A Field-Theoretic Approach to the Wiener Sausage
NASA Astrophysics Data System (ADS)
Nekovar, S.; Pruessner, G.
2016-05-01
The Wiener Sausage, the volume traced out by a sphere attached to a Brownian particle, is a classical problem in statistics and mathematical physics. Initially motivated by a range of field-theoretic, technical questions, we present a single loop renormalised perturbation theory of a stochastic process closely related to the Wiener Sausage, which, however, proves to be exact for the exponents and some amplitudes. The field-theoretic approach is particularly elegant and very enjoyable to see at work on such a classic problem. While we recover a number of known, classical results, the field-theoretic techniques deployed provide a particularly versatile framework, which allows easy calculation with different boundary conditions even of higher momenta and more complicated correlation functions. At the same time, we provide a highly instructive, non-trivial example for some of the technical particularities of the field-theoretic description of stochastic processes, such as excluded volume, lack of translational invariance and immobile particles. The aim of the present work is not to improve upon the well-established results for the Wiener Sausage, but to provide a field-theoretic approach to it, in order to gain a better understanding of the field-theoretic obstacles to overcome.
A microscopic field theoretical approach for active systems
NASA Astrophysics Data System (ADS)
Alaimo, F.; Praetorius, S.; Voigt, A.
2016-08-01
We consider a microscopic modeling approach for active systems. The approach extends the phase field crystal (PFC) model and allows us to describe generic properties of active systems within a continuum model. The approach is validated by reproducing results obtained with corresponding agent-based and microscopic phase field models. We consider binary collisions, collective motion and vortex formation. For larger numbers of particles we analyze the coarsening process in active crystals and identify giant number fluctuation in a cluster formation process.
Field theoretical approach for bio-membrane coupled with flow field
NASA Astrophysics Data System (ADS)
Oya, Y.; Kawakatsu, T.
2013-02-01
Shape deformation of bio-membranes in flow field is well known phenomenon in biological systems, for example red blood cell in blood vessel. To simulate such deformation with use of field theoretical approach, we derived the dynamical equation of phase field for shape of membrane and coupled the equation with Navier-Stokes equation for flow field. In 2-dimensional simulations, we found that a bio-membrane in a Poiseuille flow takes a parachute shape similar to the red blood cells.
Field-theoretic approach to fluctuation effects in neural networks
Buice, Michael A.; Cowan, Jack D.
2007-05-15
A well-defined stochastic theory for neural activity, which permits the calculation of arbitrary statistical moments and equations governing them, is a potentially valuable tool for theoretical neuroscience. We produce such a theory by analyzing the dynamics of neural activity using field theoretic methods for nonequilibrium statistical processes. Assuming that neural network activity is Markovian, we construct the effective spike model, which describes both neural fluctuations and response. This analysis leads to a systematic expansion of corrections to mean field theory, which for the effective spike model is a simple version of the Wilson-Cowan equation. We argue that neural activity governed by this model exhibits a dynamical phase transition which is in the universality class of directed percolation. More general models (which may incorporate refractoriness) can exhibit other universality classes, such as dynamic isotropic percolation. Because of the extremely high connectivity in typical networks, it is expected that higher-order terms in the systematic expansion are small for experimentally accessible measurements, and thus, consistent with measurements in neocortical slice preparations, we expect mean field exponents for the transition. We provide a quantitative criterion for the relative magnitude of each term in the systematic expansion, analogous to the Ginsburg criterion. Experimental identification of dynamic universality classes in vivo is an outstanding and important question for neuroscience.
Kauppinen, P K; Hyttinen, J A; Kööbi, T; Malmivuo, J
1999-04-20
This study was conducted to demonstrate the potentiality of lead field theoretical approach in analyzing bioimpedance (BI) measurements. Anatomically accurate computer models and the lead field theory were used to develop BI measurement configurations capable of detecting more localized BI changes in the human body. The methods were applied to assess the measurement properties of conventional impedance cardiography (ICG) and such BI measurement configurations as can be derived using (i) the 12-lead electrocardiography (ECG) and (ii) the international 10-20 electroencephalography (EEG) electrode systems. Information as to how various electrode configurations are sensitive to detecting conductivity changes in different tissues and organs was thus obtained. Theoretical results with the 12-lead system suggested that, compared to conventional ICGs, significantly more selective ICG configurations can be derived for cardiovascular structures. In addition to theoretical investigations, clinical test measurements were made with the 12-lead system to establish whether characteristic waveforms are available. Sensitivity distributions obtained with the 10-20 electrode system give promise of the possibility of monitoring noninvasively cerebrospinal fluid (CSF) impedance changes related to impending epileptic seizures. PMID:10372161
NASA Astrophysics Data System (ADS)
Taghian, Toloo; Sheikh, Abdul; Narmoneva, Daria; Kogan, Andrei
2015-03-01
Application of external electric field (EF) as a non-pharmacological, non-invasive tool to control cell function is of great therapeutic interest. We developed a theoretical-experimental approach to investigate the biophysical mechanisms of EF interaction with cells in electrode-free physiologically-relevant configuration. Our numerical results demonstrated that EF frequency is the major parameter to control cell response to EF. Non-oscillating or low-frequency EF leads to charge accumulation on the cell surface membrane that may mediate membrane initiated cell responses. In contrast, high-frequency EF penetrates the cell membrane and reaches cell cytoplasm, where it may directly activate intracellular responses. The theoretical predictions were confirmed in our experimental studies of the effects of applied EF on vascular cell function. Results show that non-oscillating EF increases vascular endothelial growth factor (VEGF) expression while field polarity controls cell adhesion rate. High-frequency, but not low frequency, EF provides differential regulation of cytoplasmic focal adhesion kinase and VEGF expression depending on the substrate, with increased expression in cells cultured on RGD-rich synthetic hydrogels, and decreased expression for matrigel culture. The authors acknowledge the financial support from the NSF (DMR-1206784 & DMR-0804199 to AK); the NIH (1R21 DK078814-01A1 to DN) and the University of Cincinnati (Interdisciplinary Faculty Research Support Grant to DN and AK).
Plimak, L.I.; Fleischhauer, M.; Olsen, M.K.; Collett, M.J.
2003-01-01
We present an introduction to phase-space techniques (PST) based on a quantum-field-theoretical (QFT) approach. In addition to bridging the gap between PST and QFT, our approach results in a number of generalizations of the PST. First, for problems where the usual PST do not result in a genuine Fokker-Planck equation (even after phase-space doubling) and hence fail to produce a stochastic differential equation (SDE), we show how the system in question may be approximated via stochastic difference equations (S{delta}E). Second, we show that introducing sources into the SDE's (or S{delta}E's) generalizes them to a full quantum nonlinear stochastic response problem (thus generalizing Kubo's linear reaction theory to a quantum nonlinear stochastic response theory). Third, we establish general relations linking quantum response properties of the system in question to averages of operator products ordered in a way different from time normal. This extends PST to a much wider assemblage of operator products than are usually considered in phase-space approaches. In all cases, our approach yields a very simple and straightforward way of deriving stochastic equations in phase space.
Mean field game theoretic approach for security in mobile ad-hoc networks
NASA Astrophysics Data System (ADS)
Wang, Yanwei; Tang, Helen; Yu, F. Richard; Huang, Minyi
2013-05-01
Game theory can provide a useful tool to study the security problem in mobile ad hoc networks (MANETs). Most existing work on applying game theories to security only considers two players in the security game model: an attacker and a defender. While this assumption is valid for a network with centralized administration, it may not be realistic in MANETs, where centralized administration is not available. Consequently, each individual node in a MANET should be treated separately in the security game model. In this paper, using recent advances in mean field game theory, we propose a novel game theoretic approach for security in MANETs. Mean field game theory provides a powerful mathematical tool for problems with a large number of players. Since security defence mechanisms consume precious system resources (e.g., energy), the proposed scheme considers not only the security requirement of MANETs but also the system resources. In addition, each node only needs to know its own state information and the aggregate effect of the other nodes in the MANET. Therefore, the proposed scheme is a fully distributed scheme. Simulation results are presented to illustrate the effectiveness of the proposed scheme.
Field Theory in Organizational Psychology: An Analysis of Theoretical Approaches in Leadership.
ERIC Educational Resources Information Center
Garcia, Joseph E.
This literature review examines Kurt Lewin's influence in leadership psychology. Characteristics of field theory are described in detail and utilized in analyzing leadership research, including the trait approach, leader behavior studies, contingency theory, path-goal theory, and leader decision theory. Important trends in leadership research are…
Theoretical Approaches to Nanoparticles
NASA Astrophysics Data System (ADS)
Kempa, Krzysztof
Nanoparticles can be viewed as wave resonators. Involved waves are, for example, carrier waves, plasmon waves, polariton waves, etc. A few examples of successful theoretical treatments that follow this approach are given. In one, an effective medium theory of a nanoparticle composite is presented. In another, plasmon polaritonic solutions allow to extend concepts of radio technology, such as an antenna and a coaxial transmission line, to the visible frequency range.
Unified theoretical approach for binary and ternary alloys via an effective field theory
NASA Astrophysics Data System (ADS)
Freitas, Augusto S.; de Albuquerque, Douglas F.
2016-01-01
We describe the phase diagram of binary and ternary disordered alloys using the mixed-bond Ising model, via effective field theory (EFT). For example, we describe the Fe-Al alloy as a mixed-bond system instead of as diluted alloy. In our approach, we obtain the percolation threshold for some lattices and describe the lines of ferro-paramagnetic transition of Fe-Al, Fe-Mn, Fe-Mn-Al and Fe-Ni-Mn alloys and we obtain good agreement with the experimental data.
NASA Astrophysics Data System (ADS)
Freire, Hermann; Corrêa, Eberth
2012-02-01
We apply a functional implementation of the field-theoretical renormalization group (RG) method up to two loops to the single-impurity Anderson model. To achieve this, we follow a RG strategy similar to that proposed by Vojta et al. (in Phys. Rev. Lett. 85:4940, 2000), which consists of defining a soft ultraviolet regulator in the space of Matsubara frequencies for the renormalized Green's function. Then we proceed to derive analytically and solve numerically integro-differential flow equations for the effective couplings and the quasiparticle weight of the present model, which fully treat the interplay of particle-particle and particle-hole parquet diagrams and the effect of the two-loop self-energy feedback into them. We show that our results correctly reproduce accurate numerical renormalization group data for weak to slightly moderate interactions. These results are in excellent agreement with other functional Wilsonian RG works available in the literature. Since the field-theoretical RG method turns out to be easier to implement at higher loops than the Wilsonian approach, higher-order calculations within the present approach could improve further the results for this model at stronger couplings. We argue that the present RG scheme could thus offer a possible alternative to other functional RG methods to describe electronic correlations within this model.
Thematic Approach to Theoretical Speculations in the Field of Educational Administration
ERIC Educational Resources Information Center
Park, Jae
2015-01-01
The purpose of this article is a critical reflection on the field of educational administration and its varied and often conflicting epistemologies. It is argued that the field of educational administration is a community of diverse epistemologies. Although epistemological heterogeneity has been persistently vilified by both theorists and…
A field-theoretic approach to the May-Leonard cyclic population dynamics model
NASA Astrophysics Data System (ADS)
Serrao, Shannon; Täuber, Uwe
Spatially extended stochastic population dynamics models with cyclic predation interactions display intriguing time evolution and spontaneous structure formation. We study a version of the May-Leonard cyclic competition model in d dimensions with diffusive particle propagation. We use the second-quantized Doi-Peliti formalism and ensuing coherent-state path integral representation to construct its continuum representation and explore its collective dynamics. Expanding the resulting action about the mean-field species concentrations enables us to compute the diagonalized harmonic propagators and hence 'masses', i.e., relaxation rates and eigenfrequencies of the fundamental modes. Furthermore, operating near the Hopf bifurcation point, we identify the validity range for the necessary time scale separation that allows us to project out the purely relaxing eigenmode. The remaining oscillating fields obey the complex Ginzburg-Landau equation, which is consistent with spiral pattern formation.
Cooper, F.
1997-09-22
This paper contains viewgraphs on unusual dileptons at Brookhaven RHIC. A field theory approach is used based on a non-equilibrium chiral phase transformation utilizing the schroedinger and Heisenberg picture.
NASA Astrophysics Data System (ADS)
Khan, Shehryar; Kubica-Misztal, Aleksandra; Kruk, Danuta; Kowalewski, Jozef; Odelius, Michael
2015-01-01
The zero-field splitting (ZFS) of the electronic ground state in paramagnetic ions is a sensitive probe of the variations in the electronic and molecular structure with an impact on fields ranging from fundamental physical chemistry to medical applications. A detailed analysis of the ZFS in a series of symmetric Gd(III) complexes is presented in order to establish the applicability and accuracy of computational methods using multiconfigurational complete-active-space self-consistent field wave functions and of density functional theory calculations. The various computational schemes are then applied to larger complexes Gd(III)DOTA(H2O)-, Gd(III)DTPA(H2O)2-, and Gd(III)(H2O)83+ in order to analyze how the theoretical results compare to experimentally derived parameters. In contrast to approximations based on density functional theory, the multiconfigurational methods produce results for the ZFS of Gd(III) complexes on the correct order of magnitude.
Khan, Shehryar; Kubica-Misztal, Aleksandra; Kruk, Danuta; Kowalewski, Jozef; Odelius, Michael
2015-01-21
The zero-field splitting (ZFS) of the electronic ground state in paramagnetic ions is a sensitive probe of the variations in the electronic and molecular structure with an impact on fields ranging from fundamental physical chemistry to medical applications. A detailed analysis of the ZFS in a series of symmetric Gd(III) complexes is presented in order to establish the applicability and accuracy of computational methods using multiconfigurational complete-active-space self-consistent field wave functions and of density functional theory calculations. The various computational schemes are then applied to larger complexes Gd(III)DOTA(H2O)(-), Gd(III)DTPA(H2O)(2-), and Gd(III)(H2O)8(3+) in order to analyze how the theoretical results compare to experimentally derived parameters. In contrast to approximations based on density functional theory, the multiconfigurational methods produce results for the ZFS of Gd(III) complexes on the correct order of magnitude. PMID:25612706
Khan, Shehryar Odelius, Michael; Kubica-Misztal, Aleksandra; Kruk, Danuta; Kowalewski, Jozef
2015-01-21
The zero-field splitting (ZFS) of the electronic ground state in paramagnetic ions is a sensitive probe of the variations in the electronic and molecular structure with an impact on fields ranging from fundamental physical chemistry to medical applications. A detailed analysis of the ZFS in a series of symmetric Gd(III) complexes is presented in order to establish the applicability and accuracy of computational methods using multiconfigurational complete-active-space self-consistent field wave functions and of density functional theory calculations. The various computational schemes are then applied to larger complexes Gd(III)DOTA(H{sub 2}O){sup −}, Gd(III)DTPA(H{sub 2}O){sup 2−}, and Gd(III)(H{sub 2}O){sub 8}{sup 3+} in order to analyze how the theoretical results compare to experimentally derived parameters. In contrast to approximations based on density functional theory, the multiconfigurational methods produce results for the ZFS of Gd(III) complexes on the correct order of magnitude.
NASA Astrophysics Data System (ADS)
Reyes-Gómez, E.; Perdomo-Leiva, C. A.; Oliveira, L. E.; de Dios-Leyva, M.
1998-04-01
A theoretical resonant-tunnelling approach is used in a detailed study of the electronic and transmission properties of quasiperiodic Fibonacci GaAs-(Ga,Al)As semiconductor superlattices, under applied electric fields. The theoretical scheme is based upon an exact solution of the corresponding Schroedinger equations in different wells and barriers, through the use of Airy functions, and a transfer-matrix technique. The calculated quasibound resonant energies agree quite well with previous theoretical parameter-based results within a tight-binding scheme, in the particular case of isolated Fibonacci building blocks. Theoretical resonant-tunnelling results for 0953-8984/10/16/009/img6 and 0953-8984/10/16/009/img7 generations of the quasiperiodic Fibonacci superlattice reveal the occurrence of anticrossings of the resonant levels with applied electric fields, together with the conduction- and valence-level wave function localization properties and electric-field-induced migration to specific regions of the semiconductor quasiperiodic heterostructure. Finally, theoretical resonant-tunnelling calculations for the interband transition energies are shown to be in quite good quantitative agreement with previously reported experimental photocurrent measurements.
Field theoretic simulations of polymer nanocomposites
Koski, Jason; Chao, Huikuan; Riggleman, Robert A.
2013-12-28
Polymer field theory has emerged as a powerful tool for describing the equilibrium phase behavior of complex polymer formulations, particularly when one is interested in the thermodynamics of dense polymer melts and solutions where the polymer chains can be accurately described using Gaussian models. However, there are many systems of interest where polymer field theory cannot be applied in such a straightforward manner, such as polymer nanocomposites. Current approaches for incorporating nanoparticles have been restricted to the mean-field level and often require approximations where it is unclear how to improve their accuracy. In this paper, we present a unified framework that enables the description of polymer nanocomposites using a field theoretic approach. This method enables straightforward simulations of the fully fluctuating field theory for polymer formulations containing spherical or anisotropic nanoparticles. We demonstrate our approach captures the correlations between particle positions, present results for spherical and cylindrical nanoparticles, and we explore the effect of the numerical parameters on the performance of our approach.
Mass Media and Socialization: Theoretic Approaches.
ERIC Educational Resources Information Center
Gordon, Thomas F.
This paper examines the major theoretical approaches to the study of socialization, with an emphasis on media effects. The three major bodies of literature studied are the major theoretic approaches utilized in the general area of developmental psychology, the theoretical paradigms evident in studies dealing more specifically with child…
Santoli, Salvatore
2010-11-01
The previously formulated tool dubbed Huyghens Engine, concerning information sensing, processing and actuating through wave motion in connection with the ubiquitous phenomenon of coupled oscillator synchronization, is applied here on the nanoscale for designing deeper metaphors of biosystem sensorimotor behaviour to attain the long sought-after bioinspired autonomous, self-propelled, walking, swimming or flying macro-/microsized robots. A nanoscale description of information processing is in terms of neural images of perception/action coherent flows of information by resonant coupling of inner nano-fields and external aerodynamic/hydrodynamic and gravitational fields in Lie group geometrizable classical functional spaces, possibly through Heisenberg's molecular field. This concerns both metaphor-free biomimicry and nanobiological research. PMID:21138018
A gauge-theoretic approach to gravity.
Krasnov, Kirill
2012-08-01
Einstein's general relativity (GR) is a dynamical theory of the space-time metric. We describe an approach in which GR becomes an SU(2) gauge theory. We start at the linearized level and show how a gauge-theoretic Lagrangian for non-interacting massless spin two particles (gravitons) takes a much more simple and compact form than in the standard metric description. Moreover, in contrast to the GR situation, the gauge theory Lagrangian is convex. We then proceed with a formulation of the full nonlinear theory. The equivalence to the metric-based GR holds only at the level of solutions of the field equations, that is, on-shell. The gauge-theoretic approach also makes it clear that GR is not the only interacting theory of massless spin two particles, in spite of the GR uniqueness theorems available in the metric description. Thus, there is an infinite-parameter class of gravity theories all describing just two propagating polarizations of the graviton. We describe how matter can be coupled to gravity in this formulation and, in particular, how both the gravity and Yang-Mills arise as sectors of a general diffeomorphism-invariant gauge theory. We finish by outlining a possible scenario of the ultraviolet completion of quantum gravity within this approach. PMID:22792040
A gauge-theoretic approach to gravity
Krasnov, Kirill
2012-01-01
Einstein's general relativity (GR) is a dynamical theory of the space–time metric. We describe an approach in which GR becomes an SU(2) gauge theory. We start at the linearized level and show how a gauge-theoretic Lagrangian for non-interacting massless spin two particles (gravitons) takes a much more simple and compact form than in the standard metric description. Moreover, in contrast to the GR situation, the gauge theory Lagrangian is convex. We then proceed with a formulation of the full nonlinear theory. The equivalence to the metric-based GR holds only at the level of solutions of the field equations, that is, on-shell. The gauge-theoretic approach also makes it clear that GR is not the only interacting theory of massless spin two particles, in spite of the GR uniqueness theorems available in the metric description. Thus, there is an infinite-parameter class of gravity theories all describing just two propagating polarizations of the graviton. We describe how matter can be coupled to gravity in this formulation and, in particular, how both the gravity and Yang–Mills arise as sectors of a general diffeomorphism-invariant gauge theory. We finish by outlining a possible scenario of the ultraviolet completion of quantum gravity within this approach. PMID:22792040
Theoretical approaches to metal chemistry
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W.; Langhoff, Stephen R.; Partridge, Harry; Halicioglu, Timur; Taylor, Peter R.
1987-01-01
Theoretical calculations on metals ranging from very accurate ab initio studies of diatomic and triatomic systems to model studies of larger clusters are presented. Recent improvements in the representation of one-particle and n-particle spaces have made possible the prediction that Al2 has a 3Pi(u) ground state, even though the 3Sigma(-)g state lies within 200/cm. Results suggest that cluster geometry varies dramatically with cluster size, and that rather large clusters are required before the bulk structure becomes optimal. Al cluster studies show that three-body terms are needed for quantitative agreement with ab initio calculations.
Theoretical Approaches to Moral/Citizenship Education.
ERIC Educational Resources Information Center
Heslep, Robert D.
Four theoretical approaches to moral/citizenship education are described and compared. Positive and negative aspects of the cognitive-decision, developmental, prosocial, and values approaches are discussed and ways of relating the four approaches to each other are suggested. The first approach, cognitive-decision, is distinctive for its…
Rethinking Theoretical Approaches to Stigma
Martin, Jack K; Lang, Annie; Olafsdottir, Sigrun
2008-01-01
A resurgence of research and policy efforts on stigma both facilitates and forces a reconsideration of the levels and types of factors that shape reactions to persons with conditions that engender prejudice and discrimination. Focusing on the case of mental illness but drawing from theories and studies of stigma across the social sciences, we propose a framework that brings together theoretical insights from micro, meso and macro level research: Framework Integrating Normative Influences on Stigma (FINIS) starts with Goffman’s notion that understanding stigma requires a language of social relationships, but acknowledges that individuals do not come to social interaction devoid of affect and motivation. Further, all social interactions take place in a context in which organizations, media and larger cultures structure normative expectations which create the possibility of marking “difference”. Labelling theory, social network theory, the limited capacity model of media influence, the social psychology of prejudice and discrimination, and theories of the welfare state all contribute to an understanding of the complex web of expectations shaping stigma. FINIS offers the potential to build a broad-based scientific foundation based on understanding the effects of stigma on the lives of persons with mental illness, the resources devoted to the organizations and families who care for them, and policies and programs designed to combat stigma. We end by discussing the clear implications this framework holds for stigma reduction, even in the face of conflicting results. PMID:18436358
New Theoretical Approaches for Human-Computer Interaction.
ERIC Educational Resources Information Center
Rogers, Yvonne
2004-01-01
Presents a critique of recent theoretical developments in the field of human-computer interaction (HCI) together with an overview of HCI practice. This chapter discusses why theoretically based approaches have had little impact on the practice of interaction design and suggests mechanisms to enable designers and researchers to better articulate…
A theoretical approach to measuring pilot workload
NASA Technical Reports Server (NTRS)
Kantowitz, B. H.
1984-01-01
Theoretical assumptions used by researchers in the area of attention, with emphasis upon errors and inconsistent assumptions used by some researchers were studied. Two GAT experiments, two laboratory studies and one field experiment were conducted.
Field-theoretical description of deep inelastic scattering
Geyer, B.; Robaschik, D.; Wieczorek, E.
1980-01-01
The most important theoretical notions concerning deep inelastic scattering are reviewed. Topics discussed are the model-independent approach, which is based on the general principles of quantum field theory, the application of quantum chromodynamics to deep inelastic scattering, approaches based on the quark--parton model, the light cone algebra, and conformal invariance, and also investigations in the framework of perturbation theory.
New Theoretical Approach Integrated Education and Technology
ERIC Educational Resources Information Center
Ding, Gang
2010-01-01
The paper focuses on exploring new theoretical approach in education with development of online learning technology, from e-learning to u-learning and virtual reality technology, and points out possibilities such as constructing a new teaching ecological system, ubiquitous educational awareness with ubiquitous technology, and changing the…
Speaking of Gender Identity: Theoretical Approaches.
ERIC Educational Resources Information Center
Freedman, Susan A.
Various definitions of gender identity have ranged from recognition of one's biological sex to an individual's sense of masculinity or femininity. For the purpose of this paper, which examines some of the theoretical approaches to the subject, gender identity will be defined as "the degree to which individuals are 'aware' of and accept their…
Information theoretic approach for accounting classification
NASA Astrophysics Data System (ADS)
Ribeiro, E. M. S.; Prataviera, G. A.
2014-12-01
In this paper we consider an information theoretic approach for the accounting classification process. We propose a matrix formalism and an algorithm for calculations of information theoretic measures associated to accounting classification. The formalism may be useful for further generalizations and computer-based implementation. Information theoretic measures, mutual information and symmetric uncertainty, were evaluated for daily transactions recorded in the chart of accounts of a small company during two years. Variation in the information measures due the aggregation of data in the process of accounting classification is observed. In particular, the symmetric uncertainty seems to be a useful parameter for comparing companies over time or in different sectors or different accounting choices and standards.
Sound velocity estimation: A system theoretic approach
Candy, J.V.; Sullivan, E.J.
1993-07-30
A system-theoretic approach is proposed to investigate the feasibility of reconstructing a sound velocity profile (SVP) from acoustical hydrophone measurements. This problem is based on a state-space representation of the normal-mode propagation model. It is shown that this representation can be utilized to investigate the so-called observability of the SVP from noisy measurement data. A model-based processor is developed to extract this information and it is shown that even in cases where limited SVP information is available, the SVP can be estimated using this approach.
A decision theoretical approach for diffusion promotion
NASA Astrophysics Data System (ADS)
Ding, Fei; Liu, Yun
2009-09-01
In order to maximize cost efficiency from scarce marketing resources, marketers are facing the problem of which group of consumers to target for promotions. We propose to use a decision theoretical approach to model this strategic situation. According to one promotion model that we develop, marketers balance between probabilities of successful persuasion and the expected profits on a diffusion scale, before making their decisions. In the other promotion model, the cost for identifying influence information is considered, and marketers are allowed to ignore individual heterogeneity. We apply the proposed approach to two threshold influence models, evaluate the utility of each promotion action, and provide discussions about the best strategy. Our results show that efforts for targeting influentials or easily influenced people might be redundant under some conditions.
A graph theoretic approach to scene matching
NASA Technical Reports Server (NTRS)
Ranganath, Heggere S.; Chipman, Laure J.
1991-01-01
The ability to match two scenes is a fundamental requirement in a variety of computer vision tasks. A graph theoretic approach to inexact scene matching is presented which is useful in dealing with problems due to imperfect image segmentation. A scene is described by a set of graphs, with nodes representing objects and arcs representing relationships between objects. Each node has a set of values representing the relations between pairs of objects, such as angle, adjacency, or distance. With this method of scene representation, the task in scene matching is to match two sets of graphs. Because of segmentation errors, variations in camera angle, illumination, and other conditions, an exact match between the sets of observed and stored graphs is usually not possible. In the developed approach, the problem is represented as an association graph, in which each node represents a possible mapping of an observed region to a stored object, and each arc represents the compatibility of two mappings. Nodes and arcs have weights indicating the merit or a region-object mapping and the degree of compatibility between two mappings. A match between the two graphs corresponds to a clique, or fully connected subgraph, in the association graph. The task is to find the clique that represents the best match. Fuzzy relaxation is used to update the node weights using the contextual information contained in the arcs and neighboring nodes. This simplifies the evaluation of cliques. A method of handling oversegmentation and undersegmentation problems is also presented. The approach is tested with a set of realistic images which exhibit many types of sementation errors.
A graph theoretic approach to scene matching
NASA Astrophysics Data System (ADS)
Ranganath, Heggere S.; Chipman, Laure J.
1991-08-01
The ability to match two scenes is a fundamental requirement in a variety of computer vision tasks. A graph theoretic approach to inexact scene matching is presented which is useful in dealing with problems due to imperfect image segmentation. A scene is described by a set of graphs, with nodes representing objects and arcs representing relationships between objects. Each node has a set of values representing the relations between pairs of objects, such as angle, adjacency, or distance. With this method of scene representation, the task in scene matching is to match two sets of graphs. Because of segmentation errors, variations in camera angle, illumination, and other conditions, an exact match between the sets of observed and stored graphs is usually not possible. In the developed approach, the problem is represented as an association graph, in which each node represents a possible mapping of an observed region to a stored object, and each arc represents the compatibility of two mappings. Nodes and arcs have weights indicating the merit or a region-object mapping and the degree of compatibility between two mappings. A match between the two graphs corresponds to a clique, or fully connected subgraph, in the association graph. The task is to find the clique that represents the best match. Fuzzy relaxation is used to update the node weights using the contextual information contained in the arcs and neighboring nodes. This simplifies the evaluation of cliques. A method of handling oversegmentation and undersegmentation problems is also presented. The approach is tested with a set of realistic images which exhibit many types of sementation errors.
Heterochromatin and complexity: a theoretical approach.
Spinelli, Gino
2003-10-01
Heterochromatin represents 30% of eukaryotic genome in Drosophila and 15% in humans. Despite extensive research spanning many decades, its evolutionary significance, as well as the forces that guarantee its maintenance, are still elusive. Many theoretical and experimental approaches have led researchers to propose several conceptual frameworks to elucidate the nature of this huge mysterious genetic material and its spreading in all eukaryotic genomes. "Junk DNA" as well as "selfish genetic material" are two examples of such attempts, but several lines of evidence suggest that such explanations are incomplete. In fact, if the selfish DNA hypothesis does not explain the mapping of genetic functions in heterochromatin, then the junk DNA hypothesis is incomplete in describing both emergence of genetic functions and their maintenance in the eukaryotic heterochromatin. Recent developments in the physics of complex systems and mathematical concepts such as fractals provide new conceptual clues to answer several basic questions concerning the emergence of heterochromatin in eukaryotic genomes, its evolutionary significance, the forces that guarantee its maintenance, and its peculiar behavior in the eukaryotic cell. The aim of this paper is to provide a new theoretical framework for the heterochromatin, considering such genetic material in physical terms as a complex adaptive system. We apply some computer calculations to demonstrate the nonlinearity of the flux of genetic information along the phylogenic tree. Fractal dimensions of representative heterochromatic sequences are provided. A theory is proposed in which heterochromatin is considered a system that evolves in a self-organized manner at the edge of cellular and environmental chaos. PMID:14523268
The celestial mechanics approach: theoretical foundations
NASA Astrophysics Data System (ADS)
Beutler, Gerhard; Jäggi, Adrian; Mervart, Leoš; Meyer, Ulrich
2010-10-01
Gravity field determination using the measurements of Global Positioning receivers onboard low Earth orbiters and inter-satellite measurements in a constellation of satellites is a generalized orbit determination problem involving all satellites of the constellation. The celestial mechanics approach (CMA) is comprehensive in the sense that it encompasses many different methods currently in use, in particular so-called short-arc methods, reduced-dynamic methods, and pure dynamic methods. The method is very flexible because the actual solution type may be selected just prior to the combination of the satellite-, arc- and technique-specific normal equation systems. It is thus possible to generate ensembles of substantially different solutions—essentially at the cost of generating one particular solution. The article outlines the general aspects of orbit and gravity field determination. Then the focus is put on the particularities of the CMA, in particular on the way to use accelerometer data and the statistical information associated with it.
Titanocene / cyclodextrin supramolecular systems: a theoretical approach
2012-01-01
Background Recently, various metallocenes were synthesized and analyzed by biological activity point of view (such as antiproliferative properties): ruthenocenes, cobaltoceniums, titanocenes, zirconocenes, vanadocenes, niobocenes, molibdocenes etc. Two main disadvantages of metallocenes are the poor hydrosolubility and the hydrolytic instability. These problems could be resolved in two ways: synthetically modifying the structure or finding new formulations with enhanced properties. The aqueous solubility of metallocenes with cytostatic activities could be enhanced by molecular encapsulation in cyclodextrins, as well as the hydrolytic instability of these compounds could be reduced. Results This study presents a theoretical approach on the nanoencapsulation of a series of titanocenes with cytotoxic activity in α-, β-, and γ-cyclodextrin. The HyperChem 5.11 package was used for building and molecular modelling of titanocene and cyclodextrin structures, as well as for titanocene/cyclodextrin complex optimization. For titanocene/cyclodextrin complex optimization experiments, the titanocene and cyclodextrin structures in minimal energy conformations were set up at various distances and positions between molecules (molecular mechanics functionality, MM+). The best interaction between titanocene structures and cyclodextrins was obtained in the case of β- and γ-cyclodextrin, having the hydrophobic moieties oriented to the secondary face of cyclodextrin. The hydrophobicity of titanocenes (logP) correlate with the titanocene-cyclodextrin interaction parameters, especially with the titanocene-cyclodextrin interaction energy; the compatible geometry and the interaction energy denote that the titanocene/β- and γ-cyclodextrin complex can be achieved. Valuable quantitative structure-activity relationships (QSARs) were also obtained in the titanocene class by using the same logP as the main parameter for the in vitro cytotoxic activity against HeLa, K562, and Fem-x cell
Field-Theoretic Studies of Nanostructured Triblock Polyelectrolyte Gels
NASA Astrophysics Data System (ADS)
Audus, Debra; Fredrickson, Glenn
2012-02-01
Recently, experimentalists have developed nanostructured, reversible gels formed from triblock polyelectrolytes (Hunt et al. 2011, Lemmers et al. 2010, 2011). These gels have fascinating and tunable properties that reflect a heterogeneous morphology with domains on the order of tens of nanometers. The complex coacervate domains, aggregated oppositely charged end-blocks, are embedded in a continuous aqueous matrix and are bridged by uncharged, hydrophilic polymer mid-blocks. We report on simulation studies that employ statistical field theory models of triblock polyelectrolytes, and we explore the equilibrium self-assembly of these remarkable systems. As the charge complexation responsible for the formation of coacervate domains is driven by electrostatic correlations, we have found it necessary to pursue full ``field-theoretic simulations'' of the models, as opposed to the familiar self-consistent field theory approach. Our investigations have focused on morphological trends with mid- and end-block lengths, polymer concentration, salt concentration and charge density.
NASA Astrophysics Data System (ADS)
Salah, Wa'el; Dolique, J.-M.
2000-06-01
The wake field generated in the cylindrical cavity of an RF photoinjector, by a strongly accelerated electron beam, has been analytically calculated (Salah, Dolique, Nucl. Instr. and Meth. A 437 (1999) 27) under the assumption that the perturbation of the field map by the exit hole is negligible as long as the ratio: exit hole radius/cavity radius is lower than approximately 1/3. Shown experimentally in the different context of a long accelerating structure formed by a sequence of bored pill-box cavity (Figuera et al., Phys. Rev. Lett. 60 (1988) 2144; Kim et al., J. Appl. Phys. 68 (1990) 4942), this often-quoted result must be checked for the wake field map excited in a photo injector cavity. Further, in the latter case, the empirical rule in question can be broken more easily because, due to causality, the cavity radius to be considered is not the physical radius but that of the part of the anode wall around the exit hole reached by the beam electromagnetic influence. We present an analytical treatment of the wake field driven in a photoinjector by the accelerated electron beam which takes this hole effect into account, whatever the hole radius may be.
Potential theoretic methods for far field sound radiation calculations
NASA Technical Reports Server (NTRS)
Hariharan, S. I.; Stenger, Edward J.; Scott, J. R.
1995-01-01
In the area of computational acoustics, procedures which accurately predict the far-field sound radiation are much sought after. A systematic development of such procedures are found in a sequence of papers by Atassi. The method presented here is an alternate approach to predicting far field sound based on simple layer potential theoretic methods. The main advantages of this method are: it requires only a simple free space Green's function, it can accommodate arbitrary shapes of Kirchoff surfaces, and is readily extendable to three-dimensional problems. Moreover, the procedure presented here, though tested for unsteady lifting airfoil problems, can easily be adapted to other areas of interest, such as jet noise radiation problems. Results are presented for lifting airfoil problems and comparisons are made with the results reported by Atassi. Direct comparisons are also made for the flat plate case.
Item Characteristic Curves: A New Theoretical Approach.
ERIC Educational Resources Information Center
Garcia-Perez, Miguel A.; Frary, Robert B.
A new approach to the development of the item characteristic curve (ICC), which expresses the functional relationship between the level of performance on a given task and an independent variable that is relevant to the task, is presented. The approach focuses on knowledge states, decision processes, and other circumstances underlying responses to…
Understanding bimolecular machines: Theoretical and experimental approaches
NASA Astrophysics Data System (ADS)
Goler, Adam Scott
This dissertation concerns the study of two classes of molecular machines from a physical perspective: enzymes and membrane proteins. Though the functions of these classes of proteins are different, they each represent important test-beds from which new understanding can be developed by the application of different techniques. HIV1 Reverse Transcriptase is an enzyme that performs multiple functions, including reverse transcription of RNA into an RNA/DNA duplex, RNA degradation by the RNaseH domain, and synthesis of dsDNA. These functions allow for the incorporation of the retroviral genes into the host genome. Its catalytic cycle requires repeated large-scale conformational changes fundamental to its mechanism. Motivated by experimental work, these motions were studied theoretically by the application of normal mode analysis. It was observed that the lowest order modes correlate with largest amplitude (low-frequency) motion, which are most likely to be catalytically relevant. Comparisons between normal modes obtained via an elastic network model to those calculated from the essential dynamics of a series of all-atom molecular dynamics simulations show the self-consistency between these calculations. That similar conformational motions are seen between independent theoretical methods reinforces the importance of large-scale subdomain motion for the biochemical action of DNA polymerases in general. Moreover, it was observed that the major subunits of HIV1 Reverse Transcriptase interact quasi-harmonically. The 5HT3A Serotonin receptor and P2X1 receptor, by contrast, are trans-membrane proteins that function as ligand gated ion channels. Such proteins feature a central pore, which allows for the transit of ions necessary for cellular function across a membrane. The pore is opened by the ligation of binding sites on the extracellular portion of different protein subunits. In an attempt to resolve the individual subunits of these membrane proteins beyond the diffraction
Approaching theoretical strength in glassy carbon nanolattices
NASA Astrophysics Data System (ADS)
Bauer, J.; Schroer, A.; Schwaiger, R.; Kraft, O.
2016-04-01
The strength of lightweight mechanical metamaterials, which aim to exploit material-strengthening size effects by their microscale lattice structure, has been limited by the resolution of three-dimensional lithography technologies and their restriction to mainly polymer resins. Here, we demonstrate that pyrolysis of polymeric microlattices can overcome these limitations and create ultra-strong glassy carbon nanolattices with single struts shorter than 1 μm and diameters as small as 200 nm. They represent the smallest lattice structures yet produced--achieved by an 80% shrinkage of the polymer during pyrolysis--and exhibit material strengths of up to 3 GPa, corresponding approximately to the theoretical strength of glassy carbon. The strength-to-density ratios of the nanolattices are six times higher than those of reported microlattices. With a honeycomb topology, effective strengths of 1.2 GPa at 0.6 g cm-3 are achieved. Diamond is the only bulk material with a notably higher strength-to-density ratio.
Planar dipolar polymer brush: field theoretical investigations
NASA Astrophysics Data System (ADS)
Mahalik, Jyoti; Kumar, Rajeev; Sumpter, Bobby
2015-03-01
Physical properties of polymer brushes bearing monomers with permanent dipole moments and immersed in a polar solvent are investigated using self-consistent field theory (SCFT). It is found that mismatch between the permanent dipole moments of the monomer and the solvent plays a significant role in determining the height of the polymer brush. Sign as well as magnitude of the mismatch determines the extent of collapse of the polymer brush. The mismatch in the dipole moments also affects the force-distance relations and interpenetration of polymers in opposing planar brushes. In particular, an attractive force between the opposing dipolar brushes is predicted for stronger mismatch parameter. Furthermore, effects of added monovalent salt on the structure of dipolar brushes will also be presented. This investigation highlights the significance of dipolar interactions in affecting the physical properties of polymer brushes. Csmd division, Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37831, USA.
Information theoretic approaches to multidimensional neural computations
NASA Astrophysics Data System (ADS)
Fitzgerald, Jeffrey D.
Many systems in nature process information by transforming inputs from their environments into observable output states. These systems are often difficult to study because they are performing computations on multidimensional inputs with many degrees of freedom using highly nonlinear functions. The work presented in this dissertation deals with some of the issues involved with characterizing real-world input/output systems and understanding the properties of idealized systems using information theoretic methods. Using the principle of maximum entropy, a family of models are created that are consistent with certain measurable correlations from an input/output dataset but are maximally unbiased in all other respects, thereby eliminating all unjustified assumptions about the computation. In certain cases, including spiking neurons, we show that these models also minimize the mutual information. This property gives one the advantage of being able to identify the relevant input/output statistics by calculating their information content. We argue that these maximum entropy models provide a much needed quantitative framework for characterizing and understanding sensory processing neurons that are selective for multiple stimulus features. To demonstrate their usefulness, these ideas are applied to neural recordings from macaque retina and thalamus. These neurons, which primarily respond to two stimulus features, are shown to be well described using only first and second order statistics, indicating that their firing rates encode information about stimulus correlations. In addition to modeling multi-feature computations in the relevant feature space, we also show that maximum entropy models are capable of discovering the relevant feature space themselves. This technique overcomes the disadvantages of two commonly used dimensionality reduction methods and is explored using several simulated neurons, as well as retinal and thalamic recordings. Finally, we ask how neurons in a
Efficient field-theoretic simulation of polymer solutions
NASA Astrophysics Data System (ADS)
Villet, Michael C.; Fredrickson, Glenn H.
2014-12-01
We present several developments that facilitate the efficient field-theoretic simulation of polymers by complex Langevin sampling. A regularization scheme using finite Gaussian excluded volume interactions is used to derive a polymer solution model that appears free of ultraviolet divergences and hence is well-suited for lattice-discretized field theoretic simulation. We show that such models can exhibit ultraviolet sensitivity, a numerical pathology that dramatically increases sampling error in the continuum lattice limit, and further show that this pathology can be eliminated by appropriate model reformulation by variable transformation. We present an exponential time differencing algorithm for integrating complex Langevin equations for field theoretic simulation, and show that the algorithm exhibits excellent accuracy and stability properties for our regularized polymer model. These developments collectively enable substantially more efficient field-theoretic simulation of polymers, and illustrate the importance of simultaneously addressing analytical and numerical pathologies when implementing such computations.
Efficient field-theoretic simulation of polymer solutions
Villet, Michael C.; Fredrickson, Glenn H.
2014-12-14
We present several developments that facilitate the efficient field-theoretic simulation of polymers by complex Langevin sampling. A regularization scheme using finite Gaussian excluded volume interactions is used to derive a polymer solution model that appears free of ultraviolet divergences and hence is well-suited for lattice-discretized field theoretic simulation. We show that such models can exhibit ultraviolet sensitivity, a numerical pathology that dramatically increases sampling error in the continuum lattice limit, and further show that this pathology can be eliminated by appropriate model reformulation by variable transformation. We present an exponential time differencing algorithm for integrating complex Langevin equations for field theoretic simulation, and show that the algorithm exhibits excellent accuracy and stability properties for our regularized polymer model. These developments collectively enable substantially more efficient field-theoretic simulation of polymers, and illustrate the importance of simultaneously addressing analytical and numerical pathologies when implementing such computations.
Biosensor commercialization strategy - a theoretical approach.
Lin, Chin-Tsai; Wang, Su-Man
2005-01-01
Biosensors are analytical devices, which use biological interactions to provide either qualitative or quantitative results. They are extensively employed in many fields such as clinical diagnosis and biomedicine, military applications, anti-terrorism, farm, garden and veterinary analysis, process control, fermentation control and analysis, pharmaceutical and drug analysis, food and drink production and analysis, pollution control and monitoring, microbiology, bacterial and viral analysis, mining, and industrial and toxic gases. The biosensor market has significantly increased and will be mushrooming in the next decade. The total biosensor market is estimated to be 10.8 billion dollars by 2007. The emerging biosensor market presents both opportunities and obstacles to start-up biosensor entrepreneurs. The major challenge and threat for these entrepreneurs is how to predict the biosensor market and how to convert promising biosensor technology into commercialized biosensors. By adopting a simple commercialization strategy framework, we identify two key elements of biosensor commercialization strategy: excludability and complementary asset. We further divide biosensor commercialization environments into four distinct sub-environments: the Attacker's Advantage, Reputation-Based Idea Trading, Greenfield Competition and Ideas Factories. This paper explains how the interaction between these two key elements shapes biosensor commercialization strategy and biosensor industry dynamics. This paper also discusses alternative commercialization strategies for each specific commercialization environment and how to choose from these alternatives. The analysis of this study further provides a good reference for start-up biosensor entrepreneurs to formulate effective biosensor commercialization strategy. PMID:15574353
Mizuno, Yuta; Arasaki, Yasuki; Takatsuka, Kazuo
2016-01-14
A complicated yet interesting induced photon emission can take place by a nonadiabatic intramolecular electron transfer system like LiF under an intense CW laser [Y. Arasaki, S. Scheit, and K. Takatsuka, J. Chem. Phys. 138, 161103 (2013)]. Behind this phenomena, the crossing point between two potential energy curves of covalent and ionic natures in diabatic representation is forced to oscillate, since only the ionic potential curve is shifted significantly up and down repeatedly (called the Dynamical Stark effect). The wavepacket pumped initially to the excited covalent potential curve frequently encounters such a dynamically moving crossing point and thereby undergoes very complicated dynamics including wavepacket bifurcation and deformation. Intramolecular electron transfer thus driven by the coupling between nonadiabatic state-mixing and laser fields induces irregular photon emission. Here in this report we discuss the complicated spectral features of this kind of photon emission induced by infrared laser. In the low frequency domain, the photon emission is much more involved than those of ultraviolet/visible driving fields, since many field-dressed states are created on the ionic potential, which have their own classical turning points and crossing points with the covalent counterpart. To analyze the physics behind the phenomena, we develop a perturbation theoretic approach to the Riccati equation that is transformed from coupled first-order linear differential equations with periodic coefficients, which are supposed to produce the so-called Floquet states. We give mathematical expressions for the Floquet energies, frequencies, and intensities of the photon emission spectra, and the cutoff energy of their harmonic generation. Agreement between these approximate quantities and those estimated with full quantum calculations is found to be excellent. Furthermore, the present analysis provides with notions to facilitate deeper understanding for the physical and
NASA Astrophysics Data System (ADS)
Mizuno, Yuta; Arasaki, Yasuki; Takatsuka, Kazuo
2016-01-01
A complicated yet interesting induced photon emission can take place by a nonadiabatic intramolecular electron transfer system like LiF under an intense CW laser [Y. Arasaki, S. Scheit, and K. Takatsuka, J. Chem. Phys. 138, 161103 (2013)]. Behind this phenomena, the crossing point between two potential energy curves of covalent and ionic natures in diabatic representation is forced to oscillate, since only the ionic potential curve is shifted significantly up and down repeatedly (called the Dynamical Stark effect). The wavepacket pumped initially to the excited covalent potential curve frequently encounters such a dynamically moving crossing point and thereby undergoes very complicated dynamics including wavepacket bifurcation and deformation. Intramolecular electron transfer thus driven by the coupling between nonadiabatic state-mixing and laser fields induces irregular photon emission. Here in this report we discuss the complicated spectral features of this kind of photon emission induced by infrared laser. In the low frequency domain, the photon emission is much more involved than those of ultraviolet/visible driving fields, since many field-dressed states are created on the ionic potential, which have their own classical turning points and crossing points with the covalent counterpart. To analyze the physics behind the phenomena, we develop a perturbation theoretic approach to the Riccati equation that is transformed from coupled first-order linear differential equations with periodic coefficients, which are supposed to produce the so-called Floquet states. We give mathematical expressions for the Floquet energies, frequencies, and intensities of the photon emission spectra, and the cutoff energy of their harmonic generation. Agreement between these approximate quantities and those estimated with full quantum calculations is found to be excellent. Furthermore, the present analysis provides with notions to facilitate deeper understanding for the physical and
Theoretical approaches to lightness and perception.
Gilchrist, Alan
2015-01-01
a better account of illusions and failures of constancy. Evidence for and against these approaches is reviewed. PMID:26492718
A first-principles theoretical approach to heterogeneous nanocatalysis.
Negreiros, Fabio R; Aprà, Edoardo; Barcaro, Giovanni; Sementa, Luca; Vajda, Stefan; Fortunelli, Alessandro
2012-02-21
A theoretical approach to heterogeneous catalysis by sub-nanometre supported metal clusters and alloys is presented and discussed. Its goal is to perform a computational sampling of the reaction paths in nanocatalysis via a global search in the phase space of structures and stoichiometry combined with filtering which takes into account the given experimental conditions (catalytically relevant temperature and reactant pressure), and corresponds to an incremental exploration of the disconnectivity diagram of the system. The approach is implemented and applied to the study of propylene partial oxidation by Ag(3) supported on MgO(100). First-principles density-functional theory calculations coupled with a Reactive Global Optimization algorithm are performed, finding that: (1) the presence of an oxide support drastically changes the potential energy landscape of the system with respect to the gas phase, favoring configurations which interact positively with the electrostatic field generated by the surface; (2) the reaction energy barriers for the various mechanisms are crucial in the competition between thermodynamically and kinetically favored reaction products; (3) a topological database of structures and saddle points is produced which has general validity and can serve for future studies or for deriving general trends; (4) the MgO(100) surface captures some major features of the effect of an oxide support and appears to be a good model of a simple oxide substrate; (5) strong cooperative effects are found in the co-adsorption of O(2) and other ligands on small metal clusters. The proposed approach appears as a viable route to advance the role of predictive computational science in the field of heterogeneous nanocatalysis. PMID:22057595
Preservation of Newspapers: Theoretical Approaches and Practical Achievements
ERIC Educational Resources Information Center
Hasenay, Damir; Krtalic, Maja
2010-01-01
The preservation of newspapers is the main topic of this paper. A theoretical overview of newspaper preservation is given, with an emphasis on the importance of a systematic and comprehensive approach. Efficient newspaper preservation implies understanding the meaning of preservation in general, as well as understanding specific approaches,…
Dramaturgical and Music-Theoretical Approaches to Improvisation Pedagogy
ERIC Educational Resources Information Center
Huovinen, Erkki; Tenkanen, Atte; Kuusinen, Vesa-Pekka
2011-01-01
The aim of this article is to assess the relative merits of two approaches to teaching musical improvisation: a music-theoretical approach, focusing on chords and scales, and a "dramaturgical" one, emphasizing questions of balance, variation and tension. Adult students of music pedagogy, with limited previous experience in improvisation, took part…
Corporate Library Impact, Part I: A Theoretical Approach
ERIC Educational Resources Information Center
Edgar, William
2004-01-01
Drawing on library and information science, strategy, and organizational theory, this article presents a theoretical approach to the determination of corporate library contribution to its parent firm. This approach departs from previous work on this topic, which focused on corporate library contribution to corporate operations and standing,…
An integrated theoretical and practical approach for teaching hydrogeology
NASA Astrophysics Data System (ADS)
Bonomi, Tullia; Fumagalli, Letizia; Cavallin, Angelo
2013-04-01
their limitations; C) by an evaluation process whose results contribute to the final examination, so that the students are evaluated on the basis of their ability to discuss theoretical subjects and/or projects and to resolving exercises and case studies either by hand calculations or by modelling. The applied hydrogeology examination is an example of the evaluation process. It involves development of a plan to resolve a real hydrogeological issue, such as the design of a hydraulic barrier for a landfill, the design of a well field to meet the supply requirements of a muncipality, or the control of possible seepage from a contaminated site close to to sensitive discharge features such as wells, springs, rivers. The students are allowed to work on computers for three consecutive mornings for a total 15 hours, and in the end are required to produce a technical report and a hydrogeological model. Obviously their solutions are neither unique nor completely optimized (just as in the real world), but the comparisons and debates among the students are important portals to learning and improvement. A second example: the groundwater pollution and remediation examination is based on the discussion of a remediation project elaborated in stages during the course, with the addition of increasing complex types of data and information. The students have one hour a week, during the course, to submit to the teacher their analysis of the problem and possible solutions. In ten years of experience all students have considered this method of examination a challenge, and found it engaging and helpful, even if unusual, at least in Italy. The University of Milano Bicocca has recently drilled a piezometric well both to monitor the flow of groundwater and to allow students to perform aquifer tests and to conduct standard groundwater sampling procedure, without any longer needing to rely on outside private donors for access to a field site. The overall approach, which includes, lectures
The State and the Quality Agenda: A Theoretical Approach
ERIC Educational Resources Information Center
Filippakou, Ourania; Tapper, Ted
2010-01-01
This article adopts a theoretical approach to analyse the evolution of the quality agenda in English higher education. Using the concept of reification, it shows how the quasi-state has attempted to build a "natural" understanding of the idea of quality. However, the policy implementation process has demonstrated the fragility of the state's…
Approach to Mars Field Geology
NASA Technical Reports Server (NTRS)
Muehlberger, William; Rice, James W.; Parker, Timothy; Lipps, Jere H.; Hoffman, Paul; Burchfiel, Clark; Brasier, Martin
1998-01-01
The goals of field study on Mars are nothing less than to understand the processes and history of the planet at whatever level of detail is necessary. A manned mission gives us an unprecedented opportunity to use the immense power of the human mind to comprehend Mars in extraordinary detail. To take advantage of this opportunity, it is important to examine how we should approach the field study of Mars. In this effort, we are guided by over 200 years of field exploration experience on Earth as well as six manned missions exploring the Moon.
Geodetic methods for detecting volcanic unrest: a theoretical approach
NASA Astrophysics Data System (ADS)
Fernández, José; Carrasco, José M.; Rundle, John B.; Araña, Vicente
In this paper we study the application of different geodetic techniques to volcanic activity monitoring, using theoretical analysis. This methodology is very useful for obtaining an idea of the most appropriate (and efficient) monitoring method, mainly when there are no records of geodetic changes previous to volcanic activity. The analysis takes into account the crustal structure of the area, its geology, and its known volcanic activity to estimate the deformation and gravity changes that might precede eruptions. The deformation model used includes the existing gravity field and vertical changes in the crustal properties. Both factors can have a considerable effect on computed deformation and gravity changes. Topography should be considered when there is a steep slope (greater than 10°). The case study of Teide stratovolcano (Tenerife, Canary Islands), for which no deformation or gravity changes are available, is used as a test. To avoid considering topography, we worked at the lowest level of Las Cañadas and examined a smaller area than the whole caldera or island. Therefore, the results are only a first approach to the most adequate geodetic monitoring system. The methodology can also be applied to active areas where volcanic risk is not associated with a stratovolcano but instead with monogenetic scattered centers, especially when sites must be chosen in terms of detection efficiency or existing facilities. The Canary Islands provide a good example of this type of active volcanic areas, and we apply our model to the island of Lanzarote to evaluate the efficiency of the monitoring system installed at the existing geodynamic station. On this island topography is not important. The results of our study show clearly that the most appropriate geodetic volcano monitoring system is not the same for all different volcanic zones and types, and the particular properties of each volcano/zone must be taken into account when designing each system.
A theoretical approach to artificial intelligence systems in medicine.
Spyropoulos, B; Papagounos, G
1995-10-01
The various theoretical models of disease, the nosology which is accepted by the medical community and the prevalent logic of diagnosis determine both the medical approach as well as the development of the relevant technology including the structure and function of the A.I. systems involved. A.I. systems in medicine, in addition to the specific parameters which enable them to reach a diagnostic and/or therapeutic proposal, entail implicitly theoretical assumptions and socio-cultural attitudes which prejudice the orientation and the final outcome of the procedure. The various models -causal, probabilistic, case-based etc. -are critically examined and their ethical and methodological limitations are brought to light. The lack of a self-consistent theoretical framework in medicine, the multi-faceted character of the human organism as well as the non-explicit nature of the theoretical assumptions involved in A.I. systems restrict them to the role of decision supporting "instruments" rather than regarding them as decision making "devices". This supporting role and, especially, the important function which A.I. systems should have in the structure, the methods and the content of medical education underscore the need of further research in the theoretical aspects and the actual development of such systems. PMID:8547968
A control theoretic model for piloted approach to landing.
NASA Technical Reports Server (NTRS)
Kleinman, D. L.; Baron, S.
1972-01-01
Using manned vehicle systems analysis, a model for manual approach to landing is developed. This model is developed and applied in the specific context of a problem of analytical evaluation of a pictorial display for longitudinal control of glide path errors. This makes it possible to discuss the model in concrete terms, and the availability of experimental data provides opportunities for checking the theoretical results obtained.
Field theoretical prediction of a property of the tropical cyclone
NASA Astrophysics Data System (ADS)
Spineanu, F.; Vlad, M.
2014-01-01
The large scale atmospheric vortices (tropical cyclones, tornadoes) are complex physical systems combining thermodynamics and fluid-mechanical processes. The late phase of the evolution towards stationarity consists of the vorticity concentration, a well known tendency to self-organization , an universal property of the two-dimensional fluids. It may then be expected that the stationary state of the tropical cyclone has the same nature as the vortices of many other systems in nature: ideal (Euler) fluids, superconductors, Bose-Einsetin condensate, cosmic strings, etc. Indeed it was found that there is a description of the atmospheric vortex in terms of a classical field theory. It is compatible with the more conventional treatment based on conservation laws, but the field theoretical model reveals properties that are almost inaccessible to the conventional formulation: it identifies the stationary states as being close to self-duality. This is of highest importance: the self-duality is known to be the origin of all coherent structures known in natural systems. Therefore the field theoretical (FT) formulation finds that the cuasi-coherent form of the atmospheric vortex (tropical cyclone) at stationarity is an expression of this particular property. In the present work we examine a strong property of the tropical cyclone, which arises in the FT formulation in a natural way: the equality of the masses of the particles associated to the matter field and respectively to the gauge field in the FT model is translated into the equality between the maximum radial extension of the tropical cyclone and the Rossby radius. For the cases where the FT model is a good approximation we calculate characteristic quantities of the tropical cyclone and find good comparison with observational data.
A note on the field-theoretical description of superfluids
NASA Astrophysics Data System (ADS)
Andrianopoli, L.; D'Auria, R.; Grassi, P. A.; Trigiante, M.
2014-02-01
Recently, a Lagrangian description of superfluids attracted some interest from the fluid/gravity-correspondence viewpoint. In this respect, the work of Dubovksy et al. has proposed a new field theoretical description of fluids, which has several interesting aspects. On another side, we have recently provided a supersymmetric extension of the original works. In the analysis of the Lagrangian structures a new invariant appeared which, although related to known invariants, provides, in our opinion, a better parametrization of the fluid dynamics in order to describe the fluid/superfluid phases. Above the critical temperature TC the fluid has a normal behavior and is invariant under the chemical-shift symmetry [8]. It is described in terms of the comoving coordinates ϕI(x) and by the U(1)-phase field ψ(x).On the other hand, below the critical temperature the chemical-shift symmetry is spontaneously broken, giving rise to the superfluid. In particular, at T=0, the superfluid is completely described in terms of ψ. One can consider, following [9], an isotropic and homogeneous background where ψ=y0t, ϕI=b01/3xI. It corresponds to taking a configuration where the fields ϕI are comoving with the normal fluid part (which is at rest in this background), the superfluid field ψ being in relative motion with respect to it. Note that the loss of interactions between the two fluids is expressed by the property that ZI=∂μψ∂μϕI=0 in the background. Small perturbations about the background (28): ψ=y0(t+π0(x)), ϕI=b01/3(xI+πI(x)) introduce a small interaction term ZI≠0. Note that the quantity BIJ-1ZIZJ=ɛ stays small in this regime, even if ϕI→0 as T→0. Given these considerations, we can make use of the relation (18) to observe that at very low temperatures the quantity y2=-X+BIJ-1ZIZJ=-X+ɛ approaches the value -X, which is not invariant under the chemical-shift symmetry. In this regime the Lagrangian F(b,y) can be expanded in powers of ɛ around the
Theoretical description of teaching-learning processes: a multidisciplinary approach.
Bordogna, C M; Albano, E V
2001-09-10
A multidisciplinary approach based on concepts from sociology, educational psychology, statistical physics, and computational science is developed for the theoretical description of teaching-learning processes that take place in the classroom. The emerging model is consistent with well-established empirical results, such as the higher achievements reached working in collaborative groups and the influence of the structure of the group on the achievements of the individuals. Furthermore, another social learning process that takes place in massive interactions among individuals via the Internet is also investigated. PMID:11531550
Considering children and health literacy: a theoretical approach.
Borzekowski, Dina L G
2009-11-01
The theoretical approaches of Paulo Freire, Jean Piaget, and Lev Vygotsky frame the consideration of children and health literacy. This article includes a general discussion of literacy from the Freirian perspective. A definition of health literacy is then presented; first, the established meaning is introduced, but then a Freirian extension is proposed. Next, the theories of cognitive development by Piaget and Vygotsky are discussed, and examples related to children's health literacy are given. Finally, there is a discussion of why it is important to encourage and enable health literacy among children and adolescents. PMID:19861482
An information theoretic approach of designing sparse kernel adaptive filters.
Liu, Weifeng; Park, Il; Principe, José C
2009-12-01
This paper discusses an information theoretic approach of designing sparse kernel adaptive filters. To determine useful data to be learned and remove redundant ones, a subjective information measure called surprise is introduced. Surprise captures the amount of information a datum contains which is transferable to a learning system. Based on this concept, we propose a systematic sparsification scheme, which can drastically reduce the time and space complexity without harming the performance of kernel adaptive filters. Nonlinear regression, short term chaotic time-series prediction, and long term time-series forecasting examples are presented. PMID:19923047
Theoretical, Methodological, and Empirical Approaches to Cost Savings: A Compendium
M Weimar
1998-12-10
This publication summarizes and contains the original documentation for understanding why the U.S. Department of Energy's (DOE's) privatization approach provides cost savings and the different approaches that could be used in calculating cost savings for the Tank Waste Remediation System (TWRS) Phase I contract. The initial section summarizes the approaches in the different papers. The appendices are the individual source papers which have been reviewed by individuals outside of the Pacific Northwest National Laboratory and the TWRS Program. Appendix A provides a theoretical basis for and estimate of the level of savings that can be" obtained from a fixed-priced contract with performance risk maintained by the contractor. Appendix B provides the methodology for determining cost savings when comparing a fixed-priced contractor with a Management and Operations (M&O) contractor (cost-plus contractor). Appendix C summarizes the economic model used to calculate cost savings and provides hypothetical output from preliminary calculations. Appendix D provides the summary of the approach for the DOE-Richland Operations Office (RL) estimate of the M&O contractor to perform the same work as BNFL Inc. Appendix E contains information on cost growth and per metric ton of glass costs for high-level waste at two other DOE sites, West Valley and Savannah River. Appendix F addresses a risk allocation analysis of the BNFL proposal that indicates,that the current approach is still better than the alternative.
Monte Carlo field-theoretic simulations of a homopolymer blend
NASA Astrophysics Data System (ADS)
Spencer, Russell; Matsen, Mark
Fluctuation corrections to the macrophase segregation transition (MST) in a symmetric homopolymer blend are examined using Monte Carlo field-theoretic simulations (MC-FTS). This technique involves treating interactions between unlike monomers using standard Monte-Carlo techniques, while enforcing incompressibility as is done in mean-field theory. When using MC-FTS, we need to account for a UV divergence. This is done by renormalizing the Flory-Huggins interaction parameter to incorporate the divergent part of the Hamiltonian. We compare different ways of calculating this effective interaction parameter. Near the MST, the length scale of compositional fluctuations becomes large, however, the high computational requirements of MC-FTS restrict us to small system sizes. We account for these finite size effects using the method of Binder cumulants, allowing us to locate the MST with high precision. We examine fluctuation corrections to the mean field MST, χN = 2 , as they vary with the invariant degree of polymerization, N =ρ2a6 N . These results are compared with particle-based simulations as well as analytical calculations using the renormalized one loop theory. This research was funded by the Center for Sustainable Polymers.
Theoretical and experimental examination of near-field acoustic levitation.
Nomura, Hideyuki; Kamakura, Tomoo; Matsuda, Kazuhisa
2002-04-01
A planar object can be levitated stably close to a piston sound source by making use of acoustic radiation pressure. This phenomenon is called near-field acoustic levitation [Y. Hashimoto et al., J. Acoust. Soc. Am. 100, 2057-2061 (1996)]. In the present article, the levitation distance is predicted theoretically by numerically solving basic equations in a compressible viscous fluid subject to the appropriate initial and boundary conditions. Additionally, experiments are carried out using a 19.5-kHz piston source with a 40-mm aperture and various aluminum disks of different sizes. The measured levitation distance agrees well with the theory, which is different from a conventional theory, and the levitation distance is not inversely proportional to the square root of the surface density of the levitated disk in a strict sense. PMID:12002842
Irreversibility of financial time series: A graph-theoretical approach
NASA Astrophysics Data System (ADS)
Flanagan, Ryan; Lacasa, Lucas
2016-04-01
The relation between time series irreversibility and entropy production has been recently investigated in thermodynamic systems operating away from equilibrium. In this work we explore this concept in the context of financial time series. We make use of visibility algorithms to quantify, in graph-theoretical terms, time irreversibility of 35 financial indices evolving over the period 1998-2012. We show that this metric is complementary to standard measures based on volatility and exploit it to both classify periods of financial stress and to rank companies accordingly. We then validate this approach by finding that a projection in principal components space of financial years, based on time irreversibility features, clusters together periods of financial stress from stable periods. Relations between irreversibility, efficiency and predictability are briefly discussed.
Theoretical analysis of magnetic field interactions with aortic blood flow
Kinouchi, Y.; Yamaguchi, H.; Tenforde, T.S.
1996-04-01
The flow of blood in the presence of a magnetic field gives rise to induced voltages in the major arteries of the central circulatory system. Under certain simplifying conditions, such as the assumption that the length of major arteries (e.g., the aorta) is infinite and that the vessel walls are not electrically conductive, the distribution of induced voltages and currents within these blood vessels can be calculated with reasonable precision. However, the propagation of magnetically induced voltages and currents from the aorta into neighboring tissue structures such as the sinuatrial node of the heart has not been previously determined by any experimental or theoretical technique. In the analysis presented in this paper, a solution of the complete Navier-Stokes equation was obtained by the finite element technique for blood flow through the ascending and descending aortic vessels in the presence of a uniform static magnetic field. Spatial distributions of the magnetically induced voltage and current were obtained for the aortic vessel and surrounding tissues under the assumption that the wall of the aorta is electrically conductive. Results are presented for the calculated values of magnetically induced voltages and current densities in the aorta and surrounding tissue structures, including the sinuatrial node, and for their field-strength dependence. In addition, an analysis is presented of magnetohydrodynamic interactions that lead to a small reduction of blood volume flow at high field levels above approximately 10 tesla (T). Quantitative results are presented on the offsetting effects of oppositely directed blood flows in the ascending and descending aortic segments, and a quantitative estimate is made of the effects of assuming an infinite vs. a finite length of the aortic vessel in calculating the magnetically induced voltage and current density distribution in tissue.
Essential amino acids interacting with flavonoids: A theoretical approach
NASA Astrophysics Data System (ADS)
Codorniu-Hernández, Edelsys; Mesa-Ibirico, Ariel; Hernández-Santiesteban, Richel; Montero-Cabrera, Luis A.; Martínez-Luzardo, Francisco; Santana-Romero, Jorge L.; Borrmann, Tobias; Stohrer, Wolf-D.
The interaction of two flavonoid species (resorcinolic and fluoroglucinolic) with the 20 essential amino acids was studied by the multiple minima hypersurface (MMH) procedures, through the AM1 and PM3 semiempirical methods. Remarkable thermodynamic data related to the properties of the molecular association of these compounds were obtained, which will be of great utility for future investigations concerning the interaction of flavonoids with proteins. These results are compared with experimental and classical force field results reported in the available literature, and new evidences and criteria are shown. The hydrophilic amino acids demonstrated high affinity in the interaction with flavonoid molecules; the complexes with lysine are especially extremely stable. An affinity order for the interaction of both flavonoid species with the essential amino acids is suggested. Our theoretical results are compared with experimental evidence on flavonoid interactions with proteins of biomedical interest.
Rainbows from inhomogeneous transparent spheres: a ray-theoretic approach.
Adam, John A; Laven, Philip
2007-02-20
A ray-theoretic account of the passage of light through a radially inhomogeneous transparent sphere has been used to establish the existence of multiple primary rainbows for some refractive index profiles. The existence of such additional bows is a consequence of a sufficiently attractive potential in the interior of the drop, i.e., the refractive index gradient should be sufficiently negative there. The profiles for which this gradient is monotonically increasing do not result in this phenomenon, but nonmonotone profiles can do so, depending on the form of n. Sufficiently oscillatory profiles can lead to apparently singular behavior in the deviation angle (within the geometrical optics approximation) as well as multiple rainbows. These results also apply to systems with circular cylindrical cross sections, and may be of value in the field of rainbow refractometry. PMID:17279138
We need theoretical physics approaches to study living systems
NASA Astrophysics Data System (ADS)
Blagoev, Krastan B.; Shukla, Kamal; affil="3" >Herbert Levine,
2013-08-01
Living systems, as created initially by the transition from assemblies of large molecules to self-reproducing information-rich cells, have for centuries been studied via the empirical toolkit of biology. This has been a highly successful enterprise, bringing us from the vague non-scientific notions of vitalism to the modern appreciation of the biophysical and biochemical bases of life. Yet, the truly mind-boggling complexity of even the simplest self-sufficient cells, let alone the emergence of multicellular organisms, of brain and consciousness, and to ecological communities and human civilizations, calls out for a complementary approach. In this editorial, we propose that theoretical physics can play an essential role in making sense of living matter. When faced with a highly complex system, a physicist builds simplified models. Quoting Philip W Anderson's Nobel prize address, 'the art of model-building is the exclusion of real but irrelevant parts of the problem and entails hazards for the builder and the reader. The builder may leave out something genuinely relevant and the reader, armed with too sophisticated an experimental probe, may take literally a schematized model. Very often such a simplified model throws more light on the real working of nature....' In his formulation, the job of a theorist is to get at the crux of the system by ignoring details and yet to find a testable consequence of the resulting simple picture. This is rather different than the predilection of the applied mathematician who wants to include all the known details in the hope of a quantitative simulacrum of reality. These efforts may be practically useful, but do not usually lead to increased understanding. To illustrate how this works, we can look at a non-living example of complex behavior that was afforded by spatiotemporal patterning in the Belousov-Zhabotinsky reaction [1]. Physicists who worked on this system did not attempt to determine all the relevant chemical intermediates
GTA: a game theoretic approach to identifying cancer subnetwork markers.
Farahmand, S; Goliaei, S; Ansari-Pour, N; Razaghi-Moghadam, Z
2016-03-01
The identification of genetic markers (e.g. genes, pathways and subnetworks) for cancer has been one of the most challenging research areas in recent years. A subset of these studies attempt to analyze genome-wide expression profiles to identify markers with high reliability and reusability across independent whole-transcriptome microarray datasets. Therefore, the functional relationships of genes are integrated with their expression data. However, for a more accurate representation of the functional relationships among genes, utilization of the protein-protein interaction network (PPIN) seems to be necessary. Herein, a novel game theoretic approach (GTA) is proposed for the identification of cancer subnetwork markers by integrating genome-wide expression profiles and PPIN. The GTA method was applied to three distinct whole-transcriptome breast cancer datasets to identify the subnetwork markers associated with metastasis. To evaluate the performance of our approach, the identified subnetwork markers were compared with gene-based, pathway-based and network-based markers. We show that GTA is not only capable of identifying robust metastatic markers, it also provides a higher classification performance. In addition, based on these GTA-based subnetworks, we identified a new bonafide candidate gene for breast cancer susceptibility. PMID:26750920
A novel theoretical approach to the analysis of dendritic transients.
Agmon-Snir, H
1995-01-01
A novel theoretical framework for analyzing dendritic transients is introduced. This approach, called the method of moments, is an extension of Rall's cable theory for dendrites. It provides analytic investigation of voltage attenuation, signal delay, and synchronization problems in passive dendritic trees. In this method, the various moments of a transient signal are used to characterize the properties of the transient. The strength of the signal is measured by the time integral of the signal, its characteristic time is determined by its centroid ("center of gravity"), and the width of the signal is determined by a measure similar to the standard deviation in probability theory. Using these signal properties, the method of moments provides theorems, expressions, and efficient algorithms for analyzing the voltage response in arbitrary passive trees. The method yields new insights into spatiotemporal integration, coincidence detection mechanisms, and the properties of local interactions between synaptic inputs in dendritic trees. The method can also be used for matching dendritic neuron models to experimental data and for the analysis of synaptic inputs recorded experimentally. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 10 PMID:8580308
A game theoretic approach for trading discharge permits in rivers.
Niksokhan, Mohammad Hossein; Kerachian, Reza; Karamouz, Mohammad
2009-01-01
In this paper, a new Cooperative Trading Discharge Permit (CTDP) methodology is designed for estimating equitable and efficient treatment cost allocation among dischargers in a river system considering their conflicting interests. The methodology consists of two main steps: (1) initial treatment cost allocation and (2) equitable treatment cost reallocation. In the first step, a Pareto front among objectives is developed using a powerful and recently developed multi-objective genetic algorithm known as Nondominated Sorting Genetic Algorithm-II (NSGA-II). The objectives of the optimization model are considered to be the average treatment level of dischargers and a fuzzy risk of violating the water quality standards. The fuzzy risk is evaluated using the Monte Carlo analysis. The best non-dominated solution on the Pareto front, which provides the initial cost allocation to dischargers, is selected using the Young Bargaining Theory (YBT). In the second step, some cooperative game theoretic approaches are utilized to investigate how the maximum saving cost of participating dischargers in a coalition can be fairly allocated to them. The final treatment cost allocation provides the optimal trading discharge permit policies. The practical utility of the proposed methodology for river water quality management is illustrated through a realistic case study of the Zarjub river in the northern part of Iran. PMID:19657175
Intelligent cognitive radio jamming - a game-theoretical approach
NASA Astrophysics Data System (ADS)
Dabcevic, Kresimir; Betancourt, Alejandro; Marcenaro, Lucio; Regazzoni, Carlo S.
2014-12-01
Cognitive radio (CR) promises to be a solution for the spectrum underutilization problems. However, security issues pertaining to cognitive radio technology are still an understudied topic. One of the prevailing such issues are intelligent radio frequency (RF) jamming attacks, where adversaries are able to exploit on-the-fly reconfigurability potentials and learning mechanisms of cognitive radios in order to devise and deploy advanced jamming tactics. In this paper, we use a game-theoretical approach to analyze jamming/anti-jamming behavior between cognitive radio systems. A non-zero-sum game with incomplete information on an opponent's strategy and payoff is modelled as an extension of Markov decision process (MDP). Learning algorithms based on adaptive payoff play and fictitious play are considered. A combination of frequency hopping and power alteration is deployed as an anti-jamming scheme. A real-life software-defined radio (SDR) platform is used in order to perform measurements useful for quantifying the jamming impacts, as well as to infer relevant hardware-related properties. Results of these measurements are then used as parameters for the modelled jamming/anti-jamming game and are compared to the Nash equilibrium of the game. Simulation results indicate, among other, the benefit provided to the jammer when it is employed with the spectrum sensing algorithm in proactive frequency hopping and power alteration schemes.
Network-theoretic approach to model vortex interactions
NASA Astrophysics Data System (ADS)
Nair, Aditya; Taira, Kunihiko
2014-11-01
We present a network-theoretic approach to describe a system of point vortices in two-dimensional flow. By considering the point vortices as nodes, a complete graph is constructed with edges connecting each vortex to every other vortex. The interactions between the vortices are captured by the graph edge weights. We employ sparsification techniques on these graph representations based on spectral theory to construct sparsified models of the overall vortical interactions. The edge weights are redistributed through spectral sparsification of the graph such that the sum of the interactions associated with each vortex is maintained constant. In addition, sparse configurations maintain similar spectral properties as the original setup. Through the reduction in the number of interactions, key vortex interactions can be highlighted. Identification of vortex structures based on graph sparsification is demonstrated with an example of clusters of point vortices. We also evaluate the computational performance of sparsification for large collection of point vortices. Work supported by US Army Research Office (W911NF-14-1-0386) and US Air Force Office of Scientific Research (YIP: FA9550-13-1-0183).
An Interacting Gauge Field Theoretic Model for Hodge Theory: Basic Canonical Brackets
NASA Astrophysics Data System (ADS)
R., Kumar; Gupta, S.; R. P., Malik
2014-06-01
We derive the basic canonical brackets amongst the creation and annihilation operators for a two (1 + 1)-dimensional (2D) gauge held theoretic model of an interacting Hodge theory where a U(1) gauge field (Aμ) is coupled with the fermionic Dirac fields (ψ and bar psi). In this derivation, we exploit the spin-statistics theorem, normal ordering and the strength of the underlying six infinitesimal continuous symmetries (and the concept of their generators) that are present in the theory. We do not use the definition of the canonical conjugate momenta (corresponding to the basic fields of the theory) anywhere in our whole discussion. Thus, we conjecture that our present approach provides an alternative to the canonical method of quantization for a class of gauge field theories that are physical examples of Hodge theory where the continuous symmetries (and corresponding generators) provide the physical realizations of the de Rham cohomological operators of differential geometry at the algebraic level.
A choice-semantical approach to theoretical truth.
Andreas, Holger; Schiemer, Georg
2016-08-01
A central topic in the logic of science concerns the proper semantic analysis of theoretical sentences, that is sentences containing theoretical terms. In this paper, we present a novel choice-semantical account of theoretical truth based on the epsilon-term definition of theoretical terms. Specifically, we develop two ways of specifying the truth conditions of theoretical statements in a choice functional semantics, each giving rise to a corresponding logic of such statements. In order to investigate the inferential strength of these logical systems, we provide a translation of each truth definition into a modal definition of theoretical truth. Based on this, we show that the stronger notion of choice-semantical truth captures more adequately our informal semantic understanding of scientific statements. PMID:27474181
Postionization fragmentation of rare-gas trimers revisited with new theoretical approaches
NASA Astrophysics Data System (ADS)
Janeček, Ivan; Cintavá, Silvie; Hrivňák, Daniel; Kalus, René; Fárník, Michal; Gadea, Florent Xavier
2009-09-01
A new theoretical approach is presented for the general treatment of nonadiabatic hybrid dynamics (mixing classical and quantum approach) and applied to the postionization of rare-gas trimers. There was an important disagreement between trajectory surface hopping (TSH) or mean field (MF) approaches and the experimental results; noteworthy, with the new method qualitative and almost quantitative agreement is found for the fragmentation ratios of ionic monomers and dimers. For the first time in the theory as in the experiment, the dimers prevail for argon while monomers strongly dominate for the heavier rare gases, krypton and xenon. A new compromise between MF and TSH approaches is proposed and the new method is found quite robust with results not too sensitive to various possible implementations.
Theoretical analysis of a cell's oscillations in an acoustic field
NASA Astrophysics Data System (ADS)
Allen, John S.; Zinin, Pavel
2005-09-01
The analysis and deformation of an individual cell in a high-frequency acoustic field is of fundamental interest for a variety of applications such as ultrasound cell separation and drug delivery. The oscillations of biological cells in a sound field are investigated using a shell model for the cell following an approach developed previously [Zinin, Ultrasonics, 30, 26-34 (1992)]. The model accounts for the three components which comprise the cell's motion: the internal fluid (cytoplasma), the cell membrane, and the surrounding fluid. The cell membrane whose thickness is small compared to the cell radius can be approximated as a thin elastic shell. The elastic properties of this shell together with the viscosities of the internal and external fluids determine the oscillations of the cell. The dipole oscillations of the cell depend on the surface area modulus and the maximum frequency for the relative change in cell area can be determined. Moreover, the higher order oscillations starting with the quadrupole oscillations are governed by the shell's shear modulus. Induced stresses in bacteria cell membranes in the vicinity of an oscillating bubble are investigated and cell rupture with respect to these stresses is analyzed.
Three approaches to classical thermal field theory
NASA Astrophysics Data System (ADS)
Gozzi, E.; Penco, R.
2011-04-01
In this paper we study three different functional approaches to classical thermal field theory, which turn out to be the classical counterparts of three well-known different formulations of quantum thermal field theory: the closed-time path (CTP) formalism, the thermofield dynamics (TFD) and the Matsubara approach.
A theoretical approach to understand spatial organization in complex ecologies.
Roman, Ahmed; Dasgupta, Debanjan; Pleimling, Michel
2016-08-21
Predicting the fate of ecologies is a daunting, albeit extremely important, task. As part of this task one needs to develop an understanding of the organization, hierarchies, and correlations among the species forming the ecology. Focusing on complex food networks we present a theoretical method that allows to achieve this understanding. Starting from the adjacency matrix the method derives specific matrices that encode the various inter-species relationships. The full potential of the method is achieved in a spatial setting where one obtains detailed predictions for the emerging space-time patterns. For a variety of cases these theoretical predictions are verified through numerical simulations. PMID:27173644
Inflation and quintessence: theoretical approach of cosmological reconstruction
Neupane, Ishwaree P; Scherer, Christoph
2008-05-15
In the first part of this paper, we outline the construction of an inflationary cosmology in the framework where inflation is described by a universally evolving scalar field {phi} with potential V ({phi}). By considering a generic situation that inflaton attains a nearly constant velocity during inflation. In the second part of this paper, we introduce a novel approach of constructing dark energy within the context of the standard scalar-tensor theory. The assumption that a scalar field might roll with a nearly constant velocity, during inflation, can also be applied to quintessence or dark energy models. For the minimally coupled quintessence, {alpha}{sub Q} {identical_to} dA(Q)/d({kappa}Q)=0 (where A(Q) is the standard matter-quintessence coupling), the dark energy equation of state in the range -1{<=}w{sub DE}<-0.82 can be obtained for 0{<=}{alpha}<0.63. For {alpha}<0.1, the model allows for only modest evolution of dark energy density with redshift. We also show, under certain conditions, that the {alpha}{sub Q}>0 solution decreases the dark energy equation of state w{sub Q} with decreasing redshift as compared to the {alpha}{sub Q} = 0 solution. This effect can be opposite in the {alpha}{sub Q}<0 case. The effect of the matter-quintessence coupling can be significant only if |{alpha}{sub Q}|{approx}>0.1, while a small coupling |{alpha}{sub Q}|<0.1 will have almost no effect on cosmological parameters, including {Omega}{sub Q}, w{sub Q} and H(z). The best fit value of {alpha}{sub Q} in our model is found to be {alpha}{sub Q}{approx_equal}0.06, but it may contain significant numerical errors, namely {alpha}{sub Q} = 0.06 {+-} 0.35, which clearly implies the consistency of our model with general relativity (for which {alpha}{sub Q} = 0) at 1{sigma} level.
Inflation and quintessence: theoretical approach of cosmological reconstruction
NASA Astrophysics Data System (ADS)
Neupane, Ishwaree P.; Scherer, Christoph
2008-05-01
In the first part of this paper, we outline the construction of an inflationary cosmology in the framework where inflation is described by a universally evolving scalar field phi with potential V (phi). By considering a generic situation that inflaton attains a nearly constant velocity, during inflation, m_{\\mathrm {P}}^{-1} |\\rmd \\phi /\\rmd N|\\equiv \\alpha+\\beta \\exp (\\beta N) (where N\\equiv \\ln a is the e-folding time), we reconstruct a scalar potential and find the conditions that have to be satisfied by the (reconstructed) potential to be consistent with the WMAP inflationary data. The consistency of our model with the WMAP result (such as ns = 0.951-0.019+0.015 and r<0.3) would require 0.16<α<0.26 and β<0. The running of the spectral index, \\widetilde {\\alpha }\\equiv \\,\\rmd n_{\\mathrm {s}}/\\rmd \\ln k , is found to be small for a wide range of α. In the second part of this paper, we introduce a novel approach of constructing dark energy within the context of the standard scalar-tensor theory. The assumption that a scalar field might roll with a nearly constant velocity, during inflation, can also be applied to quintessence or dark energy models. For the minimally coupled quintessence, \\alpha _{Q}\\equiv \\,\\rmd A(Q)/\\rmd (\\kappa Q)=0 (where A(Q) is the standard matter-quintessence coupling), the dark energy equation of state in the range -1<=wDE<-0.82 can be obtained for 0<=α<0.63. For α<0.1, the model allows for only modest evolution of dark energy density with redshift. We also show, under certain conditions, that the αQ>0 solution decreases the dark energy equation of state wQ with decreasing redshift as compared to the αQ = 0 solution. This effect can be opposite in the αQ<0 case. The effect of the matter-quintessence coupling can be significant only if |\\alpha _{Q}| \\gtrsim 0.1 , while a small coupling |αQ|<0.1 will have almost no effect on cosmological parameters, including ΩQ, wQ and H(z). The best fit value of αQ in
We need theoretical physics approaches to study living systems
NASA Astrophysics Data System (ADS)
Blagoev, Krastan B.; Shukla, Kamal; affil="3" >Herbert Levine,
2013-08-01
Living systems, as created initially by the transition from assemblies of large molecules to self-reproducing information-rich cells, have for centuries been studied via the empirical toolkit of biology. This has been a highly successful enterprise, bringing us from the vague non-scientific notions of vitalism to the modern appreciation of the biophysical and biochemical bases of life. Yet, the truly mind-boggling complexity of even the simplest self-sufficient cells, let alone the emergence of multicellular organisms, of brain and consciousness, and to ecological communities and human civilizations, calls out for a complementary approach. In this editorial, we propose that theoretical physics can play an essential role in making sense of living matter. When faced with a highly complex system, a physicist builds simplified models. Quoting Philip W Anderson's Nobel prize address, 'the art of model-building is the exclusion of real but irrelevant parts of the problem and entails hazards for the builder and the reader. The builder may leave out something genuinely relevant and the reader, armed with too sophisticated an experimental probe, may take literally a schematized model. Very often such a simplified model throws more light on the real working of nature....' In his formulation, the job of a theorist is to get at the crux of the system by ignoring details and yet to find a testable consequence of the resulting simple picture. This is rather different than the predilection of the applied mathematician who wants to include all the known details in the hope of a quantitative simulacrum of reality. These efforts may be practically useful, but do not usually lead to increased understanding. To illustrate how this works, we can look at a non-living example of complex behavior that was afforded by spatiotemporal patterning in the Belousov-Zhabotinsky reaction [1]. Physicists who worked on this system did not attempt to determine all the relevant chemical intermediates
Is there a weak mixed polarity background field? Theoretical arguments
NASA Technical Reports Server (NTRS)
Spruit, H. C.; Title, A. M.; Van Ballegooijen, A. A.
1987-01-01
A number of processes associated with the formation of active regions produce 'U-loops': fluxtubes having two ends at the photosphere but otherwise still embedded in the convection zone. The mass trapped on the field lines of such loops makes them behave in a qualitatively different way from the 'omega-loops' that form active regions. It is shown that U-loops will disperse though the convection zone and form a weak (down to a few gauss) field that covers a significant fraction of the solar surface. This field is tentatively identified with the inner-network fields observed at Kitt Peak and Big Bear. The process by which these fields escape through the surface is described; a remarkable property is that it can make active region fields apparently disappear in situ. The mixed polarity moving magnetic features near sunspots are interpreted as a locally intense form of this disappearance by escape of U-loops.
Conjugate field approaches for active array compensation
NASA Technical Reports Server (NTRS)
Acosta, R. J.
1989-01-01
Two approaches for calculating the compensating feed array complex excitations are namely, the indirect conjugate field matching (ICFM) and the direct conjugate field matching (DCFM) approach. In the ICFM approach the compensating feed array excitations are determined by considering the transmitting mode and the reciprocity principle. The DCF, in contrast calculates the array excitations by integrating directly the induced surface currents on the reflector under a receiving mode. DCFM allows the reflector to be illuminated by an incident plane wave with a tapered amplitude. The level of taper can effectively control the sidelobe level of the compensated antenna pattern. Both approaches are examined briefly.
Theoretical investigation of hyperfine field parameters through mossbauer gamma ray
Ali, Sikander; Hashim, Mohd
2012-06-05
When a Mossbauer gamma-ray emitting or absorbing nucleus is placed in a crystalline environment, the quadrupole moment of the nucleus interacts with the electric field gradient set up by the ligands around it. In the transition |7/2>{yields}|5/2> twelve lines are obtained. Applying the multipole radiation field theory and density matrix formalism, the determinant of coherency matrix, intensity and degree of polarization have been calculated for each line.
Game Theoretic Approach to Post-Docked Satellite Control
NASA Technical Reports Server (NTRS)
Hiramatsu, Takashi; Fitz-Coy, Norman G.
2007-01-01
This paper studies the interaction between two satellites after docking. In order to maintain the docked state with uncertainty in the motion of the target vehicle, a game theoretic controller with Stackelberg strategy to minimize the interaction between the satellites is considered. The small perturbation approximation leads to LQ differential game scheme, which is validated to address the docking interactions between a service vehicle and a target vehicle. The open-loop solution are compared with Nash strategy, and it is shown that less control efforts are obtained with Stackelberg strategy.
Faraday effect: A field theoretical point of view
NASA Astrophysics Data System (ADS)
Ganguly, Avijit K.; Konar, Sushan; Pal, Palash B.
1999-11-01
We analyze the structure of the vacuum polarization tensor in the presence of a background electromagnetic field in a medium. We use various discrete symmetries and crossing symmetry to constrain the form factors obtained for the most general case. From these symmetry arguments, we show why the vacuum polarization tensor has to be even in the background field when there is no background medium. Taking then the background field to be purely magnetic, we evaluate the vacuum polarization to linear order in it. The result shows the phenomenon of Faraday rotation, i.e., the rotation of the plane of polarization of a plane polarized light passing through this background. We find that the usual expression for Faraday rotation, which is derived for a non-degenerate plasma in the non-relativistic approximation, undergoes substantial modification if the background is degenerate and/or relativistic. We give explicit expressions for Faraday rotation in completely degenerate and ultra-relativistic media.
Theoretical and experimental approaches for the hypercube-embedding problem
Chen Woeikae.
1991-01-01
The hypercube-embedding problem, a restricted version of the general mapping problem, is the problem of mapping a set of communicating processes to a hypercube multiprocessor. The goal is to find a mapping that minimizes the length of the paths between communicating processes so that communication overhead is minimized. Unfortunately, the hypercube-embedding problem has been shown to be NP-hard, even for trees. This thesis studies both experimental and theoretical issues for the hypercube-embedding problem. Many heuristics have been proposed for hypercube embedding. For experimental studies, a versatile test bed is established for the evaluation of heuristics. Extensive experiments were performed for a wide range of hypercube-embedding heuristics chosen from the literature. Overall, ten different heuristics are evaluated. It is shown that two of the new heuristic proposed are particularly successful in comparison with other heuristics. For theoretical studies, a simple linear-time heuristic is presented which embeds arbitrary binary trees to hypercubes with expansion 1 and average dilation no more than 2.
On some theoretical problems of laser wake-field accelerators
NASA Astrophysics Data System (ADS)
Bulanov, S. V.; Esirkepov, T. Zh.; Hayashi, Y.; Kiriyama, H.; Koga, J. K.; Kotaki, H.; Mori, M.; Kando, M.
2016-06-01
Enhancement of the quality of laser wake-field accelerated (LWFA) electron beams implies the improvement and controllability of the properties of the wake waves generated by ultra-short pulse lasers in underdense plasmas. In this work we present a compendium of useful formulas giving relations between the laser and plasma target parameters allowing one to obtain basic dependences, e.g. the energy scaling of the electrons accelerated by the wake field excited in inhomogeneous media including multi-stage LWFA accelerators. Consideration of the effects of using the chirped laser pulse driver allows us to find the regimes where the chirp enhances the wake field amplitude. We present an analysis of the three-dimensional effects on the electron beam loading and on the unlimited LWFA acceleration in inhomogeneous plasmas. Using the conditions of electron trapping to the wake-field acceleration phase we analyse the multi-equal stage and multiuneven stage LWFA configurations. In the first configuration the energy of fast electrons is a linear function of the number of stages, and in the second case, the accelerated electron energy grows exponentially with the number of stages. The results of the two-dimensional particle-in-cell simulations presented here show the high quality electron acceleration in the triple stage injection-acceleration configuration.
On some theoretical problems of laser wake-field accelerators
NASA Astrophysics Data System (ADS)
Bulanov, S. V.; Esirkepov, T. Zh.; Hayashi, Y.; Kiriyama, H.; Koga, J. K.; Kotaki, H.; Mori, M.; Kando, M.
2016-06-01
> Enhancement of the quality of laser wake-field accelerated (LWFA) electron beams implies the improvement and controllability of the properties of the wake waves generated by ultra-short pulse lasers in underdense plasmas. In this work we present a compendium of useful formulas giving relations between the laser and plasma target parameters allowing one to obtain basic dependences, e.g. the energy scaling of the electrons accelerated by the wake field excited in inhomogeneous media including multi-stage LWFA accelerators. Consideration of the effects of using the chirped laser pulse driver allows us to find the regimes where the chirp enhances the wake field amplitude. We present an analysis of the three-dimensional effects on the electron beam loading and on the unlimited LWFA acceleration in inhomogeneous plasmas. Using the conditions of electron trapping to the wake-field acceleration phase we analyse the multi-equal stage and multiuneven stage LWFA configurations. In the first configuration the energy of fast electrons is a linear function of the number of stages, and in the second case, the accelerated electron energy grows exponentially with the number of stages. The results of the two-dimensional particle-in-cell simulations presented here show the high quality electron acceleration in the triple stage injection-acceleration configuration.
A Game-Theoretical Approach to Multimedia Social Networks Security
Liu, Enqiang; Liu, Zengliang; Shao, Fei; Zhang, Zhiyong
2014-01-01
The contents access and sharing in multimedia social networks (MSNs) mainly rely on access control models and mechanisms. Simple adoptions of security policies in the traditional access control model cannot effectively establish a trust relationship among parties. This paper proposed a novel two-party trust architecture (TPTA) to apply in a generic MSN scenario. According to the architecture, security policies are adopted through game-theoretic analyses and decisions. Based on formalized utilities of security policies and security rules, the choice of security policies in content access is described as a game between the content provider and the content requester. By the game method for the combination of security policies utility and its influences on each party's benefits, the Nash equilibrium is achieved, that is, an optimal and stable combination of security policies, to establish and enhance trust among stakeholders. PMID:24977226
A system approach to pharmacodynamics. I: Theoretical framework.
Veng-Pedersen, P; Gillespie, W R
1988-01-01
A general theoretical framework is constructed for the relationship between a pharmacokinetic response r (e.g., systemic drug concentration or input rate), and an observed pharmacologic effect response E. The overall relationship may be described mathematically by E = omega(r) = omega p(omega b(omega r(r))) where omega is an operator that describes the overall relationship, and omega r, omega b, and omega p are operators that describe the contributions of components of the pharmacodynamic system. The kinetic basis for applying certain general mathematical properties such as linearity are discussed. The result is the introduction of various specific mathematical structures that may be applied to pharmacodynamic systems [e.g., E = phi t(r), E = phi t(psi r*r), E = phi p(psi p*phi b(r)), and E = phi p(psi p*phi b(psi r*r))]. PMID:3346822
A lattice-theoretic approach to multigranulation approximation space.
He, Xiaoli; She, Yanhong
2014-01-01
In this paper, we mainly investigate the equivalence between multigranulation approximation space and single-granulation approximation space from the lattice-theoretic viewpoint. It is proved that multigranulation approximation space is equivalent to single-granulation approximation space if and only if the pair of multigranulation rough approximation operators [Formula in text] forms an order-preserving Galois connection, if and only if the collection of lower (resp., upper) definable sets forms an (resp., union) intersection structure, if and only if the collection of multigranulation upper (lower) definable sets forms a distributive lattice when n = 2, and if and only if [Formula in text]. The obtained results help us gain more insights into the mathematical structure of multigranulation approximation spaces. PMID:25243226
A Lattice-Theoretic Approach to Multigranulation Approximation Space
He, Xiaoli
2014-01-01
In this paper, we mainly investigate the equivalence between multigranulation approximation space and single-granulation approximation space from the lattice-theoretic viewpoint. It is proved that multigranulation approximation space is equivalent to single-granulation approximation space if and only if the pair of multigranulation rough approximation operators (Σi=1nRi¯,Σi=1nRi_) forms an order-preserving Galois connection, if and only if the collection of lower (resp., upper) definable sets forms an (resp., union) intersection structure, if and only if the collection of multigranulation upper (lower) definable sets forms a distributive lattice when n = 2, and if and only if ∀X⊆U, Σi=1nRi_(X)=∩i=1nRi_(X). The obtained results help us gain more insights into the mathematical structure of multigranulation approximation spaces. PMID:25243226
Development of Warp Yarn Tension During Shedding: A Theoretical Approach
NASA Astrophysics Data System (ADS)
Ghosh, Subrata; Chary, Prabhakara; Roy, Sukumar
2015-10-01
Theoretical investigation on the process of development of warp yarn tension during weaving for tappet shedding is carried out, based on the dynamic nature of shed geometry. The path of warp yarn on a weaving machine is divided into four different zones. The tension developed in each zone is estimated for every minute rotation of the bottom shaft. A model has been developed based on the dynamic nature of shed geometry and the possible yarn flow from one zone to another. A computer program, based on the model of shedding process, is developed for predicting the warp yarn tension variation during shedding. The output of the model and the experimental values of yarn tension developed in zone-D i.e. between the back rest and the back lease rod are compared, which shows a good agreement between them. The warp yarn tension values predicted by the model in zone-D are 10-13 % lesser than the experimentally measured values. By analyzing the theoretical data of the peak value of developed yarn tension at four zones i.e. zone-A, zone-B, zone-C and zone-D, it is observed that the peak yarn tension value of A, B, C-zones are much higher than the peak tension near the back rest i.e. at zone-D. It is about twice or more than the yarn tension near the back rest. The study also reveals that the developed yarn tension peak values are different for the extreme positions of a heald. The impact of coefficient of friction on peak value of yarn tension is nominal.
Unified Theoretical Approach to Electron-Ion Recombination
NASA Astrophysics Data System (ADS)
Pradhan, Anil
1998-05-01
Electron-ion recombination occurs via the electron continuum and embedded resonances that are coupled to each other and thus unified in nature. However, theoretical methods generally separate the two as ``radiative recombination" (RR), referring to recombination through the non-resonant continuum, and ``di-electronic recombination" (DR) through the autoionizing resonances. A computationally unified scheme(S.N. Nahar and A.K. Pradhan, Phys.Rev.Lett.) 68,1488(1992); H.L. Zhang and A.K. Pradhan, Phys.Rev.Lett. 78,195(1997) is described that employs the coupled channel R-matrix method, and detailed balance (the Milne relation), to obtain photo-recombination cross sections including both the continuum and resonant recombination in an ab intio manner. In the energy region corresponding to high-n Rydberg resonances, where the background recombination (RR) is negligibly small, a precise theory of DR (R.H. Bell and M.J. Seaton, J.Phys.B) 18,1589(1985) yields DR collision strengths consistent with their threshold behaviour leading to the cross section for electron impact excitation. For highly charged ions the relativistic fine structure and the effect of radiation damping of resonances are considered. Theoretical cross sections agree well with recent experiments on ion stograge rings and the electron-beam-ion-trap (EBIT). Total electron-ion recombination rates can be obtained for practical applications. For many complex atomic systems, such as the important Iron-peak elements, the new results differ considerably from those hitherto available.
Some theoretical and numerical results for delayed neural field equations
NASA Astrophysics Data System (ADS)
Faye, Grégory; Faugeras, Olivier
2010-05-01
In this paper we study neural field models with delays which define a useful framework for modeling macroscopic parts of the cortex involving several populations of neurons. Nonlinear delayed integro-differential equations describe the spatio-temporal behavior of these fields. Using methods from the theory of delay differential equations, we show the existence and uniqueness of a solution of these equations. A Lyapunov analysis gives us sufficient conditions for the solutions to be asymptotically stable. We also present a fairly detailed study of the numerical computation of these solutions. This is, to our knowledge, the first time that a serious analysis of the problem of the existence and uniqueness of a solution of these equations has been performed. Another original contribution of ours is the definition of a Lyapunov functional and the result of stability it implies. We illustrate our numerical schemes on a variety of examples that are relevant to modeling in neuroscience.
The Acquisition of Chinese Relative Clauses: Contrasting Two Theoretical Approaches
ERIC Educational Resources Information Center
Hu, Shenai; Gavarró, Anna; Vernice, Mirta; Guasti, Maria Teresa
2016-01-01
This study examines the comprehension of relative clauses by Chinese-speaking children, and evaluates the validity of the predictions of the Dependency Locality Theory (Gibson, 1998, 2000) and the Relativized Minimality approach (Friedmann, Belletti & Rizzi, 2009). One hundred and twenty children from three to eight years of age were tested by…
Theoretical and Methodological Approaches to Social Sciences and Knowledge Management
ERIC Educational Resources Information Center
Lopez-Varela, Asuncion, Ed.
2012-01-01
This is a unique and groundbreaking collection of questions and answers coming from higher education institutions on diverse fields and across a wide spectrum of countries and cultures. It creates routes for further innovation, collaboration amidst the Sciences (both Natural and Social), the Humanities, and the private and public sectors of…
Advancing the theoretical foundation of the partially-averaged Navier-Stokes approach
NASA Astrophysics Data System (ADS)
Reyes, Dasia Ann
The goal of this dissertation is to consolidate the theoretical foundation of variable-resolution (VR) methods in general and the partially-averaged Navier-Stokes (PANS) approach in particular. The accurate simulation of complex turbulent flows remains an outstanding challenge in modern computational fluid dynamics. High-fidelity approaches such as direct numerical simulations (DNS) and large-eddy simulation (LES) are not typically feasible for complex engineering simulations with current computational technologies. Low-fidelity approaches such as Reynolds-averaged Navier-Stokes (RANS), although widely used, are inherently inadequate for turbulent flows with complex flow features. VR bridging methods fill the gap between DNS and RANS by allowing a tunable degree of resolution ranging from RANS to DNS. While the utility of VR methods is well established, the mathematical foundations and physical characterization require further development. This dissertation focuses on the physical attributes of fluctuations in partially-resolved simulations of turbulence. The specific objectives are to: (i) establish a framework for assessing the physical fidelity of VR methods to examine PANS fluctuations; (ii) investigate PANS simulations subject to multiple resolution changes; (iii) examine turbulent transport closure modeling for partially-resolved fields; (iv) examine the effect of filter control parameters in the limit of spectral cut-off in the dissipative region; and (v) validate low-Reynolds number corrections with RANS for eventual implementation with PANS. While the validation methods are carried out in the context of PANS, they are considered appropriate for all VR bridging methods. The key findings of this dissertation are summarized as follows. The Kolmogorov hypotheses are suitably adapted to describe fluctuations of partially-resolved turbulence fields, and the PANS partially-resolved field is physically consistent with the adapted Kolmogorov hypotheses. PANS
Photodynamic therapy: Theoretical and experimental approaches to dosimetry
NASA Astrophysics Data System (ADS)
Wang, Ken Kang-Hsin
Singlet oxygen (1O2) is the major cytotoxic species generated during photodynamic therapy (PDT), and 1O 2 reactions with biological targets define the photodynamic dose at the most fundamental level. We have developed a theoretical model for rigorously describing the spatial and temporal dynamics of oxygen (3O 2) consumption and transport and microscopic 1O 2 dose deposition during PDT in vivo. Using experimentally established physiological and photophysical parameters, the mathematical model allows computation of the dynamic variation of hemoglobin-3O 2 saturation within vessels, irreversible photosensitizer degradation due to photobleaching, therapy-induced blood flow decrease and the microscopic distributions of 3O2 and 1O 2 dose deposition under various irradiation conditions. mTHPC, a promising photosensitizer for PDT, is approved in Europe for the palliative treatment of head and neck cancer. Using the theoretical model and informed by intratumor sensitizer concentrations and distributions, we calculated photodynamic dose depositions for mTHPC-PDT. Our results demonstrate that the 1O 2 dose to the tumor volume does not track even qualitatively with long-term tumor responses. Thus, in this evaluation of mTHPC-PDT, any PDT dose metric that is proportional to singlet oxygen creation and/or deposition would fail to predict the tumor response. In situations like this one, other reporters of biological response to therapy would be necessary. In addition to the case study of mTHPC-PDT, we also use the mathematical model to simulate clinical photobleaching data, informed by a possible blood flow reduction during treatment. In a recently completed clinical trial at Roswell Park Cancer Institute, patients with superficial basal cell carcinoma received topical application of 5-aminolevulinic acid (ALA) and were irradiated with 633 nm light at 10-150 mW cm-2 . Protoporphyrin IX (PpIX) photobleaching in the lesion and the adjacent perilesion normal margin was monitored by
Theoretical Aspects of Magnetic Fields for Gamma Ray Bursts
NASA Astrophysics Data System (ADS)
Hanami, Hitoshi
We propose magnetic cannon ball mechanism in which the collapse of a magnetosphere onto a black hole can generate strong outward Poynting flux which drives a baryon-free fireball called the magnetic cannon ball. In the early stage, the magnetic fields in the cannon ball can prepare the explanation for the cycrotoron absorptions observed by GINGA. The magnetic cannon ball can drive, in general, a relativistic outflow which interacts with the interstellar matter and forms a shock. The magnetic field in the shock approximately equal to 104 G can induce the synchrotron radiations with peaks at approximately equal to 10^2 keV observed. This magnetic field in the cannon ball can also confine the high energy protons (gamma_p > 30) which are required for delayed photons (>25 GeV) following a burst on 1994 February 17. Accretion induced collapse of a white dwarf of > 109 G, merger of a close binary and failed type Ib supernovae are possible scenarios even without the rotation of the central object. This mechanism works at the final phase of gravitational collapse even after a neutrino driven fireball proposed in most scenarios for gamma ray bursts. Twice bursts, which consist of primary neutrino driven fireball and secondary magnetic cannon ball can be induced sometime, can be explained in this model. It suggests that the magnetic cannon ball works some parts in multiple populations and delayed or multiple burst events. The final remnant in the model should be a black hole. It implies that any gamma ray bursts can have no optical counter part if they do not have a companion in a binary.
An information-theoretic approach to microseismic source location
NASA Astrophysics Data System (ADS)
Prange, Michael D.; Bose, Sandip; Kodio, Ousmane; Djikpesse, Hugues A.
2015-04-01
There has been extensive work on seismic source localization, going as far back as Geiger's 1912 paper, that is based on least-squares fitting of arrival times. The primary advantage of time-based methods over waveform-based methods (e.g. reverse-time migration and beam forming) is that simulated arrival times are considerably more reliable than simulated waveforms, especially in the context of an uncertain velocity model, thereby yielding more reliable estimates of source location. However, time-based methods are bedeviled by the unsolved challenges of accurate time picking and labelling of the seismic phases in the waveforms for each event. Drawing from Woodward's canonical 1953 text on the application of information theory to radar applications, we show that time-based methods can be applied directly to waveform data, thus capturing the advantages of time-based methods without being impacted by the aforementioned hindrances. We extend Woodward's approach to include an unknown distortion on wavelet amplitude and phase, showing that the related marginalization integrals can be analytically evaluated. We also provide extensions for correlation-based location methods such as relative localization and the S-P method. We demonstrate this approach through applications to microseismic event location, presenting formulations and results for both absolute and relative localization approaches, with receiver arrays either in a borehole or on the surface. By properly quantifying uncertainty in our location estimates, our formulations provide an objective measure for ranking the accuracy of microseismic source location methodologies.
BL Herculis stars - Theoretical models for field variables
NASA Technical Reports Server (NTRS)
Carson, R.; Stothers, R.
1982-01-01
Type II Cepheids with periods between 1 and 3 days, commonly designated as Bl Herculis stars, have been modeled here with the aim of interpreting the wide variety of light curves observed among the field variables. Previously modeled globular cluster members are used as standard calibration objects. The major finding is that only a small range of luminosities is capable of generating a large variety of light curve types at a given period. For a mass of approximately 0.60 solar mass, the models are able to reproduce the observed mean luminosities, dispersion of mean luminosities, periods, light amplitudes, light asymmetries, and phases of secondary features in the light curves of known BL Her stars. It is possible that the metal-rich variables (which are found only in the field) have luminosities lower than those of most metal-poor variables. The present revised mass for BL Her, a metal-rich object, is not significantly different from the mean mass of the metal-poor variables.
Oxidative dissolution of silver nanoparticles: A new theoretical approach.
Adamczyk, Zbigniew; Oćwieja, Magdalena; Mrowiec, Halina; Walas, Stanisław; Lupa, Dawid
2016-05-01
A general model of an oxidative dissolution of silver particle suspensions was developed that rigorously considers the bulk and surface solute transport. A two-step surface reaction scheme was proposed that comprises the formation of the silver oxide phase by direct oxidation and the acidic dissolution of this phase leading to silver ion release. By considering this, a complete set of equations is formulated describing oxygen and silver ion transport to and from particles' surfaces. These equations are solved in some limiting cases of nanoparticle dissolution in dilute suspensions. The obtained kinetic equations were used for the interpretation of experimental data pertinent to the dissolution kinetics of citrate-stabilized silver nanoparticles. In these kinetic measurements the role of pH and bulk suspension concentration was quantitatively evaluated by using the atomic absorption spectrometry (AAS). It was shown that the theoretical model adequately reflects the main features of the experimental results, especially the significant increase in the dissolution rate for lower pH. Also the presence of two kinetic regimes was quantitatively explained in terms of the decrease in the coverage of the fast dissolving oxide layer. The overall silver dissolution rate constants characterizing these two regimes were determined. PMID:26921758
Exploring Job Satisfaction of Nursing Faculty: Theoretical Approaches.
Wang, Yingchen; Liesveld, Judy
2015-01-01
The Future of Nursing report identified the shortage of nursing faculty as 1 of the barriers to nursing education. In light of this, it is becoming increasingly important to understand the work-life of nursing faculty. The current research focused on job satisfaction of nursing faculty from 4 theoretical perspectives: human capital theory, which emphasizes the expected monetary and nonmonetary returns for any career choices; structural theory, which emphasizes the impact of institutional features on job satisfaction; positive extrinsic environment by self-determination theory, which asserts that a positive extrinsic environment promotes competency and effective outcomes at work; and psychological theory, which emphasizes the proposed relationship between job performance and satisfaction. In addition to the measures for human capital theory, institutional variables (from structural theory and self-determination theory), and productivity measures (from psychological theory), the authors also selected sets of variables for personal characteristics to investigate their effects on job satisfaction. The results indicated that variables related to human capital theory, especially salary, contributed the most to job satisfaction, followed by those related to institutional variables. Personal variables and productivity variables as a whole contributed as well. The only other variable with marginal significance was faculty's perception of institutional support for teaching. PMID:26653042
Is DNA a metal, semiconductor or insulator? A theoretical approach
NASA Astrophysics Data System (ADS)
Rey-Gonzalez, Rafael; Fonseca-Romero, Karen; Plazas, Carlos; Grupo de Óptica e Información Cuántica Team
Over the last years, scientific interest for designing and making low dimensional electronic devices with traditional or novel materials has been increased. These experimental and theoretical researches in electronic properties at molecular scale are looking for developing efficient devices able to carry out tasks which are currently done by silicon transistors and devices. Among the new materials DNA strands are highlighted, but the experimental results have been contradictories pointing to behaviors as conductor, semiconductor or insulator. To contribute to the understanding of the origin of the disparity of the measurements, we perform a numerical calculation of the electrical conductance of DNA segments, modeled as 1D disordered finite chains. The system is described into a Tight binding model with nearest neighbor interactions and a s orbital per site. Hydration effects are included as random variations of self-energies. The electronic current as a function of applied bias is calculated using Launder formalism, where the transmission probability is determined into the transfer matrix formalism. We find a conductor-to-semiconductor-to-insulator transition as a function of the three effects taken into account: chain size, intrinsic disorder, and hydration We thank Fundación para la Promoción de la Investigación y la Tecnología, Colombia, and Dirección de Investigación de Bogotá, Universidad Nacional de Colombia, for partial financial support.
Approaching theoretical strength in glassy carbon nanolattices.
Bauer, J; Schroer, A; Schwaiger, R; Kraft, O
2016-04-01
The strength of lightweight mechanical metamaterials, which aim to exploit material-strengthening size effects by their microscale lattice structure, has been limited by the resolution of three-dimensional lithography technologies and their restriction to mainly polymer resins. Here, we demonstrate that pyrolysis of polymeric microlattices can overcome these limitations and create ultra-strong glassy carbon nanolattices with single struts shorter than 1 μm and diameters as small as 200 nm. They represent the smallest lattice structures yet produced--achieved by an 80% shrinkage of the polymer during pyrolysis--and exhibit material strengths of up to 3 GPa, corresponding approximately to the theoretical strength of glassy carbon. The strength-to-density ratios of the nanolattices are six times higher than those of reported microlattices. With a honeycomb topology, effective strengths of 1.2 GPa at 0.6 g cm(-3) are achieved. Diamond is the only bulk material with a notably higher strength-to-density ratio. PMID:26828314
A Game Theoretic Approach to Cyber Attack Prediction
Peng Liu
2005-11-28
The area investigated by this project is cyber attack prediction. With a focus on correlation-based prediction, current attack prediction methodologies overlook the strategic nature of cyber attack-defense scenarios. As a result, current cyber attack prediction methodologies are very limited in predicting strategic behaviors of attackers in enforcing nontrivial cyber attacks such as DDoS attacks, and may result in low accuracy in correlation-based predictions. This project develops a game theoretic framework for cyber attack prediction, where an automatic game-theory-based attack prediction method is proposed. Being able to quantitatively predict the likelihood of (sequences of) attack actions, our attack prediction methodology can predict fine-grained strategic behaviors of attackers and may greatly improve the accuracy of correlation-based prediction. To our best knowledge, this project develops the first comprehensive framework for incentive-based modeling and inference of attack intent, objectives, and strategies; and this project develops the first method that can predict fine-grained strategic behaviors of attackers. The significance of this research and the benefit to the public can be demonstrated to certain extent by (a) the severe threat of cyber attacks to the critical infrastructures of the nation, including many infrastructures overseen by the Department of Energy, (b) the importance of cyber security to critical infrastructure protection, and (c) the importance of cyber attack prediction to achieving cyber security.
Theoretical study of phosphorene tunneling field effect transistors
Chang, Jiwon; Hobbs, Chris
2015-02-23
In this work, device performances of tunneling field effect transistors (TFETs) based on phosphorene are explored via self-consistent atomistic quantum transport simulations. Phosphorene is an ultra-thin two-dimensional (2-D) material with a direct band gap suitable for TFETs applications. Our simulation shows that phosphorene TFETs exhibit subthreshold slope below 60 mV/dec and a wide range of on-current depending on the transport direction due to highly anisotropic band structures of phosphorene. By benchmarking with monolayer MoTe{sub 2} TFETs, we predict that phosphorene TFETs oriented in the small effective mass direction can yield much larger on-current at the same on-current/off-current ratio than monolayer MoTe{sub 2} TFETs. It is also observed that a gate underlap structure is required for scaling down phosphorene TFETs in the small effective mass direction to suppress the source-to-drain direct tunneling leakage current.
Is there a field-theoretic explanation for precursor biopolymers?
Rosen, Gerald
2002-08-01
A Hu-Barkana-Gruzinov cold dark matter scalar field phi may enter a weak isospin invariant derivative interaction that causes the flow of right-handed electrons to align parallel to (inverted delta phi). Hence, in the outer regions of galaxies where (inverted delta phi) is large, as in galactic halos, the derivative interaction may induce a chirality-imbued quantum chemistry. Such a chirality-imbued chemistry would in turn be conducive to the formation of abundant precursor biopolymers on interstellar dust grains, comets and meteors in galactic halo regions, with subsequent delivery to planets in the inner galactic regions where phi and (inverted delta phi) are concomitantly near zero and left-right symmetric terrestrial quantum chemistry prevails. PMID:12458734
An information theoretic approach to macromolecular modeling: I. Sequence alignments.
Aynechi, Tiba; Kuntz, Irwin D
2005-11-01
We are interested in applying the principles of information theory to structural biology calculations. In this article, we explore the information content of an important computational procedure: sequence alignment. Using a reference state developed from exhaustive sequences, we measure alignment statistics and evaluate gap penalties based on first-principle considerations and gap distributions. We show that there are different gap penalties for different alphabet sizes and that the gap penalties can depend on the length of the sequences being aligned. In a companion article, we examine the information content of molecular force fields. PMID:16254389
Theoretical Investigation of Field-Line Quality in a Driven Spheromak
Cohen, R H; Berj, H; Cohen, B I; Fowler, T K; Glasser, A H; Hooper, E B; Lo Destro, L L; Morse, E C; Pearlstein; Rognlien, T D; Ryutov, D D; Sovince, C R; Woodruff, S
2002-10-07
Theoretical studies aimed at predicting and diagnosing field-line quality in a spheromak are described. These include nonlinear 3-D MHD simulations, stability studies, analyses of confinement in spheromaks dominated by either open (stochastic) field lines or approximate flux surfaces, and a theory of fast electrons as a probe of field-line length.
Theoretical approach to oxygen atom degradation of silver
NASA Technical Reports Server (NTRS)
Fromhold, Albert T., Jr.; Noh, Seung; Beshears, Ronald; Whitaker, Ann F.; Little, Sally A.
1987-01-01
Based on available Rutherford backscattering spectrometry (RBS), proton induced X-ray emission (PIXE) and ellipsometry data obtained on silver specimens subjected to atomic oxygen attack in low Earth orbit STS flight 41-G, a theory was developed to model the oxygen atom degradation of silver. The diffusion of atomic oxygen in a microscopically nonuniform medium is an essential constituent of the theory. The driving force for diffusion is the macroscopic electrochemical potential gradient developed between the specimen surface exposed to the ambient and the bulk of the silver specimen. The longitudinal electric effect developed parallel to the gradient is modified by space charge of the diffusing charged species. Lateral electric fields and concentration differences also exist due to the nonuniform nature of the medium. The lateral concentration differences are found to be more important than the lateral electric fields in modifying the diffusion rate. The model was evaluated numerically. Qualitative agreement exists between the kinetics predicted by the theory and kinetic data taken in ground-based experiments utilizing a plasma asher.
Robust Orbit Determination and Classification: A Learning Theoretic Approach
NASA Astrophysics Data System (ADS)
Sharma, S.; Cutler, J. W.
2015-11-01
Orbit determination involves estimation of a non-linear mapping from feature vectors associated with the position of the spacecraft to its orbital parameters. The de facto standard in orbit determination in real-world scenarios for spacecraft has been linearized estimators such as the extended Kalman filter. Such an estimator, while very accurate and convergent over its linear region, is hard to generalize over arbitrary gravitational potentials and diverse sets of measurements. It is also challenging to perform exact mathematical characterizations of the Kalman filter performance over such general systems. Here we present a new approach to orbit determination as a learning problem involving distribution regression and, also, for the multiple-spacecraft scenario, a transfer learning system for classification of feature vectors associated with spacecraft, and provide some associated analysis of such systems.
Quantum cognition: a new theoretical approach to psychology.
Bruza, Peter D; Wang, Zheng; Busemeyer, Jerome R
2015-07-01
What type of probability theory best describes the way humans make judgments under uncertainty and decisions under conflict? Although rational models of cognition have become prominent and have achieved much success, they adhere to the laws of classical probability theory despite the fact that human reasoning does not always conform to these laws. For this reason we have seen the recent emergence of models based on an alternative probabilistic framework drawn from quantum theory. These quantum models show promise in addressing cognitive phenomena that have proven recalcitrant to modeling by means of classical probability theory. This review compares and contrasts probabilistic models based on Bayesian or classical versus quantum principles, and highlights the advantages and disadvantages of each approach. PMID:26058709
Modeling of laccase inhibition by formetanate pesticide using theoretical approaches.
Martins, Ana C V; Ribeiro, Francisco W P; Zanatta, Geancarlo; Freire, Valder N; Morais, Simone; de Lima-Neto, Pedro; Correia, Adriana N
2016-04-01
The inhibition of laccase enzymatic catalytic activity by formetanate hydrochloride (FMT) was investigated by cyclic voltammetry and by quantum chemical calculations based on density functional theory with a protein fragmentation approach. The cyclic voltammograms were obtained using a biosensor prepared by enzyme immobilization on gold electrodes modified with gold nanoparticles and 4-aminophenol as the target molecule. The decrease in the peak current in the presence of FMT was used to characterize the inhibition process. The calculations identified Asp206 as the most relevant moiety in the interaction of FMT with the laccase enzymatic ligand binding domain. The amino acid residue Cys453 was important, because the Cys453-FMT interaction energy was not affected by the dielectric constant, although it was not a very close residue. This study provides an overview of how FMT inhibits laccase catalytic activity. PMID:26720841
Theoretical approach to explore the production routes of astatine radionuclides
NASA Astrophysics Data System (ADS)
Maiti, Moumita; Lahiri, Susanta
2009-02-01
To fulfill the recent thrust of astatine radionuclides in the field of nuclear medicine, various production routes have been explored in the present work. The possible production routes of At209-211 comprise both light- and heavy-ion-induced reactions at the bombarding energy range starting from threshold to a maximum of 100 MeV. Excitation functions of those radionuclides, produced through various production routes, have been calculated by using nuclear reaction model codes TALYS, ALICE91, and PACE-II and are compared with the available measured data. Contributions of various reaction mechanisms, such as direct, pre-equilibrium, and equilibrium reactions, to the total reaction cross section have been studied using the codes. Results show that the equilibrium reaction dominates in all cases over other reaction mechanisms.
Theoretical approach to explore the production routes of astatine radionuclides
Maiti, Moumita; Lahiri, Susanta
2009-02-15
To fulfill the recent thrust of astatine radionuclides in the field of nuclear medicine, various production routes have been explored in the present work. The possible production routes of {sup 209-211}At comprise both light- and heavy-ion-induced reactions at the bombarding energy range starting from threshold to a maximum of 100 MeV. Excitation functions of those radionuclides, produced through various production routes, have been calculated by using nuclear reaction model codes TALYS, ALICE91, and PACE-II and are compared with the available measured data. Contributions of various reaction mechanisms, such as direct, pre-equilibrium, and equilibrium reactions, to the total reaction cross section have been studied using the codes. Results show that the equilibrium reaction dominates in all cases over other reaction mechanisms.
Theoretical Triangulation as an Approach for Revealing the Complexity of a Classroom Discussion
ERIC Educational Resources Information Center
van Drie, Jannet; Dekker, Rijkje
2013-01-01
In this paper we explore the value of theoretical triangulation as a methodological approach for the analysis of classroom interaction. We analyze an excerpt of a whole-class discussion in history from three theoretical perspectives: interactivity of the discourse, conceptual level raising and historical reasoning. We conclude that using…
NASA Astrophysics Data System (ADS)
Pandey, R. S.; Kaur, Rajbir
2015-10-01
Electromagnetic electron cyclotron (EMEC) waves with temperature anisotropy in the magnetosphere of Uranus have been studied in present work. EMEC waves are investigated using method of characteristic solution by kinetic approach, in presence of AC field. In 1986, Voyager 2 encounter with Uranus revealed that magnetosphere of Uranus exhibit non-Maxwellian high-energy tail distribution. So, the dispersion relation, real frequency and growth rate are evaluated using Lorentzian Kappa distribution function. Effect of temperature anisotropy, AC frequency and number density of particles is found. The study is also extended to oblique propagation of EMEC waves in presence and absence of AC field. Through comprehensive mathematical analysis it is found that when EMEC wave propagates parallel to intrinsic magnetic field of Uranus, its growth is more enhanced than in case of oblique propagation. Results are also discussed in context to magnetosphere of Earth and also gives theoretical explanation to existence of high energetic particles observed by Voyager 2 in the magnetosphere of Uranus. The results can present a further insight into the nature of electron-cyclotron instability condition for the whistler mode waves in the outer radiation belts of Uranus or other space plasmas.
System-theoretical approach to multistage image processing
NASA Astrophysics Data System (ADS)
Grudin, Maxim A.; Timchenko, Leonid I.; Harvey, David M.; Gel, Vladimir P.
1996-08-01
We present a novel three-dimensional network and its application to pattern analysis. This is a multistage architecture which investigates partial correlations between structural image components. Mathematical description of the multistage hierarchical processing is provided together with the network architecture. Initially the image is partitioned to be processed in parallel channels. In each channel, the structural components are transformed and subsequently separated depending on their informational activity, to be mixed with the components from other channels for further processing. This procedure of temporal decomposition creates a flexible processing hierarchy, which reflects structural image complexity. An output result is represented as a pattern vector, whose components are computed one at a time to allow the quickest possible response. While several applications of the multistage network are possible, this paper represents an algorithm applied to image classification. The input gray-scale image is transformed so that each pixel contains information about the spatial structure of its neighborhood. A three-level representation of gray-scale image is used in order for each pixel to contain the maximum amount of structural information. The investigation of spatial regularities at all hierarchical levels provides a unified approach to pattern analysis. The most correlated information is extracted first, making the algorithm tolerant to minor structural changes.
Vaccine adjuvant technology: from theoretical mechanisms to practical approaches.
Schijns, V E J C; Tangerås, A
2005-01-01
Poorly immunogenic antigens depend on vaccine adjuvants to evoke an immune response. In addition, adjuvants largely determine the magnitude, quality, time of onset and the duration of immune responses to co-administered antigens. As late as 1989, Janeway aptly called adjuvants: "the immunologist's dirty little secret". This statement reflected the ignorance on the mechanisms of action of most known adjuvants. Yet, rational vaccine design involves a logical choice of adjuvant based on a knowledge of their mode of action and their effects on product efficacy and safety. However, even today the key processes critical for immune induction in general and those evoked by vaccine adjuvants in particular are being disputed among immunologists. This paper presents the four most important concepts likely to explain some of the mechanisms of vaccine adjuvants. They include: (i) the geographical concept of immune reactivity; (ii) the depot concept; (iii) the hypothesis of pathogen-structure recognition, and (iv) the damage/endogenous danger theory. These paradigms are based on observations gathered in mammalian species, largely in murine models. In aquatic animals the processes underlying immune induction will at least partly overlap those in mammals. However, due to inherent species differences, certain pathways may be different. Rational vaccine design, a difficult goal in mammals, is further hampered in aquatic animals by the lack of immunological tools in these species. Extensive trial and error-based approaches have yielded adjuvant candidates for various fish species, with acceptable safety and proven efficacy, some of which are presented. PMID:15962475
How to measure soundscapes. A theoretical and practical approach
NASA Astrophysics Data System (ADS)
Schulte-Fortkamp, Brigitte
2002-11-01
Noise sources interact with the specific acoustic and environmental makeup, topography, meteorology, land use pattern, and lifestyle. The evaluation of soundscapes needs subject-related methodological procedures. With such suitable measurements a way has to be found that allows us to rely on different dimensions on reaction to noise. Improving the soundscape of an urban environment imposes to account for the qualitative appreciation as a cognitive judgment given by listeners and, particularly, for the interaction between acoustic dimensions and other sensory modalities in qualitative judgments of an urban environment (Maffiolo). The structure of the residential area that is, the combination of noise sources are important for the judgment of a soundscope and are also important as subjective parameters which are relevant in people's point of view. Moreover, the relationship of both define the background for assessments. Studies are needed on the subject and its capability in perception and interpretation; studies on the subject inside the society, studies on the social and cultural context, and field studies including physical measurements. Soundscapes may be defined in its effects on man and vice versa and probably acoustical ecology will serve to understand the function of soundscapes.
Conductivity of pure graphene: Theoretical approach using the polarization tensor
NASA Astrophysics Data System (ADS)
Klimchitskaya, G. L.; Mostepanenko, V. M.
2016-06-01
We obtain analytic expressions for the conductivity of pristine (pure) graphene in the framework of the Dirac model using the polarization tensor in (2+1) dimensions defined along the real frequency axis. It is found that at both zero and nonzero temperature T the in-plane and out-of-plane conductivities of graphene are equal to each other with a high precision and essentially do not depend on the wave vector. At T =0 the conductivity of graphene is real and equal to σ0=e2/(4 ℏ ) up to small nonlocal corrections in accordance with many authors. At some fixed T ≠0 the real part of the conductivity varies between zero at low frequencies ω and σ0 for optical ω . If ω is fixed, the conductivity varies between σ0 at low T and zero at high T . The imaginary part of the conductivity of graphene is shown to depend on the ratio of ω to T . In accordance with the obtained asymptotic expressions, at fixed T it varies from infinity at ω =0 to a negative minimum value reached at some ω , and then approaches to zero with further increase of ω . At fixed ω the imaginary part of the conductivity varies from zero at T =0 , reaches a negative minimum at some T , and then goes to infinity together with T . The numerical computations of both the real and imaginary parts of the conductivity are performed. The above results are obtained in the framework of quantum electrodynamics at nonzero temperature and can be generalized for graphene samples with nonzero mass gap parameter and chemical potential.
NASA Astrophysics Data System (ADS)
Titvinidze, Irakli; Schwabe, Andrej; Potthoff, Michael
2014-07-01
The magnetic ground-state properties of the periodic Anderson model with a regular depletion of the correlated sites are analyzed within different theoretical approaches. We consider the model on the one-dimensional chain and on the two-dimensional square lattice with hopping between nearest neighbors. At half-filling and with correlated impurities present at every second site, the depleted Anderson lattice is the most simple system where the indirect magnetic coupling mediated by the conduction electrons is ferromagnetic. We discuss the underlying electronic structure and the possible mechanisms that result in ferromagnetic long-range order. To this end, different numerical and analytical concepts are applied to the depleted Anderson and also to the related depleted Kondo lattice and are contrasted with each other. This includes numerical approaches, i.e., Hartree-Fock theory, density-matrix renormalization and dynamical mean-field theory, as well as analytical concepts, namely a variant of the Lieb-Mattis theorem and the concept of flat-band ferromagnetism, and, finally, perturbative approaches, i.e., the effective RKKY exchange in the limit of weak coupling and the "inverse indirect magnetic exchange" in the limit of strong coupling between the conduction band and the impurities.
NASA Astrophysics Data System (ADS)
Grimm, G. W.; Potts, A. J.
2015-12-01
The Coexistence Approach has been used infer palaeoclimates for many Eurasian fossil plant assemblage. However, the theory that underpins the method has never been examined in detail. Here we discuss acknowledged and implicit assumptions, and assess the statistical nature and pseudo-logic of the method. We also compare the Coexistence Approach theory with the active field of species distribution modelling. We argue that the assumptions will inevitably be violated to some degree and that the method has no means to identify and quantify these violations. The lack of a statistical framework makes the method highly vulnerable to the vagaries of statistical outliers and exotic elements. In addition, we find numerous logical inconsistencies, such as how climate shifts are quantified (the use of a "center value" of a coexistence interval) and the ability to reconstruct "extinct" climates from modern plant distributions. Given the problems that have surfaced in species distribution modelling, accurate and precise quantitative reconstructions of palaeoclimates (or even climate shifts) using the nearest-living-relative principle and rectilinear niches (the basis of the method) will not be possible. The Coexistence Approach can be summarised as an exercise that shoe-horns a plant fossil assemblages into coexistence and then naively assumes that this must be the climate. Given the theoretical issues, and methodological issues highlighted elsewhere, we suggest that the method be discontinued and that all past reconstructions be disregarded and revisited using less fallacious methods.
Craciun, Stefan; Brockmeier, Austin J; George, Alan D; Lam, Herman; Príncipe, José C
2011-01-01
Methods for decoding movements from neural spike counts using adaptive filters often rely on minimizing the mean-squared error. However, for non-Gaussian distribution of errors, this approach is not optimal for performance. Therefore, rather than using probabilistic modeling, we propose an alternate non-parametric approach. In order to extract more structure from the input signal (neuronal spike counts) we propose using minimum error entropy (MEE), an information-theoretic approach that minimizes the error entropy as part of an iterative cost function. However, the disadvantage of using MEE as the cost function for adaptive filters is the increase in computational complexity. In this paper we present a comparison between the decoding performance of the analytic Wiener filter and a linear filter trained with MEE, which is then mapped to a parallel architecture in reconfigurable hardware tailored to the computational needs of the MEE filter. We observe considerable speedup from the hardware design. The adaptation of filter weights for the multiple-input, multiple-output linear filters, necessary in motor decoding, is a highly parallelizable algorithm. It can be decomposed into many independent computational blocks with a parallel architecture readily mapped to a field-programmable gate array (FPGA) and scales to large numbers of neurons. By pipelining and parallelizing independent computations in the algorithm, the proposed parallel architecture has sublinear increases in execution time with respect to both window size and filter order. PMID:22255367
Schrödinger Approach to Mean Field Games
NASA Astrophysics Data System (ADS)
Swiecicki, Igor; Gobron, Thierry; Ullmo, Denis
2016-03-01
Mean field games (MFG) provide a theoretical frame to model socioeconomic systems. In this Letter, we study a particular class of MFG that shows strong analogies with the nonlinear Schrödinger and Gross-Pitaevskii equations introduced in physics to describe a variety of physical phenomena. Using this bridge, many results and techniques developed along the years in the latter context can be transferred to the former, which provides both a new domain of application for the nonlinear Schrödinger equation and a new and fruitful approach in the study of mean field games. Utilizing this approach, we analyze in detail a population dynamics model in which the "players" are under a strong incentive to coordinate themselves.
A mean field approach to watershed hydrology
NASA Astrophysics Data System (ADS)
Bartlett, Mark; Porporato, Amilcare
2016-04-01
Mean field theory (also known as self-consistent field theory) is commonly used in statistical physics when modeling the space-time behavior of complex systems. The mean field theory approximates a complex multi-component system by considering a lumped (or average) effect for all individual components acting on a single component. Thus, the many body problem is reduced to a one body problem. For watershed hydrology, a mean field theory reduces the numerous point component effects to more tractable watershed averages, resulting in a consistent method for linking the average watershed fluxes to the local fluxes at each point. We apply this approach to the spatial distribution of soil moisture, and as a result, the numerous local interactions related to lateral fluxes of soil water are parameterized in terms of the average soil moisture. The mean field approach provides a basis for unifying and extending common event-based models (e.g. Soil Conservation Service curve number (SCS-CN) method) with more modern semi-distributed models (e.g. Variable Infiltration Capacity (VIC) model, the Probability Distributed (PDM) model, and TOPMODEL). We obtain simple equations for the fractions of the different source areas of runoff, the spatial variability of runoff, and the average runoff value (i.e., the so-called runoff curve). The resulting space time distribution of soil moisture offers a concise description of the variability of watershed fluxes.
Armas-Pérez, Julio C.; Londono-Hurtado, Alejandro; Guzmán, Orlando; Hernández-Ortiz, Juan P.; Pablo, Juan J. de
2015-07-28
A theoretically informed coarse-grained Monte Carlo method is proposed for studying liquid crystals. The free energy functional of the system is described in the framework of the Landau-de Gennes formalism. The alignment field and its gradients are approximated by finite differences, and the free energy is minimized through a stochastic sampling technique. The validity of the proposed method is established by comparing the results of the proposed approach to those of traditional free energy minimization techniques. Its usefulness is illustrated in the context of three systems, namely, a nematic liquid crystal confined in a slit channel, a nematic liquid crystal droplet, and a chiral liquid crystal in the bulk. It is found that for systems that exhibit multiple metastable morphologies, the proposed Monte Carlo method is generally able to identify lower free energy states that are often missed by traditional approaches. Importantly, the Monte Carlo method identifies such states from random initial configurations, thereby obviating the need for educated initial guesses that can be difficult to formulate.
Armas-Perez, Julio C.; Londono-Hurtado, Alejandro; Guzman, Orlando; Hernandez-Ortiz, Juan P.; de Pablo, Juan J.
2015-07-27
A theoretically informed coarse-grained Monte Carlo method is proposed for studying liquid crystals. The free energy functional of the system is described in the framework of the Landau-de Gennes formalism. The alignment field and its gradients are approximated by finite differences, and the free energy is minimized through a stochastic sampling technique. The validity of the proposed method is established by comparing the results of the proposed approach to those of traditional free energy minimization techniques. Its usefulness is illustrated in the context of three systems, namely, a nematic liquid crystal confined in a slit channel, a nematic liquid crystal droplet, and a chiral liquid crystal in the bulk. It is found that for systems that exhibit multiple metastable morphologies, the proposed Monte Carlo method is generally able to identify lower free energy states that are often missed by traditional approaches. Importantly, the Monte Carlo method identifies such states from random initial configurations, thereby obviating the need for educated initial guesses that can be difficult to formulate.
Armas-Pérez, Julio C; Londono-Hurtado, Alejandro; Guzmán, Orlando; Hernández-Ortiz, Juan P; de Pablo, Juan J
2015-07-28
A theoretically informed coarse-grained Monte Carlo method is proposed for studying liquid crystals. The free energy functional of the system is described in the framework of the Landau-de Gennes formalism. The alignment field and its gradients are approximated by finite differences, and the free energy is minimized through a stochastic sampling technique. The validity of the proposed method is established by comparing the results of the proposed approach to those of traditional free energy minimization techniques. Its usefulness is illustrated in the context of three systems, namely, a nematic liquid crystal confined in a slit channel, a nematic liquid crystal droplet, and a chiral liquid crystal in the bulk. It is found that for systems that exhibit multiple metastable morphologies, the proposed Monte Carlo method is generally able to identify lower free energy states that are often missed by traditional approaches. Importantly, the Monte Carlo method identifies such states from random initial configurations, thereby obviating the need for educated initial guesses that can be difficult to formulate. PMID:26233107
Theoretical study of the photodissociation of Li2+ in one-color intense laser fields
NASA Astrophysics Data System (ADS)
Li, Yuanjun; Jiang, Wanyi; Khait, Yuriy G.; Hoffmann, Mark R.
2011-05-01
A theoretical treatment of the photodissociation of the molecular ion Li2+ in one-color intense laser fields, using the time-dependent wave packet approach in a Floquet Born-Oppenheimer representation, is presented. Six electronic states 1,2 2Σg+, 1,2 2Σu+, 1 2Πg, and 1 2Πu are of relevance in this simulation and have been included. The dependences of the fragmental dissociation probabilities and kinetic energy release (KER) spectra on pulse width, peak intensity, polarization angle, wavelength, and initial vibrational level are analyzed to interpret the influence of control parameters of the external field. Three main dissociation channels, 1 2Σg+ (m = -1), 2 2Σg+ (m = -2), and 2 2Σu+ (m = -3), are seen to dominate the dissociation processes under a wide variety of laser conditions and give rise to well separated groups of KER features. Different dissociation mechanisms for the involved Floquet channels are discussed.
Charles, P. H. Crowe, S. B.; Langton, C. M.; Trapp, J. V.; Cranmer-Sargison, G.; Thwaites, D. I.; Kairn, T.; Knight, R. T.; Kenny, J.
2014-04-15
Purpose: This work introduces the concept of very small field size. Output factor (OPF) measurements at these field sizes require extremely careful experimental methodology including the measurement of dosimetric field size at the same time as each OPF measurement. Two quantifiable scientific definitions of the threshold of very small field size are presented. Methods: A practical definition was established by quantifying the effect that a 1 mm error in field size or detector position had on OPFs and setting acceptable uncertainties on OPF at 1%. Alternatively, for a theoretical definition of very small field size, the OPFs were separated into additional factors to investigate the specific effects of lateral electronic disequilibrium, photon scatter in the phantom, and source occlusion. The dominant effect was established and formed the basis of a theoretical definition of very small fields. Each factor was obtained using Monte Carlo simulations of a Varian iX linear accelerator for various square field sizes of side length from 4 to 100 mm, using a nominal photon energy of 6 MV. Results: According to the practical definition established in this project, field sizes ≤15 mm were considered to be very small for 6 MV beams for maximal field size uncertainties of 1 mm. If the acceptable uncertainty in the OPF was increased from 1.0% to 2.0%, or field size uncertainties are 0.5 mm, field sizes ≤12 mm were considered to be very small. Lateral electronic disequilibrium in the phantom was the dominant cause of change in OPF at very small field sizes. Thus the theoretical definition of very small field size coincided to the field size at which lateral electronic disequilibrium clearly caused a greater change in OPF than any other effects. This was found to occur at field sizes ≤12 mm. Source occlusion also caused a large change in OPF for field sizes ≤8 mm. Based on the results of this study, field sizes ≤12 mm were considered to be theoretically very small for 6
Crystal nucleation in the hard-sphere system revisited: a critical test of theoretical approaches.
Tóth, Gyula I; Gránásy, László
2009-04-16
The hard-sphere system is the best known fluid that crystallizes: the solid-liquid interfacial free energy, the equations of state, and the height of the nucleation barrier are known accurately, offering a unique possibility for a quantitative validation of nucleation theories. A recent significant downward revision of the interfacial free energy from approximately 0.61kT/sigma(2) to (0.56 +/- 0.02)kT/sigma(2) [Davidchack, R.; Morris, J. R.; Laird, B. B. J. Chem. Phys. 2006, 125, 094710] necessitates a re-evaluation of theoretical approaches to crystal nucleation. This has been carried out for the droplet model of the classical nucleation theory (CNT), the self-consistent classical theory (SCCT), a phenomenological diffuse interface theory (DIT), and single- and two-field variants of the phase field theory that rely on either the usual double-well and interpolation functions (PFT/S1 and PFT/S2, respectively) or on a Ginzburg-Landau expanded free energy that reflects the crystal symmetries (PFT/GL1 and PFT/GL2). We find that the PFT/GL1, PFT/GL2, and DIT models predict fairly accurately the height of the nucleation barrier known from Monte Carlo simulations in the volume fraction range of 0.52 < varphi < 0.54, whereas the CNT, SCCT, PFT/S1, and PFT/S2 models underestimate it significantly. PMID:19320450
Awareness of music therapy practices and factors influencing specific theoretical approaches.
Choi, Byung-Chuel
2008-01-01
The investigator identified music therapists' theoretical awareness of their practices and analyzed factors influencing their specific theoretical orientations and models. A 2-page survey was mailed to 500 board-certified music therapists in the United States; 272 returned surveys were analyzed. Data analysis revealed that respondents': (a) adoption of current theoretical approaches is contingent on the attended college, area of practice, and their age groups; (b) work satisfaction is not a function of involvement with theoretical orientations but rather of their area of practice and attendance at national music therapy conferences; (c) involvement in music making is not a function of theoretical orientations but of academic degrees; (d) emphasis on client's musical growth and aesthetic quality of music was not a function of theoretical orientations or any other investigated factor; (e) satisfaction with past education was not a function of involvement with theoretical orientations but of the area of practice; (f) desire to expand their theoretical knowledge was not a function of theoretical orientations but of academic degrees. PMID:18447575
NASA Astrophysics Data System (ADS)
Kripal, Ram; Yadav, Awadhesh Kumar
2015-06-01
Zero field splitting parameters (ZFSPs) D and E of Cr3+ ion doped ammonium oxalate monohydrate (AOM) are calculated with formula using the superposition model. The theoretically calculated ZFSPs for Cr3+ in AOM crystal are compared with the experimental value obtained by electron paramagnetic resonance (EPR). Theoretical ZFSPs are in good agreement with the experimental ones. The energy band positions of optical absorption spectra of Cr3+ in AOM crystal calculated with CFA package are in good match with the experimental values.
NASA Astrophysics Data System (ADS)
Cheng, Jin; Hon, Yiu-Chung; Seo, Jin Keun; Yamamoto, Masahiro
2005-01-01
The Second International Conference on Inverse Problems: Recent Theoretical Developments and Numerical Approaches was held at Fudan University, Shanghai from 16-21 June 2004. The first conference in this series was held at the City University of Hong Kong in January 2002 and it was agreed to hold the conference once every two years in a Pan-Pacific Asian country. The next conference is scheduled to be held at Hokkaido University, Sapporo, Japan in July 2006. The purpose of this series of biennial conferences is to establish and develop constant international collaboration, especially among the Pan-Pacific Asian countries. In recent decades, interest in inverse problems has been flourishing all over the globe because of both the theoretical interest and practical requirements. In particular, in Asian countries, one is witnessing remarkable new trends of research in inverse problems as well as the participation of many young talents. Considering these trends, the second conference was organized with the chairperson Professor Li Tat-tsien (Fudan University), in order to provide forums for developing research cooperation and to promote activities in the field of inverse problems. Because solutions to inverse problems are needed in various applied fields, we entertained a total of 92 participants at the second conference and arranged various talks which ranged from mathematical analyses to solutions of concrete inverse problems in the real world. This volume contains 18 selected papers, all of which have undergone peer review. The 18 papers are classified as follows: Surveys: four papers give reviews of specific inverse problems. Theoretical aspects: six papers investigate the uniqueness, stability, and reconstruction schemes. Numerical methods: four papers devise new numerical methods and their applications to inverse problems. Solutions to applied inverse problems: four papers discuss concrete inverse problems such as scattering problems and inverse problems in
NASA Astrophysics Data System (ADS)
Kripal, Ram; Yadav, Awadhesh Kumar
2015-01-01
The zero field splitting parameter D of Cr3+ doped diammonium hexaaqua magnesium sulfate (DHMS) are calculated with perturbation formula using crystal field (CF) parameters from superposition model. The theoretically calculated ZFS parameters for Cr3+ in DHMS single crystal are compared with the experimental value obtained by electron paramagnetic resonance (EPR). The theoretical ZFS parameter D is similar to that from experiment. The energy band positions of optical absorption spectra of Cr3+ doped DHMS single crystal are calculated with CFA package, which are in good match with experimental values.
NASA Astrophysics Data System (ADS)
Grimm, Guido W.; Potts, Alastair J.
2016-03-01
The Coexistence Approach has been used to infer palaeoclimates for many Eurasian fossil plant assemblages. However, the theory that underpins the method has never been examined in detail. Here we discuss acknowledged and implicit assumptions and assess the statistical nature and pseudo-logic of the method. We also compare the Coexistence Approach theory with the active field of species distribution modelling. We argue that the assumptions will inevitably be violated to some degree and that the method lacks any substantive means to identify or quantify these violations. The absence of a statistical framework makes the method highly vulnerable to the vagaries of statistical outliers and exotic elements. In addition, we find numerous logical inconsistencies, such as how climate shifts are quantified (the use of a "centre value" of a coexistence interval) and the ability to reconstruct "extinct" climates from modern plant distributions. Given the problems that have surfaced in species distribution modelling, accurate and precise quantitative reconstructions of palaeoclimates (or even climate shifts) using the nearest-living-relative principle and rectilinear niches (the basis of the method) will not be possible. The Coexistence Approach can be summarised as an exercise that shoehorns a plant fossil assemblage into coexistence and then assumes that this must be the climate. Given the theoretical issues and methodological issues highlighted elsewhere, we suggest that the method be discontinued and that all past reconstructions be disregarded and revisited using less fallacious methods. We outline six steps for (further) validation of available and future taxon-based methods and advocate developing (semi-quantitative) methods that prioritise robustness over precision.
A minimax approach to mean field games
NASA Astrophysics Data System (ADS)
Averboukh, Yu V.
2015-07-01
An initial boundary value problem for the system of equations of a determined mean field game is considered. The proposed definition of a generalized solution is based on the minimax approach to the Hamilton-Jacobi equation. We prove the existence of the generalized (minimax) solution using the Nash equilibrium in the auxiliary differential game with infinitely many identical players. We show that the minimax solution of the original system provides the \\varepsilon-Nash equilibrium in the differential game with a finite number of players. Bibliography: 34 titles.
New approaches to nonlinear diffractive field propagation.
Christopher, P T; Parker, K J
1991-07-01
In many domains of acoustic field propagation, such as medical ultrasound imaging, lithotripsy shock treatment, and underwater sonar, a realistic calculation of beam patterns requires treatment of the effects of diffraction from finite sources. Also, the mechanisms of loss and nonlinear effects within the medium are typically nonnegligible. The combination of diffraction, attenuation, and nonlinear effects has been treated by a number of formulations and numerical techniques. A novel model that incrementally propagates the field of baffled planar sources with substeps that account for the physics of diffraction, attenuation, and nonlinearity is presented. The model accounts for the effect of refraction and reflection (but not multiple reflections) in the case of propagation through multiple, parallel layers of fluid medium. An implementation of the model for axis symmetric sources has been developed. In one substep of the implementation, a new discrete Hankel transform is used with spatial transform techniques to propagate the field over a short distance with diffraction and attenuation. In the other substep, the temporal frequency domain solution to Burgers' equation is implemented to account for the nonlinear accretion and depletion of harmonics. This approach yields a computationally efficient procedure for calculating beam patterns from a baffled planar, axially symmetric source under conditions ranging from quasilinear through shock. The model is not restricted by the usual parabolic wave approximation and the field's directionality is explicitly accounted for at each point. Useage of a harmonic-limiting scheme allows the model to propagate some previously intractable high-intensity nonlinear fields. Results of the model are shown to be in excellent agreement with measurements performed on the nonlinear field of an unfocused 2.25-MHz piston source, even in the near field where the established parabolic wave approximation model fails. Next, the model is used to
Field dependence of gaseous-ion mobility - Theoretical tests of approximate formulas.
NASA Technical Reports Server (NTRS)
Hahn, H.; Mason, E. A.
1972-01-01
The approximate formulas considered include relations based on the Wannier free-flight theory, the Kihara medium-field expansion, and the Frost-Patterson interpolation formulas. A few accurate theoretical results are available for testing the foregoing formulas. Cases concerning high fields, intermediate fields, and resonant charge transfer are examined. It is found that of the formulas tested, the one based on the Wannier free-flight theory is the most flexible, since it can be used for all fields and all ion-neutral force laws and mass ratios.
[Theoretical perspectives on medicine and the medical profession: an anthropological approach].
Queiroz, M de S
1991-08-01
The medical field and profession are studied from the theoretical point of view of the social sciences. The most representative works on this subject are presented. The analysis shows that conservative positivism and orthodox Marxism are the main obstacles to development in this field of study. At the same time it suggests the concept of culture and the anthropological method of research as the best means for the overcoming of some of the main contradictions which paralyse its progress. PMID:1820621
ERIC Educational Resources Information Center
Feldner, Matthew T.; Monson, Candice M.; Friedman, Matthew J.
2007-01-01
Although efforts to prevent posttraumatic stress disorder (PTSD) have met with relatively limited success, theoretically driven preventive approaches with promising efficacy are emerging. The current article critically reviews investigations of PTSD prevention programs that target persons at risk for being exposed to a traumatic event or who have…
Understanding Older Adults' Physical Activity Behavior: A Multi-Theoretical Approach
ERIC Educational Resources Information Center
Grodesky, Janene M.; Kosma, Maria; Solmon, Melinda A.
2006-01-01
Physical inactivity is a health issue with serious consequences for older adults. Investigating physical activity promotion within a multi-theoretical approach may increase the predictive strength of physical activity determinants and facilitate the development and implementation of effective interventions for older adults. This article examines…
Making a Traditional Study-Abroad Program Geographic: A Theoretically Informed Regional Approach
ERIC Educational Resources Information Center
Jokisch, Brad
2009-01-01
Geographers have been active in numerous focused study-abroad programs, but few have created or led language-based programs overseas. This article describes the development of a Spanish language program in Ecuador and how it was made geographic primarily through a theoretically informed regional geography course. The approach employs theoretical…
ERIC Educational Resources Information Center
Golden, Linda L.; And Others
1990-01-01
The general-information-theoretic approach was used to identify informational overlap and asymmetry between variables, using affective, cognitive, and behavioral measures. Using the chi-squared test, no significant differences were found in response rates, demographics, or patronage frequency of three stores between numerical (n=453) and graphic…
Can realistic interaction be useful for nuclear mean-field approaches?
NASA Astrophysics Data System (ADS)
Nakada, H.; Sugiura, K.; Inakura, T.; Margueron, J.
2016-07-01
Recent applications of the M3Y-type semi-realistic interaction to the nuclear mean-field approaches are presented: i) Prediction of magic numbers and ii) isotope shifts of nuclei with magic proton numbers. The results exemplify that the realistic interaction, which is derived from the bare 2 N and 3 N interaction, furnishes a new theoretical instrument for advancing nuclear mean-field approaches.
A theoretical investigation of the sound radiation fields associated with a Bellmouth inlet
NASA Technical Reports Server (NTRS)
Meyer, W. L.; Zinn, B. T.
1983-01-01
Analytical results are obtained by numerical integration of a cylindrically symmetric integral representation of the external solutions of the Helmholtz equation. The accuracy of this method is checked by comparisons of computed results with 'exact' solutions generated by the point source method. In all cases, the average error for the amplitude and phase of the points calculated in the field is found to be less than ten percent. Theoretical studies which model experiments run for the NASA Langely Bellmouth inlet configuration are presented and comparisons are made with the experimental results. In all cases very good agreement is obtained between the experimental and theoretically calculated values.
A theoretical investigation of the sound radiation fields associated with a Bellmouth inlet
NASA Astrophysics Data System (ADS)
Meyer, W. L.; Zinn, B. T.
1983-04-01
Analytical results are obtained by numerical integration of a cylindrically symmetric integral representation of the external solutions of the Helmholtz equation. The accuracy of this method is checked by comparisons of computed results with 'exact' solutions generated by the point source method. In all cases, the average error for the amplitude and phase of the points calculated in the field is found to be less than ten percent. Theoretical studies which model experiments run for the NASA Langely Bellmouth inlet configuration are presented and comparisons are made with the experimental results. In all cases very good agreement is obtained between the experimental and theoretically calculated values.
A group theoretical approach to structural transitions of icosahedral quasicrystals and point arrays
NASA Astrophysics Data System (ADS)
Zappa, Emilio; Dykeman, Eric C.; Geraets, James A.; Twarock, Reidun
2016-04-01
In this paper we describe a group theoretical approach to the study of structural transitions of icosahedral quasicrystals and point arrays. We apply the concept of Schur rotations, originally proposed by Kramer, to the case of aperiodic structures with icosahedral symmetry; these rotations induce a rotation of the physical and orthogonal spaces invariant under the icosahedral group, and hence, via the cut-and-project method, a continuous transformation of the corresponding model sets. We prove that this approach allows for a characterisation of such transitions in a purely group theoretical framework, and provide explicit computations and specific examples. Moreover, we prove that this approach can be used in the case of finite point sets with icosahedral symmetry, which have a wide range of applications in carbon chemistry (fullerenes) and biology (viral capsids).
Elementary Theoretical Forms for the Spatial Power Spectrum of Earth's Crustal Magnetic Field
NASA Technical Reports Server (NTRS)
Voorhies, C.
1998-01-01
The magnetic field produced by magnetization in Earth's crust and lithosphere can be distinguished from the field produced by electric currents in Earth's core because the spatial magnetic power spectrum of the crustal field differs from that of the core field. Theoretical forms for the spectrum of the crustal field are derived by treating each magnetic domain in the crust as the point source of a dipole field. The geologic null-hypothesis that such moments are uncorrelated is used to obtain the magnetic spectrum expected from a randomly magnetized, or unstructured, spherical crust of negligible thickness. This simplest spectral form is modified to allow for uniform crustal thickness, ellipsoidality, and the polarization of domains by an periodically reversing, geocentric axial dipole field from Earth's core. Such spectra are intended to describe the background crustal field. Magnetic anomalies due to correlated magnetization within coherent geologic structures may well be superimposed upon this background; yet representing each such anomaly with a single point dipole may lead to similar spectral forms. Results from attempts to fit these forms to observational spectra, determined via spherical harmonic analysis of MAGSAT data, are summarized in terms of amplitude, source depth, and misfit. Each theoretical spectrum reduces to a source factor multiplied by the usual exponential function of spherical harmonic degree n due to geometric attenuation with attitude above the source layer. The source factors always vary with n and are approximately proportional to n(exp 3) for degrees 12 through 120. The theoretical spectra are therefore not directly proportional to an exponential function of spherical harmonic degree n. There is no radius at which these spectra are flat, level, or otherwise independent of n.
NASA Astrophysics Data System (ADS)
Politano, A.; Chiarello, G.; Cupolillo, A.
2015-08-01
The discovery of quasi-two-dimensional (Q2D) crystals has started a new era of materials science. Novel materials, atomically thin and mechanically, thermally and chemically stable, with a large variety of electronic properties are available and they can be assembled in ultrathin flexible devices. Understanding collective electronic excitations (plasmons) in Q2D systems is mandatory for engineering applications in plasmonics. In view of recent developments in the emerging field of graphene-based plasmonics, the correspondence between the theoretically calculated quantities and the observables experimentally measured in Q2D crystals is still unsatisfactory. Motivated by recent Nazarov’s findings (Nazarov 2015 New J. Phys. 17 073018), here we discuss some crucial issues of current theoretical approaches as well as the computational methods applied to two-dimensional materials with special emphasis to cover their peculiarities, range of application and pitfalls.
Tenforde, T.S.; Gaffey, C.T.; Moyer, B.R.; Budinger, T.F.
1983-01-01
Simultaneous measurements were made of the electrocardiogram (ECG) and the intraarterial blood pressure of adult male Macaca monkeys during acute exposure to homogeneous stationary magnetic fields ranging in strength up to 1.5 tesla. An instantaneous, field strength-dependent increase in the ECG signal amplitude at the locus of the T wave was observed in fields greater than 0.1 tesla. The temporal sequence of this signal in the ECG record and its reversibility following termination of the magnetic field exposure are consistent with an earlier suggestion that it arises from a magnetically induced aortic blood flow potential superimposed on the native T-wave signal. No measurable alterations in blood pressure resulted from exposure to fields up to 1.5 tesla. This experimental finding is in agreement with theoretical calculations of the magnetohydrodynamic effect on blood flow in the major arteries of the cardiovascular system. 27 references, 1 figure, 1 table.
Sharma, Suresh C.; Gupta, Neha
2015-12-15
A theoretical modeling for the catalyst-assisted growth of graphene sheet in the presence of plasma has been investigated. It is observed that the plasma parameters can strongly affect the growth and field emission properties of graphene sheet. The model developed accounts for the charging rate of the graphene sheet; number density of electrons, ions, and neutral atoms; various elementary processes on the surface of the catalyst nanoparticle; surface diffusion and accretion of ions; and formation of carbon-clusters and large graphene islands. In our investigation, it is found that the thickness of the graphene sheet decreases with the plasma parameters, number density of hydrogen ions and RF power, and consequently, the field emission of electrons from the graphene sheet surface increases. The time evolution of the height of graphene sheet with ion density and sticking coefficient of carbon species has also been examined. Some of our theoretical results are in compliance with the experimental observations.
Dynamical gap generation in graphene nanoribbons: An effective relativistic field theoretical model
Chaves, A. J.; Paula, W. de; Frederico, T.; Lima, G. D.; Cordeiro, C. E.; Delfino, A.
2011-04-15
We show that the assumption of a nontrivial zero band gap for a graphene sheet within an effective relativistic field theoretical model description of interacting Dirac electrons on the surface of graphene describes the experimental band gap of graphene nanoribbons for a wide range of widths. The graphene band gap is dynamically generated, corresponding to a nontrivial gapless solution, found in the limit of an infinitely wide graphene ribbon. The nanoribbon band gap is determined by the experimental graphene work function.
Investigation of the interfacial tension of complex coacervates using field-theoretic simulations
Kumar, Rajeev
2012-01-01
Complex coacervation, a liquid-liquid phase separation that occurs when two oppositely charged polyelectrolytes are mixed in a solution, has the potential to be exploited for many emerging applications including wet adhesives and drug delivery vehicles. The ultra-low interfacial tension of coacervate systems against water is critical for such applications, and it would be advantageous if molecular models could be used to characterize how various system properties (e.g., salt concentration) affect the interfacial tension. In this article we use field-theoretic simulations to characterize the interfacial tension between a complex coacervate and its supernatant. After demonstrating that our model is free of ultraviolet divergences (calculated properties converge as the collocation grid is refined), we develop two methods for calculating the interfacial tension from field-theoretic simulations. One method relies on the mechanical interpretation of the interfacial tension as the interfacial pressure, and the second method estimates the change in free energy as the area between the two phases is changed. These are the first calculations of the interfacial tension from full field theoretic simulation of which we are aware, and both the magnitude and scaling behaviors of our calculated interfacial tension agree with recent experiments.
NASA Technical Reports Server (NTRS)
Elliott, D. G.
1977-01-01
Measurements of reaction rail currents, reaction rail voltages, and airgap magnetic fields in tests of the Linear Induction Motor Research Vehicle (LIMRV) were compared with theoretical calculations from the mesh/matrix theory. It was found that the rail currents and magnetic fields predicted by the theory are within 20 percent of the measured currents and fields at most motor locations in most of the runs, but differ by as much as a factor of two in some cases. The most consistent difference is a higher experimental than theoretical magnetic field near the entrance of the motor and a lower experimental than theoretical magnetic field near the exit. The observed differences between the theoretical and experimental magnetic fields and currents do not account for the differences of as much as 26 percent between the theoretical and experimental thrusts.
NASA Astrophysics Data System (ADS)
Mastour, N.; Mejatty, M.; Bouchriha, H.
2015-06-01
A theoretical approach based on the rate equation of exciton density for the electroluminescence quenching in (polymers-quantum dots) nanocomposite is developed. It is shown that the light intensity observed in the nanocomposite depends respectively on the quantum dots concentration, the injected charge carriers, the exciton density, and the Förster energy transfer between polymer and quantum dots. We have found that the significant reduction of the light intensity is related to the exciton density profiles which exhibit a monotonic decrease with the increase of Förster transfer mechanism. Our theoretical approach for the electroluminescence agrees with experimental results observed in hybrid structure (MEH-PPV) with CdSe quantum dots. The maximum of exciton density is also estimated and we have obtained a value for the exciton diffusion length of 10 nm which is consistent with the available experimental results.
Nuclear radii calculations in various theoretical approaches for nucleus-nucleus interactions
Merino, C.; Novikov, I. S.; Shabelski, Yu.
2009-12-15
The information about sizes and nuclear density distributions in unstable (radioactive) nuclei is usually extracted from the data on interaction of radioactive nuclear beams with a nuclear target. We show that in the case of nucleus-nucleus collisions the values of the parameters depend somewhat strongly on the considered theoretical approach and on the assumption about the parametrization of the nuclear density distribution. The obtained values of root-mean-square radii (R{sub rms}) for stable nuclei with atomic weights A=12-40 vary by approximately 0.1 fm when calculated in the optical approximation, in the rigid target approximation, and using the exact expression of the Glauber theory. We present several examples of R{sub rms} radii calculations using these three theoretical approaches and compare these results with the data obtained from electron-nucleus scattering.
Field-theoretic model of inhomogeneous supramolecular polymer networks and gels
NASA Astrophysics Data System (ADS)
Mohan, Aruna; Elliot, Richard; Fredrickson, Glenn H.
2010-11-01
We present a field-theoretic model of the gelation transition in inhomogeneous reversibly bonding systems and demonstrate that our model reproduces the classical Flory-Stockmayer theory of gelation in the homogeneous limit. As an illustration of our model in the context of inhomogeneous gelation, we analyze the mean-field behavior of an equilibrium system of reacting trifunctional units in a good solvent confined within a slit bounded by parallel, repulsive walls. Our results indicate higher conversions and, consequently, higher concentrations of gel following the gelation transition near the center of the slit relative to the edges.
Field-theoretic model of inhomogeneous supramolecular polymer networks and gels.
Mohan, Aruna; Elliot, Richard; Fredrickson, Glenn H
2010-11-01
We present a field-theoretic model of the gelation transition in inhomogeneous reversibly bonding systems and demonstrate that our model reproduces the classical Flory-Stockmayer theory of gelation in the homogeneous limit. As an illustration of our model in the context of inhomogeneous gelation, we analyze the mean-field behavior of an equilibrium system of reacting trifunctional units in a good solvent confined within a slit bounded by parallel, repulsive walls. Our results indicate higher conversions and, consequently, higher concentrations of gel following the gelation transition near the center of the slit relative to the edges. PMID:21054065
NASA Astrophysics Data System (ADS)
Dawar, Anit; Chandra, Amita
2012-11-01
The influence of electric field on the diffusion limited aggregation has been observed experimentally. The observation provides experimental confirmation of the theoretical model proposed by Zhi-Jie Tan et al. [Phys. Lett. A 268 (2000) 112]. Most strikingly, a transition from a disordered ramified pattern to an ordered pattern (chain-like growth) has been observed. The growth is governed by diffusion, convection and migration in an electric field which give rise to the different patterns. This Letter can also be considered as an experimental evidence of computer simulated fractal growth given by Huang and Hibbert [Physica A 233 (1996) 888].
Fast polynomial approach to calculating wake fields
Goldstein, C.I.; Peierls, R.F.
1997-06-15
In the computation of transverse wake field effects in accelerators, it is necessary to compute expressions of the form given in equations (1). It is usually desired to compute this a large number of times, the values of z{sub i} and x{sub i} being different at each iteration, other quantities remaining the same. The problem in practical applications is that the computational work grows as N{sub m}{sup 2}. Thus even using parallel computation to achieve speedup, the elapsed time to obtain a result still increases linearly with N{sub m}. The authors introduce here an approximate method of evaluating the sum in (1) whose computational work increases only as N{sub m}logN{sub m}. It involves some significant initial computation which does not have to be repeated at each subsequent iteration. The basis of the approach is to replace the individual contributions of a group of distant macroparticles with a local series expansion. In this respect it is similar in spirit to the so called fast multipole method.
NASA Astrophysics Data System (ADS)
Toida, Mieko
2016-07-01
The electric field parallel to the magnetic field in nonlinear magnetosonic waves in three component plasmas (two-ion-species plasma and electron-positron-ion plasma) is theoretically studied based on a three-fluid model. In a two-ion-species plasma, a magnetosonic mode has two branches, high-frequency mode and low-frequency mode. The parallel electric field E ∥ and its integral along the magnetic field, F = - ∫ E ∥ d s , in the two modes propagating quasiperpendicular to the magnetic field are derived as functions of the wave amplitude ɛ and the density ratio and cyclotron frequency ratio of the two ion species. The theory shows that the magnitude of F in the high-frequency-mode pulse is much greater than that in the low-frequency-mode pulse. Theoretical expressions for E ∥ and F in nonlinear magnetosonic pulses in an electron-positron-ion plasma are also obtained under the assumption that the wave amplitudes are in the range of ( m e / m i ) 1 / 2 < ɛ < 1 , where m e / m i is the electron to ion mass ratio.
NASA Astrophysics Data System (ADS)
Sholtes, Joel; Werbylo, Kevin; Bledsoe, Brian
2014-10-01
Theoretical approaches to magnitude-frequency analysis (MFA) of sediment transport in channels couple continuous flow probability density functions (PDFs) with power law flow-sediment transport relations (rating curves) to produce closed-form equations relating MFA metrics such as the effective discharge, Qeff, and fraction of sediment transported by discharges greater than Qeff, f+, to statistical moments of the flow PDF and rating curve parameters. These approaches have proven useful in understanding the theoretical drivers behind the magnitude and frequency of sediment transport. However, some of their basic assumptions and findings may not apply to natural rivers and streams with more complex flow-sediment transport relationships or management and design scenarios, which have finite time horizons. We use simple numerical experiments to test the validity of theoretical MFA approaches in predicting the magnitude and frequency of sediment transport. Median values of Qeff and f+ generated from repeated, synthetic, finite flow series diverge from those produced with theoretical approaches using the same underlying flow PDF. The closed-form relation for f+ is a monotonically increasing function of flow variance. However, using finite flow series, we find that f+ increases with flow variance to a threshold that increases with flow record length. By introducing a sediment entrainment threshold, we present a physical mechanism for the observed diverging relationship between Qeff and flow variance in fine and coarse-bed channels. Our work shows that through complex and threshold-driven relationships sediment transport mode, channel morphology, flow variance, and flow record length all interact to influence estimates of what flow frequencies are most responsible for transporting sediment in alluvial channels.
Decision support models for solid waste management: Review and game-theoretic approaches
Karmperis, Athanasios C.; Aravossis, Konstantinos; Tatsiopoulos, Ilias P.; Sotirchos, Anastasios
2013-05-15
Highlights: ► The mainly used decision support frameworks for solid waste management are reviewed. ► The LCA, CBA and MCDM models are presented and their strengths, weaknesses, similarities and possible combinations are analyzed. ► The game-theoretic approach in a solid waste management context is presented. ► The waste management bargaining game is introduced as a specific decision support framework. ► Cooperative and non-cooperative game-theoretic approaches to decision support for solid waste management are discussed. - Abstract: This paper surveys decision support models that are commonly used in the solid waste management area. Most models are mainly developed within three decision support frameworks, which are the life-cycle assessment, the cost–benefit analysis and the multi-criteria decision-making. These frameworks are reviewed and their strengths and weaknesses as well as their critical issues are analyzed, while their possible combinations and extensions are also discussed. Furthermore, the paper presents how cooperative and non-cooperative game-theoretic approaches can be used for the purpose of modeling and analyzing decision-making in situations with multiple stakeholders. Specifically, since a waste management model is sustainable when considering not only environmental and economic but also social aspects, the waste management bargaining game is introduced as a specific decision support framework in which future models can be developed.
Theoretical model of the electric field produced by charged particles in windblown sand flux
NASA Astrophysics Data System (ADS)
Zheng, Xiaojing; He, Lihong; Zhou, Youhe
2004-08-01
Taking into account the coupled interactions among wind velocity, sand movement, and the electric field, we develop a general theoretical model for calculating the electric fields produced by charged sand particles in the three sand movement types, saltation, suspension and creep, quantifying the electric field of a point charge by Coulomb's law. The numerical results of the electric field are in good agreement with both the field data and the wind tunnel experimental results. The profile of the electric field intensity produced by charged particles in windblown sand flux is quantitatively analyzed in detail and compared with those generated by charged particles only in the saltation layer or in the creep layer. The results demonstrate that the profile of the electric field produced by charged particles in one sand movement type is different from that by those in other types and that the signs of the charge acquired by the particles also alter the features of the profile. Finally, the effects of the wind velocity and the charge of the windblown sand particles on the electric field intensity are discussed.
NASA Astrophysics Data System (ADS)
Fahim-Al-Fattah, Md.; Rahman, Md. Tawabur; Islam, Md. Sherajul; Bhuiyan, Ashraful G.
2016-02-01
This paper presents a detailed study of theoretical performance of graphene field effect transistor (GFET) using analytical approach. GFET shows promising performance in terms of faster saturation as well as extremely high cutoff frequency (3.9THz). A significant shift of the Dirac point as well as an asymmetrical ambipolar behavior is observed on the transfer characteristics. Similarly, an approximate symmetrical capacitance-voltage (C-V) characteristics is obtained where it has guaranteed the consistency because it shows a significant saturation both in the accumulation and inversion region. In addition, a high transconductance of 6800uS at small channel length (20nm) along with high cutoff frequency (3.9THz) has been observed which demands for high speed field effect devices.
Cheng, Zhongtao; Liu, Dong; Luo, Jing; Yang, Yongying; Zhou, Yudi; Zhang, Yupeng; Duan, Lulin; Su, Lin; Yang, Liming; Shen, Yibing; Wang, Kaiwei; Bai, Jian
2015-05-01
A field-widened Michelson interferometer (FWMI) is developed to act as the spectral discriminator in high-spectral-resolution lidar (HSRL). This realization is motivated by the wide-angle Michelson interferometer (WAMI) which has been used broadly in the atmospheric wind and temperature detection. This paper describes an independent theoretical framework about the application of the FWMI in HSRL for the first time. In the framework, the operation principles and application requirements of the FWMI are discussed in comparison with that of the WAMI. Theoretical foundations for designing this type of interferometer are introduced based on these comparisons. Moreover, a general performance estimation model for the FWMI is established, which can provide common guidelines for the performance budget and evaluation of the FWMI in the both design and operation stages. Examples incorporating many practical imperfections or conditions that may degrade the performance of the FWMI are given to illustrate the implementation of the modeling. This theoretical framework presents a complete and powerful tool for solving most of theoretical or engineering problems encountered in the FWMI application, including the designing, parameter calibration, prior performance budget, posterior performance estimation, and so on. It will be a valuable contribution to the lidar community to develop a new generation of HSRLs based on the FWMI spectroscopic filter. PMID:25969300
NASA Astrophysics Data System (ADS)
Li, Xin; Zhou, Wei-Man; Liu, Wei-Hua; Wang, Xiao-Li
2015-05-01
Field emission properties of zinc oxide (ZnO) nanoparticles (NPs) decorated carbon nanotubes (CNTs) are investigated experimentally and theoretically. CNTs are in situ decorated with ZnO NPs during the growth process by chemical vapor deposition using a carbon source from the iron phthalocyanine pyrolysis. The experimental field emission test shows that the ZnO NP decoration significantly improves the emission current from 50 μA to 275 μA at 550 V and the reduced threshold voltage from 450 V to 350 V. The field emission mechanism of ZnO NPs on CNTs is theoretically studied by the density functional theory (DFT) combined with the Penn-Plummer method. The ZnO NPs reconstruct the ZnO-CNT structure and pull down the surface barrier of the entire emitter system to 0.49 eV so as to reduce the threshold electric field. The simulation results suggest that the presence of ZnO NPs would increase the LDOS near the Fermi level and increase the emission current. The calculation results are consistent with the experiment results. Project supported by the National Natural Science Foundation of China (Grant Nos. 91123018, 61172040, and 61172041) and the Natural Science Foundation of Shaanxi Province, China (Grant No. 2014JM7277).
Near-field study of magneto-optical samples: theoretical comparison of transversal and polar effects
NASA Astrophysics Data System (ADS)
Van Labeke, Daniel; Vial, A.; Barchiesi, Dominique
1996-09-01
The density of integration of magneto-optical devices is limited by diffraction of light. Recently some groups have proposed to use Near-Field Microscopy to overcome this limitation and some experiments have been performed both in transmission and reflection. In this paper we study theoretically magneto-optical effect in near-field. We consider a magneto-optical sample with details smaller than the wavelength. This sample is modelled as a multilayer rough structure. At least one layer has magneto-optical properties. The corrugation at the interfaces are very small compared to the optical wavelength. We do not consider the writing problem and the experiment is only modelled in the reading mode. Moreover, the magnetic properties are considered in the saturation regime. For this study we use an extension of the method that we used to describe near- field microscope with isotropic sample. The diffracted fields are determined in each layer by using a perturbative version of the Rayleigh method which leads to the resolution of a linear equation for each diffracted wave. The near- field above the sample is thus obtained by summing all the diffracted waves. We consider two geometries for the magnetization: polar effect where the magnetization is perpendicular to the sample and transversal effect where it is in the plane. We compare near-field images obtained in transmission and reflection by changing magnetization orientation. Comparisons with far-field results are also proposed.
Carvalho, Brígida Gimenez; Peduzzi, Marina; Mandú, Edir Nei Teixeira; Ayres, José Ricardo de Carvalho Mesquita
2012-01-01
This theoretical reflection intends to show the inter-subjective relationship that takes place in health and nursing practices under the following theoretical perspectives: Institutional Analysis, Psychodynamics of Labor and the Theory of Communicative Action, with an emphasis on the latter. Linking these concepts to the Marxist approach to work in the field of health emerges from recognizing the need for its continuous reconstruction-in this case, with a view to understand the interaction and communication intrinsic to work in action. The theory of Communicative Action seeks to consider these two inextricable dimensions: work as productive action and as interaction. The first corresponds to instrumental action based on technical rules with a production-guided rationale. The second refers to the interaction that takes place as communicative action and seeks understanding among subjects. We assume that adopting this theoretical perspective in the analysis of health and nursing practices opens new possibilities for clarifying its social and historical process and inter-subjective connections. PMID:22481717
Sugimura, A; Zakharov, A V
2011-08-01
The peculiarities in the dynamic of the director reorientation in a liquid crystal (LC) film under the influence of the electric E field directed at an angle α to the magnetic B field have been investigated both experimentally and theoretically. Time-resolved deuterium NMR spectroscopy is employed to investigate the field-induced director dynamics. Analysis of the experimental results, based on the predictions of hydrodynamic theory including both the director motion and fluid flow, provides an evidence for the appearance of the spatially periodic patterns in 4-n-pentyl-4'-cyanobiphenyl LC film, at the angles α>60∘, in response to the suddenly applied E. These periodic distortions produce a lower effective rotational viscosity. This gives a faster response of the director rotation than for a uniform mode, as observed in our NMR experiment. PMID:21929001
NASA Technical Reports Server (NTRS)
Wolf, R. A.; Kamide, Y.
1983-01-01
Advanced techniques considered by Kamide et al. (1981) seem to have the potential for providing observation-based high time resolution pictures of the global ionospheric current and electric field patterns for interesting events. However, a reliance on the proposed magnetogram-inversion schemes for the deduction of global ionospheric current and electric field patterns requires proof that reliable results are obtained. 'Theoretical' tests of the accuracy of the magnetogram inversion schemes have, therefore, been considered. The present investigation is concerned with a test, involving the developed KRM algorithm and the Rice Convection Model (RCM). The test was successful in the sense that there was overall agreement between electric fields and currents calculated by the RCM and KRM schemes.
Quantum-field-theoretic analysis of inflation dynamics in a (2+1)-dimensional universe
Samiullah, M. ); Eboli, O. ); Pi, S. )
1991-10-15
We reexamine inflationary scenarios based on slow-rollover transitions, which occur under various initial conditions of the inflation-driving scalar field. We examine inflation dynamics using a recently developed calculational technique for studying a quantum-field-theoretic system in an external environment that is itself changing with time. This method, based on the functional Schroedinger picture, uses a self-consistent Gaussian approximation that, unlike ordinary perturbation theory, reflects some of the nonlinearities of the full quantum theory. Our treatment is confined to planar universes, where the approximation techniques do not suffer from well-known problems associated with scalar field self-interactions in four-dimensional space-time. However, for these toy models we can present concrete and explicit results.
Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.
2015-02-17
We demonstrate that a non-perturbative framework for the treatment of the excitations of single walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. Asmore » a result, we test this theory explicitly on the data reported in [NanoLetters 5, 2314 (2005)] and [Phys. Rev. B 82, 195424 (2010)] and so demonstrate the method works over a wide range of reported excitonic spectra.« less
NASA Astrophysics Data System (ADS)
Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.
2015-02-01
We demonstrate that a nonperturbative framework for the treatment of the excitations of single-walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. We test this theory explicitly on the data reported by Dukovic et al. [Nano Lett. 5, 2314 (2005), 10.1021/nl0518122] and Sfeir et al. [Phys. Rev. B 82, 195424 (2010), 10.1103/PhysRevB.82.195424] and so demonstrate the method works over a wide range of reported excitonic spectra.
Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.
2015-02-17
We demonstrate that a non-perturbative framework for the treatment of the excitations of single walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. As a result, we test this theory explicitly on the data reported in [NanoLetters 5, 2314 (2005)] and [Phys. Rev. B 82, 195424 (2010)] and so demonstrate the method works over a wide range of reported excitonic spectra.
Embury, J.D. |; Han, K.
1999-04-01
The usual method of introducing engineers to the concept of dislocations and their role in plastic flow is to compare an estimate of the theoretical strength of solid (of order {micro}/30 where {micro} is the shear modulus) and the observed strength of either single crystals ({mu}/10{sup 4}) or practical engineering material such as structural steels where the yield stress in shear is of order {mu}/10{sup 3}. However, if one considers the problem in reverse, one can consider the accumulation of dislocations as an important mechanism by which one can produce engineering materials in which the strength level approaches the theoretical strength. If one assumes that the flow stress can be expressed in terms of te mean free path between stored dislocations or as the square root of the global dislocation density, then one can see the influence of dislocation density in a diagrammatic form. It is clear that the strengthening by dislocation accumulation due to large imposed plastic strains represents an important approach both to the development of new, potentially valuable, engineering materials and an important area of basic understanding in terms of the mechanical response of materials close to their theoretical strength. Thus, this article will survey some of the factors which influence dislocation accumulation at large strains and the consequences of such accumulation processes.
Illustrating the quantum approach with an Earth magnetic field MRI
NASA Astrophysics Data System (ADS)
Pars Benli, Kami; Dillmann, Baudouin; Louelh, Ryma; Poirier-Quinot, Marie; Darrasse, Luc
2015-05-01
Teaching imaging of magnetic resonance (MR) today is still as challenging as it has always been, because it requires admitting that we cannot express fundamental questions of quantum mechanics with straightforward language or without using extensive theory. Here we allow students to face a real MR setup based on the Earth's magnetic field. We address the applied side of teaching MR using a device that is affordable and that proves to be sufficiently robust, at universities in Orsay, France, and San Sebastian, Spain, in experimental practicals at undergraduate and graduate levels. We specifically present some of the advantages of low field for measuring R2 relaxation rates, reaching a power of separation of 1.5 μmol on Mn(II) ions between two water bottles each of half a liter. Finally we propose key approaches for the lecturers to adopt when they are asked to pass from theoretical knowledge to teachable knowhow. The outcomes are fast calibration and the MR acquisition protocols, demonstrating the reproducibility of energy transfer during the saturation pulses, and the quantitative nature of MR, with water protons and a helium-3 sample.
Shafii, Mohammad Ali Meidianti, Rahma Wildian, Fitriyani, Dian; Tongkukut, Seni H. J.; Arkundato, Artoto
2014-09-30
Theoretical analysis of integral neutron transport equation using collision probability (CP) method with quadratic flux approach has been carried out. In general, the solution of the neutron transport using the CP method is performed with the flat flux approach. In this research, the CP method is implemented in the cylindrical nuclear fuel cell with the spatial of mesh being conducted into non flat flux approach. It means that the neutron flux at any point in the nuclear fuel cell are considered different each other followed the distribution pattern of quadratic flux. The result is presented here in the form of quadratic flux that is better understanding of the real condition in the cell calculation and as a starting point to be applied in computational calculation.
Ofenheimer, Aldo; Buchmayr, Bruno; Kolleck, Ralf
2005-08-05
The influence of strain paths (loading history) on material formability is well known in sheet forming processes. Sophisticated experimental methods are used to determine the entire shape of strain paths of forming limits for aluminum AA6016-T4 alloy. Forming limits for sheet metal in as-received condition as well as for different pre-deformation are presented. A theoretical approach based on Arrieux's intrinsic Forming Limit Stress Curve (FLSC) concept is employed to numerically predict the influence of loading history on forming severity. The detailed experimental strain paths are used in the theoretical study instead of any linear or bilinear simplified loading histories to demonstrate the predictive quality of forming limits in the state of stress.
Giger, J N; Davidhizar, R E
1990-09-01
The purpose of the study was to determine if there is a relationship between types of entry-level preparatory nursing programmes in which a nurse receives basic nursing education and conceptual and theoretical approaches to patient care. A secondary purpose of the study was to determine if there is a relationship between entry-level basic preparatory nursing education and nursing leadership, the ability to make nursing diagnosis, and implementation, as well as evaluation of the nursing process. Three nursing practice categories were identified and included: professional, all-nurse and technical. Useable data collected by short-essay questionnaire from 343 out of 344 sample subjects were computed to determine the relationship, if any, between basic preparatory nursing education and conceptual and theoretical approaches to patient care. Decisions about three null hypotheses were made at the 0.05 level of significance utilizing analysis of covariance and the 0.01 level of significance utilizing chi-square analysis. For Hypothesis 1, the main effect for degree work when covaried with Verbal Scholastic Aptitude Test scores, Quantitative Scholastic Aptitude Test scores, time and age indicated a significance of 0.001 for all item associations in the professional, all-nurse and technical categories utilizing analysis of covariance, and 0.001 utilizing chi-square analysis. For Hypotheses 2 and 3, the main effect for degree work when covaried with the aforementioned variables indicated a significance of 0.001 utilizing analysis of covariance, and 0.001 utilizing chi-square analysis. In conclusion, the findings from the study suggest that graduates of baccalaureate degree programmes do vary in conceptual and theoretical approach to nursing care in specific nursing care situations.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2229698
Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Chuaqui, H.
2012-02-27
Plasma series resonance (PSR) effect is well known in geometrically asymmetric capacitively couple radio frequency plasma. However, plasma series resonance effect in geometrically symmetric plasma has not been properly investigated. In this work, a theoretical approach is made to investigate the plasma series resonance effect and its influence on Ohmic and stochastic heating in geometrically symmetric discharge. Electrical asymmetry effect by means of dual frequency voltage waveform is applied to excite the plasma series resonance. The results show considerable variation in heating with phase difference between the voltage waveforms, which may be applicable in controlling the plasma parameters in such plasma.
NASA Astrophysics Data System (ADS)
Son, Taehwang; Kim, Donghyun
2015-03-01
We present a theoretical approach to single nanoparticle detection using surface plasmon scattering microscopy. Through rigorous coupled wave analysis assuming light incidence on a gold coated BK7 glass substrate under total internal reflection condition for a 200-nm polystyrene as targets attached to the gold film, it was found that surface plasmon polariton induced by incident light on the gold thin film is perturbed. As a result, parabolic waves were observed in the reflection plane. By varying angles of incidence and wavelengths, optimum incident conditions for surface plasmon scattering microscopy were obtained.
A Maximum-Likelihood Approach to Force-Field Calibration.
Zaborowski, Bartłomiej; Jagieła, Dawid; Czaplewski, Cezary; Hałabis, Anna; Lewandowska, Agnieszka; Żmudzińska, Wioletta; Ołdziej, Stanisław; Karczyńska, Agnieszka; Omieczynski, Christian; Wirecki, Tomasz; Liwo, Adam
2015-09-28
A new approach to the calibration of the force fields is proposed, in which the force-field parameters are obtained by maximum-likelihood fitting of the calculated conformational ensembles to the experimental ensembles of training system(s). The maximum-likelihood function is composed of logarithms of the Boltzmann probabilities of the experimental conformations, calculated with the current energy function. Because the theoretical distribution is given in the form of the simulated conformations only, the contributions from all of the simulated conformations, with Gaussian weights in the distances from a given experimental conformation, are added to give the contribution to the target function from this conformation. In contrast to earlier methods for force-field calibration, the approach does not suffer from the arbitrariness of dividing the decoy set into native-like and non-native structures; however, if such a division is made instead of using Gaussian weights, application of the maximum-likelihood method results in the well-known energy-gap maximization. The computational procedure consists of cycles of decoy generation and maximum-likelihood-function optimization, which are iterated until convergence is reached. The method was tested with Gaussian distributions and then applied to the physics-based coarse-grained UNRES force field for proteins. The NMR structures of the tryptophan cage, a small α-helical protein, determined at three temperatures (T = 280, 305, and 313 K) by Hałabis et al. ( J. Phys. Chem. B 2012 , 116 , 6898 - 6907 ), were used. Multiplexed replica-exchange molecular dynamics was used to generate the decoys. The iterative procedure exhibited steady convergence. Three variants of optimization were tried: optimization of the energy-term weights alone and use of the experimental ensemble of the folded protein only at T = 280 K (run 1); optimization of the energy-term weights and use of experimental ensembles at all three temperatures (run 2
A study of Ti-doped WO3 thin films using comparative theoretical and experimental approach
NASA Astrophysics Data System (ADS)
Paez, Aurelio
Metal oxides like Tungsten Oxide (WO3) are well documented and characterized in the literature, with uses in darkening windows and mirrors, flat computer displays, solar panel cooling, and sensors (of interest in this study). Ti doping of WO3 is less documented and the focus of this study. Sample thin films of pure WO3 and varyingly Ti doped WO3 were prepared using Radio Frequency magnetron sputtering (RF) (13.56 MHz) to grow thin films on a silicon substrate. This study aims to compare multiple Ti doping percentages in WO3 theoretically and then compare with experimental data taken from thin films of various Ti doping levels grown at temperatures ranging from room temperature to 400 0°C. Characterization of the materials was to be conducted using Fourier Transform Infrared Spectroscopy, Raman Spectroscopy, X-ray diffraction, and other theoretical and simulated approaches. Theoretical calculations optimized Ti doping at somewhere between 6.25% and 12%. Experimental data indicates that under the given growing conditions optimal Ti doping is 5%. The percentage of Ti may be able to be increased and the material retain desired characteristics with an increased growth temperature above 400 0°C as annealing samples post-growth has no positive impact on the thin film structure.
An Alternative Theoretical Approach to Escape Decision-Making: The Role of Visual Cues
Javůrková, Veronika; Šizling, Arnošt Leoš; Kreisinger, Jakub; Albrecht, Tomáš
2012-01-01
Escape enables prey to avoid an approaching predator. The escape decision-making process has traditionally been interpreted using theoretical models that consider ultimate explanations based on the cost/benefit paradigm. Ultimate approaches, however, suffer from inseparable extra-assumptions due to an inability to accurately parameterize the model's variables and their interactive relationships. In this study, we propose a mathematical model that uses intensity of predator-mediated visual stimuli as a basic cue for the escape response. We consider looming stimuli (i.e. expanding retinal image of the moving predator) as a cue to flight initiation distance (FID; distance at which escape begins) of incubating Mallards (Anas platyrhynchos). We then examine the relationship between FID, vegetation cover and directness of predator trajectory, and fit the resultant model to experimental data. As predicted by the model, vegetation concealment and directness of predator trajectory interact, with FID decreasing with increased concealment during a direct approach toward prey, but not during a tangential approach. Thus, we show that a simple proximate expectation, which involves only visual processing of a moving predator, may explain interactive effects of environmental and predator-induced variables on an escape response. We assume that our proximate approach, which offers a plausible and parsimonious explanation for variation in FID, may serve as an evolutionary background for traditional, ultimate explanations and should be incorporated into interpretation of escape behavior. PMID:22427851
Recent Developments in Fully Fluctuating Field-Theoretic Simulations of Polymer Melts and Solutions.
Delaney, Kris T; Fredrickson, Glenn H
2016-08-11
We review the latest developments in computational methods for direct simulation of fully fluctuating field theories of polymeric assemblies. In this context, we describe a newly developed theoretical and computational framework for accurately computing fluctuation-corrected phase diagrams of mesostructured polymer systems and report the first such complete phase diagram for a diblock copolymer melt. The method is based on complex Langevin sampling of a UV regularized field-theoretic model, with Helmholtz free energies computed using thermodynamic integration. UV regularization ensures that the free energies do not have an arbitrary reference; they can be compared between incommensurate phases, permitting for the first time the computation of order-order transitions with fluctuation corrections. We further demonstrate that computed free energies are accurate in the disordered phase by comparison to perturbation theory on the one-loop level. Importantly, we note that our method uses no uncontrolled approximations beyond the initial definition of a coarse-grained molecular model for the polymer melt or solution. The method can be applied straightforwardly to melts and solutions containing multiple species with diverse polymer architectures. PMID:27414265
Theoretical analysis of the microwave-drill near-field localized heating effect
NASA Astrophysics Data System (ADS)
Jerby, E.; Aktushev, O.; Dikhtyar, V.
2005-02-01
The microwave-drill principle [Jerby et al., Science 298, 587 (2002)] is based on a localized hot-spot effect induced by a near-field coaxial applicator. The microwave drill melts the nonmetallic material locally and penetrates mechanically into it to shape the hole. This paper presents a theoretical analysis of the thermal-runaway effect induced in front of the microwave drill. The model couples the Maxwell's and heat equations including the material's temperature-dependent properties. A finite-difference time-domain algorithm is applied in a two-time-scale numerical model. The simulation is demonstrated for mullite, and benchmarked in simplified cases. The results show a temperature rise of ˜103K/s up to 1300K within a hot spot confined to a ˜4-mm width (˜0.1 wavelength). The input-port response to this near-field effect is modeled by equivalent time-varying lumped-circuit elements. Besides the physical insight, this theoretical study provides computational tools for design and analysis of microwave drills and for their real-time monitoring and adaptive impedance matching.
Suflita, Joseph M.; Duncan, Kathleen E.
2010-08-14
The Joint United States - European Union Theoretical and Practical Course on Molecular Approaches for in situ Biodegradation was held May 24 through June 7 at The University of Oklahoma. Twenty-four graduate and postgraduate students from both the United States and the European Union attended the course. Nine states and ten European countries were represented. Students were assigned living quarters and laboratory partners to maximize interactions between US and EU participants as well as to mix people with different technical backgrounds together. The students used the latest methods in molecular biology to characterize beneficial microorganisms and genes involved in the biodegradation of pollutants at a nearby landfill as well as an active hydrocarbon-producing site, part of which is undergoing bioremediation. Seminars by distinguished scientists were organized to expose the students to the breadth of the environmental field, including field assay and engineering applications, laboratory scale bioreactors, microbiology, genetics, regulation, pathway analysis, design of recombinant bacteria, and application of the associated techniques to the field. Lectures were given by various OU faculty on the principles behind the techniques to be used in the laboratory. These lectures included troubleshooting hints and encouraged questions and comments from the audience. The laboratory experiments covered chemical, microbiological, and molecular genetic analyses of soils; bioavailability of contaminants; enrichment cultures; gene probing; PCR amplification of known genes and gene families; identification of microbes based traditional and nontraditional approaches, nutritional capabilities, and 16S rRNA sequence; mRNA detection; and enzyme assays. Field trips were made to the USGS landfill field sampling site, and to the Tall Grass Prairie Preserve, a Nature Conservancy site which also featured long-term studies of bioremediation of crude oil and brine spills by one of the
Electric-field induced mutation of DNA: a theoretical investigation of the GC base pair.
Cerón-Carrasco, José P; Jacquemin, Denis
2013-04-01
It is known that intense external electric fields affect the proton transfer (PT) reactions in simple chemical systems, such as hydrated chlorhydric acid or formic acid dimer. Accordingly, electric fields might be used to modulate the PT reactions responsible for the spontaneous mutation mechanism in DNA. In this contribution, we investigate the effect of these fields on the tautomeric equilibria of the guanine-cytosine (GC) base pair in order to gain further insight into this hypothesis. This task is performed with both density functional theory (DFT) and second-order Møller-Plesset (MP2) approaches. Our results demonstrate that electric fields not only drastically alter the rate constants of PT but also tune the mechanism of the PT reactions in the GC base pair. PMID:23338206
Avian genetics: A field and ecological approach
Cooke, F.; Buckley, P.A.
1987-01-01
The authors wanted to present the ecological/population approach they used in their own research, and a compendium of carefully referred chapters written by invited experts was essential. The book follows the historical evolution of work in avian genetics, proceeding from a discussion of Mendelian (i.e. classical) genes through quantitative genetics, chromosomal genetics, biochemical genetics, to extensive treatment of population genetics, and concluding with some examples of long-term studies. In this book concentration has been more on intra- than on inter-specific variation; in that sense the approach has been more genetic than evolutionary or taxonomic.
Semiclassical and quantum field theoretic bounds for traversable Lorentzian stringy wormholes
Nandi, Kamal Kanti; Zhang Yuanzhong; Kumar, K.B. Vijaya
2004-09-15
A lower bound on the size of a Lorentzian wormhole can be obtained by semiclassically introducing the Planck cutoff on the magnitude of tidal forces (Horowitz-Ross constraint). Also, an upper bound is provided by the quantum field theoretic constraint in the form of the Ford-Roman Quantum Inequality for massless minimally coupled scalar fields. To date, however, exact static solutions belonging to this scalar field theory have not been worked out to verify these bounds. To fill this gap, we examine the wormhole features of two examples from the Einstein frame description of the vacuum low energy string theory in four dimensions which is the same as the minimally coupled scalar field theory. Analyses in this paper support the conclusion of Ford and Roman that wormholes in this theory can have sizes that are indeed only a few order of magnitudes larger than the Planck scale. It is shown that the two types of bounds are also compatible. In the process, we point out a 'wormhole' analog of naked black holes.
UQ and Decision Making for Groundwater Contamination: A Measure-Theoretic Approach
NASA Astrophysics Data System (ADS)
Mattis, S. A.; Dawson, C.; Butler, T.
2014-12-01
The movement of contaminant plumes in underground aquifers is highly dependent on many hydrogeological parameters. We model the transport with an advection, diffusion, reaction system requiring the specification of porosity, flow direction, flow speed, dispersivities, and effects of geochemical reactions. It is often prohibitively expensive or impossible to make accurate and reliable measurements of these parameters in the field. It is also difficult to know the position and shape of a contaminant plume at a given time or the exact details of the source of the contamination, e.g. size, location, origin time, and magnitude. If decisions are to be made regarding contaminant remediation strategies or predictions of future contaminant concentrations in and near water-supply wells, then these uncertain hydrogeological and source parameters need to be analyzed and estimated. We utilize a measure-theoretic framework to formulate and solve the physics-based stochastic inverse problem to quantify the uncertainty for these parameters. We solve the model using both analytical and finite element solutions. We define quantities of interest (QoI) for the groundwater contaminant problem in terms of observable field measurements. We develop adjoint problems to compute accurate and reliable a posteriori error estimates of the QoIs. The adjoint solutions are also useful in the solution of the inverse problem. The measure-theoretic formulation and solution of the inverse problem and modeling framework define a solution as a probability measure on the parameter domain. In the typical case where the number of output quantities is less than the number of parameters, the inverse of the map from parameters to data defines a type of generalized contour map where the geometry plays a pivotal role in determining an optimal set of QoI. We determine and analyze solutions for geometrically distinct QoI defining reduced-dimension set-valued inverses for this measure-theoretic inverse framework.
NASA Astrophysics Data System (ADS)
Karaboga, F.; Soykan, U.; Dogruer, M.; Ozturk, B.; Yildirim, G.; Cetin, S.; Terzioglu, C.
2013-09-01
The aim of this multidisciplinary study is to characterize a title compound, p-benzophenoneoxycarbonylphenyl acrylate (BPOCPA) synthesized by condensation reaction of p-acryloyloxybenzoyl chloride (ABC) with 4-hydroxybenzophenone (HBP) by means of experimental and theoretical evidences. The spectroscopic properties of the compound are experimentally examined by Fourier transformation-infrared (FTIR) spectra (in the region 400-4000 cm-1) and nuclear magnetic resonance (NMR) chemical shifts (with a frequency of 400 MHz). For the theoretical studies, the optimized molecular structures, vibrational frequencies including infrared intensities and Raman activities, corresponding vibrational spectra interpreted with the aid of normal coordinate analysis based on scaled density functional force field, atomic charges, thermodynamic properties, 1H and 13C NMR chemical shifts, JCH and JCC coupling constants belonging to the BPOCPA compound are analyzed in the ground state by the way of the density functional theory (B3LYP) with the standard 6-311++G(d,p) level of theory for the first time. All the results obtained show that the calculated vibrational frequencies and chemical shifts are observed to be in good agreement with the available experimental findings. According to the comparison between experimental results and theoretical data, the calculation level chosen plays an important role in understanding of dynamics of the title compound studied in this work. The self-consistent field (SCF) energy of the molecule in six different solvent media is also analyzed at the same basis set by applying both the Onsager and Polarizable Continuum Model (PCM). It is found that the SCF energies deduced from the methods reduce with the enhancement of the solvent polarity as a consequence of the increment in the stability of the compound studied. Besides, the changes of the PCM calculations are found to be higher than those of the Onsager ones, confirming that the former method displays a
ERIC Educational Resources Information Center
Maracci, Mirko; Cazes, Claire; Vandebrouck, Fabrice; Mariotti, Maria Alessandra
2013-01-01
Mathematics education as a research domain is characterized by a plurality of theoretical approaches. Acknowledging the existence of such diversity and the risks of an excessive theoretical fragmentation does not mean to search for a unifying theory but to urge the community to develop strategies for coping with this diversity. This article is…
A new approach to observe toroidal magnetic fields of magnetars
NASA Astrophysics Data System (ADS)
Murakami, H.; Makishima, K.; Enoto, T.; Nakano, T.; Furuta, Y.; Nakazawa, K.
2016-06-01
Over the last decade, observational evidence has amounted that magnetars harbor enormous surface dipole magnetic fields (MFs) of B_{d} = 10^{14-15} {G}. Theoretically, we expect even stronger toroidal MFs B_{t} (e.g., Takiwaki+2009), which is observationally supported by a discovery of low-B_{d} magnetars (e.g., SGR 0418+5729; Rea+2013). Here, we will present a new approach to access B_{t} more directly. {Suzaku} allows us to simultaneously observe a soft thermal component and a distinct hard X-ray tail of magnetars. Extensively analyzing two magnetars, 4U 0142+61 and 1E 1547.0-5408, we found that their hard X-ray pulses suffered from slow phase modulations (Makishima+2014, 2015). This can be interpreted as a manifestation of free precession, under an axial deformation by ˜0.01%. If this effect is attributed to the magnetic stress, B_{t}˜10^{16} G is inferred. We further found that, within 6 years observation of 4U 0142+61, the modulation periods remained constant, while the amplitude gradually increased from < 0.4 to ˜1.3 sec. These results suggest the shift of the hard X-ray emission region (or direction).
A new approach to observe toroidal magnetic fields of magnetars
NASA Astrophysics Data System (ADS)
Murakami, H.; Makishima, K.; Enoto, T.; Nakano, T.; Furuta, Y.; Nakazawa, K.
2016-06-01
Over the last decade, observational evidence has amounted that magnetars harbor enormous surface dipole magnetic fields (MFs) of B_{d} = 10^{14-15} {G}. Theoretically, we expect even stronger toroidal MFs B_{t} (e.g., Takiwaki+2009), which is observationally supported by a discovery of low-B_{d} magnetars (e.g., SGR 0418+5729; Rea+2013). Here, we will present a new approach to access B_{t} more directly. Suzaku allows us to simultaneously observe a soft thermal component and a distinct hard X-ray tail of magnetars. Extensively analyzing two magnetars, 4U 0142+61 and 1E 1547.0-5408, we found that their hard X-ray pulses suffered from slow phase modulations (Makishima+2014, 2015). This can be interpreted as a manifestation of free precession, under an axial deformation by ˜0.01%. If this effect is attributed to the magnetic stress, B_{t}˜10^{16} G is inferred. We further found that, within 6 years observation of 4U 0142+61, the modulation periods remained constant, while the amplitude gradually increased from < 0.4 to ˜1.3 sec. These results suggest the shift of the hard X-ray emission region (or direction).
A Theoretical Method for Characterizing Nonlinear Effects in Paul Traps with Added Octopole Field.
Xiong, Caiqiao; Zhou, Xiaoyu; Zhang, Ning; Zhan, Lingpeng; Chen, Yongtai; Chen, Suming; Nie, Zongxiu
2015-08-01
In comparison with numerical methods, theoretical characterizations of ion motion in the nonlinear Paul traps always suffer from low accuracy and little applicability. To overcome the difficulties, the theoretical harmonic balance (HB) method was developed, and was validated by the numerical fourth-order Runge-Kutta (4th RK) method. Using the HB method, analytical ion trajectory and ion motion frequency in the superimposed octopole field, ε, were obtained by solving the nonlinear Mathieu equation (NME). The obtained accuracy of the HB method was comparable with that of the 4th RK method at the Mathieu parameter, q = 0.6, and the applicable q values could be extended to the entire first stability region with satisfactory accuracy. Two sorts of nonlinear effects of ion motion were studied, including ion frequency shift, Δβ, and ion amplitude variation, Δ(C(2n)/C0) (n ≠ 0). New phenomena regarding Δβ were observed, although extensive studies have been performed based on the pseudo-potential well (PW) model. For instance, the |Δβ| at ε = 0.1 and ε = -0.1 were found to be different, but they were the same in the PW model. This is the first time the nonlinear effects regarding Δ(C(2n)/C0) (n ≠ 0) are studied, and the associated study has been a challenge for both theoretical and numerical methods. The nonlinear effects of Δ(C(2n)/C0) (n ≠ 0) and Δβ were found to share some similarities at q < 0.6: both of them were proportional to ε, and the square of the initial ion displacement, z(0)(2). PMID:25924875
NASA Astrophysics Data System (ADS)
Laachi, Nabil; Iwama, Tatsuhiro; Delaney, Kris T.; Kim, Bongkeun; Bristol, Robert; Shykind, David; Weinheimer, Corey J.; Fredrickson, Glenn H.
2014-03-01
We have investigated the directed self-assembly (DSA) of cylinder-forming block copolymers inside cylindrical guiding templates. To complement and corroborate our experimental study, we use field-theoretic simulations to examine the fluctuations-induced variations in the size and position of the cylindrical microdomain that forms in the middle of the guiding hole. Our study goes beyond the usual mean-field approximation and self-consistent field theory simulations (SCFT) and incorporates the effects of thermal fluctuations in the description of the self-assembly process using complex Langevin (CL) dynamics. In both our experimental and modeling efforts, we focus on minor-block-attractive sidewalls and bottom substrates and neutral top surfaces and explore the properties of the formed cylinders, including fluctuations in the center position and the size of the domain, for various prepattern conditions. Our results indicate robust critical dimensions (CD) of the DSA cylinders relative to the incoming CD, with a sigma CD < 0.9nm. Likewise, we find that the DSA cylinders are accurately registered in the center of the guiding hole, with deviations in the hole-inhole distance on the order of ≍ 0.7-1nm, translating to errors in the hole-to-hole distance of ≍ 1-1.5nm.
NASA Astrophysics Data System (ADS)
Weber, Jeffrey K.; Pande, Vijay S.
2013-09-01
The protein folding problem has long represented a "holy grail" in statistical physics due to its physical complexity and its relevance to many human diseases. While past theoretical work has yielded apt descriptions of protein folding landscapes, recent large-scale simulations have provided insights into protein folding that were impractical to obtain from early theories. In particular, the role that non-native contacts play in protein folding, and their relation to the existence of misfolded, β-sheet rich trap states on folding landscapes, has emerged as a topic of interest in the field. In this paper, we present a modified model of heteropolymer freezing that includes explicit secondary structural characteristics which allow observations of "intramolecular amyloid" states to be probed from a theoretical perspective. We introduce a variable persistence length-based energy penalty to a model Hamiltonian, and we illustrate how this modification alters the phase transitions present in the theory. We find, in particular, that inclusion of this variable persistence length increases both generic freezing and folding temperatures in the model, allowing both folding and glass transitions to occur in a more highly optimized fashion. We go on to discuss how these changes might relate to protein evolution, misfolding, and the emergence of intramolecular amyloid states.
Sebai, Jihane
2016-01-01
Various organizational, functional or structural issues have led to a review of the foundations of the former health care system based on a traditional market segmentation between general practice and hospital medicine, and between health and social sectors and marked by competition between private and public sectors. The current reconfiguration of the health care system has resulted in “new” levers explained by the development of a new organizational reconfiguration of the primary health care model. Coordinated care structures (SSC) have been developed in this context by making coordination the cornerstone of relations between professionals to ensure global, continuous and quality health care. This article highlights the contributions of various theoretical approaches to the understanding of the concept of coordination in the analysis of the current specificity of health care. PMID:27392057
NASA Astrophysics Data System (ADS)
Harada, Naoki; Sato, Shintaro; Yokoyama, Naoki
2013-09-01
Nanometer-scale, single-gate graphene nanoribbon Schottky barrier field-effect transistors (FETs) were theoretically investigated using self-consistent atomistic simulation. The device geometry was determined by referring to the International Technology Roadmap for Semiconductors. The target performance levels were the requirements specified in the roadmap for 2024, particularly a maximum leakage current of 0.1 A/m, an on-current of 2017 A/m, and a delay time of 0.13 ps. The device conditions needed to meet these requirements were found to be a bandgap larger than 1.1 eV, a supply voltage of 0.6 V, and a gate length of 7 nm.
Constraints on field theoretical models for variation of the fine structure constant
NASA Astrophysics Data System (ADS)
Steinhardt, Charles L.
2005-02-01
Recent theoretical ideas and observational claims suggest that the fine structure constant α may be variable. We examine a spectrum of models in which α is a function of a scalar field. Specifically, we consider three scenarios: oscillating α, monotonic time variation of α, and time-independent α that is spatially varying. We examine the constraints imposed upon these theories by cosmological observations, particle detector experiments, and “fifth force” experiments. These constraints are very strong on models involving oscillation but cannot compete with bounds from the Oklo subnuclear reactor on models with monotonic timelike variation of α. One particular model with spatial variation is consistent with all current experimental and observational measurements, including those from two seemingly conflicting measurements of the fine structure constant using the many multiplet method on absorption lines.
Calculation of membrane bending rigidity using field-theoretic umbrella sampling.
Smirnova, Y G; Müller, M
2015-12-28
The free-energy change of membrane shape transformations can be small, e.g., as in the case of membrane bending. Therefore, the calculation of the free-energy difference between different membrane morphologies is a challenge. Here, we discuss a computational method - field-theoretic umbrella sampling - to compute the local chemical potential of a non-equilibrium configuration and illustrate how one can apply it to study free-energy changes of membrane transformations using simulations. Specifically, the chemical potential profile of the bent membrane and the bending rigidity of membrane are calculated for a soft, coarse-grained amphiphile model and the MARTINI model of a dioleoylphosphatidylcholine (DOPC) membrane. PMID:26723640
Model-free information-theoretic approach to infer leadership in pairs of zebrafish.
Butail, Sachit; Mwaffo, Violet; Porfiri, Maurizio
2016-04-01
Collective behavior affords several advantages to fish in avoiding predators, foraging, mating, and swimming. Although fish schools have been traditionally considered egalitarian superorganisms, a number of empirical observations suggest the emergence of leadership in gregarious groups. Detecting and classifying leader-follower relationships is central to elucidate the behavioral and physiological causes of leadership and understand its consequences. Here, we demonstrate an information-theoretic approach to infer leadership from positional data of fish swimming. In this framework, we measure social interactions between fish pairs through the mathematical construct of transfer entropy, which quantifies the predictive power of a time series to anticipate another, possibly coupled, time series. We focus on the zebrafish model organism, which is rapidly emerging as a species of choice in preclinical research for its genetic similarity to humans and reduced neurobiological complexity with respect to mammals. To overcome experimental confounds and generate test data sets on which we can thoroughly assess our approach, we adapt and calibrate a data-driven stochastic model of zebrafish motion for the simulation of a coupled dynamical system of zebrafish pairs. In this synthetic data set, the extent and direction of the coupling between the fish are systematically varied across a wide parameter range to demonstrate the accuracy and reliability of transfer entropy in inferring leadership. Our approach is expected to aid in the analysis of collective behavior, providing a data-driven perspective to understand social interactions. PMID:27176333
Model-free information-theoretic approach to infer leadership in pairs of zebrafish
NASA Astrophysics Data System (ADS)
Butail, Sachit; Mwaffo, Violet; Porfiri, Maurizio
2016-04-01
Collective behavior affords several advantages to fish in avoiding predators, foraging, mating, and swimming. Although fish schools have been traditionally considered egalitarian superorganisms, a number of empirical observations suggest the emergence of leadership in gregarious groups. Detecting and classifying leader-follower relationships is central to elucidate the behavioral and physiological causes of leadership and understand its consequences. Here, we demonstrate an information-theoretic approach to infer leadership from positional data of fish swimming. In this framework, we measure social interactions between fish pairs through the mathematical construct of transfer entropy, which quantifies the predictive power of a time series to anticipate another, possibly coupled, time series. We focus on the zebrafish model organism, which is rapidly emerging as a species of choice in preclinical research for its genetic similarity to humans and reduced neurobiological complexity with respect to mammals. To overcome experimental confounds and generate test data sets on which we can thoroughly assess our approach, we adapt and calibrate a data-driven stochastic model of zebrafish motion for the simulation of a coupled dynamical system of zebrafish pairs. In this synthetic data set, the extent and direction of the coupling between the fish are systematically varied across a wide parameter range to demonstrate the accuracy and reliability of transfer entropy in inferring leadership. Our approach is expected to aid in the analysis of collective behavior, providing a data-driven perspective to understand social interactions.
A Graph-Theoretical Approach for Tracing Filamentary Structures in Neuronal and Retinal Images.
De, Jaydeep; Cheng, Li; Zhang, Xiaowei; Lin, Feng; Li, Huiqi; Ong, Kok Haur; Yu, Weimiao; Yu, Yuanhong; Ahmed, Sohail
2016-01-01
The aim of this study is about tracing filamentary structures in both neuronal and retinal images. It is often crucial to identify single neurons in neuronal networks, or separate vessel tree structures in retinal blood vessel networks, in applications such as drug screening for neurological disorders or computer-aided diagnosis of diabetic retinopathy. Both tasks are challenging as the same bottleneck issue of filament crossovers is commonly encountered, which essentially hinders the ability of existing systems to conduct large-scale drug screening or practical clinical usage. To address the filament crossovers' problem, a two-step graph-theoretical approach is proposed in this paper. The first step focuses on segmenting filamentary pixels out of the background. This produces a filament segmentation map used as input for the second step, where they are further separated into disjointed filaments. Key to our approach is the idea that the problem can be reformulated as label propagation over directed graphs, such that the graph is to be partitioned into disjoint sub-graphs, or equivalently, each of the neurons (vessel trees) is separated from the rest of the neuronal (vessel) network. This enables us to make the interesting connection between the tracing problem and the digraph matrix-forest theorem in algebraic graph theory for the first time. Empirical experiments on neuronal and retinal image datasets demonstrate the superior performance of our approach over existing methods. PMID:26316029
NASA Astrophysics Data System (ADS)
Joyce, Arthur A.; Goman, Michelle
2012-11-01
In this article we discuss two theoretical approaches to landscape studies in archaeology: the ecological and social/symbolic. We suggest that an integrated approach can provide a more effective means through which archaeologists and earth scientists can model the complex interplay between people and the environment. Our perspective views peoples' engagements with the landscape as simultaneously ecological and social, material and symbolic. To illustrate this synthetic approach we discuss our research from the highland and lowland regions of the Mexican state of Oaxaca using archaeological, ethnographic, ethnohistorical, paleoecological, and geomorphological data. In highland Oaxaca we examine the ways in which political and religious principles were embedded in the landscape as well as the social, symbolic, and material dimensions of anthropogenic landscape change during the Formative period. For the coastal lowlands, we discuss the social and ecological implications of the transition to sedentism and the effects of anthropogenic landscape change during the Formative period. We also examine the interplay between politics and land use during the Classic and Postclassic periods.
Pant, Sanjay; Lombardi, Damiano
2015-10-01
A new approach for assessing parameter identifiability of dynamical systems in a Bayesian setting is presented. The concept of Shannon entropy is employed to measure the inherent uncertainty in the parameters. The expected reduction in this uncertainty is seen as the amount of information one expects to gain about the parameters due to the availability of noisy measurements of the dynamical system. Such expected information gain is interpreted in terms of the variance of a hypothetical measurement device that can measure the parameters directly, and is related to practical identifiability of the parameters. If the individual parameters are unidentifiable, correlation between parameter combinations is assessed through conditional mutual information to determine which sets of parameters can be identified together. The information theoretic quantities of entropy and information are evaluated numerically through a combination of Monte Carlo and k-nearest neighbour methods in a non-parametric fashion. Unlike many methods to evaluate identifiability proposed in the literature, the proposed approach takes the measurement-noise into account and is not restricted to any particular noise-structure. Whilst computationally intensive for large dynamical systems, it is easily parallelisable and is non-intrusive as it does not necessitate re-writing of the numerical solvers of the dynamical system. The application of such an approach is presented for a variety of dynamical systems--ranging from systems governed by ordinary differential equations to partial differential equations--and, where possible, validated against results previously published in the literature. PMID:26292167
Evolutionary Game Theoretic Approach to Self-Organized Data Aggregation in Delay Tolerant Networks
NASA Astrophysics Data System (ADS)
Kabir, K. Habibul; Sasabe, Masahiro; Takine, Tetsuya
Custody transfer in delay tolerant networks (DTNs) provides reliable end-to-end data delivery by delegating the responsibility of data transfer among special nodes (custodians) in a hop-by-hop manner. However, storage congestion occurs when data increases and/or the network is partitioned into multiple sub-networks for a long time. The storage congestion can be alleviated by message ferries which move around the network and proactively collect data from the custodians. In such a scenario, data should be aggregated to some custodians so that message ferries can collect them effectively. In this paper, we propose a scheme to aggregate data into selected custodians, called aggregators, in a fully distributed and autonomous manner with the help of evolutionary game theoretic approach. Through theoretical analysis and several simulation experiments, taking account of the uncooperative behavior of nodes, we show that aggregators can be selected in a self-organized manner and the number of aggregators can be controlled to a desired value.
NASA Astrophysics Data System (ADS)
Galiana-Merino, J. J.; Rosa-Cintas, S.; Rosa-Herranz, J.; Garrido, J.; Peláez, J. A.; Martino, S.; Delgado, J.
2016-05-01
Array measurements of ambient noise have become a useful technique to estimate the surface wave dispersion curves and subsequently the subsurface elastic parameters that characterize the studied soil. One of the logistical handicaps associated with this kind of measurements is the requirement of several stations recording at the same time, which limits their applicability in the case of research groups without enough infrastructure resources. In this paper, we describe the theoretical basis of the ESAC method and we deduce how the number of stations needed to implement any array layout can be reduced to only two stations. In this way, we propose a new methodology to implement an N stations array layout by using only M stations (M < N), which will be recording in different positions of the original prearranged N stations geometry at different times. We also provide some practical guidelines to implement the proposed approach and we show different examples where the obtained results confirm the theoretical foundations. Thus, the study carried out reflects that we can use a minimum of 2 stations to deploy any array layout originally designed for higher number of sensors.
Suno, Hiroya
2011-10-01
We study theoretically the ground and excited bound states of the bosonic rare gas van der Waals trimer Ne(3). A slow variable discretization approach is adopted to solve the nuclear Schrödinger equation, in which the Schrödinger equation in hyperangular coordinates is solved using basis splines at a series of fixed finite-element methods discrete variable representation hyper-radii. We consider not only zero total nuclear orbital angular momentum, J = 0, states but also J > 0 states. By using the best empirical neon dimer interaction potentials, all the bound state energy levels of Ne(3) will be calculated for total angular momenta up to J = 6, as well as their average root-mean-square radii. We also analyze the wave functions in hyperspherical coordinates for several selected bound states. PMID:21992310
A Game-Theoretic Approach to Branching Time Abstract-Check-Refine Process
NASA Technical Reports Server (NTRS)
Wang, Yi; Tamai, Tetsuo
2009-01-01
Since the complexity of software systems continues to grow, most engineers face two serious problems: the state space explosion problem and the problem of how to debug systems. In this paper, we propose a game-theoretic approach to full branching time model checking on three-valued semantics. The three-valued models and logics provide successful abstraction that overcomes the state space explosion problem. The game style model checking that generates counter-examples can guide refinement or identify validated formulas, which solves the system debugging problem. Furthermore, output of our game style method will give significant information to engineers in detecting where errors have occurred and what the causes of the errors are.
Understanding Confounding Effects in Linguistic Coordination: An Information-Theoretic Approach
Gao, Shuyang; Ver Steeg, Greg; Galstyan, Aram
2015-01-01
We suggest an information-theoretic approach for measuring stylistic coordination in dialogues. The proposed measure has a simple predictive interpretation and can account for various confounding factors through proper conditioning. We revisit some of the previous studies that reported strong signatures of stylistic accommodation, and find that a significant part of the observed coordination can be attributed to a simple confounding effect—length coordination. Specifically, longer utterances tend to be followed by longer responses, which gives rise to spurious correlations in the other stylistic features. We propose a test to distinguish correlations in length due to contextual factors (topic of conversation, user verbosity, etc.) and turn-by-turn coordination. We also suggest a test to identify whether stylistic coordination persists even after accounting for length coordination and contextual factors. PMID:26115446
Information-Theoretic Approaches for Evaluating Complex Adaptive Social Simulation Systems
Omitaomu, Olufemi A; Ganguly, Auroop R; Jiao, Yu
2009-01-01
In this paper, we propose information-theoretic approaches for comparing and evaluating complex agent-based models. In information theoretic terms, entropy and mutual information are two measures of system complexity. We used entropy as a measure of the regularity of the number of agents in a social class; and mutual information as a measure of information shared by two social classes. Using our approaches, we compared two analogous agent-based (AB) models developed for regional-scale social-simulation system. The first AB model, called ABM-1, is a complex AB built with 10,000 agents on a desktop environment and used aggregate data; the second AB model, ABM-2, was built with 31 million agents on a highperformance computing framework located at Oak Ridge National Laboratory, and fine-resolution data from the LandScan Global Population Database. The initializations were slightly different, with ABM-1 using samples from a probability distribution and ABM-2 using polling data from Gallop for a deterministic initialization. The geographical and temporal domain was present-day Afghanistan, and the end result was the number of agents with one of three behavioral modes (proinsurgent, neutral, and pro-government) corresponding to the population mindshare. The theories embedded in each model were identical, and the test simulations focused on a test of three leadership theories - legitimacy, coercion, and representative, and two social mobilization theories - social influence and repression. The theories are tied together using the Cobb-Douglas utility function. Based on our results, the hypothesis that performance measures can be developed to compare and contrast AB models appears to be supported. Furthermore, we observed significant bias in the two models. Even so, further tests and investigations are required not only with a wider class of theories and AB models, but also with additional observed or simulated data and more comprehensive performance measures.
Field theoretic treatment of an effective action for a model of catalyzed autoamplification
NASA Astrophysics Data System (ADS)
Tchernookov, Martin; Warmflash, Aryeh; Dinner, Aaron R.
2010-01-01
Reaction-diffusion models can exhibit continuous phase transitions in behaviors, and their dynamics at criticality often exhibit scalings with key parameters that can be characterized by exponents. While models with only a single field that transitions between absorbing and nonabsorbing states are well characterized and typically fall in the directed percolation universality class, the effects of coupling multiple fields remain poorly understood. We recently introduced a model which has three fields: one of which relaxes exponentially, one of which displays critical behavior, and one of which has purely diffusive dynamics but exerts an influence on the critical field [Tchernookov , J. Chem. Phys. 130, 134906 (2009)]. Simulations suggested that this model is in a universality class distinct from other reaction-diffusion systems studied previously. Although the three fields give rise to interesting physics, they complicate analysis of the model with renormalization-group methods. Here, we show how to systematically simplify the action for this model such that analytical expressions for the exponents of this universality class can be obtained by standard means. We expect the approach taken here to be of general applicability in reaction-diffusion systems with coupled order parameters that display qualitatively different behaviors close to criticality.
Field theoretic treatment of an effective action for a model of catalyzed autoamplification.
Tchernookov, Martin; Warmflash, Aryeh; Dinner, Aaron R
2010-01-01
Reaction-diffusion models can exhibit continuous phase transitions in behaviors, and their dynamics at criticality often exhibit scalings with key parameters that can be characterized by exponents. While models with only a single field that transitions between absorbing and nonabsorbing states are well characterized and typically fall in the directed percolation universality class, the effects of coupling multiple fields remain poorly understood. We recently introduced a model which has three fields: one of which relaxes exponentially, one of which displays critical behavior, and one of which has purely diffusive dynamics but exerts an influence on the critical field [Tchernookov, J. Chem. Phys. 130, 134906 (2009)]. Simulations suggested that this model is in a universality class distinct from other reaction-diffusion systems studied previously. Although the three fields give rise to interesting physics, they complicate analysis of the model with renormalization-group methods. Here, we show how to systematically simplify the action for this model such that analytical expressions for the exponents of this universality class can be obtained by standard means. We expect the approach taken here to be of general applicability in reaction-diffusion systems with coupled order parameters that display qualitatively different behaviors close to criticality. PMID:20365328
Comparison of GOCE-GPS gravity fields derived by different approaches
NASA Astrophysics Data System (ADS)
Baur, O.; Bock, H.; Höck, E.; Jäggi, A.; Krauss, S.; Mayer-Gürr, T.; Reubelt, T.; Siemes, C.; Zehentner, N.
2014-10-01
Several techniques have been proposed to exploit GNSS-derived kinematic orbit information for the determination of long-wavelength gravity field features. These methods include the (i) celestial mechanics approach, (ii) short-arc approach, (iii) point-wise acceleration approach, (iv) averaged acceleration approach, and (v) energy balance approach. Although there is a general consensus that—except for energy balance—these methods theoretically provide equivalent results, real data gravity field solutions from kinematic orbit analysis have never been evaluated against each other within a consistent data processing environment. This contribution strives to close this gap. Target consistency criteria for our study are the input data sets, period of investigation, spherical harmonic resolution, a priori gravity field information, etc. We compare GOCE gravity field estimates based on the aforementioned approaches as computed at the Graz University of Technology, the University of Bern, the University of Stuttgart/Austrian Academy of Sciences, and by RHEA Systems for the European Space Agency. The involved research groups complied with most of the consistency criterions. Deviations only occur where technical unfeasibility exists. Performance measures include formal errors, differences with respect to a state-of-the-art GRACE gravity field, (cumulative) geoid height differences, and SLR residuals from precise orbit determination of geodetic satellites. We found that for the approaches (i) to (iv), the cumulative geoid height differences at spherical harmonic degree 100 differ by only ; in the absence of the polar data gap, SLR residuals agree by . From our investigations, we conclude that real data analysis results are in agreement with the theoretical considerations concerning the (relative) performance of the different approaches.
Luan, Chongbiao; Lin, Zhaojun Zhao, Jingtao; Wang, Yutang; Lv, Yuanjie; Chen, Hong; Wang, Zhanguo
2014-07-28
The theoretical model of the polarization Coulomb field scattering (PCF) caused by the polarization charge density variation at the AlGaN/AlN interface in strained AlGaN/AlN/GaN heterostructure field-effect transistors has been developed. And the theoretical values for the electron drift mobility, which were calculated using the Matthiessen's rule that includes PCF, piezoelectric scattering, polar optical-phonon scattering, and interface roughness scattering, are in good agreement with our experimental values. Therefore, the theoretical model for PCF has been confirmed.
Logarithmic conformal field theory: a lattice approach
NASA Astrophysics Data System (ADS)
Gainutdinov, A. M.; Jacobsen, J. L.; Read, N.; Saleur, H.; Vasseur, R.
2013-12-01
Logarithmic conformal field theories (LCFT) play a key role, for instance, in the description of critical geometrical problems (percolation, self-avoiding walks, etc), or of critical points in several classes of disordered systems (transition between plateaux in the integer and spin quantum Hall effects). Much progress in their understanding has been obtained by studying algebraic features of their lattice regularizations. For reasons which are not entirely understood, the non-semi-simple associative algebras underlying these lattice models—such as the Temperley-Lieb algebra or the blob algebra—indeed exhibit, in finite size, properties that are in full correspondence with those of their continuum limits. This applies not only to the structure of indecomposable modules, but also to fusion rules, and provides an ‘experimental’ way of measuring couplings, such as the ‘number b’ quantifying the logarithmic coupling of the stress-energy tensor with its partner. Most results obtained so far have concerned boundary LCFTs and the associated indecomposability in the chiral sector. While the bulk case is considerably more involved (mixing in general left and right moving sectors), progress has also recently been made in this direction, uncovering fascinating structures. This study provides a short general review of our work in this area.
Nonsmooth optimization approaches to VDA of models with on/off parameterizations: Theoretical issues
NASA Astrophysics Data System (ADS)
Jiang, Zhu; Kamachi, Masafumi; Guangqing, Zhou
2002-05-01
Some variational data assimilation problems of time-and space-discrete models with on/ off parameterizations can be regarded as nonsmooth optimization problems. Some theoretical issues related to those problems is systematically addressed. One of the basic concept in nonsmooth optimization is subgradient, a generalized notation of a gradient of the cost function. First it is shown that the concept of subgradient leads to a clear definition of the adjoint variables in the conventional adjoint model at singular points caused by on/ off switches. Using an illustrated example of a multi-layer diffusion model with the convective adjustment, it is proved that the solution of the conventional adjoint model can not be inter-preted as Gateaux derivatives or directional derivatives, at singular points, but can be interpreted as a subgradient of the cost function. Two existing smooth optimization approaches are then reviewed which are used in current data assimi-lation practice. The first approach is the conventional adjoint model plus smooth optimization algorithms. Some conditions under which the approach can converge to the minimal are discussed. Another approach is smoothing and regularization approach, which removes some thresholds in physical parameterizations. Two nonsmooth optimization approaches are also reviewed. One is the subgradient method, which uses the conventional adjoint model. The method is convergent, but very slow. Another approach, the bundle methods are more efficient. The main idea of the bundle method is to use the minimal norm vector of subdifferential, which is the convex hull of all subgradients, as the descent director. However finding all subgradients is very difficult in general. Therefore bundle methods are modified to use only one subgradient that can be calculated by the conventional adjoint model. In order to develop an efficient bundle method, a set-valued adjoint model, as a generalization of the conventional adjoint model, is proposed. It
Theoretical investigation of alignment-dependent intense-field fragmentation of acetylene
NASA Astrophysics Data System (ADS)
Doblhoff-Dier, Katharina; Kitzler, Markus; Gräfe, Stefanie
2016-07-01
We analyze the alignment-dependent dissociative and nondissociative ionization of acetylene, C2H2 . Numerical models describing the yield of the singly and doubly charged ions (C2H2+,C2H22 +) and several fragmentation and isomerization channels (C2H++H+ ,CH++CH+ ,CH2++C+ ) as a function of the relative alignment angle between the laser polarization axis and the molecular axis are presented. We apply and compare two different approaches. The first is based on time-dependent density functional theory. The second is a quasi-single-particle approach using the Dyson orbitals. We find good agreement between the results of both methods. A comparison of our theoretical predictions with experimental data allows us to show that the alignment-dependent yield of most reaction channels is described to high accuracy assuming sequential ionization. However, for some of the fragmentation channels, namely, CH++CH+ and C2H++H+ , we find non-negligible influence of recollisional ionization.
MAGNETARS VERSUS HIGH MAGNETIC FIELD PULSARS: A THEORETICAL INTERPRETATION OF THE APPARENT DICHOTOMY
Pons, Jose A.; Perna, Rosalba
2011-11-10
Highly magnetized neutron stars (NSs) are characterized by a bewildering range of astrophysical manifestations. Here, building on our simulations of the evolution of magnetic stresses in the NS crust and its ensuing fractures, we explore in detail, for the middle-aged and old NSs, the dependence of starquake frequency and energetics on the relative strength of the poloidal (B{sub p}) and toroidal (B{sub tor}) components. We find that, for B{sub p} {approx}> 10{sup 14} G, since a strong crustal toroidal field B{sub tor} {approx} B{sub p} is quickly formed on a Hall timescale, the initial toroidal field needs to be B{sub tor} >> B{sub p} to have a clear influence on the outbursting behavior. For initial fields B{sub p} {approx}< 10{sup 14} G, it is very unlikely that a middle-aged (t {approx} 10{sup 5} years) NS shows any bursting activity. This study allows us to solve the apparent puzzle of how NSs with similar dipolar magnetic fields can behave in a remarkably different way: an outbursting 'magnetar' with a high X-ray luminosity, or a quiet, low-luminosity, 'high-B' radio pulsar. As an example, we consider the specific cases of the magnetar 1E 2259+586 and the radio pulsar PSR J1814-1744, which at present have a similar dipolar field {approx}6 Multiplication-Sign 10{sup 13} G. We determine for each object an initial magnetic field configuration that reproduces the observed timing parameters at their current age. The same two configurations also account for the differences in quiescent X-ray luminosity and for the 'magnetar/outbursting' behavior of 1E 2259+586 but not of PSR J1814-1744. We further use the theoretically predicted surface temperature distribution to compute the light curve for these objects. In the case of 1E 2259+586, for which data are available, our predicted temperature distribution gives rise to a pulse profile whose double-peaked nature and modulation level are consistent with the observations.
Gelo, Omar Carlo Gioacchino; Salvatore, Sergio
2016-07-01
Notwithstanding the many methodological advances made in the field of psychotherapy research, at present a metatheoretical, school-independent framework to explain psychotherapy change processes taking into account their dynamic and complex nature is still lacking. Over the last years, several authors have suggested that a dynamic systems (DS) approach might provide such a framework. In the present paper, we review the main characteristics of a DS approach to psychotherapy. After an overview of the general principles of the DS approach, we describe the extent to which psychotherapy can be considered as a self-organizing open complex system, whose developmental change processes are described in terms of a dialectic dynamics between stability and change over time. Empirical evidence in support of this conceptualization is provided and discussed. Finally, we propose a research design strategy for the empirical investigation of psychotherapy from a DS approach, together with a research case example. We conclude that a DS approach may provide a metatheoretical, school-independent framework allowing us to constructively rethink and enhance the way we conceptualize and empirically investigate psychotherapy. (PsycINFO Database Record PMID:27177027
Ultrafast dynamics of finite Hubbard clusters: A stochastic mean-field approach
NASA Astrophysics Data System (ADS)
Lacroix, Denis; Hermanns, S.; Hinz, C. M.; Bonitz, M.
2014-09-01
Finite lattice models are a prototype for interacting quantum systems and capture essential properties of condensed matter systems. With the dramatic progress in ultracold atoms in optical lattices, finite fermionic Hubbard systems have become directly accessible in experiments, including their ultrafast dynamics far from equilibrium. Here, we present a theoretical approach that is able to treat these dynamics in any dimension and fully includes inhomogeneity effects. The method consists in stochastic sampling of mean-field trajectories and is—for not too large two-body interaction strength—found to be much more accurate than time-dependent mean-field at the same order of numerical costs. Furthermore, it can well compete with recent nonequilibrium Green function approaches using second-order Born approximation, which are of substantially larger complexity. The performance of the stochastic mean-field approach is demonstrated for Hubbard clusters with up to 512 particles in one, two, and three dimensions.
An effectiveness analysis of healthcare systems using a systems theoretic approach
Chuang, Sheuwen; Inder, Kerry
2009-01-01
provides a systematic search for improving the impact of accreditation on quality of care and hence on the accreditation/performance correlation. Conclusion There is clear value in developing a theoretical systems approach to achieving quality in health care. The introduction of the systematic surveyor-based search for improvements creates an adaptive-control system to optimize health care quality. It is hoped that these outcomes will stimulate further research in the development of strategic planning using systems theoretic approach for the improvement of quality in health care. PMID:19852837
A theoretical study of the feasibility of acoustical tweezer: Ray acoustics approach
NASA Astrophysics Data System (ADS)
Lee, Jungwoo; Shung, Kirk
2005-04-01
Optical tweezer has been found to have many biomedical applications in trapping macromolecules and cells. For the trapping mechanism, there has to be a sharp spatial change in axial optical intensity and the particle size must be much greater than the wavelength. Similar phenomenon may exist in acoustics. This work was undertaken to demonstrate theoretically that it is possible to acoustically trap particles near the focal point if certain conditions are met. Acoustic force exerted on fat tissue in ultrasonic fields is analyzed in ray acoustics regime where the wavelength of acoustic beam is much smaller than the size of the particle. In this paper, the analysis is therefore based on the field pattern produced by a strongly focused 100 MHz ultrasonic transducer with Gaussian intensity distribution. The magnitude of force and Fresnel coefficients at various positions are calculated. According to the simulation results, acoustical tweezer works particularly when the beam width at focus is one wavelength and the tolerance of acoustic impedance mismatch between two media lies within 6.7%. [Work supported by NIH Grant P41-EB2182.
Effective field theory: A modern approach to anomalous couplings
Degrande, Céline; Centre for Particle Physics and Phenomenology , Université Catholique de Louvain, Chemin du Cyclotron 2, B-1348 Louvain-la-Neuve ; Greiner, Nicolas; Max-Planck-Institut für Physik, Föhringer Ring 6, 80805 München ; Kilian, Wolfgang; University of Siegen, Fachbereich Physik, D-57068 Siegen ; Mattelaer, Olivier; Mebane, Harrison; Stelzer, Tim; Willenbrock, Scott; Zhang, Cen; Centre for Particle Physics and Phenomenology , Université Catholique de Louvain, Chemin du Cyclotron 2, B-1348 Louvain-la-Neuve
2013-08-15
We advocate an effective field theory approach to anomalous couplings. The effective field theory approach is the natural way to extend the standard model such that the gauge symmetries are respected. It is general enough to capture any physics beyond the standard model, yet also provides guidance as to the most likely place to see the effects of new physics. The effective field theory approach also clarifies that one need not be concerned with the violation of unitarity in scattering processes at high energy. We apply these ideas to pair production of electroweak vector bosons. -- Highlights: •We discuss the advantages of effective field theories compared to anomalous couplings. •We show that one need not be concerned with unitarity violation at high energy. •We discuss the application of effective field theory to weak boson physics.
Cell death following BNCT: a theoretical approach based on Monte Carlo simulations.
Ballarini, F; Bakeine, J; Bortolussi, S; Bruschi, P; Cansolino, L; Clerici, A M; Ferrari, C; Protti, N; Stella, S; Zonta, A; Zonta, C; Altieri, S
2011-12-01
In parallel to boron measurements and animal studies, investigations on radiation-induced cell death are also in progress in Pavia, with the aim of better characterisation of the effects of a BNCT treatment down to the cellular level. Such studies are being carried out not only experimentally but also theoretically, based on a mechanistic model and a Monte Carlo code. Such model assumes that: (1) only clustered DNA strand breaks can lead to chromosome aberrations; (2) only chromosome fragments within a certain threshold distance can undergo misrejoining; (3) the so-called "lethal aberrations" (dicentrics, rings and large deletions) lead to cell death. After applying the model to normal cells exposed to monochromatic fields of different radiation types, the irradiation section of the code was purposely extended to mimic the cell exposure to a mixed radiation field produced by the (10)B(n,α) (7)Li reaction, which gives rise to alpha particles and Li ions of short range and high biological effectiveness, and by the (14)N(n,p)(14)C reaction, which produces 0.58 MeV protons. Very good agreement between model predictions and literature data was found for human and animal cells exposed to X- or gamma-rays, protons and alpha particles, thus allowing to validate the model for cell death induced by monochromatic radiation fields. The model predictions showed good agreement also with experimental data obtained by our group exposing DHD cells to thermal neutrons in the TRIGA Mark II reactor of the University of Pavia; this allowed to validate the model also for a BNCT exposure scenario, providing a useful predictive tool to bridge the gap between irradiation and cell death. PMID:21481595
The Electromagnetic Dipole Radiation Field through the Hamiltonian Approach
ERIC Educational Resources Information Center
Likar, A.; Razpet, N.
2009-01-01
The dipole radiation from an oscillating charge is treated using the Hamiltonian approach to electrodynamics where the concept of cavity modes plays a central role. We show that the calculation of the radiation field can be obtained in a closed form within this approach by emphasizing the role of coherence between the cavity modes, which is…
Approach to non-equilibrium behaviour in quantum field theory
Kripfganz, J.; Perlt, H.
1989-05-01
We study the real-time evolution of quantum field theoretic systems in non-equilibrium situations. Results are presented for the example of scalar /lambda//phi//sup 4/ theory. The degrees of freedom are discretized by studying the system on a torus. Short-wavelength modes are integrated out to one-loop order. The long-wavelength modes considered to be the relevant degrees of freedom are treated by semiclassical phase-space methods. /copyright/ 1989 Academic Press, Inc.
GRAIL gravity field determination using the Celestial Mechanics Approach
NASA Astrophysics Data System (ADS)
Arnold, Daniel; Bertone, Stefano; Jäggi, Adrian; Beutler, Gerhard; Mervart, Leos
2015-11-01
The NASA mission GRAIL (Gravity Recovery and Interior Laboratory) inherited its concept from the GRACE (Gravity Recovery and Climate Experiment) mission to determine the gravity field of the Moon. We present lunar gravity fields based on the data of GRAIL's primary mission phase. Gravity field recovery is realized in the framework of the Celestial Mechanics Approach, using a development version of the Bernese GNSS Software along with Ka-band range-rate data series as observations and the GNI1B positions provided by NASA JPL as pseudo-observations. By comparing our results with the official level-2 GRAIL gravity field models we show that the lunar gravity field can be recovered with a high quality by adapting the Celestial Mechanics Approach, even when using pre-GRAIL gravity field models as a priori fields and when replacing sophisticated models of non-gravitational accelerations by appropriately spaced pseudo-stochastic pulses (i.e., instantaneous velocity changes). We present and evaluate two lunar gravity field solutions up to degree and order 200 - AIUB-GRL200A and AIUB-GRL200B. While the first solution uses no gravity field information beyond degree 200, the second is obtained by using the official GRAIL field GRGM900C up to degree and order 660 as a priori information. This reduces the omission errors and demonstrates the potential quality of our solution if we resolved the gravity field to higher degree.
Zlatar, Matija; Gruden, Maja; Vassilyeva, Olga Yu; Buvaylo, Elena A; Ponomarev, A N; Zvyagin, S A; Wosnitza, J; Krzystek, J; Garcia-Fernandez, Pablo; Duboc, Carole
2016-02-01
The aim of this work was to determine and understand the origin of the electronic properties of Mn(IV) complexes, especially the zero-field splitting (ZFS), through a combined experimental and theoretical investigation on five well-characterized mononuclear octahedral Mn(IV) compounds, with various coordination spheres (N6, N3O3, N2O4 in both trans (trans-N2O4) and cis configurations (cis-N2O4) and O4S2). High-frequency and -field EPR (HFEPR) spectroscopy has been applied to determine the ZFS parameters of two of these compounds, MnL(trans-N2O4) and MnL(O4S2). While at X-band EPR, the axial-component of the ZFS tensor, D, was estimated to be +0.47 cm(-1) for MnL(O4S2), and a D-value of +2.289(5) cm(-1) was determined by HFEPR, which is the largest D-magnitude ever measured for a Mn(IV) complex. A moderate D value of -0.997(6) cm(-1) has been found for MnL(trans-N2O4). Quantum chemical calculations based on two theoretical frameworks (the Density Functional Theory based on a coupled perturbed approach (CP-DFT) and the hybrid Ligand-Field DFT (LF-DFT)) have been performed to define appropriate methodologies to calculate the ZFS tensor for Mn(IV) centers, to predict the orientation of the magnetic axes with respect to the molecular ones, and to define and quantify the physical origin of the different contributions to the ZFS. Except in the case of MnL(trans-N2O4), the experimental and calculated D values are in good agreement, and the sign of D is well predicted, LF-DFT being more satisfactory than CP-DFT. The calculations performed on MnL(cis-N2O4) are consistent with the orientation of the principal anisotropic axis determined by single-crystal EPR, validating the calculated ZFS tensor orientation. The different contributions to D were analyzed demonstrating that the d-d transitions mainly govern D in Mn(IV) ion. However, a deep analysis evidences that many factors enter into the game, explaining why no obvious magnetostructural correlations can be drawn in this
NASA Astrophysics Data System (ADS)
Stoisser, C. M.; Audebert, S.
2008-05-01
In order to describe the state-of-the-art on cracked rotor related problems, the current work presents the comprehensive theoretical, numerical and experimental approach adopted by EDF for crack detection in power plant rotating machinery. The work mainly focuses on the theoretical cracked beam model developed in the past years by S. Andrieux and C. Varé and associates both numerical and experimental aspects related to the crack detection problem in either turboset or turbo pump units. The theoretical part consists of the derivation of a lumped cracked beam model from the three-dimensional formulation of the general problem of elasticity with unilateral contact conditions on the crack lips, valid for any shape and number of cracks in the beam section and extended to cracks not located in a cross-section. This leads to the assessment of the cracked beam rigidity as a function of the rotation angle, in case of pure bending load or bending plus shear load. In this way the function can be implemented in a 1D rotordynamics code. An extension of the cracked beam model taking into account the torsion behaviour is also proposed. It is based on the assumption of full adherence between crack lips, when the crack closes, and on an incremental formulation of deformation energy. An experimental validation has been carried out using different cracked samples, both in static and dynamic configurations, considering one or three elliptic cracks in the same cross-section and helix-shaped cracks. Concerning the static configuration, a good agreement between numerical and experimental results is found. It is shown to be equal to 1% maximal gap of the beam deflection. Concerning the dynamical analysis, the main well-known indicator 2× rev. bending vibration component at half critical speed is approximated at maximum by 18% near the crack position. Our experiments also allowed for the observation of the bending and torsion resonance frequency shifts determined by the extra
NASA Astrophysics Data System (ADS)
Chanteur, Gerard
A multi-spacecraft mission with at least four spacecraft, like CLUSTER, MMS, or Cross-Scales, can determine the local geometry of the magnetic field lines when the size of the cluster of spacecraft is small enough compared to the gradient scale lengths of the magnetic field. Shen et al. (2003) and Runov et al. (2003 and 2005) used CLUSTER data to estimate the normal and the curvature of magnetic field lines in the terrestrial current sheet: the two groups used different approaches. Reciprocal vectors of the tetrahedron formed by four spacecraft are a powerful tool for estimating gradients of fields (Chanteur, 1998 and 2000). Considering a thick and planar current sheet model and making use of the statistical properties of the reciprocal vectors allows to discuss theoretically how physical and geometrical errors affect these estimations. References Chanteur, G., Spatial Interpolation for Four Spacecraft: Theory, in Analysis Methods for Multi-Spacecraft Data, ISSI SR-001, pp. 349-369, ESA Publications Division, 1998. Chanteur, G., Accuracy of field gradient estimations by Cluster: Explanation of its dependency upon elongation and planarity of the tetrahedron, pp. 265-268, ESA SP-449, 2000. Runov, A., Nakamura, R., Baumjohann, W., Treumann, R. A., Zhang, T. L., Volwerk, M., V¨r¨s, Z., Balogh, A., Glaßmeier, K.-H., Klecker, B., R‘eme, H., and Kistler, L., Current sheet oo structure near magnetic X-line observed by Cluster, Geophys. Res. Lett., 30, 33-1, 2003. Runov, A., Sergeev, V. A., Nakamura, R., Baumjohann, W., Apatenkov, S., Asano, Y., Takada, T., Volwerk, M.,V¨r¨s, Z., Zhang, T. L., Sauvaud, J.-A., R‘eme, H., and Balogh, A., Local oo structure of the magnetotail current sheet: 2001 Cluster observations, Ann. Geophys., 24, 247-262, 2006. Shen, C., Li, X., Dunlop, M., Liu, Z. X., Balogh, A., Baker, D. N., Hapgood, M., and Wang, X., Analyses on the geometrical structure of magnetic field in the current sheet based on cluster measurements, J. Geophys. Res
A game-theoretic approach for calibration of low-cost magnetometers under noise uncertainty
NASA Astrophysics Data System (ADS)
Siddharth, S.; Ali, A. S.; El-Sheimy, N.; Goodall, C. L.; Syed, Z. F.
2012-02-01
Pedestrian heading estimation is a fundamental challenge in Global Navigation Satellite System (GNSS)-denied environments. Additionally, the heading observability considerably degrades in low-speed mode of operation (e.g. walking), making this problem even more challenging. The goal of this work is to improve the heading solution when hand-held personal/portable devices, such as cell phones, are used for positioning and to improve the heading estimation in GNSS-denied signal environments. Most smart phones are now equipped with self-contained, low cost, small size and power-efficient sensors, such as magnetometers, gyroscopes and accelerometers. A magnetometer needs calibration before it can be properly employed for navigation purposes. Magnetometers play an important role in absolute heading estimation and are embedded in many smart phones. Before the users navigate with the phone, a calibration is invoked to ensure an improved signal quality. This signal is used later in the heading estimation. In most of the magnetometer-calibration approaches, the motion modes are seldom described to achieve a robust calibration. Also, suitable calibration approaches fail to discuss the stopping criteria for calibration. In this paper, the following three topics are discussed in detail that are important to achieve proper magnetometer-calibration results and in turn the most robust heading solution for the user while taking care of the device misalignment with respect to the user: (a) game-theoretic concepts to attain better filter parameter tuning and robustness in noise uncertainty, (b) best maneuvers with focus on 3D and 2D motion modes and related challenges and (c) investigation of the calibration termination criteria leveraging the calibration robustness and efficiency.
Network-Based Enriched Gene Subnetwork Identification: A Game-Theoretic Approach
Razi, Abolfazl; Afghah, Fatemeh; Singh, Salendra; Varadan, Vinay
2016-01-01
Identifying subsets of genes that jointly mediate cancer etiology, progression, or therapy response remains a challenging problem due to the complexity and heterogeneity in cancer biology, a problem further exacerbated by the relatively small number of cancer samples profiled as compared with the sheer number of potential molecular factors involved. Pure data-driven methods that merely rely on multiomics data have been successful in discovering potentially functional genes but suffer from high false-positive rates and tend to report subsets of genes whose biological interrelationships are unclear. Recently, integrative data-driven models have been developed to integrate multiomics data with signaling pathway networks in order to identify pathways associated with clinical or biological phenotypes. However, these approaches suffer from an important drawback of being restricted to previously discovered pathway structures and miss novel genomic interactions as well as potential crosstalk among the pathways. In this article, we propose a novel coalition-based game-theoretic approach to overcome the challenge of identifying biologically relevant gene subnetworks associated with disease phenotypes. The algorithm starts from a set of seed genes and traverses a protein–protein interaction network to identify modulated subnetworks. The optimal set of modulated subnetworks is identified using Shapley value that accounts for both individual and collective utility of the subnetwork of genes. The algorithm is applied to two illustrative applications, including the identification of subnetworks associated with (i) disease progression risk in response to platinum-based therapy in ovarian cancer and (ii) immune infiltration in triple-negative breast cancer. The results demonstrate an improved predictive power of the proposed method when compared with state-of-the-art feature selection methods, with the added advantage of identifying novel potentially functional gene subnetworks
A theoretical study of the feasibility of acoustical tweezers: Ray acoustics approach
NASA Astrophysics Data System (ADS)
Lee, Jungwoo; Ha, Kanglyeol; Shung, K. Kirk
2005-05-01
The optical tweezer has been found to have many biomedical applications in trapping macromolecules and cells. For the trapping mechanism, there has to be a sharp spatial change in axial optical intensity and the particle size must be much greater than the wavelength. Similar phenomenon may exist in acoustics. This work was undertaken to demonstrate theoretically that it is possible to acoustically trap particles near the focal point where most of the acoustic energy is concentrated if certain conditions are met. Acoustic force exerted on a fluid particle in ultrasonic fields is analyzed in a ray acoustics regime where the wavelength of acoustic beam is much smaller than the size of the particle. In order to apply the acoustical tweezer to manipulating macromolecules and cells whose size is in the order of a few microns or less, a prerequisite is that the ultrasound wavelength has to be much smaller than a few microns. In this paper, the analysis is therefore based on the field pattern produced by a strongly focused 100 MHz ultrasonic transducer with Gaussian intensity distribution. For the realization of acoustic trapping, negative axial radiation force has to be generated to pull a particle towards a focus. The fat particle considered for acoustic trapping in this paper has an acoustic impedance of 1.4 MRayls. The magnitude of the acoustic axial radiation force that has been calculated as the size of the fat particle is varied from 8λ to 14λ. In addition, both Fresnel coefficients at various positions are also calculated to assess the interaction of reflection and refraction and their relative contribution to the effect of the acoustical tweezer. The simulation results show that the feasibility of the acoustical tweezer depends on both the degree of acoustic impedance mismatch and the degree of focusing relative to the particle size. .
Strategic exploration of battery waste management: A game-theoretic approach.
Kaushal, Rajendra Kumar; Nema, Arvind K; Chaudhary, Jyoti
2015-07-01
Electronic waste or e-waste is the fastest growing stream of solid waste today. It contains both toxic substances as well as valuable resources. The present study uses a non-cooperative game-theoretic approach for efficient management of e-waste, particularly batteries that contribute a major portion of any e-waste stream and further analyses the economic consequences of recycling of these obsolete, discarded batteries. Results suggest that the recycler would prefer to collect the obsolete batteries directly from the consumer rather than from the manufacturer, only if, the incentive return to the consumer is less than 33.92% of the price of the battery, the recycling fee is less than 6.46% of the price of the battery, and the price of the recycled material is more than 31.08% of the price of the battery. The manufacturer's preferred choice of charging a green tax from the consumer can be fruitful for the battery recycling chain. PMID:26060193
NASA Astrophysics Data System (ADS)
Chen, Gang; Tian, Hua; Xie, Wei; Zhong, Wei
2013-09-01
Next-generation wireless networks will integrate multiple wireless access technologies and the users will access the network using one of several available radio access technologies. In this paper, we study the spectrum access problem in heterogeneous multipleinput multiple-output (MIMO) networks through a game theoretic approach. The spectrum access problem in the considered system model is defined as joint network selection and discrete power control. We formulate the problem as a noncooperative game where the players are the multi-mode terminals and. The proposed common utility function takes both transmission rate and the power consumption into account. This game is shown to be a potential game which possess at least one pure strategy Nash equilibrium (NE) and the optimal strategy profile which maximizes the total energy efficiency of the heterogeneous MIMO network constitutes a pure strategy NE of our proposed game. Furthermore, we prove that the price of anarchy of the proposed game is equal to 1. In order to achieve the pure strategy NE, we design an iterative spectrum access algorithm. The convergence and the complexity of our designed algorithm is discussed. It is shown that the designed algorithm can achieve optimal performance with low complexity.
NASA Astrophysics Data System (ADS)
Schouten, Stefan; Middelburg, Jack J.; Hopmans, Ellen C.; Sinninghe Damsté, Jaap S.
2010-07-01
Intact polar membrane lipids (IPLs) are frequently used as markers for living microbial cells in sedimentary environments. The assumption with these studies is that IPLs are rapidly degraded upon cell lysis and therefore IPLs present in sediments are derived from in situ microbial production. We used a theoretical approach to assess whether IPLs in surface sediments can potentially represent fossilized IPLs derived from the upper part of the water column and whether IPLs can be preserved during sediment burial. Previous studies which examined the degradation kinetics of IPLs show that phospholipids, i.e. ester-linked lipids with a phosphor-containing head group, degrade more rapidly than glycosidic ether lipids, i.e. ether-linked lipids with a glycosidically bound sugar moiety. Based on these studies, we calculate that only a minor fraction of phospholipids but a major fraction of glycosidic ether lipids biosynthesized in the upper part of the water column can potentially reach deep-sea surface sediments. Using a simple model and power law kinetic degradation parameters reported in the literature, we also evaluated the degradation of IPLs during sediment burial. Our model predicts a log-log relationship between IPL concentrations and depth, consistent with what has been observed in studies of IPLs in subsurface sediments. Although our results do not exclude production of IPLs in subsurface sediment, they do suggest that IPLs present in the deep biosphere may contain a substantial fossil component potentially masking in situ IPL production.
New Insights on the Reaction Pathway Leading to Lactyl-ThDP: A Theoretical Approach.
Lizana, Ignacio; Jaña, Gonzalo A; Delgado, Eduardo J
2015-08-24
In all ThDP-dependent enzymes, the catalytic cycle is initiated with the attack of the C2 atom of the ylide intermediate on the Cα atom of a pyruvate molecule to form the lactyl-ThDP (L-ThDP) intermediate. In this study, the reaction between the ylide intermediate and pyruvate leading to the formation of L-ThDP is addressed from a theoretical point of view. The study includes molecular dynamics, exploration of the potential energy surface by means of QM/MM calculations, and reactivity analysis on key centers. The results show that the reaction occurs via a concerted mechanism in which the carboligation and the proton transfers occur synchronically. It is also observed that during the reaction the protonation state of the N1' atom changes: the reaction starts with the ylide having the N1' atom deprotonated and reaches a transition state showing the N1' atom protonated. This conversion leads to the reaction path of minimum energy, with an activation energy of about 20 kcal mol(-1). On the other hand, it is also observed that the approaching distance between the pyruvate and the ylide, i.e., the Cα-C2 distance, plays a fundamental role in the reaction mechanism since it determines the nucleophilic character of key atoms of the ylide, which in turn trigger the elemental reactions of the mechanism. PMID:26222831
NASA Astrophysics Data System (ADS)
Praveena, R.; Sadasivam, K.
2016-05-01
Synthetic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are found to be toxic, hence non-carcinogenic naturally occurring radical scavengers especially flavonoids have gained considerable importance in the past two decades. In the present investigation, the radical scavenging activity of C-glycosyl flavonoids is evaluated using theoretical approach which could broaden its scope in therapeutic applications. Gas and solvent phase studies of structural and molecular characteristics of C-glycosyl flavonoid, isovitexin is investigated through hydrogen atom transfer mechanism (HAT), Electron transfer-proton transfer (ET-PT) and Sequential proton loss electron transfer (SPLET) by Density functional theory (DFT) using hybrid parameters. The computed values of the adiabatic ionization potential, electron affinity, hardness, softness, electronegativity and electrophilic index indicate that isovitexin possess good radical scavenging activity. The behavior of different -OH groups in polyphenolic compounds is assessed by considering electronic effects of the neighbouring groups and the overall geometry of molecule which in turn helps in analyzing the antioxidant capacity of the polyphenolic molecule. The studies indicate that the H-atom abstraction from 4'-OH site is preferred during the radical scavenging process. From Mulliken spin density analysis and FMOs, B-ring is found to be more delocalized center and capable of electron donation. Comparison of antioxidant activity of vitexin and isovitexin leads to the conclusion that isovitexin acts as a better radical scavenger. This is an evidence for the importance of position of glucose unit in the flavonoid.
NASA Astrophysics Data System (ADS)
Kannan, Srinivasa Ramanujam; Chandrasekar, V.
2016-05-01
Even though both the rain measuring instruments, radar and radiometer onboard the TRMM observe the same rain scenes, they both are fundamentally different instruments. Radar is an active instrument and measures backscatter component from vertical rain structure; whereas radiometer is a passive instrument that obtains integrated observation of full depth of the cloud and rain structure. Further, their spatial resolutions on ground are different. Nevertheless, both the instruments are observing the same rain scene and retrieve three dimensional rainfall products. Hence it is only natural to seek answer to the question, what type of information about radiometric observations can be directly retrieved from radar observations. While there are several ways to answer this question, an informational theoretic approach using neural networks has been described in the present work to find if radiometer observations can be predicted from radar observations. A database of TMI brightness temperature and collocated TRMM vertical attenuation corrected reflectivity factor from the year 2012 was considered. The entire database is further classified according to surface type. Separate neural networks were trained for land and ocean and the results are presented.
Combination of real options and game-theoretic approach in investment analysis
NASA Astrophysics Data System (ADS)
Arasteh, Abdollah
2016-02-01
Investments in technology create a large amount of capital investments by major companies. Assessing such investment projects is identified as critical to the efficient assignment of resources. Viewing investment projects as real options, this paper expands a method for assessing technology investment decisions in the linkage existence of uncertainty and competition. It combines the game-theoretic models of strategic market interactions with a real options approach. Several key characteristics underlie the model. First, our study shows how investment strategies rely on competitive interactions. Under the force of competition, firms hurry to exercise their options early. The resulting "hurry equilibrium" destroys the option value of waiting and involves violent investment behavior. Second, we get best investment policies and critical investment entrances. This suggests that integrating will be unavoidable in some information product markets. The model creates some new intuitions into the forces that shape market behavior as noticed in the information technology industry. It can be used to specify best investment policies for technology innovations and adoptions, multistage R&D, and investment projects in information technology.
NASA Astrophysics Data System (ADS)
Beragoui, Manel; Aguir, Chadlia; Khalfaoui, Mohamed; Enciso, Eduardo; Torralvo, Maria José; Duclaux, Laurent; Reinert, Laurence; Vayer, Marylène; Ben Lamine, Abdelmottaleb
2015-03-01
The present work involves the study of bovine serum albumin adsorption onto five functionalized polystyrene lattices. The adsorption measurements have been carried out using a quartz crystal microbalance. Poly(styrene-co-itaconic acid) was found to be an effective adsorbent for bovine serum albumin molecule adsorption. The experimental isotherm data were analyzed using theoretical models based on a statistical physics approach, namely monolayer, double layer with two successive energy levels, finite multilayer, and modified Brunauer-Emmet-Teller. The equilibrium data were then analyzed using five different non-linear error analysis methods and it was found that the finite multilayer model best describes the protein adsorption data. Surface characteristics, i.e., surface charge density and number density of surface carboxyl groups, were used to investigate their effect on the adsorption capacity. The combination of the results obtained from the number of adsorbed layers, the number of adsorbed molecules per site, and the thickness of the adsorbed bovine serum albumin layer allows us to predict that the adsorption of this protein molecule can also be distinguished by monolayer or multilayer adsorption with end-on, side-on, and overlap conformations. The magnitudes of the calculated adsorption energy indicate that bovine serum albumin molecules are physisorbed onto the adsorbent lattices.
Miki, Takeshi; Yokokawa, Taichi; Matsui, Kazuaki
2014-02-01
Ecosystems have a limited buffering capacity of multiple ecosystem functions against biodiversity loss (i.e. low multifunctional redundancy). We developed a novel theoretical approach to evaluate multifunctional redundancy in a microbial community using the microbial genome database (MBGD) for comparative analysis. In order to fully implement functional information, we defined orthologue richness in a community, each of which is a functionally conservative evolutionary unit in genomes, as an index of community multifunctionality (MF). We constructed a graph of expected orthologue richness in a community (MF) as a function of species richness (SR), fit the power function to SR (i.e. MF = cSR(a)), and interpreted the higher exponent a as the lower multifunctional redundancy. Through a microcosm experiment, we confirmed that MF defined by orthologue richness could predict the actual multiple functions. We simulated random and non-random community assemblages using full genomic data of 478 prokaryotic species in the MBGD, and determined that the exponent in microbial communities ranged from 0.55 to 0.75. This exponent range provided a quantitative estimate that a 6.6-8.9% loss limit in SR occurred in a microbial community for an MF reduction no greater than 5%, suggesting a non-negligible initial loss effect of microbial diversity on MF. PMID:24352945
Optimal hemoglobin concentration and high altitude: a theoretical approach for Andean men at rest.
Villafuerte, Francisco C; Cárdenas, Rosa; Monge-C, Carlos
2004-05-01
The beneficial role of erythrocytosis for O2 transport has been questioned by evidence from bloodletting and hemodilution research as well as by studies suggesting the existence of an "optimal" hematocrit (Hct) or hemoglobin concentration ([Hb]) value. To assess to what extent erythrocytosis is beneficial in Andean men at high altitude, we examined and discussed optimal [Hb] using a mathematical approach by modeling the mixed (mean) venous Po2 (Pv(O2)) and arterial O2 content, considering for both the relation between [Hb] and arterial Po2. Relations of [Hb] to other physiological variables such as cardiac output and convective arterial O2 transport were also discussed, revealing the importance of Pv(O2) in this model. Our theoretical analysis suggests that increasing [Hb] allows increase and maintenance of Pv(O2) with only moderate declines in arterial Po2 as a consequence of moderate increases in altitude, reaching its maximum at the optimal [Hb] of 14.7 g/dl. Our analysis also shows that [Hb] corresponding to high arterial O2 content and O2 transport values is apparently not quite advantageous for improvement of oxygenation. Furthermore, chronic mountain sickness is discussed as an insightful example of the effects of excessive erythrocytosis at high altitude. PMID:14672972
On the group-theoretical approach to the study of interpenetrating nets.
Baburin, Igor A
2016-05-01
Using group-subgroup and group-supergroup relations, a general theoretical framework is developed to describe and derive interpenetrating 3-periodic nets. The generation of interpenetration patterns is readily accomplished by replicating a single net with a supergroup G of its space group H under the condition that site symmetries of vertices and edges are the same in both H and G. It is shown that interpenetrating nets cannot be mapped onto each other by mirror reflections because otherwise edge crossings would necessarily occur in the embedding. For the same reason any other rotation or roto-inversion axes from G \\ H are not allowed to intersect vertices or edges of the nets. This property significantly narrows the set of supergroups to be included in the derivation of interpenetrating nets. A procedure is described based on the automorphism group of a Hopf ring net [Alexandrov et al. (2012). Acta Cryst. A68, 484-493] to determine maximal symmetries compatible with interpenetration patterns. The proposed approach is illustrated by examples of twofold interpenetrated utp, dia and pcu nets, as well as multiple copies of enantiomorphic quartz (qtz) networks. Some applications to polycatenated 2-periodic layers are also discussed. PMID:27126113
A game theoretic approach to a finite-time disturbance attenuation problem
NASA Technical Reports Server (NTRS)
Rhee, Ihnseok; Speyer, Jason L.
1991-01-01
A disturbance attenuation problem over a finite-time interval is considered by a game theoretic approach where the control, restricted to a function of the measurement history, plays against adversaries composed of the process and measurement disturbances, and the initial state. A zero-sum game, formulated as a quadratic cost criterion subject to linear time-varying dynamics and measurements, is solved by a calculus of variation technique. By first maximizing the quadratic cost criterion with respect to the process disturbance and initial state, a full information game between the control and the measurement residual subject to the estimator dynamics results. The resulting solution produces an n-dimensional compensator which expresses the controller as a linear combination of the measurement history. A disturbance attenuation problem is solved based on the results of the game problem. For time-invariant systems it is shown that under certain conditions the time-varying controller becomes time-invariant on the infinite-time interval. The resulting controller satisfies an H(infinity) norm bound.
Theoretical investigation of hyperfine fields in fluoromethanes and transition metal oxides
NASA Astrophysics Data System (ADS)
Gopalakrishnan, Gowri
Ab-initio Hartree-Fock Cluster procedure has been used to study Nuclear Quadrupole Interaction effects in molecular solid systems and Magnetic Hyperfine properties in antiferromagnetic transition metal oxides. Using the molecular orbital wave functions obtained from the Hartree-Fock calculations, the nuclear quadrupole interaction parameters, namely, the asymmetry parameter and quadrupole coupling constants are calculated at the fluorine site in CHsb{4-n}Fsb{n} (n = 1,2,3) and CHClFsb2 molecules. In addition to these molecules, the possibility of complexing of HF* molecule to these host molecules is also investigated. This complex formation is found to give rise to a second frequency at the fluorine site arising from the fluorine atom of the HF* hydrogen bonded to the host molecule. All of these results agree well with those from Time Dependent Perturbed Angular Distribution measurements of quadrupole interactions at the fluorine site in these systems. Theoretical investigations have also been carried out for the transition metal oxides NiO and MnO in antiferromagnetic state. The location of the muon in the two oxides and the associated electronic structure and muon hyperfine properties have been investigated. Eight equilibrium positions for the muon are found around each oxygen ion in the crystal, of which two are found to have substantially stronger stability than the other six. Direct and exchange contributions to the contact and dipolar hyperfine fields from within the cluster and dipolar fields from outside, are evaluated for each of the equilibrium locations of the muon and are shown to lead to three sets of hyperfine fields. The nature of the potential experienced by the muon as it travels between the equilibrium sites is studied to understand its dynamics inside the solid. The rates of hopping between each of the two equivalent most stable sites, where the muon most strongly trapped, and the other six sites are studied. In each case, the combination of
Magnetic Hyperfine Fields in Lu_2 V_2 O_7 : A Model Approach
NASA Astrophysics Data System (ADS)
Agzamova, Polina; Nikiforov, Anatoliy; Nazipov, Dmitriy
2016-02-01
We report a theoretical approach to the investigation of the magnetic hyperfine interaction on the ^{51} V nucleus in Lu_2 V_2 O_7 with the view of understanding the orbital ordering pattern in this compound. First, we have evaluated the vanadium 3d^1 -level splitting (Δ ) under the crystal field with the D _{3d} -symmetry using the point charges approximation. Second, we have calculated the exchange interaction constant (J) using the ab initio approach. It is shown that the crystal field energy is much stronger than the exchange interaction one and hence the orbital liquid state cannot occur in Lu_2 V_2 O_7 . Finally we have analyzed the magnetic hyperfine field affecting the vanadium nucleus leaning upon these results.
Subjective evaluation and electroacoustic theoretical validation of a new approach to audio upmixing
NASA Astrophysics Data System (ADS)
Usher, John S.
Audio signal processing systems for converting two-channel (stereo) recordings to four or five channels are increasingly relevant. These audio upmixers can be used with conventional stereo sound recordings and reproduced with multichannel home theatre or automotive loudspeaker audio systems to create a more engaging and natural-sounding listening experience. This dissertation discusses existing approaches to audio upmixing for recordings of musical performances and presents specific design criteria for a system to enhance spatial sound quality. A new upmixing system is proposed and evaluated according to these criteria and a theoretical model for its behavior is validated using empirical measurements. The new system removes short-term correlated components from two electronic audio signals using a pair of adaptive filters, updated according to a frequency domain implementation of the normalized-least-means-square algorithm. The major difference of the new system with all extant audio upmixers is that unsupervised time-alignment of the input signals (typically, by up to +/-10 ms) as a function of frequency (typically, using a 1024-band equalizer) is accomplished due to the non-minimum phase adaptive filter. Two new signals are created from the weighted difference of the inputs, and are then radiated with two loudspeakers behind the listener. According to the consensus in the literature on the effect of interaural correlation on auditory image formation, the self-orthogonalizing properties of the algorithm ensure minimal distortion of the frontal source imagery and natural-sounding, enveloping reverberance (ambiance) imagery. Performance evaluation of the new upmix system was accomplished in two ways: Firstly, using empirical electroacoustic measurements which validate a theoretical model of the system; and secondly, with formal listening tests which investigated auditory spatial imagery with a graphical mapping tool and a preference experiment. Both electroacoustic
NASA Astrophysics Data System (ADS)
Zhao, Xiao-Feng; Huang, Si-Xun; Du, Hua-Dong
2011-02-01
This paper puts forward possibilities of refractive index profile retrieval using field measurements at an array of radio receivers in terms of variational adjoint approach. The derivation of the adjoint model begins with the parabolic wave equation for a smooth, perfectly conducting surface and horizontal polarization conditions. To deal with the ill-posed difficulties of the inversion, the regularization ideas are introduced into the establishment of the cost function. Based on steepest descent iterations, the optimal value of refractivity could be retrieved quickly at each point over height. Numerical experiments demonstrate that the method works well for low-distance signals, while it is not accurate enough for long-distance propagations. Through curve fitting processing, however, giving a good initial refractivity profile could generally improve the inversions.
Sexuality Education for Young People: A Theoretically Integrated Approach from Australia
ERIC Educational Resources Information Center
Goldman, Juliette D. G.
2010-01-01
Background: Teachers of sexuality education can often be uncertain about what theoretical basis and pedagogical strategies to use in their teaching. Sexuality educational programmes designed by teachers can often show few evident theoretical principles that have been applied in its construction. Thus, there seems to be a dearth of evidence of ways…
A hydrodynamic approach to non-equilibrium conformal field theories
NASA Astrophysics Data System (ADS)
Bernard, Denis; Doyon, Benjamin
2016-03-01
We develop a hydrodynamic approach to non-equilibrium conformal field theory. We study non-equilibrium steady states in the context of one-dimensional conformal field theory perturbed by the T\\bar{T} irrelevant operator. By direct quantum computation, we show, to first order in the coupling, that a relativistic hydrodynamic emerges, which is a simple modification of one-dimensional conformal fluids. We show that it describes the steady state and its approach, and we provide the main characteristics of the steady state, which lies between two shock waves. The velocities of these shocks are modified by the perturbation and equal the sound velocities of the asymptotic baths. Pushing this approach further, we are led to conjecture that the approach to the steady state is generically controlled by the power law t -1/2, and that the widths of the shocks increase with time according to t 1/3.
ERIC Educational Resources Information Center
Matsumoto, Mitsuko
2015-01-01
Some argue that the field of study of "education and conflict" has yet to be solidified since its emergence in the 1990s, partly due to the weak theory base. This article reviews the literature on the "contribution" of schooling in contemporary violent conflict, via three strands of theoretical ideas, to demonstrate the…
Iwasa, Takeshi; Takenaka, Masato; Taketsugu, Tetsuya
2016-03-28
A theoretical method to compute infrared absorption spectra when a molecule is interacting with an arbitrary nonuniform electric field such as near-fields is developed and numerically applied to simple model systems. The method is based on the multipolar Hamiltonian where the light-matter interaction is described by a spatial integral of the inner product of the molecular polarization and applied electric field. The computation scheme is developed under the harmonic approximation for the molecular vibrations and the framework of modern electronic structure calculations such as the density functional theory. Infrared reflection absorption and near-field infrared absorption are considered as model systems. The obtained IR spectra successfully reflect the spatial structure of the applied electric field and corresponding vibrational modes, demonstrating applicability of the present method to analyze modern nanovibrational spectroscopy using near-fields. The present method can use arbitral electric fields and thus can integrate two fields such as computational chemistry and electromagnetics. PMID:27036436
Game-theoretic approach for improving cooperation in wireless multihop networks.
Ng, See-Kee; Seah, Winston K G
2010-06-01
Traditional networks are built on the assumption that network entities cooperate based on a mandatory network communication semantic to achieve desirable qualities such as efficiency and scalability. Over the years, this assumption has been eroded by the emergence of users that alter network behavior in a way to benefit themselves at the expense of others. At one extreme, a malicious user/node may eavesdrop on sensitive data or deliberately inject packets into the network to disrupt network operations. The solution to this generally lies in encryption and authentication. In contrast, a rational node acts only to achieve an outcome that he desires most. In such a case, cooperation is still achievable if the outcome is to the best interest of the node. The node misbehavior problem would be more pronounced in multihop wireless networks like mobile ad hoc and sensor networks, which are typically made up of wireless battery-powered devices that must cooperate to forward packets for one another. However, cooperation may be hard to maintain as it consumes scarce resources such as bandwidth, computational power, and battery power. This paper applies game theory to achieve collusive networking behavior in such network environments. In this paper, pricing, promiscuous listening, and mass punishments are avoided altogether. Our model builds on recent work in the field of Economics on the theory of imperfect private monitoring for the dynamic Bertrand oligopoly, and adapts it to the wireless multihop network. The model derives conditions for collusive packet forwarding, truthful routing broadcasts, and packet acknowledgments under a lossy wireless multihop environment, thus capturing many important characteristics of the network layer and link layer in one integrated analysis that has not been achieved previously. We also provide a proof of the viability of the model under a theoretical wireless environment. Finally, we show how the model can be applied to design a generic
Bich, Leonardo; Damiano, Luisa
2007-10-01
In this article, we would like to discuss some aspects of a theoretical framework for Artificial Life, focusing on the problem of an explicit definition of living systems useful for an effective artificial construction of them. The limits of a descriptive approach will be critically discussed, and a constructive (synthetic) approach will be proposed on the basis of the autopoietic theory of Maturana and Varela. PMID:17629715
NASA Astrophysics Data System (ADS)
Bich, Leonardo; Damiano, Luisa
2007-10-01
In this article, we would like to discuss some aspects of a theoretical framework for Artificial Life, focusing on the problem of an explicit definition of living systems useful for an effective artificial construction of them. The limits of a descriptive approach will be critically discussed, and a constructive (synthetic) approach will be proposed on the basis of the autopoietic theory of Maturana and Varela.
An algorithmic and information-theoretic approach to multimetric index construction
Schoolmaster, Donald R., Jr.; Grace, James B.; Schweiger, E. William; Guntenspergen, Glenn R.; Mitchell, Brian R.; Miller, Kathryn M.; Little, Amanda M.
2013-01-01
The use of multimetric indices (MMIs), such as the widely used index of biological integrity (IBI), to measure, track, summarize and infer the overall impact of human disturbance on biological communities has been steadily growing in recent years. Initially, MMIs were developed for aquatic communities using pre-selected biological metrics as indicators of system integrity. As interest in these bioassessment tools has grown, so have the types of biological systems to which they are applied. For many ecosystem types the appropriate biological metrics to use as measures of biological integrity are not known a priori. As a result, a variety of ad hoc protocols for selecting metrics empirically has developed. However, the assumptions made by proposed protocols have not be explicitly described or justified, causing many investigators to call for a clear, repeatable methodology for developing empirically derived metrics and indices that can be applied to any biological system. An issue of particular importance that has not been sufficiently addressed is the way that individual metrics combine to produce an MMI that is a sensitive composite indicator of human disturbance. In this paper, we present and demonstrate an algorithm for constructing MMIs given a set of candidate metrics and a measure of human disturbance. The algorithm uses each metric to inform a candidate MMI, and then uses information-theoretic principles to select MMIs that capture the information in the multidimensional system response from among possible MMIs. Such an approach can be used to create purely empirical (data-based) MMIs or can, optionally, be influenced by expert opinion or biological theory through the use of a weighting vector to create value-weighted MMIs. We demonstrate the algorithm with simulated data to demonstrate the predictive capacity of the final MMIs and with real data from wetlands from Acadia and Rocky Mountain National Parks. For the Acadia wetland data, the algorithm identified
Mie scattering of highly focused, scalar fields: an analytic approach.
Moore, Nicole J; Alonso, Miguel A
2016-07-01
We present a method for modeling the scattering of a focused scalar field incident on a spherical particle. This approach involves the expansion of the incident field in an orthonormal basis of closed-form solutions of the Helmholtz equation which are nonparaxial counterparts of Laguerre-Gaussian beams. This method also allows for the analytic calculation of the forces and torques exerted on a particle at any position with respect to the beam's focus. PMID:27409679
Stretching of a polymer chain anchored to a surface: the massive field theory approach
NASA Astrophysics Data System (ADS)
Usatenko, Zoryana
2014-09-01
Taking into account the well-known correspondence between the field theoretical φ4 O(n)-vector model in the limit n → 0 and the behaviour of long-flexible polymer chains, the investigation of stretching of an ideal and a real polymer chain with excluded volume interactions in a good solvent anchored to repulsive and inert surfaces is performed. The calculations of the average stretching force which arises when the free end of a polymer chain moves away from a repulsive or inert surface are performed up to one-loop order of the massive field theory approach in fixed space dimensions d = 3. The analysis of the obtained results indicates that the average stretching force for a real polymer chain anchored to a repulsive surface demonstrates different behaviour for the cases \\tilde{z}\\ll1 and \\tilde{z}\\gg1 , where \\tilde{z}=z^\\prime/Rz . Besides, the results obtained in the framework of the massive field theory approach are in good agreement with previous theoretical results for an ideal polymer chain and results of a density functional theory approach for the region of small applied forces when deformation of a polymer chain in the direction of the applied force is not bigger than the linear extension of a polymer chain in this direction. The better agreement between these two methods is observed in the case where the number of monomers increases and the polymer chain becomes longer.
Spherical wave decompostion approach to ultrasonic field calculations
Griffice, C.P.; Seydel, J.A.
1981-12-01
A simple, flexible, accurate, and comprehensive numerical method is presented for theoretically analyzing the diffraction field of a continuous wave transducer of arbitrary size, shape, and frequency. Using the extensively studied circular transducer for comparison, numerical results are shown for an unfocused transducer with uniform velocity excitation as well as for a focused transducer with Gaussian velocity excitation. Data concerning the execution time, program size, and convergence of the method are also presented for its implementation as a design tool on a minicomputer system.
The effective field theorist's approach to gravitational dynamics
NASA Astrophysics Data System (ADS)
Porto, Rafael A.
2016-05-01
We review the effective field theory (EFT) approach to gravitational dynamics. We focus on extended objects in long-wavelength backgrounds and gravitational wave emission from spinning binary systems. We conclude with an introduction to EFT methods for the study of cosmological large scale structures.
Moving beyond the Galloway diagrams for delta classification: A graph-theoretic approach.
NASA Astrophysics Data System (ADS)
Tejedor, Alejandro; Longjas, Anthony; Caldwell, Rebecca; Edmonds, Douglas; Zaliapin, Ilya; Foufoula-Georgiou, Efi
2016-04-01
Delta channel networks self-organize to a variety of stunning and complex patterns in response to different forcings (e.g., river, tides and waves) and the physical properties of their sediment (e.g., particle size, cohesiveness). Understanding and quantifying properties of these patterns is an essential step to solve the inverse problem of inferring process from form. A recently introduced framework based on spectral graph theory allows us to assess delta channel network complexity from a topologic (channel connectivity) and dynamic (flux exchange) perspective [Tejedor et al., 2015a,b]. We demonstrate the potential of this framework, together with numerical and experimental deltas, wherein different delta properties can be varied individually, to replace the qualitative approach still in use today [Galloway, 1975; Orton and Reading, 1993]. Specifically, in this work we have examined the effect of sediment parameters (grain size, cohesiveness) on the channel structure of river dominated deltas generated by a morphodynamic model (Delft3D). Our analysis shows that deltas with coarser incoming sediment are more complex topologically (increased number of looped pathways) but simpler dynamically (reduced flux exchange between subnetworks). We capitalize on the combined approach of controlled simulation (with known drivers) and quantitative comparison by positioning field and simulated deltas in the so-called TopoDynamic space to open up a path to provide valuable information towards a refined classification and inference scheme of delta morphology. Furthermore, numerical deltas allow us to explore the delta channel structure not only in a spatially explicit manner but also temporally, since the complete temporal record of delta evolution is available
2014-01-01
Background High-throughput methods for biological measurements generate vast amounts of quantitative data, which necessitate the development of advanced approaches to data analysis to help understand the underlying mechanisms and networks. Reconstruction of biological networks from measured data of different components is a significant challenge in systems biology. Results We use an information theoretic approach to reconstruct phosphoprotein-cytokine networks in RAW 264.7 macrophage cells. Cytokines are secreted upon activation of a wide range of regulatory signals transduced by the phosphoprotein network. Identifying these components can help identify regulatory modules responsible for the inflammatory phenotype. The information theoretic approach is based on estimation of mutual information of interactions by using kernel density estimators. Mutual information provides a measure of statistical dependencies between interacting components. Using the topology of the network derived, we develop a data-driven parsimonious input–output model of the phosphoprotein-cytokine network. Conclusions We demonstrate the applicability of our information theoretic approach to reconstruction of biological networks. For the phosphoprotein-cytokine network, this approach not only captures most of the known signaling components involved in cytokine release but also predicts new signaling components involved in the release of cytokines. The results of this study are important for gaining a clear understanding of macrophage activation during the inflammation process. PMID:24964861
Diaz, Carlos; Llovera, Ligia; Echevarria, Lorenzo; Hernández, Florencio E
2015-02-01
Herein, we present a simple and versatile theoretical-experimental approach to assess the tautomeric distribution on 5(6)-aminobenzimidazole (5(6)-ABZ) derivatives in solution via one-photon absorption. The method is based on the optimized weighted sum of the theoretical spectra of the corresponding tautomers. In this article we show how the choice of exchange-correlation functional (XCF) employed in the calculations becomes crucial for the success of the approach. After the systematic analysis of XCFs with different amounts of exact-exchange we found a better performance for B3LYP and PBE0. The direct test of the proposed method on omeprazole, a well-known 5(6)-benzimidazole based pharmacotherapeutic, demonstrate its broader applicability. The proposed approach is expected to find direct applications on the tautomeric analysis of other molecular systems exhibiting similar tautomeric equilibria. PMID:25510544
Anderson, Rachel M; Yancey, David F; Zhang, Liang; Chill, Samuel T; Henkelman, Graeme; Crooks, Richard M
2015-05-19
The objective of the research described in this Account is the development of high-throughput computational-based screening methods for discovery of catalyst candidates and subsequent experimental validation using appropriate catalytic nanoparticles. Dendrimer-encapsulated nanoparticles (DENs), which are well-defined 1-2 nm diameter metal nanoparticles, fulfill the role of model electrocatalysts. Effective comparison of theory and experiment requires that the theoretical and experimental models map onto one another perfectly. We use novel synthetic methods, advanced characterization techniques, and density functional theory (DFT) calculations to approach this ideal. For example, well-defined core@shell DENs can be synthesized by electrochemical underpotential deposition (UPD), and the observed deposition potentials can be compared to those calculated by DFT. Theory is also used to learn more about structure than can be determined by analytical characterization alone. For example, density functional theory molecular dynamics (DFT-MD) was used to show that the core@shell configuration of Au@Pt DENs undergoes a surface reconstruction that dramatically affects its electrocatalytic properties. A separate Pd@Pt DENs study also revealed reorganization, in this case a core-shell inversion to a Pt@Pd structure. Understanding these types of structural changes is critical to building correlations between structure and catalytic function. Indeed, the second principal focus of the work described here is correlating structure and catalytic function through the combined use of theory and experiment. For example, the Au@Pt DENs system described earlier is used for the oxygen reduction reaction (ORR) as well as for the electro-oxidation of formic acid. The surface reorganization predicted by theory enhances our understanding of the catalytic measurements. In the case of formic acid oxidation, the deformed nanoparticle structure leads to reduced CO binding energy and therefore
Theoretical approach to the ground state of spherically confined Yukawa plasmas
NASA Astrophysics Data System (ADS)
Henning, Christian; Bonitz, Michael; Piel, Alexander; Ludwig, Patrick; Baumgartner, Henning
2007-11-01
Recently spherical 3D dust crystals (aka Yukawa balls) were discovered [1], which allow direct observation of strong correlation phenomena and the structure of which is well explained by computer simulations of charged Yukawa interacting particles within an external parabolic confinement [2]. Here we present an analytical approach to the ground state of these systems using the minimization of the system's energy. Applying the non-local mean-field approximation we show that screening has a dramatic effect on the density profile, which can be derived explicitly [3]. In addition the local density approximation allows for the inclusion of correlations, which further improves the results in the regime of large screening [4]. Comparisons with MD simulations of Yukawa balls show excellent agreement.[1] O. Arp et al. Phys. Rev. Lett. 93, 165004 (2004)[2] M. Bonitz et al., Phys. Rev. Lett. 96, 075001 (2006)[3] C. Henning et al., Phys. Rev. E 74, 056403 (2006)[4] C. Henning at al., Phys. Rev. E (2007)
This project investigated an innovative approach for transport of inorganic species under the influence of electric fields. This process, commonly known as electrokinetics uses low-level direct current (dc) electrical potential difference across a soil mass applied through inert...
NASA Technical Reports Server (NTRS)
El-Kaddah, N.; Szekely, J.
1982-01-01
A mathematical representation for the electromagnetic force field and the fluid flow field in a coreless induction furnace is presented. The fluid flow field was represented by writing the axisymmetric turbulent Navier-Stokes equation, containing the electromagnetic body force term. The electromagnetic body force field was calculated by using a technique of mutual inductances. The kappa-epsilon model was employed for evaluating the turbulent viscosity and the resultant differential equations were solved numerically. Theoretically predicted velocity fields are in reasonably good agreement with the experimental measurements reported by Hunt and Moore; furthermore, the agreement regarding the turbulent intensities are essentially quantitative. These results indicate that the kappa-epsilon model provides a good engineering representation of the turbulent recirculating flows occurring in induction furnaces. At this stage it is not clear whether the discrepancies between measurements and the predictions, which were not very great in any case, are attributable either to the model or to the measurement techniques employed.
Batista Ferrer, Harriet; Audrey, Suzanne; Trotter, Caroline; Hickman, Matthew
2015-01-01
Background Interventions to increase uptake of Human Papillomavirus (HPV) vaccination by young women may be more effective if they are underpinned by an appropriate theoretical model or framework. The aims of this review were: to describe the theoretical models or frameworks used to explain behaviours in relation to HPV vaccination of young women, and: to consider the appropriateness of the theoretical models or frameworks used for informing the development of interventions to increase uptake. Methods Primary studies were identified through a comprehensive search of databases from inception to December 2013. Results Thirty-four relevant studies were identified, of which 31 incorporated psychological health behaviour models or frameworks and three used socio-cultural models or theories. The primary studies used a variety of approaches to measure a diverse range of outcomes in relation to behaviours of professionals, parents, and young women. The majority appeared to use theory appropriately throughout. About half of the quantitative studies presented data in relation to goodness of fit tests and the proportion of the variability in the data. Conclusion Due to diverse approaches and inconsistent findings across studies, the current contribution of theory to understanding and promoting HPV vaccination uptake is difficult to assess. Ecological frameworks encourage the integration of individual and social approaches by encouraging exploration of the intrapersonal, interpersonal, organisational, community and policy levels when examining public health issues. Given the small number of studies using such approach, combined with the importance of these factors in predicting behaviour, more research in this area is warranted. PMID:26314783
GRAIL Gravity Field Determination Using the Celestial Mechanics Approach
NASA Astrophysics Data System (ADS)
Arnold, Daniel; Jäggi, Adrian; Bertone, Stefano; Beutler, Gerhard; Meyer, Ulrich; Mervart, Leos; Bock, Heike
2014-05-01
To determine the gravity field of the Moon, the NASA mission GRAIL (Gravity Recovery and Interior Laboratory) inherits its concept from the GRACE (Gravity Recovery and Climate Experiment) mission. The use of inter-satellite Ka-band range-rate (KBRR) observations enables data acquisition even when the spacecraft are not tracked from the Earth. The data allows for a highly accurate estimation of the lunar gravity field on both sides of the Moon, which is crucial to improve the understanding of its internal structure and thermal evolution. In this presentation we discuss GRAIL-based lunar gravity fields generated with the Celestial Mechanics Approach. KBRR observations and position data (GNI1B products) are used to solve for the lunar gravity field parameters in a generalized orbit determination problem. Apart from normalized spherical harmonic coefficients up to degrees n ≤ 200, also arc- and satellite-specific parameters, like initial state vectors and pseudo-stochastic pulses, are set up as common parameters for all measurement types. The latter shall compensate for imperfect models of non-gravitational accelerations, e.g., caused by solar radiation pressure. In addition, especially for the data of the primary mission phase, it is essential to estimate time bias parameters for the KBRR observations. We compare our results from the nominal and from the extended mission phase with the official Level 2 gravity field models first released in October 2013. Our results demonstrate that the lunar gravity field can be recovered with a high quality by adapting the Celestial Mechanics Approach, even when using pre-GRAIL or pre-SELENE gravity field models as a priori fields and when replacing sophisticated models of non-gravitational accelerations by appropriately spaced and constrained pseudo-stochastic pulses.
GOCE gravity field models following the time-wise approach
NASA Astrophysics Data System (ADS)
Brockmann, Jan Martin; Höck, Eduard; Loth, Ina; Mayer-Gürr, Torsten; Pail, Roland; Schuh, Wolf-Dieter; Zehentner, Norbert
2015-04-01
Since the launch of the European Space Agency's (ESA) Gravity field and Ocean Circulation Explorer (GOCE) satellite in 2009 and its end in 2013, a sequence of official GOCE gravity field models was released. One of the series of models follows the so called time-wise approach (EGM_TIM). They are purely based on GOCE observations such that they are independent of any other gravity field information available and describe the Earth's gravity field as seen by GOCE. Recently, the fifth release, EGM_TIM_RL05, was computed and made available to users. The models of the time-wise series were computed within the ESA funded High-level Processing Facility (HPF) and are part of the official ESA GOCE products. Calibrated gravity gradients in the gradiometer reference frame and the satellites position as derived by GPS measurements entered the solutions as observations. Together with the spherical harmonic coefficients, a realistic the full covariance matrix is provided reflecting the model quality. This contribution summarizes the gravity field models derived with the time-wise approach. The method is summarized and the progress along the five releases is highlighted. Special focus is put on the final release 5, the gravity field model which includes all data collected during the entire GOCE mission. This model, parametrized as 78,957 spherical harmonic coefficients (spatial resolution of 71 km), was determined from 4*109,799,264 gravity gradient measurements and 108,754,709 three dimensional positions within a joint least squares adjustment procedure. As this gravity field models only depend on GOCE observations, the gain of GOCE compared to other missions and other gravity field products can be clearly demonstrated. With release 5 of the time-wise model, a pure GOCE based model with a mean global accuracy of 2.4 cm at a spatial resolution of 100 km for the geoid is available (0.7 mGal for gravity anomalies).
NASA Technical Reports Server (NTRS)
Bridges, N. T.; Laity, J. E.
2001-01-01
rocks on Mars should erode at a rate of 7.7 to 210 micrometers/yr. These rates cannot have operated over the entire history of the Pathfinder site or elsewhere on Mars, because craters, knobs, and other obstacles would be quickly worn away. More likely, rock abrasion occurs over short time periods when sand supplies are sufficient and saltation friction speeds are frequently reached. Depletion or exhaustion of sand and a decline in wind fluxes at speeds greater than that of saltation friction will then act to reduce the rate of further abrasion. We are currently engaged in a new set of wind tunnel experiments coupled with theoretical models and field studies that address rock abrasion and ventifact formation on Mars and Earth. These studies have implications for the Noachian, when sand supplies were probably more plentiful and the threshold friction speed was possibly lower because of a more dense atmosphere. Under these conditions, erosion rates from the wind could have been much greater than to day, contributing, along with probable fluvial erosion, to the Noachian landscape that is in limited preservation today.
Morini, Filippo; Deleuze, Michael S.; Watanabe, Noboru; Takahashi, Masahiko
2015-03-07
The influence of thermally induced nuclear dynamics (molecular vibrations) in the initial electronic ground state on the valence orbital momentum profiles of furan has been theoretically investigated using two different approaches. The first of these approaches employs the principles of Born-Oppenheimer molecular dynamics, whereas the so-called harmonic analytical quantum mechanical approach resorts to an analytical decomposition of contributions arising from quantized harmonic vibrational eigenstates. In spite of their intrinsic differences, the two approaches enable consistent insights into the electron momentum distributions inferred from new measurements employing electron momentum spectroscopy and an electron impact energy of 1.2 keV. Both approaches point out in particular an appreciable influence of a few specific molecular vibrations of A{sub 1} symmetry on the 9a{sub 1} momentum profile, which can be unravelled from considerations on the symmetry characteristics of orbitals and their energy spacing.
Degenerate approach to the mean field Bose-Hubbard Hamiltonian
NASA Astrophysics Data System (ADS)
Belemuk, Alexander M.; Ryzhov, Valentin N.
2016-04-01
A degenerate variant of mean field perturbation theory for the on-site Bose-Hubbard Hamiltonian is presented. We split the perturbation into two terms and perform exact diagonalization in the two-dimensional subspace corresponding to the degenerate states. The final relations for the second order ground state energy and first order wave function do not contain singularities at integer values of the chemical potentials. The resulting equation for the phase boundary between superfluid and Mott states coincides with the prediction from the conventional mean field perturbation approach.
PDF approach for turbulent scalar field: Some recent developments
NASA Technical Reports Server (NTRS)
Gao, Feng
1993-01-01
The probability density function (PDF) method has been proven a very useful approach in turbulence research. It has been particularly effective in simulating turbulent reacting flows and in studying some detailed statistical properties generated by a turbulent field There are, however, some important questions that have yet to be answered in PDF studies. Our efforts in the past year have been focused on two areas. First, a simple mixing model suitable for Monte Carlo simulations has been developed based on the mapping closure. Secondly, the mechanism of turbulent transport has been analyzed in order to understand the recently observed abnormal PDF's of turbulent temperature fields generated by linear heat sources.
Approaches to the sign problem in lattice field theory
NASA Astrophysics Data System (ADS)
Gattringer, Christof; Langfeld, Kurt
2016-08-01
Quantum field theories (QFTs) at finite densities of matter generically involve complex actions. Standard Monte Carlo simulations based upon importance sampling, which have been producing quantitative first principle results in particle physics for almost forty years, cannot be applied in this case. Various strategies to overcome this so-called sign problem or complex action problem were proposed during the last thirty years. We here review the sign problem in lattice field theories, focusing on two more recent methods: dualization to worldline type of representations and the density-of-states approach.
Participatory Planning in a School District: A Study Using Three Theoretical Approaches.
ERIC Educational Resources Information Center
Edlefson, Carla; And Others
Traditionally, studies of educational innovations have based evaluations on accomplishment of officially-stated ends. This study, however, explores alternative theoretical frameworks for evaluation. Project Redesign took place in an upper-middle-class suburb with the pseudonym "Meadow City." The project was funded by the National Institute of…
The Interpretation of Classically Quantified Sentences: A Set-Theoretic Approach
ERIC Educational Resources Information Center
Politzer, Guy; Van der Henst, Jean-Baptiste; Delle Luche, Claire; Noveck, Ira A.
2006-01-01
We present a set-theoretic model of the mental representation of classically quantified sentences (All P are Q, Some P are Q, Some P are not Q, and No P are Q). We take inclusion, exclusion, and their negations to be primitive concepts. We show that although these sentences are known to have a diagrammatic expression (in the form of the Gergonne…
Rahal, M; Winter, J; Taylor, J; Donaldson, N
2000-09-01
A theoretical investigation of different electroneurogram recording techniques using electrode cuffs is presented. A new screened tripole arrangement is proposed with a higher inherent signal to interference ratio than the true tripole, which also allows the nulling of the residual electromyogram signal. The reduction in interference is small because the electrode impedance is large compared to the source resistance. PMID:11008430
Explaining Teacher-Student Interactions in Early Childhood: An Interpersonal Theoretical Approach
ERIC Educational Resources Information Center
Thijs, Jochem; Koomen, Helma; Roorda, Debora; ten Hagen, Judith
2011-01-01
The present study used an interpersonal theoretical perspective to examine the interactions between Dutch teachers and kindergartners. Interpersonal theory provides explanations for dyadic interaction behaviors by stating that complementary behaviors (dissimilar in terms of control, and similar in terms of affiliation) elicit and sustain each…
Revolution in Field Science: Apollo Approach to Inaccessible Surface Exploration
NASA Astrophysics Data System (ADS)
Clark, P. E.
2010-07-01
The extraordinary challenge mission designers, scientists, and engineers, faced in planning the first human expeditions to the surface of another solar system body led to the development of a distinctive and even revolutionary approach to field work. Not only were those involved required to deal effectively with the extreme limitation in resources available for and access to a target as remote as the lunar surface; they were required to developed a rigorous approach to science activities ranging from geological field work to deploying field instruments. Principal aspects and keys to the success of the field work are discussed here, including the highly integrated, intensive, and lengthy science planning, simulation, and astronaut training; the development of a systematic scheme for description and documentation of geological sites and samples; and a flexible yet disciplined methodology for site documentation and sample collection. The capability for constant communication with a ‘backroom’ of geological experts who make requests and weigh in on surface operations was innovative and very useful in encouraging rapid dissemination of information to the greater community in general. An extensive archive of the Apollo era science activity related documents provides evidence of the principal aspects and keys to the success of the field work. The Apollo Surface Journal allows analysis of the astronaut’s performance in terms of capability for traveling on foot, documentation and sampling of field stations, and manual operation of tools and instruments, all as a function of time. The application of these analysis as ‘lessons learned’ for planning the next generation of human or robotic field science activities on the Moon and elsewhere are considered here as well.
Unstable infinite nuclear matter in stochastic mean field approach
Colonna, M.; Chomaz, P. Laboratorio Nazionale del Sud, Viale Andrea Doria, Catania )
1994-04-01
In this article, we consider a semiclassical stochastic mean-field approach. In the case of unstable infinite nuclear matter, we calculate the characteristic time of the exponential growing of fluctuations and the diffusion coefficients associated to the unstable modes, in the framework of the Boltzmann-Langevin theory. These two quantities are essential to describe the dynamics of fluctuations and instabilities since, in the unstable regions, the evolution of the system will be dominated by the amplification of fluctuations. In order to make realistic 3D calculations feasible, we suggest to replace the complicated Boltzmann-Langevin theory by a simpler stochastic mean-field approach corresponding to a standard Boltzmann evolution, complemented by a simple noise chosen to reproduce the dynamics of the most unstable modes. Finally we explain how to approximately implement this method by simply tuning the noise associated to the use of a finite number of test particles in Boltzman-like calculations.
Theoretical interpretation of upstreaming electrons and elevated conics on auroral field lines
Ashour-Abdalla, M.; Schriver, D.
1989-01-01
Recent VIKING satellite observations in the auroral zone have shown the association of elevated ion conics (conics with a low energy cutoff above zero) with upward streaming electrons in the presence of low frequency electric field fluctuations. A self-consistent particle simulation was developed which assumed the presence of a steady state electric field on auroral zone field lines capable of accelerating ions up the magnetic field lines. Results from this study show that a low frequency ion-ion two stream instability can be excited. This low frequency instability creates a fluctuating electric field which heats the ions oblique to the magnetic field forming distributions similar to the elevated ion comics. The ion-ion waves also interact resonantly with electrons and accelerates them in the direction of the ion beam.
On Theoretical Broadband Shock-Associated Noise Near-Field Cross-Spectra
NASA Technical Reports Server (NTRS)
Miller, Steven A. E.
2015-01-01
The cross-spectral acoustic analogy is used to predict auto-spectra and cross-spectra of broadband shock-associated noise in the near-field and far-field from a range of heated and unheated supersonic off-design jets. A single equivalent source model is proposed for the near-field, mid-field, and far-field terms, that contains flow-field statistics of the shock wave shear layer interactions. Flow-field statistics are modeled based upon experimental observation and computational fluid dynamics solutions. An axisymmetric assumption is used to reduce the model to a closed-form equation involving a double summation over the equivalent source at each shock wave shear layer interaction. Predictions are compared with a wide variety of measurements at numerous jet Mach numbers and temperature ratios from multiple facilities. Auto-spectral predictions of broadband shock-associated noise in the near-field and far-field capture trends observed in measurement and other prediction theories. Predictions of spatial coherence of broadband shock-associated noise accurately capture the peak coherent intensity, frequency, and spectral width.
NASA Technical Reports Server (NTRS)
Hess, R. A.; Wheat, L. W.
1975-01-01
A control theoretic model of the human pilot was used to analyze a baseline electronic cockpit display in a helicopter landing approach task. The head down display was created on a stroke written cathode ray tube and the vehicle was a UH-1H helicopter. The landing approach task consisted of maintaining prescribed groundspeed and glideslope in the presence of random vertical and horizontal turbulence. The pilot model was also used to generate and evaluate display quickening laws designed to improve pilot vehicle performance. A simple fixed base simulation provided comparative tracking data.
A conservative approach for flow field calculations on multiple grids
NASA Technical Reports Server (NTRS)
Kathong, Monchai; Tiwari, Surendra N.
1988-01-01
In the computation of flow fields about complex configurations, it is very difficult to construct body-fitted coordinate systems. An alternative approach is to use several grids at once, each of which is generated independently. This procedure is called the multiple grids or zonal grids approach and its applications are investigated in this study. The method follows the conservative approach and provides conservation of fluxes at grid interfaces. The Euler equations are solved numerically on such grids for various configurations. The numerical scheme used is the finite-volume technique with a three-state Runge-Kutta time integration. The code is vectorized and programmed to run on the CDC VPS-32 computer. Some steady state solutions of the Euler equations are presented and discussed.
Approaches, field considerations and problems associated with radio tracking carnivores
Sargeant, A.B.
1979-01-01
The adaptation of radio tracking to ecological studies was a major technological advance affecting field investigations of animal movements and behavior. Carnivores have been the recipients of much attention with this new technology and study approaches have varied from simple to complex. Equipment performance has much improved over the years, but users still face many difficulties. The beginning of all radio tracking studies should be a precise definition of objectives. Study objectives dictate type of gear required and field procedures. Field conditions affect equipment performance and investigator ability to gather data. Radio tracking carnivores is demanding and generally requires greater time than anticipated. Problems should be expected and planned for in study design. Radio tracking can be an asset in carnivore studies but caution is needed in its application.
NASA Astrophysics Data System (ADS)
Conde, J. C.; Riveiro, A.; Comesana, R.; Pou, J.
2011-11-01
The properties of orthopaedic/dental implants can be tuned through the laser surface modifications that take place during a laser ablation process. Processing assisted by a laser is adequate to produce macro- and micro-structures on metallic alloys and polymer surfaces in order to improve their biological response. The evaluation of the minimum energy density that causes an optimum ablation process on different kinds of surfaces was theoretically established by numerical simulation of the thermal process and some experiments have been systematically carried out to produce a periodic pattern in the surface. The selection of the laser power has been predicted from numerical analysis solving of the heat conduction differential equation using commercial software, ANSYS (11.0). This analysis has allowed us to predict the extent and the depth of the holes. The theoretical results agree with the experimental measurements that were carried out by profilometry.
Ni, Yi; Liu, Chenchen; Chen, Qinmiao; Zhu, Xifang; Dou, Xiaoming
2015-10-01
Programmed step electric field strength is a simple-to-use technique that has already been reported to be effective to enhance the efficiency or speed of DNA electrophoresis. However, a global understanding and the details of this technique are still vague. In this paper, we investigated the influence of programmed step electric field strength by theoretical calculation and concentrated on a basic format named as two-step electric field strength. Both subtypes of two-step electric field strength conditions were considered. The important parameters, such as peak spacing, peak width, resolution, and migration time, were calculated in theory to understand the performance of DNA electrophoresis under programmed step electric field strength. The influence of two-step electric field strength on DNA electrophoresis was clearly revealed on a diagram of resolution versus migration time. Both resolution and speed of DNA electrophoresis under two-step electric field strength conditions are simply expressed by the shape of curves in the diagram. The possible shapes of curve were explored by calculation and shown in this paper. The subtype II of two-step electric field strength brings drastic variation on the resolution. Its limitations of enhancement and deterioration of resolution were predicted in theory. PMID:26289302
Conceptual and empirical problems with game theoretic approaches to language evolution
Watumull, Jeffrey; Hauser, Marc D.
2014-01-01
The importance of game theoretic models to evolutionary theory has been in formulating elegant equations that specify the strategies to be played and the conditions to be satisfied for particular traits to evolve. These models, in conjunction with experimental tests of their predictions, have successfully described and explained the costs and benefits of varying strategies and the dynamics for establishing equilibria in a number of evolutionary scenarios, including especially cooperation, mating, and aggression. Over the past decade or so, game theory has been applied to model the evolution of language. In contrast to the aforementioned scenarios, however, we argue that these models are problematic due to conceptual confusions and empirical difficiences. In particular, these models conflate the comptutations and representations of our language faculty (mechanism) with its utility in communication (function); model languages as having different fitness functions for which there is no evidence; depend on assumptions for the starting state of the system, thereby begging the question of how these systems evolved; and to date, have generated no empirical studies at all. Game theoretic models of language evolution have therefore failed to advance how or why language evolved, or why it has the particular representations and computations that it does. We conclude with some brief suggestions for how this situation might be ameliorated, enabling this important theoretical tool to make substantive empirical contributions. PMID:24678305
Conceptual and empirical problems with game theoretic approaches to language evolution.
Watumull, Jeffrey; Hauser, Marc D
2014-01-01
The importance of game theoretic models to evolutionary theory has been in formulating elegant equations that specify the strategies to be played and the conditions to be satisfied for particular traits to evolve. These models, in conjunction with experimental tests of their predictions, have successfully described and explained the costs and benefits of varying strategies and the dynamics for establishing equilibria in a number of evolutionary scenarios, including especially cooperation, mating, and aggression. Over the past decade or so, game theory has been applied to model the evolution of language. In contrast to the aforementioned scenarios, however, we argue that these models are problematic due to conceptual confusions and empirical difficiences. In particular, these models conflate the comptutations and representations of our language faculty (mechanism) with its utility in communication (function); model languages as having different fitness functions for which there is no evidence; depend on assumptions for the starting state of the system, thereby begging the question of how these systems evolved; and to date, have generated no empirical studies at all. Game theoretic models of language evolution have therefore failed to advance how or why language evolved, or why it has the particular representations and computations that it does. We conclude with some brief suggestions for how this situation might be ameliorated, enabling this important theoretical tool to make substantive empirical contributions. PMID:24678305
Yablonskiy, Dmitriy A.; Sukstanskii, Alexander L.; He, Xiang
2012-01-01
Quantitative evaluation of brain hemodynamics and metabolism, particularly the relationship between brain function and oxygen utilization, is important for understanding normal human brain operation as well as pathophysiology of neurological disorders. It can also be of great importance for evaluation of hypoxia within tumors of the brain and other organs. A fundamental discovery by Ogawa and co-workers of the BOLD (Blood Oxygenation Level Dependent) contrast opened a possibility to use this effect to study brain hemodynamic and metabolic properties by means of MRI measurements. Such measurements require developing theoretical models connecting MRI signal to brain structure and functioning and designing experimental techniques allowing MR measurements of salient features of theoretical models. In our review we discuss several such theoretical models and experimental methods for quantification brain hemodynamic and metabolic properties. Our review aims mostly at methods for measuring oxygen extraction fraction, OEF, based on measuring blood oxygenation level. Combining measurement of OEF with measurement of CBF allows evaluation of oxygen consumption, CMRO2. We first consider in detail magnetic properties of blood – magnetic susceptibility, MR relaxation and theoretical models of intravascular contribution to MR signal under different experimental conditions. Then, we describe a “through-space” effect – the influence of inhomogeneous magnetic fields, created in the extravascular space by intravascular deoxygenated blood, on the MR signal formation. Further we describe several experimental techniques taking advantage of these theoretical models. Some of these techniques - MR susceptometry, and T2-based quantification of oxygen OEF – utilize intravascular MR signal. Another technique – qBOLD – evaluates OEF by making use of through-space effects. In this review we targeted both scientists just entering the MR field and more experienced MR researchers
Theoretical investigation of boundary contours of ground-state atoms in uniform electric fields
NASA Astrophysics Data System (ADS)
Shi, Hua; Zhao, Dong-Xia; Yang, Zhong-Zhi
2015-12-01
The boundary contours were investigated for first 54 ground-state atoms of the periodic table when they are in uniform electric fields of strengths 106, 107 and 108 V/m. The atomic characteristic boundary model in combination with an ab-initio method was employed. Some regularities of the deformation of atoms, ΔR, in above electric fields are revealed. Furthermore, atomic polarisabilities of the first 54 elements of the periodic table are shown to correlate strongly with the mean variation rate of atomic radial size divided by the strength of the electric field F, ?, which provides a predictive method of calculating atomic polarisabilities of 54 atoms.
Theoretical study on the HIV-1 integrase-5CITEP complex based on polarized force fields
NASA Astrophysics Data System (ADS)
Wei, Caiyi; Mei, Ye; Zhang, Dawei
2010-07-01
Molecular dynamics studies of 5CITEP binding with HIV-1 integrase (IN) are presented using both polarized and nonpolarized force fields. When nonpolarized force field is used, the ligand drifts away from the original binding site. However, this depressing behavior can be curbed by introducing electronic polarization effect into the force field that stabilizes the protein structure and keeps the ligand in the binding pocket. Moreover, simulation under polarized force field gives a binding energy of -4.85 kcal/mol which is in excellent agreement with the experimental Δ G of -4.38 kcal/mol. The results demonstrate the importance of intra-protein electronic polarization in stabilizing the binding complex of IN-5CITEP and accurately predicting the binding energy.
Primordial statistical anisotropies: the effective field theory approach
NASA Astrophysics Data System (ADS)
Akbar Abolhasani, Ali; Akhshik, Mohammad; Emami, Razieh; Firouzjahi, Hassan
2016-03-01
In this work we present the effective field theory of primordial statistical anisotropies generated during anisotropic inflation involving a background U(1) gauge field. Besides the usual Goldstone boson associated with the breaking of time diffeomorphism we have two additional Goldstone bosons associated with the breaking of spatial diffeomorphisms. We further identify these two new Goldstone bosons with the expected two transverse degrees of the U(1) gauge field fluctuations. Upon defining the appropriate unitary gauge, we present the most general quadratic action which respects the remnant symmetry in the unitary gauge. The interactions between various Goldstone bosons leads to statistical anisotropy in curvature perturbation power spectrum. Calculating the general results for power spectrum anisotropy, we recover the previously known results in specific models of anisotropic inflation. In addition, we present novel results for statistical anisotropy in models with non-trivial sound speed for inflaton fluctuations. Also we identify the interaction which leads to birefringence-like effects in anisotropic power spectrum in which the speed of gauge field fluctuations depends on the direction of the mode propagation and the two polarization of gauge field fluctuations contribute differently in statistical anisotropy. As another interesting application, our EFT approach naturally captures interactions generating parity violating statistical anisotropies.
NASA Astrophysics Data System (ADS)
Mikki, Said M.
Although electromagnetism was developed originally as a branch of theoretical physics, the wide spread proliferation of wireless communications and other applications since the turn of the 20th century quickly transformed the field into a well-defined discipline standing by itself as an autonomous part of engineering. This in turn accelerated the growth of both numerical techniques and practical designs aiming all to improve technology. However, one negative drawback was the increasing isolation between the practicality of engineering electromagnetism and the depth and sophistication of the tools that had been developed solely within electromagnetic theory as a branch of theoretical physics. In this dissertation, we propose a new look to engineering electromagnetism from the perspective of theoretical physics. We show that techniques usually associated with abstract physical models in theoretical physics can be successfully employed to enhance our understanding of problems in engineering electromagnetism. Also, such adaptations of theoretical methods allow for new kinds of applications to be invented. This dissertation is organized in two main parts. Part I is concerned with the particle swarm optimization (PSO) method. We first construct a physical theory for the particle swarm optimization and show how this could open the door not just for deeper understanding of the algorithm itself, but also for new techniques to improve the performance of the method when applied to engineering electromagnetics problems. Inspired by the wider perspective derived from physics, we apply quantum effects to the basic (classical) PSO and derive a new general quantum PSO (QPSO) algorithm suitable for engineering electromagnetism. The new method will be shown to be superior to the classical counterpart when applied to some practical problems. A detailed case study that was formulated extensively in our work is the infinitesimal dipole model (IDM), which can simulate arbitrary antennas
NASA Astrophysics Data System (ADS)
Zuo, Wanlong; Ben, Shuai; Lv, Hang; Zhao, Lei; Guo, Jing; Liu, Xue-Shen; Xu, Haifeng; Jin, Mingxing; Ding, Dajun
2016-05-01
Nonsequential double ionization (NSDI) of carbon disulfide CS2 in strong 800-nm laser fields is studied experimentally and theoretically. A knee structure is observed in the intensity-dependent double ionization (DI) yield in linearly polarized laser fields, which exhibits a strong dependence on the laser ellipticity. The electron momentum distributions and energy trajectories after DI in both linearly and circularly polarized laser fields are investigated by employing the two-dimensional classical ensemble method. The results clearly show the evidence of NSDI in the strong-field DI of CS2 molecules. It is demonstrated that, similar to that of atoms, NSDI of CS2 molecules is produced via laser-driven electron recollision with the ion core and presents electron-electron correlations in the process. Analysis indicates that both mechanisms in atomic strong-field NSDI, i.e., recollision impact ionization and recollision excitation with subsequent ionization, may also be contributed to NSDI of CS2 in strong laser fields. Further studies are no doubt necessary for a full understanding of the underlying physical mechanism of molecular strong-field NSDI, due to the multicenter character of the molecular structure and the complex molecular excited states that could be involved in the ionization.
Theoretical and experimental validation of treatment planning for narrow MLC defined photon fields.
Lydon, J M
2005-06-01
In intensity modulated radiotherapy (IMRT), the use of small fields where electronic equilibrium does not exist is becoming more common and presents difficulties for both the measurement and calculation of dose to such fields. Pinnacle(3) (Version 6.2b) allows the user to specify a total minimum open area for each IMRT segment, which can result in sub-segments with widths of only a few millimetres. The dose for 6 MV narrow MLC defined fields between 0.1 and 3 cm in width was investigated using Kodak extended dose range film (EDR2), ionization chamber and MOSFET dosimeters and BEAMnrc Monte Carlo calculations, and these results were used to determine the accuracy of Pinnacle(3) dose calculation for narrow MLC segments. The incident fluences calculated by Pinnacle(3) and BEAMnrc were also compared. Results show that if a fluence and dose grid resolution of 0.1 cm is used, Pinnacle(3) dose agrees with the EDR2 and BEAMnrc to within 5% for field widths between 0.5 and 3.0 cm. However, Pinnacle(3) will underestimate the dose by up to 45% for the 0.1 and 0.3 cm wide fields. It is shown that the source size in the Pinnacle(3) beam model and both the fluence and dose grid resolutions have a significant effect on the accuracy of dose calculation for field widths of 1.0 cm and less. For single segment fields, Pinnacle(3) agrees with EDR2 and BEAMnrc to within 0.1 cm at the field edges and underestimates the penumbra width by up to 0.08 cm. Results for multiple segment fields showed that an MLC transmission of 1.7% and a 0.06 cm inward shift of MLCs prior to beam delivery gave the closest agreement between Pinnacle(3) and measurement. The multiple segment fields also revealed a pattern of low dose troughs of up to 7% in the Pinnacle(3) dose profiles. PMID:15901964
NASA Astrophysics Data System (ADS)
Odio, Oscar F.; Martínez, Ariel; Martínez, Ricardo; Crespo-Otero, Rachel; Montero-Cabrera, Luis A.
2011-01-01
The acrylamide polymerization in presence of diosgenin has been investigated by experimental and theoretical methods. NMR spectroscopy shows the absence of copolymerization. Viscosimetric and dilatometric experiments support the occurrence of transfer reactions that retard the polymerization. The mechanism was studied at the MPWB1K/6-31G(d,p)//B3LYP/6-31G(d,p) level of theory. Transfer, homopropagation, copolymerization and reinitiation reactions were considered either in gas or solution phase. According to results, the retardation seems to be originated by the formation of an allylic radical in the ring B of diosgenin that reinitiates acrylamide polymerization at slow rate.
Experimental and theoretical approach of nanocrystalline TiO2 with antifungal activity
NASA Astrophysics Data System (ADS)
Longo, Valeria M.; Picon, Francini C.; Zamperini, Camila; Albuquerque, Anderson R.; Sambrano, Julio R.; Vergani, Carlos E.; Machado, Ana L.; Andrés, Juan; Hernandes, Antônio C.; Varela, José A.; Longo, Elson
2013-07-01
Using a solvothermal method for this research we synthesized nanocrystalline titanium dioxide (nc-TiO2) anatase particles with a mean diameter of 5.4 nm and evaluated their potential antifungal effect against planktonic cells of Candida albicans without UV radiation. To complement experimental data, we analyzed structural and electronic properties of both the bulk and the (1 0 1) surface of anatase by first-principles calculations. Based on experimental and theoretical results, a reactive O2H and OH species formation mechanism was proposed to explain the key factor which facilitates the antifungal activity.
Nuclear Magnetic Moment of {sup 210}Fr: A Combined Theoretical and Experimental Approach
Gomez, E.; Aubin, S.; Sprouse, G. D.; Orozco, L. A.; Iskrenova-Tchoukova, E.; Safronova, M. S.
2008-05-02
We measure the hyperfine splitting of the 9S{sub 1/2} level of {sup 210}Fr, and find a magnetic dipole hyperfine constant A=622.25(36) MHz. The theoretical value, obtained using the relativistic all-order method from the electronic wave function at the nucleus, allows us to extract a nuclear magnetic moment of 4.38(5){mu}{sub N} for this isotope, which represents a factor of 2 improvement in precision over previous measurements. The same method can be applied to other rare isotopes and elements.
Practical approaches to field problems of stationary combustion systems
Lee, S.W.
1997-09-01
The CANMET Energy Technology Centre (CETC) business plan dictates collaboration with industrial clients and other government agencies to promote energy efficiency, health and safety, pollution reduction and productivity enhancement. The Advanced Combustion Technologies group of CETC provides consultation to numerous organizations in combustion related areas by conducting laboratory and field investigations of fossil fuel-fired combustion equipment. CETC, with its modern research facilities and technical expertise, has taken this practical approach since the seventies and has assisted many organizations in overcoming field problems and in providing cost saving measures and improved profit margins. This paper presents a few selected research projects conducted for industrial clients in north and central America. The combustion systems investigated are mostly liquid fuel fired, with the exception of the utility boiler which was coal-fired. The key areas involved include fuel quality, fuel storage/delivery system contamination, waste derived oils, crude oil combustion, unacceptable pollutant emissions, ambient soot deposition, slagging, fouling, boiler component degradation, and particulate characterization. Some of the practical approaches taken to remedy these field problems on several combustion systems including residential, commercial and industrial scale units are discussed.
Five Faces of Cognition: Theoretical Influences on Approaches to Learning Disabilities.
ERIC Educational Resources Information Center
Hresko, Wayne P.; Reid, D. Kim
1981-01-01
The label "cognitive" has been used to designate five substantially different approaches to the study of learning disabilities: information processing, metacognition, genetic epistemology, cognitive behavior modification, and the specific abilities model. (Author)
ERIC Educational Resources Information Center
Toner, John A.; And Others
1994-01-01
The Program for Organizational Interdisciplinary Self-Education teaches group self-education skills such as team development, management, and maintenance. Training includes defining and negotiating team member roles, case study approach, group simulations, and problem solving. (SK)
Hill, D.W.; Sharp, J.M. Jr. . Dept. of Geological Sciences)
1993-02-01
In the Texas Gulf Coastal Plain, there is a history of oil and gas production extending over 2 to 5 decades. Concurrent with this production history, there has been unprecedented population growth accompanied by vastly increased groundwater demands. Land subsidence on both local and regional bases in this geologic province has been measured and predicted in several studies. The vast majority of these studies have addressed the problem from the standpoint of groundwater usage while only a few have considered the effects of oil and gas production. Based upon field-based computational techniques (Helm, 1984), a model has been developed to predict land subsidence caused by oil and gas production. This method is applied to the Big Hill Field in Jefferson County, Texas. Inputs include production data from a series of wells in this field and lithologic data from electric logs of these same wells. Outputs include predicted amounts of subsidence, the time frame of subsidence, and sensitivity analyses of compressibility and hydraulic conductivity estimates. Depending upon estimated compressibility, subsidence, to date, is predicted to be as high as 20 cm. Similarly, depending upon estimated vertical hydraulic conductivity, the time frame may be decades for this subsidence. These same methods can be applied to other oil/gas fields with established production histories as well as new fields when production scenarios are assumed. Where subsidence has been carefully measured above petroleum reservoir, the model may be used inversely to calculate sediment compressibilities.
NASA Astrophysics Data System (ADS)
Xin, Xu; Xiaohong, Hu; Ye, Feng; Yuanshan, Liu; Wei, Zhang; Zhi, Yang; Wei, Zhao; Yishan, Wang
2016-03-01
We study the spatiotemporal evolution of the electromagnetic field inside a microresonator showing an anomalous dispersion at the pump wavelength by using the normalized Lugiato-Lefever equation. Unlike the traditional single continuous wave (CW) pumping, an additional pump source consisting of periodical pulse train with variable repetition rate is adopted. The influences of the microresonator properties and the pump parameters on the field evolution and the electromagnetic field profile are analyzed. The simulation results indicate that, in the anomalous dispersion regime, both increases of the input pulse amplitude and the repetition frequency can result in the field profiles consisting of multiple peaks. A series of equidistant pulses can also be obtained by increasing the CW pump power. In addition, we find that a large physical detuning between the pump laser carrier and the cavity resonance frequency also causes the splitting of the inside field. Project supported by the National Major Scientific Instrumentation Development Program of China (Grant No. 2011YQ120022), CAS/SAFEA International Partnership Program for Creative Research Teams, China, and the National Natural Science Foundation of China (Grant No. 61275164).
NASA Astrophysics Data System (ADS)
Palanisamy, R.
1987-04-01
The remote-field eddy current effect refers to low-frequency eddy current nondestructive testing (NDT) phenomenon in tubular conductors in which the behavior of both amplitude and phase of induced magnetic field are in apparent contradiction to the well-known ``skin-effect'' theory. Near-equal detection sensitivity across the wall thickness, the ability to measure wall thickness, and the absence of lift-off problems are some of the attractive features of this technique. Despite its early recognition and useful application in down-hole inspection of oil-well casing, no development of adequate scientific basis that could explain this phenomenon has been reported in the open literature. Modeling of the remote-field eddy current phenomenon using the axisymmetric finite element computer code is described in this paper. The results presented show that the finite element numerical technique originally developed for the computation of fields in electrical and magnetic devices can be used as well for the modeling of remote-field eddy current NDT problems.
Maity, Supratim; Banerjee, Diptonil; Das, Nirmalya Sankar; Chattopadhyay, Kalyan Kumar
2016-05-01
Here a dual approach has been adopted to study the effect of both synthesis as well as annealing temperature on the electron field emission property of differently synthesized carbon nanotubes (CNTs) that include solid state chemical reaction as well as chemical vapour deposition (CVD). Experimental findings were supported by theoretical simulation. All the samples were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy, Raman spectroscopy, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). XRD as well as TEM study confirms the amorphous nature (aCNTs) of the samples for both the synthesis techniques which is attributed to lower synthesis temperature. Prominent morphological differences of these two types of aCNTs are clearly observed from both FESEM and TEM images. It is found that electron field emission characteristics of aCNTs synthesized by CVD shows better field emission properties as compared to aCNTs synthesized by solid state reaction. Finite element based simulation shows that temperature has prominent effect on morphology, screening effect or degree of graphitization that leads to improved field emission characteristics for the CVD synthesized aCNTs. PMID:27483810
Ab-Initio Hamiltonian Approach to Light Nuclei And to Quantum Field Theory
Vary, J.P.; Honkanen, H.; Li, Jun; Maris, P.; Shirokov, A.M.; Brodsky, S.J.; Harindranath, A.; de Teramond, G.F.; Ng, E.G.; Yang, C.; Sosonkina, M.; /Ames Lab
2012-06-22
Nuclear structure physics is on the threshold of confronting several long-standing problems such as the origin of shell structure from basic nucleon-nucleon and three-nucleon interactions. At the same time those interactions are being developed with increasing contact to QCD, the underlying theory of the strong interactions, using effective field theory. The motivation is clear - QCD offers the promise of great predictive power spanning phenomena on multiple scales from quarks and gluons to nuclear structure. However, new tools that involve non-perturbative methods are required to build bridges from one scale to the next. We present an overview of recent theoretical and computational progress with a Hamiltonian approach to build these bridges and provide illustrative results for the nuclear structure of light nuclei and quantum field theory.
Snodin, A. P.; Ruffolo, D.; Matthaeus, W. H. E-mail: david.ruf@mahidol.ac.th
2013-01-01
The turbulent random walk of magnetic field lines plays an important role in the transport of plasmas and energetic particles in a wide variety of astrophysical situations, but most theoretical work has concentrated on determination of the asymptotic field line diffusion coefficient. Here we consider the evolution with distance of the field line random walk using a general ordinary differential equation (ODE), which for most cases of interest in astrophysics describes a transition from free streaming to asymptotic diffusion. By challenging theories of asymptotic diffusion to also describe the evolution, one gains insight on how accurately they describe the random walk process. Previous theoretical work has effectively involved closure of the ODE, often by assuming Corrsin's hypothesis and a Gaussian displacement distribution. Approaches that use quasilinear theory and prescribe the mean squared displacement ({Delta}x {sup 2}) according to free streaming (random ballistic decorrelation, RBD) or asymptotic diffusion (diffusive decorrelation, DD) can match computer simulation results, but only over specific parameter ranges, with no obvious 'marker' of the range of validity. Here we make use of a unified description in which the ODE determines ({Delta}x {sup 2}) self-consistently, providing a natural transition between the assumptions of RBD and DD. We find that the minimum kurtosis of the displacement distribution provides a good indicator of whether the self-consistent ODE is applicable, i.e., inaccuracy of the self-consistent ODE is associated with non-Gaussian displacement distributions.
NASA Astrophysics Data System (ADS)
Claret, A.
2016-04-01
Aims: Recent observations of very fast rotating stars show systematic deviations from the von Zeipel theorem and pose a challenge to the theory of gravity-darkening exponents (β1). In this paper, we present a new insight into the problem of temperature distribution over distorted stellar surfaces to try to reduce these discrepancies. Methods: We use a variant of the numerical method based on the triangles strategy, which we previously introduced, to evaluate the gravity-darkening exponents. The novelty of the present method is that the theoretical β1 is now computed as a function of the optical depth, that is, β1 ≡ β1(τ). The stellar evolutionary models, which are necessary to obtain the physical conditions of the stellar envelopes/atmospheres inherent to the numerical method, are computed via the code GRANADA. Results: When the resulting theoretical β1(τ) are compared with the best accurate data of very fast rotators, a good agreement for the six systems is simultaneously achieved. In addition, we derive an equation that relates the locus of constant convective efficiency in the Hertzsprung-Russell (HR) diagram with gravity-darkening exponents.
Paul, Thomas J; Hoffmann, Zachary; Wang, Congzhou; Shanmugasundaram, Maruda; DeJoannis, Jason; Shekhtman, Alexander; Lednev, Igor K; Yadavalli, Vamsi K; Prabhakar, Rajeev
2016-07-21
In this combined experimental (deep ultraviolet resonance Raman (DUVRR) spectroscopy and atomic force microscopy (AFM)) and theoretical (molecular dynamics (MD) simulations and stress-strain (SS)) study, the structural and mechanical properties of amyloid beta (Aβ40) fibrils have been investigated. The DUVRR spectroscopy and AFM experiments confirmed the formation of linear, unbranched and β-sheet rich fibrils. The fibrils (Aβ40)n, formed using n monomers, were equilibrated using all-atom MD simulations. The structural properties such as β-sheet character, twist, interstrand distance, and periodicity of these fibrils were found to be in agreement with experimental measurements. Furthermore, Young's modulus (Y) = 4.2 GPa computed using SS calculations was supported by measured values of 1.79 ± 0.41 and 3.2 ± 0.8 GPa provided by two separate AFM experiments. These results revealed size dependence of structural and material properties of amyloid fibrils and show the utility of such combined experimental and theoretical studies in the design of precisely engineered biomaterials. PMID:27387853
2011-01-01
Fatty acid biosynthesis of Mycobacterium tuberculosis was analyzed using graph theory and influential (impacting) proteins were identified. The graphs (digraphs) representing this biological network provide information concerning the connectivity of each protein or metabolite in a given pathway, providing an insight into the importance of various components in the pathway, and this can be quantitatively analyzed. Using a graph theoretic algorithm, the most influential set of proteins (sets of {1, 2, 3}, etc.), which when eliminated could cause a significant impact on the biosynthetic pathway, were identified. This set of proteins could serve as drug targets. In the present study, the metabolic network of Mycobacterium tuberculosis was constructed and the fatty acid biosynthesis pathway was analyzed for potential drug targeting. The metabolic network was constructed using the KEGG LIGAND database and subjected to graph theoretical analysis. The nearness index of a protein was used to determine the influence of the said protein on other components in the network, allowing the proteins in a pathway to be ordered according to their nearness indices. A method for identifying the most strategic nodes to target for disrupting the metabolic networks is proposed, aiding the development of new drugs to combat this deadly disease. PMID:21453530
A thematic analysis of theoretical models for translational science in nursing: mapping the field.
Mitchell, Sandra A; Fisher, Cheryl A; Hastings, Clare E; Silverman, Leanne B; Wallen, Gwenyth R
2010-01-01
The quantity and diversity of conceptual models in translational science may complicate rather than advance the use of theory. This paper offers a comparative thematic analysis of the models available to inform knowledge development, transfer, and utilization. Literature searches identified 47 models for knowledge translation. Four thematic areas emerged: (1) evidence-based practice and knowledge transformation processes, (2) strategic change to promote adoption of new knowledge, (3) knowledge exchange and synthesis for application and inquiry, and (4) designing and interpreting dissemination research. This analysis distinguishes the contributions made by leaders and researchers at each phase in the process of discovery, development, and service delivery. It also informs the selection of models to guide activities in knowledge translation. A flexible theoretical stance is essential to simultaneously develop new knowledge and accelerate the translation of that knowledge into practice behaviors and programs of care that support optimal patient outcomes. PMID:21074646
A Thematic Analysis of Theoretical Models for Translational Science in Nursing: Mapping the Field
Mitchell, Sandra A.; Fisher, Cheryl A.; Hastings, Clare E.; Silverman, Leanne B.; Wallen, Gwenyth R.
2010-01-01
Background The quantity and diversity of conceptual models in translational science may complicate rather than advance the use of theory. Purpose This paper offers a comparative thematic analysis of the models available to inform knowledge development, transfer, and utilization. Method Literature searches identified 47 models for knowledge translation. Four thematic areas emerged: (1) evidence-based practice and knowledge transformation processes; (2) strategic change to promote adoption of new knowledge; (3) knowledge exchange and synthesis for application and inquiry; (4) designing and interpreting dissemination research. Discussion This analysis distinguishes the contributions made by leaders and researchers at each phase in the process of discovery, development, and service delivery. It also informs the selection of models to guide activities in knowledge translation. Conclusions A flexible theoretical stance is essential to simultaneously develop new knowledge and accelerate the translation of that knowledge into practice behaviors and programs of care that support optimal patient outcomes. PMID:21074646
Theoretical study of alignment dynamics of magnetic oblate spheroids in rotating magnetic fields
NASA Astrophysics Data System (ADS)
Tan, Mingyang; Song, Han; Dhagat, Pallavi; Jander, Albrecht; Walker, Travis W.
2016-06-01
Magnetic composites containing anisotropic magnetic particles can achieve properties not possible in corresponding bulk or thin films of the magnetic material. In this work, we discuss how planar magnetic anisotropy may be achieved in a composite by aligning disk-shaped particles in an in-plane rotating magnetic field. Previous efforts have reported a simple model of aligning particles in a high-frequency rotating magnetic field. However, no complete analytic solution was proposed. Here, we provide a full analytic solution that describes the alignment dynamics of microdisks in a rotating field that covers the entire frequency range. We also provide simplified solutions at both high-frequency and low-frequency limits through asymptotic expansions for easy implementation into industrial settings. The analytic solution is confirmed by numerical simulation and shows agreement with experiments.
NASA Technical Reports Server (NTRS)
Forman, M. A.
1975-01-01
It has been shown previously (Anath et al., 1973 and Kane, 1974) that 20 to 25% of days, the diffusion component of the cosmic-ray neutron diurnal anisotropy is directed more than 30 degrees away from the ecliptic projection of the interplanetary magnetic field averaged over the same 24 hours. A number of explanations for this deviation are discussed and it is concluded that transverse gradient drifts due to gradients perpendicular to the ecliptic are likely, that diurnal variations in the diffusion component of the neutron anisotropy may affect results from single stations and that the 24 hour mean interplanetary magnetic field may not be the field appropriate to the streaming equation at neutron monitor energies.
Schakel, M. D.; Slob, E. C.; Heller, H. K. J.; Smeulders, D. M. J.
2011-04-01
A full-waveform seismoelectric numerical model incorporating the directivity pattern of a pressure source is developed. This model provides predictions of coseismic electric fields and the electromagnetic waves that originate from a fluid/porous-medium interface. An experimental setup in which coseismic electric fields and interface responses are measured is constructed. The seismo-electric origin of the signals is confirmed. The numerically predicted polarity reversal of the interfacial signal and seismoelectric effects due to multiple scattering are detected in the measurements. Both the simulated coseismic electric fields and the electromagnetic waves originating from interfaces agree with the measurements in terms of travel times, waveform, polarity, amplitude, and spatial amplitude decay, demonstrating that seismoelectric effects are comprehensively described by theory.
Iida, Kenji; Noda, Masashi; Nobusada, Katsuyuki
2014-09-28
We propose a theoretical approach for optical response in electrochemical systems. The fundamental equation to be solved is based on a time-dependent density functional theory in real-time and real-space in combination with its finite temperature formula treating an electrode potential. Solvation effects are evaluated by a dielectric continuum theory. The approach allows us to treat optical response in electrochemical systems at the atomistic level of theory. We have applied the method to surface-enhanced Raman scattering (SERS) of 4-mercaptopyridine on an Ag electrode surface. It is shown that the SERS intensity has a peak as a function of the electrode potential. Furthermore, the real-space computational approach facilitates visualization of variation of the SERS intensity depending on an electrode potential.
NASA Astrophysics Data System (ADS)
Nichols, Jonathan M.; Trickey, Stephen T.; Seaver, Mark
2005-05-01
An information-theoretic approach is described for detecting damage-induced nonlinearities in structures. Both the time-delayed mutual information and time-delayed transfer entropy are presented as methods for computing the amount of information transported between points on a structure. By comparing these measures to "linearized" surrogate data sets, the presence and degree of nonlinearity in a system may be deduced. For a linear, five-degree-of-freedom system both mutual information and transfer entropy are derived. An algorithm is then described for computing both quantities from time-series data and is shown to be in agreement with theory. The approach successfully deduces the amount of damage to the structure even in the presence of simulated temperature fluctuations. We then demonstrate the approach to be effective in detecting varying levels of impact damage in a thick composite plate structure.
NASA Astrophysics Data System (ADS)
Kenkre, V. M.; Parris, P. E.; Dunlap, D. H.
2001-03-01
Calculations are presented to address the possibility of designing materials and nanostructures with controllable charge transport capabilities. Building upon the current understanding of the relation between the mobility of photoinjected charges in molecularly-doped polymers and the disordered dipolar environment through which they move, we show how the relative alignment of permanent electric dipoles in the nanostructure associated can enhance or reduce the field dependent mobility of carriers injected into the sample. We consider domains which arise in liquid crystals as well as those induced by poling with an external field.
NASA Astrophysics Data System (ADS)
Elyasi, Majid; Daeizadeh, Vahid
2011-01-01
In the fine-blanking process, a smooth cut surface over almost the entire thickness of the material and high degree of dimensional accuracy are produced Previous research on fine-blanking was carried out mainly to develop this technology and clarify its mechanism In this paper the effect of the shape of the workpiece, material tensile strength and initial blank thickness on forming force in fine-blanking process was studied by theoretical formulation and experimental approach The theoretical formulation was used as a tool to carry out the predication of fine-blanking force The obtained results indicated that by increasing the shape of the workpiece the forces in fine-blanking process is increased Also, by increasing the initial blank thickness and the material tensile strength, the forces in fine-blanking process is increased
Imaging through strong turbulence with a light field approach.
Wu, Chensheng; Ko, Jonathan; Davis, Christopher C
2016-05-30
Under strong turbulence conditions, object's images can be severely distorted and become unrecognizable throughout the observing time. Conventional image restoring algorithms do not perform effectively in these circumstances due to the loss of good references on the object. We propose the use a plenoptic sensor as a light field camera to map a conventional camera image onto a cell image array in the image's sub-angular spaces. Accordingly, each cell image on the plenoptic sensor is equivalent to the image acquired by a sub-aperture of the imaging lens. The wavefront distortion over the lens aperture can be analyzed by comparing cell images in the plenoptic sensor. By using a modified "Laplacian" metric, we can identify a good cell image in a plenoptic image sequence. The good cell image corresponds with the time and sub-aperture area on the imaging lens where wavefront distortion becomes relatively and momentarily "flat". As a result, it will reveal the fundamental truths of the object that would be severely distorted on normal cameras. In this paper, we will introduce the underlying physics principles and mechanisms of our approach and experimentally demonstrate its effectiveness under strong turbulence conditions. In application, our approach can be used to provide a good reference for conventional image restoring approaches under strong turbulence conditions. This approach can also be used as an independent device to perform object recognition tasks through severe turbulence distortions. PMID:27410119
Armas-Pérez, Julio C; Hernández-Ortiz, Juan P; de Pablo, Juan J
2015-12-28
A theoretically informed Monte Carlo method is proposed for Monte Carlo simulation of liquid crystals on the basis of theoretical representations in terms of coarse-grained free energy functionals. The free energy functional is described in the framework of the Landau-de Gennes formalism. A piecewise finite element discretization is used to approximate the alignment field, thereby providing an excellent geometrical representation of curved interfaces and accurate integration of the free energy. The method is suitable for situations where the free energy functional includes highly non-linear terms, including chirality or high-order deformation modes. The validity of the method is established by comparing the results of Monte Carlo simulations to traditional Ginzburg-Landau minimizations of the free energy using a finite difference scheme, and its usefulness is demonstrated in the context of simulations of chiral liquid crystal droplets with and without nanoparticle inclusions. PMID:26723642
NASA Astrophysics Data System (ADS)
Armas-Pérez, Julio C.; Hernández-Ortiz, Juan P.; de Pablo, Juan J.
2015-12-01
A theoretically informed Monte Carlo method is proposed for Monte Carlo simulation of liquid crystals on the basis of theoretical representations in terms of coarse-grained free energy functionals. The free energy functional is described in the framework of the Landau-de Gennes formalism. A piecewise finite element discretization is used to approximate the alignment field, thereby providing an excellent geometrical representation of curved interfaces and accurate integration of the free energy. The method is suitable for situations where the free energy functional includes highly non-linear terms, including chirality or high-order deformation modes. The validity of the method is established by comparing the results of Monte Carlo simulations to traditional Ginzburg-Landau minimizations of the free energy using a finite difference scheme, and its usefulness is demonstrated in the context of simulations of chiral liquid crystal droplets with and without nanoparticle inclusions.
GOCE Gravity fields established by the Celestial Mechanics Approach
NASA Astrophysics Data System (ADS)
Meyer, U.; Jaeggi, A.; Bock, H.; Beutler, G.
2011-12-01
The Celestial Mechanics Approach (CMA) was generalized to accept not only GPS- and K-Band-observations, but also the gradiometer Level 2 observables of the GOCE mission. The gradiometer observable is modeled as a linear function of the gravity field parameters and the parameters of a piece-wise linear function, which absorbs the deficiencies of the band-limited gradiometer observable including its once-, twice-, etc. per rev biases. The spacing of successive piecewise linear (and continuous) functions is typically of the order of one to few minutes. The piecewise linear functions have to be defined in a way not to absorb the gravity signal in the measurement bandwidth of the GOCE gradiometer observable. The resulting gravity fields are by construction independent of the underlying a priori gravity field. We analyze about six months of GOCE level 2 data and generate (a) GPS-only solutions, (b) gradiometer-only solutions based on the three diagonal elements of the gravity tensor, (c) combinations of solutions (a) and (b), and (d) combinations of the solutions of type (c) with static GRACE solutions, which were generated with the CMA, as well. Currently, for proof of concept purposes, the gravity fields are limited to degree n=160. Our analysis clearly reveals the spectrally resolved contributions of the individual solution types mentioned on the combined solutions.
Theoretical Developments in Decision Field Theory: Comment on Tsetsos, Usher, and Chater (2010)
ERIC Educational Resources Information Center
Hotaling, Jared M.; Busemeyer, Jerome R.; Li, Jiyun
2010-01-01
Tsetsos, Usher, and Chater (2010) presented several criticisms of decision field theory (DFT) involving its distance function, instability under externally controlled stopping times, and lack of robustness to various multialternative choice scenarios. Here, we counter those claims with a specification of a distance function based on the…
Zou, Yong; Wang, Changzhen; Peng, Ruiyun; Wang, Lifeng; Hu, Xiangjun
2015-04-01
A change of the transmembrane voltage is considered to cause biophysical and biochemical responses in cells. The present study focuses on the cellular transmembrane voltage (Δφ) induced by external fields. We detail analytical equations for the transmembrane voltage induced by external high-frequency (above the relaxation frequency of the cell membrane) fields on cells of a spherical shape in suspensions and layers. At direct current (DC) and low frequencies, the cell membrane was assumed to be non-conductive under physiologic conditions. However, with increasing frequency, the permittivity of the cytoplasm/extracellular medium and conductivity of the membrane must be accounted for. Our main work is to extend application of the analytical solution of Δφ to the high-frequency range. We first introduce the transmembrane voltage generated by DC and low-frequency exposures on a single cell. Then, we focus on cell suspensions exposed to high-frequency fields. Using the effective medium theory and the reasonable assumption, the approximate analytical solution of Δφ on cells in suspensions and layers can be derived. Phenomenological effective medium theory equations cannot be used to calculate the local electric field of cell suspensions, so we raised a possible solution based on the Bergman theory. PMID:25528063
Role of word-of-mouth for programs of voluntary vaccination: A game-theoretic approach.
Bhattacharyya, Samit; Bauch, Chris T; Breban, Romulus
2015-11-01
We propose a model describing the synergetic feedback between word-of-mouth (WoM) and epidemic dynamics controlled by voluntary vaccination. The key feature consists in combining a game-theoretic model for the spread of WoM and a compartmental model describing VSIR disease dynamics in the presence of a program of voluntary vaccination. We evaluate and compare two scenarios for determinants of behavior, depending on what WoM disseminates: (1) vaccine advertising, which may occur whether or not an epidemic is ongoing and (2) epidemic status, notably disease prevalence. Understanding the synergy between the two strategies could be particularly important for designing voluntary vaccination campaigns. We find that, in the initial phase of an epidemic, vaccination uptake is determined more by vaccine advertising than the epidemic status. As the epidemic progresses, epidemic status becomes increasingly important for vaccination uptake, considerably accelerating vaccination uptake toward a stable vaccination coverage. PMID:26367185
Toward a theoretical approach to medical error reporting system research and design.
Karsh, Ben-Tzion; Escoto, Kamisha Hamilton; Beasley, John W; Holden, Richard J
2006-05-01
The release of the Institute of Medicine (Kohn et al., 2000) report "To Err is Human", brought attention to the problem of medical errors, which led to a concerted effort to study and design medical error reporting systems for the purpose of capturing and analyzing error data so that safety interventions could be designed. However, to make real gains in the efficacy of medical error or event reporting systems, it is necessary to begin developing a theory of reporting systems adoption and use and to understand how existing theories may play a role in explaining adoption and use. This paper presents the results of a 9-month study exploring the barriers and facilitators for the design of a statewide medical error reporting system and discusses how several existing theories of technology acceptance, adoption and implementation fit with many of the results. In addition we present an integrated theoretical model of medical error reporting system design and implementation. PMID:16182233
A theoretical approach to study the melting temperature of metallic nanowires
NASA Astrophysics Data System (ADS)
Arora, Neha; Joshi, Deepika P.
2016-05-01
The physical properties of any material change with the change of its size from bulk range to nano range. A theoretical study to account for the size and shape effect on melting temperature of metallic nanowires has been done. We have studied zinc(Zn), indium (In),lead (Pb) and tin (Sn) nanowires with three different cross sectional shapes like regular triangular, square and regular hexagonal. Variation of melting temperature with the size and shape is graphically represented with the available experimental data. It was found that melting temperature of the nanowires decreases with decrement in the size of nanowire, due to surface effect and at very small size the most probable shape also varies with material
Purification of Germanium Crystals by Zone Refinement: Theoretical and Experimental Approaches
NASA Astrophysics Data System (ADS)
Yang, Gang; Guan, Yutong; Wang, Guojian; Mei, Hao; Jian, Fanyi; Mei, Dongming; Crystal Growth Team
2015-03-01
The results of single germanium crystals grown from zone-refined germanium ingots, identified by photon thermal ionization spectroscopy (PTIS), show that there are four main impurities, aluminum (Al), phosphor (P), boron (B) and gallium (Ga) in the crystals. Based the PTIS results, we investigated the influences of zone speed, zone width and the number of passes on effective segregation coefficient of Al, P and Ga in the process of zone refinement, then the further calculation of distribution of Al, P and Ga along the zone refined ingots has been conducted. In terms of trend of impurity distribution, the calculated results have a very good agreement with the experimental results. We report both the theoretical calculations and the experimental results. This work is supported by DOE grant DE-FG02-10ER46709 and the state of South Dakota.
Formation of Virtual Organizations in Grids: A Game-Theoretic Approach
NASA Astrophysics Data System (ADS)
Carroll, Thomas E.; Grosu, Daniel
The execution of large scale grid applications requires the use of several computational resources owned by various Grid Service Providers (GSPs). GSPs must form Virtual Organizations (VOs) to be able to provide the composite resource to these applications. We consider grids as self-organizing systems composed of autonomous, self-interested GSPs that will organize themselves into VOs with every GSP having the objective of maximizing its profit. We formulate the resource composition among GSPs as a coalition formation problem and propose a game-theoretic framework based on cooperation structures to model it. Using this framework, we design a resource management system that supports the VO formation among GSPs in a grid computing system.
Toward a theoretical approach to medical error reporting system research and design
Karsh, Ben-Tzion; Escoto, Kamisha Hamilton; Beasley, John W.; Holden, Richard J.
2014-01-01
The release of the Institute of Medicine (Kohn et al., 2000) report “To Err is Human”, brought attention to the problem of medical errors, which led to a concerted effort to study and design medical error reporting systems for the purpose of capturing and analyzing error data so that safety interventions could be designed. However, to make real gains in the efficacy of medical error or event reporting systems, it is necessary to begin developing a theory of reporting systems adoption and use and to understand how existing theories may play a role in explaining adoption and use. This paper presents the results of a 9-month study exploring the barriers and facilitators for the design of a statewide medical error reporting system and discusses how several existing theories of technology acceptance, adoption and implementation fit with many of the results. In addition we present an integrated theoretical model of medical error reporting system design and implementation. PMID:16182233
Cold collisions of ground-state calcium atoms in a laser field: A theoretical study
Bussery-Honvault, Beatrice; Launay, Jean-Michel; Moszynski, Robert
2003-09-01
State-of-the-art ab initio techniques have been applied to compute the potential-energy curves for the ground X {sup 1}{sigma}{sub g}{sup +} and excited {sup 1}{pi}{sub g}(4s3d) states of the calcium dimer in the Born-Oppenheimer approximation. The weakly bound ground state was calculated by symmetry-adapted perturbation theory, while the strongly bound excited state was computed using a combination of the linear-response theory within the coupled-cluster singles and doubles framework for the core-valence electronic correlation and of the full configuration interaction for the valence-valence correlation. The ground-state potential has been corrected by considering the relativistic terms resulting from the first-order many-electron Breit theory, and the retardation corrections. The magnetic electronic transition dipole moment governing the {sup 1}{pi}{sub g}(leftarrow){sup 1}{sigma}{sub g}{sup +} transitions has been obtained as the first residue of the polarization propagator computed with the coupled-cluster method restricted to single and double excitations. The computed energies and transition moments have been analytically fitted and used in the dynamical calculations of the rovibrational energy levels, ground-state scattering length, photoassociation intensities at ultralow temperatures, and spontaneous emission coefficients from the {sup 1}{pi}{sub g}(4s3d) to the X {sup 1}{sigma}{sub g}{sup +} state. The spectroscopic constants of the theoretical ground-state potential are in a good agreement with the experimental values derived from the Fourier-transform spectra [O. Allard et al., Eur. Phys. J. D (to be published)]. The theoretical s-wave scattering length for the ground state is a=44 bohrs, suggesting that it should be possible to obtain a stable Bose-Einstein condensate of calcium atoms. Finally, the computed photoassociation intensities and spontaneous emission coefficients suggest that it should be possible to obtain cold calcium molecules by
Inverse field-based approach for simultaneous B₁ mapping at high fields - a phantom based study.
Jin, Jin; Liu, Feng; Zuo, Zhentao; Xue, Rong; Li, Mingyan; Li, Yu; Weber, Ewald; Crozier, Stuart
2012-04-01
Based on computational electromagnetics and multi-level optimization, an inverse approach of attaining accurate mapping of both transmit and receive sensitivity of radiofrequency coils is presented. This paper extends our previous study of inverse methods of receptivity mapping at low fields, to allow accurate mapping of RF magnetic fields (B(1)) for high-field applications. Accurate receive sensitivity mapping is essential to image domain parallel imaging methods, such as sensitivity encoding (SENSE), to reconstruct high quality images. Accurate transmit sensitivity mapping will facilitate RF-shimming and parallel transmission techniques that directly address the RF inhomogeneity issue, arguably the most challenging issue of high-field magnetic resonance imaging (MRI). The inverse field-based approach proposed herein is based on computational electromagnetics and iterative optimization. It fits an experimental image to the numerically calculated signal intensity by iteratively optimizing the coil-subject geometry to better resemble the experiments. Accurate transmit and receive sensitivities are derived as intermediate results of the optimization process. The method is validated by imaging studies using homogeneous saline phantom at 7T. A simulation study at 300MHz demonstrates that the proposed method is able to obtain receptivity mapping with errors an order of magnitude less than that of the conventional method. The more accurate receptivity mapping and simultaneously obtained transmit sensitivity mapping could enable artefact-reduced and intensity-corrected image reconstructions. It is hoped that by providing an approach to the accurate mapping of both transmit and receive sensitivity, the proposed method will facilitate a range of applications in high-field MRI and parallel imaging. PMID:22391489
Zhang, Y; Joines, W T; Jirtle, R L; Samulski, T V
1993-08-01
The magnitude of E-field patterns generated by an annular array prototype device has been calculated and measured. Two models were used to describe the radiating sources: a simple linear dipole and a stripline antenna model. The stripline model includes detailed geometry of the actual antennas used in the prototype and an estimate of the antenna current based on microstrip transmission line theory. This more detailed model yields better agreement with the measured field patterns, reducing the rms discrepancy by a factor of about 6 (from approximately 23 to 4%) in the central region of interest where the SEM is within 25% of the maximum. We conclude that accurate modeling of source current distributions is important for determining SEM distributions associated with such heating devices. PMID:8258444
Five Faces of Cognition: Theoretical Influences on Approaches to Learning Disabilities.
ERIC Educational Resources Information Center
Hresko, Wayne P.; Reid, D. Kim
1988-01-01
The article points out that the label "cognitive" has been used to designate five substantially different approaches to learning disabilities: information processing, metacognition, genetic epistemology, cognitive behavior modification, and the specific-abilities model. Despite the similar label, the instructional interventions of these approaches…
Subgraph Covers: An Information-Theoretic Approach to Motif Analysis in Networks
NASA Astrophysics Data System (ADS)
Wegner, Anatol E.
2014-10-01
Many real-world networks contain a statistically surprising number of certain subgraphs, called network motifs. In the prevalent approach to motif analysis, network motifs are detected by comparing subgraph frequencies in the original network with a statistical null model. In this paper, we propose an alternative approach to motif analysis where network motifs are defined to be connectivity patterns that occur in a subgraph cover that represents the network using minimal total information. A subgraph cover is defined to be a set of subgraphs such that every edge of the graph is contained in at least one of the subgraphs in the cover. Some recently introduced random graph models that can incorporate significant densities of motifs have natural formulations in terms of subgraph covers, and the presented approach can be used to match networks with such models. To prove the practical value of our approach, we also present a heuristic for the resulting NP hard optimization problem and give results for several real-world networks.
ERIC Educational Resources Information Center
Gardner, Frank L.; Moore, Zella E.
2004-01-01
While traditional cognitive-behavioral skills-training-based approaches to athletic performance enhancement posit that negative thoughts and emotions must be controlled, eliminated, or replaced for athlete-clients to perform optimally, recent evidence suggests that efforts to control, eliminate, or suppress these internal states may actually have…
A Theoretical Framework for Media Law Courses (Approaches to Teaching Freedom of Expression).
ERIC Educational Resources Information Center
Helle, Steven
1991-01-01
Suggests that most students prefer teachers have a theme that provides coherence and cohesiveness to media law courses. Explains how libertarian and neoliberal themes can guide learning and enumerates some of the principles of the two theories. Identifies drawbacks of the case analysis approach to such courses. (SG)
Algebraic Structures, Physics and Geometry from a Unified Field Theoretical Framework
NASA Astrophysics Data System (ADS)
Cirilo-Lombardo, Diego Julio
2015-10-01
Starting from a Unified Field Theory (UFT) proposed previously by the author, the possible fermionic representations arising from the same spacetime are considered from the algebraic and geometrical viewpoint. We specifically demonstrate in this UFT general context that the underlying basis of the single geometrical structure P( G, M) (the principal fiber bundle over the real spacetime manifold M with structural group G) reflecting the symmetries of the different fields carry naturally a biquaternionic structure instead of a complex one. This fact allows us to analyze algebraically and to interpret physically in a straighforward way the Majorana and Dirac representations and the relation of such structures with the spacetime signature and non-hermitian (CP) dynamic operators. Also, from the underlying structure of the tangent space, the existence of hidden (super) symmetries and the possibility of supersymmetric extensions of these UFT models are given showing that Rothstein's theorem is incomplete for that description. The importance of the Clifford algebras in the description of all symmetries, mainly the interaction of gravity with the other fields, is briefly discussed.
Theoretical investigation of single dopant in core/shell nanocrystal in magnetic field
NASA Astrophysics Data System (ADS)
Talbi, A.; Feddi, E.; Oukerroum, A.; Assaid, E.; Dujardin, F.; Addou, M.
2015-09-01
The control of single dopant or "solitary dopant" in semiconductors constitute a challenge to achieve new range of tunable optoelectronic devices. Knowing that the properties of doped monocrystals are very sensitive to different external perturbations, the aim of this study is to understand the effect of a magnetic field on the ground state energy of an off-center ionized donor in a core/shell quantum dot (CSQD). The binding energies with and without an applied magnetic field are determined by the Ritz variational method taking into account the electron-impurity correlation in the trial wave function deduced from the second-order perturbation. It has been found that the external magnetic field affects strongly the binding energy, and its effect varies as a function of the core radius and the shell thickness. We have shown the existence of a threshold ratio (a / b) crit which represents the limit between the tridimensional and the spherical surface confinement. In addition our analysis demonstrates the important influence of the position of ionized donor in the shell material.
Analytical Psychology: A Review of a Theoretical Approach and Its Application to Counseling.
ERIC Educational Resources Information Center
Ziff, Katherine K.
Analytical psychology is a field supported by training centers, specially trained analysts, and a growing body of literature. While it receives much recognition, it remains mostly outside the mainstream of counseling and counselor education. This document presents a brief history of analytical psychology and how it has been revisited and renamed…
The excursion set approach in non-Gaussian random fields
NASA Astrophysics Data System (ADS)
Musso, Marcello; Sheth, Ravi K.
2014-04-01
Insight into a number of interesting questions in cosmology can be obtained by studying the first crossing distributions of physically motivated barriers by random walks with correlated steps: higher mass objects are associated with walks that cross the barrier in fewer steps. We write the first crossing distribution as a formal series, ordered by the number of times a walk upcrosses the barrier. Since the fraction of walks with many upcrossings is negligible if the walk has not taken many steps, the leading order term in this series is the most relevant for understanding the massive objects of most interest in cosmology. For walks associated with Gaussian random fields, this first term only requires knowledge of the bivariate distribution of the walk height and slope, and provides an excellent approximation to the first crossing distribution for all barriers and smoothing filters of current interest. We show that this simplicity survives when extending the approach to the case of non-Gaussian random fields. For non-Gaussian fields which are obtained by deterministic transformations of a Gaussian, the first crossing distribution is simply related to that for Gaussian walks crossing a suitably rescaled barrier. Our analysis shows that this is a useful way to think of the generic case as well. Although our study is motivated by the possibility that the primordial fluctuation field was non-Gaussian, our results are general. In particular, they do not assume the non-Gaussianity is small, so they may be viewed as the solution to an excursion set analysis of the late-time, non-linear fluctuation field rather than the initial one. They are also useful for models in which the barrier height is determined by quantities other than the initial density, since most other physically motivated variables (such as the shear) are usually stochastic and non-Gaussian. We use the Lognormal transformation to illustrate some of our arguments.
Optimal Surface Segmentation in Volumetric Images—A Graph-Theoretic Approach
Li, Kang; Wu, Xiaodong; Chen, Danny Z.; Sonka, Milan
2008-01-01
Efficient segmentation of globally optimal surfaces representing object boundaries in volumetric data sets is important and challenging in many medical image analysis applications. We have developed an optimal surface detection method capable of simultaneously detecting multiple interacting surfaces, in which the optimality is controlled by the cost functions designed for individual surfaces and by several geometric constraints defining the surface smoothness and interrelations. The method solves the surface segmentation problem by transforming it into computing a minimum s-t cut in a derived arc-weighted directed graph. The proposed algorithm has a low-order polynomial time complexity and is computationally efficient. It has been extensively validated on more than 300 computer-synthetic volumetric images, 72 CT-scanned data sets of different-sized plexiglas tubes, and tens of medical images spanning various imaging modalities. In all cases, the approach yielded highly accurate results. Our approach can be readily extended to higher-dimensional image segmentation. PMID:16402624
Reid, David W; Doell, Faye K; Dalton, E Jane; Ahmad, Saunia
2008-12-01
The systemic-constructivist approach to studying and benefiting couples was derived from qualitative and quantitative research on distressed couples over the past 10 years. Systemic-constructivist couple therapy (SCCT) is the clinical intervention that accompanies the approach. SCCT guides the therapist to work with both the intrapersonal and the interpersonal aspects of marriage while also integrating the social-environmental context of the couple. The theory that underlies SCCT is explained, including concepts such as we-ness and interpersonal processing. The primary components of the therapy are described. Findings described previously in an inaugural monograph containing extensive research demonstrating the long-term utility of SCCT are reviewed. (PsycINFO Database Record (c) 2010 APA, all rights reserved). PMID:22122535
Planning additional drilling campaign using two-space genetic algorithm: A game theoretical approach
NASA Astrophysics Data System (ADS)
Kumral, Mustafa; Ozer, Umit
2013-03-01
Grade and tonnage are the most important technical uncertainties in mining ventures because of the use of estimations/simulations, which are mostly generated from drill data. Open pit mines are planned and designed on the basis of the blocks representing the entire orebody. Each block has different estimation/simulation variance reflecting uncertainty to some extent. The estimation/simulation realizations are submitted to mine production scheduling process. However, the use of a block model with varying estimation/simulation variances will lead to serious risk in the scheduling. In the medium of multiple simulations, the dispersion variances of blocks can be thought to regard technical uncertainties. However, the dispersion variance cannot handle uncertainty associated with varying estimation/simulation variances of blocks. This paper proposes an approach that generates the configuration of the best additional drilling campaign to generate more homogenous estimation/simulation variances of blocks. In other words, the objective is to find the best drilling configuration in such a way as to minimize grade uncertainty under budget constraint. Uncertainty measure of the optimization process in this paper is interpolation variance, which considers data locations and grades. The problem is expressed as a minmax problem, which focuses on finding the best worst-case performance i.e., minimizing interpolation variance of the block generating maximum interpolation variance. Since the optimization model requires computing the interpolation variances of blocks being simulated/estimated in each iteration, the problem cannot be solved by standard optimization tools. This motivates to use two-space genetic algorithm (GA) approach to solve the problem. The technique has two spaces: feasible drill hole configuration with minimization of interpolation variance and drill hole simulations with maximization of interpolation variance. Two-space interacts to find a minmax solution
NASA Astrophysics Data System (ADS)
Yashiki, Satoshi
2016-09-01
We analyze the controllability of interference phenomena between partially coherent fields by introducing the Wigner distribution function (WDF) and entropy, which is defined using the intensity matrix [H. Gamo, J. Opt. Soc. Am. 47, 976 (1957)]. The analytical derivation of the WDF and entropy is presented for a partially coherent imaging system consisting of two pinholes illuminated by a circular source. It is shown that the WDF, defined in the 4D space–spatial frequency region, and entropy can be useful tools to understand how one can freely and quantitatively control the interference when any optical components in the partially coherent imaging system are changed.
NASA Technical Reports Server (NTRS)
Ziebell, L. F.; Wu, C. S.; Yoon, Peter H.
1991-01-01
A theory of generation of radio waves observed by ground-based facilities in the frequency range 150-700 kHz is discussed. This work is a continuation of an earlier discussion (Wu et al., 1989) in which it was proposed that the trapped electrons along the auroral field lines can lead to a cyclotron instability which amplifies the whistler waves observed at ground level. The objective of the present study is to investigate the propagation effect on the wave amplification and to examine whether the proposed mechanism is indeed viable.
An information theoretic approach for generating an aircraft avoidance Markov Decision Process
NASA Astrophysics Data System (ADS)
Weinert, Andrew J.
Developing a collision avoidance system that can meet safety standards required of commercial aviation is challenging. A dynamic programming approach to collision avoidance has been developed to optimize and generate logics that are robust to the complex dynamics of the national airspace. The current approach represents the aircraft avoidance problem as Markov Decision Processes and independently optimizes a horizontal and vertical maneuver avoidance logics. This is a result of the current memory requirements for each logic, simply combining the logics will result in a significantly larger representation. The "curse of dimensionality" makes it computationally inefficient and unfeasible to optimize this larger representation. However, existing and future collision avoidance systems have mostly defined the decision process by hand. In response, a simulation-based framework was built to better understand how each potential state quantifies the aircraft avoidance problem with regards to safety and operational components. The framework leverages recent advances in signals processing and database, while enabling the highest fidelity analysis of Monte Carlo aircraft encounter simulations to date. This framework enabled the calculation of how well each state of the decision process quantifies the collision risk and the associated memory requirements. Using this analysis, a collision avoidance logic that leverages both horizontal and vertical actions was built and optimized using this simulation based approach.
Secondary electrospray ionization of complex vapor mixtures. Theoretical and experimental approach.
Vidal-de-Miguel, Guillermo; Herrero, Ana
2012-06-01
In secondary electrospray ionization (SESI) systems, gaseous analytes exposed to an electrospray plume become ionized after charge is transferred from the charging electrosprayed particles (the charging agent) to the vapor species. Currently available SESI models are valid for simplified systems having only one type of electrosprayed species, which ionizes only one single vapor species, and for the limit of low vapor concentration. More realistic models require considering other effects. Here we develop a theoretical model that accounts for the effects of high vapor concentration, saturation effects, interferences between different vapor species, and electrosprays producing different types of species from the liquid phase. In spite of the relatively high complexity of the problem, we find simple relations between the different ionic species concentrations that hold independently of the particular ion source configuration. Our model suggests that an ideal SESI system should use highly concentrated charging agents composed preferably of only one dominating species with low mobility. Experimental measurements with a MeOH-H(2)O-NH(3) electrospray and a mixture of fatty acids and lactic acid served to test the theory, which gives good qualitative results. These results also suggest that the SESI ionization mechanism is primarily based on ions rather than on charged droplets. PMID:22528202
Theoretical approaches to bird migration. The white stork as a case study
NASA Astrophysics Data System (ADS)
Kölzsch, A.; Blasius, B.
2008-04-01
Birds are often considered to be one of the best studied groups of organisms. However, only a few investigations have been devoted to a theoretical analysis of avian migration patterns in time and space. This paper is meant to be a first step into this direction. We start by presenting different types of observational data sets that are available and discuss their advantages and disadvantages for use in quantitative analysis of bird movement and migration. Based on ring recovery and satellite telemetry data we perform a statistical analysis of the migratory patterns of the white stork Ciconia ciconia. We find that standard methods from random walk theory can be applied, but have to be carefully interpreted and possibly modified to analyse migration movement data which are dominated by seasonal drift. Our analysis reveals two different modes of movement fast, directed migration and slow, undirected resting. Furthermore, we present a conceptional network model of avian migration. In our model a number of discrete breeding, resting and wintering habitats are linked by migration in the form of seasonally driven transition probabilities that are described by a unimodal circular function of time. Our study emphasises the need for more rigorous quantitative data analysis and mathematical modelling to gain a better understanding of the dynamic processes of avian migration.
NASA Astrophysics Data System (ADS)
Fujita, H.; Fujita, N.
2002-01-01
Grain size in polycrystalline materials was changed from larger than phi 10 mum to smaller than phi 10 nm, and the effects of both grain size and strain rate on the strength has been investigated from a view point of heterogeneous deformation. Grains of phi10 nm or less in size were obtained by crystallization of amorphous alloys. The experimental results are summarized as follows: (a) Heterogeneous deformation is effectively suppressed when grain size decreases smaller than about phi0.1 mum. As a result, the strength remarkably increases in this grain size range, and takes the maximum value when grains of phi10 nm in size are homogeneously formed, (b) When grain size becomes smaller than phi10 nm, those ultrafine grains are embedded into the amorphous matrix, and the strength decreases with increasing volume fraction of amorphous phase. (c) Heterogeneous deformation is also effectively suppressed by increasing strain rate in general as well as decreasing grain size. The maximum strength obtained experimentally is compared with the theoretical strengths estimated under various conditions.
NASA Astrophysics Data System (ADS)
Georgopoulos, Stéfanos L.; Diniz, Renata; Yoshida, Maria I.; Speziali, Nivaldo L.; Santos, Hélio F. Dos; Junqueira, Geórgia Maria A.; de Oliveira, Luiz F. C.
2006-08-01
Experimental and theoretical investigations of squarate salts [M 2(C 4O 4)] (M=Li, Na, K and Rb) were performed aiming to correlate the structures, vibrational analysis and aromaticity. Powder X-ray diffraction data show that these compounds are not isostructural, indicating that the metal-squarate and hydrogen bonds to water molecules interactions play a significant role on the the crystal packing. The infrared and Raman assigments suggest an equalization of the C-C bond lengths with the increasing of the counter-ion size. This result is interpreted as an enhancement in the electronic delocalization and consequently in the degree of aromaticity for salts with larger ions. Quantum mechanical calculations for structures, vibrational spectra and aromaticity index are in agreement with experimental finding, giving insights at molecular level for the role played by distinct complexation modes to the observed properties. Comparison between our results and literature, regarding molecular dynamics in different chemical environments, shows that aromaticity and hydrogen bonds are the most important forces driving the interactions in the solid structures of squarate ion.
Deurloo, Kirsten E I; Holsheimer, Jan; Bergveld, Piet
2003-10-01
The performance of cathode-anode configurations in a cuff electrode to stimulate a single fascicle in a nerve trunk has been investigated theoretically. A three-dimensional volume conductor model of a nerve trunk with four fascicles in a cuff electrode and a model of myelinated nerve fiber stimulation were used to calculate the recruitment of 15 m fibers in each fascicle. The effect of a monopole, a transverse bipole (anode opposite the cathode), and a narrow transverse tripole (guarded cathode) in selectively stimulating 15 m fibers in each fascicle has been quantified and presented as recruitment curves. It is predicted that selective fascicle stimulation is advanced most by stimulation with a bipole in a plane perpendicular to the axis of the nerve trunk. Monopoles and conventional longitudinal tripoles perform less well, as does a longitudinal tripole with an additional "steering" anode. Apart from transverse bipolar stimulation an additional anode may be used to maximally fit the area of excitation to the topography of the fascicle to be recruited. As compared to monopolar and longitudinal tripolar stimulation, the slope of the recruitment curves in transverse bipolar stimulation is reduced considerably, thus allowing improved fine tuning of nerve (and thus force) recruitment. Another advantage of this method is a minimal number of cable connections to the cuff electrode. The cost of the improved selectivity is an increased stimulation current. PMID:22151073
NASA Astrophysics Data System (ADS)
Abbehausen, Camilla; de Paiva, Raphael E. F.; Formiga, André L. B.; Corbi, Pedro P.
2012-10-01
The tautomeric equilibrium of the thione/thiol forms of 1,3-thiazolidine-2-thione was studied by nuclear magnetic resonance, infrared and ultraviolet-visible spectroscopies. Density functional theory was used to support the experimental data and indicates the predominance of the thione tautomer in the solid state, being in agreement with previously reported crystallographic data. In solution, the tautomeric equilibrium was evaluated using 1H NMR at different temperatures in four deuterated solvents acetonitrile, dimethylsulfoxide, chloroform and methanol. The equilibrium constants, K = (thiol)/(thione), and free Gibbs energies were obtained by integration of N bonded hydrogen signals at each temperature for each solvent, excluding methanol. The endothermic tautomerization is entropy-driven and the combined effect of solvent and temperature can be used to achieve almost 50% thiol concentrations in solution. The nature of the electronic transitions was investigated theoretically and the assignment of the bands was made using time-dependent DFT as well as the influence of solvent on the energy of the most important bands of the spectra.
Information Theoretic Approaches to Rapid Discovery of Relationships in Large Climate Data Sets
NASA Technical Reports Server (NTRS)
Knuth, Kevin H.; Rossow, William B.; Clancy, Daniel (Technical Monitor)
2002-01-01
Mutual information as the asymptotic Bayesian measure of independence is an excellent starting point for investigating the existence of possible relationships among climate-relevant variables in large data sets, As mutual information is a nonlinear function of of its arguments, it is not beholden to the assumption of a linear relationship between the variables in question and can reveal features missed in linear correlation analyses. However, as mutual information is symmetric in its arguments, it only has the ability to reveal the probability that two variables are related. it provides no information as to how they are related; specifically, causal interactions or a relation based on a common cause cannot be detected. For this reason we also investigate the utility of a related quantity called the transfer entropy. The transfer entropy can be written as a difference between mutual informations and has the capability to reveal whether and how the variables are causally related. The application of these information theoretic measures is rested on some familiar examples using data from the International Satellite Cloud Climatology Project (ISCCP) to identify relation between global cloud cover and other variables, including equatorial pacific sea surface temperature (SST), over seasonal and El Nino Southern Oscillation (ENSO) cycles.
A theoretical treatment of two approaches to SBS mitigation with two-tone amplification.
Dajani, Iyad; Zeringue, Clint; Bronder, T J; Shay, Thomas; Gavrielides, Athanasios; Robin, Craig
2008-09-01
A technique that employs two seed signals for the purpose of mitigating stimulated Brillouin scattering (SBS) effects in narrow-linewidth Yb-doped fiber amplifiers is investigated theoretically by constructing a self-consistent model that incorporates the laser gain, SBS, and four-wave mixing (FWM). The model reduces to solving a two-point boundary problem consisting of an 8x8 system of coupled nonlinear differential equations. Optimal operating conditions are determined by examining the interplay between the wavelength separation and power ratio of the two seeds. Two variants of this 'two-tone' amplification are considered. In one case the wavelength separation is precisely twice the Brillouin shift, while the other case considers a greater wavelength separation. For the former case, a two-fold increase in total output power over a broad range of seed power ratios centered about a ratio of approximately 2 is obtained, but with fairly large FWM. For the latter case, this model predicts an approximately 100% increase in output power (at SBS threshold with no signs of FWM) for a 'two-tone' amplifier with seed signals at 1064nm and 1068nm, compared to a conventional fiber amplifier with a single 1068nm seed. More significantly for this case, it is found that at a wavelength separation greater than 10nm, it is possible to appreciably enhance the power output of one of the laser frequencies. PMID:18773034
Solubility of caffeine from green tea in supercritical CO2: a theoretical and empirical approach.
Gadkari, Pravin Vasantrao; Balaraman, Manohar
2015-12-01
Decaffeination of fresh green tea was carried out with supercritical CO2 in the presence of ethanol as co-solvent. The solubility of caffeine in supercritical CO2 varied from 44.19 × 10(-6) to 149.55 × 10(-6) (mole fraction) over a pressure and temperature range of 15 to 35 MPa and 313 to 333 K, respectively. The maximum solubility of caffeine was obtained at 25 MPa and 323 K. Experimental solubility data were correlated with the theoretical equation of state models Peng-Robinson (PR), Soave Redlich-Kwong (SRK), and Redlich-Kwong (RK). The RK model had regressed experimental data with 15.52 % average absolute relative deviation (AARD). In contrast, Gordillo empirical model regressed the best to experimental data with only 0.96 % AARD. Under supercritical conditions, solubility of caffeine in tea matrix was lower than the solubility of pure caffeine. Further, solubility of caffeine in supercritical CO2 was compared with solubility of pure caffeine in conventional solvents and a maximum solubility 90 × 10(-3) mol fraction was obtained with chloroform. PMID:26604372
Improving the uptake of independent dialysis using the Humanbecoming theoretical approach.
Duteau, Jennifer
2013-01-01
Soaring healthcare costs, increasing rates of chronic illness, and an aging population have left Canada struggling to meet the growing demands for quality health care. Hospitals battle to cope with altering patient demand, higher costs, provincially imposed global budgets, fast developing technology, rigid rules, new drugs, and social inequalities that lead to poor health. Canadian population health trends have played an important role in examining innovation opportunities that can dictate terms for the effective re-design of Canada's health system. Independent (home) dialysis is associated with cost savings and improved quality of life in comparison with hospital-based hemodialysis treatment. Despite this, independent dialysis has failed to increase at the same rate as hospital-based treatment for chronic kidney disease. One probable reason is the lack of healthcare providers to truly understand the patient experience of living with chronic kidney disease. Qualitative data have shown that patients living with chronic kidney disease desire independence and minimal impact to their quality of life. Parse's Humanbecoming theory has been widely accepted in nursing practice as a theoretical base in which to gain an understanding of the lived experience. The values and assumptions of the Humanbecoming theory are also congruent with patient-centered care practice and transferable to all areas of healthcare practice and disciplines. PMID:23520988
Ghiasi, Mina; Oskouie, Afsaneh Arefi; Saeidian, Hamdollah
2012-02-01
Topiramate, an antiepileptic drug, was synthesized with an improved protocol and identified by (1)H NMR, (13)C NMR, (1)H-(1)H COSY, HMQC and HMBC spectrum. In parallel, density functional theory (DFT) using B3LYP functional and split-valance 6-311++G** basis set has been used to optimize the structures and conformers of Topiramate. Also experimental and theoretical methods have been used to correlate the dependencies of (1)J and (2)J involving (1)H and (13)C on the C1-C2 (ω) and C1-O1 (θ) torsion angles in the glycosidic part of Topiramate. New Karplus equations are proposed to assist in the structural interpretation of these couplings. Importantly, due to the sensitivity of some couplings, most notably (2)J(H1R,H1S), (2)J(C2,H1R) and (2)J(C2,H1S) values depend on both C-C (ω) and C-O (θ) torsion angles. Analyses of experimental coupling constants for protons on the pyranose ring of Topiramate indicate a twist boat structure for Topiramate in solution. In all calculations solvent effects were considered using a polarized continuum model (PCM). PMID:22188614
Hagemann, Ian S; O'Neill, Patrick K; Erill, Ivan; Pfeifer, John D
2015-09-01
The information-theoretic concept of Shannon entropy can be used to quantify the information provided by a diagnostic test. We hypothesized that in tumor types with stereotyped mutational profiles, the results of NGS testing would yield lower average information than in tumors with more diverse mutations. To test this hypothesis, we estimated the entropy of NGS testing in various cancer types, using results obtained from clinical sequencing. A set of 238 tumors were subjected to clinical targeted NGS across all exons of 27 genes. There were 120 actionable variants in 109 cases, occurring in the genes KRAS, EGFR, PTEN, PIK3CA, KIT, BRAF, NRAS, IDH1, and JAK2. Sequencing results for each tumor were modeled as a dichotomized genotype (actionable mutation detected or not detected) for each of the 27 genes. Based upon the entropy of these genotypes, sequencing was most informative for colorectal cancer (3.235 bits of information/case) followed by high grade glioma (2.938 bits), lung cancer (2.197 bits), pancreatic cancer (1.339 bits), and sarcoma/STTs (1.289 bits). In the most informative cancer types, the information content of NGS was similar to surgical pathology examination (modeled at approximately 2-3 bits). Entropy provides a novel measure of utility for laboratory testing in general and for NGS in particular. This metric is, however, purely analytical and does not capture the relative clinical significance of the identified variants, which may also differ across tumor types. PMID:26227479
Laser cooling of MgCl and MgBr in theoretical approach
Wan, Mingjie; Shao, Juxiang; Huang, Duohui; Yang, Junsheng; Cao, Qilong; Jin, Chengguo; Wang, Fanhou; Gao, Yufeng
2015-07-14
Ab initio calculations for three low-lying electronic states (X{sup 2}Σ{sup +}, A{sup 2}Π, and 2{sup 2}Π) of MgCl and MgBr molecules, including spin-orbit coupling, are performed using multi-reference configuration interaction plus Davidson correction method. The calculations involve all-electronic basis sets and Douglas–Kroll scalar relativistic correction. Spectroscopic parameters well agree with available theoretical and experimental data. Highly diagonally distributed Franck-Condon factors f{sub 00} for A{sup 2}Π{sub 3/2,1/2} (υ′ = 0) → X{sup 2}Σ{sup +}{sub 1/2} (υ″ = 0) are determined for both MgCl and MgBr molecules. Suitable radiative lifetimes τ of A{sup 2}Π{sub 3/2,1/2} (υ′ = 0) states for rapid laser cooling are also obtained. The proposed laser drives A{sup 2}Π{sub 3/2} (υ′ = 0) → X{sup 2}Σ{sup +}{sub 1/2} (υ″ = 0) transition by using three wavelengths (main pump laser λ{sub 00}; two repumping lasers λ{sub 10} and λ{sub 21}). These results indicate the probability of laser cooling MgCl and MgBr molecules.
NASA Astrophysics Data System (ADS)
Solano, Rafael Pérez; Ramirez-Perez, Francisco I.; Castorena-Gonzalez, Jorge A.; Anell, Edgar Alvarado; Gutiérrez-Juárez, Gerardo; Polo-Parada, Luis
2012-03-01
The distinctive spectral absorption characteristics of cancer cells make photoacoustic techniques useful for detection in vitro and in vivo. Here we report on our evaluation of the photoacoustic signal produced by a series of monolayers of different cell lines in vitro. Only the melanoma cell line HS936 produced a detectable photoacoustic signal in which amplitude was dependent on the number of cells. This finding appears to be related to the amount of melanin available in these cells. Other cell lines (i.e. HL60, SK-Mel-1, T47D, Hela, HT29 and PC12) exhibited values similar to a precursor of melanin (tyrosinase), but failed to produce sufficient melanin to generate a photoacoustic signal that could be distinguished from background noise. To better understand this phenomenon, we determined a formula for the time-domain photoacoustic wave equation for a monolayer of cells in a non-viscous fluid on the thermoelastic regime. The theoretical results showed that the amplitude and profile of the photoacoustic signal generated by a cell monolayer depended upon the number and distribution of the cells and the location of the point of detection. These findings help to provide a better understanding of the factors involved in the generation of a photoacoustic signal produced by different cells in vitro and in vivo.
A field theory approach to the dynamics of classical particles
NASA Astrophysics Data System (ADS)
McCowan, David; Mazenko, Gene
2012-02-01
For nearly 30 years, mode-coupling theory (MCT) has been regarded as the de facto theoretic description of dense fluids and the transition from the fluid to glassy state. But MCT is limited by its ad hoc construction and lacks a mechanism to institute corrections. We present a new fundamental theory for the kinetics of systems of classical particles which represents a unification of kinetic theory, Brownian motion and field theory. It is developed from first principles via a self-consistent perturbation in terms of an effective two-body potential, and we use this theory to investigate the existence of ergodic-nonergodic (ENE) transitions near the liquid-glass transition. After a brief introduction of the theory, we will address the development of a kinetic equation of the memory function form. The memory function kernel (or self-energy) determined by the theory shares properties with the MCT form, however our theory provides the crucial advantage of well-defined, perturbative corrections.
NASA Astrophysics Data System (ADS)
Liang, Yilong; Cahill, Nathan D.; Saber, Eli; Messinger, David W.
2015-10-01
In this paper, we propose a game-theoretic tree matching algorithm for object detection in high resolution (HR) remotely sensed images, where, given a scene image and an object image, the goal is to determine whether or not the object exists in the scene image. To that effect, tree based representations of the images are obtained using a hierarchical scale space approach. The nodes of the tree denote regions in the image and edges represent the relative containment between different regions. Once we have the tree representations of each image, the task of object detection is reformulated as a tree matching problem. We propose a game-theoretic technique to search for the node correspondences between a pair of trees. This method involves defining a non-cooperative matching game, where strategies denote the possible pairs of matching regions and payoffs determine the compatibilities between these strategies. Trees are matched by finding the evolutionary stable states (ESS) of the game. To validate the effectiveness of the proposed algorithm, we perform experiments on both synthetic and HR remotely sensed images. Our results demonstrate the robustness of the tree representation with respect to different spatial variations of the images, as well as the effectiveness of the proposed game-theoretic tree matching algorithm.
David, Allan E.; Cole, Adam J.; Chertok, Beata; Park, Yoon Shin; Yang, Victor C.
2011-01-01
Magnetic nanoparticles (MNP) continue to draw considerable attention as potential diagnostic and therapeutic tools in the fight against cancer. Although many interacting forces present themselves during magnetic targeting of MNP to tumors, most theoretical considerations of this process ignore all except for the magnetic and drag forces. Our validation of a simple in vitro model against in vivo data, and subsequent reproduction of the in vitro results with a theoretical model indicated that these two forces do indeed dominate the magnetic capture of MNP. However, because nanoparticles can be subject to aggregation, and large MNP experience an increased magnetic force, the effects of surface forces on MNP stability cannot be ignored. We accounted for the aggregating surface forces simply by measuring the size of MNP retained from flow by magnetic fields, and utilized this size in the mathematical model. This presumably accounted for all particle-particle interactions, including those between magnetic dipoles. Thus, our “corrected” mathematical model provided a reasonable estimate of not only fractional MNP retention, but also predicted the regions of accumulation in a simulated capillary. Furthermore, the model was also utilized to calculate the effects of MNP size and spatial location, relative to the magnet, on targeting of MNPs to tumors. This combination of an in vitro model with a theoretical model could potentially assist with parametric evaluations of magnetic targeting, and enable rapid enhancement and optimization of magnetic targeting methodologies. PMID:21295085
Theoretical development of Monte Carlo codes for modeling cumulus cloud fields
NASA Technical Reports Server (NTRS)
Welch, R. M.
1984-01-01
Reflected fluxes are calculated for stratocumulus cloud fields as a function of skycover, cloud aspect ratio, and cloud shape. Cloud liquid water volume is held invariant as cloud shape is varied so that the results can be utilized more effectively by general circulation models and climate models. On the basis of required accuracy in the Earth Radiation Budget Experiment program, an order of magnitude value of 10 W/sq m is used to estimate significant differences between plane parallel and broken cloudiness. This limit is exceeded for cloud covers between 10% and 90%, indicating that plane paralel calculations are not satisfactory at most values of cloud cover. The choice of cloud shape also leads to large differences in reflected fluxes. These differences are traced to the anisotropic intensity pattern out the cloud sides, to the size and shape of the holes between clouds, and to variations in cloud area as viewed from the solar direction. An empirical relationship for effective cloud cover is given at solar zenith angle of theta = 60 deg. This relationship allows for the relatively accurate (delta F = 10 - 15 W/sq m.) computation of broken cloud field reflected fluxes from plane parallel calculations.
NASA Technical Reports Server (NTRS)
Whiting, Ellis E.
1990-01-01
Future space vehicles returning from distant missions or high earth orbits may enter the upper regions of the atmosphere and use aerodynamic drag to reduce their velocity before they skip out of the atmosphere and enter low earth orbit. The Aeroassist Flight Experiment (AFE) is designed to explore the special problems encountered in such entries. A computer code was developed to calculate the radiative transport along line-or-sight in the general 3-D flow field about an arbitrary entry vehicle, if the temperatures and species concentrations along the line-of-sight are known. The radiative heating calculation at the stagnation point of the AFE vehicle along the entry trajectory was performed, including a detailed line-by-line accounting of the radiative transport in the vacuum ultraviolet (below 200 nm) by the atomic N and O lines. A method was developed for making measurements of the haze particles in the Titan atmosphere above 200 km altitude. Several other tasks of a continuing nature, to improve the technical ability to calculate the nonequilibrium gas dynamic flow field and radiative heating of entry vehicles, were completed or advanced.
NASA Astrophysics Data System (ADS)
Aminzadeh, M.; Or, D.
2015-12-01
The drying of porous surfaces involves pores invasion at a sequence reflecting their respective capillary size (large pores invaded first similar to drainage). The emptying of an evaporating pore is accompanied by changes in the thermal field forming on the surface around the invaded pore that consequently affects surface temperature and energy partitioning over the drying surface. A novel experimental system was designed to systematically evaluate the coupling between surface temperature and evaporative flux from individual and clusters of pores drilled into rough glass surfaces connected to a liquid reservoir. Details of thermal fields around individual evaporating pores were observed for sparse and dense pore spacings including measurements of evaporating flux dynamics and results were compared with PCEB model [Aminzadeh and Or, 2014] predictions. We observed drying-induced pore emptying sequences of sintered glass bead surfaces by visual and thermal imaging using high resolution infrared imager. The links between pore emptying sequence at a drying surface inferred from pore size distribution, and surface temperature dynamics offer a possibility of predicting energy partitioning over drying terrestrial surfaces.
NASA Astrophysics Data System (ADS)
Przyklenk, A.; Hördt, A.; Radić, T.
2016-05-01
Capacitively-Coupled Resistivity (CCR) is conventionally used to emulate DC resistivity measurements and may provide important information about the ice content of material in periglacial areas. The application of CCR theoretically enables the determination of both electrical parameters, i.e. the resistivity and the electrical permittivity, by analyzing magnitude and phase shift spectra. The electrical permittivity may dominate the impedance, especially in periglacial areas or regions of hydrogeological interest. However, previous theoretical work suggested that the phase shift may strongly depend on electrode height above ground, implying that electrode height must be known with great accuracy to determine electrical permittivity. Here, we demonstrate with laboratory test measurements, theoretical modelling and by analysing the Jacobian matrix of the inversion, that the sensitivity towards electrode height is drastically reduced if the electrical permittivity is frequency dependent in a way that is typical for ice. For the fist time, we used a novel broadband CCR device "Chameleon" for a field test located in one of the ridge galleries beneath the crest of Mount Zugspitze. A permanently ice covered bottom of a tunnel was examined. For the inversion of the measured spectra, the frequency dependance of the electrical parameters was parameterized in 3 different ways. A Debye Model for pure ices, a Cole-Cole Model for pure ices and a dual Cole-Cole Model including interfacial water additionally. The frequency-dependent resistivity and permittivity spectra obtained from the inversion, including low and high frequency limits, agree reasonably well with laboratory and field measurements reported in the literature.
NASA Astrophysics Data System (ADS)
Przyklenk, A.; Hördt, A.; Radić, T.
2016-05-01
Capacitively-Coupled Resistivity (CCR) is conventionally used to emulate DC resistivity measurements and may provide important information about the ice content of material in periglacial areas. The application of CCR theoretically enables the determination of both electrical parameters, i.e. the resistivity and the electrical permittivity, by analyzing magnitude and phase shift spectra. The electrical permittivity may dominate the impedance, especially in periglacial areas or regions of hydrogeological interest. However, previous theoretical work suggested that the phase shift may strongly depend on electrode height above ground, implying that electrode height must be known with great accuracy to determine electrical permittivity. Here, we demonstrate with laboratory test measurements, theoretical modelling and by analysing the Jacobian matrix of the inversion, that the sensitivity towards electrode height is drastically reduced if the electrical permittivity is frequency dependent in a way that is typical for ice. For the fist time, we used a novel broadband CCR device "Chameleon" for a field test located in one of the ridge galleries beneath the crest of Mount Zugspitze. A permanently ice covered bottom of a tunnel was examined. For the inversion of the measured spectra, the frequency dependance of the electrical parameters was parameterized in 3 different ways. A Debye Model for pure ices, a Cole-Cole Model for pure ices and a dual Cole-Cole Model including interfacial water additionally. The frequency-dependent resistivity and permittivity spectra obtained from the inversion, including low and high frequency limits, agree reasonably well with laboratory and field measurements reported in the literature.
NASA Astrophysics Data System (ADS)
Jalkanen, K. J.; Jürgensen, V. Würtz; Claussen, A.; Rahim, A.; Jensen, G. M.; Wade, R. C.; Nardi, F.; Jung, C.; Degtyarenko, I. M.; Nieminen, R. M.; Herrmann, F.; Knapp-Mohammady, M.; Niehaus, T. A.; Frimand, K.; Suhai, S.
We report on our work with vibrational absorption, vibrational circular dichroism, Raman scattering, Raman optical activity, and surface-enhanced Raman spectroscopy to study protein and DNA structure, hydration, and the binding of ligands, drugs, pesticides, or herbicides via a combined theoretical and experimental approach. The systems we have studied systematically are the amino acids (L-alanine, L-tryptophan, and L-histidine), peptides (N-4271 acetyl L-alanine N?-methyl amide, N-acetyl L-tryptophan N?-methyl amide, N-acetyl L-histidine N?-methyl amide, L-alanyl L-alanine, tri-L-serine, N-acetyl L-alanine L-proline L-tyrosine N?-methyl amide, Leu-enkephalin, cyclo-(gly-L-pro)3, N-acetyl (L-alanine)n N?-methyl amide), 3-methyl indole, and a variety of small molecules (dichlobenil and 2,6-dochlorobenzamide) of relevance to the protein systems under study. We have used molecular mechanics, the SCC-DFTB, SCC-DFTB+disp, RHF, MP2, and DFT methodologies for the modeling studies with the goal of interpreting the experimentally measured vibrational spectra for these molecules to the greatest extent possible and to use this combined approach to understand the structure, function, and electronic properties of these molecules in their various environments. The application of these spectroscopies to biophysical and environmental assays is expanding, and therefore a thorough understanding of the phenomenon from a rigorous theoretical basis is required. In addition, we give some exciting and new preliminary results which allow us to extend our methods to even larger and more complex systems. The work presented here is the current state of the art to this ever and fast changing field of theoretical spectroscopic interpretation and use of VA, VCD, Raman, ROA, EA, and ECD spectroscopies.
Analysis of optically variable devices using a photometric light-field approach
NASA Astrophysics Data System (ADS)
Soukup, Daniel; Å tolc, Svorad; Huber-Mörk, Reinhold
2015-03-01
Diffractive Optically Variable Image Devices (DOVIDs), sometimes loosely referred to as holograms, are popular security features for protecting banknotes, ID cards, or other security documents. Inspection, authentication, as well as forensic analysis of these security features are still demanding tasks requiring special hardware tools and expert knowledge. Existing equipment for such analyses is based either on a microscopic analysis of the grating structure or a point-wise projection and recording of the diffraction patterns. We investigated approaches for an examination of DOVID security features based on sampling the Bidirectional Reflectance Distribution Function (BRDF) of DOVIDs using photometric stereo- and light-field-based methods. Our approach is demonstrated on the practical task of automated discrimination between genuine and counterfeited DOVIDs on banknotes. For this purpose, we propose a tailored feature descriptor which is robust against several expected sources of inaccuracy but still specific enough for the given task. The suggested approach is analyzed from both theoretical as well as practical viewpoints and w.r.t. analysis based on photometric stereo and light fields. We show that especially the photometric method provides a reliable and robust tool for revealing DOVID behavior and authenticity.
A New Approach to Reduce Number of Split Fields in Large Field IMRT
Lee, Chen-Chiao; Wu, Andrew; Garg, Madhur; Mutyala, Subhakar; Kalnicki, Shalom; Sayed, Gary; Mah, Dennis
2011-04-01
Intensity-modulated radiation therapy (IMRT) has been applied for treatments of primary head with neck nodes, lung with supraclavicular nodes, and high-risk prostate cancer with pelvis wall nodes, all of which require large fields. However, the design of the Varian multileaf collimator requires fields >14 cm in width to be split into 2 or more carriage movements. With the split-field technique, both the number of monitor units (MUs) and total treatment time are significantly increased. Although many different approaches have been investigated to reduce the MU, including introducing new leaf segmentation algorithms, none have resulted in widespread success. In addition, for most clinics, writing such algorithms is not a feasible solution, particularly with commercial treatment planning systems. We introduce a new approach that can minimize the number of split fields and reduce the total MUs, thereby reducing treatment time. The technique is demonstrated on the Eclipse planning system V7.3, but could be generalized to any other system.
Devereux, Mike; Gresh, Nohad; Piquemal, Jean-Philip; Meuwly, Markus
2014-08-01
A supervised, semiautomated approach to force field parameter fitting is described and applied to the SIBFA polarizable force field. The I-NoLLS interactive, nonlinear least squares fitting program is used as an engine for parameter refinement while keeping parameter values within a physical range. Interactive fitting is shown to avoid many of the stability problems that frequently afflict highly correlated, nonlinear fitting problems occurring in force field parametrizations. The method is used to obtain parameters for the H2O, formamide, and imidazole molecular fragments and their complexes with the Mg(2+) cation. Reference data obtained from ab initio calculations using an auc-cc-pVTZ basis set exploit advances in modern computer hardware to provide a more accurate parametrization of SIBFA than has previously been available. PMID:24965869
A graph theoretic approach to global earthquake sequencing: A Markov chain model
NASA Astrophysics Data System (ADS)
Vasudevan, K.; Cavers, M. S.
2012-12-01
We construct a directed graph to represent a Markov chain of global earthquake sequences and analyze the statistics of transition probabilities linked to earthquake zones. For earthquake zonation, we consider the simplified plate boundary template of Kagan, Bird, and Jackson (KBJ template, 2010). We demonstrate the applicability of the directed graph approach to hazard-related forecasting using some of the properties of graphs that represent the finite Markov chain. We extend the present study to consider Bird's 52-plate zonation (2003) describing the global earthquakes at and within plate boundaries to gain further insight into the usefulness of digraphs corresponding to a Markov chain model.
Fawzy, Manal; Nasr, Mahmoud; Helmi, Shacker; Nagy, Heba
2016-11-01
Biomass of Oryza sativa (OS) was tested for the removal of Cd(II) ions from synthetic and real wastewater samples. Batch experiments were conducted to investigate the effects of operating parameters on Cd(II) biosorption. Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive x-ray spectroscopy were used to examine the surface characteristics of the Cd(II)-loaded biomass. The maximum removal efficiency of Cd(II) was 89.4% at optimum pH 6.0, biosorbent dose 10.0 g L(-1), initial Cd(II) 50 mg L(-1), and biosorbent particle size 0.5 mm. The applicability of Langmuir and Freundlich isotherms to the sorbent system implied the existence of both monolayer and heterogeneous surface conditions. Kinetic studies revealed that the adsorption process of Cd(II) followed the pseudo-second-order model (r2: 0.99). On the theoretical side, an adaptive neuro-fuzzy inference system (ANFIS) was applied to select the operating parameter that mostly influences the Cd(II) biosorption process. Results from ANFIS indicated that pH was the most influential parameter affecting Cd(II) removal efficiency, indicating that the biomass of OS was strongly pH sensitive. Finally, the biomass was confirmed to adsorb Cd(II) from real wastewater samples with removal efficiency close to 100%. However, feasibility studies of such systems on a large-scale application remain to be investigated. PMID:27185086
Linear game non-contextuality and Bell inequalities—a graph-theoretic approach
NASA Astrophysics Data System (ADS)
Rosicka, M.; Ramanathan, R.; Gnaciński, P.; Horodecki, K.; Horodecki, M.; Horodecki, P.; Severini, S.
2016-04-01
We study the classical and quantum values of a class of one- and two-party unique games, that generalizes the well-known XOR games to the case of non-binary outcomes. In the bipartite case the generalized XOR (XOR-d) games we study are a subclass of the well-known linear games. We introduce a ‘constraint graph’ associated to such a game, with the constraints defining the game represented by an edge-coloring of the graph. We use the graph-theoretic characterization to relate the task of finding equivalent games to the notion of signed graphs and switching equivalence from graph theory. We relate the problem of computing the classical value of single-party anti-correlation XOR games to finding the edge bipartization number of a graph, which is known to be MaxSNP hard, and connect the computation of the classical value of XOR-d games to the identification of specific cycles in the graph. We construct an orthogonality graph of the game from the constraint graph and study its Lovász theta number as a general upper bound on the quantum value even in the case of single-party contextual XOR-d games. XOR-d games possess appealing properties for use in device-independent applications such as randomness of the local correlated outcomes in the optimal quantum strategy. We study the possibility of obtaining quantum algebraic violation of these games, and show that no finite XOR-d game possesses the property of pseudo-telepathy leaving the frequently used chained Bell inequalities as the natural candidates for such applications. We also show this lack of pseudo-telepathy for multi-party XOR-type inequalities involving two-body correlation functions.
NASA Astrophysics Data System (ADS)
Turchyn, Alexandra V.; Brüchert, Volker; Lyons, Timothy W.; Engel, Gregory S.; Balci, Nurgul; Schrag, Daniel P.; Brunner, Benjamin
2010-04-01
Kinetic isotope effects related to the breaking of chemical bonds drive sulfur isotope fractionation during dissimilatory sulfate reduction (DSR), whereas oxygen isotope fractionation during DSR is dominated by exchange between intercellular sulfur intermediates and water. We use a simplified biochemical model for DSR to explore how a kinetic oxygen isotope effect may be expressed. We then explore these relationships in light of evolving sulfur and oxygen isotope compositions (δ 34S SO4 and δ 18O SO4) during batch culture growth of twelve strains of sulfate-reducing bacteria. Cultured under conditions to optimize growth and with identical δ 18O H2O and initial δ 18O SO4, all strains show 34S enrichment, whereas only six strains show significant 18O enrichment. The remaining six show no (or minimal) change in δ 18O SO4 over the growth of the bacteria. We use these experimental and theoretical results to address three questions: (i) which sulfur intermediates exchange oxygen isotopes with water, (ii) what is the kinetic oxygen isotope effect related to the reduction of adenosine phosphosulfate (APS) to sulfite (SO 32-), (iii) does a kinetic oxygen isotope effect impact the apparent oxygen isotope equilibrium values? We conclude that oxygen isotope exchange between water and a sulfur intermediate likely occurs downstream of APS and that our data constrain the kinetic oxygen isotope fractionation for the reduction of APS to sulfite to be smaller than 4‰. This small oxygen isotope effect impacts the apparent oxygen isotope equilibrium as controlled by the extent to which APS reduction is rate-limiting.
NASA Technical Reports Server (NTRS)
Perez-Davis, Marla E.; Gaier, James R.
1990-01-01
In the foreseeable future, an expedition may be undertaken to explore the planet Mars. Some of the power source options being considered for such a mission are photovoltaics, regenerative fuel cells and nuclear reactors. In addition to electrical power requirements, environmental conditions en route to Mars, in the planetary orbit and on the Martian surface must be simulated and studied in order to anticipate and solve potential problems. Space power systems components such as photovoltaic arrays, radiators, and solar concentrators may be vulnerable to degradation in the Martian environment. Natural characteristics of Mars which may pose a threat to surface power systems include high velocity winds, dust, ultraviolet radiation, large daily variation in temperature, reaction to components of the soil, atmosphere and atmospheric condensates as well as synergistic combinations. Most of the current knowledge of the characteristics of the Martian atmosphere and soil composition was obtained from the Viking 1 and 2 missions in 1976. A theoretical study is presented which was used to assess the effects of the Martian atmospheric conditions on the power systems components. A computer program written at NASA-Lewis for combustion research that uses a free energy minimization technique was used to calculate chemical equilibrium for assigned thermodynamic states of temperature and pressure. The power system component materials selected for this study include: silicon dioxide, silicon, carbon, copper, and titanium. Combinations of environments and materials considered include: (1) Mars atmosphere with power surface material, (2) Mars atmosphere and dust component with power surface material, and (3) Mars atmosphere and hydrogen peroxide or superoxide or superoxide with power system material. The chemical equilibrium calculations were performed at a composition ratio (oxidant to reactant) of 100. The temperature for the silicon dioxide material and silicon, which simulate
In situ solid-state NMR for heterogeneous catalysis: a joint experimental and theoretical approach.
Zhang, Weiping; Xu, Shutao; Han, Xiuwen; Bao, Xinhe
2012-01-01
In situ solid-state NMR is a well-established tool for investigations of the structures of the adsorbed reactants, intermediates and products on the surface of solid catalysts. The techniques allow identifications of both the active sites such as acidic sites and reaction processes after introduction of adsorbates and reactants inside an NMR rotor under magic angle spinning (MAS). The in situ solid-state NMR studies of the reactions can be achieved in two ways, i.e. under batch-like or continuous-flow conditions. The former technique is low cost and accessible to the commercial instrument while the latter one is close to the real catalytic reactions on the solids. This critical review describes the research progress on the in situ solid-state NMR techniques and the applications in heterogeneous catalysis under batch-like and continuous-flow conditions in recent years. Some typical probe molecules are summarized here to detect the Brønsted and Lewis acidic sites by MAS NMR. The catalytic reactions discussed in this review include methane aromatization, olefin selective oxidation and olefin metathesis on the metal oxide-containing zeolites. With combining the in situ MAS NMR spectroscopy and the density functional theoretical (DFT) calculations, the intermediates on the catalyst can be identified, and the reaction mechanism is revealed. Reaction kinetic analysis in the nanospace instead of in the bulk state can also be performed by employing laser-enhanced MAS NMR techniques in the in situ flow mode (163 references). PMID:21743940
Abnormalities of functional brain networks in pathological gambling: a graph-theoretical approach
Tschernegg, Melanie; Crone, Julia S.; Eigenberger, Tina; Schwartenbeck, Philipp; Fauth-Bühler, Mira; Lemènager, Tagrid; Mann, Karl; Thon, Natasha; Wurst, Friedrich M.; Kronbichler, Martin
2013-01-01
Functional neuroimaging studies of pathological gambling (PG) demonstrate alterations in frontal and subcortical regions of the mesolimbic reward system. However, most investigations were performed using tasks involving reward processing or executive functions. Little is known about brain network abnormalities during task-free resting state in PG. In the present study, graph-theoretical methods were used to investigate network properties of resting state functional magnetic resonance imaging data in PG. We compared 19 patients with PG to 19 healthy controls (HCs) using the Graph Analysis Toolbox (GAT). None of the examined global metrics differed between groups. At the nodal level, pathological gambler showed a reduced clustering coefficient in the left paracingulate cortex and the left juxtapositional lobe (supplementary motor area, SMA), reduced local efficiency in the left SMA, as well as an increased node betweenness for the left and right paracingulate cortex and the left SMA. At an uncorrected threshold level, the node betweenness in the left inferior frontal gyrus was decreased and increased in the caudate. Additionally, increased functional connectivity between fronto-striatal regions and within frontal regions has also been found for the gambling patients. These findings suggest that regions associated with the reward system demonstrate reduced segregation but enhanced integration while regions associated with executive functions demonstrate reduced integration. The present study makes evident that PG is also associated with abnormalities in the topological network structure of the brain during rest. Since alterations in PG cannot be explained by direct effects of abused substances on the brain, these findings will be of relevance for understanding functional connectivity in other addictive disorders. PMID:24098282
Perez-Davis, M.E.; Gaier, J.R.
1994-09-01
In the foreseeable future, an expedition may be undertaken to explore the planet Mars. Some of the power source options being considered for such a mission are photovoltaics, regenerative fuel cells and nuclear reactors. In addition to electrical power requirements, environmental conditions en route to Mars, in the planetary orbit and on the Martian surface must be simulated and studied in order to anticipate and solve potential problems. Space power systems components such as photovoltaic arrays, radiators, and solar concentrators may be vulnerable to degradation in the Martian environment. Natural characteristics of Mars which may pose a threat to surface power systems include high velocity winds, dust, ultraviolet radiation, large daily variations in temperature, reaction to components of the soil, atmosphere and atmospheric condensates as well as synergistic combinations. Most of the current knowledge of the characteristics of the Martian atmosphere and soil composition was obtained from the Viking 1 and 2 missions in 1976. This paper presents a theoretical study used to assess the effects of the Martian atmospheric conditions on the power systems components. A computer program written at NASA Lewis Research Center in 1961 to 1962 for combustion research that uses a free-energy minimization technique was used to calculate chemical equilibrium for assigned thermodynamic states of temperature and pressure. The power system component materials selected for this study include: Silicon dioxide, silicon, carbon, copper, and titanium. Combinations of environments and materials considered in this study include: (1) Mars atmosphere with power surface material, (2) Mars atmosphere and dust component with power surface material, (3) Mars atmosphere and hydrogen peroxide or superoxide with power system material.
A theoretical design of graphene-based spin field-effect transistors
NASA Astrophysics Data System (ADS)
Liu, Lixue; Liu, Shudun; Zhu, Wenguang
The search for a feasible design of graphene-based materials for spintronics applications has been intensified in recent years. Encouraged by recent experimental achievements, here we propose a new scheme to realize graphene-based spin field-effect transistors. The new design is constituted of a half-hydrogenated graphene nanoroad embedded in a fully-hydrogenated graphene. Using first-principles density function theory calculations, we demonstrate that such a design can convert non-magnetic pristine graphene into a bipolar ferromagnetic semiconductor. More importantly, the magnetism of such a nanoroad is very robust: independent of its width and orientation. We also discuss the stability of such nanoroads, as well as a simple design of an all-electric controlled device for generation and detection of a fully spin-polarized electric current.
NASA Technical Reports Server (NTRS)
Suess, S. T.; Thomas, B. T.; Nerney, S. F.
1985-01-01
Observations of the azimuthal component of the IMF are evaluated through the use of an MHD model which shows the effect of magnetic flux tubes opening in the outer solar system. It is demonstrated that the inferred meridional transport of magnetic flux is consistent with predictions by the MHD model. The computed azimuthal and radial magnetic flux deficits are almost identical to the observations. It is suggested that the simplest interpretation of the observations is that meridional flows are created by a direct body force on the plasma. This is consistent with the analytic model of Nerney and Suess (1975), in which such flux deficits in the IMF arise naturally from the meridional gradient in the spiralling field.
Theoretical and experimental engine-inlet flow fields for fighter forebodies
NASA Technical Reports Server (NTRS)
Yaros, S. F.
1984-01-01
The capability of two numerical methods, one for transonic and one for supersonic flows, to predict the flow fields about representative fighter aircraft forebodies in the vicinity of the engine inlets was examined. The Mach number range covered was 0.9 to 2.5 and the angle-of-attack range was 0 deg to 25 deg. The computer progams that implement each of the numerical methods are described as to their features and usage, and results are compared with comprehensive wind tunnel data. Although both prediction methods were inviscid, results show that the aerodynamic effects of the forebody, with and without a wing, can be simulated fairly well. Futher work is needed to include the effects of viscosity, including vortex shedding.
Pasin, Gauthier; Iung, Christophe; Gatti, Fabien; Richter, Falk; Léonard, Céline; Meyer, Hans-Dieter
2008-10-14
The present paper is devoted to a full quantum mechanical study of the intramolecular vibrational energy redistribution in HFCO and DFCO. In contrast to our previous studies [Pasin et al., J. Chem. Phys. 124, 194304 (2006) and 126, 024302 (2007)], the dynamics is now performed in the presence of an external time-dependent field. This more closely reflects the experimental conditions. A six-dimensional dipole surface is computed. The multiconfiguration time-dependent Hartree method is exploited to propagate the corresponding six-dimensional wave packets. Special emphasis is placed on the excitation of the out-of-plane bending vibration and on the dissociation of the molecule. In the case of DFCO, we predict that it is possible to excite the out-of-plane bending mode of vibration and to drive the dissociation to DF+CO with only one laser pulse with a fixed frequency and without excitation of an electronic state. PMID:19045144
Field-Theoretical Approach to Many-Body Perturbation Theory: Combining MBPT and QED
Lindgren, Ingvar; Salomonson, Sten; Hedendahl, Daniel
2007-12-26
Many-Body Perturbation Theory (MBPT) is today highly developed. The electron correlation of atomic and molecular systems can be evaluated to essentially all orders of perturbation theory--also relativistically (RMBPT)--by means of techniques of Coupled-Cluster type. When high accuracy is needed, effects beyond RMBPT will enter, i.e., effects of retarded Breit interaction and of radiative effects (Lamb shift), effects normally referred to as QED effects. These effects can be evaluated by means of special techniques, like S-matrix formulation, which cannot simultaneously treat electron correlation. It would for many applications be desirable to have access to a numerical technique, where effects of electron correlation and of QED could be treated on the same footing. Such a technique is presently being developed and gradually implemented at our laboratory. Some numerical results will be given.
Field Theoretical Approach to the Formation of Junctions of Cosmic Strings
Salmi, Petja
2007-11-20
Superstring theory predicts the potential formation of string networks with junctions. Kinematic constraints for junction formation were derived in [1], based on Nambu-Goto action. Here we test these constraints numerically within the framework of Abelian-Higgs model and report on good agreement with the analytical predictions.
Kinematic constraints on formation of bound states of cosmic strings: Field theoretical approach
Salmi, P.; Achucarro, A.; Copeland, E. J.; Kibble, T. W. B.; Putter, R. de; Steer, D. A.
2008-02-15
Superstring theory predicts the potential formation of string networks with bound states ending in junctions. Kinematic constraints for junction formation have been derived within the Nambu-Goto thin string approximation. Here we test these constraints numerically in the framework of the Abelian-Higgs model in the Type-I regime and report on good agreement with the analytical predictions. We also demonstrate that strings can effectively pass through each other when they meet at speeds slightly above the critical velocity permitting bound-state formation. This is due to reconnection effects that are beyond the scope of the Nambu-Goto approximation.
NASA Astrophysics Data System (ADS)
Gladysiewicz, M.; Janicki, L.; Misiewicz, J.; Sobanska, M.; Klosek, K.; Zytkiewicz, Z. R.; Kudrawiec, R.
2016-09-01
Polarization engineering of GaN-based heterostructures opens a way to develop advanced transistor heterostructures, although measurement of the electric field in such heterostructures is not a simple task. In this work, contactless electroreflectance (CER) spectroscopy has been applied to measure the electric field in GaN-based heterostructures. For a set of GaN(d = 0, 5, 15, and 30 nm)/AlGaN(20 nm)/GaN(buffer) heterostructures a decrease of electric field in the GaN(cap) layer from 0.66 MV cm‑1 to 0.27 MV cm‑1 and an increase of the electric field in the AlGaN layer from 0.57 MV cm‑1 to 0.99 MV cm‑1 have been observed with the increase in the GaN(cap) thickness from 5–30 nm. For a set of GaN(20 nm)/AlGaN(d = 10, 20, 30, and 40 nm)/GaN(buffer) heterostructures a decrease of the electric field in the AlGaN layer from 1.77 MV cm‑1 to 0.64 MV cm‑1 and an increase of the electric field in the GaN layer from 0.57 MV cm‑1 to 0.99 MV cm‑1 were observed with the increase in the AlGaN thickness from 10–40 nm. To determine the distribution of the electric field in these heterostructures the Schrödinger and Poisson equations are solved in a self-consistent manner and matched with experimental data. It is shown that the built-in electric field in the GaN(cap) and AlGaN layers obtained from measurements does not reach values of electric field resulting only from polarization effects. The measured electric fields are smaller due to a screening of polarization effects by free carriers, which are inhomogeneously distributed across the heterostructure and accumulate at interfaces. The results clearly demonstrate that CER measurements supported by theoretical calculations are able to determine the electric field distribution in GaN-based heterostructures quantitatively, which is very important for polarization engineering in this material system.
Costa, Dominique; Garrain, Pierre-Alain; Baaden, Marc
2013-04-01
Interactions between biomolecules and inorganic surfaces play an important role in natural environments and in industry, including a wide variety of conditions: marine environment, ship hulls (fouling), water treatment, heat exchange, membrane separation, soils, mineral particles at the earth's surface, hospitals (hygiene), art and buildings (degradation and biocorrosion), paper industry (fouling) and more. To better control the first steps leading to adsorption of a biomolecule on an inorganic surface, it is mandatory to understand the adsorption mechanisms of biomolecules of several sizes at the atomic scale, that is, the nature of the chemical interaction between the biomolecule and the surface and the resulting biomolecule conformations once adsorbed at the surface. This remains a challenging and unsolved problem. Here, we review the state of art in experimental and theoretical approaches. We focus on metallic biomaterial surfaces such as TiO(2) and stainless steel, mentioning some remarkable results on hydroxyapatite. Experimental techniques include atomic force microscopy, surface plasmon resonance, quartz crystal microbalance, X-ray photoelectron spectroscopy, fluorescence microscopy, polarization modulation infrared reflection absorption spectroscopy, sum frequency generation and time of flight secondary ion mass spectroscopy. Theoretical models range from detailed quantum mechanical representations to classical forcefield-based approaches. PMID:23015529
Chomiak, Taylor; Hu, Bin
2009-01-01
Background The biological process underlying axonal myelination is complex and often prone to injury and disease. The ratio of the inner axonal diameter to the total outer diameter or g-ratio is widely utilized as a functional and structural index of optimal axonal myelination. Based on the speed of fiber conduction, Rushton was the first to derive a theoretical estimate of the optimal g-ratio of 0.6 [1]. This theoretical limit nicely explains the experimental data for myelinated axons obtained for some peripheral fibers but appears significantly lower than that found for CNS fibers. This is, however, hardly surprising given that in the CNS, axonal myelination must achieve multiple goals including reducing conduction delays, promoting conduction fidelity, lowering energy costs, and saving space. Methodology/Principal Findings In this study we explore the notion that a balanced set-point can be achieved at a functional level as the micro-structure of individual axons becomes optimized, particularly for the central system where axons tend to be smaller and their myelin sheath thinner. We used an intuitive yet novel theoretical approach based on the fundamental biophysical properties describing axonal structure and function to show that an optimal g-ratio can be defined for the central nervous system (≈0.77). Furthermore, by reducing the influence of volume constraints on structural design by about 40%, this approach can also predict the g-ratio observed in some peripheral fibers (≈0.6). Conclusions/Significance These results support the notion of optimization theory in nervous system design and construction and may also help explain why the central and peripheral systems have evolved different g-ratios as a result of volume constraints. PMID:19915661
Locating a weak change using diffuse waves: Theoretical approach and inversion procedure
NASA Astrophysics Data System (ADS)
Rossetto, Vincent; Margerin, Ludovic; Planès, Thomas; Larose, Éric
2011-02-01
We describe a time-resolved monitoring technique for heterogeneous media. Our approach is based on the spatial variations of the cross-coherence of diffuse waves acquired at fixed positions but at different dates. The technique applies to all kind of waves, provided that waveforms can be acquired with a sampling frequency much larger than the wave frequency. To locate and characterize a weak change that occurred between successive acquisitions, we use a maximum likelihood approach combined with a diffusive propagation model. We characterize this technique, locating a weak change using diffuse waves, called LOCADIFF, with the aid of numerical simulations. In several illustrative examples, we show that the change can be located with a precision of a few wavelengths and that its effective scattering cross-section can be retrieved. We investigate how the accuracy and precision of the method depends on the number of source-receiver pairs, on the time window used to compute the cross-correlation and on the errors in the propagation model. Applications can be found in nondestructive testing, seismology, radar, and sonar location.
Theoretical approach for enhanced mass transfer effects in-duct flue gas desulfurization processes
Not Available
1990-08-22
While developing dry sorbent duct injection flue gas desulfurization processes may offer significant improvement in capital cost and process simplicity compared to wet scrubbing systems, the economics of this technology can be improved significantly by an improvement in sorbent utilization. While a general understanding of the mechanism by which the sorbents operate is known, a much more detailed knowledge of reaction rate-controlling phenomena, the role of inherent reactivity, and mass transfer effects and their interaction in needed. Objectives of this project are threefold: 1. Mass transfer investigation--determine the controlling physical and chemical processes that limit sorbent utilization. In particular, determine whether mass transfer is a controlling factor in in-duct flue gas desulfurization and establish the relative contributions of gas- and liquid-phase mass transfer and inherent sorbent reactivity. 2. Field test support--evaluate various sorbents, operating conditions and process schemes to support large-scale field testings at Meredosia and Beverly. 3. Mass transfer enhancement--examine various techniques that will enable sorbent utilization rates of at least 75 percent to be achieved. Sorbents investigated were Ca(OH){sub 2}, Mississippi hydrate and Mississippi slaked lime. Epsom Salt was investigated as an additive. Agglomeration of Ca(OH){sub 2} solids was also investigated. 3 refs., 92 figs., 23 tabs.
Designing an optimal software intensive system acquisition: A game theoretic approach
NASA Astrophysics Data System (ADS)
Buettner, Douglas John
The development of schedule-constrained software-intensive space systems is challenging. Case study data from national security space programs developed at the U.S. Air Force Space and Missile Systems Center (USAF SMC) provide evidence of the strong desire by contractors to skip or severely reduce software development design and early defect detection methods in these schedule-constrained environments. The research findings suggest recommendations to fully address these issues at numerous levels. However, the observations lead us to investigate modeling and theoretical methods to fundamentally understand what motivated this behavior in the first place. As a result, Madachy's inspection-based system dynamics model is modified to include unit testing and an integration test feedback loop. This Modified Madachy Model (MMM) is used as a tool to investigate the consequences of this behavior on the observed defect dynamics for two remarkably different case study software projects. Latin Hypercube sampling of the MMM with sample distributions for quality, schedule and cost-driven strategies demonstrate that the higher cost and effort quality-driven strategies provide consistently better schedule performance than the schedule-driven up-front effort-reduction strategies. Game theory reasoning for schedule-driven engineers cutting corners on inspections and unit testing is based on the case study evidence and Austin's agency model to describe the observed phenomena. Game theory concepts are then used to argue that the source of the problem and hence the solution to developers cutting corners on quality for schedule-driven system acquisitions ultimately lies with the government. The game theory arguments also lead to the suggestion that the use of a multi-player dynamic Nash bargaining game provides a solution for our observed lack of quality game between the government (the acquirer) and "large-corporation" software developers. A note is provided that argues this multi
NASA Astrophysics Data System (ADS)
Kang, P. K.; Le Borgne, T.; Dentz, M.; Bour, O.; Juanes, R.
2014-12-01
Quantitative modeling of flow and transport through fractured geological media is challenging due to the inaccessibility of the underlying medium properties and the complex interplay between heterogeneity and small scale transport processes such as heterogeneous advection, matrix diffusion, hydrodynamic dispersion and adsorption. This complex interplay leads to anomalous (non-Fickian) transport behavior, the origin of which remains a matter of debate: whether it arises from variability in fracture permeability (velocity heterogeneity), connectedness in the fracture network (velocity correlation), or interaction between fractures and matrix. Here we show that this uncertainty of heterogeneity- vs. correlation-controlled transport can be resolved by combining convergent and push-pull tracer tests because flow reversibility is strongly dependent on correlation, whereas late-time scaling of breakthrough curves is mainly controlled by heterogeneity. We build on this insight, and propose a Lagrangian statistical model that takes the form of a continuous time random walk (CTRW) with correlated particle velocities. In this framework, flow heterogeneity and flow correlation are quantified by a Markov process of particle transition times that is characterized by a distribution function and a transition probability. Our transport model captures the anomalous behavior in the breakthrough curves for both push-pull and convergent flow geometries, with the same set of parameters. We validate our model in the Ploemeur observatory in France. Thus, the proposed correlated CTRW modeling approach provides a simple yet powerful framework for characterizing the impact of flow correlation and heterogeneity on transport in fractured media.
NASA Astrophysics Data System (ADS)
Kang, Peter K.; Le Borgne, Tanguy; Dentz, Marco; Bour, Olivier; Juanes, Ruben
2015-02-01
Flow and transport through fractured geologic media often leads to anomalous (non-Fickian) transport behavior, the origin of which remains a matter of debate: whether it arises from variability in fracture permeability (velocity distribution), connectedness in the flow paths through fractures (velocity correlation), or interaction between fractures and matrix. Here we show that this uncertainty of distribution- versus correlation-controlled transport can be resolved by combining convergent and push-pull tracer tests because flow reversibility is strongly dependent on velocity correlation, whereas late-time scaling of breakthrough curves is mainly controlled by velocity distribution. We build on this insight, and propose a Lagrangian statistical model that takes the form of a continuous time random walk (CTRW) with correlated particle velocities. In this framework, velocity distribution and velocity correlation are quantified by a Markov process of particle transition times that is characterized by a distribution function and a transition probability. Our transport model accurately captures the anomalous behavior in the breakthrough curves for both push-pull and convergent flow geometries, with the same set of parameters. Thus, the proposed correlated CTRW modeling approach provides a simple yet powerful framework for characterizing the impact of velocity distribution and correlation on transport in fractured media.
Theoretical and experimental flow fields for a supersonic cruise fighter forebody
NASA Technical Reports Server (NTRS)
Yaros, S. F.
1985-01-01
The capability of two numerical methods to predict the flow field about a representative supersonic cruise aircraft was examined. The two codes were a small-disturbance transonic program of Boppe and a conservative form full-potential transonic program of Shankar and Szema. For the former code, comparisons were made with wind-tunnel data at Mach numbers of 0.6, 0.9, and 1.2 and angles of attack of 0 deg, 5 deg, and 10 deg (7.5 deg instead of 10 deg at a Mach number of 1.2). Predictions from the two codes were compared at a Mach number of 1.2 and an angle of attack of 7.5 deg. The comparison criteria were contours of local angle of attack, local angle of sideslip, and local Mach number. The comparisons indicated that both codes may be considered useful for design applications, depending on the degree of accuracy required by the user's solution. Both solutions show an inaccuracy in their predictions, particularly as Mach number and/or angle of attack increases, because of their lack of viscous effects and any mechanisms to predict vortex development.
Theoretical and Applied Research in the Field of Higher Geodesy Conducted in Rzeszow
NASA Astrophysics Data System (ADS)
Kadaj, Roman; Świętoń, Tomasz
2016-06-01
Important qualitative changes were taking place in polish geodesy in last few years. It was related to application of new techniques and technologies and to introduction of European reference frames in Poland. New reference stations network ASG-EUPOS, together with Internet services which helps in precise positioning was created. It allows to fast setting up precise hybrid networks. New, accurate satellite networks became the basis of new definitions in the field of reference systems. Simultaneously arise the need of new software, which enables to execute the geodetic works in new technical conditions. Authors had an opportunity to participate in mentioned undertakings, also under the aegis of GUGiK, by creation of methods, algorithms and necessary software tools. In this way the automatic postprocessing module (APPS) in POZGEO service, a part of ASG-EUPOS system came into being. It is an entirely polish product which works in Trimble environment. Universal software for transformation between PLETRF89, PL-ETRF2000, PULKOWO'42 reference systems as well as defined coordinate systems was created (TRANSPOL v. 2.06) and published as open product. An essential functional element of the program is the quasi-geoid model PL-geoid-2011, which has been elaborated by adjustment (calibration) of the global quasi-geoid model EGM2008 to 570 geodetic points (satellite-leveling points). Those and other studies are briefly described in this paper.
Arefin, Ahmed Shamsul; Vimieiro, Renato; Riveros, Carlos; Craig, Hugh; Moscato, Pablo
2014-01-01
In this paper we analyse the word frequency profiles of a set of works from the Shakespearean era to uncover patterns of relationship between them, highlighting the connections within authorial canons. We used a text corpus comprising 256 plays and poems from the 16th and 17th centuries, with 17 works of uncertain authorship. Our clustering approach is based on the Jensen-Shannon divergence and a graph partitioning algorithm, and our results show that authors' characteristic styles are very powerful factors in explaining the variation of word use, frequently transcending cross-cutting factors like the differences between tragedy and comedy, early and late works, and plays and poems. Our method also provides an empirical guide to the authorship of plays and poems where this is unknown or disputed. PMID:25347727
Arefin, Ahmed Shamsul; Vimieiro, Renato; Riveros, Carlos; Craig, Hugh; Moscato, Pablo
2014-01-01
In this paper we analyse the word frequency profiles of a set of works from the Shakespearean era to uncover patterns of relationship between them, highlighting the connections within authorial canons. We used a text corpus comprising 256 plays and poems from the 16th and 17th centuries, with 17 works of uncertain authorship. Our clustering approach is based on the Jensen-Shannon divergence and a graph partitioning algorithm, and our results show that authors' characteristic styles are very powerful factors in explaining the variation of word use, frequently transcending cross-cutting factors like the differences between tragedy and comedy, early and late works, and plays and poems. Our method also provides an empirical guide to the authorship of plays and poems where this is unknown or disputed. PMID:25347727
Theoretical Approaches for Understanding the Interplay Between Stress and Chemical Reactivity.
Kochhar, Gurpaul S; Heverly-Coulson, Gavin S; Mosey, Nicholas J
2015-01-01
The use of mechanical stresses to induce chemical reactions has attracted significant interest in recent years. Computational modeling can play a significant role in developing a comprehensive understanding of the interplay between stresses and chemical reactivity. In this review, we discuss techniques for simulating chemical reactions occurring under mechanochemical conditions. The methods described are broadly divided into techniques that are appropriate for studying molecular mechanochemistry and those suited to modeling bulk mechanochemistry. In both cases, several different approaches are described and compared. Methods for examining molecular mechanochemistry are based on exploring the force-modified potential energy surface on which a molecule subjected to an external force moves. Meanwhile, it is suggested that condensed phase simulation methods typically used to study tribochemical reactions, i.e., those occurring in sliding contacts, can be adapted to study bulk mechanochemistry. PMID:26233311
Theoretical aspects of pressure and solute denaturation of proteins: A Kirkwood-buff-theory approach
NASA Astrophysics Data System (ADS)
Ben-Naim, Arieh
2012-12-01
A new approach to the problem of pressure-denaturation (PD) and solute-denaturation (SD) of proteins is presented. The problem is formulated in terms of Le Chatelier principle, and a solution is sought in terms of the Kirkwood-Buff theory of solutions. It is found that both problems have one factor in common; the excluded volumes of the folded and the unfolded forms with respect to the solvent molecules. It is shown that solvent-induced effects operating on hydrophilic groups along the protein are probably the main reason for PD. On the other hand, the SD depends on the preferential solvation of the folded and the unfolded forms with respect to solvent and co-solvent molecules.
Binarisms, regressive outcomes and biases in the drug policy interventions: a theoretical approach.
Gerevich, József
2005-01-01
The golden age of drug policy was characterized by the informal regulation of drug use. Formalization of the control over regulation and its increasingly strict, aggressive character led to the emergence of a binary attitude. The main binarisms: pharmaceutical or drug; ban or tolerance; punishment or treatment; psychopathological or pathopsychological approach; subjective or objective knowledge; traditional or alternative. On the basis of Kuhn's paradigm theory, these binarisms can be integrated. Drug policy interventions based on the binary attitude have had regressive effects. Using the work of Sam Sieber, the author distinguishes nine regressive influences: functional imbalance, perverse diagnosis, ricochet, overload, goal displacement, exploitation, provocation, classification, and placation. The regressive influences have caused the escalation of "the drug problem," which in turn has led to further regressive interventions. This vicious circle could be broken by eliminating the four biases--the paternalistic, elitist, rationalist, and activist biases--underlying the regressive interventions. PMID:15830729
A billiard-theoretic approach to elementary one-dimensional elastic collisions
NASA Astrophysics Data System (ADS)
Redner, S.
2004-12-01
A simple relation is developed between the elastic collisions of freely moving particles in one dimension and a corresponding billiard system. For two particles with masses m1 and m2 on the half-line x>0 that approach an elastic barrier at x=0, the corresponding billiard system is an infinite wedge. The collision history of the two particles can be easily inferred from the corresponding billiard trajectory. This connection explains the classic demonstrations of the "dime on the superball" and the "baseball on the basketball" that are a staple in elementary physics courses. It also is shown that three elastic particles on an infinite line and three particles on a finite ring correspond, respectively, to the motion of a billiard ball in an infinite wedge and on a triangular billiard table. It is shown how to determine the angles of these two sets in terms of the particle masses.
NASA Astrophysics Data System (ADS)
Klüner, Thorsten
2010-05-01
Photodesorption of small molecules from surfaces is one of the most fundamental processes in surface photochemistry. Despite its apparent simplicity, a microscopic understanding beyond a qualitative picture still poses a true challenge for theory. While the dynamics of nuclear motion can be treated on various levels of sophistication, all approaches suffer from the lack of sufficiently accurate potential energy surfaces, in particular for electronically excited states involved in the desorption scenario. In the last decade, a systematic and accurate methodology has been developed which allows a reliable calculation of accurate ground and excited state potential energy surfaces (PES) for different adsorbate-substrate systems. These potential energy surfaces serve as a prerequisite for subsequent quantum dynamical wave packet calculations, which allow for a direct simulation of experimentally observable quantities such as quantum state resolved velocity distributions. In the first part of this review, we will focus on scalar properties of desorbing diatomic molecules from insulating surfaces, where we also present a recently developed strategy of obtaining accurate potential energy surfaces using quantum chemical approaches. In general, diatomic molecules on large band gap materials such as oxide surfaces are studied which allows the use of sufficiently large cluster models and accurate ab initio methods beyond density functional theory (DFT). In the second part, we will focus on the vectorial aspects of the dynamics of nuclear motion and present simulations of experimentally accessible observables such as velocity distributions, Doppler profiles and alignment parameters. For each system, the microscopic mechanism of photodesorption is elucidated. We will demonstrate that the driving force of surface photochemistry is strongly dependent on details of the electronic structure of the adsorbate-substrate systems. This implies that great caution is advisable if
Spectral Synthesis via Mean Field approach to Independent Component Analysis
NASA Astrophysics Data System (ADS)
Hu, Ning; Su, Shan-Shan; Kong, Xu
2016-03-01
We apply a new statistical analysis technique, the Mean Field approach to Independent Component Analysis (MF-ICA) in a Bayseian framework, to galaxy spectral analysis. This algorithm can compress a stellar spectral library into a few Independent Components (ICs), and the galaxy spectrum can be reconstructed by these ICs. Compared to other algorithms which decompose a galaxy spectrum into a combination of several simple stellar populations, the MF-ICA approach offers a large improvement in efficiency. To check the reliability of this spectral analysis method, three different methods are used: (1) parameter recovery for simulated galaxies, (2) comparison with parameters estimated by other methods, and (3) consistency test of parameters derived with galaxies from the Sloan Digital Sky Survey. We find that our MF-ICA method can not only fit the observed galaxy spectra efficiently, but can also accurately recover the physical parameters of galaxies. We also apply our spectral analysis method to the DEEP2 spectroscopic data, and find it can provide excellent fitting results for low signal-to-noise spectra.
Mean field approach to fluctuations of surface line defects
NASA Astrophysics Data System (ADS)
Margetis, Dionisios
2011-03-01
Below the roughening transition temperature, the dynamics of crystal surfaces are driven by the motion of line defects (steps) of atomic size. According to the celebrated Burton Cabrera-Frank (BCF) model, the steps move by mass conservation, as adsorbed atoms (adatoms) diffuse on terraces and attach/detach at step edges. The resulting deterministic equations of motion incorporate nonlinear couplings due to entropic and elastic-dipole step-step interactions. In this talk, I will discuss a formal theory for stochastic aspects of step motion by adding noise to the BCF model in 1+1 dimensions. I will define systematically a ``mean field'' that enables the conversion of the coupled, nonlinear stochastic equations for the distance between neighboring steps (terrace widths) to a single Langevin-type equation for an effective terrace width. In the course of my study, I invoke the Bogoliubov-Born-Green Kirkwood-Yvon (BBGKY) hierarchy for joint terrace-width probability densities and a decorrelation ansatz for terrace widths. By using an example drawn from epitaxial growth (with material deposition from above), I will compare the mean field approach to an exact result from a linearized growth model. [D. Margetis, J. Phys A: Math. Theor. 43, 065003 (2010).] This work was supported by NSF under Grant DMS-0847587.
NASA Astrophysics Data System (ADS)
Daher, Walid; Pistre, Séverin; Kneppers, Angeline; Bakalowicz, Michel; Najem, Wajdi
2011-10-01
SummaryManaged Aquifer Recharge (MAR) is an emerging sustainable technique that has already generated successful results and is expected to solve many water resource problems, especially in semi-arid and arid zones. It is of great interest for karst aquifers that currently supply 20-25% of the world's potable water, particularly in Mediterranean countries. However, the high heterogeneity in karst aquifers is too complex to be able to locate and describe them simply via field observations. Hence, as compared to projects in porous media, MAR is still marginal in karst aquifers. Accordingly, the present work presents a conceptual methodology for Aquifer Rechargeability Assessment in Karst - referred to as ARAK. The methodology was developed noting that artificial recharge in karst aquifers is considered an improbable challenge to solve since karst conduits may drain off recharge water without any significant storage, or recharge water may not be able to infiltrate. The aim of the ARAK method is to determine the ability of a given karst aquifer to be artificially recharged and managed, and the best sites for implementing artificial recharge from the surface. ARAK is based on multi-criteria indexation analysis modeled on karst vulnerability assessment methods. ARAK depends on four independent criteria, i.e. Epikarst, Rock, Infiltration and Karst. After dividing the karst domain into grids, these criteria are indexed using geological and topographic maps refined by field observations. ARAK applies a linear formula that computes the intrinsic rechargeability index based on the indexed map for every criterion, coupled with its attributed weighting rate. This index indicates the aptitude for recharging a given karst aquifer, as determined by studying its probability first on a regional scale for the whole karst aquifer, and then by characterizing the most favorable sites. Subsequently, for the selected sites, a technical and economic feasibility factor is applied, weighted
Maity, S; Gorai, A K; Pal, A K
2006-06-01
This paper elucidates the basic approach of determining the path coefficients and its significance in the road traffic noise annoyance. Path model not only outline the direct effect of the traffic noise on the nearby residents but also indicate the indirect effect via other variables. In this study seven variables were considered for determining road traffic noise annoyance. However the same would be equally applicable for other situations like aircraft noise, rail noise, and industry noise with the different variables. At the outset a priori path model was designed and then on the basis of the partial regression coefficient values for the different paths, the revised path model was developed. The standardized partial regression coefficients known as path coefficients, determine the strength of the linkage among variables. Some of the paths in the model were not statistically significant. Revised path models were developed by deleting the insignificant paths whose values were found above 5% level. In the revised path model, thus the direct and indirect effect due to a particular variable causing the road traffic noise annoyance could be observed. PMID:16917695
Mechanisms-based viscoplasticity: Theoretical approach and experimental validation for steel 304L
Zubelewicz, Aleksander; Oliferuk, Wiera
2016-01-01
We propose a mechanisms-based viscoplasticity approach for metals and alloys. First, we derive a stochastic model for thermally-activated motion of dislocations and, then, introduce power-law flow rules. The overall plastic deformation includes local plastic slip events taken with an appropriate weight assigned to each angle of the plane misorientation from the direction of maximum shear stress. As deformation progresses, the material experiences successive reorganizations of the slip systems. The microstructural evolution causes that a portion of energy expended on plastic deformation is dissipated and the rest is stored in the defect structures. We show that the reorganizations are stable in a homogeneously deformed material. The concept is tested for steel 304L, where we reproduce experimentally obtained stress-strain responses, we construct the Frost-Ashby deformation map and predict the rate of the energy storage. The storage is assessed in terms of synchronized measurements of temperature and displacement distributions on the specimen surface during tensile loading. PMID:27026209
NASA Astrophysics Data System (ADS)
Hancer, Mehmet; Arkaz, Harun
2015-11-01
Although there are many viable approaches to induce hydrophobicity, a superhydrophobic surface could only be fabricated by combination of surface chemistry modification and roughness enhancement. In this study, surface roughness was obtained by 12 nm SiO2 nanoparticles (NPs) which were chemically modified using a self-assembled monolayer of perfluorodecyltrichlorosilane. The SiO2 NPs which were rendered hydrophobic, then successfully dispersed into a poly silicon (silsesquioxane) matrix at varying concentrations from 0.5 to 4%. The NPs dispersed polymer suspension was then spray coated on to glass and aluminum coupons in order to achieve polymer thin film nanocomposites. The results were revealed a superhydrophobic surface with a water contact angle exceeding 178° with low hysteresis and bouncing water droplet behavior. Furthermore the composite film reliability (hot-humid and ice build-up) was tested in an environmental control chamber by precisely adjusting both temperature (85 °C) and relative humidity (85 RH). Taber abrasion testing was applied in order to gain insights into the abrasion resistance of nanocomposite film. Finally, ice formation was simulated at -20 °C on the superhydrophobic nanocomposite film coated substrates.
Mechanisms-based viscoplasticity: Theoretical approach and experimental validation for steel 304L.
Zubelewicz, Aleksander; Oliferuk, Wiera
2016-01-01
We propose a mechanisms-based viscoplasticity approach for metals and alloys. First, we derive a stochastic model for thermally-activated motion of dislocations and, then, introduce power-law flow rules. The overall plastic deformation includes local plastic slip events taken with an appropriate weight assigned to each angle of the plane misorientation from the direction of maximum shear stress. As deformation progresses, the material experiences successive reorganizations of the slip systems. The microstructural evolution causes that a portion of energy expended on plastic deformation is dissipated and the rest is stored in the defect structures. We show that the reorganizations are stable in a homogeneously deformed material. The concept is tested for steel 304L, where we reproduce experimentally obtained stress-strain responses, we construct the Frost-Ashby deformation map and predict the rate of the energy storage. The storage is assessed in terms of synchronized measurements of temperature and displacement distributions on the specimen surface during tensile loading. PMID:27026209
NASA Astrophysics Data System (ADS)
Sethi, Arun; Bhatia, Akriti; Maurya, Atul; Panday, Anil; Bhatia, Gitika; Shrivastava, Atul; Singh, Ranvijay Pratap; Prakash, Rohit
2013-11-01
Synthesis of a number of pregnane derivatives including the glycoside has been described in detail. These compounds were synthesized by reaction of 3β-acetoxy-5, 16-pregnadiene-20-one, derived from diosgenin and then treating it with different nucleophilic reagents. The structures of these newly synthesized compounds were established on the basis of their physical, chemical and spectral data. The molecular geometry of compounds were calculated in ground state by density functional theory method (DFT/B3LYP) using 6-31G (d,p) basis set. 1H NMR chemical shifts were also studied using gauge-including atomic orbital (GIAO) approach, which were found in good agreement with the experimental values. The study of electronic properties such as UV-Vis spectral analysis, HOMO and LUMO energy calculations were performed with time dependent DFT (TD-DFT). Global and local reactivity descriptors were calculated to study the reactive sites within the molecules. These compounds were also evaluated for their anti-dyslipidemic (Triton model) and in vitro anti-oxidant activities. Out of these, compound 9 showed potent anti-dyslipidemic and anti-oxidant activity.
Cantegreil-Kallen, Inge; Rigaud, Anne-Sophie
2009-12-01
Alzheimer's disease has a negative impact on family relationships and may trigger conflicts between the main caregiver and other family members. The systemic approach evidences the impact of dementia on structural and functional characteristics of the family system. Systemic family therapy is especially indicated in crisis situations such as emergency hospitalization or institutionalization of the patient, and when the family members do not agree on when and how to introduce care and support services at the patient's home. In this case, the aim of the intervention is to restore the communication between all the family members in order to find an agreement for the best management of the patients. Since September 2006, systemic family therapy has been offered in the memory clinic of the Broca Hospital to families having a member suffering from Alzheimer's disease. The involvement of the families was accomplished by the direct participation of the patient, main caregiver (spouse), grown-up children and grandchildren. The aim was to obtain an agreement for the access of support and care services at home from all the family members. The intervention was based on a step-by-step procedure and comprehended five sessions. The primary results of a pilot study are presented. PMID:20031507
Mechanisms-based viscoplasticity: Theoretical approach and experimental validation for steel 304L
NASA Astrophysics Data System (ADS)
Zubelewicz, Aleksander; Oliferuk, Wiera
2016-03-01
We propose a mechanisms-based viscoplasticity approach for metals and alloys. First, we derive a stochastic model for thermally-activated motion of dislocations and, then, introduce power-law flow rules. The overall plastic deformation includes local plastic slip events taken with an appropriate weight assigned to each angle of the plane misorientation from the direction of maximum shear stress. As deformation progresses, the material experiences successive reorganizations of the slip systems. The microstructural evolution causes that a portion of energy expended on plastic deformation is dissipated and the rest is stored in the defect structures. We show that the reorganizations are stable in a homogeneously deformed material. The concept is tested for steel 304L, where we reproduce experimentally obtained stress-strain responses, we construct the Frost-Ashby deformation map and predict the rate of the energy storage. The storage is assessed in terms of synchronized measurements of temperature and displacement distributions on the specimen surface during tensile loading.
NASA Astrophysics Data System (ADS)
Tejedor, A.; Foufoula-Georgiou, E.; Longjas, A.; Zaliapin, I. V.
2014-12-01
River deltas are intricate landscapes with complex channel networks that self-organize to deliver water, sediment, and nutrients from the apex to the delta top and eventually to the coastal zone. The natural balance of material and energy fluxes which maintains a stable hydrologic, geomorphologic, and ecological state of a river delta, is often disrupted by external factors causing topological and dynamical changes in the delta structure and function. A formal quantitative framework for studying river delta topology and transport dynamics and their response to change is lacking. Here we present such a framework based on spectral graph theory and demonstrate its value in quantifying the complexity of the delta network topology, computing its steady state fluxes, and identifying upstream (contributing) and downstream (nourishment) areas from any point in the network. We use this framework to construct vulnerability maps that quantify the relative change of sediment and water delivery to the shoreline outlets in response to possible perturbations in hundreds of upstream links. This enables us to evaluate which links (hotspots) and what management scenarios would most influence flux delivery to the outlets, paving the way of systematically examining how local or spatially distributed delta interventions can be studied within a systems approach for delta sustainability.
Surface enhanced Raman spectroscopic studies on aspirin : An experimental and theoretical approach
NASA Astrophysics Data System (ADS)
Premkumar, R.; Premkumar, S.; Rekha, T. N.; Parameswari, A.; Mathavan, T.; Benial, A. Milton Franklin
2016-05-01
Surface enhanced Raman scattering (SERS) studies on aspirin molecule adsorbed on silver nanoparticles (AgNPs) were investigated by experimental and density functional theory approach. The AgNPs were synthesized by the solution-combustion method and characterized by the X-ray diffraction and high resolution-transmission electron microscopy techniques. The averaged particle size of synthesized AgNPs was calculated as ˜55 nm. The normal Raman spectrum (nRs) and SERS spectrum of the aspirin were recorded. The molecular structure of the aspirin and aspirin adsorbed on silver cluster were optimized by the DFT/ B3PW91 method with LanL2DZ basis set. The vibrational frequencies were calculated and assigned on the basis of potential energy distribution calculation. The calculated nRs and SERS frequencies were correlated well with the observed frequencies. The flat-on orientation was predicted from the nRs and SERS spectra, when the aspirin adsorbed on the AgNPs. Hence, the present studies lead to the understanding of adsorption process of aspirin on the AgNPs, which paves the way for biomedical applications.
2011-01-01
Background Surprisal analysis is a thermodynamic-like molecular level approach that identifies biological constraints that prevents the entropy from reaching its maximum. To examine the significance of altered gene expression levels in tumorigenesis we apply surprisal analysis to the WI-38 model through its precancerous states. The constraints identified by the analysis are transcription patterns underlying the process of transformation. Each pattern highlights the role of a group of genes that act coherently to define a transformed phenotype. Results We identify a major transcription pattern that represents a contraction of signaling networks accompanied by induction of cellular proliferation and protein metabolism, which is essential for full transformation. In addition, a more minor, "tumor signature" transcription pattern completes the transformation process. The variation with time of the importance of each transcription pattern is determined. Midway through the transformation, at the stage when cells switch from slow to fast growth rate, the major transcription pattern undergoes a total inversion of its weight while the more minor pattern does not contribute before that stage. Conclusions A similar network reorganization occurs in two very different cellular transformation models: WI-38 and the cervical cancer HF1 models. Our results suggest that despite differences in a list of transcripts expressed in different cancer models the rationale of the network reorganization remains essentially the same. PMID:21410932
NASA Astrophysics Data System (ADS)
Fenicia, Fabrizio; Kavetski, Dmitri; Savenije, Hubert H. G.
2011-11-01
This paper introduces a flexible framework for conceptual hydrological modeling, with two related objectives: (1) generalize and systematize the currently fragmented field of conceptual models and (2) provide a robust platform for understanding and modeling hydrological systems. In contrast to currently dominant "fixed" model applications, the flexible framework proposed here allows the hydrologist to hypothesize, build, and test different model structures using combinations of generic components. This is particularly useful for conceptual modeling at the catchment scale, where limitations in process understanding and data availability remain major research and operational challenges. The formulation of the model architecture and individual components to represent distinct aspects of catchment-scale function, such as storage, release, and transmission of water, is discussed. Several numerical strategies for implementing the model equations within a computationally robust framework are also presented. In the companion paper, the potential of the flexible framework is examined with respect to supporting more systematic and stringent hypothesis testing, for characterizing catchment diversity, and, more generally, for aiding progress toward more unified hydrological theory at the catchment scale.
Theoretical studies of aluminum and aluminide alloys using CALPHAD and first-principles approach
NASA Astrophysics Data System (ADS)
Jiang, Chao
Heat-treatable aluminum alloys have been widely used in the automobile and aerospace industries as structural materials due to their light weight and high strength. To study the age-hardening process in heat-treatable aluminum alloys, the Gibbs energies of the strengthening metastable phases, e.g. theta ' and theta″, are critical. However, those data are not included in the existing thermodynamic databases for aluminum alloys due to the semi-empirical nature of the CALPHAD approach. In the present study, the thermodynamics of the Al-Cu system, the pivotal age-hardening system, is remodeled using a combined CALPHAD and first-principles approach. The formation enthalpies and vibrational formation entropies of the stable and metastable phases in the Al-Cu system are provided by first-principles calculations. Special Quasirandom Structures (SQS's) are applied to model the substitutionally random fee and bee alloys. SQS's for binary bee alloys are developed and tested in the present study. Finally, a self-consistent thermodynamic description of the Al-Cu system including the two metastable theta″ and theta' phases is obtained. During welding of heat-treatable aluminum alloys, a detrimental phenomenon called constitutional liquation, i.e. the local eutectic melting of second-phase particles in a matrix at temperatures above the eutectic temperature but below the solidus of the alloy, may occur in the heat-affected zone (HAZ). In the present study, diffusion code DICTRA coupled with realistic thermodynamic and kinetic databases is used to simulate the constitutional liquation in the model Al-Cu system. The simulated results are in quantitative agreement with experiments. The critical heating rate to avoid constitutional liquation is also determined through computer simulations. Besides the heat-treatable aluminum alloys, intermetallic compounds based on transition metal aluminides, e.g. NiAl and FeAl, are also promising candidates for the next-generation of high
NASA Astrophysics Data System (ADS)
Karabacak, Mehmet; Cinar, Zeliha; Cinar, Mehmet
2012-01-01
In this work, the molecular conformation, vibrational and electronic analysis of para-aminohippuric acid (pAHA, C 9H 10N 2O 3) were presented for the ground state using experimental techniques (FT-IR, FT-Raman and UV) and density functional theory (DFT) employing B3LYP exchange correlation with the 6-311++G(d,p) basis set. FT-IR and FT-Raman spectra were recorded in the regions of 400-4000 cm -1 and 50-4000 cm -1, respectively. The UV absorption spectra of the compound that dissolved in ethanol and water solution were recorded in the range of 190-400 nm. Potential energy curve was computed by means of scanning NCC dbnd O torsion angle. The geometry optimization and the energies associated possible four conformers (C1-C4) were computed. The computational results diagnose the most stable conformer of pAHA as the C1 form. Optimized structure of compound was interpreted and compared with the earlier reported experimental values. The complete assignments of fundamental vibrations were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. A study on the electronic properties, such as frontier molecular energies, absorption wavelengths and oscillator strengths, were predicted by time-dependent DFT (TD-DFT) approach, while taking solvent effects into account. To investigate non-linear optical properties: polarizability, anisotropy of polarizability and molecular first hyperpolarizability of molecule were computed. Thermodynamic properties (heat capacity, entropy and enthalpy) of the title compound at different temperatures were calculated.
NASA Astrophysics Data System (ADS)
Tejedor, Alejandro; Longjas, Anthony; Zaliapin, Ilya; Foufoula-Georgiou, Efi
2015-04-01
River deltas are landforms with complex channel networks that deliver water, sediment and nutrient fluxes from rivers to oceans or inland water bodies via multiple pathways. Most of the deltas are subject to anthropogenic and natural perturbations causing topological and dynamical changes in the delta structure and function. We present a quantitative framework based on spectral graph theory within which a systematic study of the topology, transport dynamics and response to change of river deltas can be performed, as well as computation of sub-networks (from apex to shoreline outlets), and contributing/nourishing areas. We introduce metrics of topologic and dynamic complexity and define a multidimensional complexity space where each delta projects. By analysis of seven deltas of different morphodynamic and environmental settings, we report a surprising power law relationship between sub-network size and its dynamic exchange with surrounding sub-networks within the deltaic system. The exponent of the relationship is universal (predicting that a sub-network twice as large leaks out to other sub-networks only 1.3 times its total flux) and the pre-exponent depends on the topologic complexity of the delta network as a whole, i.e., the ensemble of the interacting sub-sub-networks. We also use the developed framework to construct vulnerability maps that quantify the relative change of sediment and water delivery to the shoreline outlets in response to possible perturbations in hundreds of upstream links. This enables us to evaluate which links (hotspots) and what management scenarios would most influence flux delivery to the outlets, paving the way for systematically examining how local or spatially distributed delta interventions can be studied within a systems approach for delta sustainability.
Figueroa, R G; Valente, M
2015-09-21
The main purpose of this work is to determine the feasibility and physical characteristics of a new teletherapy device of radiation therapy based on the application of a convergent x-ray beam of energies like those used in radiotherapy providing highly concentrated dose delivery to the target. We have denominated it Convergent Beam Radio Therapy (CBRT). Analytical methods are developed first in order to determine the dosimetry characteristic of an ideal convergent photon beam in a hypothetical water phantom. Then, using the PENELOPE Monte Carlo code, a similar convergent beam that is applied to the water phantom is compared with that of the analytical method. The CBRT device (Converay(®)) is designed to adapt to the head of LINACs. The converging beam photon effect is achieved thanks to the perpendicular impact of LINAC electrons on a large thin spherical cap target where Bremsstrahlung is generated (high-energy x-rays). This way, the electrons impact upon various points of the cap (CBRT condition), aimed at the focal point. With the X radiation (Bremsstrahlung) directed forward, a system of movable collimators emits many beams from the output that make a virtually definitive convergent beam. Other Monte Carlo simulations are performed using realistic conditions. The simulations are performed for a thin target in the shape of a large, thin, spherical cap, with an r radius of around 10-30 cm and a curvature radius of approximately 70 to 100 cm, and a cubed water phantom centered in the focal point of the cap. All the interaction mechanisms of the Bremsstrahlung radiation with the phantom are taken into consideration for different energies and cap thicknesses. Also, the magnitudes of the electric and/or magnetic fields, which are necessary to divert clinical-use electron beams (0.1 to 20 MeV), are determined using electromagnetism equations with relativistic corrections. This way the above-mentioned beam is manipulated and guided for its perpendicular impact
NASA Astrophysics Data System (ADS)
Boughariou, F.; Chouikhi, S.; Kallel, A.; Belgaroui, E.
2015-12-01
In this paper, we present a new theoretical and numerical formulation for the electrical and thermal breakdown phenomena, induced by charge packet dynamics, in low-density polyethylene (LDPE) insulating film under dc high applied field. The theoretical physical formulation is composed by the equations of bipolar charge transport as well as by the thermo-electric coupled equation associated for the first time in modeling to the bipolar transport problem. This coupled equation is resolved by the finite-element numerical model. For the first time, all bipolar transport results are obtained under non-uniform temperature distributions in the sample bulk. The principal original results show the occurring of very sudden abrupt increase in local temperature associated to a very sharp increase in external and conduction current densities appearing during the steady state. The coupling between these electrical and thermal instabilities reflects physically the local coupling between electrical conduction and thermal joule effect. The results of non-uniform temperature distributions induced by non-uniform electrical conduction current are also presented for several times. According to our formulation, the strong injection current is the principal factor of the electrical and thermal breakdown of polymer insulating material. This result is shown in this work. Our formulation is also validated experimentally.
NASA Astrophysics Data System (ADS)
Qi, Huan
Direct metal deposition (DMD), a laser-cladding based solid freeform fabrication technique, is capable of depositing multiple materials at desired composition which makes this technique a flexible method to fabricate heterogeneous components or functionally-graded structures. The inherently rapid cooling rate associated with the laser cladding process enables extended solid solubility in nonequilibrium phases, offering the possibility of tailoring new materials with advanced properties. This technical advantage opens the area of synthesizing a new class of materials designed by topology optimization method which have performance-based material properties. For better understanding of the fundamental phenomena occurring in multi-material laser cladding with coaxial powder injection, a self-consistent 3-D transient model was developed. Physical phenomena including laser-powder interaction, heat transfer, melting, solidification, mass addition, liquid metal flow, and species transportation were modeled and solved with a controlled-volume finite difference method. Level-set method was used to track the evolution of liquid free surface. The distribution of species concentration in cladding layer was obtained using a nonequilibrium partition coefficient model. Simulation results were compared with experimental observations and found to be reasonably matched. Multi-phase material microstructures which have negative coefficients of thermal expansion were studied for their DMD manufacturability. The pixel-based topology-optimal designs are boundary-smoothed by Bezier functions to facilitate toolpath design. It is found that the inevitable diffusion interface between different material-phases degrades the negative thermal expansion property of the whole microstructure. A new design method is proposed for DMD manufacturing. Experimental approaches include identification of laser beam characteristics during different laser-powder-substrate interaction conditions, an
A Probabilistic Approach to Receptive Field Mapping in the Frontal Eye Fields
Mayo, J. Patrick; Morrison, Robert M.; Smith, Matthew A.
2016-01-01
Studies of the neuronal mechanisms of perisaccadic vision often lack the resolution needed to determine important changes in receptive field (RF) structure. Such limited analytical power can lead to inaccurate descriptions of visuomotor processing. To address this issue, we developed a precise, probabilistic technique that uses a generalized linear model (GLM) for mapping the visual RFs of frontal eye field (FEF) neurons during stable fixation (Mayo et al., 2015). We previously found that full-field RF maps could be obtained using 1–8 dot stimuli presented at frame rates of 10–150 ms. FEF responses were generally robust to changes in the number of stimuli presented or the rate of presentation, which allowed us to visualize RFs over a range of spatial and temporal resolutions. Here, we compare the quality of RFs obtained over different stimulus and GLM parameters to facilitate future work on the detailed mapping of FEF RFs. We first evaluate the interactions between the number of stimuli presented per trial, the total number of trials, and the quality of RF mapping. Next, we vary the spatial resolution of our approach to illustrate the tradeoff between visualizing RF sub-structure and sampling at high resolutions. We then evaluate local smoothing as a possible correction for situations where under-sampling occurs. Finally, we provide a preliminary demonstration of the usefulness of a probabilistic approach for visualizing full-field perisaccadic RF shifts. Our results present a powerful, and perhaps necessary, framework for studying perisaccadic vision that is applicable to FEF and possibly other visuomotor regions of the brain. PMID:27047352
2012-01-01
Background There is little systematic operational guidance about how best to develop complex interventions to reduce the gap between practice and evidence. This article is one in a Series of articles documenting the development and use of the Theoretical Domains Framework (TDF) to advance the science of implementation research. Methods The intervention was developed considering three main components: theory, evidence, and practical issues. We used a four-step approach, consisting of guiding questions, to direct the choice of the most appropriate components of an implementation intervention: Who needs to do what, differently? Using a theoretical framework, which barriers and enablers need to be addressed? Which intervention components (behaviour change techniques and mode(s) of delivery) could overcome the modifiable barriers and enhance the enablers? And how can behaviour change be measured and understood? Results A complex implementation intervention was designed that aimed to improve acute low back pain management in primary care. We used the TDF to identify the barriers and enablers to the uptake of evidence into practice and to guide the choice of intervention components. These components were then combined into a cohesive intervention. The intervention was delivered via two facilitated interactive small group workshops. We also produced a DVD to distribute to all participants in the intervention group. We chose outcome measures in order to assess the mediating mechanisms of behaviour change. Conclusions We have illustrated a four-step systematic method for developing an intervention designed to change clinical practice based on a theoretical framework. The method of development provides a systematic framework that could be used by others developing complex implementation interventions. While this framework should be iteratively adjusted and refined to suit other contexts and settings, we believe that the four-step process should be maintained as the primary
NASA Astrophysics Data System (ADS)
Pejov, Ljupčo; Petreska, Irina; Kocarev, Ljupčo
2015-12-01
A theoretical proof of the concept that a particularly designed graphene-based moletronics device, constituted by two semi-infinite graphene subunits, acting as source and drain electrodes, and a central benzenoid ring rotator (a "quantum dot"), could act as a field-controllable molecular switch is outlined and analyzed with the density functional theory approach. Besides the ideal (0 K) case, we also consider the operation of such a device under realistic operating (i.e., finite-temperature) conditions. An in-depth insight into the physics behind device controllability by an external field was gained by thorough analyses of the torsional potential of the dot under various conditions (absence or presence of an external gating field with varying strength), computing the torsional correlation time and transition probabilities within the Bloembergen-Purcell-Pound formalism. Both classical and quantum mechanical tunneling contributions to the intramolecular rotation were considered in the model. The main idea that we put forward in the present study is that intramolecular rotors can be controlled by the gating field even in cases when these groups do not possess a permanent dipole moment (as in cases considered previously by us [I. Petreska et al., J. Chem. Phys. 134, 014708-1-014708-12 (2011)] and also by other groups [P. E. Kornilovitch et al., Phys. Rev. B 66, 245413-1-245413-7 (2002)]). Consequently, one can control the molecular switching properties by an external electrostatic field utilizing even nonpolar intramolecular rotors (i.e., in a more general case than those considered so far). Molecular admittance of the currently considered graphene-based molecular switch under various conditions is analyzed employing non-equilibrium Green's function formalism, as well as by analysis of frontier molecular orbitals' behavior.
Pejov, Ljupčo; Petreska, Irina; Kocarev, Ljupčo
2015-12-28
A theoretical proof of the concept that a particularly designed graphene-based moletronics device, constituted by two semi-infinite graphene subunits, acting as source and drain electrodes, and a central benzenoid ring rotator (a "quantum dot"), could act as a field-controllable molecular switch is outlined and analyzed with the density functional theory approach. Besides the ideal (0 K) case, we also consider the operation of such a device under realistic operating (i.e., finite-temperature) conditions. An in-depth insight into the physics behind device controllability by an external field was gained by thorough analyses of the torsional potential of the dot under various conditions (absence or presence of an external gating field with varying strength), computing the torsional correlation time and transition probabilities within the Bloembergen-Purcell-Pound formalism. Both classical and quantum mechanical tunneling contributions to the intramolecular rotation were considered in the model. The main idea that we put forward in the present study is that intramolecular rotors can be controlled by the gating field even in cases when these groups do not possess a permanent dipole moment (as in cases considered previously by us [I. Petreska et al., J. Chem. Phys. 134, 014708-1-014708-12 (2011)] and also by other groups [P. E. Kornilovitch et al., Phys. Rev. B 66, 245413-1-245413-7 (2002)]). Consequently, one can control the molecular switching properties by an external electrostatic field utilizing even nonpolar intramolecular rotors (i.e., in a more general case than those considered so far). Molecular admittance of the currently considered graphene-based molecular switch under various conditions is analyzed employing non-equilibrium Green's function formalism, as well as by analysis of frontier molecular orbitals' behavior. PMID:26723699
Pejov, Ljupčo; Petreska, Irina; Kocarev, Ljupčo
2015-12-28
A theoretical proof of the concept that a particularly designed graphene-based moletronics device, constituted by two semi-infinite graphene subunits, acting as source and drain electrodes, and a central benzenoid ring rotator (a “quantum dot”), could act as a field-controllable molecular switch is outlined and analyzed with the density functional theory approach. Besides the ideal (0 K) case, we also consider the operation of such a device under realistic operating (i.e., finite-temperature) conditions. An in-depth insight into the physics behind device controllability by an external field was gained by thorough analyses of the torsional potential of the dot under various conditions (absence or presence of an external gating field with varying strength), computing the torsional correlation time and transition probabilities within the Bloembergen-Purcell-Pound formalism. Both classical and quantum mechanical tunneling contributions to the intramolecular rotation were considered in the model. The main idea that we put forward in the present study is that intramolecular rotors can be controlled by the gating field even in cases when these groups do not possess a permanent dipole moment (as in cases considered previously by us [I. Petreska et al., J. Chem. Phys. 134, 014708-1–014708-12 (2011)] and also by other groups [P. E. Kornilovitch et al., Phys. Rev. B 66, 245413-1–245413-7 (2002)]). Consequently, one can control the molecular switching properties by an external electrostatic field utilizing even nonpolar intramolecular rotors (i.e., in a more general case than those considered so far). Molecular admittance of the currently considered graphene-based molecular switch under various conditions is analyzed employing non-equilibrium Green’s function formalism, as well as by analysis of frontier molecular orbitals’ behavior.
Pietrucci, Fabio; Saitta, Antonino Marco
2015-12-01
Increasing experimental and theoretical evidence points to formamide as a possible hub in the complex network of prebiotic chemical reactions leading from simple precursors like H2, H2O, N2, NH3, CO, and CO2 to key biological molecules like proteins, nucleic acids, and sugars. We present an in-depth computational study of the formation and decomposition reaction channels of formamide by means of ab initio molecular dynamics. To this aim we introduce a new theoretical method combining the metadynamics sampling scheme with a general purpose topological formulation of collective variables able to track a wide range of different reaction mechanisms. Our approach is flexible enough to discover multiple pathways and intermediates starting from minimal insight on the systems, and it allows passing in a seamless way from reactions in gas phase to reactions in liquid phase, with the solvent active role fully taken into account. We obtain crucial new insight into the interplay of the different formamide reaction channels and into environment effects on pathways and barriers. In particular, our results indicate a similar stability of formamide and hydrogen cyanide in solution as well as their relatively facile interconversion, thus reconciling experiments and theory and, possibly, two different and competing prebiotic scenarios. Moreover, although not explicitly sought, formic acid/ammonium formate is produced as an important formamide decomposition byproduct in solution. PMID:26598679
NASA Astrophysics Data System (ADS)
Mukwembi, Simon
2008-02-01
We study the effects of the rate of replacement of dead cells by either healthy cells or by infected cells on HIV infection dynamics through a graph-theoretic approach. Our framework takes into account a reasonable amount of the immune action to any pathogen and the local cell interactions that occur in the lymph nodes. Our results, in an extremal case where dead cells are highly likely to be replaced by healthy cells, show that all cells become healthy in a finite number of steps of given order and infection stops propagating. Further, for this extremal case, we give an algebraic formula for the number of infected cells at any given time in the HIV progression. We also find a sufficient condition, determined by dead cell replacement rate, which guarantees that an infected patient is continually positive, and give bounds on the number of infected, healthy and dead cells at any given time. We apply our theoretical results to a recently proposed model of the HIV infection dynamics.
Pietrucci, Fabio; Saitta, Antonino Marco
2015-01-01
Increasing experimental and theoretical evidence points to formamide as a possible hub in the complex network of prebiotic chemical reactions leading from simple precursors like H2, H2O, N2, NH3, CO, and CO2 to key biological molecules like proteins, nucleic acids, and sugars. We present an in-depth computational study of the formation and decomposition reaction channels of formamide by means of ab initio molecular dynamics. To this aim we introduce a new theoretical method combining the metadynamics sampling scheme with a general purpose topological formulation of collective variables able to track a wide range of different reaction mechanisms. Our approach is flexible enough to discover multiple pathways and intermediates starting from minimal insight on the systems, and it allows passing in a seamless way from reactions in gas phase to reactions in liquid phase, with the solvent active role fully taken into account. We obtain crucial new insight into the interplay of the different formamide reaction channels and into environment effects on pathways and barriers. In particular, our results indicate a similar stability of formamide and hydrogen cyanide in solution as well as their relatively facile interconversion, thus reconciling experiments and theory and, possibly, two different and competing prebiotic scenarios. Moreover, although not explicitly sought, formic acid/ammonium formate is produced as an important formamide decomposition byproduct in solution. PMID:26598679
Ab initio, theoretical and Monte Carlo approaches for the magnetocaloric effect in DyNi4Si
NASA Astrophysics Data System (ADS)
Laghrissi, Ayoub; Salmani, El Mehdi; Ez-Zahraouy, Hamid; Benyoussef, Abdelilah
2016-08-01
The magnetic and magnetocaloric properties of DyNi4Si alloys in YNi4Si-type orthorhombic structure have been investigated by using a combination of first-principles calculations and mean field theory, effective field theory, and Monte Carlo simulation. We find that Magnetic results of DyNi4Si compound show ferromagnetic-type ordering at 19 K, the magnetization-field isotherms for DyNi4Si exhibit hysteresis loop at 2 K due to strong magnetic anisotropy. The non-saturating behavior and the value of the magnetic moment of 7.7 μB/fu in 140 kOe at 2 K where the theoretical value for DyNi4Si only is about 10 μB, this suggest a not completely ordered ferromagnetic state of DyNi4Si (Morozkin et al., 2015) [2]. The isothermal entropy changes for H=14 T at T=22 K is -ΔS=15.6 J/(kg K). The obtained results are in good agreement with available experimental data. This study allows the suggestion of the compatible Ising model for a new class of compound YNi4Si-type, which shows magnetocaloric behavior at low temperature.
Propagating phase interface with intermediate interfacial phase: Phase field approach
NASA Astrophysics Data System (ADS)
Momeni, Kasra; Levitas, Valery I.
2014-05-01
An advanced three-phase phase field approach (PFA) is suggested for a nonequilibrium phase interface that contains an intermediate phase, in particular, a solid-solid interface with a nanometer-sized intermediate melt (IM). A thermodynamic potential in the polar order parameters is developed that satisfies all thermodynamic equilibrium and stability conditions. The special form of the gradient energy allowed us to include the interaction of two solid-melt interfaces via an intermediate melt and obtain a well-posed problem and mesh-independent solutions. It is proved that for stationary 1D solutions to two Ginzburg-Landau equations for three phases, the local energy at each point is equal to the gradient energy. Simulations are performed for β ↔δ phase transformations (PTs) via IM in an HMX energetic material. The obtained energy IM width dependence is described by generalized force-balance models for short- and long-range interaction forces between interfaces but not far from the melting temperature. A force-balance model is developed that describes phase field results even 100 K below the melting temperature. The effects of the ratios of width and energies of solid-solid and solid-melt interfaces, temperature, and the parameter characterizing interaction of two solid-melt interfaces, on the structure, width, energy of the IM and interface velocity are determined by finite element method. Depending on parameters, the IM may appear by continuous or discontinuous barrierless disordering or via critical nucleus due to thermal fluctuations. The IM may appear during heating and persist during cooling at temperatures well below than it follows from sharp-interface approach. On the other hand, for some parameters when IM is expected, it does not form, producing an IM-free gap. The developed PFA represents a quite general three-phase model and can be extended to other physical phenomena, such as martensitic PTs, surface-induced premelting and PTs, premelting
Geosynergetic Approach for Analyze of Rock State, Theoretical and Experimental Redlts
NASA Astrophysics Data System (ADS)
Hachay, O. A.; Khachay, A. Y.; Khachay, O. Y.
2012-04-01
releasing the system returns to the same phase trajectory attracting area. That is confirmed by detailed analyze of phase trajectories of seismic massive response before and after high energetic rock burst. In the book [5] is developed a new mathematical method for modeling of processes in local active continuum, which are energetically influenced from an outer energy source. The common cause of chaotization and stochastization of dynamical system movements are its losses of stability and exponential recession of near located phase trajectories together with its common boundedness and its common compression. The mathematical result coincides as a whole with the practical result: in the phase area the smaller attracting phase trajectories area exists where can occur an exponential recession of them, then the movement character changes and the further movement of phase points lead to return to the same attracting area. These movements can occur in resonance or spontaneous mood. The work was supported by the grant RFBR 10-05-00013. 1. Hachay, O.A., and Khachay, O.Yu. 2009. "Results of electromagnetic and seismic monitoring of the state of rock massive by use the approach of the open dynamical systems,"presented at the EGU2009 - EGU General Assembly 2009, session: Thermo- hydro- mechanical coupling in stressed rock, 19 April 19 - 24 April 2009. 2. Hachay, O.A. "Synergetic events in geological medium and nonlinear features of wave propagation," presented at the EGU2009 - EGU General Assembly 2009, session: Solid Earth geocomplexity: surface processes, morphology and natural resources over wide ranges of scale, 19 April 19 - 24 April 2009. 3. Chulichkov, A.I. 2003. Mathematical models of nonlinear dynamics. Moscow: Phismatlit, p.420. 4. Malineckiy, G.G. 2007. Mathematical base of synergetics. Moscow: LKI, p.375. 5. Naimark, Yu.I.and Landa, P.S. 2009. Stochastic and Chaotic oscillations. Moscow: Knigniy dom "LIBROKOM", p.424.
Kurouski, Dmitry; Large, Nicolas; Chiang, Naihao; Greeneltch, Nathan; Carron, Keith T; Seideman, Tamar; Schatz, George C; Van Duyne, Richard P
2016-03-01
Simplicity and low cost has positioned inkjet paper- and fabric-based 3D substrates as two of the most commonly used surface-enhanced Raman spectroscopy (SERS) platforms for the detection and the identification of chemical and biological analytes down to the nanogram and femtogram levels. The relationship between far-field and near-field properties of these 3D SERS platforms remains poorly understood and warrants more detailed characterization. Here, we investigate the extremely weak optical scattering observed from commercial and home-fabricated paper-, as well as fabric-based 3D SERS substrates. Using wavelength scanned surface-enhanced Raman excitation spectroscopy (WS-SERES) and finite-difference time-domain (FDTD) calculations we were able to determine their near-field SERS properties and correlate them with morphological and far-field properties. It was found that nanoparticle dimers, trimers, and higher order nanoparticle clusters primarily determine the near-field properties of these substrates. At the same time, the far-field response of 3D SERS substrates either originates primarily from the monomers or cannot be clearly defined. Using FDTD we demonstrate that LSPR bands of nanoparticle aggregates near perfectly overlap with the maxima of the near-field surface-enhanced Raman scattering responses of the 3D SERS substrates. This behaviour of far-field spectroscopic properties and near-field surface-enhanced Raman scattering has not been previously observed for 2D SERS substrates, known as nanorod arrays. The combination of these analytical approaches provides a full spectroscopic characterization of 3D SERS substrates, while FDTD simulation can be used to design new 3D SERS substrates with tailored spectral characteristics. PMID:26858996
Theoretical investigation of the behavior of CuSe2O5 compound in high magnetic fields
NASA Astrophysics Data System (ADS)
Saghafi, Z.; Jahangiri, J.; Mahdavifar, S.; Hadipour, H.; Farjami Shayesteh, S.
2016-01-01
Based on the analytical and numerical approaches, we investigate thermodynamic properties of CuSe2O5 compound at high magnetic fields which is a candidate for the strong intra-chain interaction in quasi one-dimensional (1D) quantum magnets. Magnetic behavior of the system can be described by the 1D spin-1/2 XXZ model in the presence of the Dzyaloshinskii-Moriya (DM) interaction. Under these circumstances, there is one quantum critical field in this compound. Below the quantum critical field the spin chain system is in the gapless Luttinger liquid (LL) regime, whereas above it one observes a crossover to the gapped saturation magnetic phase. Indications on the thermodynamic curves confirm the occurrence of such a phase transition. The main characteristics of the LL phase are gapless and spin-spin correlation functions decay algebraic. The effects of zero-temperature quantum phase transition are observed even at rather high temperatures in comparison with the counterpart compounds. In addition, we calculate the Wilson ratio in the model. The Wilson ratio at a fixed temperature remains almost independent of the field in the LL region. In the vicinity of the quantum critical field, the Wilson ratio increases and exhibits anomalous enhancement.
A theory-based approach to thermal field-flow fractionation of polyacrylates.
Runyon, J Ray; Williams, S Kim Ratanathanawongs
2011-09-28
A theory-based approach is presented for the development of thermal field-flow fractionation (ThFFF) of polyacrylates. The use of ThFFF for polymer analysis has been limited by an incomplete understanding of the thermal diffusion which plays an important role in retention and separation. Hence, a tedious trial-and-error approach to method development has been the normal practice when analyzing new materials. In this work, thermal diffusion theories based on temperature dependent osmotic pressure gradient and polymer-solvent interaction parameters were used to estimate thermal diffusion coefficients (D(T)) and retention times (t(r)) for different polymer-solvent pairs. These calculations identified methyl ethyl ketone as a solvent that would cause significant retention of poly(n-butyl acrylate) (PBA) and poly(methyl acrylate) (PMA). Experiments confirmed retention of these two polymers that have not been previously analyzed by ThFFF. Theoretical and experimental D(T)s and t(r)s for PBA, PMA, and polystyrene in different solvents agreed to within 20% and demonstrate the feasibility of this theory-based approach. PMID:21872869
Dark energy or modified gravity? An effective field theory approach
Bloomfield, Jolyon; Flanagan, Éanna É.; Park, Minjoon; Watson, Scott E-mail: eef3@cornell.edu E-mail: gswatson@syr.edu
2013-08-01
We take an Effective Field Theory (EFT) approach to unifying existing proposals for the origin of cosmic acceleration and its connection to cosmological observations. Building on earlier work where EFT methods were used with observations to constrain the background evolution, we extend this program to the level of the EFT of the cosmological perturbations — following the example from the EFT of Inflation. Within this framework, we construct the general theory around an assumed background which will typically be chosen to mimic ΛCDM, and identify the parameters of interest for constraining dark energy and modified gravity models with observations. We discuss the similarities to the EFT of Inflation, but we also identify a number of subtleties including the relationship between the scalar perturbations and the Goldstone boson of the spontaneously broken time translations. We present formulae that relate the parameters of the fundamental Lagrangian to the speed of sound, anisotropic shear stress, effective Newtonian constant, and Caldwell's varpi parameter, emphasizing the connection to observations. It is anticipated that this framework will be of use in constraining individual models, as well as for placing model-independent constraints on dark energy and modified gravity model building.
Data, Methods, and Theoretical Implications
ERIC Educational Resources Information Center
Hannagan, Rebecca J.; Schneider, Monica C.; Greenlee, Jill S.
2012-01-01
Within the subfields of political psychology and the study of gender, the introduction of new data collection efforts, methodologies, and theoretical approaches are transforming our understandings of these two fields and the places at which they intersect. In this article we present an overview of the research that was presented at a National…
NASA Astrophysics Data System (ADS)
Limkumnerd, Surachate
2014-03-01
Interest in thin-film fabrication for industrial applications have driven both theoretical and computational aspects of modeling its growth. One of the earliest attempts toward understanding the morphological structure of a film's surface is through a class of solid-on-solid limited-mobility growth models such as the Family, Wolf-Villain, or Das Sarma-Tamborenea models, which have produced fascinating surface roughening behaviors. These models, however, restrict the motion of an incidence atom to be within the neighborhood of its landing site, which renders them inept for simulating long-distance surface diffusion such as that observed in thin-film growth using a molecular-beam epitaxy technique. Naive extension of these models by repeatedly applying the local diffusion rules for each hop to simulate large diffusion length can be computationally very costly when certain statistical aspects are demanded. We present a graph-theoretic approach to simulating a long-range diffusion-attachment growth model. Using the Markovian assumption and given a local diffusion bias, we derive the transition probabilities for a random walker to traverse from one lattice site to the others after a large, possibly infinite, number of steps. Only computation with linear-time complexity is required for the surface morphology calculation without other probabilistic measures. The formalism is applied, as illustrations, to simulate surface growth on a two-dimensional flat substrate and around a screw dislocation under the modified Wolf-Villain diffusion rule. A rectangular spiral ridge is observed in the latter case with a smooth front feature similar to that obtained from simulations using the well-known multiple registration technique. An algorithm for computing the inverse of a class of substochastic matrices is derived as a corollary.
NASA Astrophysics Data System (ADS)
Assadi, Amir H.; Eghbalnia, Hamid
2000-06-01
In standard differential geometry, the Fundamental Theorem of Space Curves states that two differential invariants of a curve, namely curvature and torsion, determine its geometry, or equivalently, the isometry class of the curve up to rigid motions in the Euclidean three-dimensional space. Consider a physical model of a space curve made from a sufficiently thin, yet visible rigid wire, and the problem of perceptual identification (by a human observer or a robot) of two given physical model curves. In a previous paper (perceptual geometry) we have emphasized a learning theoretic approach to construct a perceptual geometry of the surfaces in the environment. In particular, we have described a computational method for mathematical representation of objects in the perceptual geometry inspired by the ecological theory of Gibson, and adhering to the principles of Gestalt in perceptual organization of vision. In this paper, we continue our learning theoretic treatment of perceptual geometry of objects, focusing on the case of physical models of space curves. In particular, we address the question of perceptually distinguishing two possibly novel space curves based on observer's prior visual experience of physical models of curves in the environment. The Fundamental Theorem of Space Curves inspires an analogous result in perceptual geometry as follows. We apply learning theory to the statistics of a sufficiently rich collection of physical models of curves, to derive two statistically independent local functions, that we call by analogy, the curvature and torsion. This pair of invariants distinguish physical models of curves in the sense of perceptual geometry. That is, in an appropriate resolution, an observer can distinguish two perceptually identical physical models in different locations. If these pairs of functions are approximately the same for two given space curves, then after possibly some changes of viewing planes, the observer confirms the two are the same.
Zhuo, Ye
2011-01-01
In this thesis, we theoretically study the electromagnetic wave propagation in several passive and active optical components and devices including 2-D photonic crystals, straight and curved waveguides, organic light emitting diodes (OLEDs), and etc. Several optical designs are also presented like organic photovoltaic (OPV) cells and solar concentrators. The first part of the thesis focuses on theoretical investigation. First, the plane-wave-based transfer (scattering) matrix method (TMM) is briefly described with a short review of photonic crystals and other numerical methods to study them (Chapter 1 and 2). Next TMM, the numerical method itself is investigated in details and developed in advance to deal with more complex optical systems. In chapter 3, TMM is extended in curvilinear coordinates to study curved nanoribbon waveguides. The problem of a curved structure is transformed into an equivalent one of a straight structure with spatially dependent tensors of dielectric constant and magnetic permeability. In chapter 4, a new set of localized basis orbitals are introduced to locally represent electromagnetic field in photonic crystals as alternative to planewave basis. The second part of the thesis focuses on the design of optical devices. First, two examples of TMM applications are given. The first example is the design of metal grating structures as replacements of ITO to enhance the optical absorption in OPV cells (chapter 6). The second one is the design of the same structure as above to enhance the light extraction of OLEDs (chapter 7). Next, two design examples by ray tracing method are given, including applying a microlens array to enhance the light extraction of OLEDs (chapter 5) and an all-angle wide-wavelength design of solar concentrator (chapter 8). In summary, this dissertation has extended TMM which makes it capable of treating complex optical systems. Several optical designs by TMM and ray tracing method are also given as a full complement of this
A Semantic Field Approach to Passive Vocabulary Acquisition for Reading Comprehension.
ERIC Educational Resources Information Center
Crow, John T.; Quigley, June R.
1985-01-01
Describes a study which compared a traditional approach to second language vocabulary instruction with the semantic field approach, which is based on the association between five related words and a key word that could be mentally substituted in context. Findings lend support to the use of the semantic field approach. (SED)
Magnetic field of Jupiter: A generalized inverse approach
Connerney, J.E.P.
1981-09-01
The estimation of planetary magnetic fields from observations of the magnetic field gathered along a spacecraft flyby trajectory is examined with the aid of generalized inverse techniques, with application to the internal magnetic field of Jupiter. Model non-uniqueness resulting from the limited spatial extent of the observations and noise on the data is explored and quantitative estimates of the model parameter resolution are found. The presence of a substantial magnetic field of external origin due to the currents flowing in the Jovian magnetodisc is found to be an important source of error in estimates of the internal Jovian field, and new models explicitly incorporating these currents are proposed. New internal field models are derived using the vector helium magnetometer observations and the high field fluxgate observations of Pioneer 11, and knowledge of the external current system gained from the Pioneer 10 and Voyagers 1 and 2 encounters.
Magnetic field of Jupiter: A generalized inverse approach
NASA Technical Reports Server (NTRS)
Connerney, J. E. P.
1981-01-01
The estimation of planetary magnetic fields from observations of the magnetic field gathered along a spacecraft flyby trajectory is examined with the aid of generalized inverse techniques, with application to the internal magnetic field of Jupiter. Model nonuniqueness resulting from the limited spatial extent of the observations and noise on the data is explored and quantitative estimates of the model parameter resolution are found. The presence of a substantial magnetic field of external origin due to the currents flowing in the Jovian magnetodisc is found to be an important source of error in estimates of the internal Jovian field, and new models explicitly incorporating these currents are proposed. New internal field models are derived using the vector helium magnetometer observations and the high field fluxgate observations of Pioneer 11, and knowledge of the external current system gained from the Pioneer 10 and Voyagers 1 and 2 encounters.
The magnetic field of Jupiter - A generalized inverse approach
NASA Technical Reports Server (NTRS)
Connerney, J. E. P.
1981-01-01
The estimation of planetary magnetic fields from observations of the magnetic field gathered along a spacecraft flyby trajectory is examined with the aid of generalized inverse techniques, with application to the internal magnetic field of Jupiter. Model non-uniqueness resulting from the limited spatial extent of the observations and noise on the data is explored and quantitative estimates of the model parameter resolution are found. The presence of a substantial magnetic field of external origin due to the currents flowing in the Jovian magnetodisc is found to be an important source of error in estimates of the internal Jovian field, and new models explicitly incorporating these currents are proposed. New internal field models are derived using the vector helium magnetometer observations and the high field fluxgate observations of Pioneer 11, and knowledge of the external current system gained from the Pioneer 10 and Voyagers 1 and 2 encounters.
Lauraguais, Amélie; El Zein, Atallah; Coeur, Cécile; Obeid, Emil; Cassez, Andy; Rayez, Marie-Thérèse; Rayez, Jean-Claude
2016-05-01
The gas-phase reactions of five methoxyphenols (three disubstituted and two trisubstituted) with nitrate radicals were studied in an 8000 L atmospheric simulation chamber at atmospheric pressure and 294 ± 2 K. The NO3 rate constants were investigated with the relative kinetic method using PTR-ToF-MS and GC-FID to measure the concentrations of the organic compounds. The rate constants (in units of cm(3) molecule(-1) s(-1)) determined were: 2-methoxyphenol (guaiacol; 2-MP), k(2-MP) = (2.69 ± 0.57 × 10(-11); 3-methoxyphenol (3-MP), k(3-MP) = (1.15 ± 0.21) × 10(-11); 4-methoxyphenol (4-MP), k(4-MP) = (13.75 ± 7.97) × 10(-11); 2-methoxy-4-methylphenol, k(2-M-4-MeP) = (8.41 ± 5.58) × 10(-11) and 2,6-dimethoxyphenol (syringol; 2,6-DMP), k(2,6-DMP) = (15.84 ± 8.10) × 10(-11). The NO3 rate constants of the studied methoxyphenols are compared with those of other substituted aromatics, and the differences in the reactivity are construed regarding the substituents (type, number and position) on the aromatic ring. This study was also supplemented by a theoretical approach of the methoxyphenol reactions with nitrate radicals. The upper limits of the NO3 overall rate constants calculated were in the same order of magnitude than those experimentally determined. Theoretical calculations of the minimum energies of the adducts formed from the reaction of NO3 radicals with the methoxyphenols were also performed using a DFT approach (M06-2X/6-31G(d,p)). The results indicate that the NO3 addition reactions on the aromatic ring of the methoxyphenols are exothermic, with energy values ranging between -13 and -21 kcal mol(-1), depending on the environment of the carbon on which the oxygen atom of NO3 is attached. These energy values allowed identifying the most suitable carbon sites for the NO3 addition on the aromatic ring of the methoxyphenols: at the exception of the 3-MP, the NO3 ipso-addition to the hydroxyl group is one of the favored sites for all the studies compounds
Abelian p-form (p = 1, 2, 3) gauge theories as the field theoretic models for the Hodge theory
NASA Astrophysics Data System (ADS)
Kumar, R.; Krishna, S.; Shukla, A.; Malik, R. P.
2014-09-01
Taking the simple examples of an Abelian 1-form gauge theory in two (1+1)-dimensions, a 2-form gauge theory in four (3+1)-dimensions and a 3-form gauge theory in six (5+1)-dimensions of space-time, we establish that such gauge theories respect, in addition to the gauge symmetry transformations that are generated by the first-class constraints of the theory, additional continuous symmetry transformations. We christen the latter symmetry transformations as the dual-gauge transformations. We generalize the above gauge and dual-gauge transformations to obtain the proper (anti-)BRST and (anti-)dual-BRST transformations for the Abelian 3-form gauge theory within the framework of BRST formalism. We concisely mention such symmetries for the 2D free Abelian 1-form and 4D free Abelian 2-form gauge theories and briefly discuss their topological aspects in our present endeavor. We conjecture that any arbitrary Abelian p-form gauge theory would respect the above cited additional symmetry in D = 2p(p = 1, 2, 3, …) dimensions of space-time. By exploiting the above inputs, we establish that the Abelian 3-form gauge theory, in six (5+1)-dimensions of space-time, is a perfect model for the Hodge theory whose discrete and continuous symmetry transformations provide the physical realizations of all aspects of the de Rham cohomological operators of differential geometry. As far as the physical utility of the above nilpotent symmetries is concerned, we demonstrate that the 2D Abelian 1-form gauge theory is a perfect model of a new class of topological theory and 4D Abelian 2-form as well as 6D Abelian 3-form gauge theories are the field theoretic models for the quasi-topological field theory.
NASA Astrophysics Data System (ADS)
Poisson, Florian; Bossy, Emmanuel
2016-03-01
Optical-resolution photoacoustic endomicroscopy (OR-PAE) allows going beyond the limited penetration depth of conventional optical-resolution photoacoustic systems. Recently, it has been shown that OR-PAE may be performed through minimally invasive multimode fibers, by raster scanning a focus spot with optical wavefront shaping [1]. Here we introduce for the first time an approach to perform OR-PAE through a multimode fiber with a full-field illumination approach. By using multiple known speckle patterns, we show that it is possible to obtain optical-diffraction limited photoacoustic images, with the same resolution as that obtained by raster scanning a focus spot, i.e that of the speckle grain size. The fluctuations patterns of the photoacoustic amplitude at each pixel in the sample plane with the series of multiple speckle illumination were used to encode each pixel. This approach with known speckle illumination requires an initial calibration stage, that consists in learn a set of fluctuation patterns pixel per pixel, which will encode patterns each pixel of the scanned area. A point-like absorber was scanned across the filed-of-view during the calibration stage to acquire the reference patterns. Image reconstruction may be carried out by cross-correlating the series of photoacoustic amplitude measured with the sample to the reference patterns obtained during the calibration stage. In this work, the approach above was carried out both theoretically with Monte-carlo simulations and experimentally through a multi-mode fiber with samples made of absorbing spheres. [1] Papadopoulos et al., " Optical-resolution photoacoustic microscopy by use of a multimode fiber", Appl. Phys. Lett., 102(21), 2013
Zheng, Yu; Gao, Yang; Chen, Ruijuan; Wang, Huiquan; Dong, Lei; Dou, Junrong
2016-10-01
Time-varying electromagnetic fields (EMF) can induce some physiological effects in neuronal tissues, which have been explored in many applications such as transcranial magnetic stimulation. Although transmembrane potentials and induced currents have already been the subjects of many theoretical studies, most previous works about this topic are mainly completed by utilizing Maxwell's equations, often by solving a Laplace equation. In previous studies, cells were often considered to be three-compartment models with different electroconductivities in different regions (three compartments are often intracellular regions, membrane, and extracellular regions). However, models like that did not take dynamic ion channels into consideration. Therefore, one cannot obtain concrete ionic current changes such as potassium current change or sodium current change by these models. The aim of the present work is to present a new and more detailed model for calculating transmembrane potentials and ionic currents induced by time-varying EMF. Equations used in the present paper originate from Nernst-Plank equations, which are ionic current-related equations. The main work is to calculate ionic current changes induced by EMF exposure, and then transmembrane potential changes are calculated with Hodgkin-Huxley model. Bioelectromagnetics. 37:481-492, 2016. © 2016 Wiley Periodicals, Inc. PMID:27438778
Peng, Wenbo; Yu, Ruomeng; He, Yongning; Wang, Zhong Lin
2016-04-26
Triboelectric nanogenerator has drawn considerable attentions as a potential candidate for harvesting mechanical energies in our daily life. By utilizing the triboelectric potential generated through the coupling of contact electrification and electrostatic induction, the "tribotronics" has been introduced to tune/control the charge carrier transport behavior of silicon-based metal-oxide-semiconductor field-effect transistor (MOSFET). Here, we perform a theoretical study of the performances of tribotronic MOSFET gated by triboelectric potential in two working modes through finite element analysis. The drain-source current dependence on contact-electrification generated triboelectric charges, gap separation distance, and externally applied bias are investigated. The in-depth physical mechanism of the tribotronic MOSFET operations is thoroughly illustrated by calculating and analyzing the charge transfer process, voltage relationship to gap separation distance, and electric potential distribution. Moreover, a tribotronic MOSFET working concept is proposed, simulated and studied for performing self-powered FET and logic operations. This work provides a deep understanding of working mechanisms and design guidance of tribotronic MOSFET for potential applications in micro/nanoelectromechanical systems (MEMS/NEMS), human-machine interface, flexible electronics, and self-powered active sensors. PMID:27077327
The BAARA (Biological AutomAted RAdiotracking) System: A New Approach in Ecological Field Studies
Řeřucha, Šimon; Bartonička, Tomáš; Jedlička, Petr; Čížek, Martin; Hlouša, Ondřej; Lučan, Radek; Horáček, Ivan
2015-01-01
Radiotracking is an important and often the only possible method to explore specific habits and the behaviour of animals, but it has proven to be very demanding and time-consuming, especially when frequent positioning of a large group is required. Our aim was to address this issue by making the process partially automated, to mitigate the demands and related costs. This paper presents a novel automated tracking system that consists of a network of automated tracking stations deployed within the target area. Each station reads the signals from telemetry transmitters, estimates the bearing and distance of the tagged animals and records their position. The station is capable of tracking a theoretically unlimited number of transmitters on different frequency channels with the period of 5–15 seconds per single channel. An ordinary transmitter that fits within the supported frequency band might be used with BAARA (Biological AutomAted RAdiotracking); an extra option is the use of a custom-programmable transmitter with configurable operational parameters, such as the precise frequency channel or the transmission parameters. This new approach to a tracking system was tested for its applicability in a series of field and laboratory tests. BAARA has been tested within fieldwork explorations of Rousettus aegyptiacus during field trips to Dakhla oasis in Egypt. The results illustrate the novel perspective which automated radiotracking opens for the study of spatial behaviour, particularly in addressing topics in the domain of population ecology. PMID:25714910
NASA Astrophysics Data System (ADS)
Thelen, Brian J.; Rickerd, Chris J.; Burns, Joseph W.
2014-06-01
With all of the new remote sensing modalities available, with ever increasing capabilities, there is a constant desire to extend the current state of the art in physics-based feature extraction and to introduce new and innovative techniques that enable the exploitation within and across modalities, i.e., fusion. A key component of this process is finding the associated features from the various imaging modalities that provide key information in terms of exploitative fusion. Further, it is desired to have an automatic methodology for assessing the information in the features from the various imaging modalities, in the presence of uncertainty. In this paper we propose a novel approach for assessing, quantifying, and isolating the information in the features via a joint statistical modeling of the features with the Gaussian Copula framework. This framework allows for a very general modeling of distributions on each of the features while still modeling the conditional dependence between the features, and the final output is a relatively accurate estimate of the information-theoretic J-divergence metric, which is directly related to discriminability. A very useful aspect of this approach is that it can be used to assess which features are most informative, and what is the information content as a function of key uncertainties (e.g., geometry) and collection parameters (e.g., SNR and resolution). We show some results of applying the Gaussian Copula framework and estimating the J-Divergence on HRR data as generated from the AFRL public release data set known as the Backhoe Data Dome.
NASA Technical Reports Server (NTRS)
Sinko, P. J.; Leesman, G. D.; Amidon, G. L.
1993-01-01
A theoretical analysis for estimating the extent of intestinal peptide and peptide analogue absorption was developed on the basis of a mass balance approach that incorporates convection, permeability, and reaction. The macroscopic mass balance analysis (MMBA) was extended to include chemical and enzymatic degradation. A microscopic mass balance analysis, a numerical approach, was also developed and the results compared to the MMBA. The mass balance equations for the fraction of a drug absorbed and reacted in the tube were derived from the general steady state mass balance in a tube: [formula: see text] where M is mass, z is the length of the tube, R is the tube radius, Pw is the intestinal wall permeability, kr is the reaction rate constant, C is the concentration of drug in the volume element over which the mass balance is taken, VL is the volume of the tube, and vz is the axial velocity of drug. The theory was first applied to the oral absorption of two tripeptide analogues, cefaclor (CCL) and cefatrizine (CZN), which degrade and dimerize in the intestine. Simulations using the mass balance equations, the experimental absorption parameters, and the literature stability rate constants yielded a mean estimated extent of CCL (250-mg dose) and CZN (1000-mg dose) absorption of 89 and 51%, respectively, which was similar to the mean extent of absorption reported in humans (90 and 50%). It was proposed previously that 15% of the CCL dose spontaneously degraded systematically; however, our simulations suggest that significant CCL degradation occurs (8 to 17%) presystemically in the intestinal lumen.(ABSTRACT TRUNCATED AT 250 WORDS).
NASA Astrophysics Data System (ADS)
Kocifaj, Miroslav
2016-09-01
The study of diffuse light of a night sky is undergoing a renaissance due to the development of inexpensive high performance computers which can significantly reduce the time needed for accurate numerical simulations. Apart from targeted field campaigns, numerical modeling appears to be one of the most attractive and powerful approaches for predicting the diffuse light of a night sky. However, computer-aided simulation of night-sky radiances over any territory and under arbitrary conditions is a complex problem that is difficult to solve. This study addresses three concepts for modeling the artificial light propagation through a turbid stratified atmosphere. Specifically, these are two-stream approximation, iterative approach to Radiative Transfer Equation (RTE) and Method of Successive Orders of Scattering (MSOS). The principles of the methods, their strengths and weaknesses are reviewed with respect to their implications for night-light modeling in different environments.
NASA Astrophysics Data System (ADS)
Elleuch, Nabil; Amamou, Walid; Ben Ahmed, Ali; Abid, Younes; Feki, Habib
2014-07-01
Single crystals of L-asparaginium picrate (LASP) were grown by slow evaporation technique at room temperature and were the subject of an X-ray powder diffraction study to confirm the crystalline nature of the synthesized compound. FT-IR and Raman spectra were recorded and analyzed with the aid of the density functional theory (DFT) calculations in order to make a suitable assignment of the observed bands. The optimum molecular geometry, normal mode wavenumbers, infrared and Raman intensities and the first hyperpolarizability were investigated with the help of B3LYP method using 6-31G(d) basis set. The theoretical FT-IR and Raman spectra of LASP were simulated and compared with the experimental data. A good agreement was shown and a reliable vibrational assignment was made. Natural bond orbital (NBO) analysis was carried out to demonstrate the various inter and intramolecular interactions that are responsible for the stabilization of the title compound leading to high NLO activity. A study on the electronic properties was performed by time-dependent DFT (TD-DFT) approach. The lowering in the HOMO and LUMO energy gap explains the eventual charge transfer interactions that take place within the molecules.
Painter, K J; Hunt, G S; Wells, K L; Johansson, J A; Headon, D J
2012-08-01
In his seminal 1952 paper, 'The Chemical Basis of Morphogenesis', Alan Turing lays down a milestone in the application of theoretical approaches to understand complex biological processes. His deceptively simple demonstration that a system of reacting and diffusing chemicals could, under certain conditions, generate spatial patterning out of homogeneity provided an elegant solution to the problem of how one of nature's most intricate events occurs: the emergence of structure and form in the developing embryo. The molecular revolution that has taken place during the six decades following this landmark publication has now placed this generation of theoreticians and biologists in an excellent position to rigorously test the theory and, encouragingly, a number of systems have emerged that appear to conform to some of Turing's fundamental ideas. In this paper, we describe the history and more recent integration between experiment and theory in one of the key models for understanding pattern formation: the emergence of feathers and hair in the skins of birds and mammals. PMID:23919127
Karabulut, Sedat; Namli, Hilmi; Leszczynski, Jerzy
2013-08-01
Molecular structures of stable tautomers of dimedone [5,5-dimethyl-cyclohexane-1,3-dione and 3-hydroxy-5,5-dimethylcyclohex-2-enone] were optimized and vibrational frequencies were calculated in five different organic solvents (dimethylsulfoxide, methanol, acetonitrile, dichloromethane and chloroform). Geometry optimizations and harmonic vibrational frequency calculations were performed at DFT 6-31+G(d,p), DFT 6-311++G(2d,2p), MP2 6-311++G (2d,2p) and MP2 aug-cc-pVDZ levels for both stable forms of dimedone. Experimental FT-IR spectra of dimedone have also been recorded in the same solvents. A new approach was developed in order to determine tautomers' ratio using both experimental and theoretical data in Lambert-Beer equation. Obtained results were compared with experimental results published in literature. It has been concluded that while DFT 6-31+G(d,p) method provides accurate enol ratio in DMSO, MeOH, and DCM, in order to obtain accurate results for the other solvents the MP2 aug-cc-pVDZ level calculations should be used for CH₃CN and CHCl₃ solutions. PMID:23922034
Painter, K. J.; Hunt, G. S.; Wells, K. L.; Johansson, J. A.; Headon, D. J.
2012-01-01
In his seminal 1952 paper, ‘The Chemical Basis of Morphogenesis’, Alan Turing lays down a milestone in the application of theoretical approaches to understand complex biological processes. His deceptively simple demonstration that a system of reacting and diffusing chemicals could, under certain conditions, generate spatial patterning out of homogeneity provided an elegant solution to the problem of how one of nature's most intricate events occurs: the emergence of structure and form in the developing embryo. The molecular revolution that has taken place during the six decades following this landmark publication has now placed this generation of theoreticians and biologists in an excellent position to rigorously test the theory and, encouragingly, a number of systems have emerged that appear to conform to some of Turing's fundamental ideas. In this paper, we describe the history and more recent integration between experiment and theory in one of the key models for understanding pattern formation: the emergence of feathers and hair in the skins of birds and mammals. PMID:23919127
NASA Astrophysics Data System (ADS)
Yurchenko, Sergei N.; Thiel, Walter; Jensen, Per
2007-10-01
We present a new computational method with associated computer program TROVE (Theoretical ROVibrational Energies) to perform variational calculations of rovibrational energies for general polyatomic molecules of arbitrary structure in isolated electronic states. The (approximate) nuclear kinetic energy operator is represented as an expansion in terms of internal coordinates. The main feature of the computational scheme is a numerical construction of the kinetic energy operator, which is an integral part of the computation process. Thus the scheme is self-contained, i.e., it requires no analytical pre-derivation of the kinetic energy operator. It is also general, since it can be used in connection with any internal coordinates. The method represents an extension of our model for pyramidal XY 3 molecules reported previously [S.N. Yurchenko, M. Carvajal, P. Jensen, H. Lin, J.J. Zheng, W. Thiel, Mol. Phys. 103 (2005) 359]. Non-rigid molecules are treated in the Hougen-Bunker-Johns approach [J.T. Hougen, P.R. Bunker, J.W.C. Johns, J. Mol. Spectrosc. 34 (1970) 136]. In this case, the variational calculations employ a numerical finite basis representation for the large-amplitude motion using basis functions that are generated by Numerov-Cooley integration of the appropriate one-dimensional Schrödinger equation.
Ronald Fowler
2004-11-30
This report describes the results of the one-year project entitled ''Improved Approaches to Design of Polymer Gel Treatments in Mature Oil Fields: Field Demonstration in Dickman Field, Ness County, Kansas''. The project was a 12-month collaboration of Grand Mesa Operating Company (a small independent), TIORCO Inc. (a company focused on improved recovery technology) and the University of Kansas. The study undertook tasks to determine an optimum polymer gel treatment design in Mississippian reservoirs, demonstrate application, and evaluate the success of the program. The project investigated geologic and engineering parameters and cost-effective technologies required for design and implementation of effective polymer gel treatment programs in the Mississippian reservoir in the Midcontinent. The majority of Mississippian production in Kansas occurs at or near the top of the Mississippian section just below the regional sub-Pennsylvanian unconformity and karst surface. Dickman Field with the extremely high water cuts and low recovery factors is typical of Mississippian reservoirs. Producibility problems in these reservoirs include inadequate reservoir characterization, drilling and completion design problems, and most significantly extremely high water cuts and low recovery factors that place continued operations at or near their economic limits. Geologic, geophysical and engineering data were integrated to provide a technical foundation for candidate selection and treatment design. Data includes core, engineering data, and 3D seismic data. Based on technical and economic considerations a well was selected for gel-polymer treatment (Grand Mesa Operating Company Tilley No.2). The treatment was not successful due to the small amount of polymer that could be injected. Data from the initial well and other candidates in the demonstration area was analyzed using geologic, geophysical and engineering data. Based on the results of the treatment and the integrated reservoir
NASA Technical Reports Server (NTRS)
Everhart, Joel Lee
1988-01-01
A theoretical examination of the slotted-wall flow field is conducted to determine the appropriate wall pressure drop (or boundary condition) equation. This analysis improves the understanding of the fluid physics of these types of flow fields and helps in evaluating the uncertainties and limitations existing in previous mathematical developments. It is shown that the resulting slotted-wall boundary condition contains contributions from the airfoil-induced streamline curvature and the non-linear, quadratic, slot crossflow in addition to an often neglected linear term which results from viscous shearing in the slot. Existing and newly acquired experimental data are examined in the light of this formulation and theoretical developments.
NASA Astrophysics Data System (ADS)
Thatcher, Evan; Stanton, Christopher; Ishioka, Kunie; Basak, Amlan; Petek, Hrvoje
2015-03-01
We present results from a joint experimental and theoretical study exploring the excitation of coupled plasmon-phonon modes in GaAs. In contrast to previous coherent phonon studies in GaAs where electrons were generated primarily in the Γ valley (E0 gap), we use a pump-probe technique with a 10 fs pulse width and a shorter 400 nm laser wavelength to photoexcite electrons predominately in the L valley (E1 gap). As a result: i) damping of the electron-hole plasma is faster and ii) diffusion of the carriers from the surface becomes important owing to the shorter absorption length. The probe pulses measure the time-dependent changes to the reflectivity due to the coupled plasmon-phonon modes created by the ultrafast photoexcitation and the subsequent depletion field screening. To model this, we solve for the time and density dependent coupled-mode frequencies allowing for ambipolar diffusion. Simulation of the coupled plasmon-phonon dynamics allows for comparison with, and a better understanding of experiments. Supported by the NSF through Grants CHE-0650756, DMR-1311845, and DMR-1311849.
NASA Astrophysics Data System (ADS)
Li, Qinyi; Tang, Ying; He, Xinhua; Li, Hang
2015-10-01
The activation energy of particle aggregation in suspensions is a very important kinetic parameter in a wide range of science and engineering applications. At present, however, there is no theory that can theoretically predict the activation energy. Because the activation energy is often less than 10 kT (where k is the Boltzmann constant and T is the temperature), it is difficult to experimentally measure. In this study, a theory for calculating the activation energy is established. Experimental measurements of the activation energy of montmorillonite aggregation were performed with different electrolyte and particle concentrations using the dynamic light scattering (DLS) technique. The validity of the theory was verified by the experiments. This study confirmed that both the method for activation energy measurements by DLS and the theory for its calculation can be applied to suspensions of polydisperse nonspherical particles. The average kinetic energy at the moment of particle collision in the aggregation process was found to be 0.2 kT, which is less than the instantaneous kinetic energy of a Brownian particle (0.5 kT) because of the viscous resistance of the water medium. This study also shows that adsorbed Na+ is strongly polarized in the electric field near the particle surface, and the polarization increases the effective charge of Na+ from +1 to +1.18.
Pacheco-Blas, M A; Novaro, O A; Pacheco-Sánchez, J H
2010-11-01
The photochemical activation of Al atoms in cryogenic matrices to induce their reaction with methane has been experimentally studied before. Here, a theoretical study of the nonadiabatic transition probabilities for the ground ((2)P:3s(2)3p(1)) and the lowest excited states ((2)S:3s(2)4s(1) and (2)D:3s(2)3d(1)) of an aluminum atom interacting with a methane molecule (CH(4)) was carried out through ab initio Hartree-Fock self-consistent field calculations. This was followed by a multiconfigurational study of the correlation energy obtained by extensive variational and perturbational configuration interaction analyses using the CIPSI program. The (2)D state is readily inserted into a C-H bond, this being a prelude to a sequence of avoided crossings with the initially repulsive (to CH(4)) lower lying states (2)P and (2)S. We then use a direct extension of the Landau-Zener theory to obtain transition probabilities at each avoided crossing, allowing the formation of an HAlCH(3) intermediate that eventually leads to the final pair of products H+AlCH(3) and HAl+CH(3). PMID:21054032
Pacheco-Blas, M. A.; Novaro, O. A.; Pacheco-Sanchez, J. H.
2010-11-07
The photochemical activation of Al atoms in cryogenic matrices to induce their reaction with methane has been experimentally studied before. Here, a theoretical study of the nonadiabatic transition probabilities for the ground ({sup 2}P:3s{sup 2}3p{sup 1}) and the lowest excited states ({sup 2}S:3s{sup 2}4s{sup 1} and {sup 2}D:3s{sup 2}3d{sup 1}) of an aluminum atom interacting with a methane molecule (CH{sub 4}) was carried out through ab initio Hartree-Fock self-consistent field calculations. This was followed by a multiconfigurational study of the correlation energy obtained by extensive variational and perturbational configuration interaction analyses using the CIPSI program. The {sup 2}D state is readily inserted into a C-H bond, this being a prelude to a sequence of avoided crossings with the initially repulsive (to CH{sub 4}) lower lying states {sup 2}P and {sup 2}S. We then use a direct extension of the Landau-Zener theory to obtain transition probabilities at each avoided crossing, allowing the formation of an HAlCH{sub 3} intermediate that eventually leads to the final pair of products H+AlCH{sub 3} and HAl+CH{sub 3}.
Marc Vanderhaeghen
2007-04-01
The theoretical issues in the interpretation of the precision measurements of the nucleon-to-Delta transition by means of electromagnetic probes are highlighted. The results of these measurements are confronted with the state-of-the-art calculations based on chiral effective-field theories (EFT), lattice QCD, large-Nc relations, perturbative QCD, and QCD-inspired models. The link of the nucleon-to-Delta form factors to generalized parton distributions (GPDs) is also discussed.
Quark mean field approach with derivative coupling for nuclear matter
Kawabata, M.; Akiyama, S.; Futami, Y.; Nakasone, T.; Yukino, T.
2008-05-15
We propose the quark mean field model including derivative coupling between quarks and scalar mesons in nuclear matter. This model concisely interprets an increasing size of the nucleon as well as a modification of coupling constant in the nuclear environment.
Nonrelativistic approach for cosmological scalar field dark matter
NASA Astrophysics Data System (ADS)
Ureña-López, L. Arturo
2014-07-01
We derive nonrelativistic equations of motion for the formation of cosmological structure in a scalar field dark matter (SFDM) model corresponding to a complex scalar field endowed with a quadratic scalar potential. Starting with the equations of motion written in the Newtonian gauge of scalar perturbations, we separate out the involved fields into relativistic and nonrelativistic parts and find the equations of motion for the latter that can be used to build up the full solution. One important assumption will be that the SFDM field is in the regime of fast oscillations, under which its behavior in the homogeneous regime is exactly that of cold dark matter. The resultant equations are quite similar to the Schrödinger-Poisson system of Newtonian boson stars plus relativistic leftovers, and they can be used to study the formation of cosmological structure in SFDM models, and others alike, to ultimately prove their viability as complete dark matter models.
FIELD-DRIVEN APPROACHES TO SUBSURFACE CONTAMINANT TRANSPORT MODELING.
Observations from field sites provide a means for prioritizing research activities. In the case of petroleum releases, observations may include spiking of concentration distributions that may be related to water table fluctuation, co-location of contaminant plumes with geochemi...
A phase-space approach for propagating field-field correlation functions
NASA Astrophysics Data System (ADS)
Gradoni, Gabriele; Creagh, Stephen C.; Tanner, Gregor; Smartt, Christopher; Thomas, David W. P.
2015-09-01
We show that radiation from complex and inherently random but correlated wave sources can be modelled efficiently by using an approach based on the Wigner distribution function. Our method exploits the connection between correlation functions and the Wigner function and admits in its simplest approximation a direct representation in terms of the evolution of ray densities in phase space. We show that next leading order corrections to the ray-tracing approximation lead to Airy-function type phase space propagators. By exploiting the exact Wigner function propagator, inherently wave-like effects such as evanescent decay or radiation from more heterogeneous sources as well as diffraction and reflection can be included and analysed. We discuss in particular the role of evanescent waves in the near-field of non-paraxial sources and give explicit expressions for the growth rate of the correlation length as a function of the distance from the source. The approximations are validated using full-wave simulations of model sources. In particular, results for the reflection of partially coherent sources from flat mirrors are given where the influence of Airy function corrections can be demonstrated. We focus here on electromagnetic sources at microwave frequencies and modelling efforts in the context of electromagnetic compatibility.
NASA Technical Reports Server (NTRS)
Bebout, Leslie; Keller, R.; Miller, S.; Jahnke, L.; DeVincenzi, D. (Technical Monitor)
2002-01-01
The Ames Exobiology Culture Collection Database (AECC-DB) has been developed as a collaboration between microbial ecologists and information technology specialists. It allows for extensive web-based archiving of information regarding field samples to document microbial co-habitation of specific ecosystem micro-environments. Documentation and archiving continues as pure cultures are isolated, metabolic properties determined, and DNA extracted and sequenced. In this way metabolic properties and molecular sequences are clearly linked back to specific isolates and the location of those microbes in the ecosystem of origin. Use of this database system presents a significant advancement over traditional bookkeeping wherein there is generally little or no information regarding the environments from which microorganisms were isolated. Generally there is only a general ecosystem designation (i.e., hot-spring). However within each of these there are a myriad of microenvironments with very different properties and determining exactly where (which microenvironment) a given microbe comes from is critical in designing appropriate isolation media and interpreting physiological properties. We are currently using the database to aid in the isolation of a large number of cyanobacterial species and will present results by PI's and students demonstrating the utility of this new approach.
Majorana-Oppenheimer Approach to Proca Field Equations
NASA Astrophysics Data System (ADS)
Tomazelli, J. L.; Fernandes, G. A. M. A.
2014-09-01
A Dirac-like equation for a massive field obeying the classical Proca equations of motion (PMO) is proposed in close analogy with Majorana's construct for Maxwell electrodynamics. Its underlying algebraic structure is examined and a plausible physical interpretation is discussed. The behavior of the PMO equations in the presence of an external electromagnetic field is also investigated in the low energy limit, via unitary transformations similar to the Foldy-Wouthuysen canonical transformation for a Dirac fermion.
NASA Astrophysics Data System (ADS)
Mishra, Amruta; Misra, S. P.; Greiner, W.
2015-07-01
We calculate the decay widths of the charmonium states, J/ψ, ψ(3686) and ψ(3770), to D\\bar {D} pairs, as well as the decay width of D* → Dπ, in isospin asymmetric strange hadronic matter, using a field theoretical model for composite hadrons with quark constituents. For this purpose, we use the quark-antiquark pair creation term of the free Dirac Hamiltonian written in terms of the constituent quark field operators, and use explicit charmonium, D, \\bar {D}, D* and π states to evaluate the matrix elements for the charmonium as well as D* decay amplitudes. The medium modifications of the partial decay widths of charmonium to D\\bar {D} pair, arising from the mass modifications of the D(\\bar {D}) and the charmonium states calculated in a chiral effective model, are also included. The results of the present investigations are then compared with the decay widths computed earlier, in a model using light quark pair creation in 3P0 state. As in 3P0 model, the decay amplitude in the present model is multiplied with a strength parameter for the light quark pair creation, which is fitted from the observed vacuum decay width. The effects of the isospin asymmetry, the strangeness fraction of the hadronic matter on the masses of the charmonium states and D(\\bar {D}) mesons and hence on the decay widths, have also been studied. The isospin asymmetry effect is observed to be dominant for high densities, leading to appreciable difference in the decay channels of the charmonium to D+ D- and D0 \\bar {D0} pairs. The decay width of D* → Dπ in the hadronic matter has also been calculated within the composite quark model in the present work, accounting for the medium modifications of the D and D* masses. The density modifications of the charmonium states and D(D*) mesons, which are observed to be appreciable at high densities, will be of relevance in the compressed baryonic matter (CBM) experiments at the future facility of FAIR, GSI, where charmed hadrons will be produced
ERIC Educational Resources Information Center
Tweeikat, Mashhour Mohammad; AL-Kaddah, Muhammad Ibrahim
2014-01-01
This paper aims at studying to what extent the female students in Child Education department at Princess Alia University College manage to apply the theoretical part in field training program. The data, which is the scope of this study, consists of 42 staff members and 36 educational supervisors responsible for the program. The two researchers…