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234 results on '"Park, Jiyun"'

1. Upper tails of subgraph counts in directed random graphs

Author

Park, Jiyun

Subjects
Mathematics - Probability, Mathematics - Combinatorics, 60F10, 60C05, 05C80, 05C35
Abstract

The upper tail problem in a sparse Erd\H{o}s-R\'enyi graph asks for the probability that the number of copies of some fixed subgraph exceeds its expected value by a constant factor. We study the analogous problem for oriented subgraphs in directed random graphs. By adapting the proof of Cook, Dembo, and Pham, we reduce this upper tail problem to the asymptotic of a certain variational problem over edge weighted directed graphs. We give upper and lower bounds for the solution to the corresponding variational problem, which differ by a constant factor of at most $2$. We provide a host of subgraphs where the upper and lower bounds coincide, giving the solution to the upper tail problem. Examples of such digraphs include triangles, stars, directed $k$-cycles, and balanced digraphs., Comment: 18 pages

Published
2024

4. A study of audio mixing methods for piano transcription in violin-piano ensembles

Author

Kim, Hyemi, Park, Jiyun, Kwon, Taegyun, Jeong, Dasaem, and Nam, Juhan

Subjects
Computer Science - Sound, Electrical Engineering and Systems Science - Audio and Speech Processing
Abstract

While piano music transcription models have shown high performance for solo piano recordings, their performance degrades when applied to ensemble recordings. This study aims to analyze the impact of different data augmentation methods on piano transcription performance, specifically focusing on mixing techniques applied to violin-piano ensembles. We apply mixing methods that consider both harmonic and temporal characteristics of the audio. To create datasets for this study, we generated the PFVN-synth dataset, which contains 7 hours of violin-piano ensemble audio by rendering MIDI files and corresponding labels, and also collected unaccompanied violin recordings and mixed them with the MAESTRO dataset. We evaluated the transcription results on both synthesized and real audio recordings datasets., Comment: To Appear IEEE ICASSP 2023

Published
2023

5. Six dimensional almost complex torus manifolds with Euler number six

Author

Jang, Donghoon and Park, Jiyun

Subjects
Mathematics - Algebraic Topology, Mathematics - Differential Geometry
Abstract

An almost complex torus manifold is a $2n$-dimensional compact connected almost complex manifold equipped with an effective action of a real $n$-dimensional torus $T^n \simeq (S^1)^n$ that has fixed points. For an almost complex torus manifold, there is a labeled directed graph which contains information on weights at the fixed points and isotropy spheres. Let $M$ be a 6-dimensional almost complex torus manifold with Euler number 6. We show that two types of graphs occur for $M$, and for each type of graph we construct such a manifold $M$, proving the existence. Using the graphs, we determine the Chern numbers and the Hirzebruch $\chi_y$-genus of $M$.

Published
2023
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6. Size of exceptional sets in weakly mixing systems

Author

Park, Jiyun and Park, Kangrae

Subjects
Mathematics - Dynamical Systems
Abstract

For any weakly mixing system $(X, \mathscr{B}, \mu, T)$ and $A, B \in \mathscr{B}$, there is a density zero set $J_{A,B}$ such that $\mu(A\cap T^{-n}B)$ converges to $\mu(A)\mu(B)$ for $n \notin J$. In this paper, we study bounds on the size of this exceptional set $J$. First, we show that, given the rate of weak mixing, we can find an upper bound on the size of $J$. We use this property to show the existence of an exceptional set $J$ of an interval exchange system with either $\left|J \cap [0, n]\right| \le Cn\log^{-a}n$ or $\left|J \cap [0, n]\right| \le Cn^{1 - \alpha}$, depending on whether or not the transformation is of rotation class. We also explicitly construct an exceptional set $J$ for the Chacon transformation and give upper and lower bounds for its size. More precisely, we show that there is a constant $C>0$ such that for any increasing function $h: \mathbb{R}_+ \to \mathbb{R}_+$ diverging to infinity, there is an exceptional set $J \subseteq \mathbb{N}$ such that $\left|J \cap [0, n]\right|\le Cf(n)$ for every Lebesgue measurable sets $A, B \subseteq [0,1]$, where $f(n) = (\log n)^{(\log \log n)^2h(n)}$. For the lower bound, we prove that for any $t>0$, there exists Lebesgue measurable sets $A, B\subseteq [0,1]$ and $C, N>0$ such that $\left|J_{A,B}\cap [0,n]\right|\geq C(\log n)^t$ for every $n>N$., Comment: 23 pages, 3 figures

Published
2023

7. Compositionally Complex Perovskite Oxides for Solar Thermochemical Water Splitting

Author

Zhang, Dawei, De Santiago, Hector A., Xu, Boyuan, Liu, Cijie, Trindell, Jamie, Li, Wei, Park, Jiyun, Rodriguez, Mark A., Coker, Eric N., Sugar, Josh, McDaniel, Anthony, Lany, Stephan, Ma, Liang, Wang, Yi, Collins, Gregory, Tian, Hanchen, Li, Wenyuan, Qi, Yue, Liu, Xingbo, and Luo, Jian

Subjects
Condensed Matter - Materials Science
Abstract

Solar thermochemical hydrogen generation (STCH) is a promising approach for eco-friendly H2 production, but conventional STCH redox compounds often suffer from thermodynamic and kinetic limitations with limited tunability. Expanding from the nascent high-entropy ceramics field, this study explores a new class of compositionally complex perovskite oxides (La0.8Sr0.2)(Mn(1-x)/3Fe(1-x)/3CoxAl(1-x)/3)O3 for STCH. In situ X-ray diffraction demonstrates the phase stability during redox cycling and in situ X-ray photoelectron spectroscopy shows preferential redox of Co. The extent of reduction increases, but the intrinsic kinetics decreases, with increased Co content. Consequently, (La0.8Sr0.2)(Mn0.2Fe0.2Co0.4Al0.2)O3-{\delta} achieves an optimal balance between the thermodynamics and kinetics properties. The combination of a moderate enthalpy of reduction, high entropy of reduction, and preferable surface oxygen exchange kinetics enables a maximum H2 yield of 395 +- 11 {\mu}mol g-1 in a short 1-hour redox duration. Entropy stabilization expectedly contributes to the structure stability during redox without phase transformation, which enables an exceptional STCH stability for >50 cycles under harsh interrupted conditions. The underlying redox mechanism is further elucidated by the density functional theory based parallel Monte Carlo computation, which represents a new computation paradigm first established here. This study suggests a new class of non-equimolar compositionally complex ceramics for STCH and chemical looping.

Published
2022

23. Effectiveness of donning and doffing personal protective equipment education using video debriefing among Korean undergraduate nursing students.

Author

Yeom, GyeJeong and Park, Jiyun

Subjects
*CROSS infection prevention, *AUDIOVISUAL materials, *SELF-evaluation, *PERSONAL protective equipment, *CROSS infection, *INFECTION control, *SATISFACTION, *T-test (Statistics), *EDUCATIONAL outcomes, *STATISTICAL sampling, *TEACHING methods, *RANDOMIZED controlled trials, *CHI-squared test, *DESCRIPTIVE statistics, *PRE-tests & post-tests, *STUDENTS, *COLLEGE students, *CLINICAL education, *LEARNING strategies, *COMPARATIVE studies, *STUDENT attitudes, *DATA analysis software, *NURSING students
Abstract

Background: The use of appropriate personal protective equipment (PPE) in healthcare settings is a very important factor of infection control activities to prevent transmission of infection. In this study, we aimed to develop a non-face-to-face method that can reduce transmission of infection and an educational method that allows self-learning and self-training, and verify the effectiveness of a donning and doffing PPE education using video debriefing on third-year nursing students in clinical train. Methods: The researcher assigned groups through random sampling using a random number table from the list of research subjects who agreed to participate. Therefore, 35 subjects in the experimental group with an education on donning and doffing PPE using video debriefing and 34 subjects in the control group with video-based training (VBT) were participated in April 2023 at a university in Incheon, South Korea. The evaluation phase involved verifying effects of the education on observer evaluation donningand doffing PPE performance and self-evaluation donningand doffing PPE performance. Satisfaction with the education also assessed immediately after intervention by the experimental group. Results: The experimental group had significantly higher scores for observer evaluationdonning (t = 7.84, p <.001) and observer evaluation doffing (t = 6.52, p <.001) PPE performances than the control group. However, there was no significant difference in self-evaluation donning (t = 0.98, p <.330) or doffing PPE performance (t = 0.17, p <.869) between the two groups. In the experimental group that applied video debriefing, learning satisfaction was 4.33 ± 0.82 points out of 5 points. Conclusions: The education on donning and doffing PPE applying video debriefing was effective. If the education developed in this study is used as a self-learning method to improve the infection control capacity necessary to respond to a disaster crisis caused by infectious diseases, it is considered to be useful for preventing the transmission of infectious diseases in the future. [ABSTRACT FROM AUTHOR]

Published
2024
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24. Risk of COVID-19 transmission on long-haul flights: During the COVID-19 pandemic.

Author

Park, Jiyun and Yeom, Gye jeong

Subjects
*COVID-19 pandemic, *COVID-19, *COMMUNICABLE diseases, *INFECTION prevention, *PUBLIC spaces
Abstract

This study aimed to determine the possibility of COVID-19 transmission through in-flight contact during flights for many patients with confirmed COVID-19 during the COVID-19 pandemic and explore infection prevention and control (IPC) methods for overseas infectious diseases. A retrospective cohort study was conducted on flight with a large number of confirmed case among. Delhi- Incheon flights in 2020. This flight was selected to confirm transmission through close contact with the cabin, with a total of 14 confirmed cases out of 190 passengers (including 10 flight attendants). After confirming COVID-19 test results for those entering Korea, we conducted an epidemiological investigation on confirmed patients to determine their general characteristics and epidemiological relevance. We analyzed the epidemiological relevance, occupational information, incubation period, and COVID-19 variation and genotype among confirmed patients who were in close contact with confirmed cases, and analyzed the possibility of transmission according to the distance of close contact in the flight. One confirmed patient was found to be highly likely to be infected due to close contact with the cabin. However, it occurred within two rows, not within 1 meter. In addition, considering the aerodynamics in the cabin and local incidence rate, infection in an unspecified number of local people could not be excluded. It was analyzed that the reason for reducing infection from close contact on board for a long time in a flight with a large number of confirmed cases was the effective IPC method. In order to prevent overseas infectious diseases caused by flights, autonomous IPC management of airlines and passengers is necessary in addition to national quarantine management such as symptom screening before boarding, wearing passenger masks while boarding, food and beverage restrictions, disinfection of public spaces, distancing between passengers, close contact management after boarding, and self-quarantine. [ABSTRACT FROM AUTHOR]

Published
2024
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27. Risk of Depression according to Cumulative Exposure to a Low-Household Income Status in Individuals with Type 2 Diabetes Mellitus: A Nationwide Population- Based Study

Author

Park, So Hee, primary, Lee, You-Bin, additional, Lee, Kyu-na, additional, Kim, Bongsung, additional, Cho, So Hyun, additional, Kwon, So Yoon, additional, Park, Jiyun, additional, Kim, Gyuri, additional, Jin, Sang-Man, additional, Hur, Kyu Yeon, additional, Han, Kyungdo, additional, and Kim, Jae Hyeon, additional

Published
2024
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29. A Real-Time Lyrics Alignment System Using Chroma And Phonetic Features For Classical Vocal Performance

Author

Park, Jiyun, Yong, Sangeon, Kwon, Taegyun, Nam, Juhan, Park, Jiyun, Yong, Sangeon, Kwon, Taegyun, and Nam, Juhan

Abstract

The goal of real-time lyrics alignment is to take live singing audio as input and to pinpoint the exact position within given lyrics on the fly. The task can benefit real-world applications such as the automatic subtitling of live concerts or operas. However, designing a real-time model poses a great challenge due to the constraints of only using past input and operating within a minimal latency. Furthermore, due to the lack of datasets for real-time models for lyrics alignment, previous studies have mostly evaluated with private in-house datasets, resulting in a lack of standard evaluation methods. This paper presents a real-time lyrics alignment system for classical vocal performances with two contributions. First, we improve the lyrics alignment algorithm by finding an optimal combination of chromagram and phonetic posteriorgram (PPG) that capture melodic and phonetics features of the singing voice, respectively. Second, we recast the Schubert Winterreise Dataset (SWD) which contains multiple performance renditions of the same pieces as an evaluation set for the real-time lyrics alignment., Comment: To Appear IEEE ICASSP 2024

Published
2024

30. Association between exercise habits and incident type 2 diabetes mellitus in patients with thyroid cancer: nationwide population-based study.

Author

Park, Jiyun, Jung, Jin-Hyung, Park, Hyunju, Song, Young Shin, Kim, Soo-Kyung, Cho, Yong-Wook, Han, Kyungdo, and Kim, Kyung-Soo

Subjects
*TYPE 2 diabetes, *THYROIDECTOMY, *THYROID cancer, *PEOPLE with diabetes, *CANCER patients
Abstract

Background: We investigated the association between exercise habits before or after thyroidectomy and incident type 2 diabetes mellitus (T2DM) in patients with thyroid cancer. Methods: An observational cohort study of 69,526 thyroid cancer patients who underwent thyroidectomy for the treatment of thyroid cancer between 2010 and 2016 was performed using the Korean National Health Information Database. Regular exercise was defined as mid-term or vigorous exercise at least 1 day in a week based on a self-reported questionnaire. Patients were divided into four groups according to exercise habits before and after thyroidectomy: persistent non-exercisers, new exercisers, exercise dropouts, and exercise maintainers. Results: During a median follow-up of 4.5 years, 2,720 (3.91%) patients developed T2DM. The incidence of T2DM per 1,000 person years was lower in patients who performed regular exercise before or after thyroidectomy than in persistent non-exercisers (10.77 in persistent non-exerciser group, 8.28 in new exerciser group, 8.59 in exercise dropout group, and 7.61 in exercise maintainer group). Compared with the persistent non-exerciser group, the new exerciser group (hazard ratio [HR] 0.87, 95% confidence interval [CI] 0.78–0.97), the exercise dropout group (HR 0.81, 95% CI 0.72–0.91), and the exercise maintainer group (HR 0.84, 95% CI 0.76–0.93) had lower risks of incident T2DM. Exercising < 1,500 MET-minutes/week in the exercise maintainer group was associated with a lower risk of incident T2DM compared with persistent non-exercisers (< 500: HR 0.80, 95% CI 0.67–0.96, P = 0.002; 500 to < 1,000: HR 0.81, 95% CI 0.71–0.93, P < 0.001; 1,000 to < 1,500: HR 0.81, 95% CI 0.69–0.94, P < 0.001). Conclusions: Regular exercise before or after thyroidectomy was associated with a lower risk of incident T2DM in patients with thyroid cancer. [ABSTRACT FROM AUTHOR]

Published
2024
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34. Local Ordering, Distortion, and Redox Activity in (La0.75Sr0.25)(Mn0.25Fe0.25Co0.25Al0.25)O3Investigated by a Computational Workflow for Compositionally Complex Perovskite Oxides

Author

Xu, Boyuan, Park, Jiyun, Zhang, Dawei, De Santiago, Héctor A, Li, Wei, Liu, Xingbo, Luo, Jian, Lany, Stephan, and Qi, Yue

Abstract

Mixing multiple cations can result in a significant configurational entropy, offer a new compositional space with vast tunability, and introduce new computational challenges. For applications such as the two-step solar thermochemical hydrogen (STCH) generation techniques, we demonstrate that using density functional theory (DFT) combined with Metropolis Monte Carlo method (DFT-MC) can efficiently sample the possible cation configurations in compositionally complex perovskite oxide (CCPO) materials, with (La0.75Sr0.25)(Mn0.25Fe0.25Co0.25Al0.25)O3as an example. In the presence of oxygen vacancies (VO), DFT-MC simulations reveal a significant increase of the local site preference of the cations (short-range ordering), compared to a more random mixing without VO. Co is found to be the redox-active element and the VOis the preferentially generated next to Co due to the stretched Co–O bonds. A clear definition of the vacancy formation energy (Evf) is proposed for CCPO in an ensemble of structures evolved in parallel from independent DFT-MC paths. By combining the distribution of Evfwith VOinteractions into a statistical model, the oxygen nonstoichiometry (δ), under the STCH thermal reduction and oxidation conditions, is predicted and compared with the experiments. Similar to the experiments, the predicted δ can be used to extract the enthalpy and entropy of reduction using the van’t Hoff method, providing direct comparisons with the experimental results. This procedure provides a full predictive workflow for using DFT-MC to obtain possible local ordering or fully random structures, understand the redox activity of each element, and predict the thermodynamic properties of CCPOs, for computational screening and design of these CCPO materials at STCH conditions.

Published
2024
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44. Compositionally Complex Perovskite Oxides for Solar Thermochemical Water Splitting

Author

Zhang, Dawei, primary, De Santiago, Héctor A., additional, Xu, Boyuan, additional, Liu, Cijie, additional, Trindell, Jamie A., additional, Li, Wei, additional, Park, Jiyun, additional, Rodriguez, Mark A., additional, Coker, Eric N., additional, Sugar, Joshua D., additional, McDaniel, Anthony H., additional, Lany, Stephan, additional, Ma, Liang, additional, Wang, Yi, additional, Collins, Gregory, additional, Tian, Hanchen, additional, Li, Wenyuan, additional, Qi, Yue, additional, Liu, Xingbo, additional, and Luo, Jian, additional

Published
2023
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45. Insulin Fact Sheet in Type 1 and 2 Diabetes Mellitus and Trends of Antidiabetic Medication Use in Insulin Users with Type 2 Diabetes Mellitus: 2002 to 2019

Author

Park, Jiyun, Kim, Gyuri, Kim, Bong-Sung; https://orcid.org/0000-0002-1022-3553, Han, Kyung-Do, Kwon, So Yoon, Park, So Hee, Lee, You-Bin, Jin, Sang-Man, Kim, Jae Hyeon, Park, Jiyun, Kim, Gyuri, Kim, Bong-Sung; https://orcid.org/0000-0002-1022-3553, Han, Kyung-Do, Kwon, So Yoon, Park, So Hee, Lee, You-Bin, Jin, Sang-Man, and Kim, Jae Hyeon

Abstract

BACKGROUND: This study investigated the trends of insulin use among Korean patients with type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). Changes in prescription of antidiabetic medications in T2DM patients taking insulin therapy were evaluated. METHODS: We analyzed data from the National Health Insurance Service database in Korea to evaluate the prevalence of insulin users and trends of insulin use in T1DM and T2DM patients from January 2002 to December 2019. We also investigated numbers and types of antidiabetic medications in insulin users with T2DM. RESULTS: The overall total number of insulin users increased from 2002 to 2019, reaching 348,254 for T2DM and 20,287 for T1DM in 2019 compared with 109,974 for T2DM and 34,972 for T1DM in 2002. The proportion of patients using basal analogs and short acting analogs have increased and those using human insulin, premixed insulin, or biphasic human insulin have decreased (rapid acting analogs: 71.85% and 24.12% in T1DM and T2DM, respectively, in 2019; basal analogs: 76.75% and 75.09% in T1DM and T2DM, respectively, in 2019). The use of other antidiabetic medication in addition to insulin increased for T2DM, especially in dual therapy, reaching up to 52.35% in 2019 compared with 16.72% in 2002. CONCLUSION: The proportion of the patients using basal or rapid acting analogs increased among all insulin users in both T1DM and T2DM patients. Among patients with T2DM, the proportion of patients using antidiabetic medications in addition to insulin was significantly increased compared to those who used insulin alone.

Published
2023

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