Vibration Suppression in a Tension-Aligned Structure Through Sequential Application and Removal of Constraints

2012 ◽  
Author(s):  
Tingli Cai ◽  
Ranjan Mukherjee ◽  
Alejandro R. Diaz
Keyword(s):  
Vibration Control ◽  
High Frequency ◽  
Vibration Suppression ◽  
Primary Role ◽  
Accurate Knowledge ◽  
Array Structure ◽  
System States ◽  
Aligned Array ◽  
Control Methodology

We present an efficient method for vibration suppression in a tension-aligned array structure using constraint actuators. The primary role of constraint actuators is to cyclically apply and remove constraints such that vibration energy is efficiently funneled into high-frequency modes of the structure, where it can be dissipated quickly and naturally due to high rates of damping. A cycle of constraint application and removal can never add energy and hence the method can potentially achieve vibration control without accurate knowledge of the system states. The vibration control methodology is applied to a tension-aligned array structure supported by a structure in compression. Our approach for vibration suppression has the potential to positively influence the development of tension-aligned architectures which are contemplated for large precision apertures in space.

Vibration Control of Nonlinear Rotating Beam Using Piezoelectric Actuator and Sliding Mode Approach

2006 ◽  
Author(s):  
X. Xue ◽  
J. Tang
Keyword(s):  
Vibration Control ◽  
Piezoelectric Actuator ◽  
Vibration Suppression ◽  
Control Method ◽  
Sliding Mode ◽  
External Disturbance ◽  
Rotating Beam ◽  
System States ◽  
Euler Bernoulli Beam ◽  
Beam Transverse Vibration

In this research, we develop a general methodology for the vibration control of nonlinear rotating beam. The dynamic model of a rotating Euler-Bernoulli beam integrated with piezoelectric actuator is formulated. An integral sliding mode control design is proposed for the vibration suppression of the system with nonlinear coupling effects between the hub rotation and the beam transverse vibration. The sliding surface is constructed using part of the system states, and the rotating hub dynamics is treated as the internal dynamics of the system under the condition that the states of the zero dynamics are bounded. The robust stability of the proposed controller is also guaranteed. A series of simulation studies demonstrate that the proposed control method can effectively suppress the beam vibrations induced by the hub rotation and the external disturbance.

Vibration Suppression in a Simple Tension-Aligned Array Structure

AIAA Journal ◽  
2014 ◽  
Vol 52 (3) ◽  
pp. 504-515 ◽  
Author(s):  
Tingli Cai ◽  
Ranjan Mukherjee ◽  
Alejandro R. Diaz
Keyword(s):  
Vibration Suppression ◽  
Simple Tension ◽  
Array Structure ◽  
Aligned Array

Sports Photography and Historical Development

2018 ◽  
Vol 5 (1) ◽  
pp. 93-115
Author(s):  
Miloš Stamenković
Keyword(s):  
Historical Development ◽  
Emotional Reaction ◽  
Main Role ◽  
Primary Role

SummarySports photography undoubtedly has a significant place in sports press and publicism. It’s main and primary role is to present sports to the readers as art, which it is. Sport is characterized by dynamic and varied movements, and the main role of sports photography is reflected in the fact that it is in this way that sport shows its essence. Having in mind that photography tells more than a thousand words it sends a clear message to the reader as well to people who are informed about events via sports portals. Sports photography is a multidimensional art for many reasons. When we say “multi”, it primarily refers to a wider range that sports photography has to offer, which means sports photography is not only directed at presenting athletes on the move and the main actors who contribute to achieving the results by their engagement – it also has the role of sports “psychophotography” which is an analysis and capture of the emotional reaction of an athlete after winning or losing from the opposing team.

Calculation-and-experimental estimation of the role of the frequency ratio in changing the endurance at two-frequency deformation modes

2019 ◽  
Vol 85 (1(I)) ◽  
pp. 64-71 ◽  
Author(s):  
M. M. Gadenin
Keyword(s):  
High Frequency ◽  
Experimental Studies ◽  
Low Frequency ◽  
Reduction Factor ◽  
Single Frequency ◽  
Cyclic Loads ◽  
Small Ratio ◽  
Harmonic Components ◽  
Deformation Modes

The cycle configuration at two-frequency loading regimes depends on the number of parameters including the absolute values of the frequencies and amplitudes of the low-frequency and high-frequency loads added during this mode, the ratio of their frequencies and amplitudes, as well as the phase shift between these harmonic components, the latter having a significant effect only with a small ratio of frequencies. Presence of such two-frequency regimes or service loading conditions for parts of machines and structures schematized by them can significantly reduce their endurance. Using the results of experimental studies of changes in the endurance of a two-frequency loading of specimens of cyclically stable, cyclically softened and cyclically hardened steels under rigid conditions we have shown that decrease in the endurance under the aforementioned conditions depends on the ratio of frequencies and amplitudes of operation low-frequency low-cycle and high-frequency vibration stresses, and, moreover, the higher the level of the ratios of amplitudes and frequencies of those stacked harmonic processes of loading the greater the effect. It is shown that estimation of such a decrease in the endurance compared to a single frequency loading equal in the total stress (strains) amplitudes can be carried out using an exponential expression coupling those endurances through a parameter (reduction factor) containing the ratio of frequencies and amplitudes of operation cyclic loads and characteristic of the material. The reduction is illustrated by a set of calculation-experimental curves on the corresponding diagrams for each of the considered types of materials and compared with the experimental data.

OBOLESCENCE AND THE DIFFUSION OF INNOVATIONS

2020 ◽  
pp. 113-130
Author(s):  
A.V. GOLUBEV ◽  
Keyword(s):  
Diffusion Of Innovations ◽  
Time Lag ◽  
Practical Implementation ◽  
Primary Role ◽  
Innovation Development ◽  
Scientific Hypothesis ◽  
Scientific Papers ◽  
The Moment ◽  
Sociological Studies

The diffusion of innovations is described as a process in a number of scientific papers. At the same time, the causes of this process have not been sufficiently studied. The author’s goal is to consider the main regularities, under which the life cycle of innovations begins, and propose measures to enhance diffusion in modern conditions. As a scientific hypothesis, the author accepts the postulate about the primary role of the obolescence of attracted innovations in this process. The analysis revealed not only the economic proportions that initiate the start of innovation promotion, but also the influence on the diffusion rate of the obsolescence degree of innovations and the market share occupied by the new product. Methodological approaches have been developed to determine economic efficiency depending on the moment of technological change-over, as well as to determine the absolute and relative speed of innovation diffusion. Sociological studies were conducted to determine the state of innovation development and the time lag between obtaining information about an innovation and its practical implementation. The author presents his “Agroopyt” information system developed to disseminate knowledge in the agricultural sphere and ensure technology transfer in agriculture. Digital methods provide for significant accelerateion of the diffusion of innovations and expand its scope.

scholarly journals Four Mutant Alleles Elucidate the Role of the G2 Protein in the Development of C4 and C3 Photosynthesizing Maize Tissues

Genetics ◽  
2001 ◽  
Vol 159 (2) ◽  
pp. 787-797
Author(s):  
Lizzie Cribb ◽  
Lisa N Hall ◽  
Jane A Langdale
Keyword(s):  
Cell Types ◽  
Bundle Sheath ◽  
Primary Role ◽  
Ribulose Bisphosphate Carboxylase ◽  
Sheath Cell ◽  
Mesophyll Cells ◽  
Phenotypic Data ◽  
Bisphosphate Carboxylase ◽  
Bundle Sheath Cell

Abstract Maize leaf blades differentiate dimorphic photosynthetic cell types, the bundle sheath and mesophyll, between which the reactions of C4 photosynthesis are partitioned. Leaf-like organs of maize such as husk leaves, however, develop a C3 pattern of differentiation whereby ribulose bisphosphate carboxylase (RuBPCase) accumulates in all photosynthetic cell types. The Golden2 (G2) gene has previously been shown to play a role in bundle sheath cell differentiation in C4 leaf blades and to play a less well-defined role in C3 maize tissues. To further analyze G2 gene function in maize, four g2 mutations have been characterized. Three of these mutations were induced by the transposable element Spm. In g2-bsd1-m1 and g2-bsd1-s1, the element is inserted in the second intron and in g2-pg14 the element is inserted in the promoter. In the fourth case, g2-R, four amino acid changes and premature polyadenylation of the G2 transcript are observed. The phenotypes conditioned by these four mutations demonstrate that the primary role of G2 in C4 leaf blades is to promote bundle sheath cell chloroplast development. C4 photosynthetic enzymes can accumulate in both bundle sheath and mesophyll cells in the absence of G2. In C3 tissue, however, G2 influences both chloroplast differentiation and photosynthetic enzyme accumulation patterns. On the basis of the phenotypic data obtained, a model that postulates how G2 acts to facilitate C4 and C3 patterns of tissue development is proposed.

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