Review of Scientific Instruments最新文献

Carbon fiber reinforced polymers (CFRPs) are widely used in fields such as aviation and aerospace. However, subtle defects can significantly impact the material's service life, making defect detection a critical priority. In this paper, delamination defects in CFRP are detected using line laser infrared thermography, and a defect characterization algorithm that combines differential thermography with a frequency-domain filter is proposed. This approach effectively eliminates the trailing phenomenon caused by line laser scanning and produces defect feature images with a higher signal-to-noise ratio. The size of the processed defects is then measured using pixel deviation values combined with K-means edge detection. The results show that the measured dimensions of defects are larger than the actual dimensions at the initial stage of cooling after excitation and smaller than the actual dimensions at the end of the cooling phase. The maximum measurement error for defect size was 2.74 mm2 throughout the measurement interval. In addition, defect depth evaluation was achieved by fitting the curve of defect depth against the peak value in the frequency domain, with the resultant R-square value were all higher than 0.9877. This confirms the validity and accuracy of the methodology used in this study.

X-ray spectroscopies are uniquely poised to describe the geometric and electronic structure of metalloenzyme active sites under a wide variety of sample conditions. UV/Vis (ultraviolet/visible) spectroscopy is a similarly well-established technique that can identify and quantify catalytic intermediates. The work described here reports the first simultaneous collection of full in situ UV/Vis and high-energy resolution fluorescence detected x-ray absorption spectra. Implementation of a fiber optic UV/Vis spectrometer and parabolic mirror setup inside the dual array valence emission spectrometer allowing for simultaneous measurement of microfluidic flow and mixing samples at the Photon-In Photon-Out X-ray Spectroscopy beamline is described, and initial results on ferricyanide and a dilute iron protein are presented. In conjunction with advanced microfluidic mixing techniques, this will allow for the measurement and quantification of highly reactive catalytic intermediates at reaction-relevant temperatures on the millisecond timescale while avoiding potential complications induced by freeze quenching samples.

This paper presents a flat-type piezoelectric motor utilizing in-plane vibration modes. Two piezoelectric ceramic plates in combination with a brass metal sheet were used to construct the stator. The superposition of two second order in-plane vibration modes can generate a traveling-wave inside the stator. The greatest advantage of the proposed motor lies in its sheet structure configuration, which significantly reduces the overall size of piezoelectric motors exploiting in-plane vibrations, particularly in terms of thickness. Meanwhile, the stator also demonstrates greater vibration displacements when compared to higher-order operating modes. Through discussing the impact of stator structure parameters on the vibration deflection angle θ, the excitation ways of operating modes were investigated. Subsequently, the finite element method was utilized to explore both the static and dynamic vibration properties of the stator. Simulation results suggest that at a steady state, stator driving points achieve vibrations at the micro-meter level, satisfying actual application requirements. Finally, a prototype motor was fabricated. Driven by two-phase alternating voltage with a frequency of 69.4 kHz, the no-load speed and stall torque of the prototype motor are 52 rpm and 3.2 mN m, respectively.

Aiming at the effects caused by stress and deformation on Micro-Electro-Mechanical System (MEMS) sensors, the stress distribution in the radiation area of the MEMS infrared light source is investigated, and by simulating and optimizing the thickness of the composite support film of the chip structure in COMSOL, a film layer thickness matching with lower stress and deformation for the MEMS infrared light source is derived. The utilization of the particle swarm algorithm and backpropagation neural network model allowed for the optimization of simulation data, enabling regression prediction over a broader range of thicknesses and providing a more precise depiction of the stress distribution trend. In addition, the specifications of the MEMS device help us to analyze the design of the support film thickness in the processing of the residual stress within the controllable range. To ensure the long-term stability and functionality of MEMS infrared light source chips in harsh environments, a comprehensive set of packaging schemes has been devised. Through simulations, it has been demonstrated that these packaging schemes effectively enhance the thermal efficiency of the light source while mitigating thermal stress and deformation that may arise during its operation. Consequently, this packaged configuration proves to be more advantageous for the sensor's normal operation under challenging conditions such as rain and temperature fluctuations, as compared to utilizing a bare chip. Finally, the manufacturing flow and layout design for the MEMS infrared light source chip are provided to guide the process of chip fabrication.

Radiation from wireless communication devices inside intelligent connected vehicles has been an expeditious growth of concern regarding possible adverse effects on human health. Due to the significant differences in the working scenarios compared to traditional mobile products, the traditional measuring systems of specific absorption rate (SAR) are not applicable to in-vehicle scenarios. This paper has developed a SAR measurement system and a SAR measurement method, which are suitable for in-vehicle scenarios. Since the measurement hardware and methods are significantly different from traditional systems, it is necessary to assess the measurement uncertainty for the new measurement system. Due to the significant influence of tissue fluid on the SAR, this paper focuses on analyzing the relationship between tissue fluid and SAR. Based on the validated electromagnetic simulation model, linear and quadratic fitting models reflecting the relationship between tissue fluid properties and SAR are established. Then, the uncertainty propagation was realized using both the Guide to the Expression of Uncertainty in Measurement and MCM (Monte Carlo Method) through these models. The results of uncertainty analysis were analyzed in combination with the fitting error. The results of the analyses show that the fitting error of the quadratic measurement model is smaller because there is no simple linear relationship between the tissue fluid properties and the SAR values, and thus, it is more reasonable to use the MCM method to evaluate the uncertainty.

This work describes the design and implementation of optics for EXCLAIM, the EXperiment for Cryogenic Large-Aperture Intensity Mapping. EXCLAIM is a balloon-borne telescope that will measure integrated line emission from carbon monoxide at redshifts z < 1 and ionized carbon ([CII]) at redshifts z = 2.5 - 3.5 to probe star formation over cosmic time in cross-correlation with galaxy redshift surveys. The EXCLAIM instrument is designed to observe at frequencies of 420-540 GHz using six microfabricated silicon integrated spectrometers with spectral resolving power R = 512 coupled to kinetic inductance detectors. A completely cryogenic telescope cooled to a temperature below 5 K provides low-background observations between narrow atmospheric lines in the stratosphere. Off-axis reflective optics use a 90-cm primary mirror to provide 4.2' full-width at half-maximum resolution at the center of the EXCLAIM band over a field of view of 22.5'. Illumination of the 1.7 K cold stop combined with blackened baffling at multiple places in the optical system ensures low (<-40 dB) edge illumination of the primary to minimize spill onto warmer elements at the top of the dewar.

Capacitive sensors are commonly used in superconducting gravimeters due to their high resolution and low drift. This study developed a cryogenic front-end circuit for superconducting gravimeters to reduce the negative effects of parasitic capacitance on capacitive sensors. The front-end circuit comprises a noiseless superconducting transformer and a low-noise cryogenic preamplifier, both of which are positioned adjacent to the capacitive sensor probe. Compared with the front-end circuit operating at 300 K, the transfer coefficient of the front-end circuit increases from 131 to 1070 V/m, and the equivalent displacement noise reduces from 1.4 × 10-10 to 5.0 × 10-11 m/Hz1/2 within a frequency band from 10-3 to 1 Hz. The temperature coefficient of the cryogenic preamplifier is 0.3%/K, and the superconducting transformer's matching factor has adjusted as low as (2.4 ± 0.2) × 10-4. The cryogenic front-end circuit was finally applied to a superconducting gravimeter. The observed gravity data satisfactorily fit the theoretical tidal model, implying good long-term stability for the developed front-end circuit.

Diagnostic tools for understanding the edge plasma behavior in fusion devices are essential. The main focus of the present work is to present the infra-red (IR) diagnostics installed on Tokamak Energy's spherical tokamak (ST40) and the IR thermographic inversion tool, Functional Analysis of Heat Flux (FAHF). FAHF is designed for multi-2D thermographic inversions within the divertor tiles using the finite difference method and an explicit time stepping scheme. ST40's re-entrant endoscope allows the acquisition of IR data with the highest available effective spatial resolution. With these data, FAHF calculates the plasma perpendicular heat flux density on the divertor-a crucial quantity for edge plasma analysis. Although FAHF demonstrates significant sensitivity to user-selected settings, precise heat flux values are recoverable by ensuring a sufficiently high resolution. Implications for the optimal resolution of both the code and the IR diagnostic system are discussed. FAHF's simplifications are shown to give an error within 10% with respect to COMSOL Multiphysics® simulations. Finally, by means of comparison with Langmuir probe heat flux data, the accuracy of the FAHF heat fluxes is estimated to be satisfactory. As such, FAHF is proven to be a precise and accurate tool for IR thermographic inversions in ST40.

The spiral generator, based on the principle of the electric field vector inversion, is capable of delivering repetitive high-voltage nanosecond pulses in the commercial portable pulsed x-ray source and gas switch trigger source. However, the spiral generator suffers from extremely low output efficiency, which significantly affects the compactness and accelerates the insulation film breakdown at electrode foil edges since the high charging voltage is required. A novel output efficiency improvement method for the spiral generator was proposed, implementing the permalloy film inside the passive layer to optimize internal voltage wave propagation processes during the pulser erection. Output characteristics and influential factors of the modified spiral generator are experimentally determined, and the wave propagation processes are analyzed. The significant output efficiency improvement (approximately from 10% to 30% combined with ferrite cores at the center) is seminal for the portable x-ray source and gas switch trigger source of compactness and long operation lifetime.

The Particle Time of Flight (PTOF) diagnostic is a chemical vapor deposition diamond-based detector and is the only diagnostic for measuring nuclear bang times of low yield (<1013) shots on the National Ignition Facility. Recently, a comprehensive study of detector impulse responses revealed certain detectors with very fast and consistent impulse responses with a rise time of <50 ps, enabling low yield burn history measurements. At the current standoff of 50 cm, this measurement is possible with fast 14 MeV neutrons from deuterium-tritium (DT) fusion plasmas. PTOF-inferred DT burn width numbers compare well with widths inferred from the gamma reaction history diagnostic on mid-yield (1013-1015) shots, where both systems are capable of making this measurement. These new capabilities could be extended to 2.5 MeV deuterium-deuterium neutrons from D plasmas and to even lower yield by reducing the detector standoff distance to 10 cm; a design for this is also presented.