基于颗粒模型的风积砂层降雨入渗深度计算及验证

为了研究沙漠干旱区降雨对砂层非饱和带水分的贡献,该文对风积砂层水分入渗过程中的水分存在形式和运移机理进行了理论和力学分析。通过以触点水为主要储水单元的立方布局颗粒模型推导出水分入渗过程中湿润深度的解析表达式,并进行验证。物理和力学分析表明,砂颗粒表面很难形成较厚的薄膜水,砂层非饱和带水分大部分以触点水的形式存在。模型计算结果表明,水分入渗的湿润深度与入渗水量和触点水湿润角有关。模型验证表明,水分入渗湿润深度的解析表达式在风积砂层入渗深度计算中具有一定的适用性,但触点水湿润角与砂颗粒粒径的函数关系还有待进一步研究当设定触点水湿润角为π/4时,比例常数为11.5。该研究可为干旱区农业规划提供依据。     

渠系前馈蓄量补偿控制时滞参数算法比较与改进

输水明渠系统控制算法主要由前馈及反馈模块组成,其中前馈模块较大程度上影响了系统控制性能。基于蓄量主动补偿的前馈控制算法受时滞参数影响较大,为比较现有多种算法实际控制性能优劣,并寻求不依赖复杂数值计算的简化时滞参数算法,该文进行了横向的算法比较与优化开发。文章基于蓄量阶跃补偿及蓄量二次补偿2类算法,结合改进比例-积分(proportional-integral,PI)反馈控制器,对典型测试渠系及实际工程渠系建模仿真,选取稳定时间、最大超调流量、绝对值误差积分(integral of absolute magnitude of error,IAE)和绝对流量变化积分(integrated absolute discharge change,IAQ)指标分析了蓄量阶跃补偿、动力波原理、水量平衡模型3种时滞参数算法的控制效果。结果显示,在实际工程渠系中,小流量工况下,蓄量阶跃补偿算法的稳定时间比水量平衡模型算法的稳定时间减小40.42%;大流量工况下,蓄量阶跃补偿算法的最大超调流量最小,仅比目标流量高3%,该算法的稳定时间比水量平衡模型算法的稳定时间减少25.45%。结果表明蓄量阶跃补偿算法控制效果较好,但该算法在推求渠池所需蓄量补偿值时需进行水面线推求,文章依据渠道蓄量变化与流量变化间的线性关系,提出简化的时滞参数显式算法。较传统数值算法,时滞参数显式算法与蓄量阶跃补偿算法的时滞参数差值百分比小于8%,在满足实际工程需求的同时,可明显减少推求所需蓄量补偿值的计算量。文章的比较结论及所提出的简化算法对输配水渠道系统,尤其是大型渠道系统调度具有一定的理论价值和应用前景。     

降雨量对洱海流域稻季氮磷湿沉降通量及浓度的影响

为了探究洱海流域稻季氮磷湿沉降规律,于2016及2017年稻季在大理洱海流域收集湿沉降样品,分析样品中总磷(total phosphorus,TP)、总氮(total nitrogen,TN)、NO_3~--N、NH_4~+-N等指标及其变化规律。结果表明,TN、TP湿沉降通量主要受降雨量支配,2016与2017年稻季单次降水TN、TP湿沉降通量与降雨量均呈极显著的线性正相关关系。TN、TP湿沉降浓度总体上随降雨量的增大而减小,同时与是否发生连续降雨及是否大规模施肥有关。以2017稻季氮素湿沉降为例,2017年稻季NH_4~+-N和NO_3~--N湿沉降对TN的占比分别为53.1%和20.6%,湿沉降以NH_4~+-N为主。可溶性无机氮(dissolved inorganic nitrogen,DIN)对TN的占比随着降雨量的增大而减小,随着连续降雨的延续而增大。2016及2017年稻季湿沉降TN质量浓度分别为0.87~4.03和0.90~6.85 mg/L,均远大于湖泊富营养化阀值,对洱海水生生态系统产生不利影响。     

Molecular community analysis of arbuscular mycorrhizal fungi associated with five selected plant species from heavy metal polluted soils

Arbuscular mycorrhizal fungi (AMF) are known to play an important role in plant tolerance to heavy metals (HMs) stress. This study aimed to understand the diversity of AMF communities associated with five selected plant species (Phytolacca americana, Rehmannia glutinosa, Perilla frutescens, Litsea cubeba and Dysphania ambrosioides) from severely HMs polluted soils in Dabaoshan Mine region, China, using molecular methods. Plant roots and rhizospheric soils were sampled from four sites, respectively. Targeting the fungal small subunit (SSU) rRNA gene, PCR-denaturing gradient gel electrophoresis (DGGE) analysis indicated that varied AMF communities colonized different plant species, and the AMF communities in rhizospheric soils were different from those in plant roots. Total six SSU rRNA gene clone libraries including four root samples and two rhizospheric soil samples were constructed. Screening clone libraries by DGGE and sequence analysis revealed that Glomus dominated all of the samples except for the roots of D. ambrosioides, while Kuklospora and Ambispora dominated the roots of D. ambrosioides and the rhizosphere of P. americana. This study indicates that diverse AMF are associated with these selected plants, and they are potentially useful to promote the phytoremediation of this HMs polluted area.     

半干旱黄土丘陵区沙棘优良品种引种栽培试验研究

1994-2003年在黄土高原半干旱区的陕西吴旗县、安塞县进行中国沙棘优良类型和俄罗斯优良沙棘品种引种试验,采用家系选择法初步筛选出5个中国沙棘生态经济型优良单株,对3个俄罗斯良种沙棘的生长适应性经济性状进行了评价。前者生长迅速、树冠好、根系发达、郁闭快、水土保持效益好,果实较大、单株产量较高、Vc和含油量较高,适于在黄土丘陵区种植;后者经济性状较好,果实大、无刺或少刺,但适应性较中国沙棘差。     

Suitability of Bi-linear Restoring Force Model in Earthquake Response Analysis

Based on the data of dynamic tests of small single-storey steel frames,the suitability of simplified hi-linear restoring force model in earthquake response analysis is discussed, and the Maximum displacement response MD, the sum of squares of the displacements in the whole vibrating history SSD, and the total dissipated energy EI are considered respectively as equivalent object.     

On Determinative Parameters of SDOF Systems in Elasto- plastic Earthquake Response

Parameters dominating elasto- plastic earthquake response of SDOF systems,relation between ground motion amplitude and elasto- plastic response of SDOF systems are presented in this paper.     

六棱大麦杂种优势与配合力的研究

对六棱大麦杂种 F_120个组合及其9个亲本12个性状的杂种优势研究表明:株粒重、单株草重、株粒数和每穗粒重的杂种优势达20～35%;主穗长、株高、单株穗数、每穗粒数、千粒重和主穗粒数的杂种优势约为10～20%;主穗小穗数为5.49%,经济系数为负向优势-1.62%。由于各性状的遗传变异均以基因的加性效应为主,各性状的遗传力较高,故预     

杂交水稻汕优2号及其父本IR24叶片衰老的研究

将杂交水稻汕优2号及其父本 IR24与桂朝2号的叶片进行衰老处理后,表明汕优2号的叶绿素和可溶蛋白质的降解及细胞膜透性增加的速度均快于IR24和桂朝2号。过氧化物酶活性和呼吸强度增加的幅度也较大。反映了汕优2号具有衰老速度快的特征。在衰老处理后的1～2天,乙烯释放量和过氧化物酶活性增加几乎是同时进行的,随后出现一个呼