76 research outputs found
Robust Beamforming and Rate-Splitting Design for Next Generation Ultra-Reliable and Low-Latency Communications
The next generation ultra-reliable and low-latency communications (xURLLC)
need novel design to provide satisfactory services to the emerging
mission-critical applications. To improve the spectrum efficiency and enhance
the robustness of xURLLC, this paper proposes a robust beamforming and
rate-splitting design in the finite blocklength (FBL) regime for downlink
multi-user multi-antenna xURLLC systems. In the design, adaptive rate-splitting
is introduced to flexibly handle the complex inter-user interference and thus
improve the spectrum efficiency. Taking the imperfection of the channel state
information at the transmitter (CSIT) into consideration, a max-min user rate
problem is formulated to optimize the common and private beamforming vectors
and the rate-splitting vector under the premise of ensuring the requirements of
transmission latency and reliability of all the users. The optimization problem
is intractable due to the non-convexity of the constraint set and the infinite
constraints caused by CSIT uncertainties. To solve it, we convert the infinite
constraints into finite ones by the S-Procedure method and transform the
original problem into a difference of convex (DC) programming. A constrained
concave convex procedure (CCCP) and the Gaussian randomization based iterative
algorithm is proposed to obtain a local minimum. Simulation results confirm the
convergence, robustness and effectiveness of the proposed robust beamforming
and rate-splitting design in the FBL regime. It is also shown that the proposed
robust design achieves considerable performance gain in the worst user rate
compared with existing transmission schemes under various blocklength and block
error rate requirements.Comment: 12 pages, 9 figure
Cooperative Beamforming Design for Multiple RIS-Assisted Communication Systems
Reconfigurable intelligent surface (RIS) provides a promising way to build
programmable wireless transmission environments. Owing to the massive number of
controllable reflecting elements on the surface, RIS is capable of providing
considerable passive beamforming gains. At present, most related works mainly
consider the modeling, design, performance analysis and optimization of
single-RIS-assisted systems. Although there are a few of works that investigate
multiple RISs individually serving their associated users, the cooperation
among multiple RISs is not well considered as yet. To fill the gap, this paper
studies a cooperative beamforming design for multi-RIS-assisted communication
systems, where multiple RISs are deployed to assist the downlink communications
from a base station to its users. To do so, we first model the general channel
from the base station to the users for arbitrary number of reflection links.
Then, we formulate an optimization problem to maximize the sum rate of all
users. Analysis shows that the formulated problem is difficult to solve due to
its non-convexity and the interactions among the decision variables. To solve
it effectively, we first decouple the problem into three disjoint subproblems.
Then, by introducing appropriate auxiliary variables, we derive the closed-form
expressions for the decision variables and propose a low-complexity cooperative
beamforming algorithm. Simulation results have verified the effectiveness of
the proposed algorithm through comparison with various baseline methods.
Furthermore, these results also unveil that, for the sum rate maximization,
distributing the reflecting elements among multiple RISs is superior to
deploying them at one single RIS
An Adaptive Spatial-Temporal Local Feature Difference Method for Infrared Small-moving Target Detection
Detecting small moving targets accurately in infrared (IR) image sequences is
a significant challenge. To address this problem, we propose a novel method
called spatial-temporal local feature difference (STLFD) with adaptive
background suppression (ABS). Our approach utilizes filters in the spatial and
temporal domains and performs pixel-level ABS on the output to enhance the
contrast between the target and the background. The proposed method comprises
three steps. First, we obtain three temporal frame images based on the current
frame image and extract two feature maps using the designed spatial domain and
temporal domain filters. Next, we fuse the information of the spatial domain
and temporal domain to produce the spatial-temporal feature maps and suppress
noise using our pixel-level ABS module. Finally, we obtain the segmented binary
map by applying a threshold. Our experimental results demonstrate that the
proposed method outperforms existing state-of-the-art methods for infrared
small-moving target detection
Towards a Pseudocapacitive Battery: Benchmarking the Capabilities of Quantized Capacitance for Energy Storage
Despite being capable of very fast charging, the pseudocapacitive properties of electrochemical capacitors still require significant research to attain energy densities comparable to that of batteries. Herein we discuss and theoretically benchmark the physics of quantized capacitance as a Faradaic charge storage mechanism, providing near “ideal” pseudocapacitive properties in the context of batterylike energy storage. Through careful electrolyte and reactant engineering, our physical analysis suggests that this less explored “pseudocapacitive battery” mechanism could provide power densities of approximately
10
4
W/L combined with volumetric energy densities in the range of 100 Wh/L (or potentially greater). These benchmarks are arrived at though a comprehensive analysis of two-dimensional (2D) graphitic nanoparticles considering the impact of solvation, electron-electron interactions, and electron transfer processes. In general, our findings indicate that 2D nanomaterials exhibiting quantized capacitance provide a promising and underexplored physical axis within electrochemical capacitors towards realizing very fast charging at energy densities comparable to that of batteries
Research on the Electromagnetic-Heat-Flow Coupled Modeling and Analysis for In-Wheel Motor
In this paper, a 15 KW in-wheel motor (IWM) is taken as the research object, and the coupling factors among the electromagnetic field, temperature field and flow field are analyzed, and the strong and weak coupling factors between the three fields are clarified, and by identifying the strong and weak coupling factors between the three fields, a three-field coupling analysis model for IWM with appropriate complexity is established, and the validity of the model is verified. In a certain driving condition, the electromagnetic field, temperature field and flow field characteristics of IWM are analyzed with the multi-field coupling model. The result shows that, after the IWM runs 8440 s under driving conditions, in this paper, the IWM electromagnetic torque of the rated working condition is 134.2 Nm, and IWM the electromagnetic torque of the peak working condition is 451.36 Nm, and the power requirement of the motor can be guaranteed. The highest temperature of the IWM is 150 °
C, which does not exceed the insulation grade requirements of the motor (155 °
C), the highest temperature of the permanent magnet (PM) is 65.6 °
C, and it does not exceed the highest operating temperature of the PM, and ensures the accurate calculation of components loss and the temperature of the motor. It can be found, through research, that the electromagnetic torque difference between unidirectional coupling and bidirectional coupling is 3.2%, the maximum temperature difference is 7.98% in the three-field coupling analysis of IWM under rated working conditions. Therefore, it is necessary to consider the influence of coupling factors on the properties of motor materials when analyzing the electromagnetic field, temperature field and flow field of IWM
it also provides some reference value for the simulation analysis of IWM in the future.
Document type: Articl
Direction dependent switching of carrier-type enabled by Fermi surface geometry
While charge carriers can typically be designated as either electron- or
hole- type, depending on the sign of the Hall coefficient, some materials defy
this straightforward classification. Here we find that LaRhGe goes
beyond this dichotomy, where the Hall resistivity is electron-like for magnetic
fields along the -axis but hole-like in the basal plane. Together with
first-principles calculations, we show that this direction-dependent switching
of the carrier type arises within a single band, where the special geometry
leads to charge carriers on the same Fermi surface orbiting as electrons along
some directions, but holes along others. The relationship between the Fermi
surface geometry and occurrence of a Hall sign reversal is further generalized
by considering tight-binding model calculations, which show that this type of
Fermi surface corresponds to a more robust means of realizing this phenomenon,
suggesting an important route for tailoring direction dependent properties for
advanced electronic device applications.Comment: 7 pages, 5 figure
A Family of Lanthanide Noncentrosymmetric Superconductors La ( = Ru, Rh, Ir; = Al, In)
We report the discovery of superconductivity in a series of
noncentrosymmetric compounds La ( = Ru, Rh, Ir; = Al, In), which
have a cubic crystal structure with space group . LaRuAl,
LaRhAl, LaIrAl, LaRuIn and LaIrIn exhibit bulk superconducting
transitions with critical temperatures of 1.77 K, 3.05 K, 1.54 K, 0.58 K
and 0.93 K, respectively. The specific heat of the LaAl compounds are
consistent with an -wave model with a fully open superconducting gap. In all
cases, the upper critical fields are well described by the
Werthamer-Helfand-Hohenberg model, and the values are well below the Pauli
limit, indicating that orbital limiting is the dominant pair-breaking
mechanism. Density functional theory (DFT) calculations reveal that the degree
of band splitting by the antisymmetric spin-orbit coupling (ASOC) shows
considerable variation between the different compounds. This indicates that the
strength of the ASOC is highly tunable across this series of superconductors,
suggesting that these are good candidates for examining the relationship
between the ASOC and superconducting properties in noncentrosymmetric
superconductors.Comment: 10 pages, 7 figure
Encode and Permute that Database! Single-Server Private Information Retrieval with Constant Online Time, Communication, and Client-Side Storage
Private Information Retrieval (PIR) facilitates the retrieval of database entries by a client from a remote server without revealing which specific entry is being queried. The preprocessing model has emerged as a significant technique for constructing efficient PIR systems, allowing parties to execute a one-time, query-independent offline phase, and then a fast online retrieval phase. In particular, Corrigan-Gibbs and Kogan (EUROCRYPT 2020) presented a new framework for constructing PIR with sublinear online time. Nevertheless, their protocol is deemed impractical in the single-server setting due to the heavy use of Fully Homomorphic Encryption (FHE). More recently, two state-of-the-art (SOTA) single-server PIR protocols (Zhou et al., S&P 2024 and Mughees-Ren, ePrint 2023) have eliminated FHE, at the price of linear offline communication. However, the client-side storage is still relatively large (), which poses challenges to practical deployment, especially when the client has limited computation and storage capabilities. To address such limitation, we propose a novel PIR protocol Pai, which only requires constant online time, communication, and client-side storage. The price we pay is only a - increase in offline communication, which would be acceptable since it is a one-time cost.Building upon our Pai, we also present a Symmetric KPIR (KSPIR) PaiKSPIR and a Chargeable KSPIR (CKSPIR) PaiCKSPIR. These two variants of PIR offer enhanced functionalities while maintaining computational complexities similar to the original Pai.
In addition to providing rigorous theoretical proofs of correctness and privacy for Pai, we have undertaken comprehensive protocol implementations and conducted extensive experiments to validate their high efficiency. Our empirical findings demonstrate that our protocols achieve notably higher online efficiency than SOTA protocols, e.g., Pai exhibits - better online communication cost and - better online time. Given the superior online time and storage, our protocol is well-suited for practical deployment
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