Towards greener city logistics: an application of agile routing algorithms to optimize the distribution of micro-hubs in Barcelona

[EN] The COVID-19 pandemic accelerated the shift towards online shopping, reshaping consumer habits and intensifying the impact on urban freight distribution. This disruption exacerbated traffic congestion and parking shortages in cities, underscoring the need for sustainable distribution models. The European Union's common transport policy advocates for innovative UFD approaches that promote intermodal transportation, reduce traffic, and optimize cargo loads. Our study addresses these challenges by proposing an agile routing algorithm for an alternative UFD model in Barcelona. This model suggests strategically located micro-hubs selected from a set of railway facilities, markets, shopping centers, district buildings, pickup points, post offices, and parking lots (1057 points in total). It also promotes intermodality through cargo bikes and electric vans. The study has two main objectives: (i) to identify a network of intermodal micro-hubs for the efficient delivery of parcels in Barcelona and (ii) to develop an agile routing algorithm to optimize their location. The algorithm generates adaptive distribution plans considering micro-hub operating costs and vehicle routing costs, and using heuristic and machine learning methods enhanced by parallelization techniques. It swiftly produces high-quality routing plans based on transportation infrastructure, transportation modes, and delivery locations. The algorithm adapts dynamically and employs multi-objective techniques to establish the Pareto frontier for each plan. Real-world testing in Barcelona, using actual data has shown promising results, providing potential scenarios to reduce CO2 emissions and improve delivery times. As such, this research offers an innovative and sustainable approach to UFD, that will contribute significantly to a greener future for cities.This research was supported by the European Commission (No. 101069782), the Spanish Ministry of Science and Innovation (PID2019-111100RB-C21/ AEI/10.13039/501100011033) and (PID2022-138860NB-I00 and RED2022134703-T), and the Barcelona City Council (22S02264-001).C. Castillo; Alvarez-Palau, E.; Panadero, J.; Juan, AA. (2024). Towards greener city logistics: an application of agile routing algorithms to optimize the distribution of micro-hubs in Barcelona. EUROPEAN TRANSPORT RESEARCH REVIEW. 16(1). https://doi.org/10.1186/s12544-024-00669-716

Strings on pp-waves and massive two dimensional field theories

We find a general class of pp-wave solutions of type IIB string theory such that the light cone gauge worldsheet lagrangian is that of an interacting massive field theory. When the light cone Lagrangian has (2,2) supersymmetry we can find backgrounds that lead to arbitrary superpotentials on the worldsheet. We consider situations with both flat and curved transverse spaces. We describe in some detail the background giving rise to the N=2 sine Gordon theory on the worldsheet. Massive mirror symmetry relates it to the deformed $CP^1$ model (or sausage model) which seems to elude a purely supergravity target space interpretation.Comment: harvmac, 26 pages, v2,3: references added, typos correcte

Monopoles, noncommutative gauge theories in the BPS limit and some simple gauge groups

For three conspicuous gauge groups, namely, SU(2), SU(3) and SO(5), and at first order in the noncommutative parameter matrix h\theta^{\mu\nu}, we construct smooth monopole --and, some two-monopole-- fields that solve the noncommutative Yang-Mills-Higgs equations in the BPS limit and that are formal power series in h\theta^{\mu\nu}. We show that there exist noncommutative BPS (multi-)monopole field configurations that are formal power series in h\theta^{\mu\nu} if, and only if, two a priori free parameters of the Seiberg-Witten map take very specific values. These parameters, that are not associated to field redefinitions nor to gauge transformations, have thus values that give rise to sharp physical effects.Comment: 30 pages, no figure

Localized Tachyons and the g_cl conjecture

We consider C/Z_N and C^2/Z_N orbifolds of heterotic string theories and Z_N orbifolds of AdS_3. We study theories with N=2 worldsheet superconformal invariance and construct RG flows. Following Harvey, Kutasov, Martinec and Moore, we compute g_cl and show that it decreases monotonically along RG flows- as conjectured by them. For the heterotic string theories, the gauge degrees of freedom do not contribute to the computation of g_cl.Comment: Corrections and clarifications made, 19 page

Data from a survey of Clostridium perfringens and Clostridium difficile shedding by dogs and cats in the Madrid region (Spain), including phenotypic and genetic characteristics of recovered isolates

Molecular basis of bacterial pathogenesis, virulence factors and antibiotic resistanc

Dynamic p-enrichment schemes for multicomponent reactive flows

We present a family of p-enrichment schemes. These schemes may be separated into two basic classes: the first, called \emph{fixed tolerance schemes}, rely on setting global scalar tolerances on the local regularity of the solution, and the second, called \emph{dioristic schemes}, rely on time-evolving bounds on the local variation in the solution. Each class of $p$-enrichment scheme is further divided into two basic types. The first type (the Type I schemes) enrich along lines of maximal variation, striving to enhance stable solutions in "areas of highest interest." The second type (the Type II schemes) enrich along lines of maximal regularity in order to maximize the stability of the enrichment process. Each of these schemes are tested over a pair of model problems arising in coastal hydrology. The first is a contaminant transport model, which addresses a declinature problem for a contaminant plume with respect to a bay inlet setting. The second is a multicomponent chemically reactive flow model of estuary eutrophication arising in the Gulf of Mexico.Comment: 29 pages, 7 figures, 3 table

Cracks in Martensite Plates as Hydrogen Traps in a Bearing Steel

It is demonstrated that a macroscopically homogeneous distribution of tiny cracks introduced into a martensitic bearing steel sample can provide powerful hydrogen traps. The phenomenon has been investigated through thermal desorption spectroscopy and hydrogen permeation measurements using both cracked and integral samples. The e↵ective hydrogen di↵usion coefficient through the cracked sample is found to be far less than in the uncracked one. Similarly, when samples are charged with hydrogen, and then subjected to thermal desorption analysis, the amount of hydrogen liberated from the cracked sample is smaller due to the trapping by the cracks. Theoretical analysis of the data shows that the traps due to cracks are so strong, that any hydrogen within the cracks can never in practice de-trap and cause harm by mechanisms that require the hydrogen to be mobile for the onset of embrittlement.W. Solano-Alvarez is very grateful for support from the Worshipful Company of Ironmongers, CONACyT, the Cambridge Overseas Trust, and the Roberto Rocca Education Programme.This is the accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s11661-014-2680-8

Single-Band Model for Diluted Magnetic Semiconductors: Dynamical and Transport Properties and Relevance of Clustered States

Dynamical and transport properties of a simple single-band spin-fermion lattice model for (III,Mn)V diluted magnetic semiconductors (DMS) is here discussed using Monte Carlo simulations. This effort is a continuation of previous work (G. Alvarez, Phys. Rev. Lett. 89, 277202 (2002)) where the static properties of the model were studied. The present results support the view that the relevant regime of J/t (standard notation) is that of intermediate coupling, where carriers are only partially trapped near Mn spins, and locally ordered regions (clusters) are present above the Curie temperature T_C. This conclusion is based on the calculation of the resistivity vs. temperature, that shows a soft metal to insulator transition near T_C, as well on the analysis of the density-of-states and optical conductivity. In addition, in the clustered regime a large magnetoresistance is observed in simulations. Formal analogies between DMS and manganites are also discussed.Comment: Revtex4, 20 figures. References updated, minor changes to figures and tex

Recreational sandboxes for children and dogs can be a source of epidemic ribotypes of Clostridium difficile

Molecular basis of bacterial pathogenesis, virulence factors and antibiotic resistanc

A fast sparse block circulant matrix vector product

In the context of computed tomography (CT), iterative image reconstruction techniques are gaining attention because high-quality images are becoming computationally feasible. They involve the solution of large systems of equations, whose cost is dominated by the sparse matrix vector product (SpMV). Our work considers the case of the sparse matrices being block circulant, which arises when taking advantage of the rotational symmetry in the tomographic system. Besides the straightforward storage saving, we exploit the circulant structure to rewrite the poor-performance SpMVs into a high-performance product between sparse and dense matrices. This paper describes the implementations developed for multi-core CPUs and GPUs, and presents experimental results with typical CT matrices. The presented approach is up to ten times faster than without exploiting the circulant structure.Romero Alcalde, E.; Tomás Domínguez, AE.; Soriano Asensi, A.; Blanquer Espert, I. (2014). 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American Journal of Roentgenology 193, 764–771 (2009)Heroux, M.A., Bartlett, R.A., Howle, V.E., Hoekstra, R.J., Hu, J.J., Kolda, T.G., Lehoucq, R.B., Long, K.R., Pawlowski, R.P., Phipps, E.T., Salinger, A.G., Thornquist, H.K., Tuminaro, R.S., Willenbring, J.M., Williams, A., Stanley, K.S.: An overview of the Trilinos project. ACM Trans. Math. Softw. 31(3), 397–423 (2005)Im, E.J., Yelick, K., Vuduc, R.: Sparsity: Optimization framework for sparse matrix kernels. International Journal of High Performance Computing Applications 18(1), 135–158 (2004)Jones, E., Oliphant, T., Peterson, P., et al.: SciPy: Open source scientific tools for Python (2001), http://www.scipy.org/Kaveh, A., Rahami, H.: Block circulant matrices and applications in free vibration analysis of cyclically repetitive structures. Acta Mechanica 217(1-2), 51–62 (2011)Kourtis, K., Goumas, G., Koziris, N.: Optimizing sparse matrix-vector multiplication using index and value compression. In: Proceedings of the 5th Conference on Computing Frontiers, CF 2008, pp. 87–96. ACM, New York (2008)Krotkiewski, M., Dabrowski, M.: Parallel symmetric sparse matrix–vector product on scalar multi-core CPUs. Parallel Computing 36(4), 181–198 (2010)Lee, B., Vuduc, R., Demmel, J., Yelick, K.: Performance models for evaluation and automatic tuning of symmetric sparse matrix-vector multiply. In: International Conference on Parallel Processing, ICPP 2004, vol. 1, pp. 169–176 (2004)Leroux, J.D., Selivanov, V., Fontaine, R., Lecomte, R.: Accelerated iterative image reconstruction methods based on block-circulant system matrix derived from a cylindrical image representation. In: Nuclear Science Symposium Conference Record, NSS 2007, vol. 4, pp. 2764–2771. IEEE (2007)NVIDIA: CUSPARSE library (2014), https://developer.nvidia.com/cusparsePan, X., Sidky, E.Y., Vannier, M.: Why do commercial CT scanners still employ traditional, filtered back-projection for image reconstruction? Inverse Problems 25, 123009 (2008)Rodríguez-Alvarez, M.J., Soriano, A., Iborra, A., Sánchez, F., González, A.J., Conde, P., Hernández, L., Moliner, L., Orero, A., Vidal, L.F., Benlloch, J.M.: Expectation maximization (EM) algorithms using polar symmetries for computed tomography CT image reconstruction. Computers in Biology and Medicine 43(8), 1053–1061 (2013)Sheep, L., Vardi, Y.: Maximum likelihood reconstruction for emmision tomography. IEEE Transactions on Medical Imaging 1, 113–122 (1982)Sidky, E.Y., Pan, X.: Image reconstruction in circular cone-beam computed tomography by constrained, total-variation minimization. Physics in Medicine and Biology 53, 4777–4807 (2008)Soriano, A., Rodríguez-Alvarez, M.J., Iborra, A., Sánchez, F., Carles, M., Conde, P., González, A.J., Hernández, L., Moliner, L., Orero, A., Vidal, L.F., Benlloch, J.M.: EM tomographic image reconstruction using polar voxels. Journal of Instrumentation 8, C01004 (2013)Thibaudeau, C., Leroux, J.D., Pratte, J.F., Fontaine, R., Lecomte, R.: Cylindrical and spherical ray-tracing for ct iterative reconstruction. In: 2011 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), pp. 4378–4381 (2011)Vuduc, R., Demmel, J.W., Yelick, K.A.: OSKI: A library of automatically tuned sparse matrix kernels. Journal of Physics: Conference Series 16(1), 521 (2005)Vuduc, R.W., Moon, H.-J.: Fast sparse matrix-vector multiplication by exploiting variable block structure. In: Yang, L.T., Rana, O.F., Di Martino, B., Dongarra, J. (eds.) HPCC 2005. LNCS, vol. 3726, pp. 807–816. Springer, Heidelberg (2005)Williams, S., Oliker, L., Vuduc, R., Shalf, J., Yelick, K., Demmel, J.: Optimization of sparse matrix-vector multiplication on emerging multicore platforms. Parallel Computing 35(3), 178–194 (2009