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分析了采用TDMA方案按固定信元封装组帧的ATM-PON系统的上行接入控制方案和基于千兆以太网的宽带无源光接入网(EthernetPON)的可变时隙TDMA动态带宽分配的接入控制方案。后一方案采用轮转调度(round-robinscheduling)的方式对各ONU进行轮询,依据它们各自缓冲区中预备发送的长度不定的数据发送请求,根据多用户接入和业务类型进行以太包调度,因此该方案能提供接入网的可扩展性以及ONU之间的统计复用,提高带宽利用率。文中提供了两种接入控制方案的流程,并着重对更具潜力的EPON系统的接入控制方案进行了详尽的分析和研究。 相似文献
95.
Wen‐Long Liu Mei‐Zhen Zou Si‐Yong Qin Yin‐Jia Cheng Yi‐Han Ma Yun‐Xia Sun Xian‐Zheng Zhang 《Advanced functional materials》2020,30(39)
Surface modification of nanomaterials is essential for their biomedical applications owing to their passive immune clearance and damage to reticuloendothelial systems. Recently, a cell membrane‐coating technology has been proposed as an ideal approach to modify nanomaterials owing to its facile functionalized process and good biocompatibility for improving performances of synthetic nanomaterials. Here, recent advances of cell membrane‐coated nanomaterials are reviewed based on the main biological functions of the cell membrane in living cells. An overview of the cell membrane is introduced to understand its functions and potential applications. Then, the applications of cell membrane‐coated nanomaterials based on the functions of the cell membrane are summarized, including physical barrier with selective permeability and cellular communication via information transmission and reception processes. Finally, perspectives of biomedical applications and challenges about cell membrane‐coated nanomaterials are discussed. 相似文献
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Zhuo Liu Ye Ma Han Ouyang Bojing Shi Ning Li Dongjie Jiang Feng Xie Dan Qu Yang Zou Yue Huang Hu Li Chaochao Zhao Puchuan Tan Min Yu Yubo Fan Hao Zhang Zhong Lin Wang Zhou Li 《Advanced functional materials》2019,29(3)
Changes in endocardial pressure (EP) have important clinical significance for heart failure patients with impaired cardiac function. As a vital parameter for evaluating cardiac function, EP is commonly monitored by invasive and expensive cardiac catheterization, which is not feasible for long‐term and continuous data collection. In this work, a miniaturized, flexible, and self‐powered endocardial pressure sensor (SEPS) based on triboelectric nanogenerator (TENG), which is integrated with a surgical catheter for minimally invasive implantation, is reported. In a porcine model, SEPS is implanted into the left ventricle and the left atrium. The SEPS has a good response both in low‐ and high‐pressure environments. The SEPS achieves the ultrasensitivity, real‐time monitoring, and mechanical stability in vivo. An excellent linearity (R 2 = 0.997) with a sensitivity of 1.195 mV mmHg?1 is obtained. Furthermore, cardiac arrhythmias such as ventricular fibrillation and ventricular premature contraction can also be detected by SEPS. The device may promote the development of miniature implantable medical sensors for monitoring and diagnosis of cardiovascular diseases. 相似文献
98.
IEEE 802.16j Mobile Multihop Relay Standard defines multi-hop relay operation in a WiMAX system. It uses a novel synchronous
multicast and broadcast transmission mechanism to achieve macro diversity. With the newly introduced synchronous delivery
constraint, the multicast data delivery algorithm should be designed differently to enhance system performance. This paper
provides Multi-Rate Selection Algorithm (MRSA) for multicast and broadcast (MBS) data delivery. It could reduce the data distribution
delay from the BS to all the RSs. Besides, we also propose the path selection algorithm to further improve the effectiveness
of MRSA. Our simulation results show that using MRSA with our shortest-path path selection algorithm, the delay for data delivery
in 802.16j MBS system could be greatly reduced. The proposed scheme could achieve the performance closed to the optimal solutions.
To the authors’ best knowledge, this is the first research work to investigate the IEEE 802.16j multicast and broadcast problem. 相似文献
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介绍了图解法分析冷原子干涉仪的基本原理,建立了空间型Raman脉冲冷原子陀螺仪的理论模型。通过对冷原子干涉仪近似数学模型的变换,研究了原子初速度与跃迁概率之间的关系,阐述了基于辅助角速度测量的原子速度扫描法测量原理。在原子干涉仪精确模型的基础上,利用Raman激光频率调制对多普勒效应进行补偿,并利用相位调制进行修正以满足原子速度扫描法中的相位关系。数值仿真计算结果表明,在辅助角速度测量量程内,经过补偿修正后的原子速度扫描法能实现对绝对角速度的高精度测量。 相似文献