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Search Results: 1 - 10 of 203593 matches for " Roland P. Malhame "
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Consensus Algorithms and the Decomposition-Separation Theorem
Sadegh Bolouki,Roland P. Malhame
Mathematics , 2013,
Abstract: Convergence properties of time inhomogeneous Markov chain based discrete and continuous time linear consensus algorithms are analyzed. Provided that a so-called infinite jet flow property is satisfied by the underlying chains, necessary conditions for both consensus and multiple consensus are established. A recenet extension by Sonin of the classical Kolmogorov-Doeblin decomposition-separation for homogeneous Markov chains to the inhomogeneous case is then employed to show that the obtained necessary conditions are also sufficient when the chain is of Class P*, as defined by Touri and Nedic. It is also shown that Sonin's theorem leads to a rediscovery and generalization of most of the existing related consensus results in the literature.
Linear Consensus Algorithms Based on Balanced Asymmetric Chains
Sadegh Bolouki,Roland P. Malhame
Mathematics , 2012,
Abstract: Multi agent consensus algorithms with update steps based on so-called balanced asymmetric chains, are analyzed. For such algorithms it is shown that (i) the set of accumulation points of states is finite, (ii) the asymptotic unconditional occurrence of single consensus or multiple consensuses is directly related to the property of absolute infinite flow for the underlying update chain. The results are applied to well known consensus models.
Theorems about Ergodicity and Class-Ergodicity of Chains with Applications in Known Consensus Models
Sadegh Bolouki,Roland P. Malhame
Mathematics , 2012,
Abstract: In a multi-agent system, unconditional (multiple) consensus is the property of reaching to (multiple) consensus irrespective of the instant and values at which states are initialized. For linear algorithms, occurrence of unconditional (multiple) consensus turns out to be equivalent to (class-) ergodicity of the transition chain (A_n). For a wide class of chains, chains with so-called balanced asymmetry property, necessary and sufficient conditions for ergodicity and class-ergodicity are derived. The results are employed to analyze the limiting behavior of agents' states in the JLM model, the Krause model, and the Cucker-Smale model. In particular, unconditional single or multiple consensus occurs in all three models. Moreover, a necessary and sufficient condition for unconditional consensus in the JLM model and a sufficient condition for consensus in the Cucker-Smale model are obtained.
Eminence Grise Coalitions: On the Shaping of Public Opinion
Sadegh Bolouki,Roland P. Malhame,Milad Siami,Nader Motee
Mathematics , 2014,
Abstract: We consider a network of evolving opinions. It includes multiple individuals with first-order opinion dynamics defined in continuous time and evolving based on a general exogenously defined time-varying underlying graph. In such a network, for an arbitrary fixed initial time, a subset of individuals forms an eminence grise coalition, abbreviated as EGC, if the individuals in that subset are capable of leading the entire network to agreeing on any desired opinion, through a cooperative choice of their own initial opinions. In this endeavor, the coalition members are assumed to have access to full profile of the underlying graph of the network as well as the initial opinions of all other individuals. While the complete coalition of individuals always qualifies as an EGC, we establish the existence of a minimum size EGC for an arbitrary time-varying network; also, we develop a non-trivial set of upper and lower bounds on that size. As a result, we show that, even when the underlying graph does not guarantee convergence to a global or multiple consensus, a generally restricted coalition of agents can steer public opinion towards a desired global consensus without affecting any of the predefined graph interactions, provided they can cooperatively adjust their own initial opinions. Geometric insights into the structure of EGC's are given. The results are also extended to the discrete time case where the relation with Decomposition-Separation Theorem is also made explicit.
Addressing the Quantitative and Qualitative: A View to Complementarity—From the Synaptic to the Social  [PDF]
James Giordano, P. Justin Rossi, Roland Benedikter
Open Journal of Philosophy (OJPP) , 2013, DOI: 10.4236/ojpp.2013.34A001
Abstract: History and anthropology reveal the perdurable human characteristic of attempting to create and employ some form of quantifiable representation of the qualitative aspects of life and the natural world. The recent revolution in the ability to quantify neurobiological processes through advanced neurotechnologies, and the announcement of comprehensive mapping of neuronal pathways as priorities both within the United States (e.g. the Brain Research through Advancing Innovative Neurotechnology, BRAIN, Initiative), and internationally (e.g. the European Union’s Human Brain Project) call forth questions about how data, both quantitative and qualitative, can and should be leveraged to sustain neuroscientific research and related applications that are ethically sound, technically viable, and socially relevant. As neuroscience evermore gains influence in medical, public, economic and political spheres, it will be important to ask (early and iteratively) what such science—as a human endeavor—seeks to achieve, and how the methods selected (whether quantitative, qualitative, or some combination thereof) may help to realize such goals. In this paper we explore potential sources of tension, alignment, and integration with respect to the quantitative and qualitative domains of neuroscientific research, its influence upon society, and the role that the field of neuroethics can—and arguably should—play in rendering balance to the use of neuroscientific knowledge as both lens into the brain, and mirror upon human thought and action. Ultimately, we propose a stance of complementarity with a view toward maximizing the benefits of both the quantitative and qualitative domains.
Wardrobe Malfunctions and the Measurement of Internet Behaviour  [PDF]
Roland Pfister
Psychology (PSYCH) , 2011, DOI: 10.4236/psych.2011.23042
Abstract: The wardrobe malfunction – an unanticipated exposure of bodily parts in the public – has become a prevailing issue in concerts, shows and other celebrity events that is reliably reported by the media. The internet as the fastest source for celebrity gossip allows measuring the impact of such wardrobe malfunctions on the public in-terest in a celebrity. This measurement in turn allows conclusions about intention, motivation, and internet be-haviour of a wide variety of internet users. The present study exemplifies the use of an innovative non-reactive measure of active interest – the Search Volume Index – to assess the impact of a variety of internet-related phe-nomena, including wardrobe malfunctions. Results indicate that interest in a celebrity increases immediately af-ter such an event and stays at a high level for about three weeks (the wardrobe plateau). This special form of ce-lebrity gossip thus meets a constant interest of a substantial proportion of internet users.
Flow and Ductility of Smectite Clay for Skin Treatment  [PDF]
Roland Pusch
Journal of Cosmetics, Dermatological Sciences and Applications (JCDSA) , 2014, DOI: 10.4236/jcdsa.2014.42010
Abstract:

It is important that pastes and creames for skin treatment have suitable rheological properties and ability to establish a good contact with the tissues while retaining their tightness. Thixotropy is desired for providing fluidity when agitated and a suitably degree of stiffening thereafter. This requires low shear resistance in the coating phase and microstructural reorganization when leaving the paste to rest. Following the principle of using only mineral components for skin treatment, use of expandable hydrophilic clay minerals should be considered. They sorb cations and positively charged organic molecules and are impermeable to fluids and gas under low pressure, hence providing oxygen-free micro-environment. They can balance pH and are excellent agents for cleaning skin.

Recursive Filtering for Zero Offset Correction of Diving Depth Time Series with GNU R Package diveMove
Sebastián P. Luque,Roland Fried
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0015850
Abstract: Zero offset correction of diving depth measured by time-depth recorders is required to remove artifacts arising from temporal changes in accuracy of pressure transducers. Currently used methods for this procedure are in the proprietary software domain, where researchers cannot study it in sufficient detail, so they have little or no control over how their data were changed. GNU R package diveMove implements a procedure in the Free Software domain that consists of recursively smoothing and filtering the input time series using moving quantiles. This paper describes, demonstrates, and evaluates the proposed method by using a “perfect” data set, which is subsequently corrupted to provide input for the proposed procedure. The method is evaluated by comparing the corrected time series to the original, uncorrupted, data set from an Antarctic fur seal (Arctocephalus gazella Peters, 1875). The Root Mean Square Error of the corrected data set, relative to the “perfect” data set, was nearly identical to the magnitude of noise introduced into the latter. The method, thus, provides a flexible, reliable, and efficient mechanism to perform zero offset correction for analyses of diving behaviour. We illustrate applications of the method to data sets from four species with large differences in diving behaviour, measured using different sampling protocols and instrument characteristics.
Laminar firing and membrane dynamics in four visual areas exposed to two objects moving to occlusion
M. A. Harvey,P. E. Roland
Frontiers in Systems Neuroscience , 2013, DOI: 10.3389/fnsys.2013.00023
Abstract: It is not known how visual cortical neurons react to several moving objects and how their firing to the motion of one object is affected by neurons firing to another moving object. Here we combine imaging of voltage sensitive dye (VSD) signals, reflecting the population membrane potential from ferret visual areas 17, 18, 19, and 21, with laminar recordings of multiunit activity, (MUA), when two bars moved toward each other in the visual field, occluded one another, and continued on in opposite directions. Two zones of peak MUA, mapping the bars' motion, moved toward each other along the area 17/18 border, which in the ferret maps the vertical meridian of the field of view. This was reflected also in the VSD signal, at both the 17/18 border as well as at the 19/21 border with a short delay. After some 125 ms at the area 19/21 border, the VSD signal increased and became elongated in the direction of motion in front of both of the moving representations. This was directly followed by the phase of the signal reversing and travelling back from the 19/21 border toward the 17/18 border, seemingly without respect for retinotopic boundaries, where it arrived at 150 ms after stimulus onset. At this point the VSD signal in front of the moving bar representations along the 17/18 border also increased and became elongated in the direction of object motion; the signal now being the linear sum of what has been observed in response to single moving bars. When the neuronal populations representing the bars were some 600 μm apart on the cortex, the dye signal and laminar MUA decreased strongly, with the MUA scaling to that of a single bar during occlusion. Despite a short rebound of the dye signal and MUA, the MUA after the occlusion was significantly depressed. The interactions between the neuronal populations mapping the bars' position, and the neurons in between these populations were, apart from 19/21 to 17/18 interaction, mainly lateral-horizontal; first excitatory and inducing firing at the site of future occlusion, then inhibitory just prior to occlusion. After occlusion the neurons that had fired already to the first bar showed delayed and prolonged inhibition in response to the second bar. Thus, the interactions that were particular to the occlusion condition in these experiments were local and inhibitory at short cortical range, and delayed and inhibitory after the occlusion when the bars moved further apart.
Limits to Poisson's ratio in isotropic materials - general result for arbitrary deformation
P. H. Mott,C. M. Roland
Physics , 2012, DOI: 10.1088/0031-8949/87/05/055404
Abstract: The lower bound usually cited for Poisson's ratio {\nu} is -1, derived from the relationship between {\nu} and the bulk and shear moduli. From consideration of the longitudinal and biaxial moduli, we recently determined that the lower bound on {\nu} for isotropic materials is actually 1/5, a value also consistent with experimental measurements on real materials. Herein we generalize this result, first by analyzing expressions for {\nu} in terms of six common elastic constants, and then by considering arbitrary strains. The results corroborate the prior finding that 1/5 <= {\nu} for linear elasticity to be applicable.
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