共查询到20条相似文献，搜索用时 46 毫秒
1.
为提高径流时间序列预测精度,提出小波包分解(WPD)与奇异谱分解(SSA)-鼠群优化(RSO)算法-回声状态网络(ESN)相混合的径流时间序列预测方法.分别利用WPD和SSA将非平稳径流时间序列分解为若干子序列,有效降低径流时间序列的复杂性;介绍RSO算法原理,在不同维度条件下选取6个典型函数对RSO算法进行仿真测试;... 相似文献
2.
基于小波分析-PSO优化ANFIS的径流组合预测模型研究 总被引：1，自引：0，他引：1
径流序列由于多种因素的影响,存在十分复杂的变化特性,如果利用常规方法直接进行预测,其预测精度一般不高.如果将径流序列分解成比较简单的序列,再利用非线性预测方法进行预测,其精度将会得到提高.利用小波分析的多分辨率分解功能对径流序列进行分解,降低了径流序列的复杂程度.利用PSO对自适应神经模糊推理系统的网络参数进行优化,提高模型结构参数的确定精度.将小波分析与PSO优化的ANFIS进行组合对径流序列进行预测,经实例验证:该模型能够提高径流预测的精度,预测效果较好. 相似文献
3.
《中国农村水利水电》2017,(7)
针对径流序列的弱相关,非线性特征,直接预测会导致精度低,建立基于经验模态分解(empirical mode decomposition,EMD)与Elman神经网络的模型进行月径流预测,选取黄河上游唐乃亥水文站1979-2009年的月径流资料为研究对象。首先利用EMD对月径流资料进行处理,得到5个固有模态函数(intrinsic mode function,IMF)和1个趋势项。为了避免分量太多导致误差过大,将分量进行重组之后得到3个子序列,然后对3个子序列进行Elman神经网络预测。结果表明,EMD与Elman神经网络组合预测精度更高,更加适合复杂的水文序列。该方法可用于径流的中长期预测中。 相似文献
4.
径流过程是地球上水文循环中的关键一环，科学准确地预测月径流的来水量对于流域的水量调度、水资源规划及管理具有十分重要的意义。然而由于径流过程的复杂性以及人类活动的影响，在变化环境中精准捕捉月径流时间序列的变化规律变得十分困难。针对月径流时间序列预测中存在的对于样本数据中先验信息识别不够彻底以及对时间步长嵌入维度难以有效地自适应选取这两点问题，设计了基于VMD-PSR-BNN的月径流时间序列预测模型。基于变分模态分解（VMD）算法对噪声良好的鲁棒性和对时序信号精确分解的特性，将月径流时间序列视为一种时序信号，利用VMD方法将月径流时间序列分解为多个相对平稳的固有模态函数（IMF），再基于相空间重构（PSR）理论对各个IMF分别进行重构，对各个重构后的IMF分别采用基于变分推理的贝叶斯神经网络（BNN）进行预测，最后将各个BNN的预测结果进行聚合重构得到月径流时间序列的最终预测结果。选取渭河流域咸阳和华县两个水文站1953-2018年的月径流时间序列进行实例分析。结果表明：VMD对月径流时间序列具有很好的分解效果，两个水文站基于VMD-PSR-BNN模型的月径流预测结果均可达到水文预报的甲级... 相似文献
5.
为提高径流预测精度,研究提出海洋捕食者算法(MPA)与长短期记忆(LSTM)神经网络相结合的径流预测方法。通过6个仿真函数对MPA、粒子群优化(PSO)算法进行测试,利用MPA优化LSTM隐藏层神经元数、训练次数等关键参数,基于主成分分析(PCA)降维和不降维处理分别建立PCA-MPA-LSTM、MPA-LSTM径流预测模型,利用云南省落却站实测数据对PCA-MPA-LSTM、MPA-LSTM模型进行训练及预测,结果与PCA-LSTM、LSTM、PCA-MPA-SVM、MPA-SVM、PCA-MPA-BP、MPA-BP模型的训练、预测结果进行比较。结果表明:①MPA仿真效果优于PSO算法,具有较好的寻优精度和全局搜索能力。②PCA-MPA-LSTM、MPA-LSTM模型对实例拟合、预测的平均相对误差分别为1.18%、2.35%和1.94%、1.96%,预测效果优于其他6种模型,具有较好的预测精度和泛化能力。③采用MPA优化LSTM关键参数能有效提高LSTM泛化能力和预测精度;数据降维模型的预测精度优于对应未降维模型的预测精度,数据降维处理能有效改善模型的预测效果。 相似文献
6.
河流径流预测作为水库调度和发电的重要前提,其预测精度直接影响水利工程的综合效益。基于径流历史数据,针对其波动和随机性提出一种小波分析-支持向量机(SVM)特征分类组合预测模型。该模型首先利用小波分解提取原始径流序列的高低频能量谱作为SVM样本标记,并对原始序列进行特征分类,分为"平稳型"和"突变型"序列,对应不同类型序列的小波近似信号和细节信号分别采用自回归和滑动平均模型(ARMA)和BP神经网络模型进行预测,再重构各序列预测结果。最后采用平均绝对百分比误差(MAPE)、均方根误差(RMSE)、希尔不等式系数(TIC)作为模型评价指标。结果表明:在3个评价指标下,所提模型都优于ARMA和BP神经网络模型,并具有更好预测稳定性。 相似文献
7.
《农业机械学报》2019,(Z1)
为提高猪舍氨气浓度预测的精度和效率,提出了基于经验模态分解和长短时记忆神经网络(EMD-LSTM)的猪舍氨气浓度预测模型。首先,将猪舍氨气浓度时间序列数据进行经验模态分解,得到不同时间尺度下的固有模态分量(IMF);然后,对IMF建立LSTM氨气浓度预测模型;最后,将各分量的预测结果相加求和作为猪舍氨气浓度的最终预测值。将本文提出的预测模型应用于江苏省宜兴市实验基地某养猪场的氨气浓度预测中,并与Elman模型、循环神经网络(RNN)模型、LSTM模型和EMD-LSTM模型进行了对比实验,结果表明,基于EMD-LSTM模型的预测精度较高,预测结果与真实值相比较,平均绝对误差、平均绝对百分误差和均方根误差为0. 072 3 mg/m~3、0. 6257%和0. 094 5 mg/m~3。 相似文献
8.
随着我国贺兰山东麓地区葡萄园的大量兴建和大规模引种,各个葡萄园内出现了以霜霉病为典型的严重的病虫害问题。针对目前酿酒葡萄霜霉病精确预测手段缺乏的问题,提出一种基于遗传算法改进长期和短期记忆神经网络的预测模型。将遗传算法(GA)加入长短期记忆神经网络(LSTM)预测模型的参数调节环节中,通过优化算法代替人工手动调参在超参数搜索空间中不断迭代得到最优超参数组合最终确定模型。再建立基于霜霉病—气象时序数据的手动调参LSTM模型和BP神经网络模型,将三种模型在测试集上进行对比试验。GA-LSTM模型的预测结果均方根误差、均方误差、平均绝对误差分别为0.410 3、0.168 4、0.245 0,均小于LSTM模型和BP神经网络模型。预测结果表明LSTM在时间序列问题的应用中预测性能优于BP神经网络模型,使用遗传算法对LSTM模型的超参数选择环节进行优化,最终得到的超参数组合优于手动调参的LSTM模型得到的超参数组合。 相似文献
9.
利用聚类分析法将径流序列分解为若干个子径流序列 ,对这些子径流序列分别建立局部神经网络模型 ,而后把这些局部模型合并成一个混合模型。当新的信息进入该模型时 ,首先用分类器判别其类别 ,以确定用混合模型中的何种局部模型加以模拟。通过与不加分类的总体神经网络模型的模拟结果加以对比 ,结果表明这种基于径流分类的降雨 -径流模型表现出了更优良的性能 ,可以较大地提高径流模拟精度。 相似文献
10.
利用长短期记忆神经网络(LSTM)构建地下水水位预测模型,解决了传统神经网络预测模型处理时序数据时未考虑时间序列的问题,同时采用多影响变量输入的方式弥补了简单时序模型处理数据时过于依赖时间的缺点。以泰安市岱岳区满庄镇姜家园村046J地下水位监测井为例,采用2001-2016年的监测资料与相关气候数据,利用长短期记忆神经网络构建了地下水水位预测模型,以控制变量的方法确定最优参数,对该井的地下水水位进行了预测,并与单变量LSTM神经网络、BP神经网络预测模型作对比。研究结果表明:基于多变量输入的LSTM神经网络模型能够通过少量历史数据准确的预测未来地下水水位变化情况,特别是在一些资料匮乏的地区,预测误差要显著低于参与对比的预测模型,预测均方根误差仅为2.052。因此,基于多变量的LSTM神经网络模型能够作为简单有效的地下水水位预测工具,为区域水资源管理提供一定的参考。 相似文献
11.
Overland water and salt flows in a set of rice paddies 总被引：1，自引：0，他引：1
E. Playn O. Prez-Coveta A. Martínez-Cob J. Herrero P. García-Navarro B. Latorre P. Brufau J. Garcs 《Agricultural Water Management》2008,95(6):645-658
Cultivation of paddy rice in semiarid areas of the world faces problems related to water scarcity. This paper aims at characterizing water use in a set of paddies located in the central Ebro basin of Spain using experimentation and computer simulation. A commercial field with six interconnected paddies, with a total area of 5.31 ha, was instrumented to measure discharge and water quality at the inflow and at the runoff outlet. The soil was classified as a Typic Calcixerept, and was characterized by a mild salinity (2.5 dS m−1) and an infiltration rate of 5.8 mm day−1. The evolution of flow depth at all paddies was recorded. Data from the 2002 rice-growing season was elaborated using a mass balance approach to estimate the infiltration rate and the evolution of discharge between paddies. Seasonal crop evapotranspiration, estimated with the surface renewal method, was 731 mm (5.1 mm day−1), very similar to that of other summer cereals grown in the area, like corn. The irrigation input was 1874 mm, deep percolation was 830 mm and surface runoff was 372 mm. Irrigation efficiency was estimated as 41%. The quality of surface runoff water was slightly degraded due to evapoconcentration and to the contact with the soil. During the period 2001–2003, the electrical conductivity of surface runoff water was 54% higher than that of irrigation water. However, the runoff water was suitable for irrigation. A mechanistic mass balance model of inter-paddy water flow permitted to conclude that improvements in irrigation efficiency cannot be easily obtained in the experimental conditions. Since deep percolation losses more than double surface runoff losses, a reduction in irrigation discharge would not have much room for efficiency improvement. Simulations also showed that rice irrigation performance was not negatively affected by the fluctuating inflow hydrograph. These hydrographs are typical of turnouts located at the tail end of tertiary irrigation ditches. In fact, these are the sites where rice has been historically cultivated in the study area, since local soils are often saline-sodic and can only grow paddy rice taking advantage of the low salinity of the irrigation water. The low infiltration rate characteristic of these saline-sodic soils (an experimental value of 3.2 mm day−1 was obtained) combined with a reduced irrigation discharge resulted in a simulated irrigation efficiency of 60%. Paddy rice irrigation efficiency can attain reasonable values in the local saline-sodic soils, where the infiltration rate is clearly smaller than the average daily rice evapotranspiration. 相似文献
12.
瓦房店市是我国重要的水果生产基地,在国内水果生产领域占有重要地位。随着水果市场化的不断深入,如何满足和适应国内外市场需求成为瓦房店市水果生产的关键问题。从瓦房店市水果生产实际出发,阐述了实施水果生产标准化的必要性,提出了发展水果生产标准化的具体措施。 相似文献
13.
对引进的谷子新品种金谷子耐旱TG118进行品种比较试验和多点试种。结果表明：该品种抗旱、耐瘠、适应性强,稳产、高产、抗病抗风抗倒伏强,品质优良,粮草兼用,种植简单,省工易管;一般产量在6000kg/hm2以上,比当地主栽品种增产20%以上。最高产量达9450kg/hm2,适于在辽西北地区推广应用。 相似文献
14.
对《种子法》存在问题的探讨 总被引：1，自引：0，他引：1
李鹏 《农业机械化与电气化》2011,(6):129-130
《种子法》是我国种植业第一部法律。自实施以来,为依法加强种子管理提供了有力的法律支撑,促进我国种子产业发生翻天覆地的变化。但随着依法管理工作的深入和种子产业的快速发展,《种子法》及配套规章的一些问题逐步显现出来。对《种子法》及配套规章存在的问题进行深入分析,对需要进一步补充的章节以及需要调整的内容进行深入探讨,以求更加完善和明确。 相似文献
15.
About 30 years have passed since the Government of Egypt embarked on implementing a series of large scale drainage projects. At present, about 3.8 million acres have been provided with drainage systems on the basis of systematic pre-drainage investigations and designs. The target is to provide drains in approximately 6.4 million acres in the Nile Valley and Delta.The implementation of the subsurface drainage system is carried out by the public sector and private contractors under direct supervision of governmental regional departments. The implementation process depends on many factors related to the drainage material, machinery, manpower, site requirements, farmers and organizations involved. Problems and constraints are sometimes challenging, however, the annual rate of implementation has gradually increased to 170,000 acre/year.This paper discusses the different aspects involved in the implementation process of drainage systems. The development in materials, machinery and construction technologies will be reviewed. Institutional and management factors are going to be also considered. 相似文献
16.
在新世纪,面对机遇和挑战,党的十六大把“社会更加和谐”作为全面建设更高水平的小康社会的一个重要目标。中国人素有社会和谐的理想;西方人自古也向往社会和谐;借鉴东西方两种和谐社会思想的经验、教训,构建社会主义和谐社会理论。 相似文献
17.
Gunter Wriedt Marijn van der Velde Alberto Aloe Fayçal Bouraoui 《Agricultural Water Management》2009,96(5):771-789
We present a pan-European irrigation map based on regional European statistics, a European land use map and a global irrigation map. The map provides spatial information on the distribution of irrigated areas per crop type which allows determining irrigated areas at the level of spatial modelling units. The map is a requirement for a European scale assessment of the impacts of irrigated agriculture on water resources based on spatially distributed modelling of crop growth and water balance. The irrigation map was compiled in a two step procedure. First, irrigated areas were distributed to potentially irrigated crops at a regional level (European statistical regions NUTS3), combining Farm Structure Survey (FSS) data on irrigated area, crop-specific irrigated area for crops whenever available, and total crop area. Second, crop-specific irrigated area was distributed within each statistical region based on the crop distribution given in our land use map. A global map of irrigated areas with a 5′ resolution was used to further constrain the distribution within each NUTS3 based on the density of irrigated areas. The constrained distribution of irrigated areas as taken from statistics to a high resolution dataset enables us to estimate irrigated areas for various spatial entities, including administrative, natural and artificial units, providing a reasonable input scenario for large-scale distributed modelling applications. The dataset bridges a gap between global datasets and detailed regional data on the distribution of irrigated areas and provides information for various assessments and modelling applications. 相似文献
18.
在介绍粉质仪和拉伸仪结构和原理的基础上,探讨了粉质曲线中吸水率、形成时间、稳定时间、弱化度和评价值等指标与面粉品质的关系,以及如何根据拉伸曲线中面团最大拉伸阻力、延伸度和拉伸曲线面积等指标来评价面团品质,并结合生产实际,概述了粉质仪和拉伸仪在面粉生产中的作用。 相似文献
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20.
车辆ABS控制算法的研究及探讨 总被引：1，自引：0，他引：1
对现代汽车的ABS控制算法作了一些简单的介绍,同时指出了它们的一些缺陷,相应地提出了几种对ABS的其它控制方法并加以探讨,其中着重论述了ABS门限值控制算法中参考车速的确定方法和基于附着系数的控制算法。 相似文献