Poe R C, Lipson E D
Biol Cybern. 1986;55(2-3):91-8. doi: 10.1007/BF00341924.
The light-growth response of the Phycomyces sporangiophore is a transient change of elongation rate in response to changes in ambient blue-light intensity. The white-noise method of nonlinear system identification (Wiener-Lee-Schetzen theory) has been applied to this response, and the results have been interpreted by system analysis methods in the frequency domain. Experiments were performed on the Phycomyces tracking machine. Gaussian white-noise stimulus patterns were applied to the logarithm of the light intensity. The log-mean intensity of the broad-band blue illumination was 0.1 Wm-2 and the standard deviation of the Gaussian white-noise was 0.58 decades. The results, in the form of temporal functions called Wiener kernels, represent the input-output relation of the light-growth response system. The transfer function, which was obtained as the Fourier transform of the first-order kernel, was analyzed in the frequency domain in terms of a dynamic model that consisted of a first-order high-pass filter, two second-order low-pass filters, a delay element, and a gain factor. Parameters in the model (cutoff frequencies, damping coefficients, latency, and gain constant) were evaluated by nonlinear least-squares methods applied to the complex-valued transfer function. Analysis of the second-order kernel in the frequency domain suggests that the residual nonlinearity of the system lies close to the input.
毛霉目孢子囊柄的光生长反应是伸长率随环境蓝光强度变化的瞬时改变。非线性系统辨识的白噪声方法（维纳 - 李 - 谢岑理论）已应用于该反应，其结果已通过频域中的系统分析方法进行解释。实验在毛霉目追踪仪上进行。高斯白噪声刺激模式施加于光强的对数。宽带蓝光照明的对数平均强度为0.1 Wm-2，高斯白噪声的标准差为0.58倍频程。以称为维纳核的时间函数形式呈现的结果代表了光生长反应系统的输入 - 输出关系。作为一阶核的傅里叶变换得到的传递函数，在频域中根据由一个一阶高通滤波器、两个二阶低通滤波器、一个延迟元件和一个增益因子组成的动态模型进行分析。通过应用于复值传递函数的非线性最小二乘法评估模型中的参数（截止频率、阻尼系数、延迟和增益常数）。频域中二阶核的分析表明系统的残余非线性接近输入。
