Dynamics Simulation Model Research Articles

Multi-Scenario Simulation of a Water–Energy Coupling System Based on System Dynamics: A Case Study of Ningbo City

In this work, based on the concept of collaborative water–energy development, a multi-scenario system dynamics simulation model of a water–energy coupling system was constructed by using the system dynamics modeling method. The model was composed of four subsystems: society, economic, water resources, and energy. Taking Ningbo City as the research location to run the simulation model, the analysis of the validity of the model showed that the relative error between the historical data and the simulation results of the model was less than 10%, which proved that the model passed the test. In this paper, based on the scenario of business an usual (BAU), three scenarios of water-saving scenario (WSS), energy-saving scenario (ESS), and comprehensive savings (CS, the comprehensive scenario considers water-saving and energy-saving together) were designed, and the simulation indexes in the three scenarios were refined in order to strengthen the control of water-saving policies, improve the effective use of water, optimize the industrial energy structure, improve the level of energy-saving-related technologies, and advance the urbanization process. The simulation results for Ningbo City from 2010 to 2030 show that the water–energy coupling system is affected by many factors, and the adjustment of a driving factor of any subsystem will have an impact on the water–energy coupling system. There are two driving factors: the first is a constant variable related to water resources, energy, society, and economic, and the second is a variable affected by time. The coupling system is based on the law of real development and is composed of causal and functional relationships between variables. Therefore, within the prediction range of 2030, the driving factors in the coupling system are controllable, and there is no uncontrollable situation. The strengthening of water-saving policies and the improvement of the coefficient of the effective utilization of water will have the optimal saving effects on water resources and energy at both the single and the coupling level; this also demonstrates that the water resource management in Ningbo City plays an extremely important role in the relationship of the water–energy coupling. The results of this study are expected to provide a valuable reference for the management and conservation of water–energy coupling in Ningbo City.

Molecular dynamics simulation and thermodynamic model of vapor–solid coexistence of the Lennard–Jones fluid in cylindrical nanopores

Molecular dynamics (MD) simulations were used to study the coexistence of solids and vapors of Lennard–Jones methane condensed within cylindrical carbon nanopores. The simulated unit cell includes both the inside and outside of the pores. This allowed us to observe the solid-vapor coexistence within the pores while simulating the pressure depression of the bulk vapor outside the pores. The condensates in the pores were cooled in stages, and the equilibrium vapor pressures were determined at each temperature. The obtained vapor–solid coexistence curves showed significantly lower shifts in pressure than those in the bulk phase. The results of the MD simulations were compared with the Clausius–Clapeyron equation starting from the triple point in the nanopores. The thermodynamic model successfully predicted the simulation results without introducing tunable parameters, demonstrating this concept’s validity. Thus, a whole Lennard-Jones phase diagram in cylindrical nanopores can now be predicted.

Collaborative Commissioning: regional funding models to support value‐based care in New South Wales

Collaborative Commissioning: regional funding models to support value‐based care in New South Wales

Comparison of the airflow characteristics and yarn properties between conventional and dual-feed-opening rotor spinning units

In order to explore the differences between conventional and dual-feed-opening rotor spinning units (RSUs), this work compares the airflow characteristics of two RSU models utilizing a computational fluid dynamics simulation model with the accuracy verified by airflow behavior observation and air pressure measurement. The effect of two different opening roller speeds on the airflow field distribution of a dual-feed-opening model is also investigated. In addition, the yarn properties of six pure and blended yarns corresponding to the two RSU models are evaluated. The results reveal that the distributions of airflow velocity vector and air pressure in the two RSU models show a strong similarity under the same boundary conditions. However, the dual-feed-opening model possesses a centrosymmetric and more balanced airflow field distribution compared to the conventional model. In addition, the dual-feed-opening yarns show a superior performance in comparison to the conventional yarns. Furthermore, for the dual-feed-opening model, there are equivalent contributions of two separated opening and fiber transmission systems to the airflow field distribution and yarn formation. Compared to the configuration with the same two opening roller speeds, the dual-feed-opening model configured with two different opening roller speeds obtains an improved blended yarn performance with having few effects on the airflow characteristics. This strength of the dual-feed-opening RSU could facilitate the production of blended and fancy yarns employing the fibers with diverse properties. This study could provide some guidelines for the manufacture of rotor-spun yarns and the future design of RSUs.

An evaluation of strategies for restoring a degraded New Zealand scallop fishery using stochastic dynamic simulation modelling

A decision-theoretical approach was used to evaluate strategies to rebuild a severely depleted scallop (Pecten novaezelandiae) populations in the Tasman Bay and Golden Bay of New Zealand. These strategies were: no intervention, cessation of seabed bottom contact fishing, and reduction of sediment and nutrient runoff from surrounding land through on-farm practices. Our approach combined outputs of estimated effects of on-farm practices on erosion and nutrient reduction with a stochastic dynamic model of the scallop populations. The most effective individual intervention is eliminating bottom contact fishing through dredging and trawling which increased scallop biomass on average by 73% compared to the no intervention scenario. Although on-farm practices have reduced sedimentation and nutrient runoff significantly (28–36% and 2%, respectively), they have no effect on scallop biomass if implemented individually and led to only marginal improvements in scallop biomass if implemented alongside cessation of bottom contact fishing (2–4%). Although our results showed, on average, substantial recovery in the scallop population when reducing seabed bottom contact and water pollution, the large uncertainty boundaries makes it unclear whether these improvements would be realized. The long-term success of such strategies will depend on the available habitat being able to sustain high densities of healthy scallop adults and recruits, a situation that has been posited in our analysis. Where scallop juvenile survival is compromised by sedimentation, nutrient pollution, or other exogenous influences, proposed interventions may be insufficient to aid recovery.

Сучасний стан розвитку методів оцінювання земель сільськогосподарського призначення

Purpose of this research is to improve the methods of valuation of agricultural land. Today, the moratorium on the purchase and sale of agricultural land has been lifted and sale of agricultural land is increasingly raised and therefore the problem of establishing an objective (market) price for agricultural land is relevant, because increasing the level of their use is an objective necessity and condition for the gradual development of society [Hubar Yu., 2020]. Methodology. A significant contribution to the study of the theory and methods of land valuation was made by A. S. Danilenko, Yu. F. Dekhtyarenko, Yu. P. Hubar, A. G. Martin, M. G. Stupen, A. M. Tretyak, G. V. Cherevko. Instead, the formation and improvement of methodological bases for the monetary valuation of agricultural land paid attention to G. D. Gutsulyk, D. S. Dobriak, О. S. Dorosh, O. F. Kovalishin. Emphasis was placed on the shortcomings of the economic assessment conducted in the Soviet period I. K. Bystryakov, S. I. Doroguntsov, Hubar Yu. P., A. M. Tretyak, M. A. Hvesyk and others. However, despite the considerable amount of scientific research in which the land was considered a means of production, tools and objects of labor (which in the current environment is insufficient), little studied and debatable are the value of land as a whole system with all its properties. This is due to the fact that agricultural land is mostly assessed differently according to the available dominant indicators (yield, value of gross output). This does not build a hierarchy on the importance of other indicators. The complexity and versatility of the problem of land valuation require the continuation and deepening of scientific research in this area. Results. The study is based on the general principles of economic and mathematical modeling, mathematical statistics, econometrics, basic and applied research. The information base of the research consisted of scientific works of domestic and foreign scientists in the field of real estate appraisal, land and city cadastres, statistics, ecology. The issue of land pricing is complex and multifaceted, the development of the land market depends on its solution. Therefore, further research should be aimed at improving the valuation of agricultural land. This process should be based on state service, taking into account the economic and political situation. This will ensure after the lifting of the moratorium on the disposal of agricultural land, the creation of a competitive environment in the land market, the objectivity of the assessment and increase the flow of funds to the state budget. Scientific novelty and practical significance. The performed researches will allow to improve the quality of determining the market value of agricultural lands for further development of land reform in Ukraine. The most important results of the study are: generalization of scientific provisions for the implementation of land valuation works and methodological approaches to determining the value of agricultural land; highlighting the disadvantages and advantages of modern methods of agricultural land valuation; proving the importance of taking into account environmental factors in the assessment of land arising from the activities of agricultural production; substantiation of the need to assess land plots with a set of physical properties of soils and spatial conditions of their implementation; development of methods for assessing the normative yield of grain crops on the basis of dynamic and statistical simulation modeling and software for its spatial implementation. It is established that the use of market-based prices will allow to make informed management decisions during the implementation of land reform in Ukraine. Individuals and legal entities on the basis of the proposed developments will be able to assess the investment attractiveness of agricultural land.

Wheel Profile Optimization of Speed-up Freight Train Based on Multi-population Genetic Algorithm

The geometric shape of the wheel tread is mathematically expressed, and geometric parameters affecting the shape of the wheel were extracted as design variables. The vehicle dynamics simulation model was established based on the vehicle suspension parameters and track conditions of the actual operation, and the comprehensive dynamic parameters of the vehicle were taken as the design objectives. The matching performance of the wheel equivalent conicity with the vehicle and track parameters was discussed, and the best equivalent conicity was determined as the constraint condition of the optimization problem; a numerical calculation program is written to solve the optimization model based on a multi-population genetic algorithm. The results show that the algorithm has a fast calculation speed and good convergence. Compared with the LM profile, the two optimized profiles effectively reduce the wheelset acceleration and improve the lateral stability of the bogie and vehicle stability during straight running. Due to the optimized profile increases the equivalent conicity under larger lateral displacement of the wheelset, the lateral wheel-rail force, derailment coefficient, wheel load reduction rate, and wear index are reduced when the train passes through the curve line. This paper provides a feasible way to ensure the speed-up operation of a freight train.

A multi-objective simulation–optimization for a joint problem of strategic facility location, workforce planning, and capacity allocation: A case study in the Royal Australian Navy

The availability of assets crucially depends on the interplay between the facility locations, workforce planning, and capacity allocation. Therefore, in this paper, we model and solve a novel multi-objective optimization problem for strategic facility location, workforce planning, and capacity allocation in the context of the military. The developed model deviates from more common approaches and adapts a dynamic capacity scheme for both the workforce and facilities to capture the dynamic nature of future demand, such as maintenance requirements for assets. The capacity allocation and workforce planning problem focus on mainly strategic decisions involving from workforce and facilities. A system dynamics (SD) simulation model enables a decision-maker to analyze the effects of decision variables by modeling the system complexities, uncertainties, and interactions between facilities, workforce, and assets. However, the simulation model neither suggests nor seeks the best solution strategy or strategies. To overcome this shortcoming, we propose a simulation–optimization approach that uses a Non-dominated Sorting Genetic Algorithm-II (NSGA-II). NSGA-II generates feasible solution strategies (candidate solutions) such as time and amount of capacity expansion and downsizing for both the workforce and facilities as well as the amount of crew recruitment. These solution strategies are fed to the simulation model where it evaluates the fitness of candidate solutions. We test the applicability of the proposed method on a realistic case study from the Royal Australian Navy. Finally, we present scenario-based sensitivity analysis arising from the decision variables to support decision-makers.

Molecular dynamics simulation and theoretical modeling of free surface effect on nanocrack initiation induced by grain boundary sliding in nanocrystalline materials

Free surfaces have significant effects on plastic deformation and fracture of nanocrystalline materials (NMs), especially for nano- or micro- scale specimens. To reveal the influence mechanism of free surfaces on crack initiation and growth, molecular dynamics (MD) simulations are carried out. The results show nanocrack initiation at triple junctions near free surfaces and the intergranular fracture due to nanocrack growth and coalescence. Based on the mechanism captured by MD, a theoretical model is established to describe the process of grain boundary (GB) dislocation evolution and nanocrack initiation. The critical stress for nanocrack initiation and the critical magnitude of GB sliding step are obtained for nanocrystalline nickel, aluminum and copper. Based on the proposed theoretical model, the fracture behaviors are discussed for the three nanomaterials.

Influence of Mold and Heat Transfer Fluid Materials on the Temperature Distribution of Large Framed Molds in Autoclave Process.

Massive composite components manufactured by autoclave curing in large framed molds are extensively used in the aerospace industry. The high temperature performance of the large framed mold is the key to achieving the desired composite part quality. This paper explores and summarizes the important thermal properties of metal and heat transfer fluid materials influencing the heating performance of large framed molds, with the aim of improving the mold temperature distribution. Considering the fluid–thermal–solid interaction inside the autoclave, a reliable computational fluid dynamics (CFD) simulation model was developed and verified by a temperature monitoring experiment to achieve the prediction of the temperature distribution of the large framed mold. Then, numerical simulations were designed on the basis of the CFD model, and the single-variable method was used to study the effects of the material thermal properties on the temperature performance of large framed molds. Our simulation predicts that when copper is used as the mold material, the temperature difference decreases by 30.63% relative to that for steel, and the heating rate increases by 3.45%. Further, when helium is used as the heat transfer medium, the temperature difference decreases by 68.27% relative to that for air, and the heating rate increases by 32.76%. This paper provides a reference for improvement of large framed mold manufacturing and autoclave process in terms of heating rate and temperature uniformity.

The solubility data, Hansen solubility parameter and dissolution thermodynamic properties of riluzole in twelve organic solvents

The solubility of riluzole in ethanol, n-propanol, n-butanol, n-pentanol, acetone, n-propyl acetate, n-amyl acetate, isopropyl acetate, N, N-dimethylacetamide (DMAC), 2-methoxyethanol, 2-propoxyethanol and acetonitrile was determined by laser detection under the external conditions of 278.15–323.15 K and 0.1 MPa. The experimental results imply that the solubility of riluzole in selected solvents is positively correlated with the temperature. The measured data was correlated with five thermodynamic models, including modified Apelblat model, λh model, NRTL model, UNIQUAC model, and Two-Suffix Margules model. And the best correlation was found in the modified Apelblat model. The solubility sequence of riluzole in selected solvents was analyzed by Hansen solubility parameter (HSP) which was calculated by using group contribution method. Meanwhile, the influence of solute–solvent interaction on the solubility of riluzole was investigated by using molecular dynamics simulation and solvent effect model (KAT-LSER model). Also, the dissolution thermodynamic properties of the dissolution process were computed and discussed via Van't hoff model. The results show that the solvent has a notable effect on the dissolution behavior of riluzole and this is an entropy-driven and endothermic process.

CONI-Net: Machine Learning of Separable Intermolecular Force Fields.

Noncovalent interactions (NCIs) play an essential role in soft matter and biomolecular simulations. The ab initio method symmetry-adapted perturbation theory allows a precise quantitative analysis of NCIs and offers an inherent energy decomposition, enabling a deeper understanding of the nature of intermolecular interactions. However, this method is limited to small systems, for instance, dimers of molecules. Here, we present a scale-bridging approach to systematically derive an intermolecular force field from ab initio data while preserving the energy decomposition of the underlying method. We apply the model in molecular dynamics simulations of several solvents and compare two predicted thermodynamic observables-mass density and enthalpy of vaporization-to experiments and established force fields. For a data set limited to hydrocarbons, we investigate the extrapolation capabilities to molecules absent from the training set. Overall, despite the affordable moderate quality of the reference ab initio data, we find promising results. With the straightforward data set generation procedure and the lack of target data in the fitting process, we have developed a method that enables the rapid development of predictive force fields with an extra dimension of insights into the balance of NCIs.

Recreating the shear band evolution in nanoscale metallic glass by mimicking the atomistic rolling deformation: a molecular dynamics study.

Rolling processes are extensively used to induce network of shear bands (SBs) in the bulk metallic glasses, which in turn enhances the overall plasticity of the specimen. However, the atomic-level understanding of shear band formation/propagation mechanism during mechanical processing is still limited. In this perspective, we have developed a molecular dynamics (MD) simulation model to recreate the rolling deformation process and investigate the SB formation in Cu-Zr metallic glass (MG) specimen. Results have shown that dense and concentrated primary SBs along with secondary branching are formed during cryo-rolling, whereas a scattered and thicker SBs are formed during hot rolling process. Meanwhile, Voronoi cluster analysis revealed that the high five-fold symmetry clusters tend to decrease, while the crystalline-like cluster increases during the hot rolling process. These findings from the study are in good agreement with previous experimental studies substantiated in literature, which shows that the model correctly predicts the shear-banding phenomenon.

Alginate Biopolymer Effect on the Electrodeposition of Manganese Dioxide on Electrodes for Supercapacitors

Electrolytic manganese dioxide (EMD) synthesized from different electrolytic baths with varying biopolymer additive concentrations has been investigated for application as an electrochemical supercapacitor. Alginic acid, also termed “alginate”, is a widely used biopolymer for various biological applications due to its physicochemical properties. Here, the EMD material synthesized with alginate crosslinking was introduced in the field of electrochemistry for supercapacitors. Different EMD and alginate composites were characterized to find the trade-off between the biopolymer content in the bath and the energy storage capability. Compared to the pristine EMD, the EMD composites at all of the alginate concentrations influenced both the physical and the electrochemical storage properties of the materials. The presence of alginate in the solution at higher concentrations altered the morphology from spindle-shaped to cactus-shaped with flutes. Rearranged morphology and enhanced particle size are attributed to the ability of the alginate to act as a template for binding the Mn2+ ions on the substrate in a relatively ordered and widely distributed manner. The EMD composite delivered 5 times higher capacitance (487 F g–1) than the pristine EMD at a current density of 1 mA cm–2 in a three-electrode system using a 2 M NaOH aqueous electrolyte. When the EMD composite was coupled with activated carbon, the asymmetric device exhibited 52 F g–1 capacitance at a current density of 2 mA cm–2 while giving excellent capacitance retention (94%) over 5000 cycles. The molecular dynamics simulation model supported the influence of alginate on ion–polymer interactions in the electrolytic bath. The simulations showed that the alginate provides a template for binding Mn2+ ions in a relatively ordered manner. It could assist the EMD/Alg composite growth in a more favorable condition for energy storage applications.

Numerical Investigation for the Resin Filling Behavior during Ultraviolet Nanoimprint Lithography of Subwavelength Moth-Eye Nanostructure

Accurate analysis of the resin filling process into the mold cavity is necessary for the high-precision fabrication of moth-eye nanostructure using the ultraviolet nanoimprint lithography (UV-NIL) technique. In this research, a computational fluid dynamics (CFD) simulation model was proposed to reveal resin filling behavior, in which the effect of boundary slip was considered. By comparison with the experimental results, a good consistency was found, indicating that the simulation model could be used to analyze the resin filling behavior. Based on the proposed model, the effects of process parameters on resin filling behavior were analyzed, including resin viscosity, inlet velocity and resin thickness. It was found that the inlet velocity showed a more significant effect on filling height than the resin viscosity and thickness. Besides, the effects of boundary conditions on resin filling behavior were investigated, and it was found the boundary slip had a significant influence on resin filling behavior, and excellent filling results were obtained with a larger slip velocity on the mold side. This research could provide guidance for a more comprehensive understanding of the resin filling behavior during UV-NIL of subwavelength moth-eye nanostructure.

Improving the cam profile of the spring operating mechanism of vacuum circuit breaker based on energy matching

High-voltage circuit breakers are important protection and control equipment in power systems. In order to understand the mechanical characteristics of vacuum circuit breaker, the mathematical relationship between the released energy of closing spring, the stored energy of opening spring and overtravel spring and the rotation angle of output crank arm is studied. The characteristic curve between the released energy of closing spring and the rotation angle of output crank arm and the characteristic curve between the stored energy of opening spring and overtravel spring and the rotation angle of output crank arm are drawn by MATLAB. In order to improve the matching of energy release and energy storage characteristic curves, a method of improving cam profile is proposed. The dynamics simulation model of spring operating mechanism of high voltage circuit breaker is established and the original cam and adjusted cam are imported into the dynamics simulation model of mechanism. The simulation results show that the adjusted cam improves the closing speed of vacuum circuit breaker. This helps to reduce the stress on the parts of the vacuum circuit breaker and increase the service life of the vacuum circuit breaker.

1인 가구 노인빈곤의 정책지렛대 탐색을 위한 다이내믹 시뮬레이션 연구

This study aims to identify the behavior pattern of elderly poverty of the singleperson households, to analyze its causal loop feedback structure, and further to investigate as well as predict its policy leverage through dynamic simulation modeling. The main findings are as follows. Firstly, the elderly poverty rate of the singleperson households increased over time, showing a non-linear and dynamic behavior pattern. Secondly, there were four main feedback loops found centering around the retirement preparation of the middle-aged. It seemed that three positive feedback loops related to the basic income security for the elderly could increase its elderly poverty rate, whereas one negative feedback loop concerning the retirement preparation of the middle-aged might lessen its poverty rate. Finally, the results of dynamic simulation modeling showed that the policies such as Public pension, Semi-public pension, Basic pension, individual pension, and job creation, if partially improved and properly combined, could be used as very useful measures to alleviate the elderly poverty of the single-person households.

Simulations of Airflow in the Roof Space of a Gothic Sanctuary Using CFD Models

For a deep understanding of the airflow in an environment of historic wooden trusses, it is necessary to analyze the object using simulation methods. To calculate the amount of air passing through the structural openings (components) using dynamic simulation, multi-zone network models based on the simplicity of modeling the individual zones are suitable. For a more detailed analysis of airflow and temperature distribution within one space, a computational fluid dynamics (CFD) simulation model was performed. The air volume through openings and surface temperatures was adopted from the multi-zone airflow network model. By using this simulation technique during a sunny summer day four characteristic states of air movement were simulated in the attic: more intense flow at noon and at midnight caused by a large temperature difference between air and surrounding surfaces and, subsequently, less intense flow when the air was mixed up effectively. The temperature distribution in the cross-sections did not only indicate an increase in temperature with increasing height (up to 50 °C at noon) but also a temperature increase near the southern roof. The surface temperature of the masonry walls was stable (19–33 °C), while the air temperature fluctuated. The image of the flow was completed by ventilation through the tower, which acted as a solar chimney. The airflow through the door to the tower was almost 0.5 m3 s−1 at summer midnight.

Performance of molecular dynamics simulation for predicting of solvation free energy of neutral solutes in methanol

Abstract In this study, molecular dynamics simulation was applied for calculating solvation free energy of 16 solute molecules in methanol solvent. The thermodynamic integration method was used because it was possible to calculate the difference in free energy in any thermodynamic path. After comparing results for solvation free energy in different force fields, COMPASS force field was selected since it had the lowest error compared to experimental result. Group-based summation method was used to compute electrostatic and van der Waals forces at 298.15 K and 1 atm. The results of solvation free energy were obtained from molecular dynamics simulation and were compared to the results from Solvation Model Density (SMD) and Universal Continuum Solvation Model (denoted as SM8), which were obtained from other research works. Average square-root-error for molecular dynamics simulation, SMD and SM8 models were 0.096091, 0.595798, and 0.70649. Furthermore, the coefficient of determination (R 2) for molecular dynamics simulation was 0.9618, which shows higher accuracy of MD simulation for calculating solvation free energy comparing to two other models.

Research on the Influence of Commercial Vehicle Electronic Control Pneumatic Braking Pressure Change Rate on Braking Ride Comfort

The paper evaluates the braking ride comfort of commercial vehicle through total weighted acceleration root mean square and Derivative of acceleration (Jerk). Based on the vehicle dynamics model, tire model and braking implement model, the commercial vehicle braking pressure, braking pressure change rate and braking ride comfort of correlation model is established. The commercial vehicle dynamics simulation model for braking pressure change rate is established by using MATLAB/Simulink software. The simulation comparison of MATLAB/Simulink and IPG/TruckMaker verify the correctness and effectiveness of the correlation model. Taking the effect of single and double braking chamber pressure change rate as an example. The effect of the unusual change of pressure change rate of the front and rear axle single braking chamber and the coaxial and ipsilateral braking chamber on the commercial vehicle braking ride comfort is analyzed by comparativing. Some theoretical basis for commercial vehicle in intelligent braking and automatic driving is provided.