RuO2/GaN Schottky contact formation with superiorforward and reverse characteristics

This is a first time report of a ruthenium oxide (RuO₂) Schottky contact on GaN. RuO₂ and Pt Schottky diodes were fabricated and their characteristics compared. When the RuO₂ Schottky contact was annealed at 500°C for 30 min, the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the RuO₂ were dramatically improved. The annealed RuO₂ /GaN Schottky contact exhibited a reverse leakage current that was at least two or three orders lower in magnitude than that of the Pt/GaN contact along with a very large barrier height of 1.46 eV, which is the highest value ever reported for a GaN Schottky system     

Enhancement of the dielectric properties of Pb(La,Ti)O3 thin films fabricated by pulsed laser deposition

PLT thin films with a thickness of 600 nm were grown by pulsed laser deposition (PLD) using different laser wavelengths of 355, 532 and 1064 nm, respectively. We have systematically investigated the variation of grain sizes depending on the process condition. A two-step process to grow (Pb_0.72La_0.28)Ti_0.93O₃ (PLT) films was adopted and verified to be useful to enlarge the grain size of the film and to enhance leakage current characteristics. Structural and electrical properties including dielectric constant, ferroelectric characteristics, and leakage current of PLT thin films were shown to be strongly influenced by grain size.     

Mechanisms of Neuroprotective Effects of Peptides Derived from Natural Materials and Their Production and Assessment

In this review, we provide an overview of the main mechanisms by which peptides derived from natural materials exhibit neuroprotective effects. We also review methods for the production of these peptides and various methods for determining their neuroprotective effects in vitro and in vivo. Neuroprotective peptides are closely associated with protection against apoptosis, with proteins related to the cell death/survival signaling pathway, with acetylcholine activity and with inhibition of oxidative stress and inflammation. Neuroprotective peptides derived from natural materials typically have a molecular weight below 1 kDa; they are most often derived using the extraction enzymes papain and alcalase. The neuroprotective peptides identified in the literature are mainly composed of hydrophobic amino acids with low molecular weight, with Asp and Glu at the N‐terminal position. These observations may guide the development of novel peptides with potential neuroprotective effects.     

Viscoplastic parameter identification of temperature‐dependent mechanical behavior of modified polyphenylene oxide polymers

Modified polyphenylene oxide (MPPO) is a widely known thermoplastic polymer and is extensively utilized for weight reduction of automobiles since it possesses outstanding mechanical properties, such as resistance and toughness. In this study, the viscoplastic behaviors of MPPO with respect to changes in temperature were identified through an approximate optimization method. For this work, parameter studies were conducted with a tensile simulation of the MPPO polymer, in accordance with the modified two‐layer viscoplastic material parameters and the suggested shift parameter. The sensitivity tendency of the force‐displacement curves was captured in accordance with the material parameters. Computational experiments for obtaining calibration error data were performed using the material parameters based on interior central composite design. Surrogate models of root mean square error relative to force and displacement were generated using the response surface method. The accuracy of the surrogate models was evaluated with R‐square. Optimization for obtaining the material parameters was performed using the non‐dominant sorting genetic algorithm‐II. The results showed that the calibration error from the finite element analysis was minimized and agreed with experimental data. POLYM. ENG. SCI., 59:E200–E211, 2019. © 2018 Society of Plastics Engineers     

Time-dependent probabilistic capacity degradation assessment of prestressed concrete piles in marine environment

As coastal infrastructure systems are continuously exposed to deterioration, it is increasingly crucial to analyse their current and future serviceability performance. This paper investigates effects of chloride corrosion on the lateral force capacity and ductility of a wharf-supporting prestressed concrete marine pile and provides new insights into the state of marine structures. A probabilistically generated finite element modelling approach is developed for piles, which includes discrete concrete pile cross-sectional models connected to steel tendon non-linear elements via a series of non-linear springs that simulate bonding behaviour. Moreover, a prestressed material model is established that incorporates alternate failure modes including stress corrosion cracking and brittle failure to capture chloride-induced pitting corrosion in piles. It is shown that various failure modes cause an overall decrease in the maximum force capacity as piles age. Specifically, the alternate failure modes result in 31 and 56% reductions in the maximum capacity of the pile and associated top pile displacement, respectively, as the age of the pile increases from 25 years to 75 years. The presented methodology and results can greatly assist in decision-making for repair or replacement of wharves and aid in the design of new wharves considering their future performance.     

All-Solid-State Ion Synaptic Transistor for Wafer-Scale Integration with Electrolyte of a Nanoscale Thickness

Neuromorphic hardware computing is a promising alternative to von Neumann computing by virtue of its parallel computation and low power consumption. To implement neuromorphic hardware based on deep neural network (DNN), a number of synaptic devices should be interconnected with neuron devices. For ideal hardware DNN, not only scalability and low power consumption, but also a linear and symmetric conductance change with a large number of conductance levels is required. Here, an all-solid-state polymer electrolyte-gated synaptic transistor (pEGST) is fabricated on an entire silicon wafer with CMOS microfabrication and initiated chemical vapor deposition process. The pEGST shows good linearity as well as symmetry in potentiation and depression, conductance levels up to 8,192, and low switching energy smaller than 20 fJ pulse⁻¹. Selected 128 levels from 8,192 are used to identify handwritten digits in the MNIST database with the aid of a multilayer perceptron, resulting in a recognition rate of 91.7%.     

Effects of pH and surface modification of TiO2 with SiOx on the photocatalytic degradation of a pyrimidine derivative

A pyrimidine derivative, 2-isopropyl-6-methyl-4-pyrimidinol (IMP), could be completely decomposed following pseudo-first-order kinetics by photocatalytic reaction using TiO₂. The effects of pH and surface modification of TiO₂ with SiO_x were studied. The degradation rate of IMP was fast in mild acidic condition (pH=6.3) and slower in strong acidic (pH=2.0) or basic (pH=10.0) condition. The main reason of the slow IMP degradation was different in strong acidic and basic conditions. In strong acidic condition, the slow degradation rate was explained by electrostatic repulsion. On the other hand, a little formation of hydroxyl radicals was considered as a main reason in strong basic condition. The result was supported by the experiments using SiO_x-loaded TiO₂, which has a lower isoelectric point than pure TiO₂.     

Genetic and environmental influences on the continuous scales of the Myers-Briggs Type Indicator: an analysis based on twins reared apart

The effects of 1/1000 field recommended concentration of the organophosphorus compounds; edifenphos and glyphosate on the immune response and protein contents were investigated after different time intervals. The cell mediated immune response assessed by proliferative response of splenocytes to mitogens; phytohemagglutinin (PHA) and concanavalin A (Con A) for T cell and lipopolysaccharide (LPS) for B cell decreased significantly in tems of the level of stimulation index in the treated fish and reached maximal depression after 4 weeks. Humoral immunity assessed as splenic antibody plaque forming cells (PFC) measured after 5 days in vitro immunization to sheep erythrocytes (SRBC's) were suppressed in a concentration dependent pattern by the two compounds. The estimated ED50 for the PFC/10(6) cells of edifenphos and glyphosate were 1.48 x 10(-2) uM and 1.65 x 10(-2) uM respectively. The data also showed that serum antibody titres in the treated fish were decreased in a time dependent manner. The total protein content of serum treated with the two pesticides was decreased after different time periods compared with control. The blood serum of treated and untreated Tilapia nilotica were analyzed electrophoretically for protein components and the percentage of proteins in each fraction was determined.     

Robust nonlinear generalised minimum variance control and fault monitoring

The first part of this paper extends the Nonlinear Generalised Minimum Variance (NGMV) controller to improve the robustness of its control or set-point tracking performance. This is achieved by replacing the Kalman filter included in the original NGMV controller with an observer to minimise the effect of uncertainty, which includes unknown disturbance, modelling error, and faults. The observer design also allows the NGMV controller to be utilised in fault monitoring. More specifically, the second part of this paper obtains the observer gain by solving a multi-objective optimisation problem through the application of a genetic algorithm so that the residual signal becomes sensitive to faults and insensitive to any other uncertainty. The control and fault monitoring performance of the extended NGMV controllers is tested by application to a nonlinear tank model.     

Performance analysis for bounded persistent disturbances in PD/PID-controlled robotic systems with its experimental demonstrations

This paper is concerned with performance analysis of proportional-derivative/proportional-integral-derivative (PD/PID) controller for bounded persistent disturbances in a robotic manipulator. Even though the notion of input-to-state stability (ISS) has been widely used to deal with the effect of disturbances in control of a robotic manipulator, the corresponding studies cannot be directly applied to the treatment of persistent disturbances occurred in robotic manipulators. This is because the conventional studies relevant to ISS consider the H_∞ performance for robotic systems, which is confined to the treatment of decaying disturbances, i.e. the disturbances those in the L₂ space. To deal with the effect of persistent disturbances in robotic systems, we first provide a new treatment of ISS in the L_∞ sense because bounded persistent disturbances should be intrinsically regarded as elements of the L_∞ space. We next derive state-space representations of trajectory tracking control in the robotic systems which allow us to define the problem formulations more clearly. We then propose a novel control law that has a PD/PID control form, by which the trajectory tracking system satisfies the reformulated ISS. Furthermore, we can obtain a theoretical argument about the L_∞ gain from the disturbance to the regulated output through the proposed control law. Finally, experimental studies for a typical 3-degrees of freedom robotic manipulator are given to demonstrate the effectiveness of the method introduced in this paper.