纳滤法制备高纯度雪莲果低聚果糖及其结构表征

采用纳滤分离技术以雪莲果为原料纯化低聚果糖，通过Box-Behnken中心组合设计（CCD）及响应面分析（RSM）建立预测低聚果糖纯度的二次多项数学模型，优化分离纯化工艺。结果表明：操作压力0.15 MPa，循环流量5.3 mL/min，pH值2.7时，纯化倍数为5，实际低聚果糖纯度为95.1%，达到P级产品标准。通过应用HPLC-MS、IR、¹H NMR及¹³C NMR等对雪莲果低聚果糖组分的纯度、组成、结构进行表征，结果表明：分离纯化得到的雪莲果低聚果糖由蔗果三糖、蔗果四糖和蔗果五糖组成，纯度为95.1%，平均包含5个果糖单元，主要是由β-呋喃构型的果糖组成。     

Fabrication of magnetically recoverable Fe3O4/CdS/g-C3N4 photocatalysts for effective degradation of ciprofloxacin under visible light

Photocatalytic technology is an environmentally safe method of eliminating organic pollutants and antibiotics in wastewater. In this research, the performance of Fe₃O₄/CdS/g-C₃N₄ (FCN) photocatalyst for degradation of antibiotics was studied. The composite photocatalysts with different concentrations of g-C₃N₄ were prepared. FCN has better photocatalytic activity than degradation dyes in removal of antibiotics under visible light. This indicates that FCN could effectively hinder the recombination of carriers, and the addition of g-C₃N₄ increases the optical response range of CdS. At the same time, the introduction of Fe₃O₄ magnetic nanoparticles overcomes the problem of difficulty in recovery of the powder photocatalyst. The photocatalytic activity is not reduced to any significant after three cycles of use.     

Influence of Different Additives on the Interaction of Quinolone Antibiotic Drug with Surfactant: Conductivity and Cloud Point Measurement Study

Conductometric and cloud point (CP) measurement studies have been performed to investigate the interaction of tetradecyltrimethylammonium bromide (TTAB) and Triton® X-100 (TX-100) with ciprofloxacin hydrochloride (CFH) in different solvents over the temperature range of 295.15–315.15 K. CFH is used for the treatment of various bacterial infections. The observed critical micelle concentration (CMC) values of TTAB were found to be reduced in the presence of electrolytes (Na₂SO₄/Na₃PO₄), and this reduction proceeds with the elevation of salt concentration. The order of the CMC of TTAB follows the trend: > >. The observed CMC values of TTAB were found to increase with increasing temperature and decrease with increasing concentration of CFH in aqueous medium. The values of Gibbs free energy of micellization () for the TTAB/TTAB + CFH mixture were found to be negative, implying spontaneous micellization. The estimated CP of TX-100 decreases with increasing concentration of TX-100 in aqueous medium. The CP values first decrease with increasing concentration of CFH and then increase at higher concentration of CFH almost in all cases investigated. The values of free energy of clouding were found to be positive in all cases studied implying that phase separation of TX-100 was nonspontaneous. The other thermodynamic parameters associated with the micellization of TTAB and the phase separation of TX-100 were estimated and explained.     

Size-dependent separation of graphene oxide by deformation of packed-gel in a chromatographic column

ABSTRACT

A deformable gel-packed chromatographic column was used to separate as-synthesized graphite oxide with different sizes. The synthesized gel (56 µm) was deformed by pressure of the fluid flow and the gaps in the gels showed a range of sizes. A suspension of graphene oxide (0.1 g/L, 10 mL) was injected, and graphene oxide in the elution had a size at 0.56 μm and 0.14 μm, whereas in half upper and bottom domain of the gel layer graphene oxide had a size at 33 µm and 2.9 µm, respectively, demonstrating that graphene oxide suspension was separated by size through gel layer.     

煤田地震勘探中多井组合爆炸法浅析

地震勘探中炸药作为激发震源的激发条件多样,采用有效的震源激发方式,才能取得高信噪比的地震原始数据。本文依据有关爆破原理,理论结合实践经验,提出在厚黄土区采用多井组合的激发方式,能有效压制噪声,增强性噪比,提高数据质量。     

Extensive evaluation and classification of low-cost dust sensors in laboratory using a newly developed test method

An extensive evaluation of low-cost dust sensors was performed using an exponentially decaying particle concentration. A total of 264 sensors including 27 sensors with light-emitting diodes (LEDs) and 237 sensors with laser lighting sources were tested. Those tested sensors were classified into 4 groups based on the deviation from the reference data obtained by a reference instrument. The response linearities of all the tested samples for PM₁, PM_2.5, and PM₁₀ were in excellent agreement with the reference instrument, except a few samples. For the measurements of PM₁ and PM_2.5, the lighting source, that is, LED or laser, did not show any significant difference in overall sensor performance. However, LED-based sensors did not perform well for PM₁₀ measurements. The 32, 24, and 16% of all the tested sensors for PM₁, PM_2.5, and PM₁₀ measurement, respectively, are in the category of Class 1 (reference instrument reading ± 20%) requirement. The performance of the low-cost dust sensors for PM₁₀ measurement was relatively less satisfactory.     

入口弯管对矿用轴流通风机气动性能影响的数值研究

以某大型矿用低压轴流式通风机为研究对象, 采用气体动力学性能试验和数值模拟的方法研究了不同入口弯管对风机性能的影响, 重点分析了入口弯管引起的叶轮内部流动特征和损失分布的变化规律。研究结果表明, 风机入口采用弯管连接缩短了进口管道的轴向长度, 节省了地下空间, 但同时来流的均匀性受到影响。弯管内气流速度梯度较大, 管道内侧易发生流动分离, 产生回流区, 增大了流体流动时的能量损失, 风机的整体性能下降。弯管与叶轮入口之间的连接长度会影响内部流场, 当附加直管段较长时, 来流均匀性得到提高, 风机性能有所改善。     

用于水质净化的氧化石墨烯膜研究进展

氧化石墨烯膜具有超高的水通量、可控的层间距以及卓越的分离性能，这些优异的特性使氧化石墨烯膜有望成为新一代膜材料并用于水环境中物质的精确分离。对氧化石墨烯膜的研究已经取得了许多重要的成果，本文系统地阐述了用于水质净化的氧化石墨烯膜的结构特性和构效关系，总结了氧化石墨烯膜典型的制备方法，重点介绍了氧化石墨烯膜的改性方式，概述了氧化石墨烯膜在多种水环境中的应用，总结并展望了氧化石墨烯膜的发展方向，为设计和合成高性能氧化石墨烯膜用于水质净化提供新的思路。     

方腔内耦合传热传质非对称流动数值模拟

对带有质热源的方腔内流体传热传质进行数值研究。针对不同Ra、Nc、Sr和Df，探究对称方腔内流体传热传质的分岔特性。结果表明：存在临界Ra_c使流体流动形态发生转变，当Ra<Ra_c时，流体流线、温度场和浓度场对称分布；当Ra>Ra_c时，流体发生偏斜。增大浮升力，流体更易发生分岔现象。增强Soret和Dufour效应可增强传热对称性并增大流体发生分岔的临界Rayleigh数。