scholarly journals Border Collision Bifurcations in a Generalized Model of Population Dynamics

2016 ◽  
Vol 2016 ◽  
pp. 1-13
Author(s):  
Lilia M. Ladino ◽  
Cristiana Mammana ◽  
Elisabetta Michetti ◽  
Jose C. Valverde
Keyword(s):  
Phase Plane ◽  
Real Data ◽  
Natural Death ◽  
Present Contribution ◽  
Fishing Activity ◽  
Border Collision Bifurcations ◽  
Abrupt Changes ◽  
Population Sizes ◽  
Piecewise Map ◽  
New Strategies

We analyze the dynamics of a generalized discrete time population model of a two-stage species with recruitment and capture. This generalization, which is inspired by other approaches and real data that one can find in literature, consists in considering no restriction for the value of the two key parameters appearing in the model, that is, the natural death rate and the mortality rate due to fishing activity. In the more general case the feasibility of the system has been preserved by posing opportune formulas for the piecewise map defining the model. The resulting two-dimensional nonlinear map is not smooth, though continuous, as its definition changes as any border is crossed in the phase plane. Hence, techniques from the mathematical theory of piecewise smooth dynamical systems must be applied to show that, due to the existence of borders, abrupt changes in the dynamic behavior of population sizes and multistability emerge. The main novelty of the present contribution with respect to the previous ones is that, while using real data, richer dynamics are produced, such as fluctuations and multistability. Such new evidences are of great interest in biology since new strategies to preserve the survival of the species can be suggested.

scholarly journals IMAGE BASED RECOGNITION OF DYNAMIC TRAFFIC SITUATIONS BY EVALUATING THE EXTERIOR SURROUNDING AND INTERIOR SPACE OF VEHICLES

2015 ◽  
Vol XL-3/W3 ◽  
pp. 161-168
Author(s):  
A. Hanel ◽  
H. Klöden ◽  
L. Hoegner ◽  
U. Stilla
Keyword(s):  
Machine Learning ◽  
Real Data ◽  
Traffic Situation ◽  
Dynamic Traffic ◽  
Interior Space ◽  
Data Set ◽  
Road Users ◽  
Vehicle Fleet ◽  
New Strategies

Today, cameras mounted in vehicles are used to observe the driver as well as the objects around a vehicle. In this article, an outline of a concept for image based recognition of dynamic traffic situations is shown. A dynamic traffic situation will be described by road users and their intentions. Images will be taken by a vehicle fleet and aggregated on a server. On these images, new strategies for machine learning will be applied iteratively when new data has arrived on the server. The results of the learning process will be models describing the traffic situation and will be transmitted back to the recording vehicles. The recognition will be performed as a standalone function in the vehicles and will use the received models. It can be expected, that this method can make the detection and classification of objects around the vehicles more reliable. In addition, the prediction of their actions for the next seconds should be possible. As one example how this concept is used, a method to recognize the illumination situation of a traffic scene is described. This allows to handle different appearances of objects depending on the illumination of the scene. Different illumination classes will be defined to distinguish different illumination situations. Intensity based features are extracted from the images and used by a classifier to assign an image to an illumination class. This method is being tested for a real data set of daytime and nighttime images. It can be shown, that the illumination class can be classified correctly for more than 80% of the images.

scholarly journals A Method for Detecting Abrupt Change of Sediment Discharge in the Loess Plateau, China

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1183 ◽  
Author(s):  
Dandan Shen ◽  
Weimin Bao ◽  
Peng Ni
Keyword(s):  
Abrupt Change ◽  
Yellow River ◽  
Moving Average ◽  
Real Data ◽  
Change Points ◽  
Sediment Discharge ◽  
Test Statistic ◽  
Abrupt Changes ◽  
Sediment Reduction

In recent decades, the streamflow and sediment of the Yellow River has decreased sharply, especially the sediment discharge. The factors that lead to this phenomenon have become a widely concerned problem of the whole society. The analysis of abrupt change points of hydrological series is the key to divide datum period, so it is an important work in the research of streamflow and sediment reduction cause. So far, many methods have been proposed to detect abrupt change. However, most methods have great uncertainty due to the deficiencies of irrational structure of test statistics, ideal hypothesis or subjectivity. In this paper, a new method called moving average difference method for abrupt change points detection is proposed. It is proved to be effective through comparison with four commonly used methods via both synthetic series and real data case study. The results show that the proposed method has four distinct advantages: (1) The test statistic structure of the method has physical significance and is intuitive to understand; (2) It is more accurate in abrupt change detection; (3) It can detect all of the abrupt change points at one time; (4) It can detect the abrupt changes and calculate the corresponding mutation intensity simultaneously.

scholarly journals Assessment of Earth Gravity Field Models in the Medium to High Frequency Spectrum Based on GRACE and GOCE Dynamic Orbit Analysis

Geosciences ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 441
Author(s):  
Thomas D. Papanikolaou ◽  
Dimitrios Tsoulis
Keyword(s):  
Gravity Field ◽  
Ocean Circulation ◽  
Real Data ◽  
Present Contribution ◽  
Earth Gravity ◽  
Orbit Analysis ◽  
Band Limited ◽  
Gravity Signal ◽  
The Individual ◽  
Gravity Field Models

An analysis of current static and time-variable gravity field models is presented focusing on the medium to high frequencies of the geopotential as expressed by the spherical harmonic coefficients. A validation scheme of the gravity field models is implemented based on dynamic orbit determination that is applied in a degree-wise cumulative sense of the individual spherical harmonics. The approach is applied to real data of the Gravity Field and Steady-State Ocean Circulation (GOCE) and Gravity Recovery and Climate Experiment (GRACE) satellite missions, as well as to GRACE inter-satellite K-band ranging (KBR) data. Since the proposed scheme aims at capturing gravitational discrepancies, we consider a few deterministic empirical parameters in order to avoid absorbing part of the gravity signal that may be included in the monitored orbit residuals. The present contribution aims at a band-limited analysis for identifying characteristic degree ranges and thresholds of the various GRACE- and GOCE-based gravity field models. The degree range 100–180 is investigated based on the degree-wise cumulative approach. The identified degree thresholds have values of 130 and 160 based on the GRACE KBR data and the GOCE orbit analysis, respectively.

Isometric relaxation of isolated diaphragm muscle: influence of load, length, time, and stimulation

1994 ◽  
Vol 76 (4) ◽  
pp. 1468-1475 ◽  
Author(s):  
C. Coirault ◽  
D. Chemla ◽  
N. Pery-Man ◽  
I. Suard ◽  
S. Salmeron ◽  
...  
Keyword(s):  
Relaxation Rate ◽  
Phase Plane ◽  
Muscle Length ◽  
Diaphragm Muscle ◽  
Loading Conditions ◽  
Total Load ◽  
Instantaneous Rate ◽  
Stimulation Mode ◽  
Abrupt Changes ◽  
Previous Loading

Determinants of the isometric relaxation rate were investigated in isolated rat diaphragm (n = 30). We tested the hypothesis that these determinants could include loading conditions, namely preload and afterload; abrupt changes in load during the contraction phase; stimulation conditions; and time. Two relaxation sequences were studied. When isometric relaxation occurred at initial muscle length (isotonic-isometric sequence), an increase in total load (P) accelerated the negative peak rate of tension decline (-dP/dtmax). Variations in initial length, stimulation, and onset of relaxation did not modify the -dP/dtmax vs. afterload relationship. When isometric relaxation was analyzed after -dP/dtmax, for a given afterload level the instantaneous rate of tension decline (-dP/dt) was a unique function of instantaneous tension, regardless of previous loading conditions, stimulation mode, or time. When the isometric relaxation occurred at end-shortening muscle length (isometric-isotonic sequence), the -dP/dtmax vs. P relationship was flat. The rate of tension decay, as attested by either -dP/dtmax or instantaneous -dP/dt vs. instantaneous tension phase plane, differed markedly depending on stimulation conditions. Thus the regulation of isometric relaxation rate differed according to the relaxation sequence. In muscle isometrically relaxing at initial muscle length, peak isometric relaxation rate was mainly determined by afterload. Conversely, in muscle isometrically relaxing at end-shortening length, isometric relaxation rate was highly dependent on the level of activation and was independent of preload and afterload.

Bifurcation Sequences and Multistability in a Two-Dimensional Piecewise Linear Map

2020 ◽  
Vol 30 (06) ◽  
pp. 2030014
Author(s):  
Wirot Tikjha ◽  
Laura Gardini
Keyword(s):  
Dynamic Behavior ◽  
Phase Plane ◽  
Piecewise Linear ◽  
Basins Of Attraction ◽  
Two Dimensional ◽  
Piecewise Linear Map ◽  
Smooth Maps ◽  
Border Collision Bifurcations ◽  
Piecewise Smooth Maps ◽  
Transcritical Bifurcations

Bifurcation mechanisms in piecewise linear or piecewise smooth maps are quite different with respect to those occurring in smooth maps, due to the role played by the borders. In this work, we describe bifurcation mechanisms associated with the appearance/disappearance of cycles, which may be related to several cases: (A) fold border collision bifurcations, (B) degenerate flip bifurcations, supercritical and subcritical, (C) degenerate transcritical bifurcations and (D) supercritical center bifurcations. Each of these is characterized by a particular dynamic behavior, and may be related to attracting or repelling cycles. We consider different bifurcation routes, showing the interplay between all these kinds of bifurcations, and their role in the phase plane in determining attracting sets and basins of attraction.

High-resolution observations of metastable γ’ precipitation in Al-15at.%Ag

1996 ◽  
Vol 54 ◽  
pp. 1004-1005
Author(s):  
N. V. Larcher ◽  
I. G. Solorzano
Keyword(s):  
Discontinuous Precipitation ◽  
Equilibrium Phase ◽  
Quantitative Description ◽  
Present Contribution ◽  
Α Phase ◽  
The Matrix ◽  
Aging Sequence ◽  
Matrix Precipitation ◽  
Considerable Detail ◽  
Kinetics Of

It is currently well established that, for an Al-Ag alloy quenched from the α phase and aged within the metastable solvus, the aging sequence is: supersaturated α → GP zones → γ’ → γ (Ag2Al). While GP zones and plate-shaped γ’ are metastable phases, continuously distributed in the matrix, formation of the equilibrium phase γ takes place at grain boundaries by discontinuous precipitation (DP). The crystal structure of both γ’ and γ is hep with the following orientation relationship with respect to the fee α matrix: {0001}γ′,γ // {111}α, <1120>γ′,γ, // <110>α.The mechanisms and kinetics of continuous matrix precipitation (CMP) in dilute Al-Ag alloys have been studied in considerable detail. The quantitative description of DP kinetics, however, has received less attention. The present contribution reports the microstructural evolution resulting from aging an Al-Ag alloy with Ag content higher than those previously reported in the literature, focusing the observations of γ' plate-shaped metastable precipitates.

CDC Pushing New Strategies for Flu Vaccination

2006 ◽  
Vol 40 (11) ◽  
pp. 12
Author(s):  
HEIDI SPLETE
Keyword(s):  
Flu Vaccination ◽  
New Strategies

Detecting Random Responses in a Personality Scale Using IRT-Based Person-Fit Indices

2019 ◽  
Vol 35 (1) ◽  
pp. 126-136 ◽  
Author(s):  
Tour Liu ◽  
Tian Lan ◽  
Tao Xin
Keyword(s):  
Experimental System ◽  
Real Data ◽  
Fit Indices ◽  
Random Response ◽  
Person Fit ◽  
Index Method ◽  
Single Person ◽  
Person Fit Index ◽  
Random Responses ◽  
Response Behaviors

Abstract. Random response is a very common aberrant response behavior in personality tests and may negatively affect the reliability, validity, or other analytical aspects of psychological assessment. Typically, researchers use a single person-fit index to identify random responses. This study recommends a three-step person-fit analysis procedure. Unlike the typical single person-fit methods, the three-step procedure identifies both global misfit and local misfit individuals using different person-fit indices. This procedure was able to identify more local misfit individuals than single-index method, and a graphical method was used to visualize those particular items in which random response behaviors appear. This method may be useful to researchers in that it will provide them with more information about response behaviors, allowing better evaluation of scale administration and development of more plausible explanations. Real data were used in this study instead of simulation data. In order to create real random responses, an experimental test administration was designed. Four different random response samples were produced using this experimental system.

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