排序方式: 共有86条查询结果,搜索用时 15 毫秒
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采用光谱与图像相结合,实现了核桃仁蛋白质和脂肪含量预测及基于完整度和色泽的核桃仁外观品质分级。选用新疆"温185"核桃仁,采集了862.9~1704.02 nm和382.19~1026.66 nm范围高光谱图像。采用多元散射校正(MSE)和标准正态化(SNV)方法进行预处理后,通过竞争性自适应重加权采样算法与相关系数法,对核桃仁样品的蛋白质含量、脂肪含量、总色差3个参数进行了特征波段筛选。通过偏最小二乘回归(PLSR)算法建立了全光谱波段与特征光谱波段的蛋白质和脂肪含量预测模型,与全光谱波段相比,蛋白质含量特征波段预测模型的验证集决定系数(R2)由0.66增长到0.91,均方根误差(RMSEP)由1.37%下降到0.78%;脂肪含量特征波段预测模型的验证集R2由0.83增长到0.93, RMSEP由0.98%下降到0.47%。在外观品质方面,采用全光谱波段、RGB光谱波段、总色差特征光谱波段为输入,采用决策树、K近邻和支持向量机算法建立了核桃仁外观品质分类模型。通过对比发现,采用总色差特征波段建模,可大幅减低冗余信息的干扰,同时分类准确率也高... 相似文献
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指出教育部考试中心2019版考研数学考试分析中关于矩阵相似试题解答中的一个错误.系统梳理了高等代数和线性代数课程中关于相似矩阵刻画的角度和方法,明确了在线性代数课程体系中3类可以作出相似判定的矩阵类别及其对应的判别方法,给出不能一般判定相似关系的第4类矩阵的基本特征,并结合实例给出在特殊情形下解决第4类矩阵相似关系判定的方法. 相似文献
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针对物理气相传输(PVT)法生长碳化硅(SiC)晶体,建立了一个二维生长动力学模型研究SiC生长腔内气相组分输运特性,该模型考虑了氩气与气相组分之间的流动耦合,Stefan流和浮力影响.研究表明:在压力较低的情况下,自然对流对气相组分的输运过程影响很小,可以忽略,而当压力增高时,自然对流强度显著增大,不可忽略.其次,随着生长温度升高对流的作用增强,生长腔内输运过程由扩散向对流转变,最终对流主导组分的输运过程.随着压力升高对流作用减弱,扩散为气相组分主要输运方式. 相似文献
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利用含时密度泛函理论研究了酮缺陷对中性和带电六卟啉芳香性的影响,并使用多维可视化技术给出了该体系基态电荷分布和电子跃迁的直观图像. 研究结果表明,芳香性是决定这类体系基态密立根电荷分布的主要因素;酮缺陷效应使得体系基态的密立根电荷分布更多地局域在六卟啉基团上,在这类体系的五氟苯基取代基上密立根电荷布居较少,同时使得体系的芳香性发生改变. 进一步,通过计算体系的跃迁密度和电荷差分密度,可视化了酮缺陷对中性和带电六卟啉芳香性的影响. 结果表明,酮缺陷加强了体系电荷转移的能力. 相似文献
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We study the effect of strain on band structure and valley-dependent transport properties of graphene heterojunctions. It is found that valley-dependent separation of electrons can be achieved by utilizing strain and on-site energies. In the presence of strain, the values of transmission can be effectively adjusted by changing the strengths of the strain, while the transport angle basically keeps unchanged. When an extra on-site energy is simultaneously applied to the central scattering region, not only are the electrons of valleys K and K' separated into two distinct transmission lobes in opposite transverse directions, but the transport angles of two valleys can be significantly changed. Therefore, one can realize an effective modulation of valley-dependent transport by changing the strength and stretch angle of the strain and on-site energies, which can be exploited for graphene-based valleytronics devices. 相似文献
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We report combined magnetic susceptibility, dielectric constant, nuclear quadruple resonance(NQR), and zero-field nuclear magnetic resonance(NMR) measurements on single crystals of multiferroics CuBr_2. High quality of the sample is demonstrated by the sharp magnetic and magnetic-driven ferroelectric transition at T_N= T_C≈ 74 K. The zero-field ~(79)Br and ~(81)Br NMR are resolved below T_N. The spin-lattice relaxation rates reveal charge fluctuations when cooled below 60 K.Evidences of an increase of NMR linewidth, a reduction of dielectric constant, and an increase of magnetic susceptibility are also seen at low temperatures. These data suggest an emergent instability which competes with the spiral magnetic ordering and the ferroelectricity. Candidate mechanisms are discussed based on the quasi-one-dimensional nature of the magnetic system. 相似文献
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