Preparation and Characterization of Precipitated Silica using Sodium Silicate Prepared from Saudi Arabian Desert Sand

The present study reveals a cost benefit process in an open system for utilizing desert sand for preparing sodium silicate or precipitated silica. A simple alkali fusion method has been developed to prepare sodium silicate directly from sand and finally pure precipitated silica by acid precipitation. The reaction weight ratio of alkali to sand reaction parameters are studied for optimizing the silica yield. About 80% pure precipitated silica has been prepared in an open system at 150 ^°C within 45 min. Wet chemical methods, FTIR, TG-DTA, XRD and SEM techniques are used to characterize the silica prepared from sand available in Saudi Arabian deserts. In the XRD pattern, the peak corresponding to silica was obtained at the diffraction angle of 21.8 ^° and it was found to be amorphous in nature.     

SmartPads: a plug-N-play configurable tangible user interface

One common concern with video games today is the lack of physical activity they demand from the user. The design of games and tangible user interfaces (TUIs) that stimulate players and engage them into fun exercising activities is starting to attract the attention of many researchers and companies. This paper presents the software and hardware design and development of a TUI intended for exercise-based games targeted mostly towards children. The proposed TUI, SmartPads, can be constructed using elemental building blocks (pads) into numerous shapes. The pads-which are individually controlled by microcontrollers-are mapped onto a computer screen in real-time. A user interacts with the TUI by stepping on the pads. To evaluate the functionality and efficiency of the TUI, we developed three games in the field of exergaming. The games also have an educational value and are integrated with multimedia output modalities to enrich children’s playing experience.

     

Catalytic combustion of selected hydrocarbon fuels on platinum: Reactivity and hetero–homogeneous interactions

This paper addresses the interactions between homogeneous and heterogeneous reactions for different hydrocarbons namely, compressed natural gas (CNG), liquefied petroleum gas (LPG), butane and dimethyl ether (DME) over platinum. Experiments are performed to study the effects of varying the temperature of the incoming mixture (T_jet), its equivalence ratio (Ø) and the Reynolds number (Re), on the reactivity limits. Computational fluid dynamic (CFD) calculations using detailed chemical kinetics for both the platinum surface and gas phase are completed for a range of methane–air mixtures to resolve the impact of varying T_jet, Ø and Re on the compositional structure of the flow. Comparison between numerical and experimental results is performed where relevant.For flameless conditions (defined by the presence of reactions on the plate without a gaseous flame), it is found for all fuels studied here that the temperature of the platinum plate, resulting from reactions with the co-flowing fuel–air mixture, increases with increasing T_jet and Re. However, with CNG, the temperature of the plate peaks near stoichiometry while for LPG, butane and DME the peak occurred at richer mixtures of Ø ≈ 1.5. The reactive limits for CNG, propane and DME are found to broaden significantly. Numerical simulations show very good agreement with the measured plate temperature at different equivalence ratios. The computed compositional structure confirms the existence of a flame inhibition effect due to the presence of the catalyst and shows interesting trends of some species at different Re, T_jet and Ø. Gas and surface chemistries seem to affect a few species such as CO, CO₂, H₂, and H₂O depending on the conditions of the co-flowing mixture. Minor species such as CH₃, CH₂O, O, HCO, and OH are largely controlled by gas-phase chemistry.     

Recovery of polarimetric Stokes images by spatial mixture models

A Bayesian approach for joint restoration and segmentation of polarization encoded images is presented with emphasis on both physical admissibility and smoothness of the solution. Two distinct models for the sought polarized radiances are used: (i) the polarized light at each site of the image is described by its Stokes vector, which directly follows a mixture of truncated Gaussians, explicitly assigning zero probability to inadmissible configurations and (ii) polarization at each site is represented by the coherency matrix, which is parameterized by a set of variables assumed to be generated by a spatially varying mixture of Gaussians. Application on real and synthetic images using the proposed methods assesses the pertinence of the approach.     

Evaluation of Vitreous and Starchy Syrian Durum (Triticum Durum) Wheat Grains: The Effect of Amylose Content on Starch Characteristics and Flour Pasting Properties

The physiochemical composition of durum wheat cultivars was studied in order to investigate the influence of vitreousness on the chemical composition of starch and its thermal and pasting properties. Six durum wheat lines were chosen and grown in northern Syria. Grains of each cultivar were visually sorted according to the degree of vitreousness into fully vitreous and fully starchy fractions. Amylose/amylopectin ratio and total starch was determined using Megazyme methods, while thermal and pasting properties were determined using DSC and RVA. Starchy kernels were higher in total starch than vitreous kernels but showed a decreased amylose content. Negative linear relations were found between amylose content, and both peak viscosity and breakdown. Trends in variation of gelatinisation characteristics were observed between vitreous and starchy kernels from the same cultivar, with higher total enthalpy being associated with starchy grains compared with vitreous grains of the same line.     

Decomposing and Solving Timetabling Constraint Networks

The binary version of the school timetabling (STT) problem is a real‐world example of a constraint network that includes only constraints of inequality. A new and useful representation for this real‐world problem, the STT_Grid, leads to a generic decomposition technique. The paper presents proofs of necessary and sufficient conditions for the existence of a solution to decomposed STT_Grids. The decomposition procedure is of low enough complexity to be practical for large problems, such as a real‐world high school.
To test the decomposition approach, a typical high school was analyzed and used as a model for generating STT_Grids of various sizes. Experiments were conducted to test the difficulty of large STT networks and their solution by decomposition. The experimental results show that the decomposition procedure enables the solution of large STT_Grids (620 variables for a real school) in reasonable time. The constraint network of a typical STT_Grid is sparse and belongs to the class of easy problems. Still, due to the sizes of STTs, good constraint satisfaction problem search techniques (i.e., BackJumping and ForwardChecking) do not terminate in reasonable times for STT_Grids that are larger than 300 variables.     

External Memory View-Dependent Simplification

In this paper, we propose a novel external-memory algorithm to support view-dependent simplification for datasets much larger than main memory. In the preprocessing phase, we use a new spanned sub-meshes simplification technique to build view-dependence trees I/O-efficiently, which preserves the correct edge collapsing order and thus assures the run-time image quality. We further process the resulting view-dependence trees to build the meta-node trees, which can facilitate the run-time level-of-detail rendering and is kept in disk . During run-time navigation, we keep in main memory only the portions of the meta-node trees that are necessary to render the current level of details, plus some prefetched portions that are likely to be needed in the near future. The prefetching prediction takes advantage of the nature of the run-time traversal of the meta-node trees, and is both simple and accurate. We also employ the implicit dependencies for preventing incorrect foldovers, as well as main-memory buffer management and parallel processes scheme to separate the disk accesses from the navigation operations, all in an integrated manner. The experiments show that our approach scales well with respect to the main memory size available, with encouraging preprocessing and run-time rendering speeds and without sacrificing the image quality.