156 research outputs found
Correction: Guidelines, consensus statements, and standards for the use of artificial intelligence in medicine: systematic review
No full text[This corrects the article DOI: 10.2196/46089.]. [Abstract copyright: ©Ying Wang, Nian Li, Lingmin Chen, Miaomiao Wu, Sha Meng, Zelei Dai, Yonggang Zhang, Mike Clarke. Originally published in the Journal of Medical Internet Research (https://www.jmir.org), 21.12.2023.
Statistical and geometric properties of tree-shifts and fractals : a dynamical perspective
No full textAbstract
This thesis investigates the statistical and geometric properties of various symbolic and geometric fractals. Utilizing techniques from dynamical systems, ergodic theory, and large deviation theory, it provides a comprehensive analysis of key questions concerning Markov subshifts on rooted d-trees, self-conformal and self-affine fractals, and their associated measures. The research is organized into four central themes: the thermodynamic formalism of Markov subshifts over d-trees, the recurrence properties in Bedford--McMullen carpets, the decay in the Fourier spectrum of self-similar measures, and the local statistics of conformal measures.
The exploration of thermodynamic formalism for Markov subshifts over d-trees aligns with current research on statistical mechanical systems on trees, providing a large deviation description for d-tree-indexed Markov chains, characterizing pressure, entropy, and dimension in this non-Euclidean setting. Regarding recurrence in fractal systems, this work extends knowledge on recurrence in self-affine fractals by examining Bedford--McMullen carpets with coinciding Hausdorff and box-counting dimensions, providing new insights into quantitative recurrence under non-conformal dynamics. The investigation of Fourier decay in self-similar measures establishes a van der Corput lemma for one-dimensional non-atomic self-similar measures, with applications to metric theorems and absolutely pointwise normality. Finally, the study of local statistics of conformal measures expands the known class of fractal scaling measures by demonstrating that projections of ergodic measures through self-conformal iterated function systems are scaling measures, unveiling deep connections between scaling measures and ergodic theory.
These results collectively contribute to a deeper understanding of the interplay between fractal geometry, probability theory, and dynamical systems, providing novel approaches to addressing problems and offering potential directions for future research. Original papers Wu, Y.-L., & Yuan, N. (2025). Quantitative recurrence problem on some Bedford-McMullen carpets. Journal of Mathematical Analysis and Applications, 543(2), 128938. https://doi.org/10.1016/j.jmaa.2024.128938 https://doi.org/10.1016/j.jmaa.2024.128938 Self-archived version Ban, J.-C., & Wu, Y.-L. (2025). On the topological pressure of axial product on trees. Stochastics and Dynamics, 25(01), 2550007. https://doi.org/10.1142/S0219493725500078 https://doi.org/10.1142/S0219493725500078 Algom, A., Chang, Y., Wu, M., & Wu, Y.-L. (2025). Van der Corput and metric theorems for geometric progressions for self-similar measures. Mathematische Annalen. https://doi.org/10.1007/s00208-025-03233-3 https://doi.org/10.1007/s00208-025-03233-3 Self-archived version Wu, M., & Wu, Y.-L. (2025). Scaling properties of invariant measures for conformal iterated function systems. Manuscript in preparation. Tiivistelmä
Tämä väitöskirja tutkii erilaisten symbolisten ja geometristen fraktaalien tilastollisia ja geometrisia ominaisuuksia. Hyödyntäen tekniikoita, jotka liittyvät dynaamisiin systeemeihin, ergodiateoriaan ja suurpoikkeamateoriaan, se tarjoaa kattavan analyysin keskeisistä kysymyksistä, jotka koskevat Markovin siirtoja juurellisilla d-puilla, itse-konformeja ja itse-affiinisia fraktaaleja sekä niihin liittyviä mittoja. Tutkimus on jaettu neljään keskeiseen teemaan: Markovin siirtojen termodynaaminen formalismi d-puilla, toistuvuuden ominaisuudet Bedford--McMullen -matoissa, Fourier-spektrin heikkeneminen itse-similaareille mitoille ja konformien mittojen paikallinen tilastollinen käyttäytyminen.
Markovin siirtojen termodynaamisen formalismin tutkiminen d-puilla on linjassa nykyisen tutkimuksen kanssa tilastollisista mekaanisista systeemeistä puilla, tarjoten suurpoikkeamateoreettisen kuvauksen d-puuindeksoiduille Markovin ketjuille, ja paineen, entropian ja ulottuvuuden karakterisoinnin tässä ei-Euklidisessa ympäristössä. Mitä tulee toistuvuuteen fraktaalisissa järjestelmissä, tämä työ laajentaa tietämystä itse-affiinisten fraktaalien toistuvuudesta tarkastelemalla Bedford--McMullen -mattoja, joiden Hausdorffin dimensio ja laatikkodimensio ovat samat, tuoden uusia näkökulmia kvantitatiiviseen toistuvuuteen ei-konformaalisissa dynamiikoissa. Fourierin heikkenemisen tutkiminen itse-similaareille mitoille luo van der Corput'n lemman yksiulotteisille ei-atomisille itse-similaareille mitoille, jolla on sovelluksia metrisiin teoreemiin ja absoluuttisesti pisteittäiseen normaalisuuteen. Viimeisenä, konformaalisten mittojen paikallisten tilastojen tutkiminen laajentaa tunnettua fraktaalisten skaalautuvien mittojen luokkaa osoittaen, että ergodisten mittojen projisoinnit itse-konformaalisten iteratiivisten funktiosysteemien kautta ovat skaalautuvia mittoja, paljastaen syviä yhteyksiä skaalautuvien mittojen ja ergodiateorian välillä.
Nämä tulokset yhdessä tarjoavat syvemmän ymmärryksen fraktaaligeometrian, todennäköisyysteorian ja dynaamisten systeemien välisestä vuorovaikutuksesta, tarjoten uusia lähestymistapoja avoimiin ongelmiin ja mahdollisia suuntaviivoja tulevalle tutkimukselle. Osajulkaisut Wu, Y.-L., & Yuan, N. (2025). Quantitative recurrence problem on some Bedford-McMullen carpets. Journal of Mathematical Analysis and Applications, 543(2), 128938. https://doi.org/10.1016/j.jmaa.2024.128938 https://doi.org/10.1016/j.jmaa.2024.128938 Rinnakkaistallennettu versio Ban, J.-C., & Wu, Y.-L. (2025). On the topological pressure of axial product on trees. Stochastics and Dynamics, 25(01), 2550007. https://doi.org/10.1142/S0219493725500078 https://doi.org/10.1142/S0219493725500078 Algom, A., Chang, Y., Wu, M., & Wu, Y.-L. (2025). Van der Corput and metric theorems for geometric progressions for self-similar measures. Mathematische Annalen. https://doi.org/10.1007/s00208-025-03233-3 https://doi.org/10.1007/s00208-025-03233-3 Rinnakkaistallennettu versio Wu, M., & Wu, Y.-L. (2025). Scaling properties of invariant measures for conformal iterated function systems. Manuscript in preparation. Academic dissertation to be presented with the assent of the Doctoral Programme Committee of Technology and Natural Sciences of the University of Oulu for public defence in the OP auditorium (L10), Linnanmaa, on 25 October 2025, at 12 noonAbstract
This thesis investigates the statistical and geometric properties of various symbolic and geometric fractals. Utilizing techniques from dynamical systems, ergodic theory, and large deviation theory, it provides a comprehensive analysis of key questions concerning Markov subshifts on rooted d-trees, self-conformal and self-affine fractals, and their associated measures. The research is organized into four central themes: the thermodynamic formalism of Markov subshifts over d-trees, the recurrence properties in Bedford--McMullen carpets, the decay in the Fourier spectrum of self-similar measures, and the local statistics of conformal measures.
The exploration of thermodynamic formalism for Markov subshifts over d-trees aligns with current research on statistical mechanical systems on trees, providing a large deviation description for d-tree-indexed Markov chains, characterizing pressure, entropy, and dimension in this non-Euclidean setting. Regarding recurrence in fractal systems, this work extends knowledge on recurrence in self-affine fractals by examining Bedford--McMullen carpets with coinciding Hausdorff and box-counting dimensions, providing new insights into quantitative recurrence under non-conformal dynamics. The investigation of Fourier decay in self-similar measures establishes a van der Corput lemma for one-dimensional non-atomic self-similar measures, with applications to metric theorems and absolutely pointwise normality. Finally, the study of local statistics of conformal measures expands the known class of fractal scaling measures by demonstrating that projections of ergodic measures through self-conformal iterated function systems are scaling measures, unveiling deep connections between scaling measures and ergodic theory.
These results collectively contribute to a deeper understanding of the interplay between fractal geometry, probability theory, and dynamical systems, providing novel approaches to addressing problems and offering potential directions for future research.Tiivistelmä
Tämä väitöskirja tutkii erilaisten symbolisten ja geometristen fraktaalien tilastollisia ja geometrisia ominaisuuksia. Hyödyntäen tekniikoita, jotka liittyvät dynaamisiin systeemeihin, ergodiateoriaan ja suurpoikkeamateoriaan, se tarjoaa kattavan analyysin keskeisistä kysymyksistä, jotka koskevat Markovin siirtoja juurellisilla d-puilla, itse-konformeja ja itse-affiinisia fraktaaleja sekä niihin liittyviä mittoja. Tutkimus on jaettu neljään keskeiseen teemaan: Markovin siirtojen termodynaaminen formalismi d-puilla, toistuvuuden ominaisuudet Bedford--McMullen -matoissa, Fourier-spektrin heikkeneminen itse-similaareille mitoille ja konformien mittojen paikallinen tilastollinen käyttäytyminen.
Markovin siirtojen termodynaamisen formalismin tutkiminen d-puilla on linjassa nykyisen tutkimuksen kanssa tilastollisista mekaanisista systeemeistä puilla, tarjoten suurpoikkeamateoreettisen kuvauksen d-puuindeksoiduille Markovin ketjuille, ja paineen, entropian ja ulottuvuuden karakterisoinnin tässä ei-Euklidisessa ympäristössä. Mitä tulee toistuvuuteen fraktaalisissa järjestelmissä, tämä työ laajentaa tietämystä itse-affiinisten fraktaalien toistuvuudesta tarkastelemalla Bedford--McMullen -mattoja, joiden Hausdorffin dimensio ja laatikkodimensio ovat samat, tuoden uusia näkökulmia kvantitatiiviseen toistuvuuteen ei-konformaalisissa dynamiikoissa. Fourierin heikkenemisen tutkiminen itse-similaareille mitoille luo van der Corput'n lemman yksiulotteisille ei-atomisille itse-similaareille mitoille, jolla on sovelluksia metrisiin teoreemiin ja absoluuttisesti pisteittäiseen normaalisuuteen. Viimeisenä, konformaalisten mittojen paikallisten tilastojen tutkiminen laajentaa tunnettua fraktaalisten skaalautuvien mittojen luokkaa osoittaen, että ergodisten mittojen projisoinnit itse-konformaalisten iteratiivisten funktiosysteemien kautta ovat skaalautuvia mittoja, paljastaen syviä yhteyksiä skaalautuvien mittojen ja ergodiateorian välillä.
Nämä tulokset yhdessä tarjoavat syvemmän ymmärryksen fraktaaligeometrian, todennäköisyysteorian ja dynaamisten systeemien välisestä vuorovaikutuksesta, tarjoten uusia lähestymistapoja avoimiin ongelmiin ja mahdollisia suuntaviivoja tulevalle tutkimukselle
Photoluminescence Characteristics of InAs self-assembled Quantum dots in InGaAs/GaAs Quantum well
No full textTemperature dependent and time-resolved photoluminescence studies of InAs self-assembled quantum dots with InGaAs strain reducing layer structure
No full textRecovering high value-added anthocyanins from blueberry pomace with ultrasound-assisted extraction
No full textFood waste is a potential source to replace fresh materials for obtaining functional ingredients. Blueberry pomace contains considerable amounts of anthocyanins. In this study, we investigated ultrasonic-assisted extraction (UAE) of anthocyanins from blueberry pomace. We used a Box-Behnken design (BBD) to screen and optimize the important factors influencing yield. The optimum extraction conditions were a temperature of 40 °C, an ultrasonic power of 400 W and an extraction time of 40 min. The optimum yield was 108.23 mg/100 g DW. In addition, we used a cation column to separate anthocyanins, and optimized the chromatographic conditions of HPLC to analyze and identify the main anthocyanins. Thirteen anthocyanins were found in blueberry pomace, of which Malvidin-3-Galactoside (22.65 %) was the highest. These findings provide a theoretical basis and optimized process parameters for the recovery of high value-added anthocyanins from blueberry pomace with ultrasound-assisted extraction, thus facilitating the comprehensive utilization of blueberry pomace
Stable Temperature Characteristics of InAs/GaAs Quantum Dots at Long Wavelength Emission
No full textThe time-resolved photoluminescence and steady photoluminescence (TRPL and PL) spectra on self-assembled InAs/GaAs quantum dots (QDs) are investigated. By depositing GaAs/InAs short period superlattices (SLs), 1. 48 μtm emission is obtained at room temperature. Temperature dependent PL measurements show that the PL intensity of the emission is very steady. It decays only to half as the temperature increases from 15 K to room temperature, while at the same time, the intensity of the other emission decreases by a factor of 5 orders of magnitude. These two emissions are attributed to large-size QDs and short period superlattices (SLs), respectively. Large-size QDs are easier to capture and confine carriers,which benefits the lifetime of PL, and therefore makes the emission intensity insensitive to the temperature
Upper and lower fast Khintchine spectra in continued fractions
No full text13 pages. Motivation and details of proofs are added.International audienceFor an irrational number , let be its continued fraction expansion. Let be a function with as . The (upper, lower) fast Khintchine spectrum for is defined as the Hausdorff dimension of the set of numbers for which the (upper, lower) limit of is equal to . The fast Khintchine spectrum was determined by Fan, Liao, Wang, and Wu. We calculate the upper and lower fast Khintchine spectra. These three spectra can be different
Upper and lower fast Khintchine spectra in continued fractions
No full text13 pages. Motivation and details of proofs are added.International audienceFor an irrational number , let be its continued fraction expansion. Let be a function with as . The (upper, lower) fast Khintchine spectrum for is defined as the Hausdorff dimension of the set of numbers for which the (upper, lower) limit of is equal to . The fast Khintchine spectrum was determined by Fan, Liao, Wang, and Wu. We calculate the upper and lower fast Khintchine spectra. These three spectra can be different
Multifractal analysis of some multiple ergodic averages in linear Cookie-Cutter dynamical systems
No full textAbstract
In this paper, we study the multiple ergodic averages of a locally constant real-valued function in linear Cookie-Cutter dynamical systems. The multifractal spectrum of these multiple ergodic averages is completely determined
Weight gain from trade
No full textM.Phil.This paper studies the effects of the economic shock on people’s health. Specifically, we study how increasing import penetration from China during 2000 and 2007 affects the adult overweight and obesity rate in the US. Using data from the Behavioral Risk Factor Surveillance System (BRFSS) survey, we find evidence suggesting the rapid growth of exposure to Chinese import penetration leads to a higher level of obesity and overweight rates at the commuting zone (CZ) level. We also find such effect is heterogeneous among different groups. The impact of Chinese trade penetration is more pronounced for the employed workers, wage earners, people aged between 34 and 44, non-white races, the male and people never graduated high school. This paper also reveals some possible mechanisms. People living in commuting zones (CZs) more exposed to Chinese import penetration experience decline in household income, rise in unemployment rate, worse mental and physical health status, deteriorated health behaviors and less affordability for medical cost. As a complement to the existing literature on Chinese trade shock, this paper provides new evidence for the health consequences of Chinese import penetration.本文研究了經濟衝擊對健康的影響。具體而言，本文研究了2000年到2007年之間日益增長的中國進口滲透對於美國成人肥胖率的影響。運用行爲風險因素監測系統數據，以通勤區為分析單位，本文表明快速增長的中國進口滲透可導致肥胖率的增加。同時本文研究發現該作用對不同人群具有異質性對於在業者工資收入者年齡在34和44嵗之間的人群非白人族群男性以及高中未畢業的人群影響更爲顯著。同時本文也探討了可能的作用機制居住在受中國進口衝擊較大通勤區的人群經歷了家庭收入下降失業率的上升較差的生理健康和心理健康狀況惡化的健康行爲和醫療費用負擔能力的下降。作爲對現有中國貿易衝擊文獻的補充，本文為中國進口衝擊帶來的可能健康影響提供了新的證據。Bao, Lingmin.Thesis M.Phil. Chinese University of Hong Kong 2019.Includes bibliographical references (leaves 35-38).Abstracts also in Chinese.Title from PDF title page (viewed on 15, April 2021)
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