Design of a Beam with Controllable Force Elements

A method for solving the problem of design of an 0.gif" alt="ldquo" align="MIDDLE" BORDER="0">intellectual0"> structure formulated for the pair optimal position of actuators, optimal control of actuators is developed. In the method proposed, physical and logical objects are treated as 0.gif" alt="ldquo" align="MIDDLE" BORDER="0">equivalent.0">     

Stochastic Analysis of Macrodispersion in a Semi‐Confined Aquifer

In this paper, the macroscopic dispersion resulting from one063x25n7150513/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0"> and two063x25n7150513/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">dimensional flows through a semi063x25n7150513/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">confined aquifer with spatially variable hydraulic conductivity K which is represented by a stationary (statistically homogeneous) random process is analyzed using the spectral representation technique. Stochastic fluctuation equations of the steady flow and solute transport are solved to construct the macroscopic dispersive flux and evaluate the resulting macrodispersivity tensor in terms of the leakage factor and input covariances describing the hydraulic conductivity in a semi063x25n7150513/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">confined aquifer bounded by a leaky layer above and an impervious stratum below. The macrodispersivity tensor is studied using some convenient forms of the log hydraulic conductivity process. The sensitivity of the resulting macrodispersivity to the input covariances is discussed along with the influence of the leakage factor for both one063x25n7150513/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0"> and two063x25n7150513/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">dimensional flows. It is found that the longitudinal macrodispersivities are increased due to the presence of leakage, while the transverse macrodispersivities are reduced due to leakage.     

Identification of stiffness, dissipation and input parameters of randomly excited non-linear systems: Capability of restricted potential models (RPM)

A dynamic identification technique in the time domain for time invariant systems under random external forces is presented. This technique is based on the use of the class of restricted potential models (RPM), which are characterized by a non-linear stiffness and a special form of damping, that is a product of the input power spectral density (PSD) matrix and the velocity gradient of a non-linear function of the total mechanical energy. By applying 0" style="vertical-align:bottom" width="21" alt="View the MathML source" title="View the MathML source" src="http://ars.els-cdn.com/content/image/1-s2.0-S0020746206000989-si21.gif"> stochastic differential calculus and by specific analytical manipulations, some algebraic equations, depending on the response statistics and on the mechanic parameters that characterize RPM, are obtained. These equations can be used for the dynamic identification of the above mechanic parameters once the response statistics of the system to be identified are evaluated. The proposed technique allows one to identify single-degree-of-freedom or multi-degrees-of-freedom systems in the case of unmeasurable input. Further, the probabilistic characteristics of the external forces can be completely estimated in terms of PSD matrix.     

Periodic Solutions of Delay Differential Equations with a Small Parameter: Existence,Stability and Asymptotic Expansion

We consider a scalar delay differential equation with a small parameter, and employ Walther010490lg78156q2/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s method to obtain a result on the existence and stability of a slowly oscillatory periodic solution that represents a refinement of the estimate for the Lipschitz constant of a returning map. We also develop a matching method and obtain asymptotic expansions of the slowly oscillatory periodic solution and its minimal period.Dedicated to Professor Shui-Nee Chow on the occasion of his 60th birthdayAMS subject classifications: 34K15; 34K20; 34C25.     

One Singularly Perturbed Problem of Turbulent Gas Dynamics

The problem of the interaction of a Prandtl013;Mayer wave with a shear layer is solved using the small parameter method for the case where the flow vorticity in the shear layer is small. A direct expansion is constructed and its inadequacy at large distances from the vortex layer is proved. The strained coordinate method is used to obtain a uniformly adequate expansion. It is shown that for certain velocity distributions in the shear layer, the characteristics in the reflected simple wave resulting from the interaction intersect each other and a shock arises in the flow. There coordinates of the shock origin and the function describing the shock shape are obtained.     

Permeability Effects of Turbulent Flow Through a Porous Insert in a Backward-Facing-Step Channel

In the present work, a k013;011035g54170869/xxlarge949.gif" alt="epsi" align="BASELINE" BORDER="0"> model, based on the work of Lee and Howell (Proceedings of the ASME-JSME Thermal Engineering Hawaii, 1987), is rigorously derived based on time average of spatially averaged Navier013;Stokes equations. The model is then employed to solve for a flow in a backward-facing step channel with a porous insert. The numerical solver is modified from the STREAM code (Lien and Leschziner, Comput. Meth. Appl. Mech. Eng. 114 (1994a) 123013;148), and it has been validated against the experimental data of Seegmiller and Driver (AIAA Journal 23 (1985) 163013;171). The code is then used to perform simulation for cases with a porous insert. The resistance of the porous insert can be altered by changing its permeability (011035g54170869/xxlarge954.gif" alt="kappa" align="BASELINE" BORDER="0">), Forchheimer011035g54170869/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s constant (F), or thickness (b). The goal is to examine the influence of each parameter on the resulting flow and turbulent kinetic energy (k) distributions. It is discovered that, by increasing the resistance of the insert, flow eventually enters a transitional regime towards relaminarization. This is due to the contribution of Darcy011035g54170869/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s and Forchheimer011035g54170869/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s terms in the governing equations, and modifying these two terms changes the levels of P_k and, hence, k and . Generally speaking, lowering 011035g54170869/xxlarge954.gif" alt="kappa" align="BASELINE" BORDER="0"> or raising F results in a greater suppression of P_k than 011035g54170869/xxlarge949.gif" alt="epsi" align="BASELINE" BORDER="0">, causing the flow to relaminarize. Meanwhile, if the pore size is reasonably large to sustain turbulence within the porous media, increasing b reduces but does not eliminate the turbulent activity in the porous insert.     

Exponential Behavior of Solutions to Stochastic Integrodifferential Equations with Distributed Delays

In this work, we study the existence, uniqueness, and exponential asymptotic behavior of mild solutions to stochastic integrodifferential delay evolution equations. We assume that the non-delay part generates a C₀-semigroup.     

Synthesis,spatial structure and spectral properties of pyrylo‐4 (thio) squaraines variously substituted in cyclobutene moiety

Synthetic routes have been developed to a number of (thio) squaraine dyes containing the residues of CH‐acids at the central cyclobutene ring. The electronic and spatial structure as well as the chemical conversions and optical behaviour of the compounds obtained have been studied both theoretically and by X‐ray diffraction analysis, ¹H NMR and electronic spectroscopy. As shown, the electronic nature and sterical characteristics of the central ring substituents give rise to some general conformational features and crystal packing regularities and also govern the spectral position of the first π–π^* absorption band. The structure–property relationships established in the study provide guidance for the purposeful design of deeply coloured (thio) squaraines. Copyright © 2015 John Wiley & Sons, Ltd.