Bilinear Amplitude and Frequency Approximation for Nonlinear Systems With Gaps or Prestress

2016 ◽  
Author(s):  
Kiran D’Souza ◽  
Meng-Hsuan Tien
Keyword(s):  
Bilinear System ◽  
Bilinear Systems ◽  
Degree Of Freedom ◽  
New Method ◽  
Time Interval ◽  
Time Intervals ◽  
Vibrational Response ◽  
Three Degree Of Freedom ◽  
System 1 ◽  
Frequency Approximation

Analysis of the dynamics of bilinear systems is critical for a variety of civil, mechanical and aerospace structures that contain gaps or prestress that are caused by cracks, delamination, joints or interfaces amongst components. Recently, a method was developed called bilinear amplitude approximation (BAA) to estimate the response of bilinear systems without gaps or prestress. This method was developed on the idea that the bilinear system can be separated into two time intervals both of which the system behaves as a distinct linear system: (1) the open state and (2) the closed or sliding state. In order to couple the linear vibrational response for each time interval, both geometric and momentum constraints are applied as transition conditions between the states. This paper expands the previous BAA method for the case where there are either gaps or prestress in the system. The new method requires the forcing magnitude to be known so that it can accurately determine when the system transitions between the two states, and the new equilibrium positions for each state for a given forcing magnitude. The new method also finds the bilinear frequency of the system, which cannot be computed using the bilinear frequency approximation (BFA) method previously developed since that method is only accurate for the zero gap and no prestress case. The new BAA and BFA methods are demonstrated on single degree of freedom and three degree of freedom systems for a variety of forcing conditions.

A new closed-form kinematics of the generalized 3-DOF spherical parallel manipulator

Robotica ◽  
1999 ◽  
Vol 17 (5) ◽  
pp. 475-485 ◽  
Author(s):  
Zhen Huang ◽  
Y. Lawrence Yao
Keyword(s):  
Closed Form ◽  
Analytical Method ◽  
Parallel Manipulator ◽  
Degree Of Freedom ◽  
New Method ◽  
Numerical Example ◽  
Three Degree Of Freedom ◽  
Spherical Parallel Manipulator

This paper presents a new method to analyze the closed-form kinematics of a generalized three-degree-of-a-freedom spherical parallel manipulator. Using this analytical method, concise and uniform solutions are achieved. Two special forms of the three-degree-of-freedom spherical parallel manipulator, i.e. right-angle type and a decoupled type, are also studied and their unique and interesting properties are investigated, followed by a numerical example.

A distinct matrix representation of the planar kinematic chains and isomorphism recognition

2019 ◽  
Vol 13 (4) ◽  
pp. 5717-5734
Author(s):  
M. S. Alam ◽  
M. Suhaib
Keyword(s):  
Mechanism Design ◽  
Design Problem ◽  
Matrix Representation ◽  
Degree Of Freedom ◽  
New Method ◽  
Structural Synthesis ◽  
Primary Condition ◽  
Secondary Conditions ◽  
Kinematic Chains ◽  
Three Degree Of Freedom

Structural synthesis of kinematic chains has been an indispensable area of the mechanism-design problem. The duplication may occur while developing kinematic chains. Therefore, an isomorphic test is required to eliminate duplication. For this purpose, the numbers of methods are proposed during recent years. However, most of the methods are complex and difficult to understand, and fulfil the only primary condition, but not the secondary conditions for isomorphism detection. In the present work, a new method is introduced to detect isomorphism in planar kinematic chains (KCs) fulfilling both primary and secondary conditions. First, KC’s are topologically transformed into skeleton diagrams, and then skeleton matrices [S] and identification strings [IS] are formulated consequently. In order to detect isomorphism, the IS is considered as an invariant string of a KC which in turn, enables the detection of isomorphism between the KCs. The proposed method accurately recognizes isomorphism up to 12 links KCs with no counter examples found in the literature. Three examples with one degree of freedom having 10 links 12 joints, 10 links 13 joints and 12 links three degree of freedom systems are introduced to reveal the reliability and strength of the proposed method.

scholarly journals Comparative analysis of several methods for blood pressure measurement in the morning in patients with arterial hypertension

2018 ◽  
Vol 17 (6) ◽  
pp. 5-12
Author(s):  
G. F. Andreeva ◽  
A. D. Deev ◽  
V. M. Gorbunov
Keyword(s):  
Blood Pressure ◽  
Blood Pressure Measurement ◽  
Blood Pressure Level ◽  
Fixed Time ◽  
Left Ventricular ◽  
New Method ◽  
Left Ventricular Myocardium ◽  
Time Interval ◽  
Time Intervals ◽  
High Level

Aim. To compare the known methods of blood pressure (BP) measurement in the morning and a new method for estimating the average morning BP for fixed time intervals, comparing their reproducibility and validity.Material and methods. We analyzed database containing 983 cases of ambulatory blood pressure monitoring (ABPM). Results of ABMP in patients with hypertension without severe associated diseases and weekly cancellation of antihypertensive therapy were analyzed. Blood pressure data per 24-hour period, day and night, level and rate of morning BP surge were assessed. In addition, we proposed new method for estimating the average morning BP level for fixed time intervals, based on calculating the average BP level for the following time windows: from 5:00 to 7:00 a.m., from 7:00 to 9:00 a.m., from 9:00 to 11:00 a.m. To assess the reproducibility of the new method, we determined correlations between the first and second group results calculated by the new method based on two repeated ABPM conducted with 1-2 weeks interval (n=90). To study the validity of the new method for measurement of average morning BP level, we used an objective validation criterion — Left Ventricular Myocardium Mass Index (LVMMI). There were performed 98 echocardiographic tests with the use of Acuson 128XP. LVMMI was calculated using the L. Teichholtz method (1976).Results. The new method for measurement of average morning BP level had good reproducibility while the reproducibility of dynamic showings of ABMP (level and rate of morning BP surge) was low. A new method for assessing morning blood pressure was characterized by a high level of validity: the indicators obtained using this technique reliably correlated with the validation criteria: LVMI and the average daily blood pressure level.Conclusion. The proposed new method for estimating the average morning level of blood pressure has a high level of validity and reproducibility. Time interval from 7 to 9 a. m. seems to be the most optimal. The maximum reproducibility of the showings was noted during this period.

On the Determination of the Workspace of Complex Planar Robotic Manipulators

1998 ◽  
Vol 120 (2) ◽  
pp. 269-278 ◽  
Author(s):  
Re´mi Ricard ◽  
Cle´ment M. Gosselin
Keyword(s):  
Robotic Manipulators ◽  
Degree Of Freedom ◽  
New Method ◽  
Three Degree Of Freedom ◽  
Joint Limits

A new method for the determination of the workspace of complex planar robotic manipulators is described in this paper. The method is based on the use of joint limits to obtain equations describing limiting curves. These limiting curves are then segmented at their mutual intersections and validated. The resulting sets of portions of curves form the envelope of the workspace. The algorithm is completely general and can be applied to any three-degree-of-freedom planar manipulator—serial, parallel or hybrid—with or without joint limits. Examples of the application of the method to a serial three-degree-of-freedom manipulator, to a hybrid three-degree-of-freedom manipulator and to a parallel three-degree-of-freedom manipulator are given.

METABOLIC STUDIES WITH 131I-LABELED THYROXINE. II.

1963 ◽  
Vol 44 (3) ◽  
pp. 475-480 ◽  
Author(s):  
R. Grinberg
Keyword(s):  
Spinal Cord ◽  
Central Nervous System ◽  
Nervous System ◽  
Optic Nerve ◽  
Pituitary Gland ◽  
Time Interval ◽  
Time Intervals ◽  
Pituitary Glands ◽  
The Central Nervous System ◽  
Tentative Explanation

ABSTRACT Radiologically thyroidectomized female Swiss mice were injected intraperitoneally with 131I-labeled thyroxine (T4*), and were studied at time intervals of 30 minutes and 4, 28, 48 and 72 hours after injection, 10 mice for each time interval. The organs of the central nervous system and the pituitary glands were chromatographed, and likewise serum from the same animal. The chromatographic studies revealed a compound with the same mobility as 131I-labeled triiodothyronine in the organs of the CNS and in the pituitary gland, but this compound was not present in the serum. In most of the chromatographic studies, the peaks for I, T4 and T3 coincided with those for the standards. In several instances, however, such an exact coincidence was lacking. A tentative explanation for the presence of T3* in the pituitary gland following the injection of T4* is a deiodinating system in the pituitary gland or else the capacity of the pituitary gland to concentrate T3* formed in other organs. The presence of T3* is apparently a characteristic of most of the CNS (brain, midbrain, medulla and spinal cord); but in the case of the optic nerve, the compound is not present under the conditions of this study.

Development and performance of a three degree of freedom large motion vibration isolation mount for the KC-135 aircraft

1993 ◽  
Author(s):  
B. TRYGGVASON ◽  
B. STEWART ◽  
S. SALCUDEAN ◽  
H. DAVIS ◽  
E. SLOOT
Keyword(s):  
Vibration Isolation ◽  
Degree Of Freedom ◽  
Large Motion ◽  
And Performance ◽  
Three Degree Of Freedom

scholarly journals Neural Network Approach for Global Solar Irradiance Prediction at Extremely Short-Time-Intervals Using Particle Swarm Optimization Algorithm

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1213
Author(s):  
Ahmed Aljanad ◽  
Nadia M. L. Tan ◽  
Vassilios G. Agelidis ◽  
Hussain Shareef
Keyword(s):  
Neural Networks ◽  
Particle Swarm Optimization ◽  
Solar Irradiance ◽  
Particle Swarm ◽  
Time Interval ◽  
Time Intervals ◽  
Swarm Optimization ◽  
Backpropagation Neural Networks ◽  
Proposed Model ◽  
Short Time

Hourly global solar irradiance (GSR) data are required for sizing, planning, and modeling of solar photovoltaic farms. However, operating and controlling such farms exposed to varying environmental conditions, such as fast passing clouds, necessitates GSR data to be available for very short time intervals. Classical backpropagation neural networks do not perform satisfactorily when predicting parameters within short intervals. This paper proposes a hybrid backpropagation neural networks based on particle swarm optimization. The particle swarm algorithm is used as an optimization algorithm within the backpropagation neural networks to optimize the number of hidden layers and neurons used and its learning rate. The proposed model can be used as a reliable model in predicting changes in the solar irradiance during short time interval in tropical regions such as Malaysia and other regions. Actual global solar irradiance data of 5-s and 1-min intervals, recorded by weather stations, are applied to train and test the proposed algorithm. Moreover, to ensure the adaptability and robustness of the proposed technique, two different cases are evaluated using 1-day and 3-days profiles, for two different time intervals of 1-min and 5-s each. A set of statistical error indices have been introduced to evaluate the performance of the proposed algorithm. From the results obtained, the 3-days profile’s performance evaluation of the BPNN-PSO are 1.7078 of RMSE, 0.7537 of MAE, 0.0292 of MSE, and 31.4348 of MAPE (%), at 5-s time interval, where the obtained results of 1-min interval are 0.6566 of RMSE, 0.2754 of MAE, 0.0043 of MSE, and 1.4732 of MAPE (%). The results revealed that proposed model outperformed the standalone backpropagation neural networks method in predicting global solar irradiance values for extremely short-time intervals. In addition to that, the proposed model exhibited high level of predictability compared to other existing models.

Real-World Experience with Artificial Intelligence-Based Triage in Transferred Large Vessel Occlusion Stroke Patients

2021 ◽  
pp. 1-6
Author(s):  
Jacob R. Morey ◽  
Xiangnan Zhang ◽  
Kurt A. Yaeger ◽  
Emily Fiano ◽  
Naoum Fares Marayati ◽  
...  
Keyword(s):  
Artificial Intelligence ◽  
Clinical Outcomes ◽  
Warning System ◽  
Large Vessel ◽  
Time Interval ◽  
Large Vessel Occlusion ◽  
Time Intervals ◽  
Vessel Occlusion ◽  
Left Behind ◽  
Stroke Center

<b><i>Background and Purpose:</i></b> Randomized controlled trials have demonstrated the importance of time to endovascular therapy (EVT) in clinical outcomes in large vessel occlusion (LVO) acute ischemic stroke. Delays to treatment are particularly prevalent when patients require a transfer from hospitals without EVT capability onsite. A computer-aided triage system, Viz LVO, has the potential to streamline workflows. This platform includes an image viewer, a communication system, and an artificial intelligence (AI) algorithm that automatically identifies suspected LVO strokes on CTA imaging and rapidly triggers alerts. We hypothesize that the Viz application will decrease time-to-treatment, leading to improved clinical outcomes. <b><i>Methods:</i></b> A retrospective analysis of a prospectively maintained database was assessed for patients who presented to a stroke center currently utilizing Viz LVO and underwent EVT following transfer for LVO stroke between July 2018 and March 2020. Time intervals and clinical outcomes were compared for 55 patients divided into pre- and post-Viz cohorts. <b><i>Results:</i></b> The median initial door-to-neuroendovascular team (NT) notification time interval was significantly faster (25.0 min [IQR = 12.0] vs. 40.0 min [IQR = 61.0]; <i>p</i> = 0.01) with less variation (<i>p</i> &#x3c; 0.05) following Viz LVO implementation. The median initial door-to-skin puncture time interval was 25 min shorter in the post-Viz cohort, although this was not statistically significant (<i>p</i> = 0.15). <b><i>Conclusions:</i></b> Preliminary results have shown that Viz LVO implementation is associated with earlier, more consistent NT notification times. This application can serve as an early warning system and a failsafe to ensure that no LVO is left behind.

scholarly journals Optimal Perturbations of an Oceanic Vortex Lens

Fluids ◽  
2018 ◽  
Vol 3 (3) ◽  
pp. 63 ◽  
Author(s):  
Thomas Meunier ◽  
Claire Ménesguen ◽  
Xavier Carton ◽  
Sylvie Le Gentil ◽  
Richard Schopp
Keyword(s):  
Normal Mode ◽  
Growth Rates ◽  
Time Interval ◽  
Time Intervals ◽  
Horizontal Structure ◽  
Azimuthal Wave ◽  
Wave Numbers ◽  
Non Linear ◽  
Long Time ◽  
Short Time

The stability properties of a vortex lens are studied in the quasi geostrophic (QG) framework using the generalized stability theory. Optimal perturbations are obtained using a tangent linear QG model and its adjoint. Their fine-scale spatial structures are studied in details. Growth rates of optimal perturbations are shown to be extremely sensitive to the time interval of optimization: The most unstable perturbations are found for time intervals of about 3 days, while the growth rates continuously decrease towards the most unstable normal mode, which is reached after about 170 days. The horizontal structure of the optimal perturbations consists of an intense counter-shear spiralling. It is also extremely sensitive to time interval: for short time intervals, the optimal perturbations are made of a broad spectrum of high azimuthal wave numbers. As the time interval increases, only low azimuthal wave numbers are found. The vertical structures of optimal perturbations exhibit strong layering associated with high vertical wave numbers whatever the time interval. However, the latter parameter plays an important role in the width of the vertical spectrum of the perturbation: short time interval perturbations have a narrow vertical spectrum while long time interval perturbations show a broad range of vertical scales. Optimal perturbations were set as initial perturbations of the vortex lens in a fully non linear QG model. It appears that for short time intervals, the perturbations decay after an initial transient growth, while for longer time intervals, the optimal perturbation keeps on growing, quickly leading to a non-linear regime or exciting lower azimuthal modes, consistent with normal mode instability. Very long time intervals simply behave like the most unstable normal mode. The possible impact of optimal perturbations on layering is also discussed.

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