Selecting alumina grades for making densely sintered alumina ceramics

Conclusions The rheological properties of slips and the properties of the castings based on the aluminas investigated are very satisfactory and correspond to those obtained for specimens based on G00 alumina. The exceptions are the increased zeta-potential values in the slips made from aluminas GA5 and G0, and the reduced kinetic stability of the slip made from alumina GK.The specimens obtained from alumina of all the grades investigated at 1750° sinter until the apparent porosity completely disappears. The castings made from GK alumina have very high deformation in firing.The highest mechanical and dielectric properties are obtained with specimens of grades GA85 and GA8 aluminas.Sintered vacuum-type products with high electrical and mechanical properties should be made by using alumina grades GA85 and GA8 specified by GOST 6912-64 (instead of G00 as specified by GOST 6912-54).Translated from Ogneupory, No. 7, pp. 39–45, July, 1970.     

Effect of the fineness of alumina and certain additives on the properties of alumina slips and products

Conclusions Slip made from ground alumina from the Podol'sk Factory possesses a high sedimentation stability, a low casting-up rate, and a high density and strength.Incorporating additions of GKZh-10 to accelerate the vibrogrinding of the alumina in preparing high-quality ceramics, needing to have high strength and dielectric properties, is undesirable. Introducing it during the ball-mill grinding for producing corundum ceramics which need not have specially outstanding properties is quite justified.The optimum quantity of magnesia in the slip from the point of view of its rheological properties is 0.07–0.2%.An addition of unfired technical alumina can be advantageously made, together with the MgO modifier, which permits a substantial reduction in the closed porosity and an increase in the apparent density of the articles.Translated from Ogneupory, No. 7, pp. 39–45, July, 1971.     

Prioritizing Highway Safety Manual’s crash prediction variables using boosted regression trees

The Highway Safety Manual (HSM) recommends using the empirical Bayes (EB) method with locally derived calibration factors to predict an agency’s safety performance. However, the data needs for deriving these local calibration factors are significant, requiring very detailed roadway characteristics information. Many of the data variables identified in the HSM are currently unavailable in the states’ databases. Moreover, the process of collecting and maintaining all the HSM data variables is cost-prohibitive. Prioritization of the variables based on their impact on crash predictions would, therefore, help to identify influential variables for which data could be collected and maintained for continued updates. This study aims to determine the impact of each independent variable identified in the HSM on crash predictions. A relatively recent data mining approach called boosted regression trees (BRT) is used to investigate the association between the variables and crash predictions. The BRT method can effectively handle different types of predictor variables, identify very complex and non-linear association among variables, and compute variable importance. Five years of crash data from 2008 to 2012 on two urban and suburban facility types, two-lane undivided arterials and four-lane divided arterials, were analyzed for estimating the influence of variables on crash predictions. Variables were found to exhibit non-linear and sometimes complex relationship to predicted crash counts. In addition, only a few variables were found to explain most of the variation in the crash data.     

Influence of thermally induced,dehydroxylated nanoclay on polymer nanocomposites

This work reports a novel approach towards a chemical-free treatment of nanoclay through extensive thermal exposure. Dehydroxylation at high temperature was utilized to enhance the influence of nanoclay on the properties of polymer. The effect of this treatment of nanoclay, on the polymer properties, with reference to Polypropylene (PP) has been investigated. The FTIR spectra revealed the successful removal of water from the intergallery spacing of the nanoclay. The maintained structural configuration of the clay was confirmed using WAXD pattern. The uniform dispersion and exfoliation of thermally treated clay layers inside the polymer matrix was confirmed through enhanced mechanical properties. Improved crystallization properties, thermal stability and flame retardant characteristic were also noticed in the nanocomposites reinforced with thermally dehydroxylated clay. This study revealed that the dehydroxylation approach of modification of nanoclay may provide much enhanced properties of polymer, without involvement of any chemical for modification.     

Oxidation behavior of SiC ceramics synthesized from processed cellulosic bio-precursor

Oxidation behavior of Si/SiC ceramic composite synthesized from processed cellulosic bio-precursor was studied in dry air over the temperature range 1200–1350 °C. The material was synthesized from processed bio-precursors (bleached bamboo kraft pulp in the form of flat board of bulk density 0.58 g cm^?3) and had a bulk density of 2.66 g cm^?3, porosity of 0.6 vol% and contents of Si and SiC phases of 39.1% and 60.3% (v/v) respectively. The process of oxidation could be described closely by a parabolic oxidation equation. An activation energy of 141.4 kJ/mol was obtained. Both the SiC and Si phases oxidized and the oxidation was mainly controlled by the transport of molecular oxygen through the growing oxide layer. Pre-oxidation at 1300 °C for 24 h in ambient air increased the strength of Si/SiC ceramics by around 46% because of the healing of the surface defects created during surface preparation by the oxide layer.     

Just process me,without knowing me: a secure encrypted domain processing based on Shamir secret sharing and POB number system

High end computational and storage resources provided by the cloud based paradigm are attracting the global infrastructure. However, the wide attacking surface of the public cloud may pose threat to security if outsourcing of the multimedia content is done without obscuring. Employing the traditional encryption schemes may serve as a feasible solution. However, processing in the encrypted domain to fetch the same services as plaintext domain may not be possible due to limitations of the encryption schemes. In this article, a secured scheme based on Shamir’s secret sharing and permutation ordered binary (POB) number system for processing of image in encrypted domain itself over the cloud severs has been proposed. Obfuscated shares are obtained by distributing the image information into multiple shares that can be sent and processed in frequency domain over the cloud servers. The performance of various image operations such as denoising, dehazing, edge sharpening, unsharp masking, contrast enhancement, etc has been validated on these encrypted shares in the frequency domain along with the comparative results in the plaintext domain. The processed image can be obtained from these processed shares only by the authentic entity possessing the secret keys.

     

A self recoverable dual watermarking scheme for copyright protection and integrity verification

Dual watermarking implies embedding of robust as well as fragile watermarks into the same cover image. It facilitates integration of copyright protection and integrity verification into the same scheme. However, most of such existing state of art approaches either lacked the feature of tamper detection and original content recovery or provided an approximation using coarser block level approach. The proposed self recoverable dual watermarking scheme integrates all the aforementioned functionalities of copyright protection, tamper detection and recovery into one scheme. The scheme is independent of the order of embedding of robust and fragile watermarks as these are embedded in different regions of the cover image. It performs tamper detection and recovery, both at the pixel level. The scheme obtains recovery information for each 2×2 image block in just eight bits which are further encoded to only four bits via mapping table. This reduction in recovery bits allows efficient embedding of copyright information which is tested against comprehensive set of attacks. The scheme is found to be robust against noises, filtering, histogram equalization, rotation, jpeg compression, motion blur etc. Besides the normalized cross correlation value, the evaluation of the extracted copyright information is also being done using various objective error metrics based on mutual relation between pixels, their values and locations respectively. The imperceptibility and visual quality of the watermarked as well as recovered image is found to be satisfactorily high. Three major categories of images: natural, texture as well as satellite have been tested in the proposed scheme. Even minute alterations can be chalked out as the detection accuracy rate has been enumerated on pixel basis. The scheme can tolerate tampering ratios upto 50 percent though the visual quality of the recovered image deteriorates with increasing tampering ratio. Comparative results based on normalized cross correlation, probability of false acceptance, probability of false rejection and peak signal to noise ratio metrics validate the efficacy of the proposed scheme over other existing state of art approaches.     

A robust alignment-free fingerprint hashing algorithm based on minimum distance graphs

Abstraction of a fingerprint in the form of a hash can be used for secure authentication. The main challenge is in finding the right choice of features which remain relatively invariant to distortions such as rotation, translation and minutiae insertions and deletions, while at the same time capturing the diversity across users. In this paper, an alignment-free novel fingerprint hashing algorithm is proposed which uses a graph comprising of the inter-minutia minimum distance vectors originating from the core point as a feature set called the minimum distance graph. Matching of hashes has been implemented using a corresponding search algorithm. Based on the experiments conducted on the FVC2002-DB1a and FVC2002-DB2a databases, we obtained an equal error rate of 2.27%. The computational cost associated with our fingerprint hash generation and matching processes is relatively low, despite its success in capturing the minutia positional variations across users.