Determination of Aldehydes in Environmental Water by Solid-Phase Microextraction and Gas Chromatography - Ion Trap Mass Spectrometry

Microwave-assisted extraction coupled to headspace solid-phase microextraction with on-fiber derivatization with gas chromatography ion trap mass spectrometry analysis is reported for the determination of aldehydes in environmental water. Hexanal, (E)-2-hexenal, heptanal, octanal, nonanal, E-2-decanal, and E, E-2,4-decadienal were employed to develop and validate this method. The effects of relevant parameters on the quantitative extraction of these analytes in this one-step procedure were systematically investigated. The aldehydes were extracted from environmental water by a poly(dimethylsiloxane)/divinylbenzene fiber using o-(2, 3, 4, 5, 6-pentafluoro)-benzylhydroxylamine as the derivatization reagent. Under microwave-assisted heating, the aldehydes were transferred from water by headspace solid phase microextraction. Thus, efficient extraction and derivatization were simultaneously achieved. The recovery values ranged from 72.2–96.9%, and the relative standard deviation was between 4.1–14% for the aldehydes. The detection limits were from 0.001–0.005 µg L^?1. The method was validated illustrating its potential for the analysis of environmental water while offering simplicity and rapid analysis.     

ZnO/C复合材料的制备与性能

为了制备ZnO/C复合材料并探讨其吸波性能,利用金属有机骨架MOF-5为前驱物,采用溶剂热法制备了ZnO/C复合材料.利用X射线衍射仪、扫描电子显微镜、傅里叶转换红外光谱分析仪与矢量网络分析仪对ZnO/C复合材料的物相组成、微观结构、形貌及性能进行了分析.结果表明,ZnO/C复合材料是由薄片状组织堆叠形成的完整立方体结构,且ZnO与C分布均匀.当复合材料涂层厚度为7 mm时,在17.18 GHz处的反射损耗可以达到最大幅值.ZnO/C复合材料在远红外区和超远红外区均具有良好的吸波性能.     

Pleurotusostreatus and Agaricus subrufescens: investigation of chemical composition and antioxidant properties of these mushrooms cultivated with different handmade and commercial supplements

In this study, the chemical composition, total phenolic content and antioxidant activity (DPPH, ORAC and FRAP assays) of A. subrufescens and P. ostreatus, cultivated with handmade and commercials supplements, were compared. Additionally, the compounds ergosterol, saccharopine, and hexitol were identified in A. subrufescens by HPLC-MS/MS. The antioxidant compound p-coumaric acid and dihexoses was found in both mushroom species. A. subrufescens presented higher total phenolic content (73.8 ± 0.6 mg GAE 100 g⁻¹) and antioxidant activity than P. ostreatus (16.6 ± 0.5 mg GAE 100 g⁻¹). The handmade supplement based on the waste of noble grains presented statistically similar phenolic content to the mushrooms cultivated with commercial ones Spawn Mate II SE (86.1 ± 1.4 and 92.9 ± 0.3 mg GAE 100 g⁻¹, respectively). Therefore, the results support the use of handmade supplements based on agro-wastes as a viable alternative to the use of high-cost commercial ones.     

Thermodynamics of Hydrogen Production Based on Coal Gasification Integrated with a Dual Chemical Looping Process

The performance of an innovative hydrogen production technology, which is based on a coal gasification system integrated with a dual chemical looping process, namely, chemical looping air separation (CLAS) and calcium looping CO₂ absorption (CaL), is evaluated. CLAS offers an advantage over other mature technologies in that it can reduce capital costs considerably. CaL is an efficient method for hydrogen production and CO₂ capturing. The proposed technologies are studied by Aspen Plus based on the Gibbs free energy minimization principle. The key factors in terms of reduction temperature, gasification pressure, temperature of water‐gas shift reaction, and water consumption, which proved to have a significant impact on the performance of the whole hydrogen generation process, are discussed.     

Stochastic analysis of progressive failure of fractured rock masses containing non-persistent joint sets using key block analysis

A stochastic key block method is developed for the analysis of complex blocky rock masses containing non-persistent joint sets. A robust block generation program is developed to model the non-persistent discontinuities. Various uncertainties of geological and geometrical parameters of the discontinuities are considered and Monte Carlo simulations of key blocks are performed. Based on the present analysis, progressive failure of a rock mass can be evaluated in a stochastic manner and the statistics of the key blocks including the total number and volume, the maximum and mean volume, shape and failure mechanism, etc. can be assessed. This approach is applied to a hypothetical horseshoe shaped tunnel in a highly fractured rock mass. Three scenarios with varying mean discontinuity size are analyzed to consider size effect on the predicted blocks and key blocks. It is shown quantitatively that a persistent discontinuity network assumption causes over-fragmentation of predicted blocks, overestimation of key blocks, and underestimation of the largest key block volume compared with non-persistent ones. More realistic representation of the discontinuities by considering the non-persistence is important to give out more reliable failure estimation of fractured rock mass. In addition, a case study application to a slope at the right bank of the Jinping I hydropower station has been conducted. Key block statistics is also helpful in support design.     

Characteristics of CO2 Absorption into Aqueous Ammonia

Abstract

Aqueous ammonia was investigated as a new absorbent of the chemical absorption process for CO₂ capture from combustion flue gas. The effects of the temperature and concentration of aqueous ammonia on CO₂ absorption in a semi‐batch reactor were studied by interpreting breakthrough curves. Raman spectroscopy analysis of CO₂ loaded aqueous ammonia provided concentration changes of bicarbonate, carbonate, and carbamate as well as CO₂ sorption capacity at given time during the absorption with 13 wt% aqueous ammonia at 25°C. It was observed that carbamate formation was dominating at the early stage of absorption. Then, the bicarbonate formation took over the domination at the later stage while the carbonate remained unchanged.     

Optimum design of mounting components of a mass property measurement system

Measurement of inertia properties of aerospace vehicle and submarine are vital to meet the intended motion objectives. The Moment of Inertia (MOI) is calculated by measuring the frequency of free torsional oscillation of the object mounted on a nearly friction less air bearing. For getting accurate measurement and to nullify the effect of undesired vibrations, the stiffness of the different components of the mounting and fixture (torsion rod, flexure) should be maintained appropriately. The optimum design of torsion rod and flexure is based on ensuring desired natural frequencies in different modes. Initiating with an analytical approach, the actual dimensions of the components are determined based on natural frequencies obtained by finite element analysis of the components. Simulated results are verified with experimental results.     

Development of a mechanical rock breakage experimental platform

With social and economic development and improvement of science and technology, tunnel boring machines, raise boring machines, reaming machines and road headers have been unprecedentedly applied to underground engineering construction. Mechanical rock breakage experiments became an indispensable mean for mechanical excavation of underground engineering. It can also guide the design and operation of excavation machines. This paper introduces the new mechanical rock breakage experimental platform developed by Beijing University of Technology. The design and manufacture of this platform considered the influence of high in situ stress, cutter head rotation and rock breakage by multi-cutters at the same time on the rock breakage process. Different tools, such as rolling cutters, scraper, ripper, and pick, for different excavation machines can be tested in the platform. It can also take into account the different rock mass structure in the sample box. Different construction conditions with different cutting tools can be realistically modeled. The experimental platform consists of a mechanical system, a hydraulic system, an automatic control system and a data acquisition system. After installation of the designed experimental platform, several tests with different construction conditions were conducted. The experimental results showed that the platform reached its design requirements.     

基于铜粉的室温气固反应自生长刺球状半导体Cu_2S纳米线阵列

本研究通过简单的气-固硫化反应对ITO玻璃上涂覆的铜颗粒膜进行硫化反应,得到了大面积的自生长刺球状结构的半导体Cu2S纳米阵列。采用SEM,TEM,EDS、XRD,以及UV-vis等方法对反应生长的半导体Cu2S纳米线阵列的微观结构及光吸收性能进行了系统研究。实验结果表明,合成的Cu2S为刺球状纳米线阵列,纳米刺球的直径分布在50~100μm之间;刺球上的纳米线为单斜晶系的Cu2S单晶,晶体生长方向为[-102];纳米线的平均直径为100nm,长度分布在20~50μm之间。合成的刺球状纳米线阵列具有良好的光吸收性能,反应20小时样品在可见光波长范围内(400~800nm)平均光吸收率达到了93%;反应30小时样品在可见光波长范围内(400~800nm)平均光吸收率达到了92%。同时两种刺球状纳米线阵列结构对于大的光线入射角仍然保持很高的光吸收性能,对光线入射角的变化不敏感。当入射光角度从0°增加到60°时,光吸收率仅下降3%,明显优于文献已报道的规则排列纳米线阵列的光吸收性能。本项研究合成方法简单,工艺可控,成本低,可以采用更广的基体材料。合成的纳米结构具有优良的综合光吸收性能,在光电领域有很好的应用潜力。