Rheological and fractal characteristics of granular sludge in an upflow anaerobic reactor

The rheological and fractal characteristics of the granular sludge in an upflow anaerobic sludge blanket (UASB) reactor were investigated in this study. The influences of sludge concentration and temperature on the rheological properties of the granular sludge were evaluated, and the Bingham model was adopted to describe its rheology. In addition, image analysis was used to determine the sludge fractal dimension. The results indicate that the UASB granular sludge showed a shear-thinning behavior. The relationships between the limiting viscosity and the sludge concentration, as well as the limiting viscosity and temperature could be respectively modeled using an exponential equation and Arrhenius equation well. The Bingham model was able to adequately describe the rheology of the granular sludge. The fractal dimension of the granular sludge, 2.79+/-0.03, was larger than that of some other aggregates, suggesting that the granular sludge were more compact and denser. Furthermore, the relationship between rheological and fractal properties of the granular sludge could be properly described with the model proposed by Shih et al. [1990. Scaling behavior of the elastic properties of colloidal. Phys. Rev. A 42, 4772-4779].     

少数民族地区特色旅游规划及设施建设研究--以江华瑶族自治县旅游发展规划研究为例

在现代化建设日新月异的今天，针对少数民族地区做好旅游发展规划，如何加强营造城市特色，突出特质景观，保护其丰富而有内涵的人文自然环境，以风貌特色吸引游人，促进地方旅游和经济发展。     

浅议建筑工程招投标的策略与技巧

介绍了我国建筑工程招投标的策略与技巧，从投标策略、报价技巧、编标策略与技巧等方面进行了论述，指出熟练掌握投标技巧是提高企业中标率的关键。     

Study on two operating conditions of a full-scale oxidation ditch for optimization of energy consumption and effluent quality by using CFD model

The operating condition of an oxidation ditch (OD) has significant impact on energy consumption and effluent quality of wastewater treatment plants (WWTPs). An experimentally validated numerical tool, based on computational fluid dynamics (CFD) model, was proposed to optimize the operating condition by considering two important factors: flow field and dissolved oxygen (DO) concentration profiles. The model is capable of predicting flow pattern and oxygen mass transfer characteristics in ODs equipped with surface aerators and submerged impellers. Performance demonstration and comparison of two operating conditions (existing and improved) were carried out in two full-scale Carrousel ODs at the Ping Dingshan WWTP in Henan, China. A moving wall model and a fan model were designed to simulate surface aerators and submerged impellers, respectively. Oxygen mass transfer in the ditch was predicted by using a unit analysis method. In aeration zones, the mass inlets representing the surface aerators were set as one source of DO. In the whole straight channel, the oxygen consumption was modeled by using modified BOD-DO model. The following results were obtained: (1) the CFD model characterized flow pattern and DO concentration profiles in the full-scale OD. The predicted flow field values were within 1.98 ± 4.28% difference from the actual measured values while the predicted DO concentration values were within −4.71 ± 4.15% of the measured ones, (2) a surface aerator should be relocated to around 15 m from the curve bend entrance to reduce energy loss caused by fierce collisions at the wall of the curve bend, and (3) DO concentration gradients in the OD under the improved operating condition were more favorable for occurrence of simultaneous nitrification and denitrification (SND).     

解读宜城民工潮

宜城市是湖北省首批小康市,位于江汉平原与南(阳)襄(樊)盆地的过渡地带,市域面积2115平方公里,耕地面积60万亩,市域人口54万,其中农村人口36万。近几年来,随着人增地减、农业生产率的提高,有限的土地和农村劳动力富余的矛盾越来越突出,加之乡镇企业二次创业、“五小”关闭,乡镇企业吸纳农民就业的能力锐减,全市农村富余劳力由1998年的     

休闲农业区域乡村景观规划设计探索

一、休闲农业的兴起随着人民生活水平的提高及农业的发展,以种养业为主的自然经济型农业正在向集约化、规模化、深加工的产业经济型农业迅速发展。同时,随着世界人口城市化速度的加快,     

轴颈温度对弹性可倾瓦推力轴承润滑性能的影响

求出了无限长可倾瓦推力轴承的热弹性流体动力润滑数值解，并详细考查了轴颈温度对轴承性能的影响．结果指出．降低轴颈温度可显著增加轴承的承载量，但不会明显改变摩擦系数．     

连拱隧道施工技术初探

随着国家环保措施的逐步加强和完善,隧道工程在公路、铁路建设中所占比例越来越高。大跨度隧道施工难度较大,连拱隧道施工相对安全、结构美观以及相对同等地质条件下的分离式隧道而言具有占地少、投资小等优点。受传统施工方法的制约,连拱隧道多以短隧为主。结合某连拱隧道施工经验,浅谈对连拱隧道施工方法的见解和对连拱隧道质量通病的控制及预防。     

如何做好混凝土原材料的质量控制

原材料质量的好坏是影响混凝土质量的关键因素。本文从水泥、掺合料、细骨料、粗骨料、外加剂等方面浅谈了如何做好混凝土原材料质量的控制问题。     

灰色系统理论下的建筑形态分析——以滇南传统建筑为例

20世纪80年代以来,灰色系统理论1）提出以后,便以一种有力的姿态立于科学之林,在学术界引起了较大的反响,并受到广泛关注。目前这一理论和方法已应用于不同学科及领域的研究之中,并获得相应的丰硕成果。文章以灰色系统理论为基础,以其模糊与不确定的特性切入建筑学学科领域的研究,通过灰色系统理论的植入及建筑“灰”的决定因素进而到建筑“灰”的形态,从空间的营造、形体的塑造、功能的使用、材料的应用等方面进行了较为深入系统的研究,探寻其蕴含的设计思想和营造理念,试图以灰色系统理论来探索建筑设计理论。