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result(s) for
"Choi, Hyunjun"
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Forecasting Stock Market Indices Using the Recurrent Neural Network Based Hybrid Models: CNN-LSTM, GRU-CNN, and Ensemble Models
2023
Various deep learning techniques have recently been developed in many fields due to the rapid advancement of technology and computing power. These techniques have been widely applied in finance for stock market prediction, portfolio optimization, risk management, and trading strategies. Forecasting stock indices with noisy data is a complex and challenging task, but it plays an important role in the appropriate timing of buying or selling stocks, which is one of the most popular and valuable areas in finance. In this work, we propose novel hybrid models for forecasting the one-time-step and multi-time-step close prices of DAX, DOW, and S&P500 indices by utilizing recurrent neural network (RNN)–based models; convolutional neural network-long short-term memory (CNN-LSTM), gated recurrent unit (GRU)-CNN, and ensemble models. We propose the averaging of the high and low prices of stock market indices as a novel feature. The experimental results confirmed that our models outperformed the traditional machine-learning models in 48.1% and 40.7% of the cases in terms of the mean squared error (MSE) and mean absolute error (MAE), respectively, in the case of one-time-step forecasting and 81.5% of the cases in terms of the MSE and MAE in the case of multi-time-step forecasting.
Journal Article
Characterization of β-Glucans from Cereal and Microbial Sources and Their Roles in Feeds for Intestinal Health and Growth of Nursery Pigs
2023
The objectives of this review are to investigate the quantitative, compositional, and structural differences of β-glucans and the functional effects of β-glucans on the intestinal health and growth of nursery pigs. Banning antibiotic feed supplementation increased the research demand for antibiotic alternatives to maintain the intestinal health and growth of nursery pigs. It has been proposed that β-glucans improve the growth efficiency of nursery pigs through positive impacts on their intestinal health. However, based on their structure and source, their impacts can be extensively different. β-glucans are non-starch polysaccharides found in the cell walls of yeast (Saccharomyces cerevisiae), bacteria, fungi (Basidiomycota), and cereal grains (mainly barley and oats). The total β-glucan content from cereal grains is much greater than that of microbial β-glucans. Cereal β-glucans may interfere with the positive effects of microbial β-glucans on the intestinal health of nursery pigs. Due to their structural differences, cereal β-glucans also cause digesta viscosity, decreasing feed digestion, and decreasing nutrient absorption in the GIT of nursery pigs. Specifically, cereal β-glucans are based on linear glucose molecules linked by β-(1,3)- and β-(1,4)-glycosidic bonds with relatively high water-soluble properties, whereas microbial β-glucans are largely linked with β-(1,3)- and β-(1,6)-glycosidic bonds possessing insoluble properties. From the meta-analysis, the weight gain and feed intake of nursery pigs increased by 7.6% and 5.3%, respectively, through the use of yeast β-glucans (from Saccharomyces cerevisiae), and increased by 11.6% and 6.9%, respectively, through the use of bacterial β-glucans (from Agrobacterium sp.), whereas the use of cereal β-glucans did not show consistent responses. The optimal use of yeast β-glucans (Saccharomyces cerevisiae) was 50 mg/kg in nursery pig diets based on a meta-analysis. Collectively, use of microbial β-glucans can improve the intestinal health of nursery pigs, enhancing immune conditions, whereas the benefits of cereal β-glucans on intestinal health were not consistent.
Journal Article
Aflatoxin B1: Challenges and Strategies for the Intestinal Microbiota and Intestinal Health of Monogastric Animals
by
Choi, Hyunjun
,
Garavito-Duarte, Yesid
,
Gormley, Alexa R.
in
aflatoxin
,
Aflatoxin B1
,
Aflatoxin B1 - toxicity
2025
The objective of this review is to investigate the impacts of aflatoxins, particularly aflatoxin B1 (AFB1), on intestinal microbiota, intestinal health, and growth performance in monogastric animals, primarily chickens and pigs, as well as dietary interventions to mitigate these effects. Aflatoxin B1 contamination in feeds disrupts intestinal microbiota, induces immune responses and oxidative damage, increases antioxidant activity, and impairs jejunal cell viability, barrier function, and morphology in the small intestine. These changes compromise nutrient digestion and reduce growth performance in animals. The negative impact of AFB1 on the % change in average daily gain (ΔADG) of chickens and pigs was estimated based on meta-analysis: ΔADG (%)chicken = −0.13 × AFB1 intake per body weight (ng/g·d) and ΔADG (%)pig = −0.74 × AFB1 intake per body weight (µg/kg·d), indicating that increasing AFB1 contamination linearly reduces the growth of animals. To mitigate the harmful impacts of AFB1, various dietary strategies have been effective. Mycotoxin-detoxifying agents include mycotoxin-adsorbing agents, such as clay and yeast cell wall compounds, binding to AFB1 and mycotoxin-biotransforming agents, such as specific strains of Bacillus subtilis and mycotoxin-degrading enzyme, degrading AFB1 into non-toxic metabolites such as aflatoxin D1. Multiple mycotoxin-detoxifying agents are often combined and used together to improve the intestinal health and growth of chickens and pigs fed AFB1-contaminated feeds. In summary, AFB1 negatively impacts intestinal microbiota, induces immune responses and oxidative stress, disrupts intestinal morphology, and impairs nutrient digestion in the small intestine, leading to reduced growth performance. Supplementing multi-component mycotoxin-detoxifying agents in feeds could effectively adsorb and degrade AFB1 co-contaminated with other mycotoxins prior to its absorption in the small intestine, preventing its negative impacts on the intestinal health and growth performance of chickens and pigs.
Journal Article
Dietary Intervention of Benzoic Acid for Intestinal Health and Growth of Nursery Pigs
2024
The objectives of this review are to investigate how benzoic acid can mitigate the negative effects of weaning stress, improve the intestinal microbiota, intestinal health, and growth of nursery pigs, determine the optimal dose level of benzoic acid for the growth rate in nursery pigs, and compare the efficacy of benzoic acid and other acids in pig feeds. After weaning, pigs are exposed to less lactose and solid feed with high acid-binding capacity at infrequent intervals, causing an increase in digesta pH, reducing protein digestion, and increasing ammonia-producing bacteria in the stomach. Benzoic acid supplementation has improved the intestinal health and growth of nursery pigs through its antimicrobial properties and pH reduction in the digesta. The positive modulation of luminal microbiota in the small intestine of pigs by benzoic acid improves intestinal morphology and enhances nutrient utilization, especially nitrogen, of nursery pigs. Benzoic acid supplementation of up to 1% in feeds also increases hippuric acid contents in the urine of nursery pigs, decreasing urinary pH, which is related to ammonia emission and barn conditions in intensive pig production. Supported by the beneficial impacts of benzoic acid, the growth performance of nursery pigs was also improved. However, excessive benzoic acid (over 2.5% up to 5%) in feeds reduces the growth performance of nursery pigs. Thus, this review conducted a meta-analysis of the results from 16 papers to determine the optimal dose level of benzoic acid for body weight gain of nursery pigs, which was found to be 0.60%. The efficacy of benzoic acid was similar to that of other organic acids, including citric acid, fumaric acid, formic acid, and formate salts. Collectively, benzoic acid supplementation can positively modulate the luminal and mucosal microbiota in the small intestine, increase nutrient utilization and intestinal health, decrease urinary pH, and improve the growth performance of nursery pigs.
Journal Article
Enhanced natural killer cell anti-tumor activity with nanoparticles mediated ferroptosis and potential therapeutic application in prostate cancer
by
Choi, Hyunjun
,
Kim, Kwang-Soo
,
Kim, Dong-Hyun
in
Anticancer properties
,
Antitumor agents
,
Apoptosis
2022
Ferroptosis provides an opportunity to overcome the cancer cell therapeutic resistance and modulate the immune system. Here an interaction between ferroptosis of cancer cells and natural killer (NK) cells was investigated with a clinical grade iron oxide nanoparticle (ferumoxytol) for potential synergistic anti-cancer effect of ferroptosis and NK cell therapy in prostate cancer. When ferumoxytol mediated ferroptosis of cancer cells was combined with NK cells, the NK cells’ cytotoxic function was increased. Observed ferroptosis mediated NK cell activation was also confirmed with IFN-γ secretion and lytic degranulation. Upregulation of ULBPs, which is one of the ligands for NK cell activating receptor NKG2D, was observed in the co-treatment of ferumoxytol mediated ferroptosis and NK cells. Additionally, HMGB1 and PD-L1 expression of cancer cells were observed in the treatment of ferroptosis + NK cells. Finally, in vivo therapeutic efficacy of ferumoxytol mediated ferroptosis and NK cell therapy was observed with significant tumor volume regression in a prostate cancer mice model. These results suggest that the NK cells’ function can be enhanced with ferumoxytol mediated ferroptosis.
Journal Article
Impacts of replacing soybean meal with processed soybean meal on intestinal health and growth of nursery pigs challenged with F18+ Escherichia coli
2025
Objective: This study aimed to investigate the impact of different level of soybean meal (SBM) replaced by soy protein concentrate on intestinal health and growth performance of nursery pigs under F18+ Escherichia coli (E. coli).Methods: Forty-eight newly weaned pigs (6.6±0.3 kg) were randomly allotted to 4 treatments arranged by 2×2 factors using randomized complete block design with initial body weight and sex as blocks. Two factors were F18+ E. coli challenge (0 or 2.1×1010 colony-forming units [CFU]) and the level of SBM (24% or 12% in phase 1 and 26% or 14% in phase 2). Pigs were fed for 25 d in 2 phases (phase 1 for 11 d and phase 2 for 14 d). At the end of study, all pigs were euthanized to collect jejunal mucosa and tissues.Results: The F18+ E. coli challenge decreased (p<0.05) overall average daily gain (ADG) and average daily feed intake (ADFI) and decreased (p<0.05) gain to feed ratio on d 7 to 11. The high SBM tended to have a greater overall ADG (p = 0.054) and ADFI (p = 0.078) compared with low SBM under F18+ E. coli challenge, but not in unchallenged conditions. The F18+ E. coli challenge increased (p<0.05) fecal score on d 7 to 18. The tumor necrosis factor-α and interleukin-1β in jejunal mucosa were decreased (p<0.05) in high SBM treatments. The high SBM tended to increase (p = 0.085) occludin expression in jejunum. high SBM increased crypt depth in jejunum under F18+ E. coli challenge, but not in unchallenged conditions (p<0.05).Conclusion: High SBM in nursery diets could alleviate the detrimental effects of F18+ E. coli challenge on growth performance of pigs under compared to low SBM inclusion, which might be attributed to decreased intestinal inflammation and improved intestinal integrity.
Journal Article
Impacts of different dietary soybean meal levels on jejunal immunity of nursery pigs at different days post-weaning
by
Choi, Hyunjun
,
Deng, Zixiao
,
Kim, Sung Woo
in
Agriculture
,
Animal Genetics and Genomics
,
Animal Physiology
2025
Background
The objective of this study was to investigate the impacts of different dietary soybean meal (SBM) levels on jejunal immunity in nursery pigs at different days post-weaning.
Methods
Forty-eight pigs (6.2 ± 0.3 kg), weaned at 21 days of age, were assigned to 2 dietary treatments (
n
= 12) in a randomized complete block design and fed for 20 or 42 d in 3 phases (10, 10, and 22 d, respectively). The dietary treatments consisted of low and high SBM diets. On d 20 and 42, jejunal mucosa and tissue samples were collected. Treatments were arranged in 2 × 2 factors with dietary SBM levels (low and high SBM diets) and days post-weaning (20 d and 42 d post-weaning).
Results
Pigs fed high SBM diets had greater (
P
< 0.05) relative abundance (RA) of jejunal
Prevotella
, tended to have greater (
P
= 0.091) jejunal IgA, had greater (
P
< 0.05) crypt depth, and tended to have lower (
P
= 0.064) villus height to crypt depth ratio (VH:CD) than pigs fed low SBM diets. Pigs at 20 d post-weaning had greater (
P
< 0.05) RA of jejunal
Lactobacillus
and had greater (
P
< 0.05) jejunal IL-8 and protein carbonyl than pigs at 42 d post-weaning. Pigs at 20 d post-weaning tended to have greater (
P
= 0.090) jejunal IgG, tended to have lower (
P
= 0.059) jejunal IgA, and had greater (
P
< 0.05) proportion (%) of Ki-67
+
cells in the jejunal crypt than pigs at 42 d post-weaning.
Conclusion
Pigs fed high SBM diets showed greater RA of
Staphylococcus
, a greater immune response, and a decreased VH:CD in the jejunum than pigs fed low SBM diets. Pigs at 20 d post-weaning were more susceptible to jejunal inflammation and intestinal damage than pigs at 42 d post-weaning, but the negative impacts of high SBM diets on jejunal inflammation and intestinal damage were consistent compared to low SBM diets at 20 d and 42 d post-weaning.
Journal Article
Enhancing creativity through a problem-based design thinking project in higher education
by
Choi, Hyunjun
,
Kim, Hyowon
,
Kim, Nooree
in
Agricultural Occupations
,
Agricultural Skills
,
Beliefs
2024
The study explored the impacts of the two-day Living LAB urban regeneration idea camp, which enhanced college students' divergent thinking skills and creative self-efficacy. Quantitative and qualitative empirical data were obtained from 35 camp participants from three universities in Korea. The quantitative results of the study revealed that camp participants' ideational fluency and creative self-efficacy significantly increased after the idea camp. Furthermore, camp participants' creative processes through group interactions were closely observed and examined. Experiencing creative process through group interactions implied the significance in problem finding and problem solving. Our findings suggest that experiential learning though a problem-based design thinking project enhances college students' creativity. Practical implications and future research are discussed.
Journal Article
Neutral detergent fiber rather than other dietary fiber types as an independent variable increases the accuracy of prediction equation for digestible energy in feeds for growing pigs
2020
ObjectiveThe objectives were to investigate correlations between energy digestibility (digestible energy [DE]:gross energy [GE]) and various fiber types including crude fiber (CF), total dietary fiber (TDF), soluble dietary fiber (SDF), insoluble dietary fiber (IDF), neutral detergent fiber (NDF), and acid detergent fiber (ADF), and to develop prediction equations for estimating DE in feed ingredients and diets for growing pigs.MethodsA total of 289 data with DE values and chemical composition of feeds from 39 studies were used to develop prediction equations for DE. The equations were validated using values provided by the National Research Council.ResultsThe DE values in feed ingredients ranged from 2,011 to 4,590 kcal/kg dry matter (DM) and those in diets ranged from 2,801 to 4,203 kcal/kg DM. In feed ingredients, DE:GE was negatively correlated (p<0.001) with NDF (r = −0.84), IDF (r = −0.83), TDF (r = −0.82), ADF (r = −0.78), and CF (r = −0.72). A best-fitting model for DE (kcal/kg) in feed ingredients was: 1,356 + (0.704 × GE, kcal/kg) − (60.3 × ash, %) − (27.7 × NDF, %) with R2 = 0.80 and p<0.001. In diets, DE:GE was negatively correlated (p<0.01) with NDF (r = −0.72), IDF (r = −0.61), TDF (r = −0.52), CF (r = −0.45), and ADF (r = −0.34). A best-fitting model for DE (kcal/kg) in diets was: 1,551 + (0.606 × GE, kcal/kg) − (22.1 × ash, %) − (25.6 × NDF, %) with R2 = 0.62 and p<0.001. All variables are expressed as DM basis. The equation developed for DE in feed ingredients had greater accuracy than a published equation for DE.ConclusionAll fiber types are reasonably good independent variables for predicting DE of swine feeds. The best-fitting model for predicting DE of feeds employed neutral detergent fiber as an independent variable.
Journal Article
Amino acid supplementation during the adaptation period did not affect the standardized ileal digestibility of amino acids in corn and soybean meal fed to pigs
2024
Objective: The objective was to determine the influence of amino acid (AA) supplementation during the adaptation period on the ileal digestibility of crude protein and AA in corn and soybean meal (SBM) fed to pigs.Methods: Six barrows with an initial body weight of 30.9±2.6 kg fitted with a T-cannula at the distal ileum were assigned to a 6×6 Latin square design with 6 dietary treatments and 6 periods. Two experimental diets contained corn or SBM as the sole AA source and an N-free diet was additionally prepared. For AA supplementation groups, an AA mixture consisted of Gly, Lys, Met, Thr, Trp, Ile, Val, His, and Phe was added to the corn diet and the N-free diet at the expense of cornstarch, and an AA mixture of Lys, Met, and Thr was added to the SBM diet. All diets contained 0.5% of chromic oxide. The 6 experimental diets were fed to the pigs for four and half days, and the 3 diets containing an AA mixture were switched to the respective diets without AA mixture during the following two and half days. Ileal digesta were collected on days 6 and 7.Results: The addition of an AA mixture during the adaptation period increased apparent ileal digestibility of Arg and Trp in corn (p<0.05) but did not affect that in SBM. The addition of an AA mixture during the adaptation period increased apparent ileal digestibility of Pro and Gly regardless of feed ingredient (p<0.05) but did not affect that of other AA. All AA except Pro in corn and SBM were unaffected by the addition of the AA mixture during the adaptation period.Conclusion: The addition of amino acids to a low-protein diet during the adaptation period does not affect the standardized ileal digestibility of indispensable amino acids in pigs.
Journal Article