Physical Design Variables Research Articles

Topology optimization of imperfect frame structures with improved manufacturability

We present a framework for robust topology optimization of frame structures under uncertainty in member geometry. Imperfect geometry is defined as a general out-of-straightness. The uncertainty in response is quantified using a second-order stochastic perturbation that allows for accurate estimation of first and second-order response statistics in the presence of geometric random imperfections. The adjoint method is employed to compute the sensitivities, allowing for the use of gradient-based optimizers. A novel approach based on the augmentation of the set of physical design variables with an “indicator set” and a SIMP-like strategy is utilized to control the complexity of the final design and arrive at optimized topologies with improved manufacturability. Numerical examples are provided to demonstrate the performance of the proposed framework where comparison is made with the deterministic designs to highlight the improvements and differences both in terms of overall topology, e.g., load path diversification, and volume re-distribution and the impact of the manufacturability considerations on the topology of the final design.

Measuring Accessibility in low density Housing: The Role of neighbourhood design

Accessibility is a key contributor to the quality of life experienced by residents and others. This paper asks how might accessibility be measured in different contexts? Quantitative analyses were undertaken, and 247 residents were surveyed in three suburbs. Pearson correlations was used to investigate the relationship between perceived accessibility and a number of independent social and physical neighbourhood design variables. The findings suggest that a quantitative method can be usefully conducted to measure the perception of residents toward their social-spatial environment. The results presented that accessibility is strongly associated with physical design features, even with interaction of socio-demographic variables. Hierarchical multiple regression was also showed that some of the physical characteristics significantly predicted accessibility particularly street type, open space provision and trees coverage after socio-economic factors controlling such as income and length of residence. This indicates that well designed neighbourhoods can be more accessible for residents. The findings also suggest that accessibility associated with the social and physical needs of residents can be critical influences that planners and decision maker need to consider when designing for sustainable environment in contemporary suburban contexts.

Automatic Generation of Design Space Conversion Maps and Its Application for the Design of Compound Split Hybrid Powertrains

Most of the prior design studies on compound split hybrids focused on the selection of optimal configurations through evaluating their performance within the physical design space, i.e., powertrain configurations. However, the authors revealed that using the compound lever for the performance analysis dramatically reduces the design space as redundant configurations exist for a single compound lever design, resulting in computational load reduction. Nevertheless, using the compound lever results in the loss of information required to realize the given configurations as these two configurations are represented by two different sets of variables. The powertrain configuration is defined by two physical design variables, i.e., gear ratios of the two planetary gears. However, the compound lever design is defined by two nonphysical design variables, α and β, which are the vertical bar lengths between the output node (vehicle) and the two motor/generators' (MG) nodes. Thus, if the compound lever is used as a design tool, the selected designs should be converted into powertrain configurations. This paper introduces an automatic methodology to generate feasible powertrain configurations for any given compound lever using generic conversion equations that express the relationship between the nonphysical design variables, α and β, and the physical design variables, gear ratios. Conversion maps relating the 252 powertrain configurations to the compound lever design space were generated, and the results confirmed that the compound lever removes the redundancy existing in the physical design space.

Earplug comfort: From subjective assessment on the field to objective measurement and simulation using augmented artificial heads

For several years, lack of comfort has been pointed out as a major reason of earplug poor efficiency as noise control solution. The great complexity of comfort makes it difficult to predict it in the earplugs design phase. It is rather considered in an empirical way by the manufacturers using trial-and-errors approaches based on subjective assessment over a panel of subjects. Furthermore, because comfort is not quantified, Occupational Health and Safety (OHS) practitioners cannot select earplugs ensuring wearer comfort. To address these issues, a major international research project funded by two OHS institutes (IRSST in Canada and INRS in France) and involving several Universities (in Canada and England) started in 2017. The main objectives are to: (1) improve the understanding of earplugs comfort as perceived by field workers with consideration of all comfort components, (2) develop laboratory tools (augmented experimental and virtual artificial heads) to measure physical design variables related to the auditory, physiological, and functional components of comfort and (3) design a battery of hybrid objective/subjective comfort indices to quantify / measure / predict the different components of comfort. The aim of this presentation will be to present the project and first results.

The influence of urban design packages on home values

PurposeThe purpose of this study is to examine the impact of neighborhood design templates on residential home values in King County, WA, USA. Previous research examines a number of individual design factors; this study combines these factors into typologies and tests for the impacts of the composite set of design features.Design/methodology/approachThe study analyzes over 27,000 home sales with a hedonic price model to measure the impacts across three large, regional submarkets. Neighborhood design categories are developed using a cluster analysis on a set of individual neighborhood attributes.FindingsThe key finding from this research is that the impact of more traditional (“urban”) design packages on home values is highly contextual. For the older and denser neighborhoods in the study area, a more traditional design results in a significantly positive impact on home values. In the new and more suburban regions of the study area, this effect is not found.Originality/valuePrior work focused on valuing design attributes individually. The study argues that neighborhood design is better conceived of as a “package”, as the value of a given design element may depend on other co-located attributes. This is the first study, to the authors’ knowledge, to treat physical neighborhood design variables as a composite whole and to attempt to value their impact on home values as such.

New explicit formulations for accurate estimation of aeration-related parameters in steady-state completely mixed activated sludge process

<p>This paper presents new and explicit equations to estimate aeration-related parameters such as standard oxygen requirement, daily energy consumption and total mass transfer coefficient for the diffused aeration. The proposed formulations are derived for the steady-state completely mixed activated sludge process based on the nonlinear regression analysis by using the Richardson’s extrapolation method and the Levenberg–Marquardt algorithm. The applicability of the proposed models has been investigated for a wide range of thirteen inputs consisting of the fundamental biological, hydraulic, and physical design variables, and tested against a total of 1500 additional computational scenarios. All estimations are proven to be satisfactory with very high determination coefficients (<em>R</em><sup>2</sup>) between 0.961–0.965, 0.967–0.972 and 0.980–0.984, respectively, for the prediction of standard oxygen requirement, daily energy consumption and total mass transfer coefficient for diffused aeration. The proposed models offer sufficiently simple and practical mathematical formulations incorporating routinely obtainable parameters, which are readily available for all activated sludge-based treatment plants. Besides eliminating the need for additional time or computational effort typically performed in the theoretical procedure, the developed equations have simple coefficients to be easily used for manual calculations with a hand-held calculator. The statistical results clearly exhibit that the proposed equations are accurate enough to be used in estimation of the studied aeration parameters based on the practical ranges of the corresponding design variables.</p>

A study of selective precipitation techniques used to recover refined iron oxide pigments for the production of paint from a synthetic acid mine drainage solution

New resource recovery methods of acid mine drainage (AMD) treatment aim to reduce waste by extracting iron contaminants in usable forms, specifically iron oxides as industrial inorganic pigments, which can be marketed and sold to subsidize treatment costs. In this study, iron oxide pigments of varying colors and properties were recovered from a synthetic AMD solution through a stepwise selective precipitation process using oxidation, pH adjustment, and filtration. Chemical and physical design variables within the process, such as alkaline addition rate, reaction temperature, drying duration, and target pH, were altered and observed for their effects on iron oxide morphology as a means of reducing—or even eliminating—the need for refining after synthesis. Resulting iron oxide pigment powders were analyzed with X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), and visually evaluated for color and coating ability. Drying duration resulted in increased redness in paint streaks and enhanced crystallinity, as amorphous phases of iron oxide transformed into hematite. Alkaline addition rate showed no effect on the crystallinity of the powders and no consistent effect on color. Conversely, increasing reaction temperature darkened the color of pigments and increased surface area of pigment particles (thus improving coating ability) without changing the crystallinity of the samples. Iron oxides precipitated at pH 3 displayed the highest purity and possessed a distinct yellow color suggestive of jarosite, while other paint streaks darkened in color as trace metal impurities increased. The choice to use lower pH for higher quality iron oxides comes with the compromise of reduced iron recovery efficiency. Manganese and nickel did not begin to precipitate out of solution up to pH 7 and thus require increased pH neutralization in the field if natural AMD is found to contain those metals. All pigments developed in this study were found to be adequate for use as paint as demonstrated in a canvas painting.

An approach for analyzing and managing flexibility in engineering systems design based on decision rules and multistage stochastic programming

ABSTRACTThis article introduces an approach to assess the value and manage flexibility in engineering systems design based on decision rules and stochastic programming. The approach differs from standard Real Options Analysis (ROA) that relies on dynamic programming in that it parameterizes the decision variables used to design and manage the flexible system in operations. Decision rules are based on heuristic-triggering mechanisms that are used by Decision Makers (DMs) to determine when it is appropriate to exercise the flexibility. They can be treated similarly as, and combined with, physical design variables, and optimal values can be determined using multistage stochastic programming techniques. The proposed approach is applied as demonstration to the analysis of a flexible hybrid waste-to-energy system with two independent flexibility strategies under two independent uncertainty drivers in an urban environment subject to growing waste generation. Results show that the proposed approach recognizes the value of flexibility to a similar extent as the standard ROA. The form of the solution provides intuitive guidelines to DMs for exercising the flexibility in operations. The demonstration shows that the method is suitable to analyze complex systems and problems when multiple uncertainty sources and different flexibility strategies are considered simultaneously.

Assessment of the Influence of Torrefied Biomass Physical Characteristics, Design and Operating Variables on Gasification Efficiency

Gasification efficiency is an important factor that determines the actual technical operation as well as the economic viability of using a gasifier system for energy production. In this study, the ...

In-plane material filters for the discrete material optimization method

This paper presents in-plane material filters for the Discrete Material Optimization method used for optimizing laminated composite structures. The filters make it possible for engineers to specify a minimum length scale which governs the minimum size of areas with constant material continuity. Consequently, engineers can target the available production methods, and thereby increase its manufacturability while the optimizer is free to determine which material to apply together with an optimum location, shape, and size of these areas with constant material continuity. By doing so, engineers no longer have to group elements together in so-called patches, so to statically impose a minimum length scale. The proposed method imposes the minimum length scale through a standard density filter known from topology optimization of isotropic materials. This minimum length scale is generally referred to as the filter radius. However, the results show that the density filter alone gives designs with large measures of non-discreteness. In order to obtain near discrete designs an additional threshold projection filter is applied, so to push the physical design variables towards their discrete bounds. However, because the projection filter is a non-linear function of the design variables, the projected variables have to be re-scaled in a final so-called normalization filter. This is done to prevent the optimizer in creating superior, but non-physical pseudo-materials. The method is demonstrated on a series of minimum compliance examples together with a minimum mass example, and the results show that the method is indeed capable of imposing a minimum length scale onto the optimized layup.

A survey of acoustic conditions in semi-open plan classrooms in the United Kingdom

This paper reports the results of a large scale, detailed acoustic survey of 42 open plan classrooms of varying design in the UK each of which contained between 2 and 14 teaching areas or classbases. The objective survey procedure, which was designed specifically for use in open plan classrooms, is described. The acoustic measurements relating to speech intelligibility within a classbase, including ambient noise level, intrusive noise level, speech to noise ratio, speech transmission index, and reverberation time, are presented. The effects on speech intelligibility of critical physical design variables, such as the number of classbases within an open plan unit and the selection of acoustic finishes for control of reverberation, are examined. This analysis enables limitations of open plan classrooms to be discussed and acoustic design guidelines to be developed to ensure good listening conditions. The types of teaching activity to provide adequate acoustic conditions, plus the speech intelligibility requirements of younger children, are also discussed.

Constrained generic substructure transformations in finite element model updating

Model updating is a powerful technique to improve finite element models of structures using measured data. One of the key requirements of updating is a set of candidate parameters that is able to correct the underlying error in the model. Often regions such as joints are very difficult to parameterise satisfactorily using physical design variables such as stiffnesses or dimensions. Parameters arising from generic element and substructure transformations are able to increase the range of candidate parameters, and furthermore are able to correct structural errors. However, unconstrained generic substructure transformations change the connectivity of the model matrices. In many instances retaining the connectivity is desirable and this paper derives constraint equations to do so. The method assumes that substructure eigenvalues are the parameters used in the global updating procedure and that the substructure eigenvector matrix is optimised to enforce the connectivity constraints. The method is demonstrated on a simple L shape test structure, where the substructure is the corner.

Rational design of hydrogels for tissue engineering: Impact of physical factors on cell behavior

When designing suitable biomaterials for tissue-engineering applications, biological and chemical parameters are frequently taken into account, while the equally important physical design variables have often been neglected. For a rational design of biomaterials, however, all variables influencing cell function and tissue morphogenesis have to be considered. This review will stress the development of cross-linked hydrogels and outline the impact of their physical properties on cell function and tissue morphogenesis. In the first part, the principles of cellular mechanosensitivity, as well as the influence of substrate mechanics on cell behavior, will be discussed. Afterwards, methods to characterize the mechanical properties of biomaterials will be presented. The subsequent chapters will address hydrogels that allow for the control of their physical qualities followed by a discussion of their use in tissue-engineering applications.

A general and effective approach for the optimal design of fiber reinforced composite structures

This paper presents a general and effective procedure based on a mathematical programming approach for composite structures optimal design, under weight, stiffness and strength criteria. Effective means that the developed approach is able to find a local optimum in few iterations, even with a large number of design variables. In addition, as the formulation may include strength constraints, it is shown that not only plies thickness but also fiber orientations should be considered as design variables. Besides this, it is explained how these angular variables can improve the structural performance. The generality of the approach is related to the fact that the developed optimization technique is not only dedicated to the design of particular laminates configurations, but is also reliable for general problems including isotropic and/or anisotropic materials, as well as other structural responses. The design problem formulation relies on a direct parameterization of the laminates in terms of the physical design variables, that is orientations and thicknesses, and not on alternative ones like the lamination parameters. Numerical applications, including a non-homogeneous composite membrane design problem and an industrial test case, are presented.

Combined Optimization of a Recurve Actuator and its Drive Circuit

The integrated modeling and combined optimization of a Recurve actuator and its drive circuit is considered. A finite element model for Euler-Bernoulli beams is developed with appropriate coupling interface to the drive circuit. The finite element model considers appropriate charge variation over the actuator and leads to an energy conservative formulation. The actuator model is coupled to the electric circuit model via a charge-voltage transfer function. The drive circuit is based on a half-bridge switching amplifier topology. Both actuator and circuit physical design variables are considered in the optimization formulation. The objective is to minimize the weight of the system while satisfying performance and stability constraints. The interactions and trade offs between the actuator and the drive circuit are investigated. Optimization results show clear interrelations between the design of the electric circuit and the actuator.

Acoustic Design Sensitivity Analysis and Optimization for Reduced Exterior Noise

A program, global acoustic design sensitivity analyzer, is developed that can perform a global acoustic design sensitivity analysis of exterior noise with respect to structural sizing design variables. A system for global acoustic design sensitivity is introduced and implemented numerically by employing the continuum sensitivity analysis. A half-scale automobile cavity model is considered as a numerical example. By using a continuum method, we obtained accurate and efe cient sensitivities when the number of design variables was large. Also, the tendency plotsof element sensitivities and energy contribution for global acousticsensitivities areavailable. Finally, a design optimization was performed to simultaneously reduce the weight and sound pressure level at interesting points and frequencies. I. Introduction T HE range of engineering problems that can be solved through numericalanalyses hasbeen greatlybroadened with the advent of high-speed digital computers. In addition, the development of the e nite element method (FEM)and the boundary element method (BEM) has also been important to engineering analysis. These two typesofanalysesareassociatedwithanalyticalstructure-bornenoise prediction. FEM is commonly used to compute the vibration of the structure emitting noise, and BEM can be used to predict the generated noise. Other methods for acoustic prediction, such as statistical energy analysis, are also available. In this paper, the focus is on FEM and BEM. In a gradient-based optimization scheme, it is important to have accurate gradients (sensitivities ) of the objective function and constraints with respect to the design variables. Formulation of global acoustic sensitivity through chain-ruled derivatives using FEM and BEM has been studied and implemented by many researchers. Coyette et al. 1 have previously investigated the computation and utilizationofacousticsensitivitieswith respecttosizingdesignvariables. Two types of sensitivities were considered. One was acoustic sensitivity with respect to the normal velocity ofvibratingstructure, and the other was structural sensitivity of structural velocities with respect to physical sizing design variables such as thickness. The acoustic sensitivities and structural sensitivities were calculated using BEM and FEM, respectively, and then these sensitivities were combined to obtain a globalacousticsensitivity.In addition,this approach was implemented to the commercial code, SYSNOISE. The same approach was presented in the articles by Cunefare et al., 2;3 who focused on e nding the best optimization formulation by comparing the relative performance and results obtained through the use of several different objective functions and constraints. They obtained acoustic sensitivities and structural sensitivities from the commercial codes NASTRAN and COMET. They also developed COMIN to combine the acoustic and structural sensitivities. Most researchers who studied global acoustic design sensitivity analysis (DSA) and acoustic optimization have used the structural sensitivity analysis module supported by commercial codes and have thus faced limitations in the accuracy and number of design variables. There are several reasons for the limitations of the semianalytical method. First, when the semianalytical method is used forstructural sensitivity analysis, a slight error could occur due to the amount of perturbation. For this paper, we used a continuum approach 4i6 to calculate the structural sensitivity combined with acoustic sensitiv

Neural networks and response surface polynomials for design of vehicle joints

Typically, design of a complex system starts by setting targets for its performance characteristics. Then, design engineers cascade these targets to the components and design the components to meet these targets. It is important to have efficient tools that check if a set of performance targets for a component corresponds to a feasible design and determine the dimensions and mass of this design. This paper describes a method to develop tools that relate response parameters that describe the performance of a component to the physical design variables that specify its geometry. Neural networks and response surface polynomials are used to rapidly predict the performance characteristics of the components given the component dimensions. The method is demonstrated on design of an automotive joint. The paper compares neural networks and response surface polynomials and shows that they are almost equally accurate for the problem considered.

The Derivation and Re-Use of Vernacular Urban Space Concepts

Vernacular urban configurations still constitute sources of inspiration for architects and urban designers. However, in most cases, instead of extracting ideas and processes, designers, in order to create an architecture that respects identity and cultural values while meeting environmental and economic requirements, tend to favour the imitation of the older configurations and end up with frozen copies from the past. This paper suggests an approach based on abstract concepts drawn from past experiences and filtered and refined through physical and environmental design variables. One of these variables is examined here and serves as a filtering technique; the shading control.

Shading as a modulator for the design of urban layouts based on vernacular experiences

Older cities' urban configurations still constitute sources of inspiration for architects and urban designers. However, in most cases, instead of extracting ideas and processes, designers, under identitarian, environmental and economical pressures, tend to favour the imitation of the older configurations and end up with frozen copies from the past. This paper suggests an approach based on abstract concepts drawn from past experiences and filtered and refined through physical and environmental design variables. One of these variables is examined here and serves as a filtering technique; the shading control.

Verbetering van numeriese modelle met behulp van eksperimentele data

There is a growing interest in techniques for the updating of numerical structural models using experimental data. This work investigates the application of two fundamentally different approaches to the problem through a practical example. In one case the structural matrices are directly adjusted to force the eigenvalues and eigenvectors of the numerical model the same as the measured values. In the second case physical design variables are adjusted to improve the agreement between the eigenvalues. Although the direct adjustment of the structural matrices is much simpler to implement than the adjustment of physical design variables and also leads to better correspondence, the application thereof is restricted because of the changes in the physical structure of the matrices and it is suggested that further research be focused on the adjustment of physical parameters.