STABILITY ANALYSIS IN PATIENTS WITH NEUROLOGICAL AND MUSCULOSKELETAL DISORDERS USING LINEAR AND NON-LINEAR APPROACHES

2015 ◽  
Vol 15 (04) ◽  
pp. 1530004
Author(s):  
MOHAMMAD KARIMI ◽  
MEISSAM SADEGHISANI ◽  
ABDUL HAFIDZ HAJI OMAR ◽  
EHSAN KOUCHAKI ◽  
MINA MIRAHMADI ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Musculoskeletal Disorders ◽  
Center Of Pressure ◽  
Linear Method ◽  
Approximate Entropy ◽  
Normal Subjects ◽  
Stability Parameters ◽  
Non Linear ◽  
The Difference ◽  
The Stability

Standing stability is controlled by musculoskeletal and neurological systems. Various methods have been used to evaluate the performance of subjects during standing including linear and non-linear methods. It is not clear which method has more sensitivity to represent the stability of subjects with various musculoskeletal disorders. Therefore, the aim of this study was to investigate the stability of the subjects with various musculoskeletal disorders by use of linear and non-linear methods. About 65 subjects including, normal and those with flatfoot, Parkinson and Perthes were recruited into this study. A Kistler forceplate was used to evaluate the stability. The difference between the linear (center of pressure excursion, velocity and path length) and non-linear (approximate entropy) parameters were evaluated using the independent t-test. The mean values of stability parameters (linear and non-linear) of flat arch subjects were more than that of normal subjects. Although there was no difference between linear stability parameters of normal and those with Parkinson disease, their mean value of non-linear parameter was less than that of normal subject (p-< 0.05). The results of stability analysis based on both linear and non-linear approaches showed that the subjects with Perthes disease were more unstable than normal subjects. It seems that non-linear method is more sensitive to represent the difference between stability of subjects with flatfoot, Parkinson and Perthes. However, if a combination of various parameters, based on linear method, is used to measure stability, the difference between stability can be enhanced. Depending on the disease condition increasing and decreasing the value of approximate entropy represent the unstability situations.

Non-linear stability analysis of micropolar fluid lubricated journal bearings with turbulent effect

2019 ◽  
Vol 71 (1) ◽  
pp. 31-39
Author(s):  
Subrata Das ◽  
Sisir Kumar Guha
Keyword(s):  
Stability Analysis ◽  
Linear Stability ◽  
Micropolar Fluid ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Turbulent Regime ◽  
Content Type ◽  
Non Linear ◽  
The Stability ◽  
Bearing System

Purpose The purpose of this paper is to investigate the effect of turbulence on the stability characteristics of finite hydrodynamic journal bearing lubricated with micropolar fluid. Design/methodology/approach The non-dimensional transient Reynolds equation has been solved to obtain the non-dimensional pressure field which in turn used to obtain the load carrying capacity of the bearing. The second-order equations of motion applicable for journal bearing system have been solved using fourth-order Runge–Kutta method to obtain the stability characteristics. Findings It has been observed that turbulence has adverse effect on stability and the whirl ratio at laminar flow condition has the lowest value. Practical implications The paper provides the stability characteristics of the finite journal bearing lubricated with micropolar fluid operating in turbulent regime which is very common in practical applications. Originality/value Non-linear stability analysis of micropolar fluid lubricated journal bearing operating in turbulent regime has not been reported in literatures so far. This paper is an effort to address the problem of non-linear stability of journal bearings under micropolar lubrication with turbulent effect. The results obtained provide useful information for designing the journal bearing system for high speed applications.

A Dynamical Model for Studying the Stability of Thermo-Solutal Convection Under the Effect of Vertical Vibration

2005 ◽  
Author(s):  
Y. P. Razi ◽  
M. Mojtabi ◽  
K. Maliwan ◽  
M. C. Charrier-Mojtabi ◽  
A. Mojtabi
Keyword(s):  
Stability Analysis ◽  
Mechanical Vibration ◽  
Stability Limit ◽  
Lewis Number ◽  
Vertical Vibration ◽  
Wave Number ◽  
Dimensionless Wave Number ◽  
Non Linear ◽  
Linear Differential ◽  
The Stability

This paper concerns the thermal stability analysis of porous layer saturated by a binary fluid under the influence of mechanical vibration. The linear stability analysis of this thermal system leads us to study the following damped coupled Mathieu equations: BH¨+B(π2+k2)+1H˙+(π2+k2)−k2k2+π2RaT(1+Rsinω*t*)H=k2k2+π2(NRaT)(1+Rsinω*t*)Fε*BF¨+Bπ2+k2Le+ε*F˙+π2+k2Le−k2k2+π2NRaT(1+Rsinω*t*)F=k2k2+π2RaT(1+Rsinω*t*)H where RaT is thermal Rayleigh number, R is acceleration ratio (bω2/g), Le is the Lewis number, k is the dimensionless wave-number, ε* is normalized porosity and N is the buoyancy ratio (H and F are perturbations of temperature and concentration fields). In the follow up, the non-linear behavior of the problem is studied via a generalization of the Lorenz model (five coupled non-linear differential equations with periodic coefficients). In the presence or absence of gravity, the stability limit for the onset of stationary as well as Hopf bifurcations is determined.

THE EFFECTS OF DRESS SHOES ON STABILITY DURING QUIET STANDING AND ENERGY CONSUMPTION WHILE WALKING

2012 ◽  
Vol 12 (05) ◽  
pp. 1250029
Author(s):  
SAED MOHSEN MIRBOD ◽  
MOHAMMAD TAGHI KARIMI ◽  
A. ESHRAGHI
Keyword(s):  
Energy Consumption ◽  
Center Of Pressure ◽  
Force Plate ◽  
Normal Subjects ◽  
Quiet Standing ◽  
P Value ◽  
Cost Index ◽  
Mean Values ◽  
Physiological Cost ◽  
The Stability

Footwear is an extremely important clothing item worn by all individuals. Currently, there is insufficient research regarding the influence of dress shoes on standing stability and energy consumption while walking. Therefore, the aim of this study was to evaluate the influence of dress shoes on the performance of normal subjects based on stability and energy consumption analysis. Fifteen normal subjects were recruited in this research study to stand and walk with and without shoes. The stability of the subjects in quiet standing was measured by the use of a force plate based on center of pressure (COP) sway. The energy consumption was evaluated by a heart rate monitoring system (Polar Electro) based on the physiological cost index (PCI). The mean values of PCI while walking with and without shoes were 0.29 ± 0.117 and 0.265 ± 0.112 beats/m, respectively (p-value > 0.05). The amplitudes of COP sways in the mediolateral and anteroposterior directions were 10.4 ± 3.5 and 25 ± 6.92 mm while standing with shoes and 9.3 ± 2.84 and 22.5 ± 5.25 mm in barefoot standing, respectively (p-value > 0.05). It can be concluded that wearing dress shoes does not influence the performance of subjects while standing or walking.

Non-Linear Transient Stability Analysis of a Rigid Rotor Supported on Journal Bearings With Rectangular Dimples

2015 ◽  
Author(s):  
Ram Turaga
Keyword(s):  
Stability Analysis ◽  
Surface Texture ◽  
Transient Stability ◽  
Equations Of Motion ◽  
Journal Bearings ◽  
Pressure Curve ◽  
Rigid Rotor ◽  
Non Linear ◽  
The Stability ◽  
Transient Stability Analysis

The influence of deterministic surface texture on the sub-synchronous whirl stability of a rigid rotor has been studied. Non-linear transient stability analysis has been performed to study the stability of a rigid rotor supported on two symmetric journal bearings with a rectangular dimple of large aspect ratio. The surface texture parameters considered are dimple depth to minimum film thickness ratio and the location of the dimple on the bearing surface. Journal bearings of different Length to diameter ratios have been studied. The governing Reynolds equation for finite journal bearings with incompressible fluid has been solved using the Finite Element Method under isothermal conditions. The trajectories of the journal center have been obtained by solving the equations of motion of the journal center by the fourth-order Runge-Kutta method. When the dimple is located in the raising part of the pressure curve the positive rectangular dimple is seen to decrease the stability whereas the negative rectangular dimple is seen to improve the stability of the rigid rotor.

The Analysis of the Systems Stability of Linear Differential Equations Based on the Transformation of Difference Schemes

2019 ◽  
Vol 20 (9) ◽  
pp. 542-549 ◽  
Author(s):  
S. G. Bulanov
Keyword(s):  
Stability Analysis ◽  
Asymptotic Stability ◽  
Differential Equations ◽  
Ordinary Differential Equations ◽  
Computer Analysis ◽  
Linear Differential Equations ◽  
System Stability ◽  
The Difference ◽  
Linear Differential ◽  
The Stability

The approach to the analysis of Lyapunov systems stability of linear ordinary differential equations based on multiplicative transformations of difference schemes of numerical integration is presented. As a result of transformations, the stability criteria in the form of necessary and sufficient conditions are formed. The criteria are invariant with respect to the right side of the system and do not require its transformation with respect to the difference scheme, the length of the gap and the step of the solution. A distinctive feature of the criteria is that they do not use the methods of the qualitative theory of differential equations. In particular, for the case of systems with a constant matrix of the coefficients it is not necessary to construct a characteristic polynomial and estimate the values of the characteristic numbers. When analyzing the system stability with variable matrix coefficients, it is not necessary to calculate the characteristic indicators. The varieties of criteria in an additive form are obtained, the stability analysis based on them being equivalent to the stability assessment based on the criteria in a multiplicative form. Under the conditions of a linear system stability (asymptotic stability) of differential equations, the criteria of the systems stability (asymptotic stability) of linear differential equations with a nonlinear additive are obtained. For the systems of nonlinear ordinary differential equations the scheme of stability analysis based on linearization is presented, which is directly related to the solution under study. The scheme is constructed under the assumption that the solution stability of the system of a general form is equivalent to the stability of the linearized system in a sufficiently small neighborhood of the perturbation of the initial data. The matrix form of the criteria allows implementing them in the form of a cyclic program. The computer analysis is performed in real time and allows coming to an unambiguous conclusion about the nature of the system stability under study. On the basis of a numerical experiment, the acceptable range of the step variation of the difference method and the interval length of the difference solution within the boundaries of the reliability of the stability analysis is established. The approach based on the computer analysis of the systems stability of linear differential equations is rendered. Computer testing has shown the feasibility of using this approach in practice.

scholarly journals Pengaruh Biopolimer Pada Stabilitas Lereng Swelling soil

2021 ◽  
Vol 5 (3) ◽  
pp. 307-316
Author(s):  
Dewi Amalia ◽  
Bagus Guritno ◽  
Geni Firuliadhim
Keyword(s):  
Stability Analysis ◽  
Slope Stability ◽  
Safety Factor ◽  
Soil Type ◽  
Analysis Program ◽  
Swelling Soil ◽  
The Difference ◽  
The Stability ◽  
Cracked Soil

Many studies have begun to develop the concept of cracked soil. The results of research related to cracked soil are able to answer the irregularities that occur, such as the difference in the results of the stability analysis which is considered safe with the conventional bishop method, while the conditions in the field are landslides. Swelling soil is soil that is susceptible to changes in water content. This type of soil is very prone to cracking. To build infrastructure on the swelling soil type, an improvement must be made, one of which is by mixing the swelling soil with biopolymer. The results of this biopolymer mixing are then modeled in the New Slope Stability Analysis Program (NSSAP) 1.0 which refers to the concept of cracked soil. From the analysis, it was found that the slope safety factor before improvement with biopolymer was 0.305 and the safety factor after improvement with biopolymer was 2.006. From the results of this study, it can be seen that the role of biopolymers in stabilizing swelling soil is quite large, which is around 558%.

On the Sensitivity of Non-Generic Bifurcation of Non-Linear Normal Modes

2007 ◽  
Author(s):  
C. H. Pak ◽  
Y. S. Choi
Keyword(s):  
Normal Mode ◽  
Natural Frequencies ◽  
Normal Modes ◽  
New Normal ◽  
Perturbed System ◽  
Saddle Node ◽  
Non Linear ◽  
The Difference ◽  
Generic Bifurcation ◽  
The Stability

It is shown that a non-generic bifurcation of non-linear normal modes may occur if the ratio of linear natural frequencies is near r-to-one, r = 1, 3, 5 ·······. Non-generic bifurcations are explicitly obtained in the systems having certain symmetry, as observed frequently in literatures. It is found that there are two kinds of non-generic bifurcations, super-critical and sub-critical. The normal mode generated by the former kind is extended to large amplitude, but that by the latter kind is limited to small amplitude which depends on the difference between two linear natural frequencies and disappears when two frequencies are equal. Since a non-generic bifurcation is not generic, it is expected generically that if a system having a non-generic bifurcation is perturbed then the non-generic bifurcation disappears and generic bifurcation appear in the perturbed system. Examples are given to verify the change in bifurcations and to obtain the stability behavior of normal modes. It is found that if a system having a super-critical non-generic bifurcation is perturbed, then two new normal modes are generated, one is stable, but the other unstable, implying a saddle-node bifurcation. If the system having a sub-critical non-generic bifurcation is perturbed, then no new normal mode is generated, but there is an interval of instability on a normal mode, implying two saddle-node bifurcations on the mode. Application of this study is discussed.

Evaluation of the Stability of the Subjects with Anterior Cruciate Injuries Reconstruction

2020 ◽  
Author(s):  
Hossein Akbari Aghdam ◽  
Mahsa Kavyani ◽  
Maryam Bosak ◽  
Mohammad Taghi Karimi ◽  
Mehdi Motififard
Keyword(s):  
Acl Reconstruction ◽  
Postural Stability ◽  
Center Of Pressure ◽  
Mean Value ◽  
P Value ◽  
Before And After ◽  
The Mean ◽  
The Difference ◽  
Anterior Cruciate ◽  
The Stability

AbstractAnterior cruciate ligament (ACL) is the most frequently injured ligament in the knee and is often injured during sport-related activities. ACL injuries influence the abilities of the subjects during standing and walking. Although early surgical intervention is preferred treatment for the majority of knee surgeons, the effect of this approach on postural stability of patients is not fully understood. Therefore, the aim of this study was to determine the difference between stability of ACL-reconstructed subjects before and after surgery. A group of 15 consecutive ACL injured patients participated in this study. Postural stability of the patients was evaluated 1 week before and 6 months after surgery (ACL reconstruction with hamstring autograft). A Kistler force plate was used to evaluate center of pressure (COP) sway during quiet standing. The mean values of the COP parameters were obtained in pre and postsurgery conditions. Paired sample t-test was used to evaluate the difference between the stability parameters of the two conditions. The significant point was set at 0.05. The mean value of path length of COP velocity in mediolateral (ML) direction was 1,485.57 ± 479.42 mm and 2,641.33 ± 996.26 mm before and after surgery, respectively (p-value = 0.01). Although the mean value of COP velocity in anteroposterior and ML directions increased after surgery, the difference was only significant for velocity in ML direction (p-value = 0.049). The results of this study showed that the standing stability of those with ACL reconstruction decreased significantly after ACL reconstruction, which may be due to the effects of the surgery on sensory mechanism of ACL and inability of patients to return to their previous deep sense perception and knee proprioception.

Stability Analysis of Unloading Slope by Interface Element Method

2012 ◽  
Vol 226-228 ◽  
pp. 1462-1466 ◽  
Author(s):  
Ying Xue Sun ◽  
Song Chen ◽  
Shuai Ran Cheng
Keyword(s):  
Rock Mass ◽  
Stability Analysis ◽  
Rock Slope ◽  
Interface Element ◽  
Rocky Slope ◽  
Natural Rock ◽  
Site Monitoring ◽  
The Difference ◽  
The Stability ◽  
Element Method

Mechanics behavior of unloading rock slope is essentially different from the natural rock slope . But, stability analysis of rocky slope during and after excavating still need these parameters and constitutional relation came from the natural rock slope, thus, the difference between the unloading rock mass and natural rock mass is neglected. The calculation result is quite different from the monitoring result. In order to analyze the stability of unloading rock slope properly, corresponding mechanics parameters including mechanics state, unloading degree and others should be determined and applied. In this paper, IEM - Sample Element Method and Interface Element Method expounded systematically and used to determine the corresponding mechanics parameters of a layered rock slope- Xishan slope of the Jiangyin Yangtze River Bridge. Then, IEM computer program based on Interface Element Method used to calculate the displacement of Xishan slope. Compare with displacement site-monitoring results, IEM is better than Finite Element Method.

SUBTLE IS THE LORD: ON THE DIFFERENCE BETWEEN NEWTONIAN (LYAPUNOV) STABILITY ANALYSIS AND GEOMETRICAL STABILITY ANALYSIS OF GRAVITATIONAL ORBITS

2011 ◽  
Vol 20 (14) ◽  
pp. 2787-2793 ◽  
Author(s):  
L. P. HORWITZ ◽  
A. YAHALOM ◽  
M. LEWKOWICZ ◽  
J. LEVITAN
Keyword(s):  
Stability Analysis ◽  
Geometric Approach ◽  
Periodic Trajectory ◽  
Large Radius ◽  
Three Body Problem ◽  
Lyapunov Stability Analysis ◽  
Dependent Potential ◽  
The Difference ◽  
The Stability ◽  
Three Body

In this essay we discuss the geometrical embedding method (GEM) for the analysis of the stability of Hamiltonian systems using geometrical techniques familiar from general relativity. This method has proven to be very effective. In particular, we show that although the application of standard Lyapunov analysis predicts that completely integrable Kepler motion is unstable, this geometrical analysis predicts the observed stability. Moreover, we apply this approach to the three body problem in which the third body is restricted to move on a circle of large radius which induces an adiabatic time dependent potential on the second body. This causes the second body to move in a very intricate but periodic trajectory. The geometric approach predicts the correct stable motion in this case as well.

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