223 research outputs found
Joint Beamforming Design for RIS-enabled Integrated Positioning and Communication in Millimeter Wave Systems
Integrated positioning and communication (IPAC) system and reconfigurable
intelligent surface (RIS) are both considered to be key technologies for future
wireless networks. Therefore, in this paper, we propose a RIS-enabled IPAC
scheme with the millimeter wave system. First, we derive the explicit
expressions of the time-of-arrival (ToA)-based Cram\'er-Rao bound (CRB) and
positioning error bound (PEB) for the RIS-aided system as the positioning
metrics. Then, we formulate the IPAC system by jointly optimizing active
beamforming in the base station (BS) and passive beamforming in the RIS to
minimize the transmit power, while satisfying the communication data rate and
PEB constraints. Finally, we propose an efficient two-stage algorithm to solve
the optimization problem based on a series of methods such as the exhaustive
search and semidefinite relaxation (SDR). Simulation results show that by
changing various critical system parameters, the proposed RIS-enabled IPAC
system can cater to both reliable data rates and high-precision positioning in
different transmission environments
Three-dimensional structure of the milky way dust: modeling of LAMOST data
We present a three-dimensional modeling of the Milky Way dust distribution by
fitting the value-added star catalog of LAMOST spectral survey. The global dust
distribution can be described by an exponential disk with scale-length of 3,192
pc and scale height of 103 pc. In this modeling, the Sun is located above the
dust disk with a vertical distance of 23 pc. Besides the global smooth
structure, two substructures around the solar position are also identified. The
one located at and is
consistent with the Gould Belt model of \citet{Gontcharov2009}, and the other
one located at and is
associated with the Camelopardalis molecular clouds.Comment: 15 pages, 6 figure, accepted by Ap
Robust Power Allocation for UAV-aided ISAC Systems with Uncertain Location Sensing Errors
Unmanned aerial vehicle (UAV) holds immense potential in integrated sensing
and communication (ISAC) systems for the Internet of Things (IoT). In this
paper, we propose a UAV-aided ISAC framework and investigate three robust power
allocation schemes. First, we derive an explicit expression of the Cram\'er-Rao
bound (CRB) based on time-of-arrival (ToA) estimation, which serves as the
performance metric for location sensing. Then, we analyze the impact of the
location sensing error (LSE) on communications, revealing the inherent coupling
relationship between communication and sensing. Moreover, we formulate three
robust communication and sensing power allocation problems by respectively
characterizing the LSE as an ellipsoidal distributed model, a Gaussian
distributed model, and an arbitrary distributed model. Notably, the
optimization problems seek to minimize the CRB, subject to data rate and total
power constraints. However, these problems are non-convex and intractable. To
address the challenges related to the three aforementioned LSE models, we
respectively propose to use the -Procedure and alternating
optimization (-AO) method, Bernstein-type inequality and successive
convex approximation (BI-SCA) method, and conditional value-at-risk (CVaR) and
AO (CVaR-AO) method to solve these problems. Finally, simulation results
demonstrate the robustness of our proposed UAV-aided ISAC system against the
LSE by comparing with the non-robust design, and evaluate the trade-off between
communication and sensing in the ISAC system
Scaling law for three-body collisions near a narrow s-wave Feshbach resonance
Ultracold atomic gases provide a controllable system to study the inelastic
processes for three-body systems, where the three-body recombination rate
depends on the scattering length scaling. Such scalings have been confirmed in
bosonic systems with various interaction strengths, but their existence with
fermionic atoms remains elusive. In this work, we report on an experimental
investigation of the scaling law for the three-body atomic loss rate in a
two-component Li Fermi gas with the scattering length . The scaling
law is validated within a certain range of near the narrow -wave
Feshbach resonance, where , and is the gas
temperature. The scaling law is observed to have an upper and a lower bound in
terms of the scattering length. For the upper bound, when , the power-law scaling is suppressed by the unitary behavior of the
resonance caused by the strong three-body collisions. For the lower bound,
, the finite range effect modifies the scaling law by the
effective scattering length . These results indicate that the three-body
recombination rate in a fermionic system could be characterized by the scaling
law associated with the generalized Efimov physics.Comment: 11 pages, 3 figures, 1 tabl
High-density lipoprotein subclass and particle size in coronary heart disease patients with or without diabetes
BACKGROUND: A higher prevalence of coronary heart disease (CHD) in people with diabetes. We investigated the high-density lipoprotein (HDL) subclass profiles and alterations of particle size in CHD patients with diabetes or without diabetes. METHODS: Plasma HDL subclasses were quantified in CHD by 1-dimensional gel electrophoresis coupled with immunodetection. RESULTS: Although the particle size of HDL tend to small, the mean levels of low density lipoprotein cholesterol(LDL-C) and total cholesterol (TC) have achieved normal or desirable for CHD patients with or without diabetes who administered statins therapy. Fasting plasma glucose (FPG), triglyceride (TG), TC, LDL-C concentrations, and HDL(3) (HDL(3b) and (3a)) contents along with Gensini Score were significantly higher; but those of HDL-C, HDL(2b+preβ2), and HDL(2a) were significantly lower in CHD patients with diabetes versus CHD patients without diabetes; The preβ(1)-HDL contents did not differ significantly between these groups. Multivariate regression analysis revealed that Gensini Score was significantly and independently predicted by HDL(2a), and HDL(2b+preβ2). CONCLUSIONS: The abnormality of HDL subpopulations distribution and particle size may contribute to CHD risk in diabetes patients. The HDL subclasses distribution may help in severity of coronary artery and risk stratification, especially in CHD patients with therapeutic LDL, TG and HDL levels
Signal Demodulation with Machine Learning Methods for Physical Layer Visible Light Communications: Prototype Platform, Open Dataset and Algorithms
In this paper, we investigate the design and implementation of machine
learning (ML) based demodulation methods in the physical layer of visible light
communication (VLC) systems. We build a flexible hardware prototype of an
end-to-end VLC system, from which the received signals are collected as the
real data. The dataset is available online, which contains eight types of
modulated signals. Then, we propose three ML demodulators based on
convolutional neural network (CNN), deep belief network (DBN), and adaptive
boosting (AdaBoost), respectively. Specifically, the CNN based demodulator
converts the modulated signals to images and recognizes the signals by the
image classification. The proposed DBN based demodulator contains three
restricted Boltzmann machines (RBMs) to extract the modulation features. The
AdaBoost method includes a strong classifier that is constructed by the weak
classifiers with the k-nearest neighbor (KNN) algorithm. These three
demodulators are trained and tested by our online open dataset. Experimental
results show that the demodulation accuracy of the three data-driven
demodulators drops as the transmission distance increases. A higher modulation
order negatively influences the accuracy for a given transmission distance.
Among the three ML methods, the AdaBoost modulator achieves the best
performance
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