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城市大气环境的大涡模拟研究进展 总被引:5,自引:0,他引:5
本文回顾城市大气污染扩散的研究实践与进展, 介绍城市大气环境流动的特点和用现代计算流体力学手段开展城市大气环境的大涡模拟研究方法, 包括: 数学模型, 控制方程、亚网格湍流模式、定解条件及其数值方法. 其中, 重点介绍中尺度到微尺度的耦合模型与适用于复杂城市下垫面(满足大涡模拟分辨率要求且计算量较小)的组合模型;并给出实际算例和结果分析, 包括准确度的统计估算和湍流特性等. 最后, 讨论城市大气环境数值模拟方法进一步改进的方向和城市大气环境流动与污染物扩散数值研究应重点关注的几个问题. 相似文献
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Lei Wang Yanpeng Qi Dongliang Wang Xianping Zhang Zhaoshun Gao Zhiyu Zhang Yanwei Ma Satoshi Awaji Gen Nishijima Kazuo Watanabe 《Physica C: Superconductivity and its Applications》2010,470(2):183-186
We report the achievement of transport critical currents in Sr0.6K0.4Fe2As2 wires and tapes with a Tc = 34 K. The wires and tapes were fabricated through an in situ powder-in-tube process. Silver was used as a chemical addition as well as a sheath material. All the wire and tape samples have shown the ability to transport superconducting current. Critical current density Jc was enhanced upon silver addition, and at 4.2 K, a largest Jc of ~1200 A/cm2 (Ic = 9 A) was achieved for 20% silver added tapes, which is the highest in iron-based wires and tapes so far. The Jc is almost field independent between 1 T and 10 T, exhibiting a strong vortex pinning. Such a high transport critical current density is attributed to the weak reaction between the silver sheath and the superconducting core, as well as an improved connectivity between grains. We also identify a weak-link behavior from the apparent drop of Jc at low fields and a hysteretic phenomenon. Finally, we found that compared to Fe, Ta and Nb tubes, Ag was the best sheath material for the fabrication of high-performance 122 type pnictide wires and tapes. 相似文献
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Xianping Zhang Lei Wang Yanpeng Qi Dongliang Wang Zhaoshun Gao Zhiyu Zhang Yanwei Ma 《Physica C: Superconductivity and its Applications》2010,470(2):104-108
Fe/Ti, Nb, and Ta sheathed SmO0.7F0.3FeAs wires were manufactured using the powder-in-tube method. A comparative study was made of the effect of sheath material on the microstructure and superconducting properties of the SmO0.7F0.3FeAs wires. Among these sheath materials, the penetration depth of Ta into the superconducting core is the largest. There was nearly no difference in the critical transition temperature of the SmO0.7F0.3FeAs wires sheathed with different materials, and the upper critical fields were approximately the same. On the other hand, it was found that Nb-sheathed wires had a higher superconducting current density than the others. Impurities existing in the superconducting core were thought to be one of the most important factors that affected the critical current density of the SmO0.7F0.3FeAs wires. 相似文献
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Zhaoshun Bi Conrad S. Chapman Pascal Salaün Constant M. G. van den Berg 《Electroanalysis》2010,22(24):2897-2907
A solid, bismuth (Bi), disk, electrode is used to determine lead (Pb) in natural waters including seawater. The diffusion layer thickness was lowered from 93 to 29 µm by stirring, and to 18 µm by using the vibrated version of the Bi electrode. The Bi electrode does not require removal of dissolved oxygen, which facilitates in situ detection. The electrode was tested for the determination of Pb in coastal seawater samples. The detection limit for Pb was 0.15 nM in acetate buffer and 0.5 nM in seawater using a 2 min deposition time. Cadmium can be determined together with Pb but the sensitivity is about 10×lower. The Bi electrode compares unfavourably to a mercury electrode in terms of sensitivity. 相似文献
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采用In-Situ PIT方法,以工业级低纯度B粉(92%)和镁粉(99%)为原料制备了19芯Fe/Cu复合包套MgB2超导线。断面扫描电镜观测表明,超导线内部超导芯分布排列均匀,Fe层都能完好包围MgB2芯体,Fe与Cu层结合紧密,填充因子0.17。750℃热处理1h后,样品超导转变温度Tc(onset)=33.5K,转变宽度ΔTc=4.8K。X光衍射检测发现,MgB2超导相中不存在其它Mg-B化合物杂项,但含有少量MgO和FeB2。多芯化后,超导芯中FeB2略有增加。四引线Ic测试发现,19芯样品在4.2K,4T时,临界电流密度为5622A/cm2,比单芯样品14400 A/cm2降低约2/3。 相似文献
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SERS and FDTD simulation of gold nanoparticles grafted on germanium wafer via galvanic displacement
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Zhaoshun Zhang Fan Liao Shuzhen Ma Suning Gao Mingwang Shao 《Surface and interface analysis : SIA》2015,47(3):398-402
Uniform and dense Au nanoparticles grown on Ge (Au/Ge) were fabricated by a facile galvanic displacement method and employed as surface‐enhanced Raman scattering (SERS) substrates. The substrates exhibited excellent reproducibility in the detection of rhodamine 6G aqueous solution with a relative standard deviation of <20%. The substrate showed a high Raman enhancement factor of 3.44 × 106. This superior SERS sensitivity was numerical confirmed by the three‐dimensional finite‐difference time‐domain method, which demonstrated a stronger electric field intensity (|E/E0|2) distribution around the Au nanoparticles grown on Ge. This facile and low‐cost prepared Au/Ge substrate with high SERS sensitivity and reproducibility might have potential applications in monitoring in situ reaction in aqueous solution. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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1,2,3,9-四氢咔唑-4-酮生产废液量大且危害严重,本文探究了NaClO、H2O2氧化处理废液的效果及存在的问题,同时提出了高温碳化处理的新工艺路线。 实验结果表明,采用NaClO、H2O2氧化处理废液未能达到理想要求,且回收的固体色泽差、无催化活性。 而废液经143 ℃蒸馏、残留液500 ℃高温碳化处理40 min后回收的氯化锌,具有良好催化活性,可使单苯腙转化率达到52.6%,实现了其在1,2,3,9-四氢咔唑-4-酮生产过程中的循环利用 。研究结果为1,2,3,9-四氢咔唑-4-酮生产废液处理及资源综合利用提供了一条新途径。 相似文献