The influence of Mn additions on the microstructure and magnetic properties of FeNiCr/60%WC composite coatings produced by laser cladding was investigated. The microstructure of FeNiCr/60%WC coatings ...was characterized using SEM, TEM and XRD. The magnetic properties of the composite coatings were examined by a vibrating sample magnetometer (VSM). The valence electron structure and magnetic moments of Fe3W3C and Fe-based solid solution were calculated according to the empirical electron theory (EET) of solids and molecules. The results showed that FeNiCr/60%WC composite coatings had a high metallurgical quality, and that Mn can stabilize the austenite region and promote the formation of Cr0.19Fe0.7Ni0.11. The relative permeability decreased significantly with increasing the addition of Mn, indicating that Mn had the potential to improve the non-magnetic properties of the composite coatings. EET results revealed that Fe3W3C was a weakly ferromagnetic phase with a magnetic moment of 0.9018, which appeared to be the main factor affecting the non-magnetic properties of the coatings. In addition, given a constant amount of Ni in the Fe-Ni-Cr alloy, the average magnetic moment of the alloy decreased with increasing Mn.
•The FeNiCr/60%WC coatings with different Mn additions were fabricated by laser cladding.•Nonmagnetic properties of laser clad FeNiCr/60%WC coatings were improved by Mn additions.•The magnetic mechanism of FeNiCr/60%WC coatings with different Mn additions was investigated.•The main factor affecting the non-magnetic properties of FeNiCr/60%WC coatings was clarified.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Metal–matrix composite (MMC) coatings were deposited by laser cladding technique with direct injection of WC–FeNiCr powder onto N1310 nonmagnetic steel matrix. Laser cladding was conducted using a ...Trumpf6000 CO2 laser. The morphology of WC–FeNiCr MMC coatings was characterized using scanning electron microscopy (SEM). Magnetic properties of WC–FeNiCr MMC coatings were examined by vibrating sample magnetometer (VSM) at room temperature. The influence of laser cladding process on the magnetic properties of coatings was investigated. It was found that the content of tungsten carbide and laser power have significant effect on the magnetic properties of composite coatings. The evolution of phase constitution at different laser power was identified by X-ray diffraction (XRD). The presence of an austenitic γ-(Fe, Ni), Cr0.19Fe0.7Ni0.11, Fe3W3C, WC and W2C phases were confirmed by the XRD analysis in the laser clad layer.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
FeNiCr/60%WC coatings were deposited by laser cladding with direct injection of FeNiCr+60%WC powder premixed with different amounts of Mo powder (0–4wt.%) onto the N1310 nonmagnetic steel. The ...morphology was characterized using a scanning electron microscope (SEM), the phase analysis was performed using an X-ray diffractometer (XRD), and the magnetic properties were examined using a vibrating sample magnetometer (VSM). The empirical electron theory (EET) of solids and molecules was used to calculate magnetic moments of Fe3W3C and Ni3Mo3C. The relative permeability of FeNiCr/60%WC composite coatings containing different amounts of Mo ranged from 1.008 to 1.052, which was significantly lower than that without Mo addition (1.104). The relative permeability decreased with increasing Mo content until a minimum was reached, and then increased with further increasing Mo content. Ni3Mo3C phase was formed initially at high Mo addition (≥2.5%) due to the metallurgical reaction between the Mo particles and the Fe-based alloys. Both Ni3Mo3C and Fe3W3C phases were weakly ferromagnetic with a magnetic moment of 0.6816 and 0.9018 respectively, which seemed to be the main factors affecting the non-magnetic properties of the cladding coatings.
•The FeNiCr/60%WC coatings with different Mo additions were fabricated by laser cladding.•The Rietveld quantitative analysis of composite coatings was made.•Nonmagnetic properties of the coatings were improved by Mo additions.•The magnetic properties and microstructure of the coatings with different Mo additions•The magnetic moments of Fe3W3C and Ni3Mo3C phase were calculated by EET.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
FeNiCr/60%WC (wt) coatings with different Ti additions were deposited on P550 substrate by laser cladding to improve their nonmagnetic properties. The microstructures and chemical and phase ...compositions were examined using SEM, TEM, EDS and XRD, and the magnetic properties were measured using a Lake Shore7410 vibrating sample magnetometer. The results show that the addition of 1.0–4.0wt.% Ti could reduce the magnetism of FeNiCr/60%WC coatings to varying extent, depending on the content of Ti added. The relative permeability decreases at first with the increasing Ti additions, reaches a minimum of 1.006 when 2.5wt.% Ti is added, and then increases with further increasing Ti additions. The XRD, SEM and TEM results show that the phase constitution of the FeNiCr/60%WC coatings with different Ti additions mainly include γ-(Fe,Ni), WC, W2C and Fe3W3C, and a small amount of TiC, FeCr and (W,Ti)C1−X. In addition, a small amount of Fe2W is observed in the coatings where Ti additions are above 4.0%. Fe2W is ferromagnetic with a total magnetic moment of 3.3924 calculated by empirical electron theory (EET) that can affect the nonmagnetic properties of FeNiCr/60%WC coatings.
•The FeNiCr/60%WC coatings with different Ti additions were fabricated by laser cladding.•Nonmagnetic properties of the coatings were improved by Ti additions.•The magnetic properties and microstructure of the coatings with different Ti additions.•The magnetic moments of Fe2W phase was calculated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper presents a symmetric dual-band multiple-input multiple-output (MIMO) antenna system tailored for fifth-generation (5G) mobile terminals. Operating within the 5G frequency bands N77/N78 ...(3.4–3.6 GHz) and N79 (4.8–5.0 GHz), the proposed MIMO system achieves high isolation between adjacent antenna elements through slotting and self-decoupling technologies. Antenna elements are strategically positioned on two frames perpendicular to the smartphone’s main board. Each antenna element integrates a rectangular microstrip radiator on the inner frame surface, accompanied by a grounded rectangular ring on the outer frame surface. The feed line, situated atop the main board, connects to an external SMA connector located at the main board’s bottom. Measurement results reveal isolations exceeding 20 dB for the lower band and 24 dB for the higher band. The fabricated and tested MIMO antenna system demonstrates excellent agreement between simulation and measurement outcomes.
Unmanned aerial vehicle (UAV) systems undergo a period of rapid development in both civil and military scenarios. A major challenge in the malicious jamming environment is to guarantee the ...reliability of UAV communications links. Frequency hopping (FH) is one of the most commonly used means of combatting the influence brought about by jamming. In this paper, we integrate low-rate codes into an anti-jamming FH communications system, and propose an efficient and low-complexity turbo-Hadamard code scheme. Tail-biting is applied to design the component convolutional-Hadamard codes, and a corresponding decode algorithm is used for implementation in the UAV hardware platform. Numerical simulation results demonstrate that the anti-jamming performance of this method is improved as compared with conventional concatenated codes. Finally, we compare the complexity and transmission efficiency of the proposed algorithm with the algorithms implemented on the field programmable gate array (FPGA) platform in detail.
Coherent fast frequency hopping (CFFH) is attracting growing attention owing to its good antijamming performance and the coherent combining ability. However, compared with the conventional ...non-coherent fast frequency hopping, CFFH requires a more precise system synchronization. In this paper, we propose a new fine synchronization algorithm for CFFH. This algorithm consists two stages, namely, open-loop stage and closed-loop stage. In the open-loop stage, a grid-based search parameter estimation method is proposed. In the closed-loop stage, we construct a fully coherent phase-locked loop (PLL) and a delay-locked loop (DLL) with decoding feedback structure to perform further fine estimation of the system clock skew and time delay, respectively. Moreover, we analyze the effect of the search parameter settings on the estimation error and derive the root mean squared error (RMSE) of estimates in the steady state of the closed-loop stage. Finally, through simulation, the RMSE performance are compared with the corresponding Cramer-Rao low bound (CRLB) and conventional code loop estimation to show the effectiveness of proposed algorithm.
Coherent frequency hopping receiver (CFHR) can improve the anti-jamming ability of wireless communication. Anti-jamming ability of CFHR is closely related to the design of anti-jamming filter. The ...anti-jamming digital CFHR implemented in the FPGA platform is more flexible, compared to the receiver down-conversion and filtered in RF analog front-end. FIR low-pass filter is usually used in anti-jamming filter field of digital CFHR. However, IIR filter and nonlinear compensation module can replace FIR filter in order to optimize the resource complexity. In this paper, we propose the simulation and implementation of the digital coherent frequency hopping receiver based on IIR and nonlinear compensation. Besides, BER performance of CFHR based on IIR is unchanged compared to FIR under different jamming conditions.
