Transmission loss predictions for dissipative silencers of arbitrary cross section in the presence of mean flow

A numerical technique is developed for the analysis of dissipative silencers of arbitrary, but axially uniform, cross section. Mean gas flow is included in a central airway which is separated from a bulk reacting porous material by a concentric perforate screen. The analysis begins by employing the finite element method to extract the eigenvalues and associated eigenvectors for a silencer of infinite length. Point collocation is then used to match the expanded acoustic pressure and velocity fields in the silencer chamber to those in the inlet and outlet pipes. Transmission loss predictions are compared with experimental measurements taken for two automotive dissipative silencers with elliptical cross sections. Good agreement between prediction and experiment is observed both without mean flow and for a mean flow Mach number of 0.15. It is demonstrated also that the technique presented offers a considerable reduction in computational expenditure when compared to a three dimensional finite element analysis

Fluctuations in the transmission properties of a quantum dot with interface roughness and impurities

We examine statistical fluctuations in the transmission properties of quantum dots with interface roughness and neutral impurities. For this purpose we employ a supercell model of quantum transport capable of simulating potential variations in three dimensions. We find that sample to sample variations in interface roughness in a quantum dot waveguide can lead to substantial fluctuations in the n=1 transmission resonance position, width and maximum. We also find that a strongly attractive impurity near the centre of a quantum dot can reduce these fluctuations. Nevertheless, the presence of more than a single impurity can give rise to a complex resonance structure that varies with impurity configuration

The Ormskirk night-time economy project : exploring positives and negatives of a Lancashire town's NTE

During November 2014, West Lancashire Borough Council (WLBC) commissioned Lancaster University (LU) to undertake a scoping study. The aim was to “conduct independent research to assist them in developing a better understanding of the positive and negative impacts of the night time economy for those residing, working and visiting Ormskirk Town Centre” (WLBC Brief November 2014). This report is in three sections, and finishes with some concluding remarks. The first section describes Ormskirk and its Night Time Economy (ONTE). The second section explains the methodology used in the research and explores the strengths and weaknesses of the approaches used. The final section sets out the findings using four main headings

Dissociative Autoionization in (1+2)-photon Above Threshold Excitation of H2 Molecules

We have theoretically studied the effect of dissociative autoionization on the photoelectron energy spectrum in (1+2)-photon above threshold ionization(ATI) of H2 molecules. We have considered excitation from the ground state X-singlet-Sigma-g+(v=0,j) to the doubly excited autoionizing states of singlet-Sigma-u+ and singlet-Pi-u+ symmetry, via the intermediate resonant B-singlet-Sigma-u+(v=5,j) states. We have shown that the photoelectron energy spectrum is oscillatory in nature and shows three distinct peaks above the photoelectron energy 0.7 eV. This feature has been observed in a recent experiment by Rottke et al, J. Phys. B, Vol. 30, p-4049 (1997).Comment: 11 pages and 4 figure

Communication increases category structure and alignment only when combined with cultural transmission

The semantic categories labeled by words in natural languages are used for communication with others, and learned by observing the productions of others who learned them in the same way. Do these processes of communication and cultural transmission affect the structure of category systems and their alignment across speakers? We examine novel category systems that emerge from communication, cultural transmission, and both processes combined. Communication alone leads to category systems that vary widely in their communicative effectiveness, and are no more structured or aligned than those created by individuals. When combined with cultural transmission, communication speeds up convergence on a learnable number of structured, aligned categories that are consistently communicatively effective. However, cultural transmission without communication eventually has similar results. Communication appears to be neither necessary nor sufficient for creating semantic category systems that are robustly effective for communication. Furthermore, category systems that emerge from cultural transmission are more aligned across speakers than the systems created by individuals, suggesting that cultural transmission allows individuals to coordinate their semantic systems more effectively than they can through shared perceptual biases alone

2010 Precision Planted Corn Performance Trials

This publication reports the results of the 2010 South Dakota corn hybrid performance trials for glyphosate-resistant hybrids. Information includes both the most recent two-year and one-year grain yields in bushels per acre and one-year bushel weight in pounds, along with grain moisture at harvest, lodging, and final stand in percentages. These performance trials are conducted by the South Dakota Crop Performance Testing program at South Dakota State University. Corn performance trial tables are listed on the inside front cover. Environmental data is listed in tables A and B, indices of brand/hybrid entries to performance table number are listed in table C, table D has the performance table footnote legends, and mailing addresses for seed companies are listed in table E

Effects of Capping on the (Ga,Mn)As Magnetic Depth Profile

Annealing can increase the Curie temperature and net magnetization in uncapped (Ga,Mn)As films, effects that are suppressed when the films are capped with GaAs. Previous polarized neutron reflectometry (PNR) studies of uncapped (Ga,Mn)As revealed a pronounced magnetization gradient that was reduced after annealing. We have extended this study to (Ga,Mn)As capped with GaAs. We observe no increase in Curie temperature or net magnetization upon annealing. Furthermore, PNR measurements indicate that annealing produces minimal differences in the depth-dependent magnetization, as both as-grown and annealed films feature a significant magnetization gradient. These results suggest that the GaAs cap inhibits redistribution of interstitial Mn impurities during annealing.Comment: 12 pages, 3 figures, submitted to Applied Physics Letter

Carrier-mediated antiferromagnetic interlayer exchange coupling in diluted magnetic semiconductor multilayers Ga1−x_{1-x}Mnx_xAs/GaAs:Be

We use neutron reflectometry to investigate the interlayer exchange coupling between Ga$_{0.97}$Mn$_{0.03}$As ferromagnetic semiconductor layers separated by non-magnetic Be-doped GaAs spacers. Polarized neutron reflectivity measured below the Curie temperature of Ga$_{0.97}$Mn$_{0.03}$As reveals a characteristic splitting at the wave vector corresponding to twice the multilayer period, indicating that the coupling between the ferromagnetic layers are antiferromagnetic (AFM). When the applied field is increased to above the saturation field, this AFM coupling is suppressed. This behavior is not observed when the spacers are undoped, suggesting that the observed AFM coupling is mediated by charge carriers introduced via Be doping. The behavior of magnetization of the multilayers measured by DC magnetometry is consistent with the neutron reflectometry results.Comment: 4 pages, 4 figure