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427 results on '"Choi, Yohan"'

1. Enhancing PM2.5 Data Imputation and Prediction in Air Quality Monitoring Networks Using a KNN-SINDy Hybrid Model

Author

Choi, Yohan, Choi, Boaz, and Choi, Jachin

Subjects
Computer Science - Machine Learning
Abstract

Air pollution, particularly particulate matter (PM2.5), poses significant risks to public health and the environment, necessitating accurate prediction and continuous monitoring for effective air quality management. However, air quality monitoring (AQM) data often suffer from missing records due to various technical difficulties. This study explores the application of Sparse Identification of Nonlinear Dynamics (SINDy) for imputing missing PM2.5 data by predicting, using training data from 2016, and comparing its performance with the established Soft Impute (SI) and K-Nearest Neighbors (KNN) methods.

Published
2024

2. Probabilistic Prime Factorization based on Virtually Connected Boltzmann Machine and Probabilistic Annealing

Author

Jung, Hyundo, Kim, Hyunjin, Lee, Woojin, Jeon, Jinwoo, Choi, Yohan, Park, Taehyeong, and Kim, Chulwoo

Subjects
Physics - Computational Physics, 60G-08, B.0
Abstract

Probabilistic computing has been introduced to operate functional networks using a probabilistic bit (p-bit), generating 0 or 1 probabilistically from its electrical input. In contrast to quantum computers, probabilistic computing enables the operation of adiabatic algorithms even at room temperature, and is expected to broaden computational abilities in non-deterministic polynomial searching and learning problems. However, previous developments of probabilistic machines have focused on emulating the operation of quantum computers similarly, implementing every p-bit with large weight-sum matrix multiplication blocks or requiring tens of times more p-bits than semiprime bits. Furthermore, previous probabilistic machines adopted the graph model of quantum computers for updating the hardware connections, which further increased the number of sampling operations. Here we introduce a digitally accelerated prime factorization machine with a virtually connected Boltzmann machine and probabilistic annealing method, designed to reduce the complexity and number of sampling operations to below those of previous probabilistic factorization machines. In 10-bit to 64-bit factorizations were performed to assess the effectiveness of the machine, and the machine offers 1.2 X 10^8 times improvement in the number of sampling operations compared with previous factorization machines, with a 22-fold smaller hardware resource. This work shows that probabilistic machines can be implemented in a cost-effective manner using a field-programmable gate array, and hence we suggest that probabilistic computers can be employed for solving various large NP searching problems in the near future., Comment: 13 pages, 4 figures, 3 extended data figures and 1 table

Published
2022

12. Heat Stress Induces Alterations in Gene Expression of Actin Cytoskeleton and Filament of Cellular Components Causing Gut Disruption in Growing–Finishing Pigs.

Author

Choi, Yohan, Park, Hyunju, Kim, Joeun, Lee, Hyunseo, and Kim, Minju

Subjects
*INTESTINAL barrier function, *GENE expression, *CYTOSKELETON, *ESTRUS, *CELL anatomy
Abstract

Simple Summary: Acute heat stress in animals impairs the intestinal barrier function, particularly tight junction (TJ) depression, which occurs in pigs owing to the lack of functional sweat glands for evaporative heat loss. However, the mechanisms by which heat stress affects TJ regulation are not fully understood. We investigated the effect of heat stress on the TJ and its interaction with potential genes using transcriptomic analysis of the porcine jejunum. We found that heat stress reduced the expression of TJ proteins and induced alterations in genes involved in the actin cytoskeleton and filament-binding pathways. We aimed to investigate the impact of heat stress (HS) on the expression of tight junction (TJ) proteins and the interaction between genes affecting intestinal barrier function using transcriptomics in the porcine jejunum. Twenty-four barrows (crossbred Yorkshire × Landrace × Duroc; average initial body weight, 56.71 ± 1.74 kg) were placed in different temperatures (normal temperature [NT]; HS) and reared for 56 days. At the end of the experiment, jejunal samples were collected from three pigs per treatment for transcriptome and reverse-transcription quantitative polymerase chain reaction (RT-qPCR) analyses. We identified 43 differentially expressed genes, involving five Kyoto Encyclopedia of Genes and Genomes pathways, eight molecular functions, seven cellular components (CCs), and nine biological processes, using gene ontology enrichment analysis. Genes associated with the actin cytoskeleton, filament-binding pathways, and TJ proteins were selected and analyzed by RT-qPCR. Significant differences in relative mRNA expression showed that downregulated genes in the HS group included ZO1, CLDN1, OCLN, PCK1, and PCK2, whereas ACTG2, DES, MYL9, MYLK, TPM1, TPM2, CNN1, PDLIM3, and PCP4 were upregulated by HS (p < 0.05). These findings indicate that HS in growing-finishing pigs induces depression in gut integrity, which may be related to genes involved in the actin cytoskeleton and filaments of CC. [ABSTRACT FROM AUTHOR]

Published
2024
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25. Swinging for the Fences? Payroll, Performance, and Risk Behavior in the Major League Baseball Draft.

Author

Barden, Jeffrey Q. and Choi, Yohan

Subjects
*BASEBALL draft, *ORGANIZATIONAL performance, *RISK-taking behavior, *AMATEUR athletes, *COLLEGE baseball, *HIGH school baseball
Abstract

This study examines the way competitive advantage and organization performance mediate the effect of potential slack—externally available resources—on organization risk behavior in Major League Baseball's amateur draft. It tests the hypotheses that local market munificence provides payroll advantage and increases on-field performance and that payroll disadvantage and poor performance increase teams' likelihood of selecting riskier high school players instead of college players. Consistent with risk sensitivity theory, results suggest that payroll disadvantage promotes risk-taking; however, on-field success encourages risk-taking early in the draft. Indeed, pick number appears to have a U-shape relationship with risk-taking where winning increases confidence earlier in the draft and low stakes promote risk-seeking later. This study contributes to the literature by suggesting that input- and outcome-based reference metrics have different effects on risk behavior and that managerial hubris may influence risk behavior through information availability rather than having a general effect. [ABSTRACT FROM AUTHOR]

Published
2021
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