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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

A demographic comparison of two elephant seal populations

McMahon, Clive Reginald 30 June 2005 (has links)
The demography of two elephant seal populations was examined and compared. This was done to investigate the reasons for the observed decreases in populations at Marion and Macquarie islands. While a well-established demographic programme had been in place at Marion Island since the 1980's (see Pistorius et al. (l999a) for a review) one had to be established at Macquarie Island. A long-term demographic programme was initiated at Macquarie Island in 1993 and hot brands were used to mark seals. Hot-iron branding was a rapid and reliable method of permanently identifying elephant seals that did not prejudice survival and did not appear to cause undue stress (in the short-term). Neither branding nor handling showed any long-term effects as measured by survival after one year. From the inter-island comparison of survivorship, age at first breeding and wean mass I concluded that the observed decreases in elephant seal numbers between the I 950s and 1990s in the Pacific and Indian Ocean sectors were driven by resource limitation in the Southern Ocean. A conglomerate of factors including local predation by killer whales and intra-specific resource competition was postulated as a cause for the inter-island (regional) differences in population trends. Presently it appears that per capita more resources are available to the Marion Island population than are available to the Macquarie Island population. The vital rates that had the greatest impact (elasticity) on fitness (population growth) for all populations i.e. Marion Island, Macquarie Island and South Georgia, were, in order of importance: (I) juvenile survival, (2) adult survival, (3) adult fecundity and (4) juvenile fecundity. At Marion Island juvenile and adult survival contributed equally to the fitness of the population while at Macquarie Island and at South Georgia Island juvenile survival was more important than adult survival in determining population fitness. The global population of elephant seals in 200 I was estimated at approximately 738 772 which represents an increase of I I % from the last world estimate (664 000). It seems clear from the evidence presented and reviewed here that the present changes in seal populations, unlike the period of direct exploitation in the 19th and 20th centuries, are neither a consequence of direct human interactions nor present-day commercial activities. While the significance of inter-specific competition between elephant seals and other Antarctic predators remain largely unknown or quantified, it would seem prudent that these relationships be studied. This is because resource competitors (toothed whales) have been increasing in number since the cessation of commercial whaling. Even though elephant seals are considered the most studied of all pinnipeds (Ling&Bryden, 1992) much remains to be learnt. Foremost are to gain a clear understanding of the in situ, diet of elephant seals and to assess the role pathogens play in the regulation of seal populations. In addition to these studies it is also important that the current long-term monitoring programmes at Marion and Macquarie islands continue, as they provide valuable base line information on the fate of elephant seal populations. / Thesis (PhD (Zoology))--University of Pretoria, 2005. / Zoology and Entomology / unrestricted
82

Geoffrey, Count of Anjou and Duke of Normandy, 1129-51

Dutton, Kathryn Ann January 2011 (has links)
Count Geoffrey V of Anjou (1129-51) features in Anglo-French historiography as a peripheral figure in the Anglo-Norman succession crisis which followed the death of his father-in-law, Henry I of England and Normandy (1100-35). The few studies which examine him directly do so primarily in this context, dealing briefly with his conquest and short reign as duke of Normandy (1144-50), with reference to a limited range of evidence, primarily Anglo-Norman chronicles. There has never been a comprehensive analysis of Geoffrey’s comital reign, nor a narrative of his entire career, despite an awareness of his importance as a powerful territorial prince and important political player. This thesis establishes a complete narrative framework for Geoffrey’s life and career, and examines the key aspects of his comital and ducal reigns. It compiles and employs a body of 180 acta relating to his Angevin and Norman administrations to do so, alongside narrative evidence from Greater Anjou, Normandy, England and elsewhere. It argues that rule of Greater Anjou prior to 1150 had more in common with neighbouring principalities such as Brittany, whose rulers had emerged in the tenth and eleventh centuries as primus inter pares, than with Normandy, where ducal powers over the native aristocracy were more wide-ranging, or royal government in England. It explores the count’s territories, the personnel of government, the dispensation of justice, revenue collection, the comital army, and Geoffrey’s ability to carry out ‘traditional’ princely duties such as religious patronage in the context of Angevin elite landed society’s virtual autonomy and tendency to rebel in the first half of the twelfth century. The character of Geoffrey’s power and authority was fundamentally shaped by the region’s tenurial and seigneurial history, and could only be conducted within that framework. This study also addresses Geoffrey’s activities as first conqueror then ruler of Normandy. The process by which the duchy was conquered is shown to be more intricate than the chroniclers’ accounts of Angevin siege warfare suggest, and the ducal reign more complex than merely a regency until Geoffrey’s son, the future Henry II (1150-89), came of age. Through use of a much wider body of evidence than previously considered in connection with Geoffrey’s career, and a charter-based methodology, this thesis provides a new and appropriate treatment of an important non-royal ruler. It situates Geoffrey in his proper context and provides an account of not only how he was presented by commentators who were sometimes geographically and temporally remote, but by his own administration and those over whom he ruled. It provides an in-depth analysis of the explicit and implicit characteristics of princely rulership, and how they were won, maintained and exploited in two different contexts.
83

Investigating monitoring options for harbour seals in Special Areas of Conservation in Scotland

Cunningham, Louise January 2007 (has links)
Managing a wild population effectively requires knowledge of the abundance and behaviour of the species. Harbour seals (Phoca vitulina) are usually counted when they come ashore at haul-out sites, and so it is important to understand how the number of seals counted at this time relates to total population size. Satellite telemetry studies confirmed that harbour seals on the west coast of Scotland showed a degree of site fidelity and coastal foraging. Most trips taken by tagged animals involved travelling only 10-30 km from haul-outs and lasted less than a day (mean 21.07 hours, SE = 0.54), although some seals travelled over 100 km. Eighteen percent of the time these tagged seals spent hauled out was in the Special Area of Conservation where they were caught. Individual seals can be recognised from their unique pelage patterns using computer-assisted photo-identification. Capture histories for adult harbour seals at a site in north-west Scotland indicated that the number of seals using the study area between April and October was 3.4 times higher than the number counted during an aerial survey made during the August moult. In the UK, aerial surveys of harbour seals are usually conducted during the first three weeks of August, when seals are moulting. These counts have a coefficient of variation of around 15%. Land-based counts made at study sites on the north-west coast of Scotland indicated that the number of seals hauled out was most consistent during the moult, but highest counts were from the pupping period. Analysis of moult counts indicated that starting surveys one week earlier (on 7th August) and surveying 1½ hours earlier in the tidal cycle would reduce the count variation. There was spatial, seasonal, diurnal and sex-related variation in the proportion of time harbour seals hauled out. Thus the relationship between counts and total population size is likely to vary spatially and temporally. This variation should be included in the estimates of the CV of correction factors. A 5% annual change in harbour seal population size was predicted to take around 14 years to detect based on annual surveys and a CV = 0.15. This detection period increases when monitoring methods with lower precision are used, or surveys are made less frequently. Trends in seal abundance at pairs of haul-out sites were not synchronous and so it is unlikely that counts from small land-based protected areas, such as Special Areas of Conservation, can be used to monitor overall population status.
84

Ecology, tourism and management of harbour seals (Phoca vitulina)

Granquist, Sandra M. January 2016 (has links)
In cases where human and wildlife are co-using the same geographical areas and resources, management issues often get complex and stakeholder conflicts are common. The Icelandic harbour seal (Phoca vitulina) population is rapidly decreasing, but direct culling of seals still occurs. At the same time seals are becoming an important resource due to increased interest in wildlife watching. Despite the complicated management situation, the Icelandic harbour seal population is one of the least studied pinniped populations in the world. Mapping the typical haul-out pattern is an important foundation for further studies. In paper I haul-out behaviour of harbour seals was investigated and a seasonal haul-out pattern was detected with the maximum number of seals hauling out during summer. A bimodal distribution curve was found during the summer time, suggesting that pupping period occurs in late May to early June, while moulting occurs in late July to early August. Tidal state, air-temperature and wind-speed affected the haul-out boots. Today, the main reason for culling harbour seals in Iceland is to reduce harbour seal predation on salmonids, despite limited knowledge on the effect of seal predation on salmonid populations and salmon angling. The diet of harbour seals that haul out in the estuary area of Bjargós and Ósar in NW-Iceland was therefore investigated using hard-part (paper II) and DNA metabarcoding analysis (paper III). Both methods showed that the main prey species were sand eels, flatfishes, gadoids, herring and capelin, while salmonids were not an important prey in this area. Based on these results, culling of harbour seals in the area is not likely to have a positive effect on salmonid angling. These results have crucial management implications, especially in the light of the severe decline in the Icelandic harbour seal population. Potential effects of seal watching tourism on the harbour seal population must also be considered in management plans. In paper IV, we investigated the effects of land based seal watching on seal behaviour and found that spatial distribution and vigilance was affected by tourists. Calm tourists behaviour had less effect, meaning that disturbance could be reduced if tourist behaviour is modified. In paper V, this line of investigation was followed by analysing knowledge transfer from academia to the tourist industry and a model was presented where a synergy effect of working interdisciplinary is hypothesised. Finally, in paper VI, the effect of signage on tourist behaviour was studied. Empirical testing showed that teleological information is more effective than ontological in terms of modifying general tourist behaviour. In this thesis, I present new knowledge on behaviour and diet of harbour seals, as well as new empirical findings on tourist behaviour in wildlife tourism settings. Further I explore interdisciplinary management approaches for seal watching tourism. The findings presented in this thesis have an important value within academic research in environmental-, life- and social sciences and the knowledge can be applied in several areas of harbour seal management in Iceland and elsewhere. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 6: Manuscript.</p>
85

Writers and writing in the Roman Army at Dura-Europos

Austin, Jacqueline F. January 2010 (has links)
This socio-palaeographic thesis maintains that behind the uniform appearance of Roman army writing was a particular, dedicated training. Focussing on the third century Dura-Europos, it uncovers evidence for the thorough schooling given to the clerks of the resident Cohors XX Palmyrenorum enabling them to fulfil their administrative duties. These include maintaining efficient documentation systems and preparing a range of accurate, legible texts, and the clerks were trained to produce a repertoire of standard military scripts. Additionally other soldiers and the more general public were taught to read and to understand, to varying degrees, but the clerks, distinct, were specialist writers who found dignity in the work that they did. This dissertation, a preliminary study, draws throughout from the camp’s rich epigraphic and papyrological evidence. It sets out the context in which clerical soldiers worked and the evidence for army literate education and then introduces Roman writing, its form and development generally, before analysing in detail the letter-forms used in one particular standard hand over the decades the cohort’s documents span. In this hand, the well-known development out of Old Roman Cursive is presented and discussed. A brief additional chapter presents the possibility that military clerks also produced camp signage.
86

從當代印章狀況探索篆刻創作之可能性. / Exploring the possibility of seal carving creations from the contemporary seal position / Cong dang dai yin zhang zhuang kuang tan suo zhuan ke chuang zuo zhi ke neng xing.

January 2009 (has links)
馮嘉儀. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 43-49). / Abstracts in Chinese and English. / Feng Jiayi. / Chapter 第一章 --- 引言 / Chapter 第一節 --- 導論 / Chapter 第二節 --- 硏究範圍、目的和方法 / Chapter 第二章 --- 中國當代篆刻發展槪略 / Chapter 第一節 --- 從附庸到獨立 / Chapter 第二節 --- 當代面貌的形成和蛻變 / Chapter 第三節 --- 寫意印風的角色與問題 / Chapter 第三章 --- 美學與功能的引申 / Chapter 第一節 --- 視覺識別 / Chapter 第二節 --- 文化創意產業 / Chapter 第三節 --- 突顯圖像美 / Chapter 第四章 --- 篆刻作爲藝術形式的思考 / Chapter 第一節 --- 製作物料和工具 / Chapter 第二節 --- 印面處理 / Chapter 第三節 --- 展示手法 / Chapter 第四節 --- 創作態度 / Chapter 第五章 --- 結語 / 參考資料 / 圖錄
87

Acoustic communication in Australian fur seals

Tripovich, Joy Sophie January 2007 (has links)
Doctor of Philosophy(PhD) / Communication is a fundamental process that allows animals to effectively transfer information between groups or individuals. Recognition plays an essential role in permitting animals to distinguish individuals based upon both communicatory and non-communicatory signals allowing animals to direct suitable behaviours towards them. Several modes of recognition exist and in colonial breeding animals which congregate in large numbers, acoustic signalling is thought to be the most effective as it suffers less from environmental degradation. Otariid seals (fur seals and sea lions) are generally colonial breeding species which congregate at high densities on offshore islands. In contrast to the other Arctocephaline species, the Australian fur seal, Arctocephalus pusillus doriferus, along with its conspecific, the Cape fur seal, A. p. pusillus, display many of the behavioural traits of sea lions. This may have important consequences in terms of its social structure and evolution. The acoustic communication of Australian fur seals was studied on Kanowna Island, Bass Strait, Australia. Analysing the acoustic structure of vocalisations and their use facilitates our understanding of the social function of calls in animal communication. The vocal repertoires of males, females, pups and yearlings were characterised and their behavioural context examined. Call structural variations in males were evident with changes in behavioural context, indicating parallel changes in the emotive state of sender. For a call to be used in vocal recognition it must display stereotypy within callers and variation between them. In Australian fur seal females and pups, individuals were found to have unique calls. Mutual mother-pup recognition has been suggested for otariids and this study supports the potential for this process to occur through the use of vocalisations. Call structural changes in pup vocalisations were also investigated over the progression of the year, from birth to weaning. Vocalisations produced by pups increased in duration, lowered in both the number of parts per call and the harmonic band containing the maximum frequency as they became older, suggesting calls are changing constantly as pups grow toward maturity. It has been suggested through descriptive reports, that the bark call produced by males is important to vocal recognition. The present study quantified this through the analysis of vocalisations produced by male Australian fur seals. Results support descriptive evidence suggesting that male barks can be used to discriminate callers. Traditional playback studies further confirmed that territorial male Australian fur seals respond significantly more to the calls of strangers than to those of neighbours, supporting male vocal recognition. This study modified call features of the bark to determine the importance to vocal recognition. The results indicate that the whole frequency spectrum was important to recognition. There was also an increase in response from males when they heard more bark units, indicating the importance of repetition by a caller. Recognition occurred when males heard between 25-75% of each bark unit, indicating that the whole duration of each bark unit is not necessary for recognition to occur. This may have particular advantages for communication in acoustically complex breeding environments, where parts of calls may be degraded by the environment. The present study examined the life history characteristics of otariids to determine the factors likely to influence and shape its vocal behaviour. Preliminary results indicate that female density, body size and the breeding environment all influence the vocal behaviour of otariids, while duration of lactation and the degree of polygyny do not appear to be influential. Understanding these interactions may help elucidate how vocal recognition and communication have evolved in different pinniped species.
88

The conflict between Grey seals (Halichoerus grypus) and the Baltic coastal fisheries : new methods for the assessment and reduction of catch losses and gear damage

Fjälling, Arne January 2006 (has links)
There is a problematic interaction going on between grey seals and the small scale coastal fisheries in the Baltic. A large number of seals are by-caught and drowned each year, and the viability of the fishery is threatened by catch losses caused by the seals. Traditional mitigation methods are not sufficient, or have in some cases not been properly evaluated. Available methods of quantifying and analysing the catch losses are also insufficient. This thesis consists of three parts, each studying a different angle of this conflict. In the first part, new models for estimating catch losses are presented. In addition to the commonly used method of counting the number of damaged fish in the nets, the new models also allow for an estimation of the hidden losses. Hidden losses may be fish that are completely removed from nets without leaving any traces, fish that escape through holes in the net torn by the seals, or even fish that are scared away from the fishing gear. Such losses were found to be significant, and hence it is now clear that the traditional models seriously underestimate the total losses. The new models also allow for a deeper analysis of the interaction process. The first presented model compares catches between adjacent days (day-pairs), the second uses nets that are pre-baited before deployment, and the third relies on a detailed inspection and repair of all seal-induced damage to the net meshes. In the second part, some traditional methods of mitigating the conflict are evaluated. A commercially available Acoustic Harassment Device was tested in a field trial. AHDs were deployed at several set-traps for salmonids for three consecutive years. The damage reducing effect was persistent throughout a season, as well as over the full three-year test period, and no “dinner bell” effect was observed. When seal attacks became frequent in the 1980´s, several of the traditional salmon traps were reinforced with newly developed extra strong net materials. These materials dramatically reduced the damage to the nets, and to some degree also the catch losses. However, the losses were still substantial, and the traditional gear was gradually phased out when better solutions emerged. In the third part, new methods of mitigating the conflict are evaluated. A salmon trap was built, using net meshes which were large enough to allow seal-chased fish to escape through, but which would still guide and confine non-stressed fish. The trap was fitted with a fish chamber with a double wall of very taut netting, separating the catch from the surroundings by a fixed distance. Interference by seals was significantly reduced with this construction. Field experiments revealed that seals used their above-water vision to locate and search out buoys of the type that are used in the fisheries. Larger buoys were more readily found than smaller. A set of trials was initiated where certain geographical areas were made unattractive for seals prior to their seasonal arrival to the region, by deploying stationary AHDs. Finally, aquarium experiments demonstrated that underwater vision and hearing were equally important in seals’ detection of fish in a test box. It was also found that there was a “near zone”, within which seals stayed focused on a fish and attempted to catch it by a quick thrust of the head. These studies strongly suggest that new seal-safe fishing gear and mitigation methods should be based on, and would benefit from, an in-depth understanding and analysis of natural seal behaviour.
89

Analysis of Instabilities and Their Impact on Friction Factor in Hole-Pattern Seals

Sekaran, Aarthi 1985- 14 March 2013 (has links)
The determination of the leakage and consequently the friction factor is an important part of analyzing the flow through a seal. This is done experimentally by means of a flat plate tester, which allows for the simplified representation of the seal pattern on a flat plate surface tested under a range of clearances and pressure drops. The setup mounts a smooth plate opposite a second plate which may be smooth or have a roughened surface while the separation between plates is held constant. The present study analyzes the phenomenon of friction factor 'upset' ? wherein it was seen that as the pressure drop across the parallel plates is increased, there is a sudden increase in the friction factor (i.e. a decrease in flow rate) at a certain Reynolds number and for any further increase in the pressure differential, the friction factor shows the expected trend and decreases slowly. This phenomenon was initially believed to be an anomaly in the rig and was attributed to choking at an upstream flow control valve. The present author differs from that view and hypothesized that the reason for the abrupt change is linked to the flow mechanics of the system and the current study analyzes the same. Preliminary analysis of available data has established that the cause for the 'upset' was not related to the switch from a normal mode resonance driven by the Helmholtz frequency of the cavities on the stator to a shear layer instability, as was seen earlier by Ha. The friction factor jump for this case is therefore proposed to be due to a change of the instability modes as the fluid passes over the cavities in the plate. A detailed analysis of the physics of the flow will be carried out via a numerical simulation using a Large Eddy Simulation (LES) model from ANSYS Fluent. Results will be validated through comparisons with experimental data from the flat plate test rig.
90

High Temperature Leakage Performance of a Hybrid Brush Seal Compared to a Standard Brush Seal and a Labyrinth Seal

Ashton, Zachary 14 January 2010 (has links)
Adequate sealing in turbomachinery reduces secondary leakage and results in more efficient and stable systems. Labyrinth seals are most common, although brush seals are popular in specialized applications. The Hybrid Brush Seal (HBS) is a novel design that adds to the bristle brush matrix a number of cantilever pads that rest on the rotor surface. Upon shaft rotation the pads lift due to the generation of a hydrodynamic gas film while the brushes effectively seal an upstream pressure. Hence the HBS has no wear and no local thermal distortion effects. Measurements of leakage versus pressure differential are obtained in a three-teeth labyrinth, a conventional brush seal, and a hybrid brush seal for operation at high temperature (300ºC), with shaft surface speeds to 27 m/s, and at supply pressures to 3.5 bar. Flow measurements are presented in terms of a flow factor to remove dependency on the air temperature and supply pressure. The measurements demonstrate the HBS leaks less (~61%) than a standard brush seal and is significantly better (~38%) than a similarly sized labyrinth seal. Predictions of flow through a labyrinth seal predict well at supply pressures under 1.7 bar but overpredict by as much as 25% at high supply pressures. A porous medium fluid flow model predicts the flow through the HBS and brush seal. The model for the HBS and brush seal underpredicts the flow rate at low supply pressures but match well at high supply pressures. Measurements of the drag torque of the test seals show the HBS has a larger torque when pressurized compared to the brush seal and labyrinth seal. This indicates that the HBS experiences a larger degree of blow-down due to the pads decreasing the clearance. The mechanical parameters of the brush seal and HBS are found based upon the flexibility function from impact load tests. A combined structural and dry friction damping model represent well the measured flexibility. An equivalent damping is found based upon the energy dissipation. Based upon the damping ratio, the HBS has twice of the viscous damping as the brush seal at a supply pressure of 2.0 bar.

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