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This study implements a comprehensive dynamic simulation using a moving-boundary method to characterize an organic Rankine cycle under assumption-free operating conditions. The novelty of the model lies in its unique methodology for determining the state vector variables and initial conditions of the system, particularly in integrating sub-models, notably the model of liquid receiver. Consequently, the implemented dynamic model accurately forecasts the system's performance, focusing solely on the boundary conditions. A comprehensive dynamic model is constructed, encompassing a wide range of scenarios and facilitating the interchangeability of models as required. One notable advantage of the model is its systematic approach, which begins each simulation by determining the system's initial conditions before conducting the dynamic model in parametric and dynamic studies. The capability and accuracy of model is confirmed through comparison with experimental data under various steady-state and dynamic conditions, while adhering to the main rules of mass and energy conservation. The prediction accuracy of the model is evaluated by mean absolute percent error. According to the results, the maximum deviations of simulation results mostly are less than 11 %. • Using moving-boundary method to simulate an ORC under assumption-free conditions. • Using unique method for determining state vector variables and initial conditions. • Dynamic model precisely forecasts system performance, focusing on boundary conditions. • The maximum deviations between the simulation and experimental results are 11 %. • The simulation shows ORC's dynamic behavior when input conditions vary. [ABSTRACT FROM AUTHOR]

Heat–power decoupling is a key issue to be addressed for the combined heat and power (CHP) unit to enhance its operational flexibility, and utilizing heat storage in district heating systems represents a viable approach. The widespread adoption of heat pumps to boost heating network also increases the complexity of managing heat storage, and the quantitative impact of heat storage has significant implications during operation. To this end, dynamic models of heating networks and heat pumps were developed. A metric, the maximum maintenance time, was established to quantitatively assess heat storage utilization. Dynamic simulations and performance analyses were conducted on a 330 MW CHP unit. The results indicate that by employing heat storage, the feasible maximum and minimum output power of the heating system can be increased by 20 MW and decreased by 45.5 MW, respectively. With the integration of a heat pump, these values can further increase by 9 MW and decrease by 158 MW, respectively, significantly enhancing the operational flexibility of CHP unit. • Dynamic models of CHP unit, heating networks and heat pump were developed. • A new index to evaluate the heat storage capacity that can be used is proposed. • Dynamic simulation and performance analysis were conducted with a 330 MW CHP unit. • The integration of heat pump can increase heat storage capacity for peak shaving. • The feasible minimum output power of the CHP unit can be decreased by 158 MW. [ABSTRACT FROM AUTHOR]

In this study, lignocellulose-derived aerogel (LA) with compression-rebound was synthesized from liquefied wood through sol-gel polymerization, aging and freeze-drying process. The results presented a gradual increase in the compressive strength, flexural strength, and maximum decomposition temperature of the LA sample with prolonged aging time from 3 to 10 h, demonstrating excellent elasticity and thermal stability. After more than 10 h, the bending strength began to decrease, indicating that the material's rigidity was greater than its elastic toughness at this time. A nonlinear viscoelastic constitutive model based on the Ogden function and parallel rheological framework showed very high correlation with experimental measurement results, and also demonstrated admirable mechanical properties. These predictions can provide an effective approach for the application of LA in buffer packaging. [Display omitted] • Lignocellulose-derived aerogels for buffer packaging was successfully obtained. • Appropriate aging time improved thermal stability and mechanical properties of LA. • High bending strength of 2.64 MPa at 50 % compression strain can be obtained. • LA-E4 achieved excellent compression rebound rate of 96.15 %. • A viscoelastic constitutive model for predicting mechanical behavior was established. [ABSTRACT FROM AUTHOR]

The increasing amount of Distributed Energy Resources (DERs) in Distribution Networks (DNs) has awakened the interest of system operators to represent how DERs will react to large disturbances. These units will respond according to the ride-through capability curves, the tripping logic settings, the local voltage magnitude, and frequency measurements. In this paper, we show the limitations of the well-known DER_A model and propose changes to represent better the ride-through capabilities and the tripping of a population of DER units. We also show the need for more than one aggregation in the same bus to represent the response of the old and modern DER technologies. To validate the new model, we run dynamic simulations of a Transmission Network (TN) and DNs with hundreds of DER units modeled in detail. The simulation results show that the proposed changes improve the representation of a population of DERs during low-voltage and low-frequency events. • Review of discrepancies between DER_A ride-through/trip logic and IEEE Std. 1547-2018. • New aggregate model for distributed energy resources with ride-through capabilities. • Validation of the new ride-through logic by comparing against disaggregated models. [ABSTRACT FROM AUTHOR]

• The service life estimation of linear guideways can be done with damage accumulation. • A model-based condition monitoring of linear guideways is mandatory. • A vibration model of the linear guideway must consider all relevant elasticities. • A vibration model can be used to estimate the pitting size. • The pitting size progression can be used to estimate a remaining service life. The paper describes two novel calculation methods that can predict the service life of linear guideways more accurately than the conventional method. The first method is based on a linear damage accumulation in each rolling contact, which can take into account changing load cycles for a statistically based long-term remaining service life estimation. Since this statistically based estimation still has some inaccuracies, a second method is proposed that uses a dynamic simulation model of the linear guideway to perform a model-based condition monitoring. With this method, a more accurate damage-based prediction of the remaining useful service life can be made in the short term. The dynamic model takes into account both the elasticity of the Hertzian rolling contact and the elasticities of the carriage and rail depending on the dynamic rolling element circulation. The model also includes a simplified pitting model which allows the actual pitting size to be calculated by comparing the simulated vibration behaviour with the measured vibration behaviour. The calculated pitting propagation velocity is used to estimate the remaining useful service life. [Display omitted] [ABSTRACT FROM AUTHOR]

The thermal inertia results in net heat absorption in natural circulation lead-cooled reactors during power variation processes, increasing the risk of core meltdown. In this study, a dynamic simulation model of a natural circulation lead-cooled fast reactor coupled with a supercritical carbon dioxide Brayton Cycle power generation system has been developed based on Vpower. The influence of thermal inertia on system operating temperature under different power variation rates was discussed. The results indicate that during power reduction, different decline rates only affect the temperature variation range of the system without impacting the final stable state. However, during power increase, different ramp rates not only affect the temperature variation range but also lead to varying degrees of system temperature rise. To address this issue, an optimized turbine throttling scheme is proposed. Compared to the original plan, the new plan successfully stabilizes the temperature at the rated value after increasing the system power. This study provides insights for the operation control strategy of similar reactor types. [ABSTRACT FROM AUTHOR]

This work investigates the heat transfer design and performance of three general types of ammonia reactors for Power-to-Ammonia (P2A). Specifically, the reactors are an adiabatic quench cooled reactor (AQCR), an adiabatic indirect cooled reactor (AICR), and an internal direct cooled reactor (IDCR). We present rigorous steady-state and dynamic models for the three reactor types. Steady-state optimisation at nominal load shows that the AICR and IDCR achieve the highest reactant conversion at 30.0% and 29.4% respectively, whereas the AQCR reaction conversion is significantly lower at 26.9%. Through open-loop simulations around the optimal operating point, we illustrate the unstable oscillatory dynamics of the AQCR. In contrast, the AICR and IDCR showcase stable and fast decaying oscillations. Nonetheless, our stability analysis reveals that the optimal operating points for all reactors are situated precariously close to the reactor extinction threshold. As a result, even minor disturbances pose a substantial risk of extinguishing the reactors at optimal operating conditions. We optimise the reactors across an operating window from 30% to 130% of its nominal load, reflecting varying load in a P2A plant. Over this operational range, the AICR and IDCR yield similar reactant conversions and demonstrate adaptability to varying loads by achieving significantly higher conversions at lower loads. In contrast, the AQCR shows a less pronounced increase in reactant conversion at reduced loads. Considering the location of the optimal operating points close to reactor extinction, we evaluate operating the reactors at a 15 K higher feed temperature than optimal value (stability margin). Our analysis demonstrates that a 15 K safety margin only slightly reduces ammonia conversion across the operating window, while ensuring stable operation even in the event of a 15% decrease in the catalyst activity. • Dynamic and steady models for three types of ammonia reactors (AQCR, AICR, IDCR). • Heat exchange design in ammonia reactors for Power-to-Ammonia operation. • Optimisation and comparison of reactor conversions at nominal load. • Step responses of the reactors to disturbances in feed temperature. • Optimal and stable operation from 30% to 130% of nominal load. [ABSTRACT FROM AUTHOR]

• The optical fiber coil with spool (OFCS) is a crucial tool for precise physics measurements. • To improve the seismic resistance of OFCSs in space applications, the vibration modes are thoroughly investigated through dynamic analysis, simulations, and experiments. • We establish a dynamic model of the OFCS based on the vibration transmission mechanism to characterize its vibration modes. • The vibration eigenfrequency and shapes are calculated under various conditions. • The experimental results validate the feasibility of the dynamic model and simulation, meanwhile, the discrepancies between the simulations and experiments are analyzed. • This study is the first of its kind to develop a comprehensive dynamic model for an OFCS, with simulations and experiments confirming its effectiveness. The optical fiber coil with spool (OFCS) is a crucial tool for precise physics measurements. To improve the seismic resistance of OFCSs in space applications, the vibration modes are thoroughly investigated through dynamic analysis, simulations, and experiments. We establish a dynamic model of the OFCS based on the vibration transmission mechanism to characterize its vibration modes. The vibration eigenfrequency and shapes are calculated and simulated under various conditions. The experimental results validate the feasibility of the dynamic model and simulation, meanwhile, the discrepancies between the simulations and experiments are analyzed. This study is the first of its kind to develop a comprehensive dynamic model for an OFCS, with simulations and experiments confirming its effectiveness. [ABSTRACT FROM AUTHOR]

• A plant-wide model is presented for continuous biomanufacturing benchmarking. • The model includes a tailored control strategy for dynamic simulation performance. • Realistic sensors and actuators consider measurement's noise and lag time. • Case study framework and examples are provided for user guidance. The pharmaceutical industry's shift towards biological therapeutics has led to a transition from conventional batch production to continuous manufacturing. This change highlights the crucial need for effective process monitoring and control strategies to ensure consistent product quality and stability. Open-source benchmark simulation models have become essential tools for refining these processes, offering a platform for testing research hypotheses. This study uses the production of Lovastatin as a case study for continuous biopharmaceutical production. A comprehensive dynamic model covering upstream and downstream components provides an integrated perspective of the production process. The study introduces a basic control system emphasizing realistic sensor and actuator integration to enhance simulation accuracy. It assesses the benchmark through open-loop and closed-loop simulations, offering an in-depth analysis of the KTB1 model's dynamic response and functionality. KTB1 represents a model-driven decision support tool that enables the evaluation of monitoring strategies, process design, process optimization, and control for biomanufacturing. [ABSTRACT FROM AUTHOR]

This study proposes a novel, eco-friendly design for a deep-sea floating mining vehicle multi-body system (DFMVMS), incorporating a floating mining vehicle (FMV) as its central mining apparatus. The comprehensive system architecture encompasses a surface mother ship, a main pipe cable, an ore transit station, an umbilical pipe cable (UPC), and the FMV, engineered for deep-sea extraction activities while preserving benthic ecosystems. To investigate the interactions among the multi-body system's components and ascertain the collective motion dynamics during operational states, initial steps involved developing mathematical models for each individual component. Subsequently, a holistic model for the entire DFMVMS was formulated by integrating these component models via coupling boundary conditions, with the model's accuracy subsequently affirmed. Analytical scenarios, including three foundational motion states of the FMV, were structured to explore the influence of FMV dynamics on the DFMVMS's overall behaviour. Moreover, specific operational scenarios were tailored to reflect two principal functions of the DFMVMS—production and transfer. The simulation results significant interplay among the movements of the system's components, highlighting UPC tension as a critical consideration in devising transfer routes. • Introduced an eco-friendly deep-sea mining system with a floating vehicle as the main equipment. • Developed a dynamic model for this complex multi-body system, including a transit station. • Validated the model through simulations of three fundamental floating vehicle operations. • Designed and simulated two real-world operational scenarios, providing practical insights. [ABSTRACT FROM AUTHOR]

Dynamic simulation is a powerful tool for accurately evaluating the thermal demands of buildings and assessing the impact of energy refurbishment actions on their final consumption. Conversely, semi-stationary models are widely adopted in commercial applications for its simplified approach, which reduce calculation times, resulting in standardized results showing a certain deviation with respect to the real energy This paper presents the energy and economic comparison between the dynamic simulation and semi-stationary approaches for the calculation of primary energy demand of residential buildings. The semi-stationary method, used by the legislation to calculate the buildings energy label, is based on an energy performance parameter, not representative of the real energy demand. Conversely, an approach based on dynamic simulation provides a more reliable estimation of the primary energy demand. The main novelty of this paper is to numerically prove that the energy and economic savings calculated by means of software based on the current legislation may be overestimated. In this work, the dynamic simulation of the building-plant system is performed by TRaNsient SYstem Simulation (TRNSYS) program. Each building apartment is divided in thermal zones, where the internal heat gains are defined in detail. The semi-stationary simulation of the building-plant system is performed according to the Italian standard UNI TS 11300. The models allow one to evaluate the yearly primary energy demand, along with the energy bill and CO 2 emissions. A specific case study is developed for a residential building located in Naples (Italy). The models are used to calculate the building energy demand for several scenarios, considering different thermal transmittances of the building elements. The results show that the semi-stationary method overestimates of primary energy saving, equal to 64.7 %, with respect to the one calculated with the dynamic approach, equal to 43.2 %. • Semi-stationary and dynamic simulations were compared for residential buildings. • Critical evaluation of energy and economic savings due to the building refurbishment. • Primary energy savings of 65 % and 43 % by semi-stationary and dynamic simulation. • Dynamic simulation is needed within the legal frame of energy efficient buildings. [ABSTRACT FROM AUTHOR]

In this study, two processes of predictive model combining dynamic simulation and regression model were presented. First, (1) the demand forecasting process defined in this study is a method of predicting energy consumption based on the simulated energy consumption of a target building, and (2) the energy saving process is a method of setting an energy reduction target based on the predicted energy consumption and providing energy saving measures to achieve the target. Specifically, there are two functions based on the regression models which are predicting actual energy consumption by inputting the energy consumption simulation data, and inversely inputting the actual energy consumption and deriving the corresponding simulation conditions. As a result of predicting building energy consumption through the demand forecasting process, the performance in the heating season showed CV-RMSE was 14.622%, and in the cooling season CV-RMSE was 5.877%. In addition, in the case study using the energy saving process, it was possible to derive the heating and cooling set temperature for 5% energy saving as an energy saving method by using weather forecast data. • Demand forecasting and energy saving of buildings. • Regression model-based process between simulation-based predictions and actual energy consumption. • Two processes combining TRNSYS and DNN model to ensure building energy management efficiency. [ABSTRACT FROM AUTHOR]

• We conduct 61 simulations to select a preferred model using the grid search method. • We constrain dynamic simulations with geodetic, seismic, and geological observations. • The 2022 Menyuan earthquake nucleated vigorously and could grow into a large event. • The fault bend and stepover act as stress barriers and terminate the rupture early. The 2022 Mw 6.6 Menyuan earthquake, which caused unexpectedly large surface offsets (about 2.6–3.5 m) relative to the moment magnitude of this event, is one of the best-recorded strike-slip events in the northeastern Tibetan plateau. Although previous studies have revealed many kinematic features of this event, the mechanism and rupture dynamic characteristics underlying unexpectedly large surface dislocations need to be clarified. In this study, based on the grid search method, we conducted 61 dynamic rupture simulations considering terrain relief to screen out a preferred dynamic model that fits the geodetic, seismic, and geological observations well. The results show that the average stress drop of the nucleation part is relatively high (11 MPa), which could provide high initial rupture energy and give this event a chance to develop into a large earthquake. However, the rupture propagating eastward is slowed and terminated by two consecutive fault bends of about 10° each, and the westward propagating one might concentrate at a shallow depth (< 3 km) on the south secondary fault after it jumps over the stepover. These results imply that the complex fault geometry (the fault bend and stepover) might terminate the rupture early so that the observed magnitude of this event (Mw 6.6) is smaller than the estimated magnitude (Mw 7.1–7.2) based on the surface offsets. Our study again shows that, due to advances in computational power and observations (coverage and quality), physics-based dynamic rupture simulations have entered an era where it is possible to fit the observed data well, which is vital for further understanding the mechanisms of earthquakes. [ABSTRACT FROM AUTHOR]

• Dynamic simulation model is able to predict real column behavior during start-up. • New start-up strategy for the pilot multiple dividing wall column is proposed. • Start-up time of the column strongly depends on the selected strategy. • Start-up of the pilot multiple dividing wall column is possible within few hours. Multiple dividing wall columns are a promising extension of the concept of dividing wall columns offering energy savings of up to 55 % compared to conventional distillation sequences for four products. This paper presents the first systematic study on the start-up of a multiple dividing wall column. The study aims to develop a start-up strategy for the first pilot multiple dividing wall column worldwide commissioned at Ulm University. The start-up process is investigated using a dynamic simulation model that facilitates the investigation of different start-up strategies and the influence of different factors on the start-up process. Based on these dynamic simulations a viable start-up procedure for the column is found. Through improvements to the procedure a significantly shortened start-up process is achieved. The dynamic response of the column shows that the cold and dry plant is able to reach the desired operating point within few hours. Simulation results are confirmed with experimental data from the pilot column. [Display omitted] [ABSTRACT FROM AUTHOR]

The deepwater S-lay pipeline maintains high tension, bending moment, and stress in the overbend section, exhibiting substantially dynamic responses due to pipe-stinger roller interactions. This paper presents a refined S-lay pipeline model capable of accurately describing the forces and deformations on the pipeline section. In this model, the pipeline is discretized into beam particles and beam elements using the vector form intrinsic finite element (VFIFE) method. Meanwhile, the equivalent beam particle technique is developed to account for both the local forces and deformations of the pipeline as well as its overall static and dynamic responses. Through program coding, a dynamic time-domain simulation was accomplished for a 12-inch pipeline being laid to a water depth of 1000 m to provide a detailed illustration of the S-lay modeling process. Furthermore, dynamic behaviours of the pipeline in the overbend were systematically investigated under various groups of the pipe diameter and the stinger roller spacing. The results indicate that the stress and deformation on the upper section of the pipeline are more significant than those on the lower section. The equivalent beam particle method extends the capabilities of the VFIFE for the detailed analyses of local dynamic behaviours of deepwater S-lay pipelines. • A refined VFIFE model of deepwater S-lay pipeline is proposed to investigate the overall and local internal forces and deformations. • The equivalent beam particle technique with the extension of the VFIFE method is developed to calculate pipeline stress and strain in the overbend section. • The accuracy and effectiveness of the refined VFIFE model are fully verified. • Significant differences of the pipeline local stress and strain between the upper and lower sections are observed. • The effects of pipe diameter and stinger roller spacing on the pipeline section behaviours are identified. [ABSTRACT FROM AUTHOR]

Power electronics converters have been widely deployed in modern power systems in different voltage levels. The complex operation characteristics of power converters, which combine different control modes and various current saturation states, are also significantly changing the power systems' behavior in fault conditions. The objective of this paper is to develop a steady-state short-circuit calculation solver for power systems with power electronics without the need of detailed dynamic models. In particular, the steady-state operation equations related to the converter control are included in the system formulation. An extended Newton–Raphson (NR) solver is proposed to compute the short-circuit equilibrium point that considers converters' operation limits. Also, an iterative algorithm is presented in order to efficiently identify the current saturation states of power converters under a specific short-circuit fault scenario. Case studies have been presented with several power systems with voltage source converters (VSCs). Dynamic simulations are included to validate the accuracy of the proposed methodology. • This paper presents an extended Newton–Raphson solver to cope with the new formulation considering power converters' operation. • An iterative algorithm that identifies the current saturation state of a converter in a specific fault scenario. • The proposed methodology has been implemented in several benchmark systems with VSCs. simulation results. [ABSTRACT FROM AUTHOR]

Barocaloric refrigeration technology is a promising candidate for next-generation refrigeration technologies attributed to its eco-friendliness, high efficiency, and mechanical stability. To date, research in this field has predominantly focused on the exploration of solid-state refrigerants. However, the development of barocaloric systems is currently hindered by a lack of both prototype models and a comprehensive theoretical foundation. Addressing this gap, this study innovatively introduces the first model of a barocaloric refrigeration system, characterized by efficient hydrostatic pressure transitions and rapid heat and cold extraction. The employed refrigerant, neopentyl glycol, is notable for its low cost and significant barocaloric effect. Through the development of a one-dimensional dynamic numerical model for the system, this study investigates the system's temperature variability and operational efficiency under varying design parameters and operating conditions. Simulations suggest that the system could achieve a maximum COP of 13.1 and a refrigeration capacity of 106.4 W at a temperature span of 10 K. Additionally, the system is capable of reaching a maximum temperature span of 18 K under no-load conditions. This research not only underscores the theoretical viability of barocaloric refrigeration, but also provide crucial theoretical support and guidance for the design and construction of the first-generation barocaloric refrigeration prototype. • A first-generation barocaloric refrigeration prototype was innovatively proposed. • A one-dimensional dynamic model for barocaloric refrigeration is established. • The system achieves a notable COP of 13.1 and refrigeration capacity of 106.4 W. • The system can achieve an impressive maximum temperature span of 18 K. [ABSTRACT FROM AUTHOR]

• Organic nanoparticles (IDQNPs) were synthesized by simple, eco-friendly reprecipitation method. • The fluorescence intensity of bulk IDQ was observed as 604 while nanoflakes showed as 1692.06. • IDQ bulk and IDQNPs were studied for their biological evaluation. • Molecular modeling and dynamic simulation were investigated of IDQ bulk compound. The study aimed to synthesize 7,7-dimethyl-10-aryl,-7,8-dihydro-5H-indeno-[1,2- b ]-quinoline-9,11(6H,10H)‑dione nanoparticles (IDQNPs) and to explore their biological activities i.e. anticancer, antioxidant and antibacterial. For this purpose, we prepared IDQNPs in a single non-solvent i.e. water by simple reprecipitation method. These nanoparticles were highly fluorescent organic nanoparticles (FONPs). The DLS measurements detected that 114 nm size of synthesized IDQNPs. A microphotograph taken using field emission scanning electron microscope (FE-SEM) of air-dried nanoparticle film showed nanoflakes with a feathery shape. Moreover, absorption and emission spectroscopy measurements displayed discrete peak of IDQNPs from their bulk molecule. The highly fluorescent IDQNPs ultimately give higher quantum yield compared to parental IDQ. Fluorescent organic nanoflakes are additionally utilized in vitro for anticancer and antimicrobial activity and antioxidant properties. Cytotoxicity of IDQ and IDQNPs were determined on the basis of measurement of in vitro growth inhibition of breast cancer cell lines in 96 well plates by using 5-fluoro uracil as a standard. The in vitro cytotoxicity of the IDQNPs assayed against MCF-7 cell lines showed higher cytotoxicity with the lower IC 50 value i.e. 3.94 than IDQ parent indicating their efficiency in killing the cancer cells even at low concentrations. Furthermore, antioxidant and antibacterial activities were done by DPPH 96 well method and well plate diffusion method respectively. IDQNPs showed significant antioxidant property against DPPH radical. The IDQ parent compound and IDQNPs suspension at concentration 5 mg, 10 mg, and 100 µL, 200 µL respectively does not show activity against E. coli and Stap. Aureus. The molecular docking and dynamic simulation study were as done for IDQ bulk material. The finding of our study recommend that IDQNPs is a suitable candidate for preclinical cancer and antioxidant studies. This report may open a new avenue in the medical field and life science. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper analyzes the dynamic character of a planar multi-degree-of-freedom industrial machine using an industrial robot as a reference model. A nonlinear dynamics model of a multi-body structure including the end effector, base and the manipulator is established using the Lagrange's principle. The validity was verified by ADAMS simulation with the established dynamic model. Focusing on the low-frequency region, the influence of the robot assembly parameters on the vertical vibration response of the body is discussed. Based on the data summary, some optimization recommendations are made. The results of this paper may contribute to the design of vibration isolation for such robotic arm structures. • Considered the nonlinear multi-body dynamics of an industrial machine. • Established a seven-degree-of-freedom nonlinear dynamics model and verified by ADAMS. • Multiple super-harmonic resonance peaks and complex soft nonlinear phenomena were observed. [ABSTRACT FROM AUTHOR]

Pumped thermal energy storage (PTES) technology offers numerous advantages as a novel form of physical energy storage. However, there needs to be a more dynamic analysis of PTES systems. This paper proposes a dynamic simulation model of the PTES system using a multi-physics domain modeling method to investigate the dynamic response of key system parameters during the system's start-up and variable operating conditions. Additionally, the impact of equipment parameters on system characteristics was analyzed. Furthermore, a comparative analysis was conducted to assess the variation in system characteristics when considering the different working medium properties. The results show that the system cavity volume should be selected as 5 m3, and the initial pressure of the system during the charge/discharge period should be selected as 2.1 MPa and 3.8 MPa, respectively. The system runs to the design operating conditions during the start-up process in about 1400 s. In the process of variable operation conditions, the power load in the charge/discharge period can be increased or reduced from the rated value by gas filling or venting, and the system characteristics change accordingly. The simulation model and research findings will offer theoretical insights for optimizing the design of the PTES system. • A dynamic simulation physical model of the PTES system was proposed. • The dynamic changes in system characteristics were analyzed. • The TES tank's thermal inertia and heat management of the PTES system were analyzed. • The effects of main equipment parameters on system characteristics were analyzed. • System characteristics were compared when using different gas properties. [ABSTRACT FROM AUTHOR]

• A contact multi-body dynamics model of an RV reducer is presented. • Vibration properties of RV reducer under excitation of faulty NBRs are studied. • The accuracy of the dynamic model has been confirmed by experimental tests. • Defect excitation has a unique periodic effect on the RV reducer's vibration. • The condition monitoring of RV reducer is supported by simulation and test data. The rotate vector (RV) reducer's needle roller bearings (NRBs) are vulnerable to wear and flaws such as fatigue spalling of the raceway material. Studying the vibration mechanism and the excitation laws of NRB failures is essential to enhancing the RV reducer's performance and comprehending its operating state. This paper presents a dynamic model of the RV reducer based on the theory of contact multibody dynamics. It integrates internal and external raceway defects and takes into account the synchronous contact interaction between NRB groups and the crankshaft and cycloidal gears, as well as the time-varying mesh stiffness in the planetary gear transmission and cycloidal pin transmission. The study demonstrates that the rolling of bearings and the meshing of internal transmission components are the primary causes of vibration in a healthy RV reducer through experimental verification and dynamic simulation analysis of the system with and without NRB failures. Both the crankshaft rotation frequency and the cycloidal gear rotation frequency affect the vibration excitation source's characteristic frequency. The vibration amplitude of the RV reducer is influenced by bearing flaws on a periodic basis. The impact of internal raceway defects is greater than that of external raceway faults, resulting in a notable rise in vibration amplitude. [ABSTRACT FROM AUTHOR]

The landing airbag system, a mechanism composed of thin-walled structures, is designed to ensure the safe landing of a lander. To investigate the dynamic behavior of the landing airbag with large deformations, a novel modeling approach incorporating gas exchange and frictional contact is proposed. The Absolute Nodal Coordinate Formulation (ANCF) is introduced to model the flexible airbag. Subsequently, the gas parameters inside the airbag are calculated by integrating the Control Volume (CV) Method and the energy conservation equation. Additionally, based on master–slave techniques, a frictional contact formulation for the thin-walled structure and the rigid plane is presented, in which the normal contact force is estimated using the penalty method, and the velocity-based friction model accounting for the stick–slip transition characterizes the tangential friction. Furthermore, the bounding box technology is adopted to improve contact detection efficiency. A series of numerical examples are performed, which demonstrates the proposed model's advantages in terms of precision and versatility. Finally, the landing dynamic characteristics of the airbag landing system for the small lunar lander are successfully revealed, and the parameter analysis for the airbag system is expected to aid the design optimization of the airbag cushioning system. • A model with good convergence and precision for pneumatic membranes is established. • The control volume method with energy conservation is used to describe gas states. • The approach considering the stick–slip transition is used for the friction. • The landing dynamic characteristics of the small lunar lander are revealed. [ABSTRACT FROM AUTHOR]

• The combined effect of switch rail structure, longitudinal coupler force and friction coefficient caused the derailment. • Longitudinal coupler force should be considered when investigating the derailment of empty freight trains. • Reducing the longitudinal coupler force and the wheel rail friction coefficient can effectively reduce derailment risk. • Installing a guard rail in front of the switch can effectively prevent freight train derailment in the turnout switch. The derailment of railway vehicles at a turnout is a worldwide concern. However, the derailment of empty freight trains in the switch section of a turnout in the diverging route is rarely concerned. Therefore, in order to analyse the derailment mechanism of empty freight trains in the turnout switch area and to propose appropriate preventive measures, field investigation and dynamic simulation of the derailment are carried out on the basis of an empty freight train derailment in the turnout switch area of the diverging route. Firstly, the background of the derailment is presented and the potential influencing factors of the derailment are analysed according to the field investigation. Secondly, a detailed train-turnout dynamic model is established, taking into account the variable cross-sections of the turnout switch rail and the effect of the longitudinal coupler force. Thirdly, based on the model, the derailment mechanism of the empty freight train is revealed through theoretical analysis and simulation calculation. Finally, the effect of the potential derailment influencing factors is analysed and preventive measures are proposed to reduce the derailment risk of the empty freight train at the turnout switch area in the diverging route. The results indicate that this derailment is caused by the combined effect of the inherent structural characteristics of the switch, the large longitudinal coupler force, and the high wheel rail friction coefficient. The possibility of derailment can be reduced by reducing the longitudinal coupler force and the wheel rail friction coefficient. In addition, the installation of a guard rail in front of the turnout can effectively prevent empty freight train derailment in the turnout area. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nonlinear dynamic model of a green ammonia synthesis system is developed. • Start-up of H 2 and N 2 subsystems and warm start-up of ammonia reactor are studied. • System dynamic responses under fluctuations of renewable energy are also analyzed. • Bed temperature, H 2 /N 2 ratio and pressure are well maintained by PID controllers. • Buffer tank decreases the reactor variation and is important for pressure control. Green ammonia production system driven by renewable electricity will be under frequent dynamic operation due to the fluctuation of renewable energy. The nonlinear dynamic model of a green ammonia synthesis system is developed and the dynamic responses of PEM (proton exchange membrane) electrolysis subsystem, PSA (Pressure swing adsorption) subsystem and ammonia synthesis subsystem during the start-up process and under the fluctuation of renewable electrical current are analyzed. The start-up dynamic results show that the hydrogen production rate of PEM electrolysis system is positively correlated to the current. The nitrogen output of PSA system is affected by the adsorption time, adsorption pressure, bed length, and air velocity. A start-up period of 300 min from the warmed-up state to the design state can maintain the temperature rise rate of the ammonia synthesis reactor at approximately 40 K/h. The dynamic results under step fluctuations of electrical current show that the PEM electrolysis subsystem and the PSA subsystem response fast compared to the ammonia synthesis reactor and buffer tanks. Using large buffer tanks to smooth the fluctuation allows the system to slide with the variation of renewable current to some extent, resulting in a higher outlet ammonia fraction when the current increases. Different volume ratios of the hydrogen tank to the nitrogen tank volume can lead to different variations of the hydrogen/nitrogen ratio. PID controllers can effectively maintain the bed temperatures, hydrogen/nitrogen ratio, and pressure of the ammonia synthesis reactor at their set points despite fluctuations in renewable electrical current. Buffer tanks are necessary to compensate for the imbalance between the flow rate fluctuation caused by current change and the flow rate regulation caused by PID controllers. [ABSTRACT FROM AUTHOR]

• Experimentally-validated model to predict size and distribution of nanoparticles. • Model couples time-resolved fluid dynamic simulations with population balance. • Increasing mixing rate, increases overall nanoparticle synthesis but not local rate. • Combination of fast mixing and high rate leads to a burst of nuclei formation. Achieving size control during nanomaterial synthesis is critical for their deployment in numerous applications due to their strong size-properties relationships. However, it remains a challenge in the field due to multi-step mechanisms in nanoparticle synthesis. In this paper, we present an experimentally-validated model able to predict the particle size and distribution of silver nanoparticles synthesised in flow reactors by coupling time-resolved fluid dynamic simulations with population balance. The model reveals fundamental correlations between reactor design and the corresponding size of the nanoparticles. It shows that increasing mixing rate, increases the overall rate of nanoparticle formation, where nanoparticle synthesis takes place homogeneously in the whole of the reaction volume. In contrast, when there is a distinguishable interface between reactant streams (i.e. low mixing rate), nucleation and growth take place in a small fraction of the reaction volume in the interface between the inlet streams. The combination of fast mixing and high average nucleation rate can lead to a burst of nuclei formation translated in small size and narrow size distribution. This work presents a new approach for the use of computational-guided design of reactors for the synthesis of nanomaterials to move the field away from current trial-and-error strategies. [ABSTRACT FROM AUTHOR]