Determination of Cr ions in biological and environmental samples by a chromium(III) membrane sensor based on 5-amino-1-phenyl-1H-pyrazole-4-carboxamide

A highly Cr³⁺-selective ionophore, based on 5-amino-1-phenyl-1H-pyrazole-4-carboxamide (APC) as a carrier, was synthesized in order to obtain a Cr³⁺ ion-selective electrode. The demonstrated characteristics of the sensor included a linear dynamic range between 1.0 × 10^− 6 and 1.0 × 10^− 1 M with a near Nernstian slope of 19.6 ± 0.4 mV per decade, a detection limit of 5.3 × 10^− 7 M, a very good selectivity for Cr³⁺ over other cations in a wide pH range (3.2-6.3). Furthermore, the newly-designed electrode presented a fast response time of 10 s with a lifetime of at least 2 months indicating no considerable potential divergence. The sensor accuracy was investigated by the potentiometric titration of a Cr(III) solution with EDTA as well as the monitoring of Cr(III) in mixtures of three and five different ions. As a result, the developed sensor provided satisfactory results after its application in the Cr³⁺ determination in biological samples (urine and synthetic plasma) and also in wastewater of chromium electroplating industries.     

Optimal retailer bidding in a DA market - a new method considering risk and demand elasticity

This paper presents a new method to determine the optimal demand function for a retailer in power markets. It assumes that the retailer purchases the energy from either the day-ahead or the regulation market and sells it to the end users through fixed and/or real-time pricing contracts. The load is assumed to be price sensitive and the retailer to be price-taker. Through participation in the market and managing its risk, the retailer attempts to maximize its profit. The proposed method is tested on a typical power market.     

High Surface Area MgO as a Highly Effective Heterogeneous Base Catalyst for Three-Component Synthesis of Tetrahydrobenzopyran and 3,4-Dihydropyrano[c]chromene Derivatives in Aqueous Media

Magnesium oxide (MgO) as a highly effective heterogeneous base catalyst effectively catalyzes the three component reaction of aryl aldehydes, malononitrile and α-hydroxy or α-amino activated C–H acids such as 1,3-cyclohexanedione, dimedone, 4-hydroxy-6-methylpyrone, 4-hydroxycoumarin, 1,3-dimethylbarbituric acid and 1,3-dimethyl-6-amino uracil to the formation of the corresponding pyran annulated heterocyclic systems. The catalyst is inexpensive and easily obtained, stable and storable, easily recycled and reused for several cycles with consistent activity.     

Surrogate-based Optimization of Horizontal Well Placement in a Mature Oil Reservoir

Abstract

Exploitation of mature oil reservoirs has forced researchers to find ways for enhancing production from such reservoirs. An effective way to do so is drilling horizontal wells. There are many advantages for these kinds of wells but they require extra investment for drilling and completion. The objective of this research is to choose location, direction, and length of a new horizontal well to maximize accumulative oil production over a planning horizon. The authors employ various metamodeling techniques in order to build a good approximate model for estimation of accumulated outflow from each well scenario. This leads to a significant reduction in the computation time. The authors built and compared 18 metamodels based on quadratic, multiplicative, and radial basis functions for the reservoir under study. Then, the best model was introduced to a global optimization search using a Genetic algorithm. Numerical results showed that 3 million barrels of more oil could be produced from the designated well as compared with those of the initial scenarios, which is a significant improvement.     

Experimental study of heat transfer enhancement using water/ethylene glycol based nanofluids as a new coolant for car radiators

Traditionally forced convection heat transfer in a car radiator is performed to cool circulating fluid which consisted of water or a mixture of water and anti-freezing materials like ethylene glycol (EG). In this paper, the heat transfer performance of pure water and pure EG has been compared with their binary mixtures. Furthermore, different amounts of Al₂O₃ nanoparticle have been added into these base fluids and its effects on the heat transfer performance of the car radiator have been determined experimentally. Liquid flow rate has been changed in the range of 2–6 l per minute and the fluid inlet temperature has been changed for all the experiments. The results demonstrate that nanofluids clearly enhance heat transfer compared to their own base fluid. In the best conditions, the heat transfer enhancement of about 40% compared to the base fluids has been recorded.     

Extraction of Lycopene from Tomato Paste by Ursodeoxycholic Acid Using the Selective Inclusion Complex Method

Lycopene, a precursor of β‐carotene with well‐known antioxidant activity and powerful health properties, can be found in many natural products such as tomato (Lycopersicon esculentum), watermelon, red pepper, and papaya. Many separation methods have been reported for extracting lycopene from its sources. The inclusion complex is an effective method for extraction and purification of organic chemicals. This procedure has 2 main components: host and guest molecules. In this study, lycopene (guest) was extracted from tomato paste by ursodeoxycholic acid, the inclusive agent (host). The molecular structure of the extracted lycopene was then confirmed by ¹HNMR and its purity was evaluated using high‐performance liquid chromatography and UV‐Vis spectrophotometry methods, in comparison with a standard product. The results indicated that the proposed separation method was very promising and could be used for the extraction and purification of lycopene from tomato paste.     

Autonomous fault-diagnosis and decision-making algorithm for determining faulty nodes in distributed wireless networks

In this paper, we address fault-diagnosis agreement (FDA) problems in distributed wireless networks (DWNs) with arbitrary fallible nodes and healthy access points. We propose a new algorithm to reach an agreement among fault-free members about the faulty ones. The algorithm is designed for fully connected DWN and can also be easily adapted to partially connected networks. Our contribution is to reduce the bit complexity of the Byzantine agreement process by detecting the same list of faulty units in all fault-free members. Therefore, the malicious units can be removed from other consensus processes. Also, each healthy unit detects a local list of malicious units, which results in lower packet transmissions in the network. Our proposed algorithm solves FDA problems in 2t+1 rounds of packet transmissions, and the bit complexity in each wireless node is O(n^t+1).     

Analysis of inverse E class power amplifier with finite DC feed in sub-nominal condition

In this work an inverse E power amplifier with finite DC feed in sub-nominal condition is discussed. In the conventional inverse E the DC feed inductor is considered very large which imposes some conditions to the circuit such as constant current drawn from voltage supply and also a large value for inductance is hard to implement on-chip so this work removes the very large condition from DC feed inductance and proposes a finite DC feed for the structure and extracts the circuit parameters and design equations with regards to this matter. Furthermore to achieve a flexible design this work uses the phase shift between input and output voltages to control efficiency, peak switch voltage and peak switch current then the value of circuit elements and the tradeoffs for every choice are discussed in details and a design guideline is presented for achieving different goals in a finite DC feed inverse E PA. Finally the circuit is simulated in the 0.18 µm CMOS technology and the results are being verified.     

Study of hardening and cyclic plastic behaviour around the crack tip of C(T) specimen made by as‐received and annealed copper

The purpose of this research is determining experimentally the characteristics of tension and cyclic plastic behaviours of as‐received and annealed coppers and studying distribution of stress/strain field near the crack tip. Samples made by pure copper were annealed at 420°C for 40 minutes in electric furnace. To determine the properties of the cyclic plastic behaviour, proper tests with symmetric strain‐controlled conditions were performed on standard samples. Chaboche nonlinear hardening model was used to determine the cyclic plastic behaviour of both materials. According to results, annealing process creates isotropic hardening in the copper and also changes its initial kinematic hardening behaviour. Effects of the annealing and hardening on the variations of the stresses and strains around the crack tip were investigated. Also, ratcheting and mean stress relaxations versus number of cycles, inside the plastic region, were studied.     

A bidirectional diode containing multilevel inverter topology with reduced switch count and driver

In this paper, a bidirectional diode containing multilevel inverter is introduced to reduce the number of switching elements especially in the case of a high number of output voltage levels. In comparison with classic and recently introduced symmetrical topologies, which are trying to reduce the switch count, this topology has a lower number of semiconductor switches in the same number of output voltage levels. This makes the proposed inverter to be a suitable choice for medium voltage applications like renewable energy applications as well as medium voltage electric drives. Moreover, it can be used in a cascaded configuration for high voltage levels. To depict the performance of the proposed structure, a comprehensive comparison is made between this topology and classic and recently proposed symmetric topologies in terms of switch and gate driver count, power losses, and cost. The performance of the proposed symmetrical 11-level converter is analyzed and simulated in MATLAB/Simulink for both PWM and selective harmonic elimination switching methods. Not only the results are desirable but also the experimental results of laboratory prototype validate the simulation results.