Papers by Keyword: Analytical Modeling

Abstract: We generalize a recent Si P-i-N reverse-recovery (RR) model to more accurately capture 4H-SiC diode behavior by adding deep-acceptor-limited anode injection, strong recombination (due to >100x shorter optimized high-level lifetimes compared to Si), and improved modeling of the depletion layer dynamics. Closed-form expressions for the growth of the depletion layer are derived, enabling analytical estimates for Q_RR, t_RR, and J_PR. The model is validated against Sentaurus RR simulations of optimized 4H-SiC P-i-N diodes spanning BV = 6–17kV and di/dt = 10 A/µs–10 kA/µs, achieving an average reduction in error of >90% for estimations of key switching performance parameters (Q_RR, t_RR, J_PR). By correctly capturing the dependence of Q_RR on di/dt, the model enables better estimates for the high-level lifetime (τ_HL) directly from the RR waveforms. The differential form enables straightforward utilization of the model to analyze non-idealized RR waveforms. Overall, the generalized model reveals a more favorable Q_RR–V_F trade-off than implied by the unmodified Si model and improves first-order device optimization prior to full design.

Abstract: In the paper the research has been performed to obtain the stress distribution through the thickness of the rolled products along the deformation zone in the conditions of roughing rolling and in the conditions of quasi-stationary temperature distribution during finishing rolling at the Steckel mill. The research has been performed by the simulation based on the Abaqus CAE 6.14-2 software and analytical modeling of the hot rolling process of coils at the Steckel mill with dimensions of 15 mm × 1500 mm, made of steel grade S355JR+AR, according to the requirements of EN 10025-2. The obtained deviations of the rolling force between simulation, analytical modeling and actual data have comparable results and a similar trend of changes through the passes, the average value of which does not exceed 1.54 % and - 1.77 %. The beginning of the continuous layer formation of equivalent stress during roughing rolling has been determined, and, accordingly, the beginning of the deformation penetration through the entire thickness of the semi-rolled product has been also determined that occurs in the pass 6 when reduction equals 14 %.

Abstract: A simple and efficient computational tool modeling the brittle thermal-cracking behavior of a spherical shell encapsulating a round inclusion is presented and compared to existing numerical techniques. Model applications to parametric studies and to particulate composite materials are proposed.

Abstract: A mathematical model, statistically based on the theory of regression and correlation, could provide a viable solution to satisfy the need to predict the time required for the ship maintenance works in dock and / or berth in the shiprepairs shipyards, as part of the ships maintenance program required by the classification societies.

Abstract: In this paper, an analytical model for modified Surrounding Gate Tunnel FET with gate stack engineering and different gate metals has been developed. Further, considering the scaling advantageous of Gate stack engineering and high degree performance of dual material engineering, the both has been integrated into a novel structure known as Surrounding Gate (SG) Tunnel FET with stacked oxide SiO₂/high-k and dual material (DM) has been proposed. The two dimensional (2D) potential at the surface and electric field mathematical models for the DMSG TFET are developed by solving 2D Poisson's equation with matching device boundary conditions. Based on the Kane's formula, mathematical expression for the band-to-band (BTB) tunneling generation rate is derived and then used to calculate the drain current. The impact on the proposed device performance due to the variation of different device parameters has also been studied. It has been found from the presented results that the ON current of the DMSG TFET with stack is 10^-6A, OFF current is 10^-13A and ON/OFF ratio is 10⁷. The mathematical results have been verified using the simulated results obtained from TCAD, a 3-D device simulator from ATLAS.

Abstract: The problem of concrete properties identification and damage location in model beam type constructions is considered on the basis of application of experimental vibration analysis. As a simple analysis model, beam structures are considered defect-free and with defects. Based on the experimental approach, the model vibrations under shock and vibration excitation are analyzed. On the basis of analytical modeling, the dynamic modulus of elasticity, the velocity of sound in the beam, and the location of the defect are calculated. A technique and an example of the location of a defect in beam type constructions are presented.

Abstract: Stress field in the ceramic layer containing multiple transverse cracks is determined using a modified 2-D shear lag approach and a finite element method.

Abstract: Steel Reinforced Grout composites have become a popular technique for strengthening masonry arches and vaults. The SRG composites are Ultra High Tensile Strength Steel unidirectional textiles applied to masonry substrate by mean of inorganic mortar. The weakness of SRG-masonry joints is the debonding at the matrix fibers interface during the stresses transfer process. In the case of arches and vaults the interface bond properties are also affected by the curved geometry of the substrate. In this work, a closed-form analytical solution to the debonding process of a thin plate bonded on a rigid substrate with constant curvature is proposed. The work provides an upgrade of the model previous prosed by the authors (Malena and de Felice 2014). In the present work the substrate curvature is such that the normal stresses arising at the interface are tensile, as in the case of reinforcing systems applied to the intrados of a masonry arch (Malena and de Felice 2014), or compressive as for reinforcing systems applied to the extrados of a masonry arch. The proposed model describes the interfacial stresses transfer mechanism in the framework of fracture mechanics by two laws describing the behavior in normal (pure opening mode: Mode I) and in tangential (in plane shear mode: Mode II) directions. The coupling deriving from curvature is introduced directly in the cohesive laws describing the bond properties. The outcomes of the proposed predictive model are validated by comparing them with the results derived from an experimental campaign of bond tests on straight and curved substrates made of bricks assembled with mortar and strengthened with SRG.

Abstract: In this paper, analytical modelling and performance analysis of novel device structures such as single gate SOI Tunnel Field Effect transistor (SG SOI TFET), Dual-Material Gate TFET (DMG TFET) and Dual Material Double Gate TFET (DMDG TFET) are proposed. The performance of the three devices is studied and compared in terms of surface potential, electric field and drain current. The DMDG TFET shows better performance in suppressing leakage current and enhancing I_ON current than the SG SOI TFET and DMG TFET. The analytical models of the devices are found to be in good agreement with the results obtained using two-dimensional TCAD device simulator.

Abstract: Cassava-leaf-enhanced carbonitriding is a surface hardening procedure that utilizes the high cyanide content that is present in processed cassava leaves to thermochemically diffuse carbon and/or nitrogen into the interstitial sites of steel. This paper presents analytical models for the prediction of carbon and nitrogen concentration profiles, as well as the total case depths associated with the diffusion of carbon and nitrogen during the cassava-leaf-enhanced carbonitriding of low carbon steel. Using Fick's second law of diffusion and approximate initial and boundary conditions, two separate analytical models were presented for intermediate and high temperature cassava-leaf-enhanced carbonitriding processes. The trends in the total case depths are shown to be qualitatively similar to experimental measurements of case depths. The implications of the results are discussed for the surface hardening of steels by carbonitriding processes.