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showing 10 items of 2078 documents
Multilayer (Al,Ga)N Structures for Solar-Blind Detection
2004
We report on solar-blind metal-semiconductor-metal (MSM) detectors fabricated on stacks of (Al,Ga)N layers with different Al mole fraction. These structures were grown by molecular beam epitaxy on sapphire substrates to allow backside illumination and a low-temperature GaN buffer layer. They consist of a 0.3-0.4-/spl mu/m active layer grown on a thick (Al,Ga)N window layer (/spl ap/1 /spl mu/m) that is transparent at the wavelength of interest. Different Al contents were used in the window layer. We observed that, in general, samples with a high Al content were cracked, which is explained in terms of mechanical strain. MSM photodetectors fabricated on these samples showed large leakage curr…
Multi-gigahertz repetition-rate-selectable passive harmonic mode locking of a fiber laser
2013
We demonstrate a passive harmonically mode-locked erbium-doped fiber laser that operates at selectable harmonics spanning from the 6th to the 928th, which corresponds to repetition rates ranging from 153 MHz to 22.2 GHz. The noteworthy laser output stability is attested by supermode suppression levels as large as 41 dB. The influence of a continuous wave background on harmonics stability is tested.
Calibration of a thermoluminescent dosimeter worn over lead aprons in fluoroscopy guided procedures
2018
Fluoroscopy guided interventional procedures provide remarkable benefits to patients. However, medical staff working near the scattered radiation field may be exposed to high cumulative equivalent doses, thus requiring shielding devices such as lead aprons and thyroid collars. In this situation, it remains an acceptable practice to derive equivalent doses to the eye lenses or other unprotected soft tissues with a dosimeter placed above these protective devices. Nevertheless, the radiation backscattered by the lead shield differs from that generated during dosimeter calibration with a water phantom. In this study, a passive personal thermoluminescent dosimeter (TLD) was modelled by means of …
Gamma-ray irradiation tests of CMOS sensors used in imaging techniques
2014
Technologically-enhanced electronic image sensors are used in various fields as diagnostic techniques in medicine or space applications. In the latter case the devices can be exposed to intense radiation fluxes over time which may impair the functioning of the same equipment. In this paper we report the results of gamma-ray irradiation tests on CMOS image sensors simulating the space radiation over a long time period. Gamma-ray irradiation tests were car ried out by means of IGS-3 gamma irradiation facility of Palermo Uni ver sity, based on 60Co sources with dif fer ent ac tiv i ties. To re duce the dose rate and re al ize a nar row gamma-ray beam, a lead-collimation sys tem was pur posely …
Variation of lattice constant and cluster formation in GaAsBi
2013
We investigate the structural properties of GaAsBi layers grown by molecular beam epitaxy on GaAs at substrate temperatures between 220–315 C. Irrespective of the growth temperature, the structures exhibited similar Bi compositions, and good overall crystal quality as deduced from X-Ray diffraction measurements. After thermal annealing at temperatures as low as 500 C, the GaAsBi layers grown at the lowest temperatures exhibited a significant reduction of the lattice constant. The lattice variation was significantly larger for Bi-containing samples than for Bi-free low-temperature GaAs samples grown as a reference. Rutherford backscattering spectrometry gave no evidence of Bi diffusing out o…
Nucleation and growth of ZnO on PMMA by low-temperature atomic layer deposition
2015
ZnO films were grown by atomic layer deposition at 35 °C on poly(methyl methacrylate) substrates using diethylzinc and water precursors. The film growth, morphology, and crystallinity were studied using Rutherford backscattering spectrometry, time-of-flight elastic recoil detection analysis, atomic force microscopy, scanning electron microscopy, and x-ray diffraction. The uniform film growth was reached after several hundreds of deposition cycles, preceded by the precursor penetration into the porous bulk and island-type growth. After the full surface coverage, the ZnO films were stoichiometric, and consisted of large grains (diameter 30 nm) with a film surface roughness up to 6 nm (RMS). T…
Changes in trunk posture and muscle responses in standing during pregnancy and postpartum
2018
Este artículo se encuentra disponible en la página web de la revista en la siguiente URL: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0194853 The aim of this study was to analyze the position of the lumbopelvic region and the muscle activation of erector spinae and biceps femoris muscles in a group of pregnant women in the third trimester. The hypothesis was that pregnancy-related biomechanical and morphological changes modify the position of the lumbopelvic region and the activation of extensor muscles. The position of the lumbar spine and pelvis in the sagittal plane, and the EMG activity of the erector spinae and biceps femoris muscles, were recorded during standing…
DEGENERATE MATRIX METHOD FOR SOLVING NONLINEAR SYSTEMS OF DIFFERENTIAL EQUATIONS
1998
Degenerate matrix method for numerical solving nonlinear systems of ordinary differential equations is considered. The method is based on an application of special degenerate matrix and usual iteration procedure. The method, which is connected with an implicit Runge‐Kutta method, can be simply realized on computers. An estimation for the error of the method is given. First Published Online: 14 Oct 2010
Robust reliable control of uncertain discrete impulsive switched systems with state delays
2013
Published version of an article in the journal: Mathematical Problems in Engineering. Also available from the publisher at: http://dx.doi.org/10.1155/2013/197819 Open access This paper is concerned with the problem of robust reliable control for a class of uncertain discrete impulsive switched systems with state delays, where the actuators are subjected to failures. The parameter uncertainties are assumed to be norm-bounded, and the average dwell time approach is utilized for the stability analysis and controller design. Firstly, an exponential stability criterion is established in terms of linear matrix inequalities (LMIs). Then, a state feedback controller is constructed for the underlyin…
Partial joint processing with efficient backhauling using particle swarm optimization
2012
In cellular communication systems with frequency reuse factor of one, user terminals (UT) at the cell-edge are prone to intercell interference. Joint processing is one of the coordinated multipoint transmission techniques proposed to mitigate this interference. In the case of centralized joint processing, the channel state information fed back by the users need to be available at the central coordination node for precoding. The precoding weights (with the user data) need to be available at the corresponding base stations to serve the UTs. These increase the backhaul traffic. In this article, partial joint processing (PJP) is considered as a general framework that allows reducing the amount …