A robust and secure perceptual hashing system based on a quantization step analysis

Perceptual hashing is conventionally used for content identification and authentication. It has applications in database content search, watermarking and image retrieval. Most countermeasures proposed in the literature generally focus on the feature extraction stage to get robust features to authenticate the image, but few studies address the perceptual hashing security achieved by a cryptographic module. When a cryptographic module is employed [1], additional information must be sent to adjust the quantization step. In the perceptual hashing field, we believe that a perceptual hashing system must be robust, secure and generate a final perceptual hash of fixed length. This kind of system should send only the final perceptual hash to the receiver via a secure channel without sending any additional information that would increase the storage space cost and decrease the security. For all of these reasons, in this paper, we propose a theoretical analysis of full perceptual hashing systems that use a quantization module followed by a crypto-compression module. The proposed theoretical analysis is based on a study of the behavior of the extracted features in response to content-preserving/content-changing manipulations that are modeled by Gaussian noise. We then introduce a proposed perceptual hashing scheme based on this theoretical analysis. Finally, several experiments are conducted to validate our approach, by applying Gaussian noise, JPEG compression and low-pass filtering.     

Low‐complexity robust adaptive generalized sidelobe canceller detector for DS/CDMA systems

A novel low computational complexity robust adaptive blind multiuser detector, based on the minimum output energy (MOE) detector with multiple constraints and a quadratic inequality (QI) constraint is developed in this paper. Quadratic constraint has been a widespread approach to improve robustness against mismatch errors, uncertainties in estimating the data covariance matrix, and random perturbations in detector parameters. A diagonal loading technique is compulsory to achieve the quadratic constraint where the diagonal loading level is adjusted to satisfy the constrained value. Integrating the quadratic constraint into recursive algorithms seems to be a moot point since there is no closed‐form solution for the diagonal loading term. In this paper, the MOE detector of DS/CDMA system is implemented using a fast recursive steepest descent adaptive algorithm anchored in the generalized sidelobe canceller (GSC) structure with multiple constraints and a QI constraint on the adaptive portion of the GSC structure. The Lagrange multiplier method is exploited to solve the QI constraint. An optimal variable loading technique, which is capable of providing robustness against uncertainties and mismatch errors with low computational complexity is adopted. Simulations for several mismatch and random perturbations scenarios are conducted in a rich multipath environment with near–far effect to explore the robustness of the proposed detector. Copyright © 2008 John Wiley & Sons, Ltd.     

An investigation of cutting forces in machining with worn ball-end mill

Reliable tool wear monitoring technique is one of the important aspects for achieving an integrated and self-adjusting manufacturing system. In this study, an analytical model is proposed to estimate the cutting forces, the tool geometry, and the chip geometry in relation to the flank wear, when milling with a ball-end mill. Modeling is based on thermomechanical modelling of oblique cutting. The worn tool geometry is decomposed into a series of axial elementary cutting edges. At any active tooth element, the flank wear geometry is calculated and the chip formation is obtained from an oblique cutting process characterised by local undeformed chip section and local cutting angles. Coated carbide ball-end tool, and a titanium workpiece material have been considered in this paper. The results found by using developed models have shown good agreement with experimental results.     

Gas phase esterification of acetic acid with ethanol over MoO3 supported on AlPO4 and the effect of modification with phosphomolybdic acid and Ce4+ ions

A series of AIPO₄–MoO₃ (APM) systems with various molybdena loadings (5–50) mol %, same modified with phosphomolybdic acid (PMA) and cerium ions, were prepared by an impregnation method and calcined at 400 °C, except for the samples modified with PMA which were calcined at 350 °C for 4 h. The catalysts were characterized by TG/DTG, XRD, IR spectroscopy, N₂ adsorption and electrical conductivity measurements. The surface acidity and basicity of the catalysts were determined by adsorption of pyridine and the dehydration–dehydrogenation of isopropyl alcohol. The catalytic esterification of acetic acid with ethanol was carried out in a convention fixed bed reactor. The results clearly revealed that the catalyst with a composition of 10 mol % MoO₃ (APM10) was the most active and selective catalyst for the production of ethyl acetate. Moreover, the yield of ethyl acetate increases on addition of PMA into APM10 while it decreases on the addition of Ce⁴⁺ ions. These results were correlated with structure, semiconductivity and the acid–base properties of the prepared catalysts. Copyright © 2003 Society of Chemical Industry     

Is Kaposi's sarcoma--associated herpesvirus ubiquitous in urogenital and prostate tissues?

Controversy exists as to whether Kaposi's sarcoma-associated herpesvirus (KSHV) is more widespread than originally reported. Recently, Monini et al reported that KSHV is ubiquitous in urogenital and prostate tissues and sperm of healthy Italian adults using nested polymerase chain reaction (PCR). We have examined for the presence of KSHV in 10 normal prostates from Italian men and 10 from men from the United States, as well as 32 prostatic, 30 vulvar, 24 ovarian, 20 cervical, and 30 testicular cancer specimens from patients from the United States. None of the patients had a history of human immunodeficiency virus infection. The samples were tested by nested PCR. The sensitivity of this assay was determined by a dilution study performed by diluting KSHV DNA from the KS-1 cells (a primary effusion lymphoma cell line which is estimated to have 16 copies of KSHV per cell) in DNA from a K562 myeloid cell line. The nested PCR that we used can detect 2.4 copies of KSHV sequences on a background of K562 DNA. All the samples were negative for KSHV sequences. Therefore, we cannot confirm the finding that KSHV sequences are ubiquitous in urogenital and prostate tissues. Furthermore, because our samples were from both the United States and Italy, the discrepancy between results is unlikely to be explained by either ethnic or environmental factors. False-positive results easily occur using nested primer PCR because of contamination. Our data argue that KSHV is not widely disseminated in urogenital tissues from nonimmunosuppressed individuals.     

Dynamic Faults in Random-Access-Memories: Concept, Fault Models and Tests

The ever increasing trend to reduce DPM levels of memories requires tests with very high fault coverage and low cost. This paper describes an important fault class, called dynamic faults, that cannot be ignored anymore. The dynamic fault behavior can take place in the absence of the static fault behavior, for which the conventional memory tests have been constructed. The concept of dynamic fault will be established and validated for both dynamic and static Random-Access-Memories. A systematic way to develop fault models for dynamic faults will be introduced. Further, it will be shown that conventional memory tests do not necessarily detect its dynamic faulty behavior, which has been shown to exist in real designs. The paper therefore also presents new memory tests to target the dynamic fault class.     

Numerical studies on a paradox for non-cooperative static load balancing in distributed computer systems

Numerical examples of a Braess-like paradox in which adding capacity to a distributed computer system may degrade the performance of all users in the system under non-cooperative optimization have been reported. Unlike the original Braess paradox, in the models examined, this behavior occurs only in the case of finitely many users and not in the case of infinite number of users and the degree of performance degradation can increase without bound. This study examines numerically some examples around the Braess-like paradox in a distributed computer system. In the numerical examples, it is observed that the worst-case degree of the paradox (WCDP) is largest in complete symmetry. The dependence of the WCDP on some system parameters is also examined.     

Cellulose nanocrystals reinforced poly(oxyethylene)

Nanocomposite materials were prepared from poly(oxyethylene) (POE) as the matrix and a stable aqueous suspension of cellulose nanocrystals extracted from tunicate as the reinforcing phase. After dissolving POE in water and mixing with the cellulose nanocrystals suspension, solid films were obtained by casting and evaporating the preparations. Resulting films were characterized using scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical analysis. Favorable interactions between cellulose and POE were evidenced and assumed to be partially responsible for a decrease of the crystallinity of the matrix. A thermal stabilization of the nanocomposites for temperatures higher than the melting temperature of POE was reported and ascribed to the formation of a rigid cellulosic network within the matrix assumed to be governed by a percolation effect. The formation of this percolating network was not altered by the matrix crystallization process and filler/POE interactions.