水流冲击多段滞留气团的三维数值模拟

针对水气两相瞬变现象,充分考虑了水体弹性、气体可压缩性、水-气交界面的动态运动以及多段气团间相互作用,采用三维CFD方法对起伏管道内含多段滞留气团的水气两相作用进行建模和模拟,选择Standard k-ε湍流模型进行模拟研究,将三维计算结果、现有一维模型计算结果与试验结果进行对比分析,并通过水气两相分布图展现动态变化过程.结果表明:与一维模型相比,三维CFD模型能够更为准确地模拟起伏管道内瞬变压力波动,并且能够清楚描述水气掺混、耦合的动态变化.水流冲击初始两段滞留气团压力波动曲线显示,多气团间的瞬变压力并非同步变化,可能呈现多气团峰值压力交替出现的情况,这与初始气团长度密切相关.水气交界面自由变化,阻断水体长度时刻发生变化,当水体运动到管道弯曲处时会产生新的阻断水体,将气团分成若干部分.     

蜗壳式离心泵外特性仿真与实验研究

为探索不同仿真方法的适用性,对ns=157的单级蜗壳离心泵不同工况的扬程和效率进行定常和非定常计算,并分别分析了定常计算时不同叶片夹角及非定常计算时不同时间步长的影响,通过与实验对比,得到的主要结论有:定常计算仅适用于额定工况外特性仿真,其扬程和效率计算误差分别为4.9%和2.9%,而定常多相位的计算误差分别为7.1%和3.2%;非定常仿真计算时,以4°为时间步长,并间隔20°保存一次计算数据,较好地预测出扬程曲线走势,额定工况扬程和效率计算误差约1.1%和1.8%,但小流量和大流量区间扬程计算误差达到10%左右。因此在水力优化设计时,若只关注高效点位置及其扬程和效率,可采用定常计算,若还关注扬程曲线走势,则应采用非定常计算。     

Threats to at-risk salmonids of the Canadian Rocky Mountain region

Trout and charr, members of the salmonid family, have high conservation value but are also susceptible to anthropogenic threats in part due to the specificity of their habitat requirements. Understanding historical and future threats facing these species is necessary to promote their recovery. Of freshwater trout and charr in the Canadian Rocky Mountain region, westslope cutthroat trout (Oncorhynchus clarkii lewisi), bull trout (Salvelinus confluentus; a charr species) and Athabasca rainbow trout (Oncorhynchus mykiss) are of conservation concern. And indeed, range contractions and declining populations are evident throughout much of their ranges. Range contraction was most evident in the southern Alberta designatable unit (DU) of westslope cutthroat trout. Diminished populations were also evident in the downstream watersheds of the Alberta bull trout range, and throughout the Athabasca rainbow trout range. We assessed historical and future threats to evaluate the relative importance of individual threats to each DU and compare their impact among species. Individual threats fall into the broad categories of angling, non-native species and genes, habitat loss and alteration, and climate change. Severity of each threat varies by DU and reflects the interaction between species’ biology and the location of the DU. Severity of threats facing each DU has changed over time, reflecting extirpation of native populations, changes in management and industry best practices, expansion of non-native species and progressing climate change. The overall threat impact for each DU indicates a high probability of substantial and continuing declines and calls for immediate action.     

菜心重要农艺性状与SSR分子标记的关联分析

菜心是华南地区的主要蔬菜,利用分子标记辅助育种发掘出与重要农艺性状相关的分子,不仅可以加速优良品种的选育进程,还可以定向地优化目标性状,培育出高产优质的菜心品种。本研究选用148份来自宁夏银川和广东南沙田间种植的菜心种质材料,采集株高、株质量、薹高、薹质量和薹粗5个重要农艺性状的数据;利用SSR标记对其进行基因分型,开展农艺性状及SSR标记的关联性分析。结果表明,在供试的菜心材料中,147个SSR标记共检测到252个变异位点,引物多态信息含量(PIC)为0.0526~0.5222,平均值为0.3793;群体结构分析将供试的菜心品种分为2个类群;银川和南沙两地菜心品种在农艺性状和SSR标记的关联分析中发现,有6个位点与相同性状存在仍显著关联(P<0.01)。这些标记能为菜心的分子辅助选择育种提供参考。     

基于有限元的汽车扭臂热锻工艺研究

文章以汽车扭杆力臂为研究对象,通过DEFORM-3D有限元分析对汽车扭杆力臂热锻工艺过程进行模拟试验,分析了成形过程中的上模载荷情况、应力应变场分布情况和温度场的变化规律。以提高产品质量和降低载荷为主要目的,给出合理的热加工参数,分析结果能为类似锻件的热模锻工艺和模具设计提供依据。     

数值模型结构不确定性对模拟结果的影响分析

以内蒙古鄂托克旗为例,基于GMS中的MODFLOW模块构建了地下水流数值模拟模型,分析了模型结构(含水层厚度、参数分区)与模型参数不确定性因素对模拟结果的影响.研究结果表明:含水层不确定情景(含水层下边界概化为隔水底板平均值870 m)与实际情况水头差值绝对值的累计和最大为701 m,对模拟结果起了主控作用;当含水层下边界概化为910,940 m时,累计和分别增加为1 013,1 593 m;与仅考虑单个不确定性因素相比,同时考虑模型参数与含水层不确定情景累计和最大为738 m,同时考虑参数分区与含水层不确定情景累计和最大为791 m.因此,在构建地下水流数值模拟模型时,应优先考虑含水层空间结构概化的合理程度,同时考虑多个不确定性因素对模拟结果的综合影响,使地下水数值模拟模型能更精确地反映真实的地下水流状况.     

Hybrid breeding for biomass yield in winter triticale: II. Combining ability and hybrid prediction

Accurate hybrid prediction and knowledge about the relative contribution of general (GCA) and specific combining ability (SCA) are of utmost importance for efficient hybrid breeding. We therefore evaluated 91 triticale single-cross hybrids in field trials at seven environments for plant height, heading time, fresh biomass, dry matter content and dry biomass. Fresh and dry biomass showed the highest proportion (23%) of variance due to SCA. Prediction accuracies based on GCA were slightly higher than based on mid-parent values. Utilizing parental kinship information yielded the highest prediction accuracies when both parental lines have been tested in other hybrid combinations, but still moderate-to-low prediction accuracies for two untested parents. Thus, hybrid prediction for biomass traits in triticale is currently promising based on mid-parent values as emphasized by our simulation study, but can be expected to shift to GCA-based prediction with an increasing importance of GCA due to selection in hybrid breeding. Moreover, the performance of potential hybrids between newly developed lines can be predicted with moderate accuracy using genomic relationship information.     

Compatibility of root growth and tuber production of potato cultivars with dynamic and static water‐saving irrigation managements

The important root characteristics of root length density (RLD) and root mass density (RMD) generally differ among irrigation managements and potato cultivars. The objective of this study was to investigate the RLD and RMD variations and their functional relationships with gross potato tuber yield for two commercial potato cultivars, Agria and Sante, under different irrigation strategies. Full irrigation and water‐saving irrigation strategies, deficit and partial root drying irrigations, were applied statically (S) and dynamically (D) based on daily crop evapotranspiration. Results showed that SPRD had significantly greater RLD (3.64 cm/cm³) and RMD (132.7 μg/cm³) than other irrigation treatments. Between the potato cultivars, Agria had significantly larger values of RLD (3.50 cm/cm³) and RMD (138.7 μg/cm³) than Sante. The functional relationship between the root growth characteristics and tuber yield showed that under water‐saving irrigations, Agria increased root mass at the expense of gross tuber yield but Sante increased root mass to maintain larger gross tuber yields. However, Agria produced more roots and gross tuber yield than Sante, and it is concluded that Agria is a more drought‐tolerant potato cultivar, which is recommended for tuber production in regions where water might be scarce. It was shown that larger root production in potatoes was associated with improved tolerance to water stress.     

Bulk pollen pollination in maize for efficient construction of introgression populations with high genome coverage

Introgression populations consist of a set of introgression lines or families, constructed by continuous backcrossing to the recurrent parent, while carrying a limited number of chromosome segments from a donor parent in their genomes. Increasing the genome coverage is an important aim when constructing introgression population. In this study, we proposed bulk pollen pollination (BPP) method and used it to increase the genome coverage of a maize introgression population. The results showed that the genome coverage of the introgression population constructed using BPP method reached 100% at BC₃ generation, which accorded with the simulation result. The BPP‐based BC₃F_1:2 population could identify most quantitative trait loci (QTL) detected using the F_2:3 population, especially major QTL. Simulation analysis showed that the genome coverage of introgression population increased with the increase of population size and the number of bulked plants, and decreased with the increase of backcross generation. Our results proved the reliability of the BPP‐based introgression population in increasing genome coverage and detecting QTL, and provided references for constructing high‐coverage introgression populations.     

气象因子对芒果园桔小实蝇种群动态的影响

桔小实蝇[Bactrocera dorsalis (Hendel)]是芒果的重要害虫之一。试验利用性引诱剂对芒果园桔小实蝇的全年种群动态进行监测，分析气象因子与其种群数量变动的相关性。结果表明，芒果园桔小实蝇雄虫种群数量一年有2个明显高峰，2月为短时高峰，3月种群活动有所下降；5月开始数量逐渐升高，至8月达到高峰，9月开始逐渐下降，到12月至1月为发生低谷。经逐步回归分析发现，气象因子显著影响桔小实蝇雄虫的数量，主要受月平均气温、月平均最低气温和月降水量综合影响。