水动力条件对全程自养脱氮工艺启动研究

CANON工艺需要部分短程硝化提供亚硝酸盐,所以CANON工艺存在溶解氧难控制的问题,特别是在反应器较小的情况。本文采用设有挡板的改良SBR,通过机械搅拌形成剧烈水流搅动,精确控制溶解氧,研究了不同搅拌速率对CANON工艺启动的影响。结果表明,机械曝气能成功启动了CANON工艺,且获得平均总氮去除率达79.40%,剪切应力的提高有利于脱氮性能的提升,机械曝气启动方式相比于鼓风曝气更加容易控制。     

基于颗粒流数值方法的岩石压剪破坏细观特征研究

压剪破坏是影响岩体工程安全的主要因素,基于颗粒流程序的伺服控制原理,采用等效晶质模型模拟了粉砂质板岩的压剪破坏过程,通过与室内试验对比验证了其适用性,并从细观角度揭示了岩石在压剪过程中的破坏机理。结果表明:裂纹增长速率与试件压剪过程中经历的弹性、塑性和破坏3个阶段具有相关性;张拉、剪切裂纹呈同步增长趋势,但峰后张拉裂纹增长速率快于剪切裂纹,即试件峰后以张拉破坏为主;随剪切角增大,由沿晶和穿晶断裂向以沿晶断裂为主转变,裂纹数量减小且扩展方向向断裂面集中;穿晶断裂的扩展更容易导致局部失稳,即在宏观上表现为塑性阶段;穿晶裂纹主要沿断裂面扩展、贯通,一定程度上可以抑制断裂面附近较大破裂块体的产生。     

旋风除尘器筒体倾斜角的仿真与优化

旋风除尘器结构简单、造价低廉、能耗极低,故得以长期应用,但其除尘效率因设计方法比较粗糙一般在60%以下,从而限制了其使用范围。很多结构参数均影响除尘器的效率,其中除尘器筒体的倾斜角度对效率的影响程度最高。以有限元理论为基础,以Fluent软件为工具,对关于除尘效率与倾斜角度依赖关系进行了系列仿真和优化,得出结论:若空气中颗粒物直径大于2.5μm,除尘器倾斜角为12.4°时,其除尘效率理论上可达到97%以上。通过实验初步验证了上述结果的可信度。     

爆炸荷载作用下岩石的变形与破坏研究(Ⅱ)

无论是矿山工程、隧道工程中钻孔爆破效率的提高、工程爆破领域爆破振动参数的预测,还是最近一系列高技术常规局部战争中钻地炸弹对地下坚固目标的破坏,在不考虑岩石中强爆炸引起的光子和电磁辐射等极端效应情况下,都亟待要求对岩石中爆炸引起的应力、变形及其它运动参数和破坏效应作出比较准确的评估。目前对此问题的研究尚只能达到大致的机理及景象的定性认识和描述,定量上的确定存在数量级的误差,尤其是爆炸和冲击的近区,误差更大。其原因在于岩石中爆炸产生的变形和破坏特征,不仅与作用时发生相应的物理及力学运动密切相关,而且强烈地受岩石自身构造缺陷水平及其变化的制约。本文概述了爆炸作用下岩石的动力变形与破坏研究之现状。研究中考虑了岩石的构造特点及其对基本力学性状的影响,并简述了其研究的新趋向。     

磨料浆液除锈机理的研究

本文将冲蚀机理引入金属除锈工艺。通过分析冲蚀的单元作用机理、冲击过程中能量平衡及影响冲蚀的诸因素，阐明了金属除锈的机理。利用刚性粒子冲击塑性材料的模型推导出了除锈效率较高的最佳射流入射角。在钢板除锈应用过程中先以９０°入射角冲击钢板，使钢板上的脆性表层很快形成赫兹裂纹，并且容易脱落，再以１６．４８°的入射角冲蚀钢板，效果理想。     

B级钢侧架圆角细节耐久性力学模型研究

根据Paris公式推导出适用于B级钢圆角细节耐久性分析的 ,在一定裂纹尺寸范围内的裂纹扩展速率公式及其检验方法 ,笔者模拟货车B级钢转 8A侧架的导框弯角内侧 (A区 )的圆角细部进行耐久性实验 ;以试验数据的检验证明 ,在 0 .4～ 4mm的尺寸范围内 ,选用的断裂力学模型是合理的 ;同时为建立合理的检修周期和寿命体系提供理论模型和安全评价基础。     

The impacts of Robinia pseudoacacia litter cover and roots on soil erosion in the Loess Plateau,China

The impacts of vegetation on soil erosion are closely associated with the combined effects of above- and below-ground components. In this study, we explore the effects and contributions of Robinia pseudoacacia litter cover and roots on soil erosion. Experiment sites under natural conditions with vegetation cover, plant roots and bare ground plots were investigated for overland flow discharges of 0.5, 1.0 and 2.0?L?s^?1 and slope gradients of 8.7%, 17.6%, 26.8%, 36.4% and 46.6%. Results indicate that litter cover and roots have a significant impact on sediment reduction; soil loss was reduced by about 57% and plant roots had a greater impact on the reduction of soil erosion than litter cover. The combination of litter cover and plant roots had a significant effect on decreasing K_r, increasing τ_c and consequently strengthening soil resistance capacity to erosion. When plants and roots existed on the slopes, K_r decreased by 81% and 66%, and τ_c increased by 319% and 246%, respectively, in comparison with bare slopes. These results illustrate the importance of high-forest in controlling soil erosion by quantifying the specific contributions of litter cover and plant roots in erosion reduction in the Loess Plateau.     

Airborne Dust Particle Counting Techniques

The paper briefly describes an electro-optical system for counting of dust particles, which is based on the scattering phenomena.Utilizing the scattering of light by various size particles present in the environment, various particle counting techniques have been developed in order to measure the scattered intensity of light. Light scatters in all directions but much more in the so-called near forward direction 17^∘ off axis, at 163^∘ from the light source in the visible range.On the basis of two techniques, the right angle and forward angle scattering, opto-mechanical systems have been developed which measure scattered intensity and particulate matter. The forward scattering Nephelometer is more sensitive and therefore is more suitable for pollution monitoring than the right angle scattering Nephelometer. Whereas the right angle scattering Nephelometer has the utility in extremely low concentration in ppb level owing to the excellent light trap efficiency in comparison to forward scattering Nephelometer. In this paper measurement techniques and measurement results associated with design and development of a real time particle analyser are also discussed.     

江苏及近海地区构造环境剪应力场的跟踪分析

利用江苏数字地震台网近两年记录的 85个中、小地震数字资料 ,调整了计算参数 ,继续对我省及邻近地区的环境剪应力场作了追踪计算。得出我省及邻区、近海地区几个应力值相对较高的需要注意的地区。