- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Off-Grid Compressive Channel Estimation for mm-Wave Massive MIMO with Hybrid Precoding
摘要： To reduce the pilot overhead and improve the channel estimation accuracy in the massive MIMO system, various channel estimation algorithms employing the sparse signal reconstruction (SSR) scheme have been proposed. However, the spatial grid division leads to the trade-off between the estimation accuracy and the computational complexity. In addition, when the true angle is not on the discretized grid point which is referred as off-grid problem, the performance of SSR-based algorithms will degrade heavily. In this letter, a novel channel estimation algorithm which achieves superior performance under the off-grid scenario is proposed. At first, the conventional joint angle of arrivals/departures (AoAs/AoDs) estimation is transformed into two one-dimensional sub-problems. Then, the SSR-based framework is presented to obtain the initial sparse-support set. By minimizing the constructed objective function, the off-grid errors regarded as adjustable parameters are iteratively refined. In addition, scatter gains are acquired by LSE. Numerical simulations are provided to illustrate the superiority of the proposed algorithm in terms of estimation accuracy and computational complexity.
关键词： channel estimation,millimeter wave,massive MIMO,off-grid refinement,Compressive sensing
更新于2025-09-23 15:23:52
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Tuning the electrical properties of graphene oxide by nitrogen ion implantation: Implication for gas sensing
摘要： Tailoring the electrical properties of graphene oxide (GO) is one of the important requirements for its application in future electronic devices. A modified Hummer’s method was employed in the preparation of GO and spray coated on glass substrates, subsequently drying at 60 °C for 6 h. The as prepared samples were implanted with 100 keV nitrogen ions at the fluences of 1E15, 5E15 and 1E16 ions/cm2. A peak shift to higher 2θ in XRD pattern indicates the reduction of GO to rGO after N ion implantation. The intensity ratio of G and D bands (IG/ID) for GO derived from the Raman analysis increased from 0.97 to 1.02 after implantation (1E16 ions/cm2). The EDS analysis confirms the implantation of N ions in GO. The electrical conductivity improved as a function of fluence, and observed to be high for the sample of 1E16 ions/cm2, and is tested for methanol sensing. Concentration dependent methanol sensing shows 5.9% response for 300 ppm. Above results show that ion implantation is a promising method for controlled reduction of GO for tuning the electrical properties.
关键词： Ion implantation,Gas sensing,Graphene oxide,Reduced graphene oxide
更新于2025-09-23 15:23:52
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AR aided Smart Sensing for In-line Condition Monitoring of IGBT Wafer
摘要： This paper describes an augmented reality (AR) aided smart sensing technique, for in-line condition monitoring of IGBT wafers. A series of signal processing algorithms are applied for enabling sensor intelligence. Based on electromagnetic infrared-visible-fusion (IVF), a supplementary palpable 3-D thermography layer is integrated with an IGBT wafer in real world environment. Before the IVF, independent component analysis (ICA) is implemented to identify defects in the wafer. The proposed AR aided smart sensing technique enhances user's perception and interaction between the industrial systems and the surrounding world. In contrast to conventional sensor techniques, it provides a non-destructive testing and evaluation (NDT&E) based high-throughput in-line condition monitoring method. The advantages of non-contact and time efficient of this smart sensing technique potentially bring huge benefit to yield management and production efficiency. AR aided smart sensing can improve the productivity, quality and reliability of power electronic materials and devices, as well as in other industrial applications.
关键词： Wafers,IGBT,Thermography,Non-destructive testing,Pulsed Eddy Current,Augmented Reality,Smart sensing
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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Semisupervised Scene Classification for Remote Sensing Images: A Method Based on Convolutional Neural Networks and Ensemble Learning
摘要： The scarcity of labeled samples has been the main obstacle to the development of scene classification for remote sensing images. To alleviate this problem, the efforts have been dedicated to semisupervised classification which exploits both labeled and unlabeled samples for training classifiers. In this letter, we propose a novel semisupervised method that utilizes the effective residual convolutional neural network (ResNet) to extract preliminary image features. Moreover, the strategy of ensemble learning (EL) is adopted to establish discriminative image representations by exploring the intrinsic information of all available data. Finally, supervised learning is performed for scene classification. To verify the effectiveness of the proposed method, it is further compared with several state-of-the-art feature representation and semisupervised classification approaches. The experimental results show that by combining ResNet features with EL, the proposed method can obtain more effective image representations and achieve superior results.
关键词： remote sensing (RS) images,Semi-supervised classification,ensemble learning (EL),scene classification,Convolutional neural networks (CNNs)
更新于2025-09-23 15:23:52
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Achieving high-resolution thermal imagery in low-contrast lake surface waters by aerial remote sensing and image registration
摘要： A two-platform measurement system for realizing airborne thermography of the Lake Surface Water Temperature (LSWT) with ~0.8 m pixel resolution (sub-pixel satellite scale) is presented. It consists of a tethered Balloon Launched Imaging and Monitoring Platform (BLIMP) that records LSWT images and an autonomously operating catamaran (called ZiviCat) that measures in situ surface/near surface temperatures within the image area, thus permitting simultaneous ground-truthing of the BLIMP data. The BLIMP was equipped with an uncooled InfraRed (IR) camera. The ZiviCat was designed to measure along predefined trajectories on a lake. Since LSWT spatial variability in each image is expected to be low, a poor estimation of the common spatial and temporal noise of the IR camera (nonuniformity and shutter-based drift, respectively) leads to errors in the thermal maps obtained. Nonuniformity was corrected by applying a pixelwise two-point linear correction method based on laboratory experiments. A Probability Density Function (PDF) matching in regions of overlap between sequential images was used for the drift correction. A feature matching-based algorithm, combining blob and region detectors, was implemented to create composite thermal images, and a mean value of the overlapped images at each location was considered as a representative value of that pixel in the final map. The results indicate that a high overlapping field of view (~95%) is essential for image fusion and noise reduction over such low-contrast scenes. The in situ temperatures measured by the ZiviCat were then used for the radiometric calibration. This resulted in the generation of LSWT maps at sub-pixel satellite scale resolution that revealed spatial LSWT variability, organized in narrow streaks hundreds of meters long and coherent patches of different size, with unprecedented detail.
关键词： Lake surface water temperature,Uncooled infrared camera,Image registration,Lake Geneva,Thermal imagery,Aerial remote sensing
更新于2025-09-23 15:23:52
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Geometric accuracy of remote sensing images over oceans: The use of global offshore platforms
摘要： The geometric accuracy of tens of millions of scenes of medium-resolution remote sensing (RS) images collected in the past 45 years has been systematically evaluated for land scenes, but the accuracy of ocean scenes is poorly known due to the lack of ground control points (GCPs). In this study, the locations of offshore platforms are first derived from time-series of Landsat-8 OLI images, and are then used as offshore reference points to systematically assess the geometric performance of RS images covering offshore oil/gas development areas. An inventory of 16,131 offshore platforms at the global scale is established, and then a novel method using the position-invariant characteristic of offshore platforms and the coherent characteristic of the geometric shift among tie-points (i.e. between sensed points from to-be-assessed images and the corresponding OLI-derived reference points) is developed for assessing the geometric accuracy of Landsat and other RS images. The method has been applied to 112,935 Landsat scenes (~1.87% of the entire archive) over oceans. The results indicate an optimal performance of Landsat OLI images (both pre-collection and Collection-1) but a less reliable performance of Landsat TM/ETM+ L1TP images. Approximately 50% of TM L1GS and ETM+ L1GT images have at least 2 pixels of geometric error. The new reference points inventory and the developed method were also applied to many other low-resolution and finer-resolution imagery (e.g. VIIRS Night-fire product, Terra/Aqua MODIS active fire product, ENVISAT ASAR, ALOS-1 PALSAR, Sentinel-1 SAR, Sentinel-2 MSI, the National Agriculture Imagery Program (NAIP) aerial images, and images from several Chinese satellites), and a quantitative description of the geometric accuracy of these sensors is also presented. The findings suggest that the new offshore reference point inventory is probably useful to help establish more robust offshore GCPs for U.S. Geological Survey (USGS) GCP library and further improve the ongoing USGS Global GCP improvement plan and European Space Agency Global Reference Image plan.
关键词： Offshore platforms,Remote sensing images,Landsat,Geometric accuracy,Ground control points
更新于2025-09-23 15:23:52
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[ASME ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - San Francisco, California, USA (Monday 27 August 2018)] ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - Next Gen Test-Vehicle to Simulate Thermal Load for IoT FPGA Applications
摘要： As semiconductor device feature size scales and circuit performance increases, power dissipation and thermal management are becoming very important. Attention to thermal considerations is required throughout the chip development cycle from preliminary architecture planning to deployment on customer board and beyond. This paper describes a versatile thermal test vehicle that can be used to address these requirements. We discuss the architecture and implementation of a specially designed test-vehicle chip, followed by its operation. The programmability and flexibility of this vehicle will be highlighted. In addition, we cover other usage of this vehicle which includes modelling of chip-level thermal behavior with different floorplan, simulating thermal loads in IoT FPGA applications, cross-calibrating thermal numerical simulators with measured silicon data and evaluating the thermal impact of different package form-factor / material (such as thermal interface material) and cooling solutions. The abovementioned chip was fabricated using 0.18um technology and assembled in a flip-chip package. The reminder of this evaluation system is a simple, inexpensive tester from which a software is run to program the chip and to measure the spatial & temporal temperature values. Measured thermal data from different use cases are presented in this paper.
关键词： on-chip temperature measurement,thermal management,package development,package-level thermal evaluation,on-die heating,IoT servers,on-die temperature sensing,characterization methodology,thermal evaluation tool
更新于2025-09-23 15:23:52
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Sensing Properties of the <I>N</I>,<I>N</I>′-Dipentyl-3,4,9, 10-Perylenedicarboximide Small Molecule for Different Concentrations and Solvents for Sensor Applications
摘要： In present study, optical parameters based on refractive index of the PTCDI-C5 molecule were calculated using the single oscillator model. Also, significant parameters such as long wavelength refractive index, average oscillator wavelength, lattice dielectric constant, ratio of the carrier concentration to the electron effective mass, carrier concentration and electron effective mass of the PTCDI-C5 molecule were obtained. Then, sensing properties of the PTCDI-C5 molecule for different concentrations and volume percents were investigated and the effects of the concentrations and volume percents on sensing parameters were investigated. Then, the optical properties of the solutions of the PTCDI-C5 semiconductor for different solvents were investigated. Finally, these parameters obtained were discussed for sensor applications and this study was compared with the similar and related studies in the literature. PTCDI-C5 can be used in the fabrication of various sensors due to good soluble, optical, sensitivity and response behaviour.
关键词： Wemple DiDomenico Technique,Sensor Applications,PTCDIC5,One Dimensional Organic Nanostructures,Sensing Parameters,Sensitivity
更新于2025-09-23 15:23:52
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Influence of Synthesis Conditions on Microstructure and NO2 Sensing Properties of WO3 Porous Films Synthesized by Non-Hydrolytic Sol–Gel Method
摘要： Nanostructured tungsten trioxide porous films were prepared by a non-hydrolytic sol–gel method following the inorganic route in which ethanol and PEG were used as the oxygen-donor and structure-directing reagent, respectively. The effects of aging time of the precursor solution, PEG content, and calcination temperature on the structure, morphology, and NO2 sensing properties of WO3 films were systematically investigated by using the techniques of X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and gas sensing measurements. The results demonstrated that a series of WO3 films with different microstructures could be obtained by manipulating the synthesis parameters. Furthermore, a suitable synthesis condition of WO3 films for NO2 sensing application was determined.
关键词： NO2,non-hydrolytic sol–gel,WO3,gas sensing,porous films
更新于2025-09-23 15:23:52