基于太赫兹时域光谱的食用油过氧化值定量分析研究

针对目前太赫兹光谱技术在食用油品质检测方面存在定性多、定量难的问题,提出一种基于衰减全反射（ATR）式太赫兹时域光谱（THz-TDS）技术的食用油过氧化值定量分析方法。首先采集不同种类、不同氧化程度食用油样本的太赫兹时域光谱图,筛选有效信号波段并提取得到光学常数,经预处理算法校正后的光学常数,结合多种化学计量学方法建立定量分析模型,实现快速、无损预测食用油的过氧化值。70个实验样本包括大豆油、菜籽油和玉米,过氧化值覆盖范围0.41~10.23 mmol·kg-1,且样本的过氧化值均匀分布。采用TeraView公司生产配有ATR检测模块的TeraPulse 4000太赫兹脉冲光谱系统采集样本THz-TDS信号,根据THz-TDS谱图信号特征筛选有效波段10~86.78 cm-1用于建模分析。通过快速傅里叶变换得到频域信号并从中提取光学常数：折射率和吸收系数,采用Savitzky-Golay7点卷积平滑分别对折射率和吸收系数进行预处理,去除干扰信号。运用SPXY算法按照3∶1比例划分校正集和预测集样本,结合主成分回归法、偏最小二乘法两种化学计量学分析方法,分别建立基于折射率和基于吸收系数的过氧化值分析模型。对模型评价指标均方根误差和相关系数进行分析,基于折射率的过氧化值分析模型采用偏最小二乘算法建模预测精度最理想,选取最优主成分数为6时,其校正集均方根误差RMSEC为0.168%、决定系数R2为0.981,预测集均方根误差RMSEP为0.231%、决定系数r2为0.977;基于吸收系数的过氧化值分析模型则采用主成分回归算法建模预测模型稳健度最好,选取最优主成分数为10时,其校正均方根误差RMSEC为0.192%、校正集决定系数R2为0.979,预测均方根误差RMSEP为0.262%、预测集决定系数r2为0.97。该研究结果的得出,验证了THz-TDS技术用于食用油过氧化值定量分析的可行性,为食用油的品质评价找到一种高精度、性能稳定、快速无损的检测方法。     

Positivity of the temperature for phase transitions with micro-movements

We focus on the thermodynamic consistency of a class of phase change models recently proposed by Frémond [Non-smooth Thermomechanics. Springer, Berlin, 2002]. By establishing a maximum principle, we prove that, under rather weak assumptions on data, the temperature remains almost everywhere strictly positive. This general result applies to all dissipative models of this class that have been taken into account in the literature.     

β_∞(Ω)中算子的小紧扰动(英文)

We consider an approximation problem related to strongly irreducible operators, that is, does the direct sum of a strongly irreducible operator in в∞(Ω) and certain operator have a small compact perturbation which is a strongly irreducible operator in в∞(Ω)? In this paper, we prove that the direct sum of any strongly irreducible operator in в∞(Ω) and certain biquasitriangular operator have small compact perturbations which are strongly irreducible operators in в∞(Ω).     

基于线性代数的浸入式课程思政教学实践

本文研究如何在线性代数课程中贯彻课程思政的教学要求.     

电子显微镜下的纳米世界

以高中阶段知识为基础,简述了扫描电子显微镜、透射电子显微镜等电镜技术的发展和基本原理,并以实际应用案例介绍了电镜技术在纳米科学领域的应用,最后给出了电镜技术的未来发展前景。     

Epitaxial growth of borophene on substrates

Borophene, a two-dimensional (2D) planar boron sheet, has attracted dramatic attention for its unique physical properties that are theoretically predicted to be different from those of bulk boron, such as polymorphism, superconductivity, Dirac fermions, mechanical flexibility and anisotropic metallicity. Nevertheless, it has long been difficult to obtain borophene experimentally due to its susceptibility to oxidation and the strong covalent bonds in bulk forms. With the development of growth technology in ultra-high vacuum (UHV), borophene has been successfully synthesized by molecular beam epitaxy (MBE) supported by substrates in recent years. Due to the intrinsic polymorphism of borophene, the choice of substrates in the synthesis of borophene is pivotal to the atomic structure of borophene. The different interactions and commensuration of borophene on various substrates can induce various allotropes of borophene with distinct atomic structures, which suggests a potential approach to explore and manipulate the structure of borophene and benefits the realization of novel physical and chemical properties in borophene due to the structure–property correspondence. In this review, we summarize the recent research progress in the synthesis of monolayer (ML) borophene on various substrates, including Ag(1 1 1), Ag(1 1 0), Ag(1 0 0), Cu(1 1 1), Cu(1 0 0), Au(1 1 1), Al(1 1 1) and Ir(1 1 1), in which the polymorphism of borophene is present. Moreover, we introduce the realization of bilayer (BL) borophene on Ag(1 1 1), Cu(1 1 1) and Ru(0 0 0 1) surfaces, which possess richer electronic properties, including better thermal stability and oxidation resistance. Then, the stabilization mechanism of polymorphic borophene on their substrates is discussed. In addition, experimental investigations on the unique physical properties of borophene are also introduced, including metallicity, topology, superconductivity, optical and mechanical properties. Finally, we present an outlook on the challenges and prospects for the synthesis and potential applications of borophene.     

Polymeric aluminum porphyrin: Controllable synthesis of ultra-low molecular weight CO2-based polyols

Carbon dioxide-based polyols with ultra-low molecular weight (ULMW, M_n < 1000 g/mol) are emergent polyurethane precursors with economic and environmental benefits. However, the lack of effective proton-tolerant catalytic systems limits the development of this field. In this work, the polymeric aluminum porphyrin catalyst (PAPC) system was applied to the copolymerization of CO₂ and propylene oxide, where sebacic acid, bisphenol A, poly(ethylene glycol), and water were used as chain transfer agents to achieve the controlled synthesis of CO₂-polyols. The molecular weight of the resulting CO₂-polyols could be facilely regulated in the range of 400–930 g/mol at low catalyst loadings, fully demonstrating its catalytic advantages of high activity, high product selectivity, and excellent proton tolerance of PAPC. Meanwhile, the catalytic efficiency of PAPC could reach up to 2.1–5.2 kg/g under organic CTA conditions, even reaching 1.9 kg/g using water as the CTA. The cPC content could be controlled within 1.0 wt% under the optimized conditions, indicating the excellent controllability of the PAPC system. ULMW CO₂-polyols combines the advantages of low viscosity (∼3000 mPa s at 25 °C), low glass transition temperature (∼−73 °C), and high carbonate unit content (∼40%), which is important for the development of high-performance polyurethanes.     

A generic model for simulating office process flows

In the field of simulation, the use of application-specific software can bring many benefits to the model-builder in terms of improved productivity and reduced skill requirements. Such software must have at its core a robust generic model for the application area which offers both the generality and sufficient detail to be able to simulate realistically. To develop such a core model, a thorough understanding of the problem area and simulation is needed. This paper describes one design for a generic core model for the simulation of office process flows where work volumes are substantial. It forms a part of a software package called SCOPE which provides a user-interface for data capture, and generates simulation models to be run using the HOCUS simulation software. Also described is the facility for static modelling which has been developed to make further use of the captured data using conventional mathematical modelling.     

Asymmetric optical cryptosystem for color image based on equal modulus decomposition in gyrator transform domains

An enhanced asymmetric cryptosystem for color image is proposed by using equal modulus decomposition (EMD) in the gyrator transform domains. In this scheme, the EMD is performed to create the effective trapdoor one-way function. Moreover, to enhance the security of the cryptosystem, the Baker mapping is considered and utilized for scrambling the RGB components of the color image. The parameters in the Baker mapping and gyrator transform can be served as the extra keys of the entire cryptosystem. Various types of attacks are considered in the robustness analysis experiments. Some numerical simulations are made to verify the validity and capability of the proposed color encryption algorithm.     

基于理想排序的群组G2赋权方法研究

合理确定专家权重是群组赋权的关键。本文在分析同类研究的基础上,提出了基于理想排序的群组G2方法来确定专家权重。论文的主要特色是根据循环修正的思路利用平均值法、Board法和Copealand法对通过一致性检验的专家排序进行重排序,从而确定评价指标的理想排序,然后通过比较各通过一致性检验的专家排序和理想排序的相关性的大小来确定专家权重,保证了专家权重合理的反映了专家差异,保证了指标最终权重反映出群体决策思想。