Decentralized DBA scheme based on power detection in TDM-PON

In this article, we propose a new decentralized hardware-based DBA scheme in TDM-PON. Of particular significance in the proposed scheme is that the bandwidth of the uplink data transmission is dynamically allocated to each ONU without the intervention of the OLT. In this way, software-based DBA processing can be eliminated in the OLT and ONUs, resulting in the simple, fast, and cost-effective operation of the DBA in TDM-PON. The performance of the proposed scheme was evaluated by performing a statistical analysis and numerical analysis of the average packet end-to-end delay. We confirmed the superior performance of the proposed scheme by comparing the results obtained for this technique with those of other EPONs.     

Creep-fatigue damage and life prediction in P92 alloy by focused ultrasound measurements

In the present study, the characteristics of creep damage in P92 alloy were investigated via nondestructive evaluation. Generally, as the hold time of a static load increases, the degradation of the material becomes more severe along with a reduction of service life. Therefore, in power plants, the reduction of creep-fatigue strength and the creep-fatigue life of high pressure vessels at high temperatures, such as steam pipes, become very important. To evaluate the effect of damage, backscattering ultrasound signals were analyzed from creep-fatigue specimens, where both static and cyclic loads had been applied simultaneously. The testing temperature trapezoidal creep-fatigue loading wave shapes with hold times ranging from 0 s to 1000 s at the maximum load were employed. The results obtained from bulk waves of focused ultrasound were compared and analyzed with the experimental parameters. The relationships between these parameters, the RMS level of backscattering signals, and the area fraction of the cavity in the creep-fatigue damage zone were investigated to evaluate the lifetime of the damaged specimens.     

P2P-based open health cloud for medicine management

Peer-to-Peer Networking and Applications - Much attention has recently been given to changes in medical services, such as remote medical services and healthcare services customized for users, where...     

Study on the role of Pt and Pd in Pt–Pd/TiO2 bimetallic catalyst for H2 oxidation at room temperature

The hydrogen safety issue is spotlighted as the hydrogen process is extended. For this reason, we studied catalysts for H₂ oxidation at room temperature to ensure hydrogen safety. Catalysts were prepared by different preparation methods and compared to evaluate the role of Pt and Pd in Pt–Pd/TiO₂ catalysts. The catalytic activity was significantly enhanced when activity metal size was small and it was exposed to catalyst surface to a high Pd ratio. For the 0.1%Pt-0.9%Pd/TiO₂ catalyst, high hydrogen conversion of 90% was obtained under the condition of 0.5% hydrogen injection. To understand the correlation between activity and characteristics of catalyst, the physicochemical characteristics of the various catalysts were investigated by X-ray photoelectron spectroscopy (XPS), temperature-programmed oxidation and reduction (TPOR) and Field Emission-Transmission Electron Microscope (FE-TEM) analysis. From these analysis, it was found that Pt served the role of highly dispersion of active metal (Pt–Pd) and as with increasing Pd ratio of active metal, hydrogen activity was increased, which indicates that hydrogen oxidation had proceeded on the Pd site. Finally, the valence state of the Pd influenced hydrogen oxidation activity of Pt–Pd/TiO₂, which increased with increasing ratio of Pd⁰/Pd_Total.     

Methods for in-cylinder EGR stratification and its effects on combustion and emission characteristics in a diesel engine

The effects of in-cylinder EGR stratification on combustion and emission characteristics are investigated in a single cylinder direct injection diesel engine. To achieve in-cylinder EGR stratification, external EGR rates of two intake ports are varied by supplying EGR asymmetrically using a separated intake runner. The EGR stratification pattern is improved using a 2-step bowl piston and an offset chamfer at the tangential intake port. When high EGR gas is supplied to the left (tangential) port, a high EGR region is formed at the central upper region of the combustion chamber. Consequently, combustion is initiated in the low EGR region, and PM is reduced significantly. When high EGR gas is supplied to the right (helical) port, a high EGR region is formed at the lower periphery of the combustion chamber. Therefore, combustion is initiated in the high EGR region, and NO_x is reduced without PM penalty. Stratified EGR potentially reduces NO_x by maximum 45%, without penalties of performance and other emissions. A proper in-cylinder swirl with stratified EGR maximizes the effects and achieves simultaneous reduction of NO_x by 7% and PM by 23%. Moreover, the robustness of stratified EGR is evaluated under various operating conditions and injection strategies.     

Nonlinear adaptive control design for ship-to-ship missiles

Ship-to-ship missiles have relatively large weight and complex cross couplings between each channel and, practically, the aerodynamic uncertainties also make it difficult to analyze and control it. In this paper, an approximate missile model is presented with parametric affine structure applicable to all operating points. An approximate minimum phase dynamics is also derived. The uncertainties in aerodynamic forces are modeled into parametric form to design a nonlinear adaptive controller.     

Stable operation of air-blowing direct methanol fuel cell stacks through uniform oxidant supply by varying fluid flow fixtures and developing the flow sensor

Air-blowing type direct methanol fuel cells (DMFCs) are becoming more attractive for portable electronic devices as alternatives to the currently used Li-ion batteries because they are quieter with less parasitic power loss than the active-type DMFCs used a compressor. However, the blower has difficulty in providing a uniform air supply with a high flow rate to the cathode manifolds of the stack. In this study, a design that allows accurate measurements of the flow distribution on the air-blowing DMFC stack is developed using a novel scientific approach and careful construction of the experimental apparatus. Using this novel experimental technique, a novel stack design is produced to improve the performance and stability of the DMFC system under air-blowing conditions. Furthermore, auxiliary devices, such as ducts, guide vanes, foams, membrane and wedges are integrated and evaluated to the stack to assist in uniform flow by the blower. In particular, the inlet foam, membrane and upper angle duct help improve the uniformity of the lateral and longitudinal flow distribution in the air-blowing stack. Finally, the air-blowing stack with these auxiliary devices shows high performance with operational stability.     

Steam reforming of methanol,ethanol and glycerol over nickel-based catalysts-A review

Depletion of non-renewable energy sources such as coal and natural gas is paving the way to generate alternative energy sources. Hydrogen, a very promising alternative energy has the highest energy density (143 MJ/kg) compared to any known fuel and it has zero air pollution due to the formation of water as the only by-product after combustion. Currently, 95% of hydrogen is produced from non-renewable sources. Hydrogen production from renewable sources is considered a promising route for development of sustainable energy production. Steam reforming of renewable sources such as methanol, ethanol and glycerol is a promising route to hydrogen production. This review covers steam reforming of these three alcohols using Ni-based catalysts with different supports. Chemistry of the steam reforming reactions is discussed. Hydrogen yield depends on operating conditions, the nature of active metal and the catalyst support. Supports play an important role in terms of hydrogen selectivity and catalyst stability because of their basic characteristics and redox properties. Synthesis of suitable catalysts that can suppress coke formation during reforming is suggested.     

Advanced Oxygen Electrocatalysis in Energy Conversion and Storage

Oxygen electrocatalysis is of great significance in electrochemical energy conversion and storage. Many strategies have been adopted for developing advanced oxygen electrocatalysts to promote these technologies. In this invited contribution, recent progress in understanding the oxygen electrochemistry from theoretical and experimental aspects is summarized. The major categories of oxygen electrocatalysts, namely, noble-metal-based compounds, transition-metal-based composites, and nanocarbons, are successively discussed for oxygen reduction and evolution. Design strategies of various oxygen electrocatalysts and their relationship on the structure–activity–performance are comprehensively addressed with the perspectives. Finally, the challenge and outlook for advanced oxygen electrocatalysts are discussed toward energy conversion and storage technologies.