1,386 research outputs found
Neural network interpolation of the magnetic field for the LISA Pathfinder Diagnostics Subsystem
LISA Pathfinder is a science and technology demonstrator of the European
Space Agency within the framework of its LISA mission, which aims to be the
first space-borne gravitational wave observatory. The payload of LISA
Pathfinder is the so-called LISA Technology Package, which is designed to
measure relative accelerations between two test masses in nominal free fall.
Its disturbances are monitored and dealt by the diagnostics subsystem. This
subsystem consists of several modules, and one of these is the magnetic
diagnostics system, which includes a set of four tri-axial fluxgate
magnetometers, intended to measure with high precision the magnetic field at
the positions of the test masses. However, since the magnetometers are located
far from the positions of the test masses, the magnetic field at their
positions must be interpolated. It has been recently shown that because there
are not enough magnetic channels, classical interpolation methods fail to
derive reliable measurements at the positions of the test masses, while neural
network interpolation can provide the required measurements at the desired
accuracy. In this paper we expand these studies and we assess the reliability
and robustness of the neural network interpolation scheme for variations of the
locations and possible offsets of the magnetometers, as well as for changes in
environmental conditions. We find that neural networks are robust enough to
derive accurate measurements of the magnetic field at the positions of the test
masses in most circumstances
UK Large-scale Wind Power Programme from 1970 to 1990: the Carmarthen Bay experiments and the Musgrove Vertical-Axis Turbines
This article describes the development of the Musgrove Vertical Axis Wind Turbine (VAWT)
concept, the UK âCarmarthen Bayâ wind turbine test programme, and UK governmentâs wind
power programme to 1990. One of the most significant developments in the story of British
wind power occurred during the 1970s, 1980s, and 1990s, with the development of the
Musgrove vertical axis wind turbine and its inclusion within the UK Governmentâs wind
turbine test programme. Evolving from a supervisorâs idea for an undergraduate project at
Reading University, the Musgrove VAWT was once seen as an able competitor to the
horizontal axis wind systems that were also being encouraged at the time by both the UK
government and the Central Electricity Generating Board, the then nationalised electricity
utility for England and Wales. During the 1980s and 1990s the most developed Musgrove
VAWT system, along with three other commercial turbine designs was tested at
Carmarthen Bay, South Wales as part of a national wind power test programme. From these
developmental tests, operational data was collected and lessons learnt, which were
incorporated into subsequent wind power operations.http://dx.doi.org/10.1260/03095240677860621
Bridge distress caused by approach embankment settlement
Surtees Bridge, which carries the A66(T) over the River
Tees near Thornaby-on-Tees in the UK, has been
showing signs of distress that predate its opening in
1981. Subsequent investigations have shown that the
bridge distress is related to unexpectedly large
settlement of the eastern approach embankment.
Recent ground investigations prompted by a proposed
widening of the river crossing have produced many new
data on the alluvial deposits underlying the site, and
explain why embankment settlement was so much larger
than originally anticipated. Comparison of the
geotechnical parameters obtained from the original and
more recent ground investigations suggests that the
original investigation significantly underestimated the
thickness of an alluvial clay layer underlying the site, and
that its coefficient of consolidation was overestimated.
Settlement analyses using geotechnical data from the
original ground investigations predict moderate
embankment settlements occurring principally during
construction. Settlement analyses based on all the
available data predict far larger embankment
settlements occurring over extended time periods. The
latter analyses predict an embankment settlement
similar to that observed and of sufficient magnitude to
cause the observed lateral displacement of the bridge
due to lateral loading of its piled foundation
Generalized Cauchy means
Given two means M and N, the operator MM,NMM,N assigning to a given mean ÎŒ the mean MM,N(ÎŒ)(x,y)=M(ÎŒ(x,N(x,y)),ÎŒ(N(x,y),y)) was defined in Berrone and Moro (Aequationes Math 60:1â14, 2000) in connection with Cauchy means: the Cauchy mean generated by the pair f, g of continuous and strictly monotonic functions is the unique solution ÎŒ to the fixed point equation MA(f),A(g)(ÎŒ)=ÎŒ, where A(f) and A(g) are the quasiarithmetic means respectively generated by f and g. In this article, the operator MM,NMM,N is studied under less restrictive conditions and a general fixed point theorem is derived from an explicit formula for the iterates MnM,NMM,Nn . The concept of class of generalized Cauchy means associated to a given family of mixing pairs of means is introduced and some distinguished families of pairs are presented. The question of equality in these classes of means remains a challenging open problem.Fil: Berrone, Lucio Renato. Universidad Nacional de Rosario. Facultad de Ciencias Exactas, IngenierĂa y Agrimensura; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentin
Solar System Processes Underlying Planetary Formation, Geodynamics, and the Georeactor
Only three processes, operant during the formation of the Solar System, are
responsible for the diversity of matter in the Solar System and are directly
responsible for planetary internal-structures, including planetocentric nuclear
fission reactors, and for dynamical processes, including and especially,
geodynamics. These processes are: (i) Low-pressure, low-temperature
condensation from solar matter in the remote reaches of the Solar System or in
the interstellar medium; (ii) High-pressure, high-temperature condensation from
solar matter associated with planetary-formation by raining out from the
interiors of giant-gaseous protoplanets, and; (iii) Stripping of the primordial
volatile components from the inner portion of the Solar System by super-intense
solar wind associated with T-Tauri phase mass-ejections, presumably during the
thermonuclear ignition of the Sun. As described herein, these processes lead
logically, in a causally related manner, to a coherent vision of planetary
formation with profound implications including, but not limited to, (a) Earth
formation as a giant gaseous Jupiter-like planet with vast amounts of stored
energy of protoplanetary compression in its rock-plus-alloy kernel; (b) Removal
of approximately 300 Earth-masses of primordial gases from the Earth, which
began Earth's decompression process, making available the stored energy of
protoplanetary compression for driving geodynamic processes, which I have
described by the new whole-Earth decompression dynamics and which is
responsible for emplacing heat at the mantle-crust-interface at the base of the
crust through the process I have described, called mantle decompression
thermal-tsunami; and, (c)Uranium accumulations at the planetary centers capable
of self-sustained nuclear fission chain reactions.Comment: Invited paper for the Special Issue of Earth, Moon and Planets
entitled Neutrino Geophysics Added final corrections for publicatio
Salmonella biofilms
Biofilm formation by Salmonellaspp. is a problem in the food industry, since biofilms may act as a persistent source of product contamination. Therefore the aim of this study was to obtain more insight in the processes involved and the factors contributing to Salmonellabiofilm formation. A collection of SalmonellaTyphimurium clinical, outbreak-related and retail product isolates, was used to determine biofilm formation capacity and to identify cellular parameters contributing to surface colonisation. The results revealed dense biofilm formation by these isolates at 25 °C and 37 °C in nutrient-rich media. However, in nutrient-low media dense biofilm formation was only observed at 25 °C with industrial isolates. In addition, temperature and medium composition were also found to influence biofilm morphology and composition. At nutrient-low conditions at 25 °C the biofilm consisted of cell clusters encapsulated by an extracellular matrix composed of curli fimbriae and cellulose. In nutrient-rich conditions a monolayer of cells with little to no extracellular matrix were observed, with a prominent role for type 1 fimbriae. This type of fimbriae was only expressed in a subset of strains and appeared to contribute to initial attachment of Salmonellacells ultimately leading to dense biofilm formation. This study also indicated that biofilm formation differs between and within the Salmonellaserovars Typhimurium, Derby, Brandenburg and Infantis, isolated from meat processing environments. And, for all serovars biofim formation contributed to the survival on stainless steel surfaces and biofilm cells were less susceptible to peracetic acid disinfection treatments. This latter effect was specifically observed in the presence of organic matter, which drastically decreased the activity of peracetic acid conceivably resulting in low level exposure of the bacterial flora facilitating survival. Furthermore, single and repeated exposure to sub-lethal concentrations of the disinfectant benzalkonium chloride rapidly selected for resistant variants. In conclusion, the results obtained in this study may contribute to the development of better strategies for Salmonella control in food processing environments.</p
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Youth Gambling: The health and wellbeing of New Zealand secondary school students in 2012
Gambling has become a widely available activity in todayâs society (Hardoon & Derevensky, 2002; Turchi & Derevensky, 2006). In fact, many researchers âhave noted that an entire generation has now grown up in an era when lottery and casino gambling is widely available and heavily advertisedâ (Volberg, Gupta, Griffiths, Ălason, & Delfabbro, 2010, p. 3). Evidence suggests that it has become a popular past-time not only for adults, but also for children and young people (Derevensky & Gupta, 2000; Gupta & Derevensky, 1998a; Hardoon & Derevensky, 2002; Jacobs, 2000; Splevins, Mireskandari, Clayton, & Blaszczynski, 2010; Turchi & Derevensky, 2006). Moreover, research indicates that gambling is one of the first risky activities that adolescents become involved with (i.e. they begin gambling prior to experimentation with alcohol, drugs, sexual behaviour) (Volberg, et al., 2010). Whilst for many youth involvement in gambling does not result in problematic behaviour, others go on to experience serious problems (Dickson, Derevensky, & Gupta, 2003).
A vast range of adolescent gambling prevalence studies that have been undertaken over the past 25 years, across different countries, and incorporating general populations as well as youth specifically. Rates of youth problem gambling have often been found to be higher than the rates identified for adults (Huang & Boyer, 2007; Shaffer & Hall, 1996; Welte, Barnes, Tidwell, & Hoffman, 2008; Williams, Page, Parke, & Rigbye, 2008), with some estimating them to be more than double those of adults (Gupta & Derevensky, 1998a; Jackson, Dowling, Thomas, Bond, & Patton, 2008; Lesieur, et al., 1991), or up to three times as high (Rigbye, 2010). However, it has also been recognised that there is far less research in this field compared to that which has explored other youth risk behaviours such as substance use (Blinn-Pike, Worthy, & Jonkman, 2010).
The gap in New Zealand-based information regarding prevalence of youth gambling has been identified previously (Bellringer, et al., 2003; Rossen, Tse, & Vaidya, 2009) and in 2003 it was recommended that research be undertaken to measure the involvement of New Zealand youth in gambling as well as associated factors and gambling-related problems (Bellringer, et al., 2003). A limited body of research has since employed various sources of data to consider youth gambling in New Zealand (e.g. Gray, 2010; Ministry of Health, 2008, 2009; Rossen, 2008; Rossen, Butler, & Denny, 2011).
An extremely valuable source of information on New Zealand youth is the University of Aucklandâs (UoA) National youth health and wellbeing surveys. To date, the UoAâs Adolescent Health Research Group (AHRG) has completed three National youth health and wellbeing surveys.
The Youth2000 Survey Series aim to provide nationally representative information on the health and wellbeing of young people attending New Zealand secondary schools. The Survey Series includes a wide range of questions about issues that contribute to the health and wellbeing of young people (such as substance use, injuries and violence, home and family) and allow researchers to take an ecological approach to identifying overall risk and protective factors in young peopleâs lives. Youthâ12, a survey of 8,500 secondary school students throughout New Zealand, is the most recent survey to be undertaken by the AHRG. The inclusion of gambling items in the Youthâ12 survey provides a unique opportunity to examine the impacts of gambling and problem gambling on secondary school students throughout New Zealand within an ecological framework.
This report was commissioned by the Ministry of Health and begins with a comprehensive review of the local and international youth gambling literature, followed by an overview of the Youth2000 Survey Series and methodology for Youthâ12. A thorough analysis of Youthâ12 gambling items was undertaken with results being reported under the following eight categories (detailed results for each set of analyses are also provided in the appendices):
- Students and their own gambling (Section Five);
- Unhealthy gambling amongst students (Section Six);
- Attitudes and motivating factors towards gambling (Section Seven);
- The impacts of othersâ gambling on students (Section Eight); and,
- Risk and protective factors for student gambling (Section Nine);
- Gambling and MÄori taitamariki in Aotearoa (Section 10);
- Gambling and Pacific young people in New Zealand (Section 11); and,
- Gambling and Asian young people in New Zealand (Section 12).
Finally, a discussion chapter provides an overview of the findings and implications
Geophysical studies with laser-beam detectors of gravitational waves
The existing high technology laser-beam detectors of gravitational waves may
find very useful applications in an unexpected area - geophysics. To make
possible the detection of weak gravitational waves in the region of high
frequencies of astrophysical interest, ~ 30 - 10^3 Hz, control systems of laser
interferometers must permanently monitor, record and compensate much larger
external interventions that take place in the region of low frequencies of
geophysical interest, ~ 10^{-5} - 3 X 10^{-3} Hz. Such phenomena as tidal
perturbations of land and gravity, normal mode oscillations of Earth,
oscillations of the inner core of Earth, etc. will inevitably affect the
performance of the interferometers and, therefore, the information about them
will be stored in the data of control systems. We specifically identify the
low-frequency information contained in distances between the interferometer
mirrors (deformation of Earth) and angles between the mirrors' suspensions
(deviations of local gravity vectors and plumb lines). We show that the access
to the angular information may require some modest amendments to the optical
scheme of the interferometers, and we suggest the ways of doing that. The
detailed evaluation of environmental and instrumental noises indicates that
they will not prevent, even if only marginally, the detection of interesting
geophysical phenomena. Gravitational-wave instruments seem to be capable of
reaching, as a by-product of their continuous operation, very ambitious
geophysical goals, such as observation of the Earth's inner core oscillations.Comment: 29 pages including 8 figures, modifications and clarifications in
response to referees' comments, to be published in Class. Quant. Gra
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