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Theory of constraints

Jean-François Müller, Zhen Liu, Vinh Son Nguyen, Trissevgeni Stavrakou, Jeremy N Harvey, Jozef Peeters
Methyl peroxy, a key radical in tropospheric chemistry, was recently shown to react with the hydroxyl radical at an unexpectedly high rate. Here, the molecular reaction mechanisms are elucidated using high-level quantum chemical methodologies and statistical rate theory. Formation of activated methylhydrotrioxide, followed by dissociation into methoxy and hydroperoxy radicals, is found to be the main reaction pathway, whereas methylhydrotrioxide stabilization and methanol formation (from activated and stabilized methylhydrotrioxide) are viable minor channels...
October 17, 2016: Nature Communications
Yong Yang
Recently, research on utilitarian walking has gained momentum due to its benefits on both health and the environment. However, our overall understanding of how built and social environments affect travel mode choice (walking or not) is still limited, and most existing frameworks on travel mode choice lack dynamic processes. After a review of several mainstream theories and a number of frameworks, we propose an integrated framework. The basic constructs in the travel mode choice function are utilities, constraints, attitudes, and habits...
September 2016: Journal of Transport & Health
M Lungova, M Krutyeva, W Pyckhout-Hintzen, A Wischnewski, M Monkenbusch, J Allgaier, M Ohl, M Sharp, D Richter
We have studied the motion of polyhedral oligomeric silsesquioxane (POSS) nanoparticles modified with poly(ethylene glycol) (PEG) arms immersed in PEG matrices of different molecular weight. Employing neutron spin echo spectroscopy in combination with pulsed field gradient (PFG) NMR we found the following. (i) For entangled matrices the center of mass mean square displacement (MSD) of the PEG-POSS particles is subdiffusive following a t^{0.56} power law. (ii) The diffusion coefficient as well as the crossover to Fickian diffusion is independent of the matrix molecular weight and takes place as soon as the center of mass has moved a distance corresponding to the particle radius-this holds also for unentangled hosts...
September 30, 2016: Physical Review Letters
Li Qiu, Yang Shi, Jianfei Pan, Bo Zhang, Gang Xu
This paper investigates the collaborative tracking control for dual linear switched reluctance machines (LSRMs) over a communication network with random time delays. Considering the spatio-temporal constraint relationship of the dual LSRMs in complex industrial processes, the collaborative tracking control scheme is proposed based on the networked motion control method. The stability conditions and the controller design method for the networked dual LSRMs are obtained from the two motors relative position error by using Lyapunov theory and delay systems approach...
October 11, 2016: IEEE Transactions on Cybernetics
N Crampe, E Ragoucy, V Rittenberg, M Vanicat
We study a one-parameter generalization of the symmetric simple exclusion process on a one-dimensional lattice. In addition to the usual dynamics (where particles can hop with equal rates to the left or to the right with an exclusion constraint), annihilation and creation of pairs can occur. The system is driven out of equilibrium by two reservoirs at the boundaries. In this setting the model is still integrable: it is related to the open XXZ spin chain through a gauge transformation. This allows us to compute the full spectrum of the Markov matrix using Bethe equations...
September 2016: Physical Review. E
Sophie Lèbre, Olivier Gascuel
Overlapping genes exist in all domains of life and are much more abundant than expected upon their first discovery in the late 1970s. Assuming that the reference gene is read in frame +0, an overlapping gene can be encoded in two reading frames in the sense strand, denoted by +1 and +2, and in three reading frames in the opposite strand, denoted by -0, -1, and -2. This motivated numerous researchers to study the constraints induced by the genetic code on the various overlapping frames, mostly based on information theory...
October 10, 2016: Journal of Theoretical Biology
Yvette Kezilas, Saskia Kohnen, Meredith McKague, Serje Robidoux, Anne Castles
Studies have shown that letter position processing changes as reading develops. Whether these changes are driven by the development of the orthographic lexicon is currently unclear. In this study, we administered a novel variant of the Reicher-Wheeler task to children aged 7-12 years (Experiment 1) and adults (Experiment 2) to clarify the role of the developing lexicon in letter position processing. The task required participants to report the identity of a letter at a specified position within 3 orthographic contexts: anagram words (e...
August 15, 2016: Journal of Experimental Psychology. Human Perception and Performance
Teige C Bourke, Catherine R Lowrey, Sean P Dukelow, Stephen D Bagg, Kathleen E Norman, Stephen H Scott
BACKGROUND: Stroke can affect our ability to perform daily activities, although it can be difficult to identify the underlying functional impairment(s). Recent theories highlight the importance of sensory feedback in selecting future motor actions. This selection process can involve multiple processes to achieve a behavioural goal, including selective attention, feature/object recognition, and movement inhibition. These functions are often impaired after stroke, but existing clinical measures tend to explore these processes in isolation and without time constraints...
October 10, 2016: Journal of Neuroengineering and Rehabilitation
Joshua S Kretchmer, Thomas F Miller Iii
We investigate the performance of the recently developed kinetically-constrained ring polymer molecular dynamics (KC-RPMD) method for the description of model condensed-phase electron transfer (ET) reactions in which solvent and donor-acceptor dynamics play an important role. Comparison of KC-RPMD with results from Golden-Rule rate theories and numerically exact quantum dynamics calculations demonstrates that KC-RPMD accurately captures the combination of electronic- and nuclear-dynamical effects throughout the Marcus (intermediate solvent friction) and Zusman (large solvent friction) regimes of ET...
October 7, 2016: Faraday Discussions
Weidong Li, Yanfei Gao, Hongbin Bei
As a commonly used method to enhance the ductility in bulk metallic glasses (BMGs), the introduction of geometric constraints blocks and confines the propagation of the shear bands, reduces the degree of plastic strain on each shear band so that the catastrophic failure is prevented or delayed, and promotes the formation of multiple shear bands. The clustering of multiple shear bands near notches is often interpreted as the reason for improved ductility. Experimental works on the shear band arrangements in notched metallic glasses have been extensively carried out, but a systematic theoretical study is lacking...
October 10, 2016: Scientific Reports
Marcos Gil-Sepulcre, Jordan C Axelson, Joan Aguiló, Lluís Solà-Hernández, Laia Francàs, Albert Poater, Lluís Blancafort, Jordi Benet-Buchholz, Gonzalo Guirado, Lluís Escriche, Antoni Llobet, Roger Bofill, Xavier Sala
A Ru(II)-pentadentate polypyridyl complex [Ru(II)(κ-N(5)-bpy2PYMe)Cl](+) (1(+), bpy2PYMe = 1-(2-pyridyl)-1,1-bis(6-2,2'-bipyridyl)ethane) and its aqua derivative [Ru(II)(κ-N(5)-bpy2PYMe)(H2O)](2+) (2(2+)) were synthesized and characterized by experimental and computational methods. In MeOH, 1(+) exists as two isomers in different proportions, cis (70%) and trans (30%), which are interconverted under thermal and photochemical conditions by a sequence of processes: chlorido decoordination, decoordination/recoordination of a pyridyl group, and chlorido recoordination...
October 7, 2016: Inorganic Chemistry
Michel Destrade, Yibin Fu, Andrea Nobili
The equations governing the appearance of flexural static perturbations at the edge of a semi-infinite thin elastic isotropic plate, subjected to a state of homogeneous bi-axial pre-stress, are derived and solved. The plate is incompressible and supported by a Winkler elastic foundation with, possibly, wavenumber dependence. Small perturbations superposed onto the homogeneous state of pre-stress, within the three-dimensional elasticity theory, are considered. A series expansion of the plate kinematics in the plate thickness provides a consistent expression for the second variation of the potential energy, whose minimization gives the plate governing equations...
September 2016: Proceedings. Mathematical, Physical, and Engineering Sciences
L J Wang, J F Xu, J X Wang
In this work, we develop the Green's function method for the solution of the peridynamic non-local diffusion model in which the spatial gradient of the generalized potential in the classical theory is replaced by an integral of a generalized response function in a horizon. We first show that the general solutions of the peridynamic non-local diffusion model can be expressed as functionals of the corresponding Green's functions for point sources, along with volume constraints for non-local diffusion. Then, we obtain the Green's functions by the Fourier transform method for unsteady and steady diffusions in infinite domains...
September 2016: Proceedings. Mathematical, Physical, and Engineering Sciences
M W Adamson, A Y Morozov, O A Kuzenkov
Mathematical models in biology are highly simplified representations of a complex underlying reality and there is always a high degree of uncertainty with regards to model function specification. This uncertainty becomes critical for models in which the use of different functions fitting the same dataset can yield substantially different predictions-a property known as structural sensitivity. Thus, even if the model is purely deterministic, then the uncertainty in the model functions carries through into uncertainty in model predictions, and new frameworks are required to tackle this fundamental problem...
September 2016: Proceedings. Mathematical, Physical, and Engineering Sciences
Carsten Murawski, Peter Bossaerts
Life presents us with problems of varying complexity. Yet, complexity is not accounted for in theories of human decision-making. Here we study instances of the knapsack problem, a discrete optimisation problem commonly encountered at all levels of cognition, from attention gating to intellectual discovery. Complexity of this problem is well understood from the perspective of a mechanical device like a computer. We show experimentally that human performance too decreased with complexity as defined in computer science...
October 7, 2016: Scientific Reports
Caroline Schuppli, Sofia I F Forss, Ellen J M Meulman, Nicole Zweifel, Kevin C Lee, Evasari Rukmana, Erin R Vogel, Maria A van Noordwijk, Carel P van Schaik
BACKGROUND: Orangutans have one of the slowest-paced life histories of all mammals. Whereas life-history theory suggests that the time to reach adulthood is constrained by the time needed to reach adult body size, the needing-to-learn hypothesis instead suggests that it is limited by the time needed to acquire adult-level skills. To test between these two hypotheses, we compared the development of foraging skills and growth trajectories of immature wild orangutans in two populations: at Tuanan (Pongo pygmaeus wurmbii), Borneo, and Suaq Balimbing (Pongo abelii), Sumatra...
2016: Frontiers in Zoology
M D Gilchrist, D MacManus, J G Murphy, B Pierrat
In order to avoid the numerical difficulties in locally enforcing the incompressibility constraint using the displacement formulation of the Finite Element Method, slight compressibility is typically assumed when simulating the mechanical response of arterial tissue. The current standard method of accounting for slight compressibility of hyperelastic soft tissue assumes an additive decomposition of the strain-energy function into a volumetric and a deviatoric part. This has been shown, however, to be inconsistent with the linear theory and results in cubes retaining their cuboid shape under hydrostatic tension and compression, which seems at variance with the reinforcement of arterial tissue with two families of collagen fibres...
October 6, 2016: Computer Methods in Biomechanics and Biomedical Engineering
Alex McAvoy, Christoph Hauert
Repeated games have a long tradition in the behavioral sciences and evolutionary biology. Recently, strategies were discovered that permit an unprecedented level of control over repeated interactions by enabling a player to unilaterally enforce linear constraints on payoffs. Here, we extend this theory of "zero-determinant" (or, more generally, "autocratic") strategies to alternating games, which are often biologically more relevant than traditional synchronous games. Alternating games naturally result in asymmetries between players because the first move matters or because players might not move with equal probabilities...
September 29, 2016: Theoretical Population Biology
Naoko Yamada, Jinmoo Heo
This article explores the factors determining whether older adults engage in the Senior Games and related leisure-time physical activity through examining the adults' salient beliefs. We conducted 10 in-depth interviews with older adults who have participated in the Senior Games. Underpinned by the planned behavior theory's framework, we explored three types of beliefs: advantages and disadvantages (behavioral beliefs), social support and pressure (normative beliefs), and facilitators and impediments (control beliefs)...
October 3, 2016: Canadian Journal on Aging, la Revue Canadienne du Vieillissement
Øyvind L Martinsen, Adrian Furnham, Thorvald Hærem
The present study on insight is based on an integration of Kaplan and Simon's (1990) information processing theory of insight, a cognitive style theory, and achievement motivation theory. The style theory is the Assimilator (rule oriented, familiarity seeking)-Explorer (novelty seeking, explorative) styles (Kaufmann, 1979). Our hypothesis is that the effectiveness of 2 types of search constraints (prior experience and solution hints) for solving insight problems is moderated by both cognitive style and achievement needs, and depending on optimal levels of achievement motivation for different task conditions...
October 2016: Journal of Experimental Psychology. General
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