排序方式: 共有54条查询结果,搜索用时 15 毫秒
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针对雾霾和沙尘天气下的场景退化问题,提出一种基于高斯模型凸优化与光幕双约束的退化场景复原算法.首先根据景深与场景亮度和饱和度之间的相关关系,利用高斯模型和凸优化估计景深;其次通过对大气光幕与场景关系作深入分析,结合最小通道平滑和景深衰减双约束获得退化场景的大气光幕;然后通过亮通道先验以及局部大气光的改进求解获得大气光值;最后基于复原模型对退化场景进行复原处理,并对沙尘场景进行颜色修正,进而实现场景复原.实验结果表明,所提算法的复原场景亮度适宜,颜色自然,细节信息丰富,在定量指标中也可以取得理想的评分,有效解决退化场景出现的偏色和细节丢失等问题. 相似文献
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宽禁带半导体材料碳化硅(SiC)凭借着其高击穿场强、高热导率、耐高温、高化学稳定性和抗辐射等优异性能,在电力电子器件领域尤其是高温、高频、高功率等应用场景下有着巨大潜力。大尺寸、高质量、低成本的单晶SiC的制备是SiC相关半导体产品规模化应用的前提。顶部籽晶溶液生长(TSSG)法生长的单晶SiC有着晶体质量高、易扩径、易p型掺杂等优势,有望成为制备单晶SiC的主流方法。但目前由于该方法涉及的生长机理复杂,研究者对其内部机理的理解还不够充分,难以对TSSG生长设备和方法进行有效的改进与优化。利用计算机对TSSG法生长单晶SiC生长过程进行数值模拟被认为是对其内部机理探究的有效途径之一。本文首先回顾了TSSG法生长单晶SiC和相关数值模拟分析的发展历程,介绍了TSSG法生长单晶SiC和数值模拟的基本原理,然后介绍了数值模拟方法计算分析TSSG法生长单晶SiC模型涉及的主要模块、影响单晶生长的主要因素(如马兰戈尼力、浮力、电磁力等),以及对数值模型的优化方法。最后,指出了数值模拟方法计算分析TSSG法生长单晶SiC在未来的重点研究方向。 相似文献
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Yuanchao Huang 《中国物理 B》2022,31(5):56108-056108
As a common impurity in 4H silicon carbide (4H-SiC), hydrogen (H) may play a role in tuning the electronic properties of 4H-SiC. In this work, we systemically explore the effect of H on the electronic properties of both n-type and p-type 4H-SiC. The passivation of H on intrinsic defects such as carbon vacancies (VC) and silicon vacancies (VSi) in 4H-SiC is also evaluated. We find that interstitial H at the bonding center of the Si-C bond (Hibc) and interstitial H at the tetrahedral center of Si (HiSi-te) dominate the defect configurations of H in p-type and n-type 4H-SiC, respectively. In n-type 4H-SiC, the compensation of HiSi-te is found to pin the Fermi energy and hinder the increase of the electron concentration for highly N-doped 4H-SiC. The compensation of Hibc is negligible compared to that of VC on the p-type doping of Al-doped 4H-SiC. We further examine whether H can passivate VC and improve the carrier lifetime in 4H-SiC. It turns out that nonequilibrium passivation of VC by H is effective to eliminate the defect states of VC, which enhances the carrier lifetime of moderately doped 4H-SiC. Regarding the quantum-qubit applications of 4H-SiC, we find that H can readily passivate VSi during the creation of VSi centers. Thermal annealing is needed to decompose the resulting VSi-nH (n=1-4) complexes and promote the uniformity of the photoluminescence of VSi arrays in 4H-SiC. The current work may inspire the impurity engineering of H in 4H-SiC. 相似文献
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利用分子光谱谱带位移、谱带强度、谱带形态等的变化,可以初步对晶体作结晶学定向。普通辉石结构OH红外光谱3组谱带值,垂直c轴方向相对于平行c轴的谱带各不相同:第一组谱带值,3 629~3 633 cm-1谱带红移到3 601~3 616 cm-1;第二组谱带值3 514~3 543 cm-1同样有红移现象;第三组3 460~3 465 cm-1的谱带值相反则有蓝移现象。相对强度上,两个方向上第一组的谱带强度相当;第二组、第三组谱带强度平行方向明显强于垂直方向。形态上则差别不大。拉曼谱垂直方向谱带强度普遍强于平行方向,谱带位置与形态基本不变。结构OH不同结晶方向的谱图性质可以反映一定的地质构造环境。 相似文献
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利用超声-微波协同萃取技术从车前草中提取熊果酸与齐墩果酸,研究建立了反相高效液相色谱法快速测定车前草中熊果酸与齐墩果酸含量的方法。采用安捷仑C18柱(4.6mm×250mm,5μm)色谱柱,流动相为乙腈-0.5%乙酸铵(体积比80∶20),流速为0.8mL/m in,UV检测波长210nm。在该色谱条件下熊果酸与齐墩果酸能在12m in内达到基线分离。熊果酸在1.01—10.1μg范围内线性关系良好,r=0.9995,平均加标回收率为98.8%,相对标准偏差RSD为1.7%(n=5);齐墩果酸的峰面积与其质量浓度在0.39—3.9μg范围内呈良好的线性关系,r=0.9992,平均加标回收率为97.9%,RSD为1.3%(n=5)。该方法简便、快速、准确,可用于车前草中熊果酸与齐墩果酸的含量测定。 相似文献
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Geometrical structures,vibrational frequencies,force constants and dissociation energies of isotopic water molecules (H2O,HDO, D2O,HTO, DTO,and T2O) under dipole electric field
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The dissociation limits of isotopic water molecules are derived for the ground state. The equilibrium geometries, the vibrational frequencies, the force constants and the dissociation energies for the ground states of all isotopic water molecules under the dipole electric fields from -0.05 a.u. to 0.05 a.u. are calculated using B3P86/6-311++G(3df,3pf). The results show that when the dipole electric fields change from -0.05 a.u. to 0.05 a.u., the bond length of H-O increases whereas the bond angle of H-O-H decreases because of the charge transfer induced by the applied dipole electric field. The vibrational frequencies and the force constants of isotopic water molecules change under the influence of the strong external torque. The dissociation energies increase when the dipole electric fields change from -0.05 a.u. to 0.05 a.u. and the increased dissociation energies are in the order of H2O, HDO, HTO, D2O, DTO, and T2O under the same external electric fields. 相似文献
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针对模拟电路多故障分类中存在拒识区域,分类效果不理想的问题,提出基于有序分割最佳偏二叉树结构的模拟电路故障诊断方法;首先分析多分类中分割次序对结果的影响,通过样本类中心欧式距离对故障分割进行排序,以此构造偏二叉树结构;然后对采样数据进行主成份分析降维压缩,最后采用支持向量机作为分类器,对故障数据进行分类;该方法可以使样本类间距离最大,提高了支持向量机模拟电路故障分类的效率和准确度;故障诊断结果表明文章提出的诊断方法在精度提高的情况下,所需训练时间和支持向量数目大大减少,更具稀疏性。 相似文献
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介绍了一种研究沸石结构的低剂量高分辨电子显微学方法,该方法可以有效降低电子束对沸石样品的辐照损伤,获得的高分辨像的分辨率优于0.18nm。提出了降低电子辐照损伤的措施,阐述了低剂量高分辨成像技术的技术要点。 相似文献