Location-aware technology spawns numerous unforeseen pervasive applications in a wide range of living, pro- duction, commence, and public services. This article provides an overview of the location, localization, and ...Location-aware technology spawns numerous unforeseen pervasive applications in a wide range of living, pro- duction, commence, and public services. This article provides an overview of the location, localization, and localizability issues of wireless ad-hoc and sensor networks. Making data geographically meaningful, location information is essential for many applications, and it deeply aids a number of network functions, such as network routing, topology control, coverage, boundary detection, clustering, etc. We investigate a large body of existing localization approaches with focuses on error control and network localizability, the two rising aspects that attract significant research interests in recent years. Error control aims to alleviate the negative impact of noisy ranging measurement and the error accumulation effect during coope- rative localization process. Network localizability provides theoretical analysis on the performance of localization approaches, providing guidance on network configuration and adjustment. We emphasize the basic principles of localization to under- stand the state-of-the-art and to address directions of future research in the new and largely open areas of location-aware technologies.展开更多
To perform an accurate fire-and-forget attack of seeker-less missile with the consideration of the localization error, a new cooperative guidance strategy of multi-missiles is proposed in this work. Firstly, an estima...To perform an accurate fire-and-forget attack of seeker-less missile with the consideration of the localization error, a new cooperative guidance strategy of multi-missiles is proposed in this work. Firstly, an estimated position of the seeker-less missile is carefully selected, based on which the slant angle of the line between the estimated and real positions of the seeker-less missile is approximately derived inspired by the localization theory of GPS(Global Position System).Then, respectively based on the guidance law considering the impact angle and time constraints, the consensus theory and the finite-time convergence approach, three cooperative guidance laws employing the previously obtained slant angle are derived for intensive attack to address either a stationary or maneuvering target. Simulation results well demonstrate the effectiveness and advantages of the proposed cooperative guidance strategy.展开更多
文摘Location-aware technology spawns numerous unforeseen pervasive applications in a wide range of living, pro- duction, commence, and public services. This article provides an overview of the location, localization, and localizability issues of wireless ad-hoc and sensor networks. Making data geographically meaningful, location information is essential for many applications, and it deeply aids a number of network functions, such as network routing, topology control, coverage, boundary detection, clustering, etc. We investigate a large body of existing localization approaches with focuses on error control and network localizability, the two rising aspects that attract significant research interests in recent years. Error control aims to alleviate the negative impact of noisy ranging measurement and the error accumulation effect during coope- rative localization process. Network localizability provides theoretical analysis on the performance of localization approaches, providing guidance on network configuration and adjustment. We emphasize the basic principles of localization to under- stand the state-of-the-art and to address directions of future research in the new and largely open areas of location-aware technologies.
基金co-supported by the National Natural Science Foundation of China (No. 11532002)the Hongjian Innovation Foundation of China (No. BQ203-HYJJ-Q2018002)
文摘To perform an accurate fire-and-forget attack of seeker-less missile with the consideration of the localization error, a new cooperative guidance strategy of multi-missiles is proposed in this work. Firstly, an estimated position of the seeker-less missile is carefully selected, based on which the slant angle of the line between the estimated and real positions of the seeker-less missile is approximately derived inspired by the localization theory of GPS(Global Position System).Then, respectively based on the guidance law considering the impact angle and time constraints, the consensus theory and the finite-time convergence approach, three cooperative guidance laws employing the previously obtained slant angle are derived for intensive attack to address either a stationary or maneuvering target. Simulation results well demonstrate the effectiveness and advantages of the proposed cooperative guidance strategy.
文摘目的:探讨多平面重组(multiplanar reformation,MPR)图像引导定位参考点标记法在宫颈癌放射治疗定位中的应用价值。方法:选取2022年05月至12月在我院肿瘤放射治疗中心进行容积旋转调强放射治疗(volumetric-modulated arc therapy,VMAT)的40例宫颈癌患者,采用随机数表法将其分为观察组和对照组,每组20例。观察组使用MPR图像引导定位参考点标记法进行定位;对照组使用常规参考点标记法进行定位。物理师进行VMAT放疗计划设计时,根据国际辐射单位及测量委员会(international commission on radiation units and measurements,ICRU)参考点的选择原则,选出靶区剂量归一的规定点并作为治疗中心点,比较两组患者治疗中心点与定位参考点位移的例数,并用位移率(%)进行描述。所有患者首次治疗及以后每周均进行一次锥形束CT(CBCT)扫描位置验证(共5次),分别采集两组患者分次间的左右X、头脚Y、腹背Z方向上的摆位误差数据及复位完成的时间,采用独立样本t检验,P<0.05为差异有统计学意义。计划靶区外放边界(M_(PTV))公式:M_(PTV)=2.5∑+0.7σ计算不同定位方式下的靶区外扩边界。结果:观察组中定位参考点与治疗中心点在三维方向上产生位移例数均为0例,而对照组在Y方向、Z方向产生位移例数分别是11例和19例,位移率分别55%和95%。观察组的平均摆位误差分别为X(-0.16±1.99)mm、Y(1.04±4.13)mm、Z(0.77±2.30)mm;对照组的平均摆位误差分别为X(0.18±2.59)mm、Y(-2.09±5.02)mm、Z(1.44±2.39)mm。两组Y、Z方向上的摆位误差有统计学意义(P<0.05)。观察组复位平均时间(9.76±2.35)min,对照组复位平均时间(13.25±3.66)min,观察组较对照组复位效率更高。观察组靶区外扩边界(M_(PTV))分别为3.82 mm、7.28 mm、4.55 mm,较对照组减少了18.20%、22.06%、6.38%。结论:在宫颈癌放射治疗定位中使用多平面重组图像引导定位参考点标记法可实现定位参考点与�
