998 resultados para band bowing coefficient


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Cashman, N. (2009). 'Politics, Passion, Prejudice: Alice Childress's Wedding Band: A Love/Hate Story in Black and White', Journal of American Studies, 43, 3, pp. 407?423 Sponsorship: APRS

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Poolton, Nigel; Ozanyan, K.B.; Wallinga, J.; Murray, A.S., (2002) 'Electrons in feldspar II: a consideration of the influence of conduction band-tail states on luminescence processes', Physics and Chemistry of Minerals 29(3) pp.217-225 RAE2008

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Science Foundation Ireland (CSET - Centre for Science, Engineering and Technology, Grant No. 07/CE/11147)

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Body Sensor Network (BSN) technology is seeing a rapid emergence in application areas such as health, fitness and sports monitoring. Current BSN wireless sensors typically operate on a single frequency band (e.g. utilizing the IEEE 802.15.4 standard that operates at 2.45GHz) employing a single radio transceiver for wireless communications. This allows a simple wireless architecture to be realized with low cost and power consumption. However, network congestion/failure can create potential issues in terms of reliability of data transfer, quality-of-service (QOS) and data throughput for the sensor. These issues can be especially critical in healthcare monitoring applications where data availability and integrity is crucial. The addition of more than one radio has the potential to address some of the above issues. For example, multi-radio implementations can allow access to more than one network, providing increased coverage and data processing as well as improved interoperability between networks. A small number of multi-radio wireless sensor solutions exist at present but require the use of more than one radio transceiver devices to achieve multi-band operation. This paper presents the design of a novel prototype multi-radio hardware platform that uses a single radio transceiver. The proposed design allows multi-band operation in the 433/868MHz ISM bands and this, together with its low complexity and small form factor, make it suitable for a wide range of BSN applications.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The substitution of a small fraction x of nitrogen atoms, for the group V elements in conventional III-V semiconductors such as GaAs and GaSb strongly perturbs the conduction band of the host semiconductor. In this thesis we investigate the effects of nitrogen states on the band dispersion, carrier scattering and mobility of dilute nitride alloys. In the supercell model we solve the single particle Hamiltonian for a very large supercell containing randomly placed nitrogen. This model predicts a gap in the density of states of GaNxAs1−x, where this gap is filled in the Green’s function model. Therefore we develop a self-consistent Green’s function (SCGF) approach, which provides excellent agreement with supercell calculations and reveals a gap in the DOS, in contrast with the results of previous non-self-consistent Green’s function calculations. However, including the distribution of N states destroys this gap, as seen in experiment. We then examine the high field transport of carriers by solving the steadystate Boltzmann transport equation and find that it is necessary to include the full distribution of N levels in order to account for the small, low-field mobility and the absence of a negative differential velocity regime observed experimentally with increasing x. Overall the results account well for a wide range of experimental data. We also investigate the band structure, scattering and mobility of carriers by finding the poles of the SCGF, which gives lower carrier mobility for GaNxAs1−x, compared to those already calculated, in better agreement with experiments. The calculated optical absorption spectra for InyGa1−yNxAs1−x and GaNxSb1−x using the SCGF agree well with the experimental data, confirming the validity of this approach to study the band structure of these materials.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Dilute bismide alloys, containing small fractions of bismuth (Bi), have recently attracted interest due to their potential for applications in a range of semiconductor devices. Experiments have revealed that dilute bismide alloys such as GaBixAs1−x, in which a small fraction x of the atoms in the III-V semiconductor GaAs are replaced by Bi, exhibit a number of unusual and unique properties. For example, the band gap energy (E g) decreases rapidly with increasing Bi composition x, by up to 90 meV per % Bi replacing As in the alloy. This band gap reduction is accompanied by a strong increase in the spin-orbit-splitting energy (ΔSO) with increasing x, and both E g and ΔSO are characterised by strong, composition-dependent bowing. The existence of a ΔSO > E g regime in the GaBixAs1−x alloy has been demonstrated for x ≳10%, a band structure condition which is promising for the development of highly efficient, temperature stable semiconductor lasers that could lead to large energy savings in future optical communication networks. In addition to their potential for specific applications, dilute bismide alloys have also attracted interest from a fundamental perspective due to their unique properties. In this thesis we develop the theory of the electronic and optical properties of dilute bismide alloys. By adopting a multi-scale approach encompassing atomistic calculations of the electronic structure using the semi-empirical tight-binding method, as well as continuum calculations based on the k•p method, we develop a fundamental understanding of this unusual class of semiconductor alloys and identify general material properties which are promising for applications in semiconductor optoelectronic and photovoltaic devices. By performing detailed supercell calculations on both ordered and disordered alloys we explicitly demonstrate that Bi atoms act as isovalent impurities when incorporated in dilute quantities in III-V (In)GaAs(P) materials, strongly perturbing the electronic structure of the valence band. We identify and quantify the causes and consequences of the unusual electronic properties of GaBixAs1−x and related alloys, and our analysis is reinforced throughout by a series of detailed comparisons to the results of experimental measurements. Our k•p models of the band structure of GaBixAs1−x and related alloys, which we derive directly from detailed atomistic calculations, are ideally suited to the study of dilute bismide-based devices. We focus in the latter part of the thesis on calculations of the electronic and optical properties of dilute bismide quantum well lasers. In addition to developing an understanding of the effects of Bi incorporation on the operational characteristics of semiconductor lasers, we also present calculations which have been used explicitly in designing and optimising the first generation of GaBixAs1−x-based devices.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Functional MRI (fMRI) can detect blood oxygenation level dependent (BOLD) hemodynamic responses secondary to neuronal activity. The most commonly used method for detecting fMRI signals is the gradient-echo echo-planar imaging (EPI) technique because of its sensitivity and speed. However, it is generally believed that a significant portion of these signals arises from large veins, with additional contribution from the capillaries and parenchyma. Early experiments using diffusion-weighted gradient-echo EPI have suggested that intra-voxel incoherent motion (IVIM) weighting inherent in the sequence can selectively attenuate contributions from different vessels based on the differences in the mobility of the blood within them. In the present study, we used similar approach to characterize the apparent diffusion coefficient (ADC) distribution within the activated areas of BOLD contrast. It is shown that the voxel values of the ADCs obtained from this technique can infer various vascular contributions to the BOLD signal.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The inoculum effect (IE) refers to the decreasing efficacy of an antibiotic with increasing bacterial density. It represents a unique strategy of antibiotic tolerance and it can complicate design of effective antibiotic treatment of bacterial infections. To gain insight into this phenomenon, we have analyzed responses of a lab strain of Escherichia coli to antibiotics that target the ribosome. We show that the IE can be explained by bistable inhibition of bacterial growth. A critical requirement for this bistability is sufficiently fast degradation of ribosomes, which can result from antibiotic-induced heat-shock response. Furthermore, antibiotics that elicit the IE can lead to 'band-pass' response of bacterial growth to periodic antibiotic treatment: the treatment efficacy drastically diminishes at intermediate frequencies of treatment. Our proposed mechanism for the IE may be generally applicable to other bacterial species treated with antibiotics targeting the ribosomes.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This dissertation explores a method of teaching the history of Civil War music and musicians through modern full-band editions of original brass band music. In the study of music history the period of the Civil War is rarely discussed, or at best, mentioned only if a student takes a specific course on the history of bands and happens to look deeply into the background of some of the early band pioneers such as Patrick Gilmore, who served in the Union Army as a bandmaster. The history of the musicians, bands, and music performed during the Civil War deserves study to provide a way for students and audiences to learn this history. This project includes lesson plans that can be used with the arrangements of the period music as well as select published music that is also representative of the period. Included with the historical information are four arrangements of original brass band music now scored for full concert band. Each arrangement includes a section scored for brass only with optional brass band parts. Historical information is provided on the Civil War period bands and how each side used them, on the composers of the music, and also on the individual compositions. The historical information can be used to supplement the lesson plans to teach the history, as well as for program notes for audiences. The research involved locating information on both Union and Confederate bands available in books, other dissertations, articles, and interviews with Civil War music historians. The original brass band music is scored for full band. This method will allow teachers and conductors to highlight this period of wind band history and to share it with both students and audiences. Included with this project are photos and video footage taken during a visit with the 1st Brigade Band of Watertown, Wisconsin, an historical organization dedicated to recreating the music and performances of an actual Civil War era band.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

SCOPUS: no.j

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The restoration problem for a band-pass linear system is examined in the case the input signal is weighted by a profile function. The singular system is evaluated analytically for three different forms of the profile function. An example of restoration process is presented.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Since their incorporation in 1993, further education (FE) colleges in England have been responsible for their own staffing and, faced with funding constraints as well as recruitment and retention targets, some have introduced a new category of staff referred to here as 'learning support workers' (LSWs). Though their employment conditions and specific duties vary considerably, LSWs' work often includes providing individual care for students. In this small-scale study, using semi-structured interviews, the perceptions of some teachers and LSWs about the nature of their relationships with each other and with students are investigated. The study is set broadly in the context of debates about the impact of public sector reform on FE colleges and teachers. A discourse analysis approach is adopted in discussion of the data. The authors conclude that although they are differently positioned in relation to traditional discourses of professionalism, both teachers and LSWs are perceived to be carrying out what Hochschild termed 'emotional labour'. The contradictory nature of emotional labour is also highlighted. Some of the implications of employing a new group of workers in FE are discussed.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Sammelrezension: 1. Lundgreen, Peter unter Mitarbeit von Jürgen Schallmann: Die Lehrer an den Schulen in der Bundesrepublik Deutschland 1949-2009, Datenhandbuch zur deutschen Bildungsgeschichte, Band XI, Göttingen: Vandenhoeck & Ruprecht 2013, (352 S.; ISBN 978-3-525-36388-5; 89,99 EUR) 2. András Németh / Ehrenhardt Skiera (Hrsg.): Lehrerbildung in Europa, Geschichte, Struktur und Reform, (Erziehung in Wissenschaft und Praxis; Bd. 9), Frankfurt am Main: Peter Lang 2012 (340 S.; ISBN 978-3-631-62454-8; 51,95 EUR)