A wavelet-based multi-dimensional temporal recurrent neural network for stencil printing performance prediction

The solder paste printing (SPP) is a critical procedure in a surface mount technology (SMT) based assembly line, which is one of the major attributes to the defect of the printed circuit boards (PCBs). The quality of SPP is influenced by multiple factors, such as the squeegee speed, pressure, the stencil separation speed, cleaning frequency, and cleaning profile. During printing, the printer environment is dynamically varying due to the physical change of solder paste, which can result in a dynamic variation of the relationships between the printing results and the influential factors. To reduce the printing defects, it is critical to understand such dynamic relationships. This research focuses on determining the printing performance during printing by implementing a wavelet filtering-based temporal recurrent neural network. To reduce the noise factor in the solder paste inspection (SPI) data, this research applies a three-dimensional dual-tree complex wavelet transformation for low-pass noise filtering and signal reconstruction. A recurrent neural network is utilized to model the performance prediction with low noise interference. Both printing sequence and process setting information are considered in the proposed recurrent network model. The proposed approach is validated using practical dataset and compared with other commonly used data mining approaches. The results show that the proposed wavelet-based multi-dimensional temporal recurrent neural network can effectively predict the printing process performance and can be a high potential approach in reducing the defects and controlling cleaning frequency. The proposed model is expected to advance the current research in the application of smart manufacturing in surface mount technology.     

基于LabVIEW的甲烷产气量自动测量系统设计

针对实验室现有的厌氧发酵装置产气测量存在费时费力、人眼读数误差较大、自动化程度低等问题,设计一种基于LabVIEW的甲烷产气量自动测量系统。提出采用排水法与称重计量法结合的测量方法,以实现产气量自动测量。称重传感器获取发酵甲烷产气排水后得到水的质量,经换算得到排水体积即甲烷产气体积。利用LabVIEW编写软件平台,采用NI USB-6251数据采集卡对发酵过程中的关键参数如甲烷产气量、温度和pH值进行实时采集、处理、显示及存储,同时控制夹管阀和蠕动泵实现自动补充排水液的功能。利用微量注射器对自动测量系统开展性能验证实验。试验结果表明:该装置的测量平均相对误差最大值为1.10%。该系统可以满足发酵实验对甲烷气体的测量需求,不仅能够提高自动化水平还可以提高测量准确性。     

The influence of sonication time on the biogenic amines formation as a critical point in uncured dry-fermented beef manufacturing

In this study, the influence of sonication time on the biogenic amines formation as a critical point in uncured dry-fermented beef manufacturing was studied. Samples of musculus semimembranosus were sonicated at different times (5 and 10 min) using ultrasound cold bath (4 °C) in acid whey (US 40 kHz and acoustic power 480 W). The effect of sonication on biogenic amine (BA) formation was investigated during 93 days of ripening period. Other parameters (pH value, water activity, microbial counts) that might provide further information on the product under study were also determined. The use of ultrasound during beef marinating in acid whey has a positive effect on retarding histamine (HIS), cadaverine (CAD), tyramine (TYR) and putrescine (PUT) formation. Moreover, the sonication treatment did not inhibit the growth of lactic acid bacteria (LAB) in dry-fermented beef during the whole ripening period. The pathogen bacteria (Staphylococcus aureus, Clostridium sp., Listeria monocytogenes) were not detected in all samples neither after 31 nor after 93 days of ripening period.     

Fun and fear: The banalization of nuclear technologies through display

How do nuclear technologies become commonplace? How have the borders between the exceptional and the banal been drawn and redrawn over the last 70 years in order to make nuclear energy part of everyday life? This special issue analyzes the role of fun and display, broadly construed, in shaping the cultural representation and the material circulation (or non‐circulation) of nuclear technologies. Four case studies, covering the United States, Great Britain, Portugal, Spain, and Ukraine from the 1950s to the 2000s, explore how specific forms of public display and playful practices of cultural production were used as means to banalize (or de‐banalize) nuclear energy. This introduction addresses the main theoretical and historiographical signposts of the special issue and outlines the different ways in which the articles explore them.     

Effect of TiB2 addition on grain orientation of porous Si3N4-TiB2 composites by magnetic field alignment technology

Textured porous Si₃N₄-TiB₂ composites were prepared by gel-casting–assisted magnetic field alignment technology and subsequent pressureless sintering in the N₂ atmosphere. The effects of TiB₂ content on grain orientation and properties of composites were studied. Results showed that using the magnetic field of 6T, Si₃N₄ grains exhibited a high a- or b-axis orientation and TiB₂ grains exhibited a high c-axis orientation. In textured green bodies, the increase in TiB₂ content from 0 to 20 wt%, the degree of texture of Si₃N₄ grains showed a slight decrease from 0.78 to 0.71. However, the degree of texture of TiB₂ grains was maintained at about 0.98 regardless of TiB₂ content. After sintering, except for the Si₃N₄ and TiB₂ phases, new TiN and BN phases also appeared in the samples. Additionally, the sintering process promotes grain orientation of Si₃N₄ and TiB₂. Herein, the degree of texture of TiB₂ reached to about 1 regardless of TiB₂ content, meaning that the complete grain orientation formed for TiB₂. Owing to the reconstruction reaction between TiB₂ and N₂, new TiN and BN phases did not form the orientation. The increase in TiB₂ contents gradually increased the apparent porosity of the textured samples from 27.9% to 39.4%, thereby leading to the decrease in bending strength from 126.8 ± 18.8 MPa to 60.3 ± 11.2 MPa and from 105.3 ± 19.8 MPa to 53.6 ± 13.0 MPa in two directions, respectively.     

思维导图在《微机原理及接口技术》教学中的应用

思维导图作为一种可视化图形思维工具，可以有效表征知识体系、层次关系。本文针对《微机原理及接口技术》课程教学现状，介绍了思维导图的特点，分析了思维导图应用于该课程教学中的作用和意义，给出了用 MindManager软件绘制的8086CPU内部结构和输入输出接口的思维导图案例。教学实践证明，思维导图在《微机原理及接口技术》课程教学中可以激发学生学习兴趣，帮助学生建立“整体-局部”思想，促进学生对知识的理解和记忆，提升教学效果。     

Offshoring and backshoring of surface finishing from the perspective of the Nordic countries

Backshoring of production to Western Europe has become an increasingly important trend after decades of offshoring. The subject is introduced by a general discussion followed by a specific analysis of the Nordic surface finishing industry. The main finding is that production quality is the main driver for backshoring of surface finishing.     

煤矿科室工作信息管理系统设计

为了提高了煤矿工作者的工作效率和矿井安全程度，设计了煤矿科室工作信息管理系统，分析了系统的关键技术，主要为J2EE技术和B/S和C/S的体系结构；根据现场调研，对系统需求进行了分析，然后设计了系统总体架构和系统功能模块。煤矿科室工作信息管理系统的应用，减少了人力资源的浪费，确保了信息的保存和查询的安全性。     

枸杞深加工产品开发现状及研究进展

枸杞作为一种药食同源的经济林果,富含多糖、类胡萝卜素、类黄酮、甜菜碱、牛磺酸等多种功能性成分,具有增强免疫调节、抗衰老、预防癌症和肿瘤生长、降低血糖和血脂水平等多种功效,消费者对枸杞相关产品的需求也日益增加。枸杞生长性状属无限花序,果实成熟期较长为每年6～10月份;然而,枸杞果实在成熟后期快速软化,使其极易受到机械损伤和病原微生物侵染,限制果实的贮藏和运输;因此,在果实成熟期为降低枸杞果实的损耗和迎合消费者对枸杞保健功能的需求,需要在成熟期内对果实进行深加工处理。阐述了枸杞的主要营养价值和保健功效,并提出传统加工产业与现代消费升级引起的供需矛盾;介绍了枸杞深加工产品和配套技术设备的相关产业现状,分析了枸杞产业精深加工的市场需求和产品研发的未来发展趋势,并指出了枸杞深加工产品和新技术、新装备在枸杞深加工产业的应用前景以及面临的难题和挑战,为枸杞深加工产业的发展提供理论参考。