Review of Scientific Instruments最新文献

A simple method to self-start a Mamyshev oscillator (MO) using an optical beam shutter (OBS) in the cavity is presented. OBS is placed inside the cavity to introduce a strong optical fluctuation by switching its state (open/close). Stable mode-locking operation is achieved in fiber MO by using an OBS without requiring any external mode-locked seed source or pump modulation.

Geomagnetic vector measurement can obtain more geomagnetic information, which is one of the main development directions of geomagnetic measurement. To date, the magnetic flux gate magnetometer is the main tool for geomagnetic vector measurement; however, its drift issue cannot be ignored. To address this issue, we propose a geomagnetic vector measurement method based on bias and compensation fields and then develop a high-stability FHD (total-field F, horizontal component H, and declination D) vector magnetometer based on a proton sensor and a magnetic field generator. In addition, a dedicated experimental platform is constructed to verify the performance of the developed magnetometer in a geomagnetic station. Compared to the flux gate magnetometer, the experimental results indicate that the fourth-order differential noise of the declination D, horizontal component H, and vertical component Z are 1″, 0.27, and 0.15 nT, respectively, which are all lower than those of the flux gate magnetometer. In addition, the horizontal component H and vertical component Z of the flux gate magnetometer indicate more than 30 and 60 nT startup drift, respectively; in contrast, the proposed FHD magnetometer shows an excellent stability during a 16 h observation time.

Vacuum freeze-drying (VFD) technology has gained extensive application across various sectors, particularly in environmental applications, where it is primarily utilized for the fabrication of environmental functional materials and the conservation of environmental organisms. This technology is applicable to soil enhancement, the remediation of aquatic pollutants, energy storage in thermoelectric materials, and the preservation of bacterial cultures. This review synthesizes the most recent advancements in VFD technology within the environmental domain, elaborating on its technical fundamentals, operational procedures, practical applications, and distinctive benefits. Furthermore, the article explores the prospective development trajectory and potential challenges for this technology in the environmental sector, offering scientific guidance for its continued application and insights into its innovative progression.

To address the challenge of quickly tuning the resonance frequency of ultrasonic transducers in real-time after manufacturing, this paper proposes integrating Terfenol-D into the horn of a piezoelectric ultrasonic transducer. In practical applications, the transducer is mechanically excited by a piezoelectric vibrator connected to an alternating current power supply, while the Terfenol-D is surrounded by a coil connected to a direct current power supply. By utilizing the delta-E (ΔE) effect of Terfenol-D, the modulus of the material changes in response to variations in the surrounding magnetic field, enabling real-time online adjustment of the resonance frequency. The resonance frequency and amplification coefficient of the transducer were analyzed using the transfer matrix method. Then, an impedance analyzer was employed to measure changes in the transducer's impedance and resonance frequency under different electric currents. Experimental results demonstrate that the resonance frequency of the transducer increases with increasing electric current. The developed piezoelectric ultrasonic transducer, featuring Terfenol-D embedded in the horn, achieves rapid and real-time resonance frequency adjustment within a specific range. This innovation provides a novel solution for complex ultrasonic application scenarios requiring frequent transducer replacements.

We have designed a new filter pack array to measure angular variations in x-ray spectra during a single shot. The filter pack was composed of repeating identical columns of aluminum and copper filters of varying thicknesses. These columns were located at different positions to measure the spectrum at each corresponding angle. This array was utilized in an experiment to measure the energy evolution of betatron x rays in a laser wakefield accelerator by curving the wakefield with a transverse density gradient, streaking the x rays across the array in front of an x-ray charge-coupled device (CCD) camera. After subtracting the background and "flattening" the image to remove spatial nonuniformities, a critical energy was calculated for each position that produced the best agreement with the measured signal. There was a clear change in critical energy with angle, shedding light on the dynamics of the electrons that traveled through the accelerator. These angles correspond to distinct emission times, covering a timescale of tens of picoseconds. The filter pack was capable of recovering these angular details without the impact of errors introduced by shot-to-shot variability.

A passive exoskeleton is a wearable robotic device that is worn on the exterior of the user's body to provide physical support and facilitate movement. Existing elbow passive exoskeletons have limitations in their assistance capabilities and range of applications. In this paper, we propose a controllable elbow passive exoskeleton (CEPE) to address these limitations. The CEPE features a ratchet-based self-energy storage mechanism (RSSM) and a Candan gravity compensation mechanism (CGCM). The CGCM counteracts gravitational forces, while the RSSM stores and releases motion energy. This paper establishes a mathematical model for the RSSM, outlines design specifications for both the RSSM and CEPE, and analyzes the influence of design parameters on the power assistance performance. Three experiments were conducted to validate the feasibility of CEPE, including static strength testing, power assistance without load, and power assistance with load. Results show that, without loading, the CEPE provides compensation effects on elbow joint torque of 68.8%, 93.8%, and 70.7% at shoulder joint angles of 0°, 30°, and 60°, respectively. With a 5 kg loading, adjusting the shoulder joint angle from 30° to 60° results in an increase in the decrease of the average absolute torque directly acting on the elbow joint, from 86% to 91.2%. The adjustable RSSM enables the CEPE to operate in four different modes, expanding its potential applications.

Tailoring optical and radiative properties has attracted significant attention recently due to its importance in advanced energy systems, nanophotonics, electro-optics, and nanomanufacturing. Metamaterials with micro- and nanostructures exhibit exotic radiative properties with tunability across the spectrum, direction, and polarization. Structures made from anisotropic or nanostructured materials have shown polarization-selective absorption bands in the mid-infrared. Characterizing the optical and radiative properties of such materials is crucial for both fundamental research and the development of practical applications. Mueller matrix ellipsometry offers a nondestructive and noninvasive technique for characterizing radiative properties. Although such ellipsometers have long been used to measure optical properties, their operational bandwidth is usually limited to the visible to near-infrared range, leaving the mid-infrared largely unexplored. In this work, a broadband mid-infrared ellipsometer, operating from 2 to 15 μm, is designed and constructed to measure 12 elements of the Mueller matrix. The results may be used to determine the full Mueller matrix under specific conditions. The performance of the ellipsometer is evaluated using nanostructured materials, including a 1D grating and a chiral F-shaped metasurface. The measurement results compared well to those obtained from rigorous-coupled-wave analysis and finite-difference time-domain simulations, suggesting that this setup offers a useful tool in optical property retrieval and the assessment of nanostructured materials.

The Micro-Computed Tomography (MCT) beamline at the Australian Synchrotron (ANSTO) offers superior capabilities in micrometer-scale spatial resolution and three-dimensional x-ray imaging. MCT is the first of the eight new BRIGHT beamlines and has been operating successfully with users for approximately two years. It is a bending magnet beamline capable of delivering a white beam, a pink beam, or a monochromatic beam in the 8-40 keV energy range using a Double Multilayer Monochromator (DMM). Ongoing development continues at the MCT beamline to extend its capabilities. In this article, we present the operation and energy calibration of the DMM, highlighting the unique advantages offered by synchrotron-based micro-CT and its application for quantitative imaging, such as density measurements using monochromatic energy.

An imaging neutral particle analyzer (INPA) has been successfully designed and implemented in the Experimental Advanced Superconducting Tokamak to detect fast ions (FIs). The system capitalizes on carbon foils to ionize charge exchange neutral particles and utilizes scintillator screens to differentiate the energy and radial distribution of the particles. The detection characteristics of the pitch angle profile and energy resolution are illustrated, and the modeling-based energy calibration has been validated with the experimental data. Furthermore, the FI redistribution during sawtooth crashes has been effectively recorded by the INPA, manifesting its functionality.

In this study, we designed a wearable multi-sensor walking boot to measure foot angular momentum and introduced a novel method to quantify forefoot rocker motion as a function of walking speed. A treadmill walking experiment was conducted with eight healthy subjects wearing the multi-sensor walking boot. Using the collected data, we calculated foot angular momentum and the average rate of change in angular momentum during the double support phase. In addition, we used linear regression analysis to quantify foot rotation patterns across increasing walking speeds, assessing the potential of this method as a walking indicator. The results demonstrated that the foot rotation pattern in the healthy group was characterized by a gradual scaling of angular momentum and its average rate of change, with strong correlations to walking speed. Based on these findings, we conclude that the proposed method for quantifying forefoot rocker motion relative to walking speed can serve as an effective indicator of normal walking.