DETERMINATION OF CRISIS PARAMETER VALUES BY DIRECT OBSERVATION OF MANIFOLD TANGENCIES

1992 ◽  
Vol 02 (02) ◽  
pp. 383-396 ◽  
Author(s):  
JOHN C. SOMMERER ◽  
CELSO GREBOGI
Keyword(s):  
Periodic Point ◽  
Chaotic System ◽  
Direct Observation ◽  
Unstable Manifold ◽  
Stable Manifold ◽  
Critical Parameter ◽  
Scaling Relation ◽  
Chaotic Transients ◽  
Parameter Values

We discuss an algorithm to find the parameter value at which a nonlinear, dissipative, chaotic system undergoes crisis. The algorithm is based on the observation that, at crisis, the unstable manifold of an unstable periodic point becomes tangent to the stable manifold of the same or another, related unstable periodic point. This geometric algorithm uses much less computation (or data) than estimating the critical parameter value by using the scaling relation for chaotic transients, τ~(p−pc)−γ. We demonstrate the algorithm in both numerical and experimental contexts.

scholarly journals Effect of data quality on estimates of farm infectiousness trends in the UK 2001 foot-and-mouth disease epidemic

2006 ◽  
Vol 4 (13) ◽  
pp. 235-241 ◽  
Author(s):  
Nicholas J Savill ◽  
Darren J Shaw ◽  
Rob Deardon ◽  
Michael J Tildesley ◽  
Matthew J Keeling ◽  
...  
Keyword(s):  
Mathematical Models ◽  
Data Quality ◽  
Foot And Mouth Disease ◽  
Mouth Disease ◽  
Inaccurate Data ◽  
Foot And Mouth ◽  
The Uk ◽  
Parameter Values

Most of the mathematical models that were developed to study the UK 2001 foot-and-mouth disease epidemic assumed that the infectiousness of infected premises was constant over their infectious periods. However, there is some controversy over whether this assumption is appropriate. Uncertainty about which farm infected which in 2001 means that the only method to determine if there were trends in farm infectiousness is the fitting of mechanistic mathematical models to the epidemic data. The parameter values that are estimated using this technique, however, may be influenced by missing and inaccurate data. In particular to the UK 2001 epidemic, this includes unreported infectives, inaccurate farm infection dates and unknown farm latent periods. Here, we show that such data degradation prevents successful determination of trends in farm infectiousness.

scholarly journals Direct observation of interlayer molecular translational motion in a smectic phase and determination of the layer order parameter

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Makina Saito ◽  
Jun Yamamoto ◽  
Ryo Masuda ◽  
Masayuki Kurokuzu ◽  
Yohei Onodera ◽  
...  
Keyword(s):  
Direct Observation ◽  
Order Parameter ◽  
Translational Motion ◽  
Smectic Phase

scholarly journals PTPS Candidate Exoplanet Host Star Radii Determination with CHARA Array

2011 ◽  
Vol 7 (S282) ◽  
pp. 203-204
Author(s):  
Paweł Zieliński ◽  
Martin Vaňko ◽  
Ellyn Baines ◽  
Andrzej Niedzielski ◽  
Aleksander Wolszczan
Keyword(s):  
Effective Temperature ◽  
Critical Parameter ◽  
Spectroscopic Analysis ◽  
Evolutionary Model ◽  
Stellar Mass ◽  
Surface Temperatures ◽  
Penn State ◽  
Chara Array ◽  
Model Dependency

AbstractWe propose to measure the radii of the Penn State - Toruń Planet Search (PTPS) exoplanet host star candidates using the CHARA Array. Stellar radii estimated from spectroscopic analysis are usually inaccurate due to indirect nature of the method and strong evolutionary model dependency. Also, the so-called degeneracy of stellar evolutionary tracks due to convergence of many tracks in the giant branch decreases the precision of such estimates. However, the radius of a star is a critical parameter for the calculation of stellar luminosity and mass, which are often not well known especially for giants. With well determined effective temperature (from spectroscopy) and radius, the luminosity may be calculated precisely. In turn also stellar mass may be estimated much more precisely. Therefore, direct radii measurements increase precision in the determination of planetary candidates masses and the surface temperatures of the planets.

scholarly journals Comparative Study of Optimization Algorithms for The Optimal Reservoir Operation

2018 ◽  
Vol 246 ◽  
pp. 01003
Author(s):  
Xinyuan Liu ◽  
Yonghui Zhu ◽  
Lingyun Li ◽  
Lu Chen
Keyword(s):  
Reservoir Operation ◽  
Optimization Problems ◽  
Optimization Algorithms ◽  
Complex Problem ◽  
Optimization Techniques ◽  
Decision Variables ◽  
Handling Methods ◽  
Optimality Algorithm ◽  
Parameter Values

Apart from traditional optimization techniques, e.g. progressive optimality algorithm (POA), modern intelligence algorithms, like genetic algorithms, differential evolution have been widely used to solve optimization problems. This paper deals with comparative analysis of POA, GA and DE and their applications in a reservoir operation problem. The results show that both GA and DES are feasible to reservoir operation optimization, but they display different features. GA and DE have many parameters and are difficult in determination of these parameter values. For simple problems with mall number of decision variables, GA and DE are better than POA when adopting appropriate parameter values and constraint handling methods. But for complex problem with large number of variables, POA combined with simplex method are much superior to GA and DE in time-assuming and quality of optimal solutions. This study helps to select proper optimization algorithms and parameter values in reservoir operation.

scholarly journals Lecture Scheduling Automation Using Genetic Algorithm

2019 ◽  
Vol 8 (5C) ◽  
pp. 1444-1447
Keyword(s):  
Genetic Algorithm ◽  
Genetic Algorithms ◽  
Test Results ◽  
Scheduling Problems ◽  
Scheduling System ◽  
Parameter Values

This paper aims produce an academic scheduling system using Genetic Algorithm (GA) to solve the academic schedule. Factors to consider in academic scheduling are the lecture to be held, the available room, the lecturers and the time of the lecturer, the suitability of the credits with the time of the lecture, and perhaps also the time of Friday prayers, and so forth. Genetic Algorithms can provide the best solution for some solutions in dealing with scheduling problems. Based on the test results, the resulting system can automate the scheduling of lectures properly. Determination of parameter values in Genetic Algorithm also gives effect in producing the solution of lecture schedule

scholarly journals An intermittent control model of flexible human gait using a stable manifold of saddle-type unstable limit cycle dynamics

2014 ◽  
Vol 11 (101) ◽  
pp. 20140958 ◽  
Author(s):  
Chunjiang Fu ◽  
Yasuyuki Suzuki ◽  
Ken Kiyono ◽  
Pietro Morasso ◽  
Taishin Nomura
Keyword(s):  
Steady State ◽  
Limit Cycle ◽  
Unstable Manifold ◽  
Control Strategy ◽  
Stable Manifold ◽  
Joint Angle ◽  
Feedback Controller ◽  
Human Gait ◽  
Intermittent Control ◽  
Saddle Type

Stability of human gait is the ability to maintain upright posture during walking against external perturbations. It is a complex process determined by a number of cross-related factors, including gait trajectory, joint impedance and neural control strategies. Here, we consider a control strategy that can achieve stable steady-state periodic gait while maintaining joint flexibility with the lowest possible joint impedance. To this end, we carried out a simulation study of a heel-toe footed biped model with hip, knee and ankle joints and a heavy head-arms-trunk element, working in the sagittal plane. For simplicity, the model assumes a periodic desired joint angle trajectory and joint torques generated by a set of feed-forward and proportional-derivative feedback controllers, whereby the joint impedance is parametrized by the feedback gains. We could show that a desired steady-state gait accompanied by the desired joint angle trajectory can be established as a stable limit cycle (LC) for the feedback controller with an appropriate set of large feedback gains. Moreover, as the feedback gains are decreased for lowering the joint stiffness, stability of the LC is lost only in a few dimensions, while leaving the remaining large number of dimensions quite stable: this means that the LC becomes saddle-type, with a low-dimensional unstable manifold and a high-dimensional stable manifold. Remarkably, the unstable manifold remains of low dimensionality even when the feedback gains are decreased far below the instability point. We then developed an intermittent neural feedback controller that is activated only for short periods of time at an optimal phase of each gait stride. We characterized the robustness of this design by showing that it can better stabilize the unstable LC with small feedback gains, leading to a flexible gait, and in particular we demonstrated that such an intermittent controller performs better if it drives the state point to the stable manifold, rather than directly to the LC. The proposed intermittent control strategy might have a high affinity for the inverted pendulum analogy of biped gait, providing a dynamic view of how the step-to-step transition from one pendular stance to the next can be achieved stably in a robust manner by a well-timed neural intervention that exploits the stable modes embedded in the unstable dynamics.

scholarly journals Motivasi Wisatawan Wanita dan Persepsi Masyarakat Lokal terhadap Klub Gay di Seminyak, Bali

2019 ◽  
Vol 7 (1) ◽  
pp. 140
Author(s):  
Dio Pratama ◽  
Saptono Nugroho
Keyword(s):  
Direct Observation ◽  
Local Community ◽  
Secondary Data ◽  
Sampling Technique ◽  
Data Sources ◽  
Primary Data ◽  
Purposive Sampling ◽  
Local Perception ◽  
Secondary Data Sources

This research was conducted to find out the motivation of female tourist to visit Gay club, the perception of the tourist and local community towards the Gay Club. The methods used in this research id descriptive qualitative. The technique of determination of informants used is purposive sampling technique. Data sources used are primary and secondary data sources. Primary data in this research is sourced from direct observation to the research location by means of observation and interviews. While secondary data in this research are the data obtained from the documentation or studies library to complement the primary data. The result of the research shows that most tourist say curious to see Gay club as a motivation for a visit; most tourist plead happy after seeing the atrractions there; most neutral against Gay tourist; most local community already know about Gay club; most local community are not disturbed; most local people are not benefitting from the presence of the Gay club. Keywords : Tourist Motivation, Community Local Perception, Gay Club

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