The Experts below are selected from a list of 94458 Experts worldwide ranked by ideXlab platform
Scott Robertson - One of the best experts on this subject based on the ideXlab platform.
-
electric potentials in magnetic Dipole Fields normal and oblique to a surface in plasma understanding the solar wind interaction with lunar magnetic anomalies
Geophysical Research Letters, 2013Co-Authors: M Horanyi, X Wang, Scott Robertson, Carollee HowesAbstract:[1] We experimentally investigated the solar wind interaction with moderate-strength lunar magnetic anomalies in which the electrons are magnetized but the ions remain unmagnetized. Previously, we studied the plasma sheaths above an insulating surface in a magnetic Dipole Field oriented parallel to the surface. In this paper, when the Dipole Field is oriented normal to the surface, the surface potential largely rises, and a potential bump forms in the sheath in the magnetic cusp region due to a significant magnetic mirror reflection of the electrons. It is also found that the electrons are shielded from the central Dipole wings and diverted into the side of the wings. When the Dipole Field obliquely intersects the surface, an asymmetric potential distribution develops. Our experimental results indicate that lunar surface charging can be greatly modified in the magnetic anomaly regions, creating extreme local electrical environments.
-
characteristics of a plasma sheath in a magnetic Dipole Field implications to the solar wind interaction with the lunar magnetic anomalies
Journal of Geophysical Research, 2012Co-Authors: M Horanyi, X Wang, Scott RobertsonAbstract:[1] The solar wind interaction with the lunar surface, especially in regions of crustal magnetic anomalies, remains of great interest for in situ plasma measurements. Small- scale laboratory experiments cannot reproduce the conditions near the lunar surface, but provide a unique opportunity to identify and examine several of the physical processes. We study plasma interaction with a magnetic Dipole Field at an insulating surface in order to understand the effect of crustal magnetic anomalies on the solar wind–lunar surface interaction. In our experiments, electrons are magnetized with gyroradii r smaller than distances from the surface d (r d. The measured potential distribution shows a non-monotonic sheath above the surface and variations on the surface along the axis of the Dipole Field. The surface near the center of the Dipole is charged more positively by ions as the electrons are magnetically shielded away. A potential minimum is found in the shielding region between the surface and the bulk plasma due to collisional and magnetic mirror trapping effects. Potential variations on the surface are the result of the inhomogeneity of the dipolar Field, showing an enhancement of the electric Field at the cusps. Enhanced electric Fields in the regions of magnetic anomalies on the lunar surface may enhance the transport of small-sized charged dust particles, possibly explaining the formation of the lunar swirls.
Anthony S R Chesman - One of the best experts on this subject based on the ideXlab platform.
-
Dipole Field assisted charge extraction in metal perovskite metal back contact solar cells
Nature Communications, 2017Co-Authors: Xiongfeng Lin, Askhat N Jumabekov, Niraj N Lal, Alexander R Pascoe, Daniel E Gomez, Noel W Duffy, Anthony S R ChesmanAbstract:Hybrid organic-inorganic halide perovskites are low-cost solution-processable solar cell materials with photovoltaic properties that rival those of crystalline silicon. The perovskite films are typically sandwiched between thin layers of hole and electron transport materials, which efficiently extract photogenerated charges. This affords high-energy conversion efficiencies but results in significant performance and fabrication challenges. Herein we present a simple charge transport layer-free perovskite solar cell, comprising only a perovskite layer with two interdigitated gold back-contacts. Charge extraction is achieved via self-assembled monolayers and their associated Dipole Fields at the metal-perovskite interface. Photovoltages of ~600 mV generated by self-assembled molecular monolayer modified perovskite solar cells are equivalent to the built-in potential generated by individual Dipole layers. Efficient charge extraction results in photocurrents of up to 12.1 mA cm−2 under simulated sunlight, despite a large electrode spacing. Simplified device concepts may become important for the development of low cost photovoltaics. Lin et al. report solar cells based on interdigitated gold back-contacts and metal halide perovskites where charge extraction is assisted via a Dipole Field generated by self-assembled molecular monolayers.
-
Dipole Field assisted charge extraction in metal perovskite metal back contact solar cells
arXiv: Applied Physics, 2017Co-Authors: Xiongfeng Lin, Askhat N Jumabekov, Niraj N Lal, Alexander R Pascoe, Daniel E Gomez, Noel W Duffy, Anthony S R ChesmanAbstract:Hybrid organic-inorganic halide perovskites are low-cost solution-processable solar cell materials with photovoltaic properties that rival those of crystalline silicon. The perovskite films are typically sandwiched between thin layers of hole and electron transport materials, which efficiently extract photogenerated charges. This affords high-energy conversion efficiencies but results in significant performance and fabrication challenges. Herein we present a simple charge transport layer-free perovskite solar cell (PSC), comprising only a perovskite layer with two interdigitated gold back-contacts. Charge extraction is achieved via self-assembled molecular monolayers (SAMs) and their associated Dipole Fields at the metal/perovskite interface. Photovoltages of approximately 600 mV generated by SAM-modified PSCs are equivalent to the built-in potential generated by individual Dipole layers. Efficient charge extraction results in photocurrents of up to 12.1 mA/cm2 under simulated sunlight, despite a large electrode spacing.
X Wang - One of the best experts on this subject based on the ideXlab platform.
-
electric potentials in magnetic Dipole Fields normal and oblique to a surface in plasma understanding the solar wind interaction with lunar magnetic anomalies
Geophysical Research Letters, 2013Co-Authors: M Horanyi, X Wang, Scott Robertson, Carollee HowesAbstract:[1] We experimentally investigated the solar wind interaction with moderate-strength lunar magnetic anomalies in which the electrons are magnetized but the ions remain unmagnetized. Previously, we studied the plasma sheaths above an insulating surface in a magnetic Dipole Field oriented parallel to the surface. In this paper, when the Dipole Field is oriented normal to the surface, the surface potential largely rises, and a potential bump forms in the sheath in the magnetic cusp region due to a significant magnetic mirror reflection of the electrons. It is also found that the electrons are shielded from the central Dipole wings and diverted into the side of the wings. When the Dipole Field obliquely intersects the surface, an asymmetric potential distribution develops. Our experimental results indicate that lunar surface charging can be greatly modified in the magnetic anomaly regions, creating extreme local electrical environments.
-
characteristics of a plasma sheath in a magnetic Dipole Field implications to the solar wind interaction with the lunar magnetic anomalies
Journal of Geophysical Research, 2012Co-Authors: M Horanyi, X Wang, Scott RobertsonAbstract:[1] The solar wind interaction with the lunar surface, especially in regions of crustal magnetic anomalies, remains of great interest for in situ plasma measurements. Small- scale laboratory experiments cannot reproduce the conditions near the lunar surface, but provide a unique opportunity to identify and examine several of the physical processes. We study plasma interaction with a magnetic Dipole Field at an insulating surface in order to understand the effect of crustal magnetic anomalies on the solar wind–lunar surface interaction. In our experiments, electrons are magnetized with gyroradii r smaller than distances from the surface d (r d. The measured potential distribution shows a non-monotonic sheath above the surface and variations on the surface along the axis of the Dipole Field. The surface near the center of the Dipole is charged more positively by ions as the electrons are magnetically shielded away. A potential minimum is found in the shielding region between the surface and the bulk plasma due to collisional and magnetic mirror trapping effects. Potential variations on the surface are the result of the inhomogeneity of the dipolar Field, showing an enhancement of the electric Field at the cusps. Enhanced electric Fields in the regions of magnetic anomalies on the lunar surface may enhance the transport of small-sized charged dust particles, possibly explaining the formation of the lunar swirls.
Jake J Abbott - One of the best experts on this subject based on the ideXlab platform.
-
a soft robot to navigate the lumens of the body using undulatory locomotion generated by a rotating magnetic Dipole Field
Intelligent Robots and Systems, 2018Co-Authors: Lan N Pham, Jake J AbbottAbstract:In this paper, we describe a soft-robotic actuation concept to enable a mesoscale medical robot to navigate the natural lumens of the body, such as blood vessels and intestines. The concept comprises a simple soft robot with two embedded permanent magnets with alternating magnetic polarity, and a rotating (nonuniform) Dipole magnetic Field that is swept over the robot, resulting in a traveling-wave undulatory motion that propels the robot forward and backward. This soft-actuation technology can be fabricated in a wide range of sizes due to its simplicity, and has the potential to be applied in a variety of diagnostic and therapeutic contexts. We conduct experiments and numerical simulations to verify the movement of the soft robot. Then, we confirm the benefits of using nonuniform Dipole Fields over using uniform Fields, as well as the benefits of alternating the polarity of the magnets embedded in the device.
-
six degree of freedom localization of an untethered magnetic capsule using a single rotating magnetic Dipole
International Conference on Robotics and Automation, 2017Co-Authors: Katie M Popek, Thomas Schmid, Jake J AbbottAbstract:This paper presents a method to estimate the six-degree-of-freedom pose of a magnetic capsule, with an embedded permanent magnet and Hall-effect sensors, using a rotating Dipole Field. The method's convergence properties as a function of the number of distinct rotation axes of the applied Field and the number of complete rotations about each axis are characterized. Across our tested workspace, the localization error was 4.9 ± 2.7 mm and 3.3 ± 1.7 degrees (mean ± standard deviation). We experimentally demonstrate this is sufficient for propulsion of a screw-type magnetic capsule through a lumen using a single Dipole to both propel and localize the capsule.
-
remote manipulation with a stationary computer controlled magnetic Dipole source
IEEE Transactions on Robotics, 2014Co-Authors: Andrew J Petruska, Arthur W Mahoney, Jake J AbbottAbstract:In this paper, we examine several magnetic control methods that utilize the fully controllable Dipole Field generated by the single stationary Dipole source. Since the magnetic Field generated by a Dipole source is nonuniform, it applies both forces and torques to magnetic objects and can be used to manipulate magnetic tools. Recently, the Omnimagnet, a computer-controlled magnetic Dipole source capable of varying both its Dipole-moment direction and magnitude, was developed to perform magnetic manipulation. The equations and methods are developed generally; therefore, they can be applied to any omnidirectional Dipole source, but their effectiveness is demonstrated using the Omnimagnet.
-
omnimagnet an omnidirectional electromagnet for controlled Dipole Field generation
IEEE Transactions on Magnetics, 2014Co-Authors: Andrew J Petruska, Jake J AbbottAbstract:An Omnimagnet is an omnidirectional electromagnet comprising a spherical ferromagnetic core inside of three orthogonal nested solenoids. It generates a magnetic Dipole Field with both a variable Dipole-moment magnitude and orientation with no moving parts. The magnetic and physical properties (e.g., Dipole moment, weight, resistance, and inductance) of any Omnimagnet are derived. These general relationships are used to design an optimal Omnimagnet subject to the constraints that it has the same Dipole-moment per applied current in any direction, each solenoid has no quadrupole contribution to the magnetic Field, and the spherical core size maximizes the strength of the resulting Dipole Field. This optimal design is analyzed using FEA tools and is verified to be Dipole-like in nature. Finally, the optimal design is constructed and its utility is demonstrated by driving a helical capsule-endoscope mockup through a transparent lumen.
-
localization method for a magnetic capsule endoscope propelled by a rotating magnetic Dipole Field
International Conference on Robotics and Automation, 2013Co-Authors: Katie M Popek, Arthur W Mahoney, Jake J AbbottAbstract:Previous research on the localization of wireless capsule endoscopes with magnetic Fields and sensors has typically utilized incremental methods. This paper provides a non-iterative solution to determine the six degree-of-freedom (6-DOF) position and orientation of a wireless capsule endoscope being actuated by a rotating magnetic Dipole. Non-iterative solutions in the past have only been used to locate immobile objects. We experimentally demonstrate that our algorithm calculates the 6-DOF position and orientation of capsules that are truly stationary as well as those that are operated in the “step-out” regime, where the magnetic Field is rotated too quickly for the capsule to rotate synchronously, but the capsule does undergo chaotic movement.
A D Kent - One of the best experts on this subject based on the ideXlab platform.
-
bimodal switching Field distributions in all perpendicular spin valve nanopillars
arXiv: Mesoscale and Nanoscale Physics, 2013Co-Authors: Daniel B Gopman, S Mangin, Daniel Bedau, Eric E Fullerton, J A Katine, A D KentAbstract:Switching Field measurements of the free layer element of 75 nm diameter spin-valve nanopillars reveal a bimodal distribution of switching Fields at low temperatures (below 100 K). This result is inconsistent with a model of thermal activation over a single perpendicular anisotropy barrier. The correlation between antiparallel to parallel and parallel to antiparallel switching Fields increases to nearly 50% at low temperatures. This reflects random fluctuation of the shift of the free layer hysteresis loop between two different magnitudes, which may originate from changes in the Dipole Field from the polarizing layer. The magnitude of the loop shift changes by 25% and is correlated to transitions of the spin-valve into an antiparallel configuration.
-
asymmetric switching behavior in perpendicularly magnetized spin valve nanopillars due to the polarizer Dipole Field
Applied Physics Letters, 2012Co-Authors: Daniel B Gopman, S Mangin, Daniel Bedau, Eric E Fullerton, J A Katine, Charleshenri Lambert, A D KentAbstract:We report the free layer switching Field distributions of spin-valve nanopillars with perpendicular magnetization. While the distributions are consistent with a thermal activation model, they show a strong asymmetry between the parallel to antiparallel and the reverse transition, with energy barriers more than 50% higher for the parallel to antiparallel transitions. The inhomogeneous dipolar Field from the polarizer is demonstrated to be at the origin of this symmetry breaking. Interestingly, the symmetry is restored for devices with a lithographically defined notch pair removed from the midpoint of the pillar cross-section along the ellipse long axis. These results have important implications for the thermal stability of perpendicular magnetized magnetic random access memory bit cells.
-
asymmetric switching behavior in perpendicularly magnetized spin valve nanopillars due to the polarizer Dipole Field
arXiv: Mesoscale and Nanoscale Physics, 2011Co-Authors: Daniel B Gopman, S Mangin, Daniel Bedau, Eric E Fullerton, J A Katine, Charleshenri Lambert, A D KentAbstract:We report the free layer switching Field distributions of spin-valve nanopillars with perpendicular magnetization. While the distributions are consistent with a thermal activation model, they show a strong asymmetry between the parallel to antiparallel and the reverse transition, with energy barriers more than 50% higher for the parallel to antiparallel transitions. The inhomogeneous dipolar Field from the polarizer is demonstrated to be at the origin of this symmetry breaking. Interestingly, the symmetry is restored for devices with a lithographically defined notch pair removed from the midpoint of the pillar cross-section along the ellipse long axis. These results have important implications for the thermal stability of perpendicular magnetized MRAM bit cells.