Isothermal flashless die forging process of Ti - alloy structural air - frame part with varying thickness rib has been modelled in this paper.The results of present study show that a upside - down trapezoid rib would...Isothermal flashless die forging process of Ti - alloy structural air - frame part with varying thickness rib has been modelled in this paper.The results of present study show that a upside - down trapezoid rib would be formed and buckling would occure as blank is reduced,if the thickness of billet is maller than or equal to the thickness of rib. During modelling process of structural air frame part with E type cross - section rib, the saddle or lap would be formed finally at the middle of transverse rib between ribs with increase in deformation.If metal is allowed to flow out at confluence of longitudinal and transverse rib, the lop defect would be eliminated,, but a pipe cavity is obvious on corresponding loca- tion of blank. of defect formation depends on distance of metal flow ,friction,temperature homoge- neity of the blank and complexity of the part.展开更多
A novel technique called physical frame time-slot switching （PFTS） is discussed and its technical and application aspects are analyzed. The format of the ethernet media access control （MAC） frame is borrowed in de...A novel technique called physical frame time-slot switching （PFTS） is discussed and its technical and application aspects are analyzed. The format of the ethernet media access control （MAC） frame is borrowed in defining the physical frame for PFTS and the transmission time for the maximum size of the MAC frame is defined as a physical frame time-slot （PFT）. Consequently, user data can be fed into PFTS and switched in a single layer sub-network in an asynchronous mode.展开更多
Generally, ring spun yarns are manufactured from roving which is produced by roving frame. In this paper, an experiment has been done producing ring spun cotton yarn directly from finisher drawn sliver eliminatin...Generally, ring spun yarns are manufactured from roving which is produced by roving frame. In this paper, an experiment has been done producing ring spun cotton yarn directly from finisher drawn sliver eliminating the roving frame. Total 3 types of yarn with the various linear density of 8 Ne, 10 Ne & 12 Ne were produced using a roving frame and without using a roving frame. In the next step, physical and mechanical properties of those yarns including unevenness, imperfections, hairiness & tenacity were investigated. The result showed that ring spun cotton yarns produced from sliver exhibited inferior physical and mechanical properties compared with samples from the conventional ring spinning system.展开更多
空间光通信具有保密性好,信息容量大,抗干扰能力强等优点,是现代通信系统研究的热点之一。脉冲位置调制(pulse position modulation,PPM)是空间光通信系统中一种性能优良的调制方式。针对空间光通信系统中信息传输速率低,设计了一种改进...空间光通信具有保密性好,信息容量大,抗干扰能力强等优点,是现代通信系统研究的热点之一。脉冲位置调制(pulse position modulation,PPM)是空间光通信系统中一种性能优良的调制方式。针对空间光通信系统中信息传输速率低,设计了一种改进的"空-空-零"的物理帧格式,以提高空间光通信系统的传输速率。针对实际空间激光数字接收机,深入开展了帧同步算法设计研究。结合设计的物理帧格式,重点研究了帧同步算法的设计,为了应对噪声等参数的变化,提出自适应相关阈值设置;考虑到工程实现,提出了一种相关滤波简化实现方法等。最后,基于FPGA完成了接收机原型系统设计,经Matlab仿真、在线仿真以及实际测试表明了该设计方案的正确性和可靠性。展开更多
文摘Isothermal flashless die forging process of Ti - alloy structural air - frame part with varying thickness rib has been modelled in this paper.The results of present study show that a upside - down trapezoid rib would be formed and buckling would occure as blank is reduced,if the thickness of billet is maller than or equal to the thickness of rib. During modelling process of structural air frame part with E type cross - section rib, the saddle or lap would be formed finally at the middle of transverse rib between ribs with increase in deformation.If metal is allowed to flow out at confluence of longitudinal and transverse rib, the lop defect would be eliminated,, but a pipe cavity is obvious on corresponding loca- tion of blank. of defect formation depends on distance of metal flow ,friction,temperature homoge- neity of the blank and complexity of the part.
基金Supported by National Natural Science Foundation of China (No. 60372065)
文摘A novel technique called physical frame time-slot switching （PFTS） is discussed and its technical and application aspects are analyzed. The format of the ethernet media access control （MAC） frame is borrowed in defining the physical frame for PFTS and the transmission time for the maximum size of the MAC frame is defined as a physical frame time-slot （PFT）. Consequently, user data can be fed into PFTS and switched in a single layer sub-network in an asynchronous mode.
文摘Generally, ring spun yarns are manufactured from roving which is produced by roving frame. In this paper, an experiment has been done producing ring spun cotton yarn directly from finisher drawn sliver eliminating the roving frame. Total 3 types of yarn with the various linear density of 8 Ne, 10 Ne & 12 Ne were produced using a roving frame and without using a roving frame. In the next step, physical and mechanical properties of those yarns including unevenness, imperfections, hairiness & tenacity were investigated. The result showed that ring spun cotton yarns produced from sliver exhibited inferior physical and mechanical properties compared with samples from the conventional ring spinning system.
文摘空间光通信具有保密性好,信息容量大,抗干扰能力强等优点,是现代通信系统研究的热点之一。脉冲位置调制(pulse position modulation,PPM)是空间光通信系统中一种性能优良的调制方式。针对空间光通信系统中信息传输速率低,设计了一种改进的"空-空-零"的物理帧格式,以提高空间光通信系统的传输速率。针对实际空间激光数字接收机,深入开展了帧同步算法设计研究。结合设计的物理帧格式,重点研究了帧同步算法的设计,为了应对噪声等参数的变化,提出自适应相关阈值设置;考虑到工程实现,提出了一种相关滤波简化实现方法等。最后,基于FPGA完成了接收机原型系统设计,经Matlab仿真、在线仿真以及实际测试表明了该设计方案的正确性和可靠性。
