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In recent years, concrete has been commonly used in the construction of many road works. However, because of the poor tensile and bending ability, temperature fluctuation, and other overload factors, the concrete structure is often cracked, broken, or damaged during use. The solutions to increase the load capacity include increasing the pavement thickness, the concrete grade, treating the road well, etc. Nonetheless, due to the limit of conventional techniques, the enhancement was unremarkable. Therefore, it is necessary to develop new technology to overcome these difficulties. Since the creation of a model using the wire mesh reinforcement for concrete pavements, the load capacity of that system was comparably improved [1]. Later, the applications of that idea for civil construction hooked many scientists up [2-6]. However, because the used system was not a three-dimensional structure, the efficiency increased insufficiently. In Vietnam, many engineers and scientists also proposed solutions to overcome these issues [7-13]. Thus, this work contributes some research results related to the development of 3D wire mesh technology as reinforcement for 3D concrete pavement and attempt at road construction and other transportation structures in Vietnam

The theoretical calculations for the low-lying vibrational H atoms adsorbed on the Pt(110) surface are presented. We use the H/Pt(110) model with the conventional ultrahigh vacuum and the density functional theory to study the phonon frequency. The nature of hydrogen atoms, which were adsorbed on the four different sites of Pt(110) surface, is shown. The most stable site of the short bridge is in agreement with previous studies. The highest stretching frequency of 2200 cm−1 and the zero-point energy (ZPE) of the H atom on top site ~ 140 meV are calculated. Our results convincingly demonstrate the need to study the local oscillation to understand the dynamics of this system.

Zigzag hexagonal boron nitride nanoribbon (h-BNNR) model in two-dimensional (2D) case is studied via molecular dynamics simulation. The model contains 10000 atoms interacted via the Tersoff bond order potential. Temperature is increased from 50 K to 7000 K in order to see the evolution of various thermodynamic quantities, structural characteristics, and the occurrence of liquid-like atoms upon heating to a molten state. Lindemann criterion for 2D case is calculated and used to observe the appearance of liquid-like atoms. Atomic mechanism is analyzed on the basis of the occurrence/growth of liquid-like atoms, the formation of clusters, coordination number, and ring statistics. The largest cluster does not contain all liquid-like atoms in the whole range of temperature in this study. After reaching a peak at the melting point of this model, the largest cluster slightly decreases indicating that the single largest cluster of liquid-like atoms tends to form a ring-like 2D liquid zigzag h-BNNR. Armchair h-BNNR is studied to compare with zigzag h-BNNR model. The melting point of armchair h-BNNR (3600 K) is close to the experimental results of hexagonal boron nitride (h-BN) (from 2800 K to 3600 K) whereas the one of zigzag h-BNNR (4522 K) is higher than that of armchair h-BNNR and plane h-BN.

Herein, the adsorption of hydrogen on pristine germanene was studied using ab initio calculations. By performing a converged density functional theory calculation, we have found the nearly degenerate nature of hydrogen at the top sites HT1 and HT2, among which HT1 is the most stable site. The adsorption of a hydrogen atom on germanene led to local structural changes in germanene. To the best of our knowledge, this is the first study on the investigation of the localized surface curvature and zero-point energy of hydrogen for 2D germanene. Moreover, we demonstrated the properties of germanene defects via the four obtained defects: the Stone–Wales (55-77), divacancy (77-555-6), divacancy (555-7), and pentagon–heptagon linear (5-7) defect. The lowest formation energy of the pentagon–heptagon linear defect is shown for the first time in this study.

We report MD simulation of the growth of graphene by the vapor deposition on a two-dimensional hBN substrate. The systems (containing carbon vapor and hBN substrate) are relaxed at high temperature (1500 K), and then it is cooled down to room one (300 K). Carbon atoms interact with the substrate via the Lennard-Jones potential while the interaction between carbon atoms is computed via the Tersoff potential. Depending on the size of the model, different crystalline honeycomb structures have been found. Structural properties of the graphene obtained at 300 K are studied by analyzing radial distribution functions (RDFs), coordination numbers, ring statistics, interatomic distances, bond-angle distributions and 2D visualization of atomic configurations. We find that the models containing various numbers of atoms have a honeycomb structure. Besides, differences in structural properties of graphene formed by the vapor deposition on the substrate and free standing one are found. Moreover, the size effect on the structure is significant.

ObjectivesTo investigate the feasibility of establishing hospital-based antimicrobial stewardship (AMS) programmes comprising action-planning, educational interventions and data feedback in two provincial-level hospitals in Viet Nam.Design and settingThis was an implementation research using participatory action process and existing resources from the Duke Antimicrobial Stewardship Outreach Network with local adjustments. A national stakeholder meeting and Strengths-Weaknesses-Opportunities-Threats (SWOT) analysis were conducted to identify gaps and potential interventions.ParticipantsHospital AMS staff implemented activities throughout the study phases. Routinely collected patient data were analysed to support planning, implementation and evaluation.InterventionsHospitals were considered as a complex adaptive system and leveraged their unique characteristics and interconnections to develop 1-year plans containing core interventions (data use, educational training, prospective audit with feedback (PAF) and evaluations).Outcome measuresWe assessed feasibility using outputs from stakeholder meeting, SWOT analysis, baseline data, planning process and implementation.ResultsThe stakeholder meeting identified three gaps for AMS at national level: supportive policies, AMS training and core competencies and collaboration. At the hospitals, AMS programmes took 1 year for planning due to lack of hospital-specific procedures and relevant staff competencies. Baseline data (January–December 2019) showed variations in antibiotic consumption: 951 days of therapy (DOT) per 1000 days present in the control and 496 in the intervention wards in hospital 1, and 737 and 714 in hospital 2, respectively. During 1-year implementation, clinical pharmacists audited 1890 antibiotic prescriptions in hospital 1 (June 2020–May 2021) and 1628 in hospital 2 (July 2020–July 2021), and will continue PAF in their daily work.ConclusionOur data confirmed the need to contextualise AMS programmes in low-income and middle-income countries (LMICs) and demonstrated the usefulness of implementation research design in assessing programme feasibility. Developing staff competencies, using local data to stimulate actions and integrating programme activities in routine hospital work are key to success in LMICs.

Modeling glassy SiC nanoribbon by cooling rapidly the SiC liquid from 8000K to 300K is carried out by molecular dynamics (MD) simulations. Two separated MD simulations are performed, one of which uses the Tersoff potential and the other one uses the Vashishta potential. The temperature dependence of various structural and thermodynamic properties of the systems is analyzed and discussed via the radial distribution functions (RDFs), the coordination number distributions, and the ring statistics. We find that the Tersoff potential is clearly more appropriate in order to obtain the glassy SiC when rapidly cooling is employed.

The hydrogen adsorption isotherm is reported on the missing row Pt(1 1 0)-(1 × 2) within the conventional ultrahigh vacuum (UHV) surface modeling. They are evaluated by the combination of the density functional theory (DFT) and the Monte Carlo (MC) simulations. The binding energy for the hydrogen adsorption is found to depend strongly on the hydrogen coverage ( Θ H ). The short bridge sites on the ridge (R) are found to be the strongest binding sites at the low coverage region. At a higher Θ H , up to 1 ML, the on-top sites of the micro-facet (F) get populated. The relative abundance of the HR and HF are investigated. The influence of the exposed ridge atoms on the adsorption properties are found to be negligible at 1/3 ML, and the presence of the trough atoms have the most influence at the intermediate coverage region.

Pd-skin/Pd3Fe(111) electrocatalyst is a promising candidate in improving the kinetics of the oxygen reduction reaction (ORR) on the cathode of proton exchange membrane fuel cells. Although experiments measured the ORR activity versus the electrode potential and theoretical studies disclosed the reaction mechanism, the correlation of the mechanism and the electrode potential is still lacking. In this work, by using the density functional theory, the correlation of the activation energy, structure, and mechanism with the electrode potential are studied for the first time for Pd-skin/Pd3Fe(111) electrocatalyst. We found that the proton and electron transferring step for the conversion of O2 to HOO and the dissociation of HOO into HO + O in the associative mechanism are the most expensive intermediate reactions that cause the highest activation energy and electrode potential loss and hence limit the performance of the fuel cells. Therefore, if one finds ways to solve the electrode potential loss of these reaction steps, the slow kinetics of the oxygen reduction reaction can be improved. We also revealed the charge exchange during the proton and electron transfers of the ORR intermediate steps.

International audience; Formation and atomic structure of two-dimensional (2D) tetra-SiC (containing entirely tetragons) are studied by molecular dynamics (MD) simulations. Models contain 6400 atoms (3200 Si atoms and 3200 C ones) interacted via so-called Vashishta's interatomic potentials. We compress initially perfect planar SiC with honeycomb structure (hexa-SiC) at three different temperatures (below and above melting point) step by step and we find hexa-tetra 2D SiC phase transition. Tetra-SiC sample obtained at temperature significantly below melting point exhibits the best quality which contains the lowest concentration of defects (non-tetragons). This tetra-SiC is stable over a wide range of density and temperature. On the other hand, we cool the obtained tetra-SiC to room temperature and it is also stable at room temperature. Evolution of various structural and thermodynamic quantities upon compression is studied and we find that it exhibits a first-order-like phase transition behavior. Detailed analysis of structure of the obtained tetra-SiC is shown via coordination number and bond-angle distributions, ring statistics, 2D visualization of atomic configurations etc. Moreover, important quantities of mechanical behaviors such as Young modulus and Poisson's ratio of the sample are found and discussed. DFT calculations show that flat tetra-SiC is stable with a band gap of around 0.97 eV. Our prediction of the existence of this new allotrope of 2D SiC can serve as a guide for further investigation in this direction including fabrication of material in practice.

In this work, we study the melting stages of two-dimensional confined germanene via atomistic molecular dynamics simulations. Evolution of structural and thermodynamic properties upon heating from perfect crystalline and polycrystalline germanene is investigated in details. The melting temperatures for the perfect crystalline and polycrystalline models are found to be 1670 K and 1540 K, respectively. Both germanene models exhibit first-order behaviors of the transition starting by formations of the Stone–Wales defects. Our MD simulation provides helpful insights into the atomic mechanism and thermodynamics of this 2D material as well as phase transitions occurred in the system.

The hydrogen vibration was investigated to analyze its affect on the hydrogen adsorption on the missing row platinum surface (H/Pt(110)-(1\(\times\)2) model) in the ultrahigh vacuum (UHV). The density functional theory (DFT) combined with the approximation oscillation of the hydrogen atom on the surface was used. When the hydrogen coverage ΘH on the surface is 100% (\(\Theta\) = 1 ML), and taking into account the vibrational effect, the bond formed at the edge of the first layer (short bridge) is the most stable site. The vibrational effect on the adsorption model H/Pt(110)-(1\(\times\)2) is significant.

The structural properties of the liquid gallium arsenides have been studied using the molecular dynamics (MD) method. Simulations were done in the basic cube under periodic boundary conditions containing 3000 ions for Ga50As50, Ga66.67As33.33 and Ga33.33As66.67 models. The microstructure of the systems has been analyzed through the partial radial distribution functions (PRDF), coordination number distributions, bond-angle distributions, inter-atomic distances, and ring statistics. The evolution of structure upon cooling from the melt of GanAsm was observed and discussed. We found that calculated data agree well with the experimental ones and with those obtained previously in other simulation works.

We have investigated the pressure-induced structural and dynamic transitions in liquid aluminosilicate (Al2O32SiO2) nanoparticles with a molecular dynamics (MD) method. Simulations were performed in spherical models under non-periodic boundary conditions containing 2596 ions with the Born–Mayer type pair potentials. In order to study the structural and dynamic changes, the models of liquid aluminosilicate nanoparticles have been built at densities ranging from 2.60 g cm−3, corresponding to the size of 4 nm, to the density of 4.2 g cm−3 at a temperature of 4200 K. The microstructure of the liquid nanoparticles has been analysed in detail through the coordination number distribution, bond-angle distribution and interatomic distances. We found a clear evidence of transition from the low density state (LDS) to high density state (HDS) structure in the models upon compression, like that observed in the bulk counterparts. This transition is accompanied by an anomalous diffusion of Al and Si atoms in the systems...

The melting of two-dimensional (2D) glassy monatomic systems is studied using the molecular dynamics simulation with Lennard–Jones–Gauss interaction potential. The temperature dependence of various structural and dynamical properties of the systems during heating is analyzed and discussed via the radial distribution functions, the coordination number distributions, the ring statistics, the mobility of atoms and their clustering. Atomic mechanism of melting is also analyzed via tendency to increase mobility and breaking clusters of atoms upon heating. We found that melting of a 2D glass does not follow any theory of the melting of 2D crystals proposed in the past. The melting exhibits a homogeneous nature, i.e. liquid-like atoms occur homogeneously throughout the system and melting proceeds further leading to the formation of an entire liquid phase. In addition, we found a defined transition temperature region in which structural and dynamical properties of systems strongly change with increasing temperature.

The issue of hydrogen (H) electroadsorption on Pt(111) is revisited to settle its theoretical description within the conventional ultrahigh vacuum (UHV) surface modeling and the semilocal Kohn–Sham level of the density functional theory (DFT). By performing a converged DFT calculation, we have confirmed nearly degenerated nature of H on the fcc hollow site (Hfcc) and H on the top site (Htop) when the nuclei are treated classically, while Hfcc is significantly more stable when the zero-point energy correction is applied. Relative abundance of the Hfcc over Htop was investigated by performing a Monte Carlo simulation using a lattice gas model parameterized by the DFT calculation. By comparing the calculated results with recent cyclic voltammetry data, we found good agreement between theory and experiment but minor discrepancy exists in that the H–H interaction is underestimated by ~ 10%. Possible origin of the discrepancy is the hydration effect neglected in our model although we cannot exclude the possibility that error of the semilocal approximation within DFT will also play a role.