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Article ; Online: Large volatility matrix analysis using global and national factor models

Choi, Sung Hoon / Kim, Donggyu

Journal of Econometrics. 2023 Aug., v. 235, no. 2 p.1917-1933

2023

Abstract: Several large volatility matrix inference procedures have been developed, based on the latent factor model. They often assumed that there are a few of common factors, which can account for volatility dynamics. However, several studies have demonstrated ... ...

Abstract	Several large volatility matrix inference procedures have been developed, based on the latent factor model. They often assumed that there are a few of common factors, which can account for volatility dynamics. However, several studies have demonstrated the presence of local factors. In particular, when analyzing the global stock market, we often observe that nation-specific factors explain their own country’s volatility dynamics. To account for this, we propose the Double Principal Orthogonal complEment Thresholding (Double-POET) method, based on multi-level factor models, and also establish its asymptotic properties. Furthermore, we demonstrate the drawback of using the regular principal orthogonal component thresholding (POET) when the local factor structure exists. We also describe the blessing of dimensionality using Double-POET for local covariance matrix estimation. Finally, we investigate the performance of the Double-POET estimator in an out-of-sample portfolio allocation study using international stocks from 20 financial markets.
Keywords	complement ; econometrics ; models ; stock exchange ; variance covariance matrix ; High-dimensionality ; Low-rank matrix ; Multi-level factor model ; POET ; Sparsity
Language	English
Dates of publication	2023-08
Size	p. 1917-1933.
Publishing place	Elsevier B.V.
Document type	Article ; Online
ZDB-ID	1460617-3
ISSN	0304-4076
ISSN	0304-4076
DOI	10.1016/j.jeconom.2023.02.004
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Design of a Diagnostic System for Patient Recovery Based on Deep Learning Image Processing

Donggyu Choi / Jongwook Jang

Diagnostics, Vol 12, Iss 273, p

For the Prevention of Bedsores and Leg Rehabilitation

2022 Volume 273

Abstract: Worldwide COVID-19 infections have caused various problems throughout different countries. In the case of Korea, problems related to the demand for medical care concerning wards and doctors are serious, which were already slowly worsening problems in ... ...

Abstract	Worldwide COVID-19 infections have caused various problems throughout different countries. In the case of Korea, problems related to the demand for medical care concerning wards and doctors are serious, which were already slowly worsening problems in Korea before the COVID-19 pandemic. In this paper, we propose the direction of developing a system by combining artificial intelligence technology with limited areas that do not require high expertise in the rehabilitation medical field that should be improved in Korea through the prevention of bedsores and leg rehabilitation methods. Regarding the introduction of artificial intelligence technology, medical and related laws and regulations were quite limited, so the actual needs of domestic rehabilitation doctors and advice on the hospital environment were obtained. Satisfaction with the test content was high, the degree of provision of important medical data was 95%, and the angular error was within 5 degrees and suitable for recovery confirmation.
Keywords	deep learning ; artificial intelligence ; diagnostic program ; rehabilitation ; human pose estimation ; Medicine (General) ; R5-920
Language	English
Publishing date	2022-01-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Design of a Diagnostic System for Patient Recovery Based on Deep Learning Image Processing: For the Prevention of Bedsores and Leg Rehabilitation.

Choi, Donggyu / Jang, Jongwook

Diagnostics (Basel, Switzerland)

2022 Volume 12, Issue 2

Abstract	Worldwide COVID-19 infections have caused various problems throughout different countries. In the case of Korea, problems related to the demand for medical care concerning wards and doctors are serious, which were already slowly worsening problems in Korea before the COVID-19 pandemic. In this paper, we propose the direction of developing a system by combining artificial intelligence technology with limited areas that do not require high expertise in the rehabilitation medical field that should be improved in Korea through the prevention of bedsores and leg rehabilitation methods. Regarding the introduction of artificial intelligence technology, medical and related laws and regulations were quite limited, so the actual needs of domestic rehabilitation doctors and advice on the hospital environment were obtained. Satisfaction with the test content was high, the degree of provision of important medical data was 95%, and the angular error was within 5 degrees and suitable for recovery confirmation.
Language	English
Publishing date	2022-01-21
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2662336-5
ISSN	2075-4418
ISSN	2075-4418
DOI	10.3390/diagnostics12020273
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Electric Field-Assisted Agglomeration of Trace Nanoparticle Impurities for Ultrahigh Purity Chemicals.

Lee, Dongryul / Lee, Donggyu / Lee, Sungjune / Park, Hee Jeong / Han, Kuk Nam / Choi, Sam-Jong / Kim, Yun Ho / Kim, Jihyun

JACS Au

2024 Volume 4, Issue 3, Page(s) 1031–1038

Abstract: With the advancement of semiconductor manufacturing technology, the effects of trace impurities in industrial chemicals have grown significantly. In industrial processes, conventional purification methods, such as filtration and distillation, have ... ...

Abstract	With the advancement of semiconductor manufacturing technology, the effects of trace impurities in industrial chemicals have grown significantly. In industrial processes, conventional purification methods, such as filtration and distillation, have reached their limits for removing nanoparticles from aqueous and acidic solutions. Especially, silicon and silicate are two fundamental byproducts in semiconductor fabrication processes. Assembly and subsequent removal of these materials at the nanoparticle level have been confronted with significant challenges. Therefore, it is imperative to develop technologies to effectively control and remove these impurities for next-generation manufacturing processes. In this study, we explored the use of electric field-assisted assembly to agglomerate silicate and silicon nanoparticles in industry-standard aqueous and acidic solutions. By applying an alternating current electric field, we induced dipole moments in the nanoparticles, which led to their agglomeration. Notably, nanoparticles smaller than 4 nm grew into significantly larger ones, with submicroparticle sizes exceeding 87 nm for silicate and reaching 130 nm for silicon. Through systematic analysis of the size distribution changes, we identified optimal agglomeration times of 10 min for silicate and 20 min for silicon, revealing effective agglomeration within the frequency range of 1-1000 kHz. The agglomerated particles were stable for 5 days. Our electric field-assisted approach to obtain assembled nanoparticles that can be subsequently removed by conventional purification processes holds promise for enhancing future microfabrication processes, such as semiconductor manufacturing, potentially improving the manufacturing yield and uniformity by reducing the number of trace particles that can act as defective sites.
Language	English
Publishing date	2024-02-06
Publishing country	United States
Document type	Journal Article
ISSN	2691-3704
ISSN (online)	2691-3704
DOI	10.1021/jacsau.3c00765
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: SalfMix: A Novel Single Image-Based Data Augmentation Technique Using a Saliency Map.

Choi, Jaehyeop / Lee, Chaehyeon / Lee, Donggyu / Jung, Heechul

Sensors (Basel, Switzerland)

2021 Volume 21, Issue 24

Abstract: Modern data augmentation strategies such as Cutout, Mixup, and CutMix, have achieved good performance in image recognition tasks. Particularly, the data augmentation approaches, such as Mixup and CutMix, that mix two images to generate a mixed training ... ...

Abstract	Modern data augmentation strategies such as Cutout, Mixup, and CutMix, have achieved good performance in image recognition tasks. Particularly, the data augmentation approaches, such as Mixup and CutMix, that mix two images to generate a mixed training image, could generalize convolutional neural networks better than single image-based data augmentation approaches such as Cutout. We focus on the fact that the mixed image can improve generalization ability, and we wondered if it would be effective to apply it to a single image. Consequently, we propose a new data augmentation method to produce a self-mixed image based on a saliency map, called SalfMix. Furthermore, we combined SalfMix with state-of-the-art two images-based approaches, such as Mixup, SaliencyMix, and CutMix, to increase the performance, called HybridMix. The proposed SalfMix achieved better accuracies than Cutout, and HybridMix achieved state-of-the-art performance on three classification datasets: CIFAR-10, CIFAR-100, and TinyImageNet-200. Furthermore, HybridMix achieved the best accuracy in object detection tasks on the VOC dataset, in terms of mean average precision.
MeSH term(s)	Neural Networks, Computer
Language	English
Publishing date	2021-12-17
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2052857-7
ISSN	1424-8220 ; 1424-8220
ISSN (online)	1424-8220
ISSN	1424-8220
DOI	10.3390/s21248444
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article: In vivo

Ahn, Joongho / Baik, Jin Woo / Kim, Donggyu / Choi, Karam / Lee, Seunghyun / Park, Sung-Min / Kim, Jin Young / Nam, Sung Hyun / Kim, Chulhong

Photoacoustics

2023 Volume 30, Page(s) 100485

Abstract: Postprandial hyperglycemia, blood glucose spikes, induces endothelial dysfunction, increasing cardiovascular risks. Endothelial dysfunction leads to vasoconstriction, and observation of this phenomenon is important for understanding acute hyperglycemia. ... ...

Abstract	Postprandial hyperglycemia, blood glucose spikes, induces endothelial dysfunction, increasing cardiovascular risks. Endothelial dysfunction leads to vasoconstriction, and observation of this phenomenon is important for understanding acute hyperglycemia. However, high-resolution imaging of microvessels during acute hyperglycemia has not been fully developed. Here, we demonstrate that photoacoustic microscopy can noninvasively monitor morphological changes in blood vessels of live animals' extremities when blood glucose rises rapidly. As blood glucose level rose from 100 to 400 mg/dL following intraperitoneal glucose injection, heart/breath rate, and body temperature remained constant, but arterioles constricted by approximately -5.7 ± 1.1% within 20 min, and gradually recovered for another 40 min. In contrast, venular diameters remained within about 0.6 ± 1.5% during arteriolar constriction. Our results experimentally and statistically demonstrate that acute hyperglycemia produces transitory vasoconstriction in arterioles, with an opposite trend of change in blood glucose. These findings could help understanding vascular glucose homeostasis and the relationship between diabetes and cardiovascular diseases.
Language	English
Publishing date	2023-03-30
Publishing country	Germany
Document type	Journal Article
ZDB-ID	2716706-9
ISSN	2213-5979
ISSN	2213-5979
DOI	10.1016/j.pacs.2023.100485
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Clinical impact of dyspnoea after ticagrelor treatment and the effect of switching to clopidogrel in patients with myocardial infarction.

Kim, Sang Hyun / Shin, Sanghoon / Choo, Eun Ho / Choi, Ik Jun / Lim, Sungmin / Moon, Donggyu / Kim, Chan Joon / Park, Mahn-Won / Kim, Min Chul / Hwang, Byung-Hee / Lee, Kwan Yong / Choi, Yun-Seok / Kim, Hee-Yeol / Yoo, Ki-Dong / Jeon, Doo Soo / Ahn, Youngkeun / Chang, Kiyuk

Thrombosis and haemostasis

2024

Abstract: Background: Dyspnoea is frequent during ticagrelor-based dual antiplatelet therapy (DAPT) for acute myocardial infarction (AMI). However, its clinical characteristics or management strategy remains uncertain.: Methods: The study assessed 2,617 AMI ... ...

Abstract	Background: Dyspnoea is frequent during ticagrelor-based dual antiplatelet therapy (DAPT) for acute myocardial infarction (AMI). However, its clinical characteristics or management strategy remains uncertain. Methods: The study assessed 2,617 AMI patients from the Ticagrelor versus Clopidogrel in Stabilized Patients with AMI (TALOS-AMI) trial. Dyspnoea during 1-month ticagrelor-based DAPT and following DAPT strategies with continued ticagrelor or de-escalation to clopidogrel from 1 to 12 months were evaluated for drug adherence, subsequent dyspnoea, major adverse cardiovascular events (MACE), and bleeding events. Results: Dyspnoea was reported by 538 patients (20.6%) during 1 month of ticagrelor-based DAPT. Adherence to allocated DAPT over the study period was lower in the continued ticagrelor arm than the de-escalation to clopidogrel, particularly among the dyspnoeic population (81.1% vs. 91.5%, p<0.001). Among ticagrelor-treated patients with dyspnoea, those switched to clopidogrel at 1 month had a lower frequency of dyspnoea at 3 months (34.3 vs. 51.7%, p<0.001) and 6 months (25.5% vs. 38.4%, p=0.002) than those continued with ticagrelor. In patients with dyspnoea in their 1-month ticagrelor-based DAPT, de-escalation was not associated with increased MACE (1.3% vs. 3.9%, hazard ratio [HR] 0.31, 95% confidence interval [CI] =0.08-1.11, p=0.07) or clinically relevant bleeding (3.2% vs. 6.2%, HR 0.51, 95% CI 0.22-1.19, p=0.12) at 1 year. Conclusions: Dyspnoea is a common side effect among ticagrelor-based DAPT in AMI patients. Switching from ticagrelor to clopidogrel after 1 month in AMI patients may provide a reasonable option to alleviate subsequent dyspnoea in ticagrelor-relevant dyspnoeic patients, without increasing the risk of ischaemic events (NCT02018055).
Language	English
Publishing date	2024-04-04
Publishing country	Germany
Document type	Clinical Trial
ZDB-ID	518294-3
ISSN	2567-689X ; 0340-6245
ISSN (online)	2567-689X
ISSN	0340-6245
DOI	10.1055/a-2299-4537
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Article ; Online: Prognostic Impact of Atrial Fibrillation in Patients with Heavily Calcified Coronary Artery Disease Receiving Rotational Atherectomy.

Jung, Jin / Seo, Yeonjoo / Her, Sung-Ho / Lee, Jae-Hwan / Lee, Kyusup / Yoo, Ki-Dong / Moon, Keon-Woong / Moon, Donggyu / Lee, Su-Nam / Jang, Won-Young / Choi, Ik-Jun / Lee, Jang-Hoon / Lee, Sang-Rok / Lee, Seung-Whan / Yun, Kyeong-Ho / Lee, Hyun-Jong

Medicina (Kaunas, Lithuania)

2023 Volume 59, Issue 10

Abstract: Background and ... ...

Abstract	Background and Objectives
MeSH term(s)	Humans ; Coronary Artery Disease/complications ; Coronary Artery Disease/surgery ; Atherectomy, Coronary/adverse effects ; Percutaneous Coronary Intervention/adverse effects ; Atrial Fibrillation/complications ; Prognosis ; Treatment Outcome ; Retrospective Studies ; Risk Factors
Language	English
Publishing date	2023-10-11
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2188113-3
ISSN	1648-9144 ; 1010-660X
ISSN (online)	1648-9144
ISSN	1010-660X
DOI	10.3390/medicina59101808
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Article ; Online: Takeover Safety Analysis with Driver Monitoring Systems and Driver–Vehicle Interfaces in Highly Automated Vehicles

Dongyeon Yu / Chanho Park / Hoseung Choi / Donggyu Kim / Sung-Ho Hwang

Applied Sciences, Vol 11, Iss 6685, p

2021 Volume 6685

Abstract: According to SAE J3016, autonomous driving can be divided into six levels, and partially automated driving is possible from level three up. A partially or highly automated vehicle can encounter situations involving total system failure. Here, we studied ... ...

Abstract	According to SAE J3016, autonomous driving can be divided into six levels, and partially automated driving is possible from level three up. A partially or highly automated vehicle can encounter situations involving total system failure. Here, we studied a strategy for safe takeover in such situations. A human-in-the-loop simulator, driver–vehicle interface, and driver monitoring system were developed, and takeover experiments were performed using various driving scenarios and realistic autonomous driving situations. The experiments allowed us to draw the following conclusions. The visual–auditory–haptic complex alarm effectively delivered warnings and had a clear correlation with the user’s subjective preferences. There were scenario types in which the system had to immediately enter minimum risk maneuvers or emergency maneuvers without requesting takeover. Lastly, the risk of accidents can be reduced by the driver monitoring system that prevents the driver from being completely immersed in non-driving-related tasks. We proposed a safe takeover strategy from these results, which provides meaningful guidance for the development of autonomous vehicles. Considering the subjective questionnaire evaluations of users, it is expected to improve the acceptance of autonomous vehicles and increase the adoption of autonomous vehicles.
Keywords	automated driving ; takeover ; human-in-the-loop simulation ; secondary task ; driver–vehicle interface ; driver monitoring system ; Technology ; T ; Engineering (General). Civil engineering (General) ; TA1-2040 ; Biology (General) ; QH301-705.5 ; Physics ; QC1-999 ; Chemistry ; QD1-999
Subject code	629
Language	English
Publishing date	2021-07-01T00:00:00Z
Publisher	MDPI AG
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Clinical impact of dyspnoea after ticagrelor treatment and the effect of switching to clopidogrel in patients with myocardial infarction

Thrombosis and Haemostasis

2024

Abstract	Background: Dyspnoea is frequent during ticagrelor-based dual antiplatelet therapy (DAPT) for acute myocardial infarction (AMI). However, its clinical characteristics or management strategy remains uncertain. Methods: The study assessed 2,617 AMI patients from the Ticagrelor versus Clopidogrel in Stabilized Patients with AMI (TALOS-AMI) trial. Dyspnoea during 1-month ticagrelor-based DAPT and following DAPT strategies with continued ticagrelor or de-escalation to clopidogrel from 1 to 12 months were evaluated for drug adherence, subsequent dyspnoea, major adverse cardiovascular events (MACE), and bleeding events. Results: Dyspnoea was reported by 538 patients (20.6%) during 1 month of ticagrelor-based DAPT. Adherence to allocated DAPT over the study period was lower in the continued ticagrelor arm than the de-escalation to clopidogrel, particularly among the dyspnoeic population (81.1% vs. 91.5%, p<0.001). Among ticagrelor-treated patients with dyspnoea, those switched to clopidogrel at 1 month had a lower frequency of dyspnoea at 3 months (34.3 vs. 51.7%, p<0.001) and 6 months (25.5% vs. 38.4%, p=0.002) than those continued with ticagrelor. In patients with dyspnoea in their 1-month ticagrelor-based DAPT, de-escalation was not associated with increased MACE (1.3% vs. 3.9%, hazard ratio [HR] 0.31, 95% confidence interval [CI] =0.08-1.11, p=0.07) or clinically relevant bleeding (3.2% vs. 6.2%, HR 0.51, 95% CI 0.22-1.19, p=0.12) at 1 year. Conclusions: Dyspnoea is a common side effect among ticagrelor-based DAPT in AMI patients. Switching from ticagrelor to clopidogrel after 1 month in AMI patients may provide a reasonable option to alleviate subsequent dyspnoea in ticagrelor-relevant dyspnoeic patients, without increasing the risk of ischaemic events (NCT02018055).
Language	English
Publishing date	2024-04-04
Publisher	Georg Thieme Verlag KG
Publishing place	Stuttgart ; New York
Document type	Article
ZDB-ID	518294-3
ISSN	2567-689X ; 0340-6245
ISSN (online)	2567-689X
ISSN	0340-6245
DOI	10.1055/a-2299-4537
Database	Thieme publisher's database

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