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The scarcity of cryogenic thermometers often stems from their high cost and lengthy lead times for calibration. Establishing an in-lab temperature calibration system is necessary to quickly make use of uncalibrated sensors or self-made sensors. This paper introduces a straightforward and high-accuracy thermometer calibration system. By employing copper screws as thermal links between the sensor platform and the cryogen-free refrigerator, temperature oscillation on the sensor platform is suppressed to a few millikelvins. In addition, this paper presents a data processing model based on clustering algorithms. These algorithms sort and group data based on distance, which is similar to human visual judgment of data. This paper discusses the parameter optimization process of the clustering algorithm to interpret the automated data process. The cryogenic temperature sensors calibrated by this system exhibited high accuracy, with relative errors of less than 1% compared to standard thermometers. Moreover, automatically processing calibration data from two uncalibrated thermometers takes just over 10 min, highlighting the effectiveness of this calibration system. [ABSTRACT FROM AUTHOR]

This paper introduces a novel digital triangular–trapezoidal double-channel shaping algorithm to enhance the counting rate of resistive anode detectors. The algorithm is based on the trapezoidal shaping algorithm and improves it. At the extreme counting rate, the trapezoidal shaping algorithm cannot alleviate the pulse pileup, so the counting rate cannot meet the requirements of a high performance detector. The triangular–trapezoidal double-channel shaping algorithm is introduced in the resistance anode detector, which can replace the trapezoidal shaping filtering algorithm to process the output signal of the resistance anode detector and obtain the single photon position information. This improvement improves the counting rate of the resistor anode detector and reduces the resolution degradation caused by pulse pileup. The algorithm is simulated by System Generator software and implemented on FPGA (field programmable gate array). The triangular–trapezoidal double-channel shaping algorithm presented in this paper plays an important role in reducing electronic noise and pulse pileup. The algorithm is subjected to simulation testing, and it can recognize signals with a minimum pulse interval of 1 µs and counting rate up to 1000 kcps. [ABSTRACT FROM AUTHOR]

For the fixed-time nonlinear system control problem, a new fixed-time stability (FxTS) theorem and an integral sliding mode surface are proposed to balance the control speed and energy consumption. We discuss the existing fixed time inequalities and set up less conservative inequalities to study the FxTS theorem. The new inequality differs from other existing inequalities in that the parameter settings are more flexible. Under different parameter settings, the exact upper bound on settling time in four cases is discussed. Based on the stability theorem, a new integral sliding mode surface and sliding mode controller are proposed. The new control algorithm is successfully applied to the fixed-time control of chaotic four-dimensional Lorenz systems and permanent magnet synchronous motor systems. By comparing the numerical simulation results of this paper's method and traditional fixed-time sliding mode control (SMC), the flexibility and superiority of the theory proposed in this paper are demonstrated. Under the same parameter settings, compared to the traditional FxTS SMC, it reduces the convergence time by 18%, and the estimated upper bound of the fixed time reduction in waiting time is 41%. In addition, changing the variable parameters can improve the convergence velocity. [ABSTRACT FROM AUTHOR]

This paper introduces the design and implementation of a prototype Digital Delay Generator (DDG) characterized by high precision, low jitter, and a wide delay range, fully realized within a Field Programmable Gate Array (FPGA). The DDG's architecture is based on an innovative combination of an embedded time-to-digital converter (TDC) and Multi-stage Time Interpolation (MTI) delay logic. The paper explores the factors influencing delay jitter during external trigger mode and carefully selects the optimal design approach for each element. The embedded TDC, which undergoes automatic calibration, accurately measures the time difference between the arrival of an external trigger and the FPGA's internal clock signal. When paired with the MTI delay logic, this allows for highly precise control over delay durations. A key aspect of this design is its sole dependence on the FPGA's built-in resources, ensuring simplicity in implementation and adaptability to various applications. Evaluation of the prototype has shown promising results, demonstrating a delay resolution as fine as 20 ps and maintaining a low jitter of 105 ps peak-to-peak (20 ps rms) when operated in the externally triggered mode. [ABSTRACT FROM AUTHOR]

This paper proposes a two-dimensional calibration method for resolving the nano-positioner pedestal micro-deformation crosstalk errors during the auction process. This refinement aims to enhance the nano-positioner's accuracy and reduce coupling crosstalk errors. The reaction force exerted by the piezoelectric actuator can cause micro-deformation in the nano-positioner sensor pedestal, causing substantial errors in uncalibrated closed-loop control. This phenomenon has been previously overlooked. According to the two-degree of freedom parallel-symmetric decoupled nano-positioner deformation characteristics, a two-dimensional calibration matrix is proposed to suppress the crosstalk between two axes caused by the micro-deformation of the sensor pedestal. Experimental results show that the calibrated closed-loop system reduces X-axis and Y-axis coupling crosstalk errors to 1/67th and 1/18th of the uncalibrated closed-loop system, respectively, concurrently enhancing the positioning accuracy to 11.8 and 17 times that of the uncalibrated closed-loop system. The calibrated closed-loop feedback control method proposed in this paper proves effective for all compact nano-positioners with pedestal deformation issues. This research provides a crucial reference for the design of nano-positioners, offering insights into enhancing their accuracy and mitigating crosstalk issues. [ABSTRACT FROM AUTHOR]

Percutaneous coronary intervention (PCI) has become a vital treatment approach for coronary artery disease, but the clinical data of PCI cannot be directly utilized due to its unstructured characteristics. The existing clinical named entity recognition (CNER) has been used to identify specific entities such as body parts, drugs, and diseases, but its specific potential in PCI clinical texts remains largely unexplored. How to effectively use CNER to deeply mine the information in the existing PCI clinical records is worth studying. In this paper, a total of 24 267 corpora are collected from the Cardiovascular Disease Treatment Center of the People's Hospital of Liaoning Province in China. We select three types of clinical record texts of fine-grained PCI surgical information, from which 5.8% of representative surgical records of PCI patients are selected as datasets for labeling. To fully utilize global information and multi-level semantic features, we design a novel character-level vector embedding method and further propose a new hybrid model based on it. Based on the classic Bidirectional Long Short-Term Memory Network (BiLSTM), the model further integrates Convolutional Neural Networks (CNNs) and Bidirectional Encoder Representations from Transformers (BERTs) for feature extraction and representation, and finally uses Conditional Random Field (CRF) for decoding and predicting label sequences. This hybrid model is referred to as BCC-BiLSTM in this paper. In order to verify the performance of the proposed hybrid model for extracting PCI surgical information, we simultaneously compare both representative traditional and intelligent methods. Under the same circumstances, compared with other intelligent methods, the BCC-BiLSTM proposed in this paper reduces the word vector dimension by 15%, and the F1 score reaches 86.2% in named entity recognition of PCI clinical texts, which is 26.4% higher than that of HMM. The improvement is 1.2% higher than BiLSTM + CRF and 0.7% higher than the most popular BERT + BiLSTM + CRF. Compared with the representative models, the hybrid model has better performance and can achieve optimal results faster in the model training process, so it has good clinical application prospects. [ABSTRACT FROM AUTHOR]

The core of electrostatic tomography (EST) is to solve the inverse problem, but the EST independent measurement data are much smaller than the value that needs to be reconstructed, resulting in a more serious inverse problem. This paper presents an improved ResNet-34 network (P-ResNet), which consists of an input layer, a residual feature extraction layer, and an output layer. The number of residual blocks is 3, 4, 4, and 3. After the second convolution in the main path of each residual block, a ReLU activation function is added to enhance the nonlinear expression ability of the network, and the generalization ability of the model is improved by introducing the L2 regularization loss function. A total of 15 930 sets of samples were simulated for the simulation test. After 200 rounds of iteration, the reconstruction results show that the network achieves high accuracy in EST image reconstruction tasks. In addition, the model is tested under different degrees of Gaussian white noise to verify its anti-noise ability. Compared with the traditional algorithms, the image correlation coefficients of this proposed model network are higher. In addition, this paper designs a small sensor to obtain the induced charge values through the principle of electrostatic induction. The reconstructed results obtained from the experimental data are consistent with the simulation results, which verifies the effectiveness and generalization ability of the proposed model. [ABSTRACT FROM AUTHOR]

Ferrite-loaded gyromagnetic nonlinear transmission line (GNLTL) provides a possible option to compress an input pulse to a narrower width for its remarkable sharpening effect. However, it is difficult to accurately predict the output of the GNLTL due to the complex interaction between the magnetic moment of ferrite and the bias magnetic field. In this paper, a finite element model of the GNLTL is established based on the Landau–Lifshitz–Gilbert equation to investigate the performance of the GNLTL. To validate this model, a prototype is used for experimental comparison. The result demonstrates good agreement between experiment and simulation. This paper further explores the influence of the bias magnetic field and the length of the GNLTL on the output pulse. Moreover, a method to sharpen the falling edge is proposed based on the reflection and superposition of the GNLTL output. Simulation and experimental results show its effectiveness and feasibility. [ABSTRACT FROM AUTHOR]

Multiple monochromatic x-ray imaging (MMI) is a technique for diagnosing the emission spectra of tracer elements in laser-driven inertial confinement fusion experiments. This study proposes an MMI method that combines a simple pinhole array with a laterally graded multilayer mirror. The method directly obtains multiple monochromatic x-ray images by regulating the multilayer thickness in different mirror positions to compensate for the energy-broadening effect. This paper presents a comprehensive design scheme, the multilayer fabrication and experimental verification of the gradient MMI imaging performance. The experimental results show that the method achieves monochromatic imaging with a spectral resolution of ∼70–90 eV in several keV energy regions. This paper presents a practical diagnostic approach for directly and synchronously capturing the spatial, temporal, and spectral information of laser plasma x rays. [ABSTRACT FROM AUTHOR]

The power transformer is the core equipment of the power system, a sudden failure of which will seriously endanger the safety of the power system. In recent years, artificial intelligence techniques have been applied to the dissolved gas analysis evaluation of power transformers to improve the accuracy and efficiency of power transformer fault diagnosis. However, most of the artificial intelligence techniques are data-driven algorithms whose performance decreases when the data are limited or significantly imbalanced. In this paper, we propose an active learning framework for power transformer dissolved gas analysis, in which the model can be dynamically trained based on the characteristics of the data and the training process. In addition, this paper also improves the original active learning spatial search strategy and uses the product of sample feature differences instead of the original sum of differences as a measure of sample difference. Compared to passive learning algorithms, the novel approach could significantly reduce the data labeling effort while improving prediction accuracy. [ABSTRACT FROM AUTHOR]

Brain–computer interface (BCI) technology based on P300 signals has a broad application prospect in the assessment and diagnosis of clinical diseases and game control. The paper of selecting key electrodes to realize a wearable intention recognition system has become a hotspot for scholars at home and abroad. In this paper, based on the rich-club phenomenon that exists in the process of intention generation, a phase lag index (PLI)-rich-club-based intention recognition method for P300 is proposed. The rich-club structure is a network consisting of electrodes that are highly connected with other electrodes in the process of P300 generation. To construct the rich-club network, this paper uses PLI to construct the brain functional network, calculates rich-club coefficients of the network in the range of k degrees, initially identifies rich-club nodes based on the feature of node degree, and then performs a descending order of betweenness centrality and identifies the nodes with larger betweenness centrality as the specific rich-club nodes, extracts the non-linear features and frequency domain features of Rich-club nodes, and finally uses support vector machine for classification. The experimental results show that the range of rich-club coefficients is smaller with intent compared to that without intent. Validation was performed on the BCI Competition III dataset by reducing the number of channels to 17 and 16 for subject A and subject B, with recognition quasi-departure rates of 96.93% and 94.93%, respectively, and on the BCI Competition II dataset by reducing the number of channels to 17 for subjects, with a recognition accuracy of 95.50%. [ABSTRACT FROM AUTHOR]

Piezoelectric actuators commonly used in microgrippers have a small stroke, and their accuracy is reduced by the transmission amplification unit, which leads to a contradiction between the clamping range and the clamping accuracy in existing piezoelectric-actuated microgrippers. This paper proposes a design scheme to divide the total clamping range of the microgripper into segments based on the compliant multistable mechanism (CMM). First, by using the stable equilibrium positions of the CMM, the total clamping range of the microgripper is divided into multiple smaller clamping sub-intervals to accommodate objects of different scales. Then, the theoretical models of the displacement amplification ratio of the microgripper amplification mechanism and the stiffness of the microgripper in different clamping sub-intervals are established, and the force-displacement characteristics of the CMM are analyzed. Next, through finite element simulation, the correctness of the theoretical analyses is verified, and it is shown that objects between 0 µm and 1.650 mm can be clamped using four clamping sub-intervals under a five times displacement amplification ratio. Finally, a microgripper of the CMM consisting of two three-segment fully compliant bistable mechanisms connected in series is designed and machined, and microgripper segmented clamping experiments are conducted. The experimental results demonstrate the feasibility of the design scheme proposed in this paper. [ABSTRACT FROM AUTHOR]

Riveting quality is crucial to an aircraft's overall aerodynamic performance and fatigue life. In order to effectively extract the point cloud of rivet heads and analyze the quality of riveting, this paper proposes a rivet flushness detection method based on the normal vector-density clustering algorithm. First, initial point cloud data sampling is based on normal vectors. Then, the density clustering algorithm is employed to cluster and extract the point cloud of rivet heads. Subsequently, the obtained point cloud of rivet heads is subjected to the random sample consensus algorithm for fitting the contour and obtaining the model parameters of the rivet head. The paper introduces a quality detection metric to describe the flushness of the rivet head. Finally, the proposed method is applied to analyze the skin and theoretical model point cloud data of rivets. The results demonstrate that the proposed method yields small errors and high accuracy compared to theoretical values. The method is further employed for quality detection and analysis of rivet flushness in practical aircraft engineering. A visualization system for rivet flushness quality detection is developed to represent the results visually. This system enhances the intuitive identification of rivet detection outcomes. Therefore, the proposed method holds significant engineering application value in rivet flushness detection. [ABSTRACT FROM AUTHOR]

Industrial robots are important components in the production and manufacturing industry. As a core component of the industrial robot, the industrial robot reducer plays a crucial role in the performance of the entire industrial robot. The error analysis and accuracy traceability of the industrial robot reducer testing instrument are of great significance in improving the quality of the precision reducer. Therefore, it is essential to calibrate the dynamic torsional moment measurement error of the instrument. The features of the dynamic torsional moment measurement error are analyzed in this paper. Based on these features, a new dynamic torsional moment measurement error calibration method is proposed based on the Bisquare curve fitting–improved Bayes particle swarm optimization–nonlinear echo state network (BCF–IBPSO–NESN) algorithm. The proposed method focuses on calibrating the dynamic torsional moment measurement error of the industrial robot reducers in real time. The experimental results show that the dynamic torsional moment measurement error of the input side torsional moment measurement module and the output side torsional moment measurement module can be reduced to ±0.05 Nm and ±1 Nm, respectively. The contribution of this paper is that the method calibrates the dynamic torsional moment measurement error. It supplies a guideline for calibrating the dynamic torsional moment measurement error of the instrument under any load. [ABSTRACT FROM AUTHOR]

A new fault diagnosis approach based on bearing current signals is proposed in this paper. First, in view of strong background noise of the current signal, the variational modal decomposition method is applied to decompose the bearing current signal to obtain multiple intrinsic mode functions, and then the intrinsic mode functions are constructed as the input feature vector according to the kurtosis. Second, to avoid the influence of random forest parameters on the random forest classifier, a random forest faulty bearing diagnostic model optimized by the whale algorithm is established. Finally, the accuracy rate and confusion matrix are adopted to evaluate the prediction effects of both established and traditional models. The classification accuracy of the real damaged bearing fault type can reach 95.11%. The fault diagnosis accuracy of manually damaged bearings can reach 93.83%. The results show that the method proposed in this paper has high accuracy and good generalization ability for bearing fault diagnosis. [ABSTRACT FROM AUTHOR]

This document is a comment on a recent paper about measuring the thermal diffusivity of anisotropic materials. The comment points out two mistakes in the paper and provides corrections. It discusses the disagreement between the expression for thermal diffusivity in the paper and a previously published formula. The comment also clarifies the controversy surrounding the representation of the thermal conductivity tensor and provides an expression for the thermal conductivity along any arbitrary direction. The document emphasizes that this expression can be found in classical textbooks on heat conduction. The authors aim to clarify the subject of heat conduction in anisotropic materials and address misconceptions and errors in a previous study. [Extracted from the article]

In this paper, derived from the proportional–derivative control and robust control, a novel practical robust control method based on a dynamic feedforward model is established by taking six-axis motion cooperative industrial robots as the research object. The nonlinear friction, parameter uncertainty, and external disturbance are taken into consideration while establishing the dynamic model of the cooperative industrial robot. The method includes a proportional–derivative control and a robust control. Lyapunov theory is used to analyze the proposed controller, and it is shown that this method can guarantee uniformly bounded and uniformly final bounded systems. Simulation and experiment results show that the proposed controller is better than proportional–integral–derivative control and mode-based proportional–derivative control in stability tracking performance and robustness. In addition, the CSPACE platform for rapid controller prototyping may reduce the arduous programming effort and offer a lot of ease for the trials. [ABSTRACT FROM AUTHOR]

Large resistive sensor arrays (RSAs) show great potential in tactile perception. However, the large number of sensors can result in great hardware overhead and bring difficulties for acquiring and processing mass data timely in transient measurement applications. This paper implements a field programmable gate array (FPGA)-based data processing system for a large RSA of 96 × 96, which shows good power consumption and high-speed wireless data update. For crosstalk-free measure, the zero potential method is improved with bus switches, leading to fewer operational amplifiers required and less negative power consumption. A real-time embedded data processing system is realized by FPGA for excellent parallel processing ability. A high-speed wireless transfer scheme with automatic regulated transfer size is proposed and realized by a wireless fidelity module, which allows timely data analysis at the remote end. Moreover, fault identification of RSAs fabricated by micro-electromechanical system technology is achieved. Tests carried out on a 32 × 32 RSA show that the total power consumption is 2209 mW, including 1261 mW of processors and 948 mW of readout circuits, corresponding to 2.15 mW/pixel. The total negative power consumption of 549 mW has been reduced by 50% compared with the zero potential method. The scanning speed is 400 fps, and the wireless transfer speed is up to 120 fps when the transceiver and receiver are 5 m apart. [ABSTRACT FROM AUTHOR]

This paper aims to study the maglev force and vibration attenuation characteristics of quasi-zero stiffness cruciform maglev isolators (CMIs). The maglev force and stiffness of CMIs were analytically computed based on equivalent charge theory, and the transfer function of the system was conducted. The effects of magnet geometry parameters and air gap on the maglev force, stiffness, and vibration transmission characteristics of the CMI system were revealed through parametric analyses. With the increase in magnet length and width, the maximum value of maglev force increases, but the displacement range of near-zero stiffness, amplitude, and phase of the system gradually decrease. With the increase in magnet height, the displacement range of near-zero stiffness increases, while the variation in the amplitude and phase of the system has minimal impact. Meanwhile, in the Halbach array, the height variation of the magnet at different positions has different impacts on the magnetic force. As the air gap increases, the maximum value of maglev force decreases, but the amplitude and phase gradually increase, and the displacement range of near-zero stiffness first rises and then decreases. Finally, an experimental study was carried out to test the vibration attenuation characteristics of CMIs, in which sinusoidal excitation, hammer strike excitation, and random excitation were applied. [ABSTRACT FROM AUTHOR]

Improving the accuracy of large measurement systems consisting of multiple laser trackers and Enhanced Reference System (ERS) points is technically challenging. In practice, standard devices with precise distance limits are often used to improve the registration accuracy of laser trackers. However, these standard devices are expensive and need to be calibrated by the Coordinate Measuring Machine (CMM). In addition, the stability of ERS points can significantly affect registration errors. Therefore, this paper proposes a laser tracker registration method based on ERS point-weighted self-calibration and thermal deformation compensation. First, a self-calibration method for simple standard devices based on multilateration measurements is presented, which only utilizes large measurement systems without additional high-precision measurement instruments. Based on this, a weighted registration optimization algorithm for the registration process of a relocation laser tracker is proposed. Then, the position errors of ERS points caused by temperature changes are calculated and compensated based on the thermal deformation coefficient of large structural components. The compensated ERS points are used for the registration of the laser trackers. Finally, the effectiveness of the proposed method is demonstrated by a field measurement experiment on a large spherical shell. Compared with the most widely used benchmark method, the proposed method reduces the average registration error of all ERS points from 0.103 to 0.02 mm. [ABSTRACT FROM AUTHOR]

The generic self-correction method for nonlinearity-induced phase error (GSCN) can effectively suppress nonlinear error. However, GSCN directly ignores the periodic error of the 2N multiplication frequency in the error analysis stage, which still leads to errors in the suppressed results. In this paper, we propose a new method named improved generic self-correction method for nonlinearity-induced phase error in three-step phase-shifting profilometry. We retain the periodic error of the 2N multiplication frequency in the error analysis stage. In addition, based on the error model, we directly use the original fringes to compute the wrapped phases with -π/6, π/6, and π/3 phase shifts, respectively. Then, we use the original wrapped phase as the target phase and shifted the other three groups of wrapped phases to the target phase. Finally, we unwrap and fuse the four sets of wrapped phases to obtain the final corrected phase. Based on experimental results, the proposed method yields excellent reconstruction results and effectively suppresses nonlinear errors, making it highly efficient and precise. [ABSTRACT FROM AUTHOR]

Vibration substantially degrades machining quality and measurement accuracy in ultra-precision processes, necessitating the implementation of vibration isolators to mitigate these effects. Magnetic vibration isolators represent a promising alternative due to their wide isolation frequency range, low energy consumption, and compatibility with vacuum environments. In designing the quasi-zero stiffness magnetic vibration isolator, the particle swarm optimization algorithm is employed to balance multiple performance indicators. To address the limitations of conventional optimization methods, which excessively prioritize stiffness and fail to encompass the entire performance spectrum of magnetic vibration isolators, this study presents an innovative optimization approach. This novel strategy directly enhances vibration isolation by integrating transmissibility and compliance considerations. Structural parameters for two types of magnetic vibration isolators were established through optimizations utilizing both conventional and innovative techniques. Simulations and experiments demonstrate that isolators developed using the proposed optimization method outperform those designed with conventional strategies, thereby validating the effectiveness of this advancement. The insights presented in this paper illuminate a novel and effective pathway for the conceptualization and refinement of magnetic vibration isolators. [ABSTRACT FROM AUTHOR]

The leakage field of a hybrid electromagnetic pulse simulator with horizontal polarization is simulated and experimentally investigated based on the finite integration technique in this paper. The field distribution characteristics and far-field radiation pattern of the simulator are given. The attenuation characteristics of the electric field at specific directions in the z = 2 m plane are also predicted by numerical data fitting. Finally, according to the ICNIRP guidelines, the safe distances that satisfy the occupational and public exposure limits are obtained, and the safety regions lower than the reference levels are given. Results show that the electric field in the α = 0° direction is mainly contributed by the main polarization component (Ey), while the total electric field in the α = 90° direction also requires consideration of the vertical component (Ez). The dominant radiation direction in the z = 2 m plane lies between α = 0° and 30°, which poses the highest demand for the safe distance around the simulator. In addition, impedance mismatch and ground reflection are the main factors affecting the waveforms of the radiated electric field. [ABSTRACT FROM AUTHOR]

The concentration of carbon dioxide (CO2) is an important indicator for coal mine safety. Real-time monitoring of CO2 concentration is of great importance for taking actions in advance to avoid the occurrence of potential accidents. To address the issues of poor portability and high cost associated with existing coal mine CO2 detection equipment, this paper develops a miniaturized CO2 detection system based on non-dispersive infrared (NDIR) technology. This sensor integrates an infrared light source and a dual-channel pyroelectric detector into a reflective gas chamber, thereby achieving an extended optical path and higher system sensitivity within limited space. Meanwhile, the noise interference was greatly mitigated by using hardware and software filtering techniques. Based on principle analysis, the Lambert–Beer law was parametrically corrected, and then, a model relationship between the dual-channel voltage ratio and concentration was established. In addition, temperature compensation for zero and span values was introduced to improve the adaptability of the detection results to temperature changes. Testing results indicate that the developed detection system can realize CO2 measurement in the concentration range of 0 to 50 000 ppm within a temperature range of 0–40 °C, with a maximum detection error of less than 0.12% and a repeatability deviation of less than 1.04%. During a stability test for 12 h, the maximum concentration drift is 0.07%, indicating that the developed system meets the requirements for monitoring CO2 safety in coal mines. [ABSTRACT FROM AUTHOR]

To examine the effect of mixed-frequency excitation conditions on the hysteresis and loss characteristics of ferromagnetic materials, this paper shows how to construct magnetic property test equipment for electrical steel using Epstein's square circle. Experiments were carried out to assess the hysteresis and loss properties of oriented silicon steel wafers under mixed-frequency sinusoidal operating conditions with different occupancy ratios. It used heterodyne extraction to investigate the effect of different occupancy ratios of industry and magnetization frequency on the hysteresis and loss characteristics of oriented silicon steel sheets. [ABSTRACT FROM AUTHOR]

Pulse forming lines (PFL) are widely applied in high-power pulsed power generators due to their high energy density and great ability with square waveform modulation. However, the three-cylinder coaxial Blumlein line (tPFL), a commonly used PFL structure, has low energy efficiency due to the difference in impedance of the outer and inner lines. In order to increase the outer line impedance and improve the output waveform of the PFL, a racetrack Blumlein pulse forming line (r-B PFL), formed by two inner cylinders, two middle cylinders, and one outer cylinder that resembles a runway shape, is proposed in this paper. The glycerin energy storage technology and the spiral line technology were applied in the PFL. Moreover, the r-B PFL was tested experimentally after its construction, yielding a satisfactory result. The PFL structure in which multiple middle cylinders share the same outer cylinder achieves a higher outer line impedance, leading to a high energy efficiency of the PFL, which contributes to the PFL development trend toward compactness and miniaturization. [ABSTRACT FROM AUTHOR]

The time-to-digital converter (TDC) implemented in a field-programmable-gate-array has garnered widespread attention due to its flexibility and high-performance capabilities. However, issues such as non-uniformity, the bubble in the tapped delay line, and the presence of certain ultra-wide delay units can significantly compromise the precision and nonlinearity of the TDC. In this paper, we propose a high-precision TDC in an Elitestek Ti60 FPGA, effectively eliminating the adverse effects of non-uniformity, the bubble, and certain ultra-wide delay units. The TDC is constructed with a 318-stage delay chain and operates at a low system clock frequency of 150 MHz. The least significant bit (LSB) of the TDC is 21.92 ps. The differential nonlinearity (DNL) is between (−0.976, 1.615) LSB and the integral nonlinearity (INL) is between (−1.446, 2.678) LSB. The TDC achieves a root-mean-square error of 14.783 ps when utilized for measuring various time intervals. [ABSTRACT FROM AUTHOR]

The discharge arc of a high-current gas spark switch has a strong mechanical effect on the electrode and adjacent objects. The measurement of this mechanical effect on the electrode plays a very important role in switch design and the theoretical study of spark discharge. However, in traditional stress measurement systems, the spatial electromagnetic interference caused by the discharge and the high electrode voltage affects the measurement accuracy and can even damage the experimental instrument. In this paper, an electrode impact stress measurement system based on PVDF piezoelectric film is designed to measure the electrode stress under a strong spatial electromagnetic field and high voltage. The experimental results show that the system can measure the impact pressure of high-voltage and high-current gas spark switch electrodes. The starting time of the stress measurement waveform shows that the shock to the electrode is formed in the initial stage of current buildup. The measured results clearly show the high magnetic field force component in the electrode impact pressure waveform. The shock waveforms induced by different pulse capacitor values, breakdown voltages, and loads are examined. It is found that the shock stress waveforms applied to the electrodes are affected by the peak value of the current, dI/dt, and the discharge duration. [ABSTRACT FROM AUTHOR]

A substation is important equipment of the power system, and there are many power equipment components in the substation. In order to better detect the working status of power equipment components, it is necessary to preprocess these components. In the actual application, the power equipment images may be noisy due to external environmental interference. Therefore, it should denoise these images in order to improve system detection performance. This paper uses the acquired power equipment images and adds noise intensity of 10, 15, 20, 25, and 30, respectively. Then, the Block-Matching and 3D Filtering (BM3D) method is used to denoise these images. BM3D includes three steps such as block combination, collaborative filtering, and integration, which has strong denoising ability. The experimental results show that the proposed method outperforms other methods in terms of denoising visual effects and evaluation indicators. Especially in terms of preserving details and textures of the denoised image, there is a significant advantage in suppressing strong noise. In summary, the proposed method can achieve encouraging denoising results, which is an effective denoising method for power equipment images. [ABSTRACT FROM AUTHOR]

The gentle yet cost-effective drying of sensitive products in the food and pharmaceutical industries is becoming increasingly important. To maintain sensitive ingredients, color, structure, and viability of micro-organisms, often freeze-drying is the only possible way to preserve the product. As many products come in as bulk material, they are dried on heated shelves resulting in poor heat and mass transport through the bed. Resulting in a very time and cost intensive process. Therefore, efforts are being made to improve the mass and heat transport of the process. The outer mass transport through the bulk can be improved by continuous mixing of the pellets, facilitating the removal of water vapor from the condenser. In addition, the issue of limited heat transport can be addressed by using volumetric energy input from microwaves. This process is called dynamic microwave freeze-drying. As dynamic microwave freeze-drying is a combined drying and mixing process, with particle properties continuously changing during drying, it is necessary to gain a more detailed insight into the process. For this purpose, a drier is designed that is capable of in situ neutron imaging, a method sensitive to a material's hydrogen content. This paper presents the design of a pilot-scale microwave freeze dryer for in situ neutron imaging and shows the first images taken during the dynamic microwave freeze-drying of bulk particles at the Center for Energy Research, Budapest Neutron Center in Budapest, Hungary. [ABSTRACT FROM AUTHOR]

In this paper, an improved CKF (Cubature Kalman Filter) target tracking method is adopted to solve the tracking and pointing problem in the field of the Active Denial System. The math model of the system is built and the precision requirement is analyzed. The improved CKF method is input as the feedforward compensation for system control to improve the system tracking performance. In the process of the iterative CKF algorithm, nonlinear means are used. The method makes full use of measurement information and estimates the target velocity acceleration model parameters through the neural network, which is used as the input of the CKF to modify the process parameters of CKF and improve the state estimation accuracy. At the same time, the limited lower bound method is used to ensure that the gain reaches the lower bound bottom line of the precision demand, so that it does not tend to zero with time, so as to avoid affecting its rapid response ability during maneuvering and so that the prediction error is also controlled within the range of the precision demand. The simulation and experimental results show the superiority of the method and make the system fully meet the design requirements. [ABSTRACT FROM AUTHOR]

This paper presents the development and application of high-fidelity neutronic models of the SPARC tokamak for the design of neutron flux monitors (NFM) for application during plasma operations. NFMs measure the neutron flux in the tokamak hall, which is related to fusion power via calibration. We have explored Boron-10 gamma-compensated ionization chambers (ICs) and parallel-plate Uranium-238 fission chambers (FCs). We plan for all NFMs to be located by the wall in the tokamak hall and directly exposed to neutrons streaming through a shielded opening in a midplane port. Our simulations primarily use a constructive solid geometry-based OpenMC model based on the true SPARC geometry. The OpenMC model is benchmarked against a detailed CAD-based MCNP6 model. The B10 ICs are equipped with high-density polyethylene (HDPE) sleeves, borated HDPE housings, and borated aluminum covers to shield out scattered neutrons, optimize detector response levels, and make calibration robust against changes in the tokamak hall. The B10 neutron absorption branching ratio may cause the detectors' responses to be non-linear to neutron flux >200 keV. However, our simulations unveil that, in the SPARC environment and with the proposed housings and sleeves, >99% of the detector responses are induced by <100 keV neutrons. U238's insensitivity to slow neutrons makes this FC a promising candidate for direct fusion neutron measurements. Along with a borated HDPE sleeve, about 60% of the FCs' responses are induced by direct neutrons. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive study of neutron calibration methodologies, specifically highlighting the capabilities for n–γ discrimination in diamond and EJ-309, and stilbene scintillation detectors. The calibration process detailed in this study includes pulse height analysis and pulse shape discrimination, relying on the analysis of charge deposition resulting from both γ and neutron interactions. Utilizing 60Co and 252Cf radiation sources, the energy spectra of these sources are obtained. The characterized detectors were used in ST40 experiments and allowed acquiring neutron signal during a plasma shot with good agreement among diamond and scintillation detectors. Then, the diamond detector was cross-calibrated against indium activation foils placed at the same location in proximity to the ST40 during plasma shots: both detectors measured a neutron flux of ≈106 cm−2 s−1 at ≈1 m distance from the tokamak center, and the discrepancy between the diamond detector and the activation foils is ≈25%. [ABSTRACT FROM AUTHOR]

A novel Imaging Neutral Particle Analyzer (INPA) was newly installed in early 2024 to enhance the understanding of fast ion confinement on Large Helical Devices (LHDs). This diagnostic system, based on a magnetic spectrometer using a scintillator, provides energy-resolved radial profiles of confined fast ions by measuring charge-exchanged fast neutrals escaping from the plasma. The system utilizes a 100 nm thick carbon foil to ionize the fast neutrals, subsequently deflecting the ions toward a scintillator via the existing local magnetic field. The fast ion energy and sightline determine the position of the scintillation, while the light intensity depends on the flux of the fast ions. The INPA features two apertures, facilitating effective measurements in both clockwise and counterclockwise magnetic field directions in the LHD. This INPA was designed as a passive measurement system that measures fast ions charge exchange with background neutrals, focusing on perpendicular beam ions from 5 to 100 keV with an energy resolution of about 5.75 keV. This paper describes the details of the design, installation, and the initial results of the INPA on the LHD. This work will contribute significantly to a deeper understanding of fast ion transport due to magnetohydrodynamic instabilities. [ABSTRACT FROM AUTHOR]

We propose a scalable system of compact, superconducting neutron monitors, which can be embedded in any existing cryogenic infrastructure of a fusion system. The pixel-based nature of the detectors allows them to be placed at intervals following the circumference of a cooled zone, e.g., a field coil, thus allowing for a tomographic measurement of the neutron flux surrounding the plasma. An early stage prototype of the superconducting bolometer is described, and the key results of a previous feasibility study of this prototype performed with cold neutrons are summarized. The bolometer can be adapted for use with fast neutrons by altering the composition and geometry of the neutron-to-heat conversion layer. This paper describes the initial feasibility considerations for implementation in a superconducting tokamak. The sensor is based on a high-temperature superconductor, making it possible to select the operation temperature in the range 1–90 K. Neutron flux numbers were found using the ITER MCNP reference model, and these were embedded in a TOPAS model to find the expected signal measured by the bolometer at the position of a toroidal field coil. The results at the coil position indicate suitable operation levels in terms of the magnitude of the measured signal, with a measurable signal of several ohm, which is much smaller than the saturation energy of the detector. Radiation hardness is estimated and found to be on the order of at least 40 years for the relevant radiation levels. The upcoming investigation activities of the project are described for both radiation testing and analytical modeling. [ABSTRACT FROM AUTHOR]

This paper presents the development of an all-in-one probe to simultaneously measure all components of the generalized Ohm's law in reversed-field pinch plasmas and tokamaks. The polyhedral configuration of the Mach probe is achieved through the specific arrangement, angle, and depth of the collimator channel apertures drilled into the surface of a hollow boron nitride cylinder encasing it. This probe includes a central Mach probe to assess the ion velocity field in three dimensions. Initial tests at the RELAX and Madison Symmetric Torus machines have confirmed the probe's effectiveness, revealing an octahedron form similar to a tetrahedron. The probe seems to function correctly and is expected to facilitate the empirical validation of two-fluid equilibria at the periphery of toroidal plasmas. [ABSTRACT FROM AUTHOR]

Magnetically confined plasma experiments generate a wealth of spectroscopic data. The first step toward extracting physical parameters is to fit a spectral model to the often complex spectra. The CXSFIT (Charge eXchange Spectroscopy FITting) spectral fitting code was originally developed for fitting charge exchange spectra on JET from the late 1980s onward and has been further developed over decades to keep up with the needs of the users. The primary use is to efficiently fit a large number of spectra with many constrained Gaussian spectral lines of which the physical parameters can be coupled in a user-friendly manner. More recent additions to the code include time-dependent couplings between parameters, flexible background subtraction, and a non-linear coupling scheme between fit parameters. The latter was a pre-requisite for implementing Zeeman and motional Stark effect multiplets in the library of spectral features. The ability to save and replay "fit recipes," even when multiple iterations are required, has ensured the traceability of the results and is one of the keys to the longevity and success of the code. The code is also in use on other tokamaks (AUG, ST-40) and to fit data from other spectroscopic diagnostics on JET. In this paper, we document the current capabilities and philosophy behind the structure of the code, including some of the algorithms used to calculate spectral features numerically efficiently. We also provide an outline of how CXSFIT could be transferred into a framework that would be able to meet the spectral fitting requirements of future devices, such as ITER. [ABSTRACT FROM AUTHOR]

Following successful campaigns on the compact high field spherical tokamak ST40, resistive gold foil bolometers have now been installed to measure the radiated power profile. Positioned on the midplane, two bolometer cameras offer perspectives of the horizontal and vertical planes, while the third camera, situated above the midplane, provides a vertical view of the top divertor plates, including the X-point and the strike points. These cameras use a commercial off-the-shelf data acquisition platform with modules specifically designed for bolometers in a Wheatstone bridge configuration, providing both phase sensitive detection and in situ calibration. This paper presents an overview of the design and functionality of all three cameras and the commissioning of the horizontal plane camera. The commissioning of the horizontal camera shows data from a range of plasma pulses, presenting a positive correlation between the relative profiles measured from the bolometer camera and an absolute extreme ultraviolet diode camera viewing along similar lines of sight. [ABSTRACT FROM AUTHOR]

The Thermal Helium Beam (THB) is a diagnostic for simultaneously measuring the electron temperature and density profiles of the plasma edge and scrape off layer (SOL). It exploits the line ratio technique of selected He line intensities, emitted by He gas puffed inside the plasma, to locally estimate the plasma properties through a dedicated collisional radiative model (CRM). Standard THB diagnostics used in nuclear fusion devices measure three HeI emission lines: 667.8, 706.5, and 728.1 nm. For the RFP experiment RFX-mod2, a new THB is designed and tested for the first time at the TCV tokamak. It acquires an additional emission line at 501.6 nm, which is exploited to estimate the radiation re-absorption, which is not negligible in regions of large neutral He densities (leading to high re-absorption) and simultaneously low electron density and temperature (lack of other excitation channels). It affects the measurements most strongly at the far SOL, while the significance of re-absorption decreases as it approaches the separatrix. In this paper, plasma density and temperature profiles of the plasma edge at the outboard midplane of TCV, measured with this newly designed THB, are presented. For the first time, the effect of radiation re-absorption on the estimation of electron temperature and density profiles is experimentally measured in a tokamak using the 501 nm line emission intensity. Different CRMs are compared with and without radiation re-absorption, showing good agreement when re-absorption is included and demonstrating how it plays an important role in the far SOL, as expected. [ABSTRACT FROM AUTHOR]

This paper presents an overview of recent hardware extensions and data analysis developments to the Wendelstein 7-X visible core spectroscopy systems. These include upgrades to prepare the in-vessel components for long-pulse operation, nine additional spectrometers, a new line of sight array for passive spectroscopy, and a coherence imaging charge exchange spectroscopy diagnostic. Progress in data analysis includes ion temperatures and densities from multiple impurity species, a statistical comparison with x-ray crystal spectrometer measurements, neutral density measurements from thermal passive Balmer-alpha emission, and a Bayesian analysis of active hydrogen emission, which is able to infer electron density and main ion temperature profiles. [ABSTRACT FROM AUTHOR]

The Space Plasma Environment Research Facility (SPERF) was built in Harbin to study the three-dimensional magnetic reconnection and wave–particle interactions relevant to space physics in laboratory settings. A 2.45 GHz Electron Cyclotron Resonance (ECR) plasma source is adopted in the device to simulate the Earth's magnetosphere and achieve the scientific goals. In this paper, the design of the ECR plasma source is presented. The structures of the microwave source, the microwave transfer system, and the antenna are introduced. Additionally, the resonant surfaces are computed to predict the locations of microwave absorption. The absorption mechanisms of the microwave in the SPERF are also discussed. The discharge experiment demonstrates the utility of the ECR source in simulating the Earth's magnetosphere. The successful operation of the source indicates that the ECR discharge is a powerful tool for creating a plasma environment in a large plasma experimental device. [ABSTRACT FROM AUTHOR]

This paper describes the application of a machine learning (ML) algorithm using a convolution neural network, first developed in Boyer et al. ["Classification and prediction of detachment in DIII-D using neural networks trained on C III imaging," Nucl. Fusion (submitted) (2024)], to detect divertor detachment in DIII-D. Detachment detection is based on images from tangentially viewing upper and lower filtered divertor cameras that measure CIII emission at 465 nm. Separate ML models are developed for lower single null and upper single null configurations with mostly closed divertor shapes. Due to the viewing angle and divertor geometry, camera images of the upper divertor show a stark contrast in CIII emission between attached and detached conditions and the model identified detachment with 100% accuracy in the test dataset. For the lower divertor images, the contrast between attached and detached conditions is lower and the model identifies detachment with 96% accuracy. This ML model will be applied to the image data after each shot to provide a rapid assessment of divertor detachment to aid operation of DIII-D with the potential extension to other devices in the future. [ABSTRACT FROM AUTHOR]

Electrospray thrusters exhibit diverse operational modes based on the nature of ejected particles. Time-of-flight mass spectrometry is frequently employed to analyze the composition of the plume. This study introduces a novel converter-based bipolar high-voltage pulse generator aimed at producing synchronized bipolar high-voltage pulses with controllable voltage levels and frequencies, specifically tailored for the study of electrospray thrusters. The proposed topology generates bipolar high-voltage rails from a low-voltage power source through the forward–flyback with Cockcroft–Walton voltage multiplier topology. Subsequently, fast high-voltage MOSFETs are employed to generate high-voltage pulses. This paper outlines the operational principles and design methodologies of the pulse generator. Experimental verification corroborates its operational principles and functionalities, revealing that the pulse rise and fall times consistently remain below 30 ns, while the voltage can be tuned within the range of 300–1000 V. An electrospray thruster was employed to conduct a thorough and practical validation of the high-voltage pulse generator. This included generating time-of-flight curves and mass spectra of the plume, resulting in precise differentiation of all particles present. [ABSTRACT FROM AUTHOR]

The advancement of the aviation sector has made the temperature measurement technology for aero-engine turbine blades essential for maintaining the engine's safe and steady performance. The non-contact temperature measurement technology is a trending research focus in turbine blade temperature measurement due to its benefits of not requiring direct touch with the object being measured and its suitability for high-temperature and high-speed conditions. This paper provides a concise overview of various key non-contact temperature measurement methods for aero-engines, such as fluorescence temperature measurement, fiber-optic temperature measurement, and radiation temperature measurement. It discusses the temperature measurement principle, technical characteristics, and the current research status both domestically and internationally. Based on this, this Review further discusses the main challenges faced by the non-contact temperature measurement technology and the development trend of the future. [ABSTRACT FROM AUTHOR]

The active magnetic compensation coil is of great significance for extensive applications, such as fundamental physics, aerospace engineering, national defense industry, and biological science. The magnetic shielding demand is increasing over past few decades, and better performances of the coil are required. To maintain normal operating conditions for some sensors, active magnetic compensation coils are often used to implement near-zero field environments. Many coil design methods have been developed to design the active compensation coil for different fields. It is opportune to review the development and challenges associated with active magnetic compensation coils. Active magnetic compensation coils are reviewed in this paper in terms of design methods, technology, and applications. Furthermore, the operational principle and typical structures of the coil are elucidated. The developments of the forward design method, inverse design method, and optimization algorithm are presented. Principles of various design methods and their respective advantages and disadvantages are described in detail. Finally, critical challenges in the active magnetic compensation coil techniques and potential research directions have been highlighted. [ABSTRACT FROM AUTHOR]

This paper introduces a method for measuring wing motion, deformation, and inertial forces in bio-inspired aircraft research using a camera motion capture system. The method involves placing markers on the wing surface and fitting rigid planes to determine the wing's spatial axis. This allows for describing the wing's rigid motion and obtaining deformation characteristics, such as deflection, twist angle, and gap distance of the forewing and hindwing. An image-based method is proposed for determining wing mass distribution, mass blocks, and mass points for inertial force measurement. The study addresses wing motion, deformation, and inertial force measurement in a real butterfly-like flapping wing vehicle and demonstrates the effectiveness of the approach. The results reveal that inertial forces play a negligible role in the generation of lift peaks and contribute minimal lift during the entire flapping cycle. Furthermore, a transitional phase between downstroke and upstroke is found in flexible wing motion, which has high lift production. This measurement approach offers a rapid and effective solution to experimental challenges in bio-inspired aircraft design and optimization. [ABSTRACT FROM AUTHOR]

Given the lack of sufficient historical data for aircraft landing gear retractor systems, a model-based fault diagnosis approach is needed to overcome this data deficiency. Meanwhile, inherent uncertainties are inevitable in engineering practice, and it is a great challenge to construct a model that accurately reflects the complexity of the actual system under uncertain conditions. Due to the urgent need for reliable model-based diagnostic methods and the need to cope with inherent uncertainties, this paper proposes an improved fault diagnostic method aimed at increasing the diagnostic efficiency of the landing gear retractor system, a critical component in aircraft take-off and landing operations. Due to a lack of historical data, the model-based fault diagnosis method can solve the problem of lack of data. The proposed uncertainty method addresses the challenge of multiple sources of uncertainty by using subsystems to reduce complexity. Fault diagnosis is achieved by comparing residuals with thresholds derived from a diagnostic bond graph (DBG) model. To address the problem of limited fault data, we modeled and simulated the landing gear retractor system using AMESim®. In addition, the linear fractional transform (LFT) approach has been used to resolve parametric uncertainties, but is unable to resolve system structural uncertainties. Therefore, we also analyzed the comparative fault diagnosis results derived from the linear fractional transformation-DBG (LFT-DBG) and the subsystem-DBG approaches. The experimental results support the effectiveness of the subsystem approach in improving fault diagnosis accuracy and reliability, highlighting its potential as a viable diagnostic strategy in aerospace engineering applications. [ABSTRACT FROM AUTHOR]

The thickness of thin films is a key parameter to understand their thinning dynamics and stability. Thickness measurements are commonly performed using interferometry. White light illumination allows us to measure the absolute thickness, but is limited to small thicknesses (< 2 μ m) or is restricted to a point with a spectrometer. Monochromatic light gives access to a broader range of thicknesses but solely in a relative manner unless a reference thickness is known. These methods are extensively used to quantify the thickness profiles of flat soap films. In contrast, they are applied to curved interfaces (bubbles) only in a few specific cases, mainly due to the complexity arising from the curvature as the optical path depends on the position. In this paper, we elucidate the influence of the curvature and show that it can be used to measure the entire and absolute thickness profiles using monochromatic light. We demonstrate the validity of the method on soap bubbles, antibubbles, and catenoid soap films. This cost-effective technique is adapted to quantitatively study the thin film dynamics in these geometries. [ABSTRACT FROM AUTHOR]

The focus of this paper is on the main challenges in brain–computer interface transfer learning: how to address data characteristic length and the source domain sample selection problems caused by individual differences. To overcome the negative migration that results from feature length, we propose a migration algorithm based on mutual information transfer (MIT), which selects effective features by calculating the entropy value of the probability distribution and conditional distribution, thereby reducing negative migration and improving learning efficiency. Source domain participants who differ too much from the target domain distribution can affect the overall classification performance. On the basis of MIT, we propose the Pearson correlation coefficient source domain automatic selection algorithm (PDAS algorithm). The PDAS algorithm can automatically select the appropriate source domain participants according to the target domain distribution, which reduces the negative migration of participant data among the source domain participants, improves experimental accuracy, and greatly reduces training time. The two proposed algorithms were tested offline and online on two public datasets, and the results were compared with those from existing advanced algorithms. The experimental results showed that the MIT algorithm and the MIT + PDAS algorithm had obvious advantages. [ABSTRACT FROM AUTHOR]

Temperature is a crucial factor influencing the accuracy of the hydrostatic leveling system (HLS), necessitating a temperature compensation test for HLS. This paper investigates HLS temperature compensation through theoretical correction and experimental verification. The influence of temperature on the accuracy of hydrostatic level products is determined through temperature tests on 34 hydrostatic level products. The optimal temperature compensation formula is derived using the non-linear curve fitting method. The HLS is enhanced with a temperature compensation algorithm and temperature sensor, resulting in a new, high-precision, and high-stability hydrostatic leveling product with temperature compensation. Experimental findings reveal that the stability of the improved hydrostatic leveling product exceeds 30% compared to products on the market and surpasses 70% compared to the original products. [ABSTRACT FROM AUTHOR]