Application of Greek lignite as an additive for controlling rheological and filtration properties of water–bentonite suspensions at high temperatures: A review

This review paper presents the results of an extensive study investigating whether addition of 3% w/w Greek lignite to 6.42% w/w water–bentonite suspensions, after being exposed to high temperatures, can prevent gelation and control filtration characteristics. Two different bentonites and eight lignites from different Greek basins have been used while a commercial lignite product has been used as standard. The lignite-free bentonite suspensions heated to 177 °C for 16 h (thermal aging) thicken considerably, increasing the yield stress and the yield point. Fluid consistency and flow behavior indices also change while no significant change is observed for plastic viscosity. Thermal aging of the suspensions results in unacceptably high fluid loss values.Addition of Greek lignite to water–bentonite suspensions, followed by thermal aging, provided the rheological stability of the suspensions by maintaining the low yield stress/point regardless of the type of bentonite. Some of the lignites performed as well as their commercial counterpart. No specific trends for rheological improvement have been identified with respect to various characteristics of lignites such as contents of humic, fulvic acids, humins and other parameters such as specific surface area and cation exchange capacity.Furthermore, addition of lignite in most cases provided very good filtration control of the water–bentonite suspensions after exposure to 177 °C, with some Greek lignites being superior to the commercial product. The same lignite parameters examined for rheological control, were also examined to determine their effect on fluid loss of these suspensions for both bentonites. The content of humic and fulvic acids of two groups of lignites showed weak inverse correlations with the fluid loss volumes for both bentonites, while all other parameters did not seem to directly correlate with the effectiveness of the lignites.     

苏皖凹凸棒石粘土水悬浮液流变性能研究

研究了3种苏皖凹凸棒石粘土水悬浮液的流变性,讨论了矿物种类、粘土颗粒大小、NaCl浓度、pH值、电解质类型、分散剂添加量等影响因素对于凹凸棒石粘土水悬浮液流变性的影响,并用卡森模型对3种凹土流型曲线进行了拟合.结果表明,不同凹土中含有少量不同杂质对流变性能影响不大;经过挤压的土样粘度明显大于原矿粉碎的样品;粘土颗粒大小、溶液pH值、电解质类型、分散剂均会较大程度的影响凹土悬浮液的流变性能,其中分散剂的降粘效果最为明显;而NaCl的浓度增加对凹土悬浮液流变性影响则很小.     

正交设计和方差分析应用于悬浮物和沉积物的EDAX分析条件试验

本文用正交试验和方差分析对悬浮物和沉积物粉末样品的EDAX分析进行了条件试验和数据处理,找出影响试验结果的主要因素和最佳分析条件,提高了分析结果的准确性。     

Hindered settling velocity of cohesive/non-cohesive sediment mixtures

New methods are proposed for predicting the hindered settling conditions encountered by concentrated suspensions containing mixtures of sand particles and mud flocs. These methods, based on two-fraction formulations, are developed by consideration of the settling characteristics of monodisperse and polydisperse solid particle suspensions applied to cohesive/non-cohesive mixtures of mud flocs and sand particles. The behaviour of these predictive methods is evaluated over a wide range of mixture conditions and compared with existing formulations, with their parametric dependence on the relative volumetric concentrations and floc/particle sizes for the mud and sand constituents established. The results indicate that consideration of the full return flow effects generated by both fractions provides the best modelling framework for predicting the hindered settling conditions over a wide range of sand–mud mixtures.     

油气悬挂技术及其在车装钻机中的应用展望

油气悬挂系统具有优越的非线性弹性特性和良好的减振性能，能大幅度改善悬挂系统的性能。介绍了油气悬挂技术在车装钻机的应用现状，指出了油气悬挂系统的引入对车装钻机等特种工程车辆发展的重要性。     

Flow Behavior of Clay-Silt to Sand-Silt Water-Rich Suspensions at Low to High Shear Rates: Implications for Slurries, Transitional Flows, and Submarine Debris-Flows

Water-rich clay to sand suspensions show a shear rate dependent flow behavior and knowledge of the appropriate rheological model is relevant for sedimentological, industrial and hydraulic studies. We present experimental rheological measurements of water-rich (40 to 60 wt%) clay to silt (population A) and silt to sand (population B) suspensions mixed in different proportions. The data evidence a shear rate dependent shear thinning-shear thickening transition. At lower shear rates, the suspensions organize in chains of particles, whereas at higher shear rates, these chains disrupt so increasing the viscosity. The viscosity, consistency and yield stress decrease as the A+B fraction decreases as the content of B particles increases. This behavior reflects the competing effects of the lubrication and frictional processes as a function of particle size and water content. Transitional flows form by the incorporation of small amounts of the finer fraction while ‘oceanic floods’ form at the estuary of rivers and the submarine debris-flows increase their velocity by incorporating water. The critical Reynolds number of the studied suspensions is ~2000±100 suggesting that the grainsize plays a major role in the laminar to turbulent transition. Our results have implications for the modeling of sediment flows and the hazard related to floods.     

渔业生产者参与实施捕捞限额制度意愿的影响因素研究

文章以上海市、浙江省和山东省113户渔业生产者的问卷调研数据为基础,通过运用Logistic回归模型分析渔业生产者参与实施捕捞限额制度意愿的影响因素。研究表明,年龄、受教育水平、渔船总功率、年均捕捞量、捕捞收入与家庭总收入比例、举报奖励额与超额价值比例以及年监管次数均对渔业生产者参与实施捕捞限额制度的意愿产生显著影响。基于实证研究结果,提出应加大渔业培训力度,切实控制渔船功率,暂不设立举报机制以及结合目前的投入控制制度推行循序渐进、逐步严格的监管机制等建议,以提高渔业生产者参与实施捕捞限额制度的意愿,为制定有效的渔业资源管理制度提供参考依据,推进渔业现代化改革。     

RHEOLOGICAL PROPERTIES OF SEDIMENT SUSPENSIONS FROM ECKERNFRDE AND KIELER FRDE BAYS,WESTERN BALTIC SEA

1 INTRODUCTION Fluid mud is defined as a dense suspension of fine-grained sediment particles averaging in density between 1.03 to 1.30 g/cm3 and between 10 to 480 g/l in concentrations by weight (Ingliss and Allen, 1957). It overlies a substrate of densit…     

Fractionation and concentration of suspended particulate matter in natural waters

A scheme for the fractionation and concentration of suspended particulate matter (SPM) from natural waters has been tested. This scheme involves the sequential use of three fractionation techniques—sieving, continuous flow centrifugation and tangential flow filtration to collect gram amounts of SPM over the entire particulate and colloidal size range. The separation scheme is able to process large samples (ca. 1001), within reasonable times (ca. 1 day) and the apparatus is portable. Reproducibility and potential artifacts introducing during the fractionation and concentration of SPM, particularly when tangential flow filtration is used, are discussed. It has been shown that there is a systematic increase in the content of organic carbon, Mg, Ca, Na, K, Cu and Zn with decreasing particle size, highlighting the importance of the colloidal ( < 1 μm) fraction.     

公众参与式地震灾情信息服务平台研究

由政府等权威机构监测、采集地震灾情信息后,向公众通告并指导公众采取应对措施,是当前防震减灾过程中的主要信息流通模式。然而,在这种信息单向流动模式中,公众缺少主动查询获取和反馈灾情信息的渠道,不利于防震减灾和灾后恢复重建。本文针对现有地震信息系统在公众信息服务方面的不足,首先分析了公众参与式地理信息系统（Public Participation Geographic Information System,PPGIS）的特点及应用,从地震灾害管理的整个周期出发,将地震灾害信息分为4大类,进行平台数据库和功能设计;随后,探讨了基于PPGIS的大众地震信息服务平台,在公众主动获取多源地震灾情和地震知识、提交和反馈灾情信息与救助需求,以及参与灾后重建等方面的作用,并分析了该平台中用户数据质量及质量控制流程;最后,在此基础上,设计并实现了基于PPGIS的大众地震灾情信息服务平台原型系统,为解决公众地震灾情获取和反馈提供了可行性方案,为类似系统的设计与实现提供了参考。