Sirvi Autor "Aavola, Heili" järgi

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In-Depth Analysis of Miscalibration In Binary Classification
(Tartu Ülikool, 2025) Aavola, Heili; Allikivi, Mari-Liis, juhendaja; Tartu Ülikool. Loodus- ja täppisteaduste valdkond; Tartu Ülikool. Arvutiteaduse instituut
Reliable probability estimates from binary classifiers are crucial for decisionmaking. While standard evaluation metrics provide an overall assessment of calibration quality, a deeper examination of miscalibration patterns can offer further insights into how calibration methods perform. This thesis presents an in-depth analysis of miscalibration patterns for five post-hoc calibration methods: Isotonic Calibration, Logistic Calibration, Beta Calibration, Histogram Binning, and Simplified Venn-Abers. Using a synthetic data framework with five diverse, known true calibration maps, we performed 100 simulation runs for each method-map combination. A suite of five specialized characterization plots was employed to visualize and understand nuanced error profiles, including accuracy, bias, variance, and directional tendencies in misestimation. The results reveal distinct behavioral characteristics and trade-offs. Parametric methods (Logistic, Beta) exhibited high stability but incurred significant systematic bias when their functional assumptions did not match the true probability landscape. Non-parametric methods (Isotonic, SVA) demonstrated superior adaptability and lower average error but with step-like outputs and slightly higher variance in complex regions. Histogram Binning showed considerable artifacts tied to its fixed-bin structure. The characterization plots successfully highlighted consistent directional biases and other nuanced error patterns not evident from aggregate metrics. This granular understanding reveals the precise behavior of different calibration methods, offering a more nuanced basis for selecting approaches tailored to specific application needs and risk sensitivities, particularly in complex or risk-sensitive contexts, moving beyond single performance scores.
Tahke faasi ja kromatograafilise eralduse kombineerimine osakestepõhisele mikrofluiidika kiibile aminohapete määramiseks
(Tartu Ülikool, 2023) Aavola, Heili; Evard, Hanno; Tartu Ülikool. Loodus- ja täppisteaduste valdkond; Tartu Ülikool. Keemia instituut
Käesolevas töös demonstreeriti, et uudne osakestepõhine mikrofluiidika võimaldab ühele kiibile kombineerida erinevaid materjale. See võimekus lubab ühel kiibil teostada mitu erinevat analüüsi sammu: analüütide eelkontsentreerimine, puhastamine ja kromatograafiline eraldus. Kiibi valmistamiseks kasutati siiditrükki. Täpsemalt demonstreeriti, et siiditrüki abil (1) on võimalik valmistada tselluloosiosakestest koosnev õhukese kihi kromatograafia plaat, mille toimimine tõestati aminohapete eraldamise abil, (2) saab trükkida silikageelist ja tugeva anioonvaheti osakestest koosneva kiibi aminohapete eelkontsentreerimiseks ja puhastamiseks, (3) on võimalik kaks eelnevat etappi ühendada, et valmistada kolmest eri materjalist koosnev kiip.