The three-degrees-of-freedom (3-DOF) parallel robot is commonly employed as a shipborne stabilized platform for real-time compensation of ship disturbances. Pose accuracy is one of its most critical ...performance indicators. Currently, neural networks have been applied to the kinematic calibration of stabilized platforms to compensate for pose errors and enhance motion accuracy. However, collecting a large amount of measured configuration data for robots entails high costs and time, which restricts the widespread use of neural networks. In this study, a “transfer network” is established by combining fine-tuning with a Back Propagation (BP) neural network. This network takes the motion transmission characteristics inherent in the ideal kinematic model as prior knowledge and transfers them to a network trained based on the actual poses. Compared with the conventional BP neural network trained by actual poses alone, the transfer network shows significant performance advantages, effectively solving the problems of low prediction accuracy and weak generalization ability in the case of small-sample measured data. Considering this, the impact pattern of the sample number of the actual pose on the effectiveness of transfer learning is revealed through the construction of multiple transfer network models under varying sample numbers of the actual pose, providing valuable marine engineering guidance. Finally, simulated sea-service experiments were conducted on the 3-UPS/S shipborne stabilized platform to validate the correctness and superiority of the proposed method.
A photonic deramp receiver based on a photonic mixer for dual-band linear frequency-modulated continuous wave radar is proposed. In the receiver, a novel modulation scheme is developed, employing a ...dual polarization quadrature phase shift keying modulator which contains four sub-Mach-Zehnder modulators (sub-MZMs). The echoes and reference signal of the first band are modulated to light waves on a pair of peak-biased sub-MZMs for tracking, while the echoes and reference signal of the second band are modulated on the other pair of null-biased sub-MZMs for imaging. An experimental system, operating in C-band and Ku-band with a bandwidth of 850 and 3600 MHz, respectively, is demonstrated and evaluated via a series of inverse synthetic aperture radar imaging tests. The results verify the idea of the dual-band radar receiver, which provides a solution for receiving dual-band echo signals with a single hardware platform.
Energy conservation, environmental protection, and intelligence are topics of interest in intelligent buildings. However, the energy requirement of various electrical equipment in intelligent ...buildings increases energy consumption. This study presents a neural network-based prediction and control system for the regulation of building environmental parameters. Neural network-based soft sensing technology can detect building environmental parameters through few sensors. The proposed system control algorithm can realize the adaptive adjustment of environmental parameters by using a neural network proportional–integral–derivative controller. Zigbee wireless communication is adopted as the information transmission medium to realize the environmental parameter measurement and network control. The soft sensing technique combined with Zigbee communication technology can effectively reduce energy consumption. The central control system analyzes the data coming from the network and regulates the environmental parameter through lifting temperature, ventilation, and switching curtains by using the neural network proportional–integral–derivative algorithm. The regulation of environmental parameters reduces unnecessary energy consumption. Finally, the effectiveness of the system is verified through simulations.
Practical applications
: This work reports an energy saving scheme. The building communication system constructed by ZigBee can reduce energy consumption and can be easily expanded. The soft sensing technique based on artificial neural network can predict temperatures by using few sensors. The neural network proportional–integral–derivative control algorithm has good performance in the regulation of environmental parameters for a time-varying system. Building energy consumption can be reduced by conducting these measures.
In this paper, the homogenized Mg-9Gd-2Nd-1.6Zn-1Zr (wt%) alloys were subjected to various equal channel angular pressing (ECAP) passes (1, 2, 4 and 8) with Bc route at 400 °C. Then, the ...microstructure evolution and strengthening mechanisms of alloys were systematically investigated. The results show that the coarse deformed grains are completely consumed by the dynamic recrystallized (DRX) grains, the number of dynamic precipitates gradually increases, and the intensity of basal texture of the alloy is gradually weakened with increasing ECAP passes. After 8 passes ECAP, the grain size is dramatically refined from 50 μm (homogenized) to 2.1 μm (8p-ECAPed), which is mainly due to the DRX, particle-stimulated nucleation (PSN) induced by broken eutectic phase and hinder grain growth of dynamic precipitates. The excellent comprehensive mechanical properties are achieved by 4 passes, and the corresponding yield strength (YS) and ultimate tensile strength (UTS) as well as elongation (EL) are 321 MPa, 378 MPa and 14.4％, respectively. This can be mainly ascribed to the combined effect of broken eutectic phase, DRX grains, kinked long period-stacking order (LPSO) and dynamic precipitates.
Xinjiang, in Northwestern China, was a key point in the prehistoric trans-Eurasian network of exchange and played an important role in facilitating the dispersal of crops across Eurasia. Millet crops ...were first cultivated and used ca. 10,000 years ago in Northern China, from where they spread via different routes, leaving intriguing traces in various sites across Xinjiang. This paper presents the latest data on millet in Xinjiang. By employing a multidisciplinary approach, including radiocarbon dating, archaeobotanical evidence, and carbon isotope datasets, this study explores potential routes by which millet entered Xinjiang and traces its expansion from the third millennium BC to the 10th century AD. The research highlights the significant role of millet in shaping the ancient economies and cultures of Xinjiang and Central Asia, while also underscoring the importance of further investigation to uncover the complex pathways of its dispersal across Eurasia.
In this work, MXene/NiO-composite-based formaldehyde (HCHO) sensing materials were successfully synthesized by an in situ precipitation method. The heterostructures between the MXene and NiO ...nanoparticles were verified by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The HCHO sensing performance of the MXene/NiO-based chemiresistive-type sensors was investigated. Compared to pure MXene and NiO materials, the sensing performance of the MXene/NiO-P2-based sensor to HCHO gas at room temperature was significantly enhanced by the formation of MXene/NiO heterojunctions. The response of the MXene/NiO-P2 sensor to 50 ppm HCHO gas was 8.8, which was much higher than that of the pure MXene and NiO. At room temperature, the detectable HCHO concentration of the MXene/NiO-P2-based sensor was 1 ppm, and the response and recovery time to 2 ppm HCHO was 279 s and 346 s, respectively. The MXene/NiO-P2 sensor also exhibited a good selectivity and a long-term stability to HCHO gas for 56 days. The in situ Fourier transform infrared (FTIR) spectra of the MXene/NiO-P2 sensor, when exposed to HCHO gas at different times, were investigated to verify the adsorption reaction products of HCHO molecules.
In order to obtain higher synthetically mechanical properties, Mg-4Al-1Si-1Gd alloy was deformed by the combination of hot extrusion and equal channel angular pressing (ECAP). The results show that ...combined deformation process can further promote grain refinement of Mg-4Al-1Si-1Gd alloy, so that Mg2Si phase distributes more uniformly and induce the precipitation of Mg17Al12 particles. With the addition of subsequent ECAP, the grain size of the alloy was reduced from 10.68 ± 0.2 μm to 2.48 ± 0.1 μm. After the hot extrusion at 300 ℃ and two passes ECAP at 200 ℃, the short rod-like Mg2Si phase was broken and evenly distributed in the matrix. Remarkably, a large number of sub-microns Mg17Al12 precipitation particles along the grain boundaries were observed, and the average particle size was 0.43 ± 0.05 μm, which can inhibit grain growth to promote grain refinement. And Mg17Al12 precipitation particles can be able to prevent the dislocation from moving in view of the Orowan mechanism. At the same time, the broken Mg2Si particles with uniform distribution can enhance the elongation of alloy by reducing the crack source. Therefore, the optimum mechanical properties can be obtained. Specifically, the tensile strength is 293.8 MPa, the yield strength is 241.5 MPa and the elongation reaches 30.1%.
A solid oxide fuel cell (SOFC) is regarded as the first choice of high-efficiency and clean power generation technology in the 21st century due to its characteristics of high power generation ...efficiency and low pollutant emission. In this paper, hydrogen is used as a fuel for SOFCs using the EBSILON platform. A sensitivity analysis of the solid oxide fuel cell–gas turbine (SOFC–GT) system with steam reinjection is carried out to investigate the effect of the steam reinjection mass flow rate on the improvement of the electrical efficiency of the system and on the values of the other parameters. The results show that the variation in the steam reinjection mass flow rate has an effect on other parameters. Changes in several parameters affect the electrical efficiency of the system, which reaches 74.11% at a pressure ratio of 10, SOFC inlet temperature of 783.15 K, turbine back pressure of 70 kPa, and steam reinjection mass flow rate of 6.16 kg/s. Future research can optimize the overall parameter selection of the system in terms of economy and other aspects.
A photonics-assisted multi-band radar transmitter operating in a wide frequency range has been proposed and experimentally demonstrated. The multi-band radar transmitter incorporates a tunable ...optoelectronic oscillator (OEO), a low-frequency RF source and a microwave photonic frequency-converting link. In the frequency-converting link, a single tone with ultra-low phase noise and a low-frequency narrow-band RF signal that are generated respectively by the OEO and the RF source, are mixed, frequency converted and bandwidth multiplied to generate multi-band transmission signals. The central frequency, bandwidth and modulation format of transmission signals are reconfigurable. A multi-band radar transmitter with an instantaneous bandwidth of 1.6 GHz is developed. The frequency range of the multi-band radar transmitter covers six bands (from S to Ka), and a moving target detection experiment verifies that the proposed system has potential in multifunctional radar applications.
We propose and demonstrate a frequency-agile coherent multiple bands generator based on an asymmetrically-coupled optoelectronic dual-loop framework with recirculating frequency-shifting. The two ...loops convert two seed signals into different frequency-shifted signals and respectively replace the original seed signals through feedback modulation, achieving repetitive frequency-shifting in the optical- and the electric-domains. When the two loops are coupled through delivering one continuously frequency-shifted light wave into the other loop to participate in the recirculating frequency-shifting, a carrier-frequency agile multiple bands signal is obtained. By properly controlling the parameters of the seed signals and the two optoelectronic loops, highly reconfigurable and coherent multiple bands can be obtained. A proof-of-concept experiment is carried out. Coherent multiband signals with stepped frequency and hopped frequency covering C- and X-bands are generated. Additionally, using the generated signals, a series of microwave imaging experiments under complex electromagnetic interference (EMI) are demonstrated, showing the advantages of the proposed method in anti-interference and high-resolution imaging.
PDF
