Stabilization of the platinum–ruthenium electrocatalyst against the dissolution of ruthenium with the incorporation of gold

The dissolution of Ru from the PtRu electrocatalyst has been identified as one of the most critical factors in degrading the performance of polymer electrolyte membrane fuel cells (PEMFC). In this work, we prepared an Au-modified PtRu catalyst (Au/PtRu) and found that the incorporation of Au could significantly stabilize the PtRu electrocatalyst against the dissolution of Ru. The X-ray photoelectron spectroscopy (XPS) characterization of the Au/PtRu catalysts revealed that the incorporation of Au increased the oxidation potential of Ru, which is the mechanism that leads to a reduction in the dissolution of Ru from the alloyed catalyst. The XPS characterization of the cathode catalyst also showed that with the PtRu as the anode catalyst Ru appeared at the cathode, but the crossover of Ru could be reduced when the anode catalyst was changed to Au/PtRu.     

Review of the Debate and the Development of Thrust Vectoring Technology

InMemoryofafriend,Dr.W.HerbstofMBB,Germany,theso-calledfatheroftheX-31experimentalthrustvectoringfighter,wholosthislifeafewyearsagowhilepilotinghisprivateairplane.BertrandRussell'"Menarebornignorant,notstupid-theyaremadestupidbyeducation."AdmiralHymanRickoverf"Thebestengineersarethosewho,inadditiontotechnicalex-pertise,havehadgoodtrainingintheliberalartsandunderstandtheworldaroundthem."ANoLD-NEWEURoPEANDEBArEONTHRUSTVECToRING"talkofthrnstvectoringi8adistrnction,and..thereisn…     

Numerical Study of the Effects of the Face Velocity on Ceramic Filter

INTRODUCTIONTheproductsofcoalcombustionsuchasNOx,SOx,COb,andparticulatehavebeenstronglyregulatedtoreducepollutionintheearthenvironment.TherecentlydevelopedCleanCoalTechnologies(CCT)knownasPressurizedFluidizedBedCombustion(PFBC)[']andintegratedGasificationCombinedCycle(IGCC)I"']providetheimprovementofthermalefficiencywithsignificalltlyreducedenvironmelltalimpacts.ThusthePFBCandIGCChaveincreasingattentiontoachievestringentenvironmentalprotection.Advancingthetechnologyofthehotg…     

Estimation of the Collection Efficiency of the AxialFlow Cyclone Dust Collector with the Fixed Guide Vanes

INTR0DUCTIONAcyclonedustcollect0r(acyclonedustcollectorissimplyabbreviatedtoacyclone)isthesimplecon-structionwithnom0vingpartsandiseasytotreatthemaintenancewiththehighreliability.Thecycloneisoneofthemostoptimaldustcollect0rsf0rseparatingthesolidparticlesofthesizebetweenXP=2pmandXr=100pm.Theaxialfl0wcycl0newiththefixedguidevanesf0rgeneratingther0tationalfl0worthevortexflowisveryeasytosettingatthevari0usl0cationsinthedustcollectorsystemandalsoisarrangedtothesimplifiedcompactsysteml1-5].How…     

Influence of the cooling rate on the ageing of lead–calcium alloys

Cast lead–calcium alloys were known to be sensitive to experimental parameters, which cause large variations on the ageing and overageing behaviour. From the study of these parameters, the quenching rate was the only significant parameter. A critical cooling rate was defined based on hardness, electrical resistivity and metallographical observations. The inconsistencies in the literature noticed on the evolutions of lead–calcium alloys can now be explained by whether or not this critical cooling rate was respected.     

What explain the short-term dynamics of the prices of CO2 emissions?

Using a Bayesian Structural VAR (BSVAR), this paper analyzes the short-term dynamics of the prices of CO₂ emissions in response to changes in the prices of oil, coal, natural gas and electricity. The results show that: (i) a positive shock to the crude oil prices has an initial positive effect on the CO₂ allowance prices, which later becomes negative; (ii) an unexpected increase in the natural gas prices reduces the price of CO₂ emissions; (iii) a positive shock to the prices of the fuel of choice, coal, has virtually no significant impact on the CO₂ prices; (iv) there is a clear positive effect of the coal prices on the CO₂ allowance prices when the electricity prices are excluded from the BSVAR system; and (v) a positive shock to the electricity prices has a negative impact on the price of the CO₂ allowances. We also find that the energy price shocks have a persistent impact on the CO₂ allowance prices, with the largest effect occurring 6 months after a shock strikes. The effect is particularly strong in the case of the shocks to the natural gas and crude oil prices. Finally, the empirical findings suggest an important degree of substitution between the three primary sources of energy (i.e., crude oil, natural gas and coal), particularly when electricity prices are excluded from the BSVAR system.     

Results of the long-term testing of the ‘Photon’ fuel cell generator

Results of the long-term testing of the Photon fuel cell generator are considered in this article. Its ability to operate with satisfactory performance for 6000–7000 h is shown. Further increase of the service life is associated with solution of the fuel cell components' corrosion problem as well as with removal of the impurities from the fuel and oxidant, which cause electrolyte carbonization.     

Study on the Effects of Flow in the Volute Casing on the Performance of a Sirocco Fan

The flow at the exit from the runner blade of a centrifugal fan with forward curved blades (a sirocco fan) sometimes separates and becomes unstable. We have conducted many researches on the impeller shape of a sirocco fan, proper inlet and exit blade angles were considered to obtain optimum performance. In this paper, the casing shape were decided by changing the circumferential angle, magnifying angle and the width, 21 sorts of casings were used. Performance tests, inner flow velocity and pressure distributions were measured as well. Computational fluid dynamic calculations were also made and compared with the experimental results. Finally, the most suitable casing shape for best performance is considered.     

A Study of the Impulse Wave Discharged from the Exits of Two Parallel Tubes

The twin impulse wave leads to very complicated flow fields, such as Mach stem, spherical waves, and vortex ring. The twin impulse wave discharged from the exits of the two tubes placed in parallel is investigated to understand the detailed flow physics associated with the twin impulse wave, compared with those in a single impulse wave. In the current study, the merging phenomena and propagation characteristics of the impulse waves are investigated using a shock tube experiment and by numerical computations. The Harten-Yee's total variation diminishing (TVD) scheme is used to solve the unsteady two-dimensional compressible Euler equations. The Mach number Ms of incident shock wave is changed below 1.5 and the distance between two-parallel tubes, L/d, is changed from 1.2 to 4.0. In the shock tube experiment, the twin impulse waves are visualized by a Schlieren optical system for the purpose of validation of computational work. The results obtained show that on the symmetric axis between two-parallel tube     

Preliminary study of the offshore wind and temperature profiles at the North of the Yucatán Peninsula

The stability conditions in the atmospheric boundary layer, the intensity of the wind speeds and consequently the energy potential available in offshore conditions are highly influenced by the distance from the coastline and the differences between the air and sea temperatures. This paper presents a preliminary research undertook to study the offshore wind and temperature vertical profiles at the North-West of the Yucatán Peninsula coast. Ten minute averages were recorded over approximately 2 years from sensors installed at two different heights on a communication tower located at 6.65 km from the coastline. The results have shown that the offshore wind is thermally driven by differential heating of land and sea producing breeze patterns which veer to blow parallel to the coast under the action of the Coriolis force. To investigate further, a dataset of hourly sea surface temperatures derived from GEOS Satellite thermal maps was combined with the onsite measured data to study its effect on the vertical temperature profile. The results suggested largely unstable conditions and the potentially development of a shallow Stable Internal Boundary Layer which occurs when warm air from the land advects over the cold sea.     

The Study of the Damage Laws of Pool Fires

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Calculation of Vertical Mixing in Plane Turbulent Buoyant Jets on the Basis of the Algebraic Model of Turbulence

An algebraic model of turbulence,involving buoyancy forces,is used for calculating velocity and temperaturefields in plane turbulent vertical jets in a non-homogeneous stagnant medium.A new approach to the solution ofthe governing system of partial differential equations (continuity,conservation of momentum,heat (buoyancy),turbulent kinetic energy,dissipation rate and mean quadratic temperature fluctuation) is suggested which isbased on the introduction of mathematical variables.Comparison is made between the results of the presentcalculations with experimental and numerical data of other authors.     

Risk Analysis in Renewable Energy： Assessment of the Vulnerability of the Environment and Community

As a result of recent accidents, society is becoming more conscious and concerned about the risk that are under to the environment and communities. A proposal of assessment of the vulnerability of the environment and community is presented here under a holistic perspective using fuzzy logic as a formal tool. An internal factor of the risk of a system under a given threat is assessed. Risk is considered as the union between the threat and the vulnerability of the environment and community. This approach shows that the reduction in either or both of them makes a reduction in the risk content as well. The main purpose of this proposal is not to obtain a single value as output; in fact the result is a map which can contribute to the different areas of the community in decision making.     

Effect of the water–steam phase transition on the electrical conductivity of porous rocks

The effect of the water–steam phase transition on electrical conductivity was experimentally investigated in volcanic and sandstone samples to support the interpretation of resistivity data to determine changes in steam saturation in geothermal reservoirs. The measurements were performed at simulated in situ conditions with controlled pore fluid chemistry, temperature, and confining and pore pressures. At constant temperature (150 °C) and confining pressure, pore fluid was withdrawn from the sample by steadily increasing the volume of the pore fluid system. At the vapor saturation pressure, the pore water progressively boiled to steam, resulting in a continuous conductivity decrease by a factor of approximately 20. The study showed that: (1) for rocks in which conduction is controlled by the pore fluid, the concurrent changes in both electrical conductivity and pore (vapor) pressure are defined by the pore size distribution; the changes in liquid–steam saturation are approximately proportional to those in conductivity and can thus be quantified; and (2) for rocks in which surface conduction is predominant there is no direct relation between conductivity, pore pressure and drained fluid volume; this implies that the conduction mechanism controls the pattern of electrical conductivity variations as steam saturation changes.     

Electrochemical characterization of electrodes in the electrochemical Bunsen reaction of the sulfur–iodine cycle

In the electrochemical Bunsen reaction, SO₂ is oxidized to H₂SO₄ at the anode while I₂ is reduced to HI at the cathode. Both electrodes were electrochemically characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The effects of H₂SO₄ concentration in the anolyte, as well as HI concentration and I₂/HI molar ratio in the catholyte, were explored. The cyclic voltammograms of platinum electrode shift with rising scan rate, indicating the irreversibility of two electrode reactions. The equivalent circuit for the cathode reaction impedance consists of an ohmic resistance of the solution, in series with a parallel combination of a charge transfer resistor and a constant phase element, yet the impedance spectra for the anode reaction can be modeled using a parallel combination of a charge transfer resistor and a constant phase element. The electrode reaction kinetics was also analyzed using the exchange current density (j₀) and the standard reaction rate constant (k⁰). The results indicate that a high electrode reaction rate in the cell can be obtained for a HI concentration of 8 mol/kg_H2O and an I₂/HI molar ratio of 0.5 in the catholyte and a H₂SO₄ concentration of 13 mol/kg_H2O in the anolyte.     

Study of the influence of the amount of PBI–H3PO4 in the catalytic layer of a high temperature PEMFC

The influence of the amount of polybenzimidazole (PBI)-H₃PO₄ (normalized with respect to the PBI loading, which expressed as C/PBI weight ratio) content in both the anode and cathode has been studied for a PBI-based high temperature proton exchange membrane (PEM) fuel cell. The electrodes prepared with different amounts of PBI have been characterized physically, by measuring the pore size distribution, and visualizing the surface microstructure. Afterwards, the electrochemical behaviour of the electrodes has been evaluated. The catalytic electrochemical activity has been measured by voltamperometry for each electrode prepared with a different PBI content, and the cell performance results have been studied, supported by the impedance spectra, in order to determine the influence of the PBI loading in each electrode. The best results have been achieved with a C/PBI weight ratio of 20, for both the anode and the cathode. A lower C/PBI weight ratio (larger amount of PBI in the catalytic layer) reduced the electrocatalytic activity, and impaired the mass transport processes, due to the large amount of polymer covering the catalyst particle, lowering the cell performance. A higher C/PBI weight ratio (lower amount of PBI in the catalytic layer) reduced the electrocatalytic activity, and slightly increased the ohmic resistance. The low amount of the polymeric ionic carrier PBI–H₃PO₄ limited the proton mobility, despite of the presence of large amounts of “free” H₃PO₄ in the catalytic layer.     

Numerical Simulation of the Flow over a Model of the Cavities on a Butterfly Wing

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The future developments of the electricity prices in view of the implementation of the Paris Agreements: Will the current trends prevail,or a reversal is ahead?

We assess the impact on the European electricity market of the European Union “Clean energy for all Europeans” package, which implements the EU Nationally Determined Contribution in Paris COP 21. We focus on the year 2030, which is the year with defined climate targets. For the assessment, we employ a game-theoretic framework of the wholesale electricity market, with high technical detail. The model is applied to two core scenarios, a Base scenario and a Low Carbon scenario to provide insights regarding the future electricity capacity, generation mix, cross-border trade and electricity prices. We also assess three additional variants of the core scenarios concerning different levels of: a) fossil and CO₂ prices; b) additional flexibility provided by batteries; c) market integration. We find that the electricity prices in 2030 substantially increase from today's level, driven by the increase in fuel and CO₂ prices. The flexibility from batteries helps in mitigating the price peaks and the price volatility. The increased low marginal cost electricity generation, the expansion of non-dispatchable and distributed capacities, and the higher market integration further reduce the market power from producers in the electricity markets from today's level.     

Numerical Study of the Effects of the Secondary Diaphragm and Contact Surface in Expansion Tubes

The interaction of the shock reflected at a secondary diaphragm with the primary contact in six cases, i.e. the strengths and shapes of the contact surface are different, were explored by numerical study. The influences of the strength and shape of the contact on the developing wave pattern and the quality of the test gas are illustrated by many kinds of figures (e.g. the time-distance diagrams of the acoustic impedance contours on the axis, the acoustic impedance contours, and the time histories of pilot and static pressures).