Incremental maintenance of aggregate and outerjoin expressions

Views stored in a data warehouse need to be kept current. As recomputing the views is very expensive, incremental maintenance algorithms are required. Over recent years, several incremental maintenance algorithms have been proposed. None of the proposed algorithms handle the general case of relational expressions involving aggregate and outerjoin operators efficiently.     

The affinity of an oligodeoxynucleotide-peptide conjugate for an RNA hairpin loop depends on stereochemistry at the DNA-peptide junction

Molecular models of an oligodeoxynucleotide-peptide conjugate complexed to an RNA hairpin loop were constructed to assess the effect of stereoisomerism at the point of attachment of the peptide to the oligodeoxynucleotide on the affinity of the conjugate for an RNA target. The peptide portion of the oligodeoxynucleotide-peptide conjugate, (L-lysine)8, was covalently attached to the N-allyl group of (D)- or (L)-aspartic alcohol that was incorporated into the interior of an antisense oligodeoxynucleotide. The stereocenter in the oligodeoxynucleotide interior originates from either (D)- or (L)-aspartic alcohol. The oligodeoxynucleotide portion of the oligodeoxynucleotide-peptide conjugate forms Watson-Crick base pairs with the single-stranded RNA that flanks the RNA hairpin loop. The positively charged peptide makes specific electrostatic contacts with the negatively charged phosphate backbone of the RNA hairpin loop when attached to the N-allyl of (D)-aspartic alcohol but does not have the proper orientation to make these electrostatic contacts when attached to the N-allyl of (L)-aspartic alcohol. This modelling study emphasizes the importance of stereocontrol at the point of branching in synthesizing oligodeoxynucleotide-peptide conjugates for binding of RNA hairpin loops.     

An Authentication Based Approach for Prevention of Spectrum Sensing Data Falsification Attacks in Cognitive Radio Network

Wireless Personal Communications - This is the era of Intelligent Cognitive Radio Network (CRN) technology that provides the available spectrum with efficient utilization. Cognitive Radio (CR)...     

Introducing robustness in multi-objective optimization

In optimization studies including multi-objective optimization, the main focus is placed on finding the global optimum or global Pareto-optimal solutions, representing the best possible objective values. However, in practice, users may not always be interested in finding the so-called global best solutions, particularly when these solutions are quite sensitive to the variable perturbations which cannot be avoided in practice. In such cases, practitioners are interested in finding the robust solutions which are less sensitive to small perturbations in variables. Although robust optimization is dealt with in detail in single-objective evolutionary optimization studies, in this paper, we present two different robust multi-objective optimization procedures, where the emphasis is to find a robust frontier, instead of the global Pareto-optimal frontier in a problem. The first procedure is a straightforward extension of a technique used for single-objective optimization and the second procedure is a more practical approach enabling a user to set the extent of robustness desired in a problem. To demonstrate the differences between global and robust multi-objective optimization principles and the differences between the two robust optimization procedures suggested here, we develop a number of constrained and unconstrained test problems having two and three objectives and show simulation results using an evolutionary multi-objective optimization (EMO) algorithm. Finally, we also apply both robust optimization methodologies to an engineering design problem.     

Segmented object manufacturing

Rapid Prototyping (RP) is a technology based on a “divide-and-conquer” strategy that enables automatic physical realization of a design without any special tooling. However, existing RP processes suffer from staircase defects since they are all based on 2.5-axis kinematics. To minimize the error due to staircase defects parts are normally built from very thin layers typically with thickness values of 0.010 to 0.300 mm. Therefore, hundreds of layers are required to produce a typical object making RP a slow and costly process. To overcome these limitations, a new RP process called Segmented Object Manufacturing (SOM) is proposed in this paper. SOM makes use of three-axis kinematics in conjunction with a novel slicing method. Slicing in SOM is based on certain visibility-based considerations and is independent of the part accuracy. Since only a few thick layers are used in the SOM technique, a part can be produced faster and cheaper with an accuracy comparable to that of CNC machining.     

Hydrogen from empty cotton boll agro-waste via thermochemical route and feasibility study of operating an IC engine in continuous mode

Hydrogen can be cited as prospective source of clean power. In this work hydrogen rich syn-gas generated from the agro-waste, empty cotton bolls was injected into an IC engine in continuous mode along with gasoline. At the air-fuel ratio of 23.40, specific fuel consumption of 0.35 kg kWh^?1, the engine could be operated with higher efficiency than with gasoline alone. A distinct reduction in emission characteristics could also be seen. Empty cotton bolls derived after removal of cotton from the flower in field, was first studied for fuel properties. The reasonably high heating value (HHV) of 17.54 MJ kg^?1 suggested that it could be a precursor to hydrogen via two stepped thermo-chemical process. The first step involved slow pyrolysis of the biomass at 500 °C for 60 min at a heating rate of 10 °C min^?1 yielding 39.71% bio-char by weight. The C, H, N, S and O contents of the produced bio-char was 59.91, 2.91, 0.72, 0.47 and 35.99% respectively and its HHV was 26.7 MJ kg^?1. Steam gasification of this bio-char, at 700 °C and water flowrate of 7 mL min^?1 exhibited maximum hydrogen yield of 67.42% (v/v) in the syn-gas mixture. Subsequent enrichment of the gas using ethanolamine/ethylene diamine and KMnO₄ solutions resulted in more than 90% (v/v) hydrogen in the combustible gas mixture and the test engine could be effectively operated.     

Automatic synthesis of quaternary quantum circuits

Quaternary encoded binary circuits are more compact than their binary counterpart. Although quaternary reversible circuits are realizable, design of such circuits is still in its infancy. This work proposes a new, enhanced method of quaternary Galois field sum of products (QGFSOP) synthesis for quaternary quantum circuits. To reduce QGFSOP product terms, the algorithm makes use of 11 newly defined quaternary Galois field (QGF) expansions (for a total of 21 QGF expansions). This algorithm achieves QGFSOP minimization with the assistance of a pseudo-Kronecker Galois field decision diagram (QGFDD). This is a novel approach for QGFSOP synthesis. Finally, QGFSOP expressions are translated into quantum cost optimized quaternary quantum circuits using: (1) newly developed quaternary quantum gate realizations of controlled Feynman and Toffoli gate that are optimized in terms of quantum cost, (2) use of composite literals consisting of 1 digit and M–S gates. Performance evaluation against existing works in the literature determined that our proposed method achieves an average QGFSOP expression product term savings of 32.66 %. Also, the synthesized QGFSOP circuits were evaluated in terms of quantum cost.     

Crystallization of Stoichiometric SbSI Glass

Congruent crystallization of antimony sulphoiodide (SbSI) glass of stoichiometric composition, which is prepared successfully for the first time using rapid melt‐quenching, has been investigated using differential scanning calorimetry (DSC). The results for glass powder show a glass transition at 127°C and two separate exothermal peaks with maxima around 140°C and 190°C. The ratio of the intensities of the exothermal peak at ~190°C to the peak at ~140°C increases as the particle size and heating rate are increased, but their total enthalpy remains constant at 62 ± 2 J/g for all DSC runs. Surface heating of the glass induced by a 520 nm CW laser shows two contracted regions: needle‐like crystalline formations at low temperature and bulk crystallization at high temperature. The observed phenomena and DSC results suggest two different kinds of crystallization of the SbSI phase: one‐dimensional crystallization at low temperature which starts from the sample surface and three‐dimensional bulk crystallization that continues the transformation to crystalline state at higher temperatures. The origin of the two different crystallizations can be traced to the strong anisotropy of the SbSI crystal structure due to the weak van der Waals interaction between covalent‐ionic chains (Sb₂S₂I₂)_n.     

Flow and temperature patterns in an inductively coupled plasma reactor: Experimental measurements and CFD simulations

Measurements of temperature patterns in an inductively coupled plasma (ICP) have been carried out experimentally. Plasma torch was operated at different RF powers in the range of 3–14 kW at near atmospheric pressure and over a wide range of sheath gas flow rate (3–25 lpm). Measurements were made at five different axial positions in ICP torch. The chordal intensities were converted into a radial intensity profile by Abel Inversion technique. Typical radial temperature profile shows an off‐axis temperature peak, which shifts toward the wall as the power increases. Temperatures in the range of 6000–14,000 K were recorded by this method. The temperature profiles in the plasma reactor were simulated using computational fluid dynamics (CFD). A good agreement was found between the CFD predictions of the flow and temperature pattern with those published in the literature as well as the temperature profiles measured in the present work. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3647–3664, 2014     

Performance analysis of a variable‐gain amplify‐and‐forward relayed mixed RF‐FSO system

In this work, an amplify‐and‐forward variable‐gain relayed mixed RF‐FSO system is studied. The considered dual‐hop system consists of a radio frequency (RF) link followed by a free space optical (FSO) channel. The RF link is affected by short‐term multipath fading and long‐term shadowing effects and is assumed to follow the generalized‐K fading distribution that approximates accurately several important distributions often used to model communication channels. The FSO channel experiences fading caused by atmospheric turbulence that is modeled by the gamma‐gamma distribution characterizing moderate and strong turbulence conditions. The FSO channel also suffers path loss and pointing error induced misalignment fading. The performance of the considered system is analyzed under the collective influence of distribution shaping parameters, pointing errors that result in misalignment fading, atmospheric turbulence, and path loss. The moment‐generating function of the Signal power to noise power ratio measured end‐to‐end for this system is derived. The cumulative distribution function for the Signal power to noise power ratio present between the source and destination receiver is also evaluated. Further, we investigate the error and outage performance and the average channel capacity for this system. The analytical expressions in closed form for the outage probability, symbol and bit error rate considering different modulation schemes and channel capacity are also derived. The mathematical expressions obtained are also demonstrated by numerical plots.