Aproximační algoritmy pro submodulární optimalizaci a aplikace

This study proposes approximation algorithms by using several strategies such as streaming, improved-greedy, stop-and-stare, and reverse influence sampling ( \RIS ) to solve three variants of the submodular optimization problem, and perform experiments of these algorithms on the well-known application problems of submodular optimization such as Influence Threshold ( \IT ) and Influence Maximization ( \IM) . Specifically, in the first problem, we propose the two single-pass streaming algorithms ( \StrA and \StrM ) for minimizing the cost of the submodular cover problem under the multiplicative and additive noise models. \StrA and \StrM provide bicriteria approximation solutions. These algorithms effectively increase performance computing the objective function, reduce complexity, and apply to big data. For the second problem, we focus on maximizing a submodular function on fairness constraints. This problem is also known as the problem of fairness budget distribution for influence maximization. We design three algorithms ( \FBIM1 , \FBIM2 , and \FBIM3 ) by combining several strategies such as the threshold greedy algorithm, dynamic stop-and-stare technique, generating samplings by reverse influence sampling framework, and seeds selection to ensure max coverage. \FBIM1 , \FBIM2 , and \FBIM3 perform effectively on big data, provide $(1/2-\epsilon)$-approximation to the optimum solutions, and require complexities of the comparison algorithms. Finally, we devise two effective streaming algorithm ( \StrI and \StrII ) to maximize the Diminishing Returns submodular (DR-submodular) function with a cardinality constraint on the integer lattice for the third problem. \StrI and \StrII provide $(1/2-\epsilon)$-approximation ratio and $(1-1/e-\epsilon)$-approximation ratio, respectively. Simultaneously, compared with the state-of-the-art, these two algorithms have reduced complexity, superior runtime performance, and negligible difference in objective function values. In each problem, we further investigate the performance of our proposed algorithms by conducting many experiments. The experimental results have indicated that our approximation algorithms provide high-efficiency solutions, outperform the-state-of-art algorithms in complexity, runtime, and satisfy the specified constraints. Some of the results have been confirmed through five publications at the Scopus international conferences (RIVF 2021, ICABDE 2021) and the SCIE journals (Computer Standards $\&$ Interfaces (Elsevier) and Mathematics (MDPI)).Tato studie navrhuje aproximační algoritmy pomocí několika strategií, jako je streamování, vylepšená chamtivost, stop-and-stare a vzorkování zpětného vlivu ( \RIS ) k vyřešení tří variant submodulárního optimalizačního problému a provádění experimentů s těmito algoritmy na dobře známé aplikační problémy submodulární optimalizace, jako je práh vlivu ( \IT ) a maximalizace vlivu ( \IM) . Konkrétně v prvním problému navrhujeme dva jednoprůchodové streamovací algoritmy ( \StrA a \StrM ) pro minimalizaci nákladů na problém submodulárního pokrytí v rámci multiplikativních a aditivních šumových modelů. \StrA a \StrM poskytují řešení aproximace bikriterií. Tyto algoritmy efektivně zvyšují výkon při výpočtu cílové funkce, snižují složitost a aplikují se na velká data. U druhého problému se zaměřujeme na maximalizaci submodulární funkce na omezeních spravedlnosti. Tento problém je také známý jako problém spravedlivého rozdělení rozpočtu pro maximalizaci vlivu. Navrhujeme tři algoritmy ( \FBIM1 , \FBIM2 a \FBIM3 ) kombinací několika strategií, jako je prahový greedy algoritmus, dynamická technika stop-and-stare, generování vzorkování pomocí rámce vzorkování s obráceným vlivem a semena výběr pro zajištění maximálního pokrytí. \FBIM1 , \FBIM2 a \FBIM3 fungují efektivně na velkých datech, poskytují $(1/2-\epsilon)$-přiblížení optimálním řešením a vyžadují složitost srovnávacích algoritmů. Nakonec jsme navrhli dva efektivní streamovací algoritmy ( \StrI a \StrII ), abychom maximalizovali submodulární (DR-submodulární) funkci klesající návraty s omezením mohutnosti na celočíselné mřížce pro třetí problém. \StrI a \StrII poskytují poměr přiblížení $(1/2-\epsilon)$ a poměr přiblížení $(1-1/e-\epsilon)$. Současně mají tyto dva algoritmy ve srovnání s nejmodernějšími algoritmy sníženou složitost, vyšší výkon za běhu a zanedbatelný rozdíl v hodnotách objektivních funkcí. V každém problému dále zkoumáme výkon námi navrhovaných algoritmů prováděním mnoha experimentů. Experimentální výsledky ukázaly, že naše aproximační algoritmy poskytují vysoce účinná řešení, překonávají nejmodernější algoritmy ve složitosti, době běhu a splňují specifikovaná omezení. Některé z výsledků byly potvrzeny prostřednictvím pěti publikací na mezinárodních konferencích Scopus (RIVF 2021, ICABDE 2021) a v časopisech SCIE (Computer Standards $\&$ Interfaces (Elsevier) a Mathematics (MDPI)).460 - Katedra informatikyvyhově

Musculoskeletal Pain and Work-related Risk Factors among Waste Collectors in Hanoi, Vietnam: A Cross-sectional Study

BACKGROUND: Musculoskeletal disorders (MSDs) are prevalent among waste collectors (WCs) in developing countries. AIM: This study aimed to investigate the prevalence of MSDs and the factors associated with the risk of persistent musculoskeletal pain among WCs in Hanoi, Vietnam. METHODS: A cross-sectional survey was utilized to study 468 WCs in 2017. The Örebro Musculoskeletal Pain Questionnaire and a questionnaire on demographic and work conditions were used to collect data. Descriptive and multivariate logistics regression analyzes were applied at a significance level of 0.05 to examine the factors related to the risk of persistent pain. FINDINGS: About 74.4% of the participants of this study experienced MSDs in at least one body region and 9.4% reported MSDs in all 10 body sites. The lower back was reported to be the most affected followed by the neck and shoulders. The risk of persistent musculoskeletal pain was significantly associated with age (odds ratio (OR) = 2.31, confidence interval (CI) = 1.05–5.09), gender (OR = 3.29, CI = 1.28–8.44), work hours (OR = 2.35, CI = 1.12–4.92), work shift (OR = 0.48, CI = 0.26–0.92), duration of poor postures of the neck (OR = 0.31, CI = 0.13–0.76), bent back (OR = 0.4 CI = 0.18–0.92) and for medial rotation (OR = 3.01, CI = 1.42–6.36), carrying heavy objects (OR = 2.94, CI = 1.15–7.48), and experience of work dissatisfaction (OR = 3.31, CI = 1.46-7.52), stress (OR = 7.14, CI = 3.14–16.24), or anxiety (OR = 6.37, CI = 3.07–13.21). CONCLUSIONS: High prevalence of MSDs among WCs and its association with self-assessed unfavorable work postures and work-related stress implies the need of mechanical and social support at work for WC to prevent the development of MSDs and persistent pain

SOCIAL-EMOTIONAL SKILLS IN STUDENTS’ LEARNING IN CAN THO UNIVERSITY, VIETNAM

Based on an overview of domestic and foreign research related to the research field of the topic; the research of the topic has determined the urgency of the topic, research objectives, research objects and scope, research hypotheses, research tasks, and methods. The research on the topic has systematized the theoretical basis for the concept and manifestation of social-emotional skills in student learning: generalizing the picture of the current situation of recognizing the importance of social-emotional skills in student learning, the level of assessment of the manifestation and educational measures of social-emotional skills in learning, and finding out the factors that affect social emotions in student learning such as from the external environment, at school, family and external social relationships. Factors from the internal environment are the self-awareness of each student. From the current situation of the problem, the study has proposed educational measures for 504 students from 8 schools and colleges in Can Tho University (CTU), Vietnam. Some measures were to educate social-emotional skills for students through soft skills topics, teach soft skills to students through extracurricular activities, and soft skills education for students through integrated teaching.  Article visualizations

Synthesis of cuprous oxide nanocubes combined with chitosan nanoparticles and its application to p-nitrophenol degradation

For the first time, cuprous oxide nanocubes (Cu2O NCBs) were successfully combined with chitosan nanoparticles (CS NPs) to generate Cu2O NCBs/CS NPs composites material with highly optical property and photocatalytic activity using a simple and eco-friendly synthetic approach at room temperature for 30 min. The synthesized Cu2O NCBs NPs/CS NPs were determined characterizations by Ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), X – ray Diffraction (XRD),  Transmission Electron Microscope (TEM) and Energy-dispersive X-ray spectroscopy (EDX). Results show that the Cu2O NCBs/CS NPs composites have an average particle size of ~3-5 nm; in which, Cu2O has the form of nanocubes (Cu2O NCBs) with size ~3-4 nm and chitosan nanoparticles with spherical shape (CS NPs) with size ~4-5 nm. In addition, the percent (%) composition of elements present in Cu2O NCBs/CS NPs composites material have been obtained respective: Cu (23.99%), O (38.18%), and C (33.61%). Moreover, Cu2O NCBs/CS NPs composites material was also investigated for photocatalytic activity applied in p-nitrophenol degradation. The obtained results showed that the catalytic capability of Cu2O NCBs/CS NPs for p-nitrophenol reduction reached the highest efficiency >55% in the treatment time of 25 min, and this efficiency was higher than that result of using ZnO@chitosan nanoparticles (ZnO@CS NPs) catalyst under the same conditions for comparison

Foodborne zoonotic trematode infections in Yen Bai, Vietnam : a situational analysis on knowledge, attitude, and practice (KAP) and risk behaviors

Publisher Copyright: © Copyright by Pacini Editore Srl, Pisa, Italy.Introduction. Foodborne Zoonotic Trematode Infections (FZTi) are neglected tropical diseases of public health concern in Vietnam. The transmission of FZTi is linked to human behavior patterns. The aims to investigate the knowledge, attitude, and practices regarding FZTi among local people. Methods. A cross-sectional study was conducted using a mixed method, which included a baseline survey and in-depth interviews. 375 participants were interviewed face-to-face in the survey, and 27 participants had the in-depth interviews. Results. The results showed that 36.3% passed the knowledge assessment, 86.7% passed the attitude assessment, and 24% passed the practical assessment. There were differences in average knowledge scores among gender (men higher than women, p = 0.006), ethnicities (Kinh higher than Dao and Tay, p < 0.001), and educational level (higher education, higher knowledge score, p < 0.001). There were differences in the frequency of eating raw fish between men and women (men higher than women, p < 0.001), and in the average practice score between men and women (women higher than men, p = 0.028). Eating raw fish and/or undercooked fish, raw vegetables, and drinking untreated water from Thac Ba lake in Yen Bai province were identified as FZTi risk behaviors. The occurrence of these risky habits can be explained by the lack of knowledge on FZTi, poor economic conditions and typical social features of local people. Conclusion. The current knowledge of local people in regard to safe eating practices is poor. They keep performing unsafe practices, which lead to infection with FZTi; therefore, an integrated control of FZTi is essential.Peer reviewe

Chemical constituents from fruits of Hydnocarpus hainanensis Merr. (Flacourtiaceae) in Vietnam

Five compounds were isolated from the fruits of Hydnocarpus hainanensis Merr. Sleum. (Flacourtiaceae). Their structures were determined by spectroscopic analysis including MS and NMR. The isolates were identified as taraktophyllin (1), hydnocarpic acid (2), 3,4-dihydroxybenzyl alcohol (3), 3,4-dihydroxybenzoic acid (4) and 3-hydroxy-4-methoxybenzoic acid (5)

Discrepancies in Infectivity of Flavivirus and SARS-CoV-2 Clinical Samples: An Improved Assay for Infectious Virus Shedding and Viremia Assessment

Infectivity and neutralizing antibody titers of flavivirus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are frequently measured using the conventional plaque assay. While the assay is useful in the determination of infectivity, conventional plaque assays generally possess lower sensitivity and are time-consuming compared to nucleic acid amplification tests. In this study, a microcrystalline cellulose (MCC), Avicel, was evaluated as an alternative to the conventional virus overlay medium, methylcellulose, for a plaque assay. The plaque assay was performed using dengue and COVID-19 clinical samples and laboratory-established flavivirus and SARS-CoV-2 strains. In virus titration of clinical samples, the plaques were significantly larger, and the virus titers were higher when Avicel MCC-containing overlay medium was used than with conventional methylcellulose overlay medium. In addition, for some clinical samples and laboratory virus strains, infectious particles were detected as plaques in the Avicel MCC-containing medium, but not in the conventional methylcellulose medium. The results suggest that the viremia titer determined using the new overlay medium containing Avicel MCC may better reflect the innate infectious and plaque-forming capabilities of clinical samples and better reflect virus infectivity

Terpenoids from leaves of Viburnum sambucinum Reinw. ex. Blume (Caprifoliaceae)

Six compounds were isolated from the leaves of Viburnum sambucinum Reinw. ex Blume (Caprifoliaceae).  The structures of the isolates were determined by spectroscopic analysis including MS and NMR. Accordingly, the isolated compounds were identified as a-amyrin (1), ursolic acid (2), 3β,28-dihydroxy-urs-12-ene (3), oleanolic acid (4), 16β-hydroxylup-20(29)-ene-3-one (5) and trans-2-phyten-1-ol (6)

Studying Magnetic Fields and Dust in M17 Using Polarized Thermal Dust Emission Observed by SOFIA/HAWC

We report on the highest spatial resolution measurement to date of magnetic fields (B-fields) in M17 using thermal dust polarization measurements taken by SOFIA/HAWC+ centered at a wavelength of 154 μm. Using the Davis–Chandrasekhar–Fermi method, in which the polarization angle dispersion calculated using the structure function technique is the quantity directly observed by SOFIA/HAWC+, we found the presence of strong B-fields of 980 ± 230 and 1665 ± 885 μG in the lower-density M17-N and higher-density M17-S regions, respectively. The B-field morphology in M17-N possibly mimics the fields in gravitationally collapsing molecular cores, while in M17-S the fields run perpendicular to the density structure. M17-S also displays a pillar feature and an asymmetric large-scale hourglass-shaped field. We use the mean B-field strengths to determine Alfvénic Mach numbers for both regions, finding that B-fields dominate over turbulence. We calculate the mass-to-flux ratio, λ, finding λ = 0.07 for M17-N and 0.28 for M17-S. These subcritical λ values are consistent with the lack of massive stars formed in M17. To study dust physics, we analyze the relationship between dust polarization fraction, p, emission intensity, I, gas column density, N(H2), polarization angle dispersion function, S, and dust temperature, T d. p decreases with intensity as I −α with α = 0.51. p tends to first increase with T d, but then decreases at higher T d. The latter feature, seen in M17-N at high T d when N(H2) and S decrease, is evidence of the radiative torque disruption effect