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EEG decoding based on motor imagery is an important part of brain–computer interface technology and is an important indicator that determines the overall performance of the brain–computer interface. Due to the complexity of motor imagery EEG feature analysis, traditional classification models rely heavily on the signal preprocessing and feature design stages. End-to-end neural networks in deep learning have been applied to the classification task processing of motor imagery EEG and have shown good results. This study uses a combination of a convolutional neural network (CNN) and a long short-term memory (LSTM) network to obtain spatial information and temporal correlation from EEG signals. The use of cross-layer connectivity reduces the network gradient dispersion problem and enhances the overall network model stability. The effectiveness of this network model is demonstrated on the BCI Competition IV dataset 2a by integrating CNN, BiLSTM and ResNet (called CLRNet in this study) to decode motor imagery EEG. The network model combining CNN and BiLSTM achieved 87.0% accuracy in classifying motor imagery patterns in four classes. The network stability is enhanced by adding ResNet for cross-layer connectivity, which further improved the accuracy by 2.0% to achieve 89.0% classification accuracy. The experimental results show that CLRNet has good performance in decoding the motor imagery EEG dataset. This study provides a better solution for motor imagery EEG decoding in brain–computer interface technology research. [ABSTRACT FROM AUTHOR]

With the development of portable EEG acquisition systems, the collected EEG has gradually changed from being multi-channel to few-channel or single-channel, thus the removal of single-channel EEG signal artifacts is extremely significant. For the artifact removal of single-channel EEG signals, the current mainstream method is generally a combination of the decomposition method and the blind source separation (BSS) method. Between them, a combination of empirical mode decomposition (EMD) and its derivative methods and ICA has been used in single-channel EEG artifact removal. However, EMD is prone to modal mixing and it has no relevant theoretical basis, thus it is not as good as variational modal decomposition (VMD) in terms of the decomposition effect. In the ICA algorithm, the implementation method based on high-order statistics is widely used, but it is not as effective as the implementation method based on second order statistics in processing EMG artifacts. Therefore, aiming at the main artifacts in single-channel EEG signals, including EOG and EMG artifacts, this paper proposed a method of artifact removal combining variational mode decomposition (VMD) and second order blind identification (SOBI). Semi-simulation experiments show that, compared with the existing EEMD-SOBI method, this method has a better removal effect on EOG and EMG artifacts, and can preserve useful information to the greatest extent. [ABSTRACT FROM AUTHOR]

In the development of analog signal compressive sensing (CS), the degradation of reconstruction performance under noise is the main bottleneck because the CS framework is very sensitive to noise. This paper proposes an adaptive channelization-based orthogonal matching pursuit algorithm (C-OMP) combining the channelization and the adaptive iteration methods. The proposed C-OMP has two steps: channel screening and global iteration. Based on the proposed method, the original signal can be recovered adaptively in high probability of success with fewer observations under the noise background. Simultaneously, the noise can be reduced as much as possible to enhance the output signal-to-noise ratio (SNR) by excluding the noise channel during the channel screening and separating noise atoms during the global iteration. The relationship between the probability of successful reconstruction and the number of observations is mathematically analyzed. Furthermore, the parameter settings, computational complexity, and output SNR are analytically evaluated. The simulation results confirm the analytical results and further demonstrate the effectiveness and advantages of the C-OMP in the noise environment. Overall, the proposed algorithm considerably improves the performance of the analog signal CS in the practical noisy environment. [ABSTRACT FROM AUTHOR]

This correspondence paper studies joint beamforming optimization and time allocation for a wireless powered two-way hybrid-relay network. As a general relaying architecture accommodating the existing relaying architectures in the literature as two special cases, we consider the two-way communication system where both energy-harvesting (EH) relays and non-EH relays exist. We aim to maximize the minimum rate by jointly optimizing the distributed beamforming vector at the relays, the energy beamforming matrix at the non-EH relays, and the EH time allocation with the energy constraints at the relays. The formulated problem is intractable to solve because the objective function and the energy constraints are highly nonconvex. We solve the optimization problem using the successive convex approximation. Simulations demonstrate that the proposed iterative algorithm considerably outperforms any existing approaches. [ABSTRACT FROM AUTHOR]

This paper studies the joint beamforming design and time allocation for a two-way energy harvesting (EH) relay network, where a single-antenna base station and a single-antenna user communicate with each other through multiple-single antenna EH relay nodes, and an external multiantenna power beacon wirelessly power the relays. Unlike the existing studies that assumed the symmetric two-way relaying scenario, we assume a more practical scenario of asymmetric two-way relaying considering different traffic demands on the downlink and uplink. In this paper, we design the optimal beamforming vectors at the relays and at the power beacon jointly with the time allocation between information and EH transmissions, in the sense of maximizing the sum rate of the asymmetric information transmission under the EH constraints at the relays, and the power constraint at the power beacon. The formulated optimization problem is nonconvex, and thus, it is difficult to solve. To solve this challenging problem, we propose an iterative algorithm based on the semidefinite relaxation and the successive convex approximation techniques. Also, to reduce the computational complexity, we propose an efficient noniterative scheme based on the maximum-ratio transmission. The performance of the proposed schemes is demonstrated through simulations. [ABSTRACT FROM AUTHOR]

In this paper, an improved sparse-aware affine projection (AP) algorithm for sparse system identification is proposed and investigated. The proposed sparse AP algorithm is realized by integrating a non-uniform norm constraint into the cost function of the conventional AP algorithm, which can provide a zero attracting on the filter coefficients according to the value of each filter coefficient. Low complexity is obtained by using a linear function instead of the reweighting term in the modified AP algorithm to further improve the performance of the proposed sparse AP algorithm. The simulation results demonstrate that the proposed sparse AP algorithm outperforms the conventional AP and previously reported sparse-aware AP algorithms in terms of both convergence speed and steady-state error when the system is sparse. [ABSTRACT FROM AUTHOR]

A compact CPW‐fed triple band‐notched antenna for ultra‐wide bandwidth (UWB) application is presented. By introducing an stepped impedance resonator‐defected ground structure (SIR‐DGS) and fork‐shaped stubs, three sharp notches are achieved at frequencies of 3.5, 5.68 and 7.48 GHz. The proposed antenna working from 2.8 to 11.3 GHz with a voltage standing wave ratio of <2 is demonstrated, except for the selected notched bands. The main advantage of the antenna is that the frequency of the notched band can be tuned easily in a wide frequency range. A good agreement between the measurement and the simulation was achieved. The measurements confirm that the technique introduces negligible antenna radiation pattern distortion, except at the triple‐notched frequencies. [ABSTRACT FROM AUTHOR]

• Thermosyphon in a vertical narrow annulus with external cooling is investigated. • The cooling power has a linear relation with the inlet water temperature. • The relationship between the LMTD and Gr*1/3 shows an excellent linearity. • A correlation is proposed to predict the natural convective heat transfer in annuli. In PWRs, the Control Rod Drive Mechanisms (CRDMs) are heated by coils and coolant, and cooled by external convection. The thermosyphon in the CRDMs has significant influences on the coil temperatures. In this work, the thermosyphon characteristics in a vertical narrow annulus closed at top with external forced convection cooling is experimentally investigated. The effects of the inlet water temperature and the velocity of external air cooling on the thermosyphon and cooling power are analyzed. The results indicate that the cooling power has a linear relation with the inlet water temperature. The external cooling condition has effects on the natural convective heat transfer and transition point in the annulus. The relationship between the Logarithmic Mean Temperature Difference and the 1/3 power of Gr*, a correction of Gr considering external forced convection heat transfer, shows an excellent linearity. A new correlation is proposed to predict the natural convective heat transfer coefficient in annuli. [ABSTRACT FROM AUTHOR]

• LDV was verified to be used to measure the flow induced vibration of rod bundle. • Flow induced vibration of a 4x4 rod bundle with space grids was tested. • Both turbulence and vortex excited vibration of the rod and space grid were obtained. • Strong vortex induced resonance was found when the flow velocity was 7.35 m/s. In order to develop a feasible method for measuring FIV of both spacer grid and rod, two experiments are conducted in this study. First, the simultaneous verification tests between the LDV and piezoelectric accelerometer have been performed. For the case of vibration occurring in a channel with water, the measured signal by the LDV need to be modified while not affecting the measured vibration value. The results show that the LDV is a good candidate for measuring vibration under flow conditions. Then, the LDV is employed to measure the FIV of a specified 4 × 4 rod bundle with spacer grids. Both turbulence and vortex excite the rod bundle, and a strong vortex induced resonance is found when the flow velocity is 7.35 m/s. The vibration intensity is amplifying with increasing the flow velocity. Moreover, 'lock-in' phenomenon and two types of vortex shedding with St numbers of 0.15 and 0.26 are found. [ABSTRACT FROM AUTHOR]

Tensile creep tests were performed at 523 K on a hot compressed Mg-2.5 wt%Nd binary alloy with peak aging (AA sample) and without aging (AS sample) in this work. The dominant creep mechanisms of AS sample were dislocation climb and pyramidal slip while AA sample was mainly dominated by cross-slip. During creep testing, only plate-like β 1 precipitate was formed in AS sample while both plate-like β 1 and lenticular β ′ phases were formed in AA sample. Moreover, AA sample had larger scale and higher density of precipitates compared to AS sample. Besides, precipitate-free zones (PFZs) were clearly observed along grain boundaries of both AS and AA samples during their secondary creep stages. And the width of PFZs was narrower in AA sample than that in AS sample. The narrower PFZs, the higher density of β 1 and β ′ phases, and the strong interactions between cross-slip and precipitates effectively enhanced the creep properties of AA sample. As a result, AA sample behaved higher creep resistance in comparison to AS sample under all applied stresses at 523 K. Thus, this method of pre-aging and hot compression is believed to have deep potential in improving the service performance of Mg–Nd series at medium to high temperatures. [ABSTRACT FROM AUTHOR]