Transient analysis of thermo-elastic waves in thick hollow cylinders using a stochastic hybrid numerical method,considering Gaussian mechanical properties

This article attempts to study the stochastic coupled thermo-elasticity of thick hollow cylinders subjected to thermal shock loading considering uncertainty in mechanical properties. The thermo-elastic governing equations based on Green–Naghdi theory (without energy dissipation) are stochastically solved using a hybrid numerical method (combined Galerkin finite element and Newmark finite difference methods). The mechanical properties are considered as random variables with Gaussian distribution, which are generated using Monte Carlo simulation method with various coefficients of variations (COVs). The effects of uncertainty in mechanical properties with various coefficients of variations on thermo-elastic wave propagation are studied in detail. Also, the maximum, mean and variance of temperature, displacement and stresses are illustrated across thickness of cylinder in various times.     

An efficient and simple synthesis of α-amino phosphonates as ‘drug like’ molecules catalyzed by silica-supported perchloric acid (HClO4–SiO2)

An efficient and direct protocol is described for the preparation of α-amino phosphonates derivatives by employing a multi-component, one-pot condensation reaction of aldehyde, amine and trialkyl phosphite in the presence of silica-supported perchloric acid (3 mol%) under solvent-free conditions. The thermal solvent-free green procedure offers advantages such as shorter reaction time, simple work-up, high yield, recovery and reusability of catalyst.     

Multiple-buyer multiple-vendor multi-product multi-constraint supply chain problem with stochastic demand and variable lead-time: A harmony search algorithm

In this paper, a multi-buyer multi-vendor supply chain problem is considered in which there are several products, each buyer has limited capacity to purchase products, and each vendor has warehouse limitation to store products. In this chain, the demand of each product is stochastic and follows a uniform distribution. The lead-time of receiving products from a vendor to a buyer is assumed to vary linearly with respect to the order quantity of the buyer and the production rate of the vendor. For each product, a fraction of the shortage is backordered and the rest are lost. The ordered product quantities are placed in multiple of pre-defined packets and there are service rate constraints for the buyers. The goal is to determine the reorder points, the safety stocks, and the numbers of shipments and packets in each shipment of the products such that the total cost of the supply chain is minimized. We show that the model of this problem is of an integer nonlinear programming type and in order to solve it a harmony search algorithm is employed. To validate the solution and to compare the performance of the proposed algorithm, a genetic algorithm is utilized as well. A numerical illustration and sensitivity analysis are given at the end to show the applicability of the proposed methodology in real-world supply chain problems.     

One-Pot Three-Component Synthesis of β -Acylaminoketones Containing a Thiophene Ring by the Use of Tetrachlorosilane-Zinc Chloride as a Binary Reagent Under Ambient Conditions

A new route for the synthesis of β -acylaminoketones containing a thiophene ring through multicomponent condensation reaction of different ketones, different aldehydes, and different nitriles with tetrachlorosilane (TCS) and zinc chloride as the binary reagent is described.     

Lewis acid catalyst free synthesis of benzimidazoles and formamidines in 1,1,1,3,3,3-hexafluoro-2-propanol

A simple, inexpensive, environmentally friendly and efficient route for the synthesis of benzimidazole and formamidine derivatives by the reaction of O-phenylenediamines or amines with orthoesters using hexafluoroisopropanol as a solvent/catalyst is described.     

Disturbance rejection-based robust control for micropositioning of piezoelectric actuators

Precise control of piezoelectric actuators used in micropositioning applications is strongly under the effect of internal and external disturbances. Undesired external forces, unmodelled dynamics, parameter uncertainties, time variation of parameters and hysteresis are some sources of disturbances. These effects not only degrade the performance efficiency, but also may lead to closed-loop instability. Several works have investigated the positioning accuracy for constant and slow time-varying disturbances. The main concern is controlling performance and also the presence of time-varying perturbations. Considering unknown source and magnitude of disturbances, the estimation of the existing disturbances would be inevitable. In this paper, a compound disturbance observer-based robust control is developed to achieve precise positioning in the presence of time-varying disturbances. In addition, a modified disturbance observer is proposed to remedy the effect of switching behaviour in the case of slow time variations. A modified Prandtl–Ishlinskii (PI) operator and its inverse are utilized for both identification and real-time compensation of the hysteresis effect. Experimental results depict that the proposed approach achieves precise micropositioning in the presence of estimated disturbances.     

Quantitative and qualitative studies of silica in different rice samples grown in north of Iran using UV-vis, XRD and IR spectroscopy techniques

Silicon is an essential trace element and is found in vegetables, fruits, cereals, water, pasta and rice (Oryza sativa). In this work, the silica content of different types of rice grains were measured. Here, we used the heteropoly blue photometric method with a double beam UV-vis spectrophotometer to determine the amount of silicon in rice samples (n = 7) that were collected in the north of Iran. The samples were digested with wet-ashing method by microwave-assisted heating and then treated with ammonium molybdate to produce a yellow color compound in acidic solution (ca. pH 1.2) and then reduced to give a heteropoly compound with a blue color. Analyses were performed using standard addition method and absorbance values were measured with double beam UV-vis spectrophotometer at λ_max = 815 nm. Results indicated that the silica content was 307-451 mg/kg for the samples. X-ray diffraction patterns and infra-red spectra were obtained from rice samples without any sample treatment.     

Lower and upper bounds for location-arc routing problems with vehicle capacity constraints

This paper addresses multi-depot location arc routing problems with vehicle capacity constraints. Two mixed integer programming models are presented for single and multi-depot problems. Relaxing these formulations leads to other integer programming models whose solutions provide good lower bounds for the total cost. A powerful insertion heuristic has been developed for solving the underlying capacitated arc routing problem. This heuristic is used together with a novel location–allocation heuristic to solve the problem within a simulated annealing framework. Extensive computational results demonstrate that the proposed algorithm can find high quality solutions. We also show that the potential cost saving resulting from adding location decisions to the capacitated arc routing problem is significant.