Strong Magnetic Environment Research Articles

An MRI Compatible Data Acquisition Device for Rat Brain Recording Inside 16.4T Magnet.

Concurrent recording of neural activities and functional magnetic resonance imaging (fMRI) data is useful for studying the neurovascular coupling relationship. This article presents a low-noise, frequency-shaping based neural recorder chip that is insensitive to radio frequency (RF) pulses and gradient echo artifacts under strong magnetic environment. To support simultaneous recording of local field potentials (LFPs), extracellular spikes, and fMRI data, a magnetic resonance imaging (MRI) compatible data acquisition (DAQ) device based on the designed recorder chip is developed with multiple circuit optimization techniques. Bench-top measurement shows that the designed DAQ device has 4.5 μV input-referred noise integrated from 300 Hz to 3000 Hz, which is not greatly affected by electromagnetic interference (EMI) at ultrahigh magnetic field (UMF, 16.4 T). In animal experiments, the designed DAQ device has been demonstrated to be capable of acquiring both the LFPs and extracellular spikes from a rat's brain before, during, and after MRI scanning. Besides, no obvious artifacts are seen from the designed DAQ device at multiple typical MRI scanning modes, and the system recovery time after gradient artifacts is reduced from more than 25 ms to less than 5 ms. The proposed DAQ device architecture based on the frequency-shaping neural recorder chip is MRI compatible and can provide highly competitive performance for concurrent recording of neural activities and fMRI data.

Simulation and Generation of the In-born Strong Magnetic Environment During Railgun Launch

The in-born strong magnetic environment during the launch process of the railgun is a potential risk for ammunition applications. Currently, there are no mature means to simulate the magnetic field environment to provide a platform for the electromagnetic safety test of ammunition. Given this problem, a strong magnetic environment generation system was designed. By establishing the theoretical model of the magnetic field generated, the difficulty of generating specific waveforms of strong magnetic fields was broken through. Besides, the strong magnetic field generator’s multi-physical field response was analyzed by using the FEM method, and its stability of structure and temperature was evaluated. Finally, the strong magnetic environment generation experiment was conducted, where the in-born magnetic field during the launch process of the railgun was generated successfully. As a result, the strong magnetic environment generation system can generate the expected strong magnetic fields. The magnetic flux density is 10 T, and the pulse width is 6.1 ms.

Analysis of strong magnetic environment interference of inspection rotary wing UAV

Analysis of strong magnetic environment interference of inspection rotary wing UAV

Structural design and analysis of pneumatic prostate seed implantation robot applied in magnetic resonance imaging environment.

The method of MRI (Magnetic Resonance Imaging) image-guided robot for prostate seed implantation has developed rapidly in recent years. During the operation, although the puncture effect guided by MRI is very good, it is difficult for conventional robots driven by motors to work normally in this environment, which reduces the accuracy of seed implantation and affects the treatment effect. First, this paper designs a pneumatic prostate seed implantation robot that is compatible with MRI; the robot is composed of an execution module and an adjustment module, and can complete the positioning and adjustment of the robot's needle entry point, the pose adjustment of the puncture needle and the completion of seed implantation in the MRI space; meanwhile, the statics simulation analysis of its key components is carried out. Then, the kinematics analysis was carried out according to the designed robot structure, and the relationship between the posture of the needle tip and the change of the pneumatic cylinder was obtained; meanwhile, using MATLAB 2020 software, combined with the method of Monte Carlo random number sampling, the simulation analysis of the workspace was carried out. Finally, an experimental prototype is constructed to conduct puncture accuracy experiments, workspace experiments and performance comparison tests in MRI environment. The statics simulation results verify that the key components of the robot designed in this paper can meet the strength requirements of the robot. The simulation results of the workspace meet the requirements of space surgery for prostate seed implantation under the guidance of MRI environment. The puncture accuracy experimented to verify that increasing the puncture speed can improve the seed implantation accuracy, and the puncture deviation of the robot is less than the average deviation of the doctor's actual operation by 6.5mm. The working space experiment shows that the pitch range is -23.3°~27.8°, the movement range in the X direction is 0~210mm, the movement range in the Y direction is 0~101mm, and the lifting range in the Z direction is 0~81mm, which meets the workspace requirements under MRI. The performance comparison test results in the MRI environment show that the robot is well compatible with MRI instruments. The pneumatic prostate seed implantation robot designed in this paper has a reasonable structure and stable dynamic performance output, and can perform precise surgical operations in the MRI strong magnetic environment. The research work in this paper provides a design reference for the related research on the positioning accuracy of minimally invasive puncture surgery guided by MRI images.

Magnetohydrodynamic Modeling of the Solar Corona with an Effective Implicit Strategy

Abstract In this paper, we design an effective and robust model to solve the 3D single-fluid solar wind plasma magnetohydrodynamics (MHD) problem of low plasma β. This MHD model is formulated on a six-component composite grid system free of polar singularities. The computational domain ranges from the solar surface to the super-Alfvénic region. As common to all MHD codes, this code must handle the physical positivity-preserving property, time-step enlargement, and magnetic field divergence-free maintenance. To maintain physical positivity, we employ a positivity-preserving Harten–Lax–van Leer Riemann solver and take a self-adjusting and positivity-preserving method for variable reconstruction. To loosen the time-step limitation, we resort to the implicit lower–upper symmetric Gauss–Seidel method and keep the sparse Jacobian matrix diagonally dominant to improve the convergence rate. To deal with the constant theme of a magnetic field that is divergence-free, we adopt a globally solenoidality-preserving approach. After establishing the solar wind model, we use its explicit and implicit versions to numerically investigate the steady-state solar wind in Carrington rotations (CRs) 2172 and 2210. Both simulations achieve almost the same results for the two CRs and are basically consistent with solar coronal observations and mapped in situ interplanetary measurements. Furthermore, we use the implicit method to conduct an ad hoc simulation by multiplying the initial magnetic field of CR 2172 with a factor of 6. The simulation shows that the model can robustly and efficiently deal with the problem of a plasma β as low as about 5 × 10−7. Therefore, the established implicit solar wind MHD model is very promising for simulating complex and strong magnetic environments.

Rolling Bearing Performance Degradation Prediction Based on FBG Signal

Aiming at the problems of low accuracy and low robustness in current prediction methods of rolling bearing performance degradation, this paper propose a performance degradation prediction method based on empirical mode decomposition (EMD) and support vector data description (SVDD). Unlike the features extracted by wavelet analysis, the EMD algorithm has better adaptive capability and can better avoid the interference of high frequency noise. fiber Bragg grating (FBG) are used to extract the bearing vibration signal. The use of FBG sensors can better avoid the interference of electromagnetic noise, so that the vibration signal can be accurately extracted in the industrial strong magnetic environment. The Empirical Mode Decomposition is used to decompose data and extract effective intrinsic mode function (IMF) components. Six features of Intrinsic Mode Function components are extracted to form feature vectors and used as training data. Because the IMF component obtained by EMD decomposition has removed most of the noise signals, the signal features are more significant and thus effectively improve the accuracy of subsequent recognition. This paper use Support Vector Data Description for performance degradation prediction and evaluates the degradation performance of the rolling bearing by calculating the degradation value. Experiments show the proposed method can detect the performance degradation process of the rolling bearing and effectively predict the remaining service life. Due to the high recognition accuracy, the proposed method is able to identify the current state of ball bearings and predict their remaining service life.

Two-dimensional numerical study of effect of magnetic field on laser-driven Kelvin-Helmholtz instability

Kelvin-Helmholtz instability is the basic physical process of fluids and plasmas. It is widely present in natural, astrophysical, and high energy density physical phenomena. With the construction of strong laser facilities, the research on high energy density physics has gained new impetus. However, in recent years the magnetized Kelvin-Helmholtz instability was rarely studied experimentally. In this work, we propose a new experimental scheme, in which a long-pulsed nanosecond laser beam is generated by a domestic starlight III laser facility. The whole target consists of two parts: the upper part that is the CH modulation layer with lower density, and the lower part that is the Al modulation layer with higher density. The laser beam is injected from one side of the CH modulation layer and generates a CH plasma outflow at the back of the target. During the transmission of the CH plasma outflow, the Al modulation layer is radiated and ionized, which makes the Al modulation layer generate an Al plasma outflow. The interaction between the Al plasma outflow and the CH plasma outflow produces a velocity shear layer, and then Kelvin-Helmholtz instability will gradually form near the Al modulation layer. In this paper, the open-source FLASH simulation program is used to conduct a two-dimensional numerical simulation of the Kelvin-Helmholtz instability generated by the laser-driven modulation target. We use the FLASH code, which is an adaptive mesh refinement program, developed by the Flash Center at the University of Chicago, and is well-known in astrophysics and space geophysics, to create a reference to the magnetohydrodynamic solution in our experiment. At present, this code introduces a complete high-energy-density physical modeling module, which is especially suitable for simulating intense laser ablation experiments. The equation of state and opacity tables of targets are based on the IONMIX4 database. The evolution of Kelvin-Helmholtz vortices, separately, in the Biermann self-generated magnetic field, the external magnetic field, and no magnetic field are investigated and compared with each other. It is found that the self-generated magnetic field hardly changes the morphology of the Kelvin-Helmholtz vortex during the evolution of Kelvin-Helmholtz instability. The external magnetic field parallel to the fluid direction can stabilize the shear flow. The magnetic field mainly stabilizes the long wave disturbance. The study results in this work can provide theoretical guidance for the next step of the Kelvin-Helmholtz experiment under a strong magnetic environment in the high energy density laser facility.

Study on influence of crack on the blade status using FBGs

The status detection for rotating parts is difficult since the sensor is influenced by the rotation in the inflammable, explosive, and strong magnetic environment. Based on the fiber Bragg grating sensing technology, this paper studies the influence of the natural frequency and deformation of a rotor blade affected by the size of crack in the blade. Test results show that the speed of the equipment and blade excited vibration frequency are two main factors or deformation and vibration frequency of the blade. With an increase in the crack depth, the blade deformation is increased while the stimulated natural frequency of the blade is decreased; at a low rotational speed, the deformation is mainly caused by the rotating speed of the blade. On the contrary, the vibration blade itself contributes to the deformation at a high speed. During the process of full speed rotation, the influence of the rotational speed on the blade deformation almost remains the same, and the influence of the natural vibration on blade deformation is increased with an increase in the rotational speed.

L204 - A gravitationally confined dark cloud in a strong magnetic environment

view Abstract Citations (55) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS L204: A Gravitationally Confined Dark Cloud in a Strong Magnetic Environment Heiles, Carl Abstract L204 is a filamentary dark cloud located in the H I expanding shell associated with the North Polar Spur. The magnetic field strength in the surrounding H I has beem measured from Zeeman splitting of the 21 cm line. The average line-of-sight component of magnetic field, B(parallel), in the H I is 4.2 micro-G. Using the observed tendency for B(parallel) and the H I velocity to correlate, it is argued that variations in B(parallel) result primarily from projection effects, that the total field strength in the H I is about 12 micro-G, and that magnetic pressure dominates gas pressure. It is argued that Alfven waves might be responsible for the observed tendency for B(parallel) and the H I line width to be anticorrelated. The field strength in the molecular portion of L204 itself is estimated, and it is argued that the small enhancement found within the dense filament is consistent with theoretical expectation. Magnetic braking should have occurred for the component of rotation perpendicular to the magnetic field. Publication: The Astrophysical Journal Pub Date: January 1988 DOI: 10.1086/165897 Bibcode: 1988ApJ...324..321H Keywords: Astronomical Spectroscopy; Dark Matter; Gravitational Effects; Hydrogen Clouds; Interstellar Magnetic Fields; Nebulae; Centimeter Waves; Radio Sources (Astronomy); Spectral Line Width; Spectrum Analysis; Zeeman Effect; Astrophysics; INTERSTELLAR: MAGNETIC FIELDS; NEBULAE: INDIVIDUAL ALPHANUMERIC: L204 (LYNDS 204); RADIO SOURCES: 21 CM RADIATION; ZEEMAN EFFECT full text sources ADS | data products SIMBAD (1)

New Mesh PMTS for High Magnetic Environments

A new type of Photo-multiplier Tube (PMT) has been developed that can be utilized in the field of high energy physics, especially in strong magnetic environments. The fine mesh configuration of the dynodes provides the PMT with such unique features as an outstanding energy pulse height resolution, a high current amplification ratio and excellent time response characteristics, even in strong magnetic fields. The position of incident light can also be detected. This report sums up the various characteristics and the results of tests.