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Příspěvky z konference Nalezeno 23,733 záznamů.  předchozí11 - 20dalšíkonec  přejít na záznam: Hledání trvalo 0.00 vteřin. 
Rope procedures for extraction and insertion of persons used by helicopter emergency medical service
Kaľavský, Peter ; Rozenberg, Róbert ; Petríček, Pavol ; Socha, Vladimír ; Socha, Luboš
The article deals with the issue of alternative ways of extraction and insertion of persons by helicopters using rope and non-rope procedures. The article provides a current general overview of rope and non-rope procedures for insertion of persons in places where a helicopter cannot touch down, as well as an overview of techniques used for extraction/transport of persons from places not permitting helicopter touchdown. The article lists advantages and disadvantages of individual methods and their applicability in the helicopter emergency medical service. The main contribution of the article is the comparison of time indicators when inserting and transporting persons by helicopters with the use of rope procedures during typical model situations. For the purposes of comparing rope procedures have been created three typical model situations for inserting two persons from a hovering helicopter and two typical model situations for extracting four persons and their transportation on board. During creating these model situations, we have taken into consideration the most frequently used rope procedures within HEMS in civil, military and police sectors of the Slovak Republic. Total insertion/extraction time was considered the basic piece of data for the comparison. Time data were obtained from flight tests, actual training, technical documentation data and on the basis of the expert estimate. Rope procedures were compared among each other and among three types of helicopters most used for these purposes in the Slovak Republic: Mi-17 LPZS, Bell-429 and AGUSTA A109K2. Processed conclusions from the comparison of each model situation within the considered alternative rope ways of extraction and insertion of persons by helicopters and the conclusions drawn from the performance comparison of HEMS helicopters in the Slovak Republic within these model situations are a significant contribution to the determination of procedures in the framework of rescue missions.
Simulation of fatigue crack propagation in the wing main spar flange
Augustin, Petr
Simulation of fatigue crack growth in the bottom flange of twin turboprop commuter aircraft wing spar is described in this paper. Analysed crack propagation scenario represents real wing full-scale fatigue test failure. Computational model of bottom flange was prepared using three-dimensional fracture mechanics software FRANC3D. Calculation of crack growth under the variable amplitude loading was performed in AFGROW code using the NASGRO equation and Wheeler retardation model. It was verified with the results of wing spar specimen fatigue test and fractograpic analysis of fatigue fracture from this experiment. Computational model was applied in the prognostic algorithm of structure health monitoring system.
A 2d aerodynamic study on morphing of the naca 2412 aerofoil
Meghani, Pratik
This paper investigates the potential of modifications of the NACA 2412 aerofoil geometry which could be implemented as a morphing wing in the Cessna 172SP. A 2D study on three morphing configurations: landing, take-off and stall maneuvering was conducted. The new geometries were designed using XFLR5. The initial aerodynamics characteristics were computed using XFOIL and compared to that of NACA 2412 in the Cessna 172SP. A selected configuration (landing) was tested at the University of Brighton wind tunnel facility and comparison to XFOIL predictions. Moreover, the ESDU 07010 report was used to extrapolate the Reynold’s number to full scale, which was necessary to obtain an approximation of the aerodynamic characteristics at actual flight. The paper presents results of ANSYS FLUENT simulations for all three configurations. Results reveal that XFOIL is suitable for morphing airfoil configuration analysis but only at low Reynolds number (Re≈500,000). Adaptive aerofoil geometry improves the lift to drag (L/D) ratio by decreasing the drag coefficient; it also expands the flight envelope by delaying stall.
Design of manufacturing simulations of a flatplate pulsating heat pipe
Pontecorvo, Matteo
Currently, a research team in the University of Brighton, in collaboration with the European Space Agency (ESA), is developing a pulsating heat pipe that will eventually be launched and tested in space, with the International Space Station (ISS) as destination, for research into passive thermal devices and their behaviour in a vacuum. The approved pulsating heat pipe design incorporates one titanium plate, which is classified as a metal, and one aluminum-oxide sapphire plate that is classified as a ceramic. At the moment, the team is faced with the challenge of bonding the two plates together since, using convectional manufacturing methods, the parts fail due to the high level of induced stress. A research into manufacturing processes to bond together titanium and sapphire is essential to ensure that the final device will operate for several weeks (maybe even months) without leaking and the need for maintenance. The project explores potential manufacturing processes aimed to bond together these materials and subsequently propose a solution. Furthermore, static and thermal analyses are carried out with the aid of SolidWorks to exploit potential points of failure due to stress concentrations induced by cooling after bonding. The results indicate that both titanium and sapphire are capable of sustaining the induced stresses but, due to the complex geometry of the pulsating heat pipe at the contact surface, the bonding agent is likely to fail due to the induced stresses.
Integrated method utilizing graph theory and fuzzy logic for safety and reliability assessment of airborne systems
Janhuba, Luboš ; Hlinka, Jiří ; Koštial, Rostislav
This paper presents integrated algorithm for airborne system safety and reliability assessment. In general aviation (mostly up to EASA CS-23) and non-military unmanned aerial vehicles industry, safety and reliability assessment process still relays almost exclusively on human judgment. Recommended practices define processes for system modelling and safety assessing are based on analyst understanding of a particular system. That is difficult and time-consuming process. Commercial computation aids are extremely expensive with restricted (or closed) access to the solution algorithms. Together with this problem, rapid development of modern airborne systems, their increasing complexity, elevates level of interconnection. Therefore, safety and reliability analyses have to continuously evolve and adapt to the extending complexity. Growing expansion brings in the field of unnamed aerial vehicles systems which consist of items without relevant reliability testing. Presented algorithm utilizes graph theory and fuzzy logic in order to develop integrated computerized mean for reliability analysis of sophisticated, highly interconnected airborne systems. Through the usage of graph theory, it is possible to create model of particular systems and its sub-systems in the form of universal data structure. Algorithm is conceived as fuzzy expert system, that emulates decision making of a human expert. That brings opportunity to partially quantify system attributes and criticality. Criticality evaluation increases level of assessment correlation with real state of system and its attributes.
Reduction in the pilot’s stress during the landing maneuver by providing accurate height information
Šplíchal, Miroslav
The article is focused on pilot stress reduction during landing by providing accurate height information. It is based on the results of the completed project TA04030510 – Assistance systems supporting the pilot’s right decisions increasing the safety of operating small civil aircraft. The landing is the most critical phase of a flight. Accidents occurring during approach and landing phases generally represent up to 40 % of all aircraft accidents. A frequent cause of these accidents is a pilot error. During project development, 112 accidents of ultralight aircraft and 152 accidents of small GA aircraft that happened from 2005 to 2015 were analyzed. In total, 48 aircraft landing-related accidents and 22 accidents in ultralight aircraft were found. Landing accidents represent 26.5% of all investigated accidents.
Aircraft leading edges minor damages detection based on thermographic survey of electrical anti-icing system
Koštial, Rostislav ; Janhuba, Luboš ; Hlinka, Jiří
Aircraft leading edge is one of the most important subjects of aircraft scheduled maintenance. Leading edge as part of the slot on transport aircraft is not critical to fatigue stress in most of the cases. However, leading edge is extremely vulnerable to the accidental damage in combination with environmental damage. Maintenance is usually provided by visual inspection before every flight. Nevertheless, development of anti-icing system based on contact electrical heating opens possibility to thermographic Nondestructive Testing (NDT) methods usage. These methods could detect minor damages, which are visually undetectable especially in the case of composite materials. This paper describes possibility of thermographic methods (using anti-icing system) application as mean of leading edge minor damage detection.
Verification and numerical simulation of advanced composite inlet in compliance of airworthiness impact requirements
Doubrava, Radek ; Oberthor, Martin ; Raška, Jan ; Bělský, Petr ; Doubrava, Karel ; Dvořák, Milan
Bird or hail stone strikes are an important phenomenon which must be considered during aircraft design. Most of major bird or hail strike incidents result from engine ingestion. As engines are the sole thrust providing mechanisms of an aircraft, it is critical to investigate and mitigate the effects of bird or hail strikes on engine inlets and systems to the greatest extent possible. The article presents application of test verified numerical simulation for design and full-scale test verification of advanced composite air inlet for new generation of jet trainer aircraft from point of view of high speed impact resistance. The physical bird and hail impact tests were performed at the Czech Aerospace Research Centre (VZLÚ) according to airworthiness requirements. The measurement during impact test were performed by high-speed camera, Fiber Bragg Grating (FGB) sensors and strain gauges in cooperation with Czech Technical University (CTU) in Prague. The results from full-scale bird and hail strike tests were compared with numerical simulation.
Stability of the sodium content in selected botanical reference materials
Kameník, Jan ; Kučera, Jan ; Borovička, Jan ; Havránek, Vladimír
Sodium mass fractions in NIST standard reference materials (SRM) SRM 1547 Peach Leaves and SRM 1515 Apple leaves determined by INAA in our laboratory in recent years has been higher than the certified values. Similarly, increased values were published for SRM 1547 by several other laboratories. The increased Na mass fractions was found also for freshly opened SRM 1547 bottle and for material originating from a different lab. Increased Na mass fractions were confirmed by ICP-MS analysis of both materials. Analysis of archived samples revealed that sodium mass fraction in materials stored in polyethylene capsules is in agreement with the certified values. The sodium content in the glass of SRM 1547 bottle was roughly 10 %. Direct measurement of the Na depth profile by micro-PIXE was not indicative whether Na is released, i.g., by a glass corrosion due to residual humidity in the botanical material. However, a model experiment with freshly prepared and pulverized peach leaves demonstrated that such a scenario is possible for leaf-based materials. Although the study was focused on two NIST materials, the process is possible for any material with rather low Na content.
Role of activation analysis in the preparation of reference materials
Kučera, Jan
The fundamentals of neutron activation analysis (NAA) and prompt gamma activation analysis (PGAA) and practices of both methods are briefly review, together with enlightening their specific role in the preparation of reference materials. The importance of homogeneity testing for the certification and use of reference materials (RMs) using NAA is appraised. Examples of the use of NAA and PGAA for the certification of element contents in environmental, biological, and material science RMs produced by world-leading institutions, such as U.S. NIST, IRMM, IAEA and by national institutions, as well, at the Nuclear Physics Institute within last almost 30 years are presented.

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