General thermal analysis of parallel-flow flat-plate solar collector absorbers

Improved equations are formulated for the transfer of heat in flat-plate solar collector absorbers, including a shape factor accounting for details of flow duct designs, and developing heat transport in the ducts. Approximate, analytical solutions are obtained in terms of perturbation series, which are applicable to practical collectors with lengths much greater than the distance between flow ducts.The primary result of the analysis is a universal-type design equation, or chart, which determines the collector efficiency factor for any duct design, heat transfer development, or other absorber-plate parameter. Collector performance is stated in terms of an effectiveness/number-of-transfer-unit relationship. Ease of use and utility of the design chart is illustrated by examples.     

DMTO – a method for Discrete Material and Thickness Optimization of laminated composite structures

This paper presents a gradient based topology optimization method for Discrete Material and Thickness Optimization of laminated composite structures, labelled the DMTO method. The capabilities of the proposed method are demonstrated on mass minimization, subject to constraints on the structural criteria; buckling load factors, eigenfrequencies, and limited displacements. Furthermore, common design guidelines or rules, referred to as manufacturing constraints, are included explicitly in the optimization problem as series of linear inequalities. The material selection and thickness variation are optimized simultaneously through interpolation functions with penalization. Numerical results for several parameterizations of a finite element model of a generic main spar from a wind turbine blade are presented. The different parameterizations represent different levels of complexity with respect to manufacturability. The results will thus give insight into the relation between potential weight saving and design complexity. The results show that the DMTO method is capable of solving the problems robustly with only few intermediate valued design variables.     

A general and flexible method of problem definition in structural optimization systems

This paper describes the implementation of a general and flexible method of formulating problems of mathematical programming in structural optimization systems. The method enables the formulation and solution of problems involving scalar, integral, min/max, max/min and possibly non-differentiable user defined functions in any conceivable mix. The mathematical formulation is based on the bound formulation, and the implementation specific details involve a parser capable of interpreting and performing symbolic differentiation of the user defined functions.     

Outage probability analysis for superposition coded symmetric relaying

Superposition coded symmetric relaying is a bandwidth-efficient cooperative scheme where each source node simultaneously transmits both its own local packet and relay packet that originated at its partner by adding the modulated local and relay signals in Euclidean space. This paper investigates the power allocation and outage probability of a superposition coded symmetric relaying system with finite-constellation signaling. We first derive the mutual information (MI) metrics for the system. The derived MI metrics consist of two parts: one represents the MI conveyed by the modulated signal corresponding to its own data, and the other represents the MI conveyed by the modulated signal corresponding to its partner’s data. Using MI based effective signal-to-noise ratio mapping technique, we attain expressions for the outage probability. Furthermore, we discuss power allocation policies that minimize the outage probability. Simulation results are presented to verify the correctness of the outage probability analysis and the benefits of the power allocation.     

Topology and thickness optimization of laminated composites including manufacturing constraints

This paper presents a gradient based optimization method for large-scale topology and thickness optimization of fiber reinforced monolithic laminated composite structures including certain manufacturing constraints to attain industrial relevance. This facilitates application of predefined fiber mats and reduces the risk of failure such as delamination and matrix cracking problems. The method concerns simultaneous determination of the optimum thickness and fiber orientation throughout a laminated structure with fixed outer geometry. The laminate thickness may vary as an integer number of plies, and possible fiber orientations are limited to a finite set. The conceptual combinatorial problem is relaxed to a continuous problem and solved on basis of interpolation schemes with penalization through the so-called Discrete Material Optimization method, explicitly including manufacturing constraints as a large number of sparse linear constraints. The methodology is demonstrated on several numerical examples.     

Ameritech's usability laboratory: from prototype to final design

. Ameritech's human factors organization was established in 1989, and from the beginning its charter assumed that user-centred design, iterative usability testing, and beginning-to-end involvement in the product-system development cycle would be central to its work. This article describes the laboratory resources that were created to support the organization. It identifies the needs of the human factors professionals using the lab that served as requirements for the design of the resources, and the interim lab that was built where implementation approaches to some of these requirements were tested and refined. It describes the final laboratory, as well as three different kinds of portable labs. The laboratory is a critical corporate resource, and while it continues to evolve as it is used, it has already demonstrated its value to the human factors organization it serves.     

Material interpolation schemes for unified topology and multi-material optimization

This paper presents two multi-material interpolation schemes as direct generalizations of the well-known SIMP and RAMP material interpolation schemes originally developed for isotropic mixtures of two isotropic material phases. The new interpolation schemes provide generally applicable interpolation schemes between an arbitrary number of pre-defined materials with given (anisotropic) properties. The method relies on a large number of sparse linear constraints to enforce the selection of at most one material in each design subdomain. Topology and multi-material optimization is formulated within a unified parametrization.