RBF神经网络可靠度分析方法在边坡稳定性研究中的应用

针对边坡稳定性可靠度分析,当状态函数无法显式表达且传统计算方法求解复杂问题困难时,提出一种基于ABAQUS和粒子群优化径向基函数神经网络的可靠度分析方法。基于ABAQUS的强度折减方法计算所选随机变量对应的安全系数,利用径向基函数神经网络的数据拟合功能,建立模型并映射出安全系数和随机变量之间的关系,构造响应面功能函数;利用蒙特卡罗生成的大量随机样本代入功能函数得到相应的安全系数,进而计算边坡的失稳概率和可靠度指标来反映边坡稳定性。研究结果表明:相对于传统方法,本文方法计算效率更高、误差更小,适合实际工程应用。     

爆破荷载作用下隧道中隔岩稳定性研究

为研究爆破动力荷载作用下隧道中隔岩稳定性评价标准,以福州地铁2号线为工程背景,结合强度折减动力分析法和数值模拟,同时考虑中隔岩塑性区贯通、位移超过规范值、计算不收敛3种判据,综合对隧道中隔岩进行动力安全系数分析,研究隧道不同净距、不同开挖进尺后行洞隧道爆破开挖对隧道整体安全系数的影响。研究结果表明:中隔岩塑性区贯通时特征点位移和规范中位移限值较为接近,可共同作为评价中隔岩稳定性的最终评价标准;隧道净距越大、进尺越小,隧道整体安全系数越高;对围岩质量较差且净距小于1.6 m的双线隧道进行爆破开挖时,建议将爆破进尺控制在2 m以内。研究结果可为类似工程提供理论参考依据。     

Fe2+EDTA溶液络合-铁还原脱除烟气中NO

提出了“Fe2 螯合剂络合-铁粉还原-酸吸收”回收法脱除烟气中NO的新工艺,重点研究了模拟烟气中O2体积分数对NO络合量的影响,以及铁粉用量、铁粉粒径、搅拌速度对NO脱除效率的影响,确定了最佳的铁粉脱氮工艺条件,并对铁粉和铁屑的脱氮效果进行了比较。结果表明,烟气中O2的体积分数从0%增加到4.2%,NO络合量下降90.2%;NO脱除效率随铁粉用量和反应器搅拌速度的增加而增加,随铁粉粒径的增加而降低;过程的最佳工艺参数为,铁粉用量0.8g,铁粉粒径≤0.077mm,搅拌速度900r·min-1,在此条件下,对O2体积分数为5%的模拟烟气在搅拌反应器中可取得90%以上的NO脱除效率;用铁粉在1台搅拌反应器中取得的NO脱除效率和用铁屑在2个鼓泡反应器串联时所取得的效率相当。     

控制稻田甲烷排放的农业技术选择

本文探讨了通过农业技术措施，控制稻田甲烷排放以及减少甲烷排放的潜力。试验结果表明：（１）用沼渣代替农家肥堆肥作基肥时，４种沼渣基肥处理中，有３种处理稻田甲烷排放通量比施农家肥的处理减少２４～６２％，比单纯施化肥处理减少１１～５６％；１种沼渣（马粪）由于腐熟度不够，其处理甲烷减排效果不明显；（２）改换氮肥的施用种类。以硝铵、硫铵代替尿素作追肥，甲烷排放通量分别减少２６％和４６％；（３）稻田的科学灌溉技术，从水用分蘖到抽穗期间，间歇落干，可以明显减少甲烷排放，而对产量无影响；（４）水稻半旱式栽培技术，也可明显抑制稻田甲烷排放。     

V2O5/AC催化剂对氨还原NO的研究

考察了V2O5/AC催化剂对NH3选择催化还原NO的影响，结果表明，以浓硝酸预氧化处理的活性焦为载体对催化剂活性有很大提高，这是由于浓硝酸预氧化后，活性焦表面产生了较多的含氧官能团可能吸附更多的NH3,并且提高了活性组分V2O5的含量，反应气氛中加入SO2后，二都活性都增加，但差异消失，这是由于SO2存在时，反应生成的SO4^2-离子的酸性强于浓硝酸预氧化产生的含氧官能团的酸性，催化剂在使用前经过煅烧和氧化对催化剂活性有很大改善。SO2存在时，V2O5含量为1wt%的催化剂活性提高。     

高速公路绿化带对交通噪声的衰减效果研究

公路绿化带可对交通噪声产生一定衰减作用,这对于减轻路域环境噪声污染具有重要意义。然而,针对高速公路绿化带种植树种、种植密度、林带宽度等多种因素对降噪效果影响的研究尚属空白。该研究采用选取试验点进行原位调查的方法,研究了山东省3条主要高速公路路侧绿化带对交通噪声的衰减效果,并探讨了林带宽度和郁闭度对噪声衰减的影响。研究结果表明,高速公路绿化带对交通噪声有一定的减轻作用,但在不同的绿化模式下,衰减效果存在较大差别。交通噪声的绿化衰减同林带宽度有很大关系,对于较宽林带,靠近声源前半部分的林带对噪声有较好的减轻作用,但后半部分的减噪效果较小。林带的对噪声的绿化衰减与林带宽度以及宽度和郁闭度的乘积均呈极显著的线性关系。     

A Numerical and Field Investigation of Surface Heat Fluxes from Small Wind-Sheltered Waterbodies in Semi-Arid Western Australia

Shelterbelts are used for a variety of purposes in agricultural environments, primarily because of their ability to improve the downwind microclimate. Excessive evaporative losses from small, agricultural water supply reservoirs in semi-arid Western Australia motivated a combined numerical modelling and field investigation into the potential for using shelterbelts to reduce evaporation from these open waterbodies. A numerical model of the disturbed momentum and turbulence fields in the region modified by the wind-shelter was employed and accounted for the presence of a waterbody downwind. The model was coupled with conservation equations for heat and moisture and sensible and latent heat fluxes were estimated from the simulated momentum, temperature and humidity fields. The numerical simulations were tested against four days of field data from two experiments conducted in the agricultural districts of southwest Western Australia that measured boundary-layer evolution over a variety of small waterbodies protected by artifical and natural wind-shelters. The model provided good predictions of windspeed during neutral conditions, but inadequate specification of the upwind boundary during non-neutral stabilities resulted in the model failing to capture any sensitivity to atmospheric stability as seen in the field data. Despite this limitation, the temperature and humidity fields were adequately captured by the model, and evaporative mass flux predictions also agreed well with estimates taken from water-balance measurements. It is concluded that well-designed wind-shelters can reduce evaporation from open waterbodies by 20–30% as a result of reductions in the velocity scales responsible for removing moisture from the water surface. The model can be used to estimate the values of various shelterbelt design parameters (e.g., porosity, height) that could be applied in the field to provide optimum evaporation reductions.     

半焦负载Na-Fe催化还原NO的研究

在石英固定床反应器上于常压下研究了煤焦负载Na或Fe催化还原NO的反应，同时研究了Na-Fe复合催化剂的催化特性。研究结果表明：Na或Fe催化剂的催化行为差异较大，低温下Na的催化活性高于相同负载量的Fe，而温度较高时，二者的催化活性顺序与低温时相反。Na的催化活性随负载量的增加而迅速增大，而Fe的催化活性随温度的升高增加迅速。在保持相同的负载量下，一定配比的Na－Fe复合催化剂的催化活性高于其中任何单一催化剂的催化活性。在不加其他还原剂的条件下，负载于煤焦上的Na-Fe复合催化剂可有效地催化还原NO，得到了高的还原转化率。复合催化剂高的催化活性预示Na-Fe在制备过程中的相互作用以及催化半焦还原NO的反应中具有协同作用。     

Putting Longline Bycatch of Sea Turtles into Perspective

Abstract:  Although some sea turtle populations are showing encouraging signs of recovery, others continue to decline. Reversing population declines requires an understanding of the primary factor(s) that underlie this persistent demographic trend. The list of putative factors includes direct turtle and egg harvest, egg predation, loss or degradation of nesting beach habitat, fisheries bycatch, pollution, and large-scale changes in oceanographic conditions and nutrient availability. Recently, fisheries bycatch, in particular bycatch from longline fisheries, has received increased attention and has been proposed as a primary source of turtle mortality. We reviewed the existing data on the relative impact of longline bycatch on sea turtle populations. Although bycatch rates from individual longline vessels are extremely low, the amount of gear deployed by longline vessels suggests that cumulative bycatch of turtles from older age classes is substantial. Current estimates suggest that even if pelagic longlines are not the largest single source of fisheries-related mortality, longline bycatch is high enough to warrant management actions in all fleets that encounter sea turtles. Nevertheless, preliminary data also suggest that bycatch from gillnets and trawl fisheries is equally high or higher than longline bycatch with far higher mortality rates. Until gillnet and trawl fisheries are subject to the same level of scrutiny given to pelagic longlines, our understanding of the overall impact of fisheries bycatch on vulnerable sea turtle populations will be incomplete.