scholarly journals (M,β)-Stability of Positive Linear Systems

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Octavian Pastravanu ◽  
Mihaela-Hanako Matcovschi
Keyword(s):  
Linear System ◽  
Linear Systems ◽  
Transient Behavior ◽  
Short Term ◽  
Time Dynamics ◽  
The Right ◽  
Long Term Behavior ◽  
Stability Concept

The main purpose of this work is to show that the Perron-Frobenius eigenstructure of a positive linear system is involved not only in the characterization of long-term behavior (for which well-known results are available) but also in the characterization of short-term or transient behavior. We address the analysis of the short-term behavior by the help of the “(M,β)-stability” concept introduced in literature for general classes of dynamics. Our paper exploits this concept relative to Hölder vectorp-norms,1≤p≤∞, adequately weighted by scaling operators, focusing on positive linear systems. Given an asymptotically stable positive linear system, for each1≤p≤∞, we prove the existence of a scaling operator (built from the right and left Perron-Frobenius eigenvectors, with concrete expressions depending onp) that ensures the best possible values for the parametersMandβ, corresponding to an “ideal” short-term (transient) behavior. We provide results that cover both discrete- and continuous-time dynamics. Our analysis also captures the differences between the cases where the system dynamics is defined by matrices irreducible and reducible, respectively. The theoretical developments are applied to the practical study of the short-term behavior for two positive linear systems already discussed in literature by other authors.

Distinguishable Brain Activation Networks for Short- and Long-Term Motor Skill Learning

2005 ◽  
Vol 94 (1) ◽  
pp. 512-518 ◽  
Author(s):  
A. Floyer-Lea ◽  
P. M. Matthews
Keyword(s):  
Motor Skill ◽  
Isometric Force ◽  
Brain Activation ◽  
Skill Learning ◽  
Anterior Cingulate ◽  
Motor Skill Learning ◽  
Short Term ◽  
Learning Stage ◽  
The Right

The acquisition of a new motor skill is characterized first by a short-term, fast learning stage in which performance improves rapidly, and subsequently by a long-term, slower learning stage in which additional performance gains are incremental. Previous functional imaging studies have suggested that distinct brain networks mediate these two stages of learning, but direct comparisons using the same task have not been performed. Here we used a task in which subjects learn to track a continuous 8-s sequence demanding variable isometric force development between the fingers and thumb of the dominant, right hand. Learning-associated changes in brain activation were characterized using functional MRI (fMRI) during short-term learning of a novel sequence, during short-term learning after prior, brief exposure to the sequence, and over long-term (3 wk) training in the task. Short-term learning was associated with decreases in activity in the dorsolateral prefrontal, anterior cingulate, posterior parietal, primary motor, and cerebellar cortex, and with increased activation in the right cerebellar dentate nucleus, the left putamen, and left thalamus. Prefrontal, parietal, and cerebellar cortical changes were not apparent with short-term learning after prior exposure to the sequence. With long-term learning, increases in activity were found in the left primary somatosensory and motor cortex and in the right putamen. Our observations extend previous work suggesting that distinguishable networks are recruited during the different phases of motor learning. While short-term motor skill learning seems associated primarily with activation in a cortical network specific for the learned movements, long-term learning involves increased activation of a bihemispheric cortical-subcortical network in a pattern suggesting “plastic” development of new representations for both motor output and somatosensory afferent information.

scholarly journals Learning from Interventions Using Hierarchical Policies for Safe Learning

2020 ◽  
Vol 34 (06) ◽  
pp. 10352-10360
Author(s):  
Jing Bi ◽  
Vikas Dhiman ◽  
Tianyou Xiao ◽  
Chenliang Xu
Keyword(s):  
Reaction Time ◽  
State Of The Art ◽  
The State ◽  
Policy Framework ◽  
Asymptotic Performance ◽  
Short Term ◽  
Learning From Demonstrations ◽  
Hierarchical Levels ◽  
Long Term Behavior

Learning from Demonstrations (LfD) via Behavior Cloning (BC) works well on multiple complex tasks. However, a limitation of the typical LfD approach is that it requires expert demonstrations for all scenarios, including those in which the algorithm is already well-trained. The recently proposed Learning from Interventions (LfI) overcomes this limitation by using an expert overseer. The expert overseer only intervenes when it suspects that an unsafe action is about to be taken. Although LfI significantly improves over LfD, the state-of-the-art LfI fails to account for delay caused by the expert's reaction time and only learns short-term behavior. We address these limitations by 1) interpolating the expert's interventions back in time, and 2) by splitting the policy into two hierarchical levels, one that generates sub-goals for the future and another that generates actions to reach those desired sub-goals. This sub-goal prediction forces the algorithm to learn long-term behavior while also being robust to the expert's reaction time. Our experiments show that LfI using sub-goals in a hierarchical policy framework trains faster and achieves better asymptotic performance than typical LfD.

scholarly journals Characterization of morphology and function of the ‘neo-atria’ after a modified Mustard operation

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Mohamed Nagy ◽  
Hatem Hosny ◽  
Amr El Sawy ◽  
Ahmed Mahgoub ◽  
Magdi H Yacoub
Keyword(s):  
Contractile Function ◽  
Postoperative Recovery ◽  
Long Term Results ◽  
3D Segmentation ◽  
Mustard Operation ◽  
The Right ◽  
And Function ◽  
Atrial Systole

Background: There is a pressing need to improve early and long-term results of the Mustard operation. A modification of the operation was introduced at the Aswan Heart Centre for this purpose which relies on creating new functional atria rather than the two rigid channels in the classical Mustard operation.Objectives: To evaluate the morphology and function of the neo-atria, shortly after modified mustard operation for a ‘neglected’ patient with TGA, VSD and severe pulmonary hypertension.Methods: A 6-year-old with neglected TGA, VSD and pulmonary hypertension presented with severe cyanosis, clubbing and haemoconcentration (Hb 22 g/dL), underwent the modified Aswan-Mustard operation (MAM) with rapid smooth postoperative recovery. Repeated 2D echograms and multi-slice CT scans, followed by 3D segmentation, were performed after the operation. The size, shape, and morphology of the neo-atria were measured and measurements of the patterns of instantaneous filling and emptying of the right and left ventricles were quantified.Results: The neo-systemic venous atrium consisted of three components with a combined volume of 78 mL/m2, all of which contributed to the reservoir, conduit, and importantly contractile function of the neo-atrium. The pulmonary venous atrium consisted of two components with a combined volume of 66 mL/m2. These measurements were made at atrial end diastole. The volumes of the systemic venous and the pulmonary venous diminished to 51 and 54 mL/m2, respectively, at the end atrial systole - indicating relatively preserved contractile functions.

Long-term and Short-term Spectral Stability Characterization of Supercontinuum Laser Sources

2006 ◽  
Author(s):  
Roberto Llorente ◽  
Marta Beltran ◽  
Joaquin Perez ◽  
Noboru Uehara ◽  
Md. Khan ◽  
...  
Keyword(s):  
Spectral Stability ◽  
Short Term ◽  
Laser Sources ◽  
Supercontinuum Laser

Hindered phenolic antioxidants as heat-oxygen stabilizers for HDPE

2020 ◽  
pp. 096739112097116
Author(s):  
Yuru Wang ◽  
He Ren ◽  
Yibin Yan ◽  
Shuyan He ◽  
Shuang Wu ◽  
...  
Keyword(s):  
Pure Oxygen ◽  
Phenolic Antioxidants ◽  
Irganox 1010 ◽  
Short Term ◽  
Scanning Calorimetry ◽  
Oxidation Induction Time ◽  
Melt Flow Rate ◽  
Stability Tests

The effects of four hindered phenolic antioxidants in the short-term heat-oxygen stability of High-Density Polyethylene (HDPE) was evaluated by the Melt Flow Rate (MFR) and Oxidation Induction Time (OIT) analyses. The results showed that Irganox 1330 and Irganox 1010 had more excellent processing property and oxidation resistance behavior in HDPE than Irganox 1024 and Irganox 3114. The OIT values of HDPE with Irganox 1330 and Irganox 1010 were up to 97.25 min and 89.73 min respectively. The long-term accelerated heat-oxygen stability tests of HDPE containing hindered phenolic antioxidants were carried out at 110°C in deionized water pressurized with pure oxygen at a pressure of 10 MPa. The characterization of the long-term heat-oxygen stability was performed by Fourier Transform Infrared (FTIR), Differential Scanning Calorimetry (DSC) and tensile testing. However, the results exhibited that the aging resistance of HDPE containing Irganox 1010 was inferior to that of HDPE containing Irganox 1024 and Irganox 3114, which is quite contrary to their short-term effect on HDPE stabilization. It may be speculated that the ester groups of Irganox 1010 undergo hydrolysis during the long-term heat-oxygen stability tests, leading to the formation of 3-(3,5-ditert-butyl-4-hydroxy-phenyl) propanoic acid and pentaerythritol.

Experimental study of the short-term and long-term behavior of perfobond connectors

2018 ◽  
Vol 150 ◽  
pp. 462-474 ◽  
Author(s):  
Jing Zhang ◽  
Xiamin Hu ◽  
Liya Kou ◽  
Bing Zhang ◽  
Yuchen Jiang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Short Term ◽  
Long Term Behavior

Echoes of the French Revolution in the Rhineland, 1830–1849

1989 ◽  
Vol 22 (2) ◽  
pp. 200-217 ◽  
Author(s):  
Jonathan Sperber
Keyword(s):  
French Revolution ◽  
Economic Effects ◽  
Left Bank ◽  
Short Term ◽  
Political Implications ◽  
The One ◽  
The Right ◽  
Grand Duchy ◽  
The French Revolution

Of all the regions of Central Europe, the Rhineland was the one most affected by the French Revolution. The area on the left bank of the Rhine belonged for almost two full decades to the First French Republic and the Napoleonic Empire; parts of the right bank were, for a shorter period, under the rule of the Napoleonic satellite state, the Grand Duchy of Berg. In studying these unusual circumstances, historians have sometimes focused on short-term political implications, asking how the Rhenish population of the 1790s responded to the Jacobin regime. They have also studied the long-term social and economic effects of the revolutionary legislation and the secularization of church lands.

Computer Analysis of Machines With Planar Motion: Part 2—Dynamics

1970 ◽  
Vol 37 (3) ◽  
pp. 703-712 ◽  
Author(s):  
B. Paul ◽  
D. Krajcinovic
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Performance ◽  
Transient Behavior ◽  
Basic Program ◽  
Design Tool ◽  
Multiple Degrees Of Freedom ◽  
Kinematic Loops ◽  
Long Term Behavior ◽  
Made In

A uniform procedure is described for establishing the dynamic equation of motion for machines with single or multiple degrees of freedom. The procedure, which utilizes the independent kinematic loops of the machine, is readily programmed for a digital computer. The basic program is largely independent of the specific machine being analyzed and is capable of treating input forces, internal springs and dampers, all of which may depend nonlinearly upon position, velocity, or time. As an example, the dynamic performance of a Stirling cycle engine is analyzed without recourse to simplifying approximations usually made in engine analysis (i.e., constant crank speed, use of approximate “rotating” and “reciprocating” weights, neglect of higher harmonics in piston motion). It is shown that the method not only predicts transient behavior, but is capable of predicting steady (long-term) behavior without loss of accuracy, or excessive computer costs. The method described satisfies the major criteria of generality, accuracy, and economy, required of a truly practical design tool.

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