查看更多>>摘要：? 2022 Elsevier LtdVariational mode extraction (VME) is a novel fault diagnosis technology, which can effectively extract a narrow-band mode from the multi-component signal. However, its performance is seriously affected by two initial parameters: the initial guess of center frequency ωd and the balance factor α. To determine these two parameters adaptively, a VME method based on the convergence property of variational mode decomposition (VMD) is proposed for the multi-fault diagnosis of rolling bearings. Firstly, we study the influence of the balance factor on the convergence characteristic of VMD, the VMD convergence tendency chart is established. Secondly, the initial center frequencies of all latent modes in the faulty signal are adaptively determined by the VMD convergence tendency chart; taking kurtosis as the evaluation index, the corresponding balance factor is optimized separately. Finally, VME is used to extract all modes one by one. The experimental analog signal and engineering application signal are analyzed by this new method and compared with ensemble empirical mode decomposition (EEMD), fast kurtogram, and single-mode VMD. The results display that the new method can accurately extract multiple fault features from the bearing compound fault signal, and the fault feature extraction accuracy is better than the above three classical signal processing methods.
查看更多>>摘要：The SARA fractions in petroleum asphalts for road paving play a dominant role in the pavement performance of asphalt binders. In this study, a rapid and accurate determination method of SARA fractions in asphalts was proposed using Mid-Infrared (MIR) spectra and Partial Least Square Regression (PLSR) modeling method. Firstly, the blending and progressive aging process employed in this study successfully prepared 84 asphalt samples with fair differences in their Saturates, Aromatics, Resins and Asphaltenes (SARA) fractions. Secondly, the SARA fractions and MIR spectra of these samples were measured and collected by standard test methods, respectively. Finally, four quantitative calibration models were developed for each fraction using MIR spectra and PLSR method, and the validation results verified the high consistency between the measured values and the predicted values as well as the reproducibility and repeatability of the proposed method. This MIR-PLSR method was able to provide a faster SARA determination than the standard test methods through a single MIR spectrum. It could probably be used for the real-time quality control of asphalt production and the in-situ quality inspection of asphalt materials in road construction using portable equipment.
查看更多>>摘要：DNA, a molecule carrying our genome, is constantly exposed to various endogenous and exogenous damaging factors. These factors may lead to the formation of single- or double-strand breaks. Recently, an atomic force microscopy emerged as an attractive tool for determination of the length of DNA fragments deposited at surfaces, allowing quantification of double-strand breaks (DSBs). In spite of this, the length of objects provided via AFM is strictly related to the image spatial resolution, which in consequence leads to underestimation of DSBs quantity. To correct this deficiency, we provide here a novel methodology based on statistics of DNA fragments length. This approach allows for highly accurate determination of the DSBs number. Moreover, we provide the software that enables to automatically calculate the number of DSBs according to the described methodology. Finally, the method is applied for characterization of the DNA plasmid fragmentation by bleomycin - an anticancer chemotherapeutic drug.
查看更多>>摘要：In this work, several commercial high-emissivity coatings have been characterized in terms of emissivity, chemical composition and dielectric properties as a function of temperature, under microwave irradiation. Accurate knowledge of their response under exposure to microwaves provides new and crucial information about their practical usability for non-contact temperature measurements in microwave environments. Due to their high metallic content, some of the studied coatings exhibited unexpected microwave-triggered reactions that hindered their use up to the maximum temperature specified by the manufacturers. Emissivity and chemical analyses before and after the heating cycles confirmed the degradation of some of the samples predicted by dielectric measurements. This work illustrates how a careful characterization of optical and dielectric properties under representative operating conditions (temperature range, microwave exposure) is vital in order to select the appropriate reference coating to obtain reliable temperature measurements in microwave applications.
查看更多>>摘要：? 2022 Elsevier LtdWith the ever-growing development for nanomaterials, the integration of nanomaterials into electronic devices and sensors requires flexible and efficient selective patterning deposition of the nanomaterials. However, existing patterning techniques of these nanomaterials is limited in practical applications due to the use of templates and tedious preparation process. Here, a facile femtosecond laser bubble printing (FsLBP) technique without mask and tedious preparation process that integrates patterning, assembly, and deposition of nanomaterials is presented. Benefiting from the advantages of this processing technology, arbitrarily patterned assembled silicon (Si) nanoparticles were successfully prepared. In addition, the effect of viscosity and surface tension of the solution in the process of FsLDW on the deposited Si nanoparticles is explored. Owing to the rough and porous structure of the assembled microwires, the microwires have a high-efficiency light trapping ability with an average reflectivity of 2% for visible light and the photodetector based on porous Si microwires exhibits a responsivity of 231 A/W under the irradiation of 365 nm ultraviolet (UV) light. Finally, a device for real-time monitoring of ultraviolet light intensity was obtained, which demonstrate the potential application of the ultrafast laser fabrication method in patterned assembly of nanomaterials.
查看更多>>摘要：? 2022 The AuthorsGridshells are unexploited structures, over which lengths measurement are difficult to do due to their size and complex curvature. To deformation measurement on a timber gridshell beam and on an entire gridshell, we used an affordable photogrammetry system that consisted of a consumer-level camera, a tripod, a mast with a gimbal to elevate the camera, a laptop, and two photogrammetric software: PhotoModeler Scanner and Metashape. The beam was subjected to a bending test, and the gridshell was loaded with 105 kg of dead load per node on its five central nodes. The maximum error in the measurement was 1.26 mm on the beam and 3.45 mm on the gridshell, which corresponded to 0.77 ‰ error relative to the span of the beam and 0.41 ‰ relative to the length of the gridshell. Three-dimensional models obtained through the proposed method serve as dimensional data with a uniform error around the object.
查看更多>>摘要：? 2022 Elsevier LtdThe purpose of the digital single-beam speckle interferometry is to extract displacement information from gray images of the specimen surface before and after deformation, which is derived primarily from the single-beam speckle interferometry. Single-beam speckle interferometry uses optical Fourier transform to extract displacement information in the frequency domain. While digital single-beam speckle interferometry uses a computer to implement optical Fourier transform after digitizing an image to extract displacement information in the frequency domain. Four phase shift images are generated by a computer and the phase shift technology is used to obtain wrapped and unwrapped fringe patterns. Furthermore, based on the fringe patterns, the direction and magnitude of the displacement can be determined automatically. The factors that may influence measurement accuracy are investigated. To validate the reliability of this method, it is used to measure displacement near the crack tip of the cracked concrete beam.
查看更多>>摘要：? 2022The Imperial Roman Baths in Sagalassos, Turkey, were built in the 2nd century C.E. and have been excavated since the 1990s. The harsh environmental conditions, especially during the winter, resulted in the accelerated decay of the building materials, material losses, and serious structural problems in the Baths. This study explores the comprehensive characterization and multiscale assessment of bricks and mortars for effective preservation of the Baths. Experimental results showed that although the interface between building materials weakened after years of accumulated degradation, the individual materials still had higher strength than those from the same period. The material scale finite element model used to understand the damage mechanism showed that brick failure was caused by the tensile stresses accumulated at the brick–mortar interface when some of the mortar crumbled and fell with deterioration. A global sensitivity analysis was also conducted to investigate the impact of individual layer thicknesses on the stress distribution in the brick and mortar composite. Results indicated that thicker bricks resulted in better confinement at mortar layer and smaller tensile stresses at the bricks.
查看更多>>摘要：? 2022 Elsevier LtdThis paper describes a novel method for the general application of measured load spectra to the bogie frames of different high-speed trains. It is based on virtual track irregularity (VTI), an inversion of the measured load history, combined with a simplified vehicle dynamics model (SVDM). First, the A/B-type bogie frames and their attached components were strain gauged to measure the field load histories in coupled operation under actual operating conditions. Then, a comparison of the measured load spectra and an attempted mutual application of the damage consistency load spectra (DCLS) were conducted. Finally, as an example, the SVDM matching the bouncing load was established, and a complete procedure was proposed for generating the VTI in the time domain. The agreement between the measured and calculated load spectra indicated that the actual load histories acting on the different bogie frames can be accurately predicted based on the VTI and SVDM.
查看更多>>摘要：? 2022 Elsevier LtdCaster and KPI are two important parameters of the wheel alignment for the stability and safety of vehicle. The previous work for the measurement of the wheel caster and KPI focuses on the 2D-target-based test. We propose an accurate 1D-target-based measurement for the caster and KPI of vehicle wheel. The invariance of kingpin position in suspension during the alignment is analyzed. The sub-pixel extraction with the high accuracy is improved for the center position of concentric circles on the 1D target. Then, the caster and KPI are initially orientated by the 1D-1D-2D-3D kingpin measurement model, which relates the 1D center positions of 1D target and the wheel kingpin. Furthermore, the optimization function of the caster and KPI is constructed by the real angle benchmarks, which define caster and KPI, respectively. The measurement method is verified by the simulation, moreover, experimentally proved by two angles of the verification instrument.
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