scholarly journals Several Theoretical and Applied Problems of Human Extreme Physiology: Mathematical Modeling

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Grygoryan R.D.
Keyword(s):  
Dynamic Responses ◽  
Main Function ◽  
Inertial Forces ◽  
Algebraic Equations ◽  
Biological Variables ◽  
Lumped Parameter ◽  
Cardiac Pump Function ◽  
Human Cardiovascular System ◽  
Control Of Parameters ◽  
Short Time

Human cardiovascular system (CVS) and hemodynamics are critically sensitive to essential alterations of mechanical inertial forces in directions of head-legs (+Gz) or legs-head (-Gz). Typically, such alterations appear during pilotage maneuvers of modern high maneuverable airspace vehicles (HMAV).The vulnerability of pilots or passengers of HMAV to these altering forces depends on their three main characteristics: amplitude, dynamics, and duration. Special protections, proposed to minimize this vulnerability, should be improved in parallel with the increasing of these hazardous characteristics of HMAVs. Empiric testing of novel protection methods and tools is both expensive and hazardous. Therefore computer simulations are encouraged. Autonomic software (AS) for simulating and theoretical investigating of the main dynamic responses of human CVS to altering Gz is developed. AS is based on a system of quantitative mathematical models (QMM) consisting of about 1300 differential and algebraic equations. QMM describes the dynamics of both CVS (the cardiac pump function, baroreceptor control of parameters of cardiovascular net presented by means of lumped parameter vascular compartments) and non-biological variables (inertial forces, and used protections). The main function of AS is to provide physiologist-researcher by visualizations of calculated additional data concerning characteristics of both external and internal environments under high sustained accelerations and short-time microgravity. Additionally, AS can be useful as an educational tool able to show both researchers and young pilots the main hemodynamic effects caused by accelerations and acute weightlessness with and without use of different protection tools and technics. In this case, AS does help users to optimize training process aimed to ensure optimal-like human tolerance to the altered physical environment. Main physiological events appearing under different scenarios of accelerations and microgravity have been tested.

Dynamics of the Gear Train Set in Wind Turbine

2011 ◽  
Vol 697-698 ◽  
pp. 701-705
Author(s):  
D.D. Ji ◽  
Y.M. Song ◽  
J. Zhang
Keyword(s):  
Wind Turbine ◽  
Dynamic Model ◽  
Harmonic Balance Method ◽  
Planetary Gear ◽  
Gear Train ◽  
Dynamic Responses ◽  
Multi Stage ◽  
Lumped Parameter ◽  
Cartesian Coordinate ◽  
The Impact

A lumped-parameter dynamic model for gear train set in wind turbine is proposed to investigate the dynamics of the speed-increasing gear box. The proposed model is developed in a universal Cartesian coordinate, which includes transversal and torsional deflections of each component, time-varying mesh stiffness, gear profile errors and external excitations. By solving the dynamic model, a modal analysis is performed. The results indicate that the modal properties of the multi-stage gear train in wind turbine are similar to those of a single-stage planetary gear set. A harmonic balance method (HBM) is used to obtain the dynamic responses of the gearing system. The responses give insight into the impact of excitations on the vibrations.

Nonlinear fluid damping models for hydraulic bushing under sinusoidal or transient excitation

2018 ◽  
Vol 233 (3) ◽  
pp. 595-604 ◽  
Author(s):  
Luke Fredette ◽  
Siddharth Rath ◽  
Rajendra Singh
Keyword(s):  
Dynamic Stiffness ◽  
Dynamic Responses ◽  
Model Parameters ◽  
Fluid Resistance ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Frequency Domains ◽  
Fluid Damping ◽  
Fully Developed Turbulent Flow ◽  
Linearized Model

Hydraulic bushings are typically characterized in terms of sinusoidal dynamic stiffness at lower frequencies over a range of excitation amplitudes. However, in practice they are also exposed to severe transient loads in conjunction with sinusoidal excitations. Three improved nonlinear, lumped parameter models for hydraulic bushings are developed with the goal of concurrently predicting amplitude-sensitive dynamic responses to both sinusoidal and step-like excitations using a common dynamic model with the same parameters. First, a fluid resistance element is introduced which extends previous formulations by relaxing the assumption of fully developed turbulent flow, and capturing the transition from laminar flow to turbulence. Second, a bleed orifice element between the two compliance chambers is incorporated to simulate leakage observed in laboratory testing. The sensitivity of the dynamic responses to linearized model parameters is used to guide the parameter identification procedure. Measured dynamic stiffness spectra and step-like responses provide experimental validation of the proposed formulations. The new formulations achieve improved predictions of dynamic stiffness or force using exactly the same set of model parameters at several excitation amplitudes in both time and frequency domains.

Analysis on the Dynamic Responses of the Broken Conductors in Transmission Lines

2011 ◽  
Vol 50-51 ◽  
pp. 511-515 ◽  
Author(s):  
Feng Li Yang ◽  
Jing Bo Yang
Keyword(s):  
Transmission Lines ◽  
Element Model ◽  
Dynamic Responses ◽  
Impact Loads ◽  
Safe Operation ◽  
Rayleigh Damping ◽  
Fea Model ◽  
Insulator Element ◽  
Reaction Forces ◽  
Short Time

Impact loads from the broken conductors are common for transmission lines, which can bring threaten to the safe operation of the transmission lines. Dynamic analysis of the conductors in transmission lines under broken load was carried out. A finite element model of seven span conductors in transmission line was established in general software ANSYS. The insulator and the phase spacer were considered in the FEA model. The broken load case can be realized by the birth-death element method in ANSYS. Stiffness of the broken conductor or insulator element was changed to be a near zero value in a very short time. Effect of the damping property of the conductors was considered by the Rayleigh damping method. Dynamic responses of displacements at the broken points and the reaction forces of the insulators were obtained. Dynamic responses for the broken conductors with different damping ratios and bundle numbers were compared.

scholarly journals A Novel Design and Optimization Software for Autonomous PV/Wind/Battery Hybrid Power Systems

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
Ali M. Eltamaly ◽  
Mohamed A. Mohamed
Keyword(s):  
Optimal Design ◽  
Power Systems ◽  
Computer Program ◽  
Energy System ◽  
Main Function ◽  
Hybrid Energy ◽  
Design And Optimization ◽  
Computer Simulation Program ◽  
Battery Energy ◽  
Short Time

This paper introduces a design and optimization computer simulation program for autonomous hybrid PV/wind/battery energy system. The main function of the new proposed computer program is to determine the optimum size of each component of the hybrid energy system for the lowest price of kWh generated and the best loss of load probability at highest reliability. This computer program uses the hourly wind speed, hourly radiation, and hourly load power with several numbers of wind turbine (WT) and PV module types. The proposed computer program changes the penetration ratio of wind/PV with certain increments and calculates the required size of all components and the optimum battery size to get the predefined lowest acceptable probability. This computer program has been designed in flexible fashion that is not available in market available software like HOMER and RETScreen. Actual data for Saudi sites have been used with this computer program. The data obtained have been compared with these market available software. The comparison shows the superiority of this computer program in the optimal design of the autonomous PV/wind/battery hybrid system. The proposed computer program performed the optimal design steps in very short time and with accurate results. Many valuable results can be extracted from this computer program that can help researchers and decision makers.

scholarly journals Heavy-Duty Gas Turbine Plant Aerothermodynamic Simulation Using Simulink

1996 ◽  
Author(s):  
G. Crosa ◽  
F. Pittaluga ◽  
A. Trucco Martinengo ◽  
F. Beltrami ◽  
A. Torelli ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Gas Turbine ◽  
Dynamic Responses ◽  
State Variables ◽  
Algebraic Equations ◽  
Heavy Duty ◽  
Combustion Chambers ◽  
Turbine Plant ◽  
Gas Turbine Plant ◽  
Heavy Duty Gas Turbine

This paper presents a physical simulator for predicting the off-design and dynamic behaviour of a single shaft heavy-duty gas turbine plant, suitable for gas-steam combined cycles. The mathematical model, which is non linear and based on the lumped parameter approach, is described by a set of first-order differential and algebraic equations. The plant components are described adding to their steady state characteristics the dynamic equations of mass, momentum and energy balances. The state variables are mass flow rates, static pressures, static temperatures of the fluid, wall temperatures and shaft rotational speed. The analysis has been applied to a 65 MW heavy-duty gas turbine plant with two off-board silo-type combustion chambers. To model the compressor, equipped with variable inlet guide vanes, a subdivision into five partial compressors is adopted, in serial arrangement, separated by dynamic blocks. The turbine is described using a one dimensional row by row mathematical model, that takes into account both the air bleed cooling effect and the mass storage among the stages. The simulation model considers also the air bleed transformations from the compressor down to the turbine. Both combustion chambers have been modelled utilising a sequence of several sub-volumes, to simulate primary and secondary zones in presence of three hybrid burners. A code has been created in Simulink environment. Some dynamic responses of the simulated plant, equipped with a proportional-integral speed regulator, are presented.

Mechanics Modeling of Multisegment Rod-Driven Continuum Robots

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
William S. Rone ◽  
Pinhas Ben-Tzvi
Keyword(s):  
Dynamic Models ◽  
Contact Forces ◽  
Lumped Parameter Model ◽  
Algebraic Equations ◽  
Continuum Robots ◽  
Modeling Approach ◽  
Lumped Parameter ◽  
Continuum Robot ◽  
Statics And Dynamics ◽  
Elastic Loading

This paper presents a novel modeling approach for the mechanics of multisegment, rod-driven continuum robots. This modeling approach utilizes a high-fidelity lumped parameter model that captures the variation in curvature along the robot while simultaneously defined by a discrete set of variables and utilizes the principle of virtual power to formulate the statics and dynamics of the continuum robot as a set of algebraic equations for the static model and as a set of coupled ordinary differential equations (ODEs) in time for the dynamic model. The actuation loading on the robot by the actuation rods is formulated based on the calculation of contact forces that result in rod equilibrium. Numerical optimization calculates the magnitudes of these forces, and an iterative solver simultaneously estimates the robot's friction and contact forces. In addition, modeling considerations including variable elastic loading among segments and mutual segment loading due to rods terminating at different disks are presented. The resulting static and dynamic models have been compared to dynamic finite element analyses and experimental results to validate their accuracy.

scholarly journals Individual differences in the course of youth depression: The importance of renitence and reversion

2019 ◽  
Author(s):  
Matt Hawrilenko ◽  
Katherine E. Masyn ◽  
Janine Cerutti ◽  
Erin C. Dunn
Keyword(s):  
Developmental Trajectories ◽  
Growth Mixture Modeling ◽  
Dynamic Responses ◽  
Depression Symptoms ◽  
Youth Depression ◽  
Growth Mixture ◽  
Key Factor ◽  
Environmental Events ◽  
Short Time ◽  
Time Frames

AbstractStudies of developmental trajectories of depression are important for understanding its etiology. Existing studies have been limited by short time frames and no studies have explored a key factor: differential patterns of responding to life events. This paper introduces a novel analytic technique, growth mixture modeling with structured residuals, to examine the course of youth depression symptoms in a large, prospective cohort (N=11,641, ages 4-16.5). Age-specific critical points were identified at ages 10 and 13 where depression symptoms spiked for a minority of children. However, most depression risk was due to dynamic responses to environmental events, drawn not from a small pool of persistently depressed children, but a larger pool of children who varied across higher and lower symptom levels.

Time constants for understanding building dynamics

2019 ◽  
Vol 41 (3) ◽  
pp. 234-246
Author(s):  
Geoffrey Levermore
Keyword(s):  
Time Constant ◽  
Plant Size ◽  
Dynamic Responses ◽  
Thermal Mass ◽  
Multiple Time ◽  
Time Constants ◽  
Building Components ◽  
Ventilation Strategies ◽  
Short Time ◽  
Gains And Losses

Building dynamics are key to summer overheating, plant sizing and ventilation strategies. Building designers need to consider the thermal mass of a building explicitly to understand fully a building’s response. Simulation programs readily show the dynamic responses but they are deduced from the solution of embedded intrinsic differential equations without simple understanding for initial design and appreciation. The admittance method gives such a simple understanding but the thermal mass effects are not obvious. Added to which the admittance is limited to a regular 24 h cycles of heat gains and losses. The Chartered Institution of Building Services Engineers (CIBSE) response factor is an approximation to the response of a building but it is limited to defining just slow or fast responses. Frequently, designers refer to heavyweight and lightweight buildings or even long and short time constants. The latter are simple and understandable. This paper explores the time constants and derives a simple multiple time constant equation to indicate thermal storage in a building. It is suggested that the simple time constant for building components is added to the data in the next edition of the CIBSE Guide A. This will aid designers in understanding a building’s winter heating and potential summer overheating and plant size implications.

Transient Behavior of Seated Human Body During Input From Caudophalad Acceleration

2000 ◽  
Author(s):  
Paul C. Lam ◽  
P. Ruby Mawasha ◽  
Ted Conway
Keyword(s):  
Human Body ◽  
High Speed ◽  
Transient Behavior ◽  
Lumped Parameter Model ◽  
Load Factor ◽  
Time Duration ◽  
Bodily Injury ◽  
Lumped Parameter ◽  
Ejection Process ◽  
Short Time

Abstract The objective of this study, is to investigate the dynamic transient response of a four degree-of-freedom lumped parameter model of the seated human body subjected to caudocephalad loading (acceleration from tail to head). The caudocephalad loading used in the model simulated the ejection process of a seated pilot from a high-speed aircraft. During ejection, ejection velocities are high and are developed over short distances hence, the accelerations are also high (10–40 g’s). The model indicates that even though acceleration is applied over short time duration (typically less than 0.25 seconds), serious bodily injury can result due to high dynamic load factor for the frequency range of body resonances.

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