Relative pose measurement for noncooperative objects is an important part of 3D shape recognition and motion tracking. The methods based on scanning point clouds have better environmental ...adaptability and stability than image-based methods. However, the discrete points obtained from a continuous surface are sparse, which leads to point-to-point dislocations in the overlapping area and seriously reduces the accuracy. Therefore, this paper proposed a relative-pose-measurement algorithm based on double-constrained intersurface mutual projections. First, the initial corresponding set was constructed using mutual projections between the areas with similar feature descriptors, and then the final corresponding set was determined through the rigid-transformation-consistency constraint to improve the accuracy of the matchings and achieve a high-accuracy relative pose measurement. In the Stanford dataset, the rotation error and translation error were reduced by 19.3% and 13.4%, respectively. Furthermore, based on the proposed evaluation method, which separated the error of the pose-measurement algorithm from that of the instrument, the experiments were carried out with a self-made swept-frequency interferometer. The rotation error was reduced by 39.8%, and the surface deviation was reduced by 4.9%, which further proved the advancement of the method.
In modern industrial production, the prediction ability of remaining useful life of bearings directly affects the safety and stability of the system. Traditional methods require rigorous physical ...modeling and perform poorly for complex systems. In this paper, an end-to-end remaining useful life prediction method is proposed, which uses short-time Fourier transform (STFT) as preprocessing. Considering the time correlation of signal sequences, a long and short-term memory network is designed in CNN, incorporating the convolutional block attention module, and understanding the decision-making process of the network from the interpretability level. Experiments were carried out on the 2012PHM dataset and compared with other methods, and the results proved the effectiveness of the method.
As a heavy metal nuclear fuel, uranium is used in various civil and military projects, resulting in environmental pollution. Uranium can enter the body through the mouth, nose and skin, threatening ...human health. The reproductive organs are sensitive to uranium. For certain exposure times, doses and modes, uranium can produce toxic effects on the reproductive organs. The reproductive toxicity of uranium can be produced through different mechanisms of action, such as changing the level of sex hormones in the body, disrupting the expression of genes or proteins related to reproduction and causing oxidative stress and inflammation. Uranium thus can cause toxic effects to the reproductive system, leading to histopathological changes and decreased conception rates, and may damage the health of the body. This paper reviews the research progress on uranium reproductive toxicity in recent years and indicates a direction for future research on uranium reproductive toxicity and its mechanisms.
We present a continuous dynamic frequency scanning interferometry (DFSI) measurement method based on motion phase synchronization compensation and calibration. By introducing heterodyne ...interferometry (HI) synchronization measurement and frequency scanning interferometry (FSI) motion phase compensation, dynamic continuous measurement is achieved and effectively suppresses the distance error introduced by the Doppler effect (DE). Based on this, the influence of the initial optical frequency deviation (OFD) of the tunable laser and the OFD of the HI laser on the dynamic absolute distance measurement (DADM) is analyzed; the relationships between the error of DADM with the variation of the OFD and the target motion parameters are investigated; and the residual DE introduced by the OFD is shown as the fundamental cause of the degradation of the accuracy of DFSI. We propose an online optical frequency measurement method based on HI combined with H 13 C 14 N gas absorption cells to resolve this problem. High-precision motion phase compensation is achieved by calibrating the optical frequency (fixed frequency) of the measured HI laser and the initial frequency of the tunable laser online during measurement and then performing motion phase calibration. To verify the effectiveness of our method, an optical frequency calibration experiment, a continuous DADM experiment, and a precision evaluation experiment were conducted, and a highly accurate continuous DADM was achieved.
Laser Doppler vibrometers (LDVs) are widely used for vibration testing in various fields. Nonlinearity errors are the key factor affecting the measurement accuracy of LDVs. The conventional Heydemann ...method cannot correct nonlinearity errors produced by noisy environments. Thus, we establish a novel model to describe dynamic nonlinearity errors produced in noisy environments and propose a compensation method to mitigate signal distortion. The performance of the proposed method is assessed by performing both simulations and experiments. The results of experiments carried out in a noisy environment indicate that the proposed method suppresses the nonlinearity to 30 nm compared to 737 nm using the conventional Heydemann correction. The proposed method can improve the accuracy of LDV measurements in industrial environments.
The frequency-scanning interferometer (FSI) is an advantageous distance measurement method. We propose an FSI-based non-cooperative target distance measurement system that is combined with a ...heterodyne interferometer. The heterodyne interferometer is parallel to the FSI and can measure the vibration of the target synchronously, and the measuring result is used to correct the Doppler effect in the FSI signal. To extract the vibration accurately, a circle fitting in the Lissajous curve is used to correct the influence of the multipath interference, which may damage the vibration measurement result, especially when the target is non-cooperative. Then, with a post-processing algorithm, the distance could be obtained. Finally, the distance to a non-cooperative target located at 15 m is experimentally measured using this method, and a standard deviation of 3.39 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> is obtained.
Hematopoietic stem cell (HSC) regeneration underlies hematopoietic recovery from myelosuppression, which is a life-threatening side effect of cytotoxicity. HSC niche is profoundly disrupted after ...myelosuppressive injury, while if and how the niche is reshaped and regulates HSC regeneration are poorly understood.
A mouse model of radiation injury-induced myelosuppression was built by exposing mice to a sublethal dose of ionizing radiation. The dynamic changes in the number, distribution and functionality of HSCs and megakaryocytes were determined by flow cytometry, immunofluorescence, colony assay and bone marrow transplantation, in combination with transcriptomic analysis. The communication between HSCs and megakaryocytes was determined using a coculture system and adoptive transfer. The signaling mechanism was investigated both in vivo and in vitro, and was consolidated using megakaryocyte-specific knockout mice and transgenic mice.
Megakaryocytes become a predominant component of HSC niche and localize closer to HSCs after radiation injury. Meanwhile, transient insulin-like growth factor 1 (IGF1) hypersecretion is predominantly provoked in megakaryocytes after radiation injury, whereas HSCs regenerate paralleling megakaryocytic IGF1 hypersecretion. Mechanistically, HSCs are particularly susceptible to megakaryocytic IGF1 hypersecretion, and mTOR downstream of IGF1 signaling not only promotes activation including proliferation and mitochondrial oxidative metabolism of HSCs, but also inhibits ferritinophagy to restrict HSC ferroptosis. Consequently, the delicate coordination between proliferation, mitochondrial oxidative metabolism and ferroptosis ensures functional HSC expansion after radiation injury. Importantly, punctual IGF1 administration simultaneously promotes HSC regeneration and hematopoietic recovery after radiation injury, representing a superior therapeutic approach for myelosuppression.
Our study identifies megakaryocytes as a last line of defense against myelosuppressive injury and megakaryocytic IGF1 as a novel niche signal safeguarding HSC regeneration.
Radionuclide tritium is widely used in the nuclear energy production industry and creates a threat to human health through radiation exposure. Herein, the radioactive elimination and radioprotective ...effect of hydrogen-rich water (HRW), a potential antioxidant with various medical applications, on tritiated water (HTO) exposure, was studied in vitro and in vivo. Results showed that intragastric administration of HRW effectively promoted the elimination of urinary tritium, decreased the level of serum tritium and tissue-bound tritium (OBT), and attenuated the genetic damage of blood cells in mice exposed to HTO (18.5 MBq/kg). Pretreatment with HRW effectively reduces tritium accumulation in HTO-treated human blood B lymphocyte AHH-1 cells. In addition, the anti-oxidative properties of HRW could attenuate the increased intracellular ROS (such as O2•-, •OH and ONOO-), resulting in reversing the exhaustion of cellular endogenous antioxidants (reduced GSH and SOD), decreasing lipid peroxidation (MDA), relieving DNA oxidative damage, and depressing cell apoptosis and cytotoxicity induced by HTO exposure. In conclusion, HRW is expected to be an effective radioactive elimination agent through the competition effect of isotope exchange or a radioprotective agent by scavenging free radicals induced by HTO exposure.
Optical frequency domain reflectometry (OFDR) is a research hotspot in fiber optic sensing technology. This technology can be used for strain, vibration and temperature sensing and has great ...application prospects in fields such as deformation analysis of aerospace components and bridge monitoring. This article analyzes the reasons for strain demodulation errors under large strains. In response to the problem of reduced similarity between the reference state signal and the measured state signal, a strain measurement method based on the similarity feature of a double-segment Rayleigh scattering spectrum is proposed. Local segments at both ends of the reference state signal are used as new fingerprint spectra, and the offset of the measured state signal similarity spectrum is synchronously searched after extension. At the same time, by revealing the mechanism of strain edge demodulation errors, a strain edge optimization method based on automatic adjustment of the sliding window center position is proposed. A comparison experiment was conducted with traditional methods to verify the effectiveness of the above method. Finally, a sensing unit length of 32.6 mm was achieved with a frequency modulation bandwidth of 5 nm, and the measurement range was from ± 2000 µɛ to ± 2500 µɛ. The measurable spectral offset was increased from 48% to 60%, with a maximum standard deviation of 1.9 µɛ.
Recently, radical difunctionalization of the feedstock 1,3-butadiene has become an attractive strategy for increasing molecular complexity. Herein, we present a novel approach that effectively ...combines radical thiol-ene chemistry with TiIII catalysis to enable a three-component aldehyde allylation using 1,3-butadiene as an allyl group source under visible light conditions. This sustainable and straightforward method has facilitated the rapid production of diverse allylic 1,3-thioalcohols with exceptional regio- and diastereoselectivity.
PDF
