基于神经网络的洮河枯期径流预报模型研究

根据洮河50年(1957～2006年)的径流量、降雨和上游径流量数据,建立了基于反馈神经网络的Elman洮河枯季径流预报模型。利用matlab7提供的神经网络工具箱进行建模训练。仿真结果表明所采用的Elman网络预报模型精度高,为人工神经网络运用到水文预测方面提供了依据。     

小波神经网络在电力系统月度负荷

在研究了电力月负荷特性的基础上提出了一种新型的月度负荷预测模型——小波神经网络负荷预测模型。该模型以非线性小波基为神经元函数,通过伸缩因子和平移因子计算小波基函数合成的小波网络,以横向和纵向历史负荷数据作为输入神经元,采用基于BP(back propagation)算法的网络自调整算法,同时还采取自判断调整步长的方法,使得跨过局部极小点的同时还加快了收敛速度。该网络不但能达到全局最优的逼近效果,还能有效地克服了人工神经元网络学习速度慢、难以合理确定网络结构、存在局部极小点的固有缺陷。应用该模型预测我国某地区月负荷,结果表明,该模型预报精度高,自适应性好,收敛速度也明显快于单纯的神经网络。     

小波神经网络在电力系统月度负荷预测中的应用

在研究了电力月负荷特性的基础上提出了一种新型的月度负荷预测模型--小波神经网络负荷预测模型.该模型以非线性小波基为神经元函数,通过伸缩因子和平移因子计算小波基函数合成的小渡网络,以横向和纵向历史负荷数据作为输入神经元,采用基于BP(back pmpagation)算法的网络自调整算法,同时还采取自判断调整步长的方法,使得跨过局部极小点的同时还加快了收敛速度.该网络不但能达到全局最优的逼近效果,还能有效地克服了人工神经元网络学习速度慢、难以合理确定网络结构、存在局部极小点的固有缺陷.应用该模型预测我国某地区月负荷,结果表明,该模型预报精度高,自适应性好,收敛速度也明显快于单纯的神经网络.     

河川径流预测方法比较研究

通过实际算例分析比较了灰色预测模型、小波分析法、小波神经网络和模糊神经网络河川径流预测方法,结果表明：灰色预测模型和小波分析法预测结果误差比较大且分布不均匀,小波神经网络和模糊神经网络预测结果明显好于灰色预测模型和小波分析法。     

应用PSO-KELM模型预测水文时间序列

水文时间序列预测对于水文水利决策有着重要的意义。鉴于水文时间序列的复杂性,提出了一种水文时间序列的混合核PSO-KELM预测模型:将极限学习机(extreme learning machine,ELM)模型应用于水文时序预测研究,基于多核学习思想,构造由径向基核函数和多项式核函数加权构成的混合核函数,其综合了径向基核函数和多项式核函数的优点,并通过粒子群算法(particle swarm optimization,PSO)对模型的参数进行寻优,避免了人工操作造成的繁琐性和主观性。兰州站年径流量和金沟河流域年径流量实测数据被用来验证新模型合理性。通过两个算例表明:新模型能够获取比BP模型、RBF模型更好的结果。     

基于VMD-PSR-BNN模型的月径流预测方法研究

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...     

基于Shapley值的农机总动力组合预测方法

应用合作博弈中的Shapley值方法,通过分配总误差来确定组合预测模型中各预测模型的权重,以此构建组合预测模型并对山西省农机总动力进行组合预测.结果表明,该组合预测模型的预测平均误差为1.81,低于选定的一元线性回归模型、三次指数平滑模型和BP神经网络模型的3.12、2.42和2.23;也低于基于方差倒数法以及基于离异系数法构建的组合预测模型的预测平均误差1.88和1.90.     

水分特征曲线Gardner模型参数的预测模型对比分析

为实现土壤水分特征曲线Gardner模型参数的预测以及精度的对比,以山西省黄土高原区农耕土壤为试验材料,进行了土壤水分特征曲线的系列试验,构建了土壤水分特征曲线Gardner拟合模型参数a、b和对应的土壤基本理化参数的数据样本;采用BP神经网络与支持向量机两种预报模型对土壤水分特征曲线Gardner模型参数a、b实现了预测,并对预测精度进行了对比。研究结果表明:随着两种模型输入变量的增加,两种预报模型的精度都得到提高;当输入变量为土壤质地、土壤容重、土壤有机质含量、土壤无机盐含量时,两种预报模型对参数a、b的平均相对误差值均在6%以下,预测模型具有可行性;同时,相比于BP神经网络而言,支持向量机预报模型精度相对较高,而且预测结果波动空间较小,离散程度较低。该成果一方面丰富了Gardner模型参数的土壤传输函数创建的途径,更为Gardner模型参数预测模型的选择提供了依据。     

基于小波方差分析的BP神经网络年径流预测

开展径流量的预测研究,将为水资源的优化配置提供科学的理论基础。以卡拉贝利水文站50年实测径流资料为例,利用Matlab软件对数据进行小波方差分析,分析不同时间尺度下的趋势性和周期性,为径流预测输入因子提供依据;再结合BP神经网络实现不同周期下的年径流的预测,结果表明,与未经小波方差分析的神经网络预测模型相比,精度高。     

基于差分模型和最小二乘法的组合预测模型在实时洪水预报中的应用

洪水预报系统因其动态性、不确定性,加大了洪水预报的难度,一直以来许多水文工作者致力于洪水预报的研究工作。最优组合预测模型具有最大信息利用原则和最小均方误差原则的特点,因而被广泛地运用在预报上。在洪水预报中,递推最小二乘算法是对洪水预报模型的参数进行校正的一种实时洪水预报方法。本文分析了最优加权组合预测模型的基本原理,提出了差分模型和衰减记忆的最小二乘递推算法的组合预测模型,并将该模型应用到实时洪水预报中。实例应用表明,所建立的预测模型具有较高精度和较好稳定性的特点,为实时洪水预报提供了一种新的途径。     

Overland water and salt flows in a set of rice paddies

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.     

瓦房店市水果生产标准化发展研究

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。     

金谷子耐旱TG118引种试种及推广应用

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。     

对《种子法》存在问题的探讨

《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。     

Review of the Egyptian experience in implementing land drainage projects

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.     

和谐社会理论建设的几点哲学思考

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。     

A European irrigation map for spatially distributed agricultural modelling

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.     

粉质仪和拉伸仪在面粉生产中的应用

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。     

农村信息化服务的现状及建设措施

分析当前我国农村信息化服务的现状,提出加强农村信息化服务的新举措。     

车辆ABS控制算法的研究及探讨

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。