钉螺静水和动水沉降试验研究

推导了钉螺静水沉速，动水沉速和动水深降距离公式，这些公式是以螺龄为基本参数进行计算的，并通过试验了各项系数，分析了钉螺静水沉降和动水沉降的基本规律。     

钉螺的静水沉速及其在江河中扩散运动方式初探

 本文讨论了钉螺在水中运动的两个问题:钉螺的静水沉速和在江河中扩散运动方式。应用泥沙运动理论对钉螺静水沉速资料进行分析,研究钉螺在静水中沉降阻力系数变化规律和阻力系数与雷诺数的关系,从而了解了大小钉螺沉降的阻力性质,并建立了大螺、中螺和幼螺不同的沉速公式。钉螺在天然河道中的扩散方式与河道水流的水力因素有关,根据长江中游和汉江中下游河流的水流特性、输沙特点,并结合钉螺在静水中沉降运动规律,提出了钉螺在上述河道中扩散运动方式的判别式。由于活钉螺的生物、生态特征对其迁移、扩散具有     

钉螺截留装置的试验研究

针对钉螺主要通过吸附在各种载体上随水流漂移扩散的特点，研制了一种与渠首节制闸融为一体的钉螺截留装置。该装置由分离池，沉降池和集螺池组成，在分离池中，借助水跃水动力作用使钉螺与载体分离，然后被分离的钉螺借助重力的作用在低流速的沉降池中沉降到集螺池中，最后将钉螺中杀灭。     

黄河流域黏性泥沙群体沉速计算分析

针对黄河流域由黏性矿物组成的黏性泥沙群体沉降特征展开研究。基于泥沙颗粒受力分析和能量守恒定律,以处于稳态的泥沙颗粒为参照物,构建了泥沙颗粒水沙界面能量耗散物理图形;建立了考虑挟沙水流运动黏性系数和紊动黏性系数的泥沙群体沉速显式表达式,并采用黄河流域典型黏性泥沙红色砒砂岩颗粒开展了泥沙群体沉速试验研究。结果表明：红色砒砂岩组成的含沙水体中泥沙群体沉速整体随含沙量增大而减小并逐渐趋于定值;当垂向平均含沙量为0.34～0.45 kg/m³时,泥沙群体沉速表现为随含沙量的增加而增大。采用试验数据对建立的公式进行验证,公式能较合理地表达水流黏性和尾流分离对泥沙颗粒沉降阻力的影响。研究结果可为黄河流域黏性泥沙淤积和输移规律研究提供参考。     

动水中非均匀沙沉降规律的试验研究

本文介绍了利用自行设计的锥形沉降筒，进行非均匀沙动承中沉降试验的研究成果，提出了非均匀沙群体沉速公式。对非均匀抄各粒径组的沉速也进行了初步探讨，得到了非均匀抄各粒径组沉速的规律。最后利用实测的沉降资料，对非均匀沙群体沉速公式进行了验证，说明了非均匀沙群体沉速公式有较好的可靠性和精度：     

钉螺起动流速试验研究

 阐述了钉螺起动流速试验研究成果。由于钉螺对河床具有吸附作用，因而钉螺起动可概括为三种不同起动状态：第一种为定床有吸附力起动，起动流速在１．０ｍ／ｓ以上；第二种为动床有吸附力起动，起动流速约在０．３～０．４ｍ／ｓ之间；第三种为无吸附力起动，起动流速在０．１４～０．１９ｍ／ｓ之间。钉螺无吸附力起动可利用钉螺起动流速公式计算。     

潮汐水流中细颗粒泥沙絮凝沉降的初步探讨

通常采用泥沙的静水沉速,以计算水流的挟沙能力,在理论上是不合适的.影响泥沙沉降的因素,在紊流中是水流的紊动扩散等,而静水中仅有布朗运动.此外,根据潮汐水流的原状水样试验及实测资料分析结果,都表明动水中泥沙的絮凝沉速较静水的絮凝沉速约大十余倍. 阿尔卡门等人认为细颗粒的紊动扩散与脉动流速平方的平均值及粒径的关系较大,就提出了紊动扩散系数公式(7).我们对该式的比例常数K_s进行尺度分析,并对天然河道的含沙量分布不均匀性提出了修正系数.最后求得泥沙絮凝前后粒数比的近似计算式(20),然后利用美国萨凡娜港湾和长江口的全潮观测资料,进行分析计算,计算结果与实测数据比较符合.此外,我们分析河道紊动强度与人工紊动试验流速梯度G之间关系,以验算实测资料,表明絮团尚未到达破裂程度.     

钉螺在动水中运动特性研究

通过试验，研究了钉螺在动水中爬行运动和钉螺在动水中的起动流速，推导了钉螺在开厣状态下起流速公式，还根据试验结果描述闻不同流速区段钉螺运动特性，分析了钉螺在渠系中扩散方式，从而为防止钉螺扩散提供了理论依据。     

細顆粒泥沙在靜水中的沉降运动

在靜水中的泥沙沉速,是研究泥沙运动規律时的一个重要指标.本文首先从泥沙的靜水沉降和水流中起动的一般規律出发,給出了細顆粒泥沙界說的分析过程和結論,并討論了在分散体系和集成体系中有关細顆粒泥沙組靜水沉速的計量标准.其次从絮擬作用对于細顆粒泥沙靜水沉降的影响出发,分析并解释了細顆粒泥沙在靜水中沉降的一般性規律.最后給出了在各种情况下計算細顆粒泥沙靜水沉速的建議公式.     

矿浆管辺水力(车入)送的试验研究

原文在试验的基础上,根据水流挟沙原理,提出了明槽和管道输送高与低浓度矿浆的临界流速公式。今仅就高浓度输送的几个问题,提出如下讨论意见。一、关于输送矿浆浓度对沉速的影响和修正系数的问题。原文正确地认为,当浓度增大到某一值后,输送临界流速由上升而变为下降,其原因在于矿砂细粒子含量的增加,使得矿浆中粒子的比表面积有较大的改变,从而引起了浑水的物理化学性质的变化。但又认为这种质变是清水动滞性系数V_0按(11)式变为V_m,从而以与沉速成反比的关系使矿砂沉速由清水中的ω_0减少到ω_m,同时用修正系数(12)式来修正低浓度公式。经将(9)、(10)式和(13)、(14)式比较后可知,文中     

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。     

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。     

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.