Synthesis and characterization of silica-coated magnetite nanoparticles modified with bis(pyrazolyl) triazine ruthenium(II) complex and the application of these nanoparticles as a highly efficient catalyst for the hydrogen transfer reduction of ketones

We present a facile and efficient method for modifying the surface of silica-coated Fe₃O₄ magnetic nanoparticles (MNPs) with bis(pyrazolyl) triazine ruthenium(II) complex [ MNPs@BPT–Ru (II) ] . Field emission-scanning electron microscopy, thermogravimetric/derivative thermogravimetry analysis, X-ray powder diffraction, Fourier-transform infrared spectroscopy, vibrating sample magnetometry, and energy-dispersive X-ray spectrometry analyses were employed for characterizing the structure of these nanoparticles. MNPs@BPT–Ru(II) nanoparticles proved to be a magnetic, reusable, and heterogeneous catalyst for the hydrogen transfer reduction of ketone derivatives. In addition, highly pure products were obtained with excellent yields in relatively short times in the presence of this catalyst. A comparison of this catalyst with those previously used for the hydrogen transfer reactions proved the uniqueness of MNPs@BPT–Ru(II) nanoparticle which is due to its inherent magnetic properties and large surface area. The presented method also had other advantages such as simple reaction conditions, eco-friendliness, high recovery ability, easy work-up, and low cost.     

Exergetic and economic evaluation of a novel integrated system for trigeneration of power,refrigeration and freshwater using energy recovery in natural gas pressure reduction stations

Journal of Thermal Analysis and Calorimetry - Nowadays, with increasing energy consumption, global warming, and many problems caused by weather conditions, the tendency to use novel methods of...     

Energy,exergy, and sensitivity analyses of a new integrated system for generation of liquid methanol,liquefied natural gas,and crude helium using organic Rankine cycle,and solar collectors

Journal of Thermal Analysis and Calorimetry - The increasing growth of helium consumption in industries and the limited resources of this element are the challenges that industries will face in the...     

A renewable approach to capture CO2 in Iran: thermodynamic and exergy analyses

Journal of Thermal Analysis and Calorimetry - This work presents numerical simulation of two-dimensional thermogravitational energy transport in a chamber filled with copper–water ( $${\hbox...     

Development of colorimetric sensor array for discrimination of herbal medicine

Today, traditional systems of medicines (such as herbal distillates) become important resources for providing healthcare benefits. The ability to discriminate among closely similar herbal products is critical to ensure their efficacy. This article proposes a pattern-based recognition approach for the rapid discrimination of herbal distillates using a low-cost and sensitive colorimetric sensor array composed of 25 indicators. The color changes of the sensor exposed to the vapor of the herbal distillates can be monitored easily with an ordinary flatbed scanner. The digital representation of the array response was analyzed with hierarchical clustering analysis (HCA) and principal component analysis (PCA). Using new variable selection strategy, 6 indicators among the 25 employed indicators were selected as discriminant elements of the array. So, a complete discrimination (with 100% accuracy) of 46 herbal distillates was achieved. The proposed sensor represented a better resolution when analytes were placed in an oven at 85 °C for 45 min. This colorimetric sensor array demonstrates excellent potential for quality assurance/control applications of herbal distillates.     

Existence results to positive solutions of fractional BVP with $${\varvec{}}$$-derivatives

This paper investigates the existence and uniqueness of positive and nondecreasing solution for nonlinear boundary value problem with fractional q-derivative

$$\begin{aligned}&D_{q}^{\alpha }u(t)+f(t,u(t))=0, \quad {0<t<1, ~3<\alpha \le 4,} \\&u(0)= D_{q}u(0)=D_{q}^{2}u(0)=0, \quad D_{q}^{2}u(1)=\beta D_{q}^{2}u(\eta ), \end{aligned}$$

where \(D_{q}^{\alpha }\) denotes the Riemann–Liouville q-derivative of order \(\alpha \), \(0<\eta <1\) and \(1-\beta \eta ^{\alpha -3}>0\). Our analysis relies a fixed point theorem in partially ordered sets. An example to illustrate our results is given.

     

Experimental and theoretical investigation of CO2 and air bubble rising velocity through kerosene and distilled water in bubble column

This paper concerns with developing of parameters which influence terminal velocities of air and CO₂ bubbles in distilled water and kerosene pools. The objective of this study is to validate and correct the formulas that were developed by previous investigators for prediction of terminal velocities. The investigation revealed that the terminal velocity of a single rigid spherical bubble in Newtonian fluids can be developed by balancing of mechanical forces acting on the bubble. However, for large bubbles, because of deforming of the bubble which is a result of interfacial tension, the effect of surface tension should be considered in the terminal velocity prediction formula. By using PSO algorithm and plotting experimental data of terminal velocity against the size of gas bubbles, the suitable equation for each of systems was chosen. Results showed that Jamialahmadi model is more practical for terminal velocity prediction. Jamialahmadi model requires a modification to be utilized for air-kerosene, CO₂-kerosene, air- distilled water and CO₂-distilled water systems. The developed PSO algorithm model is accurate for prediction of experimental data with an average R² value of 0.9722.     

Designing different nanomagnets via delocalization of cobalt magnetic moment inside narrow single walled carbon nanotubes

Density functional theory calculations were employed to study the effects of chirality and diameter of single walled carbon nanotubes (SWCNTs) on electronic, structural and magnetic properties of cobalt-doped (9,0), (5,5) and (5,0) nanotube systems. The (9,0) and (5,5) SWCNTs have similar diameters but different chiralities, whereas the (5,0) tube has a very small diameter. The Co-SWCNT systems are considered with four different possible arrangements, three of which are stable and only substitution of the Co with one of the carbon atoms on the surface of the SWCNTs is an exemption. Although the quasi-metallic band gap of the (9,0) SWCNT is eliminated by the cobalt doping process, metallic features of the (5,5) and (5,0) nanotubes remain unchanged. On the other hand, delocalization of the cobalt’s magnetization and inducement of a noticeable magnetization to the tubes provide a vast area of possible total magnetizations for the Co-SWCNT systems. The results are applicable to spintronics and useful for designing other nanomagnetic systems.     

Energy,exergy and pinch analyses of an integrated cryogenic natural gas process based on coupling of absorption–compression refrigeration system,organic Rankine cycle and solar parabolic trough collectors

Journal of Thermal Analysis and Calorimetry - The natural gas entering the liquefaction cycle usually consists of nitrogen, ethane, propane and also heavier hydrocarbons which are economically...