Academic literature on the topic 'Strong comparison principle'
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Journal articles on the topic "Strong comparison principle"
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Lucia, M., and S. Prashanth. "Strong comparison principle for solutions of quasilinear equations." Proceedings of the American Mathematical Society 132, no. 4 (November 19, 2003): 1005–11. http://dx.doi.org/10.1090/s0002-9939-03-07285-x.
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Roselli, Paolo, and Berardino Sciunzi. "A strong comparison principle for the $p$-Laplacian." Proceedings of the American Mathematical Society 135, no. 10 (October 1, 2007): 3217–25. http://dx.doi.org/10.1090/s0002-9939-07-08847-8.
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Boyadzhiev, Georgi, and Nikolai Kutev. "Strong Maximum Principle for Viscosity Solutions of Fully Nonlinear Cooperative Elliptic Systems." Mathematics 9, no. 22 (November 22, 2021): 2985. http://dx.doi.org/10.3390/math9222985.
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In this paper, we consider the validity of the strong maximum principle for weakly coupled, degenerate and cooperative elliptic systems in a bounded domain. In particular, we are interested in the viscosity solutions of elliptic systems with fully nonlinear degenerated principal symbol. Applying the method of viscosity solutions, introduced by Crandall, Ishii and Lions in 1992, we prove the validity of strong interior and boundary maximum principle for semi-continuous viscosity sub- and super-solutions of such nonlinear systems. For the first time in the literature, the strong maximum principle is considered for viscosity solutions to nonlinear elliptic systems. As a consequence of the strong interior maximum principle, we derive comparison principle for viscosity sub- and super-solutions in case when on of them is a classical one. The main novelty of this work is the reduction of the smoothness of the solution. In the literature the strong maximum principle is proved for classical C2 or generalized C1 solutions, while we prove it for semi-continuous ones.
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Prashanth, S. "Strong Comparison Principle for Radial Solutions of Quasi-Linear Equations." Journal of Mathematical Analysis and Applications 258, no. 1 (June 2001): 366–70. http://dx.doi.org/10.1006/jmaa.2000.7515.
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Gigli, Nicola, and Chiara Rigoni. "A Note About the Strong Maximum Principle on RCD Spaces." Canadian Mathematical Bulletin 62, no. 02 (January 7, 2019): 259–66. http://dx.doi.org/10.4153/cmb-2018-022-9.
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Xing, Yang. "A strong comparison principle of plurisubharmonic functions with finite pluricomplex energy." Michigan Mathematical Journal 56, no. 3 (December 2008): 563–81. http://dx.doi.org/10.1307/mmj/1231770360.
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Capogna, Luca, and Xiaodan Zhou. "Strong comparison principle for $p$-harmonic functions in Carnot-Caratheodory spaces." Proceedings of the American Mathematical Society 146, no. 10 (July 13, 2018): 4265–74. http://dx.doi.org/10.1090/proc/14113.
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Jarohs, Sven. "Strong Comparison Principle for the Fractional p-Laplacian and Applications to Starshaped Rings." Advanced Nonlinear Studies 18, no. 4 (November 1, 2018): 691–704. http://dx.doi.org/10.1515/ans-2017-6039.
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AbstractIn the following, we show the strong comparison principle for the fractional p-Laplacian, i.e. we analyze\quad\left\{\begin{aligned} \displaystyle(-\Delta)^{s}_{p}v+q(x)\lvert v\rvert% ^{p-2}v&\displaystyle\geq 0&&\displaystyle\phantom{}\text{in ${D}$},\\ \displaystyle(-\Delta)^{s}_{p}w+q(x)\lvert w\rvert^{p-2}w&\displaystyle\leq 0&% &\displaystyle\phantom{}\text{in ${D}$},\\ \displaystyle v&\displaystyle\geq w&&\displaystyle\phantom{}\text{in ${\mathbb% {R}^{N}}$},\end{aligned}\right.where {s\in(0,1)}, {p>1}, {D\subset\mathbb{R}^{N}} is an open set, and {q\in L^{\infty}(\mathbb{R}^{N})} is a nonnegative function. Under suitable conditions on s, p and some regularity assumptions on v, w, we show that either {v\equiv w} in {\mathbb{R}^{N}} or {v>w} in D. Moreover, we apply this result to analyze the geometry of nonnegative solutions in starshaped rings and in the half space.
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Benedikt, Jiří, Petr Girg, Lukáš Kotrla, and Peter Takáč. "The strong comparison principle in parabolic problems with thep-Laplacian in a domain." Applied Mathematics Letters 98 (December 2019): 365–73. http://dx.doi.org/10.1016/j.aml.2019.06.035.
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Попова, Анна. "ON THE REGULATION AND CONTENT OF A LEGAL FRAMEWORK FOR HUMAN INTERACTION WITH ARTIFICIAL INTELLIGENCE, ROBOTS AND OBJECTS OF ROBOTICS." Rule-of-law state: theory and practice 16, no. 4-1 (April 1, 2020): 64–75. http://dx.doi.org/10.33184/pravgos-2020.4.7.
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Due to the emergence of technological solutions that allow creating systems based on strong artificial intelligence (AI), and the high probability of developing super-strong AI in the near future, special презумпцию невиновности человека attention has recently been paid to the legal problems of regulating the interaction of humans and society with new intelligent agents. The purpose of the research is to analyze modern legal principles of interaction between humans and artificial intelligence, neural networks and intelligent robots, which are the necessary basis for forming modern legislation in this area in Russia and foreign countries. Methods: empirical methods of comparison, description, interpretation; theoretical methods of formal and dialectical logic are used. Special scientific methods are used: comparative-legal, legal-dogmatic. Results: the study allows us to determine a number of relevant legal principles of human interaction with AI as well as with robots and other objects of robotics, based on a comparative legal analysis of the current legislation. They are the principle of humanism; the principle of justice; the prohibition of discrimination when using AI, robots and objects of robotics; the presumption of human innocence; the principle of human innocence; the principle of respect for human dignity; the principle of confidentiality; the principle of disclosure of information on the development, production and use of robots and artificial intelligence; the principle of autonomy of will when using systems equipped with AI; the principle of the presumption of consent; the principle of informed consent to the use (impact) of systems equipped with AI.
Dissertations / Theses on the topic "Strong comparison principle"
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Santos, Telma João. "Some versions of the Strong Maximum Principal for elliptic integral functionals." Doctoral thesis, Universidade de Évora, 2011. http://hdl.handle.net/10174/9506.
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The Strong Maximum Principle (SMP) is a well-known property, which can be recognized as a kind of uniqueness result for solutions of Partial Differential Equations. Through the necessary conditions of optimality it is applicable to minimizers in some classes of variational problems as well. The work is devoted to various versions of SMP in such variational setting, which hold also if the respective Euler-Lagrange equations are no longer valid. We prove variational SMP for some types of integral functionals in the traditional sense as well as obtain an extension of this principle, which can be seen as an extremal property of a series of specific functions.
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GOFFI, ALESSANDRO. "Topics in nonlinear PDEs: from Mean Field Games to problems modeled on Hörmander vector fields." Doctoral thesis, Gran Sasso Science Institute, 2019. http://hdl.handle.net/20.500.12571/9808.
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This thesis focuses on qualitative and quantitative aspects of some nonlinear PDEs arising in optimal control and differential games, ranging from regularity issues to maximum principles. More precisely, it is concerned with the analysis of some fully nonlinear second order degenerate PDEs over Hörmander vector fields that can be written in Hamilton-Jacobi-Bellman and Isaacs form and those arising in the recent theory of Mean Field Games, where the prototype model is described by a coupled system of PDEs involving a backward Hamilton-Jacobi and a forward Fokker-Planck equation. The thesis is divided in three parts.
The first part is devoted to analyze strong maximum principles for fully nonlinear second order degenerate PDEs structured on Hörmander vector fields, having as a particular example fully nonlinear subelliptic PDEs on Carnot groups. These results are achieved by introducing a notion of subunit vector field for these nonlinear degenerate operators in the spirit of the seminal works on linear equations. As a byproduct, we then prove some new strong comparison principles for equations that can be written in Hamilton-Jacobi-Bellman form and Liouville theorems for some second order fully nonlinear degenerate PDEs.
The second part of the thesis deals with time-dependent fractional Mean Field Game systems. These equations arise when the dynamics of the average player is described by a stable Lévy process to which corresponds a fractional Laplacian as diffusion operator. More precisely, we establish existence and uniqueness of solutions to such systems of PDEs with regularizing coupling among the equations for every order of the fractional Laplacian $sin(0,1)$. The existence of solutions is addressed via the vanishing viscosity method and we prove that in the subcritical regime the equations are satisfied in classical sense, while if $sleq1/2$ we find weak energy solutions. To this aim, we develop an appropriate functional setting based on parabolic Bessel potential spaces. We finally show uniqueness of solutions both under the Lasry-Lions monotonicity condition and for short time horizons.
The last part focuses on the regularizing effect of evolutive Hamilton-Jacobi equations with Hamiltonian having superlinear growth in the gradient and unbounded right-hand side. In particular, the analysis is performed both for viscous Hamilton-Jacobi equations and its fractional counterpart in the subcritical regime via a duality method. The results are accomplished exploiting the regularity of solutions to Fokker-Planck-type PDEs with rough velocity fields in parabolic Sobolev and Bessel potential spaces respectively.
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Sörensen, Susanne. "Five English Verbs : A Comparison between Dictionary meanings and Meanings in Corpus collocations." Thesis, Högskolan i Halmstad, Sektionen för humaniora (HUM), 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-6091.
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In Norstedts Comprehensive English-Swedish Dictionary (2000) it is said that the numbered list of senses under each headword is frequency ordered. Thus, the aim of this study is to see whether this frequency order of senses agrees with the frequencies appearing in the British National Corpus (BNC). Five English, polysemous verbs were studied. For each verb, a simple search in the corpus was carried out, displaying 50 random occurrences. Each collocate was encoded with the most compatible sense from the numbered list of senses in the dictionary. The encoded tokens were compiled and listed in frequency order. This list was compared to the dictionary's list of senses. Only two of the verbs reached agreement between the highest ranked dictionary sense and the most frequent sense in the BNC simple search. None of the verbs' dictionary orders agreed completely with the emerged frequency order of the corpus occurrences, why complementary collocational learning is advocated.
Books on the topic "Strong comparison principle"
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Donlan, Chris. Individual Differences. Edited by Roi Cohen Kadosh and Ann Dowker. Oxford University Press, 2015. http://dx.doi.org/10.1093/oxfordhb/9780199642342.013.66.
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This article discusses the results of three studies that have attempted to identify the factors underlying individual differences in mathematics. Holloway and Ansari (2009), explored the relation between basic number processing and attainment in primary school mathematics. Mazzocco et al. (2011) used a non-symbolic comparison task as an indicator of a preschool child’s Approximate Number System (ANS). Goebel et al. (2014), who tested the number knowledge of 173 six-year olds using a number identification task. All three studies tested specific hypotheses by making use of individual differences and associations between them. They also strongly validate two fundamental principles: that correlational models are limited by the measurements they contain, and that evidence consistent with a particular hypothesis does not necessarily constitute strong evidence in its favour. This article concludes by providing an overview of the topics covered in this book concerning individual differences in mathematics.
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Michaela, Hailbronner. Part IV Independent Constitutional Institutions, 17 Constitutional Legitimacy and the Separation of Powers: Looking Forward. Oxford University Press, 2016. http://dx.doi.org/10.1093/law/9780198759799.003.0018.
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This chapter takes a critical look at a number of the themes running through the book. It begins by arguing that the basis for constitutional legitimacy in many African states is tied to the turn against past ‘regimes of horror’, rather than rooted in strong expressions of popular sovereignty, but that this may well provide a sufficiently strong basis for judicial authority nevertheless. It also demonstrates how the strong concern with avoiding past mistakes influences African understandings of the separation of powers as a predominantly negative concept, designed to restrain state and in particular executive power, rather than to guide and steer it—in contrast to the broad aspirational provisions included in many African constitutions today. Finally, the chapter cautions against rejecting too readily political question doctrines where other principled arguments for judicial deference are lacking. The chapter concludes with a call for more South–South comparisons.
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Biewener, Andrew, and Sheila Patek. Animal Locomotion. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198743156.001.0001.
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This book provides a synthesis of the physical, physiological, evolutionary, and biomechanical principles that underlie animal locomotion. An understanding and full appreciation of animal locomotion requires the integration of these principles. Toward this end, we provide the necessary introductory foundation that will allow a more in-depth understanding of the physical biology and physiology of animal movement. In so doing, we hope that this book will illuminate the fundamentals and breadth of these systems, while inspiring our readers to look more deeply into the scientific literature and investigate new features of animal movement. Several themes run through this book. The first is that by comparing the modes and mechanisms by which animals have evolved the capacity for movement, we can understand the common principles that underlie each mode of locomotion. A second is that size matters. One of the most amazing aspects of biology is the enormous spatial and temporal scale over which organisms and biological processes operate. Within each mode of locomotion, animals have evolved designs and mechanisms that effectively contend with the physical properties and forces imposed on them by their environment. Understanding the constraints of scale that underlie locomotor mechanisms is essential to appreciating how these mechanisms have evolved and how they operate. A third theme is the importance of taking an integrative and comparative evolutionary approach in the study of biology. Organisms share much in common. Much of their molecular and cellular machinery is the same. They also must navigate similar physical properties of their environment. Consequently, an integrative approach to organismal function that spans multiple levels of biological organization provides a strong understanding of animal locomotion. By comparing across species, common principles of design emerge. Such comparisons also highlight how certain organisms may differ and point to strategies that have evolved for movement in diverse environments. Finally, because convergence upon common designs and the generation of new designs result from historical processes governed by natural selection, it is also important that we ask how and why these systems have evolved.
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Veech, Joseph A. Habitat Ecology and Analysis. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198829287.001.0001.
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Habitat is crucial to the survival and reproduction of individual organisms as well as persistence of populations. As such, species-habitat relationships have long been studied, particularly in the field of wildlife ecology and to a lesser extent in the more encompassing discipline of ecology. The habitat requirements of a species largely determine its spatial distribution and abundance in nature. One way to recognize and appreciate the over-riding importance of habitat is to consider that a young organism must find and settle into the appropriate type of habitat as one of the first challenges of life. This process can be cast in a probabilistic framework and used to better understand the mechanisms behind habitat preferences and selection. There are at least six distinctly different statistical approaches to conducting a habitat analysis – that is, identifying and quantifying the environmental variables that a species most strongly associates with. These are (1) comparison among group means (e.g., ANOVA), (2) multiple linear regression, (3) multiple logistic regression, (4) classification and regression trees, (5) multivariate techniques (Principal Components Analysis and Discriminant Function Analysis), and (6) occupancy modelling. Each of these is lucidly explained and demonstrated by application to a hypothetical dataset. The strengths and weaknesses of each method are discussed. Given the ongoing biodiversity crisis largely caused by habitat destruction, there is a crucial and general need to better characterize and understand the habitat requirements of many different species, particularly those that are threatened and endangered.
Book chapters on the topic "Strong comparison principle"
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van Strien, Marjorie, and Jan Schmidt-Burbach. "Promoting elephant-friendly tourism." In The elephant tourism business, 247–58. Wallingford: CABI, 2021. http://dx.doi.org/10.1079/9781789245868.0020.
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Abstract The village of Sauraha in Nepal is a principal entry point to Chitwan National Park and has been influenced by multiple events over the past few years, affecting the local tourism dynamics and specific tourism products like elephant-back safaris. The global debate on animal welfare visibly influences the local market dynamics for elephant safaris. At the same time, there are other local factors at play that may be of stronger influence. The destination has been affected by local political and economic challenges that have increased cost of operations, intensified competition and challenged potential visitors. Furthermore, Sauraha is attracting emerging markets with different values and expectations in comparison with the traditional markets and which are charged lower prices for services. This chapter explores the impact of these recent events facing the destination Sauraha and reveals how understanding this is key to informing a tailor-made strategy to improve welfare for captive elephants. This research was conducted in the context of an ongoing partnership between World Animal Protection and the Elephant Owners' Association of Sauraha, and involved interviews with stakeholders in Sauraha and Kathmandu, as well as a visitor survey. Findings show that there is an increasing interest among private elephant owners to consider alternative management styles, especially to alleviate personal liability.
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Cuesta, Mabel, and Peter Takáč. "A Strong Comparison Principle for the Dirichlet p-Laplacian." In Reaction Diffusion Systems, 79–87. CRC Press, 2020. http://dx.doi.org/10.1201/9781003072195-8.
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Della Rocca, Michael. "The Call of Parmenides." In The Parmenidean Ascent, 1–23. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780197510940.003.0001.
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Chapter 1 advances an interpretation of Parmenides as rejecting all distinctions and all non-being and as thus espousing a radical form of monism. Parmenides’ monism is so radical that, according to him, non-being cannot even be thought of or spoken of. Strong textual evidence is marshalled for seeing Parmenides’ rejection of distinctions as driven by his explicit and implicit commitment to the Principle of Sufficient Reason, the PSR, according to which each fact or thing has an explanation. The Parmenidean rejection of all distinctions amounts to a paradox in part because, in saying that non-being cannot be thought or said, Parmenides seems to be speaking of non-being. Comparison of Parmenides’ paradoxical view and Wittgenstein’s position in his Tractatus Theologico-Politicus is developed. Important secondary literature on Parmenides is engaged with, particularly the writings of G. E. L. Owen and Alexander Mourelatos.
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Walden, Kenneth. "Great Beyond All Comparison." In Rethinking the Value of Humanity, 181—C7.P96. Oxford University PressNew York, 2023. http://dx.doi.org/10.1093/oso/9780197539361.003.0008.
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Abstract Many people find comparisons of the value of persons distasteful, even immoral. But what can be said in support of the claim that persons have incomparable worth? This chapter considers an argument purporting to show that the value of persons is incomparable because it is so great—because it is infinite. The argument rests on two claims: that the value of our capacity for valuing must equal or exceed the value of things valued and that our capacity for valuing is unbounded in a very strong sense. After laying out this argument, I consider its implications for how we should regard each other. In particular, I suggest that it complicates efforts to understand morality as a system of principles. Instead, I propose that an aesthetic attitude, not unlike our experience of the sublime, is an apt response to humanity’s infinite value.
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Moller, Astrid. "Egypt under the Saite Dynasty." In Naukratis. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780198152842.003.0007.
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Only after considering the social background of the countries involved is it possible to determine whether we are indeed talking about a ‘port of trade’. For this reason, we first examine Egyptian society at the time of the Saites, and thereafter focus attention on its Greek counterpart. It is only when this change of perspective has been undertaken that we can cease to regard Naukratis unthinkingly as a Greek colony, and can grasp fully the phenomenon that it represents. It is primarily from Herodotus’ Second Book, supplemented by Egyptian and oriental sources, that we learn about the Egyptian Late Period, of which the Saite dynasty is a part. Egyptologists regard this period as somewhat peripheral, especially with respect to our particular interest, the economy; for this reason, it will occasionally be necessary to construct analogies, drawing on examples from the Middle and New Kingdoms. It can be assumed that the picture will have appeared somewhat different in the so-called Intermediate Periods, which are thus rendered invalid for purposes of comparison, the lack of strong central administration leading to a loss of influence on the part of the centres of redistribution. According to Polanyi, the dominant pattern of integration is determined by the manner in which land and work are allocated. The prevalent social and economic system in Egypt is characterized principally by redistribution, although a closer examination results in a more differentiated view. Agriculture, the basis of every pre-industrial economy, functions in Egypt according to a system of instructions and quota calculations. Taxes and dues are used to support the court and the bureaucracy, but are also redistributed to the producers, who thereby participate in Egypt’s ‘surplus society’. The bureaucracy is maintained by the producers, but simultaneously ensures that the system continues to function, thereby setting itself up as the ruling class. The desire for social prestige is typical of this elite, and finds expression in titles, dress, and the cult of the dead. In principle, all land in ancient Egypt belonged to the Pharaoh; however, it is possible to distinguish two forms of land ownership.
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Bos, Beth, and Theressa Engel. "Designing Elementary Mathematics Games using Effective Mathematics Teaching Practices." In Handbook of Research on Transforming Mathematics Teacher Education in the Digital Age, 406–32. IGI Global, 2016. http://dx.doi.org/10.4018/978-1-5225-0120-6.ch016.
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Problem-solving digital games that make sense of mathematics do not happen by accident but by careful design. This chapter looks at a popular design framework, Game Network Analysis (GaNA), and examines how teachers can use it to turn popular digital games into strong mathematical experiences grounded in effective teaching practices that use play, purposeful explorations, and focused dialogue to make mathematical concepts more meaningful. The chapter involves a careful study of the GaNA framework in comparison with the eight Mathematics Teaching Practices of Principles to Actions: Ensuring Mathematical Success for All. The findings encourage further analysis of the GaNA framework in terms of specific academic areas. Explicit clarification is needed to use the framework to effectively move mathematics education toward its future potential.
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West-Eberhard, Mary Jane. "Principles of Development and Evolution." In Developmental Plasticity and Evolution. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195122343.003.0012.
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So far, I have outlined the general properties of phenotypes, shown how they relate to development, and presented a model of adaptive evolution based on established principles of development and genetics. Now, using this general framework, I can summarize how developmental plasticity facilitates evolution. Jacob (1977) characterized evolution as “tinkering.” It shuffles and recombines what is already there. Frazzetta (1975), in another felicitous comparison with machines, wrote that evolution manages “the gradual improvement of a machine while it is running” (p. 20). Both of these qualities are possible due to characteristics of phenotypes that are not shared with most machines. Tinkering works because the phenotype is made of recombinable modular components that can be turned off and on in different conditions and can function in more than one context, what Gerhart and Kirshner (1997; Kirschner and Gerhart, 1998) call “weak linkage” to any particular use. Improvement without disruption of function works because of the remarkable active flexibility, and redundancy, in the development of parts. As a result of these two qualities—modularity and plasticity—an organism has the unmachinelike ability to respond to a new situation or to a new gene with the production of a new trait, and then to multiply, through reproduction, the ability to produce this trait. Differential reproduction starts the cycle of variation, selection, and cross-generational change that we call evolution—the most unmachinelike process of all. Many reasons have been given to believe that evolutionary change is difficult and even resisted in a well-adapted population (see chapter 1). The evolution of a novel specialization requires that a single lineage persist while undergoing extensive change. The conditions sometimes mentioned as favoring directional evolution, such as strong competition, very different or changing environments, small founder populations, or very long periods of time (see Mayr, 1982b), also favor population extinction. The idea of developmental cohesiveness, outlined in chapter 1, led to the further belief that major developmental change early in ontogeny would be disruptive. The cohesiveness theme persists even though it long has been clear that innovation does not occur exclusively by terminal addition (see chapter 1).
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A. Cara, Michel. "Multivariate Approach to Reading Comprehension and Sight-Reading." In Music in Health and Diseases. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.100130.
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This chapter focuses on the study of the relationship between reading of music and verbal texts and it seeks to define an ecological music reading task that allows comparison of musical and verbal domains. Participants were preservice music students who performed different music reading tasks correlated with a verbal text comprehension test. A Principal Component Analysis (PCA), was performed, explaining 91,5% of the variance. The following two axes were defined: one related to reading compression and the other to music performance variables. The relationship between the selected variables in the factorial plane, particularly the strong association between sight-reading and literal comprehension, suggest that sight-reading is a relevant factor with regards to the study of musical and verbal domains.
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Cananea, Giacinto della, and Mads Andenas. "Administrative Procedure and Judicial Review: A ‘Common Core’ Research." In Judicial Review of Administration in Europe, 3–20. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198867609.003.0001.
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This chapter begins by explaining why judicial review of administration is interesting terrain for a comparative analysis, also in the light of European and international principles. It is helpful to bear in mind that, for a long period of time, a strand of thought in public law has contested not just the usefulness, but even the possibility of a meaningful comparison between national systems of judicial review. It is important, however, to take cognisance of two fundamental dimensions of change: one is the increasing specialization of the courts that exercise control over administrative power and the other is the emergence of common principles at European and international level. The chapter then highlights the importance of procedural fairness and propriety, although the legal relevance and significance of these principles will differ depending upon the history of any society and its political choices. It also addresses some methodological issues, including the nature of the 'factual analysis' and the choice of legal systems.
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Doveton, John H. "Saturation-Height Functions." In Principles of Mathematical Petrophysics. Oxford University Press, 2014. http://dx.doi.org/10.1093/oso/9780199978045.003.0012.
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As observed by Worthington (2002), “The application of saturation-height functions forms part of the intersection of geologic, petrophysical, and reservoir engineering practices within integrated reservoir description.” It is also a critical reference point for mathematical petrophysics; the consequences of deterministic and statistical prediction models are finally evaluated in terms of how closely the estimates conform to physical laws. Saturations within a reservoir are controlled by buoyancy pressure applied to pore-throat size distributions and pore-body storage capacities within a rock unit that varies both laterally and vertically and may be subdivided into compartments that are not in pressure communication. Traditional lithostratigraphic methods describe reservoir architecture as correlative rock units, but the degree to which this partitioning matches flow units must be carefully evaluated to reconcile petrofacies with lithofacies. Stratigraphic correlation provides the fundamental reference framework for surfaces that define structure and isopach maps and usually represent principal reflection events in the seismic record. In some instances, there is a strong conformance between lithofacies and petrofacies, but all too commonly, this is not the case, and petrofacies must be partitioned and evaluated separately. Failure to do this may result in invalid volumetrics and reservoir models that are inadequate for fluid-flow characterization. A dynamic reservoir model must be history matched to the actual performance of the reservoir; this process often requires adjustments of petrophysical parameters to improve the reconciliation between the model’s performance and the history of production. Once established, the reservoir model provides many beneficial outcomes. At the largest scale, the model assesses the volumetrics of hydrocarbons in place. Within the reservoir, the model establishes any partitioning that may exist between compartments on the basis of pressure differences and, therefore, lack of communication. Lateral trends within the model trace changes in rock reservoir quality that control anticipated rates and types of fluids produced in development wells. Because the modeled fluids represent initial reservoir conditions, comparisons can be made between water saturations of the models and those calculated from logs in later wells, helping to ascertain sweep efficiency during production.
Conference papers on the topic "Strong comparison principle"
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Achten, Peter A. J. "Power Density of the Floating Cup Axial Piston Principle." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59006.
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The floating cup principle is a new concept for hydrostatic pumps, motors and transformers. It features a large number of pistons, which enables a strong reduction of the pressure pulsations and fluid borne noise. The pistons are arranged in a double ring, back-to-back configuration, and are locked onto the rotor. Each piston has a separate, cuplike cylinder, which is floating on a rotating barrel plate. This article will discuss the consequences of the floating cup design on the power density of pumps and motors. For current axial piston units the trend is towards larger tilt angles of the barrel. In slipper type machines, the tilt angles can be as large as 21°, whereas in bent axis machines the tilt angle can even be increased to 45°. For a 24 piston floating cup machine, the tilt angle of each barrel is however limited to about 12°. The object of the article is to prove that the reduced tilt angle does not need to have a detrimental effect on the power density of the hydrostatic machine. After giving a brief description of the floating cup principle, the article will focus on the design aspects that limit the barrel tilt angle. After this, the main parameters that govern the power density are discussed. A comparison with a slipper type pump is made.
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Jiang, Zhen, Xi Wang, Huairong Chen, and Yunlai Wang. "Design of Speed Closed-Loop Control With Variable Pressure Difference Valve for Aero Engine." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14737.
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Abstract Focusing on the advantages of simple structure, quick response and good static performance when fuel system using variable pressure difference valve (VPDV) and the development trend to full authority digital engine control (FADEC) of modern engine, this paper aims to propose a design method of digital speed closed-loop control system based on fuel metering unit (FMU) using VPDV. Firstly, the working principle of a real engine with VPDV is introduced, and the nonlinear AMESim model of the system is established. Secondly, the static analysis of VPDV and metering valve is carried out, and the principle of speed closed-loop control of the hydraulic mechanical system is revealed. Therefore, we built the structure of digital speed control circuit with VPDV. Thirdly, a PI controller is designed for the model augmented by the engine and VPDV, and the parameters of the controller are optimized by the differential evolution (DE) algorithm. Moreover, the controller of gain scheduling is applied to the engine nonlinear model simulation platform. Simulation results illustrated that the designed digital speed closed-loop control can realize the function of speed regulation, and has the advantages of good servo performance and strong stability in comparison with the original hydraulic mechanical control system.
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Kus, Umit, and Jacques Chauvin. "A Rapid Method for Predicting Global and Local Performance of Cascades With Special Emphasis on the Calculation of the Transition Region." In ASME 1994 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1994. http://dx.doi.org/10.1115/94-gt-256.
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The principle of a rapid method of cascade performance prediction is presented. It is based on a strong coupling between a potential flow approach and an integral boundary layer method, and takes into account laminar, transitional and turbulent regimes as well as the separated regions. Special emphasis is given to the transitional region. In addition to a pre-existing bubble separation model and following an extensive literature survey, two transition onset and three transition length criteria have been incorporated in the method as well as a Görtler type approach. Comparison of the criteria on typical cascades show that they are relatively coherent between themselves and lead to a satisfactory prediction of the global performance for a large number of different compressor and turbine cascades among which the NACA and DCA cascades discussed in this paper. Local boundary layer performance is compared with Deutsch and Zierke’s data, where, unhappily, transition is chiefly through separation bubbles. The comparison shows the validity of Roberts ‘bubble transition model. Applying the Görtler curvature approach gives similar results to the other criteria. The global performance prediction for this case is also satisfactory. Additionally, parametric studies are carried out on the effect of external turbulence level.
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Palamara, Matthew J., Stephen D. Smith, Adam P. Walker, Richard A. Basel, and Gregory A. Meyer. "Development of an Advanced PWR Reactor Internals System Finite Element Model for Flow-Induced Vibration Analyses." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45278.
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The reactor vessel internals (RVI) are located within the reactor vessel, which is part of the reactor coolant system (RCS) loop in Westinghouse nuclear plant designs. Historically, the coolant passing through the RCS loop has been highly turbulent and has generated significant turbulence-induced excitation (TE) for the RVI. In an effort to analytically quantify the response of RVI structures due to TE for new designs, a methodology is employed which combines both first principle concepts as well as operational experience. As part of this process, TE-induced forcing functions are developed based upon the numerous flow fields around the components of interest. After the TE-induced forcing functions are developed, they are applied to a system finite element model (SFEM), in a transient dynamic finite element analysis to capture dynamic system-level interactions. To benchmark the response of the numerical model, both narrowband and broadband model responses are compared to empirical data extrapolated from model-scale flow-induced vibration test results. This comparison shows a strong agreement between the empirical data and the SFEM, validating that the dynamic response and system interactions of RVI structures due to TE can be accurately characterized through numerical simulation of the system.
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Zhou, Wen-li, Jian Pu, Tiao Zhang, Jian-hua Wang, Wei-long Wu, and Hang Su. "Wall Curvature Effect on Overall Thermal Performances of Film Cooling Covered by Thermal Barrier Coatings With Various Geometries." In ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-82796.
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Abstract Film cooling coupling with surface thermal barrier coating (TBC) has been widely adopted, bringing to an intensive need of comprehensive overall thermal characteristics. In present work, combined effects of hole-geometry, wall curvature, and cooling air flowrate on the metal overall effectiveness and wall heat flux were discussed. Typical local regions of turbine vanes were simplified as convex, concave, and flat walls. Spraying TBC generated four hole-configurations, including Standard Cylindrical-hole (SC), transverse Trenched-hole (TT-hole), and two modified trenched-holes with Semicircle-shaped Trench (ST) and Sine Wave-shaped Trench (SWT). The ST reduces the exposed area and the SWT improves the fluid-diversion effect of TT. Based on the engine-matched hot-side Biot-numbers, overall cooling effectiveness measurements were carried out under typical blowing ratios (BRs) from 0.5 to 2.0, through capturing wall temperatures by an infrared thermal sensor and thermocouples. Conjugate heat transfer simulations were also conducted, showing good agreement with the experimental data and hence providing additional insights into the heat transfer features and film cooling jet behaviors. The results indicated that the wall curvature effects on overall thermal parameters are relatively weaker, in comparison with the hole-geometry and BR. The trenches can further weaken the wall curvature effect. Comparisons of trench-designs reveals that achievement of strong fluid-diversion in trench is an important principle of trench-modification, which can acquire not only superior overall cooling characteristics, but also a relatively large ability to prevent the hot gas ingestion and the hole-blockages by harmful contaminant-depositions.
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Mulay, Shirish. "Thermal Simulation and Experimental Comparison of a Printhead." In ASME 2007 5th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2007. http://dx.doi.org/10.1115/icnmm2007-30165.
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Thermal inkjet technology (TIJ) has been the widely preferred method of inkjet printing since its market inception in 1985. Thermal inkjet technology continues to enjoy a greater unit market share for printers than any other printing technology. In this presentation history of inkjet printing will be discussed. In the recent past, thermal inkjets have made great strides. Speed of printing is a strong function of the swath size and can be increased by increasing the chip size. Photo quality printing has reached new levels by reducing drop size and spot size. This has been achieved by increasing nozzle density, increasing frequency of printing and using multiple pass printing to optimize quality. However, to improve speed of printing single pass resolution is an important parameter. The paper presents the simple working principle of the inkjet printhead. The physics of printhead operation will be shown briefly. A thermal analysis is carried out on the printhead. Simulations of printing on paper has been carried out for hypothetical print densities and compared with simple experiments. The scales that appear range from microns to millimeters. Short term and long term analysis has been carried out. Figure 1 shows the cross-section of a part of the printhead. The parts depicted in Figure 1 shows the plastic body, chip along with the vias for ink flow. In the analysis, die bond, encapsulant, tab circuit, nozzle plate have been included but not included in Figure 1 for clarity. Temperature as a function of time and was measured by the temperature sensing resistor (tsr). The parameter considered in this study was the density of printing, uni or bi directional printing and excess energy supplied to the chip. Current, voltage, time for printing and drop mass was measured. Temperature was monitored during the printing process. The effects of temperature on the viscosity, surface tension have been neglected in the study. A commercial code from Flow Science was used for the CFD analysis. The boundary conditions used were (i) Bottom boundary was set with velocity inflow rate and temperature (ii) top boundary conditions have heat transfer coefficient to ambient and exit pressure conditions (ambient pressure) and (iii) all sides have heat transfer coefficients. The appropriate properties have been used in the simulations, namely, density, specific heat and thermal conductivity of the different materials associated with the nozzle plate, tab circuit, die-bond and the plastic body is made of Noryl. The mesh sized varied from the smallest of 1 micron to the largest being a fraction of millimeter. Results of chip temperature response versus time are shown in Figure 2. Files of known density were generated by using Corel Draw package and printed. Figure two shows the response to seven pages of printing. It also shows the chip cooling off. The temperature response curve shows that the system can be divided in to three time constants. The first time constant is extremely fast and can be related to chip parameters. The third time constant is a very slow one and can be identified with the printhead body and its surroundings, like the ambient temperature, convective heat transfer to the surroundings etc. The intermediate time constant is a function of the assembly of chip to the printhead body and it’s surrounding cross section, i.e. the heat spreader. Figure 3 shows the temperature response (simulation) to a hypothetical printing case and an excess energy of 5%. Some part of the geometry has been changed for purpose of confidentiality. The energy levels in the standard case are not what one would use in regular printing. The temperature response is generally dependent on geometry and the package of chip encapsulation. For the geometry chosen, the temperature changes by the same amount in Celsius as the percent rate of energy changes at the heater level. For example, in Figure 3 the energy changes by 5 percent and the steady state temperature increases by 5 C.
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Zhu, Lei, Shouhua Sun, and Taozhong Xu. "Development and Application of the 3-D Core Fuel Management Transport Program for HFETR." In 2016 24th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icone24-60365.
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The High Flux Engineering Test Reactor (HFETR) is loaded with complex geometry assemblies, taking on strong heterogeneity. These features call for more advanced core analysis and fuel management methodologies compared with traditional PWR. Based on the two-step method, a fuel management simulation platform HEFT was developed, which is a 3-D core fuel management transport calculation program of HFETR. In HEFT, the lattice code HEFT-lat has the abilitiesto describe complex assembly geometriesof HFETR, whereby mitigate errors brought by geometrical approximations.DNTR, a triangular mesh nodal SN method code, is employed to solve the transport equation. This paper introduces the development backgrounds of HEFT, introduces the principle and function of the three main modules of HEFT, that is HEFT-lat?HEFT-core and HEFT-int, the calculation method of lattice parameter and reactor loop calculation method are described. By follow-up calculation of 81-I to 89-II of HFETR core and comparison of intial critical keff, the control rod position during shutting down and the neutron flux, thus obtains the calculation deviation. The result shows the validity of the HEFT code, the lattice and reactor core calculation model. Thus, HEFT has already successfully applied to the fuel management calculation of HFETR.
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Geier, Sebastian M., Peter Wierach, Thorsten Mahrholz, and Michael Sinapius. "Carbon Nanotube Strain Measurements via Tensile Testing." In ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/smasis2014-7572.
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Discovering and characterizing new smart materials is an urgent need to close the performance-gaps of standard active materials. There is still the demand for a material providing high modulus, low density and large strain. Carbon materials catch scientific attention since a while but one sort among these is of special interest, carbon nanotubes (CNTs). Beside excellent material properties another interesting feature was first mentioned 1999 — the active behavior of paper-like mats made of CNTs. The CNT-papers are electrical activated using a double-layer interaction of ions provided by an electrolyte and the charged high surface area of the paper formed by carbon tubes. Until now the mechanism behind the strain generation of CNT-based architectures is unknown. The principle of the mechanism reveals the potential of carbon tubes to be or not to be a resilient smart material in order to use the strong carbon bonds instead of weak van der Waals force as linking between the tubes. This paper presents further investigations about the mechanical composition of CNT-papers as well as vertical aligned CNT-arrays using an actuated tensile test set-up. For better comparison the experiments are conducted in dry, wet and wet/charged conditions. Especially in the case of CNT-arrays it is essential to preload the specimens because their curly CNT-structure superimposes the vertical orientation of the arrays. While the CNT-paper is tested in an one molar sodium chloride solution, the hydrophilic character of CNT-arrays requires an ionic liquid (IL). It is found that the mechanical properties of CNT-papers drop significantly by wetting and further more by charging what indicates an electrostatic dominated effect. In contrast the CNT-arrays show similar results independent of their test-conditions and an active, reversible behavior of tube-elongation by charging. These results indicate strongly a quantum-mechanical effect of the single tubes.
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Kang, Can, Shengnan Xiao, Dong Liu, and Feng Zhang. "Water Jet Performance Variation for Intrusion of a Cylinder Central-Body." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30184.
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Based on Karman vortex street principle, central-body nozzle is expected to arouse cavitation in the discharged jet and then result in strong impact on acted object. To discover the influence of central-body on flow characteristics, under the same jet pressure of 15MPa, comparison between the two free water jet fields produced respectively by a central-body nozzle and a round nozzle was conducted. Phase Doppler particle anemometry (PDPA) was applied to measure velocity distribution, turbulent fluctuation and droplet diameter distribution at different traverse sections. Experimental results show that although the annular jet tends to concentrate soon after the central body, the radial diffusion of the jet discharged from the central-body nozzle is more obvious. For the two jets kinetic energy is well remained along the jet direction and high-velocity zone is wider near the jet axis of the central-body nozzle. For the jet discharged from the central-body nozzle, turbulent fluctuation near the jet axis is relatively weak. As for possible cavitation, the position is right after the central body and the reachable distance of cavitation effect is short, which produces an inevitable restriction on the nozzle’s application. And similar Sauter mean diameter (SMD) distribution profiles are found in the two jet fields especially when distance between nozzle and traverse section gets large. The study here provides quantitative and comparative information for the two nozzles and can be referred to in further study and optimal design of central-body nozzle.
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Stieglitz, Ina, and Peter Ehrhard. "A Hybrid Model for the Simulation of Electroosmotic Flows in Microchannels, Induced by Internal Electrodes." In ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30750.
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In general, the modeling of electroosmotic flows can be approached in two fundamentally–different ways. (i) The thickness of electrical double layer (EDL) is ignored and the effect of the electrical forces within the EDL is imaged into a modified kinematic boundary condition, the so-called Helmholtz–Smoluchowski slip condition. This approach is numerically simple and inexpensive, but implies several restrictions. (ii) The EDL is fully resolved, using a first–principle approach based on differential conservation equations for mass, momentum, and charge. This approach is enormously elaborate and numerically expensive, but appears to be applicable for a much wider range of problems. As an example, the treatment of internal electrodes, adjacent to insulating walls at defined zeta potential, appears difficult with the simple approach (i), since any non–continuous potential distribution at the wall leads to a singularity of the electrical field strength. To avoid these difficulties, we develop a hybrid model which, on the one hand, electrically resolves the EDL to reveal a perfectly-continuous potential distribution in the complete microchannel. On the other hand, the flow equations are solved in the fluid bulk only, not comprising the EDL. Hence, the effect of the EDL is still incorporated by means of modified kinematic boundary conditions. The advantage of this hybrid model is, firstly, to avoid artificial singularities of the electrical field strength, where regions of different surface charge meet. These singularities are clearly artificial, since they result from neglecting the extend of the EDL. Secondly, the hybrid model, at each time step, needs to solve only once for the potential distribution, which makes it numerically inexpensive and simple. Hence, systematic parameter studies are within reach. We apply the hybrid model to investigate the influence of internal electrodes onto the flow field, driven by electroosmosis in a modular rectangular microchannel. As internal electrodes can be positioned at lower distances (if compared to external electrodes), they can be operated at lower voltages and still ensure strong electrical field strength. Systematic studies on the effect of different electrode positions and voltages are presented, leading to optimized settings for specific tasks as pumping or mixing. Further, a comparison to first-principle simulations using the approach (ii) is presented for selected cases. This demonstrates that the hybrid model perfectly captures the dominant physics.
Reports on the topic "Strong comparison principle"
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Willi, Joseph, Keith Stakes, Jack Regan, and Robin Zevotek. Evaluation of Ventilation-Controlled Fires in L-Shaped Training Props. UL's Firefighter Safety Research Institute, October 2016. http://dx.doi.org/10.54206/102376/mijj9867.
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Investigations of recent firefighter line of duty deaths caused by rapid fire progression have highlighted a deficiency in firefighters’ understanding of how certain tactics affect the fire dynamics of ventilation-controlled fires. Many fires are in a ventilation-limited, decay state by the time firefighters arrive at the scene, meaning that introducing additional ventilation to the environment has the potential to cause rapid and intense fire growth. To more effectively teach firefighters about the potential effects of ventilation on a compartment fire, ventilation-controlled fires should be gener- ated during training. Safely creating such fires while maintaining compliance with NFPA 1403: Standard on Live-Fire Training Evolutions allows instructors to educate students on this important principle of fire dynamics in the training environment. Structures utilized for live-fire training have evolved from typical concrete burn buildings to now include smaller purpose-built props, like those constructed from steel shipping containers or wood and gypsum board. Such props have been embraced by organizations due to their cost-effectiveness and potential to improve fire behavior training. Obtaining a thorough understanding of the capa- bilities and limitations of such props is critical for instructors to convey accurate messages during training and properly prepare firefighters for scenarios they’ll encounter in the field. Experiments were conducted to quantify the fire environment in L-shaped props with different wall constructions. One prop had an interior wall lining of gypsum board over wood studs and fiberglass insulation. The two other props were constructed from metal shipping containers with corrugated steel walls; one had ceilings and walls comprised solely of the corrugated steel, while the other had ceilings and walls comprised of rolled steel sheeting over mineral wool insulation with the corrugated steel wall as its backing. Three fuel packages were compared between the props: one contained furnishings mainly composed of synthetic materials and foam plastics; another contained wooden pallets and straw; and the third contained wooden pallets, straw, and oriented strand board (OSB). A stochastic approach was used to compare data between replicate tests and quantify the repeatability of the different props and fuel packages, all of which were deemed sufficiently repeatable. Comparisons of data between the three props revealed that thermal conditions between experiments in the two metal props were indistinguishable, suggesting that the additional layer of insulation did not significantly alter the fire environment. Additionally, thermal conditions in the gypsum-lined prop were more severe than those in the metal props. The effects of ventilation changes on fire conditions were also analyzed across various prop and fuel load combinations. Lastly, the response of the thermal environment in each prop during interior suppression was evaluated, and the results implied that the thermal exposure to the firefighter was more severe in the metal props than the gypsum prop for a brief period following the start of suppression.
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Carpita, Nicholas C., Ruth Ben-Arie, and Amnon Lers. Pectin Cross-Linking Dynamics and Wall Softening during Fruit Ripening. United States Department of Agriculture, July 2002. http://dx.doi.org/10.32747/2002.7585197.bard.
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Our study was designed to elucidate the chemical determinants of pectin cross-linking in developing fruits of apple and peach and to evaluate the role of breakage cross-linkages in swelling, softening, and cell separation during the ripening. Peaches cell walls soften and swell considerably during the ripening, whereas apples fruit cells maintain wall firmness but cells separate during late stages of ripening. We used a "double-reduction" technique to show that levels of non-methyl esters of polyuronic acid molecules were constant during the development and ripening and decreased only in overripe fruit. In peach, methyl and non-methyl esters increased during the development and decreased markedly during the ripening. Non-methyl ester linkages in both fruit decreased accompanied fruit softening. The identity of the second component of the linkage and its definitive role in the fruit softening remain elusive. In preliminary examination of isolated apples cell walls, we found that phenolic compounds accumulate early in wall development but decrease markedly during ripening. Quantitative texture analysis was used to correlate with changes to wall chemistry from the fresh-picked ripe stage to the stage during storage when the cell separation occurs. Cell wall composition is similar in all cultivars, with arabinose as the principal neutral sugar. Extensive de-branching of these highly branched arabinans pre-stages softening and cell-cell separation during over-ripening of apple. The longer 5-arabinans remain attached to the major pectic polymer rhamnogalacturonan I (RG I) backbone. The degree of RG I branching, as judged from the ratios of 2-Rha:2,4-Rha, also decreases, specially after an extensive arabinan de-branching. Loss of the 4-Rham linkages correlated strongly with the softening of the fruit. Loss of the monomer or polymer linked to the RG I produce directly or indirectly the softening of the fruit. This result will help to understand the fruit softening and to have better control of the textural changes in fruit during the ripening and especially during the storage. 'Wooliness', an undesirable mealy texture that is induced during chilling of some peach cultivars, greatly reduces the fruit storage possibilities. In order to examine the hypothesis that the basis for this disorder is related to abnormality in the cell wall softening process we have carried out a comparative analysis using the resistant cultivar, Sunsnow, and a sensitive one, Hermosa. We investigated the activity of several pectin- and glycan-modifying enzymes and the expression of their genes during ripening, chilling, and subsequent shelf-life. The changes in carbohydrate status and in methyl vs. non-methyl uronate ester levels in the walls of these cultivars were examined as well to provide a basis for comparison of the relevant gene expression that may impact appearance of the wooly character. The activities of the specific polygalacturonase (PGase) and a CMC-cellulase activities are significantly elevated in walls of peaches that have become wooly. Cellulase activities correlated well with increased level of the transcript, but differential expression of PGase did not correspond with the observed pattern of mRNA accumulation. When expression of ethylene biosynthesis related genes was followed no significant differences in ACC synthase gene expression was observed in the wooly fruit while the normal activation of the ACC oxidase was partially repressed in the Hermosa wooly fruits. Normal ripening-related loss of the uronic acid-rich polymers was stalled in the wooly Hermosa inconsistent with the observed elevation in a specific PGase activity but consistent with PG gene expression. In general, analysis of the level of total esterification, degree of methyl esterification and level of non-methyl esters did not reveal any major alterations between the different fruit varieties or between normal and abnormal ripening. Some decrease in the level of uronic acids methyl esterification was observed for both Hermosa and Sunsnow undergoing ripening following storage at low temperature but not in fruits ripening after harvest. Our results support a role for imbalanced cell wall degradation as a basis for the chilling disorder. While these results do not support a role for the imbalance between PG and pectin methyl esterase (PME) activities as the basis for the disorder they suggest a possible role for imbalance between cellulose and other cell wall polymer degradation during the softening process.