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Browsing by Subject "jää"

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  • Characterization of a small high-Arctic glacier system via historical observations and numerical modelling 
    Vainio, Tomi (2022)
    Small arctic glaciers have in general been consistently neglected with respect to the collection of long time-series observations. Available data is often a product of multiple independent and separate studies, thus gaps in the data sets are common. Numerical modelling provides one solution to alleviate existing gaps in knowledge, while historical observations can be used to assess model accuracy. The Foxfonna ice cap and associated glacier were investigated with the aid of the numerical modelling software, Elmer/Ice. The goal was to reproduce core glaciological characteristics of the entire glacier system from a 3D simulation based on multiple digital elevation models (DEMs) between the years 1961-2021. The methods proved capable of providing additional information on the glaciological characteristics of a small glacier system, such as Foxfonna. Issues primarily arose from the steady state assumption and the difficulty of producing simulations for a dynamically varying glacier system.
  • Sokerikuorrutteen säilyminen pakkasvarastossa 
    Narinen, Lauri (2019)
    Controlling crystallization is an important factor in the production of food, whether it is preventing crystallization or enabling it, depending on the food product. To control crystallization, one must understand the theory behind crystallization and the components in food that affect crystallization. In sugar icing the most obvious components are sugars and water that affect crystallization. Also, the frozen storage has an important role concerning shelf-life of the sugar icing. The aim of this study was to prolong the shelf-life of the sugar icing on top of the donuts and to understand the phenomena that have an influence on the quality of the sugar icing during freezer storage. The experimental part of the study was divided into two parts. Preliminary tests were conducted in the first part. In these preliminary tests the aim was to measure the temperature and relative humidity during the melting of donuts in its packaging and to evaluate the applicability of ultracentrifuge and Karl Fischer titration in the measurement of the sugar icings properties. In the main experiment part, the water activity was measured from the different parts of the donut, the freezing of the sugar icing as well as its viscosity were evaluated and the shelf-life of the sugar icing on top of the donuts was evaluated. Karl Fischer titration was found to be a suitable method for measurement of water content of sugar icings. Also, the ultracentrifuge was found to be a suitable method to measure the liquid phase of the sugar icing. In the measurement of the conditions during the melting of the donuts it was detected that the conditions in the package that was open during the melting of the products, balanced with the conditions surrounding the packaging rather quickly. At the same in the closed package the conditions remained same during melting even though the melting was done in different surrounding conditions. The shelf-life of the donuts was found to be shortest in those icings that had less water or if the water was less free in the icing. The longest shelf-life was found to be in the coated sugar icings. Methods to prolong the shelf-life of the sugar icing on top of the donut were found in this study. Also, the phenomena affecting the quality of the sugar icing during frozen storage were discovered to some extent but to understand them even further requires more research.

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