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41.
This paper addresses the problem of building large-scale geometric maps of indoor environments with mobile robots. It poses the map building problem as a constrained, probabilistic maximum-likelihood estimation problem. It then devises a practical algorithm for generating the most likely map from data, along with the most likely path taken by the robot. Experimental results in cyclic environments of size up to 80 by 25 meter illustrate the appropriateness of the approach. 相似文献
42.
Heinz‐Dieter Bürger 《真空研究与实践》2004,16(2):67-70
The use of the high evaporation enthalpy of water is one of the oldest technologies of refrigeration for food preservation used by the mankind. One could nearly celebrate the true 5000th anniversary of this technology. Nowadays we call the refrigeration by evaporation from wet surfaces “adiabatic refrigeration”, it regulates, for instance, our body heat by evaporating sweat. After the introduction of some vacuum pumps into the experimental scientific works, 250 years ago, namely in Great Britan, the modern form of “artificial” refrigeration began its career, the evaporation of liquids under the absence of permanent gasses in vacuum. The vacuum refrigeration has been nearly abruptly stopped by the development of compression refrigeration processes, about 150 years ago. Only after world war 2, a reintroduction of vacuum refrigeration began again. Now, at the beginning of the 3. milennium, there are good chances for recovering terrain. 相似文献
43.
K. Hackl W. Zhang M. Schmidt‐Baldassari U. Hoppe 《Materialwissenschaft und Werkstofftechnik》2004,35(5):284-288
The asymmetry associated with martensitic transformations observed in tension/compression experiments of shape‐memory‐alloys (SMAs) is investigated on the basis of a recently suggested micromechanical model. The approach is based on crystallographic theory and utilizes a framework of energy minimization in a finite deformation context. Polycrystalline NiTi under tension demonstrates smaller phase‐transformation start‐strain, differe phase‐transformation stress‐levels and flatter phase‐transformation stress‐strain slopes than that under compression in our numerical simulation. The phase‐transformation start‐stress is followed to have a linear relationship with respect to the temperature within a certain range. These results agree well with experimental results reported in the literature. 相似文献
44.
45.
Reinhold Kleiner Dieter Koelle John Clarke 《Journal of Low Temperature Physics》2007,149(5-6):230-260
We investigate the characteristics and noise performance of rf Superconducting Quantum Interference Devices (SQUIDs) by solving
the corresponding Langevin equations numerically and optimizing the model parameters with respect to noise energy. After introducing
the basic concepts of the numerical simulations, we give a detailed discussion of the performance of the SQUID as a function
of all relevant parameters. The best performance is obtained in the crossover region between the dispersive and dissipative
regimes, characterized by an inductance parameter β′
L
≡2π
LI
0/Φ
0≈1; L is the loop inductance, I
0 the critical current of the Josephson junction, and Φ
0 the flux quantum. In this regime, the lowest (intrinsic) values of noise energy are a factor of about 2 above previous estimates
based on analytical approaches. However, several other analytical predictions, such as the inverse proportionality of the
noise energy on the tank circuit quality factor and the square of the coupling coefficient between the tank circuit and the
SQUID loop, could not be well reproduced. The optimized intrinsic noise energy of the rf SQUID is superior to that of the
dc SQUID at all temperatures. Although for technologically achievable parameters this advantage shrinks, particularly at low
thermal fluctuation levels, we give examples for realistic parameters that lead to a noise energy comparable to that of the
dc SQUID even in this regime.
相似文献
46.
47.
Jaroslaw Domaradzki Danuta Kaczmarek Dieter Schmeisser Radoslaw Wasielewski Damian Wojcieszak 《Vacuum》2008,82(10):1007-1012
This work presents the influence of annealing on the structure and stoichiometry of europium (Eu)-doped titanium dioxide (TiO2). Thin films were fabricated by magnetron sputtering from a metallic Ti-Eu target in oxygen atmosphere and deposited on silicon and SiO2 substrates. After deposition the selected samples were additionally annealed in air up to 1070 K.Film properties were examined by means of X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) and the results were analyzed together with the undoped TiO2 thin films prepared under similar technological conditions.XRD results showed that depending on the Eu content, as-deposited thin films consisted of the TiO2-anatase or TiO2-rutile.An additional annealing will result in the growth of anatase crystals up to 35 nm, but anatase to rutile phase transformation has not been recorded. AFM images display high quality and a dense nanocrystalline structure. From the XPS Ti2p spectra the 4+oxidation state of Ti was confirmed. The O1s XPS spectra displayed the presence of an O2− photoelectron peak accompanied by an additional broader peak that originates from hydroxyl species chemisorbed at the sample surface. It has been found that Eu dopant increases the OH− content on the surface of prepared TiO2:Eu thin films. The calculated O/Ti ratio was in the range of 1.85-2.04 depending on the sample. 相似文献
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50.
在变化的媒体世界中,宽带载体很快也参与了"围绕媒体内容的竞争",这对于从事印刷信息的企业也是如此.在新的条件下,把他们的品牌、甚至制作的内容以及多年的经验都运用在竞争的优势中.本文旨在介绍宽带的竞争,以激励德国出版业未来的发展情况. 相似文献