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Gradientní segmentace snímků očního pozadí / Gradient boosted segmentation of retinal fundus imagesGoliaš, Matúš January 2021 (has links)
Title: Gradient boosted segmentation of retinal fundus images Author: Matúš Goliaš Department: Department of Software and Computer Science Education Supervisor: Doc. RNDr. Elena Šikudová PhD., Department of Software and Computer Science Education Abstract: Over the recent years, there has been an increase in the use of automatic methods in medical diagnosis. A significant number of publications have analysed eye disorders and diseases. One of the most severe eye conditions is glaucoma. It damages optic nerves and causes gradual loss of vision. An essential step towards a faster diagnosis of this disease is accurate segmentation of the optic disc and cup. This task is difficult due to many retinal defects, different image acquisition techniques, and artefacts caused by imaging devices. This thesis describes an iterative threshold-based algorithm for extraction of the optic disc. An objective function quantifying object similarity to the optic disc is defined to direct the iteration. Following that, we introduce a superpixel-based classification algorithm for extraction of the optic cup. We propose the use of gradient boosted decision trees which outperform random forest and support vector machine. In addition, we evaluate the proposed algorithms and their alternatives on a publicly available retinal fundus...
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Classification of Video Traffic : An Evaluation of Video Traffic Classification using Random Forests and Gradient Boosted TreesAndersson, Ricky January 2017 (has links)
Traffic classification is important for Internet providers and other organizations to solve some critical network management problems.The most common methods for traffic classification is Deep Packet Inspection (DPI) and port based classification. These methods are starting to become obsolete as more and more traffic are being encrypted and applications are starting to use dynamic ports and ports of other popular applications. An alternative method for traffic classification uses Machine Learning (ML).This ML method uses statistical features of network traffic flows, which solves the fundamental problems of DPI and port based classification for encrypted flows.The data used in this study is divided into video and non-video traffic flows and the goal of the study is to create a model which can classify video flows accurately in real-time.Previous studies found tree-based algorithms to work well in classifying network traffic. In this study random forest and gradient boosted trees are examined and compared as they are two of the best performing tree-based classification models.Random forest was found to work the best as the classification speed was significantly faster than gradient boosted trees. Over 93% correctly classified flows were achieved while keeping the random forest model small enough to keep fast classification speeds. / HITS, 4707
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Měření úvěrového rizika podniků zpracovatelského průmyslu v České republice / Credit Risk Measurement in Manufacturing Industry Companies in the Czech RepublicKaras, Michal January 2013 (has links)
The purpose of this doctoral thesis is to create a new bankruptcy prediction model and also to design how to use this model for the purposes of credit risk measuring. The starting-point of this work is the analysis of traditional bankruptcy models. It was found out that the traditional bankruptcy model are not enough effective in the current economic conditions and it is necessary to create a new ones. Based on the identified deficiencies of the traditional models a set of two new model series was created. The first series of the created models is based on the use of parametric methods, and the second one is based on the use of newer nonparametric approach. Moreover, a set of factors which are able to identify an imminent bankruptcy was analyzed. It was found, that significant signs of imminent bankruptcy can be identified even five years before the bankruptcy occurs. Based on these findings a new model was created. This model incorporates variables of static and even dynamic character for bankruptcy prediction purposes. The overall classification accuracy of this model is 92.27% of correctly classified active companies and 95.65% of correctly classified bankrupt companies.
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Short-term Forecasting of EV Charging Stations Power Consumption at Distribution Scale / Korttidsprognoser för elbils laddstationer Strömförbrukning i distributionsskalaClerc, Milan January 2022 (has links)
Due to the intermittent nature of renewable energy production, maintaining the stability of the power supply system is becoming a significant challenge of the energy transition. Besides, the penetration of Electric Vehicles (EVs) and the development of a large network of charging stations will inevitably increase the pressure on the electrical grid. However, this network and the batteries that are connected to it also constitute a significant resource to provide ancillary services and therefore a new opportunity to stabilize the power grid. This requires to be able to produce accurate short term forecasts of the power consumption of charging stations at distribution scale. This work proposes a full forecasting framework, from the transformation of discrete charging sessions logs into a continuous aggregated load profile, to the pre-processing of the time series and the generation of predictions. This framework is used to identify the most appropriate model to provide two days ahead predictions of the hourly load profile of large charging stations networks. Using three years of data collected at Amsterdam’s public stations, the performance of several state-of-the-art forecasting models, including Gradient Boosted Trees (GBTs) and Recurrent Neural Networks (RNNs) is evaluated and compared to a classical time series model (Auto Regressive Integrated Moving Average (ARIMA)). The best performances are obtained with an Extreme Gradient Boosting (XGBoost) model using harmonic terms, past consumption values, calendar information and temperature forecasts as prediction features. This study also highlights periodical patterns in charging behaviors, as well as strong calendar effects and an influence of temperature on EV usage. / På grund av den intermittenta karaktären av förnybar energiproduktion, blir upprätthållandet av elnäts stabilitet en betydande utmaning. Dessutom kommer penetrationen av elbilar och utvecklingen av ett stort nät av laddstationer att öka trycket på elnätet. Men detta laddnät och batterierna som är anslutna till det utgör också en betydande resurs för att tillhandahålla kompletterande tjänster och därför en ny möjlighet att stabilisera elnätet. För att göra sådant bör man kunna producera korrekta kortsiktiga prognoser för laddstationens strömförbrukning i distributions skala. Detta arbete föreslår ett fullständigt prognos protokoll, från omvandlingen av diskreta laddnings sessioner till en kontinuerlig förbrukningsprofil, till förbehandling av tidsserier och generering av förutsägelser. Protokollet används för att identifiera den mest lämpliga metoden för att ge två dagars förutsägelser av timförbrukning profilen för ett stort laddstation nät. Med hjälp av tre års data som samlats in på Amsterdams publika stationer utvärderas prestanda för flera avancerade prognosmodeller som är gradient boosting och återkommande neurala nätverk, och jämförs med en klassisk tidsseriemodell (ARIMA). De bästa resultaten uppnås med en XGBoost modell med harmoniska termer, tidigare förbrukningsvärden, kalenderinformation och temperatur prognoser som förutsägelse funktioner. Denna studie belyser också periodiska mönster i laddningsbeteenden, liksom starka kalendereffekter och temperaturpåverkan på elbilar-användning.
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Telecommunications Trouble Ticket Resolution Time Modelling with Machine Learning / Modellering av lösningstid för felanmälningar i telenät med maskininlärningBjörling, Axel January 2021 (has links)
This report explores whether machine learning methods such as regression and classification can be used with the goal of estimating the resolution time of trouble tickets in a telecommunications network. Historical trouble ticket data from Telenor were used to train different machine learning models. Three different machine learning classifiers were built: a support vector classifier, a logistic regression classifier and a deep neural network classifier. Three different machine learning regressors were also built: a support vector regressor, a gradient boosted trees regressor and a deep neural network regressor. The results from the different models were compared to determine what machine learning models were suitable for the problem. The most important features for estimating the trouble ticket resolution time were also investigated. Two different prediction scenarios were investigated in this report. The first scenario uses the information available at the time of ticket creation to make a prediction. The second scenario uses the information available after it has been decided whether a technician will be sent to the affected site or not. The conclusion of the work is that it is easier to make a better resolution time estimation in the second scenario compared to the first scenario. The differences in results between the different machine learning models were small. Future work can include more information and data about the underlying root cause of the trouble tickets, more weather data and power outage information in order to make better predictions. A standardised way of recording and logging ticket data is proposed to make a future trouble ticket time estimation easier and reduce the problem of missing data. / Den här rapporten undersöker om maskininlärningsmetoder som regression och klassificering kan användas för att uppskatta hur lång tid det tar att lösa en felanmälan i ett telenät. Data från tidigare felanmälningar användes för att träna olika maskininlärningsmodeller. Tre olika klassificerare byggdes: en support vector-klassificerare, en logistic regression-klassificerare och ett neuralt nätverk-klassificerare. Tre olika regressionsmodeller byggdes också: en support vector-regressor, en gradient boosted trees-regressor och ett neuralt nätverk-regressor. Resultaten från de olika modellerna jämfördes för att se vilken modell som är lämpligast för problemet. En undersökning om vilken information och vilka datavariabler som är viktigast för att uppskatta tiden det tar att lösa felanmälan utfördes också. Två olika scenarion för att uppskatta tiden har undersökts i rapporten. Det första scenariot använder informationen som är tillgänglig när en felanmälan skapas. Det andra scenariot använder informationen som finns tillgänglig efter det har bestämts om en tekniker ska skickas till den påverkade platsen. Slutsatsen av arbetet är att det är lättare att göra en bra tidsuppskattning i det andra scenariot jämfört med det första scenariot. Skillnaden i resultat mellan de olika maskininlärningsmodellerna var små. Framtida arbete inom ämnet kan använda information och data om de bakomliggande orsakerna till felanmälningarna, mer väderdata och information om elavbrott. En standardiserad metod för att samla in och logga data för varje felanmälan föreslås också för att göra framtida tidsuppskattningar bättre och undvika problemet med datapunkter som saknas.
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Radar based tank level measurement using machine learning : Agricultural machines / Nivåmätning av tank med radar sensorer och maskininlärningThorén, Daniel January 2021 (has links)
Agriculture is becoming more dependent on computerized solutions to make thefarmer’s job easier. The big step that many companies are working towards is fullyautonomous vehicles that work the fields. To that end, the equipment fitted to saidvehicles must also adapt and become autonomous. Making this equipment autonomoustakes many incremental steps, one of which is developing an accurate and reliable tanklevel measurement system. In this thesis, a system for tank level measurement in a seedplanting machine is evaluated. Traditional systems use load cells to measure the weightof the tank however, these types of systems are expensive to build and cumbersome torepair. They also add a lot of weight to the equipment which increases the fuel consump-tion of the tractor. Thus, this thesis investigates the use of radar sensors together witha number of Machine Learning algorithms. Fourteen radar sensors are fitted to a tankat different positions, data is collected, and a preprocessing method is developed. Then,the data is used to test the following Machine Learning algorithms: Bagged RegressionTrees (BG), Random Forest Regression (RF), Boosted Regression Trees (BRT), LinearRegression (LR), Linear Support Vector Machine (L-SVM), Multi-Layer Perceptron Re-gressor (MLPR). The model with the best 5-fold crossvalidation scores was Random For-est, closely followed by Boosted Regression Trees. A robustness test, using 5 previouslyunseen scenarios, revealed that the Boosted Regression Trees model was the most robust.The radar position analysis showed that 6 sensors together with the MLPR model gavethe best RMSE scores.In conclusion, the models performed well on this type of system which shows thatthey might be a competitive alternative to load cell based systems.
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