1,790 research outputs found
Using sources of opportunity to compensate for receiver mismatch in HF arrays
Ā© 2001 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.The spatial processing performance of adaptive sensor arrays is often limited by the nonidentical frequency responses of the receivers in the array over the passband of interest. Addressed here is the problem of estimating digital compensation for mismatches between receiver passbands in high frequency (HF) antenna arrays using interference sources of opportunity. A mathematical model of ionospherically-propagated multipath HF interference is used to develop an adaptive algorithm which estimates the receiver frequency response corrections for each receiver. The effectiveness of the proposed algorithm is experimentally demonstrated and compared against (1) a commonly used least squares technique, and (2) a highly accurate calibration system using data collected by the receiving antenna array of the Jindalee over-the-horizon radar near Alice Springs in central AustraliaFabrizio, G.A.; Gray, D.A.; Turley, M.D
Magneto-elastic coupling and competing entropy changes in substituted CoMnSi metamagnets
We use neutron diffraction, magnetometry and low temperature heat capacity to
probe giant magneto-elastic coupling in CoMnSi-based antiferromagnets and to
establish the origin of the entropy change that occurs at the metamagnetic
transition in such compounds. We find a large difference between the electronic
density of states of the antiferromagnetic and high magnetisation states. The
magnetic field-induced entropy change is composed of this contribution and a
significant counteracting lattice component, deduced from the presence of
negative magnetostriction. In calculating the electronic entropy change, we
note the importance of using an accurate model of the electronic density of
states, which here varies rapidly close to the Fermi energy.Comment: 11 pages, 9 figures. Figures 4 and 6 were updated in v2 of this
preprint. In v3, figures 1 and 2 have been updated, while Table II and the
abstract have been extended. In v4, Table I has updated with relevant neutron
diffraction dat
Hyaluronan Associated Inflammation and Microenvironment Remodelling Influences Breast Cancer Progression
Production of intense, coherent, tunable narrowāband lymanāalpha radiation
Nearly transform limited pulses of 1216 Ć
radiation have been generated by sum frequency generation in 0.1 to 10 torr of mercury vapor. The summed input beams, consisting of photons at 3127 Ć
and 5454 Ć
originate in 1 MHz bandāwidth ringādye laser oscillators. The beams are amplified in pulsedādye amplifiers pumped by the frequency doubled output of a Nd:YAG laser. The 3127 Ć
photons are tuned to be resonant with the twoāphoton 61S to 71S mercury transition. The VUV radiation can be tuned by varying the frequency of the third nonāresonant photon. We have also observed difference frequency generation at 2193 Ć
and intense fluorescence from the 61P state at 1849 Ć
. We have studied the intensity and linewidth dependence of the 1849 Ć
fluorescence and 1216 Ć
sum frequency signals on input beam intensity, mercury density, and buffer gas pressure and composition.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87716/2/49_1.pd
Mostly Minnesota Art Song: Songs by Barber, Campbell, Erickson, Larsen, Maurer, Phipps-Kettlewell, Rossi, and Thomas
Tracks 1-6 are from David Evan Thomas\u27 Divine Images collection, based on the poetry of William Blake. Tracks 16-20 are from Brian G. Campbell\u27s collection This is My Letter to the World: Five Emily Dickinson Songs.https://digitalcommons.csbsju.edu/music_recordings/1014/thumbnail.jp
Towards improved socio-economic assessments of ocean acidificationās impacts
Ocean acidification is increasingly recognized as a component of global change that could have a wide range of impacts on marine organisms, the ecosystems they live in, and the goods and services they provide humankind. Assessment of these potential socio-economic impacts requires integrated efforts between biologists, chemists, oceanographers, economists and social scientists. But because ocean acidification is a new research area, significant knowledge gaps are preventing economists from estimating its welfare impacts. For instance, economic data on the impact of ocean acidification on significant markets such as fisheries, aquaculture and tourism are very limited (if not non-existent), and non-market valuation studies on this topic are not yet available. Our paper summarizes the current understanding of future OA impacts and sets out what further information is required for economists to assess socio-economic impacts of ocean acidification. Our aim is to provide clear directions for multidisciplinary collaborative research
Landauer Theory, Inelastic Scattering and Electron Transport in Molecular Wires
In this paper we address the topic of inelastic electron scattering in
mesoscopic quantum transport. For systems where only elastic scattering is
present, Landauer theory provides an adequate description of transport that
relates the electronic current to single-particle transmission and reflection
probabilities. A formalism proposed recently by Bonca and Trugman facilitates
the calculation of the one-electron transmission and reflection probabilities
for inelastic processes in mesoscopic conductors connected to one-dimensional
ideal leads. Building on their work, we have developed a self-consistent
procedure for the evaluation of the non-equilibrium electron distributions in
ideal leads connecting such mesoscopic conductors to electron reservoirs at
finite temperatures and voltages. We evaluate the net electronic current
flowing through the mesoscopic device by utilizing these non-equilibrium
distributions. Our approach is a generalization of Landauer theory that takes
account of the Pauli exclusion principle for the various competing elastic and
inelastic processes while satisfying the requirement of particle conservation.
As an application we examine the influence of elastic and inelastic scattering
on conduction through a two site molecular wire with longitudinal phonons using
the Su-Schrieffer-Heeger model of electron-phonon coupling.Comment: 25 pages, 8 figure
Evaluation of range of motion restriction within the hip joint
In Total Hip Arthroplasty, determining the impingement free range of motion requirement is a complex task. This is because in the native hip, motion is restricted by both impingement as well as soft tissue restraint. The aim of this study is to determine a range of motion benchmark which can identify motions which are at risk from impingement and those which are constrained due to soft tissue. Two experimental methodologies were used to determine motions which were limited by impingement and those motions which were limited by both impingement and soft tissue restraint. By comparing these two experimental results, motions which were limited by impingement were able to be separated from those motions which were limited by soft tissue restraint. The results show motions in extension as well as flexion combined with adduction are limited by soft tissue restraint. Motions in flexion, flexion combined with abduction and adduction are at risk from osseous impingement. Consequently, these motions represent where the maximum likely damage will occur in femoroacetabular impingement or at most risk of prosthetic impingement in Total Hip Arthroplasty
āSo many women suffer in silenceā: A thematic analysis of womenās written accounts of coping with endometriosis
Objective: To understand womenās experiences of coping with endometriosis, and impact on their lives. Design: Women accessed an online questionnaire through a UK-based endometriosis charity website. Methods: Thirty-four women, aged 22-56 years, with self-reported medically-diagnosed endometriosis, 30 of whom were White, responded to open-ended questions, analysed using inductive thematic analysis. Results: Participants spoke about their lives being a constant struggle, where they tried to maintain their personal and working lives whilst dealing with long-term pain. Women had to ābattleā for an accurate diagnosis, and had limited faith in health professionals. Coping strategies included avoidance of social events to conserve energy (self-pacing), and avoiding taking painkillers to retain alertness. Women did not feel able to be honest with family and friends about their symptoms, and felt socially isolated and misunderstood. Conclusions: Implications for health professionals are discussed, including the need for earlier diagnosis and taking womenās symptoms more seriously at referral; understanding the need to conserve energy in the context of long-term pain; that not taking pain medication may be an active choice to retain alertness; and that avoiding being honest with friends and family and subsequent feelings of isolation may be common experiences relevant to designing treatment programmes
High-pressure melt curve of shock-compressed tin measured using pyrometry and reflectance techniques
We have developed a new technique to measure the melt curve of a shocked metal sample and have used it to measure the high-pressure solid-liquid phase boundary of tin from 10 to 30āGPa and 1000 to 1800āK. Tin was shock compressed by plate impact using a single-stage powder gun, and we made accurate, time-resolved radiance, reflectance, and velocimetry measurements at the interface of the tin sample and a lithium fluoride window. From these measurements, we determined temperature and pressure at the interface vs time. We then converted these data to temperature vs pressure curves and plotted them on the tin phase diagram. The tin sample was initially shocked into the high-pressure solid Ī³ phase, and a subsequent release wave originating from the back of the impactor lowered the pressure at the interface along a constant entropy path (release isentrope). When the release isentrope reaches the solid-liquid phase boundary, melt begins and the isentrope follows the phase boundary to low pressure. The onset of melt is identified by a significant change in the slope of the temperature-pressure release isentrope. Following the onset of melt, we obtain a continuous and highly accurate melt curve measurement. The technique allows a measurement along the melt curve with a single radiance and reflectance experiment. The measured temperature data are compared to the published equation of state calculations. Our data agree well with some but not all of the published melt curve calculations, demonstrating that this technique has sufficient accuracy to assess the validity of a given equation of state model
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