Analysis and comparison of weather models for solar irradiance forecasts in Sweden

Solar radiation is affected in a variety of different ways through the atmosphere and on its way down to the Earth’s surface. Clouds are the main factor in this attenuation of solar radiation, but aerosols, ozone and other different gases have a significant impact too. Understanding these processes is fundamental to solar forecasting. However, the atmosphere is constantly changing, which makes forecasting weather a challenging task even with today’s complex numerical weather prediction models. In this study of solar irradiance, two different numerical weather models are analyzed: the global IFS-model and the regional ensemble prediction system MEPS. Both models include normal forecasts and ensemble forecasts. This analytical comparison was made in forecasts of up to 24 hours of three locations in Sweden over the time period of 2017-04-01 to 2017-06-30. The purpose was to see differences in the accuracy of the models, and also to see the influence of ensemble forecasts. Ensemble forecasts are used to better handle uncertainties in the weather and are more frequently used in today’s weather prediction. Observation data collected from SMHI’s radiation network was used as reference values in order to get forecasting errors. A generally better result for the ensemble forecasts was identified. Some variations between the stations were also detected where especially the result from one of the three stations was different. That was a location far away from the other two indicating that topography and climatology can affect the precision of the weather models. The regional high-resolution MEPS-model had overall better solar irradiance forecasts during the analyzed time, but the model had a consistent negative bias. A consistent problem with the MEPS-model is most likely that it predicts too much clouds which leads to less amount of solar irradiance in the forecasts.Vad tänker du på när du hör ordet solprognos? För vissa är det viktigt i planeringen av semestern, andra kanske för att skydda sig mot farlig UV-strålning. Vad många inte vet är att solprognoser är en viktig komponent i vårt energisamhälle där förnyelsebara energikällor som solkraft och vindkraft ökar kraftigt runt om i världen. Att göra träffsäkra prognoser för inkommande solstrålning har dock visat sig vara svårt för meteorologerna på grund av snabba och osäkra förändringar i atmosfären. Osäkerheten och variabiliteten för solstrålningen beror framförallt på molnen men också aerosoler, ozon och andra gaser i atmosfären. För att förutse solstrålning och andra meteorologiska parametrar används numeriska vädermodeller där avancerade superdatorer behövs. Genom att veta atmosfärens nuvarande tillstånd och sedan använda fysikens lagar kan man alltså med hjälp av datorer köra simulationer som får fram hur atmosfären och vädret kommer att se ut. Trots att olika vädermodeller bygger på samma fysikaliska teorier och lagar så finns det ändå ofta signifikanta skillnader mellan dem. I den här studien jämförs och analyseras två numeriska vädermodeller för solprognoser i Sverige. Det är den globala modellen IFS och den regionala modellen MEPS (som bygger på modellen HARMONIE-AROME) som jämförs i solprognoser på upp till 24 timmar. Normala prognoser men även de båda vädermodellernas ensembleprognoser analyseras under tidsperioden 2017-04-01 till 2017-06-30. Ensembleprognoser är sannolikhetsprognoser som numera används för att försöka förbättra väderprognoser. Resultatet visar att ensembleprognoser generellt förbättrar prognoserna för solstrålning i Sverige. Den regionala och högupplösta modellen MEPS visar sig för det mesta vara träffsäkrare än den globala IFS-modellen. Detta trots att MEPS har en tydlig tendens att förutse för lite solstrålning. Olika platser i Sverige undersöktes och resultatet varierar dock en aning mellan platserna. Troligtvis beror detta på skillnader i modellernas fysikaliska egenskaper och i att hantera topografi och olika meteorologiska förhållanden

Investigation of ECG electrodes for burn wounds

This project aims to investigate a variety of electrodes for ECG (electrocardiogram) measurements and find suitable ones for burn wounded skin in association with the Burn center in Uppsala University Hospital.   To this purpose, the electrical properties (in particular, electrical impedance and equivalent circuit) of electrodes and the influence of the skin on the electrical properties are looked into, and various common artefacts in ECG measurements are investigated, such as wandering baseline (caused by perspiration, respiration, patient movement and poor electrode contact), muscle tremor artefact, 50-60 Hz power line interference and measurement noise.   Simulation of a burn wound was done by putting Ringer’s acetate between two electrodes gel to gel. Six different electrodes made with either a solid or wet gel for the electrolyte were tested, three of which (Ambu Bluesensor L-00-S/25, Ambu Bluesensor R-00-S/25, Milmedtek T-VO01) have wet gel, and three of which (3M 2670-5, Medtronic Arbo, and Ambu Whitesensor WSP30-00-S/50) have solid gel.   The tests showed that the impedance of the electrodes changed as expected and was in almost all cases lowered. An increase in phase shift was also observed with burn wound simulation but could not be proven to relate with increased polarization.   The results showed its wet gel and adhesive developed for sweaty/wet skin, Ambu Bluesensor R-00-S/25 is recommended.   Suggestions for further investigation would be to see if the interference could be solved by impedance balancing the electrodes or to investigate if there is a greater coupling between the wet burn wounds and the main 230V 50Hz network causing higher currents and voltage drops in the body increasing the risk of common mode to differential mode conversion

"Jag har hittat en bok!" : En studie om skolors klassbesök på bibliotek

The aim of this thesis is to investigate the role of class visits to public- or school-libraries during school hours, regarding students of ages 7- 10. The research is founded on a case study on Burträsk library, and uses qualitative interviews with librarians and teachers at the nearby elementary school, and non-intrusive observations of class visits. The research questions were: - What is the function of the school's class visits to the library, for the students' reading and desire to read? - What thoughts and attitudes do the teachers and librarians who work with class visits have, about reading-promoting activities and children's reading? - How do these thoughts and attitudes express themselves, in the work with class visits? The study finds that the teachers and librarians who are part of the study have a pragmatic approach to children's reading, which places more emphasis on the children’s joy to read, than that they read a particular type of literature. The teachers 'work creates a joyful view of reading in most children who participate in class visits, and class visits seem to be of great importance for the children' s desire to read

"Jag har hittat en bok!" : En studie om skolors klassbesök på bibliotek

The aim of this thesis is to investigate the role of class visits to public- or school-libraries during school hours, regarding students of ages 7- 10. The research is founded on a case study on Burträsk library, and uses qualitative interviews with librarians and teachers at the nearby elementary school, and non-intrusive observations of class visits. The research questions were: - What is the function of the school's class visits to the library, for the students' reading and desire to read? - What thoughts and attitudes do the teachers and librarians who work with class visits have, about reading-promoting activities and children's reading? - How do these thoughts and attitudes express themselves, in the work with class visits? The study finds that the teachers and librarians who are part of the study have a pragmatic approach to children's reading, which places more emphasis on the children’s joy to read, than that they read a particular type of literature. The teachers 'work creates a joyful view of reading in most children who participate in class visits, and class visits seem to be of great importance for the children' s desire to read

"Jag har hittat en bok!" : En studie om skolors klassbesök på bibliotek

The aim of this thesis is to investigate the role of class visits to public- or school-libraries during school hours, regarding students of ages 7- 10. The research is founded on a case study on Burträsk library, and uses qualitative interviews with librarians and teachers at the nearby elementary school, and non-intrusive observations of class visits. The research questions were: - What is the function of the school's class visits to the library, for the students' reading and desire to read? - What thoughts and attitudes do the teachers and librarians who work with class visits have, about reading-promoting activities and children's reading? - How do these thoughts and attitudes express themselves, in the work with class visits? The study finds that the teachers and librarians who are part of the study have a pragmatic approach to children's reading, which places more emphasis on the children’s joy to read, than that they read a particular type of literature. The teachers 'work creates a joyful view of reading in most children who participate in class visits, and class visits seem to be of great importance for the children' s desire to read

Pass-by noise contribution analysis of electric vehicles

In the modern urban lifestyle, more and more people are exposed to noise pollution in form of traffic noise. As a response to this, the automotive OEMs (Original Equipment Manufacturer) are put under pressure to reduce the emitted noise from vehicles. To be able to meet the upcoming, stricter regulations, the automotive OEMs seeks new techniques to be able to front load the pass-by noise engineering in the vehicle development process and to identify and understand the different sources that contributes to the exterior noise.Earlier exterior sources ranking using ASQ (Airborn Source Quantification) with an energetic approach during pass-by noise test has yielded very good and reliable results for an ICE (Internal Combustion Engine) vehicle.In this Master Thesis, two exterior source ranking methods have been tested and evaluated for an electric vehicle during in-room pass-by noise test. The two methods were: ASQ and OPA (Operational Path Analysis). In total, five models were built from the two methods and each model was evaluated for, in total, three driving conditions corresponding to the current ISO362-1:2007 and the proposed, revised version.The results show that the ASQ models are not capable to correctly estimate the engine contribution due to its high tonality. Moreover, it was seen that the energetic ASQ model is very sensitive to small changes. Both ASQ models underestimated the tire noise.The OPA model on the other hand managed to estimate the total contribution very well. Both the engine contribution and the tire contributions are well estimated. Nevertheless, OPA as method has several weaknesses and building an OPA model is not a straightforward task. Its weaknesses and the process to reach a final OPA model are discussed in this thesis.It was seen that one of the most crucial steps in an OPA model is to have clean references to get meaningful results. A MIMO-FIR filter was therefore used to filter out engine harmonics from the tire references. Its principles and importance for the end results are also discussed.Included is also an overview of the basic principles in TPA (Transfer Path Analysis), ASQ, OPA and in room pass by noise test as well as a description of the test campaign

Measuring the Risk-neutral Probability Distribution of Equity Index Options

The focus of this master thesis is to develop a model that measures the risk-neutral probability distributionof the future value of a portfolio consisting of options on the S&P 500 index. The cornerstone of the model is an explicit and thorough construction of the local volatility surface. The parametric model of Coleman etal. (1998), with some modifications, is used, representing the local volatility surface through a bicubic spline. The local volatility surface is optimized to be consistent with market data on option prices, futures contracts and Overnight Index Swap (OIS) interest rates. Repricing of options is done through a finite difference method (FDM) approach presented by Andersen and Brotherton-Ratcliffe (1998), using the Crank-Nicholson scheme. An interior point solver is used to minimize the squared pricing error weighted by liquidity in each option. Fast and accurate gradients of the objective function are obtained using the Automatic Differentiation library Autograd.The local volatility surface is constructed for multiple dates and the systematic changes are analyzed through Principal Component Analysis (PCA) of the logarithmic local variance. A stochastic process is assigned to the local volatility surface using the sensitivities towards systematic changes identified through the PCA. Using a Gaussian Kernel Density Estimator, the probability density function (PDF) of the future value of the portfolio is measured. The method requires simulated portfolio values, which are achieved through FDM pricing using simulations of the local volatility surface and the underlying index. The cumulative distribution function (CDF) is finally computed by integration of the PDF. To evaluate the measured probability distribution, a normal CDF inversion of 106 measured out-of-sample CDF values are compared to theoretical normal distribution quantiles with Q-Q plots. The constructed local volatility surface is consistent with market prices to an extent where it is more accurate for more liquid options. It is in most cases realistic with respect to smoothness, but have an unexpectedly large offset from the at-the-money strike level in the skew structure. It is unstable from date to date and also significantly dependent on choice of parameters, limited by computational power, and input data. The unstable construction of the local volatility surface results in measurement noise that cause negative auto correlation in the principal components, which impairs their explanatory ability. The main result show that the shape of the probability distribution is measured accurately, but the standard deviation (or volatility) is overestimated

Measuring the Risk-neutral Probability Distribution of Equity Index Options

The focus of this master thesis is to develop a model that measures the risk-neutral probability distributionof the future value of a portfolio consisting of options on the S&P 500 index. The cornerstone of the model is an explicit and thorough construction of the local volatility surface. The parametric model of Coleman etal. (1998), with some modifications, is used, representing the local volatility surface through a bicubic spline. The local volatility surface is optimized to be consistent with market data on option prices, futures contracts and Overnight Index Swap (OIS) interest rates. Repricing of options is done through a finite difference method (FDM) approach presented by Andersen and Brotherton-Ratcliffe (1998), using the Crank-Nicholson scheme. An interior point solver is used to minimize the squared pricing error weighted by liquidity in each option. Fast and accurate gradients of the objective function are obtained using the Automatic Differentiation library Autograd.The local volatility surface is constructed for multiple dates and the systematic changes are analyzed through Principal Component Analysis (PCA) of the logarithmic local variance. A stochastic process is assigned to the local volatility surface using the sensitivities towards systematic changes identified through the PCA. Using a Gaussian Kernel Density Estimator, the probability density function (PDF) of the future value of the portfolio is measured. The method requires simulated portfolio values, which are achieved through FDM pricing using simulations of the local volatility surface and the underlying index. The cumulative distribution function (CDF) is finally computed by integration of the PDF. To evaluate the measured probability distribution, a normal CDF inversion of 106 measured out-of-sample CDF values are compared to theoretical normal distribution quantiles with Q-Q plots. The constructed local volatility surface is consistent with market prices to an extent where it is more accurate for more liquid options. It is in most cases realistic with respect to smoothness, but have an unexpectedly large offset from the at-the-money strike level in the skew structure. It is unstable from date to date and also significantly dependent on choice of parameters, limited by computational power, and input data. The unstable construction of the local volatility surface results in measurement noise that cause negative auto correlation in the principal components, which impairs their explanatory ability. The main result show that the shape of the probability distribution is measured accurately, but the standard deviation (or volatility) is overestimated