134 research outputs found
Simultaneously Transmitting and Reflecting Surface (STARS) for Terahertz Communications
A simultaneously transmitting and reflecting surface (STARS) aided terahertz
(THz) communication system is proposed. A novel power consumption model is
proposed that depends on the type and resolution of the STARS elements. The
spectral efficiency (SE) and energy efficiency (EE) are maximized in both
narrowband and wideband THz systems by jointly optimizing the hybrid
beamforming at the base station (BS) and the passive beamforming at the STARS.
1) For narrowband systems, independent phase-shift STARSs are investigated
first. The resulting complex joint optimization problem is decoupled into a
series of subproblems using penalty dual decomposition. Low-complexity
element-wise algorithms are proposed to optimize the analog beamforming at the
BS and the passive beamforming at the STARS. The proposed algorithm is then
extended to the case of coupled phase-shift STARS. 2) For wideband systems, the
spatial wideband effect at the BS and STARS leads to significant performance
degradation due to the beam split issue. To address this, true time delayers
(TTDs) are introduced into the conventional hybrid beamforming structure for
facilitating wideband beamforming. An iterative algorithm based on the
quasi-Newton method is proposed to design the coefficients of the TTDs.
Finally, our numerical results confirm the superiority of the STARS over the
conventional reconfigurable intelligent surface (RIS). It is also revealed that
i) there is only a slight performance loss in terms of SE and EE caused by
coupled phase shifts of the STARS in both narrowband and wideband systems, and
ii) the conventional hybrid beamforming achieves comparable SE performance and
much higher EE performance compared with the full-digital beamforming in
narrowband systems but not in wideband systems, where the TTD-based hybrid
beamforming is required for mitigating wideband beam split.Comment: 17 pages, 12 figure
Near-Field Communications: What Will Be Different?
The design dilemma of "What will be different between near-field
communications (NFC) and far-field communications (FFC)?" is addressed from
four perspectives. 1) From the channel modelling perspective, the differences
between near-field and far-field channel models are discussed. A novel Green's
function-based channel model is proposed for continuous-aperture antennas,
which is contrasted to conventional channel models tailored for
spatially-discrete antennas. 2) From the performance analysis perspective,
analytical results for characterizing the degrees of freedom and the power
scaling laws in the near-field region are provided for both spatially-discrete
and continuous-aperture antennas. 3) From the beamforming perspective,
far-field beamforming is analogous to a "flashlight" that enables beamsteering,
while near-field beamforming can be likened to a "spotlight" that facilitates
beamfocusing. As a further advance, a couple of new beamforming structures are
proposed for exploiting the new characteristics of NFC. 4) From the application
perspective, new designs are discussed in the context of promising
next-generation technologies in NFC, where our preliminary numerical results
demonstrate that distance-aware target sensing and enhanced physical layer
security can be realized in NFC. Finally, several future research directions of
NFC are discussed.Comment: 9 pages, 5 figures, submit to possible IEEE journa
NOMA-aided Joint Communication, Sensing, and Multi-tier Computing Systems
A non-orthogonal multiple access (NOMA)-aided joint communication, sensing,
and multi-tier computing (JCSMC) framework is proposed. In this framework, a
multi-functional base station (BS) carries out target sensing, while providing
edge computing services to the nearby users. To enhance the computation
efficiency, the multi-tier computing structure is exploited, where the BS can
further offload the computation tasks to a powerful Cloud server (CS). The
potential benefits of employing NOMA in the proposed JCSMC framework are
investigated, which can maximize the computation offloading capacity and
suppress the inter-function interference. Based on the proposed framework, the
transmit beamformer of the BS and computation resource allocation at the BS and
the CS are jointly optimized to maximize the computation rate subject to the
communication-computation causality and the sensing quality constraints. Both
partial and binary computation offloading modes are considered: 1) For the
partial offloading mode, a weighted minimum mean square error based alternating
optimization algorithm is proposed to solve the corresponding non-convex
optimization problem. It is proved that a KKT optimal solution can be obtained;
2) For the binary offloading mode, the resultant highly-coupled mixed-integer
optimization problem is first transformed to an equivalent but more tractable
form. Then, the reformulated problem is solved by utilizing the alternating
direction method of multipliers approach to obtain a nearly optimal solution.
Finally, numerical results verify the effectiveness of the proposed algorithms
and the proposed NOMA-aided JCSMC frameworkComment: 30 pages, 8 figure
Clinical Progress of Acupuncture in the Treatment of ACL after Reconstructive Surgery
Anterior cruciate ligament (ACL) injury of the knee is one of the common sports injuries, and ACL reconstruction is currently the mainstream treatment. However,ACL reconstruction often produces postoperative complications such as swelling, pain, muscle atrophy, joint adhesion and stifness, and timely interventional rehabilitation is needed for patients to recover the expected level. Studies have shown that acupuncture treatment can regulate infammatory factors and related signalling pathways, etc., and has obvious efcacy in joint rehabilitation after ACL reconstruction. The authors collated clinical reports on the use of acupuncture therapy such as general acupuncture, electroacu-puncture, moxibustion with acupuncture, snap needling, and ethnic acupuncture in the rehabilitation process after ACL reconstruction in re-cent years, to explore the feasibility and efectiveness of the intervention of acupuncture therapy, with the aim of providing a more systematic reference for the treatment ofACL injury in the future clinic after surgery
Near-Field Communications: A Tutorial Review
Extremely large-scale antenna arrays, tremendously high frequencies, and new
types of antennas are three clear trends in multi-antenna technology for
supporting the sixth-generation (6G) networks. To properly account for the new
characteristics introduced by these three trends in communication system
design, the near-field spherical-wave propagation model needs to be used, which
differs from the classical far-field planar-wave one. As such, near-field
communication (NFC) will become essential in 6G networks. In this tutorial, we
cover three key aspects of NFC. 1) Channel Modelling: We commence by reviewing
near-field spherical-wave-based channel models for spatially-discrete (SPD)
antennas. Then, uniform spherical wave (USW) and non-uniform spherical wave
(NUSW) models are discussed. Subsequently, we introduce a general near-field
channel model for SPD antennas and a Green's function-based channel model for
continuous-aperture (CAP) antennas. 2) Beamfocusing and Antenna Architectures:
We highlight the properties of near-field beamfocusing and discuss NFC antenna
architectures for both SPD and CAP antennas. Moreover, the basic principles of
near-field beam training are introduced. 3) Performance Analysis: Finally, we
provide a comprehensive performance analysis framework for NFC. For near-field
line-of-sight channels, the received signal-to-noise ratio and power-scaling
law are derived. For statistical near-field multipath channels, a general
analytical framework is proposed, based on which analytical expression for the
outage probability, ergodic channel capacity, and ergodic mutual information
are derived. Finally, for each aspect, the topics for future research are
discussed.Comment: 45 pages, 35 figures; submitted to possible IEEE journa
Enhanced Anti-diabetic Effect of Berberine Combined With Timosaponin B2 in Goto-Kakizaki Rats, Associated With Increased Variety and Exposure of Effective Substances Through Intestinal Absorption
Objective: Inspired by the traditionally clinical application of herb pair Zhimu-Huangbo to treat diabetes, a combination of plant ingredients, timosaponin B2 (TB-2) and berberine (BBR), was evaluated for their anti-diabetic efficacy and cooperative mechanisms.Methods: The efficacy and pharmacokinetics of orally administered TB-2 (33.3 mg/kg/day), BBR (66.7 mg/kg/day), and TB-2+BBR (100 mg/kg/day) were evaluated in spontaneously non-obese diabetic Goto-Kakizaki (GK) rats, and metformin (200 mg/kg/day) was used as a positive control. The comparative exposure of the parent drugs, timosaponin A3 (TB-2 metabolite), and M1–M5 (BBR metabolites) was quantified in the portal vein plasma (before hepatic disposition), liver, and systemic plasma (after hepatic disposition) of normal rats on single and combination treatments. Cooperative mechanism of TB-2 and BBR on intestinal absorption and hepatic metabolism was investigated in Caco-2 cells and primary hepatocytes, respectively.Results: After a 6-week experiment, non-fasting and fasting blood glucose levels and oral glucose tolerance test results showed that TB-2+BBR treatments (100 mg/kg/day) displayed significantly anti-diabetic efficacy in GK rats, comparable to that on metformin treatments. However, no significant improvement was observed on TB-2 or BBR treatments alone. Compared to single treatments, combination treatments led to the increased circulating levels of BBR by 107% in GK rats. In normal rats, the hepatic exposure of BBR, timosaponin A3, and M1–M5 was several hundred folds higher than their circulating levels. Co-administration also improved the levels in the plasma and liver by 41–114% for BBR, 141–230% for TB-2, and 12–282% for M1–M5. In vitro, the interaction between TB-2 and BBR was mediated by intestinal absorption, rather than hepatic metabolism.Conclusion: Combining TB-2 and BBR enhanced the anti-diabetic efficacy by increasing the in vivo variety of effective substances, including the parent compounds and active metabolites, and improving the levels of those substances through intestinal absorption. This study is a new attempt to assess the effects of combined plant ingredients on diabetes by scientifically utilizing clinical experience of an herb pair
Production of Polyhydroxybutyrate by Bacillus axaraqunsis BIPC01 using Petrochemical Wastewater as Carbon Source
Norms and Spread of the Fibonacci and Lucas RSFMLR Circulant Matrices
Circulant type matrices have played an important role in networks engineering. In this paper, firstly, some bounds for the norms and spread of Fibonacci row skew first-minus-last right (RSFMLR) circulant matrices and Lucas row skew first-minus-last right (RSFMLR) circulant matrices are given. Furthermore, the spectral norm of Hadamard product of a Fibonacci RSFMLR circulant matrix and a Lucas RSFMLR circulant matrix is obtained. Finally, the Frobenius norm of Kronecker product of a Fibonacci RSFMLR circulant matrix and a Lucas RSFMLR circulant matrix is presented
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