The meshless approach for solving 2D variable-order time-fractional advection–diffusion equation arising in anomalous transport

In this paper, with the aim of extending an elegant and straightforward numerical approximation to describe one of the most common physical phenomena has been undertaken. In this regard, the generalization of advection–diffusion equation, namely, the time-fractional advection–diffusion equation with understanding sense variable-order fractional derivative, is taken into consideration. An efficient and accurate approach is relying on the Kansa scheme and finite difference method to provide a mathematical framework to treat the spatial discretization and temporal term, respectively. The meshless collocation approach is utilized for interior scattered points and those on the boundary. Thus, the problem under consideration is reduced to a system of linear algebraic equations. The use of the radial basis function as shape function brings many advantages for proposal numerical method in terms of improved accuracy by setting an appropriate shape parameter and applied for solving high-dimensional models without extra cost. The validity and accuracy of the proposed approach is investigated by four various examples involving three benchmark examples and a practical application of pollution transfer phenomena.

     

A New Searchable Encryption Scheme with Integrity Preservation Property

Wireless Personal Communications - Searchable encryption schemes allow documents’ owners to store their encrypted documents on servers, search for the desired keyword and then download only...     

A social recommender system using item asymmetric correlation

Recommender systems have been one of the most prominent information filtering techniques during the past decade. However, they suffer from two major problems, which degrade the accuracy of suggestions: data sparsity and cold start. The popularity of social networks shed light on a new generation of such systems, which is called social recommender system. These systems act promisingly in solving data sparsity and cold start issues. Given that social relationships are not available to every system, the implicit relationship between the items can be an adequate option to replace the constraints. In this paper, we explored the effect of combining the implicit relationships of the items and user-item matrix on the accuracy of recommendations. The new Item Asymmetric Correlation (IAC) method detects the implicit relationship between each pair of items by considering an asymmetric correlation among them. Two dataset types, the output of IAC and user-item matrix, are fused into a collaborative filtering recommender via Matrix Factorization (MF) technique. We apply the two mostly used mapping models in MF, Stochastic Gradient Descent and Alternating Least Square, to investigate their performances in the presence of sparse data. The experimental results of real datasets at four levels of sparsity demonstrate the better performance of our method comparing to the other commonly used approaches, especially in handling the sparse data.     

Hydrothermal Preparation, Crystal Structures, Spectroscopic and Thermal Analyses of Cadmium(II) and Cobalt(II) Coordination Polymers With Pyridine-2,3-dicarboxylic Acid

Two novel 1D coordination polymers, [M(μ-2,3-pydc)(H₂O)₃]_n (M = Cd for 1 and Co for 2) (2,3-pydcH₂ = pyridine-2,3-dicarboxylic acid) have been hydrothermally synthesized. Both complexes were characterized by elemental analysis and by IR and UV–Vis spectroscopy. Their molecular and crystal structures were determined by X-ray crystal structure analysis and their thermal stability by TGA-DTA methods. Compound 1 crystallizes in the orthorhombic Pca2 space group, while compound 2 crystallizes in the triclinic P−1 space group. Polymeric chains of 1 and 2 are composed of M(II) ions bridged by pyridine-2,3-dicarboxylate ions (2,3-pydc) in N,O,O′ fashion. Distorted octahedral coordination geometry around the metal ions is completed by three water molecules. A wide range of hydrogen bonding (of the O–H···O type) is also present in the crystal structures. These interactions lead to formation of a 3D structure for 1 and 2D network for 2.     

Acylation of Pyrroles and their Free (N‐H)‐Derivatives via Palladium‐Catalyzed Carbopalladation of Nitriles

An efficient regioselective synthesis of 2‐acylpyrroles via palladium‐catalyzed addition of pyrroles with benzonitriles and subsequent hydrolysis is developed. The direct acylation reaction of protected as well as (NH)‐free pyrroles proceeded smoothly to afford 2‐acylpyrrole scaffolds of high biological interest.

     

Effect of Phosphorous Inoculation on Creep Behavior of a Hypereutectic Al-Si Alloy

Creep behavior of Al-Si hypereutectic alloys inoculated with phosphorus was investigated using the impression creep testing. The results showed that at stress regimes of up to 400-450 MPa and temperatures up to 300 °C, no significant creep deformation occurred in both uninoculated and inoculated specimens; however, at temperatures above 300 °C, the inoculated alloys presented better creep properties. Creep data were used to calculate the stress exponent of steady-state creep rate, n, and creep activation energy, Q, for different additive conditions where n was found varied between 5 and 8. Owing to the fact that most alloys have lower values for n (4, 5), threshold stress was estimated for studied conditions. The creep governing mechanisms for different conditions are discussed here, with a particular attention to the effect of phosphorous addition on the microstructural features, including number of primary silicon particles, mean primary silicon spacing, and morphology and distribution of eutectic silicon.     

Novel extracellular hyper acidophil and thermostable α‐amylase from Micrococcus sp.NS 211

Among several bacteria examined in this study, a hyper acidophil and thermostable Micrococcus sp.NS 211 designated as M.Amy NS 211 was selected for production of amylase using starch agar plates with following incubation at 85°C. Identification by 16SrRNA on selected bacterium disclosed the highest similarity for protean regions of this gene, 27 F and 1492R as Micrococcus sp.NS 211. Although activity of M.Amy NS 211 was established at temperatures between 70 and 110°C and pH ranges 1.2–8.0, the optimum temperature and pH was achieved at 85°C and 3.5 in sodium citrate buffer system respectively. Two‐step chromatography was performed using (CM Bio‐Gel A) and (Bio‐Gel A‐150) columns to purify 84 kDa hyper acidophil and thermostable α‐amylase. SDS‐PAGE analysis showed molecular mass and amylolytic activity as single band. Enhancement of enzyme activity was obtained in presence of 5 mM MnCl₂ (298%), CaCl₂ (347%), FeCl₂ (211%), MgCl₂ (253%), ZnCl₂ (146%), NiCl (142%), NaCl (141%), Na‐sulfate (153%) while inhibition was observed with (5 mM) EDTA, PMSF (3 mM), urea (8 M), and SDS (1%) at 143, 134, 43, and 119%, respectively. M.Amy NS 211 can be applied in laundry detergents, textile, and modern relevant industrial processes at extreme temperatures and under acidic conditions.