Swiss Institute of Technology

Lausanne, Switzerland

Swiss Institute of Technology

Lausanne, Switzerland
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Schmid M.,Inspire AG | Wegener K.,Swiss Institute of Technology
AIP Conference Proceedings | Year: 2016

An appropriate thermal behavior of polymer powders is essential for successful application in Selective Laser Sintering (SLS) process. A narrow and not sufficient "Sintering-Window" is a primary hurdle for a lot of semi-crystalline Polymers in this connection. Thermo-analytical (DSC) measurements are used to understand the behavior of polymers during SLS-process and to reveal the difference between proper and less proper thermal properties. Commercial PA12-SLS powders are investigated in this sense and compared to a non-commercial one. Thus, the contribution summarizes some very basic polymer properties essential for successful SLS application and explains consequently at the same time why just very few polymers are applicable to SLS today. © 2016 Author(s).

Emmons M.C.,University of California at Los Angeles | Karnani S.,University of California at Los Angeles | Trono S.,Swiss Institute of Technology | Mohanchandra K.P.,University of California at Los Angeles | And 2 more authors.
International Journal of Optomechatronics | Year: 2010

This study investigates the influence of strain state distribution on the accuracy of embedded optical fiber Bragg gratings (FBGs) used as strain sensors. An optical fiber embedded parallel to adjacent structural fibers in a graphite epoxy quasi-isotropic [(90/ ± 45/0)S]3 lay-up is evaluated with mechanical loading parallel to the fiber optic direction. Finite element analysis (FEA) is used to evaluate the fiber optic sensors' responses both in the far field and near field regions of the mechanical grips. Comparison between experimental fiber optic strains, strain gauges, and FEA provides good correlation in the far field with differences of less than 1%. However, in the near field region, some discrepancies are found and attributed to birefringence arising from complex strain states. © Taylor & Francis Group, LLC.

Johnson D.H.,Vanderbilt University | Venuto C.,University of Rochester | Ritchie M.D.,Pennsylvania State University | Morse G.D.,State University of New York at Buffalo | And 4 more authors.
Pharmacogenetics and Genomics | Year: 2014

Background: Atazanavir-associated hyperbilirubinemia can cause premature discontinuation of atazanavir and avoidance of its initial prescription. We used genomewide genotyping and clinical data to characterize determinants of atazanavir pharmacokinetics and hyperbilirubinemia in AIDS Clinical Trials Group protocol A5202. Methods: Plasma atazanavir pharmacokinetics and indirect bilirubin concentrations were characterized in HIV-1-infected patients randomized to atazanavir/ritonavir-containing regimens. A subset had genomewide genotype data available. Results: Genomewide assay data were available from 542 participants, of whom 475 also had data on estimated atazanavir clearance and relevant covariates available. Peak bilirubin concentration and relevant covariates were available for 443 participants. By multivariate analysis, higher peak on-treatment bilirubin levels were found to be associated with the UGT1A1 rs887829 T allele (P=6.4×10-12), higher baseline hemoglobin levels (P=4.9×10-13), higher baseline bilirubin levels (P=6.7×10-12), and slower plasma atazanavir clearance (P=8.6×10-11). For peak bilirubin levels greater than 3.0 mg/dl, the positive predictive value of a baseline bilirubin level of 0.5 mg/dl or higher with hemoglobin concentrations of 14 g/dl or higher was 0.51, which increased to 0.85 with rs887829 TT homozygosity. For peak bilirubin levels of 3.0 mg/dl or lower, the positive predictive value of a baseline bilirubin level less than 0.5 mg/dl with a hemoglobin concentration less than 14 g/dl was 0.91, which increased to 0.96 with rs887829 CC homozygosity. No polymorphism predicted atazanavir pharmacokinetics at genomewide significance. Conclusion: Atazanavir-associated hyperbilirubinemia is best predicted by considering UGT1A1 genotype, baseline bilirubin level, and baseline hemoglobin level in combination. Use of ritonavir as a pharmacokinetic enhancer may have abrogated genetic associations with atazanavir pharmacokinetics. © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins.

Brunschwiler T.,IBM | Madhour Y.,IBM | Madhour Y.,Swiss Institute of Technology | Tick T.,IBM | And 2 more authors.
Proceedings - Electronic Components and Technology Conference | Year: 2013

An innovative approach for electrical chip to substrate and chip to chip interconnects is proposed. The coexistence of solder balls and rails on a chip is discussed, supporting power delivery and heat removal for high-performance flip-chip-onboard and 3D stack applications. The concept enables further bandwidth and current density scaling at a high count of interconnects for signaling, but also at a high solder area fill factor for power delivery and heat removal. The rail-shaped solder joints are also compatible with the current floorplans of microprocessors with voltages arranged in lines. After reflow, solder rails compared to balls can result in a much larger maximal solder width relative to their pads. Therefore, a staggered array arrangement was proposed to minimize shorting risk. In addition, a solder height engineering strategy utilizing modulated pad shapes is discussed to yield equal solder heights for balls and rails present on the same device. However, improper rail design was found to lead to two instability types: 1) Balling and 2) Asymmetric Solder Accumulation. The first is the result of a solder height to width ratio of larger than approximately 0.6 considering long rail lines. The second occurs due to fabrication imperfections. The initial non-symmetric pad/solder shape can cause the accumulation of solder at one rail end (typically the end with the larger area) after reflow. The stability of Bow Tie Rails against Asymmetric Solder Accumulation was investigated to provide design rules for a robust rail design. Accordingly, a solder shape phase diagram indicating the parameters of the three identified phases is compiled. Experimental investigations of reflown solder shapes were complemented with numerical results using a surface energy minimization tool called Surface Evolver. A prediction quality of better than 9% was identified indicating the applicability of the tool to perform solder shape designs. The solver was also capable to predict the mentioned instabilities, rendering the tool even more valuable. Finally, a thermal interface resistance benchmark of ball and rail-like interconnects is performed in a bulk thermal tester. The rail interface with a solder fill factor of 57% yielded a 7 times reduced interface resistance. © 2013 IEEE.

Baritaux J.-C.,Swiss Institute of Technology | Unser M.,Swiss Institute of Technology
2010 7th IEEE International Symposium on Biomedical Imaging: From Nano to Macro, ISBI 2010 - Proceedings | Year: 2010

We propose new soft-prior approach for incorporating structural a priori in FDOT reconstruction. The technique is a non-linear regularization scheme based on the penalization of the (2, 1)-mixed norm. We solve the numerical reconstruction problem with an iterative thresholding-type algorithm. We present simulation results that demonstrate an improvement both in resolution and fluorophore concentration estimation, compared to prior-free approaches. © 2010 IEEE.

Amado A.,Swiss Institute of Technology | Schmid M.,Inspire AG | Levy G.,Inspire AG | Wegener K.,Swiss Institute of Technology
22nd Annual International Solid Freeform Fabrication Symposium - An Additive Manufacturing Conference, SFF 2011 | Year: 2011

This paper introduces a new Selective Laser Sintering (SLS) powder characterization methodology. A better understanding regarding powder flow processing range is targeted. Intrinsic properties of polymers are given from the basic chemical structure and non-intrinsic ones describe characteristics caused from pre-processing and production. The non-intrinsic ones are dedicated to the powder. Understanding the particle size distribution and shape coupled with its ability to flow under the particular SLS processing conditions is desired. In this direction, a system called Revolution Powder Analyzer is employed and the dynamic powder behavior is characterized in nearly roll spreading conditions. This allows a sensitive differentiation of powders regarding their flow-ability and predicts, to a certain extent, the behavior under SLS conditions.

Cevher V.,Swiss Institute of Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

We propose and analyze acceleration schemes for hard thresholding methods with applications to sparse approximation in linear inverse systems. Our acceleration schemes fuse combinatorial, sparse projection algorithms with convex optimization algebra to provide computationally efficient and robust sparse recovery methods. We compare and contrast the (dis)advantages of the proposed schemes with the state-of-the-art, not only within hard thresholding methods, but also within convex sparse recovery algorithms. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Cevher V.,Swiss Institute of Technology | Becker S.,IBM | Schmidt M.,Simon Fraser University
IEEE Signal Processing Magazine | Year: 2014

This article reviews recent advances in convex optimization algorithms for big data, which aim to reduce the computational, storage, and communications bottlenecks. We provide an overview of this emerging field, describe contemporary approximation techniques such as first-order methods and randomization for scalability, and survey the important role of parallel and distributed computation. The new big data algorithms are based on surprisingly simple principles and attain staggering accelerations even on classical problems. © 2014 IEEE.

Uemura H.,Swiss Institute of Technology | Krismer F.,Swiss Institute of Technology | Kolar J.W.,Swiss Institute of Technology
2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013 | Year: 2013

For a Three-Level Three-phase T-type (3LTTC) rectifier and inverter of a high efficiency Uninterruptible Power Supply (UPS) with an output power of 20 kVA, most suitable semiconductor components are selected. For this purpose, this paper details conduction and switching loss models of T-type rectifiers and inverters, compares the total semiconductor losses achieved for RB-IGBTs and for different types of conventional IGBTs, and evaluates the improvements achieved if the Si rectifier diodes are replaced by SiC Schottky Barrier Diodes (SiC SBDs). The switching loss model is parameterized with measured switching losses. According to the results of this comparison, the rectifier preferably employs RB-IGBTs to realize the bi-directional switch and SiC SBDs for the rectifier diodes; switching frequencies up to 32.5 kHz are feasible for total semiconductor losses of the rectifier of 250W. For the inverter, a realization of the bi-directional switch using an anti-series connection of conventional IGBT/SiC SBD modules is found to be most suitable and facilitates a switching frequency of 19.7 kHz for maximum allowed losses of 250 W. © 2013 IEEE.

News Article | March 23, 2016

On Aug. 5, 1914, the world’s first electric traffic signal was installed in the United States. Located in Cleveland, the device was an improvement on a traffic light put up in London in 1868 that used two arms to signal. For approximately 150 years, traffic lights have been notifying motorists, pedestrians, and bicyclists when it’s safe to venture into an intersection. But with the advent of autonomous vehicles, the Massachusetts Institute of Technology (MIT), the Swiss Institute of Technology, and the Italian National Research Council are exploring more efficient methods to replace traffic lights. Publishing in PLOS One, the international team advocated the use of slot-based systems for intersections, which they believe can double the amount of traffic an intersection can handle all while running more smoothly. The research was published last week. “New information and control systems are paving the way to novel traffic management approaches,” wrote the researchers in their study. “For example, vehicles might communicate with roadside infrastructure and other vehicles to produce better-coordinated flows. Furthermore, autonomous driving is starting to enable the careful control of vehicle trajectories and the synchronization of their arrival times at intersections.” Already, car companies are starting to implement such autonomous technologies in their vehicles. General Motors, with their 2017 Cadillac CTS, plans on introducing Dedicated Short Range Communications, which allows the vehicle to communicate mobility and safety information to other vehicles. The new MIT principle, dubbed “Light Traffic,” works similarly to the slot-based control systems employed by airports for plane management, according to the researchers. Each vehicle is assigned a time slot, which indicates when it’ll be safe for it to pass through the intersection. Then the vehicle tweaks its speed to ensure it reaches the intersection at the designated time. “The doubling of bottleneck capacity, as promised by (slot-based intersections), has the potential of significantly reducing overall congestion and improving the stability and predictability of traffic,” said the researchers. Additionally, slot-based intersections “would probably also have beneficial effects on car emissions, as they would reduce the ‘stop-and-go’ effect induced by traffic light queuing,” the researchers added. Establish your company as a technology leader! For more than 50 years, the R&D 100 Awards have showcased new products of technological significance. You can join this exclusive community!  .

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