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- 实验方案
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Gaussian distribution in current-conduction mechanism of (Ni/Pt) Schottky contacts on wide bandgap AlInGaN quaternary alloy
摘要： The current-conduction mechanisms of the as-deposited and annealed at 450 °C (Ni/Pt) Schottky contacts on AlInGaN quaternary alloy have been investigated in the temperature range of 80–320 K. The zero-bias barrier height (BH) (ΦB0) and ideality factor (n) of them were evaluated using thermionic emission (TE) theory. The ΦB0 and n values calculated from the I-V characteristics show a strong temperature dependence. Such behavior of ΦB0 and n is attributed to Schottky barrier inhomogeneities. Therefore, both the ΦB0 vs n and ΦB0 vs q/2kT plots were drawn to obtain evidence on the Gaussian distribution (GD) of the barrier height at the metal/semiconductor interface. These plots show two different linear parts at low and intermediate temperatures for as-deposited and annealed Schottky contacts. Thus, the mean value of ΦB0 and standard deviation (σ0) was calculated from the linear parts of the ΦB0 vs q/kT plots for both samples. The values of the effective Richardson constant (A*) and mean BH were obtained from the modified Richardson plots which included the effect of barrier inhomogeneity. These values of Richardson constant and barrier height for as-deposited contacts were found to be 19.9 A cm?2 K?2 and 0.59 eV, respectively, at low temperature, but 43.3 A cm?2 K?2 and 1.32 eV, respectively, at intermediate temperatures. These values of Richardson constant and barrier height for annealed contacts were found to be 19.6 A cm?2 K?2 and 0.37 eV, respectively, at low temperature, but 42.9 A cm?2 K?2 and 1.54 eV, respectively, at intermediate temperatures. It is clear that the value of the Richardson constant obtained for as-deposited and annealed samples by using double-GD for intermediate temperatures is close to the theoretical value of AlInGaN (=44.7 A cm?2 K?2). Therefore, I-V-T characteristics for the as-deposited and annealed Schottky contacts in the temperature range of 80–320 K can be successfully explained based on TE theory with double-GD of the BHs.
关键词： AlInGaN,barrier height,Schottky contacts,Gaussian distribution,thermionic emission
更新于2025-09-11 14:15:04
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Modulation of acoustic radiation forces on three-layered nucleate cells in a focused Gaussian beam
摘要： The acoustic cell manipulation is of great interest to many applications. A three-layered micro-shell (TLS) model is proposed to simulate the three-layered nucleate cell. Acoustic radiation forces (ARFs) of a focused Gaussian beam on the TLS are studied theoretically. The ARF may change from positive to negative if the TLS moves across the centre of the beam waist. It is found that the geometry parameters of the TLS have great influence on the ARF. The positive ARF increases with the inner core radius while the negative ARF grows strong at first and then descends. With increasing thickness of the outer shell, the positive ARF is enhanced while the negative ARF is depressed and might even turn into positive. We further found that sound velocities in the TLS also affect the ARF significantly.
关键词： acoustic radiation forces,acoustic cell manipulation,three-layered nucleate cells,focused Gaussian beam
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE 3rd International Conference on Image, Vision and Computing (ICIVC) - Chongqing (2018.6.27-2018.6.29)] 2018 IEEE 3rd International Conference on Image, Vision and Computing (ICIVC) - Detection of Vehicle Flow in Video Surveillance
摘要： Existing detection algorithms of vehicle flow in video detect moving objects by per pixel, so they may be corrupted by noises and the computational costs are high. In this paper, we propose a robust moving vehicle detection algorithm with background dictionary learning. An improved vehicle flow detection algorithm based on virtual regions and virtual lines is presented. To do this, we firstly divide an image into multiple image patches that have the same sizes. Each patch is an object or a background. Then, a background dictionary is learnt for each patch. The similarity between a patch and the background dictionary is measured, upon which a patch is distinguished as an object or a background. Additionally, the virtual detection line is used and combined into the virtual regions to detect the vehicles. Experimental results demonstrate the real-time and accuracy of the proposed detection algorithm.
关键词： background dictionary,video,Gaussian model,vehicle flow detection
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Moving Target Detection and Tracking Based on Gmphd Filter in SAR System
摘要： In this paper, a novel moving target detection and tracking approach is presented based on Gaussian mixture probability hypothesis density (GMPHD) filter in synthetic aperture radar (SAR). Based on the advantages of GMPHD filter and the characteristics of moving target in SAR imagery, GMPHD filter is employed on potential moving target candidates extracted from a sequence of temporal and spatial sub-aperture SAR images to detect and track the moving targets in heavy clutter environment. Utilizing the tracking algorithm, the states and the number of moving targets are obtained over time. Simultaneously, the strong ground stationary clutter lacking of the dynamic behavior is eliminated finally. Both simulation and real Gotcha data set processing results are provided to demonstrate the effectiveness of the proposed approach.
关键词： Clutter suppression,Gaussian mixture probability hypothesis density (GMPHD) filter,Moving target tracking,Ground moving target indication (GMTI),Synthetic aperture radar (SAR)
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - The Sensagri Sentinel-2 Lai Green and Brown Product: from Algorithm Development Towards Operational Mapping
摘要： While the mapping of LAI green (LAIG) is well established, current operational products are not calibrated for LAI brown (LAIB), i.e. LAI estimation over senescent vegetation. With Sentinel-2 (S2) new opportunities are opened to estimate LAI brown. An explicit distinction between LAIG and LAIB can be achieved thanks to the S2 bands in the red edge (B5:705 nm and B6:740 nm) and in the shortwave infrared (B11:1610 nm). By using LAI ground measurements data from multiple campaigns together with available S2 data, independent LAIG and LAIB models were optimized using Gaussian processes regression (LAIG: R2=0.89, NRMSE=7.1%; LAIB: R2=0.75, NRMSE=13.7%). These models can then be combined into LAIGB composite maps. The uncertainty estimates were used to map only those LAI estimated values that fall within a 50% uncertainty threshold. As only the vegetated areas fall within that threshold there is no need to apply additional masks. For multiple European core test sites, LAIGB composite maps were generated from S2 images, enabling to quantify when crops start senescing across the European regions.
关键词： Gaussian processes regression,LAI green,Sentinel-2,LAI brown
更新于2025-09-10 09:29:36
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Investigation on Reconstruction for Frequency Domain Photoacoustic Imaging via TVAL3 Regularization Algorithm
摘要： Photoacoustic imaging (PAI) has been widely investigated by researchers from a range of areas. According to the differences between excitation laser sources, PAI can be categorized into two main types, namely the time-domain and frequency-domain PAI. Although the frequency-domain approach is more portable and economic than the other alternative, the low intensity of excitation source may lead to a lower signal-to-noise ratio (SNR). This paper aiming to propose the suitable scheme for image reconstruction, we focus on the model-based PAI system and make great efforts to reduce the impact of noise algorithmically. Three regularization algorithms, i.e., Least Square QR-factorization, Tikhonov, and Total Variation minimization by Augmented Lagrangian and alternating direction algorithms (TVAL3) are studied. By choosing three important parameters as criteria, i.e., the peak SNR, image quality index, and time consumption during different situations, the most effective regularization algorithm amongst has been selected. Based on simulation results and detailed discussions, TVAL3 algorithm performs better than the other two for model-based signal reconstruction. The result is pivotal for effective PAI in high quality and highly ef?cient biomedical tomography and microimaging.
关键词： imaging parameters,Photoacoustic imaging (PAI),regularization algorithms,white Gaussian noise (WGN),stochastic noise (SN)
更新于2025-09-10 09:29:36
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[IEEE 2018 International Symposium in Sensing and Instrumentation in IoT Era (ISSI) - Shanghai, China (2018.9.6-2018.9.7)] 2018 International Symposium in Sensing and Instrumentation in IoT Era (ISSI) - Image Denoising Using Asymmetric Gaussian Mixture Models
摘要： Finite mixture models are widely applied in image denoising because they have sound mathematical basis and the results are interpretable. In a manner of speaking, they can give a mathematical description of natural images by clustering. Usually assume that per-component of natural images follow a mixture of Gaussian(GMM) when doing image denoising. However, it is well- know that most of natural images are intricate and of which the distribution is highly non-Gaussian. So there remain problems that GMM cannot fix. In this paper, we introduce the asymmetric Gaussian mixture models into the finite mixture model, in which GMM is a special case. Asymmetric Gaussian Mixture (AGM) can model asymmetric distribution which is more conform to the data of natural images. We do some experiments in image denoising under different noise scales and types. The AGM can have better results compare to The GMM.
关键词： image denoising,priors,asymmetric Gaussian mixture models,expected patch log likelihood
更新于2025-09-10 09:29:36
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[IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Real Sources in Complex Spaces
摘要： We utilize complex transformation optics (CTO) to mimic complex source point (CSP) fields. It is shown that the CSP fields can be exactly reproduced via planar metamaterial slabs associated with the proper complex coordinate transformations. CTO extends the real-valued coordinate transformations to complex-valued coordinate transformations. Of conventional TO, one can also control the amplitude of the fields in addition to their phase paths. In the present paper, we demonstrate that CSP fields can be produced through appropriate material tensors prescribed by the corresponding complex coordinate transformations.
关键词： Complex transformation optics,complex source point,metamaterials,Gaussian beams
更新于2025-09-10 09:29:36
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Simulating terahertz absorption of fluorinated phenylacetylene biphenyl liquid crystal molecules
摘要： Based on the density functional theory, ten kinds of fluoro-substituted liquid crystal derivative molecules, 4-butyl-4’-[(4-butylphenyl)acetylene]biphenyl, are simulated using Gaussian09 package with Opt+Freq optimization type and B3LYP/6-311g basis set. Comparing the substituted position and number of fluorine atoms, the absorption in terahertz region is discussed. Because measurement data of liquid crystal material absorption is lacking, we can only compare in the range of 0.3?3 THz. The results show that the calculation results have the same trend as the experimental measurement absorption curve of related literature. As a conclusion, our calculations can better reflect the absorption of molecular materials and provide effective suggestions for the design and synthesis of related molecules.
关键词： Gaussian simulation,absorption,fluorine liquid crystal,spectrum,terahertz
更新于2025-09-10 09:29:36
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A Markovian Approach to Unsupervised Change Detection with Multiresolution and Multimodality SAR Data
摘要： In the framework of synthetic aperture radar (SAR) systems, current satellite missions make it possible to acquire images at very high and multiple spatial resolutions with short revisit times. This scenario conveys a remarkable potential in applications to, for instance, environmental monitoring and natural disaster recovery. In this context, data fusion and change detection methodologies play major roles. This paper proposes an unsupervised change detection algorithm for the challenging case of multimodal SAR data collected by sensors operating at multiple spatial resolutions. The method is based on Markovian probabilistic graphical models, graph cuts, linear mixtures, generalized Gaussian distributions, Gram–Charlier approximations, maximum likelihood and minimum mean squared error estimation. It bene?ts from the SAR images acquired at multiple spatial resolutions and with possibly different modalities on the considered acquisition times to generate an output change map at the ?nest observed resolution. This is accomplished by modeling the statistics of the data at the various spatial scales through appropriate generalized Gaussian distributions and by iteratively estimating a set of virtual images that are de?ned on the pixel grid at the ?nest resolution and would be collected if all the sensors could work at that resolution. A Markov random ?eld framework is adopted to address the detection problem by de?ning an appropriate multimodal energy function that is minimized using graph cuts.
关键词： Markov random ?elds (MRF),maximum likelihood (ML) estimation,synthetic aperture radar (SAR),Gram–Charlier approximation,multiresolution data fusion,multimodality data fusion,graph cuts,minimum mean squared error (MMSE) estimation,generalized Gaussian
更新于2025-09-10 09:29:36