Surface Decomposition of Doped PrBaMn₂O_5+δInduced by in Situ Nanoparticle Exsolution:Quantitative Characterization and Catalytic Effect in Methane Dry Reforming Reaction

The exsolution of metallic nanoparticles (NPs) from perovskite oxides is a promising strategy for synthesizing supported catalysts. The associated segregation of A-site cations on the surface is challenging to investigate experimentally and is often detrimental to the catalytic performance. In this work, we found that during the in situ exsolution of Ni-Co bimetallic nanoparticles from Pr0.45Ba0.45Mn1–x(Co1/3 Ni2/3)xO3±δ, A-site cation enrichment occurred on the surface when x is 0.1; yet, the perovskite surface decomposed when x reached 0.2, forming a thin layer comprising various nanocrystalline oxides, which partially blocked the active sites of the exsolved Ni-Co particles. A hydration and carbonation reaction facilitated the conversion of nanocrystalline BaO species into large and highly crystallized BaCO3 particles. This enabled the exposure of more Ni-Co active sites and offered a chance to quantify that the decomposed surface layer accounts for ∼7.2 wt % of the total perovskite. Because of this unique feature, the surface-decomposed catalyst showed higher activity in the dry methane reforming reaction with better stability. Importantly, the regeneration feature was not hampered as the complete exsolution-dissolution recyclability of the catalyst remained

An interactive speech training system with virtual reality articulation for Mandarin-speaking hearing impaired children

The present project involved the development of a novel interactive speech training system based on virtual reality articulation and examination of the efficacy of the system for hearing impaired (HI) children. Twenty meaningful Mandarin words were presented to the HI children via a 3-D talking head during articulation training. Electromagnetic Articulography (EMA) and graphic transform technology were used to depict movements of various articulators. In addition, speech corpuses were organized in listening and speaking training modules of the system to help improve language skills of the HI children. Accuracy of virtual reality articulatory movement was evaluated through a series of experiments. Finally, a pilot test was performed to train two HI children using the system. Preliminary results showed improvement in speech production by the HI children, and the system was recognized as acceptable and interesting for children. It can be concluded that the training system is effective and valid in articulation training for HI children. © 2013 IEEE.published_or_final_versio

A membrane-free flow electrolyzer operating at high current density using earth-abundant catalysts for water splitting

Electrochemical water splitting is one of the most sustainable approaches for generating hydrogen. Because of the inherent constraints associated with the architecture and materials, the conventional alkaline water electrolyzer and the emerging proton exchange membrane electrolyzer are suffering from low efficiency and high materials/operation costs, respectively. Herein, we design a membrane-free flow electrolyzer, featuring a sandwich-like architecture and a cyclic operation mode, for decoupled overall water splitting. Comprised of two physically-separated compartments with flowing H(2)-rich catholyte and O(2)-rich anolyte, the cell delivers H(2) with a purity >99.1%. Its low internal ohmic resistance, highly active yet affordable bifunctional catalysts and efficient mass transport enable the water splitting at current density of 750 mA cm(−2) biased at 2.1 V. The eletrolyzer works equally well both in deionized water and in regular tap water. This work demonstrates the opportunity of combining the advantages of different electrolyzer concepts for water splitting via cell architecture and materials design, opening pathways for sustainable hydrogen generation

Cathodoluminescent images and spectra of single crystals of Y2O2S:Tb3+ and Gd2O2S:Tb3+ nanometer sized phosphor crystals excited in a field emission scanning transmission electron microscope

Cathodoluminescence (CL) spectra have been collected from single nanometer-sized crystals of Y1.98Tb0.02O2S and Gd1.98Tb0.02O2S using a Gatan Vulcan cathodoluminescence imaging spectrometer. Slight variations observed in the CL spectra taken from the crystals are explained, and discussed in relation to bulk samples

Operando studies of electrochemical denitrogenation and its mitigation of N-doped carbon catalysts in alkaline media

N-doped carbons (NCs) have excellent electrocatalytic performance in oxygen reduction reaction, particularly in alkaline conditions, showing great promise of replacing commercial Pt/C catalysts in fuel cells and metal-air batteries. However, NCs are vulnerable when biased at high potentials, which suffer from denitrogenation and carbon corrosion. Such material degradation drastically undermines the activity, yet its dynamic evolution in response to the applied potentials is challenging to examine experimentally. In this work, we used differential electrochemical mass spectroscopy coupled with an optimized cell and observed the dynamic behaviors of NCs under operando conditions in KOH electrolyte. The corrosion of carbon occurred at ca. 1.2 V vs RHE, which was >0.3 V below the measured onset potential of water oxidation. Denitrogenation proceeded in parallel with carbon corrosion, releasing both NO and NO2. Combined with the ex situ characterizations and density-functional theory calculations, we identified that the pyridinic nitrogen moieties were particularly in peril. Three denitrogenation pathways were also proposed. Finally, we demonstrated that transferring the oxidation reaction sites to the well-deposited metal hydroxide with optimized loading was effective in suppressing the N leaching. This work showed the dynamic evolution of NC under potential bias and might cast light on understanding and mitigating NC deactivation for practical applications

Parameter Selection of Oscillator Resonant Circuit Based on Stochastic Differential Equation

Because the choice of oscillator resonant circuit parameters depends mostly on experience, we propose nonlinear differential equations to describe an oscillator based on an equivalent circuit of the oscillator and then to describe the internal electrical noise of the oscillator by introducing a stochastic term that establishes a nonlinear stochastic differential equation to analyse the oscillator\u27s behavior. For optimization of the oscillator resonant circuit parameters, first, we used Advanced Design System (simulation software of the Agilent company) to verify the conclusion, and then, using a 10MHz Pierce crystal oscillator, provided experimental evidence