农田土壤水分变化特征分析

1概述田间土壤墒情是农田耕作层土壤含水率的俗称。田间土壤墒情的监测,作为非工程节水的配套技术,是农业用水和区域水资源管理的一项基础工作,对农田灌溉排水的合理实施、农作物的增产与节约用水、四水转化关系的分析和提高水资源利用     

土壤墒情自动监测与人工烘干法比测研究

以连云港孙沟站为例,介绍了土壤墒情自动监测系统比测方法。历时4个月,收集21组数据,将率定后的机测体积含水量与烘干法所测的重量含水量通过干容重换算得到的土壤体积含水量进行比测。机测的含水量与土壤实际含水量相关性很好。数据合格率为85.7%,大于80%的要求。土壤墒情自动监测系统运行稳定可靠,无数据丢失。土壤墒情自动监测系统可以替代人工监测,将为抗旱决策提供完整、及时、准确的墒情数据。     

千封土壤墒情浅析

2013年开封地区降水量偏少,旱情发展严峻。及时掌握监测的土壤墒情信息,对抗旱减灾、农业灌溉、政府职能部门领导决策具有重要的指导作用。文章叙述了土壤墒情的概念、测墒方法及其优缺点、土壤墒情的观测时间、墒情要素及旱情标准,并对2013年开封旱情做了分析,探讨了逐步完善的测墒改进措施,展望了未来土壤墒情的监测趋势。     

田间持水量测定成果合理性分析

田间持水量是土壤排除重力水后的最大土壤含水量,是对作物有效的最高土壤水含量,也是进行土壤墒情评价的重要依据。由于田间持水量测定方法、测定条件等的不同,导致测定结果也不尽相同,为此对田间持水量测定成果进行合理性分析非常必要。从测定方法、测定条件、土壤质地、退水过程、墒情评价等方面,阐述了墒情站点的田间持水量测定成果合理性分析过程,为土壤田间持水量测定、成果分析验证、墒情评价、旱情分析等提供借鉴和参考。     

移动墒情自动测报系统设计的思考

由于我国墒情信息自动采集起步较晚,在站网布设、仪器设备研发、信息采集等方面存在诸多问题,已严重影响了我国土壤墒情监测和抗旱减灾工作。为此,进一步规范土壤墒情自动监测系统设计与工程建设,保证土壤墒情自动测报质量就显得十分重要。目前,我国现有墒情监测方式主要分为人工墒情监测、固定墒情自动监测、移动墒情自动监测三种。其中,移动墒情自动监测以其机动灵活、简单方便、快速高效等特点,在土壤墒情监测工作中发挥了重要的作用,已成为土壤墒情信息采集主要方式之一。文章从生产实际出发,结合有关国家墒情项目设计和技术规范,系统地论述了移动墒情自动测报系统设计的基本思路与方法,提出了移动墒情站点布设原则、监测功能、仪器配置、信息传输与接收方式等,为土壤墒情工程设计、站网建设、监测与评价、运行管理等提供借鉴和参考。     

基于农田灌溉监测管理技术应用

针对当前农田灌溉水利用监测手段落后、点多面广工作量大、监测信息管理技术水平低下等问题,提出农田灌溉水利用监测管理技术应用研究。运用土壤水分运行原理、灌溉水量平衡、水利经济等分析方法,采用国产E生态固定智能式墒情监测设备,基于B/S系统结构和终端程序共访中心数据库构架下的相联网技术设计研发,实现了农田用水定额、灌溉水利用率、土壤墒情、灌溉制度、作物灌溉效益的自动化监测管理目标,为现代化农业灌溉水资源有效利用管理提供了技术支持。     

沙箱法测定土壤田间持水量实验研究

田间持水量可以反应土壤对作物水分的供给状况,通过和土壤结构以及其他土壤水分参数的结合,可以有效监测土壤旱情.但是传统的室内和田间测定方法都较为复杂,为实际土壤墒情监测带来了一定难度[1,2].本研究采用优化的沙箱法测量田间持水量,通过对淮北平原的三种代表性土壤进行了试验,结果显示沙箱法对于测定土壤田间持水量具有可靠性和实用性,为土壤墒情的日常监测工作提供了便捷有效的测定手段.     

卫星遥感技术在黑龙江省土壤墒情监测中的应用

在干旱灾害防御工作中，土壤墒情的高低是判断干旱的重要指标之一，也是启动应急响应开展各类抗旱行动的判别依据。当前黑龙江省采取多种方式获取土壤墒情数据，全方位做好土壤墒情监测工作，及时掌握旱情发展变化，既坚持传统的人工抗旱报表方法和气象部门的人工取土测墒外，还通过卫星遥感技术以及固定移动土壤墒情监测仪器获取墒情数据。文章介绍了卫星遥感技术与自动土壤墒情测报技术的优势和劣势，及其在黑龙江省土壤墒情监测中的应用，并对今后的土壤墒情监测工作提出了4方面的建议。     

河南省土壤墒情监测发展及土壤特性参数测量

河南是农业大省,全省耕地面积为792.6万hm2,居全国第3位,是全国重要的优质农产品生产基地。近几年,河南省连续发生了不同程度的旱灾,影响了粮食生产。河南省水文水资源局自2002年开始,就开始建设土壤墒情监测站点,为抗旱夺丰收提供了科学依据。本文介绍了河南省土壤墒情监测系统的发展以及采用的监测仪器及基本原理,阐述了河南省测量确定土壤田间持水量等特性参数的测量方法。     

江苏省墒情自动监测系统的设计与应用

为准确迅速地掌握江苏省主要地区土壤墒情信息,按照《国家防汛抗旱指挥系统二期工程(江苏部分)墒情采集系统》项目要求,共建立江苏省13个水文分局的27个固定墒情自动监测站和40个移动墒情自动监测站。以固定墒情自动监测站的设计及应用为例,详细论述了该墒情监测系统的背景、设计及应用情况,并对系统监测的准确性进行测试与分析。结果表明,该系统实现了江苏地区土壤墒情监测、信息传输的自动化,可以实时掌握全省的土壤墒情状况,为防汛抗旱工作提供准确的依据,其设计理念及相关应用经验可以供相关地区参考借鉴。     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera

Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m^?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m^?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m^?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m^?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m^?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river.     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。