A Performance Analysis of a Joint LMDS/ Satellite Communication Network

The goal of this research is to provide a performance analysis of a joint terrestrial/ satellite communication network. The systems of interest are the Local Multipoint Distribution Service (LMDS) terrestrial system and the proposed Teledesic satellite network. This analysis is performed using the OPNET network simulation tool. Simulations are run for twelve separate scenarios involving three factors which include: number of users, modulation type, and Quality of Service (QoS). The key metrics for characterizing simulation scenarios are the end-to-end delay, bit error rate, and average system throughput. The results obtained display the benefit of improved throughput, approximately 20 Mbps for the low user load and approximately 8 to 11 Mbps for the high user load, when the modulation schemes where changed. This improvement comes at the expense the bit error rate. For example, the bit error rate increased by a factor of 5 for the low user load when changing from BPSK to QPSK and by a factor of 1.5 for the QPSK to 8-PSK change. The peak end-to-end delay results, ranging from .053 seconds to .446 seconds, proved to support real-time voice communication for all but one scenario (BPSK/ high user load). The QoS proved to be a benefit for scenarios with a high user load (150 users) increasing the average throughput by 2 to 4 Mbps. The QoS also reduced the peak end-to-end delay, narrowing the range from .04 to .104 seconds. The analysis of these three main operational characteristics gives a fundamental look at the joint network\u27s performance capabilities

I see what you mean

The ability to understand and predict others' behavior is essential for successful interactions. When making predictions about what other humans will do, we treat them as intentional systems and adopt the intentional stance, i.e., refer to their mental states such as desires and intentions. In the present experiments, we investigated whether the mere belief that the observed agent is an intentional system influences basic social attention mechanisms. We presented pictures of a human and a robot face in a gaze cuing paradigm and manipulated the likelihood of adopting the intentional stance by instruction: in some conditions, participants were told that they were observing a human or a robot, in others, that they were observing a human-like mannequin or a robot whose eyes were controlled by a human. In conditions in which participants were made to believe they were observing human behavior (intentional stance likely) gaze cuing effects were significantly larger as compared to conditions when adopting the intentional stance was less likely. This effect was independent of whether a human or a robot face was presented. Therefore, we conclude that adopting the intentional stance when observing others' behavior fundamentally influences basic mechanisms of social attention. The present results provide striking evidence that high-level cognitive processes, such as beliefs, modulate bottom-up mechanisms of attentional selection in a top-down manner

Models of organometallic complexes for optoelectronic applications

Organometallic complexes have potential applications as the optically active components of organic light emitting diodes (OLEDs) and organic photovoltaics (OPV). Development of more effective complexes may be aided by understanding their excited state properties. Here we discuss two key theoretical approaches to investigate these complexes: first principles atomistic models and effective Hamiltonian models. We review applications of these methods, such as, determining the nature of the emitting state, predicting the fraction of injected charges that form triplet excitations, and explaining the sensitivity of device performance to small changes in the molecular structure of the organometallic complexes.Comment: To appear in themed issue of J. Mat. Chem. on the modelling of material

On interference effects in concurrent perception and action

Recent studies have reported repulsion effects between the perception of visual motion and the concurrent production of hand movements. Two models, based on the notions of common coding and internal forward modeling, have been proposed to account for these phenomena. They predict that the size of the effects in perception and action should be monotonically related and vary with the amount of similarity between what is produced and perceived. These predictions were tested in four experiments in which participants were asked to make hand movements in certain directions while simultaneously encoding the direction of an independent stimulus motion. As expected, perceived directions were repelled by produced directions, and produced directions were repelled by perceived directions. However, contrary to the models, the size of the effects in perception and action did not covary, nor did they depend (as predicted) on the amount of perception–action similarity. We propose that such interactions are mediated by the activation of categorical representations

Conventional type-II superconductivity in locally non-centrosymmetric LaRh2_2As2_2 single crystals

We report on the observation of superconductivity in LaRh$_2$As$_2$, which is the analogue without $f$-electrons of the heavy-fermion system with two superconducting phases CeRh$_2$As$_2$. A zero-resistivity transition, a specific-heat jump and a drop in magnetic ac susceptibility consistently point to a superconducting transition at a transition temperature of $T_c = 0.28$\,K. The magnetic field-temperature superconducting phase diagrams determined from field-dependent ac-susceptibility measurements reveal small upper critical fields $\mu_{\mathrm{0}}H_{c2} \approx 12$\,mT for $H\parallel ab$ and $\mu_{\mathrm{0}}H_{c2} \approx 9$\,mT for $H\parallel c$. The observed $H_{c2}$ is larger than the estimated thermodynamic critical field $H_c$ derived from the heat-capacity data, suggesting that LaRh$_2$A$s_2$ is a type-II superconductor with Ginzburg-Landau parameters $\kappa^{ab}_{GL} \approx 1.9$ and $\kappa^{c}_{GL}\approx 2.7$. The microscopic Eliashberg theory indicates superconductivity to be in the weak-coupling regime with an electron-phonon coupling constant $\lambda_{e-ph} \approx 0.4$. Despite a similar $T_c$ and the same crystal structure as the Ce compound, LaRh$_2$As$_2$ displays conventional superconductivity, corroborating the substantial role of the 4$f$ electrons for the extraordinary superconducting state in CeRh$_2$As$_2$.Comment: 11 pages, 8 figure

Nanophotonic modulators and photodetectors using silicon photonic and plasmonic device concepts

Nanophotonic modulators and photodetectors are key building blocks for high-speed optical interconnects in datacom and telecom networks. Besides power efficiency and high electro-optic bandwidth, ultra-compact footprint and scalable co-integration with electronic circuitry are indispensable for highly scalable communication systems. In this paper, we give an overview on our recent progress in exploring nanophotonic modulators and photodetectors that combine the specific strengths of silicon photonic and plasmonic device concepts with hybrid integration approaches. Our work comprises electro-optic modulators that exploit silicon-organic hybrid (SOH) and plasmonic-organic hybrid (POH) integration to enable unprecedented energy efficiency and transmission speed, as well as waveguide-based plasmonic internal photo-emission detectors (PIPED) with record-high sensitivities and bandwidths

Photonic-Electronic Ultra-Broadband Signal Processing: Concepts, Devices, and Applications

Combining photonic integrated circuits (PIC) with millimeter-wave electronics opens novel perspectives in generation and detection of ultra-broadband signals with disruptive potential for a wide variety of applications. Here, we will give an overview on our recent progress in the field of ultra-broadband photonic-electronic signal processing, covering device concepts such as silicon plasmonic integration, signal processing concepts such as Kramers-Kronig-based phase reconstruction of THz signals, as well as application demonstrations in the field of high-speed wireless data transmission

Acting while perceiving: assimilation precedes contrast

To explore the nature of specific interactions between concurrent perception and action, participants were asked to move one of their hands in a certain direction while simultaneously observing an independent stimulus motion of a (dis)similar direction. The kinematics of the hand trajectories revealed a form of contrast effect (CE) in that the produced directions were biased away from the perceived directions (“Experiment 1”). Specifically, the endpoints of horizontal movements were lower when having watched an upward as opposed to a downward motion. However, when participants moved under higher speed constraints and were not presented with the stimulus motion prior to initiating their movements, the CE was preceded by an assimilation effect, i.e., movements were biased toward the stimulus motion directions (“Experiment 2”). These findings extend those of related studies by showing that CEs of this type actually correspond to the second phase of a bi-phasic pattern of specific perception–action interference

100 Gbit/s serial transmission using a silicon-organic hybrid (SOH) modulator and a duobinary driver IC

100 Gbit/s three-level (50 Gbit/s 00K) signals are generated using a silicon-organic hybrid modulator and a BiCMOS duobinary driver IC at a BER of 8.5x10(-5)(<10(-12)). We demonstrate dispersion-compensated transmission over 5 km