Cross‐sectional profiles of sand ripples,megaripples, and dunes: a method for discriminating between formational mechanisms     

James R. Zimbelman  Steven H. Williams  Andrew K. Johnston 《地球表面变化过程与地形》2012,37(10):1120-1125

Cross‐sectional profiles of sand ripples, megaripples, and sand dunes provide a useful tool for discriminating between formation by ripple and dune processes. Feature width, defined as the basal break in slope along the profile to either side of the crest, represents a good standard for comparison of profile attributes across more than three orders of magnitude. Aspect ratio (height/width) as a function of log width separates measurements into clusters representing differing mechanisms of formation. Scaling both height and distance for individual profiles by feature width facilitates comparison of profile shapes across three orders of magnitude in width. The data presented here should prove useful for evaluating possible mechanisms of origin for aeolian features observed remotely, including on planetary bodies. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

连续流气提式流化床启动过程中好氧颗粒污泥的形成机制   总被引：4，自引：0，他引：4  

周丹丹  刘孟媛  侯典训  王紫嫣  梁爽  董双石 《吉林大学学报(地球科学版)》2012,42(1):212-219

探讨连续流气提式好氧颗粒污泥流化床(CAFB)反应器的运行特征,对该工艺颗粒污泥形成过程、形成机理和颗粒性质进行分析。以市政污泥为接种污泥,以醋酸钠为碳源,在连续运行方式下培养好氧颗粒污泥。研究结果表明：CAFB反应器启动的第4－5天即有大量颗粒污泥形成,颗粒直径800~1 000 μm,比重1.006,生物相丰富,能够分泌大量胞外聚合物。当COD有机负荷高达8 和13 kg/(m³·d)时,对COD处理效率均维持在93%~97%,COD出水质量浓度仅为30~80 mg/L,引起启动后期丝状菌的大量繁殖,污泥流失。进一步提高污泥负荷有望控制污泥膨胀。  相似文献   

微生物絮凝剂投加方式对好氧颗粒污泥性能的影响     

宋志伟  王秋旭  宁婷婷  任南琪  李立欣 《吉林大学学报(地球科学版)》2015,45(1):247-254

为提高好氧污泥颗粒化速度, 采用微生物絮凝剂, 探讨在好氧颗粒污泥培养过程中微生物絮凝剂的投加方式对颗粒污泥理化性能及生物降解效能的影响。结果表明:微生物絮凝剂每隔2、3、5、7 d投加一次时, 均可培养出成熟的好氧颗粒污泥, 微生物絮凝剂的投加方式对好氧污泥颗粒化的影响较显著;微生物絮凝剂最佳投加方式为每5天投加一次, 此时颗粒化速度快, 颗粒形成时间由未投加的60 d缩短为42 d, 好氧颗粒污泥疏水性好, 污泥体积指数稳定在40 mL/g左右, 沉降速度达35.06 m/h, COD、氨氮和总磷的去除率分别为96.55%、93.29%和87.29%。  相似文献   

砂卵石粗粒土颗粒外形特征测量与评定初探     

郑星  敖大华  李裕忠  张胜  宋晓伟 《岩土力学》2018,39(5):1805-1810

粗粒土颗粒的外形特征是影响其力学特性及渗流特性的重要因素之一。采用室内试验分析的手段对颗粒的外形特征进行了研究。选取粒径分别为10～20、20～40、40～60 mm的两种不同形状的砂卵石粗粒土颗粒,在风干状态下通过排水法分别测定其体积,通过蜡膜厚度估算法测定其表面积,对颗粒体积及表面积关系进行数学拟合,建立了一定粒径范围内两种不同外形砂卵石粗粒土颗粒体积与表面积之间的函数关系。通过类比,发现试验所得出的两个拟合函数关系式和同体积标准球体的体积与表面积关系式具有十分相似的形式,据此提出了类圆度的概念及类圆度系数的计算方法,为颗粒外形特征的定量描述提供了一种方法与思路。  相似文献   

吲哚类杂环芳香族有机物在好氧和厌氧条件下的微生物降解途径   总被引：2，自引：0，他引：2  

王莹莹  叶彩云  范延臻  顾继东 《矿物岩石地球化学通报》2003,22(2):170-173

用红树林的底泥通过富集培养得到在好氧或厌氧条件下能完全矿化吲哚的细菌，并对降解过程及中间代谢产物进行了鉴定。此研究中，吲哚化合物是培养液中的唯一碳和能量来源，而厌氧条件包括有产甲烷和硫酸盐还原。结果表明，不论在哪种条件下，吲哚噪降解过程分二步敖基化反应，分别发生在2和3位上，形成氧化吲哚和靛红。同时，1、2或3位上的甲基替代使1—甲基吲哚，2—甲基吲哚和3—甲基吲哚的降解受到严重抑制。显然，杂环类芳香族化合物的代谢有其共同点，同时不同替代会完全改变有机物的可降解程度。  相似文献   

黄土微结构区域变化规律及与湿陷性相关性研究   总被引：4，自引：1，他引：4  

薛武海  王桂生  陈志新 《地下水》2005,27(4):310-312,316

黄土中的微结构是影响黄土湿陷的重要因素。本文运用扫描电子显微镜对黄土微结构进行观察并对统计数据进行了分析，结果表明黄土微结构在区域上存在一定的变化规律。即，由西北的粒状、支架接触式结构，逐渐过渡到东南的凝块、镶嵌胶结式结构。通过对黄土矿物颗粒接触关系和孔隙与湿陷性的关系的分析，并根据非饱和土粒间吸力理论分析，认为支架结构孔隙为黄土湿陷变形提供了空间条件，而黄土微结构吸力空间分布的不均匀性是引起黄土湿陷的根本原因。  相似文献   

Aerobic landfill test cells and their implications for sustainable waste disposal   总被引：2，自引：0，他引：2  

Adam D. Read  Mark Hudgins  & Paul Phillips 《The Geographical journal》2001,167(3):235-247

Municipal Solid Waste (MSW) landfills world-wide are experiencing the consequences of conventional landfilling techniques, whereby anaerobic conditions are created within the landfill waste. Under anaerobic conditions, slow stabilization of the waste mass occurs, producing methane, (an explosive, 'greenhouse' gas) and toxic leachate over long periods of time. As a potential solution, it was demonstrated that the aerobic degradation of MSW within a landfill can significantly increase the rate of waste decomposition and settlement, decrease the production of methane gas, reduce the level of toxic organics in the leachate and decrease quantities of landfill leachate that need treatment. This paper summarizes the successful results of two separate aerobic landfill projects located in Georgia (USA) and discusses the potential economic and environmental impacts to world-wide solid waste management.  相似文献   

Predicting dynamic failure of dense granules from static compression tests     

R.E. Maxim  A.D. SalmanM.J. Hounslow 《International Journal of Mineral Processing》2006

This paper shows how static failure loads can be used to predict impact failure of granules. A theoretical model is presented that gives the maximum force experienced during impact and equates this to experimentally measured static failure load to define a critical impact velocity for impact failure. A granule will fail if the predicted theoretical maximum force during impact due to the impact velocity is greater than the real force required to produce failure in that particular granule.  相似文献   

栉孔扇贝血细胞的显微和超微结构     

张维翥  吴信忠  孙敬锋  李登峰 《热带海洋学报》2007,26(3):57-62

通过光镜、扫描电镜和透射电镜观察栉孔扇贝Chlamys farreri血细胞的形态、结构特征,对其分类进行了初步研究。根据细胞的大小、形态和结构特征可将血细胞分成5种类型:Ⅰ型小透明细胞,大小约2.44±0.11μm,约占45%—50%;Ⅱ型大透明细胞,大小约4.83±0.28μm,约占15%—20%;Ⅲ型小颗粒细胞,大小约4.07±0.15μm,约占15%—20%;Ⅳ型中颗粒细胞,大小约7.20±0.26μm,约占20%—25%和Ⅴ型大颗粒细胞,大小约13.87±0.73μm,约占3%—5%。血细胞在血淋巴中的平均密度为(3.03±0.11)×107cell.ml—1,其中颗粒细胞占42.6%,透明细胞占57.4%。透射电镜观察结果表明,颗粒细胞的细胞质颗粒可区分成3种类型:Ⅰ型高电子密度颗粒,Ⅱ型低电子密度颗粒和Ⅲ型中等电子密度颗粒。  相似文献   

Effect of Hydrocarbons and Decontaminating Substances on Bacterial Flora of Coastal Sediments     

Ermanno Crisafi  Renata Zaccone  Lucrezia Genovese  Rosabruna La Ferla  Teresa Luciana Maugeri 《Marine Ecology》1989,10(4):365-375

Abstract. Seventy six samples of coastal sediments collected in the Straits of Messina were studied in order to evaluate the effects of an oil spill and the consequent "clean-up" operations on heterotrophic acrobic bacteria.
In addition, in vitro tests were carried out to estimate the effects of five dispersants on the growth and oil degrading capacity of marine strains isolated from the same sediments.  相似文献