Dynamic response of honeycomb-FGS shells subjected to the dynamic loading using non-polynomial higher-order IGA

The main goal of this study is to use higher-order isogeometric analysis(IGA)to study the dynamic response of sandwich shells with an auxetic honeycomb core and two different functionally graded materials(FGM)skin layers(namely honeycomb-FGS shells)subjected to dynamic loading.Touratier's non-polynomial higher-order shear deformation theory(HSDT)is used due to its simplicity and performance.The governing equation is derived from Hamilton's principle.After verifying the present approach,the effect of input parameters on the dynamic response of honeycomb-FGS shells is carried out in detail.

Prevalence, risk factors, and BRAF mutation of colorectal sessile serrated lesions among Vietnamese patients

BACKGROUND Sessile serrated lesions(SSLs)are considered precancerous colorectal lesions that should be detected and removed to prevent colorectal cancer.Previous studies in Vietnam mainly investigated the adenoma pathway,with limited data on the serrated pathway.AIM To evaluate the prevalence,risk factors,and BRAF mutations of SSLs in the Vietnamese population.METHODS This is a cross-sectional study conducted on patients with lower gastrointestinal symptoms who underwent colonoscopy at a tertiary hospital in Vietnam.SSLs were diagnosed on histopathology according to the 2019 World Health Organi-zation classification.BRAF mutation analysis was performed using the Sanger DNA sequencing method.The multivariate logistic regression model was used to determine SSL-associated factors.RESULTS There were 2489 patients,with a mean age of 52.1±13.1 and a female-to-male ratio of 1:1.1.The prevalence of SSLs was 4.2%[95%confidence interval(CI):3.5-5.1].In the multivariate analysis,factors significantly associated with SSLs were age≥40[odds ratio(OR):3.303;95%CI:1.607-6.790],male sex(OR:2.032;95%CI:1.204-3.429),diabetes mellitus(OR:2.721;95%CI:1.551-4.772),and hypertension(OR:1.650,95%CI:1.045-2.605).The rate of BRAF mutations in SSLs was 35.5%.CONCLUSION The prevalence of SSLs was 4.2%.BRAF mutations were present in one-third of SSLs.Significant risk factors for SSLs included age≥40,male sex,diabetes mellitus,and hypertension.

An isogeometric analysis approach for dynamic response of doubly-curved magneto electro elastic composite shallow shell subjected to blast loading

For the first time, the isogeometric analysis(IGA) approach is used to model and analyze free and forced vibrations of doubly-curved magneto-electro-elastic(MEE) composite shallow shell resting on the visco-Pasternak foundation in a hygro-temperature environment. The doubly-curved MEE shallow shell types include spherical shallow shell, cylindrical shallow shell, saddle shallow shell, and elliptical shallow shell subjected to blast load are investigated. The Maxwell equation and electromagnetic boundary conditions are used to determine the vary of the electric and magnetic potentials. The MEE shallow shell's equations of motion are derived from Hamilton's principle and refined higher-order shear theory. Then, the IGA method is used to derive the laws of natural frequencies and dynamic responses of the shell under various boundary conditions. The accuracy of the model and method is verified through reliable numerical comparisons. Aside from this, the impact of the input parameters on the free and forced vibration of the doubly-curved MEE shallow shell is examined in detail. These results may be useful in the design and manufacture of military structures such as warships, fighter aircraft, drones and missiles.

Comparative Chemical Research in Essential Oils from Six Apiaceae Species Growing in the Northern Region of Vietnam

Our study aimed to compare the essential oil(EO)concentration and composition of several Apiaceae species growing in the Northern region of Vietnam.The yields of EOs from materials ranged from 0.03%(root EO of Angelica acutiloba and aerial parts EO of Heracleum bivittatum)-0.27%(leaf EO of Xyloselinum vietnamense).Gas chromatography-mass spectrometry(GC-MS)allowed the identification of 74 components in the EOs of six Apiaceae species,making up 94.4%–100.0%of the oils.In EO from Angelica acutiloba,(Z)-ligustilide accounted for an extremely large proportion(94.9%).EO of Angelica pubescens was dominated by six character-istic components includingα-pinene(21.5%),β-phellandrene(18.1%),p-cymene(12.2%),3-methylnonane(8.7%),o-cymene(8.1%),and D-sylvestrene(6.2%).The EO from Cryptotaenia japonica was characterized by high amounts ofα-selinene(48.7%),β-selinene(23.7%),and trans-β-farnesene(5.4%).The EOs from leaves and stems of Xyloselinum vietnamense were characterized by high concentrations of sabinene(69.8%and 33.8%),4-terpineol(8.7%and 7.4%)andβ-pinene(4.0%and 6.5%)while EOs from aerial parts and root of Xylo-selinum leonidii comprise four characteristic monoterpenes includingα-pinene(28.2%and 52.8%),β-pinene(7.9%and 10.3%),β-phellandrene(7.6%and 15.3%),and sabinene(3.0%and 4.1%).Additionally,cryptone is also one of the major components in the EO of Xyloselinum leonidii(13.2%in the aerial parts oil and 2.8%in the root oil).In the EOs isolated from the aerial parts and root of Heracleum bivittatum,α-pinene(22.5%and 70.2%)andβ-pinene(43.2%and 20.0%)were the predominant monoterpenes.Sabinene appeared in the EO from aerial parts of Heracleum bivittatum with a relatively high concentration(13.5%)while bornyl acetate(5.1%)was also one of the main components in the EO from its aerial parts but was not detected in other Apiaceae species in the present study.These databases help identify and control the quality of plant material studied from the family Apiaceae growing in Vietnam.

Carbon Footprint in Waste Sector of Hydropower Plant: A Case Study of Nam Theun 2 Hydropower Plant

While hydropower is generally considered a clean energy source, it is important to recognize that their waste can still contribute to greenhouse gas emissions (GHG). The purpose of this study is to assess the carbon footprint associated with the waste sector throughout the operational phase of the Nam Theun 2 hydropower plant in Laos. Understanding the environmental impact of the waste sector is crucial for ensuring the plant’s sustainability. This study utilizes the theoretical estimation method recommended in the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, as well as the Requirements for Specification with guidance at the organization level for quantification and reporting of GHG emissions and removals. We emphasize the significance of implementing sustainable waste management practices to reduce GHG emissions and minimize the environmental impact of hydropower operations. By conducting a comprehensive analysis, this paper also provides insights into the environmental implications of waste management in hydropower plants and identifies strategies to mitigate the carbon footprint in the waste sector. The findings contribute to a better understanding of the environmental sustainability of hydropower plants and provide valuable guidance for policymakers, energy producers, and environmental practitioners involved in hydropower plant design and operation.

Stand dynamics of old-growth hemlock forests in central Bhutan are shaped by natural disturbances

Understanding how past disturbances have influenced the development of forests is critical for deciphering their current structure and composition and forecasting future changes.In this study,dendrochronological methods were applied to uncover the disturbance history of old-growth hemlock-dominated forests in central Bhutan.Analysis of tree-ring samples from two old-growth hemlock stands,located in two different topographic settings,identified the importance of gap-phase dynamics in facilitating recruitment and growth releases and producing complex,multi-aged structure s over time.One site showed evidence of a near stand-replacing disturbance in the late 1700s,while the other showed no evide nce of high-severity disturbance at any time over the last 400 years.At both sites low-to medium-severity disturbances,some of which appear to be associated with cyclones originating in the Bay of Bengal,dominated the disturbance regime.The hemlock stands exhibited a significant positive association between cyclone occurrence and growth release events and between recruitment pulses and growth release events.From 1800 to 1970 there was an increase in recruitment of angiosperm tree species at most sites and a corresponding decline in conifer recruitment.Over the past 50 years there has been little new recruitment;this may be due to light limitation in the understory from shade-tolerant angiosperms and bamboo in the lower strata of these stands.Significant variations in disturbance dynamics and recruitment were observed across the study sites,suggesting that other factors,such as topography and climate,may be influencing long-term stand development patterns.This study highlights the complex interplay between historical disturbance regimes and tree recruitment in shaping the age and size structures of old-growth hemlock forests in central Bhutan.It also provides new insights into the dynamics of these forests that can be used to support effective forest conservation and management in the future.

Spiritual Forests—A Nature Conservation Model of Ethnic Minority Communities in Central Viet Nam

This paper aims to analyze and evaluate a model of forest conservation and management of ethnic minority (or indigenous) people in central Vietnam, often referred to as the spiritual forest. These forests, called sacred forest or ghost forests by the ethnic minority people in Thua Thien Hue province, have existed for a long time among forest residents. However, they have recently declined, both in quality and quantity, due to various factors, including changes in society, economy, environment, and perception, among other reasons. Based on research conducted in A Luoi district, Thua Thien Hue province with household interviews, group discussions, and field surveys, we find that spiritual forest retains religious and human significance. They are also often among the last remaining natural forests left due to deforestation by human activities. The research results indicate challenges that conservation of spiritual forest may face, while giving recommendations derived from communities for sustainable forest development and conservation in the region.

Dynamic analysis of bio-inspired helicoid laminated composite plates resting on Pasternak foundation excited by explosive loading

This paper uses isogeometric analysis(IGA)based on higher-order shear deformation theory(HSDT)to study the dynamic response of bio-inspired helicoid laminated composite(B-iHLC)plates resting on Pasternak foundation(PF)excited by explosive loading.IGA takes advantage of non-uniform rational Bspline(NURBS)basic functions to exactly represent the structure geometry models and the attainment of higher-order approximation conditions.This method also ensures a C1 continuous function in the analysis of transverse shear deformation via HSDT.Furthermore,IGA eliminates the requirement for correction factors and delivers accurate results.Pasternak foundation with two stiffness parameters:springer stiffness(k_(1))and shear stiffness(k_(2)).The derivation of the governing equations is based on Hamilton's principle.The proposed method is validated through numerical examples.A comprehensive analysis of the impact of geometrical parameters,material properties,boundary conditions(BCs),and foundation stiffness on dynamic response of B-i HLC plates is carried out.

Performance evaluation of high/ultra-high-degree global geopotential models over Vietnam using GNSS/leveling data

The availability of many high-degree Global Geopotential Models(GGMs), namely EGM2008, EIGEN-6C4,GECO, SGG-UGM-1, SGG-UGM-2, XGM2019e_2159, and GGMPlus, challenges users regarding which model is best for Vietnam. This study, therefore, evaluates their performance by comparing them with GNSS/leveling data over Vietnam. Results show that their absolute and relative performances are largely independent of topographic conditions and geographical location and can be ranked into three classes:(1)XGM2019e_2159 has the highest accuracy,(2) the models EIGEN-6C4, GECO, SGG-UGM-1, SGG-UGM-2, and GGMPlus, have a very similar level of medium accuracy, while(3) EGM2008 is found to be the least accurate. In an absolute sense, the differences between GNSS/leveling and EGM2008-based height anomalies have a standard deviation(STD) of 0.290 ± 0.010 m, whereas, for XGM2019e_2159, this is 0.156 ± 0.006 m.All other models have STDs of(0.18-0.19) ± 0.007 m. Regarding relative performance without fitting, all GGMs have comparable accuracies for baseline length of 5-20 km, while for baselines longer than 20 km,the STD of XGM2019e_2159 is 1.5 ppm-0.5 ppm(approximately 19%-40%) lower compared with EGM2008, and 0.5 ppm-0.25 ppm(approximately 7%-36%) lower compared with EIGEN6C4, GECO,SGG-UGM-1, SGG-UGM-2, and GGMPlus. In addition, the STDs decrease significantly from 20 to 12 ppm in the range of 5-10 km, slightly from 12 to 6 ppm for 10-35 km, very slightly from 6 to 2.5 ppm for35-200 km, and then remain almost unchanged for longer baselines. After fitting, the relative accuracies of all GGMs are at the same level with negligible STD/RMSE values. Furthermore, only EGM2008 experiences significant regional differences, while other GGMs show more homogeneous spatial variation of absolute accuracy over Vietnam. These findings can contribute to the development of local quasigeoid models in Vietnam and may be helpful with the improvement of GGMs in the future.

Assessing the Impact of Industrial Zones on the Environmental Pollution in Hai Phong’s Coastal Areas, Vietnam

Pollution in the coastal areas negatively affects biochemical indicators of seawater, human health and marine organisms. Hai Phong is a coastal city of Vietnam with the development of socio-economic activities, representing through an increasing number of industrial zones. This study is to evaluate the pollution of large industrial zones in Hai Phong city using numerical models. The numerical simulation (MIKE 21 SW, FM, ECO Lab) models were applied to simulate the wave propagation, hydraulic regime, water quality in coastal Hai Phong area. The MIKE 21 ECO Lab model was used to evaluate sources of waste from the large coastal industrial zones to some aquaculture zones. The calibration and validation results of wave propagation and the hydrodynamic models were resonably good, with Nash coefficient ranging from 0.65 to 0.90 and a percent bias (PBIAS) from 5.6% to 9.4%. The simulation results of water quality and concentration of pollutants (DO, BOD5, COD, TSS, Fe, and Coliform) in 2023 at the aquaculture locations show that the BOD5, COD, and TSS concentrations were higher than the allowable limits stated in the national technical regulation on surface water quality (QCVN 08:2023/BTNMT) and lower than the allowable limits stated in the national technical regulation on marine water quality (QCVN 10:2023/BTNMT). The outcomes of this study will provide more information to support managers to come up with a better socio-economic development plan for Hai Phong city to achieve sustainable development.

A Dual-Support Smoothed Particle Hydrodynamics for Weakly Compressible Fluid Inspired By the Dual-Horizon Peridynamics

A dual-support smoothed particle hydrodynamics(DS-SPH)that allows variable smoothing lengths while satisfying the conservations of linear momentum,angular momentum and energy is developed.The present DS-SPH is inspired by the dual-support,a concept introduced from dual-horizon peridynamics from the authors and applied here to SPH so that the unbalanced interactions between the particles with different smoothing lengths can be correctly considered and computed.Conventionally,the SPH formulation employs either the influence domain or the support domain.The concept of dual-support identifies that the influence domain and the support domain involves the duality and should be simultaneously in the SPH formulation when variable smoothing lengths are used.The DS-SPH formulation can be implemented into conventional SPH codes with minimal changes and also without compromising the computational efficiency.A number of numerical examples involving weakly compressible.fluid are presented to demonstrate the capability of the method.

Biomass accumulation of Panax vietnamensis in cell suspension cultures varies with addition of plant growth regulators and organic additives

Objective: To evaluate the impact of plant growth regulators including kinetin(KN),benzyl adenine and naphthalene acetic acid, yeast extract and casein hydrolyzate on biomass accumulation of Vietnamese ginseng Panax vietnamensis(P. vietnamensis) in cell suspension culture.Methods: Cell suspension cultures were established from friable calluses derived from leaves and petioles of 3-year-old in-vitro P. vietnamensis plants. The cell suspension cultures were grown in Murashige and Skoog basal media supplemented with various concentrations of KN, benzyl adenine, naphthalene acetic acid, and yeast extract and casein hydrolyzate.Results: All tested factors generated an increase in the cell biomass of P. vietnamensis in suspension culture, but the impact of each varies depended on the factor type, concentration, and incubation period. Addition of 2.0 mg/L KN resulted in the largest biomass increase after 24 d,(57.0 ± 0.9) and(3.1 ± 0.1) mg/m L fresh and dry weight, respectively,whereas addition of benzyl adenine or naphthalene acetic acid produced optimum levels of Panax cell biomass at 1.0 and 1.5 mg/L, respectively. Addition of the elicitor yeast extract led to a 1.4–2.4 fold increase in biomass of P. vietnamensis, while addition of casein hydrolyzate enhanced biomass accumulation 1.8–2.6 fold.Conclusions: The addition of each factor causes significant changes in biomass accumulation of P. vietnamensis. The largest biomass accumulation is from cultures grown in MS media containing 2.0 mg/L KN for 24 d. The outcome of the present study provides new insights into the optimal suspension culture conditions for studies on the in vitro cell biomass production of P. vietnamensis.

Perceived ill-health and health seeking behavior in two communities in the nam theun 2 hydroelectric project area in Lao Peoples Democratic Republic

Objective:To compare perceived ill-health and health seeking behavior between two communities affected by the large Nam Theun 2 hydroelectric project in central Lao People’s Democratic Republic(PDR).Methods: Two different affected areas;Nakai plateaubeing remote,sparcely populated and mountainous,and Xe Bang Fai lowland plains,more densely populated and comparatively affluent were included.Data were obtained from two cross-sectional household-based health and socio-economic surveys.Results:We found pronounced differences in the frequency of self-reported fever,cough,headache and myalgia according to location.On the Nakai plateau,45.1%of the individuals with ill-health report(recall period;2 weeks) went to a local health volunteer compared to only 7.2%in the Xe Bang Fai area(P 【 0.001 ).In Nakai,there were disproportionately more illiterates seeking help from local health volunteers when compared to those who attended at least primary schooling(49.2%versus 17.5%,P 【0.01 ).Self-medication with antimalarials was more common in Xe Bang Fai than on Nakai(32.3%versus 7.0%,P 【 0.001).The mean amount of money spent per health consultation was US $ 1.7 in Nakai and US $ 7.2 in Xe Bang Fai.Conclusion:The observed differences in self-reported ill-health and health seeking behavior among these two Lao communities need to be considered when implementing setting-specific mitigation measures as part of the public health action plan of the Nam Theun 2 hydroelectric project.

Infectious keratitis in Vietnam:etiology,organisms,and management at Vietnam National Eye Hospital

AIM:To report the etiologies,risk factors,treatments,and outcomes of infectious keratitis(IK)at a major Vietnamese eye hospital.METHODS:This is a retrospective review of all cases of IK at Vietnam National Eye Hospital(VNEH)in Hanoi,Vietnam.Medical histories,demographics,clinical features,microbiological results,and treatment outcomes were reviewed.RESULTS:IK was diagnosed in 1974 eyes of 1952 patients,with ocular trauma being the greatest risk factor for IK(34.2%),frequently resulting from an agriculturerelated injur y(53.3%).The mean duration between symptom onset and presentation to VNEH was 19.3±14.4 d,and 98.7%of patients had been treated with topical antibiotic and/or antifungal agents prior to evaluation at VNEH.Based on smear results of 1706 samples,the most common organisms identified were bacteria(n=1107,64.9%)and fungi(n=1092,64.0%),with identification of both bacteria and fungi in 614(36.0%)eyes.Fifty-five of 374 bacterial cultures(14.7%)and 426 of 838 fungal cultures(50.8%)were positive,with the most commonly cultured pathogens being Pseudomonas aeruginosa,Streptococcus pneumonia,Fusarium spp.,and Aspergillus spp.Corneal perforation and descemetocele developed in 391(19.8%)and 93(4.7%)eyes,respectively.Medical treatment was successful in resolving IK in 50.4%eyes,while 337(17.1%)eyes underwent penetrating or anterior lamellar keratoplasty.Evisceration was performed in 7.1%of eyes,most commonly in the setting of fungal keratitis.CONCLUSION:Ocular trauma is a major risk factor for IK in Vietnam,which is diagnosed in almost 400 patients each year at VNEH.Given this,and as approximately one quarter of the eyes that develop IK require corneal transplantation or evisceration,greater emphasis should be placed on the development of prevention and treatment programs for IK in Vietnam.

Leaf fossils of Sabalites(Arecaceae)from the Oligocene of northern Vietnam and their paleoclimatic implications

Recent paleobotanical investigations in Vietnam provide a good opportunity to improve our understanding of the biodiversity and paleoclimatic conditions in the geological past of Southeast Asia.Palms(Arecaceae)are a diverse family of typical thermophilous plants with a relatively low tolerance for freezing.In this study,we describe well-preserved fossil palm leaves from the Oligocene Dong Ho Formation of Hoanh Bo Basin,northern Vietnam.Characters of the fossil leaves,such as a fan-shaped costapalmate lamina,an unarmed petiole,a costa slightly enlarged at the base that then tapers distally into the blade,and well-preserved amphistomatic leaves with cuticles,suggest that they represent a new fossil species,which we herein designate Sabalites colaniae A.Song,T.Su,T.V.Do et Z.K.Zhou sp.nov.Together with other paleontological and palaeoclimatic evidence,we conclude that a warm climate prevailed in northern Vietnam and nearby areas during the Oligocene.

Locally weighted learning based hybrid intelligence models for groundwater potential mapping and modeling: A case study at Gia Lai province, Vietnam

The groundwater potential map is an important tool for a sustainable water management and land use planning,particularly for agricultural countries like Vietnam.In this article,we proposed new machine learning ensemble techniques namely AdaBoost ensemble(ABLWL),Bagging ensemble(BLWL),Multi Boost ensemble(MBLWL),Rotation Forest ensemble(RFLWL)with Locally Weighted Learning(LWL)algorithm as a base classifier to build the groundwater potential map of Gia Lai province in Vietnam.For this study,eleven conditioning factors(aspect,altitude,curvature,slope,Stream Transport Index(STI),Topographic Wetness Index(TWI),soil,geology,river density,rainfall,land-use)and 134 wells yield data was used to create training(70%)and testing(30%)datasets for the development and validation of the models.Several statistical indices were used namely Positive Predictive Value(PPV),Negative Predictive Value(NPV),Sensitivity(SST),Specificity(SPF),Accuracy(ACC),Kappa,and Receiver Operating Characteristics(ROC)curve to validate and compare performance of models.Results show that performance of all the models is good to very good(AUC:0.75 to 0.829)but the ABLWL model with AUC=0.89 is the best.All the models applied in this study can support decision-makers to streamline the management of the groundwater and to develop economy not only of specific territories but also in other regions across the world with minor changes of the input parameters.

Prevalence and Patterns of Divorce in Vietnam： Tradition, Modernity, and Individualism

In Vietnam, divorce traditionally was considered scandalous for women, so there was a strong pressure against divorce, especially for women. While divorce has long been culturally discouraged and limited, divorce has been rapidly increasing after the renovation policy in late 1980s with alternative causes, consequences, etc Modernization is a process of transforming ＂traditional＂ society to ＂modern＂ one, in order to achieve economic development and growth, to innovate politics and to enhance their social structure towards a political, social, and economic system similar to those of western developed countries. In the field of marriage, family, and kinship, modernization process experiences the maintenance of traditional values and the appearance of the new modern values. This paper aims to examine trend and correlates of divorce and to identify social and cultural factors influencing the divorce decision, using data of divorce profiles of one district court in 10 years （i.e., 2000-2009） with total divorce profiles analyzed are 2,033 cases, of which 499 divorce couples in a rural district and 1,534 divorced couples in an urban area.

Scientific Research in Universities of Vietnam in Present and Its Effects on Training Quality

In this paper, the author presented an overview of scientific research in universities of Vietnam in present and analyzed and assessed its effects on the quality of education in universities. The information to write this article was obtained in the references and from the management practice for the universities and the research institute.

The Genetic Relationship of Vietnamese Pigs in Central Highlands Assessed by Cytochrome b

To estimate the genetic relationship of Vietnamese pigs in Central Highlands, we compared cytochrome b sequences of Vietnamese wild boars and Vietnamese domestic pigs with other Asian and European wild boars. The results showed that there were two wild boar populations locating in Vietnam Central Highlands including wild boars of group I and wild boars of group II. The Vietnamese wild boars of group II and domestic pigs were genetically close to Asian A1 and Asian A2 wild boar groups, whereas the Vietnamese wild boars of group I were genetically distinct from Asian A1, Asian A2 wild boar groups. The phylogenetic tree demonstrated that the Vietnamese wild boars of group I were clustered in one clade which was distinct from Asian wild boars and Europe wild boars. In addition, the Vietnamese wild boars of group I were estimated to have diverged from European wild boars at 421500 YBP, indicating that Vietnamese wild boar of group I could be isolated from other Asian wild boars. The single nucleotide polymorphism analysis showed that three Asian haplotypes were contributed in Vietnamese wild boars including A3 (TATG) haplotype in Vietnamese wild boar of group I and A1 (CATA) haplotype and A2 (CATG) haplotype in Vietnamese wild boars of group II. The A1 haplotype and A2 haplotype were also distributed in Vietnamese domestic pigs. Thus, there is a high possibility that Vietnam Central Highlands is a principal source for research on genetic diversity in Asian wild boar and domestic pig populations.

A Study on the Selection of the Logistics Centre Location—Vietnam-Based Logistics Sector

Logistics can be considered as the major drive of the economy.Logistics centres play a significant role in the entire logistics networks from the point of materials sourcing to the point of last mile delivery.The efficiency of a logistics network depends on the existence of logistics centres to connect and integrate entire logistics system.This article discusses the importance of selection of the logistics centre location and recommends the procedure to specify the appropriate logistics centre location as a case of Vietnam-based logistics sector.