Search

The transformation from multibody models to lumped-parameter models is a crucial aspect of vehicle dynamics research. The velocity transformation method is adopted in this research, and the suspension multibody model is described using only one degree of freedom. It is found that the equivalent mass of the system is time-dependent during the simulation process, as observed in numerical simulations. Further symbolic calculations are conducted to derive the analytical form of the equivalent mass, and the results show that once the static parameters are determined, the equivalent mass of the suspension system is determined solely by the vertical position of the suspension upright, which reveals the kinematics characteristic of the equivalent mass of the suspension system. It is found that the equivalent mass experiences smaller changes when the suspension is compressed from the middle position, but larger changes when the suspension is extended. Furthermore, by comparing the multibody model, the lumped-parameter model with static mass, and the proposed lumped-parameter model considering the kinematics characteristic of the equivalent unsprung mass, the proposed model produces simulation results that more closely match the original multibody model than the model with static mass. The improvements in accuracy can be up to 20% under certain evaluation metrics. [ABSTRACT FROM AUTHOR]

A deep understanding of the internal ballistic process and the factors affecting it is of primary importance to efficiently design a gun system and ensure its safe management. One of the main goals of internal ballistics is to estimate the gas pressure into the combustion chamber and the projectile muzzle velocity in order to use the propellant to its higher efficiency while avoiding over-pressure phenomena. Dealing with the internal ballistic problem is a complex undertaking since it requires handling the interaction between different constituents during a transient time lapse with very steep rise of pressure and temperature. Several approaches have been proposed in the literature, based on different assumptions and techniques. Generally, depending on the used mathematical framework, they can be classified into two categories: computational fluid dynamics-based models and lumped-parameter ones. By focusing on gun systems, this paper offers a review of the main contributions in the field by mentioning their advantages and drawbacks. An insight into the limitations of the currently available modelling strategies is provided, as well as some considerations on the choice of one model over another. Lumped-parameter models, for example, are a good candidate for performing parametric analysis and optimisation processes of gun systems, given their minimum requirements of computer resources. Conversely, CFD-based models have a better capacity to address more sophisticated phenomena like pressure waves and turbulent flow effects. The performed review also reveals that too little attention has been given to small calibre guns since the majority of currently available models are conceived for medium and large calibre gun systems. Similarly, aspects like wear phenomena, bore deformations or projectile-barrel interactions still need to be adequately addressed and our suggestion is to dedicate more effort on it.

AbstractGravity-driven flashing of superheated water, the topic of this paper, is a phase change phenomenon that is tightly linked with some of the safety issues of a spent-fuel-pool loss-of-cooling accident. As detailed in this article, the phenomenon has been empirically studied and characterized within the Aquarius laboratory-scale experimental device. Primarily, the performed tests unveil the occurrence conditions of the gravity-driven flashing phenomenon in a pool heated from below and its coupling with the degassing of dissolved gases that may take place within the liquid. Next, a set of dimensionless correlations describing the studied heat and mass transfers is derived from the data and presented for both the single-phase and the two-phase regimes of any conducted test. Then, a lumped-parameter model, relying on those correlations and describing the studied physics, is introduced. The model resolves the coupled mass and energy balance equations of the heated liquid pool. Last, this model is used to simulate a selected reference test. The performed simulations are successfully compared with the available empirical data, with moderate discrepancies, thereby verifying the adequateness of the proposed model. [ABSTRACT FROM AUTHOR]

A deep understanding of the internal ballistic process and the factors affecting it is of primary importance to efficiently design a gun system and ensure its safe management. One of the main goals of internal ballistics is to estimate the gas pressure into the combustion chamber and the projectile muzzle velocity in order to use the propellant to its higher efficiency while avoiding over-pressure phenomena. Dealing with the internal ballistic problem is a complex undertaking since it requires handling the interaction between different constituents during a transient time lapse with very steep rise of pressure and temperature. Several approaches have been proposed in the literature, based on different assumptions and techniques. Generally, depending on the used mathematical framework, they can be classified into two categories: computational fluid dynamics-based models and lumped-parameter ones. By focusing on gun systems, this paper offers a review of the main contributions in the field by mentioning their advantages and drawbacks. An insight into the limitations of the currently available modelling strategies is provided, as well as some considerations on the choice of one model over another. Lumped-parameter models, for example, are a good candidate for performing parametric analysis and optimisation processes of gun systems, given their minimum requirements of computer resources. Conversely, CFD-based models have a better capacity to address more sophisticated phenomena like pressure waves and turbulent flow effects. The performed review also reveals that too little attention has been given to small calibre guns since the majority of currently available models are conceived for medium and large calibre gun systems. Similarly, aspects like wear phenomena, bore deformations or projectile-barrel interactions still need to be adequately addressed and our suggestion is to dedicate more effort on it. [ABSTRACT FROM AUTHOR]

Radical or partial nephrectomy, commonly used for the treatment of kidney tumors, is a surgical procedure with a risk of high blood loss. The primary aim of this study is to quantify blood loss and elucidate the redistribution of blood flux and pressure between the two kidneys and the abdominal aorta during renal resection. We have developed a robust research methodology that introduces a new lumped-parameter mathematical model, specifically focusing on the vasculature of both kidneys using a non-Newtonian Carreau fluid. This model, a first-order approximation, accounts for the variation in the total impedance of the vasculature when various vessels are severed in the diseased kidney (assumed to be the left in this work). The model offers near real-time estimations of the flow–pressure redistribution within the vascular network of the two kidneys and the downstream aorta for several radical or partial nephrectomy scenarios. Notably, our findings indicate that the downstream aorta receives an approximately 1.27 times higher percentage of the redistributed flow from the diseased kidney compared to that received by the healthy kidney, in nearly all examined cases. The implications of this study are significant, as they can inform the development of surgical protocols to minimize blood loss and can assist surgeons in evaluating the adequacy of the remaining kidney vasculature. [ABSTRACT FROM AUTHOR]

BACKGROUND: Computational modeling of physiology has become a routine element in the development, evaluation, and safety testing of many types of medical devices. Members of the Food and Drug Administration have recently published a manuscript detailing the development, validation, and sensitivity testing of a computational model for blood volume, cardiac stroke volume, and blood pressure, noting that such a model might be useful in the development of closed-loop fluid administration systems. In the present study, we have expanded on this model to include the pharmacologic effect of sodium nitroprusside and calibrated the model against our previous experimental animal model data. METHODS: Beginning with the model elements in the original publication, we added six new parameters to control the effect of sodium nitroprusside: two for the onset time and clearance rates, two for the stroke volume effect (which includes venodilation as a hidden element), and two for the direct effect on arterial blood pressure. Using this new model, we then calibrated the predictive performance against previously collected animal study data using nitroprusside infusions to simulate shock with the primary emphasis on MAP. Root-mean-squared error (RMSE) was calculated, and the performance was compared to the performance of the model in the original study. RESULTS: RMSE of model-predicted MAP to actual MAP was lower than that reported in the original model, but higher for SV and CO. The individually fit models showed lower RMSE than using the population average values for parameters, suggesting the fitting process was effective in identifying improved parameters. Use of partially fit models after removal of the lowest variance population parameters showed a very minor decrement in improvement over the fully fit models. CONCLUSION: The new model added the clinical effects of SNP and was successfully calibrated against experimental data with an RMSE of

In this paper, a launching system with a novel charge structure was proposed to improve the interior ballistic performance. According to the working characteristics of the novel launching system, a lumped‐parameter model was established. The parameters of the propellant and the interior ballistic characteristics of the launching system were obtained by experiments. According to the experimental results, the accuracy of the lumped‐parameter model was verified by code. The simulated results were in good agreement with the experimental results. Based on the lumped‐parameter model, the propellant parameters, such as the impetus, the burning rate, the web thickness, and the charge mass, were investigated to understand the interior ballistic performances of the launching system. An optimization method was proposed to design the propellant parameters of the launching system. The results show that the optimal scheme can increase the velocity of the projectile by 9.54 %. Compared with the traditional launching method, the velocity of the projectile is increased by 37.09 % while the peak pressure in the barrel has no change. [ABSTRACT FROM AUTHOR]

Despite all the literature on building energy management, building-stock-scale models depicting its impact for energy-market-scale optimisation models are lacking. To address this shortcoming, an open-source tool called ArchetypeBuildingModel.jl has been developed for aggregating building-stock-level data into simplified lumped-capacitance thermal models compatible with existing open-source energy-system modelling frameworks. This paper aims to demonstrate the feasibility of these simplified thermal models by comparing their performance against dedicated building simulation software, as well as examining their sensitivity to key modelling and parameter assumptions. Modelling and parameter assumptions comparable to the existing literature achieved an acceptable performance according to ASHRAE Guideline 14 across all tested buildings and nodal configurations. The most robust performance was achieved with a period of variations above 13 days and interior node depth between 0.1 and 0.2 for structural thermal mass calibrations, and with external shading coefficients between 0.6 and 1.0 and solar heat gain convective fractions between 0.4 and 0.6 for solar heat gain calibrations. Furthermore, three-plus-node lumped-capacitance thermal models are recommended when modelling buildings with structures varying in terms of thermal mass. Nevertheless, the ArchetypeBuildingModel.jl performance was found to be robust against uncertain key parameter assumptions, making it plausible for energy-market-scale applications. [ABSTRACT FROM AUTHOR]

Dynamic soil-structure interaction (SSI) significantly impacts structural vibration. Over the past few decades, numerous simplified models were developed to analyze dynamic SSI on homogeneous soil. In this study, however, a lumped-parameter model is adopted to investigate the dynamic behavior of rectangular foundations overlying nonuniform soil. The simplified three-parameter model is utilized to analyze the torsional vibration of rectangular foundations on layered soil with linearly varying shear-wave velocities. Non-dimensional parameters (shear-wave velocity ratios, layer depth ratios, and mass ratios) are also investigated herein. The frequency-magnification curves of the foundation using three-parameter model are found to agree well with theoretical solutions. Consistent agreements are also observed at the resonant response and its corresponding frequency ratio. Additionally, the resultant resonant magnification factors against mass ratios clearly show the impacts of the whipping effect resulting from soil-foundation interactions. The proposed model excels in simulating layered soil and includes fewer parameters than existing lumped-parameter models. The proposed model also demonstrates the adaptivity and reliability to simulate the dynamic responses calculated from the published in-situ experimental data. The time-domain application based on the proposed model effectively estimates the structural displacement of the soil-foundation-superstructure system. This research could contribute to the SSI analysis regarding the torsional vibration of a foundation on nonuniform soil.

The purpose of this research is to initiate an investigation of the nonlinear material strain-rate damping effects on the amplitude and frequencies of some Euler-Bernoulli Beams. It is well known that the dynamic behaviors of most heat-treated metals can be modelled by using the power-law strain-rate dependent constitutive equations. Lumped parameter models for approximations of dynamic vibration of the power-law Euler-Bernoulli Beam subject to power-law strain-rate damping and concentrated loads are formulated. Analytic formulas of the lumped parameters, including effective the train-rate damping, are derived. The lumped-parameters are also evaluated numerically by a low-order Galerkin Method to validate and compare the lumped parameter model with another numerical model. Numerical examples made of some heat-treated aluminum and stainless-steel alloys are presented to illustrate the implications of the aforementioned lumped-parameter models on the dynamics of the beams. The results obtained in this work cover with the classical results in the literature for linear the materials as special cases. The novel lumped parameter models can provide useful insights for crashworthiness analysis of structures of heat treated metals and thermal plastics.

Liquid Organic Hydrogen Carriers (LOHCs) feature a highly variable rate of hydrogen release if held at constant pressure and temperature, but in real-life applications hydrogen release must be controlled to match end-user demand. The aim of this paper is to provide an overall assessment of LOHC systems' controllability, within a general framework regardless of the specific application field. Hydrogen discharge can be controlled through the reactor pressure and temperature; thus, a PI controller is introduced acting on three control variables independently: discharge pressure; thermal fluid inlet temperature; thermal fluid mass flow rate. A quantile analysis is performed on the uncontrolled hydrogen release: practical values of the energy-to-power ratios for LOHC systems are 2–6 h. A normalised release time is introduced to assess the efficiency of the control system. Temperature control leads to the best results, with an efficiency higher than 90% for the entire load range, while pressure control leads to satisfactory performance only at low loads. The mass flow rate control is the least effective, with efficiencies always below 80%. Sensitivity analysis highlights the temperature control strategy as the best fit to enhance controllability across the whole power range. Pressure control presents a more variable trend. • Liquid Organic Hydrogen Carriers release hydrogen at highly variable flow rates • Flow rate control systems are required to meet end-user demand • Control variables: discharge pressure, thermal fluid inlet temperature and flow rate • Heat transfer fluid inlet temperature provides the most effective control • Very good controllability expected with synergic pressure and temperature controls [ABSTRACT FROM AUTHOR]

Liquid organic hydrogen carriers (LOHCs) are considered a promising hydrogen storage technology. Heat must be exchanged with an external medium, such as a heat transfer fluid, for the required chemical reactions to occur. Batch reactors are simple but useful solutions for small-scale storage applications, which can be modelled with a lumped-parameter approach, adequately reproducing their dynamic performance. For such reactors, power is consumed to circulate the external heat transfer fluid and stir the organic liquid inside the reactor, and heat transfer performance and power consumption are two key parameters in reactor optimisation. Therefore, with reference to the hydrogen release phase, this paper describes a procedure to optimise the reactor thermal design, based on a lumped-parameter model, in terms of heat transfer performance and minimum power consumption. Two batch reactors are analysed: a conventional jacketed reactor with agitation nozzles and a half-pipe coil reactor. Heat transfer performance is evaluated by introducing a newly defined dimensionless parameter, the Heat Transfer Ratio (HTR), whose value directly correlates to the heat rate required by the carrier's dehydrogenation reaction. The resulting model is a valid tool for adequately reproducing the hydrogen storage behaviour within dynamic models of complex and detailed energy systems. • Thermal design of hydrogen storage systems based on LOHC batch reactors is analysed • Design is optimised to ensure effective heat transfer and minimum power consumption • Novel dimensionless parameter (Heat Transfer Ratio, HTR) is introduced • A threshold HTR value is identified, above which only marginal gains are achieved • The lumped-parameter model can be deployed in complex energy system dynamic models [ABSTRACT FROM AUTHOR]

The treatment of critically ill patients remains an evolving and controversial issue. Mechanical circulatory support through a percutaneous approach for the management of cardiogenic shock has taken place in recent years. The combined use of IABP and the Impella 2.5 device may have a role to play for this group of patients. A simulation approach may help with a quantitative assessment of the achievable degree of assistance. In this paper, we analyse the interaction between the Impella 2.5 pump applied as the LVAD and IABP using the numerical simulator of the cardiovascular system developed in our laboratory. Starting with pathological conditions reproduced using research data, the simulations were performed by setting different rotational speeds for the LVAD and driving the IABP in full mode (1:1) or partial mode (1:2, 1:3 and 1:4). The effects induced by drug administration during the assistance were also simulated. The haemodynamic parameters under investigation were aa follows: mean aortic pressure, systolic and diastolic aortic pressure, mean pulmonary arterial pressure, mean left and right atrial pressure, cardiac output, cardiac index, left and right ventricular end-systolic volume, left ventricular end-diastolic volume and mean coronary blood flow. The energetic variables considered in this study were as follows: left and right ventricular external work and left and right atrial pressure-volume area. The outcome of our simulations shows that the combined use of IABP and Impella 2.5 achieves adequate support in the acute phase of cardiogenic shock compared to each standalone device. This would allow further stabilisation and transfer to a transplant centre should the escalation of treatment be required. [ABSTRACT FROM AUTHOR]

In 2021, approximately 51% of patients diagnosed with kidney tumors underwent surgical resections. One possible way to reduce complications from surgery is to minimise the associated blood loss, which, in the case of partial nephrectomy, is caused by the inadequate repair of branching arteries within the kidney cut during the tumor resection. The kidney vasculature is particularly complicated in nature, consisting of various interconnecting blood vessels and numerous bifurcation, trifurcation, tetrafurcation, and pentafurcation points. In this study, we present a mathematical lumped-parameter model of a whole kidney, assuming a non-Newtonian Carreau fluid, as a first approximation of estimating the blood loss arising from the cutting of single or multiple vessels. It shows that severing one or more blood vessels from the kidney vasculature results in a redistribution of the blood flow rates and pressures to the unaltered section of the kidney. The model can account for the change in the total impedance of the vascular network and considers a variety of multiple cuts. Calculating the blood loss for numerous combinations of arterial cuts allows us to identify the appropriate surgical protocols required to minimise blood loss during partial nephrectomy as well as enhance our understanding of perfusion and account for the possibility of cellular necrosis. This model may help renal surgeons during partial organ resection in assessing whether the remaining vascularisation is sufficient to support organ viability. [ABSTRACT FROM AUTHOR]

The ride comfort provided by a vehicle to the driver and the passengers is an important feature, directly correlated to the technical characteristics of the suspension system of the vehicle. In the literature, several lumped-parameter models simulating the vehicle and the driver are proposed for the computational evaluation of ride comfort. In order to quantify ride comfort, other than the values of acceleration, metrics such as seat effective amplitude transmissibility (SEAT) and seat-to-head transmissibility (STHT) are utilized. In this paper, a quarter car model is coupled with a six-degree-of-freedom lumped-parameter model, consisting of the driver’s seat and the driver. A sensitivity analysis is performed on the values of the lumped parameters of the seated human body with regard to ride comfort in order to evaluate the effect of their accuracy relative to the ride comfort evaluation. The results of the sensitivity analysis revealed that the values of the mass, the stiffness and the damping parameters of the seated human model influence the ride-comfort metrics to a different extent. Furthermore, it was depicted that ride-comfort metrics were affected in different manners depending on the characteristics of the excitation of the vehicle, yet less than 10% Finally, the importance of the consideration of single-disturbance excitations in such sensitivity studies emerged.

Despite all the literature on building energy management, building-stock-scale models depicting its impact for energy-market-scale optimisation models are lacking. To address this shortcoming, an open-source tool called ArchetypeBuildingModel.jl has been developed for aggregating building-stock-level data into simplified lumped-capacitance thermal models compatible with existing open-source energy-system modelling frameworks. This paper aims to demonstrate the feasibility of these simplified thermal models by comparing their performance against dedicated building simulation software, as well as examining their sensitivity to key modelling and parameter assumptions. Modelling and parameter assumptions comparable to the existing literature achieved an acceptable performance according to ASHRAE Guideline 14 across all tested buildings and nodal configurations. The most robust performance was achieved with a period of variations above 13 days and interior node depth between 0.1 and 0.2 for structural thermal mass calibrations, and with external shading coefficients between 0.6 and 1.0 and solar heat gain convective fractions between 0.4 and 0.6 for solar heat gain calibrations. Furthermore, three-plus-node lumped-capacitance thermal models are recommended when modelling buildings with structures varying in terms of thermal mass. Nevertheless, the ArchetypeBuildingModel.jl performance was found to be robust against uncertain key parameter assumptions, making it plausible for energy-market-scale applications.

There is increasing interest in the use of novel elastomers with inherent or modified advanced dielectric and mechanical properties, as components of dielectric elastomer actuators (DEA). This requires corresponding techniques to assess their electro-mechanical performance. A common way to test dielectric materials is the fabrication of actuators with pre-stretch fixed by a stiff frame. This results in the problem that the electrode size has an influence on the achievable actuator displacement and strain, which is detrimental to the comparability of experiments. This paper presents an in-depth study of the active-to-passive ratio with the aim of investigating the influence of the coverage ratio on uniaxial actuator displacement and strain. To model the effect, a simple lumped-parameter model is proposed. The model shows that the coverage ratio for maximal displacement is 50%. To validate the model results, experiments are carried out. For this, a rectangular, fiber-reinforced DEA is used to assess the relation of the coverage ratio and deformation. Due to the stiffness of the fibers, highly anisotropic mechanical properties are achieved, leading to the uniaxial strain behavior of the actuator, which allows the validation of the one-dimensional model. To consider the influence of the simplifications in the lumped-parameter model, the results are compared to a hyperelastic model. In summary, it is shown that the ratio of the active-to-passive area has a significant influence on the actuator deformation. Both the model and experiments confirm that an active-to-passive ratio of 50% is particularly advantageous in most cases. [ABSTRACT FROM AUTHOR]

• Lumped-parameter models are established for investigating the dynamic behaviors of the cantilever and hinged-hinged Power-law Euler-Bernoulli Beams. • Novel effective damping ratios are developed analytically in the lumped-parameter models for power-law materials subject to nonlinear strain-rate damping. • The combined effects of the lumped parameters of the dynamic behaviors of the beams are analyzed. • The models can provide useful insights into crashworthiness of structures of heat treated metal and thermal plastic structures. The purpose of this research is to initiate an investigation of the nonlinear material strain-rate damping effects on the amplitude and frequencies of some Euler-Bernoulli Beams. It is well known that the dynamic behaviors of most heat-treated metals can be modelled by using the power-law strain-rate dependent constitutive equations. Lumped parameter models for approximations of dynamic vibration of the power-law Euler-Bernoulli Beam subject to power-law strain-rate damping and concentrated loads are formulated. Analytic formulas of the lumped parameters, including effective the train-rate damping, are derived. The lumped-parameters are also evaluated numerically by a low-order Galerkin Method to validate and compare the lumped parameter model with another numerical model. Numerical examples made of some heat-treated aluminum and stainless-steel alloys are presented to illustrate the implications of the aforementioned lumped-parameter models on the dynamics of the beams. The results obtained in this work cover with the classical results in the literature for linear the materials as special cases. The novel lumped parameter models can provide useful insights for crashworthiness analysis of structures of heat treated metals and thermal plastics. [ABSTRACT FROM AUTHOR]

The ride comfort provided by a vehicle to the driver and the passengers is an important feature, directly correlated to the technical characteristics of the suspension system of the vehicle. In the literature, several lumped-parameter models simulating the vehicle and the driver are proposed for the computational evaluation of ride comfort. In order to quantify ride comfort, other than the values of acceleration, metrics such as seat effective amplitude transmissibility (SEAT) and seat-to-head transmissibility (STHT) are utilized. In this paper, a quarter car model is coupled with a six-degree-of-freedom lumped-parameter model, consisting of the driver's seat and the driver. A sensitivity analysis is performed on the values of the lumped parameters of the seated human body with regard to ride comfort in order to evaluate the effect of their accuracy relative to the ride comfort evaluation. The results of the sensitivity analysis revealed that the values of the mass, the stiffness and the damping parameters of the seated human model influence the ride-comfort metrics to a different extent. Furthermore, it was depicted that ride-comfort metrics were affected in different manners depending on the characteristics of the excitation of the vehicle, yet less than 10% Finally, the importance of the consideration of single-disturbance excitations in such sensitivity studies emerged. [ABSTRACT FROM AUTHOR]

Background: Computational modeling of physiology has become a routine element in the development, evaluation, and safety testing of many types of medical devices. Members of the Food and Drug Administration have recently published a manuscript detailing the development, validation, and sensitivity testing of a computational model for blood volume, cardiac stroke volume, and blood pressure, noting that such a model might be useful in the development of closed-loop fluid administration systems. In the present study, we have expanded on this model to include the pharmacologic effect of sodium nitroprusside and calibrated the model against our previous experimental animal model data. Methods: Beginning with the model elements in the original publication, we added six new parameters to control the effect of sodium nitroprusside: two for the onset time and clearance rates, two for the stroke volume effect (which includes venodilation as a "hidden" element), and two for the direct effect on arterial blood pressure. Using this new model, we then calibrated the predictive performance against previously collected animal study data using nitroprusside infusions to simulate shock with the primary emphasis on MAP. Root-mean-squared error (RMSE) was calculated, and the performance was compared to the performance of the model in the original study. Results: RMSE of model-predicted MAP to actual MAP was lower than that reported in the original model, but higher for SV and CO. The individually fit models showed lower RMSE than using the population average values for parameters, suggesting the fitting process was effective in identifying improved parameters. Use of partially fit models after removal of the lowest variance population parameters showed a very minor decrement in improvement over the fully fit models. Conclusion: The new model added the clinical effects of SNP and was successfully calibrated against experimental data with an RMSE of <10% for mean arterial pressure. Model-predicted MAP showed an error similar to that seen in the original base model when using fluid shifts, heart rate, and drug dose as model inputs. [ABSTRACT FROM AUTHOR]

Aortic disease has a significant impact on quality of life. The involvement of the aortic arch requires the preservation of blood supply to the brain during surgery. Deep hypothermic circulatory arrest is an established technique for this purpose, although neurological injury remains high. Additional techniques have been used to reduce risk, although controversy still remains. A three-way cannulation approach, including both carotid arteries and the femoral artery or the ascending aorta, has been used successfully for aortic arch replacement and redo procedures. We developed circuits of the circulation to simulate blood flow during this type of cannulation set up. The CARDIOSIM© cardiovascular simulation platform was used to analyse the effect on haemodynamic and energetic parameters and the benefit derived in terms of organ perfusion pressure and flow. Our simulation approach based on lumped-parameter modelling, pressure–volume analysis and modified time-varying elastance provides a theoretical background to a three-way cannulation strategy for aortic arch surgery with correlation to the observed clinical practice. [ABSTRACT FROM AUTHOR]

Cardiac diseases and failure make up one of largest contributions to global mortality and significantly detriment the quality of life for millions of others. Disorders in the valves of the left ventricle are a prominent example of heart disease, with prolapse, regurgitation, and stenoses—the three main valve disorders. It is widely known that mitral valve prolapse increases the susceptibility to cardiac arrhythmia. Here, we investigate stenoses and regurgitation of the mitral and aortic valves in the left ventricle using a synergistic low-order numerical model. The model synergy derives from the incorporation of the mechanical, chemical, and electrical elements. As an alternative framework to the time-varying elastance (TVE) method, it allows feedback mechanisms at work in the heart to be considered. The TVE model imposes the ventricular pressure–volume relationship using a periodic function rather than calculating it consistently. Using our synergistic approach, the effects of valve disorders on the mechano-electric-feedback (MEF) are investigated. The MEF is the influence of cellular mechanics on the electrical activity, and significantly contributes to the generation of arrhythmia. We further investigate stenoses and regurgitation of the mitral and aortic valves and their relationship with the MEF and generation of arrhythmia. Mitral valve stenosis is found to increase the sensitivity to arrhythmia-stimulating systolic stretch, and reduces the sensitivity to diastolic stretch. Aortic valve stenosis does not change the sensitivity to arrhythmia-stimulating stretch, and regurgitation reduces it. A key result is found when valve regurgitation is accompanied by diastolic stretch. In the presence of MEF disorder, ectopic beats become far more frequent when accompanied by valve regurgitation. Therefore, arrhythmia resulting from a disorder in the MEF will be more severe when valve regurgitation is present. [ABSTRACT FROM AUTHOR]

Heart diseases are one of the leading causes of death worldwide, and a dysfunction of the cardiac electrical mechanisms is responsible for a significant portion of these deaths. One of these mechanisms, the mechano-electric feedback (MEF), is the electrical response of the heart to local mechanical changes in the environment. This electrical response, in turn, leads to macroscopic changes in heart function. In this paper, we demonstrate that the MEF plays a crucial role in mechanical generation and recovery from arrhythmia which has been observed in experimental studies. To this end, we investigate the cardiac response to a mechanical stimulation using a minimal, multiscale model of the heart which couples the organ level dynamics (left ventricular pressure and volume) and contractile dynamics. By including a mechanical stimulation into the model as a (short, sudden) impulse in the muscle microscale stress, we investigate how the timing, amplitude and duration of the impulse affect the cardiac cycle. In particular, when introduced in the diastolic period of the cardiac cycle, the pulse rate can be stabilised, and ectopic beats and bifurcation can be eliminated, either temporarily or permanently. The stimulation amplitude is a key indicator to this response. We find an optimal value of the impulse amplitude above or below which the impulse maximises the stabilisation. As a result a dysfunction of the MEF can be helped using a mechanical stimulation, by allowing the heart to recover its pumping power. On the other hand, when the mechanical stimulation is introduced towards the end of systole, arrhythmia can be generated.

To investigate the dynamic characteristics of proton exchange membrane fuel cells (PEMFCs) on maritime vessels, a lumped-parameter model for the PEMFC systems was developed based on a hybrid vessel propulsion systems model. Simulations and analyses of the dynamic characteristics of PEMFCs were conducted under typical sailing conditions. The results reveal a noticeable hysteresis in the operating temperature of PEMFC stacks during vessel voyages, with a delay of about 25 s, leading to significant overvoltage in activation, ohmic, and concentration differences. Significant variations in vessel loads can cause large fluctuations in the component gas pressures in the cathode and anode flow paths within 16.6–19.8 kPa and 78.57–93.06 kPa, respectively. A comparison of different humidification levels for cathode and anode gases demonstrates that, at the same moment, as the humidification of cathode and anode gases increases from 20 % to 100 %, the water content in the proton membrane increases from 2.29 to 13.47, the ohmic impedance decreases from 1.35 mΩ/cm2 to 0.174 mΩ/cm2, and the overshoot of the fuel cell voltage decreases. The output delay decreases from 25 s to 8 s, enhancing overall fuel cell performance. These findings are significant for optimizing the design, performance, and real-time control of marine PEMFC systems. • An energy management strategy optimizes the output power of a PEMFC system in a hybrid vessel. • A lumped-parameter model was developed to study PEMFC dynamics under typical vessel conditions. • Revealed the impact of gas humidification variations on the dynamic characteristics of the PEMFC system. [ABSTRACT FROM AUTHOR]

This review is devoted to presenting the history of the CARDIOSIM© software simulator platform, which was developed in Italy to simulate the human cardiovascular and respiratory systems. The first version of CARDIOSIM© was developed at the Institute of Biomedical Technologies of the National Research Council in Rome. The first platform version published in 1991 ran on a PC with a disk operating system (MS-DOS) and was developed using the Turbo Basic language. The latest version runs on PC with Microsoft Windows 10 operating system; it is implemented in Visual Basic and C++ languages. The platform has a modular structure consisting of seven different general sections, which can be assembled to reproduce the most important pathophysiological conditions. One or more zero-dimensional (0-D) modules have been implemented in the platform for each section. The different modules can be assembled to reproduce part or the whole circulation according to Starling's law of the heart. Different mechanical ventilatory and circulatory devices have been implemented in the platform, including thoracic artificial lungs, ECMO, IABPs, pulsatile and continuous right and left ventricular assist devices, biventricular pacemakers and biventricular assist devices. CARDIOSIM© is used in clinical and educational environments. [ABSTRACT FROM AUTHOR]

• Computationally efficient and accurate adsorption chiller model. • Avoiding discretization of heat exchanger models by operator splitting. • Model validation for two real-world adsorption chillers. • Broad application range established in terms of a characteristic number. • 70% increase of computational efficiency compared to state-of-the-art model. Reliable and computationally efficient models are crucial to improve the performance of adsorption chillers. However, modeling of adsorption chillers is challenging due to the intrinsic process dynamics. Currently, adsorption chillers are most often represented by 1-d, lumped-parameter models that use lumped models for all components but resolve the heat exchangers in one spatial dimension. Still, accurate simulations require fine discretization leading to poor computational efficiency. To increase computational efficiency, here, an alternative modeling approach is proposed that avoids discretization by applying operator splitting. The benefits of the proposed modeling approach are demonstrated in two real-world case studies. First, the resulting adsorption chiller model is calibrated and validated with experimental data of a lab-scale one-bed adsorption chiller: The proposed model retains the accuracy of a state-of-the-art model while increasing computational efficiency by up to 70%. Second, the proposed model is applied to a commercial two-bed adsorption chiller with excellent accuracy. Finally, the validity of model is tested by varying the ratio between the overall heat transfer coefficient and the heat capacity rate of the fluid in the heat exchangers. The proposed model is shown to be well suited for the conditions present in most adsorption chillers. [ABSTRACT FROM AUTHOR]

In the paper an original approach to efficiency map optimal synthesis is presented. A permanent magnet motor, working as controlled AC motor of synchronous type (PMSM), is selected as a case study. The first target of this research is to derive a lumped-parameter model of the motor (low-fidelity model), validated by magnetic field analysis (high-fidelity model). In turn, the end target is these two models application in a cost-effective optimisation procedures, where the goal is to identify the motor geometry maximizing the map area which is encompassed by a prescribed value for the motor efficiency. [ABSTRACT FROM AUTHOR]

In this study, we conducted experiments and numerical analysis on a 270 kW industrial-scale centrifugal compressor used in the fuel supply system of an LNG carrier in order to improve the lumped-parameter surge model by considering the viscosity in the pipeline and to confirm whether the improved model would be applicable. The steady and unsteady compressor performance curves were constructed using measurements and predictions, respectively. The flow through the pipeline was assumed to be both steady and unsteady, and each governing equation under the assumptions was derived in accordance with the lumped-parameter model. In the steady flow case, the surge behavior of the modified model was in a good agreement with the lumped-parameter model at surge parameter B = 4.8716. In the unsteady flow case, however, the modified model showed a deviation from the lumped-parameter model, and the simulation from the modified model described the surge behavior 5% more accurately than the lumped-parameter model. Through experiments and numerical analysis, this study showed that the present models are useful and applicable for describing the surge behavior of an industrial-scale single-stage centrifugal compressor. [ABSTRACT FROM AUTHOR]

The breakdown of cardiac self-organization leads to heart diseases and failure, the number one cause of death worldwide. Within the traditional time-varying elastance model, cardiac self-organization and breakdown cannot be addressed due to its inability to incorporate the dynamics of various feedback mechanisms consistently. To face this challenge, we recently proposed a paradigm shift from the time-varying elastance concept to a synergistic model of cardiac function by integrating mechanical, electric and chemical activity on micro-scale sarcomere and macro-scale heart. In this paper, by using our synergistic model, we investigate the mechano-electric feedback (MEF) which is the effect of mechanical activities on electric activity—one of the important feedback loops in cardiac function. We show that the (dysfunction of) MEF leads to various forms of heart arrhythmias, for instance, causing the electric activity and left-ventricular volume and pressure to oscillate too fast, too slowly, or erratically through periodic doubling bifurcations or ectopic excitations of incommensurable frequencies. This can result in a pathological condition, reminiscent of dilated cardiomyopathy, where a heart cannot contract or relax properly, with an ineffective cardiac pumping and abnormal electric activities. This pathological condition is then shown to be improved by a heart assist device (an axial rotary pump) since the latter tends to increase the stroke volume and aortic pressure while inhibiting the progression (bifurcation) to such a pathological condition. These results highlight a nontrivial effect of a mechanical pump on the electric activity of the heart.

Due to their large deformation, high energy density, and high compliance, dielectric elastomer actuators (DEAs) have found a number of applications in several areas of mechatronics and robotics. Among the many types of DEAs proposed in the literature, rolled DEAs (RDEAs) represent one of the most popular configurations. RDEAs can be effectively used as compact muscle-like actuators for soft robots, since they allow eliminating the need for external motors or compressors while providing at the same time a flexible and lightweight structure with self-sensing capabilities. To effectively design and control complex RDEA-driven systems and robots, accurate and numerically efficient mathematical models need to be developed. In this work, we propose a novel lumped-parameter model for silicone-based, thin and tightly rolled RDEAs. The model is grounded on a free-energy approach, and permits to describe the electro-mechanically coupled response of the transducer with a set of nonlinear ordinary differential equations. After deriving the constitutive relationships, the model is validated by means of an extensive experimental campaign, conducted on three RDEA specimens having different geometries. It is shown how the developed model permits to accurately predict the effects of several parameters (external load, applied voltage, actuator geometry) on the RDEA electro-mechanical response, while maintaining an overall simple mathematical structure. [ABSTRACT FROM AUTHOR]

A number of simple models containing frequency‐independent elements have been presented to simulate unbounded soil in dynamic soil‐structure interaction problems. Most of the existing models were established through a traditional top‐down strategy with significant computational complexities. This study develops an alternative method based on a bottom‐up strategy, in which the optimal element layout is determined by an adaptive refinement procedure considering finite modularized units. This innovation eliminates the need for lengthy procedures to establish simple models. The proposed three‐parameter model is used to simulate the layered soil for rigid foundations undergoing vertical vibration. The accuracy of the model is validated by comparing the magnified responses obtained when a foundation is subjected to harmonic forces with those obtained via theoretical solutions and advanced numerical simulations. The proposed model is found to effectively simulate a layered half‐space and a soil layer on rock. Compared to two existing models, the proposed model performs better and has fewer parameters and a higher degree of adaptivity. Therefore, the adaptivity of simple models obtained using the proposed method may allow simulation of a variety of layered soil systems. [ABSTRACT FROM AUTHOR]

In this paper, a new Kelvin-Voigt type beam model of a microelectromechanical resonator made of power-law materials taking into account internal strain-rate damping is proposed and the corresponding lumped-parameter model is derived. Analytical formulas of the lumped parameters in the model are presented. And the pull-in solution is analyzed based on the lumped-parameter model. It is demonstrated analytically and numerically that the internal damping plays an important role in the pull-in solution as well as in determination of the amplitudes and frequencies of the resonator. The hysteresis loops are provided for this model with initial conditions using numerical simulations. The approximation of the electrostatic force in the lumped-parameter model can describe the relations between amplitudes and frequencies with different values of the stiffness and damping coefficients quite well. [ABSTRACT FROM AUTHOR]

Dynamic soil-structure interaction (SSI) significantly impacts structural vibration. Over the past few decades, numerous simplified models were developed to analyze dynamic SSI on homogeneous soil. In this study, however, a lumped-parameter model is adopted to investigate the dynamic behavior of rectangular foundations overlying nonuniform soil. The simplified three-parameter model is utilized to analyze the torsional vibration of rectangular foundations on layered soil with linearly varying shear-wave velocities. Non-dimensional parameters (shear-wave velocity ratios, layer depth ratios, and mass ratios) are also investigated herein. The frequency-magnification curves of the foundation using three-parameter model are found to agree well with theoretical solutions. Consistent agreements are also observed at the resonant response and its corresponding frequency ratio. Additionally, the resultant resonant magnification factors against mass ratios clearly show the impacts of the whipping effect resulting from soil-foundation interactions. The proposed model excels in simulating layered soil and includes fewer parameters than existing lumped-parameter models. The proposed model also demonstrates the adaptivity and reliability to simulate the dynamic responses calculated from the published in-situ experimental data. The time-domain application based on the proposed model effectively estimates the structural displacement of the soil-foundation-superstructure system. This research could contribute to the SSI analysis regarding the torsional vibration of a foundation on nonuniform soil. [ABSTRACT FROM AUTHOR]

A simple model, for the estimation of changes in the nuclear fuel element cladding temperature as well as the conditions of the formation of the onset of nucleate boiling, is proposed. The results of this estimation are sufficient to assess the effect of the transient with the peak of the reactor's power on the device's safety, without the need for time-consuming thermal calculations. The basic parameters determined using the proposed model are the maximum wall temperature of the device in a hot spot, the time constant of the wall temperature change, and the course of changes in the onset of nucleate boiling ratio in time. The model may be used for investigating the thermal behavior of thin heat-generating and water-cooled elements (such as fuel elements or uranium irradiation targets) during rapid power rise. The results of the temperature estimation with the proposed model were tested considering the hot spot in the MR-6 type nuclear fuel. The SN code with coupled kinetics and thermal-hydraulics, developed in the MARIA reactor was used to validate the results. The maximum cladding temperature, the thermal time constant and the onset of nucleate boiling ratio parameter simulated by the SN code and the proposed scheme appeared to be very consistent.

In recent years, the need for portable, low-cost, and eco-friendly devices for testing and monitoring has arisen. Paper-based devices have emerged as a response to these needs due to the properties induced by capillarity, flexibility, disposability, and biodegradability. In this work, the authors explored the possibility of tuning the hygro-mechanical response of paper-based cantilever beams using glycerol. A lumped-parameter model with non-linear stiffness is used to describe the dynamic response of the beams using three parameters. An experimental method based on resonance frequency tests is used to study the influence of glycerol on the dynamic response of four different beam configurations. The obtained results demonstrate that the resonance frequency of paper-based mechanical systems can be easily tuned by the imbibition of a glycerol–water solution. This study could lead to the development of tunable paper-based mechanical systems for specific applications such as energy harvesters and hygro-mechanical-based sensors. [ABSTRACT FROM AUTHOR]

A permanent magnet traction motor integrated with a planetary gearbox is studied. A machine of this kind can be employed as a propulsion motor in off-road machines like agricultural tractors that have to produce either very high traction forces at low speeds or reach higher traveling speeds at lower torques. In principle, a constant power curve as a function of speed is desired, which means that the output torque of the drive system should be inversely proportional to the operating speed of the off-road machine. Such driving conditions are challenging as the electric motor has to be heavily overloaded at the lowest speeds. Therefore, it is essential to accurately evaluate not only the electromagnetic performance but also the thermal performance of the machine. This paper studies the integration principles of an electrical machine and a planetary gear. The integration poses some new challenges to the design. For example, also the lubrication and cooling can, and, in practice, must be integrated into the system. The thermal performance of the motor and cooling with the lubrication oil of the gear were analyzed. The long-term tests with the oil cooling system were carried out to verify the successful integration.

In karst catchments where only sparse temporal monitoring is performed, it is generally difficult to correctly assess the overall hydrodynamics of the basin. However, sparse temporal spring-discharge data may contain information of major importance for the characterization of such catchments, especially when sparse spring-discharge data over a long period are available and combined with higher frequency discharge and/or piezometric-level data. This paper proposes a methodology for the characterization and hydrodynamic modeling of karst catchments by coupling sparse temporal data of discharge at a karstic spring over a 30-year measurement period, with higher frequency (i.e. hourly) data of hydrodynamic (piezometry, discharge), physicochemical (temperature, electrical conductivity) and meteorological data over a short monitoring period of 21 months. The study area is the Oeillal spring catchment, one of the main outlets of the Fontfroide-Montredon limestone aquifer located at the border of the Narbonne-Sigean sedimentary basin, southern France. The present study focuses on the use of numerical tools such as time-series analysis (recession analysis, auto-correlation and cross-correlation analysis) coupled with a lumped-parameter modeling approach, to assess the hydrodynamic behaviour of the karst system. The main results of the study highlight the necessity to couple the results from lumped-parameter rainfall-runoff modeling with results from high-resolution time-series analysis to evaluate the physical significance of the model, since classical numerical performance criteria such as the Nash-Sutcliff efficiency, Kling-Gupta efficiency and balance error, can be poorly estimated when only subsampled time series exist for model calibration. [ABSTRACT FROM AUTHOR]

Copyright of DYNA - Ingeniería e Industria is the property of Publicaciones Dyna SL and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The impact of adopting different dynamic soil–structure interaction (SSI) models on the assessment of seismic fragility functions for buildings with pile foundations is studied herein. Given the importance on seismic response of the coupling of structure, foundation and soil, and the challenges posed on modelling dynamic SSI, especially when soil nonlinearity plays a significant role, the linear substructure approach is initially adopted by implementing two different models, followed by the use of a nonlinear pile-head macro-element. The first model is one-dimensional and includes, between the foundation node and the ground, only a translational elastic spring and a dashpot, whose stiffness and viscous damping are retrieved from the real and imaginary parts of the dynamic impedance at the first natural frequency of the structure. The second and more refined model is a Lumped-Parameter Model accounting for frequency dependence of the coupled horizontal and rotational impedances in a two-dimensional response. A nonlinear pile-head macro-element model is introduced afterwards to explore the sensitivity of fragility functions to the linearity assumption. This approach models the soil nonlinear behaviour at near-field, as well as the far-field dynamic impedance and energy dissipation through radiation damping, by condensing the entire soil-foundation system into a single nonlinear element at the base of the superstructure. In all models, the superstructure is represented in a simplified way as a nonlinear single-degree-of-freedom system. The comparison between the adopted approaches is evaluated in terms of their effects on the characterisation of fragility functions for unreinforced masonry buildings with pile foundations. [ABSTRACT FROM AUTHOR]

A nanoresonator can be applied as a biochemical sensor based on the change in the mass of the nanoresonator, and the mass change can be interpreted in the frequency domain. In this paper, we present an open-loop spectrum analyzer integrated circuit (IC) for a nanoresonator. The circuit determines the frequency characteristics of a nanoresonator, such as quality factor (Q-factor) and resonant frequency, and detects minute resistance changes of the nanoresonator that result in changes in Q-factor or resonant frequency. The proposed nanoresonator driver circuit is implemented using an open-loop system, and to characterize the open-loop frequency response of the nanoresonator, the IC includes a voltage-controlled oscillator, a transimpedance amplifier, and a 16-bit delta-sigma analog-to-digital converter. To compensate for the parasitic components that cause the distortions of the phase and magnitude response, a shunt-capacitance cancelling amplifier is used to cancel the effect of the shunt-parasitic capacitance of the nanoresonator. The simulated target nanoresonator is modeled using the Butterworth-Van Dyke equivalent circuit model with a resonant frequency of 10 MHz. The proposed nanoresonator driver circuit is fabricated using a standard 0.18 μm complementary metal oxide semiconductor process with an active area of 2.346 mm². The simulated resistive sensitivity of the IC is 5.1 mV/kΩ. [ABSTRACT FROM AUTHOR]

The breakdown of cardiac self-organization leads to heart diseases and failure, the number one cause of death worldwide. The left ventricular pressure-volume relation plays a key role in the diagnosis and treatment of heart diseases. Lumped-parameter models combined with pressure-volume loop analysis are very effective in simulating clinical scenarios with a view to treatment optimization and outcome prediction. Unfortunately, often invoked in this analysis is the traditional, time-varying elastance concept, in which the ratio of the ventricular pressure to its volume is prescribed by a periodic function of time, instead of being calculated consistently according to the change in feedback mechanisms (e.g., the lack or breakdown of self-organization) in heart diseases. Therefore, the application of the time-varying elastance for the analysis of left ventricular assist device (LVAD)-heart interactions has been questioned. We propose a paradigm shift from the time-varying elastance concept to a synergistic model of cardiac function by integrating the mechanical, electric, and chemical activity on microscale sarcomere and macroscale heart levels and investigating the effect of an axial rotary pump on a failing heart. We show that our synergistic model works better than the time-varying elastance model in reproducing LVAD-heart interactions with sufficient accuracy to describe the left ventricular pressure-volume relation. [ABSTRACT FROM AUTHOR]

This paper considers an optimal control problem of large-scale gas supply systems. Solving this problem, we must take into account line packing in systems modeling. For unsteady-state gas flow modeling, a lumped-parameter model is proposed. On the base of this model the paper elaborates a system of ordinary differential equations to imitate unsteady-state gas flow in pipeline system of selectable configuration and provides the integration algorithm using the global gradient method. Adduced an example of calculating a circuitous gas supply system demonstrates the adequacy of the proposed model. The paper includes the mathematical formulation of a technical diagnostics problem of large pipeline system equipment in case of unsteady-state gas flow. The estimation of technical state is reduced to the constrained optimization problem. On the base of the lumped parameters model, we propose an algorithm of the solution of this problem and use it for identification of the gas supply system of selectable configuration. The numerical experiments demonstrate that the algorithm converges with good speed. The paper contains a description of an optimal control concept of large-scale pipeline system. Stated ideas can be applied in case of the system collapse. • For unsteady-state gas flow modeling a lumped-parameter model is proposed. • A method for integrating this system is recommended. • A method for estimating parameters of gas transportation system model is proposed. • A concept of large pipeline system control is described. [ABSTRACT FROM AUTHOR]

This paper addresses a simple and computationally efficient dynamic model for brushless permanent magnet (PM) motors under PM demagnetization faults. The impact of stator slots and spatial disposition of the windings are taken into account to improve the accuracy of a lumped-parameter $abc$ model. This model is suitable for tracking the dynamic behavior of fault components, as it can be accompanied by any control scheme and/or be used for model-based fault detection schemes. In addition, parameters of this model can be automatically tuned by an optimization process in the offline phase of the healthy machine. Finite-element simulations are carried out for proving the effectiveness of the proposed model. Verification is done in both time and frequency domains for four PM motors with different rotor and stator configurations. The simulation results are experimentally verified. [ABSTRACT FROM AUTHOR]

A consistent lumped-parameter model (LPM) is established to characterize the dynamic response of single and group piles in a homogeneous half-space subjected to coupled lateral-rocking vibrations. The proposed model comprises adjustable modules that can adapt to simulate a wide range of pile foundation configurations. This study utilizes a metaheuristic algorithm to solve a bicriteria optimization problem, aiming to determine both the layout and parameters of the optimal LPM. The optimal model is created to approximately reproduce the amplitude and phase angle of a soil-pile interaction (SPI) system undergoing harmonic loadings. Besides, the proposed model using frequency-independent elements allows for rapid computation of dynamic responses in the SPI system. Several analyses in the time and frequency domains validate the performance of the proposed model undergoing forced vibrations and seismic excitations. The analyzed results prove the capability and accuracy of the proposed model in approximating the dynamic responses of SPI systems. The results presented demonstrate the significant potential of the proposed model for dynamic structural analysis, particularly when accounting for structural nonlinearities in the time domain. [ABSTRACT FROM AUTHOR]

• A parameter design method based on response law of geometric parameters for the piezoelectric actuator is provided. • The lumped-parameter model effectively predicts the dynamic behavior of the PTW wingbeat system and can be validated. • A theoretical foundation for the optimization of the wing-actuator pairing in the flapping wing system is laid. Aiming at the challenge of predicting the dynamic behavior of the flapping wing in the piezoelectric-transmission-wing (PTW) wingbeat system, a lumped-parameter model coupling piezoelectric structural mechanics and flapping-wing aerodynamics is proposed to address the challenge caused by the fluid-structure interaction (FSI). Firstly, a model describing the piezoelectric mechanical response is established, which has the ability to better predict the mechanical response of the piezoelectric actuator under high electric field and low-frequency driving conditions. In order to verify the validity and accuracy, tip deflection, stiffness and blocking force experiments as well as data comparisons are performed to substantiate the findings. Secondly, a comprehensive and reasonable lumped-parameter dynamic model is constructed based on the analysis of the transmission mechanics based on pseudo-rigid-body theory and the improved aerodynamic modeling of the wing, along with the aforementioned piezoelectric mechanical modeling. Thirdly, simulation and dynamic response experiments of the wingbeat system are carried out. Results show that the simulation data are in good agreement with the experimental values, which indicates the accuracy of the model in predicting the dynamic behavior of the flapping wing powered by the piezoelectric actuator. Moreover, some interesting phenomena such as the pitch oscillation of the wing and the dependence of the flapping motion on the driving frequency have been demonstrated in the simulation and the wingbeat experiment, respectively. The research findings of this article offer three types of assistance: (1) providing a parameter design method for piezoelectric actuators to achieve the desired mechanical response; (2) predicting and explaining the dynamic behavior of the PTW wingbeat system; and (3) providing a theoretical foundation for the parameter design and optimization of the wing-actuator pairing in the flapping wing system. [Display omitted] [ABSTRACT FROM AUTHOR]

• This study proposes a brain tissue microcirculation lumped-parameter model based on computed tomography angiography to accurately calculate the change to microcirculatory perfusion within brain tissue in real time, which can quickly and accurately locate the ischemic cortical regions and is expected to replace the complex and heavily radiated computed tomography perfusion examination. • This study quantitatively studies the risk of different the circle of Willis anatomical structures in the event of stenosis of the blood-feeding artery and predicts the different brain tissue damage and neurological deficits that may result. • The model provides a reference value for early diagnosis and preoperative planning of cerebrovascular diseases, and provides a reliable reference scheme for non-invasive diagnosis of clinical cerebral ischemia with significant application value. Clinical diagnosis of ischemic stroke commonly relies on examining cerebral perfusion changes by using computed tomography perfusion (CTP) techniques. However, the radiation dose in CTP is quite higher in comparison to computed tomography angiography (CTA), with associated costs and time. Hence, this study established a lumped-parameter model (LPM) of brain tissue microcirculation (BTM) based on CTA, aiming to achieve real-time calculation of cerebral perfusion. After validation of calculated flow results with clinical data, the BTM-LPM model was used to examine the changes in cerebral perfusion following ischemic stroke, in which the effects of nine anatomical structures of the Circle of Willis (CoW) together with various distribution patterns of stenosis in the feeding arteries were considered. When compared the calculated flow results from BTM-LPM with the clinically measured data of literature, the mean squared error (MSE) value for the feeding arteries was 3.9 % and its total value for microcirculatory flow in each region was 0.1 %. Notably, the calculation time was 35.6 s. In the case of the CoW missing the left and right posterior communicating artery, a 60 % stenosis of the basilar artery is likely to cause ischemic damage to some temporal and occipital lobes of the right and left hemispheres. While in the case of the CoW missing the anterior communicating artery and the left posterior communicating artery, ischemic damage to the entire frontal lobe and parts of the temporal and parietal lobes of the left hemisphere was found when 80 % stenosis occurred in the left internal carotid artery. The BTM-LPM proposed in this study could accurately calculate cerebral perfusion in real time and demonstrated the importance of CoW anatomy in different ischemic injuries to cerebral tissue. The calculated cerebral perfusion would be a reference value for early diagnosis and preoperative planning of different ischemic injuries to cerebral tissue, thereby the BTM-LPM holds great promising for replacing CTP examination. [Display omitted] [ABSTRACT FROM AUTHOR]

The torsional vibrations of traction drive shafting system of EMU is one of key factors on heavily influence the running smoothness,safety and reliability of high-speed train. The torsional vibrations of a typical traction drive shafting system of EMU are investigated. After a concise introduction,the traction drive shafting system is simplified and equivalent to a lumped-parameters model with five moment of inertias and four torsional stiffness coefficients. Then,considering the meshing relationship of driving and driven gears,an undamped free torsional vibration equation of this lumped model is established by using direct stiffness method. At last,the natural frequency and mode shapes of this shafting system are obtained with the help of MATLAB software. On the other hand,a MATLAB/Simulink simulation model is also constructed according to above lumped-parameters model equation. And subsequently,the acceleration and displacement Bode plots of shafting system are calculated from this simulation model,these amplitude-frequency results are very useful to verify the natural frequencies obtained directly from the lumped model equation. Results show that the established lumped mass model is available to simulate the torsional vibration characteristics of traction drive shafting system,and the torsional resonance and fatigue problems may mainly happen on the driving side of shafting system. The research works are very useful for the future study on the dynamic design and optimization of traction drive shafting system of EMU.