Dissertations / Theses on the topic 'Airborne and field campaigns'

This thesis describes spectrally-resolved radiance measurements, recorded using the Imperial College-built Tropospheric Airborne Fourier Transform Spectrometer (TAFTS), to validate the current parameterisation of the far-infrared foreign- broadened continuum of atmospheric water vapour in line-by-line radiative transfer models. The current parameterisation is not based on measurement through the centre of the far-IR spectral region, but is constructed by interpolation from measurements either side of the band. Accurate knowledge of this parameterisation is essential as the far-IR contribution to the planetary outgoing longwave radiation (OLR) is significant. The research takes the form of a radiative closure study, comparing the radiance measurements with simulated radiances modelled using the measured atmospheric state (temperature, humidity) profile as input. The profile information was recorded, alongside the radiance measurements, aboard the UK Met Office / FAAM (Facility for Airborne Atmospheric Measurements) BAe-146 research aircraft, during the first of two field campaigns as part of the CAVIAR (Continuum Absorption in the Visible and Infrared and its Atmospheric Relevance) project. This thesis provides an overview of the relevant atmospheric physics and Fourier Transform Spectroscopy, including a description of TAFTS; the construction of the atmospheric profiles from the various in-situ, radiosonde and model datasets; the calibration of the radiances measured by TAFTS and derivation of the foreign- broadened water vapour continuum between 114−540 cm−1 within the framework of the line-by-line radiative transfer model (LBLRTM v12.0). The resulting continuum is compared to other relevant recent studies. The measurements from this study suggest an increase in continuum strength up to 11% at 238.6 cm−1, decreasing steadily to a reduction of 55% at 114 cm−1 and 54% at 513 cm−1. However, the uncertainties in these measurements are considerable, and might equally suggest an increase in continuum strength.

Light field photography offers a new approach to digitally captured images. These commercially available cameras are able to capture the 4D light field in a single image. This allows for a variety of image processing capabilities that traditional cameras do not offer. For example, the image can be digitally refocused after it is captured and its depth can be estimated. In terms of application, these capabilities could be beneficial on airborne platforms. However, a limitation of currently available light field cameras is that they are not fully functional at medium or long ranges. If these cameras were to capture light fields at longer ranges, they would have a practical application when mounted on low-flying aircrafts. This dissertation takes current light field photography techniques and modifies them so they work better to capture medium-range images. The majority of cameras that capture the 4D light field use a microlens array to modulate the incoming light before it hits the image sensor. Previous work using printed modulation masks garnered the same effect obtained by microlens arrays. This dissertation details the development of a modulation mask that has medium-range applications. A new way of extracting the 4D light field from raw images that uses a digital Fourier transform is presented. This method works for images captured with microlens arrays and printed mask cameras. Two prototype cameras were built and tested to demonstrate some of these concepts. The concepts demonstrated by these cameras could be used in the future designs of light field cameras.

La disponibilité de nouveaux moyens d’acquisition en télédétection, satellitaire (PLEIADES, HYPXIM), aéroportée ou par drone (UAV) à très haute résolution spatiale ouvre la voie à leur utilisation pour l’étude de milieux complexes telles que les villes. En particulier, la connaissance de la ville pour l’étude des îlots de chaleur, la planification urbaine, l’estimation de la biodiversité de la végétation et son état de santé nécessite au préalable une étape de classification des matériaux qui repose sur l’utilisation de l’information spectrale accessible en télédétection hyperspectrale 0,4-2,5μm. Une des principales limitations des méthodes de classification réside dans le non traitement des zones à l’ombre. Des premiers travaux ont montré qu’il était possible d’exploiter l’information radiative dans les ombres des bâtiments. En revanche, les méthodes actuelles ne fonctionnent pas dans les ombres des arbres du fait de la porosité de leur couronne. L’objectif de cette thèse vise à caractériser les propriétés optiques de surface à l’ombre de la végétation arborée urbaine au moyen d’outils de transfert radiatif et de correction atmosphérique. L’originalité de ce travail est d’étudier la porosité d’un arbre via la grandeur de transmittance de la couronne. La problématique a donc été abordée en deux temps. Premièrement, la caractérisation de la transmittance d’un arbre isolé a été menée avec l’utilisation de l’outil DART à travers la mise en œuvre d’un plan d’expériences et d’études de sensibilité qui ont permis de la relier à des paramètres biophysiques et externes. Une campagne de mesures terrain a ensuite été réalisée afin d’évaluer son estimation à partir de différents niveaux de modélisation de l’arbre, dont un modèle réel acquis par mesures lidar terrestre. Deuxièmement, une nouvelle méthode de correction atmosphérique 3D adaptée à la végétation urbaine, ICARE-VEG, a été développée à partir des résultats précédents. Une campagne aéroportée et de mesures terrain UMBRA a été dédiée à sa validation. Ses performances comparées à d’autres outils existants ouvrent de larges perspectives pour l’interprétation globale d’une image par télédétection et pour souligner la complexité de modéliser des processus physiques naturels à une échelle spatiale très fine
The new advances in remote sensing acquisitions at very high spatial resolution, either spaceborne (PLEIADES, HYPXIM), airborne or unmanned aerial vehicles borne, open the way for the study of complex environments such as urban areas. In particular, the better understanding of urban heat islands, urban planning, vegetation biodiversity, requires the knowledge of detailed material classification mapsbased on the use of spectral information brought by hyperspectral imagery 0.4-2.5μm. However, one of the main limitations of classification methods relies on the absence of shadow processing. Past studies have demonstrated that spectral information was possible to be extracted from shadows cast by buildings. But existing methods fail in shadows cast by trees because of their crown porosity. The objective of this thesis aims to characterize surface optical properties in urban tree shadows by means of radiative transfer and atmospheric correction tools. The originality of this work is to study the tree crown porosity through the analysis of the tree crown transmittance. Therefore, the issue has been divided into two parts. Firstly, an experimental design with the use of DART tool has been carried out in order to examine the relationships between the transmittance of an isolated tree and different biophysical and external variables. Then, the estimation of the tree crown transmittance has been assessed with several tree 3D modelling strategies derived from reference terrestrial lidar acquisitions. Secondly, a new atmospheric correction method appropriate to the processing of tree shadows, ICARE-VEG, was implemented fromthese previous results. An airborne and field campaign UMBRA was dedicated to its validation. Moreover, its performances was compared to other existing tools. Finally, the conclusions open large outlooks to the overall interpretation of remote sensing images and highlight the complexity to model physical natural processes with finer spatial resolutions

Thesis (M.P.A.)--Kutztown University of Pennsylvania, 2003.
Source: Masters Abstracts International, Volume: 45-06, page: 2925. Typescript. Abstract precedes thesis as preliminary leaves iii-iv. Includes bibliographical references (leaf 70).

Datasets of PM10 measured gravimetrically and its key components from different locations (background, suburban, roadside, kerbside) in London during the period 2001 to 2012 have been collected and analysed. During this period a number of regulatory requirements and other initiatives, including a Low Emission Zone, were introduced targeting the reduction of PM10 because of its known adverse health effects. Analysis across the whole timescale was confounded by a change of filter substrate in 2007 but no evidence of any noticeable reduction in overall PM10 concentrations was found at the study sites. The contribution of the coarse fraction increased at Marylebone Road suggesting that road abrasion and brake and tyre wear from traffic sources became increasingly important. Pollution episodes, when PM10 concentrations exceeded 50 μg m-3, were particularly noticeable in springtime and associated with increased ammonium nitrate concentrations. Ammonium sulphate concentrations reduced by approximately 30% at the time of the introduction of ultra-low sulphur fuel in the UK in 2007 signifying the importance of local sources of sulphate to PM10 concentrations. A high concentration (6.5 μg m-3) of chloride in the fine fraction of PM10 at one of the sites in early November suggests that not all chloride concentrations may be associated with sea-salt and that anthropogenic chloride can make a significant contribution to pollution episodes. Particulate black carbon from vehicle emissions has independently been linked to adverse health outcomes. The use of transmissometry and reflectometry to measure and compare the light absorbing properties of equivalent black carbon concentrations (EBC) on archived filters of different substrates was investigated. Equations for calculating daily EBC concentrations were determined and may be used at locations where measurements would not otherwise be available. A decrease in the region of 7% in overall mean EBC concentrations was detected at Marylebone Road after 2010. However, daily concentrations at all locations did not change in line with PM10 concentrations indicating a need for a separate long term monitoring programme of ambient EBC concentrations to track the results of exhaust abatement technologies and policies.

Understanding uncertainty is an important part of any scientific measurement process and the ability to evaluate and understand uncertainty is a requirement of the International Standards for quality control. The basic uncertainties relating to the measurement of airborne sound insulation in the field can be assessed using the methods in BS5725. However, identifying the components that contribute to the total variability is beyond the scope of the standard and more detailed information requires a more advanced approach. Recent developments in the “Guide to the expression of uncertainty in measurement” (GUM) suggest an approach can be used where identification of the input variables and their likely contribution will result in a solution that can be modelled providing enough information is available. However, recent research on uncertainty in sound insulation using GUM has identified problems involving the correlation between frequency bands, which leads to an overestimate of uncertainty. An empirical approach is used in this thesis, which incorporates advanced analysis of variance (ANOVA) and a specific model called Gauge Repeatability and Reproducibility (GRR). It enables the components of variance in the measurement system to be partitioned and provides an estimate of their contribution. In addition, ANOVA highlights any interaction between factors. In the GRR, carried out on a lightweight timber floor and a heavyweight concrete floor, significant interaction was detected between the operator and part. Good agreement is obtained in the repeatability and reproducibility calculated for each construction and the samples are combined with measurements of test elements that provide a wider range of sound insulation performance. The uncertainty associated with the instrumentation, operator, interaction and part are calculated in each case. It is shown that the interaction component is important and should be contained in any approach evaluating uncertainty. Further evidence reveals that the total uncertainty in the measurement process is dependent on the construction being measured.

In this thesis, I report the results from the first randomized field experiments conducted in collaboration with party-affiliated candidates and campaigns in the United Kingdom. The papers presented as part of this thesis test both the limits and possibilities of campaign influence, in a partisan political environment. During election campaigns parties provide signals to voters, voluntarily or involuntarily imposing a structure, and thereby constraints, on individuals’ electoral decisions. By integrating insights about heuristic and social decision-making into the experimental campaign literature, I formulate testable hypotheses about the direct and indirect effects of party cues on campaign mobilization and persuasion. The first paper, The Heuristic Function of Party Affiliation in Voter Mobilization Campaigns, addresses how the provision of party cues, used during campaign phone calls, affects turnout among party supporters, opponents and unattached voters. The second paper on Household Partisan Composition and Voter Mobilization, explores the spillover effects from the previous experiment, testing whether campaign-induced mobilization between household members is conditioned by the partisan composition of a household, and the partisan intensity of a campaign message. Paper three investigates if candidates who are Reaching Across The Partisan Divide can win over supporters of rival parties. In the fourth paper, I test if Impersonal, But Noticeable methods of voter contact, such as door hangers and text messages, affect the turnout decisions of partisans and unattached voters. The final paper, The National Effects of Subnational Representation, highlights the importance of local party organization for the outcomes of national elections. The results of this thesis show the electoral consequences of direct and indirect interactions between campaigns and voters of different partisanship, and point to strategies that allow constituency campaigns to successfully navigate challenging partisan environments.

Ice nucleating particles (INPs), which are a small fraction of the total aerosol population, are capable of catalyzing ice formation under atmospheric conditions. INPs may therefore influence the development, albedo, and lifetime of mixed-phase and ice clouds, and ultimately indirectly effect climate. As this aerosol indirect effect represents one of the largest sources of uncertainty in our understating of climate processes, measurements that quantify and characterize the atmospheric INP population are needed. The micro-orifice uniform deposit impactor-droplet freezing technique (MOUDI-DFT) was developed to measure INP concentrations in the atmosphere as a function of size and temperature in the immersion mode. The first campaign using the MOUDI-DFT was conducted in a Colorado forest. The concentrations of INPs and bioparticles were increased and correlated during and following rainfall events, and their size distributions were similar. This indicates that rainfall-associated mechanisms of bioparticle release may influence the abundance and efficiency of INPs in this region. The MOUDI-DFT was next used at a coastal site in Western Canada. INP concentrations were strongly correlated with those of fluorescent bioparticles and the size distributions of these particles were similar, suggesting bioparticles were an important source of INPs during this study. Despite the predominance of marine air masses, no evidence of a marine INP source was found. Six parameterizations of ice nucleation were tested and found to be poor predictors of the measured INP concentrations, identifying a need to develop INP parameterizations appropriate for coastal environments. Finally, size-resolved INP measurements from six ground-level sites in North America and one in Europe were presented, covering Arctic, alpine, coastal, marine, agricultural, and suburban environments. On average, 78 % of INPs were supermicron in size and 53 % were in the coarse mode (> 2.5 micrometers). Large particles were therefore a significant component of the ground-level INP in these diverse locations. The results presented in this dissertation increase our understanding of atmospheric INP concentrations, composition, and size. This information can be used to constrain INP sources, improve modeling of their long-distance transport and related indirect climate effects, and determine the ability of existing instrumentation to capture the full INP population.
Science, Faculty of
Chemistry, Department of
Graduate

Atmospheric aerosols impact the quality of our life in many direct and indirect ways. Inhalation of aerosols can have harmful effects on human health. Aerosols also have climatic impacts by absorbing or scattering solar radiation, or more indirectly through their interactions with clouds. Despite a better understanding of several relevant aerosol properties and processes in the past years, they remain the largest uncertainty in the estimate of global radiative forcing. The uncertainties arise because although aerosols are ubiquitous in the Earth's atmosphere they are highly variable in space, time and their physicochemical properties. This makes in-situ measurements of aerosols vital in our effort towards reducing uncertainties in the estimate of global radiative forcing due to aerosols. This study is an effort to characterize atmospheric aerosols at a regional scale, in southern Arizona and eastern Pacific Ocean, based on ground and airborne observations of aerosols. Metals and metalloids in particles with aerodynamic diameter (Dp) smaller than 2.5μm are found to be ubiquitous in southern Arizona. The major sources of the elements considered in the study are identified to be crustal dust, smelting/mining activities and fuel combustion. The spatial and temporal variability in the mass concentrations of these elements depend both on the source strength and meteorological conditions. Aircraft measurements of aerosol and cloud properties collected during various field campaigns over the eastern Pacific Ocean are used to study the sources of nitrate in stratocumulus cloud water and the relevant processes. The major sources of nitrate in cloud water in the region are emissions from ships and wildfires. Different pathways for nitrate to enter cloud water and the role of meteorology in these processes are examined. Observations of microphysical properties of ambient aerosols in ship plumes are examined. The study shows that there is an enhancement in the number concentration of giant cloud condensation nuclei (Dp>2 μm) in ship plumes relative to the unperturbed background regions over the ocean.

Recent research has emphasized the need to professionally manage campsites for long-term use, particularly in light of rising visitation to natural protected areas worldwide. Camping regulations vary considerably along the length of any long-distance trail due to the many land types and management agencies involved. Large proportions of long-distance trails have at-large camping policies, resulting in camping problems associated with visitor-chosen or developed campsites. Several long-term monitoring studies in areas with at-large camping policies indicate the expansion and proliferation of individual campsites, and growth of overall camping related impacts, to be a substantial managerial concern. This research evaluates the relative influence of environmental and topographic factors, both collected in the field and modeled in GIS using high-resolution topography (LiDAR) data, on areal measures of campsite impact utilizing Least Absolute Shrinkage and Selection Operator (LASSO) penalized regression for factor selection and Ordinary Least Squares (OLS) for regressions. Chosen variables in regressions explained 64% of the variation in campsite size and 61% of the variation in the area of vegetation loss on a campsite. Results indicate four variables managers can utilize to enhance the sustainability of campsites: use level, overnight site type, and terrain characteristics relating to slope and topographic roughness. Results support indirect management methods that rely on the design and location of campsites and trails and not the effectiveness of enforcement or restricting visitor freedom. In the face of rising use, techniques and concepts presented aid in identifying or creating ecologically sustainable campsites.
Master of Science

Falkenberg area is located in southwest Sweden formed in the Sveconorwegian orogen and contains an extremely complex geological structure. Multiple geophysical datasets have been acquired and together with available petrophysical information, models corresponding to the subsurface geological structures were generated. The collected data comprise ground magnetic, AMT (Audio Magnetotelluric) and RMT (Radio Magnetotelluric) data. The available airborne magnetic and ground gravity data acquired by the Geological Survey of Sweden (SGU) as well as the reflection seismic section from a study made by Uppsala University further aids in obtaining substantially improved interpretation of the geometry of the structures along the AMT profile. The principal objective of this profile was to delineate and map the possible deformation zone crossed by the profile. The AMT study was expected to complement existing geophysical data and improve existing interpretations. The Ullared deformation zone contains decompressed eclogite facies rocks. The presented results were obtained by comparison of different geophysical methods along the profile. The susceptibility model and resistivity model show that eclogites have higher resistivity and susceptibility than the surrounding structures. However use of the Occam type of inversion on the AMT data, makes the resistivity model smoother than the susceptibility model and as a results it is difficult to estimate the dip of the structures. The AMT profile and the seismic section show the same dip direction (NE) for the eclogite bearing structures although due to the smoothing in the AMT model the dips seen in the seismic section cannot be recovered in the resistivity model.

A chemical ionisation mass spectrometer (CIMS) was developed and utilised for measurements onboard the Facility for Atmospheric Airborne Measurements (FAAM) BAe-146 aircraft. The I- ionisation scheme was implemented to detect nitric acid (HNO3), formic acid (HC(O)OH), hydrogen cyanide (HCN) and dinitrogen pentoxide (N2O5) simultaneously at a sampling frequency of 1 Hz. Sensitivities ranged from 35±6 ion counts pptv-1 s-1 for HC(O)OH to 4±0.9 ion counts pptv-1 s-1 for HCN and limits of detection from 37 ppt for HNO3 and 5 ppt for HCN. Trace gas concentrations of species such as HC(O)OH are currently under predicted in global models. In order to understand their role in controlling air quality, it is crucial that their production pathways and abundance are accurately measured and constrained. To date, airborne measurements of these trace gases have been difficult as a result of instrumental limitations on an aircraft such as limit of detection and sampling frequency. The first UK airborne measurements of HC(O)OH and HNO3 confirmed that HC(O)OH is under predicted by up to a factor of 2 in a trajectory model that implements the full Master Chemical Mechanism (MCM) and Common Representative Intermediate Scheme (CRI). The inclusion of a primary vehicle source enabled the model to reproduce the concentrations observed; verifying that direct sources are under represented. Secondary formation of HC(O)OH was observed through its correlation with HNO3 and ozone (O3), indicating a strong photochemical production source. Hydroxyl (OH) concentrations were estimated for the first time in a flight around the UK using the HC(O)OH and HNO3 measurements. A biomass burning (BB) plume identification technique is applied to data obtained from Canadian biomass fires using HCN as a marker. A 6 sigma above background approach to defining a plume resulted in a higher R2 correlating value for the normalised excess mixing ratio (NEMR) to carbon monoxide (CO) when compared to current methods in the literature. The NEMR obtained from this work; 3.76±0.02 pptv ppbv-1, lies within the range found in the literature. This NEMR is then used to calculate a global emission total for HCN of 0.92 Tg (N) yr-1 when incorporated into the global tropospheric model STOCHEM CRI. The first direct N2O5 airborne measurements on an aircraft at night are compared to indirect measurements taken by a broadband cavity enhancement absorption spectrometer. An average R2 correlation coefficient of 0.87 observed over 8 flights for 1 Hz measurements indicates the selectiveness of the I- ionisation scheme to detect N2O5 directly, without nitrate (NO3) interference.

Gravity gradient tensor (GGT) data contains the second derivatives of the Earth’s gravitational potential in three orthogonal directions. GGT data can be measured either using land, airborne, marine or space platforms. In the last two decades, the applications of GGT data in hydrocarbon exploration, mineral exploration and structural geology have increased considerably. This work focuses on developing new interpretation techniques for GGT data as well as pseudo-gravity gradient tensor (PGGT) derived from measured magnetic field. The applications of developed methods are demonstrated on a GGT data set from the Vredefort impact structure, South Africa and a magnetic data set from the Särna area, west central Sweden. The eigenvectors of the symmetric GGT can be used to estimate the position of the causative body as well as its strike direction. For a given measurement point, the eigenvector corresponding to the maximum eigenvalue points approximately toward the center of mass of the source body. For quasi 2D structures, the strike direction of the source can be estimated from the direction of the eigenvectors corresponding to the smallest eigenvalues. The same properties of GGT are valid for the pseudo-gravity gradient tensor (PGGT) derived from magnetic field data assuming that the magnetization direction is known. The analytic signal concept is applied to GGT data in three dimensions. Three analytic signal functions are introduced along x-, y- and z-directions which are called directional analytic signals. The directional analytic signals are homogenous and satisfy Euler’s homogeneity equation. Euler deconvolution of directional analytic signals can be used to locate causative bodies. The structural index of the gravity field is automatically identified from solving three Euler equations derived from the GGT for a set of data points located within a square window with adjustable size. For 2D causative bodies with geometry striking in the y-direction, the measured gxz and gzz components of GGT can be jointly inverted for estimating the parameters of infinite dike and geological contact models. Once the strike direction of 2D causative body is estimated, the measured components can be transformed into the strike coordinate system. The GGT data within a set of square windows for both infinite dike and geological contact models are deconvolved and the best model is chosen based on the smallest data fit error.
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 730

Organic aerosols represent one of the main sources of uncertainty affecting attempts to quantify anthropogenic climate change. The diverse physical and chemical properties of organic aerosols and the varied pathways involved in their formation and aging form the basis of this uncertainty, preventing extensive and accurate representation within regional and global scale models. This inability to constrain the radiative forcings produced by organic aerosols within the atmosphere consequently acts as a limitation to the wider objective of providing reliable projections of future climate. Biomass burning constitutes one of the main anthropogenic contributions to the global atmospheric organic aerosol (OA) burden, particularly in tropical regions where the potential for perturbations to the climate system is also enhanced due to higher average levels of solar irradiance. Emissions from biomass burning have been the subject of an intense research focus in recent years, involving a combination of field campaigns and laboratory studies. These experiments have aimed to improve the limited understanding of the processes involved in the evolution of biomass burning organic aerosol (BBOA) and contribute towards the development of more robust parameterisations for climate and chemical transport models. The main objective of this thesis was to use datasets acquired from several different global regions to perform a broad analysis of the BBOA fraction, with the extensive temporal and spatial scales provided by such measurements enabling investigation of a number of key uncertainties, including regional variability in emissions and the role of secondary organic aerosol (SOA) formation in aging smoke plumes. Measurements of BBOA mass concentration obtained using Aerodyne Research Inc. Aerosol Mass Spectrometers (AMS) were used to calculate characteristic ΔOA/ΔCO ratios for different environments, accounting for the effects of dilution and contrasting fire sizes to give a proportional representation of OA production. High levels of variability in average ΔOA/ΔCO were observed both between and within different regions. The scale of this variability consistently exceeded any differences between plumes of different ages, while a widespread absence of any sustained increase in ΔOA/ΔCO with aging indicates that SOA formation does not provide a net increase in OA mass. Despite this lack of OA enhancement, increasing proportions of oxygenated OA components in aged plumes highlight the chemical transformations occurring during the evolution of BBOA, and the additional influence of OA loss through evaporation or deposition. Potential drivers of variability in ΔOA/ΔCO at source, such as changes in fuel types and combustion conditions, were investigated for controlled fires carried out within a combustion chamber. These laboratory experiments revealed a number of complex relationships between BB emissions and source conditions. Although ΔOA/ΔCO was shown to be influenced by both fuel properties and transitions between flaming and smouldering combustion phases, the extent of these effects was limited, while variability between fires exceeded levels observed for ambient measurements. These findings emphasise the complexity of the BBOA lifecycle and the need to address the extensive uncertainties associated with its various constituent processes, in order to improve understanding of eventual climate impacts from biomass burning.

Rapidly initiated at the national, regional, and local levels, the American glider pilot training program came about due to a perceived need after successful German operations at the outset of World War II. Although the national program successfully produced the required number of pilots to facilitate combat operations, numerous changes and improvisation came to characterize the program. Like other American military initiatives in the twentieth century, the War Department applied massive amounts of effort, dollars, and time to a program that proved to be short-lived in duration because it was quickly discarded when new technologies appeared. At the local level, the real loser was Lamesa, Texas. Bearing the brunt of these changes by military decision makers, the citizens of Lamesa saw their hard-fought efforts to secure an airfield fall quickly by the wayside in the wake of changing national defense priorities. As generations continue to pass and memories gradually fade, it is important to document and understand the relationship between this military platform that saw limited action and a small Texas town that had a similarly short period of significance to train the pilots who flew the aircraft.

Les Hydrocarbures Aromatiques Polycycliques (HAP) sont des polluants dont la concentration est réglementée dans l’air ambiant, en raison de leurs caractères cancérigène et/ou mutagène. Ces composés, émis lors de combustions incomplètes, peuvent réagir dans l’atmosphère avec les principaux oxydants atmosphériques pour former des dérivés oxygénés (OHAP) et nitrés (NHAP), dont la toxicité est potentiellement encore plus importante. Dans ce contexte, ce travail a été réalisé par la combinaison de deux approches complémentaires : études de réactivité en atmosphère contrôlée et études de terrain, afin de mieux comprendre le devenir (formation/dégradation) de ces composés dans l’atmosphère. Ainsi, des particules naturelles, prélevées dans l’air ambiant, ont été exposées en réacteur à différents oxydants atmosphériques(O3, OH et NO2/O3). Les résultats montrent la dégradation effective des HAP et le benzo[a]pyrène, seul HAP réglementé aujourd’hui en Europe, apparait comme le composé le plus réactif. De plus, la formation significative de OHAP et NHAP a été mise en évidence, même si les quantités observées sont trop faibles pour boucler le bilan de masse, illustrant la formation de produits non détectés/détectables dans ce travail. La dégradation des HAP ayant été démontrée sur des particules naturelles, la question du lieu majoritaire de dégradation (atmosphère/support de prélèvement) a été étudiée au cours de différents échantillonnages atmosphériques, mettant en parallèle des préleveurs équipés ou non de pièges à ozone de type dénudeur. Ces études, bien que n’ayant pas permis de répondre définitivement à cette question, ont montré la formation de certains dérivés de HAP sur les supports d’échantillonnage. Suite à ces conclusions, des mesures ont été déployées sur le terrain, sur des sites de typologies différentes dans la région parisienne. Les concentrations en HAP, OHAP et NHAP mesurées se sont avérées 10 fois plus importantes sur un site trafic que sur un site périurbain. De plus, les différentes espèces mesurées sur chacun des sites ont montré que, contrairement aux HAP et OHAP, les NHAP majoritaires différaient selon la typologie du site. Ainsi, le site trafic a été identifié comme étant majoritairement influencé par des sources primaires, à l’opposé du site périurbain sur lequel les espèces secondaires étaient plus abondantes. Les études granulométriques ont montré que la distribution entaille des OHAP et NHAP particulaires était liée à leurs origines (primaire/secondaire). De plus, les OHAP et NHAP apparaissent associés à 85 % à la fraction la plus fine de l’aérosol (Dp < 2,5 µm), accentuant l’intérêt de leur étude d’un point de vue sanitaire. Enfin, la combinaison de l’étude de la distribution granulométrique de certains composés identifiés comme primaire ou secondaire, à celle des profils chimiques des NHAP ouOHAP, a permis de proposer des pistes quant à l’origine majoritaire de ces familles de composés dans l’air ambiant
Polycyclic Aromatic Hydrocarbon (PAH) concentrations are regulated in ambient air because of theirmutagenic and carcinogenic properties. They are largely emitted by combustion processes and may react withmain atmospheric oxidants to form oxygenated (OPAH) and nitrated (NPAH) derivatives, which can be moretoxic than their parent PAHs. In this work, PAH derivatives were studied using the combination of twocomplementary approaches: laboratory reactivity experiments in controlled conditions and field studies, inorder to better understand their source and fate in the atmosphere. Reactivity study of PAHs adsorbed onnatural particles was carried out by exposing ambient particles to atmospheric oxidants (O3, OH and NO2/O3)in appropriate reactors. Large decays of PAH concentrations were observed, benzo[a]pyrene (B[a]P, which isthe only regulated PAH in Europe), appearing as the most reactive. The formation of OPAHs and NPAHs wasshowed. Nevertheless, quantities of both NPAHs and OPAHs formed were not sufficient to explain the totalamount of PAHs that react, highlighting the formation of other compounds, not detected in this work. PAHdegradation may occur in the atmosphere during the transport of air masses or directly on the filter during thesampling. The study of the major degradation processes was performed during field studies, using two highvolume samplers, one being equipped with an ozone scrubber. Even if, results were not enough to clearlyconclude about the relative importance of both degradation processes, the significant formation of some PAHderivatives on the sampling filter was observed. Then, field campaigns were led on different typologies ofsampling sites around Paris. PAH, OPAH and NPAH concentrations were about ten times higher at traffic sitethan at the suburban one. Moreover, for both OPAHs and PAHs, the major compounds were similar at bothsites, in contrary to the case of NPAHs that appeared different. The traffic site appeared strongly influenced byprimary emissions, whereas high amounts of secondary species were quantified at suburban site. Particle sizedistribution of OPAHs and NPAHs showed their strong association to the finest part of aerosols (Dp < 2.5 μm),highlighting the strong interest of this study considering sanitary impacts. Finally, the study of the particle sizedistribution of primary and/or secondary identified compounds, combined with chemical NPAH and OPAHprofiles, allowed to provide indications about the major origin of PAH derivatives in the atmosphere

L'augmentation importante de la population mondiale, et par conséquent de ses besoins, exerce une pression de plus en plus importante sur les surfaces forestières. L'outil le mieux adapté au suivi des forêts, à l'échelle du globe, est la télédétection. C'est dans ce contexte que se situe ce travail de thèse, qui vise à améliorer l'estimation des paramètres biophysiques des arbres à partir de données de télédétection. L'originalité de ce travail a été d'étudier cette estimation des paramètres biophysiques en menant plusieurs études de sensibilité avec une démarche expérimentale sur des données expérimentales et sur des données simulées. Tout d'abord, l'étude s'est portée sur des séries temporelles de mesures de diffusiométrie radar obtenues sur deux sites : l'un constitué d'un cèdre en zone tempérée et l'autre d'une parcelle de forêt tropicale. Puis, cette étude de sensibilité a été poursuivie en imageant, avec une résolution élevée, plusieurs parcelles aux configurations différentes à l'intérieur d'une forêt de pin. Enfin, des données optiques et radars simulées ont été fusionnés afin d'évaluer l'apport de la fusion de données optique et radar dans l'inversion des paramètres biophysiques.

The appearance and development of the Internet created a new paradigm in the marketing area, where companies are becoming increasingly focused on developing a customer centricity strategy in order to create a more engaging relationship with the customers. This Work Project aims to analyse, measure and evaluate the impact of PCDIGA’s communication channels and respective strategies to establish contact with their customers, namely through marketing campaigns via e-mail or social media platforms. According to the data collected and knowledge gathered, some recommendations, suggestion for improvements and initiatives were proposed in order to align with a customer-centric strategy.

Introduction: No standard method exists for enumerating fungal aerosols, impeding the development of reliable exposure-response data. A field comparison of four bioaerosol samplers, the Reuter Centrifugal Sampler (RCS), the Andersen N6 Single Stage (N6), the Surface Air System Super 90, and the Air-o-Cell sampler (AOC), was conducted in a variety of public buildings for the measurement of fungal aerosols to compare sampling performance efficiencies and to collect baseline data for a pool of buildings Methods: Sampling was conducted at 75 sites in public buildings from June-October 2001 in the greater Vancouver area, British Columbia. Four locations were sampled at each site (1 common area, 2 offices, and 1 outdoor sample). Each location was sampled in parallel, collecting approximately 150 litres of air for each sample. Malt extract agar was used for all growth media. Sequential duplicates were taken at each location. Fixedand mixed-effects regression models were constructed to examine the relationships between each method pair and to develop between-sampler calibration equations. Samplers were also scored and ranked on a combination of performance and other sampler characteristics. A survey of a panel of academics and consultants that regularly used bioaerosol sampling equipment for fungal aerosols was conducted to guide the comparison. Results: Data from approximately 592 samples (60 different buildings) were available for analysis from each instrument. Differences were found between samplers for overall yield, detection limits, and reproducibility. Fixed- and mixed-effect models indicated location of the sample to be a confounder in the relationship of all method pairs, and interaction was also found for all except the N6-RCS comparison. Six final models were suggested to serve as possible calibration curves to convert measurements made with one sampler to those made with another. Surveys from 10 professionals were available to weight the other sampler characteristics. The final ranking for this comparison had the N6 and AOC ranked highest and the SAS and RCS the lowest. Conclusions: Concentration data is dependent on the sampling methodology utilized for assessment and should be considered before conducting investigations of bioaerosols in different environments. Exposure guidelines cannot be created until a standard methodology is available.

Student Number : 9807515F - MSc Dissertation - School of Computational and Applied Mathematics - Faculty of Science
Statistical and algebraic techniques of subspace tracking were tested for filtering the earth’s response from airborne magnetic field gradients in order to discriminate the relatively small response (dipole) of objects on the earth’s surface, such as UXO. Filtering the data was not very effective with these methods but a subspace was found in the data for the magnitude of the magnetic moment of the dipole. This subspace is easily obtained using the singular value decomposition and can be used for an approximate location, without depth estimation, as well as the relative size of the dipole.

碩士
國立交通大學
機械工程系
89
The application of mini-environment clean room for the reduction and control of particulate contamination level has progressed from the development and evaluation stages to its current status as a preferred alternative for new high technology manufacturing facilities. Yield improvement, reduced operating cost, efficient use of floor space, reduced gowning cost, and great productivity are some of benefits derived from this technology. The objective of this research is to study the flow field and airborne particles control in non-rectangular mini-environment clean room by the computer software STAR-CD. The three-dimensional code used to predict the air velocity, concentration distribution and the particle traces based on a finite volume approach. The results prompted a design change. The new design is shown to have a desirable airflow for a more effective performance in mini-environment clean room. The traces of particles with different sizes are different in the same turbulent flow. And particular attention was paid to air re-circulation zones that could potentially trap particles generated during the process.

碩士
國立成功大學
測量工程學系碩博士班
92
Quick measurements of gravity over wide areas and no terrain limit are the superiority of the airborne gravimetry . The accuracy and error model of airborne gravity affected by methods of determining airborne gravity . 　　In the study , Kalman filter for determining airborne gravity disturbance vectors from airborne GPS/INS measurement data is applied , and furthermore , Least Squares Collocation is used to improve the accuracy . The results of the experiments have shown that the internal precision of the estimated gravity is about ±4mgal, and the external precision about ±8mgal.

The indirect effects of a nearby lightning strike on an airborne vehicle with its long trailing conducting plume is not well understood. Since airborne vehicles and its payload are expensive, their loss as a result of either a direct strike or due to the induced current and voltage of a nearby lightning strike is not desirable. The electromagnetic field generated due to the induced current on the skin of the vehicle may get coupled with the internal circuitry through the apertures on the vehicle body. If the coupled electromagnetic energy is more than the damage threshold level of the sensitive devices of the control circuit, they may fail which may lead to aborting the mission or a possible degradation in the vehicle performance. It has been reported that lightning induced phenomena was the cause of malfunctioning as well as aborting of some of the lunar missions. So in the present work, the computation of induced current and voltage on the skin of the vehicle body in the presence of an ionized long trailing exhaust plume has been attempted. The lightning channel is assumed to be vertical to the ground plane and extends up to a height of 7.5 km. The radiated electric and magnetic fields from the lightning channel at different heights from 10 m to 10 km and for lateral distances varying from 20 m to 10 km from the lightning channel are computed and the field waveforms are presented. For the computation of the radiated electric and magnetic fields from the lightning channel, modified transmission line with exponential current decay (MTLE) model for representing the lightning channel and the Heidler’s expression for the lightning channel base current are used. The peak amplitude of the lightning current used is 12 kA with a maximum current derivative of 40 kA/µs. It is seen that the vertical electric field in general, is bipolar in nature and that the height at which the change in polarity reversal takes place increases with increase of lateral distance from the lightning channel. The vertical electric field just above the ground is unipolar for all lateral distances from the channel and this is because the contribution due to the image of the lightning channel dominates the vertical electric field. The horizontal electric field is always unipolar for all heights and all lateral distances from the lightning channel studied. The effect of variation in the rate of rise of lightning current (di/dt) and the velocity of lightning current on the radiated electric and magnetic fields for the above heights and distances have also been studied. It is seen that the variation in maximum current derivative does not have a significant influence on the electric field when ground is assumed as a perfect conductor but it influences significantly the horizontal electric field when ground has finite conductivity. The velocity of propagation of lightning current on the other hand has a significant influence for both perfectly as well as finitely conducting ground conditions. For the computation of the induced current and voltage on the body of the airborne vehicle due to the coupling of the above mentioned electromagnetic fields radiated from a near by lightning discharge, the vehicle and its exhaust plume have been modeled as a transmission line and Finite Difference Time Domain (FDTD) numerical technique has been used for the computation. Regardless of the vehicle size, the structure can be modeled as a nonuniform transmission line consisting of a series of sections consisting of capacitive and inductive components. These components of the vehicle and its exhaust plume are computed using the Method of Moment (MoM) technique. The interaction of the electromagnetic wave with the plume depends on the electrical conductivity as well as the gas dynamic characteristics of the plume. Hence, in this research work an attempt has also been made to study the electrical conductivity (σe) and permittivity (εe) as well as the gas dynamic properties of the exhaust plume taking into consideration its turbulent nature. In general, the airborne vehicle can be considered as perfectly conducting (conductivity 3x107 S/m) where as the plume has finite conductivity. The electrical properties of an airborne vehicle exhaust plume such as electrical conductivity and the permittivity and their distribution along axial and radial directions depend on several factors. They are (i) propellant composition, (ii) impurity content in the propellants which generate ionic charge particles in the exhaust and (iii) the characteristics of the exhaust plume intensive parameters such as temperature, pressure, velocity and the presence of shock waves. These properties of the exhaust plume are computed in the two separate regions of interest as discussed next. The first region is inside the combustion chamber and up to the nozzle throat of the vehicle and the second region is from the throat to the exterior i.e., the ambient atmosphere or the downstream of the plume. In the first region where chemical reaction kinetics have to be considered, NASA Chemical Equilibrium with Application (CEA) software package has been used to compute the intensive parameters of the fluid at the throat of the nozzle. The pressure in the combustion chamber is taken as 4410 kPa and the back pressure at the exit plane is taken as 101.325 kPa. In the second region, FLUENT software package have been used for the fluid dynamic study of the exhaust plume from the vehicle nozzle throat to the exterior domain. The data obtained from the first region using CEA provides the parameters at the nozzle throat that are used as input parameters for the second region. In the study, a conical nozzle configuration of throat radius (rt) of 0.0185 m (nozzle exit plane radius is 0.05 m), half cone angle of 18º and nozzle expansion ratio (Ae/At) of 7.011 are used. The contour plot of the intensive parameters of the exhaust plume and the mass fraction of the charged particles are presented. The vehicle exhaust flow passes through different types of expansion and compression waves. In the present work, simulation is done for a slightly under expanded nozzle i.e. nozzle exit static pressure is slightly more than the ambient static pressure. Since the exit pressure is more than the ambient pressure, the exhaust gases expand to reach the ambient pressure. As the expansion waves reach the contact discontinuity (i.e. the boundary where the outer edge of the gas flow meets the free stream air), they again reflect back inward to create compression waves. These compression waves force the flow to turn back inward and increase its pressure. If the compression waves are strong enough, they will merge into an oblique shock wave. In the present work, more than eight such barrel shocks are captured. When the shock waves are generated, Mach number reduces sharply and static temperature and static pressure increases where as the total temperature of the exhaust remains constant in the shock wave formations. The characteristics of the plume such as pressure, temperature, velocity and concentration of the charged particles (i.e., e¯, Na+ and Cl¯) and neutral species such as CO, CO2 , Cl, H, HCl, H2O, H2 , N2, Na, NaCl, O, OH and O2 along axial and radial directions in the external domain have been studied. The above parameters are used to compute the collision frequencies and plasma frequencies of the charged particles as well as the number density of the species along axial and radial directions of the exhaust plume. These parameters are used to compute the effective conductivity distribution in the axial and radial directions for an incident electromagnetic field of frequency 1 MHz. The peak value of the conductivity computed is 0.12 S/m near the exit plane and it reduces to 0.02 S/m at an axial distance of 7.5 m from the exit plane which is well within the range suggested in the published literature. It has been observed that the oscillation in the conductivity along axial direction is a reflection of the shock wave formation in the exhaust plume. The electrical conductivity and the relative permittivity of the exhaust plume have been computed for three different radii of the nozzle at the exit plane i.e., 0.025 m, 0.05 m and 0.075 m. It is seen that the distribution of the conductivity and relative permittivity along the axial direction of the exhaust are independent of the nozzle exit plane radius. To study the coupling of lightning electromagnetic field with the vehicle and its exhaust plume two cases have been considered. These are (i) when the vehicle and its exhaust plume are at certain height above the ground and (ii) when the exhaust plume is touching the ground. The dimensions of the vehicle used in the study are as follows: length of the vehicle is 20 m and the length of its exhaust plume is 75 m. The radius of the vehicle is taken as 0.5 m. The vehicle and its exhaust plume are assumed to be at a lateral distance of 250 m from the lightning channel. In case one, when the vehicle and its inhomogeneous exhaust plume tip is at a height of 10 m above the ground, both the ends are open. So the reflection coefficients of the current wave and voltage wave at the end points are -1 and +1 respectively irrespective of the characteristic impedances of the vehicle and its exhaust plume. So when the reflected current propagates it will tend to reduce along the length of the object. Hence, the induced current at the end points are zero and the currents in the end segments are less than those in the intermediate segments. The spatial distribution of the peak magnitude of the time varying induced current, |Imax|, in each segment along the length of the vehicle without and with the exhaust plume are presented. In case of vehicle without plume, the maximum value of the induced current is at the middle segment of the vehicle and its value is 4.8 A. The presence of the inhomogeneous plume enhances the maximum value of the induced current to 33 A and its position is shifted to the exhaust plume side. When the voltage wave propagates, it will enhance the induced voltage in the vehicle body. The time varying potential difference between the end points of the vehicle without plume and the vehicle with its exhaust plume which drives the induced current are computed and it is seen that the potential difference for the vehicle without plume is unipolar whereas it is bipolar for the vehicle with exhaust plume. The lightning induced current on the skin of the vehicle will generate an electromagnetic field which may couple with the internal electronic devices and circuits through the apertures. The amount of electromagnetic energy that will be transmitted through an aperture on the vehicle skin and coupled with the internal electronic equipments depends on the characteristics of the induced current on the skin of the vehicle, the electrical size, shape, orientation and location of the aperture and the location of the internal electronic devices with respect to the aperture. So the time varying induced current and its di/dt at three different locations on the vehicle body i.e., tail of the vehicle, middle of the vehicle and vehicle nose are computed. It is seen that the induced current on the vehicle and its di/dt in the absence of the plume are oscillating in nature but they are critically damped in the presence of the trailing inhomogeneous exhaust plume. It also shows that the enhancement of induced current and its di/dt at the tail are much more than at the middle or at the nose of the vehicle which is true for an electrically short vehicle i.e., lv/λmin ≈ 0.067 as cited in the literature. So the presence of an aperture on the skin of the vehicle near to tail will transmit maximum electromagnetic energy into the inside of the vehicle. Therefore during design of the electrically short airborne vehicles, any aperture should be avoided near the tail of the vehicle or internal electronic devices should be placed away from the tail of the vehicle. In case 2, when the plume is touching the ground, the transient induced current in the plume will propagate into the soil. The effective impedance for smaller currents will be quite high (the inductance and capacitance effect are not taken into consideration for calculating the impedance. So the impedance of the soil is dominated by only the resistance). However, as soon as the current exceeds a certain value, the resulting soil gradient can reach the breakdown gradient of the soil i.e., 200-500 kV/m as cited in literature resulting in soil ionization. This will effectively lower the soil impedance. These dynamic characteristics of the soil resistance with induced current are incorporated by considering the expression for the soil resistance. To study the effect of soil resistivity on the time varying induced current and the voltage, computations have been done for various resistivities of the soil i.e., 0 Ωm, 100 Ωm and 200 Ωm. For soil resistivity of 0 Ωm, the reflection coefficients at the ground and at the open ends for the current wave are +1 and -1 respectively. So at the ground end, the reflected current wave will enhance and at the open end it will diminish as it propagates along the length of the vehicle and its exhaust. As the resistivity of the soil increases, the reflection coefficient of the current at the ground end decreases from +1, so the peak magnitude of the current reduces along the length till the length is half of the total length of the plume and the vehicle. Therefore, the peak magnitude of the induced current in the ground segment is much more than the peak magnitude of the current in the segment at the open end. For a finitely conducting plume, the peak value of the potential difference between the two ends of the vehicle and its exhaust plume are 92 kV, 91 kV and 90 kV for soil resistivities of 0 Ωm 100 Ωm and 200 Ωm respectively. Therefore the influence of the soil resistivity on the induced current is found to be not much significant. The spatial distribution of the peak magnitude of the time varying induced current in each segment along the length of the vehicle with inhomogeneous exhaust plume for the above three different soil resistivities are presented at a lateral distance of 250 m from the lightning channel. It is seen that when the plume is touching the ground, the induced current on the vehicle at the tail, middle and nose sections are marginally more than when the vehicle and its exhaust are at a height of 10 m above the ground. The effects of different parameters such as peak value and maximum di/dt of lightning current, velocity of lightning current, lateral distance of the vehicle from lightning channel and the height of the tip of the exhaust plume above the ground on the induced current and voltage on the airborne vehicle have also been studied. The peak amplitude of the lightning current used are 30 kA and 100 kA in addition to 12 kA mentioned earlier for the field computation. Also maximum di/dt values of 40 kA/µs and 120 kA/µs for the lightning current have been used for the computation. It is observed that the induced current increases with increase of the peak value, maximum di/dt as well as the velocity of propagation of the lightning current where as the induced current will reduce with increase of lateral distance and height of the tip of the exhaust plume above the ground. As an offshoot of the present work, the axial and radial distribution of the parameter, σe/ωεe (loss tangent of the exhaust plume) for an incident electromagnetic wave (lightning electromagnetic field) frequency of 1 MHz have been computed to study the conducting properties of the exhaust plume. σe/ωεe of the exhaust plume at 1 MHz frequency varies from 2324 to 365. Since σe/ωεe >>1, the plume behaves as a good conductor and the displacement currents can be neglected. In addition to this, the variation of parameter σe/ωεe for frequency ranges of 0.1 MHz to 5 GHz are also studied where σe and εe are the maximum effective conductivity and permittivity of the exhaust plume at the chosen frequency of an incident EM wave. It shows that the parameter σe/ωεe is 1.8x104 at 0.1 MHz and reduces to 0.45 for 5 GHz and its value is 1 at a frequency of 2.285 GHz. Therefore at lower EM wave frequency, the exhaust plume behaves as a good conductor and that conductivity reduces with increase of the frequency. The exhaust plume in the present study behaves as a good conductor below or at the EM wave frequency of 2.285 GHz. The microwave attenuation of electromagnetic wave through the ionized plume (the angle of incidence of microwave is 90o and transmission of microwave is always transverse to the exhaust plume) has also been studied using the above electrical characteristics computed and it is seen that the attenuation follows the axial variation in the conductivity of each cross section of the plume. In the present work, a theoretical model has also been developed to compute the microwave attenuation through the vehicle exhaust plume using the electrical conductivity computed earlier for any angle of incidence of the microwave. The thesis also lists some additional topics for further studies.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1998.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 180-198).

Society’s dependence on electronic and electrical systems has increased rapidly over the past few decades, and people are relying more and more on these gadgets in their daily life because of the efficiency in operation which these systems can offer. This has revolutionized many areas of electrical and electronics engineering including power sector, telecommunication sector, transportation and many other allied areas. With progress in time, the sophistication in the systems also increased. Also as the systems size reduced from micro level to nano level, the compactness of the systems increased. This paved the way for development in the digital electronics leading to new and efficient IC 0s that came into existence. Power sector also faced a resurge in its technology. Most of the analog meters are now replaced by digital meters. The increased sophistication and compactness in the digital system technology made it susceptible to electromagnetic interference especially from High Power Electromagnetic Sources. Communication, data processing, sensors, and similar electronic devices are vital parts of the modern technological environment. Damage or failures in these devices could lead to technical or financial disasters as well as injuries or the loss of life. Electromagnetic Interference (EMI) can be explained as any malicious generation of electromagnetic energy introducing noise or signals into electric and electronic systems, thus disrupting, confusing or damaging these systems. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the circuit. These effects can range from a simple degradation of data to a total loss of data. The source may be any object, artificial or natural, that carries rapidly changing electrical currents, such as an electrical circuit. The sources of electromagnetic interference can be either unintentional or intentional. The sources producing electromagnetic interference can be of different power levels, different frequency of operation and of different field strength. One such classification of these sources are the High Power Electromagnetic Sources (HPEM) High Power Electromagnetic environment refers to sources producing very high peak electromagnetic fields at very high power levels. These power levels coupled with the extremely high magnitude of the fields are sufficient to cause disastrous effects on the electrical and electronic systems. There has been a lot of developments in the field of the source technology of HPEM sources so that they are now one of the strongest sources of electromagnetic interference. High Power Electromagnetic environment refers to the sources producing very high peak electromagnetic fields at very high power levels. These power levels coupled with the extremely high magnitude of the fields are sufficient to cause disastrous effects on the electrical and electronic systems. HPEM environments are categorized based on the source characteristics such as the peak electric field, often called threat level, frequency coverage or bandwidth, average power density and energy content. The sources of electromagnetic interference can be either unintentional or intentional. Some examples of unintentional sources are the increased use of electromagnetic spectrum which generates disturbance to various systems operating in that frequency band, poor design of systems without taking care of other systems present nearby as well as lightning. Intentional sources are High altitude Electromagnetic Pulse (HEMP) or Nuclear Electromagnetic Pulse (NEMP) due to nuclear detonations, Ultra Wide Band (UWB) field from Impulse Radiating Antennas (IRA), Nar-row band fields like those coming from High Power Microwaves (HPM), High Intensity Radio Frequency (HIRF) sources. Of these the lightning is natural and all other sources are man-made. The significant progress in the Intentional High-Power Electromagnetic (HPEM) sources and antenna technologies and the easy access to simple HPEM systems for anyone entail the need to determine the susceptibility of electronic equipment as well as coupling of these fields with systems such as cables (buried as well as aerial), airborne vehicle etc. to these types of threats. Buried cables are widely used in the communication and power sectors due to their efficient functioning in urban cities and towns. These cables are more prone to electromagnetic interferences from HPEM sources. The buried communication cables or even the buried data cables are connected to sensitive equipments and hence even a slight rise in the voltage or the current at the terminals of the equipments can become a serious problem for the smooth operation of the system. In the first part of the thesis the effect of the electromagnetic field due to these sources on the cables laid underground has been studied. The second part of this thesis deals with the study of the interaction of the EM field from the above mentioned HPEM sources with an airborne vehicle. Airborne vehicle and its payload are extremely expensive so that any destruction to these as a result of the voltages and currents induced on the vehicle on account of the incoming HPEM fields can be quite undesirable. The incoming electromagnetic fields will illuminate the vehicle along its axis which results in the induction of currents and voltages. These currents and voltages will get coupled to the internal control circuits that are extremely sensitive. If the induced voltage/ current magnitude happen to be above the damage threshold level of these circuits then it will result in either a malfunction of the circuit or a permanent damage of it, with both of them being detrimental to the success of the mission. This will even result in the abortion of the mission or possible degradation of the vehicle performance. Hence it is worthwhile to see what will be the influence of an incoming HPEM electromagnetic field on the airborne vehicle with and without the presence of an exhaust plume. In this work, the HPEM sources considered are NEMP, IRA and HPM. The electromagnetic fields produced by the EMP can induce large voltage and current transients in electrical and electronic circuits which can lead to a possible malfunction or permanent damage of the systems. The electric field at the earth 0s surface can be modelled as a double exponential pulse as per the IEC standard 61000-2-9. The NEMP field incident on the earth’s surface is considered as that coming from a source at a distance far away from the earth’s surface; hence a plane wave approximation has been used. Impulse radiating antennas are the ones that are used as the major source of ultra wide band radiation. These are highly powerful antennas that use a pulsed power source as the input and this power source is conditioned to get an extremely sharp rise time pulse. These antennas are very high power antennas that are capable of producing a significant electromagnetic field. Impulse radiating antenna is a paraboloidal reflector and hence is an aperture antenna. Initially the radiated field due to this aperture needs to be found out at any observation point from the antenna. In this thesis, the aperture distribution method is used to accurately determine the field due to the aperture. In this method the field reflected from the surface of the reflector is first found on an imaginary plane through the focal point of the reflector that is normal to the axis of the reflector, by using the principles of geometrical optics, which then is extended to the observation point. The IRA considered for the present work is the one of the most powerful IRA as per the published literature available in the open domain. This has an input voltage of 1.025 MV. The far field electric field measured at the boresight (at r =85 m) being equal to 62 kV/m, and the uncorrected pulse rise time (10%-90%) is 180 ps for this IRA. HPM sources are usually electromagnetic radiators having a reflector with a horn antenna kept at their focal point for excitation. HPM sources generally operate in single mode or at tens or hundreds of Hz repetition rates. Many HPM radiators are developed in the world each with their own peculiar geometry and power levels. In the present thesis, a single waveguide (WR-975) fed HPM antenna assembly has been studied. The chosen waveguide has a cut-o_ frequency of 1 GHz and a power level of 10 GW. The wavelength associated with the waveguide is 0.3 m. The field pattern shows a definite peak in its response when the frequency is 1 GHz, the cut-off frequency of the waveguide. The electric field coming out of the HPEM sources travel through the medium that is either air alone or a combination of air and soil respectively depending upon whether the circuit on which the coupling is analysed is an airborne vehicle or an underground cable. The media plays a major role in the coupling, as the field magnitude is influenced by the characteristic properties of the media. As height increases the magnitude of the electric field decreases for all types of sources and also the time before which the field waveform starts is increased. The electric field in the soil is decided by the soil properties such as its conductivity and permittivity. The soil is modelled in frequency domain and the high frequency behaviour of soils is considered with its conductivity and permittivity taken as functions of frequency, as the incident field has high frequency components. A soil medium can be electromagnetically viewed as a four component dielectric mixture consisting of soil particles, air voids, bound water, and free water. When electric field is incident on the soil, it gets polarized. This is as a result of a wide variety of processes, including polarization of electrons in the orbits around atoms, distortion of molecules, reorientation of water molecules, accumulation of charge at interfaces, and electrochemical reactions. Whatever is the HPEM source, an increase in the soil conductivity results in an increased attenuation of the field. Also there is a significant loss of high frequency components in the GHz range in the field due to the selective absorption by the soil. This effect causes the percentage attenuation to be maximum for HPM and minimum for NEMP and IRA lying in between these two extremities. Increase in permittivity of the soil causes attenuation of the electric field for all HPEM sources. This is due to the relaxation mechanisms in the soil due to atomic- or molecular-scale resonances. The coupling of the electromagnetic fields due to HPEM sources is considered in the first phase. Two cables are considered (i) buried shielded and (ii) buried shielded twisted pair cables. The results are arrived at using the Enhanced Transmission Line model. The induced current is more for a shielded cable than a twisted pair cable of the same configuration. The induced current magnitude depends upon the type of the HPEM source, the depth of burial of the cable and the point on the cable where the current/ voltage is computed. Current is maximum at the centre of the cable for a matched termination and the voltage is the minimum at this point. The ratio of the induced current in the inner conductor with respect to the shield current of a shielded cable is the least for an HPM, and maximum for NEMP. This is due to the fact that higher frequencies are absorbed more by the shield of the cable. This affects HPM induced current the maximum and NEMP the least because of the presence of the lower frequency components in NEMP. Induced current in the twisted pair cable depends upon the number of pairs of the cable and the pitching of the cable. The electromagnetic field from the HPEM sources propagates with less attenuation in air due to the lower resistance this medium offers for electromagnetic wave propagation. Hence any system in air, be it electrical or electronic, will be under the strong illumination by these electromagnetic fields. As the second part of this thesis, the influence of the electromagnetic fields from all the three HPEM sources on an airborne vehicle in flight is analysed. For this part of study, the Electromagnetic (EM) fields radiated by all the three sources at different heights from the earth 0s surface have been computed. The coupling study has been done for the case of a vehicle with plume as well as without plume. For the second case, the electromagnetic modelling of the plume has been done taking into consideration its conductivity, which in turn depends on the different ionic species present in the plume. The species of the exhaust plume depends upon the chemical reactions taking place in the combustion chamber of the nozzle of the vehicle. The presence of the alkali metals as impurity in the airborne vehicle propellant will generate considerable ion particles such as Na+, Cl in addition to e- in the plume mixture during combustion which makes the plume electrically conducting. But it does not influence the pressure, temperature and velocity of the plume. After the nozzle throat, the exhaust plume regains the supersonic speed, so the flow of the exhaust plume is assumed as compressible flow in the second region. The electrons have high collision frequency, high number density, high plasma frequency and lower molecular mass and hence the highly mobile electrons dominate the heavy ion particle in the computation of the electrical conductivity of the plume. The plume conductivity decreases marginally from the axis till a distance equal to the nozzle radius but the peak value increases sharply towards the exit plane edge of the nozzle radius. The induced current is computed using Method of Moments. The induced current depends upon the type of interference source, its characteristics, whether the plume is present or not and the type of the plume. The HPM induces maximum current in the vehicle because of the fact that the plume has a tendency to become more conductive at these frequencies. The induced currents due to the EM fields from IRA and NEMP comes after the HPM. The presence of the plume enhances the magnitude of the induced current. If the plume is homogeneous then the current induced in it is more.