Nitrile rubbers (copolymers of butadiene and acrylonitrile) are widely used throughout the aerospace, automobile, construction and footwear industries. The useful properties of nitrile rubbers include excellent resistance to the action of oils, petroleum fuels and solvents, combined with good heat and abrasion resistance. These properties derive from the polar nature of the cyanide group on the polymer chain and rubbers with high oil resistance contain 40 - 50 mole % acrylonitrile. Unfortunately, at low temperatures the elastomeric properties of such rubbers are poor. One of the objectives of this work was to investigate whether the working temperature range of nitrile rubbers could be extended by chemicalmodification, in particular by grafting poly (tetrahydrofuran) (PTHF) onto the nitrile rubber. PTHF is a low melting, crystalline polymer with a glass transition temperature, Tg, of -84°C, above which it is rubbery. The polymerisation of THF can be initiated by the generation of suitable carbonium ions which attack the ethereal oxygen of the THF molecule forming an oxonium ion. Propagation occurs via this oxonium ion intermediate by a cationic, ring-opening mechanism. This 'living' polymerisation can be terminated by many nucleophilic reagents such as water, methanol, etc. In view of the polymerisation characteristics of THF, it can be grafted to a nitrile rubber backbone by two distinct methods. The first is a 'grafting from' technique, which involves initiation of the THF polymerisation from carbonium ion sites generated on the polymer backbone. In these experiments, described in Chapter 2, the parent rubbers were first functionalised by dihalocarbenation, bromination and allyl bromination, and on reaction with a suitable silver salt cationic centres were generated on the backbone. This method proved to be unsuitable for preparing well-defined graft copolymers of PTHF. The second process, a 'grafting onto' technique, involved a 'coupling' reaction between 'living' PTHF and functional groups previously attached to the nitrile rubber backbone. This method, which was finally chosen to prepare a range of graft copolymers of PTHF, is described in Chapters 3 and 4. One to 3 mole % of the diene residues in the nitrile rubber were first epoxidised then treated with HC1 to open the epoxide rings to yield chlorohydrin groups. The hydroxyl substituents functioned as terminators in a 'coupling' reaction with the 'living' PTHF to form a graft copolymer. Since polymerisation of THF at room temperature is fairly slow the lengths of the grafted chains could be controlled by monitoring the time from initiation to termination. The graft copolymers and precursors were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and for solvent resistance. The DSC results show that grafting with PTHF reduces the Tg of low nitrile rubbers but has little effect on the Tg of high nitrile rubbers. This is believed to be due to a greater degree of phase separation of the PTHF component in the high nitrile rubbers. Consequently, the physical properties of these PTHF-high nitrile rubber grafts are not those of a homogeneous amorphous blend of the two components, TGA of the PTHF graft copolymers suggest that the PTHF graft destabilises the nitrile rubber to heat. However, PTHF is well known to be susceptible to hydroperoxidation and it is likely that thisc effect is attributable to peroxides rather than the PTHF chains per se. An antioxidant should be capable of inhibiting hydroperoxidation. Finally, the solvent resistance of the PTHF graft copolymers, especially from high nitrile rubbers, is lower than that of the original nitrile rubber.

Ice growth may rapidly degrade the aerodynamic performance of an aircraft. It can also severely damage structures such as communication towers or power lines. Subsequently, de-icing and anti-icing systems have been developed and a number of codes designed to predict ice shapes. When ice accretion starts, two different types of ice can appear, depending on the temperature and conditions. All of the incoming fluid may freeze almost instantaneously and turn into rime ice. Alternatively, a fraction of the incoming fluid may freeze and turn into glaze ice while the other part remains liquid and may flow over the ice. Previous work on ice accretion has mainly targeted the ice shape and neglected the owing water layer. The present study focuses on this. A set of governing equations is derived for both rime ice growth and coupled ice growth and water flow. When rime ice accretes, a mass balance is used to calculate the shape. In the presence of both ice and water, the ice growth is governed by an energy balance and the water flow by a mass balance. These equations are solved numerically for the water flow alone and the coupled ice growth and water flow for two- and three-dimensional at inclined planes. The behaviour of both ice and water is studied. The model is then extended to deal with arbitrary substrates and solutions are sought for industrially important applications such as ice accretion on power lines or aerofoils. This research work forms part of the ICECREMO project. ICECREMO is a three-dimensional ice accretion and water flow code developed collaboratively by DERA, British Aerospace, Rolls Royce, GKN Westlands Helicopters and Cranfield University under the auspices of the UK department of Trade and Industry.

An experimental and theoretical study of erosion in centrifugal compressor impellers is presented. An experimental rig using laser anemometry techniques was employed to create a database of particle restitution ratios for a range of materials. This data was unique in that the particle rebound was measured in a quiescent condition where the aerodynamic effects had been minimised, and also parametric factors not previously available were included. These values were incorporated into the existing Particle Trajectory Code developed by Cranfield University and Rolls Royce PLC. The code is used to calculate the trajectories of discrete particles in three dimensional gas turbine geometries, and the ensuing erosion. It was modified to include the effects of the periodic boundary conditions, particle fragmentation, splitter blades, and variations in inlet dust concentration profile. Flowfield calculations were performed on a Rolls Royce GEM-2 and splittered GEM-60 impeller, which both represent the high pressure stage of the axial + centrifugal compression system of GEM engines. A procedure developed by Tourlidakis, for the analysis of steady viscous flow in high speed centrifugal compressors with tip leakage, was used to generate the flowfields. The GEM-2 impeller flowfield was analysed at 1009c speed, and validated with calculations and measurements which had been taken for previous projects. Simulated erosion data under the same conditions was checked using practical results obtained in a Rolls Royce PLC Helicopter Engine Environmental Protection Programme, and good agreement was achieved. In order to provide a qualitative, experimental assessment of erosion, a GEM-60 impeller was coated with four layers of paint of different colours. Two sizes of quartz particle, each at three different vane heights, were then seeded into the impeller while it was run cold at (the maximum) 70% speed. The erosion patterns generated compared well with the results generated by the Particle Trajectory Code.

No description available.

The existing air transportation system is approaching a bottleneck because its dominant huband- spoke model results in a concentration of a large percentage of the air traffic at a few hub airports. Advanced technologies are greatly needed to enhance the transportation capabilities of the small airports in the U.S.A., and distribute the high volume of air traffic at the hub airports to those small airports, which are mostly non-controlled airports. Currently, two major focus areas of research are being pursued to achieve this objective. One focus concentrates on the development of tools to improve operations in the current Air Traffic Management system. A more long-term research effort focuses on the development of decentralized Air Traffic Management techniques. This dissertation takes the latter approach and seeks to analyze the degree of decentralization for scheduling aircraft landings in the dynamic operational environment at single runway noncontrolled airports. Moreover, it explores the feasibility and capability of scheduling aircraft landings within uninterrupted free-flight environment in which there is no existence of Air Traffic Control (ATC). First, it addresses the approach of developing static optimization algorithms for scheduling aircraft landings and, thus, analyzes the capability of automated aircraft landing scheduling at single runway non-controlled airports. Then, it provides detailed description of the implementation of a distributed Air Traffic Management (ATM) system that achieves decentralized aircraft landing scheduling with acceptable performance whereas a solution to the distributed coordination issues is presented. Finally real-time Monte Carlo flight simulations of multi-aircraft landing scenarios are conducted to evaluate the static and dynamic performance of the aircraft landing scheduling algorithms and operation concepts introduced. Results presented in the dissertation demonstrate that decentralized aircraft landing scheduling at single runway non-controlled airports can be achieved. It is shown from the flight simulations that reasonable performance of decentralized aircraft landing scheduling is achieved with successful integration of publisher/subscriber communication scheme and aircraft landing scheduling model. The extension from the non-controlled airport application to controlled airport case is expected with suitable amendment, where the reliance on centralized air traffic management can be reduced gradually in favor of a decentralized management to provide more airspace capacity, flight flexibility, and increase operation robustness.

Our national commercial and cargo airlines have great revenue because of rapid developed economics. Especially after the open sky policy. Aviation capacity grows very fast. The convenient of air transportation brings booming economics to the general public; however it also brings destructive environment of airport neighborhood, lower the living quality. Under the aircraft noise for a long term would affect people¡¦s life and work seriously, cause people different level of physical and psychological damages. Citizen views the present monitoring operation of aircraft noise and causes serious environmental pollution issues. Although the government studies airside noise improvement and reward system aggressively, the contestation continues for three years. Every individual airport has conflict with close-by residents frequently. The issue of rationality and fairness of the official aircraft noise prevention and airport reward system is important and meet the exigencies of the moment. This study views the past three years document of aircraft noise prevention and airport reward system, refer to varies information of national and international similar system, analysis and study the reasonable standard level of aircraft noise and related regulations for schools, hospitals residents. Further to offering some strategies and methods to improve the aircraft noise prevention and airport reward system.

The U.S. Navy first took official notice of aviation in 1910, but its development of carrier aviation lagged behind Great Britain??s until the 1920s. The first American aircraft carrier, the Langley, commissioned in 1919, provided the Navy with a valuable platform to explore the potential uses of carrier aviation, but was usually limited to scouting and fleet air defense in the U.S. Navy??s annual interwar exercises called fleet problems. This began to change in 1929 with the introduction of the carriers Lexington and Saratoga in Fleet Problem IX. After this exercise, which included a raid by aircraft from the Saratoga that ??destroyed?? the Pacific side of the Panama Canal, the carriers were assigned a wider variety of roles over the next five years of exercises. During this time, the carriers gained their independence from the battle line, which the smaller and slower Langley had been unable to do. Reflecting the advanced capabilities of the new carriers, the fleet problems conducted during Admiral William Veazie Pratt??s tenure as Chief of Naval Operations, 1930-1933, began to test the employment of the new carriers as the centerpiece of one of the opposing fleets within the exercises. The Lexington and Saratoga were used offensively during these exercises, employing their aircraft to sink surface ships, though not battleships, and successfully strike targets ashore. The carriers became successful in spite of the unreliability of early 1930s carrier aircraft, particularly the torpedo bombers, that could carry heavy payloads. Lessons learned from the Lexington and Saratoga Fleet Problems IX through XIV influenced the design of the next generation of American aircraft carriers, the Yorktownclass, which were authorized in 1933. These new carriers were faster and much larger than the carrier Ranger, commissioned in 1934 and designed before the Lexington and Saratoga began participating in the exercises. Features incorporated into the Yorktownclass based on operational experience included the reduced need for large surface batteries because of the use of escort vessels, the emphasis of armoring against shellfire over aerial bombs and torpedoes, and the capability to launch large numbers of aircraft quickly.

Thesis (Ph.D.) -- University of Texas at Arlington, 2008.

Thesis (M.S. in Operations Research and M.S. in Systems Engineering)--Naval Postgraduate School, June 2004. / Thesis advisor(s): David Olwell. Includes bibliographical references (p. 217-224). Also available online.

Thesis (M.S. in M.E.)--School of Mechanical Engineering, Georgia Institute of Technology, 2004. Directed by W. Steven Johnson. / Includes bibliographical references (leaves 161-163).