聚丙烯腈纤维在水浴牵伸过程中应力-应变曲线的研究

主要考察了聚丙烯腈纤维在水浴牵伸过程中的应力—应变曲线，以及温度、牵伸速率、水分对应力—应变曲线的影响。结果表明：聚丙烯腈纤维在水温为室温(26℃)、30℃～70℃时属于细颈牵伸，在80℃、90℃时是类橡胶牵伸，当水温低于60℃和牵伸速率太快时纤维易产生毛丝。所以在牵伸过程中，水温不能低于60％，牵伸速率要适中，在本实验条件下，200mm／min、500mm／min比较合适，而且在水中牵伸比在空气中牵伸效果好，可获得较大的牵伸率。     

表面处理对Ti-6-22-22合金高温疲劳寿命的影响

采用喷丸和离子注入对Ti-6-22-22合金机械加工样品进行表面处理,研究表面处理对Ti-6-22-22合金室温和高温疲劳寿命的影响.结果表明,喷丸和离子注入对材料疲劳S-N曲线的影响与实验温度有关.喷丸和离子注入对Ti-6-22-22合金的室温疲劳强度影响较小,400℃时的疲劳强度明显提高.SEM断口分析显示,400℃长寿命疲劳后的表面处理样品裂纹在亚表面萌生.     

切削数据库中用Matlab与VC混合编程实现数据可视化

切削数据库中数据的可视化处理是一重要研究方向。采用试验数据,对切削数据库中刀具磨损等曲线用Matlab数值计算及图形处理软件与Visual C 混合编程进行可视化图形处理,得到能够脱离Matlab环境运行的曲线图形模块的方法。使用这种方法,可以大大缩短软件的开发周期。此方法在图像处理等需要大量计算的工程应用场合有广泛的应用价值。     

混凝土受拉力学性能统一计算方法

对近20年国内进行的C10-C110强度等级的混凝土受拉力学性能的试验资料进行了重分析，结果表明，随着混凝土强度等级的提高，混凝土的轴心抗拉强度、劈拉强度、受拉弹性模量及受拉峰值应变等各力学性能指标和轴心受拉应力一应变关系曲线均具有连续变化规律．基于统计分析方法，提出了C10-C110强度等级混凝土轴心抗拉强度、劈拉强度及受拉峰值应变等力学性能指标统一计算公式和混凝土轴心受拉应力-应变全曲线计算公式，计算结果与实测结果吻合较好，对开展混凝土结构的非线性有限元分析和设计具有参考价值．     

国外500kV变压器过励磁保护的分析

根据国外过励磁保护在绍兴电力局500kV变电站的应用情况,以500kV凤仪变#3主变ABB过励磁保护为例,着重分析了其基本原理、与变压器过励磁特性曲线的配合、存在的保护死区以及整定调试等问题。     

A New Yellow Long Lasting Phosphor Y2O2S∶Ti

A new kind of doped rare earth free phosphor Y2O2S∶xTi(0＜x≤0.10) with doped Ti as activative center was synthesized by solid state reaction and sintered at 1200 ℃ for 2.5 h under reducing atmosphere. XRD patterns, photoluminescence spectra, time-resolved phosphorescence spectra and decay curves of the phosphor were investigated. XRD results reveal that a single Y2O2S phase exists with Ti content up to 6%(mol fraction). Yellow long lasting phosphorescence for present materials was observed in the dark with naked eye after the removal of the excitation light. From the time-resolved phosphorescence spectra the broad emission band centered at 565 nm was confirmed to be responsible for the long lasting phosphorescence which could maintain above 1 h. The possible mechanism responsible for the long lasting phosphorescence of the Y2O2S∶Ti phosphor was proposed.     

Multi-degree reduction of NURBS curves based on their explicit matrix representation and polynomial approximation theory

NURBS curve is one of the most commonly used tools in CAD systems and geometric modeling for its various specialties, which means that its shape is locally adjustable as well as its continuity order, and it can represent a conic curve precisely. But how to do degree reduction of NURBS curves in a fast and efficient way still remains a puzzling problem. By applying the theory of the best uniform approximation of Chebyshev polynomials and the explicit matrix representation of NURBS curves, this paper gives the necessary and sufficient condition for degree reducible NURBS curves in an explicit form. And a new way of doing degree reduction of NURBS curves is also presented, including the multi-degree reduction of a NURBS curve on each knot span and the multi-degree reduction of a whole NURBS curve. This method is easy to carry out, and only involves simple calculations. It provides a new way of doing degree reduction of NURBS curves, which can be widely used in computer graphics and industrial design.     

Three-Dimensional Implicit Curve Interpolation

An approach to 3D implicit curve interpolation in computer numerical systems (CNC) is presented. A 3D implicit curve is the intersection of two implicit surfaces. Geometric entities of 3D implicit curves are related to motion entities along the curve. The results are then used to develop real-time 3D implicit curve interpolation. An improved interpolation scheme has been proposed to augment the initial interpolation scheme to eliminate the cumulative point deviations. Simulations of implicit curve interpolation have been carried out to verify the effectiveness of the proposed algorithm. They also demonstrate that under typical machining conditions, the interpolation error for the improved scheme is well within the accuracy requirements of typical machines. The example has an application potential for tool-path interpolation when tool paths are obtained by intersecting an implicit design surface by drive cylinders. These show that the proposed algorithm is potentially useful for the machining of implicit surfaces.     

带双参数六次Said-Ball曲线的扩展

为了满足曲线的设计要求,针对六次Said-Ball曲线不能调整曲线形状的不足,一个含有双形状参数的六次多项式基函数被给出,探讨了所构造的基函数的性质。基于该基函数定义了带有双形状参数的六次Said-Ball扩展曲线,分析了2段扩展曲线连续拼接应满足的条件。在给定控制多边形的情况下,通过改变形状参数值,可以调整曲线形状,增强了曲线的表达能力,弥补了六次Said-Ball曲线不能调整曲线形状的不足。该方法是不仅实用而且有效,在计算机辅助几何设计中可以得到广泛地应用。     

Power grand composite curves shaping for adaptive energy management of hybrid microgrids

This work proposes a systematic approach for the adaptive identification and implementation of efficient power management strategies (PMS) in the course of operation of hybrid renewable energy microgrids. The approach is based on the temporal evolution of the system power grand composite curve (PGCC), which is adaptively shaped on-line and within short-term time intervals to form a sequence of decisions indicating the instant and duration of activation of different subsystems. It builds on from previous work where the potential for system performance enhancement could not be exploited through pre-specified PMS identified off-line. More specifically, it involves a stored energy targeting step that exploits the PGCC to identify the desired operational profile of an accumulator during a prediction horizon in order to satisfy the system operating goals. The identified energy targets are subsequently enforced through a sequence of control actions that enable the exact matching of the PGCC hence resulting in a new PMS. The method is elaborated graphically for multiple potential operating goals and is supported by a formal mathematical model that captures system structural and temporal characteristics. It is implemented on an actual hybrid microgrid considering multiple RES-based energy generation and storage options for expected and unexpected weather conditions.