49 research outputs found
Simulation Study of Carbon Vacancy Trapping Effect on Low Power 4H-SiC MOSFET Performance
No full textThe carbon vacancy in 4H-SiC is an important recombination center of the minority carrier and a direct consequence of SiC-based device degradation. In 4H-SiC, this defect acts as the primary carrier-lifetime killer. Whether, low-energy electron radiation exposure or high temperature processing in an inert ambient gas will produce the carbon vacancy defect. Despite, the extensiveness of the studies concerning the defect’s modeling and characterization, numerous essential questions remain. Amongst them, we have the impact of these defects on the performance of 4H-SiC MOSFET. Herein, the influence of intrinsic defect states, namely, Z1/2 and EH6/7 centers, on the 4H-SiC MOSFET electrical outputs is examined via 2D numerical simulation. The obtained results show that the traps act to increase the device on-state resistance (RON), reduce the channel mobility, increase the threshold voltage (Vth). Besides, the increase of the temperature leads to less influence of the traps on the threshold variation. Furthermore, due to their locations in the bandgap, the impact of both Z1/2 and EH6/7 centers at room temperature on the device electrical outputs is extreme. For high temperature the EH6/7 have the severest impact because of the cross section temperature dependency
A 3D extension to cortex like mechanisms for 3D object class recognition
Get PDFWe introduce a novel 3D extension to the hierarchical visual cortex model used for prior work in 2D object recognition. Prior work on the use of the visual cortex standard model for the explicit task of object class recognition has solely concentrated on 2D imagery. In this paper we discuss the explicit 3D extension of each layer in this visual cortex model hierarchy for use in object recognition in 3D volumetric imagery. We apply this extended methodology to the automatic detection of a class of threat items in Computed Tomography (CT) security baggage imagery. The CT imagery suffers from poor resolution and a large number of artefacts generated through the presence of metallic objects. In our examination of recognition performance we make a comparison to a codebook approach derived from a 3D SIFT descriptor and demonstrate that the visual cortex method out-performs in this imagery. Recognition rates in excess of 95% with minimal false positive rates are demonstrated in the detection of a range of threat item
Utilisation de techniques non destructives pour la caractérisation d'isolants utilisés en électrotechnique
No full text66 f. : ill. ; 30 cm. (+ CD-Rom
An experimental survey of metal artefact reduction in computed tomography
Get PDFWe present a survey of techniques for the reduction of streaking artefacts caused by metallic objects in X-ray Computed Tomography (CT) images. A comprehensive review of the existing state-of- the-art Metal Artefact Reduction (MAR) techniques, drawn almost exclusively from the medical CT literature, is supported by an experimental comparison grounded in an evaluation based on a standard scienti c comparison protocol for MAR methods using a software generated medical phan- tom image. This experimental comparison is further extended by considering novel applications of CT imagery consisting of isolated metal objects with no surrounding tissue, as is encountered in typical engineering and security screening CT applications. We nd that the performance of twelve state-of-the-art MAR techniques to be fairly consistent across the two domains and demonstrate the feasibility of a reference-free quantitative performance measure. The literature review and experi- mentation demonstrate several trends. In particular, the major limitations of state-of-the-art MAR techniques are a dependence on prior knowledge, a sensitivity to input parameters and a shortage of comprehensive performance analyses. This study thus extends previous works by: comparing several state-of-the-art MAR techniques; considering both medical and non-medical applications and performing a comprehensive quantitative analysis, taking into account image quality as well as computational requirements
Parameter Identification of Induction Motors using Variable-weighted Cost Function of Genetic Algorithms
No full textCopolymerization of ε-caprolactone with Epichlorohydrin by a Green Catalyst, Maghnite
Get PDFMost of the cationic initiators used in the synthesis of copolymers are expensive. They may be poisoned by products of the reaction or impurities present in the monomer feed, and contain heavy metals, such as chromium, mercury, antimony, etc., that presents environmental disposal problems for the user. Maghnite is a montmorillonite sheet silicate clay that is exchanged with protons to produce Maghnite-H+ (Mag-H+). This non-toxic and cheaper cationic catalyst was used for the copolymerization of ε-caprolactone (CL) with epichlorohydrin (ECH).The effects of the amounts of Mag-H+ and the temperature on the synthesis of poly (ε-caprolactone-co-epichlorohydrin) were studied. Increasing Maghnite-H+ proportion and temperature produced the increase in copolymerization yield. The copolymer obtained was characterized by 1H-NMR and IR spectroscopy. Copyright © 2012 BCREC UNDIP. All rights reserved
H-infinity Robust Controller for Precise Temperature Regulation in an Agricultural Growth Chamber Prototype
Get PDFTemperature regulation is crucial for crop yield optimization in controlled environment agriculture, yet achieving such accuracy is challenging due to system nonlinearities and external disturbances. Since H_(∞ )control is an established theory, its experimental validation on low-cost hardware for agricultural systems remains limited. This paper presents robust control for a nonlinear system, targeting an internal temperature of growth chamber agriculture. Moreover, the primary contribution is the demonstration of a systematic and practical methodology for designing, implementing, and validating an H_(∞ ) controller on an Arduino-based growth chamber prototype, bridging the gap between complex control theory and accessible implementation. A simplified linearized thermal model was derived from a lumped parameter approach using energy balance equations. A second-order weighting function was systematically designed using loop-shaping principles to guarantee robust performance against unmodeled dynamics and sensor noise. The resulting controller was synthesized in MATLAB and deployed on an Arduino Mega microcontroller for experimental testing. Simulations predicted high-precision tracking with a Root Mean Square Error (RMSE) of 0.037 °C and an Integral Absolute Error (IAE) of 0.70. Subsequent experimental validation under real-world conditions confirmed the controller's efficacy, achieving stable temperature regulation within ±2 °C of the set point. The experimental validation yielded an RMSE of 1.04 °C and an IAE of 0.924, highlighting a notable but analyzed performance gap between the idealized simulation and the physical implementation. The results of this work were also compared with MPC and PID controllers, showing the proposed approach demonstrated satisfactory performance and confirming the robustness and stability of the control strategy in practical conditions. This work concludes that the H_(∞ ) framework provides a computationally efficient pathway to achieving robust temperature control on accessible hardware, making advanced control techniques more feasible for distributed agricultural applications
