- 标题
- 摘要
- 关键词
- 实验方案
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Parallel domain decomposition methods for a quantum-corrected drift–diffusion model for MOSFET devices
摘要： In this paper, we describe parallel domain decomposition methods based on the restricted additive Schwarz (RAS) method for a quantum-corrected drift-diffusion (QCDD) model for MOSFET devices. We have developed hybrid Message Passing Interface (MPI)/OpenMP parallelization algorithms of the QCDD system. For internode parallelization, two extensions of the RAS method are newly developed for the QCDD model. For intranode parallelization, we combine the conjugate gradient (CG) and BiCGSTAB procedures with a splitting-up operator method to realize parallelization of the incomplete factorization. The parallel numerical results for a three-dimensional Si bulk n-MOSFET on a multi-core NEC SX-ACE parallel computer are demonstrated. The intranode parallel numerical results are further evaluated on a many-core Cray XC40 parallel computer.
关键词： Restricted additive Schwarz method,Domain decomposition method,Numerical methods,Device simulation,Semiconductor,quantum-corrected drift–diffusion model
更新于2025-09-23 15:21:21
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Effects of Anisotropy Field and Easy Axis Dispersions on Squareness Ratio for HDDR-Processed Nd-Fe-B Powders
摘要： Nd-Fe-B magnetic powders produced by the hydrogenation-decomposition-desorption-recombination process have a lower squareness ratio than sintered magnets. In this paper, the anisotropy ?eld (Hk) distribution was assumed to be a horizontally ?ipped lognormal distribution and the effect of the Hk dispersion on the squareness ratio was investigated by using a micromagnetic simulator. As a result, the squareness ratio was very similar to the experimental demagnetization loop, when (cid:2)Hk(cid:3) was 5500 kA/m and σ Hk/(cid:2)Hk(cid:3) was 30%. Moreover, we investigated the easy axis dispersion of grains on squareness ratio in consideration of soft magnetic or nonmagnetic grain boundaries. As a result, the squareness ratio for the nonmagnetic grain boundary was closer to the experimental value; however, it is dif?cult to describe the experimental demagnetization loop by only considering the easy axis dispersion.
关键词： hydrogenation-decomposition-desorption-recombination (HDDR)-processed Nd-Fe-B,horizontally ?ipped lognormal distribution,Anisotropy ?eld and easy axis dispersions,squareness ratio
更新于2025-09-23 15:21:21
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Direct quantitative material decomposition employing grating-based X-ray phase-contrast CT
摘要： Dual-energy CT has opened up a new level of quantitative X-ray imaging for many diagnostic applications. The energy dependence of the X-ray attenuation is the key to quantitative material decomposition of the volume under investigation. This material decomposition allows the calculation of virtual native images in contrast enhanced angiography, virtual monoenergetic images for beam-hardening artifact reduction and quantitative material maps, among others. These visualizations have been proven beneficial for various diagnostic questions. Here, we demonstrate a new method of ‘virtual dual-energy CT’ employing grating-based phase-contrast for quantitative material decomposition. Analogue to the measurement at two different energies, the applied phase-contrast measurement approach yields dual information in form of a phase-shift and an attenuation image. Based on these two image channels, all known dual-energy applications can be demonstrated with our technique. While still in a preclinical state, the method features the important advantages of direct access to the electron density via the phase image, simultaneous availability of the conventional attenuation image at the full energy spectrum and therefore inherently registered image channels. The transfer of this signal extraction approach to phase-contrast data multiplies the diagnostic information gained within a single CT acquisition. The method is demonstrated with a phantom consisting of exemplary solid and fluid materials as well as a chicken heart with an iodine filled tube simulating a vessel. For this first demonstration all measurements have been conducted at a compact laser-undulator synchrotron X-ray source with a tunable X-ray energy and a narrow spectral bandwidth, to validate the quantitativeness of the processing approach.
关键词： Dual-energy CT,virtual non-contrast images,grating-based phase-contrast,electron density,effective atomic number,material decomposition,quantitative X-ray imaging,virtual monoenergetic images
更新于2025-09-23 15:21:21
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The reactivity of solid rubrene with potassium: competition between intercalation and molecular decomposition
摘要： We present the synthesis and characterization of the K+ intercalated rubrene (C42H28) phase, K2Rubrene (K2R) and identify the co-existence of amorphous and crystalline materials in samples where the crystalline component is phase pure. We suggest this is characteristic of many intercalated alkali metal-polyaromatic hydrocarbon (PAH) systems, including those for which superconductivity has been claimed. The systematic investigation of K-rubrene solid state reactions using both K and KH sources reveals complex competition between K intercalation and the decomposition of rubrene, producing three K-intercalated compounds, namely, K2R, K(RR*), and KxR? (where R* and R? are rubrene decomposition derivatives C42H26 and C30H20, respectively). K2R is obtained as the major phase over a wide composition range and is accompanied by the formation of amorphous by-products from the decomposition of rubrene. K(RR*) is synthesized as a single phase and KxR? is obtained only as a secondary phase to the majority K2R phase. The crystal structure of K2R was determined using high resolution powder X-ray diffraction, revealing that the structural rearrangement from pristine rubrene creates two large voids per rubrene within the molecular layers in which K+ is incorporated. K+ cations accommodated within the large voids interact strongly with the neighbouring rubrene via η6, η3 and η2 binding modes to the tetracene cores and the phenyl groups. This contrasts with other intercalated PAHs where only a single void per PAH is created and the intercalated K+ weakly interact with the host. The decomposition products of rubrene are also examined using solution NMR, highlighting the role of the breaking of C-CPhenyl bonds. For the crystalline decomposition derivative products K(RR*) and KxR?, a lack of definitive structural information with regards to R* and R? prevents the crystal structures being determined. The study illustrates the complexity in accessing solvent-free alkali metal salts of reduced PAH of the type claimed to afford superconductivity.
关键词： crystal structure,decomposition,rubrene,intercalation
更新于2025-09-23 15:21:21
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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) - THz Quantum Cascade Lasers with Optimized Beam Divergence
摘要： Huynen decomposition (HD) as the first formalized target decomposition has not been widely accepted. The preference for symmetry and regularity restricts not only its application but also its unification with other target dichotomies. The nonuniqueness issue then arises because we may have different dichotomies of radar targets, but we have no idea on how to select them. In this paper, a unified Huynen dichotomy is developed by extending HD for a full preference for symmetry and regularity, nonsymmetry, irregularity, and their couplings. It covers all of the existing dichotomies and provides a unified selection mechanism for them. Scattering preference is identified as a main feature of target dichotomy, and its concise description is devised by relating each dichotomy to a canonical scattering. A scattering degree of preference (SDoP) parameter is defined to measure the preference of each dichotomy. In virtue of an adaptive combination and permutation of SDoPs, a scattering pyramid description of the mixed scattering is developed, which has better discrimination of target than entropy/alpha. An SDoP/alpha classification is further proposed by statistical modeling of the unified dichotomy, which is a competent alternative to entropy/alpha. The excellent performance of unified dichotomy makes us believe that the existing concerns on HD are well treated and the Huynen–Cloude controversy, in a sense, may be ended.
关键词： target extraction,target decomposition,unsupervised classification,Huynen decomposition (HD),radar polarimetry
更新于2025-09-23 15:21:01
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[IEEE 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Guangzhou, China (2019.5.19-2019.5.22)] 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Ultrawideband Tightly Coupled Dipole Array with 70?° Scanning for Millimeter-Wave Bands
摘要： Cloud computing enables customers with limited computational resources to outsource their huge computation workloads to the cloud with massive computational power. However, in order to utilize this computing paradigm, it presents various challenges that need to be addressed, especially security. As eigen-decomposition (ED) and singular value decomposition (SVD) of a matrix are widely applied in engineering tasks, we are motivated to design secure, correct, and efficient protocols for outsourcing the ED and SVD of a matrix to a malicious cloud in this paper. In order to achieve security, we employ efficient privacy-preserving transformations to protect both the input and output privacy. In order to check the correctness of the result returned from the cloud, an efficient verification algorithm is employed. A computational complexity analysis shows that our protocols are highly efficient. We also introduce an outsourcing principle component analysis as an application of our two proposed protocols.
关键词： eigen-decomposition,principle component analysis,singular value decomposition,Cloud computing,secure outsourcing
更新于2025-09-23 15:21:01
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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Simulation of Full Responses of Triaxial Induction Logging in 1D Layered Arbitrarily Anisotropic Formations
摘要： Triaxial induction tools can be used to evaluate thinly laminated sand-shale sequences and fractured beds. This type of reservoirs exhibit transversely isotropy (TI) or arbitrarily anisotropy (also called as biaxial anisotropy (BA)). There have been several papers to study the responses in the TI model or the simpli?ed BA model whose conductivity principal coordinate is always consistent with the formation coordinate. However, little work covers the most general biaxial anisotropic model whose conductivity tensor’s orientation is arbitrary. We introduce the Euler angles, then the general biaxial anisotropic conductivity tensor can be determined by three principal components and three ordered Euler angles. To derive the electromagnetic (EM) ?elds in arbitrarily anisotropic medium, we ?rst convert the Maxwell’s equation of frequency-spatial domain into frequency-wavenumber domain by 2D Fourier transform, and obtain an ordinary di?erential system about horizontal components of EM ?elds. Using eigenvalue decomposition of the system matrix, this system can be decomposed into two group of equations associated with upward and downward eigen-waves respectively. We derive the solutions of EM ?elds in frequency-wavenumber domain by introducing transmission matrix, both local and generalized re?ection matrix and propagator matrix After that, we use 2D Gauss-Legendre quadrature to calculate inverse Fourier transformation and obtain Green’s function for simulation of the tri- axial induction responses. The numerical results are compared with 3D numerical method in both vertical and deviated wells and the agreement is satisfactory. Finally, we investigate the response characteristics in several formations with di?erent Euler angles The results show that triaxial induction responses are remarkably in?uenced by Euler angles even if the values of three principal components of conductivity tensor remain unchanged. Compare to the responses of the simpli?ed BA model, those of general BA model are more complex and contain more nonzero components. The results indicate that using TI model or the simpli?ed BA model in complex environment may cause large errors. Our algorithm are more practical than algorithms based on the simpli?ed model because the real depositional environments are usually complicated.
关键词： Maxwell’s equation,biaxial anisotropy,eigenvalue decomposition,Triaxial induction logging,Euler angles,Fourier transform,Gauss-Legendre quadrature
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Zhenjiang, China (2019.8.4-2019.8.8)] 2019 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Modification of Wettability Property of NITI Alloy by Laser Texturing and Carbon Ion Implantation
摘要： Nonlocal self-similarity of images has attracted considerable interest in the field of image processing and has led to several state-of-the-art image denoising algorithms, such as block matching and 3-D, principal component analysis with local pixel grouping, patch-based locally optimal wiener, and spatially adaptive iterative singular-value thresholding. In this paper, we propose a computationally simple denoising algorithm using the nonlocal self-similarity and the low-rank approximation (LRA). The proposed method consists of three basic steps. First, our method classifies similar image patches by the block-matching technique to form the similar patch groups, which results in the similar patch groups to be low rank. Next, each group of similar patches is factorized by singular value decomposition (SVD) and estimated by taking only a few largest singular values and corresponding singular vectors. Finally, an initial denoised image is generated by aggregating all processed patches. For low-rank matrices, SVD can provide the optimal energy compaction in the least square sense. The proposed method exploits the optimal energy compaction property of SVD to lead an LRA of similar patch groups. Unlike other SVD-based methods, the LRA in SVD domain avoids learning the local basis for representing image patches, which usually is computationally expensive. The experimental results demonstrate that the proposed method can effectively reduce noise and be competitive with the current state-of-the-art denoising algorithms in terms of both quantitative metrics and subjective visual quality.
关键词： self-similarity,Back projection,patch grouping,image denoising,low-rank approximation (LRA),singular value decomposition (SVD)
更新于2025-09-23 15:21:01
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Boosted photocatalytic elimination toward Cr(VI) and organic pollutants over BUC-21/Cd0.5Zn0.5S under LED visible Light
摘要： Series BUC-21/Cd0.5Zn0.5S (B100CX, X = 20, 60, 100) were prepared by simple ball-milling the mixture of BUC-21 and Cd0.5Zn0.5S at 30 HZ for 20 min. The photocatalytic activities of B100CX under the illuminance of low power LED visible light were estimated. According to influencing factor experiments, it was revealed that B100CX composites displayed better Cr(VI) sequestration performances than pristine BUC-21 and individual Cd0.5Zn0.5S, resulting from the effective separation of photo-induced electron-hole pairs and the inhibited aggregation of the Cd0.5Zn0.5S nano-particles. The photoluminescence, electrochemical analysis, active species trapping experiments and electron spin resonance (ESR) provided further evidence for improved photocatalytic activity. After three cycles, the photocatalytic sequestration efficiency of Cr(VI) by B100C100 was still reach more than 90%, implying that B100C100 had remarkable recyclability and stability. At last, the corresponding photocatalytic mechanism over B100CX was proposed and verified by some techniques.
关键词： BUC-21,organic pollutant decomposition,Cd0.5Zn0.5S,Cr(VI) sequestration,photocatalysis
更新于2025-09-23 15:21:01
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[IEEE 2019 International Applied Computational Electromagnetics Society Symposium - China (ACES) - Nanjing, China (2019.8.8-2019.8.11)] 2019 International Applied Computational Electromagnetics Society Symposium - China (ACES) - Double-Ridge Waveguide Mode Analysis based on FDTD-SVD Method
摘要： In this paper,hybrid finite-difference time-domain method(FDTD) and singular value decomposition(SVD),denoted by FDTD-SVD,is applied to analyze the double-ridge waveguide dominant mode. Double-ridge waveguide (WRD) without fillets and WRD with small fillets are analyzed.The simulation results show WRD without fillets can achieve a single-mode operation of 10TE from 35GHz to 112 GHz. For WRD with small fillets, its single-mode operation frequency band is 35-116GHz.These results are almost consistent with the detailed parametric study result(38-120GHz)based on Ansys HFSS, which proves that the FDTD-SVD method is simple and more effective. In addition, the transmission performance of WRD can be improved by adding fillets and enlarging the radius of fillets.
关键词： mode analysis,singular value decomposition(SVD),finite-difference time-domain method(FDTD),double-ridge waveguide(WRD)
更新于2025-09-23 15:21:01