粮食烘干机温度控制系统的设计

设计一套粮食烘干机温度控制系统,以粮食烘干机水分测量系统为前置,用于谷物类粮食烘干过程中的变温控制.温度控制核心为STM32F103C8T6单片机,依靠步进电机驱动单元对可控硅调压器完成功率控制.绘制出PCB(Printed Circuit Board)板的布局布线,完成控制系统制作并进行联调测试.基于粮食烘干机水分测...     

High‐Efficiency PbS Quantum‐Dot Solar Cells with Greatly Simplified Fabrication Processing via “Solvent‐Curing”

PbS quantum‐dot (QD) solar cells are promising candidates for low‐cost solution‐processed photovoltaics. However, the device fabrication usually requires ten more times film deposition and rinsing steps, which is not ideal for scalable manufacturing. Here, a greatly simplified deposition processing is demonstrated by replacing methanol with acetonitrile (ACN) as the rinsing solvent. It is discovered that ACN can effectively “cure” the film cracks generated from the volume loss during the solid‐state ligand‐exchange process, which enables the deposition of thick and dense films with much fewer deposition steps. Meanwhile, due to the aprotic nature of ACN, fewer trap states can be introduced during the rinsing process. As a result, with only three deposition steps for the active layer, a CPVT‐certified 11.21% power conversion efficiency is obtained, which is the highest efficiency ever reported for PbS QD solar cells employing a solid‐state ligand‐exchange process. More importantly, the simple film‐deposition processing provides an opportunity for the future application of QDs in low‐cost printing of optoelectronic devices.     

基于转子辅助槽的PMSM电磁振动噪声削弱方法研究

电机气隙中的径向电磁力作用于定子齿部,通过定子、机座传递到空气中,产生了振动噪声。针对实际工程中噪声突出问题,解析径向电磁力得到产生振动噪声的主要阶次和频率,分析电机的定子模态得到不同空间阶次下的频率。考虑电机转子凸极,提出一种转子开辅助槽配合增加气隙宽度的方法改善电机的声振特性。通过搭建优化前后的电机有限元模型,在加速工况下对比6f₁和12f₁频率(f₁为基波频率)的电磁力,以及24阶次和48阶次下的A计权声压级,验证所提方法的有效性。最后在实际样机上测试加速工况下24阶次和48阶次的振动水平和声压级。试验结果表明,所提转子开辅助槽配合改变气隙宽度的方法能够有效降低电机整体的振动噪声。     

一种可变增益的音频放大电路设计及实现

针对音频设备应用,需要对动态范围大的声音信号进行预处理,使声音信号维持在一个合理的幅度内,保证声音输出的良好效果,以避免由于信号过大造成后级电路产生严重失真损坏音质,或信号过小受到噪声干扰使声音淹没等现象。文中提出了一种可自动控制增益的音频放大电路,该电路主要由前置放大电路、峰值检测器、阈值检测模块、可变增益放大器构成,可以实现20 Hz～20 kHz的自动增益控制。     

聚天冬氨酸凝胶的制备及生物降解性

以丙三醇三缩水甘油醚为交联剂制备聚天冬氨酸凝胶,考察了凝胶的热性能和黏弹性,并采用平板培养和液体培养法考察了凝胶的生物降解性。结果表明:丙三醇三缩水甘油醚交联凝胶具有良好的吸水保水性,且耐热性和黏弹性更优,平板试验证明凝胶也具有良好的生物降解性,液体培养法证明交联剂的种类和用量对凝胶的降解有较大影响,交联度均为60%的凝胶,交联剂为丙三醇三缩水甘油醚时第9天降解率为49.3%,较交联剂为乙二醇二缩水甘油醚制备的凝胶低9.2%,说明在相同交联度下丙三醇三缩水甘油醚形成的网络结构更致密;交联剂均为丙三醇三缩水甘油醚时,交联度为40%的第9天降解率为59.8%,较交联度为60%的凝胶提高了17.5%,交联度增加,降解速率降低。     

基于粗糙度测量和颜色距离的织物缺陷检测方法

针对周期性纹理背景影响织物缺陷检测效果的问题,提出了一种基于粗糙度测量和颜色距离的织物缺陷检测方法。该方法先将待检测图像由RGB颜色空间转换到HSV颜色空间,并分别对三通道进行同态滤波处理,以提升缺陷与背景之间的对比度;利用粗糙度测量对织物图像进行分类,并将同一类别的织物图像分成大小相同且互不重叠的图像分块,分别估计各个图像分块与其八邻域图像分块的颜色距离,从而实现对缺陷的粗定位;最后对粗定位图像分块进行显著性和二值化处理,有效减少了周期性纹理背景对检测结果的影响。实验结果表明:与近期4种方法相比,本文方法对周期性纹理织物图像表现出了较好的检测效果,检测准确率更高。     

异步BCI的大脑工作和空闲状态的辨识方法研究

基于事件相关电位的脑-机接口系统难以检测大脑的空闲状态,限制了被试在任意时间输出指令的自由。利用欧德堡范式同时诱发N200电位、P300电位和瞬态视觉诱发电位。根据瞬态视觉诱发电位的频域特征区分大脑的工作状态和空闲状态;在工作状态下利用N200和P300电位的时域特征识别被试的控制意图,从而构建异步的脑-机接口系统。通过对7名健康被试进行发送指令与观看视频反馈两种状态的实验,实现大脑的工作状态和空闲状态之间的切换。该方法识别大脑状态或者意图的准确率为98.21%,与基于事件相关电位识别空闲状态的方法相比提高了50.89%。     

羊乳清蛋白部分和深度水解工艺、水解物致敏性及肽谱分析

利用羊乳清蛋白制备低致敏性配料是目前乳品工业的研究热点。乳清蛋白是乳中主要的蛋白质之一,也是引起婴幼儿过敏反应的主要成分,将蛋白质水解为小分子肽是降低其致敏性的有效方法。以山羊乳清蛋白为原料,研究了部分水解乳清蛋白和深度水解乳清蛋白的水解工艺和水解物特性(水解度、分子质量分布和β-乳球蛋白抗原性),并利用液相色谱串联质谱法(LC-MS/MS) 比较了部分水解和深度水解工艺中过敏表位酶切位点的差异。研究结果表明,中性蛋白酶和碱性蛋白酶对羊乳清蛋白水解效果较好,其中碱性蛋白酶的水解度最高,达21.26%。经电泳分析,单酶水解后的产物中仍存在大分子多肽链,深度水解工艺需要复合酶水解。在酶底比为4000U/g时,使用碱性蛋白酶在pH值为10.0、温度为55℃条件下水解羊乳清蛋白1.0h,部分水解产物的水解度为12.31%,分子质量在5kDa以下的多肽占95.18%,β-乳球蛋白抗原性下降率为9.40%。中性蛋白酶和碱性蛋白酶的质量比为1∶1,酶底比为6000U/g,在pH值为8.5、温度为50℃条件下,水解羊乳清蛋白3.0h,深度水解产物的水解度为35.58%,分子质量低于3kDa的多肽为97.26%,β-乳球蛋白抗原性下降率为40.97%。部分水解和深度水解均能破坏β-乳球蛋白的大部分过敏表位,但相较于部分水解,深度水解能更大程度地降低乳清蛋白的致敏性。研究旨在为低致敏性羊水解乳清蛋白的生产提供一定的理论参考。     

An All-Scale Hierarchical Architecture Induces Colossal Room-Temperature Electrocaloric Effect at Ultralow Electric Field in Polymer Nanocomposites

Composed of electrocaloric (EC) ceramics and polymers, polymer composites with high EC performances are considered as promising candidates for next-generation all-solid-state cooling devices. Their mass application is limited by the low EC strength, which requires very high operational voltage to induce appreciable temperature change. Here, an all-scale hierarchical architecture is proposed and demonstrated to achieve high EC strength in poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)-based nanocomposites. On the atomic scale, highly polarizable hierarchical interfaces are induced by incorporating BiFeO₃ (BFO) nanoparticles in Ba(Zr_0.21Ti_0.79)O₃ (BZT) nanofibers (BFO@BZT_nfs); on the microscopic scale, percolation of the interfaces further raises the polarization of the composite nanofibers; on the mesoscopic scale, orthotropic orientation of BFO@BZT_nfs leads to much enhanced breakdown strength of the nanocomposites. As a result, an ultrahigh EC strength of ≈0.22 K m MV⁻¹ is obtained at an ultralow electric field of 75 MV m⁻¹ in nanocomposites filled with the orthotropic composite nanofibers, which is by far the highest value achieved in polymer nanocomposites at a moderate electric field. Results of high-angle annular dark-field scanning transmission electron microscopy, in situ scanning Kelvin probe microscopy characterization, and phase-field simulations all indicate that the much enhanced EC performances can be attributed to the all-scale hierarchical structures of the nanocomposite.