- 标题
- 摘要
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- 实验方案
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Field Characteristics of Spin-Torque Diode Sensitivity in the Presence of a Bias Current
摘要： The use of the spin-torque diode effect, which is generated upon the current-induced transfer of spin angular momentum in magnetic tunnel junctions, opens the prospect of considerably improving microwave sensitivity in the gigahertz frequency band over that of semiconductor Schottky diodes. In this work, the spin-diode effect of microwave signal rectification in a magnetic tunnel junction upon the resonant excitation of spin waves in the free magnetic layer as a result of the current-induced spin-transfer torque effect is analyzed theoretically. Frequency characteristics of the resonant response of a spin-torque diode to a microwave signal are calculated in the linear macrospin approximation as functions of the direction and value of the applied magnetic field and bias current. It is shown that with zero bias current, the maximum rectified voltage across a junction is obtained in the geometry of mutually perpendicular magnetizations of magnetic layers; as the resonant frequency of oscillations in a magnetic field increases, this voltage drops at the retained equilibrium orientation of spins in the layers. After the bias current is switched on, the resonance amplitude of forced oscillations of the free layer spins upon microwave excitation grows sharply at the critical point of the spin-torque diode's loss of equilibrium state stability. The linewidth at this point is limited only by nonlinear effects. Improving spin-torque diode sensitivity is important for its use in microwave holographic vision systems.
关键词： macrospin model,microwave sensitivity,ferromagnetic resonance,magnetic tunnel junction,portable spin-torque diode
更新于2025-09-19 17:15:36
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Critical Review on the Utilization of Handheld and Portable Raman Spectrometry in Meat Science
摘要： Traditional methods for the determination of meat quality-relevant parameters are rather time-consuming and destructive, whereas spectroscopic methods offer fast and non-invasive measurements. This review critically deals with the application of handheld and portable Raman devices in the meat sector. Some published articles on this topic tend to convey the impression of unrestricted applicability of mentioned devices in this field of research. Furthermore, results are often subjected to over-optimistic interpretations without being underpinned by adequate test set validation. On the other hand, deviations in reference methods for meat quality assessment and the inhomogeneity of the meat matrix pose a challange to Raman spectroscopy and multivariate models. Nonetheless, handheld and portable Raman devices show considerable potential for some applications in the meat sector.
关键词： handheld,portable,meat,mobile,review,Raman spectroscopy,meat quality
更新于2025-09-19 17:15:36
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[IEEE 2019 Photonics North (PN) - Quebec City, QC, Canada (2019.5.21-2019.5.23)] 2019 Photonics North (PN) - Effect of Aberrations in Femtosecond Laser Writing Using the Phase Mask Technique
摘要： The impedance plethysmography (IP) has long been used to monitor respiration. The IP signal is also suitable for portable monitoring of respiration due to its simplicity. However, this signal is very susceptible to motion artifact (MA). As a result, MA reduction is an indispensable part of portable acquisition of the IP signal. Often, the amplitude of the MA is much larger than the amplitude of the respiratory component in the IP signal. This study proposes a novel filtering method to remove the high-amplitude MA’s from the IP signal. The proposed method combines the idea of ε-tube loss function and an autoregressive exogenous model to estimate the MA while leaving the periodic respiratory component of the IP signal intact. Also, a regularization method is used to find the best filter coefficients that maximize the regularity of the output signal. The results indicate that the proposed method can effectively remove the MA, outperforming the popular MA reduction methods. Several different performance measures are used for the comparison and the differences are found to be statistically significant.
关键词： epsilon-tube,impedance plethysmography,portable monitoring of respiration,motion artifact reduction,Autoregressive exogenous model
更新于2025-09-19 17:13:59
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A portable non-enzyme photoelectrochemical ascorbic acid sensor based on BiVO4 electrode under 20?W LED light
摘要： BiOI film was electrodeposited deposited on fluorine doped tin oxide (FTO), then it was transformed into a nanoporous BiVO4 film by annealing at 420 ?C. The BiVO4/FTO electrode is used as photoelectrochemical (PEC) sensor to detect ascorbic acid (AA) for the first time. Under illumination of low power 20 W LED lamp, the current density of the sensor increases with the increase of AA concentration. The proposed PEC sensor exhibited a sensitive detection for AA in a wide range from 5 μM to 300 μM with a low detection limit of 1 μM (S/N=3) and sensitivity of 293 μA mM-1 cm-2. A portable AA detection device was constructed with a 20W LED lamp as the light source, BiVO4/FTO electrode as an anode, Pt as a cathode, and ammeter as a photoelectric signal receiver. The concentration of AA detected by this device is close to that measured by the electrochemical workstation (RSD<10%), which makes the sensor practical and portable.
关键词： Nanoporous BiVO4,Ascorbic acid,Portable device,Photoelectrochemical sensor
更新于2025-09-19 17:13:59
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Colorimetric Polymerase Chain Reaction Enabled by a Fast Light-Activated Substrate Chromogenic Detection Platform
摘要： Miniaturization of nucleic acid tests (NATs) into portable, inexpensive detection platforms may aid disease diagnosis in point-of-care (POC) settings. Colorimetric signals are ideal readouts for portable NATs, and it remains of high demand to develop color readouts that are simple, quantitative and versatile. Thus motivated, we report a Fast Light-Activated Substrate cHromogenic polymerase chain reaction (FLASH PCR) that uses DNA intercalating dyes (DIDs) to enable colorimetric nucleic acid detection and quantification. The FLASH system is established on our finding that DID-DNA intercalation can promote the rapid photooxidation of chromogenic substrates through light-induced production of singlet oxygen. Using this principle, we have successfully converted DID-based fluorescent PCR assays into colorimetric FLASH PCR. To demonstrate the practical applicability of FLASH PCR to POC diagnosis, we also fabricated two readout platforms, including a portable electronic FLASH reader and a paper-based FLASH strip. Using the FLASH reader, we were able to detect as low as 60 copies of DNA standards, a limit of detection (LOD) comparable with commercial quantitative PCR. The FLASH strip further enables the reader-free detection of PCR amplicons by converting the colorimetric signal into the visual measurement of distance as a readout. Finally, the practical applicability of the FLASH PCR was demonstrated by the detection and/or quantification of nucleic acid markers in diverse clinical and biological samples.
关键词： FLASH,Singlet Oxygen,Photooxidation,DNA Intercalating Dyes,Colorimetric,Nucleic Acid Tests,Paper-based Strip,Point-of-Care,Portable Electronic Reader,Polymerase Chain Reaction
更新于2025-09-19 17:13:59
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Reliability and agreement of a novel portable laser height metre
摘要： Background Human height is a simple measure with great applicability. Usually, stadiometers are used to measure height accurately. However, these may be impractical to transport and expensive. Therefore, we developed a portable and low-cost laser height metre (LHM). Objective We aimed to (1) determine intrarater and interrater reliability of our LHM and compare it to a wall-fixed stadiometer, (2) examine its agreement with the same stadiometer, and (3) determine the minimum number of recordings needed to obtain an accurate and reliable height measurement using the LHM. Methods We recruited 32 participants (18+ years)–both men and women. Two raters performed assessments on the same day blinded to each other and their reference standard measurements. We calculated intraclass correlation coefficient (ICC), coefficient of variation (CV), standard error of measurement (SEM), and Bland-Altman plots with limits of agreement (LOA). Results For both the LHM and stadiometer, we found ICC values of 0.99–1.00 (95% CI: 0.997–1.000) for both intrarater and interrater reliability. Regarding LHM intrarater reliability, SEM, CV, and LOA were 0.34 cm, 0.16%, and -1.07 to 0.73 cm, respectively. In terms of LHM interrater reliability, SEM, CV, and LOA were 0.27 cm, 0.12%, and -0.32 to 0.84 cm, respectively. As to agreement with stadiometers using one measurement, the mean difference was -0.14 cm and LOA ranged from -0.81 to 0.77 cm. Conclusion A portable and low-cost LHM, for measuring body height once, showed an excellent reproducibility within and between raters along with an acceptable agreement with a stadiometer thereby representing a suitable alternative.
关键词： portable,laser height metre,stadiometer,reliability,agreement
更新于2025-09-19 17:13:59
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A portable miniaturized laser heterodyne radiometer (mini-LHR) for remote measurements of column CH4 and CO2
摘要： We present the design of a portable version of our miniaturized laser heterodyne radiometer (mini-LHR) that simultaneously measures methane (CH4) and carbon dioxide (CO2) in the atmospheric column. The mini-LHR fits on a backpack frame, operates autonomously, and requires no infrastructure because it is powered by batteries charged by a folding 30 W solar panel. Similar to our earlier instruments, the mini-LHR is a passive laser heterodyne radiometer that operates by collecting sunlight that has undergone absorption by CH4 and CO2. Within the mini-LHR, sunlight is mixed with light from a distributive feedback (DFB) laser centered at approximately 1.64 μm where both gases have absorption features. The laser scans across these absorption features roughly every minute and the resulting beat signal is collected in the radio frequency (RF). Scans are averaged into half hour and hour data products and analyzed using the Planetary Spectrum Generator (PSG) retrieval to extract column mole fractions. Instrument performance is demonstrated through two deployments at significantly different sites in interior Alaska and Hawaii. The resolving power (λ/?λ) is greater than 500,000 at 1.64 μm with precisions of better than 20 ppb and 1 ppm for CH4 and CO2, respectively. Because mini-LHR instruments are portable and can be co-located, they can be used to characterize bias between larger, stationary, column observing instruments. In addition, mini-LHRs can be deployed quickly to respond to transient events such as methane leaks or can be used for field studies targeting geographical regions.
关键词： atmospheric column,carbon dioxide,methane,portable,miniaturized laser heterodyne radiometer
更新于2025-09-19 17:13:59
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Determining DHO detection limits for a frequency domain THz spectrometer coupled to a light-weight multi-pass sample cell
摘要： A terahertz spectrometer connected to a custom fabricated, light-weight multi-meter multi-pass sample cell was employed to measure the 1.492 THz, 1.507 THz and 1.523 THz molecular transitions of DHO over various pressures. We will report on the detectable concentrations of the DHO achieved with the portable instrument.
关键词： portable instrument,DHO,terahertz spectroscopy,multi-pass sample cell
更新于2025-09-16 10:30:52
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Portable Optical Fiber Bragg Grating Sensor for Monitoring Traffic Density
摘要： The paper examines the development of a portable sensor strip with fiber optic Bragg grating for monitoring urban traffic density up to 80 kph. It contains a 2.5-m-long and a 2-cm-high sensor created from a combination of silicone addition rubber (bicomponent addition silicone rubber) and Bragg grating placed inside a carbon tube. The design of the portable sensor permits traffic density and cars crossings to be monitored and detected in a single lane. The functionality of the sensor was verified in real traffic; the results of this study are based on the detection of 1518 vehicles of different types and sizes. According to the measurements, the sensor is characterized by a high detection rate of 98.946%.
关键词： portable sensor,car detection,Fiber Bragg Grating,optical fiber,density traffic monitoring
更新于2025-09-16 10:30:52
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[IEEE 2019 41st Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC) - Berlin, Germany (2019.7.23-2019.7.27)] 2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - A prototype system of portable laser speckle imager based on embedded graphics processing unit platform
摘要： Laser speckle contrast imaging (LSCI) is a high-resolution full-field optical technique for measuring blood flow, which has been widely used in clinical and biomedical research. However, most of the current LSCI instruments are bulky, limiting their application settings. In this work, we proposed a prototype system of portable laser speckle imager. Different from the desktop laser speckle systems that utilize personal computer (PC), our system was designed with embedded GPU system (Jetson TX2, NVIDIA, USA) and a LCD touch screen (16.5 × 12.4 cm in size, 380 g in weight). In-vivo experiments showed that the portable GPU-based system had comparable performance with our laboratory LSCI system. Such a portable LSCI imager could be potentially used in a situation that requires for easy operation and installation, such as intraoperative monitoring or bedside diagnosis.
关键词： Laser speckle contrast imaging,portable,blood flow,embedded GPU,real-time monitoring
更新于2025-09-12 10:27:22