《优质碳素结构钢热轧钢带》08版国家标准解读

简要介绍了2008版《优质碳素结构钢热轧钢带》国家标准的修订原则及主要变化,同时对相关原因及背景进行了说明。     

气调醇化过程中片烟细菌群落结构的变化

气调醇化是片烟醇化的一种方法。微生物尤其是细菌在片烟醇化过程中对烟叶的吸食品质起着至关重要的作用。为研究气调醇化过程中片烟细菌群落结构变化规律,利用Illumina MiSeq测序平台比较气调防霉杀虫阶段（S1）、气调醇化阶段（S2）及气调保质阶段（S3）共36份样品的细菌16S rDNA序列的多样性。结果表明,从S1到S3的过程中,片烟中细菌的物种丰富度和多样性水平呈增加趋势。S1阶段片烟的优势种群为鞘氨醇单胞菌属、假单胞菌属和甲基杆菌属,其占比在整个气调醇化过程中呈逐渐下降趋势;S2阶段的优势种群为芽孢杆菌属、鞘氨醇单胞菌属和伯克霍尔德菌属,其中芽孢杆菌属和伯克霍尔德菌属在整个气调醇化过程中占比呈先上升后下降的趋势;S3阶段细菌种群分布较为均匀。非度量多维尺度分析结果表明,3个醇化阶段的样品可以较明显地区分开来。可见,气调醇化过程中片烟的细菌种群组成非常丰富,不同醇化阶段活跃的微生物类群有所不同,鞘氨醇单胞菌属、假单胞菌属和甲基杆菌属主要在醇化前期参与了烟叶醇化过程,而芽孢杆菌属和伯克霍尔德菌属则主要在醇化后期发挥着微生物醇化的作用。     

Effects of transverse rumble strips on safety of pedestrian crosswalks on rural roads in China

The primary objective of this study is to evaluate the impacts of transverse rumble strips in reducing crashes and vehicle speeds at pedestrian crosswalks on rural roads in China. Using crash data reported at 366 sites, the research team conducted an observational before-after study using a comparison group and the Empirical Bayesian (EB) method to evaluate the effectiveness of transverse rumble strips in reducing crashes at pedestrian crosswalks. It was found that transverse rumble strips may reduce expected crash frequency at pedestrian crosswalks by 25%. The research team collected more than 15,000 speed observations at 12 sites. The speed data analysis results show that transverse rumble strips significantly reduce vehicle speeds in vicinity of pedestrian crosswalks on rural roads with posted speed limits of 60 km/h and 80 km/h. On average, the mean speed at pedestrian crosswalks declined 9.2 km/h on roads with a speed limit of 60 km/h; and 11.9 km/h on roads with a speed limit of 80 km/h. The 85th percentile speed declined 9.1 km/h on roads with a speed limit of 60 km/h; and 12.0 km/h on roads with a speed limit of 80 km/h. However, the speed reduction impacts were not found to be statistically significant for the pedestrian crosswalk on the road with a speed limit of 40 km/h. The study also looked extensively at the influence area of transverse rumble strips on rural roads. Speed profiles developed in this study show that the influence area of transverse rumble strips is generally less than 0.3 km.     

Diffraction of elastic waves by four rigid strips embedded in an infinite orthotropic medium

In the present paper, the elastodynamic response of four coplanar rigid strips embedded in an infinite orthotropic medium due to elastic waves incident normally on the strips is analyzed. The resulting mixed boundary-value problem is solved by an integral-equation method. The normal stress and the vertical displacement are derived in closed analytic form. Numerical values of stress-intensity factors at the edges of the strips and vertical displacements at point in the plane of the strips for several orthotropic materials are calculated and plotted graphically to show the effect of material orthotropy.     

Repair and strengthening of RC flat slab bridges using CFRPs

This paper reports on experimental investigations made of the performance of two separate CFRP based repair/strengthening schemes (a laminate strip scheme and a fabric system) adopted on two 40% scale model flat slab bridges. The models contained typical features of a large class of multi-span RC flat slab bridges with cantilever ends commonly found in the State of Victoria, Australia, that are now over 60 years old. The models had been previously tested to incipient collapse conditions under the critical design load case so were severely damaged prior to repair/strengthening. The performance was gauged using dynamic testing (experimental modal analysis) and static testing, again to incipient collapse. Both of the repair/strengthening systems were found to perform satisfactorily, suggesting that either could be used as a viable remedial strengthening strategy for this class of bridge structure.     

Hotspot propagation in superconductive strip detectors

Hotspots formed in superconductive strips due to interaction with particles are considered. The superconductive strip detector is considered in terms of a model of one-dimensional superconductor. D.C. electric current flowing through a film leads to Joule heating of the normal phase and causes either expansion or collapse of the hotspot. It is shown that the energy of a particle can be obtained by measuring the length of the expanding hotspot.     

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.     

采用阶梯形微带馈线的高隔离度超宽带MIMO天线

提出了一种小型二端口超宽带(UWB)多输入多输出(MIMO)天线。该天线由两个相同的矩形单极子和缺陷地结构(DGS)组成,通过改进阶梯形微带馈电线,在介质基板底层和顶层添加H 形枝节,并在辐射贴片上添加矩形条,提高了天线的带宽和隔离度。实验结果表明:该天线在1~20 GHz 工作频带内的隔离度大于21 dB,包络相关系数小于0.02。实测与仿真结果相符,表明该天线适用于UWB MIMO 系统,且该天线结构紧凑,尺寸仅为22 mm×29 mm×0.8 mm,可用于便携式通信设备。