高精度光电编码器莫尔条纹信号质量分析方法

针对莫尔条纹信号质量对高精度编码器细分误差的影响,提出了基于离散傅里叶变换分析莫尔条纹信号质量的方法。该方法利用信号重构和傅里叶变换算法得到信号参数,真实地反应了莫尔条纹信号质量,提高了细分误差测量的准确性。编码器转动时,采集相位差为/2 的两路精码正弦光电信号,通过对采样信号的重构得到信号波形,利用离散傅里叶变换算法分析重构波形,求解信号的直流分量、幅值、相位和谐波分量等各项参数。最后,根据信号参数与细分误差的关系得到光电编码器的细分误差值,并进行了实验验证。实验结果表明,对某24 位绝对式光电轴角编码器细分误差进行测量,细分误差的峰值为+0.48和-0.21。相对于传统的细分误差测量方法,此方法测量速度快,测量精度高,适用于工作现场。     

超声酶解法提取桑叶功能性物质的工艺条件优化

目的 探究超声酶解法中不同因素对桑叶黄酮、生物碱及多糖提取含量的影响,并对工艺条件进行优化。方法 以3种物质(黄酮、生物碱和多糖)的提取含量为考察指标,首先确定不同酶种类对3种物质提取含量的影响,通过单因素试验得到溶液pH、酶添加量、超声功率、超声时间、乙醇体积分数和料液比的最佳条件,再利用响应面法对提取工艺进行优化,得出最佳提取工艺条件。结果 最适酶种类为复合酶(纤维素酶与果胶酶比例为1:1,m:m);最佳工艺条件为酶解温度50℃、超声时间50min、料液比1:46(g/mL)、超声功率360 W、乙醇体积分数60%、酶添加量2.0%、溶液pH=6.0, 3种物质提取含量分别为黄酮(39.84±0.59) mg/g、生物碱(14.62±0.41) mg/g、多糖(202.82±1.94) mg/g。结论 超声酶解法能有效提高桑叶中黄酮、生物碱和多糖的提取含量,且复合酶效果最好,优化后的工艺条件准确可靠,可用于桑叶黄酮、生物碱及多糖的提取。     

裸眼3D显示液晶光栅贴合控制参数设计与实现

文章根据视差液晶光栅立体显示原理和莫尔条纹形成规律．提出了一种视差液晶光栅贴合控制参数的设计规则及工艺指导方式。通过对实际产品立体效果的影响分析。得出了设计控制的关键因素：贴合间隙的厚度和光栅与显示屏之间贴合允许最大倾斜角度,根据贴合允许的最大倾斜角度推导出了贴合对位标记垂直方向上的最大允许误差。实验验证和量产实践表明,文中提出的理论和方法能很好地应用于裸眼3D显示液晶光栅贴合控制的设计与量产工艺控制。     

桑叶化学成分的研究

目的研究中药桑叶的化学成分。方法用石油醚提取桑叶乙醇提取物，石油醚部分用柱色谱、薄层色谱等方法分离，用光谱学方法分析化合物的结构。结果分离并鉴定了8个化合物，分别是β-谷甾醇（Ⅰ），大黄素甲醚（Ⅱ），三十四烷酸（Ⅲ），三十四醇（Ⅳ），豆甾醇（Ⅴ），羽扇豆醇（Ⅵ），硬脂酸（Ⅶ），胡萝卜苷（Ⅷ）。结论化合物Ⅱ，Ⅲ，Ⅳ，Ⅵ，Ⅶ是首次从桑叶属植物中分离得到的。     

Parameter identification of discrete systems via discrete Chebyshev transformation

Abstract

A new method is proposed for the parameter identification of linear time‐invariant discrete single‐input‐single‐output systems by the application of the discrete Chebyshev transformation. The input and output data sequences of a system represented by difference equation are first transformed into discrete Chebyshev spectra. Using spectrum matching, the parameter identification problem becomes the solution of a set of overdetermined simultaneous linear algebraic equations. Examples with and without noise contamination are given to illustrate the new method.     

Thermal environment effects on wave dispersion behavior of inhomogeneous strain gradient nanobeams based on higher order refined beam theory

In this article, an analytical model for the wave propagation analysis of inhomogeneous functionally graded (FG) nanobeam in thermal environment is developed based on nonlocal strain gradient theory, in which the stress accounts for not only the nonlocal elastic stress field but also the strain gradients stress field. The nanobeam is modeled through a higher order shear deformable refined beam theory which has a trigonometric shear stress function. The temperature field supposed to have a nonlinear distribution across the nanobeam thickness. Temperature-dependent material properties of nanobeams are spatially graded based on Mori–Tanaka model. The governing equations of the temperature-dependent functionally graded (FG) nanobeam are derived using the Hamilton’s principle. Numerical examples show that the characteristics of the wave propagation of FG nanobeam are influenced by various parameters such as nonlocality parameter, length scale parameter, gradient index, and temperature changes.     

钙盐处理对真丝纤维力学性能的影响

测定了硝酸钙溶液处理后真丝纤维的力学性能，比较并研究了处理温度对丝纤维性能的影响。结果发现，真丝纤维经硝酸钙溶液处理后，产生重量损失，丝纤维的断裂强度下降，这一趋势并随着处理温度的提高、处理时间的延长更加明显。     

桑树皮黄酮的超声波提取及体外抗氧化作用研究

采用超声波提取法对桑树皮中总黄酮进行提取,通过单因素及正交试验确定了桑树皮黄酮超声波提取法的最佳工艺条件:物料粒度大于60目,使用80%乙醇,功率为325W,料液比1:10条件下提取30min,黄酮的得率为7.841‰.利用清除DPPH自由基的能力和还原力作为指标测定了桑树皮黄酮的抗氧化活性.结果表明,桑树皮黄酮有较强的抗氧化能力.超声波提取法与常规热回流提取法的效果及黄酮提取物的抗氧化作用相当.     

A micromechanical model for the mechanical degradation of natural fiber reinforced composites induced by moisture absorption

This paper develops a micromechanical model to study the mechanical degradation of natural fiber reinforced composites (NFRCs) induced by moisture absorption. Since the moisture absorption and the mechanical degradation of the composite are correlated, a modified Mori–Tanaka method with a damage variable is proposed. A set of micromechanical equations are established to describe the modulus loss of NFRCs. After specifying this model with different inclusion shapes, the overall swelling deformation and the mechanical degradation of the randomly oriented and the unidirectional straight natural fiber reinforced composites are studied in detail. Theoretical predicted results of the randomly oriented straight fiber reinforced composite are compared with experimental ones from literature and a good agreement is obtained. Further numerical results demonstrate that a stiffer matrix can reduce both the moisture absorption and the mechanical degradation of natural fibers.     

Too real for comfort? Uncanny responses to computer generated faces

As virtual humans approach photorealistic perfection, they risk making real humans uncomfortable. This intriguing phenomenon, known as the uncanny valley, is well known but not well understood. In an effort to demystify the causes of the uncanny valley, this paper proposes several perceptual, cognitive, and social mechanisms that have already helped address riddles like empathy, mate selection, threat avoidance, cognitive dissonance, and psychological defenses. In the four studies described herein, a computer generated human character’s facial proportions, skin texture, and level of detail were varied to examine their effect on perceived eeriness, human likeness, and attractiveness. In Study I, texture photorealism and polygon count increased human likeness. In Study II, texture photorealism heightened the accuracy of human judgments of ideal facial proportions. In Study III, atypical facial proportions were shown to be more disturbing on photorealistic faces than on other faces. In Study IV, a mismatch in the size and texture of the eyes and face was especially prone to make a character eerie. These results contest the depiction of the uncanny valley as a simple relation between comfort level and human likeness. This paper concludes by introducing a set of design principles for bridging the uncanny valley.