Building Model as a Service to support geosciences

Modeling is a fundamental methodology for simulating the past, understanding the present and predicting the future of the geospatial systems and phenomena. However, modeling in the geospatial science poses several challenges, including complex model setup, repetition in model setup, requirement for large, scalable computing resources, and management of a large amount of model output. To address these challenges, we propose Model as a Service (MaaS) by leveraging the latest advancement of cloud computing. MaaS enables various geoscience models to be published as services, and these services can be accessed through a simple web interface. MaaS automates the processes of configuring machines, setting up and running models, and managing model outputs. The computing resources are automatically provisioned by MaaS in a cloud environment. A proof-of-concept MaaS prototype is presented using a global climate change model (ModelE). Experimental results show that the MaaS prototype significantly simplifies model setup, accelerates model simulation and enhances model output by providing a web-based, on-demand, scalable modeling environment.     

Growth of ZnO nanoparticles from nanowhisker precursor with a simple solvothermal route

Methods of preparing nanoparticles have long been a topic experiencing extensive investigation. Among those methods developed, using template or polymer and surfactant as capping reagents were often effective. However, obtaining nanoparticles in high amounts and high purity still remains an unresolved challenge. Here, a simple two-step solvothermal method without using any surfactant or coating reactant to prepare ZnO nanoparticles with high purity in large scale was developed. X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the as-prepared ZnO nanoparticles, and the formation process of the nanoparticles was discussed finally.     

Preparation and properties of sliver and nitrogen co-doped TiO2 photocatalyst

TiO₂ photocatalysts co-doped with different content of Ag and N were prepared by sol–gel method combined with microwave chemical method. The samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), ultraviolet–visible diffuse reflectance spectrum (UV–vis) and photo-luminescence emission spectrum (PL). The photocatalytic activity was investigated by photocatalytic degradation of methylene blue (MB) under irradiation of fluorescent lamp. The results indicate that Ag and N co-doping can restrain the increase of grain size, broaden the absorption spectrum to visible light region, and inhibit the recombination of the photo-generated electron–hole pairs. Moreover, the photocatalytic activity of Ag–N–TiO₂ in MB degradation is remarkable improved. The degradation rate of the sample with Ag:TiO₂ = 0.05 at%, N:TiO₂ = 18.50 wt% in 5 h is 93.44%, which is much higher than that of Degussa P25 (39.40%).     

The AMWCNTs supported porous nanocarbon composites for high-performance supercapacitor

The porous nanocarbons supported by acid-treated multiwall carbon nanotubes (PC@ACNTs) were prepared by the combination of the hydrothermal polymerization of glucose on ACNTs, carbonization under N₂ protection and final activation with ZnCl₂. The materials were characterized by transmission electron microscopy, X-ray powder diffraction and Raman spectra. The results indicated that the ACNTs distributed uniformly into the framework of the porous carbon. The composites showed the high BET specific surface area up to 1712 m² g⁻¹ and good conductivity. The electrochemical measurements indicated that the composites processed good performances for electrochemical energy storage (210 F g⁻¹ at 0.5 A g⁻¹), and high stability (>99.9%), much higher than the corresponding ACNTs, porous carbons and the samples prepared by using raw MWCNTs as source. The good performance of PC@ACNTs composites was relative with the synergy of good conductivity of ACNTs and large specific surface areas of PC.     

Pyroelectric properties of Mn-doped lead zirconate–lead titanate–lead magnesium niobate ceramics

The pyroelectric properties of MnO₂ doped compositions in the Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃–PbZrO₃ system have been investigated for an uncooled pyroelectric infrared detecting application, looking primarily at compositions in the PbZrO₃-rich corner of the phase diagram. A processing route from the metal oxides through to the poled ceramic has been developed, which has reduced the size and frequency of defects in the sintered ceramic necessary for producing thin (∼200 μm) ceramic wafers. The electrical properties relevant to the pyroelectric application (dielectric constant, tanδ and pyroelectric coefficient) have been surveyed with respect to composition to produce the best values of the pyroelectric ‘figure of merit’ F_D=p/{c′(εε_otanδ)^1/2} at room temperature. The effects of compositional changes in the ceramic on the two phase transitions from: the ferroelectric low temperature to ferroelectric high temperature phases (F_R(LT) to F_R(HT)) and the ferroelectric high temperature to paraelectric phases at the Curie point have also been investigated. The consequential changes of the electrical properties are reported. The resisitivity of the ceramic proved insensitive to either the amounts of excess lead or manganese doping levels.     

Pt nanoparticles modified by rare earth oxides: Electronic effect and influence to catalytic hydrogenation of 3-phenoxybenzaldehyde

The rare earth elements (La, Ce, Nd, Sm, Pr, and Gd) modified Pt/Al₂O₃ catalysts were prepared by the colloidal deposition and chemical reduction methods, respectively. Pt nanoparticles with average size 3 ± 0.5 nm were uniformly dispersed on the surface of Al₂O₃ for the samples prepared by the colloidal deposition method, which exhibited higher activities in the hydrogenation of 3-phenoxybenzadehyde than the corresponding samples prepared by chemical reduction method. Moreover, except Gd, the catalysts modified by rare earth elements showed better catalytic performance than unmodified Pt/Al₂O₃. For Pt–Ce/Al₂O₃ catalyst, when the weight percent of Pt and Ce was 0.5 and 0.25, respectively, the hydrogenation conversion of 3-phenoxybenzaldehyde was 97.3% after 6 h reaction. This activity improvement is due to the electronic interaction between Pt and rare earth elements, which was investigated by X-ray photoelectron spectroscopy.     

基于遗传算法的卫星磁模型研究

针对卫星磁特性研究与磁试验,建立了卫星多磁偶极子模型,分离了线性和非线性部分,利用遗传算法,以测点的模拟值和测量值之差的均方根作为目标函数,搜索多磁偶极子的位置,同时检测拟合误差,使得目标函数达到最优的同时,拟合误差也满足要求.最后对卫星静止状态和加电状态的磁性进行了计算,试验结果表明,用该方法建立卫星磁场模型精度高,磁矩和磁场的误差均小于5%,并且对测量误差不敏感,具有很强的鲁棒性.     

One-step solution synthesis of monodispersed ZnO nanowhiskers at low-temperature

In this paper, a one-step wet-chemical approach to synthesize monodispersed ZnO nanowhiskers is reported. Depending on the synthetic conditions used, the nanosized ZnO can be formed directly in aqueous solution at low-temperature. From the investigation of differential scanning calorimetry (DSC), thermogravimetry (TG) and X-ray diffraction (XRD), the resultant powders without high-temperature calcining were confirmed to be ZnO, and its crystal phase was hexagonal wurtzite structure, transmission electron microscope (TEM) observation revealed that ZnO nanowhiskers have diameters ranging from 30 to 50 nm and lengths up to 500 nm.     

Investigation of defects in N-doped ZnO powders prepared by a facile solvothermal method and their UV photocatalytic properties

A facile synthetic procedure for N-doped ZnO powders was proposed. In this work, N-doped ZnO crystals were synthesized in diethylene glycol (DEG) with ammonia solution via solvothermal process. Incorporated N concentration increases with the amount of ammonia solution. In order to confirm the defects of as-gained ZnO powders, the samples were characterized by XRD, PL, and EPR. In our results, the N-related defects were considered to be (N)_O centers as acceptors, other than (N₂)_O. And, the donors defects were confirmed to H_i. UV photocatalytic activity of the N-doped ZnO crystals was assessed from the photodegradation kinetics of methyl orange (MO). The result shows that the UV photocatalytic activity of N-doped ZnO decreases with the incorporated N concentration. This was caused by abundant acceptors hindered the photoinduced holes generating.     

激光薄膜和基底在不同空间环境中的损伤性能研究进展

随着激光在航天器中应用的增加,出现了激光系统在空间环境中失效的现象。激光薄膜和基底元件(包括晶体和玻璃)是激光产生和输出的重要组成部分,空间环境对它们损伤性能的影响直接关系到激光系统的稳定性、使用寿命和光束质量,因此它们的空间损伤效应成为急需研究和论证的问题。总结了国内外激光薄膜和基底在不同空间环境(包括真空度、温度、污染、空间辐照等)的性能变化、损伤机理和改进措施,为用于航天器的激光薄膜和基底元件的性能评估、预测和性能改进提供理论依据和分析方法。