FQL‐RED: an adaptive scalable schema for active queue management

In a potentially congested network, random early detection (RED) active queue management (AQM) proved effective in improving throughput and average queuing delay. The main disadvantage of RED is its sensitive parameters that are impossible to estimate perfectly and adjust manually because of the dynamic nature of the network. For this reason, RED performs differently during different phases of a scenario and there is no guarantee that it will have optimal performance. Giving adaptability to RED has been the subject of broad research studies ever since RED was proposed. After a substantial study of AQM schemes and presenting a novel categorization for so‐called modern approaches utilizing artificial intelligence tools to improve AQM, this paper proposes an algorithm enhancing RED as an add‐on patch that makes minimal changes to the original RED. Being built on the basis of AQM schemes like ARED and Fuzzy‐RED, this algorithm inherits adaptability and is able to adjust RED inaccurate parameters regarding network traffic status, trying to optimize throughput and average queuing delay in a scenario. This algorithm is a Q‐learning method enhanced with a fuzzy inference system to provide RED with self‐adaptation and improved performance as a result. Given the name of FQL‐RED, this algorithm outperformed RED, ARED, and Fuzzy‐RED, as the OPNET simulations show. Copyright © 2010 John Wiley & Sons, Ltd.     

Polyaniline-supported acid as an efficient and reusable catalyst for a one-pot synthesis of β-acetamido ketones via a four-component condensation reaction

Polyaniline-supported acid salts such as polyaniline-hydrochloride, polyaniline-sulfate and polyaniline-nitrate were prepared by oxidation of aniline using ammonium persulfate as oxidizing agents. Polyaniline salts were used as catalyst for the preparation of β-acetamido ketones. Polyaniline-sulfate salt was found to be the best catalyst for the preparation of β-acetamido ketones. Present methodology offers several advantages, such as cheaper process, easy synthesis of stable catalyst, simple work-up procedure, and excellent activity with less amount of catalyst and in addition, the catalyst can be easily recovered after completion of the reaction and reusable without affecting its activity.     

Influence of the molecular weight of chitosan on the spinnability of chitosan/poly(vinyl alcohol) blend nanofibers

The electrospinning of the biopolymer chitosan (CS) and poly(vinyl alcohol) (PVA) was investigated with 90% acetic acid as the solvent and with different CS/PVA ratios. The long chains of high‐molecular‐weight CS prevented it from forming nanofibers in a high‐voltage field. The treatment of CS under high‐temperature alkali conditions reduced its molecular weight exponentially with the treatment time and caused a reduction of the viscosity consequently. PVA, acting as a plasticizer and accompanied by the alkali‐treated CS of lower viscosity, made the electrospinning of CS/PVA blends possible. The effects of the duration of the alkali treatment on the molecular weight of CS and its viscosity were investigated and optimized. The diameter of the bicomponent nanofiber decreased proportionally with the increase in the CS portion, whereas the surface porosity increased inversely. Fourier transform infrared studies illustrated that the alkali treatment or blending of CS with PVA had no effect on its chemical nature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Photoactive Electrodes Incorporating Electrosprayed Bacterial Reaction Centers

Highly efficient light absorption and charge separation within the photosystem and reaction center (RC) complexes of photosynthetic plants and bacteria are of great interest for solar cell and photo detector applications, since they offer almost unity quantum yield and expected ultimate power conversion efficiencies of more than 18% and 12%, respectively. In addition, the charge separated states created by these protein complexes are very long lived compared to conventional semiconductor solar cells. In this work, a novel technique is presented for the deposition of photosynthetic protein complexes, by electrospraying RCs of Rhodobacter sphaeroides onto highly ordered pyrolytic graphite (HOPG) electrodes. Remarkably, it is shown that the RCs not only survive exposure to the high electric fields but also yield peak photocurrent densities of up to 7 μA cm^?2, which is equal to the highest value reported to date.     

Spectral estimation of the energy-band-structure parameters of nanoparticles of potassium polytitanate modified in transition metal salt solutions

An approach to spectral analysis of the energy-band-structure parameters (bandgap width and Urbach energy) of potassium polytitanate (PPT) nanoparticles modified by transition metals is proposed, which can provide a basis for the synthesis of new photocatalytic materials. It is established that the modified PPT samples are characterized by reduced values of the bandgap width and higher values of the Urbach energy as compared to the initial material. Possible mechanisms of this phenomenon are discussed.     

Optimal visual sensor placement for coverage based on target location profile

The proper placement of visual sensors across a sensor field for covering targets with arbitrary location and orientation is a mission-critical decision in surveillance applications. The specifics of sensor deployment in these applications not only determine the maximum achievable coverage, but it also affects the quality of the target’s appearance in cameras for subsequent use in vision tasks. However, the inaccuracies inherent in localization techniques and the lack of knowledge regarding the target orientation render existing proposals insufficient for real-life scenarios. In this paper, we address both challenges. First, we extend the conventional point representation of targets with a circular model to account for full-angle coverage of targets with known location yet with unknown orientation from all directions. We then assume, in the absence of precise location information, a trajectory profile of targets could instead be generated through the importance sampling of the environment, indicating spots where the target is most likely located. This profile-based abstraction enables us to capture the uncertainty in target’s location by encircling every agglomeration of proximal samples within one cluster. Each cluster can then be viewed as a virtual macroscopic circular target for which we formulate the coverage problem in terms of a Binary Integer Programming (BIP) model. We have also taken into account the presence of obstruction in between multiple targets by calculating the angles of view of the sensors in an occlusion-dependant manner, effectively determining optimal placement for maximal instead of full-angle coverage. Evaluation results derived from our simulation experiments reveal that the proposed mechanism can effectively achieve high coverage accuracy with minimum number of deployed sensors.     

Two-phase cooling characteristics of a saturated free falling circular jet of HFE7100 on a heated disk: Effect of jet length

Direct jet impingement boiling heat transfer operating at low flow rates is of great interest for the localized moderate heat fluxes from the targets with delicate mechanical structure, where the aggressive techniques such as high-speed jets are not suitable. Boiling heat transfer from an upward facing disk targeted by a falling jet was studied experimentally at different volumetric flow rates and various jet lengths. The working fluid was chosen to be the dielectric liquid HFE7100 and the heated spot was an 8-mm diameter disk. Using previous CHF correlations in their original form, valid at very low volumetric flow rates, results in large disagreements since it was found that variation in the jet length changes the boiling characteristics. It is demonstrated that although the circular hydraulic jump formation within the heater diameter may suppress the heat transfer under certain conditions, moving the jet closer to the target may significantly improve the boiling curves at the critical heat flux (CHF) regime. At low flow rates, the CHF increases as the jet length decreases while for moderate and high flow rates the boiling curves show approximately a universal behavior for different jet lengths. For such low flow rates, the effect of jet length on boiling curves was shown to be related to the variation of the cross section of the falling jet and the formation of hydraulic jump at radial distances smaller than the heater diameter. The current CHF results for different jet lengths are correlated by including the effect of jet length in the previous correlation proposed by Sharan and Lienhard.     

Dynamic model for market-based capacity investment decision considering stochastic characteristic of wind power

This paper proposes a decentralized market-based model for long-term capacity investment decisions in a liberalized electricity market with significant wind power generation. In such an environment, investment and construction decisions are based on price signal feedbacks and imperfect foresight of future conditions in electricity market. System dynamics concepts are used to model structural characteristics of power market such as, long-term firms’ behavior and relationships between variables, feedbacks and time delays. For conventional generation units, short-term price feedback for generation dispatching of forward market is implemented as well as long-term price expectation for profitability assessment in capacity investment. For wind power generation, a special framework is proposed in which generation firms are committed depending on the statistical nature of wind power. The method is based on the time series stochastic simulation process for prediction of wind speed using historical and probabilistic data. The auto-correlation nature of wind speed and the correlation with demand fluctuations are modeled appropriately. The Monte Carlo simulation technique is employed to assess the effect of demand growth rate and wind power uncertainties. Such a decision model enables the companies to find out the possible consequences of their different investment decisions. Different regulatory policies and market conditions can also be assessed by ISOs and regulators to check the performance of market rules. A case study is presented exhibiting the effectiveness of the proposed model for capacity expansion of electricity markets in which the market prices and the generation capacities are fluctuating due to uncertainty of wind power generation.