3D Coupling Effect Research Articles

Comparison of Two-Dimensional and Three- Dimensional Responses for Vortex-Induced Vibrations of a Rectangular Prism

The accurate prediction of the amplitudes of vortex-induced vibrations (VIV) is important in wind-resistant design. Wind tunnel tests of scaled section models have been commonly used. However, the amplitude prediction processes were usually inaccurate because of insufficient evaluations of three-dimensional (3D) effects. This study presents experimental measurements of VIV responses in a prototype rectangular prism and its 1:1 two-dimensional section model in smooth flow. The results show that the section model vibrates with the same Reynolds number, equivalent mass, frequency, and damping ratio as those of the prototype prism without scale effects. The VIV amplitudes can be qualitatively and quantitatively measured and analyzed. The measured VIV lock-ins of these two models agree with each other. However, the prototype prism produces a 20% higher maximum amplitude than the section model. Several classical VIV mathematical models are used to validate the wind tunnel test results. This confirms that the 3D coupling effects of the modal shape and the imperfect correlations of excitation forces positively contribute to the maximum amplitude. Based on the section model outcomes, the amplified factor of 1.2 is found to be appropriate for the amplitude prediction of VIV for the present prism, and it can also provide a reference for other structures.

Enhanced coupling effects in vertical double-gate FinFETs

Vertical double-gate (DG) FinFETs fabricated on SOI wafers show good gate control, reasonable threshold voltage and high carrier mobility despite the absence of the top-gate. The 3D coupling effect between the two lateral-gates and the back-gate is investigated based on experimental and simulation results. We compare DG and triple-gate FinFETs with various fin widths. Front-channel characteristics are easily tuned by applied bias at the back-gate if the fin is not too narrow. We highlight that vertical DG FinFET is more appropriate device for dynamic threshold voltage adjustment than triple-gate FinFET. An analytical model is proposed to quantify the coupling effect in DG FinFET by solving 2D Poisson equation. The body potential profile and coupling effect are modeled. A very good agreement is obtained between experiments, 3D simulations and the proposed model.

Remote carrier trapping in FinFETs with ONO buried layer: Temperature effects

The charge trapping mechanisms are studied at room and high temperature in advanced SOI FinFETs fabricated on SiO2–Si3N4–SiO2 (ONO) multi-layer buried insulator (BOX). By applying appropriate back-gate and/or drain bias, the buried nitride layer can trap charges. The coupling mechanism between front and back interfaces enables the front-channel drain current to reflect the presence or absence of trapped/injected charges in the BOX. In this work, the charge trapping/detrapping is induced by a constant drain or back-gate bias or during the scanning of the back-gate voltage. According to the polarity of the trapped charges and their location along the channel, various current levels are observed leading to a memory effect. In order to clarify the charge trapping and coupling mechanisms, the temperature of operation was used as additional experimental parameter. The amount of trapped charges depends not only on the bias conditions but also on temperature and fin geometry. We discuss the 3D coupling effects between the channel and the remote trapped charges.

Performance of a non-tapered 3D morphing wing with integrated compliant ribs

Morphing wings have a high potential for improving the performance and reducing the fuel consumption of modern aircraft. Thanks to its simplicity, the compliant belt-rib concept is regarded by the authors as a promising solution. Using the compliant rib designed by Hasse and Campanile as a starting point, a compliant morphing wing made of composite materials is designed. Innovative methods for optimal placing of the actuation and for the quantification of the morphing are used. The performance of the compliant morphing wing in terms of three-dimensional (3D) structural behaviour and aerodynamic properties, both two- and three-dimensional, is presented and discussed. The fundamental importance of considering 3D coupling effects in the determination of the performance of morphing aerofoils is shown.

Free Vibration of Three-Dimensional Orthotropic Uniform Shear Beam-Columns with Generalized End Conditions

The free vibration analysis of asymmetrical three-dimensional (3D) uniform shear beam-columns with generalized boundary conditions (semirigid flexural and torsional restraints, lateral bracings, and lumped masses at both ends) subjected to an eccentric end axial load in addition to a linearly distributed eccentric axial load along its span is presented in a classic manner. The five coupled governing equations of dynamic equilibrium (i.e., two shear equations, two bending moment equations, and the pure torsion moment equation) are sufficient to determine the natural frequencies and modal shapes. The proposed model which is an extension of a 2D model presented previously by the writer includes the simultaneous 3D coupling effects among the lateral deflections, deformations of the cross section along the member (shear, torsional and rotational), the translational, rotational and torsional inertias of all masses considered, an eccentric end axial load in addition to a linearly distributed axial load along its span, and the end restraints. Deformations caused by shear forces and pure torsion are considered. The effects of axial deformations, warping torsion and torsional stability are not included. The proposed model shows that the dynamic behavior of 3D shear beam-columns is highly sensitive to the coupling effects just mentioned, particularly in members with both ends free to rotate. Analytical results indicate that except for doubly symmetric members with concentric axial loads and with perfectly clamped ends, the natural frequencies and modal shapes of 3D shear beam-columns are determined from the eigenvalues of a full 8×8 matrix, rather than from the uncoupled equations of transverse (or shear-wave equations) and torsional moment equilibrium. Two comprehensive examples are presented that show the effectiveness of the proposed method.

Special size effects in advanced single-gate and multiple-gate SOI transistors

State-of-the-art SOI transistors require a very small body. This paper examines the effects of body thinning and thin-gate oxide in SOI MOSFETs on their electrical characteristics. In particular, the influence of film thickness on the interface coupling and carrier mobility is discussed. Due to coupling, the separation between the front and back channels is difficult in ultra-thin SOI MOSFETs. The implementation of the front-gate split C-V method and its limitations for determining the front- and back-channel mobility are described. The mobility in the front channel is smaller than that in the back channel due to additional Coulomb scattering. We also discuss the 3D coupling effects that occur in FinFETs with triple-gate and omega-gate configurations. In low-doped or tall fins the corner effect is suppressed. Narrow devices are virtually immune to substrate effects due to a strong lateral coupling between the two lateral sides of the gate. Short-channel effects are drastically reduced when the lateral coupling screens the drain influence.