Current-voltage characteristics of carbon nanotube FETS

U ovom radu ispitivane su karakteristike FETova izrađenih na bazi ugljeničnih nanotuba (CNT FETova). U prvom delu rada, predstavljene su neke osnovne osobine ugljeničnih nanotuba. Zatim je razvijen analitički model strujno-naponskih karakteristika CNT FETova koji dobro opisuje ponašanje ove savremene nanoelektronske naprave. Na bazi predloženog modela urađene 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 izrađenih na bazi ugljeničnih nanotuba (CNT FETova). U prvom delu rada, predstavljene su neke osnovne osobine ugljeničnih nanotuba. Zatim je razvijen analitički model strujno-naponskih karakteristika CNT FETova koji dobro opisuje ponašanje ove savremene nanoelektronske naprave. Na bazi predloženog modela urađene 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-$b$ cutoff in the $b$-$N_{\text{HI}}$ set by the thermal state of intergalactic medium (IGM). We fit this cutoff as a function of redshift over the range $2.0\leq z \leq 3.4$, which allows us to measure the evolution of the IGM temperature-density ($T= T_0 (\rho/ \rho_0)^{\gamma-1}$) relation parameters $T_0$ and $\gamma$. We calibrate our measurements against Ly$\alpha$ 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 $T_0$ shows a suggestive peak at $z=2.8$, while our evolution of $\gamma$ is consistent with $\gamma\simeq 1.4$ and disfavors inverted temperature-density relations. Our measured evolution of $T_0$ and $\gamma$ are generally in good agreement with previous determinations in the literature. Both the peak in the evolution of $T_0$ at $z = 2.8$, as well as the high temperatures $T_0\simeq 15000-20000\,$K that we observe at $2.4 < z < 3.4$, 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 $t_\mathrm{age}$ and obscured sky fractions $\Omega_\mathrm{obsc}$ 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 $t_\mathrm{age}$ and $\Omega_\mathrm{obsc}$ 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 $(22\,\mathrm{Myr})$ and unobscured $\Omega_\mathrm{obsc}<35\%$, whereas three others are either younger than $(10\,\mathrm{Myr})$ or highly obscured $(\Omega_\mathrm{obsc}>70\%)$.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 tehnoloških 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 rješenja 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 tehnološkim 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 – 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 omogućila je značajne rezultate u području integracije različitih CAx sustava kao što su CAD, CAM, CAE i drugi programski sustavi. Da bi se uspješno povezali sustavi automatiziranog projektiranja proizvoda, odnosno CAD sustavi i sustavi automatizirane proizvodnje, odnosno CAM sustavi, potrebna je automatizacija projektiranja tehnološkog procesa izrade, dakle CAPP sustavi, koji predstavljaju most između 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