Sharif Digital Repository

In this paper we introduce two innovative image and video watermarking algorithms. The paper's main emphasis is on the use of chaotic maps to boost the algorithms' security and resistance against attacks. By encrypting the watermark information in a one dimensional chaotic map, we make the extraction of watermark for potential attackers very hard. In another approach, we select embedding positions by a two dimensional chaotic map which enables us to satisfactorily distribute watermark information throughout the host signal. This prevents concentration of watermark data in a corner of the host signal which effectively saves it from being a target for attacks that include cropping of the... 

Using two different capacitive cell probes; and monitoring capacitance and resistance values of the air and water liquids, the cell length and conductance effects of the water liquids are studied. Variations of the dielectric air capacitance and reactance capacitance parameter of liquids with cylinder length are investigated. In another study the probe length affects on the capacitance and resistance measurements for the liquid filling process are investigated. Different theories are also developed to calculate the capacitance values for the constructed probes. Capacitance per unit length from the Coulomb theory is different from the Gauss law that is a constant value. Measured air... 

In order to compare the frictional resistance of three kinds of ship’s hull coatings (foul release, SPC copper, SPC TBT) in the unfouled conditions, the numerical studies have been made. Simulations have been carried out for different Reynolds numbers in the range of 2.85 × 106-5.5 × 106 based on the plate length and flow velocity. Antifouling coatings have larger mean roughness than foul release. The results have indicated that frictional resistance coefficient of foul release test plate is lower than SPC copper and SPC TBT test plates. The total resistance obtained by computational fluid dynamics has been compared with the experimental data and its good agreement has proven the ability of... 

Proper functioning of electrical connectors used in high oscillation is of great importance. Vibrations in connector pins cause stress and electrical resistance variations in the contact surface. In the present paper, the impacts of vibrational loads on electrical connectors is being modeled using the finite element method, and the electrical resistance oscillations of the connectors will be examined. Ultimately, the parameters affecting the electrical resistance oscillations of contacts will be determined and their relations with oscillations in electrical resistance are specified as well. © 2018 by the authors; licensee Growing Science, Canada, 2018 Growing Science Ltd. All rights reserved... 

Low-cost ethanol vapor sensors are fabricated by electrospinning of TiS2/PVP fibers on pre-patterned metal electrodes. TiS2 ribbons have been synthesized through sulfuration of titanium (Ti) foil using chemical vapor transport (CVT). We found selective and stable responses at a low concentration of ethanol vapor (2 ppm) at room temperature with the transient response and recovery times experimentally around 60 s and 2 s respectively. The relatively high responses of sensors (6800% at 18 ppm) are attributable to the synergy effect of TiS2/PVP composite structure. The mechanism of sensing is discussed based on proton hopping while the sensors exposed to ethanol vapor. © 2019 Wiley-VCH Verlag... 

Electrophosphating is a novel method that is used for accelerating the low-temperature phosphating bath. In this study, Zn–Mn phosphate coating was fabricated on mild steel substrate using the cathodic electrochemical method. Afterward, the effect of electrolyte pH and applied current density was investigated on coating properties. Microstructure, phase analysis and corrosion resistance of coating were evaluated using SEM, X-ray diffraction, potentiodynamic, immersion test and electrochemical impedance spectroscopy tests, respectively. Results indicated that the metallic and nonmetallic phases are present in the coating fabricated by the cathodic electrochemical method. The results of the... 

Stator resistance PI compensator is one of the simplest methods proposed to estimate stator resistance. This method is based on the real time stator resistance correction regarding the variations of the stator current magnitude, which must be a constant value when the stator flux and motor torque are constant. This reference value can be calculated using the flux and torque commands and motor parameters. In this paper, it is shown that for DTC systems using digital controller with limited sampling frequency, stator current vector amplitude varies as a function of speed, sampling period, and switching strategy. Effects of sampling frequency, motor speed, and switching strategy on this current... 

The Ni-base superalloy GTD-111 is widely used in manufacturing of the first stage blades of high power land-based gas turbines. In spite of its important role in increasing the performance of gas turbines, due to high temperature capability, there are little data on the microstructure, deformation mechanisms and mechanical properties of the alloy. The aim of present paper is to determine in details these properties. Microstructural characteristics of the alloy were assessed by means of optical, scanning and transmission electron microscopy. The tensile behaviour of GTD-111 has been studied in the temperature range 25-900 °C. The results showed abnormal variations in tensile properties with... 

Scaled model test in towing tank is a common method to predict the ship resistance in calm water. The scale effects are dominant in these tests because the Reynolds and Froude numbers of the model and full-scale ship cannot be equal. There is a sufficient amount of knowledge about the displacement hulls which have limited speed ranges in most cases. However, scarcity of published data on high-speed crafts is noticed. The influence of the model length on ship resistance varies in different speeds, so it should be studied in more detail. The extrapolation method of model ship resistance to full scale is studied in this paper for high-speed monohulls. Resistance model tests of semi-displacement... 

All of the presented solutions in this book focused on using MLC phase change memory (PCM) due to density advantage and prolonging PCM lifetime. However, resistance drift can be one of the challenging issues for MLC PCMs. While it is desired to have the density advantage of MLC, the trade-off is resistance drift. Since MLCs have closely separated resistance regions, drift has a chance of overlapping intermediate regions. It may then bring out either single bit or multi-bit soft error. Indeed, drift source is related to the semi amorphous resistance regions that are metastable vs time and temperature while crystalline resistance proves to be stable across time and temperature. This chapter... 

In this research, solar cells sensitized with CdS and PbS Nanocrystalline metal sulfides, chemically grown by SILAR, were fabricated and characterized. PV experiments including I-V test in the presence of light and dark,Vocdecay, and Electrochemical impedance spectroscopy were performed on the Cells made through this method in the presence of light and dark and in the time period of 2, 3, 6 and 10 days. From these experiments, the changes in indicators including fill factor, efficiency, open-circuit voltage, short-circuit current, lifetime of electrons in nanostructured anode electrode, recombination resistance and capacitance of the anode electrode-electrolyte interface were observed. Also,... 

The effective resistance or two-point resistance between two nodes of a resistor network is the potential difference that appears across them when a unit current source is applied between the nodes as terminals. This concept arises in problems which deal with graphs as electrical networks including random walks, distributed detection and estimation, sensor networks, distributed clock synchronization, collaborative filtering, clustering algorithms and etc. In the previous paper (Jafarizadeh et al. in J. Math. Phys. 50:023302, 2009) a recursive formula for evaluation of effective resistances on the so-called distance-regular networks was given based on the Christoffel-Darboux identity. In this... 

Biodegradable chitosan nanoparticles (CSNPs) with an intrinsic antimicrobial activity may be a good choice to improve the effectiveness of antimicrobial photodynamic inactivation (APDI). The aim of this study was to investigate the effect of CSNPs on the efficiency of methylene blue (MB)-mediated APDI of Staphylococcus aureus and Pseudomonas aeruginosa biofilms. We also assessed the phototoxicity of MB + CSNPs towards human fibroblasts. Methods: CSNPs were prepared using ionic gelation method and characterized by dynamic light scattering (DLS) and field-emission scanning electron microscope (FESEM). Biofilms were developed in a 96-well polystyrene plate for 24 h. In vitro phototoxic effect... 

Nano-titania, up to 8 wt%, was added to magnesite–dolomite refractory matrix. The phase and microstructure analyses of samples heated up to 1650 °C for 3 h were studied by XRD and SEM/EDS, respectively. The physical properties are reported in terms of bulk density, apparent porosity, and hydration resistance. In addition, the mechanical behavior was studied by a cold crushing strength (CCS), and flexural strength at 1200 °C test. As a result, it was found that the presence of nano-TiO2 in the magnesite–dolomite matrix induced titanates formation (Mg2TiO4 and CaTiO3), which improved the sintering process. Nano-titania influenced the bonding structure through a direct bonding enhancement. In... 

In this study, a comprehensive investigation was carried out on the effects of environmental condition on physical and chemical properties of Cold-Briquetted Iron and Carbon (CBIC), Cold Direct Reduced Iron (CDRI), and Hot-Briquetted Iron (HBI). The results showed that cold briquetting of CDRI decreases its specific surface area by 51%, which has a significant effect on its oxidation resistance and mechanical strength. Microscopic observations revealed that the oxidation products are formed in near-surface porosities during aging, which protects the fresh material underneath from environmental oxidants, resulting in retarding further oxidation. The oxidation behavior of the samples showed... 

This paper introduces a straightforward technique for parameters estimation of the RC equivalent circuit model of a battery cell with the main aim of its implementation in real-time digital simulator frameworks. The RC model parameters are precisely estimated by the analysis of the battery cell voltage curve during relaxation time using the pulse current test. In this regard, Least-squares fitting is used to mitigate the error of the battery cell voltage response, which leads to a precise estimation of the RC model parameters as a function of the state-of-charge. Exponential and Gaussian functions are utilized to define the resistances and the capacitances in the RC model respectively based... 

Polycrystalline (Pr1-xBax)Ba2Cu3O 7-δ samples with 0.0 < x < 0.6 are prepared by the standard solid state reaction technique. X-ray diffraction and resistivity measurements are performed. For x < 0.3, the 123 phase is formed, but for x > 0.3, due to the solubility limit, the 123 phase is not the dominant phase. The normalized resistivity increases with the increase of Ba doping to about x = 0.08, and then decreases in the 123 phase up to x = 0.3. The existence of an extremum in the resistivity is explained as the competition between scattering by impurities and increase of the number of carriers by Ba doping. For x > 0.3, due to a large increase in the non-123 phase formation, the...