In this paper, a W-Re-Os thin film was prepared on the Ba-W cathode substrate by using ion beam sputtering. The effectst of the sputtering time and sputtering gas pressure on the microstructure and thermionic emission performance of the cathode were systematically studied. The surface film properties including morphology, thickness uniformity, and compositionwere characterized by SEM, X-ray thickness gauge, and EDS. The emission performance was evaluated using a dynamic vacuum testing system. The results show that the optimal performance was achieved with a sputtering deposition time of 2.5 h and a sputtering pressure of $7.0 \times 10^{-3} \mathrm{~Pa}$. Under these conditions, the element homogeneity exceeds 99 %. Consequently, the cathode demonstrates superior emission performance.

To improve the thermionic emission performance of the rare-earth refractory yttrium salt cathode used in the magnetron, the influence of Sc2O3 doping on its thermionic emission properties is investigated. Cathodes are fabricated by incorporating different weight percentages of Sc2O3 into the rare-earth refractory yttrium salt matrix, and their thermionic emission properties are systematically evaluated. The experimental findings reveal that the doping of Sc2O3 significantly enhances the thermionic emission capability of the cathode. Notably, Sc2O3 with a doping concentration of 3% has the most significant improvement in emission performance. The 3% Sc2O3-doped cathode can achieve a thermionic emission current density of 3.85 A/cm2 under an anode voltage of 300 V at 1600 degrees C. In contrast, under the same conditions, the undoped cathode provides a current density of only 1.66 A/cm2, indicating a 132% increase in thermionic emission efficiency when doped with 3% Sc2O3. By using the Richardson line method coupled with data-fitting algorithms, the absolute zero work functions for undoped and Sc2O3-doped cathodes (3%, 7%, and 11%) are determined to be 1.42, 0.93, 0.98, and 1.11 eV, respectively. The lifespan assessment indicates that at 1400 degrees C the cathode doped with 3% Sc 2O3 remains stable for over 4200 h under an initial load of 0.5 A/cm2 without significant degradation. Finally, those cathodes are analyzed by the XRD, SEM, EDS, AES respectively. The analyses show that during thermionic emission testing, the Sc2O3 and Y2Hf2O7 undergo substitutional solid solution reactions, forming the ScxY(2-x)Hf2O[7+(3/2)x] solid solution. This process causes lattice distortion in the Y2Hf2O7, which makes it in a high-energy state, thus reducing the work function on the cathode surface. At the same time, Sc from Sc2O3 displaces Y in the Y2Hf2O7 unit cells, with the displaced Y existing in the form of metal, which enhances the electrical conductivity of the cathode surface. Additionally, the ScxY(2-x)Hf2O[7+(3/2)x] solid solution generates a substantial number of Vo2+ oxygen vacancies and free electrons, thereby further augmenting surface conductivity. All in all, these mechanisms contribute to significantly improving the thermionic emission capability of the cathode.

To improve the thermionic emission performance of the rare-earth refractory yttrium salt cathode used in the magnetron, the influence of Sc2O3 doping on its thermionic emission properties was explored. Cathodes were fabricated by incorporating different weight percentages of Sc2O3 into the rare-earth refractory yttrium salt matrix, and their thermionic emission properties were systematically evaluated. The experimental findings revealed that the doping of Sc2O3 significantly enhances the thermionic emission capability of the cathode. Notably, a doping concentration of 3wt% Sc2O3 yielded the most pronounced improvement in emission performance. The 3wt% Sc2O3-doped cathode could achieve a thermionic emission current density of 3.85A/cm2 under a 300 V anode voltage at 1600℃. In contrast, the undoped cathode supplied a current density of merely 1.66A/cm2 under identical conditions, demonstrating a 132% enhancement in thermionic emission efficiency with 3wt% Sc2O3 doping. Utilizing the Richardson line method coupled with data-fitting algorithms, the absolute zero work functions for undoped and Sc2O3-doped cathodes (3wt%, 7wt%, and 11wt%) were determined to be 1.42, 0.93, 0.98, and 1.11 eV, respectively. Longevity assessments indicated that the 3wt% Sc2O3-doped cathode had been stable for over 4200 hours without significant degradation under an initial load of 0.5 A/cm2 at 1400℃. Finaly, those cathodes had been analyzed by the XRD, SEM, EDS, AES respectively. The analysis results showed that during thermionic emission testing, the Sc2O3 and Y2Hf2O7 had undergone substitutional solid solution reactions, forming the ScxY(2-x)Hf2O[7+(3/2)x] solid solution. This process induced lattice distortion in the Y2Hf2O7, placing it in a high-energy state and thereby reducing the work function on the cathode’s surface. Concurrently, Sc from Sc2O3 displaced Y within the Y2Hf2O7 unit cells, with the displaced Y existing in a metallic form, which enhanced the electrical conductivity of the cathode's surface. Additionally, the ScxY(2-x)Hf2O[7+(3/2)x] solid solution generated a substantial number of Vo2+ oxygen vacancies and free electrons, further augmenting surface conductivity. Collectively, these mechanisms contributed to a marked enhancement in the cathode's thermionic emission capacity.

As a key equipment in high-speed railway operation, rails inevitably produce various fatigue cracks during long-term service, which are major safety hazards in the railway transportation. In order to achieve intelligent detection of the rail fatigue cracks, the PCA-adaboost.M2 algorithm based on ultrasonic guided waves is proposed for the classification and identification of rail fatigue cracks. First, a rail fatigue crack detection system based on an ultrasonic guided wave was established to obtain ultrasonic guided wave signals at different depths of the rail fatigue cracks. Then, five time-frequency domain features of the ultrasonic guided wave (the maximum, the mean, the variance, the center of gravity frequency, and the frequency variance) were extracted, and the five main components of the ultrasonic guided wave were extracted by the principal component analysis (PCA) method and are used for classification and recognition of the adaboost and the adaboost.M2 algorithm, separately. The experimental results show that the ultrasonic guided wave based on the PCA-adaboost.M2 algorithm proposed has good performance in quantitative detection of the rail fatigue crack depth. The ultrasonic guided wave based on the PCA-adaboost.M2 algorithm proposed in this paper provides a method for detecting the rail fatigue crack depth.

Poly-L-lactic acid (PLLA) microwell patterns were fabricated using a lithography-based replica molding method to develop neural stem cell-based assays. Hippocampal neural stem cells (NSCs) were cultured on microwell patterns to construct a multi-dimensional culture system model in which cells within the microwells were mainly cultured with three-dimensional cellular aggregates (MW-3D cells), and cells on the top surfaces were mainly cultured with two-dimensional single-layer adherent cultures (TS-2D cells). It was found that self-renewal and MW-3D cell-directed migration and transformation regulate the construction of this model. Patterns without channel connections occurred earlier in the construction of this model than those with channel connections, due to the tendency of NSCs to extend to both sides along the direction of the channels. Self-renewal and stemness maintenance of NSCs within the microwells were promoted by the patterns with the channel connections as a suitable microenvironment for a prolonged period of time, and can be used to build quasi-one-dimensional neural networks within the microwells. This will become a practical model for studying the functional behavior of NSCs, with different culture systems dynamically assembled on the same platform for stem cell research and the development of stem cell-based assays. Multi-dimensional culture system model of the hippocampal NSCs on microwell patterns. (a-b) Hippocampal NSCs were stained with Nestin and DAPI after 7 days on the (a) 100–0 μm and (b) 120–40 μm patterns. Images were obtained by multi-slice scanning with CLSM, volume rendering of the image sequence, and overlaying of the confocal fluorescence images with phase-contrast micrographs. (c-d) Cross-sectional views of the 3D reconstructed confocal microscopic images of DAPI and Nestin were used to analyze the distribution of cells inside the microwells.

This paper introduces an in-line Mach-Zehnder fibre-optic interferometer (IMZI) based on two multimode fibre tapers for high-precision curvature and vibration detection. The IMZI was formed by fusing the structure of multimode fibre taper (MFT)-single-mode fibre (SMF)-MFT. By inducing non-adiabatic tapering in the multimode fibre (MMF), the cladding modes of the MMF were excited effectively, which in turn stimulate high-order cladding modes within the SMF, substantially enhancing the sensitivity of the fibre sensor. In curvature sensing experiments, the sensor demonstrated an exceptionally high intensity sensitivity of approximately 97.5 dB/m-1 and a wavelength sensitivity of roughly -24.2 nm/m-1. When affixed to a cantilever beam, the IMZI proved to be effective for vibration measurements, offering a sensitivity of 23.27 mV/nm and a signal-to-noise ratio (SNR) of 50 dB at 1000 Hz.

This study presents the fabrication of polylactic acid microwell patterns using a lithography-based replica molding method for the development of three-dimensional (3D) neural cell-based assays. SH-SY5Y human neuroblastoma cells interfaced with these patterns, and cell growth and morphological characteristics were evaluated with and without an inhibitor of the rho-associated coiled-coil kinase (ROCK) signaling pathway. The results revealed that the culture systems of SH-SY5Y cells on the microwell patterns could be categorized as two-dimensional (2D), 3D, and near-two-dimensional (N2D), according to their location within a dynamic multidimensional culture system. Furthermore, the geometric features of the patterns significantly impact the efficiency of the conversion model, which was characterized by the proliferation and percentage of cells in different culture systems. The rearrangement of the microfilament cytoskeleton and morphological spreading of cells on the patterns were suppressed by the downregulation of the ROCK signaling pathway. The inhibition of the ROCK signaling pathway had a time-dependent effect on the proliferation and migration of cells on the patterned substrate, where topographical cues, cell morphology, and density played pivotal roles. Consequently, the proposed system serves as a practical model for studying the functional behaviors of neural cells by dynamically assembling multidimensional culture systems on the same platform, facilitating the development of cell-based assays. ROCK-myosin II signaling pathway on the morphology and actin cytoskeleton of SH-SY5Y cells. Immunofluorescent staining for F-actin of FS-2D cells growing on flat substrates and N2D cells or 3D cells cultured on 100–20 μm pattern for 24 h with or without Y-27632 (d–f) and blebbistatin (g–i) treatment or without any treatment (a–c). Scale bar: 20 μm

In Impulsive noise environments, the three-dimensional multiple signal classification (3D-MUSIC) algorithm would lose robustness to 3D direction of arrival (DOA) estimation of sources. In this paper, the correntropy-based correlation and correntropy-based operator replace the uniform circular array covariance matrix of 3D-MUSIC, respectively, which achieves 3D-DOA estimation in impulsive noise environments. The simulations indicate that the two proposed methods are effective.

Rail safety is very important, and fatigue cracking is one of the important factors affecting rail safety. Therefore, it is an urgent need to develop a safe and effective rail fatigue crack detection technology. Ultrasonic guided wave technology plays an important role in rail detection because of its long propagation distance and small attenuation. In order to realize the quantitative detection of rail fatigue crack, an ultrasonic guided wave technology based on particle swarm optimization-extreme learning machine (PSO-ELM) algorithm for evaluating the rail fatigue crack depth is proposed. The finite element method is used to establish the ultrasonic guided wave model in the rail, and the rail fatigue crack at different depths is simulated. The ultrasonic guided wave selected through the time window function of the excitation signal is used for analysis, and then nine features such as the time domain and the frequency domain of the ultrasonic guided wave are extracted. The PSO-ELM algorithm is used to identify the rail fatigue crack with different depths, and an ultrasonic guided wave-based detection system for the rail fatigue crack is built to verify the relevant theoretical results. The results of finite element simulation and the experiment show that ultrasonic guided wave technology based on PSO-ELM algorithm proposed can quantitatively evaluate the rail fatigue crack with different depths, with an accuracy of more than 99.95 %, which provides an effective method for the rail fatigue crack detection.

Compact rat-race ring couplers with T type capacitor loading and T type stepped impedance loading are presented in this paper. The occupied area of the coupler with T type capacitor loading is a little larger than that of the coupler with T type stepped impedance loading. The bandwidth of the coupler with T type capacitor loading is better than that of the coupler with T type stepped impedance loading. The conclusions are supported both by simulation and measurement.

In order to prolong the service life and high-temperature stability of direct-heated cathode, a novel cathode is proposed and prepared, in which La2O3, Gd2O3, and HfO2 are used as raw materials for the first time. The X-ray diffraction (XRD) structure characterization shows that emission material consists of La2O3 and La2Hf2O7 two compounds. The thermionic emission results indicate that this kind cathode can supply a current density of about 5.5 A/cm2 at 1600 °C. The energy dispersive spectroscopy (EDS) detection manifests the emission material distributes homogeneously around the W–Re base. The cathode has been working stably for 10 920 h without obvious fall at 1550 °C with the loading of 0.65 A/cm2 in life test process.

As the performance of the vacuum electron devices largely depends on the properties of their cathodes, developing efficient and durable thermionic cathode is necessary and highly desired to meet the boosting requirements of the vacuum electron devices. This paper mainly describes the research progress in W-Re base direct-heated cathodes used in high-power continuous wave magnetrons, which include the $\boldsymbol{Sc_{2}O_{3}}$ doped Y-Gd-Hf-O pressed series cathodes and the $La_{2}Hf_{2}O_{7}$ cathode. The current density of the pressed Y-Gd-Hf-O cathode can remain to 87.5% of the initial one after continuous electron bombardment for 480 $\boldsymbol{h}$ , and the best emission ability of 2.79 $A/cm^{2}$ has reached with the 5/2 molar ratio of the $\boldsymbol{Y_{2}O_{3}/HfO_{2}}$ at $1500^{\circ}C$ . The lifetime of the $\boldsymbol{L_{2}Hf_{2}O_{7}}$ cathode is beyond 10000 $\boldsymbol{h}$ at $155\theta{\ }^{\circ}C$ with the loading of 0.65 $A/cm^{2}$ .

This study presents a three-dimensional direction-of-arrival (3D-DOA) estimation model based on convolutional neural networks in non-Gaussian environments. First, four covariance matrices from a uniform triangular array (UTA) are normalized via the infinite norm. Secondly, they are fed into a neural network to estimate four 1D-DOAs. Lastly, 3D-DOA estimation can be achieved with algebraic post-processing. The simulation results demonstrate that the 3D-DOA estimation accuracy and computing speed of the proposed model are effective and superior.

A compact four-way Wilkinson power divider network with meander high impedance transmission lines and port impedance matching networks is presented in this letter. Firstly, a compact four-way Wilkinson power divider network with high port impedance is designed using meander high impedance transmission lines. Secondly, port impedance matching networks using distributed parameters L-section matching networks are designed to match the high port impedance to ordinary 50 ohm. The proposed power divider network effectively reduces occupied area to 37.1% of conventional one. The design is validated both by simulation and measurement.

To improve the pressed Y-Gd-Hf-O cathode emission ability, different molar ratio for Y 2 O 3 to HfO 2 are selected for testing. The highest DC emission current of 2. 79 A/cm 2 at 1500 °C occurs when the ratio is 5/2. The emission mechanism is discussed based on the analysis of surface constituents and emission behavior for the cathode. It is concluded that the copious electrons emit from a semiconductor layer of Y 2 O 3-x on the W-Re base after the activation and aging process. Its emission property is up to the surface semiconductor Y 2 O 3-x contents.

In order to improve the output power and service life of the high-power magnetron, a new type of Gd2Hf2O7 ceramic cathode was developed. We had tested the thermal emission and service life characteristics of the Gd2Hf2O7 ceramic cathode. The results show that the cathode can provide 0.10A/cm(2), 1.93A/cm(2) current density at 1300 degrees C br, 1600 degrees C br respectively under 300V anode voltage. The service life of the cathode is more than 4000 h with a load of 0.5A/cm(2) at 1500 degrees C br.

In order to improve the output power and service life of the high-power magnetron, a new type of Gd 2 Hf 2 0 7 ceramic cathode was developed. We had tested the thermal emission and service life characteristics of the Gd 2 Hf 2 0 7 ceramic cathode. The results show that the cathode can provide $\boldsymbol{0.10\mathrm{A}/\text{cm}^{2},1.93\mathrm{A}/\text{cm}^{2}}$ current density at 1300°C br, 1600°C br respectively under 300V anode voltage. The service life of the cathode is more than 4000 h with a load of 0.5A/cm 2 at 1500°Cbr.

To improve the Y-Gd-Hf-O cathodes anti-electron bombardment ability, a scandia doped cathode is prepared by a pressing technique combined with sintering in hydrogen atmosphere. The tested result shows that the emitting current from the cathode operating at 1550 degrees C can remain to 87.5% of the initial one after continuous electron bombardment of 10 W for 480 h, reflecting a better anti-electron bombardment capability. The surface microstructure analysis result indicates that a cermet structure has been formed. A n-type semiconductor Y2O3-x, layer has generated on the cathode surface after being sintered and activated at high temperature, which is favorable for enhancing the thermionic emission, improving the surface conductivity, and lowering the work function.

A compact rat-race ring coupler with modified T type capacitor loading is presented in this paper. Two variable parameters are added to the conventional T type capacitor loading structure, and adjusting these two parameters can control the position and width of harmonic suppression stop-band. The new coupler effective reduces the occupied area to 14.1% of the conventional one. The design is validated both by simulation and measurement.

A dual-laser source is used to study the propagation and scattering characteristics of ultrasound generated in the specimen containing branched-breaking defects. This propagation process between ultrasonic wave and the branched-breaking defects is analyzed in detail, when the inclination of the branched-breaking defects changes from 30° to 60° (the depth of the branched-breaking defects changes from 0 mm to 0.5 mm), the maximum amplitude of the R-wave signal spectrum gradually decreases. When the depth of the branched-breaking defects changes from 0.5 mm to 1.0 mm, the R-wave signal spectrum has no any change. The method of dual-laser source generated ultrasonic wave is used to identify and analyze the branch surface-breaking defects.