Browsing by Subject "Mixing"

Now showing 1 - 5 of 5

Open Access
Discriminative fine-grained mixing for adaptive compression of data streams
(Institute of Electrical and Electronics Engineers, 2014) Gedik, B.
This paper introduces an adaptive compression algorithm for transfer of data streams across operators in stream processing systems. The algorithm is adaptive in the sense that it can adjust the amount of compression applied based on the bandwidth, CPU, and workload availability. It is discriminative in the sense that it can judiciously apply partial compression by selecting a subset of attributes that can provide good reduction in the used bandwidth at a low cost. The algorithm relies on the significant differences that exist among stream attributes with respect to their relative sizes, compression ratios, compression costs, and their amenability to application of custom compressors. As part of this study, we present a modeling of uniform and discriminative mixing, and provide various greedy algorithms and associated metrics to locate an effective setting when model parameters are available at run-time. Furthermore, we provide online and adaptive algorithms for real-world systems in which system parameters that can be measured at run-time are limited. We present a detailed experimental study that illustrates the superiority of discriminative mixing over uniform mixing. © 2013 IEEE.
Open Access
Empirical mode decomposition aided by adaptive low pass filtering
(IEEE, 2012) Öztürk, Onur; Arıkan, Orhan; Çetin, A. Enis
Empirical Mode Decomposition (EMD) is an adaptive signal analysis technique which derives its basis functions from the signal itself. EMD is realized through successive iterations of a sifting process requiring local mean computation. For that purpose, local minima and maxima of the signal are assumed to constitute proper local time scales. EMD lacks accuracy, however, experiencing the so-called mode mixing phenomenon in the presence of noise which creates artificial extrema. In this paper, we propose adaptively filtering the signal in Discrete Cosine Transform domain before each local mean computation step to prevent mode mixing. Denoising filter thresholds are optimized for a product form criterion which is a function of the preserved energy and the eliminated number of extrema of the signal after filtering. Results obtained from synthetic signals reveal the potential of the proposed technique. © 2012 IEEE.
Open Access
Modeling of an ac-electro-osmosis based microfluidic mixer
(ASME, 2017) Uslu, H. Dilara; Canpolat, Ç.; Çetin, Barbaros
The purpose of this study is presenting an active micromixer, which is based on AC electro-osmotic flow driven on 3D micro wires. In order to solve governing equations of AC electroosmosis, a commercial software COMSOL Multiphysics® is implemented. Different wire configurations with various imposed electric fields and flow rates are tested for evaluating mixing efficiencies. The analyses show that mixing performance is significantly improved by number of the wires as well as wire orientation. It is also revealed that the degree of mixing can also be controlled by the tuning of the applied voltage for a given flow rate.
Open Access
Morphological control of mesoporosity and nanoparticles within Co3O4-CuO electrospun nanofibers: quantum confinement and visible light photocatalysis performance
(American Chemical Society, 2017-09) Pradhan, A. C.; Uyar, Tamer
The one-dimensional (1D) mesoporous and interconnected nanoparticles (NPs) enriched composite Co3O4-CuO nanofibers (NFs) in the ratio Co:Cu = 1/4 (Co3O4-CuO NFs) composite have been synthesized by electrospinning and calcination of mixed polymeric template. Not merely the mesoporous composite Co3O4-CuO NFs but also single mesoporous Co3O4 NFs and CuO NFs have been produced for comparison. The choice of mixed polymer templates such as polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) for electrospinning is responsible for the formation of 1D mesoporous NFs. The HR-TEM result showed evolution of interconnected nanoparticles (NPs) and creation of mesoporosity in all electrospun NFs. The quantum confinement is due to NPs within NFs and has been proved by the surface-enhanced Raman scattering (SERS) study and the UV-vis-NRI diffuse reflectance spectra (DRS). The high intense photoluminescence (PL) spectra showing blue shift of all NFs also confirmed the quantum confinement phenomena. The lowering of PL spectrum after mixing of CuO in Co3O4 nanofibers framework (Co3O4-CuO NFs) proved CuO as an efficient visible light response low cost cocatalyst/charge separator. The red shifting of the band gap in composite Co3O4-CuO NFs is due to the internal charge transfer between Co2+ to Co3+ and Cu2+, proved by UV-vis absorption spectroscopy. Creation of oxygen vacancies by mixing of CuO and Co3O4 also prevents the electron-hole recombination and enhances the photocatalytic activity in composite Co3O4-CuO NFs. The photocurrent density, Mott-Schottky (MS), and electrochemical impedance spectroscopy (EIS) studies of all NFs favor the high photocatalytic performance. The mesoporous composite Co3O4-CuO NFs exhibits high photocatalytic activity toward phenolic compounds degradation as compared to the other two NFs (Co3O4 NFs and CuO NFs). The kinetic study of phenolic compounds followed first order rate equation. The high photocatalytic activity of composite Co3O4-CuO NFs is attributed to the formation of mesoporosity and interconnected NPs within NFs framework, quantum confinement, extended light absorption property, internal charge transfer, and effective photogenerated charge separations.
Open Access
Numerical analysis of mixing performance in sinusoidal microchannels based on particle motion in droplets
(Springer Verlag, 2015) Özkan, A.; Erdem, E. Y.
This numerical study was conducted to analyze and understand the parameters that affect the mixing performance of droplet-based flow in sinusoidal microfluidic channels. Finite element analysis was used for modeling fluid flow and droplet formation inside the microchannels via tracking interface between the two heterogeneous fluids along with multiple particle trajectories inside a droplet. The solutions of multiphase fluid flow and particle trajectories were coupled with each other so that drag on every single particle changed in every time step. To solve fluid motion in multiphase flow, level set method was used. Parametric study was repeated for different channel dimensions and different sinusoidal channel profiles. These results were compared with mixing in droplets inside a straight microchannel. Additionally, tracking of multiple particles inside a droplet was performed to simulate the circulating flow profile inside the droplets. Based on the calculation of the dispersion length, particle trajectories, and velocities inside droplets, it is concluded that having smaller channel geometries increases the mixing performance inside the droplet. This also shows that droplet-based fluid flow in microchannels is very suitable for performing chemical reactions inside droplets as it will occur faster. Moreover, narrower and sinusoidal microchannels showed better dispersion length difference compared to straight and wider microchannels.