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Beyond von Neumann's architecture, artificial neural network-based neuromorphic computing in a simple two-terminal resistive switching device is considered the future potential technology for simultaneous data processing and storage. These are also compatible with low-power consumption nanoelectronic devices and, thus, suitable for applications such as image recognition toward solving complex pattern recognition problems. Herein, motivated by the human biological brain, we successfully synthesized low-cost RRAM devices using the thermal oxidation of Cu, i.e., CuO as the active material together with Cu as the top electrode and FTO as the bottom contact for a two-terminal resistive switching device, and investigated characteristics for neuromorphic computing. Cu/CuO/FTO-based devices showed excellent bipolar analog RRAM characteristics with 150 repeatable cycles, retention for 11 000 s, and DC pulse endurance for 5000 cycles. Moreover, devices exhibit a remarkable mimicking ability, demonstrating spike time-dependent plasticity (STDP), pulse-paired facilitation (PPF), synaptic weight, and learning and forgetting characteristics, substantiating the recognition ability. Furthermore, the artificial neural network synaptic membrane exhibits excellent long-term (LTP) and short-term (STP) potentiation for six consecutive cycles. Thus, the present work on Cu/CuO/FTO-based devices provides a detailed understanding of CuO active material-based resistive switching with a potential for neuromorphic computing beyond the von Neumann architecture. [ABSTRACT FROM AUTHOR]

In this work, microstructure dependent impact-induced failure of hydroxyl-terminated polybutadiene (HTPB)–cyclo-tetra-methylene-tetra-nitramine (HMX) energetic material samples is studied using the cohesive finite element method (CFEM). The CFEM model incorporates experimentally measured viscoplastic constitutive behavior, experimentally measured interface level separation properties, and phenomenological temperature increase due to mechanical impact based on viscoplastic and frictional energy dissipation. Nanoscale dynamic impact experiments were used to obtain parameters for a strain-rate dependent power law viscoplastic constitutive model in the case of bulk HTPB and HMX as well as the HTPB–HMX interfaces. An in situ mechanical Raman spectroscopy (MRS) setup was used to obtain bilinear cohesive zone model parameters to simulate interface separation. During analyses, the impact-induced viscoplastic energy dissipation and the frictional contact dissipation at the failed HTPB–HMX interfaces is found to have a significant contribution toward local temperature rise. Microstructures having circular HMX particles show a higher local temperature rise as compared to those with diamond or irregularly shaped HMX particles with sharp edges indicating that the specific particle surface area has a higher role in temperature rise than particle shape and sharp edges. Regions within the analyzed microstructures near the HTPB–HMX interfaces with a high-volume fraction of HMX particles were found to have the maximum temperature increase. [ABSTRACT FROM AUTHOR]

A silicon photonic crystal waveguide based design of a highly-compact transverse-magnetic pass polarization filter has been proposed in this paper. The device utilizes both the index guiding and bandgap property simultaneously to realize its operation as a polarizer. Optimizations of different device-parameters, such as the radius of the holes, width, thickness, and length of the waveguide, have been performed for attaining its paramount performance. A small waveguide length, in the order of 5 μ m, has shown a high extinction ratio, i.e., 45 dB, at the wavelength of 1550 nm. A uniform bandwidth of ≈ 120 nm is observed, beyond the extinction ratio of 40 dB, along with a remarkably low insertion loss, i.e., ≈ 0.6 dB. Investigations are also performed to evaluate performances of the polarizer under possible fabrication disorders, which depicts a sustained performance up to at least a random fabrication disorder of 30 nm. These merits make the polarizer suitable for applications in densely integrable photonic integrated circuits. [ABSTRACT FROM AUTHOR]

This investigation analyzes the propagation of nonlinear ion-acoustic waves (IAWs) in an unmagnetized, collisionless plasma composed of inertial positive ions and inertialess Maxwellian positrons as well as the inertialess non-Maxwellian electrons that obey (r, q)-distribution. To observe the impact of particle trapping on the nonlinear IAWs in an electron–positron–ion plasma, the Korteweg–De Vries (KdV) and modified KdV (mKdV) equations are derived using a reductive perturbation method. In the distribution function, the spectral parameters (r, q) put up their contribution to the flatness and high-energy tails, respectively. An important aspect of this investigation is the determination of well-known quasi-periodic solutions, multi-soliton solutions, breathers, and shocks under the variation of different physical parameters, especially spectral indices (r, q). Finally, the interaction of solitons is also presented for discussion of the complete profile. In addition, a detailed comparison, especially in a periodic wave, is made between the generalized (r, q)-distribution and the limiting cases of Kappa and Maxwellian distributions. The results presented in this study contribute to a better understanding of the characteristics of both high- and low-energy parts of the electron distribution function as well as the formation of periodic, soliton, multi-soliton, breathers, and shocks in space and astrophysical plasmas. [ABSTRACT FROM AUTHOR]

In this paper, we present a surface decontamination system that substitutes traditional chemicals and scrubbing agents, which will be useful for the general public during a pandemic. The technique is based on a hybrid process in which UV-C light and its photons interact with metal oxide nano-catalysts to generate hydroxyl radicals, which can enhance the deactivation process, and the system can work even in the shadow regions via a dry process. The optimum number of UV light sources in combination with TiO2 nanoparticles catalysts on aluminum plates have been used synergistically in the system. The UV dose in the disinfection chamber has been optimized, which is between 60 and 500 mJ/cm2 throughout the disinfection chamber. The concentration of hydroxyl radicals is reported more than 25 000 ions/cm3 within the disinfection chamber. These ions are circulated throughout the disinfection volume. The disinfection efficiency has been tested on bacteria and spores, and the obtained results are correlated. Around 8 log reductions in the counts of the test bacteria of Escherichia coli and Klebsiella pneumoniae have been achieved in just 2 min of exposure in the continuous operation of the system. Tests have also been performed on Geobacillus stearothermophilus spores, and the method described here is the result of multiple tests, a review of the scientific literature, and the incorporation of current laboratory practice. The deactivation tested in the system is larger than that of known bacteria and viruses in terms of UV-doses, signifying its utility during the pandemic. [ABSTRACT FROM AUTHOR]

In this work, magnetoelectric properties of a co-sintered bilayered composite of non-lead based piezoelectric 0.97(Bi0.5Na0.5TiO3)-0.03(K0.47Na0.47Li0.06Nb0.74Sb0.06Ta0.2O3) and magnetostrictive Co0.6Zn0.4Fe1.7Mn0.3O4 are presented. Similar optimal sintering conditions of the individual components lead to a very clean interface as evidenced in the scanning electron microscopy, angle dispersive X-ray diffraction, and energy-dispersive X-ray (EDX) results. Clean interface results in strong intimate mechanical coupling between both components and causes a maximum transfer of induced strain, leading to a large magnetoelectric coupling ~142 mV/cm.Oe measured in longitudinally magnetized-transversely polarized configuration (L-T mode). Remnant polarization ~32 μC/cm2, remnant magnetization ~0.50 emu/g, and sufficiently high self biased magnetoelectricity ~135 mV/cm Oe (L-T mode) were observed for this composite. [ABSTRACT FROM AUTHOR]

The present work addresses the solvatochromic shift of phenol blue (PB) dye. For this purpose the results of Car–Parrinello molecular dynamics (CPMD) simulations for PB in gas phase are compared with results obtained for PB in water from CPMD hybrid quantum mechanics-molecular mechanics (CPMD-QM/MM) calculations. The absorption spectra were obtained using the intermediate neglect of differential overlap/spectroscopic-configuration interaction (INDO/CIS) method and were calculated for a multitude of configurations of the trajectory. The calculated λmax for PB in gas phase was found to be about 535 nm, which is considerably lower than the λmax reported for PB in nonpolar solvents. Different solvation shells for PB in water have been defined based on the solute-all-atoms and solvent center of mass radial distribution function (g(rX–O)). The electronic excitation energies for PB computed in the presence of solvent molecules in an increasing number of solvation shells were calculated in a systematic way to evaluate their contributions to the solvatochrmic shift. The inclusion of solvent molecules in the hydration shell yields a λmax of 640 nm, which contributes to almost 78% of the solvatochromic shift. The inclusion of solvent molecules up to 10 Å in the g(rX–O) rdf yields a λmax of 670 nm which is in good agreement with the experimentally reported value of 654–684 nm. Overall, the present study suggests that the combined CPMD-QM/MM and INDO-CIS approach can be used successfully to model solvatochromic shifts of organic dye molecules. [ABSTRACT FROM AUTHOR]

Pyrylium dyes having the same basic chemical structure, differing only to a specific substituent, have been used as novel materials for multiphoton three-dimensional data storage. Electronic absorption spectra, two-photon and three-photon absorption properties of this class of pyrylium dyes, have been studied theoretically and compared to experimental results. The effects of the counteranion, the surrounding solvent, and electron releasing and electron withdrawing groups in specific positions of the basic structure have been explored in detail. It is argued that on grounds of the quality of experimental spectroscopic agreement, the computed two- and three-photon data may be used in pulse propagation simulations of three-dimensional recording in optical memories. [ABSTRACT FROM AUTHOR]

We demonstrate the prospects of computing two photon absorption cross sections of open-shell systems by applying recently developed spin-restricted time-dependent density functional response theory using the pyrrole radical as an example. The spin multiplicity effects on two photon absorption cross sections of this species are investigated for the doublet, quartet, and sextet states. It is found that irrespective of the exchange-correlation functional employed, the two photon cross sections increase with the increase in spin multiplicity. This result indicates that two photon cross sections of paramagnetic compounds can be controlled by manipulating their spin states and this opens new possibilities for design of hybrid magneto-optical materials. [ABSTRACT FROM AUTHOR]

This paper presents response theory based on a spin-restricted Kohn-Sham formalism for computation of time-dependent and time-independent nonlinear properties of molecules with a high spin ground state. The developed approach is capable to handle arbitrary perturbations and constitutes an efficient procedure for evaluation of electric, magnetic, and mixed properties. Apart from presenting the derivation of the proposed approach, we show results from illustrating calculations of static and dynamic hyperpolarizabilities of small Si(3n+1)H(6n+3) (n=0,1,2) clusters which mimic Si(111) surfaces with dangling bond defects. The results indicate that the first hyperpolarizability tensor components of Si(3n+1)H(6n+3) have an ordering compatible with the measurements of second harmonic generation in SiO2/Si(111) interfaces and, therefore, support the hypothesis that silicon surface defects with dangling bonds are responsible for this phenomenon. The results exhibit a strong dependence on the quality of basis set and exchange-correlation functional, showing that an appropriate set of diffuse functions is required for reliable predictions of the first hyperpolarizability of open-shell compounds. [ABSTRACT FROM AUTHOR]

We report the effect of processing parameters such as (1) uniaxial and (2) isostatic pressings on ferroelectric behavior of lead zirconate titanate (PZT) having Zr/Ti ratio 65/35. The effect of temperature (-125–250 °C) on pinched loop characteristics of uniaxially pressed PZT is also reported. Polycrystalline ceramic samples were synthesized by solid-state reaction technique and sintered at 1250 °C. The density was estimated to be 7.63 and 7.58 g/cc for the uniaxially and isostatically pressed samples, respectively, prepared by conventional ball milling. X-ray diffraction analysis confirmed single phase formation with rhombohedral structure. All samples pressed uniaxially and isostatically showed pinched hysteresis loops at room temperature that disappear at higher temperatures. The remnant polarization (Pr) and coercive field (Eo) for the uniaxially pressed samples become well defined in magnitude and shape at higher measurement temperatures below phase transition temperature (Tc), but at low temperatures a distorted-loop-like structure was observed indicating low polarization properties. The effect of ferroelectric switching cycles on the PZT samples with and without annealing in oxygen is also discussed. [ABSTRACT FROM AUTHOR]

Mn[sub x]Ni[sub 0.5-x]Zn[sub 0.5]Fe[sub 2]O[sub 4] ferrites with x = 0.05, 0.1, 0.2, 0.3, and 0.4, have been synthesized by the citrate precursor method and investigated for their magnetic properties. The initial relative permeability is observed to increase with increase in manganese concentration up to x = 0.2 followed by a decrease, the maximum value being 632. An initial increase followed by a subsequent decrease of saturation magnetization with increase in x is observed. Curie temperature is observed to decrease continuously from 488 to 418 °C when x increases from 0.05 to 0.4. Frequency variation of complex initial permeability indicates that resonance peak due to domain wall oscillations is at a frequency above 13 MHz. Saturation magnetization is observed to increase by about 22% when the sintering temperature is increased from 1200 to 1400 °C. Initial permeability and B-H loops are observed to increase and constrict, respectively, with increase in sintering temperature. [ABSTRACT FROM AUTHOR]

The dielectric properties of Mn[sub x]Ni[sub 0.5-x]Zn[sub 0.5]Fe[sub 2]O[sub 4] ferrites with x varying from 0.05 to 0.4 synthesized by the citrate precursor method have been investigated as a function of frequency, temperature, composition, and sintering temperature. An increase in the dielectric constant is observed with the increase in Mn concentration except for x = 0.3. Dispersion in the dielectric constant with frequency in the range of 100 Hz-1 MHz is observed. Resonance peaks were observed in tan δ[sub ∈] versus frequency curves for all samples. A shift in the resonance frequency towards higher frequency is observed with increase in temperature. The peak height also increases with increase in temperature. Possible mechanisms contributing to these processes have been discussed. From the temperature variation of the dielectric relaxation, activation energies for various samples have been calculated and compared with those obtained from dc resistivity. [ABSTRACT FROM AUTHOR]

Spin injection into solid-state devices is commonly performed by use of ferromagnetic metal electrodes. Here, we present a spin injector design without permanent magnet; rather, the spin selectivity is determined by a chiral tunneling barrier. The chiral tunneling barrier is composed of an ultrathin Al2O3 layer that is deposited on top of a chiral self-assembled monolayer (SAM), which consists of cysteine or oligopeptide molecules. The experimentally observed magnetoresistance can be up to 20% at room temperature, and it displays an uncommon asymmetric curve as a function of the applied magnetic field. These findings show that the spin injector transmits only one spin orientation, independent of external magnetic field. The sign of the magnetoresistance depends on the handedness of the molecules in the SAM, which act as a spin filter, and the magnitude of the magnetoresistance depends only weakly on temperature. [ABSTRACT FROM AUTHOR]

To explore the magnetoelectric effect in lead free bulk ceramics, solid solutions of BaZr0.05(FexTi1-3x/4)0.95O3 have been synthesized using conventional solid state reaction route with x = 0.000 to 0.020 in steps of 0.005. A small amount of Fe content shows an immense effect on properties of barium zirconium titanate. Room temperature X-ray diffraction studies substantiate the formation and purity of these polycrystalline samples in an orthorhombic crystal system. Temperature dependent dielectric study revealed a decrease in ferroelectric Curie temperature with a decrease in dielectric constant values as x varied from 0.000 to 0.020. Ferroelectricity is still maintained and well saturated loops are observed with Fe substitution at these levels; although the remnant polarization Pr values decrease substantially with increasing Fe content. The best value of magnetoelectric coupling coefficient (α) at room temperature is found to be 145.30 mV/cm.Oe for x = 0.015 sample. In conclusion, in a non-Pb based simple perovskite system a reasonably large magnetoelectric coupling is demonstrated. [ABSTRACT FROM AUTHOR]

Thin films of Ba(Zr[sub 0.15]Ti[sub 0.85])O[sub 3] were crystallized in situ at several different oxygen background pressures and temperatures. The optimal temperature and pressure for obtaining films with smooth surface morphology and good electrical properties was found to be 675 °C and 300 mTorr, respectively. Films grown at this temperature were found to have a P[sub r] of 3.31 μC/cm[sup 2] and an E[sub c] of 93.5 kV/cm. Low field dielectric measurements and C-V measurements were performed in order to study the dielectric behavior of the films. A tunability of ∼45% was recorded on the films. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]