Spaceborne miniaturized UHF dual band helix antenna with a small frequency ratio

This study proposes a novel miniaturized circularly polarized (CP) ultrahigh frequency (UHF) quadrifilar helix antenna for spaceborne applications. The dual-band operation is realized using four inverted-U shaped helical strips (IUSHSs) that are rotated and alternately arranged on the four faces of a hollow polyimide cuboid in a sequential rotation manner, which effectively reduces the size of the antenna. Furthermore, the four IUSHSs are connected by a cross-shape strip at the top of the antenna to control the dual resonant frequencies, resulting in a small dual-band frequency ratio. The proposed antenna is both lightweight and robust when compared with the conventional miniaturized CP antennas operating at similar bands with similar performance. In particular, its compact radiator provides effective miniaturized spaceborne solution without the need of high-dielectric coefficient materials. A device for spaceborne application that operates at 402/505 MHz is designed, fabricated, measured, and in-orbit tested with a weight of 651 g and an effective size of 0.161 7 0.161 7 0.228 λ3402MHz (λ402MHz is the wavelength at 402 MHz). The measured gain and axial ratio of the proposed antenna are better than 5.32 dBi and 2.18 dB, respectively, within 2 and 12 MHz bandwidth for the two bands. The test results proved that the methods used to design the proposed antenna are effective

Spontaneous Browning of White Adipose Tissue Improves Angiogenesis and Reduces Macrophage Infiltration After Fat Grafting in Mice

Background: Fat grafting is a frequently used technique; however, its survival/ regeneration mechanism is not fully understood. The browning of white adipocytes, a process initiated in response to external stimuli, is the conversion of white to beige adipocytes. The physiologic significance of the browning of adipocytes following transplantation is unclear.Methods: C57BL/6 mice received 150 mg grafts of inguinal adipose tissue, and then the transplanted fat was harvested and analyzed at different time points to assess the browning process. To verify the role of browning of adipocytes in fat grafting, the recipient mice were allocated to three groups, which were administered CL316243 or SR59230A to stimulate or suppress browning, respectively, or a control group after transplantation.Results: Browning of the grafts was present in the center of each as early as 7 days post-transplantation. The number of beige cells peaked at day 14 and then decreased gradually until they were almost absent at day 90. The activation of browning resulted in superior angiogenesis, higher expression of the pro-angiogenic molecules vascular endothelial growth factor A (VEGF-A) and fibroblast growth factor 21 (FGF21), fewer macrophages, and ultimately better graft survival (Upregulation, 59.17% ± 6.64% vs. Control, 40.33% ± 4.03%, *p < 0.05), whereas the inhibition of browning led to poor angiogenesis, lower expression of VEGF-A, increased inflammatory macrophages, and poor transplant retention at week 10 (Downregulation, 20.67% ± 3.69% vs. Control, 40.33% ± 4.03%, *p < 0.05).Conclusion: The browning of WAT following transplantation improves the survival of fat grafts by the promotion of angiogenesis and reducing macrophage

Outage Analysis of Relay-Assisted NOMA in Cooperative Cognitive Radio Networks with SWIPT

In this paper, we investigate a relay-assisted cooperative spectrum sharing for the considered non-orthogonal multiple access (NOMA) scheme in cognitive radio networks, where the relay node assists the base station (BS) to transmit the superimposed composite signal to two receivers by utilizing an amplified-and-forward (AF) technique with simultaneous wireless information and power transfer (SWIPT). The exact expressions for outage probabilities of two receivers are derived in closed forms. Moreover, a joint optimization of power allocation and the proportion of information splitting for energy harvesting is proposed in terms of energy efficiency (EE) maximization under required data reliability. Simulation results validate the analytical results since the analytical results match well with simulation results and demonstrate the performance advantages of the proposed scheme over other schemes and direct transmission

Remaining useful life with self-attention assisted physics-informed neural network

Remaining useful life (RUL) prediction as the key technique of prognostics and health management (PHM) has been extensively investigated. The application of data-driven methods in RUL prediction has advanced greatly in recent years. However, a large number of model parameters, low prediction accuracy, and lack of interpretability of prediction results are common problems of current data-driven methods. In this paper, we propose a Physics-Informed Neural Networks (PINNs) with Self-Attention mechanism-based hybrid framework for aircraft engine RUL prognostics. Specifically, the self-attention mechanism is employed to learn the differences and interactions between features, and reasonably map high-dimensional features to low-dimensional spaces. Subsequently, PINN is utilized to regularize the end-to-end prediction network, which maps features to RUL. The RUL prediction framework termed AttnPINN has verified its superiority on the Commercial Modular AeroPropulsion System Simulation (C-MAPSS) dataset. It achieves state-of-the-art prediction performance with a small number of parameters, resulting in computation-light features. Furthermore, its prediction results are highly interpretable and can accurately predict failure modes, thereby enabling precise predictive maintenance.</p