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

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

Consumer Spending and Aggregate Shocks

Consumer spending is widely considered to be the engine that drives economic growth and prosperity. This dissertation employs theoretical, empirical and computational methods to study the interaction between consumer decisions at the microeconomic level and the evolution of consumption at the macroeconomic level. The first chapter provides a unified account of the U.S. consumption and residential investment dynamics over the last 15 years. Conventional wisdom holds that the consumption boom-bust cycle of the 2000s was caused by homeowners financing their consumption through home equity extraction. However, most of the funds extracted by homeowners are spent on home improvement rather than consumption. This association is strongest among young households. I rationalize these findings using a life-cycle model with home equity-based borrowing subject to borrowing frictions. The boom-bust cycles in consumption and residential investment implied by this model capture several key features of the corresponding cycles found in U.S. data. The model provides a more subtle explanation of the role played by home equity extractors in the consumption cycle. Although extractors individually spent only a small fraction of their extracted funds on consumption, they collectively accounted for much of the consumption boom because the share of extracting households increased rapidly in the early 2000s. The second chapter uses a novel dataset on federal government disaster-relief spending, combined with both household and state-level consumption, income and employment data, to answer the question of whether government spending can have a large effect on private consumption and income. My estimates show that the demand shock created by government disaster-relief spending has a large multiplier effect because of its effects on the labor market. I provide direct empirical evidence in support of the job-creation channel emphasized in New Keynesian models of the transmission of government spending shocks. My analysis has broader implications for the design of government spending programs. The third chapter evaluates the effects of the Housing Provident Fund program, the largest public housing program in China. It was created in 1999 to enhance homeownership and to make housing more affordable. This program involves a mandatory savings scheme that requires participating workers to deposit a fraction of their income into the program. Past deposits are refunded when the worker purchases a house, or retires. The program provides mortgages at subsidized rates to facilitate these home purchases. Given the empirical challenges in evaluating the success of this program, I use a calibrated life-cycle model to quantify the effectiveness of these polices. My analysis shows that a housing program with these features is expected to increase the rate of homeownership by 4 percentage points in steady state. In addition, the average home size increases by 21% relative to the baseline model. These results are largely unaffected by the existence of employer contributions. I discuss the economic mechanisms by which these outcomes are achieved.PHDEconomicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138557/1/xqzhou_1.pd