Membrane bioreactor for treatment of pharmaceutical wastewater containing acetaminophen

Treatment of pharmaceutical wastewater is a real challenge for wastewater engineers. In this study, a pilot-scale system including an external loop airlift membrane bioreactor (ELAMBR) was applied for treatment of a synthetic pharmaceutical wastewater. The performance of this system was evaluated in removal of acetaminophen as the main pollutant of a pharmaceutical wastewater. A conventional activated sludge (CAS process) laboratory system was used in parallel with this system to compare both systems in regard to their ability for acetaminophen removal. The performance of the ELAMBR system was monitored for approximately one month to investigate the long-term operational stability of the system and possible effects of solids retention time on the efficiency of removal of acetaminophen. The removal efficiency was significantly higher in the ELAMBR system than the CAS process. 100% of the acetaminophen was removed after 2 days in this system. The results also showed that initial concentration of acetaminophen, chemical oxygen demand (COD) and mixed liquid suspended solids (MLSS) are the most effective parameters in removal of a pollutant such as acetaminophen. This study demonstrates the usefulness of ELAMBR system for pharmaceutical wastewater treatment with the advantages such as: (i) simple operation and maintenance, (ii) efficient removal of pharmaceutical pollutant and COD and (iii) low-energy consumption.     

Analytical Models for Single-Hop and Multi-Hop Ad Hoc Networks

There is considerable interest in modeling the performance of ad hoc networks analytically. This paper presents approximate analytical models for the throughput performance of single-hop and multi-hop ad hoc networks. The inherent complexity of analysis of a multi-hop ad hoc network together with the fact that the behavior of a node is dependent not only on its neighbors' behavior, but also on the behavior of other unseen nodes makes multi-hop network analysis extremely difficult. However, our approach in this paper to analyze multi-hop networks offers an accurate approximation with moderate complexity. Our approach is based on characterizing the behavior of a node by its state and the state of the channel it sees. This approach is used to carry out an analysis of single-hop and multi-hop ad hoc networks in which different nodes may have different traffic loads. In order to validate the model, it is applied to IEEE 802.11-based networks, and it is shown through extensive simulations that the model is very accurate. Farshid Alizadeh-Shabdiz received his B.Sc. in 1989 at University of Science and Technology, M.Sc. in 1991 at Tehran University, Iran, and D.Sc. in 2004 at the George Washington University. He is a senior research engineer in Advanced Solution Group, part of Cross Country Automotive Services, and he is also a part time faculty member at Boston University. Dr. Alizadeh-Shabdiz was part of the design and implementation team of the three first satellite-based mobile networks: ICO global medium orbit satellite network voice and data services, Thuraya GEO satellite network, and the first phase of Inmarsat high speed data network. His research interests include MAC layer, physical layer and network layer of wireless and satellite networks. Suresh Subramaniam received the Ph.D. degree in electrical engineering from the University of Washington, Seattle, in 1997. He is an Associate Professor in the Department of Electrical and Computer Engineering at the George Washington University, Washington, DC. His research interests are in the architectural, algorithmic, and performance aspects of communication networks, with particular emphasis on optical and wireless ad hoc networks. Dr. Subramaniam is a co-editor of the books “Optical WDM Networks – Principles and Practice” and “Emerging Optical Network Technologies: Architectures, Protocols, and Performance”. He has been on the program committees of several conferences including Infocom, ICC, Globecom, and Broadnets, and served as TPC Co-Chair for the 2004 Broadband Optical Networking Symposium. He currently serves on the editorial boards of Journal of Communications and Networks and IEEE Communications Surveys and Tutorials. He is a co-recipient of the Best Paper Award at the 1997 SPIE Conference on All-Optical Communication Systems.     

Fracture Model for Flexural Failure of Beams Retrofitted with CARDIFRC

A new retrofitting technique based on a material [Cardiff Fiber Reinforced Concrete (CARDIFRC)] compatible with concrete has been developed at Cardiff University. It overcomes some of the problems associated with the current techniques based on externally bonded steel plates and fiber-reinforced plastic laminates which are due to the mismatch of their tensile strength and stiffness with that of the concrete structure being retrofitted. CARDIFRC is characterized by high tensile/flexural strength and high energy-absorption capacity (i.e., ductility). The special characteristics of CARDIFRC make it particularly suitable for repair, remedial and upgrading activities (i.e., retrofitting) of existing concrete structures. It has been shown that damaged reinforced concrete beams can be successfully strengthened and rehabilitated in a variety of different retrofit configurations using precast CARDIFRC strips adhesively bonded to the prepared surfaces of the damaged beams. To predict the moment resistance of the beams retrofitted in this manner an analytical model is introduced in the present paper. This model takes a fracture mechanics approach and follows the initiation and growth of the flexural crack that eventually leads to the failure of the retrofitted beams. The results of this analytical model are found to be in very good agreement with the test results.     

Friction Force Microscopy of Lubricin and Hyaluronic Acid between Hydrophobic and Hydrophilic Surfaces

Lubricin and hyaluronic acid (HA), molecular constituents of synovial fluid, have long been theorized to play a role in joint lubrication and wear protection. While lubricin has been shown to function as a boundary lubricant, conflicting evidence exists as to the boundary lubricating ability of hyaluronic acid. Here, we use colloidal force microscopy to explore the friction behavior of these two molecules on the microscale between chemically uniform hydrophilic (hydroxyl-terminated) and hydrophobic (methyl-terminated) surfaces in physiological buffer solution. Behaviors on both surfaces are physiologically relevant since the heterogeneous articular cartilage surface contains both hydrophilic and hydrophobic elements. Friction between hydrophobic surfaces was initially high (μ=1.1, at 100nN of applied normal load) and was significantly reduced by lubricin addition while friction between hydrophilic surfaces was initially low (μ=0.1) and was slightly increased by lubricin addition. At lubricin concentrations above 200 μg/ml, friction behavior on the two surfaces was similar (μ=0.2) indicating that nearly all interaction between the two surfaces was between adsorbed lubricin molecules rather than between the surfaces themselves. In contrast, addition of HA did not appreciably alter the frictional behavior between the model surfaces. No synergistic effect on friction behavior was seen in a physiological mixture of lubricin and HA. Lubricin can equally mediate the frictional response between both hydrophilic and hydrophobic surfaces, likely fully preventing direct surface-to-surface contact at sufficient concentrations, whereas HA provides considerably less boundary lubrication.     

A mechanistic analysis of viscous fingering in low-tension polymer flooding in heavy-oil reservoirs

Modeling of the low tension polymer flooding (LTPF) in heavy oil reservoirs suffers from the paucity of detailed knowledge of viscous instability or fingering effects. Major limitations of previous approaches for studying viscous fingering in immiscible displacements are that the reported experiments have been conducted utilizing the linear displacements schemes in the media with high, single-phase permeabilities. Consequently, viscous instability has not been studied in low-permeability media and using the displacement schemes similar to the oil-field patterns (e.g., five-spot). To help understand viscous fingering in LTPF in heavy oil reservoirs and to overcome the limitations of previous studies, we conducted experiments in the low-permeability, one-quarter, five-spot patterns. New insights into the main driving mechanisms for viscous fingering are proposed. In summary, the mechanisms of spreading, splitting, coalescence, and microscopic crossflow drive the finger growth. In addition, the viscous fingers are readily initiated in the porous medium, but they can be damped out before traveling very far. This damping of the viscous fingers is due to the flow of the two phases in a direction transverse to the direction of bulk fluid movement as a result of dispersive processes such as stream splitting. Also, the initially-developed fingers may deteriorate over the time of displacement. This depends on the distance between the injector and producer and width of the porous medium. The presence of instabilities that look like fingers and stable displacements behind the unstable front were discovered. The results also indicate that a stable zone exists and progresses at varying velocities. Finally, we reveal three different types of displacements that occur in LTPF: stable displacements, displacement with macroscopic viscous fingering, and displacements with both macroscopic and microscopic viscous fingering.     

Hydrodynamic Pressure Generation in a Pocketed Thrust Washer

The objective of this study was to experimentally investigate hydrodynamic pressure generation in surface-pocketed thrust washers. A novel method of pressure mapping was developed to allow for in situ measurement of the pressure generated by surface modifications. Thin-film pressure transducers, located just below the thrust washer surface, were used to measure pressure variations as a function of the operating conditions. Contour maps showing the cavitation region and the location of peak pressure were clearly displayed. The experimental work presented maps the pressure profiles with real-time, high-resolution sensors. The thin-film pressure transducers were used to investigate the pressure interactions between surface features. In addition to the experimental setup, a model of the contact was developed using ANSYS FLUENT. Cavitation, friction, film thickness, and load support were all compared with experimental results and the two were shown to be in good agreement. The model demonstrated an accurate prediction of the pressure profile but varied slightly with the predicted load support of the thrust washer. The simulation was then used to optimize the pocket density for the experimental operating conditions. The optimal bearing design had the highest load-carrying capacity with a low friction coefficient.     

Performance Characteristics of Perfluoroalkylpolyether Synthetic Lubricants

An extensive test program was conducted to determine the performance characteristics (friction, wear, temperature) of a linear high temperature perfluoroalkylpolyether (PFPE) and two branched PFPE lubricants under normal and severe operating conditions. These include temperatures up to 200° C and Hertzian pressures as high as 2.8 GPa. A four-ball wear tester was used to measure wear scar and a two-disk machine was used to measure friction. The linear perfluoroalkylpolyether lubricant demonstrated low friction and wear at elevated temperatures under the test conditions considered. A bearing testing apparatus was used to measure friction and temperature of tapered roller bearings under various operating conditions for a branched PFPE and the results are reported.     

CMOL implementation of spiking neurons and spike‐timing dependent plasticity

Successful implementation of spiking neural networks onto CMOS‐Molecular (CMOL) architecture has already been proposed, but the ability of dynamic learning has not yet been addressed. Here, we propose a spiking neural topology with spike‐timing‐dependent learning ability and provide its basic building blocks that are easily mapped onto CMOL architecture. The learning method modifies state of synaptic switches, using spatially and temporally local information which is available at the synapse when state modification is performed. The performance of the proposed topology is analyzed with regards to pre‐ and post‐synaptic spike timing, and simulation results are provided for a synapse with spike‐timing‐dependent plasticity properties. Furthermore, its performance as spike‐timing correlation learning and synchrony detection in a small feed‐forward network is demonstrated as a case example. Copyright © 2010 John Wiley & Sons, Ltd.     

Estimation of reactivity ratios of styrene/butyl acrylate copolymer by ordinary and generalized least square methods

A novel generalized least square (GLS) estimator program was employed for determination of styrene (STY)/butyl acrylate (BA) reactivity ratios synthesized by solution copolymerization method. The monomer reactivity ratios as well as the 95 % individual confidence limits were determined by application of conventional linear methods like Finemann–Ross, Ezrielev–Brokhina–Roskin, Joshi–Joshi, Kelen–Tudos, modified Kelen–Tudos, extended Kelen–Tudos and Mao–Huglin. The estimation process was performed by applying techniques based on ordinary least square (OLS) and GLS approaches and the results were compared. The results showed a fairly good agreement between the experimental and calculated copolymer compositions. The model was then successfully validated through handling regression models with error terms that are heteroskedastic or autocorrelation, or both and clearly showed that the model was able to predict the reactivity ratios by accounting response error structure. Based on the copolymer compositions determined by ¹H NMR, the reactivity ratios of STY and BA were found to be 0.886634 and 0.216369, respectively, by Mao–Huglin method through the GLS approach, and this new estimation method shows the best linear estimations for the monomer reactivity ratios. The present paper shows a new estimation integral approach for determining the monomer reactivity ratios by different conventional linear methods at low and high conversions in EViews software and the calculated values are discussed in terms of regression models.