On the moment stability of gaussian random linear systems

1964 ◽  
Vol 9 (3) ◽  
pp. 301-303 ◽  
Author(s):  
N. Bershad ◽  
P. Derusso
Keyword(s):  
Linear Systems ◽  
The Moment ◽  
Moment Stability

scholarly journals Surgery or general medicine: a study of the reasons underlying the choice of medical specialty

2004 ◽  
Vol 122 (3) ◽  
pp. 81-86 ◽  
Author(s):  
Patrícia Lacerda Bellodi
Keyword(s):  
Influencing Factor ◽  
Medical Knowledge ◽  
General Medicine ◽  
Medical Specialty ◽  
Educational Context ◽  
The Moment ◽  
Intellectual Activities ◽  
Brazilian Studies ◽  
Moment Stability ◽  
De Medicina

CONTEXT: The reality of medical services in Brazil points towards expansion and diversification of medical knowledge. However, there are few Brazilian studies on choosing a medical specialty. OBJECTIVE: To investigate and characterize the process of choosing the medical specialty among Brazilian resident doctors, with a comparison of the choice between general medicine and surgery. TYPE OF STUDY: Stratified survey. SETTING: Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo (HC-FMUSP). METHODS: A randomized sample of resident doctors in general medicine (30) and surgery (30) was interviewed. Data on sociodemographic characteristics and the moment, stability and reasons for the choice of specialty were obtained. RESULTS: The moment of choice between the two specialties differed. Surgeons (30%) choose the specialty earlier, while general doctors decided progressively, mainly during the internship (43%). Most residents in both fields (73% general medicine, 70% surgery) said they had considered another specialty before the current choice. The main reasons for general doctors' choice were contact with patients (50%), intellectual activities (30%) and knowledge of the field (27%). For surgeons the main reasons were practical intervention (43%), manual activities (43%) and the results obtained (40%). Personality was important in the choice for 20% of general doctors and for 27% of surgeons. DISCUSSION: The reasons found for the choice between general medicine and surgery were consistent with the literature. The concepts of wanting to be a general doctor or a surgeon are similar throughout the world. Personality characteristics were an important influencing factor for all residents, without statistical difference between the specialties, as was lifestyle. Remuneration did not appear as a determinant. CONCLUSION: The results from this group of Brazilian resident doctors corroborated data on choosing a medical specialty from other countries with different social and educational characteristics. This congruence indicates that the choice involves very similar desires and needs in different settings and has little dependence on the students' educational context.

scholarly journals MOMENT LYAPUNOV EXPONENTS AND STOCHASTIC STABILITY OF A THIN-WALLED BEAM SUBJECTED TO AXIAL LOADS AND END MOMENTS

2021 ◽  
Vol 19 (2) ◽  
pp. 209
Author(s):  
Goran Janevski ◽  
Predrag Kozić ◽  
Ratko Pavlović ◽  
Strain Posavljak
Keyword(s):  
Lyapunov Exponent ◽  
Lyapunov Exponents ◽  
Degrees Of Freedom ◽  
Simulation Method ◽  
Stochastic Dynamic ◽  
Regular Perturbation ◽  
Thin Walled ◽  
The Moment ◽  
Moment Stability ◽  
Moment Lyapunov Exponents

In this paper, the Lyapunov exponent and moment Lyapunov exponents of two degrees-of-freedom linear systems subjected to white noise parametric excitation are investigated. The method of regular perturbation is used to determine the explicit asymptotic expressions for these exponents in the presence of small intensity noises. The Lyapunov exponent and moment Lyapunov exponents are important characteristics for determining both the almost-sure and the moment stability of a stochastic dynamic system. As an example, we study the almost-sure and moment stability of a thin-walled beam subjected to stochastic axial load and stochastically fluctuating end moments.  The validity of the approximate results for moment Lyapunov exponents is checked by numerical Monte Carlo simulation method for this stochastic system.

Risk analysis in environmental systems

2002 ◽  
Vol 29 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Elhadi Shakshuki ◽  
Kumaraswamy Ponnambalam ◽  
Tassew Wodaj
Keyword(s):  
Risk Analysis ◽  
Linear Systems ◽  
Large Scale ◽  
Probabilistic Models ◽  
Large Scale Systems ◽  
Second Moment ◽  
Environmental Systems ◽  
Inherent Feature ◽  
The Moment ◽  
Uncertainty Information

Uncertainty is an inherent feature of environmental systems, which makes probabilistic models important. Environmental risk assessment is an important but time consuming task. For large-scale systems, use of linear systems with uncertainty information on parameters and inputs is one of the few possible methods to assess risk. To estimate risk, it is necessary to have at least the first two moments of output variables. This paper describes an efficient method developed for second-moment analysis of linear systems with uncertain coefficients. The main objective is to provide the means and the variances of the output and to provide efficient formulation and automation of the moment equations. This method is demonstrated in two real-world applications of environmental modeling.Key words: uncertainty, second-moment methods, risk analysis, reliability, linear systems.

scholarly journals A Theoretical Investigation of the Effect of the Stochasticity in the Material Properties on the Chatter Detection During Turning

2017 ◽  
Author(s):  
Henrik T. Sykora ◽  
Daniel Bachrathy ◽  
Gabor Stepan
Keyword(s):  
White Noise ◽  
Time Evolution ◽  
Material Properties ◽  
Discretization Method ◽  
Chatter Detection ◽  
Turning Process ◽  
Stochastic Parameters ◽  
Stability Chart ◽  
The Moment ◽  
Moment Stability

In this work the effect of the inhomogeneous material properties are investigated in regenerative turning processes by introducing white noise in the cutting coefficient. The model is a one degree of freedom linear delayed oscillator with stochastic parameters. A full discretization method is used to calculate the time evolution of the second moment to determine the moment stability of the turning process. The resultant stability chart is compared with the deterministic turning model.

The Response of a Rectangular Thin Plate Subjected to In-Plane Narrow Band Noise Excitation

2015 ◽  
Vol 764-765 ◽  
pp. 379-382
Author(s):  
Gen Ge ◽  
Jing Xian Wei ◽  
Wen Di Zhang
Keyword(s):  
Floquet Theory ◽  
Narrow Band ◽  
Multiple Scale ◽  
Order Moment ◽  
Narrow Band Noise ◽  
Band Noise ◽  
Steady State Responses ◽  
The Moment ◽  
State Responses ◽  
Moment Stability

One stochastic dynamical model of a thin rectangular plate subject to in-plate parametrical narrow band noise excitation is proposed based on elastic theory and Galerkin’s approach. At first the model is simplified applying the multiple scale method and the averaged equation in Ito form is obtained. Secondly, the stochastic moment stability of the steady state responses are analyzed by Floquet theory and the moment method. Finally, the second order moment of the system is obtained, which can be used to estimate the variance of the responses. The numerical results agree with the theatrical analysis.

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