Efterfrågan av väderskyddande ställningar inom byggproduktion har ökat under de senaste åren. En konsekvens vid användning av väderskydd är att ställningen tar upp större laster vid vind och nederbörd, vilket ökar risken för att konstruktionen kollapsar. Under vintern 2016/2017 rasade två väderskydd på Kungliga Tekniska Högskolans område efter ett kraftigt snöfall vilket gav författarna idén till denna examensrapport. Syftet med rapporten är att utreda varför väderskyddade ställningar rasar genom att undersöka processen för uppförande och användande av väderskydd i produktion samt gällande lagar och regler. Rapporten gjordes i samarbete med Skanska och således studerades enbart företagets egna tillvägagångssätt. Litteraturstudier och en genomförd kvalitativ undersökning på tre projekt ligger till grund för rapportens diskussion och slutsatser. Genom studie av Arbetsmiljöverkets föreskrifter (AFS) drogs slutsatsen att dessa är tillräckliga för att förebygga att olyckor sker. Studierna visade även att Skanskas säkerhetsarbete är välutvecklat med detaljerade arbetsmetoder för ett säkert arbete med ställningar och väderskydd. Skanska har även gjort egna tillägg som kompletterar AFS:en för ett säkrare arbete. Rapporten påvisar även ett behov av utredningar från Arbetsmiljöverket när väderskydd kollapsar för att förebygga allvarliga olyckor i framtiden. / The demand for weather protected scaffolding in building production has increased during recent years. A consequence when using weather protection is that the scaffolding will have to endure bigger loads from wind and snow, which increases the risk of a collapse. During the winter of 2016/2017 two weather protected scaffoldings collapsed by heavy snowfall at the site of KTH (the Royal Institution of Technology) in Stockholm, Sweden. This gave the authors the idea of this report. The purpose of the report is to investigate why weather protected scaffoldings collapses by examining the procedure of building and using weather protection in production and also a study of the current regulations regarding the subject. The report was made in cooperation with Skanska and therefore only the company’s intern procedure was studied. During the studies of the Swedish Work Environment Authority’s statute book a conclusion was made that the statute book was sufficient enough to prevent accidents to occur. The studies also showed that Skanska’s safety work is well developed with it’s detailed working methods for a safe work environment regarding scaffolding and weather protection. Skanska has made own additions to the statute book in order to improve safety even more. The report also shows a need of an investigation made of the Swedish Work Environment Authority when a weather protected scaffolding has collapsed to prevent serious accidents in the future.

A commercial-off-the-shelf Ku-band Frequency Modulated Continuous Wave (FMCW) synthetic aperture radar (SAR) system is coupled with a custom built two-dimensional scanning system. This system is installed in an alpine environment and pointed at a snow-unstable mountain slope for the duration of a Utah winter. The radar scanning system, designed to be capable of mapping a snowpack and its layers, is employed to create a series of three-dimensional images from a remote location. Individual images demonstrate the ability to directly detect snow layers, Furthermore, successive images are compared to track volume magnitude and phase values over the course of winter, including many snow deposition and melt events. The digital signal processing techniques used to create a high-resolution voxel (a three-dimensional pixel) map describing these snow layers is discussed. Results are discussed and further work is suggested for improving upon the results of this work.

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For migratory birds the highly dynamic atmosphere plays a significant role during every part of their migratory flight. It is essential for the success of their reproduction that they arrive at the breeding areas in the right time span and in good condition. It follows then a successful and timely migration to their breeding areas is of critical importance to these bird populations. Seemingly, different weather conditions can either be beneficial or detrimental and specifically wind is thought to be the greatest factor for a successful migration. Migratory birds have to, due to various cues, decide when to stop for stopovers as well as decide for next take off from that stopover site. In this study I’ve examined if four different abiotic factors, (wind direction, wind speed, temperature and precipitation) affect snow bunting’s propensity to do stopovers at a coastal site in north of Sweden during spring migration. I’ve also examined if there is a variation in arrival at said site between the years during spring migration. To make this study possible I’ve captured snow buntings at Umedeltat field station during spring 2018 and combined my data with data from 2017 as well as data from 2012. I found no significant correlation with either wind speed, temperature nor precipitation and captured birds. I suggest that a longer study that takes into account more abiotic factors and examines the roles of spatial and temporal patterns during migration of snow buntings needs to be conducted. As the climatic conditions are changing in western Europe it is of importance to monitor how birds are influenced by weather, especially an Arctic-breeding bird, as the climate change is presumed to be greater in those regions.

<p> Proposed theories concerning the nature and mode of formation of limestone scallops are examined. Some progress is made toward a purely theoretical understanding. Scallop formation is simulated by generation on blocks of Plaster of Paris in a laboratory flume under known and controlled conditions and the relationships between the resulting features, the generating conditions and the base material examined. Field Evidence both confirms these relationships and reveals other unsuspected factors. The similarity between these features and others found on ablating snow surfaces is investigated and the same laws found to apply. </p> / Thesis / Doctor of Philosophy (PhD)

Grain sorghum provides energy-rich seeds for waterfowl. I conducted experiments in 22 sorghum fields in Arkansas, Mississippi, and Louisiana during falls 2006 – 2007 to evaluate abundance of ratoon grain (i.e., second crop after harvest), waste grain, and natural seeds. I also conducted surveys of wintering waterfowl in flooded croplands and moist-soil wetlands to evaluate if ducks and geese differentially used habitats. Fertilized plots in 2007 produced >4 times more ratoon grain (x = 219.57 ± 39.65 [SE] kg/ha) than other treatments. Fertilized plots in southern regions of my study area produced ~5 times more ratoon grain (x = 262.93 ± 50.28 kg/ha) than others. Mallards and other ducks used moist-soil wetlands (x >65 ducks/ha) more than other habitats. I did not observe geese using flooded sorghum. I recommend not manipulating sorghum stubble after harvest, fertilizing, and flooding it after ratoon grain has matured, and integrating moist-soil wetlands into agricultural lands.

Human activities and expansion have created novel disturbance patterns across Earth’s landscapes. Disturbance is an ecological interruption after which ecosystem recovery or transition into a new state can occur, affecting biodiversity, ecosystem functioning, and theavailability of ecosystem services. Fire and herbivory are two of the most widespread forces of disturbance which shape ecosystems globally. In temperate forest ecosystems, fire affects forest composition, which influences the diversity and resilience of ecosystems (chapters 1 and 2) and forest canopy structure, which is important to snowpack accumulation and the availability of water resources (chapters 3 and 4). In chapter one, the effects of conifer competition, which occurs under fire suppression, and ungulate herbivory on aspen regeneration and recruitmentwere examined. It was found that conifer competition, and ungulate herbivory both drastically reduced successful aspen regeneration and recruitment and had a larger effect than climatic or topographical variables. In chapter two, this understanding was used to investigate mechanicaland fire interventions by the National Forest Service in a mixed aspen conifer forest experiencing fire suppression and heavy ungulate herbivory. Untreated forests failed to recruit aspen suckers successfully due to conifer competition and ungulate browsing. Fire treatments were successful in restoring aspen habitat, but mechanical treatments failed due to heavy ungulate use, despitethe treatment eliciting high sucker densities. In chapter three, fire severity was found to have important implications for snowpack accumulation and snow-water content in alpine forests. High burn severity, which is projected to become more common under future climaticconditions, led to deeper and denser snowpack possibly buffering the effects of water loss in a warmer climate. In chapter four, the interaction between topography and vegetation in burned forest conditions was evaluated. It was found that topographical aspect likely mediates the effect of vegetation on snowpack and may have an opposite effect on snow accumulation and melt on north vs south facing aspects. A synthesis of studies from different regions further supports the idea that this relationship between fire and snow is heavily dependent on latitude, elevation, and slope angle. Together, these findings demonstrate that the resilience and persistence of aspenforest ecosystems in changing disturbance regimes depend on complex interactions among disturbance type, disturbance severity, landscape position, and hydrology. These interactions should be integrated into management strategies to protect ecosystems and ensure ecosystemservices for growing human populations in the western United States.

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