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Most of the existing approaches for flight collision avoidance are concerned with local traffic alone for which the separation is based on the pairwise analysis of aircraft trajectory trends, which is not efficient with regard to some flight path requirements along waypoints. The purpose of this paper is to deal with the global collision avoidance problem which aims at separating aircraft taking into consideration the global traffic in a given area instead of considering them pairwise. It aims to model the concept of global collision avoidance and propose a validated algorithm for the purpose in the framework of free‐flight.

The collision avoidance procedure computes online the appropriate speed and heading for each aircraft, at each sampling time‐instant, to generate a collision‐free flight trajectory along scheduled waypoints. The method accounts for automatic assignment of priority indexes that are updated from one control time horizon to the next. The paper considers here the case of aircraft flying at the same altitude, but the proposed method is easily extendable to the general 3D situation. Owing to the predictive features that are inherent to collision avoidance, the collision‐free trajectories are generated using model predictive control approach. A simulation example is presented in the end and its results show the suitability of the proposed approach.

Since the model predictive control approach is used, the collision avoidance procedure is anticipative; therefore, the avoidance capability depends only on the prediction horizon rather than on the control horizon.

The computation of the trajectory guidance information (speed and heading) at each time‐step is fast, therefore the proposed method is well suited for online processing requirements in real world applications.

The paper provides a flexible modelling framework and a computationally effective algorithm, both based on model predictive control concepts, to cope with global collision avoidance for flight safety enhancement in the framework of free‐flight.

This paper is concerned with an online parameter estimation algorithm for nonlinear uncertain time‐varying systems for which no stochastic information is available.

The estimation procedure, called nonlinear learning rate adaptation (NLRA), computes an individual adaptive learning rate for each parameter instead of using a single adaptive learning rate for all the parameters as done in stochastic approximation, each individual learning rate being controlled by a meta‐learning rate rule for the sake of minimizing the measurement prediction error. The method does not require stochastic information about the system model and the measurement noise covariance matrices contrarily to the Kalman filtering. Numerical results about aircraft navigation trajectory tracking show that the method is able to estimate reliably time‐varying parameters even in presence of measurement noise.

The proposed algorithm is practically insensitive to changes in the meta‐learning rate. Therefore, the performance of the method is stable with respect to the tuning parameter of the algorithm.

The proposed NLRA method may be adopted for recursive parameter estimation of uncertain systems when no stochastic information is available. It may also be used for process regulation and dynamic system stabilization in feedback control applications.

Provides a method for fast and practical computation of parameter estimates without requiring to know the model and measurement noise covariance matrices contrarily to existing stochastic estimation methods.

Much attention has been given to adoption and diffusion, defined as the degree of market penetration, of Information and Communications Technologies (ICT) in recent years (Carter, Jambulingam, Gupta, & Melone, 2001; Kiiski & Pohjola, 2002; Milner, 2003; Benhabib & Spiegel, 2005). The theory of diffusion of innovations considers how a new idea spreads throughout the market over time. The ability to accurately predict new product diffusion is of concern to designers, marketers, managers, and researchers alike. However, although the diffusion process of new products is generally accepted as following an s-curve pattern, where diffusion starts slowly, grows exponentially, peaks, and then declines (as shown in Fig. 1), there is considerable disagreement about what factors affect diffusion and how to measure diffusion rates (Bagchi, Kirs, & Lopez, 2008).

The purpose of this paper is to calculate the probability of collision of flying aircraft crossing on straight paths in any direction.

The probability of deviations from the intended flight paths is used to calculate the probability of collision that is integrated over time to cover whole events.

The probabilities of collision are calculated in terms of the r.m.s. position errors and encounter geometry, that is aircraft velocities and flight path angles and crossing angles.

The method does not apply to aircraft flying in parallel tracks at the same velocity in air corridors: that case has been covered elsewhere, as well as the case of climbing or descending aircraft.

International Civil Aviation Organization (ICAO) specifies as target level of safety (TLS) a probability of collision not exceeding 5×10⁻⁹ per hour. To meet the ICAO TLS standard, it is necessary to calculate collision probabilities for all stages of flight.

A low collision probability is a safety metric; the value does depend on a realist choice of probability distribution.

Calculates the probability of collision for crossing flights, corresponding to a common scenario on air traffic management.

Drones have become an important element within hospitality and tourism. The purpose of this study is to identify the corpus of knowledge and create a research agenda that establishes appropriate guidelines for future study of drone application in hospitality and tourism.

This work has been undertaken using a mixed-methods approach that combines quantitative and qualitative research and includes a review of the literature related to the study of drone use in hospitality and tourism.

The mixed-methods review identified gaps in the research, potential areas of study to enhance the scientific literature and potential uses of drones in tourism and hospitality for researchers, consumers and industry professionals.

This study makes an original contribution by establishing an integrated framework, which led to a synthesis of the research corpus and provided a holistic conceptualisation of the relationship between tourism and drones. In addition, the research agenda proposed will help boost and consolidate this emerging field of research.

无人机已经成为接待和旅游中的一个重要元素。本研究的主要目的是确定知识库, 并建立一个研究议程, 为未来无人机在酒店和旅游业的应用研究建立适当的指导方针。

这项工作采用了混合方法, 将定量和定性研究结合起来, 包括对与酒店和旅游业中无人机使用研究有关的文献进行回顾。

混合方法审查确定了研究中的差距、加强科学文献的潜在研究领域, 以及研究人员、消费者和行业专业人士在旅游和酒店业的无人机应用潜力。

这项研究通过建立一个综合框架做出了原创性的贡献, 它综合合成了研究语料库, 并对旅游和无人机之间的关系提供了一个整体的概念化。此外, 提出的研究议程将有助于促进和巩固这一新兴的研究领域。

Los drones se han convertido en un elemento importante dentro de la hostelería y el turismo. El objetivo principal de este estudio es identificar el corpus de conocimiento y crear una agenda de investigación que establezca las directrices adecuadas para el estudio futuro de la aplicación de los drones en la hostelería y el turismo.

Este trabajo se ha realizado utilizando un enfoque de métodos mixtos que combina la investigación cuantitativa y cualitativa e incluye una revisión de la literatura relacionada con el estudio del uso de drones en hostelería y turismo.

La revisión de métodos mixtos identificó lagunas en la investigación, áreas potenciales de estudio para mejorar la literatura científica y potencial de las aplicaciones de los drones en el turismo y la hostelería para investigadores, consumidores y profesionales del sector.

Este estudio aporta una contribución original al establecer un marco integrado, que conduce a una síntesis del corpus de investigación y proporciona una conceptualización holística de la relación entre el turismo y los drones. Además, la agenda de investigación propuesta contribuirá a impulsar y consolidar este campo de investigación emergente.

The purpose of this study is to develop an operational level decision support system model for air traffic controllers (ATCos) within the framework of the Flexible Use of Airspace (FUA) concept to enable more efficient use of airspace capacity. This study produces a systematic solution to the route selection process so that the ATCo can determine the most efficient route with an operational decision support system model using Dijkstra’s Shortest Path Algorithm.

In this study, a new decision support system model for ATCos in decision-making positions was recommended and used. ATCos use this model as a main model for determining the shortest and safest route for aircraft as an operational-level decision support system. Dijkstra Algorithm, used in the model, is defined step by step and then explained with the pseudocode.

It has been determined that when the FUA concept and DSS are used while the ATCo chooses a route, significant fuel, time and capacity savings are achieved in flight operations. Emissions resulting from the negative environmental effects of air transportation are reduced, and significant capacity increase can be achieved. The operational level decision support system developed in the study was tested with 55 scenarios on the Ankara–Izmir flight route compared to the existing fixed route. The results for the proposed most efficient route were achieved at 11.22% distance (nm), 9.36%-time (min) savings and 837.71 kg CO₂ emission savings.

As far as the literature is reviewed, most studies aimed at increasing airspace efficiency produce solutions that try to improve rather than replace the normal process. Considering the literature positioning of this study compared to other studies, the proposed model provides a new systematic solution to the problems that cause human-induced route inefficiency within the framework of the FUA concept.

Invasive transit-time ultrasonic flow measurement involves the use of ultrasonic transducers, which sense the flowing fluid and are the most important parts of an ultrasonic flowmeter. In this study, two ultrasonic transducers were designed, numerically simulated and fabricated to be used in an ultrasonic gas flowmeter.

PZT-5H piezoceramic elements with specific dimensions were designed and used as beating heart inside the transducers. Different methods, including impedance-frequency analysis, optical emission spectroscopy and performance tests in pressurized chambers were used to evaluate the piezoelectric elements, ultrasonic transducer housings and the fabricated transducers, respectively. In addition, finite element method results showed its ability for design stages of ultrasonic transducer.

Experimental results for transit time difference (TTD) and the normalized received voltage were compared with simulation results at the same conditions. There was a quite good agreement between the two method results. Extensive simulation results showed that under the considered range of environmental conditions, the change of acoustic path length has the most impact on TTD, with respect to temperature and pressure. A change of 1 mm in acoustic path length leads to 0.74 per cent change in TTD, approximately. In addition, for normalized received voltage, 1 bar change in pressure has the most impact and its value is as high as 3.76 per cent.

This method is possibly used in ultrasonic gas flowmeter fabrication.

In this work, design, fabrication, experimental tests and numerical simulation of ultrasonic transducers are presented.

The purpose of this paper is to describe a multisource system for nondestructive inspection of welded elements exploited in aircraft industry developed in West Pomeranian University of Technology, Szczecin in the frame of CASELOT project. The system task is to support the operator in flaws identification of welded aircraft elements using data obtained from X-ray inspection and 3D triangulation laser scanners.

For proper defects detection a set of special processing algorithms were developed. For easier system exploitation and integration of all components a user friendly interface in LabVIEW environment was designed.

It is possible to create the fully independent, intelligent system for welds’ flaws detection. This kind of technology might be crucial in further development of aircraft industry.

In this paper a number of innovative solutions (new algorithms, algorithms’ combinations) for defects’ detection in welds are presented. All of these solutions are the basis of presented complete system. One of the main original solution is a combination of the systems based on 3D triangulation laser scanner and X-ray testing.