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This work introduces a new permutation-symmetry-adapted machine learning diabatization procedure, termed the diabatization by equivariant neural network (DENN). In this approach, the permutation symmetric and anti-symmetric elements in diabatic potential energy metrics (DPEMs) were simultaneously simulated by the equivariant neural network. The diabatization by deep neural network scheme was adopted for machine learning diabatization, and non-zero diabatic coupling was included to increase accuracy in the near degenerate region. Based on DENN, the global DPEMs for 11A′ and 21A′ states of MgH2 have been constructed. To the best of our knowledge, these are the first global DPEMs for the MgH2 system. The root-mean-square-errors (RMSEs) for diagonal elements (H11 and H22) and the off-diagonal element (H12) around the conical intersection region were 5.824, 5.307, and 5.796 meV, respectively. The RMSEs of global adiabatic energies for two adiabatic states were 4.613 and 12.755 meV, respectively. The spectroscopic calculations of the 11A′ state in the linear HMgH region are in good agreement with the experiment and previous theoretical results. The differences between calculated frequencies and corresponding experiment values are 1.38 and 1.08 cm−1 for anti-symmetric stretching fundamental vibrational frequency and first overtone. The global DPEMs obtained in this work should be useful for further quantum mechanics dynamic simulations on the MgH2 system. [ABSTRACT FROM AUTHOR]

In this study, the principle of minimum potential energy has been used to deduce the mapping relationship between beam deformation and rail deformation with consideration of the constraint effects of a subgrade system. Based on the above mapping relationship, a dynamic simulation analysis on the train-track-bridge coupled system has been carried out. Taking the index of riding comfort as the investigation object, in combination with the specified limits in the relevant specification, an analysis has been carried out to determine the control threshold of beam deformation of high-speed railways. According to the simulation results, the dynamic response of different types of high-speed trains shows significantly different sensitivities to the pier settlement and the beam faulting. The threshold value in settlement control in the case of simultaneous settlement of two adjacent piers is smaller than that in the case of the single-pier settlement. Under the operating condition of beam faulting, the wheel unloading rate is more sensitive to the faulting of the beams than the vertical acceleration and Sperling's ride index. To avoid the vertical acceleration specified limit of car body, it is recommended to maintain the pier settlement to less than 9.7 mm, and the beam faulting to less than 5.3 mm. [ABSTRACT FROM AUTHOR]

Fundamental understanding of water confined in graphene is crucial to optimally design and operate sustainable energy, water desalination, and bio-medical systems. However, the current understanding predominantly remains in the static properties near the graphene surfaces. In this paper, a key water transport property, i.e., self-diffusivity, is examined under confinement by various graphene nanogap sizes (Lz = 0.7-4.17nm), using molecular dynamics simulations with various graphene-water interatomic potentials (Simple Point Charge (SPC/E) and TIP3P water models). It is found that the water self-diffusivity nearly linearly decreases as the graphene-water interatomic potential energy increases at a given nanogap size. It also decreases as the graphene nanogap size decreases down to Lz = 1.34 nm; however, it shows the peak water self-diffusivity at Lz = 0.8 nm and then continues to decrease. The peak water self-diffusivity is related to the significant change of the overlapping surface force, and associated, nonlinear local water density distribution. The in-plane water selfdiffusivity is higher up to nearly an order of magnitude than that of the out-of-plane due to the geometrical confinement effect by the graphene nanogap. The obtained results provide a roadmap to fundamentally understand the water transport properties in the graphene geometries and surface interactions. [ABSTRACT FROM AUTHOR]

Effectively homogenizing microstructure heterogeneity within the coarse-graining volume is a long-lasting challenge in crystal plasticity theories. In this paper, we propose a data-based homogenization method that utilizes discrete dislocation dynamic simulations to derive the nearfield correction stress (back stress) for continuum models. This stress accounts for the effective stress field induced by microstructure heterogeneity under the length scale of a coarse-graining volume, providing a physically based homogenization approach. To bridge the gap between discrete and continuous regimes, we introduce two versions of the nearfield correction stress, as well as a criterion based on microstructure and numerical parameters to determine the discrete and continuous transition. Moreover, by analyzing the mathematical connections with the work-conjugated gradient plasticity theory, we further provide a physical explanation for the observed material length scale in the thermodynamically consistent back stress term. This work presents a novel methodology for effectively addressing microstructure heterogeneity and advancing the understanding and modeling of material behavior bridging different length scales. • Data-based homogenization approach addressing the internal stress field within coarse-graining volumes at high strain gradient. • A criterion for the transition between discrete and continuous modelings based on microstructure and numerical length scales. • Physical explanation of the material length scale linked to defect energy potential as the average spacing that hinders heterogeneity within coarse-graining volumes. [ABSTRACT FROM AUTHOR]

Research activities with regard to membrane construction at HFT Stuttgart In the presented article we give an overview to some of the recent and ongoing research projects at Hochschule für Technik Stuttgart (HFT) in the context of membrane buildings. One of the major challenges in the context of membrane building is the regulation of the radiative heat flux entering the building as well as thermal losses across the building envelope while still providing comfortable room temperature and daylight use for the inhabitants. The accomplishment of this task, investigated by means of measurements and numerical simulation was the scope of several research projects at HFT Stuttgart. Within the research project "SoFt" the compatibility of insulation and translucency was investigated and realized within the roof construction of a sports center in Germany. One of the objects of the research project "FMESG" was the realization and numerical simulation of an angle‐selective static solution for partial shading, analogous to a miniature saw tooth roof configuration, up to the point of a working prototype. The project "Follow‐e2" tackled the influence of low emissivity surface coatings on the energy balance of membrane constructions by means of numerical simulation. Within the project "FLEX‐G" the potential for reduction of energy demand by dynamic shading with electrochromic elements was investigated by means of dynamic building simulation and heuristic optimization. [ABSTRACT FROM AUTHOR]

Realistic simulation of Madden–Julian Oscillation (MJO) propagation in coupled global climate models remains a common problem. In this study, the ability of 20 coupled models from Coupled Model Intercomparison Project Phase 5 (CMIP5) in simulating MJO is examined using dynamics-oriented diagnostics. The diagnostics focus on dynamic and thermodynamic structures of MJOs on three dimensions, which help to identify the shortcomings of models and evaluate whether they could reproduce MJO for the right reason. According to the simulation performance of the eastward propagation of MJO, the "good" models and "poor" models are detected. The dynamics-oriented diagnostics are further applied to the good models, poor models, and all models to establish a linkage between MJO simulation skill and their dynamic/thermodynamic structures. Results show that the simulations of good models have the following common features: (1) a horizontal zonal structural asymmetry in low-level zonal wind, upper-level diabatic heating and divergence; (2) a preceding eastward propagation of boundary layer moisture convergence; and (3) a rearward-tilted vertical structure of diabatic heating, equivalent potential temperature and available potential energy generation. The poor models that fail to capture these three-dimensional structures do not reproduce the eastward propagation of MJO. More than half of these 20 CMIP5 models still have difficulties in simulating these dynamic/thermodynamic structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • A GCN-based ML model is developed to predict physical properties of MD simulation. • The ML model is employed for prediction of potential energy of solid–liquid system of metals. • The learned ML model gives a good prediction on the property of training data. • The ML model has generalization performance to predict from unknown graph structures. • The graph representation can be a good notation to predict properties from MD simulations. A graph convolutional networks (GCN)-based machine learning (ML) model is constructed to predict physical properties of metallic materials from graph representation of atomic configuration of molecular dynamics (MD) simulation. The developed ML model is employed for the prediction of time variation of the potential energy of a solid–liquid biphasic system of nickel. The learned ML model gives a good prediction on the property of training data. Moreover, it is confirmed that the ML model has generalization performance sufficient to make adequate predictions on unknown graph structures despite the lack of information on interatomic distances in the graph representation. It is significant in this study to show that the graph representation can be a good notation for the prediction of various properties from MD simulations since there is no established notation for atomic configuration of MD simulation especially for large-scale system of metallic materials. [ABSTRACT FROM AUTHOR]

• Replacement of thermal generator is a simple and efficient building retrofit action. • Three generators are compared using environmental, energy and economic metrics. • A building stock energy model for Italy has been defined (4 buildings, 3 climates). • Heat pumps are preferrable for emission reduction, but lead to high operative costs. • The flexibility of hybrid heat pump allows for high savings on all the objectives. In many countries, old inefficient generators are used for heating purposes. A way to improve energy efficiency in those countries can be the choice of the most suitable heating generators to replace the current ones, without the inconveniences caused by other retrofit measures. In this context, we present a methodology to choose the most appropriate generator through dynamic simulations applied to building stock energy models. Economic, energetic, and environmental parameters guide the choice. The methodology is applied in the Italian residential building scenario, where the most widespread heating device is traditional boiler. Three options are considered: condensing boiler, heat pump, and hybrid heat pump (an alternative-working system with a condensing boiler and heat pump). For a detailed analysis, a white-box bottom-up building stock energy model is defined, through a statistical analysis, consisting of four building typologies in three different external climates. An hourly dynamic building-system simulation has been performed to obtain energy performance, emissions, and operational costs. The results have demonstrated that condensing boiler allows limited economic, environmental, and energy savings (8 - 14 %), compared to traditional boiler. The highest economic savings are obtained with the hybrid heat pump (20 %), while the heat pump alone leads to higher costs, but the highest savings in emissions and non-renewable primary energy (25 - 50 %). The flexibility offered by the hybrid heat pump allows to obtain high savings in different cost scenarios, but also to further reduce CO 2 emissions by implementing an environmental-based control strategy. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Thermal-pressure effect on energy state of Cu-Zr MG during each separate fabrication stage was investigated. • Applying pressure during quenching is effective to obtain high energy state MG. • Dominant Cu-centered polyhedron <0, 0, 12, 0> reaches the maximum under 30 GPa. • The sample fabricated under 30 GPa has most improved plasticity with higher potential energy and smaller atomic volume. Abstract Combined application of thermal and pressure are effective to obtain structure excited metallic glass with high energy state. This work studied the thermal-pressure effects on energy state, atomic level structure and tensile behavior during each separate fabrication stage (heating, equilibrating, and quenching) of Cu 50 Zr 50 metallic glasses by dynamic simulation. It is found that quenching under pressure is the most effective approach obtaining high energy state Cu 50 Zr 50 metallic glass among 4 designed methods. For the effective approach, the potential energy increases and the atomic volume decreases with pressure for Cu 50 Zr 50 metallic glass when the pressure is below 30 GPa, and the latter reaches its minimum at 30 GPa. Moreover, Cu-centered full icosahedron <0, 0, 12, 0> plays a dominant role in the formation of high energy structure, and Cu 50 Zr 50 metallic glass fabricated by method 3 under 30 GPa shows the most improved plasticity. [ABSTRACT FROM AUTHOR]

The potential energy profile of microhydrated fluorine ion reaction with methyl iodine has been characterized by extensive electronic structure calculations. Both hydrogen-bonded F-(H2O)---HCH2I and ion-dipole F-(H2O)---CH3I complexes are formed for the reaction entrance and the PES in vicinity of these complexes is very flat, which may have important implications for the reaction dynamics. The water molecule remains on the fluorine side until the reactive system goes to the SN2 saddle point. It can easily move to the iodine side with little barrier, but in a nonsynchronous reaction path after the dynamical bottleneck to the reaction, which supports the previous prediction for microsolvated SN2 systems. The influence of solvating water molecule on the reaction mechanism is probed by comparing with the influence of the nonsolvated analogue and other microsolvated SN2 systems. Taking the CCSD(T) single-point calculations based on MP2-optimized geometries as benchmark, the DFT functionals B97-1 and B3LYP are found to better characterize the potential energy profile for the title reaction and are recommended as the preferred methods for the direct dynamics simulations to uncover the dynamic behaviors. [ABSTRACT FROM AUTHOR]

Europe has set a clear path to guide Member States into the accomplishment of the nearly zero energy buildings (nZEBs) target. To this regard, within EPBD recast directive, a cost optimality procedure has been defined. This study presents different cost optimal solutions of building and technical systems for nZEBs in Italy. In total 40 economically and technically feasible energy efficiency measures for a high performing single family house were analyzed. Special attention was devoted to the study of the building technical systems. Achieving a net zero balance required a high efficient system combined with high insulation and a large PV system, which plays a key role in the nearly and net zero building energy balance. Three net zero energy balance solutions, based on all electric systems, were presented. Net ZEB solutions allowed also the building carbon footprint to be reduced by 40% compared to the reference case study. Without proper financial subsides, net ZEB solutions are still far for being economic feasible, having a global cost 212–313 €/m 2 higher than cost optimal solutions. In conclusion, this paper aims to present guidelines for designing reference building envelope and technical systems solution for residential nZEB. [ABSTRACT FROM AUTHOR]

[Display omitted] DNAs' photostability is significant to the normal function of organisms. P-Z is a hydrogen bonded artificial DNA base pair, where P and Z represent 2-amino-imidazo[1,2-a]-1,3,5-triazin-4(8H)one and 6-amino-5nitro-2(1H)-pyridone, respectively. The excited-state relaxation mechanism of P-Z pair is investigated using static TDDFT calculations combined with the non-adiabatic dynamic simulations at TDDFT level. The roles of nitro rotation, nitro out-of-plane deformation, and single proton transfer (SPT) along hydrogen bond are revealed. The results of potential energy profile calculations demonstrate that the SPT processes along the hydrogen bonds are unfavorable to occur statically, which is in great contrast to the natural base pair. The non-adiabatic dynamic simulations show that the excited-state nitro rotation and nitro out-of-plane deformation are the two important relaxation channels which lead to the fast internal conversion to S 0 state. The SPT from Z to P is also observed, followed by distortion on P, inducing the fast internal conversion to S 0 state. However, this channel (decay via SPT process) plays minor roles on the excited-state relaxation mechanism statistically. This work shows the great differences of the excited-state relaxation mechanism between the natural base pairs and artificial base pair, also sheds new light into the role of hydrogen bond and nitro group in P-Z base pair. [ABSTRACT FROM AUTHOR]

Abstract: Planetary gear is widely used in different areas due to its advantages such as compactness, large torque-to-weight ratio, large transmission ratios, reduced noise and vibrations. However, the tooth faults like cracks are seldom concentrated. In this paper, a mesh stiffness model of internal gear pair with a tooth root crack in the ring gear is derived based on the potential energy principle. The mesh stiffness model is incorporated into the dynamic model of a one-stage planetary gear set with 21-degree-of-freedom (DOF) to investigate the effect of the internal gear tooth root crack. The crack cases with different dimensions are designed in this paper to demonstrate their influences on the mesh stiffness and the dynamic performance of the planetary gear set. The simulated results show that bigger reduction in mesh stiffness is caused by the growth in the crack size. And the impulsive vibrations and sidebands can be observed in the dynamic response of the planetary gear set in time and frequency domains, respectively. Both their amplitudes increase as the crack propagation which supply the possibility for them to be the indicators in the condition monitoring and fault diagnosis of planetary gear system. [Copyright &y& Elsevier]

Gear dynamics analysis based on time-varying meshing stiffness (TMS) is an important means to understand the gear fault mechanism. Based on Jones bearing theory, a bearing statics model was established and introduced into a gear system. The lateral–torsion coupling vibration model of the gear shaft was built by using a Timoshenko beam element. The lumped parameter method was used to build the dynamic model of a gear pair. The dynamic model of a spur gear system was formed by integrating the component model mentioned above. The influence of rectangular and elliptical spalling on TMS was analyzed by the potential energy method (PEM). The fault feature of tooth spalling was studied by dynamic simulation and verified by experiments. It is found that the gear system will produce a periodic shock response owing to the periodic change of the number of meshing gear teeth. Due to the contact loss and the decrease of TMS, a stronger shock response will be generated when the spalling area is engaged. In the spectrum, some sidebands will appear in the resonance region. The results can provide a theoretical guide for the health monitoring and diagnosis of gear systems. [ABSTRACT FROM AUTHOR]

• The coulombic interactions are dominant contributors to the total potential energy. • The water–mineral interaction and substrate structure reflect the H 2 O dynamics. • The cyclic T-M coupling contributes a wide band distribution after 1000th cycles. • The decrease around 1.7 Å indicates a weaken H-Bond and greater rotational freedom. In this work, we make a first attempt at performing a molecular dynamic simulation to gain insights into the transport characteristics of H 2 O molecules confined in sandwiched albite-quartz system, where a mechanical loading couples a thermal cycling was carried out·H 2 O molecules were placed within the vacuum gap of the albite-quartz slab to accomplish the sandwich model. Based on the viewpoint of energetics aspect, the coulombic interactions are the dominant contributors to the total potential energy. The diffusion coefficient, orientation parameter and hydrogen bonding were examined for analysis of the transport characteristics of confined H 2 O molecules. Not only the water–mineral interaction but also the substrate structure reflects the dynamics of confined H 2 O molecules, as evident by qualitatively analyzing the trajectories of some selected H 2 O molecules located in different regions. The cyclic thermal–mechanical (T-M) coupling contribute a wide band distribution after 1000th cycles instead of two distinct peaks after the 100th cycles. The decrease in amplitude occurring primarily around 1.7 Å is indicative of a weaken H-Bond and a greater rotational freedom of those molecules, leading to the gathering of H 2 O molecules near quartz and albite slabs and a dense arrangement of the H 2 O molecules in the inter-spacing region, which could be ascribed to the interconnected aspect of diffusion process. [ABSTRACT FROM AUTHOR]

• MD simulation was applied to study the kinetics of methane hydrate growth. • A kinetics model based on the non-equilibrium thermodynamics was considered. • Two-parametric model had a constant parameter in all the operational conditions.. • The hydrate formation is a process proceeding on a natural path. In the present work, the molecular dynamic simulation was applied for studying the kinetics of methane hydrate growth. Several parameters such as the changes of potential energy, the MSD of molecules, the number of methane molecules near the solid/liquid interface and the position of liquid/solid interfaces with time were considered. The results showed that the potential energy and MSD of molecules in the layers near the interfaces significantly decreases implying that the growth proceeds in these layers. The maximum rate of growth or migration of methane molecules to the interfaces is observed around 2 ns. Moreover, a kinetics model was considered to predict hydrate growth kinetics. It is based on the irreversible and non-equilibrium thermodynamics and the concept of the thermodynamic natural path. The proposed model is a two-parametric model that one parameter was estimated to be a nearly constant value in the range from −1.05 to 1.46, but another one is a kinetic parameter dependent on the operational conditions. The model can well predict the entire process of hydrate formation, since the affinity, as a driving force of the process, shows that the hydrate formation is a process proceeding on a natural path. [ABSTRACT FROM AUTHOR]

• A methodology for rating buildings energy flexibility performance is introduced. • A Flexibility Performance Indicator (FPI) is defined. • The FPI takes into account the flexibility event duration, capacity and efficiency. • A huge influence of building envelope thermal properties on FPI is highlighted. • Storage systems can effectively improve the flexibility due to HVAC systems. In the present energy scenario, buildings are playing more and more as energy prosumers. They can use and produce energy and also actively manage their energy demand. The energy flexibility quantifies their potential to adjust the energy demand on the basis of external requests. The objective of this paper is to propose a method for buildings energy flexibility labelling at design conditions in the same fashion as the energy performance label. The flexibility quantification is based on the calculation of four flexibility parameters, which contribute to the definition of the Flexibility Performance Indicator. In order to assess the Flexibility Performance Indicator, buildings dynamic simulations are necessary and the boundary conditions (i.e. demand response event, representative day, comfort constraints) to be considered during the evaluation are provided as part of the proposed methodology. The method was applied to different Italian buildings, which differ for geographic location and design specifications and, in particular, the effects of building structure, heating/cooling systems and energy storage systems were compared. Results show that the climatic conditions affect the flexibility performance, while the building feature more relevant is the thermal mass of the building envelope, more than that provided by the distribution system. A sensitivity analysis to evaluate how the results are influenced by the proposed boundary conditions was also performed. Their choice confirms to have a relevant impact on flexibility quantification, then their unique definition has a paramount importance within this methodology. [ABSTRACT FROM AUTHOR]