Non-Linear Intracranial Dynamics of Shunt Siphoning

2003 ◽  
Author(s):  
Vanessa A. Capanzano ◽  
Jifeng Peng ◽  
Lili Zheng ◽  
Michael Egnor ◽  
Mark Washgul
Keyword(s):  
Cerebrospinal Fluid ◽  
Side Effects ◽  
Linear Model ◽  
Van Der Pol Oscillator ◽  
Van Der Pol ◽  
Non Linear ◽  
Negative Effect

Siphoning is commonly associated with shunts, a treatment used in patients suffering from Hydrocephalus. Siphoning is known to have a negative effect on intracranial dynamics. In this paper, a model will be developed for the intracranial dynamics in the presence of siphoning based on the assumption of pulsatile intracranial dynamics as a forced non-linear van der Pol oscillator. This non-linear model is used to simulate how various degrees of siphoning can effect intracranial dynamics and create an understanding of painful side effects, such as vascular headaches. The model suggests that vascular headaches are due to an increase in the amplitude of arterial pulsations caused by the force exerted on the cranium by siphoning rather than due to volume shifts of cerebrospinal fluid (CSF).

Suppression of limit cycle oscillations in the van der Pol oscillator by means of passive non-linear energy sinks

2006 ◽  
Vol 13 (1) ◽  
pp. 41-75 ◽  
Author(s):  
Young S. Lee ◽  
Alexander F. Vakakis ◽  
Lawrence A. Bergman ◽  
D. Michael McFarland
Keyword(s):  
Limit Cycle ◽  
Van Der Pol Oscillator ◽  
Limit Cycle Oscillations ◽  
Van Der Pol ◽  
Non Linear

scholarly journals Self- excited oscillation under the influence of non - linear frictions

1982 ◽  
Vol 4 (3) ◽  
pp. 7-10
Author(s):  
Nguyen Van Dao
Keyword(s):  
Equilibrium Position ◽  
The Self ◽  
Van Der Pol Oscillator ◽  
Van Der Pol ◽  
Excited System ◽  
Non Linear ◽  
Excited Oscillation

In this article the influence of friction R1, R2 on Van der Pol oscillator is considered. It turned out that the mentioned frictions decrease the amplitude of self – excited oscillations and they stabilize the equilibrium position of the self – excited system.

NUMERICAL SOLUTION FOR DUFFING-VAN DER POL OSCILLATOR VIA BLOCK METHOD

2020 ◽  
Vol 10 (1) ◽  
pp. 1857-8365
Author(s):  
A. F. Nurullah ◽  
M. Hassan ◽  
T. J. Wong ◽  
L. F. Koo
Keyword(s):  
Numerical Solution ◽  
Van Der Pol Oscillator ◽  
Block Method ◽  
Van Der Pol

scholarly journals Influence of the Porosity of Polymer Foams on the Performances of Capacitive Flexible Pressure Sensors

Sensors ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 1968 ◽  
Author(s):  
Sylvie Bilent ◽  
Thi Hong Nhung Dinh ◽  
Emile Martincic ◽  
Pierre-Yves Joubert
Keyword(s):  
Experimental Data ◽  
Linear Model ◽  
Dielectric Material ◽  
Pressure Sensors ◽  
Volume Ratio ◽  
Measurement Range ◽  
Polymer Foams ◽  
First Order ◽  
Non Linear ◽  
Flexible Pressure Sensors

This paper reports on the study of microporous polydimethylsiloxane (PDMS) foams as a highly deformable dielectric material used in the composition of flexible capacitive pressure sensors dedicated to wearable use. A fabrication process allowing the porosity of the foams to be adjusted was proposed and the fabricated foams were characterized. Then, elementary capacitive pressure sensors (15 × 15 mm2 square shaped electrodes) were elaborated with fabricated foams (5 mm or 10 mm thick) and were electromechanically characterized. Since the sensor responses under load are strongly non-linear, a behavioral non-linear model (first order exponential) was proposed, adjusted to the experimental data, and used to objectively estimate the sensor performances in terms of sensitivity and measurement range. The main conclusions of this study are that the porosity of the PDMS foams can be adjusted through the sugar:PDMS volume ratio and the size of sugar crystals used to fabricate the foams. Additionally, the porosity of the foams significantly modified the sensor performances. Indeed, compared to bulk PDMS sensors of the same size, the sensitivity of porous PDMS sensors could be multiplied by a factor up to 100 (the sensitivity is 0.14 %.kPa−1 for a bulk PDMS sensor and up to 13.7 %.kPa−1 for a porous PDMS sensor of the same dimensions), while the measurement range was reduced from a factor of 2 to 3 (from 594 kPa for a bulk PDMS sensor down to between 255 and 177 kPa for a PDMS foam sensor of the same dimensions, according to the porosity). This study opens the way to the design and fabrication of wearable flexible pressure sensors with adjustable performances through the control of the porosity of the fabricated PDMS foams.

Analysis of Single Buffer Random Polling System With State-Dependent Input Process and Server/Station Breakdowns

2018 ◽  
Vol 9 (1) ◽  
pp. 22-50 ◽  
Author(s):  
Thomas Y.S. Lee
Keyword(s):  
Steady State ◽  
Linear Model ◽  
Repair Process ◽  
Polling System ◽  
Steady State Analysis ◽  
Relaxation System ◽  
Polling Model ◽  
State Dependent ◽  
Non Linear ◽  
State Analysis

Models and analytical techniques are developed to evaluate the performance of two variations of single buffers (conventional and buffer relaxation system) multiple queues system. In the conventional system, each queue can have at most one customer at any time and newly arriving customers find the buffer full are lost. In the buffer relaxation system, the queue being served may have two customers, while each of the other queues may have at most one customer. Thomas Y.S. Lee developed a state-dependent non-linear model of uncertainty for analyzing a random polling system with server breakdown/repair, multi-phase service, correlated input processes, and single buffers. The state-dependent non-linear model of uncertainty introduced in this paper allows us to incorporate correlated arrival processes where the customer arrival rate depends on the location of the server and/or the server's mode of operation into the polling model. The author allows the possibility that the server is unreliable. Specifically, when the server visits a queue, Lee assumes that the system is subject to two types of failures: queue-dependent, and general. General failures are observed upon server arrival at a queue. But there are two possibilities that a queue-dependent breakdown (if occurs) can be observed; (i) is observed immediately when it occurs and (ii) is observed only at the end of the current service. In both cases, a repair process is initiated immediately after the queue-dependent breakdown is observed. The author's model allows the possibility of the server breakdowns/repair process to be non-stationary in the number of breakdowns/repairs to reflect that breakdowns/repairs or customer processing may be progressively easier or harder, or that they follow a more general learning curve. Thomas Y.S. Lee will show that his model encompasses a variety of examples. He was able to perform both transient and steady state analysis. The steady state analysis allows us to compute several performance measures including the average customer waiting time, loss probability, throughput and mean cycle time.

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