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A stable CS-FEM for the static and seismic stability of a single square tunnel in the soil where the shear strength increases linearly with depth

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第4期14卷 1253-1265页

作者： H.C.nguyen l.nguyen-son Department of Civil and Environmental Engineering Imperial College LondonLondonUK Department of Civil Engineering and Industrial Design University of LiverpoolLiverpoolUK Faculty of Civil Engineering Ho Chi Minh City University of Technology(HUTECH)Ho Chi Minh CityViet Nam

A numerical procedure using a stable cell-based smoothed finite element method(CS-FEM)is presented for estimation of stability of a square tunnel in the soil where the shear strength increases linearly with depth.The kinematically admissible displacement fields are approximated by uniform quadrilateral elements in conjunction with the strain smoothing technique,eliminating volumetric locking issues and the singularity associated with the MohreCoulomb model.First,a rich set of simulations was performed to compute the static stability of a square tunnel with different geometries and soil conditions.The presented results are in excellent agreement with the upper and lower bound solutions using the standard finite element method(FEM).The stability charts and tables are given for practical use in the tunnel design,along with a newly proposed formulation for predicting the undrained stability of a single square tunnel.Second,the seismic stability number was computed using the present numerical approach.Numerical results reveal that the seismic stability number reduces with an increasing value of the horizontal seismic acceleration(a_(h)),for both cases of the weightless soil and the soil with unit weight.Third,the link between the static and seismic stability numbers is described using corrective factors that represent reductions in the tunnel stability due to seismic loadings.It is shown from the numerical results that the corrective factor becomes larger as the unit weight of soil mass increases;however,the degree of the reduction in seismic stability number tends to reduce for the case of the homogeneous soil.Furthermore,this advanced numerical procedure is straightforward to extend to three-dimensional(3D)limit analysis and is readily applicable for the calculation of the stability of tunnels in highly anisotropic and heterogeneous soils which are often encountered in practice.

关键词： Tunnels Stability limit analysis Cell-based smoothed finite element method (CS-FEM) Second-order cone programming(SOCP)

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A comparative study on kinetics and dynamics of two dump truck lifting mechanisms using MATlAB simscape

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Theoretical & Applied Mechanics letters 2024年第2期14卷 146-156页

作者： Thong Duc Hong Minh Quang Pham son Cong Tran lam Quang Tran Truong Thanh nguyen Faculty of Transportation Engineering Ho Chi Minh City University of Technology(HCMUT)Ho Chi Minh City 700000Vietnam Vietnam National University Ho Chi Minh City(VNU-HCM) Ho Chi Minh City 700000Vietnam Industrial Maintenance Training Center Ho Chi Minh City University of Technology(HCMUT)Ho Chi Minh City 700000Vietnam

In this paper,two lifting mechanism models with opposing placements,which use the same hydraulic hoist model and have the same angle of 50°,have been developed.The mechanical and hydraulic simulation models are established using MATlAB Simscape to analyze their kinetics and dynamics in the lifting and holding stages.The simulation findings are compared to the analytical calculation results in the steady state,and both methods show good agreement.In the early lifting stage,Model 1 produces greater force and discharges goods in the container faster than Model 2.Meanwhile,Model 2 reaches a higher force and ejects goods from the container cleaner than its counterpart at the end lifting stage.The established simulation models can consider the effects of dynamic loads due to inertial moments and forces generated during the system operation.It is crucial in studying,designing,and optimizing the structure of hydraulic-mechanical systems.

关键词： Dump truck lifting mechanism Hydraulic MATlAB Simscape Kinetic dynamic analysis

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High-temperature corrosion of sintered RE_(2)Si_(2)O_(7)(RE=Yb and Ho)environmental barrier coating materials by volcanic ash

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1628-1638页

作者： Ayahisa Okawa son Thanh nguyen Tadachika Nakayama Thi-Mai-Dung Do Hisayuki Suematsu Shu Yin Takuya Hasegawa Tsuneo Suzuki Takashi Goto Koichi Niihara Institute of Multidisciplinary Research for Advanced Materials Tohoku UniversitySendai 980-8577Japan Department of Creative Engineering National Institute of TechnologyKushiro 084-0916Japan Extreme Energy-Density Research Institute Nagaoka University of TechnologyNagaoka 940-2188Japan Advanced Institute for Materials Research(WPI-AIMR) Tohoku UniversitySendai 980-8577Japan

Rare-earth silicates are promising environmental barrier coatings(EBCs)that can protect SiC_(f)/Si C_(m)substrates in next-genera tion gas turbine blades.Notably,RE_(2)Si_(2)O_(7)(RE=Yb and Ho)shows potential as an EBC due to its coefficient of thermal expansion(CTE)compatible with substrates and high resistance to water vapor corrosion.The target operating temperature for next-generation tur bine blades is 1400°C.Corrosion is inevitable during adhesion to molten volcanic ash,and thus,understanding the corrosion behavior o the material is crucial to its reliability.This study investigates the high-temperature corrosion behavior of sintered RE_(2)Si_(2)O_(7)(RE=Yb and Ho).Samples were prepared using a solid-state reaction and hot-press method.They were then exposed to volcanic ash at 1400°C for 224,and 48 h.After 48 h of exposure,volcanic ash did not react with Yb_(2)Si_(2)O_(7)but penetrated its interior,causing damage.Meanwhile Ho_(2)Si_(2)O_(7)was partially dissolved in the molten volcanic ash,forming a reaction zone that prevented volcanic ash melts from penetrating the interior.With increasing heat treatment time,the reaction zone expanded,and the thickness of the acicular apatite grains increased The Ca:Si ratios in the residual volcanic ash were mostly unchanged for Yb_(2)Si_(2)O_(7)but decreased considerably over time for Ho_(2)Si_(2)O_(7).Th Ca in volcanic ash was consumed and formed apatite,indicating that RE^(3+)ions with large ionic radii(Ho>Yb)easily precipitated apatit from the volcanic ash.

关键词： environmental barrier coating volcanic ash rare-earth disilicate corrosion

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Push forward lC-MS-based therapeutic drug monitoring and pharmacometabolomics for anti-tuberculosis precision dosing and comprehensive clinical management

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Journal of Pharmaceutical Analysis 2024年第1期14卷 16-38页

作者： nguyen Quang Thu nguyen Tran Nam Tien nguyen Thi Hai Yen Thuc-Huy Duong nguyen Phuoc long Huy Truong nguyen Department of Pharmacology and PharmacoGenomics Research Center Inje University College of MedicineBusan47392Republic of Korea Department of Chemistry University of EducationHo Chi Minh City700000Viet Nam Faculty of Pharmacy Ton Duc Thang UniversityHo Chi Minh City700000Viet Nam

The spread of tuberculosis(TB),especially multidrug-resistant TB and extensively drug-resistant TB,has strongly motivated the research and development of new anti-TB drugs.New strategies to facilitate drug combinations,including pharmacokinetics-guided dose optimization and toxicology studies of first-and second-line anti-TB drugs have also been introduced and recommended.liquid chromatography-mass spectrometry(lC-MS)has arguably become the gold standard in the analysis of both endo-and exo-genous compounds.This technique has been applied successfully not only for therapeutic drug monitoring(TDM)but also for pharmacometabolomics analysis.TDM improves the effectiveness of treatment,reduces adverse drug reactions,and the likelihood of drug resistance development in TB patients by determining dosage regimens that produce concentrations within the therapeutic target window.Based on TDM,the dose would be optimized individually to achieve favorable outcomes.Pharmacometabolomics is essential in generating and validating hypotheses regarding the metabolism of anti-TB drugs,aiding in the discovery of potential biomarkers for TB diagnostics,treatment monitoring,and outcome evaluation.This article highlighted the current progresses in TDM of anti-TB drugs based on lC-MS bioassay in the last two decades.Besides,we discussed the advantages and disadvantages of this technique in practical use.The pressing need for non-invasive sampling approaches and stability studies of anti-TB drugs was highlighted.lastly,we provided perspectives on the prospects of combining lC-MS-based TDM and pharmacometabolomics with other advanced strategies(pharmacometrics,drug and vaccine developments,machine learning/artificial intelligence,among others)to encapsulate in an all-inclusive approach to improve treatment outcomes of TB patients.

关键词： Tuberculosis Therapeutic drug monitoring lC-MS MIPD Pharmacometabolomics Precision medicine

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Tungsten-based nanocatalysts with different structures for visible light responsive photocatalytic degradation of bisphenol A

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Journal of Environmental Sciences 2024年第5期139卷 569-588页

作者： Hai Bang Truong Thi Thu loan Doan nguyen Tien Hoang nguyen Van Tam Minh Kim nguyen le Gia Trung Jin Seog Gwag nguyen Tien Tran Optical Materials Research Group Science and Technology Advanced InstituteVan Lang UniversityHo Chi Minh CityViet Nam Faculty of Applied Technology School of TechnologyVan Lang UniversityHo Chi Minh CityViet Nam The University of Da Nang University of Science and Technology54 Nguyen Luong BangDa NangViet Nam The University of Da Nang University of Science and Education459 Ton Duc Thang St.Lien ChieuDa Nang 550000Viet Nam Institute of Veterinary Science and Technology 31ha zoneTrau QuyGia LamHa Noi 12400Viet Nam Department of Physics Yeungnam UniversityGyeongsanGyeongbuk 38541Republic of Korea Center for Advanced Chemistry Institute of Research and DevelopmentDuy Tan University03 Quang TrungDa Nang 550000Viet Nam Faculty of Natural Sciences Duy Tan University03 Quang TrungDa Nang 550000Viet Nam

Environmental pollution,such as water contamination,is a critical issue that must be absolutely addressed.Here,three different morphologies of tungsten-based photocatalysts(WO_(3)nanorods,WO_(3)/WS_(2)nanobricks,WO_(3)/WS_(2)nanorods)are made using a simple hydrothermal method by changing the solvents(H_(2)O,DMF,aqueous HCl solution).The as-prepared nanocatalysts have excellent thermal stability,large porosity,and high hydrophilicity.The results show all materials have good photocatalytic activity in aqueous media,with WO_(3)/WS_(2)nanorods(NRs)having the best activity in the photodegradation of bisphenol A(BPA)under visible-light irradiation.This may originate from increased migration of charge carriers and effective prevention of electron–hole recombination in WO_(3)/WS_(2)NRs,whereby this photocatalyst is able to generate more reactive·OH and·O_(2)^(–)species,leading to greater photocatalytic activity.About 99.6% of BPA is photodegraded within 60 min when using 1.5 g/l WO_(3)/WS_(2)NRs and 5.0 mg/l BPA at pH 7.0.Additionally,the optimal conditions(pH,catalyst dosage,initial BPA concentration)for WO_(3)/WS_(2)NRs are also elaborately investigated.These rod-like heterostructures are expressed as potential catalysts with excellent photostability,efficient reusability,and highly active effectivity in different types of water.In particular,the removal efficiency of BPA by WO_(3)/WS_(2)NRs reduces by only 1.5% after five recycling runs and even reaches 89.1%in contaminated lake water.This study provides promising insights for the nearly complete removal of BPA from wastewater or different water resources,which is advantageous to various applications in environmental remediation.

关键词： Photodegradation Bisphenol A Tungsten-based nanocatalyst Structure Nanorod

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Some Mean Convergence Theorems for the Maximum of Normed Double Sums of Banach Space Valued Random Elements

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Acta Mathematica Sinica,English Series 2024年第7期40卷 1727-1740页

作者： Andrew ROSAlSKY lê V?n THàNH nguyen Thi THUY Department of Statistics University of Florida Department of Mathematics Vinh University High School for Gifted Students Vinh University

In this correspondence, we establish mean convergence theorems for the maximum of normed double sums of Banach space valued random elements. Most of the results pertain to random elements which are M-dependent. We expand and improve a number of particular cases in the literature on mean convergence of random elements in Banach spaces. One of the main contributions of the paper is to simplify and improve a recent result of li, Presnell, and Rosalsky [Journal of Mathematical Inequalities, 16, 117–126(2022)]. A new maximal inequality for double sums of M-dependent random elements is proved which may be of independent interest. The sharpness of the results is illustrated by four examples.

关键词： Double sum mean convergence Rademacher type p Banach space Banach space valued random element M -dependent random elements 60F25 60B11 60B12

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Chebyshev polynomial-based Ritz method for thermal buckling and free vibration behaviors of metal foam beams

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Applied Mathematics and Mechanics(English Edition) 2024年第5期45卷 891-910页

作者： N.D.nguyen T.N.nguyen Faculty of Civil Engineering Ho Chi Minh City University of Technology and EducationHo Chi Minh City 71309Viet Nam Faculty of Engineering and Technology Kien Giang UniversityChau Thanh 92000Viet Nam

This study presents the Chebyshev polynomials-based Ritz method to examine the thermal buckling and free vibration characteristics of metal foam beams.The analyses include three models for porosity distribution and two scenarios for thermal distribution.The material properties are assessed under two conditions,i.e.,temperature dependence and temperature independence.The theoretical framework for the beams is based on the higher-order shear deformation theory,which incorporates shear deformations with higher-order polynomials.The governing equations are established from the lagrange equations,and the beam displacement fields are approximated by the Chebyshev polynomials.Numerical simulations are performed to evaluate the effects of thermal load,slenderness,boundary condition(BC),and porosity distribution on the buckling and vibration behaviors of metal foam beams.The findings highlight the significant influence of temperature-dependent(TD)material properties on metal foam beams'buckling and vibration responses.

关键词： Ritz method Chebyshev function buckling vibration metal foam beam higher-order beam theory(HOBT)

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Transient responses of double-curved sandwich two-layer shells resting on Kerr's foundations with laminated three-phase polymer/GNP/fiber surface and auxetic honeycomb core subjected to the blast load

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Defence Technology（防务技术） 2024年第5期35卷 222-247页

作者： nguyen Thi Hai Van Thi Hong nguyen Researcher&lecturer Faculty of Industrial EducationThe University of Danang-University of Technology and Education48 Cao ThangDanang550000Viet Nam Researcher&lecturer Faculty of Mechanical EngineeringThuyloi University175 Tay SonDong DaHanoi100000Viet Nam

This work uses refined first-order shear theory to analyze the free vibration and transient responses of double-curved sandwich two-layer shells made of auxetic honeycomb core and laminated three-phase polymer/GNP/fiber surface subjected to the blast load.Each of the two layers that make up the double-curved shell structure is made up of an auxetic honeycomb core and two laminated sheets of three-phase polymer/GNP/fiber.The exterior is supported by a Kerr elastic foundation with three characteristics.The key innovation of the proposed theory is that the transverse shear stresses are zero at two free surfaces of each layer.In contrast to previous first-order shear deformation theories,no shear correction factor is required.Navier's exact solution was used to treat the double-curved shell problem with a single title boundary,while the finite element technique and an eight-node quadrilateral were used to address the other boundary requirements.To ensure the accuracy of these results,a thorough comparison technique is employed in conjunction with credible statements.The problem model's edge cases allow for this kind of analysis.The study's findings may be used in the post-construction evaluation of military and civil works structures for their ability to sustain explosive loads.In addition,this is also an important basis for the calculation and design of shell structures made of smart materials when subjected to shock waves or explosive loads.

关键词： Blast load Two-layer shell Polymer/GNP/Fiber surface Auxetic honeycomb Shear connectors

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Is convenience really king? Comparative evaluation of catastrophic costs due to tuberculosis in the public and private healthcare sectors of Viet Nam: a longitudinal patient cost study

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贫困所致传染病(英文) 2024年第2期13卷 1-12页

作者： nguyen Hoa Binh Quang Vo luan nguyen Forse Rachel Jeanette Wiemers Anja Maria Christine Huynh Huy Ba Dong Thuy Thi Thu Phan Yen Thi Hoang Creswell Jacob Dang Thi Minh Ha nguyen lan Huu Shedrawy Jad l?nnroth Knut nguyen Tuan Dinh Van Dinh luong Annerstedt Kristi Sidney Codlin Andrew James National lung Hospital Ha Noi Viet Nam Friends for International TB Relief Ha Noi Viet Nam Department of Global Public Health WHO Collaboration Centre On Tuberculosis and Social Medicine Karolinska Institute Stockholm Sweden Stop TB Partnership Geneva Switzerland Pham Ngoc Thach Hospital Ho Chi Minh City Viet Nam

Background In Viet Nam, tuberculosis (TB) represents a devastating life-event with an exorbitant price tag, partly due to lost income from daily directly observed therapy in public sector care. Thus, persons with TB may seek care in the private sector for its flexibility, convenience, and privacy. Our study aimed to measure income changes, costs and catastrophic cost incurrence among TB-affected households in the public and private sector.Methods Between October 2020 and March 2022, we conducted 110 longitudinal patient cost interviews, among 50 patients privately treated for TB and 60 TB patients treated by the National TB Program (NTP) in Ha Noi, Hai Phong and Ho Chi Minh City, Viet Nam. Using a local adaptation of the WHO TB patient cost survey tool, participants were interviewed during the intensive phase, continuation phase and post-treatment. We compared income levels, direct and indirect treatment costs, catastrophic costs using Wilcoxon rank-sum and chi-squared tests and associated risk factors between the two cohorts using multivariate regression.Results The pre-treatment median monthly household income was significantly higher in the private sector versus NTP cohort (USD 868 vs USD 578;P=0.010). However, private sector treatment was also significantly costlier (USD 2075 vs USD 1313;P=0.005), driven by direct medical costs which were 4.6 times higher than costs reported by NTP participants (USD 754 vs USD 164;Plted in no significant difference in catastrophic costs between the two cohorts (Private: 55% vs NTP: 52%;P=0.675). Factors associated with catastrophic cost included being a single-person household [adjusted odds ratio [(aOR=13.71; 95% confidence interval (CI): 1.36–138.14;P=0.026], unemployment during treatment (aOR=10.86; 95%CI: 2.64–44.60;Plated stigma (aOR=37.90; 95%CI: 1.72–831.73;P=0.021).Conclusions Persons with TB in Viet Nam face similarly high risk of catastrophic costs whether treated in the public or private sector. Patient costs could be

关键词： Tuberculosis Patient cost Catastrophic cost Private sector Comparative analysis Viet Nam

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Prognostic value of N-terminal pro B-type natriuretic peptide and troponin Ⅰ in children with dengue shock syndrome

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Asian Pacific Journal of Tropical Medicine 2024年第4期17卷 166-172页

作者： Truyen Phuoc le Phung nguyen The nguyen University of Medicine and Pharmacy at Ho Chi Minh city Ho Chi Minh CityVietnam Children's Hospital 1 Ho Chi Minh CityVietnam

Objective:To investigate the contribution of N-terminal pro B-type natriuretic peptide(NT-pro BNP)and troponin Ⅰ to mortality in children with dengue shock syndrome.Methods:A longitudinal study was conducted on children with dengue shock syndrome in a hospital in southern Vietnam.Detailed clinical histories,physical examinations,and laboratory parameters,including NT-pro BNP and troponin Ⅰ,were recorded.A comparison between survival and non-survival was carried out to identify factors influencing mortality.Results:A total of 107 patients with a median age of 9 years were included in the study.Among them,63.6%(68/107)presented with compensated shock,36.4%(39/107)had hypotensive shock,23.4%(25/107)required mechanical ventilation,and 12.1%(13/107)died.The NT-pro BNP levels were 3.9 pmol/l(IQR:1.9,10.3)and 15.2 pmol/l(5.8,46.3),while the median high sensitivity troponin Ⅰ levels were 20 pg/l(6,95)and 62 pg/l(12,325)at the first and second measurements,respectively.The mortality group exhibited higher rates of hypotensive shock,prolonged shock,lactate levels,liver damage,NT-pro BNP,and troponin Ⅰ levels.Hypotensive shock(OR 12.96,95%CI 2.70-62.30,P=0.004),prolonged shock(OR 39.40,95%CI 6.68-232.70,P1000 IU/l(OR 9.50,95%CI 2.63-34.34,P=0.041),and NT-pro BNP>7 pmol/l(OR 44.40,95%CI 5.44-362.20,P=0.001)were identified as predictive factors for mortality in dengue shock syndrome.Conclusions:The NT-pro BNP level could serve as a potential biomarker for predicting mortality in children with dengue shock syndrome.

关键词： Dengue shock syndrome Cardiac enzyme NT-pro BNP TroponinⅠ

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