Last Mile Delivery with Parcel Lockers: evaluating the environmental impact of eco-conscious consumer behavior

In recent months, online sales have experienced a sharp surge also due to the COVID pandemic. In this paper, we propose a new location and routing problem for a last mile delivery service based on parcel lockers and introduce a mathematical formulation to solve it by means of a MIP solver (Gurobi).The presence of parcel locker stations avoids the door-to-door delivery by companies but requires that consumers move from home to collect their parcels. Potential location of locker stations is known but not all of them need to be opened. The problem minimizes the global environmental impact in terms of distances traveled by both the delivery company and the consumers deciding the optimal number of stations that have to be opened.How much do the number and location of lockers impact on environment? Is the behavior of consumers a critical aspect of such optimization? To this aim we have solved 1680 instances and analyzed diferent scenarios varying the number of consumers and potential parcel lockers, the maximum distance a consumer is willing to travel to reach a locker station, and the maximum distance we may assume the same consumer is willing to travel by foot or by bicycle.The experimental results draw interesting conclusions and managerial insights providing important rules of thumbs for environmental decision makers.Copyright (c) 2022 The Authors. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/

Improved Smoothing Algorithms for Lattice Gauge Theory

The relative smoothing rates of various gauge field smoothing algorithms are investigated on ${\cal O}(a^2)$-improved \suthree Yang--Mills gauge field configurations. In particular, an ${\cal O}(a^2)$-improved version of APE smearing is motivated by considerations of smeared link projection and cooling. The extent to which the established benefits of improved cooling carry over to improved smearing is critically examined. We consider representative gauge field configurations generated with an ${\cal O}(a^2)$-improved gauge field action on \1 lattices at $\beta=4.38$ and \2 lattices at $\beta=5.00$ having lattice spacings of 0.165(2) fm and 0.077(1) fm respectively. While the merits of improved algorithms are clearly displayed for the coarse lattice spacing, the fine lattice results put the various algorithms on a more equal footing and allow a quantitative calibration of the smoothing rates for the various algorithms. We find the relative rate of variation in the action may be succinctly described in terms of simple calibration formulae which accurately describe the relative smoothness of the gauge field configurations at a microscopic level

The electric dipole moment of the nucleon from simulations at imaginary vacuum angle theta

We compute the electric dipole moment of proton and neutron from lattice QCD simulations with N_f=2 flavors of dynamical quarks at imaginary vacuum angle theta. The calculation proceeds via the CP odd form factor F_3. A novel feature of our calculation is that we use partially twisted boundary conditions to extract F_3 at zero momentum transfer. As a byproduct, we test the QCD vacuum at nonvanishing theta.Comment: 22 pages, 10 figure

Quark propagator in a covariant gauge

Using mean--field improved gauge field configurations, we compare the results obtained for the quark propagator from Wilson fermions and Overlap fermions on a \3 lattice at a spacing of $a=0.125(2)$ fm.Comment: 5 pages, 8 figures, talk given by F.D.R. Bonnet at LHP 2001 workshop, Cairns, Australi

Improving the lattice axial vector current

For Wilson and clover fermions traditional formulations of the axial vector current do not respect the continuum Ward identity which relates the divergence of that current to the pseudoscalar density. Here we propose to use a point-split or one-link axial vector current whose divergence exactly satisfies a lattice Ward identity, involving the pseudoscalar density and a number of irrelevant operators. We check in one-loop lattice perturbation theory with SLiNC fermion and gauge plaquette action that this is indeed the case including order $O(a)$ effects. Including these operators the axial Ward identity remains renormalisation invariant. First preliminary results of a nonperturbative check of the Ward identity are also presented.Comment: 7 pages, 3 figures, Proceedings of the 33rd International Symposium on Lattice Field Theory, 14-18 July 2015, Kobe, Japa

Nucleon isovector structure functions in (2+1)-flavor QCD with domain wall fermions

We report on numerical lattice QCD calculations of some of the low moments of the nucleon structure functions. The calculations are carried out with gauge configurations generated by the RBC and UKQCD collaborations with (2+1)-flavors of dynamical domain wall fermions and the Iwasaki gauge action ($\beta = 2.13$). The inverse lattice spacing is $a^{-1} = 1.73$ GeV, and two spatial volumes of ((2.7{\rm fm})^3) and ((1.8 {\rm fm})^3) are used. The up and down quark masses are varied so the pion mass lies between 0.33 and 0.67 GeV while the strange mass is about 12 % heavier than the physical one. The structure function moments we present include fully non-perturbatively renormalized iso-vector quark momentum fraction, (_{u-d}), helicity fraction, (< x >_{\Delta u - \Delta d}), and transversity, (_{\delta u - \delta d}), as well as an unrenormalized twist-3 coefficient, (d_1). The ratio of the momentum to helicity fractions, (_{u-d}/_{\Delta u - \Delta d}), does not show dependence on the light quark mass and agrees well with the value obtained from experiment. Their respective absolute values, fully renormalized, show interesting trends toward their respective experimental values at the lightest quark mass. A prediction for the transversity, (0.7 _{\delta u -\delta d} < 1.1), in the (\bar{\rm MS}) scheme at 2 GeV is obtained. The twist-3 coefficient, (d_1), though yet to be renormalized, supports the perturbative Wandzura-Wilczek relation.Comment: 14 pages, 22 figures

Crystal structure of liganded and unliganded forms of bovine plasma retinol-binding protein.

The three-dimensional structures of bovine plasma retinol-binding protein (bRBP) complexed with retinol (space group P2(1)2(1)2(1), a = 46.08, b = 49.12, c = 76.10 A) and of the unliganded protein prepared in vitro by extracting retinol with ethyl ether (space group P2(1)2(1)2(1), a = 46.55, b = 48.97, c = 76.87 A) have been solved at 1.9 and 1.7 A resolution, respectively. The final crystallographic R factors are 0.190 for holobRBP and 0.196 for the unliganded bRBP. The model for the bovine holoprotein is quite similar to that of the human protein, with which it exhibits 92% sequence similarity. The root mean square deviation between the alpha-carbons in the two proteins is 0.31 A. The retinol binding site is almost completely preserved. The loops that surround the opening of the beta-barrel are also particularly conserved, in contrast with the presence of several substitutions in parts of the RBP molecule opposite the opening of the calyx that binds retinol. Despite the fact that unliganded bovine RBP was prepared and crystallized using procedures completely different from those used to obtain the unliganded human RBP, the conformational differences between unliganded and liganded forms of bRBP are almost identical to those found previously between the same forms of human RBP. They mainly involve a few residues in the region extending from amino acid residues 32 to 37. Therefore, similar differences are very likely to exist between holoRBP and the physiologically occurring apoprotein. A not yet identified electron density, different in shape and orientation from retinol, also occupies the central cavity of the beta-barrel in the unliganded bRBP, as found for unliganded human RBP. The functional consequences of the conformational change induced by the removal of retinol on the interaction between RBP and transthyretin, coupled with the conservation of the entrance loops of the beta-barrel in mammalian RBPs, are consistent with their participation in molecular interactions