The friction of rubber on ice and snow surfaces is complex. Deeper scientific understanding is important for optimising performance of tyres in winter. Rubber, ice and snow systems exhibit frictional behaviour which depends on their material properties. The viscoelastic nature of rubber results in a higher real contact area compared to most other solids. At temperatures close or below the glass transition temperature, the frictional behaviour of rubber changes and its hardness increases. Thus, the real area of contact decreases, while the dissipation in the bulk of the rubber increases. Sliding of rubber on ice or snow leads to a temperature increase at the interface because of frictional heating, this can cause the surface to melt which decreases friction significantly. In this study we measured the friction of rubber on ice and snow and related the behaviour to mechanisms that occur. Key parameters affecting friction were examined and quantified. For this work a cold room and a new linear tribometer were specially designed and constructed. The rubber samples were made from various compounds and had different geometries. Typically they were the size of a “tread block element”. The geometries were chosen systematically to investigate the effects of surface area, sharp/rounded edges and sipes (small slits in the tread block that are used on snow tyres). A significant part of the work was developing consistent and reproducible ice and snow surfaces. New protocols were devised for these. The ice surfaces were made of de-ionised water, tap water and de-ionised water with salt. For the snow surface production: artificial snow was made and then compacted in a specially manufactured press, resulting in hard packed snow tracks for testing. Static and dynamic friction were investigated. Both were affected by speed, load, temperature and ice composition. The dynamic friction behaviour on ice was explained in terms of melt-water formation and the real area of contact of the rubber. The static friction was significantly affected by the losses inside the rubber bulk, the adhesive forces at the interface, and the time of stationary contact before the test. The investigation of rubber sliding on snow showed some similarities with sliding on ice; the surface of the rubber block slides over snow particles resulting in similar mechanisms as are seen on ice. However with snow there can also be a “ploughing” effect, where snow is cut by the leading edge of a sharp tread block. This effect contributes to friction. Experiments were made with simple rounded edged samples to avoid ploughing; the results showed the same trends as seen on ice, i.e. lower friction with increased speed, load and temperature. Investigations of siped tread blocks showed the same friction at low speeds as tread blocks without sipes. At higher speeds siped blocks exhibited less, or no, decrease in friction; more sipes gave less friction decrease. Our industrial collaborator, Michelin, made vehicle tests on snow using whole tyres with similar tread blocks. The trends they found were identical to our tests despite the dynamics of the system being more complex. This indicates how powerful the approach of using simple systematic experiments is for generating deeper understanding of the processes involved in sliding on ice and snow.

Soil water content (SWC) measurements are crucial worldwide for hydrological predictions, agricultural activities, and monitoring the progress of reclamation on disturbed land from industrial activities. In colder climates, snow water equivalent (SWE) measurements are equally important, and directly contribute to improved spring water supply forecasting. Both these variables, SWC and SWE, are commonly measured with either point-scale (e.g. soil cores for SWC and snow tubes for SWE) or large-scale (remote sensing) methods. The cosmic-ray soil moisture probe (CRP) was recently developed to fill this gap between small- and large-scale measurements. The CRP provides an average SWC reading in a landscape-scale measurement footprint (300 m radius) by taking advantage of the relationship between aboveground neutrons and soil water. Although the CRP has proved accurate in relatively homogenous sites, it has not been validated at highly heterogeneous sites. Since snow is simply frozen water, the CRP also has the potential for monitoring SWE at the landscape-scale. However, no calibration has been developed for measuring SWE with the CRP. This thesis aimed to further validate the use of a CRP for measuring SWC at a highly heterogeneous site, and calibrate a CRP for monitoring landscape-scale SWE at an agriculture field. The heterogeneous site used to validate the CRP for SWC measurement was an oil sand reclamation site made up of multiple test plots of varying soil layer treatments. Despite the clear differences in soil texture at the site, the CRP-monitored SWC compared accurately to sampled soil water content and a network of soil moisture probes. With the use of modeling, it was also possible to downscale the CRP measurement to the plot scale. For calibrating the CRP for monitoring SWE, an empirical calibration function was developed based on the relationship between the CRP-measured neutrons and SWE from snow surveys with snow tubes. Using the calibration equation, CRP-estimated SWE closely matched SWE measured from snow surveys. Differences were attributed to mid winter and spring melting of the snowpack along with varying soil water content in the top of the soil profile. This research demonstrates the usefulness of the CRP for monitoring SWC at unique sites and its ability to monitor SWE at the landscape-scale.

Treeline ecotone scrub, the suite of tall woody plant communities that bridge the boundary between tall forest and higher altitude open summit heaths, is a rare and little studied transition habitat in the UK. Individual species have recently attracted emergency measures to secure their future, but little is known about the current dynamics of the habitats. This thesis increases knowledge of treeline scrub dynamics, particularly in relation to young plants, and develops an understanding of the management required for future conservation. Climate and land use are the main drivers of treeline scrub dynamics, while land use policy will shape the future land use. This study focussed on three species: Betula nana, Salix myrsinites and Juniperus communis, as representatives of the main scrub communities. Firstly, the range of environmental conditions and the current land uses the species tolerate were surveyed for a large number of sites. This enabled the existing sites to be characterised to inform the selection of potential new sites for restoration. Secondly, experiments tested the response of young plants to the interaction between wind exposure and simulated browsing, and, separately, to over-wintering under snow. No evidence was found to suggest that declining snow cover will adversely affect the species, but while the response of the species to increasing exposure and browsing was complex heavy browsing is likely to limit expansion in the absence of specific management. Finally, a review of current land use policy identified that treeline ecotone scrub was included in existing implementation strategies. However, a survey of the understanding of and attitudes to these habitats by key individuals involved in creating, implementing and influencing policy demonstrated that restoration is unlikely to happen within the current structure, except through the interests of non-governmental organisations with a nature conservation focus.

Thesis (PhD)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT:This work is concerned with the numerical simulation of the aeolian snow transportation process (drifting or wind blown snow) and especially the snow deposition and erosion phenomenon (snow drift). The research work is interested in modelling the atmospheric boundary layer wind flow and its associated snow drifting processes around threedimensional obstacles by means of computational fluid dynamics (CFD). A modelling method is required to predict and evaluate the snow drifting phenomenon surrounding the SANAE IV research station in Antarctica. This station is of an elevated design to ensure that wind blown snow may travel around the structure relatively undisturbed and without deposition near the structure. This design is partly successful but localised drifts are formed especially leeward of the interconnecting structures that join the main building sections together. The theoretical and numerical description to describe the turbulent transport of the two-phase mixture of air and snow particles is investigated. This theory is subsequently employed to describe the snow deposition and erosion process and two models are developed to determine the deposition flux onto the snow surface. These models presented and discussed are a threshold based approach and a conservative based approach. The first model is dependent on a threshold shear velocity to determine the onset of either erosion or deposition. The second model determines the deposition or erosion flux based on the conservation of the snow mass transport in the near surface control volume. A numerical scheme that evaluates the snow deposition flux at the surface and forces a temporal surface adaptation during the simulation is established and implemented in a commercial CFD software code by means of user subroutines. Various test cases for which observed snow drift data are available are numerically modelled to validate the snow drift schemes presented in this work. These tests include the wind driven snow accumulation around a three-dimensional cube, around two adjacent three-dimensional cubes and near a typical porous snow fence. The results indicate that both methods can predict realistic snow drifts for a variety of wind flow conditions but also show that the conservative approach is superior to the threshold based approach in describing the snow drift process around obstacles. This model allows drifts to form not only in areas of low flow velocities but also under high shear conditions. The theoretical investigation and the development and validation of the conservatively based snow drift scheme shows that drift formation depends strongly on the near surface flow divergence and secondary flow structures. To resolve the snow drift formation under a variety of flow conditions a three-dimensional field solution is required to determine velocity and snow concentration gradients and include the effects of near surface convective and turbulent entrainment. The model is applied to numerically simulate and predict snow drifting around the SANAE IV base for a moderate as well as a high wind speed event. The predicted snow drift around the base agrees favourably with the observed drifts at the station. Further numerical simulations are carried out to evaluate the effects a few design modifications may have on the snow deposition. These results suggest that a simple baffle plate installation near the bottom of the interconnecting link structures may minimise the snow accumulation leeward of that area. This study shows that to achieve realistic numerical snow drift predictions around, on or near obstacles, a conservative based snow drift scheme should be considered using some form of temporal terrain adaptation strategy. Only then does one include a sufficient level of important flow effects such as deposition along near surface boundaries of strong flow divergence which plays as an important role as vertical settling and entrainment in determining deposition rates. / AFRIKAANSE OPSOMMING:Hierdie studie behels die numeriese simulasie van windgedrewe sneeubeweging asook die daarmee gepaardgaande sneeu neerslag en erosie eienskappe. Die navorsing het verder belang in die berekening van die atmosferiese grenslaag vloei en die simulasie van sneeu neerslag naby drie-dimensionele strukture deur gebruik te maak van berekeningsvloeimeganika (BVM). ‘n Berekeningsmetodiek is nodig om die eienskappe van die sneeu neerslag rondom die SANAE IV navorsingsstasie in Antarktika te voorspel en te evalueer. Die bogrondse struktuur is spesifiek so ontwerp om te verseker dat wind gedrewe sneeu hoofsaaklik onversteurd verby die struktuur kan beweeg sonder neerslag teenaan die struktuur. Die ontwerp is grotendeels suksesvol alhoewel sneeu neerslag wel lokaal plaasvind, wind af vanaf die aansluitings strukture tussen die hoof geboue. Die teoretiese en numeriese beskrywing van die twee-fase lug- en sneeumengsel beweging word ondersoek en gebruik om die sneeu neerslag en erosie einskappe te beskryf. Twee modelle wat hierdie verskynsel beskryf word beskryf en bespreek naamlik ‘n drumpel gebaseerde benadering en ‘n konserwatief gebaseerde benadering. Die eerste model is afhanklik van ‘n drumpel skuifsnelheid om die aanvang van of erosie of neerslag te bereken. Die tweede model bereken die neerslag eerder gebaseer op die behoud van die sneeu massa vloei in die kontrole volume naby aan die oppervlak. ‘n Numeriese metode is ontwikkel en geimplementeer in ‘n kommersiële BVM sagteware pakket deur van gebruikerssubroetines gebruik te maak. Die ontwikkelde kode evalueer die sneeu neerslag vloed by die oppervlak en forseer ‘n tydafhanklike oppervlak aanpassing gedurende die simulasie. Die sneeu neerslag metode wat beskryf word in hierdie studie word ge-evalueer teen verskeie toetsgevalle waarvoor daar waargenome sneeu neerslag resultate beskikbaar is. Hierdie toetse sluit in die wind gedrewe sneeu neerslag rondom ‘n drie-dimensionele kubus, rondom twee naby geleë kubusse en naby ‘n tipiese poruese sneeu heining. Die resultate dui aan dat beide die metodes realistiese sneeu neerslag voorspel vir verskeie wind toestande. Die studie wys ook dat die konserwatief gebaseerde benadering vir die beskrywing van die sneeu neerslag proses meer akkuraat is as die drumpel gebaseerde benadering aangesien die neerslagvoorspel kan word nie net alleenlik in gebiede met lae vloeisnelhede nie, maar ook in gebiede waar hoë skuifsnelhede teenwoordig is. Die teoretiese ondersoek, ontwikkeling en toepassing van die konserwatief gebaseerde model dui daarop dat die neerslag afhanklik is van die divergensie van die vloeiveld asook van die sekondêre vloei patrone naby die oppervlak. Ten einde die sneeu neerslag vir verskeie toestande op te los is dit nodig om snelheids- en sneeukonsentrasie gradiënte te kan bereken in ‘n drie-dimensionele vloei veld om sodoende die invloed van naby-oppervlak konveksie en turbulente verspreiding in ag te neem. Die metode word toegepas deur die sneeu neerslag rondom die SANAE IV navorsingsstasie te voorspel vir ‘n gematigde asook ‘n hoë wind snelheid toestand. Die sneeu neerslag voorspelling stem gunstig ooreen met die waargenome neerslag by die struktuur. Verdere numeriese simulasies is uitgevoer om die invloed van ontwerpsverandering op die neerslag te evalueer. Uit hierdie resultate blyk dit dat ‘n eenvoudige plaat struktuur onder die aansluitingsstrukture die sneeu neerslag wind af mag verminder. Hierdie navorsingsstudie dui daarop dat ‘n tydafhanklike terrein aanpassing strategie saam met die konserwatiewe neerslag model noodsaaklik is ten einde realistiese resultate te behaal vir die sneeu opbou rondom of naby strukture. Sodoende word genoegsame vlakke van belangrike vloei verskynsels, soos die invloed van vloei divergensie, in ag geneem wat net so ‘n belangrik rol in neerslag speel soos vertikale afsetting.

Inventory-prediction equations describing snowpack water content as functions of readily available or easily obtained inventory variables were developed for use in the ponderosa pine type in Arizona. Although empirical in nature, these equations include parameters assumed to index interception of precipitation inputs, obstruction of direct beam solar radiation, and re-radiation from trees onto the snowpack. Primary consideration was given to forest cover variables in synthesizing the inventory-prediction equations I because currently proposed water improvement programs designed to increase water yield derived from snow consist essentially of vegetative manipulations. Additional independent variables evaluated include potential direct beam solar radiation, elevation, soil, and precipitation inputs. All of the inventory-prediction equations describing a particular snowpack condition were not statistically equivalent in terms of the standard error of estimate or the coefficient of determination. Equations including basal area, bole area I volume, and height-index as expressions of forest cover density were generally better than equations with point density, sum of diameters, and number of trees. Inventory-prediction equations developed to describe snowpack dynamics throughout the accumulation period showed similar statistical form, except as possibly attributable to different precipitation inputs. Equations for characterizing residual snowpacks during spring runoff were statistically weak, possibly because factors other than those considered in this study control the runoff process. The inventory-prediction equations were developed to estimate the mean snowpack water content on a basin, and to describe the trade-off , or the rate of exchange, between snowpack water content and forest-site variables on a decision-making unit. The equations do not necessarily predict changes in recoverable water yield resulting from the implementation of a land management system, however. Nonbiotic characteristics of the land, L e., topographic features, geologic formations, and soil . properties, could conceivably control water yield to the extent that changes predicted by the inventory-prediction equations could be masked. Because of limitations in predicting potential changes in recoverable water yield, it was assumed that a land management system that maximizes snowpack water content on site would also provide the maximum potential for increasing recoverable water yield derived from snow. Management guidelines designed to allow snowpack water content to be maximized on site can be formulated within the framework of the inventory-prediction equations, multiple use management constraints, and forest-based product benefits and costs. Management guidelines indicate that the greatest gain in snowpack water content on site would be realized on decision-making units where the greatest reduction in forest cover density could be prescribed. However, a timber production constraint may limit the array of management possibilities. This constraint was defined as 35 to 40 square feet of basal area or 1,050 to 1,175 cubic feet of volume per acre, depending upon the existing growth percent and the intermingling of tree volumes and size classes. The potential increase in snowpack water content on site will be determined by the magnitude of the reduction in forest cover density and how close management re-direction can approach the timber production constraint. The proportion of the snowpack water content on site converted to recoverable water yield is dependent upon the runoff efficiency.

The relationship between specific synoptic and mesoscale snowfall producing system types and their associated mean upper-level flow patterns are examined to determine their impacts on snowfall magnitudes in central Indiana. Chi-square and ANOVA tests are conducted to determine the relationship of the 850mb temperature, the 1000-500mb thickness, 500mb flow pattern, and phase of the Southern Oscillation Index to snowfall amounts for the period of record 1974-2003. Results suggest that variables such as the 1000-500mb thickness, system type, and phase of the Southern Oscillation Index do affect the magnitude of snowfall in central Indiana on a variety of temporal scales ranging from days to entire seasons. / Department of Geography

nforme final de Seminario para optar al grado de Licenciada en Lengua y Literatura Hispánica con mención en Literatura / En este primer capítulo nos proponemos mostrar un panorama general acerca de la ciencia ficción (en adelante CF) y las problemáticas que pueden desprenderse de ella, para así tener una base sobre la cual instalar nuestros análisis personales de diferentes novelas del género. La primera parte del Seminario de Grado el curso se enfocó en abordar lo que más adelante expondremos, es decir, la historia del género, su definición, y sus distintas manifestaciones en subgéneros; para lo cual leímos y vimos varias o bras que resultan representativas de la CF. Además, se dedicó tiempo a procesar la bibliografía con la que trabajaremos, y a discutir distintos aspectos de la misma. Así, durante la segunda parte del curso, enfocada a la producción de nuestros informes fin ales, pudimos aplicar y ampliar lo visto en clases en función de la obra que cada uno decidió analizar. Antes de comenzar, es pertinente mencionar un suceso que tomó lugar tras asistir al primer encuentro de seminario de grado: nos enteramos de que todos manejamos un nivel de inglés que nos permite leer en el idioma. Este aspecto resultó relevante, pues la gran mayoría de las obras y bibliografía de ciencia ficción es producida por angloparlantes. Luego de llegar un acuerdo común, el profesor guía decidió reestructurar el programa del curso, en función de incluir textos actuales que carecen de traducciones. Tal decisión impactó nuestro paso por el seminario, pues el espectro de posibilidades para elegir nuestro objeto de estudio se vio favorablemente ampliado.

In Pacific North America, a substantial amount of the streamflow available during the dry summer months originates from melting mountain snowpacks. Since the start of the twenty-first century, these mountain snowpacks have been declining due to the impacts of global climate change and could have severe implications for future water availability in many regions. To develop robust predictive models of future water availability derived from mountainous snowpacks, the longest possible data record is required. However, instrumental data for snow measurements, when available, are limited to a length of only five or six decades in most regions of Pacific North America. In this study, tree-rings from snow-depth sensitive tree species (mountain hemlock (Tsuga mertensiana (Bong.) Carrière) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.)) were used as a proxy to develop a 258-year record of precipitation as snow (PAS) for the southern Coast Mountains of British Columbia. Four snow models were evaluated based on a suite of dendroclimatological model diagnostics. From these, one PAS reconstruction was carried out. The reconstruction was unable to properly validate using the leave-one-out cross validation method. This result is attributed to the combination of a short calibration period, a potentially weak climate signal, and the absence of signal enhancement. Despite this outcome the research resulted in number of inferences and recommendations useful for future research. / Graduate

This thesis analyses 21st century filmic, televisual and comic “Snow White” adaptations. The research is interdisciplinary, bringing together scholarship on gender, childhood, ageing, adaptation, media and fairy tales. The first half of the thesis contextualises the broader historical and sociocultural conversation “Snow White” tellings are immersed in by nature of their shared culture and history. It also identifies the tale’s core and traces the tale’s formation as a tale type from the seventeenth to the twenty–first century. The second half of this thesis moves to an analysis of two films (Mirror Mirror, 2012; Snow White and the Huntsman, 2012), a television series (Once Upon a Time, 2011–present) and a comic book series (Fables, 2002–2015). It considers the kinds of stories about female growth and ageing different media adaptations of “Snow White” enable, and contemplates how issues of time and temporality and growth and ageing play out in these four versions. In analysing the relationship between form and content, this thesis illustrates how a study of different media adaptations of “Snow White” can enrich fairy–tale scholarship and the fairy–tale canon. It also details the imaginative space different media adaptations of “Snow White” provide when engaging with dominant discourses around female growth and ageing in the West. Using “Snow White” as a case study, this thesis centrally facilitates a dialogue between ageing, childhood, fairy–tale and adaptation studies.

Dealing with the issue of spring flood events is primarily based on their causes. It is therefore important to study the processes of snow accumulation and snowmelt especially in mountain areas where the development of snow water equivalent (SWE) is primarily observed. The snow water equivalent indicates amount of the water in the snow and thus represents a runoff volume during the spring melting period and demonstrates the flood risk potential. In this thesis the lumped modelling approach of the rainfall-runoff model HEC- HMS was used. The model was applied in the Bystřice River basin in the Ore Mountains where the field measurements of the snow cover and SWE is carried out. Applied temperature-index method is the well-developed method because it takes into account both the melting during precipitation and melting in the period without any precipitation and aims to capture snow energy balance by means of air temperature. Three winter periods (2006, 2008 and 2009) were simulated. The evolution of the snow water equivalent was observed and the agreement between observed and simulated hydrographs was assessed in the closure profile Ostrov. Published results show the influence of winter course and character on the model capability to simulate the snow water equivalent and runoff. The observed and...