Thermo-economic optimization of solar air heaters with arcuate-shaped obstacles

Journal of Thermal Analysis and Calorimetry - In this study, thermo-economic optimization of single-pass SAHs (solar air heaters) with obstacles of arcuate shape has been carried out. The research...     

Headspace Solid-Phase Microextraction GC–MS for Rapid Rice Aroma Analysis Using Optimization Tools

A key feature of rice acceptance by consumers is closely related to its aroma. A few decades of research on rice aroma indicated associated difficulties which arise from its complicated volatile composition. Our investigation seeks to resolve this highly complicated aroma profile using an experimental design for headspace solid-phase microextraction GC–MS. The Plackett–Burman methodology was used as a factor screening method for the headspace solid-phase microextraction procedure and GC–MS analysis, and a central composite design was implemented as an optimization methodology for both steps. Optimization of the extraction procedure and GC–MS analysis leads to a highly resolved rice aroma profile resulting in 66 new constituents. A total of 123 constituents were identified by implementing the procedure on Champa rice from the south of Iran.     

An eigenvector-based approach for improved parameter variation for multibody mechanical systems

Optimal design of complex multibody mechanical systems involving numerous design parameters and constraints is a challenging problem. System parameters are typically determined through a recursive process which leads to a set of nominal values. While these nominal values satisfy design constraints they generally result in suboptimal performance. In practice, nominal design values can undergo a final adjustment step to improve performance while ensuring that design constraints are not violated. In this article, we present a framework for design parameter variation to optimize the performance of a multibody system. As an example, we apply the proposed method to an exploration rover and show that the proposed approach provides superior results compared to the standard sensitivity derivative approach.     

Copper and nickel immobilized on cytosine@MCM-41: as highly efficient,reusable and organic–inorganic hybrid nanocatalysts for the homoselective synthesis of tetrazoles and pyranopyrazoles

In this work, a green approach is reported for efficient synthesis of biologically active tetrazole and pyranopyrazole derivatives in the presence of Cu-Cytosine@MCM-41 and Ni-Cytosine@MCM-41 (copper (II) and nickel (II) catalyst on the modified MCM-41 using cytosine). The synthesis of tetrazoles and pyranopyrazoles in the presence of these catalysts was performed in green solvents such as water or poly (ethylene glycol) (PEG). All products were obtained in high TOF (turnover frequency) numbers in the presence of these catalysts, which indicate the high efficiency of these catalysts in the synthesis of tetrazole and pyranopyrazole derivatives. The prepared catalysts were characterized by various techniques such as BET, TGA, XRD, FT-IR, SEM, EDS, WDX, TEM, and AAS. Mesoporous structure of these catalysts was confirmed by nitrogen adsorption–desorption isotherms. These catalysts can be recovered and reused for several runs without significant change in their catalytic activity or metal capacity. The recovered catalysts have been characterized by XRD, SEM, EDS, WDX, FT-IR and AAS techniques, by which their heterogeneous nature has been confirmed.     

Effective photocatalytic degradation of an azo dye over nanosized Ag/AgBr-modified TiO<Subscript>2</Subscript> loaded on zeolite

Zeolite-based photocatalysts were prepared by the sol-gel and deposition methods. The photocatalysts were characterised by X-ray diffraction, nitrogen adsorption-desorption isotherms, FTIR spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectrometry. The activity of the prepared photocatalysts was evaluated by the UV-induced degradation of acid blue 92, a textile dye in common use. The effect of various parameters, such as catalyst concentration, initial dye concentration, thiosulphate concentration and pH, on the rate and efficiency of the photocatalytic degradation of acid blue 92 was investigated. The results showed that each parameter influenced the degradation rate and efficiency in a particular way. It was also found that, under optimised conditions, Ag/AgBr/TiO₂/zeolite exhibited the highest photocatalytic performance. A comparison of catalytic activity when exposed to visible light under the same conditions showed that the photocatalysts containing AgBr had the highest activity.     

Production of fibroin nanopowder through electrospraying

Fibroin is a biomaterial and in the powder form, has found applications such as food and cosmetic additive as well as drug delivery. Various methods have been employed to produce fibroin powder with different particle size range. In this study, a novel and original application of electrospraying technique capable of producing fibroin nanopowder is presented. Our technique is based on electrospraying of dilute fibroin solution in formic acid. Moreover, the effect of variables in electrospraying, namely, concentration of fibroin solution, voltage, feed rate, and needle–collector distance, on average particle size of fibroin nanopowder has been studied. The result of this study showed that electrospraying is capable of producing fibroin nanopowder with average particle size as low as 80 nm. In fact in comparison to other methods reported in the literature, electrospraying alongside with the precipitation method produce fibroin nanopowder with the lowest particle size. However, nanopowder obtained through electrospraying technique enjoys a more uniform spherical shape and size. As far as the variables are concerned, it was ascertained that lower concentrations, lower feed rates and longer needle–collector distances lead to a decrease in the average particle size of fibroin nanopowder. Increasing voltage up to 20 kV decreases the particle size; but with higher voltages the average particle size increases. FT-IR and XRD studies showed that the fibroin nanopowder has a β-sheets structure, similar to fibroin filaments but with a lower crystallinity index.     

An additive model approach for estimating returns to scale in imprecise data envelopment analysis

In this paper, additive model is used to provide an alternative approach for estimating returns to scale in data envelopment analysis. The proposed model is developed in both stochastic and fuzzy data envelopment analysis. Deterministic (crisp) equivalents are obtained which correspond to the stochastic and fuzzy models. Numerical examples are, also, used to illustrate the proposed approaches.     

Stability and hyperstability of orthogonally $$*$$- m-ho mo morphis ms in orthogonally Lie $$C^*$$C-algebras: a fixed point approach

Recently Eshaghi et al. introduced orthogonal sets and proved the real generalization of the Banach fixed point theorem on these sets. In this paper, we prove the real generalization of Diaz–Margolis fixed point theorem on orthogonal sets. By using this fixed point theorem, we study the stability of orthogonally \(*\)-m-homomorphisms on Lie \(C^*\)-algebras associated with the following functional equation:

$$\begin{aligned} \begin{aligned}&f(2x+y)+f(2x-y)+(m-1)(m-2)(m-3)f(y)\\&\quad =2^{m-2}[f(x+y)+f(x-y)+6f(x)]. \end{aligned} \end{aligned}$$

for each \(m=1,2,3,4.\). Moreover, we establish the hyperstability of these functional equations by suitable control functions.

     

Studies of intramolecular hydrogen bonding in protonated and non-protonated hexahydropyridinobenzodioxins

The conformational stability of hexahydropyridobenzodioxin and related derivatives in both protonated and non-protonated forms have been investigated by means of ab initio molecular orbital methods as well as semi-empirical AM1 and PM3 methods. One of the cis conformers (cis2e) has been found to be most stable due to the formation of an intramolecular hydrogen bond, other conformers including the trans isomer cannot form this interaction but are of different stability because of the orientation of the polar oxygens and the nitrogen. The effect of the intramolecular hydrogen bonding on the stability of hexahydropyridobenzodioxin and its methylated derivatives has been examined using various basis sets levels. In protonated form, both the semi-empirical and ab initio calculations give excellent agreement in energetic order; however, different orderings of conformer stabilities are observed by different computational methods in non-protonated form. The results provide insight into the intramolecular hydrogen bonding in computational studies of biologically important molecules.