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1.
Highly accurate real‐time localization is of fundamental importance for the safety and efficiency of planetary rovers exploring the surface of Mars. Mars rover operations rely on vision‐based systems to avoid hazards as well as plan safe routes. However, vision‐based systems operate on the assumption that sufficient visual texture is visible in the scene. This poses a challenge for vision‐based navigation on Mars where regions lacking visual texture are prevalent. To overcome this, we make use of the ability of the rover to actively steer the visual sensor to improve fault tolerance and maximize the perception performance. This paper answers the question of where and when to look by presenting a method for predicting the sensor trajectory that maximizes the localization performance of the rover. This is accomplished by an online assessment of possible trajectories using synthetic, future camera views created from previous observations of the scene. The proposed trajectories are quantified and chosen based on the expected localization performance. In this study, we validate the proposed method in field experiments at the Jet Propulsion Laboratory (JPL) Mars Yard. Furthermore, multiple performance metrics are identified and evaluated for reducing the overall runtime of the algorithm. We show how actively steering the perception system increases the localization accuracy compared with traditional fixed‐sensor configurations. 相似文献
2.
A highly transparent and thermally stable copolymer of 1‐adamantyl methacrylate and styrene
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Thermal and optical properties of copolymers of 1‐adamantyl methacrylate (AdMA) and styrene (St) prepared by free radical polymerization in the bulk are investigated. The copolymer forms an azeotrope when the composition is AdMA/St = 55/45 mol%. The glass transition temperature and decomposition temperature of the azeotropic copolymer are 170 and ca 340 °C, respectively. The refractive index increases nonlinearly with St content from 1.522 to 1.591. The light scattering loss at 633 nm is 28.1 dB km?1, which is less than half of that of polystyrene. The total optical loss including molecular vibrational absorption, which is evaluated using a copolymer‐based optical fiber, is 292–645 dB km?1 at 500–700 nm. These values correspond to transmittances of 86–93% for a 1 m optical path length. © 2014 Society of Chemical Industry 相似文献
3.
Toshimitsu Suzuki Osamu Yamada Yasuhiko Takahashi Yoshihisa Watanabe 《Fuel Processing Technology》1985,10(1):33-43
Hydroliquefaction of low-sulfur Australian coals (Wandoan and Yallourn) was studied using iron carbonyl complexes as catalyst. The addition of Fe(CO)5 (2.8 wt% Fe of coal) increased coal conversion from 48.6 to 85.2% for Wandoan coal, and from 36.7 to 69.7% for Yallourn coal in 1-methylnaphthalene at 425°C under an initial hydrogen pressure of 50 kg cm?2. When molecular sulfur was added to iron carbonyls (Fe(CO)5, Fe2(CO)9 and Fe3(CO)12), higher coal converions ( > 92%) and higher oil yields (>46%) were obtained, along with an increase in the amount of hydrogen transferred to coal from the gas phase (0.2 to 2.8%, d.a.f. coal basis). In the liquefaction studies using a hydrogen donor solvent, tetralin, Fe(CO)5S catalyst increased the amount of hydrogen absorbed from the gaseous phase and decreased the amount of naphthalene dehydrogenated from tetralin. The direct hydrogen transfer reaction from molecular hydrogen to coal fragment radicals seems to be a major reaction pathway. Organic sulfur compounds, dimethyldisulfide and benzothiophene, and inorganic FeS2 and NiS were found to be good sulfur sources to Fe(CO)5. From X-ray diffraction analyses of liquefaction residues, it is concluded that Fe(CO)5 was converted into pyrrhotite (Fe1?xS) when sulfur was present, but into Fe3O4 in the absence of sulfur. 相似文献
4.
This paper introduces the Precise Rendering Method, which generates accurately anti-aliased and highlighted images from tessellated polygons. The Precise Rendering Method first solves the aliasing problems of hidden surface removal by using the Cross Scanline Algorithm. This algorithm can exactly calculate polygon areas projected onto each pixel by using horizontal and vertical scanlines. Aliasing artifacts in shading are then prevented by the Reflection Intergration Method, which analytically integrates the intensity of reflection in the solid angle defined by surface normals at vertices of the projected area. Several synthesized images are created to show the efficiency of the Precise Rendering Method. 相似文献
5.
Na-oyoshi Iwasaki Takanori Miyake Eriko Yagasaki Toshimitsu Suzuki 《Catalysis Today》2006,111(3-4):391-397
Attention has been increasingly paid to the partial oxidation of lower alkanes to synthesis gas, due to its intrinsic energy saving process. We studied the partial oxidation of ethane (POE) on Co loaded on various supports. The POE performance varied as follows: Y2O3, CeO2, ZrO2, La2O3 SiO2, Al2O3, TiO2 > MgO. Comparing Y2O3 and CeO2, the carbon deposition during the POE was negligible on CeO2 and therefore CeO2 was the most preferable support. By changing space velocity and O2 partial pressure, reaction mechanism of POE was studied and it was revealed that two-step mechanism was prevailing; combustion of ethane to H2O and CO2 and subsequent reforming of ethane with H2O and CO2 to synthesis gas. Co/CeO2 catalyst exhibited high and stable catalytic activity for 10 h; high ethane conversion of 18% (maximum ethane conversion 20% at O2/C2H6 = 0.2) with H2 and CO selectivities of 93 and 84%, respectively. 相似文献
6.
Maki Itoh Toshimitsu Suzuki Yoshihiko Tsujimoto Ken-ichi Yoshii Yoshinobu Takegami Yoshihisa Watanabe 《Fuel》1983,62(1):98-102
Thermal cracking of tar-sand bitumens has been carried out using a two-stage pyrolysis reactor with temperature zones of 440°C and 750–800°C, respectively. Feedstocks were pyrolysed in the first stage into cracked oils, which were carried to the second stage for subsequent pyrolysis. Only 12–14 wt% of ethylene was obtained from tar-sand bitumens at the residence time of 1.2 s in the second stage, although 27 and 16 wt% were obtained from Taching and Iranian heavy vacuum residues, respectively. The tar-sand bitumens contain shorter paraffinic straight-chains and have more branched molecules than the vacuum residues of petroleum. A straight-chain paraffin index is proposed, with which a good correlation was obtained between ethylene yield and the fraction of straight-chain paraffin carbons in the heavy oil. 相似文献
7.
Preparation of zinc ferrite in the presence of carbon material and its application to hot-gas cleaning 总被引:3,自引:0,他引:3
In order to develop an efficient absorbent of H2S in coal gasification, zinc ferrite (ZnFe2O4) was prepared in the presence of carbon materials such as activated carbon (AC), activated carbon fiber (ACF), and Yallourn coal (YL). The absorption behavior of absorbents for H2S was examined using a fixed-bed flow type reactor equipped with a quadrupole mass spectrometer.Carbon material-supported ZnFe2O4 exhibited larger desulfurization capacity for H2S than unsupported ferrites. They could efficiently remove H2S from 4000 ppm levels in a simulated coal gasification gas to less than 1 ppm at 500 °C. The absorption capacity of H2S with ZnFe2O4/AC, ZnFe2O4/ACF, and ZnFe2O4/YL exhibited nearly 100% of stoichiometric amount of loaded metal species. They could be regenerated by an air oxidation in O2-Ar (50 vol%) at 450 °C for 30 min. The regenerated ferrite can be used for repeated absorption of H2S with a very slight decrease in the absorption capacity. 相似文献
8.
M. Shiomi D. Takano K. Osakada M. Otsu 《International Journal of Machine Tools and Manufacture》2003,43(3):1737
In order to improve the mechanical properties of products, a forming process of a solid material at a temperature just below the melting point is proposed. The material is deformed at the semi-solid temperature due to the heat generation caused by plastic deformation. The tensile strength, elongation, hardness and toughness of the aluminium alloy (Al–7%Si–0.3%Mg) billet extruded at temperatures between 500 and 550 °C are compared with those of the billet extruded in the hot forming (450 °C) and the semi-solid (560 °C) temperatures. The billet temperature during forming is evaluated by the finite element simulation. The tensile strength and hardness of the billet extruded at 550 °C just below the solidus temperature are higher than those for a billet at 450 °C, and they are almost the same as those for a billet deformed at 560 °C in the semi-solid region. The elongation and toughness of the extruded billet at 550 °C are lower than those for a billet at 450 °C. The forming load at 550 °C is almost half of that at 450 °C. Cracking on the surface of the extruded billet occurs at a high punch speed. The calculated temperature when the solid billet is extruded in the semi-solid state agrees well with the experimental one at which the tensile and hardness are improved. 相似文献
9.
Abstract The dynamic properties of doubly-scattered speckles produced at the image plane have been investigated using a scattering model that consists of a coherent Gaussian beam, a cascade of two moving diffusers and a single imaging lens. Dependence of the fluctuation speed of time-varying image speckles on the velocities of the diffusers is found to change with the size of illuminating speckles and the width of the point-spread function of the imaging lens. When the point-spread function and the focal position satisfy certain conditions, three kinds of velocity information—the velocity of each diffuser, the average velocity of the diffusers and the velocity difference between the diffusers—can be obtained by measuring a temporal correlation length of the time-varying speckle intensity. Experimental results confirm the theoretical predictions. 相似文献
10.
Hiro-aki Nishimoto Kiyoharu Nakagawa Na-oki Ikenaga Toshimitsu Suzuki 《Catalysis Letters》2002,82(3-4):161-167
Ru-loaded Y2O3 catalyst was investigated for the partial oxidation of methane to synthesis gas. Ru(0.5 wt%)/Y2O3 catalyst afforded a high CH4 conversion of 27% at a CH4:O2 ratio of 5 to give nearly a 1:2 ratio of CO and H2 with a selectivity of 75% at 873 K. Ru(0.5 wt%)/Y2O3 catalyst maintained high catalytic activity over 10 h in the partial oxidation of methane. Carbon deposition of the catalyst surface in the reaction of CH4 was examined by thermogravimetric analyses, and it was found that no carbon deposition occurred on the Ru(0.5 wt%)/Y2O3 catalyst. The synthesis-gas production proceeded basically via a two-step reaction consisting of methane combustion to give H2O and CO2, followed by the reforming of methane from CO2 and steam. 相似文献