École Polytechnique Fédérale de Lausanne
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Stabilized platinum electrodes for ferroelectric film deposition using Ti, Ta and Zr adhesion layers
No full textPt-based metallizations using different adhesion layers (Ti. Zr and Ta) were studied for use as electrodes for Ferroelectric thin films on oxidized silicon substrates. Different ways of oxidizing the adhesion layers prior to ferroelectric film growth are compared. with regard to obtaining stable. adherent Pt films of well-defined (111) orientation, while avoiding lead diffusion through the electrode. Upon in-situ deposition of PbTiO3 nt high excess lead flux. lead diffusion through the Pt film was found to depend strongly on the adhesion layer and the stabilization treatment. Pre-oxidation reduces leed diffusion during the later processing Ti diffuses through the electrode upon oxidation. whereas Ta and Zr stay in piece, in analogy to the diffusivities in the corresponding oxides. A novel oxidation treatment was developed to produce stable. adherent metallizations with controlled orientation and good barrier properties against lead diffusion.LCMaeder, T Ecole Polytech Fed Lausanne, Lab Ceram, CH-1015 Lausanne, Switzerland Ecole Polytech Fed Lausanne, Lab Ceram, CH-1015 Lausanne, Switzerland, 121YD, Times Cited:28, Cited References Count:2
Sputtered silicon carbide thin films as protective coating for MEMS applications
No full textThere is a need for chemically resistant coatings that protect the exposed surface of microfluidics components. Pinhole free films with low stress and a good uniformity on flat and inclined surfaces are required. In this study, amorphous silicon carbide (SiC) thin films have been deposited by RF magnetron sputtering on hat surfaces and into micromachined cavities of Si (100). The variation of RF power, deposition pressure and substrate bias voltage have been studied. Depending on the deposition conditions, the film stress can be adjusted from - 1400 MPa to + 100 MPa. Modifications of the deposition rate and the morphology between normal and inclined (54.7 degrees) planes have been observed. Optimal chemical stability was found with slightly compressive (-100 MPa) SiC thin films. No degradation of the protective layer has been observed after 3 h in KOH at 80 degrees C. (C) 2000 Elsevier Science S.A. All rights reserved.LCLedermann, N Ecole Polytech Fed Lausanne, Lab Ceram, CH-1015 Lausanne, Switzerland Ecole Polytech Fed Lausanne, Lab Ceram, CH-1015 Lausanne, Switzerland Ecole Polytech Fed Lausanne, Lab Met Chim, CH-1015 Lausanne, Switzerland Mettler Toledo GmbH, CH-8606 Greifensee, Switzerland295BGCited References Count:1
The Distributed Karhunen-Loève Transform
Get PDFThe Karhunen–Loève transform (KLT) is a key ele- ment of many signal processing and communication tasks. Many recent applications involve distributed signal processing, where it is not generally possible to apply the KLT to the entire signal; rather, the KLT must be approximated in a distributed fashion. This paper investigates such distributed approaches to the KLT, where several distributed terminals observe disjoint subsets of a random vector. We introduce several versions of the distributed KLT. First, a local KLT is introduced, which is the optimal solution for a given terminal, assuming all else is fixed. This local KLT is different and in general improves upon the marginal KLT which simply ignores other terminals. Both optimal approximation and compression using this local KLT are derived. Two important special cases are studied in detail, namely, the partial observation KLT which has access to a subset of variables, but aims at reconstructing them all, and the conditional KLT which has access to side information at the decoder. We focus on the jointly Gaussian case, with known correlation structure, and on approximation and compression problems. Then, the distributed KLT is addressed by considering local KLTs in turn at the various terminals, leading to an iterative algorithm which is locally convergent, sometimes reaching a global optimum, depending on the overall correlation structure. For com- pression, it is shown that the classical distributed source coding techniques admit a natural transform coding interpretation, the transform being the distributed KLT. Examples throughout illustrate the performance of the proposed distributed KLT. This distributed transform has potential applications in sensor networks, distributed image databases, hyper-spectral imagery, and data fusion.LCAVLIN
Water-Exchange Study Revealed Unexpected Substitution Behavior of [(CO)2(NO)Re(H2O)3]2+ in Aqueous Media
No full textThe pH-dependent water-exchange rates of [(CO)2(NO)Re(H2Ocis)2(H2Otrans)]2+ (1) in aq. media were investigated by means of 17O NMR spectroscopy at 298 K. Because of the low pKa value found for 1 (pKa = 1.4 ± 0.3), the water-exchange rate const. kobsH2Otrans/cis was analyzed with a two-pathway model in which kReH2Otrans/cis and kReOHH2Otrans/cis denote the water-exchange rate consts. in trans or cis position to the nitrosyl ligand on 1 and on the monohydroxo species [(CO)2(NO)Re(H2O)2(OH)]+ (2), resp. Whereas the rate consts. kReOHH2Otrans and kReOHH2Ocis were detd. as (4.2 ± 2) ´ 10-3 s-1 and (5.8 ± 2) ´ 10-4 s-1, resp., kReH2Otrans and kReH2Ocis were too small to be detd. in the presence of the much more reactive species 2. Apart from the water exchange, an unexpectedly fast Cº16O ® Cº*O exchange was also obsd. via NMR and IR spectroscopy. It was found to proceed through 1 and 2, with rate consts. kReCO and kReOHCO of (19 ± 4) ´ 10-3 s-1 and (4 ± 3) ´ 10-3 s-1, resp. On the other hand, Nº16O ® Nº*O exchange was not obsd.LCI
On a graph coloring problem arising from discrete tomography
No full textAn extension of the basic image reconstruction problem in discrete tomography is considered: given a graph and a family of chains together with vectors , one wants to find a partition of such that for each and each color , . An interpretation in terms of scheduling is presented.\\ We consider special cases of graphs and identify polynomially solvable cases; general complexity results are established in this case and also in the case where is required to be a proper vertex -coloring of . Finally we examine also the case of (proper) edge -colorings and determine its complexity status.ROS
Use of Dipicolinate-Based Complexes for Producing Ion-Imprinted Polystyrene Resins for the Extraction of Yttrium-90 and Heavy Lanthanide Cations
No full textHighly selective separation of yttrium (and lanthanides) is of interest for the design of radiopharmaceuticals, and an efficient method based on the ion-imprinting concept is proposed here. The synthesis and structural, thermodynamic and photophysical characterization of complexes of trivalent yttrium and lanthanides with two new vinyl derivatives of dipicolinic acid, HL1 and L2, are described. The feasibility of using ion-imprinted resins for yttrium and lanthanide separation is demonstrated. The resins were obtained by copolymerization with styrene and divinylbenzene and subsequent acid treatment to remove the metal ion. High-resolution Eu luminescence experiments revealed that the geometry of the complexation sites is well preserved in the imprinted polymers. The ion-imprinted polymer based on HL1 proved to be particularly well adapted for yttrium extraction, having a sizeable capacity (8.9 +- 0.2 g/mg resin) and a fast rate of extraction (t1/2 = 1.7 min). In addition, lighter and heavier lanthanide ions are separated. Finally, the resin displays high selectivity for yttrium and lanthanide cations against alkali and alkaline earth metals. For instance, in a typical experiment, 10 mg of yttrium was extracted from 5 g of milk ash sample by 2 g of the resin. The good separation properties displayed by the resin based on HL1 open interesting perspectives for the production of highly pure 90Y and radiolanthanides for medical applications, and for trace analysis of these radiochemicals in food and in the environment.LCS
Designing Message-Dependent Deadlock Free Networks on Chips for Application-Specific Systems on Chips
Get PDFNetworks on Chip (NoC) has emerged as the paradigm for designing scalable communication architecture for Systems on Chips (SoCs). Avoiding the conditions that can lead to deadlocks in the network is critical for using NoCs in real designs. Methods that can lead to deadlock-free operation with minimum power and area overhead are important for designing application-specific NoCs. A major class of deadlocks that occur in NoCs are due to the dependencies among the resources shared by different message types. In this work, we consider the problem of avoiding message-dependent deadlocks during the NoC topology synthesis phase. We show that by considering this issue during topology synthesis, we can obtain a significantly better NoC design than traditional methods, where the deadlock avoidance issue is dealt with separately. Our experiments on several SoC benchmarks show that our proposed scheme provides large reduction in NoC power consumption (an average of 38.5%) and NoC area (an average of 30.7%) when compared to traditional approaches.LSI1ES
Preemptive open shop scheduling with multiprocessors: polynomial cases and applications
Get PDFThis paper addresses a multiprocessor generalization of the preemptive open-shop scheduling problem. The set of processors is partitioned into two groups and the operations of the jobs may require either single processors in either group or simultaneously all processors from the same group. We consider two variants depending on whether preemptions are allowed at any fractional time point or only at integral time points. We shall show that the former problem can be solved in polynomial time, and provide sufficient conditions under which the latter problem is tractable. Applications to course scheduling and hypergraph edge coloring are also discussed.ROS