- 标题
- 摘要
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- 实验方案
- 产品
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Cross correlation peak-seeking technique of BOTDR based on the incomplete Brillouin spectrum
摘要： Considered the limitation of sweeping frequency technique, Brillouin optical time domain reflectometer (BOTDR) can only perceive slow external interference. It greatly limits the scope of application. For perceiving rapid external interference, a method of cross correlation peak-seeking technique based on incomplete Brillouin spectrum (IBS) is proposed, and the feasibility of the method is verified under the background of the monitoring of sound barriers along the high-speed railway. The numerical simulation results indicate that the probability that obtains an accurate peak frequency error within the 0.50 MHz can reach 49/50, when frequency interval for sweeping is 5 MHz and number of splicing IBS is 80. In addition, to select the optimal parameters of the system, we also take a further analysis on the effect of the splicing times and the frequency interval for sweeping on the peak detection accuracy. This method is significant to extend the application of BOTDR from slow changing fields to rapid changing fields.
关键词： Optical time domain reflectometry,Brillouin scattering,Optical fiber measurement applications
更新于2025-09-23 15:22:29
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Volumetric measurement of dentoalveolar defects by means of intraoral 3D scanner and gravimetric model
摘要： The aim of this study was to evaluate the accuracy in volumetric measurements obtained on an experimental model using an intraoral scanner and a gravimetric method. Three identical partial dentate maxillary acrylic models with three fabricated alveolar defects, in anterior and posterior regions, were scanned using an intraoral scanner (20 scans/defects). The defects differed in terms of size and distance of neighbouring teeth. As references, replicas of each defect were created using a dimensional stable silicone impression material. After measuring the mass of each replica, the volume was calculated by dividing the mass of each replica by the density of the impression material. The defects had a volume, according to the gravimetric method, ranging from 40.5 to 143.7 mm3. The scans were imported to metrology software for analyses. Accuracy was determined in terms of trueness and precision. The mean trueness for all defect types was 0.168 mm3 (SD 0.691, range 2.82). There was no statistical significant difference between the mean trueness for all defects measured (p = 0.910). The mean precision for all defect types was 0.147 mm3 (SD 0.524, range 2.86). There were no statistical significant differences between the dental models in regard to mean precision (p = 0.401), however, there were statistical significant differences between defects in position 1 and 2 (p = 0.002) and 1 and 3 (p = 0.001). Based on the findings of this study, the intraoral scanner utilized in the current study presented an acceptable level of accuracy when measuring volume of defects.
关键词： Volumetric measurement,Intraoral scanning,Surgical techniques,Wound healing,Tissue alterations
更新于2025-09-23 15:22:29
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Improving the Signal-to-noise Ratio of Super Resolution Imaging Based on Single Pixel Camera
摘要： Based on the theories of single pixel camera and compressed sensing image reconstruction, the sparse basis, the projection method of measurement matrix and the signal reconstruction algorithm are optimized. Firstly, for the sparse representation of image, the restraint matrix is designed combining the characteristics of wavelet sparse coefficients to enhance the sparse representation ability of the discrete wavelet base, which improves the quality of image reconstruction and imaging by single pixel camera. Then in the single pixel camera system, the projection method is improved according to the characteristics of the DMD micro-mirror, and a new bilateral projection method based on the block diagonal measurement matrix is proposed to realize the super resolution imaging of the outdoor scene, reducing the number of measurement and improving the imaging quality. Finally, for the algorithm of image reconstruction, combining the characteristics of convex optimization and non-convex optimization algorithms, a new algorithm from convex optimization approximately to non convex optimization algorithm is proposed, and compared with traditional image reconstruction algorithm such as greedy pursuit algorithm, minimum norm algorithm and image interpolation, the peak signal to noise ratio (PSNR) and imaging quality of reconstructed images are effectively improved. The feasibility of the proposed methods is demonstrated by simulation experiments and imaging experiments of single pixel camera.
关键词： measurement matrix,Single pixel camera,sparse representation,super resolution,image reconstruction
更新于2025-09-23 15:22:29
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GB-SAR Interferometry Based on Dimension-Reduced Compressive Sensing and Multiple Measurement Vectors Model
摘要： To reduce the data acquisition time and the high-level sidelobes produced by conventional focusing methods for ground-based synthetic aperture radar interferometry, we present a new method to provide accurate displacement maps based on the dimension-reduced compressive sensing (CS) method combined with the multiple measurement vectors (MMVs) model. The proposed CS method consists in selecting the supported area of targets, estimated by the fast conventional method with undersampled data. The following sparse reconstruction is applied only to the selected areas. The MMV-based approach allows increasing the coherence and the precision of displacement estimates. Two experiments are carried out to assess the performance of the proposed method.
关键词： multiple measurement vectors (MMVs) model,SAR interferometry,Compressive sensing (CS),ground-based synthetic aperture radar (GB-SAR),SAR
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Multi-Frequency Microwave Resonance Cavity for Nondestructive Core Plug Measurements
摘要： This work describes the theory, design and testing of a multi-frequency microwave cavity. The cavity measures the complex permittivity of core plugs of rocks, consolidated soil or sea ice. The core plugs can have commercially available diameter dimensions (0.02 meters - 0.038 meters) and for maximum height of 0.055 meters. The cavity measures the complex permittivity at five resonant frequencies between 1 GHz and 3.5 GHz of the TM0np mode. An infrared temperature sensor measures the temperature of the core plug under testing. This cavity allows for a more accurate characterization of the core composition. Initial complex permittivity measurements of six different shale core plugs were conducted. Results show that permittivity spectra can be correlated to the clay content and total organic content (TOC) of the shales. The latter is a function of the maturity of the rock. Moreover, initial results indicate the importance of water and salinity on shale samples.
关键词： sea ice,dielectric measurement,geology,Permittivity measurement,soil,well logging,geophysical measurement,microwave measurements
更新于2025-09-23 15:21:21
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A three-step displacement measurement method for a 3-DOF macro-micro positioning stage
摘要： A high-performance displacement measurement method for the displacement measurement of a three degree of freedom (3-DOF) macro-micro positioning stage based on the micro-vision measurement system is proposed. The method is built up by three steps. In the first step, a fast search algorithm combined with triangular relations and a ring projection with illumination and noise correction is adopted to achieve the selection of candidate pixels. Subsequently, an orientation code based algorithm is adopted to determine the integer-pixel displacement and rotation angle estimation. The third step is to obtain the sub-pixel displacement through a similarity function based algorithm. Simulations are carried out, and the results show that the proposed method has the characteristics of translation and rotation invariance, and the matching accuracy can reach 0.01-pixel theoretically. Moreover, the proposed method consumes less time than that of the orientation code and pseudo-Zernike moment based algorithm. Finally, a capacitance sensor measurement system is established to compare the accuracy of the proposed method. The experiment results demonstrate that it has a high accuracy.
关键词： sub-pixel displacement,orientation code,displacement measurement,macro-micro positioning stage,micro-vision measurement system
更新于2025-09-23 15:21:21
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[IEEE 2018 11th International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP) - Budapest (2018.7.18-2018.7.20)] 2018 11th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP) - Multi point strain and temperature sensing based on Brillouin optical time domain reflectometry
摘要： In this paper, multiple points of strain and temperature measurement in real-time is investigated using a Brillouin optical time domain reflectometry (BOTDR) system. The Brillouin frequency shift (BFS) is analysed with strain and temperature effects applied at various locations of the sensing fibre. In addition, a passive depolarizer was employed in order to reduce the polarization noise. The strain and temperature coefficients are found to be 0.79 MHz/oC and 0.057 MHz/με.
关键词： Brillouin gain spectrum,strain measurement,temperature measurement
更新于2025-09-23 15:21:21
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An Optoelectronic Pulse Drive for Quantum Voltage Synthesizer
摘要： An optoelectronic pulse drive system based on commercially available telecoms optoelectronic components and a field-programmable gate array has been developed. In order to allow the use of ac-coupled optoelectronic components, a method of adding and subtracting complementary pulses was developed. The system was used to drive a Josephson junction array to synthesize quantum-accurate voltage waveforms. These waveforms will be used in voltage waveform metrology applications. Results from the synthesis of sinusoidal unipolar voltage waveforms from 3 to 300 kHz are presented. The margin of operation was measured and shown to require an optical pulse height stability better than 0.15 mW. The use of delta–sigma code with repeated sections, suitable for a quantum voltage digitizer was also examined. A test code corresponding to a delta–sigma feedback loop rate of 250 MHz was used to synthesize a 3.125 kHz sinusoidal waveform.
关键词： Josephson arbitrary waveform synthesizer,optoelectronics,metrology,Josephson arrays,measurement,voltage measurement
更新于2025-09-23 15:21:21
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Evaluation method for the performance of light screen array measurement system based on semi-physical simulation
摘要： The paper presents a method to evaluate the performance of light screen array measurement system (LSA for short) objectively and scienti?cally. We put forward the scheme of semi-physical veri?cation platform based on arbitrary waveform generator (AWG), and this instrument is used as a substitute for light screen detector in the LSA. according to some main characteristics of dynamic signal, the waveform ?les of two simulation signals with a certain time interval are compiled and created through con?guring some options through a signal waveform edition software. Furthermore, these waveform ?les are downloaded into the AWG to generate two channel simulation signals. Then, the time interval of these two signals can be measured in the signal acquisition & processing module of LSA. Finally, we can compare the di?erence between true values and measured results. Through experiment and analysis, the proposed method can meet the requirement of performance evaluation on the LSA, and it is superior to the other previous methods.
关键词： Semi-physical simulation,Noise environment,Waveform modeling and editing,Photoelectric measurement,Dynamic signal generation
更新于2025-09-23 15:21:21
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Setup to Study the in Situ Evolution of Both Photoluminescence and Absorption during the Processing of Organic or Hybrid Semiconductors
摘要： In situ measurement techniques, applied during the solution processing of novel semiconductors such as organic semiconductors or hybrid perovskites, have become more and more important to understand their film formation. In that context, it is crucial to determine how the optical properties, namely photoluminescence (PL) and absorption, evolve during processing. However, until now PL and absorption have mostly been investigated independently, significantly reducing the potential insights into film formation dynamics. To tackle this issue we present the development of a detection system that allows simultaneous measurement of full absorption and PL spectra during solution processing of the investigated film. We also present a spin-coater system attachable to the detection system, where the temperature of the substrate on which the film is processed can be changed. We performed test measurements by spin coating the well-known conjugated polymer P3HT demonstrating the potential of this technique. By considering absorption and corresponding PL, we extract the PL quantum yield (PLQY) during processing, which decreases with substrate temperature. Furthermore, we identify a significant red shift of the PL just prior to the onset of the aggregation process, indicating the importance of chain planarization prior to solid film formation.
关键词： photoluminescence,in situ measurement,organic semiconductors,hybrid perovskites,spin-coating,film formation,absorption,P3HT
更新于2025-09-23 15:21:21