scholarly journals Square Kilometre Array Station Configuration Using Two-Stage Beamforming

2013 ◽  
Vol 30 ◽  
Author(s):  
Aziz Jiwani ◽  
Tim Colegate ◽  
Nima Razavi-Ghods ◽  
Peter J. Hall ◽  
Shantanu Padhi ◽  
...  
Keyword(s):  
Signal Processing ◽  
Radio Astronomy ◽  
Effective Area ◽  
The Other ◽  
Processing Load ◽  
Two Stage ◽  
Square Kilometre Array ◽  
Cost Benefits ◽  
Sparse Aperture ◽  
Aperture Arrays

AbstractThe lowest frequency band (70–450 MHz) of the Square Kilometre Array (SKA) will consist of sparse aperture arrays grouped into geographically localised patches or stations. Signals from thousands of antennas in each station will be beamformed to produce station beams which form the inputs for the central correlator. Two-stage beamforming within stations can reduce SKA-low signal processing load and costs, but has not been previously explored for the irregular station layouts now favoured in radio astronomy arrays. This paper illustrates the effects of two-stage beamforming on sidelobes and effective area, for two representative station layouts (regular and irregular gridded tiles on an irregular station). The performance is compared with a single-stage, irregular station. The inner sidelobe levels do not change significantly between layouts, but the more distant sidelobes are affected by the tile layouts; regular tile creates diffuse, but regular, grating lobes. With very sparse arrays, the station effective area is similar between layouts. At lower frequencies, the regular tile significantly reduces effective area, hence sensitivity. The effective area is highest for a two-stage irregular station, but it requires a larger station extent than the other two layouts. Although there are cost benefits for stations with two-stage beamforming, we conclude that more accurate station modelling and SKA-low configuration specifications are required before design finalisation.

scholarly journals The Murchison Widefield Array: The Square Kilometre Array Precursor at Low Radio Frequencies

2013 ◽  
Vol 30 ◽  
Author(s):  
S. J. Tingay ◽  
R. Goeke ◽  
J. D. Bowman ◽  
D. Emrich ◽  
S. M. Ord ◽  
...  
Keyword(s):  
Signal Processing ◽  
System Level ◽  
Radio Frequency Interference ◽  
Astronomy Observatory ◽  
Square Kilometre Array ◽  
Expected Performance ◽  
Low Levels ◽  
Radio Frequencies ◽  
Murchison Widefield Array ◽  
Aperture Arrays

AbstractThe Murchison Widefield Array (MWA) is one of three Square Kilometre Array Precursor telescopes and is located at the Murchison Radio-astronomy Observatory in the Murchison Shire of the mid-west of Western Australia, a location chosen for its extremely low levels of radio frequency interference. The MWA operates at low radio frequencies, 80–300 MHz, with a processed bandwidth of 30.72 MHz for both linear polarisations, and consists of 128 aperture arrays (known as tiles) distributed over a ~3-km diameter area. Novel hybrid hardware/software correlation and a real-time imaging and calibration systems comprise the MWA signal processing backend. In this paper, the as-built MWA is described both at a system and sub-system level, the expected performance of the array is presented, and the science goals of the instrument are summarised.

Impulsivity and Aggression: A Meta-analysis Using the UPPS Model of Impulsivity

2019 ◽  
Author(s):  
Konrad Bresin
Keyword(s):  
Structural Equation Modeling ◽  
Sensation Seeking ◽  
Structural Equation ◽  
Meta Analysis ◽  
The Other ◽  
Equation Modeling ◽  
Negative Urgency ◽  
Two Stage ◽  
Trait Impulsivity

Trait impulsivity has long been proposed to play a role in aggression, but the results across studies have been mixed. One possible explanation for the mixed results is that impulsivity is a multifaceted construct and some, but not all, facets are related to aggression. The goal of the current meta-analysis was to determine the relation between the different facets of impulsivity (i.e., negative urgency, positive urgency, lack of premeditation, lack of perseverance, and sensation seeking) and aggression. The results from 93 papers with 105 unique samples (N = 36, 215) showed significant and small-to-medium correlations between each facet of impulsivity and aggression across several different forms of aggression, with more impulsivity being associated with more aggression. Moreover, negative urgency (r = .24, 95% [.18, .29]), positive urgency (r = .34, 95% [.19, .44]), and lack of premeditation (r = .23, 95% [.20, .26]) had significantly stronger associations with aggression than the other scales (rs < .18). Two-stage meta-analytic structural equation modeling showed that these effects were not due to overlap among facets of impulsivity. These results help advance the field of aggression research by clarifying the role of impulsivity and may be of interest to researchers and practitioners in several disciplines.

scholarly journals LLISP: Low-Light Image Signal Processing Net via Two-Stage Network

IEEE Access ◽  
2021 ◽  
Vol 9 ◽  
pp. 16736-16745
Author(s):  
Hongjin Zhu ◽  
Yang Zhao ◽  
Rongjie Wang ◽  
Ronggang Wang ◽  
Weiqiang Chen ◽  
...  
Keyword(s):  
Signal Processing ◽  
Low Light ◽  
Two Stage ◽  
Light Image

Micro- and Nano-instrument Power

2006 ◽  
Vol 973 ◽  
Author(s):  
Vassili Karanassios
Keyword(s):  
Signal Processing ◽  
Chemical Analysis ◽  
Data Acquisition ◽  
Cancer Diagnosis ◽  
Paradigm Shift ◽  
The Other ◽  
Paradigm Shifts ◽  
Comparable Performance ◽  
Wireless Interface ◽  
Capsule Size

ABSTRACTFor the last several years, we have been developing and characterizing “mobile” micro- and nano-instruments for use on-site (e.g., in the field). Although such portable, battery-operated instruments are much smaller that their laboratory-scale counterparts, sometimes they provide comparable performance and they often offer improved capabilities. As such, they are expected to cause a paradigm shift in classical chemical analysis by allowing practioners to “bring the lab (or part of it) to the sample”. Two classes of examples will be used as the means with which to illustrate the power of micro- and nano-instruments. One class involves a “patient” as the sample and an ingestible capsule-size spectrometer used for cancer diagnosis of the gastro intestinal tack as (part of) “the lab”. The other involves the “environment” as the sample and a portable, battery-operated, miniaturized instrument that utilizes a PalmPilot™ with a wireless interface for data acquisition and signal processing as (part of) “the lab”. To discuss how to electrically power such miniaturized instruments, mobile energy issues will be addressed. Particular emphasis will be paid to current or anticipated future applications and to the paradigm shifts that may prove essential in powering the next generation of miniaturized instruments.

scholarly journals Two Types of Prothrombin in Vitamin K Deficiency

1970 ◽  
Vol 23 (03) ◽  
pp. 633-637 ◽  
Author(s):  
H. C Hemker ◽  
Annemarie D. Muller ◽  
E. A Loeliger
Keyword(s):  
Vitamin K ◽  
Oral Anticoagulants ◽  
Coagulation Factors ◽  
The Other ◽  
Vitamin K Deficiency ◽  
Two Stage ◽  
K Deficiency

SummaryIn vitamin K deficiency (either absolute or induced by oral anticoagulants) two types of prothrombin occur. One is not distinguishable from normal prothrombin. It generates thrombin quickly in a medium in which the factors V, VII and X, thromboplastin and Ca++ are present in sufficient amounts. The other is converted into thrombin much more slowly under the same conditions. In the onestage prothrombin assay only the first form is measured, in a two-stage prothrombin assay both forms are estimated. This accounts for the well-known discrepancy between these two tests in vitamin K deficiency. The abnormal prothrombin can be considered one of the Proteins Induced by Vitamin K Absence. The occurrence of this kind of proteins fits in the concept of the action of vitamin K as a co-factor in a system that converts polypeptide-precursors into coagulation factors.

scholarly journals Profile Inferences on Restricted Additive Partially Linear EV Models

2013 ◽  
Vol 2013 ◽  
pp. 1-9
Author(s):  
Xiuli Wang
Keyword(s):  
Least Squares ◽  
Asymptotic Distribution ◽  
The Other ◽  
Finite Sample ◽  
Test Statistic ◽  
Two Stage ◽  
Chi Square ◽  
Partially Linear ◽  
Profile Least Squares ◽  
Restricted Estimator

We consider the testing problem for the parameter and restricted estimator for the nonparametric component in the additive partially linear errors-in-variables (EV) models under additional restricted condition. We propose a profile Lagrange multiplier test statistic based on modified profile least-squares method and two-stage restricted estimator for the nonparametric component. We derive two important results. One is that, without requiring the undersmoothing of the nonparametric components, the proposed test statistic is proved asymptotically to be a standard chi-square distribution under the null hypothesis and a noncentral chi-square distribution under the alternative hypothesis. These results are the same as the results derived by Wei and Wang (2012) for their adjusted test statistic. But our method does not need an adjustment and is easier to implement especially for the unknown covariance of measurement error. The other is that asymptotic distribution of proposed two-stage restricted estimator of the nonparametric component is asymptotically normal and has an oracle property in the sense that, though the other component is unknown, the estimator performs well as if it was known. Some simulation studies are carried out to illustrate relevant performances with a finite sample. The asymptotic distribution of the restricted corrected-profile least-squares estimator, which has not been considered by Wei and Wang (2012), is also investigated.

completed machine would almost certainly be less than half that of a completed machine of the same kind. How s1(3) operates has been the subject of a detailed and critical analysis by Robert Goff J in the case of BP Exploration Co Ltd v Hunt (No 2), the defendant was granted a concession to explore for oil in Libya. He did not have the physical resources to carry out the exploration himself, so he sold a half share in the concession to BP, on condition that they would bear the initial cost of exploration. Accordingly, under this arrangement, BP’s expenses at the outset were likely to be very substantial, but on the assumption that oil was discovered, that expenditure would be recouped as oil continued to come on stream. The nature of the contract was that should oil not be discovered, the risk would be borne by BP, but, on the assumption that oil was discovered, BP’s expenses would be paid for out of the defendant’s receipts. Oil was discovered in 1967, but in 1971, the Libyan Government expropriated BP’s share of the concession and, in 1973, the defendant’s share was also expropriated. Accordingly, BP had received some payment, but this went only so far as to cover two-thirds of their initial expenditure. On the other hand, since the defendant had no expenses, all moneys received by him amounted to profit once the concession had been paid for. Goff J adopted a two stage approach to s1(3), stating that it was necessary first to identify and value what benefit had been conferred on the defendant, since on the wording of s1(3), this set a ceiling on the amount which could be awarded by way of a just sum. Secondly, it was necessary to award a just sum, taking account of the value of the benefit conferred and the cost to the performer of the work he had done prior to the frustrating event. For these purposes, the benefit to the defendant will be assessed by reference to the end product of the service provided by the other party: BP Exploration Co Ltd v Hunt (No 2) [1979] 1 WLR 783, p 799

1995 ◽  
pp. 388-392
Keyword(s):  
Critical Analysis ◽  
The Other ◽  
Two Stage ◽  
Initial Cost ◽  
Other Hand ◽  
Physical Resources ◽  
The Subject ◽  
To Come ◽  
The Cost
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