Design of FIR filters with reduced computations

The performance of a symmetric nonrecursive filter can be improved by multiple use of the same filter. The method is based on an Amplitude Change Function (ACF). An approach to the design of nonrecursive filters using an ACF is discussed in this paper. The prototype filter chosen is a Recursive Running Sum (RRS) filter which does not require any multipliers for its implementation. The required filter specifications are met by multiple use of the RRS filters. The overall filter requires a much smaller number of multiplications and adders than the one designed using the conventional method. It is shown that this method provides reduced noise due to coefficient quantization and product quantization compared with the conventional design technique.     

Key-space analysis of double random phase encryption technique

We perform a numerical analysis on the double random phase encryption/decryption technique. The key-space of an encryption technique is the set of possible keys that can be used to encode data using that technique. In the case of a strong encryption scheme, many keys must be tried in any brute-force attack on that technique. Traditionally, designers of optical image encryption systems demonstrate only how a small number of arbitrary keys cannot decrypt a chosen encrypted image in their system. However, this type of demonstration does not discuss the properties of the key-space nor refute the feasibility of an efficient brute-force attack. To clarify these issues we present a key-space analysis of the technique. For a range of problem instances we plot the distribution of decryption errors in the key-space indicating the lack of feasibility of a simple brute-force attack.     

Recent trends in metal ion based hydrogel biomaterials for tissue engineering and other biomedical applications

Recently,the metal ion cross-linked hydrogels have gained enormous interest because of its excellent properties like self-healing,fast recovery,biocompatibility and high mechanical properties combined with multi-stimuli responsiveness.In this review article,we have summarized the recent trends in the development of metal ion cross-linked hydrogels for tissue engineering and biomedical applications.A number of metal ions and their contribution in the synthesis of various cross-linked hydrogels are discussed with respect to their crosslinking mechanisms,compositions,physio-chemical and biological properties.A special emphasis has been given to ferric(Fe³⁺)ion cross-linked hydrogels and their different combinations owing to their numerous researches reported in the recent past with exceptional properties.The application of these metal ion based hydrogels in biomedical applications including tissue engineering,sensing,wound healing,drug delivery and as tissue adhesive and tissue sealants are reviewed with specific examples.Importantly,the application of these metal ion cross-linked hydrogels as inks in 3 D printing is explained in a separate section.Finally,the possible toxic effects of the different metal ions and their effects have been scrutinized.Future directions and comprehensive applications of the hydrogels are highlighted.     

Paraxial speckle-based metrology systems with an aperture

Digital speckle photography can be used in the analysis of surface motion in combination with an optical linear canonical transform (LCT). Previously [D. P. Kelly et al. Appl. Opt.44, 2720 (2005)] it has been shown that optical fractional Fourier transforms (OFRTs) can be used to vary the range and sensitivity of speckle-based metrology systems, allowing the measurement of both the magnitude and direction of tilting (rotation) and translation motion simultaneously, provided that the motion is captured in two separate OFRT domains. This requires two bulk optical systems. We extend the OFRT analysis to more general LCT systems with a single limiting aperture. The effect of a limiting aperture in LCT systems is examined in more detail by deriving a generalized Yamaguchi correlation factor. We demonstrate the benefits of using an LCT approach to metrology design. Using this technique, we show that by varying the curvature of the illuminating field, we can effectively change the output domain. From a practical perspective this means that estimation of the motion of a target can be achieved by using one bulk optical system and different illuminating conditions. Experimental results are provided to support our theoretical analysis.     

57Fe Mössbauer and positron lifetime studies of Al-Cu-Fe quasicrystals

Al_61·4Cu_22·7Fe_15·9, Al_63·2Cu_21·8Fe₁₅ and Al₇₁Cu₁₄Fe₁₅ have been studied by Mössbauer, positron annihilation and X-ray diffraction techniques. The positron lifetime, measured as a function of temperature, in Al_61·4Cu_22·7Fe_15·9 shows a two-step increase. This is found to be due to the dynamics of phasons associated with Al and Cu, having activation energies of 0·43 eV and 0·78 eV respectively. In the case of Al₇₁Cu₁₄Fe₁₅, a phase transformation from the quasicrystalline-crystalline phase at ≈ 550°C is observed.     

Influence of Lipids Isolated from Soybean Seed on Different Properties of Cassava Starch

The effect of lipids isolated from soybean seeds on the properties of cassava starch was investigated. Both polar and non‐polar lipid fractions were complexed with starch and the physicochemical and rheological properties were examined. The FTIR spectra of the complexed starches showed all the absorption bands characteristic of native starch with an extra minor peak at 2355 cm^‐1.The complexes prepared using the polar lipid fraction in diethyl ether as solvent exhibited a swelling volume of 32.5 mL/g compared to 36.9 mL/g for petroleum ether as solvent. A similar effect was observed with the non‐polar fraction. The apparent amylose content of the complexes was found to be lowered as a result of complexation. Total and soluble amylose contents and water‐binding capacity of the complexes were higher while their enzyme digestibility was noticeably lowered. The peak viscosity of the complexes was suppressed as a result of complexation. The polar layer exhibited a greater influence on the viscometric properties of the complexes with a higher breakdown ratio and hence higher stability. When compared to native starch, the percentage light transmittance of the complexes was noticeably reduced. The results indicate a considerable influence of the isolated lipid fractions on starch properties which can be useful in food and industrial applications.     

Companding in signal processing

The authors consider the use in signal processing of noise reduction techniques such as syllabic companding (compressing and expanding), developed for transmission and storage. Applications discussed include increasing selectivity in single sinusoid detection. Whether or not companding will be useful in a given filtering application depends on the type and response of the filter and the type of signals present at the input.<>