A numerical model for calculation of stress intensity factors in particle-reinforced metal–matrix composites

A two-dimensional finite element model was developed to study effects of particle diameter, mechanical properties of the fiber and matrix materials and loading conditions (Mode 1 and Mixed-Mode). A theoretical model was proposed to calculate the stress intensity factor for an interface crack in Particle-Reinforced Metal–Matrix Composites. The displacement Correlation Method was used to calculate the stress intensity factors K ₁ and K ₂. In the present model the fiber and matrix materials were modeled in linear elastic conditions. The interface crack was considered between the fiber and matrix, without the presence of the interphase. Obtained results show that the key role on the stress intensity factors played by the relative elastic properties of the fiber and matrix. The results also show that K ₁ and absolute K ₂ values increase for both Mode 1 and mixed-mode loading condition once Young’s modulus of the fiber material increases. The values of K ₁ and K ₂ stress intensity factors decrease when the fiber volume fraction increases for Mode 1 loading.     

Chemical bonding structure of TiO2 thin films grown on n-type Si

Titanium dioxide thin films were obtained by RF magnetron sputtering system with different Ar and O atmospheres. Chemical bonding structures of the thin films were investigated using the Fourier transform infrared spectroscopy (FTIR) in the range of 400-7500 cm^− 1 for as-deposited and conventionally thermal annealed films at different temperature in air. These structural characterizations of the films were carried out by describing the low-frequency fluctuations of the FTIR spectra using the noninvasive (i.e. error controllable) procedure of the optimal linear smoothing. This approach is based on the criterion of the minimal relative error in selection of the proper smoothing window. It allows the receiving an optimal separation of a possible trend from the high-frequency fluctuations, defined as a random sequence of the relative fluctuations possessing zero trends. Thus, the noise can be read and extra information about the structures was then obtained by comparing with the experimental results. In the film annealed at 900 °C, the rutile phase was the dominant crystalline phase as revealed by infrared spectroscopy. At the annealing temperatures lower than 900 °C, both the anatase and the rutile phases were coexisting. In addition, symmetric and asymmetric Si-O-Si vibrations modes were observed at around 1000 cm^− 1 and 800 cm^− 1, respectively. These peaks suggest that a thin SiO₂ film was formed at the TiO₂/Si interface during the growth and the annealing of the TiO₂ films. It was also observed that the reactivity between TiO₂ film and Si substrate is increased with the increasing annealing temperature.     

Strain analysis of the GaN epitaxial layers grown on nitridated Si(111) substrate by metal organic chemical vapor deposition

The strain analysis of GaN film on nitridated Si(111) substrate with different growth times between 0 and 660 s via metal organic chemical vapor deposition (MOCVD) was conducted based on the precise measurement of the lattice parameters by using high-resolution X-ray diffraction (HR-XRD). The nitridation time (NT) was changed at a fixed growth condition. The a- and c-lattice parameters were measured, followed by the in-plane and out-of-plane strains. Then, the biaxial and hydrostatic components were extracted from the total strain values obtained, and were then discussed in the present study as functions of the NT. The biaxial strain and stress are also strongly affected by the non-uniformity of the SiN_x buffer layer thickness.     

A transparent electrode with water-oxidizing activity

Hydrogen production by water splitting is a promising method to store energy. Water-oxidation reaction is a bottleneck in water-splitting systems. Herein, a mononuclear nickel(II) phosphine complex with 1,2-bis(dicyclohexylphosphino)ethane ligand, was synthesized and characterized by X-ray crystallography method. The water-oxidizing catalyst under the electrochemical condition was studied. The role of Ni compound for the water-oxidation reaction on the surface of fluorine-doped tin oxide as one of the true catalysts was investigated by the electrochemical methods and Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM/EDX) Spectroscopy. The big ligand around the Ni ion causes a very small size of Ni-based particles on the surface of the electrode, which are the active catalysts for the water-oxidation reaction. Such small nanosized Ni-based compounds are transparent and have no effect on the transparency of the obtained fluorine-doped tin oxide. Thus, it is a promising method to synthesize a transparent fluorine-doped tin oxide with water-oxidizing activity.     

Progress and perspectives in micro direct methanol fuel cell

Micro Direct Methanol Fuel cells (μDMFC) are of considerable interest for both academic laboratories and industries to commercialize, since the energy demand has been increased. Although intensive researches are conducted to understand μDMFC, many challenges still remain to be solved to exploit them for real commercial applications. The pros and cons of various substrate materials used and various designs fabricated so far for fuel delivery are highlighted. One of the existing problems is membrane swelling, which has been reduced by the polymer modification recently. The removal of evolved CO₂ gas in the anode and reduction of water flooding in the cathode are accomplished through the advanced materials fabrication is discussed. The important parameters such as fuel, water, air and thermal managements to increase cell performance by material manipulation and design are outlined in this review. A handful of companies are trying μDMFC technology toward real commercial strides. We have also presented an update of the achievements so far by these companies.     

A survey on computation offloading and service placement in fog computing-based IoT

The Journal of Supercomputing - In recent years, fog computing has emerged as a computing paradigm to support the computationally intensive and latency-critical applications for resource limited...     

Manganese compounds as water oxidizing catalysts for hydrogen production via water splitting: From manganese complexes to nano-sized manganese oxides

For hydrogen production by water splitting, the water oxidation half reaction is overwhelmingly rate limiting and needs high over-voltage (∼1 V), which results in low conversion efficiencies when working at current densities required. At this high voltage, other chemicals will be also oxidized and this would be environmentally unacceptable for large-scale H₂ production.