A low noise 0.9 GHz FBAR clock

A low noise 0.9 GHz FBAR clock consisting of an oscillator and divider circuit for single-sided-to-differential conversion for a high-speed interleaved pipeline A/D-converter was designed, realized with an in-house FBAR and a commercial 0.35 μm CMOS process, and tested. The circuit showed very good jitter and phase noise performance. A temperature coefficient of –47 ppm/K was measured.     

Dispersion and mirror transmission characteristics of bulk acoustic wave resonators

A heterodyne laser interferometer is used for a detailed study of the acoustic wave fields excited in a 932-MHz solidly mounted ZnO thin-film BAW resonator. The sample is manufactured on a glass substrate, which also allows direct measurement of the vibration fields from the bottom of the acoustic mirror. Vibration fields are measured both on top of the resonator and at the mirror-substrate interface in a frequency range of 350 to 1200 MHz. Plate wave dispersion diagrams are calculated from the experimental data in both cases and the transmission characteristics of the acoustic mirror are determined as a function of both frequency and lateral wave number. The experimental data are compared with 1-D and 2-D simulations to evaluate the validity of the modeling tools commonly used in mirror design. All the major features observed in the 1-D model are identified in the measured dispersion diagrams, and the mirror transmission characteristics predicted for the longitudinal waves, by both the 1-D and the 2-D models, match the measured values well.     

High quality GaAs nanowires grown on glass substrates

We report for the first time the growth of GaAs nanowires directly on low-cost glass substrates using atmospheric pressure metal organic vapor phase epitaxy via a vapor-liquid-solid mechanism with gold as catalyst. Substrates used in this work were of float glass type typically seen in household window glasses. Growth of GaAs nanowires on glass were investigated for growth temperatures between 410 and 580 °C. Perfectly cylindrical nontapered nanowires with a growth rate of ~33 nm/s were observed at growth temperatures of 450 and 470 °C, whereas highly tapered pillar-like wires were observed at 580 °C. Nanowires grew horizontally on the glass surface at 410 °C with a tendency to grow in vertically from the substrate as the growth temperature was increased. X-ray diffraction and transmission electron microscopy revealed that the nanowires have a perfect zinc blende structure with no planar structural defects or stacking faults. Strong photoluminescence emission was observed both at low temperature and room temperature indicating a high optical quality of GaAs nanowires. Growth comparison on impurity free fused silica substrate suggests unintentional doping of the nanowires from the glass substrate.     

Agents in Electronic Commerce: Component Technologies for Automated Negotiation and Coalition Formation

Automated negotiation and coalition formation among self-interested agents are playing an increasingly important role in electronic commerce. Such agents cannot be coordinated by externally imposing their strategies. Instead the interaction protocols have to be designed so that each agent is motivated to follow the strategy that the protocol designer wants it to follow. This paper reviews six component technologies that we have developed for making such interactions less manipulable and more efficient in terms of the computational processes and the outcomes: 1. OCSM-contracts in marginal cost based contracting, 2. leveled commitment contracts, 3. anytime coalition structure generation with worst case guarantees, 4. trading off computation cost against optimization quality within each coalition, 5. distributing search among insincere agents, and 6. unenforced contract execution. Each of these technologies represents a different way of battling self-interest and combinatorial complexity simultaneously. This is a key battle when multi-agent systems move into large-scale open settings.     

AWESOME: A general multiagent learning algorithm that converges in self-play and learns a best response against stationary opponents

Two minimal requirements for a satisfactory multiagent learning algorithm are that it 1. learns to play optimally against stationary opponents and 2. converges to a Nash equilibrium in self-play. The previous algorithm that has come closest, WoLF-IGA, has been proven to have these two properties in 2-player 2-action (repeated) games—assuming that the opponent’s mixed strategy is observable. Another algorithm, ReDVaLeR (which was introduced after the algorithm described in this paper), achieves the two properties in games with arbitrary numbers of actions and players, but still requires that the opponents' mixed strategies are observable. In this paper we present AWESOME, the first algorithm that is guaranteed to have the two properties in games with arbitrary numbers of actions and players. It is still the only algorithm that does so while only relying on observing the other players' actual actions (not their mixed strategies). It also learns to play optimally against opponents that eventually become stationary. The basic idea behind AWESOME (Adapt When Everybody is Stationary, Otherwise Move to Equilibrium) is to try to adapt to the others' strategies when they appear stationary, but otherwise to retreat to a precomputed equilibrium strategy. We provide experimental results that suggest that AWESOME converges fast in practice. The techniques used to prove the properties of AWESOME are fundamentally different from those used for previous algorithms, and may help in analyzing future multiagent learning algorithms as well. Editors: Amy Greenwald and Michael Littman     

Anytime coalition structure generation: an average case study

Coalition formation is a key topic in multiagent systems. One would prefer a coalition structure that maximizes the sum of the values of the coalitions, but often the number of coalition structures is too large to allow for exhaustive search for the optimal one. We present experimental results for three anytime algorithms that search the space of coalition structures. We show that, in the average case, all three algorithms do much better than the recently established theoretical worst case results in Sandholm et al. (1999a). We also show that no one algorithm is dominant. Each algorithm's performance is influenced by the particular instance distribution, with each algorithm outperforming the others for different instances. We present a possible explanation for the behaviour of the algorithms and support our hypothesis with data collected from a controlled experimental run.     

Design and evaluation of prosody-based non-speech audio feedback for physical training application

Methodological support for the design of non-speech user interface sounds for human–computer interaction is still fairly scarce. To meet this challenge, this paper presents a sound design case which, as a practical design solution for a wrist-computer physical training application, outlines a prosody-based method for designing non-speech user interface sounds. The principles used in the design are based on nonverbal communicative functions of prosody in speech acts, exemplifying an interpersonal approach to sonic interaction design. The stages of the design process are justified with a theoretical analysis and three empirical sub-studies, which comprise production and recognition tasks involving four communicative functions. The final evaluation study indicates that the resulting sounds of the design process successfully served these functions. In all, this study suggests that prosody-based sound design provides widely applicable means to attribute meaningful, interaction-derived qualities to non-speech sounds for interactive applications.     

Step-transition perturbation approach for pixel-structured nonparaxial diffractive elements

An extension of an approximate step-transition perturbation method is presented that permits numerically efficient diffraction analysis of pixel-structured surface profiles in the nonparaxial domain. Comparison with the rigorous diffraction theory of gratings shows that the method is reasonably accurate provided that the pixel size exceeds approximately two wavelengths even if the structure contains isolated pixels.