ICML Exploration & Exploitation challenge: Keep it simple!

International audienceRecommendation has become a key feature in the economy of a lot of companies (online shopping, search engines...). There is a lot of work going on regarding recommender systems and there is still a lot to do to improve them. Indeed nowadays in many companies most of the job is done by hand. Moreover even when a supposedly smart recommender system is designed, it is hard to evaluate it without using real audience which obviously involves economic issues. The ICML Exploration & Exploitation challenge is an attempt to make people propose efficient recommendation techniques and particularly focuses on limited computational resources. The challenge also proposes a framework to address the problem of evaluating a recommendation algorithm with real data. We took part in this challenge and achieved the best performances; this paper aims at reporting on this achievement; we also discuss the evaluation process and propose a better one for future challenges of the same kind

Les expressions du référent national en néerlandais contemporain

Expressions of national referents are used to refer to organisms, products, social or professional statuts, events who are typical for a society like a nation. With languages who are spoken in several countries (like Dutch) we can see that the expressions are not onderstood in others countries.Les expressions des référents nationaux désignent des organismes, des produits, des statuts sociaux ou professionnels, des événements propres à une société du type Etat-nation. Pour une langue parlée dans plusieurs pays (comme le néerlandais), on peut montrer que ces expressions ne sont pas comprises d'un pays à l'autre

Intragrating sensing using chirped optical fibre Bragg gratings

This thesis describes a study of intragrating position (localised heat source) and strain measurement sensor systems. The design, development and performance of intensity (power) reflection spectrum based intragrating sensing systems employing chirped fibre Bragg gratings (CFBGs) are investigated. Intragrating sensing is the process of obtaining a continuous profile of a measurand over the grating length from either the amplitude or phase, or both the amplitude and phase of its measured reflection response. Techniques for intragrating sensing employing conventional fibre Bragg gratings have been reviewed and analysed in order to design an intragrating sensor which overcomes the problems associated with the existing sensor systems. The inability to determine the position of the disturbance, direction of the strain gradient and the broadening of the spectra together with the reduction in reflectance complicates the grating inverse reconstruction technique to recover the disturbance profile and is also computationally expensive. Thus the selection of CFBGs is desirable because each Bragg wavelength in the broadband reflection spectrum from a CFBG corresponds to particular local position along the grating. Thus a change in the reflection intensity spectrum, due to a disturbance, at a particular wavelength can be quantified to a local position in the grating and hence the spatial distribution of the measurand can be evaluated. The thesis consists of four major sections: fabrication of CFBGs, sensor calibration, intragrating position and strain measurements. Techniques for the production and controlling the spectral response of CFBGs suitable for intragrating sensing application were investigated using two fabrication techniques; the prism interferometer and the scanning phase mask system. The modelling and experimental results showed that fabrication constraints exist for designing a suitable sensor for intragrating measurements with the prism technique, and thus most of the gratings used for this research were fabricated with the scanning phase mask system. The analysis of results for strain/temperature characterisation, showed that CFBGs fabricated in hydrogenated standard telecommunications fibre have a temperature coefficient approximately 20% higher than standard FBGs in the 1550 nm region with identical strain coefficients. Thus a simple technique for strain-independent temperature measurement is proposed and demonstrated using a sensor head with a combination of a standard FBG and a CFBG. This is an additional finding of the research. The intragrating position measurements within a CFBG sensor were investigated as a function of grating strength. Five linear CFBGs of chirp rate 20 nm/cm, approximate length of 15 mm with varying levels of reflectance (6-53%), fabricated with the scanning phase mask technique were employed for the determination of the centre position of a localised heat source within a CFBG. An iterative approach in conjunction with a fast Fourier transform (FFT) was implemented for solving the inverse problem of obtaining the nonuniform temperature distribution from the measured intensity reflection spectrum. The extracted temperature distribution was characterised by the three parameters of amplitude, width and the centre position. The precision of the inferred centre position of the localised heat source was investigated as a function of grating strength. It was demonstrated that the centre position root mean square (rms) error generally improves with grating strength up to approximately 30% peak reflectance and then decreases with further increase in grating strength for both the high and moderate temperature amplitudes which were investigated. A position rms error below 0.03 mm and a repeatability rms error of 0.005 mm were obtained for the centre position measurements with the CFBG intragrating sensor for grating strengths in the range 20-30%. The position rms error reported is the best to date for CFBG based intragrating sensing systems. The intragrating strain measurements were investigated using three embedded CFBGs sensors to determine nonuniform strain distribution near a stress concentration within a notched aluminium specimen subjected to an axial tensile force. The strain distribution was determined from the analysis of the intensity reflection spectrum through the use of an integration method which did not require an initial strain distribution hypothesis. The best case performance was obtained with the sensor having a reflectance of around 23%. The shape of the recovered strain distributions were in reasonable agreement with that predicted by the finite element method (FEM) modelling however some discrepancies were noted. These are most likely due to incomplete transfer of surface strain within the specimen through 3-layers (host/adhesive/fibre) to the fibre core. A repeatability rms error of less than 4 me [mu epsilon] in the extracted strain profiles was obtained

Türkiye'deki demiryolu altyapısının, ekonomik büyüme ve nüfusa olan etkisi

Bu çalışma ulaşım altyapısı ve iki önemli değişkenæ demografik ve ekonomik değişkenler arasındaki deneysel ilişkiyi araştırmaktadır. İl bazında demiryolu uzunlukları, nüfus yoğunluğu ve tarımsal üretim değişkenleri, sırasıyla ulaşım altyapısı, demografik ve ekonomik ölçümler için kullanılmıştır. Bu çalışmanın en önemli katkısı, yazarın bilgisi dahilinde Türkiye'deki tek örneği olan veri setleridir. Türkiye için panel ekonometri veri analizi uygulanan il bazındaki bu veri setleri, zaman ve alan çerçevesinde ilişkileri araştırmak için kullanılmıştır. Değişkenler arasındaki ilişkiyi 1856 ve 2007 yılları arasında ortaya çıkarmak için panel regresyon, panel birim kök, panel eşbütünleşme ve panel nedensellik test metotları gerçekleştirilmiştir. Ulaşım altyapısı ve ekonomik gelişim değişkenleri arasındaki ilişki, farklı pek çok gelişmiş ve/veya endüstrileşmiş bölge için deneysel olarak analiz edilmiştir. Ayrıca, ulaşım altyapısı ve demografik değişkenler arasındaki ilişkiler de aynı şekilde analiz edilmiştir. Bu çalışma ise gelişmekte ve endüstrileşmekte olan Türkiye için deneysel analizler bulundurmaktadır. Bunun için, çalışmanın ikinci önemli katkısı bu analizlerdir. Üstelik ulaşım altyapısı değişkenlerinin, ekonomik ve demografik değişkenler üzerindeki etkilerini inceleyen deneysel çalışmalar geniş bir şekilde bu çalışmada sunulmuştur. Buna ilaveten, Osmanlı İmparatorluğu ve Türkiye Cumhuriyeti dönemlerindeki demiryolu ağının ve demiryolu yapım aşamalarının tarihsel gelişimleri de çalışmada sunulan diğer önemli bölümlerdir. This study explores the empirical relationship between transportation infrastructure and two measuresæ demographic and economic activity. Railway lengths, population density and agricultural production at province level base used as datasets for transportation infrastructure, demographic and economic activity measures, respectively. The most important contribution of this study is related with the datasets, which should probably be the first example for the knowledge of the author in Turkey. Using province level panel data for Turkey, panel econometric methods are applied to investigate these relationships in time and space. Panel regression, panel unit root, panel cointegration and panel causality testing procedures are performed to sort out the linkage between measures for the sample period between 1856 and 2007. The relationship between transportation infrastructure and economic development measures is empirically analyzed for many different developed or industrialized regions. Besides, the relationship between transportation infrastructure and demographic measures is also investigated in the same way. This study provides an empirical process for Turkey as a developing and not industrialized country. Therefore, this is the second important contribution of this study. In addition, an extensive overview of the empirical literature, investigating the effects of transportation infrastructure on economic and demographic measures, is provided in this study. Furthermore, a brief history of the railway constructions and railway network expansion during the Ottoman Empire and Republic of Turkey is also presented

Strain-independent temperature measurements using a standard and a chirped fibre Bragg grating

Chirped fibre Bragg gratings (CFBGs) fabricated in hydrogenated plain telecom fibre have a temperature coefficient approximately 20% higher than standard FBGs with identical strain coefficients. Thus a simple technique for strain-independent temperature measurement is proposed

La mémoire des figures impériales chez Claudien

International audienceSeveral references to earlier emperors can be found in Claudian’s politic poems addressed to Emperor Honorius ; among them are Theodosius, his father, and Trajan, the model for the optimus princeps. This paper aims at analysing how the poet makes use of these references to show the very young Prince of the West what a good emperor is and to legitimatize him (and, at the same time, to legitimatize Stilicho’s place, which has no legal basis) : to achieve this goal, Claudian draws on the double idea of the dynastic transfer of imperial power and the choice of the best possible man. Analysing this allows a better understanding of the functioning of the imperial panegyric, which goes beyond the mere praise in Claudian’s poetry : it creates and shapes the reality it describes – and so the figure of the Prince – in a performative way. The chronological perspective of this study shows also how Claudian’s discourse evolves as Honorius grows from childhood to maturity.Les poèmes politiques que Claudien a écrits pour l’Empereur Honorius sont émaillés de références à des empereurs antérieurs, parmi lesquels Théodose, son père, et Trajan, modèle achevé de l’optimus princeps. L’objet de cet article est d’étudier comment, au travers de ces références, le poète entreprend de dessiner pour le tout jeune Prince d’Occident la figure du bon empereur et de définir sa légitimité (ainsi que celle du régent Stilicon, qu’aucune disposition légale ne justifie) entre transmission dynastique du pouvoir et choix du meilleur. Se voit ainsi précisé le fonctionnement du panégyrique impérial, qui ne se limite pas chez Claudien à la simple louange : le discours crée et met en forme sa propre réalité, jusqu’à se faire performatif, et modeler le personnage loué. La perspective chronologique qui a été choisie montre en outre l’évolution du propos de Claudien à mesure qu’Honorius passe de l’enfance à l’âge adulte

Intra-grating sensing with a chirped fibre Bragg grating employing an integration method

A method to recover arbitrary temperature profiles along a chirped fibre Bragg grating sensor is presented. We demonstrate a nonlinear look up table method to recover the shape, width and position of a disturbance in temperature after compensating for distortions in the result of integrating changes in the power reflectance spectrum