Numerical study of combustion processes in afterburners

Mathematical models and numerical methods are presented for computer modeling of aeroengine afterburners. A computer code GEMCHIP is described briefly. The algorithms SIMPLER, for gas flow predictions, and DROPLET, for droplet flow calculations, are incorporated in this code. The block correction technique is adopted to facilitate convergence. The method of handling irregular shapes of combustors and flameholders is described. The predicted results for a low-bypass-ratio turbofan afterburner in the cases of gaseous combustion and multiphase spray combustion are provided and analyzed, and engineering guides for afterburner optimization are presented

Are product spreads useful for forecasting? An empirical evaluation of the Verleger hypothesis

Notwithstanding a resurgence in research on out-of-sample forecasts of the price of oil in recent years, there is one important approach to forecasting the real price of oil which has not been studied systematically to date. This approach is based on the premise that demand for crude oil derives from the demand for refined products such as gasoline or heating oil. Oil industry analysts such as Philip Verleger and financial analysts widely believe that there is predictive power in the product spread, defined as the difference between suitably weighted refined product market prices and the price of crude oil. Our objective is to evaluate this proposition. We derive from first principles a number of alternative forecasting model specifications involving product spreads and compare these models to the no-change forecast of the real price of oil. We show that not all product spread models are useful for out-of-sample forecasting, but some models are, even at horizons between one and two years. The most accurate model is a time-varying parameter model of gasoline and heating oil spot spreads that allows the marginal product market to change over time. We document MSPE reductions as high as 20% and directional accuracy as high as 63% at the two-year horizon, making product spread models a good complement to forecasting models based on economic fundamentals, which work best at short horizons

The Role of Attitudes, Social Norms, and Perceived Behavioral Control as Factors Influencing Urban and Suburban Residential Adoption of Stormwater Best Management Practices

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. Nonpoint source pollution conveyed by stormwater in urban areas poses a significant threat to quality of waterbodies in the US. In the absence of systematic regulations on household stormwater management, municipalities rely largely on educational programs to encourage voluntary adoption of lawncare best management practices (BMPs) by residents who slow down and temporarily capture excess stormwater and filter out pollutants entering waterways. The current literature on factors influencing urban dwellers’ adoption of lawncare BMPs mostly focuses on demographics, barriers to adoption, and effectiveness of education and outreach programs. This study applies the reasoned action approach (RAA) behavioral theory to investigate how the combination of individuals’ attitudes, social norms, and perceived behavioral control may affect their decision to adopt three lawncare BMPs, including mulching and fertilizer/pesticide avoidance, and support a municipal ban on lawncare chemicals. We use survey data (n = 235) from residents in two neighboring cities in central Maine, USA. We found that perceived behavioral control predicted fertilizer/pesticide avoidance and mulching, and that beliefs and attitudes toward the outcomes of adopting lawncare BMPS were positively associated with mulching and support for a municipal ban on lawncare chemicals. We observed statistically significant but inconsistent associations between several independent variables—including descriptive and injunctive social norms, gender, level of education, age, and home ownership status—and our dependent variables of interest. The findings provide insights into an underexplored set of factors and confirmatory evidence for previously tested factors influencing urban residents’ BMP adoption, and suggest new strategies and communication frames for environmental managers and researchers

Is the Discretionary Income Effect of Oil Price Shocks a Hoax?

The transmission of oil price shocks has been a question of central interest in macroeconomics since the 1970s. There has been renewed interest in this question after the large and persistent fall in the real price of oil in 2014-16. In the context of this debate, Ramey (2017) makes the striking claim that the existing literature on the transmission of oil price shocks is fundamentally confused about the question of how to quantify the effect of oil price shocks. In particular, she asserts that the discretionary income effect on private consumption, which plays a central role in contemporary accounts of the transmission of oil price shocks to the U.S. economy, makes no economic sense and has no economic foundation. Ramey suggests that the literature has too often confused the terms-of-trade effect with this discretionary income effect, and she makes the case that the effects of the oil price decline of 2014-16 on private consumption are smaller for a multitude of reasons than suggested by empirical models of the discretionary income effect. We review the main arguments in Ramey (2017) and show that none of her claims hold up to scrutiny

Electromechanically induced absorption in a circuit nano-electromechanical system

A detailed analysis of electromechanically induced absorption (EMIA) in a circuit nano-electromechanical hybrid system consisting of a superconducting microwave resonator coupled to a nanomechanical beam is presented. By performing two-tone spectroscopy experiments we have studied EMIA as a function of the drive power over a wide range of drive and probe tone detunings. We find good quantitative agreement between experiment and theoretical modeling based on the Hamiltonian formulation of a generic electromechanical system. We show that the absorption of microwave signals in an extremely narrow frequency band (\Delta\omega/2\pi <5 Hz) around the cavity resonance of about 6 GHz can be adjusted over a range of more than 25 dB on varying the drive tone power by a factor of two. Possible applications of this phenomenon include notch filters to cut out extremely narrow frequency bands (< Hz) of a much broader band of the order of MHz defined by the resonance width of the microwave cavity. The amount of absorption as well as the filtered frequency is tunable over the full width of the microwave resonance by adjusting the power and frequency of the drive field. At high drive power we observe parametric microwave amplification with the nanomechanical resonator. Due to the very low loss rate of the nanomechanical beam the drive power range for parametric amplification is narrow, since the beam rapidly starts to perform self-oscillations.Comment: 16 pages, 5 figure

Meandering river sandstone architecture characterization based on seisimic sedimentology in Kumkol South oilfields [RETRACTED ARTICLE]

1460-1471To improve the finely architecture characterization of meandering river sand body in wide well space oilfield, this study identified the meandering river sand body of Layer MI-1 of Kumkol South Oilfield in South Turgai Basin. Under the guidance of the sedimentary pattern of meandering channel sand body, this study establishes the log-seismic reservoir characterization method by applying reservoir characterization，seismic sedimentology and seismic forward simulation with well logging and seismic data. The different levels of meandering river sand body which include the composite meandering belts, single meandering belt, single point bar and single point bar inner are finely studied in Layer MI-1 of Kumkol South Oilfield. Based on the researches mentioned above, the recognition method and criteria of composite channel are studied. Specifically, the cosine phase seismic attribute can be used to recognize the lateral boundaries of composite channel when the thickness of composite channels >8 m. And the frequency division data can be used to recognize the vertical boundaries of composite channels when the thickness of composite channels >9 m. The recognition methods of the abandon channel and the mud stone between channels are also studied. Specifically, the sweet, waveform classification and the three-instantaneous information can improve the recognition of single channel boundary. Six boundaries are recognized in layer MI-1. Finally, the recognition method and criteria of lateral accretionary layers are studied. In the sedimentary and seismic data conditions of study area, the synthetic seismic information can improve the recognition of the lateral accretionary layers when the thickness of point bar >12 m and the thickness of lateral accretionary layers >1. 5 m

Annuity savings, non-annuity savings, health investment and bequests with or without private information.

Master'sMASTER OF SOCIAL SCIENCE