Uncertain Loading and Quantifying Maximum Energy Concentration within Composite Structures

We introduce a systematic method for identifying the worst case load among all boundary loads of fixed energy. Here the worst case load is defined to be the one that delivers the largest fraction of input energy to a prescribed subdomain of interest. The worst case load is identified with the first eigenfunction of a suitably defined eigenvalue problem. The first eigenvalue for this problem is the maximum fraction of boundary energy that can be delivered to the subdomain. We compute worst case boundary loads and associated energy contained inside a prescribed subdomain through the numerical solution of the eigenvalue problem. We apply this computational method to bound the worst case load associated with an ensemble of random boundary loads given by a second order random process. Several examples are carried out on heterogeneous structures to illustrate the method

In All Likelihood, Deep Belief Is Not Enough

Statistical models of natural stimuli provide an important tool for researchers in the fields of machine learning and computational neuroscience. A canonical way to quantitatively assess and compare the performance of statistical models is given by the likelihood. One class of statistical models which has recently gained increasing popularity and has been applied to a variety of complex data are deep belief networks. Analyses of these models, however, have been typically limited to qualitative analyses based on samples due to the computationally intractable nature of the model likelihood. Motivated by these circumstances, the present article provides a consistent estimator for the likelihood that is both computationally tractable and simple to apply in practice. Using this estimator, a deep belief network which has been suggested for the modeling of natural image patches is quantitatively investigated and compared to other models of natural image patches. Contrary to earlier claims based on qualitative results, the results presented in this article provide evidence that the model under investigation is not a particularly good model for natural image

Is co-creation still an innovative innovation strategy across generations?

Co-creation, the process of involving customers in the innovation process, has gained popularity in recent years as a way for companies to tap into customer knowledge, skills, and insights and to create value for both the company and their customers. Co-creation as an innovation strategy has already been used for many years. However, the extent to which co creation is still perceived as an innovative innovation strategy among younger generations has not been researched. This paper aims to review the literature on co-creation and innovation to answer the question: Is co-creation still perceived as an innovative innovation strategy? A systematic review of the literature was conducted, and the results suggest that co-creation is still perceived as an innovative innovation strategy. In order to test the differences in perceptions between generations, a survey was conducted to test these possible differences. Our study found that younger generations have still higher perceptions of innovation ability, perceive higher trust in companies and their products, and have higher quality perceptions of products which result from a co-creation strategy. The study also found that the level of digital literacy of consumers has a partial influence on these perceptions. Further research is needed to more fully understand the factors that influence the perceived innovativeness of co creation and to identify best practices for implementing co-creation as an innovation strategy.A co-criação, o processo de envolvimento dos clientes no processo de inovação, ganhou popularidade nos últimos anos como forma de as empresas explorarem os conhecimentos, competências e insights dos clientes e criarem valor tanto para a empresa como para os seus clientes. A co-criação como estratégia de inovação já tem sido utilizada há muitos anos. Contudo, a medida em que a co-criação ainda é vista como uma estratégia de inovação inovadora entre as gerações mais jovens não tem sido investigada. Este artigo visa rever a literatura sobre co-criação e inovação para responder à questão: A co-criação ainda é percebida como uma estratégia inovadora de inovação? Foi realizada uma revisão sistemática da literatura, e os resultados sugerem que a co-criação ainda é percebida como uma estratégia de inovação inovadora. A fim de testar as diferenças de percepção entre gerações, foi realizado um inquérito para testar estas possíveis diferenças. O nosso estudo descobriu que as gerações mais jovens ainda têm percepções mais elevadas da capacidade de inovação, percebem uma maior confiança nas empresas e nos seus produtos, e têm percepções de maior qualidade dos produtos que resultam de uma estratégia de co-criação. O estudo descobriu também que o nível de literacia digital dos consumidores tem uma influência sobre estas percepções. É necessária mais investigação para compreender melhor os factores que influenciam a percepção de inovação da co-criação e para identificar as melhores práticas de implementação da co-criação como uma estratégia de inovação

Surfactant induced flows in thin liquid films : an experimental study

The topic of the experimental work summarized in my thesis is the flow in thin liquid films induced by non-uniformly distributed surfactants. The flow dynamics as a consequence of the deposition of a droplet of an insoluble surfactant onto a thin liquid film covering a solid substrate where discussed as a starting point in Chapter 2. A strong focus in this context was on the effect of the conditions in the vicinity of the surfactant source. It was shown, by application of interference and fluorescence microscopy, that the radially outwards directed displacement of the subphase, induced by the surfactant induced Marangoni stresses, is strongly influenced by the conditions near the surfactant source, i.e. the supply of surfactant from the source as the spreading proceeds. A novel oscillatory contact line instability of the surfactant droplet was described that modulates the flow rate of liquid from under the droplet. Considering conditions relevant to surfactant spreading in an oil reservoir in Chapter 3 the influence of a chemically imposed confinement on the sub-phase, along the surface of which a surfactant spreads, was investigated. A pronounced transition in the morphology evolution of the flowing thin film was found to be induced by the spatial restriction imposed through chemical surface patterns. The experimental results are in excellent agreement with numerical simulations reported by Myroslava Hanyak. Considering conditions in an oil reservoir, results for the spreading of surfactants along liquid-air interfaces can only give a first order approximation. The studies of Chapter 3 were therefore extended to the interface between two thin liquid films in Chapter 4. Here the spreading of a surfactant, soluble in one phase, is studied along the liquid-liquid interface of thin films. Resembling reservoir conditions, the films were subject to both, physical confinement as well as confinement imposed by a wettability pattern. In the context of surfactant spreading, it is a conceptually entirely new discovery, that surfactant induced Marangoni flows cannot only transport surfactants along fluid interfaces but can also efficiently transport surfactants along interfaces exhibiting considerably sized discontinuities. All existing literature in the field of surfactant spreading exclusively regarded continuous fluid interfaces. This novel phenomenon was the topic of Chapter 5. The convective surfactant spreading along discontinuous interfaces is directly relevant to the spreading of surfactants in an oil reservoir. In these porous underground rock formations the oil-water interface is not necessarily connected, such that surfactant spreading through a reservoir involves transport over interface discontinuities. Besides the spreading of surfactants, I also studied the self-propulsion of surfactant droplets. The results of my experimental studies were presented in Chapter 6 and 7. Self-propulsion dynamics exhibited by insoluble surfactant droplets on thin liquid films are systematically investigated in Chapter 6. Several modes of motion were described from directed continuous propulsion over a meandering mode of propulsion, that can also be exhibited by a pair of droplets in a synchronized fashion, to an intermittent form of propagation. The systematic study of the various modes of propulsion is complemented with the outline of a potential application in microfluidic devices in Chapter 7. In this context I am describing the novel phenomenon of transporting solid cargo particles using these self-propelling droplets which can be routed across micro-fluidic networks by controlling the temperature field around the drop e.g. using an infrared laser. The independence from external power sources, integrated electrodes or heating elements to propel the droplets, makes the concept specifically interesting for applications in inexpensive, single-use-type devices. In this thesis surfactant induced flows are studied in a wide range of system configurations. Confinement effects on the spreading dynamics are investigated systematically. These studies are complemented by the presentation of novel phenomena such as the Marangoni driven convective transport of surfactants along discontinuous interfaces

Extraction of Displacement Fields in Heterogeneous Media Using Optimal Local Basis Functions

The Multiscale Spectral Generalized Finite Element Method (MS-GFEM) was developed in recent work by Babuska and Lipton. The method uses optimal local shape functions, optimal in the sense of the Kolmogorov n-width, to approximate solutions to a second order linear elliptic partial differential equation with L-infinity coefficients. In this dissertation an implementation of MS-GFEM over a two subdomain partition of unity is outlined and several numerical experiments are presented. The method is applied to compute local fields inside high contrast particle suspensions. The method\u27s performance is evaluated for various examples with different contrasts between reinforcement particles and matrix material. The numerical experiments are shown to agree with a new theoretical estimate that shows the convergence rate is independent of the elastic properties of particles and matrix materials. A new domain decomposition method based on MS-GFEM is presented. Numerical computations using this iterative method are discussed and the theoretical convergence rate is provided. It is shown that the convergence rate is given by the same near-exponential bound given for MS-GFEM. A systematic method for identifying the worst case load amongst all boundary loads of a fixed energy is introduced. Here the worst case load delivers the largest fraction of input energy into a prescribed subdomain of interest. This leads to an eigenvalue problem, for which the largest eigenvalue is the maximum fraction of energy which concentrates in the subdomain. The associated eigenfunctions are the worst case solutions. These eigenfunctions are related back to the MS-GFEM shape functions and numerical results are presented for several different geometries

Mesoscopic simulation of diffusive contaminant spreading in gas flows at low pressure

Many modern production and measurement facilities incorporate multiphase systems at low pressures. In this region of flows at small, non-zero Knudsen- and low Mach numbers the classical mesoscopic Monte Carlo methods become increasingly numerically costly. To increase the numerical efficiency of simulations hybrid models are promising. In this contribution, we propose a novel efficient simulation approach for the simulation of two phase flows with a large concentration imbalance in a low pressure environment in the low intermediate Knudsen regime. Our hybrid model comprises a lattice-Boltzmann method corrected for the lower intermediate Kn regime proposed by Zhang et al. for the simulation of an ambient flow field. A coupled event-driven Monte-Carlo-style Boltzmann solver is employed to describe particles of a second species of low concentration. In order to evaluate the model, standard diffusivity and diffusion advection systems are considered.Comment: 9 pages, 8 figure

Configuration Lifting: Verification meets Software Configuration

Configurable software is ubiquitous, and the term Soft-ware Product Line (SPL) has been coined for it lately. It remains a challenge, however, how such software can be verified over all variants. Enumerating all variants and an-alyzing them individually is inefficient, as knowledge can-not be shared between analysis runs. Instead of enumera-tion we present a new technique called lifting that converts all variants into a meta-program, and thus facilitates the configuration-aware application of verification techniques like static analysis, model checking and deduction-based approaches. As a side-effect, lifting provides a technique for checking software feature models, which describe soft-ware variants, for consistency. We demonstrate the feasibility of our approach by check-ing configuration dependent hazards for the highly config-urable Linux kernel which possesses several thousand of configurable features. Using our techniques, two novel bugs in the kernel configuration system were found.