410 research outputs found
Detecting LFM Parameters in Joint Communications and Radar Frequency Bands
As the traditional radar waveform, linear frequency modulation (LFM) is widely used in military applications to detect targets. Recently, civilian applications such as internet of vehicle and unmanned aerial vehicle also apply LFM waveform to sense the nearby surroundings information. However, this complicated environment usually contain other waveforms, which may adversely influence LFM signal. Thus, there has been increasing interest in using the same radio spectrum to enable the radar and communication signals to coexist. In this poster, we select the orthogonal frequency division multiplexing (OFDM) signal as the communication waveform and discuss how to detect LFM parameters under communication and radar spectrum sharing scenarios. Firstly, the traditional method, the discrete chirp Fourier transform (DCFT), is applied in this scenario to estimated LFM parameters. Secondly, the alternative approach, the Hough transform, is proposed by considering the intrinsic feature of OFDM receivers. Through simulations, we demonstrate the DCFT method and the use of the Hough transform to confirm that these can be identified to a high degree of accuracy.Signal Procssing in the Information Ag
Shape-function modelling of horse hoof
Hoof injury is a threat to the modern sports horse and to the racing horse industry. The shape
of the hoof wall is believed to be important in achieving optimal force distribution (i.e. balance)
within the foot. The external shape of the hoof wall is often altered by farriers. Many authors
have reported that high-risk injuries are related to the external hoof shape, but, due to a poor
understanding of the effects of external shape variations on biomechanical performance, it is
not yet clear how hoof external shape is related to injury or balance. This thesis does not
consider injury but how hoof shape may affect strain and displacement distribution in the hoof wall.
This thesis presents a body of work to address two major aims: to develop validated
engineering tools and test protocols for capturing and characterization of the shape of the hoof
wall; and to investigate how variation in shape factors of the hoof wall affect its biomechanical
functions by finite element (FE) simulation. [Continues.
A review of the clinical characteristics and management of immunosuppressed patients living with HIV or solid organ transplants infected with SARS-CoV-2 omicron variants
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) omicron strain was first detected in South Africa in November 2021. Although clinical responses to SARS-CoV-2 depend on host immunity, it remains uncertain how immunosuppression affects subsequent coronavirus disease 2019-related (COVID-19-related) incidence, severity, and mortality, especially with respect to the omicron strain. Conversely, immunosuppressants are often thought to predispose to infection. To explore the associations between host immunity and infection with SARS-CoV-2 omicron variants, here we discuss two groups of immunosuppressed patients: organ transplant recipients, who generally receive exogenous immunosuppressants, and Human Immunodeficiency Virus (HIV)-infected patients, who often have disease-related immunosuppression. In summarizing the clinical features and prognoses of HIV-infected patients and human organ transplant recipients infected with SARS-CoV-2 omicron variants, we provide new insights into the pathogenesis of omicron SARS-CoV-2 and provide a framework for the management of these patients now and in the future
Programmable coherent linear quantum operations with high-dimensional optical spatial modes
A simple and flexible scheme for high-dimensional linear quantum operations
on optical transverse spatial modes is demonstrated. The quantum Fourier
transformation (QFT) and quantum state tomography (QST) via symmetric
informationally complete positive operator-valued measures (SIC POVMs) are
implemented with dimensionality of 15. The matrix fidelity of QFT is 0.85,
while the statistical fidelity of SIC POVMs and fidelity of QST are ~0.97 and
up to 0.853, respectively. We believe that our device has the potential for
further exploration of high-dimensional spatial entanglement provided by
spontaneous parametric down conversion in nonlinear crystals
Subnatural-Linewidth Polarization-Entangled Photon Pairs with Controllable Temporal Length
We demonstrate an efficient experimental scheme for producing
polarization-entangled photon pairs from spontaneous four-wave mixing (SFWM) in
a laser-cooled Rb atomic ensemble, with a bandwidth (as low as 0.8 MHz)
much narrower than the rubidium atomic natural linewidth. By stabilizing the
relative phase between the two SFWM paths in a Mach-Zehnder interferometer
configuration, we are able to produce all four Bell states. These
subnatural-linewidth photon pairs with polarization entanglement are ideal
quantum information carriers for connecting remote atomic quantum nodes via
efficient light-matter interaction in a photon-atom quantum network.Comment: Title changed, published version, 5 pages + 3 pages Supplemental
Materia
Universal linear optical operations on discrete phase-coherent spatial modes
Linear optical operations are fundamental and significant for both quantum
mechanics and classical technologies. We demonstrate a non-cascaded approach to
perform arbitrary unitary and non-unitary linear operations for N-dimensional
phase-coherent spatial modes with meticulously designed phase gratings. As
implemented on spatial light modulators (SLMs), the unitary transformation
matrix has been realized with dimensionalities ranging from 7 to 24 and the
corresponding fidelities are from 95.1% to 82.1%. For the non-unitary
operators, a matrix is presented for the tomography of a 4-level quantum system
with a fidelity of 94.9%. Thus, the linear operator has been successfully
implemented with much higher dimensionality than that in previous reports. It
should be mentioned that our method is not limited to SLMs and can be easily
applied on other devices. Thus we believe that our proposal provides another
option to perform linear operation with a simple, fixed, error-tolerant and
scalable scheme
Magnetic flutter effect on validated edge turbulence simulations
Small magnetic fluctuations () are intrinsically
present in a magnetic confinement plasma due to turbulent currents. While the
perpendicular transport of particles and heat is typically dominated by
fluctuations of the electric field, the parallel stream of plasma is affected
by fluttering magnetic field lines. In particular through electrons, this
indirectly impacts the turbulence dynamics. Even in low beta conditions, we
find that turbulent transport can be reduced by more than a factor
2 when magnetic flutter is included in our validated edge turbulence
simulations of L-mode ASDEX Upgrade. The primary reason for this is the
stabilization of drift-Alfv\'en-waves, which reduces the phase shifts of
density and temperature fluctuations with respect to potential fluctuations.
This stabilization can be qualitatively explained by linear analytical theory,
and appreciably reinforced by the flutter nonlinearity. As a secondary effect,
the steeper temperature gradients and thus higher increase the impact
of the ion-temperature-gradient mode on overall turbulent transport. With
increasing beta, the stabilizing effect on turbulence increases,
balancing the destabilization by induction, until direct electromagnetic
perpendicular transport is triggered. We conclude that including flutter is
crucial for predictive edge turbulence simulations
One-shot ultraspectral imaging with reconfigurable metasurfaces
One-shot spectral imaging that can obtain spectral information from thousands
of different points in space at one time has always been difficult to achieve.
Its realization makes it possible to get spatial real-time dynamic spectral
information, which is extremely important for both fundamental scientific
research and various practical applications. In this study, a one-shot
ultraspectral imaging device fitting thousands of micro-spectrometers (6336
pixels) on a chip no larger than 0.5 cm, is proposed and demonstrated.
Exotic light modulation is achieved by using a unique reconfigurable
metasurface supercell with 158400 metasurface units, which enables 6336
micro-spectrometers with dynamic image-adaptive performances to simultaneously
guarantee the density of spectral pixels and the quality of spectral
reconstruction. Additionally, by constructing a new algorithm based on
compressive sensing, the snapshot device can reconstruct ultraspectral imaging
information (/~0.001) covering a broad (300-nm-wide)
visible spectrum with an ultra-high center-wavelength accuracy of 0.04-nm
standard deviation and spectral resolution of 0.8 nm. This scheme of
reconfigurable metasurfaces makes the device can be directly extended to almost
any commercial camera with different spectral bands to seamlessly switch the
information between image and spectral image, and will open up a new space for
the application of spectral analysis combining with image recognition and
intellisense
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