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The development of hardware-based cognitive computing systems critically hinges upon the integration of memristor devices capable of versatile weight expression across a spectrum of resistance levels while preserving consistent electrical properties. This investigation aims to explore the practical implementation of a digit recognition system utilizing memristor devices with minimized weighting levels. Through the process of weight quantization for digits represented by 25 or 49 input signals, the study endeavors to ascertain the feasibility of digit recognition via neural network computation. The integration of memristor devices into the system architecture is poised to streamline the representation of the resistors required for weight expression, thereby facilitating the realization of neural-network-based cognitive systems. To minimize the information corruption in the system caused by weight quantization, we introduce the concept of “weight range” in this work. The weight range is the range between the maximum and minimum values of the weights in the neural network. We found that this has a direct impact on weight quantization, which reduces the number of digits represented by a weight below a certain level. This was found to help maintain the information integrity of the entire system despite the reduction in weight levels. Moreover, to validate the efficacy of the proposed methodology, quantized weights are systematically applied to an array of double-layer neural networks. This validation process involves the construction of cross-point array circuits with dimensions of 25 × 10 and 10 × 10, followed by a meticulous examination of the resultant changes in the recognition rate of randomly generated numbers through device simulations. Such endeavors contribute to advancing the understanding and practical implementation of hardware-based cognitive computing systems leveraging memristor devices and weight quantization techniques.

Abstract The oxygen vacancies and hydrogen in oxide semiconductors are regarded as the primary sources of charge carriers and various studies have investigated the effect of hydrogen on the properties of oxide semiconductors. However, the carrier generation mechanism between hydrogen and oxygen vacancies in an a-IGZO semiconductor has not yet been clearly examined. In this study we investigated the effect of hydrogen and the variation mechanisms of electrical properties of a thin film supplied with hydrogen from the passivation layer. SiOx and SiNx, which are used as passivation or gate insulator layers in the semiconductor process, respectively, were placed on the top or bottom of an a-IGZO semiconductor to determine the amount of hydrogen penetrating the a-IGZO active layer. The hydrogen diffusion depth was sufficiently deep to affect the entire thin semiconductor layer. A large amount of hydrogen in SiNx directly affects the electrical resistivity of a-IGZO semiconductor, whereas in SiOx, it induces a different behavior from that in SiNx, such as inducing an oxygen reaction and O–H bond behavior change at the interface of an a-IGZO semiconductor. Moreover, the change in electrical resistivity owing to the contribution of free electrons could be varied based on the bonding method of hydrogen and oxygen.

Asymmetrical electrical properties induced by local acceptor-like defect states in oxide semiconductor thin-film transistors are investigated. In addition, we report on the origin of asymmetrical transport characteristics depending on the drain voltage level. In particular, we observe that these asymmetrical properties depend strongly on this level. Numerical calculations demonstrate that potential barrier lowering in the local area occurs at the drain electrode's edge.

Asymmetric sized single oxide diode (InZnOx/CuOx) with single resistor (Ti-doped NiO) device (1D-1R) was integrated into a crossbar array at room temperature to provide high current through the diode while keeping resistance switching localized in a small area. The Ti (0.1 wt %) doped NiO layer was fabricated inside an inverted cone-structure to localize switching and improve general device performance. We were able observe resistance switching up to around 100 cycles in the 1D-1R structure. In addition, the addition of the diode to the structure acted as an external resistance suppressing overflow current during Ti-doped NiO switching from a high resistance state to a low resistance state, thus improving switching distribution in both low (average = 3.2×10-5 Ω, standard deviation = 1.3×10-6) and high (average = 2.8×10-6 Ω, standard deviation = 6.7×10-7) resistance states.

Heavy metals have adverse effects on microalgae metabolism and growth. Photosynthesis and lipid profile are quite sensitive to heavy metal toxicity. The impact of hexavalent chromium—Cr(VI) on photosynthesis and lipid accumulation in Mucidosphaerium pulchellum and Micractinium pusillum exposed to different concentrations (0–500 μg L−1) was investigated for 11 days. A significant (p < 0.05) increase in lipid content was observed with increasing Cr(VI) concentration. However, growth was suppressed at higher concentrations exceeding 100 μg L−1. Addition of Cr(VI) in the cell culture medium showed a negative effect on quantum yield (Fv/Fm), and a photosynthetic inhibition of >65% was noted in both species at 500 μg L−1. However, the lipid gravimetric analysis presented inner cell lipid content up to 36% and 30% of dry weight biomass for M. pulchellum and M. pusillum, respectively. The fatty acids profiles of both microalgae species showed higher levels of hexadecenoic acid as well as ω3, ω6, and ω7 fatty acids. The effect of Cr(VI) on photosynthesis and lipid accumulation in both microalgae species was concentration and exposure time dependent. This shows that an appropriate concentration of Cr(VI) in culture medium could be beneficial for higher lipid accumulation in freshwater eukaryotic microalgae species.

Hydrogen in oxide systems plays a very important role in determining the major physical characteristics of such systems. In this study, we investigated the effect of hydrogen in oxide host systems for various oxygen environments that acted as amorphous oxide semiconductors. The oxygen environment in the sample was controlled by the oxygen gas partial pressure in the radio-frequency-sputtering process. It was confirmed that the hydrogen introduced by the passivation layer not only acted as a “killer„ of oxygen deficiencies but also as the “creator„ of the defects depending on the density of oxide states. Even if hydrogen is not injected, its role can change owing to unintentionally injected hydrogen, which leads to conflicting results. We discuss herein the correlation with hydrogen in the oxide semiconductor with excess or lack of oxygen through device simulation and elemental analysis.

The tetragonality (c/a) of a PbZr0.2Ti0.8O3 (PZT) thin film on La0.7Sr0.3MnO3/0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-PT) substrates was controlled by applying an electric field on the PMN-PT substrate. The piezoelectric response of the PZT thin film under various biaxial strains was observed using time-resolved micro X-ray diffraction. The longitudinal piezoelectric coefficient (d33) was reduced from 29.5 to 14.9 pm/V when the c/a ratio of the PZT film slightly changed from 1.051 to 1.056. Our results demonstrate that the tetragonality of the PZT thin film plays a critical role in determining d33, and in situ strain engineering using electromechanical substrate is useful in excluding the extrinsic effect resulting from the variation in the film thickness or the interface between substrate. [ABSTRACT FROM AUTHOR]

Bilateral patella tendon rupture is rare, particulary when associated with osteogenesis imperfecta. Brittleness of the bone in osteogenenesis imperfect patients may cause this rupture. We report on this rare case and suggest the direct repair with the additional wire loop as a proper treatment option for patients with the substantial rupture of patella tendon. [ABSTRACT FROM AUTHOR]

We report an experimental method to overcome the long processing time required for fabricating graphite films by a transfer process from a catalytic layer to a substrate, as well as our study of the growth process of graphite films using a pulsed laser deposition combined with in-situ monitoring based on reflection high-energy electron diffraction technique. We monitored the structural evolution of nano-crystalline graphite films directly grown on AlN-coated Si substrates without any catalytic layer. We found that the carbon films grown for less than 600 s cannot manifest the graphite structure due to a high defect density arising from grain boundaries; however, the carbon film can gradually become a nano-crystalline graphite film with a thickness of approximately up to 5 nm. The Raman spectra and electrical properties of carbon films indicate that the nano-crystalline graphite films can be fabricated, even at the growth temperature as low as 850 °C within 600 s. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to determine the correlation between the fracture patterns and the complications in patients with femoral neck fracture treated with internal fixation. Materials and Methods: The study comprises 45 patients with femoral neck fracture treated with multiple screws or compression hip screw between May 2008 and April 2012. The mean age was 48 years at the time of the surgery and the mean duration from initial injury to surgery was 20 hours. The fracture patterns were identified according to the anatomical location, the Garden classification and the Pauwels classification. The occurrence of nonunion and avascular necrosis were reviewed with clinical results including Harris hip score and Lunceford hip function test. The correlation between the fracture pattern and occurrence of complications were analyzed. Results: Fracture site union was achieved in 40 hips with the average union time of 17 weeks. Five nonunions occurred which showed high likelihood to occur in subcapital type, displaced (Garden stage III or IV) and Pauwels type III fractures (P<0.05). Avascular necrosis was developed in 10 hips which was mostly in subcapital type and Pauwels type III fracture but no statistical significance was found (P>0.05). The mean Harris hip score was 91 points, and Lunceford functional results were excellent in 15 hips, good in 24, fair in 4 and poor in 2. Conclusion: There was high risk of nonunion in subcapital type fracture, displaced fracture (Garden stage III and IV) and vertically oriented fracture (Pauwels type III). Careful attention is needed in these fracture types. [ABSTRACT FROM AUTHOR]

We present an experimental strategy via X-ray irradiation combined with time-resolved X-ray diffraction to reduce a coercive field of ferroelectric thin films. We found in real-time that X-ray irradiation enables the irreversible phase transition from a polar to non-polar phase in ferroelectric poly(vinylidene fluoride-trifluoroethylene) thin films. The non-polar regions act as initial nucleation sites for opposite domains thus reducing the coercive field, directly related to the switching of domains, by 48%. [ABSTRACT FROM AUTHOR]

K-doped ZnO films were prepared on Al2O3(0001) substrates by solution deposition. For the prepared thin films of Zn1-xKxO (x=0.002, 0.01, 0.02, 0.05, 0.1), we carried out x-ray diffraction, transmittance spectroscopy, photoluminescence, Hall measurement and x-ray photoemission spectroscopy study, and found that properties like the crystallinity, optical band gap, carrier concentrations and chemical binding states changed at a K doping concentration of 2 mol %. From these results, we suggest that the doped K in ZnO films processed by the sol–gel method plays a different role at K doping concentrations below 2 mol % and above 2 mol %. [ABSTRACT FROM AUTHOR]

Epitaxial oxide ferroelectric films exhibit emerging phenomena arising from complex domain configurations even at pseudoequilibrium, including the creation of domain states unfavored in nature and abrupt piezoelectric coefficients around morphotropic phase boundaries. The nanometer-sized domain configurations and their domain switching dynamics under external stimuli are directly linked to the ultrafast manipulation of ferroelectric thin films; however, complex domain switching dynamics under homogeneous electric fields has not been fully explored, especially at the nanosecond timescale. This Letter reports the nanosecond dynamics of ferroelastic-domain switching from the 90° to 180° direction using time-resolved x-ray microdiffraction under homogeneous electric fields onto an epitaxial Pb(Zr0.35, Ti0.65)O3 film capacitor. It is found that the application of electric fields induces spatially heterogeneous domain switching processes via intermediate domain structures with rotated polarization vectors. In addition, the domain switching time is shown to be inversely proportional to the magnitude of the applied electric field, and electric fields higher than 480 kV/cm are found to complete the ferroelastic switching within nanoseconds. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a new formulation of the multivehicle point-to-point network problem to be utilised in urban air mobility (UAM) vertiport-to-vertiport network operations. Vehicle routing problems (VRPs) and their variants have previously been studied and applied in real-world situations, but these problems require additional depot locations, and not all the vehicles can travel to all the locations. In UAM operations, additional depot locations may not be required, and all vehicles can travel to all locations, meaning that existing routing problems are not suitable for application to the management of UAMs. Therefore, we propose a new formulation for UAM vertiport-to-vertiport operation by introducing new constraints. In addition, we integrate dynamic scheduling with the flight mission by controlling cruise speed and waiting in each UAM at each vertiport location to generate an arrival and departure schedule for different vertiports that can avoid collisions and increase the number of vehicles. A computational experiment is conducted using an MILP model, and the results show that although our formulation satisfies the problem definition, the computation time increases exponentially with an increase in the problem size. A case study is conducted in the Seoul area involving five vertiports, with 10- and 15-vehicle scenarios studied. This case study shows that the cruise speed variable is active only for the lower and upper bounds under dynamic scheduling, whereas the waiting time variable can be controlled between user-defined limits that can be applied to the management of vertiport-to-vertiport UAM operations.

Optical excitation perturbs the balance of phenomena selecting the tilt orientation of domain walls within ferroelectric thin films. The high carrier density induced in a low-strain BaTiO3 thin film by an above-band-gap ultrafast optical pulse changes the tilt angle that 90° a/c domain walls form with respect to the substrate-film interface. The dynamics of the changes are apparent in time-resolved synchrotron x-ray scattering studies of the domain diffuse scattering. Tilting occurs at 298 K, a temperature at which the a/b and a/c domain phases coexist but is absent at 343 K in the better ordered single-phase a/c regime. Phase coexistence at 298 K leads to increased domain-wall charge density, and thus a larger screening effect than in the single-phase regime. The screening mechanism points to new directions for the manipulation of nanoscale ferroelectricity. [ABSTRACT FROM AUTHOR]

Electric-field-driven phase transformation phenomena in multiferroic BiFeO3 are directly linked to the functionalities of electronic devices based on multiferroic materials. Understanding how the transformation evolves at the nanoscale under the influence of an electric field will provide fascinating insights into key parameters that utilize the transformation features. Here, we report both the electric-field-driven transient and permanent phase transformations in highly strained BiFeO3 thin films and their transformation dynamics at the nanoscale. We found that two distinct transient and permanent phase transformations were triggered below and above a coercive voltage of the polymorphic phase, indicating that ferroelectric polarization switching could promote permanent phase transformations. We also found that the transient transformations evolve via complex phase boundary motions between the coexisting phases, whereas permanent transformations occurred via nucleation of the other phases.

Weakly coupled ferroelectric/dielectric superlattice thin-film heterostructures exhibit complex nanoscale polarization configurations that arise from a balance of competing electrostatic, elastic, and domain-wall contributions to the free energy. A key feature of these configurations is that the polarization can locally have a significant component that is along the thin-film surface normal direction with an overall configuration maintaining zero net in-plane polarization. PbTiO_{3}/SrTiO_{3} thin-film superlattice heterostructures on a conducting SrRuO_{3} bottom electrode on SrTiO_{3} have a room-temperature stripe nanodomain pattern with a nanometer-scale lateral period. Ultrafast time-resolved x-ray free electron laser diffraction and scattering experiments reveal that above-bandgap optical pulses induce propagating acoustic pulses and a perturbation of the domain diffuse scattering intensity arising from the nanoscale stripe domain configuration. With 400-nm optical excitation, two separate acoustic pulses are observed: a high-amplitude pulse resulting from strong optical absorption in the bottom electrode and a weaker pulse arising from the depolarization-field-screening effect due to absorption directly within the superlattice. The picosecond scale variation of the nanodomain diffuse scattering intensity is consistent with a larger polarization change than would be expected due to the polarization-tetragonality coupling of uniformly polarized ferroelectrics. The polarization change is consistent, instead, with polarization rotation facilitated by the reorientation of the in-plane component of the polarization at the domain boundaries of the striped polarization structure. The complex steady-state configuration within these ferroelectric heterostructures leads to ultrafast polarization rotation phenomena that have previously been available only through the selection of bulk crystal composition.