scholarly journals Synthetic Aircraft Trajectories Generated with Multivariate Density Models

2021 ◽  
Vol 13 (1) ◽  
pp. 7
Author(s):  
Timothé Krauth ◽  
Jérôme Morio ◽  
Xavier Olive ◽  
Benoit Figuet ◽  
Raphael Monstein
Keyword(s):  
Risk Estimation ◽  
Optimal Path ◽  
Random Sets ◽  
Collision Risk ◽  
High Stakes ◽  
Estimation Capacity ◽  
Aircraft Trajectory ◽  
Multivariate Density ◽  
Aircraft Trajectories

Aircraft trajectory generation is a high stakes problem with a wide scope of applications, including collision risk estimation, capacity management and airspace design. Most generation methods focus on optimizing a criterion under constraints to find an optimal path, or on predicting aircraft trajectories. Nevertheless, little in the way of contribution has been made in the field of the artificial generation of random sets of trajectories. This work proposes a new approach to model two-dimensional flows in order to build realistic artificial flight paths. The method has the advantage of being highly intuitive and explainable. Experiments were conducted on go-arounds at Zurich Airport, and the quality of the generated trajectories was evaluated with respect their shape and statistical distribution. The last part of the study explores strategies to extend the work to non-regularly shaped trajectories.

scholarly journals An Estimation of Ship Collision Risk Based on Relevance Vector Machine

2021 ◽  
Vol 9 (5) ◽  
pp. 538
Author(s):  
Jinwan Park ◽  
Jung-Sik Jeong
Keyword(s):  
Machine Learning ◽  
Decision Making ◽  
Risk Estimation ◽  
Good Method ◽  
Relevance Vector Machine ◽  
Machine Learning Algorithms ◽  
Support Vector ◽  
Collision Risk ◽  
Estimation Model ◽  
Ship Collision

According to the statistics of maritime collision accidents over the last five years (2016–2020), 95% of the total maritime collision accidents are caused by human factors. Machine learning algorithms are an emerging approach in judging the risk of collision among vessels and supporting reliable decision-making prior to any behaviors for collision avoidance. As the result, it can be a good method to reduce errors caused by navigators’ carelessness. This article aims to propose an enhanced machine learning method to estimate ship collision risk and to support more reliable decision-making for ship collision risk. In order to estimate the ship collision risk, the conventional support vector machine (SVM) was applied. Regardless of the advantage of the SVM to resolve the uncertainty problem by using the collected ships’ parameters, it has inherent weak points. In this study, the relevance vector machine (RVM), which can present reliable probabilistic results based on Bayesian theory, was applied to estimate the collision risk. The proposed method was compared with the results of applying the SVM. It showed that the estimation model using RVM is more accurate and efficient than the model using SVM. We expect to support the reasonable decision-making of the navigator through more accurate risk estimation, thus allowing early evasive actions.

Separation Standards—II

1966 ◽  
Vol 19 (2) ◽  
pp. 169-186 ◽  
Author(s):  
P. G. Reich
Keyword(s):  
One Dimension ◽  
Collision Risk ◽  
Practical Applications ◽  
Upper Limit ◽  
Intensive Observation ◽  
Relative Errors ◽  
Separation Standards

In the first part of this series of papers an outline was given of the approach made at the Royal Aircraft Establishment to the problems of estimating collision risk and of specifying the quality of navigation needed to make separation standards safe. It was stressed that estimates should be based on intensive observation of flying errors, rather than on speculative theories, and that it is more feasible to develop ‘upper limit’ estimating techniques than those which purport to give the exact risk. In summary, a list of seven ‘requirements’ was given, as a reminder of the essential principles which can so easily be overlooked in the piecemeal task of relating separation standards to collision risk.The purpose of this paper is to show some of the theoretical techniques which have been developed at R.A.E. to satisfy five of these requirements. (The remaining two do not call for special techniques and will be dealt with when practical applications are described in Part III.) The paper contains three Appendixes, dealing with the frequency of losing separation in one dimension, the computation of P's from the assumed tail shapes, and the treatment of relative errors. These are not included here but will appear in the off-printed version which may be obtained from the Royal Aircraft Establishment.Both this paper and the paper that follows by Mr. Attwooll are crown copyright and are reproduced with the permission of H.M. Stationery Office.

Organisation of running events – reducing exclusions and improving the quality of life

2021 ◽  
Vol 67 (3) ◽  
pp. 95-109
Author(s):  
Jacek Łuczak ◽  
Keyword(s):  
Quality Of Life ◽  
Risk Factors ◽  
Risk Estimation ◽  
Vital Role ◽  
Sporting Events ◽  
Estimation Risk ◽  
Technical Problems ◽  
Self Confidence ◽  
Social Nature

Physical activity is a basic factor of human development – it brings satisfaction, vitality, energy, has a therapeutic dimension and affects the quality of life. Among the large group of amateur athletes, there are people vulnerable to social exclusions related to disabilities, psychological dysfunctions, sex and social status. For these people sport is a cure for loneliness and lack of self-confidence, as well as it positively affects their motivation to overcome barriers, which is reflected in other spheres of their lives. One sport that in particular integrates different social groups is running, as confirmed by the growing number of amateur runners, training activities dedicated to them and running events organised for them. However, it is important that organisers of such events ensure the safety of participants and take care of their satisfaction and comfort by holistic planning of all organisational activities. The study hypothesised that factors concerning the safety, comfort and satisfaction of participants play a vital role in organising running events. The aim of the article was to identify and assess the risk of organising running competitions for amateurs in the context of ensuring safety and satisfaction for all participants of the event. In particular, the author noted the risk factors of a social nature, conducive to integration, associated with countering exclusions. The paper presents test results for national competitions involving 21 and 42 km runs. The identification of risk factors was performed by 10 experts (the Delphi method) and 27 representatives of 7 running events organised in Poland (2017–2018) (risk estimate, a questionnaire) took part in the risk estimation. Risk estimation was carried out on the basis of average (effect and probability). The results of the study provide unequivocal information about the spheres of organising sporting events which in the highest degree can affect the safety and comfort of their participants and the perception of the competition itself. Among the key risks there were: inadequate financial and organisational resources, route capacity, or technical problems. Moreover, the paper includes an attempt to discuss results of other research.

scholarly journals A Rasch-Based Validation of ELT Certificate-LORT

2020 ◽  
Vol 13 (9) ◽  
pp. 94
Author(s):  
Xin Qu
Keyword(s):  
Teacher Candidates ◽  
Rating Scales ◽  
Rating Scale ◽  
Qualitative Interviews ◽  
Structured Interviews ◽  
High Stakes ◽  
Efl Teacher ◽  
The Difference ◽  
Group Interviews

The present study was executed with the purpose of validating ELT Certificate Lesson Observation and Report Task (ELTC-LORT), which was developed by China Language Assessment to certify China’s EFL teachers by performance-based testing. The ELT Certificate has high-stakes considering its impacts on candidates’ recruitment, ELT in China and quality of education, so it is crucially important for its validation so as to guarantee fairness and justice. The validity of task construct and rating rubric went through a process suited for many-facet Rasch measurement supplemented with qualitative interviews. Participants (N = 40) were provided with a video excerpt from a real EFL lesson, and required to deliver a report on the teacher’s performance. Two raters graded the records of the candidates’ reports using rating scales developed to measure EFL teacher candidates’ oral English proficiency and ability to analyze and evaluate teaching. Many-facet Rasch analysis demonstrated a successful estimation, with a noticeable spread among the participants and their traits, proving the task functioned well in measuring candidates’ performance and reflecting the difference of their ability. The raters were found to have good internal self-consistency, but not the same leniency. The rating scales worked well, with the average measures advancing largely in line with Rasch expectations. Semi-structured interviews as well as focus group interviews were executed to provide knowledge regarding the raters’ performance levels and the functionalities of the rating scale items. The findings provide implications for further research and practice of the Certificate.

scholarly journals Quantifying the closeness to a set of random curves via the mean marginal likelihood

2020 ◽  
Author(s):  
Cédric Rommel ◽  
Joseph Frédéric Bonnans ◽  
Baptiste Gregorutti ◽  
Pierre Martinon
Keyword(s):  
Marginal Likelihood ◽  
Marginal Density ◽  
Random Curves ◽  
Practical Applications ◽  
Random Functions ◽  
Practical Usefulness ◽  
Class Of Estimators ◽  
The Mean ◽  
Multivariate Density ◽  
Aircraft Trajectories

In this paper, we tackle the problem of quantifying the closeness of a newly observed curve to a given sample of random functions, supposed to have been sampled from the same distribution. We define a probabilistic criterion for such a purpose, based on the marginal density functions of an underlying random process. For practical applications, a class of estimators based on the aggregation of multivariate density estimators is introduced and proved to be consistent. We illustrate the effectiveness of our estimators, as well as the practical usefulness of the proposed criterion, by applying our method to a dataset of real aircraft trajectories.

scholarly journals Using HMM Approach for Assessing Quality of Value at Risk Estimation: Evidence from PSE Listed Company

2017 ◽  
Vol 65 (5) ◽  
pp. 1687-1694
Author(s):  
Tomáš Konderla ◽  
Václav Klepáč
Keyword(s):  
At Risk ◽  
Value At Risk ◽  
Stock Exchange ◽  
Risk Estimation ◽  
Listed Company ◽  
Mixture Distribution ◽  
Normal Mixture ◽  
Development Characteristic ◽  
The Common

The article points out the possibilities of using Hidden Markov model (abbrev. HMM) for estimation of Value at Risk metrics (abbrev. VaR) in sample. For the illustration we use data of the company listed on Prague Stock Exchange in range from January 2011 to June 2016. HMM approach allows us to classify time series into different states based on their development characteristic. Due to a deeper shortage of existing domestic results or comparison studies with advanced volatility governed VaR forecasts we tested HMM with univariate ARMA‑GARCH model based VaR estimates. The common testing via Kupiec and Christoffersen procedures offer generalization that HMM model performs better that volatility based VaR estimation technique in terms of accuracy, even with the simpler HMM with normal‑mixture distribution against previously used GARCH with many types of non‑normal innovations.

scholarly journals An Improved A-Star Algorithm Considering Water Current, Traffic Separation and Berthing for Vessel Path Planning

2019 ◽  
Vol 9 (6) ◽  
pp. 1057 ◽  
Author(s):  
Chenguang Liu ◽  
Qingzhou Mao ◽  
Xiumin Chu ◽  
Shuo Xie
Keyword(s):  
Path Planning ◽  
Path Length ◽  
Optimal Path ◽  
Water Current ◽  
Path Generation ◽  
Collision Risk ◽  
A Algorithm ◽  
Risk Models ◽  
Planning Methods ◽  
Path Cost

A traditional A-Star (A*) algorithm generates an optimal path by minimizing the path cost. For a vessel, factors of path length, obstacle collision risk, traffic separation rule and manoeuvrability restriction should be all taken into account for path planning. Meanwhile, the water current also plays an important role in voyaging and berthing for vessels. In consideration of these defects of the traditional A-Star algorithm when it is used for vessel path planning, an improved A-Star algorithm has been proposed. To be specific, the risk models of obstacles (bridge pier, moored or anchored ship, port, shore, etc.) considering currents, traffic separation, berthing, manoeuvrability restriction have been built firstly. Then, the normal path generation and the berthing path generation with the proposed improved A-Star algorithm have been represented, respectively. Moreover, the problem of combining the normal path and the berthing path has been also solved. To verify the effectiveness of the proposed A-Star path planning methods, four cases have been studied in simulation and real scenarios. The results of experiments show that the proposed A-Star path planning methods can deal with the problems denoted in this article well, and realize the trade-off between the path length and the navigation safety.

European Studies to Investigate the Feasibility of using 1000 ft Vertical Separation Minima above FL 290. Part II. Precision Radar Data Analysis and Collision Risk Assessment

1992 ◽  
Vol 45 (1) ◽  
pp. 91-106 ◽  
Author(s):  
D. Harrison ◽  
G. Moek
Keyword(s):  
North Atlantic ◽  
Risk Estimation ◽  
Radar Data ◽  
Vertical Separation ◽  
Collision Risk ◽  
European Studies ◽  
North Atlantic Region ◽  
Atlantic Region ◽  
Technical Performance ◽  
The North

This paper is the second of a series of three papers, documenting the European studies into the feasibility of 1000 ft vertical separation minima above FL290. The paper discusses the vertical collision risk estimation methodology and an assessment of the collision risk against a target level of safety.The analysis indicates the technical feasibility of a reduced vertical separation minima in the North Atlantic Region. However, for current operations and technical performance within European continental airspace, the risk estimation indicates that a 1000 ft minima is not technically feasible.The contents of this paper reflect the views of the authors concerned; they do not necessarily reflect the official views or policy of the CAA or NLR.

Parallel Ant Colony Optimization Algorithm Based on Multiplicate Pheromon Declining

2012 ◽  
Vol 433-440 ◽  
pp. 3577-3583
Author(s):  
Yan Zhang ◽  
Hao Wang ◽  
Yong Hua Zhang ◽  
Yun Chen ◽  
Xu Li
Keyword(s):  
Ant Colony Optimization ◽  
Optimization Algorithm ◽  
Ant Colony Algorithm ◽  
Optimal Path ◽  
Ant Colony ◽  
Ant Colony Optimization Algorithm ◽  
Computing Power ◽  
Slow Convergence ◽  
The Impact

To overcome the defect of the classical ant colony algorithm’s slow convergence speed, and its vulnerability to local optimization, the authors propose Parallel Ant Colony Optimization Algorithm Based on Multiplicate Pheromon Declining to solve Traveling Salesman Problem according to the characteristics of natural ant colony multi-group and pheromone updating features of ant colony algorithm, combined with OpenMP parallel programming idea. The new algorithm combines three different pheromone updating methods to make a new declining pheromone updating method. It effectively reduces the impact of pheromone on the non-optimal path in the ants parade loop to subsequent ants and improves the parade quality of subsequent ants. It makes full use of multi-core CPU's computing power and improves the efficiency significantly. The new algorithm is compared with ACO through experiments. The results show that the new algorithm has faster convergence rate and better ability of global optimization than ACO.

Sign in / Sign up

Export Citation Format

Share Document