Using heterogeneous silane patterns to maintain adhesion and decrease water penetration into epoxy/aluminum interfaces

Silanes are used for surface modification to improve dispersion, bind biomaterials, improve adhesion, etc. Their use in improving adhesion in composite materials is widespread, and for these systems there is a growing need for both increased adhesion performance and resistance to water penetration across polymer/oxide interfaces. The present work reports adhesion results obtained using patterned, binary combinations of adhesion-promoting and non-adhesion-promoting silanes patterned onto an oxide surface. The effects of pattern shape, texture (feature size) and the fractional coverage of the adhesion promoter are explored for the bonding of epoxy matrices to aluminum oxide surfaces using combinations of γ-glycidoxypropyltrimethoxysilane (GPS), an adhesion promoter, and either octadecyltrichlorosilane (ODTS) as a hydrophobic non-adhesion promoter, or vinyltrimethoxysilane (VMS) as a water scavenger. In addition to dry tests, samples are submerged in boiling water for 48 h, and in 50°C water for 4 h to determine if water penetrated into the interface, thereby reducing the adhesion. Climbing drum peel tests reveal that heterogeneity of silane primer substrates can influence the adhesion and increase the durability to water penetration. Adhesion enhancement is attributed to the blocking of lateral diffusion of water by barriers due to the presence of the hydrophobic silane. Results show that due to exposure to water at 50°C for 4 h, the adhesion is reduced by 46% in the homogeneous samples but only by 20% in the heterogeneous samples. In contrast, the use of VMS was ineffective in preventing the loss of adhesion due to water penetration.     

Comparative experimental study on effects of conventional and ultrasonic deep cold rolling processes on Ti–6Al–4V

Abstract

The present paper presents the experimental studies on the treatment of Ti–6Al–4V using conventional and ultrasonic deep cold rolling (CDCR and UDCR) processes. The UDCR process is a novel technique in which the ultrasonic technology was incorporated into the concept of the CDCR process, which enables use of superimposed dynamic forces onto considerably reduced static forces applied on a part surface during treatments by UDCR. Considerable improvements in surface topography and near surface characteristics of treated material were achieved in the present study. Both processes exhibited comparable results in surface finish and induced compressive residual stresses, while the UDCR process produced superior results than the CDCR process in work hardening. The investigations suggest that the UDCR process could provide technological benefits for the treatment of thin walled aerospace components to be carried out without geometry distortion, which would lead to improved fatigue life and resistance to failure mechanisms.     

Top-hat selection transformation for infrared dim small target enhancement

Abstract

To improve the performance of top-hat transformation for infrared dim small target enhancement, a top-hat selection transformation is proposed in this paper. First, the top-hat selection transformation is defined and analysed based on analysing and improving of classical top-hat transformation. Then, the top-hat selection transformation is used to enhance infrared dim small targets. The calculation of parameters used in top-hat selection transformation for infrared dim small target enhancement is discussed in detail. Various experiments verified that top-hat selection transformation was effective for infrared dim small target enhancement.     

Enhancing the Signal-to-Interference Ratio in Digital Direct-Sequence Spread-Spectrum Receivers

Digital direct-sequence spread-spectrumreceivers are known to suffer from severe impairments indeterministic types of interference, due to inherentanalog-to-digital converter nonlinearities. In thepresent paper a noncoherent digital direct-sequencespread-spectrum receiver with an integrated adaptiveinterference reduction scheme is presented. Adaptiveinterference reduction is accomplished by exploring the nonlinearity of a 2-bit analog-to-digitalconverter with a pair of magnitude thresholds centeredaround a fixed sign threshold. The magnitude thresholdsare adjusted by means of a statistical control loop. The received signal's magnitudedistribution and zero crossings are used to estimate thecomposition of the interference. The performance of theproposed receiver in the presence of combined additive white Gaussian noise and continuous-waveinterference has been investigated and compared to thebehavior of ideal digital receivers of comparably lowcomplexity as the approach presented. The digitalreceivers studied for comparison use either single-bithard-limiters or 2-bit analog-to-digital converters withadaptive thresholds.     

Forty-Sixth Annual Exhibition of the Institute of Physics and the Physical Society

Abstract

The frequency histogram of connected elements (FHCE) is a recently proposed algorithm that has successfully been applied in various medical image segmentation tasks. The FHCE is based on the idea that most pixels belong to the same class as their neighbouring pixels. However, the FHCE performance relies to a great extent on the optimal selection of a threshold parameter. Since evaluating segmentation results is a highly subjective process, a collection of threshold values must typically be examined. No algorithm has been proposed to automate the determination of the threshold parameter value of the FHCE. This study presents a method based on the fuzzy C-means clustering algorithm, designed to automatically generate optimal threshold values for the FHCE. This new approach was applied as a part of a structured sequence of image processing steps in order to facilitate segmentation of microcalcifications in digitized mammograms. A unique threshold value was generated for each mammogram, taking into account the different grey-level patterns based on different compositions of various breast tissues in it. The segmentation algorithm was tested on 100 mammograms (50 collected from the Mammographic Image Analysis Society and 50 normal mammograms onto which a number of simulated microcalcifications were generated). The algorithm was able to detect subtle microcalcifications with sensitivity ranging from 93 to 98%, False alarm ratio from 3 to 5% and false negatives variability from 2 to 3%.     

Selective image enhancement using attribute morphology

Abstract

Numerous applications in image interpretation involve feature extraction. In many low-contrast images, this process is pre-empted by an image enhancement phase to improve the quality of features and accentuate fine details. Few attempts at image enhancement have focused on a selective approach, whereby features are enhanced based on their characteristics. This technical note presents preliminary work on a novel image enhancement algorithm based on attribute morphology. The algorithm is amorphous, that is, it does not rely on the shape of a neighbourhood operator, but rather on a feature attribute such as area or contrast. The algorithm can be directed towards differently shaped structures simultaneously without undue noise amplification. The algorithm is demonstrated through the enhancement of features in various biological images.