Application of hybrid binomial Langevin-multiple mapping conditioning method to reacting jet flow

The hybrid binomial Langevin-MMC (Multiple Mapping Conditioning) method combines the advantages of the binomial Langevin and MMC models in a consistent manner to overcome difficulties in each. The binomial Langevin method provides joint velocity-scalar statistics, but the treatment of scalars is complex since specification of the bounds is not trivial. The MMC method is capable of dealing with the mixing of any number of scalars, but it can be difficult to specify coefficients involving averages of the scalars and the introduced reference space. The difficulties are overcome by using the velocity statistics from the binomial Langevin model to obtain the reference variable for MMC and, subsequently, the mixing of MMC scalars is performed in a manner that minimises the difference between the mixture fractions for each submodel. The current work expands past studies of NO conversion in a mixing layer to include a study of the Sandia D Flame in preparation for the application to more complex combustion phenomena. Results compare favourably with experimental data and other models

Possibilities of assessment of reliability of an anthropotechnical system

"Reliability and safety characteristics [7] of an anthropotechnical system are the basic information about the correctness of relation between a man (e.g. pilot) and a helicopter (machine). Methods of defining them are still an open problem. The article presents an innovative way of definition of reliability characteristics of a pilot and a helicopter engine as well as an entire anthropotechnical system. Described are theoretical bases of this method, which are various configurations of the ""equation of state"" describing relations pilot – helicopter and helicopter – pilot [8, 9]. Defined was the set of ""numbers of limit state violations"" of the parameter of pilot’s physical condition aP and technical state of the helicopter aS, which as ""premises of damage"" were used for calculation of estimators of reliability characteristics. It is noteworthy that these characteristics could be particularly useful in the process of comparing different pilots and helicopters in various situations appearing in the course of utilisation

Variational transition state theory based surface chemistry for the C2H6/H2/O2/Pt system

A reaction class-based framework for the development of heterogeneous mechanisms is applied to study the (partial) oxidation of ethane over platinum. The rate parameters for the surface chemistry were derived using a systematic application of variational transition state theory (VTST) for adsorption, desorption, and Eley–Rideal reactions coupled with two-dimensional (2D) collision theory for reactions occurring on the surface. The approach removes the need for the experimental determination of surface sticking coefficients and the associated major uncertainties. The barrier heights were determined using the unity bond index–quadratic exponential potential (UBI–QEP) method. The combined gas- and surface-phase chemistry was evaluated against independent data sets obtained from three experimental configurations. The associated 18 cases cover a wide range of residence times, stoichiometries (0.1 < ϕ < 10.4), and inlet pressures (1–12 bar). The work highlights the generality of the VTST approach that is shown to outperform the customary sticking coefficient-based methods for key aspects. A sensitivity analysis highlights the importance of the O2 and CO adsorption pathways

Hybrid binomial Langevin-multiple mapping conditioning modeling of a reacting mixing layer

A novel, stochastic, hybrid binomial Langevin-multiple mapping conditioning (MMC) model—that utilizes the strengths of each component—has been developed for inhomogeneous flows. The implementation has the advantage of naturally incorporating velocity-scalar interactions through the binomial Langevin model and using this joint probability density function (PDF) to define a reference variable for the MMC part of the model. The approach has the advantage that the difficulties encountered with the binomial Langevin model in modeling scalars with nonelementary bounds are removed. The formulation of the closure leads to locality in scalar space and permits the use of simple approaches (e.g., the modified Curl’s model) for transport in the reference space. The overall closure was evaluated through application to a chemically reacting mixing layer. The results show encouraging comparisons with experimental data for the first two moments of the PDF and plausible results for higher moments at a relatively modest computational cost

Mixture-fraction based hybrid binomial-langevin–MMC modelling applied to auto-ignition in vitiated flow

A new hybrid binomial Langevin–MMC (Multiple Mapping Conditioning) modelling approach is proposed. The mixture fraction derived from the binomial Langevin model is used to specify the reference variable for MMC. The modified Curl’s model is used to close the stochastic MMC mixing term. The new model is applied to a jet burner with a vitiated co-flow (the 'Cabra burner') with methane as the fuel. The first- and second-order statistics show good agreement with experimental data

Chronic Cold Exposure Increases Skeletal Muscle Oxidative Structure and Function in Monodelphis domestica, a Marsupial Lacking Brown Adipose Tissue

Monodelphis domestica (Marsupialia: Didelphidae) was used as a model animal to investigate and compare muscle adaptation to exercise training and cold exposure. The experimental treatment consisted of four groups of animals: either warm or cold acclimation temperature and with or without endurance exercisetraining. Maximal aerobic capacity during a running Vo2max test in the warm-exercised or cold-exposed (with or without without exercise) groups was about 130 mL O2/kg/min, significantlyhigher than the warm-acclimated controls at 113.5mL O2/kg/min. Similarly, during an acute cold challenge (Vo2summit ), maximal aerobic capacity was higher in these three experimental groups at ∼95 mL O2/kg/min compared with 80.4mL O2/kg/min in warm-acclimated controls. Respiratory exchange ratio was significantly lower (0.89-0.68), whereas relative heart mass 0.52%-0.73%) and whole-body muscle mitochondrialvolume density (2.59 to 3.04 cm[sup3]) were significantly higher following cold exposure. Chronic cold exposure was a stronger stimulus than endurance exercise training for tissue specific adaptations. Although chronic cold exposure and enduranceexercise are distinct challenges, physiological adaptations to each overlap such that the capacities for aerobic performance in response to both cold exposure and running are increased by either or both treatments

Possibilities of assessment of reliability of an anthropotechnical system

"Reliability and safety characteristics [7] of an anthropotechnical system are the basic information about the correctness of relation between a man (e.g. pilot) and a helicopter (machine). Methods of defining them are still an open problem. The article presents an innovative way of definition of reliability characteristics of a pilot and a helicopter engine as well as an entire anthropotechnical system. Described are theoretical bases of this method, which are various configurations of the ""equation of state"" describing relations pilot – helicopter and helicopter – pilot [8, 9]. Defined was the set of ""numbers of limit state violations"" of the parameter of pilot’s physical condition aP and technical state of the helicopter aS, which as ""premises of damage"" were used for calculation of estimators of reliability characteristics. It is noteworthy that these characteristics could be particularly useful in the process of comparing different pilots and helicopters in various situations appearing in the course of utilisation

It's a gas: oxidative dehydrogenation of propane over boron nitride catalysts

Boron nitride and related boron-containing materials have recently been suggested as very promising catalysts in the oxidative dehydrogenation of propane. The high selectivity toward propylene at comparably high conversion significantly exceeds the performance of established vanadium-based catalysts. In the current work we show that the high selectivity toward propylene and ethylene is fully consistent with a gas-phase conversion mechanism and that it can be modeled reasonably well by the recent detailed microkinetic reaction mechanism of Hashemi and co-workers [ Proc. Combust. Inst. 2019, 37, 461]. Our analysis, using six heterogeneous catalytic reaction pathways, each representing a hypothetical limit case, shows that the boron nitride catalyst is responsible for initiating the gas-phase chemistry. The increased conversion of propane in cases with water cofeed, as well as the trends in the selectivities of minor species upon dilution of the catalytic bed and upon varying the C3H8/O2 inlet ratio, as observed by Venegas and Hermans [ Org. Process Res. Dev. 2018, 22, 1644], are here explained as gas-phase phenomena. Hence, the oxidative dehydrogenation of propane over boron nitride catalysts is an example of a coupled gas and catalytic chemistry system. The current work also highlights the importance of modeling of the complete heated zone, including the rear heat shields and reactor padding if present