Дисертації з теми "Extinction methods"

Phylogenetic diversity (PD) is a measure of species biodiversity quantified by how much of an evolutionary tree is spanned by a subset of species. In this thesis, we study optimization problems that aim to find species sets with maximum PD in different scenarios, and examine random extinction models under various assumptions to predict the PD of species that will still be present in the future. Optimizing PD with Dependencies is a combinatorial optimization problem in which species form an ecological network. Here, we are interested in selecting species sets of a given size that are ecologically viable and that maximize PD. The NP-hardness of this problem is proved and it is established which special cases of the problem are computationally easy and which are computationally hard. It is also shown that it is NP-complete to decide whether the feasible solution obtained by the greedy algorithm is optimal. We formulate the optimization problem as an integer linear program and find exact solutions to the largest food web currently in the empirical literature. In addition, we give a generalization of PD that can be used for example when we do not know the true evolutionary history. Based on this measure, an optimization problem is formulated. We discuss the complexity and the approximability properties of this problem. In the generalized field of bullets model (g-FOB), species are assumed to become extinct with possibly different probabilities, and extinction events are independent. We show that under this model the distribution of future phylogenetic diversity converges to a normal distribution as the number of species grows. When extinction probabilities are influenced by some binary character on the tree, the state-based field of bullets model (s-FOB) represents a more realistic picture. We compare the expected loss of PD under this model to that under the associated g-FOB model and find that the former is always greater than or equal to the latter. It is natural to further generalize the s-FOB model to allow more than one binary character to affect the extinction probabilities. The expected future PD obtained for the resulting trait-dependent field of bullets model (t-FOB) is compared to that for the associated g-FOB model and our previous result is generalized.

We study the integral Galactic extinction and reddening based on the galaxy catalog of the South Galactic Cap u-band Sky Survey (SCUSS), where u-band galaxy number counts and u - r color distribution are used to derive the Galactic extinction and reddening respectively. We compare these independent statistical measurements with the reddening map of Schlegel et al. (SFD) and find that both the extinction and reddening from the number counts and color distribution are in good agreement with the SFD results at low extinction regions (E(B - V)(SFD) < 0.12 mag). However, for high extinction regions (E(B - V)(SFD) > 0.12 mag), the SFD map overestimates the Galactic reddening systematically, which can be approximated by a linear relation Delta E(B - V)= 0.43[ E(B - V)(SFD) - 0.12]. By combining the results from galaxy number counts and color distribution, we find that the shape of the Galactic extinction curve is in good agreement with the standard R-V = 3.1 extinction law of O'Donnell.

Interstellar extinction and reddening are inescapable sources of uncertainty in the study of astronomical objects. Many creative ways to measure its effects have been developed, two of them being evaluated in this study. I apply two recently improved methods to estimate extinction toward individual stars, one based on interstellar absorption of sodium and the other based on opacity maps of the interstellar medium. The methods are applied to 14 stars in the local neighborhood, all within a distance of 250 pc from the Sun, and their results are compared. I find that both methods have severe limitations and large uncertainties, but can still be useful under the right conditions. I also provide suggestions on how the methods can be improved.
Interstellär extinktion och rödfärgning är oundvikliga osäkerhetskällor i studiet av astronomiska objekt. Många kreativa sätt att mäta dess effekter har utvecklats, av vilka två utvärderas i denna studie. Jag tillämpar två nyligen förbättrade metoder för att uppskatta utsläckning mot enskilda stjärnor, en baserad på interstellär absorption av natrium och den andra baserad på opacitetskartor över det interstellära mediet. Metoderna tillämpas på 14 stjärnor i solens närområde, alla inom ett avstånd av 250 pc, och deras resultat jämförs. Jag finner att båda metoderna har allvarliga begränsningar och stora osäkerheter, men ändå kan vara användbara under rätt förutsättningar. Jag ger också förslag på hur metoderna kan förbättras.

Thesis (MScEng)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Water flows required for fire protection (fire flows) from water distribution systems (WDS) in rural towns in the Western Cape Province, South Africa, were evaluated as part of this research project. The fire flow requirements specified in different South African guidelines, as well as a number of international standards, were compared. Various guidelines and codes used in South Africa, including the South African National Standards, specify fire flow requirements according to the risk category of the area concerned. Alternative methods of firefighting and new firefighting technologies that can reduce the reliance on potable water resources for firefighting were evaluated. The traditional method of designing a WDS to provide potable water for firefighting, commonly employed in South African municipal areas formed the focus of the study. The potential fire risk costs (potential costs of damages if a fire was to occur) should also be considered, in addition to the network construction costs, when designing a WDS, in order to determine the most economically feasible option. Data obtained from the fire departments of three municipalities in rural towns of the Western Cape, was analysed to determine the actual flow rates that were required to extinguish fires in these towns. The records considered covered approximately one year in each case and included a total of 564 fire incident reports suitable for this study. According to the data, a small fraction (11%) of the fires was extinguished using water from the WDS by connecting firefighting equipment directly to a fire hydrant. The majority of the fires were extinguished by means of water ejected from a firefighting vehicle. This method implies the use of water drawn from the potable network at a certain location; the water is shuttled by firefighting vehicles, from either the fire station or from a central abstraction point in the WDS. The location of the said abstraction point was found to have a notable impact on the WDS and this received attention in this study. The data showed that 99.8% of the flows required in rural towns were lower than the flows recommended for moderate risk areas in typical South African guidelines. Hydraulic modelling of a hypothetical WDS model was conducted to illustrate that the provision of fire flows according to commonly used South African fire flow standards leads to higher costs. The latter hypothetical case study illustrates that designing a network to provide fire flows according to the referred standards resulted in 15% higher costs, compared to designing a network that would have provided for the actual recorded fire flows according to the data set obtained from the selected rural towns compiled for this study. The hypothetical case study also showed that the cost for a WDS, where sufficient pressure is required at all hydrants during peak fire flows, is 2.4% higher than the cost for a distribution system where water is supplied via predetermined hydrants for refilling firefighting vehicles. A WDS with central, predetermined abstraction points for refilling firefighting vehicles offers a solution to providing fire flows in areas where the distribution systems may be inadequate. The revision of the current fire flow standards of South Africa would, therefore, be a logical next step along with the reassessment of methods used for supplying fire flows.
AFRIKAANSE OPSOMMING: Water vloei vir brandbestryding (brandvloei) uit waterverspreidingstelsels (WVS) in plattelandse dorpe in die Wes-Kaap, Suid Afrika, is as deel van hierdie navorsingsprojek geëvalueer. Die brandvloei soos gespesifiseer in verskillende Suid-Afrikaanse riglyne, asook ʼn aantal internasionale standaarde is vergelyk. Verskeie riglyne en kodes wat in Suid-Afrika gebruik word, insluitende die Suid-Afrikaanse Nasionale Standaarde, spesifiseer brandvloei-vereistes op grond van die risiko-kategorie van ʼn spesifieke gebied. ʼn Verskeidenheid alternatiewe metodes vir brandbestryding en nuwe brandbestrydings-tegnologieë is ondersoek, om sodoende die afhanklikheid van ons beperkte drinkbare waterbronne vir brandbestryding te verminder. Die tradisionele metode om water aan munisipale areas te voorsien, die gebruik van ʼn WVS, is ook geassesseer. Hierdie metodes dui daarop dat die potensiële brandgevaar-kostes (potensiële koste van skade indien ʼn brand sou plaas vind) ook in ag geneem moet word, tesame met die konstruksie kostes van ʼn WVS, om sodoende die mees ekonomies haalbare netwerk te bepaal. Data wat verkry is vanaf die brandweer departement van drie plattelandse munisipaliteite in die Wes-Kaap is ontleed om die werklike vloei-tempos vas te stel wat nodig was om brande te blus in hierdie dorpe. Die data is verkry vir ʼn tydperk van een jaar en 564 brandverslae was bruikbaar vir die doeleindes van hierdie studie. Volgens die data was ʼn lae aantal (11%) van die brande geblus vanuit die WVS deur die koppeling van brandbestrydingstoerusting direk aan ʼn brandkraan. Die meeste van die brande is geblus met behulp van water wat voorsien is deur ʼn brandbestrydingsvoertuig. Met hierdie metode word water deur die brandbestrydings-voertuie aangery vanaf die brandweerstasie of onttrek vanuit ʼn sentrale ontrekkingspunt in die WVS. Daar is gevind dat die ligging van laasgenoemde ontrekkingspunt ʼn beduidende impak op die WVS het – hierdie aspek is daarom verder ondersoek. Die data het getoon dat 99.8% van die vloei-tempo’s wat nodig is om brande te blus in plattelandse dorpe, laer is as die brandvloei riglyne vir matige risiko-areas volgens tipes Suid-Afrikaanse standaarde. Hidrouliese modellering van ʼn hipotetiese WVS is uitgevoer om te illustreer dat die verskaffing van brandvloei volgens die standaarde wat algemeen gebruik word, hoër kostes tot gevolg het. Die laasgenoemde hipotetiese gevallestudie illustreer dat ʼn netwerk ontwerp om brandvloei te verskaf volgens die huidige standaarde 15% duurder is as vir netwerke wat ontwerp is om die werklike aangetekende brandvloei te voorsien soos getoon deur die veld-data wat vir hierdie studie verkry is. Die hipotetiese gevallestudie het ook getoon dat die koste vir ʼn WVS, waar voldoende drukke gehandhaaf moet word by alle brandkrane terwyl piek brand vloeie voorsien word, 2.4% duurder is as vir ʼn WVS waar die brandvloei verskaf word by voorafbepaalde brandkrane vir die hervulling van brandbestrydingsvoertuie. ʼn WVS met sentrale onttrekkingspunte vir die hervulling van brandbestrydingsvoertuie, bied ʼn metode om brandvloei te voorsien in gebiede waar die WVS onvoldoende is, bv. informele nedersettings. Die hersiening van die huidige brandvloei standaarde van Suid Afrika sou dus ʼn logiese volgende stap wees, tesame met die herevaluering van die metodes wat gebruik word vir die verskaffing van brandvloei.

Habitat loss and fragmentation are believed to be two of the main reasons for high extinction rates of species, resulting in decreased biodiversity. According to the island biogeography theory, the species richness in a patch, here a semi-natural grassland, is dependent on the landscape composition, and therefore changes in the landscape composition will result in changes in the species richness of the grassland. However, this change in species richness may be delayed for several years, causing an extinction debt. The aim of this study was to examine the change of species richness of vascular plants in Swedish semi-natural grasslands between 2007 and 2020 and investigate if there is evidence of an extinction debt and evaluate what factors causes changes in the plant community. Data of species richness and occurrence for 40 semi-natural grasslands, as well as data of landscape changes in area and connectivity between the 1950:s and the 2000:s for these grasslands, were analysed. This study found that changes in species richness in semi-natural grasslands were affected by the changes in connectivity of the landscape. However, the effect depended on the degree of specialisation of the species to semi-natural grassland. Between 2007 and 2020, the species richness of semi- natural grasslands specialist decreased, while the species richness of non-specialist species increased. This resulted in a mean increase of overall species richness between 2007 and 2020. Observed immigration of new non-specialist species appears to suggest that, not only the connectivity, but also the habitat types in the matrix surrounding the semi-natural grasslands may substantially influence the species composition in the grassland; this is in contrast to what is predicted by the original theory of island biogeography. Species that were classified as specialist were more vulnerable to ceased management, such as grazing, than to area and connectivity decrease. This was likely because the ceased management increased the competition for light. The results also indicated that re-established management of abandoned grasslands may increase specialist species richness, highlighting the need for management actions taken in order to reverse extinction debt.

Le but de ce travail est de déterminer par méthodes optiques la distribution de taille (pdf) des nanoparticules de suie, agrégats de morphologie fractale. Après des études préliminaires qui utilisent DDSCAT pour valider la théorie RDG-FA et permettent de convertir un rayon de giration en rayon de mobilité, deux diagnostics optiques sont étudiés. Le premier consiste à exploiter une mesure d'extinction spectrale de la lumière. Nous montrons que pour exploiter ce signal, il faut connaître les propriétés optiques des suies, leur préfacteur et dimension fractale, la loi de distribution et le diamètre des sphérules primaires. Le second diagnostic tire parti de la mesure angulaire de la diffusion de la lumière. Nous montrons qu'il est possible de déterminer la pdf à l'aide de la mesure de diffusion à trois angles. Il faut supposer la loi de distribution et la dimension fractale. Cette deuxième approche, in-situ, est plus appropriée que la première pour déterminer optiquement la pdf des suies.

Branching processes are stochastic processes describing the evolution of populations of individuals which reproduce and die independently of each other according to specific probability laws. We consider a particular class of branching processes, called Markovian binary trees, where the lifetime and birth epochs of individuals are controlled by a Markovian arrival process.

Our objective is to develop numerical methods to answer several questions about Markovian binary trees. The issue of the extinction probability is the main question addressed in the thesis. We first assume independence between individuals. In this case, the extinction probability is the minimal nonnegative solution of a matrix fixed point equation which can generally not be solved analytically. In order to solve this equation, we develop a linear algorithm based on functional iterations, and a quadratic algorithm, based on Newton's method, and we give their probabilistic interpretation in terms of the tree.

Next, we look at some transient features for a Markovian binary tree: the distribution of the population size at any given time, of the time until extinction and of the total progeny. These distributions are obtained using the Kolmogorov and the renewal approaches.

We illustrate the results mentioned above through an example where the Markovian binary tree serves as a model for female families in different countries, for which we use real data provided by the World Health Organization website.

Finally, we analyze the case where Markovian binary trees evolve under the external influence of a random environment or a catastrophe process. In this case, individuals do not behave independently of each other anymore, and the extinction probability may no longer be expressed as the solution of a fixed point equation, which makes the analysis more complicated. We approach the extinction probability, through the study of the population size distribution, by purely numerical methods of resolution of partial differential equations, and also by probabilistic methods imposing constraints on the external process or on the maximal population size.

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Les processus de branchements sont des processus stochastiques décrivant l'évolution de populations d'individus qui se reproduisent et meurent indépendamment les uns des autres, suivant des lois de probabilités spécifiques.

Nous considérons une classe particulière de processus de branchement, appelés arbres binaires Markoviens, dans lesquels la vie d'un individu et ses instants de reproduction sont contrôlés par un MAP. Notre objectif est de développer des méthodes numériques pour répondre à plusieurs questions à propos des arbres binaires Markoviens.

La question de la probabilité d'extinction d'un arbre binaire Markovien est la principale abordée dans la thèse. Nous faisons tout d'abord l'hypothèse d'indépendance entre individus. Dans ce cas, la probabilité d'extinction s'exprime comme la solution minimale non négative d'une équation de point fixe matricielle, qui ne peut être résolue analytiquement. Afin de résoudre cette équation, nous développons un algorithme linéaire, basé sur l'itération fonctionnelle, ainsi que des algorithmes quadratiques, basés sur la méthode de Newton, et nous donnons leur interprétation probabiliste en termes de l'arbre que l'on étudie.

Nous nous intéressons ensuite à certaines caractéristiques transitoires d'un arbre binaire Markovien: la distribution de la taille de la population à un instant donné, celle du temps jusqu'à l'extinction du processus et celle de la descendance totale. Ces distributions sont obtenues en utilisant l'approche de Kolmogorov ainsi que l'approche de renouvellement.

Nous illustrons les résultats mentionnés plus haut au travers d'un exemple où l'arbre binaire Markovien sert de modèle pour des populations féminines dans différents pays, et pour lesquelles nous utilisons des données réelles fournies par la World Health Organization.

Enfin, nous analysons le cas où les arbres binaires Markoviens évoluent sous une influence extérieure aléatoire, comme un environnement Markovien aléatoire ou un processus de catastrophes. Dans ce cas, les individus ne se comportent plus indépendamment les uns des autres, et la probabilité d'extinction ne peut plus s'exprimer comme la solution d'une équation de point fixe, ce qui rend l'analyse plus compliquée. Nous approchons la probabilité d'extinction au travers de l'étude de la distribution de la taille de la population, à la fois par des méthodes purement numériques de résolution d'équations aux dérivées partielles, ainsi que par des méthodes probabilistes en imposant des contraintes sur le processus extérieur ou sur la taille maximale de la population.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

Dans le cadre de ses études sur la détonique, le CEA de Gramat s'intéresse à la dispersion de liquides dans l'air, avec des contraintes de haute vitesse/énergie, et des aspects multi-échelles. La mesure de la granulométrie du liquide dispersé suscite un vif intérêt et s'avère complexe car aucune solution commerciale n'est utilisable dans ces conditions particulières. Toutefois, dans ces conditions et avec l'impossibilité d'utiliser des sources laser en environnement pyrotechnique, aucune solution commerciale n'est disponible. Pour ce travail de thèse, une nouvelle méthode d'identification de la granulométrie a donc été développée, et se base sur une mesure dite "par extinction", particulièrement simple de déploiement et robuste en environnement sévère. Il s'agit d'une approche multispectrale (mesure avec des caméras ou un spectromètre) faisant appel à une méthode d'inversion régularisée au sens de Tikhonov, s'appuyant sur la mesure de transmissions spectrales, et qui permet de reconstruire la granulométrie de ce dernier a posteriori à l'aide de la loi de Beer-Lambert combinée au modèle de Mie. De par la complexité des phénomènes liée à l'usage d'explosif pour la dispersion, la méthode développée a été testée sur des dispersions de liquide reproduites à petite échelle sur des sprays. La méthode générale a été développée en exploitant les informations spectrales provenant de sprays d'eau contrôlés et confinés dans une enceinte placée dans un spectromètre infrarouge à transformée de Fourier (haute résolution). Cependant, cet appareillage étant peu adapté aux conditions terrain, la méthode de mesure a été dégradée en utilisant des caméras permettant des mesures à "faible résolution" mais plus rapides. Ainsi, l'utilisation d'une caméra infrarouge opérant en bande spectrale 2-5 µm avec des filtres spectraux et d'un corps noir plan a été testée pour suivre l'évolution de granulométrie du spray en fonction du temps. Par la suite, cette méthode a pu être appliquée à des dispersions d'eau par explosif et a fourni des résultats prometteurs. La démarche complète de mesure et d'analyse a donc pu être validée à chaque étape de l'étude
As part of its studies on detonation, the CEA at Gramat is interested in the dispersion of liquids in air, with high speed/energy constraints and multi-scale aspects. Measuring the particle size of the dispersed liquid is attracting a great deal of interest, but is proving complex because no commercial solution can be used under these particular conditions. However, under these conditions and given the impossibility of using laser sources in a pyrotechnic environment, no commercial solution is available. For this thesis, a new granulometry identification method was developed, based on a measurement known as "extinction", which is particularly easy to deploy and robust in harsh environments. This is a multispectral approach (measurement with cameras or a spectrometer) using a regularised inversion method in the sense of Tikhonov, based on the measure of spectral transmissions and which makes it possible to reconstruct the granulometry of the latter a posteriori using the Beer-Lambert law combined with the Mie model. Given the complexity of the phenomena involved in using explosives for dispersion, the method developed was tested on liquid dispersions reproduced on a small scale on sprays. The general method was developed by exploiting spectral information from controlled water sprays confined in an enclosure placed in a Fourier transform infrared spectrometer (high resolution). However, as this equipment is poorly suited to field conditions, the measurement method was downgraded by using cameras that allow "low resolution" but faster measurements. The use of an infrared camera operating in the 2-5 µm spectral band with spectral filters and a flat black body was therefore tested to monitor changes in spray particle size as a function of time. This method was subsequently applied to water dispersions using explosives, with promising results. The complete measurement and analysis process was therefore validated at each stage of the study

One of the challenges facing engineers is to provide clean, sustainable, affordable and reliable electricity. One of the major pollutants associated with coal combustion is CO2. A proposed technology for efficiently capturing CO2 while producing electricity is pressurized oxy-combustion (POC). The first objective of this work is to design, build and demonstrate an exhaust system for a 20 atmosphere oxy-coal combustor. The second objective of this work is to design and build mounts for a two-color laser extinction method in the POC. The POC reactor enables the development of three key technologies: a coal dry-feed system, a high pressure burner, and an ash management system. This work focuses on cooling the flue gas by means of a spray quench and heat exchanger; controlling the reactor pressure and removing ash from the flue gas. Designs and models of each component in the exhaust systems are presented. Methods to test and assemble each system are also discussed. The spray quench flow rate was measured as a function of pump pressure. Theoretical models for the required amount of water in the spray quench, the flue gas composition, the length and number of tubes in the heat exchanger, and the cyclone collection efficiency are presented. The combined exhaust system is assembled and ready to be tested once issues involving the control system and burner are resolved.

With the rapid development of the industry all over the world, the consumption of fossil fuel of human activities has reached an extremely high level which result in an incredible dust emission level nowadays. As one of the major environment challenges today, dust pollution has become a vital issue that the human beings have to face and resolve.    To tackle the dust pollution problem, a reliable measurement of the dust concentration level is essential. In recent years, methods with different principles are used to detect the dust concentration have been developed. The methods developed based on the scattering principle and the extinction principle for dust concentration measurement have a series of virtues such as high measurement speed, excellent precision and can be useful for real time monitoring.    This thesis reviewed the popular theories that are applied in the field which are light scattering (Mie theory) and light extinction (Lambert-beer theory). Matlab simulation is used to verify the possibility of the determined physical quantities related to the concentration measurement in the theory analysis. A new method using the ratio of scattering intensity and extinction intensity is discussed in this thesis providing a more accurate result eliminating the drawbacks of the scattering method and the extinction method.

*‘Pasja’ (Brassica campestris x napus) and kale (Brassica oleracea var. acephala L.) were grown at Lincoln, Canterbury, New Zealand in 2008 with different levels of phosphorus (P) fertiliser. Banded or broadcast P fertiliser was applied at 0, 20, 40 and 60 kg P/ha at establishment. Total dry matter (DM) production, the proportion of the leaf and stem and leaf area development were measured over time and related to the biophysical environment. For ‘Pasja’, final DM increased with P rate from 3730 kg DM/ha to ~4900 kg DM/ha at 60 kg P/ha. For kale the increase was from 8710 kg DM/ha for the control to ~11000 kg DM/ha for all P treatments. The leaf to stem ratio declined from 22-31 at 17 days after emergence to 10.4 at the final harvest for ‘Pasja’, which meant the crop was effectively made up mainly of leaf (~90%). The ratio for kale declined from 2.7 at 24 days after emergence to 0.64 at the final harvest. The leaf to stem ratio for both species did not respond to either the method of application or rate of P. Seedling DM accumulation increased with applied P over the first 10 to 17 DAE for ‘Pasja’ and kale respectively. The crops went from shoot growth priority to root growth. The phyllochron of both species was unaffected by P application but responded linearly to the temperature above 0°C. For ‘Pasja’ the phyllochron was 60°Cd compared with 109°Cd for kale. As a consequence ‘Pasja’ developed its canopy and reached critical leaf area index (LAIcrit) earlier than kale. Leaf area index (LAI) for the control crops of both species was lower than for P fertiliser treatments with a maximum of 3.6 for ‘Pasja’ and 3.8 for kale. There was no difference in leaf area indices among the P fertiliser treatments for ‘Pasja’, while kale LAI differed with the rate of P application up to 40 kg P/ha. Total accumulated intercepted solar radiation (RIcum) was 8 and 11% greater for ‘Pasja’ and kale crops respectively when P was applied compared with the control. Thus, the difference in total dry matter yield due to P application was attributed to the difference in RIcum. Neither the method of application or rate of P applied affected the radiation use efficiency (RUE) of either crop. For ‘Pasja’ the RUE was 1.1 g DM/MJ PAR and for kale 1.33 g DM/MJ PAR. Based on this research, it was concluded that P application increased RIcum as a result of increased LAI. The difference in total DM yield was attributed to differences in RIcum. It is recommended that farmers growing ‘Pasja’ and kale under similar conditions to this experiment should apply 40 kg P/ha for ‘Pasja’ and band 20 kg P/ha for kale. *‘Pasja’ is considered both as a species and cultivar in this document as it marketed as such in New Zealand. Technically ‘Pasja’ is a leaf turnip.

In this study, first a necessary background is provided to readers. Then a novel approach to stochastically perturb the disease transmission coefficient was investigated, which is a key parameter in susceptible-infected-susceptible (SIS) models. Motivated by the papers [5] and [2], the disease transmission coefficient was perturbed with a Gaussian white noise, formally modelled as the time derivative of a mean reverting Ornstein-Uhlenbeck process. It has been remarked that, thanks to a suitable representation of the solution to the deterministic SIS model, this perturbation is rigorous and supported by a Wong- Zakai approximation argument that consists in smoothing the singular Gaussian white noise and then taking limit of the solution from the approximated model. It has been proven that the stochastic version of the classic SIS model obtained this way preserves a crucial feature of the deterministic equation: the reproduction number dictating the two possible asymptotic regimes for the infection, i.e. extinction and persistence, remains unchanged. Then the class of perturbing noises for which this property holds were identified and propose simple sufficient conditions for that. All the theoretical discoveries are illustrated and discussed with the help of several numerical simulations.

Theorie auto-coherente de la diffraction par un cristal statistiquement deforme en remplacant le cristal etudie par un cristal modele donnant le meme spectre de diffraction. Pour le cristal reel, deux solutions sont envisagees: solution analytique pour un cristal qui a la forme d'une plaquette, infinie dans la geometrie de transmission; solution numerique pour un cristal de forme convexe qui peut etre remplace par une sphere

Radars, as the name suggests, were traditionally used for Radio Detection and Ranging. Nevertheless, advances in high resolution electromagnetic simulations, Ultra Wide-Band sources, signal processing and computer technologies have resulted in a possible perception of radars as sensors for target discrimination. In this thesis, the feasibility of discrimination between targets even with minor variations in structure and material composition on the basis of radar echoes is effectively demonstrated. It is well-known that the echoes from any target are affected by its natural frequencies which are dependent only on the shape and material composition of the target, and independent of the aspect angle or the incident waveform. The E-pulse technique is based on the fact that incident waveforms can be designed that uniquely annihilate the echoes from chosen regions of a target, and forms the basis of the method of discrimination proposed in this thesis. Earlier methods reported in the literature, effectively discriminated only between different classes of targets with substantial variations in the overall dimensions of the body. Discrimination of targets of the same class with a minor structural modification or with a material coating on specific areas was rather difficult. This thesis attempts and successfully validates a method which comprehensively addresses this problem. The key idea of this method is to use the higher frequency resonances (which characterise the finer details of a target) in the E-pulse technique. An obviously important aspect of target discrimination is therefore that of precisely estimating the natural frequencies for each target and understanding the changes in these frequencies, and their associations with the changes in structure and material composition. Current approaches to determine these frequencies are either based In the time or frequency domains. While the latter approach comprises the computation of the roots of a related determinantal equation, in the time domain, the natural frequencies are extracted from the response of a target to an impulse. Such a response can either be generated from actual experiments or by simulating the scattering response using Computational Electromagnetic (CEM) techniques. In this work, the impulse response is obtained from the frequency response of the scatterers in the frequency range of interest. Since no single CEM technique can effectively cover the entire range of frequencies needed for the E-Pulse synthesis. The Method of Moments and Physical Optics have been used for low and high frequency scattering respectively. The results obtained using the latter technique are validated by comparing with those obtained using Method of Moments at the transition frequencies and Geometrical Theory of Diffraction (GTD). The natural frequencies (i.e., poles of a corresponding transfer function) are extracted from the impulse response using Prony's algorithm. One of the parameters in this method is the number of such poles (i.e.. the order of the transfer function) present in the response, and the accuracy of the computed pole values depends on this assumed order. Here, the Hankel singular values of a transfer function is used to estimate the number of poles. This in turn implies that a specific norm of the error between a transfer function corresponding to the frequency response generated earlier, and a transfer function with an assumed order obtained using Prony's method is minimised. In the thesis, a wide range of target shapes are considered for purposes of illustration: wires, cylinders, spheres, plates and complex bodies such as aircraft, and the discrimination capability is demonstrated by introducing minor perturbations in their shape and/or material composition. .The following cases are considered here: (a) Wires: Conducting wires with a protrusion in one segment; conducting wire from another coated with a dielectric in a segment, (b) Cylinders: Conducting cylinders with one perturbed; conducting cylinders with a portion scrapped off in the middle, (c) Plates: Conducting plates with a elongation on one comer; conducting plate with another one with a hole in the centre, (d) Spheres: Conducting spheres with different radii; conducting spheres with Radar Absorbing Material coated spheres with different coating thickness; conducting spheres with chiral coated spheres with varying coating thickness, (e) Aircraft: Canonical model of MiG-29 aircraft from a similar one with stores placed under the wing.

Radars, as the name suggests, were traditionally used for Radio Detection and Ranging. Nevertheless, advances in high resolution electromagnetic simulations, Ultra Wide-Band sources, signal processing and computer technologies have resulted in a possible perception of radars as sensors for target discrimination. In this thesis, the feasibility of discrimination between targets even with minor variations in structure and material composition on the basis of radar echoes is effectively demonstrated. It is well-known that the echoes from any target are affected by its natural frequencies which are dependent only on the shape and material composition of the target, and independent of the aspect angle or the incident waveform. The E-pulse technique is based on the fact that incident waveforms can be designed that uniquely annihilate the echoes from chosen regions of a target, and forms the basis of the method of discrimination proposed in this thesis. Earlier methods reported in the literature, effectively discriminated only between different classes of targets with substantial variations in the overall dimensions of the body. Discrimination of targets of the same class with a minor structural modification or with a material coating on specific areas was rather difficult. This thesis attempts and successfully validates a method which comprehensively addresses this problem. The key idea of this method is to use the higher frequency resonances (which characterise the finer details of a target) in the E-pulse technique. An obviously important aspect of target discrimination is therefore that of precisely estimating the natural frequencies for each target and understanding the changes in these frequencies, and their associations with the changes in structure and material composition. Current approaches to determine these frequencies are either based In the time or frequency domains. While the latter approach comprises the computation of the roots of a related determinantal equation, in the time domain, the natural frequencies are extracted from the response of a target to an impulse. Such a response can either be generated from actual experiments or by simulating the scattering response using Computational Electromagnetic (CEM) techniques. In this work, the impulse response is obtained from the frequency response of the scatterers in the frequency range of interest. Since no single CEM technique can effectively cover the entire range of frequencies needed for the E-Pulse synthesis. The Method of Moments and Physical Optics have been used for low and high frequency scattering respectively. The results obtained using the latter technique are validated by comparing with those obtained using Method of Moments at the transition frequencies and Geometrical Theory of Diffraction (GTD). The natural frequencies (i.e., poles of a corresponding transfer function) are extracted from the impulse response using Prony's algorithm. One of the parameters in this method is the number of such poles (i.e.. the order of the transfer function) present in the response, and the accuracy of the computed pole values depends on this assumed order. Here, the Hankel singular values of a transfer function is used to estimate the number of poles. This in turn implies that a specific norm of the error between a transfer function corresponding to the frequency response generated earlier, and a transfer function with an assumed order obtained using Prony's method is minimised. In the thesis, a wide range of target shapes are considered for purposes of illustration: wires, cylinders, spheres, plates and complex bodies such as aircraft, and the discrimination capability is demonstrated by introducing minor perturbations in their shape and/or material composition. .The following cases are considered here: (a) Wires: Conducting wires with a protrusion in one segment; conducting wire from another coated with a dielectric in a segment, (b) Cylinders: Conducting cylinders with one perturbed; conducting cylinders with a portion scrapped off in the middle, (c) Plates: Conducting plates with a elongation on one comer; conducting plate with another one with a hole in the centre, (d) Spheres: Conducting spheres with different radii; conducting spheres with Radar Absorbing Material coated spheres with different coating thickness; conducting spheres with chiral coated spheres with varying coating thickness, (e) Aircraft: Canonical model of MiG-29 aircraft from a similar one with stores placed under the wing.

The aim of this work is to develop a multiple scattering inversion procedure for the aerosol extinction coefficient profile retrieval and error assessment for nadir and multi-angle passive remote sensing instruments. The procedure will be applied for the tropospheric aerosol extinction coefficient profile retrieval from SCIAMACHY nadir simulated measurements using atmospheric windows and oxygen A-band wavelengths. Also the contemporary use of atmospheric windows and oxygen A-band wavelengths will be discussed. SCIAMACHY simulated measurement has been used because, due to calibration real data procedure problems, until now SCIAMACHY data are not available.
Università degli Studi di Genova. DIpartimento Per lo studio del TErritorio e delle sue RISorse (DIPTERIS)
Unpublished
1.10. TTC - Telerilevamento
open

Victor Wong studied human acquisition learning over multiple contexts using virtual reality. He found that learning an association over multiple contexts can impact subsequent extinction training. This suggests that fears acquired over multiple contexts may be more difficult to treat using exposure-based therapies and will need to be augmented for effectiveness.

This practice-led PhD explores being ‘with’ frontline sites of ecological disturbance as a witness, or ‘with-ness’ (Akomolafe 2020), connecting ethics with empathy by co-devising modes for embodied solidarity through creative encounters and co-authoring. By investigating connections between human and more-than-human agents and focussing on situational, relational ethics, this approach connects my body, the wounded bodies of ecosystems and the public/social body who find this artwork in the willing acknowledgement of ecological trauma or ecocide. Ecocide is defined as ‘unlawful or wanton acts committed with the knowledge that there is a substantial likelihood of severe and widespread or longterm damage to the environment being caused by those acts’ (Siddique 2021). Entangled Solidarity describes the experiential phenomena of art as a method to discreetly translate witnessed/with-nessed acts of ecological disturbance, highlighting interdependent, relational, creative disturbances that draw attention to ecological intimacies. Entangled Solidarity is site and place-specific, conspiring together with places that have been wilfully disturbed by human activity. Experiences are translated into testimonial artworks using experimental media; immersive and participatory installation and philosophical fieldwork. Collaborating with samples and elements foraged from these vulnerable places, Entangled Solidary embodies a sensitivity to, and presence with, inherent codified origin stories of materials. This thesis investigates research-creation as studio practice, gallerybased outcomes, and happenings – Poetic Gestures and field philosophy. These Poetic Gestures are contextualised alongside the practices of contemporary artists whose work demonstrates active engagement between artist and site/material relationships and considers political and ethical relationships as processes. The emergent compositions become integral to the viewer’s construction of meaning and ability to hold multiple viewpoints. This work seeks to reconfigure the artist/site/material/audience towards an awareness of Entangled Solidarity. Phenomenology as a method, alongside ecofeminist, post-human theories and First Nations knowledge systems, new materialism, field philosophy and queer theory, scaffold and give depth to these Poetic Gestures and creative propositions. This research-creation process and the artefacts developed over the course of this thesis serve as testimonies that evidence new strategies for engaging with ecocide/ecological trauma sites with sincerity and care. Entangled Solidarity can provide a framework for a relational ethos and site-responsive creative practice, integrating the liveliness/animacy of materials as a relational presence for applying convivial ethics as research-creation.

Problematic child sleep is a common issue facing parents around the world, particularly during infancy, and can have deleterious effects on many aspects of health and wellbeing for the child, parents and broader family unit. Substantial literature exists on child sleep interventions, within academic, professional and general public settings. The most common intervention recommended for problematic child sleep behaviours employs behaviour theory’s concept of extinction, which involves ignoring a crying child to various degrees. Due to media and popular literature, such methods are widely known and also likely used outside of clinical settings. However, for decades, multiple sources have described parental resistance to implementing such methods and little is known about their uptake in the community. When extinction is the primary intervention recommended, this resistance potentially leaves parents without support or treatment for sleep problems, which can have significant health and wellbeing ramifications on the child, parent and broader family unit. Despite regular mention of parents’ reticence to utilise extinction sleep interventions, evidence of and explanation for this reticence is limited. Minimal space has been given to the voices of those most affected by and involved in managing child sleep problems - the parents. A transactional systems model of child sleep (Sadeh & Anders, 1993; Sadeh et al., 2010) illustrates the importance that parents and the family’s broader context play in understanding and altering child sleep. Therefore, this thesis sought to contextualise this model within an Australian context and explored (1) Australian parents’ use of three common, extinction-based sleep interventions (unmodified extinction, graduated extinction, and extinction with parent presence) and (2) views on managing sleep with their young child. Specifically, those with a child aged 6-18-months were targeted as extinction-based sleep interventions are usually recommended from 6-months of age and sleep problems are common in this age range. The paucity of previous evidence on parent perspectives on managing child sleep and use of extinction within the community meant this thesis used an exploratory, mixed methods approach to meet objectives. An online survey collected 1,344 complete responses from Australian parents (98% mothers) of a 6-18-month-old assessing factors relating to child sleep, including night-waking cognitions, parenting efficacy, psychological distress, sleep information access, extinction use and demographics. From this quantitative data, descriptive and path analyses were used to ascertain mothers’ use of extinction interventions, reasons for use or non-use, and factors which predicted use. To capture parents’ broader perspectives on child sleep, a qualitative descriptive design was also employed. Forty mothers from metropolitan (n = 3) and regional areas (n = 5) of three Australian states contributed their reflections within semi-structured, individual and group interviews. Quantitative results showed 53% of mothers had not used any of the extinction interventions, and graduated extinction was more popular than unmodified extinction or extinction with parent presence. Mothers typically used extinction for more functional reasons, while those who did not indicated more emotional and philosophical reasons. Generally, mothers valued socially sourced sleep information over professionals, the Internet over books, and information in postnatal classes over antenatal. The initial path model showed mothers’ cognitions about their child’s night-waking and perceptions of the extinction interventions were strong predictors of their use of extinction (R2 values = .24-.54). Various child, demographic and family factors were then incorporated into the model and were significant predictors of mothers’ night-waking cognitions, however, their contributions were generally small (R2 values = .09-.12). Thematic analysis of the interview data resulted in three themes, and sub-themes and dimensions within these, representing mothers’ thoughts on how they manage sleep with their young children. Theme one was “Do we have a sleep problem?” and comprised of four sub-themes, “Expectations and beliefs about what is normal”, “Is there something else effecting my child’s behaviour?”, “Comparing my child to other children”, and “How does the child’s behaviour affect my family?”. Theme two was “We have a problem, what can we do?” with three sub-themes, “Seek and find information”, “Making a choice” and “Seek support”. Theme three was “Living with my choices”, with three sub-themes, “Being judged”, “Dealing with judgement” and “Owning, embracing and accepting”. The themes highlighted how varied mothers’ perceptions of and responses to sleep challenges could be, and the emotional journey they experienced while managing sleep within their family context. The thesis findings are discussed in combination with quantitative and qualitative results to complement and contextualise each other; a valuable feature when examining the interconnected and complex nature of parents’ management of child sleep. Three key deductions are discussed based on these combined results; (1) extinction promotion is disproportionate to its use, (2) night-time parenting choices are highly personalised, and (3) child sleep information and support for mothers requires improvement. Recommendations are made for future research and clinical practice. Principally, there is a need for alternative, evidence-based, sleep intervention options to be available to parents wanting support. Extinction, the dominant sleep intervention, is not acceptable to a substantial proportion of Australian parents for a variety of reasons. A range of intervention options are required to address this variety. Further sleep intervention research is needed to provide options, and to assess how best to engage parents with professionals who can provide appropriate information and support. The findings within this thesis may not be representative of the views of fathers and different cultural groups who were underrepresented. This thesis contributes new information to the field by not only indicating the uptake of extinction sleep interventions in the Australian community, but also identifying reasons for using and not using these interventions. It also provides new, comprehensive information on how mothers make sleep-related decisions related to their young children. This information is important to advance future sleep intervention research and practice guidelines in accordance with the needs and preferences of parents, and subsequently reduce gaps in treatment acceptance.

碩士
國立東華大學
電機工程學系
94
Raman fiber amplifier is more and more important due to the successful development of high power laser diode. Because Raman amplifier is distributed amplifier, the noise in amplifier will increase gradually. Double Rayleigh scattering is the most important noise. Noise performance become a key condition in Raman amplifier. In our thesis, we built a structure based on modified time domain extinction method(TDE method), observe the measurement of double Rayleigh scattering by changing the modulate frequency of AOM, the duty cycle of AOM, and the resolution of OSA. We hope to develop a measurement method of measure double Rayleigh backscattering. According the results of the measurement, we decide to setup the duty cycle of AOM1 and AOM2 in 10% and 50%, the frequency is set in 1MHz to measure the double Rayleigh scattering. We use the TDE method by our setup to compare noise characteristic of the five types of Raman/EDFA hybrid amplifier with different pumping direction and different order of EDFA and Raman amplifier to measure the double Rayleigh scattering. We get 56.8dB to 61.8dB Optical Signal to Noise Ratio(OSNR) in the optimum configuration that used EDFA in front of backward pumping RA. In the Raman amplifier, the transmission signal will produce highly double Rayleigh backscattering, it will reduce the noise performance. For this, this thesis setup a system can measure the double Rayleigh back scattering effective, it will be helpful for measure the double Rayleigh backscattering. We also find the optimum structure of Raman/EDFA hybrid fiber amplifier.

This thesis investigates the molecular evolutionary and macroevolutionary consequences of flight loss in insects. Chapter 2 tests the hypothesis that flightless groups have smaller effective population sizes than related flighted groups, expected to result in a consistent pattern of increased non-synonymous to synonymous ratios in flightless lineages due to the greater effect of genetic drift in smaller populations. Chapter 3 tests the hypothesis that reduced dispersal and species-level traits such as range size associated with flightlessness increase extinction rates, which over the long term will counteract increased speciation rates in flightless lineages, leading to lower net diversification. The wide-spread loss of flight in insects has led to increased molecular evolutionary rates and is associated with decreased long-term net diversification. I demonstrate that the fundamental trait of dispersal ability has shaped two forms of diversity—molecular and species—in the largest group of animals, and that microevolutionary and macroevolutionary patterns do not necessarily mirror each other.
Generously funded by NSERC with a Canada Graduate Scholarship and the Government of Ontario with an Ontario Graduate Scholarship to T. Fatima Mitterboeck; NSERC with a Discovery Grant to Dr. Sarah J. Adamowicz