Computing with populations of monotonically tuned neurons

The parametric variation in neuronal discharge according to the values of sensory or motor variables strongly influences the collective behavior of neuronal populations. A multitude of studies on the populations of broadly tuned neurons (e.g., cosine tuning) have led to such well-known computational principles as population coding, noise suppression, and line attractors. Much less is known about the properties of populations of monotonically tuned neurons. In this letter, we show that there exists an efficient weakly biased linear estimator for monotonic populations and that neural processing based on linear collective computation and least-square error learning in populations of intensity-coded neurons has specific generalization capacities.     

Improved electrical properties using SrTiO3/Y2O3 bilayer dielectrics for MIM capacitor applications

In this paper, we show that the capacitance–voltage linearity of MIM structures can be enhanced using SrTiO₃ (STO)/Y₂O₃ dielectric bilayers. The C(V) linearity is significantly improved by combining two dielectric materials with opposite permittivity-voltage responses. Three STO/Y₂O₃ stacks with different thicknesses were realized and compared to a 20 nm STO single layer structure. We observed that an increase in the Y₂O₃ thickness leads to an improvement in the voltage linearity, while maintaining an overall capacitance density greater than 10 fF/μm².     

Acoustic waves in the vicinity of the normal to the surface of piezoelectric crystals

The acoustic wave propagation in the vicinity of the normal to the plane surface confining a piezoelectric crystal of arbitrary symmetry is theoretically studied. An octet formalism arid a perturbation theory have been put forward to describe the wave fields in the region of concern. The developed mathematical approach has been applied to several problems. Specifically, the derivation of the transfer matrix for the normal direction to the surface has been discussed. Furthermore, we have discussed how to estimate the electric potential induced outside the piezoelectric material by a normally incident wave. In addition, an analytical expression has been derived for the numerical factor in the function describing the asymptotic behavior of quasielectrostatic Green's function for half-infinite piezoelectric substrates at small values of the wave vector     

Dielectric relaxations of lead zirconate titanate films up to millimeter-wave frequencies

Modern high-frequency applications critically depend on the availability of data on the dielectric properties of functional materials in the microwave and millimeter-wave range. This paper investigates the dielectric response of polycrystalline lead zirconate titanate (PZT) thin films prepared by solution deposition at frequencies between 10 MHz and 70 GHz and temperatures of 305–395 K by measuring the S-parameters of coplanar waveguides (CPW). The real and imaginary parts of the permittivity of the PZT film are de-coupled from the electrical properties of both the fused silica substrate and the copper electrodes. Two dielectric relaxations are identified: one around 850 MHz, with room-temperature permittivity dropping from 1080 to 560, and one around 36 GHz, with permittivity dropping below 100, respectively. The low-frequency relaxation shows a shift to lower frequencies with increasing temperature; it is explained by the conventional Arlt model of mechanical shear mode resonance across the film thickness. The high-frequency relaxation, which is practically independent of temperature, is attributed to the response of ferroelectric domain walls.     

A mathematical framework for passenger screening optimization via a multi-objective evolutionary approach

Concerns regarding the smuggling of dangerous items into commercial flights escalated after the failed Christmas day bomber attack. As a result, the Transportation Security Agency (TSA) has strengthened its efforts to detect passengers carrying hazardous items by installing novel screening technologies and by increasing the number of random pat-downs performed at security checkpoints nationwide. However, the implementation of such measures has raised privacy and health concerns among different groups thus making the design and evaluation of new inspection strategies strongly necessary. This research presents a mathematical framework to design passenger inspection strategies that include the utilization of novel and traditional technologies (i.e. body scanners, explosive detection systems, explosive trace detectors, walk-through metal detectors, and wands) offered by multiple manufacturers, to identify three types of items: metallic, bulk explosives (i.e. plastic, liquids, gels), and traces of explosives. A multiple objective optimization model is proposed to optimize inspection security, inspection cost, and processing time; an evolutionary approach is used to solve the model. The result is a Pareto set of quasi-optimal solutions representing multiple inspection strategies. Each strategy is different in terms of: (1) configuration, (2) the screening technologies included, (3) threshold calibration, and consequently, (4) inspection security, inspection cost, and processing time.     

Calibration of a white light interferometer for the measurement of micro-scale dimensions

Calibration is central to most measurement procedures. This is especially true in those cases where a large number of difficult-to-identify and difficult-to-control factors hinder the experimenters in their efforts to obtain reliable measurement results. Dimensional measurements of features on the micro- and nano-scales is one such case. A white-light interferometer (WLI) microscope can perform measurements of a variety of measurands over a broad dimensional range: from surface texture characterisations on the nano-scale to measurements of step heights of several millimetres. Calibration methods based on the hypothesis of a linear calibration curve can be inadequate to express the relationship between measurement results and traceable reference materials (RMs). A calibration procedure built into a commercially available WLI microscope is critically compared with methods presented in an international standard. This comparison is enabled by a cost-effective procedure for establishing traceable RMs in the micro-range. Advantages of calibration procedures based on more than one RM are then demonstrated within the ranges from 180.5 to 219.5 μm and from 1.5 to 501.5 μm. Calibration methods involving regression modelling of transformed measurement results are considered for these two intervals to overcome the highlighted weaknesses of the calibration procedure built in the examined WLI.     

Emerging Advancements in Polypyrrole MXene Hybrid Nanoarchitectonics for Capacitive Energy Storage Applications

Journal of Inorganic and Organometallic Polymers and Materials - Recent advancement in nanotechnology has brought about the discovery of various nanomaterials such as graphene (GN),...