From bricks-and-mortar to bricks-and-clicks: logistics networks in omni-channel grocery retailing

Purpose: The advent of grocery sales through online channels necessitates that bricks-and-mortar retailers redefine their logistics networks if they want to compete online. Because the general understanding of such bricks-and-clicks logistics systems for grocery is still limited, the purpose of this paper is to analyze the internal logistics networks used to serve customers across channels by means of an exploratory study with retailers from different contexts. Design/methodology/approach: A total of twelve case companies from six European countries participated in this exploratory study. Face-to-face interviews with managers were the primary source for data collection. The heterogeneity of our sample enabled us to build a common understanding of logistics networks in grocery retailing on multiple channels and to understand the advantages of different warehousing, picking, internal transportation and last-mile delivery systems. Findings: Bricks-and-mortar grocery retailers are leveraging their existing logistics structures to fulfill online orders. Logistics networks are mostly determined by the question of where to split case packs into customer units. In non-food logistics channel integration is mostly seen as beneficial, but in grocery retailing this depends heavily on product, market and retailer specifics. The data from our heterogeneous sample reveals six distinct types for cross-channel order fulfillment. Practical implications: Our qualitative analysis of different design options can serve as decision support for retailers developing logistics networks to serve customers across channels. Originality/value: The paper shows the internal and external factors that drive the decisionmaking for omni-channel logistics networks for previously store-based grocery retailers. Thereby it makes a step towards building a contingency and configuration theory of retail networks design. It discusses in particular the differences between grocery and non-food omni-channel retailing, lastmile delivery systems and market characteristics in the decision-making of retail networks design

Iterative solution of systems of linear equations in microwave circuits using a block quasi-minimal residual algorithm

The electric properties of monolithic microwave integrated circuits that are connected to transmission lines are described in terms of their scattering matrix using Maxwell's equations. Using a finite-volume method the corresponding three-dimensional boundary value problem of Maxwell's equations in the frequency domain can be solved by means of a two-step procedure. An eigenvalue problem for non-symmetric matrices yields the wave modes. The eigenfunctions determine the boundary values at the ports of the transmission lines for the calculation of the fields in the three-dimensional structure. The electromagnetic fields and the scattering matrix elements are achieved by the solution of large-scale systems of linear equations with indefinite complex symmetric coefficient matrices. In many situations, these matrix problems need to be solved repeatedly for different right-hand sides, but with the same coefficient matrix. The block quasi-minimal residual algorithm is a block Krylov subspace iterative method that incorporates deflation to delete linearly and almost linearly dependent vectors in the underlying block Krylov sequences

Numerical simulation for lossy microwave transmission lines including PML

Finite-difference analysis of transmission lines including lossy materials and radiation effects leads to a complex eigenvalue problem. A method is presented which preserves sparseness and delivers only the small number of interesting modes out of the complete spectrum. The propagation constants are found solving a sequence of eigenvalue problems of modified matrices with the aid of the shift-and-invert mode of the Arnoldi method. In an additional step non physical Perfectly Matched Layer modes are eliminated

Simulation of microwave and semiconductor laser structures including absorbing boundary conditions

The transmission properties of microwave and optical structures can be described in terms of their scattering matrix using a three-dimensional boundary value problem for Maxwell's equations. The computational domain is truncated by electric or magnetic walls, open structures are treated using the Perfectly Matched Layer (PML) Absorbing Boundary Condition. The boundary value problem is solved by a finite-volume scheme. This results in a two-step procedure: an eigenvalue problem for general complex matrices and the solution of a large-scale system of linear equations with indefinite symmetric complex matrices. The modes of smallest attenuation are located in a longsome region bounded by two parabolas, and are found solving a sequence of eigenvalue problems of modified matrices. To reduce the execution times a coarse and a fine grid, and two levels of parallelization can be used. For the computation of the discrete grid equations, advanced preconditioning techniques are applied to reduce the dimension and the number of iterations solving the large-scale systems of linear algebraic equations. These matrix problems need to be solved repeatedly for different right-hand sides, but with the same coefficient matrix. The used block quasi-minimal residual algorithm is a block Krylov subspace iterative method that incorporates deflation to delete linearly and almost linearly dependent vectors in the block Krylov sequences. Special attention is paid to the PML which causes significantly increased number of iterations within Krylov subspace methods

Numerical techniques in the simulation of microwave and laser structures including PML

The properties of circuit structures can be described in terms of their scattering matrix. For the simulation of these structures, we use a Finite Difference Frequency Domain (FDFD) method in order to solve the three dimensional boundary value problem, governed by Maxwells equations. For the computation of the discrete grid equations, advanced preconditioning techniques are applied to reduce the dimension and the number of iterations solving the large-scale systems of linear algebraic equations by means of a block Krylov subspace method. The computational domain is truncated by electric or magnetic walls, open structures are treated using the Perfectly Matched Layer (PML) absorbing boundary condition. Calculating the excitation at the structures ports, one obtains an eigenvalue problem and thus large-scale systems of linear algebraic equations. The interesting modes of smallest attenuation are found solving a sequence of eigenvalue problems of modified matrices. Non-physical PML modes are detected by checking the eigenfunctions. Due to the high wavenumbers that have to be treated in optoelectronic device simulations, the number of modified eigenvalue problems as well as the dimension of the problem grows substantially in comparison to microwave structures. To reduce the execution times a coarse and a fine grid and parallelization techniques are used

On the Computation of Eigen Modes for Lossy Microwave Transmission Lines Including Perfectly Matched Layer Boundary Conditions

Design of microwave circuits requires detailed knowledge on the electromagnetic properties of the transmission lines used. This can be obtained by applying the Maxwellian equations to a longitudinally homogeneous waveguide structure, which results in an eigenvalue problem for the propagation constant. Using a finite-volume approach we get an algebraic formulation. In the presence of losses or absorbing boundary conditions its system matrix is complex. A method is presented which avoids the computation of all eigenvalues to find the few propagating modes one is interested in. Special attention is paid to the so-called Perfectly Matched Layer boundary conditions

Eigen mode computation of microwave and laser structures including PML

The field distribution at the ports of the transmission line structure is computed by applying Maxwell's equations to the structure. Assuming longitudinal homogeneity an eigenvalue problem can be derived, whose solutions correspond to the propagation constants of the modes. The nonsymmetric sparse system matrix is complex in the presence of losses and Perfectly Matched Layer. The propagation constants are found solving a sequence of eigenvalue problems of modified matrices with the aid of the invert mode of the Arnoldi method. Using coarse and fine grids, and a new parallel sparse linear solver, the method, first developed for microwave structures, can be applied also to high dimensional problems of optoelectronics

Configurable Fault Tolerant Circuits and System Level Integration for Self-Awareness

Scaling minimum features of ICs down to the 10nm- area and below has allowed high integration rates in electronics. Scaling at supply voltages of 1V and below also implies a rising level of stress which drives aging effects that reduce switching speed and the expected life time. Additionally, vulnerability from particle radiation is increased. Hence, fault detection and on-line correction become a must for many applications. However, not only fault tolerance but self-awareness becomes also an advantage. Provided that by being aware of its own healthy state allow optimized configurations regarding system operation modes and configurable hardware mechanism. This paper shows a preliminary work in a configurable circuit and explores its configuration possibilities when integrated into a complete system

Endowashers: an overlooked risk for possible post-endoscopic infections

Background: Prevention of post-endoscopy infections is an important objective to assure patient safety. Endowashers, or high throughput irrigation water pumps, are a frequently used device on endoscopes. Recommendations published by professional bodies and regulatory health agencies cover not only adequate reprocessing of fiber-endoscopes but also state accepted methods of regular microbial sampling. Although major instruments like endoscopes are covered by these recommendations, other devices used as optional add-ons for endoscopes are not included