京杭运河底泥起动和冲刷率试验研究

京杭运河是南水北调东线工程的重要输水通道,减少底泥冲刷引起的污染对保护其水质有重要的作用。利用文献中的底泥起动流速公式和冲刷率公式,推导出起动摩阻流速与湿密度公式、摩阻流速与冲刷率公式。以京杭运河底泥在水槽内进行不同湿密度的起动试验和不同水流条件下的冲刷率试验。试验结果用最小二乘法进行拟合,得到底泥起动时临界起动摩阻流速与湿密度的相关关系,冲刷时摩阻流速与冲刷率的相关关系。结果表明,有关试验数据的相关性较好,对实际工程应用有一定的指导意义。     

京杭运河底泥起动和冲刷率试验研

京杭运河是南水北调东线工程的重要输水通道，减少底泥冲刷引起的污染对保护其水质有重要的作用。利用文献中的底泥起动流速公式和冲刷率公式，推导出起动摩阻流速与湿密度公式、摩阻流速与冲刷率公式。以京杭运河底泥在水槽内进行不同湿密度的起动试验和不同水流条件下的冲刷率试验。试验结果用最小二乘法进行拟合，得到底泥起动时临界起动摩阻流速与湿密度的相关关系,冲刷时摩阻流速与冲刷率的相关关系。结果表明，有关试验数据的相关性较好，对实际工程应用有一定的指导意义。     

山区性河道整治工程冲刷深度分析与计算初探

河道堤岸建设与人民群众生命财产安全息息相关,堤岸设计是否合理显得尤为重要。在河道整治工程尤其是山区性河道整治工程的设计中,河流冲刷深度的确定,对堤岸设计起关键的指导作用。通常,河流的冲刷深度与流速、水深、泥沙粒径等多种因素有关,并主要受水流流速控制。为了确定冲刷深度的计算方法,自19世纪以来,国内外专家学者通过研究及理论推导,提出了很多用于计算河道冲刷深度的公式,但这些公式大多为经验公式,且各有侧重,计算值差别较大。因此在具体的河道整治工程中,对各种冲刷深度计算方法进行比较分析十分必要。以西苕溪上游的山区性河道护岸设计为例,研究探讨如何结合工程实际和相关设计规范,合理计算冲刷深度,指导堤岸设计,保障防汛安全。     

单圆柱桥墩冲刷的三维数值模拟

桥梁防护中由于桥墩周围的绕流冲刷极其复杂,迄今对该绕流流态及其与河床冲刷关系的认识仍不完善。为了深入分析圆柱桥墩周围的三维水流结构及冲刷现象,利用Flow-3d三维模拟软件对不同流速下的圆柱绕流流态进行数值模拟并和模型实验对比另对圆柱桥墩周围的冲刷做了初步的模拟分析。结果表明,Flow-3d可以清楚地反映桥墩周围的水流流态并通过了模型实验结果验证。说明Flow-3d可以准确模拟单圆柱绕流并获得流场的三维瞬时流速和冲刷现象,本研究可为河床中桥墩附近的冲刷计算和防护设计提供重要的参考。     

崩岸规模的一种预测模型探讨

为了能够对崩岸规模进行预测，根据崩岸的类型和机理，利用泥沙运动力学和土力学理论，建立了一种预测崩岸规模的数学模型。此模型考虑了水流的侧向冲刷和底部冲刷，两者冲刷量取决于河岸土质、河床特性、水流的作用。通过算例表明此模型是合理的。     

出山店水库泄水闸局部冲刷及动床模拟试验研究

低水头闸坝工程泄洪时普遍存在消能不充分、出池水流强烈冲刷下游河床等问题,直接威胁到泄水建筑物乃至整个水利枢纽的安全。在相同水力条件下通过10组不同试验材料的局部冲刷试验,研究局部冲刷的机理,分析冲刷部位的流速、流态情况,总结试验材料的不均匀系数和孔隙率对冲刷结果的影响。在此基础上,类比于伊兹巴什公式,运用曲线拟合的方法,得到新的冲粒料起动流速经验公式,为以后的局部冲刷试验选择试验材料提供了一定的依据。     

径流冲刷条件下坡地养分随地表径流迁移数学模型

径流冲刷是土壤养分随地表径流流失的重要影响因素之一。为了模拟径流冲刷作用对土壤养分流失的影响,依据饱和土壤条件下有效混合深度概念,建立了径流冲刷条件下坡面土壤养分向地表径流传递的有效混合深度模型。利用试验数据对模型径流养分质量浓度变化过程的效果进行了检验,结果显示不完全混合模型在模拟径流养分质量浓度随放水时间的变化方面效果较好,决定系数均在0.9以上。通过不完全混合模型计算径流养分累计流失量,与实测数据差异很小,当养分为硝态氮时,计算值与实测值之间的相对误差分别为6.6%(柠条)和5.9%(大豆),当养分为水溶性磷时,相对误差分别为1.1%(柠条)和2.3%(大豆),说明模型的模拟精度较高。在选择模型时,应根据计算精度和参数获取方便性等情况综合确定。     

一种新试验方法下二灰稳定粒料抗冲刷性能的研究

鉴于几种传统试验方法对养护龄期较长的半刚性基层混合料试件冲刷效果不理想的现状,在比较国内外冲刷试验设备的基础上,提出了一种简便有效的半刚性基层材料冲刷试验方法.基于新的试验方法,并采用冲刷率作为抗冲刷性能的指标,研究了不同养护龄期、不同水压和冲刷时间下二灰稳定粒料的抗冲刷性,最后简要分析了冲刷率与试件强度之间的关系.试验表明:二灰稳定粒料试件的冲刷率,随试件养护龄期的增加而迅速减小,到90 d龄期时受冲刷水的影响很小;随二灰稳定粒料试件的抗压强度逐渐增加,其抵抗水冲刷的能力逐渐增强.     

输电线路塔基全风化花岗岩坡面径流冲刷侵蚀试验研究

经现场调查发现全风化花岗岩塔基的主要破坏形式之一为坡面冲刷,而目前全风化花岗岩坡面冲刷实验还没有相关报道.本文通过径流冲刷试验,研究了输电线路塔基全风化花岗岩边坡坡面冲刷的变化规律,并应用侵蚀模数的概念来评价坡面的抗侵蚀能力.同一种土体不同干密度冲刷试验结果表明,对于不同干密度的全风化花岗岩边坡干密度越大冲刷量越小;对于一定干密度的全风化花岗岩冲刷量随着时间的增加而增加,当坡面形成冲沟时冲刷量明显变大并最后趋于稳定;通过不同土体冲刷实验发现了两种极容易冲刷土体.     

汉江崔家营水库修建后坝下游河床

以崔家营航电枢纽为代表,运用一维非恒定非均匀泥沙数学模型预测了枢纽下游河道冲刷趋势,数学模型预测成果表明航电枢纽修建后坝下游河道最大累计冲刷量与河床冲刷厚度均不大。通过对丹江口水库建库前后下游河道来水来沙和河床观测资料进行分析后发现,由于丹江口水库运行后下游河道发生了长时段、长距离的冲刷侵蚀,河床已较丹江口水库建库前有较明显的下切和粗化。另外因枢纽抬高水位不大,枢纽的兴建不会导致坝下游河床发生较大幅度调整。数学模型计算成果,可以为航电枢纽相关方面设计提供参考。     

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。