Design and Optimization of Compressor Airfoils by Using Class Function / Shape Function Methodology

International audienceThis paper describes a new design method for high Reynolds number subsonic compressor blade sections for industrial gas turbines and compressors. The focus is on the middle and end stages, where the Reynolds numbers are about 2 to 6 × 10 6 and the Mach numbers between 0.4 and 0.8. The new design method combines i) a parametric geometry definition method, ii) a fast blade-to-blade flow solver, and iii) an optimization tool with a suitable objective function. The development of a new blade section is based on a conventional NACA-65 design, subsequently modified to an optimized CSM profile, where CSM means Class Function / Shape Function Methodology. The new profile shapes are obtained by superimposing a camber line and a thickness distribution. Both the camber line and the thickness distribution are prescribed as analytical functions to cut down the CPU-time for geometry set up and to guarantee smooth geometries. Numerical calculations are performed by applying the two-dimensional blade-to-blade solver MISES. The optimization method used in this paper is the single-objective genetic algorithm (SOGA) from the DAKOTA library. The objective function consists of 5 components and takes into account the whole loss polar. The corresponding computing time is relatively short-that is 1 to 2 days. At high Reynolds number, the new profiles show decreased design point losses and increased operating limits compared to corresponding results using conventional NACA-65 profiles. In addition, the present results show close agreement with those produced by so-called high performance profiles of the relevant literature

Overlay Accuracy Limitations of Soft Stamp UV Nanoimprint Lithography and Circumvention Strategies for Device Applications

In this work multilevel pattering capabilities of Substrate Conformal Imprint Lithography (SCIL) have been explored. A mix & match approach combining the high throughput of nanoimprint lithography with the excellent overlay accuracy of electron beam lithography (EBL) has been exploited to fabricate nanoscale devices. An EBL system has also been utilized as a benchmarking tool to measure both stamp distortions and alignment precision of this mix & match approach. By aligning the EBL system to 20 mm x 20 mm and 8 mm x 8 mm cells to compensate pattern distortions of order of $3 \mu m$ over 6 inch wafer area, overlay accuracy better than $1.2 \mu m$ has been demonstrated. This result can partially be attributed to the flexible SCIL stamp which compensates deformations caused by the presence of particles which would otherwise significantly reduce the alignment precision

Reflective arrayed waveguide gratings based on Sagnac loop reflectors with custom spectral response

© 2014 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibitedIn this paper, a model for the analysis and design of a reflective Arrayed Waveguide Grating is presented. The device consists of one half of a regular AWG where each arm waveguide in the array is terminated with a phase shifter and a Sagnac loop reflector. By individually adjusting the phase shifter and Sagnac reflectivity in each arm, additional functionality to that previously reported in the literature is attained, since this enables tailoring the spectral response of the AWG. The design and experimental demonstration of Gaussian pass-band shape devices in Silicon-on-Insulator technology are reported. Methods to obtain flattened and arbitrary spectral responses are described and supported by simulation results. (C) 2014 Optical Society of AmericaThe authors acknowledge financial support by the Spanish MINECO projects TEC2010-21337, TEC2013-42332-P; FEDER UPVOV 10-3E-492 and UPVOV 08-3E-008. B. Gargallo acknowledges financial support through FPI grant BES-2011-046100. The authors thank J.S. Fandino for helpful discussions.Gargallo Jaquotot, BA.; Muñoz Muñoz, P.; Baños López, R.; Giesecke, AL.; Bolten, J.; Wahlbrink, T.; Kleinjans, H. (2014). Reflective arrayed waveguide gratings based on Sagnac loop reflectors with custom spectral response. Optics Express. 22(12):14348-14362. https://doi.org/10.1364/OE.22.014348S14348143622212Brackett, C. A. (1990). Dense wavelength division multiplexing networks: principles and applications. IEEE Journal on Selected Areas in Communications, 8(6), 948-964. doi:10.1109/49.57798Kirchain, R., & Kimerling, L. (2007). A roadmap for nanophotonics. 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Monolithic InP Multiwavelength Coherent Receiver Using a Chirped Arrayed Waveguide Grating. Journal of Lightwave Technology, 29(4), 536-541. doi:10.1109/jlt.2010.2097240Munoz, P., Pastor, D., & Capmany, J. (2002). Modeling and design of arrayed waveguide gratings. Journal of Lightwave Technology, 20(4), 661-674. doi:10.1109/50.996587Jinguji, K., Takato, N., Hida, Y., Kitoh, T., & Kawachi, M. (1996). Two-port optical wavelength circuits composed of cascaded Mach-Zehnder interferometers with point-symmetrical configurations. Journal of Lightwave Technology, 14(10), 2301-2310. doi:10.1109/50.541222Soldano, L. B., & Pennings, E. C. M. (1995). Optical multi-mode interference devices based on self-imaging: principles and applications. Journal of Lightwave Technology, 13(4), 615-627. doi:10.1109/50.372474Bachmann, M., Besse, P. A., & Melchior, H. (1994). General self-imaging properties in N × N multimode interference couplers including phase relations. 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Journal of Lightwave Technology, 13(3), 447-455. doi:10.1109/50.372441Munoz, P., Pastor, D., Capmany, J., Ortega, D., Pujol, A., & Bonar, J. R. (2004). AWG Model Validation Through Measurement of Fabricated Devices. Journal of Lightwave Technology, 22(12), 2763-2777. doi:10.1109/jlt.2004.833275Kleijn, E., Smit, M. K., & Leijtens, X. J. M. (2013). New Analytical Arrayed Waveguide Grating Model. Journal of Lightwave Technology, 31(20), 3309-3314. doi:10.1109/jlt.2013.2281612Bogaerts, W., Dumon, P., Thourhout, D. V., Taillaert, D., Jaenen, P., Wouters, J., … Baets, R. G. (2006). Compact Wavelength-Selective Functions in Silicon-on-Insulator Photonic Wires. IEEE Journal of Selected Topics in Quantum Electronics, 12(6), 1394-1401. doi:10.1109/jstqe.2006.884088Pathak, S., Van Thourhout, D., & Bogaerts, W. (2013). Design trade-offs for silicon-on-insulator-based AWGs for (de)multiplexer applications. 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Protocol for the Cognitive Interventions and Nutritional Supplements (CINS) trial: A randomized controlled multicenter trial of a brief intervention (BI) versus a BI plus cognitive behavioral treatment (CBT) versus nutritional supplements for patients with long-lasting muscle and back pain

Background: Brief intervention programs are clinically beneficial, and cost efficient treatments for low back pain, when offered at 8-12 weeks, compared with treatment as usual. However, about 30% of the patients do not return to work. The European Guidelines for treatment of chronic low back pain recommends Cognitive Behavioral Therapy (CBT), but conclude that further research is needed to evaluate the effectiveness of CBT for chronic low back pain. Methods/Design: The aim of the multicenter CINS trial (Cognitive Interventions and Nutritional Supplements) is to compare the effectiveness of 4 different interventions; Brief Intervention, Brief Intervention and CBT, Brief Intervention and nutritional supplements of seal oil, and Brief Intervention and nutritional supplements of soy oil. All participants will be randomly assigned to the interventions. The nutritional supplements will be tested in a double blind design. 400 patients will be recruited from a population of chronic low back pain patients that have been sick listed for 2-10 months. Four outpatient clinics, located in different parts of Norway, will participate in recruitment and treatment of the patients. The Brief Intervention is a one session cognitive, clinical examination program based on a non-injury model, where return to normal activity and work is the main goal, and is followed by two booster sessions. The CBT is a tailored treatment involving 7 sessions, following a detailed manual. The nutritional supplements consist of a dosage of 10 grams of either soy or seal oil (capsules) per day for 3 months, administered in a double blind design. All patients will be followed up with questionnaires after 3, 6 and 12 months, while sick leave data will be collected up to at least 24 months after randomization. The primary outcome of the study is sick leave and will be based on register data from the National Insurance Administration. Secondary outcomes include self-reported data on disability, pain, and psychological variables. Conclusions: To our knowledge, the CINS trial will be the largest, randomized trial of psychological and nutritional interventions for chronic low back pain patients to date. It will provide important information regarding the effectiveness of CBT and seal oil for chronic low back pain patients

Populist Mobilization: A New Theoretical Approach to Populism*

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112280/1/j.1467-9558.2011.01388.x.pd

Thermodynamic and Rotordynamic Assessment of Conventional and Ultra-High Bypass Ratio Engines

Due to the economical aspiration to increase the efficiency and several ecological regulations to reduce CO2 and noise emissions, aircraft and engine manufacturer have to increase the bypass ratio of gas turbines. But, the higher the bypass ratio of a gas turbine is the larger the rotating masses are. Thus, concerning the system stability due to the change of the eigenbehavior of the aircraft in its structure, the dynamic influences of gyroscopic moments as the consequence of the angular momentum of the engine are an uncertainty and need to be investigated carefully. This paper compares two gas turbines, a conventional one with a bypass ratio of 5 and one with an ultra-high bypass ratio of 17. Two different approaches are presented. On the one hand, a comparison regarding the thermodynamical cycle process, on the other hand, using a multibody formulation, a model of a Coanda wing with each of the engines mounted over the airfoil is presented. The analysis conducts the structural coupling and dynamical influences on the wing structure arising during their operation at specific design points. The comparison of the dynamic influences should show which structural effects on the wing structure come along with the trade-off due to increased thermodynamic efficiency

Evaluation of Ultra-High Bypass Ratio Engines for an Over-Wing Aircraft Configuration

Today, main hub airports are already at their capacity limit and hence, smaller airports get more interesting to provide point-to-point connections. Unfortunately, the use of regional airports induces an increased environmental footprint for the population living around it. In an attempt to solve the related problems, unconventional aircraft and engine designs are required. The research project Coordinated Research Centre 880 aims at examing the fundamentals of a single-aisle aircraft powered by two geared ultra-high bypass turbofan engines mounted over the wing. Low direct operating costs, noise shielding due to the over-wing configuration, and short runway lengths are the main advantages of such an aircraft. Highlighting the performance, economical and noise benefits of a geared ultra-high bypass engine is the key aim of this paper. This assessment includes a correspondingly adjusted aircraft. Open literature values are applied to design the two investigated bypass ratios; an engine with a bypass ratio of 5 respectively 17. Furthermore, a variable bypass nozzle area for the ultra-high bypass ratio engine is analyzed. Finally, the three engines are evaluated based on aircraft direct operating costs and an initial engine noise assessment. This study concludes that increasing the bypass ratio from 5 to 17 drops the direct operating costs by 5.6% and can reduce the sound at the source for a selected operating condition by up to 7dB. During the different flight phases the reduction in specific fuel consumption ranges between 18% to 40%. Applying a variable bypass nozzle leads to a further decrease by 0.6% for the direct operating costs. Opening the bypass nozzle during several flight phases stabilizes the fan shown by the surge margin increase. It is concluded that this unconventional aircraft configuration with ultra-high bypass ratio engines mounted over the wing has the potential to relieve main hub airports by also reducing the environmental impact

50 GBit/s Photodetectors Based on Wafer-Scale Graphene for Integrated Silicon Photonic Communication Systems

Optical data links are the backbone of today’s telecommunication infrastructure. The integration of electronic and optic components on one chip is one of the most attractive routes to further increase the system performance. Here, we present the fabrication of photodetectors based on CVD-grown graphene on silicon photonic waveguides. The devices operate bias-free in the C-band at 1550 nm and show an extrinsic −3 dB bandwidth of 41 GHz. We demonstrate that these detectors work at data rates up to 50 GBit/s with excellent signal integrity