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Insights into anti-thermal quenching of photoluminescence from SrCaGa4O8 based on defect state and application in temperature sensing
摘要： Herein, a self-activated phosphor SrCaGa4O8 with excellent thermal stability was synthesized by high temperature solid state reaction method. It exhibited the broad emission range from 300 to 600 nm under 220 nm excitation, which may be caused by the intrinsic defects of host. Specifically, with the temperature increasing, the photoluminescence (PL) color changed from bluish to yellow-green and the maximum of PL intensity at 550 nm was obtained when reaching 493 K. From thermoluminescence curves and high temperature spectra, it was found that the anti-thermal quenching phenomenon could be dependent on the self-compensation of the carriers. Accordingly, the results of temperature-dependent intensity ratio and sensitivity show that SrCaGa4O8 may have potential in the optical temperature sensing.
关键词： Energy transfer,Self-activated phosphor,Optical properties,Anti-thermal quenching,Sensors
更新于2025-09-23 15:22:29
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Morphology Controllable Synthesis of Hierarchical WO3 Nanostructures and C2H2 Sensing Properties
摘要： In this paper, we reported the morphology controllable synthesis of hierarchical WO3 nanostructures, i.e. nanorods, nanospheres and nanoflowers, via a facile hydrothermal route. All the obtained WO3 nanostructures were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET), respectively. A possible growth mechanism for the three various nanomaterials was proposed in detail. WO3 based gas sensors were fabricated with the synthesized nanomaterials and the gas sensing performances to acetylene (C2H2), one of the fault characteristic gases dissolved in power transformer oil, were systematically measured. It was found that the sensor based on nanosheet-assembled nanoflowers with largest surface (56.74 m2g-1) exhibits the highest sensing performance including gas response (32.31) and response-recovery time (12 s, 17 s) to 200 ppm C2H2. The results indicate that WO3 sensing materials could be a promising choice for synthesizing high-performance C2H2 sensors for the judgement of the early latent faults of the oil immersed transformer.
关键词： Hierarchical WO3,Gas sensors,Growth mechanism,C2H2 sensing performances
更新于2025-09-23 15:22:29
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Plasmoelectronic-Based Ultrasensitive Assay of Tumor Suppressor microRNAs Directly in Patient Plasma: Design of Highly Specific Early Cancer Diagnostic Technology
摘要： It is becoming understood that microRNAs hold great promise for non-invasive liquid biopsies for screening for different types of cancer, but current state-of-the-art RT-PCR and microarray techniques have sensitivity limitations that currently restrict their use. Herein, we report a new transduction mechanism involving delocalization of photoexcited conduction electrons wavefunction of gold triangular nanoprism (Au TNP) in the presence of -ssDNA/microRNA duplexes. This plasmoelectronic effect increases the electronic dimension of Au TNPs and substantially affects their localized surface plasmon resonance (LSPR) properties that together allow us to achieve a sensitivity for microRNA assay as low as 140 zeptomolar concentrations for our nanoplasmonic sensors. We show that the position of a single base-pair mismatch in the -ssDNA/microRNA duplex dramatically alters the LSPR properties and detection sensitivity. The unprecedentedly high sensitivity of nanoplasmonic sensors has allowed us to assay four different microRNAs (microRNA-10b, -182, -143 and -145) from bladder cancer patient plasma (50 μL/sample). For the first time, we demonstrate the utility of a label-free, nanoplasmonic sensor in quantification of tumor suppressor microRNAs - the level of tumor suppressor microRNAs goes down in cancer patient as compared to normal healthy individuals - in metastatic and non-metastatic bladder cancer patient plasma. Our statistical analysis of patient samples unequivocally suggests that the tumor suppressor microRNAs are more specific biomarkers (p-value of <0.0001) than oncogenic microRNAs for differentiation between metastatic and non-metastatic bladder cancer, and non-metastatic cancer from healthy individuals. This work demonstrating the electron wavefunctions delocalization dependent ultrasensitive LSPR properties of noble metal nanoparticles has a great potential for fabrication of miniaturized and extremely powerful sensors to investigate microRNA properties in other cancers (for example breast, lung, and pancreatic) through liquid biopsy.
关键词： nanoplasmonic sensors,ultrasensitive detection,microRNAs,LSPR,liquid biopsy,bladder cancer,plasmoelectronic effect
更新于2025-09-23 15:22:29
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[ACM Press Proceedings of the 14th EAI International Conference - Melbourne, VIC, Australia (2017.11.07-2017.11.10)] Proceedings of the 14th EAI International Conference on Mobile and Ubiquitous Systems Computing Networking and Services - Sensor Agnostic Photoplethysmogram Signal Quality Assessment using Morphological Analysis
摘要： In this article, we propose a method to assess the clinical usability of fingertip Photoplethysmogram (PPG) waveform, collected from medical grade oximeter (train data) and smartphone (test data). We introduce a set of novel Signal Quality Indices (SQIs) to represent the noise characteristics of the PPG waveform. The SQIs are presented to a random forest classifier to discriminate between clean and noisy signals. The proposed method was evaluated on datasets annotated by four experts, resulting into a sensitivity and specificity of (92 + ? 4.7 % , 95 + ? 4.6 % , 95.4 + ? 3.1 %) on train and test data respectively. Further we applied the proposed method on PPG waveform of clinically proven control and disease population of Coronary Artery Disease (CAD), which resulted into (77 %,77 %) of sensitivity and specificity respectively.
关键词： Artefact,Noise Detection,Photoplethysmogram,Wearable Sensors,Morphology,Mobile Health
更新于2025-09-23 15:22:29
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Properties of Porous Silicon Precipitated with Nickel for Gas Sensors
摘要： The preparation and properties of modified porous silicon is discussed and a proposal of a sensitive layer for a gas detector is presented. The modification is done by precipitation and electrochemical deposition of nickel. The morphology of sample surfaces is examined by atomic force microscopy and scanning electron microscopy (SEM). SEM-coupled energy dispersive spectroscopy is used to analyse the chemical composition of the samples. Magnetic response is measured with a SQUID magnetometer. Electrochemical impedance spectroscopy is used to study the sensitivity of the samples to isopropanol vapour in the presence of alternating electric current. A series of samples prepared with a higher anodic current density show higher sensitivity to isopropanol vapours in comparison to a lower anodic current.
关键词： Electrochemical Impedance Spectroscopy,Porous Silicon,Gas Sensors,SQUID,Electroless Nickel Deposition,Atomic Force Microscopy
更新于2025-09-23 15:22:29
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Response Time of a Fiber Bragg Grating Based Hydrogen Sensor for Transformer Monitoring
摘要： We developed and optimized a new fiber optic sensor using palladium foils attached to optical fiber Bragg gratings (FBG) for hydrogen measurements. Fifteen in parallel processed sensors were characterized and qualified in two custom tailored experimental set ups and their response to a 5% hydrogen/nitrogen gas mixture and the same gas bubbled trough transformer oil was measured. The hydrogen response is similar for both medium and close to the theoretical maximum sensitivity, but the response time was found to be very different, much slower in oil than in gas. A theoretical comparison of hydrogen diffusion trough palladium and hydrogen absorption on the palladium surface as well as a measurement of the hydrogen uptake and diffusion trough the oil to the sensor have been done to investigate the origin of the different response time. They indicate that the response time determining step is the absorption of hydrogen on the palladium surface and that this process is slowed down in oil compared to a pure gas environment.
关键词： hydrogen sensor,fibre Bragg grating (FBG),fiber sensor,palladium based sensors,hydrogen diffusion and absorption in oil
更新于2025-09-23 15:22:29
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FVI—A Floating Vegetation Index Formed with Three Near-IR Channels in the 1.0–1.24 μm Spectral Range for the Detection of Vegetation Floating over Water Surfaces
摘要： Through the analysis of hyperspectral imaging data collected over water surfaces covered by floating vegetation, such as Sargassum and algae, we observed that the spectra commonly contain a reflectance peak centered near 1.07 μm. This peak results from the competing effects between the well-known vegetation reflectance plateau in the 0.81–1.3 μm spectral range and the absorption effects above 0.75 μm by liquid water within the vegetation and in the surrounding water bodies. In this article, we propose a new index, namely the floating vegetation index (FVI), for the hyperspectral remote sensing of vegetation over surface layers of oceans and inland lakes. In the formulation of the FVI, one channel centered near 1.0 μm and another 1.24 μm are used to form a linear baseline. The reflectance value of the third channel centered at the 1.07-μm reflectance peak above the baseline is defined as the FVI. Hyperspectral imaging data acquired with the AVIRIS (Airborne Visible Infrared Imaging Spectrometer) instrument over the Gulf of Mexico and over salt ponds near Moffett Field in southern portions of the San Francisco Bay were used to demonstrate the success in detecting Sargassum and floating algae with this index. It is expected that the use of this index for the global detection of floating vegetation from hyperspectral imaging data to be acquired with future satellite sensors will result in improved detection and therefore enhanced capability in estimating primary production, a measure of how much carbon is fixed per unit area per day by oceans and inland lakes.
关键词： Sargassum,sensors,remote sensing,hyperspectrum,vegetation index,algae
更新于2025-09-23 15:22:29
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Smart Optical Catheters for Epidurals
摘要： Placing the needle inside the epidural space for locoregional anesthesia is a challenging procedure, which even today is left to the expertise of the operator. Recently, we have demonstrated that the use of optically sensorized needles significantly improves the effectiveness of this procedure. Here, we propose an optimized configuration, where the optical fiber strain sensor is directly integrated inside the epidural catheter. The new design allows the solving of the biocompatibility issues and increases the versatility of the former configuration. Through an in vivo study carried out on a porcine model, we confirm the reliability of our approach, which also opens the way to catheter monitoring during insertion inside biological spaces.
关键词： medical optics instrumentation,fiber optics sensors,clinical applications,fiber Bragg gratings
更新于2025-09-23 15:22:29
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Hand Gesture Recognition in Automotive Human–Machine Interaction Using Depth Cameras
摘要： In this review, we describe current Machine Learning approaches to hand gesture recognition with depth data from time-of-flight sensors. In particular, we summarise the achievements on a line of research at the Computational Neuroscience laboratory at the Ruhr West University of Applied Sciences. Relating our results to the work of others in this field, we confirm that Convolutional Neural Networks and Long Short-Term Memory yield most reliable results. We investigated several sensor data fusion techniques in a deep learning framework and performed user studies to evaluate our system in practice. During our course of research, we gathered and published our data in a novel benchmark dataset (REHAP), containing over a million unique three-dimensional hand posture samples.
关键词： time-of-flight sensors,hand gesture recognition,automotive,human–machine interaction,neural networks
更新于2025-09-23 15:22:29
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Left-Handed Metamaterial-Inspired Unit Cell for S-Band Glucose Sensing Application
摘要： This paper presents an oval-shaped sensor design for the measurement of glucose concentration in aqueous solution. This unit cell sensing device is inspired by metamaterial properties and is analytically described for better parametric study. The mechanism of the sensor is a sensing layer with varying permittivity placed between two nozzle-shaped microstrip lines. Glucose aqueous solutions were characterized considering the water dielectric constant, from 55 to 87, and were identified with a transmission coefficient at 3.914 GHz optimal frequency with double negative (DNG) metamaterial properties. Consequently, the sensitivity of the sensor was estimated at 0.037 GHz/(30 mg/dL) glucose solution. The design and analysis of this sensor was performed using the finite integration technique (FIT)-based Computer Simulation Technology (CST) microwave studio simulation software. Additionally, parametric analysis of the sensing characteristics was conducted using experimental verification for the justification. The performance of the proposed sensor demonstrates the potential application scope for glucose level identification in aqueous solutions regarding qualitative analysis.
关键词： sensors,metamaterial,glucose,diabetes
更新于2025-09-23 15:22:29