- 标题
- 摘要
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- 实验方案
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An assessment of semi-analytical models based on the absorption coefficient in retrieving the chlorophyll-a concentration from a reservoir
摘要： Monitoring chlorophyll-a (Chl-a) concentrations in inland waters is crucial for water quality management, since Chl-a is a proxy for phytoplankton biomass and, thus, for ecological health of a water environment. Chl-a concentration can be retrieved through the inherent optical properties (IOPs) of a water system, which, in turn, can be remotely sensed obtained. Quasi-analytical algorithm (QAA), originally developed for ocean waters, can also retrieve IOPs for inland waters after re-parameterizations. This study is aimed at assessing the performance of sixteen schemes composed by QAA original and re-parameterized versions followed by models that use absorption coefficients as inputs for estimating Chl-a concentration in Ibitinga reservoir, located at Tietê River cascading system, S?o Paulo State, Brazil. It was verified that only QAAV5 based schemes were able to obtain reasonable estimates for image data and that by four models tested presented similar and acceptable results for QAAV5 outputs. The best model were applied to a Ocean and Land Colour Instrument (OLCI) image. Light absorption in the reservoir showed to be dominated by colored dissolved organic matter (CDOM), and wide spatial and temporal variability of optical and water quality properties was observed.
关键词： water quality monitoring,satellite data.,Trophic status,inland water
更新于2025-09-23 15:23:52
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Determination of 17β-estradiol by surface-enhanced Raman spectroscopy merged with hybridization chain reaction amplification on Au@Ag core-shell nanoparticles
摘要： The authors describe an aptamer-based assay for 17β-estradiol. It relies on the combined use of surface enhanced Raman scattering (SERS) and hybridization chain reaction (HCR). The aptamer against 17β-estradiol is applied as the recognition probes, and this results in excellent specificity. Specific recognition of target 17β-estradiol induce the freedom of DNA 2, which will open the stem-loop structure of probe 1 on the Au@Ag and form the partial dsDNA structure. With the nicking enzyme, the partial dsDNA will be hydrolyzed and the reside ssDNA on Au@Ag will form a small stem-loop structure. With the help of the other probe 2 modified Au@Ag and pre-immobilized probe 3 on the well of the microplate, an enzyme-free HCR can occur and tremendous Au@Ag can be assembled along the formed dsDNA in HCR, which can act as the excellent substrate for Raman measurement and greatly amplify the Raman signal of R6G on the Au@Ag. Afterwards, the key factor, ratio between probe 2-Au@Ag (P2) and probe1-Au@Ag (P1), affects the detection sensitivity is systematically optimized for the best sensing performance. The SERS signal of R6G, best measured at 1651 cm?1, increases linearly in the wide range from 1 pM to 10 nM. The detection limit can be as low as 0.1 pM.
关键词： Estrogen,Hybridization chain reaction,SERS,Food safety,Aptamer,Gold nanoparticle,Signal amplification,Environment monitoring
更新于2025-09-23 15:23:52
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A review of Quartz Crystal Microbalances for Space Applications
摘要： The aim of this work is a technical review about Quartz Crystal Microbalance (QCM) sensors used in space missions, i.e. Space Shuttle flights, i.e. NASA Space Transportation System (NASA STS) and satellite missions, that aimed at monitoring the contamination generated by outgassing processes of materials onboard satellites and sensitive payloads. The contamination processes are critical for scientific instrumentation (e.g. optics, telescopes, detectors) because scientific measurements and performances can be jeopardized or worsened by uncontrolled contamination. This issue has been addressed by the space agencies, e.g. NASA, ESA and JAXA that have implemented many different studies to monitor the material outgassing and degradation in space environment. During the past years, the QCM sensors have become the baseline solution for measuring material outgassing and characterizing the on-orbit contamination environment. This work summarizes the main QCM applications in Space and their findings, providing an overview of the sensors’ performances in terms of stability, power, data rate, measurement accuracy and resolution. Different QCM technologies will be compared highlighting the advantages of their use for the next space missions and instrumentations that require an accurate monitoring of contamination environment. In particular, due to more severe contamination requirements for next payloads and instrumentations, QCM sensors would be useful to estimate the cleanliness degree by evaluating the induced contamination and degradation on sensitive instrumentations.
关键词： quartz crystal microbalance,contamination monitoring,spacecraft contamination,molecular and particulate contamination,outgassing,satellite contamination
更新于2025-09-23 15:23:52
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Automatic signal quality check and equipment condition surveillance based on trivalent logic diagnosis theory
摘要： In the field of fault diagnosis, inadequate signals measured for equipment condition monitoring may cause incorrect diagnostic results and reduce the accuracy and reliability of the equipment diagnosis system. This paper proposes a method of signal quality check and equipment condition surveillance based on trivalent logic theory, signal histogram analysis and principal component analysis (PCA), in order to automatically evaluate the quality of measured signals to ensure that the signals are real and valid for the condition diagnosis of equipment, and automatically judge the equipment state for condition surveillance. The novelty of this paper are summarized as: (1) Trivalent logic has been expanded appropriately into the trivalent logic diagnosis theory, so that it can be applied to verify the signal quality in the acquisition process for fault diagnosis and equipment condition surveillance; (2) In order to directly and effectively extract features of a signal following any probability density distribution, the histograms of the signal measured for equipment condition diagnosis is used to substitute time domain symptom parameters which have been generally used in equipment diagnosis technology; (3) PCA is used to integrate the histograms to realize signal quality check and equipment condition surveillance on the basis of the trivalent logic diagnosis theory. By the method proposed in this paper, the moment when the signal for equipment condition diagnosis is relatively stable can be found, and the unfavorable signal can be avoided for ensuring the accuracy and reliability of the equipment condition diagnosis. Simulation signals and real signals measured in various conditions from a blower are respectively used to verify the effectiveness of the proposed method.
关键词： Condition monitoring,Fault diagnosis,Measurement errors,Histograms,Vibration measurement
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Symposium on Medical Measurements and Applications (MeMeA) - Rome (2018.6.11-2018.6.13)] 2018 IEEE International Symposium on Medical Measurements and Applications (MeMeA) - A Multi-label Architecture for Vision-based Measurement of Intervals of Pain
摘要： Vision-based measurement of pain can provide significant advantage in patient care and cost reduction. The subjective nature of pain, however, poses metrological challenges yet to be addressed. With this work, we designed and validated a measurement architecture for automatically estimating intervals of pain over time based on the analysis of facial expressions. A reference measurement procedure was set up for labelling subjective levels of pain as observed by a set of independent evaluators. By means of a multi-label strategy, the system was calibrated for managing the uncertainty of the information provided by the evaluators at the ground-truth level. Results obtained for different coverage probability values support the efficacy of the proposed platform and motivate further investigations.
关键词： vision-based measurement,pain monitoring,reference measurement procedure,ordinal quantity,Analysis of facial expression,multi-label classification
更新于2025-09-23 15:23:52
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Sensitive Damage Detection of Reinforced Concrete Bridge Slab by ``Time-Variant Deconvolution'' of SHF-Band Radar Signal
摘要： In this paper, we focus on ground-penetrating radar (GPR) for infrastructural health monitoring, especially for the monitoring of reinforced concrete (RC) bridge slab. Due to the demand of noncontact and high-speed monitoring technique which can handle vast amounts of aging infrastructures, GPR is a promising tool. However, because radar images consist of many reflected waves, they are usually difficult to interpret. Furthermore, the spatial resolution of system is not enough considering the thickness of target damages, cracks, and segregation are millimeter-to-centimeter order while the wavelength of ordinary GPR ultrahigh-frequency band is over 10 cm. To address these problems, for the purpose of sensitive damage detection, we propose a new algorithm based on deconvolution utilizing a super high-frequency (SHF) band system. First, a distribution of reflection coefficient is inversely estimated by 1-D bridge slab model. Because concrete is found to be a lossy medium at SHF band, we consider the attenuation of signal in deconvolution. The algorithm is called 'time-variant deconvolution' in this paper. After the validation by simulation, the effects of the algorithm and frequency band on damage detection accuracy are evaluated by a field experiment. Though the results show a 1-mm horizontal crack is not detected by measured waves, when it is filled with water, it is detected by time-variant deconvolution. Moreover, the 1-mm dried crack is detected only by time-variant deconvolution at SHF band, which greatly emphasizes the peaks of the reflection coefficient of the crack.
关键词： thin cracks and segregation detection,Ground-penetrating radar (GPR),infrastructural health monitoring,time-variant deconvolution
更新于2025-09-23 15:23:52
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Measuring bulk density variations in a moving powder bed via terahertz in-line sensing
摘要： Monitoring the relative density of static or moving powder inside a process line is essential for manufacturing high-quality products. The aim of this study was to predict density variations in a moving powder bed using terahertz reflection technology. We systematically investigated three grades (varying true density and particle size) of two materials: lactose and silicified microcrystalline cellulose (SMCC). These six powders specifically differ in their compressibility, which can be applied to assess the sensitivity and applicability of our method. The powders were filled into a round container, and terahertz reflection measurements were acquired continuously during the container's rotation. The setup allowed to adjust the relative density by compacting the powders into specific powder bed heights. Each powder was compacted to various relative densities (compression pressures up to 100 kPa). We calculated the surface refractive index based on the in-line terahertz measurements acquired during rotation, which has a linear dependence on the relative density of the powder. This was confirmed by correlating the refractive index values with the theoretical relative densities based on the bulk and true densities of the powder. The coefficient of determination (R2) was larger than 0.962 (Lactohale 100) for all six powders, with the highest coefficients for Lactohale 220 (R2 = 0.996) and SMCC 50 LD (R2 = 0.995). The results suggest that the proposed method can resolve relative densities averaged across the powder bed that are as small as 0.3% (Lactohale 100). The high acquisition rate of the terahertz system (15 Hz) made it possible to determine the powder density in 230 positions uniformly distributed throughout the container, facilitating the investigation of the relative density uniformity in the container as a function of the powder bed height. It was observed that SMCC powders undergo a smaller change in the relative density variations upon compaction than the lactose powders. Moreover, the relative density maps clearly indicate local density differences in the powder bed for all powders. The relative density variations that were introduced by packing of the container prevailed throughout the compaction process for all samples with the exception of Lactohale 220. The presented approach allows a precise resolution of the spatial distribution of relative density, which facilitates an in-depth analysis of powder behavior upon compaction.
关键词： Powder density,Process monitoring,Process analyzer,Terahertz in-line sensing,Capsule filling
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - L-Band SAR Interferometric Analysis for Flood Detection in Urban Area - a Case Study in 2015 Joso Flood, Japan
摘要： In this paper, we examine the potential of interferometric analysis using L-band synthetic aperture radar (SAR) for flood monitoring. The integration of amplitude and interferometric coherence is one of the novel methods for flood monitoring in urban area. However, its accuracy has not been evaluated especially in case of L-band SAR data. Here, we used the 2015 September flood in Joso city, Ibaraki prefecture, Japan for the evaluation of the latest L-band SAR satellite ALOS-2 PALSAR-2.
关键词： PALSAR-2,Disaster monitoring,ALOS-2,Interferometry,Flood detection
更新于2025-09-23 15:23:52
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Numerical and experimental investigation of damage severity estimation using Lamb wave–based imaging methods
摘要： In this article, estimation of crack size, shape, and orientation was investigated numerically and experimentally using Lamb waves. A hybrid global–local approach was used in conjunction with the imaging methods for the numerical simulation. The hybrid global–local approach allowed fast and efficient prediction of scattering wave signals for Lamb wave interaction with crack from various incident directions. The simulation results showed the directionality effect of the scattering wave signals and suggested an optimum transmitter–sensor configuration. Two imaging methods were used: one involves the synthetic time reversal concept and the other involves Gaussian distribution function. Both imaging methods show very good agreement during simulations. Experiments were designed and conducted based on the simulated results. A network of eight piezoelectric wafer active sensors was used to capture the scattering waves from the crack. Both the pitch-catch and pulse-echo experimental modes were used. The directionality effect of incident Lamb waves on the imaging results was studied. The effect of summation, multiplication, and combined algorithms for each imaging method was studied. It was found that both methods can successfully predict the crack size and orientation. An attempt was made to use these imaging methods for detecting and sizing smaller sized damage (1- to 3-mm-diameter hole). It was found that these methods can successfully localize the hole, but size estimation was a bit challenging because of the smaller dimensions. The scattering waves for various hole sizes were studied.
关键词： synthetic time reversal,crack sizing,Structural health monitoring,wave propagation,scattering waves
更新于2025-09-23 15:23:52
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Optische Koh?renztomografie
摘要： With telematics and technologies like “Digital Impression”, “CAD/CAM” or “3D-radiography” the digitalization has reached the dental practice by now. The desire for more efficient diagnostics is especially addressed by 3D-radiography. A noninvasive imaging technology with a considerable diagnostic potential is the optical coherence tomography. In this article, promising examples of OCT use in operative dentistry are presented that raise expectations of a wide range of applications of this innovative technology in dentistry.
关键词： restoration assessment,caries diagnosis,optical coherence tomography,restorative therapy with composite,monitoring,tomography
更新于2025-09-23 15:23:52