502 research outputs found

    Autonomous Locomotion Mode Transition Simulation of a Track-legged Quadruped Robot Step Negotiation

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    Multi-modal locomotion (e.g. terrestrial, aerial, and aquatic) is gaining increasing interest in robotics research as it improves the robots environmental adaptability, locomotion versatility, and operational flexibility. Within the terrestrial multiple locomotion robots, the advantage of hybrid robots stems from their multiple (two or more) locomotion modes, among which robots can select from depending on the encountering terrain conditions. However, there are many challenges in improving the autonomy of the locomotion mode transition between their multiple locomotion modes. This work proposed a method to realize an autonomous locomotion mode transition of a track-legged quadruped robot steps negotiation. The autonomy of the decision-making process was realized by the proposed criterion to comparing energy performances of the rolling and walking locomotion modes. Two climbing gaits were proposed to achieve smooth steps negotiation behaviours for energy evaluation purposes. Simulations showed autonomous locomotion mode transitions were realized for negotiations of steps with different height. The proposed method is generic enough to be utilized to other hybrid robots after some pre-studies of their locomotion energy performances

    Early Science with the Large Millimetre Telescope: Molecules in the Extreme Outflow of a proto-Planetary Nebula

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    Extremely high velocity emission likely related to jets is known to occur in some proto-Planetary Nebulae. However, the molecular complexity of this kinematic component is largely unknown. We observed the known extreme outflow from the proto-Planetary Nebula IRAS 16342-3814, a prototype water fountain, in the full frequency range from 73 to 111 GHz with the RSR receiver on the Large Millimetre Telescope. We detected the molecules SiO, HCN, SO, and 13^{13}CO. All molecular transitions, with the exception of the latter are detected for the first time in this source, and all present emission with velocities up to a few hundred km s−1^{-1}. IRAS 16342-3814 is therefore the only source of this kind presenting extreme outflow activity simultaneously in all these molecules, with SO and SiO emission showing the highest velocities found of these species in proto-Planetary Nebulae. To be confirmed is a tentative weak SO component with a FWHM ∼\sim 700 km s−1^{-1}. The extreme outflow gas consists of dense gas (nH2>_{\rm H_2} > 104.8^{4.8}--105.7^{5.7} cm−3^{-3}), with a mass larger than ∼\sim 0.02--0.15 M⊙_{\odot}. The relatively high abundances of SiO and SO may be an indication of an oxygen-rich extreme high velocity gas.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Society Letter

    Within-wing isotopic (δ2H, δ13C, δ15N) variation of monarch butterflies: implications for studies of migratory origins and diet

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    Increasingly, stable isotope measurements are being used to assign individuals to broad geographic origins based on established relationships between animal tissues and tissue-specific isoscapes. In particular, the eastern North American population of the monarch butterfly (Danaus plexippus) has been the subject of several studies using established δ2H and δ13C wing-tissue isoscapes to infer natal origins of migrating and overwintering individuals. However, there has been no study investigating potential variance that can derive from sub-sampling different regions of the wings, especially those regions differing in pigmentation (orange versus black). Within-wing isotopic (δ2H, δ13C, δ15N) variance of 40 monarch butterflies collected from natural overwinter mortality on Mexican roost sites were split evenly into two groups: unwashed samples and those washed in a 2:1 chloroform:methanol solvent. Isotopic variance in δ2H and δ13C was related to pigment (within-wing range 5‰ and 0.5‰, respectively), but not region of subsampling. This variance was reduced 3 to 4 fold through solvent washing that removed pigmented surface scales and any adhered oils. Wing δ15N was similarly influenced by pigment (range 0.3‰), but this effect was not reduced through washing. We recommend future isotopic studies of monarchs and other butterflies for migration research to use the same region for sub-sampling consistently and to wash samples with solvent to reduce isotopic variance related to uncontrolled variance in discrimination (δ2H, δ13C, δ15N) and/or adsorbed water vapor (δ2H). These data also need to be included in description of methods

    Improved THETA-1 for light olefins oligomerization to diesel: Influence of textural and acidic properties

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    The increase in diesel demand, especially in Europe, and the need for high fuel quality requirements are forcing refiners to move into additional processes for production of high cetane diesel in order to meet the present market trends. Oligomerization of light olefins into middle distillate range products is a viable option. The fuel produced through this technology is environmentally friendly, free of sulfur and aromatics, and the adequate choice of the heterogeneous catalyst will direct the selectivity towards low branched oligomers, which will result in a high quality product. In this work we show the benefits of combining basic desilication treatments for generation of additional mesoporosity in mono-directional Theta-1 zeolite, with selective acid dealumination steps that restore not only the microporosity to values close to those of the parent samples, but also the total and strong Bronsted acidity. These modified Theta-1 zeolites present an outstanding catalytic behavior for oligomerization of propene, with a largely increased initial activity, a much higher resistance to deactivation with time on stream, and an improved selectivity to products in the diesel fraction, as compared to the original microporous Theta-1.The authors thank BP Products of North America for their financial support and permission to publish this work, and Consolider Ingenio 2010-Multicat, the "Severo Ochoa Program", and MAT2012-31657 for financial support. R. Sanchis is acknowledged for technical support.Martínez, C.; Doskocil, EJ.; Corma Canós, A. (2014). Improved THETA-1 for light olefins oligomerization to diesel: Influence of textural and acidic properties. Topics in Catalysis. 57(6-9):668-682. https://doi.org/10.1007/s11244-013-0224-xS668682576-9Bellussi G, Mizia F, Calemma V, Pollesel P, Millini R (2012) Microporous Mesoporous Mater 164:127–134Bellussi G, Carati A, Millini R (2010) In: Cejka J, Corma A, Zones S (eds) Zeolites and Catalysis. Wiley-VCH Verlag GmbH & Co., Weinheim, pp 449–491Martinez C, Corma A (2011) Coord Chem Rev 255:1558–1580de Klerk A (2005) Ind Eng Chem Res 44:3887–3893de Klerk A (2006) Energy Fuels 20:439–445de Klerk A (2006) Energy Fuels 20:1799–1805Egloff G (1936) Ind Eng Chem Res 28:1461–1467Degnan TF Jr, Smith CM, Venkat CR (2001) Appl Catal A Gen 221:283–294Apelian MR, Boulton JR, Fung AS (1994) US5284989, to Mobil OilQuann RJ, Green LA, Tabak SA, Krambeck FJ (1988) Ind Eng Chem Res 27:565–570Tabak SA, Krambeck FJ, Garwood WE (1986) AIChE J 32:1526–1531Corma A, Martínez C, Doskocil EJ (2013) J Catal 300:183–196Martens JA, Ravishankar R, Mishin IE, Jacobs PE (2000) Angew Chem Int Ed Engl 39:4376–4379Martens JA, Verrelst WH, Mathys GM, Brown SH, Jacobs PA (2005) Angew Chem Int Ed Engl 117(5833–583):6Pater JPG, Jacobs PA, Martens JA (1998) J Catal 179:477–482Tabak SA (1981) US4254295, to Mobil OilOccelli ML, Hsu JT, Galya LG (1985) J Mol Catal A: Chem 32:377–390Tabak SA (1984) US4504693, to Mobil Oil CorpKholer E, Schmidt F, Wernicke HJ, Pontes MD, Roberts HL (1995, Summer) Hydrocarbon Technology InternationalMartens JA, Verduijn JP (1995) WO95/19945, to Exxon Chemical Patents Inc.Verrelst WH (1995) Martens LRM, WO95/22516, to Exxon Chemical Patents Inc.Verrelst WH, Martens LRM (2000) US6143942, to Exxon Chemical Patents Inc.Verrelst WH, Martens LRM, Verduijn JP (2006) US6013851, to Exxon Chemical Patents Inc.Dakka JM, Mathys GMK, Puttemans MPH (2003) WO03/035583 to Exxon-Mobil Chemical LimitedMatias P, Sa CC, Graca I, Lopes JM, Carvalho AP, Ramoa RF, Guisnet M (2011) Appl Catal A 399:100–109Chal R, Gérardin C, Bulut M, van Donk S (2011) ChemCatChem 3:67–81Perez-Ramirez J, Christensen CH, Egeblad K, Groen JC (2008) Chem Soc Rev 37:2530–2542Verboekend D, Perez-Ramirez J (2011) Catal Sci Technol 1:879–890Serrano DP, Escola JM, Pizarro P (2013) Chem Soc Rev 42:4004–4035Verboekend D, Chabaneix AM, Thomas K, Gilson JP, Perez-Ramirez J (2011) Cryst Eng Comm 13:3408–3416Emeis CA (1993) J Catal 141:347–354Perego C, Peratello S (1999) Catal Today 52:133–145Abello S, Bonilla A, Perez-Ramirez J (2009) Appl Catal A Gen 364:191–198Corma A, Martinez C, Doskocil EJ, Yaluris G (2011) WO2011002631A2, to BP Oil International Limited. BP Corporation North America Inc., UKCorma A, Martinez C, Doskocil EJ, Yaluris G (2011) WO2011002630A2, to BP Oil International Limited. BP Corporation North America Inc, UKHan S, Heck RH, DiGuiseppi FT (1993) US5234875, to Mobil Oil CorporationPeratello S, Molinari M, Bellussi G, Perego C (1999) Catal Today 52:271–27

    Ranked Adjusted Rand: integrating distance and partition information in a measure of clustering agreement

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    BACKGROUND: Biological information is commonly used to cluster or classify entities of interest such as genes, conditions, species or samples. However, different sources of data can be used to classify the same set of entities and methods allowing the comparison of the performance of two data sources or the determination of how well a given classification agrees with another are frequently needed, especially in the absence of a universally accepted "gold standard" classification. RESULTS: Here, we describe a novel measure – the Ranked Adjusted Rand (RAR) index. RAR differs from existing methods by evaluating the extent of agreement between any two groupings, taking into account the intercluster distances. This characteristic is relevant to evaluate cases of pairs of entities grouped in the same cluster by one method and separated by another. The latter method may assign them to close neighbour clusters or, on the contrary, to clusters that are far apart from each other. RAR is applicable even when intercluster distance information is absent for both or one of the groupings. In the first case, RAR is equal to its predecessor, Adjusted Rand (HA) index. Artificially designed clusterings were used to demonstrate situations in which only RAR was able to detect differences in the grouping patterns. A study with larger simulated clusterings ensured that in realistic conditions, RAR is effectively integrating distance and partition information. The new method was applied to biological examples to compare 1) two microbial typing methods, 2) two gene regulatory network distances and 3) microarray gene expression data with pathway information. In the first application, one of the methods does not provide intercluster distances while the other originated a hierarchical clustering. RAR proved to be more sensitive than HA in the choice of a threshold for defining clusters in the hierarchical method that maximizes agreement between the results of both methods. CONCLUSION: RAR has its major advantage in combining cluster distance and partition information, while the previously available methods used only the latter. RAR should be used in the research problems were HA was previously used, because in the absence of inter cluster distance effects it is an equally effective measure, and in the presence of distance effects it is a more complete one
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