• Nuclear Engineering and Technology
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• 제39권1호
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• pp.75-84
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• 2007

This paper presents a closed-form model for evaluating the restraint effect of pressure induced bending on the opening of a circumferential through-wall crack, which is considered plastic deformation behavior. Three-dimensional finite element analyses with different crack lengths, restraint conditions, pipe geometries, magnitudes of internal pressure, and tensile properties were used to investigate the influence of each parameter on the pressure-induced bending restraint on the crack opening displacement. From these investigations, an analytical model based on elastic-perfectly plastic material was developed in terms of the crack length, symmetric restraint length, mean radius to thickness ratio, axial stress corresponding to the internal pressure, and normalized crack opening displacement evaluated from a linear-elastic crack opening condition. Finite element analyses results demonstrate that the proposed analytical model reliably estimated the restraint effect of pressure-induced bending on the plastic crack opening of a circumferential through-wall crack and properly reflected the dependence on each parameter within the range over which the analytical expression was derived.

• Journal of Magnetics
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• 제17권1호
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• pp.19-26
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• 2012

This paper deals with the performance analysis and estimation of the electrical parameters of a permanent magnet synchronous generator (PMSG) for hydrokinetic energy conversion applications using vortex induced vibration (VIV). The analytical solutions for the magnetic fields produced by permanent magnets (PMs) and stator winding currents are obtained using a 2D polar coordinate system and a magnetic vector potential. An analytical expression for the 2D permeance is also derived, which takes into account stator skew effects. Based on these magnetic field solutions and the 2D permeance function, electrical circuit parameters such as the backemf constant and the air-gap inductance are obtained analytically. The performances of the PMSG are investigated using the estimated electrical circuit parameters and an equivalent circuit (EC). All analytical results are validated extensively using 2D finite element (FE) analyses. Experimental measurements for parameters such as the back-emf and inductance are also presented to confirm the analyses.

• JSTS:Journal of Semiconductor Technology and Science
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• 제4권1호
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• pp.63-73
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• 2004

A simple analytical model has been presented for the study of the optical bistability using a $GaAs-Al_{0.32}Ga_{0.68}As$ multiple quantum well (MQW) p-i-n diode structure. The calculation of the optical absorption is based on a semi-emperical model which is accurately valid for a range of wells between 5 and 20 nm and the electric field F< 200kV/cm . The electric field dependent analytical expression for the responsivity is presented. An attempt has been made to derive the analytical relationship between the incident optical power ( $(P_{in})$ ) and the voltage V across the device when the diode is reverse biased by a power supply in series with a load resistor. The relationship between $P_{in}$ and $P_{out}$ (i.e. transmitted optical power) is also presented. Numerical results are presented for a typical case of well size $L_Z=10.5nm,\;barrier\;size\;L_B=9.5nm$ optical wave length l = 851.7nm and electric field F? 100kV/cm. It has been shown that for the values of $P_{in}$ within certain range, the device changes its state in such a way that corresponding to every value of $P_{in}$ , two stable states and one unstable state of V as well as of $P_{out}$ are obtained which shows the optically controlled bistable nature of the device.

• 비파괴검사학회지
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• 제31권6호
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• pp.609-615
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• 2011

Excitation and propagation of electromagnetic field of a cylindrical coil above an arbitrary number of conductive plates for pulsed eddy current testing(PECT) are very complex problems due to their complicated physical properties. In this paper, analytical modeling of PECT is established by Fourier series based on truncated region eigenfunction expansion(TREE) method for a single air-cored coil above stratified conductive structures(SCS) to investigate their integrity. From the presented expression of PECT, the coil impedance due to SCS is calculated based on analytical approach using the generalized reflection coefficient in series form. Then the multilayered structures manufactured by non-ferromagnetic (STS301L) and ferromagnetic materials (SS400) are investigated by the developed PECT model. Good prediction of analytical model of PECT not only contributes to the development of an efficient solver but also can be applied to optimize the conditions of experimental setup in PECT.

• Structural Engineering and Mechanics
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• 제70권5호
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• pp.525-534
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• 2019

An analytical research on buckling of simply supported thin plate with variable thickness under bi-axial compression is presented in this paper. Combining the perturbation technique, Fourier series expansion and Galerkin methods, the linear governing differential equation of the plate with arbitrary thickness variation under bi-axial compression is solved and the analytical expression of the critical buckling load is obtained. Based on that, numerical analysis is carried out for the plates with different thickness variation forms and aspect ratios under different bi-axial compressions. Four different thickness variation forms including linear, parabolic, stepped and trigonometric have been considered in this paper. The calculated critical buckling loads and buckling modes are presented and compared with the published results in the tables and figures. It shows that the analytical expressions derived by the theoretical method in this paper can be effectively used for buckling analysis of simply supported thin plates with arbitrary thickness variation, especially for the stepped thickness that used in engineering widely.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권11호
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• pp.5410-5426
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• 2019

With the advent of the fifth-generation (5G) era, Massive multiple-input multiple-output (MIMO) relay systems have experienced the rapid development. Recently, the performance analysis models of Massive MIMO relay systems have been proposed, which are mostly based on Rayleigh fading channels. In order to create a more suitable model for 5G Internet of Things scenarios, our study is based on the Rician fading channels, where line-of-sight (LOS) path exists in the channels. In this paper, we assume the channel state information (CSI) is perfect. In this case, we use statistical information to derive the analytical exact closed-form expression for the achievable sum rate of the uplink for the Massive MIMO two-hop relay system over Rician fading channels. Moreover, considering the different communication scenarios, we derive the analytical exact closed-form expression for the achievable sum rates of the uplink for other three scenarios. Finally, based on these expressions, we make simulations and analyze the performance under different transmit powers and Rician-factors, which provides a theoretical basis and reference for further research.

• 한국연소학회지
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• 제13권1호
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• pp.23-30
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• 2008

An analytical expression for the turbulent burning velocity is derived from the asymptotic zone conditional transport equation at the leading edge. It is given as a sum of laminar and turbulent contributions, the latter of which is given as a product of turbulent diffusivity in unburned gas and inverse scale of wrinkling at the leading edge. It was previously shown that the inverse scale is equal to four times the maximum flame surface density in the wrinkled flamelet regime [1]. The linear behavior between $U_T$ and u' shows deviation with the inverse scale decreasing due to the effect of a finite flamelet thickness at higher turbulent intensities. DNS results show that $U_T/S^0_{Lu}$ may be given as a function of two dimensionless parameters, $u'/S^0_{Lu}$ and $l_t/\delta_F$, which may be transformed into another relationship in terms of $u'/S^0_{Lu}$, and Ka. A larger $l_t/{\delta}_F$ or a smaller Ka leads to a smaller scale of wrinkling, hence a larger turbulent burning velocity in the limited range of $u'/S^0_{Lu}$. Good agreement is achieved between the analytical expression and the turbulent burning velocities from DNS in both wrinkled and thickened-wrinkled flame regimes.

• Steel and Composite Structures
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• 제31권5호
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• pp.469-488
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• 2019

We in this paper study nonlinear bending of a functionally graded porous nanobeam subjected to multiple physical load based on the nonlocal strain gradient theory. For more reasonable analysis of nanobeams made of porous functionally graded magneto-thermo-electro-elastic materials (PFGMTEEMs), both constituent materials and the porosity appear gradient distribution in the present expression of effective material properties, which is much more suitable to the actual compared with the conventional expression of effective material properties. Besides the displacement function regarding physical neutral surface is introduced to analyze mechanical behaviors of beams made of FGMs. Then we derive nonlinear governing equations of PFGMTEEMs beams using the principle of Hamilton. To obtain analytical solutions, a two-step perturbation method is developed in nonuniform electric field and magnetic field, and then we use it to solve nonlinear equations. Finally, the analytical solutions are utilized to perform a parametric analysis, where the effect of various physical parameters on static bending deformation of nanobeams are studied in detail, such as the nonlocal parameter, strain gradient parameter, the ratio of nonlocal parameter to strain gradient parameter, porosity volume fraction, material volume fraction index, temperature, initial magnetic potentials and external electric potentials.

• Geomechanics and Engineering
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• 제24권6호
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• pp.599-610
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• 2021

Conduits are commonly installed below the ground for utility conveyance around the world. Vertical load on a buried conduit is an important parameter that needs to be known to ensure its safe design and installation. Consideration of soil arching in load calculations helps achieve a more realistic and efficient design. In the past, considering the arching effect, the design charts have been presented for use by practicing engineers to calculate the vertical load on the conduit buried below the level ground. There are currently no design charts for calculating the vertical load on the conduit buried under a sloping ground. In this paper, an attempt has been made to present the derivation of a generalized analytical expression considering that the soil mass overlying the conduit has a sloping face and the arching phenomenon takes place. The developed generalized expression has been used to present some design charts considering specific values of slope geometry, soil properties and burial depths. Furthermore, analytical results for specific soil parameters have been compared with the results extracted from a commercial software PLAXIS 2D, for a developed numerical model and an independent study.

• Transactions on Electrical and Electronic Materials
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• 제4권4호
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• pp.13-17
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• 2003

This paper deals with the edge effect in thin insulating films, focusing on their dependence on film thickness. The finding is that the electric field is lowered at the edge as the film thickness is reduced, which, in turn, is closely related to dielectric breakdown voltage. In order to analyze this phenomenon, a simple capacitor model is introduced with which dependence of dielectric breakdown voltage around the electrode edge on the film thickness is explained. Due to analytical difficulty to get the expression of electrical field strength at the edge, an equivalent circuit approach is used to find the voltage expression first and then the electric field expression using it. The relation gets to an agreement with the experimental findings shown in the paper. This outcome may be extended to solve similar problems in multi-layer insulating films.