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The respiratory syncytial virus is a major cause of acute respiratory tract infection in young children. However, molecular characteristics analysis was not as much of its’ burden, especially in developing countries as well as Viet Nam. Therefore, we performed molecular evolutionary analyses of the G gene of RSV-A sequences which were collected from pediatric severe acute respiratory infection patients in north Viet Nam from 2017–2020. The Bayesian Markov Chain Monte Carlo method was used to conduct phylogenetic analyses and a time scale for evolution. We also calculated population dynamics, estimated the natural selection pressure and potential N-glycosylation sites. The results indicated the majority of study sequences were classified into the ON1 genotype. There were three strains belonging to the non-ON1 genotype with p-distance = 0.048. Besides, even though most of the Vietnamese sequences were identified as ON1 genotype, all of them had no 72-nucleotide duplication in the second hypervariable region of the G gene. The molecular evolutionary rate of the RSV-A G gene in northern Viet Nam was estimated to be 1.32 × 10− 3 substitutions/site/year. Each year, the shifts of the N-glycosylation pattern within the G gene of Vietnamese sequences were observed. Moreover, five amino acid substitution sites were related to positive selection pressure. These results were the first report of the molecular evolution of the RSV-A G gene detected in Viet Nam after 2015.

This paper presents complete steps for the construction and solution algorithm for a projection-based reduced order model coupled with an artificial neural net model. The reduced model is constructed based on the Galerkin projection of the equations governing the physical processes on reduced subspaces obtained by the Proper Orthogonal Decomposition method. The projection is done using numerical discretisation schemes implemented in the commonly used OpenFOAM® platform. The neural net model is trained using the Nonlinear AutoRegressive eXogenous model network (NARX) architecture. The reduced order models are demonstrated for true predictions of incompressible flows at low Reynolds numbers driven by various boundary conditions. Compared with the full CFD simulations, this model shows excellent agreement while only requiring a fraction of the computational resources.

This paper presents the design of wireless sensor network (WSN) based on low-power wide area network technology for high-tech agriculture. This WSN allows the farmer to collect data such as air temperature, air humidity, soil moisture. The WSN system consists of components: 02 wireless sensor nodes, 01 gateway, 01 cloud server and smartphone app. This WSN tested for data transmission in two zones: zone 1 (dense urban environments) at a distance of 500m and zone 2 (urban environments - less obstacles) at a distance of 1,500m and 1,700m. The data collected at different times of the day and updated every 15 minutes. The results show that the wireless sensor network system operates stably, data constantly updated to LoRa Server and there was not data packet loss. The power consumption of sensor node and gateway determined in three operating modes: transmitting, receiving, turn-off. This shows the advantages of LoRa technology in the development of wireless sensor network which is the distance of data transmission distance and low power consumption. Besides this WSN also tested in the net house of aquaponics of the Research Center for High-tech Application in Agriculture (RCHAA), University of Science, Vietnam National University-HCM. The results show that the WSN system is working reliably and promising which brings significantly benefits to smart agriculture as aquaponics, clean vegetable farms, aquaculture farms…

Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive disorder caused by deleterious mutations in the α‑L‑iduronidase (IDUA) gene. Until now, MPS I in Vietnamese has been poorly addressed. Five MPS I patients were studied with direct DNA sequencing using Illumina technology confirming pathogenic variants in the IDUA gene. Clinical characteristics, additional laboratory results, and family history were collected. All patients have presented with the classical characteristic of MPS I, and α‑L‑iduronidase activity was low with the accumulation of glycosaminoglycans. Three variants in the IDUA gene (c.1190‑10C&gt, A (Intronic), c.1046A&gt, G (p.Asp349Gly), c.1862G&gt, C (p.Arg621Pro) were identified. The c.1190‑10C&gt, A variant represents six of the ten disease alleles, indicating a founder effect for MPS I in the Vietnamese population. Using biochemical and genetic analyses, the precise incidence of MPS I in this population should accelerate early diagnosis, newborn screening, prognosis, and optimal treatment

Our paper contributes to existing literature by empirically investigate the trade structure and trade performance between Korea and ASEAN. Overall, trade activities between Korea and almost major ASEAN economies have significantly focused on capital goods, medium and high technology goods, while the remaining ASEAN countries’ exports over Korea have been mainly primary and low technology goods. There has been a higher complementarity in between Korea’s exports and ASEAN’s imports compared with between ASEAN’s exports and Korea’s imports. Estimation results show that ASEAN’s GDP and income have larger impacts than those of Korea on aggregate trade flows as well as sectoral level between two sides. Additionally, geographical conditions are critical factors impeding Korea-ASEAN trade. Meanwhile, other factors in the estimation model have mixed impacts on components of Korea-ASEAN trade structure. Finally, there is a significant room for Korea’s trade expansion with ASEAN, particularly new and less developed members in future.

Organic photovoltaics (OPVs) based on nonfullerene acceptors are now approaching commercially viable efficiencies. One key to their success is efficient charge separation with low potential loss at the donor-acceptor heterojunction. Due to the lack of spectroscopic probes, open questions remain about the mechanisms of charge separation. Here, we study charge separation of a model system composed of the donor, poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))

This paper proposes a method for localizing a gunshot event using four acoustic sensor nodes mounted at the four corners of a rectangular working area. Each of these nodes involves three sensors to acquire acoustic signals of any gunshot inside the working area. The approach analyzes individual signals received by the nodes to identify sound events using false alarm probability and determine their emission directions exploiting a minimum mean square error estimator and the time difference of arrival of the events. The gunshot location is the quadrilateral center of four crossing points resulting from pairs of adjacent event emission directions. For evaluating the proposed method, a signal including ten real gunshots recorded by a nearby acoustic sensor is delayed and attenuated according to a theoretical wave propagation model to create various signal patterns, which simulates signals received by the installed sensor nodes. Furthermore, the Gaussian noise is added to the simulated signals to emulate the influence of wave propagation environment. This article also implements some mechanisms to compute the time difference of arrival for comparison. They are comprised of the first crossing of threshold and signal, maximum amplitude, Akaike’s Information Criterion, and the cross-correlation function. Hence, one of them can be selected for a real application. Experimental results show that the proposed method achieves high accuracy of gunshot localization.

Using two-dimensional electronic and electronic-vibrational spectroscopies, we find that charge generation via both electron and hole transfer pathways are mediated by bound polaron pairs and delocalized charge-transfer states in non-fullerene organic photovoltaics.

Let I be an ideal of a local commutative noetherian ring ( $$R, {{\mathfrak {m}}}$$ ) and M a finitely generated R-module. We study some properties of the top formal local cohomology module $${\mathcal {F}}^l_I(M)=\mathop {\varprojlim }H^l_{{{\mathfrak {m}}}}(M{/}I^tM)$$ with $$l=\mathrm {dim}M{/}I M$$ . In particular, we show that, in the case $$M \ne IM$$ , $${\mathcal {F}}^l_I(M)$$ is artinian if and only if $$l>\mathrm {dim}{\overline{M}}/I{\overline{M}}$$ where $${\overline{M}}=M/ H^0_I(M)$$ . As a consequence, we have $$ \mathrm {dim}{\overline{M}}/I{\overline{M}}=\sup \{i \in {\mathbb {Z}}\mid {\mathcal {F}}^i_I(M) \text { is not artinian}\},$$ provided that $${\overline{M}} \ne I{\overline{M}}$$ .

Wake-induced vibrations are considered distinctively different from well-known vortex induced vibrations where bluff body structures vibrate under vortex shedding in the wake of flows passing through them. Understanding characteristics of wake-induced vibrations plays an important role in design of marine-offshore structures such as platform columns, risers operating at high Reynolds number currents. This work presents an extensive study of wake-induced vibrations using a computational fluid dynamics approach. The numerical model is based on an incompressible Navier-Stokes flow solver with a hybrid detached eddy simulation (DES) approach for turbulence modelling of high Reynold number flows. The hybrid DES approach is first validated for wake-induced vibrations at subcritical Reynolds number ranging from 10 3 − 10 5 . Comparison between numerical results and experiment shows very good agreement in prediction of downstream cylinder responses including amplitudes, frequency and phase angle. Data from numerical simulations is then used to characterize and study mechanisms of wake-induced vibrations by looking at detailed force components and their frequencies in relation to cylinder responses. The effect of different Reynolds number flow conditions in tandem cylinder responses are also analysed in the present work. It is found that Reynolds number has strong influence in changing response amplitude and frequency of cylinders in wake-induced vibrations.

Raising capital efficiently for the operations is considered a fundamental decision for any firms. Since the 1960s, various theories on capital structure have been developed. Various empirical studies had also been conducted to examine the appropriateness of these theories in different markets. Unfortunately, evidence is mixed. In the context of Vietnam, a rising powerful economy in the Asia Pacific region, this important issue has been largely ignored. This paper is conducted to provide additional evidence on this important issue. In addition, different factors affecting the capital structure decisions from the Vietnamese listed firms are examined. The Generalized Method of Moment approach is employed on the sample of 227 listed firms in Ho Chi Minh City stock exchange over the period from 2008 to 2017. Findings from this study suggest that the Vietnamese listed firms follow the trade-off theory to determine their capital structure (i.e., to determine the optimal debt level). In contrast, no evidence has been found to confirm that the pecking order theory can explain the financing decisions of the Vietnamese listed firms, as previously expected. In addition, findings from this study also indicate that &lsquo, Fund flow deficit&rsquo, and &lsquo, Change in sales&rsquo, are the most two important factors that affect the amount of debt issued for the Vietnamese listed firms. Implications for academics, practitioners, and the Vietnamese government have also been emerged from the findings of this paper.

Mangrove forests can ameliorate the impacts of typhoons and storms, but their extent is threatened by coastal development. The northern coast of Vietnam is especially vulnerable as typhoons frequently hit it during the monsoon season. However, temporal change information in mangrove cover distribution in this region is incomplete. Therefore, this study was undertaken to detect change in the spatial distribution of mangroves in Thanh Hoa and Nghe An provinces and identify reasons for the cover change. Landsat satellite images from 1973 to 2020 were analyzed using the NDVI method combined with visual interpretation to detect mangrove area change. Six LULC classes were categorized: mangrove forest, other forests, aquaculture, other land use, mudflat, and water. The mangrove cover in Nghe An province was estimated to be 66.5 ha in 1973 and increased to 323.0 ha in 2020. Mangrove cover in Thanh Hoa province was 366.1 ha in 1973, decreased to 61.7 ha in 1995, and rose to 791.1 ha in 2020. Aquaculture was the main reason for the loss of mangroves in both provinces. Overall, the percentage of mangrove loss from aquaculture was 42.5% for Nghe An province and 60.1% for Thanh Hoa province. Mangrove restoration efforts have contributed significantly to mangrove cover, with more than 1300 ha being planted by 2020. This study reveals that improving mangrove restoration success remains a challenge for these provinces, and further refinement of engineering techniques is needed to improve restoration outcomes.

This work presents a development of computational fluid dynamic model for numerical simulations of flow induced vibrations, important physical phenomena characterizing operations of various engineering structures, especially offshore installations including risers and platforms. We propose an application of detached eddy simulation (DES) approach for simulations of incompressible Navier–Stokes flows over cylindrical structures coupled with its rigid body motions. In this approach, a hybrid turbulence model based on Reynolds average Navier–Stokes (RANS) and large eddy simulations (LES) is implemented for modelling of high Reynolds number flows over free oscillating cylinders where near wall flow features are modelled with RANS and LES is employed for resolving wake dynamics. The proposed approach is validated against several experimental set ups of fixed cylinder as well as cylinders under vortex induced vibrations. A straightforward implementation of the proposed DES approach provides more reliable and accurate numerical results than traditional URANS for high Reynolds number flows in predictions of forces acting on cylinders and their responses. Numerical experiment using the presented approach for cylinder with single degree of freedom (cross flow oscillations) and two degree of freedoms (in-plane oscillations) shows that it is able to capture VIV fundamental characteristics and predict accurately responses of cylinders at various reduced velocities and mass ratios. Numerical prediction is in good agreement with earlier experimental studies for presented benchmark test cases. It shows a great potential of the proposed approach for design and analysis of structures under flow induced vibrations.

We propose an unstructured mesh adaptation approach for unsteady high speed compressible Navier–Stokes applications involving blasts and explosions with the presence of strong shock waves propagating in three dimensional complex domains. The idea is to identify the locations of critical physics locally and then re-mesh these regions based on solution derived metrics. The approach ensures both geometry fidelity and mesh validity, especially for areas near complex geometries, a task that is always a challenge in mesh adaptation. The proposed adaptivity is applied for simulations of blast wave propagations and compared with available data in literature. The results show that the proposed method is fully robust and efficient for computational fluid dynamics (CFD) problems in complex three-dimensional domains.

This paper explores how consumers’ perceptions of corporate social responsibility (CSR) influence their attitude and purchase intention in Vietnam. The study used a quantitative approach in which a survey was conducted. Among many respondents, the final 222 responses from various respondents across Vietnam were utilized in this paper. Key findings from this study are as follows. First, consumers (one stakeholder) are one key motive for organizations to become engaged in CSR. Second, consumers have a strong interest in an organization that they perceive to be responsible for its workers and community. Third, the concept of CSR in Vietnam is rooted in business and ethics, reflecting that Vietnamese consumers want business organizations to behave responsibly. On balance, the findings imply that CSR is influenced by the context in which it is practiced. Consumers expect business organizations to take their social responsibilities seriously, in line with the expectations of Vietnamese society.

Pre-print of a journal article, The paper aims to investigate factors that influence the speed of price adjustment in response to shocks by Vietnamese firms using a multivariate ordered probit model with survey data. The results first indicate that whether state or time-dependent price reviewing causes firms to adjust their prices faster after shocks may depend critically on not only the size of shocks but also the economic conditions. Second, we provide evidence that firms used the rule of thumb in price setting tend to adjust their prices more slowly in response to all kind of shocks than their counterparts who based on the market conditions, and that firms whose prices are influenced by competitors tend to be more flexible in reaction to shocks. In addition, we find that menu costs and contracts are the two most important theories in explaining price stickiness. However, they seem to induce firms to respond more slowly only to shocks that drive prices downwards, rather than to shocks that move prices upwards. Finally, the degree of competition, the market share, the size of firms, the practice of quantity discounts, the share of state ownership, and the sector where firms operate all matter for how quickly and asymmetrically firms react to shocks. Keywords: Price adjustment; survey data; multivariate ordered probit

Patient-specific computational fluid dynamics (CFD) modelling of the left ventricle (LV) is a promising technique for the visualisation of ventricular flow patterns throughout a cardiac cycle. While significant progress has been made in improving the physiological quality of such simulations, the methodologies involved for several key steps remain significantly operator-dependent to this day. This dependency limits both the efficiency of the process as well as the consistency of CFD results due to the labour-intensive nature of current methods as well as operator introduced uncertainties in the modelling process. In order to mitigate this dependency, we propose a semi-automated method for patient-specific computational flow modelling of the LV. Using magnetic resonance imaging derived coarse geometry data of a patient's LV endocardium shape throughout a cardiac cycle, we then proceed to refine the geometry to eliminate rough edges before reconstructing meshes for all time frames and finally numerically solving for the intra-ventricular flow. Using a sample of patient-specific volunteer data, we demonstrate that our semi-automated, minimal operator involvement approach is capable of yielding CFD results of the LV that are comparable to other clinically validated LV flow models in the literature.

Wake induced vibration is a distinctive phenomena of fluid-elastic instability arising from interactions of a body in the wakes of another bluff body and characteristically different from the well-understood vortex induced vibrations. This work presents a fluid-structure interactions numerical model as an alternative tool for investigation of wake induced vibrations. In an attempt to better understand mechanisms of wake induced motions, a simplified model of two cylinders in tandem arrangement with different diameters under cross flow was considered in this work. Cross flow velocity conditions vary from moderate to high Reynolds number (Re = 2 × 103–5 × 104) in the same range as many experiment reported recently in literature. A hybrid detached eddy simulation approach is used for turbulence modelling at those high Reynolds number conditions in order to resolve complex near body flow features as well as in the wake regions. The proposed model is first validated through extensive benchmarking with experimental studies for responses of tandem cylinders at the same flow conditions as in physical experiment. With good agreement to experimental data, the model was extended for simulations of cylinders of different diameters in tandem arrangement. For different diameters between upstream and downstream cylinders, the fundamental frequencies of shedded vortices from the cylinders are essentially different. It is observed from the present study that responses of the downstream cylinder are characterized not only the geometrical parameters such as distances and diameter differences between the cylinders but also the Reynolds number. As contrast to many experimental studies, at constant Reynolds number, downstream cylinders are found to have multiple lock-in regions in a wide range of reduced velocities. This distinctive behaviour of the cylinders at constant Reynolds numbers and diameter ratios suggests strong evidence of complicated mechanism of wake-induced vibrations phenomena. Further analysis of results from high fidelity numerical simulations were carried out for detailed investigations of force amplitudes and frequencies. The current analysis revealed multiple frequency content of the force; thus explaining high response amplitudes of the downstream cylinder at high reduced velocity.

This paper contributes towards a more complete approach to capture very strong shocks in various applications of high speed compressible Navier–Stokes flows including blasts and explosions using second order finite volume method on unstructured grids. The HLLC Riemann solver is employed to solve for fluxes at cell interfaces with second order approximation of local Riemann states, thus obtaining second order accuracy. In order to stabilize solutions due to high order approximation of solutions in the presence of discontinuities, several strategies are presented in this work. Slope limiters are first explored on unstructured grid to maintain monotonicity of the solution reconstruction following local extremum diminishing (LED) or total variation diminishing (TVD) criteria. The hybrid HLLC/HLLE scheme is appended to eliminate shock instabilities in very strong shock cases. To improve resolution of shocks, a local mesh adaptation scheme is used to increase mesh resolution in areas of high gradients. The scheme only regenerates mesh locally and is proven to be robust and efficient for capturing of unsteady shock propagation applications. Comparisons on the accuracy and performance of different methods on various applications are drawn to suggest a more robust and efficient method for capturing shocks on unstructured grids.

We develop a new methodology that controls for both the timing of annual earnings news ( Asquith et al., 1989 ) and the performance prior to split announcements ( Barber and Lyon, 1996 ) to evaluate the information content of stock splits. In contrast to existing evidence, we find that stock splits in aggregate are followed by positive abnormal future earnings growth, suggesting that stock splits contain information about future, rather than past, operating performance. When we use changes in breadth of institutional ownership as a new metric of information content to corroborate our findings, we find that splits with the greatest increase in breadth experience positive post-split abnormal returns and positive abnormal earnings growth. Together, our results suggest that some splits contain positive information about future performance, and that sophisticated market participants such as institutional investors are able to select these splits.

This work presents a computational fluid dynamic (CFD) model to simulate blood flows through the human heart's left ventricles (LV), providing patient-specific time-dependent hemodynamic characteristics from reconstructed MRI scans of LV. These types of blood flow visualization can be of great asset to the medical field helping medical practitioners better predict the existence of any abnormalities in the patient, hence offer an appropriate treatment. The methodology employed in this work processed geometries obtained from MRI scans of patient-specific LV throughout a cardiac cycle using computer-aided design tool. It then used unstructured mesh generation techniques to generate surface and volume meshes for flow simulations; thus provided flow visualization and characteristics in patient-specific LV. The resulting CFD model provides three dimensional velocity streamlines on the geometries at specific times in a cardiac cycle, and they are compared with existing literature findings, such as data from echocardiography particle image velocimetry. As an important flow characteristic, vortex formation of the blood flow of healthy as well as diseased subjects having a LV dysfunction condition are also obtained from simulations and further investigated for potential diagnosis. The current work established a pipeline for a non-invasive diagnostic tool for diastolic dysfunction by generating patient-specific LV models and CFD models in the spatiotemporal dimensions. The proposed framework was applied for analysis of a group of normal subjects and patients with cardiac diseases. Results obtained using the numerical tool showed distinct differences in flow characteristics in the LV between patient with diastolic dysfunction and healthy subjects. In particular, vortex structures do not develop during cardiac cycles for patients while it was clearly seen in the normal subjects. The current LV CFD model has proven to be a promising technology to aid in the diagnosis of LV conditions leading to heart failures.

In 1996, the first exchange-traded funds (ETFs) designed to track a subset of the Morgan Stanley Capital International country indices were approved under the name World Equity Benchmarks (acronym “WEBS”™). We examine the impact of early WEBS-trading on the liquidity of corresponding closed-end country funds (CECFs), previously one of the main avenues for retail investors to achieve country-specific equity exposure. We document a decline in both the trading volume and the trading frequency for CECFs, suggesting that some investors migrate to WEBS. At the same time, the market depth for CECFs increases and the bid-ask spread for CECFs decreases following the introduction of WEBS. Our results support the hypothesis that despite the decline in volume and trading frequency, the liquidity of CECFs is favorably affected by the advent of WEBS.

The article presents a research project carried out at University of Languages and International Studies, Hanoi, on the integration of explicit listening strategy and sub-skill instructions into listening lessons. A strategy and sub-skill integrated syllabus was devised and implemented in eight consecutive weeks. The research aimed at investigating how students improved their listening habits after being taught listening strategies and sub-skills explicitly, as well as their engagement with and perception of this new teaching method. Data were collected via individual interviews, observations, and narrative frames. The results revealed some positive effects of the intervention on students’ listening skills and habits: students knew to use strategies in listening, which led to the acquisition of listening sub-skills and improvement in their listening comprehension. Factors affecting students’ engagement with and their perceptions of the new teaching method were also substantially explored. Based on the findings, relevant pedagogical implications were proposed with the aim of equipping English teachers with practical guidelines on how to integrate explicit strategy and sub-skill instructions into their listening classes.