Search results for "aeronautics"
showing 10 items of 148 documents
Methodological frontier in operational analysis for roundabouts: a review
2016
Several studies and researches have shown that modern roundabouts are safe and effective as engineering countermeasures for traffic calming, and they are now widely used worldwide. The increasing use of roundabouts and, more recently, turbo and flower roundabouts, has induced a great variety of experiences in the field of intersection design, traffic safety, and capacity modeling. As for unsignalized intersections, which represent the starting point to extend knowledge about the operational analysis to roundabouts, the general situation in capacity estimation is still characterized by the discussion between gap acceptance models and empirical regression models. However, capacity modeling mu…
Machining Economics and Optimization
2008
This chapter provides comprehensive knowledge regarding economical considerations and possible optimization methods of machining operations. The background of machining economics, including costs, time and productivity, related for typical machining operations (such as turning, milling and drilling) is outlined. The components of machining costs and time related to the cutting speed are distinguished, and appropriate mathematical models are presented. Optimization procedures allowing selection of optimal values of cutting speed and feed rate based on tool life and energy efficiency criteria are overviewed. In the first case, the economic cutting speed and cutting speed corresponding to the …
La alimentación en los viajes espaciales tripulados: desde el Programa Gemini hasta la ISS/Shuttle
2014
Los alimentos espaciales han tenido una gran importancia en el desarrollo de las misiones espaciales tripuladas ya que constituyen la única fuente de energía y nutrientes para el ser humano fuera del planeta Tierra. Dichos alimentos han experimentado una gran evolución desde el inicio del Programa Mercury hasta las actuales misiones a la International Space Station (ISS). En un primer momento eran diseñados para ofrecer una gran densidad energética y nutritiva y actualmente se da prioridad a las características organolépticas y psicológicas, ya que contribuyen a un mayor consumo y un mejor estado nutricional de los astronautas. El objetivo del presente estudio es hacer un análisis retrospec…
Rendezvous Guidance Trajectories via Multiple-Subarc Sequential Gradient-Restoration Algorithm
2009
We consider the three-dimensional rendezvous between a target spacecraft in a circular orbit and a chaser spacecraft with an initial separation distance and an initial separation velocity. We assume that the chaser spacecraft has variable mass and that its trajectory is governed by three controls, one determining the thrust magnitude and two determining the thrust direction. We employ the Clohessy–Wiltshire equations, describing the relative motion of the chaser vis-a-vis the target, and the multiple-subarc sequential gradient-restoration algorithm to produce first optimal trajectories and then guidance trajectories for the following problems: P1—minimum time, fuel free; P2—minimum fuel, ti…
Cogeneration plant in a pasta factory: Energy saving and environmental benefit
2007
Abstract Italy produces approximately 4,520,000 tons of pasta annually, which is about 67% of its total productive potential. As factories need electric and thermal energy simultaneously, combined heat and power (CHP) systems are the most suitable. This paper describes a feasibility study of a CHP plant in a pasta factory in Italy while analyzing energy saving and environmental benefits. Commercially available CHP systems suitable for the power range of energy demand in pasta production use reciprocating engines or gas turbines. This study demonstrates how their use can reduce both energy costs and CO2 equivalent greenhouse gas emission in the environment. An economic analysis was performed…
Different Wings Flowfields Interaction on the Wing-Propeller Coupling
1997
A high-portability numerical technique based on the method of free wake analysis (FWA) is described that analyzes the interference between an aircraft propeller and a wing having different planforms and computes the influence of the wing aerodynamic field on the propeller performance. For an isolated propeller and wing, the models employed are based on the FWA and Prandtl theory, respectively. The performance of the propeller in the presence of the wing is related to the wing angle of attack and to the variation of wing circulation and the corresponding induced velocity at the propeller disk. A numerical model, previously and successfully used, was implemented to account for the effects of …
Evaluation of the Safety Performance of Turbo Roundabouts by Means of a Potential Accident Rate Mode
2015
Turbo roundabouts are a particular road intersection layout, designed to increase the safety of double-lane roundabouts, while maintaining their excellent capacity. The main feature of this new concept of roundabout is the impossibility to move from one lane to another, provided by physical barriers marking the lanes. The paper shows an application to turbo roundabouts of a potential accident rate model, aiming to evaluate their safety improvement. Themodel is based on the concept of potential conflict: each vehicle involved in a general intersection performs a series of maneuvers which potentially imply a crash, according to the actual traffic. The number of accidents related to each criti…
Control design for a hypersonic aircraft using a switched linear parameter-varying system approach
2012
This paper is concerned with the control problem of an air-breathing hypersonic aircraft using a switched linear-parameter-varying systems approach. The rigid non-linear longitudinal model of a generic hypersonic aircraft is adopted with the aim of verifying the design methodology of the developed controller and switching logic. By linearizing the non-linear model of the hypersonic aircraft at trim points and dividing the velocity range into several parts, a switched linear parameter-varying model for the underlying system is derived. With the aid of multiple Lyapunov-like functions technique, controllers that ensure the tracking of given commands of the closed-loop system are designed und…
Analysis of driving cycles effects on power supply requirements of a fuel cell powered light-weight electric vehicle
2015
In this paper, fuel cell powered lightweight vehicles are addressed. A MATLAB/Simulink simulation model including motor, electrical drive, the fuel cell and power electronics systems is implemented. The model is well suited to perform the driving cycle test, which reproduces the speed pattern of an electric vehicle through urban, rural or motorway routes. This paper aims at investigating the most suited driving cycle to design high performances hybrid power supply for electric vehicles in terms of cruising range, cost and size of the power supply equipment. For this purpose, a legislative and a real-world driving cycles are selected. Effects of driving cycles on the power system requirement…
How to formulate an accident prediction model for urban intersections.
2009
Several safety prediction models and methods have been developed to eliminate the relationship between the expected accident frequency and various urban intersection geometry and operational attributes. It is generally accepted that accident rates tend to be higher at intersections than on through sections of a road. This is particularly frequent in urban area where roads are characterized by intersections in close succession; moreover, the safe and effective operations of the urban road system can be significantly affected by safety conditions at intersections. In this paper models and methods designed to understand and to predict the accident process at urban intersections are reviewed. I…