排序方式: 共有46条查询结果,搜索用时 31 毫秒
1.
Gavin Paul Stephen Webb Dikai Liu Gamini Dissanayake 《Robotics and Autonomous Systems》2011,59(7-8):543-554
This paper presents a system for Autonomous eXploration to Build A Map (AXBAM) of an unknown, 3D complex steel bridge structure using a 6 degree-of-freedom anthropomorphic robot manipulator instrumented with a laser range scanner. The proposed algorithm considers the trade-off between the predicted environment information gain available from a sensing viewpoint and the manipulator joint angle changes required to position a sensor at that viewpoint, and then obtains collision-free paths through safe, previously explored regions. Information gathered from multiple viewpoints is fused to achieve a detailed 3D map. Experimental results show that the AXBAM system explores and builds quality maps of complex unknown regions in a consistent and timely manner. 相似文献
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Kuya Takami Tomonari Furukawa Makoto Kumon Daisuke Kimoto Gamini Dissanayake 《Autonomous Robots》2016,40(2):343-359
This paper presents a nonvisible field-of-view (NFOV) target estimation approach that incorporates optical and acoustic sensors. An optical sensor can accurately localize a target in its field-of-view whereas the acoustic sensor could estimate the target location over a much larger space, but only with limited accuracy. A recursive Bayesian estimation framework where observations of the optical and acoustic sensors are probabilistically treated and fused is proposed in this paper. A technique to construct the observation likelihood when two microphones are used as the acoustic sensor is also described. The proposed technique derives and stores the interaural level difference of observations from the two microphones for different target positions in advance and constructs the likelihood through correlation. A parametric study of the proposed acoustic sensing technique in a controlled test environment, and experiments with an NFOV target in an actual indoor environment are presented to demonstrate the capability of the proposed technique. 相似文献
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Jonathan Hodges Tamer Attia Janindu Arukgoda Changkoo Kang Mickey Cowden Luan Doan Ravindra Ranasinghe Karim Abdelatty Gamini Dissanayake Tomonari Furukawa 《野外机器人技术杂志》2019,36(1):183-203
This paper presents a generalized multistage bayesian framework to enable an autonomous robot to complete high‐precision operations on a static target in a large field. The proposed framework consists of two multistage approaches, capable of dealing with the complexity of high‐precision operation in a large field to detect and localize the target. In the multistage localization, locations of the robot and the target are estimated sequentially when the target is far away from the robot, whereas these locations are estimated simultaneously when the target is close. A level of confidence (LOC) for each detection criterion of a sensor and the associated probability of detection (POD) of the sensor are defined to make the target detectable with different LOCs at varying distances. Differential entropies of the robot and target are used as a precision metric for evaluating the performance of the proposed approach. The proposed multistage observation and localization approaches were applied to scenarios using an unmanned ground vehicle (UGV) and an unmanned aerial vehicle (UAV). Results with the UGV in simulated environments and then real environments show the effectiveness of the proposed approaches to real‐world problems. A successful demonstration using the UAV is also presented. 相似文献
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Santoshrupa Dumpala Jacek B. Jasinski Gamini U. Sumanasekera Mahendra K. Sunkara 《Carbon》2011,(8):2725-2734
Conical carbon nanotube (CCNT) arrays were synthesized over a large area of approximately 1 cm2 or more on graphite and tungsten foil substrates. Experimental observations reveal that nucleation is caused by catalyst metal cluster in the initial stages, but the tapered morphology occurs due to the difference in the rates of vertical growth by attachment carbon atoms at edges of growing graphene sheets and radial growth with epitaxial nucleation of new graphene layers near bottom at the substrate. The above mechanism is supported through re-growth experiments on straight multi-walled nanotubes and growth kinetics data, which suggest a linear relationship between the growth rate and ratio of diameter to length (d/l) of CCNT. 相似文献
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K.A.T. Amalka Perera S. Gaveshana Anuradha G.R. Asoka Kumara M. Lal Paranawitharana R.M. Gamini Rajapakse H.M.N. Bandara 《Electrochimica acta》2011,(11):19
Design, Development, fabrication and investigation of the I–V characteristics of the DSSC based on interconnected 15 nm SnO2 nanoparticles covered with a nano-scale thin layer of CaCO3 are described. The presence of CaCO3 has been confirmed by its characteristic XRD pattern and EDX plots. The thickness of the protective layer can be conveniently controlled by the molar ratio of SnO2:CaCO3 used in the preparation of the thin film and the optimum conditions for best performance of the DSSC are presented together with possible explanations for the variations observed when the molar ratio is changed. An optimum light-to-electricity conversion efficiency of 5.4% in the presence of a layer of CaCO3 has been obtained which is 3.2 times enhancement over the cell prepared without CaCO3. The characterization of the surface using different techniques is explained. 相似文献
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Vaddiraju S Mohite A Chin A Meyyappan M Sumanasekera G Alphenaar BW Sunkara MK 《Nano letters》2005,5(8):1625-1631
Indium nitride (InN) nanowire synthesis using indium (In) vapor transport in a dissociated ammonia environment (reactive vapor transport) is studied in detail to understand the nucleation and growth mechanisms involved with the so-called "self-catalysis" schemes. The results show that the nucleation of InN crystal occurs first on the substrate. Later, In droplets are formed on top of the InN crystals because of selective wetting of In onto InN crystals. Further growth via liquid-phase epitaxy through In droplets leads the growth in one dimension (1D), resulting in the formation of InN nanowires. The details about the nucleation and growth aspects within these self-catalysis schemes are rationalized further by demonstrating the growth of heteroepitaxially oriented nanowire arrays on single-crystal substrates and "tree-like" morphologies on a variety of substrates. However, the direct nitridation of In droplets using dissociated ammonia results in the spontaneous nucleation and basal growth of nanowires directly from the In melt surface, which is quite different from the above-mentioned nucleation mechanism with the reactive vapor transport case. The InN nanowires exhibit a band gap of 0.8 eV, whereas the mixed phase of InN and In(2)O(3) nanowires exhibit a peak at approximately 1.9 eV in addition to that at 0.8 eV. 相似文献
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Controlled synthesis and enhanced field emission characteristics of conical carbon nanotubular arrays 总被引:1,自引:0,他引:1
Santoshrupa Dumpala Abdelilah Safir David Mudd Robert W. Cohn Mahendra K. Sunkara Gamini U. Sumanasekera 《Diamond and Related Materials》2009,18(10):1262-1266
Conical carbon nanotubes (CCNTs) with unique structural characteristics arising from their tapered morphologies compared to uniform diameter carbon nanotubes, have been shown to exhibit enhanced field emission properties and support high current densities. Specifically, several CCNT arrays with different morphological characteristics (tip radius, aspect ratio, density and wall structure) were synthesized by variations in the process parameters using a microwave plasma chemical vapor deposition (MWCVD) reactor. The field emission characteristics for a CCNT array sample with a tip radius of 5 nm, density of 108/cm2 and having the highest aspect ratio exhibited a low turn-on electric field (< 0.7 V/μm) and a high field enhancement factor (β > 7500). Other samples with lower emission characteristics were attributed either to the presence of field screening effect resulting from higher CCNT density or due to the corresponding tip and wall characteristics. 相似文献
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Excitonic and free-carrier transitions in single-wall carbon nanotubes are distinguished using field-enhanced photocurrent spectroscopy. Electric field dissociation allows for the detection of bound-exciton states that otherwise would not contribute to the photocurrent. Excitonic states associated with both the ground-state semiconductor and the ground-state metallic nanotube transitions are resolved. The observation of a metallic excitonic state corroborates recent predictions of a symmetry gap existing in metallic nanotubes. 相似文献