Can the addition of a dielectric improve the figure of merit of a tunable material?

The influence of addition of a low-loss linear dielectric material to a tunable ferroelectric material has been investigated in terms of the electrostatic consideration. The calculations of the dielectric loss and dielectric non-linearity of ferroelectric-dielectric composites have been performed by using three different models. On the basis of results obtained, the figure of merit of the composite material has been evaluated. No improvement of the figure of merit of composite material compared to the pure ferroelectric has been observed for the considered models.     

Combustion of a Mixture of Aluminum and a Titanium‐Containing Raw Material in the Presence of Additives

A model of the gasphase component of combustion of an aluminum mixture with metal oxides is described. By the example of titanium reduction from its oxide, it is shown that atomic oxygen formed thereby facilitates gasphase oxidation of aluminum and decreases metal yield. The effect of graphite, activated carbon, and diesel fuel on combustionwave velocity and temperature is considered. Two waves (cold and hot ones) are observed in the system titanium oxide–ferric oxide–aluminum–carboncontaining additives. Hydrocarbon additives inhibit the aluminumoxidation reaction by oxygen contained in air in the first wave, and graphite and activated carbon play the same role in the second wave in the titaniumreduction reaction. Experimental confirmation is found for the fact that the action of additives increases the amount of aluminum consumed directly for titanium reduction in the second wave, which enhances exothermality of the process.     

Initiation of Ignition by the Action of a High‐Current Pulsed Discharge on a Gas

The possibility of nonthermal initiation of chemical reactions by a uniform pulsed nanosecond discharge is demonstrated. Dependences of variation of the ignition delay on initial conditions are obtained. It is shown that the main role in combustion initiation under conditions of a pulsed gas discharge in the case of moderate electric fields and low degree of ionization belongs to reactions of dissociation quenching of electronexcited levels of nitrogen.     

Late Stage C?H Activation of a Privileged Scaffold; Synthesis of a Library of Benzodiazepines

A library of over twenty 5‐(2‐arylphenyl)‐1,3‐dihydro‐2H‐1,4‐benzodiazepin‐2‐ones has been formed by a microwave‐mediated late‐stage palladium‐catalysed arylation of 1,4‐benzodiazepines using diaryliodonium salts. This can also be applied to nordazepam (7‐chloro‐5‐phenyl‐1,3‐dihydro‐2H‐1,4‐benzodiazepin‐2‐one), the active metabolite of diazepam, and subsequent N‐alkylation and/or H/D exchange allows further diversification towards elaborated pharmaceuticals and their 3,3′‐deuterated analogues.

     

Effect of a Gas‐Phase Reaction on the Combustion Performance of a Sandwich Layered System

This paper considers a sandwich layered combustion model (an oxidizer and a fuel) that takes into account condensed and gasphase chemical reactions and transverse heat and mass transfer. Under particular simplifications, algebraic expressions are obtained for the burning rates of the components and the temperature and concentration of gaseous reagents on the burning surface. Calculated dependences of the burning rate on the sandwich size agree with experiments.     

The biodesulphurization of a semianthracite coal in a packed-bed system☆

The purpose of this study was to improve the desulphurization yield of a high sulphur-content semianthracite from northern Spain adapted to the process conditions of a packed-bed reactor, for which three 5-kg packed columns of coal were set up with the pH stabilized at 1.5. The process was begun by inoculating the first column with a culture obtained from micro-organisms native to the coal itself, mainly Thiobacillus ferrooxidans and Leptospirillum ferrooxidans, grown in a stirred reactor. The percolate of this column was then used to seed the second column, the percolate of which was then inoculated into the last one. The purpose was to obtain from the last column a better adapted and more active biomass which would give a better desulphurization yield for coal. Results show an increased yield from the first column to the last over the first 20 days of treatment, but the total desulphurization in the third column was less than expected, owing to a high precipitation of jarosite.     

Spatial Structure of a Reacting Turbulent Swirling Jet Flow with Combustion of a Propane–Air Mixture

Results of an experimental study of the spatial structure of a reacting flow during combustion of a propane–air mixture in a turbulent swirling jet escaping into atmospheric air are presented. The fuel-to-air equivalence ratio is φ = 0.7, and the Reynolds number of the jet is Re = 5 · 10³. The time-averaged spatial distributions of velocity, local density, and concentrations of the main species of the gas mixture are measured in low-swirl and high-swirl flows. In both cases, the flame front is stabilized in the internal mixing layer formed by the axial region of jet retardation, where hot combustion products are concentrated. In a high-swirl flow, the temperature distributions in the cross section y/d = 0.5 show that the region with the maximum temperature of the gas is located at the periphery of the central recirculation zone. Moreover, in the case of a high-swirl flow, there exists a recirculation zone at the axis, and the CO₂ concentration is twice higher than in a low-swirl jet. The opposite situation is observed for O₂.     

Experimental Study of Ignition of a Gasoline–Air Mixture in a Constant‐Volume Combustion Chamber

The characteristics of flamekernel development in a premixed gasoline–air mixture in a cylindrical constantvolume combustion chamber are measured. The experiments are performed with an initial temperature of 393 K, pressure of 6 bar, and equivalence ratio = 0.8 with the use of various ignition systems and spark plugs. The schlieren pictures of the process are presented, and the measured results for flame velocity, heatrelease rate, and mass fraction of the burnt fuel are analyzed.     

Is a Calorie Really a Calorie? Metabolic Advantage of Low-Carbohydrate Diets

The first law of thermodynamics dictates that body mass remains constant when caloric intake equals caloric expenditure. It should be noted, however, that different diets lead to different biochemical pathways that are not equivalent when correctly compared through the laws of thermodynamics. It is inappropriate to assume that the only thing that counts in terms of food consumption and energy balance is the intake of dietary calories and weight storage. Well-controlled studies suggest that calorie content may not be as predictive of fat loss as is reduced carbohydrate consumption. Biologically speaking, a calorie is certainly not a calorie. The ideal weight loss diet, if it even exists, remains to be determined, but a high-carbohydrate/low-protein diet may be unsatisfactory for many obese individuals.     

Simulation of Catalytic Combustion of Methane in a Monolith Honeycomb Reactor

1 INTRODUCTION Monolith honeycomb reactor plays an important role in catalytic combustion[1] such as combustion chambers for gas turbines used in power generation where methane is the main reactant. It contains hun-dreds of parallel channels that are often of the order of 1—2mm in diameter. The catalyst may be dispersed within a washcoat that is coated onto the surface of the channels[2] where catalytic combustion occurs. Com-pared to conventional gas-phase combustion, catalytic combusti…     

Improvement of a cementation process by ultrasound: case of the cadmium–zinc couple at a RDE

This paper describes the impact of low frequency (20kHz) ultrasound (US) on Cd(II)/Zn cementation implemented on a RDE geometry. With and without US the reaction is mass-transfer controlled with two-step first-order kinetics mainly connected to deposit evolution. US improves the kinetics but to a lower extent than expected from electrochemical Cd(II) reduction. The favourable turbulence enhancement due to the deposit without US is not present when applying US because the deposit is continually removed from the surface. The influence of parameters such as temperature, initial concentration of reactants and US power is also analysed.     

Catalytic oxidation of methanol to methyl formate over silver – a new purpose of a traditional catalysis system

Catalytic reaction was performed in the unregarded temperature region over silver catalysts with long catalytic lifetime for the conversion of methanol to methyl formate. O-saturated or O-saturated silver catalysts were studied individually to identify the roles of O, O in the oxidative esterification of methanol over an unsupported polycrystalline silver catalyst. A synergic process is proposed based on the coexistence of -oxygen species and -oxygen species on the surface of polycrystalline silver at about 573 K.     

Modeling of a Reverse Flow Reactor for Methanol Synthesis Modeling of a Reverse Flow Reactor for Methanol Synthesis

An accurate one-dimensional, heterogeneous model taking account of axial dispersion and heat transfer to the reactor wall, and heat conduction through the reactor wall for methanol synthesis in a bench scale reactor under periodic reversal of flow direction is presented. Adjustable parameters in this model are the effectiveness factors for each of the three reactions occurring in the synthesis and a factor for the bed to wall heat transfer coefficient correlation. Experimental data were used to evaluate these parameters and reasonable values of these parameters were obtained. The model was found to closely predict the reactor performance under a wide range of operating conditions, such as carbon oxide concentrations, volumetric flow rate, and cyclic period.     

Numerical Simulation of Thermochemical Conversion of a High–Ash Coal in a Low-Temperature Fluidized Bed under Pressure

The paper considers a mathematical model, an algorithm, and a program for calculating nonstationary processes of air gasification of a high-ash coal under pressure in a pilot-scale circulating fluidized bed gasifier reactor. The effect of operation parameters on the course of the process is analyzed. It is shown that hot spots (short-duration local heatings) can form at various points of the bed, at which maximum temperature can be close or even exceed the fluid slagging point. Possible mechanisms of formation of hot spots are analyzed.     

Initiation of homogeneous combustion in a high-velocity jet of a fuel–air mixture by an optical discharge

The effect of a focused pulsed-periodic beam of a CO₂ laser on initiation and evolution of combustion in subsonic and supersonic flows of homogeneous fuel–air mixtures (H₂ + air and CH₄ + air) is experimentally studied. The beam generated by the CO₂ laser propagates across the flow and is focused by a lens at the jet axis. The flow structure is determined by a schlieren system with a slot and a plane knife aligned in the streamwise direction. The image is recorded by a high-speed camera with an exposure time of 1.5 μs and a frame frequency of 1000 s^?1. The structure of the combustion region is studied by an example of inherent luminescence of the flame at the wavelengths of OH and CH radicals. The distribution of the emission intensity of the mixture components in the optical discharge region is investigated in the present experiments by methods of emission spectroscopy.     

Direct computation of the performance of sequential procedures based on a sequence of t-statistics,with application to a confidence interval for μ/σ in a normal population

Formulas are derived for the direct computation — as opposed to simulation or approximation — of sequential procedures that are based on a sequence of t-statistics. This is applied to the numerical computation of the performance of a one-sided confidence interval for γ = μ/σ in a normal population, when the probability of covering the true value γ as well as the probability of covering the false value γ ? d, for given d > 0,is specified.