scholarly journals Simple model for the power-law blinking of single semiconductor nanocrystals

2002 ◽  
Vol 66 (23) ◽  
Author(s):  
Rogier Verberk ◽  
Antoine M. van Oijen ◽  
Michel Orrit
Keyword(s):  
Simple Model ◽  
Power Law ◽  
Semiconductor Nanocrystals

scholarly journals The emergence of heterogeneous scaling in research institutions

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Keith A. Burghardt ◽  
Zihao He ◽  
Allon G. Percus ◽  
Kristina Lerman
Keyword(s):  
Simple Model ◽  
Power Law ◽  
Scientific Discovery ◽  
Emergent Behavior ◽  
Research Institutions ◽  
Zipf's Law ◽  
Production Of Knowledge ◽  
Economy Of Scale ◽  
Scientific Papers ◽  
New Institutions

AbstractResearch institutions provide the infrastructure for scientific discovery, yet their role in the production of knowledge is not well characterized. To address this gap, we analyze interactions of researchers within and between institutions from millions of scientific papers. Our analysis reveals that collaborations densify as each institution grows, but at different rates (heterogeneous densification). We also find that the number of institutions scales with the number of researchers as a power law (Heaps’ law) and institution sizes approximate Zipf’s law. These patterns can be reproduced by a simple model in which researchers are preferentially hired by large institutions, while new institutions complimentarily generate more new institutions. Finally, new researchers form triadic closures with collaborators. This model reveals an economy of scale in research: larger institutions grow faster and amplify collaborations. Our work deepens the understanding of emergent behavior in research institutions and their role in facilitating collaborations.

The time to failure of fiber bundles subjected to random loads

1979 ◽  
Vol 11 (03) ◽  
pp. 527-541 ◽  
Author(s):  
Howard M. Taylor
Keyword(s):  
Simple Model ◽  
Power Law ◽  
Failure Time ◽  
Constant Load ◽  
Asymptotic Distributions ◽  
Asymptotic Independence ◽  
Time To Failure ◽  
Random Load ◽  
The Mean ◽  
Wave Induced

The effect on cable reliability of random cyclic loading such as that generated by the wave-induced rocking of ocean vessels deploying these cables is examined. A simple model yielding exact formulas is first explored. In this model, the failure time of a single fiber under a constant load is assumed to be exponentially distributed, and the random loadings are a two-state stationary Markov process. The effect of load on failure time is assumed to follow a power law breakdown rule. In this setting, exact results concerning the distribution of bundle or cable failure time, and especially the mean failure time, are obtained. Where the fluctuations in load are frequent relative to bundle life, such as may occur in long-lived cables, it is shown that randomness in load tends to decrease mean bundle life, but it is suggested that the reduction in mean life often can be restored by modestly reducing the base load on the structure or by modestly increasing the number of elements in the bundle. In later pages this simple model is extended to cover a broader range of materials and random loadings. Asymptotic distributions and mean failure times are given where fibers follow a Weibull distribution of failure time under constant load, and loads that are general non-negative stationary processes subject only to some mild condition of asymptotic independence. When the power law breakdown exponent is large, the mean time to bundle failure depends heavily on the exact form of the marginal probability distribution for the random load process and cannot be summarized by the first two moments of this distribution alone.

scholarly journals The Diversity of Broad Emission-Line Profiles

1997 ◽  
Vol 159 ◽  
pp. 197-198
Author(s):  
Giovanna M. Stirpe ◽  
Andrew Robinson ◽  
David J. Axon
Keyword(s):  
Simple Model ◽  
Emission Line ◽  
Power Law ◽  
Active Galaxies ◽  
Broad Line ◽  
Line Profiles ◽  
Broad Emission ◽  
Power Law Function ◽  
Broad Emission Line ◽  
Almost All

AbstractWe present preliminary results from a study of broad-line profiles in active galaxies. A simple model in which the emissivity is a broken power-law function of radius, and the BLR clouds emit anisotropically, yields very good fits to almost all the Ha profiles in our data base.

Extending the Theory of Creep to Viscoplasticity

1994 ◽  
Vol 116 (1) ◽  
pp. 67-75 ◽  
Author(s):  
A. D. Freed ◽  
K. P. Walker ◽  
M. J. Verrilli
Keyword(s):  
Steady State ◽  
Simple Model ◽  
Power Law ◽  
Copper Alloy ◽  
Theoretical Framework ◽  
Kinetics Equation ◽  
Creep Theory ◽  
Material Functions

A viscoplastic theory is developed that reduces to creep theory analytically under steady-state conditions. A fairly simple model is constructed from this theoretical framework by defining material functions that have close ties to the physics of inelasticity; consequently, the model is characterized easily. The computational characteristics of the model are enhanced, in general, by converting the kinetics equation from a hyperbolic relationship to a power-law relationship. The resulting model is applied to copper and to the copper alloy, NARloy Z.

THE RELATION OF JET QUENCHING AND POWER-LAW OBSERVED IN pT-DISTRIBUTIONS IN RELATIVISTIC HEAVY-ION COLLISIONS

2006 ◽  
Vol 15 (04) ◽  
pp. 865-876
Author(s):  
WANG LI ◽  
XIAO DONG WANG
Keyword(s):  
Simple Model ◽  
Power Law ◽  
Recent Observation ◽  
Fractal Dimensions ◽  
Heavy Ion ◽  
High Energy ◽  
Jet Quenching ◽  
Relativistic Heavy Ion Collisions ◽  
Distribution Data ◽  
Ion Collisions

Recent observation of high-pT hadron spectra suppression and mono-jet production in central Au-Au collisions and Cu-Cu collisions at RHIC have confirmed the long predicted phenomenon of jet quenching in high-energy-ion collisions. Detailed analyses of the experimental data show parton energy loss as the mechanism for the discovered jet quenching. Preconception-free analyses of the inclusive invariant transverse-momentum distribution data taken from the measurements of Au-Au collisions at [Formula: see text] and [Formula: see text] have been performed. It is observed that the distribution exhibits for pT≥2 GeV/c remarkably good power-law behavior (pT-scaling) with general regularities. It may explain the data coming from the STAR or PHENIX to some extent. Using the power-law by a simple model, its underlying geometrical structure has to be understood in terms of fractal dimensions. A simple model is proposed which approximately reproduces the above-mentioned data for the phenomenon, and it affords a new way to research the QGP matter and jet quenching. Further heavy-ion collision experiments are suggested.

The time to failure of fiber bundles subjected to random loads

1979 ◽  
Vol 11 (3) ◽  
pp. 527-541 ◽  
Author(s):  
Howard M. Taylor
Keyword(s):  
Simple Model ◽  
Power Law ◽  
Failure Time ◽  
Constant Load ◽  
Asymptotic Distributions ◽  
Asymptotic Independence ◽  
Time To Failure ◽  
Random Load ◽  
The Mean ◽  
Wave Induced

The effect on cable reliability of random cyclic loading such as that generated by the wave-induced rocking of ocean vessels deploying these cables is examined. A simple model yielding exact formulas is first explored. In this model, the failure time of a single fiber under a constant load is assumed to be exponentially distributed, and the random loadings are a two-state stationary Markov process. The effect of load on failure time is assumed to follow a power law breakdown rule. In this setting, exact results concerning the distribution of bundle or cable failure time, and especially the mean failure time, are obtained. Where the fluctuations in load are frequent relative to bundle life, such as may occur in long-lived cables, it is shown that randomness in load tends to decrease mean bundle life, but it is suggested that the reduction in mean life often can be restored by modestly reducing the base load on the structure or by modestly increasing the number of elements in the bundle.In later pages this simple model is extended to cover a broader range of materials and random loadings. Asymptotic distributions and mean failure times are given where fibers follow a Weibull distribution of failure time under constant load, and loads that are general non-negative stationary processes subject only to some mild condition of asymptotic independence. When the power law breakdown exponent is large, the mean time to bundle failure depends heavily on the exact form of the marginal probability distribution for the random load process and cannot be summarized by the first two moments of this distribution alone.

scholarly journals Multiscale behavior of a simple model for stock markets

2005 ◽  
Vol 2005 (2) ◽  
pp. 111-117
Author(s):  
Juan R. Sánchez
Keyword(s):  
Time Series ◽  
Simple Model ◽  
Power Law ◽  
Real World ◽  
Stock Markets ◽  
Time Range ◽  
Scaling Exponents ◽  
World Markets ◽  
Long Time ◽  
With Memory

The multiscale behavior of a recently reported model for stock markets is presented. It has been shown that indexes of real-world markets display absolute returns with memory properties on a long-time range, a phenomenon known as cluster volatility. The multiscale characteristics of an index are studied by analyzing the power-law scaling of the volatility correlations which display nonunique scaling exponents. Here such analysis is done on an artificial time series produced by a simple model for stock markets. After comparison, excellent agreements with the multiscale behavior of real-time series are found.

Size dependent thermal vibrations and melting in nanocrystals

1994 ◽  
Vol 9 (5) ◽  
pp. 1307-1314 ◽  
Author(s):  
Frank G. Shi
Keyword(s):  
Melting Point ◽  
Simple Model ◽  
Melting Temperature ◽  
Present Model ◽  
Semiconductor Nanocrystals ◽  
Quantitative Agreement ◽  
Bulk Crystal ◽  
Size Dependent ◽  
Measurable Parameter ◽  
Thermal Vibrations

A simple model for the size-dependent amplitude of the atomic thermal vibrations of a nanocrystal is presented which leads to the development of a model for the size dependent melting temperature in nanocrystals on the basis of Lindemann's criterion. The two models are in terms of a directly measurable parameter for the corresponding bulk crystal, i.e., the ratio between the amplitude of thermal vibrations for surface atoms and that for interior ones. It is shown that the present model for the melting temperature offers not only a qualitative but even an excellent quantitative agreement with the experimentally observed size-dependent superheating, as well as melting point suppression in both the supported and embedded metallic and semiconductor nanocrystals.

scholarly journals A Simple Model of Large Scale Organization in Evolution

1998 ◽  
Vol 09 (07) ◽  
pp. 1025-1032 ◽  
Author(s):  
S. C. Manrubia ◽  
M. Paczuski
Keyword(s):  
Mathematical Model ◽  
Simple Model ◽  
Probability Distribution ◽  
Introduced Species ◽  
Power Law ◽  
Large Scale ◽  
General Relation ◽  
Ecological Niches ◽  
Interacting Species ◽  
Extinction Event

A mathematical model of interacting species filling ecological niches left by the extinction of others is introduced. Species organize themselves into genera of all sizes. The size of a genus on average grows linearly with its age, confirming a general relation between Age and Area proposed by Willis. The ecology exhibits punctuated equilibrium. Analytic and numerical results show that the probability distribution of genera sizes, genera lifetimes, and extinction event sizes are the same power law P(x)~ 1/x2, consistent with paleontological data.

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