Transient ζ‐potential measurements in hydrophobic,TOPAS microfluidic substrates

We utilize time‐resolved electrokinetic measurements in order to study the electrokinetic properties of silica and TOPAS microfluidic channels as a function of the time history of the fluid–solid interface. In pressure‐driven flow through TOPAS microchannels, the ζ‐potential as inferred from streaming potential measurements decays exponentially by a factor of 1.5 with a characteristic decay time of 3 h after the initial formation of the fluid–solid interface. A similar exponential decay is observed immediately after water is exchanged for ethanol as the solvent in the system. In electroosmotically driven flow through TOPAS microchannels, the ζ‐potential as inferred through current monitoring experiments was constant in time. No electrokinetic transients were observed in silica microchannels under these flow conditions.     

An extensible, programmable, commercial-grade platform for internet service architecture

With their increasingly sophisticated applications, users promote the notion that there is more to a network (be it an intranet, or the Internet) than mere L1-3 connectivity. In what shapes a next generation service contract between users and the network, users want the network to offer services that are as ubiquitous and dependable as dial tones. Typical services include application-aware firewalls, directories, nomadic support, virtualization, load balancing, alternate site failover, etc. To fulfill this vision, a service architecture is needed. That is, an architecture wherein end-to-end services compose, on-demand, across network domains, technologies, and administration boundaries. Such an architecture requires programmable mechanisms and programmable network devices for service enabling, service negotiation, and service management. The bedrock foundation of the architecture, and also the key focus of the paper, is an open-source programmable service platform that is explicitly designed to best exploit commercial-grade network devices. The platform predicates a full separation of concerns, in that control-intensive operations are executed in software, whereas, data-intensive operations are delegated to hardware. This way, the platform is capable of performing wire-speed content filtering, and activating network services according to the state of data and control flows. The paper describes the platform and some distinguishing services realized on the platform.     

Fuzzy approaches for multiple objective linear fractional optimization

The problem of finding a solution to a multiple objective linear fractional program arises in several real world situations.In this paper we advocate that fuzzy sets theory provides a basis for solving this problem with sufficient consistency and rigorousness.After representing imprecise aspirations of the decision maker by structured linguistic variables or converting the original problem via approximations or change of variables into a multiple objective linear program, techniques of fuzzy linear programming may be used to reach a satisfactory solution.It is shown that under reasonable restrictions, this solution is efficient (Pareto optimal) for the original problem. Numerical examples are also included for illustration.     

Damping of plasmons in electron liquid

An expression for the width of the plasmon excitations in electron liquid has been obtained using the mode coupling approximation. It is shown that the exact weak coupling (r_s → 0) results of the plasmon width in the long wavelength limit is obtained as a very special case in this approach.     

Sintering of titanium dioxide nanoparticles: a comparison between molecular dynamics and phenomenological modeling

Molecular dynamics simulations were used to determine the melting points of anatase and rutile nanoparticles. The melting points decrease with decrease in particle diameter and are in reasonable agreement with the empirical formula derived by Buffat and Borel. The phenomenological model of Koch and Friedlander is unable to predict the temperature rise during initial stages of sintering with acceptable accuracy. It is argued that the Koch and Friedlander assumption of linear surface reduction rate upon sintering may be inadequate for the time scales under consideration. A theoretical model using direct area measurement from molecular dynamics simulations and a single adjustable parameter is able to predict temperature rise during initial stages of sintering within acceptable error limits.     

Foaming in aqueous solutions of hexadecyltrimethylammonium bromide and silica nanoparticles: Measurement and analysis of rheological and interfacial properties

The properties of aqueous foams stabilized by a mixture of negatively charged silica nanoparticles and hexadecyltrimethylammonium bromide were studied in this work. Rheological properties of the foams were studied. The interaction between nanoparticles and surfactant molecules in the bulk phase was studied by zeta potential and size measurements of the particles. The interaction at the interface was studied by means of interfacial shear rheology, surface pressure measurement, and atomic force microscopy. It was found that foams were more stable at low surfactant concentrations, though the foamability was low. This was due to the formation of a strong viscoelastic film of surfactant-laden particles at the air–water interface. A suitable mechanism has been proposed to explain the stability of foams in the presence of nanoparticles at different surfactant concentrations.     

Total synthesis of Carpatamides A–D

A synthetic strategy was developed for the synthesis of the common core structure of Carpatamides A–D. The total synthesis of Carpatamides A and C was completed in 6 steps and of Carpatamides B and D in 7 steps, by employing the Wittig olefination, olefin cross metathesis and acid amine coupling reactions as key steps.     

A Compressed Sensing Approach to Resolve The Energy Hole Problem in Large Scale WSNs

Sensor nodes in close proximity to the sink experience heavy traffic than the nodes which are far from the sink. Since, the continuous monitoring and reporting of events throughout the network involves the nodes closer to the sink to be part of the relay, the transmission load is hardly even throughout the network. The uneven energy consumption in the network eventually results nodes near the sink to die out quickly, creating energy holes in the network. This work proposes a compressive in-network data processing scheme, to resolve the energy hole problem and to improve the network lifetime. The sensed data is transmitted to the sink through a three-level clustering scheme. A few designated nodes in the first and second level apply compressed sensing and obtain weighted samples of the received data. A lossless compression is applied at the nodes in the third level before it is finally transmitted to the sink. Results show the proposed scheme to be is 43.75% transmission efficient and is able to resolve the energy hole problem efficiently by distributing the load evenly over the network.     

An online cost-efficient protection scheme for quick recovery in all-optical WDM mesh networks

Since a single fiber carries a huge amount of data in optical WDM networks, a fiber cut even for a brief period is a very serious event. Designing schemes to prevent disruption of user traffic and recovery techniques from failures is thus an important area of research. Since a single fiber cut is the most common type of fault, in this paper we address the problem of protecting all-optical WDM mesh networks from single link failure. Our proposed online protection scheme is an improvement over an existing approach and is not only cost-efficient in terms of network resource consumption but can also provide quick recovery from a link failure. We first provide an ILP formulation for the problem and then propose a heuristic solution iStreams that can provide near-optimal solution in polynomial time. Performance comparisons with some well-known schemes of protection show that our heuristic algorithm can be a better choice for conserving resource while providing quick recovery from a link failure.     

BER assessment of FFT-OFDM against WHT-OFDM over different fading channel

Wavelets are brought into the wireless communication field as an orthogonal base of multi-carrier modulation and are now considered as a significant measure. Also, wavelets do contain the capability to improve bandwidth efficiency even more along with lower inter-symbol interference and inter-carrier interference. Appropriately, a BER versus SNR analysis is done for fast Fourier transform (FFT) based OFDM framework and wavelet haar transform (WHT) based OFDM framework in this work. The evaluationis demonstrated over Rayleigh and Rician fading channel utilizing dissimilar M-PSK modulation levels intended for FFT-OFDM and WHT-OFDM. The performance of the simulated test-bed is investigated via BER assessment as a function of SNR. The imitation outcome reports a significant improvement in BER of the simulated system using WHT-OFDM in comparison to FFT-OFDM for both Rayleigh and Rician fading channel. Also, the BER performance of both FFT-OFDM and WHT-OFDM is superior in Rician fading channel in comparison to Rayleigh fading channel.