Static and Dynamic Bending Responses of the Human Cervical Spine

1998 ◽  
Vol 120 (6) ◽  
pp. 693-696 ◽  
Author(s):  
L. M. Voo ◽  
F. A. Pintar ◽  
N. Yoganandan ◽  
Y. K. Liu
Keyword(s):  
Cervical Spine ◽  
High Speed ◽  
Dynamic Stiffness ◽  
Bending Moment ◽  
Dynamic Tests ◽  
Validation Data ◽  
Static Tests ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Dynamic Bending

The quasi-static and dynamic bending responses of the human mid-lower cervical spine were determined using cadaver intervertebral joints fixed at the base to a six-axis load cell. Flexion bending moment was applied to the superior end of the specimen using an electrohydraulic piston. Each specimen was tested under three cycles of quasi-static load-unload and one high-speed dynamic load. A total of five specimens were included in this study. The maximum intervertebral rotation ranged from 11.0 to 15.4 deg for quasi-static tests and from 22.9 to 34.4 deg for dynamic tests. The resulting peak moments at the center of the intervertebral joint ranged from 3.8 to 6.9 Nm for quasi-static tests and from 14.0 to 31.8 Nm for dynamic tests. The quasi-static stiffness ranged from 0.80 to 1.35 Nm/deg with a mean of 1.03 Nm/deg (±0.11 Nm/deg). The dynamic stiffness ranged from 1.08 to 2.00 Nm/deg with a mean of 1.50 Nm/deg (±0.17 Nm/deg). The differences between the two stiffnesses were statistically significant (p < 0.01). Exponential functions were derived to describe the quasi-static and dynamic moment-rotation responses. These results provide input data for lumped-parameter models and validation data for finite element models to better investigate the biomechanics of the human cervical spine.

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.

scholarly journals An Automated Real-Time Localization System in Highway and Tunnel Using UWB DL-TDoA Technology

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Long Wen ◽  
Jinkun Han ◽  
Liangliang Song ◽  
Qi Zhang ◽  
Kai Li ◽  
...  
Keyword(s):  
Real Time ◽  
High Speed ◽  
Signal Propagation ◽  
Time Difference ◽  
Base Stations ◽  
Ultra Wideband ◽  
Shielding Effect ◽  
Dynamic Tests ◽  
Static Tests ◽  
Localization System

There exists an electromagnetic shielding effect on radio signals in a tunnel, which results in no satellite positioning signal in the tunnel scenario. Moreover, because vehicles always drive at a high speed on the highway, the real-time localization system (RTLS) has a bottleneck in a highway scenario. Thus, the navigation and positioning service in tunnel and highway is an important technology difficulty in the construction of a smart transportation system. In this paper, a new technology combined downlink time difference of arrival (DL-TDoA) is proposed to realize precise and automated RTLS in tunnel and highway scenarios. The DL-TDoA inherits ultra-wideband (UWB) technology to measure the time difference of radio signal propagation between the location tag and four different location base stations, to obtain the distance differences between the location tag and four groups of location base stations. The proposed solution achieves a higher positioning efficiency and positioning capacity to achieve dynamic RTLS. The DL-TDoA technology based on UWB has several advantages in precise positioning and navigation, such as positioning accuracy, security, anti-interference, and power consumption. In the final experiments on both static and dynamic tests, DL-TDoA represents high accuracy and the mean errors of 11.96 cm, 37.11 cm, 50.06 cm, and 87.03 cm in the scenarios of static tests and 30 km/h, 60 km/h, and 80 km/h in dynamic tests, respectively, which satisfy the requirements of RTLS.

Piercing of Cylindrical Tubes

1981 ◽  
Vol 103 (3) ◽  
pp. 255-260 ◽  
Author(s):  
W. Johnson ◽  
S. R. Reid ◽  
S. K. Ghosh
Keyword(s):  
High Speed ◽  
Tube Length ◽  
Dynamic Tests ◽  
Central Section ◽  
Penetration Process ◽  
Static Tests ◽  
Modes Of Failure ◽  
Sequence Of Events ◽  
Punch Load ◽  
Cylindrical Tubes

Experiments are described in which cylindrical tubes were perforated normally at their central section. Quasi-static tests were performed using mainly square-section punches possessing pointed pyramidal heads of semi-angle 30 deg, the tubes being supported along their support generator. The dynamic tests comprised high-speed penetration of tubes using conically headed cylindrical projectiles. The equipment and experimental procedures are briefly described and results are presented showing typical punch load-penetration curves, the variation of punch load with tube length and that of a nondimensional characteristic punch load (defined later) with length-to-diameter ratio of the tubes. Typical specimens and the sequence of events during the course of a penetration process are also illustrated. The characteristics of petalling and plugging modes of failure together with those effects which are specifically dynamic in character are reported.

Analytical Coupled Modeling and Model Validation of Hydraulic On/Off Valves

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
John Mahrenholz ◽  
John Lumkes
Keyword(s):  
High Speed ◽  
Eddy Currents ◽  
Hydraulic Systems ◽  
Coupled Modeling ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Fluid Transients ◽  
Pressure Ripple ◽  
Valve Dynamics ◽  
Fully Coupled

The goal of this paper is to describe a method for modeling high speed on/off valves. This model focuses on the nonlinearities of the electromagnetic, fluidic, and mechanical domains, specifically within solenoid driven poppet style valves. By including these nonlinearities, the model accurately predicts valve transition time for different driving voltages and valve strokes. The model also predicts fluid transients such as pressure ripple. Unique attributes of the model are the inclusion of the effect of eddy currents and fringing while still being fully coupled with the fluid and mechanical domains. A prototype was constructed and used to experimentally validate the model. By developing accurate lumped parameter models, valve dynamics can be applied to hydraulic systems to accurately capture their dynamics.

Dynamic Axial Compression of Square CFRP/Aluminium Tubes

2019 ◽  
Vol 794 ◽  
pp. 202-207
Author(s):  
Rafea Dakhil Hussein ◽  
Dong Ruan ◽  
Guo Xing Lu ◽  
Jeong Whan Yoon ◽  
Zhan Yuan Gao
Keyword(s):  
Energy Absorption ◽  
Specific Energy ◽  
Fibre Composite ◽  
Dynamic Tests ◽  
Carbon Fibre Composite ◽  
Specific Energy Absorption ◽  
Static Tests ◽  
Crushing Force ◽  
Cfrp Tubes ◽  
The Impact

Carbon fibre composite tubes have high strength to weight ratios and outstanding performance under axial crushing. In this paper, square CFRP tubes and aluminium sheet-wrapped CFRP tubes were impacted by a drop mass to investigate the effect of loading velocity on the energy absorption of CFRP/aluminium tubes. A comparison of the quasi-static and dynamic crushing behaviours of tubes was made in terms of deformation mode, peak crushing force, mean crushing force, energy absorption and specific energy absorption. The influence of the number of aluminium layers that wrapped square CFRP tubes on the crushing performance of tubes under axial impact was also examined. Experimental results manifested similar deformation modes of tubes in both quasi-static and dynamic tests. The dynamic peak crushing force was higher than the quasi-static counterpart, while mean crushing force, energy absorption and specific energy absorption were lower in dynamic tests than those in quasi-static tests. The mean crushing force and energy absorption decreased with the crushing velocity and increased with the number of aluminium layers. The impact stroke (when the force starts to drop) decreased with the number of aluminium layers.

scholarly journals Analysis of the dynamic characteristics of downsized aerostatic thrust bearings with different pressure equalizing grooves at high or ultra-high speed

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110180
Author(s):  
Ruzhong Yan ◽  
Haojie Zhang
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Rotation Speed ◽  
Dynamic Stiffness ◽  
Simulation Method ◽  
Perturbation Amplitude ◽  
Thrust Bearings ◽  
Supply Pressure ◽  
Ultra High Speed ◽  
Air Film

This study adopts the DMT(dynamic mesh technology) and UDF(user defined functions) co-simulation method to study the dynamic characteristics of aerostatic thrust bearings with equalizing grooves and compare with the bearing without equalizing groove under high speed or ultra high speed for the first time. The effects of air film thicness, supply pressure, rotation speed, perturbation amplitude, perturbation frequency, and cross section of the groove on performance characteristics of aerostatic thrust bearing are thoroughly investigated. The results show that the dynamic stiffiness and damping coefficient of the bearing with triangular or trapezoidal groove have obvious advantages by comparing with that of the bearing without groove or with rectangular groove for the most range of air film thickness, supply pressure, rotation speed, perturbation amplitude, especially in the case of high frequency, which may be due to the superposition of secondary throttling effect and air compressible effect. While the growth range of dynamic stiffness decreases in the case of high or ultra-high rotation speed, which may be because the Bernoulli effect started to appear. The perturbation amplitude only has little influence on the dynamic characteristic when it is small, but with the increase of perturbation amplitude, the influence becomes more obvious and complex, especially for downsized aerostatic bearing.

H∞Control for PMLSM Suspension Platform Based on PDFF

2011 ◽  
Vol 383-390 ◽  
pp. 6886-6892
Author(s):  
Jia Kuan Xia ◽  
Yi Na Wang ◽  
Yi Biao Sun
Keyword(s):  
Feedback Linearization ◽  
High Speed ◽  
Normal Force ◽  
Dynamic Stiffness ◽  
Linearization Method ◽  
Dynamic Decoupling ◽  
Fast Tracking ◽  
Speed Controller ◽  
Simulation Results ◽  
Proportional Controller

Permanent magnet linear synchronous motor (PMLSM) suspension system has the merits of no friction, high-speed, high response and so on, using the normal force achieve the mover suspension. The servo performance is affected by the nonlinear coupling between the horizontal trust and vertical normal force, parameters uncertainties and load disturbances. The feedback linearization method is used to achieve the dynamic decoupling of the PMLSM suspicion system and decoupling it Into two linear subsystems; to solve the conflict between disturbance restraint and fast tracking performance, increase the robustness and dynamic stiffness for system, H∞ speed controller based on PDFF and position proportional controller are designed. Simulation results show that the proposed control strategy guarantees the high speed and high precision positioning performance for horizontal axis; the good rigidity and stability for normal suspension length and the strong robustness against load disturbances and parameters variations for the two axes.

Lumped parameter models for two-ventricle and healthy and failing extracardiac Fontan circulations

2021 ◽  
Author(s):  
Matthew G Doyle ◽  
Marina Chugunova ◽  
S Lucy Roche ◽  
James P Keener
Keyword(s):  
Single Ventricle ◽  
Left Ventricular ◽  
Sensitivity Analyses ◽  
Surgical Strategies ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Fontan Failure ◽  
Existence Of Periodic Solutions ◽  
Mathematical Definitions ◽  
Extracardiac Fontan

Abstract Fontan circulations are surgical strategies to treat infants born with single ventricle physiology. Clinical and mathematical definitions of Fontan failure are lacking, and understanding is needed of parameters indicative of declining physiologies. Our objective is to develop lumped parameter models of two-ventricle and single-ventricle circulations. These models, their mathematical formulations and a proof of existence of periodic solutions are presented. Sensitivity analyses are performed to identify key parameters. Systemic venous and systolic left ventricular compliances and systemic capillary and pulmonary venous resistances are identified as key parameters. Our models serve as a framework to study the differences between two-ventricle and single-ventricle physiologies and healthy and failing Fontan circulations.

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