A watermarking-based image authentication scheme in the discrete cosine transform (DCT) domain robust to JPEG compression is presented. The binary authentication code is generated from a ...pseudo-random sequence based on a secret key and a block-dependent feature, protecting the scheme against cut-and-paste attacks. The watermark is embedded in low-frequency DCT coefficients selected by the secret key using a modified quantisation index modulation approach. Before embedding, the selected coefficients are quantised using the JPEG quantisation matrix for a selected quality factor, protecting the scheme against JPEG compression with higher quality factors. Experimental results show that the proposed technique achieves very good watermark imperceptibility and is able to detect and locate malicious attacks with good precision. Compared with other existing schemes, the proposed algorithm achieves better performance regarding false positive and false negative detection rates and in discriminating malicious attacks from JPEG compression.
A simple, fast and accurate amplitude estimation algorithm of sinusoidal signals for DSP based instrumentation is proposed. It is shown that eight samples, used in two steps, are sufficient. A ...practical analytical formula for amplitude estimation is obtained. Numerical results are presented. Simulations have been performed when the sampled signal is affected by white Gaussian noise and when the samples are quantized on a given number of bits.
This paper focuses on synthesis and characterization of Zr/Ti and Ti/Zr nitride multilayer coatings by magnetron plasma sputtering to enhance the tribologic properties. The synthesis of nitrides was ...achieved by non-reactive deposition using Ti or Zr nitride targets or by reactive deposition using Ti or Zr targets in the presence of nitrogen. The formation of nitride layers was highlighted by XRD, EDX and XPS investigations, while the tribologic properties were made with HFRR equipment. The tribological study showed that the coefficient of friction and wear scar diameter decrease in multilayer films with zirconium nitride as the upper layer.
This article presents an improved morphological image representation that can be used for image compression, obtaining very high compression rates. The new image representation described in this work ...is called skeleton structure and is a natural extension of the morphologic structure. This article will present its theoretical background, introduce the new representation, and show some application examples.
Zirconium and zirconium nitride coatings were deposited via magnetron sputtering by using high-purity zirconium or zirconium nitride targets. As a particularity, the zirconium nitride coatings were ...deposited by using a ZrN target via non-reactive mode or by using a Zr target via reactive technique, in argon/nitrogen environment. Depending on the time deposition, coatings with different thicknesses (200, 500 and 1000 nm) have been obtained. Chemical and phase composition, thickness of the coating and morphology of the surfaces were investigated by highly sensitive X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and X-Ray diffraction (XRD). The wear tests have been performed by High Frequency Reciprocating Rig (HFRR). The wear scar diameters decrease with an increase of coatings thickness, while the friction coefficient for the coatings with 500 nm thickness revealed the lowest values for friction coefficients, for all type of coatings
The paper presents different methods of using MC34063 and muA78S40 monolithic switching regulator subsystems to construct dual switching power supplies with step-down and step-up converters. General ...description of MC34063 and muA78S40 operation modes, mathematical design applied on numerical examples, PSpice under ORCAD simulation of the whole switching power supply and practical implementations are included. Some practical considerations are also specified.
In this paper we propose a robust blind private watermarking algorithm for image copyright protection. The algorithm is based on wavelet packets. Our basic idea is to decompose the original image ...into a series of details at different scales by using wavelet packets; a binary image used as a watermark is then embedded into the different levels of details. The embedding process includes: usage of an unique (secret) binary identification key to select the wavelet decomposition scheme, wavelet packet decomposition, selection of the wavelet coefficient groups to be used for hiding the watermark, insertion of the watermark in the corresponding group of coefficients by modifying the mean value of the group and inverse wavelet transform. Experiments showed that our algorithm does only minimal degradation to the original image and can improve the robustness of watermarking against different attacks
This paper addresses the gray scale image interpolation by means of mathematical morphology. The new image interpolation method, called skeleton interpolation is based on morphological 3D binary ...skeleton. This article will present the theoretical background of the morphological image interpolation, deduce the new representation and show some application examples. Computer simulations illustrate results.
This paper presents a simulation method for UMTS radio link in the presence of the Rayleigh fading, for different user equipment speeds. The propagation channel simulation method is described in ...detail. Finally, as an application of the presented radio link simulation, some results are highlighted for different user equipment speeds and a number of interesting conclusions are highlighted.
We will present a security/disaster scenario for a communications system with multiple access and code division in direct sequence where a number of sources communicate concurrently over the same ...physical channel. Since the main difference between the underground communications and the terrestrial one is the communications medium, we have investigated the specific propagation problems in dielectric medium for 16QAM and QPSK modulated signals. We found that QPSK technique is a better choice for propagation at large distances (over 200m) while for short distance transmissions, the 16QAM has some clear advantages.
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