A variable-accuracy metamodel-based architecture for global MDO under uncertainty

A method for simulation-based multidisciplinary robust design optimization (MRDO) of problems affected by uncertainty is presented. The challenging aspects of simulation-based MRDO are both algorithmic and computational, since the solution of a MRDO problem typically requires simulation-based multidisciplinary analyses (MDA), uncertainty quantification (UQ) and optimization. Herein, the identification of the optimal design is achieved by a variable-accuracy, metamodel-based optimization, following a multidisciplinary feasible (MDF) architecture. The approach encompasses a variable (i) density of the design of experiments for the metamodel training, (ii) sample size for the UQ analysis by quasi Monte Carlo simulation and (iii) tolerance for the multidisciplinary consistency in MDA. The focus is on two-way steady fluid-structure interaction problem, assessed by partitioned solvers for the hydrodynamic and the structural analysis. Two analytical test problems are shown, along with the design of a racing-sailboat keel fin subject to the stochastic variation of the yaw angle. The method is validated versus a standard MDF approach to MRDO, taken as a benchmark and solved by fully coupled MDA, fully converged UQ, without metamodels. The method is evaluated in terms of optimal design performances and number of simulations required to achieve the optimal solution. For the current application, the optimal configuration shows performances very close to the benchmark solution. The convergence analysis to the optimum shows a promising reduction of the computational cost.     

On the asymptotic accuracy of reduced-order models

International Journal of Control, Automation and Systems - Popular model reduction methods can easily be adapted to retain the asymptotic response to inputs with rational transform. To this...     

Cumulative stabilizing effects of hydrophobic interactions on the surface of the neutral protease from Bacillus subtilis

Using genetically engineered mutants of the neutral pro-teasefrom Bacillus stearothermophilus (BsteNP), it had been shownthat the surface-exposed structural motif constituted by Phe63embedded in a four amino acid hydrophobic pocket is criticalfor the thermal stability of the thermophilic neutral proteasesfrom Bacilli. To measure the stabilizing contribution of eachhydrophobic interaction taking place between Phe63 and the hydrophobicpocket, we grafted this structural motif in the neutral proteasefrom the mesophile Bacillus subtilis (BsubNP). This was accomplishedby first creating the Thr63Phe mutant of BsubNP and then generatinga series of mutants in which the four amino acids which in thermolysinsurround Phe63 and form the hydrophobic pocket were added oneafter the other. By analysing the thermal stability of eachmutant it was found that the 2°C destabilizing effect ofthe Thr63Phe substitution was completely suppressed by the additionof the four amino acid hydrophobic pocket, each replacementproviding a stabilizing contribution of approxi mately 0.8–1°C.These results are discussed in the light of the peculiar mechanismof thermal inactivation of proteolytic enzymes.     

Model reference adaptive control of discrete‐time piecewise linear systems

This article presents a switched model reference adaptive controller for discrete‐time piecewise linear systems. In the spirit of the work by Landau in the late seventies, proof of asymptotic stability of the closed‐loop error system is obtained, recasting its dynamics as a feedback system and showing the feedforward and the feedback paths are both passive. The challenge is that both paths can be piecewise linear. Numerical results show excellent performance of the proposed controller even in the face of sudden variations of the plant parameters. Copyright © 2012 John Wiley & Sons, Ltd.     

An SLA-based Broker for Cloud Infrastructures

The breakthrough of Cloud comes from its service oriented perspective where everything, including the infrastructure, is provided “as a service”. This model is really attractive and convenient for both providers and consumers, as a consequence the Cloud paradigm is quickly growing and widely spreading, also in non commercial contexts. In such a scenario, we propose to incorporate some elements of volunteer computing into the Cloud paradigm through the Cloud@Home solution, involving into the mix nodes and devices provided by potentially any owners or administrators, disclosing high computational resources to contributors and also allowing to maximize their utilization. This paper presents and discusses the first step towards Cloud@Home: providing quality of service and service level agreement facilities on top of unreliable, intermittent Cloud providers. Some of the main issues and challenges of Cloud@Home, such as the monitoring, management and brokering of resources according to service level requirements are addressed through the design of a framework core architecture. All the tasks committed to the architecture’s modules and components, as well as the most relevant component interactions, are identified and discussed from both the structural and the behavioural viewpoints. Some encouraging experiments on an early implementation prototype deployed in a real testing environment are also documented in the paper.     

An approach for capturing the Voice of the Customer based on Virtual Prototyping

The need for companies to improve their competitiveness may lead to innovation and the reconceptualization of traditional products and processes, with companies making an effort to enhance product elements related to functionality, attractiveness, technology and sustainability, and implementing mass-customisation concepts. Mass-customised products are developed to satisfy specific customer needs, in line with increasing demand for product variety and customisation. The analysis of what customers really want, capturing the Voice of the Customer (VOC), is one of the strategies used to establish effective product development processes. Using a VOC survey, it is possible to transform customer needs into the functional and psychological requirements of the product. This paper presents a methodology based on Virtual Reality (VR) technologies to support the capturing of the VOC in regard to the visual, haptic and auditory characteristics of products. This method can be applied to the beginning of the product development process, to allow companies to deduce from the data the requirements of new industrial customised products. A flexible and interactive Virtual Prototype (VP) of a product category is then developed as a product platform in a draft version by designers and configured according to customer needs, using an immersive VR environment. This method, based on the use of VP, reduces the number of physical prototypes that need to be manufactured during the product development process, thus reducing overall costs. In addition, the VP based method supports the mass-customisation process of products through the real-time integration and collection of data for product configuration preferences, involving as many users as possible representative of the target users of the new products. To demonstrate this process a case study concerning the development of the VP for a washing machine, a summary of test sessions with users and results are presented. Specifically, the results presented in this paper are related to improvements in capturing the VOC and reductions in Virtual Prototyping cost and time.     

A white emitting poly(phenylenevinylene)

A white emitting copolymer with the polyphenylenevinylene (PPV) structure is obtained via the Stille cross-coupling reaction. Substitution of hydrogen atoms with fluorine atoms on the vinylene units of poly(1,4-dialkoxyphenylenevinylene) shifts the emission from orange-red to blue. White emission is obtained by combining dialkoxyphenylenedifluorovinylene and dialkoxyphenylenevinylene units in proper ratio. The two complementary emitters are obtained separately by Stille polymerization reaction. Then, the two reaction mixtures are combined without purification in different ratios and further reacted in similar experimental conditions. A white luminescent material is obtained using 99/1 mixing ratio. OLED devices fabricated with this copolymer shows near-white emission with CIE (0.30, 0.40) and excellent stability in the range 10–200 cd/m².     

Novel hybrid MRAC-LQ control schemes: synthesis,analysis and applications

LQ optimal controllers are widely used in many applications as they provide a simple and effective solution to optimal control problems. There are many examples in the literature that show the lack of robustness of such controllers when the process is subject to parameter variations or when some dynamics are neglected. The hybrid algorithms proposed in this work extend the family of model reference minimal control synthesis adaptive controllers and address the issue of enhancing the robustness of LQ regulators. The main idea behind the approach is to seek a simple and alternative route to implement the LQ regulator via the MCS algorithm which is effective also in those practical cases when the LQ action itself fails. The stability of all the proposed control schemes is proved and the performance on a set of representative examples shows the effectiveness of the approach.     

PHYSICAL MODEL FOR THE ENGINEERING ANALYSISOF THE THERMOELASTICLTY OF SOLID BODIES

Latin lettersa--V~ diedon in the mol~ d~ cellb~Vector diedon in the ~ dboc Cellc~VeCtor inchon in the moleculax ~ cellc~Speilic heat capeity(J' kg~ l' K~' )D--Finite sabin tensorE--Sthen tenSOrG~Metric ten8Orh--hanetrical ~e ie~ in themolectilar dMc cellL~an(J)m--Mass(kg) N~ n~ Of Particlesp~Hy~c mpsme(Pa)q--toe heat now rate (w.m-= )--POSihon(m)S--Vector ghhon in the molecthedwtc referee(m)S--Sness tensor(N' m-' )t~(s)T~(K)u--Vector displacement(m)~boas pennal(J)~Arbitw constant…