Orthotropic piezoelectric patches for control of symmetric laminates via an integral equation

Formulation of the problem for the feedback displacement control of a vibrating laminated plate with orthotropic piezoelectric sensors and actuators is given in terms of an integral equation. The objective is to develop a formulation which facilitates the numerical solution to obtain the eigenfrequencies and eigenfunctions of the piezo-controlled plate. The control is carried out via piezoelectric sensors and actuators which are of orthorhombic crystal class mm² with poling in the z direction. The initial formulation of the problem is given in terms of a differential equation which is the conventional formulation most often used in the literature. The conversion to an integral equation formulation is achieved by introducing an explicit Green’s function. Explicit expressions for the kernel of the integral equation are given and the method of solution using the new formulation is outlined. The solution technique involves approximating the integral equation with an infinite system of linear equations and using a finite number of these equations to obtain the numerical results.     

Sliding window criterion codes and concatenation scheme formitigating timing-jitter-induced errors in WDM fiber transmissions

We propose a concatenated coding scheme, which effectively reduces bit errors induced by soliton-soliton collisions (SSC) in wavelength division multiplexing (WDM) soliton transmission systems. A block line coding scheme, the sliding window criterion (SWC) code, is developed based on the nature of SSC-induced timing jitter in soliton communications. We show, by simplified collision model simulations, that the SWC code alone can decrease the SSC-induced timing jitter and, by concatenation to a Reed-Solomon (RS) code, improve both the bit rate and the channel spacing capacity in WDM systems. We compare the performance of our scheme both analytically and by simulations with those of various RS codes and concatenated RS-convolutional code used in optical fiber transmission systems, and show that high redundancy (overhead) does not always give better code performance. Finally, by using full simulations, we show that the SWC code is an effective and promising technique for dispersion-managed fiber WDM systems     

Exploring the influence of the built environment on human experience through a neuroscience approach: A systematic review

The built environment provides a habitat for the most sophisticated mammal in our universe, the human being. Developments in science and technology are forcing us to reconsider the priority of human needs in current theories of architecture and the built environment. Newly developed theories and methodologies in neuroscience have allowed us to improve and deepen our knowledge of human experience in the built environment. The potential of the relationship between neuroscience and architecture for knowledge creation generates an increasing interest in theoretical and methodological approaches to explore this intersection. Thus, a common ground on which to conduct interdisciplinary studies investigating developing and emerging concepts at the intersection must be established. However, few reviews in the literature have systematically examined developing and emerging concepts at the intersection of neuroscience and architecture. The present review aims to examine the existing literature systematically to explain the influence of the built environment on human experience by using approaches from neuroscience by examining the conceptualizations in the field. The study is conducted as a systematic qualitative review that analyzes and synthesizes the developing and emerging concepts that have appeared in the ever-evolving literature. The study concludes with an overall discussion about these concepts as a means of deeply understanding the influence of the built environment on human experience, responses to the environment based on approaches from neuroscience, and their potential for providing further directions for future research.     

Comparison of antioxidant capacity of cow and ewe milk kefirs

This research aimed to evaluate the effects of using either grain or commercial starter culture on the antioxidative capacity of cow and ewe milk kefirs. The antioxidant capacity of kefir samples during fermentation and 21 d of storage was assessed by using 3 assays: 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical cation decolorization; 2,2-diphenyl-1-picrylhydrazyl (DPPH^?) radical scavenging activity assay; and Fe⁺³-reducing power (ferric reducing antioxidant power assay, FRAP). Vitamin E and β-carotene contents were also quantified. All kefir samples exhibited varying values for DPPH, ABTS, and FRAP assays depending on the starter culture and milk type. Vitamin E and β-carotene contents were similar in all kefir samples during storage. The results of this study suggest that milk type (cow or ewe) and culture type (kefir grains or commercial starter) were the significant parameters for the antioxidative activity of kefir.     

Multiobjective Design of Laminated Cylindrical Shells for Maximum Pressure and Buckling Load

Abstract: Multiobjective design of a laminated cylindrical shell is obtained with the objectives defined as the maximization of axial load and external and internal pressures subject to a strength constraint. The failure under axial load and external pressure may occur by buckling. The ply angle is taken as the design variable. The weighted global criterion method is employed to solve the vector-optimization problem, which involves minimization of the distance to ideal solution vector in L₂ metric. A symmetrically laminated and balanced shell is considered as an example. Pareto optimal solutions are given for two- and three-objective design problems, and numerical results are presented in the form of tradeoff curves and surfaces. The effects of problem parameters are investigated, and the results are given for various weighting factors and shape parameters.     

Optimal design of hybrid laminates with discrete ply angles for maximum buckling load and minimum cost

The design of hybrid symmetric laminated plates consisting of high-stiffness surface and low-stiffness core layers is presented. In the first problem the maximization of buckling load is carried out over a discrete set of ply angles. In the second problem the minimum number of high-stiffness plies is determined for a given buckling load to minimize the material cost. Boolean variables are introduced to specify stacking sequence. Solution of the linear optimization problem yields an optimal stacking sequence. The effect of hybridization is investigated for various problem parameters such as the aspect ratio of the laminate and the number of plies. The optimal designs are obtained with upper bound constraints on the effect of bending-twisting coupling stiffnesses. Results are given for hybrid graphite-epoxy/glass-epoxy laminates under both uniaxial and biaxial loadings.     

Minimum cost design of hybrid composite cylinders with temperature dependent properties

Laminated composite cylinders are optimized with the objective of minimizing the material costs by means of hybridization. They are modelled as thick cylinders working under internal and/or external pressures. The optimal designs are subject to a lower bound on the failure pressure determined by the maximum stress criteria. The cylinders are constructed such that the stress patterns match the material properties by placing the stronger material in high stress areas and the weaker material in low stress areas. The resulting structure is of hybrid construction and the cost minimization is achieved not only by using an inexpensive material but also by minimizing the amount of the expensive material used in the design. The effect of temperature change on the stresses and the material properties is included in the analysis. Numerical results are given for graphite/glass hybrid cylinders and the efficiencies of the designs are shown to be substantial by comparing the costs of hybrid and non-hybrid designs. It is also shown that neglecting the effect of temperature on the stiffness and strength parameters of the materials would lead to underdesign and premature failure.     

Structure-function of cytochromes P450 and flavin-containing monooxygenases: implications for drug metabolism

This article is a report on a symposium held at Experimental Biology '98 in San Francisco, California. Recent developments in site-directed mutagenesis, computer-modeling, and mechanistic analysis of cytochromes P450 and flavin-containing monooxygenases are described. A unifying theme is the elaboration of general approaches for understanding and predicting the function of individual forms of these enzymes. A related goal is the production of soluble forms of mammalian cytochromes P450 for X-ray crystallography.     

Optimization of shear-deformable laminated plates under buckling and strength criteria

A shear deformable laminated theory is used to study the optimal design of rectangular plates under biaxial compressive loads. Such loads lead to plate failure by buckling or material failure which corresponds to the violation of the selected strength criterion. The minimum of the two loads (buckling load or material failure load) determines the critical failure load for a given set of problem parameters. At the optimum values of the ply angles, buckling or both failure criteria may be operational depending on the laminate thickness. The present study investigates the effect of laminate thickness on the optimal design and gives numerical results for symmetrically laminated angle-ply plates.     

Analysis of the in-plane properties of hybrid glass/carbon woven fabric composites

In the present study, standard solutions for the in-plane stiffness properties of a satin weave are expanded to a symmetrical laminate solution. Arbitrary unit cell sizes and orientations can now be incorporated. Once the properties of a single hybrid glass-carbon weave are established, they can be used to explain the behaviour of the laminate. It is found that a 0/45/0 laminate provides the best in-plane stiffness properties when the thicknesses of the three layers are identical. It is also shown that an error introduced to the angular orientation of the layup can lead to a significant change in laminate behaviour.