Integration of local–global upscaling and grid adaptivity for simulation of subsurface flow in heterogeneous formations     

M. Gerritsen  J. V. Lambers 《Computational Geosciences》2008,12(2):193-208

We propose a methodology, called multilevel local–global (MLLG) upscaling, for generating accurate upscaled models of permeabilities or transmissibilities for flow simulation on adapted grids in heterogeneous subsurface formations. The method generates an initial adapted grid based on the given fine-scale reservoir heterogeneity and potential flow paths. It then applies local–global (LG) upscaling for permeability or transmissibility [7], along with adaptivity, in an iterative manner. In each iteration of MLLG, the grid can be adapted where needed to reduce flow solver and upscaling errors. The adaptivity is controlled with a flow-based indicator. The iterative process is continued until consistency between the global solve on the adapted grid and the local solves is obtained. While each application of LG upscaling is also an iterative process, this inner iteration generally takes only one or two iterations to converge. Furthermore, the number of outer iterations is bounded above, and hence, the computational costs of this approach are low. We design a new flow-based weighting of transmissibility values in LG upscaling that significantly improves the accuracy of LG and MLLG over traditional local transmissibility calculations. For highly heterogeneous (e.g., channelized) systems, the integration of grid adaptivity and LG upscaling is shown to consistently provide more accurate coarse-scale models for global flow, relative to reference fine-scale results, than do existing upscaling techniques applied to uniform grids of similar densities. Another attractive property of the integration of upscaling and adaptivity is that process dependency is strongly reduced, that is, the approach computes accurate global flow results also for flows driven by boundary conditions different from the generic boundary conditions used to compute the upscaled parameters. The method is demonstrated on Cartesian cell-based anisotropic refinement (CCAR) grids, but it can be applied to other adaptation strategies for structured grids and extended to unstructured grids.  相似文献   

Hydrometallurgical processing and recovery of molybdenum trioxide from spent catalyst   总被引：5，自引：0，他引：5  

Kyung Ho Park  B. Ramachandra Reddy  D. Mohapatra  Chul-Woo Nam 《International Journal of Mineral Processing》2006,80(2-4):261-265

Hydrometallurgical processing of spent hydrodesulphurisation (HDS) catalyst for the recovery of molybdenum using sodium carbonate and hydrogen peroxide mixtures was investigated. The results indicated that the recovery of molybdenum was largely dependent on the concentrations of Na₂CO₃ and H₂O₂ in the reaction medium, which controls the acidity of the leach liquor and carry over of impurities such as Al, Ni, P, Si and V. Leaching process was exothermic and leaching efficiency of molybdenum decreased with increasing solid to liquid ratio. Large scale leaching of spent catalyst, under optimum conditions: 20% pulp density, 85 g/L Na₂CO₃, 10 vol.% H₂O₂ and 1 h reaction, resulted a leaching efficiency of 84% Mo. The obtained leach liquor contained (g/L): Mo — 22.0, Ni — 0.015 and Al — 0.82, P — 1.1, Si — 0.094 and minor quantities of V — 8 mg/L, As and Co — < 1 mg/L. Recovery of Mo from leach solution as MoO₃ of 97.30% purity was achieved by ammonium molybdate precipitation method.  相似文献   

大洋粘土制备白炭黑后的铝回收实验研究     

刘娟娟  张培萍  石学法  吕华华  王宝君  邵冬梅 《吉林大学学报(地球科学版)》2006,(Z1)

为了回收大洋粘土制备白炭黑后残液中的Al3 ,并获得氧化铝超细粉体,实验选用NH3.H2O为沉淀剂,在常温下采用沉淀法使残液中Al3 以氢氧化铝形式沉淀并去除其它杂质离子,然后将得到的沉淀在1200℃灼烧,保温1h。利用IR和XRD测试了产物的物相组成和结构,证实实验可以获得纯度较高的α-Al2O3;而SEM和粒度分析结果显示产物粒度细小,部分颗粒可以达到纳米级;BET结果显示Al2O3的比表面积可达32m2/g。根据氧化铝结构和性能等优选的实验条件为大洋粘土的进一步开发利用提供了参考依据。  相似文献   

Application of membrane technology for water treatment： Ultrasound-associated cleaning of fouled microfiltration membranes     

Rui CHEN Xiaoli WANG Yonggang ZHANG Xueqi FU 《中国地球化学学报》2006,25(B08):128-129

The use of membranes is a widely employed, versatile, and effective separation process. One of the limiting aspects in applying microfiltration （MF） for wastewater treatment is that of problems with membrane fouling and consequent flux reduction. Membrane fouling occurs by the irreversible deposition of retained particles, colloids, macromolecules, salts, etc. at the membrane surface and/or inside the membrane. The predominant fouling mechanisms observed with MF membranes are classified as three categories： the build-up of a cake layer on the membrane surface, blocking of membrane pores, and adsorption of fouling material on the membrane surface or in the pore walls. Although many techniques have been developed to overcome fouling, studies on membrane cleaning still seem to be insufficient for practical membrane filtration systems. Current membrane cleaning technologies include hydraulic, chemical, and mechanical methods. Ultrasound （US） has been widely used as a method of cleaning materials because of the cavitation phenomenon. In this study, US cleaning technique was applied to removing the fouling of polyvinglidenefluoride （PVDF） MF membrane, which was used to treat yeast cell and isolated soybean protein （ISP） solution, respectively. The US employed 40 kHz frequency and the output power of 1.43-2.85 W/cm^2. The evolution of the cleaning effect is followed by the measurements of the flux recovery rate （FRstat） and the cleaning time cycle. Results showed that the membrane property, which was fouled by yeast cell solution, could be recovered by water cleaning with US irradiation. And the cleaning time with the same FRstat decreased with the increase of US intensity.  相似文献   

Exploring the spatial and temporal dynamics of land use in Xizhuang watershed of Yunnan, southwest China     

Xu Jianchu  Ai Xihui  Deng Xiqing 《International Journal of Applied Earth Observation and Geoinformation》2005,7(4):299-309

Over the last two decades, China has introduced a series of agricultural and forestland use reforms, aiming to feed the largest population in the world and maintain ecological services locally and nationally. This paper studies the impacts of local government-driven reforestation on land use and land cover change, as well as its further impacts on livelihoods of upland farmers in Xizhuang watershed. An analysis of aerial photographs and ASTER satellite imagery from 1987 to 2002, respectively, showed that the forest has significantly increased at the expense of decreasing farmland. However, the monoculture reforestation of pine has caused both biophysical and socio-economic consequences. This case study also shows forestry decentralization in China remains incomplete. Land use and land cover change is also a political economic issue. Some of the reforms designed to protect forest resources have had a negative impact on rural livelihoods.  相似文献   

Isothermal annealing of partially metamict zircon: evidence for a three-stage recovery process     

T. Geisler 《Physics and Chemistry of Minerals》2002,29(6):420-429

 Raman spectroscopy and the powder diffraction technique have been used to monitor the recovery process of two partially metamict zircons (2.6 and 4.8 × 10¹⁸ α-decays g⁻¹) from Sri Lanka during a series of isothermal annealing experiments in the temperature range from 870 to 1622 K. These experiments show for the first time that structural recovery in partially metamict zircon proceeds via three distinct recovery stages, each of which occurs within a distinct time-temperature regime. Whereas the first two stages have previously been recognized (recovery of damaged crystalline remnants and epitaxial recrystallization), the third stage has not yet been identified as a single activated process. It is suggested that anisotropic defect annealing during the first stage at low temperatures, where the structure recovers preferentially along the a(b) plane, produces a geometrical situation where large structural rearrangements are necessary to remove the remaining defects inside the crystalline material. This situation is approximately reached when the amorphous domains start to recrystallize. The reason for anisotropic annealing can be found in a different connectivity between polyhedral linkages in both directions of the zircon lattice. High apparent activation energies, in the range of 6.4 to 7.9 eV, were determined for the third recovery stage from the Raman data, which are interpreted to reflect large structural rearrangements (i.e. polyhedral tilting) associated with the final recovery of the c axis. This explains the occurrence of a distinct recrystallization stage without defect annealing. Finally, it should be mentioned that the first recovery stage is not necessarily expected to occur in less damaged zircon crystals (<∼2 × 10¹⁸ α-decays g⁻¹), since less stable defects along the basal plane might have already been self-annealed during radiation damage accumulation under ambient temperatures. Received: 6 September 2001 / Accepted: 25 February 2002  相似文献   

污水渗滤土地处理系统中的复氧方式及效果   总被引：24，自引：0，他引：24  

何江涛  张达政  陈鸿汉  汤鸣皋 《水文地质工程地质》2003,30(1):103-106,109

复氧是困扰人工快渗、构造湿地等污水渗滤土地处理系统已久的问题。国际上目前采用的方法主要有3种：一是采用干湿交替的工作方式进行系统复氧，一是设置通气管对系统内部进行复氧，再一是利用植物的根系对系统内部进行复氧。研究结果表明，干湿交替的工作方式对系统的复氧条件有明显改善，而小水力负荷周期的工作方式对系统的复氧更为有效。通气管的设置通常与间歇性布水工作方式相结合，其效果通常要明显好于单纯采用干湿交替的工作方式。植物根系对系统的复氧，常因植物不同类型面具有不同的氧传输能力，植物根茎所能到达的范围往往决定了系统有效处理部位的大小。  相似文献   

The Origin and Significance of Antarctic Meteorites     

Ralph Harvey   《Chemie der Erde / Geochemistry》2003,63(2):93-147

  相似文献   

深海二叠——三叠系界线研究现状   总被引：4，自引：0，他引：4  

叶玫  冯庆来 《地质科技情报》1997,16(3):47-51

综述了深海二叠（Ｐ）－－三叠系（Ｔ）界线研究现状，介绍了深海Ｐ－Ｔ界线附近岩石地层，生物地层、缺氧事件及生物绝灭和复苏的研究进展，指出了深海Ｐ－Ｔ界线，缺氧事件和生物绝灭研究的分歧、不足及其症结。  相似文献   

地史转折期的生态系   总被引：7，自引：2，他引：7  

殷鸿福  童金南 《地学前缘》1997,(Z2)

生态系的演变是地球各圈层系统耦合关系变化的直接标志。地史转折期的生态系具有复杂的生物内涵，在绝灭—残存—复苏过程中，各生物类别的演替遵循着一定的生存型式。大绝灭后生态系复苏的原动力是绝灭后迁入避难所的复活类型和大绝灭末期高压环境中产生的祖先类型的新生和辐射发展。全面了解绝灭后生态系的组成和结构，对于正确认识地史转折期，即圈层耦合结点处的地质作用型式和过程具有重要作用。  相似文献