Integrated Learning Particle Swarm Optimizer for global optimization

This study proposes a novel Integrated Learning Particle Swarm Optimizer (ILPSO), for optimizing complex multimodal functions. The algorithm modifies the learning strategy of basic PSO to enhance the convergence and quality of solution. The ILPSO approach finds the diverged particles and accelerates them towards optimal solution. This novel study also introduces the particle’s updating strategy based on hyperspherical coordinates system. This is especially helpful in handling evenly distributed multiple minima. The proposed technique is integrated with comprehensive learning strategy to explore the solution effectively. The performance comparison is carried out against different high quality PSO variants on the set of standard benchmark functions with and without coordinate rotation and with asymmetric initialization. Proposed ILPSO algorithm is efficient in terms of convergence rate, solution accuracy, standard deviation, and computation time compared with other PSO variants. Friedman non-parametric statistical test followed by Dunn post analysis results indicate that the proposed ILPSO algorithm is an effective technique to optimize complex multimodal functions of higher dimension.     

Home-grown school feeding: promoting local production systems diversification through nutrition sensitive agriculture

The consumption of some non-staple crops such as legumes and dark, green leafy vegetables can address common deficiencies in key nutrients such as vitamin A and iron; however, limited markets and supply chain development impede their production and accessibility to consumers. This study investigates the pathways to promote agricultural production and dietary diversity for a local market intervention called Home-Grown School Feeding (HGSF). School feeding menus from 24 districts across 10 regions in Ghana during the 2014–15 school year were analysed in terms of food groups and several individual foods. The menus were then compared with food groups produced by households during the past year or consumed in the past seven days using data collected from a household survey. Greater inter-food group diversity in the menus was associated with higher production levels for tubers and dark, leafy green vegetables in the South and cereals in the North. A correspondence between the frequency in which a food group appeared in a menu and the share of households who consumed foods from the food group was also noted. Key issues, such as optimizing supply chains, enabling farm linkages and supporting diverse nutrient rich food groups, that underlie the success of Home-Grown School Feeding and other agricultural policies with similar goals of promoting production and dietary diversity are highlighted through commodity specific examples. The findings of this study may help strengthen operational linkages between agriculture production and nutrition for HGSF and other similar interventions.     

FPGA implementation and performance study of spectrum sensing based on entropy estimation using cyclic features

This work presents a spectrum sensing technique based on the entropy of frequency domain autocorrelation of receiving signal at different cyclic frequencies. The performance of the proposed sensing technique is compared with other sensing techniques such as energy detection using Bayesian and Neyman–Pearson criteria, entropy estimation under frequency domain, cyclostationary feature detection. The performance of sensing algorithms is also analyzed for single node and multinode/cooperative environment under most probable channel effects such as fading, shadowing, receiver’s uncertainty and free space path loss using Monte-Carlo methods. Simulation results reveal that the proposed sensing technique is able to detect signals of signal-to-noise ratio up to −24 dB with five nodes in cooperation while maintaining a false alarm probability of 0.1 and a detection probability of 0.9. The proposed sensing algorithm is also implemented in Virtex-4 Field Programmable Gate Arrays.     

Direct imaging of the spatial and energy distribution of nucleation centres in ferroelectric materials

Macroscopic ferroelectric polarization switching, similar to other first-order phase transitions, is controlled by nucleation centres. Despite 50 years of extensive theoretical and experimental effort, the microstructural origins of the Landauer paradox, that is, the experimentally observed low values of coercive fields in ferroelectrics corresponding to implausibly large nucleation activation energies, are still a mystery. Here, we develop an approach to visualize the nucleation centres controlling polarization switching processes with nanometre resolution, determine their spatial and energy distribution and correlate them to local microstructure. The random-bond and random-field components of the disorder potential are extracted from positive and negative nucleation biases. Observation of enhanced nucleation activity at the 90 composite function domain wall boundaries and intersections combined with phase-field modelling identifies them as a class of nucleation centres that control switching in structural-defect-free materials.     

A Supramolecular Nanocomposite as a Near‐Infrared‐Transmitting Optical Filter for Security and Forensic Applications

Visibly opaque but near‐infrared (NIR)‐transparent materials are an essential component for night‐vision photography, security imaging, and forensic applications. Herein, the development of a novel supramolecular black dye from a diketopyrrolopyrrole (DPP)‐based low‐molecular‐weight organogelator is described. In the solution state, the monomer of DPP–Amide exhibits a deep green color with a broad absorption in the visible region due to firm intramolecular charge transfer from the donor to the acceptor unit. Interestingly, due to the synergistic effect of H‐bonding and π‐stacking, DPP–Amide can form a black organogel in toluene with complete spectral coverage from 300 to 800 nm, and transmits beyond 850 nm. In the gel state, complete visible‐spectrum coverage is achieved due to the simultaneous formation of both H‐ and J‐type aggregates, which is confirmed via absorption studies. To create a free‐standing NIR‐transmitting elastomeric black filter, nanoscopic molecular aggregates of DPP–Amide (0.15 wt%) are embedded into a poly(dimethylsiloxane) matrix. This nanocomposite possesses high NIR transparency with good thermal and photostability for practical applications. Finally, the use of the developed material for NIR photography, security, and forensic‐related applications is demonstrated.     

A Phase Diagram for Epitaxial PbZr1−xTixO3 Thin Films at the Bulk Morphotropic Boundary Composition

A phase diagram of temperature versus strain was constructed for a (001)-oriented PbZr_{1− x} Ti _x O₃ epitaxial single crystal thin film near the bulk morphotropic boundary composition ( x =0.47) on an (001)-oriented cubic substrate. The phase-field approach is employed. It is shown that a mixture of distorted rhombohedral, orthorhombic, and tetragonal phases exists under small values of strain, i.e., close to the in-plane clamped boundary condition. This result contradicts thermodynamic calculations assuming a single-domain state that predicted a single distorted rhombohedral phase under similar strains. Furthermore, it is demonstrated that under a large tensile strain current phase-field simulations showed a tetragonal phase with a ₁ /a ₂ twin structures as the stable state whereas thermodynamic calculations predicted an orthorhombic phase.     

Determining the equation of state of amorphous solids at high pressure using optical microscopy

A method to determine the volumetric equation of state of amorphous solids using optical microscopy in a diamond anvil cell is described. The method relies on two- dimensional image acquisition and analysis to quantify changes in the projected image area with compression. The area analysis methods prove to be robust against improper focusing and lighting conditions while providing the accuracy necessary to deduce small area changes, which correspond to small volume changes in an isotropic material. The image capture, area analysis method is used to determine the compression of cubic crystals, yielding results in good agreement with diffraction and volumetric measurements. As a proof of concept, the equation of state of amorphous red phosphorus is measured up to 12 GPa under hydrostatic conditions where the quantified volume change between the red and black phases is approximately ΔV/V(0) ≈ 0.05 after a reduction of volume nearing 35% at 8 GPa. A large hysteresis is present during decompression and eventually results in a 15% permanent densification relative to the starting volume, which is attributed to a pressure induced crystallization from red to black phosphorus. The robustness of the technique is also demonstrated by measuring the equation of state of GeSe(2) glasses for semi transparent samples and As(2)O(3) in which gold coating is used as a contrasting aid.     

Tailoring the microstructural,magnetic and dielectric properties of vanadium ions substituted nickel ferrite nanocrystals

This paper describes the composition-dependent microstructural, magnetic and dielectric properties of vanadium ions doped nickel ferrite nanoparticles. All the nanoferrite samples (NiV_xFe_2-xO₄: x = 0.00, 0.05, 0.10 and 0.15) were prepared using conventional co-precipitation method. X-ray diffraction patterns verified the single cubic spinel phase formation and achievement of nanosized ferrite particles with a homogeneous distribution, which was also supported by HRTEM micrographs. Mean crystallite diameter was seen in the range of 05 nm to 12 nm as evaluated from Williamson-Hall (W-H) curves for the different doped samples. A compressive nature microstrain was noticed in all the samples and was also seen to reduce with the enhancement of vanadium ions content. A blue shift was detected in the indirect band gap for higher vanadium doped samples. Magnetization at the saturation point as well as coercive field both were observed to reduce at room temperature with increasing vanadium concentration in nanosized nickel ferrites. Room temperature dielectric characteristics of all the synthesized samples ensured that the elementary charge conduction process was governed by the hopping of electrons. Cole-Cole plots also showed that the grain boundaries play an important task in deciding the dielectric responses.