scholarly journals The distance-decay function of geographical gravity model: Power law or exponential law?

2015 ◽  
Vol 77 ◽  
pp. 174-189 ◽  
Author(s):  
Yanguang Chen
Keyword(s):  
Gravity Model ◽  
Power Law ◽  
Distance Decay ◽  
Decay Function ◽  
Exponential Law

scholarly journals Measuring the Destination Accessibility of Cycling Transfer Trips in Metro Station Areas: A Big Data Approach

2019 ◽  
Vol 16 (15) ◽  
pp. 2641 ◽  
Author(s):  
Xueying Wu ◽  
Yi Lu ◽  
Yaoyu Lin ◽  
Yiyang Yang
Keyword(s):  
Positive Association ◽  
Distance Decay ◽  
Decay Function ◽  
Metro Station ◽  
Negative Exponential Function ◽  
Transfer Mode ◽  
Last Mile ◽  
Trip Distance ◽  
Using Data ◽  
Negative Exponential

Cycling is a green, sustainable, and healthy choice for transportation that has been widely advocated worldwide in recent years. It can also encourage the use of public transit by solving the “last-mile” issue, because transit passengers can cycle to and from transit stations to achieve a combination of speed and flexibility. Cycling as a transfer mode has been shown to be affected by various built environment characteristics, such as the urban density, land-use mix, and destination accessibility, that is, the ease with which cyclists can reach their destinations. However, cycling destination accessibility is loosely defined in the literature and the methods of assessing cycling accessibility is often assumed to be equivalent to walking accessibility using the same decay curves, such as the negative exponential function, which ignores the competitive relationship between cycling and walking within a short distance range around transit stations. In this study, we aim to fill the above gap by measuring the cycling destination accessibility of metro station areas using data from more than three million bicycle-metro transfer trips from a dockless bicycle-sharing program in Shenzhen, China. We found that the frequency of bicycle-metro trips has a positive association with a trip distance of 500 m or less and a negative association with a trip distance beyond 500 m. A new cycling accessibility metric with a lognormal distribution decay curve was developed by considering the distance decay characteristics and cycling’s competition with walking. The new accessibility model outperformed the traditional model with an exponential decay function, or that without a distance decay function, in predicting the frequency of bicycle-metro trips. Hence, to promote bicycle-metro integration, urban planners and government agencies should carefully consider the destination accessibility of metro station areas.

scholarly journals Derivation of Conservation Laws for the Magma Equation Using the Multiplier Method: Power Law and Exponential Law for Permeability and Viscosity

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
N. Mindu ◽  
D. P. Mason
Keyword(s):  
Conservation Laws ◽  
Power Law ◽  
Travelling Waves ◽  
Travelling Wave ◽  
Multiplier Method ◽  
Reduction Theorem ◽  
Double Reduction ◽  
Exponential Law ◽  
Spatial Derivatives ◽  
Derivatives Of

The derivation of conservation laws for the magma equation using the multiplier method for both the power law and exponential law relating the permeability and matrix viscosity to the voidage is considered. It is found that all known conserved vectors for the magma equation and the new conserved vectors for the exponential laws can be derived using multipliers which depend on the voidage and spatial derivatives of the voidage. It is also found that the conserved vectors are associated with the Lie point symmetry of the magma equation which generates travelling wave solutions which may explain by the double reduction theorem for associated Lie point symmetries why many of the known analytical solutions are travelling waves.

Some Theoretical Aspects of Destination Choice and Their Relevance to Production-Constrained Gravity Models

1983 ◽  
Vol 15 (8) ◽  
pp. 1121-1132 ◽  
Author(s):  
A S Fotheringham
Keyword(s):  
Spatial Structure ◽  
Gravity Model ◽  
Distance Decay ◽  
Gravity Models ◽  
Destination Choice ◽  
Agglomeration Effects ◽  
Decay Parameters

Aspects of destination choice which concern relationships between destinations are explored in the context of a production-constrained gravity model. It is shown that, if competition exists between destinations or, alternatively, if agglomeration effects are present, the gravity model is misspecified and estimated distance-decay parameters obtained from the model are related to spatial structure.

Photoluminescence and Electroluminescence in Partially Oxidized Porous Silicon

1994 ◽  
Vol 358 ◽  
Author(s):  
L. Tsybeskov ◽  
S. P. Duttagupta ◽  
P. M. Fauchet
Keyword(s):  
Activation Energy ◽  
Porous Silicon ◽  
Power Law ◽  
Current Density ◽  
Crystalline Silicon ◽  
Exponential Law ◽  
Current Voltage ◽  
Device Applications ◽  
Current Voltage Characteristics ◽  
Oxidized Porous Silicon

ABSTRACTThe results of photoluminescence (PL) and electroluminescence (EL) studies from partially oxidized porous silicon (POPS) layers are presented. The PL from POPS is stable, peaks at 600-570 nm and its temperature dependence can be fitted by an exponential law with an activation energy Ea « 10 meV. The current-voltage characteristics of Au-(POPS)-crystalline silicon (c-Si) structures follow a power law I = Vn. When the index n becomes higher than 3, electroluminescence (EL) is found. The EL peaks at 760 nm and is stable for more than 100 hours of operation. The intensity of the EL is a linear function of current for all measured structures up to current density J ≈ 1 A/cm2. Our results suggest that partially oxidized porous silicon is more useful for device applications than freshly anodized porous silicon which has unstable properties or than fully oxidized porous silicon in which transport is poor.

scholarly journals Use of mathematical laws for optimizing the dose of swollen and dry bentonite during the fining of white wines. Part II : influence on the volume of lies and economics

OENO One ◽  
2003 ◽  
Vol 37 (2) ◽  
pp. 123
Author(s):  
Richard Marchal ◽  
S. Weingartner ◽  
Philippe Jeandet ◽  
Franck Chatelain
Keyword(s):  
Power Law ◽  
White Wine ◽  
White Wines ◽  
Good Relationship ◽  
Exponential Law ◽  
Low Efficiency ◽  
The Cost ◽  
Higher Doses

<p style="text-align: justify;">A Sauvignon white wine was fined with a dry bentonite (BS), e.g directly incorporated in the wine without swelling treatment, or with the same bentonite swelled in water 24 hours before utilization (BG). The volumes of lees generated by the fining were situated between 0,27 and 1,51 % (v/v) for BS, and between 1,07 and 4,59 % (v/v) for BG. The relation between the quantity of bentonite introduced in the wine (g/hl) and the volume of lees (v/v) follows a power law. The volume of lees only increased by 70 % when the dose of swelled bentonite was doubled; for higher doses of bentonite (rarely used), one can observe a packing of the lees. For BS, lees were approximately twice more volumetric when the dose was doubled. We also observe very good relationship between the clarifying efficiency and the volume of lees. When the clarifying efficiency of BG increased by 10 % the volume of lees increased by 74 %. For BS, when the clarifying efficiency increased by 10 % the volume of lees increased by 86 % because of its low efficiency during clarification. The decrease of the natural proteic haze risk and the volume of lees generated by bentonite fining were also closely correlated by an exponential law. For BG, the mathematical law showed that when the volume of lees increased by 0,1 % (v/v), colloidal haze risk decreased only by 22 %. On the contrary, for BS, when the volume of lees increased by 0,1 %, proteic haze risk decreased by 44 %. Finally, the estimation of the cost of fining showed that the use of a non swelled bentonite was economically more interesting than the utilization of a swelled bentonite. This was true when this Sauvignon wine is sold both in bottle or in bulk. For the studied wine, the estimated winning was 115 euros for 10 hl sold in bulk.</p>

scholarly journals An Analysis of Mobility Patterns in Sexual Homicide

2019 ◽  
Vol 24 (2) ◽  
pp. 178-202 ◽  
Author(s):  
Julien Chopin ◽  
Stefano Caneppele ◽  
Eric Beauregard
Keyword(s):  
Crime Scene ◽  
Distance Decay ◽  
Mobility Patterns ◽  
Spatial Mobility ◽  
National Data ◽  
Decay Function ◽  
Data Set ◽  
Sexual Homicide ◽  
Safe Place

This article—based on a national data set ( N = 173)—focuses on extrafamilial sexual homicides and their spatial mobility. The study combines the location of the crime scene and the offenders and victims’ residences in mobility crime triangles. The findings reveal that most of the homicides fall within the categories of offender mobility and total mobility. Our results show the validity of the distance decay function, with over 70% of homicides occurring within 10 km of the offender’s residence. It appears that under certain circumstances, sexual murderers perceive their surroundings as a safe place to commit a homicide. Finally, the study proposes a four-category spatial typology of sexual homicide.

EXPERIMENTAL OBSERVATION OF INTERMITTENCY IN COUPLED CHAOTIC PENDULUMS

1999 ◽  
Vol 09 (10) ◽  
pp. 1907-1916 ◽  
Author(s):  
H. J. T. SMITH ◽  
JAMES A. BLACKBURN ◽  
GREGORY L. BAKER
Keyword(s):  
Experimental Data ◽  
Experimental Observation ◽  
Conditional Probability ◽  
Power Law ◽  
Coupling Strength ◽  
Chaotic Motion ◽  
Threshold Level ◽  
Exponential Law ◽  
Angular Velocities ◽  
The Difference

We have experimentally realized on–off intermittency in a pair of mutually coupled damped driven pendula. The pendula interacted bidirectionally via a torque which was proportional to the difference in their angular velocities. Experimental data show that the intervals of synchronized chaotic motion are distributed in agreement with the theory for on–off intermittency: The conditional probability of short laminar times is found to follow a power law whilst the conditional probability of long laminar times follows the expected exponential law. The experimental data also reveal that the intermittent properties vary with the coupling strength, and that the average laminar time inferred from the results depends on the choice of threshold level.

DIFFUSIONAL MODEL FOR NOISY ON–OFF INTERMITTENCY

1999 ◽  
Vol 09 (02) ◽  
pp. 355-359 ◽  
Author(s):  
A. ČENYS ◽  
J. ULBIKAS ◽  
A. N. ANAGNOSTOPOULOS ◽  
G. L. BLERIS
Keyword(s):  
Critical Point ◽  
Power Law ◽  
Statistical Properties ◽  
Exponential Law ◽  
Universal Distribution ◽  
Diffusional Model

Statistical properties of the laminar lengths for the noisy on–off intermittency are studied analytically. The universal distribution of the laminar phases is obtained at the critical point. It can be approximated by the power law with the exponent -3/2 and the exponential law describing fast falloff.

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