Abstract available in the 9th Annual Coaches and Sport Science College .

Space geodesy is one of the disciplines that contributes uniquely to the global society; its applications have grown to such an extent that system Earth is better understood today. The current accuracy of the Global Navigation Satellite Systems (GNSS) technique is below centimetre level and this allows very accurate determination of velocity field parameters. This study focused on utilizing GNSS to determine the inter-continental plate velocity field for Africa in support of the African Geodetic Reference Frame (AFREF). Data spanning 12.4 years were processed in the International Terrestrial Reference Frame (ITRF2008) using GAMIT/GLOBK 10.4 (developed at the Massachusetts Institute of Technology). Primarily, processing of data focused on International GNSS Service (IGS) stations with a few non-IGS stations (which are of geodetic quality) included, such as Hamburg (HAMB) and Matjiesfontein (MATJ). The same data set was analysed using the Combination and Analyses of Terrestrial Reference Frame (CATREF) software developed at Institut National de l’Information Géographique et Forestière (IGN). Validation of the results was achieved through comparison of the velocity solution from this study with a solution obtained from a core of IGS GNSS stations processed by the Jet Propulsion Laboratory (JPL). No significant differences were evident between the GAMIT/GLOBK 10.4, CATREF and JPL solutions. The results from the Matjiesfontein station indicated that the proposed Matjiesfontein Observatory site shows no significant vertical or horizontal local motion; this information is valuable in that there is no obvious local site instability. The velocity field as derived by GNSS displays no unexpected deviations and supports current understanding of the motion of the Nubian, Somalian and Arabian plates. Furthermore, the comparison of the velocity vectors derived from the IGS station HRAO, Satellite Laser Ranging (SLR) MOBLAS-6 station and 26 m Very Long Baseline Interferometry (VLBI) telescope, which are collocated at the Hartebeesthoek Radio Astronomy Observatory (HartRAO) indicated good agreement and both techniques exhibit no significant vertical motion. This study also contributed to the first computation of the AFREF solution. It is envisaged that as more stations are added to the sparsely distributed current network, more accurate results and better tectonic models can be derived. The availability of station velocities will facilitate adjustments within the AFREF. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Geography, Geoinformatics and Meteorology / unrestricted

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20924号 / 理博第4376号 / 新制||理||1628(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 田上 高広, 教授 山路 敦, 教授 平原 和朗 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

No abstract provided. / Thesis / Master of Science (MSc) / Scope and contents: The probability of fission as a function of primary fragment velocities has been obtained by removing the neutron emission and instrumental dispersions from the velocities determined by Stein with time-of-flight techniques for the thermal neutron fission of u235. Each velocity was increased by 0.69% to make the average kinetic energy per fission agree with the calorimetric value of 167.1 Mev. Excitation energy distributions were obtained by using the primary fragment masses given by Cameron and assuming that the most probable charge distribution for a given mass ratio i s that which leads to the greatest energy release. Evaporation theory was used to determine the number of prompt neutrons emitted. When the excitation energy is divided equally between the fragments and a nuclear temperature of 0.59 Mev is used, the average number of neutrons emitted is 2.95 per fission.

Huvudskador inom alpin skidsport är bland de allvarligaste skador som kroppen utsätts för. Tidigare studier på huvudskador som genomförts på grenar såsom Störtlopp, Super-G, Storslalom, Skicross, Freestyle och Snowboard visar att standarder som finns på skyddsutrustning inte är tillräckliga. Ännu har ingen videoanalys genomförts på disciplinen Slalom med fokus på huvudets islag med underlaget under olyckor trots att dylika händelser har rapporterats. Certifieringar av hjälmar inom dessa discipliner skiljer sig och har genom åren påverkats av studier och forskning. Detta har resulterat i regeländringar och ökade krav på säkerhetsstandarder satta av Internationella Skidförbundet (FIS). Videoanalyser av olyckstillfällen inom snösport omfattar en hel del antaganden vilket medför problematik för okända variabler då de sker genom rekonstruktioner. De variabler som är kända utnyttjas för att uppskatta dessa okända värden. Denna avhandling syftade till att rekonstruera olyckor i slalomdisciplinen för att undersöka vilka hastigheter som faktiskt uppstår vid huvudkollison mot underlaget, samt därefter utröna eventuella samband mellan utövarens färdhastighet och underlagets lutning. Detta för att möjligen påverka eller upplysa om de faktiska hastigheter som uppstår för att validera de standardiserade certifieringar som idag är stadgade. Resultatet av den här studien visar tendenser på att en minskad lutning på underlaget ger en högre islagshastighet för huvudet mot underlaget. Färdhastigheten enskilt påverkar inte i lika stor uträckning som lutningen men bidrar till att öka islagshastigheten. I ett av de åtta analyserade fallen uppmättes 5,94 m/s, vilket överskred de testkrav för hjälmar satta till 5,42 m/s enligt EN-1007:2007 Klass B skyddscertifiering. / Head injuries in alpine skiing are the most serious injuries exposed to the human body. Previous studies applied to Downhill, Super-G, Giant Slalom, Skicross, Freestyle and Snowboard shows that safety standards on protection equipment may not be enough. In the slalom discipline no such video analysis studies have yet been deployed on head impacts in the Slalom discipline, although several incidents have been reported. Certifications for helmets in the respective disciplines differ and each of them have become influenced by studies and research throughout the years. This has resulted in rule changes and increased standards set by the International Ski Federation (FIS). Video analysis of athletes in snow sports causes problems with unknown variables based on rough reconstruction of past events, which lead to assumptions. To estimate these unknown values known variables play a critical role. This thesis aimed to reconstruct accidents in the slalom discipline to investigate the velocities for head collisions normal to the ground. Hence evaluate the relationship between the athlete’s travel speeds and the slope angle. This is to influence or inform about the speeds that arise to validate the standardized certifications that are currently stipulated. The result of this study shows tendencies that head collisions on lower slope angle results in a higher impact velocity. The travel speed alone does not affect to the same extent as the slope angle, but in combination the effect is to a greater degree. In one of the eight cases the impact velocity exceeded 5,42 m/s for the absorptions test according to EN-1007:2007 Class B certification, the highest measured value was 5,94 m/s. / <p>Betygsdatum 2023-06-07</p>

No description available.

Despite their relatively small ice volume, mountain glaciers contributed nearly one third of global sea level rise since 2000, with one of the largest total mass loss rates (73 ± 17 Gt a-1) occurring in the Yukon-Alaska region. However, there is uncertainty surrounding how ice dynamics are being affected by such losses and whether glacier flow instabilities, such as surges, are changing in a warming climate. The St. Elias Mountains contain a major cluster of surge-type glaciers, yet a detailed analysis of their characteristics, including surge frequency, morphology, magnitude, and propensity over time has not been undertaken on a regional basis. This thesis presents a review of surging behaviour and an updated surge event inventory in the St. Elias Mountains, and quantifies the processes influencing both surging and non-surging glacier velocity variability using a variety of remote sensing and field measurements. An updated inventory of surge-type glaciers and observed surge events (1874-2023), compiled from existing inventories, recently published articles, and velocity analysis, is used to analyze the characteristics of surge-type glaciers and velocity patterns during surge events. The modern (1985-2023) trends in annual, winter and summer velocities of selected surge-type glaciers is then used to classify dynamic instability events into 4 categories. While 231 glaciers were classified as surge-type, only 42 were observed to have experienced rapid velocity events over the period 1985-2023, through either direct measurements or remote sensing observations. For glaciers with observed rapid velocity events, these predominantly fall into two categories: Alaskan-style surges with short active and quiescent phases, and glacier pulses, which are velocity accelerations that are limited in both magnitude and extent. An unnamed former tributary to Kluane Glacier underwent a dramatic surge from 2013-18. Using a combination of air photos, remote sensing and field observations, the characteristics and changes of ‘Little Kluane Glacier’ were reconstructed from the 1940s until 2021. While only the single full surge of 2013-18 was identified, it is likely that a partial surge of just the upper north arm occurred between 1963 and 1972. Repeat Digital Elevation Models (DEMs) and velocity profiles show that the recent surge initiated from the upper north arm accumulation area in 2013, which developed into a full surge of the main trunk from 2017-18. Terminus positions show long-term retreat from 1949-2017, followed by rapid advance of >2 km from May to September 2018, with surface velocities reaching a peak of ~3600 m a-1 in summer 2018 over the lower ablation area. This was likely enhanced by the drainage of supraglacial lakes and streams to the glacier bed through crevassing as the surge progressed. Changes in surface topography caused by initial mass movement, the resulting reorganization of the supraglacial hydrological system, and ponding of surface water, may drive a partial surge into a full surge, and therefore exert a direct control on glacier dynamics. In May 2016, Kaskawulsh Glacier underwent a dramatic proglacial hydrologic reorganization instigated by the rapid drainage of proglacial Slims Lake: as a result, water which previously drained north into Ä’äy Chú, (Slims River) toward Lhú’áán Män (Kluane Lake), was redirected south into Kaskawulsh River, eventually flowing into the Gulf of Alaska. A long-term (up to ∼120 year) record of terminus retreat, thinning and surface velocities from in-situ and remote sensing observations is used to determine the impact of this reorganization on glacier dynamics. After an initial deceleration during the late 1990s, terminus velocities increased at a rate of 3 m a-2 from 2000-12, while the area of proglacial Slims Lake increased simultaneously. The rapid drainage of the lake substantially altered the velocity profile of the adjacent glacier, decreasing annual velocities by 48% within 3 km of the terminus between 2015 and 2021, at an average rate of ∼12.5 m a-2. A key cause of the rapid drop in glacier motion was a reduction in flotation of the lower part of the terminus after lake drainage. This has important implications for glacier dynamics and provides one of the first assessments of the impacts of a rapid proglacial lake drainage event on local terminus velocities. The results of this study provide an examination of factors controlling glacier dynamics, as well as the characteristics of rapid glacier velocity events, in the St. Elias Mountains. This provides insights into the behaviour of mountain glaciers, how they are changing in a warming climate, controls on glacier surging, and the hazards they may pose for downstream communities, which are particularly vulnerable to disturbances.

No description available.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A trial closure of the emergency gate of the Berg River Dam was undertaken by the Trans- Caledon Tunnel Authority (TCTA) on 12 June 2008. The air vent downstream of the emergency gate was designed to introduce air to mitigate the negative pressures that were expected in the conduit during emergency gate operations. The emergency gate has to close when the radial gate at the downstream end of the outlet conduit fails. Contrary to the theoretical design, the measured air vent velocities in the field indicated that, while the emergency gate was closing, very large volumes of air were apparently continuously being released from the air vent, commencing when the gate was about 30% closed (i.e. 70% open). This is in contrast to what the design intended, namely that air should have been drawn into the vent. This thesis is concerned with the testing of a 1:14.066 physical model representing the outlet works and air vent of the Berg River Dam as a means to determine the reasons for the release of large volumes of air from the air vent during the trial closure in 2008. It also seeks solutions to mitigate the excessive airflow from the air vent. It was concluded that the air velocity in the air vent was independent of the rate of closure of the emergency gate, but to increase with increasing water head. The problem at the Berg River Dam was determined to be one of air blowback. Modifications were made to the configuration of the model in order to determine whether the configuration of the outlet works caused air to be released from the air vent. It was determined that the downward sloping roof at the outlet of the conduit, used to accommodate the radial gate chamber, was the cause of the air blowback phenomenon. An additional air vent was fitted directly onto the conduit at the constriction was found to be ineffective in reducing the air blowback. It was concluded that there are no rational structural change that can prevent or inhibit a recurrence of the blowback phenomenon in the Berg River Dam outlet conduit. The recommendation follows that the outlet conduit should not be constricted by any structural or mechanism further downstream in the conduit. / AFRIKAANSE OPSOMMING: ʼn Toetssluiting van die noodsluis van die Bergrivierdam is op 12 Junie 2008 deur die TCTA (Trans-Caledon Tunnel Authority) uitgevoer. Die lugskag stroomaf van die noodsluis is ontwerp om lug in te voer om die verwagte negatiewe drukke tydens die noodsluissluiting te beperk. Die noodsluis moet sluit indien die radiaalsluis aan die einde van die uitlaatpyp sou faal. In teenstelling met die teoretiese ontwerp, het die gemete lugsnelhede in die lugskag in die veld aangedui dat groot volumes lug voortdurend uit die lugskag vrygelaat word wanneer die noodsluis ongeveer 30% toe is (dit wil sê 70% oop). Dit is in teenstelling met die ontwerp, want die lugskag is ontwerp vir die insuig van lug. Hierdie tesis het ten doel om die redes vir die vrylating van groot volumes lug uit die lugskag vas te stel met behulp van ʼn 1:14.066 fisiese skaalmodel van die uitlaatwerke en lugskag van die Bergrivierdam soos getoets tydens die inwydingstoetssluiting in 2008. Die toetse op die model het getoon dat die lugsnelheid in die lugskag onafhankik van die sluistoemaak tyd is, maar verhoog met die toename in die watervlak. Die Bergrivier dam probleem was bepaal as die van lug terugslag. Die model is gewysig ten einde te bepaal of die spesifieke samestelling van die uitlaatwerke die oorsaak van die vrystelling van lug uit die lugskag is. Die analises en verandering aan die uitleg toon aan dat die skuins afwaartse dak van die uitlaattonnel om die radiaalsluiskamer te huisves die rede was vir die vrylating van die lug uit die lugskag. ‘n Addisionele lugskag was gebou in die dak van die uitlaattonnel reg bo die sametrekking, maar was oneffektief om die terug vloei van lug te verminder. Die gevolgtrekking is dat daar geen rasionele strukturele verandering aangebring kan word aan die Bergrivier dam om die vrystelling van lug uit die lugskag te verhoed of te verminder nie. ’n Aanbeveling vir toekomstige ontwerpe is dus dat die uitlaattonnel nie beperkend by die uitlaatend moet wees nie.

HD 11112 is an old, Sun-like star that has a long-term radial velocity (RV) trend indicative of a massive companion on a wide orbit. Here we present direct images of the source responsible for the trend using the Magellan Adaptive Optics system. We detect the object (HD 11112B) at a separation of 2 2 (100 au) at multiple wavelengths spanning 0.6-4 mu m. and show that it is most likely a gravitationally bound cool white dwarf. Modeling its spectral energy distribution suggests that its mass is 0.9-1.1M(circle dot), which corresponds to very high eccentricity, near edge-on orbits from a. Markov chain Monte Carlo analysis of the RV and imaging data together. The total age of the white dwarf is > 2 sigma, which is discrepant with that of the primary star under most assumptions. The problem can be resolved if the white dwarf progenitor was initially a double white dwarf binary that then merged into the observed high-mass white dwarf. HD 11112B is a unique and intriguing benchmark object that can be used to calibrate atmospheric and evolutionary models of cool white dwarfs and should thus continue to be monitored by RV and direct imaging over the coming years.