It was proposed that perfect invisibility cloaks can be constructed for hiding objects from electromagnetic illumination (Pendry et al., Science 312, p. 1780). The cylindrical cloaks experimentally demonstrated (Schurig et al., Science 314, p. 997) and theoretically proposed (Cai et al., Nat. Photon. 1, p. 224) have however simplified material parameters in order to facilitate easier realization as well as to avoid infinities in optical constants. Here we show that the cylindrical cloaks with simplified material parameters inherently allow the zeroth-order cylindrical wave to pass through the cloak as if the cloak is made of a homogeneous isotropic medium, and thus visible. To all high-order cylindrical waves, our numerical simulation suggests that the simplified cloak inherits some properties of the ideal cloak, but finite scatterings exist.
标签： invisibility constructed proposed electrom
上传时间： 2013-12-18
上传用户：13215175592
The existence of numerous imaging modalities makes it possible to present different data present in different modalities together thus forming multimodal images. Component images forming multimodal images should be aligned, or registered so that all the data, coming from the different modalities, are displayed in proper locations. The term image registration is most commonly used to denote the process of alignment of images , that is of transforming them to the common coordinate system. This is done by optimizing a similarity measure between the two images. A widely used measure is Mutual Information (MI). This method requires estimating joint histogram of the two images. Experiments are presented that demonstrate the approach. The technique is intensity-based rather than feature-based. As a comparative assessment the performance based on normalized mutual information and cross correlation as metric have also been presented.
标签： present modalities existence different
上传时间： 2017-04-03
上传用户：qunquan
-The existence of numerous imaging modalities makes it possible to present different data present in different modalities together thus forming multimodal images. Component images forming multimodal images should be aligned, or registered so that all the data, coming from the different modalities, are displayed in proper locations. Mutual Information is the similarity measure used in this case for optimizing the two images. This method requires estimating joint histogram of the two images. The fusion of images is the process of combining two or more images into a single image retaining important features from each. The Discrete Wavelet Transform (DWT) has become an attractive tool for fusing multimodal images. In this work it has been used to segment the features of the input images to produce a region map. Features of each region are calculated and a region based approach is used to fuse the images in the wavelet domain.
标签： present modalities existence different
上传时间： 2014-03-04
上传用户：15736969615
Aircrack-ng is an 802.11 WEP and WPA-PSK keys cracking program that can recover keys once enough data packets have been captured. It implements the standard FMS attack along with some optimizations like KoreK attacks, as well as the all-new PTW attack, thus making the attack much faster compared to other WEP cracking tools. In fact, Aircrack-ng is a set of tools for auditing wireless networks.
标签： keys Aircrack-ng cracking WPA-PSK
上传时间： 2013-12-25
上传用户：bruce
The Schumann resonance frequencies are a set of eigenmodes in the extremely low frequency (ELF) portion of the electromagnetic field spectrum. These frequencies are only present for planetary-like bodies with a substantial ionosphere acting as a perfect electric conductor, thus forming a resonance cavity with the surface. In this example, the Schumann resonance frequencies for the Earth are calculated.
标签： frequencies eigenmodes resonance extremely
上传时间： 2014-12-09
上传用户：stella2015
Most satellite dish actuators send a series of pulses to indicate their position. By counting pulses the positioner knows where the dish is pointing. It is possible to use a serial port and Linux with RTAI patches in order to count these pulses, thus minimising the external hardware required for a positioner. The zip contains instructions, circuit diagrams and example code.
标签： satellite actuators counting indicate
上传时间： 2014-12-03
上传用户：netwolf
data are often used interchangeably, they are actually very different. Data is a set of unrelated information, and as such is of no use until it is properly evaluated. Upon evaluation, once there is some significant relation between data, and they show some relevance, then they are converted into information. Now this same data can be used for different purposes. thus, till the data convey some information, t
标签： interchangeably are different unrelated
上传时间： 2017-09-26
上传用户：cxl274287265
In recent years, cellular voice networks have transformed into powerful packet-switched access networks for both voice communication and Internet access. Evolving Universal Mobile Telecommunication System (UMTS) networks and first Long Term Evolution (LTE) installations now deliver bandwidths of several megabits per second to individual users, and mobile access to the Internet from handheld devices and notebooks is no longer perceived as slower than a Digital Subscriber Line (DSL) or cable connection. Bandwidth and capacity demands, however, keep rising because of the increasing number of people using the networks and because of bandwidth-intensive applications such as video streaming. thus, network manufacturers and network operators need to find ways to continuously increase the capacity and performance of their cellular networks while reducing the cost.
标签： BRINGING NETWORKS Beyond and 3G 4G
上传时间： 2020-05-26
上传用户：shancjb
The surge of mobile data traffic forces network operators to cope with capacity shortage. The deployment of small cells in 5G networks is meant to reduce latency, backhaul traffic and increase radio access capacity. In this context, mobile edge computing technology will be used to manage dedicated cache space in the radio access network. thus, mobile network operators will be able to provision OTT content providers with new caching services to enhance the quality of experience of their customers on the move.
上传时间： 2020-05-26
上传用户：shancjb
Multiple-Input Multiple-Output (MIMO) systems have recently been the subject of intensive consideration in modem wireless communications as they offer the potential of providing high capacity, thus unleashing a wide range of applications in the wireless domain. The main feature of MIMO systems is the use of space-time processing and Space-Time Codes (STCs). Among a variety of STCs, orthogonal Space-Time Block Codes (STBCs) have a much simpler decoding method, compared to other STCs
标签： Orthogonal Space-Time Processing Complex
上传时间： 2020-05-26
上传用户：shancjb
