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.

scholarly journals DYNAMIC BEHAVIOR OF TWO ELASTICALLY CONNECTED NANOBEAMS UNDER A WHITE NOISE PROCESS

2020 ◽  
Vol 18 (2) ◽  
pp. 219
Author(s):  
Ivan R. Pavlović ◽  
Ratko Pavlović ◽  
Goran Janevski ◽  
Nikola Despenić ◽  
Vladimir Pajković
Keyword(s):  
Lyapunov Exponent ◽  
White Noise ◽  
Axial Loading ◽  
Regular Perturbation ◽  
White Noise Process ◽  
Noise Process ◽  
Asymptotic Expressions ◽  
Moment Lyapunov Exponent ◽  
The Moment ◽  
Moment Stability

This paper investigates the almost-sure and moment stability of a double nanobeam system under stochastic compressive axial loading. By means of the Lyapunov exponent and the moment Lyapunov exponent method the stochastic stability of the nano system is analyzed for different system parameters under an axial load modeled as a wideband white noise process. The method of regular perturbation is used to determine the explicit asymptotic expressions for these exponents in the presence of small intensity noises.

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.

scholarly journals The softness distribution index: towards the creation of guidelines for the modeling of soft-bodied robots

2019 ◽  
pp. 027836491989345
Author(s):  
Giovanna A Naselli ◽  
Barbara Mazzolai
Keyword(s):  
Material Properties ◽  
Soft Robotics ◽  
Dimensionless Quantity ◽  
Unified Framework ◽  
Soft Body ◽  
Computational Burden ◽  
Highly Nonlinear ◽  
Nonlinear Mechanical ◽  
Distribution Index ◽  
The Moment

Modeling soft robots is not an easy task owing to their highly nonlinear mechanical behavior. So far, several researchers have tackled the problem using different approaches, each having advantages and drawbacks in terms of accuracy, ease of implementation, and computational burden. The soft robotics community is currently working to develop a unified framework for modeling. Our contribution in this direction consists of a novel dimensionless quantity that we call the softness distribution index (SDI). The SDI for a given soft body is computed based on the distribution of its structural properties. We show that the index can serve as a tool in the choice of a modeling technique among multiple approaches suggested in literature. At the moment, the investigation is limited to bodies performing planar bending. The aim of this work is twofold: (i) to highlight the importance of the distribution of the geometrical and material properties of a soft robotic link/body throughout its structure; and (ii) to demonstrate that a classification based on this distribution provides guidelines for the modeling.

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.

scholarly journals EXPERIMENTAL DETERMINATION OF OPTIMAL PARAMETERS OF MOBILE TELECONFERENCES

2021 ◽  
Vol 2 (14) ◽  
pp. 68-86
Author(s):  
Andrii Byts ◽  
Volodymyr Sokolov ◽  
Nataliia Mazur ◽  
Valerii Kozachok ◽  
Anatoly Bessalov
Keyword(s):  
White Noise ◽  
Video Transmission ◽  
Video Stream ◽  
Video Playback ◽  
Corporate Networks ◽  
Video Information ◽  
The Moment ◽  
Very High

The article considers the problem of ensuring the availability and integrity of wireless subscribers in cellular and other wireless corporate networks. The article aims to determine the threshold values for the moment of failure of video transmission, quantitative parameters, artifacts, and the number of errors for the image. Show the dependence of the integrity of data transmitted in real-time on the characteristics of the environment. Two approaches were used to assess the quality of video information: qualitative (image recognition assessment) and quantitative (error measurement). Because the research program was written in the Kotlin programming language, a library written in Java or Kotlin was required. After searching the library, it turned out that only three libraries meet such parameters as reliability, relevance, and availability of documentation: Jaffree, Xuggler, and VLCJ. After gathering information, it was found that the most common screen extensions for desktops are 1366 × 768 and for phones—360 × 640. An error occurred that RTP did not support more than one connection. Also, the RTSP protocol could not pass the experiment on codecs other than MP4V. The experiment stopped earlier than necessary without error. Judging by the indicators, this was a very high CPU load. All other protocols were successfully tested, and results were obtained. During the experiments, we encountered various video anomalies. The worst was the video playback problem with the MJPG codec. Other anomalies were also identified: frame delay, incorrect frame rendering, white noise, and white noise mixed with frames. It is clear how up to 128 kbps experiments are successful and then begin to stop the video stream without error information. According to the results of experiments, the H.264 codec performs best.

scholarly journals The Influence of the Material Properties on the Ultimate Behaviour of Aluminium H-shaped Beams

2021 ◽  
Vol 15 (1) ◽  
pp. 176-188
Author(s):  
Rosario Montuori ◽  
Elide Nastri ◽  
Vincenzo Piluso ◽  
Alessandro Pisapia
Keyword(s):  
Material Properties ◽  
Slenderness Ratio ◽  
Bending Moment ◽  
Constitutive Law ◽  
Rotation Capacity ◽  
Moment Gradient ◽  
Dimensional Parameters ◽  
The Moment ◽  
Plastic Rotation Capacity ◽  
Ultimate Resistance

Background: In this paper, the influence of the Ramberg-Osgood exponent on the ultimate behaviour of the H-shaped (or I-shaped) aluminium beams subjected to non-uniform bending moment is investigated. Methods: In particular, the results of a wide parametric analysis recently carried out by the authors are herein exploited to point out the influence of the material properties. The flange slenderness, the flange-to-web slenderness ratio, and the non-dimensional shear length, accounting for the moment gradient, are the main non-dimensional parameters governing the ultimate resistance and the rotation capacity of H-shaped aluminium beams. Results: The influence of these parameters was investigated considering four different materials covering both low yielding-high hardening alloys and high yielding-low hardening alloys, which are characterised by significant differences in the values of the Ramberg-Osgood exponent of the stress-strain constitutive law of the material. Conclusion: Finally, empirical formulations for predicting the non-dimensional ultimate flexural strength and the plastic rotation capacity of H-section aluminium beams under moment gradient have been provided as a function of the Ramberg-Osgood exponent and all the above non-dimensional parameters.

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