1,518 research outputs found
Evaluation of historic, current and future water demand in the Olifants River Catchment, South Africa
Poverty / Mapping
Maximum population transfer in a periodically driven two-level system
We study the dynamics of a two-level quantum system under the influence of
sinusoidal driving in the intermediate frequency regime. Analyzing the Floquet
quasienergy spectrum, we find combinations of the field parameters for which
population transfer is optimal and takes place through a series of well defined
steps of fixed duration. We also show how the corresponding evolution operator
can be approximated at all times by a very simple analytical expression. We
propose this model as being specially suitable for treating periodic driving at
avoided crossings found in complex multi-level systems, and thus show a
relevant application of our results to designing a control protocol in a
realistic molecular modelComment: 7 pages, 6 figure
The Poincare-Birkhoff theorem in Quantum Mechanics
Quantum manifestations of the dynamics around resonant tori in perturbed
Hamiltonian systems, dictated by the Poincar\'e--Birkhoff theorem, are shown to
exist. They are embedded in the interactions involving states which differ in a
number of quanta equal to the order of the classical resonance. Moreover, the
associated classical phase space structures are mimicked in the
quasiprobability density functions and their zeros.Comment: 5 pages, 3 figures, Full resolution figures available at
http://www.df.uba.ar/users/wisniaki/publications.htm
Whale-watch vessel noise levels with applications to whale-watching guidelines and conservation
The number and size of whale-watching and swim-with-cetacean vessels are increasing worldwide, but the noise impact on targeted species depends on vessel source characteristics, which remain largely unquantified. Here, we report the acoustic characteristics from 13 whale-watching vessels from Australia and Canary Islands. Acoustic recorders were deployed to measure the frequency-weighted sound levels (for low [LF], mid [MF] and high frequency [HF] cetacean hearing types) of motor sailing, catamarans, and motor vessels operating at 4–8 kn representing the slow speed of whale-watch scenarios. The highest estimated source levels (SLs) were recorded from large catamarans with inboard engines (LF = 160 ± 3, MF = 148 ± 2, HF = 146 ± 2 dB re 1 µPa m). The lowest SLs were from smaller motor vessels and particularly by a hybrid vessel powered by electrical outboard engines (LF = 140 ± 3, MF = 136 ± 2, HF = 134 ± 2 dB re 1 µPa m). We demonstrate that at the same speed and distance, different vessels may produce very different received levels to the animals. To reduce disturbance to cetaceans we recommend tourism vessels meet a broadband (0.2–10 kHz) SL limit of <150 dB re 1 µPa (RMS) when within 500 m of cetaceans
Earth Occultation Imaging of the Low Energy Gamma-Ray Sky with GBM
The Earth Occultation Technique (EOT) has been applied to Fermi's Gamma-ray
Burst Monitor (GBM) to perform all-sky monitoring for a predetermined catalog
of hard X-ray/soft gamma-ray sources. In order to search for sources not in the
catalog, thus completing the catalog and reducing a source of systematic error
in EOT, an imaging method has been developed -- Imaging with a Differential
filter using the Earth Occultation Method (IDEOM). IDEOM is a tomographic
imaging method that takes advantage of the orbital precession of the Fermi
satellite. Using IDEOM, all-sky reconstructions have been generated for ~sim 4
years of GBM data in the 12-50 keV, 50-100 keV and 100-300 keV energy bands in
search of sources otherwise unmodeled by the GBM occultation analysis. IDEOM
analysis resulted in the detection of 57 sources in the 12-50 keV energy band,
23 sources in the 50-100 keV energy band, and 7 sources in the 100-300 keV
energy band. Seventeen sources were not present in the original GBM-EOT catalog
and have now been added. We also present the first joined averaged spectra for
four persistent sources detected by GBM using EOT and by the Large Area
Telescope (LAT) on Fermi: NGC 1275, 3C 273, Cen A, and the Crab
The development of a resource-efficient photovoltaic system
This paper presents the measures taken in the demonstration of the photovoltaic case study developed within the European project ‘Towards zero waste in industrial networks’ (Zerowin), integrating the D4R (Design for recycling, repair, refurbishment and reuse) criteria at both system and industrial network level. The demonstration is divided into three phases. The first phase concerns the development of a D4R photovoltaic concept, the second phase focused on the development of a specific component of photovoltaic systems and the third phase was the demonstration of the D4R design in two complete photovoltaic systems (grid-connected and stand-alone). This paper includes a description of the installed photovoltaic systems, including a brief summary at component level of the lithium ion battery system and the D4R power conditioning system developed for the pilot installations. Additionally, industrial symbioses within the network associated with the photovoltaic systems and the production model for the network are described
A feature-rich transmission spectrum for WASP-127b
WASP-127b is one of the lowest density planets discovered to date. With a
sub-Saturn mass () and super-Jupiter radius
(), it orbits a bright G5 star, which is about to
leave the main-sequence. We aim to explore WASP-127b's atmosphere in order to
retrieve its main atmospheric components, and to find hints for its intriguing
inflation and evolutionary history. We used the ALFOSC spectrograph at the NOT
telescope to observe a low resolution (, seeing limited) long-slit
spectroscopic time series during a planetary transit, and present here the
first transmission spectrum for WASP-127b. We find the presence of a strong
Rayleigh slope at blue wavelengths and a hint of Na absorption, although the
quality of the data does not allow us to claim a detection. At redder
wavelengths the absorption features of TiO and VO are the best explanation to
fit the data. Although higher signal-to-noise ratio observations are needed to
conclusively confirm the absorption features, WASP-127b seems to posses a
cloud-free atmosphere and is one of the best targets to perform further
characterization studies in the near future.Comment: Accepted for Publication A&A Letters, May 22nd, 201
A 0535+26: an X-ray/Optical Tour
We compiled X-ray and Optical observations of the accreting X-ray binary
system A 0535+262 since its discovery in 1975, that will allow us to shed light
on the unpredictable behavior of this binary system. We present the data in
terms of the Be-disk interaction with the neutron star companion. In addition,
we show recent results from the continuous monitoring of this source by the
Gamma-ray Burst Monitor(GBM), on board the Fermi observatory, since its launch
in 2008 June 11.Comment: 4 pages, 5 figures, Conference proceeding of "Astrophysics of Neutron
Stars 2010 - a conference in honor of M. Ali Alpar", 2-6 August 2010, Cesme,
Izmir, Turke
Study on the vibration characteristics of the telescope T80 in the Javalambre astrophysical observatory (JAO) aimed at detecting invalid images
The location of large telescopes, generally far from the data processing centers, represents a logistical problem for the supervision of the capture of images. In this work, we carried out a preliminary study of the vibration signature of the T80 telescope at the Javalambre Astrophysical Observatory (JAO). The study analyzed the process of calculating the displacement that occurs because of the vibration in each of the frequencies in the range of interest. We analyzed the problems associated with very low frequencies by means of simulation, finding the most critical vibrations below 20 Hz, since they are the ones that generate greater displacements. The work also relates previous studies based on simulation with the real measurements of the vibration of the telescope taken remotely when it is subjected to different positioning movements (right ascension and/or declination) or when it performs movement actions such as those related to filter trays or mirror cover. The obtained results allow us to design a remote alarm system to detect invalid images (taken with excess vibration)
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