Query verification schemes for cloud-hosted databases: a brief survey

Database query verification schemes provide correctness guarantees for database queries. Typically such guarantees are required and advisable where queries are executed on untrusted servers. This need to verify query results, even though they may have been executed on one’s own database, is something new that has arisen with the advent of cloud services. The traditional model of hosting one’s own databases on one’s own servers did not require such verification because the hardware and software were both entirely within one’s control, and therefore fully trusted. However, with the economical and technological benefits of cloud services beckoning, many are now considering outsourcing both data and execution of database queries to the cloud, despite obvious risks. This survey paper provides an overview into the field of database query verification and explores the current state of the art in terms of query execution and correctness guarantees provided for query results. We also provide indications towards future work in the area.     

Synthesis of biodiesel from Scenedesmus sp. by microwave and ultrasound assisted in situ transesterification using tungstated zirconia as a solid acid catalyst

Oleaginous Scenedesmus sp. was cultivated phototrophically in an open pond for biofuels production. The culture was harvested and subsequently dewatered and dried. The chemical properties of the Scenedesmus sp. lipids were determined as per standard ASTM methods. Biodiesel was synthesized by in situ transesterification from dried biomass using microwave and sonication techniques with tungstated zirconia (WO₃/ZrO₂) as a solid acid catalyst. In situ transesterification allowed minimizing the requirement of solvents by merging the two steps (i.e. extraction of lipid and conversion to biodiesel) to a single step. The use of a solid catalyst effectively reduces the purification cost of biodiesel due to ease of separation and potential for reuse. The conversion of Scenedesmus sp. lipids to biodiesel was determined by GC. Box–Behnken design was used for optimization of the variables to optimize the biodiesel yield and conversion. The efficiency of the two processes was compared.     

Pervaporation removal of volatile organic compounds from aqueous solutions using the highly permeable PIM‐1 membrane

Wastewater containing volatile organic compounds (VOCs) is generated in various industrial processes and is seriously harmful to the natural environment and human health. Its treatment has become extremely important due to increasing environment concerns. Here, a high permeable membrane for fast and high‐efficient VOCs removal from aqueous solutions by pervaporation is reported. The as‐prepared PIM‐1 membrane allows ultrafast permeation of VOCs and exhibits excellent VOCs selectivity, particularly for ethyl acetate, dimethyl ether, and acetonitrile. Typically, the PIM‐1 membrane exhibits an ultrahigh flux and separation factor of 39.5 kg μm m^?2 h^?1 and 189, respectively, in the pervaporation of 1.0 mol% aqueous ethyl acetate solution. Furthermore, the solubility‐diffusion mechanism is revealed in the pervaporation of 10 kinds of 1.0 mol% VOCs solutions. It is found that the pervaporation performance is affected directly by physicochemical properties of VOCs. Moreover, effects of feed composition and temperature on the pervaporation are studied in details. © 2015 American Institute of Chemical Engineers AIChE J, 62: 842–851, 2016     

Physicochemical,mineralogy,and thermo-kinetic characterisation of newly discovered Nigerian coals under pyrolysis and combustion conditions

In this study,the physicochemical,microstructural,mineralogical,thermal,and kinetic properties of three newly discovered coals from Akunza (AKZ),Ome (OME),and S...     

Calculating the steady-state polarizations of quantum cellular automata (QCA) circuits

We present on the use of well-known stochastic methods for computing the steady-state polarizations of quantum cellular automata (QCA) circuits. Typically, a Boltzmann distribution, which requires the exploration of the complete configuration space of an \(N\) -cell QCA circuit, is used to compute the \(2^N\) steady-states of the QCA circuit. However, the exponential growth in states as the circuit size grows makes computing the Boltzmann distribution infeasible for large circuits. Thus, we approximate the Boltzmann distribution of a QCA circuit by conducting a partial exploration of the complete configuration space by means of a Monte Carlo method, simulated annealing, and a genetic algorithm. The approximated Boltzmann distribution from each method was able to compute the steady-state polarizations with a very high degree of accuracy, with the simulated annealing algorithm producing the best results.     

Simultaneous adsorption of a mixture of paraquat and dye by NaY zeolite covered with alkylsilane

The surfaces of NaY zeolite particles were modified by the alkylsilylation of n-octadecyltrichlorosilane (OTS). Two kinds of modified NaY zeolites were prepared; one with its external surface partially and the other fully covered with alkylsilyl groups. Since the size of OTS is bigger than the pore diameter of NaY, it is attached on the external surface, leaving the internal pore accessible to adsorbate molecules. As a result of alkylsilylation, the adsorption properties of these sorbents were improved. The adsorption properties of these materials were tested by their reaction in a mixture of paraquat and blue dye. The results demonstrate that the alkysilylated NaY materials are capable of simultaneous adsorption of paraquat and blue dye. Paraquat was selectively adsorbed into the internal pore of the zeolite whereas the dye on the externally attached alkylsilyl groups of the sorbent; displaying the unique bimodal amphiphilic character of the alkylsilylated NaY zeolites.     

Exploiting the orbital motion of water particles for energy extraction from waves

In wave motion, the water particles are known to follow orbital paths. This orbital motion was used to drive five-bladed Savonius rotors. Experiments were performed on an array of four rotors placed in a two-dimensional (2-D) wave channel. The flow around the rotors was documented using particle image velocimetry measurements. The submergence of the rotors and the distance between them were varied, and the rotational speeds of the rotors (N_n) were recorded at different wave frequencies. It was found that rotational speeds increased with an increase in the wave frequency, as it amplified the wave height that increased the kinetic energy of the particles in their orbital motion. The rotational speeds decreased when the distance between the rotors increased. High rotational speeds are recorded when the array of the rotors is placed close to the water surface at the smallest centre-to-centre distance between the rotors.     

Simulation of a hydrogen/natural gas engine and modelling of engine operating parameters

At the present work for improving the engine performance and decrease of emissions, a port injection gasoline engine is converted into direct injection. Engine performance behavior was investigated by AVL Fire software with adding hydrogen to natural gas from 0% up to 30%. Validation of the simulated model and experimental results show good confirmation. To determine the relationship between independent variables engine speed, ignition timing, injection timing and H₂% versus the dependent variables including engine performance parameters, specific fuel consumption, CO and statistical analysis models were used. Comparison between different errors models shows that Radial basis function model with training algorithm Bayesian regularization back propagation can estimate better engine performance variables. The results showed that adding hydrogen to natural gas cause the output power, torque, fuel consumption efficiency increase and specific fuel consumption drop. Also, CO decreases when ignition and injection timing be advanced and engine speed reaches to its largest.