We analyze, both analytically and numerically, the effectiveness
of cloaking an infinite cylinder from observations by electromagnetic
waves in three dimensions. We show that, as truncated approximations
of the ideal permittivity and permeability tensors tend towards
the singular ideal cloaking fields, so that the anisotropy ratio tends to
infinity, the D and B fields blow up near the cloaking surface. Since
the metamaterials used to implement cloaking are based on effective
medium theory, the resulting large variation in D and B will pose a
challenge to the suitability of the field averaged characterization of "
and 碌. We also consider cloaking with and without the SHS (softand-
hard surface) lining, shown in [6] to be theoretically necessary
for cloaking in the cylindrical geometry. We demonstrate numerically
that cloaking is significantly improved by the SHS lining, with both
the far field of the scattered wave significantly reduced and the blow
up of D and B prevented.
nTIM PATRICK has been working professionally as a software architect and developer for nearly
25 years. By day he develops custom business applications in Visual Basic for small to medium-
sized organizations. He is a Microsoft Certified Solution Developer (MCSD). In April 2007,
Microsoft awarded Tim with its Most Valuable Professional (MVP) award for his work in sup-
porting and promoting Visual Basic and its community of users. Tim received his under-
graduate degree in computer science from Seattle Pacific University. You can contact him
through his web site, www.timaki.com.
Digital Modulation Techniques are those echniques through which we convert digital signals into analog signal which can be transmitted through transmission medium...this program demostrate some of the basics techniques
Writing essays and dissertations can be a major concern for overseas students studying at English-medium colleges and universities. Virtually all courses contain a large degree of written assessment and it is essential to ensure that your writing skills meet the necessary standard. Academic Writing is a new kind of writing course for all international students who have to write exams or coursework in English. This practical book thoroughly explains the writing process and covers all the key writing skills.
msp430The LDC1312 and LDC1314 are 2- and 4-channel,
1? Easy-to-use – minimal configuration required
12-bit inductance to digital converters (LDCs) for
? Measure up to 4 sensors with one IC
inductive sensing solutions. With multiple channels ? Multiple channels support environmental and and support for remote sensing, the LDC1312 and aging compensation LDC1314 enable the performance and reliability benefits of inductive sensing to be realized at minimal? Multi-channel remote sensing provides lowest cost and power. The products are easy to use, onlysystem cost requiring that the sensor frequency be within 1 kHz ? Pin-compatible medium and high-resolution and 10 MHz to begin sensing. The wide 1 kHz to 10 options MHz sensor frequency range also enables use of very small PCB coils, further reducing sensing– LDC1312/4: 2/4-ch 12-bit LDC solution cost and size.– LDC1612/4: 2/4-ch 28
The capability of radio waves to provide almost instantaneous distant communications
without interconnecting wires was a major factor in the explosive growth of communica-
tions during the 20th century. With the dawn of the 21st century, the future for communi-
cations systems seems limitless. The invention of the vacuum tube made radio a practical
and affordable communications medium.
This thesis is about wireless communication in shared radio spectrum. Its origin and
motivation is ideally represented by the two quotations from above. In this thesis, the
support of Quality-of-Service (QoS) in cognitive radio networks is analyzed. New
approaches to distributed coordination of cognitive radios are developed in different
spectrum sharing scenarios. The Wireless Local Area Network (WLAN) 802.11 proto-
col of the Institute of Electrical and Electronics Engineers (IEEE) (IEEE, 2003) with
its enhancement for QoS support (IEEE, 2005d) is taken as basis. The medium Access
Control (MAC) of 801.11(e) is modified to realize flexible and dynamic spectrum
assignment within a liberalized regulation framework.
Wireless is one of the most rapidly developing technologies in our time, with dazzling
new products and services emerging on an almost daily basis. These developments present
enormous challenges for communications engineers, as the demand for increased wireless
capacity grows explosively. Indeed, the discipline of wireless communications presents
many challenges to designers that arise as a result of the demanding nature of the physical
medium and the complexities in the dynamics of the underlying network.
The ever-increasing demand for private and sensitive data transmission over wireless net-
works has made security a crucial concern in the current and future large-scale, dynamic,
and heterogeneous wireless communication systems. To address this challenge, computer
scientists and engineers have tried hard to continuously come up with improved crypto-
graphic algorithms. But typically we do not need to wait too long to find an efficient way
to crack these algorithms. With the rapid progress of computational devices, the current
cryptographic methods are already becoming more unreliable. In recent years, wireless re-
searchers have sought a new security paradigm termed physical layer security. Unlike the
traditional cryptographic approach which ignores the effect of the wireless medium, physi-
cal layer security exploits the important characteristics of wireless channel, such as fading,
interference, and noise, for improving the communication security against eavesdropping
attacks. This new security paradigm is expected to complement and significantly increase
the overall communication security of future wireless networks.
Wireless networking is undergoing a transformation from what has
been primarily a medium for supporting voice traffic between telephones,
into what is increasingly becoming a medium for supporting traffic among
a variety of digital devices transmitting media of many types (voice,
data, images, video. etc.) Wireline networking underwent a similar
transformation in the 1990s, which led to an enormous build-up in the
capacity of such networks, primarily through the addition of new optical
fiber, switches and other infrastructure.
