The confinement losses in air-guiding photonic bandgap fibers （PBGFs） with air hole missing are studied with the full-vector finite-element method. It is confirmed that there are two loss peaks （1.555 and 1.598 μm...The confinement losses in air-guiding photonic bandgap fibers （PBGFs） with air hole missing are studied with the full-vector finite-element method. It is confirmed that there are two loss peaks （1.555 and 1.598 μm） if there is a hole missing in the cladding far from the core. The closer to the core the hole missing is, the larger the confinement losses are, and even no mode could propagate in the core. The main power of the fundamental mode leaks from the core to the cladding defect. The quality of PBGFs can be improved through controlling the number and position of defects.展开更多
Aiming at the application of a wireless sensor network to locating miners in underground mine,we design a wireless sensor network location node system,considering the communication performance and the intrinsic safety...Aiming at the application of a wireless sensor network to locating miners in underground mine,we design a wireless sensor network location node system,considering the communication performance and the intrinsic safety. The location node system consists of a mobile node,several fixed nodes,and a sink node,all of whose circuits were designed based on CC2430. A varistor and a RC circuit were used in the reset circuit of a sensor node to guarantee the intrinsic safety by reducing discharge energy,the theoretical analysis of the discharge energy shows that the reset circuit is an intrinsic safety one. The analysis and simulation about the performance of the location node system are discussed,such as network communication delay and packet loss rate,the results show that the highest network communication delay of the system is about 0.11 seconds,and the highest packet loss rate is about 0.13,which assures the location node system has a high reliability,and can locate miners in the underground mine.展开更多
针对2.0~25.0μm波段传输的限制损耗问题,文章采用数值模拟方法研究影响碲基硫系光子晶体光纤(photonic crystal fiber,PCF)限制损耗的主要因素。光纤纤芯和包层材料采用Ge 20 As 20 Se 15 Te 45玻璃,通过改变纤芯直径、空气孔直径和空...针对2.0~25.0μm波段传输的限制损耗问题,文章采用数值模拟方法研究影响碲基硫系光子晶体光纤(photonic crystal fiber,PCF)限制损耗的主要因素。光纤纤芯和包层材料采用Ge 20 As 20 Se 15 Te 45玻璃,通过改变纤芯直径、空气孔直径和空气孔层数等参数进行2.0~25.0μm波段限制损耗的计算,结果表明,影响限制损耗的最大因素是纤芯直径,限制损耗随着纤芯直径和空气孔直径的增大而显著降低,随着空气孔层数的增加而降低;优化设计出一种低限制损耗的PCF,结果表明,当纤芯直径和节距为8.0μm、空气孔直径为7.2μm、包层空气孔层数为4时,该PCF在2.0~25.0μm波长范围的限制损耗低于1.4×10^(-6) dB/m,满足低损耗传输要求。文章研究结果对2.0~25.0μm波段光信号的传输具有一定的意义。展开更多
Transmission Control Protocol （TCP） in infrastructure based vehicular net- works is dedicated to support reliable Intemet services for mobile users. However, an end-to- end TCP flow not only experiences some com- mo...Transmission Control Protocol （TCP） in infrastructure based vehicular net- works is dedicated to support reliable Intemet services for mobile users. However, an end-to- end TCP flow not only experiences some com- mon challenges in wireless mobile networks, such as high packet loss rate, medium access competition, unstable wireless bandwidth, and dynamic topology, etc., but also suffers from performance degradation due to traffic congestion at the Road-Side Units （RSUs） that connect the wireline and wireless networks. In order to address the challenging issues related to reliable TCP transmissions in infrastruc- ture based vehicular networks, we propose an RSU based TCP （R-TCP） scheme. For wireline source nodes, R-TCP adopts a novel flow control mechanism to adjust transmission rates according to the status of bottleneck link. Specifically, during the short wireless connec- tion time in Infrastructure based vehicular net- works, R-TCP quickly chooses an ideal trans- mission rate for data transmissions instead of activating the slow start algorithm after the connection is established, and successfully avoids the oscillation of the transmission rate. Simulation results show that R-TCP achieves great advantages than some relate proposals in terms of throughput, end-to-end delay, and packet loss rate.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 61077084)
文摘The confinement losses in air-guiding photonic bandgap fibers （PBGFs） with air hole missing are studied with the full-vector finite-element method. It is confirmed that there are two loss peaks （1.555 and 1.598 μm） if there is a hole missing in the cladding far from the core. The closer to the core the hole missing is, the larger the confinement losses are, and even no mode could propagate in the core. The main power of the fundamental mode leaks from the core to the cladding defect. The quality of PBGFs can be improved through controlling the number and position of defects.
基金Projects 20070411065 supported by the China Postdoctoral Science Foundation0801028B by the Jiangsu Postdoctoral Science Research Foundation
文摘Aiming at the application of a wireless sensor network to locating miners in underground mine,we design a wireless sensor network location node system,considering the communication performance and the intrinsic safety. The location node system consists of a mobile node,several fixed nodes,and a sink node,all of whose circuits were designed based on CC2430. A varistor and a RC circuit were used in the reset circuit of a sensor node to guarantee the intrinsic safety by reducing discharge energy,the theoretical analysis of the discharge energy shows that the reset circuit is an intrinsic safety one. The analysis and simulation about the performance of the location node system are discussed,such as network communication delay and packet loss rate,the results show that the highest network communication delay of the system is about 0.11 seconds,and the highest packet loss rate is about 0.13,which assures the location node system has a high reliability,and can locate miners in the underground mine.
文摘针对2.0~25.0μm波段传输的限制损耗问题,文章采用数值模拟方法研究影响碲基硫系光子晶体光纤(photonic crystal fiber,PCF)限制损耗的主要因素。光纤纤芯和包层材料采用Ge 20 As 20 Se 15 Te 45玻璃,通过改变纤芯直径、空气孔直径和空气孔层数等参数进行2.0~25.0μm波段限制损耗的计算,结果表明,影响限制损耗的最大因素是纤芯直径,限制损耗随着纤芯直径和空气孔直径的增大而显著降低,随着空气孔层数的增加而降低;优化设计出一种低限制损耗的PCF,结果表明,当纤芯直径和节距为8.0μm、空气孔直径为7.2μm、包层空气孔层数为4时,该PCF在2.0~25.0μm波长范围的限制损耗低于1.4×10^(-6) dB/m,满足低损耗传输要求。文章研究结果对2.0~25.0μm波段光信号的传输具有一定的意义。
基金supported in part by Fundamental Research Funds for the Central Universities of China under Grant(N140405004) partly by National Natural Science Foundation of China(61373159)+1 种基金partly by Educational Committee of Liaoning Province science and technology research projects under Grant (L2013096)partly by Key Laboratory Project Funds of Shenyang Ligong University (4771004kfs03)
文摘Transmission Control Protocol （TCP） in infrastructure based vehicular net- works is dedicated to support reliable Intemet services for mobile users. However, an end-to- end TCP flow not only experiences some com- mon challenges in wireless mobile networks, such as high packet loss rate, medium access competition, unstable wireless bandwidth, and dynamic topology, etc., but also suffers from performance degradation due to traffic congestion at the Road-Side Units （RSUs） that connect the wireline and wireless networks. In order to address the challenging issues related to reliable TCP transmissions in infrastruc- ture based vehicular networks, we propose an RSU based TCP （R-TCP） scheme. For wireline source nodes, R-TCP adopts a novel flow control mechanism to adjust transmission rates according to the status of bottleneck link. Specifically, during the short wireless connec- tion time in Infrastructure based vehicular net- works, R-TCP quickly chooses an ideal trans- mission rate for data transmissions instead of activating the slow start algorithm after the connection is established, and successfully avoids the oscillation of the transmission rate. Simulation results show that R-TCP achieves great advantages than some relate proposals in terms of throughput, end-to-end delay, and packet loss rate.
