- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[IEEE 2019 5th International Conference on Signal Processing, Computing and Control (ISPCC) - Solan, India (2019.10.10-2019.10.12)] 2019 5th International Conference on Signal Processing, Computing and Control (ISPCC) - Technical Survey and review on MPPT techniques to attain Maximum Power of Photovoltaic system
摘要： The lp (0 < p < 1) regularization has attracted a great attention in the compressive sensing field, because it can obtain sparser solutions than the well-known l1 regularization. Recently, we developed an approximate general analytic thresholding representation for any lp regularization with 0 < p < 1. The derived thresholding representations are exact for the well-known soft-threshold filtering for l1 regularization and the hard-threshold filtering for l0 regularization. Because the lp regularization is a nonconvex problem, an iterative algorithm can only converge to local optima instead of the global optimum. In this paper, we propose an alternating iteration algorithm for computed tomography reconstruction in a thresholding form based on our general analytic thresholding representation for better convergent properties. The alternating iteration algorithm alternatively minimizes one l1 and one lp (0 < p < 1) regularized objective functions. While the lp regularization can help to find a sparser solution, the l1 regularization can help to monitor the solution not away from the global optimum. Both numerical simulations and phantom experiments are performed to evaluate the proposed alternating iteration algorithm. Compared with the lp (0 < p < 1) regularization using a single p, the proposed alternating iteration algorithm reduces more data measurements for accurate reconstruction and is more robust for projection noise.
关键词： Compressive sensing,lp regularization,least square solution,image reconstruction,alternating iteration,computed tomography
更新于2025-09-19 17:13:59
-
[IEEE 2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems (MEMS) - Vancouver, BC, Canada (2020.1.18-2020.1.22)] 2020 IEEE 33rd International Conference on Micro Electro Mechanical Systems (MEMS) - 3D Laser Nanoprinting
摘要： Digital phantoms are vital for various biomedical researches. Traditional phantoms include theoretical models and voxel models reconstructed from medical images. It has been demonstrated that the homogeneous phantom filled with uniform tissue is accurate enough for wearable antenna design, body-centric channel modeling, etc. Therefore, it is interesting and necessary to investigate the novel approach of generating digital phantoms using an optical noncontact measurement system. In this letter, the point cloud data are first obtained; then, they are simplified via principal component analysis; finally, by applying surface reconstruction and mesh simplification techniques, a digital Chinese phantom is established. To verify the usability of the phantom, numerical calculation is performed to check E-fields at different positions on the body. Results sufficiently prove the feasibility of the train of thought presented in this letter.
关键词： noncontact measurement system,point cloud data,Digital phantom,numerical calculation,surface reconstruction,principal component analysis (PCA)
更新于2025-09-19 17:13:59
-
[IEEE 2019 Smart Grid Conference (SGC) - Tehran, Iran (2019.12.18-2019.12.19)] 2019 Smart Grid Conference (SGC) - Introducing a novel method for improving the design of off-grid photovoltaic systems
摘要： Two-color pyrometric methods have been widely used in noncontact temperature measurement area. However, it is difficult to get synchronous monochromatic images for two-color pyrometric formula. Some researches use beam splitter to obtain two or more optical paths to capture the different monochromatic images, but the complex optical paths will bring spatiotemporal matching errors. Another method uses color camera to capture the Red, Green, Blue (RGB) channel images as the RGB monochromatic images, but substituting the Dirac delta function for spectral response function will result in the inaccuracy of the measurement results. In fact, the RGB monochromatic images can be obtained from the color image if the irradiance attenuations from color channel to single wavelength are calibrated. In this paper, a novel 3-D reconstruction method is proposed to measure the temperature distribution of combustion flame. First, the irradiance attenuations are calibrated to calculate the synchronous monochromatic images at R and G wavelengths. Second, the tomographic reconstruction of flame monochromatic emissive power is improved with visual hull restriction so that the energy distribution is more reasonable. Finally, the 3-D temperature distribution is calculated from the reconstructed monochromatic emissive power fields at R and G wavelengths using two-color pyrometric method. The alcohol and butane flames are tested in the laboratory-scale test rig. The experimental results indicate that our approach performs well in flame temperature field reconstruction.
关键词： irradiance,3-D reconstruction,two-color pyrometry,flame temperature distribution,temperature field measurement
更新于2025-09-19 17:13:59
-
[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Marked improvement of the photoresponsivity of BaSi <sub/>2</sub> light absorbers by increasing growth temperature and three-step growth method
摘要： The lp (0 < p < 1) regularization has attracted a great attention in the compressive sensing field, because it can obtain sparser solutions than the well-known l1 regularization. Recently, we developed an approximate general analytic thresholding representation for any lp regularization with 0 < p < 1. The derived thresholding representations are exact for the well-known soft-threshold filtering for l1 regularization and the hard-threshold filtering for l0 regularization. Because the lp regularization is a nonconvex problem, an iterative algorithm can only converge to local optima instead of the global optimum. In this paper, we propose an alternating iteration algorithm for computed tomography reconstruction in a thresholding form based on our general analytic thresholding representation for better convergent properties. The alternating iteration algorithm alternatively minimizes one l1 and one lp (0 < p < 1) regularized objective functions. While the lp regularization can help to find a sparser solution, the l1 regularization can help to monitor the solution not away from the global optimum. Both numerical simulations and phantom experiments are performed to evaluate the proposed alternating iteration algorithm. Compared with the lp (0 < p < 1) regularization using a single p, the proposed alternating iteration algorithm reduces more data measurements for accurate reconstruction and is more robust for projection noise.
关键词： Compressive sensing,lp regularization,least square solution,image reconstruction,alternating iteration,computed tomography
更新于2025-09-19 17:13:59
-
Attosecond pulse shaping using a seeded free-electron laser
摘要： Attosecond pulses are central to the investigation of valence- and core-electron dynamics on their natural timescales1–3. The reproducible generation and characterization of attosecond waveforms has been demonstrated so far only through the process of high-order harmonic generation4–7. Several methods for shaping attosecond waveforms have been proposed, including the use of metallic filters8,9, multilayer mirrors10 and manipulation of the driving field11. However, none of these approaches allows the flexible manipulation of the temporal characteristics of the attosecond waveforms, and they suffer from the low conversion efficiency of the high-order harmonic generation process. Free-electron lasers, by contrast, deliver femtosecond, extreme-ultraviolet and X-ray pulses with energies ranging from tens of microjoules to a few millijoules12,13. Recent experiments have shown that they can generate subfemtosecond spikes, but with temporal characteristics that change shot-to-shot14–16. Here we report reproducible generation of high-energy (microjoule level) attosecond waveforms using a seeded free-electron laser17. We demonstrate amplitude and phase manipulation of the harmonic components of an attosecond pulse train in combination with an approach for its temporal reconstruction. The results presented here open the way to performing attosecond time-resolved experiments with free-electron lasers.
关键词： high-order harmonic generation,Attosecond pulses,temporal reconstruction,free-electron laser
更新于2025-09-19 17:13:59
-
LED Arrays of Laser Printers as Valuable Sources of Electromagnetic Waves for Acquisition of Graphic Data
摘要： Classi?ed information may be derivable from unintended electromagnetic signals. This article presents a technical analysis of LED arrays used in monochrome computer printers and their contribution to unintentional electromagnetic emanations. Analyses were based on realistic type sizes and distribution of glyphs. Usable pictures were reconstructed from intercepted radio frequency (RF) emanations. We observed di?erences in the legibility of information receivable at a distance that we attribute to di?erent ways used by printer designers to control the LED arrays, particularly the di?erence between relatively high voltage single-ended waveforms and lower-voltage di?erential signals. To decode the compromising emanations required knowledge of—or guessing—printer operating parameters including resolution, printing speed, and paper size. Measurements were carried out across di?erences in construction and control of the LED arrays in tested printers.
关键词： laser printer,graphic information,non-invasive data acquisition,electromagnetic in?ltration,pattern recognition,LED array,compromising emanations,reconstruction,image processing
更新于2025-09-19 17:13:59
-
Red-emitting distributed-feedback ridge-waveguide laser based on high-order surface grating
摘要： Eigenvalue-based algorithm is generally acknowledged to be a promising method for spectrum sensing. However, it possesses high computational complexity, because the sampled covariance matrix and the corresponding eigenvalues are calculated. Furthermore, the detection performance of eigenvalue-based algorithms experiences a huge decline when the received signals are uncorrelated. Therefore, compressed sensing is adopted to reduce the computational complexity and introduce the relevance for multiple received signals. First, the sampled covariance matrix and its eigenvalues are calculated under the non-reconstruction framework of compressed sensing. The corresponding standard condition number of the eigenvalues is employed as test statistic to perform spectrum sensing. Then, the impact of the measurement matrix on the detection performance is discussed, and the computational complexity is analyzed. Next, the measurement matrix is optimized to improve the detection performance. In addition, a novel method of setting decision threshold is proposed to maintain a stable false alarm probability for the proposed spectrum sensing algorithm, and its computational complexity is compared with some existing methods. Finally, the corresponding simulations are performed to testify the theoretical results. Theoretical analysis and simulation results certify the effectiveness and validity of the proposed method.
关键词： standard condition number (SCN),sampled covariance matrix,non-reconstruction framework,Compressed sensing
更新于2025-09-19 17:13:59
-
PC458: Hyaluronic acid and laser in the therapy concept of periimplant inflammation - a 3-year clinical observation study
摘要： Anterior implant treatment is a difficult process for dental practitioner that requires experience and attention due to the patients’ high aesthetic and functional expectations. Following the loss of tooth severe hard and soft tissue alterations may take place. Regenerative techniques have been widely tested in various materials and clinical approaches; bone grafting alone, including autografts, allografts, xenografts and alloplasts; membrane alone, whether absorbable or not; and membrane in conjunction with grafting.
关键词： papilla reconstruction,implant dentistry,guided bone regeneration,peri-implant diseases
更新于2025-09-19 17:13:59
-
[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Performance comparison of co-located fixed-tilt and single-axis tracker arrays
摘要： In preoperative planning for mandibular reconstructive surgery, it is necessary to determine the osteotomy lines for fibular shaping and the proper placement of fibular segments in the mandible. Although virtual surgical planning has been utilized in preoperative decision making, current software designs require manual operation and a trial-and-error process to refine the reconstruction plan. We have developed volumetric fibular transfer simulation software that can quickly design a preoperative plan based on direct volume manipulation and quantitative comparison with the patient’s original mandible. We propose three quantitative shape indicators—volume ratio, contour error, and maximum projection—for symmetrical lesions of the mandible, and have implemented a parallel computation algorithm for the semiautomatic placement of fibular segments. Using this virtual planning software, we conducted a retrospective study of the computed tomography data from nine patients. We found that combining direct volume manipulation with real-time local search of placement improved the applicability of the planning system to optimize mandibular reconstruction.
关键词： Fibular transfer,mandibular reconstruction,shape indicator and volume manipulation,surgical planning
更新于2025-09-19 17:13:59
-
Dual-Core Photonic Crystal Fiber-Based Plasmonic RI Sensor in the Visible to Near-IR Operating Band
摘要： With the steadily increasing spatial resolution of synthetic aperture radar images, the need for a consistent but locally adaptive image enhancement rises considerably. Numerous studies already showed that adaptive multilooking, able to adjust the degree of smoothing locally to the size of the targets, is superior to uniform multilooking. This study introduces a novel approach of multiscale and multidirectional multilooking based on intensity images exclusively but applicable to an arbitrary number of image layers. A set of 2-D circular and elliptical filter kernels in different scales and orientations (named Schmittlets) is derived from hyperbolic functions. The original intensity image is transformed into the Schmittlet coefficient domain where each coefficient measures the existence of Schmittlet-like structures in the image. By estimating their significance via the perturbation-based noise model, the best-fitting Schmittlets are selected for image reconstruction. On the one hand, the index image indicating the locally best-fitting Schmittlets is utilized to consistently enhance further image layers, e.g., multipolarized, multitemporal, or multifrequency layers, and on the other hand, it provides an optimal description of spatial patterns valuable for further image analysis. The final validation proves the advantages of the Schmittlets over six contemporary speckle reduction techniques in six different categories (preservation of the mean intensity, equivalent number of looks, and preservation of edges and local curvature both in strength and in direction) by the help of four test sites on three resolution levels. The additional value of the Schmittlet index layer for automated image interpretation, although obvious, still is subject to further studies.
关键词： Adaptive filters,digital filters,image analysis,image reconstruction,image representations,image edge analysis,image enhancement,synthetic aperture radar (SAR)
更新于2025-09-19 17:13:59