Sharif Digital Repository

Abstract: Complex and large scale systems and networks have evolved in many fields: from communication data networks, banking, financial systems, bio-engineering and robotics to, amongst others, industrial control systems. In control engineering, the main driving force behind the expansion of large-scale complex systems has been the relatively low cost of installing advanced instrumentation hardware, the low cost of attaining high computing power and the desire to 'see' and `monitor¿ as much of the process as possible  

In this paper, the metric theory of Diophantine approximation associated with mixed type small linear forms is investigated. We prove Khintchine–Groshev type theorems for both the real and complex number systems. The motivation for these metrical results comes from their applications in signal processing. One such application is discussed explicitly. © Springer Nature Switzerland AG 2020  

Objectives. This article describes the reduction of unsafe behaviors observed at a fertilizer complex by implementation of a behavior-based safety (BBS) program via a behavior observation form developed by a multidisciplinary team. Methods. Six observation categories, i.e., position of people, reaction of people, personal protective equipment (PPE), tools used, operating procedures and housekeeping, are used to monitor safe and unsafe behaviors for a period of 18 months. Results. Safe behaviors increased from 57 to 70% and unsafe behaviors reduced from 40 to 26%. Behaviors of employees working in various sections of fertilizer complex such as ammonia, urea, utility, bagging/shipping and... 

Metamaterials are manmade structures that have attained considerable attention over the past 2 decades in the modern fields like cloaking, sensing, and imaging owing to their ability to harness electromagnetic fields. In this regard, we have inspected the dielectric properties of the hyperbolic metamaterials (HMM) made of metallic nanorods and dielectric medium at the infrared wavelength regime. The periodically arranged subwavelength-sized metallic nanorods embedded in the silicon dioxide (SiO 2) substrate glass. The spacing between two adjacent nanorods is of subwavelength in size. Furthermore, effective permittivity of the metamaterial has been analyzed by employing the Maxwell Garnett... 

Indium substituted Cu[sbnd]Ni nanoferrites with nominal compositions Cu 0.5 Ni 0.5 In x Fe 2-x O 4 (x = 0.00–0.32)were successfully synthesized by sol-gel auto ignition method. X-ray diffraction patterns illustrated the single phase spinel structure for x ≤ 0.24. The lattice parameter ‘a’ increased from 8.3349 to 8.3723 Å and then it decreased for x = 0.32. X-ray density increased from 5.43 to 5.79 g/cm 3 . The average crystallite sizes lie in the range 33.21–17.78 nm. The cell volume was increased from 579.03 to 586.86 Å 3 with the substitution of indium ions into the spinel lattice of copper nickel ferrites. The compositional dependence of tetrahedral and octahedral radii was explained on... 

Heat transport features of a dusty fluid flow within a resistive porous medium are numerically interpreted under the magnetohydrodynamic environment. Fluid and dust phase characteristics are overlooked against the preeminent parameters. The main concern, in this work, is to analyze how much the resistive porous media affects the dusty flow in the presence of Lorentz force. The use of convection boundary conditions will aid attain the desired heat transfer rate in engineering applications. The nonlinear partial differential equations governing the fluid and dust phase are transmuted into a system of coupled and highly nonlinear ordinary differential equations which are first discretized using... 

Based on exclusive thermal dynamic of nanomaterials, various applications are noted in engineering and industrial processes. Owing to such thermal impact, the researchers have presented comprehensive research on nanomaterials. While claiming novel applications of nanofluids, the stability of nanomaterials is important for which less attention has been paid. On this end, the aim of current research is to predict the thermal instability of graphene nanoparticles with suspension of water base fluid due to transient Hartmann flow. The Poiseuille flow of water-based nanoparticles subject to the magnetic force is assumed between two plates. The numerical outcomes are predicted with implementation... 

The mixed nano-ferrites materials Cu0.6Zn0.4HoxFe2−xO4 (0.00 ≤ x ≤ 0.12) were prepared via the sol–gel auto combustion technique. The TGA curve established the annealing temperature (500 °C) for phase formation. The single exothermic peak on the DSC plot occurred at 341 °C temperature. XRD patterns of these nano ferrites verified single phase formation of the FCC cubic structure. The lattice constant a was increased from 8.4244 to 8.4419 Å and then its value decreased to 8.4319 Å. Crystallite size was found in the range of 7 to 16 nm. The surface morphology of the samples was observed from the scanning electron microscope (SEM) images. The grain size was found within the range of 90 nm to... 

The mixed nano-ferrites materials Cu0.6Zn0.4HoxFe2−xO4 (0.00 ≤ x ≤ 0.12) were prepared via the sol–gel auto combustion technique. The TGA curve established the annealing temperature (500 °C) for phase formation. The single exothermic peak on the DSC plot occurred at 341 °C temperature. XRD patterns of these nano ferrites verified single phase formation of the FCC cubic structure. The lattice constant a was increased from 8.4244 to 8.4419 Å and then its value decreased to 8.4319 Å. Crystallite size was found in the range of 7 to 16 nm. The surface morphology of the samples was observed from the scanning electron microscope (SEM) images. The grain size was found within the range of 90 nm to... 

We demonstrate for the first time the application of p-NiFe2O4/n-Fe2O3 composite thin films as anode materials for light-assisted electrolysis of water. The p-NiFe2O4/n-Fe2O3 composite thin films were deposited on planar fluorinated tin oxide (FTO)-coated glass as well as on 3D array of nanospike (NSP) substrates. The effect of substrate (planar FTO and 3D-NSP) and percentage change of each component (i.e., NiFe2O4 and Fe2O3) of composite was studied on photoelectrochemical (PEC) water oxidation reaction. This work also includes the performance comparison of p-NiFe2O4/n-Fe2O3 composite (planar and NSP) devices with pure hematite for PEC water oxidation. Overall, the nanostructured... 

In present research six samples of nano X-type hexagonal ferrites with general formula SrBaMg2-xCoxDyyFe28-yO46 (x = 0–1; y = 0–0.1 with step size of 0.2 and 0.02, respectively) were synthesized by sol–gel technique. The temperature required for the phase formation of these materials was estimated using thermogravimetric analysis. X-ray diffraction patterns revealed the pure phase of the prepared materials up to the doping concentration of x = 0.4, y = 0.04 along with the second phase for higher doping concentration. The secondary phase appeared due to the solubility limit of higher ionic radius Dy3+ ions into the hexagonal lattice. The mean crystalline size decreased from 29 to 18 nm while... 

Co2+ and Cr3+-substituted SrBaCu2-xCoxCryFe28-yO46 X-type hexaferrite with x = y = 0, 0.1 to 0.5 (step = 0.1) were prepared through auto-combustion sol–gel method and sintered at 1250 °C for 5 h which was found from thermal analysis. The thermal investigation, phase detection, spectral, magnetic, and dielectric characteristics of the prepared composition were investigated by TGA, XRD, FTIR, VSM, and dielectric measurement. XRD patterns of the entire composition confirmed the development of a single phase of X-type structure. The enhancement in the lattice parameters and cell volume was observed by varying the Co–Cr concentration, attributed to the larger ionic radii substitution. FTIRspectra... 

Thermal performance of magnetically driven Casson nanofluid over a nonlinear stretching sheet under the influence of entropy, activation energy and convective boundary conditions was analyzed numerically, employing the quasi-linearization method (QLM). The collective behavior of thermophoretic diffusion and Brownian motion along with special effects of viscous dissipation, thermal radiation, heat generation and joule heating are considered in the energy equation for the flow problem. The addition of nanoparticles helps to stabilize the flowing of a nanofluid and maintain the symmetry of the flowing structure. The governing highly nonlinear coupled differential equations of velocity,... 

The original version of the article was inadvertently published with the ethical code in Ethical Considerations section. This has been corrected with this erratum. The revised texts are given below. © 2021, Springer Science+Business Media, LLC, part of Springer Nature  

In the energy system, various sources are used to fulfill the energy demand of large buildings. The energy management of large-scale buildings is very important. The proposed system comprises solar PVs, energy storage systems, and electric vehicles. Demand response (DR) schemes are considered in various studies, but the analysis of the impact of dynamic DR on operational cost has been ignored. So, in this paper, renewable energy resources and storages are integrated considering the demand response strategies such as real-time pricing (RTP), critical peak pricing (CPP), and time of use (ToU). The proposed system is mapped in a linear model and simulated in MATLAB using linear programming... 

Recently, photoelectrochemical conversion (PEC) of water into fuel is attracting great attention of researchers due to its outstanding benefits. Herein, a systematic study on PEC of water using CuFe2O4/ α-Fe2O3 composite thin films is presented. CuFe2O4/ α-Fe2O3 composite thin films were deposited on two different substrates; (1) planner FTO glass and (2) 3-dimensional nanospike (NSP). The films on both substrates were characterized and tested as anode material for photoelectrochemical water splitting reaction. During PEC studies, it was observed that the ratio between two components of composite is crucial and highest PEC activity results were achieved by 1:1 component ratio (CF-1) of... 

Currently, materials with outstanding absorption abilities, such as thin size, better absorbing power, and light weight are the need of industry to resolve the electromagnetic issues. However, the research on optimizing the composition of the material, microstructure and the structure of the absorber are also the important factors for enhancing the absorption features. A metamaterial microwave absorber (MMA) based on nano ferrites with desirable absorption peaks is proposed and simulated. Sol-gel auto combustion route is used to prepare the nanosized Sm doped Co ferrite with Co1+xSmxFe2-2xO4 at x = 0.00, 0.03, 0.06, 0.09, respectively. XRD, VSM, FESEM, and VNA were employed to evaluate the... 

The hybrid power system is a combination of renewable energy power plants and conventional energy power plants. This integration causes power quality issues including poor settling times and higher transient contents. The main issue of such interconnection is the frequency variations caused in the hybrid power system. Load Frequency Controller (LFC) design ensures the reliable and efficient operation of the power system. The main function of LFC is to maintain the system frequency within safe limits, hence keeping power at a specific range. An LFC should be supported with modern and intelligent control structures for providing the adequate power to the system. This paper presents a... 

Coccidiosis is a significant disease of poultry and is usually treated using various synthetic anticoccidial drugs. However, the effectiveness of this approach has been compromised due to drug resistance. Medicinal plants are being considered as potential alternatives to these drugs. As part of ongoing research, an investigation was conducted to assess the anticoccidial potential of Linum usitatissimum seed extract (LUE) and its impact on hematological parameters in broiler chickens with experimental coccidiosis. A total of 108 broiler chicks were divided into six groups. The chicks in Groups I, II, and III were given plant extract at three different concentrations: 4%, 5%, and 6%,... 

Nowadays, artificial intelligence (AI) and machine learning (ML) are playing a tremendous role in all aspects of human life and they have the remarkable potential to solve many problems that classic sciences are unable to solve appropriately. Neuroscience and especially psychiatry is one of the most important fields that can use the potential of AI and ML. This study aims to develop an ML-based model to detect the relationship between resiliency and hope with the stress of COVID-19 by mediating the role of spiritual well-being. An online survey is conducted to assess the psychological responses of Iranian people during the Covid-19 outbreak in the period between March 15 and May 20, 2020, in...