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In this paper, we study the following two-dimesional system of difference equations ... where the parameters a;b; c;d and the initial values x i; y i, i 2 f1;2;3;4;5;6g, are real numbers. We show that some subclasses of nonlinear two-dimensional system of difference equations are solvable in closed form. We also describe the forbidden set of solutions of the system of differ- ence equations. Some numerical examples are given to demonstrate the theoretical results. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study of the forward and inverse kinematics of a six-degrees-of-freedom (DoF) spatial manipulator with a novel architecture. Developed by Systemantics India Pvt. Ltd., Bangalore, and designated as the H6A (i.e., Hybrid 6-Axis), this manipulator consists of two arm-like branches, which are attached to a rigid waist at the proximal end and are coupled together via a wrist assembly at the other. Kinematics of the manipulator is challenging due to the presence of two multi-DoF passive joints: a spherical joint in the right arm and a universal in the left. The forward kinematic problem has eight solutions, which are derived analytically in the closed form. The inverse kinematic problem leads to $160$ solutions and involves the derivation of a $40$ -degree polynomial equation, whose coefficients are obtained as closed-form symbolic expressions of the pose parameters of the end-effector, thus ensuring the generality of the results over all possible inputs. Furthermore, the analyses performed lead naturally to the conditions for various singularities involved, including certain non-trivial architecture singularities. The results are illustrated via numerical examples which are validated extensively. [ABSTRACT FROM AUTHOR]

In this paper, we represent that the following three-dimensional system of difference equations x n + 1 = α y n + a y n y n − β z n − 1 , y n + 1 = β z n + b z n z n − γ x n − 1 , z n + 1 = γ x n + c x n x n − α y n − 1 , n ∈ ℕ 0 , where the parameters a, b, c, α, β, γ and the initial values x−i, y−i, z−i, i ∈ {0, 1}, are real numbers, can be solved in closed form by using transformation. We analyzed the solutions in 10 different cases depending on whether the parameters are zero or nonzero. It is noteworthy to depict that the solutions of some particular cases of this system are presented in terms of generalized Fibonacci numbers. Note that our results considerably extend and improve some recent results in the literature. [ABSTRACT FROM AUTHOR]

The sheet flexure is commonly used to provide support stiffness in flexure mechanisms for precision applications. While the sheet flexure is often analyzed in a simplified form, e.g. by assuming planar deformation or linearized stiffness, the deformation in practice is spatial and sufficiently large that nonlinear effects due to the geometric stiffness are significant. This paper presents a compact analytical model for the nonlinear stiffness characteristics of spatially deforming sheet flexures under general 3-D load conditions at moderate deformations. This model provides closed-form expressions in a mixed stiffness and compliance matrix format that is tailored to flexure mechanism analysis. The effects of bending, shear, elongation, torsion and warping deformation are taken into account, so that the stiffness in all directions, including the in-plane lateral support direction, is modeled accurately. The model is verified numerically against beam and shell-based finite elements. The approach for deriving closed-form solutions in a nonlinear context is detailed in this paper. The Hellinger–Reissner variational principle with a specific physically motivated set of low-order interpolation functions is shown to be well-suited to the geometrically nonlinear analysis of flexures. An extension of the derivation approach to the nonlinear closed-form analysis of general flexure mechanisms consisting of multiple sheet flexures connected in parallel is presented. This is demonstrated with the case of a spatially deforming parallelogram flexure mechanism and a cross-hinge flexure mechanism. • 3-D closed-form nonlinear stiffness model for sheet flexures at moderate deformations. • Geometrically nonlinear bending, torsion, elongation, shear, warping and Wagner effects. • Derivation using a mixed variational principle and custom interpolation functions. • Verification by means of nonlinear beam and plate finite elements. • Energy-based closed-form modeling of general sheet flexure mechanisms in parallel. [ABSTRACT FROM AUTHOR]

In this paper, we consider the valuation of variance swaps under a modified Heston model with a stochastic mean-reversion level, as a time-dependent mean reversion level for the variance of the Heston volatility model could provide better fit into the term structure of implied volatility and variance swap curve (Byelkina and Levin, in: Sixth World Congress of the Bachelier Finance Society, Toronto 2010; Forde and Jacquier in Appl Math Financ 17:241-259). We present a closed-form pricing formula for discretely sampled variance swaps based on the dimensional reduction technique. The validity of the newly derived formula is demonstrated through the comparison with the Monte Carlo simulation. The influence of introducing the stochastic mean-reversion level on variance swap prices is further investigated with numerical experiments. [ABSTRACT FROM AUTHOR]

• Exploring the class of models assuming mixture distributions for random utilities or disutilities. • Extension of the Combination of Random Utility Models (CoRUM) framework. • Latent class structure with different utility specification, marginals, variance and correlation. • Different classes of risk aversion, leveraging q-product GEV models. • Special Weibull-based and qGumbel-based instances. • Able to outperform other heteroskedastic closed-form RUM in-sample and out-of-sample. This paper investigates the class of random utility models (RUM) derived under the assumption of random utilities or disutilities following mixture distributions. We introduce a general framework embedding the models of Mattsson et al. (2014) and the q-product GEV model of Chikaraishi and Nakayama, (2016) while extending the investigations of Papola (2016). New closed-form models are obtained, with mixtures of covariance matrices, mathematical forms of utility (additive, multiplicative or in-between), variances of utilities (heteroscedasticity) and marginal distributions. The models are compared in two cross-validation exercises, based on a real dataset of travel mode preferences, outperforming existing heteroscedastic and homoscedastic closed-form models in terms of both in-sample and out-of-sample goodness of fit. The behavioural implications of the models are also discussed. [ABSTRACT FROM AUTHOR]

This paper presents a compact model for the DC current of Schottky barrier field-effect transistors at deep cryogenic temperatures, close to absolute zero kelvin. The proposed model is physics based and calculates the injection current over a device's Schottky barriers, by considering physical effects at these temperatures (e.g. quantum oscillations, band tail effect, phonon-assisted tunneling, etc.). For model verification, it is compared to measurements performed on nanowire Schottky barrier transistors at a temperature of 5.5 K. [ABSTRACT FROM AUTHOR]

• Adapted four asymmetric models to route choice by parameterization. • Tested the asymmetric models by GPS data collected from taxis and bicycles. • Revealed and compared the route choice patterns of driving and cycling. Among the discrete choice contexts discussed in the transportation literature, route choice is particularly challenging, for which several model structures with different assumptions were developed. Recently, a group of closed-form multinomial models with asymmetric choice probability functions have been proposed to resolve the class imbalance problem in mode choice. However, these asymmetric models can hardly be estimated when the choice sets vary with observations. This paper fills the gap between the asymmetric models and the existing literature, and also adapt the models to route choice by proposing three approaches to further parameterize the shape parameter. This paper also tests the asymmetric models by two independent GPS datasets: taxi data collected in Guangzhou as well as bicycle data collected in Tel Aviv. Comparative analysis is conducted between taxi drivers and cyclists on their route choice behavior. The results indicate the existence of class imbalance in both cases. Moreover, the asymmetric models have case-dependent performance, and different parameterizations correspond to different interpretations of the asymmetry in route choice. [ABSTRACT FROM AUTHOR]

An important issue in derivative pricing that hasn't been explored much until very recently is the impact of short selling to the price of an option. This paper extends a recent publication in this area to the case in which a ban of short selling of the underlying alone is somewhat less 'effective' than the extreme case discussed by Guo and Zhu [Equal risk pricing under convex trading constraints. J. Econ. Dyn. Control, 2017, 76, 136–151]. The case presented here is closer to reality, in which the effect of a ban on the underlying of an option alone may quite often be 'diluted' due to market interactions of the underlying asset with other correlated assets. Under a new assumption that there exists at least a correlated asset in the market, which is allowed to be short sold and thus can be used by traders for hedging purposes even though short selling of the underlying itself is banned, a new closed-form equal-risk pricing formula for European options is successfully derived. The new formula contains two distinguishable advantages; (a) it does not induce any significantly extra burden in terms of numerically computing option values, compared with the effort involved in using the Black–Scholes formula, which is still popularly used in finance industry today; (b) it remains simple and elegant as only one additional parameter beyond the Black–Scholes formula is introduced, to reflect the dilution effect to the ban as a result of market interactions. [ABSTRACT FROM AUTHOR]

Summary: Partially submerged c′ − φ′ slopes with a horizontal water table exhibit a critical pool level at which the factor of safety becomes a minimum. The phenomenon was first identified using finite element methods, but in this paper, a more thorough analytical investigation is presented. The approach described herein assumes a rigid block sliding with a circular failure mechanism, combined with optimization software to identify the critical circle. The method is initially validated against known slope solutions that assume circular and log‐spiral mechanisms and shown to give excellent agreement, especially for flatter slopes. The method is then applied to partially submerged slopes with a focus on the critical pool level. Through detailed investigation of the overturning and restoring moments in the stability analyses, the critical pool level phenomenon is shown to lie in the trade‐off between the destabilizing effects of internal pore pressures on soil strength and the stabilizing effect of external hydrostatic water pressures on the slope surface. [ABSTRACT FROM AUTHOR]

It is well known that superposition coding, namely separately encoding the independent sources, is optimal for symmetric multilevel diversity coding (SMDC) (Yeung-Zhang 1999) for any $L\geq 2$ , where $L$ is the number of levels of the coding system. However, the characterization of the coding rate region therein involves uncountably many linear inequalities and the constant term (i.e., the lower bound) in each inequality is given in terms of the solution of a linear optimization problem. Thus this implicit characterization of the coding rate region does not enable the determination of the achievability of a given rate tuple. In principle, the achievability of a given rate tuple can be determined by direct computation, but the complexity is prohibitive even for $L=5$. In this paper, for any fixed $L$ , we obtain in closed form a finite set of linear inequalities for characterizing the coding rate region. We further show by the symmetry of the problem that only a much smaller subset of this finite set of inequalities needs to be verified in determining the achievability of a given rate tuple. Yet, the cardinality of this smaller set grows at least exponentially fast with $L$. We also present a subset entropy inequality, which together with our explicit characterization of the coding rate region, is sufficient for proving the optimality of superposition coding. [ABSTRACT FROM AUTHOR]

The subject of localization has received great deal attention in the past decades. Although it is perhaps a well-studied problem, there is still roomfor improvement. Traditional localizationmethods usually assume the number of sensors is sufficient for providing desired performance. However, this assumption is not always satisfied in practice. This paper studies the time of arrival (TOA)-based source positioning in the presence of sensor position errors. An error refined solution is developed for reducing the mean-squared-error (MSE) and bias in small sensor network (the number of sensors is fewer) when the noise or error level is relatively large. TheMSE performance is analyzed theoretically and validated by simulations. Analytical and numerical results show the proposed method attains the Cramér-Rao lower bound (CRLB). It outperforms the existing closed-form methods with slightly raising computation complexity, especially in the larger noise/error case. [ABSTRACT FROM AUTHOR]

This paper studies the performance of the classical integral force feedback (IFF) controller for suppressing the forced response of a single degree of freedom (SDOF) system. An ℋ∞ optimization criterion is used to derive the optimal feedback gain of the IFF controller contributed as a complement for the state of the art. This optimal gain is calculated in the closed-form based on a SDOF system which is then applied to a two degrees of freedom system to study its adaptability. It is found that the ℋ∞ optimal gain can be easily transposed into multi-degrees of freedom applications without introducing too many errors. An equivalent mechanical model is also developed to enable a straightforward interpretation of the physics behind the IFF controller. [ABSTRACT FROM AUTHOR]

In this paper, a physics-based DC compact model for Schottky barrier field-effect transistors at deep cryogenic temperatures is presented. The model uses simplified tunneling equations at temperatures of ϑ ≈ 0 K in order to calculate the field emission injection current at the device's Schottky barriers. Additionally, an empirical expression for including resonant tunneling effects is introduced. The compact model is also compared to and verified by measurements performed on ultra-thin body and buried oxide SOI Schottky barrier field-effect transistors and is able to capture the signature of resonant tunneling effects in the transfer characteristics. • Presents a DC compact model for Schottky barrier field-effect transistors. • Model is physics-based, closed-form and for deep cryogenic temperature environment. • Field emission current at the Schottky barrier is calculated. • Verification is done on measurements. [ABSTRACT FROM AUTHOR]

Designing an axial flux permanent magnet machine is complex and computationally intensive. This paper proposes a new closed-form method for concurrent design and analysis of a multi-stage axial flux permanent magnet machine. The method will provide a simpler modeling solution to machine designers. By calculating magnetic and electric properties, the design space of an axial flux permanent magnet is created for initial design. This paper demonstrates the feasibility of the new closed-form method by showing that the results obtained from the proposed method correlate with the finite element analysis results. The design space is also evaluated and analyzed by taking into account various parameters, including copper losses, permanent magnet density, phase voltages, and torque waveform. Finally, a multi-objective analysis is performed to compare two different designs of an axial flux permanent magnet machine. The proposed method also provides a useful guide for the initial design state. [ABSTRACT FROM AUTHOR]

This paper studies the eigenbuckling of Mindlin plate with two adjacent edges clamped and the remaining edges simply supported or clamped by using the separation of variables method, and the concise and explicit closed-form solutions are obtained for the first time. The cases involving free edges can also be dealt with if there are two opposite edges simply supported. The closed-form solutions are in good agreement with the existing solutions, thus the validity of present method and accuracy of the obtained solutions are verified. This paper proves to be a major development of analytical method since it has long been acknowledged that the eigenbuckling of rectangular plates without two parallel edges simply supported are not amenable to analytical solutions. [ABSTRACT FROM AUTHOR]

This paper presents a closed-form solution of rough conductor surface impedance in terms of material DC conductivity and RMS roughness. Surface roughness is modeled by position-dependent conductivity at conductor-dielectric boundary to account for protrusion of rough conductor into dielectric, which was first proposed in the Gradient model. Analytic solution is obtained by approximating the Gauss cumulative distribution function, used to model the position-dependent conductivity in the Gradient model, with a square of hyperbolic tangent. Closed-form solutions are compared with numerical solutions of the Gradient model and are in good agreement up to a frequency of 100 GHz. Derived surface impedance is causal, which has been shown by numerical Hilbert transform. [ABSTRACT FROM AUTHOR]

This paper proposes an efficient (semi-closed-form) zero-forcing (ZF) precoder design for the weighted sum-rate maximization problem under per-antenna power constraint (PAPC). Existing approaches for this problem are based on either interior-point methods that do not favorably scale with the problem size or subgradient methods that are widely known to converge slowly. To address these shortcomings, our proposed method is derived from three elements: minimax duality, alternating optimization (AO), and successive convex approximation (SCA). Specifically, the minimax duality is invoked to transform the considered problem into an equivalent minimax problem, for which we then recruit AO and SCA to find a saddle point, which enables us to take advantages of closed-form expressions and hence achieve fast convergence rate. Moreover, the complexity of the proposed method scales linearly with the number of users, compared to cubically for the standard interior-point methods. We provide an analytical proof for the convergence of the proposed method and numerical results to demonstrate its superior performance over existing approaches. Our proposed method offers a powerful tool to characterize the achievable rate region of ZF schemes under PAPC for massive multiple-input multiple-output. [ABSTRACT FROM PUBLISHER]

The problem of recovering the low-rank and sparse components of a matrix is known as the stable principal component pursuit (SPCP) problem. It has found many applications in compressed sensing, image processing, and web data ranking. This paper proposes a generalized inexact Uzawa method for SPCP with nonnegative constraints. The main advantage of our method is that the resulting subproblems all have closed-form solutions and can be executed in distributed manners. Global convergence of the method is proved from variational inequalities perspective. Numerical experiments show that our algorithm converges to the optimal solution as other distributed methods, with better performances. [ABSTRACT FROM AUTHOR]

In this paper, a modified Black–Scholes (B–S) model is proposed, based on a revised assumption that the range of the underlying price varies within a finite zone, rather than being allowed to vary in a semi-infinite zone as presented in the classical B–S theory. This is motivated by the fact that the underlying price of any option can never reach infinity in reality; a trader may use our new formula to adjust the option price that he/she is willing to long or short. To develop this modified option pricing formula, we assume that a trader has a view on the realistic price range of a particular asset and the log-returns follow a truncated normal distribution within this price range. After a closed-form pricing formula for European call options has been successfully derived, some numerical experiments are conducted. To further demonstrate the meaning of the proposed model, empirical studies are carried out to compare the pricing performance of our model and that of the B–S model with real market data. [ABSTRACT FROM AUTHOR]

In this paper, 2-D axisymmetric modeling of thermal-stress of solid material induced by an annular long pulsed laser was presented using closed-form solutions. Physical model of annular long pulsed laser irradiation was established and closed-form solutions of thermal-stress were obtained by analytical method based on thermo-elasticity theory. Thermal-stress of silicon material induced by an annular long pulsed laser was simulated. Results show that, when the silicon material is irradiated by an annular long pulsed laser, the thermal-stress on the surface of the material is the largest, and with the increase of the depth, the thermal-stress is gradually reduced. On the silicon surface, when the inside radius of the annular laser is fixed, the greater the outside radius, the larger region of the higher thermal-stress occupies. When the width between inside radius and outside radius of the annular laser is fixed, for the radial component of the thermal-stress, the smaller the irradiation center location, the greater the maximum value of stress; for the hoop and axial components, the difference of the maximum stress for different irradiation center location is not obvious. With the increase of the pulse width of annular long pulsed laser, the maximum value of the thermal-stress is also gradually increased. [ABSTRACT FROM AUTHOR]

In this paper, modeling of annular long pulsed laser heating solid material was presented using closed-form solutions. Heat conduction model of annular long pulsed laser heating was established and analytical solutions for temperature were obtained by integral transform method. Annular long pulsed laser heating silicon material was modeled for different parameters. Modeling results show that, when the silicon material is irradiated by an annular long pulsed laser, the temperature rise in the region of laser irradiation is higher than that in the region of no laser irradiation. On the silicon surface, the temperature rise is the largest. And as the depth increases, the temperature rise decreases gradually. When the inside radius of the annular laser is fixed, the greater the outside radius, the larger region of the higher temperature rise. But the difference of temperature rise is not obvious for different laser irradiation areas. When the width between inside radius and outside radius of the annular laser is fixed, with the irradiation center location toward the edge of the material, the region of higher temperature rise is also close to the edge of the material, and the maximum of the temperature rise is located in the irradiation center. With the increase of pulse width of the annular long pulsed laser, the maximum value of the temperature rise is also gradually increased. [ABSTRACT FROM AUTHOR]

This paper provides closed-form expressions for the process zone lengths and load-displacement responses of cohesive zone modeling, for the popular mode I double cantilever beam (DCB) test, the mode II end notched flexure (ENF) test and the mixed-mode I/II bending (MMB) test of composite materials. By incorporating traction-separation laws that consist of only one quasi-brittle softening segment, the problems are formulated and analytically solved for homogenous material or mid-plane symmetric laminates within the framework of classical lamination theory (CLT). The solutions of the MMB test are obtained by the superposition method. Having been known as depending on the mode mixity, the material and interfacial fracture properties, the process zone length is found as a system parameter that is also influenced by the specimen geometry, including the thickness and the crack length, especially for mode II. Based on the parametric studies and the comparison against finite element (FE) simulations, suggestions for estimating the process zone length are provided. [ABSTRACT FROM AUTHOR]

In this paper, we reconsider a two-server heterogeneous retrial queue with threshold policy. However, the computation time with the existing method is prohibitively large for certain values of the threshold parameter. Applying the spectral expansion method, we derive a closed-form expression for the eigenvalues and eigenvectors matrix that are needed to determine the steady-state distribution of a quasi-birth-death process describing the queue. As a result, the computation time for the performance measures does not depend on the threshold parameter. [ABSTRACT FROM AUTHOR]

Closed-form solutions for cohesive zone modeling within the framework of classical lamination theory (CLT), for the popular mode I double cantilever beam (DCB) test, the mode II end notched flexure (ENF) test and mixed-mode I/II bending (MMB) test are provided in this paper. Zero-thickness virtual multi-linear traction–separation laws are introduced to simulate the cohesive interactions between potential crack surfaces. The problem is formulated by solution forms corresponding to each segment of the cohesive laws and using appropriate boundary and continuity conditions. Detailed algorithms for each case are provided to clearly show the influence of the cohesive zone law on the ensuing crack growth. The superposition method used for mixed-mode growth in the MMB test for homogenous material or mid-plane symmetric laminates is proved both theoretically and numerically. Comprehensive parametric studies are performed on the crack growth response and the process zone length, revealing their relations to the delamination length, cohesive parameters, the shape of the traction–separation laws and the mode mixity. With applicability to general multilayered structures, and the capability to incorporate arbitrary, piecewise linear cohesive constitutive laws, the closed-form solutions can serve as a tool to determine the accuracy of numerical solutions used in conjunction with finite element simulations. [ABSTRACT FROM AUTHOR]

The paper presents new approach to the evaluation of matrix functions operating over tensors that are essential part of formulation of complex nonlinear material models in mechanics of solids. A method is presented how to automatically derive numerically efficient closed-form representation of an arbitrary matrix function and its first and second derivatives for 3×3 matrices with real eigenvalues. The method offers an unique solution to the standard problem of ill-conditioning in the vicinity of multiple equal eigenvalues which is characteristic for all closed-form representations. A compiled library of subroutines with derived closed-form representation of most commonly used matrix functions along with their first and second derivatives has been created and is available for the use in general finite element environments. Consequently, the matrix functions can become as accurate, efficient and commonly available as their scalar counterparts, resulting in more common use of advanced strain and stress measures, such as Hencky strain measure which have so far been considered difficult for implementation. Accuracy and efficiency of the derived closed-form representations was compared with corresponding truncated series expansion and a speed up between 20 and 80 times has been observed depending on the matrix. The proposed methodology was tested on a set of selected nonlinear material models where matrix functions play an essential part in nonlinear finite element formulation. [ABSTRACT FROM AUTHOR]

This paper focuses on the primary development of novel numerical and analytical techniques of the modal damped vibration energy harvesters with arbitrary proof mass offset. The key equations of electromechanical finite element discretisation using the extended Lagrangian principle are revealed and simplified to give matrix and scalar forms of the coupled system equations, indicating the most relevant numerical technique for the power harvester research. To evaluate the performance of the numerical study, the analytical closed-form boundary value equations have been developed using the extended Hamiltonian principle. The results from the electromechanical frequency response functions (EFRFs) derived from two theoretical studies show excellent agreement with experimental studies. The benefit of the numerical technique is in providing effective and quick predictions for analysing parametric designs and physical properties of piezoelectric materials. Although analytical technique provides a challenging process for analysing the complex smart structure, it shows complementary study for validating the numerical technique. [ABSTRACT FROM AUTHOR]

Abstract: To date, despite the significant development in the field of structural mechanics, there still remains a paradox in the solutions available for a classical shell buckling problem. The difference in strength between a cylindrical shell under uniform axial compression and that under pure bending is not quite well investigated. This lack of research is reflected in the wide variations in the elastic bending strength and the slenderness limits given in current international design standards. The discrepancies in the available classical solutions and hence the design rules have initiated the current research. The main aim of this paper is to present a closed-form solution for the elastic buckling strength of unstiffened circular cylinders under pure bending using a new simplified energy approach employing the well-known Ritz method. Two types of analyses are presented for cylinders with large (D/t>200) and medium (100

Abstract: Closed-form solutions to compute annual failure probabilities are helpful in the implementation of performance-based engineering. Closed-form solutions to compute the annual failure probability have been proposed in the context of seismic hazard using a linear approximation in the logarithmic scale for the hazard curves. However, a linear approximation is found to significantly deviate from the actual seismic hazard curve and hence can result in significant errors in the computation of the annual failure probability. This paper develops a closed-form solution to compute the annual failure probability of systems using a novel Second-order Logarithmic Formulation (SOLF) to model the hazard curves. Thereafter, we illustrate the proposed closed-form solution by computing the annual failure probabilities for reinforced concrete (RC) bridges subject to the seismic hazard of San Francisco, CA and Memphis, TN. We demonstrate that SOLF yields accurate estimates of the annual failure probabilities whereas the existing linear logarithmic formulation can significantly over or under estimates such probabilities. The proposed formulation is general and is expected to yield accurate estimates for hazards other than the seismic hazard (e.g., hurricanes and floods). [Copyright &y& Elsevier]

Nowadays fiber-reinforced composites have gained popularity as more applications have arisen in the last years. Nonetheless, the lack of proper design methodologies and regulations has slowed down its adoption as an innovative material with an enhanced capacity of energy absorption. The present paper proposed a closed-form model for moment–curvature fully compatible with international standards as Model Code 2010 and RILEM. Due to the easy implementation and computational efficiency of closed-forms, the proposed model pretends to enhance the design methodology for flexural verification. Validation of the model has been made through comparison with other models found in literature and in contrast with computational ideal results simulated by commercial software. The analysis conducted shows that the best accordance with the ideal reference results is obtained by using the proposed model, reaching average errors below 1.5% at service and ultimate limit states. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a one-dimensional model describing the ultrasonic wave propagation in a poroelastic medium immersed in fluid. Motivation of this study arises from simulating the in vitro transverse transmission test on cancellous bone. Biot’s theory is used for modeling the porous bone tissue. The solution is obtained by using the Laplace transform technique. First, closed-form solutions of reflected and transmitted waves are provided in the Laplace domain. Then, the time-dependent solutions are computed by using the Convolution Quadrature Method. Some numerical simulations are carried out, showing that the proposed model could be used as an efficient tool for analyzing the dynamic behavior of cancellous bone in the orthotropy directions. [Copyright &y& Elsevier]

Abstract: In this paper, a fast interactive image segmentation method is developed. The method combines the GrabCut algorithm with the multilevel banded closed-form (MLBCF) technique to achieve the acceleration. The GrabCut method is first applied on a low-resolution image to obtain the segmentation. The coarse labeling is then propagated to the higher-resolution level by using the banded closed-form method with the locally linear assumption. Some post-processing, such as alpha thresholding, probability classification and multi-seeds banded Graph Cuts, is applied to assign the final labeling. For experimental comparison, we also implement the multilevel banded Graph Cuts (MLBGC) method based on GrabCut algorithm. Experiments using synthesized noisy images and real natural scene images demonstrate the superior performance of the proposed method in terms of segmentation accuracy, computation efficiency and memory usage. [Copyright &y& Elsevier]

Abstract: Acquiring insight in the structural behaviour of tall buildings of irregular geometry is challenging. The contribution of the shaft torsional rigidity and the in-plane floor stiffness are difficult to model. At discrete changes in geometry, disturbances occur in the force flow, whose magnitude and influence field are difficult to estimate and whose influence may not be disregarded. FEM programs provide a quick result for a particular building, but cannot answer the general question how the building response is governed by decisive structural parameters. In this paper, this want is supplied by developing a closed-form super element method for two frequently occurring building types. The building is divided in a very small number of super elements. Only at the heights where changes in properties of the building occur, a node between super elements is introduced. For each super element the stiffness matrix and load vector is derived on basis of a set of simultaneous differential, resulting in closed-form solutions. The foundation stiffness is accounted for. The primary aim of the presented super element method is to increase understanding of the structural behaviour of irregular tall buildings. [Copyright &y& Elsevier]

This paper presents a closed-form analytical technique for analyzing surface PM machines equipped with fractional-slot concentrated windings. Since this class of winding configuration deviates significantly from conventional sinusoidal distributions, classical steady-state phasor or dq analytical techniques cannot be used to provide accurate results. The presented analytical model provides a fast and reliable method to analyze and compare candidate machine designs. Stator slotting effects are taken into consideration and a wide range of concentrated winding configurations can be analyzed. This technique is capable of analyzing the machine both below (constant-torque) and above (flux-weakening) base speed. Average torque, cogging torque, and ripple torque are all evaluated. Analytical results are verified using finite element analysis. [ABSTRACT FROM AUTHOR]

Physical optics (PO) is a well-known asymptotic technique for evaluating the fields scattered from an object. Evaluation of a surface integral forms the crux of this technique. In this paper, the PO integral is formulated for plane-wave incidence and far-field observation. Then, this integral is converted to the time domain and interpreted as a Radon transform. When the integration domain is a triangle, this interpretation yields a closed-form expression that can be employed in both the frequency and time domains. The efficacy of using the derived closed-form expression in the frequency domain is demonstrated through numerical examples. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 284–288, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20612 [ABSTRACT FROM AUTHOR]