Sharif Digital Repository

In this paper we propose a new automatic method for discriminating original and tampered images based on 'JPEG ghost detection' method, which is a subset of format-based image forensics approaches. The inconsistency of quality factors indicates that the photo is a composite one created from at least two different cameras and therefore it is a manipulated photo. Our classification algorithm first extracts the ghost border. Then the image is classified as original or tampered groups by thresholding a distance in feature space. © 2016 IEEE  

We synthesized TiO2 nanoparticles by pulsed laser ablation of titanium target immersed in an aqueous solution of surfactant sodium dodecyl sulfate (SDS) or deionized water. The surfactant concentration dependence on size of TiO2 nanoparticles was investigated. The maximum amount of nanoparticles (with mean size of 40 nm in diameter) was obtained in an aqueous solution of 0.001 M SDS. We have also studied the effect of laser wavelength on growth of TiO2 nanoparticles. UV/visible spectroscopy and Scanning Electron Microscopy observations were employed for characterization of optical properties and particle sizes respectively. As TiO2 is a famous photocatalyst, we have also done photocatalytic... 

The Co nanowire arrays were synthesized by electrodeposition in polycarbonate template (PC) with 4 μm thickness. Electron field emission properties of cobalt nanowires were studied for wires with different aspect ratios, R ranged between 10 and 60, while the diameter of wires was fixed about 50 nm. The field emission properties of the samples showed low turn on electric field (Eto) with values varying between 2.9 and 11.3 V/μm showing a minimum value for R = 20 (Eto < 3 V/μm). On the other hand, the enhancement factor shows a peak for nanowires length about 1 μm. Field emission data using the Fowler-Nordhiem theory showed nearly straight-line nature confirming cold field emission of... 

In spite of various works which were carried out on CdO and porous Si (PSi) separately, the interesting properties of CdO/PSi/Si system are not known well. In this work, we study the photoconductivity of deposited CdO layer on PSi/Si system. PS and CdO layers were prepared by electrochemical anodisation of p-type crystalline silicon and pulsed laser deposition (PLD) of cadmium oxide target. Then samples were annealed in air at 500°C to increase their optical transmissions to a value as large as 90% for wavelengths above 700 nm. The XRD study reveals that the annealed films are polycrystalline with grain size of about 25 nm. SEM micrograph of the CdO/PSi/Si system indicates that CdO layer has... 

This paper presents the study of the structural and optical properties of copper doped cadmium sulfide thin films prepared by pulsed Nd:YAG laser. The copper concentration in the targets was varied from 0.05% to 5% in weight and they were heated at a temperature of 500°C in air for one hour. It was observed that annealing un-doped and doped thin films at temperatures above 160°C leads to an abrupt increase in the optical transmission, changing from dark brownish to transparent yellowish. For annealed samples at 300°C, increasing Cu concentration from 0.0% to 2%, leads to an increase in the optical transmission up to 80%, at a wavelength of about 700 nm. XRD patterns showed the hexagonal... 

The ability of 5G wireless communication networks to effectively and simultaneously interact with incoming signals is made possible by antenna arrays, which play a vital role in assisting the functioning of 5G wireless communication networks. The utilization of beamforming enables the enhancement of signal strength, expansion of coverage area, and reduction of interference, thereby optimizing the performance of the communication networks. This paper introduces a deep learning approach that utilizes a deep neural network (DNN). This approach establishes an appropriate framework to implement beamforming for planar antenna arrays. The DNN utilizes the desired radiation pattern as an input to... 

The deployment of 5G networks requires advanced antenna technologies to meet the increasing demands for high-capacity and low-latency communication. Antenna arrays, known for their beamforming capabilities, are vital in achieving these goals. However, sidelobes in the antenna radiation pattern can introduce errors and significantly impact the system's overall performance. This paper proposes a novel beamforming optimization technique for linear antenna arrays (LLA) in 5G networks. Our approach leverages the power of metaheuristic algorithms, precisely the Grasshopper Optimization Algorithm (GOA), to optimize the array configuration and reduce the Sidelobe Levels (SLL). The main objective is... 

A new magnetic, catalytic nanocomposite of Hal-MT-Cys-Ag/MNCD was fabricated and utilized for catalyzing reductive de-colorization of methyl orange and rhodamin B in aqueous media at room temperature. To prepare this material, Cl-functionalized halloysite nanoclay was successively reacted with melamine and 2,4,6-trichloro-1,3,5-triazine to furnish multi-nitrogen containing ligand on halloysite surface. Then, magnetic carbon dots were crafted through a facile method and decorated with Ag nanoparticles and cysteine to furnish Cys-Ag/MNCD species. The final nanocomposite was obtained via incorporation of this latter species onto functionalized halloysite. This new composite was characterized... 

Spam mails are unwanted mails sent to large number of users. Spam mails not only consume the network resources, but cause security threats as well. This paper proposes an efficient technique to detect, and to prevent spam mail in the sender side rather than the receiver side. This technique is based on a counter set on the sender server. When a mail is transmitted to the server, the mail server checks the number of the recipients based on its counter policy. The counter policy performed by the mail server is based on some pre-defined criteria. When the number of recipients exceeds the counter policy, the mail server discontinues the rest of the process, and sends a failure mail to sender of... 

Spam mails are unwanted mails sent to large number of users. Spam mails not only consume the network resources, but cause security threats as well. This paper proposes an efficient technique to detect, and to prevent spam mail in the sender side rather than the receiver side. This technique is based on a counter set on the sender server. When a mail is transmitted to the server, the mail server checks the number of the recipients based on its counter policy. The counter policy performed by the mail server is based on some pre-defined criteria. When the number of recipients exceeds the counter policy, the mail server discontinues the rest of the process, and sends a failure mail to sender of... 

The Co nanowires were electrodeposited in polycarbonate membrane (PCT). SEM, TEM and XPS techniques were used to characterize the morphology, structure and size of nanowires as well as chemical composition. The influence of different mediums was studied on the optical absorption of dispersed cobalt nanowires. The absorption spectrum of cobalt nanowires in water showed a broad shoulder at 290 nm, but in ethanol solution it was not observed in the visible region of the spectra up to 200 nm. Cobalt nanowires dispersed in methanol presented a peak at 236 nm. We attribute the data to oxidation of cobalt in water and low dielectric constant of methanol relative to ethanol and water. We found... 

In this study, the perturbed hard sphere chain equation of state is utilized to calculate the activity of water in binary and ternary solutions of polyethylene glycol (PEG), salt and water. The liquid density of the binary and ternary solutions is also predicted. To estimate the water activity in PEG-water binary systems, a linear correlation is obtained for the binary interaction parameter between water and PEG. Then, using this correlation and without introducing any additional binary parameters, the water activities are predicted in ternary solutions of water, salt and PEG with different molecular weights (MW). Our results show that the mean absolute average relative deviation (AARD %) of... 

This paper presents a new group key management protocol, CKC (Code for Key Calculation) for secure IP multicast. In this protocol which is based on logical key hierarchy, only the group key needs to be sent to new member at join. Then, using the group key current members and the new member calculate the necessary keys by node codes and one-way hash function. A node code is a random number assigned to each node to help users calculate necessary keys. Again, at leave server just sends the new group key to the remaining members. By this key, members calculate necessary keys using node codes and one-way hash function. The security of the keys is based on one-wayness of hash function. The results... 

This paper presents a new group key management protocol, CKC (Code for Key Calculation). This protocol is based on logical key hierarchy. When a new member joins the group, server sends only the group key for that member. Then, current members and the new member calculate the necessary keys using node codes and one-way hash function. Node code is a code which is assigned to each node of the key tree. Again at leave, server just sends the new group key to remaining members. By this key, members calculate necessary keys using node codes and one-way hash function. The security of the keys is based on one-wayness of hash function. The results show that CKC reduces computational and communication... 

The finite element method has been used to predict the stress intensity factors for cracked annular discs under constant central torque. Linear elastic fracture mechanics finite element analyses have been performed and the results are demonstrated in the form of crack configuration factors. To this end, the extensive ranges of crack configuration factors have been employed while considering the effect of disc stiffness. Then, the finite element results are applied to develop equivalent prediction equations using a statistical multiple nonlinear regression model. The accuracy of this model is measured using a multiple coefficient of determination, R2, where 0 ≤R2 ≤1. This coefficient is found... 

A heterogeneous magnetic copper catalyst was prepared via anchoring of copper sulfate onto multi-layered poly(2-dimethylaminoethyl acrylamide)-coated magnetic nanoparticles and was characterized using various techniques. The catalyst was found to be active, effective and selective for one-pot three-component reaction of alkyl halide, sodium azide and alkyne, known as copper-catalyzed click synthesis of 1,2,3-triazoles. As little as 0.3 mol% of catalyst was found to be effective under the optimum conditions. The catalyst could also be recycled and reused up to seven times without significant loss of activity. Thermal stability, high loading level of copper on catalyst, broad diversity of... 

Potential effects of folates on the treatment of several human diseases like cognitive function, neural tube defects, coronary heart disease and certain kinds of cancers have been discovered. However, the stability of folic acid against adverse conditions is a great concern. The present study investigates various alginate (A)–pectin (P) gastrointestinal-resistant hydrogel to immobilize folic acid. This involves evaluating different compositions of alginate–pectin to achieve higher encapsulation efficiency and stability during simulated gastric (SG) and simulated intestinal (SI) conditions. Coated alginate hydrogels with pectin resulted significant (p < 0.05) better protection of folic acid... 

The rational design of composite catalysts is critically essential for electrochemical water splitting. Here, we report on a novel hierarchical composite that comprises NiFeSe2 nanoparticles and NiCo2O4 nanoflakes supported on nickel foam (NF) as an efficient electrocatalyst for the hydrogen evolution reaction (HER). The conjunction of the NiFeSe2 nanoparticles and NiCo2O4 nanoflakes introduces a new synergistic effect for the HER, resulting in an improved NiCo2O4 catalyst. The as-prepared NiFeSe2/NiCo2O4/NF electrode exhibited an enhanced HER activity, with a low overpotential of 83 mV at a current density of 10 mA cm−2, a low Tafel slope of 45 mV dec−1, and an excellent long-term... 

CdSe nanowires were grown in polycarbonate track etched membrane with pore diameter of 80 nm by an electrochemical deposition technique. The mechanism of the growth was studied during the potentiostatic deposition of nanowires. X-ray photoelectron spectroscopy and energy dispersive spectrometry results showed binding of fragments and fraction of atoms for the CdSe nanowires. Microstructure and morphology of synthesized CdSe nanowires were observed by scanning electron microscopy. Optical spectrophotometry technique was used to determine the energy band gap of CdSe nanowires. It was found that the nanowires were resistive in the dark and exhibited a pronounced visible light photoconductivity....