Handbook of Convergence Theorems for (Stochastic) Gradient Methods

This is a handbook of simple proofs of the convergence of gradient and stochastic gradient descent type methods. We consider functions that are Lipschitz, smooth, convex, strongly convex, and/or Polyak-{\L}ojasiewicz functions. Our focus is on ``good proofs'' that are also simple. Each section can be consulted separately. We start with proofs of gradient descent, then on stochastic variants, including minibatching and momentum. Then move on to nonsmooth problems with the subgradient method, the proximal gradient descent and their stochastic variants. Our focus is on global convergence rates and complexity rates. Some slightly less common proofs found here include that of SGD (Stochastic gradient descent) with a proximal step, with momentum, and with mini-batching without replacement.Comment: From v2 to v3: Added new sections about SSP (Stochastic Proximal Point) and SPS (Stochastic Polyak Stepsize). Added proof for SGD for nonconvex functions. Simplified some statements for SGD. Corrected various errors and misprint

Model Consistency for Learning with Mirror-Stratifiable Regularizers

International audienceLow-complexity non-smooth convex regular-izers are routinely used to impose some structure (such as sparsity or low-rank) on the coefficients for linear predictors in supervised learning. Model consistency consists then in selecting the correct structure (for instance support or rank) by regularized empirical risk minimization. It is known that model consistency holds under appropriate non-degeneracy conditions. However such conditions typically fail for highly correlated designs and it is observed that regularization methods tend to select larger models. In this work, we provide the theoretical underpinning of this behavior using the notion of mirror-stratifiable regular-izers. This class of regularizers encompasses the most well-known in the literature, including the 1 or trace norms. It brings into play a pair of primal-dual models, which in turn allows one to locate the structure of the solution using a specific dual certificate. We also show how this analysis is applicable to optimal solutions of the learning problem, and also to the iterates computed by a certain class of stochastic proximal-gradient algorithms

Improvements in automotive company external logistics

Abstract (English) This paper purpose is to contribute in the continuous improvement development of automotive company external logistics, adapting current processes and supplying materials methods to new stage of the plant. Within this broad objective, the study is focused on the specific case of new model B299, and the attempt to achieve a target figure in order to reducing its components transport cost from European suppliers which are located more than 2.500 kilometers from the plant, in a rate of around 5%. The main objective of this paper is to study the possibilities of obtaining cost savings in logistics (procure parts). Thus, it will be necessary to establish an analysis methodology in oder to identifying opportunities for reduction transport costs through duplication of equipment and dies. Published data have been modified by privacy & confidential commercial reasons

Thin-film silicon detectors for particle detection

Integrated particle sensors have been developed using thin-film on ASIC technology. For this purpose, hydrogenated amorphous silicon diodes, in various configurations, have been optimized for particle detection. These devices were first deposited on glass substrates to optimize the material properties and the dark current of very thick diodes (with thickness up to 50 μm). Corresponding diodes were later directly deposited on CMOS readout chips. These integrated particle sensors have been characterized using light pulse illumination and beta particle irradiation from 63Ni and 90Sr sources. Direct detection of single low- and high-energy beta particles have been demonstrated. The application of this new integrated particle sensor concept for medical imaging is also discussed

The role of a firm's absorptive capacity and the technology transfer process in clusters: How effective are technology centres in low-tech clusters?

This paper analyses how the internal resources of small- and medium-sized enterprises determine access (learning processes) to technology centres (TCs) or industrial research institutes (innovation infrastructure) in traditional low-tech clusters. These interactions basically represent traded (market-based) transactions, which constitute important sources of knowledge in clusters. The paper addresses the role of TCs in low-tech clusters, and uses semi-structured interviews with 80 firms in a manufacturing cluster. The results point out that producer–user interactions are the most frequent; thus, the higher the sector knowledge-intensive base, the more likely the utilization of the available research infrastructure becomes. Conversely, the sectors with less knowledge-intensive structures, i.e. less absorptive capacity (AC), present weak linkages to TCs, as they frequently prefer to interact with suppliers, who act as transceivers of knowledge. Therefore, not all the firms in a cluster can fully exploit the available research infrastructure, and their AC moderates this engagement. In addition, the existence of TCs is not sufficient since the active role of a firm's search strategies to undertake interactions and conduct openness to available sources of knowledge is also needed. The study has implications for policymakers and academia

The economic geography of the meso-global spaces: integrating multinationals and clusters at the local-global level

This is an author's accepted manuscript of an article published in: “European Planning Studies"; Volume 21, Issue 7, 2013; copyright Taylor & Francis; available online at: http://dx.doi.org/10.1080/09654313.2013.733853[EN] The local global phenomenon literature is fragmented between the fields of international business and economic geography (EG). In the case of the latter, the literature, produced within the global production networks (GPNs) and global value chain frameworks, does not address the central role of firms, especially multinationals which co-locate and connect territories along GPNs. This paper develops a cross-field conceptual integration in order to enrich the EG perspective, using qualitative research methodology to test the framework. The results have important implications for scholars and policymakers.We are very thankful to the “Ministry of Economics” funding ECO2010:17318 and “Generalitat Valenciana” for its support in visiting the London School of Economics and Political Science (BEST 2011 grants)Hervás Oliver, JL.; Boix Domenech, R. (2012). The economic geography of the meso-global spaces: integrating multinationals and clusters at the local-global level. European Planning Studies. 21(7):1064-1080. https://doi.org/10.1080/09654313.2013.733853S1064108021

Characterization of protons accelerated from a 3 TW table-top laser system

[EN] We report on benchmark tests of a 3 TW/50 fs, table-top laser system specifically developed for proton acceleration with an intrinsic pump rate up to 100 Hz. In two series of single-shot measurements differing in pulse energy and contrast the successful operation of the diode pumped laser is demonstrated. Protons have been accelerated up to 1.6 MeV in interactions of laser pulses focused on aluminium and mylar foils between 0.8 and 25 mu m thickness. Their spectral distributions and maximum energies are consistent with former experiments under similar conditions. These results show the suitability of our system and provide a reference for studies of laser targets at high repetition rate and possible applications.This project has been funded by Centro para el Desarrollo Tecnologico Industrial (CDTI, Spain) within the INNPRONTA program, grant no. IPT-20111027, by EUROSTARS project E9113, and by the Spanish Ministry for Economy and Competitiveness within the Retos-Colaboracion 2015 initiative, ref. RTC-2015-3278-1.Bellido-Millán, PJ.; Lera, R.; Seimetz, M.; Ruiz-De La Cruz, A.; Torres Peiró, S.; Galán, M.; Mur, P.... (2017). Characterization of protons accelerated from a 3 TW table-top laser system. Journal of Instrumentation. 12:1-12. https://doi.org/10.1088/1748-0221/12/05/T05001S11212Daido, H., Nishiuchi, M., & Pirozhkov, A. S. (2012). Review of laser-driven ion sources and their applications. Reports on Progress in Physics, 75(5), 056401. doi:10.1088/0034-4885/75/5/056401Macchi, A., Borghesi, M., & Passoni, M. (2013). Ion acceleration by superintense laser-plasma interaction. Reviews of Modern Physics, 85(2), 751-793. doi:10.1103/revmodphys.85.751Ledingham, K., Bolton, P., Shikazono, N., & Ma, C.-M. (2014). Towards Laser Driven Hadron Cancer Radiotherapy: A Review of Progress. Applied Sciences, 4(3), 402-443. doi:10.3390/app4030402Kraft, S. D., Richter, C., Zeil, K., Baumann, M., Beyreuther, E., Bock, S., … Pawelke, J. (2010). Dose-dependent biological damage of tumour cells by laser-accelerated proton beams. New Journal of Physics, 12(8), 085003. doi:10.1088/1367-2630/12/8/085003Yogo, A., Sato, K., Nishikino, M., Mori, M., Teshima, T., Numasaki, H., … Daido, H. (2009). Application of laser-accelerated protons to the demonstration of DNA double-strand breaks in human cancer cells. Applied Physics Letters, 94(18), 181502. doi:10.1063/1.3126452Fritzler, S., Malka, V., Grillon, G., Rousseau, J. P., Burgy, F., Lefebvre, E., … Ledingham, K. W. D. (2003). Proton beams generated with high-intensity lasers: Applications to medical isotope production. Applied Physics Letters, 83(15), 3039-3041. doi:10.1063/1.1616661Kishimura, H., Morishita, H., Okano, Y. H., Okano, Y., Hironaka, Y., Kondo, K., … Nemoto, K. (2004). Enhanced generation of fast protons from a polymer-coated metal foil by a femtosecond intense laser field. Applied Physics Letters, 85(14), 2736-2738. doi:10.1063/1.1803915Nakamura, S., Iwashita, Y., Noda, A., Shirai, T., Tongu, H., Fukumi, A., … Wada, Y. (2006). Real-Time Optimization of Proton Production by Intense Short-Pulse Laser with Time-of-Flight Measurement. Japanese Journal of Applied Physics, 45(No. 34), L913-L916. doi:10.1143/jjap.45.l913Nishiuchi, M., Fukumi, A., Daido, H., Li, Z., Sagisaka, A., Ogura, K., … Nakamura, S. (2006). The laser proton acceleration in the strong charge separation regime. Physics Letters A, 357(4-5), 339-344. doi:10.1016/j.physleta.2006.04.053Yogo, A., Daido, H., Fukumi, A., Li, Z., Ogura, K., Sagisaka, A., … Itoh, A. (2007). Laser prepulse dependency of proton-energy distributions in ultraintense laser-foil interactions with an online time-of-flight technique. Physics of Plasmas, 14(4), 043104. doi:10.1063/1.2721066Robinson, A. P. L., Foster, P., Adams, D., Carroll, D. C., Dromey, B., Hawkes, S., … Neely, D. (2009). Spectral modification of laser-accelerated proton beams by self-generated magnetic fields. New Journal of Physics, 11(8), 083018. doi:10.1088/1367-2630/11/8/083018Nemoto, K., Maksimchuk, A., Banerjee, S., Flippo, K., Mourou, G., Umstadter, D., & Bychenkov, V. Y. (2001). Laser-triggered ion acceleration and table top isotope production. Applied Physics Letters, 78(5), 595-597. doi:10.1063/1.1343845Lee, K., Park, S. H., Cha, Y.-H., Lee, J. Y., Lee, Y. W., Yea, K.-H., & Jeong, Y. U. (2008). Generation of intense proton beams from plastic targets irradiated by an ultraintense laser pulse. Physical Review E, 78(5). doi:10.1103/physreve.78.056403Yogo, A., Daido, H., Bulanov, S. V., Nemoto, K., Oishi, Y., Nayuki, T., … Tajima, T. (2008). Laser ion acceleration via control of the near-critical density target. Physical Review E, 77(1). doi:10.1103/physreve.77.016401Lee, K., Lee, J. Y., Park, S. H., Cha, Y.-H., Lee, Y. W., Kim, K. N., & Jeong, Y. U. (2011). Dominant front-side acceleration of energetic proton beams from plastic targets irradiated by an ultraintense laser pulse. Physics of Plasmas, 18(1), 013101. doi:10.1063/1.3496058OKIHARA, S., SENTOKU, Y., SUEDA, K., SHIMIZU, S., SATO, F., MIYANAGA, N., … SAKABE, S. (2002). Energetic Proton Generation in a Thin Plastic Foil Irradiated by Intense Femtosecond Lasers. Journal of Nuclear Science and Technology, 39(1), 1-5. doi:10.1080/18811248.2002.9715150McKenna, P., Ledingham, K. W. D., Spencer, I., McCany, T., Singhal, R. P., Ziener, C., … Clark, E. L. (2002). Characterization of multiterawatt laser-solid interactions for proton acceleration. Review of Scientific Instruments, 73(12), 4176-4184. doi:10.1063/1.1516855Spencer, I., Ledingham, K. W. D., McKenna, P., McCanny, T., Singhal, R. P., Foster, P. S., … Davies, J. R. (2003). Experimental study of proton emission from 60-fs, 200-mJ high-repetition-rate tabletop-laser pulses interacting with solid targets. Physical Review E, 67(4). doi:10.1103/physreve.67.046402Kaluza, M., Schreiber, J., Santala, M. I. K., Tsakiris, G. D., Eidmann, K., Meyer-ter-Vehn, J., & Witte, K. J. (2004). Influence of the Laser Prepulse on Proton Acceleration in Thin-Foil Experiments. Physical Review Letters, 93(4). doi:10.1103/physrevlett.93.045003Ceccotti, T., Lévy, A., Popescu, H., Réau, F., D’Oliveira, P., Monot, P., … Martin, P. (2007). Proton Acceleration with High-Intensity Ultrahigh-Contrast Laser Pulses. Physical Review Letters, 99(18). doi:10.1103/physrevlett.99.185002Neely, D., Foster, P., Robinson, A., Lindau, F., Lundh, O., Persson, A., … McKenna, P. (2006). Enhanced proton beams from ultrathin targets driven by high contrast laser pulses. Applied Physics Letters, 89(2), 021502. doi:10.1063/1.2220011Steinke, S., Henig, A., Schnürer, M., Sokollik, T., Nickles, P. V., Jung, D., … Habs, D. (2010). Efficient ion acceleration by collective laser-driven electron dynamics with ultra-thin foil targets. Laser and Particle Beams, 28(1), 215-221. doi:10.1017/s0263034610000157Strickland, D., & Mourou, G. (1985). Compression of amplified chirped optical pulses. Optics Communications, 56(3), 219-221. doi:10.1016/0030-4018(85)90120-8Yogo, A., Kondo, K., Mori, M., Kiriyama, H., Ogura, K., Shimomura, T., … Bolton, P. R. (2014). Insertable pulse cleaning module with a saturable absorber pair and a compensating amplifier for high-intensity ultrashort-pulse lasers. Optics Express, 22(2), 2060. doi:10.1364/oe.22.002060Trisorio, A., Grabielle, S., Divall, M., Forget, N., & Hauri, C. P. (2012). Self-referenced spectral interferometry for ultrashort infrared pulse characterization. Optics Letters, 37(14), 2892. doi:10.1364/ol.37.002892Seimetz, M., Bellido, P., Soriano, A., Garcia Lopez, J., Jimenez-Ramos, M. C., Fernandez, B., … Benlloch, J. M. (2015). Calibration and Performance Tests of Detectors for Laser-Accelerated Protons. IEEE Transactions on Nuclear Science, 62(6), 3216-3224. doi:10.1109/tns.2015.2480682Nürnberg, F., Schollmeier, M., Brambrink, E., Blažević, A., Carroll, D. C., Flippo, K., … Roth, M. (2009). Radiochromic film imaging spectroscopy of laser-accelerated proton beams. Review of Scientific Instruments, 80(3), 033301. doi:10.1063/1.3086424Oishi, Y., Nayuki, T., Fujii, T., Takizawa, Y., Wang, X., Yamazaki, T., … Andreev, A. A. (2005). Dependence on laser intensity and pulse duration in proton acceleration by irradiation of ultrashort laser pulses on a Cu foil target. Physics of Plasmas, 12(7), 073102. doi:10.1063/1.1943436Nishiuchi, M., Daito, I., Ikegami, M., Daido, H., Mori, M., Orimo, S., … Yoshiyuki, T. (2009). Focusing and spectral enhancement of a repetition-rated, laser-driven, divergent multi-MeV proton beam using permanent quadrupole magnets. Applied Physics Letters, 94(6), 061107. doi:10.1063/1.3078291Antici, P., Fuchs, J., d’ Humières, E., Lefebvre, E., Borghesi, M., Brambrink, E., … Pépin, H. (2007). Energetic protons generated by ultrahigh contrast laser pulses interacting with ultrathin targets. Physics of Plasmas, 14(3), 030701. doi:10.1063/1.2480610Green, J. S., Carroll, D. C., Brenner, C., Dromey, B., Foster, P. S., Kar, S., … Zepf, M. (2010). Enhanced proton flux in the MeV range by defocused laser irradiation. New Journal of Physics, 12(8), 085012. doi:10.1088/1367-2630/12/8/085012Zeil, K., Kraft, S. D., Bock, S., Bussmann, M., Cowan, T. E., Kluge, T., … Schramm, U. (2010). The scaling of proton energies in ultrashort pulse laser plasma acceleration. New Journal of Physics, 12(4), 045015. doi:10.1088/1367-2630/12/4/045015Nishiuchi, M., Daido, H., Yogo, A., Orimo, S., Ogura, K., Ma, J., … Azuma, H. (2008). Efficient production of a collimated MeV proton beam from a polyimide target driven by an intense femtosecond laser pulse. Physics of Plasmas, 15(5), 053104. doi:10.1063/1.2928161Macchi, A., Sgattoni, A., Sinigardi, S., Borghesi, M., & Passoni, M. (2013). Advanced strategies for ion acceleration using high-power lasers. Plasma Physics and Controlled Fusion, 55(12), 124020. doi:10.1088/0741-3335/55/12/124020Fuchs, J., Antici, P., d’ Humières, E., Lefebvre, E., Borghesi, M., Brambrink, E., … Audebert, P. (2005). Laser-driven proton scaling laws and new paths towards energy increase. Nature Physics, 2(1), 48-54. doi:10.1038/nphys199Schwoerer, H., Pfotenhauer, S., Jäckel, O., Amthor, K.-U., Liesfeld, B., Ziegler, W., … Esirkepov, T. (2006). Laser-plasma acceleration of quasi-monoenergetic protons from microstructured targets. Nature, 439(7075), 445-448. doi:10.1038/nature04492Margarone, D., Klimo, O., Kim, I. J., Prokůpek, J., Limpouch, J., Jeong, T. M., … Korn, G. (2012). Laser-Driven Proton Acceleration Enhancement by Nanostructured Foils. Physical Review Letters, 109(23). doi:10.1103/physrevlett.109.234801Flippo, K. A., d’ Humières, E., Gaillard, S. A., Rassuchine, J., Gautier, D. C., Schollmeier, M., … Hegelich, B. M. (2008). Increased efficiency of short-pulse laser-generated proton beams from novel flat-top cone targets. Physics of Plasmas, 15(5), 056709. doi:10.1063/1.291812

The kinome of Phytophthora infestans reveals oomycete-specific innovations and links to other taxonomic groups

<p>Abstract</p> <p>Background</p> <p>Oomycetes are a large group of economically and ecologically important species. Its most notorious member is <it>Phytophthora infestans</it>, the cause of the devastating potato late blight disease. The life cycle of <it>P. infestans </it>involves hyphae which differentiate into spores used for dispersal and host infection. Protein phosphorylation likely plays crucial roles in these stages, and to help understand this we present here a genome-wide analysis of the protein kinases of <it>P. infestans </it>and several relatives. The study also provides new insight into kinase evolution since oomycetes are taxonomically distant from organisms with well-characterized kinomes.</p> <p>Results</p> <p>Bioinformatic searches of the genomes of <it>P. infestans</it>, <it>P. ramorum</it>, and <it>P. sojae </it>reveal they have similar kinomes, which for <it>P. infestans </it>contains 354 eukaryotic protein kinases (ePKs) and 18 atypical kinases (aPKs), equaling 2% of total genes. After refining gene models, most were classifiable into families seen in other eukaryotes. Some ePK families are nevertheless unusual, especially the tyrosine kinase-like (TKL) group which includes large oomycete-specific subfamilies. Also identified were two tyrosine kinases, which are rare in non-metazoans. Several ePKs bear accessory domains not identified previously on kinases, such as cyclin-dependent kinases with integral cyclin domains. Most ePKs lack accessory domains, implying that many are regulated transcriptionally. This was confirmed by mRNA expression-profiling studies that showed that two-thirds vary significantly between hyphae, sporangia, and zoospores. Comparisons to neighboring taxa (apicomplexans, ciliates, diatoms) revealed both clade-specific and conserved features, and multiple connections to plant kinases were observed. The kinome of <it>Hyaloperonospora arabidopsidis</it>, an oomycete with a simpler life cycle than <it>P. infestans</it>, was found to be one-third smaller. Some differences may be attributable to gene clustering, which facilitates subfamily expansion (or loss) through unequal crossing-over.</p> <p>Conclusion</p> <p>The large sizes of the <it>Phytophthora </it>kinomes imply that phosphorylation plays major roles in their life cycles. Their kinomes also include many novel ePKs, some specific to oomycetes or shared with neighboring groups. Little experimentation to date has addressed the biological functions of oomycete kinases, but this should be stimulated by the structural, evolutionary, and expression data presented here. This may lead to targets for disease control.</p