Automatic 3D model creation with velocity-based surface deformations

The virtual worlds of Computer Graphics are populated by geometric objects, called models. Researchers have addressed the problem of synthesizing models automatically. Traditional modeling approaches often require a user to guide the synthesis process and to look after the geometry being synthesized, but user attention is expensive, and reducing user interaction is therefore desirable. I present a scheme for the automatic creation of geometry by deforming surfaces. My scheme includes a novel surface representation; it is an explicit representation consisting of points and edges, but it is not a traditional polygonal mesh. The novel surface representation is paired with a resampling policy to control the surface density and its evolution during deformation. The surface deforms with velocities assigned to its points through a set of deformation operators. Deformation operators avoid the manual computation and assignment of velocities, the operators allow a user to interactively assign velocities with minimal effort. Additionally, Petri nets are used to automatically deform a surface by mimicking a user assigning deformation operators. Furthermore, I present an algorithm to translate from the novel surface representations to a polygonal mesh. I demonstrate the utility of my model generation scheme with a gallery of models created automatically. The scheme's surface representation and resampling policy enables a surface to deform without requiring a user to control the deformation; self-intersections and hole creation are automatically prevented. The generated models show that my scheme is well suited to create organic-like models, whose surfaces have smooth transitions between surface features, but can also produce other kinds of models. My scheme allows a user to automatically generate varied instances of richly detailed models with minimal user interaction

Electrical characterization of nitrogen containing III-V semiconductors

Several nitrogen containing III-V compound semiconductors, together with GaInAs and AlGaAs, were electrically characterized. The main technique used was deep level transient spectroscopy (DLTS), but also current voltage (I-V), capacitance voltage (C-V), isothermal transient spectroscopy (ITS) and Hall measurements were employed. As a contribution to the DLTS technique, the use of inductors in DLTS was theoretically and experimentally researched. A new technique to get the real Schottky series capacitance and resistance is proposed. Its application to AlGaAs is shown. Si-doped GaInAs and GaInNAs with small In and N content, lattice matched to GaAs, grown by molecular beam epitaxy (MBE), were studied by DLTS. Samples were studied after growth and after various thermal treatments. Several deep levels were found, and their properties (activation energy, capture cross section, density) were examined as a function of the annealing treatment. The GaInAs sample showed three deep levels, which are suspected to be related with deep levels M5, EL4 and EL10. The GaInNAs samples with medium and heavy Si-doping were also studied. The medium Si-doped sample showed five deep levels, whose concentrations varied upon annealing temperature. The analysis suggested they are related to EL2, off-centre substitutional oxygen in As sites, clustering of GaNAs and GaInAs, intrinsic to GaAs and high disorder introduced. The heavy Si-doped sample showed one deep level, the concentration of which was reduced with increasing annealing temperature, and it is suspected to also be intrinsic to GaAs. InN grown by metal-organic vapour phase epitaxy (MOVPE) was studied. Growth temperature strongly affects the island size, optical quality and electrical properties of the material. Several metal contacts (Au, Ag, Pt, Pd, Cu, Ni, Ge, Ti, Cr and Al) were tested and studied by I-V. Only Pt and Ge yielded some Schottky contact behavior, but were very unstable. Al contacts annealed at 550 °C for 1 min formed stable rectifying contacts.reviewe

Doping distribution of an operating organic light-emitting diode: a raman map analysis

We present confocal Raman spectroscopy (CSRS) maps of Poly(9,9-dioctylfluorene) (PFO)-based organic light emitting diode under operation. The CSRS analysis of the OLEDs was performed in normal room conditions. The non-emissive spots presented higher Raman intensity and broadening of the vibrational bands in comparison with the luminescent ones. The phenomenon is associated with an increase in the PFO - * absorption band and hence modification of the PFO doping which becomes favorable to the excitation wavelength, thus the Raman spectrum is enhanced. To the authors’ knowledge this image technique had been missed for the OLED technology

Obtention of solar cell parameters, through convergence of iterative cycles. Part 1: Theoretical analysis and cycles proposal

In this Part 1 of this series of articles, two iterative cycles are proposed to accurately determine the shunt resistance ( ), the series resistance ( ), the ideality factor ( ), the light current ( ), and the saturation current ( ) of solar cells, within the one diode model. First, and are obtained linearly fitting , where is a new defined current . Then, and are obtained using Procedure A and B proposed in [2]. Once these four solar cell parameters are obtained, a correction to is deduced and applied. The deduction of these five solar cell parameters is reused to recalculate and the iterative cycles are redone till some convergence criteria is achieved. The accuracy and number of cycles necessary to achieve reasonable results are tested and discussed on ideal (noiseless) current voltage ( ) curves with measured points per voltage of , 21, 51 and 101 . These two cycles are compared with two different common parameter extraction methods. The results given in this Part 1 are used in Part 2 to calculate the five solar cell parameters of curves found in the literature. [Abstract copyright: © 2022 Elsevier Ltd.

Solar cell parameter accuracy improvement, via refinement of the Co-Content function:Part 1: Theoretical analysis

In this Part 1 of this series of articles, the accuracy on the obtention of the shunt resistance (R sh), the series resistance (R s), the ideality factor (n), the light current (I lig), and the saturation current (I sat), via the use of the Co-content function CCV,I= ∫ 0VI-IscdV (where Isc=IV=0 ) is investigated theoretically, as function of the number of measured points per voltage ( PV ) and percentage noise ( pn ). Reasonable values are obtained for R sh, R s, and I lig, with PV = 11 measurement points per V if the pn is 0.1% or less. For a reasonable determination of n at least PV = 101 measurement points per V are needed. I sat determination requires pn of 0.01% or lower with at least PV = 101 measured points per V and should be evaluated at large values of V. The results given in this Part 1 are used in Part 2 to discuss the reported application of the CCV,I to obtain R sh, R s, n, I lig, and I sat found in the literature

Solar cell parameter accuracy improvement, via refinement of the Co-Content function:Part 2: Discussion on the experimental application

In this Part 2 of this series of articles, a discussion of the literature reported obtention of the solar cell parameters (the shunt resistance (R sh ), the series resistance (R s ), the ideality factor (n), the light current (I lig ), and the saturation current (I sat )), via the use of the Co-content function CCV,I= ∫0VI-IscdV (where Isc=I(V=0) ) is given. The results reported in Part 1, namely, the accuracy dependence of the determination of R sh , R s , n, I lig , and I sat , as a function of the number of measured points per voltage ( PV ) and percentage noise ( pn ) is used to analyse the reported solar cell parameters. In one case, the application of CCV,I to solar panels is discussed, revealing that it can also be used in the case of solar panels, and not only for laboratory-made solar cells, in voltage ranges larger than [0 V, 1 V]. In another case, the application of CCV,I to IV curves showing the roll-over effect is discussed. It is found that the roll-over effect has a pernicious effect in the solar parameter extraction, and then the CCV,I should be calculated before the roll-over effect takes place. In a third case, the importance of the correct determination of Isc on the correct calculation of CCV,I is discussed

Reconstrucción tomográfica 3D de descargas eléctricas

120 páginas. Maestría en Ciencias de la Computación.Se expone la investigación y desarrollo de los procesos de computo que se han llevado a cabo para generar un modelo de un objeto de la vida real, este objeto, son las descargas eléctricas, se aborda el problema desde una perspectiva computacional en función de los algoritmos requeridos para el procesamiento de la información y a la reconstrucción tomográfica 3D del modelo de la descarga eléctrica, el modelo se implementa a través del método de las mallas simplex

Obtention of solar cell parameters, through convergence of iterative cycles. Part 2: Application to experimental current-voltage measurements

In this Part 2 of this series of articles, the application of the iterative cycles CycleA and CycleB proposed in Part 1, to determine the solar cell parameters (the shunt resistance (Rsh), the series resistance (Rs), the ideality factor (n), the light current (Ilig), and the saturation current (Isat)) on experimental current voltage (IV) and current density (JV) curves, is given. Several number of measured points per voltage (PV) are attempted, from approximately [Formula presented] to [Formula presented]. In one case, the application of the iterative cycles to IV curves showing the roll-over effect is discussed, while in another case, their application to solar panels is analysed, revealing that the iterative cycles can also be used in the case of solar panels, and not only for laboratory-made solar cells, in voltage ranges larger than [0 V,1 V]. Also, cases in darkness and under illumination are evaluated. In most cases, reasonable values are obtained for Rsh, Rs, n,Isat and Ilig, which simulated properly the IV or JV curves. © 2022 The Autho

Deep levels in GaInNAs grown by molecular beam epitaxy and their concentration reduction with annealing treatment

Deep-level transient Fourier spectroscopy (DLTFS) technique is used to investigate the thermal-annealing behaviour of at least five deep levels in two samples of Ga0.987In0.013N0.0043As0.9957, one medium doped with Si (2 × 1016 cm−3) and the second one heavily doped with Si (1 × 1018 cm−3) grown by molecular beam epitaxy (MBE). The thermal-annealing study was done at 650, 700, 750 and 800 °C for 5 min. One main electron trap with activation energy of 0.97 eV, a capture cross section of 5.5 × 10−11 cm2 and a density of 3.2 × 1014 cm−3 is detected for the medium-doped as-grown sample. For the heavily doped sample one main electron trap with activation energy of 0.35 eV, a capture cross section of 7.1 × 10−14 cm2 and a density of 2.2 × 1015 cm−3 is detected. For the heavily doped sample, this electron trap only decreases its density as the annealing temperature increases. No more deep centres appear with annealing. For the medium-doped sample, the main electron trap decreases its density as the annealing temperature increases, but unlike the heavily doped sample, four more deep centres appear, depending on the annealing temperature. Their annealing temperature dependence and possible origin of the electron traps are reported for the first time