Evolving Patterns: Correlated Systems of Interaction

Over the last four decades, the onset of computation has enabled architects and designers to employ generative patterns in their exploration of emergent social, material and spatial systems. Theodore Spyropoulos provides an overview of the field and discusses how it has been developed by the Design Research Lab (DRL) at the Architectural Association into an ‘Adaptive Ecologies’ agenda. In the context of parametric urbanism, the DRL has explored models of living through behavioural patterns found in nature, examining the role of the singular and the collective. Copyright © 2009 John Wiley & Sons, Ltd.     

Steam reforming of heptane in a fluidized bed membrane reactor

n-Heptane served as a model compound to study steam reforming of naphtha as an alternative feedstock to natural gas for production of pure hydrogen in a fluidized bed membrane reactor. Selective removal of hydrogen using Pd₇₇Ag₂₃ membrane panels shifted the equilibrium-limited reactions to greater conversion of the hydrocarbons and lower yields of methane, an intermediate product. Experiments were conducted with no membranes, with one membrane panel, and with six panels along the height of the reactor to understand the performance improvement due to hydrogen removal in a reactor where catalyst particles were fluidized. Results indicate that a fluidized bed membrane reactor (FBMR) can provide a compact reformer for pure hydrogen production from a liquid hydrocarbon feedstock at moderate temperatures (475-550 °C). Under the experimental conditions investigated, the maximum achieved yield of pure hydrogen was 14.7 moles of pure hydrogen per mole of heptane fed.     

Forced circulation solar water heater performance prediction by TRNSYS and ANN

The design and applicability of solar water heating systems requires a satisfactory prediction of collector outlet water temperature and the useful energy delivered over a wide range of climatic conditions. Transient system simulation program is extensively used for this purpose, and recently artificial neural networks have also been considered. This article presents the results of a study carried out to compare the performance prediction by these two methods in a tropical location under different climatic conditions. Experimental collector outlet temperature, storage tank temperatures and the useful energy values were compared with the results of the simulation by these two methods. Hourly and daily values under different conditions were also compared. Details of the experimental set up and observations, the modeling procedure used and the statistical measures to compare the capabilities of the two methods under clear, partly cloudy, and cloudy conditions have been described. The prediction of both the methods are found to be good for both hourly and daily estimations, and the specific requirements for satisfactory performance prediction of each of the methods have been detailed.     

Sequential Application of Simplex Designs in Optimisation and Evolutionary Operation

A technique for empirical optimisation is presented in which a sequence of experimental designs each in the form of a regular or irregular simplex is used, each simplex having all vertices but one in common with the preceding simplex, and being completed by one new point. Reasons for the choice of design are outlined, and a formal procedure given. The performance of the technique in the presence and absence of error is studied and it is shown (a) that in the presence of error the rate of advance is inversely proportional to the error standard deviation, so that replication of observations is not beneficial, and (b) that the “efficiency” of the technique appears to increase in direct proportion to the number of factors investigated. It is also noted that, since the direction of movement from each simplex is dependent solely on the ranking of the observations, the technique may be used even in circumstances when a response cannot be quantitatively assessed. Attention is drawn to the ease with which second-order designs having the minimum number of experimental points may be derived from a regular simplex, and a fitting procedure which avoids a direct matrix inversion is suggested. In a brief appendix one or two new rotatable designs derivable from a simplex are noted.     

Investigating Reliability on Fuel Cell Model Identification. Part II: An Estimation Method for Stochastic Parameters

An alternative way to process data from polarization measurements for fuel cell model validation is proposed. The method is based on re‐ and subsampling of I–V data, with which repetitive estimations are obtained for the model parameters. This way statistics such as standard deviations and correlations between the parameters may be experimentally derived. Histograms may also be produced, approximating the probability distributions that they follow. Two experimental case studies are discussed. In the first case, observations are made on the behavior of the parameter values for two mathematical models. As the number of data points (measurement points) employed in the estimation of the parameters increases, parameters with high variances converge to specific values. On the contrary, parameters with small variances diverge linearly. The parameters' histograms do not usually follow normal distributions rather they show a connection between the number of peaks in the graphs and correlations of the parameters. The second case study is an application on a fast degraded SOFC button cell, where the values and the histograms of the parameters are compared before and after degradation.     

Operating Conditions Corresponding to Optimal Final Properties of Activated Sludge Using the DOE and RSM Techniques

Abstract

This paper presents the influence of four relevant factors on the flocculation behavior in the activated sludge process: organic loading rate (COD), solid retention time (SRT), dissolved oxygen (DO), and calcium ion concentration, and links them to a selected set of process responses: sludge volume index (SVI), turbidity, organic removal rate (COD), and suspended solids (SS) removal. The “Design of Experiments” (DOE) and the “Response Surface Methods” (RSM) approaches are used to establish the operating conditions corresponding to optimal final properties of the activated sludge. Using these techniques, the results show that it is indeed feasible to locate the operating conditions which optimize the flocculation process and the sludge settling properties. The study represents a first attempt to evaluate the flocculation process in activated sludge using the DOE/RSM approach.     

高分子实验中的探究教学设计

实验在高分子教学中占有十分重要的地位,它是培养学生综合实践能力的最佳途径。而实验能否发挥出预期的功能,则取决于教师对整个实验教学的设计情况。在高分子实验教学的设计中引入探究性元素对培养学生的综合素质和科研能力有着十分重要的意义。     

Statistical DOE-ILP based power-performance-process (P3) optimization of nano-CMOS SRAM

As technology continues to scale, maintaining important figures of merit of Static Random Access Memories (SRAMs), such as power dissipation and an acceptable Static Noise Margin (SNM), becomes increasingly challenging. In this paper, we address SRAM instability and power (leakage) dissipation in scaled-down technologies by presenting a novel design flow for simultaneous power minimization, performance maximization and process variation tolerance (P3) optimization of nano-CMOS circuits. The 45 and 32 nm technology node standard 6-Transistor (6T) and 8T SRAM cells are used as example circuits for demonstration of the effectiveness of the flow. Thereafter, the SRAM cell is subjected to a dual threshold voltage (dual-V_Th) assignment based on a novel statistical Design of Experiments-Integer Linear Programming (DOE-ILP) approach. Experimental results show 61% leakage power reduction and 13% increase in the read SNM. In addition, process variation analysis of the optimized cell is conducted considering the variability effect in twelve device parameters. To the best of the authors' knowledge, this is the first study which makes use of statistical DOE-ILP for optimization of conflicting targets of stability and power in the presence of process variations in SRAMs.     

Discrete element analysis of experiments on mixing and stoking of monodisperse spheres on a grate

Understanding the details of the mixing and stoking process on grate firing systems is crucial for the optimization of the combustion process in waste or biomass incineration plants. The Discrete Element Method (DEM) can help to obtain further information on the mixing process within a bed of fuel particles. Especially the influence of a change in operational parameters can be examined avoiding large experimental effort. In the current paper five simulations for a generic grate are compared with the corresponding experiments. The experiments were carried out throughout an anterior parameter study on mixing and stoking on a grate [Sudbrock F.; Simsek E.; Wirtz S.; Scherer V.: “An experimental analysis of the influence of operational parameters on mixing and stoking of a monodisperse granulate on a grate”, Powder Technology 198, Issue 1, 29-37, 2010] [19]. The system considered is equipped with vertically moving bars which induce stoking. In a first approach monodisperse plastic spheres are used. The grate is encased by a transparent polycarbonate housing which provides optical access to the movement of the particles in the wall planes. The mixing process is measured and quantified by image analysis of the front wall of the grate. The mixing behaviour of the particle assembly observed in experiments and simulation appears to be very similar indicating that DEM is able to predict the particle mixing in the bed. In order to quantify the visual observations the mixing behaviour has been evaluated by different mixing parameters. They are compared in dependence of the number of strokes of the grate bars. A good agreement between measurements and simulations could be observed.     

Modeling of Drying of Highly Shrinking Materials Using Hydrogels as an Example

The work presents a model of convective drying of a highly shrinking material of cylindrical shape. To identify the effective diffusivity as a function of local temperature and moisture content the problem was solved as an inverse problem. A set of experimental data served for model validation. The optimization algorithms were used to solve PDE system and fit numerically obtained curves to the experimental data using the effective diffusivity as the only adjustable parameter.