scholarly journals Special features of short-duration processes in condensed media

2021 ◽  
Vol 2056 (1) ◽  
pp. 012031
Author(s):  
Tatyana A. Khantuleva ◽  
Victor M. Kats
Keyword(s):  
Short Duration ◽  
Dynamic Structure ◽  
Nonlocal Theory ◽  
System Response ◽  
Unstable State ◽  
Inertial Effects ◽  
Turbulent Structures ◽  
Structure Transition ◽  
Wide Range ◽  
Stationary Loading

Abstract The problem of the short-duration processes is considered on the base of the nonlocal theory of non-equilibrium transport, taking into account inertial effects. The system temporal evolution out of equilibrium connected to the dynamic structure transition described by the Speed-Gradient principle (SG-principle or SGP) developed in control theory and cybernetic physics. In the manuscript, we show that retardation of the system response to the short-duration loading due to inertial effects influences on the system evolution and can change its direction. The response to the shock loading of condensed matter is compared to quasi-stationary loading in a wide range of conditions. The short duration loading can lead the system into the structure unstable state and even give rise to self-organization of turbulent structures in the medium. The use of SGP for the modelling of such processes opens new possibilities to control them.

Large Eddy Simulations of Staggered Parallel-Plate Flows

2005 ◽  
Author(s):  
M. V. Pham ◽  
F. Plourde ◽  
S. K. Doan
Keyword(s):  
Heat Transfer ◽  
Numerical Simulations ◽  
Heat Transfer Enhancement ◽  
Parallel Plate ◽  
Large Scale ◽  
Primary Objective ◽  
Transfer Enhancement ◽  
Turbulent Structures ◽  
Wide Range ◽  
Large Eddy

Heat transfer enhancement is a subject of major concern in numerous fields of industry and research. Having received undivided attention over the years, it is still studied worldwide. Given the exponential growth of computing power, large-scale numerical simulations are growing steadily more realistic, and it is now possible to obtain accurate time-dependent solutions with far fewer preliminary assumptions about the problems. As a result, an increasingly wide range of physics is now open for exploration. More specifically, it is time to take full advantage of large eddy simulation technique so as to describe heat transfer in staggered parallel-plate flows. In fact, from simple theory through experimental results, it has been demonstrated that surface interruption enhances heat transfer. Staggered parallel-plate geometries are of great potential interest, and yet many numerical works dedicated to them have been tarnished by excessively simple assumptions. That is to say, numerical simulations have generally hypothesized lengthwise periodicity, even though flows are not periodic; moreover, the LES technique has not been employed with sufficient frequency. Actually, our primary objective is to analyze turbulent influence with regard to heat transfers in staggered parallel-plate fin geometries. In order to do so, we have developed a LES code, and numerical results are compared with regard to several grid mesh resolutions. We have focused mainly upon identification of turbulent structures and their role in heat transfer enhancement. Another key point involves the distinct roles of boundary restart and the vortex shedding mechanism on heat transfer and friction factor.

Artificial Neural Network and the Taguchi Method Application for Robust Wheatstone Bridge Design

1994 ◽  
Author(s):  
Jung-eui Hong ◽  
Cihan H. Dagli ◽  
Kenneth M. Ragsdell
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Wheatstone Bridge ◽  
Parameter Design ◽  
System Response ◽  
Measurement Circuit ◽  
Wide Range ◽  
Reduce Measurement Error ◽  
On Line ◽  
Artificial Neural

Abstract The primary function of the Wheatstone bridge is to measure an unknown resistance. The elements of this well-known measurement circuit will take on different values depending upon the range and accuracy required for a particular application. The Taguchi approach to parameter design is used to select values for the measurement circuit elements so as to reduce measurement error. Next we introduce the use of an artificial neural network to extrapolate limited experimental results to predict system response over a wide range of applications. This approach can be employed for on-line quality control of the manufacture of such device.

Evaluation of the Impact of Short Duration Music Listening on Autonomic State (Preprint)

2021 ◽  
Author(s):  
Garry Elvin ◽  
Paras Patel ◽  
Petia Sice ◽  
Chirine Riachy ◽  
Nigel Osborne ◽  
...  
Keyword(s):  
Heart Rate ◽  
Nervous System ◽  
Autonomic Nervous System ◽  
Short Duration ◽  
System Response ◽  
Time Interval ◽  
Music Listening ◽  
Autonomic Nervous ◽  
The Impact ◽  
Change In Mean

BACKGROUND Heart rate variability (HRV), or the variation in the time interval between consecutive heartbeats, is a proven measure for assessing changes in autonomic activity. An increase in variability suggests an upregulation of the parasympathetic nervous system (PNS). Music was shown to have an effect on the limbic system, respiratory rate, and blood pressure. However, there have been relatively few empirical investigations on the effect of music on HRV compared to mean heart rate (HR). Also, the majority of studies have been experimental rather than interventional, reporting significant changes in HRV as a function of musical characteristics, such as tempo, genre, and valence. OBJECTIVE The aim of this pilot study is to evaluate the impact of short duration music listening on the autonomic nervous system response of healthy adults. METHODS Six participants (three males and three females) were tested to investigate the effect of listening to music on HR and HRV. Electrocardiographic (ECG) data was recorded at a sampling rate of 1000 Hz using an eMotion Faros 360 device produced by Bittium Biosignals. The data was collected while the participants listened to four pre-selected songs in a random order separated by a relaxation period of 5 minutes. Data was then cleaned and processed through Kubious HRV 2.0 software. Statistical analysis using Wilcoxon signed rank test was carried out for the time and frequency domains. RESULTS For all but one song that is shorter than 3 minutes (song 1), we observed a statistically significant increase in Standard Deviation of the RR intervals (SDRR) (song 1: P=.125, r=.333; song 2: P=.023, r=.575; song 3: P=.014, r=.635; song 4: P=.014, r=.635) and in the Low Frequency (LF) component of the cardiac spectrogram (song 1: P=.300, r=.151; song 2: P=.038, r=.514; song 3: P=.014, r=.635; song 4: P=.014, r=.635) with a large effect size r, indicating increased HRV. No significant change in mean HR was observed (song 1: P=.173 r=-.272; song 2: P=.058, r=-.454; song 3: P=.125, r=-.333; song 4: P=.232. r=-.212). CONCLUSIONS Listening to pre-selected songs of longer duration than 3 minutes 30 seconds is associated with significant increases in HRV measures, especially SDRR and LF. Music thus has the potential to overcome autonomic nervous system (ANS) dysregulation and thereby benefit health and wellbeing.

Numerical simulation of ship propulsion transients and full-scale validation

2003 ◽  
Vol 217 (1) ◽  
pp. 41-52 ◽  
Author(s):  
U Campora ◽  
M Figari
Keyword(s):  
Full Scale ◽  
Operating Conditions ◽  
Dynamics Simulation ◽  
Normal Operation ◽  
System Response ◽  
Prime Mover ◽  
Software Environment ◽  
Simulation Code ◽  
Ship Propulsion ◽  
Wide Range

The paper describes a mathematical model for the dynamics simulation of ship propulsion systems. The model, developed in a MATLAB-SIMULINK software environment, is structured in modular form; the various elements of the system are described as individuals blocks (hull, prime mover, gear, waterjet, etc.) and linked together to take their interactions into account. In this way it is possible to characterize the dynamic behaviour of both the single component and the whole propulsion plant. The model may be used to analyse the system response at off-design and transient conditions. In particular, the developed computer simulation code may be considered as a useful tool to facilitate the correct matching of the prime mover (diesel or gas turbine) to the propulsor (waterjet or propeller) in a wide range of operating conditions. The paper shows the application of the methodology to a cruise ferry used to validate the model results through a full-scale test campaign conducted by the authors during normal operation of the ship.

scholarly journals Autonomic Nervous System Response during Light Physical Activity in Adolescents with Anorexia Nervosa Measured by Wearable Devices

Sensors ◽  
2019 ◽  
Vol 19 (12) ◽  
pp. 2820 ◽  
Author(s):  
Lucia Billeci ◽  
Alessandro Tonacci ◽  
Elena Brunori ◽  
Rossella Raso ◽  
Sara Calderoni ◽  
...  
Keyword(s):  
Physical Activity ◽  
Heart Rate ◽  
Nervous System ◽  
Anorexia Nervosa ◽  
Autonomic Nervous System ◽  
System Response ◽  
Light Physical Activity ◽  
Autonomic Nervous ◽  
Wide Range ◽  
Low Energy Availability

Anorexia nervosa (AN) is associated with a wide range of disturbances of the autonomic nervous system. The aim of the present study was to monitor the heart rate (HR) and the heart rate variability (HRV) during light physical activity in a group of adolescent girls with AN and in age-matched controls using a wearable, minimally obtrusive device. For the study, we enrolled a sample of 23 adolescents with AN and 17 controls. After performing a 12-lead electrocardiogram and echocardiography, we used a wearable device to record a one-lead electrocardiogram for 5 min at baseline for 5 min during light physical exercise (Task) and for 5 min during recovery. From the recording, we extracted HR and HRV indices. Among subjects with AN, the HR increased at task and decreased at recovery, whereas among controls it did not change between the test phases. HRV features showed a different trend between the two groups, with an increased low-to-high frequency ratio (LF/HF) in the AN group due to increased LF and decreased HF, differently from controls that, otherwise, slightly increased their standard deviation of NN intervals (SDNN) and the root mean square of successive differences (RMSSD). The response in the AN group during the task as compared to that of healthy adolescents suggests a possible sympathetic activation or parasympathetic withdrawal, differently from controls. This result could be related to the low energy availability associated to the excessive loss of fat and lean mass in subjects with AN, that could drive to autonomic imbalance even during light physical activity.

System Dynamic Modeling of Vapor Compression Cycles

2012 ◽  
Author(s):  
Eric S. Miller ◽  
Soumya S. Patnaik ◽  
Milind A. Jog
Keyword(s):  
Thermal Management ◽  
Dynamic Behavior ◽  
Lagrangian Method ◽  
System Response ◽  
Vapor Compression ◽  
Wide Range ◽  
Compression Cycle ◽  
Cycle Systems ◽  
Component Models ◽  
And Control

Vapor Compression cycle Systems (VCSs) are being considered for thermal management aboard modern aircraft where dynamic changes in heat loads are very common. Predicting dynamic behavior of VCSs is critical to design, sizing, and control of aircraft thermal management systems. A novel Lagrangian method to model the dynamic behavior of VCSs has been developed. This approach divides each fluid flow into a large number of elements having fixed mass, but variable volume and position. At discrete time steps, heat transferred to or from each mass element is determined by component models. This paper gives simulation results showing system startup under PID feedback control. Then, from steady state, the system response to an increase in heat load, an increase in sink availability, a decrease in valve throttle and an increase in compressor speed are simulated and the results reported. Results indicate that the Lagrangian method can provide results for a wide range of cases and that VCC systems require extensive control to meet performance objectives.

Compensator Design for a MEMS Gyroscope With Quadratic Optimal Control

2010 ◽  
Author(s):  
Wei Cui ◽  
Wei Xue ◽  
Xiaolin Chen
Keyword(s):  
Dynamic Range ◽  
Linear Quadratic Regulator ◽  
Control Algorithms ◽  
System Response ◽  
Linear Quadratic ◽  
Control Effort ◽  
Mems Gyroscope ◽  
Compensator Design ◽  
Wide Range ◽  
Parameter Perturbations

A number of control algorithms have been reported to adopt force balancing scheme into MEMS vibratory gyroscope systems. In practice, however, many algorithms are difficult to implement with electronic circuits. This paper designs and analyzes a lead compensator for a MEMS gyroscope via the Linear Quadratic Regulator (LQR) technique. LQR optimizes and balances the control effort and system response swiftness. Simulation shows the gyroscope achieves high linearity, wide dynamic range, and high robustness to fabrication uncertainties with this efficient compensator design. The closed-loop scale factor uniformity error is 0.7% under ±10% parameter perturbations. The compensator designed in this paper exhibits comparable outstanding performance compared to other reported control algorithms. The method reported in this paper is proved to be effective and can be used in a wide range of applications.

The Effect of Gravity and Rotor Configuration on Dry Friction Whip and Safe Rotor/Stator Clearance

2019 ◽  
Author(s):  
Rajiv Kumar Vashisht
Keyword(s):  
Mathematical Model ◽  
Fault Diagnosis ◽  
Dry Friction ◽  
Rotating Machinery ◽  
Degree Of Freedom ◽  
System Response ◽  
Rich Variety ◽  
Wide Range ◽  
Clearance Level ◽  
High Degree

Abstract A mathematical model is developed for a real rotor/stator system with high degrees-of-freedoms, multiple disks, flexible bearing supports and couplings. The safe clearance level for coasting up of the rotor is calculated for a general high degree-of-freedom rotor/stator system. The harmful phenomena of dry friction whip, which is generally observable for simple 2 degree-of-freedom Jeffcott rotors in the absence of gravity only, can be proved to exist (in real rotor/stator systems) even in the presence of gravity for a wide range of clearance levels. In case of Jeffcott rotors, by fixing the clearance and increasing the rotor spin frequency, the response of the system follows the pattern: No rub - Forward Annular Rub (FAR) - Partial Forward Whirl (PFW) - Partial Backward Whirl (PBW) - dry whip (WHIP). In case of a real rotor/stator system, at certain frequencies, the system directly jumps to dry whip. The simulated results show a rich variety of system dynamics including FAR, PFW and WHIP in case of vertical rotors where the effect of gravity is neglected. For horizontal rotors, under the effect of gravity, the system response contains multi-harmonics, chaotic responses and multi-period vibrations. Based on these responses, a robust fault diagnosis strategy can be designed to identify the rubbing action in rotating machinery.

Direct Numerical Simulation of a Turbulent Flow on an Oscillating Wall Using Cut-Cell Based Immersed Boundary Method

2016 ◽  
Author(s):  
Chiaki Kino
Keyword(s):  
Turbulent Flow ◽  
Nuclear Power ◽  
Power Plants ◽  
Separated Flow ◽  
Immersed Boundary ◽  
Turbulent Structures ◽  
Flow Induced Vibration ◽  
Production Term ◽  
Large Eddy Simulation Model ◽  
Wide Range

The flow-induced vibration of a pipe is an important issue in various engineering fields, and this phenomenon is widely observed in nuclear power plants. Although turbulent structures play important roles in the velocity and pressure fields in a pipe, only a few studies have been conducted on the turbulent flow on an oscillating wall. In this study, direct numerical simulations were conducted to establish a large eddy simulation model for a turbulent flow on an oscillating wall and scrutinize the energy transfer between the grid scale (GS) and sub-grid scale (SGS). Although energy is generally transferred from the GS to SGS (forward scatter), it is likely that energy is transferred from the SGS to GS (backward scatter) under specific conditions. The present numerical results indicated that backward scatter exists in the production term in the case of a static wavy wall. On the other hand, such backward scatter could not be observed in the case of an oscillating wall. It is well known that separated flows and backward flows are generated behind the crest. Stronger backward flows accelerate the main flow and enhance the velocity gradients in a wide range behind the crest. In the case of an oscillating wall, the development of separated flow is immature because the shape of the wall is not fixed. Eventually, the backward scatter is deemed to be suppressed.

Sound-Induced Motion of a Nanoscale Fiber

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
R. N. Miles ◽  
J. Zhou
Keyword(s):  
Particle Motion ◽  
Surrounding Medium ◽  
System Response ◽  
Acoustic Excitation ◽  
Mechanical Motion ◽  
Thin Fiber ◽  
Reasonable Approximation ◽  
Wide Range ◽  
Resonant Behavior ◽  
Induced Motion

An analysis is presented of the motion of a thin fiber, supported on each end, due to a sound wave that propagates in the direction perpendicular to its long axis. Predicted and measured results indicate that when fibers or hairs having a diameter measurably less than 1 μm are subjected to air-borne acoustic excitation, their motion can be a very reasonable approximation to that of the acoustic particle motion at frequencies spanning the audible range. For much of the audible range of frequencies resonant behavior due to reflections from the supports tends to be heavily damped so that the details of the boundary conditions do not play a significant role in determining the overall system response. Thin fibers are thus constrained to simply move with the surrounding medium. These results suggest that if the diameter or radius is chosen to be sufficiently small, incorporating a suitable transduction scheme to convert its mechanical motion into an electronic signal could lead to a sound sensor that very closely depicts the acoustic particle motion over a wide range of frequencies.

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