Review of Scientific Instruments最新文献

Long-term exposure to particulate matter, especially submicron particulate matter (PM1), poses significant health risks by inducing oxidative stress and inflammation. This paper reports an optimally designed virtual impactor (VI) integrated with a quartz crystal microbalance (QCM) sensor for the classification and detection of PM1 particles. Computational fluid dynamics simulations were employed to optimize the included angles and outlet size of the VI's flow channels, minimizing eddy formation and reducing airflow impact on the sidewalls of the flow channels, thereby enhancing the durability of the VI. The VI was fabricated using 3D printing, and its optimization effectiveness was validated by assessing particle wall loss. The performance of the PM1 detection system was examined by classifying SiO2 particles ranging from 0.2 to 2 µm using the VI and detecting PM1 particles with the QCM sensor. Results showed that after classification, the majority of particles in the major flow channels were PM1. The frequency shift of the QCM sensor showed a linear correlation with the mass of particles deposited on its surface. Moreover, the system's performance was found to be comparable to that of commercial instruments.

Efficient identification of the flocculation state of waste drilling fluid remains a significant challenge. This study proposes an improved You Only Look Once version 8 nano-algorithm (YOLOv8n), specifically optimized for real-time monitoring of drilling fluid flocculation under field conditions. The algorithm employs MobileNetV3 as the backbone network to minimize memory usage, improve detection speed, and reduce computational requirements. The integration of the efficient multi-scale attention mechanism into the cross-stage partial fusion module effectively mitigates detail loss, resulting in improved detection performance for images with high similarity. The wise intersection over union loss function is employed to accelerate bounding box convergence and improve inference accuracy. Experimental results show that the enhanced YOLOv8n algorithm achieves an average recognition accuracy of 98.6% on the experimental dataset, a 4.8% improvement over the original model. In addition, the model size and parameter count are reduced to 2.9 MB and 2.8 Giga Floating-Point Operations Per Second (GFLOPS), respectively, compared to the original model, reflecting a reduction of 3.2 MB and 5.3 GFLOPS. As a result, the proposed flocculation recognition algorithm is highly deployable and effectively predicts flocculation state changes across varying working conditions.

Quantum technology exploits fragile quantum electronic phenomena whose energy scales demand ultra-low electron temperature operation. The lack of electron-phonon coupling at cryogenic temperatures makes cooling the electrons down to a few tens of millikelvin a non-trivial task, requiring extensive efforts on thermalization and filtering high-frequency noise. Existing techniques employ bulky and heavy cryogenic metal-powder filters, which prove ineffective at sub-GHz frequency regimes and unsuitable for high-density quantum circuits such as spin qubits. In this work, we realize ultra-compact and lightweight on-chip cryogenic filters based on the attenuation characteristics of finite ground-plane coplanar waveguides. These filters are made of aluminum on sapphire substrates using standard microfabrication techniques. The attenuation characteristics are measured down to a temperature of 500 mK in a dilution refrigerator in a wide frequency range of a few hundred kHz to 8.5 GHz. We find their performance is superior by many orders compared to the existing filtering schemes, especially in the sub-GHz regime, negating the use of any lumped-element low-pass filters. The compact and scalable nature makes these filters a suitable choice for high-density quantum circuits such as quantum processors based on quantum dot spin qubits.

The measurement of thermal conductivities of anisotropic materials and atomically thin films is pivotal for the thermal design of next-generation electronic devices. Frequency-domain thermoreflectance (FDTR) is a pump-probe technique that is known for its accurate and straightforward approach to determining thermal conductivity and stands out as one of the most effective methodologies. Existing research has focused on advancing a measurement system that incorporates beam-offset FDTR. In this approach, the irradiation positions of the pump and probe lasers are spatially offset to enhance sensitivity to in-plane thermal conductivity. Previous implementations primarily adjusted the laser positions by modifying the mirror angle, which inadvertently distorted the laser spot. Such distortion significantly compromises measurement accuracy, which is especially critical in beam-offset FDTR, where the spot radius has a crucial impact on measured values. This study introduces an advanced FDTR measurement system that realizes probe laser offset without inducing spot distortion, utilizing a relay optical system. The system was applied to measure the thermal conductivities of both isotropic standard materials and anisotropic samples, including highly oriented pyrolytic graphite and graphene. The findings corroborate those of prior studies, validating the measurement's reliability in terms of sensitivity. This development of a beam-offset FDTR system without laser spot distortion establishes a robust basis for accurate thermal conductivity values of anisotropic materials via thermoreflectance methods.

We design and construct an ultrafast optical spectroscopy instrument that integrates both on-site in situ high-pressure technique and low-temperature tuning capability. Conventional related instruments rely on off-site tuning and calibration of the high pressure. Recently, we have developed an on-site in situ technique, which has the advantage of removing repositioning fluctuation. That instrument only works at room temperature, which greatly hampers its application to the investigation of correlated quantum materials. Here, we further integrate low temperature functioning to this instrument, by overcoming enormous technical challenges. We demonstrate on-site in situ high-pressure ultrafast spectroscopy under a tunable temperature, from liquid-helium to above-room temperatures. During the pressure and temperature tuning process, the sample neither moves nor rotates, allowing for reliable systematic pressure- and temperature-dependence data acquisition. Ultrafast dynamics under 10-60 GPa at 130 K, as well as 40-300 K at 15 GPa, is achieved. Increasing and decreasing pressure within 5-40 GPa range at 79 K has also been achieved. The precisions are 0.1 GPa and 0.1 K. Significantly, temperature-induced pressure drifting is overcome by our double-pneumatic membrane technique. Our low temperature on-site in situ system enables precise pressure and temperature control, opening the door for reliable investigation of ultrafast dynamics of excited quantum states, especially phase transitions in correlated materials, driven by both pressure and temperature.

Cosmic Explorer is a next-generation ground-based gravitational-wave observatory that is being designed in the 2020s and is envisioned to begin operations in the 2030s together with the Einstein Telescope in Europe. The Cosmic Explorer concept currently consists of two widely separated L-shaped observatories in the United States, one with 40 km-long arms and the other with 20 km-long arms. This order of magnitude increase in scale with respect to the LIGO-Virgo-KAGRA observatories will, together with technological improvements, deliver an order of magnitude greater astronomical reach, allowing access to gravitational waves from remnants of the first stars and opening a wide discovery aperture to the novel and unknown. In addition to pushing the reach of gravitational-wave astronomy, Cosmic Explorer endeavors to approach the lifecycle of large scientific facilities in a way that prioritizes mutually beneficial relationships with local and Indigenous communities. This article describes the (scientific, cost and access, and social) criteria that will be used to identify and evaluate locations that could potentially host the Cosmic Explorer observatories.

Real-time moving target trajectory prediction is highly valuable in applications such as automatic driving, target tracking, and motion prediction. This paper examines the projection of three-dimensional random motion of an object in space onto a sensing plane as an illustrative example. Historical running trajectory data are used to train a reserve network. The trained network model is subsequently used to predict future trajectories. In the experiment, a network model trained on 20 000 frames of random running trajectory data was used to predict trajectories for 1-20 future frames, and 5000 frames were used for testing. The results showed prediction errors for 80% of the predictions of less than 0.01%, 0.8%, and 4% for 1, 10, and 20 future frames, respectively.

In response to the problem of noise interference in the knock detection signal received by the pickup in the ceramic sheet knock non-destructive testing, a noise removal method is proposed based on the improved secretary bird optimization algorithm (ISBOA) optimized variational mode decomposition (VMD) combined with wavelet thresholding. First, the secretary bird optimization algorithm is improved by using the Newton-Raphson search rule and smooth exploitation variation strategy. Second, the ISBOA is used to select the key parameters in the VMD. Third, the signal is subjected to the VMD decomposition to obtain the intrinsic mode functions (IMFs), and permutation entropy of each IMF component is calculated to divide it into effective signal component or noise component. Finally, the effective signal component is denoised by using improved wavelet thresholding, and the processed IMFs components are reconstructed to obtain the denoised signal. The denoising of simulated signal with 5 dB signal-to-noise ratio shows that the signal-to-noise ratio of the signal is improved by 11.59 dB and the root mean square error is reduced by 73.6%, which is the most significant denoising effect of the method compared to other similar algorithms. In addition, tests on the knock detection signals of ceramic pieces with different types of defects also show that the method has wide applicability and an excellent denoising effect.

This article presents an experimental setup capable of providing high spatial and temporal resolution measurements of neutral gas puff injection using a glow discharge to excite the neutral gas and an ultra-high-speed camera to record the emitted light. Using the proposed setup, the shape and propagation velocity of a thermal deuterium gas puff at 1 bar have been measured. The cloud has a conical shape and a propagation velocity of vprop = 1870 ± 270 m/s. Furthermore, a code has been developed with the aim of studying the relation between the propagation velocity and the initial injection velocity of the gas. The simulations show that an initial injection velocity in the range of vinj ∼ 1650-1950 m/s can reproduce a propagation velocity of vprop = 1870 ± 270 m/s.