École Polytechnique Fédérale de Lausanne
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The Electronic Journal: A Collaborative and Co-operative Learning Environment for Web-based Experimentation
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Introducing e-Learning Solutions and Flexibility in Higher Education: Objectives and Challenges
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Efficient Stimulated Raman Pumping for Quantum-State Resolved Surface Reactivity Measurements
No full textWe describe the use of stimulated Raman pumping in a molecular beam to perform quantum state resolved gas-surface reactivity measurements for molecules prepared in totally symmetric vibrational states. Vibrational states of homonuclear diatomics as well as totally symmetric vibrations of polyatomic molecules cannot be prepared by direct infrared excitation but are accessible through stimulated Raman pumping by two laser fields when the difference between the incident laser frequencies matches the vibration. We generate a suitable resonant pair of high-energy pump and Stokes laser beams in an injection seeded Raman amplifier filled with the sample gas and equipped with internal gas recirculation. The ability to partially saturate the Raman pumping process in the molecular beam is used to quantify the fraction of vibrationally excited molecules in the irradiated volume, which is needed for quantitative reactivity measurements. We illustrate the method with state resolved reactivity measurements for CH4, prepared in its symmetric C-H stretch vibration on a Ni(100) single crystal surface.LCP
Mapping and Configuration Methods for Multi-Use-Case Networks on Chips
Get PDFTo provide a scalable communication infrastructure for Systems on Chips (SoCs), Networks on Chips (NoCs), a communication centric design paradigm is needed. To be cost effective, SoCs are often programmable and integrate several different applications or use-cases on to the same chip. For the SoC platform to support the different use-cases, the NoC architecture should satisfy the performance constraints of each individual use-case. In this work we motivate the need to consider multiple use-cases during the NoC design process. We present a method to ef ciently map the applications on to the NoC architecture, satisfying the design constraints of each individual use-case. We also present novel ways to dynamically recon- gure the network across the different use-cases and explore the possibility of integrating Dynamic Voltage and Frequency Scaling (DVS/DFS) techniques with the use-case centric NoC design methodology. We validate the performance of the design methodology on several SoC applications. The dynamic recon guration of the NoC integrated with DVS/DFS schemes results in large power savings for the resulting NoC systems.LSI
Electrochemical promotion of RuO2 catalysts for the gas phase combustion of C2H4
No full textThe influence of the polarization of the RuO2/YSZ interface on the electrochem. promotion of RuO2 catalysts was studied by temp. programmed desorption and high temp. cyclic voltammetry measurements. The desorption activation energy of adsorbed oxygen decreases from 2.32 eV at 380 mV to 7.26 eV at 600 mV by polarizing of the RuO2/YSZ interface. A higher oxide (RuO3) might be formed at the RuO2/YSZ interface during anodic polarization. [on SciFinder (R)]GGE
Measurement and Analysis of Single-Hop Delay on an IP Backbone Network
Get PDFWe measure and analyze the single-hop packet delay through operational routers in the Sprint Internet protocol (IP) backbone network. After presenting our delay measurements through a single router for OC-3 and OC-12 link speeds, we propose a methodology to identify the factors contributing to single-hop delay. In addition to packet processing, transmission, and queueing delay at the output link, we observe the presence of very large delays that cannot be explained within the context of a first-in first-out output queue model. We isolate and analyze these outliers. Results indicate that there is very little queueing taking place in Sprint’s backbone. As link speeds increase, transmission delay decreases and the dominant part of single-hop delay is packet processing time. We show that if a packet is received and transmitted on the same linecard, it experiences less than 20 s of delay. If the packet is transmitted across the switch fabric, its delay doubles in magnitude. We observe that processing due to IP options results in single-hop delays in the order of milliseconds. Milliseconds of delay may also be experienced by packets that do not carry IP options. We attribute those delays to router idiosyncratic behavior that affects less than 1% of the packets. Finally, we show that the queueing delay distribution is long-tailed and can be approximated with aWeibull distribution with the scale parameter a = 0.5 and the shape parameter b = 0.6 to 0.82.LCAINDY
NIR Lanthanide Luminescence by Energy Transfer from Appended Terpyridine-Boradiazaindacene Dyes
No full textMononuclear trivalent lanthanide complexes with formula [Ln(L)(NO3)3] [in which L=4,4-difluoro-8-(2:2;6:2-terpyridin-4-yl)-1,3,5,7-tetramethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indacene (Boditerpy)] are reported for Ln=Yb, Nd, Er, La and Gd. According to the crystal structure of the Yb complex, the lanthanide ion is bound to the terdentate terpyridine and the inner coordination sphere of the nine-coordinate lanthanide ion is completed by three bidentate nitrate anions. The coordination polyhedron can be described as a distorted tricapped antiprism. The terpyridine chelate is almost planar and tilted by nearly 60° from the indacene subunit. FT-IR spectra confirm the bidentate binding mode of the nitrate anions for the other complexes. NMR and ES-MS spectra (through characteristic isotopic patterns) confirm the chemical formulation. The complexes have high molar absorption coefficients in the visible spectral region (65 000 M-1 cm-1 at 529 nm) and display sizeable NIR luminescence (900 to 1600 nm, for Ln=Yb, Nd and Er), upon irradiation through the electronic state of the indacene moiety at 514 nm. Crystal-field splitting was analysed at low temperature. The quantum yield of the Yb solution (10-4 M) in dichloromethane amounts to 0.31 %, corresponding to a sensitisation efficacy of the ligand of ca. 63 %.LCS
