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The combustion instability characteristics in a model dump combustor with an exhaust nozzle were experimentally investigated. The first objective was to understand the effects of operating conditions and geometric conditions on combustion instability. The second objective was to examine more generalised parameters that affect the onset of combustion instability. Three different premixed gases consisting of air and hydrocarbon fuels (C2H4, C2H6, C3H8) were burnt in the dump combustor at various inlet velocity, equivalence ratio and combustion chamber length. Dynamic pressure transducer and photomultiplier tube with a bandpass filter were used to measure pressure fluctuation and CH* chemiluminescence data. Peak frequencies and their maximum power spectral densities of pressure fluctuations at same equivalence ratios showed different trends for each fuel. However, the dynamic combustion characteristics of pressure fluctuations displayed consistent results under similar characteristics chemistry times regardless of the used hydrocarbon fuels. The results showed that characteristic chemistry time and characteristic convection time influenced combustion instabilities. It was found that the convective-acoustic combustion instability could be prevented by increasing the characteristic chemistry time and characteristic convection time.
Complex oxides and semiconductors exhibit distinct yet complementary properties owing to their respective ionic and covalent natures. By electrically coupling complex oxides to traditional semiconductors within epitaxial heterostructures, enhanced or novel functionalities beyond those of the constituent materials can potentially be realized. Essential to electrically coupling complex oxides to semiconductors is control of the physical structure of the epitaxially grown oxide, as well as the electronic structure of the interface. Here we discuss how composition of the perovskite A- and B-site cations can be manipulated to control the physical and electronic structure of semiconductor—complex oxide heterostructures. Two prototypical heterostructures, Ba1−xSrxTiO3/Ge and SrZrxTi1−xO3/Ge, will be discussed. In the case of Ba1−xSrxTiO3/Ge, we discuss how strain can be engineered through A-site composition to enable the re-orientable ferroelectric polarization of the former to be coupled to carriers in the semiconductor. In the case of SrZrxTi1−xO3/Ge we discuss how B-site composition can be exploited to control the band offset at the interface. Analogous to heterojunctions between compound semiconducting materials, control of band offsets, i.e., band-gap engineering, provides a pathway to electrically couple complex oxides to semiconductors to realize a host of functionalities.
Complex oxides and semiconductors exhibit distinct yet complementary properties
owing to their respective ionic and covalent natures. By electrically coupling
oxides to semiconductors within epitaxial heterostructures, enhanced or novel
functionalities beyond those of the constituent materials can potentially be
realized. Key to electrically coupling oxides to semiconductors is controlling
the physical and electronic structure of semiconductor – crystalline
oxide heterostructures. Here we discuss how composition of the oxide can be
manipulated to control physical and electronic structure in
Ba1-xSrxTiO3/ Ge and
SrZrxTi1-xO3/Ge heterostructures. In the
case of the former we discuss how strain can be engineered through composition
to enable the re-orientable ferroelectric polarization to be coupled to carriers
in the semiconductor. In the case of the latter we discuss how composition can
be exploited to control the band offset at the semiconductor - oxide interface.
The ability to control the band offset, i.e. band-gap engineering, provides a
pathway to electrically couple crystalline oxides to semiconductors to realize a
host of functionalities.
In interpreting radiocarbon dating results, it is important that archaeologists distinguish uncertainties derived from random errors and those from systematic errors, because the two must be dealt with in different ways. One of the problems that archaeologists face in practice, however, is that when receiving dating results from laboratories, they are rarely able to critically assess whether differences between multiple 14C dates of materials are caused by random or systematic errors. In this study, blind tests were carried out to check four possible sources of errors in dating results: repeatability of results generated under identical field and laboratory conditions, differences in results generated from the same sample given to the same laboratory submitted at different times, interlaboratory differences of results generated from the same sample, and differences in the results generated between inner and outer rings of wood. Five charred wood samples, collected from the Namgye settlement and Hongreyonbong fortress, South Korea, were divided into 80 subsamples and submitted to five internationally recognized 14C laboratories on a blind basis twice within a 2-month interval. The results are generally in good statistical accordance and present acceptable errors at an archaeological scale. However, one laboratory showed a statistically significant variance in ages between batches for all samples and sites. Calculation of the Bayesian partial posterior predictive p value and chi-squared tests rejected the null hypothesis that the errors randomly occurred, although the source of the error is not specifically known. Our experiment suggests that it is necessary for users of 14C dating to establish an organized strategy for dating sites before submitting samples to laboratories in order to avoid possible systematic errors.
Depression is common after acute coronary syndrome (ACS) with adverse effects on prognosis. There is little evidence on whether depression treatment improves quality of life (QoL) in ACS patients. The aim of this study was to investigate the effects of co-morbid depression and its treatment on QoL in ACS.
In total, 1152 patients were recruited at baseline, 2–14 weeks after a confirmed ACS episode, and 828 were followed 1 year thereafter. Of 446 baseline participants with co-morbid depressive disorders, 300 were randomized to a 24-week double blind trial of escitalopram or placebo, while the remaining 146 received medical treatment only (MTO). QoL was measured by the World Health Organization Quality of Life –Abbreviated form (WHOQOL-BREF).
At baseline, QoL was significantly lower in patients with co-morbid depressive disorder than those without. QoL improvement was significantly greater in those receiving escitalopram than those receiving placebo over the 24-week treatment period. In the 1-year follow-up, the better outcomes associated with escitalopram remained evident against both placebo and MTO.
Depression was significantly associated with worse QoL even in patients with recently developed ACS. Depression treatment was associated with QoL improvement in ACS patients in the 24-week treatment period, the effects of which extended to 1 year.