Abstract We investigated the relationship between composite multiscale entropy (CMSE) and absorption coefficient, refractive index within the terahertz (THz) region by using six concentrations (5000, 1000, 500, 50, 10, and 5 µg/ml) of bovine serum albumin (BSA) aqueous solutions. Variational mode decomposition (VMD) method served as a preprocessing tool was attempted to introduce to decompose THz signal into three mode functions. An exhaustive search optimization with the criteria of maximizing coefficient of determination and minimizing the error bars for linear fitting was conducted to select the parameter of controlling bandwidth in VMD. The results demonstrate a number of linear models can validate the linear relationship between the selected sample entropy and absorption coefficient, refractive index at specific frequency. Additionally, the nonlinear behavior between the selected sample entropy and concentration of BSA is similar to that between absorption coefficient and concentration. The bridge between THz optical properties of the material and CMSE is established preliminarily.

中文翻译：

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太赫兹脉冲系统研究牛血清白蛋白溶液复合多尺度熵与光学性质的关系

摘要 我们使用六种浓度（5000、1000、500、50、10 和 5 µg/ml）的牛血清白蛋白研究了复合多尺度熵 (CMSE) 与吸收系数、太赫兹 (THz) 区域内的折射率之间的关系。 (BSA) 水溶液。尝试引入作为预处理工具的变分模式分解（VMD）方法将太赫兹信号分解为三个模式函数。以最大化决定系数和最小化线性拟合的误差条为准则进行详尽的搜索优化，以选择VMD中控制带宽的参数。结果表明，许多线性模型可以验证所选样品熵与吸收系数、特定频率下的折射率之间的线性关系。此外，所选样品熵与 BSA 浓度之间的非线性行为类似于吸收系数与浓度之间的非线性行为。初步建立了材料的太赫兹光学特性与CMSE之间的桥梁。