This letter presents an extremely low-profile dual-band antenna based on a single-layer square microstrip patch for 5G mobile application. The antenna has a height of only 0.8 mm (about 0.009λ _L at 3.45 GHz) and a footprint of 30×30 mm ² (0.345×0.345λ _L ² ). The TM ₁₀ mode at around 3.56 GHz and the TM ₁₁ mode at around 4.91 GHz for the antenna are obtained by etching a pair of symmetrical circular notches and a narrow rectangular slot on the square patch. The TM _1/2,0 mode at around 3.45 GHz and the TM _1/2,1 mode at around 4.83 GHz of the antenna are generated by further placing two 2-order matrix-style shorting pins. The combination of the four modes can overcome the effect of insufficient bandwidth due to the very low profile, resulting in 3.4–3.6 GHz (partial 5G N78 band) and 4.79–4.94 GHz (partial 5G N79 band) dual-band operation. The measured results are also presented.

Currently, terahertz metamaterials are studied in many fields, but it is a major challenge for a metamaterial structure to perform multiple functions. This paper proposes and studies a switchable multifunctional multilayer terahertz metamaterial. Using the phase-transition properties of vanadium dioxide (VO₂), metamaterials can be controlled to switch transmission and reflection. Transmissive metamaterials can produce an electromagnetically induced transparency-like (EIT-like) effect that can be turned on or off according to different polarization angles. The reflective metamaterial is divided into I-side and II-side by the middle continuous VO₂ layer. The I-side metamaterials can realize linear-to-circular polarization conversion from 0.444 to 0.751 THz when the incident angle of the y-polarized wave is less than 30°. The II-side metamaterials can realize linear-to-linear polarization conversion from 0.668 to 0.942 THz when the incident angle of the y-polarized wave is less than 25°. Various functions can be switched freely by changing the conductivity of VO₂ and the incident surface. This enables metamaterials to be used as highly sensitive sensors, optical switches, and polarization converters, which provides a new strategy for the design of composite functional metamaterials.

There is no consensus on how to establish models of osteonecrosis of the femoral head (ONFH) in large mammals. The aim of this study was to investigate the effectiveness of a novel canine model of ONFH, induced by a navigated injection of absolute ethanol. Using three-dimensional reconstruction and rapid prototyping manufacturing techniques, a new template was designed and processed to navigate the ethanol injection. The femoral heads of 18 adult dogs were injected with ethanol. Macroscopic, X-ray and histological examinations were performed at 3, 6, and 9 weeks after the operation. Further, computed tomography (CT), magnetic resonance imaging (MRI), and radionuclide scans were performed 6 weeks postoperatively. Three weeks after the operation, the femoral heads showed evidence of osteonecrosis including increasing numbers of empty lacunae, decreased hematopoietic cells, and destroyed adipose tissue in the medullary cavity, which increased in severity at the subsequent follow-up evaluations at 6 and 9 weeks. Fractured trabeculae and fibrous tissue were noted 9 weeks postoperatively. Image analysis also revealed evidence of osteonecrosis, such as several osteopenic areas with sclerotic rims on the X-ray, several areas of low bone mineral density with sclerosis on the CT scan, increased uptake of the nuclide species in MRI, and an inhomogeneous long T2 signal on the radioisotopic images. Ethanol injection navigated by our novel template was successful in establishing a canine model of ONFH. This model can be used to test new treatment modalities for human ONFH.

A low profile broadband multimode patch antenna is proposed for 5G mobile applications. The proposed antenna is made up of a single metal patch, a FR-4 dielectric substrate layer, an air cavity, and eight metal pins. The patch can form a magnetic wall by adding the eight metal pins, which can also generate a pair of TM _1/2,0 modes and TM ₁₀ mode. Based on these modes, two narrow rectangles with 0.169λ (about 0.011λ at 3.9 GHz) are etched on the patch, which can simultaneously form two kinds of new modes (TM _1/2,1 and TM _1/2,2 ) to achieve the broadband operation (3.3∼4.2 GHz). To ensure the accuracy of this principle, the antenna sample is made and measured. The measured outcomes are in good accordance with the simulated ones, and the sample can still operate at 3.3∼4.2 GHz, covering the 5G N77 band. The in-band total efficiency can reach up to -0.491 dB (89.3%). The maximum gain in the entire band is 9.4 dB.

Alignment technology plays an important role in navigation, and is used extensively throughout military and civilian applications. However, the existing in-flight alignment methods cannot be applied to the low-cost based strap-down inertial navigation system/global positioning system integrated navigation system, used in short-endurance and high-speed rotation flight bodies, since they cannot quickly obtain alignment results to meet the accuracy requirements of a flight body with special movement characteristics of short-endurance and high-speed rotation. In this paper, in order to solve this challenging problem of alignment for flight body with short-endurance and high-speed rotation, a fast in-flight alignment method based on the Lie group is proposed. First, an in-flight alignment model based on vector observations was established by using the Lie group. Second, addressing the problem that the alignment accuracy is greatly affected by the low-cost inertial sensor bias, an improved unscented Kalman filter was constructed in the Lie group on the basis of fully considering the characteristics of the system equations to estimate and feedback the correlated errors. Finally, a trajectory simulation of high-speed flight body and field semi-physical test was carried out to evaluate the proposed method. Evaluation of the system performance in comparison with existing state-of-the-art methods indicated that the proposed in-flight alignment method has better alignment accuracy and faster alignment velocity for a low-cost strap-down inertial navigation system/global positioning system integrated navigation system.