949 research outputs found
Some Considerations on Tunneling Losses in Field-Effect Devices for Low-Voltage Microcontrollers
The loss power density associated with the tunneling current in a typical MOS cell with a
floating gate is evaluated for high electric-field strengths in the oxide layer. Furthermore,
problems related to oxide thickness are discussed
Evaluation of Bonding Orbitals in Amorphous Silicon by Means of the Chemical Pseudopotential Method
The chemical pseudopotential method has been used by a number of workers in order to study the
valence bands of amorphous tetrahedrally bonded semiconductors. However, various problems related
to this method are unsolved. In this paper, a theoretical formulation tending to clarify some of these.
problems is presented.
This formulation concerns bonding orbitals and is valid, in principle, for amorphous silicon
A Discussion on the Phonon Density of States of Amorphous Germanium for the Infrared Range
A theoretical formulation for the phonon density of states of amorphous germanium in
the infrared range is proposed. This formulation is based upon the quasi-harmonic
approximation and is compared with previous results
Selecting background galaxies in weak-lensing analysis of galaxy clusters
In this paper, we present a new method to select the faint, background
galaxies used to derive the mass of galaxy clusters by weak lensing.
The method is based on the simultaneous analysis of the shear signal, that
should be consistent with zero for the foreground, unlensed galaxies, and of
the colors of the galaxies: photometric data from the COSMic evOlution Survey
are used to train the color selection. In order to validate this methodology,
we test it against a set of state-of-the-art image simulations of mock galaxy
clusters in different redshift [] and mass
[] ranges, mimicking medium-deep multicolor
imaging observations (e.g. SUBARU, LBT).
The performance of our method in terms of contamination by unlensed sources
is comparable to a selection based on photometric redshifts, which however
requires a good spectral coverage and is thus much more observationally
demanding. The application of our method to simulations gives an average ratio
between estimated and true masses of . As a further test,
we finally apply our method to real data, and compare our results with other
weak lensing mass estimates in the literature: for this purpose we choose the
cluster Abell 2219 (), for which multi-band (BVRi) data are publicly
available.Comment: MNRAS, Accepted 2016 February 2
High resolution spectroscopic analysis of seven giants in the bulge globular cluster NGC 6723
Globular clusters associated with the Galactic bulge are important tracers of
stellar populations in the inner Galaxy. High resolution analysis of stars in
these clusters allows us to characterize them in terms of kinematics,
metallicity, and individual abundances, and to compare these fingerprints with
those characterizing field populations. We present iron and element ratios for
seven red giant stars in the globular cluster NGC~6723, based on high
resolution spectroscopy. High resolution spectra () of seven K
giants belonging to NGC 6723 were obtained with the FEROS spectrograph at the
MPG/ESO 2.2m telescope. Photospheric parameters were derived from FeI
and FeII transitions. Abundance ratios were obtained from line-to-line spectrum
synthesis calculations on clean selected features. An intermediate metallicity
of [Fe/H] dex and a heliocentric radial velocity of
were found for NGC 6723. Alpha-element
abundances present enhancements of dex,
dex, dex, and
dex. Similar overabundance is found for the iron-peak Ti with
dex. Odd-Z elements Na and Al present abundances of
dex and dex, respectively. Finally,
the s-element Ba is also enhanced by dex. The enhancement
levels of NGC 6723 are comparable to those of other metal-intermediate bulge
globular clusters. In turn, these enhancement levels are compatible with the
abundance profiles displayed by bulge field stars at that metallicity. This
hints at a possible similar chemical evolution with globular clusters and the
metal-poor of the bulge going through an early prompt chemical enrichment
Rigorous luminosity function determination in presence of a background: theory and application to two intermediate redshift clusters
In this paper we present a rigorous derivation of the luminosity function
(LF) in presence of a background. Our approach is free from the logical
contradictions of assigning negative values to positively defined quantities
and avoid the use of incorrect estimates for the 68 % confidence interval
(error bar). It accounts for Poisson fluctuations ignored in previous
approaches and does not requires binning of the data. The method is extensible
to more complex situations, does not require the existence of an
environment--independent LF, and clarifies issues common to field LF
derivations. We apply the method to two clusters of galaxies at intermediate
redshift (z~0.3) with among the deepest and widest K_s observations ever taken.
Finally, we point out short-comings of flip--flopping magnitudes.Comment: MNRAS, in pres
Factors Influencing Lease Revenue and Non-industrial Landowners' Willingness to allow Hunting Access
Despite the fact that earnings associated with selling hunting leases could significantly contribute to landowners' incomes, only a small minority of them allow access on their lands for a fee. Based on a sample survey of Mississippi state landowners, we analyzed landowners' willingness to participate in supplying leases as well as factors influencing lease revenue per fee acre. While landowners' decision to allow hunting access and factors influencing lease revenue per acre were jointly modeled consistent with Heckman's analysis of sample selectivity bias, the hunting lease revenue function was specified in accordance with Rosen's hedonic pricing theory. Empirical results showed landowners' concerns about control over their land, loss of privacy and damage to property, and accident liability insurance reduced their willingness to allow hunting access; and, in contrast, increase in total land holding, race and residential location increased the probability of participation. With regards to factors explaining differences in lease revenue per fee acre, analysis showed that location, expertise in managing fee hunting enterprise, provision of services, and certain wildlife habitats account for systematic variations in lease revenues. These findings have implications for landowners' management of their lands, the design of extension programs, and public agencies engaged in the provision of natural resource based recreation.Marginal lands, Mississippi, Incentive programs, Recreation, Wildlife enterprises, Farm Management, Q510, Q260,
On the Sensitivity of the Tunneling Current to Electric Field in a MOSFET with Two Gates
A theoretical model to evaluate the sensitivity of the tunneling current to the electric field
in an n-channel MOSFET with two gates is proposed. This sensitivity is calculated in a
real situation
Some Results on PIN and ITO Photodiodes
In this paper, various contributions concerning generalized photodiodes and ITO photodiodes are
reported. In particular, calculations related to the bandwidth of the equivalent circuit ot a PIN photodiode
are performed and compared to experimental considerations. In addition, an ITO structure on
a layer n-type GaAs is examined. An ITO-HEMT is also considered
A New Mathematical Model for Cluster Calculation in Tetrahedrally Bonded Amorphous Semiconductors
Tetrahedraily bonded amorphous semiconductors exhibit a structure suitable for applying the so-called
extended Hückel theory (EHT) to determine the electronic density of states by means of the cluster
calculation. In the following, a new mathematical model based on EHT is established. The results
obtained from this model have sufficient accuracy for applications and provide a useful methodology
that combines adequately with the spectrum computations. Density of valence states has been obtained
experimentally with monochromatized X-rays and the theoretical results obtained in this paper are in
good agreement with these experiments
- …