期刊文献+
共找到4篇文章
< 1 >
每页显示 20 50 100
基于混凝土表面SO_(4)^(2-)浓度时变的扩散模型预测研究
1
作者 任青阳 任小坤 靳红华 《混凝土》 CAS 北大核心 2024年第1期78-83,共6页
为探究混凝土在硫酸盐侵蚀下的腐蚀破坏情况,通过考虑混凝土表面SO_(4)^(2-)浓度时变规律,改进现有的扩散-反应方程组,结合水泥水化、腐蚀产物填充和损伤度函数建立了硫酸盐侵蚀下混凝土扩散模型。采用Comsol Multiphysics软件模拟在不... 为探究混凝土在硫酸盐侵蚀下的腐蚀破坏情况,通过考虑混凝土表面SO_(4)^(2-)浓度时变规律,改进现有的扩散-反应方程组,结合水泥水化、腐蚀产物填充和损伤度函数建立了硫酸盐侵蚀下混凝土扩散模型。采用Comsol Multiphysics软件模拟在不同硫酸盐浓度侵蚀下,不同侵蚀龄期内混凝土各截面SO_(4)^(2-)浓度,并将模型计算值与实测值进行对比。结果表明:在硫酸盐浓度为5%和10%的侵蚀条件下,考虑混凝土表面SO_(4)^(2-)浓度时变过程的模型计算值和实测值的最大误差分别为17.46%及19.69%,验证了模型的合理性与适用性。最后通过建立的SO_(4)^(2-)侵蚀混凝土最大深度预测模型,发现硫酸盐侵蚀混凝土的最大侵蚀深度在侵蚀前期快速增加,随着侵蚀龄期的延长而逐渐变缓,以期为混凝土的耐久性评估提供参考。 展开更多
关键词 混凝土 硫酸盐侵蚀 表面离子浓度时变 深度预测
下载PDF
城市地区危险气体扩散与人口暴露模拟
2
作者 郑茂辉 金敏 韩新 《深圳大学学报(理工版)》 EI CAS 北大核心 2013年第3期287-293,共7页
以伦敦中心城区示踪气体扩散试验为例,对城市建筑群中危险气体的迁移扩散以及周边人口暴露风险进行数值模拟分析.通过计算流体力学模型和暴露模型的耦合,模拟街区尺度近地面气云扩散过程,结合地理信息系统和建筑物数据库估算受影响的人... 以伦敦中心城区示踪气体扩散试验为例,对城市建筑群中危险气体的迁移扩散以及周边人口暴露风险进行数值模拟分析.通过计算流体力学模型和暴露模型的耦合,模拟街区尺度近地面气云扩散过程,结合地理信息系统和建筑物数据库估算受影响的人口及其潜在的暴露水平,求解建筑物周围的时变质量浓度和暴露剂量分布.近地面的质量浓度时间序列表明,气云扩散受建筑物和道路布局影响显著;泄漏停止后部分建筑物背风向和狭窄街段内质量浓度稀释滞后,可能对人群健康构成潜在威胁. 展开更多
关键词 大气污染 城市环境安全 危险气体 人口暴露 数值模拟 时变浓度 流体力学 地理信息系统 建筑物
下载PDF
Predication of plasma concentration of remifentanil based on Elman neural network 被引量:1
3
作者 汤井田 曹扬 +1 位作者 肖嘉莹 郭曲练 《Journal of Central South University》 SCIE EI CAS 2013年第11期3187-3192,共6页
Due to the nature of ultra-short-acting opioid remifentanil of high time-varying,complex compartment model and low-accuracy of plasma concentration prediction,the traditional estimation method of population pharmacoki... Due to the nature of ultra-short-acting opioid remifentanil of high time-varying,complex compartment model and low-accuracy of plasma concentration prediction,the traditional estimation method of population pharmacokinetics parameters,nonlinear mixed effects model(NONMEM),has the abuses of tedious work and plenty of man-made jamming factors.The Elman feedback neural network was built.The relationships between the patients’plasma concentration of remifentanil and time,patient’age,gender,lean body mass,height,body surface area,sampling time,total dose,and injection rate through network training were obtained to predict the plasma concentration of remifentanil,and after that,it was compared with the results of NONMEM algorithm.In conclusion,the average error of Elman network is 6.34%,while that of NONMEM is 18.99%.The absolute average error of Elman network is 27.07%,while that of NONMEM is 38.09%.The experimental results indicate that Elman neural network could predict the plasma concentration of remifentanil rapidly and stably,with high accuracy and low error.For the characteristics of simple principle and fast computing speed,this method is suitable to data analysis of short-acting anesthesia drug population pharmacokinetic and pharmacodynamics. 展开更多
关键词 Elman neural network REMIFENTANIL plasma concentration predication model
下载PDF
Atmospheric Methane over the Past 2000 Years from a Sub-tropical Ice Core, Central Himalayas
4
作者 LI Jiule XU Baiqing +2 位作者 YAO Tandong WANG Ninglian Ken MacClune 《Journal of Mountain Science》 SCIE CSCD 2010年第1期1-14,共14页
A high-resolution 2ooo-year methane record has been constructed from an ice core recovered at 7200 m a.s.1, on the Dasuopu Glacier in the central Himalayas. This sub-tropical methane record reveals an increasing trend... A high-resolution 2ooo-year methane record has been constructed from an ice core recovered at 7200 m a.s.1, on the Dasuopu Glacier in the central Himalayas. This sub-tropical methane record reveals an increasing trend in the concentration of methane during the industrial era that is similar to observations from polar regions. However, we also observed the differences in the atmospheric methane mixing ratio between this monsoon record and those from polar regions during pre-industrial times. In the time interval o N 1850 A.D., the average methane concentration in the Dasuopu ice core was 782±40 ppbv and the maximum temporal variation exceeded 200 ppbv. The difference gradient of methane concentration in Dasuopu ice core with Greenland and Antarctica cores are 66±40 ppbv and 107±40 ppbv, respectively. This suggests that the tropical latitudes might have acted as a major global methane source in preindustrial times. In addition, the temporal fluctuation of the pre-industrial methane records suggests that monsoon evolution incorporated with high methane emission from south Asia might be responsible for the relatively high methane concentration observed in the Dasuopu ice core around A.D. 800 and A.D. 1600. These results provide a rough understanding of the contribution of tropical methane source to the global methane budget and also the relationship betweenatmospheric methane and climate change. 展开更多
关键词 climate change ice core air bubble atmospheric methane Dasuopu Glacier centralHimalayas
下载PDF
上一页 1 下一页 到第
使用帮助 返回顶部