改进粒子群优化（MPSO）算法在动     

罗志平  周新志  王标 《中国农村水利水电》2007,(6):43-45

基于在水资源不充足的情况下，对都江堰灌区六大渠干水资源的合理分配，使农业效益达到最大。首先建立灌区优化配水模型，并将粒子群优化算法（PSO）及其改进的算法应用于该模型。分别对标准PSO、两种改进PSO（MPSO）算法与遗传算法进行仿真对比，结果显示采用PSO算法及其MPSO在农业经济效益上可获得更好的寻优效果，提高了水资源的利用率。  相似文献   

保种群体遗传结构变化的模拟研究     

芒来 《内蒙古农业大学学报(自然科学版)》1991,(2)

本文运用电子计算机模拟的方法,分析了影响畜禽保种的主要因素,并通过不同参数组合(包括起始基因频率、群体有效含量和世代数等)的模拟试验得出三个主要结论: 1 在有性繁殖的有限群体中,原封不动地保存群体基因库中的每个基因(包括频率很低的基因)是根本不可能的。 2 在完全实行随机交配的情况下,长期保存频率较高的基因也需要相当大的群体才有可能。 3 频率较高基因的保存也不能单纯依靠群体大小,还需借助于选择。只有这样才能在小群体内长期保存频率较高的基因。  相似文献   

卵泡刺激素受体基因作为产仔数候选基因的研究   总被引：8，自引：1，他引：8  

张淑君  熊远著  邓昌彦  郑嵘  蒋思文  肖森木  夏瑜  徐建祥  刘晓华  王春芳  阮征  宫时玉 《华中农业大学学报》2002,21(6):506-508

分析了FSHR基因2个位点（FSHRA、FSHRB）的PCR－SSCP、PCR－RFLPs多态性，利用SAS软件分析了多态性与母猪产仔数间连锁关系。找到了1个影响产仔数的新的变异位点FSHRB，该位点多态性显著地影响猪产仔数性状，即基因型BB的产仔数显著地高于AB、AA基因型。结果显示出该位点具有作为常规选育的辅助选择的有效的分子标记潜力。  相似文献   

基于改进粒子群算法的烧结配料预测模型     

黄晶晶  万丽丽  秦岭 《湖南农业大学学报(自然科学版)》2011,(3):90-94

针对烧结配料系统中的非线性、复杂性和相关性，基于BP神经网络建立烧结配料的预测模型，并采用粒子群算法对预测模型参数进行优化。为了克服粒子群算法的局部收敛性，在迭代过程中，根据迭代次数对惯性权重进行动态非线性调整，从而提高算法的搜索能力。仿真结果表明，所提出的改进粒子群算法与传统的粒子群算法比较，收敛速度快、迭代次数少、具有较强的全局寻优能力。  相似文献   

Interspecific differences in early life‐history traits in a species complex of stream‐resident galaxiids          下载免费PDF全文

Peter E. Jones  Gerard P. Closs 《Ecology of Freshwater Fish》2016,25(2):211-224

Fish differentially provision resources to eggs and larvae to optimise survival during the critical early life‐history period. Resource allocation is limited by a trade‐off between egg size and fecundity, and the optimal strategy varies with habitat type. This study examines the consequences of egg size differences for the early life‐histories of four closely related galaxiid species which occur in contrasting habitat types on the South Island, New Zealand. Headwater species had substantially larger water‐hardened eggs, longer incubation times, and newly hatched larvae were on average up to 41% longer than lower catchment species. Significant interspecific differences in gape diameter, eye diameter and myomere depth were also observed. Swimming ability was positively associated with larval length at hatch. Interspecific differences in length and swimming ability were generally maintained throughout the larval period, despite larvae being reared under relatively benign conditions where many other studies suggest initial differences should disappear. These results demonstrate the consequences of differential maternal provisioning to the egg for larval traits. The larger larvae of headwater species are likely to be more resistant to starvation and have improved foraging ability compared to lower catchment species; traits which are likely to confer them survival advantages in the low productivity, food‐scarce environments they occupy. The smaller larvae of lower catchment species are likely to be a consequence of females investing in fecundity in these relatively resource‐rich streams.  相似文献   

Census and effective population sizes of white‐spotted charr (Salvelinus leucomaenis) in a fragmented landscape          下载免费PDF全文

Shoichiro Yamamoto  Hitoshi Kubota  Koh Hasegawa  Tomoyuki Nakamura 《Ecology of Freshwater Fish》2016,25(4):612-621

Several habitat models have been proposed to predict population size for stream fishes and to guide habitat assessment and monitoring techniques. However, most models do not incorporate the potential advantage of molecular genetic markers. We conducted a field survey and microsatellite DNA analyses to quantify the relationships among genetic diversity, census/effective population size and habitat variables in fragmented populations of white‐spotted charr (Salvelinus leucomaenis). The census population size significantly increased with the stream length, the number of pools and a pool‐riffle sequence index, a proxy for channel‐unit habitat type complexity within reaches. Population density was correlated with the pool‐riffle sequence index only. Genetic diversity and effective population size were not correlated with the habitat variables or census population size. There was a lack of isolation‐by‐distance population structure in the studied populations. Our results suggest that stream length and the number of pools within reaches associated with habitat complexity are the habitat variables that explain the majority of variation in population size of white‐spotted charr. Our findings provide further evidence that census population size per se is a poor indicator of the inclusive genetic diversity within populations in a fragmented landscape.  相似文献   

A quick method of soil moisture determination     

《Communications in Soil Science and Plant Analysis》2012,43(5):795-805

Abstract

The method described here is useful for the quick determination of soil moisture, especially when many determinations are to be made at a time. The only pieces of apparatus required are some wide‐mouthed conical flasks, a few pieces of glass rod and a balance. The principle involves recording the weight of the flask filled with water and soil sample of known weight (A). This flask weight (H), and the predetermined soil particle density (D_p) and weight of the water‐filled flask (G) are then used to calculate moisture percentage (MP) in the soil sample from the formula:

The method was compared with conventional oven‐drying technique for a wide range of soil textures, moisture contents and other contrasting soil properties. The results obtained showed that the accuracy, precision and simplicity of the method are good, particularly for rapid practical uses.  相似文献   

Investigation of the Effect of Mesh Size on the Effectiveness of Hotplate Aqua Regia Extractions     

《Communications in Soil Science and Plant Analysis》2012,43(2):159-166

Aqua regia extractions with subsequent inductively coupled plasma determinations are a very common method of elemental analysis of soils and sediments. Before extraction, the material must be dried and sieved. Small variations in this early step can have a significant impact on the later outcomes, especially for unassisted (for example, without ultrasonic or microwave) extraction procedures. Therefore the impact of mesh size on the sieving process was investigated. A mesh size of 2.0 mm or greater yielded unacceptably high variations between the subsamples and a very poor recovery rate when compared to a 0.063-mm sieve. A mesh size of 0.3 mm resulted in the best outcomes, losing nearly no material in the fine sediment samples and about a tenth in the coarse samples. The precision was high for the 0.3-mm samples as well, only negligibly surpassed by the 0.1-mm samples for some materials.  相似文献   

基于粒子群的多BP网络并行非线性预测控制     

段向军  钱锋 《湖南农业大学学报(自然科学版)》2010,(2):32-35

针对传统预测控制算法在解决非线性系统控制问题时，存在难以建立精确的数学模型、控制精度不高等缺点，提出一种新的非线性系统预测控制方案。以多BP神经网络作为并行预测模型，克服误差积累以及网络规模庞大的缺点；运用粒子群优化(PSO)算法完成非线性预测控制的滚动优化。仿真表明，该方案的控制效果比常规动态矩阵控制效果有所提高，该方案是可行和有效的。  相似文献   

农业机械手钳的人机安全设计     

楚杰 《农机化研究》2010,32(3)

分析了应用较为普遍的农业机械工具—农业手钳的人机安全学设计因素,并通过实验计算得出以人机工程学为基础的手钳的参数设计。主要从人机工程学的角度出发,通过分析手钳在使用时的舒适度和把手尺寸,以评估设计的合理性。同时,分别针对男女群体正态分布的第5百分位、第5 0百分位和第9 5百分位的测量数据进行手柄设计和尺寸评估,得出农业机械手钳的科学合理性尺寸设计。  相似文献