中梁上盖板焊接反变形压型工艺探讨

针对中梁上盖板压制反变形时弯曲角度小、回弹量大,成形质量不稳定的现状,分析了Q450NQR1高强钢的成形特性,阐述了压型模具的结构及工作原理.通过计算工艺参数,指出了现有工艺的不足,提出了改进措施.结果表明:新模具可使反变形波动合理,压型返修率明显降低,提高了工效.     

数控技术在木工车床上的应用

随着家具、建材等木材需求行业的飞速发展,传统的木工机械已经不能满足要求。数控技术应用于木工机械成为了大势所趋。与传统木工车床相比,数控车床具有自动送料、通用车刀取代特制仿形刀具、数控车刀运行轨迹、图形输入等优点,在提高产品加工精度的同时,克服了传统木工车床手动单条装料、不同规格产品须制作仿行刀具、频繁调试等缺陷,更好地满足市场发展需求。     

活塞环工艺技术综述

活塞环性能的优劣直接影响到内燃机的整体性能,随着现代内燃机的发展,对于活塞环提出了越来越高的要求。要实现活塞环的特性,加工技术就尤为重要,本文阐述了现代活塞环生产技术特点,并与传统加工方法进行对比,对它们的优缺点进行了分析,并体现了现代活塞环技术的发展趋势。     

Weighted PLS-discriminant analysis with application to conventional sensory profiling

Within the framework of sensory conventional profiling, we propose a general strategy of weight assignment to the various statistical units (products × assessors). This means that for each product, an assessor who does not agree with the other assessors on the evaluation of the product under consideration will be down-weighted thus limiting their impact on the outcome of the analysis. The weights are derived from similarity measures between assessors which reflect the extent to which the assessors agree on the position of each product in the perceptual space. The weights are used to compute the usual statistical parameters such as means and variance-covariance matrices. They are also used to compute the PLS-discriminant components which reflect directions of discrimination among the products. The usefulness of the strategy of weight assignment is demonstrated on the basis of a case study where it is shown that it improves the stability of the representation of the products to small perturbations.     

一种降低末级高速缓存污染的软件控制插入策略

 现有高速缓存替换算法大多无法有效识别数据的局部性特征,导致高速缓存内即将被访问到的数据可能被未来不会被访问到的数据所替换,造成高速缓存污染问题.末级高速缓存污染引发的性能损失随着处理器和存储器之间性能差距的扩大而不断增大,成为制约系统性能提升的重要瓶颈之一.本文针对末级高速缓存污染问题,在剖视分析访存密集型程序的页一级访存行为基础上,提出一种软件控制末级高速缓存插入策略.本方法通过控制和指导页一级数据插入位置,限制局部性差的数据页在末级高速缓存中的访问空间,达到降低末级高速缓存污染的目的.实验结果表明,相对于LRU和DIP策略,本文方法能够有效降低末级高速缓存失效率,提高程序性能.     

海缆路由探测中浅地层剖面仪的现状及应用

浅地层剖面仪以其高效和经济性成为了海底地质情况和海缆路由的有力勘查手段。本文在介绍浅地层剖面仪工作原理及其技术发展历程的基础上,以实例展现了浅地层剖面仪的应用效果;通过调研阐述了国内外浅地层剖面仪的发展现状,着重论述了国外各大厂家的商品化Chirp和SES型浅地层剖面仪及其关键技术指标,对浅地层剖面仪在海缆探测中存在的...     

Depth profiling of Al2O3 + TiO2 nanolaminates by means of a time-of-flight energy spectrometer

Atomic layer deposition (ALD) is currently a widespread method to grow conformal thin films with a sub-nm thickness control. By using ALD for nanolaminate oxides, it is possible to fine tune the electrical, optical and mechanical properties of thin films. In this study the elemental depth profiles and surface roughnesses were determined for Al₂O₃ + TiO₂ nanolaminates with nominal single-layer thicknesses of 1, 2, 5, 10 and 20 nm and total thickness between 40 nm and 60 nm. The depth profiles were measured by means of a time-of-flight elastic recoil detection analysis (ToF-ERDA) spectrometer recently installed at the University of Jyväskylä. In TOF-E measurements ⁶³Cu, ³⁵Cl, ¹²C and ⁴He ions with energies ranging from 0.5 to 10 MeV, were used and depth profiles of the whole nanolaminate film could be analyzed down to 5 nm individual layer thickness.