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81.
82.
分别采用溶解性葡萄糖和颗粒性淀粉作为配水中的有机物,考察了混凝(烧杯试验)及造拉流化床时有机物的去除特性.研究表明,对于溶解性有机物(COD)而言,混凝对其去除效果非常有限,去除率仅为13.3% ,而大部分的颗粒性有机物可通过混凝作用去除;造粒流化床时溶解性有机物(COD)的去除率高达97.8% ,远远高于混凝及强化一级处理(CEPT)的.由于颗粒的形成,使得造粒流化床所去除的污染物不仅包括混凝可沉淀和可混凝但不可沉淀两部分,甚至还去除了相当一部分不可混凝的污染物,这是造粒流化床去除效率较高的原因.另外,颗粒的形成对于去除溶解性有机物的强化作用要明显高于对颗粒性有机物的. 相似文献
83.
Granular flows are systems of complex dry particulates whose behavior is difficult to predict during sliding contact. Existing
computational tools used to simulate granular flows are particle dynamics, cellular automata (CA), and continuum modeling.
In the present investigation, another numerical tool—the explicit finite element method (FEM)—is analyzed as a potential technique
for simulating granular flow. For this purpose, explicit dynamic finite element models of parallel shear cells were developed.
These models contained 52 particles and consisted of granules that are both round and multi-shaped (diamond, triangle, and
rectangle). Each parallel shear cell consisted of a smooth stationary top wall and a rough bottom surface that was given a
prescribed velocity of U = 0.7 in/sec (1.78 cm/s). The coefficient of friction (COF) between the particle–particle and particle–wall collisions was
varied between 0.0 and 0.75. Utilizing the output of the simulations, results are presented for the shear behavior, particle
kinetic energy, and particle stresses within the shear cell as a function of time. As a means of validating the explicit technique
for granular flow, a 75 particle, zero roughness, couette shear cell model (solid fraction of 0.50) is subsequently presented
for which direct comparisons are made to the results published by Lun. [Lun, C.K. et al.: Phys. Fluids 8, 2868–2883 (1996)] Overall, the results indicate that the explicit FEM is a powerful tool for simulating granular flow phenomena
in sliding contacts. In fact, the explicit method demonstrated several advantages over existing numerical techniques while
providing equivalent accuracy to the molecular dynamics (MD) approach. These advantages included being able to monitor the
collision (sub-surface and surface) stresses and kinetic energies of individual particles over time, the ability to analyze
any particle shape, and the ability to capture force chains during granular flow. 相似文献
84.
铁矿烧结过程微细颗粒物排放行为 总被引:1,自引:0,他引:1
采用ELPI+设备(荷电低压撞击器)对铁矿烧结过程微细颗粒物进行在线检测与采样,利用场发射扫描电子显微镜(FESEM EDS)对采集的颗粒物形貌特征进行分析,研究铁矿烧结过程中微细颗粒物的排放行为。研究结果表明,PM10大量释放集中在烧结升温段,且颗粒物质量浓度与数目浓度在粒径分布上有较大差异,其中质量浓度峰值区间为5.37~10.00 μm,数目浓度峰值区间为0.10~0.16 μm;形貌特征上,微细颗粒物呈规则的球形、方块形和片状;不同粒径物质组成差异明显,其中颗粒物中的K、Na主要以KCl和NaCl的形式存在,含量随颗粒物粒级的增大而略有降低。 相似文献
85.
针对常规预交联颗粒调剖剂存在的耐温抗盐性能较差的问题,合成了耐温抗盐预交联颗粒调刮剂,确定了其最佳原料配方:有机单体用量100-150 g,抗温材料用量70-100 g,结构增强剂用量5-10 g。并进行了中试放大试验,评价了调剖剂中试产品的热稳定性、抗盐性、膨胀速率、强度、韧性等,同时挂于文13-298油井尾管处进行了现场评价。结果表明,耐温抗盐预交联颗粒调剖剂用文三联注入水配制,于135℃下老化60 d,膨胀倍数达8-12,并保持较好的韧性、强度、抗盐性及热稳定性,可以满足文东、文南等区块温度为120℃以上、矿化度为22×104mg/L以上油藏的调剖要求。 相似文献
86.
Sai Wang Bang‐Ke Luo Ying‐Jun Qin Lin‐Hui Su Simon D. Stewart Tuan‐Tuan Wang Jin‐Peng Tang Bai‐Dong He Jin‐Hua Zhang Hsing‐Juh Lin Yang Yang 《河流研究与利用》2020,36(7):1124-1136
Understanding the trophic discrimination (?13C and ?15N) between consumers and diets in fluvial systems remains difficult because of the variable food sources and complex predator–prey interactions from headwaters to the estuaries. Here, stable carbon (δ13C) and nitrogen (δ15N) isotopes in fish and invertebrates from a large subtropical river in southern China were determined to explore trophic discrimination in conjunction with a gut content analysis. The ?13C values showed significant differences (p < .05) among functional feeding groups, with fish, shrimp, and insect scrapers presenting higher ?13C values (1.20 ± 0.23‰ to 1.51 ± 0.31‰) than other groups. The ?15N values varied significantly between invertebrates (0.64 ± 0.17‰ of insect collector‐gatherers to 1.63 ± 0.36‰ of shrimp predators) and fish (1.98 ± 0.19‰ of detritivores to 2.71 ± 0.43‰ of crustaceavores) and exhibited an increasing tendency from primary to secondary consumers. A linear regression analysis revealed that the longitudinal changes in ?13C and ?15N were closely associated with the δ13C of periphyton, the δ15N of particulate organic matter (POM) in water, and the relative contribution (%) of periphyton and organic detritus to the diet composition of consumers. These results indicated that discrimination factors might not only be influenced by the isotope signatures of basal food sources but also downstream shifts in dominant food items utilized by consumers. In particular, trophic discrimination between periphyton– and detritus–based food chains, such as “epilithic diatoms–shrimp scrapers–crustaceavorous fish” and “POM–bivalves–molluscivorous fish,” displayed regionally specific patterns. When back‐calculating to the diet assimilation and trophic position in subtropical streams and rivers, we suggest using the basin‐scale ?13C value of 0.96 ± 0.26‰ for all consumers and ?15N values of 1.07 ± 0.32‰ for invertebrates and 2.38 ± 0.37‰ for fish. 相似文献
87.
88.
在激光雷达海洋探测技术中,为了实时监测海水中悬浮颗粒物粒径分布,需要对激光雷达接收信号进行处理和反演计算。根据Mie散射理论,用聚苯乙烯粒子作为研究样本,取三种不同粒径的聚苯乙烯粒子,分别配制不同浓度的溶液、测量了不同散射角、不同光波长下的散射系数随浓度的变化关系。测量结果表明:在散射角为15°,光波长范围为450 nm~700 nm时,散射系数与浓度具有很好的单调递增性;对1∶1∶1 的三种粒径聚苯乙烯溶液进行了测量,结果说明混合物散射系数与同种浓度下三种单粒径的散射系数之和基本一致,具有很强的线性相关性;通过实验与理论比较,在适合波段内,反演误差小,反演精度较高。 相似文献
89.
基于VIIRS数据洪泽湖悬浮物浓度估算算法研究 总被引:1,自引:0,他引:1
基于2012~2015年洪泽湖4次星地同步试验数据,建立了较高精度的水体悬浮物浓度单波段(671 nm)模型(R~2=0.74,RMSE=8.58 mg/L),并进行了验证(R~2=0.72,RMSE=11.98 mg/L);然后,将该算法成功应用到了2012~2015年464景VIIRS无云影像上.结果表明,洪泽湖悬浮物浓度呈现春夏低、秋冬高的季节特征和东、中部高,西、北部低的空间分布特征;在年际变化尺度上,悬浮物浓度年均值呈现较小的减少趋势.总体来说,VIIRS在浑浊水体悬浮物浓度上表现了较好的探测能力,在湖泊水色遥感领域具有较大潜力. 相似文献
90.
The concentration of aerosol particles, largely caused by traffic volume and often enhanced during temperature inversion episodes in the cold season, can be a concern for human health in the urban environment. This particulate matter is typically recorded as PM10, the total mass of particles below 10 μm in diameter. It is suspected that, within the PM10 class, ultrafine particles ( < 100 nm) may be responsible for causing respiratory and cardiovascular diseases. Because of their low mass, ultrafine particles are hard to detect, and researchers try to utilize PM10 in combination with nitrogen oxides NOx and other trace gases to monitor their dynamic evolution. To meet pollution standards set by national government and European Union regulation, the city of Klagenfurt, Austria, began using calcium magnesium acetate as a deicer on 11 January 2012, hoping to literally glue pollutants to the ground and thereby reducing pollution concentrations. With the statistical methodology developed in this article, the dynamic evolution of PM10 and NOx is traced for the time period starting 4 January and ending 25 January 2012, and a change in dynamics is found. The findings are based on on‐line monitoring procedures that sequentially detect structural breaks in the mean and the parameter values of an autoregressive moving average process. These are defined in terms of model residuals and one‐step ahead predictors. Theoretical properties are studied, and a simulation study shows that the proposed procedures work well in finite samples. 相似文献