6,782 research outputs found
Raising Student Achievement Levels Through Target-setting and Academic Monitoring: A Case Study of Developments at Key Stage 3 in a Secondary School
Evidence for the conclusions and recommendations are based on interviews with tutors and students from Year 8 conducted by the Head of Year, who then provides an overview from her perspective. The findings are contrasted against the examples of effective target-setting provided by the DfEE Standards and Effectiveness Unit (DfEE, 1998b) and the Office for Standards in Education (Ofsted, 1996). The new scheme is also reviewed in the light of the call for equal opportunities by, amongst others, the Department for Education and Employment (DfEE, 1998c) and against the body of evidence provided by the research on school improvement (e.g. Stoll and Mortimore, 1995; Creemers, 1997
Ultrafast spatio-temporal dynamics of terahertz generation by ionizing two-color femtosecond pulses in gases
We present a combined theoretical and experimental study of spatio-temporal
propagation effects in terahertz (THz) generation in gases using two-color
ionizing laser pulses. The observed strong broadening of the THz spectra with
increasing gas pressure reveals the prominent role of spatio-temporal reshaping
and of a plasma-induced blue-shift of the pump pulses in the generation
process. Results obtained from (3+1)-dimensional simulations are in good
agreement with experimental findings and clarify the mechanisms responsible for
THz emission
Strange Quark PDFs and Implications for Drell-Yan Boson Production at the LHC
Global analyses of Parton Distribution Functions (PDFs) have provided
incisive constraints on the up and down quark components of the proton, but
constraining the other flavor degrees of freedom is more challenging.
Higher-order theory predictions and new data sets have contributed to recent
improvements. Despite these efforts, the strange quark PDF has a sizable
uncertainty, particularly in the small x region. We examine the constraints
from experiment and theory, and investigate the impact of this uncertainty on
LHC observables. In particular, we study W/Z production to see how the s-quark
uncertainty propagates to these observables, and examine the extent to which
precise measurements at the LHC can provide additional information on the
proton flavor structure.Comment: 14 pages, 11 figures, added reference
Observations of the Crab Nebula with H.E.S.S. Phase II
The High Energy Stereoscopic System (H.E.S.S.) phase I instrument was an
array of four mirror area Imaging Atmospheric Cherenkov
Telescopes (IACTs) that has very successfully mapped the sky at photon energies
above GeV. Recently, a telescope was added to
the centre of the existing array, which can be operated either in standalone
mode or jointly with the four smaller telescopes. The large telescope lowers
the energy threshold for gamma-ray observations to several tens of GeV, making
the array sensitive at energies where the Fermi-LAT instrument runs out of
statistics. At the same time, the new telescope makes the H.E.S.S. phase II
instrument. This is the first hybrid IACT array, as it operates telescopes of
different size (and hence different trigger rates) and different field of view.
In this contribution we present results of H.E.S.S. phase II observations of
the Crab Nebula, compare them to earlier observations, and evaluate the
performance of the new instrument with Monte Carlo simulations.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherland
Konsekvensvurdering av utslipp av olje fra kabelbrudd i Drøbaksundet, Oslofjord
Årsliste 2008NIVA har vurdert miljøkonsekvensene av utslipp av 4000 l høyraffinert mineralolje fra Statnetts undersjøiske kabel mellom Solberg og Brenntangen i Drøbaksundet. Utslippet skjedde i perioden 17-26 april 2008 og var synlig som tynn oljefilm som spredte seg i flere retninger. Stranding ble observer på østsiden mellom Brenntangen og Emmerstad. Kabeloljen er lite vannløselig, regnes ikke som miljøfarlig, men er lite nedbrytbar og kan muligens bioakkumulere. Toksisitetstester med brukt kabelolje viste lav giftighet og det er liten sannsynlighet for skade på det pelagiske økosystemet. Det var ingen synlig tilgrising av strender og liten sannsynlighet for økologisk skade i strandsonen, men lokale blåskjell viste svake tegn til å ha akkumulert oljerelatert PAH. Det er ingen rapport om skadet sjøfugl. Videre tiltak mot oljesølet og oppfølgende miljøovervåking ansees å være lite nyttig.Statnett S
Kinetic Inductance of Josephson Junction Arrays: Dynamic and Equilibrium Calculations
We show analytically that the inverse kinetic inductance of an
overdamped junction array at low frequencies is proportional to the admittance
of an inhomogeneous equivalent impedance network. The bond in this
equivalent network has an inverse inductance
, where is the Josephson
coupling energy of the bond, is the ground-state phase
of the grain , and is the usual magnetic phase factor. We use this
theorem to calculate for square arrays as large as .
The calculated is in very good agreement with the low-temperature
limit of the helicity modulus calculated by conventional equilibrium
Monte Carlo techniques. However, the finite temperature structure of ,
as a function of magnetic field, is \underline{sharper} than the
zero-temperature , which shows surprisingly weak structure. In
triangular arrays, the equilibrium calculation of yields a series of
peaks at frustrations , where is an integer , consistent with experiment.Comment: 14 pages + 6 postscript figures, 3.0 REVTe
Discovering a junction tree behind a Markov network by a greedy algorithm
In an earlier paper we introduced a special kind of k-width junction tree,
called k-th order t-cherry junction tree in order to approximate a joint
probability distribution. The approximation is the best if the Kullback-Leibler
divergence between the true joint probability distribution and the
approximating one is minimal. Finding the best approximating k-width junction
tree is NP-complete if k>2. In our earlier paper we also proved that the best
approximating k-width junction tree can be embedded into a k-th order t-cherry
junction tree. We introduce a greedy algorithm resulting very good
approximations in reasonable computing time.
In this paper we prove that if the Markov network underlying fullfills some
requirements then our greedy algorithm is able to find the true probability
distribution or its best approximation in the family of the k-th order t-cherry
tree probability distributions. Our algorithm uses just the k-th order marginal
probability distributions as input.
We compare the results of the greedy algorithm proposed in this paper with
the greedy algorithm proposed by Malvestuto in 1991.Comment: The paper was presented at VOCAL 2010 in Veszprem, Hungar
Status and Plans for the Array Control and Data Acquisition System of the Cherenkov Telescope Array
The Cherenkov Telescope Array (CTA) is the next-generation atmospheric
Cherenkov gamma-ray observatory. CTA will consist of two installations, one in
the northern, and the other in the southern hemisphere, containing tens of
telescopes of different sizes. The CTA performance requirements and the
inherent complexity associated with the operation, control and monitoring of
such a large distributed multi-telescope array leads to new challenges in the
field of the gamma-ray astronomy. The ACTL (array control and data acquisition)
system will consist of the hardware and software that is necessary to control
and monitor the CTA arrays, as well as to time-stamp, read-out, filter and
store -at aggregated rates of few GB/s- the scientific data. The ACTL system
must be flexible enough to permit the simultaneous automatic operation of
multiple sub-arrays of telescopes with a minimum personnel effort on site. One
of the challenges of the system is to provide a reliable integration of the
control of a large and heterogeneous set of devices. Moreover, the system is
required to be ready to adapt the observation schedule, on timescales of a few
tens of seconds, to account for changing environmental conditions or to
prioritize incoming scientific alerts from time-critical transient phenomena
such as gamma ray bursts. This contribution provides a summary of the main
design choices and plans for building the ACTL system.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.0589
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