P2P大规模流媒体调度技术研究

随着宽带、IPV6、3G等技术的日渐成熟,流媒体应用已成为Internet承载的重要业务.调度技术是保证大规模可信流媒体服务质量的关键问题之一.对典型流媒体调度和分发技术进行综述,归纳分析了基于P2P网络环境下树型、网状以及混合拓扑结构的流媒体技术的优缺点,对mesh网下的资源发布于查找、服务节点选择、数据块调度等进行了重点分析和评述.依据流媒体应用的发展趋势,预测了P2P大规模可信流媒体调度技术在适应复杂网络,及结合云技术等方面的研究方向与内容.     

Dynamic subcarrier and power allocation based on cooperative game theory in symmetric cooperative OFDMA networks

In order to improve the efficiency and fairness of radio resource utilization,a scheme of dynamic cooperative subcarrier and power allocation based on Nash bargaining solution(NBS-DCSPA) is proposed in the uplink of a three-node symmetric cooperative orthogonal frequency division multiple access(OFDMA) system.In the proposed NBS-DCSPA scheme,resource allocation problem is formulated as a two-person subcarrier and power allocation bargaining game(SPABG) to maximize the system utility,under the constraints of each user’s maximal power and minimal rate,while considering the fairness between the two users.Firstly,the equivalent direct channel gain of the relay link is introduced to decide the transmission mode of each subcarrier.Then,all subcarriers can be dynamically allocated to the two users in terms of their selected transmission mode.After that,the adaptive power allocation scheme combined with dynamic subcarrier allocation is optimized according to NBS.Finally,computer simulation is conducted to show the efficiency and fairness performance of the proposed NBS-DCSPA scheme.     

IEEE 802.11 DCF对TCP性能的影响及算法改进

本文讨论了IEEE 802.11 DCF两种方式(RTS/CTS和CSMA/CA)混合工作时TCP的性能,发现高负载时TCP流存在不稳定的问题.基于此提出了RWB(Reserve Window Backoff)算法,该算法从联合优化的角度出发,减轻了WLAN MAC接入机制和TCP拥塞控制之间的不良影响,从而提高了TCP的吞吐量,改善了TCP流的稳定性.文中通过仿真对算法进行了分析和研究.     

一种用于微波射频识别卡的圆极化微带天线

本文设计了一种用于微波非接触式射频识别卡的圆极化微带天线 ,采用AnsoftEnsemble7.0和Optimetrics模块分别进行仿真和优化 ,使输入、输出端口驻波比 ,左、右旋圆极化隔离度等参数满足系统性能要求。对加工的样品进行测试 ,结果显示 ,天线中心谐振频率为 5 .8GHz,左、右旋圆极化隔离度约 2 0dB ,天线有效方向角6 0° ,天线增益为 5dBi,达到实用化要求     

用影射法求解KdV方程

应用影射法求解KdV方程,得到了KdV方程的物理上有意义的两种类型的行波解,即孤立波解和Jacobi椭圆函数解,并绘图加以说明.     

约瑟夫森结(阵列)与谐振器的耦合效应研究

利用一种新的电路模型系统研究了约瑟夫森结(阵列)与谐振器的耦合效应.以结的电压自锁定台阶幅度ΔI为目标值,得到了谐振电路的电阻R、谐振频率fr对耦合的影响规律,并给出了合理解释;以结阵列的相位互锁定强度IL为目标,研究了IL对锁定电压VL的依赖关系,同时,通过相关计算将其与通常电路模型下得到的结果进行了比较.     

多子阵干涉合成孔径声呐

在完成了轨道式干涉合成孔径声呐(InSAS)原理样机的基础上,研制开发了一种新型的水面拖曳式干涉合成孔径声呐系统.成像算法采用非停走停运动误差补偿的多子阵逐线算法.试验数据表明该系统稳定可靠,并成功获取了干涉合成孔径图像,其距离和方位分辨率分别达到了5 cm和10 cm,测深精度优于国际海道测量组织(IHO)标准.     

Design studies on the 4π γ-ray calorimeter for the ETF experiment at HIRFL-CSR

A high detection efficiency calorimeter which is used to detect γ-rays with energies from 1 MeV up to 10 MeV as well as light charged particles has been proposed. Design of the geometry, results of the crystal tests and Monte Carlo simulations are presented in this paper. The simulation results confirm that the calorimeter can obtain high detection efficiency and good energy resolution with the current designed geometry. And the calorimeter is competent for the future External Target Facility (ETF) experiments.     

邻二氮菲分光光度法测定黄芪中铁的溶出率

邻二氮菲分光光度法测定黄芪中铁的溶出率,研究了不同溶剂对铁的溶出率的影响。检测波长510nm,在0.1—6μg·mL-1的范围内符合比耳定律,相关系数r=0.9995,检出限为13.7μg·L-1,方法回收率为96.1%—102.3%,精密度为0.38%—2.31%。测定结果表明,分别以水、不同浓度乙醇、不同浓度盐酸作溶剂,灰化后再用水提取铁的溶出率最高,达到44.0%,直接用酸、水、乙醇作溶剂,溶出率依次降低。本法简便、易行,且重现性好。     

MAGNETIZATION CHARACTERISTICS OF YBaCuO BULK MATERIAL FABRICATED BY THE SEEDING TECHNIQUE

YBaCuO (YBCO) bulk materials with large superconductive domains were fab-ricated using a small SmBa₂Cu₃O_x grain as the seed for growth, The capacities of strong flux pinning and well grain linking in the material have been shown in the investigations on magnetization loop end ac susceptibility. The strong flux pinning made it possible for the large YBCO bulk to capture a great dea. l of flux and keep the residual magnetism stable. The residual field intensity H_rem was shown to have a maximum of 0.125 T after the 0.5 T NdFeB magnetizing field was moved away. We did not find much decline of H_rem in a short time. The magnetized YBCO bulk pro-duced repulsive force upon another YBCO bulk as the permanent magnet did. We measured and calculated the force between two YBCO bulks. The theoretical result was in agreement with the experimental one by and large.