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Real-time model predictive control based on dual gradient projection: Theory and fixed-point FPGA implementation
No full textThis paper proposes a method to design robust model predictive control (MPC) laws for discrete-time linear systems with hard mixed constraints on states and inputs, in case of only an inexact solution of the associated quadratic program is available, because of real-time requirements. By using a recently proposed dual gradient-projection algorithm, it is proved that the discrepancy of the optimal control law as compared with the obtained one is bounded even if the solver is implemented in fixed-point arithmetic. By defining an alternative MPC problem with tightened constraints, a feasible solution is obtained for the original MPC problem, which guarantees recursive feasibility and asymptotic stability of the closed-loop system with respect to a set including the origin, also considering the presence of external disturbances. The proposed MPC law is implemented on a field-programmable gate array in order to show the practical applicability of the method
La notion d’Ornement dans les documents d’archives et les biographies d’artistes (XVIeme-XVIIIeme siècles)
No full textPeer-Group Detection of Banks and Resilience to Distress
No full textThe paper looks at the importance of the true business model in shaping the risk profile of
financial institutions. We adopt a novel indirect clustering approach to enrich the classic bank
business model classification on a global data set including about 11,000 banks, both listed and
non-listed representing more than 180 countries over the period 2005-2014. A comprehensive
list of global distress events, which combines bankruptcies, liquidations, defaults, distressed
mergers, and public bailouts, is regressed against financial statement ratios (i.e. proxies for
CAMELS) and controlling for macro and sectoral effects using a rare-event logit model. Our
findings suggest that individual characteristics along with macro and sectoral factors contribute
differently, sometimes with opposite sign, to the likelihood of distress and to the volatility
of business models with the exception of liquidity whose contribution appears exogenous to
business model choice. By capturing the switching behaviour across groups, we find that
business model volatility exacerbates vulnerability and distress, especially if moving from
wholesale-oriented to deposit oriented groups
A computational framework for the interplay between delamination and wrinkling in functionally graded thermal barrier coatings
No full textStiff films bonded to compliant substrates are used in a wide range of technological applications and especially in thermal barrier coatings (TBC). Thin films can be made of Functionally Graded Materials (FGMs) with a heterogeneous composition that usually range from a metallic to a ceramic phase. Aiming at investigating the phenomenon of delamination of thin FGM layers from compressed elastic substrates, a fully 3D nonlinear computational framework combining nonlinear fracture mechanics based on a novel interface element formulation for large displacements and a solid shell finite element to model the thin film is proposed. A comprehensive numerical analysis of delamination in TBCs is carried out, paying a special attention to the interplay between fracture and wrinkling instabilities. Results of the computations are also compared with benchmark 2D semi-analytical results, showing good accuracy of the proposed method that can be applied to general 3D configurations that are difficult to address by semi-analytical approaches
Learning to Count Leaves in Rosette Plants
No full textCounting the number of leaves in plants is important for plant phenotyping, since it can be used to assess plant growth stages. We propose a learning-based approach for counting leaves in rosette (model) plants. We relate image-based descriptors learned in an unsupervised fashion to leaf counts using a supervised regression model. To take advantage of the circular and coplanar arrangement of leaves and also to introduce scale and rotation invariance, we learn features in a log-polar representation. Image patches extracted in this log-polar domain are provided to K-means, which builds a codebook in a unsupervised manner. Feature codes are obtained by projecting patches on the codebook using the triangle encoding, introducing both sparsity and specifically designed representation. A global, per-plant image descriptor is obtained by pooling local features in specific regions of the image. Finally, we provide the global descriptors to a support vector regression framework to estimate the number of leaves in a plant. We evaluate our method on datasets of the \textit{Leaf Counting Challenge} (LCC), containing images of Arabidopsis and tobacco plants. Experimental results show that on average we reduce absolute counting error by 40% w.r.t. the winner of the 2014 edition of the challenge -a counting via segmentation method. When compared to state-of-the-art density-based approaches to counting, on Arabidopsis image data ~75% less counting errors are observed. Our findings suggest that it is possible to treat leaf counting as a regression problem, requiring as input only the total leaf count per training image
Welfare effects of uniform and differential pricing schemes: an analysis through quadratic programming
No full textMultiscale asymptotic homogenization analysis of thermo-diffusive composite materials
No full textIn this paper an asymptotic homogenization method for the analysis of composite materials with periodic microstructure in presence of thermodiffusion is described. Appropriate down-scaling relations correlating the microscopic fields to the macroscopic displacements, temperature and chemical potential are introduced. The effects of the material inhomogeneities are described by perturbation functions derived from the solution of recursive cell problems. Exact expressions for the overall elastic and thermodiffusive constants of the equivalent first order thermodiffusive continuum are derived. The proposed approach is applied to the case of a two-dimensional bi-phase orthotropic layered material, where the effective elastic and thermodiffusive properties can be determined analytically. Considering this illustrative example and assuming periodic body forces, heat and mass sources acting on the medium, the solution performed by the first order homogenization approach is compared with the numerical results obtained by the heterogeneous model
Military Conflict and the Rise of Urban Europe
No full textWe present new evidence about the relationship between military conflict and city
population growth in Europe from the fall of Charlemagne’s empire to the start of
the Industrial Revolution. Military conflict was a main feature of European history.
We argue that cities were safe harbors from conflict threats. To test this argument,
we construct a novel database that geocodes the locations of more than 800 conflicts
between 800 and 1799. We find a significant, positive, and robust relationship that
runs from conflict exposure to city population growth. Our analysis suggests that
military conflict played a key role in the rise of urban Europe
Images, Invisibility, and Motion: Brief Essay on Chronophotography, Cinema, and Optical Unconscious
No full textThis paper is based on an analysis of the notion of “Optical Unconscious” by Walter Benjamin.
It seeks to present an interpretation of this notion in connection with the historical relationship between the birth of cinematic technology on the one hand and, and research conducted during the same period in the field of physiology investigating human and animal movement on the other hand.
To this end I will analyze the following three concepts: (a) alienation, (b) automatism and (c) invisibility.
(a) In Minutiae, Close-up, Microanalysis, Carlo Ginzburg formulates an analogy to describe the “optical unconscious” and juxtaposes it with a page from Marcel Proust in which the alien gaze of the narrator parallels the imperturbable lens of a camera and he experiences the physiognomy of the objects in their anonymous being.
Through reference to this passage, I seek to prove that the meaning of the photographic image does not reside in its ability to reflect its object as something real and familiar, but rather in its ability to alienate this object and make it foreign to the observer.
(b) This paper will link this impersonality of the subject to the concept of automatism and analyze this link through William K.L. Dickson’s Kinetoscopic Record of a Sneeze (1894) as an example of the many images of the time that depicted an involuntary movement on the part of the represented subject, namely an action or series of actions beyond the subject’s control.
I assert that this idea of displaying the ordinariness of an involuntary action constitutes a specificity that both photographic and cinematographic technology are based on.
(c) The comprehensive meaning of the represented subject therefore depends on the device, otherwise it would have been doomed to invisibility. In order to clarify what kind of invisibility is at stake here, my study will take a step back to examine the historical origins of the photo-cinematographic tools used in experimental physiology and the role that representation came to have (the idea of the autonomy of the representation).
Finally, in order to clarify these hypotheses, I shall analyze the case of the French physiologist Étienne-Jules Marey.
By studying physiological theories on motion at the end of XIX Century, this paper will bring the relationship between photography and cinema back to its historical origins and highlight moments of intersection
The Water Suitcase of Migrants: Assessing Virtual Water Fluxes Associated to Human Migration
No full textDisentangling the relations between human migrations and water resources is relevant for food security and trade policy in water-scarce countries. It is commonly believed that human migrations are beneficial to the water endowments of origin countries for reducing the pressure on local resources. We show here that such belief is over-simplistic. We reframe the problem by considering the international food trade and the corresponding virtual water fluxes, which quantify the water used for the production of traded agricultural commodities. By means of robust analytical tools, we show that migrants strengthen the commercial links between countries, triggering trade fluxes caused by food consumption habits persisting after migration. Thus migrants significantly increase the virtual water fluxes and the use of water in the countries of origin. The flux ascribable to each migrant, i.e. the "water suitcase", is found to have increased from 321 m3/y in 1990 to 1367 m3/y in 2010. A comparison with the water footprint of individuals shows that where the water suitcase exceeds the water footprint of inhabitants, migrations turn out to be detrimental to the water endowments of origin countries, challenging the common perception that migrations tend to relieve the pressure on the local (water) resources of origin countries