     

Ultrasonic vibration mill-grinding of single-crystal silicon carbide for pressure sensor diaphragms

Single-crystal silicon carbide (SiC) has gained tremendous attention for harsh-environment sensor applications due to its high-temperature tolerance and chemical resistance. However, there are many technological challenges in the fabrication of single-crystal SiC sensing microstructures such as thin SiC diaphragms for pressure sensors. This paper presents an ultrasonic vibration mill-grinding (UVMG) technique for the fabrication of 6H-SiC sensor diaphragms. The fundamental machining characteristics of UVMG are investigated experimentally compared with conventional mill-grinding (CMG). The experimental results show that the axial grinding force in UVMG is reduced by 60–70% compared to that in CMG. In addition, the wheel loading is severe in CMG, while the issue of wheel loading is significantly alleviated in UVMG due to the discontinuous cutting characteristic achieved in this method. As a result, sharp increase of the axial grinding force, which is accompanied by the crack of SiC workpiece, happens frequently in CMG after a total grinding depth of 200 µm. By contrast, the axial grinding force is stable in UVMG during the total grinding depth of at least 900 µm. The ultrasonic vibration in UVMG results in rough surface finish due to the material-removal mechanism of brittle fracture. However, by taking the advantages of better machining stability in UVMG and better surface roughness in CMG, extremely thin SiC sensor diaphragms with satisfactory surface quality can be achieved. Finally, we demonstrate the successful fabrication of a thin SiC diaphragm with a thickness of 20.3 µm.     

Prevailing Research Trends in Carbon Nanohorn and Polymer-based Hybrids

This review outlines research progress on carbon nanohorn (CNH) and polymer/CNH hybrids including structure, properties, application, and future stance. Carbon nanohorn is a type of nanocarbon existing as dahlia-like, bud-like, and seed-like structures. Most widely known form is single-walled carbon nanaohorn with diameter of ～5?nm and tube length ～50?nm. Polymers such as polystyrene, polyaniline, polythiophene, poly(vinylalcohol), poly(methylmethacrylate), poly(ethyleneglycol), polycaprolactone, polyimide, poly(2-aminopyridine), and nylon have been interacted with CNH using various techniques. Structural and physical properties of fine-tuned carbon nanohorn and polymer/CNH hybrids have been used for versatile applications such as dye-sensitized solar cell, supercapacitor, drug delivery, fuel cell, and sensors.     

Seismic life-cycle cost analysis of ageing highway bridges under chloride exposure conditions: modelling and recommendations

Chloride-induced corrosion of highway bridges constitutes a critical form of environmental deterioration and may result in significant escalation of seismic life-cycle costs due to increased fragility during earthquake events. Most of existing literature tends to adopt simplistic uniform area loss assumptions in lieu of potentially complex, yet realistic and more detrimental, pitting corrosion models for seismic vulnerability analysis. Since the degree of deterioration depends on the severity and duration of exposure, there exists a need to investigate the influence of uniform vs. pitting corrosion assumption on seismic life-cycle costs for varied chloride exposure conditions. A case-study example of a highway bridge in Central and Southeastern US reveals consideration of pitting corrosion as critical for extreme exposures compared to relatively minor settings. Subsequently this study provides recommendations to aid bridge engineers and stakeholders to balance between computational cost and accuracy of results to aid prompt decisions on rehabilitation of ageing bridges in different exposure conditions. A framework is also included to compute seismic life-cycle costs from generic measures of corrosion, independent of assumed exposure scenario. This framework is particularly helpful for seismic loss assessment of highway bridges in chloride exposure zones with periodic field measurements to estimate the extent of structural deterioration.     

Identifying cooperation for innovation―a comparison of data sources

ABSTRACT

The value of social network analysis is critically dependent on the comprehensive and reliable identification of actors and their relationships. We compare regional knowledge networks based on different types of data sources, namely, co-patents, co-publications, and publicly subsidized collaborative R&D projects. Moreover, by combining these three data sources, we construct a multilayer network that provides a comprehensive picture of intraregional interactions. By comparing the networks based on the data sources, we address the problems of coverage and selection bias. We observe that using only one data source leads to a severe underestimation of regional knowledge interactions, especially those of private sector firms and independent researchers.