Browsing by Author "Zhang, Y."
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Item Bright Solitons in a Two-Dimensional Spin-Orbit-Coupled Dipolar Bose-Einstein Condensate(American Physical Society, 2015-07-27) Xu, Y.; Zhang, Y.; Zhang, Chuanwei; Zhang, ChuanweiWe study a two-dimensional spin-orbit-coupled dipolar Bose-Einstein condensate with repulsive contact interactions by both the variational method and the imaginary-time evolution of the Gross-Pitaevskii equation. The dipoles are completely polarized along one direction in the two-dimensional plane to provide an effective attractive dipole-dipole interaction. We find two types of solitons as the ground states arising from such attractive dipole-dipole interactions: a plane-wave soliton with a spatially varying phase and a stripe soliton with a spatially oscillating density for each component. Both types of solitons possess smaller size and higher anisotropy than the soliton without spin-orbit coupling. Finally, we discuss the properties of moving solitons, which are nontrivial because of the violation of Galilean invariance.Item Gilbreth 2.0: An Industrial Cloud Robotics Pick-and-Sort Application(Institute of Electrical and Electronics Engineers Inc.) Zhang, Y.; Li, Lianjun; Nicho, J.; Ripperger, M.; Fumagalli, Andrea; Veeraraghavan, M.; Li, Lianjun; Fumagalli, AndreaIn prior work, we proposed an autonomous object pickand-sort procedure for an industrial robotics application called Gilbreth. In this work, we developed improvements to two critical components of this application: object recognition and motion planning, integrated the new modules to create Gilbreth 2.0, and evaluated its performance. We used a Convolutional Neural Network (CNN) based object-recognition technique, which reduced object recognition time by a factor of 10 when compared to our previous solution, which used correspondence grouping. But this reduction in object recognition time came at a cost of requiring CNN model training time, which was 3 hours with just 13 object types. Our motion planning pipeline improvement was primarily to place constraints on the time threshold for each phase of the robot arm motion. This change enabled an improvement in the percentage of successful trajectories while keeping variance small. Finally, we evaluated the overall pick-and-sort performance of Gilbreth 2.0. We found that if the mean inter-object spawning time was 14 sec, while the mean service time for the robot arm to execute all phases of its motion was 13 sec, an overall pick-and-sort success rate of 71.3% could be achieved. We identified the causes of the failures, and found that further improvements are required to reduce motionplanning failure and grasping failure, and excess-load failure can be reduced further by increasing the inter-object spawning intervals. © 2019 IEEE.Item Gilbreth: A Conveyor-Belt Based Pick-and-Sort Industrial Robotics Application(Institute of Electrical and Electronics Engineers Inc.) Zhang, Y.; Li, Lianjun; Ripperger, M.; Nicho, J.; Veeraraghavan, M.; Fumagalli, Andrea; Li, Lianjun; Fumagalli, AndreaThis paper describes an industrial robotics application, named Gilbreth, for picking up objects of different types from a moving conveyor belt and sorting the objects into bins according to type. The environment, which consists of a moving conveyor belt, a break beam sensor, a 3D camera Kinect sensor, a UR10 industrial robot arm with a vacuum gripper, and different object types such as gears, pulleys, piston rods, was inspired by the NIST ARIAC competition. A first version of the Gilbreth application was implemented leveraging many ROS and ROS-I packages. Gazebo was used to simulate the environment, and six external ROS nodes were implemented to execute the required functions. Experimental measurements of CPU usage and processing times of ROS nodes were obtained. Object recognition required the highest processing times that were on par with the time required for the robot arm to execute its movement between four poses: pick approach, pick, pick retreat and place. A need for enhancing the performance of object recognition and Gazebo simulation was identified.Item Interacting Spin-Orbit-Coupled Spin-1 Bose-Einstein Condensates(American Physical Society, 2016-02-10) Sun, Kuei; Qu, Chunlei; Xu, Yong; Zhang, Y.; Zhang, Chaunwei; H-3571-2011 (Zhang, C); Sun, Kuei; Qu, Chunlei; Xu, Yong; Zhang, ChaunweiThe recent experimental realization of spin-orbit (SO) coupling for spin-1 ultracold atoms opens an interesting avenue for exploring SO-coupling-related physics in large-spin systems, which is generally unattainable in electronic materials. In this paper, we study the effects of interactions between atoms on the ground states and collective excitations of SO-coupled spin-1 Bose-Einstein condensates (BECs) in the presence of a spin-tensor potential. We find that ferromagnetic interaction between atoms can induce a stripe phase exhibiting in-phase or out-of-phase modulating patterns between spin-tensor and zero-spin-component density waves. We characterize the phase transitions between different phases using the spin-tensor density as well as the collective dipole motion of the BEC. We show that there exists a double maxon-roton structure in the Bogoliubov-excitation spectrum, attributed to the three band minima of the SO-coupled spin-1 BEC.Item Static and Dynamic Electronic Characterization of Organic Monolayers Grafted on a Silicon Surface(Royal Society of Chemistry) Pluchery, O.; Zhang, Y.; Benbalagh, R.; Caillard, Louis; Gallet, J. J.; Bournel, F.; Lamic-Humblot, A.; Salmeron, M.; Chabal, Yves J.; Rochet, F.; Caillard, Louis; Chabal, Yves J.Organic layers chemically grafted on silicon offer excellent interfaces that may open up the way for new organic-inorganic hybrid nanoelectronic devices. However, technological achievements rely on the precise electronic characterization of such organic layers. We have prepared ordered grafted organic monolayers (GOMs) on Si(111), sometimes termed self-assembled monolayers (SAMs), by a hydrosilylation reaction with either a 7-carbon or an 11-carbon alkyl chain, with further modification to obtain amine-terminated surfaces. X-ray photoelectron spectroscopy (XPS) is used to determine the band bending (~0.3 eV), and ultraviolet photoelectron spectroscopy (UPS) to measure the work function (~3.4 eV) and the HOMO edge. Scanning tunneling microscopy (STM) confirms that the GOM surface is clean and smooth. Finally, conductive AFM is used to measure electron transport through the monolayer and to identify transition between the tunneling and the field emission regimes. These organic monolayers offer a promising alternative to silicon dioxide thin films for fabricating metal-insulator-semiconductor (MIS) junctions. We show that gold nanoparticles can be covalently attached to mimic metallic nano-electrodes and that the electrical quality of the GOMs is completely preserved in the process.;Item Tailoring Interface Structure and Enhancing Thermal Conductivity of Cu/Diamond Composites by Alloying Boron to the Cu Matrix(Elsevier Inc.) Bai, G.; Wang, Luhua; Zhang, Y.; Wang, X.; Wang, Jinguo; Kim, Moon J.; Zhang, H.; Wang, Luhua; Wang, Jinguo; Kim, Moon J.Diamond particles reinforced Cu matrix (Cu/diamond) composites were prepared by alloying 0.1–1.0 wt% B to the Cu matrix in order to tailor the interface structure. The interface structure evolves from discrete triangular carbides into continuous jig-saw carbides depending on the availability of boron source in the Cu-B matrix. We report the highest thermal conductivity of 868 W/mK so far in boron-modified Cu/diamond composites, which originates from the discontinuous carbide interface in the Cu-B/diamond composites. The parallel connection of interfacial thermal resistances of the discontinuous carbide interface reduces the total interfacial thermal resistance and therefore promotes phonon transfer across the Cu/diamond interface. We clarify the formation mechanism of discontinuous carbide interface in the Cu-B/diamond composites and demonstrate the decisive role of discrete triangular carbides in enhancing thermal conductivity of Cu/diamond composites. The results help to establish the method of metal matrix alloying to prepare Cu/diamond composites with high thermal conductivity for thermal management applications. © 2019 Elsevier Inc.Item Tunable Coefficient of Thermal Expansion of Cu-B/Diamond Composites Prepared by Gas Pressure Infiltration(Elsevier Ltd) Bai, G.; Zhang, Y.; Dai, J.; Wang, L.; Wang, X.; Wang, Jinguo; Kim, Moon J.; Chen, X.; Zhang, H.; Wang, Jinguo; Kim, Moon J.Cu-B matrix composites reinforced with diamond particles (Cu-B/diamond) were prepared by gas pressure infiltration (GPI). The effect of boron addition in the range of 0–1.0 wt% on the thermal expansion behavior of the Cu-B/diamond composites was evaluated. The coefficient of thermal expansion (CTE) of the Cu-B/diamond composites initially decreases and then increases with increasing boron content. The minimum CTE value of 4.88 × 10 -6 /K is obtained at 0.5 wt% B addition, which satisfies the requirement of CTE of semiconductors (range of 4–8 × 10⁻⁶ /K) for electronic packaging applications. The variation of CTE of the Cu-B/diamond composites is attributed to the formation of interfacial carbides and their morphological evolution. The interface structure evolves from discrete triangular carbides into continuous carbide layer with increasing boron content. The increase in the quantity of discrete carbides enhances the interface, but the formation of continuous carbides impairs the interfacial bonding of the Cu-B/diamond composites. The results suggest that alloying B to Cu matrix is an effective route to tune the coefficient of thermal expansion of Cu/diamond composites. © 2019 Elsevier B.V.