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General Assembly and Scientific Symposium, URSI

作者： Abdulkadir C. Yücel Hakan Bağci Eric Michielssen Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA Division of Physical Sciences and Engineering King Abdullah University of Science and Technology Thuwal Saudi Arabia

Stochastic methods have been used extensively to quantify effects due to uncertainty in system parameters (e.g. material, geometrical, and electrical constants) and/or excitation on observables pertinent to electromagnetic compatibility and interference (EMC/EMI) analysis (e.g. voltages across mission-critical circuit elements). In recent years, stochastic collocation (SC) methods, especially those leveraging generalized polynomial chaos (gPC) expansions, have received significant attention. SC-gPC methods probe surrogate models (i.e. compact polynomial input-output representations) to statistically characterize observables. They are nonintrusive, that is they use existing deterministic simulators, and often cost only a fraction of direct Monte-Carlo (MC) methods. Unfortunately, SC-gPC-generated surrogate models often lack accuracy (i) when the number of uncertain/random system variables is large and/or (ii) when the observables exhibit rapid variations.

关键词： Stochastic processes Random variables Computational modeling Electromagnetic compatibility Electromagnetic interference Iterative methods Adaptation models

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Comparison of Au-In transient liquid phase bonding designs for SiC power semiconductor device packaging

Comparison of Au-In transient liquid phase bonding designs f...

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2011 IMAPS International Conference on High Temperature Electronics Network, HiTEN 2011

作者： Grummel, Brian Mustain, Habib A. John Shen, Z. Hefner, Allen R. Dept. of Electrical Engineering and Computer Science University of Central Florida Orlando FL United States Semiconductor Electronics Division Physical Measurement Laboratory National Institute of Standards and Technology Gaithersburg MD United States Cree Inc. Durham NC United States

ISBN: (纸本)0930815939

Transient liquid phase (TLP) bonding is an advanced die-attach technique for wide-bandgap power semiconductor and high-temperature packaging. TLP bonding advances current soldering techniques by raising the melting point to over 500 °C without detrimental high-lead materials. The bond also has greater reliability and rigidity due in part to a bonding temperature of 200 °C that drastically lowers the peak bond stresses. Furthermore, the thermal conductivity is increased 67 % while the bond thickness is substantially reduced, lowering the thermal resistance by an order of magnitude. This work provides an in-depth examination of the TLP fabrication methodology utilizing mechanical and thermal experimental characterization data along with thermal reliability results.

关键词： Wide band gap semiconductors

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On the statistics of uplink inter-cell interference with greedy resource allocation

On the statistics of uplink inter-cell interference with gre...

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International Symposium on Wireless Communication Systems (ISWCS)

作者： Hina Tabassum Ferkan Yilmaz Zaher Dawy Mohamed Slim Alouini Physical Sciences and Engineering Division King Abdullah University for Science and Technology Thuwal Saudi Arabia Department of Electrical and Computer Engineering American University of Beirut Beirut Lebanon

In this paper, we introduce a new methodology to model the uplink inter-cell interference (ICI) in wireless cellular networks. The model takes into account both the effect of channel statistics (i.e., path loss, shadowing, fading) and the resource allocation scheme in the interfering cells. Firstly, we derive a semi-analytical expression for the distribution of the locations of the allocated user in a given cell considering greedy resource allocation with maximum signal-to-noise ratio (SNR) criterion. Based on this, we derive the distribution of the uplink ICI from one neighboring cell. Next, we compute the moment generating function (MGF) of the cumulative ICI observed from all neighboring cells and discuss some examples. Finally, we utilize the derived expressions to evaluate the outage probability in the network. In order to validate the accuracy of the developed semi-analytical expressions, we present comparison results with Monte Carlo simulations. The major benefit of the proposed mechanism is that it helps in estimating the distribution of ICI without the knowledge of instantaneous resource allocations in the neighbor cells. The proposed methodology applies to any shadowing and fading distributions. Moreover, it can be used to evaluate important network performance metrics numerically without the need for time-consuming Monte Carlo simulations.

关键词： Interference Fading Resource management Signal to noise ratio Shadow mapping Probability density function Downlink

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Sum rate maximization in the uplink of multi-cell OFDMA networks

Sum rate maximization in the uplink of multi-cell OFDMA netw...

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International Wireless Communications and Mobile Computing Conference, IWCMC

作者： Hina Tabassum Zaher Dawy Mohamed Slim Alouini Physical Sciences and Engineering Division King Abdullah University for Science and Technology Thuwal Saudi Arabia Department of Electrical and Computer Engineering American University of Beirut Beirut Lebanon

Resource allocation in orthogonal frequency division multiple access (OFDMA) networks plays an imperative role to guarantee the system performance. However, most of the known resource allocation schemes are focused on maximizing the local throughput of each cell, while ignoring the significant effect of inter-cell interference. This paper investigates the problem of resource allocation (i.e., subcarriers and powers) in the uplink of a multi-cell OFDMA network. The problem has a non-convex combinatorial structure and is known to be NP hard. Firstly, we investigate the upper and lower bounds to the average network throughput due to the inherent complexity of implementing the optimal solution. Later, a centralized sub-optimal resource allocation scheme is developed. We further develop less complex centralized and distributed schemes that are well-suited for practical scenarios. The computational complexity of all schemes has been analyzed and the performance is compared through numerical simulations. Simulation results demonstrate that the distributed scheme achieves comparable performance to the centralized resource allocation scheme in various scenarios.

关键词： Resource management Throughput Complexity theory Interference Signal to noise ratio Upper bound Fading

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A generalized and parameterized interference model for cognitive radio networks

A generalized and parameterized interference model for cogni...

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IEEE Workshop on Signal Processing Advances in Wireless Communications (SPAWC)

作者： Nurul H. Mahmood Ferkan Yilmaz Mohamed-Slim Alouini Department of Electronics & Telecommunication Norwegian University of Science and Technology Trondheim Norway Electrical Engineering Division of Physical Sciences and Engineering King Abdullah University for Science and Technology Thuwal Makkah Saudi Arabia

For meaningful co-existence of cognitive radios with primary system, it is imperative that the cognitive radio system is aware of how much interference it generates at the primary receivers. This can be done through statistical modeling of the interference as perceived at the primary receivers. In this work, we propose a generalized model for the interference generated by a cognitive radio network, in the presence of small and large scale fading, at a primary receiver located at the origin. We then demonstrate how this model can be used to estimate the impact of cognitive radio transmission on the primary receiver in terms of different outage probabilities. Finally, our analytical findings are validated through some selected computer-based simulations.

关键词： Interference Fading Analytical models Cognitive radio Numerical models Receivers Computational modeling

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A high-gain wide-input-range time amplifier with an open-loop architecture and a gain equal to current bias ratio

A high-gain wide-input-range time amplifier with an open-loo...

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IEEE Asian Conference on Solid-State Circuits (ASSCC)

作者： Hye-Jung Kwon Jae-seung Lee Jae-Yoon Sim Hong-June Park Department of Electronic and Electrical Engineering Pohang University of Science and Technology Pohang South Korea Division of IT Conversion Engineering WCU program Pohang University of Science and Technology Pohang South Korea

Recently, time amplifiers are used in time-to-digital converters (TDC) because the time resolution is better than the voltage resolution in modern integrated circuits. However, the conventional time amplifiers are limited in their time gain and input time difference range, because of their positive-feedback closed-loop architecture. An open-loop time amplifier is proposed in this work to achieve a large time gain up to 120 and a wide range of input time difference(10ps~2ns). Besides, the time gain is the same as the current bias ratio. The worst-case average gain error which shows linear characteristics of the time amplifier is smaller than 5.3% The proposed time amplifier was successfully used in the monitoring circuit for threshold voltage variations of NMOS and PMOS FETs. The monitoring circuit consists of VCDL, time amplifier and TDC. The circuit was implemented by 0.13μm CMOS process.

关键词： Tin Threshold voltage Monitoring Voltage measurement Clocks MOSFET circuits

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Synthesis and Second-Order Nonlinear Optical Properties of New Coumaromethacrylate-Methylmethacrylate Copolymers

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MRS Online Proceedings Library 2011年第1期173卷 601-606页

作者： R. A. Henry J. M. Hoover A. Knoesen S. T. Kowel G. A. Lindsay M. A. Mortazavi Research Department Chemistry Division China Lake USA Department of Electrical Engineering and Computer Science Organized Research Program on Polymeric Ultrathin Film Systems University of California Davis USA

The synthesis and second-order nonlinear optical (NLO) properties of a new family of optically nonlinear coumarin dye-containing polymers is reported. Polymerizable coumaromethacrylate (CMA) monomers having various alkyl spacers (C2 to C5) between the polymerizable group and the chromophore were prepared and copolymerized with methylmethacrylate (MMA) and other vinyl monomers. The CMA copolymers had high chromophoric content (up to 18 × 1020) and glass transitions as high as 132°C. Spin cast films were prepared on BK7 substrates and oriented by corona-onset poling at elevated temperatures (COPET). The poled CMA copolymer films were characterized for spectroscopic absorption and second harmonic properties. A comparison of the nonlinear optical properties of poled CMA-MMA copolymers to poled guest-host systems is made. Relative to guest/host systems, CMA-MMA copolymer films exhibit larger and much more stable second-order nonlinear optical properties.

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Practical realization of a microwave Bessel beam launcher

Practical realization of a microwave Bessel beam launcher

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General Assembly and Scientific Symposium, URSI

作者： Oksana Manzhura Edip Niver Mohamed A. Salem Electrical and Computer Engineering Department New Jersey Institute of Technology Newark NJ USA Physical Sciences and Engineering Division King Abdullah University of Science and Technology (KAUST) Thuwal Saudi Arabia

An experimental setup is realized to practically generate Bessel beams in the microwave regime. The setup, which consists of a series of circular loop antennas inserted coaxially inside a circular metallic waveguide, excites the waveguide's transverse-electric modes such that their superposition forms a Bessel beam at the open-end of the waveguide. The excitation currents are calculated from the needed excitation coefficients of each guided mode, which, in turn, are calculated from the modal decomposition of the beam. The efficiency of the setup is evaluated and the obtained experimental results are compared to the theoretical estimates.

关键词： Microwave amplifiers Microwave antennas Apertures Phase shifters Voltage control

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Superior warm-white light-emitting diodes integrated with quantum dot nanophosphors for high luminous efficacy and color rendering

Superior warm-white light-emitting diodes integrated with qu...

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Conference on Lasers and Electro-Optics (CLEO)

作者： Sedat Nizamoglu Talha Erdem Xiao Wei Sun Hilmi Volkan Demir Department of Electrical and Electronics Engineering Department of Physics UNAM-Institute of Materials Science and Nanotechnology Bilkent University Ankara Turkey School of Electrical and Electronic Engineering Microelectronics Division School of Physical and Mathematical Sciences Physics and Applied Physics Division Nanyang Technological University Singapore

Quantum dot nanophoshor hybridized warm-white LEDs are reported to exhibit high photometric performance of luminous efficacy exceeding 350 lm/W opt and color rendering index close to 90 at correlated color temperatures

ISBN: (纸本)9781557529107

关键词： Light emitting diodes Color Nanocrystals Optical sensors Rendering (computer graphics) Stimulated emission Integrated optics

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Room-temperature, high-efficiency conversion of Mott-Wannier excitons to Frenkel excitons in hybrid semiconductor quantum dot/polymer composites

Room-temperature, high-efficiency conversion of Mott-Wannier...

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Conference on Lasers and Electro-Optics (CLEO)

作者： Sedat Nizamoglu Xiao Wei Sun Hilmi Volkan Demir Department of Electrical and Electronics Engineering Department of Physics and UNAM-Institute of Materials Science and Nanotechnology Bilkent University Ankara Turkey School of Electrical and Electronic Engineering Microelectronics Division School of Physical and Mathematical Sciences Physics and Applied Physics Division Nanyang Technological University Singapore

Efficient conversion from Mott-Wannier to Frenkel excitons at room temperature is observed in hybrid inorganic/organic composites of CdSe/ZnS core/shell heteronanocrystals in MDMO-PPV homopolymers at a rate of 0.2628 ... 详细信息

ISBN: (纸本)9781557529107

关键词： Excitons Energy exchange Polymers Temperature measurement Interconnected systems Physics Photoluminescence

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