• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2
  • Tagged with
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Solvent extraction of antimony and tin from speiss leachate

Sundell, Oscar January 2017 (has links)
This work is a cooperation with Boliden Minerals AB, who recently has been interested in recovering more valuable elements from their byproducts. For this case, solvent extraction was chosen as a potential method of recovering these valuables, as it is a method considered to be ideal for separation of trace elements from large amounts of other substances. The goal for this work was to execute manual extraction experiments as a preparation for a bigger project at LTU. The objectives of this thesis included the investigation of the selectivity for extraction of tin and antimony, using different concentrations of hydrochloric acid in the feed solution, analysis of the equilibrium isotherms for Sn and Sb at 8M of HCl as well as the evaluation of the number of steps needed for future extraction experiments, using the McCabe- Thiele method. By executing manual experiments with a speiss precipitate dissolved in hydrochloric acid, the results obtained indicated that the selectivity increased with a higher content of HCl in the feed solution. Using different ratios between the aqueous and organic phase, the equilibrium curves denoted a pushback effect, causing antimony to migrate back into the aqueous phase at the saturation level of tin. By constructing a McCable-Thiele diagram according to the equilibrium curves, the number of steps could be evaluated to three.
2

Evaluating machine learning methods for detecting sleep arousal / Evaluering av maskininlärningsmetoder för detektion av sömnstörningar

Ivarsson, Anton, Stachowicz, Jacob January 2019 (has links)
Sleep arousal is a phenomenon that affects the sleep of a large amount of people. The process of predicting and classifying arousal events is done manually with the aid of certified technologists, although some research has been done on automation using Artificial Neural Networks (ANN). This study explored how a Support Vector Machine performed(SVM) compared to an ANN on this task. Polysomnography (PSG) is a sort of sleep study which produces the data that is used in classifying sleep disorders. The PSG-data used in this thesis consists of 13 wave forms sampled at or resampled at 200Hz. There were samples from 994 patients totalling approximately 6.98 1010 data points, processing this amount of data is time consuming and presents a challenge. 2000 points of each signal was used in the construction of the data set used for the models. Extracted features included: Median, Max, Min, Skewness, Kurtosis, Power of EEG-band frequencies and more. Recursive feature elimination was used in order to select the best amount of extracted features. The extracted data set was used to train two ”out of the box” classifiers and due to memory issues the testing had to be split in four batches. When taking the mean of the four tests, the SVM scored ROC AUC of 0,575 and the ANN 0.569 respectively. As the difference in the two results was very modest it was not possible to conclude that either model was better suited for the task at hand. It could however be concluded that SVM can perform as well as ANN on PSG-data. More work has to bee done on feature extraction, feature selection and the tuning of the models for PSG-data to conclude anything else. Future thesis work could include research questions as ”Which features performs best for a SVM in the prediction of Sleep arousals on PSG-data” or ”What feature selection technique performs best for a SVM in the prediction of Sleep arousals on PSG-data”, etc. / Sömnstörningar är en samling hälsotillstånd som påverkar sömnkvaliteten hos en stor mängd människor. Ett exempel på en sömnstörning är sömnapne. Detektion av dessa händelser är idag en manuell uppgift utförd av certifierade teknologer, det har dock på senare tid gjorts studier som visar att Artificella Neurala Nätverk (ANN) klarar att detektera händelserna med stor träffsäkerhet. Denna studie undersöker hur väl en Support Vector Machine (SVM) kan detektera dessa händelser jämfört med en ANN. Datat som används för att klassificera sömnstörningar kommer från en typ av sömnstudie kallad polysomnografi (PSG). Den PSG-data som används i denna avhandling består av 13 vågformer där 12 spelats in i 200Hz och en rekonstruerats till 200Hz. Datan som används i denna avhandling innehåller inspelningar från 994 patienter, vilket ger totalt ungefär·6.98 1010 datapunkter. Att behandla en så stor mängd data var en utmaning. 2000 punkter från vare vågform användes vid konstruktionen av det dataset som användes för modellerna. De attribut som extraherades innehöll bland annat: Median, Max, Min, Skewness, Kurtosis, amplitud av EEG-bandfrekvenser m.m. Metoden Recursive Feature Elimination användes för att välja den optimala antalet av de bästa attributen. Det extraherade datasetet användes sedan för att träna två standard-konfigurerade modeller, en SVM och en ANN. På grund av en begräning av arbetsminne så var vi tvungna att dela upp träningen och testandet i fyra segment. Medelvärdet av de fyra testen blev en ROC AUC på 0,575 för en SVM, respektive 0,569 för ANN. Eftersom skillnaden i de två resultaten var väldigt marginella kunde vi inte dra slutsatsen att endera modellen var bättre lämpad för uppgiften till hands. Vi kan dock dra slutsatsen att en SVM kan prestera lika väl som ANN på PSG-data utan konfiguration. Mer arbete krävs inom extraheringen av attributen, attribut-eliminationen och justering av modellerna. Framtida avhandlingar skulle kunna göras med frågeställningarna: “Vilka attributer fungerar bäst för en SVM inom detektionen av sömnstörningar på PSG-data” eller ”Vilken teknik för attribut-elimination fungerar bäst för en SVM inom detektionen av sömnstörningar på PSG-data”, med mera.

Page generated in 0.0793 seconds