Characteristics of high-sulfate wastewater treatment by two-phase anaerobic digestion process with Jet-loop anaerobic fluidized bed

A new anaerobic reactor, Jet-loop anaerobic fluidized bed （JLAFB）, was designed for treating high-sulfate wastewater. The treatment characteristics, including the effect of influent COD/SO42 ratio and alkalinity and sulfide inhibition in reactors, were discussed for a JLAFB and a general anaerobic fiuidized bed （AFB） reactor used as sulfate-reducing phase and methane-producing phase, respectively, in two-phase anaerobic digestion process. The formation of granules in the two reactors was also examined. The results indicated that COD and sulfate removal had different demand of influent COD/SO4^2- ratios. When total COD removal was up to 85%, the ratio was only required up to 1.2, whereas, total sulfate removal up to 95% required it exceeding 3.0. The alkalinity in the two reactors increased linearly with the growth of influent alkalinity. Moreover, the change of influent alkalinity had no significant effect on pH and volatile fatty acids （VFA） in the two reactors. Influent alkalinity kept at 400-500 mg/L could meet the requirement of the treating process. The JLAFB reactor had great advantage in avoiding sulfide and free-H2S accumulation and toxicity inhibition on microorganisms. When sulfate loading rate was up to 8. 1 kg/（m^3.d）, the sulfide and free-H2S concentrations in JLAFB reactor were 58.6 and 49.7 mg/L, respectively. Furthermore, the granules, with offwhite color, ellipse shape and diameters of 1.0-3.0 mm, could be developed in JLAFB reactor. In granules, different groups of bacteria were distributed in different layers, and some inorganic metal compounds such as Fe, Ca, Mg etc. were found.     

Insights from life history theory for an explicit treatment of trade‐offs in conservation biology

As economic and social contexts become more embedded within biodiversity conservation, it becomes obvious that resources are a limiting factor in conservation. This recognition is leading conservation scientists and practitioners to increasingly frame conservation decisions as trade‐offs between conflicting societal objectives. However, this framing is all too often done in an intuitive way, rather than by addressing trade‐offs explicitly. In contrast, the concept of trade‐off is a keystone in evolutionary biology, where it has been investigated extensively. I argue that insights from evolutionary theory can provide methodological and theoretical support to evaluating and quantifying trade‐offs in biodiversity conservation. I reviewed the diverse ways in which trade‐offs have emerged within the context of conservation and how advances from evolutionary theory can help avoid the main pitfalls of an implicit approach. When studying both evolutionary trade‐offs (e.g., reproduction vs. survival) and conservation trade‐offs (e.g., biodiversity conservation vs. agriculture), it is crucial to correctly identify the limiting resource, hold constant the amount of this resource when comparing different scenarios, and choose appropriate metrics to quantify the extent to which the objectives have been achieved. Insights from studies in evolutionary theory also reveal how an inadequate selection of conservation solutions may result from considering suboptimal rather than optional solutions when examining whether a trade‐off exits between 2 objectives. Furthermore, the shape of a trade‐off curve (i.e., whether the relationship between 2 objectives follows a concave, convex, or linear form) is known to affect crucially the definition of optimal solutions in evolutionary biology and very likely affects decisions in biodiversity conservation planning too. This interface between evolutionary biology and biodiversity conservation can therefore provide methodological guidance to support decision makers in the difficult task of choosing among conservation solutions. Percepciones de la Teoría de Historia de Vida para una Tratamiento Explícito de las Compensaciones en la Biología de la Conservación     

储罐池火特性研究进展

总结了常见池火特性参数如燃烧速率、火焰形态、火焰脉动、热辐射通量的半经验公式,计算得出燃烧速率、火焰拖曳直径、火焰脉动随储罐直径变化规律,火焰倾角随风速变化规律,热辐射通量随距离的变化规律,确定了多个公式的适用范围,指出了多个特性参数存在的问题,并提出了未来的研究方向。     

圆拱形缺陷对砂岩力学特征影响的试验研究

为研究含圆拱形预制缺陷砂岩的力学特征,在板状黄砂岩试样内预制了不同α值的圆拱形缺陷。采用YNS-2000型电液伺服控制试验系统和数字照相采集系统研究了不同圆拱形缺陷倾角α对黄砂岩力学特征和破坏模式的影响规律。研究结果表明:试样峰值强度、平均模量和割线模量随着α的增大呈先减小后增大再减小趋势,α=30°试样峰值强度和峰值应变均最小,α=75°试样峰值强度和应变均达到最大;预制圆拱形缺陷α对试样起裂应力、起裂位置和破坏模式均具有重要影响,随着α值的增大,试样起裂应力总体呈先减小后增大再减小趋势,当α=30°时,试样的平均起裂应力最小,其值为10.90 MPa;当α=75°时,试样的平均起裂应力最大,其值为18.91 MPa。     

障碍物对瓦斯煤尘爆炸火焰传播规律的影响

为了进一步探究瓦斯煤尘耦合爆炸火焰的传播规律,用自行搭建的半封闭垂直管道爆炸试验系统,研究障碍物对瓦斯煤尘耦合爆炸火焰传播规律的影响。研究结果表明:障碍物能显著提高瓦斯煤尘爆炸火焰的传播速度,其加速机理主要是障碍物诱导的湍流区会促进火焰的传播;火焰在传播过程中的加速度不是一直增加,随着火焰速度的增加会出现上下波动;煤尘的加入会使瓦斯爆炸产生的火焰传播速度显著增大及速度的最大值距离点火端较远;通过障碍物时爆炸产生的火焰形状发生较大的改变,出现拉伸和褶皱现象。     

多目标优化在锻造毛坯形状优化设计中的应用

以形状相对简单的单工序锻件为研究对象,以同时获得材料消耗最小和变形程度最均匀的终锻件为优化目标,对锻造过程毛坯形状进行多目标优化设计的研究。给出了单工序锻件形状优化设计的总的目标函数及其各子目标函数的表示方法及计算表达式,以毛坯的高径(宽)比作为优化设计的变量,基于刚粘塑性有限元理论,采用黄金分割法进行优化迭代,编制了相应的程序,并对一典型的轴对称H型锻件的毛坯形状进行了多目标的优化设计,取得了明显的效果。     

小型燃油锅炉波形炉胆旋压成形工艺

波形炉胆是小型卧式锅壳式燃油燃气锅炉的重要部件 ,它的质量直接影响着锅炉的正常运行。采用模型压制成形工艺制造波形炉胆存在诸多缺点 ,难以保证其制造质量。文中介绍的波形炉胆旋压成形工艺却非常适合生产波形炉胆 ,可以明显提高产品质量和生产效率。     

Turbulence-Based Models for Gas Transfer Analysis with Channel Shape Factor Influence

Gas transfer through surface water of streams is an effective process for the environmental quality of the aquatic ecosystem. Several theoretical approaches have been proposed to estimate gas transfer rate. This paper is devoted to present a turbulence-based model and to compare it with other 3 turbulence-based modeling frameworks that provide an estimation of gas-transfer coefficient K_L at the air-water interface. These models were derived for the reaeration process. In this paper, they have been verified both for reaeration and volatilization using experimental data collected in a laboratory rectangular flume and in a circular sewer reach. These data refer to oxygen absorption and cyclohexane volatilization, respectively. Comparison of results for oxygen shows that the tested models exhibit an average absolute difference between their results and the experimental data ranging from 12.5% and 25.6%. Also, the scaling analysis of the experimental data support both small-eddy based models and the model proposed by the authors. Moreover, volatilization results show that the process is also affected by a channel shape factor, which was, finally, quantified.     

A parametric model of child body shape in seated postures

Objective: The shape of the current physical and computational surrogates of children used for restraint system assessments is based largely on standard anthropometric dimensions. These scalar dimensions provide valuable information on the overall size of the individual but do not provide good guidance on shape or posture. This study introduced the development of a parametric model that statistically predicts individual child body shapes in seated postures with a few given parameters.

Methods: Surface geometry data from a laser scanner of children ages 3 to 11 (n = 135) were standardized by a 2-level fitting method using intermediate templates. The standardized data were analyzed by principal component analysis (PCA) to efficiently describe the body shape variance. Parameters such as stature, body mass index, erect sitting height, and 2 posture variables related to torso recline and lumbar spine flexion were associated with the PCA model using regression.

Results: When the original scan data were compared with the predictions of the model using the given subject dimensions, the average root mean square error for the torso was 9.5 mm, and the 95th percentile error was 17.35 mm.

Conclusions: For the first time, a statistical model of child body shapes in seated postures is available. This parametric model allows the generation of an infinite number of virtual children spanning a wide range of body sizes and postures. The results have broad applicability in product design and safety analysis. Future work is needed to improve the representation of hands and feet and to extend the age range of the model. The model presented in this article is publicly available online through HumanShape.org.     

废旧电路板破碎机设计研究

电路板因为具有韧性高、多组分的特性,在处理过程中不易被破碎。辊式破碎机具有结构简单、工作可靠、能耗低等特点,可用于废旧电路板的粗碎环节。该类辊式破碎机主要由电机、减速器、轴、齿辊、齿轮等组成,齿盘的齿牙形状、尺寸、排列可按电路板物料性质进行设计。首先通过设计计算并使用UG NX软件建立虚拟样机,分析了片状物料在破碎中受力情况;再使用Nastran模块对辊式破碎机的重要部件齿盘进行有限元分析,得出齿盘上承受载荷比较大的位置并对此提出了强化措施。