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[IEEE 2018 IEEE Biomedical Circuits and Systems Conference (BioCAS) - Cleveland, OH, USA (2018.10.17-2018.10.19)] 2018 IEEE Biomedical Circuits and Systems Conference (BioCAS) - A 6.25 Mbps, 12.4 pJ/bit DQPSK Backscatter Wireless Uplink for the NeuroDisc Brain-Computer Interface
摘要： Wireless brain-computer interfaces (BCIs) used for fundamental neuroscience research in freely moving non-human primates (NHPs) require communication systems capable of transferring large volumes of recorded neural data while consuming minimal power. We introduce a 6.25 Mbps differential quadrature phase-shift keying (DQPSK) backscatter wireless uplink for the NeuroDisc BCI, operating in the 902-928 MHz industrial, scientific, and medical (ISM)-band. The backscatter uplink consumes 77.5 μW (only 0.06% of the system power budget), yielding a communication energy efficiency of 12.4 pJ/bit, while the measured error vector magnitude of the DQPSK constellation is 9.69%. The neural recording front-end has a measured input-referred noise of 2.35 μVrms at a maximum sampling rate of 20 kSps. We present end-to-end recording and wireless uplink validation with pre-recorded neural data as well as in vivo recordings from a pigtail macaque.
关键词： implanted biomedical devices,neural recording,backscatter communication
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Conference on RFID Technology & Application (RFID-TA) - Macau, Macao (2018.9.26-2018.9.28)] 2018 IEEE International Conference on RFID Technology & Application (RFID-TA) - Perfectly Synchronized Streaming from Digitally Modulated Multiple Backscatter Sensor Tags
摘要： This paper proposes a multiple access method, referred to as Multiple Subcarrier Multiple Access (MSMA), for perfectly synchronized concurrent data collection from a group of passive backscatter wireless sensor tags and its experimental evaluation. By achieving less than 128 micro second synchronization error, backscatter communications can be applied to structural health monitoring of artifacts such as civil structures and machineries. In MSMA, each sensor tag uses a dedicated subcarrier frequency to produce a modulated backscatter. The sensor data is superposed onto the subcarrier either with an analog or a digital modulation. The inevitable harmonics among the subcarriers, stemming from the backscatter principle, can be rejected by numerically calculating the harmonic replicas and subtracting them from the observed signal in a software defined receiver. A frame based signal processing in the receiver results in no relative synchronization error among subcarriers even after the interference rejection. Since the interference rejection can be done before the demodulation and decoding, the concurrency can be secured irrespective to the choice of modulation method. We developed a prototype of MSMA using LabVIEW communications Software Defined Radio environment and prototype sensor tags using discrete electrical parts. The performances and limitation of MSMA using digitally modulated subcarriers are evaluated both in wired and wireless environments with up to four backscatter sensors.
关键词： Structural Health Monitoring,Software Defined Radio,Interference Rejection,Passive backscatter
更新于2025-09-23 15:22:29
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Multispectral Airborne LiDAR Data in the Prediction of Boreal Tree Species Composition
摘要： Multispectral light detection and ranging (LiDAR) instruments, such as Optech Titan, record intensities at multiple wavelengths and these intensities can be used for tree species prediction in the same way as multispectral image data. In this paper, our main objective was to compare the accuracy of tree species prediction in a boreal forest area using multispectral LiDAR, the 1064-nm wavelength channel ('unispectral LiDAR'), and unispectral LiDAR with auxiliary aerial image data. We also evaluated the effect of the widely used intensity range correction method. We classified the main tree species of field plots using linear discriminant analysis (LDA) and predicted the species-specific volume proportions (%) for Scots pine (Pinus sylvestris), Norway spruce (Picea abies), and broadleaved trees using the k-nearest neighbor imputation. The effect of intensity correction on prediction errors for the dominant tree species was evaluated using optimal parameters derived from: 1) minimal intensity difference between flight lines; 2) parameters suggested by theory; and 3) uncorrected data. Although the range correction increased the classification accuracy slightly, it was observed to be ambiguous, and not consistent with theory for canopy echoes. Regardless, the intensity values were useful for the prediction of dominant tree species and species' volume proportions. The results for the dominant tree species classification using multispectral LiDAR [overall accuracy (OA) 88.2%, kappa 0.79] were comparable to the use of unispectral LiDAR and aerial images (OA 89.1%, kappa 0.81). We conclude that the multispectral LiDAR may become a useful tool in operational species-specific forest inventories.
关键词： laser backscatter intensity,k-nearest neighbor (k-NN),Intensity correction,linear discriminant analysis (LDA),multispectral airborne laser scanning,tree species classification
更新于2025-09-23 15:22:29
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Dependence of h-BN film thickness as grown on nickel single crystal substrates of different orientation
摘要： Chemical vapor deposition of 2D materials has been an active area of research in recent years because it is a scalable process for obtaining thin films that can be used to fabricate devices. The growth mechanism for hexagonal boron nitride (h-BN) on metal catalyst substrates has been described to be either surface energy driven or diffusion driven. In this work, h-BN is grown in a CVD system on Ni single crystal substrates as a function of Ni crystallographic orientation to clarify the competing forces acting on the growth mechanism. We observed that the thickness of the h-BN film depends on the Ni substrate orientation, with the growth rate increasing from the (100) surface to the (111) surface, and the highest on the (110) surface. We associate the observed results with surface reactivity and diffusivity differences for different Ni orientations. Boron and nitrogen diffuse and precipitate from the Ni bulk to form thin multilayer h-BN. Our results serve to clarify the h-BN CVD growth mechanism which has been previously ascribed to a surface energy-driven growth mechanism.
关键词： surface diffusion,electron backscatter diffraction,growth mechanism,hexagonal boron nitride
更新于2025-09-23 15:21:01
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[ACM Press the 2018 ACM International Joint Conference and 2018 International Symposium - Singapore, Singapore (2018.10.08-2018.10.12)] Proceedings of the 2018 ACM International Joint Conference and 2018 International Symposium on Pervasive and Ubiquitous Computing and Wearable Computers - UbiComp '18 - A Visible Light Backscatter Communication Solution for Low-cost Parking Space Detection
摘要： We introduce an intelligent parking space detection system based on PassiveVLC, a visible light backscatter communication technology. Its substrate is retroreflection – by instrumenting retroreflector in each parking space, we are able to detect the vacancy of parking space based on whether the lighting infrastructure receives the light reflection or not from that particular parking lot. We further design and implement a MAC protocol to improve the scalability of our system.
关键词： MAC,Parking Space Detection,Visible Light Backscatter Communication,PassiveVLC
更新于2025-09-23 15:21:01
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Characterization and correlation of microstructure and hardness of Tia??6Ala??4V sheet surface-treated by pulsed laser
摘要： A hot-rolled Tie6Ale4V (Ti-64) sheet was surface-treated by pulsed laser at two different powers (100 and 200 W), with microstructural features and hardness before and after the laser surface treatment (LST) systematically investigated. Results show that after the LST at both powers there are two modi?cation zones with distinct microstructural characteristics: melted zone (MZ) near the laser beam center, completely composed of ?ne martensitic plates with dense {10e11} nanotwins inside them; heat-affected zone (HAZ) far away from the laser beam center, comprised of mixed structures of short-rod b particles, martensitic plates and untransformed bulk a grains. Hardness measurements reveal that the hardness of the Ti-64 sheet can be markedly increased (especially in the MZ) after the LST. In-depth analyses suggest that the hardness increase in the MZ can be ascribed to combined contributions from grain re?nement, presence of nanotwins and solid solution of alloying elements, while only the structural re?nement by ?ne plate structures contributes to hardening in the HAZ. Comparisons between both the LSTed specimens reveal that increasing the laser power from 100 W to 200 W can effectively enlarge the laser-modi?ed zones (both the MZ and the HAZ) and simultaneously re?ne plate structures, leading to further hardness increase.
关键词： Ti-6Ale4V,Hall-petch relation,Hardness,Electron backscatter diffraction,Pulsed laser
更新于2025-09-23 15:19:57
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Radiation fog formation alerts using attenuated backscatter power from automatic lidars and ceilometers
摘要： Radiation fog occurs over many locations around the world in stable atmospheric conditions. Air traffic at busy airports can be significantly disrupted because low visibility at the ground makes it unsafe to take off, land and taxi on the ground. Current numerical weather prediction forecasts are able to predict general conditions favorable for fog formation, but not the exact time or location of fog occurrence. A selected set of observations available in near-real time at strategic locations could also be useful to track the evolution of key processes and key parameters that drive fog formation. Such observations could complement the information predicted by numerical weather prediction (NWP) models that is made available to airport forecasters in support of their fog forecast. This paper presents an experimental setup based on collocated automatic lidar and ceilometer measurements, relative humidity measurements and horizontal visibility measurements to study hygroscopic growth of fog condensation nuclei. This process can take several minutes to hours, and can be tracked using lidar- or ceilometer-attenuated backscatter profiles. Based on hygroscopic growth laws we derive a set of parameters that can be used to provide alerts minutes to hours prior to formation of radiation fog. We present an algorithm that uses the temporal evolution of attenuated backscatter measurements to derive pre-fog formation alerts. The performance of the algorithm is tested on 45 independent pre-fog situations at two locations (near Paris, France, and Brussels, Belgium). We find that an alert for pre-fog conditions predominantly occurs 10–50 min prior to fog formation at an altitude ranging 0 to 100 m above ground. In a few cases, alerts can occur up to 100 min prior to fog formation. Alert durations are found to be sensitive to the relative humidity conditions found a few hours prior to the fog.
关键词： hygroscopic growth,fog formation alerts,automatic lidars and ceilometers,attenuated backscatter power,Radiation fog
更新于2025-09-23 15:19:57
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A Turbulence-Oriented Approach to Retrieve Various Atmospheric Parameters Using Advanced Lidar Data Processing Techniques
摘要： The article is aimed at presenting a semi-empirical model coded and computed in the programming language Python, which utilizes data gathered with a standard biaxial elastic lidar platform in order to calculate the altitude profiles of the structure coefficients of the atmospheric refraction index C2N(z) and other associated turbulence parameters. Additionally, the model can be used to calculate the PBL (Planetary Boundary Layer) height, and other parameters typically employed in the field of astronomy. Solving the Fernard–Klett inversion by correlating sun-photometer data obtained through our AERONET site with lidar data, it can yield the atmospheric extinction and backscatter profiles α(z) and β(z), and thus obtain the atmospheric optical depth. Finally, several theoretical notions of interest that utilize the solved parameters are presented, such as approximated relations between C2N(z) and the atmospheric temperature profile T(z), and between the scintillation of backscattered lidar signal and the average wind speed profile U(z). These obtained profiles and parameters also have several environmental applications that are connected directly and indirectly to human health and well-being, ranging from understanding the transport of aerosols in the atmosphere and minimizing the errors in measuring it, to predicting extreme, and potentially-damaging, meteorological events.
关键词： RCS,temperature profile,structure coefficients,environment,human health,atmospheric extinction,atmospheric backscatter,wind speed profile,lidar,turbulence
更新于2025-09-19 17:15:36
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The effect of fluorescence on surface dose with superficial X-rays incident on tissue with underlying lead
摘要： An Advanced Markus chamber on the surface of solid water phantom was used to determine surface dose reduction, with either a lead or air interface, as a function of surface-interface separation (t). The beam quality dependence of dose reduction was investigated using the 50 kV, 100 kV and 150 kV beams of an Xstrahl 150 superficial X-ray unit. For each beam the dose correction factor, DCF(t), namely the ratio of surface dose (t) to surface dose (t = 100 mm), was determined. Monte Carlo simulations of DCF(t) with a lead interface were compared with corresponding measured values. Simulated spectra were calculated at the phantom surface for full backscatter (t = 100 mm) and with either a lead or air interface at 2 mm or 8 mm depth. For each depth and beam quality lead fluorescent radiation at the surface was evident. The variation of DCF(t) for each beam and field size exhibits a minima at t ≈ 5 mm and in the range 1 mm ≤ t ≤ 40 mm surface dose reduction is larger for 100 kV than 150 kV. Monte Carlo simulated DCF(t) are consistent with corresponding measured DCF(t). From simulated spectra L-series fluorescent X-rays (≈ 15 keV) emanating from lead at t = 2 mm are evident for all beams and fluorescent K-series X-rays only occur with 100 kV and 150 kV beams.
关键词： Superficial X-rays,Backscatter reduction due to lead
更新于2025-09-19 17:15:36
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Surface microstructural characteristics and hardness of Cr-coated Zr702 sheet processed by pulsed laser
摘要： Microstructural characteristics and hardness of Cr-coated Zr702 sheet after the laser surface treatment (LST) were characterized and investigated by combined use of electron backscatter diffraction, electron channeling contrast imaging, energy dispersive spectrometry and hardness measurement. Results show that after the LST processing at 100 W, three zones with different microstructural characteristics are presented from the surface to the matrix: melted zone (MZ), solid-state phase transformation zone (SSPTZ) and matrix. Surface alloying with Cr occurs in the MZ, leading to the formation of a large number of discontinuous netlike ZrCr2 Laves phases. The SSPTZ is comprised of untransformed bulk α grains with internal substructures and fine martensitic plates. The appearance of such substructures can be attributed to dislocation movements induced by thermal stresses while the martensitic plates result from rapid β→α transformation induced by the pulsed laser. Hardness measurements show that the LST can remarkably increase surface hardness (by ~110%) of the Cr-coated Zr702 sheet, which can be ascribed to strengthening/hardening effects by solid solution of Cr, the formation of dense second phases and significant grain refinement.
关键词： Electron backscatter diffraction,Microstructure,Hardness,Laves phase,Zr702 sheet,Laser surface processing
更新于2025-09-19 17:13:59