Al2O3-TiC-4%Co(volume fraction) composites(ATC) with high toughness (7.8±0.8 MPa·m1/2) and strength (782±60 MPa) were fabricated. In comparison with Al2O3-TiC composites(AT), the fracture toughness was ...Al2O3-TiC-4%Co(volume fraction) composites(ATC) with high toughness (7.8±0.8 MPa·m1/2) and strength (782±60 MPa) were fabricated. In comparison with Al2O3-TiC composites(AT), the fracture toughness was significantly improved by 60%. The crack paths, generated by Vickers indentation on the polished surfaces of both composites, were analyzed from a fractal point of view to distinguish the possible toughening mechanisms involved. Quantitative evaluation of indentation cracks indicates that the crack deflection plays a more effective role. Cracks of the ATC composites show higher deflection angles and more deflections along the path. ATC composites present higher fractal dimension (D=1.07) than AT composites (D=1.02), which is directly related to the higher fracture toughness. A significant relationship between crack path and toughness is evident: the more irregular the geometry of the crack, the higher the fracture toughness.展开更多
为解决密集部署Wi-Fi网络中的同频干扰问题,提出了一种基于协同调度和频率复用思想的干扰协调方案。首先,通过接入点间协作,设计了一种基于接收信号强度指示(Received Signal Strength Indication,RSSI)的干扰识别策略;其次,以时延、业...为解决密集部署Wi-Fi网络中的同频干扰问题,提出了一种基于协同调度和频率复用思想的干扰协调方案。首先,通过接入点间协作,设计了一种基于接收信号强度指示(Received Signal Strength Indication,RSSI)的干扰识别策略;其次,以时延、业务量、传输能力为指标设计用户调度算法,并利用图染色算法对被调度的用户进行分组;最后,以系统吞吐量最大为优化目标,利用伏格尔法为用户分配带宽资源。仿真结果表明,所提出的方案在密集网络场景下能够有效减小同频干扰,提升系统的吞吐量和频谱效率。展开更多
日常生活中使用GPS(global position system)进行定位,但GPS无法在室内工作,准确地进行室内定位成为研究的热点之一。在早期的研究中,围绕Wi-Fi指纹进行了大量的实验与改进,但Wi-Fi指纹受到环境因素制约,定位误差较大。针对这一问题,提...日常生活中使用GPS(global position system)进行定位,但GPS无法在室内工作,准确地进行室内定位成为研究的热点之一。在早期的研究中,围绕Wi-Fi指纹进行了大量的实验与改进,但Wi-Fi指纹受到环境因素制约,定位误差较大。针对这一问题,提出一种多信息融合的室内定位算法。首先通过Wi-Fi指纹进行粗略的定位,获取Wi-Fi接入设备的MAC地址以及其信号强度RSSI(received signal strength indication),通过kNN(k nearest neighbor)算法进行分类,得到top-n候选集。再通过地磁信号与图片信息进行候选集的过滤。最后利用社交信息,给出人在室内的最终定位结果。在Android平台和服务器上对该系统进行验证,实验结果表明提出的多信息融合的方法比Wi-Fi指纹的定位算法精度明显提高。展开更多
文摘Al2O3-TiC-4%Co(volume fraction) composites(ATC) with high toughness (7.8±0.8 MPa·m1/2) and strength (782±60 MPa) were fabricated. In comparison with Al2O3-TiC composites(AT), the fracture toughness was significantly improved by 60%. The crack paths, generated by Vickers indentation on the polished surfaces of both composites, were analyzed from a fractal point of view to distinguish the possible toughening mechanisms involved. Quantitative evaluation of indentation cracks indicates that the crack deflection plays a more effective role. Cracks of the ATC composites show higher deflection angles and more deflections along the path. ATC composites present higher fractal dimension (D=1.07) than AT composites (D=1.02), which is directly related to the higher fracture toughness. A significant relationship between crack path and toughness is evident: the more irregular the geometry of the crack, the higher the fracture toughness.
文摘为解决密集部署Wi-Fi网络中的同频干扰问题,提出了一种基于协同调度和频率复用思想的干扰协调方案。首先,通过接入点间协作,设计了一种基于接收信号强度指示(Received Signal Strength Indication,RSSI)的干扰识别策略;其次,以时延、业务量、传输能力为指标设计用户调度算法,并利用图染色算法对被调度的用户进行分组;最后,以系统吞吐量最大为优化目标,利用伏格尔法为用户分配带宽资源。仿真结果表明,所提出的方案在密集网络场景下能够有效减小同频干扰,提升系统的吞吐量和频谱效率。
文摘日常生活中使用GPS(global position system)进行定位,但GPS无法在室内工作,准确地进行室内定位成为研究的热点之一。在早期的研究中,围绕Wi-Fi指纹进行了大量的实验与改进,但Wi-Fi指纹受到环境因素制约,定位误差较大。针对这一问题,提出一种多信息融合的室内定位算法。首先通过Wi-Fi指纹进行粗略的定位,获取Wi-Fi接入设备的MAC地址以及其信号强度RSSI(received signal strength indication),通过kNN(k nearest neighbor)算法进行分类,得到top-n候选集。再通过地磁信号与图片信息进行候选集的过滤。最后利用社交信息,给出人在室内的最终定位结果。在Android平台和服务器上对该系统进行验证,实验结果表明提出的多信息融合的方法比Wi-Fi指纹的定位算法精度明显提高。
