3,722 research outputs found

    Optimised solutions to the last-mile delivery problem in London using a combination of walking and driving

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    Inspired by actual parcel delivery operations in London, this paper describes a two-echelon distribution system that combines the use of driving and walking as part of last-mile deliveries in urban areas for a single driver. The paper presents an optimisation model that explicitly treats and integrates the driving and walking elements, and describes a branch-and-cut algorithm that uses new valid inequalities specifically tailored for the problem at hand. Computational results based on real instances obtained from a courier operating in London are presented to show the performance of the algorithm

    Beta-blocker therapy is not associated with mortality after intracerebral hemorrhage

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    BackgroundBeta-blocker therapy has been suggested to have neuroprotective properties in the setting of acute stroke; however, the evidence is weak and contradictory. We aimed to examine the effects of pre-admission therapy with beta-blockers (BB) on the mortality following spontaneous intracerebral hemorrhage (ICH). MethodsRetrospective analysis of the Helsinki ICH Study database. ResultsA total of 1013 patients with ICH were included in the analysis. Patients taking BB were significantly older, had a higher premorbid mRS score, had more DNR orders, and more comorbidities as atrial fibrillation, hypertension, diabetes mellitus, ischemic heart disease, and heart failure. After adjustment for age, pre-existing comorbidities, and prior use of antithrombotic and antihypertensive medications, no differences in in-hospital mortality (OR 1.1, 95% CI 0.8-1.7), 12-month mortality (OR 1.3, 95% CI 0.9-1.9), and 3-month mortality (OR 1.2, 95% CI 0.8-1.7) emerged. ConclusionPre-admission use of BB was not associated with mortality after ICH.Peer reviewe

    Phase separation in the Edwards model

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    The nature of charge transport within a correlated background medium can be described by spinless fermions coupled to bosons in the model introduced by Edwards. Combining numerical density matrix renormalization group and analytical projector-based renormalization methods we explore the ground-state phase diagram of the Edwards model in one dimension. Below a critical boson frequency any long-range order disappears and the system becomes metallic. If the charge carriers are coupled to slow quantum bosons the Tomonaga-Luttinger liquid is attractive and finally makes room for a phase separated state, just as in the t-J model. The phase boundary separating repulsive from the attractive Tomonaga-Luttinger liquid is determined from long-wavelength charge correlations, whereas fermion segregation is indicated by a vanishing inverse compressibility. On approaching phase separation the photoemission spectra develop strong anomalies.Comment: 6 pages, 5 figures, final versio

    On the moment dynamics of stochastically delayed linear control systems

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    In this article, the dynamics and stability of a linear system with stochastic delay and additive noise are investigated. It is assumed that the delay value is sampled periodically from a stationary distribution. A semi‚Äźdiscretization technique is used to time‚Äźdiscretize the system and derive the mean and second‚Äźmoment dynamics. These dynamics are used to obtain the stationary moments and the corresponding necessary and sufficient stability conditions. The application of the proposed method is illustrated through the analysis of the Hayes equation with stochastic delay and additive noise. The method is also applied to the control design of a connected automated vehicle. These examples illuminate the effects of stochastic delays on the robustness of dynamical systems

    Gain and time resolution of 45 őľ\mum thin Low Gain Avalanche Detectors before and after irradiation up to a fluence of 101510^{15} neq_{eq}/cm2^2

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    Low Gain Avalanche Detectors (LGADs) are silicon sensors with a built-in charge multiplication layer providing a gain of typically 10 to 50. Due to the combination of high signal-to-noise ratio and short rise time, thin LGADs provide good time resolutions. LGADs with an active thickness of about 45 őľ\mum were produced at CNM Barcelona. Their gains and time resolutions were studied in beam tests for two different multiplication layer implantation doses, as well as before and after irradiation with neutrons up to 101510^{15} neq_{eq}/cm2^2. The gain showed the expected decrease at a fixed voltage for a lower initial implantation dose, as well as for a higher fluence due to effective acceptor removal in the multiplication layer. Time resolutions below 30 ps were obtained at the highest applied voltages for both implantation doses before irradiation. Also after an intermediate fluence of 3√ó10143\times10^{14} neq_{eq}/cm2^2, similar values were measured since a higher applicable reverse bias voltage could recover most of the pre-irradiation gain. At 101510^{15} neq_{eq}/cm2^2, the time resolution at the maximum applicable voltage of 620 V during the beam test was measured to be 57 ps since the voltage stability was not good enough to compensate for the gain layer loss. The time resolutions were found to follow approximately a universal function of gain for all implantation doses and fluences.Comment: 17 page
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