252 research outputs found
Enhanced Gas-Flow-Induced Voltage in Graphene
We show by systemically experimental investigation that gas-flow-induced
voltage in monolayer graphene is more than twenty times of that in bulk
graphite. Examination over samples with sheet resistances ranging from 307 to
1600 {\Omega}/sq shows that the induced voltage increase with the resistance
and can be further improved by controlling the quality and doping level of
graphene. The induced voltage is nearly independent of the substrate materials
and can be well explained by the interplay of Bernoulli's principle and the
carrier density dependent Seebeck coefficient. The results demonstrate that
graphene has great potential for flow sensors and energy conversion devices
An Optical Sensor Design: Concurrent Multi-axis Force Measurement and Tactile Perception.
PhD ThesesForce and tactile sensing have experienced a surge of interest over recent decades, as they
convey useful information about the direct physical interaction between the sensor and the external
environment. A robot end effector is a device designed to interact with the environment.
End effectors such as robotic hands and grippers can be used to pick up, place or generally
manipulate objects. There is a clear need to equip such end effectors with appropriate sensing
means to be able to measure tactile and force information. Work to date has explored these two
modalities separately. Tactile sensors have been developed for integration with gripper fingertips
or as skins embedded with the outer side of manipulators, mainly to measure normal force and
its distribution across a surface patch. On the other hand, force sensors have commonly been
integrated with the joints of robotic arms or fingers to measure external multi-axis forces and
torques via the connected links.
We observe that a force sensor cannot measure tactile information, and current tactile sensors
cannot accurately measure force information. This can become a particular issue when
integrating force sensors remotely to measure forces indirectly, especially if the connecting link
is flexible or, generally, difficult to model potentially impacting negatively on the force estimates.
We aim to provide a solution for an integrated sensor capable of measuring tactile and
force information at the point of contact, i.e., on the fingertip of a robot hand or arm.
In this thesis, we explore the idea of integrating the two sensing modalities, tactile and force
sensing, in one sensor housing with the signal acquisition being performed by a single monocular
camera acting as the transducer. The hypothesis is that an integrated force/tactile sensor will
perform in a better way than having these sensor modalities separated. This thesis shows that
an integrated sensor achieves a tactile sensing performance comparable to existing vision-based
tactile sensors and at the same time proves to provide more accurate force sensor information
whilst extending the field of similar vision-based sensors from 3 DoF to 6 DoF. In addition,
the tactile sensing element of our sensor is not affected by the patterns superimposed on to the
flexible element of comparable vision-based sensors used to infer force information. In this
thesis, we have implemented several sensor prototypes; designs and experimental analyses for
each prototype are being provided. The manufactured sensor prototypes prove the validity of the
proposed vision-based dual-modality sensing approach, and the proposed sensing principle and
structure shows high versatility and accuracy, as well as the potential for further miniaturization,
making the proposed concept suitable for integration with standard robot end effectors
Newton Polygons of Cyclic Covers of the Projective Line Branched at Three Points
We review the Shimura–Taniyama method for computing the Newton polygon of an abelian variety with complex multiplication. We apply this method to cyclic covers of the projective line branched at three points. As an application, we produce multiple new examples of Newton polygons that occur for Jacobians of smooth curves in characteristic p. Under certain congruence conditions on p, these include: the supersingular Newton polygon for each genus g with 4 ≤ g ≤ 11; nine non-supersingular Newton polygons with p-rank 0 with 4 ≤ g ≤ 11; and, for all g ≥ 5, the Newton polygon with p-rank g − 5 having slopes 1∕5 and 4∕5
Magnetic Proximity Effect and Interlayer Exchange Coupling of Ferromagnetic/Topological Insulator/Ferromagnetic Trilayer
Magnetic proximity effect between topological insulator (TI) and
ferromagnetic insulator (FMI) is considered to have great potential in
spintronics. However, a complete determination of interfacial magnetic
structure has been highly challenging. We theoretically investigate the
interlayer exchange coupling of two FMIs separated by a TI thin film, and show
that the particular electronic states of the TI contributing to the proximity
effect can be directly identified through the coupling behavior between two
FMIs, together with a tunability of coupling constant. Such FMI/TI/FMI
structure not only serves as a platform to clarify the magnetic structure of
FMI/TI interface, but also provides insights into designing the magnetic
storage devices with ultrafast response.Comment: 7 pages, 4 figure
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