Impact of module design on the performance of membrane bioreactors treating municipal wastewater

Membranes are located in a membrane module that physically seals and isolates the feed stream from the permeate flux in membrane bioreactors (MBRs). Therefore, module type, structure, and geometrical configuration are critical design considerations affecting membrane performance in MBRs. In this study, impact of membrane module design on treatment and filtration performance of MBRs was investigated. For this purpose, two flat sheet membrane modules with different outlet structures and module geometries, including rectangular- and D-shaped, were tested. In addition to the differences in outlet structure and module geometry, size of circular structures which supported membranes in rectangular- and D-shaped modules differed from each other. Considering the results, permeate quality was not affected from the change in the module design. However, the most remarkable impact of the module design was observed on the transmembrane pressure (TMP) evolution and fouling potential. D-shaped membrane module including smaller circular structures resulted in a decrease in fouling potential and thus, this module could be operated longer time in comparison to rectangular-shaped membrane module without a severe TMP increase. The observed differences in TMP increase and fouling potential lead to the hypothesis that module design is a critical factor affecting filtration performance in MBRs.     

Structural and Physicochemical Properties of a Polymerizable Surfactant Synthesized from <Emphasis Type="Italic">N</Emphasis>-Methylol Acrylamide

A new polymerizable nonionic surfactant with reactive vinyl groups has been synthesized from N‐methylol acrylamide using a two‐step procedure. The structure of the surfactant molecule was characterized by Fourier transform infrared, ¹H nuclear magnetic resonance and mass spectroscopy. The surface active properties alongside its self‐assembly properties were investigated by surface tension, electrical conductivity, and fluorescence spectroscopy measurements. As compared with other nonionic surfactants, this study showed that this polymerizable surfactant possesses slightly a higher critical micelle concentration (CMC) value and the surface tension value at CMC. The obtained CMC values were compatible among measurements, ca. 0.02–0.038 M. The evidence of micelle formation also provided by the zeta potential measurements and the obtained zeta potential values showed that the polymerizable surfactant solutions had limited stability. The hydrolysis stability and solubility of the polymerizable surfactant were also investigated. The solubility results have shown that it was soluble in polar solvents while insoluble in nonpolar solvents both at room temperature and 40 °C. The acidic and basic hydrolysis of the surfactant increased as the temperature increased and the hydrolysis stability was 180 min (basic medium) and 55 min (acidic medium) at 80 °C.     

Investigation of the Sharkskin melt instability using optical Fourier analysis

An optical method allowing the characterization of melt flow instabilities typically occurring during an extrusion process of polymers and polymer compounds is presented. It is based on a camera-acquired image of the extruded compound with a reference length scale. Application of image processing and transformation of the calibrated image to the frequency domain yields the magnitude spectrum of the instability. The effectiveness of the before mentioned approach is shown on Styrene-butadiene rubber (SBR) compounds, covering a wide range of silica filler content, extruded through a Göttfert capillary rheometer. The results of the image-based analysis are compared with the results from the sharkskin option, a series of highly sensitive pressure transducers installed inside the rheometer. A simplified version of the code used to produce the optical analysis results is included as supplementary material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48806.     

A comparative study on water-based coatings prepared in the presence of oligomeric and conventional protective colloids

Poly(vinyl acetate-co-butyl acrylate) latexes were prepared by using semi-continuous emulsion polymerization method in presence of two different protective colloids which were oligomeric N-methylol acrylamide and conventional poly(vinyl alcohol). The effects of these protective colloids on colloidal, surface and film properties of latexes were examined. Poly(vinyl acetate-co-butyl acrylate) synthesized with oligomeric N-methylol acrylamide, which was characterized by FT-IR, NMR and MALDI-TOF MS, was found to have lower viscosity, finer particle size, better latex stability, lower polydispersity, higher T_g and better film forming behavior compared to those synthesized from the poly(vinyl alcohol).     

Operational and maintenance data collection

This article presents an effort to collect operational and maintenance data on 240 power generation, power distribution and heating, ventilation, and air conditioning (HVAC) items, including gas turbine generators, diesel engine generators, electrical switchgear, cables, circuit breakers, boilers, piping, valves, pumps, motors, and chillers.     

Assessment of obsessive-compulsive symptom dimensions: Development and evaluation of the Dimensional Obsessive-Compulsive Scale.

Although several measures of obsessive-compulsive (OC) symptoms exist, most are limited in that they are not consistent with the most recent empirical findings on the nature and dimensional structure of obsessions and compulsions. In the present research, the authors developed and evaluated a measure called the Dimensional Obsessive-Compulsive Scale (DOCS) to address limitations of existing OC symptom measures. The DOCS is a 20-item measure that assesses the four dimensions of OC symptoms most reliably replicated in previous structural research. Factorial validity of the DOCS was supported by exploratory and confirmatory factor analyses of 3 samples, including individuals with OC disorder, those with other anxiety disorders, and nonclinical individuals. Scores on the DOCS displayed good performance on indices of reliability and validity, as well as sensitivity to treatment and diagnostic sensitivity, and hold promise as a measure of OC symptoms in clinical and research settings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phase transformations,dislocations and hardening behavior in uniaxially compressed silicon nanospheres

Molecular dynamics has been used to simulate the uniaxial compression of single crystal silicon nanospheres using the Tersoff potential. The resulting yield behavior is shown to vary with changes in temperature, sphere size, and crystallographic orientation with respect to the loading direction. Only compression along the [1 0 0] crystallographic direction resulted in the formation of the β-Sn phase. A temperature dependent hardening response is observed in all orientations independent of the β-Sn phase transformation. Dislocation activity is detected at elevated temperatures in the largest sphere indicating a critical temperature and size for nucleation. Consequences of these dislocations to simulating strength properties at the nanoscale are discussed.     

Design and performance evaluation of a fuzzy based traffic conditioner for differentiated services

The current Internet can only provide the best-effort services. By growing the Internet and its applications, new services with different requirements are developed. The differentiated services (Diffserv) [S. Blake, M. Carlson, E. Davies, Z. Wang, W. Weiss, An Architecture for Differentiated Services, IETF RFC 2475, 1998; K. Nichols, V. Jacobson, L. Zhang, A Two-bit Differentiated Services Architecture for the Internet, IETF RFC 2638, July 1999; T. Li, Y. Rekhter, A Provider Architecture for Differentiated Services and Traffic Engineering (PASTE), IETF RFC 2430, October 1998] is a scalable model for providing end-to-end quality of services. A Diffserv router consists of different components including classifier, meter, marker, dropper, shaper and scheduler. In this paper, we use the benefits of the fuzzy logic controller to design a fuzzy based traffic conditioner for Internet differentiated services. Our proposed model consists of three major parts: a fuzzy meter/marker (FM), a fuzzy active queue management (FAQM) algorithm and a fuzzy scheduler (FS). The proposed FM used to measure and mark the input traffic is based on the single rate three colors meter (srTCM) mechanism [J. Heinane, et al., A Single Rate Three Color Marker, RFC 2697, September 1999]. The FM meters an IP packet stream and marks its packets GREEN, YELLOW, or RED. The proposed FAQM is a fuzzy implementation of the well-known BLUE active queue management (AQM) algorithm [W. Feng, D. Kandlur, D. Saha, K. Shin, BLUE: A New Class of Active Queue Management Algorithms U. Michigan CSE-TR-387-99, April 1999]. To achieve a good throughput and reasonable packet loss ratio, the proposed FAQM mechanism employs a fuzzy logic controller. The third part of the proposed fuzzy traffic conditioner is FS. It is based on the traditional weighted fair queue (WFQ) mechanism [A. Demers, S. Keshav, S. Shenker, Analysis and simulation of a fair queueing algorithm, in: SIGCOMM Symposium on Communications Architectures and Protocols, Austin, Texas, September 1989, pp. 1–12] that tunes the weight of each queue by a fuzzy logic controller. To evaluate the performance of the proposed model, we developed a software in C++ environment to simulate it. Different network topologies with different traffic parameters were performed. The simulation results easily helped us to judge the merit of the proposed FM, FAQM and FS because of their remarkable performance over the traditional non-fuzzy mechanisms.     

Folding pathway of a lattice model for proteins

The folding of a protein-like heteropolymer is studied by using direct simulation of a lattice model that folds rapidly to a well-defined "native" structure. The details of each molecular folding event depend on the random initial conformation as well as the random thermal fluctuations of the polymer. By analyzing the statistical properties of hundreds of folding events, a classical folding "pathway" for such a polymer is found that includes partially folded, on-pathway intermediates that are shown to be metastable equilibrium states of the polymer. These results are discussed in the context of the "classical" and "new" views of folding.     

Kinematic data on primate head and neck posture: implications for the evolution of basicranial flexion and an evaluation of registration planes used in paleoanthropology

Kinematic data on primate head and neck posture were collected by filming 29 primate species during locomotion. These were used to test whether head and neck posture are significant influences on basicranial flexion and whether the Frankfurt plane can legitimately be employed in paleoanthropological studies. Three kinematic measurements were recorded as angles relative to the gravity vector, the inclination of the orbital plane, the inclination of the neck, and the inclination of the Frankfurt plane. A fourth kinematic measurement was calculated as the angle between the neck and the orbital plane (the head-neck angle [HNA]). The functional relationships of basicranial flexion were examined by calculating the correlations and partial correlations between HNA and craniometric measurements representing basicranial flexion, orbital kyphosis, and relative brain size (Ross and Ravosa [1993] Am. J. Phys. Anthropol. 91:305-324). Significant partial correlations were observed between relative brain size and basicranial flexion and between HNA and orbital kyphosis. This indicates that brain size, rather than head and neck posture, is the primary influence on flexion, while the degree of orbital kyphosis may act to reorient the visual field in response to variation in head and neck posture. Regarding registration planes, the Frankfurt plane was found to be horizontal in humans but inclined in all nonhuman primates. In contrast, nearly all primates (including humans) oriented their orbits such that they faced anteriorly and slightly inferiorly. These results suggest that for certain functional craniometric studies, the orbital plane may be a more suitable registration plane than Frankfurt "Horizontal."