Studying the pulverization mechanisms of low-cross-link-density natural rubber with and without carbon black

The effects of the temperature in the different heating zones and the rotating speed of the screw in the Solid State Shear Extrusion (SSSE) process were studied to obtain a better understanding of the pulverization mechanisms of the low-cross-link-density natural rubber. Results showed that providing a range of both temperature and normal stress was required to pulverize cross-linked natural rubber, but shear stress plays the most important role to produce fine particles. Two rubber samples were provided with the same composition, but one with carbon black (CB) and the other one without, and were pulverized at the same process conditions to show the effect of the material mechanical properties on the produced particles' average size. The average produced particle size of the sample without CB was considerably smaller than the one with, and they were electrostatically charged. Based on this result, under combination of the shear and normal stresses, adding hard particles (in this case CB) to the cross-linked rubber increases its dissipation energy, therefore less energy is restored for the material fracture.     

New measurement of particle size distribution by a buoyancy weighing-bar method

The rates which particles from JIS Test Powders 1, Class 2 (silica sand), Class 3 (silica sand), Class 16 (calcium carbonate, heavy), and JIS Test Powder 2, Class GBM-20 (barium titanate glass) settled out of homogenous suspensions were determined using the principles of the buoyancy weighing-bar method as well as a sedimentation balance. Samples were standardized by Japanese Industrial Standard, and the dispersing agent was NaPP or NaHMP, while the viscosity improver was a starch syrup solution. Although constructing a handmade sedimentation balance is difficult, developing a handmade weighing tool capable of measuring particle size distribution is easy. Herein three weighing-bars, which were composed of aluminum, stainless steel, and copper, were used to measure the particle size distribution. However, an aluminum slit-cylinder occasionally replaced the weighing-bars. The weighing data obtained via an analytical balance were controlled by connecting the balance to a personal computer with an RS-232C interface, and the determined particle size agreed well with the data obtained by Andreasen analyses and the sedimentation balance.     

The effect of particle size distribution on the properties of blended cements incorporating GGBFS and natural pozzolan (NP)

This paper investigates the effect of particle size distribution on the properties of blended cements incorporating ground granulated blast-furnace slag (GGBFS) and natural pozzolan (NP). Pure Portland cement (PPC), NP and GGBFS were used to obtain blended cements that contain 10, 20, 30% additives. The cements were produced by intergrinding and separate grinding and then blending. Each group had two different Blaine fineness of 280 m²/g and 480 m²/g. According to the particle size distribution (PSD) curves, 46% of the coarser specimens and 69% of the finer specimens passed through the 20 μm sieve. It was observed that the separately ground specimens were relatively finer than the interground ones and had higher compressive strength and sulfate resistance. The separately ground coarser specimens had the lowest heat of hydration. The separately ground finer specimens, which had the highest compressive strength and sulfate resistance, had the highest percent passing for each sieve size. For these specimens 34, 69, 81 and 99% passed through 5, 20, 30 and 55 μm sieves, respectively. For the interground specimens, which had the same fineness, the respective values for the same sieves were 32, 68, 75 and 94%.     

基于PSD3XX与ADMC401接口设计的静止无功发生器系统

文章介绍了PSD3XX系列芯片的基本功能和ADMC401芯片的功能特点 ,结合硬件电路图详细分析了两者的接口设计 ,并对其软件环境和需要注意的问题进行了说明 ,最后以静止无功发生器为例 ,介绍了ADMC401 PSD311两片系统的应用方法 ,同时给出了系统的硬件结构图     

概率统计函数在工件表面形貌分析中的应用

介绍概率统计函数中的自相关函数(ACF)和功率谱密度函数(PSD)在工件形貌分析中的应用。运用自相关函数和功率谱密度函数,可以识别机械加工后工件表面的特征,判断其中是否含有周期信号以及它们的频率,还可以反映出不同频率的成分在整个信号中所占的比重,从而估计在加工过程中各种因素特别是变化着的因素对表面加工质量的影响。     

用PSD芯片实现单片机电路的扩展

可编程外围器件PSD应用于单片机系统后,可大幅度地简化单片机外围电路的设计,减小系统体积,降低功耗,增强系统可靠性。介绍了PSD系列产品的类型和性能,结合实例阐述了PSD与MCU的接口方式,并给出了开发软件PSDsoftExpress的使用流程。     

PCBA结构参数与振动谱型对BGA焊点疲劳寿命的影响

为获得印制电路板组件(PCBA)的板厚、芯片布局等结构参数和随机振动谱型(功率谱密度,PSD)变化对球栅阵列(BGA)封装芯片焊点振动疲劳寿命的影响,利用HYPERMESH软件建立了带BGA封装芯片的PCBA三维有限元网格模型,并采用ANSYS软件对PCBA有限元模型进行了随机振动响应分析。结果表明,随着PCB厚度增加,BGA焊点振动疲劳寿命呈现明显提升的趋势,当PCB厚度由1.2 mm增加到2.2 mm时,BGA焊点振动疲劳寿命N由45363大幅增加到557386;合理的芯片安装间距能够明显增加焊点振动疲劳寿命,特别是当芯片安装在靠近固定约束并处于两个约束对称中间位置时;当PCBA的第一阶固有频率位于随机振动谱最大幅值对应的频率区间时,BGA焊点的振动疲劳寿命会明显降低。     

基于小波理论的PSD测试系统的数据分析

位敏探测器(PSD)技术作为光电技术的重要组成部分,在各学科领域得到广泛应用.随着对PSD系统信号精度的要求越来越高,要求研究出更好的去噪效果的方法.针对PSD系统信号的特性,选择db8、sym8、coif8对含噪的信号进行处理和对比,并通过MATLAB中的小波GUI软件进行数字仿真,并对仿真结果进行比较,从而得出最适...     

PSD 法测量直管弯曲度的步长优化研究

简要介绍ＰＳＤ法测量直管弯曲度的原理，建立了直管弯曲度模型，并利用频谱分析的方法给出了该模型的频谱分析，并根据误差限确定了优化步长，为简单有效地测量提供了依据．     

基于峰值频率设计UWB脉冲的算法

根据Rayleigh脉冲峰值频率与脉冲形状参数α、求导阶数n的关系提出了一种设计超宽带脉冲的新算法。不像其它算法只能设计出一个脉冲,本算法可以设计出无数个满足FCC频谱规划的脉冲,即能够求出所有满足条件的α值,并给出了α的取值范围。