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旋翼式无人机的发展和趋势
Development and Trend of Unmanned Rotorcraft
 [PDF]

张天航, 白金平
Artificial Intelligence and Robotics Research (AIRR) , 2013, DOI: 10.12677/AIRR.2013.21003
Abstract:
旋翼式无人机的高速发展已经受到了各个领域的高度重视,本文介绍了旋翼式无人机的大体分类、技术组成、应用领域、发展现状,并预测了旋翼式无人机未来的发展趋势。
With the rapid development of the unmanned rotorcraft, more and more attention has been paid on it in many field. In this paper, the general classification, technical composition, applications and development situation of un-manned rotorcraft is introduced. And the development trend of unmanned rotorcraft in the future is also predicted.
Toposes in General Theory of Relativity  [PDF]
Alexandr K. Guts,Egor B. Grinkevich
Physics , 1996,
Abstract: We study in this paper different topos-theoretical approaches to the problem of construction of General Theory of Relativity. In general case the resulting space-time theory will be non-classical, different from that of the usual Einstein theory of space-time. This is a new theory of space-time, created in a purely logical manner. Four possibitities are investigated: axiomatic approach to causal theory of space-time, the smooth toposes as a models of Theory of Relativity, Synthetic Theory of Relativity, and space-time as Grothendieck topos.
Gain-of-Sensitivity Mutations in a Trim5-Resistant Primary Isolate of Pathogenic SIV Identify Two Independent Conserved Determinants of Trim5α Specificity  [PDF]
Kevin R. McCarthy,Aaron G. Schmidt,Andrea Kirmaier,Allison L. Wyand,Ruchi M. Newman,Welkin E. Johnson
PLOS Pathogens , 2013, DOI: 10.1371/journal.ppat.1003352
Abstract: Retroviral capsid recognition by Trim5 blocks productive infection. Rhesus macaques harbor three functionally distinct Trim5 alleles: Trim5αQ, Trim5αTFP and Trim5CypA. Despite the high degree of amino acid identity between Trim5αQ and Trim5αTFP alleles, the Q/TFP polymorphism results in the differential restriction of some primate lentiviruses, suggesting these alleles differ in how they engage these capsids. Simian immunodeficiency virus of rhesus macaques (SIVmac) evolved to resist all three alleles. Thus, SIVmac provides a unique opportunity to study a virus in the context of the Trim5 repertoire that drove its evolution in vivo. We exploited the evolved rhesus Trim5α resistance of this capsid to identify gain-of-sensitivity mutations that distinguish targets between the Trim5αQ and Trim5αTFP alleles. While both alleles recognize the capsid surface, Trim5αQ and Trim5αTFP alleles differed in their ability to restrict a panel of capsid chimeras and single amino acid substitutions. When mapped onto the structure of the SIVmac239 capsid N-terminal domain, single amino acid substitutions affecting both alleles mapped to the β-hairpin. Given that none of the substitutions affected Trim5αQ alone, and the fact that the β-hairpin is conserved among retroviral capsids, we propose that the β-hairpin is a molecular pattern widely exploited by Trim5α proteins. Mutations specifically affecting rhesus Trim5αTFP (without affecting Trim5αQ) surround a site of conservation unique to primate lentiviruses, overlapping the CPSF6 binding site. We believe targeting this site is an evolutionary innovation driven specifically by the emergence of primate lentiviruses in Africa during the last 12 million years. This modularity in targeting may be a general feature of Trim5 evolution, permitting different regions of the PRYSPRY domain to evolve independent interactions with capsid.
Measurement Theory and General Relativity  [PDF]
Bahram Mashhoon
Physics , 2000, DOI: 10.1007/b13593
Abstract: The theory of measurement is employed to elucidate the physical basis of general relativity. For measurements involving phenomena with intrinsic length or time scales, such scales must in general be negligible compared to the (translational and rotational) scales characteristic of the motion of the observer. Thus general relativity is a consistent theory of coincidences so long as these involve classical point particles and electromagnetic rays (geometric optics). Wave optics is discussed and the limitations of the standard theory in this regime are pointed out. A nonlocal theory of accelerated observers is briefly described that is consistent with observation and excludes the possibility of existence of a fundamental scalar field in nature.
Diffusion in the general theory of relativity  [PDF]
Joachim Herrmann
Physics , 2010, DOI: 10.1103/PhysRevD.82.024026
Abstract: The Markovian diffusion theory in the phase space is generalized within the framework of the general theory of relativity. The introduction of moving orthonormal frame vectors both for the position as well the velocity space enables to bypass difficulties in the general relativistic stochastic calculus. The general relativistic Kramers equation in the phase space is derived both in the parametrization of phase space proper time and the coordinate time. The transformation of the obtained diffusion equation under hypersurface-preserving coordinate transformations is analyzed and diffusion in the expanding universe is studied. It is shown that the validity of the fluctuation-dissipation theorem ensures that in the quasi-steady state regime the result of the derived diffusion equation is consistent with the kinetic theory in thermodynamic equilibrium.
What if ... General Relativity is not the theory?  [PDF]
Orfeu Bertolami
Physics , 2011,
Abstract: The nature of gravity is fundamental to understand the scaffolding of the Universe and its evolution. Einstein's general theory of relativity has been scrutinized for over ninety five years and shown to describe accurately all phenomena from the solar system to the Universe. However, this success is achieved in the case of the largest scales provided one admits contributions to energy-momentum tensor involving dark components such as dark energy and dark matter. Moreover, the theory has well known shortcomings, such as the problem of singularities, the cosmological constant problem and the well known initial conditions problems for the cosmological description. Furthermore, general relativity also does not fit the well known procedures that allow for the quantization of the other fundamental interactions. In this discussion we briefly review the experimental bounds on the foundational principles of general relativity, and present three recent proposals to extend general relativity or, at least, to regard it under different perspectives.
General Relativity As an Aether Theory  [PDF]
Maurice J. Dupre,Frank J. Tipler
Physics , 2010, DOI: 10.1142/S0218271812500113
Abstract: Most early twentieth century relativists --- Lorentz, Einstein, Eddington, for examples --- claimed that general relativity was merely a theory of the aether. We shall confirm this claim by deriving the Einstein equations using aether theory. We shall use a combination of Lorentz's and Kelvin's conception of the aether. Our derivation of the Einstein equations will not use the vanishing of the covariant divergence of the stress-energy tensor, but instead equate the Ricci tensor to the sum of the usual stress-energy tensor and a stress-energy tensor for the aether, a tensor based on Kelvin's aether theory. A crucial first step is generalizing the Cartan formalism of Newtonian gravity to allow spatial curvature, as conjectured by Gauss and Riemann.
The New Evolution for SIA Rotorcraft UAV Project  [PDF]
Juntong Qi,Dalei Song,Lei Dai,Jianda Han,Yuechao Wang
Journal of Robotics , 2010, DOI: 10.1155/2010/743010
Abstract: This paper describes recent research on the design, implement, and testing of a new small-scaled rotorcraft Unmanned Aerial Vehicle (RUAV) system—ServoHeli-40. A turbine-powered UAV weighted less than 15?kg was designed, and its major components were tested at the Shenyang Institute of Automation, Chinese Academy of Sciences in Shenyang, China. The aircraft was designed to reach a top speed of more than 20?mps, flying a distance of more than 10 kilometers, and it is going to be used as a test-bed for experimentally evaluating advanced control methodologies dedicated on improving the maneuverability, reliability, as well as autonomy of RUAV. Sensors and controller are all onboard. The full system has been tested successfully in the autonomous mode using the multichannel active modeling controller. The results show that in a real windy environment the rotorcraft UAV can follow the trajectory which was assigned by the ground control station exactly, and the new control method is obviously more effective than the one in the past year's research. 1. Introduction Unmanned aerial vehicles (UAVs) are useful for many applications where human intervention is considered difficult or dangerous. Traditionally, the fixed-wing UAV has been served as the unit for these dangerous tasks because the control is easy. Rotary-wing UAV, on the other hand, can be used in many different tasks where the fixed-wing one is unable to achieve, such as vertical take-off/landing, hovering, lateral flight, pirouette, and bank-to-turn. Due to the versatility in maneuverability, helicopters are capable to fly in and out of restricted areas and hover efficiently for long periods of time. These characteristics make RUAV applicable for many military and civil applications. However, the control of RUAV is difficult. Although some control algorithms have been proposed [1–6], most of them were verified by simulation instead of real experiments. One reason for this is due to the complicate, nonlinear, and inherently unstable dynamics, which has cross coupling between main and tail rotor, and lots of time-varying aerodynamic parameters. Another reason is that the flight test is in high risk. If an RUAV lost its control, it would never be stabilized again. Based on our UAV research in [7], this paper details the development of a new unmanned helicopter (UAV) test bed—ServoHeli-40 (Figure 1) and the advanced control experiments performed toward achieving full autonomous flight. The experimental platform which has 40 kilograms takeoff weight is designed and finished by our research group in
General relativity histories theory
Savvidou, Ntina;
Brazilian Journal of Physics , 2005, DOI: 10.1590/S0103-97332005000200016
Abstract: the canonical description is based on the prior choice of a spacelike foliation, hence making a reference to a spacetime metric. however, the metric is expected to be a dynamical, fluctuating quantity in quantum gravity. after presenting the developments in the history projection operator histories theory in the last seven years - giving special emphasis on the novel temporal structure of the formalism - we show how this problem can be solved in the histories formulation of general relativity. we implement the 3+1 decomposition using metric-dependent foliations which remain spacelike with respect to all possible lorentzian metrics. this allows us to find an explicit relation of covariant and canonical quantities which preserves the spacetime character of the canonical description. in this new construction we have a coexistence of the spacetime diffeomorphisms group diff(m) and the dirac algebra of constraints.
General Relativity Histories Theory  [PDF]
Ntina Savvidou
Physics , 2004,
Abstract: The canonical description is based on the prior choice of a spacelike foliation, hence making a reference to a spacetime metric. However, the metric is expected to be a dynamical, fluctuating quantity in quantum gravity. After presenting the developments in the History Projection Operator histories theory in the last seven years--giving special emphasis on the novel temporal structure of the formalism--we show how this problem can be solved in the histories formulation of general relativity. We implement the 3+1 decomposition using metric-dependent foliations which remain spacelike with respect to all possible Lorentzian metrics. This allows us to find an explicit relation of covariant and canonical quantities which preserves the spacetime character of the canonical description. In this new construction we have a coexistence of the spacetime diffeomorphisms group Diff(M) and the Dirac algebra of constraints.
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