粉煤灰对水泥胶砂力学性能的试验研究

针对大掺量粉煤灰对水泥胶砂力学性能的影响规律进行试验研究,结果表明,合理选择粉煤灰的掺量能有效提高水泥胶砂的力学性能;粉煤灰的掺入导致水泥胶砂早期强度低,但有利于后期强度的增加.另外,粉煤灰能降低水泥胶砂脆性系数,有利于提高其抗裂性能.     

矿渣和粉煤灰混凝土的抗裂性能研究

矿渣作为掺合料在混凝土中的应用日益普及,掺量也不断提高,尤其在硫酸盐、氯离子和海水侵蚀环境的混凝土中,矿渣粉和粉煤灰是不可或缺的重要组分。研究发现,掺入矿渣粉和粉煤灰使水泥胶砂的脆性系数明显减小,而且随着掺量增大,脆性系数具有减小的趋势,有利于降低胶砂和混凝土的开裂倾向。从长期来看,矿渣混凝土抗裂性优于空白混凝土,而粉煤灰混凝土与空白混凝土大致相当,或稍优。延长养护时间,可减小混凝土的脆性系数,提高极限拉伸值。     

掺粉煤灰和磷渣混凝土的性能试验研究

研究了掺粉煤灰、磷渣对混凝土力学性能、耐久性和变形性能的影响。结果表明,混凝土的抗压强度和极限拉伸值均随着粉煤灰掺量的增加而降低;用磷渣等量替代粉煤灰后,混凝土强度与普通混凝土相比基本相当或略高,极限拉伸值增加较多,干缩也略有增加;在混凝土中掺入适量的粉煤灰或磷渣均有利于改善混凝土的抗渗性和抗冻性。     

粉煤灰与矿渣粉对水泥水化热及胶砂强度影响

对单掺粉煤灰、单掺矿渣粉及双掺粉煤灰和矿渣粉进行了水泥水化热试验和水泥胶砂强度及扫描电镜分析,试验结果表明,粉煤灰的掺入,降低了胶砂的早期强度,但后期强度增长较快;单掺矿渣微粉的胶砂,当掺量不大于50%时,其7 d的强度已达到纯水泥砂浆的强度;双掺矿渣粉和粉煤灰的胶砂,可以发挥矿渣粉早期强度高和粉煤灰后期强度增长快的特点,两种优势互补,其效果较佳.     

粉煤灰与磷矿渣对水泥水化热及胶砂强度的影响

试验研究了单掺粉煤灰和复掺磷矿渣与粉煤灰(PF料)对水泥水化热及水泥胶砂强度的影响,结果表明:水泥水化热随粉煤灰和PF料掺量的增大而降低;与纯水泥相比,掺粉煤灰或PF料的水泥7 d水化热降低百分率均低于掺合料(粉煤灰、PF料)替代水泥的百分率;复掺PF料的胶砂抗压强度比单掺粉煤灰高,且PF料对延迟放热峰值出现时间比粉煤灰好。     

掺磷渣、粉煤灰对水泥水化热的影响研究

试验研究了单掺磷渣、粉煤灰,复掺磷渣与粉煤灰对水泥水化热的影响。研究结果表明,对于单掺磷渣,水泥水化热随磷渣的掺量增加而降低,但水泥水化热降低的比例小于磷渣掺量增加的比例。随着龄期的增长,7 d的水化热要明显大于3 d的水化热。龄期越长,水泥水化热随着磷渣的掺量增加而降低的比例越小。等量的粉煤灰(单掺)、磷渣与粉煤灰(复掺)在掺入水泥后的水化热和单掺磷渣的水化热相差不大,具有与单掺磷渣类似的规律性。     

矿物掺合料改善水泥砂浆脆性和抗裂性的研究

随着高强混凝土在工程中的不断应用,混凝土的水灰比越来越小,减小水灰比虽然可以提高混凝土或砂浆的抗压强度,但同时也会使其脆性增强、抗裂性变差。矿物掺合材料在工程中使用很广泛,它们的掺入对混凝土的脆性、强度都会产生影响。选取三种工程中较常采用的矿物掺合材料——粉煤灰、硅灰和MgO粉末,通过改变掺量和掺加方式来研究它们对砂浆强度、脆性的影响。试验结果表明,砂浆脆性随着自身强度的提高和养护龄期的延长而不断增强。随着胶凝材料含量的增大,砂浆的抗压强度提高,同时其脆性有一定程度下降。粉煤灰掺量越高,砂浆脆性下降得越多,但粉煤灰的掺入对砂浆早期强度的发展会产生不利影响。掺入一定量的硅灰不仅能提高砂浆的抗压强度,而且能很好地降低其脆性,提高抗裂性。掺入MgO粉末也能降低砂浆的脆性,但同时对其抗压强度特别是早期抗压强度有明显降低作用。因此,在实际工程中,建议双掺适量粉煤灰和硅灰,这不仅可以显著降低砂浆的脆性,而且可以弥补粉煤灰对早期强度的不利影响,使中后期强度不低于甚至高于基准砂浆的强度。     

硅灰对胶砂性能影响的试验研究

为研究硅灰对水泥胶砂力学性能、干缩性能的影响,在不同水胶比下研究了不同掺量硅灰对水泥胶砂的流动性、抗压强度、抗折强度和干缩率的影响。试验结果表明,2种水胶比下水泥胶砂的跳桌流动度呈现相同变化趋势,均随着硅灰掺量提高而降低;硅灰的掺入对不同水胶比的水泥胶砂强度均有提升,0.40水胶比下,10%硅灰掺量28 d抗压和抗折强度较基准组分别提升17.7%、11.0%,0.45水胶比下,10%硅灰掺量28 d抗压和抗折强度较基准组分别提升21%和12%;硅灰的掺入会提升2种水胶比胶砂的干缩率,均随着掺量的增加而增大,水胶比为0.40时干缩率更大,水胶比为0.45时60 d干缩率较基准组提升更明显。     

粉煤灰与硅灰对水泥胶砂抗酸腐蚀性能的影响

通过对7组水泥胶砂受硝酸腐蚀前基准强度及腐蚀后质量损失率和中性化深度的研究,分析了粉煤灰、硅灰对胶砂抗酸腐蚀性能的影响。结果表明:在硝酸腐蚀条件下,随粉煤灰掺量增大,胶砂的质量损失率呈降低趋势,中性化深度呈增大趋势,粉煤灰的掺量为15%时,胶砂抗酸腐蚀性能改善较为明显;随硅灰掺量增大,胶砂的质量损失率呈先降低后增大趋势,中性化深度呈增大趋势,硅灰掺量为5%时,胶砂抗酸腐蚀性能改善较为明显;按单掺最优掺量混掺粉煤灰和硅灰,对胶砂的抗酸腐蚀性能的超叠加效应不显著;对掺加掺合料的胶砂,决定其抗酸腐蚀性能的主要因素是胶凝材料组成而不是强度。     

矿渣和粉煤灰对胶砂力学性能的影响研究

矿渣和粉煤灰作为掺合料在混凝土中的应用日益广泛,掺量也不断提高,尤其在硫酸盐、氯离子和海水侵蚀环境的混凝土中,掺合料是不可或缺的重要组分。该文研究了大掺量矿渣和粉煤灰对水泥胶砂力学性能的影响规律,结果表明,水泥胶砂的早期强度随着掺合料掺量的增加而降低,但掺合料的加入有利于提高水泥胶砂的后期强度,提高其折压比,降低其脆性系数,从而改善其抗裂性能。     

长江中游四大家鱼发江生态水文因子分析及生态水文目标确定

基于长江中游四大家鱼发江量历次调查数据,采用宜昌站作为长江中游水文情势变化分析的控制站,基于其1900~2004年共105年的日径流资料,采用每年5~6月涨水过程数、总涨水日数、平均每次涨水过程日数等3项生态水文指标,分析了四大家鱼发江量与3项生态水文因子的变化关系,认为产卵场所处江段每年5~6月的总涨水日数是决定家鱼苗发江量多寡的一个重要环境因子。根据IHA方法,对宜昌站105年来的生态水文指标分析表明,长江宜昌站生态水文过程的改变并不明显,5~6月总涨水日数变化趋势不显著,显示长江中游影响四大家鱼苗发江量的生态流量过程改变不明显,与前人得出的葛洲坝枢纽修建后四大家鱼的产卵条件和卵苗江汛规律没有变化这一认识一致。但是,随着三峡水库的运行,下游河道的生态环境流量过程会有较大改变,本文建议三峡水库的调控以保障长江中游每年5~6月的总涨水日数维持在22.1±7.2范围内为生态水文目标,即可从生态环境流量过程方面补偿水利工程对中游四大家鱼鱼苗发江量的影响。     

Seminar on Water and Energy,Stockholm, Sweden,August 21, 2005

Abstract

In Europe the implementation of the Water Framework Directive (WFD) will have major implications for water resources management. Part of the Directive requires Member States to implement a comprehensive system of controls (licences) on the allocation and abstraction (withdrawal) of surface and groundwater resources. This paper describes the development of a procedure to help assess and set abstraction licences for agricultural irrigation. The methodology is described with reference to Scotland, a country with limited abstraction control previously and where irrigation is supplemental to rainfall. The methodology combines spatial climatic information using a Geographical Information System (GIS) with data derived from a water balance computer model. The procedure enables the volumetric irrigation demand in a ‘design’ dry year for a given site to be estimated, taking into account local variations in climate, soil type, land use and irrigation practices. The approach provides a scientifically robust framework to allow the regulatory authority to assess the ‘reasonable’ water requirements of individual irrigators and hence develop allocations to satisfy the range of competing demands (e.g. agriculture, industry, and environment) on water resources. The methodology is applicable in other temperate countries where water abstraction controls are required and where appropriate datasets are available. The application of the procedure and its methodological limitations are described.     

Stakeholder-driven,enquiry-driven,or stakeholder-relevant,enquiry-driven science?

There is currently debate within the international hydrological community on whether hydrological science should give priority to providing measurements, knowledge, and understanding pre-determined as being needed by stakeholders, or priority to more basic enquiry-driven science that will stimulate the continued health and growth of hydrology as an important Earth science discipline. Two recent major international initiatives in hydrology reflect these two perspectives. One, the Hydrology for the Environment, Life, and Policy (HELP) program, is primarily fostered by UNESCO-IHP and is focused on stimulating the stakeholder-driven hydrological science required in specific catchments that have become members of a global network. The second, the decade on Prediction in Ungauged Basins (PUB), which is appropriately managed by IAHS, is primarily driven by scientific enquiry and is focused on creating new scientific methods and understanding, albeit with practical application ultimately in mind. This paper summarizes the nature, origins, growth, and progress of these two international programs but also describes the subtly different approach that has been adopted by the U.S. National Science Foundation's (NSF's) Center for Sustainability of semi-Arid Hydrology and Riparian Areas (SAHRA). NSF is a federal agency whose primary goal is to ‘enable the future’ by stimulating novel science. Because SAHRA is a federally-funded entity supported by an agency with this goal, the Center clearly cannot operate in stakeholder-driven, response mode in competition with the already effective private U.S. consultancy industry. Nonetheless, SAHRA's mission is to create knowledge and build understanding that will enhance the prospects of sustainable water management in semi-arid regions, especially the southwestern U.S. To resolve this apparent conflict, SAHRA looks ahead to future stakeholder needs and builds its research agenda around selected critical stakeholder-relevant questions that require substantial and sustained investment in basic, multidisciplinary, enquiry-driven science. This paper describes SAHRA's approach and reports on associated research and outreach activities.     

Growth,Reproduction, Mortality,Distribution, and Biomass of Freshwater Drum in Lake Erie

Predominant age-groups in the Lake Erie freshwater drum Aplodinotus grunniens population were 3, 4, and 5 as determined from gill net, trap net, bottom trawl, and midwater trawl samples. Age and growth calculations indicated that females grew faster than males. However, the length-weight relation did not differ between sexes and was described by the equation: log W = ?5.4383 + 3.1987 log L. Some males became sexually mature at age 2 and all were mature by age 6. Females matured 1 year later than males. Three sizes of eggs were present in ovaries; the average total number was 127,000 per female for 20 females over a length range of 270 to 478 mm. Seasonal analysis of the ovary-body weight ratio indicated that spawning extended from June to August. A total annual mortality rate of 49% for drum aged 4 through 11 was derived from catch-curve analysis. Freshwater drum were widely distributed throughout Lake Erie in 1977–1979, the greatest concentration being in the western basin. They moved into warm, shallow water (less than 10 m deep) during summer, and returned to deeper water in late fall. Summer biomass estimates for the western basin, based on systematic surveys with bottom trawls, were 9,545 t in 1977 and 2,333 t in 1978.     

水-能源-粮食纽带关系定量研究方法综述

在总结水-能源-粮食纽带关系研究中, 使用频率较高或潜力较大的 8 种水-能源-粮食纽带关系定量研究方法为: 水-能源-粮食纽带关系工具 2.0( WEF Nexus Tool 2.0) ; 生命周期评价( LCA) ; 可计算的一般均衡模型( CGE) ; 系统动力学模型( SD) ; 气候、土地、能源与水资源策略( CLEWS) ; 基于社会生态系统代谢的多尺度综合评价( MuSIASEM ) ; 市场配置/ 市场配置系统集成模型( MARKAL/ TIMES) 和水资源评价规划模型-长期能源替代规划系统 ( WEAP2LEAP) 。通过总结各研究方法的产生、发展及特性, 并引用案例讨论其适用范围, 分析其优缺点和在使用 时需要注意的问题。在此基础上, 对未来水2能源2粮食纽带关系定量研究方法的发展趋势进行讨论, 认为伴随可持 续发展问题关注度的上升与水-能源-粮食纽带关系内在机理的挖掘, 未来的水-能源-粮食纽带关系定量研究方法将 更加注重量化的精确性和数据的互通以及跨学科研究和多方法的耦合。本文可为水-能源-粮食纽带关系定量研究方法的选择和更新优化提供参考。     

Survival,Growth, and Movement of Subadult Humpback Chub,Gila Cypha,in the Little Colorado River,Arizona

Ecologists estimate vital rates, such as growth and survival, to better understand population dynamics and identify sensitive life history parameters for species or populations of concern. Here, we assess spatiotemporal variation in growth, movement, density, and survival of subadult humpback chub living in the Little Colorado River, Grand Canyon, AZ from 2001–2002 and 2009–2013. We divided the Little Colorado River into three reaches and used a multistate mark‐recapture model to determine rates of movement and differences in survival and density between sites for different cohorts. Additionally, site‐specific and year‐specific effects on growth were evaluated using a linear model. Results indicate that summer growth was higher for upstream sites compared with downstream sites. In contrast, there was not a consistent spatial pattern across years in winter growth; however, river‐wide winter growth was negatively related to the duration of floods from 1 October to 15 May. Apparent survival was estimated to be lower at the most downstream site compared with the upstream sites; however, this could be because in part of increased emigration into the Colorado River at downstream sites. Furthermore, the 2010 cohort (i.e. fish that are age 1 in 2010) exhibited high apparent survival relative to other years. Movement between reaches varied with year, and some years exhibited preferential upstream displacement. Improving understanding of spatiotemporal effects on age 1 humpback chub survival can help inform current management efforts to translocate humpback chub into new locations and give us a better understanding of the factors that may limit this tributary's carrying capacity for humpback chub. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.