A complete factorization of paraunitary matrices with pairwisemirror-image symmetry in the frequency domain

The problem of designing orthonormal (paraunitary) filter banks has been addressed in the past. Several structures have been reported for implementing such systems. One of the structures reported imposes a pairwise mirror-image symmetry constraint on the frequency responses of the analysis (and synthesis) filters around π/2. This structure requires fewer multipliers, and the design time is correspondingly less than most other structures. The filters designed also have much better attenuation. We characterize the polyphase matrix of the above filters in terms of a matrix equation. We then prove that the structure reported in a paper by Nguyen and Vaidyanathan (1988), with minor modifications, is complete. This means that every polyphase matrix whose filters satisfy the mirror-image property can be factorized in terms of the proposed structure     

Statistical evaluation of parameters in grinding

The influence of longitudinal feed, cross feed and depth of cut on grinding wheel wear and surface roughness has been investigated using regression analysis. The mathematical models thus developed have been used to select the levels of machining variables such that wheel wear can be reduced without affecting surface finish.     

Further aspects of the differential capacitance of iron

The differential capacitance of high purity zone-refined iron was measured using a single pulse technique. Capacitance behaviour in dilute solutions of sodium perchlorate showed that an unambiguous assignment of a value to the pzc is not possible from the capacitance minima. Measurements in sodium halides showed a different behaviour with I⁻ than with F⁻, Cl⁻ and Br⁻. Electrode capacitance in an aqueous solution of furoic-acid-sodium-furoate buffer was determined over 300 mV on either side of the open-circuit potential. The effect of specifically adsorbed furoate ions on the morphology of the capacitance curves is very striking.     

Carbon Fiber–Bismaleimide Composites Filled with Nickel‐Coated Single‐Walled Carbon Nanotubes for Lightning‐Strike Protection

Multifunctional carbon fiber composites are imperative for next‐generation lightweight aircraft structures. However, lightning‐strike protection is a feature that is lacking in many modern carbon fiber high‐temperature polymer systems, due to their high electrical resistivity. This work presents a study on processing, materials optimization, and property development of high‐temperature bismaleimide (BMI)–carbon fiber composites filled with nickel‐coated single‐walled carbon nanotubes (Ni‐SWNTs) based on three key factors: i) dispersion of Ni‐SWNTs, ii) their surface coverage on the carbon plies and, iii) the composite surface resistivity. Atomic force microscopy analysis revealed that coating purified SWNTs with nickel enabled improved dispersion which resulted in uniform surface coverage on the carbon plies. The electrical resistivity of the baseline composite system was reduced by ten orders of magnitude by the addition of 4 wt% Ni‐SWNTs (calculated with respect to the weight of a single carbon ply). Ni‐SWNT–filled composites showed a reduced amount of damage to simulated lightning strike compared to their unfilled counterparts, as indicated by the minimal carbon fiber pull‐out.     

Shape memory alloy actuator design: CASMART collaborative best practices and case studies

One goal of the Consortium for the Advancement of Shape Memory Alloy Research and Technology is to compile the collective design experiences of our member organizations into a single medium that researchers and engineers may use to make efficient and effective decisions when developing shape memory alloy (SMA) components and systems. Recent work toward this goal is presented through the framework of six fundamental design aspects we have identified, which include evaluation, alloy selection, processing and fabrication, testing and properties, modeling, and system integration considerations including control system design. Each aspect is documented in the light of enabling the design engineer to access the tools and information needed to successfully design and develop SMA systems. Application of these aspects is illustrated through case studies resulting from our own SMA designs. It is shown that there is not an obvious single, linear route a designer can adopt to navigate the path from concept to product. Each application brings unique challenges that demand a particular emphasis and priority for each engineering aspect involved in the development of a system actuated by SMAs.     

Chemical changes and diastatic activity in grains of sorghum (Sorghum bicolor) cultivars during germination

Grain samples from nine sorghum (Sorghum bicolor (L) Moench) cultivars were germinated for 16, 48, 96 and 144 h, and changes in their diastatic activity, protein, starch, soluble sugars, tannin and total phenols contents were studied. The diastatic activity increased up to 96 h of germination and decreased at 144 h. Diastatic activity showed significant variation among cultivars, which ranged from 10.0 to 88.3 units at 48 h and from 20.0 to 150.4 units at 96 h germination. In general, starch content decreased while soluble sugars increased during germination. Variation in protein content during germination was appreciable among the cultivars.     

Effect of different stages of tensile deformation on micromagnetic parameters in high-strength, low-alloy steel

The influence of tensile deformation on the magnetic Barkhausen emissions (MBE) and hysteresis loop has been studied in a high-strength, low-alloy steel (HSLA) and its weldment. The magnetic measurements were made both in loaded and unloaded conditions for different stress levels. The rootmean-square (RMS) voltage of the MBE has been used for analysis. This study shows that the preyield and postyield deformation can be identified from the change in the the MBE profile. The initial elastic deformation showed a linear increase in the MBE level in the loaded condition, and the MBE level remained constant in the unloaded condition. The microplastic yielding, well below the macroyield stress, significantly reduces the MBE, indicating the operation of grain-boundary dislocation sources below the macroyield stress. This is indicated by the slow increase in the MBE level in the loaded condition and the decrease in the MBE level in the unloaded condition. The macroyielding resulted in a significant increase in the MBE level in the loaded condition and, more clearly, in the unloaded condition. The increase in the MBE level during macroyielding has been attributed to the grain rotation phenomenon, in order to maintain the boundary integrity between adjacent grains, which would preferentially align the magnetic domains along the stress direction. With progressive plastic deformation, the MBE level remains more or less constant in the loaded condition and decreases linearly with strain in the unloaded condition. This constant MBE behavior in the loaded condition is attributed to the opposing effect of applied tensile stress (which tends to align the domains along the stress direction) and the dislocation density (which reduces the domain-wall displacement). The decreasing MBE in the unloaded condition is attributed to the combined effect of compressive residual stress at the surface layers (which tends to align the domain wall perpendicular to the stress direction) and the dislocation density. This study shows that MBE during tensile deformation can be classified into four stages: (1) perfectly elastic, (2) microplastic yielding, (3) macroyielding, and (4) progressive plastic deformation. A multimagnetic parameter approach, combining the hysteresis loop and MBE, has been suggested to evaluate the residual stresses.     

Development of engineered probiotics with tailored functional properties and their application in food science

Food Science and Biotechnology - The potential health benefits of probiotics may not be cognized because of the substantial curtailment in their viability during food storage and passage through...     

A systematic review on selection characterization and implementation of probiotics in human health

Food Science and Biotechnology - Probiotics are live bacteria found in food that assist the body's defence mechanisms against pathogens by reconciling the gut microbiota. Probiotics are...