桩基础影响下既有地铁隧道截面内力计算研究∗

城市已建地铁隧道的保护是目前市政建设中需要考虑的重要问题之一,针对非挤土桩和挤土桩两种桩型新建桩基础影响下既有地铁隧道的截面内力计算展开研究。采用"二阶段"法研究思想,首先基于桩基础荷载传递法、Mindlin位移解及柱孔扩张理论,分别计算得到非挤土桩和挤土桩在隧道截面位置处产生的土体位移。之后,将隧道衬砌简化为环形弹性地基梁模型,同时考虑土体抗力的影响,并将土体位移施加到环形地基梁模型,从而得到2种桩型引起的隧道衬砌截面的内力分布。研究过程中将理论结果与既有土工离心机试验进行了对比分析。研究结果表明:①计算方法得到的衬砌内力与既有文献土工离心式试验值差别不大且趋势一致,验证了计算方法的合理性;②挤土桩施工引起的隧道弯矩最大值增量远大于非挤土桩在极限荷载时的增量;③隧道截面弯矩最大值位置与桩端-隧道圆心相对位置有直接关系,大约位于桩端-隧道圆心连线相交处。     

基于FDS的加油站便利店火灾模拟

为了研究加油站便利店火灾的发展规律,选择合理的疏散路线,使用 FDS软件对某加油站便利店进行火灾数值模拟。通过观察烟气扩散和动态升温过程,分析便利店的烟气扩散和升温规律,对比分析不同疏散路线上温度、烟气层高度和能见度的数据变化规律,分析选择不同疏散路线对人员安全疏散的影响。结果表明:在无火灾报警设备的情况下,卫生间等有隔断的设施会延迟设施内人员获得火灾信息的时间,不利于安全疏散;同等高度下靠墙区域受高温烟气影响较中央开阔区域更大;疏散时选择合理的疏散路线可以显著延长安全疏散时间。     

常州市春节期间污染物相关性分析

分析了常州市2017年春节前后各污染物浓度的关联性和差异性。结果表明,除O_3外,春节期间各污染物均值均低于春节前后,春节前后随着污染源的变化,污染物之间的相关性表现出较为明显的差异。SO_2与PM_(2.5)、PM_(10)、CO和NO_2的相关性均较春节前后有显著下降;爆竹集中燃放时间段,CO与综合指数、PM_(2.5)和PM_(10)之间的相关系数0.96;而在烟花爆竹燃放相对较少的初三和初四,该相关系数0.6。工业减产停产和机动车使用减少对空气质量改善有较大贡献,而在不利气象条件下,烟花爆竹可导致空气质量在短时间内恶化。     

Simulating chemistry–aerosol–cloud–radiation–climate feedbacks over the continental U.S. using the online-coupled Weather Research Forecasting Model with chemistry (WRF/Chem)

The chemistry–aerosol–cloud–radiation–climate feedbacks are simulated using WRF/Chem over the continental U.S. in January and July 2001. Aerosols can reduce incoming solar radiation by up to ?9% in January and ?16% in July and 2-m temperatures by up to 0.16 °C in January and 0.37 °C in July over most of the continental U.S. The NO₂ photolysis rates decrease in July by up to ?8% over the central and eastern U.S. where aerosol concentrations are high but increase by up to 7% over the western U.S. in July and up to 13% over the entire domain in January. Planetary boundary layer (PBL) height reduces by up to ?23% in January and ?24% in July. Temperatures and wind speeds in July in big cities such as Atlanta and New York City reduce at/near surface but increase at higher altitudes. The changes in PBL height, temperatures, and wind speed indicate a more stable atmospheric stability of the PBL and further exacerbate air pollution over areas where air pollution is already severe. Aerosols can increase cloud optical depths in big cities in July, and can lead to 500–5000 cm^?3 cloud condensation nuclei (CCN) at a supersaturation of 1% over most land areas and 10–500 cm^?3 CCN over ocean in both months with higher values over most areas in July than in January, particularly in the eastern U.S. The total column cloud droplet number concentrations are up to 4.9 × 10⁶ cm^?2 in January and up to 11.8 × 10⁶ cm^?2 in July, with higher values over regions with high CCN concentrations and sufficient cloud coverage. Aerosols can reduce daily precipitation by up to 1.1 mm day^?1 in January and 19.4 mm day^?1 in July thus the wet removal rates over most of the land areas due to the formation of small CCNs, but they can increase precipitation over regions with the formation of large/giant CCN. These results indicate potential importance of the aerosol feedbacks and an urgent need for their accurate representations in current atmospheric models to reduce uncertainties associated with climate change predictions.     

限氮和限磷对活性污泥合成聚羟基烷酸的影响

聚羟基烷酸(PHA)是微生物在不平衡营养条件下贮存的一种胞内聚合物,限磷和限氮两种方式均有助于活性污泥中的混合菌群合成PHA,研究考察了两种不同方式下活性污泥合成PHA的情况。实验结果表明,当C∶N为125时,活性污泥中PHA的合成量达到细胞干重的59%;当C∶P为750时,活性污泥积累的最大PHA含量占细胞干重的37%,说明限氮和限磷两种方式对活性污泥合成PHA均有很大影响,且限氮方式更有效。     

水资源生态足迹分析——以安康市为例

根据生态足迹分析方法,建立了水资源生态足迹概念模型,确定了计算水资源帐户生态足迹所需的3个关键参数,即平均水资源产量、均衡因子和地区产量因子,计算了安康市1996—2007年水资源生态足迹和生态承载力。引入水资源生态足迹压力指数、万元GDP水资源生态足迹、累积水资源生态足迹等指标,利用水足迹模型评价水资源可持续发展程度的全面性和对比性。结果表明,计算结果可客观评价安康市水资源可持续发展与利用情况,为地区水资源的可持续利用与管理提供了科学的依据。     

Atmospheric deposition of phthalate esters in a subtropical city

In Chinese cities, air pollution has become a serious and aggravating environmental problem undermining the sustainability of urban ecosystems and the quality of urban life. Bulk atmospheric deposition samples were collected two-weekly, from February 2007 to January 2008, at three representative areas, one suburban and two urbanized, in the subtropical city, Guangzhou, China, to assess the deposition fluxes and seasonal variations of phthalate esters (PAEs). Sixteen PAE congeners in bulk deposition samples were measured and the depositional fluxes of ∑₁₆PAEs ranged from 3.41 to 190 μg m^?2 day^?1, and were highly affected by local anthropogenic activities. The significant relationship between PAEs and particulate depositional fluxes (correlation coefficient R² = 0.72, P < 0.001) showed PAEs are associated primarily with particles. Temporal flux variations of PAEs were influenced by seasonal changes in meteorological parameters, and the deposition fluxes of PAEs were obviously higher in wet season than in dry season. Diisobutyl phthalate (DiBP), Di-n-butyl phthalate (DnBP), and Di(2-ethylhexyl) phthalate (DEHP) dominated the PAE pattern in bulk depositions, which is consistent with a high consumption of the plasticizer market in China. PAE profiles in bulk deposition showed similarities exhibited in both time and space, and a weak increase of high molecular weight PAE (HMW PAE) contribution in the wet season compared to those in the dry season. Average atmospheric deposition fluxes of PAEs in the present study were significantly higher than those from other studies, reflecting strong anthropogenic inputs as a consequence of rapid industrial and urban development in the region.     

常熟市耕地资源时空演变特征

基于卫星遥感影像数据,GIS空间分析技术和统计分析方法相结合,利用耕地面积缩减强度指数、空间叠加等方法分析了常熟市耕地资源的时空演变特征,揭示了苏南经济发达地区耕地资源减少的规律。研究发现,随着经济发展,常熟耕地资源逐渐减少,且因城区和工业用地扩张引起的耕地非农转化指向十分强烈,居民点空间的指向呈逐渐减弱的态势。从空间演变规律看,常熟耕地非农化主要表现在：1）经济增长越快,发展水平越高,耕地减少越快;2）在城市、港口区的镇耕地减少更快;3）港区和工业区的建设,使其周边耕地非农化速度加快;4）道路交通的扩张是耕地非农转化的一个稳定因素;5）不同时期,耕地非农占用的空间指向不同：从20世纪80年代被居民点用地占用逐渐变迁为2000年以后的被工业用地、城镇用地、港口用地占用为主。城市发展、港区建设、交通建设、农村居民点建设、工业化推进和经济发展是耕地资源缩减的主导影响因子.     

资源型城市贵阳市的生态可持续发展研究

生态可持续发展是资源型城市可持续发展的基础。应用生态足迹的方法,对资源型城市贵阳市的生态可持续发展做了定量评估,并分析了影响贵阳市生态可持续发展的社会经济驱动力。贵阳市1999年-2007年间生态足迹从1.447 hm2/cap增长到2.472hm2/cap,而生态承载力从0.551 hm2/cap下降至0.509 hm2/cap,生态足迹远超出生态承载力,生态系统处于不可持续发展状况。但贵阳市生态效率在不断改善,从1999年的0.500万元GDP/hm2生态足迹增长到2007年的0.787万元GDP/hm2生态足迹,生态系统改善仍存在一定契机。人口增加、能耗增加等因素会导致贵阳市生态足迹增加,而增加农作物播种面积则可减少生态足迹。应用生态足迹的方法,有利于分析资源型城市可持续发展的相关问题,最后就如何缓解贵阳市生态系统压力,促进贵阳市生态可持续发展进行了探讨。     

大港油田苦咸再生水反渗透工艺自动控制研究

分析了大港油田污水回用深度处理工程苦咸再生水反渗透工艺仪表配置及自动控制方式,介绍了苦咸再生水反渗透系统亟待解决的各类问题。着重论述了仪表设置、余氯控制、结垢污堵控制、微生物污堵控制的实际运行方式,探讨了苦咸再生水反渗透工艺的技术可行性和可靠性。