A 60-GHz 38-pJ/bit 3.5-Gb/s 90-nm CMOS OOK Digital Radio

A 60-GHz fully integrated bits-in bits-out on–off keying (OOK) digital radio has been designed in a standard 90-nm CMOS process technology. The transmitter provides 2 dBm of output power at a 3.5-Gb/s data rate while consuming 156 mW of dc power, including the on-chip 60-GHz frequency synthesizer. A pulse-shaping filter has been integrated to support high data rates while maintaining spectral efficiency. The receiver performs direct-conversion noncoherent demodulation at data rates up to 3.5 Gb/s while consuming 108 mW of dc power, for a total average transceiver energy consumption of 38 pJ/bit in time division duplex operation. To the best of the authors' knowledge, this is the lowest energy per bit reported to date in the 60-GHz band for fully integrated single-chip CMOS OOK radios.      

Inkjet Printed Large‐Area Flexible Few‐Layer Graphene Thermoelectrics

Graphene‐based organic nanocomposites have ascended as promising candidates for thermoelectric energy conversion. In order to adopt existing scalable printing methods for developing thermostable graphene‐based thermoelectric devices, optimization of both the material ink and the thermoelectric properties of the resulting films are required. Here, inkjet‐printed large‐area flexible graphene thin films with outstanding thermoelectric properties are reported. The thermal and electronic transport properties of the films reveal the so‐called phonon‐glass electron‐crystal character (i.e., electrical transport behavior akin to that of few‐layer graphene flakes with quenched thermal transport arising from the disordered nanoporous structure). As a result, the all‐graphene films show a room‐temperature thermoelectric power factor of 18.7 µW m^?1 K^?2, representing over a threefold improvement to previous solution‐processed all‐graphene structures. The demonstration of inkjet‐printed thermoelectric devices underscores the potential for future flexible, scalable, and low‐cost thermoelectric applications, such as harvesting energy from body heat in wearable applications.     

Reparameterization for statistical state estimation applied to differential equations

The ensemble Kalman filter is a widely applied data assimilation technique useful for improving the forecast of computational models. The main computational cost of the ensemble Kalman filter comes from the numerical integration of each ensemble member forward in time. When the computational model involves a partial differential equation, the degrees of freedom of the solution in the discretization of the spatial domain are oftentimes used for the representation of the state of the system, and the filter is applied to this state vector. We propose a method of approximating the state of a partial differential equation in a representation space developed separately from the numerical method. This representation space represents a reparameterization of the state vector and can be chosen to retain desirable physical features of the solutions. We apply the ensemble Kalman filter to this representation of the state, and numerically demonstrate that acceptable results are obtained with substantially smaller ensemble sizes.     

Persistent luminescence — Quo vadis?

The present status of the persistent luminescence mechanisms is reviewed and the remaining unsolved details are discussed. These details include the identification and role of defects in the Eu²⁺-doped and R³⁺ co-doped alkaline earth aluminates (MAl₂O₄) and disilicates (M₂MgSi₂O₇; M:Ca, Sr, Ba) which can be partly resolved by the thermoluminescence (TL) measurements. The use of the synchrotron radiation - presently only sparsely used in the studies of persistent luminescence - is introduced: the oxidation state of the presumed R²⁺/R³⁺/R^IV species occurring in the persistent luminescence materials during the luminescence processes were examined with synchrotron radiation XANES (and EXAFS) methods. The band gap energies (E_g), the defect-related luminescence as well as the 4f⁷→4f⁶5d¹ transition energies were derived from the synchrotron radiation excitation spectra of the materials. Subsequently, the early steps of the density functional theory (DFT) calculations involving the solution of the persistent luminescence mechanisms (band gap energies, position of the Eu²⁺ levels) are discussed. Some remaining challenges are eventually highlighted.     

从手机大战看探寻创新企业之路

手机制造商们面临的问题,不是手机越来越难制造．或是难销售：而是越来越难在销售中盈利。这意味着公司必须做出一个明确的选择——是仅仅成为创新者．还是成为创新企业     

The complexity of maximum matroid-greedoid intersection and weighted greedoid maximization

The maximum intersection problem for a matroid and a greedoid, given by polynomial-time oracles, is shown NP-hard by expressing the satisfiability of boolean formulas in 3-conjunctive normal form as such an intersection. The corresponding approximation problems are shown NP-hard for certain approximation performance bounds. Moreover, some natural parameterized variants of the problem are shown W[P]-hard. The results are in contrast with the maximum matroid-matroid intersection which is solvable in polynomial time by an old result of Edmonds. We also prove that it is NP-hard to approximate the weighted greedoid maximization within 2^nO(1) where n is the size of the domain of the greedoid.     

On potential isomorphism and non-structure

We show in the paper that for any non-classifiable countable theory T there are non-isomorphic models and that can be forced to be isomorphic without adding subsets of small cardinality. By making suitable cardinal arithmetic assumptions we can often preserve stationary sets as well. We also study non-structure theorems relative to the Ehrenfeucht-Fraïssé game. The research of the first and second author was partially supported by Academy of Finland grant 40734 Mathematics Subject Classification (2000): 03C55, 03C45     

Performance Analysis of Maximum SNR Scheduling with an Infrastructure Relay Link

We consider infrastructure-based amplify-and-forward (AF) relaying for extending downlink and uplink coverage areas of a cellular base station. The base station serves multiple mobile users via a multi-hop backhaul relay link by sharing out access link channel resources with maximum signal-to-noise ratio (SNR) scheduling. We analyze the performance of the system by deriving closed-form expressions for outage probability, outage capacity, ergodic capacity, average end-to-end SNR and amount of fading (AoF). These measures show that maximum SNR scheduling of multiple users in a cellular relay link offers significant diversity, capacity and SNR improvement over single-user transmission and round robin scheduling. We also relate performance of the relay link to that of a distributed antenna system (DAS), and show that the noisy wireless backhaul relay link induces tolerable performance deterioration compared to deploying a cable-connected distributed antenna.