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Ultrawideband Dispersion Control of a Metamaterial Surface for Perfectly-Matched-Layer-Like Absorption

Physical Review Letters 2013年第18期111卷 187402-187402页

作者： Dexin Ye Zhiyu Wang Kuiwen Xu Huan Li Jiangtao Huangfu Zheng Wang Lixin Ran Laboratory of Applied Research on Electromagnetics (ARE) Zhejiang University Hangzhou 310027 China Department of Physics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Electrical and Computer Engineering Microelectronics Research Center the University of Texas at Austin Texas 78758 USA

Narrow bandwidth is a fundamental issue plaguing practical applications of metamaterial absorbers. In this Letter, we show that by deliberately controlling the dispersion and dissipation of a metamaterial, an ultrawideband perfect metamaterial absorber with complex-valued constitutive parameters strictly satisfying the modified model of a perfectly matched layer, can be achieved. The nearly perfect power absorption, better than 99%, was experimentally observed in an unprecedented bandwidth of 39%, approaching the theoretical Rozanov limit. We expect a wide range of applications to emerge from this general concept.

关键词： LIGHT propagation ENERGY dissipation BANDWIDTHS ULTRA-wideband radar DIGITAL communications

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SWIFT: A Secure Web Domain Filter in Hardware

SWIFT: A Secure Web Domain Filter in Hardware

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International Workshop on Informatics for Intelligent Context-Awarenterprise Systems

作者： Vlado Altmann Jens Rohrbeck Jan Skodzik Peter Danielis Dirk Timmermann Maik Roennau Matthias Ninnemann University of Rostock Institute of Applied Microelectronics and Computer Engineering 18051 Rostock Germany Nokia Siemens Networks GmbH & Co. KG Broadband Access Division 17489 Greifswald Germany

ISBN: (纸本)9781467362399

The risk of becoming a victim of spam and phishing attacks increases in today's Internet. Various Web sites exhibit violent or illegal content. Unfortunately, many users are not able to protect themselves and their networks. Already now, some countries deploy systems to filter Web content. However, the existing solutions show high latency or overblocking. Thus, a novel Web filtering concept to protect users at the Internet service provider level is presented. The proposed system is able to detect and block illegal and threatening Web sites. The suggested scalable hardware-based approach can examine Internet domains in wire speed without overblocking. The Web filter serves as security measure for all connected users, especially for users with limited IT expert knowledge. The system is fully transparent for all network devices. Setup and maintenance can be made only by the Internet service provider administrator. Consequently, the suggested security system itself is safe from attacks from users and from the network side.

关键词： network devices system

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Dethroning transport layer security in the embedded world

Dethroning transport layer security in the embedded world

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2012 5th International Conference on New Technologies, Mobility and Security, NTMS 2012

作者： Unger, Sebastian Pfeiffer, Stefan Timmermann, Dirk Institute of Applied Microelectronics and Computer Engineering University of Rostock Germany

ISBN: (纸本)9781467302296

Developing a security concept feasible for a large number of cooperating embedded devices is crucial for the practical relevance of visions such as the Internet of Things, Ambient Assisted Living or Pervasive Computing. However, designing these concepts in conjunction with new technologies usually is more expensive. Thus, new technologies often rely on existing security techniques on lower layers of the network stack. Especially the Transport Layer Security (TLS) protocol suite is a very popular solution because TLS is a widely spread and well accepted protocol. However, TLS is not ideal for the realm of embedded devices and it does not provide all the necessary features. We state that a comprehensive security framework for large distributed systems of embedded devices has to be implemented on application level. We investigate on the applicability and adaptability of the Web Service (WS) Security specification suite since it offers such a desired comprehensive security framework. Furthermore, its base technology - Web Services - has already been ported to the domain of embedded devices by means of the Devices Profile for Web Services (DPWS). However, WS Security imposes a dramatic overhead on message sizes and parsing efforts for providing confidentiality, integrity and authenticity. Thus, in this paper we discuss two variants of WS Security that decrease the imposed overhead but remain compatible to the classical WS Security. A performance analysis shows that our proposed solutions have no significant drawback compared to the state of the art - TLS - but even provide a richer feature set. © 2012 IEEE.

关键词： Ubiquitous computing

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Secure information flow awareness for smart wireless eHealth systems

Secure information flow awareness for smart wireless eHealth...

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9th International Multi-Conference on Systems, Signals and Devices, SSD 2012

作者： Pfeiffer, Stefan Unger, Sebastian Timmermann, Dirk Lehmann, Andreas Institute of Applied Microelectronics and Computer Engineering University of Rostock Germany Institute of Computer Science University of Rostock Germany

ISBN: (纸本)9781467315906

Usually, safety and robustness are considered as the most important issues when designing and developing smart and wireless eHealth systems for ambient support of patients and physicians. However, information security is an indispensable design criterion due to the sensitive and critical nature of aggregated information from eHealth applications. Therefore, preventing undesired information leaks and illegal information flows is crucial for designing smart mHealth and mobile medical assistant systems. Due to the rapidly increasing complexity of these systems, finding information flow violations manually is nearly impossible. That is why there is a need for formally-based and tool supported verification methods of security properties. © 2012 IEEE.

关键词： Security of data

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Time Synchronization in the DHT-based P2P Network Kad for Real-Time Automation Scenarios

Time Synchronization in the DHT-based P2P Network Kad for Re...

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IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks

作者： Jan Skodzik Peter Danielis Vlado Altmann Dirk Timmermann University of Rostock Institute of Applied Microelectronics and Computer Engineering 18051 Rostock Germany Tel./Fax: +49 381 498-7284 / -1187251

ISBN: (纸本)9781467358279

In this paper, an approach to synchronize the P2P network Kad to be applied in automation scenarios is presented. The approach bases on a deterministic algorithm to synchronize the network, which is required for hard real-time applications. Todays Industrial Ethernet solutions include and support machine to machine communication in automation scenarios. However, instead of allowing direct communication, the communication relies on centralized structures, which are deficient in resilience and scalability However, instead of allowing direct communication, the communication relies on centralized structures. The presented decentralized approach benefits from nodes helping to synchronize the network. However, the higher the number of helping nodes the higher is the time deviation on the nodes of the network, which contrary results in a higher time error. Therefore, a trade-off between synchronization performance and time error has to be determined to meet predefined constraints depending on the application scenario. Moreover, the individual clock drift of every device is considered to define necessary re-synchronization intervals of the network. Additionally, the optimum number of nodes to synchronize the Kad based network has been identified and the resulting synchronization performance and generated traffic are determined. Furthermore, an approach is presented to handle the dynamic churn of nodes.

关键词： Peer-to-Peer Kad Synchronization Automation

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Passive RFID tomographic imaging for device-free user localization

Passive RFID tomographic imaging for device-free user locali...

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2012 9th Workshop on Positioning, Navigation and Communication, WPNC'12

作者： Wagner, Benjamin Patwari, Neal Timmermann, Dirk Institute of Applied Microelectronics and Computer Engineering University of Rostock Germany SPAN Lab. Department of Electrical and Computer Engineering University of Utah Salt Lake City UT United States

ISBN: (纸本)9781467314398

Localization of users is an important part of location aware systems and smart environments. It forms a major data source for superimposed intention recognition systems. In RF device-free localization (DFL), the person being tracked does not need to wear a RF transmitter or receiver in order to be located. Instead, they are tracked using the changes in signal strength measured on static links in a wireless network. This work presents a new algorithm for RF DFL using passive RFID networks. We formulate and show how a tomographic imaging algorithm provides both low computational complexity and highly accurate position estimates. Using measurements conducted in an indoor environment with various human positions, we find the algorithm can locate the human with as low as 30 cm mean location error. © 2012 IEEE.

关键词： Radio frequency identification (RFID)

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Classification of user positioning techniques and systems for intelligent environments 42

Classification of user positioning techniques and systems fo...

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42. Jahrestagung der Gesellschaft fur Informatik e.V. ,GI, Informatik 2012 - 42nd Annual Meeting of the German Informatics Society (GI), Informatics 2012

作者： Wagner, Benjamin Timmermann, Dirk Institute of Applied Microelectronics and Computer Engineering University of Rostock Richard-Wagner-Straße 31 Rostock-Warnemünde18119 Germany

ISBN: (纸本)9783885796022

One of the most important observation parameters for smart environments and ambient intelligence is the position of users. Over the last years huge research efforts have been spent on new algorithms, technologies, and systems for the localization of users and objects. The spread of these technologies results in a wide range of application scenarios and manifold combinations of measurements and algorithms. One fundamental task in designing smart environments is the choice of a localization system which fits into the ambient infrastructure, is applicable to the underlying application scenario, and provides localization results in desired form and accuracy. At this stage, it is very difficult to compare the published systems in order to opt for a specific solution. In this work existing systems and techniques are evaluated and documented under different characteristics facing two goals. The first one is to give an overview about the state of the art of user localization techniques and secondly to make these techniques comparable in order to fit the right technique to a given application. Therefore, intrinsic system characteristics are documented. © 2012 Gesellschaft fur Informatik (GI). All rights reserved.

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Time Coding Output Neurons in Digital Artificial Neural Networks

Time Coding Output Neurons in Digital Artificial Neural Netw...

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International Joint Conference on Neural Networks

作者： Ralf Joost Ralf Salomon Institute of Applied Microelectronics and Computer Engineering University of Rostock

ISBN: (纸本)9781467314886

Previous research has proposed several platforms for the direct hardware implementation of neural networks. Most of these platforms employ a small number of special-purpose processors that emulate a given number of neurons. By contrast, this paper proposes a light-weight hardware model, called time coded output (TiCO) neuron, which codes its internal activation as the duration of its output pulses. Since the implementation of such a neuron requires only about 200 logical elements, standard state-of-the-art field-programmable gate arrays may host several hundreds of neurons on a single chip. Due to its output coding and its low footprint, TiCO neurons are particularly suited for the usage in embedded systems.

关键词： Neuron design Hardware implementation FPGA Pulse width modulation Neurons output pulse Platform Embedded systems Artificial neural networks Logical elements Neural network hardware model Output Field programmable gate arrays

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A Web Service-based Communication Architecture for Smartphone/WPAN Sensor Ensembles

A Web Service-based Communication Architecture for Smartphon...

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Institute of Electrical and Electronics Engineers International Conference on Emerging Technologies & Factory Automation

作者： Nico Laum Christian Lerche Frank Golatowski Dirk Timmermann Institute of Applied Microelectronics and Computer Engineering University of Rostock

ISBN: (纸本)9781467347358

There are many applications that use low power wireless sensors to monitor people's vital signs or the environment around people, For mobile applications, smartphones with Internet access have become a commonly used tool to make this data remotely accessible. However, the yet presented architectures are quite complex and lack flexibility. Our aim was to investigate how existing communication architectures for smartphone/WPAN sensor ensembles can be simplified and to provide a transparent solution where the smartphone doesn't require knowledge about sensors for which it serves as an Internet gateway. We therefore present an IP-based communication architecture, that allows applications to easily integrate remote sensor data of mobile users based on existing Internet standards. In particular, our solution provides simple Web service-based APIs and does not require the smartphone to process sensor data. Instead, the smartphone becomes a transparent gateway as it only forwards DP packets.

关键词： Web services IPv6 IEEE 802.15.4 Bluetooth Low Energy 6L0WPAN CoAP Internet of Things

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Dethroning Transport Layer Security in the Embedded World

Dethroning Transport Layer Security in the Embedded World

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New Technologies, Mobility and Security (NTMS)

作者： Sebastian Unger Stefan Pfeiffer Dirk Timmermann Institute of Applied Microelectronics and Computer Engineering University of Rostock Germany

关键词： Payloads Simple object access protocol Protocols Encryption

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