Spontaneous Ignition Characteristics of Hydrocarbon Fuel-air Mixtures

Although the subject of spontaneous ignition of liquid fuels has received considerable attention in the past, the role of fuel evaporation in the overall spontaneous ignition process is still unclear. A main purpose of this research is to carry out measurements of ignition delay times, using fuels of current and anticipated future aeronautical interest, at test conditions that are representative of those encountered in modern gas turbine engines. Attention is focused on the fuel injection process, in particlar the measurement and control of man fuel drop size and fuel-air spatial distribution. The experiments are designed to provide accurate information on the role of fuel evaporation processes in determining the overall ignition delay time. The second objective is to examine in detail the theoretical aspects of spontaneous ignition in order to improve upon current knowledge and understanding of the basic processes involved, so that the results of the investigation can find general and widespead application

On the optimality of interest-bearing reserves in economies of overlapping generations

Econometrics

Optical and electrical activity of defects in rare earth implanted Si

A common technique for introducing rare earth atoms into Si and related materials for photonic applications is ion implantation. It is compatible with standard Si processing, and also allows high, non-equilibrium concentrations of rare earths to be introduced. However, the high energies often employed mean that there are collision cascades and potentially severe end-of-range damage. This paper reports on studies of this damage, and the competition it may present to the optical activity of the rare earths. Er-, Si, and Yb-implanted Si samples have been investigated, before and after anneals designed to restore the sample crystallinity. The electrical activity of defects in as-implanted Er, Si, and Yb doped Si has been studied by Deep Level Transient Spectroscopy (DTLS) and the related, high resolution technique, Laplace DLTS (LDLTS), as a function of annealing. Er-implanted Si, regrown by solid phase epitaxy at 600degrees C and then subject to a rapid thermal anneal, has also been studied by time-resolved photoluminescence (PL). The LDLTS studies reveal that there are clear differences in the defect population as a function of depth from the surface, and this is attributed to different defects in the vacancy-rich and interstitial-rich regions. Defects in the interstitial-rich region have electrical characteristics typical of small extended defects, and these may provide the precursors for larger structural defects in annealed layers. The time-resolved PL of the annealed layers, in combination with electron microscopy, shows that the Er emission at 1.54microns contains a fast component attributed to non-radiative recombination at deep states due to small dislocations. It is concluded that there can be measurable competition to the radiative efficiency in rare-earth implanted Si that is due to the implantation and is not specific to Er.</p

Should bank reserves earn interest?

This article examines the effects and desirability of paying interest on required reserves. Scott Freeman and Joseph Haslag demonstrate that a policy of paying interest on reserves can make everyone better off, even if the interest must be financed by a tax on capital. An essential part of this policy is an open market operation that offsets any changes in the value of money.Bank reserves

Air frame drag balance Patent

Device for measuring drag forces in flight test

Sedimentary organic molecules: Origins and information content

To progress in the study of organic geochemistry, we must dissect the processes controlling the composition of sedimentary organic matter. Structurally, this has proven difficult. Individual biomarkers can often be recognized, but their contribution to total organic materials is small, and their presence does not imply that their biochemical cell mates have survived. We are finding, however, that a combination of structural and isotopic lines of evidence provides new information. A starting point is provided by the isotopic compositions of primary products (degradation products of chlorophylls, alkenones derived from coccoliths). We find strong evidence that the isotopic difference between primary carbonate and algal organic material can be interpreted in terms of the concentration of dissolved CO2. Moreover, the isotopic difference between primary and total organic carbon can be interpreted in terms of characteristic isotopic shifts imposed by secondary processes (responsive, for example, to O2 levels in the depositional environment. In favorable cases, isotopic compositions of a variety of secondary products can be interpreted in terms of flows of carbon, and, therefore, in terms of specific processes and environmental conditions within the depositional environment