NOS525钢热锻模具早期开裂失效分析

采用直读光谱仪、数显洛氏硬度计、光学显微镜、扫描电镜及能谱仪,对NOS525钢热锻模具早期开裂失效件的化学成分含量、断口特征形貌及金相组织进行检测和分析。结果显示,显微组织中的马氏体针尤为细长,该组织属于晶粒粗大的过热组织,主要原因为:模具在热处理过程中高温区加热时间过长,造成组织晶粒的急剧长大,且随着基体组织中碳含量的增加,马氏体形态由条状转变为针状,材料强度降低且脆性增大。由扫描电镜检测得知,模具开裂断面呈准解理断口及出现条状撕裂棱,表明组织中存在低硬度的软点区,断口表面的撕裂棱特征形貌属于淬火后未转变的残余奥氏体组织。残余奥氏体在应力作用下易发生马氏体相变,从而增加组织应力,进一步加大了材料开裂风险,降低模具的使用性能。同时,热锻模具在使用过程中,工作面存在冷却不及时或冷却不彻底的现象,使得模腔凹槽部位产生明显的热疲劳裂纹。     

基于QT、GDAL处理遥感影像GeoTIFF数据的应用

GeoTIFF图像格式可以存储各种地理信息,因此在遥感图像领域应用十分广泛.但随着遥感影像的数据量迅速增长,如何提高对海量影像数据调度及显示成为急需解决的问题.本文利用开源库GDAL实现了对海量遥感影像GeoTIFF格式文件的地理信息读取,通过建立图形金字塔的方式对影像数据进行快速索引,最后利用跨平台QT语言开发,实现GeoTIFF格式文件在各种不同操作系统下放大、缩小及全屏显示.     

一个高效可完全模拟的n取1茫然传输协议

茫然传输(oblivious transfer, OT)是一个重要的密码学基础工具,可以被应用到许多密码学协议的构造中去,例如安全多方计算、隐私信息检索等.在n取1茫然传输场景中有2个参与方,即发送方S和接收方R.发送方有n个输入值,接收方希望得到其中某一个值.与此同时协议要保证发送方不知道接收方的选择信息,且接收方除了得到自己选择的值以外不知道其他输入值的相关信息.已有的OT\\+1\\-n协议仅能保证参与方的输入隐私性或实现单边模拟,均不能实现完全模拟.完全模拟意味着在理想/现实模拟范例中,当接收方或发送方被分别腐化时,协议都可以被模拟,较之于只保证隐私性和单边模拟,其安全性更强.首次在标准恶意敌手模型下,基于判定Diffie-Hellamn (decisional Diffie-Hellamn, DDH)困难问题假设构造了一个高效、可完全模拟的OT\\+1\\-n协议,该协议的思想主要基于双模式加密机制,并结合知识的零知识证明系统.协议具有常数轮交互复杂度,且计算和通信复杂度仅与n线性相关.     

适用于智能环境的高效安全云辅助模式匹配协议

以机器学习、人工智能、物联网等技术所构建的智能环境正在改变人们的生活、工作及思维方式.智能环境下数据存储和处理的方式也在不断改变,其中安全和效率是2个重要的因素.就安全而言,在数据共享的前提下保护隐私势在必行.就效率而言,智能环境中存在诸多资源受限的设备,针对这些设备如何设计高效的算法或协议直接决定其可行性.从以上2个需求出发,研究适用于智能环境中的安全高效模式匹配问题.传统的安全模式匹配协议中模式持有方需要执行大量的公钥操作,因此不适用于手机等资源受限设备作为模式持有方的场景.首次在双云服务器辅助的安全两方计算模型下给出安全模式匹配协议的功能函数,并基于茫然传输(oblivious transfer, OT)给出协议的具体构造.假设云服务器和参与方之间不合谋,协议在半诚实敌手模型下是安全的.协议需要4轮交互,模式方仅需要执行少量的异或操作,而复杂的OT协议主要集中在数据库方和云服务器之间.此外,使用OT扩展(OT extension)技术可以将所有OT协议的数量从O(nm)降至O(k),其中n和m是数据库方和模式方的输入长度,k是OT扩展协议中基础OT的数目,其远小于nm.     

Mass spectrometry based proteomics as foodomics tool in research and assurance of food quality and safety

BackgroundAs a comprehensive discipline that studies food and nutrition, foodomics requires reliable qualitative and quantitative information about the food proteome component in order to extract new integrative information from the complex multivariable space of omics. This new information is necessary to achieve a higher level of understanding of processes in food science and technology, consequently new functions of food and improved markers of food quality and safety and completely transform concept of food safety.Scope and approachWe are making an effort to present mass spectrometry (MS) based proteomic approaches that are being utilized in different proteomic studies, not necessarily in the field of foodomics, which are important and have the potential to advance this field. Current analytical capabilities of MS-based proteomics together with sample preparation procedures and quantification strategies, and recent technical developments were presented.Key findings and conclusionsMS-based proteomics enables the analysis of different aspects of proteins and provides a variety of approaches for reliable quantification of individual proteins and/or food proteome. This is a complex field and its successful implementation requires a dedicated analyst, a thorough design of sample preparation procedure, the selection of an MS technique and approach, an adequate type of mass spectrometer, a thorough data analysis and validation. Improvements in the technology of mass spectrometers are continuously expanding capabilities of MS-based proteomics.     

基于最大熵的光学层析图像重建

基于最大熵的光学层析图像的正则化重建方法是将图像重建问题转化为对目标函数的优化问题,进而用基于梯度的迭代图像重建方法实现对目标函数的求解。针对此优化问题,给出了一个具体的梯度求解方法。实验证明,该方法能够降低光学层析图像重建的病态性,提高图像重建质量。     

Long Non-Coding RNA KCNQ1OT1 Regulates Protein Kinase CK2 Via miR-760 in Senescence and Calorie Restriction

Long non-coding RNAs (lncRNAs) play important biological roles. Here, the roles of the lncRNA KCNQ1OT1 in cellular senescence and calorie restriction were determined. KCNQ1OT1 knockdown mediated various senescence markers (increased senescence-associated β-galactosidase staining, the p53-p21^Cip1/WAF1 pathway, H3K9 trimethylation, and expression of the senescence-associated secretory phenotype) and reactive oxygen species generation via CK2α downregulation in human cancer HCT116 and MCF-7 cells. Additionally, KCNQ1OT1 was downregulated during replicative senescence, and its silencing induced senescence in human lung fibroblast IMR-90 cells. Additionally, an miR-760 mimic suppressed KCNQ1OT1-mediated CK2α upregulation, indicating that KCNQ1OT1 upregulated CK2α by sponging miR-760. Finally, the KCNQ1OT1–miR-760 axis was involved in both lipopolysaccharide-mediated CK2α reduction and calorie restriction (CR)-mediated CK2α induction in these cells. Therefore, for the first time, this study demonstrates that the KCNQ1OT1–miR-760–CK2α pathway plays essential roles in senescence and CR, thereby suggesting that KCNQ1OT1 is a novel therapeutic target for an alternative treatment that mimics the effects of anti-aging and CR.     

Functionalization of carbon nanomaterials for advanced polymer nanocomposites: A comparison study between CNT and graphene

The allotropes of carbon nanomaterials (carbon nanotubes, graphene) are the most unique and promising substances of the last decade. Due to their nanoscale diameter and high aspect ratio, a small amount of these nanomaterials can produce a dramatic improvement in the properties of their composite materials. Although carbon nanotubes (CNTs) and graphene exhibit numerous extraordinary properties, their reported commercialization is still limited due to their bundle and layer forming behavior. Functionalization of CNTs and graphene is essential for achieving their outstanding mechanical, electrical and biological functions and enhancing their dispersion in polymer matrices. A considerable portion of the recent publications on CNTs and graphene have focused on enhancing their dispersion and solubilization using covalent and non-covalent functionalization methods. This review article collectively introduces a variety of reactions (e.g. click chemistry, radical polymerization, electrochemical polymerization, dendritic polymers, block copolymers, etc.) for functionalization of CNTs and graphene and fabrication of their polymer nanocomposites. A critical comparison between CNTs and graphene has focused on the significance of different functionalization approaches on their composite properties. In particular, the mechanical, electrical, and thermal behaviors of functionalized nanomaterials as well as their importance in the preparation of advanced hybrid materials for structures, solar cells, fuel cells, supercapacitors, drug delivery, etc. have been discussed thoroughly.     

不同疲劳试验中改性沥青混合料疲劳性能对比

使用四点弯曲疲劳试验(4PB)、两点梯形梁疲劳试验(2PB)和overlay tester(OT)试验3种试验方法,对工程上常用的7种沥青混合料疲劳性能进行了测试.结果表明:在3种疲劳试验中,掺加6%(质量分数,下同)SBS的改性沥青混合料疲劳性能均较好,同时掺加10%TB胶粉和3%SBS的改性沥青混合料、掺加4.5%SBS的改性沥青混合料和同时掺加4.5%SBS及0.4%多聚磷酸(PPA)的改性沥青混合料疲劳性能均一般,掺加3%SBS的改性沥青混合料疲劳性能较差,温拌剂改性沥青混合料和埃索基质沥青混合料的疲劳性能最差;提高SBS掺量可以有效地提高沥青混合料的疲劳性能;添加TB胶粉和PPA可以在不同程度上提高SBS改性沥青混合料的疲劳寿命,但其对疲劳性能的影响力逊于SBS;不同试验方法中沥青混合料疲劳性能的排序具有一致性,具体排序稍有不同.     

The combined use of order tracking techniques for enhanced Fourier analysis of order components

Order tracking is one of the most important vibration analysis techniques for diagnosing faults in rotating machinery. It can be performed in many different ways, each of these with distinct advantages and disadvantages. However, in the end the analyst will often use Fourier analysis to transform the data from a time series to frequency or order spectra. It is therefore surprising that the study of the Fourier analysis of order-tracked systems seems to have been largely ignored in the literature. This paper considers the frequently used Vold-Kalman filter-based order tracking and computed order tracking techniques. The main pros and cons of each technique for Fourier analysis are discussed and the sequential use of Vold-Kalman filtering and computed order tracking is proposed as a novel idea to enhance the results of Fourier analysis for determining the order components. The advantages of the combined use of these order tracking techniques are demonstrated numerically on an SDOF rotor simulation model. Finally, the approach is also demonstrated on experimental data from a real rotating machine.