538 research outputs found
Current-voltage characteristics of carbon nanotube FETS
U ovom radu ispitivane su karakteristike FETova izraÄenih na bazi ugljeniÄnih nanotuba (CNT FETova). U prvom delu rada, predstavljene su neke osnovne osobine ugljeniÄnih nanotuba. Zatim je razvijen analitiÄki model strujno-naponskih karakteristika CNT FETova koji dobro opisuje ponaÅ”anje ove savremene nanoelektronske naprave. Na bazi predloženog modela uraÄene su simulacije. Dobijeni rezultati su u saglasnosti sa prethodno publikovanim. .In this paper, one of the most actual devices - carbon nanotube field effect transistor (CNT FET) is investigated. At the beginning, the nanotube properties are presented. The main contribution of this paper is the new analytical model of CNT FET current-voltage characteristics. Developed model describes behavior of CNT FET in very good manner and, at the same time, the model is relatively simple. Using the developed model, simulations were performed. The results obtained by using proposed model are in very good agreement with already known and published ones.
Current-voltage characteristics of carbon nanotube FETS
U ovom radu ispitivane su karakteristike FETova izraÄenih na bazi ugljeniÄnih nanotuba (CNT FETova). U prvom delu rada, predstavljene su neke osnovne osobine ugljeniÄnih nanotuba. Zatim je razvijen analitiÄki model strujno-naponskih karakteristika CNT FETova koji dobro opisuje ponaÅ”anje ove savremene nanoelektronske naprave. Na bazi predloženog modela uraÄene su simulacije. Dobijeni rezultati su u saglasnosti sa prethodno publikovanim. .In this paper, one of the most actual devices - carbon nanotube field effect transistor (CNT FET) is investigated. At the beginning, the nanotube properties are presented. The main contribution of this paper is the new analytical model of CNT FET current-voltage characteristics. Developed model describes behavior of CNT FET in very good manner and, at the same time, the model is relatively simple. Using the developed model, simulations were performed. The results obtained by using proposed model are in very good agreement with already known and published ones.
A New Measurement of the Temperature Density Relation of the IGM From Voigt Profile Fitting
We decompose the Lyman-{\alpha} (Ly{\alpha}) forest of an extensive sample of
74 high signal-to-noise ratio and high-resolution quasar spectra into a
collection of Voigt profiles. Absorbers located near caustics in the peculiar
velocity field have the smallest Doppler parameters, resulting in a low-
cutoff in the - set by the thermal state of intergalactic
medium (IGM). We fit this cutoff as a function of redshift over the range
, which allows us to measure the evolution of the IGM
temperature-density () relation parameters
and . We calibrate our measurements against Ly forest
simulations, using 21 different thermal models of the IGM at each redshift,
also allowing for different values of the IGM pressure smoothing scale. We
adopt a forward-modeling approach and self-consistently apply the same
algorithms to both data and simulations, propagating both statistical and
modeling uncertainties via Monte Carlo. The redshift evolution of shows a
suggestive peak at , while our evolution of is consistent with
and disfavors inverted temperature-density relations. Our
measured evolution of and are generally in good agreement with
previous determinations in the literature. Both the peak in the evolution of
at , as well as the high temperatures K
that we observe at , strongly suggest that a significant episode
of heating occurred after the end of HI reionization, which was most likely the
cosmic reionization of HeII.Comment: Accepted for publication in ApJ, 23 pages, 26 figures, machine
readable tables available onlin
Modeling the HeII Transverse Proximity Effect: Constraints on Quasar Lifetime and Obscuration
The HeII transverse proximity effect - enhanced HeII Ly{\alpha} transmission
in a background sightline caused by the ionizing radiation of a foreground
quasar - offers a unique opportunity to probe the emission properties of
quasars, in particular the emission geometry (obscuration, beaming) and the
quasar lifetime. Building on the foreground quasar survey published in
Schmidt+2017, we present a detailed model of the HeII transverse proximity
effect, specifically designed to include light travel time effects, finite
quasar ages, and quasar obscuration. We post-process outputs from a
cosmological hydrodynamical simulation with a fluctuating HeII UV background
model, plus the added effect of the radiation from a single bright foreground
quasar. We vary the age and obscured sky fractions
of the foreground quasar, and explore the resulting
effect on the HeII transverse proximity effect signal. Fluctuations in IGM
density and the UV background, as well as the unknown orientation of the
foreground quasar, result in a large variance of the HeII Ly{\alpha}
transmission along the background sightline. We develop a fully Bayesian
statistical formalism to compare far UV HeII Ly{\alpha} transmission spectra of
the background quasars to our models, and extract joint constraints on
and for the six Schmidt+2017 foreground
quasars with the highest implied HeII photoionization rates. Our analysis
suggests a bimodal distribution of quasar emission properties, whereby one
foreground quasar, associated with a strong HeII transmission spike, is
relatively old and unobscured ,
whereas three others are either younger than or highly
obscured .Comment: 19 pages, 6 figures, submitted to Ap
Examining subgrid models of supermassive black holes in cosmological simulation
While supermassive black holes (SMBHs) play an important role in galaxy and
cluster evolution, at present they can only be included in large-scale
cosmological simulation via subgrid techniques. However, these subgrid models
have not been studied in a systematic fashion. Using a newly-developed fast,
parallel spherical overdensity halo finder built into the simulation code
FLASH, we perform a suite of dark matter-only cosmological simulations to study
the effects of subgrid model choice on relations between SMBH mass and dark
matter halo mass and velocity dispersion. We examine three aspects of SMBH
subgrid models: the choice of initial black hole seed mass, the test for
merging two black holes, and the frequency of applying the subgrid model. We
also examine the role that merging can play in determining the relations,
ignoring the complicating effects of SMBH-driven accretion and feedback. We
find that the choice of subgrid model can dramatically affect the black hole
merger rate, the cosmic SMBH mass density, and the low-redshift relations to
halo properties. We also find that it is possible to reproduce observations of
the low-redshift relations without accretion and feedback, depending on the
choice of subgrid model.Comment: 12 pages, 12 figures, revised from referee comments, accepted by Ap
Techno-economic method for evaluation and selection of flexible manufacturing systems (FMS)
To find best FMS solutions, experts use numerous multicriteria methods for evaluation and ranking, methods based on artificial intelligence, and multicriteria optimization methods. Presented in this paper is a developed technoeconomic method for evaluation and selection of FMS based on productivity. The method is based on group technology (GT) process planning
Design and economic justification of group blanks application
Within the manufacturing process planning, blanks are either selected or designed, respectively forms of input material for the manufacture of products. Reviewed in this paper are three types of group blanks: group castings, group forgings manufactured by closed die forging and free forging, and group blanks manufactured by pressing melted metal in casts. The paper also presents requisites for design and evaluation of economic justification of group blanks application
Tehnoekonomska metoda za ocjenu i izbor fleksibilnih tehnoloŔkih sustava (FTS)
To find best FMS solutions, experts use numerous multicriteria methods for evaluation and ranking, methods based on artificial intelligence, and multicriteria optimization methods. Presented in this paper is a developed technoeconomic method for evaluation and selection of FMS based on productivity. The method is based on group technology (GT) process planning.Za izbor najpovoljnijih rjeŔenja FTS koriste se brojne multikriterijske ekspertske metode vrijednovanja i rangiranja, metode ustrojene na primjeni umjetne inteligencije, kao i metode multikriterijske optimizacije. U ovom radu prikazuje se razvijena tehnoekonomska metoda za ocjenu i izbor FTS na temelju proizvodnosti. Metoda je utemeljena na tehnoloŔkim osnovama koje se obrazuju na principima grupne tehnologije (GT)
Modeliranje odljevaka u RPPP sustavu za dijelove klipno-cilindarskog sklopa motora sa unutarnjim sagorjeva njem
Development of information technology industry provided great possibilities in the area of integration of different CAx systems, such as CAD, CAM, CAE and others. In order to successfully link systems of automated-design (or Computer Aided Design - CAD) with automated manufacturing systems (or Computer Aided Manufacturing ā CAM), automation of manufacturing process planning is needed, i.e. CAPP (Computer-Aided Process Planning) systems can bridge a gap between design and manufacturing. In this paper is shown design of casting blanks in CAPP system for parts of piston-cylinder assembly of internal combustion engines in a manufacturing system.Dostignuta razina razvoja informacijskih tehnologija omoguÄila je znaÄajne rezultate u podruÄju integracije razliÄitih CAx sustava kao Å”to su CAD, CAM, CAE i drugi programski sustavi. Da bi se uspjeÅ”no povezali sustavi automatiziranog projektiranja proizvoda, odnosno CAD sustavi i sustavi automatizirane proizvodnje, odnosno CAM sustavi, potrebna je automatizacija projektiranja tehnoloÅ”kog procesa izrade, dakle CAPP sustavi, koji predstavljaju most izmeÄu projektiranja i proizvodnje. U ovom radu se prikazuje modeliranje odljevaka u integriranom CAPP sustavu za dijelove klipno-cilindarskog sklopa motora sa unutarnjim sagorjevanjem u jednom proizvodnom sustavu
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