The P-graph approach for systematic synthesis of wastewater treatment networks

Wastewater treatment consists of three or four sequential stages: preliminary, primary, secondary, and tertiary. Each stage can comprise multiple alternative technologies that can perform the same tasks with different efficiencies, operating times, and costs. Thus, we propose a systematic approach for designing wastewater treatment networks by utilizing principles of mathematical modeling and generating an exhaustive enumeration of all the possible technologies and their connections during the early stages of designing a treatment facility. Some of these structures are nonintuitive and include recycling, reprocessing, bypasses, and multiple technologies in parallel or series to remove the same contaminant. The nonintuitive structures with multiple technologies may provide a measure of resilience compared to typical heuristic designs. Thus, the combination of P-graph methodology and the sequence of treatment technologies predicted via the optimization algorithm from the maximal structure is based on holistic considerations and does not lead to suboptimal solutions.     

A membrane filter method for the enumeration of aquatic ammonifiers

A standard procedure for the enumeration of heterotrophic bacteria, utilizing heterotrophic plate count medium (m-HPC), has been modified to allow bacterial ammonifier populations also to be counted. Nessler's reagent was included as an outside indicator to ascertain what portion of the population is capable of ammonification. Typically the ammonifier population varied among aquatic habitats, ranging from 0.08 to 37.0% of the heterotrophic population in river water samples, 0.2 to 10.6% for irrigation water samples, and 1.4 to 3.0% for pond and lake water samples.     

Biofilm in the sediment phase of a sanitary gravity sewer

Microbial activity of the sediment phase in a 1.5-km-long concrete sewer section with a cement pipe in a 540-mm diameter was investigated in this paper. SEM examinations and elementary composition analyses of the sediment samples have identified the presence of a biofilm layer at the sediment surface. Bacterial counting results with a DNA-staining technique have revealed that the amount of bacteria in this layer was 2.1 x 10(11)cellg(-1) dry wt, which is close to that of activated sludge. ATP content in the sewer biofilm was found relatively high, demonstrating that the sewer biofilm is active. Throughout the entire 1.5-km sewer section, the biofilm activity was maintained at almost the same level. Lab-scale sediment oxygen uptake flux (SOUF) tests showed that the shear flow velocity above the sediment phase linearly increases the SOUF, which of the potential value was determined to be 32gO(2)m(-2) day(-1) at an estimated shear flow velocity of 0.055ms(-1) at 25 degrees C in the sewer line, provided that the mean flow velocity was 1.5ms(-1), and the mean water depth was 220mm. Such a high SOUF value further endorsed the existence of the active sewer biofilm.     

焦平面探测器阵列响应率非均匀性补偿

用于8~12um波段的HgCdTe光电探测器焦平面阵列的性能受到阵列中各探测器单元的非均匀性的限制。如果大量像元探测器的阵列要达到小的等效噪声温差(NETD),这种非均匀性必须在阵列的制造或通过校正每个单元探测器输出的补偿中降低。本文通过对光电二极管的性能分析,可知,如果探测器阵列非均匀性的主要来源是诸如探测器面积的不同所引起的,用线性二点校正方案来补偿,是个非常好的方法。如果是阵列单元的光谱带宽变化,则非线性还要留下残余量。     

基于枚举法的断块油藏层系重组优化设计

高含水期多油层断块油藏,纵向非均质性严重,层间动用程度差异明显,层系重组是减小层间干扰、提高中低渗储层动用程度的有效手段。文中采用枚举法,穷举出可能方案,综合考虑技术、经济两方面,筛选出采收率和经济效益都较高的重组方案。技术方面以累计产油量为评价指标,建立了多油层非活塞水驱油模型,根据B-L水驱油理论,预测各划分方案累计产油量。同时,考虑经济效益约束,采用净现值法,进行动态经济评价。以某断块油藏为例,计算结果表明:14个小层划分为2套层系,共有8 191种重组方案,采用渗流阻力级差约束后筛选,保留64种,经开发指标预测和经济效益评价,第63种为最优方案。其钻井数为2,油价3 500元/t时,其净现值为430万元。     

Two-Level Designs to Estimate All Main Effects and Two-Factor Interactions

We study the design of two-level experiments with N runs and n factors large enough to estimate the interaction model, which contains all the main effects and all the two-factor interactions. Yet, an effect hierarchy assumption suggests that main effect estimation should be given more prominence than the estimation of two-factor interactions. Orthogonal arrays (OAs) favor main effect estimation. However, complete enumeration becomes infeasible for cases relevant for practitioners. We develop a partial enumeration procedure for these cases and we establish upper bounds on the D-efficiency for the interaction model based on arrays that have not been generated by the partial enumeration. We also propose an optimal design procedure that favors main effect estimation. Designs created with this procedure have smaller D-efficiencies for the interaction model than D-optimal designs, but standard errors for the main effects in this model are improved. Generated OAs for 7–10 factors and 32–72 runs are smaller or have a higher D-efficiency than the smallest OAs from the literature. Designs obtained with the new optimal design procedure or strength-3 OAs (which have main effects that are not correlated with two-factor interactions) are recommended if main effects unbiased by possible two-factor interactions are of primary interest. D-optimal designs are recommended if interactions are of primary interest. Supplementary materials for this article are available online.     

Alignment空间中的一个计数结果

Alignment空间是一种由广义差错产生的度量空间,其中的序列结构分析在应用领域中起到了越来越重要的作用.本文主要对Alignment空间F2*中Alignment距离为2的序列结构进行了研究,提出Alignment距离分布的概念,得到了长度为n并且Alignment距离为2的序列对数目的解析表达式.     

I/O-efficient join dependency testing,Loomis–Whitney join,and triangle enumeration

We revisit two fundamental problems in database theory. The join-dependency (JD) testing problem is to determine whether a given JD holds on a relation r. We prove that the problem is NP-hard even if the JD involves only relations each of which has only two attributes. The JD-existence testing problem is to determine if there exists any non-trivial JD satisfied by r. We present an I/O-efficient algorithm in the external memory model, which in fact settles the closely related Loomis–Whitney enumeration problem. As a side product, we solve the triangle enumeration problem with the optimal I/O-complexity, improving a recent result of Pagh and Silvestri in PODS'14.     

匀质条带五块布局方式及其生成算法

针对矩形毛坯无约束二维布局问题,提出一种匀质条带五块布局方式。这种布局方式将板材划分为5个矩形块,每个块由包含同种毛坯的匀质条带组成。构造五块布局方式的生成算法:首先采用动态规划方法生成所有可能尺寸的块中匀质条带的最优布局;然后采用隐式枚举和分支定界技术考察板材所有可能的五块划分方式,按照板材布局价值最大原则确定板材的最优五块划分,得到最终的五块布局方式图。数值实验结果表明,这种算法能有效地提高板材布局价值。     

Low-temperature water–gas shift reaction over supported Cu catalysts

The low-temperature water–gas shift (WGS) reaction has been carried out at a very high gas hourly space velocity (GHSV) of 36,201 h⁻¹ over supported Cu catalysts prepared by an incipient wetness impregnation method. The preparation method was optimized to get a highly active CeO₂ supported Cu catalyst for low-temperature WGS. Co-precipitated Cu–CeO₂ exhibited excellent catalytic performance as well as 100% CO₂ selectivity. The high activity and stability of co-precipitated Cu–CeO₂ catalyst is correlated to its easier reducibility, high surface area and the nano-sized CeO₂ with CuO species interacting with the support.