degradation factor
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Symmetry ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1615
Author(s):  
Yi Zhang ◽  
Yingying Nie ◽  
Liheng Chen

In this study, the problem of observer-based adaptive sliding mode control is discussed for nonlinear systems with sensor and actuator faults. The time-varying actuator degradation factor and external disturbance are considered in the system simultaneously. In this study, the original system is described as a new normal system by combining the state vector, sensor faults, and external disturbance into a new state vector. For the augmented system, a new sliding mode observer is designed, where a discontinuous term is introduced such that the effects of sensor and actuator faults and external disturbance will be eliminated. In addition, based on a tricky design of the observer, the time-varying actuator degradation factor term is developed in the error system. On the basis of the state estimation, an integral-type adaptive fuzzy sliding mode controller is constructed to ensure the stability of the closed-loop system. Finally, the effectiveness of the proposed control methods can be illustrated with a numerical example.


DNA Repair ◽  
2021 ◽  
pp. 103202
Author(s):  
Oluwasegun T. Akinniyi ◽  
Joseph C. Reese

Author(s):  
Yi Zhang ◽  
Yingying Nie ◽  
Zhiyuan Dong ◽  
Liheng Chen

In this paper, the problem of observer-based adaptive sliding mode control is discussed for nonlinear systems with sensor and actuator faults. The time-varying actuator degradation factor and external disturbance are considered in the system simultaneously. In this study, the original system is described as a new normal system by combining the state vector, sensor faults and external disturbance into a new state vector. For the augmented system, a new sliding mode observer is designed, where a discontinuous term is introduced such that the effects of sensor and actuator faults and external disturbance will be eliminated. In addition, based on a tricky design of the observer, the time-varying actuator degradation factor term is developed in the error system. On the basis of the state estimation, an integral-type adaptive fuzzy sliding mode controller is constructed to ensure the stability of the closed-loop system. Finally, the effectiveness of the proposed control methods can be illustrated with a numerical example.


2021 ◽  
pp. 36-40
Author(s):  
P. S. Efendyan ◽  
M. A. Abrahamyan ◽  
K. R. Nersisyan

The changing dynamics of agricultural lands throughout 2005-2020 has been investigated. Transformation of agricultural lands is related to various unresolved legislative issues. According to the research results the efficient use of agricultural lands is interfered with the current legislative environment, degradation factor, huge amount of unused soils registered in the agricultural land assets and soil fragmentation. To eliminate the mentioned factors and to reduce their effect, it is necessary to make legislative changes and to implement land management activities.


2020 ◽  
Vol 27 (2) ◽  
pp. 345-358
Author(s):  
Naima Bouazza ◽  
Kaouider Cherifi ◽  
Brahim Babali ◽  
Mohammed Bouazza

This study provides bibliographical note on the syntaxonomy of the vegetation of Tlemcen, Hafir, Moutas of North-western Algeria, including the associations and alliances of the different higher units found in the Hafir forest and the Moutas Reserve. In this work, we observed modifications of forest and pre-forest structures according to bioclimatic variations. However, in this region, the xericity of the climate is not the only factor destroying the plant cover, anthropization is also a degradation factor. While being aware of the negative consequences, man, through their abusive cultivation, illegal logging, overgrazing, urbanization, the depletion of natural resources;, inhibits the evolution of vegetation, participates in the replacement of a rich plant cover by another and more xerophytic plant cover with thorny and/or toxic feature. The landscape is dominated, for the most part, by open and degraded formations based on therophytes and chamaephytes, linked to Rosmarinetea and Cisto-Lavanduletea. The tree structures in Hafir and the Moutas reserve, still occupy only minimal areas subject to the destructive actions of man and his flock. These formations are still linked to the Quercetea ilicis. These ecosystems are marked by a regressive evolution (forest, pre-forest, scrub, scrubland and therophytization). Bangladesh J. Plant Taxon. 27(2): 345-358, 2020 (December)


Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6249
Author(s):  
Rubén Usamentiaga ◽  
Alberto Fernández ◽  
Juan Luis Carús

Solar energy is mostly harnessed in arid areas where a high concentration of atmospheric dust represents a major environmental degradation factor. Gravitationally settled particles and other solid particles on the surface of the photovoltaic panels or thermal collectors greatly reduce the absorbed solar energy. Therefore, frequent cleaning schedules are required, consuming high quantities of water in regions where water precipitation is rare. The efficiency of this cleaning maintenance is greatly improved when methods to estimate the degree of cleanness are introduced. This work focuses on the need for better detecting the degradation created by dust deposition, considering experimental data based on different air pollutants, and analyzing the resulting thermal and visible signatures under different operating environments. Experiments are performed using six different types of pollutants applied to the surface of parabolic trough collectors while varying the pollutant density. The resulting reflectivity in the visible and infrared spectrum is calculated and compared. Results indicate that the pollutants can be distinguished, although the reflectivity greatly depends on the combination of the particle size of the pollutant and the applied amount, with greater impact from pollutants with small particles.


2020 ◽  
Vol 36 (5) ◽  
pp. 707-719
Author(s):  
C.-C. Lin ◽  
M.-Z. Jiang ◽  
F.-L. Yang

ABSTRACTThis work examines the μ(I) relation that describes the effective friction coefficient μ of a dense granular flow as a function of flow inertial number I, at the center of a rotating drum from its flow onset to steady state using DEM. We want to see how the internal friction coefficient of an accelerating flow may be predicted so that the associated tangential stress can be estimated with the proper knowledge of the normal stress. Under the three investigated drum speeds (3, 4.5 and 6 rpm), the bulk normal stress, σn(y), is found to be a consistent linear depth profile throughout the flow development with a slope degraded from the hydrostatic value, Ph(y), due to lateral wall friction. With the discovery of a non-constant depth-decaying effective wall friction coefficient, we derive analytically a wall-degradation factor K(h) to give σn(y)= K(h)Ph(y). The depth profile of tangential stress, however, varies in time from a concave shape upon acceleration, τa(y), to a more linear trend at the steady state, τss(y). Hence, the μa-Ia profile (with μa=τ/σn) upon flow acceleration offsets from the steady μss(Iss) relation. A pseudo-steady acceleration modification number, ΔI, is proposed to shift the inertial number in the acceleration phase to I* = Ia+ΔI so that the μa-I* data converge to μss(Iss). This finding shall allow us to predict a transient tangential stress by τa(y) = μss(I*)K(y)Ph(y) using the well-accepted knowledge of steady flow rheology, hydrostatic pressure, and the currently developed wall-degradation factor.


2020 ◽  
Vol 15 (2) ◽  
pp. 1-5
Author(s):  
Luciano Mendes Camillo ◽  
Marcos Paulo Braga de Lima ◽  
Marco Aurélio Pinhel Peixoto ◽  
Marcello Marcelino Correa ◽  
Salvador Pinillos Gimenez

The zero temperature coefficient (ZTC) is investigated by three-dimensional numerical simulations in the Metal-Oxide-Semiconductor (MOS) Field Effect Transistor (MOSFET) with the ellipsoidal (EM) and conventional rectangular gate geometries (CM), considering the same channel widths (W), gate areas (Ag) and bias condition (BC).   In this work an improved simple model which predicts the ZTC point taking into account only the mobility degradation factor (c) and threshold voltage (Vth) parameters as function of temperature is proposed in the linear and saturation operation regions. The analysis takes into account the temperature variations of the threshold voltage and the mobility degradation factor. Although simple, the model predictions present a good agreement with the numerical simulations results.


2020 ◽  
Author(s):  
Atsushi Masuda

Degradation phenomena of photovoltaic cells and modules were systematically and in detail studied by observing those exposed outdoors and subjecting those to various indoor acceleration tests. Those degradation phenomena were roughly classified into three categories; less incident light into photovoltaic cells, less collection of photogenerated carriers, and less photovoltaic ability itself. Degradation mechanisms of photovoltaic cells and modules were clarified by microscopic physical and chemical analyses. Based on the mechanisms, it was found that key materials for improving reliability are encapsulants and electrodes. Improvement methods of reliability for photovoltaic cells and modules were also proposed. Prediction of lifetime by indoor acceleration test methods is also important although the prediction is quite difficult using the artificial test methods with only one or two degradation factor(s). Remaining issues of reliability and durability will be also presented.


2020 ◽  
Vol 853 ◽  
pp. 187-192
Author(s):  
Naoki Yokokawa ◽  
Toshihiro Senga ◽  
Tadashi Yamauchi ◽  
Shigeyuki Date

As a countermeasure against deterioration of reinforced concrete structures that have suffered from salt damage, materials containing salt adsorbents have been developed. In this study, the basic properties of the “Hybrid Epoxy Resin Repair Agent” in which a functional adsorbent was added to an epoxy resin were grasped and verified. As a result, chloride ion adsorption effect assuming repair of salt damage and sulfate ion adsorption effect assuming chemical erosion repair was confirmed.


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