Investigation on characteristics of pressure fluctuation in a centrifugal pump with clearance flow

Journal of Mechanical Science and Technology - Clearance flow has great impact on pressure fluctuation of centrifugal pumps. Numerical calculations are performed to study the pressure fluctuation...     

Illuminating Diverse Concomitant DNA Logic Gates and Concatenated Circuits with Hairpin DNA-Templated Silver Nanoclusters as Universal Dual-Output Generators

Exquisite administration of a new type of hairpin DNA-templated silver nanoclusters (H-AgNCs) as universal dual-output generators in DNA-based logic systems is reported. Diverse concomitant contrary logic gates (CCLGs) with opposite functions (YES^{^}NOT, OR^{^}NOR, INHIBIT^{^}IMPLICATION, XOR^{^}XNOR, and MAJORITY^{^}MINORITY) and extended concatenated logic circuits are presented and some of them perform specific functions, such as parity generators and checkers. The introduction of H-AgNCs as noncovalent signal reporters avoids tedious and high-cost labeling procedures. Of note, the concomitant feature of CCLGs attributed to the dual-emitter AgNCs conduces to reducing the time and cost to devise multiple logic gates. As compared to previous ones, this design eliminates numerous substances (e.g., organic dyes) and unstable components (hydrogen peroxide), which not only decreases the complexity of logic performs and improves repeatability of operation, but also makes it convenient to connect distinct DNA-based logic gates. It is worthy to anticipate that the cost-effective strategy will inspire researchers to develop much more complex logic systems and contribute to the field of molecular computing.     

基于加权K近邻算法的缺失数据填补研究

针对数据缺失问题,本文在完全随机缺失的前提下,对完整数据集进行不同比例的挖空处理,并使用K近邻算法进行缺失值填补;采用交叉验证法优化K值;最后借用高斯函数,对传统K近邻算法进行加权处理,提出加权K近邻算法.实验结果表明,不论K取值多大,加权K近邻算法填补效果均优于传统K近邻算法;且K=2时,两种算法填补效果达到最佳.     

BMR反应器与絮凝技术在雨水泵站排水应急设施工程中的应用

南方某雨水泵站排水应急设施工程设计规模为15000 t/d,工程设计采用"BMR反应器+高密度沉淀器"主体工艺,结合其水质特点对其工程设计及运行效果进行探讨分析,结果表明:出水CODCr、BOD5、NH3-N、TP等指标均可达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)中一级A标准和《汾江河流域水污染物排放标准》(DB 44/1366—2014)中城镇污水处理厂排放标准.同时,该工艺辅助投加NFSSS高效纳米复合絮凝剂,对脱氮除磷具有辅助促进作用,使污泥浓度显著提高,污泥膨胀现象减少,系统稳定运行.     

中外荷载规范雪荷载取值及控制影响因素对比分析

基于对当今中外荷载规范雪荷载章节的梳理，以雪荷载对应取值及控制因素的差异为视角进行了深入的对比剖析，得出各国规范体系构架存在较高相似性，均采用由地面雪荷载（基本雪压）乘上一系列用以量化计算的控制因素系数而获得屋面雪荷载值，而屋面雪荷载按作用效应又可划分为基本雪荷载、漂移雪荷载与滑落雪荷载三类，且各类别在不同规范中取值具有差别。由此建议在中国新版建筑荷载规范雪荷载章节继承完善基本雪荷载和漂移雪荷载，并补充对屋面滑落雪荷载取值规定。另外，总结了各国规范中雪荷载控制影响因素，可归为外界环境与建筑本身两大类，并依据国外规范对控制因素的考虑权重，选取影响较大且我国规范尚未考虑的因素进行详细探讨。由此建议引入考虑降雨量与坡屋顶特性的雨雪联合因素，考虑宏观地貌气候与周围环境的建筑暴露状态因素，考虑室内采暖温度与屋面热阻的建筑采暖因素及考虑屋面光滑程度的屋面材料因素，以达到优化规范体系构架的目的。     

影像空间分辨率对蚀变信息提取结果的影响研究

脉状蚀变分布广泛且蚀变规模一般较小，遥感影像空间分辨率对此类蚀变提取影响严重。为了评估不同空间分辨率数据对脉状矿化蚀变信息的提取能力，以甘肃北山金滩子地区为例，应用航空高光谱CASI/SASI数据，将像元重采样至5、10、15、20和30 m共5种空间分辨率模式；以JPL光谱库中白云母矿物光谱曲线为参考，利用光谱匹配滤波法提取区内白云母化蚀变。不同规模蚀变带在5种分辨率模式下像元光谱表明：面状蚀变由于面积较大，空间分辨率变化对像元光谱吸收特征影响较小；脉状蚀变带特别是较窄脉状蚀变带随着空间分辨率的降低，混合像元影响越来越强，像元光谱的吸收特征越来越浅，30 m空间分辨率时吸收特征最弱。5种空间分辨率影像的白云母矿物提取结果表明较窄蚀变带(宽约1~5 m)在5~15 m空间分辨率图像中均线状特征明显，在20 m分辨率数据结果中仅断续出现，在30 m空间分辨率结果中仅个别像元被突出。     

Field experiment on coalmine heat disaster governance using cold source from surface water

Regarding the lack of cold source for underground cooling systems from either mine inflow or return air, field experiments were taken in a high temperature deep coal mine with abundant cold source from...     

Au/AgI Dimeric Nanoparticles for Highly Selective and Sensitive Colorimetric Detection of Hydrogen Sulfide

The development of Au/AgI dimeric nanoparticles (NPs) is reported for highly selective colorimetric detection of hydrogen sulfide (H₂S). The detection mechanism is designed by taking advantage of the chemical transformation of AgI to Ag₂S upon reacting with sulfide, which leads to a shift in the plasmonic band of the attached Au NPs. The plasmonic shift is accompanied by a color change of the solution from purplish red to blue and finally to light green depending on the concentration of sulfide, thus enables a naked‐eye readout and UV–vis quantitation of the sulfide exposure. The Au/AgI dimeric NPs are further immobilized in agarose gels to produce test strips, which can be used for both naked‐eye readout and quantitative detection of sulfide using UV–vis spectroscopy thanks to its transparency in the visible region. Compared to commercial Pb(Ac)₂ test papers, the agarose gel strip has superior performance for detecting sulfide in terms of sensitivity, selectivity, stability, and fidelity. The agarose gel is also capable of detecting gaseous H₂S at important concentration thresholds, suggesting its practicability in real life applications. The potential of agarose gels is further highlighted by its ability in the enrichment and colorimetric detection of gaseous H₂S released during cell cultivation.