Aeronautical engineering: A continuing bibliography with indexes (supplement 252)

This bibliography lists 425 reports, articles, and other documents introduced into the NASA scientific and technical information system in April 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Carbon balance of a rain-fed maize field

This thesis analyses micrometeorological measurements carried out from June 2004 until October 2006 in the framework of the INTERREG IIIa Project Nr. 3c.10 ”Impacts of climate change on vegetation in the Upper Rhine Valley”. The study addresses the exchange processes of carbon, water and energy of a rain-fed field under maize-fallow rotation. Measurements with an ultrasonic anemometer-thermometer, an open-path CO2/H2O infra-red gas analyser and of the meteorological drivers such as photosynthetic photon flux density (PPFD), temperature and precipitation give insight in the interaction between atmosphere, soil and vegetation. Energy balance considerations show similar patterns of the energy flux densities for vegetation periods and bare field conditions. Energy balance closure is 80 % and 52 %, respectively. A closer look shows a clear diurnal pattern with bad closure during nighttime and an increasing closure fraction during daytime, in fact resulting in an overshooting in late afternoon. Evapotranspiration shows a clear seasonal pattern with maximum values of ~3.5 mm d-1 reached in mid-July. The total water need for the three subsequent years is 321, 397, and 422 mm per kg kernels (yield). The water use efficiency shows a strong relationship with PPFD and the amount of biomass. The focus of the study is on carbon balance. During the three subsequent vegetation periods 930, 785, and 841 g C m-2 are sequestered, respectively. The yield is 455, 417, and 340 g C m-2. About 40 % of the biomass remaining on the field at harvest are decomposed during the dormant season. The resulting numbers for the carbon balance show a ”yearly” sink of this agroecosystem of ~250 g C m-2. Besides unlimited photosynthetic active radiation the combination of the optimal temperature range with the needed precipitation amount corresponding to the need of the actual growth stage are essential for optimal maize growth

IN VIVO analysis of ocular morphological changes during phakic accommodation

The principal theme of this thesis is the in vivo examination of ocular morphological changes during phakic accommodation, with particular attention paid to the ciliary muscle and crystalline lens. The investigations detailed involved the application of high-resolution imaging techniques to facilitate the acquisition of new data to assist in the clarification of aspects of the accommodative system that were poorly understood. A clinical evaluation of the newly available Grand Seiko Auto Ref/ Keratometer WAM-5500 optometer was undertaken to assess its value in the field of accommodation research. The device was found to be accurate and repeatable compared to subjective refraction, and has the added advantage of allowing dynamic data collection at a frequency of around 5 Hz. All of the subsequent investigations applied the WAM-5500 for determination of refractive error and objective accommodative responses. Anterior segment optical coherence tomography (AS-OCT) based studies examined the morphology and contractile response of youthful and ageing ciliary muscle. Nasal versus temporal asymmetry was identified, with the temporal aspect being both thicker and demonstrating a greater contractile response. The ciliary muscle was longer in terms of both its anterior (r = 0.49, P <0.001) and overall length (r = 0.45, P = 0.02) characteristics, in myopes. The myopic ciliary muscle does not appear to be merely stretched during axial elongation, as no significant relationship between thickness and refractive error was identified. The main contractile responses observed were a thickening of the anterior region and a shortening of the muscle, particularly anteriorly. Similar patterns of response were observed in subjects aged up to 70 years, supporting a lensocentric theory of presbyopia development. Following the discovery of nasal/ temporal asymmetry in ciliary muscle morphology and response, an investigation was conducted to explore whether the regional variations in muscle contractility impacted on lens stability during accommodation. A bespoke programme was developed to analyse AS-OCT images and determine whether lens tilt and decentration varied between the relaxed and accommodated states. No significant accommodative difference in these parameters was identified, implying that any changes in lens stability with accommodation are very slight, as a possible consequence of vitreous support. Novel three-dimensional magnetic resonance imaging (MRI) and analysis techniques were used to investigate changes in lens morphology and ocular conformation during accommodation. An accommodative reduction in lens equatorial diameter provides further evidence to support the Helmholtzian mechanism of accommodation, whilst the observed increase in lens volume challenges the widespread assertion that this structure is incompressible due to its high water content. Wholeeye MRI indicated that the volume of the vitreous chamber remains constant during accommodation. No significant changes in ocular conformation were detected using MRI. The investigations detailed provide further insight into the mechanisms of accommodation and presbyopia, and represent a platform for future work in this field

Advanced Strategies for Robot Manipulators

Amongst the robotic systems, robot manipulators have proven themselves to be of increasing importance and are widely adopted to substitute for human in repetitive and/or hazardous tasks. Modern manipulators are designed complicatedly and need to do more precise, crucial and critical tasks. So, the simple traditional control methods cannot be efficient, and advanced control strategies with considering special constraints are needed to establish. In spite of the fact that groundbreaking researches have been carried out in this realm until now, there are still many novel aspects which have to be explored

Investigating the mechanism of fatigue in subclinical hypothyroidism

MD ThesisSubclinical hypothyroidism (SCH) is a common medical condition affecting 4-10% of the population. Unlike overt hypothyroidism, clinical manifestations are unclear and treatment remains controversial. It is known that fatigue may improve with levothyroxine in these patients but the mechanisms linking symptoms with abnormal tissue function are poorly understood. It was hypothesized that fatigue in patients with SCH is caused by peripheral tissue functional changes and that these changes are reversible with levothyroxine treatment. The objective of the study was to quantify the specific abnormalities in cerebral blood flow, cardiac function, cardiac and muscular energetic function, and autonomic function in patients with SCH, and to measure the changes in these abnormalities after levothyroxine therapy with any associated impact on fatigue. This was a pilot study as no previous studies looking into the mechanism of fatigue in patients with SCH have been reported. Subjects with SCH (TSH 4.0 -10.0 mU/L, normal free T4) and fatigue were studied before and after levothyroxine therapy and were compared with age and gendermatched healthy controls (HC). Cerebral blood flow (CBF) was measured by MR arterial spin labelling. Cardiac function was measured using impedance cardiography. Cardiac and calf muscle energetic functions were measured by 31-Phosphorous Magnetic Resonance Spectroscopy. Autonomic function was assessed using heart rate variability. At baseline, patients with SCH had increased CBF, impaired cardiac function, and lower cardiac and calf muscle energetic function, compared with HC. Autonomic function was equal to that of HC. After levothyroxine treatment, CBF decreased, cardiac function was unchanged, and cardiac energetic function improved. Calf muscle energetic function did not improve but autonomic function tests did. Although fatigue improved after levothyroxine treatment, these improvements were not correlated with peripheral tissue functional changes. Novel physiological abnormalities in both CBF and cardiac and calf muscle energetic functions have been demonstrated by these studies. Improvements were seen in CBF, ii cardiac energetic function and autonomic function after levothyroxine treatment. These parameters may play a role in the reduction of fatigue and warrant further investigation.BUPA charity foundatio

AN INTELLIGENT NAVIGATION SYSTEM FOR AN AUTONOMOUS UNDERWATER VEHICLE

The work in this thesis concerns with the development of a novel multisensor data fusion (MSDF) technique, which combines synergistically Kalman filtering, fuzzy logic and genetic algorithm approaches, aimed to enhance the accuracy of an autonomous underwater vehicle (AUV) navigation system, formed by an integration of global positioning system and inertial navigation system (GPS/INS). The Kalman filter has been a popular method for integrating the data produced by the GPS and INS to provide optimal estimates of AUVs position and attitude. In this thesis, a sequential use of a linear Kalman filter and extended Kalman filter is proposed. The former is used to fuse the data from a variety of INS sensors whose output is used as an input to the later where integration with GPS data takes place. The use of an adaptation scheme based on fuzzy logic approaches to cope with the divergence problem caused by the insufficiently known a priori filter statistics is also explored. The choice of fuzzy membership functions for the adaptation scheme is first carried out using a heuristic approach. Single objective and multiobjective genetic algorithm techniques are then used to optimize the parameters of the membership functions with respect to a certain performance criteria in order to improve the overall accuracy of the integrated navigation system. Results are presented that show that the proposed algorithms can provide a significant improvement in the overall navigation performance of an autonomous underwater vehicle navigation. The proposed technique is known to be the first method used in relation to AUV navigation technology and is thus considered as a major contribution thereof.J&S Marine Ltd., Qinetiq, Subsea 7 and South West Water PL

Primordial black holes and their gravitational-wave signatures

In the recent years, primordial black holes (PBHs) have emerged as one of the most interesting and hotly debated topics in cosmology. Among other possibilities, PBHs could explain both some of the signals from binary black hole mergers observed in gravitational wave detectors and an important component of the dark matter in the Universe. Significant progress has been achieved both on the theory side and from the point of view of observations, including new models and more accurate calculations of PBH formation, evolution, clustering, merger rates, as well as new astrophysical and cosmological probes. In this work, we review, analyse and combine the latest developments in order to perform end-to-end calculations of the various gravitational wave signatures of PBHs. Different ways to distinguish PBHs from stellar black holes are emphasized. Finally, we discuss their detectability with LISA, the first planned gravitational-wave observatory in space.Comment: 161 pages, 47 figures, comments welcom