22,162 research outputs found
X-ray luminescence computed tomography using a focused X-ray beam
Due to the low X-ray photon utilization efficiency and low measurement
sensitivity of the electron multiplying charge coupled device (EMCCD) camera
setup, the collimator based narrow beam X-ray luminescence computed tomography
(XLCT) usually requires a long measurement time. In this paper, we, for the
first time, report a focused X-ray beam based XLCT imaging system with
measurements by a single optical fiber bundle and a photomultiplier tube (PMT).
An X-ray tube with a polycapillary lens was used to generate a focused X-ray
beam whose X-ray photon density is 1200 times larger than a collimated X-ray
beam. An optical fiber bundle was employed to collect and deliver the emitted
photons on the phantom surface to the PMT. The total measurement time was
reduced to 12.5 minutes. For numerical simulations of both single and six fiber
bundle cases, we were able to reconstruct six targets successfully. For the
phantom experiment, two targets with an edge-to-edge distance of 0.4 mm and a
center-to-center distance of 0.8 mm were successfully reconstructed by the
measurement setup with a single fiber bundle and a PMT.Comment: 39 Pages, 12 Figures, 2 Tables, In submission (under review) to JB
Recommended from our members
Versatile stochastic dot product circuits based on nonvolatile memories for high performance neurocomputing and neurooptimization.
The key operation in stochastic neural networks, which have become the state-of-the-art approach for solving problems in machine learning, information theory, and statistics, is a stochastic dot-product. While there have been many demonstrations of dot-product circuits and, separately, of stochastic neurons, the efficient hardware implementation combining both functionalities is still missing. Here we report compact, fast, energy-efficient, and scalable stochastic dot-product circuits based on either passively integrated metal-oxide memristors or embedded floating-gate memories. The circuit's high performance is due to mixed-signal implementation, while the efficient stochastic operation is achieved by utilizing circuit's noise, intrinsic and/or extrinsic to the memory cell array. The dynamic scaling of weights, enabled by analog memory devices, allows for efficient realization of different annealing approaches to improve functionality. The proposed approach is experimentally verified for two representative applications, namely by implementing neural network for solving a four-node graph-partitioning problem, and a Boltzmann machine with 10-input and 8-hidden neurons
Recommended from our members
Photovoltaic and Behind-the-Meter Battery Storage: Advanced Smart Inverter Controls and Field Demonstration
Measurement of the Transmission Phase of an Electron in a Quantum Two-Path Interferometer
A quantum two-path interferometer allows for direct measurement of the
transmission phase shift of an electron, providing useful information on
coherent scattering problems. In mesoscopic systems, however, the two-path
interference is easily smeared by contributions from other paths, and this
makes it difficult to observe the \textit{true} transmission phase shift. To
eliminate this problem, multi-terminal Aharonov-Bohm (AB) interferometers have
been used to derive the phase shift by assuming that the relative phase shift
of the electrons between the two paths is simply obtained when a smooth shift
of the AB oscillations is observed. Nevertheless the phase shifts using such a
criterion have sometimes been inconsistent with theory. On the other hand, we
have used an AB ring contacted to tunnel-coupled wires and acquired the phase
shift consistent with theory when the two output currents through the coupled
wires oscillate with well-defined anti-phase. Here, we investigate thoroughly
these two criteria used to ensure a reliable phase measurement, the anti-phase
relation of the two output currents and the smooth phase shift in the AB
oscillation. We confirm that the well-defined anti-phase relation ensures a
correct phase measurement with a quantum two-path interference. In contrast we
find that even in a situation where the anti-phase relation is less
well-defined, the smooth phase shift in the AB oscillation can still occur but
does not give the correct transmission phase due to contributions from multiple
paths. This indicates that the phase relation of the two output currents in our
interferometer gives a good criterion for the measurement of the \textit{true}
transmission phase while the smooth phase shift in the AB oscillation itself
does not.Comment: 5 pages, 4 figure
Testing microelectronic biofluidic systems
According to the 2005 International Technology Roadmap for Semiconductors, the integration of emerging nondigital CMOS technologies will require radically different test methods, posing a major challenge for designers and test engineers. One such technology is microelectronic fluidic (MEF) arrays, which have rapidly gained importance in many biological, pharmaceutical, and industrial applications. The advantages of these systems, such as operation speed, use of very small amounts of liquid, on-board droplet detection, signal conditioning, and vast digital signal processing, make them very promising. However, testable design of these devices in a mass-production environment is still in its infancy, hampering their low-cost introduction to the market. This article describes analog and digital MEF design and testing method
- …