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3962. Fixed-time tracking control for nonholonomic mobile robot
- Creator:
- Ou, Meiying, Sun, Haibin, Zhang, Zhenxing, Li, Lingchun, and Wang, Xiang-ao
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- trajectory tracking, nonholonomic mobile robot systems, and fixed-time control
- Language:
- English
- Description:
- This paper investigates the fixed-time trajectory tracking control problem for a nonholonomic mobile robot. Firstly, the tracking error system is derived for the mobile robot by the aid of a global invertible transformation. Then, based on the unified error dynamics and by using the fixed-time control method, continuous fixed-time tracking controllers are developed for the mobile robot such that the robot can track the desired trajectory in a fixed time. Moreover, the settling time is independent of the system initial conditions and only determined by the controller parameters. Finally, numerical simulations are provided to demonstrate the effectiveness of the theoretical results.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3963. Flattening the curve of moral imagination
- Creator:
- Beran, Ondřej
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- COVID-19 crisis, economic concerns, moral dilemmas, moral luck, and remorse
- Language:
- Slovak
- Description:
- In this paper, I discuss some moral dilemmas related to the COVID-19 crisis and their framing (mainly) in the public debate. The key assumption to engage with is this: that we need primarily to take into account the long-term economic consequences of the proposed safety measures of social distancing. I argue that the long-term economic concerns, though legitimate, cannot suspend the irreducibly moral nature of the demand placed on the decision-makers by those who are vulnerable, at risk, or in need of medical treatment. This is discussed in relation to two points: 1) The political endeavour and rhetoric of “flattening the curve” is not necessarily short-sighted but expresses the acknowledgment of a legitimate expectation placed on elected representatives. 2) Not being able to prevent harm (to those who are in real need, or otherwise vulnerable) may lead to genuine moral distress, even if it is not clear whether it was in one’s, or anybody’s, powers to prevent the situation, or even if the best possible outcome has been otherwise reached. The second point may be understood as a part of the broader context of the established criticisms of utilitarianism.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3964. Flavonoid responses in wheat grown at elevated CO2: green versus senescent leaves
- Creator:
- Peñuelas, J., Estiarte, M., and Kimball, B. A.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- carbon based secondary compounds (CBSC), isoorientin, leaf age, litter, phenolics, tricin, and Triticum aestivum
- Language:
- Multiple languages
- Description:
- We compared flavonoids in green, mature, and senescing flag leaves of wheat grown under ambient (AC - 370 μmol mol-1) and elevated (EC - 550 μmol mol-1) concentrations of CO2 in a FACE (Free Air CO2 Enrichment) system. The concentrations of flag leaf flavonoids (e.g., isoorientin and tricin) decreased to one third in mature leaves, and the majoritary isoorientin almost disappeared in senescing leaves. Flavonoid concentrations increased in green well-developed flag leaves under EC (46 % isoorientin and 55 % tricin), whereas the differences disappeared in mature and senescing flag leaves. Predictions of changes in litter phenolic concentrations and their effects on decomposition rates under EC based on changes in green leaves need to be revised. and J. Peñuelas, M. Estiarte, B. A. Kimball.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3965. Flexibilní lékařské endoskopy
- Creator:
- Křížek, Miloslav
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Language:
- Czech
- Description:
- This article deals with flexible medical endoscopes which with help of optical fibres and CCD elements enable doctors to examine noninvasively human body cavities, to document found facts and to establish the diagnosis. In addition, via these instruments it is also possible to apply surgical tools for therapeutical operation.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3966. Flood regime of rivers in the Danube River basin
- Creator:
- Pekárová, Pavla
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Language:
- Slovak
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3967. Floods effects on rivers morphological changes application to the Medjerda River in Tunisia
- Creator:
- Gharbi, Mohamed, Soualmia, Amel, Dartus, Denis, and Masbernat, Lucien
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- floods, hydrodynamics, sediment transport, modelling, and river morphology
- Language:
- Slovak
- Description:
- In Tunisia especially in the Medjerda watershed the recurring of floods becoming more remarkable. In order to limit this risk, several studies were performed to examine the Medjerda hydrodynamic. The analysis of results showed that the recurrences of floods at the Medjerda watershed is strongly related to the sediment transport phenomena. Initially, a one dimensional modelling was conducted in order to determine the sediment transport rate, and to visualize the river morphological changes during major floods. In continuity of this work, we will consider a two-dimensional model for predicting the amounts of materials transported by the Medjerda River. The goal is to visualize the Medjerda behaviour during extreme events and morphological changes occurred following the passage of the spectacular flood of January 2003. As a conclusion for this study, a comparative analysis was performed between 1D and 2D models results. The objective of these comparisons is to visualize the benefits and limitations of tested models. The analysis of the results demonstrate that 2D model is able to calculate the flow variation, sediment transport rates, and river morphological changes during extreme events for complicated natural domains with high accuracy comparing with 1D Model.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3968. Flow characteristics at trapezoidal broad-crested side weir
- Creator:
- Říha, Jaromír and Zachoval, Zbyněk
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- broad-crested side weir, experimental research, flow characteristics, and hydraulics
- Language:
- Slovak
- Description:
- Broad-crested side weirs have been the subject of numerous hydraulic studies; however, the flow field at the weir crest and in front of the weir in the approach channel still has not been fully described. Also, the discharge coefficient of broad–crested side weirs, whether slightly inclined towards the stream or lateral, still has yet to be clearly determined. Experimental research was carried out to describe the flow characteristics at low Froude numbers in the approach flow channel for various combinations of in- and overflow discharges. Three side weir types with different oblique angles were studied. Their flow characteristics and discharge coefficients were analyzed and assessed based on the results obtained from extensive measurements performed on a hydraulic model. The empirical relation between the angle of side weir obliqueness, Froude numbers in the up- and downstream channels, and the coefficient of obliqueness was derived.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3969. Flow characteristics of rectangular broad-crested weirs with sloped upstream face
- Creator:
- Goodarzi, Ehsan, Farhoudi, Javad, and Shokri, Naser
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- broad crested weir, upstream face slope, flow surface pattern, discharge coefficient, correction factor, separation zone, velocity profile, priepad širokou priepadovou hranou, sklon návodného povrchu, tvar povrchu hladiny, výtokový koeficient, korekčný faktor, oblasť separácie, and profily rýchlosti prúdenia
- Language:
- Slovak
- Description:
- The hydraulic characteristics of flow over rectangular broad-crested weirs with varying upstream slopes were experimentally studied. A series of laboratory experiments was performed to investigate the effects of changing upstream slopes from 90º to 75º, 60º, 45º, 30º, 22.5º, 15º, and 10º on the flow surface pattern, discharge coefficient values, approach velocity profile and flow separation zone. In addition, a new mathematical relationship for water surface profile and a new correction factor to estimate discharge coefficient over weirs with various upstream slopes were introduced. The results showed decreasing upstream slopes from 90º to 10º leading to increasing discharge coefficient values and dissipation of the separation zone. and Práca obsahuje výsledky experimentálneho štúdia prietoku vody cez pravouhlý priepad so širokou priepadovou hranou s rozdielnymi sklonmi návodného povrchu priepadu. Uskutočnili sme sériu laboratórnych pokusov s cieľom štúdia vplyvu rôznych sklonov návodného povrchu priepadu od 90°, 75°, 60°, 45°, 30°, 22,5°, 15°, až po 10° na tvar hladiny, hodnoty prietokového súčiniteľa, rýchlostné profily a na prúdenie v oblasti separácie. Okrem toho boli zistené nové matematické vzťahy na výpočet tvaru hladiny, ako aj nové korekčné faktory na určenie prietokových súčiniteľov cez priepad s rozdielnymi sklonmi návodného povrchu. Z výsledkov vyplýva, že znižujúce sa sklony návodného povrchu priepadu od 90° po 10° vedú k zvýšeniu prietokového súčiniteľa a k disipácii oblasti separácie.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3970. Flow control using synthetic jet actuators
- Creator:
- Uruba, Václav
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- synthetic jet, continuous jet, actuator, flow control, boundary layer separation, mixing, jet vectoring, and skin friction
- Language:
- English
- Description:
- A synthetic jet can be produced over broad range of time and length-scales. Theirs unique attributes make them attractive fluidic actuators for various flow-control tasks. Generation, evolution and interaction of synthetic jets are reviewed in the presented paper. Application of this actuator type ranging from separation and turbulence control, control to thrust vectoring and mixing augmentation to skin friction control is shown. and Obsahuje seznam literatury
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public